WO2007088992A1 - Light transmitting electromagnetic wave shielding film, optical filter and plasma display panel - Google Patents

Light transmitting electromagnetic wave shielding film, optical filter and plasma display panel Download PDF

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Publication number
WO2007088992A1
WO2007088992A1 PCT/JP2007/051852 JP2007051852W WO2007088992A1 WO 2007088992 A1 WO2007088992 A1 WO 2007088992A1 JP 2007051852 W JP2007051852 W JP 2007051852W WO 2007088992 A1 WO2007088992 A1 WO 2007088992A1
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WIPO (PCT)
Prior art keywords
electromagnetic wave
wave shielding
light transmitting
shielding film
group
Prior art date
Application number
PCT/JP2007/051852
Other languages
French (fr)
Inventor
Hirotomo Sasaki
Original Assignee
Fujifilm Corporation
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Publication date
Priority claimed from JP2006023209A external-priority patent/JP4705857B2/en
Priority claimed from JP2006023096A external-priority patent/JP4705856B2/en
Application filed by Fujifilm Corporation filed Critical Fujifilm Corporation
Publication of WO2007088992A1 publication Critical patent/WO2007088992A1/en

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K9/00—Screening of apparatus or components against electric or magnetic fields
    • H05K9/0073—Shielding materials
    • H05K9/0094—Shielding materials being light-transmitting, e.g. transparent, translucent
    • H05K9/0096—Shielding materials being light-transmitting, e.g. transparent, translucent for television displays, e.g. plasma display panel

Definitions

  • the present invention relates to an electromagnetic wave shielding material which shields electromagnetic waves generated from front faces of displays such as CRT (cathode ray tube), PDP (plasma display panel), liquid crystal display, ELP (electroluminescence panel (which may also be called “EL”)) and FED (field emission display) and has a light transmitting property; and an optical filter and a plasma display panel, each equipped with the light transmitting electromagnetic wave shielding film.
  • displays such as CRT (cathode ray tube), PDP (plasma display panel), liquid crystal display, ELP (electroluminescence panel (which may also be called “EL”)) and FED (field emission display) and has a light transmitting property; and an optical filter and a plasma display panel, each equipped with the light transmitting electromagnetic wave shielding film.
  • EMI electro-magnetic interferences
  • Electromagnetic waves must be shielded in order to overcome the problem of the above-described EMI and for this purpose, use of the property of metals that they do not transmit electromagnetic waves is effective.
  • Examples of the method now employed include formation of a chassis from a metal or highly conductive substance, insertion of a metal plate between circuit boards, and covering of a cable with a metal foil. Since an operator needs to recognize characters displayed on a CRT or PDP display, however, the display is required to have transparency. The above-described methods using a metal were therefore unsuited as an electromagnetic wave shielding method because the front face of the display often becomes opaque in any one of these methods.
  • PDP which emits a greater amount of electromagnetic waves compared with CRT or the like, is required to have stronger electromagnetic wave shielding performance.
  • the electromagnetic wave shielding performance can be conveniently represented in terms of surface resistivity. While a light emitting electromagnetic wave shielding film for CRT is required to have a surface resistivity of about 300 ⁇ /sq or less, while that for PDP is required to have a surface resistivity of 2.5 ⁇ /sq or less. In consumer plasma television utilizing PDP, the surface resistivity must be adjusted to 1.5 ⁇ /sq or less, more desirably 0.1 ⁇ /sq or less. Thus, the shielding film for PDP is required to have a markedly high conductivity.
  • the shielding film for CRT is required to have a visible light transmittance of about 70% or greater, while that for PDP is required to have a visible light transmittance of about 80% or greater. Electromagnetic wave shielding films having still higher transparency are demanded.
  • a typical material is a metal mesh prepared by etching while utilizing photolithography.
  • the conventional metal mesh prepared by etching while utilizing photolithography can shield strong electromagnetic waves because this process utilizing photolithography enables minute processing and therefore a metal mesh with high aperture ratio (high transmission) can be prepared.
  • this process requires high cost because of complex manufacturing steps. There is accordingly a demand for the improvement of the process.
  • processes for obtaining a metal mesh by printing a paste or ink containing metal particles into a lattice pattern have been proposed.
  • the metal mesh available by the conventional printing process as described above is characterized in that it can be prepared by a smaller number of steps and therefore can be prepared at a lower production cost compared with a metal mesh prepared by etching while utilizing photolithography. It has, on the other hand, the following problems.
  • the first problem of the metal mesh available by the conventional printing method is that it can be prepared the conductivity of the metal mesh tends to be smaller than that of a metal mesh obtained by etching of a metal foil so that it is disadvantageous from the viewpoint of an electromagnetic wave shielding performance.
  • the second problem of it is that adhesion between the metal mesh and support is not sufficient so that durability against physical or mechanical actions such as scratching, that is, surface hardness is week.
  • the third point is that it cannot satisfy the durabilities which an electromagnetic wave shielding film used for displays is required to have and their improvement is desired.
  • an electromagnetic shielding film When an electromagnetic shielding film is used for PDP, for example, it has been prepared by aligning the mesh pattern of the electromagnetic wave shielding material with the module or front plate of PDP or optical filter material using glass as a substrate. This process cannot avoid a loss of the shielding material and even if a rolled shielding material is used in order to improve the productivity, it takes time for aligning each mesh pattern with the panel, failing to increase the production rate sufficiently.
  • the above-described electromagnetic shielding film is required to have near infrared ray shielding performance as an important property for preventing malfunction of a remote controller. Improvement in the luminance of PDP has recently been followed by an increase in the emission amount of near infrared rays so that a higher level of near infrared ray shielding performance is required.
  • the electromagnetic wave shielding film is presumed to have an infrared ray shielding function by adhering thereto the corresponding functional layer.
  • the electromagnetic wave shielding film is not continuous as described above and an optical filter is fabricated while making a large loss, however, the film having an infrared ray shielding function can inevitably be used intermittently.
  • the electromagnetic wave shielding film used for PDP must inevitably have an antireflective function as well as the electromagnetic wave shielding function and near infrared ray shielding function.
  • the film having this antireflective function or such functional film is also a rolled film similar to a film having a near infrared ray shielding function so that if the electromagnetic wave shielding film has a discontinuous mesh pattern, a portion of the antireflective film not provided for use remains as a loss when the antireflective film is adhered to it.
  • An object of the invention is to provide a light transmitting electromagnetic wave shielding film which can be prepared by a smaller number of steps compared with those of the preparation process of a metal mesh by etching while utilizing photolithography, is low in cost, and has sufficient conductivity, that is, sufficient electromagnetic wave shielding performance.
  • Another object of the invention is to provide a light transmitting electromagnetic wave shielding film having sufficient surface hardness, excellent in adhesion, excellent in durabilities such as heat resistance and wet heat resistance, and having a high light transmittance with less light scattering; and an optical filter and a plasma display panel each using the film.
  • the present inventors have carried out an extensive investigation. As a result it has been found that insertion of an adhesion facilitating layer between a transparent substrate and a printed pattern composed mainly of silver is effective, leading to the completion of the invention.
  • the present inventors have found that the conductivity of a light transmitting electromagnetic wave shielding film can be improved by subjecting a printed pattern composed mainly of silver to electrolytic plating.
  • a light transmitting electromagnetic wave shielding film which comprises: a transparent substrate; a first adhesion facilitating layer; and a printed pattern composed mainly of silver, in this order, wherein the printed pattern composed mainly of silver is a printed pattern of a conductive composition containing silver in an amount of 60 mass% or greater relative to metals constituting the printed pattern.
  • the light transmitting electromagnetic wave shielding film according to any of (1) to (6) above, which further comprises: a second adhesion facilitating layer provided on a surface of the transparent substrate having no printed pattern; and an adhesive layer on the second adhesion facilitating layer, wherein the adhesive layer has a peel strength of 20 N/m or greater when brought into contact with glass.
  • a process for preparing a light transmitting electromagnetic wave shielding film comprising: disposing a first adhesion facilitating layer on a transparent substrate; and then disposing a printed pattern composed mainly of silver on the first adhesion facilitating layer, wherein the printed pattern composed mainly of silver is a printed pattern of a conductive composition containing silver in an amount of 60 mass% or greater relative to metals constituting the printed pattern.
  • An optical filter for plasma display panel which comprises a light transmitting electromagnetic wave shielding film as described in any of (1) to (8) above.
  • a plasma display panel which comprises a light transmitting electromagnetic wave shielding film as described in any of (1) to (8) above.
  • a light transmitting electromagnetic wave shielding film which comprises: a transparent substrate; and mesh-like thin lines composed mainly of silver and each having a width of from 1 ⁇ m to 30 ⁇ m, wherein the mesh-like thin lines are obtained by forming a mesh pattern on the transparent substrate by printing, and then electrolytic plating the mesh pattern, and the mesh-like thin lines are continuous for at least 3 m in a lengthwise direction of the light transmitting electromagnetic wave shielding film.
  • An optical filter which comprises a light transmitting electromagnetic wave shielding film as described in any of (14) to (22) above.
  • a plasma display panel which comprises a light transmitting electromagnetic wave shielding film as described in any of (14) to (22) above.
  • FIG. 1 is a schematic view illustrating an exemplary example of an electrolytic plating tank preferably employed for the electrolytic plating in the invention, wherein 10 denotes electrolytic plating tank; 11 denotes plating bath; 12a and 12b denote feeder rollers; 13 denotes anode plates; 14 denotes guide rollers; 15 denotes plating solution; 16 denotes film; and 17 denotes draining roller.
  • 10 denotes electrolytic plating tank
  • 11 denotes plating bath
  • 12a and 12b denote feeder rollers
  • 13 denotes anode plates
  • 14 denotes guide rollers
  • 15 denotes plating solution
  • 16 denotes film
  • 17 denotes draining roller.
  • the term “mesh” in the “continuous mesh pattern” as used herein means a mesh pattern composed of a plurality of thin lines or a mesh composed of a plurality of thin lines in accordance with the examples in the related industry.
  • the term “continuous” means that the film is long as a rolled film and in this long film, the same patterns are repeated continuously in the lengthwise direction without a break.
  • Electromagnetic wave shielding film may sometimes be called “film” simply insofar as it is not confused with another constituent (constituent film) to be stacked because it is supported by a transparent substrate in the film form.
  • transparent plastic substrates for example, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene (PE), polypropylene (PP), polystyrene and EVA, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, and other resins such as polyether ether ketone (PEEK), polysulfone (PSF), polyether sulfone (PES), polycarbonate (PC), polyamide, polyimide, acrylic resin, and triacetyl cellulose (TAC).
  • PET polyethylene terephthalate
  • PP polypropylene
  • EVA vinyl resins
  • vinyl resins such as polyvinyl chloride and polyvinylidene chloride
  • PEEK polyether ether ketone
  • PSF polysulfone
  • PES polyether sulfone
  • PC polycarbonate
  • TAC triacetyl cellulose
  • the transparent plastic material is preferably a polyethylene terephthalate film.
  • the transparent substrate has a thickness of preferably from 5 to 200 ⁇ m, more preferably from 10 to 130 ⁇ m, still more preferably from 40 to 80 ⁇ m from the standpoints of handling property, and visible light transmittance.
  • the total visible light transmittance of a plastic transparent substrate used for this purpose is preferably from 70 to 100%, more preferably from 85 to 100%, especially preferably from 90 to 100%. Further, in the invention, transparent plastic substrates colored in such a degree as not to interfere with the object of the present invention are also usable.
  • the transparent plastic substrate in the invention may be used either as a single layer or as a multilayer film obtained using two or more layers in combination.
  • a glass plate can be used as the transparent substrate.
  • a reinforced glass having a surface equipped with a reinforcing layer is preferred for the use in an electromagnetic shielding film for display.
  • reinforced glass available by the air- cooling method is preferred in view of safety because crushed pieces thereof are small and do not have sharp end surfaces, even if it is broken.
  • the printed pattern composed mainly of silver and the mesh-like thin lines composed mainly of silver (conductive metal portions) in the invention will next be described.
  • "mesh-like thin lines composed mainly of silver” means a printed pattern composed mainly of silver which is treated with electrolytic plating.
  • the printing method known ones such as gravure printing, offset printing, typographic printing, screen printing, flexographic printing and inkjet printing can be used. Of these, screen printing, offset printing and intaglio printing are preferred, with screen printing and gravure printing are especially preferred.
  • the transparent substrate may be subjected to surface treatment or an anchor coat layer may be formed thereon.
  • surface treatment application of a primer, plasma treatment and corona discharge treatment are effective.
  • the transparent substrate has a critical surface tension of preferably 3.5 x 10 "4 N/cm or greater, more preferably 4.0 x 10 "4 N/cm or greater.
  • the conductive metal portion is preferably inclined at from 30° to 60°, more preferably at from 40° to 50°, most preferably at from 43° to 47° relative to the lengthwise direction of the light transmitting electromagnetic wave shielding film.
  • a paste or ink to be used for printing contains preferably, in addition to a metal or metal compound for obtaining a conductive pattern by printing, a solvent for dispersing it, a binder and a dispersant.
  • the metal examples include fine particles of silver, copper, nickel, palladium, gold, platinum and tin.
  • the printed pattern in the invention is composed mainly of silver. It may contain silver singly or a mixture obtained by mixing at least two metals including silver.
  • the "printed pattern composed mainly of silver” means a printed pattern containing silver in an amount of 60 mass% or greater relative to the metals constituting the pattern.
  • mass ratio is equal to weight ratio.
  • Metal compounds may be used in the invention.
  • the term "metal compounds” means metal oxides or organic metal compounds. Compounds which are easily reduced or decomposed by the external application of energy and therefore can be imparted with conductivity are preferred.
  • the metal oxides are preferably gold oxide and silver oxide. Silver oxide is especially preferred because it has self reducing property.
  • the organic metal compounds are preferably silver acetate and silver citrate having a relatively small molecular weight.
  • a metal-containing paste is prepared preferably from a metal of a nano- order size (from 5 to 60 nm).
  • a metal-oxide-containing paste is prepared preferably using a metal oxide of a nano-order size, a reducing agent necessary for the reduction of the metal oxide and a solvent, while an organic-metal-oxide-containing paste is prepared preferably using an organic metal compound having a low decomposition temperature and a solvent.
  • Use of a paste using a metal oxide of a nano-order size and an organic metal compound in combination not only enables printing of even thin lines but also, by selecting the structures of the reducing agent and organic metal compound as needed, promotes the reduction and decomposition of the metal oxide into the corresponding metal under conditions not damaging a flexible film when external energy is applied to add conductivity and promotes fusion bonding between metals, thereby reducing the resistivity further.
  • the metal oxide can be reduced without a reducing agent, for example, when it can be self-reduced by heating, the addition of the reducing agent is not always necessary.
  • the solvent can be selected as needed, depending on the printing method or regulating method of the viscosity of the paste and high-boiling-point solvents such as carbitol and propylene glycol are usable. The solvent will be described later in detail.
  • the viscosity of the paste can be set as needed depending on the printing method or solvent, it is preferably 5 mPa-s or greater but not greater than 20000 mPa-s.
  • thermoplastic resins such as polyester resins, polyvinyl butyral resins, ethyl cellulose resins, (meth)acrylic resins, polyethylene resins, polystyrene resins, polyamide resins and thermosetting resins such as polyester-melamine resins, melamine resins, epoxy-melamine resins, phenolic resins, epoxy resins, amino resins, polyimide resins and (meth)acrylic resins. Two or more of these resins may be used after copolymerization or blending if necessary.
  • the solvent usable in the invention include alcohols such as hexanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, stearyl alcohol, ceryl alcohol, cyclohexanol and terpineol; and alkyl ethers such as ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol monophenyl ether, diethylene glycol, diethylene glycol monobutyl ether (butyl carbitol), cellosolve acetate, butyl cellosolve acetate, carbitol acetate, and butyl carbitol acetate.
  • a proper one may be selected as needed in consideration of printability and workability.
  • the amount of the solvent is determined by the viscosity of the ink or paste. It is usually from 100 to 500 parts by mass, preferably from 100 to 300 parts by mass based on 100 parts by mass of the binder in consideration of the amount of the above-described metal powder.
  • those of the binder and solvent are from 10 " to 10 and from 1 to 10 , respectively, per metal, preferably those of the binder and solvent are from 10 "3 to 10 and from 10 to 10 3 , respectively, per metal.
  • the conductive metal portion after printing is preferably baked at high temperature, by which organic components are removed and at the same time fine metal particles adhere to each other, resulting in a reduction in surface resistivity.
  • the baking temperature is, for example, from 50 to 1000 0 C, preferably from 70 to 600°C
  • baking time is, for example, from 3 to 600 minutes, preferably from 10 to 300 minutes.
  • the light transmitting electromagnetic wave shielding film of the invention has good conductivity because it has a conductive metal portion.
  • the surface resistivity of the light transmitting electromagnetic wave shielding film of the invention is preferably 10 ⁇ /sq or less, more preferably 2.5 ⁇ /sq or less, still more preferably 1.5 ⁇ /s or less, most preferably 0.1 ⁇ /sq or less.
  • the conductive metal preferably has a geometric configuration consisting of triangles such as equilateral triangle, isosceles triangle and right triangle, quadrangles such as square, rectangle, rhomboid, parallelogram and trapezoid, (equilateral) hexagon and (equilateral) octagon in combination, and is more preferably a mesh consisting of these geometric configurations.
  • the line width of the conductive metal portion is preferably from 1 to 40 ⁇ m, more preferably 1 to 30 ⁇ m, further more preferably 20 ⁇ m or less, and the distance between lines is preferably 100 ⁇ m or more. Further, the conductive metal portion may have a portion having a line width greater than 40 ⁇ m for the purpose of ground connection or the like. In view of making the image less outstanding, the line width of the conductive metal portion is more preferably less than 15 ⁇ m.
  • the conductive metal portion is preferably as thin as possible because it widens the viewing angle of the display.
  • the thickness is preferably from 1 ⁇ m or greater but not greater than 20 ⁇ m, more preferably 1 ⁇ m or greater but not greater than 13 ⁇ m, still more preferably 2 ⁇ m or greater but not greater than 10 ⁇ m, most preferably 3 ⁇ m or greater but not greater than 7 ⁇ m.
  • the conductive metal portion is preferably in the form of patterns.
  • the conductive metal portion may be made of a single layer or two or more layers.
  • the conductive metal portion in the invention has an aperture ratio of preferably 85% or greater, more preferably 90% or greater, most preferably 95% or greater in consideration of the visible light transmittance.
  • aperture ratio means a ratio of portions not having thin lines constituting a mesh in the total area, and for example, the aperture ratio of a mesh in the square lattice form having a line width of 10 ⁇ m and a pitch of 200 ⁇ m is almost 90%.
  • the aperture ratio of 98% or less is preferred from the viewpoint of the relationship between the surface resistivity and line width.
  • Calendering treatment that is, treatment with calender rolls preferably employed in the invention will next be described.
  • the calender rolls are usually equipped with at least a pair of rolls.
  • plastic rolls made of epoxy, polyimide, polyamide or polyimidoamide or metal rolls are employed. Treatment with a pair of metal rolls is especially preferred.
  • the linear pressure is preferably 1960 N/cm (200 kgf/cm), more preferably 2940 N/cm (300 kgf/cm) or greater.
  • the calendering treatment is carried out preferably at from 10 to 100°C, more preferably from 10 to 50°C.
  • a long rolled film can be continuously treated by this calendering.
  • the mesh-like thin lines must be continuous for 3 m or greater in the lengthwise direction of the light transmitting electromagnetic wave shielding film.
  • the continuous thin lines are preferably as long as possible because they can reduce a production loss of a material of an optical filter.
  • the continuous length is therefore preferably 2000 m or less. It is preferably 100 m or greater but not greater than 1000 m, more preferably 200 m or greater but not greater than 800 m, most preferably 300 m or greater but not greater than 500 m.
  • the thickness of the transparent substrate is preferably 200 ⁇ m or less, more preferably 20 ⁇ m or greater but not greater than 180 ⁇ m, most preferably 50 ⁇ m or greater but not greater than 120 ⁇ m.
  • Electrolytic plating to be applied to the invention will next be described.
  • Electrolytic plating is preferably a step of plating with at least one material selected from copper, nickel, zinc, tin and cobalt. An example of electrolytic plating will next be described.
  • FIG. 1 illustrates an example of an electrolytic plating tank suited for plating treatment in the invention.
  • the electrolytic plating tank 10 shown in FIG. 1 can give continuous plating treatment to a long film 16.
  • the arrow indicates the traveling direction of the film 16.
  • the electrolytic plating tank 10 is equipped with a plating bath 11 for storing a plating solution 15 therein.
  • a pair of anode plates 13 are arranged in parallel to each other in the plating bath 11 and inside the anode plates 13, a pair of guide rollers 14 are located rotatably in parallel with the anode plates 13.
  • the guide rollers 14 are movable in a vertical direction, whereby plating time of the film 16 can be regulated.
  • each pair of feeder rollers (cathodes) 12a and 12b for guiding the film 16 to the plating bath 11 and at the same time feeding a current to the film 16 is disposed rotatably.
  • a draining roller 17 is disposed rotatably below the feeder roller 12b on the outlet side above the plating bath 11.
  • a water washing spray (not illustrated) for removing the plating solution from the film is disposed between this draining roller 17 and feeder roller 12b on the outlet side.
  • the anode plates 13 are connected to a plus terminal of a power supply (not illustrated) via an electric wire (not illustrated), while feeder rollers 12a and 12b are connected to a minus terminal of the power supply (not illustrated.
  • the distance (distance La in FIG. 1) between the surface of the plating solution and the lowest portion of the face where the feeder roller 12a on the inlet side is contiguous to the film 16 is adjusted to preferably from 0.5 cm to 15 cm, more preferably from 1 cm to 10 cm, still more preferably from 1 cm to 7 cm.
  • the distance (distance Lb shown in FIG. 1) between the surface of the plating solution and the lowest portion of the face where the feeder roller 12b is contiguous to the film 16 is preferably from 0.5 cm to 15 cm.
  • the plating solution 15 is stored in the plating bath 11.
  • a plating solution containing from 30 g/L to 300 g/L of copper sulfate pentahydrate and from 30 g/L to 300 g/L of sulfuric acid can be used.
  • nickel plating nickel sulfate, nickel hydrochloride or the like can be used, while for iron silver plating, a plating solution containing silver cyanide or the like is usable.
  • the plating solution may contain an additive such as surfactant, sulfur compound or nitrogen compound.
  • the film 16 is set while being rolled around a supply reel (not illustrated) and rolling of the film 16 around a conveyor roller (not illustrated) is started so that the surface of the film 16 on which plating is to be formed is brought into contact with the feeder rollers 12a and 12b.
  • a voltage is applied to the anode plates 13 and feeder rollers 12a and 12b and the film 16 is reeled out while being brought into contact with the feeder rollers 12a and 12b.
  • the film 16 is introduced into the plating bath 11 and dipped in the plating solution 15 to form copper plating.
  • the plating solution 15 attached to the film 16 is wiped off by passing it between the draining rollers 17 and the solution is collected in the plating bath 11. This operation is repeated in a plurality of electrolytic plating tanks. At the end of the operation, the film is washed with water and then reeled into a take-up reel (not illustrated).
  • the conveying speed of the film 16 is set within a range of from 1 m/min to 30 min/min.
  • the conveying speed of the film 16 is preferably within a range of from 1 m/min to 10 m/min, more preferably from 2 m/min to 5 m/min.
  • the number of the electrolytic plating tanks it is preferred that from two to ten tanks, more preferably from three to six tanks are continued.
  • the applied voltage is preferably within a range of from IV to 100 V, more preferably within a range of from 2V to 60V.
  • the applied voltage to them is preferably reduced in stages.
  • the current on the inlet side of the first tank is preferably from IA to 3OA, more preferably from 2 A to 1OA.
  • the feeder rollers 12a and 12b are preferably in contact with the entire surface of the film (80% of the contacted area is substantially brought into an electrical contact with the rollers).
  • the film Prior to the plating in the electrolytic plating tank, the film is preferably washed with water and an acid.
  • the solution used for acid washing may contain sulfuric acid or the like.
  • the thickness of the conductive metal portion to be electrolytically plated is preferably as thin as possible because it widens the viewing angle of the display.
  • the film is required to be thinner in order to satisfy the demand for density heightening. From such a viewpoint, the thickness of the conductive metal portion after electrolytic plating is preferably less than 9 ⁇ m, more preferably 0.1 ⁇ m or greater but less than 5 ⁇ m, still more preferably 0.1 ⁇ m or greater but less than 3 ⁇ m.
  • electroless plating may be given prior to the electrolytic plating. Electrolytic plating is conducted preferably without electroless plating, because the number of steps can be decreased, which leads to improvements in the productivity and cost.
  • electroless plating known electroless plating technology can be employed.
  • electroless plating technology employed for printing circuit boards can be used.
  • the electroless plating is preferably, electroless copper plating.
  • Examples of the chemical species contained in the electroless copper plating solution include copper sulfate, copper chloride, reducing agents such as formalin and glyoxylic acid, copper ligands such as EDTA and triethanolamine, and additives for stabilizing the bath or improving the smoothness of the plating film such as polyethylene glycol, yellow prussiate of potash and bipyridine.
  • the transparent substrate having a mesh pattern formed thereon by printing has a surface resistivity of from 1 ⁇ /D to 1000 ⁇ /D
  • electrolytic plating can be given to it.
  • the surface resistivity is preferably from 1 ⁇ /D to 500 ⁇ /D, more preferably from 1 ⁇ /D to 100 ⁇ /D.
  • the light transmitting electromagnetic wave shielding film of the invention may contain a rust inhibitive.
  • Rust inhibitives such as nitrogenous organic heterocyclic compounds and organic mercapto compounds are preferred in the invention.
  • nitrogenous organic heterocyclic compounds include imidazole, benzimidazole, benzindazole, benzotriazole, benzoxazole, benzothiazole, pyridine, quinoline, pyrimidine, piperidine, piperazine, quinoxaline and morpholine. These compounds may have a substituent such as alkyl, carboxyl or sulfo group.
  • organic mercapto compounds examples include alkylmercapto compounds, aryl mercapto compounds and heterocyclic mercapto compounds.
  • Z-SM wherein, Z represents an alkyl, aromatic or heterocyclic group substituted by at least one group selected from the class consisting of hydroxyl group, -SO 3 M 2 group, -COOM 2 group (in which M 2 represents a hydrogen atom, an alkali metal atom or an ammonium group), amino group and ammonio group or substituted by a substituent having at least one group selected from the above-described class; and M represents a hydrogen atom, an alkali metal atom or amidino group (which may form a hydrohalide or sulfonate).
  • R 21 and R 22 each represents a hydrogen atom or alkyl group with the proviso that R 21 and R 22 do not simultaneously represent a hydrogen atom and the alkyl group may have a substituent;
  • R 23 and R 24 each represents a hydrogen atom or alkyl group,
  • R 25 represents a hydroxyl group, amino group, alkyl group or phenyl group,
  • R 26 and R 27 each represents a hydrogen atom, alkyl group, acyl group or -COOM 22 with the proviso that R 26 and R 27 do not simultaneously represent a hydrogen atom;
  • M 21 represents a hydrogen atom, alkali metal atom or ammonium group,
  • M 22 represents a hydrogen atom, alkyl group, alkali metal atom, aryl group or aralkyl group, and
  • m stands for 0, 1 or 2.
  • X 40 represents a hydrogen atom, hydroxyl group, lower alkyl group, lower alkoxy group, halogen atom, carboxyl group or sulfo group
  • M 41 and Ma each represents a hydrogen atom, alkali metal atom or ammonium group.
  • the alkyl group represented by Z in the formula (2) is preferably a C 1-30 alkyl group, especially preferably a linear, branched or cyclic C 2-20 alkyl group which may have a substituent in addition to the above-described substituent.
  • the aromatic group represented by Z is preferably a C 6-32 monocycle or fused ring which may have a substituent in addition to the above-described substituent.
  • the heterocyclic group represented by Z is preferably a C 1-32 monocycle or fused ring; is a 5- or 6-membered ring having, in one ring thereof, from 1 to 6 hetero atoms selected independently from nitrogen, oxygen and sulfur; and may have a substituent in addition to the above-described substituent.
  • the compound When the heterocyclic group is tetrazole, however, the compound has neither a substituted nor unsubstituted naphthyl group as a substituent.
  • the compounds represented by the formula (2) those having as Z a heterocyclic group with at least 2 nitrogen atoms are preferred.
  • the compounds represented by the formula (2) are preferably represented by the following formula (2-a):
  • Z is a group necessary for forming a nitrogen-containing unsaturated 5-membered heterocycle or 6-membered heterocycle (such as pyrrole, imidazole, pyrazole, pyrimidine, pyridazine or pyrazine ring), is a compound having at least one -SM group or thione group, and has at least one substituent selected from the class consisting of hydroxyl group, -COOM group, -SO 3 M group, substituted or unsubstituted amino group, and substituted or unsubstituted ammonio group.
  • R 11 and R 12 each independently represents a hydrogen atom, -SM group, halogen atom, alkyl group (which may be substituted), alkoxy group (which may be substituted), hydroxyl group, -COOM group, -SO 3 M group, alkenyl group (which may be substituted), amino group (which may be substituted), carbamoyl group (including substituted one), or phenyl group (which may be substituted), or R 11 and R 12 may form a ring. They can form a 5-membered ring or 6-membered ring, preferably a nitrogenous heterocycle.
  • M has the same meaning as defined in the formula (2).
  • Z is a group forming a heterocyclic compound having at least two nitrogen atoms and may have a substituent other than the -SM group or thione group.
  • substituent include halogen atoms, lower alkyl groups (including substituted ones, preferably alkyl groups having 5 or less carbon atoms such as methyl and ethyl), lower alkoxy groups (including substituted ones, preferably alkoxy groups having 5 or less carbon atoms such as methoxy, ethoxy and butoxy), lower alkenyl groups (including substituted ones and, preferably alkenyl groups having 5 or less carbon atoms), carbamoyl group and phenyl group.
  • compounds represented by the following formulas A to F are especially preferred.
  • R 21 , R 22 , R 2 , and R 2 each independently represents a hydrogen atom, -SM group, halogen atom, lower alkyl group (which may be substituted, preferably an alkyl group having 5 or less carbon atoms such as methyl or ethyl), lower alkoxy group (which may be substituted, preferably an alkoxy group having 5 or less carbon atoms), hydroxyl group, - COOM 2 , -SO 3 M 5 group, lower alkenyl group (which includes a substituted one and is preferably an alkenyl group having 5 or less carbon atoms), amino group, carbamoyl group or phenyl group. At least one of them represents an -SM group.
  • M, M 2 and M 5 each represents a hydrogen atom, alkali metal atom or ammonium group.
  • the substituent other than -SM is preferably a water soluble group such as hydroxy, -COOM 2 , -SO 3 M 5 or amino group.
  • the amino group represented by R 21 , R 22 , R 23 or R 24 is a substituted or unsubstituted amino group.
  • a lower alkyl group is a preferable substituent.
  • the ammonium group represented by M, M 2 or M 5 is a substituted or unsubstituted ammonium group, preferably an unsubstituted ammonium group.
  • L 1 , L 2 and L 3 each independently represents a hydrogen atom, halogen atom or optional substituent to be bound with the ring via any one of a carbon atom, nitrogen atom, oxygen atom, sulfur atom and phosphorus atom, with the proviso that L 1 , L 2 and L 3 may be the same or different, but at least one of L 1 , L 2 , L 3 and R 0 represents an -SM group (in which M represents an alkali metal atom, hydrogen atom or ammonium group).
  • the optional substituent represented by L 1 , L 2 or L 3 or the substituent represented by R 0 include halogen atoms (such as fluorine, chlorine, bromine and iodine atoms), alkyl groups (including aralkyl, cycloalkyl and active methine groups), alkenyl groups, alkynyl groups, aryl groups, heterocyclic groups, quaternized nitrogen- atom-containing heterocyclic groups (such as pyridinio group), acyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, carbamoyl group, carboxyl group or salts thereof, sulfonylcarbamoyl group, acylcarbamoyl groups, sulfamoylcarbamoyl group, carbazoyl group, oxalyl group, oxamoyl group, cyano group, thiocarbamoyl group, hydroxyl group, alkoxy
  • the optional substituent represented by L 1 , L 2 or L 3 or the substituent represented by R 0 is more preferably a C 0-15 substituent and, more specifically, a chlorine atom, alkyl group, aryl group, heterocyclic group, acyl group, alkoxycarbonyl group, carbamoyl group, carboxyl group or salt thereof, cyano group, alkoxy group, aryloxy group, acyloxy group, amino group, (alkyl, aryl or heterocyclic) amino group, hydroxyamino group, N-substituted saturated or unsaturated nitrogenous heterocyclic group, acylamino group, sulfonamide group, ureido group, thioureido group, sulfamoylamino group, nitro group, mercapto group (alkyl, aryl or heterocyclic) thio group, sulfo group or salt thereof, or sulfamoyl group; more preferably an alky
  • L 1 , L 2 , L 3 and R 0 represents an -SM group (in which M represents an alkali metal atom, hydrogen atom or ammonium group).
  • the alkali metal atom is more specifically Na, K, Li, Mg, Ca or the like and they are present as a counter cation of -S " .
  • M is preferably a hydrogen atom, ammonium group, Na + or K + , especially preferably a hydrogen atom.
  • compounds represented by the following formulas (1-A) and (1-B) are preferred.
  • R 1 to R 4 each independently represents a hydrogen atom, halogen atom, or optional substituent coupled with a ring via a carbon atom, nitrogen atom, oxygen atom, sulfur atom or phosphorus atom. They have the same meanings as described above in L 1 , L 2 and L 3 in the formula (1) and are similar in their preferable range. R 1 and R 3 however do not simultaneously represent a hydroxyl group. R to R may be the same or different but at least one of them is an -SM group.
  • M represents a hydrogen atom, alkali metal atom or ammonium group.
  • R 1 and R 2 may be coupled each other to form a fused ring with a hydrocarbon ring, heterocycle or aromatic ring.
  • At least one of R 1 to R 4 represents an -SM group, more preferably at least two of R 1 to R 4 represent -SM groups.
  • at least two of R 1 to R 4 are -SM groups, preferably R 4 and R 1 , or R 4 and R 3 represent -SM groups.
  • R 10 represents a mercapto group, hydrogen atom or optional substituent
  • X represents a water soluble group or a substituent substituted with a water soluble group
  • Y represents a water soluble group or a substituent substituted with a water soluble group
  • R 20 represents a hydrogen atom or an optional substituent
  • Y 2 represents a water soluble group or a substituent substituted with a water soluble group
  • R 30 represents a hydrogen atom or an optional substituent.
  • R 10 and Y 1 however do not represent a hydroxyl group.
  • R 10 represents a mercapto group, a hydrogen atom or optional substituent.
  • the optional substituent include the optional substituents described above in R 1 to R 4 of formula (1-A).
  • R 10 preferably represents a mercapto group, hydrogen atom, or group selected from the following C 0-15 substituents.
  • the C 0-15 substituents include amino groups, alkyl groups, aryl groups, alkoxyl groups, aryloxy groups, acylamino groups, sulfonamide group, alkylthio groups, arylthio groups, alkylamino groups, and arylamino groups.
  • X represents a water soluble group or a substituent substituted with a water soluble group.
  • water soluble group as used herein means a sulfonic acid group or carboxylic acid group or a salt of these acids, a salt such as an ammonio group, or a group containing a dissociative group which is partially or completely dissociable by an alkaline developing solution, more specifically a sulfo group (or a salt thereof), carboxyl group (or a salt thereof), hydroxyl group, mercapto group, amino group, ammonio group, sulfonamido group, acylsulfamoyl group, sulfonylsulfamoyl group, active methine group, or a substituent containing any of these groups.
  • active methine group means a methyl group substituted with two electron attractive groups, more specifically, dicyanomethyl, ⁇ -cyano- ⁇ -ethoxycarbonylmethyl and ⁇ -acetyl- ⁇ -ethoxycarbonylmethyl groups.
  • the substituent represented by X in formula (1-A-l) is the above-described water soluble group or substituent substituted with the above- described water soluble group.
  • the substituent is a C 0-15 substituent such alkyl group, aryl group, heterocyclic group, alkoxyl group, aryloxy group, heterocyclic oxy group, acyloxy group, alkyl-, aryl- or heterocyclic amino group, acylamino group, sulfonamide group, ureide group, thioureide group, imide group, sulfamoylamino group, alkyl-, aryl- or heterocyclic thio group, alkyl- or arylsulfonyl group, sulfamoyl group, or amino group, preferably a C 1-10 alkyl group (in particular, a methyl group substituted with an amino group), aryl group, aryloxy group, amino group, alkyl-, aryl- or heterocyclic amino group, or an alkyl-, aryl- or heterocyclic thio group.
  • the compound represented by formula (1-A-l) is more preferably represented by the following formula (1-A-l -a): 1-A-1-a
  • R 11 has the same meaning as R 10 in formula (1-A-l) and the preferred range of the substituent is also the same.
  • R 12 and R 13 may be the same or different and each represents a hydrogen atom, alkyl group, aryl group or heterocyclic group with the proviso that at least one of R 12 and R 13 has a water soluble group.
  • water soluble group means a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group, mercapto group, amino group, ammonio group, sulfonamide group, acylsulfamoyl group, sulfonylsulfamoyl group, active methine group, or substituent containing any of these groups, preferably a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group or amino group.
  • R 12 and R 13 each preferably represents an alkyl group or aryl group.
  • R 12 and R 13 each represents an alkyl group
  • the alkyl group is preferably a substituted or unsubstituted C 1-4 alkyl group, and the substituents thereof include a water soluble group, especially preferably a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group or amino group.
  • R 12 and R 13 are each preferably an alkyl group or an aryl group and when R 12 and R 13 each represents an alkyl group, the alkyl group is preferably a substituted or unsubstituted C 1-4 alkyl group and the substituent thereof is preferably a water soluble group, especially preferably a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group or amino group.
  • R 12 and R 13 each represents an aryl group
  • the aryl group is preferably a substituted or unsubstituted C 6-10 phenyl group, and the substituent thereof is preferably a water soluble group, especially preferably a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group or amino group.
  • one of R 12 and R 13 represents an alkyl group and the other one represents an aryl group, they may be coupled to each other to form a cyclic structure. A saturated heterocycle may be formed by the cyclic structure.
  • Y 1 represents a water soluble group or a substituent substituted with a water soluble group and has the same meaning as X in formula (1-A-l).
  • a water-soluble group or the substituent substituted with a water-soluble group each represented by Y 1 in formula (l-A-2) an active methine group, or the following group substituted with a water soluble group such as amino group, alkoxyl group, aryloxy group, alkylthio group, arylthio group, alkyl group or aryl group is preferred.
  • Y 1 represents more preferably an active methine group, or an alkyl-, aryl- or heterocyclic amino group substituted with a water soluble group, in which the water-soluble group is especially preferably a hydroxyl group, a carboxyl group or salt thereof, or a sulfo group or salt thereof.
  • Especially preferred examples of Y 1 include alkyl-, aryl- and heterocyclic amino groups each substituted with a hydroxyl group, carboxyl group (or salt thereof) or sulfo group (or salt thereof), which is represented by an -N(R 01 )(R 02 ) group.
  • R 01 and R 02 each has the same meaning as R 12 and R 13 in formula (1-A), respectively and the preferred range of the substituent is also the same.
  • R 20 represents a hydrogen atom or an optional substituent.
  • the optional substituent include the same substituents as described in R 1 to R 4 in the formula (1-A).
  • R 20 is preferably a hydrogen atom or group selected from the following Co-i 5 substituents such as hydroxyl group, amino groups, alkyl groups, aryl groups, alkoxyl groups, aryloxy groups, acylamino groups, sulfonamide group, alkylthio groups, arylthio groups, alkylamino groups, arylamino groups, and hydroxylamino groups.
  • R is most preferably a hydrogen atom.
  • Y 2 represents a water soluble group or a substituent substituted with a water soluble group
  • R 30 represents a hydrogen atom or an optional substituent.
  • Y 2 and R 30 in formula (l-A-3) have the same meanings as Y 1 and R 20 in formula (l-A-2), respectively and the preferred ranges of the substituents are also the same.
  • R 5 to R 7 in formula (1-B) have the same meanings as R 1 to R 4 in formula (1-A), and the preferred ranges are also the same.
  • As the compound represented by formula (1-B) 5 that represented by the formula (1-B-l) is especially preferred.
  • R 50 has the same meaning as R 5 to R 7 in formula (1-B), more preferably a water soluble group or substituent substituted with a water soluble group each represented by X, Y 1 and Y 2 in formulas (1-A-l) to (l-A-3).
  • the compound represented by formula (1-B-l) is most preferably represented by formula (1-B-l-a).
  • R 51 and R 52 have the same meanings as R 12 and R 13 in the formula (1-A-l-a) and the preferred ranges of them are also the same.
  • the alkyl group represented by R 21 , R 22 , R 23 , R 24 or R 25 is preferably a C 1-3 alkyl group such as methyl, ethyl or propyl.
  • the alkyl group represented by R 26 or R 27 is preferably a C 1-5 alkyl group such as methyl, ethyl, propyl, butyl or pentyl, while the acyl group represented by R 26 or R 27 is preferably an acyl group having 18 or less carbon atoms such as acetyl or benzoyl.
  • the alkyl group represented by M 22 is preferably a C 1-4 alkyl group such as methyl, ethyl, propyl or butyl; the aryl group represented by M 22 is, for example, phenyl or naphthyl; and the aralkyl group represented by M 22 is preferably an aralkyl group having 15 or less carbon atoms such as benzyl or phenethyl.
  • the lower alkyl group represented by X 40 in the formula (5) is preferably a linear or branched C 1-5 alkyl group such as methyl, ethyl or isopropyl. Specific examples of the compounds represented by the formula (5) will next be shown but the compounds of the invention are not limited to them.
  • the above-described rust inhibitives may be used either singly or in combination.
  • the rust inhibitive to be used in the invention can be applied to a conductive metal portion after preparing an aqueous solution of it and dipping therein a transparent substrate having the conductive metal portion formed thereover.
  • the rust inhibiting treatment is applied preferably to the conductive metal portion after it is baked.
  • the aqueous solution of the rust inhibitive to be applied is prepared so that it contains the compound represented by any one of the formulas (1), (2), (3) and (5), for example, at a concentration of from 10 "6 to 10 '1 mole, preferably, from 10 "5 to 10 "2 mole in 1 liter of the aqueous solution.
  • the pH of the aqueous solution is adjusted preferably to from 2 to 12 in order to dissolve the rust inhibitive therein.
  • an alkali or acid such as sodium hydroxide or sulfuric acid, but also a phosphoric acid or salt thereof, carbonate, acetic acid or salt thereof, or boric acid or salt thereof is usable as a buffer.
  • a phosphoric acid or salt thereof carbonate, acetic acid or salt thereof, or boric acid or salt thereof is usable as a buffer.
  • the light transmitting electromagnetic wave shielding film of the invention has an adhesion facilitating layer between the printed pattern composed mainly of silver and the transparent substrate (support).
  • the adhesion facilitating layer can be preferably provided between the mesh-like thin lines and the transparent substrate (support).
  • the adhesion facilitating layer of the invention will next be described.
  • the adhesion facilitating layer may be a monolayer or multilayer.
  • adhesion facilitating layer composed of two layers as described below on the surface of the substrate having no printed pattern or mesh-like thin lines (conductive metal portion) formed thereover.
  • First layer an antistatic layer composed essentially of a water dispersible or water soluble synthetic resin, carbodiimide compound and conductive metal oxide particles
  • Second layer a surface layer (which will not be a surface layer when another constituent layer is stacked thereover, but it is the uppermost layer of the adhesion facilitating layer) composed essentially of a water dispersible or water soluble synthetic resin and a crosslinking agent.
  • the adhesion facilitating layer has the antistatic layer and surface layer stacked over the transparent substrate (support) in the order of mention.
  • the antistatic layer of the invention has been imparted with conductivity so that the haze of a low static support available by disposing an antistatic layer over the support is 3% or less and the surface electric resistance on the surface layer of the printed pattern thus available falls within a range of from 8 x 10 6 to 6 x 10 8 ⁇ .
  • the antistatic layer thus formed can prevent the generation of failures which will otherwise occur due to the dust attracted by static electricity generated during the preparation process handling the plastic support.
  • haze as used herein means a value as measured in accordance with JIS K-6714 under the measuring conditions at 25°C and 60%RH by using a hazemeter ("HGM- 2DP", trade name; product of Suga Test Instruments).
  • the antistatic layer contains conductive metal oxide particles and it usually contains a binder further.
  • the conductive metal oxide particles are preferably acicular particles having a ratio of a long axis to a short axis (long axis/short axis) ranging from 3 to 50, especially preferably from 10 to 50.
  • the short axis of such acicular particles preferably falls within a range of from 0.01 to 0.1 ⁇ m, especially preferably from 0.01 to 0.02 ⁇ m.
  • the long axis of them preferably falls within a range of from 0.1 to 5.0 ⁇ m, especially preferably from 0.1 to 2.0 ⁇ m.
  • Examples of the material of the conductive metal oxide particles include ZnO, TiO 2 , SnO 2 , Al 2 O 3 , In 2 O 3 , MgO, BaO, and MoO 3 , complex oxides thereof, and these metal oxides containing a hetero atom further.
  • Preferred metal oxides are SnO 2 , ZnO, Al 2 O 3 , TiO 2 , In 2 O 3 , and MgO, more preferably SnO 2 , ZnO, In 2 O 3 , and TiO 2 , with SnO 2 being most preferred.
  • the metal oxide containing a minor amount of a hetero atom examples include metal oxides doped with from 0.01 to 30 mole% (preferably from 0.1 to 10 mole%) of a hetero atom such as ZnO doped with Al or In, TiO 2 doped with Nb or Ta, In 2 O 3 doped with Sn, and SnO 2 doped with Sb, Nb or halogen atom.
  • a hetero atom such as ZnO doped with Al or In, TiO 2 doped with Nb or Ta, In 2 O 3 doped with Sn, and SnO 2 doped with Sb, Nb or halogen atom.
  • the amount of the hetero atom is less than 0.01 mole%, sufficient conductivity cannot be given to the oxide or complex oxide.
  • the amount exceeds 30 mole% on the other hand, the degree of blackening of particles increases and the antistatic layer darkens. Amounts outside the above-described range are therefore not suited.
  • metal oxides and complex metal oxides containing a minor amount of a hetero atom are preferred as the material of the conductive metal oxide particles in the invention. Moreover, those having an oxygen defect in their crystal structure are preferred.
  • Preferred as the conductive metal oxide particles containing a minor amount of a hetero atom are SnO 2 particles doped with antimony, especially SnO 2 particles doped with from 0.2 to 2.0 mole% of antimony. Use of metal oxide particles such as antimony-doped SnO 2 having the above-described short axis length and long axis length is therefore advantageous for forming a transparent antistatic layer having good conductivity.
  • acicular metal oxide particles such as antimony-doped SnO 2
  • the acicular metal oxide particles extend parallel to each other in the long-axis direction on the surface of the antistatic layer, but they extend only by a length corresponding to their diameter along the short axis in the thickness direction of the layer.
  • acicular metal oxide particles are easily brought into contact with each other and high conductivity can be attained even by the use of a small amount of the particles. Surface electric resistivity can therefore be reduced without damaging the transparency.
  • the acicular metal oxide particles have a short axis diameter at least equal to the thickness of the antistatic layer so they rarely protrude from the surface. Even if they protrude from the surface, the protruded portion is small enough to be covered with the surface layer disposed on the antistatic layer. During the transport of the transparent substrate, elimination of the protruded portion from the layer and dropping-off as a dust do not occur and such particles are therefore advantageous.
  • the antistatic layer in the invention usually contains a binder for dispersing and supporting the conductive metal oxide particles.
  • a binder for dispersing and supporting the conductive metal oxide particles.
  • Various polymers such as acrylic resin, vinyl resin, polyurethane resin and polyester resin are usable as the material of the binder.
  • a hardened material of a polymer (preferably, acrylic resin, vinyl resin, polyurethane resin or polyester resin) and a carbodiimide compound is preferred in order to prevent powder fall.
  • the polymer has any of methylol group, hydroxyl group, carboxyl group and glycidyl group so that it can be crosslinked with a carbodiimide compound.
  • hydroxyl group and carboxyl group are preferred, of which the carboxyl group is especially preferred.
  • An amount of the hydroxyl group or carboxyl group in the polymer is preferably from 0.0001 to 10 equivalent/kg, especially preferably, from 0.01 to 1 equivalent/kg.
  • acrylic resin examples include homopolymers of any of monomers selected from acrylic acid, acrylate such as alkyl acrylate, acrylamide, acrylonitrile, methacrylic acid, methacrylate such as alkyl methacrylate, methacrylamide and methacrylonitrile and copolymers available by the polymerization of two or more of these monomers.
  • homopolymers of any of monomers selected from acrylates such as alkyl acrylate and methacrylates such as alkyl methacrylate and copolymers available by the polymerization of two or more of these monomers are preferred.
  • acrylic resin is a polymer composed mainly of the above-described composition and available by partly using a monomer having any of a methylol group, hydroxyl group, carboxyl group and amino group to facilitate crosslinking reaction with a carbodiimide compound.
  • vinyl resin examples include polyvinyl alcohol, acid-modified polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl methyl ether, polyolefin, ethylene/butadiene copolymers, polyvinyl acetate, vinyl chloride/vinyl acetate copolymers, vinyl chloride/(meth)acrylate copolymers and ethylene/vinyl acetate copolymers (preferably ethylene/vinyl acetate/(meth)acrylate copolymers).
  • polyvinyl alcohol acid-modified polyvinyl alcohol, polyvinyl formal, polyolefin, ethylene/butadiene copolymers and ethylene/vinyl acetate copolymers (preferably ethylene/vinyl acetate/acrylate copolymers) are preferred.
  • the above-described vinyl resin is made into a crosslinkable polymer by leaving a vinyl alcohol unit in a polymer such as polyvinyl alcohol, acid modified polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl methyl ether or polyvinyl acetate, thereby obtaining the polymer having a hydroxyl group; or by using, as a part of the starting materials, a monomer having any of a methylol group, hydroxyl group, carboxyl group or amino group for the other polymers.
  • a polymer such as polyvinyl alcohol, acid modified polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl methyl ether or polyvinyl acetate
  • polyurethane resin examples include polyurethanes derived from polyisocyanate and any one or a mixture of polyhydroxy compounds (such as ethylene glycol, propylene glycol, glycerin and trimethylolpropane), aliphatic polyester type polyols obtained by the reaction between a polyhydroxy compound and a polybasic acid, polyether polyols (such as poly(oxypropylene ether)polyol and poly(oxyethylene-propylene ether)polyol), polycarbonate polyols and polyethylene terephthalate polyol.
  • polyhydroxy compounds such as ethylene glycol, propylene glycol, glycerin and trimethylolpropane
  • aliphatic polyester type polyols obtained by the reaction between a polyhydroxy compound and a polybasic acid
  • polyether polyols such as poly(oxypropylene ether)polyol and poly(oxyethylene-propylene ether)polyol
  • polycarbonate polyols and
  • a hydroxyl group which has remained unreacted after the reaction between a polyol and a polyisocyanate may be utilized as a functional group capable of crosslinking with a carbodiimide compound.
  • polyester resin Polymers obtained by the reaction between a polyhydroxy compound (such as ethylene glycol, propylene glycol, glycerin and trimethylolpropane) and a polybasic acid are usually used as the polyester resin.
  • a polyhydroxy compound such as ethylene glycol, propylene glycol, glycerin and trimethylolpropane
  • a polybasic acid for example, a hydroxyl group and carboxyl group which have remained after the reaction between a polyol and a polybasic acid may be utilized as a functional group capable of crosslinking with a carbodiimide compound. It is needless to say that a third component having a functional group such as hydroxyl group may be added.
  • acrylic resins and polyurethane resins are preferred, with acrylic resins being especially preferred.
  • carbodiimide compound to be used in the invention use of a compound having, in the molecule thereof, a plurality of carbodiimide structures is preferred.
  • Polycarbodiimide is usually synthesized by the condensation reaction of an organic diisocyanate.
  • an organic group of the organic diisocyanate is used for the synthesis of the compound having, in the structure thereof, a plurality of carbodiimide structures.
  • Either one of an aromatic or aliphatic group or a mixture thereof is usable. From the standpoint of the reactivity, an aliphatic group is especially preferred.
  • organic isocyanates organic diisocyanates and organic triisocyanates are used.
  • organic isocyanates aromatic isocyanates and aliphatic isocyanates, and mixtures thereof are usable.
  • Examples of the organic monoisocyanates include isophorone isocyanate, phenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate and naphthyl isocyanate.
  • the carbodiimide compound usable in the invention is commercially available as, for example, "Carbodilite V-02-L2" (trade name; product of Nisshinbo).
  • the carbodiimide compound in the invention is added preferably in an amount of from 1 to 200 mass%, more preferably from 5 to 100 mass% relative to the binder.
  • a coating solution for forming the antistatic layer is prepared by adding the conductive metal oxide particles as are or as a dispersion having them dispersed in a solvent such as water (containing a dispersant and/or a binder as needed) to a water dispersion or an aqueous solution containing the above- described binder (such as polymer, carbodiimide compound and proper additive) and mixing them (and dispersing as needed).
  • a solvent such as water (containing a dispersant and/or a binder as needed)
  • a water dispersion or an aqueous solution containing the above- described binder (such as polymer, carbodiimide compound and proper additive) and mixing them (and dispersing as needed).
  • the coating solution for forming the antistatic layer can be applied onto the surface (having no printed pattern formed thereon) of a plastic film such as a polyester film by a well known coating method such as dip coating, air knife coating, curtain coating, wire bar coating, gravure coating, or extrusion coating
  • the plastic film such as polyester film to be applied may be a film before sequential biaxial orientation, before simultaneous biaxial orientation, after monoaxial orientation but before re-orientation, or after biaxial orientation.
  • the surface of the plastic support onto which the coating solution for forming the antistatic layer is applied is preferably subjected in advance to surface treatment such as ultraviolet treatment, corona treatment or glow discharge treatment.
  • the thickness of the antistatic layer in the invention is preferably within a range of from 0.01 ⁇ m to 1 ⁇ m, more preferably from 0.01 ⁇ m to 0.2 ⁇ m. Adjustment of the film thickness to 0.01 ⁇ m or greater facilitates uniform application of a coating agent, whereby the antistatic layer can be obtained without uneven coating. When the thickness is 1 ⁇ m or greater, the resulting antistatic layer is excellent in antistatic performance and scratch resistance.
  • An amount of the conductive metal oxide particles in the antistatic layer preferably ranges from 10 to 1000 mass%, more preferably from 100 to 500 mass% relative to the binder (for example, total of the polymer and carbodiimide compound). Addition of them in an amount of 10 mass% or greater enables the antistatic layer to have sufficient antistatic properties. Addition of them in an amount not greater than 1000 mass% can suppress the haze level of the antistatic layer.
  • additives such as matting agent, surfactant and lubricant may be added in combination as needed.
  • matting agent examples include particles of an oxide such as silicon oxide, aluminum oxide or magnesium oxide having a particle size of from 0.001 to 10 ⁇ m, and particles of a polymer or copolymer such as polymethyl methacrylate or polystyrene.
  • surfactant examples include known anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants.
  • lubricant examples include natural waxes such as carnauba wax; phosphate esters of a higher C 8-22 alcohol or amino salts thereof; palmitic acid, stearic acid, and behenic acid and esters thereof; and silicone compounds.
  • a surface layer is laid over the antistatic layer in the invention.
  • the surface layer mainly serves to give an adhesion property to an adhesive layer and to assist the function of preventing elimination of the conductive metal oxide particles from the antistatic layer.
  • various polymers such as acrylic resins, vinyl resins, polyurethane resins and polyester resins can usually be employed and the polymers as described above as the binder in the antistatic layer are preferred.
  • epoxy compounds are preferred because they do not adversely affect the printed pattern to be brought into contact with the surface layer at the roll take-up time during the preparation process.
  • Preferred examples of the epoxy compound include l,4-bis(2',3'- epoxypropyloxy)butane, 1,3,5-triglycidyl isocyanurate, l,3-diglycidyl-5-( ⁇ -acetoxy- ⁇ - oxypropyl) isocyanurate, sorbitol polyglycidyl ethers, polyglycerol polyglycidyl ethers, pentaerythritol polyglycidyl ethers, diglycerol polyglycidyl ether, l,3,5-triglycidyl(2- hydroxyethyl) isocyanurate, glycerol polyglycerol ethers and trimethylolpropane polyglycidyl ethers.
  • They are commercially available, for example, as "Denacol EX-521" or "Denacol Ex-614B" (each, trade name; product of Nagase Chemtex) but the epoxy resin
  • epoxy compounds can be used in combination with other compounds such as curing agents as described in The Theory of the Photographic Process, Third edition, by C.E.K. Meers and T.H. James, (1966); U.S. Pat. Nos. 3316095, 3232764, 3288775, 2732303, 3635718, 3232763, 2732316, 2586168, 3103437, 3017280, 2983611, 2725294, 2725295, 3100704, 3091537, 3321313, 3543292 and 3125449; and U.K. Patent Application Nos. 994869 and 1167207.
  • Typical examples include aldehyde compounds and derivatives thereof such as melamine compounds having at least two (preferably at least three) methylol and/or alkoxymethyl groups and melamine resins which are polycondensates thereof or rnelamine-urea resins, mucochloric acid, mucobromic acid, mucophenoxychloric acid, mucophenoxybromic acid, formaldehyde, glyoxal, monomethylglyoxal, 2,3-dihydroxy-l,4- dioxane, 2,3-dihydroxy-5-methyl-l,4-dioxane succinaldehyde, 2,5- dimethoxytetrahydrofuran, and glutaraldehyde; active vinyl compounds such as divinylsulfone-N,N' -ethylenebis(vinylsulfonylacetamide), 1 ,3 -bis(vinylsulfonyl)-2- propanol, methylenebismaleimide
  • the surface layer may be formed, for example, by adding the polymer, epoxy compound and necessary additives to a solvent (containing a dispersant and a binder if necessary) such as water, mixing them (and dispersing if necessary) to prepare a coating solution for forming the surface layer.
  • a solvent containing a dispersant and a binder if necessary
  • water containing a dispersant and a binder if necessary
  • the coating solution for forming the surface layer is then applied onto the antistatic layer of the invention by a well known application method such as dip coating, air knife coating, curtain coating, wire bar coating, gravure coating, or extrusion coating, whereby the surface layer can be formed.
  • the surface layer has a thickness of preferably from 0.01 to 1 ⁇ m, more preferably from 0.01 to 0.2 ⁇ m.
  • the light transmitting electromagnetic wave shielding film of the invention is preferably bonded via an adhesive layer when incorporated in an optical filter, liquid crystal display plate, plasma display panel or other image display panel.
  • an adhesive having a refractive index of from 1.40 to 1.70 is preferred in the invention.
  • a reduction in the visible light transmittance can be prevented by decreasing a difference in the refractive index between the adhesive and the transparent substrate to be used in the invention.
  • the adhesive layer having a refractive index of from 1.40 to 1.70 can suppress a reduction in the visible light transmittance so that it is preferred in the invention.
  • the adhesive usable in the invention preferably flows under heat or pressure. That demonstrating fluidity by heating at 200°C or less or applying a pressure of 1 kgf/cm 2 (98 kPa) or greater is especially preferred.
  • This fluidity facilitates adhesion of the electromagnetic wave shielding adhesive film to an object even having a curved surface or complex shape by lamination or press molding, especially press molding.
  • the softening temperature of the adhesive is preferably 200°C or less. Since as an electromagnetic wave shielding adhesive film, it is usually employed at a temperature less than 80°C, it has preferably a softening temperature of 8O 0 C or greater. From the standpoint of processability, a softening temperature of from 80 to 120 0 C is most preferred.
  • the term "softening temperature” as used herein means a temperature at which the viscosity of the material is decreased to below 10 12 poise (10 13 Pa-s). Fluidity can usually be observed in one to ten seconds at the softening temperature.
  • urethane acrylate, epoxy acrylate and polyether acrylate are excellent in adhesion.
  • epoxy acrylate examples include (metha)acrylic acid adducts of 1,6-hexandiol diglycidyl ether, neopenthylglycol diglycidyl ether, allyl alcohol diglycidyl ether, resorcinol diglycidyl ether, diglycidyl adipate, diglycidyl phthalate, polyethylene glycol diglycidyl ester, trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether, and sorbitol-tetraglycidyl ether.
  • metalha acrylic acid adducts of 1,6-hexandiol diglycidyl ether, neopenthylglycol diglycidyl ether, allyl alcohol diglycidyl ether, resorcinol diglycidyl ether,
  • the softening temperature of the polymer serving as the adhesive is preferably 200°C or less, more preferably 150°C or less in view of the handling property. Since as an electromagnetic wave shielding adhesive film, it is usually used at a temperature of 80 0 C or less, it has preferably a softening temperature of from 8O 0 C to 12O 0 C from the standpoint of processability.
  • the polymer having a weight average molecular weight (as measured by gel permeation chromatography using the calibration curve of standard polystyrene, which will equally hereinafter) of 1000 or greater is preferred.
  • the molecular weight of 1000 or greater heightens the coagulation force of the adhesive composition, thereby improving the adhesion to the object.
  • the adhesive to be used in the invention may contain an additive such as diluent, plasticizer, antioxidant, filler, colorant, ultraviolet absorber and/or tackif ⁇ er as needed.
  • the thickness of the adhesive layer is preferably from 5 to 50 ⁇ m, especially preferably at least the thickness of the conductive layer and within a range of from 20 to 50 ⁇ m.
  • the adhesive covering the geometric configuration preferably has a difference of 0.14 or less in a refractive index from the transparent substrate.
  • a difference in the refractive index between the adhesive layer and the adhesive for covering the geometric configuration is preferably 0.14 or less.
  • Difference in the refractive index between the transparent substrate and the adhesive or between the adhesive and the adhesive layer may lead to a reduction in a visible light transmittance.
  • a reduction of the visible light transmittance is preferably small.
  • Acrylic resins are well known as a material resistant to time-dependent discoloration and are therefore preferred in the invention.
  • the adhesive can have a desired viscoelasticity by mixing a plurality of acrylic polymers different in molecular weight.
  • epoxy acrylates, urethane acrylates, polyether acrylates, polyester acrylates and the like are usable. Of these, epoxy acrylates and polyether acrylates are excellent in adhesion.
  • epoxy acrylates examples include (meth)acrylic acid adducts of 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, allyl alcohol dilgycidyl ether, resocinol diglycidyl ether, diglycidyl adipate, diglycidyl phthalate, polyethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether, and sorbitol tetraglycidyl ether.
  • Epoxy acrylates have in the molecule thereof a hydroxyl group so that they are effective for improving the adhesion. Two or more of these copolymer resins may be used in combination if necessary.
  • the polymer to be employed as a main component of the adhesive has a weight average molecular weight of 1,000 or greater. The polymer having a molecular weight of 1,000 or greater improves adhesion to the object owing to the high coagulation force of the composition.
  • amines such as triethylenetetramine, xylenediamine, diaminodiphenylmethane
  • acid anhydrides such as phthalic anhydride, maleic anhydride, dodecylsuccinic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic anhydride, dia
  • the amount of the crosslinking agent is selected from a range of from 0.1 to 50 parts by mass, preferably from 1 to 30 parts by mass based on 100 parts by mass of the polymer. Amounts of 0.1 part by mass or greater provide sufficient curing, while amounts not greater than 50 parts by mass improve adhesion without causing excessive crosslinking.
  • the resin composition of the adhesive used in the invention may contain additives such as diluent, plasticizer, antioxidant, filler and tackif ⁇ er as needed.
  • the resin composition of the adhesive is applied to the surface of the transparent substrate in order to cover therewith a portion or entire surface of the base material of the constituent material having thereon a geometric configuration drawn with the conductive material and an adhesive film of the invention can be obtained by drying of the solvent and curing under heat.
  • the resulting adhesive film having an electromagnetic wave shielding property and transparency is, with the adhesive thereof, directly attached to a display such as CRT, PDP, liquid crystal or EL or attached to a plate or sheet such as acryl plate or glass plate for the use as a display.
  • This adhesive film is used similarly for an observation window or chassis of a measuring instrument, measuring apparatus or manufacturing apparatus emitting electromagnetic waves. Moreover, it is attached to the windows of a building or automobile which may be exposed to interference with electromagnetic waves emitted from a power pylon or high-tension wire.
  • the geometric configuration drawn with a conductive material is preferably equipped with a ground wire.
  • the transparent substrate has an uneven surface and has a haze for scattering light
  • application of a resin having a refractive index close to that of the transparent plastic substrate or adhesion of a resin sheet to the uneven surface to planarize the surface makes it possible to minimize irregular reflection and contributes to appearance of transparency.
  • the geometric configuration drawn with the conductive material of the invention cannot be macroscopically viewed because of a very small line width. Owing to a sufficient large pitch in addition to the small line width, apparent transparency is presumed to be accomplished.
  • the pitch of the geographic configuration is however small enough compared with the wavelength of the electromagnetic waves to be shielded so that the shielding film of the invention is presumed to exhibit an excellent shielding property.
  • the printed pattern composed mainly of silver can be stacked over the transparent substrate without inserting an adhesive layer therebetween when a film of an ethylene- vinyl acetate copolymer resin having high thermal adhesiveness or a film of a thermal adhesive resin such as ionomer resin is used either singly or as a film stack with another resin film, but stacking is usually performed by dry lamination using an adhesive layer.
  • the adhesive constituting the adhesive layer include acrylic resins, polyester resins, polyurethane resins, polyvinyl alcohol resins, vinyl chloride/vinyl acetate copolymer resins and ethylene/vinyl acetate copolymer resins.
  • Thermosetting resins and ionizing radiation curable resins are also usable.
  • the surface of the display is generally made of glass so that the transparent substrate and glass plate of the light transmitting electromagnetic wave shielding film are bonded with an adhesive.
  • Generation of air bubbles or peeling between the adhered surfaces cause problems such as distortion of an image or difference in color from that indicated on a display without air bubbles or peeling.
  • Air bubbles and peeling each occurs owing to the peeling of the adhesive from the plastic film or glass plate. There is a possibility of these phenomena occurring on both the transparent substrate side and glass plate side. They occur on the side with a weaker adhesive force. An adhesive force of the adhesive with each of the transparent substrate and glass plate must be high.
  • the adhesive force between the adhesive layer and each of the transparent substrate and glass plate is preferably 10 g/cm or greater, more preferably 30 g/cm or greater at 8O 0 C.
  • An adhesive having an adhesive force exceeding 2000 g/cm is sometimes undesired because of difficulty in bonding work with it. It can however be used if it does not cause such a problem.
  • a slip sheet (separator) can be laid on the adhesive at a portion not facing with the transparent substrate in order to avoid a contact with an undesired portion.
  • the adhesive is preferably transparent. More specifically, the adhesive has a light transmittance of preferably 70% or greater, more preferably 80% or greater, most preferably from 85 to 92%.
  • the adhesive having a low haze is preferred.
  • the haze is preferably from 0 to 3%, more preferably from 0 to 1.5%.
  • the adhesive to be used in the invention is preferably colorless in order not to change the color indicated on a display. If the adhesive is made of a colored resin but is thin, it can be regarded as colorless. In addition, the adhesive is not required to be colorless when a display is colored intentionally as described later.
  • the adhesive having the above-described properties examples include acrylic resins, ⁇ -olefin resins, vinyl acetate resins, acrylic copolymer resins, urethane resins, epoxy resins, vinylidene chloride resins, vinyl chloride resins, ethylene-vinyl acetate resins, polyamide resins and polyester resins. Of these, acrylic resins are preferred.
  • the adhesion of the adhesive can be improved by decreasing the amount of a crosslinking agent to be added, adding a tackifier or changing the terminal group of its molecule upon synthesis of the adhesive by the polymerization process.
  • the adhesion can also be improved by modifying the surface of the transparent substrate or glass plate. Examples of the surface modification method include physical methods such as corona discharge treatment and plasma glow treatment, and formation of an undercoat layer for improving the adhesion.
  • the thickness of the adhesive layer is preferably from about 5 to 50 ⁇ m from the standpoints of transparency, colorlessness and handling property.
  • the adhesive layer is made of an adhesive, it is preferably as thin as possible within the above-described range, specifically from about 1 to 20 ⁇ m. The thickness may exceed the above-described range when the adhesive layer does not change the color indicated on a display itself and its transparency falls within the above-described range. (Peel strength)
  • the adhesive strength of the light transmitting electromagnetic wave shielding film of the invention which has an adhesive layer formed over the adhesion facilitating layer, with a glass substrate is preferably as follows.
  • a sample film attached to glass has preferably a peel strength of 20 N/m or greater when 180°C peel strength is measured at 100 mm/niin.
  • the above-described peel strength of the film when it is left at 60°C and relative humidity of 90% for 72 hours is preferably 20 N/m or greater and the above-described peel strength of the film when it is left at 60°C and relative humidity of 90% for 250 hours is preferably 20 N/m or greater.
  • the conductive metal portion for use in the light transmitting electromagnetic wave shielding material has preferably a line width of 1 ⁇ m or greater but not greater than 40 ⁇ m, more preferably 1 ⁇ m or greater but not greater than 30 ⁇ m, further more preferably 5 ⁇ m or greater but not greater than 30 ⁇ m, most preferably from 10 ⁇ m or greater but not greater than 25 ⁇ m.
  • the distance between lines is preferably 50 ⁇ m or greater but not greater than 500 ⁇ m, more preferably 200 ⁇ m or greater but not greater than 400 ⁇ m, most preferably 250 ⁇ m or greater but not greater than 350 ⁇ m.
  • the conductive metal portion for use in ground connection may have a portion having a line width greater than 20 ⁇ m.
  • the conductive metal portion in the invention has preferably an aperture ratio of preferably 85% or greater, more preferably 90% or greater, most preferably 95% or greater in consideration of the visible light transmittance.
  • aperture ratio means a ratio of portions not having thin lines constituting a mesh in the total area, and for example, the aperture ratio of a mesh in the square lattice form having a line width of 15 ⁇ m and pitch of 300 ⁇ m has an aperture ratio of 90%.
  • the term "light transmitting portion” as used herein means a transparent portion of the light transmitting electromagnetic wave shielding film other than the conductive metal portion.
  • the transmittance of the light transmitting portion is, as described above, is 90% or greater, preferably 95% or greater, more preferably 97% or greater, still more preferably 98% or greater, most preferably 99% or greater in terms of the minimum transmittance in a wavelength region of from 380 to 780 nm except the contribution of the light absorption and reflection of the support.
  • the mesh pattern in the invention is preferably continuous for 3 m or greater in the lengthwise direction of the light transmitting electromagnetic wave shielding film.
  • the greater the number of continuous mesh patterns the more preferred because a loss of the optical filter material during the production can be reduced.
  • the continuous length is therefore preferably 2000 m or less. It is preferably 100 m or greater but not greater than 1000 m, more preferably 200 m or greater but not greater than 800 m, most preferably 300 m or greater but not greater than 500 m.
  • the thickness of the support is preferably 200 ⁇ m or less, more preferably 20 ⁇ m or greater but not greater than 180 ⁇ m, most preferably 50 ⁇ m or greater but not greater than 120 ⁇ m.
  • pattern obtained by the intersection of thin linear lines substantially parallel to each other means a so-called lattice pattern in which two adjacent linear lines constituting the lattice are parallel to each other or within parallel ⁇ 2°.
  • the mesh pattern is preferably inclined at from 30° to 60°, more preferably from 40° to 50°, most preferably from 43° to 47° relative to the traveling direction. It is usually difficult to prepare a mask for the mesh pattern inclined at from 40° to 50° relative to the frame and tends to cause problems such as easy appearance of unevenness and high cost. In this method, unevenness at about 45° can be prevented so that the invention has a marked advantage over the patterning by screen printing. [Peelable protective film]
  • the light transmitting electromagnetic wave shielding film of the invention may have a peelable protective film.
  • the electromagnetic wave shielding sheet does not always have a protective film on both sides thereof.
  • the sheet may have a protective film only on a mesh- like metal foil of a film stack but not necessarily on the side of the transparent substrate film.
  • the sheet may have a protective film only on the side of the transparent substrate film of the film stack but not necessarily on the metal foil.
  • a film stack obtained by stacking a metal foil over a transparent substrate film via an adhesive layer is prepared.
  • a film made of an acrylic resin, polycarbonate resin, polypropylene resin, polyethylene resin, polystyrene resin, polyester resin, cellulose resin, polysulfone resin or polyvinyl chloride resin is usable.
  • a film made of a polyester resin such as polyethylene terephthalate resin having excellent mechanical strength and high transparency is usually preferred.
  • the thickness of the transparent substrate film it is preferably from about 50 ⁇ m to 200 ⁇ m in order to improve the resistance to bending without losing the mechanical strength.
  • the thickness can be increased further, but when the electromagnetic wave shielding sheet 1 is stacked over another transparent substrate, the thickness is not limited to the above-described range.
  • the transparent substrate film may be subjected to corona discharge treatment either on one side or both sides thereof, or an adhesion facilitating layer may be laid over the film.
  • the electromagnetic wave shielding sheet is used after stacking a sheet having an effect of reinforcing the upper most surface, giving an antireflective property, giving an antifouling property or the like over both sides of the substrate having the film stack thereover via an infrared cut filter layer so that the above-described protective film must be peeled off when such further stacking is performed. It is therefore preferred to stack the protective film releasably on the metal foil side.
  • the protective film has preferably a peel strength of from 5 mN/25 mm width to 5 N/25 mm width, more preferably from 10 mN/25 mm width to 100 mN/25 mm width when stacked over the metal foil.
  • the peel strength below the lower limit is not preferred because peeling occurs easily and there is a danger of the protective film being peeled during handling or by the careless contact.
  • the peel strength exceeding the upper limit is also not preferred because too large force is necessary for peeling and in addition, there is a danger of the mesh-like metal foil being peeled from the transparent substrate film (or from the adhesive layer) during peeling.
  • the protective film stacked over the lower surface side of the film stack (which may have a blackening layer) obtained by stacking a mesh-like metal foil on a transparent substrate film via an adhesive layer, that is, the protective film stacked on the side of the transparent substrate film is formed for protecting the lower surface of the transparent substrate film from damage during handling or by the careless contact.
  • this protective film must also be peeled off when another film is stacked over the film stack so that it is desired to stack, over the transparent substrate film, the protective film releasably therefrom.
  • the peel strength is, similar to the above-described protective film, preferably from 5 mN/25 mm width to 5 N/25 mm width, more preferably from 10 mN/25 mm width to 100 mN/25 mm width. Below the lower limit, peeling occurs easily and there is a danger of the protective film being peeled off during handling or by careless contact. The peel strength exceeding the upper limit requires a large force for peeling. Peel strength outside the above-described range is therefore not preferred.
  • the protective film stacked on the side of the transparent substrate film is preferably resistant to etching conditions, for example, dipping for several minutes in an etchant of about 5 0 C, particularly resistant to the alkali component thereof.
  • etching conditions for example, dipping for several minutes in an etchant of about 5 0 C, particularly resistant to the alkali component thereof.
  • dry etching is performed, on the other hand, it is preferably resistant to temperature conditions of about 100 0 C.
  • the photosensitive resin preferably has an adhesive force to prevent its peeling during etching and drifting in the etchant owing to the coating solution attached even to the reverse side of the film stack.
  • the protective film preferably has durability against pollution by an etchant containing iron chloride or copper chloride or resistant to etching or pollution by a resist removal solution such as alkali solution.
  • a resin film made of a polyolefin resin such as polyethylene resin and polypropylene resin, polyester resin such as polyethylene terephthalate resin, polycarbonate resin, or acrylic resin is preferred.
  • the surface on the side of the protective film which will be the uppermost surface when the film is adhered to the film stack is preferably subjected to corona discharge treatment or an adhesion facilitating layer is stacked over the surface in advance.
  • an acrylate, rubber or silicone adhesive is usable as an adhesive constituting the protective film.
  • the above-described materials of the film and above-described materials of the adhesive for the protective film can also be used for the protective film formed on the metal foil side.
  • protective films stacked over the side of the transparent substrate film and on the side of the metal foil protective films different in material may be used, but the same protective film can be used. [Blackening treatment]
  • the light transmitting electromagnetic wave shielding film of the invention or an optical film having the film incorporated therein may have been subjected to blackening treatment.
  • Blackening treatment is disclosed in JP-A-2003-188576.
  • the blackening layer formed by the blackening treatment can give an antireflective effect in addition to a rust inhibitive effect.
  • the blackening layer is formed, for example, by Co-Cu alloy plating.
  • the blackening layer formed on the conductive mesh patterns can prevent the reflection of their surface.
  • the conductive mesh patterns having the blackening layer formed thereon may be subjected to chromate treatment for rust inhibition.
  • the chromate treatment comprises dipping in a solution composed mainly of chromic acid or dichromate and then drying to form a rust inhibitive film. Chromate treatment may be performed on either one or both surfaces of the conductive mesh patterns. Alternatively, a commercially available copper foil subjected to chromate treatment may be utilized.
  • the constitution containing a blackening layer as described in JP-A-11-266095 may be employed. Described specifically, a first blackening layer is laid over a conductive metal portion. After the above-described electrolytic plating on the first blackening layer, a second blackening layer is formed over the resulting plated layer. At least the first blackening layer must be conductive when electrolytic plating is given onto the first blackening layer.
  • the conductive blackening layer can be formed using a conductive compound of, for example, nickel (Ni), zinc (Zn) or Cu (copper), or can be formed using an electrodeposition ionic polymer material, for example, an electrodeposition coating material.
  • the blackening layer is laid in a known manner (refer to, for example, FIG. 5 of JP- A- 11 -266095), for example, by dipping a transparent support having a conductive metal portion formed thereon in an electrolyte solution containing a blackening material, followed by electrochemical plating.
  • a black plating bath having a sulfate nickel salt as a main component can be used as the bath (black plating bath) of an electrolyte solution containing the above-described blackening material.
  • a commercially available black plating bath can also be used.
  • the usable black plating bath examples include black plating bath ("Nobloy SNC", trade name; Sn-Ni alloy, product of Shimizu), black plating bath “Nikka Black”, trade name; Sn-Ni alloy, product of Nihon Kagaku Sangyo), and black plating bath ("Eboni chromium 85 Series", trade name; Cr type, product of Kinzoku Kako Gijutsu).
  • black plating bath various ones containing Zn, Cu or the like are usable in the invention.
  • the Cu surface is blackened as copper sulfide (CuS) by treatment with hydrogen sulfide (H 2 S), whereby the second blackening layer is formed.
  • the blackening agent for the second blackening layer in the invention can easily be prepared using a sulfide compound.
  • Many blackening agents are commercially available.
  • “Copper black CuO”, “Copper black CuS”, and selenium series “Copper black No. 65" (each, trade name; product of Isolate Chemical) and "Ebonol C Special” (trade name; product of Meltex) are usable.
  • the etching resist pattern may be removed from the electromagnetic wave shielding plate of the invention, or it may be left without removal.
  • the removal of the etching resist pattern may be followed by the blackening treatment of the surface of the remaining metal conductive layer.
  • plating method of black copper (Cu) or black nickel (Ni) or known blackening method such as chemical blackening can be employed.
  • functional layers each having a function may be additionally provided as required.
  • These functional layers can be prepared in accordance with the respective specifications, depending on their using purpose.
  • an antireflective layer imparted with an antireflective function and having an adjusted refraction index and film thickness, a non-glare and anti-glare layer (both have a glare preventing function), a near infrared ray absorbing layer comprising a compound or metal which absorbs near infrared rays, a layer having a color tone adjusting function which absorbs a visible light in a specific wavelength region, an antifouling layer having a function of facilitating removal of stains such as finger prints, a hard coat layer resistant to damage, a layer having an impact absorbing function, a scattering preventing function of broken glass pieces and the like can be provided.
  • These functional layers may be disposed on both sides having the printed pattern and support therebetween, or may be disposed on the same side.
  • These functional films may be directly adhered to PDP, or may be adhered not to a plasma display panel itself but to a transparent substrate such as glass plate or acrylic resin plate. These functional films are referred to as optical filters (or simply "filters"). ⁇ Functional Film>
  • the light transmitting electromagnetic wave shielding film When the light transmitting electromagnetic wave shielding film is incorporated in a display (particularly, a plasma display), functional films having the below-described functions are preferably adhered to the light transmitting electromagnetic wave shielding film to impart it with these functions. Each functional film can be adhered directly or indirectly to the light transmitting electromagnetic wave shielding film via an adhesive or the like. (Antireflective properties -antiglare properties)
  • antireflective (AR) properties for preventing reflection of an external light antiglare (AG) properties for preventing reflection of a mirror image
  • antireflective-antiglare (ARAG) properties having these two properties are preferably imparted to the light transmitting electromagnetic wave shielding film.
  • the visible light reflectance when a functional film having antireflective-antiglare properties is adhered to the light transmitting electromagnetic wave shielding film is preferably 2% or less, more preferably 1.3% or less, still more preferably 0.8% or less.
  • Such a functional film can be formed by laying a functional layer having antireflective and antiglare properties on a proper transparent substrate.
  • the antireflective layer can be formed, for example, by stacking, over the transparent substrate, a single layer of a thin film made of a transparent fluorine polymer resin, magnesium fluoride, silicone resin or silicon oxide while adjusting its optical film thickness to a 1/4 wavelength or a multilayer of at least two thin films different in refractive index and made of an inorganic compound such as metal oxide, fluoride, suicide, nitride or sulfide or an organic compound such as silicone resin, acrylic resin or fluorine resin.
  • the antiglare layer can be made of a layer having a surface with minute irregularities of from about 0.1 ⁇ m to 10 ⁇ m. More specifically, it can be formed by dispersing particles of an inorganic compound or organic compound such as silica, organic silicon compound, melamine, acryl or the like in a thermosetting or photocurable resin such as acrylic resin, silicon resin, melamine resin, urethane resin, alkyd resin or fluorine resin to form an ink, applying the ink to the substrate and then curing.
  • the particles have an average particle size of preferably from about 1 to 40 ⁇ m.
  • the antiglare layer can also be formed by applying the above-described thermosetting or photocurable resin, pressing a mold having a desired gloss or desired surface condition against the resin and then curing.
  • the light transmitting electromagnetic wave shielding film having an antiglare layer formed thereon has a haze of preferably from 0.5% or greater but not greater than 20%, more preferably 1% or greater but not greater than 10%. Sufficient antiglare property cannot be obtained when the haze is too small, while too large haze tends to deteriorate the vividness of the transmitted image. (Hard coat property)
  • the functional film has preferably a hard coat property in order to provide the light transmitting electromagnetic wave shielding film with scratch resistance.
  • the material of the hard coat layer include thermosetting resins and photocurable resins such as acrylic resins, silicon resins, melamine resins, urethane resins, alkyd resins and fluorine resins. No particular limitation is imposed on the kind and formation method of them.
  • the hard coat layer has a thickness of preferably from 1 to 50 ⁇ m. It is preferred to form the above-described antireflective layer and/or antiglare layer on the hard coat layer because functional films having scratch resistance, and antireflective properties and/or antiglare properties are available.
  • the light transmitting electromagnetic wave shielding film provided with the hard coat property has preferably a surface hardness of at least H in terms of pencil hardness in accordance with JIS (K-5400), more preferably 2H, still more preferably 3H. (Antistatic property)
  • the light transmitting electromagnetic wave shielding film is preferably provided with an antistatic property in order to prevent attachment of dusts due to static electricity or electrostatic charging due to the contact with human bodies.
  • a film having a high conductivity is usable as a functional film having an antistatic property.
  • the conductivity is, in terms of surface resistivity, preferably about 10 11 ⁇ /D.
  • the highly conductive film can be formed by laying an antistatic layer on the transparent substrate.
  • the antistatic agent to be added to the antistatic layer include "Pellestat" (trade name; product of Sanyo Kasei) and "Electro slipper” (trade name; product of Kao).
  • the antistatic layer may be formed using known transparent conductive films including ITO or a conductive film having, dispersed therein, conductive ultrafme particles such as ITO ultrafme particles or tin oxide ultraf ⁇ ne particles.
  • the antistatic property may be given to the shielding film by incorporating conductive fine particles in the hard coat layer, antireflective layer, antiglare layer or the like. (Antifouling property)
  • the light transmitting electromagnetic wave shielding film having an antifouling property is desired because it can prevent contaminations such as fingerprints or facilitates removal of stains.
  • a functional film having an antifouling property is available, for example, by adding a compound having an antifouling property onto the transparent substrate.
  • the compound having an antifouling property insofar as it has non- wettability with water and/or oil or fat and examples of it include fluorine compounds and silicon compounds.
  • Specific examples of the fluorine compounds include "OPTOOL” (trade name; product of Daikin Industries) and "Takata Quantum” (trade mark, product of NOF). (Ultraviolet shielding property)
  • the light transmitting electromagnetic wave shielding film is preferably provided with an ultraviolet shielding property in order to prevent deterioration of the transparent substrate or colorant which will be described later.
  • the functional film having an ultraviolet shielding property can be formed by incorporating an ultraviolet absorber in the transparent substrate itself or providing an ultraviolet absorption layer on the transparent substrate.
  • the transmittance in a ultraviolet region having a wavelength shorter than 380 nm is 20% or less, preferably 10% or less, more preferably 5% or less.
  • the functional film having an ultraviolet shielding property is available by forming, over the transparent substrate, a layer containing an ultraviolet absorber or an inorganic compound capable of reflecting or absorbing ultraviolet rays.
  • the ultraviolet absorber conventionally known ultraviolet absorbers such as benzotriazole and benzophenone are usable. No particular limitation is imposed on its kind and concentration because they are determined, depending on the dispersibility or solubility in a medium in which the compound is to be dispersed or dissolved, absorption wavelength-absorption coefficient, thickness of the medium, or the like.
  • the functional film having an ultraviolet shielding property preferably exhibits smaller absorption in a visible light region and causes neither a marked reduction in visible light transmittance nor color development such as yellowing.
  • a layer having an ultraviolet shielding property is preferably located outside the colorant-containing layer.
  • the light transmitting electromagnetic wave shielding film preferably has a gas barrier property, because when it is used under a temperature and humidity environment higher the ordinary temperature and humidity environment, atmospheric moisture may cause deterioration of a colorant, which will be described later; coagulation of the moisture in the adhesive used for adhesion or on the interface between the adhered surfaces occurs, thereby causing cloudiness; or phase separation and precipitation of the adhesive occur owing to the moisture, thereby causing cloudiness.
  • the functional film has preferably a water vapor permeability of 10 g/m 2 -day or less, more preferably 5 g/m 2 -day or less. (Other optical properties)
  • a plasma display radiates near infrared rays at a high intensity.
  • the light transmitting electromagnetic wave shielding film is used particularly for the plasma display, it is preferred to provide the film with a near infrared ray shielding property.
  • a functional film having a near infrared ray shielding property has preferably a transmittance of 25% or less, more preferably 15% or less, still more preferably 10% or less, each at a wavelength range of from 800 to 1000 nm.
  • the infrared ray shielding layer for example, near infrared absorbing layer is a layer containing a near infrared absorbing colorant such as metal complex compound or is a silver sputtered layer.
  • the silver sputtered layer has a dielectric layer and a metal layer stacked alternately on the substrate by sputtering so that it can shield light of 1000 nm or greater including near infrared rays, far infrared rays and even electromagnetic waves.
  • the dielectric layer contains a transparent metal oxide such as indium oxide or zinc oxide as a dielectric substance. Metals contained in the metal layer are usually silver and silver- palladium alloy.
  • the above-described silver sputtered layer usually has a constitution obtained by stacking a dielectric layer and then thereover stacking three layers, five layers, seven layers or eleven layers.
  • a layer capable of absorbing visible light in a specific wavelength range and therefore having a color tone adjusting function is a layer for correcting emitted light in order to overcome the above-described problem. It therefore contains a colorant which absorbs light of around 595 nm.
  • the antireflective layer provided with antireflective properties can be formed by, for the purpose of suppressing the reflection of external light, thereby preventing lowering of a contrast, stacking, as a single layer or multilayer, an inorganic substance such as metal oxide, fluoride, suicide, boride, carbide, nitride or sulfide by vacuum deposition, sputtering, ion plating or ion beam assist method or by stacking, as a single layer or multilayer, resins different in refractive index such as acrylic resins and fluorine resins over the functional layer. Or a film subjected to antireflective treatment may be adhered to the film.
  • an inorganic substance such as metal oxide, fluoride, suicide, boride, carbide, nitride or sulfide by vacuum deposition, sputtering, ion plating or ion beam assist method or by stacking, as a single layer or multilayer, resins different in refractive index such as acrylic resin
  • a non-glare or anti-glare layer can be formed by preparing an ink of fine powders such as silica, melamine or acryl and then applying the ink to the surface.
  • the ink can be cured by heat or light.
  • a film subjected to non-glare or anti-glare treatment may be adhered to the film.
  • the light transmitting electromagnetic wave shielding film of the invention has good electromagnetic wave shielding property and light transmitting property so that it is particularly useful as a film for display panel.
  • a display panel film made of the light transmitting electromagnetic wave shielding film of the invention can also be used as an optical filter for plasma display panel after having the above-described functional transparent layers disposed on the film.
  • Such members can be applied to the front of displays such as CRT, PDP, liquid crystal and EL, microwave ovens, electronic apparatuses and printed wiring boards. They are particularly useful for PDP.
  • the PDP of the invention features a high electromagnetic wave shielding capacity, high contrast and high brightness and can be manufactured at a low cost.
  • a light transmitted therethrough is preferably neutral gray or blue gray in order to keep or improve the light emission properties and contrast of the plasma display.
  • a white color having a color temperature a little higher than that of the standard white color is sometimes preferred.
  • a color plasma display is said to be insufficient in its color reproducibility.
  • the emission spectrum of a red display exhibits several emission peaks within a wavelength range of from about 580 ran to 700 nm. Owing to relatively strong emission peaks on a short-wavelength side, red light emission becomes near orange and inferior in color purity.
  • the functional film having a function of selectively reducing unnecessary light emissions from a light emitter or discharged gas which is a cause for the inferior color purity is therefore preferred.
  • optical properties can be controlled by the use of a colorant.
  • Use of a near infrared ray absorber is effective for shielding near infrared rays.
  • Use of a colorant capable of selectively absorbing unnecessary light emissions is effective for reducing unnecessary light emissions.
  • the color tone of the optical filter can also be improved by using a colorant having proper absorption in a visible range.
  • colorant ordinarily employed dyes and pigments having a desired absorption wavelength in a visible region or compounds known as a near infrared absorber are usable.
  • examples include commercially available organic colorants such as anthraquinone, phthalocyanine, methine, azomethine, oxazine, immonium, azo, styryl, coumarin, porphyrin, dibenzofuranone, diketopyrrolopyrrole, rhodamine, xanthene, pyrromethene, dithiol, and diiminium compounds.
  • the temperature on the panel surface of a plasma display is high. Since the temperature of the light transmitting electromagnetic wave shielding film increases with an increase in the ambient temperature, the colorant preferably has heat resistance and does not to cause deterioration, for example, at about 80 0 C.
  • Some colorants have poor light resistance.
  • an ultraviolet absorber to a functional film or to form a layer which does not permit transmission of ultraviolet light, thereby protecting the colorants from deterioration due to ultraviolet light or visible light.
  • colorants in addition to those susceptible to temperature or light, susceptible to humidity or a plurality of these factors.
  • Deterioration in colorants may change the transmission properties of an optical filter, which may sometimes result in a change in the color tone or deterioration in the near infrared ray shielding capacity.
  • Colorants preferably have high solubility or dispersibility in a solvent in order to dissolve or disperse in a resin composition for the formation of the transparent substrate or in a coating composition for the formation of the coating layer.
  • the concentration of the colorant can be determined as needed, depending on the absorption wavelength- absorption coefficient of the colorant, transmission properties- transmittance which the light transmitting electromagnetic wave shielding film is required to have, kind of the medium in which the colorant is to be dispersed, or the kind or thickness of a coating film.
  • the colorant When the colorant is contained in the functional film, it may be added to the transparent substrate or a colorant-containing layer may be applied to the surface of the substrate. Two or more colorants different in absorption wavelength may be mixed and contained in one layer or two or more layers may each contain a colorant.
  • a functional film containing the colorant is preferably placed so that the colorant-containing layer is not brought into contact with a metal silver portion or conductive metal portion on the light transmitting electromagnetic wave shielding film.
  • the light transmitting electromagnetic wave shielding film having a functional film attached thereto is usually mounted on a display so that the functional film is located on the outside and the adhesive layer is located on the display side.
  • the metal silver portion or conductive metal portion is preferably earthed. It is therefore preferred to form a conduction portion for earthing on the light transmitting electromagnetic wave shielding film and bring this conduction portion into electrical contact with an earthing portion of the display itself.
  • the conduction portion is preferably located around the metal silver portion or conductive metal portion along the periphery of the light transmitting electromagnetic wave shielding film.
  • the conduction portion may be a mesh pattern layer or an unpatterned layer, for example, a metal foil solid layer.
  • an unpatterned conduction portion such as a metal foil solid layer is preferred.
  • the conduction portion is, as a metal foil solid, not patterned and/or the conduction portion has sufficiently high mechanical strength, it can be preferably used as an electrode as is.
  • an electrode at the conduction portion in order to protect the conduction portion and/or in order to improve the electrical contact with the earthing portion when the conduction portion is a mesh pattern layer.
  • the shape of the electrode it has preferably such a shape that the entire conduction portion is covered therewith.
  • a paste made of a single substance such as silver, copper, nickel, aluminum, chromium, iron, zinc or carbon, alloy of two or more of these single substances, mixture of the above-described single substance or alloy with a synthetic resin, or mixture of the above-described single substance or alloy with a borosilicate glass is usable.
  • Printing and application of the paste can be performed in a conventional manner.
  • a commercially available conductive tape is also used preferably.
  • As the conductive tape a one-sided adhesive type or double-sided adhesive type tape using a carbon-dispersed conductive adhesive and having conductivity on both sides thereof is preferred.
  • the thickness of the electrode is not particular limited, but is from about several ⁇ m to several mm.
  • the light transmitting electromagnetic wave shielding film of the invention has good electromagnetic wave shielding property and light transmitting property so that it can be applied to the front face of displays such as CRT, PDP, liquid crystal and EL, microwave ovens, electronic devices and printed wiring boards. It is particularly useful for PDP.
  • the invention makes it possible to provide an optical filter excellent in optical properties and capable of maintaining or improving the image quality of a plasma display without severely damaging its luminance.
  • the invention makes it possible to provide an optical filter excellent in the shielding performance of electromagnetic waves which are emitted from the plasma display and may have an adverse health effect, and capable of effectively shielding near infrared rays at from about 800 to 1000 nm irradiated from the plasma display so that it has no adverse effect on the wavelength used by a remote controller of a peripheral electronic device or transmission-system optical communication and can prevent malfunction of them.
  • the invention also makes it possible to provide an optical filter excellent in weather resistance at a low cost.
  • a light transmitting electromagnetic wave shielding film with a conductive pattern was prepared by preparing a support, forming an adhesion facilitating layer on both sides of a transparent substrate (support), and printing a paste made of silver. ⁇ Transparent substrate>
  • a polyethylene terephthalate resin obtained by polycondensation with antimony trioxide as a main catalyst and having an intrinsic viscosity of 0.66 was dried to give a water content of 50 ppm or less and was melted in an extruder having a heater temperature set at from 280 to 300 0 C.
  • the PET resin thus melted was discharged from a die portion onto a chill roll to which static electricity had been applied, whereby an amorphous base was obtained.
  • the amorphous base thus obtained was stretched by 3.1 times in the base traveling direction and 3.9 times in the width direction to yield a support having a thickness of 96 ⁇ m.
  • a paste was then prepared by mixing these particles with a binder composed of a solvent containing methyl ethyl ketone and an acrylic resin.
  • a binder composed of a solvent containing methyl ethyl ketone and an acrylic resin.
  • Coating solutions having the below-described composition were applied to each sample of the invention successively and dried, whereby a back layer was formed.
  • the biaxially-stretched polyethylene terephthalate support was subjected, on the surface thereof, to corona discharge treatment under the conditions of 727 J/m 2 while feeding at a feed speed of 105 m/min and an antistatic layer coating solution having the below-described composition was applied to the resulting support by the bar coat process.
  • the coating solution was applied in an amount of 7.1 cc/m 2 and then dried at 180°C for 1 minute in an air float drying zone, whereby an antistatic layer was obtained. (Antistatic layer coating solution)
  • Carbodiimide compound (“Carbodilite V-02-L2: trade name; product of Nisshinbo, solid content: 40%) 6.4 parts by mass
  • NAROACTY HN- 100 trade name; product of Sanyo
  • a surface layer coating solution having the below-described composition was then applied onto the antistatic layer while keeping the feeding speed at 105 m/min.
  • Epoxy compound ("Denacol EX-521", trade name; product of Nagase Chemtex, solid content: 100%) 1.2 parts by mass
  • Adhesion facilitating layer adhesion facilitating layer for silver paste printing>
  • an adhesion facilitating layer for silver paste printing was applied to the transparent substrate on the side opposite to the back layer.
  • the below-described silver paste was applied to the transparent substrate thus obtained by the screen printing.
  • the mesh pattern thus obtained was a silver lattice-like mesh having a line width of 18 ⁇ m and pitch of 300 ⁇ m.
  • the sample was then calendered by passing it between calender rollers made of two pairs of metal rolls under a linear pressure of 2940 N/cm (300 kgf/cm).
  • the sample was then subjected to rust inhibiting treatment with an aqueous solution of benzotriazole (0.01 mole/L).
  • the rust inhibiting treatment was performed by dipping the sample in the aqueous solution for 3 minutes.
  • Example 1-1 The sample obtained above was designated as "Sample 1-1" as shown in Table 1-1, while a sample without an adhesion facilitating layer for Ag pasting and a sample not subjected to calendering were prepared respectively.
  • ⁇ Evaluation method> (Surface resistivity)
  • the discoloration degree of the pattern made of silver was evaluated.
  • the sample showing the evidence of discoloration was rated as B, while the sample showing no evidence of discoloration was rated A.
  • Example 1-1 the sample of the invention obtained in Example 1-1 s excellent in time-dependent change in peel strength under heat and wet conditions and also excellent in surface hardness. By the calendering treatment, it can have markedly high conductivity and therefore have a high electromagnetic wave shielding property.
  • Example 1-3 (Fabrication of optical filter)
  • a glass plate was stacked, via an acrylic light transmitting adhesive having a thickness of 25 ⁇ m, over a film piece obtained by removing a 20-mm peripheral portion from the light transmitting electromagnetic wave shielding film obtained in Example 1-1 and having a light transmitting electromagnetic wave shielding capacity.
  • Colorants ("PS- Red-G” and "PS-Violet-RC", each trade name; product of Mitsui Chemical) for regulating the transmission properties of an optical filter were incorporated in the acrylic light transmitting adhesive layer.
  • An antireflective film (“Realook 772 UV”, trade name; product of NOF) having an infrared ray shielding capacity was stacked, via an adhesive, over the other main surface of the glass plate, whereby an optical filter was fabricated.
  • the metal mesh of the optical filter thus obtained was black so that the display image was not tinged with a metal color. In addition, it had electromagnetic wave shielding capacity and infrared ray shielding capacity which did not have an adverse effect on its practical use. Use of the antireflective layer contributed to excellent visibility. Moreover, owing to the colorants added to the filter, it had a toning function. As a result, it is suited as an optical filter for plasma display or the like. [Example 2-1] A plastic film having a mesh pattern was prepared by preparing a transparent substrate as described below, disposing an adhesion facilitating layer on both sides of the transparent substrate, and printing a paste made of silver. ⁇ Transparent substrate>
  • PET polyethylene terephthalate
  • the PET resin thus melted was discharged from a die portion onto a chill roll to which static electricity had been applied, whereby an amorphous base was obtained.
  • the amorphous base thus obtained was stretched by 3.1 times in the base traveling direction and 3.9 times in the width direction to yield a transparent substrate having a thickness of 96 ⁇ m.
  • a paste was then prepared by mixing these particles with a binder composed of a solvent containing methyl ethyl ketone and an acrylic resin. ⁇ Silver paste printing>
  • the silver paste was printed on the transparent substrate thus obtained by the intaglio printing using a rolled cylinder.
  • the length of the sample was set at 100 m.
  • the sample was then heated at 130 0 C for 10 minutes.
  • the mesh pattern thus obtained was a silver lattice-like mesh having a line width of 18 ⁇ m and pitch of 300 ⁇ m.
  • Coating solutions having the below-described compositions were successively applied to each sample of the invention and dried under the below-described conditions, whereby a back layer was formed.
  • the transparent support was subjected, on the surface thereof, to corona discharge treatment under the conditions of 727 J/m 2 while feeding at a feed speed of 105 m/min and an antistatic layer coating solution having the below-described composition was applied to the resulting support by the bar coating process.
  • the coating solution was applied in an amount of 7.1 cc/m 2 and then dried at 180 0 C for 1 minute in an air float drying zone, whereby an antistatic layer was obtained. (Antistatic layer coating solution)
  • Carbodiimide compound (“Carbodilite V-02-L2: trade name; product of Nisshinbo, solid content: 40%) 6.4 parts by mass
  • NAROACTY HN- 100 trade name; product of Sanyo Chemical, solid content: 100%
  • Dispersion of granular silica particles (“Seahostar KE-W30”, trade name; product of Nippon Shokubai, 0.3 ⁇ m, solid content: 20%) 5.0 parts by mass
  • a surface layer coating solution having the below-described composition was then applied onto the antistatic layer while keeping the feed speed at 105 m/min.
  • Epoxy compound ("Denacol EX-521", trade name; product of Nagase Chemtex, solid content: 100%) 1.2 parts by mass
  • ⁇ Adhesion facilitating layer adhesion facilitating layer on the side of mesh-like thin lines>
  • the adhesion facilitating layer was prepared on the support on the side opposite to the back layer.
  • plating was performed using plating solutions as described below, whereby a conductive film having a conductive metal portion made of silver and copper was prepared.
  • the surface resistivity of the film before electrolytic plating was 8 ⁇ /D.
  • Electrolytic plating 2 35 0 C 30 seconds
  • composition of electrolytic copper plating solution (a replenisher solution has also a similar composition)
  • Rinsing solution formulation of IL (common to Rinsing 1 to 6)
  • Deionized water having a conductivity of 5 ⁇ S/cm or less 1000 mL pH adjusted to pH 6.5
  • An aqueous solution of benzotriazole (0.01 mole/L) was used for rust inhibiting treatment.
  • the rust inhibiting treatment was performed by dipping in the aqueous solution for 3 minutes.
  • a scratch test using a pencil was performed in accordance with JIS Scratch hardness (pencil method) and the sample from which a pattern portion made of silver was removed was evaluated as B, while the sample from which a pattern portion made of silver was not removed was evaluated as A. (Evaluation of peel strength)
  • the discoloration degree of the pattern made of silver was evaluated.
  • the sample showing the evidence of discoloration was rated as B, while the sample showing no evidence of discoloration was rated A.
  • Example 2-4 (Fabrication of optical filter)
  • a glass plate was stacked, via an acrylic light transmitting adhesive having a thickness of 25 ⁇ m, over a film piece obtained by removing a 20-mm peripheral portion from the light transmitting electromagnetic wave shielding film obtained in Example 2-1.
  • Colorants ("PS-Red-G” and "PS-Violet-RC", each trade name; product of Mitsui Chemical) for regulating the transmission properties of an optical filter were incorporated in the acrylic light transmitting adhesive layer.
  • An antireflective film (“Realook 772 UV”, trade name; product of NOF) having an infrared ray shielding capacity was stacked, via an adhesive, over the other main surface of the glass plate, whereby an optical filter was fabricated.
  • the metal mesh of the optical filter thus obtained was black.
  • the display image was not tinged with a metal color.
  • it had electromagnetic wave shielding capacity and infrared ray shielding capacity which did not adversely affect its practical use.
  • the antireflective layer contributed to excellent visibility of the optical filter. Owing to the colorant added to the filter, it had a toning function. As a result, it is suited as an optical filter for plasma display or the like.
  • the present invention makes it possible to provide, at a high productivity, a light transmitting electromagnetic wave shielding film excellent in chemical resistance such as brine resistance, excellent in durabilities such as heat resistance and wet heat resistance, having a high electromagnetic wave shielding property, and exhibiting a high light transmittance with less light scattering; and a film for display panel, optical filter for display panel and plasma display panel each using the film.
  • the present invention makes it possible to provide a light transmitting electromagnetic wave shielding film which can be prepared by a smaller number of steps compared with the steps of a metal mesh preparation process using etching while utilizing photolithography, is available at a low cost, and has sufficient conductivity, that is, sufficient electromagnetic wave shielding property, or which has sufficient surface hardness, is excellent in adhesion, is excellent in durabilities such as heat resistance and wet heat resistance, and has a high light transmittance with less light scattering; and an optical filter and plasma display panel using the film.

Abstract

A light transmitting electromagnetic wave shielding film comprising: a transparent substrate; a first adhesion facilitating layer; and a printed pattern composed mainly of silver, in this order, wherein the printed pattern is a printed pattern of a conductive composition containing silver in an amount of 60 mass% or greater relative to metals constituting the pattern; a light transmitting electromagnetic wave shielding film comprising: a transparent substrate; and mesh-like thin lines composed mainly of silver and each having a width of from 1 µm to 30 µm, wherein the mesh-like thin lines are obtained by forming a mesh pattern on the transparent substrate by printing, and then electrolytic plating the mesh pattern, and the mesh-like thin lines are continuous for at least 3 m in a lengthwise direction of the shielding film; and a display panel film, a display panel optical filter and a plasma display panel using the shielding film.

Description

DESCRIPTION
LIGHT TRANSMITTING ELECTROMAGNETIC WAVE SHIELDING FILM5 OPTICAL FILTER AND PLASMA DISPLAY PANEL
Technical Field
The present invention relates to an electromagnetic wave shielding material which shields electromagnetic waves generated from front faces of displays such as CRT (cathode ray tube), PDP (plasma display panel), liquid crystal display, ELP (electroluminescence panel (which may also be called "EL")) and FED (field emission display) and has a light transmitting property; and an optical filter and a plasma display panel, each equipped with the light transmitting electromagnetic wave shielding film.
Background Art
In recent years, electro-magnetic interferences (EMI) have rapidly increased with an increase in utilization of various electric installations and electronics applied equipments. It has been pointed out that EMI not only causes malfunctions and damages to electronic or electric apparatuses, but also damages health of operators of these apparatuses. It is therefore required to suppress the intensity of electromagnetic waves emitted from electronic or electric apparatuses within a range of standards or regulations.
Electromagnetic waves must be shielded in order to overcome the problem of the above-described EMI and for this purpose, use of the property of metals that they do not transmit electromagnetic waves is effective. Examples of the method now employed include formation of a chassis from a metal or highly conductive substance, insertion of a metal plate between circuit boards, and covering of a cable with a metal foil. Since an operator needs to recognize characters displayed on a CRT or PDP display, however, the display is required to have transparency. The above-described methods using a metal were therefore unsuited as an electromagnetic wave shielding method because the front face of the display often becomes opaque in any one of these methods.
In particular, PDP, which emits a greater amount of electromagnetic waves compared with CRT or the like, is required to have stronger electromagnetic wave shielding performance. The electromagnetic wave shielding performance can be conveniently represented in terms of surface resistivity. While a light emitting electromagnetic wave shielding film for CRT is required to have a surface resistivity of about 300 Ω/sq or less, while that for PDP is required to have a surface resistivity of 2.5 Ω/sq or less. In consumer plasma television utilizing PDP, the surface resistivity must be adjusted to 1.5 Ω/sq or less, more desirably 0.1 Ω/sq or less. Thus, the shielding film for PDP is required to have a markedly high conductivity.
Further, with regard to transparency, the shielding film for CRT is required to have a visible light transmittance of about 70% or greater, while that for PDP is required to have a visible light transmittance of about 80% or greater. Electromagnetic wave shielding films having still higher transparency are demanded.
In order to overcome the above-described problems, various materials and processes capable of satisfying both the electromagnetic wave shielding property and optical transparency such as those described below by utilizing a metal mesh having apertures have so far been proposed. A typical material is a metal mesh prepared by etching while utilizing photolithography. The conventional metal mesh prepared by etching while utilizing photolithography can shield strong electromagnetic waves because this process utilizing photolithography enables minute processing and therefore a metal mesh with high aperture ratio (high transmission) can be prepared. In spite of such an advantage, this process requires high cost because of complex manufacturing steps. There is accordingly a demand for the improvement of the process. As a process for preparing a metal mesh at a low cost, processes for obtaining a metal mesh by printing a paste or ink containing metal particles into a lattice pattern have been proposed.
For example, a process of preparing an electromagnetic wave shielding material by printing a dispersion of fine conductive particles such as silver by the inkjet method, followed by heating and baking is disclosed in JP-A-2003-318593.
A process of preparing an electromagnetic wave shielding film by printing a paste containing a silver compound, and heating to promote the reduction-decomposition into the corresponding metal, thereby promoting fusion bonding between metals is disclosed in JP- A-2004- 119880.
Disclosure of the Invention
The metal mesh available by the conventional printing process as described above is characterized in that it can be prepared by a smaller number of steps and therefore can be prepared at a lower production cost compared with a metal mesh prepared by etching while utilizing photolithography. It has, on the other hand, the following problems.
The first problem of the metal mesh available by the conventional printing method is that it can be prepared the conductivity of the metal mesh tends to be smaller than that of a metal mesh obtained by etching of a metal foil so that it is disadvantageous from the viewpoint of an electromagnetic wave shielding performance.
The second problem of it is that adhesion between the metal mesh and support is not sufficient so that durability against physical or mechanical actions such as scratching, that is, surface hardness is week.
The third point is that it cannot satisfy the durabilities which an electromagnetic wave shielding film used for displays is required to have and their improvement is desired.
As a result of the investigation by the present inventors, it has been elucidated that since a dispersion of fine particles of a metal or metal compound is printed, the metal phase of the metal mesh tends to form not a complete continuous phase but a coagulation phase of fine metal particles having a large surface area. This may be a cause of the above- described problems.
By the conventional formation process of a metal mesh using etching while utilizing photolithography, only a mesh pattern of a certain area can be formed and a mesh extending, without interruption, for at least several ten meters in the lengthwise direction of a roll cannot be formed. When a metal mesh is formed by etching while using photolithography, exposure is repeated intermittently in the unit of a photo mask size by using a photomask-feed exposure system and exposure cannot be performed continuously over an entire long roll film.
When an electromagnetic shielding film is used for PDP, for example, it has been prepared by aligning the mesh pattern of the electromagnetic wave shielding material with the module or front plate of PDP or optical filter material using glass as a substrate. This process cannot avoid a loss of the shielding material and even if a rolled shielding material is used in order to improve the productivity, it takes time for aligning each mesh pattern with the panel, failing to increase the production rate sufficiently.
The above-described electromagnetic shielding film is required to have near infrared ray shielding performance as an important property for preventing malfunction of a remote controller. Improvement in the luminance of PDP has recently been followed by an increase in the emission amount of near infrared rays so that a higher level of near infrared ray shielding performance is required.
The electromagnetic wave shielding film is presumed to have an infrared ray shielding function by adhering thereto the corresponding functional layer. Insofar as the electromagnetic wave shielding film is not continuous as described above and an optical filter is fabricated while making a large loss, however, the film having an infrared ray shielding function can inevitably be used intermittently.
In addition, the electromagnetic wave shielding film used for PDP must inevitably have an antireflective function as well as the electromagnetic wave shielding function and near infrared ray shielding function. The film having this antireflective function or such functional film is also a rolled film similar to a film having a near infrared ray shielding function so that if the electromagnetic wave shielding film has a discontinuous mesh pattern, a portion of the antireflective film not provided for use remains as a loss when the antireflective film is adhered to it.
With the foregoing in view, the invention has been completed. An object of the invention is to provide a light transmitting electromagnetic wave shielding film which can be prepared by a smaller number of steps compared with those of the preparation process of a metal mesh by etching while utilizing photolithography, is low in cost, and has sufficient conductivity, that is, sufficient electromagnetic wave shielding performance. Another object of the invention is to provide a light transmitting electromagnetic wave shielding film having sufficient surface hardness, excellent in adhesion, excellent in durabilities such as heat resistance and wet heat resistance, and having a high light transmittance with less light scattering; and an optical filter and a plasma display panel each using the film.
The present inventors have carried out an extensive investigation. As a result it has been found that insertion of an adhesion facilitating layer between a transparent substrate and a printed pattern composed mainly of silver is effective, leading to the completion of the invention.
Further, the present inventors have found that the conductivity of a light transmitting electromagnetic wave shielding film can be improved by subjecting a printed pattern composed mainly of silver to electrolytic plating.
The present invention will be described below. (I) A light transmitting electromagnetic wave shielding film, which comprises: a transparent substrate; a first adhesion facilitating layer; and a printed pattern composed mainly of silver, in this order, wherein the printed pattern composed mainly of silver is a printed pattern of a conductive composition containing silver in an amount of 60 mass% or greater relative to metals constituting the printed pattern.
(2) The light transmitting electromagnetic wave shielding film as described in (1) above, wherein the printed pattern is treated with calender rolls.
(3) The light transmitting electromagnetic wave shielding film as described in (1) or (2) above, wherein the printed pattern contains a rust inhibitive.
(4) The light transmitting electromagnetic wave shielding film as described in any of (1) to (3) above, which further comprises a peelable protective film.
(5) The light transmitting electromagnetic wave shielding film as described in any of (l) to (4) above, wherein the transparent substrate is a plastic film.
(6) The light transmitting electromagnetic wave shielding film as described in any of (1) to (5) above, wherein the printed pattern is a mesh pattern which is made of thin lines each having a line width of from 1 μm to 40 μm and continues for 3 m or greater.
(7) The light transmitting electromagnetic wave shielding film according to any of (1) to (6) above, which further comprises: a second adhesion facilitating layer provided on a surface of the transparent substrate having no printed pattern; and an adhesive layer on the second adhesion facilitating layer, wherein the adhesive layer has a peel strength of 20 N/m or greater when brought into contact with glass.
(8) The light transmitting electromagnetic wave shielding film as described in (7) above, wherein the adhesive layer has a peel strength of 20 N/m or greater when brought into contact with glass after left for 72 hours at 60°C and relative humidity of 90% or greater.
(9) A process for preparing a light transmitting electromagnetic wave shielding film, the process comprising: disposing a first adhesion facilitating layer on a transparent substrate; and then disposing a printed pattern composed mainly of silver on the first adhesion facilitating layer, wherein the printed pattern composed mainly of silver is a printed pattern of a conductive composition containing silver in an amount of 60 mass% or greater relative to metals constituting the printed pattern.
(10) The process for preparing a light transmitting electromagnetic wave shielding film as described in (9) above, which further comprises subjecting the printed pattern to a treatment with calender rolls.
(11) The process for preparing a light transmitting electromagnetic wave shielding film as described in (10) above, wherein the treatment with calender rolls is performed at a linear pressure of 1960 N/cm (200 kgf/cm) or greater.
(12) An optical filter for plasma display panel, which comprises a light transmitting electromagnetic wave shielding film as described in any of (1) to (8) above.
(13) A plasma display panel, which comprises a light transmitting electromagnetic wave shielding film as described in any of (1) to (8) above.
(14) A light transmitting electromagnetic wave shielding film, which comprises: a transparent substrate; and mesh-like thin lines composed mainly of silver and each having a width of from 1 μm to 30 μm, wherein the mesh-like thin lines are obtained by forming a mesh pattern on the transparent substrate by printing, and then electrolytic plating the mesh pattern, and the mesh-like thin lines are continuous for at least 3 m in a lengthwise direction of the light transmitting electromagnetic wave shielding film.
(15) The light transmitting electromagnetic wave shielding film as described in (14) above, wherein the transparent substrate has a surface resistivity of from 1 Ω/D to 100 Ω/D after the formation of the mesh pattern by printing, and the mesh pattern is then subjected to continuous electrolytic plating.
(16) The light transmitting electromagnetic wave shielding film as described in (14) or (15) above, wherein after the formation of the mesh pattern by printing, the mesh pattern is subjected to a treatment with calender rolls.
(17) The light transmitting electromagnetic wave shielding film as described in (16) above, wherein the treatment with calender rolls is performed at a linear pressure of 1960 N/cm (200 kgf/cm) or greater.
(18) The light transmitting electromagnetic wave shielding film as described in any of (14) to (17) above, wherein the mesh-like thin lines contain a rust inhibitive.
(19) The light transmitting electromagnetic wave shielding film as described in any of (14) to (18) above, which further comprises a first adhesion facilitating layer between the transparent substrate and the mesh-like thin lines.
(20) The light transmitting electromagnetic wave shielding film as described in any of (14) to (19) above, which further comprises: a second adhesion facilitating layer provided on a surface of the transparent substrate having no mesh-like thin lines; and an adhesive layer on the second adhesion facilitating layer, wherein the adhesive layer has a peel strength of 20 N/m or greater when brought into contact with glass.
(21) The light transmitting electromagnetic wave shielding film as described in (20) above, wherein the peel strength after leaving the light transmitting electromagnetic wave shielding film for 72 hours at 60°C and relative humidity of 90% or greater is 20 N/m or greater.
(22) The light transmitting electromagnetic wave shielding film as described in any of (14) to (21) above, wherein the electrolytic plating is performed with at least one material selected from the group consisting of copper, nickel, zinc, tin and cobalt.
(23) An optical filter, which comprises a light transmitting electromagnetic wave shielding film as described in any of (14) to (22) above.
(24) A plasma display panel, which comprises a light transmitting electromagnetic wave shielding film as described in any of (14) to (22) above.
Brief Description of the Drawing
FIG. 1 is a schematic view illustrating an exemplary example of an electrolytic plating tank preferably employed for the electrolytic plating in the invention, wherein 10 denotes electrolytic plating tank; 11 denotes plating bath; 12a and 12b denote feeder rollers; 13 denotes anode plates; 14 denotes guide rollers; 15 denotes plating solution; 16 denotes film; and 17 denotes draining roller.
Best Mode For Carrying Out the Invention
The present invention will hereinafter be described more specifically.
The term "mesh" in the "continuous mesh pattern" as used herein means a mesh pattern composed of a plurality of thin lines or a mesh composed of a plurality of thin lines in accordance with the examples in the related industry. The term "continuous" means that the film is long as a rolled film and in this long film, the same patterns are repeated continuously in the lengthwise direction without a break.
The term "electromagnetic wave shielding film" may sometimes be called "film" simply insofar as it is not confused with another constituent (constituent film) to be stacked because it is supported by a transparent substrate in the film form. [Transparent Substrate]
As the transparent substrate (transparent support) to be used in the present invention, transparent plastic substrates, for example, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene (PE), polypropylene (PP), polystyrene and EVA, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, and other resins such as polyether ether ketone (PEEK), polysulfone (PSF), polyether sulfone (PES), polycarbonate (PC), polyamide, polyimide, acrylic resin, and triacetyl cellulose (TAC).
In view of transparency, heat resistance, ease of handling and price, the transparent plastic material is preferably a polyethylene terephthalate film. The transparent substrate has a thickness of preferably from 5 to 200 μm, more preferably from 10 to 130 μm, still more preferably from 40 to 80 μm from the standpoints of handling property, and visible light transmittance.
Since an electromagnetic wave shielding material for display panel is required to have transparency, a substrate having high transparency is desired. The total visible light transmittance of a plastic transparent substrate used for this purpose is preferably from 70 to 100%, more preferably from 85 to 100%, especially preferably from 90 to 100%. Further, in the invention, transparent plastic substrates colored in such a degree as not to interfere with the object of the present invention are also usable.
The transparent plastic substrate in the invention may be used either as a single layer or as a multilayer film obtained using two or more layers in combination.
In the invention, a glass plate can be used as the transparent substrate. Although no particular limitation is imposed on the kind of the glass plate, use of a reinforced glass having a surface equipped with a reinforcing layer is preferred for the use in an electromagnetic shielding film for display. Further, reinforced glass available by the air- cooling method is preferred in view of safety because crushed pieces thereof are small and do not have sharp end surfaces, even if it is broken. [Printed pattern composed mainly of silver] [Mesh-like thin lines composed mainly of silver]
The printed pattern composed mainly of silver and the mesh-like thin lines composed mainly of silver (conductive metal portions) in the invention will next be described. In this specification, "mesh-like thin lines composed mainly of silver" means a printed pattern composed mainly of silver which is treated with electrolytic plating.
As the printing method, known ones such as gravure printing, offset printing, typographic printing, screen printing, flexographic printing and inkjet printing can be used. Of these, screen printing, offset printing and intaglio printing are preferred, with screen printing and gravure printing are especially preferred.
The transparent substrate may be subjected to surface treatment or an anchor coat layer may be formed thereon. As the surface treatment, application of a primer, plasma treatment and corona discharge treatment are effective. After such a treatment, the transparent substrate has a critical surface tension of preferably 3.5 x 10"4 N/cm or greater, more preferably 4.0 x 10"4 N/cm or greater.
In the invention, the conductive metal portion is preferably inclined at from 30° to 60°, more preferably at from 40° to 50°, most preferably at from 43° to 47° relative to the lengthwise direction of the light transmitting electromagnetic wave shielding film.
A paste or ink to be used for printing contains preferably, in addition to a metal or metal compound for obtaining a conductive pattern by printing, a solvent for dispersing it, a binder and a dispersant.
Examples of the metal include fine particles of silver, copper, nickel, palladium, gold, platinum and tin. The printed pattern in the invention is composed mainly of silver. It may contain silver singly or a mixture obtained by mixing at least two metals including silver.
The "printed pattern composed mainly of silver" means a printed pattern containing silver in an amount of 60 mass% or greater relative to the metals constituting the pattern. When two or more metals are used in the invention, it is possible to cover the one metal with the other metal. (In this specification, mass ratio is equal to weight ratio.)
Metal compounds may be used in the invention. The term "metal compounds" means metal oxides or organic metal compounds. Compounds which are easily reduced or decomposed by the external application of energy and therefore can be imparted with conductivity are preferred. The metal oxides are preferably gold oxide and silver oxide. Silver oxide is especially preferred because it has self reducing property. The organic metal compounds are preferably silver acetate and silver citrate having a relatively small molecular weight. A metal-containing paste is prepared preferably from a metal of a nano- order size (from 5 to 60 nm). A metal-oxide-containing paste is prepared preferably using a metal oxide of a nano-order size, a reducing agent necessary for the reduction of the metal oxide and a solvent, while an organic-metal-oxide-containing paste is prepared preferably using an organic metal compound having a low decomposition temperature and a solvent. Use of a paste using a metal oxide of a nano-order size and an organic metal compound in combination not only enables printing of even thin lines but also, by selecting the structures of the reducing agent and organic metal compound as needed, promotes the reduction and decomposition of the metal oxide into the corresponding metal under conditions not damaging a flexible film when external energy is applied to add conductivity and promotes fusion bonding between metals, thereby reducing the resistivity further. When the metal oxide can be reduced without a reducing agent, for example, when it can be self-reduced by heating, the addition of the reducing agent is not always necessary. The solvent can be selected as needed, depending on the printing method or regulating method of the viscosity of the paste and high-boiling-point solvents such as carbitol and propylene glycol are usable. The solvent will be described later in detail. Although the viscosity of the paste can be set as needed depending on the printing method or solvent, it is preferably 5 mPa-s or greater but not greater than 20000 mPa-s.
As the binder to be contained in the paste or ink to be used in the invention, any one of the thermoplastic resins such as polyester resins, polyvinyl butyral resins, ethyl cellulose resins, (meth)acrylic resins, polyethylene resins, polystyrene resins, polyamide resins and thermosetting resins such as polyester-melamine resins, melamine resins, epoxy-melamine resins, phenolic resins, epoxy resins, amino resins, polyimide resins and (meth)acrylic resins. Two or more of these resins may be used after copolymerization or blending if necessary.
Specific examples of the solvent usable in the invention include alcohols such as hexanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, stearyl alcohol, ceryl alcohol, cyclohexanol and terpineol; and alkyl ethers such as ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol monophenyl ether, diethylene glycol, diethylene glycol monobutyl ether (butyl carbitol), cellosolve acetate, butyl cellosolve acetate, carbitol acetate, and butyl carbitol acetate. A proper one may be selected as needed in consideration of printability and workability.
Use of a higher alcohol as a solvent may presumably cause deterioration in the drying property or fluidity of the ink so that use of it in combination with butyl carbitol, butyl cellosolve, ethyl carbitol, butyl cellosolve acetate or butyl carbitol acetate which has better drying property than the higher alcohol is recommended. The amount of the solvent is determined by the viscosity of the ink or paste. It is usually from 100 to 500 parts by mass, preferably from 100 to 300 parts by mass based on 100 parts by mass of the binder in consideration of the amount of the above-described metal powder.
With regards to the component ratios (mass ratios) of the metal, binder and solvent, those of the binder and solvent are from 10" to 10 and from 1 to 10 , respectively, per metal, preferably those of the binder and solvent are from 10"3 to 10 and from 10 to 103, respectively, per metal.
The conductive metal portion after printing is preferably baked at high temperature, by which organic components are removed and at the same time fine metal particles adhere to each other, resulting in a reduction in surface resistivity. The baking temperature is, for example, from 50 to 10000C, preferably from 70 to 600°C, and baking time is, for example, from 3 to 600 minutes, preferably from 10 to 300 minutes.
The light transmitting electromagnetic wave shielding film of the invention has good conductivity because it has a conductive metal portion. The surface resistivity of the light transmitting electromagnetic wave shielding film of the invention is preferably 10 Ω/sq or less, more preferably 2.5 Ω/sq or less, still more preferably 1.5 Ω/s or less, most preferably 0.1 Ω/sq or less.
In the conductive metal portion of the invention, the conductive metal preferably has a geometric configuration consisting of triangles such as equilateral triangle, isosceles triangle and right triangle, quadrangles such as square, rectangle, rhomboid, parallelogram and trapezoid, (equilateral) hexagon and (equilateral) octagon in combination, and is more preferably a mesh consisting of these geometric configurations.
In the invention, a lattice mesh consisting of squares is most preferred.
The line width of the conductive metal portion is preferably from 1 to 40 μm, more preferably 1 to 30 μm, further more preferably 20 μm or less, and the distance between lines is preferably 100 μm or more. Further, the conductive metal portion may have a portion having a line width greater than 40 μm for the purpose of ground connection or the like. In view of making the image less outstanding, the line width of the conductive metal portion is more preferably less than 15 μm.
When the film is used for a display panel, the conductive metal portion is preferably as thin as possible because it widens the viewing angle of the display. The thickness is preferably from 1 μm or greater but not greater than 20 μm, more preferably 1 μm or greater but not greater than 13 μm, still more preferably 2 μm or greater but not greater than 10 μm, most preferably 3 μm or greater but not greater than 7 μm. The conductive metal portion is preferably in the form of patterns. The conductive metal portion may be made of a single layer or two or more layers.
The conductive metal portion in the invention has an aperture ratio of preferably 85% or greater, more preferably 90% or greater, most preferably 95% or greater in consideration of the visible light transmittance. The term "aperture ratio" means a ratio of portions not having thin lines constituting a mesh in the total area, and for example, the aperture ratio of a mesh in the square lattice form having a line width of 10 μm and a pitch of 200 μm is almost 90%. Although there is no particular upper limit on the aperture ratio of the conductive metal portion in the invention, the aperture ratio of 98% or less is preferred from the viewpoint of the relationship between the surface resistivity and line width.
[Treatment with calender rolls]
Calendering treatment, that is, treatment with calender rolls preferably employed in the invention will next be described.
It is preferred in the invention to treat the mesh pattern (printed pattern), which has been formed on the transparent substrate by printing, by calender rolls. This treatment makes it possible to improve the conductivity of the printed pattern portion composed mainly of silver, thereby enabling heightening of electromagnetic wave shielding performance.
The calender rolls are usually equipped with at least a pair of rolls. For the calendering treatment, plastic rolls made of epoxy, polyimide, polyamide or polyimidoamide or metal rolls are employed. Treatment with a pair of metal rolls is especially preferred. The linear pressure is preferably 1960 N/cm (200 kgf/cm), more preferably 2940 N/cm (300 kgf/cm) or greater.
The calendering treatment is carried out preferably at from 10 to 100°C, more preferably from 10 to 50°C.
A long rolled film can be continuously treated by this calendering.
In the invention, the mesh-like thin lines must be continuous for 3 m or greater in the lengthwise direction of the light transmitting electromagnetic wave shielding film. The continuous thin lines are preferably as long as possible because they can reduce a production loss of a material of an optical filter. When the continuous length is too long, on the other hand, a diameter of their roll becomes large, the roll becomes heavy, and a pressure at the center of the roll becomes strong, which may cause problems relating to adhesion or deformation. The continuous length is therefore preferably 2000 m or less. It is preferably 100 m or greater but not greater than 1000 m, more preferably 200 m or greater but not greater than 800 m, most preferably 300 m or greater but not greater than 500 m.
Owing to the similar reasons, the thickness of the transparent substrate is preferably 200 μm or less, more preferably 20 μm or greater but not greater than 180 μm, most preferably 50 μm or greater but not greater than 120 μm.
Electrolytic plating to be applied to the invention will next be described. Electrolytic plating is preferably a step of plating with at least one material selected from copper, nickel, zinc, tin and cobalt. An example of electrolytic plating will next be described.
FIG. 1 illustrates an example of an electrolytic plating tank suited for plating treatment in the invention. The electrolytic plating tank 10 shown in FIG. 1 can give continuous plating treatment to a long film 16. The arrow indicates the traveling direction of the film 16. The electrolytic plating tank 10 is equipped with a plating bath 11 for storing a plating solution 15 therein. A pair of anode plates 13 are arranged in parallel to each other in the plating bath 11 and inside the anode plates 13, a pair of guide rollers 14 are located rotatably in parallel with the anode plates 13. The guide rollers 14 are movable in a vertical direction, whereby plating time of the film 16 can be regulated.
Above the plating bath 11, each pair of feeder rollers (cathodes) 12a and 12b for guiding the film 16 to the plating bath 11 and at the same time feeding a current to the film 16 is disposed rotatably. A draining roller 17 is disposed rotatably below the feeder roller 12b on the outlet side above the plating bath 11. A water washing spray (not illustrated) for removing the plating solution from the film is disposed between this draining roller 17 and feeder roller 12b on the outlet side.
The anode plates 13 are connected to a plus terminal of a power supply (not illustrated) via an electric wire (not illustrated), while feeder rollers 12a and 12b are connected to a minus terminal of the power supply (not illustrated.
When the electrolytic plating tank 10 has, for example, a dimension of from 10 cm x 10 cm x 10 cm to 100 cm x 200 cm x 300 cm, the distance (distance La in FIG. 1) between the surface of the plating solution and the lowest portion of the face where the feeder roller 12a on the inlet side is contiguous to the film 16 is adjusted to preferably from 0.5 cm to 15 cm, more preferably from 1 cm to 10 cm, still more preferably from 1 cm to 7 cm. The distance (distance Lb shown in FIG. 1) between the surface of the plating solution and the lowest portion of the face where the feeder roller 12b is contiguous to the film 16 is preferably from 0.5 cm to 15 cm.
A method of reinforcing the conductivity by forming a copper plating layer on the mesh-like silver thin lines of the film by using a plating apparatus equipped with the electrolytic plating tank 10.
The plating solution 15 is stored in the plating bath 11. When copper plating is performed, a plating solution containing from 30 g/L to 300 g/L of copper sulfate pentahydrate and from 30 g/L to 300 g/L of sulfuric acid can be used. For nickel plating, nickel sulfate, nickel hydrochloride or the like can be used, while for iron silver plating, a plating solution containing silver cyanide or the like is usable. The plating solution may contain an additive such as surfactant, sulfur compound or nitrogen compound.
The film 16 is set while being rolled around a supply reel (not illustrated) and rolling of the film 16 around a conveyor roller (not illustrated) is started so that the surface of the film 16 on which plating is to be formed is brought into contact with the feeder rollers 12a and 12b.
A voltage is applied to the anode plates 13 and feeder rollers 12a and 12b and the film 16 is reeled out while being brought into contact with the feeder rollers 12a and 12b. The film 16 is introduced into the plating bath 11 and dipped in the plating solution 15 to form copper plating. The plating solution 15 attached to the film 16 is wiped off by passing it between the draining rollers 17 and the solution is collected in the plating bath 11. This operation is repeated in a plurality of electrolytic plating tanks. At the end of the operation, the film is washed with water and then reeled into a take-up reel (not illustrated).
The conveying speed of the film 16 is set within a range of from 1 m/min to 30 min/min. The conveying speed of the film 16 is preferably within a range of from 1 m/min to 10 m/min, more preferably from 2 m/min to 5 m/min.
Although no particular limitation is imposed on the number of the electrolytic plating tanks, it is preferred that from two to ten tanks, more preferably from three to six tanks are continued.
The applied voltage is preferably within a range of from IV to 100 V, more preferably within a range of from 2V to 60V. When a plurality of electrolytic plating tanks is arranged, the applied voltage to them is preferably reduced in stages. The current on the inlet side of the first tank is preferably from IA to 3OA, more preferably from 2 A to 1OA.
The feeder rollers 12a and 12b are preferably in contact with the entire surface of the film (80% of the contacted area is substantially brought into an electrical contact with the rollers).
Prior to the plating in the electrolytic plating tank, the film is preferably washed with water and an acid. The solution used for acid washing may contain sulfuric acid or the like.
When the film is used as an electromagnetic wave shielding film of a display, the thickness of the conductive metal portion to be electrolytically plated is preferably as thin as possible because it widens the viewing angle of the display. As a conductive wiring material, the film is required to be thinner in order to satisfy the demand for density heightening. From such a viewpoint, the thickness of the conductive metal portion after electrolytic plating is preferably less than 9 μm, more preferably 0.1 μm or greater but less than 5 μm, still more preferably 0.1 μm or greater but less than 3 μm.
When the film just before the electrolytic plating has a surface resistivity of from 1 Ω/D to 1000 Ω/D, electroless plating may be given prior to the electrolytic plating. Electrolytic plating is conducted preferably without electroless plating, because the number of steps can be decreased, which leads to improvements in the productivity and cost.
For electroless plating, known electroless plating technology can be employed. For example, electroless plating technology employed for printing circuit boards can be used. The electroless plating is preferably, electroless copper plating.
Examples of the chemical species contained in the electroless copper plating solution include copper sulfate, copper chloride, reducing agents such as formalin and glyoxylic acid, copper ligands such as EDTA and triethanolamine, and additives for stabilizing the bath or improving the smoothness of the plating film such as polyethylene glycol, yellow prussiate of potash and bipyridine.
In the invention, insofar as the transparent substrate having a mesh pattern formed thereon by printing has a surface resistivity of from 1 Ω/D to 1000 Ω/D, electrolytic plating can be given to it. The surface resistivity is preferably from 1 Ω/D to 500 Ω/D, more preferably from 1 Ω/D to 100 Ω/D.
The light transmitting electromagnetic wave shielding film of the invention may contain a rust inhibitive.
Rust inhibitives such as nitrogenous organic heterocyclic compounds and organic mercapto compounds are preferred in the invention.
Preferred examples of the nitrogenous organic heterocyclic compounds include imidazole, benzimidazole, benzindazole, benzotriazole, benzoxazole, benzothiazole, pyridine, quinoline, pyrimidine, piperidine, piperazine, quinoxaline and morpholine. These compounds may have a substituent such as alkyl, carboxyl or sulfo group.
Examples of the organic mercapto compounds include alkylmercapto compounds, aryl mercapto compounds and heterocyclic mercapto compounds.
Organic mercapto compounds represented by the below-described formula (2) are preferred. Formula (2)
Z-SM wherein, Z represents an alkyl, aromatic or heterocyclic group substituted by at least one group selected from the class consisting of hydroxyl group, -SO3M2 group, -COOM2 group (in which M2 represents a hydrogen atom, an alkali metal atom or an ammonium group), amino group and ammonio group or substituted by a substituent having at least one group selected from the above-described class; and M represents a hydrogen atom, an alkali metal atom or amidino group (which may form a hydrohalide or sulfonate).
Organic mercapto compounds represented by the following formula (1), (3) or (5) are also preferred. Formula (1):
Figure imgf000022_0001
wherein, -D= and -E= each independently represents a -CH= group, -C(R0)= group or -N= group in which R0 represents a substituent, L1, L2 and L3 each independently represents a hydrogen atom, halogen atom or optional substituent to be bound with the ring via any one of a carbon atom, nitrogen atom, oxygen atom, sulfur atom and phosphorous atom, with the proviso that at least one of L , L2, L3 and R0 represents an -SM group (in which M represents an alkali metal atom, a hydrogen atom or an ammonium group). Formula (3)
( 3 )
Figure imgf000023_0001
wherein, R21 and R22 each represents a hydrogen atom or alkyl group with the proviso that R21 and R22 do not simultaneously represent a hydrogen atom and the alkyl group may have a substituent; R23 and R24 each represents a hydrogen atom or alkyl group, R25 represents a hydroxyl group, amino group, alkyl group or phenyl group, R26 and R27 each represents a hydrogen atom, alkyl group, acyl group or -COOM22 with the proviso that R26 and R27 do not simultaneously represent a hydrogen atom; M21 represents a hydrogen atom, alkali metal atom or ammonium group, M22 represents a hydrogen atom, alkyl group, alkali metal atom, aryl group or aralkyl group, and m stands for 0, 1 or 2. Formula (5)
Figure imgf000023_0002
wherein, X40 represents a hydrogen atom, hydroxyl group, lower alkyl group, lower alkoxy group, halogen atom, carboxyl group or sulfo group, and M41 and Ma each represents a hydrogen atom, alkali metal atom or ammonium group.
A description will next be made of the compound represented by the formula (2).
The alkyl group represented by Z in the formula (2) is preferably a C1-30 alkyl group, especially preferably a linear, branched or cyclic C2-20 alkyl group which may have a substituent in addition to the above-described substituent. The aromatic group represented by Z is preferably a C6-32 monocycle or fused ring which may have a substituent in addition to the above-described substituent. The heterocyclic group represented by Z is preferably a C1-32 monocycle or fused ring; is a 5- or 6-membered ring having, in one ring thereof, from 1 to 6 hetero atoms selected independently from nitrogen, oxygen and sulfur; and may have a substituent in addition to the above-described substituent. When the heterocyclic group is tetrazole, however, the compound has neither a substituted nor unsubstituted naphthyl group as a substituent. Of the compounds represented by the formula (2), those having as Z a heterocyclic group with at least 2 nitrogen atoms are preferred.
The compounds represented by the formula (2) are preferably represented by the following formula (2-a):
Figure imgf000024_0001
In the above formula, Z is a group necessary for forming a nitrogen-containing unsaturated 5-membered heterocycle or 6-membered heterocycle (such as pyrrole, imidazole, pyrazole, pyrimidine, pyridazine or pyrazine ring), is a compound having at least one -SM group or thione group, and has at least one substituent selected from the class consisting of hydroxyl group, -COOM group, -SO3M group, substituted or unsubstituted amino group, and substituted or unsubstituted ammonio group. In the formula, R11 and R12 each independently represents a hydrogen atom, -SM group, halogen atom, alkyl group (which may be substituted), alkoxy group (which may be substituted), hydroxyl group, -COOM group, -SO3M group, alkenyl group (which may be substituted), amino group (which may be substituted), carbamoyl group (including substituted one), or phenyl group (which may be substituted), or R11 and R12 may form a ring. They can form a 5-membered ring or 6-membered ring, preferably a nitrogenous heterocycle. M has the same meaning as defined in the formula (2). Preferably, Z is a group forming a heterocyclic compound having at least two nitrogen atoms and may have a substituent other than the -SM group or thione group. Examples of the substituent include halogen atoms, lower alkyl groups (including substituted ones, preferably alkyl groups having 5 or less carbon atoms such as methyl and ethyl), lower alkoxy groups (including substituted ones, preferably alkoxy groups having 5 or less carbon atoms such as methoxy, ethoxy and butoxy), lower alkenyl groups (including substituted ones and, preferably alkenyl groups having 5 or less carbon atoms), carbamoyl group and phenyl group. In the formula (2-a), compounds represented by the following formulas A to F are especially preferred.
wherein, R21, R22, R2 , and R2 each independently represents a hydrogen atom, -SM group, halogen atom, lower alkyl group (which may be substituted, preferably an alkyl group having 5 or less carbon atoms such as methyl or ethyl), lower alkoxy group (which may be substituted, preferably an alkoxy group having 5 or less carbon atoms), hydroxyl group, - COOM2, -SO3M5 group, lower alkenyl group (which includes a substituted one and is preferably an alkenyl group having 5 or less carbon atoms), amino group, carbamoyl group or phenyl group. At least one of them represents an -SM group. M, M2 and M5 each represents a hydrogen atom, alkali metal atom or ammonium group. The substituent other than -SM is preferably a water soluble group such as hydroxy, -COOM2, -SO3M5 or amino group.
The amino group represented by R21, R22, R23 or R24 is a substituted or unsubstituted amino group. A lower alkyl group is a preferable substituent. The ammonium group represented by M, M2 or M5 is a substituted or unsubstituted ammonium group, preferably an unsubstituted ammonium group.
Specific examples of the compound represented by the formula (2) will next be shown, but the invention is not limited by them.
Figure imgf000026_0001
R 21 R 22 »23
2-1 H OH SH
2-2 H SH OH
2-3 OH H SH
2-4 OH H SH
2-5 H NH2 SH
2-6 H SK SO3K
2-7 COOH H SH
Figure imgf000027_0001
Figure imgf000027_0002
R21 R22
2-15 SH OH
2-16 NH2 SH
2-17 SH COOH
2-18 SH SO3H
2-19 SH OH
Figure imgf000028_0001
R21 R22
2-20 SH COOH
2-21 NH2 SH
2-22 SH COOH
2-23 SH SO3H
2-24 SH OH
Figure imgf000028_0002
R21 R22 R23 R24 -25 NH2 H H SH -26 COOH H SH SH -27 OH H H SH -28 H NH2 H SH -29 SH COOH H H -30 H H SO3H SH
Figure imgf000029_0001
R21 R23
2-31 SH OH H
2-32 SH H COOH
2-33 H OH SH
2-34 SO3H SH SH
2-35 H SH SO3H
2-36 NH2 H SH
2-37 NH2 SH H
2-38 H NH2 SNa
2-39 SH NH2 H
Compounds represented by the formula (1), (3) or (5) will next be described.
The compound represented by the formula (1) will be described in detail. In the formula (1), -D= and -E= each independently represents a -CH= group, -C(R0)= group or - N= group in which R0 represents a substituent. L1, L2 and L3 each independently represents a hydrogen atom, halogen atom or optional substituent to be bound with the ring via any one of a carbon atom, nitrogen atom, oxygen atom, sulfur atom and phosphorus atom, with the proviso that L1, L2 and L3 may be the same or different, but at least one of L1, L2, L3 and R0 represents an -SM group (in which M represents an alkali metal atom, hydrogen atom or ammonium group).
Specific examples of the optional substituent represented by L1, L2 or L3 or the substituent represented by R0 include halogen atoms (such as fluorine, chlorine, bromine and iodine atoms), alkyl groups (including aralkyl, cycloalkyl and active methine groups), alkenyl groups, alkynyl groups, aryl groups, heterocyclic groups, quaternized nitrogen- atom-containing heterocyclic groups (such as pyridinio group), acyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, carbamoyl group, carboxyl group or salts thereof, sulfonylcarbamoyl group, acylcarbamoyl groups, sulfamoylcarbamoyl group, carbazoyl group, oxalyl group, oxamoyl group, cyano group, thiocarbamoyl group, hydroxyl group, alkoxy groups (including groups containing recurring units of an ethylenoxy or propylenoxy group), aryloxy groups, heterocyclic oxy groups, acyloxy groups, (alkoxy or aryloxy)carbonyloxy groups, carbamoyloxy group, sulfonyloxy group, amino groups, (alkyl, aryl or heterocyclic) amino groups, hydroxyamino groups, N- substituted saturated or unsaturated nitrogenous heterocyclic groups, acylamino groups, sulfonamide groups, ureido group, thioureido group, imide groups, (alkoxy or aryloxy)carbonylamino groups, sulfamoylamino groups, semicarbazide group, thiosemicarbazide group, hydrazino group, ammonio group, oxamoylamino groups, (alkyl or aryl)sulfonylureido groups, acylureido groups, acylsulfamoylamino groups, nitro group, mercapto group, (alkyl, aryl or heterocyclic) thio groups, (alkyl or aryl)sulfonyl groups, (alkyl or aryl)sulfinyl groups, sulfo group or salts thereof, sulfamoyl group, acylsulfamoyl groups, sulfonylsulfamoyl group or salts thereof, and groups containing a phosphoramide or phosphate ester structure. These substituents may be replaced further by another substituent selected from the above-described substituents.
The optional substituent represented by L1, L2 or L3 or the substituent represented by R0 is more preferably a C0-15 substituent and, more specifically, a chlorine atom, alkyl group, aryl group, heterocyclic group, acyl group, alkoxycarbonyl group, carbamoyl group, carboxyl group or salt thereof, cyano group, alkoxy group, aryloxy group, acyloxy group, amino group, (alkyl, aryl or heterocyclic) amino group, hydroxyamino group, N-substituted saturated or unsaturated nitrogenous heterocyclic group, acylamino group, sulfonamide group, ureido group, thioureido group, sulfamoylamino group, nitro group, mercapto group (alkyl, aryl or heterocyclic) thio group, sulfo group or salt thereof, or sulfamoyl group; more preferably an alkyl group, aryl group, heterocyclic group, alkoxycarbonyl group, carbamoyl group, carboxy group or salt thereof, alkoxy group, aryloxy group, acyloxy group, amino group, (alkyl, aryl or heterocyclic) amino group, hydroxyamino group, N- substituted saturated or unsaturated nitrogenous heterocyclic group, acylamino group, sulfonamide group, ureido group, thioureido group, sulfamoylamino group, mercapto group (alkyl, aryl or heterocyclic) thio group, or sulfo group or salt thereof; most preferably an amino group, alkyl group, aryl group, alkoxy group, aryloxy group, alkylamino group, aryl amino group, alkylthio group, arylthio group, mercapto group, carboxyl group or salt thereof, or sulfo group or salt thereof. In the formula (1), L1, L2, L3 and R0 may be coupled each other to form a fused ring in which a hydrocarbon ring, heterocycle or aromatic ring has been condensed.
In the formula (1), at least one of L1, L2, L3 and R0 represents an -SM group (in which M represents an alkali metal atom, hydrogen atom or ammonium group). The alkali metal atom is more specifically Na, K, Li, Mg, Ca or the like and they are present as a counter cation of -S". M is preferably a hydrogen atom, ammonium group, Na+ or K+, especially preferably a hydrogen atom. Of the compounds represented by the formula (1), compounds represented by the following formulas (1-A) and (1-B) are preferred.
1-A R3 1 -B R β
The formula (1-A) will next be described in detail. R1 to R4 each independently represents a hydrogen atom, halogen atom, or optional substituent coupled with a ring via a carbon atom, nitrogen atom, oxygen atom, sulfur atom or phosphorus atom. They have the same meanings as described above in L1, L2 and L3 in the formula (1) and are similar in their preferable range. R1 and R3 however do not simultaneously represent a hydroxyl group. R to R may be the same or different but at least one of them is an -SM group. M represents a hydrogen atom, alkali metal atom or ammonium group. R1 and R2 may be coupled each other to form a fused ring with a hydrocarbon ring, heterocycle or aromatic ring.
In formula (1-A), at least one of R1 to R4 represents an -SM group, more preferably at least two of R1 to R4 represent -SM groups. When at least two of R1 to R4 are -SM groups, preferably R4 and R1, or R4 and R3 represent -SM groups.
In the invention, of the compounds represented by the formula (1-A), compounds represented by the following formulas (1-A-l) to (l-A-3) are especially preferred.
Figure imgf000032_0001
In the formula (1-A-l), R10 represents a mercapto group, hydrogen atom or optional substituent, and X represents a water soluble group or a substituent substituted with a water soluble group. In the formula (l-A-2), Y represents a water soluble group or a substituent substituted with a water soluble group, and R20 represents a hydrogen atom or an optional substituent. In formula (l-A-3), Y2 represents a water soluble group or a substituent substituted with a water soluble group, and R30 represents a hydrogen atom or an optional substituent. R10 and Y1 however do not represent a hydroxyl group.
Compounds represented by formula (1-A-l), (l-A-2) or (l-A-3) will next be described in detail.
In formula (1-A-l), R10 represents a mercapto group, a hydrogen atom or optional substituent. Examples of the optional substituent include the optional substituents described above in R1 to R4 of formula (1-A). R10 preferably represents a mercapto group, hydrogen atom, or group selected from the following C0-15 substituents. Examples of the C0-15 substituents include amino groups, alkyl groups, aryl groups, alkoxyl groups, aryloxy groups, acylamino groups, sulfonamide group, alkylthio groups, arylthio groups, alkylamino groups, and arylamino groups.
In formula (1-A-l), X represents a water soluble group or a substituent substituted with a water soluble group. The term "water soluble group" as used herein means a sulfonic acid group or carboxylic acid group or a salt of these acids, a salt such as an ammonio group, or a group containing a dissociative group which is partially or completely dissociable by an alkaline developing solution, more specifically a sulfo group (or a salt thereof), carboxyl group (or a salt thereof), hydroxyl group, mercapto group, amino group, ammonio group, sulfonamido group, acylsulfamoyl group, sulfonylsulfamoyl group, active methine group, or a substituent containing any of these groups. The term "active methine group" as used herein means a methyl group substituted with two electron attractive groups, more specifically, dicyanomethyl, α-cyano-α-ethoxycarbonylmethyl and α-acetyl- α-ethoxycarbonylmethyl groups. The substituent represented by X in formula (1-A-l) is the above-described water soluble group or substituent substituted with the above- described water soluble group. The substituent is a C0-15 substituent such alkyl group, aryl group, heterocyclic group, alkoxyl group, aryloxy group, heterocyclic oxy group, acyloxy group, alkyl-, aryl- or heterocyclic amino group, acylamino group, sulfonamide group, ureide group, thioureide group, imide group, sulfamoylamino group, alkyl-, aryl- or heterocyclic thio group, alkyl- or arylsulfonyl group, sulfamoyl group, or amino group, preferably a C1-10 alkyl group (in particular, a methyl group substituted with an amino group), aryl group, aryloxy group, amino group, alkyl-, aryl- or heterocyclic amino group, or an alkyl-, aryl- or heterocyclic thio group.
The compound represented by formula (1-A-l) is more preferably represented by the following formula (1-A-l -a): 1-A-1-a
Figure imgf000034_0001
In the formula, R11 has the same meaning as R10 in formula (1-A-l) and the preferred range of the substituent is also the same. R12 and R13 may be the same or different and each represents a hydrogen atom, alkyl group, aryl group or heterocyclic group with the proviso that at least one of R12 and R13 has a water soluble group. The term "water soluble group" as used herein means a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group, mercapto group, amino group, ammonio group, sulfonamide group, acylsulfamoyl group, sulfonylsulfamoyl group, active methine group, or substituent containing any of these groups, preferably a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group or amino group. R12 and R13 each preferably represents an alkyl group or aryl group. When R12 and R13 each represents an alkyl group, the alkyl group is preferably a substituted or unsubstituted C1-4 alkyl group, and the substituents thereof include a water soluble group, especially preferably a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group or amino group. R12 and R13 are each preferably an alkyl group or an aryl group and when R12 and R13 each represents an alkyl group, the alkyl group is preferably a substituted or unsubstituted C1-4 alkyl group and the substituent thereof is preferably a water soluble group, especially preferably a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group or amino group. When R12 and R13 each represents an aryl group, the aryl group is preferably a substituted or unsubstituted C6-10 phenyl group, and the substituent thereof is preferably a water soluble group, especially preferably a sulfo group (or salt thereof), carboxyl group (or salt thereof), hydroxyl group or amino group. When one of R12 and R13 represents an alkyl group and the other one represents an aryl group, they may be coupled to each other to form a cyclic structure. A saturated heterocycle may be formed by the cyclic structure.
In the formula (l-A-2), Y1 represents a water soluble group or a substituent substituted with a water soluble group and has the same meaning as X in formula (1-A-l). As the water-soluble group or the substituent substituted with a water-soluble group each represented by Y1 in formula (l-A-2), an active methine group, or the following group substituted with a water soluble group such as amino group, alkoxyl group, aryloxy group, alkylthio group, arylthio group, alkyl group or aryl group is preferred. Y1 represents more preferably an active methine group, or an alkyl-, aryl- or heterocyclic amino group substituted with a water soluble group, in which the water-soluble group is especially preferably a hydroxyl group, a carboxyl group or salt thereof, or a sulfo group or salt thereof. Especially preferred examples of Y1 include alkyl-, aryl- and heterocyclic amino groups each substituted with a hydroxyl group, carboxyl group (or salt thereof) or sulfo group (or salt thereof), which is represented by an -N(R01)(R02) group. R01 and R02 each has the same meaning as R12 and R13 in formula (1-A), respectively and the preferred range of the substituent is also the same.
In the formula (l-A-2), R20 represents a hydrogen atom or an optional substituent. Examples of the optional substituent include the same substituents as described in R1 to R4 in the formula (1-A). R20 is preferably a hydrogen atom or group selected from the following Co-i 5 substituents such as hydroxyl group, amino groups, alkyl groups, aryl groups, alkoxyl groups, aryloxy groups, acylamino groups, sulfonamide group, alkylthio groups, arylthio groups, alkylamino groups, arylamino groups, and hydroxylamino groups. R is most preferably a hydrogen atom.
In formula (l-A-3), Y2 represents a water soluble group or a substituent substituted with a water soluble group, and R30 represents a hydrogen atom or an optional substituent. Y2 and R30 in formula (l-A-3) have the same meanings as Y1 and R20 in formula (l-A-2), respectively and the preferred ranges of the substituents are also the same.
The compound represented by formula (1-B) will next be described in detail. R5 to R7 in formula (1-B) have the same meanings as R1 to R4 in formula (1-A), and the preferred ranges are also the same. As the compound represented by formula (1-B)5 that represented by the formula (1-B-l) is especially preferred.
Figure imgf000036_0001
In the formula (1-B-l), R50 has the same meaning as R5 to R7 in formula (1-B), more preferably a water soluble group or substituent substituted with a water soluble group each represented by X, Y1 and Y2 in formulas (1-A-l) to (l-A-3). The compound represented by formula (1-B-l) is most preferably represented by formula (1-B-l-a). Formula (1-B-l-a):
Figure imgf000036_0002
In the formula (1-B-l-a), R51 and R52 have the same meanings as R12 and R13 in the formula (1-A-l-a) and the preferred ranges of them are also the same.
Specific examples of the compound represented by the formula (1) will next be shown, but compounds of the formula (1) usable in the invention are not limited to them.
Figure imgf000037_0001
Figure imgf000037_0002
Figure imgf000038_0001
Figure imgf000038_0002
Figure imgf000039_0001
Figure imgf000040_0001
Figure imgf000040_0002
In the formula (3), the alkyl group represented by R21, R22, R23, R24 or R25 is preferably a C1-3 alkyl group such as methyl, ethyl or propyl. The alkyl group represented by R26 or R27 is preferably a C1-5 alkyl group such as methyl, ethyl, propyl, butyl or pentyl, while the acyl group represented by R26 or R27 is preferably an acyl group having 18 or less carbon atoms such as acetyl or benzoyl. The alkyl group represented by M22 is preferably a C1-4 alkyl group such as methyl, ethyl, propyl or butyl; the aryl group represented by M22 is, for example, phenyl or naphthyl; and the aralkyl group represented by M22 is preferably an aralkyl group having 15 or less carbon atoms such as benzyl or phenethyl.
Various processes for the synthesis of the compounds represented by the formula (3) are known. Of them, the Strecker-amino acid synthesis process which is known as a synthesis process of an amino acid may be employed. Acetylation of an amino acid is performed in an aqueous solution while adding an alkali and acetic anhydride thereto alternately.
Specific examples of the compounds represented by the formula (3) will next be shown, but the compounds of the invention are not limited only to them.
Figure imgf000041_0001
3-4 3-5 CH3 3-6 CH3
H3CV ^H3 C=O C=O
N CH3 HN CH3 HN CH3
HC-CH — C-SH HC CH2 — C SH HC CH2 C SH O=C CH3 CH3 C=O CH3 C=O CH3 NH, CeHδ NH2
SNa
Figure imgf000041_0002
The lower alkyl group represented by X40 in the formula (5) is preferably a linear or branched C1-5 alkyl group such as methyl, ethyl or isopropyl. Specific examples of the compounds represented by the formula (5) will next be shown but the compounds of the invention are not limited to them.
Figure imgf000042_0001
In the invention, the above-described rust inhibitives may be used either singly or in combination.
The rust inhibitive to be used in the invention can be applied to a conductive metal portion after preparing an aqueous solution of it and dipping therein a transparent substrate having the conductive metal portion formed thereover. The rust inhibiting treatment is applied preferably to the conductive metal portion after it is baked. The aqueous solution of the rust inhibitive to be applied is prepared so that it contains the compound represented by any one of the formulas (1), (2), (3) and (5), for example, at a concentration of from 10"6 to 10'1 mole, preferably, from 10"5 to 10"2 mole in 1 liter of the aqueous solution. The pH of the aqueous solution is adjusted preferably to from 2 to 12 in order to dissolve the rust inhibitive therein. For the pH adjustment, not only an alkali or acid such as sodium hydroxide or sulfuric acid, but also a phosphoric acid or salt thereof, carbonate, acetic acid or salt thereof, or boric acid or salt thereof is usable as a buffer. [Adhesion facilitating layer]
The light transmitting electromagnetic wave shielding film of the invention has an adhesion facilitating layer between the printed pattern composed mainly of silver and the transparent substrate (support). The adhesion facilitating layer can be preferably provided between the mesh-like thin lines and the transparent substrate (support).
The preferable adhesion facilitating layer of the invention will next be described. The adhesion facilitating layer may be a monolayer or multilayer.
In the invention, it is preferred to form an adhesion facilitating layer (back layer) composed of two layers as described below on the surface of the substrate having no printed pattern or mesh-like thin lines (conductive metal portion) formed thereover. (Constitution of the adhesion facilitating layer)
First layer: an antistatic layer composed essentially of a water dispersible or water soluble synthetic resin, carbodiimide compound and conductive metal oxide particles
Second layer: a surface layer (which will not be a surface layer when another constituent layer is stacked thereover, but it is the uppermost layer of the adhesion facilitating layer) composed essentially of a water dispersible or water soluble synthetic resin and a crosslinking agent.
The adhesion facilitating layer has the antistatic layer and surface layer stacked over the transparent substrate (support) in the order of mention. The antistatic layer of the invention has been imparted with conductivity so that the haze of a low static support available by disposing an antistatic layer over the support is 3% or less and the surface electric resistance on the surface layer of the printed pattern thus available falls within a range of from 8 x 106 to 6 x 108 Ω. The antistatic layer thus formed can prevent the generation of failures which will otherwise occur due to the dust attracted by static electricity generated during the preparation process handling the plastic support.
The term "haze" as used herein means a value as measured in accordance with JIS K-6714 under the measuring conditions at 25°C and 60%RH by using a hazemeter ("HGM- 2DP", trade name; product of Suga Test Instruments).
The antistatic layer contains conductive metal oxide particles and it usually contains a binder further. The conductive metal oxide particles are preferably acicular particles having a ratio of a long axis to a short axis (long axis/short axis) ranging from 3 to 50, especially preferably from 10 to 50. The short axis of such acicular particles preferably falls within a range of from 0.01 to 0.1 μm, especially preferably from 0.01 to 0.02 μm. The long axis of them preferably falls within a range of from 0.1 to 5.0 μm, especially preferably from 0.1 to 2.0 μm.
Examples of the material of the conductive metal oxide particles include ZnO, TiO2, SnO2, Al2O3, In2O3, MgO, BaO, and MoO3, complex oxides thereof, and these metal oxides containing a hetero atom further. Preferred metal oxides are SnO2, ZnO, Al2O3, TiO2, In2O3, and MgO, more preferably SnO2, ZnO, In2O3, and TiO2, with SnO2 being most preferred. Examples of the metal oxide containing a minor amount of a hetero atom include metal oxides doped with from 0.01 to 30 mole% (preferably from 0.1 to 10 mole%) of a hetero atom such as ZnO doped with Al or In, TiO2 doped with Nb or Ta, In2O3 doped with Sn, and SnO2 doped with Sb, Nb or halogen atom. When the amount of the hetero atom is less than 0.01 mole%, sufficient conductivity cannot be given to the oxide or complex oxide. When the amount exceeds 30 mole%, on the other hand, the degree of blackening of particles increases and the antistatic layer darkens. Amounts outside the above-described range are therefore not suited. Accordingly, metal oxides and complex metal oxides containing a minor amount of a hetero atom are preferred as the material of the conductive metal oxide particles in the invention. Moreover, those having an oxygen defect in their crystal structure are preferred. Preferred as the conductive metal oxide particles containing a minor amount of a hetero atom are SnO2 particles doped with antimony, especially SnO2 particles doped with from 0.2 to 2.0 mole% of antimony. Use of metal oxide particles such as antimony-doped SnO2 having the above-described short axis length and long axis length is therefore advantageous for forming a transparent antistatic layer having good conductivity. This makes it possible to easily prepare a material equipped with a low-charged transparent substrate having a haze not greater than 3% and a surface layer having a surface electric resistivity falling within a range of from 8 x 106 to 6 χ 108 Ω.
Use of acicular metal oxide particles (such as antimony-doped SnO2) having the above-described short axis length and long axis length advantageously contributes to the formation of the transparent antistatic layer having good conductivity because of the following reason. The acicular metal oxide particles extend parallel to each other in the long-axis direction on the surface of the antistatic layer, but they extend only by a length corresponding to their diameter along the short axis in the thickness direction of the layer. Compared with ordinary spherical particles, such acicular metal oxide particles are easily brought into contact with each other and high conductivity can be attained even by the use of a small amount of the particles. Surface electric resistivity can therefore be reduced without damaging the transparency. In addition, the acicular metal oxide particles have a short axis diameter at least equal to the thickness of the antistatic layer so they rarely protrude from the surface. Even if they protrude from the surface, the protruded portion is small enough to be covered with the surface layer disposed on the antistatic layer. During the transport of the transparent substrate, elimination of the protruded portion from the layer and dropping-off as a dust do not occur and such particles are therefore advantageous.
The antistatic layer in the invention usually contains a binder for dispersing and supporting the conductive metal oxide particles. Various polymers such as acrylic resin, vinyl resin, polyurethane resin and polyester resin are usable as the material of the binder. A hardened material of a polymer (preferably, acrylic resin, vinyl resin, polyurethane resin or polyester resin) and a carbodiimide compound is preferred in order to prevent powder fall. In view of maintenance of good working environment and prevention of air pollution in the invention, it is preferred to use them as a water soluble polymer and water soluble carbodiimide compound or to use them as an aqueous dispersion such as an emulsion. The polymer has any of methylol group, hydroxyl group, carboxyl group and glycidyl group so that it can be crosslinked with a carbodiimide compound. Of these groups, hydroxyl group and carboxyl group are preferred, of which the carboxyl group is especially preferred. An amount of the hydroxyl group or carboxyl group in the polymer is preferably from 0.0001 to 10 equivalent/kg, especially preferably, from 0.01 to 1 equivalent/kg.
Examples of the acrylic resin include homopolymers of any of monomers selected from acrylic acid, acrylate such as alkyl acrylate, acrylamide, acrylonitrile, methacrylic acid, methacrylate such as alkyl methacrylate, methacrylamide and methacrylonitrile and copolymers available by the polymerization of two or more of these monomers. Of these, homopolymers of any of monomers selected from acrylates such as alkyl acrylate and methacrylates such as alkyl methacrylate and copolymers available by the polymerization of two or more of these monomers are preferred. They are for example homopolymers of any of monomers selected from acrylates and methacrylates each having a C1-6 alkyl group and copolymers available by the polymerization of two or more of these monomers. The above-described acrylic resin is a polymer composed mainly of the above-described composition and available by partly using a monomer having any of a methylol group, hydroxyl group, carboxyl group and amino group to facilitate crosslinking reaction with a carbodiimide compound.
Examples of the vinyl resin include polyvinyl alcohol, acid-modified polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl methyl ether, polyolefin, ethylene/butadiene copolymers, polyvinyl acetate, vinyl chloride/vinyl acetate copolymers, vinyl chloride/(meth)acrylate copolymers and ethylene/vinyl acetate copolymers (preferably ethylene/vinyl acetate/(meth)acrylate copolymers). Of these, polyvinyl alcohol, acid-modified polyvinyl alcohol, polyvinyl formal, polyolefin, ethylene/butadiene copolymers and ethylene/vinyl acetate copolymers (preferably ethylene/vinyl acetate/acrylate copolymers) are preferred. To facilitate crosslinking reaction with a carbodiimide compound, the above-described vinyl resin is made into a crosslinkable polymer by leaving a vinyl alcohol unit in a polymer such as polyvinyl alcohol, acid modified polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl methyl ether or polyvinyl acetate, thereby obtaining the polymer having a hydroxyl group; or by using, as a part of the starting materials, a monomer having any of a methylol group, hydroxyl group, carboxyl group or amino group for the other polymers.
Examples of the polyurethane resin include polyurethanes derived from polyisocyanate and any one or a mixture of polyhydroxy compounds (such as ethylene glycol, propylene glycol, glycerin and trimethylolpropane), aliphatic polyester type polyols obtained by the reaction between a polyhydroxy compound and a polybasic acid, polyether polyols (such as poly(oxypropylene ether)polyol and poly(oxyethylene-propylene ether)polyol), polycarbonate polyols and polyethylene terephthalate polyol. In the above- described polyurethane resin, for example, a hydroxyl group which has remained unreacted after the reaction between a polyol and a polyisocyanate may be utilized as a functional group capable of crosslinking with a carbodiimide compound.
Polymers obtained by the reaction between a polyhydroxy compound (such as ethylene glycol, propylene glycol, glycerin and trimethylolpropane) and a polybasic acid are usually used as the polyester resin. In the above-described polyester resin, for example, a hydroxyl group and carboxyl group which have remained after the reaction between a polyol and a polybasic acid may be utilized as a functional group capable of crosslinking with a carbodiimide compound. It is needless to say that a third component having a functional group such as hydroxyl group may be added.
Of the above-described polymers, acrylic resins and polyurethane resins are preferred, with acrylic resins being especially preferred.
As a carbodiimide compound to be used in the invention, use of a compound having, in the molecule thereof, a plurality of carbodiimide structures is preferred.
Polycarbodiimide is usually synthesized by the condensation reaction of an organic diisocyanate. No particular limitation is imposed on the organic group of the organic diisocyanate to be used for the synthesis of the compound having, in the structure thereof, a plurality of carbodiimide structures. Either one of an aromatic or aliphatic group or a mixture thereof is usable. From the standpoint of the reactivity, an aliphatic group is especially preferred.
As raw materials for the synthesis, organic isocyanates, organic diisocyanates and organic triisocyanates are used.
As the organic isocyanates, aromatic isocyanates and aliphatic isocyanates, and mixtures thereof are usable.
Specific examples include 4,4'-diphenylmethane diisocyanate, 4,4- diphenyldimethylmethane diisocyanate, 1,4-phenylene diisocyanate, 2,4-trylene diisocyanate, 2,6-trylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, xylylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 4,4'- dicyclohexylmethane diisocyanate and 1,3-phenylene diisocyanate. Examples of the organic monoisocyanates include isophorone isocyanate, phenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate and naphthyl isocyanate.
The carbodiimide compound usable in the invention is commercially available as, for example, "Carbodilite V-02-L2" (trade name; product of Nisshinbo).
The carbodiimide compound in the invention is added preferably in an amount of from 1 to 200 mass%, more preferably from 5 to 100 mass% relative to the binder.
In order to form the antistatic layer of the invention, a coating solution for forming the antistatic layer is prepared by adding the conductive metal oxide particles as are or as a dispersion having them dispersed in a solvent such as water (containing a dispersant and/or a binder as needed) to a water dispersion or an aqueous solution containing the above- described binder (such as polymer, carbodiimide compound and proper additive) and mixing them (and dispersing as needed). The coating solution for forming the antistatic layer can be applied onto the surface (having no printed pattern formed thereon) of a plastic film such as a polyester film by a well known coating method such as dip coating, air knife coating, curtain coating, wire bar coating, gravure coating, or extrusion coating. The plastic film such as polyester film to be applied may be a film before sequential biaxial orientation, before simultaneous biaxial orientation, after monoaxial orientation but before re-orientation, or after biaxial orientation. The surface of the plastic support onto which the coating solution for forming the antistatic layer is applied is preferably subjected in advance to surface treatment such as ultraviolet treatment, corona treatment or glow discharge treatment.
The thickness of the antistatic layer in the invention is preferably within a range of from 0.01 μm to 1 μm, more preferably from 0.01 μm to 0.2 μm. Adjustment of the film thickness to 0.01 μm or greater facilitates uniform application of a coating agent, whereby the antistatic layer can be obtained without uneven coating. When the thickness is 1 μm or greater, the resulting antistatic layer is excellent in antistatic performance and scratch resistance. An amount of the conductive metal oxide particles in the antistatic layer preferably ranges from 10 to 1000 mass%, more preferably from 100 to 500 mass% relative to the binder (for example, total of the polymer and carbodiimide compound). Addition of them in an amount of 10 mass% or greater enables the antistatic layer to have sufficient antistatic properties. Addition of them in an amount not greater than 1000 mass% can suppress the haze level of the antistatic layer.
To the antistatic layer and the below-described surface layer in the invention, additives such as matting agent, surfactant and lubricant may be added in combination as needed. Examples of the matting agent include particles of an oxide such as silicon oxide, aluminum oxide or magnesium oxide having a particle size of from 0.001 to 10 μm, and particles of a polymer or copolymer such as polymethyl methacrylate or polystyrene. Examples of the surfactant include known anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants. Examples of the lubricant include natural waxes such as carnauba wax; phosphate esters of a higher C8-22 alcohol or amino salts thereof; palmitic acid, stearic acid, and behenic acid and esters thereof; and silicone compounds.
A surface layer is laid over the antistatic layer in the invention. The surface layer mainly serves to give an adhesion property to an adhesive layer and to assist the function of preventing elimination of the conductive metal oxide particles from the antistatic layer. As the material of the surface layer, various polymers such as acrylic resins, vinyl resins, polyurethane resins and polyester resins can usually be employed and the polymers as described above as the binder in the antistatic layer are preferred.
As the crosslinking agent to be used for the surface layer, epoxy compounds are preferred because they do not adversely affect the printed pattern to be brought into contact with the surface layer at the roll take-up time during the preparation process.
Preferred examples of the epoxy compound include l,4-bis(2',3'- epoxypropyloxy)butane, 1,3,5-triglycidyl isocyanurate, l,3-diglycidyl-5-(γ-acetoxy-β- oxypropyl) isocyanurate, sorbitol polyglycidyl ethers, polyglycerol polyglycidyl ethers, pentaerythritol polyglycidyl ethers, diglycerol polyglycidyl ether, l,3,5-triglycidyl(2- hydroxyethyl) isocyanurate, glycerol polyglycerol ethers and trimethylolpropane polyglycidyl ethers. They are commercially available, for example, as "Denacol EX-521" or "Denacol Ex-614B" (each, trade name; product of Nagase Chemtex) but the epoxy resins are not limited thereto.
Further, these epoxy compounds can be used in combination with other compounds such as curing agents as described in The Theory of the Photographic Process, Third edition, by C.E.K. Meers and T.H. James, (1966); U.S. Pat. Nos. 3316095, 3232764, 3288775, 2732303, 3635718, 3232763, 2732316, 2586168, 3103437, 3017280, 2983611, 2725294, 2725295, 3100704, 3091537, 3321313, 3543292 and 3125449; and U.K. Patent Application Nos. 994869 and 1167207.
Typical examples include aldehyde compounds and derivatives thereof such as melamine compounds having at least two (preferably at least three) methylol and/or alkoxymethyl groups and melamine resins which are polycondensates thereof or rnelamine-urea resins, mucochloric acid, mucobromic acid, mucophenoxychloric acid, mucophenoxybromic acid, formaldehyde, glyoxal, monomethylglyoxal, 2,3-dihydroxy-l,4- dioxane, 2,3-dihydroxy-5-methyl-l,4-dioxane succinaldehyde, 2,5- dimethoxytetrahydrofuran, and glutaraldehyde; active vinyl compounds such as divinylsulfone-N,N' -ethylenebis(vinylsulfonylacetamide), 1 ,3 -bis(vinylsulfonyl)-2- propanol, methylenebismaleimide, 5-acetyl-l,3-diacryloyl-hexahydro-s-triazine, 1,3,5- triacryloyl-hexahydro-s-triazine, and 1,3,5-trivinylsulfonyl-liexahydro-s-triazine; active halogen compounds such as sodium salt of 2,4-dichloro-6-hydroxy-s-triazine, sodium salt of 2,4-dichloro-6-(4-sulfoanilino)-s-triazine, 2,4-dichloro-6-(2-sulfoethylamino)-s-triazine, and N,N'-bis(2-chloroethylcarbamyl)piperazine; ethyleneimine compounds such as bis(2,3-epoxypropyl)methylpropylammonium-p-toluenesulfonate, 2,4,6-triethylene-s- triazine, l,6-hexamethylene-N,N'-bisethylene urea and bis-β-ethyleneiminoethylthioether; methane sulfonate compounds such as l,2-di(methanesulfonoxy)ethane, 1,4- di(methanesulfonoxy)butane and l,5-di(methanesulfonoxy)pentane; carbodiimide compounds such as dicyclohexylcarbodiimide and l-dicyclohexyl-3-(3- trimethylaminopropyl)carbodiimide hydrochloride; isoxazole compounds such as 2,5- dimethylisoxazole; inorganic compounds such as chromium alum and chromium acetate; dehydration condensation type peptide reagents such as N-carboethoxy-2-isopropoxy-l,2- dihydroquinoline and N-(l-morpholinocarboxy)-4-methylpyridinium chloride; active ester compounds such as N,N'-adipoyldioxydisuccinimide and N5N'- terephthaloyldioxydisuccinimide; isocyanates such as toluene-2,4-diisocyanate and 1,6- hexamethylene diisocyanate; and epichlorohydrin compounds such as a polyamide- polyamine-epichlorohydrin reaction product. The curing agents are however not limited thereto.
The surface layer may be formed, for example, by adding the polymer, epoxy compound and necessary additives to a solvent (containing a dispersant and a binder if necessary) such as water, mixing them (and dispersing if necessary) to prepare a coating solution for forming the surface layer.
The coating solution for forming the surface layer is then applied onto the antistatic layer of the invention by a well known application method such as dip coating, air knife coating, curtain coating, wire bar coating, gravure coating, or extrusion coating, whereby the surface layer can be formed. The surface layer has a thickness of preferably from 0.01 to 1 μm, more preferably from 0.01 to 0.2 μm. By adjusting the thickness to 0.01 μm or greater, the function of the surface layer for preventing elimination of the conductive metal oxide particles from the antistatic layer becomes sufficient, while adjustment of the thickness to 1 μm or less facilitates uniform application of the coating agent, whereby uneven coating of the surface layer can be avoided. [Adhesive layer]
An adhesive layer preferably employed in the invention will next be described.
The light transmitting electromagnetic wave shielding film of the invention is preferably bonded via an adhesive layer when incorporated in an optical filter, liquid crystal display plate, plasma display panel or other image display panel.
Use of an adhesive having a refractive index of from 1.40 to 1.70 is preferred in the invention. A reduction in the visible light transmittance can be prevented by decreasing a difference in the refractive index between the adhesive and the transparent substrate to be used in the invention. The adhesive layer having a refractive index of from 1.40 to 1.70 can suppress a reduction in the visible light transmittance so that it is preferred in the invention.
The adhesive usable in the invention preferably flows under heat or pressure. That demonstrating fluidity by heating at 200°C or less or applying a pressure of 1 kgf/cm2 (98 kPa) or greater is especially preferred. This fluidity facilitates adhesion of the electromagnetic wave shielding adhesive film to an object even having a curved surface or complex shape by lamination or press molding, especially press molding. For this purpose, the softening temperature of the adhesive is preferably 200°C or less. Since as an electromagnetic wave shielding adhesive film, it is usually employed at a temperature less than 80°C, it has preferably a softening temperature of 8O0C or greater. From the standpoint of processability, a softening temperature of from 80 to 1200C is most preferred. The term "softening temperature" as used herein means a temperature at which the viscosity of the material is decreased to below 1012 poise (1013 Pa-s). Fluidity can usually be observed in one to ten seconds at the softening temperature.
As typical examples of the adhesive which shows fluidity by heating or application of pressure, following thermoplastic resins can be given. Examples of the usable thermoplastic resins include (di)enes such as natural rubber (refractive index n=1.52), polyisoprene (n=1.521), poly-l,2-butadiene (n=1.50), polyisobutane (n=1.505 to 1.51), polybutane (n=1.513), poly-2-heptyl-l,3-butadiene (n=1.50), poly-2-t-butyl-l,3-butadiene (n=1.506) and poly- 1,3 -butadiene (n=1.515), polyethers such as polyoxyethylene (n=1.456), polyoxypropylene (n=1.450), polyvinyl ethyl ether (n=1.454), polyvinyl hexyl ether (n=1.459) and polyvinyl butyl ether (n=1.456), polyesters such as polyvinyl acetate (n=1.467), and polyvinyl propionate (n=1.467), polyurethane (n=1.5 to 1.6), ethyl cellulose (n=1.479), polyvinyl chloride (n=1.54 to 1.55), polyacrylonitrile (n=1.52), polymethacrylonitrile (n=1.52), polysulfone (n=1.633), polysulfide (n=1.6) phenoxy resin (n=1.5 to 1.6), and poly(meth)acrylates such as polyethyl acrylate (n=1.469), polybutyl acrylate (n=1.466), poly-2-ethylhexyl acrylate (n=1.463), poly-t-butyl acrylate (n=1.464), poly-3-ethoxypropyl acrylate (n=1.465), polyoxycarbonyl tetramethacrylate (n=1.465), polymethyl acrylate (n=1.472 to 1.480), polyisopropyl methacrylate (n=1.473), polydodecil methacrylate (n= 1.474), polytetradecyl methacrylate (n= 1.475), poly-n-propyl methacrylate (n=1.484), poly-3,3,5-trimethylcyclohexyl methacrylate (n=1.484), polyethyl methacrylate (n=1.485), poly-2-nitro-2-methylpropyl methacrylate (n=1.487), poly-1,1- diethylpropyl methacrylate (n=1.489), and polymethyl methacrylate (n=1.489). Two or more of these acrylic polymers may be copolymerized, or may be mixed as needed.
As copolymer resins of an acrylic resin and a resin other than the acrylic resin, epoxy acrylate (n=1.48 to 1.60), urethane acrylate (n=1.5 to 1.6), polyether acrylate (n=1.48 to 1.49), and polyester acrylate (n=1.48 to 1.54) are also usable. Of these, urethane acrylate, epoxy acrylate and polyether acrylate are excellent in adhesion. Examples of the epoxy acrylate include (metha)acrylic acid adducts of 1,6-hexandiol diglycidyl ether, neopenthylglycol diglycidyl ether, allyl alcohol diglycidyl ether, resorcinol diglycidyl ether, diglycidyl adipate, diglycidyl phthalate, polyethylene glycol diglycidyl ester, trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether, and sorbitol-tetraglycidyl ether. Polymers, such as epoxy acrylate, having in the molecule thereof a hydroxyl group are effective for improving adhesion. These copolymer resins may be use in combination of two or more if necessary. The softening temperature of the polymer serving as the adhesive is preferably 200°C or less, more preferably 150°C or less in view of the handling property. Since as an electromagnetic wave shielding adhesive film, it is usually used at a temperature of 800C or less, it has preferably a softening temperature of from 8O0C to 12O0C from the standpoint of processability. The polymer having a weight average molecular weight (as measured by gel permeation chromatography using the calibration curve of standard polystyrene, which will equally hereinafter) of 1000 or greater is preferred. The molecular weight of 1000 or greater heightens the coagulation force of the adhesive composition, thereby improving the adhesion to the object. The adhesive to be used in the invention may contain an additive such as diluent, plasticizer, antioxidant, filler, colorant, ultraviolet absorber and/or tackifϊer as needed. The thickness of the adhesive layer is preferably from 5 to 50 μm, especially preferably at least the thickness of the conductive layer and within a range of from 20 to 50 μm.
The adhesive covering the geometric configuration preferably has a difference of 0.14 or less in a refractive index from the transparent substrate. When the conductive material is stacked over the transparent substrate via an adhesive layer, a difference in the refractive index between the adhesive layer and the adhesive for covering the geometric configuration is preferably 0.14 or less. Difference in the refractive index between the transparent substrate and the adhesive or between the adhesive and the adhesive layer may lead to a reduction in a visible light transmittance. When the difference of the refractive index is 0.14 or less, a reduction of the visible light transmittance is preferably small. Examples of the material of the adhesive capable of satisfying such a requirement include, when the transparent substrate is made of polyethylene terephthalate (n=1.575; refractive index), bisphenol A epoxy resins, bisphenol F epoxy resins, tetrahydroxyphenylmethane epoxy resins, novolac epoxy resins, resorcin epoxy resins, polyalcohol-polyglycol epoxy resins, polyolefin epoxy resins and alicylic or halogenated bisphenol epoxy resins (each having a refractive index of from 1.55 to 1.60). Examples of the material other than the epoxy resins include dienes such as natural rubber (n=1.52), polyisoprene (n=1.521), poly- 1,2-butadiene (n=1.50), polyisobutene (n= from 1.505 to 1.51), polybutene (n=1.5125), poly-2-heptyl- 1,3 -butadiene (n=1.50), poly-2-t-butyl- 1,3 -butadiene (n=1.506) and poly- 1,3-butadiene (n=1.515), polyethers such as polyoxyethylene (n=1.4563), polyoxypropylene (n=1.4495), polyvinyl ethyl ether (n=1.454), polyvinyl hexyl ether (n=1.4591) and polyvinyl butyl ether (n=1.4563), polyesters such as polyvinyl acetate (n=1.4665) and polyvinyl propionate (n=1.4665), polyurethane (n= from 1.5 to 1.6), ethyl cellulose (n=1.479), polyvinyl chloride (n= from 1.54 to 1.55), polyacrylonitrile (n=1.52), polymethacrylonitrile (n=1.52), polysulfone (n=1.633), polysulfide (n=1.6) and phenoxy resin (n= from 1.5 to 1.6). They contribute to exhibition of a desirable visible light transmittance. Acrylic resins are well known as a material resistant to time-dependent discoloration and are therefore preferred in the invention. Examples include poly(meth)acrylates such as polyethyl acrylate (n=1.4685), polybutyl acrylate (n=1.466), poly-2-ethylhexyl acrylate (n= 1.463), poly-t-butyl acrylate (n= 1.4638), poly-3- ethoxypropyl acrylate (n= 1.465), polyoxycarbonyl tetramethacrylate (n= 1.465), polymethyl acrylate (n= from 1.472 to 1.480), polyisopropyl methacrylate (n=1.4728), polydodecyl methacrylate (n=1.474), polytetradecyl methacrylate (n=1.4746), poly-n- propyl methacrylate (n=1.484), poly-3,3,5-trimethylcyclohexyl methacrylate (n=1.484), polyethyl methacrylate (n=1.485), poly-2-nitro-2-methylpropyl methacrylate (n=1.4868), polytetracarbanyl methacrylate (n=1.4889), poly-l,l-diethylpropyl methacrylate (n=1.4889), and polymethyl methacrylate (n=1.4893); and acrylic acid and methacrylic acid. Two or more of these acrylic polymers may be copolymerized, or may be mixed as needed.
The adhesive can have a desired viscoelasticity by mixing a plurality of acrylic polymers different in molecular weight.
As copolymer resins of an acrylic resin and a resin other than the acrylic resin, epoxy acrylates, urethane acrylates, polyether acrylates, polyester acrylates and the like are usable. Of these, epoxy acrylates and polyether acrylates are excellent in adhesion. Examples of the epoxy acrylates include (meth)acrylic acid adducts of 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, allyl alcohol dilgycidyl ether, resocinol diglycidyl ether, diglycidyl adipate, diglycidyl phthalate, polyethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether, and sorbitol tetraglycidyl ether. Epoxy acrylates have in the molecule thereof a hydroxyl group so that they are effective for improving the adhesion. Two or more of these copolymer resins may be used in combination if necessary. The polymer to be employed as a main component of the adhesive has a weight average molecular weight of 1,000 or greater. The polymer having a molecular weight of 1,000 or greater improves adhesion to the object owing to the high coagulation force of the composition.
Examples of the curing agent (crosslinking agent) for the adhesive include amines such as triethylenetetramine, xylenediamine, diaminodiphenylmethane, acid anhydrides such as phthalic anhydride, maleic anhydride, dodecylsuccinic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic anhydride, diaminodiphenylsulfone, tris(dimethylaminomethyl)phenol, polyamide resins, dicyandiamide and ethylmethyl imidazole. They may be used either singly or in combination. The amount of the crosslinking agent is selected from a range of from 0.1 to 50 parts by mass, preferably from 1 to 30 parts by mass based on 100 parts by mass of the polymer. Amounts of 0.1 part by mass or greater provide sufficient curing, while amounts not greater than 50 parts by mass improve adhesion without causing excessive crosslinking. The resin composition of the adhesive used in the invention may contain additives such as diluent, plasticizer, antioxidant, filler and tackifϊer as needed. The resin composition of the adhesive is applied to the surface of the transparent substrate in order to cover therewith a portion or entire surface of the base material of the constituent material having thereon a geometric configuration drawn with the conductive material and an adhesive film of the invention can be obtained by drying of the solvent and curing under heat. The resulting adhesive film having an electromagnetic wave shielding property and transparency is, with the adhesive thereof, directly attached to a display such as CRT, PDP, liquid crystal or EL or attached to a plate or sheet such as acryl plate or glass plate for the use as a display. This adhesive film is used similarly for an observation window or chassis of a measuring instrument, measuring apparatus or manufacturing apparatus emitting electromagnetic waves. Moreover, it is attached to the windows of a building or automobile which may be exposed to interference with electromagnetic waves emitted from a power pylon or high-tension wire. The geometric configuration drawn with a conductive material is preferably equipped with a ground wire.
Even when the transparent substrate has an uneven surface and has a haze for scattering light, application of a resin having a refractive index close to that of the transparent plastic substrate or adhesion of a resin sheet to the uneven surface to planarize the surface makes it possible to minimize irregular reflection and contributes to appearance of transparency. The geometric configuration drawn with the conductive material of the invention cannot be macroscopically viewed because of a very small line width. Owing to a sufficient large pitch in addition to the small line width, apparent transparency is presumed to be accomplished. The pitch of the geographic configuration is however small enough compared with the wavelength of the electromagnetic waves to be shielded so that the shielding film of the invention is presumed to exhibit an excellent shielding property.
As described in JP-A-2003- 188576, the printed pattern composed mainly of silver can be stacked over the transparent substrate without inserting an adhesive layer therebetween when a film of an ethylene- vinyl acetate copolymer resin having high thermal adhesiveness or a film of a thermal adhesive resin such as ionomer resin is used either singly or as a film stack with another resin film, but stacking is usually performed by dry lamination using an adhesive layer. Examples of the adhesive constituting the adhesive layer include acrylic resins, polyester resins, polyurethane resins, polyvinyl alcohol resins, vinyl chloride/vinyl acetate copolymer resins and ethylene/vinyl acetate copolymer resins. Thermosetting resins and ionizing radiation curable resins (such as UV curable resins and electron beam curable resins) are also usable.
The surface of the display is generally made of glass so that the transparent substrate and glass plate of the light transmitting electromagnetic wave shielding film are bonded with an adhesive. Generation of air bubbles or peeling between the adhered surfaces cause problems such as distortion of an image or difference in color from that indicated on a display without air bubbles or peeling. Air bubbles and peeling each occurs owing to the peeling of the adhesive from the plastic film or glass plate. There is a possibility of these phenomena occurring on both the transparent substrate side and glass plate side. They occur on the side with a weaker adhesive force. An adhesive force of the adhesive with each of the transparent substrate and glass plate must be high. More specifically, the adhesive force between the adhesive layer and each of the transparent substrate and glass plate is preferably 10 g/cm or greater, more preferably 30 g/cm or greater at 8O0C. An adhesive having an adhesive force exceeding 2000 g/cm is sometimes undesired because of difficulty in bonding work with it. It can however be used if it does not cause such a problem. A slip sheet (separator) can be laid on the adhesive at a portion not facing with the transparent substrate in order to avoid a contact with an undesired portion.
The adhesive is preferably transparent. More specifically, the adhesive has a light transmittance of preferably 70% or greater, more preferably 80% or greater, most preferably from 85 to 92%. The adhesive having a low haze is preferred. The haze is preferably from 0 to 3%, more preferably from 0 to 1.5%. The adhesive to be used in the invention is preferably colorless in order not to change the color indicated on a display. If the adhesive is made of a colored resin but is thin, it can be regarded as colorless. In addition, the adhesive is not required to be colorless when a display is colored intentionally as described later.
Examples of the adhesive having the above-described properties include acrylic resins, α-olefin resins, vinyl acetate resins, acrylic copolymer resins, urethane resins, epoxy resins, vinylidene chloride resins, vinyl chloride resins, ethylene-vinyl acetate resins, polyamide resins and polyester resins. Of these, acrylic resins are preferred. The adhesion of the adhesive can be improved by decreasing the amount of a crosslinking agent to be added, adding a tackifier or changing the terminal group of its molecule upon synthesis of the adhesive by the polymerization process. The adhesion can also be improved by modifying the surface of the transparent substrate or glass plate. Examples of the surface modification method include physical methods such as corona discharge treatment and plasma glow treatment, and formation of an undercoat layer for improving the adhesion.
The thickness of the adhesive layer is preferably from about 5 to 50 μm from the standpoints of transparency, colorlessness and handling property. When the adhesive layer is made of an adhesive, it is preferably as thin as possible within the above-described range, specifically from about 1 to 20 μm. The thickness may exceed the above-described range when the adhesive layer does not change the color indicated on a display itself and its transparency falls within the above-described range. (Peel strength)
The adhesive strength of the light transmitting electromagnetic wave shielding film of the invention, which has an adhesive layer formed over the adhesion facilitating layer, with a glass substrate is preferably as follows.
A sample film attached to glass has preferably a peel strength of 20 N/m or greater when 180°C peel strength is measured at 100 mm/niin. Moreover, the above-described peel strength of the film when it is left at 60°C and relative humidity of 90% for 72 hours is preferably 20 N/m or greater and the above-described peel strength of the film when it is left at 60°C and relative humidity of 90% for 250 hours is preferably 20 N/m or greater.
The conductive metal portion for use in the light transmitting electromagnetic wave shielding material has preferably a line width of 1 μm or greater but not greater than 40 μm, more preferably 1 μm or greater but not greater than 30 μm, further more preferably 5 μm or greater but not greater than 30 μm, most preferably from 10 μm or greater but not greater than 25 μm. The distance between lines is preferably 50 μm or greater but not greater than 500 μm, more preferably 200 μm or greater but not greater than 400 μm, most preferably 250 μm or greater but not greater than 350 μm. The conductive metal portion for use in ground connection may have a portion having a line width greater than 20 μm. The conductive metal portion in the invention has preferably an aperture ratio of preferably 85% or greater, more preferably 90% or greater, most preferably 95% or greater in consideration of the visible light transmittance. The term "aperture ratio" means a ratio of portions not having thin lines constituting a mesh in the total area, and for example, the aperture ratio of a mesh in the square lattice form having a line width of 15 μm and pitch of 300 μm has an aperture ratio of 90%. [Light transmitting portion]
The term "light transmitting portion" as used herein means a transparent portion of the light transmitting electromagnetic wave shielding film other than the conductive metal portion. The transmittance of the light transmitting portion is, as described above, is 90% or greater, preferably 95% or greater, more preferably 97% or greater, still more preferably 98% or greater, most preferably 99% or greater in terms of the minimum transmittance in a wavelength region of from 380 to 780 nm except the contribution of the light absorption and reflection of the support.
The mesh pattern in the invention is preferably continuous for 3 m or greater in the lengthwise direction of the light transmitting electromagnetic wave shielding film. The greater the number of continuous mesh patterns, the more preferred because a loss of the optical filter material during the production can be reduced. When the number of continuous mesh patterns is too many, on the other hand, a diameter of their roll becomes large, the roll becomes heavy, and a pressure at the center of the roll becomes strong, which may cause problems relating to adhesion or deformation. The continuous length is therefore preferably 2000 m or less. It is preferably 100 m or greater but not greater than 1000 m, more preferably 200 m or greater but not greater than 800 m, most preferably 300 m or greater but not greater than 500 m.
Owing to the similar reasons, the thickness of the support is preferably 200 μm or less, more preferably 20 μm or greater but not greater than 180 μm, most preferably 50 μm or greater but not greater than 120 μm.
The term "pattern obtained by the intersection of thin linear lines substantially parallel to each other" as used herein means a so-called lattice pattern in which two adjacent linear lines constituting the lattice are parallel to each other or within parallel ± 2°.
The mesh pattern is preferably inclined at from 30° to 60°, more preferably from 40° to 50°, most preferably from 43° to 47° relative to the traveling direction. It is usually difficult to prepare a mask for the mesh pattern inclined at from 40° to 50° relative to the frame and tends to cause problems such as easy appearance of unevenness and high cost. In this method, unevenness at about 45° can be prevented so that the invention has a marked advantage over the patterning by screen printing. [Peelable protective film]
The light transmitting electromagnetic wave shielding film of the invention may have a peelable protective film.
The electromagnetic wave shielding sheet (transmitting electromagnetic wave shielding film) does not always have a protective film on both sides thereof. As illustrated in FIG. 2(a) of JP-A-2003-188576, the sheet may have a protective film only on a mesh- like metal foil of a film stack but not necessarily on the side of the transparent substrate film. As illustrated in FIG. 2(b) of the above-described publication, on the other hand, the sheet may have a protective film only on the side of the transparent substrate film of the film stack but not necessarily on the metal foil.
The constitution of the film stack of the electromagnetic wave shielding sheet obtained by stacking, over the transparent substrate film, at least an electromagnetic wave shielding layer made of the mesh-like metal foil having apertures arranged densely and therefore having transparency; and preparation process of the film stack will next be described with reference to FIGS. 3 (a) to (f) of the above-described publication. A film stack obtained by stacking a metal foil over a transparent substrate film via an adhesive layer is prepared. As the transparent substrate film, a film made of an acrylic resin, polycarbonate resin, polypropylene resin, polyethylene resin, polystyrene resin, polyester resin, cellulose resin, polysulfone resin or polyvinyl chloride resin is usable. A film made of a polyester resin such as polyethylene terephthalate resin having excellent mechanical strength and high transparency is usually preferred. Although no particular limitation is imposed on the thickness of the transparent substrate film, it is preferably from about 50 μm to 200 μm in order to improve the resistance to bending without losing the mechanical strength. The thickness can be increased further, but when the electromagnetic wave shielding sheet 1 is stacked over another transparent substrate, the thickness is not limited to the above-described range. The transparent substrate film may be subjected to corona discharge treatment either on one side or both sides thereof, or an adhesion facilitating layer may be laid over the film.
The electromagnetic wave shielding sheet is used after stacking a sheet having an effect of reinforcing the upper most surface, giving an antireflective property, giving an antifouling property or the like over both sides of the substrate having the film stack thereover via an infrared cut filter layer so that the above-described protective film must be peeled off when such further stacking is performed. It is therefore preferred to stack the protective film releasably on the metal foil side.
The protective film has preferably a peel strength of from 5 mN/25 mm width to 5 N/25 mm width, more preferably from 10 mN/25 mm width to 100 mN/25 mm width when stacked over the metal foil. The peel strength below the lower limit is not preferred because peeling occurs easily and there is a danger of the protective film being peeled during handling or by the careless contact. The peel strength exceeding the upper limit is also not preferred because too large force is necessary for peeling and in addition, there is a danger of the mesh-like metal foil being peeled from the transparent substrate film (or from the adhesive layer) during peeling.
In the electromagnetic wave shielding sheet, the protective film stacked over the lower surface side of the film stack (which may have a blackening layer) obtained by stacking a mesh-like metal foil on a transparent substrate film via an adhesive layer, that is, the protective film stacked on the side of the transparent substrate film is formed for protecting the lower surface of the transparent substrate film from damage during handling or by the careless contact.
Similar to the above-described protective film, this protective film must also be peeled off when another film is stacked over the film stack so that it is desired to stack, over the transparent substrate film, the protective film releasably therefrom. The peel strength is, similar to the above-described protective film, preferably from 5 mN/25 mm width to 5 N/25 mm width, more preferably from 10 mN/25 mm width to 100 mN/25 mm width. Below the lower limit, peeling occurs easily and there is a danger of the protective film being peeled off during handling or by careless contact. The peel strength exceeding the upper limit requires a large force for peeling. Peel strength outside the above-described range is therefore not preferred.
The protective film stacked on the side of the transparent substrate film is preferably resistant to etching conditions, for example, dipping for several minutes in an etchant of about 50C, particularly resistant to the alkali component thereof. When dry etching is performed, on the other hand, it is preferably resistant to temperature conditions of about 1000C. When dip coating of the film stack is performed to stack a photosensitive resin thereover, the photosensitive resin preferably has an adhesive force to prevent its peeling during etching and drifting in the etchant owing to the coating solution attached even to the reverse side of the film stack. The protective film preferably has durability against pollution by an etchant containing iron chloride or copper chloride or resistant to etching or pollution by a resist removal solution such as alkali solution. Use of a resin film made of a polyolefin resin such as polyethylene resin and polypropylene resin, polyester resin such as polyethylene terephthalate resin, polycarbonate resin, or acrylic resin as a film constituting the protective film is preferred. From the above-described standpoint, the surface on the side of the protective film which will be the uppermost surface when the film is adhered to the film stack is preferably subjected to corona discharge treatment or an adhesion facilitating layer is stacked over the surface in advance.
As an adhesive constituting the protective film, an acrylate, rubber or silicone adhesive is usable.
The above-described materials of the film and above-described materials of the adhesive for the protective film can also be used for the protective film formed on the metal foil side.
As the protective films stacked over the side of the transparent substrate film and on the side of the metal foil, protective films different in material may be used, but the same protective film can be used. [Blackening treatment]
The light transmitting electromagnetic wave shielding film of the invention or an optical film having the film incorporated therein may have been subjected to blackening treatment.
Blackening treatment is disclosed in JP-A-2003-188576. The blackening layer formed by the blackening treatment can give an antireflective effect in addition to a rust inhibitive effect. The blackening layer is formed, for example, by Co-Cu alloy plating. The blackening layer formed on the conductive mesh patterns can prevent the reflection of their surface. The conductive mesh patterns having the blackening layer formed thereon may be subjected to chromate treatment for rust inhibition. The chromate treatment comprises dipping in a solution composed mainly of chromic acid or dichromate and then drying to form a rust inhibitive film. Chromate treatment may be performed on either one or both surfaces of the conductive mesh patterns. Alternatively, a commercially available copper foil subjected to chromate treatment may be utilized.
As another example, the constitution containing a blackening layer as described in JP-A-11-266095 may be employed. Described specifically, a first blackening layer is laid over a conductive metal portion. After the above-described electrolytic plating on the first blackening layer, a second blackening layer is formed over the resulting plated layer. At least the first blackening layer must be conductive when electrolytic plating is given onto the first blackening layer. The conductive blackening layer can be formed using a conductive compound of, for example, nickel (Ni), zinc (Zn) or Cu (copper), or can be formed using an electrodeposition ionic polymer material, for example, an electrodeposition coating material.
The blackening layer is laid in a known manner (refer to, for example, FIG. 5 of JP- A- 11 -266095), for example, by dipping a transparent support having a conductive metal portion formed thereon in an electrolyte solution containing a blackening material, followed by electrochemical plating. In the invention, a black plating bath having a sulfate nickel salt as a main component can be used as the bath (black plating bath) of an electrolyte solution containing the above-described blackening material. A commercially available black plating bath can also be used. Specific examples of the usable black plating bath include black plating bath ("Nobloy SNC", trade name; Sn-Ni alloy, product of Shimizu), black plating bath "Nikka Black", trade name; Sn-Ni alloy, product of Nihon Kagaku Sangyo), and black plating bath ("Eboni chromium 85 Series", trade name; Cr type, product of Kinzoku Kako Gijutsu). As the black plating bath, various ones containing Zn, Cu or the like are usable in the invention. After formation of the conductive mesh pattern, a second blackening layer is formed thereon. For example, when the metal to be electrolytically plated is Cu, the Cu surface is blackened as copper sulfide (CuS) by treatment with hydrogen sulfide (H2S), whereby the second blackening layer is formed. The blackening agent for the second blackening layer in the invention can easily be prepared using a sulfide compound. Many blackening agents are commercially available. "Copper black CuO", "Copper black CuS", and selenium series "Copper black No. 65" (each, trade name; product of Isolate Chemical) and "Ebonol C Special" (trade name; product of Meltex) are usable.
The etching resist pattern may be removed from the electromagnetic wave shielding plate of the invention, or it may be left without removal. When the etching resist pattern is removed, the removal of the etching resist pattern may be followed by the blackening treatment of the surface of the remaining metal conductive layer. For this blackening treatment, plating method of black copper (Cu) or black nickel (Ni) or known blackening method such as chemical blackening can be employed.
[Layers of the light transmitting electromagnetic wave shielding film having functions other than electromagnetic wave shielding function]
In the invention, functional layers each having a function may be additionally provided as required. These functional layers can be prepared in accordance with the respective specifications, depending on their using purpose. For example, for use as an electromagnetic wave shielding material for a display, an antireflective layer imparted with an antireflective function and having an adjusted refraction index and film thickness, a non-glare and anti-glare layer (both have a glare preventing function), a near infrared ray absorbing layer comprising a compound or metal which absorbs near infrared rays, a layer having a color tone adjusting function which absorbs a visible light in a specific wavelength region, an antifouling layer having a function of facilitating removal of stains such as finger prints, a hard coat layer resistant to damage, a layer having an impact absorbing function, a scattering preventing function of broken glass pieces and the like can be provided. These functional layers may be disposed on both sides having the printed pattern and support therebetween, or may be disposed on the same side.
These functional films may be directly adhered to PDP, or may be adhered not to a plasma display panel itself but to a transparent substrate such as glass plate or acrylic resin plate. These functional films are referred to as optical filters (or simply "filters"). <Functional Film>
When the light transmitting electromagnetic wave shielding film is incorporated in a display (particularly, a plasma display), functional films having the below-described functions are preferably adhered to the light transmitting electromagnetic wave shielding film to impart it with these functions. Each functional film can be adhered directly or indirectly to the light transmitting electromagnetic wave shielding film via an adhesive or the like. (Antireflective properties -antiglare properties)
Any one of antireflective (AR) properties for preventing reflection of an external light, antiglare (AG) properties for preventing reflection of a mirror image, and antireflective-antiglare (ARAG) properties having these two properties are preferably imparted to the light transmitting electromagnetic wave shielding film.
These performances enable to overcome the difficulty in viewing a display which will otherwise be disturbed by the reflection of a lighting apparatus. In addition, by reducing a visible light reflectance on the film surface, not only reflection can be prevented but also contrast and the like can be improved. The visible light reflectance when a functional film having antireflective-antiglare properties is adhered to the light transmitting electromagnetic wave shielding film is preferably 2% or less, more preferably 1.3% or less, still more preferably 0.8% or less.
Such a functional film can be formed by laying a functional layer having antireflective and antiglare properties on a proper transparent substrate.
The antireflective layer can be formed, for example, by stacking, over the transparent substrate, a single layer of a thin film made of a transparent fluorine polymer resin, magnesium fluoride, silicone resin or silicon oxide while adjusting its optical film thickness to a 1/4 wavelength or a multilayer of at least two thin films different in refractive index and made of an inorganic compound such as metal oxide, fluoride, suicide, nitride or sulfide or an organic compound such as silicone resin, acrylic resin or fluorine resin.
The antiglare layer can be made of a layer having a surface with minute irregularities of from about 0.1 μm to 10 μm. More specifically, it can be formed by dispersing particles of an inorganic compound or organic compound such as silica, organic silicon compound, melamine, acryl or the like in a thermosetting or photocurable resin such as acrylic resin, silicon resin, melamine resin, urethane resin, alkyd resin or fluorine resin to form an ink, applying the ink to the substrate and then curing. The particles have an average particle size of preferably from about 1 to 40 μm.
The antiglare layer can also be formed by applying the above-described thermosetting or photocurable resin, pressing a mold having a desired gloss or desired surface condition against the resin and then curing.
The light transmitting electromagnetic wave shielding film having an antiglare layer formed thereon has a haze of preferably from 0.5% or greater but not greater than 20%, more preferably 1% or greater but not greater than 10%. Sufficient antiglare property cannot be obtained when the haze is too small, while too large haze tends to deteriorate the vividness of the transmitted image. (Hard coat property)
The functional film has preferably a hard coat property in order to provide the light transmitting electromagnetic wave shielding film with scratch resistance. Examples of the material of the hard coat layer include thermosetting resins and photocurable resins such as acrylic resins, silicon resins, melamine resins, urethane resins, alkyd resins and fluorine resins. No particular limitation is imposed on the kind and formation method of them. The hard coat layer has a thickness of preferably from 1 to 50 μm. It is preferred to form the above-described antireflective layer and/or antiglare layer on the hard coat layer because functional films having scratch resistance, and antireflective properties and/or antiglare properties are available.
The light transmitting electromagnetic wave shielding film provided with the hard coat property has preferably a surface hardness of at least H in terms of pencil hardness in accordance with JIS (K-5400), more preferably 2H, still more preferably 3H. (Antistatic property)
The light transmitting electromagnetic wave shielding film is preferably provided with an antistatic property in order to prevent attachment of dusts due to static electricity or electrostatic charging due to the contact with human bodies.
As a functional film having an antistatic property, a film having a high conductivity is usable. The conductivity is, in terms of surface resistivity, preferably about 1011 Ω/D.
The highly conductive film can be formed by laying an antistatic layer on the transparent substrate. Examples of the antistatic agent to be added to the antistatic layer include "Pellestat" (trade name; product of Sanyo Kasei) and "Electro slipper" (trade name; product of Kao). The antistatic layer may be formed using known transparent conductive films including ITO or a conductive film having, dispersed therein, conductive ultrafme particles such as ITO ultrafme particles or tin oxide ultrafϊne particles. The antistatic property may be given to the shielding film by incorporating conductive fine particles in the hard coat layer, antireflective layer, antiglare layer or the like. (Antifouling property)
The light transmitting electromagnetic wave shielding film having an antifouling property is desired because it can prevent contaminations such as fingerprints or facilitates removal of stains. A functional film having an antifouling property is available, for example, by adding a compound having an antifouling property onto the transparent substrate. No limitation is imposed on the compound having an antifouling property insofar as it has non- wettability with water and/or oil or fat and examples of it include fluorine compounds and silicon compounds. Specific examples of the fluorine compounds include "OPTOOL" (trade name; product of Daikin Industries) and "Takata Quantum" (trade mark, product of NOF). (Ultraviolet shielding property)
The light transmitting electromagnetic wave shielding film is preferably provided with an ultraviolet shielding property in order to prevent deterioration of the transparent substrate or colorant which will be described later. The functional film having an ultraviolet shielding property can be formed by incorporating an ultraviolet absorber in the transparent substrate itself or providing an ultraviolet absorption layer on the transparent substrate.
In order to satisfy the ultraviolet shielding performance necessary for protecting a colorant, the transmittance in a ultraviolet region having a wavelength shorter than 380 nm is 20% or less, preferably 10% or less, more preferably 5% or less. The functional film having an ultraviolet shielding property is available by forming, over the transparent substrate, a layer containing an ultraviolet absorber or an inorganic compound capable of reflecting or absorbing ultraviolet rays. As the ultraviolet absorber, conventionally known ultraviolet absorbers such as benzotriazole and benzophenone are usable. No particular limitation is imposed on its kind and concentration because they are determined, depending on the dispersibility or solubility in a medium in which the compound is to be dispersed or dissolved, absorption wavelength-absorption coefficient, thickness of the medium, or the like.
The functional film having an ultraviolet shielding property preferably exhibits smaller absorption in a visible light region and causes neither a marked reduction in visible light transmittance nor color development such as yellowing.
When the functional film has a layer containing therein a colorant, which will be described later, a layer having an ultraviolet shielding property is preferably located outside the colorant-containing layer. (Gas barrier property)
The light transmitting electromagnetic wave shielding film preferably has a gas barrier property, because when it is used under a temperature and humidity environment higher the ordinary temperature and humidity environment, atmospheric moisture may cause deterioration of a colorant, which will be described later; coagulation of the moisture in the adhesive used for adhesion or on the interface between the adhered surfaces occurs, thereby causing cloudiness; or phase separation and precipitation of the adhesive occur owing to the moisture, thereby causing cloudiness.
It is essential to prevent penetration of moisture into the colorant-containing layer or adhesive layer to avoid such colorant deterioration or cloudiness. Accordingly, the functional film has preferably a water vapor permeability of 10 g/m2-day or less, more preferably 5 g/m2-day or less. (Other optical properties)
A plasma display radiates near infrared rays at a high intensity. When the light transmitting electromagnetic wave shielding film is used particularly for the plasma display, it is preferred to provide the film with a near infrared ray shielding property.
A functional film having a near infrared ray shielding property has preferably a transmittance of 25% or less, more preferably 15% or less, still more preferably 10% or less, each at a wavelength range of from 800 to 1000 nm.
Some of the above-described transparent functional films will next be described more specifically. The infrared ray shielding layer, for example, near infrared absorbing layer is a layer containing a near infrared absorbing colorant such as metal complex compound or is a silver sputtered layer. The silver sputtered layer has a dielectric layer and a metal layer stacked alternately on the substrate by sputtering so that it can shield light of 1000 nm or greater including near infrared rays, far infrared rays and even electromagnetic waves. The dielectric layer contains a transparent metal oxide such as indium oxide or zinc oxide as a dielectric substance. Metals contained in the metal layer are usually silver and silver- palladium alloy. The above-described silver sputtered layer usually has a constitution obtained by stacking a dielectric layer and then thereover stacking three layers, five layers, seven layers or eleven layers.
In the PDP, since a fluorescent substance emitting blue light emits red light in addition to blue light, though slightly, a portion which must be displayed in blue is displayed undesirably in purplish blue. A layer capable of absorbing visible light in a specific wavelength range and therefore having a color tone adjusting function is a layer for correcting emitted light in order to overcome the above-described problem. It therefore contains a colorant which absorbs light of around 595 nm.
The antireflective layer provided with antireflective properties can be formed by, for the purpose of suppressing the reflection of external light, thereby preventing lowering of a contrast, stacking, as a single layer or multilayer, an inorganic substance such as metal oxide, fluoride, suicide, boride, carbide, nitride or sulfide by vacuum deposition, sputtering, ion plating or ion beam assist method or by stacking, as a single layer or multilayer, resins different in refractive index such as acrylic resins and fluorine resins over the functional layer. Or a film subjected to antireflective treatment may be adhered to the film.
A non-glare or anti-glare layer can be formed by preparing an ink of fine powders such as silica, melamine or acryl and then applying the ink to the surface. The ink can be cured by heat or light. A film subjected to non-glare or anti-glare treatment may be adhered to the film.
The light transmitting electromagnetic wave shielding film of the invention has good electromagnetic wave shielding property and light transmitting property so that it is particularly useful as a film for display panel. A display panel film made of the light transmitting electromagnetic wave shielding film of the invention can also be used as an optical filter for plasma display panel after having the above-described functional transparent layers disposed on the film. Such members can be applied to the front of displays such as CRT, PDP, liquid crystal and EL, microwave ovens, electronic apparatuses and printed wiring boards. They are particularly useful for PDP.
The PDP of the invention features a high electromagnetic wave shielding capacity, high contrast and high brightness and can be manufactured at a low cost.
When the light transmitting electromagnetic wave shielding film is used for a plasma display, a light transmitted therethrough is preferably neutral gray or blue gray in order to keep or improve the light emission properties and contrast of the plasma display. In addition, a white color having a color temperature a little higher than that of the standard white color is sometimes preferred.
A color plasma display is said to be insufficient in its color reproducibility. In particular, the emission spectrum of a red display exhibits several emission peaks within a wavelength range of from about 580 ran to 700 nm. Owing to relatively strong emission peaks on a short-wavelength side, red light emission becomes near orange and inferior in color purity. The functional film having a function of selectively reducing unnecessary light emissions from a light emitter or discharged gas which is a cause for the inferior color purity is therefore preferred.
These optical properties can be controlled by the use of a colorant. Use of a near infrared ray absorber is effective for shielding near infrared rays. Use of a colorant capable of selectively absorbing unnecessary light emissions is effective for reducing unnecessary light emissions. Thus desirable optical properties are available. The color tone of the optical filter can also be improved by using a colorant having proper absorption in a visible range.
As the colorant, ordinarily employed dyes and pigments having a desired absorption wavelength in a visible region or compounds known as a near infrared absorber are usable. Although no particular limitation is imposed on the kind of it, examples include commercially available organic colorants such as anthraquinone, phthalocyanine, methine, azomethine, oxazine, immonium, azo, styryl, coumarin, porphyrin, dibenzofuranone, diketopyrrolopyrrole, rhodamine, xanthene, pyrromethene, dithiol, and diiminium compounds.
The temperature on the panel surface of a plasma display is high. Since the temperature of the light transmitting electromagnetic wave shielding film increases with an increase in the ambient temperature, the colorant preferably has heat resistance and does not to cause deterioration, for example, at about 800C.
Some colorants have poor light resistance. When use of such colorants has an influence on the deterioration in the emission of the plasma display or deterioration due to external light such as ultraviolet light or visible light, it is preferred as described above to add an ultraviolet absorber to a functional film or to form a layer which does not permit transmission of ultraviolet light, thereby protecting the colorants from deterioration due to ultraviolet light or visible light.
This will apply to colorants, in addition to those susceptible to temperature or light, susceptible to humidity or a plurality of these factors. Deterioration in colorants may change the transmission properties of an optical filter, which may sometimes result in a change in the color tone or deterioration in the near infrared ray shielding capacity.
Colorants preferably have high solubility or dispersibility in a solvent in order to dissolve or disperse in a resin composition for the formation of the transparent substrate or in a coating composition for the formation of the coating layer.
The concentration of the colorant can be determined as needed, depending on the absorption wavelength- absorption coefficient of the colorant, transmission properties- transmittance which the light transmitting electromagnetic wave shielding film is required to have, kind of the medium in which the colorant is to be dispersed, or the kind or thickness of a coating film.
When the colorant is contained in the functional film, it may be added to the transparent substrate or a colorant-containing layer may be applied to the surface of the substrate. Two or more colorants different in absorption wavelength may be mixed and contained in one layer or two or more layers may each contain a colorant.
Some colorants deteriorate when brought into contact with a metal. When such a colorant is used, a functional film containing the colorant is preferably placed so that the colorant-containing layer is not brought into contact with a metal silver portion or conductive metal portion on the light transmitting electromagnetic wave shielding film.
The light transmitting electromagnetic wave shielding film having a functional film attached thereto is usually mounted on a display so that the functional film is located on the outside and the adhesive layer is located on the display side.
For the purpose of avoiding deterioration in the electromagnetic wave shielding capacity of the light transmitting electromagnetic wave shielding film, the metal silver portion or conductive metal portion is preferably earthed. It is therefore preferred to form a conduction portion for earthing on the light transmitting electromagnetic wave shielding film and bring this conduction portion into electrical contact with an earthing portion of the display itself. The conduction portion is preferably located around the metal silver portion or conductive metal portion along the periphery of the light transmitting electromagnetic wave shielding film. The conduction portion may be a mesh pattern layer or an unpatterned layer, for example, a metal foil solid layer. To form a good electrical contact with the earthing portion of the display itself, an unpatterned conduction portion such as a metal foil solid layer is preferred.
When the conduction portion is, as a metal foil solid, not patterned and/or the conduction portion has sufficiently high mechanical strength, it can be preferably used as an electrode as is.
It is sometimes preferred to form an electrode at the conduction portion in order to protect the conduction portion and/or in order to improve the electrical contact with the earthing portion when the conduction portion is a mesh pattern layer. Although no particular limitation is imposed on the shape of the electrode, it has preferably such a shape that the entire conduction portion is covered therewith.
As the material for the electrode, a paste made of a single substance such as silver, copper, nickel, aluminum, chromium, iron, zinc or carbon, alloy of two or more of these single substances, mixture of the above-described single substance or alloy with a synthetic resin, or mixture of the above-described single substance or alloy with a borosilicate glass is usable. Printing and application of the paste can be performed in a conventional manner. A commercially available conductive tape is also used preferably. As the conductive tape, a one-sided adhesive type or double-sided adhesive type tape using a carbon-dispersed conductive adhesive and having conductivity on both sides thereof is preferred. The thickness of the electrode is not particular limited, but is from about several μm to several mm.
The light transmitting electromagnetic wave shielding film of the invention has good electromagnetic wave shielding property and light transmitting property so that it can be applied to the front face of displays such as CRT, PDP, liquid crystal and EL, microwave ovens, electronic devices and printed wiring boards. It is particularly useful for PDP. The invention makes it possible to provide an optical filter excellent in optical properties and capable of maintaining or improving the image quality of a plasma display without severely damaging its luminance. In addition, the invention makes it possible to provide an optical filter excellent in the shielding performance of electromagnetic waves which are emitted from the plasma display and may have an adverse health effect, and capable of effectively shielding near infrared rays at from about 800 to 1000 nm irradiated from the plasma display so that it has no adverse effect on the wavelength used by a remote controller of a peripheral electronic device or transmission-system optical communication and can prevent malfunction of them. The invention also makes it possible to provide an optical filter excellent in weather resistance at a low cost.
Examples
The characteristics of the invention will hereinafter be described specifically by Examples and Comparative Examples. The materials, using amounts, ratios, details of the treatment and treatment procedures shown below in Examples can be changed as needed insofar as they do not depart from the gist of the invention. It should therefore be noted that the scope of the invention is not construed limitedly by the below-described specific examples. [Example 1-1]
A light transmitting electromagnetic wave shielding film with a conductive pattern was prepared by preparing a support, forming an adhesion facilitating layer on both sides of a transparent substrate (support), and printing a paste made of silver. <Transparent substrate>
A polyethylene terephthalate resin obtained by polycondensation with antimony trioxide as a main catalyst and having an intrinsic viscosity of 0.66 was dried to give a water content of 50 ppm or less and was melted in an extruder having a heater temperature set at from 280 to 3000C.
The PET resin thus melted was discharged from a die portion onto a chill roll to which static electricity had been applied, whereby an amorphous base was obtained. The amorphous base thus obtained was stretched by 3.1 times in the base traveling direction and 3.9 times in the width direction to yield a support having a thickness of 96 μm. Preparation of silver paste>
After reduction of a silver nitrate solution to prepare fine metal silver particles in accordance with the silver-sol preparation process by Carey-Lea (refer to: M. Carey Lea, Brit. J. Photog., 24, 297(1877) and 27, 279(1880)), a gold chloride acid solution was added thereto to prepare fine silver-gold particles composed mainly of silver. The resulting particles were subjected to ultrafiltration to remove the by-produced salt. As a result of microscopic observation of the size of the resulting fine particles, it was about 10 nm.
A paste was then prepared by mixing these particles with a binder composed of a solvent containing methyl ethyl ketone and an acrylic resin. <Adhesion facilitating layer: back layer>
Coating solutions having the below-described composition were applied to each sample of the invention successively and dried, whereby a back layer was formed.
The biaxially-stretched polyethylene terephthalate support was subjected, on the surface thereof, to corona discharge treatment under the conditions of 727 J/m2 while feeding at a feed speed of 105 m/min and an antistatic layer coating solution having the below-described composition was applied to the resulting support by the bar coat process.
The coating solution was applied in an amount of 7.1 cc/m2 and then dried at 180°C for 1 minute in an air float drying zone, whereby an antistatic layer was obtained. (Antistatic layer coating solution)
Distilled water 78.1 parts by mass
Polyacrylic resin ("Jurymer ET-410", trade name; product of Nippon Junyaku, solid content: 30%) 30.9 parts by mass
Acicular tin oxide particles ("FS-IOD", trade name; product of Ishihara Sangyo, solid content: 20%) 131.1 parts by mass
Carbodiimide compound ("Carbodilite V-02-L2: trade name; product of Nisshinbo, solid content: 40%) 6.4 parts by mass
Surfactant ("Sandet BL", trade name; product of Sanyo
Chemical, solid content: 44.6%) 1.4 parts by mass
Surfactant (NAROACTY HN- 100", trade name; product of Sanyo
Chemical, solid content: 100%) 0.7 part by mass
Dispersion of granular silica particles ("Seahostar KE- W30", trade name; product of Nippon Shokubai, 0.3 μm, solid content: 20%) 5.0 parts by mass
A surface layer coating solution having the below-described composition was then applied onto the antistatic layer while keeping the feeding speed at 105 m/min.
The solution was applied in an amount of 5.05 cmVm2 and then dried at 16O0C for 1 minute in an air float drying zone, whereby a two-layer back layer was obtained. (Surface layer coating solution)
Distilled water 941.0 parts by mass
Polyacrylic resin ("Jurymer ET-410", trade name; product of Nippon Junyaku, solid content: 30%) 57.3 parts by mass
Epoxy compound ("Denacol EX-521", trade name; product of Nagase Chemtex, solid content: 100%) 1.2 parts by mass
Surfactant ("Sandet BL", trade name; product of Sanyo
Chemical, solid content: 44.6%) 0.5 part by mass
<Adhesion facilitating layer: adhesion facilitating layer for silver paste printing>
In a similar manner to that employed for the preparation of the back layer except for the omission of the acicular tin oxide particles, an adhesion facilitating layer for silver paste printing was applied to the transparent substrate on the side opposite to the back layer.
<Silver paste printing>
The below-described silver paste was applied to the transparent substrate thus obtained by the screen printing.
Heat treatment at 130°C was then performed for 10 minutes. The mesh pattern thus obtained was a silver lattice-like mesh having a line width of 18 μm and pitch of 300 μm.
The sample was then calendered by passing it between calender rollers made of two pairs of metal rolls under a linear pressure of 2940 N/cm (300 kgf/cm).
The sample was then subjected to rust inhibiting treatment with an aqueous solution of benzotriazole (0.01 mole/L). The rust inhibiting treatment was performed by dipping the sample in the aqueous solution for 3 minutes.
The rust inhibiting treatment was followed by washing with water and drying, whereby a sample of the invention was obtained. (Preparation of Comparative sample)
The sample obtained above was designated as "Sample 1-1" as shown in Table 1-1, while a sample without an adhesion facilitating layer for Ag pasting and a sample not subjected to calendering were prepared respectively. <Evaluation method> (Surface resistivity)
Surface resistivity was measured using a low resistivity meter "Loresta GP/ASP probe" (trade name; product of Mitsubishi Chemical). (Surface hardness)
A scratch test using a pencil was performed and the sample from which a pattern portion made of silver was removed was evaluated as B, while the sample from which a pattern portion made of silver was not removed was evaluated as A. (Evaluation of peel strength)
An acrylic adhesive in the sheet form was adhered to the adhesion facilitating layer of each sample on the side opposite to the mesh pattern side and it was stacked over the glass substrate.
The above-described 180° peel strength was measured. Each sample exhibited a peel strength of 20 N/m or greater. After storage for 72 hours at 60° and relative humidity of 90%, the 180° peel strength was also measured. (Wet heat resistance)
After the sample was stored for 72 hours at 60°C and relative humidity of 90%, the discoloration degree of the pattern made of silver was evaluated. The sample showing the evidence of discoloration was rated as B, while the sample showing no evidence of discoloration was rated A.
Table 1-1
Figure imgf000082_0001
As is apparent from Table 1-1, the sample of the invention obtained in Example 1-1 s excellent in time-dependent change in peel strength under heat and wet conditions and also excellent in surface hardness. By the calendering treatment, it can have markedly high conductivity and therefore have a high electromagnetic wave shielding property. [Example 1-2]
In a similar manner to Example 1-1 except that mesh pattern made of silver was formed by intaglio printing, an electromagnetic wave shielding film was formed. As a result of evaluation on the resulting film in a similar manner to Example 1-1, the electromagnetic wave shielding film thus obtained had high conductivity and was excellent in surface hardness and time-dependent wet and heat resistance. [Example 1-3] (Fabrication of optical filter)
A glass plate was stacked, via an acrylic light transmitting adhesive having a thickness of 25 μm, over a film piece obtained by removing a 20-mm peripheral portion from the light transmitting electromagnetic wave shielding film obtained in Example 1-1 and having a light transmitting electromagnetic wave shielding capacity. Colorants ("PS- Red-G" and "PS-Violet-RC", each trade name; product of Mitsui Chemical) for regulating the transmission properties of an optical filter were incorporated in the acrylic light transmitting adhesive layer. An antireflective film ("Realook 772 UV", trade name; product of NOF) having an infrared ray shielding capacity was stacked, via an adhesive, over the other main surface of the glass plate, whereby an optical filter was fabricated.
The metal mesh of the optical filter thus obtained was black so that the display image was not tinged with a metal color. In addition, it had electromagnetic wave shielding capacity and infrared ray shielding capacity which did not have an adverse effect on its practical use. Use of the antireflective layer contributed to excellent visibility. Moreover, owing to the colorants added to the filter, it had a toning function. As a result, it is suited as an optical filter for plasma display or the like. [Example 2-1] A plastic film having a mesh pattern was prepared by preparing a transparent substrate as described below, disposing an adhesion facilitating layer on both sides of the transparent substrate, and printing a paste made of silver. <Transparent substrate>
A polyethylene terephthalate (PET) resin obtained by polycondensation with antimony trioxide as a main catalyst and having an intrinsic viscosity of 0.66 was dried to give a water content of 50 ppm or less and was melted in an extruder having a heater temperature set at from 280 to 3000C.
The PET resin thus melted was discharged from a die portion onto a chill roll to which static electricity had been applied, whereby an amorphous base was obtained. The amorphous base thus obtained was stretched by 3.1 times in the base traveling direction and 3.9 times in the width direction to yield a transparent substrate having a thickness of 96 μm. Preparation of silver paste>
After reduction of a silver nitrate solution to prepare fine metal silver particles in accordance with the silver-sol preparation process by Carey-Lea (refer to: M. Carey Lea, Brit. J. Photog., 24, 297(1877) and 27, 279(1880)), a gold chloride acid solution was added thereto to prepare fine silver-gold particles having silver as a main component. The resulting particles were subjected to ultrafiltration to remove the by-produced salt. As a result of microscopic observation of the size of the resulting fine particles, it was about 10 nm.
A paste was then prepared by mixing these particles with a binder composed of a solvent containing methyl ethyl ketone and an acrylic resin. <Silver paste printing>
The silver paste was printed on the transparent substrate thus obtained by the intaglio printing using a rolled cylinder. The length of the sample was set at 100 m. The sample was then heated at 1300C for 10 minutes. The mesh pattern thus obtained was a silver lattice-like mesh having a line width of 18 μm and pitch of 300 μm.
The sample was then calendered by passing it between calender rollers made of two pairs of metal rolls under a linear pressure of 2940 N/cm (300 kgf/cm). <Adhesion facilitating layer: back layer>
Coating solutions having the below-described compositions were successively applied to each sample of the invention and dried under the below-described conditions, whereby a back layer was formed.
The transparent support was subjected, on the surface thereof, to corona discharge treatment under the conditions of 727 J/m2 while feeding at a feed speed of 105 m/min and an antistatic layer coating solution having the below-described composition was applied to the resulting support by the bar coating process.
The coating solution was applied in an amount of 7.1 cc/m2 and then dried at 1800C for 1 minute in an air float drying zone, whereby an antistatic layer was obtained. (Antistatic layer coating solution)
Distilled water 781.7 parts by mass
Polyacrylic resin ("Jurymer ET-410", trade name; product of Nippon Junyaku, solid content: 30%) 30.9 parts by mass
Acicular tin oxide particles ("FS-10D", trade name; product of Ishihara Sangyo, solid content: 20%) 131.1 parts by mass
Carbodiimide compound ("Carbodilite V-02-L2: trade name; product of Nisshinbo, solid content: 40%) 6.4 parts by mass
Surfactant ("Sandet BL", trade name; product of Sanyo
Chemical, solid content: 44.6%) 1.4 parts by mass
Surfactant ("NAROACTY HN- 100", trade name; product of Sanyo Chemical, solid content: 100%) 0.7 part by mass Dispersion of granular silica particles ("Seahostar KE-W30", trade name; product of Nippon Shokubai, 0.3 μm, solid content: 20%) 5.0 parts by mass
A surface layer coating solution having the below-described composition was then applied onto the antistatic layer while keeping the feed speed at 105 m/min.
The solution was applied in an amount of 5.05 cc/m2 and then dried at 160°C for 1 minute in an air float drying zone, whereby a two-layer back layer was prepared. (Surface layer coating solution)
Distilled water 941.0 parts by mass
Polyacrylic resin ("Jurymer ET-410", trade name; product of Nippon Junyaku, solid content: 30%) 57.3 parts by mass
Epoxy compound ("Denacol EX-521", trade name; product of Nagase Chemtex, solid content: 100%) 1.2 parts by mass
Surfactant ("Sandet BL", trade name; product of Sanyo
Chemical, solid content: 44.6%) 0.5 part by mass
<Adhesion facilitating layer: adhesion facilitating layer on the side of mesh-like thin lines> In a similar manner to that employed for the preparation of the back layer except for the omission of the acicular tin oxide particles, the adhesion facilitating layer was prepared on the support on the side opposite to the back layer. <Electrolytic plating>
After printing the silver paste, plating was performed using plating solutions as described below, whereby a conductive film having a conductive metal portion made of silver and copper was prepared. The surface resistivity of the film before electrolytic plating was 8 Ω/D. Plating treatment
Acid washing 35°C 30 seconds Electrolytic plating 1 35 °C 30 seconds
Electrolytic plating 2 35 0C 30 seconds
Electrolytic plating 3 35 0C 30 seconds
Electrolytic plating 4 35 °C 30 seconds
Rinsing 3* 35 0C 10 seconds
Rinsing 4* 35 0C 10 seconds
Rust inhibitive solution 35 0C 30 seconds
Rinsing 5* 25 0C 60 seconds
Rinsing 6* 25 °C 60 seconds
Drying 50 °C 60 seconds
*Washing with water was performed by a two-tank counterflow system from Rinsing 2 to 3, from Rinsing 4 to 3 and from Rinsing 6 to 5. [Electrolytic plating solution: formulation of IL]
Composition of electrolytic copper plating solution (a replenisher solution has also a similar composition)
Copper sulfate pentahydrate 75 g
Sulfuric acid 19O g
Hydrochloric acid (35%) 0.06 mL
"Copper Gleam PCM" 5 mL
(trade name; product of Rohm and Haas Electronic Materials) Pure water to make 1 liter Balance
[Rinsing solution: formulation of IL (common to Rinsing 1 to 6)] Deionized water (having a conductivity of 5 μS/cm or less) 1000 mL pH adjusted to pH 6.5
An aqueous solution of benzotriazole (0.01 mole/L) was used for rust inhibiting treatment. The rust inhibiting treatment was performed by dipping in the aqueous solution for 3 minutes.
The rust inhibiting treatment was followed by washing with water and drying, whereby a sample of the invention was obtained. [Examples 2-2 and 2-3 and Comparative Example 2-1]
Various samples were prepared under the conditions shown in Table 2-1. <Evaluation method> (Surface resistivity)
Surface resistivity was measured using a low resistivity meter "Loresta GP/ASP probe" (trade name; product of Mitsubishi Chemical). (Surface hardness)
A scratch test using a pencil was performed in accordance with JIS Scratch hardness (pencil method) and the sample from which a pattern portion made of silver was removed was evaluated as B, while the sample from which a pattern portion made of silver was not removed was evaluated as A. (Evaluation of peel strength)
An acrylic adhesive in the sheet form was adhered to the adhesion facilitating layer of each sample on the side opposite to the mesh pattern side and it was stacked over the glass substrate.
The above-described 180° peel strength was measured. Each sample exhibited a peel strength of 20 N/m or greater. After storage for 72 hours at 60° and relative humidity of 90%, the 180° peel strength was also measured. (Wet heat resistance)
After the sample was stored for 72 hours at 600C and relative humidity of 90%, the discoloration degree of the pattern made of silver was evaluated. The sample showing the evidence of discoloration was rated as B, while the sample showing no evidence of discoloration was rated A.
Evaluation results are shown in Table 2-1.
Table 2-1
Figure imgf000089_0001
As is apparent from Table 2-1, the samples of the invention obtained in Examples exhibit good conductivity (low surface resistivity) and have good peel strength after the time passage under heat and wet conditions. The sample of Example 2-2 is a little inferior in surface hardness and peel strength after time passage under wet and heat conditions because it has no adhesion facilitating layer on the side of mesh-like thin lines. [Example 2-4] (Fabrication of optical filter)
A glass plate was stacked, via an acrylic light transmitting adhesive having a thickness of 25 μm, over a film piece obtained by removing a 20-mm peripheral portion from the light transmitting electromagnetic wave shielding film obtained in Example 2-1. Colorants ("PS-Red-G" and "PS-Violet-RC", each trade name; product of Mitsui Chemical) for regulating the transmission properties of an optical filter were incorporated in the acrylic light transmitting adhesive layer. An antireflective film ("Realook 772 UV", trade name; product of NOF) having an infrared ray shielding capacity was stacked, via an adhesive, over the other main surface of the glass plate, whereby an optical filter was fabricated.
The metal mesh of the optical filter thus obtained was black. When the optical filter was used for a plasma display panel, the display image was not tinged with a metal color. In addition, it had electromagnetic wave shielding capacity and infrared ray shielding capacity which did not adversely affect its practical use. The antireflective layer contributed to excellent visibility of the optical filter. Owing to the colorant added to the filter, it had a toning function. As a result, it is suited as an optical filter for plasma display or the like.
Industrial Applicability
By inserting an adhesion facilitating layer between a transparent support and a printed pattern composed mainly of silver, the present invention makes it possible to provide, at a high productivity, a light transmitting electromagnetic wave shielding film excellent in chemical resistance such as brine resistance, excellent in durabilities such as heat resistance and wet heat resistance, having a high electromagnetic wave shielding property, and exhibiting a high light transmittance with less light scattering; and a film for display panel, optical filter for display panel and plasma display panel each using the film.
The present invention makes it possible to provide a light transmitting electromagnetic wave shielding film which can be prepared by a smaller number of steps compared with the steps of a metal mesh preparation process using etching while utilizing photolithography, is available at a low cost, and has sufficient conductivity, that is, sufficient electromagnetic wave shielding property, or which has sufficient surface hardness, is excellent in adhesion, is excellent in durabilities such as heat resistance and wet heat resistance, and has a high light transmittance with less light scattering; and an optical filter and plasma display panel using the film. The entire disclosure of each and every foreign patent application from which the benefit of foreign priority has been claimed in the present application is incorporated herein by reference, as if fully set forth.

Claims

1. A light transmitting electromagnetic wave shielding film, which comprises: a transparent substrate; a first adhesion facilitating layer; and a printed pattern composed mainly of silver, in this order, wherein the printed pattern composed mainly of silver is a printed pattern of a conductive composition containing silver in an amount of 60 mass% or greater relative to metals constituting the printed pattern.
2. The light transmitting electromagnetic wave shielding film according to claim 1, wherein the printed pattern is treated with calender rolls.
3. The light transmitting electromagnetic wave shielding film according to claim 1 or 2, wherein the printed pattern contains a rust inhibitive.
4. The light transmitting electromagnetic wave shielding film according to any of claims 1 to 3, which further comprises a peelable protective film.
5. The light transmitting electromagnetic wave shielding film according to any of claims 1 to 4, wherein the transparent substrate is a plastic film.
6. The light transmitting electromagnetic wave shielding film according to any of claims 1 to 5, wherein the printed pattern is a mesh pattern which is made of thin lines each having a line width of from 1 μm to 40 μm and continues for 3 m or greater.
7. The light transmitting electromagnetic wave shielding film according to any of claims 1 to 6, which further comprises: a second adhesion facilitating layer provided on a surface of the transparent substrate having no printed pattern; and an adhesive layer on the second adhesion facilitating layer, wherein the adhesive layer has a peel strength of 20 N/m or greater when brought into contact with glass.
8. The light transmitting electromagnetic wave shielding film according to claim 7, wherein the adhesive layer has a peel strength of 20 N/m or greater when brought into contact with glass after left for 72 hours at 600C and relative humidity of 90% or greater.
9. A process for preparing a light transmitting electromagnetic wave shielding film, the process comprising: disposing a first adhesion facilitating layer on a transparent substrate; and then disposing a printed pattern composed mainly of silver on the first adhesion facilitating layer, wherein the printed pattern composed mainly of silver is a printed pattern of a conductive composition containing silver in an amount of 60 mass% or greater relative to metals constituting the printed pattern.
10. The process for preparing a light transmitting electromagnetic wave shielding film according to claim 9, which further comprises subjecting the printed pattern to a treatment with calender rolls.
11. The process for preparing a light transmitting electromagnetic wave shielding film according to claim 10, wherein the treatment with calender rolls is performed at a linear pressure of 1960 N/cm (200 kgf/cm) or greater.
12. An optical filter for plasma display panel, which comprises a light transmitting electromagnetic wave shielding film according to any of claims 1 to 8.
13. A plasma display panel, which comprises a light transmitting electromagnetic wave shielding film according to any of claims 1 to 8.
14. A light transmitting electromagnetic wave shielding film, which comprises: a transparent substrate; and mesh-like thin lines composed mainly of silver and each having a width of from 1 μm to 30 μm, wherein the mesh-like thin lines are obtained by forming a mesh pattern on the transparent substrate by printing, and then electrolytic plating the mesh pattern, and the mesh-like thin lines are continuous for at least 3 m in a lengthwise direction of the light transmitting electromagnetic wave shielding film.
15. The light transmitting electromagnetic wave shielding film according to claim 14, wherein the transparent substrate has a surface resistivity of from 1 Ω/D to 100 Ω/D after the formation of the mesh pattern by printing, and the mesh pattern is then subjected to continuous electrolytic plating.
16. The light transmitting electromagnetic wave shielding film according to claim 14 or 15, wherein after the formation of the mesh pattern by printing, the mesh pattern is subjected to a treatment with calender rolls.
17. The light transmitting electromagnetic wave shielding film according to claim 16, wherein the treatment with calender rolls is performed at a linear pressure of 1960 N/cm (200 kgf/cm) or greater.
18. The light transmitting electromagnetic wave shielding film according to any of claims 14 to 17, wherein the mesh-like thin lines contain a rust inhibitive.
19. The light transmitting electromagnetic wave shielding film according to any of claims 14 to 18, which further comprises a first adhesion facilitating layer between the transparent substrate and the mesh-like thin lines.
20. The light transmitting electromagnetic wave shielding film according to any of claims 14 to 19, which further comprises: a second adhesion facilitating layer provided on a surface of the transparent substrate having no mesh-like thin lines; and an adhesive layer on the second adhesion facilitating layer, wherein the adhesive layer has a peel strength of 20 N/m or greater when brought into contact with glass.
21. The light transmitting electromagnetic wave shielding film according to claim 20, wherein the peel strength after leaving the light transmitting electromagnetic wave shielding film for 72 hours at 60°C and relative humidity of 90% or greater is 20 N/m or greater.
22. The light transmitting electromagnetic wave shielding film according to any of claims 14 to 21, wherein the electrolytic plating is performed with at least one material selected from the group consisting of copper, nickel, zinc, tin and cobalt.
23. An optical filter, which comprises a light transmitting electromagnetic wave shielding film according to any of claims 14 to 22.
24. A plasma display panel, which comprises a light transmitting electromagnetic wave shielding film according to any of claims 14 to 22.
PCT/JP2007/051852 2006-01-31 2007-01-30 Light transmitting electromagnetic wave shielding film, optical filter and plasma display panel WO2007088992A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2006-023209 2006-01-31
JP2006023209A JP4705857B2 (en) 2006-01-31 2006-01-31 Translucent film, process for producing translucent film, translucent electromagnetic wave shield film, process for producing translucent electromagnetic wave shield film, optical filter and plasma display panel
JP2006023096A JP4705856B2 (en) 2006-01-31 2006-01-31 Translucent film, process for producing translucent film, translucent electromagnetic wave shield film, process for producing translucent electromagnetic wave shield film, optical filter, and plasma display panel
JP2006-023096 2006-01-31

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JP2004146536A (en) * 2002-10-23 2004-05-20 Mitsui Chemicals Inc Filter for display
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