WO2010055742A1 - Conductive paste, electromagnetic wave-shielding film using same, and electromagnetic wave-shielding flexible printed wiring board - Google Patents

Conductive paste, electromagnetic wave-shielding film using same, and electromagnetic wave-shielding flexible printed wiring board Download PDF

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Publication number
WO2010055742A1
WO2010055742A1 PCT/JP2009/067715 JP2009067715W WO2010055742A1 WO 2010055742 A1 WO2010055742 A1 WO 2010055742A1 JP 2009067715 W JP2009067715 W JP 2009067715W WO 2010055742 A1 WO2010055742 A1 WO 2010055742A1
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Prior art keywords
isocyanate
conductive paste
metal powder
component
urethane
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PCT/JP2009/067715
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French (fr)
Japanese (ja)
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浩平 下田
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住友電気工業株式会社
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Priority to CN2009801051008A priority Critical patent/CN101952902B/en
Publication of WO2010055742A1 publication Critical patent/WO2010055742A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • 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
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/09—Use of materials for the conductive, e.g. metallic pattern
    • H05K1/092—Dispersed materials, e.g. conductive pastes or inks
    • H05K1/095—Dispersed materials, e.g. conductive pastes or inks for polymer thick films, i.e. having a permanent organic polymeric binder
    • 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
    • H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
    • H05K9/0083—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising electro-conductive non-fibrous particles embedded in an electrically insulating supporting structure, e.g. powder, flakes, whiskers
    • 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
    • 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
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/0213—Electrical arrangements not otherwise provided for
    • H05K1/0216—Reduction of cross-talk, noise or electromagnetic interference
    • H05K1/0218—Reduction of cross-talk, noise or electromagnetic interference by printed shielding conductors, ground planes or power plane
    • 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
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/03—Use of materials for the substrate
    • H05K1/0393—Flexible materials
    • 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
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/01—Dielectrics
    • H05K2201/0137—Materials
    • H05K2201/0145—Polyester, e.g. polyethylene terephthalate [PET], polyethylene naphthalate [PEN]

Definitions

  • the present invention relates to a conductive paste, an electromagnetic wave shielding film using the conductive paste, and an electromagnetic wave shielding flexible printed wiring board, and more particularly to a flexible printed wiring board that requires bending resistance.
  • the conductive paste is a paste obtained by mixing a conductive filler such as carbon black, graphite powder, noble metal powder, copper powder, nickel powder, etc., a binder resin, and a solvent. This is applied onto a film or substrate by a method such as screen printing to form a pattern, and the resin is solidified to form conductive wiring. With recent downsizing and weight reduction of electronic components, highly conductive conductive pastes are required for such applications.
  • Patent Document 1 discloses a conductive silver paste using silver as a conductive filler.
  • the shape of the silver powder used as the conductive filler is not limited, and it is granular, scale-like, plate-like, dendritic, cocoon-like, dice-like, or the like having a size of 0.1 to 100 ⁇ m.
  • the binder resin a saturated copolymerized polyester resin and a blocked isocyanate are used.
  • Patent Document 2 discloses a silver powder in which primary particles having a particle diameter of 0.1 to 5 ⁇ m are three-dimensionally connected in order to improve the bending resistance of a conductive paste, and a number average molecular weight.
  • An electrically conductive paste mainly composed of 3000 or more binders, a curing agent and a solvent is disclosed.
  • the binder include polyurethane resins and polyester resins.
  • Patent Document 3 discloses a conductive silver paste having improved conductivity and shielding characteristics by combining silver powder having a specific particle diameter, and an electromagnetic wave shielding film using the same.
  • the shield layer formed by applying and solidifying the conductive paste has heat resistance, surface smoothness, and bending resistance in addition to conductivity and electromagnetic shielding properties. Sex is required.
  • a movable part such as a hinge part of a mobile phone
  • durability at a smaller bending radius is required due to downsizing of the device, so that it is a problem to improve the bending resistance.
  • the polyester resin is a resin obtained by condensation polymerization of an acid component such as a polyvalent carboxylic acid or an acid anhydride and an alcohol component such as a polyhydric alcohol.
  • the polyester resin is appropriately selected by selecting the type of the acid component or alcohol component. Its characteristics can be controlled. For example, when many flexible components such as aliphatic dicarboxylic acid are used, the flexibility is improved. However, if a large amount of flexible components are used, the heat resistance is lowered and the required characteristics cannot be satisfied. In order to increase the heat resistance, it is necessary to increase the proportion of rigid aromatic components such as terephthalic acid, but this reduces flexibility.
  • the present invention provides a conductive paste capable of forming an electromagnetic wave shielding layer having both flexibility and heat resistance and excellent bending resistance, and an electromagnetic wave shielding film using the same.
  • the present invention is a conductive paste containing a conductive metal powder, a urethane-modified polyester resin, and a blocked isocyanate, and the urethane-modified polyester resin reacts an isocyanate component containing an acid component, an alcohol component, and an aromatic isocyanate.
  • the total of aromatic components contained in the acid component, alcohol component, and isocyanate component is 5 mol% or more and 50 mol% or less with respect to the total of the acid component, alcohol component, and isocyanate component.
  • This is a conductive paste (first invention of the present application).
  • the binder resin a urethane-modified polyester resin modified with an isocyanate component containing an aromatic isocyanate is used.
  • the sum total of the aromatic component contained in an acid component, an alcohol component, and an isocyanate component shall be 5 mol% or more and 50 mol% or less with respect to the sum total of an acid component, an alcohol component, and an isocyanate component.
  • the hydroxyl value of the urethane-modified polyester resin is preferably 5 mgKOH / g or more and 60 mgKOH / g or less (the second invention of the present application).
  • the hydroxyl value is an index indicating the molecular weight with respect to the number of crosslinking points (hydroxyl groups that react with blocked isocyanate) of the urethane-modified polyester resin. When the hydroxyl value is large, the molecular weight is small, and when the hydroxyl value is small, the molecular weight is large.
  • the hydroxyl value is less than 5 mgKOH / g, the molecular weight is large and the flexibility is excellent, but the heat resistance is lowered by reducing the number of crosslinking points for reacting with the blocked isocyanate.
  • the hydroxyl value exceeds 60 mgKOH / g, the molecular weight decreases, and the heat resistance is improved but the flexibility is lowered.
  • the blocked isocyanate has a number average molecular weight of 500 or more and 3000 or less, and is preferably a polyfunctional block polyisocyanate compound in which an adduct isocyanate of an isocyanate monomer and a polyhydroxy compound is blocked with a blocking agent (the third of the present application invention). Since such an adduct type isocyanate has a large amount of functional groups (isocyanate groups) in one molecule, the crosslinking density of the urethane-modified polyester resin after the reaction can be increased, and the heat resistance can be improved.
  • the mixing ratio of the urethane-modified polyester resin and the blocked isocyanate is 0.8 or more in terms of the molar ratio (NCO / OH) of the hydroxyl group (OH) of the urethane-modified polyester resin and the isocyanate group (NCO) of the blocked isocyanate. It is preferable that it is 3.0 or less (the fourth invention of the present application).
  • the amount of blocked isocyanate is less than this range, the crosslinking density of the urethane-modified polyester resin is lowered, and the heat resistance is lowered.
  • the heat resistance may become low because the isocyanate which does not contribute to reaction remains in binder resin.
  • a more preferable range of the molar ratio is 1.0 or more and 2.0 or less.
  • the conductive metal powder is composed of a metal powder A having an average particle diameter of 0.5 ⁇ m to 20 ⁇ m and a metal powder B having an average particle diameter of 100 nm or less, and the content ratio of the metal powder A and the metal powder B is a weight ratio. 99.5: 0.5 to 70:30, and the content ratio of the conductive metal powder is preferably 50% by weight to 85% by weight with respect to the solid content of the conductive paste. 5 invention).
  • the content ratio of the conductive metal powder is increased, the conductivity is improved. However, when the content is too high, the flexibility of the conductive paste is lowered and the bending resistance is deteriorated, so that both conductivity and bending resistance are achieved.
  • the content ratio of the conductive metal powder is preferably 50% by weight or more and 85% by weight or less.
  • the conductivity is improved and the smoothness of the surface after the conductive paste is applied can be improved. Since the smoothness of the surface affects the electromagnetic shielding characteristics as well as the electrical conductivity, the electromagnetic shielding characteristics can be further improved by improving the electrical conductivity and smoothness.
  • the present invention also provides an electromagnetic wave shielding film having a layer made of the above conductive paste on a substrate (the sixth invention of the present application). Moreover, the electromagnetic wave shield flexible printed wiring board which has a layer which consists of said electroconductive paste is provided (this invention 7th invention).
  • Such an electromagnetic wave shielding film and an electromagnetic wave shielding flexible printed wiring board are excellent in bending resistance and heat resistance, conductivity, and electromagnetic wave shielding characteristics.
  • a conductive paste capable of forming an electromagnetic wave shielding layer having both flexibility and heat resistance and excellent in bending resistance, an electromagnetic wave shielding film using the same, and an electromagnetic wave shielding flexible printed wiring board. Can do.
  • the urethane-modified polyester resin used in the present invention will be described.
  • the urethane-modified polyester resin is obtained by reacting an acid component, an alcohol component, and a urethane component.
  • a polyester resin is obtained by condensation polymerization of an acid component such as a polyvalent carboxylic acid or an anhydride thereof and an alcohol component such as a polyhydric alcohol.
  • a urethane-modified polyester resin is obtained by reacting the terminal hydroxyl group of the obtained polyester resin with an isocyanate component.
  • the isocyanate component is preferably added and reacted after the reaction between the acid component and the alcohol component, but the acid component, the alcohol component, and the isocyanate component may be reacted at the same time.
  • the acid component is not particularly limited as long as it is a polyvalent carboxylic acid or an anhydride thereof.
  • aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, orthophthalic acid and the like, succinic acid, adipic acid
  • examples thereof include aliphatic dicarboxylic acids such as glutaric acid and sebacic acid and anhydrides thereof, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and anhydrides thereof. Two or more of these may be used in combination.
  • the alcohol component is not particularly limited as long as it is a polyhydric alcohol.
  • ethylene glycol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexane examples thereof include aliphatic glycols such as diols, aromatic glycols, alicyclic glycols, trivalent or higher alcohols such as trimethylolpropane and pentaerythritol. Two or more of these may be used in combination.
  • the isocyanate component has two or more isocyanate groups in one molecule, and an aromatic isocyanate having an aromatic ring in the molecule is essential.
  • aromatic isocyanate include xylene diisocyanate, tolylene diisocyanate, 4,4 'diphenylmethane diisocyanate, naphthalene diisocyanate, and biphenylene diisocyanate. Two or more of these may be used in combination.
  • aliphatic diisocyanate such as trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, trimethylene diisocyanate, alicyclic diisocyanate such as cyclohexane diisocyanate, etc. are used in combination as long as the spirit of the present invention is not impaired. May be.
  • the total of aromatic components in the acid component, alcohol component, and isocyanate component is 5 mol% or more and 50 mol% or less with respect to the total of all components. These materials are reacted in a conventional manner to obtain a urethane-modified polyester resin.
  • the blocked isocyanate used in the present invention is obtained by blocking the terminal isocyanate group of a polyfunctional isocyanate with a blocking agent.
  • the blocking agent is dissociated by heating, and an isocyanate group is generated. This isocyanate group reacts with the hydroxyl group of the urethane-modified polyester resin to crosslink the urethane-modified polyester resin.
  • the blocking agent examples include compounds having an active hydroxyl group such as alcohols, phenols, acid amides, oximes, and active methylene.
  • any isocyanate such as trimethylene diisocyanate, hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI) can be used.
  • HDI hexamethylene diisocyanate
  • MDI diphenylmethane diisocyanate
  • an adduct type isocyanate of an isocyanate monomer and a polyhydroxy compound represented by the general formula (I) is preferable.
  • R1 to R3 represent a group obtained by removing an isocyanate group from an aliphatic, alicyclic or aromatic diisocyanate, and R4 represents a group obtained by removing a hydroxyl group from a polyhydric alcohol compound.
  • a polyhydroxy compound is a compound having two or more hydroxyl groups in one molecule, such as glycerin, trimethylolethane, trimethylolpropane, 1,4-butanediol, neopentylglycol, 1,6-hexanediol, etc. Is done.
  • the diisocyanate include trimethylene diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate.
  • any metal such as copper, gold, silver, platinum, nickel, and alloys thereof can be used, but it is preferable to use silver powder excellent in conductivity.
  • the shape is not particularly limited, and examples thereof include a spherical shape, a scale shape, and a granular shape.
  • the content of the conductive metal powder can be arbitrarily selected according to the required characteristics. Increasing the content of the conductive metal powder can improve the conductivity, but if the content of the conductive metal powder is too large, the adhesion (cohesive force) between the resin component and the conductive metal powder will be weak, and after coating When voids enter the conductive paste, the printability and adhesiveness are affected. In addition, the conductivity also decreases. For this reason, it is preferable that content of electroconductive metal powder shall be 95% or less with respect to the whole solid content of electroconductive paste.
  • the content of the conductive metal powder is increased, the conductive paste becomes hard and the flexibility is lowered.
  • the content of the conductive metal powder is preferably 50% or more and 85% or less with respect to the total solid content of the conductive paste.
  • a metal powder A having an average particle size of 0.5 ⁇ m to 20 ⁇ m and a metal powder having an average particle size of 100 nm or less are used in combination, and the content ratio of the metal powder A and the metal powder B is expressed by weight ratio.
  • 99.5: 0.5 to 70:30 is preferable.
  • the content ratio of the metal powder A and the metal powder B exceeds 99.5: 0.5 and the metal powder A increases, the combination effect decreases and the conductivity decreases.
  • the content ratio exceeds 70:30 and the metal powder B is increased the amount of the metal powder B is increased, which is not preferable.
  • a more preferable content ratio of the metal powder A and the metal powder B is 99: 1 to 90:10.
  • the average particle size of the metal powder A is preferably 0.5 ⁇ m to 20 ⁇ m. If the thickness is 0.5 ⁇ m or less, the conductivity is lowered. On the other hand, if the average particle size exceeds 20 ⁇ m, fine printing becomes difficult. For the same reason, it is preferable to use a material having a maximum particle size that does not contain an extremely large particle size, and one having a maximum particle size in the range of 20 ⁇ m to 50 ⁇ m is preferable.
  • the particle diameter is the maximum diameter of each particle, and the average value is the average particle diameter. For the measurement, a scanning electron microscope (SEM) or the like is used.
  • the metal powder A not only one type but also a plurality of powders having different average particle sizes and shapes can be used in combination.
  • the conductivity and smoothness after coating can be further improved.
  • Metal powder B is a metal powder having an average particle size of 100 nm or less. Nano-sized powders may be agglomerated, but the average particle size refers to the particle size of primary particles. Such nano-sized powders have a large surface area and thus a large surface activity. Therefore, in order to protect the surface and suppress secondary aggregation, it is preferable to use a material whose surface is coated with an organic substance. Examples of the organic substance include polycarboxylic acid and polyacrylic acid.
  • the metal powder B having an average particle size of 100 nm or less can be produced, for example, as follows. Silver nitrate is dissolved in a mixed solvent of water and lower alcohol, and the pH is adjusted to 11 or more with aqueous ammonia. Silver particles are precipitated by adding L-ascorbic acid as a reducing agent and polyacrylic acid as a dispersing agent dissolved in the mixed solvent. The precipitated silver particles are obtained by filtration, washing and drying in a state where secondary aggregation is suppressed by the dispersant.
  • the average particle diameter of the silver particles can be changed depending on pH, temperature, concentration of each material, mixing method, and the like.
  • the silver particles produced through the above steps are obtained in a state where the surface of the generated silver particles is coated with the dispersant, particularly by using a dispersant in the reaction step. Since the dispersant is in a state of covering the surface of the silver particles at the generation stage, it is hardly affected by the outside air, and the silver particles are not easily agglomerated. Even if agglomeration occurs, the dispersing agent intervenes, so that agglomeration can be easily broken with an organic solvent or the like. Moreover, the dispersibility to resin is also favorable.
  • the above conductive metal powder, urethane-modified polyester resin, and blocked isocyanate are mixed to prepare a conductive paste.
  • the urethane-modified polyester resin and the blocked isocyanate are used after being dissolved in a solvent. Any solvent can be used as long as it can dissolve the resin, and examples thereof include ester-based, ether-based, ketone-based, ether-ester-based, alcohol-based, hydrocarbon-based, and amine-based organic solvents. .
  • a high boiling point solvent with good printability is preferable, and specifically, carbitol acetate, butyl carbitol acetate, and the like are particularly preferable.
  • additives such as thickeners and leveling agents can be added to the conductive silver paste of the present invention in order to improve printing workability.
  • inorganic fillers such as carbon and silica as long as the performance of the present invention is not impaired.
  • the electromagnetic wave shielding film of the present invention has a layer made of the above conductive paste on a substrate. After apply
  • a polyester film, a polyimide film, etc. can be used as a base material. In view of flexibility, a polyimide film is preferable.
  • FIG. 1 is a schematic cross-sectional view illustrating an example of an electromagnetic wave shielding film.
  • a conductive paste layer 2 is provided on the substrate 1.
  • a protective film 8 may be provided on the conductive paste layer 2. The protective film 8 is peeled off during use.
  • FIG. 2 is a schematic cross-sectional view illustrating an example of an electromagnetic wave shield flexible printed wiring board.
  • a wiring made of a copper foil 5 is formed on a base material 4, and a cover lay covers the wiring.
  • the coverlay includes a coverlay film 6a made of polyimide or the like and a coverlay adhesive 6b.
  • An electromagnetic wave shielding film 3 is attached to the cover lay side of the flexible printed wiring board.
  • a conductive paste layer may be provided by directly applying a conductive paste to a flexible printed wiring board.
  • the coating thickness of the conductive paste is not particularly limited, but is preferably in the range of 10 ⁇ m to 50 ⁇ m. If the thickness is 10 ⁇ m or less, desirable electromagnetic wave shielding characteristics cannot be obtained, but if the thickness is 50 ⁇ m or more, the flexibility of the shield layer is deteriorated and the bending resistance is deteriorated.
  • Examples of the method for applying the conductive paste include screen printing, intaglio printing, lithographic printing, and dispenser. Screen printing is most preferably used from the viewpoint of the fineness, film thickness, and productivity of the wiring to be formed.
  • the conductive paste of the present invention can be directly applied to a flexible printed wiring board and solidified to form an electromagnetic wave shielding layer. Also by such a method, an electromagnetic wave shield flexible printed wiring board having a layer made of the conductive paste of the present invention can be obtained. Similarly, an electromagnetic wave shielding casing having a layer made of the conductive paste of the present invention can be obtained by applying it to the casing of an electronic device such as a personal computer or a mobile phone.
  • Examples 1 to 3, Comparative Examples 1 to 3 Preparation of conductive paste
  • a urethane-modified polyester obtained by reacting the acid component, alcohol component and isocyanate component shown in Table 1 was prepared. Specifically, the acid component and alcohol component listed in Table 1 and a mixed solvent of butyl carbitol acetate and butyl carbitol are put into a four-necked flask and heated to 60 ° C. under a nitrogen stream, and then the isocyanate compound is further added. The mixture was added and heated at 80 ° C. for 5 hours to synthesize urethane-modified polyester.
  • the produced urethane-modified polyester resin was mixed with a scaly silver powder having an average particle size of 3.0 ⁇ m, a spherical silver powder having an average particle size of 25 nm, and a blocked isocyanate as a conductive metal powder to prepare a conductive paste.
  • the compounding ratio of the urethane-modified polyester and the blocked isocyanate was an equimolar molar ratio, and the compounding ratio of the conductive metal powder was the following ratio.
  • a non-adhesive copper-clad laminate (two-layer CCL) in which a copper foil was laminated on a polyimide film was prepared, and a copper foil portion was selectively etched by a subtractive method to form a pattern having a line width of 50 ⁇ m. Further, a cover lay film was stuck thereon to produce a flexible printed wiring board for evaluation.
  • the conductive paste was applied to the cover lay film side of the flexible printed wiring board by a screen printing method and thermally cured in an oven furnace. Further, for the sliding flexibility evaluation sample, a solder resist was applied on the conductive paste and thermally cured in an oven furnace.
  • Comparative Example 1 In Comparative Example 1 in which the total of aromatic components contained in the acid component, alcohol component, and isocyanate component is less than 5 mol% with respect to the total of the acid component, alcohol component, and isocyanate component, the adhesion after reflow treatment is Low and heat resistance is poor. Similarly, Comparative Example 2 in which the aromatic component is not included in the isocyanate component also has low adhesion after reflow treatment and poor heat resistance. Further, in Comparative Example 3 in which the total of the aromatic components exceeds 50 mol%, the adhesion is good but the sliding flexibility is poor.
  • Example 4 By changing the degree of polymerization of the urethane-modified polyester resin, urethane-modified polyester resins having different hydroxyl values were produced. Using this resin, a conductive paste was prepared in the same manner as in Examples 1 to 3, and the adhesion strength, sliding flexibility and volume resistivity after reflow treatment were evaluated. The results are shown in Table 2.
  • the hydroxyl value of the urethane-modified polyester resin correlates with the adhesion after reflow treatment, and the adhesion increases as the hydroxyl value increases.
  • the adhesion is 0.8 N / cm, which is a slightly low value.
  • Example 8 in which the hydroxyl value exceeds 60 mgKOH / g has poor flexibility and results in a slightly low number of sliding and bending.
  • polyfunctional block polyisocyanate compounds having various number average molecular weights were prepared.
  • the polyfunctional block polyisocyanate compound is obtained by blocking the end of an adduct type isocyanate of an isocyanate monomer and a polyhydroxy compound with a blocking agent.
  • a conductive paste was prepared in the same manner as in Examples 1 to 3 in combination with the urethane-modified polyester resin described in Example 1, and the adhesive strength after reflow treatment, sliding flexibility, volume resistivity Evaluated.
  • Example 9 In all the samples, the adhesiveness, sliding flexibility, and specific resistance satisfy the required characteristics, but in Example 9 in which the number average molecular weight of the polyfunctional block polyisocyanate compound is less than 500, the number of sliding flexures is 8. The result is somewhat low at 10,000 times. Moreover, in Example 13 in which the number average molecular weight exceeds 3000, the volume resistance is slightly high.
  • Example 14 Using the urethane-modified polyester resin and the polyfunctional block polyisocyanate compound used in Example 1, and changing the NCO / OH ratio by changing the blending ratio of both, a conductive paste was prepared in the same manner as in Examples 1 to 3, The adhesive strength, sliding flexibility, and volume resistivity after the reflow treatment were evaluated. As a result, as shown in Table 4, in Example 14 in which the NCO / OH ratio is less than 0.8, the volume resistance value is slightly high. This is presumed to be because the crosslinking density decreases when the NCO / OH ratio is low. Moreover, in Example 18 in which the NCO / OH ratio exceeds 3.0, the adhesion after the reflow treatment is slightly low. If the NCO / OH ratio is high, it is presumed that the heat resistance is lowered due to the excess curing agent remaining.
  • Example 19 As conductive metal powder, metal powder A having an average particle diameter of 4.8 ⁇ m and metal powder B having an average particle diameter of 30 nm were prepared. By changing the content ratio of the metal powder A and the metal powder B, a conductive paste was produced in the same manner as in the methods described in Examples 1 to 3, and the adhesion strength, sliding flexibility, and volume resistivity after the reflow treatment were evaluated. . At this time, the total weight of the metal powder A and the metal powder B was obtained by multiplying the weight sum of the weight of the urethane-modified polyester resin and the blocked isocyanate by 2.333.
  • Example 19 in which the content ratio of the metal powder A and the metal powder B was less than 99.5: 0.5, the volume resistivity was slightly high. Further, in Example 23 in which the content ratio of the metal powder A and the metal powder B exceeds 70:30, the effect of improving the characteristics is not particularly seen. Since the metal powder having an average particle size of nano-size is expensive, the content ratio of the metal powder A and the metal powder B is 99.5: 0.5 to 70:30 in consideration of the characteristics and cost of the conductive paste. The range of is preferable.
  • Example 24 As conductive metal powder, metal powder A having an average particle diameter of 4.8 ⁇ m and metal powder B having an average particle diameter of 30 nm were prepared. Here, the content ratio of the metal powder A and the metal powder B is fixed at 90:10, and the content ratio of the metal powder obtained by adding the metal powder A and the metal powder B is changed to produce a conductive paste, and the reflow treatment is performed. The subsequent adhesion, sliding flexibility, and volume resistivity were evaluated. As a result, as shown in Table 6, in Example 24 in which the metal powder content ratio was less than 50% by weight, the volume resistance was slightly high. Further, in Example 28 in which the metal powder content ratio exceeds 85% by weight, the sliding bending performance is slightly low.
  • the present invention relates to a conductive paste, an electromagnetic wave shielding film using the conductive paste, and an electromagnetic wave shielding flexible printed wiring board, and can be suitably used particularly for a flexible printed wiring board requiring bending resistance.

Abstract

A conductive paste containing a conductive metal powder, a urethane-modified polyester resin and a block isocyanate, wherein the urethane-modified polyester resin is obtained by reacting an acid component, an alcohol component and an isocyanate component containing an aromatic isocyanate, and the total of the aromatic components contained in the acid component, alcohol component and isocyanate component is not less than 5 mol% but not more than 50 mol% of the total of the acid component, alcohol component and isocyanate component.  The conductive paste has a good balance between flexibility and heat resistance, and is capable of forming a shielding layer having excellent bending resistance.  An electromagnetic wave-shielding film using the conductive paste and an electromagnetic wave-shielding flexible printed wiring board are also disclosed.

Description

導電性ペースト及びそれを用いた電磁波シールドフィルム、電磁波シールドフレキシブルプリント配線板Conductive paste, electromagnetic shielding film using the same, and electromagnetic shielding flexible printed wiring board
　本発明は、導電性ペースト及びそれを用いた電磁波シールドフィルム、電磁波シールドフレキシブルプリント配線板に関し、特に、耐屈曲性が要求されるフレキシブルプリント配線板に関するものである。 The present invention relates to a conductive paste, an electromagnetic wave shielding film using the conductive paste, and an electromagnetic wave shielding flexible printed wiring board, and more particularly to a flexible printed wiring board that requires bending resistance.
　導電性ペーストは、カーボンブラックやグラファイト粉、貴金属粉、銅粉、ニッケル粉、等の導電性フィラーと、バインダーとなる樹脂、溶剤を混合してペースト状にしたものである。これをフィルムや基板上にスクリーン印刷等の方法で塗布してパターン形成し、樹脂を固化することにより、導電性の配線を形成する。最近の電子部品のコンパクト化、軽量化に伴い、このような用途には、高導電性の導電性ペーストが要求されている。 The conductive paste is a paste obtained by mixing a conductive filler such as carbon black, graphite powder, noble metal powder, copper powder, nickel powder, etc., a binder resin, and a solvent. This is applied onto a film or substrate by a method such as screen printing to form a pattern, and the resin is solidified to form conductive wiring. With recent downsizing and weight reduction of electronic components, highly conductive conductive pastes are required for such applications.
　特許文献１には、導電性フィラーとして銀を用いた導電性銀ペーストが開示されている。導電性フィラーとして用いる銀粉の形状は、制限がなく、粒状、鱗片状、板状、樹枝状、粟状、サイコロ状等で、その大きさが０．１～１００μｍのものを使用している。また、バインダー樹脂としては、飽和共重合ポリエステル樹脂及びブロックイソシアネートを使用している。また、特許文献２には、導電性ペーストの耐屈曲性を向上するために、粒子径０．１～５μｍの１次粒子が３次元上につながって形成された銀粉末と、数平均分子量が３０００以上のバインダー、硬化剤及び溶剤を主成分とする導電性ペーストが開示されている。バインダーとしては、ポリウレタン樹脂やポリエステル樹脂が例示されている。 Patent Document 1 discloses a conductive silver paste using silver as a conductive filler. The shape of the silver powder used as the conductive filler is not limited, and it is granular, scale-like, plate-like, dendritic, cocoon-like, dice-like, or the like having a size of 0.1 to 100 μm. As the binder resin, a saturated copolymerized polyester resin and a blocked isocyanate are used. Patent Document 2 discloses a silver powder in which primary particles having a particle diameter of 0.1 to 5 μm are three-dimensionally connected in order to improve the bending resistance of a conductive paste, and a number average molecular weight. An electrically conductive paste mainly composed of 3000 or more binders, a curing agent and a solvent is disclosed. Examples of the binder include polyurethane resins and polyester resins.
　また、導電性ペーストは、電磁波シールド材料としても使用されている。特に、最近は、情報の高速伝達のために、より高周波帯域の周波数を用いるようになってきており、今まで以上の電磁波シールド特性を持つ導電性ペーストが要求されている。特許文献３には、特定の粒径を持つ銀粉末を組み合わせることで導電性、シールド特性を向上した導電性銀ペーストとそれを用いた電磁波シールドフィルムが開示されている。 The conductive paste is also used as an electromagnetic shielding material. In particular, recently, frequencies in a higher frequency band have been used for high-speed transmission of information, and there has been a demand for a conductive paste having an electromagnetic shielding characteristic higher than ever. Patent Document 3 discloses a conductive silver paste having improved conductivity and shielding characteristics by combining silver powder having a specific particle diameter, and an electromagnetic wave shielding film using the same.
　フレキシブルプリント配線板のシールド層として、導電性ペーストを使用する場合、導電性ペーストを塗布、固化してなるシールド層には、導電性や電磁波シールド特性の他に耐熱性、表面平滑性、耐屈曲性が求められる。特に、携帯電話のヒンジ部等の可動部に用いる場合、機器の小型化によって、より小さい屈曲半径での耐久性が求められているため、耐屈曲性を向上させることが課題となる。 When using a conductive paste as the shield layer of a flexible printed wiring board, the shield layer formed by applying and solidifying the conductive paste has heat resistance, surface smoothness, and bending resistance in addition to conductivity and electromagnetic shielding properties. Sex is required. In particular, when it is used for a movable part such as a hinge part of a mobile phone, durability at a smaller bending radius is required due to downsizing of the device, so that it is a problem to improve the bending resistance.
　特許文献３に記載の導電性ペーストでは、塗布、硬化後の耐熱性と柔軟性を両立するために、バインダー樹脂としてポリエステル樹脂を使用することが好ましいと記載されている。しかし、現在求められている耐屈曲性を実現するためには、さらに耐屈曲性を向上する必要がある。 In the conductive paste described in Patent Document 3, it is described that it is preferable to use a polyester resin as a binder resin in order to achieve both heat resistance and flexibility after coating and curing. However, in order to realize the bending resistance currently required, it is necessary to further improve the bending resistance.
　耐屈曲性を向上させるためには、柔軟性が必要であり、バインダー樹脂には、柔軟な樹脂であるポリエステル樹脂が使用されてきた。ポリエステル樹脂は、多価カルボン酸や酸無水物などの酸成分と、多価アルコール等のアルコール成分とを縮合重合して得られる樹脂であり、酸成分、アルコール成分の種類を選択することによって適宜その特性をコントロールすることができる。例えば脂肪族ジカルボン酸等の柔軟な成分を多く用いると柔軟性が向上する。しかし、柔軟な成分を多く用いると耐熱性が低下し、必要な特性を満たすことができない。耐熱性を上げるためには、テレフタル酸等の剛直な芳香族成分の割合を増やす必要があるが、そうすると柔軟性が低下することとなる。 Flexibility is necessary to improve the bending resistance, and a polyester resin that is a flexible resin has been used as the binder resin. The polyester resin is a resin obtained by condensation polymerization of an acid component such as a polyvalent carboxylic acid or an acid anhydride and an alcohol component such as a polyhydric alcohol. The polyester resin is appropriately selected by selecting the type of the acid component or alcohol component. Its characteristics can be controlled. For example, when many flexible components such as aliphatic dicarboxylic acid are used, the flexibility is improved. However, if a large amount of flexible components are used, the heat resistance is lowered and the required characteristics cannot be satisfied. In order to increase the heat resistance, it is necessary to increase the proportion of rigid aromatic components such as terephthalic acid, but this reduces flexibility.
　そこで本発明は上記の問題に鑑み、柔軟性と耐熱性を両立し、耐屈曲性に優れた電磁波シールド層を形成可能な導電性ペースト、及びそれを用いた電磁波シールドフィルムを提供することを課題とする。 Therefore, in view of the above problems, the present invention provides a conductive paste capable of forming an electromagnetic wave shielding layer having both flexibility and heat resistance and excellent bending resistance, and an electromagnetic wave shielding film using the same. And
　本発明は、導電性金属粉末、ウレタン変性ポリエステル樹脂、及びブロックイソシアネートを含有する導電性ペーストであって、前記ウレタン変性ポリエステル樹脂は、酸成分、アルコール成分、及び芳香族イソシアネートを含むイソシアネート成分を反応させて得られ、前記酸成分、アルコール成分、及びイソシアネート成分に含まれる芳香族成分の合計が、前記酸成分、アルコール成分、及びイソシアネート成分の合計に対して５モル％以上５０モル％以下であることを特徴とする、導電性ペーストである（本願第１の発明）。 The present invention is a conductive paste containing a conductive metal powder, a urethane-modified polyester resin, and a blocked isocyanate, and the urethane-modified polyester resin reacts an isocyanate component containing an acid component, an alcohol component, and an aromatic isocyanate. The total of aromatic components contained in the acid component, alcohol component, and isocyanate component is 5 mol% or more and 50 mol% or less with respect to the total of the acid component, alcohol component, and isocyanate component. This is a conductive paste (first invention of the present application).
　バインダー樹脂として、芳香族イソシアネートを含むイソシアネート成分で変性したウレタン変性ポリエステル樹脂を用いる。また、酸成分、アルコール成分、及びイソシアネート成分に含まれる芳香族成分の合計を、酸成分、アルコール成分、及びイソシアネート成分の合計に対して５モル％以上５０モル％以下とする。このような分子構造とすることで、耐屈曲性に必要な柔軟性と、耐熱性とを両立することができる。 As the binder resin, a urethane-modified polyester resin modified with an isocyanate component containing an aromatic isocyanate is used. Moreover, the sum total of the aromatic component contained in an acid component, an alcohol component, and an isocyanate component shall be 5 mol% or more and 50 mol% or less with respect to the sum total of an acid component, an alcohol component, and an isocyanate component. By adopting such a molecular structure, it is possible to achieve both flexibility and heat resistance necessary for bending resistance.
　前記ウレタン変性ポリエステル樹脂の水酸基価は、５ｍｇＫＯＨ／ｇ以上６０ｍｇＫＯＨ／ｇ以下とすることが好ましい（本願第２の発明）。水酸基価は、ウレタン変性ポリエステル樹脂の架橋点（ブロックイソシアネートとの反応する水酸基）数に対する分子量を示す指標となり、水酸基価が大きいと分子量が小さく、水酸基価が小さいと分子量が大きくなる。水酸基価が５ｍｇＫＯＨ／ｇよりも小さいと分子量が大きく、柔軟性には優れるが、ブロックイソシアネートと反応するための架橋点が少なくなることで耐熱性が低下する。また、水酸基価が６０ｍｇＫＯＨ／ｇを超えると逆に分子量が小さくなり、耐熱性は、向上するが柔軟性が低下する。 The hydroxyl value of the urethane-modified polyester resin is preferably 5 mgKOH / g or more and 60 mgKOH / g or less (the second invention of the present application). The hydroxyl value is an index indicating the molecular weight with respect to the number of crosslinking points (hydroxyl groups that react with blocked isocyanate) of the urethane-modified polyester resin. When the hydroxyl value is large, the molecular weight is small, and when the hydroxyl value is small, the molecular weight is large. When the hydroxyl value is less than 5 mgKOH / g, the molecular weight is large and the flexibility is excellent, but the heat resistance is lowered by reducing the number of crosslinking points for reacting with the blocked isocyanate. On the other hand, when the hydroxyl value exceeds 60 mgKOH / g, the molecular weight decreases, and the heat resistance is improved but the flexibility is lowered.
　前記ブロックイソシアネートは、数平均分子量が５００以上３０００以下であり、イソシアネートモノマーとポリヒドロキシ化合物とのアダクト型イソシアネートの末端をブロック剤でブロックした多官能ブロックポリイソシアネート化合物であると好ましい（本願第３の発明）。このようなアダクト型イソシアネートは、１分子中の官能基（イソシアネート基）量が多いため、反応後のウレタン変性ポリエステル樹脂の架橋密度を上げることができ、耐熱性を向上することができる。 The blocked isocyanate has a number average molecular weight of 500 or more and 3000 or less, and is preferably a polyfunctional block polyisocyanate compound in which an adduct isocyanate of an isocyanate monomer and a polyhydroxy compound is blocked with a blocking agent (the third of the present application invention). Since such an adduct type isocyanate has a large amount of functional groups (isocyanate groups) in one molecule, the crosslinking density of the urethane-modified polyester resin after the reaction can be increased, and the heat resistance can be improved.
　前記ウレタン変性ポリエステル樹脂と前記ブロックイソシアネートの混合比は、前記ウレタン変性ポリエステル樹脂の水酸基（ＯＨ）と、前記ブロックイソシアネートのイソシアネート基（ＮＣＯ）とのモル比率（ＮＣＯ／ＯＨ）換算で０．８以上３．０以下であると好ましい（本願第４の発明）。ブロックイソシアネート量がこの範囲よりも少ないと、ウレタン変性ポリエステル樹脂の架橋密度が低くなり、耐熱性が低くなる。また、ブロックイソシアネート量がこの範囲よりも多い場合、反応に寄与しないイソシアネートがバインダー樹脂中に残留することで耐熱性が低くなる場合がある。さらに好ましいモル比率の範囲は、１．０以上２．０以下である。 The mixing ratio of the urethane-modified polyester resin and the blocked isocyanate is 0.8 or more in terms of the molar ratio (NCO / OH) of the hydroxyl group (OH) of the urethane-modified polyester resin and the isocyanate group (NCO) of the blocked isocyanate. It is preferable that it is 3.0 or less (the fourth invention of the present application). When the amount of blocked isocyanate is less than this range, the crosslinking density of the urethane-modified polyester resin is lowered, and the heat resistance is lowered. Moreover, when there are more block isocyanate amounts than this range, the heat resistance may become low because the isocyanate which does not contribute to reaction remains in binder resin. A more preferable range of the molar ratio is 1.0 or more and 2.0 or less.
　前記導電性金属粉末は、平均粒径が０．５μｍ～２０μｍの金属粉末Aと、平均粒径が１００ｎｍ以下の金属粉末Ｂとからなり、金属粉末Ａと金属粉末Ｂの含有比率が、重量比で９９．５：０．５～７０：３０であると共に、前記導電性金属粉末の含有比率が、導電性ペーストの固形分量に対して５０重量％以上８５重量％以下であると好ましい（本願第５の発明）。導電性金属粉末の含有比率を高くすると導電性は、向上するが、高すぎると導電性ペーストの柔軟性が低下し、耐屈曲性が悪くなるため、導電性と耐屈曲性とを両立するためには、導電性金属粉末の含有比率を５０重量％以上８５重量％以下とすることが好ましい。 The conductive metal powder is composed of a metal powder A having an average particle diameter of 0.5 μm to 20 μm and a metal powder B having an average particle diameter of 100 nm or less, and the content ratio of the metal powder A and the metal powder B is a weight ratio. 99.5: 0.5 to 70:30, and the content ratio of the conductive metal powder is preferably 50% by weight to 85% by weight with respect to the solid content of the conductive paste. 5 invention). When the content ratio of the conductive metal powder is increased, the conductivity is improved. However, when the content is too high, the flexibility of the conductive paste is lowered and the bending resistance is deteriorated, so that both conductivity and bending resistance are achieved. In this case, the content ratio of the conductive metal powder is preferably 50% by weight or more and 85% by weight or less.
　また、良好な導電性を得るために、粒径の異なる金属粉末Ａと金属粉末Ｂとを特定の含有比率で組み合わせて使用することが好ましい。比較的粒径の大きい金属粉末Ａ同士の隙間をナノサイズの金属粉末Ｂが充填することによって、導電性が向上すると共に、導電性ペーストを塗布した後の表面の平滑性を向上できる。表面の平滑性及は、導電性と共に電磁波シールド特性に影響するため、導電性と平滑性を向上することで電磁波シールド特性をさらに向上できる。 Further, in order to obtain good conductivity, it is preferable to use a combination of metal powder A and metal powder B having different particle sizes in a specific content ratio. By filling the gaps between the metal powders A having relatively large particle sizes with the nano-sized metal powder B, the conductivity is improved and the smoothness of the surface after the conductive paste is applied can be improved. Since the smoothness of the surface affects the electromagnetic shielding characteristics as well as the electrical conductivity, the electromagnetic shielding characteristics can be further improved by improving the electrical conductivity and smoothness.
　また、本発明は、上記の導電性ペーストからなる層を基材上に有する電磁波シールドフィルムを提供する（本願第６の発明）。また、上記の導電性ペーストからなる層を有する電磁波シールドフレキシブルプリント配線板を提供する（本願第７の発明）。このような電磁波シールドフィルム及び電磁波シールドフレキシブルプリント配線板は、耐屈曲性に優れるとともに、耐熱性、導電性、電磁波シールド特性にも優れるものである。 The present invention also provides an electromagnetic wave shielding film having a layer made of the above conductive paste on a substrate (the sixth invention of the present application). Moreover, the electromagnetic wave shield flexible printed wiring board which has a layer which consists of said electroconductive paste is provided (this invention 7th invention). Such an electromagnetic wave shielding film and an electromagnetic wave shielding flexible printed wiring board are excellent in bending resistance and heat resistance, conductivity, and electromagnetic wave shielding characteristics.
　本発明により、柔軟性と耐熱性とを両立でき、耐屈曲性に優れた電磁波シールド層を形成可能な導電性ペースト、及びそれを用いた電磁波シールドフィルム、電磁波シールドフレキシブルプリント配線板を提供することができる。 According to the present invention, there are provided a conductive paste capable of forming an electromagnetic wave shielding layer having both flexibility and heat resistance and excellent in bending resistance, an electromagnetic wave shielding film using the same, and an electromagnetic wave shielding flexible printed wiring board. Can do.
本発明の電磁波シールドフィルムの断面模式図である。It is a cross-sectional schematic diagram of the electromagnetic wave shielding film of this invention. 本発明の電磁波シールドフレキシブルプリント配線板の断面模式図である。It is a cross-sectional schematic diagram of the electromagnetic wave shield flexible printed wiring board of this invention.
　以下、本発明の実施の形態を説明する。なお、図面の説明においては、同一要素には同一符号を付し、重複する説明を省略する。また、図面の寸法比率は、説明のものと必ずしも一致していない。
本発明に使用するウレタン変性ポリエステル樹脂について説明する。ウレタン変性ポリエステル樹脂とは、酸成分と、アルコール成分、及びウレタン成分とを反応して得られるものである。一般にポリエステル樹脂は、多価カルボン酸又はその無水物等の酸成分と多価アルコール等のアルコール成分とを縮合重合して得られる。ここで得られたポリエステル樹脂の末端水酸基をイソシアネート成分と反応させることで、ウレタン変性ポリエステル樹脂が得られる。このように、イソシアネート成分は、酸成分とアルコール成分との反応後に加えて反応させることが好ましいが、酸成分、アルコール成分、イソシアネート成分を同時に反応させても良い。 Embodiments of the present invention will be described below. In the description of the drawings, the same reference numerals are assigned to the same elements, and duplicate descriptions are omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.
The urethane-modified polyester resin used in the present invention will be described. The urethane-modified polyester resin is obtained by reacting an acid component, an alcohol component, and a urethane component. In general, a polyester resin is obtained by condensation polymerization of an acid component such as a polyvalent carboxylic acid or an anhydride thereof and an alcohol component such as a polyhydric alcohol. A urethane-modified polyester resin is obtained by reacting the terminal hydroxyl group of the obtained polyester resin with an isocyanate component. As described above, the isocyanate component is preferably added and reacted after the reaction between the acid component and the alcohol component, but the acid component, the alcohol component, and the isocyanate component may be reacted at the same time.
　酸成分としては、多価カルボン酸又はその無水物であれば特に限定されず、例えばフタル酸、イソフタル酸、テレフタル酸、オルソフタル酸等の芳香族ジカルボン酸及びその無水物、コハク酸、アジピン酸、グルタル酸、セバシン酸等の脂肪族ジカルボン酸及びその無水物、マレイン酸、フマル酸、イタコン酸等の不飽和ジカルボン酸やその無水物が例示される。これらは、２種以上併用しても良い。 The acid component is not particularly limited as long as it is a polyvalent carboxylic acid or an anhydride thereof. For example, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, orthophthalic acid and the like, succinic acid, adipic acid, Examples thereof include aliphatic dicarboxylic acids such as glutaric acid and sebacic acid and anhydrides thereof, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and anhydrides thereof. Two or more of these may be used in combination.
　アルコール成分としては、多価アルコールであれば特に限定されず、例えば、エチレングリコール、ジエチレングリコール、トリエチレングリコール、ネオペンチルグリコール、１，３－プロパンジオール、１，４－ブタンジオール、１，４－シクロヘキサンジオール等の脂肪族グリコール、芳香族グリコール、脂環族グリコール、トリメチロールプロパン、ペンタエリスリトール等の３価以上のアルコール等が例示される。これらは、２種以上併用しても良い。 The alcohol component is not particularly limited as long as it is a polyhydric alcohol. For example, ethylene glycol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexane Examples thereof include aliphatic glycols such as diols, aromatic glycols, alicyclic glycols, trivalent or higher alcohols such as trimethylolpropane and pentaerythritol. Two or more of these may be used in combination.
　イソシアネート成分は、１分子中にイソシアネート基を２個以上有するものであり、分子中に芳香環を有する芳香族イソシアネートを必須とする。芳香族イソシアネートとしては、キシレンジイソシアネート、トリレンジイソシアネート、４，４’ジフェニルメタンジイソシアネート、ナフタレンジイソシアネート、ビフェニレンジイソシアネート等が例示される。これらは、２種以上併用しても良い。また、本発明の趣旨を損ねない範囲で、芳香族イソシアネートと併用して、トリメチルヘキサメチレンジイソシアネート、ヘキサメチレンジイソシアネート、トリメチレンジイソシアネート等の脂肪族ジイソシアネート、シクロヘキサンジイソシアネート等の脂環族ジイソシアネート等を併用しても良い。 The isocyanate component has two or more isocyanate groups in one molecule, and an aromatic isocyanate having an aromatic ring in the molecule is essential. Examples of the aromatic isocyanate include xylene diisocyanate, tolylene diisocyanate, 4,4 'diphenylmethane diisocyanate, naphthalene diisocyanate, and biphenylene diisocyanate. Two or more of these may be used in combination. In addition, in combination with aromatic isocyanate, aliphatic diisocyanate such as trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, trimethylene diisocyanate, alicyclic diisocyanate such as cyclohexane diisocyanate, etc. are used in combination as long as the spirit of the present invention is not impaired. May be.
　上述したように、酸成分、アルコール成分、イソシアネート成分中の芳香族成分の合計は、全成分の合計に対して５モル％以上５０モル％以下とする。これらの材料を常法により反応させて、ウレタン変性ポリエステル樹脂を得る。 As described above, the total of aromatic components in the acid component, alcohol component, and isocyanate component is 5 mol% or more and 50 mol% or less with respect to the total of all components. These materials are reacted in a conventional manner to obtain a urethane-modified polyester resin.
　本発明に使用するブロックイソシアネートは、多官能イソシアネートの末端イソシアネート基をブロック剤で封鎖したものである。加熱によりブロック剤が解離し、イソシアネート基が生成する。このイソシアネート基がウレタン変性ポリエステル樹脂の水酸基と反応してウレタン変性ポリエステル樹脂を架橋する。 The blocked isocyanate used in the present invention is obtained by blocking the terminal isocyanate group of a polyfunctional isocyanate with a blocking agent. The blocking agent is dissociated by heating, and an isocyanate group is generated. This isocyanate group reacts with the hydroxyl group of the urethane-modified polyester resin to crosslink the urethane-modified polyester resin.
　ブロック剤としては、アルコール類、フェノール類、酸アミド類、オキシム類、活性メチレン等、活性水酸基を持つ化合物が例示される。 Examples of the blocking agent include compounds having an active hydroxyl group such as alcohols, phenols, acid amides, oximes, and active methylene.
　多官能イソシアネートとしては、トリメチレンジイソシアネート、ヘキサメチレンジイソシアネート（ＨＤＩ）、ジフェニルメタンジイソシアネート（ＭＤＩ）等、任意のイソシアネートを使用することができる。中でも、一般式（Ｉ）で示される、イソシアネートモノマーとポリヒドロキシ化合物とのアダクト型イソシアネートが好ましい。 As the polyfunctional isocyanate, any isocyanate such as trimethylene diisocyanate, hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI) can be used. Among these, an adduct type isocyanate of an isocyanate monomer and a polyhydroxy compound represented by the general formula (I) is preferable.
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
　（式中、Ｒ１～Ｒ３は、脂肪族、脂環族又は芳香族ジイソシアネートからイソシアネート基を除いた基を表し、Ｒ４は、多価アルコール化合物から水酸基を除いた基を表す。） (Wherein R1 to R3 represent a group obtained by removing an isocyanate group from an aliphatic, alicyclic or aromatic diisocyanate, and R4 represents a group obtained by removing a hydroxyl group from a polyhydric alcohol compound.)
　ポリヒドロキシ化合物は、１分子中に２個以上の水酸基を有する化合物であり、グリセリン、トリメチロールエタン、トリメチロールプロパン、１，４－ブタンジオール、ネオペンチルグリコール、１，６－ヘキサンジオール等が例示される。また、ジイソシアネートとしては、トリメチレンジイソシアネート、ヘキサメチレンジイソシアネート、ジフェニルメタンジイソシアネート等が例示される。 A polyhydroxy compound is a compound having two or more hydroxyl groups in one molecule, such as glycerin, trimethylolethane, trimethylolpropane, 1,4-butanediol, neopentylglycol, 1,6-hexanediol, etc. Is done. Examples of the diisocyanate include trimethylene diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate.
　本発明に使用する導電性金属粉末は、銅、金、銀、白金、ニッケル等、任意の金属及びその合金を使用することができるが、導電性に優れる銀粉末を使用することが好ましい。また、形状は、特に限定されず、球状、鱗片状、顆粒状等が例示される。 As the conductive metal powder used in the present invention, any metal such as copper, gold, silver, platinum, nickel, and alloys thereof can be used, but it is preferable to use silver powder excellent in conductivity. The shape is not particularly limited, and examples thereof include a spherical shape, a scale shape, and a granular shape.
　導電性金属粉末の含有量は、求められる特性に応じて任意に選択できる。導電性金属粉末の含有量を増やすと導電性を向上できるが、導電性金属粉末の含有量が多すぎると樹脂成分と導電性金属粉末との密着力（凝集力）が弱くなり、塗工後の導電性ペースト中に空隙が入ることで、印刷性や接着性の低下に影響する。また、導電性も逆に低下することとなる。このため、導電性金属粉末の含有量は、導電性ペーストの固形分量全体に対して９５％以下とすることが好ましい。 The content of the conductive metal powder can be arbitrarily selected according to the required characteristics. Increasing the content of the conductive metal powder can improve the conductivity, but if the content of the conductive metal powder is too large, the adhesion (cohesive force) between the resin component and the conductive metal powder will be weak, and after coating When voids enter the conductive paste, the printability and adhesiveness are affected. In addition, the conductivity also decreases. For this reason, it is preferable that content of electroconductive metal powder shall be 95% or less with respect to the whole solid content of electroconductive paste.
　また、導電性金属粉末の含有量を増やすと導電性ペーストが硬くなり柔軟性が低下する。導電性ペーストの導電性と柔軟性とを両立するためには、導電性金属粉末の含有量を導電性ペーストの固形分量全体に対して５０％以上８５％以下とすることが好ましい。 Also, when the content of the conductive metal powder is increased, the conductive paste becomes hard and the flexibility is lowered. In order to achieve both the conductivity and flexibility of the conductive paste, the content of the conductive metal powder is preferably 50% or more and 85% or less with respect to the total solid content of the conductive paste.
　導電性金属粉末として、平均粒径が０．５μｍ～２０μｍの金属粉末Ａと、平均粒径が１００ｎｍ以下の金属粉末とを併用し、金属粉末Ａと金属粉末Ｂの含有比率を、重量比で９９．５：０．５～７０：３０とすると好ましい。金属粉末Ａと金属粉末Ｂとの含有比率が９９．５：０．５を超えて金属粉末Ａが増加すると、組み合わせ効果が減少し、導電性が低下する。また、含有比率が７０：３０を超えて金属粉末Ｂが増加すると、金属粉末Ｂの増量によりコスト高となり好ましくない。更に好ましい金属粉末Ａと金属粉末Ｂの含有比率は、９９：１～９０：１０である。 As the conductive metal powder, a metal powder A having an average particle size of 0.5 μm to 20 μm and a metal powder having an average particle size of 100 nm or less are used in combination, and the content ratio of the metal powder A and the metal powder B is expressed by weight ratio. 99.5: 0.5 to 70:30 is preferable. When the content ratio of the metal powder A and the metal powder B exceeds 99.5: 0.5 and the metal powder A increases, the combination effect decreases and the conductivity decreases. On the other hand, when the content ratio exceeds 70:30 and the metal powder B is increased, the amount of the metal powder B is increased, which is not preferable. A more preferable content ratio of the metal powder A and the metal powder B is 99: 1 to 90:10.
　金属粉末Ａの平均粒径は、０．５μｍ～２０μｍが好ましい。０．５μｍ以下では、導電性が低下する。また、平均粒径が２０μｍを超えると微細な印刷加工が困難になる。また、同様の理由で、最大粒径が極端に大きいものを含まないものを使用することが好ましく、最大粒径が２０μｍ～５０μｍの範囲にあるものが好適である。なお、粒径は、個々の粒子の最大径とし、その平均値を平均粒径としている。計測には、走査型電子顕微鏡（ＳＥＭ）等を用いる。 The average particle size of the metal powder A is preferably 0.5 μm to 20 μm. If the thickness is 0.5 μm or less, the conductivity is lowered. On the other hand, if the average particle size exceeds 20 μm, fine printing becomes difficult. For the same reason, it is preferable to use a material having a maximum particle size that does not contain an extremely large particle size, and one having a maximum particle size in the range of 20 μm to 50 μm is preferable. The particle diameter is the maximum diameter of each particle, and the average value is the average particle diameter. For the measurement, a scanning electron microscope (SEM) or the like is used.
　金属粉末Ａとしては、１種類のみでなく、平均粒径や形状の異なる複数の粉末を組み合わせて使用することもできる。例えば、鱗片状の銀粉末と球状の銀粉末を組み合わせて使用することで、導電性及び塗工後の平滑性を更に向上できる。 As the metal powder A, not only one type but also a plurality of powders having different average particle sizes and shapes can be used in combination. For example, by using a combination of scaly silver powder and spherical silver powder, the conductivity and smoothness after coating can be further improved.
　金属粉末Ｂは、平均粒径が１００ｎｍ以下の金属粉末である。ナノサイズの粉末は、粉末同士が凝集することがあるが、平均粒径とは、１次粒子の粒径をさすものとする。また、このようなナノサイズの粉末は、比表面積が大きいため、表面活性が大きい。よって表面を保護して２次凝集を抑えるために、表面が有機物で被覆されているものを用いるのが好ましい。有機物としては、ポリカルボン酸、ポリアクリル酸等が例示される。 Metal powder B is a metal powder having an average particle size of 100 nm or less. Nano-sized powders may be agglomerated, but the average particle size refers to the particle size of primary particles. Such nano-sized powders have a large surface area and thus a large surface activity. Therefore, in order to protect the surface and suppress secondary aggregation, it is preferable to use a material whose surface is coated with an organic substance. Examples of the organic substance include polycarboxylic acid and polyacrylic acid.
　平均粒径が１００ｎｍ以下の金属粉末Ｂは、例えば以下のようにして作製できる。硝酸銀を水と低級アルコールの混合溶剤に溶解し、アンモニア水でｐＨを１１以上に調整する。これに還元剤としてＬ－アスコルビン酸と分散剤としてポリアクリル酸を前記混合溶剤に溶解したものを加えることにより銀粒子が析出する。析出した銀粒子は、分散剤により２次凝集を抑えられた状態で濾過、洗浄、乾燥して得られる。銀粒子の平均粒子径は、ｐＨ、温度、各素材の濃度、混合の仕方等で変更できる。 The metal powder B having an average particle size of 100 nm or less can be produced, for example, as follows. Silver nitrate is dissolved in a mixed solvent of water and lower alcohol, and the pH is adjusted to 11 or more with aqueous ammonia. Silver particles are precipitated by adding L-ascorbic acid as a reducing agent and polyacrylic acid as a dispersing agent dissolved in the mixed solvent. The precipitated silver particles are obtained by filtration, washing and drying in a state where secondary aggregation is suppressed by the dispersant. The average particle diameter of the silver particles can be changed depending on pH, temperature, concentration of each material, mixing method, and the like.
　上記の工程を経て作成される銀粒子は、特に反応工程で分散剤を用いることにより、生成された銀の粒子の表面が分散剤で被覆された状態で得られる。生成段階で分散剤が銀の粒子の表面を被覆した状態となるため、外気の影響を受けにくく、且つ銀の粒子同士が２次凝集しにくい状態となる。たとえ凝集しても、分散剤が介在するため、有機溶剤等で簡単に凝集を破壊できる。また、樹脂への分散性も良好である。 The silver particles produced through the above steps are obtained in a state where the surface of the generated silver particles is coated with the dispersant, particularly by using a dispersant in the reaction step. Since the dispersant is in a state of covering the surface of the silver particles at the generation stage, it is hardly affected by the outside air, and the silver particles are not easily agglomerated. Even if agglomeration occurs, the dispersing agent intervenes, so that agglomeration can be easily broken with an organic solvent or the like. Moreover, the dispersibility to resin is also favorable.
　上記の導電性金属粉末、ウレタン変性ポリエステル樹脂、ブロックイソシアネートを混合して導電性ペーストを作製する。ウレタン変性ポリエステル樹脂及びブロックイソシアネートは、溶剤に溶解して用いる。溶剤は、樹脂を溶解可能であるもので有れば任意のものを使用でき、エステル系、エーテル系、ケトン系、エーテルエステル系、アルコール系、炭化水素系、アミン系の有機溶剤が例示される。導電性ペーストをスクリーン印刷して用いる場合には、印刷性の良い高沸点溶剤が好ましく、具体的には、カルビトールアセテート、ブチルカルビトールアセテートなどが特に好ましい。 The above conductive metal powder, urethane-modified polyester resin, and blocked isocyanate are mixed to prepare a conductive paste. The urethane-modified polyester resin and the blocked isocyanate are used after being dissolved in a solvent. Any solvent can be used as long as it can dissolve the resin, and examples thereof include ester-based, ether-based, ketone-based, ether-ester-based, alcohol-based, hydrocarbon-based, and amine-based organic solvents. . When the conductive paste is used after screen printing, a high boiling point solvent with good printability is preferable, and specifically, carbitol acetate, butyl carbitol acetate, and the like are particularly preferable.
　また、本発明の導電性銀ペーストには、印刷作業性向上のため、増粘剤、レベリング剤等の添加物を加えることもできる。更に本発明の性能を損なわない範囲で、カーボンやシリカ等の無機フィラーを添加することも可能である。これらの材料をボールミル、３本ロール、回転撹拌脱泡機などにより混合、分散して均一な状態とし、導電性ペーストを作製する。 In addition, additives such as thickeners and leveling agents can be added to the conductive silver paste of the present invention in order to improve printing workability. Furthermore, it is also possible to add inorganic fillers such as carbon and silica as long as the performance of the present invention is not impaired. These materials are mixed and dispersed by a ball mill, three rolls, a rotary stirring defoaming machine or the like to obtain a uniform state, and a conductive paste is produced.
　本発明の電磁波シールドフィルムは、上記の導電性ペーストからなる層を基材上に有するものである。上記の導電性ペーストを基材上に塗布した後、溶媒を乾燥させて固化することで電磁波シールドフィルムが得られる。基材としては、ポリエステルフィルム、ポリイミドフィルム等を用いることができる。屈曲性を考慮すると、ポリイミドフィルムが好ましい。図１は、電磁波シールドフィルムの一例を表す断面模式図である。基材１の上に、導電性ペースト層２を有している。導電性ペースト層を保護するために、導電性ペースト層２の上に保護フィルム８を設けても良い。保護フィルム８は、使用時に剥がされる。 The electromagnetic wave shielding film of the present invention has a layer made of the above conductive paste on a substrate. After apply | coating said electroconductive paste on a base material, an electromagnetic wave shielding film is obtained by drying a solvent and solidifying. A polyester film, a polyimide film, etc. can be used as a base material. In view of flexibility, a polyimide film is preferable. FIG. 1 is a schematic cross-sectional view illustrating an example of an electromagnetic wave shielding film. A conductive paste layer 2 is provided on the substrate 1. In order to protect the conductive paste layer, a protective film 8 may be provided on the conductive paste layer 2. The protective film 8 is peeled off during use.
　上記の電磁波シールドフィルムをフレキシブルプリント配線板の片面又は両面に貼り付けることで、本発明の電磁波シールドフレキシブルプリント配線板が得られる。図２は、電磁波シールドフレキシブルプリント配線板の一例を表す断面模式図である。フレキシブルプリント配線板７は、基材４上に銅箔５からなる配線が形成されており、その上をカバーレイが被覆している。カバーレイは、ポリイミド等からなるカバーレイフィルム６ａとカバーレイ接着剤６ｂとから構成される。フレキシブルプリント配線板のカバーレイ側に電磁波シールドフィルム３が貼り付けられている。なお、導電性ペーストを直接フレキシブルプリント配線板に塗布して導電性ペースト層を設けても良い。 The electromagnetic wave shielding flexible printed wiring board of the present invention can be obtained by attaching the above electromagnetic shielding film to one or both sides of the flexible printed wiring board. FIG. 2 is a schematic cross-sectional view illustrating an example of an electromagnetic wave shield flexible printed wiring board. In the flexible printed wiring board 7, a wiring made of a copper foil 5 is formed on a base material 4, and a cover lay covers the wiring. The coverlay includes a coverlay film 6a made of polyimide or the like and a coverlay adhesive 6b. An electromagnetic wave shielding film 3 is attached to the cover lay side of the flexible printed wiring board. Note that a conductive paste layer may be provided by directly applying a conductive paste to a flexible printed wiring board.
　導電性ペーストの塗布厚みは、特に制限されないが、１０μｍ～５０μｍの範囲とすることが好ましい。厚みが１０μｍ以下であると望ましい電磁波シールド特性が得られない反面、厚みを５０μｍ以上とするとシールド層の柔軟性が悪くなり、耐屈曲特性が低下する。 The coating thickness of the conductive paste is not particularly limited, but is preferably in the range of 10 μm to 50 μm. If the thickness is 10 μm or less, desirable electromagnetic wave shielding characteristics cannot be obtained, but if the thickness is 50 μm or more, the flexibility of the shield layer is deteriorated and the bending resistance is deteriorated.
　導電性ペーストの塗布方法としては、スクリーン印刷、凹版印刷、平板印刷、ディスペンサー等が例示される。形成される配線の精細性、膜厚、また、生産性の点から、スクリーン印刷が最も好適に用いられる。 Examples of the method for applying the conductive paste include screen printing, intaglio printing, lithographic printing, and dispenser. Screen printing is most preferably used from the viewpoint of the fineness, film thickness, and productivity of the wiring to be formed.
　また、本発明の導電性ペーストをフレキシブルプリント配線板に直接塗布、固化して電磁波シールド層とすることもできる。このような方法によっても、本発明の導電性ペーストからなる層を有する電磁波シールドフレキシブルプリント配線板が得られる。同様に、パソコンや携帯電話等の電子機器の筐体に塗布することで、本発明の導電性ペーストからなる層を有する電磁波シールド筐体が得られる。 Also, the conductive paste of the present invention can be directly applied to a flexible printed wiring board and solidified to form an electromagnetic wave shielding layer. Also by such a method, an electromagnetic wave shield flexible printed wiring board having a layer made of the conductive paste of the present invention can be obtained. Similarly, an electromagnetic wave shielding casing having a layer made of the conductive paste of the present invention can be obtained by applying it to the casing of an electronic device such as a personal computer or a mobile phone.
　次に発明を実施するための最良の形態を実施例により説明する。実施例は、本発明の範囲を限定するものではない。 Next, the best mode for carrying out the invention will be described by way of examples. The examples are not intended to limit the scope of the invention.
（実施例１～３、比較例１～３）
（導電性ペーストの作製）
　表１に記載の酸成分、アルコール成分及びイソシアネート成分を反応させて得られるウレタン変性ポリエステルを準備した。具体的には、四つ口フラスコに表１記載の酸成分とアルコール成分、及び酢酸ブチルカルビトールとブチルカルビトールの混合溶剤を入れて窒素気流下で６０℃に加熱した後、さらにイソシアネート化合物を添加して８０℃５時間加熱し、ウレタン変性ポリエステルを合成した。 (Examples 1 to 3, Comparative Examples 1 to 3)
(Preparation of conductive paste)
A urethane-modified polyester obtained by reacting the acid component, alcohol component and isocyanate component shown in Table 1 was prepared. Specifically, the acid component and alcohol component listed in Table 1 and a mixed solvent of butyl carbitol acetate and butyl carbitol are put into a four-necked flask and heated to 60 ° C. under a nitrogen stream, and then the isocyanate compound is further added. The mixture was added and heated at 80 ° C. for 5 hours to synthesize urethane-modified polyester.
　作製したウレタン変性ポリエステル樹脂に、導電性金属粉末として平均粒子３．０μｍの鱗片状銀粉末と平均粒子径２５ｎｍの球状銀粉末、及びブロックイソシアネートを混合して導電性ペーストを作製した。ウレタン変性ポリエステルとブロックイソシアネートの配合比は、等量モル比とし、導電性金属粉末の配合比率は、以下の比率とした。
・鱗片状銀粉末の配合比（重量）＝（ウレタン変性ポリエステル樹脂の重量＋ブロックイソシアネートの重量）×２．１
・球状銀粉末の配合比（重量）＝（ウレタン変性ポリエステル樹脂　重量＋ブロックイソシアネート　重量）×０．２３３ The produced urethane-modified polyester resin was mixed with a scaly silver powder having an average particle size of 3.0 μm, a spherical silver powder having an average particle size of 25 nm, and a blocked isocyanate as a conductive metal powder to prepare a conductive paste. The compounding ratio of the urethane-modified polyester and the blocked isocyanate was an equimolar molar ratio, and the compounding ratio of the conductive metal powder was the following ratio.
-Blending ratio (weight) of scaly silver powder = (weight of urethane-modified polyester resin + weight of blocked isocyanate) x 2.1
-Blending ratio (weight) of spherical silver powder = (urethane-modified polyester resin weight + blocked isocyanate weight) x 0.233
（評価用試料の作製）
　ポリイミドフィルムに銅箔を積層した無接着剤銅貼積層板（２層ＣＣＬ）を準備し、サブトラクティブ法により銅箔部分を選択的にエッチングし、線幅５０μｍのパターンを形成した。さらにこの上にカバーレイフィルムを貼り付けて評価用のフレキシブルプリント配線板を作製した。このフレキシブルプリント配線板のカバーレイフィルム側に上記の導電性ペーストをスクリーン印刷法により塗布し、オーブン炉で熱硬化した。さらに摺動屈曲性評価用サンプルについては、導電性ペースト上にソルダーレジストを塗布し、オーブン炉で熱硬化した。 (Preparation of sample for evaluation)
A non-adhesive copper-clad laminate (two-layer CCL) in which a copper foil was laminated on a polyimide film was prepared, and a copper foil portion was selectively etched by a subtractive method to form a pattern having a line width of 50 μm. Further, a cover lay film was stuck thereon to produce a flexible printed wiring board for evaluation. The conductive paste was applied to the cover lay film side of the flexible printed wiring board by a screen printing method and thermally cured in an oven furnace. Further, for the sliding flexibility evaluation sample, a solder resist was applied on the conductive paste and thermally cured in an oven furnace.
（導電性ペーストの評価：体積固有抵抗）
　この試料を幅５ｍｍで切り出し、４端子法による抵抗値測定（端子間距離１００ｍｍ）及び表面粗さ計による銀ペースト硬化膜の厚み測定を行い、体積固有抵抗を算出した。 (Evaluation of conductive paste: volume resistivity)
This sample was cut out at a width of 5 mm, and the resistance value was measured by the 4-terminal method (distance between terminals: 100 mm) and the thickness of the cured silver paste film was measured by a surface roughness meter, and the volume resistivity was calculated.
（導電性ペーストの評価：体積固有抵抗）
　この試料を最高温度２６０℃に設定したリフロー炉に２回通した後、銀ペースト硬化膜とカバーレイフィルム間に切り欠きを作り、銀ペースト硬化膜を１８０°方向に折り曲げて、５０ｍｍ／分の速度で引っ張ることで密着強度を測定した。 (Evaluation of conductive paste: volume resistivity)
This sample was passed twice through a reflow oven set at a maximum temperature of 260 ° C., then a notch was made between the silver paste cured film and the coverlay film, the silver paste cured film was bent in the 180 ° direction, and 50 mm / min. The adhesion strength was measured by pulling at a speed.
（導電性ペーストの評価：摺動屈曲試験）
　上記と同様に、試料を最高温度２６０℃のリフロー炉に２回通した後、ストローク１００ｍｍ、１５秒／サイクル、摺動屈曲半径１．０ｍｍの条件で摺動屈曲させ、配線抵抗が２０％上昇した時点の摺動屈曲回数を評価した。以上の結果を表１に示す。なお、それぞれの評価項目において、密着強度０．８Ｎ／ｃｍ以上、摺動屈曲回数７万回以上、体積固有抵抗９０×１０－６Ω・ｃｍ以下が良好範囲である。 (Evaluation of conductive paste: sliding bending test)
Similar to the above, after passing the sample twice through a reflow furnace with a maximum temperature of 260 ° C., the sample was slid and bent under the conditions of a stroke of 100 mm, 15 seconds / cycle and a sliding bend radius of 1.0 mm, and the wiring resistance increased by 20%. The number of sliding bends at the time of the evaluation was evaluated. The results are shown in Table 1. In each evaluation item, the adhesion strength is 0.8 N / cm or more, the number of sliding and bending is 70,000 times or more, and the volume resistivity is 90 × 10 −6 Ω · cm or less.
Figure JPOXMLDOC01-appb-T000002
 　
Figure JPOXMLDOC01-appb-T000002
 　
　酸成分、アルコール成分、イソシアネート成分に含まれる芳香族成分の合計が、前記酸成分、アルコール成分、イソシアネート成分の合計に対して５モル％未満である比較例１では、リフロー処理後の密着力が低く、耐熱性が劣っている。同様に、イソシアネート成分に芳香族成分が含まれない比較例２でもリフロー処理後の密着力が低く、耐熱性が劣っている。また、芳香族成分の合計が５０モル％を超える比較例３では、密着力は、良好であるが摺動屈曲性が悪い。 In Comparative Example 1 in which the total of aromatic components contained in the acid component, alcohol component, and isocyanate component is less than 5 mol% with respect to the total of the acid component, alcohol component, and isocyanate component, the adhesion after reflow treatment is Low and heat resistance is poor. Similarly, Comparative Example 2 in which the aromatic component is not included in the isocyanate component also has low adhesion after reflow treatment and poor heat resistance. Further, in Comparative Example 3 in which the total of the aromatic components exceeds 50 mol%, the adhesion is good but the sliding flexibility is poor.
（実施例４～８）
　ウレタン変性ポリエステル樹脂の重合度を変えることで、水酸基価の異なるウレタン変性ポリエステル樹脂を作製した。この樹脂を用いて、実施例１～３と同様に導電性ペーストを作製し、リフロー処理後の密着力、摺動屈曲性、体積固有抵抗を評価した。結果を表２に示す。 (Examples 4 to 8)
By changing the degree of polymerization of the urethane-modified polyester resin, urethane-modified polyester resins having different hydroxyl values were produced. Using this resin, a conductive paste was prepared in the same manner as in Examples 1 to 3, and the adhesion strength, sliding flexibility and volume resistivity after reflow treatment were evaluated. The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　ウレタン変性ポリエステル樹脂の水酸基価とリフロー処理後の密着力とは、相関しており、水酸基価が大きくなるほど密着力が向上している。水酸基価が５ｍｇＫＯＨ／ｇ未満の実施例４では、密着力が０．８Ｎ／ｃｍであり、やや低い値となっている。また、水酸基価が６０ｍｇＫＯＨ／ｇを超える実施例８は、柔軟性に乏しく、摺動屈曲回数がやや低い結果となっている。 The hydroxyl value of the urethane-modified polyester resin correlates with the adhesion after reflow treatment, and the adhesion increases as the hydroxyl value increases. In Example 4 having a hydroxyl value of less than 5 mgKOH / g, the adhesion is 0.8 N / cm, which is a slightly low value. Moreover, Example 8 in which the hydroxyl value exceeds 60 mgKOH / g has poor flexibility and results in a slightly low number of sliding and bending.
（実施例９～１３）
　表３に記載のように、種々の数平均分子量を持つ多官能ブロックポリイソシアネート化合物を準備した。多官能ブロックポリイソシアネート化合物は、イソシアネートモノマーとポリヒドロキシ化合物とのアダクト型イソシアネートの末端をブロック剤でブロックしたものである。これを硬化剤として用い、実施例１に記載のウレタン変性ポリエステル樹脂と組み合わせて実施例１～３と同様に導電性ペーストを作製し、リフロー処理後の密着力、摺動屈曲性、体積固有抵抗を評価した。 (Examples 9 to 13)
As shown in Table 3, polyfunctional block polyisocyanate compounds having various number average molecular weights were prepared. The polyfunctional block polyisocyanate compound is obtained by blocking the end of an adduct type isocyanate of an isocyanate monomer and a polyhydroxy compound with a blocking agent. Using this as a curing agent, a conductive paste was prepared in the same manner as in Examples 1 to 3 in combination with the urethane-modified polyester resin described in Example 1, and the adhesive strength after reflow treatment, sliding flexibility, volume resistivity Evaluated.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　全てのサンプルにおいて、密着性、摺動屈曲性、比抵抗は、要求特性を満たしているが、多官能ブロックポリイソシアネート化合物の数平均分子量が５００未満の実施例９では、摺動屈曲回数が８万回とやや低い結果となっている。また、数平均分子量が３０００を超える実施例１３では、体積抵抗がやや高くなっている。 In all the samples, the adhesiveness, sliding flexibility, and specific resistance satisfy the required characteristics, but in Example 9 in which the number average molecular weight of the polyfunctional block polyisocyanate compound is less than 500, the number of sliding flexures is 8. The result is somewhat low at 10,000 times. Moreover, in Example 13 in which the number average molecular weight exceeds 3000, the volume resistance is slightly high.
（実施例１４～１８）
　実施例１で使用したウレタン変性ポリエステル樹脂と多官能ブロックポリイソシアネート化合物を用い、両者の配合比率を変えることでＮＣＯ／ＯＨ比率を変えて実施例１～３と同様に導電性ペーストを作製し、リフロー処理後の密着力、摺動屈曲性、体積固有抵抗を評価した。結果、表４に示すように、ＮＣＯ／ＯＨ比率が０．８未満の実施例１４では、体積抵抗値がやや高くなっている。これは、ＮＣＯ／ＯＨ比率が低いと架橋密度が低下するからであると推測される。また、ＮＣＯ／ＯＨ比率が３．０を超える実施例１８では、リフロー処理後の密着力がやや低くなっている。ＮＣＯ／ＯＨ比率が高いと、過剰の硬化剤が残留することで耐熱性が低下するためであると推測される。 (Examples 14 to 18)
Using the urethane-modified polyester resin and the polyfunctional block polyisocyanate compound used in Example 1, and changing the NCO / OH ratio by changing the blending ratio of both, a conductive paste was prepared in the same manner as in Examples 1 to 3, The adhesive strength, sliding flexibility, and volume resistivity after the reflow treatment were evaluated. As a result, as shown in Table 4, in Example 14 in which the NCO / OH ratio is less than 0.8, the volume resistance value is slightly high. This is presumed to be because the crosslinking density decreases when the NCO / OH ratio is low. Moreover, in Example 18 in which the NCO / OH ratio exceeds 3.0, the adhesion after the reflow treatment is slightly low. If the NCO / OH ratio is high, it is presumed that the heat resistance is lowered due to the excess curing agent remaining.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
（実施例１９～２３）
　導電性金属粉末として、平均粒径が４．８μｍの金属粉末Ａと、平均粒径が３０ｎｍの金属粉末Ｂを準備した。金属粉末Ａと金属粉末Ｂの含有比率を変え、実施例１～３に記載の方法と同様に導電性ペーストを作製し、リフロー処理後の密着力、摺動屈曲性、体積固有抵抗を評価した。この時、金属粉末Ａと金属粉末Ｂとの総重量は、ウレタン変性ポリエステル樹脂の重量とブロックイソシアネートとの重量和を２．３３３倍した配合とした。
　結果、表５記載のように、金属粉末Ａと金属粉末Ｂの含有比率が９９．５：０．５未満の実施例１９では、体積固有抵抗がやや高い結果となっている。また、金属粉末Ａと金属粉末Ｂの含有比率が７０：３０を超える実施例２３では、特性の向上効果は、特に見られない。平均粒径がナノサイズの金属粉末は、高価であるので、導電性ペーストの特性とコストを考慮すると、金属粉末Ａと金属粉末Ｂの含有比率は、９９．５：０．５～７０：３０の範囲が好ましい。 (Examples 19 to 23)
As conductive metal powder, metal powder A having an average particle diameter of 4.8 μm and metal powder B having an average particle diameter of 30 nm were prepared. By changing the content ratio of the metal powder A and the metal powder B, a conductive paste was produced in the same manner as in the methods described in Examples 1 to 3, and the adhesion strength, sliding flexibility, and volume resistivity after the reflow treatment were evaluated. . At this time, the total weight of the metal powder A and the metal powder B was obtained by multiplying the weight sum of the weight of the urethane-modified polyester resin and the blocked isocyanate by 2.333.
As a result, as shown in Table 5, in Example 19 in which the content ratio of the metal powder A and the metal powder B was less than 99.5: 0.5, the volume resistivity was slightly high. Further, in Example 23 in which the content ratio of the metal powder A and the metal powder B exceeds 70:30, the effect of improving the characteristics is not particularly seen. Since the metal powder having an average particle size of nano-size is expensive, the content ratio of the metal powder A and the metal powder B is 99.5: 0.5 to 70:30 in consideration of the characteristics and cost of the conductive paste. The range of is preferable.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
（実施例２４～２８）
　導電性金属粉末として、平均粒径が４．８μｍの金属粉末Ａと、平均粒径が３０ｎｍの金属粉末Ｂを準備した。ここで、金属粉末Ａと金属粉末Ｂの含有比率は、９０：１０に固定し、金属粉末Ａと金属粉末Ｂとを合計した金属粉末の含有比率を変えて導電性ペーストを作製し、リフロー処理後の密着力、摺動屈曲性、体積固有抵抗を評価した。
　結果、表６記載のように、金属粉末含有比率が５０重量％未満の実施例２４では、体積抵抗がやや高い結果となっている。また、金属粉末含有比率が８５重量％を超える実施例２８では、摺動屈曲性能がやや低い。金属粉末含有比率が高すぎると柔軟性が劣るからであると推測される。
　今回開示された実施の形態および実施例は、全ての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は、上記した説明でなく請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内のすべての変更が含まれることが意図される。 (Examples 24 to 28)
As conductive metal powder, metal powder A having an average particle diameter of 4.8 μm and metal powder B having an average particle diameter of 30 nm were prepared. Here, the content ratio of the metal powder A and the metal powder B is fixed at 90:10, and the content ratio of the metal powder obtained by adding the metal powder A and the metal powder B is changed to produce a conductive paste, and the reflow treatment is performed. The subsequent adhesion, sliding flexibility, and volume resistivity were evaluated.
As a result, as shown in Table 6, in Example 24 in which the metal powder content ratio was less than 50% by weight, the volume resistance was slightly high. Further, in Example 28 in which the metal powder content ratio exceeds 85% by weight, the sliding bending performance is slightly low. It is estimated that the flexibility is inferior when the metal powder content is too high.
It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
本発明は、導電性ペースト及びそれを用いた電磁波シールドフィルム、電磁波シールドフレキシブルプリント配線板に関し、特に耐屈曲性が要求されるフレキシブルプリント配線板に好適に利用することができる。 The present invention relates to a conductive paste, an electromagnetic wave shielding film using the conductive paste, and an electromagnetic wave shielding flexible printed wiring board, and can be suitably used particularly for a flexible printed wiring board requiring bending resistance.
１　　基材
２　　導電性ペースト層
３　　保護フィルム
４　　基材
５　　銅箔
６ａ　カバーレイフィルム
６ｂ　カバーレイ接着剤
７　　フレキシブルプリント配線板
８　　保護フィルム DESCRIPTION OF SYMBOLS 1 Base material 2 Conductive paste layer 3 Protective film 4 Base material 5 Copper foil 6a Coverlay film 6b Coverlay adhesive 7 Flexible printed wiring board 8 Protective film
特開平１－１５９９０６号公報JP-A-1-159906 特開平１－３０６２４０号公報JP-A-1-306240 特開２００５－２９４２５４号公報JP 2005-294254 A

Claims (7)

  1. 　導電性金属粉末、ウレタン変性ポリエステル樹脂、及びブロックイソシアネートを含有する導電性ペーストであって、
    前記ウレタン変性ポリエステル樹脂は、酸成分、アルコール成分、及び芳香族イソシアネートを含むイソシアネート成分を反応させて得られ、
    前記酸成分、アルコール成分、イソシアネート成分に含まれる芳香族成分の合計が、前記酸成分、アルコール成分、イソシアネート成分の合計に対して５モル％以上５０モル％以下であることを特徴とする、導電性ペースト。     A conductive paste containing conductive metal powder, urethane-modified polyester resin, and blocked isocyanate,
    The urethane-modified polyester resin is obtained by reacting an acid component, an alcohol component, and an isocyanate component containing an aromatic isocyanate,
    The total of aromatic components contained in the acid component, alcohol component, and isocyanate component is 5 mol% or more and 50 mol% or less with respect to the total of the acid component, alcohol component, and isocyanate component. Sex paste.
  2. 　前記ウレタン変性ポリエステル樹脂の水酸基価が、５ｍｇＫＯＨ／ｇ以上６０ｍｇＫＯＨ／ｇ以下であることを特徴とする、請求項１に記載の導電性ペースト。 The conductive paste according to claim 1, wherein the urethane-modified polyester resin has a hydroxyl value of 5 mgKOH / g or more and 60 mgKOH / g or less.
  3. 　前記ブロックイソシアネートは、数平均分子量が５００以上３０００以下であり、イソシアネートモノマーとポリヒドロキシ化合物とのアダクト型イソシアネートの末端をブロック剤でブロックした多官能ブロックポリイソシアネート化合物である、請求項１又は２に記載の導電性ペースト。 The block isocyanate is a polyfunctional block polyisocyanate compound having a number average molecular weight of 500 or more and 3000 or less, wherein a terminal of an adduct type isocyanate of an isocyanate monomer and a polyhydroxy compound is blocked with a blocking agent. The conductive paste as described.
  4. 　前記ウレタン変性ポリエステル樹脂と、前記ブロックイソシアネートの混合比は、前記ウレタン変性ポリエステル樹脂の水酸基（ＯＨ）と、前記ブロックイソシアネートのイソシアネート基（ＮＣＯ）とのモル比率（ＮＣＯ／ＯＨ）換算で０．８以上、３．０以下である、請求項１～３のいずれか１項に記載の導電性ペースト。 The mixing ratio of the urethane-modified polyester resin and the blocked isocyanate is 0.8 in terms of the molar ratio (NCO / OH) of the hydroxyl group (OH) of the urethane-modified polyester resin and the isocyanate group (NCO) of the blocked isocyanate. The conductive paste according to any one of claims 1 to 3, wherein the conductive paste is 3.0 or less.
  5. 　前記導電性金属粉末は、平均粒径が０．５μｍ～２０μｍの金属粉末Aと、平均粒径が１００ｎｍ以下の金属粉末Ｂとからなり、金属粉末Ａと金属粉末Ｂの含有比率が、重量比で９９．５：０．５～７０：３０であると共に、前記導電性金属粉末の含有比率が、導電性ペーストの固形分量に対して５０重量％以上８５重量％以下であることを特徴とする、
    請求項１～４のいずれか１項に記載の導電性ペースト。     The conductive metal powder is composed of a metal powder A having an average particle diameter of 0.5 μm to 20 μm and a metal powder B having an average particle diameter of 100 nm or less, and the content ratio of the metal powder A and the metal powder B is a weight ratio. 99.5: 0.5 to 70:30, and the content ratio of the conductive metal powder is 50 wt% or more and 85 wt% or less with respect to the solid content of the conductive paste. ,
    The conductive paste according to any one of claims 1 to 4.
  6. 　請求項１～５のいずれか１項に記載の導電性ペーストからなる層を基材上に有する、電磁波シールドフィルム。 An electromagnetic wave shielding film having a layer made of the conductive paste according to any one of claims 1 to 5 on a substrate.
  7. 　請求項１～５のいずれか１項に記載の導電性ペーストからなる層を有する、電磁波シールドフレキシブルプリント配線板。 An electromagnetic shielding flexible printed wiring board having a layer made of the conductive paste according to any one of claims 1 to 5.
PCT/JP2009/067715 2008-11-14 2009-10-13 Conductive paste, electromagnetic wave-shielding film using same, and electromagnetic wave-shielding flexible printed wiring board WO2010055742A1 (en)

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TW201030766A (en) 2010-08-16
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CN101952902B (en) 2012-09-05
CN101952902A (en) 2011-01-19

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