WO2012120884A1 - Flaked silver powder and method for manufacturing same, electroconductive composition, electroconductive sheet, electromagnetic shielding sheet, and layered body having electroconductive pattern - Google Patents

Flaked silver powder and method for manufacturing same, electroconductive composition, electroconductive sheet, electromagnetic shielding sheet, and layered body having electroconductive pattern Download PDF

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Publication number
WO2012120884A1
WO2012120884A1 PCT/JP2012/001582 JP2012001582W WO2012120884A1 WO 2012120884 A1 WO2012120884 A1 WO 2012120884A1 JP 2012001582 W JP2012001582 W JP 2012001582W WO 2012120884 A1 WO2012120884 A1 WO 2012120884A1
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WIPO (PCT)
Prior art keywords
silver powder
conductive
flaky silver
powder
less
Prior art date
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PCT/JP2012/001582
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French (fr)
Japanese (ja)
Inventor
祐司 西山
冨永　浩史
英宣 小林
西田　元紀
誠一 松本
雄史 杉谷
Original Assignee
東洋インキＳｃホールディングス株式会社
トーヨーケム株式会社
福田金属箔粉工業株式会社
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Publication of WO2012120884A1 publication Critical patent/WO2012120884A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/06—Alloys based on silver
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06—Metallic powder characterised by the shape of the particles
    • B22F1/068—Flake-like particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
    • 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
    • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
    • 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
    • H05K2201/02—Fillers; Particles; Fibers; Reinforcement materials
    • H05K2201/0203—Fillers and particles
    • H05K2201/0242—Shape of an individual particle
    • H05K2201/0245—Flakes, flat particles or lamellar particles

Definitions

  • the present invention relates to a flaky silver powder and a method for producing the same. Moreover, it is related with the electroconductive composition containing the said flaky silver powder, the electroconductive sheet using an electroconductive composition, an electromagnetic wave shielding sheet, and a laminated body with an electroconductive pattern.
  • conductive compositions mainly composed of resin and conductive particles have been used as printed wiring boards as conductive sheets for coating applications, electromagnetic shielding applications, and laminates with conductive patterns for printed circuit formation applications. These are used in electronic parts such as electronic devices, and various proposals have been made (for example, Patent Documents 1 to 5).
  • Patent Document 1 has a flaky particle size, a laser diffraction method 50% particle size of 3 to 8 ⁇ m, an apparent density of 0.4 to 1.1 g / cm 3 , and a BET method specific surface area of 1.5.
  • a flaky silver powder for a conductive paste, characterized in that it is ⁇ 4.0 m 2 / g, and a method for producing the same are described.
  • flaky silver powder A having an average particle diameter of 3 to 8 ⁇ m, a specific surface area of 1.5 to 4.0 m 2 / g, and an apparent density of 0.4 to 1.1 g / cm 3
  • flaky silver powder B having an average particle diameter of 3 to 10 ⁇ m, a specific surface area of 0.6 to 1.2 m 2 / g, and an apparent density of 1.5 to 2.1 g / cm 3
  • a resin A conductive paste composition is described.
  • This composition contains 30 to 95 parts by weight of flaky silver powder A with respect to a total weight of 100 parts of flaky silver powder A and flaky silver powder B, and flaky silver powder A with respect to the solid content of the conductive paste.
  • the flaky silver powder B is contained in an amount of 35 to 85% by weight.
  • Patent Document 3 describes a method for producing silver powder by a wet reduction method in order to obtain silver powder having fine particles, excellent dispersibility (low cohesiveness), and a large crystallite diameter. ing. Specifically, it is described that a silver chelate complex slurry using ethylenediaminetetraacetate as a complexing agent is used as a raw material and manufactured using a wet reduction method.
  • the average particle diameter D50 is It is described that flake silver powder having an aspect ratio ([average major axis ( ⁇ m)] / [average thickness ( ⁇ m)]) of 6 to 15 is 10 to 13 ⁇ m.
  • This flaky silver powder describes a method in which spherical silver powder having a predetermined particle diameter and media beads having a predetermined particle diameter are mixed and stirred in a bead mill to plastically deform the particles of the spherical silver powder to form a flake.
  • Patent Document 5 primary particles and aggregated particles obtained by agglomerating primary particles, the conductive particles having an average particle size of 0.5 to 20 ⁇ m and a specific surface area of 0.07 to 1.7 m 2 / g, A conductive paste composed of a binder mainly composed of a thermosetting resin is disclosed.
  • Cost reduction of the conductive composition can be realized by reducing the proportion of conductive particles.
  • strength with respect to a to-be-adhered body can be raised by decreasing the ratio of electroconductive particle and increasing the ratio of resin.
  • the ratio of the conductive particles in the conductive composition is reduced, there is a problem that the conductive characteristics are deteriorated. For this reason, the technique which implement
  • the present invention has been made in view of the above-mentioned background, and an object thereof is to provide a flaky silver powder excellent in conductive properties, a method for producing the same, and a conductive composition. Furthermore, it is providing the laminated body with an electroconductive sheet, an electromagnetic wave shielding sheet, and an electroconductive pattern using this electroconductive composition.
  • the flaky silver powder according to the present invention has a 50% particle diameter in a laser diffraction method of 3 ⁇ m or more and 8 ⁇ m or less, and an apparent density of 0.25 g / cm 3 or more and 0.5 g / cm 3 or less.
  • the surface resistance value of the conductive film having a dry film thickness of 15 ⁇ m when the flaky silver powder is contained in 100 parts by weight with respect to 100 parts by weight of the polyester resin is 0.4 ⁇ / ⁇ or less.
  • the BET specific surface area of the flaky silver powder is preferably 1 m 2 / g or more and 3.5 m 2 / g or less.
  • the method for producing flaky silver powder according to the present invention comprises a step of classifying, dispersing and pulverizing uncrushed flaky silver powder in a semi-free vortex centrifugal swirling airflow environment.
  • the pulverized silver powder has a 50% particle size of 3 ⁇ m or more and 8 ⁇ m or less in a laser diffraction method, an apparent density of 0.25 g / cm 3 or more and 0.5 g / cm 3 or less, and a polyester type
  • the surface resistance value of the conductive film having a dry film thickness of 15 ⁇ m is 0.4 ⁇ / ⁇ or less.
  • the silver powder separated by the classification / dispersion / pulverization step can be mixed and used.
  • the semi-free vortex centrifugal type means that air is swirled by providing guide vanes, etc. without a rotating body inside the device, and centrifugal force is applied to the particles by the swirling motion, and the swirling flow itself produces particles. This is a method that uses a drag force.
  • the conductive composition according to the present invention contains at least the flaky silver powder and the resin of the above aspect.
  • the electroconductive sheet which concerns on this invention has at least the layer formed from the electroconductive composition of the said aspect.
  • the laminated body with a conductive pattern which concerns on this invention comprises a base material and the conductive pattern formed on the said base material, and the said conductive pattern is formed with the conductive composition of the said aspect. It is.
  • the electromagnetic wave shielding sheet according to the present invention is obtained by laminating a conductive layer and an insulating layer formed from the conductive composition of the above aspect.
  • the electromagnetic wave shielding sheet according to the present invention is obtained by laminating a conductive layer and an insulating layer formed from the conductive composition of the above aspect.
  • the laminate with a conductive pattern according to the present invention includes a base material and a conductive pattern formed on the base material, and the conductive pattern is formed of the conductive composition of the above aspect. is there.
  • the flaky silver powder of the present invention has succeeded in reducing the surface resistance value by making it a bulky particle shape having the above-mentioned specific range of 50% particle size and the above-described specific range of apparent density, and is high. Conductivity was realized. More specifically, the surface resistance value when blended in the same amount as that of the polyester resin could be an excellent value of 0.4 ⁇ / ⁇ or less, and the conductivity of the flaky silver powder itself could be increased.
  • the present invention there is an excellent effect that it is possible to provide a flaky silver powder having excellent conductive properties and a method for producing the same. Furthermore, there exists the outstanding effect that the electroconductive composition containing the said flaky silver powder, the electroconductive sheet using this electroconductive composition, an electromagnetic wave shielding sheet, and a laminated body with an electroconductive pattern can be provided.
  • FIG. 2 is a schematic plan view taken along the line II-II in FIG. 1.
  • the graph which shows the particle size distribution for demonstrating the fine powder and coarse powder of flaky silver powder which concern on this invention.
  • the flaky silver powder according to the present invention has a 50% particle size (hereinafter simply referred to as “50% particle size”) in a laser diffraction method of 3 ⁇ m or more and 8 ⁇ m or less, and an apparent density of 0.25 g /
  • the 50% particle size of the flaky silver powder according to the present invention means the particle size at an integrated value of 50% in the particle size distribution determined by the laser diffraction method, and the distribution curve of the integrated% obtained by integrating the particles is 50%.
  • the particle size distribution by the laser diffraction method is a so-called laser diffraction / scattering method, in which a particle group is irradiated with laser light, and a diffraction / scattered image detected from the intensity distribution pattern of the diffraction / scattered light emitted therefrom. And the particle diameter was determined.
  • the flaky silver powder according to the present invention can suppress an increase in the surface area of the particles by setting the 50% particle size to 3 ⁇ m or more. As a result, the contact resistance can be suppressed and the conductivity can be kept good. Further, by setting the 50% particle size to 8 ⁇ m or less, it is possible to make the overlapping of the particles good and keep the contact area between the particles good. As a result, the conductivity can be maintained in a good state.
  • a more preferable range of the 50% particle size of the flaky silver powder is 4 ⁇ m or more and 7 ⁇ m or less, and a particularly preferable range is 5.3 ⁇ m or more and 6.2 ⁇ m or less.
  • the apparent density is very low. By setting the apparent density to 0.5 g / cm 3 or less, it is possible to provide good conductivity while reducing the amount of flaky silver powder added to the conductive composition. Moreover, when the apparent density of the flaky silver powder is 0.25 g / cm 3 or more, an increase in viscosity when mixed with a resin and used as a conductive composition can be suppressed. For this reason, a highly reliable conductive composition can be provided. A more preferable apparent density is 0.3 g / cm 3 or more and 0.4 g / cm 3 or less, and a particularly preferable apparent density is 0.36 g / cm 3 or more and 0.4 g / cm 3 or less.
  • the flaky silver powder according to the present invention has a surface resistance value of a conductive film having a dry film thickness of 15 ⁇ m, when the flaky silver powder is contained in 100 parts by weight with respect to 100 parts by weight of the polyester resin, of 0.4 ⁇ / ⁇ or less. belongs to.
  • a more preferable range of the surface resistance value is less than 0.4 ⁇ / ⁇ , and more preferably 0.35 ⁇ / ⁇ or less.
  • the surface resistance value is a coating film obtained by applying and drying a conductive composition obtained by blending and mixing 100 parts by weight of a polyester resin and 100 parts by weight of flaky silver powder so that the film thickness becomes 15 ⁇ m. Is obtained by measuring. A diluting solvent can be added as needed.
  • Byron 200 manufactured by Toyobo Co., Ltd. (Tg: 67 ° C.), Byron 240 (Tg: 60 ° C.), Byron 300 (Tg: 7 ° C.), Byron 500 (Tg: 4 ° C.), Byron 600 (Tg: 47 ° C.), etc. Is mentioned.
  • Examples of the method for mixing 100 parts by weight of the flaky silver powder with 100 parts by weight of the polyester resin include a mixer, a dissolver, a Hoover muller, a three-roll mill, and a sand mill.
  • a conductive composition containing 100 parts by weight of flaky silver powder is applied to 100 parts by weight of a polyester resin with a bar coater, and dried at 100 ° C. for 2 minutes to form a coating film having a dry film thickness of 15 ⁇ m. .
  • the BET specific surface area of the flaky silver powder is preferably 1 m 2 / g or more and 3.5 m 2 / g or less.
  • the BET specific surface area is preferably 1 m 2 / g or more and 3.5 m 2 / g or less.
  • a more preferable range of the BET specific surface area is 1.2 m 2 / g or more and 2.5 m 2 / g or less, and a particularly preferable range is 1.5 m 2 / g or more and 1.9 m 2 / g or less.
  • the conductive composition according to the present invention contains at least a resin and conductive particles, and uses the aforementioned flaky silver powder as the conductive particles. That is, as the conductive particles, the 50% particle diameter is 3 ⁇ m or more and 8 ⁇ m or less, the apparent density is 0.25 g / cm 3 or more and 0.5 g / cm 3 or less, and the weight of the polyester resin is 100 weight.
  • the surface resistance value of the conductive film having a dry film thickness of 15 ⁇ m when containing 100 parts by weight of flaky silver powder with respect to the part contains at least flaky silver powder having a resistance of 0.4 ⁇ / ⁇ or less.
  • the flaky silver powder according to the present invention has a surface resistance value of a conductive film having a dry film thickness of 15 ⁇ m when the flaky silver powder is contained in 100 parts by weight with respect to 100 parts by weight of the polyester resin. ⁇ Excellent conductive properties due to use of the following. For this reason, when the flaky silver powder of the present invention is used as the conductive particles of the conductive composition, it is possible to reduce the content of conductive particles for designing desired conductive characteristics as compared with the conventional flaky silver powder. It becomes. Therefore, the conductive composition according to the present invention can realize strength and excellent adhesion to the adherend. In addition, the cost can be reduced.
  • the resin contained in the conductive composition according to the present invention is not particularly limited, but as an example, polyurethane resin, (unsaturated) polyester resin, alkyd resin, butyral resin, acetal resin, polyamide resin, (meth) acrylic resin, Styrene / (meth) acrylic resin, polystyrene resin, nitrocellulose, benzylcellulose, cellulose (tri) acetate, casein, shellac, gelatin, gilsonite, rosin, rosin ester, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, hydroxyethylcellulose, hydroxypropyl Cellulose, methylcellulose, ethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, carboxymethyl Ethyl cellulose, carboxymethyl nitrocellulose, ethylene / vinyl alcohol resin, styrene / maleic anhydride resin, polybutadiene resin, polyvinyl chloride resin
  • a urethane resin and an epoxy resin it is more preferable to contain a urethane resin and an epoxy resin.
  • a urethane resin and an epoxy resin it is possible to improve adhesion and adhesion to an adherend when a dry film is formed. Moreover, the heat resistance of the dry film can be improved.
  • a solvent can be added as necessary to facilitate printing and coating.
  • the solvent to be used is not particularly limited. Examples thereof include aliphatic hydrocarbon organic solvents such as n-hexane, n-heptane, and n-octane, and cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, cyclooctane, and the like.
  • Alicyclic hydrocarbon solvents aromatic hydrocarbon solvents such as toluene and xylene, ketone organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethyl carbonate, methyl acetate, ethyl acetate, n-propyl acetate, acetic acid Ester solvents such as butyl and propylene glycol monoethyl ether acetate Alcohol solvents such as methanol, ethanol, n-propanol, isopropanol and butanol, propylene glycol monomethyl ether, propylene glycol monoethyl Ether and the like.
  • the conductive composition according to the present invention may contain a conductive filler other than the flaky silver powder of the present invention.
  • a conductive filler other than the flaky silver powder of the present invention.
  • Specific examples include metal powders such as silver, copper, and nickel; alloy powders such as solder; copper powder that has been subjected to silver plating; fillers such as glass fibers, plastics, and carbon that have been subjected to metal plating.
  • Examples of the shape of the metal powder include a spherical shape, a flake shape, a dendritic shape, and a fibrous shape. From the viewpoint of improving the conductive properties, it is preferable to use the flaky silver powder of the present invention alone as a conductive filler. However, even in this case, other conductive fillers may be included as long as the characteristics are not affected.
  • the content of the flaky silver powder having the above characteristics of the conductive composition according to the present invention can be appropriately designed according to the use and needs, but when the flaky silver powder according to the present invention is used as the conductive particles.
  • the amount of flaky silver powder is less than 25 parts by weight, desired conductivity may not be obtained.
  • the amount is more than 900 parts by weight, the dry film may become brittle because the resin is relatively decreased.
  • the conductive composition according to the present invention can be produced by weighing a resin, a solvent, and flaky silver powder, and then mixing and dispersing additives as necessary.
  • the mixing or dispersing method is not particularly limited, and for example, a mixer, a dissolver, a hoover muller, a three roll mill, a sand mill or the like can be used.
  • additives to be added as necessary include UV absorbers, UV stabilizers, radical scavengers, fillers, thixotropic agents, anti-aging agents, antioxidants, antistatic agents, flame retardants, and thermal conductivity.
  • Examples include improvers, plasticizers, anti-sagging agents, antifouling agents, antiseptics, bactericides, antifoaming agents, leveling agents, antiblocking agents, curing agents, thickeners, dispersants, silane coupling agents, etc. it can.
  • the conductive composition according to the present invention can be applied to various uses including a conductive sheet, a laminate with a conductive pattern, and the like.
  • a conductive sheet for example, it can be used as an antenna circuit for non-contact type IC media, a conductive circuit for printed circuit boards, a conductive material for printed electronics, a conductive ink for forming various electrode materials such as a touch panel and a solar cell, and a conductive paste.
  • it can utilize suitably as a mesh film
  • it can be used as a film for imparting conductivity to a non-conductive material, such as a conductive cloth.
  • the conductive composition of the present invention can be used in general members such as electronic devices and electronic components.
  • the “sheet” is not limited to a film thickness, and includes a film-like, sheet-like, or plate-like thing in a narrow sense.
  • the electromagnetic wave shielding property at a frequency of 1 GHz is preferably 40 dB or more, and more preferably 60 dB or more.
  • the electromagnetic wave shielding property is that a conductive composition containing 100 parts by weight of flaky silver powder with respect to 100 parts by weight of a polyester resin is formed on a polyimide film having a thickness of 12.5 ⁇ m and a conductive layer having a thickness of 15 ⁇ m.
  • a coating film was obtained by coating and drying, and this was determined by measuring by the KEC method.
  • the KEC method refers to a method of measuring electromagnetic shielding properties using an electromagnetic shielding effect measuring device developed by Kansai Electronics Industry Promotion Center (KEC).
  • the conductive sheet according to the present invention has at least a dry film composed of a conductive layer formed from a conductive composition.
  • the laminated body with a pattern concerning this invention has at least the conductive pattern formed on the base material.
  • a conductive pattern or a dry film (hereinafter collectively referred to as “conductive layer”) is obtained by forming a conductive composition on a substrate by printing, coating, or the like.
  • gravure printing flexographic printing, screen printing, inkjet printing, dispenser printing, spray coating, spin coating, die coating, lip coating, comma coating, knife coating, dip coating, curtain coating, roll coating, bar coating. Etc. can be used.
  • the printing form may be solid coating or pattern printing such as a wiring circuit.
  • the thickness of the conductive layer is preferably 0.5 ⁇ m to 100 ⁇ m. If it is less than 0.5 ⁇ m, the conductivity may be insufficient. On the other hand, when it exceeds 100 ⁇ m, there is a possibility that it takes time to dry after printing and applying the conductive composition.
  • the substrate examples include plastic films such as polyester, polycarbonate, polyimide, and polyphenylene sulfide. Further, the base material may be subjected to a peeling treatment, a corona treatment or an easy adhesion treatment for improving the adhesion with the dry film.
  • the thickness of the substrate is preferably 1 ⁇ m to 250 ⁇ m. When the substrate is less than 1 ⁇ m, the strength as a sheet may be weakened. On the other hand, if it exceeds 250 ⁇ m, printing / coating may be difficult.
  • the conductive sheet according to the present invention may be used for a conductive adhesive sheet, a conductive adhesive sheet, and the like.
  • a conductive sheet formed from the conductive composition according to the present invention and a pressure-sensitive adhesive layer or adhesive layer formed from a known pressure-sensitive adhesive or adhesive can be laminated to form a conductive sheet.
  • the conductive layer alone may be used as a conductive adhesive sheet or a conductive adhesive sheet.
  • the conductive sheet or the laminate with a conductive pattern according to the present invention preferably includes an insulating layer on one surface of the conductive layer.
  • the conductive sheet having an insulating layer may be referred to as an electromagnetic wave shielding sheet.
  • the electromagnetic wave shielding sheet may have two or more insulating layers.
  • the thickness of the insulating layer is not particularly limited, but is preferably 0.5 ⁇ m to 200 ⁇ m. When the thickness of the insulating layer is less than 0.5 ⁇ m, there is a possibility that a crack may occur when the sheet is bent. On the other hand, when it exceeds 200 ⁇ m, the total thickness of the conductive layer and the insulating layer is increased, and the flexibility of the sheet may be insufficient.
  • the formation method of an insulating layer can utilize a conventionally well-known method without a restriction
  • the insulating layer used in the conductive sheet or the laminate with a conductive pattern according to the present invention is not particularly limited, but is preferably formed using an insulating resin.
  • an insulating resin for example, a film formed from an acrylic resin, a urethane resin, a polyester resin, an epoxy resin, a phenol resin, a polycarbonate resin, or a plastic film such as polyester, polycarbonate, polyimide, or polyphenylene sulfide can be used.
  • the insulating layer may contain a silane coupling agent, an antioxidant, a pigment, a dye, a tackifier resin, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling regulator, a filler, a flame retardant, and the like as necessary. It can also be included.
  • the manufacturing method of the flaky silver powder according to the present invention is not particularly limited, an example of a preferable manufacturing method will be described below.
  • flaky silver powder is obtained by the flaking process.
  • a known method can be used without limitation.
  • Commercially available flaky silver powder may be used as the raw material powder.
  • flaky silver powder is classified, dispersed and pulverized in a semi-free vortex centrifugal swirling airflow environment to obtain flaky silver powder.
  • flaky silver powder before classification, dispersion, and pulverization treatment in a semi-free vortex centrifugal swirling airflow environment is referred to as “unbroken flaky silver powder”.
  • the method for producing flaky silver powder according to the present invention will be described more specifically.
  • the granular silver powder obtained by a known method such as an atomizing method, an electrolytic method, or a chemical reduction method can be suitably used.
  • the stirring ball mill includes a container having a cylindrical inner surface and a stirring blade provided in the container.
  • granular silver powder, balls, a solvent, and a processing agent are charged in the container of the stirring ball mill, and a centrifugal force of 5 to 300 G is applied to the balls by the stirring blades in the container, and the granular silver powder is removed from the balls.
  • the granular silver powder is made into flakes to obtain uncrushed flaky silver powder.
  • the flaky silver powder (uncrushed flaky silver powder) that is secondarily agglomerated by entanglement or adhesion is usually caused by the particles colliding in the flaky process in the obtained flaky silver powder. Arise.
  • the dispersibility of the particles may decrease, and there is also a problem that viscosity fluctuation such as increase in viscosity occurs in the conductive composition.
  • the uncrushed flaky silver powder is not particularly limited as long as the flaky silver powder is obtained, but is preferably in the following range from the viewpoint of easily obtaining the flaky silver powder having the characteristic range according to the present invention. That is, the 50% particle size of uncrushed flaky silver powder is preferably in the range of 3.1 ⁇ m to 10 ⁇ m, more preferably 5 ⁇ m to 7 ⁇ m. Further, the BET specific surface area of the uncrushed flaky silver powder is preferably 1 m 2 / g or more and 3.5 m 2 / g or less, more preferably 1.5 m 2 / g or more and 2.5 m 2 / g or less. .
  • apparent density of the non-disintegration flaky silver powder 0.45 g / cm 3 or more, preferably 0.85 g / cm 3 or less, more preferably 0.47 g / cm 3 or more, 0.75 g / cm 3 or less.
  • FIG. 1 is a schematic cross-sectional view of an example of a swirling airflow classifying / dispersing device
  • FIG. 2 is a schematic plan view taken along the line II-II in FIG. Note that the apparatus configuration illustrated in FIGS. 1 and 2 is an example, and various apparatuses can be used without departing from the gist of the present invention.
  • the swirling airflow classifying / dispersing device 10 includes a raw material inlet 11, a classification zone 12, a guide vane 13, a coarse powder collection unit 14, a coarse powder extraction port 15, a fine powder extraction port 16, a blowing unit 17, and the like.
  • the raw material input port 11 is an entrance for inputting unbroken flaky silver powder. For example, a predetermined amount of uncrushed flaky silver powder 1 as a raw material is supplied from a raw material supply machine 20 at a predetermined timing.
  • the classification zone 12 is a zone that generates a semi-free vortex centrifugal swirling airflow, and is a zone through which the uncrushed flaky silver powder 1 introduced from the raw material inlet 11 passes first.
  • the classification zone 12 is formed in a substantially circular shape in plan view, and an airflow blowing portion 17 for forming a semi-free vortex centrifugal swirling airflow is provided on the outer peripheral side wall of the classification zone 12.
  • the swirling airflow is generated by the main air 21.
  • secondary air is introduced into the classification zone 12 from the blowing nozzle 18.
  • the main air 21 blowing section 17 and the secondary air blowing nozzle 18 are arranged so as to surround the classification zone 12, and the main air 21 blowing section 17 is divided into a plurality of sections by the guide vanes 13.
  • the blowout part 17 of the main air 21 and the blowout nozzle 18 of the secondary air 22 may be completely or partially separated by a partition plate (not shown). May be adjusted.
  • the guide vane 13 plays a role for guiding the blowing portion 17 of the main air 21 and the secondary air 22 from the blowing nozzle 18 to the classification zone 12.
  • the coarse powder collection unit 14 is a zone for collecting flaky silver powder (hereinafter simply referred to as “coarse powder 3”) mainly composed of coarse powder having a particle size larger than the set classification point. This is an outlet for taking out the coarse powder 3.
  • the fine powder outlet 16 is an outlet for taking out flaky silver powder having a particle size mainly composed of fine powder (hereinafter simply referred to as “fine powder 2”) from a set classification point.
  • fine powder 3 is collected in the coarse powder collecting unit 14 installed at the lower part of the classifying device.
  • fine powder 2 is collected from a fine powder outlet 16 provided at the upper part of the swirling airflow classifying / dispersing device 10 by a cyclone or bag filter for collecting fine powder.
  • FIG. 3 is an explanatory diagram showing an example of the particle size distribution of the coarse powder 3 and the fine powder 2 separated by the swirling airflow classifying / dispersing device 10. Although it varies depending on the particle size distribution of the uncrushed flaky silver powder to be used, when it has a particle size distribution as shown in FIG. 3, flaky silver powder having a particle size larger than the classification point is mainly obtained as the coarse powder 3. On the other hand, flaky silver powder having a particle size smaller than the classification point is obtained mainly as fine powder 2.
  • the pulverized silver powder according to the present invention is obtained by collecting the fine powder 2 and the coarse powder 3 obtained by the swirling airflow classifying / dispersing device.
  • the flaky silver powder according to the present invention is preferably used by mixing the total amount of each of the coarse powder 3 and fine powder 2 obtained after classification and dispersion.
  • a general classification process in order to obtain a powder having a predetermined particle size distribution, either one of two types of fine powder 2 and coarse powder 3 obtained by the classification process is removed, or in the case of gas phase classification The operation of cutting both coarse powder 3 and fine powder 2 to obtain an intermediate particle size powder is performed.
  • the obtained fine powder is classified again, and the fine powder is removed to obtain a predetermined particle size distribution.
  • the fine powder is removed to obtain a predetermined particle size distribution.
  • the classification, dispersion, and pulverization treatment by the swirl type airflow classification / dispersion device of the present invention increases the monodispersity of the particles by separating particles adhering by secondary aggregation, and the coarse particles obtained after classification / dispersion.
  • the powder 3 and the fine powder 2 can be mixed and used in their entirety. For this reason, loss can be eliminated and cost reduction can be realized.
  • the setting of the classification point itself has no particular meaning. Therefore, when setting classification / dispersion / disintegration conditions, it is preferable to set by focusing on the classification ratio.
  • the classification ratio is defined as the ratio of the recovered amount of fine powder and coarse powder obtained after classification / dispersion / pulverization treatment.
  • the method of mixing the obtained coarse powder 3 and fine powder 2 is not particularly limited, and a conventionally known mixer such as a ball mill, a rocking mill, a V-type blender, or a vibration mill can be used. However, from the viewpoint of preventing particle re-aggregation and particle shape change, it is preferable to use a V-type blender with low kinetic energy for mixing coarse powder 3 and fine powder 2.
  • the fine powder 2 and the coarse powder 3 can be used alone. Depending on the application and needs, only the fine powder 2 or only the coarse powder 3 may be used, or the fine powder 2 and the coarse powder 3 may be mixed at an arbitrary ratio.
  • the particle size can be adjusted by changing the setting of the classification point or the like in addition to changing according to the ratio of the fine powder 2 and the coarse powder 3 as described above.
  • the classification ratio is defined by the relationship between the centrifugal force and the drag force caused by the swirling airflow as described above, and can be appropriately adjusted depending on the air volume of the swirling airflow. Therefore, the classification ratio need not be specified.
  • the classification ratio may be in the range of the classification ratio in which the properties of the highly monodispersed flaky silver powder according to the present invention satisfy a predetermined range according to the particle size and apparent density of the uncrushed flaky silver powder. That is, it is preferable to adjust the classification ratio so that the apparent density and 50% particle size of the powder obtained by mixing the fine powder after classification, dispersion, and pulverization and the coarse powder are in a predetermined range.
  • the swirling airflow is increased excessively, the collision with the inner wall surface of the apparatus becomes severe and damage and deformation of the particles may increase, so it is preferable to set an appropriate airflow.
  • Patent Document 3 As an alternative to the method of performing the crushing treatment with a high energy ball mill, a high-speed conductor collision type airflow type pulverizer, an impact type pulverizer, a gauge mill, a medium stirring type mill, a high hydraulic pressure pulverizer, etc.
  • the following methods have been proposed.
  • As a first method the dried silver powder in an agglomerated state is crushed using a wind circulator utilizing centrifugal force.
  • a silver powder slurry containing silver powder in an aggregated state is pulverized using a fluid mill using centrifugal force.
  • Patent Documents 4 and 5 as a method for crushing the aggregated particles, a method is disclosed in which the particles are introduced into a rotating device with centrifugal force and wind energy is applied relatively. Specifically, a method is disclosed in which a turbulent vortex centrifugal air classifier manufactured by Nissin Engineering Co., Ltd. is used for circulation, and particles in an agglomerated state collide with each other to perform a pulverization treatment. ing.
  • the method of adding particles to a rotating device with centrifugal force as in Patent Documents 4 and 5 and applying wind energy relatively tends to change the shape of a soft metal such as silver powder. There is. Further, since the classification blades attached to the classification rotor and the silver powder particles collide, there is a problem that the silver powder is easily damaged or the silver powder is agglomerated.
  • a characteristic point of the swirling airflow classifying / dispersing device is that a drive unit (movable unit) such as a rotor is not provided at least in the region where the powder is present.
  • a drive unit such as a rotor
  • the classification blades attached to the rotor collide with the silver powder particles, so that aggregation is likely to occur and the particle shape is likely to change.
  • these problems can be avoided by not providing a drive unit such as a rotor.
  • a forced vortex centrifugal classifier classifies particles by applying the centrifugal force generated by the rotation of the rotor and the drag of the air that passes through the machine to the particles. It tends to occur and the particle shape is likely to change. As a result, it becomes difficult to reduce the apparent density, and high conductivity cannot be obtained.
  • the flaky silver powder according to the present invention has substantially the same particle shape as that of the uncrushed flaky silver powder by classification, dispersion, and pulverization treatment in a semi-free vortex centrifugal swirling airflow environment (the following ( This was confirmed by the degree of crushing of the formula 2).
  • the BET specific surface area is based on the BET theory based on low-temperature and low-humidity physical adsorption of an inert gas, by adsorbing molecules having a known adsorption occupation area on the surface of the powder particles at the temperature of liquid nitrogen, and calculating the ratio of the sample from the amount. Determine the surface area.
  • the molecules to be adsorbed are gas molecules such as nitrogen and krypton, and are much smaller than the powder particles as the sample. Therefore, even if the particles are agglomerated and overlap each other like crushed flaky silver powder, gas molecules can easily enter between the particles, so if there is no change in the particle shape, the BET ratio before and after crushing It is believed that the surface area value does not change. Therefore, if the ratio of the BET specific surface area before and after crushing is defined as the crushing degree, the crushing degree is 1 unless the particle shape is changed.
  • the value of the crushing degree is an index that can reflect the change in the particle shape.
  • the BET specific surface area of the powder after pulverization is determined using a value obtained by mixing the total amount of coarse powder and fine powder.
  • the pulverization degree is 0.90 or more and 1.15 or less
  • high conductivity can be expressed by adding a smaller amount than before. More preferably, it is 0.94 or more and 1.12 or less. Particularly preferably, it is 1 or more and 1.12 or less.
  • the flaky silver powder according to the present invention is substantially monodispersed by the following (formula 3) that the flaky silver powder is substantially monodispersed by classification, dispersion, and crushing treatment in a semi-free vortex centrifugal swirling airflow environment. This was confirmed by the apparent density change rate.
  • “monodispersed” means that the powder is not aggregated and the particles are substantially separated from each other.
  • the apparent density change rate of the powder after classification, dispersion, and pulverization is obtained using a value obtained by mixing the total amount of coarse powder and fine powder.
  • the degree of pulverization and the rate of change in apparent density are indices for comparing the state of the entire powder before and after pulverization, and are values defined when the total amount of coarse powder and fine powder is mixed. Therefore, the degree of particle shape change and monodispersity of each of coarse powder and fine powder cannot be estimated from the degree of pulverization and the apparent density change rate. However, if the knowledge that the particle shape does not change and is in a monodispersed state is obtained from the pulverization degree and apparent density change rate of the powder after mixing the coarse powder and the fine powder, the intermediate process product It can be said that each of the coarse powder and the fine powder is monodispersed without any change in the particle shape. Therefore, the degree of particle shape change and monodispersity of the coarse powder and fine powder can be determined from the degree of pulverization and the apparent density change rate when the coarse powder and fine powder are mixed.
  • the adhering particles are separated and dispersed by the particle size.
  • the apparent density expressed by the filling amount of the powder in the specified container is significantly lower than that before crushing. Therefore, the degree of monodispersion can be estimated from the magnitude of the apparent density change rate.
  • the apparent density change rate may be reduced or the apparent density may be increased (the apparent density change rate becomes a negative value). It is also assumed that the overlap between particles becomes coarse due to the deformation of the particles and the apparent density change rate increases.
  • the apparent density change rate is 18% or more, when the flaky silver powder of the present invention is used as a conductive filler, high conductivity can be realized by adding a smaller amount than before.
  • a more preferable range of the apparent density change rate is 25% or more and 70% or less. When the apparent density change rate is 70% or less, good monodispersity can be secured.
  • the swirling flow generated by the main air 21 can be rectified and accelerated by using the secondary air 22 of the swirling airflow classifying / dispersing device.
  • Two secondary airs 22 are provided on the upper and lower sides, and classification and dispersion processing are performed in two stages in the classification zone 12. More specifically, first, classification / dispersion of uncrushed flaky silver powder can be promoted by the secondary air 22 on the upper side of the classification zone 12.
  • fine particles adhering to coarse particles that could not be completely classified and dispersed on the upper side of the classification zone 12 by the secondary air 22 at the lower part of the classification zone 12 are classified and dispersed again to form uncrushed flakes.
  • the classification and dispersion of silver powder can be further promoted.
  • centrifugal force is applied to the unbroken flaky silver powder by the swirling airflow in the swirling airflow classification / dispersing device.
  • the drag can be applied to the unbroken flaky silver powder by the swirling flow itself.
  • classification, dispersion, and pulverization are performed according to the balance between centrifugal force and drag applied to the unbroken flaky silver powder.
  • the two-stage classification / dispersion is performed with the secondary air 22 in the upper and lower stages in the classification zone 12, and the classification / dispersion / crushing process is promoted, so that the adhesion between the silver powders is peeled off with high accuracy.
  • monodispersity can be increased. As a result, the monodispersity of the particles can be promoted without substantially changing the particle shape.
  • the state of particle aggregation is remarkably improved by performing classification, dispersion, and pulverization of uncrushed flaky silver powder in a semi-free vortex centrifugal swirling airflow environment. can do.
  • the apparent density can be reduced.
  • a flaky silver powder having a dry film thickness of 15 ⁇ m and a surface resistance value of 0.4 ⁇ / ⁇ or less when 100 parts by weight of the flaky silver powder is contained with respect to 100 parts by weight of the system resin can be obtained.
  • the flaky silver powder is considered to have a shape close to primary particles, the advantages of the original particle shape of the flaky silver powder can be maximized. Furthermore, since the amount of resin in the conductive layer is relatively increased as compared with the conventional case, the adhesion of the conductive layer to the substrate and the adhesive force to the adherend can be increased. In addition, cost reduction can be realized. Moreover, according to the flaky silver powder according to the present invention, since the monodispersity of the particles is high, the uniformity of the particles is good, and it has excellent characteristics such that viscosity fluctuation such as an increase in viscosity in the conductive composition hardly occurs. .
  • the 50% particle size was measured using SALD-3000J manufactured by Shimadzu Corporation. Further, the BET specific surface area was measured using Flowsorb II2300 manufactured by Shimadzu Corporation.
  • the apparent density was determined by an apparent density test method for metal powder defined in JIS Z 2504: 2000, using a funnel with an orifice having a hole diameter of 5 mm.
  • Example 1 As test powder, 50% particle size 6.1 ⁇ m, BET specific surface area 1.7 m 2 / g, apparent density 0.53 g / cm 3 (“Nanomelt Ag-XF301S” manufactured by Fukuda Metal Foil Industry Co., Ltd.) Crushed flaky silver powder was used.
  • a swirling airflow classifying / dispersing device a swirling airflow classifier Aerofine Classifier AC-20 manufactured by Nissin Engineering Co., Ltd. was used. 3.4 kg of the above-mentioned uncrushed flaky silver powder was weighed and put into the above-described swirling airflow classifying / dispersing apparatus to perform classification, dispersion, and pulverizing treatment. The whole amount of the obtained coarse powder and fine powder was mixed with a ball mill.
  • Example 2 Example 1 with the exception that unbroken flaky silver powder having a 50% particle size of 5.9 ⁇ m, a BET specific surface area of 1.4 m 2 / g, and an apparent density of 0.53 g / cm 3 was used as the test powder. Similarly, classification, dispersion, and crushing were performed.
  • Example 3 A swirling airflow classifying / dispersing device using uncrushed flaky silver powder having a 50% particle size of 5.6 ⁇ m, a BET specific surface area of 1.6 m 2 / g and an apparent density of 0.47 g / cm 3 as a test powder. Classification, dispersion, and pulverization were performed in the same manner as in Example 1 except that the amount charged into the reactor was 3.4 kg.
  • Example 4 A swirling airflow classifying / dispersing device using uncrushed flaky silver powder having a 50% particle size of 5.1 ⁇ m, a BET specific surface area of 1.8 m 2 / g, and an apparent density of 0.59 g / cm 3 as a test powder. Classification, dispersion, and pulverization were performed in the same manner as in Example 1 except that the amount charged to 11.6 kg was changed to 11.6 kg.
  • Example 5 A swirling airflow classifying / dispersing device using uncrushed flaky silver powder having a 50% particle size of 6.2 ⁇ m, a BET specific surface area of 1.8 m 2 / g and an apparent density of 0.59 g / cm 3 as a test powder.
  • the input amount to was 8.0 kg.
  • the other conditions were the same as in Example 1.
  • Example 6 Coarse powder (50% particle size 6.4 ⁇ m, BET specific surface area 1.4 m 2 / g, apparent density 0.34 g / cm 3 ) obtained by crushing in Example 1 is mixed with fine powder. Without using it.
  • Example 7 Fine powder (50% particle size: 4.0 ⁇ m, BET specific surface area: 2.4 m 2 / g, apparent density: 0.42 g / cm 3 ) obtained by crushing in Example 1 And used as is without mixing.
  • Example 8 Coarse powder (50% particle size: 7.6 ⁇ m, BET specific surface area: 1.1 m 2 / g, apparent density: 0.36 g / cm 3 ) obtained by crushing treatment in Example 2 And used as is without mixing.
  • Example 9 Fine powder (50% particle size: 4.9 ⁇ m, BET specific surface area: 1.9 m 2 / g, apparent density: 0.37 g / cm 3 ) obtained by crushing in Example 2 And used as is without mixing.
  • Comparative Example 1 As the test powder, uncrushed flaky silver powder having a 50% particle size of 6.7 ⁇ m, a BET specific surface area of 1.2 m 2 / g, and an apparent density of 0.61 g / cm 3 was used. A commercially available forced vortex centrifugal classifier was used for classification, dispersion, and crushing treatment. The above-mentioned uncrushed flaky silver powder was put into the above-mentioned forced vortex centrifugal classifier and subjected to classification, dispersion, and pulverization treatment. Then, the total amount of each of the obtained coarse powder and fine powder was mixed with a ball mill.
  • Comparative Example 2 As the test powder, the same uncrushed flaky silver powder as in Comparative Example 1 was used. For the classification, dispersion, and crushing treatment, a commercially available airflow collision pulverizer was used. When using an airflow collision type pulverizer as a powder dispersion method, coarse powder and fine powder are separated by a high-speed swirling airflow. High conductivity for shape change cannot be obtained.
  • Comparative Example 3 As the test powder, the same uncrushed flaky silver powder as in Comparative Example 1 was used. A commercially available rotary hammer type pulverizer was used for classification, dispersion, and pulverization.
  • the rotary hammer type pulverizer is characterized in that it is pulverized by the impact force of a swing hammer rotating at high speed and the impact effect of a liner, and has a built-in classification mechanism, so that there is little over-pulverization.
  • Comparative Example 4 As the test powder, unbroken flaky silver powder having a 50% particle size of 4.9 ⁇ m, a BET specific surface area of 1.7 m 2 / g, and an apparent density of 0.59 g / cm 3 was used as it was. That is, it was used as it was without performing classification, dispersion, and crushing treatment.
  • Comparative Example 5 Using the uncrushed flaky silver powder used in Comparative Example 1, a conductive composition was prepared according to the formulation shown in Table 2.
  • FIG. 4 shows a scanning electron micrograph of the unbroken flaky silver powder used in Example 1.
  • 5A shows a scanning electron micrograph of the flaky silver powder coarse powder obtained in Example 1
  • FIG. 5B shows a scanning electron micrograph of the flaky silver powder fine powder obtained in Example 1. Show. It can be seen that the uncrushed flaky silver powder in FIG. In contrast, in the flaky silver powder of the present invention in FIGS. 5A and 5B, it can be seen that the particles are separated and dispersed for each grain. That is, it can be seen that the monodispersity of the flaky silver powder is increased by performing classification, dispersion, and crushing treatment in a semi-free vortex centrifugal swirling airflow environment.
  • the conductive composition was applied and dried so that a conductive layer having a thickness of 15 ⁇ m could be formed on a polyethylene terephthalate film having a thickness of 100 ⁇ m. Thereby, the electroconductive sheet was obtained.
  • the surface resistance value of the obtained conductive sheet was measured using a four-point probe of “Lorester GP” manufactured by Mitsubishi Chemical Analytech. The evaluation criteria of the surface resistance value are as follows. ⁇ : Less than 0.3 ⁇ / ⁇ ⁇ : 0.3 ⁇ / ⁇ or more, 0.4 ⁇ / ⁇ or less ⁇ : Over 0.4 ⁇ / ⁇
  • Electromagnetic wave shielding measurement Each 100 parts by weight of the flaky silver powder obtained in Examples 1 to 9 and Comparative Examples 1 to 4 and 100 parts by weight of a polyester resin (Byron 200 manufactured by Toyobo Co., Ltd.) are blended and mixed to make the conductivity. A composition was obtained. In Comparative Example 5, 150 parts by weight of the flaky silver powder of Comparative Example 1 is mixed with 100 parts by weight of the polyester resin. Next, the conductive composition was applied and dried so that a conductive layer having a thickness of 15 ⁇ m could be formed on a polyimide film having a thickness of 12.5 ⁇ m. Thereby, an electromagnetic wave shielding film was obtained. The electromagnetic wave shielding property of the obtained electromagnetic wave shielding film was measured by the KEC method.
  • Electromagnetic shielding at a frequency of 1 GHz is 60 dB or more
  • O Electromagnetic shielding at a frequency of 1 GHz is 40 dB or more and less than 60 dB
  • X An electromagnetic shielding at a frequency of 1 GHz is less than 40 dB
  • Tables 1 and 2 show the measurement results of apparent density change rate (%), surface resistance value, electromagnetic wave shielding property, and adhesiveness.
  • the degree of particle aggregation or dispersion before and after classification / dispersion / pulverization treatment is more appropriate to judge by the apparent density and BET specific surface area values before and after treatment than by 50% particle size. It is. This is because the value of the 50% particle size is uneven due to the measurement principle due to the flaky particles.
  • the flaky silver powder of the present invention has a flake shape in which the thickness is extremely thin, and shows a shape considerably different from the sphere as shown in FIGS. It depends.
  • the apparent density 50% particle size, and BET specific surface area, the apparent density is the one that most reflects the state of the particles before and after classification, dispersion, and pulverization.
  • the flaky silver powder according to Comparative Example 1 has a slightly high degree of pulverization and a very low apparent density change rate, which suggests that the surface resistance value is high.
  • the 50% particle size is in the range of 3 ⁇ m to 8 ⁇ m and the apparent density is in the range of 0.25 g / cm 3 to 0.5 g / cm 3.
  • the resistance value could not be obtained.
  • the flaky silver powder according to Comparative Examples 2 and 3 has a high apparent density change rate, the degree of pulverization is also high, suggesting that the particle shape is changed and the surface resistance value is high. .
  • the surface resistance values of the conductive compositions containing the flaky silver powder according to Examples 1 to 9 were all 0.4 ⁇ / ⁇ or less, and it was found that they had excellent low resistance characteristics. From the values of the degree of pulverization and the apparent density change rate, the flaky silver powders according to Examples 1 to 9 have substantially the shape of particles by classification, dispersion, and pulverization treatment in a semi-free vortex centrifugal swirling airflow environment. It can be seen that the monodispersity can be improved without any change. As a result, the conductive composition containing the flaky silver powder according to Examples 1 to 9 is considered to improve the surface resistance value and the electromagnetic wave shielding property.

Abstract

Provided are: a flaked silver powder that exhibits exceptional electroconductivity characteristics as well as exceptional adhesiveness to an adherend, and that makes it possible to reduce costs; a method for manufacturing the flaked silver powder; and an electroconductive composition containing the flaked silver powder. This flaked silver powder has a 50% particle diameter of 3 to 8 μm according to laser diffractometry, and an apparent density of 0.25 to 0.5 g/cm3. The surface resistivity of an electroconductive film having a dry thickness of 15 μm and containing 100 weight parts of the flaked silver powder per 100 weight parts of a polyester resin is equal to or less than 0.4 Ω/sq.

Description

フレーク状銀粉、及びその製造方法、並びに導電性組成物、導電性シート、電磁波シールド性シート及び導電パターン付き積層体Flaky silver powder, method for producing the same, conductive composition, conductive sheet, electromagnetic wave shielding sheet, and laminate with conductive pattern
　本発明は、フレーク状銀粉、及びその製造方法に関する。また、前記フレーク状銀粉を含む導電性組成物、並びに導電性組成物を用いた導電性シート、電磁波シールド性シート及び導電パターン付き積層体に関する。 The present invention relates to a flaky silver powder and a method for producing the same. Moreover, it is related with the electroconductive composition containing the said flaky silver powder, the electroconductive sheet using an electroconductive composition, an electromagnetic wave shielding sheet, and a laminated body with an electroconductive pattern.
　樹脂と導電性粒子を主成分とする導電性組成物は、従来より、コーティング用途、電磁波シールド用途などの導電性シートや、印刷による回路形成用途などの導電パターン付き積層体等として、プリント配線板、電子機器などの電子部品等に使用されており、種々の提案がなされている（例えば、特許文献１～５）。 Conventionally, conductive compositions mainly composed of resin and conductive particles have been used as printed wiring boards as conductive sheets for coating applications, electromagnetic shielding applications, and laminates with conductive patterns for printed circuit formation applications. These are used in electronic parts such as electronic devices, and various proposals have been made (for example, Patent Documents 1 to 5).
　特許文献１には、フレーク状の粒径を有し、レーザー回折法５０％粒径が３～８μｍ、見掛密度が０．４～１．１ｇ／ｃｍ３、ＢＥＴ法比表面積が１．５～４．０ｍ２／ｇであることを特徴とする導体ペースト用のフレーク状銀粉、及びその製造方法が記載されている。 Patent Document 1 has a flaky particle size, a laser diffraction method 50% particle size of 3 to 8 μm, an apparent density of 0.4 to 1.1 g / cm 3 , and a BET method specific surface area of 1.5. A flaky silver powder for a conductive paste, characterized in that it is ˜4.0 m 2 / g, and a method for producing the same are described.
　特許文献２においては、３～８μｍの平均粒径、１．５～４．０ｍ２／ｇの比表面積、及び０．４～１．１ｇ／ｃｍ３の見掛密度を有する薄片状銀粉Ａと、３～１０μｍの平均粒径、０．６～１．２ｍ２／ｇの比表面積、及び１．５～２．１ｇ／ｃｍ３の見掛密度を有する薄片状銀粉Ｂと、樹脂とを含有する導電性ペースト組成物が記載されている。この組成物は、薄片状銀粉Ａと薄片状銀粉Ｂとの合計重量１００部に対して、薄片状銀粉Ａが３０～９５重量部含有され、導電性ペーストの固形分に対して薄片状銀粉Ａと薄片状銀粉Ｂとの合計が３５～８５重量％含有されていることを特徴としている。 In Patent Document 2, flaky silver powder A having an average particle diameter of 3 to 8 μm, a specific surface area of 1.5 to 4.0 m 2 / g, and an apparent density of 0.4 to 1.1 g / cm 3 Contains flaky silver powder B having an average particle diameter of 3 to 10 μm, a specific surface area of 0.6 to 1.2 m 2 / g, and an apparent density of 1.5 to 2.1 g / cm 3 , and a resin A conductive paste composition is described. This composition contains 30 to 95 parts by weight of flaky silver powder A with respect to a total weight of 100 parts of flaky silver powder A and flaky silver powder B, and flaky silver powder A with respect to the solid content of the conductive paste. And the flaky silver powder B is contained in an amount of 35 to 85% by weight.
　特許文献３においては、微粒であり、かつ優れた分散性（低凝集性）を備え、かつ、大きな結晶子径を備えた銀粉を得るために、湿式還元法により銀粉を製造する方法が記載されている。具体的には、錯化剤としてエチレンジアミンテトラ酢酸塩を用いた銀キレート錯体スラリーを原料として湿式還元法を用いて製造することが記載されている。 Patent Document 3 describes a method for producing silver powder by a wet reduction method in order to obtain silver powder having fine particles, excellent dispersibility (low cohesiveness), and a large crystallite diameter. ing. Specifically, it is described that a silver chelate complex slurry using ethylenediaminetetraacetate as a complexing agent is used as a raw material and manufactured using a wet reduction method.
　特許文献４においては、導電性ペーストとして導体形成を行った場合の導体抵抗の低減が可能で、かつ、ＵＶ硬化型接着剤にも適用可能なフレーク銀粉を提供するために、平均粒径Ｄ５０が１０μｍ～１３μｍ、アスペクト比（［平均長径（μｍ）］／［平均厚さ（μｍ）］）が６～１５であるフレーク銀粉を用いることが記載されている。このフレーク銀粉は、所定の粒径を備える球状銀粉と、所定粒径のメディアビーズとをビーズミル内で混合攪拌することで球状銀粉の粒子を塑性変形させてフレーク化する方法が記載されている。 In Patent Document 4, in order to provide a flake silver powder that can reduce conductor resistance when a conductor is formed as a conductive paste and can also be applied to a UV curable adhesive, the average particle diameter D50 is It is described that flake silver powder having an aspect ratio ([average major axis (μm)] / [average thickness (μm)]) of 6 to 15 is 10 to 13 μm. This flaky silver powder describes a method in which spherical silver powder having a predetermined particle diameter and media beads having a predetermined particle diameter are mixed and stirred in a bead mill to plastically deform the particles of the spherical silver powder to form a flake.
　特許文献５においては、一次粒子と一次粒子が凝集した凝集粒子で構成され、その平均粒径が０．５～２０μｍ、比表面積が０．０７～１．７ｍ２／ｇの導電性粒子と、熱硬化性樹脂を主成分とするバインダーで構成される導電性ペーストが開示されている。 In Patent Document 5, primary particles and aggregated particles obtained by agglomerating primary particles, the conductive particles having an average particle size of 0.5 to 20 μm and a specific surface area of 0.07 to 1.7 m 2 / g, A conductive paste composed of a binder mainly composed of a thermosetting resin is disclosed.
特開２００３－０５５７０１号公報Japanese Patent Laid-Open No. 2003-055701 特開２００４－１１１０５７号公報JP 2004-111057 A 特開２００４－１０００１３号公報JP 2004-100013 A 特開２００７－２５４８４５号公報JP 2007-254845 A 特開２００４－２６５９０１号公報JP 2004-265901 A
　昨今の電子機器の高性能化の要求に伴って、導電性組成物についてもより優れた特性が求められている。具体的には、強度、被着体に対する優れた密着力を有する導電性組成物であって、かつ、導電性等の特性を満足し、さらに、低コスト化も可能な導電性組成物が求められている。 With the recent demand for higher performance of electronic devices, more excellent properties are required for conductive compositions. Specifically, there is a demand for a conductive composition having strength and excellent adhesion to an adherend, satisfying characteristics such as conductivity, and capable of reducing costs. It has been.
　導電性組成物の低コスト化は、導電性粒子の割合を少なくすることにより実現することができる。また、導電性粒子の割合を少なくして樹脂の割合を増加することにより、被着体に対する密着力や強度を高めることができる。しかしながら、導電性組成物中の導電性粒子の割合を少なくすると、導電特性が低下してしまうという問題があった。このため、導電性粒子そのものにおいて、高導電性化を実現する技術が切望されていた。 Cost reduction of the conductive composition can be realized by reducing the proportion of conductive particles. Moreover, the adhesive force and intensity | strength with respect to a to-be-adhered body can be raised by decreasing the ratio of electroconductive particle and increasing the ratio of resin. However, if the ratio of the conductive particles in the conductive composition is reduced, there is a problem that the conductive characteristics are deteriorated. For this reason, the technique which implement | achieves high electroconductivity in electroconductive particle itself was anxious.
　本発明は、上記背景に鑑みてなされたものであり、その目的とするところは、導電特性に優れたフレーク状銀粉、及びその製造方法、並びに、導電性組成物を提供することである。さらに、この導電性組成物を用いた導電性シート、電磁波シールド性シート及び導電パターン付き積層体を提供することである。 The present invention has been made in view of the above-mentioned background, and an object thereof is to provide a flaky silver powder excellent in conductive properties, a method for producing the same, and a conductive composition. Furthermore, it is providing the laminated body with an electroconductive sheet, an electromagnetic wave shielding sheet, and an electroconductive pattern using this electroconductive composition.
　本発明者らは、上記課題を克服すべく鋭意検討を重ね、以下の態様において、上記課題を解決できることを見出し、本発明を完成するに至った。すなわち、本発明に係るフレーク状銀粉は、レーザー回折法における５０％粒径が、３μｍ以上、８μｍ以下であり、見掛密度が、０．２５ｇ／ｃｍ３以上、０．５ｇ／ｃｍ３以下であり、かつ、ポリエステル系樹脂１００重量部に対して当該フレーク状銀粉を１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下のものである。フレーク状銀粉のＢＥＴ比表面積は、１ｍ２／ｇ以上、３．５ｍ２／ｇ以下とすることが好ましい。 The inventors of the present invention have made extensive studies to overcome the above-mentioned problems, and found that the above-mentioned problems can be solved in the following aspects, and have completed the present invention. That is, the flaky silver powder according to the present invention has a 50% particle diameter in a laser diffraction method of 3 μm or more and 8 μm or less, and an apparent density of 0.25 g / cm 3 or more and 0.5 g / cm 3 or less. In addition, the surface resistance value of the conductive film having a dry film thickness of 15 μm when the flaky silver powder is contained in 100 parts by weight with respect to 100 parts by weight of the polyester resin is 0.4Ω / □ or less. The BET specific surface area of the flaky silver powder is preferably 1 m 2 / g or more and 3.5 m 2 / g or less.
　本発明に係るフレーク状銀粉の製造方法は、未解砕フレーク状銀粉に対して、半自由渦遠心式の旋回式気流環境下において分級・分散・解砕する工程を具備し、分級・分散・解砕後の銀粉が、レーザー回折法における５０％粒径が３μｍ以上、８μｍ以下であり、見掛密度が０．２５ｇ／ｃｍ３以上、０．５ｇ／ｃｍ３以下であり、かつ、ポリエステル系樹脂１００重量部に対して当該フレーク状銀粉を１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下であるものである。前記分級・分散・解砕する工程によって分別された銀粉は、混合して用いることができる。なお、解砕とは、凝集した状態の粉末にエネルギーを与えて実質的に一粒毎に粒子を分離させて、粒子の分散性を向上させることをいう。また、半自由渦遠心式とは、装置内部に回転体を持たずに案内羽根等を設けて空気の旋回流を作り、その旋回する動きで粒子に遠心力を働かせ、旋回の流れそのもので粒子に抗力を働かせる方式をいう。 The method for producing flaky silver powder according to the present invention comprises a step of classifying, dispersing and pulverizing uncrushed flaky silver powder in a semi-free vortex centrifugal swirling airflow environment. The pulverized silver powder has a 50% particle size of 3 μm or more and 8 μm or less in a laser diffraction method, an apparent density of 0.25 g / cm 3 or more and 0.5 g / cm 3 or less, and a polyester type When 100 parts by weight of the flaky silver powder is contained relative to 100 parts by weight of the resin, the surface resistance value of the conductive film having a dry film thickness of 15 μm is 0.4Ω / □ or less. The silver powder separated by the classification / dispersion / pulverization step can be mixed and used. In addition, crushing means giving energy to the powder of the aggregated state, isolate | separating a particle | grain substantially for every grain, and improving the dispersibility of a particle | grain. Also, the semi-free vortex centrifugal type means that air is swirled by providing guide vanes, etc. without a rotating body inside the device, and centrifugal force is applied to the particles by the swirling motion, and the swirling flow itself produces particles. This is a method that uses a drag force.
　本発明に係る導電性組成物は、上記態様のフレーク状銀粉と樹脂とを少なくとも含有するものである。 The conductive composition according to the present invention contains at least the flaky silver powder and the resin of the above aspect.
　本発明に係る導電性シートは、上記態様の導電性組成物から形成された層を少なくとも有するものである。また、本発明に係る導電パターン付き積層体は、基材と、前記基材上に形成された導電パターンとを具備し、前記導電パターンが、上記態様の導電性組成物により形成されているものである。また、本発明に係る電磁波シールド性シートは、上記態様の導電性組成物から形成された導電層、及び絶縁層が積層されたものである。
　本発明に係る電磁波シールド性シートは、上記態様の導電性組成物から形成された導電層、及び絶縁層が積層されたものである。
　本発明に係る導電パターン付き積層体は、基材と、前記基材上に形成された導電パターンと、を具備し、前記導電パターンが、上記態様の導電性組成物により形成されているものである。 The electroconductive sheet which concerns on this invention has at least the layer formed from the electroconductive composition of the said aspect. Moreover, the laminated body with a conductive pattern which concerns on this invention comprises a base material and the conductive pattern formed on the said base material, and the said conductive pattern is formed with the conductive composition of the said aspect. It is. Moreover, the electromagnetic wave shielding sheet according to the present invention is obtained by laminating a conductive layer and an insulating layer formed from the conductive composition of the above aspect.
The electromagnetic wave shielding sheet according to the present invention is obtained by laminating a conductive layer and an insulating layer formed from the conductive composition of the above aspect.
The laminate with a conductive pattern according to the present invention includes a base material and a conductive pattern formed on the base material, and the conductive pattern is formed of the conductive composition of the above aspect. is there.
　本発明のフレーク状銀粉は、上述した特定範囲の５０％粒径および上述した特定範囲の見掛密度を有した嵩高い粒子形状とすることにより、表面抵抗値を低下させることに成功し、高い導電性を実現できた。より詳細には、ポリエステル樹脂と同量で配合した場合の表面抵抗値を０．４Ω／□以下という優れた値にすることができ、フレーク状銀粉そのものの導電性を高めることができた。 The flaky silver powder of the present invention has succeeded in reducing the surface resistance value by making it a bulky particle shape having the above-mentioned specific range of 50% particle size and the above-described specific range of apparent density, and is high. Conductivity was realized. More specifically, the surface resistance value when blended in the same amount as that of the polyester resin could be an excellent value of 0.4Ω / □ or less, and the conductivity of the flaky silver powder itself could be increased.
　本発明によれば、導電特性に優れたフレーク状銀粉、及びその製造方法を提供することができるという優れた効果がある。さらに、前記フレーク状銀粉を含有する導電性組成物、及びこの導電性組成物を用いた導電性シート、電磁波シールド性シート及び導電パターン付き積層体を提供することができるという優れた効果がある。 According to the present invention, there is an excellent effect that it is possible to provide a flaky silver powder having excellent conductive properties and a method for producing the same. Furthermore, there exists the outstanding effect that the electroconductive composition containing the said flaky silver powder, the electroconductive sheet using this electroconductive composition, an electromagnetic wave shielding sheet, and a laminated body with an electroconductive pattern can be provided.
本発明に係る旋回式気流分級・分散装置の一例を示す模式的断面図。The typical sectional view showing an example of the swirl type air current classification and dispersion device concerning the present invention. 図１のＩＩ－ＩＩ切断線における模式的平面図。FIG. 2 is a schematic plan view taken along the line II-II in FIG. 1. 本発明に係るフレーク状銀粉の微粉と粗粉を説明するための粒径分布を示すグラフ。The graph which shows the particle size distribution for demonstrating the fine powder and coarse powder of flaky silver powder which concern on this invention. 実施例１で用いた分級・分散・解砕処理前の未解砕フレーク状銀粉の走査型電子顕微鏡写真。The scanning electron micrograph of the unbroken flaky silver powder before classification, dispersion, and pulverization used in Example 1. 実施例１に係るフレーク状銀粉の粗粉の走査型電子顕微鏡写真。The scanning electron micrograph of the coarse powder of the flaky silver powder which concerns on Example 1. FIG. 実施例１に係るフレーク状銀粉の微粉の走査型電子顕微鏡写真。The scanning electron micrograph of the fine powder of the flaky silver powder which concerns on Example 1. FIG.
　以下、本発明を適用した実施形態の一例について説明する。なお、本発明の趣旨に合致する限り、他の実施形態も本発明の範疇に属し得ることは言うまでもない。また、以降の図における各部材のサイズや比率は、説明の便宜上のものであり、実際のものとは異なる。 Hereinafter, an example of an embodiment to which the present invention is applied will be described. It goes without saying that other embodiments may also belong to the category of the present invention as long as they match the gist of the present invention. Moreover, the size and ratio of each member in the following drawings are for convenience of explanation, and are different from actual ones.
　本発明に係るフレーク状銀粉は、レーザー回折法における５０％粒径（以降、単に「５０％粒径」と略記する）が、３μｍ以上、８μｍ以下であり、見掛密度が、０．２５ｇ／ｃｍ３以上、０．５ｇ／ｃｍ３以下であり、かつ、ポリエステル系樹脂１００重量部に対して当該フレーク状銀粉を１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下となるものである。なお、本発明に係るフレーク状銀粉の５０％粒径とは、レーザー回折法によって求めた粒度分布における積算値５０％での粒径を意味し、粒子を積算した積算％の分布曲線が５０％のときの横軸の粒径と交差するポイントの粒子径をいう。ここで、レーザー回折法による粒度分布とは、いわゆるレーザー回折・散乱法であり、粒子群にレーザー光を照射し、そこから発せられる回折・散乱光の強度分布パターンから検出された回折・散乱像を解析し粒子径を求めたものである。 The flaky silver powder according to the present invention has a 50% particle size (hereinafter simply referred to as “50% particle size”) in a laser diffraction method of 3 μm or more and 8 μm or less, and an apparent density of 0.25 g / The surface resistance value of the conductive film having a dry film thickness of 15 μm when cm 3 or more and 0.5 g / cm 3 or less and 100 parts by weight of the flaky silver powder is contained with respect to 100 parts by weight of the polyester resin, 0.4Ω / □ or less. The 50% particle size of the flaky silver powder according to the present invention means the particle size at an integrated value of 50% in the particle size distribution determined by the laser diffraction method, and the distribution curve of the integrated% obtained by integrating the particles is 50%. The particle diameter at the point that intersects the particle diameter on the horizontal axis. Here, the particle size distribution by the laser diffraction method is a so-called laser diffraction / scattering method, in which a particle group is irradiated with laser light, and a diffraction / scattered image detected from the intensity distribution pattern of the diffraction / scattered light emitted therefrom. And the particle diameter was determined.
　本発明に係るフレーク状銀粉は、５０％粒径を３μｍ以上とすることにより、粒子の表面積が増加するのを抑制できる。その結果、接触抵抗を抑制して導電性を良好に保つことができる。また、５０％粒径を８μｍ以下とすることにより、粒子同士の重なりを良好な状態とし、粒子間の接触面積を良好に保つことができる。その結果、導電性を良好な状態に保つことができる。フレーク状銀粉の５０％粒径のより好ましい範囲は、４μｍ以上、７μｍ以下であり、特に好ましい範囲は、５．３μｍ以上、６．２μｍ以下である。 The flaky silver powder according to the present invention can suppress an increase in the surface area of the particles by setting the 50% particle size to 3 μm or more. As a result, the contact resistance can be suppressed and the conductivity can be kept good. Further, by setting the 50% particle size to 8 μm or less, it is possible to make the overlapping of the particles good and keep the contact area between the particles good. As a result, the conductivity can be maintained in a good state. A more preferable range of the 50% particle size of the flaky silver powder is 4 μm or more and 7 μm or less, and a particularly preferable range is 5.3 μm or more and 6.2 μm or less.
　本発明に係るフレーク状銀粉の特徴の１つとして、見掛密度が非常に低いことが挙げられる。見掛密度を０．５ｇ／ｃｍ３以下とすることにより、導電性組成物中のフレーク状銀粉の添加量を少なくしつつ良好な導電性を提供することができる。また、フレーク状銀粉の見掛密度を０．２５ｇ／ｃｍ３以上とすることにより、樹脂と混合して導電性組成物として利用する場合の粘度上昇を抑制することができる。このため、信頼性の高い導電性組成物を提供することができる。より好ましい見掛密度は、０．３g／ｃｍ３以上、０．４g／ｃｍ３以下であり、特に好ましい見掛密度は、０．３６g／ｃｍ３以上、０．４g／ｃｍ３以下である。 One of the characteristics of the flaky silver powder according to the present invention is that the apparent density is very low. By setting the apparent density to 0.5 g / cm 3 or less, it is possible to provide good conductivity while reducing the amount of flaky silver powder added to the conductive composition. Moreover, when the apparent density of the flaky silver powder is 0.25 g / cm 3 or more, an increase in viscosity when mixed with a resin and used as a conductive composition can be suppressed. For this reason, a highly reliable conductive composition can be provided. A more preferable apparent density is 0.3 g / cm 3 or more and 0.4 g / cm 3 or less, and a particularly preferable apparent density is 0.36 g / cm 3 or more and 0.4 g / cm 3 or less.
　また、本発明に係るフレーク状銀粉は、ポリエステル系樹脂１００重量部に対してフレーク状銀粉を１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下のものである。表面抵抗値のより好ましい範囲は、０．４Ω／□未満であり、さらに好ましくは０．３５Ω／□以下である。なお、表面抵抗値は、ポリエステル系樹脂１００重量部とフレーク状銀粉１００重量部を配合し混合して得られた導電性組成物を、膜厚が１５μｍになるように塗布・乾燥させた塗膜を測定して求めたものである。必要に応じて希釈溶剤を加えることができる。ポリエステル系樹脂は、従来公知のものを制限なく用いることができる。例えば、東洋紡績社製バイロン２００（Ｔｇ：６７℃）、バイロン２４０（Ｔｇ：６０℃）、バイロン３００（Ｔｇ：７℃）、バイロン５００（Ｔｇ：４℃）バイロン６００（Ｔｇ：４７℃）等が挙げられる。 Further, the flaky silver powder according to the present invention has a surface resistance value of a conductive film having a dry film thickness of 15 μm, when the flaky silver powder is contained in 100 parts by weight with respect to 100 parts by weight of the polyester resin, of 0.4Ω / □ or less. belongs to. A more preferable range of the surface resistance value is less than 0.4Ω / □, and more preferably 0.35Ω / □ or less. The surface resistance value is a coating film obtained by applying and drying a conductive composition obtained by blending and mixing 100 parts by weight of a polyester resin and 100 parts by weight of flaky silver powder so that the film thickness becomes 15 μm. Is obtained by measuring. A diluting solvent can be added as needed. A conventionally well-known thing can be used for a polyester-type resin without a restriction | limiting. For example, Byron 200 manufactured by Toyobo Co., Ltd. (Tg: 67 ° C.), Byron 240 (Tg: 60 ° C.), Byron 300 (Tg: 7 ° C.), Byron 500 (Tg: 4 ° C.), Byron 600 (Tg: 47 ° C.), etc. Is mentioned.
　ポリエステル系樹脂１００重量部に対してフレーク状銀粉１００重量部を混合させる方法としては、例えばミキサー、ディソルバー、フーバーマーラー、３本ロールミル、サンドミル等が挙げられる。ポリエステル系樹脂１００重量部に対してフレーク状銀粉１００重量部を含有する導電性組成物をバーコーターで塗布し、例えば、１００℃で２分間乾燥させることにより乾燥膜厚１５μｍの塗膜を形成する。 Examples of the method for mixing 100 parts by weight of the flaky silver powder with 100 parts by weight of the polyester resin include a mixer, a dissolver, a Hoover muller, a three-roll mill, and a sand mill. A conductive composition containing 100 parts by weight of flaky silver powder is applied to 100 parts by weight of a polyester resin with a bar coater, and dried at 100 ° C. for 2 minutes to form a coating film having a dry film thickness of 15 μm. .
　フレーク状銀粉のＢＥＴ比表面積は、１ｍ２／ｇ以上、３．５ｍ２／ｇ以下であることが好ましい。ＢＥＴ比表面積を１ｍ２／ｇ以上とすることにより、粒子間の接触点数を良好な状態とし、良好な導電性を得ることができる。また、ＢＥＴ比表面積を３．５ｍ２／ｇ以下とすることにより、樹脂に混合して導電性組成物とする場合に、粘度の上昇を抑制して信頼性を高めることができる。ＢＥＴ比表面積のより好ましい範囲は、１．２ｍ２／ｇ以上、２．５ｍ２／ｇ以下であり、特に好ましい範囲は、１．５ｍ２／ｇ以上、１．９ｍ２／ｇ以下である。 The BET specific surface area of the flaky silver powder is preferably 1 m 2 / g or more and 3.5 m 2 / g or less. By setting the BET specific surface area to 1 m 2 / g or more, the number of contact points between particles can be made good and good conductivity can be obtained. In addition, by setting the BET specific surface area to 3.5 m 2 / g or less, when mixed with a resin to form a conductive composition, an increase in viscosity can be suppressed and reliability can be improved. A more preferable range of the BET specific surface area is 1.2 m 2 / g or more and 2.5 m 2 / g or less, and a particularly preferable range is 1.5 m 2 / g or more and 1.9 m 2 / g or less.
　本発明に係る導電性組成物は、樹脂と導電性粒子を少なくとも含有するものであって、導電性粒子として前述のフレーク状銀粉を用いるものである。すなわち、導電性粒子として、５０％粒子径が３μｍ以上、８μｍ以下であり、見掛密度が、０．２５ｇ／ｃｍ３以上、０．５ｇ／ｃｍ３以下であり、かつ、ポリエステル系樹脂１００重量部に対してフレーク状銀粉を１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下となるフレーク状銀粉を少なくとも含有するものである。 The conductive composition according to the present invention contains at least a resin and conductive particles, and uses the aforementioned flaky silver powder as the conductive particles. That is, as the conductive particles, the 50% particle diameter is 3 μm or more and 8 μm or less, the apparent density is 0.25 g / cm 3 or more and 0.5 g / cm 3 or less, and the weight of the polyester resin is 100 weight. The surface resistance value of the conductive film having a dry film thickness of 15 μm when containing 100 parts by weight of flaky silver powder with respect to the part contains at least flaky silver powder having a resistance of 0.4Ω / □ or less.
　本発明に係るフレーク状銀粉は、前述したとおり、ポリエステル系樹脂１００重量部に対してフレーク状銀粉を１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下のものを用いているので導電特性に優れる。このため、本発明のフレーク状銀粉を導電性組成物の導電性粒子として用いた場合、所望の導電特性に設計するための導電性粒子の含有量を従来のフレーク状銀粉よりも減らすことが可能となる。従って、本発明に係る導電性組成物は、強度、被着体に対する優れた密着力を実現することが可能となる。また、低コスト化を図ることが可能となる。 As described above, the flaky silver powder according to the present invention has a surface resistance value of a conductive film having a dry film thickness of 15 μm when the flaky silver powder is contained in 100 parts by weight with respect to 100 parts by weight of the polyester resin. □ Excellent conductive properties due to use of the following. For this reason, when the flaky silver powder of the present invention is used as the conductive particles of the conductive composition, it is possible to reduce the content of conductive particles for designing desired conductive characteristics as compared with the conventional flaky silver powder. It becomes. Therefore, the conductive composition according to the present invention can realize strength and excellent adhesion to the adherend. In addition, the cost can be reduced.
　本発明に係る導電性組成物に含有する樹脂は、特に限定されないが、一例として、ポリウレタン樹脂、（不飽和）ポリエステル樹脂、アルキッド樹脂、ブチラール樹脂、アセタール樹脂、ポリアミド樹脂、（メタ）アクリル樹脂、スチレン／（メタ）アクリル樹脂、ポリスチレン樹脂、ニトロセルロース、ベンジルセルロース、セルロース（トリ）アセテート、カゼイン、シェラック、ゼラチン、ギルソナイト、ロジン、ロジンエステル、ポリビニルアルコール、ポリビニルピロリドン、ポリアクリルアミド、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、メチルセルロース、エチルセルロース、ヒドロキシエチルメチルセルロース、ヒドロキシプロピルメチルセルロース、カルボキシメチルセルロース、カルボキシメチルエチルセルロース、カルボキシメチルニトロセルロース、エチレン／ビニルアルコール樹脂、スチレン／無水マレイン酸樹脂、ポリブタジエン樹脂、ポリ塩化ビニル樹脂、ポリ塩化ビニリデン樹脂、ポリフッ化ビニリデン樹脂、ポリ酢酸ビニル樹脂、エチレン／酢酸ビニル樹脂、塩化ビニル／酢酸ビニル樹脂、塩化ビニル／酢酸ビニル／マレイン酸樹脂、フッ素樹脂、シリコン樹脂、エポキシ樹脂、フェノキシ樹脂、フェノール樹脂、マレイン酸樹脂、尿素樹脂、メラミン樹脂、ベンゾグアナミン樹脂、ケトン樹脂、石油樹脂、塩素化ポリオレフィン樹脂、変性塩素化ポリオレフィン樹脂、塩素化ポリウレタン樹脂等が挙げられる。これらのうち、ウレタン樹脂とエポキシ樹脂を含有する事がより好ましい。ウレタン樹脂とエポキシ樹脂を用いることにより、乾燥被膜にした際の被着体に対する密着性や接着力を向上させることができる。また、乾燥被膜の耐熱性を向上させることができる。 The resin contained in the conductive composition according to the present invention is not particularly limited, but as an example, polyurethane resin, (unsaturated) polyester resin, alkyd resin, butyral resin, acetal resin, polyamide resin, (meth) acrylic resin, Styrene / (meth) acrylic resin, polystyrene resin, nitrocellulose, benzylcellulose, cellulose (tri) acetate, casein, shellac, gelatin, gilsonite, rosin, rosin ester, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, hydroxyethylcellulose, hydroxypropyl Cellulose, methylcellulose, ethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, carboxymethyl Ethyl cellulose, carboxymethyl nitrocellulose, ethylene / vinyl alcohol resin, styrene / maleic anhydride resin, polybutadiene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinylidene fluoride resin, polyvinyl acetate resin, ethylene / vinyl acetate resin, chloride Vinyl / vinyl acetate resin, vinyl chloride / vinyl acetate / maleic acid resin, fluorine resin, silicone resin, epoxy resin, phenoxy resin, phenol resin, maleic acid resin, urea resin, melamine resin, benzoguanamine resin, ketone resin, petroleum resin, Examples include chlorinated polyolefin resins, modified chlorinated polyolefin resins, and chlorinated polyurethane resins. Among these, it is more preferable to contain a urethane resin and an epoxy resin. By using a urethane resin and an epoxy resin, it is possible to improve adhesion and adhesion to an adherend when a dry film is formed. Moreover, the heat resistance of the dry film can be improved.
　本発明に係る導電性組成物には、例えば印刷や塗布を行い易くするために、必要に応じて溶剤を加えることができる。使用する溶剤は、特に限定されないが、一例としては、ｎ－ヘキサン、ｎ－ヘプタン、ｎ－オクタンなどの脂肪族炭化水素系有機溶剤、及びシクロヘキサン、メチルシクロヘキサン、エチルシクロヘキサン、シクロヘプタン、シクロオクタンなどの脂環族炭化水素系溶剤、トルエン、キシレンなどの芳香族炭化水素系溶剤、アセトン，メチルエチルケトン、メチルイソブチルケトン、炭酸ジメチルなどのケトン系有機溶剤、酢酸メチル、酢酸エチル、酢酸ｎ－プロピル、酢酸ブチル、プロピレングリコールモノエチルエーテルアセテートなどのエステル系溶剤メタノール、エタノール、ｎ－プロパノール、イソプロパノール、ブタノールなどのアルコール系溶剤、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテルなどが挙げられる。 In the conductive composition according to the present invention, for example, a solvent can be added as necessary to facilitate printing and coating. The solvent to be used is not particularly limited. Examples thereof include aliphatic hydrocarbon organic solvents such as n-hexane, n-heptane, and n-octane, and cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, cyclooctane, and the like. Alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents such as toluene and xylene, ketone organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethyl carbonate, methyl acetate, ethyl acetate, n-propyl acetate, acetic acid Ester solvents such as butyl and propylene glycol monoethyl ether acetate Alcohol solvents such as methanol, ethanol, n-propanol, isopropanol and butanol, propylene glycol monomethyl ether, propylene glycol monoethyl Ether and the like.
　本発明に係る導電性組成物は、本発明のフレーク状銀粉以外の導電性フィラーを含有していてもよい。具体的には、銀、銅、ニッケル等の金属粉；はんだ等の合金粉；銀めっき処理された銅粉；金属めっき処理されたガラス繊維、プラスチック、カーボンなどのフィラーなどが挙げられる。金属粉の形状としては、球状、フレーク状、樹枝状、繊維状などが挙げられる。導電特性を良好にする観点からは、導電性フィラーとして本発明のフレーク状銀粉を単独で用いることが好ましい。但し、この場合であっても、特性に影響を与えない範囲であれば他の導電性フィラーが含まれていてもよい。 The conductive composition according to the present invention may contain a conductive filler other than the flaky silver powder of the present invention. Specific examples include metal powders such as silver, copper, and nickel; alloy powders such as solder; copper powder that has been subjected to silver plating; fillers such as glass fibers, plastics, and carbon that have been subjected to metal plating. Examples of the shape of the metal powder include a spherical shape, a flake shape, a dendritic shape, and a fibrous shape. From the viewpoint of improving the conductive properties, it is preferable to use the flaky silver powder of the present invention alone as a conductive filler. However, even in this case, other conductive fillers may be included as long as the characteristics are not affected.
　本発明に係る導電性組成物の上記特性のフレーク状銀粉の含有量は、用途やニーズに応じて、適宜設計することができるが、導電性粒子として本発明に係るフレーク状銀粉を用いる場合には、樹脂１００重量部に対して、フレーク状銀粉の含有量を２５重量部以上、９００重量部以下とすることが好ましい。低コスト化、強度、被着体に対する優れた密着力の観点からは、５０重量部以上、４００重量部以下とすることが好ましい。フレーク状銀粉が２５重量部より少ない場合、所望の導電性が得られない恐れがある。一方、９００重量部より多い場合、相対的に樹脂が少なくなるために乾燥被膜が脆くなる恐れがある。 The content of the flaky silver powder having the above characteristics of the conductive composition according to the present invention can be appropriately designed according to the use and needs, but when the flaky silver powder according to the present invention is used as the conductive particles. Is preferably 25 parts by weight or more and 900 parts by weight or less with respect to 100 parts by weight of the resin. From the viewpoint of cost reduction, strength, and excellent adhesion to the adherend, it is preferably 50 parts by weight or more and 400 parts by weight or less. When the amount of flaky silver powder is less than 25 parts by weight, desired conductivity may not be obtained. On the other hand, when the amount is more than 900 parts by weight, the dry film may become brittle because the resin is relatively decreased.
　本発明に係る導電性組成物は、樹脂、溶剤、及びフレーク状銀粉を秤取った後、必要に応じて添加剤を混合して、分散することにより製造することができる。混合や分散方法は、特に制限はなく、例えばミキサー、ディソルバー、フーバーマーラー、３本ロールミル、サンドミル等を用いることができる。必要に応じて添加する添加剤の例としては、紫外線吸収剤、紫外線安定剤、ラジカル捕捉剤、充填剤、チクソトロピー付与剤、老化防止剤、酸化防止剤、帯電防止剤、難燃剤、熱伝導性改良剤、可塑剤、ダレ防止剤、防汚剤、防腐剤、殺菌剤、消泡剤、レベリング剤、ブロッキング防止剤、硬化剤、増粘剤、分散剤、シランカップリング剤等を挙げることができる。 The conductive composition according to the present invention can be produced by weighing a resin, a solvent, and flaky silver powder, and then mixing and dispersing additives as necessary. The mixing or dispersing method is not particularly limited, and for example, a mixer, a dissolver, a hoover muller, a three roll mill, a sand mill or the like can be used. Examples of additives to be added as necessary include UV absorbers, UV stabilizers, radical scavengers, fillers, thixotropic agents, anti-aging agents, antioxidants, antistatic agents, flame retardants, and thermal conductivity. Examples include improvers, plasticizers, anti-sagging agents, antifouling agents, antiseptics, bactericides, antifoaming agents, leveling agents, antiblocking agents, curing agents, thickeners, dispersants, silane coupling agents, etc. it can.
　本発明に係る導電性組成物は、導電性シート、導電パターン付き積層体等をはじめとする種々の用途に応用することができる。例えば、非接触型ＩＣメディアのアンテナ回路や、プリント基板の導電回路、印刷エレクトロニクス用導電材料、タッチパネル及び太陽電池等の各種電極材を形成する導電性インキ、導電性ペーストとして利用することができる。また、電磁波シールド用メッシュ膜、電磁波シールド用導電性薄膜、静電気帯電防止膜、導電性接着剤として好適に利用できる。さらに、非導電性物への導電性付与膜、例えば導電布等として使用できる。また、導電性ペーストを用いたプリント配線基板のビア（Via）および貫通穴（Through　Hole Via）の穴埋めなどに用いてもよい。なお、これらは一例であって、電子機器、電子部品等の部材全般において本発明の導電性組成物を用いることができる。なお、本明細書において「シート」とは、膜厚に限定されず、狭義のフィルム状、シート状、板状のものを含むものとする。 The conductive composition according to the present invention can be applied to various uses including a conductive sheet, a laminate with a conductive pattern, and the like. For example, it can be used as an antenna circuit for non-contact type IC media, a conductive circuit for printed circuit boards, a conductive material for printed electronics, a conductive ink for forming various electrode materials such as a touch panel and a solar cell, and a conductive paste. Moreover, it can utilize suitably as a mesh film | membrane for electromagnetic wave shielding, a conductive thin film for electromagnetic wave shielding, an antistatic film, and a conductive adhesive. Furthermore, it can be used as a film for imparting conductivity to a non-conductive material, such as a conductive cloth. Moreover, you may use for the filling of the via | veer (Via) and through-hole (Through Hole | Via) of a printed wiring board using an electrically conductive paste. These are merely examples, and the conductive composition of the present invention can be used in general members such as electronic devices and electronic components. In the present specification, the “sheet” is not limited to a film thickness, and includes a film-like, sheet-like, or plate-like thing in a narrow sense.
　電磁波シールド用途に用いる場合には、周波数１ＧＨｚにおける電磁波シールド性が４０ｄＢ以上であることが好ましく、より好ましくは６０ｄＢ以上である。なお、電磁波シールド性は、ポリエステル系樹脂１００重量部に対してフレーク状銀粉を１００重量部含有する導電性組成物を、厚さ１２．５μｍのポリイミドフィルム上に厚さ１５μｍの導電層を形成するように塗布・乾燥させることにより塗膜を得、これをＫＥＣ法により測定して求めたものである。ポリエステル系樹脂としては、特に制限はなく、前述したものを好適に適用することができる。なお、ＫＥＣ法とは、社団法人関西電子工業振興センター（ＫＥＣ）が開発した電磁波シールド効果測定装置を用いて電磁波シールド性を測定する方法をいう。 When used for electromagnetic wave shielding, the electromagnetic wave shielding property at a frequency of 1 GHz is preferably 40 dB or more, and more preferably 60 dB or more. The electromagnetic wave shielding property is that a conductive composition containing 100 parts by weight of flaky silver powder with respect to 100 parts by weight of a polyester resin is formed on a polyimide film having a thickness of 12.5 μm and a conductive layer having a thickness of 15 μm. Thus, a coating film was obtained by coating and drying, and this was determined by measuring by the KEC method. There is no restriction | limiting in particular as polyester-type resin, What was mentioned above can be applied suitably. The KEC method refers to a method of measuring electromagnetic shielding properties using an electromagnetic shielding effect measuring device developed by Kansai Electronics Industry Promotion Center (KEC).
　本発明に係る導電性シートは、導電性組成物から形成された導電層からなる乾燥被膜を少なくとも有する。本発明に係るパターン付き積層体は、基材上に形成された導電パターンを少なくとも有する。導電パターンや乾燥被膜（以下、これらをまとめて「導電層」と称する）は、導電性組成物を基材上に、印刷・塗布等により形成することにより得られる。 The conductive sheet according to the present invention has at least a dry film composed of a conductive layer formed from a conductive composition. The laminated body with a pattern concerning this invention has at least the conductive pattern formed on the base material. A conductive pattern or a dry film (hereinafter collectively referred to as “conductive layer”) is obtained by forming a conductive composition on a substrate by printing, coating, or the like.
　上記印刷・塗布は、例えばグラビア印刷、フレキソ印刷、スクリーン印刷、インクジェット印刷、ディスペンサー印刷、スプレーコート、スピンコート、ダイコート、リップコート、コンマコート、ナイフコート、ディップコート、カーテンコート、ロールコート、バーコート等を用いることができる。また印刷形態は、ベタ塗りあってもよいし、配線回路などのパターン印刷であってもよい。 For example, gravure printing, flexographic printing, screen printing, inkjet printing, dispenser printing, spray coating, spin coating, die coating, lip coating, comma coating, knife coating, dip coating, curtain coating, roll coating, bar coating. Etc. can be used. Further, the printing form may be solid coating or pattern printing such as a wiring circuit.
　上記導電層の厚さは０．５μｍ～１００μｍが好ましい。０．５μｍに満たない場合、導電性が不足する恐れがある。一方、１００μｍを超える場合、導電性組成物を印刷・塗布した後に乾燥に時間がかかる恐れがある。 The thickness of the conductive layer is preferably 0.5 μm to 100 μm. If it is less than 0.5 μm, the conductivity may be insufficient. On the other hand, when it exceeds 100 μm, there is a possibility that it takes time to dry after printing and applying the conductive composition.
　上記基材は、例えば、ポリエステル、ポリカーボネート、ポリイミド、ポリフェニレンサルファイドなどのプラスチックフィルムを挙げることができる。また、基材は、剥離処理や、乾燥被膜との密着性を向上させるためのコロナ処理や易接着処理を施してもよい。基材の厚さは、１μｍ～２５０μｍが好ましい。基材が１μｍに満たない場合、シートとしての強度が弱くなる恐れがある。一方、２５０μｍを超える場合、印刷・塗布が困難になる場合もある。 Examples of the substrate include plastic films such as polyester, polycarbonate, polyimide, and polyphenylene sulfide. Further, the base material may be subjected to a peeling treatment, a corona treatment or an easy adhesion treatment for improving the adhesion with the dry film. The thickness of the substrate is preferably 1 μm to 250 μm. When the substrate is less than 1 μm, the strength as a sheet may be weakened. On the other hand, if it exceeds 250 μm, printing / coating may be difficult.
　本発明に係る導電性シートは、導電性粘着シート、導電性接着シートなどに用いてもよい。例えば、本発明に係る導電性組成物から形成した導電層と、公知の粘着剤あるいは接着剤から形成した粘着剤層あるいは接着剤層を積層して導電性シートとすることができる。また、プラスチックフィルムを基材として用い、導電層、粘着剤層等とを順次積層してもよい。また、導電性組成物に粘着性あるいは接着性を有する樹脂を用いることで、導電層単独で導電性粘着シートあるいは導電性接着シートとして用いてもよい。 The conductive sheet according to the present invention may be used for a conductive adhesive sheet, a conductive adhesive sheet, and the like. For example, a conductive sheet formed from the conductive composition according to the present invention and a pressure-sensitive adhesive layer or adhesive layer formed from a known pressure-sensitive adhesive or adhesive can be laminated to form a conductive sheet. Moreover, you may laminate | stack a conductive layer, an adhesive layer, etc. one by one using a plastic film as a base material. Moreover, by using a resin having adhesiveness or adhesiveness for the conductive composition, the conductive layer alone may be used as a conductive adhesive sheet or a conductive adhesive sheet.
　本発明に係る導電性シートや導電パターン付き積層体は、導電層の一方の面に絶縁層を具備することが好ましい。ここで絶縁層を有する導電性シートを電磁波シールド性シートということがある。電磁波シールド性シートは、絶縁層を２層以上有してもよい。絶縁層の厚さは、特に限定されないが、０．５μｍ～２００μｍが好ましい。絶縁層の厚さが０．５μｍ未満の場合、シートを折り曲げた際に亀裂が入る恐れがある。一方、２００μｍを超える場合、導電層と絶縁層を足した厚みが厚くなり、シートの柔軟性が不足する恐れがある。なお、絶縁層の形成方法は、従来公知の方法を制限なく利用することができる。 The conductive sheet or the laminate with a conductive pattern according to the present invention preferably includes an insulating layer on one surface of the conductive layer. Here, the conductive sheet having an insulating layer may be referred to as an electromagnetic wave shielding sheet. The electromagnetic wave shielding sheet may have two or more insulating layers. The thickness of the insulating layer is not particularly limited, but is preferably 0.5 μm to 200 μm. When the thickness of the insulating layer is less than 0.5 μm, there is a possibility that a crack may occur when the sheet is bent. On the other hand, when it exceeds 200 μm, the total thickness of the conductive layer and the insulating layer is increased, and the flexibility of the sheet may be insufficient. In addition, the formation method of an insulating layer can utilize a conventionally well-known method without a restriction | limiting.
　本発明に係る導電性シートや導電パターン付き積層体等に用いる絶縁層は、特に限定されないが、絶縁性の樹脂を用いて形成することが好ましい。例えば、アクリル樹脂、ウレタン樹脂、ポリエステル樹脂、エポキシ樹脂、フェノール樹脂、ポリカーボネート樹脂などから形成したフィルムや、ポリエステル、ポリカーボネート、ポリイミド、ポリフェニレンサルファイドなどのプラスチックフィルムを使用することができる。 The insulating layer used in the conductive sheet or the laminate with a conductive pattern according to the present invention is not particularly limited, but is preferably formed using an insulating resin. For example, a film formed from an acrylic resin, a urethane resin, a polyester resin, an epoxy resin, a phenol resin, a polycarbonate resin, or a plastic film such as polyester, polycarbonate, polyimide, or polyphenylene sulfide can be used.
　本発明において絶縁層は、必要に応じてシランカップリング剤、酸化防止剤、顔料、染料、粘着付与樹脂、可塑剤、紫外線吸収剤、消泡剤、レベリング調整剤、充填剤、難燃剤等を含むこともできる。 In the present invention, the insulating layer may contain a silane coupling agent, an antioxidant, a pigment, a dye, a tackifier resin, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling regulator, a filler, a flame retardant, and the like as necessary. It can also be included.
　本発明に係るフレーク状銀粉の製造方法は、特に限定されないが、以下、好ましい製造方法の一例について説明する。 Although the manufacturing method of the flaky silver powder according to the present invention is not particularly limited, an example of a preferable manufacturing method will be described below.
　まず、原料粉を用意する。原料粉として粒状銀粉を用いる場合には、フレーク化工程によりフレーク状の銀粉を得る。フレーク状の銀粉を得る方法は、公知の方法を制限なく用いることができる。原料粉として、市販のフレーク状の銀粉を用いてもよい。 First, prepare raw powder. When granular silver powder is used as the raw material powder, flaky silver powder is obtained by the flaking process. As a method for obtaining the flaky silver powder, a known method can be used without limitation. Commercially available flaky silver powder may be used as the raw material powder.
　次いで、上記フレーク状の銀粉を半自由渦遠心式の旋回式気流環境下において分級・分散・解砕処理し、フレーク状銀粉を得る。本明細書においては、半自由渦遠心式の旋回式気流環境下による分級・分散・解砕処理前のフレーク状の銀粉を「未解砕フレーク状銀粉」と称する。　 Next, the flaky silver powder is classified, dispersed and pulverized in a semi-free vortex centrifugal swirling airflow environment to obtain flaky silver powder. In the present specification, flaky silver powder before classification, dispersion, and pulverization treatment in a semi-free vortex centrifugal swirling airflow environment is referred to as “unbroken flaky silver powder”. *
　以下、より具体的に、本発明に係るフレーク状銀粉の製造方法について説明する。粒状銀粉のフレーク化工程は、例えば、公知の攪拌ボールミルを用いる方法の場合には、アトマイズ法、電解法、又は化学還元法などの公知の方法で得られた粒状銀粉を好適に利用できる。攪拌ボールミルは、円筒状の内面を有する容器と、その容器内に設けられた攪拌翼とを備えたものである。フレーク化工程では、攪拌ボールミルの容器内には、粒状銀粉、ボール、溶媒、及び処理剤が仕込まれ、容器内の攪拌翼によって、ボールに５～３００Ｇの遠心力が加わり、粒状銀粉にボールからのせん断応力が作用し、粒状銀粉がフレーク化されて、未解砕フレーク状銀粉が得られる。 Hereinafter, the method for producing flaky silver powder according to the present invention will be described more specifically. In the flaking process of the granular silver powder, for example, in the case of a method using a known stirring ball mill, the granular silver powder obtained by a known method such as an atomizing method, an electrolytic method, or a chemical reduction method can be suitably used. The stirring ball mill includes a container having a cylindrical inner surface and a stirring blade provided in the container. In the flaking process, granular silver powder, balls, a solvent, and a processing agent are charged in the container of the stirring ball mill, and a centrifugal force of 5 to 300 G is applied to the balls by the stirring blades in the container, and the granular silver powder is removed from the balls. Thus, the granular silver powder is made into flakes to obtain uncrushed flaky silver powder.
　銀粉をフレーク化すると、通常、得られたフレーク状銀粉の中に、フレーク化工程で粒子同士が衝突することで、絡みや付着により２次凝集したフレーク状銀粉（未解砕フレーク状銀粉）が生じる。このように、粒子同士の凝集が発生すると、粒子の分散性が低下してしまう場合があり、また、導電性組成物中において粘度上昇等の粘度変動が生じるという問題もある。 When the silver powder is flaked, the flaky silver powder (uncrushed flaky silver powder) that is secondarily agglomerated by entanglement or adhesion is usually caused by the particles colliding in the flaky process in the obtained flaky silver powder. Arise. Thus, when aggregation of particles occurs, the dispersibility of the particles may decrease, and there is also a problem that viscosity fluctuation such as increase in viscosity occurs in the conductive composition.
　未解砕フレーク状銀粉は、フレーク状銀粉が得られれば特に限定されないが、本発明に係る特性範囲を有するフレーク状銀粉を容易に得る観点からは、以下の範囲のものであることが好ましい。すなわち、未解砕フレーク状銀粉の５０％粒径は、３．１μｍ以上、１０μｍ以下の範囲であることが好ましく、より好ましくは５μｍ以上、７μｍ以下である。また、未解砕フレーク状銀粉のＢＥＴ比表面積は、１ｍ２／ｇ以上、３．５ｍ２／ｇ以下が好ましく、より好ましくは１．５ｍ２／ｇ以上、２．５ｍ２／ｇ以下である。さらに、未解砕フレーク状銀粉の見掛密度は、０．４５ｇ／ｃｍ３以上、０．８５ｇ／ｃｍ３以下であることが好ましく、より好ましくは０．４７ｇ／ｃｍ３以上、０．７５ｇ／ｃｍ３以下である。 The uncrushed flaky silver powder is not particularly limited as long as the flaky silver powder is obtained, but is preferably in the following range from the viewpoint of easily obtaining the flaky silver powder having the characteristic range according to the present invention. That is, the 50% particle size of uncrushed flaky silver powder is preferably in the range of 3.1 μm to 10 μm, more preferably 5 μm to 7 μm. Further, the BET specific surface area of the uncrushed flaky silver powder is preferably 1 m 2 / g or more and 3.5 m 2 / g or less, more preferably 1.5 m 2 / g or more and 2.5 m 2 / g or less. . Further, apparent density of the non-disintegration flaky silver powder, 0.45 g / cm 3 or more, preferably 0.85 g / cm 3 or less, more preferably 0.47 g / cm 3 or more, 0.75 g / cm 3 or less.
　半自由渦遠心式の旋回式気流環境下において分級・分散・解砕する工程においては、半自由渦遠心式の旋回式気流環境下による分級・分散・解砕処理が可能な分級・分散・解砕処理装置（以下、「旋回式気流分級・分散装置」と略記する）に、未解砕フレーク状銀粉を投入する。そして、旋回式気流分級・分散装置において、分級・分散・解砕処理を施す。本発明に係る旋回式気流分級・分散装置の具体的な例としては、日清エンジニアリング社製の旋回気流式分級機エアロファインクラシファイアＡＣ－２０を例示することができる。 In the process of classification, dispersion, and crushing in a semi-free vortex centrifugal swirling airflow environment, classification, dispersion, and solution that can be classified, dispersed, and crushed in a semi-free vortex centrifugal swirling airflow environment Uncrushed flaky silver powder is put into a crushing apparatus (hereinafter abbreviated as “swirl type airflow classifying / dispersing apparatus”). Then, classification, dispersion, and crushing are performed in the swirling airflow classification / dispersion device. As a specific example of the swirling airflow classifying / dispersing device according to the present invention, a swirling airflow classifier Aerofine Classifier AC-20 manufactured by Nisshin Engineering can be exemplified.
　図１に、旋回式気流分級・分散装置の一例の模式的断面図を、図２に図１のＩＩ－ＩＩ切断線における模式的平面図を示す。なお、図１、図２において例示した装置構成は、一例であり、本発明の趣旨を逸脱しない範囲で、種々の装置を利用することができる。 FIG. 1 is a schematic cross-sectional view of an example of a swirling airflow classifying / dispersing device, and FIG. 2 is a schematic plan view taken along the line II-II in FIG. Note that the apparatus configuration illustrated in FIGS. 1 and 2 is an example, and various apparatuses can be used without departing from the gist of the present invention.
　旋回式気流分級・分散装置１０は、原料投入口１１、分級ゾーン１２、案内羽根１３、粗粉回収部１４、粗粉取出し口１５、微粉取出し口１６、吹き出し部１７等を有する。原料投入口１１は、未解砕フレーク状銀粉を投入するための入り口部である。例えば、原料供給機２０から原料である未解砕フレーク状銀粉１が、所定のタイミングで所定量投入されるようになっている。 The swirling airflow classifying / dispersing device 10 includes a raw material inlet 11, a classification zone 12, a guide vane 13, a coarse powder collection unit 14, a coarse powder extraction port 15, a fine powder extraction port 16, a blowing unit 17, and the like. The raw material input port 11 is an entrance for inputting unbroken flaky silver powder. For example, a predetermined amount of uncrushed flaky silver powder 1 as a raw material is supplied from a raw material supply machine 20 at a predetermined timing.
　分級ゾーン１２は、半自由渦遠心式の旋回気流を生じさせるゾーンであり、原料投入口１１から投入された未解砕フレーク状銀粉１が最初に通過するゾーンである。分級ゾーン１２は、平面視において概略円形状に形成されており、半自由渦遠心式の旋回気流を形成するための気流の吹き出し部１７が分級ゾーン１２の外周部側壁に設けられている。 The classification zone 12 is a zone that generates a semi-free vortex centrifugal swirling airflow, and is a zone through which the uncrushed flaky silver powder 1 introduced from the raw material inlet 11 passes first. The classification zone 12 is formed in a substantially circular shape in plan view, and an airflow blowing portion 17 for forming a semi-free vortex centrifugal swirling airflow is provided on the outer peripheral side wall of the classification zone 12.
　旋回式気流は、メインエアー２１によって生じる。メインエアー２１の上方、下方からは、２次エアーが吹き出しノズル１８から分級ゾーン１２に導入される。メインエアー２１の吹き出し部１７及び２次エアーの吹き出しノズル１８は、分級ゾーン１２を取り囲むように配置され、メインエアー２１の吹き出し部１７は案内羽根１３によって複数に区画されている。メインエアー２１の吹き出し部１７と２次エアー２２の吹き出しノズル１８は、仕切り板（不図示）によって完全に、若しくは一部が分離されていてもよいし、仕切り板を設けずに、領域によって風量を調整するようにしてもよい。案内羽根１３は、メインエアー２１の吹き出し部１７と２次エアー２２を吹き出しノズル１８から分級ゾーン１２に誘導するための役割を担う。 The swirling airflow is generated by the main air 21. From above and below the main air 21, secondary air is introduced into the classification zone 12 from the blowing nozzle 18. The main air 21 blowing section 17 and the secondary air blowing nozzle 18 are arranged so as to surround the classification zone 12, and the main air 21 blowing section 17 is divided into a plurality of sections by the guide vanes 13. The blowout part 17 of the main air 21 and the blowout nozzle 18 of the secondary air 22 may be completely or partially separated by a partition plate (not shown). May be adjusted. The guide vane 13 plays a role for guiding the blowing portion 17 of the main air 21 and the secondary air 22 from the blowing nozzle 18 to the classification zone 12.
　粗粉回収部１４は、設定した分級点より粒径の大きい粗粉を主とするフレーク状銀粉（以下、単に「粗粉３」という）を回収するゾーンであり、粗粉取出し口１５は、粗粉３を取出すための取出し口である。また、微粉取出し口１６は、設定した分級点より微粉を主とする粒径のフレーク状銀粉（以下、単に「微粉２」という）を取出すための取出し口である。旋回式気流分級・分散装置１０においては、原料粉を分級・分散後、分級装置下部に設置された粗粉回収部１４に粗粉３が回収される。また、旋回式気流分級・分散装置１０の上部に設けられた微粉取出口１６から微粉回収用のサイクロン若しくはバグフィルターにて微粉２が回収される。 The coarse powder collection unit 14 is a zone for collecting flaky silver powder (hereinafter simply referred to as “coarse powder 3”) mainly composed of coarse powder having a particle size larger than the set classification point. This is an outlet for taking out the coarse powder 3. The fine powder outlet 16 is an outlet for taking out flaky silver powder having a particle size mainly composed of fine powder (hereinafter simply referred to as “fine powder 2”) from a set classification point. In the swirling airflow classifying / dispersing device 10, after the raw material powder is classified and dispersed, the coarse powder 3 is collected in the coarse powder collecting unit 14 installed at the lower part of the classifying device. Further, fine powder 2 is collected from a fine powder outlet 16 provided at the upper part of the swirling airflow classifying / dispersing device 10 by a cyclone or bag filter for collecting fine powder.
　図３に、旋回式気流分級・分散装置１０によって分けられる粗粉３と微粉２の粒径分布の一例の説明図を示す。用いる未解砕フレーク状銀粉の粒度分布によって異なるが、図３に示すような粒度分布を有する場合、分級点よりも大きな粒径を持つフレーク状銀粉が主として粗粉３として得られる。一方、分級点よりも小さな粒径を持つフレーク状銀粉が主として微粉２として得られる。 FIG. 3 is an explanatory diagram showing an example of the particle size distribution of the coarse powder 3 and the fine powder 2 separated by the swirling airflow classifying / dispersing device 10. Although it varies depending on the particle size distribution of the uncrushed flaky silver powder to be used, when it has a particle size distribution as shown in FIG. 3, flaky silver powder having a particle size larger than the classification point is mainly obtained as the coarse powder 3. On the other hand, flaky silver powder having a particle size smaller than the classification point is obtained mainly as fine powder 2.
　その後、旋回式気流分級・分散装置によって得られた微粉２と粗粉３を回収することによって本発明に係るフレーク状銀粉を得る。本発明に係るフレーク状銀粉は、分級・分散後に得られた粗粉３及び微粉２各々全量を混合して用いることが好ましい。一般的な分級処理においては、所定の粒度分布を有する粉末を得るために、分級処理によって得られた微粉２、粗粉３の２種類のうちのいずれかを除去したり、気相分級の場合に多く行われる、粗粉３及び微粉２のいずれもカットして中間粒度の粉末を得たりする操作が行われる。後者の場合、まず粗粉を除去した後に、得られた微粉を再度分級して微粉を除去して所定の粒度分布とする操作を行なう。しかしながら、所定の粒度分布よりも外側の粒度をカットして使用すると、銀のように非常に高価な金属を扱う場合、ロスが増え、コスト面で非常に損失が大きくなる。 Thereafter, the pulverized silver powder according to the present invention is obtained by collecting the fine powder 2 and the coarse powder 3 obtained by the swirling airflow classifying / dispersing device. The flaky silver powder according to the present invention is preferably used by mixing the total amount of each of the coarse powder 3 and fine powder 2 obtained after classification and dispersion. In a general classification process, in order to obtain a powder having a predetermined particle size distribution, either one of two types of fine powder 2 and coarse powder 3 obtained by the classification process is removed, or in the case of gas phase classification The operation of cutting both coarse powder 3 and fine powder 2 to obtain an intermediate particle size powder is performed. In the latter case, first, after removing the coarse powder, the obtained fine powder is classified again, and the fine powder is removed to obtain a predetermined particle size distribution. However, if a particle size outside the predetermined particle size distribution is cut and used, when a very expensive metal such as silver is handled, the loss increases, and the loss becomes very large in terms of cost.
　本発明の旋回式気流分級・分散装置による分級・分散・解砕処理は、２次凝集によって付着している粒子同士を剥離して粒子の単分散性を高め、分級・分散後に得られた粗粉３及び微粉２各々全量を混合して用いることができる。このため、ロスを無くして低コスト化を実現することができる。本発明のように、分級・分散処理後の粉末を混合して使用する場合は、分級点の設定そのものには特に意味はない。そのため、分級・分散・解砕条件を設定する際には分級比に着目して設定するのが好ましい。ここで、分級比は分級・分散・解砕処理後に得られた微粉、及び粗粉の回収量の比として定義する。
Figure JPOXMLDOC01-appb-M000001
 The classification, dispersion, and pulverization treatment by the swirl type airflow classification / dispersion device of the present invention increases the monodispersity of the particles by separating particles adhering by secondary aggregation, and the coarse particles obtained after classification / dispersion. The powder 3 and the fine powder 2 can be mixed and used in their entirety. For this reason, loss can be eliminated and cost reduction can be realized. When the powder after classification / dispersion treatment is mixed and used as in the present invention, the setting of the classification point itself has no particular meaning. Therefore, when setting classification / dispersion / disintegration conditions, it is preferable to set by focusing on the classification ratio. Here, the classification ratio is defined as the ratio of the recovered amount of fine powder and coarse powder obtained after classification / dispersion / pulverization treatment.
Figure JPOXMLDOC01-appb-M000001
　得られた粗粉３及び微粉２を混合する方法は特に限定されず、ボールミル、ロッキングミル、Ｖ型ブレンダー、振動ミル等の従来公知の混合機を用いることができる。しかし、粒子の再凝集、及び粒子の形状変化を防止する観点からは、粗粉３及び微粉２の混合は、運動エネルギーが低いＶ型ブレンダーを用いるのが好ましい。 The method of mixing the obtained coarse powder 3 and fine powder 2 is not particularly limited, and a conventionally known mixer such as a ball mill, a rocking mill, a V-type blender, or a vibration mill can be used. However, from the viewpoint of preventing particle re-aggregation and particle shape change, it is preferable to use a V-type blender with low kinetic energy for mixing coarse powder 3 and fine powder 2.
　無論、５０％粒径が３μｍ以上、８μｍ以下の範囲内であれば、微粉２、粗粉３をそれぞれ単独で利用することも可能である。用途、ニーズに応じて、微粉２のみ、若しくは粗粉３のみを利用したり、微粉２、粗粉３を任意の割合で混合したりしてもよい。所望の粒径を得る方法としては、上記のように微粉２、粗粉３の割合等に応じて変更する他、分級点の設定変更等により調整することができる。 Of course, if the 50% particle size is in the range of 3 μm or more and 8 μm or less, the fine powder 2 and the coarse powder 3 can be used alone. Depending on the application and needs, only the fine powder 2 or only the coarse powder 3 may be used, or the fine powder 2 and the coarse powder 3 may be mixed at an arbitrary ratio. As a method of obtaining a desired particle size, the particle size can be adjusted by changing the setting of the classification point or the like in addition to changing according to the ratio of the fine powder 2 and the coarse powder 3 as described above.
　旋回式気流分級・分散装置の機構から考えた場合、例えば旋回気流の風量が増えると遠心力が増大し、粒子に作用する抗力が低下する。そして、微粉回収用のサイクロン若しくはバグフィルターへ向かう微粉の量が減少し、分級比が小さくなる。また、分級比は、前述のように旋回気流による遠心力、及び抗力との関係により規定されるものであり、旋回気流の風量によって適宜調整することが可能である。従って、分級比は、特に規定する必要はない。分級比は、未解砕フレーク状銀粉の粒度、及び見掛密度に応じて、本発明による単分散性の高いフレーク状銀粉の特性が所定の範囲を満足する分級比の範囲であればよい。つまり、分級比を調整して、分級・分散・解砕後の微粉、及び粗粉を混合した粉末の見掛密度、及び５０％粒径が所定の範囲になるよう設定することが好ましい。但し、旋回気流を増加させ過ぎると装置内壁面との衝突が激しくなり、粒子の損傷や変形も増える恐れがあるので、適切な風量に設定することが好ましい。 Considering the mechanism of the swirling airflow classifying / dispersing device, for example, when the air volume of the swirling airflow increases, the centrifugal force increases and the drag acting on the particles decreases. And the quantity of the fine powder which goes to the cyclone or bag filter for fine powder collection decreases, and a classification ratio becomes small. Moreover, the classification ratio is defined by the relationship between the centrifugal force and the drag force caused by the swirling airflow as described above, and can be appropriately adjusted depending on the air volume of the swirling airflow. Therefore, the classification ratio need not be specified. The classification ratio may be in the range of the classification ratio in which the properties of the highly monodispersed flaky silver powder according to the present invention satisfy a predetermined range according to the particle size and apparent density of the uncrushed flaky silver powder. That is, it is preferable to adjust the classification ratio so that the apparent density and 50% particle size of the powder obtained by mixing the fine powder after classification, dispersion, and pulverization and the coarse powder are in a predetermined range. However, if the swirling airflow is increased excessively, the collision with the inner wall surface of the apparatus becomes severe and damage and deformation of the particles may increase, so it is preferable to set an appropriate airflow.
　従来より、粒子の凝集状態を改善する方法としては、種々の粉砕機、ミル、分級機を用いて解砕処理を施す方法が知られている。上記特許文献３においては、高エネルギーボールミル、高速導体衝突式気流型粉砕機、衝撃式粉砕機、ゲージミル、媒体攪拌型ミル、高水圧式粉砕装置等により解砕処理を施す方法に代わる方法として、以下の方法が提案されている。第１の方法として、凝集状態にある乾燥した銀粉を、遠心力を利用した風力サーキュレータを用いて解砕処理する方法である。第２の方法として、凝集状態にある銀粉を含有した銀粉スラリーを、遠心力を利用した流体ミルを用いて解粒処理する方法である。 Conventionally, as a method for improving the agglomeration state of particles, a method of performing pulverization using various pulverizers, mills, and classifiers is known. In Patent Document 3, as an alternative to the method of performing the crushing treatment with a high energy ball mill, a high-speed conductor collision type airflow type pulverizer, an impact type pulverizer, a gauge mill, a medium stirring type mill, a high hydraulic pressure pulverizer, etc. The following methods have been proposed. As a first method, the dried silver powder in an agglomerated state is crushed using a wind circulator utilizing centrifugal force. As a second method, a silver powder slurry containing silver powder in an aggregated state is pulverized using a fluid mill using centrifugal force.
　上記特許文献４及び５においては、凝集状態の粒子の解砕方法として、遠心力を伴う回転性の装置に粒子を投入して、相対的に風力エネルギーを加える方法が開示されている。具体的には、日清エンジニアリング社製の強制渦遠心式空気分級機である「ターボクラシファイア」を用いてサーキュレーションさせ、凝集状態にある粒子同士を衝突させて解粒処理を行う方法が開示されている。しかしながら、上記特許文献４及び５のような遠心力を伴う回転性の装置に粒子を投入して相対的に風力エネルギーを加える方法は、銀粉のような柔らかい金属においては形状が変化しやすいという問題がある。また、分級ローターに取り付けられた分級羽根と銀粉の粒子が衝突するので、銀粉の損傷や銀粉の凝集が生じやすいという問題がある。 In the above Patent Documents 4 and 5, as a method for crushing the aggregated particles, a method is disclosed in which the particles are introduced into a rotating device with centrifugal force and wind energy is applied relatively. Specifically, a method is disclosed in which a turbulent vortex centrifugal air classifier manufactured by Nissin Engineering Co., Ltd. is used for circulation, and particles in an agglomerated state collide with each other to perform a pulverization treatment. ing. However, the method of adding particles to a rotating device with centrifugal force as in Patent Documents 4 and 5 and applying wind energy relatively tends to change the shape of a soft metal such as silver powder. There is. Further, since the classification blades attached to the classification rotor and the silver powder particles collide, there is a problem that the silver powder is easily damaged or the silver powder is agglomerated.
　本発明に係る旋回式気流分級・分散装置の特徴点として、少なくとも粉体の存在領域にローターなどの駆動部（可動部）が設けられていないことが挙げられる。ローターなどの駆動部が粉体の存在領域に設けられていると、ローターに取り付けられた分級羽根と銀粉の粒子が衝突するので、凝集が生じやすく、粒子形状が変化しやすくなる。本発明に係る旋回式気流分級・分散装置によれば、ローターなどの駆動部を設けないことにより、これらの問題を回避することができる。例えば、強制渦遠心式分級機は、ローターの回転による遠心力と機内を通過する空気の抗力を粒子に働かせることで分級を行うが、前述の通り分級羽根と銀粉の粒子が衝突するので凝集が生じやすく、粒子形状が変化しやすくなる。その結果、見掛密度を小さくすることが困難となり、高い導電性が得られない。 A characteristic point of the swirling airflow classifying / dispersing device according to the present invention is that a drive unit (movable unit) such as a rotor is not provided at least in the region where the powder is present. When a drive unit such as a rotor is provided in the region where the powder is present, the classification blades attached to the rotor collide with the silver powder particles, so that aggregation is likely to occur and the particle shape is likely to change. According to the swirl type airflow classifying / dispersing device according to the present invention, these problems can be avoided by not providing a drive unit such as a rotor. For example, a forced vortex centrifugal classifier classifies particles by applying the centrifugal force generated by the rotation of the rotor and the drag of the air that passes through the machine to the particles. It tends to occur and the particle shape is likely to change. As a result, it becomes difficult to reduce the apparent density, and high conductivity cannot be obtained.
　本発明に係るフレーク状銀粉は、半自由渦遠心式の旋回式気流環境下における分級・分散・解砕処理によって、実質的に未解砕フレーク状銀粉から粒子形状変化していないことを下記（式２）の解砕度により確認した。
Figure JPOXMLDOC01-appb-M000002
 　なお、上記ＢＥＴ比表面積は、不活性気体の低温低湿物理吸着によるＢＥＴ理論に基づいて、粉体粒子表面に吸着占有面積の判った分子を液体窒素の温度で吸着させ、その量から試料の比表面積を求める。吸着させる分子は窒素やクリプトンなどの気体分子であり、試料である粉体粒子よりもはるかに小さい。そのため、未解砕フレーク状銀粉のように凝集して粒子同士が重なっていても、気体分子が粒子と粒子の間に容易に侵入できるため、粒子形状の変化がなければ解砕前後でＢＥＴ比表面積の値は変化しないと考えられる。よって、解砕前後のＢＥＴ比表面積の比を解砕度とすれば、粒子形状が変化していなければ解砕度は１となる。 The flaky silver powder according to the present invention has substantially the same particle shape as that of the uncrushed flaky silver powder by classification, dispersion, and pulverization treatment in a semi-free vortex centrifugal swirling airflow environment (the following ( This was confirmed by the degree of crushing of the formula 2).
Figure JPOXMLDOC01-appb-M000002
 The BET specific surface area is based on the BET theory based on low-temperature and low-humidity physical adsorption of an inert gas, by adsorbing molecules having a known adsorption occupation area on the surface of the powder particles at the temperature of liquid nitrogen, and calculating the ratio of the sample from the amount. Determine the surface area. The molecules to be adsorbed are gas molecules such as nitrogen and krypton, and are much smaller than the powder particles as the sample. Therefore, even if the particles are agglomerated and overlap each other like crushed flaky silver powder, gas molecules can easily enter between the particles, so if there is no change in the particle shape, the BET ratio before and after crushing It is believed that the surface area value does not change. Therefore, if the ratio of the BET specific surface area before and after crushing is defined as the crushing degree, the crushing degree is 1 unless the particle shape is changed.
　一方、解砕処理によって、粒子が折れ曲がったり、破断したり、機械的に凝集を起こすなど粒子形状に変化があれば、粒子の表面積も変化するため、解砕度は１から離れた値を取ることになる。従って、解砕度の値は粒子形状の変化を反映しうる指標である。但し、解砕度を求めるに際しては、解砕後の粉末のＢＥＴ比表面積は粗粉、及び微粉全量を混合した場合の値を使用して求めるものとする。解砕度が０．９０以上、１．１５以下であれば、本発明のフレーク状銀粉を導電フィラーとして用いた際に、従来よりも少量添加で高い導電性を発現できる。より好ましくは０．９４以上、１．１２以下である。特に好ましくは１以上、１．１２以下である。 On the other hand, if the particle shape is changed, such as when the particle is bent, broken, or mechanically agglomerated by the crushing process, the surface area of the particle also changes. It will be. Therefore, the value of the crushing degree is an index that can reflect the change in the particle shape. However, when determining the degree of pulverization, the BET specific surface area of the powder after pulverization is determined using a value obtained by mixing the total amount of coarse powder and fine powder. When the pulverization degree is 0.90 or more and 1.15 or less, when the flaky silver powder of the present invention is used as a conductive filler, high conductivity can be expressed by adding a smaller amount than before. More preferably, it is 0.94 or more and 1.12 or less. Particularly preferably, it is 1 or more and 1.12 or less.
　また、本発明に係るフレーク状銀粉は、半自由渦遠心式の旋回式気流環境下における分級・分散・解砕処理によって、フレーク状銀粉が実質的に単分散であることを下記（式３）の見掛密度変化率により確認した。なお、ここで「単分散」とは、粉体において凝集がなく粒子が実質的に一粒毎に分離された状態にあるものをいう。
Figure JPOXMLDOC01-appb-M000003
 　但し、見掛密度変化率を求めるに際しては、分級・分散・解砕後の粉末の見掛密度変化率は粗粉、及び微粉全量を混合した場合の値を使用して求めるものとする。 Further, the flaky silver powder according to the present invention is substantially monodispersed by the following (formula 3) that the flaky silver powder is substantially monodispersed by classification, dispersion, and crushing treatment in a semi-free vortex centrifugal swirling airflow environment. This was confirmed by the apparent density change rate. Here, “monodispersed” means that the powder is not aggregated and the particles are substantially separated from each other.
Figure JPOXMLDOC01-appb-M000003
 However, when the apparent density change rate is obtained, the apparent density change rate of the powder after classification, dispersion, and pulverization is obtained using a value obtained by mixing the total amount of coarse powder and fine powder.
　解砕度、及び見掛密度変化率は、前述のとおり、解砕前後における粉末全体の状態を比較する指標であり、粗粉と微粉全量を混合した場合に定義した値である。そのため、粗粉、若しくは微粉の各々単独の粒子形状変化の度合いや単分散性を、解砕度、及び見掛密度変化率から見積もることはできない。しかし、粗粉と微粉全量を混合処理した後の粉末の解砕度と見掛密度変化率から、粒子形状の変化がなく、かつ単分散の状態であるという知見が得られれば、中間工程品である粗粉と微粉各々は、粒子形状の変化なく単分散であると言える。従って、粗粉と微粉の粒子形状変化の度合いと単分散性は、粗粉と微粉全量を混合した際の解砕度、及び見掛密度変化率より判定することができる。 As described above, the degree of pulverization and the rate of change in apparent density are indices for comparing the state of the entire powder before and after pulverization, and are values defined when the total amount of coarse powder and fine powder is mixed. Therefore, the degree of particle shape change and monodispersity of each of coarse powder and fine powder cannot be estimated from the degree of pulverization and the apparent density change rate. However, if the knowledge that the particle shape does not change and is in a monodispersed state is obtained from the pulverization degree and apparent density change rate of the powder after mixing the coarse powder and the fine powder, the intermediate process product It can be said that each of the coarse powder and the fine powder is monodispersed without any change in the particle shape. Therefore, the degree of particle shape change and monodispersity of the coarse powder and fine powder can be determined from the degree of pulverization and the apparent density change rate when the coarse powder and fine powder are mixed.
　半自由渦遠心式の旋回式気流環境下における分級・分散・解砕処理によって、粒子が解砕されて付着粒子が分離し、粒子サイズで分散化することで単分散となれば、粒子と粒子の重なりが粗となって、規定の容器内の粉体の充填量で表わされる見掛密度の値は、解砕前よりも大きく下がる。そのため、見掛密度変化率の大きさから単分散の度合いを見積もることができる。逆に、過剰な解砕により粒子が破断すれば見掛密度変化率は小さくなったり、若しくは見掛密度が上昇したりする（見掛密度変化率が負の値となる）と考えられる。粒子の変形によって粒子同士の重なりが粗となって見掛密度変化率が大きくなる場合も想定される。従って、見掛密度変化率が大きくても、それだけでは高い導電性が得られるわけではない。すなわち、解砕度と見掛密度変化率は両方とも満たしていることが必要で、片方だけを満たしていても高い導電性は得られない。しかしながら、解砕度は満たすが見掛密度変化率は満たさないということは実際には起こり得ず、分級・分散・解砕処理では実質的に粒子形状が変化せずに単分散されるので、自ずと解砕度、及び見掛密度変化率の両方を満たすことになる。 If the particles are crushed by the classification, dispersion, and pulverization treatment in a semi-free vortex centrifugal swirling airflow environment, the adhering particles are separated and dispersed by the particle size. As a result, the apparent density expressed by the filling amount of the powder in the specified container is significantly lower than that before crushing. Therefore, the degree of monodispersion can be estimated from the magnitude of the apparent density change rate. Conversely, if the particles break due to excessive crushing, the apparent density change rate may be reduced or the apparent density may be increased (the apparent density change rate becomes a negative value). It is also assumed that the overlap between particles becomes coarse due to the deformation of the particles and the apparent density change rate increases. Therefore, even if the apparent density change rate is large, high conductivity cannot be obtained by itself. That is, it is necessary that both the crushing degree and the apparent density change rate are satisfied, and high conductivity cannot be obtained even if only one of them is satisfied. However, it cannot actually happen that the degree of pulverization is satisfied but the apparent density change rate is not satisfied, and in the classification, dispersion, and pulverization treatment, the particle shape is substantially unchanged without being changed. Naturally, both the degree of crushing and the apparent density change rate are satisfied.
　見掛密度変化率が１８％以上であれば、本発明のフレーク状銀粉を導電フィラーとして用いた際に、従来よりも少量添加で高い導電性を実現できる。見掛密度変化率のより好ましい範囲は２５％以上、７０％以下である。見掛密度変化率が７０％以下とすることにより、良好な単分散性を確保することができる。 If the apparent density change rate is 18% or more, when the flaky silver powder of the present invention is used as a conductive filler, high conductivity can be realized by adding a smaller amount than before. A more preferable range of the apparent density change rate is 25% or more and 70% or less. When the apparent density change rate is 70% or less, good monodispersity can be secured.
　以下、旋回式気流分級・分散装置１０において、粒子の単分散性が高いフレーク状銀粉が得られる理由について説明する。本発明においては、旋回式気流分級・分散装置の２次エアー２２を用いることにより、メインエアー２１によって生じる旋回流を整流・加速させることができる。この２次エアー２２は上下に２つ備え付けられており、分級ゾーン１２において２段階で分級・分散処理を行う。より具体的には、まず、分級ゾーン１２の上部側にある２次エアー２２によって、未解砕フレーク状銀粉の分級・分散を促進させることができる。また、分級ゾーン１２の下部の２次エアー２２によって、分級ゾーン１２の上部側では完全に分級・分散できなかった粗粒子に付着した微粒子を再度分級・分散処理することで、未解砕フレーク状銀粉の分級・分散をさらに促進させることができる。 Hereinafter, the reason why flake-like silver powder having high monodispersibility of particles can be obtained in the swirling airflow classifying / dispersing device 10 will be described. In the present invention, the swirling flow generated by the main air 21 can be rectified and accelerated by using the secondary air 22 of the swirling airflow classifying / dispersing device. Two secondary airs 22 are provided on the upper and lower sides, and classification and dispersion processing are performed in two stages in the classification zone 12. More specifically, first, classification / dispersion of uncrushed flaky silver powder can be promoted by the secondary air 22 on the upper side of the classification zone 12. In addition, fine particles adhering to coarse particles that could not be completely classified and dispersed on the upper side of the classification zone 12 by the secondary air 22 at the lower part of the classification zone 12 are classified and dispersed again to form uncrushed flakes. The classification and dispersion of silver powder can be further promoted.
　本発明に係る半自由渦遠心式の旋回式気流環境下による分級・分散・解砕処理によれば、旋回式気流分級・分散装置内の旋回気流により未解砕フレーク状銀粉に遠心力を加え、旋回の流れそのものによって未解砕フレーク状銀粉に抗力を加えることができる。そして、未解砕フレーク状銀粉に加えられる遠心力と抗力のバランスによって、分級・分散・解砕処理を行なう。これに加えて、分級ゾーン１２において上下２段階の２次エアー２２にて２段階の分級・分散を行い、分級・分散・解砕処理を促進することで、銀粉同士の付着を高精度で剥離し、単分散性を高めることが可能となる。その結果、実質的に粒子形状変化を起こさずに、粒子の単分散性を促進させることが可能となる。 According to the classification, dispersion, and pulverization treatment in the semi-free vortex centrifugal swirling airflow environment according to the present invention, centrifugal force is applied to the unbroken flaky silver powder by the swirling airflow in the swirling airflow classification / dispersing device. The drag can be applied to the unbroken flaky silver powder by the swirling flow itself. Then, classification, dispersion, and pulverization are performed according to the balance between centrifugal force and drag applied to the unbroken flaky silver powder. In addition to this, the two-stage classification / dispersion is performed with the secondary air 22 in the upper and lower stages in the classification zone 12, and the classification / dispersion / crushing process is promoted, so that the adhesion between the silver powders is peeled off with high accuracy. In addition, monodispersity can be increased. As a result, the monodispersity of the particles can be promoted without substantially changing the particle shape.
　従来の種々の分級機、粉砕機を用いた粒子の解砕方法においては、前述したように、粒子同士、又は粒子と装置駆動部との衝突、付着によって粒子の凝集、粒子形状変化が問題となっていた。すなわち、実質的に粒子形状変化がなく、粒子の単分散性が高いフレーク状銀粉を得ることは困難であった。そのため、導電性組成物中のフレーク状銀粉の添加量を少なくしつつ、導電性を向上させることはできなかった。 In the conventional particle pulverization method using various classifiers and pulverizers, as described above, there is a problem of particle aggregation or particle shape change due to collision or adhesion between particles or between particles and the device drive unit. It was. That is, it was difficult to obtain flaky silver powder having substantially no change in particle shape and high monodispersibility of particles. Therefore, it was not possible to improve conductivity while reducing the amount of flaky silver powder added to the conductive composition.
　一方、本発明によれば、未解砕フレーク状銀粉に対して、半自由渦遠心式の旋回式気流環境下において分級・分散・解砕する工程を行うことによって、粒子の凝集状態を著しく改善することができる。これによって見掛密度を低下させることができる。５０％粒径が３μｍ以上、８μｍ以下であり、かつ、見掛密度が０．２５ｇ／ｃｍ３以上、０．５ｇ／ｃｍ３以下の範囲の分散性の高いフレーク状銀粉を用いることにより、ポリエステル系樹脂１００重量部に対して当該フレーク状銀粉を１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下のフレーク状銀粉を得ることができる。その結果、従来よりも少量添加で高い導電性を実現することが可能となる。 On the other hand, according to the present invention, the state of particle aggregation is remarkably improved by performing classification, dispersion, and pulverization of uncrushed flaky silver powder in a semi-free vortex centrifugal swirling airflow environment. can do. As a result, the apparent density can be reduced. By using flaky silver powder having high dispersibility having a 50% particle size of 3 μm or more and 8 μm or less and an apparent density in the range of 0.25 g / cm 3 or more and 0.5 g / cm 3 or less, polyester is obtained. A flaky silver powder having a dry film thickness of 15 μm and a surface resistance value of 0.4 Ω / □ or less when 100 parts by weight of the flaky silver powder is contained with respect to 100 parts by weight of the system resin can be obtained. As a result, it is possible to achieve high conductivity by adding a smaller amount than in the prior art.
　本発明に係る導電性組成物は、フレーク状銀粉が、１次粒子に近い形状となっていると考えられるため、フレーク状銀粉本来の粒子形状が有する利点を最大限に生かすことができる。さらに、従来よりも導電層中の樹脂量が相対的に増えるため、導電層の基材に対する密着性、被着体に対する接着力を高めることができる。また、低コスト化を実現することが可能となる。しかも、本発明に係るフレーク状銀粉によれば、粒子の単分散性が高いので、粒子の均一性がよく、導電性組成物中の粘度上昇等の粘度変動が生じにくいという優れた特性を有する。 In the conductive composition according to the present invention, since the flaky silver powder is considered to have a shape close to primary particles, the advantages of the original particle shape of the flaky silver powder can be maximized. Furthermore, since the amount of resin in the conductive layer is relatively increased as compared with the conventional case, the adhesion of the conductive layer to the substrate and the adhesive force to the adherend can be increased. In addition, cost reduction can be realized. Moreover, according to the flaky silver powder according to the present invention, since the monodispersity of the particles is high, the uniformity of the particles is good, and it has excellent characteristics such that viscosity fluctuation such as an increase in viscosity in the conductive composition hardly occurs. .
≪実施例≫
　以下、実施例を示して本発明を更に詳細に説明するが、本発明はこれらによって限定されるものではない。なお、５０％粒径は、島津製作所社製のＳＡＬＤ－３０００Ｊを使用して測定した。また、ＢＥＴ比表面積は島津製作所社製フローソーブＩＩ２３００を使用して測定した。見掛密度は、オリフィスの孔径が５ｍｍの漏斗を用い、ＪＩＳ　Ｚ　２５０４：２０００に定められた金属粉の見掛密度試験方法により求めた。 <Example>
EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by these. The 50% particle size was measured using SALD-3000J manufactured by Shimadzu Corporation. Further, the BET specific surface area was measured using Flowsorb II2300 manufactured by Shimadzu Corporation. The apparent density was determined by an apparent density test method for metal powder defined in JIS Z 2504: 2000, using a funnel with an orifice having a hole diameter of 5 mm.
《実施例１》
　供試粉末として、５０％粒径６．１μｍ、ＢＥＴ比表面積１．７ｍ２／ｇ、見掛密度０．５３ｇ／ｃｍ３（福田金属箔粉工業社製「ナノメルトＡｇ－ＸＦ３０１Ｓ」）である未解砕フレーク状銀粉を用いた。旋回式気流分級・分散装置として、日清エンジニアリング社製の旋回気流式分級機エアロファインクラシファイアＡＣ－２０を用いた。前述の未解砕フレーク状銀粉３．４ｋｇを秤取り、前述の旋回式気流分級・分散装置に投入し、分級・分散・解砕処理を行った。得られた粗粉、及び微粉の各全量をボールミルにて混合した。 Example 1
As test powder, 50% particle size 6.1 μm, BET specific surface area 1.7 m 2 / g, apparent density 0.53 g / cm 3 (“Nanomelt Ag-XF301S” manufactured by Fukuda Metal Foil Industry Co., Ltd.) Crushed flaky silver powder was used. As a swirling airflow classifying / dispersing device, a swirling airflow classifier Aerofine Classifier AC-20 manufactured by Nissin Engineering Co., Ltd. was used. 3.4 kg of the above-mentioned uncrushed flaky silver powder was weighed and put into the above-described swirling airflow classifying / dispersing apparatus to perform classification, dispersion, and pulverizing treatment. The whole amount of the obtained coarse powder and fine powder was mixed with a ball mill.
《実施例２》
　供試粉末として、５０％粒径５．９μｍ、ＢＥＴ比表面積１．４ｍ２／ｇ、見掛密度０．５３ｇ／ｃｍ３である未解砕フレーク状銀粉を用いた以外は、実施例１と同様に分級・分散・解砕処理を行った。 Example 2
Example 1 with the exception that unbroken flaky silver powder having a 50% particle size of 5.9 μm, a BET specific surface area of 1.4 m 2 / g, and an apparent density of 0.53 g / cm 3 was used as the test powder. Similarly, classification, dispersion, and crushing were performed.
《実施例３》
　供試粉末として、５０％粒径５．６μｍ、ＢＥＴ比表面積１．６ｍ２／ｇ、見掛密度０．４７ｇ／ｃｍ３である未解砕フレーク状銀粉を用い、旋回式気流分級・分散装置への投入量を３．４ｋｇとした以外は、実施例１と同様に分級・分散・解砕処理を行った。 Example 3
A swirling airflow classifying / dispersing device using uncrushed flaky silver powder having a 50% particle size of 5.6 μm, a BET specific surface area of 1.6 m 2 / g and an apparent density of 0.47 g / cm 3 as a test powder. Classification, dispersion, and pulverization were performed in the same manner as in Example 1 except that the amount charged into the reactor was 3.4 kg.
《実施例４》
　供試粉末として、５０％粒径５．１μｍ、ＢＥＴ比表面積１．８ｍ２／ｇ、見掛密度０．５９ｇ／ｃｍ３である未解砕フレーク状銀粉を用い、旋回式気流分級・分散装置への投入量を１１．６ｋｇとした以外は、実施例１と同様に分級・分散・解砕処理を行った。 Example 4
A swirling airflow classifying / dispersing device using uncrushed flaky silver powder having a 50% particle size of 5.1 μm, a BET specific surface area of 1.8 m 2 / g, and an apparent density of 0.59 g / cm 3 as a test powder. Classification, dispersion, and pulverization were performed in the same manner as in Example 1 except that the amount charged to 11.6 kg was changed to 11.6 kg.
《実施例５》
　供試粉末として、５０％粒径６．２μｍ、ＢＥＴ比表面積１．８ｍ２／ｇ、見掛密度０．５９ｇ／ｃｍ３である未解砕フレーク状銀粉を用い、旋回式気流分級・分散装置への投入量を８．０ｋｇとした。それ以外の条件は、実施例１と同様とした。 Example 5
A swirling airflow classifying / dispersing device using uncrushed flaky silver powder having a 50% particle size of 6.2 μm, a BET specific surface area of 1.8 m 2 / g and an apparent density of 0.59 g / cm 3 as a test powder. The input amount to was 8.0 kg. The other conditions were the same as in Example 1.
《実施例６》
　実施例１にて解砕処理を行って得られた粗粉（５０％粒径６．４μｍ、ＢＥＴ比表面積１．４ｍ２／ｇ、見掛密度０．３４ｇ／ｃｍ３）を微粉と混合せずに、そのまま用いた。 Example 6
Coarse powder (50% particle size 6.4 μm, BET specific surface area 1.4 m 2 / g, apparent density 0.34 g / cm 3 ) obtained by crushing in Example 1 is mixed with fine powder. Without using it.
《実施例７》
　実施例１にて解砕処理を行って得られた微粉（５０％粒径：４．０μｍ、ＢＥＴ比表面積：２．４ｍ２／ｇ、見掛密度：０．４２ｇ／ｃｍ３）を粗粉と混合せずに、そのまま用いた。 Example 7
Fine powder (50% particle size: 4.0 μm, BET specific surface area: 2.4 m 2 / g, apparent density: 0.42 g / cm 3 ) obtained by crushing in Example 1 And used as is without mixing.
《実施例８》
　実施例２にて解砕処理を行って得られた粗粉（５０％粒径：７．６μｍ、ＢＥＴ比表面積：１．１ｍ２／ｇ、見掛密度：０．３６ｇ／ｃｍ３）を微粉と混合せずにそのまま用いた。 Example 8
Coarse powder (50% particle size: 7.6 μm, BET specific surface area: 1.1 m 2 / g, apparent density: 0.36 g / cm 3 ) obtained by crushing treatment in Example 2 And used as is without mixing.
《実施例９》
　実施例２にて解砕処理を行って得られた微粉（５０％粒径：４．９μｍ、ＢＥＴ比表面積：１．９ｍ２／ｇ、見掛密度：０．３７ｇ／ｃｍ３）を粗粉と混合せずにそのまま用いた。 Example 9
Fine powder (50% particle size: 4.9 μm, BET specific surface area: 1.9 m 2 / g, apparent density: 0.37 g / cm 3 ) obtained by crushing in Example 2 And used as is without mixing.
《比較例１》
　供試粉末として、５０％粒径６．７μｍ、ＢＥＴ比表面積１．２ｍ２／ｇ、見掛密度０．６１ｇ／ｃｍ３である未解砕フレーク状銀粉を用いた。分級・分散・解砕処理は、市販の強制渦遠心式分級機を用いた。前述の未解砕フレーク状銀粉を前述の強制渦遠心式分級機に投入し、分級・分散・解砕処理を行った。そして、得られた粗粉、及び微粉各々全量をボールミルにて混合した。 << Comparative Example 1 >>
As the test powder, uncrushed flaky silver powder having a 50% particle size of 6.7 μm, a BET specific surface area of 1.2 m 2 / g, and an apparent density of 0.61 g / cm 3 was used. A commercially available forced vortex centrifugal classifier was used for classification, dispersion, and crushing treatment. The above-mentioned uncrushed flaky silver powder was put into the above-mentioned forced vortex centrifugal classifier and subjected to classification, dispersion, and pulverization treatment. Then, the total amount of each of the obtained coarse powder and fine powder was mixed with a ball mill.
《比較例２》
　供試粉末として、比較例１と同じ未解砕フレーク状銀粉を用いた。分級・分散・解砕処理は、市販の気流衝突式粉砕機を用いた。粉末の分散方式として気流衝突式粉砕機を用いた場合、高速旋回気流により粗粉と微粉を分離するが、超音速のジェット気流によって粒子同士を衝突させ粉砕を行うため、粒子同士の凝集・粒子形状変化が生じるための高い導電性が得られない。 << Comparative Example 2 >>
As the test powder, the same uncrushed flaky silver powder as in Comparative Example 1 was used. For the classification, dispersion, and crushing treatment, a commercially available airflow collision pulverizer was used. When using an airflow collision type pulverizer as a powder dispersion method, coarse powder and fine powder are separated by a high-speed swirling airflow. High conductivity for shape change cannot be obtained.
《比較例３》
　供試粉末として、比較例１と同様の未解砕フレーク状銀粉を用いた。分級・分散・解砕処理は、市販の回転ハンマー式粉砕機を用いた。回転ハンマー式粉砕機は、高速で回転するスイングハンマの衝撃力とライナによる衝突効果によって粉砕を行い、分級機構を内蔵しているため、過粉砕が少ないという特徴がある。 << Comparative Example 3 >>
As the test powder, the same uncrushed flaky silver powder as in Comparative Example 1 was used. A commercially available rotary hammer type pulverizer was used for classification, dispersion, and pulverization. The rotary hammer type pulverizer is characterized in that it is pulverized by the impact force of a swing hammer rotating at high speed and the impact effect of a liner, and has a built-in classification mechanism, so that there is little over-pulverization.
《比較例４》
　供試粉末として、５０％粒径４．９μｍ、ＢＥＴ比表面積１．７ｍ２／ｇ、見掛密度０．５９ｇ／ｃｍ３である未解砕フレーク状銀粉をそのまま用いた。すなわち、分級・分散・解砕処理を行なわずにそのまま用いた。 << Comparative Example 4 >>
As the test powder, unbroken flaky silver powder having a 50% particle size of 4.9 μm, a BET specific surface area of 1.7 m 2 / g, and an apparent density of 0.59 g / cm 3 was used as it was. That is, it was used as it was without performing classification, dispersion, and crushing treatment.
《比較例５》
　比較例１で使用した未解砕フレーク状銀粉を用いて、表２の配合で導電性組成物を作製した。 << Comparative Example 5 >>
Using the uncrushed flaky silver powder used in Comparative Example 1, a conductive composition was prepared according to the formulation shown in Table 2.
　図４に、実施例１で用いる未解砕フレーク状銀粉の走査型電子顕微鏡写真を示す。また、図５Ａに、実施例１で得られたフレーク状銀粉の粗粉の走査型電子顕微鏡写真を、図５Ｂに、実施例１で得られたフレーク状銀粉の微粉の走査型電子顕微鏡写真を示す。図４の未解砕フレーク状銀粉は、粒子同士が付着して凝集が生じていることがわかる。これに対して、図５Ａ，図５Ｂにおける本発明のフレーク状銀粉においては、一粒毎に粒子が分離して分散されていることがわかる。すなわち、半自由渦遠心式の旋回式気流環境下において分級・分散・解砕処理を施すことによって、フレーク状銀粉の単分散性が高まることがわかる。 FIG. 4 shows a scanning electron micrograph of the unbroken flaky silver powder used in Example 1. 5A shows a scanning electron micrograph of the flaky silver powder coarse powder obtained in Example 1, and FIG. 5B shows a scanning electron micrograph of the flaky silver powder fine powder obtained in Example 1. Show. It can be seen that the uncrushed flaky silver powder in FIG. In contrast, in the flaky silver powder of the present invention in FIGS. 5A and 5B, it can be seen that the particles are separated and dispersed for each grain. That is, it can be seen that the monodispersity of the flaky silver powder is increased by performing classification, dispersion, and crushing treatment in a semi-free vortex centrifugal swirling airflow environment.
（表面抵抗値測定）
　導電フィラーとして上記実施例１～９及び比較例１～４にて得られたフレーク状銀粉１００重量部をそれぞれ秤取り、それぞれにポリエステル系樹脂（東洋紡績社製バイロン２００、数平均分子量１７，０００、ガラス転移温度６７℃、水酸基価５ＫＯＨｍｇ／ｇ、酸価２ＫＯＨｍｇ未満）１００重量部を配合し、混合することにより導電性組成物を得た。比較例５は、ポリエステル系樹脂１００重量部に対して、比較例１のフレーク状銀粉を１５０重量部混合したものである。次いで、厚さ１００μｍのポリエチレンテレフタレートフィルム上に厚さ１５μｍの導電層が形成できるように導電性組成物を塗工・乾燥した。これにより、導電性シートを得た。得られた導電性シートの表面抵抗値を、三菱化学アナリテック社製「ロレスターＧＰ」の四探針プローブを用いて測定した。表面抵抗値の評価基準は以下の通りである。
　　◎：　０．３Ω/□未満
　　○：　０．３Ω/□以上、０．４Ω/□以下　
　　×：　０．４Ω/□超え (Surface resistance measurement)
As conductive fillers, 100 parts by weight of the flaky silver powder obtained in Examples 1 to 9 and Comparative Examples 1 to 4 were respectively weighed, and polyester resin (Byron 200 manufactured by Toyobo Co., Ltd., number average molecular weight 17,000, respectively) was weighed. And 100 parts by weight of a glass transition temperature of 67 ° C., a hydroxyl value of 5 KOH mg / g, and an acid value of less than 2 KOH mg) were mixed and mixed to obtain a conductive composition. In Comparative Example 5, 150 parts by weight of the flaky silver powder of Comparative Example 1 is mixed with 100 parts by weight of the polyester resin. Next, the conductive composition was applied and dried so that a conductive layer having a thickness of 15 μm could be formed on a polyethylene terephthalate film having a thickness of 100 μm. Thereby, the electroconductive sheet was obtained. The surface resistance value of the obtained conductive sheet was measured using a four-point probe of “Lorester GP” manufactured by Mitsubishi Chemical Analytech. The evaluation criteria of the surface resistance value are as follows.
◎: Less than 0.3Ω / □ ○: 0.3Ω / □ or more, 0.4Ω / □ or less
×: Over 0.4Ω / □
（電磁波シールド性測定）
　上記実施例１～９及び比較例１～４にて得られたフレーク状銀粉１００重量部それぞれと、ポリエステル系樹脂（東洋紡績社製バイロン２００）１００重量部を配合し、混合することで導電性組成物を得た。比較例５は、ポリエステル系樹脂１００重量部に対して、比較例１のフレーク状銀粉を１５０重量部混合したものである。次いで、厚さ１２．５μｍのポリイミドフィルム上に厚さ１５μｍの導電層が形成できるように導電性組成物を塗工・乾燥した。これにより、電磁波シールドフィルムを得た。得られた電磁波シールドフィルムの電磁波シールド性を、ＫＥＣ法により測定を行った。評価基準は以下の通りである。
　　◎：周波数１ＧＨｚにおける電磁波シールド性が６０ｄＢ以上
　　○：周波数１ＧＨｚにおける電磁波シールド性が４０ｄＢ以上、６０ｄＢ未満
　　×：周波数１ＧＨｚにおける電磁波シールド性が４０ｄＢ未満 (Electromagnetic wave shielding measurement)
Each 100 parts by weight of the flaky silver powder obtained in Examples 1 to 9 and Comparative Examples 1 to 4 and 100 parts by weight of a polyester resin (Byron 200 manufactured by Toyobo Co., Ltd.) are blended and mixed to make the conductivity. A composition was obtained. In Comparative Example 5, 150 parts by weight of the flaky silver powder of Comparative Example 1 is mixed with 100 parts by weight of the polyester resin. Next, the conductive composition was applied and dried so that a conductive layer having a thickness of 15 μm could be formed on a polyimide film having a thickness of 12.5 μm. Thereby, an electromagnetic wave shielding film was obtained. The electromagnetic wave shielding property of the obtained electromagnetic wave shielding film was measured by the KEC method. The evaluation criteria are as follows.
A: Electromagnetic shielding at a frequency of 1 GHz is 60 dB or more O: Electromagnetic shielding at a frequency of 1 GHz is 40 dB or more and less than 60 dB X: An electromagnetic shielding at a frequency of 1 GHz is less than 40 dB
　上記実施例１～９及び比較例１～５のサンプルについて、５０％粒径、見掛密度、ＢＥＴ比表面積、上記式（２）より得られた解砕度、上記式（３）より得られた見掛密度変化率（％）、表面抵抗値、電磁波シールド性、接着性の測定結果を表１及び表２に示す。なお、分級・分散・解砕処理前後における粒子の凝集又は分散の度合いについては、５０％粒径で判定するよりも、見掛密度、及びＢＥＴ比表面積の処理前後の値によって判定するのが妥当である。５０％粒径の値は、粒子がフレーク状であることに起因して、測定原理上、ばらつきが生じてしまうためである。これは、５０％粒径の測定においては、粒子にレーザーを照射した際に発せられる回折・散乱光の強度分布パターンが粒子の大きさに応じて変化することを利用し、測定された粒度は球相当径であるのに対して、本発明のフレーク状銀粉は厚みが極端に薄くなったフレーク形状を有しており、図４、５に示すように球形とはかなり異なる形状を示していることによる。見掛密度、５０％粒径、ＢＥＴ比表面積のうち、分級・分散・解砕処理前後による粒子の状態を最も反映しているのは、見掛密度である。
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
 For the samples of Examples 1 to 9 and Comparative Examples 1 to 5, 50% particle size, apparent density, BET specific surface area, degree of crushing obtained from the above formula (2), obtained from the above formula (3) Tables 1 and 2 show the measurement results of apparent density change rate (%), surface resistance value, electromagnetic wave shielding property, and adhesiveness. The degree of particle aggregation or dispersion before and after classification / dispersion / pulverization treatment is more appropriate to judge by the apparent density and BET specific surface area values before and after treatment than by 50% particle size. It is. This is because the value of the 50% particle size is uneven due to the measurement principle due to the flaky particles. This is because, in the measurement of 50% particle size, the intensity distribution pattern of diffracted / scattered light emitted when a particle is irradiated with a laser changes according to the size of the particle. In contrast to the sphere equivalent diameter, the flaky silver powder of the present invention has a flake shape in which the thickness is extremely thin, and shows a shape considerably different from the sphere as shown in FIGS. It depends. Of the apparent density, 50% particle size, and BET specific surface area, the apparent density is the one that most reflects the state of the particles before and after classification, dispersion, and pulverization.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
　比較例１～４に係るフレーク状銀粉を含有する導電性組成物の表面抵抗値は、いずれも、０．４Ω／□を超えており、表面抵抗値が高いことがわかった。また、電磁波シールド性を検討すると、比較例１～４においては、いずれも×という判定であったのに対し、実施例１～９においては、いずれも○若しくは◎であった。接着力については、表１及び表２より、比較例５以外のサンプルにおいては、問題ないことがわかった。 The surface resistance values of the conductive compositions containing the flaky silver powder according to Comparative Examples 1 to 4 all exceeded 0.4Ω / □, indicating that the surface resistance value was high. Further, when the electromagnetic wave shielding property was examined, all of Comparative Examples 1 to 4 were judged as “poor”, whereas in Examples 1 to 9, all were “good” or “◎”. About adhesive force, it turned out from Table 1 and Table 2 that there is no problem in samples other than Comparative Example 5.
　比較例１に係るフレーク状銀粉は、解砕度がやや高く、見掛密度変化率が非常に低いために、表面抵抗値が高くなっているものと示唆される。比較例２、比較例３においては、５０％粒径が３μｍ～８μｍの範囲にあり、かつ見掛密度が０．２５ｇ／ｃｍ３～０．５ｇ／ｃｍ３の範囲にあるが、良好な表面抵抗値を得ることができなかった。比較例２及び３に係るフレーク状銀粉は、見掛密度変化率が高いものの、解砕度も高いことから、粒子形状が変化しており、表面抵抗値が高くなっているものと示唆される。 The flaky silver powder according to Comparative Example 1 has a slightly high degree of pulverization and a very low apparent density change rate, which suggests that the surface resistance value is high. In Comparative Examples 2 and 3, the 50% particle size is in the range of 3 μm to 8 μm and the apparent density is in the range of 0.25 g / cm 3 to 0.5 g / cm 3. The resistance value could not be obtained. Although the flaky silver powder according to Comparative Examples 2 and 3 has a high apparent density change rate, the degree of pulverization is also high, suggesting that the particle shape is changed and the surface resistance value is high. .
　一方、実施例１～９に係るフレーク状銀粉を含有する導電性組成物の表面抵抗値は、いずれも０．４Ω／□以下であり、優れた低抵抗値特性を有することがわかった。実施例１～９に係るフレーク状銀粉は、解砕度と見掛密度変化率の値より、半自由渦遠心式の旋回式気流環境下による分級・分散・解砕処理によって粒子の形状を実質的に変化させることなく、単分散性が高められることがわかる。その結果、実施例１～９に係るフレーク状銀粉を含有する導電性組成物は、表面抵抗値や電磁波シールド性を改善するものと考えられる。 On the other hand, the surface resistance values of the conductive compositions containing the flaky silver powder according to Examples 1 to 9 were all 0.4Ω / □ or less, and it was found that they had excellent low resistance characteristics. From the values of the degree of pulverization and the apparent density change rate, the flaky silver powders according to Examples 1 to 9 have substantially the shape of particles by classification, dispersion, and pulverization treatment in a semi-free vortex centrifugal swirling airflow environment. It can be seen that the monodispersity can be improved without any change. As a result, the conductive composition containing the flaky silver powder according to Examples 1 to 9 is considered to improve the surface resistance value and the electromagnetic wave shielding property.
　この出願は、２０１１年３月１０日に出願された日本出願特願２０１１－０５３２１８を基礎とする優先権を主張し、その開示の全てをここに取り込む。 This application claims priority based on Japanese Patent Application No. 2011-053218 filed on March 10, 2011, the entire disclosure of which is incorporated herein.
１　　　未解砕フレーク状銀粉
２　　　微粉
３　　　粗粉
１０　　旋回式気流分級・分散装置
１１　　原料投入口
１２　　分級ゾーン
１３　　案内羽根
１４　　粗粉回収部
１５　　粗粉取出し口
１６　　微粉取出し口
１７　　吹き出し部
１８　　吹き出しノズル
２０　　原料供給機 DESCRIPTION OF SYMBOLS 1 Uncracked flaky silver powder 2 Fine powder 3 Coarse powder 10 Swirling airflow classifying / dispersing device 11 Raw material input port 12 Classification zone 13 Guide vane 14 Coarse powder collecting unit 15 Coarse powder taking out port 16 Fine powder taking out port 17 Blowing unit 18 Blowing nozzle 18 20 Raw material feeder

Claims (8)

  1. 　レーザー回折法における５０％粒径が、３μｍ以上、８μｍ以下であり、
    　見掛密度が、０．２５ｇ／ｃｍ３以上、０．５ｇ／ｃｍ３以下であり、
    　かつ、ポリエステル系樹脂１００重量部に対して１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下であるフレーク状銀粉。     50% particle diameter in laser diffraction method is 3 μm or more and 8 μm or less,
    The apparent density is 0.25 g / cm 3 or more and 0.5 g / cm 3 or less,
    And the flaky silver powder whose surface resistance value of the conductive film with a dry film thickness of 15 micrometers when it contains 100 weight part with respect to 100 weight part of polyester-type resin is 0.4 ohm / square or less.
  2. 　ＢＥＴ比表面積が、１ｍ２／ｇ以上、３．５ｍ２／ｇ以下であることを特徴とする請求項１に記載のフレーク状銀粉。 BET specific surface area, 1 m 2 / g or more, flaky silver powder according to claim 1, characterized in that 3.5 m 2 / g or less.
  3. 　未解砕フレーク状銀粉に対して、半自由渦遠心式の旋回式気流環境下において分級・分散・解砕する工程を具備し、
    　分級・分散・解砕後の銀粉が、
    　レーザー回折法における５０％粒径が３μｍ以上、８μｍ以下であり、
    　見掛密度が０．２５ｇ／ｃｍ３以上、０．５ｇ／ｃｍ３以下であり、
    　かつ、ポリエステル系樹脂１００重量部に対して１００重量部含有したときの乾燥膜厚１５μｍの導電被膜の表面抵抗値が、０．４Ω／□以下であるフレーク状銀粉の製造方法。     It comprises the steps of classifying, dispersing, and crushing uncrushed flaky silver powder in a semi-free vortex centrifugal swirling airflow environment,
    Silver powder after classification, dispersion and crushing
    50% particle size in laser diffraction method is 3 μm or more and 8 μm or less,
    The apparent density is 0.25 g / cm 3 or more and 0.5 g / cm 3 or less,
    And the manufacturing method of the flaky silver powder whose surface resistance value of the conductive film with a dry film thickness of 15 micrometers when it contains 100 weight part with respect to 100 weight part of polyester-type resin is 0.4 ohm / square or less.
  4. 　前記分級・分散・解砕する工程によって分別された銀粉を混合することを特徴とする請求項３に記載のフレーク状銀粉の製造方法。 4. The method for producing flaky silver powder according to claim 3, wherein the silver powder separated by the classification, dispersion, and crushing steps is mixed.
  5. 　樹脂と、請求項１又は２に記載のフレーク状銀粉とを少なくとも含有する導電性組成物。 A conductive composition containing at least a resin and the flaky silver powder according to claim 1.
  6. 　請求項５に記載の導電性組成物から形成された層を少なくとも有する導電性シート。 A conductive sheet having at least a layer formed from the conductive composition according to claim 5.
  7. 　請求項５に記載の導電性組成物から形成された導電層、及び絶縁層が積層された電磁波シールド性シート。 An electromagnetic wave shielding sheet in which a conductive layer formed from the conductive composition according to claim 5 and an insulating layer are laminated.
  8. 　基材と、
    　前記基材上に形成された導電パターンと、を具備し、
    　前記導電パターンが、請求項５に記載の導電性組成物により形成されている導電パターン付き積層体。     A substrate;
    A conductive pattern formed on the substrate,
    The laminated body with a conductive pattern in which the said conductive pattern is formed with the conductive composition of Claim 5.
PCT/JP2012/001582 2011-03-10 2012-03-08 Flaked silver powder and method for manufacturing same, electroconductive composition, electroconductive sheet, electromagnetic shielding sheet, and layered body having electroconductive pattern WO2012120884A1 (en)

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Publication number Priority date Publication date Assignee Title
JPH03135482A (en) * 1989-10-20 1991-06-10 Onoda Cement Co Ltd Pneumatic classifier
JP2000157933A (en) * 1998-11-25 2000-06-13 Tomoegawa Paper Co Ltd Classifier and flow straightening device
JP2003055701A (en) * 2001-08-10 2003-02-26 Fukuda Metal Foil & Powder Co Ltd Silver powder for conductive paste and its manufacturing method and conductive paste using the silver powder

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03135482A (en) * 1989-10-20 1991-06-10 Onoda Cement Co Ltd Pneumatic classifier
JP2000157933A (en) * 1998-11-25 2000-06-13 Tomoegawa Paper Co Ltd Classifier and flow straightening device
JP2003055701A (en) * 2001-08-10 2003-02-26 Fukuda Metal Foil & Powder Co Ltd Silver powder for conductive paste and its manufacturing method and conductive paste using the silver powder

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