JP7736427B2 - Conductive paste composition and its use, and resin particles used in the conductive paste composition - Google Patents

Description

The present invention relates to a conductive paste composition, its use, and resin particles used in the conductive paste composition.

In recent years, pastes containing conductive materials with electronic conductivity have been developed. Such conductive pastes are expected to have diverse functions in a variety of applications, such as electrode materials for electronic devices such as batteries and capacitors, water-repellent layers for fuel cells, diffusion layers for fuel cells, thermal conductive materials, conductive inks, light-emitting elements, wiring materials, reinforcing materials, and black pigments.
For example, secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride secondary batteries, and nickel-cadmium secondary batteries, which can be used repeatedly by charging, are used in electronic devices. Rapid development of secondary batteries is progressing for use in portable electronic devices, hybrid vehicles, electric vehicles, and the like.
The conductive paste contains a conductive material and a solvent, and is used for various purposes after being applied and dried.
Patent Document 1 discloses a method for obtaining a conductive film by applying a conductive composition containing a binder resin, a conductivity imparting agent, and an organic solvent to a substrate and then drying the applied composition.
Patent Document 2 discloses a conductive paste containing an elastomer composition containing silica particles, a conductive filler, and a solvent.
Patent Document 3 discloses a conductive paste containing silver particles and an organic solvent.

Japanese Patent Application Laid-Open No. 2019-12630 Japanese Patent Application Laid-Open No. 2018-174125 International Publication No. 2018/008270

However, it has been confirmed that the conductive composition described in Patent Document 1, the conductive paste described in Patent Document 2, and the conductive paste described in Patent Document 3 have insufficient dispersion stability and coatability of the paste.
An object of the present invention is to provide a conductive paste composition having excellent dispersion stability and coatability, a conductive film composition obtained using the conductive paste composition, and uses thereof.

As a result of extensive research to solve the above problems, the inventors discovered that a conductive paste composition containing a polymer component, specific resin particles, a conductive material, and a liquid medium provides excellent dispersion stability and coatability of the conductive paste, leading to the present invention.

That is, the conductive paste composition of the present invention is a conductive paste composition containing a polymer component (A), resin particles (B), a conductive material (C), and a liquid medium (D), and the particles (B) are composed of an outer shell made of a thermoplastic resin and an organic compound encapsulated therein.

The thermoplastic resin is preferably a polymer of a polymerizable component containing a nitrile monomer.
The ratio (d ₁ /d ₂ ) of the inner diameter (d ₁ ) to the outer diameter (d ₂ ) of the particles (B) is preferably 0.1 or more and 0.999 or less.
It is preferred that the organic compound is in gaseous and/or liquid form.
The material (C) is preferably at least one selected from furnace black, acetylene black, ketjen black, carbon nanofibers, carbon nanotubes, graphite, and graphene.
The component (A) is preferably at least one selected from the group consisting of acrylic polymers, fluorine-based polymers, diene-based polymers, vinyl-based polymers, and cellulose-based polymers.

The conductive film composition of the present invention comprises a dried product of the conductive paste composition.
The secondary battery of the present invention includes the conductive film composition.
The fuel cell of the present invention comprises at least one selected from the above-mentioned conductive film composition and its fired product.
The resin particles of the present invention are resin particles used in a conductive paste composition, and are composed of an outer shell made of a thermoplastic resin and an organic compound encapsulated therein.

The conductive paste composition of the present invention is excellent in dispersion stability and coatability of the conductive paste.
The conductive film composition of the present invention has excellent uniformity.

FIG. 2 is a schematic view showing an example of resin particles (B). FIG. 1 is a schematic diagram illustrating an example of a fuel cell. FIG. 1 is a schematic diagram of an expansion process section of a manufacturing apparatus for manufacturing resin particles by a dry thermal expansion method.

The conductive paste composition of the present invention contains a polymer component (A), resin particles (B), a conductive material (C), and a liquid medium (D). The components that make up the conductive paste composition are described in detail below.

[Polymer component (A)]
The polymer component (A) (hereinafter, sometimes simply referred to as component (A)) functions as a dispersing aid for the components contained in the conductive paste composition, an agent for improving the coatability of the conductive paste composition, and a binder between the conductive materials when the conductive paste composition is dried, as well as a binder between the conductive film composition (described later) and the substrate.

Examples of the component (A) include acrylic polymers; fluorine-based polymers such as vinylidene fluoride polymers (PVDF), fluorinated ethylene-propylene copolymers, polytetrafluoroethylene (PTFE), perfluoroalkoxyalkanes (PFA), ethylene-tetrafluoroethylene copolymers (ETFE), perfluoroethylenepropene copolymers (FEP), and polychlorotrifluoroethylene (PCTFE); vinyl-based polymers such as polyvinyl acetate, polyvinyl stearate, polyvinyl alcohol, and polyvinylpyrrolidone; and di-polymers such as polybutadiene, polyisoprene, and styrene-butadiene copolymers (SBR). Examples of such polymers include ene-based polymers; cellulose-based polymers such as methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose; styrene-based polymers such as styrene-vinyl chloride copolymer and styrene-vinyl acetate copolymer; urethane-based polymers; polysiloxane-based polymers such as dimethylpolysiloxane; phenol-based polymers; olefin-based polymers such as polyethylene, polypropylene, and poly-1-butene; ketone-based polymers; amide-based polymers; polyphenylene oxide-based polymers; epoxy-based polymers; polyester-based polymers; nylon-based polymers; natural rubber; polypeptides; and proteins, and these may be used alone or in combination of two or more.
Component (A) is preferably at least one selected from acrylic polymers, fluorine-based polymers, vinyl polymers, diene polymers, and cellulose-based polymers, as this improves the dispersion stability of the conductive paste.

Examples of component (A) include KF Polymer (manufactured by Kureha Corporation, polyvinylidene fluoride resin), Kynar series (manufactured by Arkema K.K., polyvinylidene fluoride resin), Solef series (manufactured by Solvay K.K., polyvinylidene fluoride resin), Polyflon series (manufactured by Daikin Industries, Ltd., polytetrafluoroethylene), Teflon (registered trademark) series (manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd., polytetrafluoroethylene), Fluon series (manufactured by AGC Inc., polytetrafluoroethylene), Almatex series (manufactured by Mitsui Chemicals, Inc., acrylic resin, polyester resin), Chemipearl series (manufactured by Mitsui Chemicals, Inc., polyolefin aqueous dispersion), Bonlon series (acrylic emulsion, Mitsui Chemicals, Inc.), Olester series (manufactured by Mitsui Chemicals, Inc., polyurethane resin), Yuban series (manufactured by Mitsui Chemicals, Inc., amino resin), Epochee series (manufactured by Mitsui Chemicals, Inc., epoxy resin), Nipol series (manufactured by Zeon Corporation, styrene-butadiene Commercially available polymer materials may also be used, such as the acrylic latex (azadiene-based latex, acrylonitrile-butadiene-based latex, acrylate-based latex), the Zaixene series (manufactured by Sumitomo Seika Chemicals Co., Ltd., polyolefin resin), the Sepolsion series (manufactured by Sumitomo Seika Chemicals Co., Ltd., nylon emulsion, polyester emulsion), the Sepolex series (manufactured by Sumitomo Seika Chemicals Co., Ltd., polyisoprene latex, chlorosulfonated polyethylene latex), Flowthene series (manufactured by Sumitomo Seika Chemicals Co., Ltd., polyethylene), Flowbrenlease (manufactured by Sumitomo Seika Chemicals Co., Ltd., polypropylene), SB latex (manufactured by JSR Corporation, styrene-butadiene-based latex), the Acrylic Emulsion AE series (manufactured by E-TECH Co., Ltd., acrylic emulsion), the Boncoat series (manufactured by DIC Corporation, acrylic emulsion, acrylic-styrene-based emulsion), the Bondic series (manufactured by DIC Corporation, polyurethane dispersion), and the Luckstar series (manufactured by DIC Corporation, butadiene resin latex).
Furthermore, component (A) may be water-repellent. When component (A) is water-repellent, the conductive film composition described below can be suitably used in fuel cells.

[Resin particles (B)]
The resin particles (B) (hereinafter sometimes simply referred to as particles (B)) are composed of an outer shell made of a thermoplastic resin and an organic compound encapsulated therein. The thermoplastic resin is a polymer obtained by polymerizing a polymerizable component.
The polymerizable component is a component that becomes a thermoplastic resin that forms the outer shell of the particles (B) through polymerization. The polymerizable component is a component that essentially contains a monomer component having one radically reactive carbon-carbon double bond and may contain a crosslinking agent having two or more radically reactive carbon-carbon double bonds. Both the monomer component and the crosslinking agent are components capable of undergoing an addition reaction, and the crosslinking agent is a component that can introduce a crosslinked structure into the thermoplastic resin.

Examples of monomer components include nitrile monomers such as acrylonitrile, methacrylonitrile, and fumaronitrile; carboxyl group-containing monomers such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, cinnamic acid, maleic acid, itaconic acid, fumaric acid, citraconic acid, and chloromaleic acid; halogenated vinyl monomers such as vinyl chloride; halogenated vinylidene monomers such as vinylidene chloride; vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl butyrate; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl ( Examples of the divalent polymerizable monomer include (meth)acrylic acid ester monomers such as (meth)acrylate, benzyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate; (meth)acrylamide monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; maleimide monomers such as N-phenylmaleimide and N-cyclohexylmaleimide; styrene monomers such as styrene and α-methylstyrene; ethylenically unsaturated monoolefin monomers such as ethylene, propylene, and isobutylene; vinyl ether monomers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl ketone monomers such as vinyl methyl ketone; N-vinyl monomers such as N-vinylcarbazole and N-vinylpyrrolidone; and vinyl naphthalene salts. Of the above-mentioned monomers, divalent polymerizable monomers may be used alone or in combination. Acrylic acid and methacrylic acid are sometimes referred to together as (meth)acrylic acid, and acrylate and methacrylate are sometimes referred to together as (meth)acrylate. Furthermore, (meth)acrylic means acrylic or methacrylic, and (meth)acrylate means acrylate or methacrylate.

The polymerizable component preferably contains a nitrile monomer as a monomer component, as this gives the resulting resin particles excellent solvent resistance and compatibility with component (A). In particular, from the standpoint of heat resistance, it is preferable for the nitrile monomer to contain acrylonitrile (AN) or methacrylonitrile (MAN).

When the nitrile monomer contains acrylonitrile, the content thereof is preferably 5 to 90% by weight based on the nitrile monomer. When the acrylonitrile content is within the above range, the heat resistance and solvent resistance of the thermoplastic resin constituting the outer shell tend to be improved. The upper limit of the acrylonitrile content is more preferably 80% by weight, and particularly preferably 70% by weight. On the other hand, the lower limit of the acrylonitrile content is more preferably 15% by weight, and particularly preferably 20% by weight.
When the nitrile monomer contains methacrylonitrile, the content thereof is preferably 5 to 90% by weight relative to the nitrile monomer. When the methacrylonitrile content is within the above range, the gas barrier properties of the outer shell tend to be improved. The upper limit of the methacrylonitrile content is more preferably 80% by weight, and particularly preferably 70% by weight. On the other hand, the lower limit of the methacrylonitrile content is more preferably 15% by weight, and particularly preferably 20% by weight.

When the nitrile monomer contains acrylonitrile (AN) and methacrylonitrile (MAN), the weight ratio of acrylonitrile to methacrylonitrile (AN/MAN) is not particularly limited, but is preferably 10/90 or more and 90/10 or less. If the AN/MAN ratio is less than 10/90, the gas barrier properties may be reduced. On the other hand, if the AN/MAN ratio exceeds 90/10, the flexibility of the outer shell may be reduced. The upper limit of AN/MAN is more preferably 80/20, and even more preferably 70/30. On the other hand, the lower limit of AN/MAN is more preferably 20/80, and even more preferably 30/70.

When the monomer component contains a nitrile monomer, the weight percentage of the nitrile monomer in the polymerizable component is not particularly limited, but is preferably 15 to 100% by weight. If the weight percentage of the nitrile monomer is less than 15% by weight, the solvent resistance of the resulting resin particles may be reduced. The upper limit of the weight percentage of the nitrile monomer is more preferably 99.5% by weight, even more preferably 99.0% by weight, particularly preferably 98.0% by weight, and most preferably 94% by weight. On the other hand, the lower limit of the weight percentage of the nitrile monomer is more preferably 30% by weight, even more preferably 40% by weight, particularly preferably 50% by weight, and most preferably 60% by weight.

When the polymerizable component contains a carboxyl group-containing monomer as a monomer component, the resulting resin particles are preferred because they have excellent heat resistance and solvent resistance. Among these, acrylic acid and methacrylic acid are preferred in terms of heat resistance.

When the monomer component contains a carboxyl group-containing monomer, the weight percentage of the carboxyl group-containing monomer in the polymerizable component is not particularly limited, but is preferably 10 to 80% by weight. If the carboxyl group-containing monomer is less than 10% by weight, sufficient improvement in solvent resistance may not be achieved. On the other hand, if the weight percentage of the carboxyl group-containing monomer is more than 80% by weight, the flexibility of the outer shell may decrease. The upper limit of the weight percentage of the carboxyl group-containing monomer is more preferably 70% by weight, even more preferably 60% by weight, particularly preferably 50% by weight, and most preferably 45% by weight. The lower limit of the weight percentage of the carboxyl group-containing monomer is more preferably 15% by weight, even more preferably 20% by weight, particularly preferably 25% by weight, and most preferably 30% by weight.

When the monomer component contains a nitrile monomer and a carboxyl group-containing monomer, the total weight proportion of the carboxyl group-containing monomer and the nitrile monomer in the polymerizable component is not particularly limited, but is preferably 25 to 100% by weight, more preferably 50 to 100% by weight, even more preferably 70 to 100% by weight, particularly preferably 80 to 100% by weight, and most preferably 90 to 100% by weight.

Furthermore, when the monomer component contains a nitrile monomer and a carboxyl group-containing monomer, the ratio of the carboxyl group-containing monomer to the total of the carboxyl group-containing monomer and the nitrile monomer is not particularly limited, but is preferably 10 to 90% by weight. If the ratio of the carboxyl group-containing monomer is less than 10% by weight, improvements in heat resistance and solvent resistance may be insufficient. Furthermore, if the ratio of the carboxyl group-containing monomer is more than 90% by weight, the flexibility of the outer shell may decrease. The upper limit of the ratio of the carboxyl group-containing monomer is more preferably 70% by weight, even more preferably 50% by weight, particularly preferably 45% by weight, and most preferably 40% by weight. On the other hand, the lower limit of the ratio of the carboxyl group-containing monomer is more preferably 15% by weight, even more preferably 20% by weight, particularly preferably 25% by weight, and most preferably 30% by weight.

When the polymerizable component contains a vinylidene chloride monomer as a monomer component, the gas barrier properties are improved. When the polymerizable component contains a (meth)acrylic acid ester monomer and/or a styrene monomer, it becomes easier to control the compatibility with component (A). When the polymerizable component contains a (meth)acrylamide monomer, the heat resistance is improved.
When the polymerizable component contains at least one monomer selected from vinylidene chloride, a (meth)acrylic acid ester monomer, a (meth)acrylamide monomer, a maleimide monomer, and a styrene monomer as a monomer component, the weight ratio of the monomer to the polymerizable monomer is preferably 80% by weight or less, more preferably 50% by weight or less, and particularly preferably 30% by weight or less. If the content is 80% by weight or more, heat resistance may decrease.

As described above, the polymerizable component may contain a crosslinking agent. By carrying out polymerization using a crosslinking agent, the gas barrier properties and solvent resistance of the resulting resin particles can be improved.
The crosslinking agent is not particularly limited, and examples thereof include aromatic divinyl compounds such as divinylbenzene; allyl methacrylate, triacryl formal, triallyl isocyanate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, polypropylene glycol#400 di(meth)acrylate, polypropylene glycol#700 di(meth)acrylate, trimethylolpropane trimethacrylate, EO modified Examples of the crosslinking agent include di(meth)acrylate compounds such as trimethylolpropane trimethacrylate, glycerin dimethacrylate, dimethylol-tricyclodecane diacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, tris(2-acryloyloxyethyl)isocyanurate, triallyl isocyanurate, triallyl cyanurate, triglycidyl isocyanurate, polytetramethylene glycol dimethacrylate, EO-modified bisphenol A dimethacrylate, neopentyl glycol dimethacrylate, nonanediol diacrylate, trimethylolpropane tri(meth)acrylate, and 3-methyl-1,5-pentanediol diacrylate. The above crosslinking agents may be used alone or in combination of two or more.

The crosslinking agent does not have to be included in the polymerizable component, but there are no particular restrictions on its content. The weight ratio of the crosslinking agent to the polymerizable component is preferably 6% by weight or less, more preferably 5% by weight or less, even more preferably 3% by weight, particularly preferably 2% by weight, and most preferably 1% by weight. On the other hand, the lower limit of the weight ratio of the crosslinking agent is preferably 0% by weight. If the weight ratio of the crosslinking agent exceeds 6% by weight, the rigidity of the thermoplastic resin outer shell may become too high.

The particles (B) encapsulate an organic compound. By encapsulating the organic compound in the particles (B), the internal pressure of the particles (B) increases, and it is thought that the particles (B) are prevented from bursting or collapsing during preparation of the conductive paste composition, resulting in the conductive paste composition having excellent dispersion stability and coatability.
Examples of organic compounds include hydrocarbons having 3 to 13 carbon atoms, such as methane, ethane, propane, (iso)butane, (iso)pentane, (iso)hexane, (iso)heptane, (iso)octane, (iso)nonane, (iso)decane, (iso)undecane, (iso)dodecane, and (iso)tridecane; hydrocarbons having more than 13 but not more than 20 carbon atoms, such as (iso)hexadecane and (iso)eicosane; hydrocarbons such as pseudocumene, petroleum ether, and petroleum fractions, such as normal paraffins and isoparaffins, having an initial boiling point of 150 to 260°C and/or a distillation range of 70 to 360°C; halides of hydrocarbons having 1 to 12 carbon atoms, such as methyl chloride, methylene chloride, chloroform, and carbon tetrachloride; methyl perfluoropropyl ether, methyl perfluorobutyl ether, and methyl perfluoroisobutyl ether. hydrofluoroethers such as tetrafluoroethane, trifluoroethane, pentafluoropropane, heptafluoropropane, hexafluoropropane, decafluoropentane, tridecafluorooctane, and the like; silanes having an alkyl group having 1 to 5 carbon atoms such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, trimethyl-n-propylsilane, and the like; compounds that generate gas upon thermal decomposition such as azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, and 4,4'-oxybis(benzenesulfonylhydrazide), and the like, and these may be used alone or in combination of two or more. The organic compound may be linear, branched, or cyclic, and is preferably aliphatic.

The organic compound may be one that vaporizes when heated. Furthermore, it is preferable for the organic compound to have a boiling point, as this vaporizes when the conductive paste is sintered, efficiently forming open cells. When the organic compound has a boiling point, there are no particular limitations on the boiling point, but it is preferably -50 to 100°C. When the boiling point of the organic compound is -50°C or higher, the organic compound tends to be efficiently encapsulated in the particles (B). On the other hand, when the boiling point of the organic compound is 100°C or lower, the internal pressure of the particles (B) tends to be sufficiently maintained. The upper limit of the boiling point of the organic compound is more preferably 70°C, even more preferably 60°C, and particularly preferably 35°C. On the other hand, the lower limit of the boiling point of the organic compound is more preferably -30°C, even more preferably -15°C.

The organic compound preferably contains a hydrocarbon having 5 or fewer carbon atoms, as this improves the pressure resistance of the particles (B). On the other hand, if the organic compound contains a hydrocarbon having 6 or more carbon atoms, the retention of the organic compound in the particles (B) can be improved. Preferred examples of hydrocarbons having 5 or fewer carbon atoms include isobutane and isopentane. Preferred examples of hydrocarbons having 6 or more carbon atoms include isohexane and isooctane.

The organic compound encapsulated in particles (B) may be in liquid, solid, or gaseous form, and from the standpoint of dispersibility, it is preferably in liquid and/or gaseous form, and more preferably in liquid or gaseous form.

The encapsulation rate of the organic compound in the particles (B) is defined as the percentage of the weight of the organic compound encapsulated in the particles (B) relative to the weight of the particles (B).
The encapsulation rate of the organic compound is not particularly limited, but is preferably 0.2 to 50 wt % relative to the weight of the particles (B). When the encapsulation rate of the organic compound is within the above range, the particles (B) can have high pressure resistance. The upper limit of the encapsulation rate of the organic compound is more preferably 40 wt %, even more preferably 35 wt %, and particularly preferably 30 wt %. On the other hand, the lower limit of the encapsulation rate of the organic compound is more preferably 0.8 wt %, even more preferably 1.2 wt %, and particularly preferably 1.5 wt %. The encapsulation rate of the organic compound in the particles (B) is measured by the method described in the examples.

The volume average particle diameter (D50) of particles (B) (hereinafter sometimes simply referred to as the average particle diameter) is not particularly limited, but is preferably 0.50 to 100 μm. When the average particle diameter of particles (B) is within this range, the dispersibility of particles (B) in the paste composition tends to be improved. The upper limit of the volume average particle diameter of particles (B) is more preferably 50 μm, even more preferably 30 μm, particularly preferably 15 μm, and most preferably 10 μm. On the other hand, the lower limit of the volume average particle diameter of particles (B) is more preferably 1.0 μm, even more preferably 1.5 μm, and particularly preferably 2.0 μm. The volume average particle diameter (D50) of particles (B) is measured by the method described in the examples.

The coefficient of variation (Cv) of the particle size distribution of the particles (B) is not particularly limited, but is preferably 50% or less, more preferably 40% or less, even more preferably 35% or less, and particularly preferably 30% or less. On the other hand, the lower limit of the coefficient of variation (Cv) of the particle size distribution of the particles (B) is preferably 3.0% or more. If the coefficient of variation (Cv) of the particle size distribution of the particles (B) exceeds 50%, the coatability of the conductive paste composition may be reduced.
The coefficient of variation (Cv) of the particle size distribution of the particles (B) is calculated by the following formulas (1) and (2).

(In the formula, s is the standard deviation of particle diameters, <x> is the average particle diameter, _xi is the diameter of the ith particle, and n is the number of particles.)

The ratio ( _d1 / _d2 ) of the inner diameter ( _d1 ) to the outer diameter ( _d2 ) of the particles (B) is not particularly limited, but is preferably 0.1 to 0.999. If the _d1 / _d2 of the particles (B) is less than 0.1, the dispersion stability of the conductive paste may decrease. On the other hand, if the _d1 / _d2 of the particles (B) is more than 0.999, the dispersion stability of the conductive paste may decrease. In addition, the pressure resistance may decrease, and the conductive paste composition or conductive film composition may be crushed during production. The upper limit of _d1 / _d2 is more preferably 0.995, even more preferably 0.990, particularly preferably 0.985, and most preferably 0.980. On the other hand, the lower limit of _d1 / _d2 is more preferably 0.35, even more preferably 0.50, particularly preferably 0.70, and most preferably 0.75. The d ₁ /d ₂ of the particles (B) is measured by the method described in the examples.

The true specific gravity of particles (B) is not particularly limited, but is preferably 0.0020 to 1.8. If the specific gravity of particles (B) is outside this range, the dispersion stability of the conductive paste may decrease. The upper limit of the true specific gravity of particles (B) is more preferably 1.1, even more preferably 0.7, particularly preferably 0.4, and most preferably 0.2. The lower limit of the true specific gravity of particles (B) is more preferably 0.0060, even more preferably 0.010, particularly preferably 0.012, and most preferably 0.015. The true specific gravity of particles (B) is measured by the method described in the examples.

Particles (B) may contain fine particles. When particles (B) contain fine particles, the dispersibility of particles (B) can be improved. When particles (B) contain fine particles, the fine particles may be attached to the surface of the resin particle, or may be inside the thermoplastic resin that is the outer shell of the resin particle. The state in which the fine particles are attached to the surface of the resin particle may be a state in which the fine particles are adsorbed onto the outer surface of the outer shell of the resin particle, a state in which the fine particles are embedded and fixed into the outer surface of the outer shell of the resin particle, or both of these states.

The fine particles may be made of either inorganic or organic materials, and may be spherical, needle-like, or plate-like in shape.
Examples of inorganic substances constituting the fine particles include wollastonite, sericite, kaolin, mica, clay, talc, bentonite, alumina silicate, pyrophyllite, montmorillonite, calcium silicate, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, glass flakes, boron nitride, silicon carbide, silica, alumina, mica, titanium dioxide, zinc oxide, magnesium oxide, zinc oxide, hydrosaltite, molybdenum disulfide, tungsten disulfide, ceramic beads, glass beads, quartz beads, glass microballoons, etc. Also, granular conductive material (C) described later may be used.

Examples of organic substances constituting the fine particles include sodium alginate, sodium polyacrylate, carboxyvinyl polymer, polyvinyl methyl ether, magnesium stearate, calcium stearate, zinc stearate, polyethylene wax, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, hydrogenated castor oil, (meth)acrylic resin, polyamide resin, silicone resin, urethane resin, polyethylene resin, polypropylene resin, fluorine-based resin, etc. Also, the above-mentioned polymer component (A) in a granular form may be used.
The inorganic or organic material constituting the fine particles may be treated with a surface treatment agent such as a silane coupling agent, paraffin wax, fatty acid, resin acid, urethane compound, or fatty acid ester, or may be untreated.

The average particle size of the fine particles is not particularly limited, but is preferably 0.001 to 30 μm, more preferably 0.005 to 25 μm, and even more preferably 0.01 to 20 μm. The average particle size of the fine particles here refers to the particle size of the fine particles measured by laser diffraction.
The ratio of the average particle size of the fine particles to the average particle size of the resin particles (average particle size of the fine particles/average particle size of the hollow resin particles) is preferably 1 or less, more preferably 0.1 or less, and even more preferably 0.05 or less, from the viewpoint of the adhesion of the fine particles to the surfaces of the resin particles.

When particles (B) contain fine particles, the weight proportion of the fine particles in particles (B) is not particularly limited, but is preferably 5 to 95% by weight, more preferably 20 to 90% by weight, even more preferably 40 to 85% by weight, and particularly preferably 60 to 80% by weight. If the weight proportion of the fine particles is less than 5% by weight, the handleability of particles (B) may decrease. On the other hand, if the weight proportion of the fine particles is 95% by weight, dispersibility may decrease.

The particles (B) may have a core-shell structure, as shown in Fig. 1, which is composed of a thermoplastic resin shell 16 and an organic compound core 17 encapsulated therein. Alternatively, the particles (B) may be heat-expandable microspheres that expand (the entire resin particles) upon heating. The hollow resin particles are preferably expanded bodies of heat-expandable microspheres, as this will provide the desired effect.
When the particles (B) contain heat-expandable microspheres, the expansion initiation temperature (Ts) of the heat-expandable microspheres is not particularly limited, but is preferably 70 to 250°C. If the Ts of the heat-expandable microspheres is outside the above range, a sufficient expansion ratio may not be obtained. The upper limit of the expansion initiation temperature of the heat-expandable microspheres is more preferably 200°C, even more preferably 180°C, particularly preferably 165°C, and most preferably 150°C. On the other hand, the lower limit of the expansion initiation temperature of the heat-expandable microspheres is more preferably 85°C, even more preferably 100°C, particularly preferably 110°C, and most preferably 115°C. The expansion initiation temperature (Ts) of the heat-expandable microspheres is measured by the method described in the examples.

When particles (B) contain heat-expandable microspheres, the maximum expansion temperature (Tmax) of the heat-expandable microspheres is not particularly limited, but is preferably 100 to 300°C. If the Tmax of the heat-expandable microspheres is outside the above range, a sufficient expansion ratio may not be achieved. The upper limit of Tmax of the heat-expandable microspheres is more preferably 250°C, even more preferably 200°C, particularly preferably 180°C, and most preferably 170°C. On the other hand, the lower limit of Tmax of the heat-expandable microspheres is more preferably 85°C, even more preferably 100°C, particularly preferably 110°C, and most preferably 115°C. The maximum expansion temperature (Tmax) of the heat-expandable microspheres is measured by the method described in the examples.

When particles (B) contain heat-expandable microspheres, the expansion ratio of the heat-expandable microspheres is not particularly limited, but is preferably 10 times or more, more preferably 20 times or more, even more preferably 30 times or more, particularly preferably 40 times or more, and most preferably 50 times or more. The upper limit of the maximum expansion ratio of the heat-expandable microspheres is preferably 300 times.

[Method for producing resin particles (B)]
Examples of methods for producing the resin particles (B) include the following methods 1) and 2).
1) A method in which an oily mixture containing a polymerizable component and an organic compound is dispersed in an aqueous dispersion medium to prepare a suspension, and the polymerizable component is polymerized to produce resin particles (resin particles (B)).
2) A method in which the resin particles obtained by the method 1) are heated and expanded to produce resin particles (B).
The method for producing the resin particles (B) will be described in detail below.

As a method for producing resin particles (resin particles (B)), there is mentioned a method in which an oily mixture containing a polymerizable component and an organic compound is dispersed in an aqueous dispersion medium to prepare a suspension, and the polymerizable component is polymerized. In the present invention, this method is also used as a method for producing heat-expandable microspheres.

The oily mixture may contain a polymerization initiator. The polymerization initiator is not particularly limited, but examples thereof include peroxides and azo compounds.
Examples of peroxides include peroxydicarbonates such as diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and dibenzyl peroxydicarbonate; diacyl peroxides such as lauroyl peroxide and benzoyl peroxide; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; peroxyketals such as 2,2-bis(t-butylperoxy)butane; hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; dialkyl peroxides such as dicumyl peroxide and di-t-butyl peroxide; and peroxyesters such as t-hexyl peroxypivalate and t-butylperoxyisobutyrate.

Examples of azo compounds include 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), and 1,1'-azobis(cyclohexane-1-carbonitrile).

There are no particular restrictions on the amount of polymerization initiator added per 100 parts by weight of the polymerizable component, but 0.05 to 10 parts by weight is preferred, 0.1 to 8 parts by weight is more preferred, and 0.2 to 5 parts by weight is even more preferred. If the amount of polymerization initiator added is less than 0.05 parts by weight, the polymerization reaction may not proceed sufficiently, resulting in a decrease in the strength of the resin particles. On the other hand, if the amount of polymerization initiator added is more than 10 parts by weight, the degree of polymerization of the polymer cannot be increased, resulting in a decrease in the strength of the resin particles. The above polymerization initiators may be used alone or in combination of two or more types.

The aqueous dispersion medium is a medium whose main component is water, such as ion-exchanged water, for dispersing the oily mixture, and may further contain alcohols such as methanol, ethanol, and propanol, or hydrophilic organic solvents such as acetone. In this invention, "hydrophilic" means a state in which the aqueous dispersion medium can be freely mixed with water. There are no particular restrictions on the amount of aqueous dispersion medium used, but it is preferable to use 100 to 1,000 parts by weight of the aqueous dispersion medium per 100 parts by weight of the polymerizable component.

The aqueous dispersion medium may further contain an electrolyte. Examples of electrolytes include sodium chloride, magnesium chloride, calcium chloride, sodium sulfate, magnesium sulfate, ammonium sulfate, and sodium carbonate. These electrolytes may be used alone or in combination. There are no particular restrictions on the electrolyte content, but it is preferable to include 0 to 50 parts by weight per 100 parts by weight of the aqueous dispersion medium.

The aqueous dispersion medium may contain at least one water-soluble compound selected from the group consisting of polyalkyleneimines having a structure in which an alkyl group substituted with a hydrophilic functional group selected from a carboxylic acid (salt) group and a phosphonic acid (salt) group is bonded to a nitrogen atom; water-soluble 1,1-substituted compounds having a structure in which a hydrophilic functional group selected from a hydroxyl group, a carboxylic acid (salt) group, and a phosphonic acid (salt) group and a heteroatom are bonded to the same carbon atom; potassium dichromate, alkali metal nitrite, metal (III) halides, boric acid, water-soluble ascorbic acids, water-soluble polyphenols, water-soluble B vitamins, and water-soluble phosphonic acids (salts). In this specification, "water-soluble" means that 1 g or more of the compound dissolves in 100 g of water.

There are no particular restrictions on the amount of water-soluble compound contained in the aqueous dispersion medium, but it is preferably 0.0001 to 1.0 part by weight, more preferably 0.0001 to 0.5 part by weight, even more preferably 0.0003 to 0.1 part by weight, and particularly preferably 0.001 to 0.05 part by weight, per 100 parts by weight of the polymerizable component.

The aqueous dispersion medium may contain a dispersion stabilizer or a dispersion stabilization aid in addition to the electrolyte and the water-soluble compound.
The dispersion stabilizer is not particularly limited, but examples thereof include tricalcium phosphate, magnesium pyrophosphate obtained by a metathesis method, calcium pyrophosphate, colloidal silica, alumina sol, magnesium hydroxide, etc. These dispersion stabilizers may be used alone or in combination of two or more. The amount of dispersion stabilizer to be added is preferably 0.05 to 100 parts by weight, more preferably 0.2 to 70 parts by weight, per 100 parts by weight of the polymerizable component.
The dispersion stabilization aid is not particularly limited, and examples thereof include surfactants such as polymer-type dispersion stabilization aids, cationic surfactants, anionic surfactants, zwitterionic surfactants, nonionic surfactants, etc. These dispersion stabilization aids may be used alone or in combination of two or more.

The aqueous dispersion medium is prepared, for example, by blending water (ion-exchanged water) with, as necessary, an electrolyte, a water-soluble compound, a dispersion stabilizer, a dispersion stabilization assistant, etc. The pH of the aqueous dispersion medium during polymerization is appropriately determined depending on the types of the water-soluble compound, dispersion stabilizer, and dispersion stabilization assistant.
In the polymerization step, the polymerization may be carried out in the presence of sodium hydroxide or sodium hydroxide and zinc chloride.

In the method for producing the resin particles (resin particles (B)), an oily mixture is suspended and dispersed in an aqueous dispersion medium so as to prepare spherical oil droplets having a predetermined particle size.
Examples of methods for suspending and dispersing the oily mixture include a method of stirring with a homomixer (e.g., manufactured by Primix Corporation) or the like, a method using a static dispersing device such as a static mixer (e.g., manufactured by Noritake Engineering Co., Ltd.), a membrane suspension method, an ultrasonic dispersion method, and other common dispersion methods.
Next, the dispersion in which the oily mixture is dispersed as spherical oil droplets in the aqueous dispersion medium is heated to initiate suspension polymerization. During the polymerization reaction, it is preferable to stir the dispersion, and the stirring may be carried out gently, for example, to a degree that prevents the floating of the monomers and the settling of the resin particles after polymerization.

The polymerization temperature can be freely set depending on the type of polymerization initiator, but is preferably controlled to a temperature between 30°C and 90°C, and more preferably between 40°C and 88°C. The reaction temperature is preferably maintained for approximately 1 to 20 hours. There are no particular restrictions on the initial polymerization pressure, but it is preferably 0 to 5 MPa, and more preferably 0.2 to 3 MPa, in gauge pressure.

The obtained slurry is filtered using a centrifuge, pressure press, vacuum dehydrator, or the like to obtain a moistened wet powder. The moisture content of the moistened powder is not particularly limited, but is preferably 10 to 50% by weight, more preferably 15 to 45% by weight, and even more preferably 20 to 40% by weight. The obtained moistened powder is dried using a tray dryer, indirect heating dryer, fluidized bed dryer, vacuum dryer, vibration dryer, flash dryer, or the like to obtain a dry powder. The moisture content of the obtained dry powder is preferably 5% by weight or less, more preferably 3% by weight or less, and further preferably 1% by weight or less.
To reduce the content of ionic substances, the obtained wet or dry powder may be washed with water and/or redispersed, then re-filtered and dried. Alternatively, the slurry may be dried using a spray dryer, fluidized bed dryer, or the like to obtain a dry powder.

As described above, the resin particles (B) can also be produced by thermally expanding the heat-expandable microspheres obtained by the above-mentioned method. In the present invention, this method also serves as a method for producing hollow resin particles. The method for thermally expanding the resin particles is not particularly limited, and may be either a dry thermal expansion method or a wet thermal expansion method.
Examples of dry thermal expansion methods include the method described in JP-A-2006-213930, particularly the internal injection method. Examples of other dry thermal expansion methods include the method described in JP-A-2006-96963. Examples of wet thermal expansion methods include the method described in JP-A-62-201231.

When the resin particles (B) contain the above-mentioned fine particles, their production method may include, for example, mixing the resin particles with the fine particles (mixing step), and heating the resulting mixture to a temperature above the softening point of the thermoplastic resin that forms the outer shell of the resin particles, thereby expanding the resin particles and adhering the fine particles to the outer surface of the outer shell of the resin particles (adhering step).

There are no particular limitations on the equipment used in the mixing process, and it can be carried out using equipment equipped with extremely simple mechanisms such as a container and stirring blades. Ordinary powder mixers capable of shaking or stirring may also be used. Examples of powder mixers include ribbon mixers and vertical screw mixers that can perform shaking or stirring. Furthermore, in recent years, efficient, multifunctional powder mixers that combine stirring devices may also be used, such as the Super Mixer (manufactured by Kawata Co., Ltd.), High Speed Mixer (manufactured by Fukae Co., Ltd.), New Gram Machine (manufactured by Seishin Enterprise Co., Ltd.), and SV Mixer (manufactured by Kobelco Eco Solutions Co., Ltd.).

The adhering step involves heating the mixture containing heat-expandable microspheres and particulate filler obtained in the mixing step to a temperature above the softening point of the thermoplastic resin that constitutes the outer shell of the heat-expandable microspheres. In this step, the heat-expandable microspheres are expanded and the particulate filler is adhered to the outer surface of the outer shell.

Heating may be carried out using a general contact heat transfer or direct heating type mixing dryer. There are no particular limitations on the functions of the mixing dryer, but it is preferable that it has the ability to adjust the temperature, disperse and mix the raw materials, and, in some cases, a pressure reducing device or a cooling device to accelerate drying. There are no particular limitations on the device used for heating, and examples include a Lödige Mixer (manufactured by Matsubo Corporation) and a Solid Air (Hosokawa Micron Corporation).
The heating temperature conditions are not particularly limited, but it is preferable to set the temperature at which the resin particles expand optimally, preferably 60 to 400°C, more preferably 70 to 300°C, and even more preferably 80 to 250°C.

[Electrically conductive material (C)]
The conductive material (C) is a component having conductivity. Examples of the conductive material (C) include carbon black such as furnace black, acetylene black, ketjen black, channel black, and lamp black; graphite such as natural graphite, artificial graphite, and expanded graphite; graphene; activated carbon; coke; carbon nanofibers, carbon nanotubes such as single-walled carbon nanotubes and multi-walled carbon nanotubes; metal fine particles such as silver, copper, tin, zinc, zinc oxide, nickel, and manganese; and composite metal fine particles such as indium tin oxide. These may be used alone or in combination of two or more.
Among the conductive materials (C), at least one selected from furnace black, acetylene black, ketjen black, carbon nanofibers, carbon nanotubes, graphite, and graphene is preferred because it provides excellent dispersibility and coatability of the conductive paste and can further improve the conductive performance.

The average particle size of the conductive material (C) is not particularly limited, but is preferably 5 to 200 nm, and more preferably 20 to 80 nm. The average particle size of the conductive carbon particles can be measured, for example, using a particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.).

[Liquid medium (D)]
The liquid medium (D) is not particularly limited as long as it is a liquid that can disperse the polymer component (A), the resin particles (B), and the conductive material (C).
Examples of liquid media include water; alkanes such as isohexane, isohexane, cyclohexane, and pentane; alcohols such as methanol, ethanol, and isopropyl alcohol; aromatic hydrocarbons such as benzene and toluene; N-methylpyrrolidone; chloroform; dimethylformamide; acetonitrile; dimethyl sulfoxide; and dimethylacetamide, and these may be used alone or in combination.
When the liquid medium (D) has a boiling point, the boiling point of the liquid medium (D) is not particularly limited, but is preferably 30 to 200°C, more preferably 50 to 170°C, even more preferably 70 to 150°C, and particularly preferably 80 to 130°C.

[Other ingredients]
The conductive paste composition of the present invention may contain other components in addition to the above components, as long as the effects of the present invention are not impaired. The other components are not particularly limited, but examples thereof include surfactants, antifoaming agents, pH adjusters, viscosity adjusters, etc.
The surfactant is not particularly limited, and examples thereof include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants, and one or more of these may be used in combination.
Examples of the antifoaming agent include polysiloxane-based antifoaming agents, mineral oil-based antifoaming agents, and fine silica powder-based antifoaming agents, and these may be used alone or in combination of two or more.
Examples of the pH adjuster include organic acids such as citric acid, oxalic acid, acetic acid, formic acid, and gluconic acid; inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, and boric acid; hydroxides of alkali (earth) metals; ammonia; carbonates; organic phosphoric acid compounds such as hydroxyethanephosphonic acid, aminotrimethylenephosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, nitrilotri(methylphosphonic acid), and 2-phosphonobutane-1,2,4-tricarboxylic acid; aminocarboxylic acid compounds such as ethylenediaminetetraacetic acid and nitrilotriacetic acid; and amine compounds, and if necessary, one or more of these may be used in combination.
Examples of viscosity adjusters include polyethylene glycol, polyethylene oxide, polyoxyethylene-polyoxypropylene block polymers, gum arabic, guar gum, xanthan gum, gelatin, corn starch, alginic acid, etc., and one or more of these may be used in combination.

[Conductive paste composition and its manufacturing method]
The conductive paste composition of the present invention contains the polymer component (A), resin particles (B), a conductive material (C), and a liquid medium (D), and has excellent dispersion stability and coatability. The conductive paste composition of the present invention is in the form of a paste.

The viscosity of the conductive paste composition of the present invention at 25°C is not particularly limited, but is preferably 1,000 to 200,000 mPa·s. When the viscosity of the conductive paste composition at 25°C is within this range, the dispersion stability of the conductive paste composition tends to be improved. The upper limit of the viscosity of the conductive paste composition at 25°C is more preferably 150,000 mPa·s, even more preferably 100,000 mPa·s, particularly preferably 80,000 mPa·s, and most preferably 50,000 mPa·s. On the other hand, the lower limit of the viscosity of the conductive paste composition at 25°C is more preferably 2,000 mPa·s, even more preferably 5,000 mPa·s, particularly preferably 8,000 mPa·s, and most preferably 10,000 mPa·s. The viscosity of the conductive paste composition can be measured, for example, using a Brookfield viscometer (BL type, manufactured by Tokyo Keiki Co., Ltd.) at 25°C.

The content of particles (B) in the conductive paste composition of the present invention is not particularly limited, but is preferably 0.5 to 30 parts by weight per 100 parts by weight of component (A). If the content of particles (B) is less than 0.5 parts by weight, the dispersion stability of the conductive paste composition may decrease. On the other hand, if the content of particles (B) is more than 30 parts by weight, the coatability of the conductive paste composition may decrease. The upper limit of the content of particles (B) is more preferably 20 parts by weight, even more preferably 15 parts by weight, and particularly preferably 10 parts by weight. On the other hand, the lower limit of the content of particles (B) is more preferably 1 part by weight, even more preferably 2 parts by weight, and particularly preferably 3 parts by weight.

The content of conductive material (C) in the conductive paste composition of the present invention is not particularly limited, but is preferably 30 to 500 parts by weight per 100 parts by weight of component (A). If the content of conductive material (C) is less than 30 parts by weight, the conductive performance may be insufficient. On the other hand, if the content of conductive material (C) is more than 500 parts by weight, the dispersion stability may decrease. The upper limit of the content of conductive material (C) is more preferably 400 parts by weight, even more preferably 300 parts by weight, particularly preferably 200 parts by weight, and most preferably 100 parts by weight. On the other hand, the lower limit of the content of conductive material (C) is more preferably 40 parts by weight, even more preferably 50 parts by weight, particularly preferably 60 parts by weight, and most preferably 70 parts by weight.

The content of liquid medium (D) per 100 parts by weight of component (A) in the conductive paste composition of the present invention is not particularly limited, but is preferably 10 to 2000 parts by weight per 100 parts by weight of component (A). If the content of liquid medium (D) is outside the above range, dispersion stability and coatability may decrease. The upper limit of the content of liquid medium (D) is more preferably 1750 parts by weight, even more preferably 1500 parts by weight, particularly preferably 1250 parts by weight, and most preferably 1000 parts by weight. On the other hand, the lower limit of the content of liquid medium (D) is more preferably 30 parts by weight, even more preferably 50 parts by weight, particularly preferably 70 parts by weight, and most preferably 100 parts by weight.

The surface tension of the conductive paste composition of the present invention at 25°C is not particularly limited, but is preferably 10 to 50 mN/m. When the surface tension of the conductive paste composition is within the above range, the coatability of the conductive paste composition tends to be improved. The upper limit of the surface tension of the conductive paste composition is more preferably 45 mN/m, even more preferably 43 mN/m, and particularly preferably 40 mN/m. On the other hand, the lower limit of the surface tension of the conductive paste composition is more preferably 15 mN/m, even more preferably 17 mN/m, and particularly preferably 20 mN/m. The surface tension of the conductive paste composition at 25°C can be measured by the plate method using an automatic surface tensiometer (CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.).

When the conductive paste composition of the present invention is used by applying it to a substrate, the contact angle with the substrate is preferably 90 to 150°, more preferably 100 to 140°. When the contact angle with the substrate is within the above range, the conductive paste composition tends to be applied more uniformly. The contact angle between the conductive paste composition and the substrate is determined by using an automatic contact angle meter (OCA20, manufactured by Eiko Instruments Co., Ltd.) to drop a droplet of about 1 microliter of the conductive paste composition onto the surface of the substrate and measure the contact angle after 30 seconds.
The substrate to which the conductive paste composition is applied may vary depending on the application of the coated material, but examples thereof include those described below.

The conductive paste composition of the present invention can be used when manufacturing components for electricity storage devices. Examples of electricity storage devices for which the conductive paste can be used include capacitors, secondary batteries, and fuel cells. It is particularly suitable for use in secondary batteries and fuel cells. When used in secondary batteries, it can be used, for example, when manufacturing electrodes. When used in fuel cells, it can be used, for example, when manufacturing water-repellent members.

When the conductive paste composition is used to manufacture a capacitor or a secondary battery, and particularly when it is used to manufacture an electrode (positive electrode and/or negative electrode), it may contain a positive electrode active material or a negative electrode active material in addition to the above components.
Examples of the positive electrode active material include lithium iron phosphate ( _LiFePO4 ), lithium manganese phosphate ( _LiMnPO4 ), lithium cobalt phosphate ( _LiCoPO4 ), iron pyrophosphate ( _Li2FeP2O7 ), _lithium cobalt oxide composite oxide ( _LiCoO2 ), spinel-type lithium manganese oxide cobalt oxide composite oxide _{( LiMn2O4} ), lithium manganese oxide composite oxide ( _LiMnO2 ), lithium nickel oxide composite oxide ( _LiNiO2 ), lithium niobate composite oxide ( _LiNbO2 ), lithium ferrate composite oxide ( _LiFeO2 ), lithium magnesium oxide composite oxide ( _LiMgO2 ), lithium calcium oxide composite oxide ( _{LiCaO2 )} , lithium cuprate composite oxide ( _LiCuO2 ), and lithium zinc oxide composite oxide (LiZnO2 _). ), lithium molybdate composite oxide (LiMoO ₂ ), lithium tantalate composite oxide (LiTaO ₂ ), lithium tungstate composite oxide (LiWO ₂ ), lithium-nickel-cobalt-aluminum composite oxide (LiNi _0.8 Co _0.15 Al _0.05 O ₂ ), lithium-nickel-cobalt-manganese composite oxide (LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ), manganese nickel oxide (LiNi _0.5 Mn _1.5 O ₄ ), manganese oxide (MnO ₂ ), lithium-excess nickel-cobalt-manganese composite oxide, nickel hydroxide (Ni(OH) ₂ ), vanadium oxides, sulfur oxides, silicate oxides, etc., and one or more of them may be used in combination.

When the conductive paste composition contains a positive electrode active material, its content is not particularly limited, but is preferably 100 to 2000 parts by weight, more preferably 500 to 1600 parts by weight, and particularly preferably 800 to 1200 parts by weight per 100 parts by weight of the conductive material (C).

Examples of negative electrode active materials include carbon materials such as natural graphite, artificial graphite, expanded graphite, activated carbon, carbon fiber, coke, soft carbon, and hard carbon; silicon-based materials; metal oxide-based materials such as SiO, SnO, SnO ₂ , CuO, and Li ₄ Ti ₅ O ₁₂ ; alloys such as Si—Al, Al—Zn, Si—Mg, Al—Ge, Si—Ge, Si—Ag, Zn—Sn, Ge—Ag, Ge—Sn, Ge—Sb, Ag—Sn, Ag—Ge, and Sn—Sb; and tin phosphate glass-based materials, and these may be used alone or in combination of two or more.
When the conductive paste composition contains a negative electrode active material, the content thereof is not particularly limited, but is preferably 100 to 2000 parts by weight, more preferably 500 to 1600 parts by weight, and particularly preferably 800 to 1200 parts by weight, relative to 100 parts by weight of the conductive material (C).

The method for producing the conductive paste composition of the present invention is not particularly limited, and examples thereof include a method of mixing the above-mentioned polymer component (A), resin particles (B), conductive material (C), and liquid medium (D) with other components, an electrode active material, and the like, as necessary.
The mixing method is not particularly limited, and can be carried out using a device equipped with an extremely simple mechanism such as a container and agitating blades. Examples of agitating blades include, but are not limited to, Max Blend blades, Tornado blades, and Full Zone blades. A general mixer capable of shaking or stirring may also be used. Examples of mixers include ribbon mixers and vertical screw mixers. Mixers may also be used. Efficient, multifunctional mixers that combine agitating devices, such as the Super Mixer (manufactured by Kawata Corporation) and High Speed Mixer (manufactured by Fukae Corporation), Newgram Machine (manufactured by Seishin Enterprise Co., Ltd.), SV Mixer (manufactured by Kobelco Eco Solutions Co., Ltd.), Filmix (Primix Corporation), Jet Paster (Nihon Spindle Manufacturing Co., Ltd.), KRC Kneader (manufactured by Kurimoto Iron Works Co., Ltd.), and planetary/revolutionary mixers (Thinky Corporation, Photo Chemical Co., Ltd.). Other than this, for example, grinding machines such as a jaw crusher, a gyratory crusher, a cone crusher, a roll crusher, an impact crusher, a hammer crusher, a rod mill, a ball mill, a vibrating rod mill, a vibrating ball mill, a disk mill, a jet mill, and a cyclone mill may be used, and ultrasonic emulsifiers, continuous twin-screw kneaders, high-pressure emulsifiers, microreactors, and the like may also be used.

[Conductive film composition and its manufacturing method]
The conductive film composition of the present invention contains the dried product of the conductive paste composition described above and has excellent uniformity. The conductive film composition may have a single layer structure containing the dried product of the conductive paste composition, or a multilayer structure having a layer containing the dried product of the conductive paste composition.

The specific gravity of the conductive film composition of the present invention is not particularly limited, but is preferably 0.2 to 6.5. If the specific gravity of the conductive film composition is outside the above range, sufficient conductivity may not be ensured, and mechanical strength may also decrease. The upper limit of the specific gravity of the conductive film composition is more preferably 5.5, even more preferably 4.5, particularly preferably 3.5, and most preferably 2.5. On the other hand, the lower limit of the specific gravity of the conductive film composition is more preferably 0.25, even more preferably 0.5, particularly preferably 0.75, and most preferably 1.0. The specific gravity of the conductive film composition is measured by the method described in the examples.

The contact angle of the conductive film composition of the present invention with water is not particularly limited, but is preferably 100° to 170°, more preferably 110° to 165°, even more preferably 120° to 165°, and particularly preferably 130° to 160°.

The thickness of the conductive film composition of the present invention is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 180 μm, even more preferably 20 to 150 μm, particularly preferably 30 to 120 μm, and most preferably 10 to 100 μm. If the thickness of the conductive film composition is outside the above range, sufficient conductivity may not be ensured, and flexibility may also be reduced.

When the conductive film composition of the present invention has voids inside, the proportion of voids in the total volume of the conductive film composition is not particularly limited, but is preferably 5 to 70%, more preferably 5 to 50%, even more preferably 10 to 40%, and particularly preferably 10 to 30%.

The conductive film composition of the present invention can be used when manufacturing components for an electricity storage device. Examples of electricity storage devices for which the conductive film composition can be used include capacitors, secondary batteries, and fuel cells. In particular, it is suitable for use in secondary batteries and fuel cells. When used in a secondary battery, it can be used, for example, when manufacturing its electrodes. When used in a fuel cell, it can be used, for example, when manufacturing its water-repellent portion.

The conductive film composition of the present invention can be produced, for example, by applying the above-mentioned conductive paste composition to a substrate and drying it.
The substrate used in the production of the conductive film composition can be appropriately selected depending on the intended use of the conductive film composition. When the conductive film composition is contained in a secondary battery, the substrate can be, for example, a conductive material such as C, Ti, Cr, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Au, Al, Ni, or an alloy containing two or more of these conductive materials (for example, stainless steel), and the shape of the substrate can be, for example, a foil substrate, a three-dimensional substrate, a perforated substrate, a porous substrate, a punched substrate, an etched substrate, a perforated substrate, or the like. The substrate preferably functions as a current collector for the electrode of the secondary battery.

When the conductive film composition is contained in a fuel cell, the substrate is preferably porous. Examples of the porous substrate (hereinafter, sometimes simply referred to as a porous substrate) include carbon-based porous substrates such as carbon paper, carbon cloth, and carbon nonwoven fabric (carbon felt). The porous substrate may also be treated with a fluorine-based resin or the like to be water-repellent.
The thickness of the porous substrate is not particularly limited, but is preferably 50 to 1000 μm, more preferably 80 to 600 μm, and particularly preferably 100 to 400 μm.

In addition to the above substrates, examples of polymer substrates include polyolefin substrates such as polyethylene and polypropylene; polycarbonate substrates; polyethylene terephthalate; polyester substrates such as polylactic acid; polystyrene substrates; polystyrene-based resins such as AS resin and ABS resin; polyamide substrates; polyvinyl chloride substrates; various polyvinylidene chloride substrates; cellophane substrates; and paper substrates.

The method for applying the conductive paste composition to the substrate is not particularly limited, and any method that can achieve a uniform coating may be used. Examples of such a method include capillary coating, spin coating, slit die coating, spray coating, dip coating, roll coating, screen printing, flexographic printing, bar coater, gravure coater, and die coater, as well as a method in which a tool such as a blade such as a doctor blade, a wire bar, or a squeegee is brought into contact with the surface of the substrate and excess paste composition is scraped off while applying a certain pressure to the surface.
In particular, when the conductive film composition is contained in a fuel cell, the use of the above-mentioned conductive paste composition is preferable because it prevents the conductive paste composition from substantially penetrating into the interior of the porous substrate, thereby preventing clogging of voids inside the substrate.

When a porous substrate is used as the substrate, it is preferable that the porous substrate has been subjected to a water-repellent treatment in advance. This can further improve the water-repellent properties of the gas diffusion layer. Furthermore, when the water-repellent layer of the present invention is provided on the surface of a conductive porous substrate, it can be more reliably formed on the substrate surface.

The drying temperature when producing a dried conductive paste composition is not particularly limited, but is preferably 50 to 200°C, more preferably 80 to 150°C, and even more preferably 100 to 130°C.
The drying temperature when producing a dried conductive paste composition is not particularly limited and can be appropriately determined depending on the drying temperature, etc., and is preferably 5 to 60 minutes, more preferably 10 to 30 minutes.
Examples of methods for producing a dried product of the conductive paste composition include warm air drying, hot air drying, vacuum drying, (far) infrared radiation drying, and electron beam radiation drying.

[Secondary battery]
The secondary battery of the present invention includes the conductive film composition described above, and includes at least an electrode and an electrolyte solution, and may also include a separator. When the conductive film composition is contained in the electrode (positive electrode and/or negative electrode), the raw materials used are uniformly dispersed in the electrode, which is preferable.

The electrolytic solution contained in the secondary battery of the present invention is obtained by mixing an electrolyte and a solvent and dissolving the electrolyte in the solvent.
Examples of electrolytes include _LiPF6 , LiAsF6 _{, LiBF4} , _LiSbF6 , _{LiAlCl4 , LiClO4} , _CF3SO3Li , _C4F9SO3Li , _CF3SOOLi , ( _{CF3CO ) 2NLi} , ( _{CF3SO2 ) 2NLi} , ( _C2F5SO2 ) _{2NLi ,} and _the like _.

The solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the electrolyte, and examples thereof include water and organic solvents.
Examples of organic solvents that can be used include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur compounds such as sulfolane and dimethyl sulfoxide. Mixtures of these may also be used. Among these, carbonates are preferred because they have a high dielectric constant and are chemically stable over a wide potential range.

The secondary battery of the present invention may include a separator, which is used in an electricity storage device to prevent a short circuit between the positive electrode and the negative electrode.
The separator is not particularly limited, and examples thereof include a microporous film separator, a nonwoven fabric separator, etc. Alternatively, one or both sides of the separator may be coated with an inorganic oxide containing an insulating inorganic oxide filler, a polyvinylidene fluoride resin, a polyaramid resin, or the like.

The resin that constitutes the separator is not particularly limited, but examples include polyolefin resins such as polyethylene, polypropylene, and polybutylene; polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamide resins such as nylon; polyamideimide resins; polyacetal resins; polystyrene resins; methacrylic resins; polyvinyl chloride resins; polycarbonate resins; polyphenylene sulfide resins, and cellulose resins.

The shape of the secondary battery of the present invention is not particularly limited, but examples thereof include coin type, cylindrical type, square type, and sheet type.
The exterior material of the secondary battery is not particularly limited, but examples thereof include a metal case, a molded resin, and an aluminum laminate film.
The type of secondary battery of the present invention is not particularly limited, and examples thereof include lithium ion secondary batteries such as lithium ion batteries, all-solid-state lithium ion batteries, and lithium ion polymer batteries; sodium ion secondary batteries such as sodium ion batteries, all-solid-state sodium ion batteries, and sodium ion polymer batteries; potassium ion secondary batteries such as potassium ion batteries, all-solid-state potassium ion batteries, and potassium ion polymer batteries; alkaline secondary batteries such as nickel-metal hydride batteries and nickel-cadmium batteries; sodium-sulfur batteries; redox flow batteries; and air batteries.

The secondary battery of the present invention can be used as a power source for various electrical devices (including electric vehicles).
Examples of electrical equipment include electronic terminals and their peripherals, home appliances, mobile transport equipment, stationary power storage equipment, and industrial equipment.

[Fuel cell]
The fuel cell of the present invention contains the above-mentioned conductive membrane composition and/or its fired product, and has at least an electrolyte membrane (1), an anode catalyst layer (2), a cathode catalyst layer (3), diffusion layers (4, 5), and current collecting layers (6, 7), as shown in Figure 2. The components constituting the fuel cell are described below.

The electrolyte membrane of the fuel cell is not particularly limited, but is preferably a composite membrane containing a proton-conductive organic substance in a porous substrate.
Examples of proton-conductive organic substances include sulfonated plastic electrolytes such as sulfonated polyether ketone, sulfonated polyether sulfone, sulfonated polyether ether sulfone, sulfonated polysulfone, sulfonated polysulfide, and sulfonated polyphenylene; sulfoalkylated plastic electrolytes such as sulfoalkylated polyether ether ketone, sulfoalkylated polyether sulfone, sulfoalkylated polyether ether sulfone, sulfoalkylated polysulfone, sulfoalkylated polysulfide, and sulfoalkylated polyphenylene; and proton-conductive polymers such as fluorine-based electrolyte materials, such as copolymers of fluorovinyl compounds and perfluoroolefins such as tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and perfluoroalkyl vinyl ethers.
In addition to the above, the proton-conducting polymer may be an ion exchange resin having a fluorine-containing polymer skeleton such as perfluorocarbon sulfonic acid resin, such as Nafion 112 and Nafion 117 manufactured by DuPont, or DOW membrane manufactured by Dow Chemical Co. One or more of the above proton-conducting polymers may be used in combination.

The proton-conductive organic material may be a proton-conductive polymer or a monomer having proton conductivity.
Examples of proton-conducting monomers include trifluoromethanesulfone; derivatives of fluorinated sulfonic acids such as tetrafluoroethanedisulfonic acid; derivatives of fluorinated diphosphoric acids such as (HO) _2OP ( _CF2 )PO(OH) ₂ and (HO) _2OP (CF2) _2PO ( _{OH ) 2} ; derivatives of _fluorinated sulfonyl acids such as ( _{CF3SO2CH2SO2CF2CF2 ) 2 and CF3SO2NHSO2C4F9 ; and the like .}

Porous substrates include organic porous substrates and inorganic porous substrates.
Examples of materials suitable for the organic porous substrate include materials obtained by imparting ionic conductivity to polymers such as polyfluorocarbon, polyethylene, polypropylene, polyisobutylene, polyalicyclic olefin, polyoxymethylene, polysulfone, polyethersulfone, polyetherethersulfone, polyphenylene sulfide, polyetheretherketone, polyparaphenylenebenzbisthiazole, polyparaphenylenebenzbisoxazole, polybenzimidazole, polyparaamide, polymethamide, polyimide, and phenolic resin. A preferred material for the organic porous substrate is polyimide.

Examples of polymers in which ionic conductivity has been imparted to polyfluorocarbon include sulfonated homo- or copolymers of perfluoroolefins such as tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and perfluoroalkoxyvinyl ether.
Examples of sulfonated perfluoroolefin homopolymers or copolymers include sulfonated polytetrafluoroethylene (PTFE), polytetrafluoroethylene-hexafluoropropylene (FEP), polytetrafluoroethylene-perfluoropropyl vinyl ether (PFA), polychlorotrifluoroethylene, polytetrafluoroethylene-perfluoro-2,2-dimethyl-1,3-dioxole, and polyperfluorobutenyl vinyl ether.

When an organic porous substrate is used, it is preferable that the proton-conductive organic substance and the organic porous substrate are made of the same material in terms of compatibility and adhesiveness of the two materials.
For polyperfluorocarbon sulfonic acid-based proton-conductive organic materials, sulfonated perfluorocarbon polymers such as PTFE, FEP, or PFA are preferred. For aromatic hydrocarbon-based proton-conductive organic materials, sulfonated polysulfone, polyether sulfone, polyether ether sulfone, polyphenylene sulfide, polyether ether ketone, polyparaphenylene benzbisthiazole, polyparaphenylene benzbisoxazole, or polybenzimidazole are preferred.

Examples of materials for _the inorganic porous substrate include silica ( _SiO2 ), zirconium oxide (ZrO2), boron oxide ( _B2O3 ), titania ( _TiO2 ), alumina ( _Al2O3 ), hydroxides of Ti, _Al , _B , and Zr, etc. The above inorganic porous substrate materials may be used alone or in combination of two or more.

Next, we will explain the anode catalyst layer and cathode catalyst layer of a fuel cell. The catalyst layer is the layer that serves as the reaction field for the electrode reaction, and its main components are a catalyst metal or catalyst metal-supported carbon and a polymer electrolyte. To obtain a fuel cell that generates sufficient output and has excellent stability over time, it is important that the diffusibility of fuel and reactant gases in the fuel cell electrodes is improved, that sufficient fuel and reactant gases are supplied to the interface between the catalyst and the electrolyte membrane, and that the diffusibility of water and carbon dioxide produced by the electrode reaction is improved so that they can be quickly discharged from the reaction system.

Known catalytic metals can be used, such as platinum, ruthenium, rhodium, palladium, iridium, gold, silver, iron, cobalt, nickel, chromium, tungsten, maggiore, vanadium, or multi-component alloys thereof. Of the above catalytic metals, platinum and platinum alloys are preferred. Metal catalyst-supported carbon particles, in which these metal catalysts are supported on carbon particles, may also be used.

Examples of carbon particles for supporting a metal catalyst include activated carbon, carbon black, graphite, and mixtures thereof.
Examples of carbon black include acetylene black, ketjenblack, furnace black, lamp black, and thermal black. Commercially available carbon blacks such as DENKABLACK (registered trademark) manufactured by Denka Co., Ltd., Valcan XC-72 and BLACKPEARLS 2000 manufactured by Cabot Corporation, and KetjenBlack EC300J manufactured by HM Royal may also be used.
The carbon particles may be hydrophilically treated, and it is particularly preferred to treat them with a carboxyl compound to make them carboxylated, or with a sulfone compound to make them sulfonated.

The electrolyte material for the catalyst layer is not particularly limited as long as it is a polymer conductive electrolyte with ionic conductivity such as that used in electrolyte membranes. Examples include fluorine-based electrolyte materials, partially fluorinated electrolyte materials, and hydrocarbon-based electrolyte materials.

The catalyst coating composition for forming the catalyst layer is preferably a liquid obtained by blending a catalyst metal or a catalyst metal-supported carbon, a polymeric conductive electrolyte, and a mixed liquid of an organic solvent and water, and uniformly dispersing the mixture using an ultrasonic disperser or the like.
Examples of organic solvents that can be used in the catalyst coating composition include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, and diethylene glycol; acetone; methyl ethyl ketone; dimethylformamide; dimethylimidazolidinone; dimethyl sulfoxide; dimethylacetamide; N-methylpyrrolidone; propylene carbonate; esters such as ethyl acetate and butyl acetate; aromatic solvents; halogenated solvents; etc. These organic solvents may be used alone or in combination of two or more.

The diffusion layer of a fuel cell is a layer that supplies fuel and oxygen to the anode catalyst layer and cathode catalyst layer, discharges water and carbon dioxide produced by the reaction, and transfers the generated electrons to the current collecting layer. The diffusion layer is made of a porous and electron-conductive material.
The main components of the diffusion layer include carbon particles such as activated carbon, carbon black, and graphite; fired products from polyacrylonitrile; fired products from pitch; carbon materials such as graphite and expanded graphite; nanocarbon materials; stainless steel; conductive materials such as molybdenum and titanium; water-repellent materials; and the above-mentioned proton-conductive polymers. The proton-conductive polymer may also function as an adhesive (binder) between other materials.

The substrate used for the diffusion layer is not particularly limited as long as it has low electrical resistance and can collect current, and examples thereof include those mainly made of conductive inorganic materials.
Examples of conductive inorganic materials include sintered bodies made from polyacrylonitrile; sintered bodies made from pitch, carbon materials such as graphite and expanded graphite; nanocarbon materials; stainless steel; molybdenum; and titanium.
The form of the conductive inorganic material is not particularly limited, but examples thereof include fibrous and particulate forms. From the viewpoint of gas permeability, fibrous forms are preferred, and carbon fiber is particularly preferred. The form of the substrate of the diffusion layer using a fibrous conductive inorganic material may be woven fabric or nonwoven fabric, and either structure may be used.

The woven fabric is not particularly limited, but may be plain weave, twill weave, satin weave, patterned weave, tapestry weave, etc. The nonwoven fabric is not particularly limited, but may be made by papermaking, needle punching, spunbonding, water jet punching, melt blowing, etc. Knitted fabrics may also be used.
The substrate of the diffusion layer may be a commercially available carbon paper such as the TGP series or SO series manufactured by Toray Industries, Inc.

When carbon fiber is used as the conductive material, examples of the substrate include woven fabrics obtained by carbonizing or graphitizing plain weave fabrics using flame-resistant spun yarns, nonwoven fabrics obtained by processing flame-resistant yarns into nonwoven fabrics using a needle punching method, a water jet punching method, or the like, followed by carbonization or graphitization, and matte nonwoven fabrics obtained by a papermaking method using flame-resistant yarns, carbonized yarns, or graphitized yarns. Among these, nonwoven fabrics are preferred because they are thin and strong.
When an inorganic conductive material made of carbon fiber is used as the substrate for the diffusion layer, examples of the carbon fiber include polyacrylonitrile-based carbon fiber, phenol-based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber. Among these, polyacrylonitrile-based carbon fiber is preferred. Furthermore, the substrate for the diffusion layer may be subjected to a water-repellent treatment using a polytetrafluoroethylene (PTFE) dispersion or the like.

The conductive membrane composition and/or its calcined product contained in the fuel cell is preferably contained in the diffusion layer. By containing the conductive membrane composition and/or its calcined product in the diffusion layer, the porosity of the water-repellent layer can be increased. Furthermore, the conductive membrane composition and/or its calcined product is preferably adjacent to the catalyst layer, and particularly preferably in contact with the catalyst layer.
Furthermore, if the above-mentioned conductive film composition and/or its fired product functions as a water-repellent material, it is believed that this will effectively discharge the water generated by the electrochemical reaction between hydrogen and oxygen during power generation in the fuel cell, thereby further suppressing flooding, which is preferable.

When the conductive film composition and/or its fired product is contained in the diffusion layer, it preferably contains the porous substrate described above, and it is particularly preferred that the conductive film composition and/or its fired product be adhered to the porous substrate. Furthermore, the conductive film composition and/or its fired product preferably contains the conductive film composition or its fired product, and more preferably contains a fired product of the conductive composition.

When the conductive film composition and/or its fired product is contained in the diffusion layer, for example, the above-mentioned conductive paste can be applied to at least one side of the diffusion layer, dried, and then fired to produce a diffusion layer containing the conductive film composition and/or its fired product.
When the diffusion layer contains a fired product of a conductive film composition, the firing temperature of the conductive film composition is not particularly limited, but is preferably 200 to 400°C, more preferably 250 to 360°C.
The baking time for the conductive film composition can be appropriately determined depending on the baking temperature and the like, and is not particularly limited, but is preferably 10 to 180 minutes, more preferably 30 to 150 minutes.

The current collecting layer of a fuel cell serves as an electrode that collects electrons from the anode catalyst layer or the diffusion layer, and is made of a conductive material, such as platinum, palladium, ruthenium, rhodium, iridium, gold, silver, copper, compounds or alloys thereof, or conductive carbon materials.
The conductive material used for the current collecting layer can be attached to the separator of the fuel cell by applying a conductive paste or conductive adhesive containing the conductive material, or by sputtering, vapor deposition, plating, thermal spraying, etc. When attaching the current collecting layer to the separator, the inner surface of the separator can be partially masked, and by forming the current collecting layer in a pattern on the separator, it is also possible to create fuel flow paths and air flow paths in the separator.

A fuel cell may have an electrolyte membrane-electrode assembly (MEA) formed by joining an electrolyte membrane and electrodes. Methods for manufacturing an MEA include, for example, directly applying the catalyst coating composition used to form the catalyst layer to the electrolyte layer, hot pressing a substrate used for the diffusion layer onto which a catalyst layer has been applied and then bonding the substrate to the electrolyte membrane, and applying a catalyst layer to a support and then transferring the coating to the electrolyte layer or diffusion layer.

When manufacturing an MEA by the transfer method, the transfer substrate may be, for example, a polytetrafluoroethylene (PTFE) sheet, a glass plate or a metal plate whose surface has been treated with a fluorine or silicone-based release agent, or the like, and further, a hot press treatment may be performed to improve bonding strength.
When an MEA is produced by a coating method, examples include a method using a coater such as a rod coater, blade coater, knife coater, die coater, curtain coater, slide coater, spray coater, spin coater, dip coater, or roll coater; or a method such as brush coating.
Methods for providing the current collecting layer on the outside of the diffusion layer include, for example, a method of directly applying a conductive paste capable of forming a current collecting layer to the diffusion layer, and a method of joining a conductive substrate to the diffusion layer by hot pressing.

A fuel distribution plate (separator) with grooves that form the fuel flow path and the oxidant flow path and an oxidant distribution plate (separator) are arranged on the outside of the MEA manufactured as described above to form a single cell, and a fuel cell can be obtained by stacking multiple such single cells via cooling plates, etc. In addition, by making the inside of the separator conductive, the separator can also function as a current collecting layer.
Fuels that can be used in fuel cells include, for example, hydrogen gas, methanol, ethanol, 1-propanol, dimethyl ether, and ammonia.

The present invention will be described in more detail in the following examples and comparative examples, but the present invention is not limited thereto. In the following examples and comparative examples, "%" means "% by weight" and "parts" means "parts by weight" unless otherwise specified. In the following production examples, examples, and comparative examples, physical properties were measured and performance evaluated as follows:

[Measurement of the Inclusion Ratio of Organic Compound in Resin Particles (B)]
First, the water content CW (%) of the dried resin particles (B) was measured using a Karl Fischer moisture meter (MKA-510N, manufactured by Kyoto Electronics Manufacturing Co., Ltd.).
Next, 1.0 g of the dried resin particles (B) was placed in a stainless steel evaporating dish with a diameter of 80 mm and a depth of 15 mm, and its weight _W1 (g) was measured. 30 ml of acetonitrile was added and uniformly dispersed, and the mixture was left at room temperature for 2 hours, and then dried at 110°C for 2 hours, after which its weight _W2 (g) was measured. The encapsulation rate CR (wt%) of the blowing agent was calculated using the following calculation formula (3).
CR=((W ₁ - _{W 2} )/1.0)×100-CW (3)

[Measurement of Volume Average Particle Diameter (D50) of Resin Particles (B)]
A Microtrac particle size distribution analyzer (model 9320-HRA, manufactured by Nikkiso Co., Ltd.) was used, and the D50 value determined by volumetric measurement was taken as the volume average particle size.

[Measurement of true specific gravity of resin particles (B)]
The true specific gravity (D _c ) of the resin particles (B) was measured by the following method.
First, the true specific gravity was measured by the liquid immersion method (Archimedes method) using isopropyl alcohol in an atmosphere at an environmental temperature of 25° C. and a relative humidity of 50%.
Specifically, a 100 cc volumetric flask was emptied and dried, and the weight (WB ₁ ) of the volumetric flask was then weighed. The weighed volumetric flask was then filled with isopropyl alcohol exactly up to the meniscus, and the weight (WB ₂ ) of the volumetric flask filled with 100 cc of isopropyl alcohol was then weighed. The 100 cc volumetric flask was also emptied and dried, and the weight (WS ₁ ) of the volumetric flask was then weighed. Approximately 50 cc of resin particles were then filled into the weighed volumetric flask, and the weight (WS ₂ ) of the volumetric flask filled with the resin particles was then weighed. The particle-filled volumetric flask was then filled with isopropyl alcohol exactly up to the meniscus, without introducing any air bubbles, and the weight (WS ₃ ) of the volumetric flask was then weighed. The obtained WB ₁ , WB ₂ , WS ₁ , WS ₂ and WS ₃ were then introduced into the following calculation formula (4) to calculate the true specific gravity (D _c ) of the resin particles (B).
D _c = {(WS ₂ - WS ₁ ) x (WB ₂ - WB ₁ )/100}/{(WB ₂ - WB ₁ ) - (WS ₃ - WS ₂ )} (4)

[Measurement of true specific gravity of thermoplastic resin constituting the outer shell of resin particles (B)]
The true specific gravity (D _p ) of the thermoplastic resin constituting the outer shell of resin particles (B) (hereinafter sometimes simply referred to as outer shell resin) was measured by dispersing 10 g of resin particles (B) in 200 ml of N,N-dimethylformamide, treating the dispersion with an ultrasonic disperser for 30 minutes, immersing the dispersion at room temperature for 24 hours, and then vacuum-heating and drying at 120° C. for 5 hours to isolate the outer shell resin. The true specific gravity D _p of the obtained outer shell resin was measured in the same manner as in the method for measuring the true specific gravity of resin particles (B) described above.

[Calculation of Shell Thickness of Resin Particles (B)]
The shell thickness <t> of the resin particles (B) was calculated using the following formula (5).
<t>=<x>/2 [1-{1-D _c (1-G/100)/D _p } ^1/3 ] (5)
<x>: average particle diameter (μm) of resin particles (B)
_Dc : True specific gravity of resin particles (B) (g/cc)
D _p : True specific gravity of the thermoplastic resin constituting the outer shell (g/cc)
CR: Inclusion rate of organic compound in resin particles (B) (% by weight)

[Calculation of the ratio (d _{1 /} d ₂ ) of the inner diameter (d ₁ ) to the outer diameter (d 2 ) of the resin particles (B)]
The ratio _{(d 1 /} d ₂ ) of the inner diameter (d ₁ ) to the outer diameter (d 2 ) of the resin particles (B) was calculated using the following formulas (6) to (8).
d ₁ =<x>-2<t> (6)
d ₂ =<x> (7)
d ₁ /d ₂ = (<x>-2<t>)/<x>=1-2<t>/<x> (8)

[Measurement of Expansion Starting Temperature (Ts) and Maximum Expansion Temperature (Tmax) of Resin Particles (B)]
A DMA (DMA Q800, manufactured by TA Instruments) was used as the measuring device. 0.5 mg of resin particles (B) was placed in an aluminum cup with a diameter of 6.0 mm (inner diameter 5.65 mm) and a depth of 4.8 mm, and an aluminum lid (5.6 mm, thickness 0.1 mm) was placed on top of the resin particle (B) layer to prepare a sample. The sample height was measured while a force of 0.01 N was applied from above using a pressure probe. With a pressure of 0.01 N applied, the sample was heated from 20°C to 300°C at a heating rate of 10°C/min, and the displacement of the pressure probe in the vertical direction was measured. The temperature at which displacement in the forward direction began was defined as the expansion beginning temperature (Ts), and the temperature at which the maximum displacement was observed was defined as the maximum expansion temperature (Tmax).

<Production Example 1>
To 450 g of ion-exchanged water, 2.5 g of adipic acid-diethanolamine condensate, 140 g of colloidal silica dispersion (effective concentration 20%), and 0.1 g of ethylenediaminetetraacetic acid tetrasodium salt were added, and the pH was adjusted to 2.5 to 3.5 to prepare an aqueous dispersion medium.
Separately, 124 g of acrylonitrile, 60 g of methacrylonitrile, 12 g of methyl methacrylate, 4 g of triethylene glycol diacrylate, 25 g of isobutane, 25 g of isopentane, and 3 parts g of di-2-ethylhexyl peroxydicarbonate (purity 70%) were mixed to prepare an oily mixture.
The aqueous dispersion medium and the oily mixture were mixed, and the resulting mixture was dispersed in a homomixer (TK Homomixer, manufactured by Primix Corporation) at a rotation speed of 12,000 rpm until the droplet size of the oily mixture reached the target resin particle size, thereby preparing a suspension.
This suspension was placed in a nitrogen-purged 1.5-liter pressure reaction vessel, pressurized to 0.5 MPa, and reacted for 15 hours at a polymerization temperature of 60°C while stirring at 80 rpm. After polymerization, the product was filtered and dried to obtain resin particles B-1. The physical properties of the obtained resin particles B-1 are shown in Table 1.

<Production Examples 2 and 3>
In Production Examples 2 and 3, resin particles B-2 to B-3 were obtained in the same manner as in Production Example 1, except that the reaction conditions in Production Example 1 were changed as shown in Table 1. The physical properties of the resulting resin particles are shown in Table 1.

<Production Example 4>
An aqueous dispersion medium was prepared by dissolving 130 g of sodium chloride in 450 g of ion-exchanged water, adding 2 g of adipic acid-diethanolamine condensate, 110 g of colloidal silica dispersion (effective concentration 20%), and 0.1 g of ethylenediaminetetraacetic acid tetrasodium salt, and adjusting the pH to 2.5 to 3.5.
Separately, 144 g of acrylonitrile, 54 g of methacrylonitrile, 2 g of triethylene glycol diacrylate, 10 g of isobutane, 40 g of isopentane, and 3 g of azoisobutyronitrile were mixed together to prepare an oily mixture.
The aqueous dispersion medium and the oily mixture were mixed, and the resulting mixture was dispersed in a homomixer (TK Homomixer, manufactured by Primix Corporation) at a rotation speed of 12,000 rpm until the droplet size of the oily mixture reached the target resin particle size, thereby preparing a suspension.
This suspension was placed in a nitrogen-purged 1.5-liter pressure reaction vessel, pressurized to 0.5 MPa, and reacted for 15 hours at a polymerization temperature of 60°C while stirring at 80 rpm. After polymerization, the product was filtered and dried to obtain resin particles B-4. The physical properties of the obtained resin particles B-4 are shown in Table 1.

<Production Examples 5 and 6>
In Production Examples 5 and 6, resin particles B-5 to B-6 were obtained in the same manner as in Production Example 4, except that the reaction conditions in Production Example 4 were changed as shown in Table 1. The physical properties of the resulting resin particles are shown in Table 1.

<Production Example 7>
An aqueous dispersion (slurry) containing 5% by weight of the resin particles B-1 obtained in Production Example 1 was prepared. According to the wet thermal expansion method described in JP-A-62-201231, this slurry was fed from a slurry inlet tube into a foaming tube (diameter 16 mm, volume 120 ml, made of SUS304TP) at a flow rate of 5 L/min, and steam (temperature: 145°C, pressure: 0.3 MPa) was further supplied from a steam inlet tube and mixed with the slurry to perform wet thermal expansion. The slurry temperature (foaming temperature) after mixing was adjusted to 120°C.
The obtained slurry containing the expanded beads was discharged from the protruding part of the expansion pipe, mixed with cooling water (water temperature 15°C), and cooled to 50 to 60°C. The cooled slurry liquid was filtered and dried to obtain resin particles B-7. The physical properties of the obtained resin particles B-7 are shown in Table 2.

<Production Example 8>
Resin particles B-8 were obtained in the same manner as in Production Example 7, except that in the wet thermal expansion method described in Production Example 7, resin particles B-1 were replaced with resin particles B-2 obtained in Production Example 2 and the expansion temperature was changed to 125° C. The physical properties of the obtained resin particles B-8 are shown in Table 2.

<Production Example 9>
Resin particles B-9 were produced by a dry thermal expansion method using resin particles B-1 obtained in Production Example 1. The internal injection method described in JP-A-2006-213930 was used as the dry thermal expansion method. Specifically, resin particles B-9 were produced by thermally expanding resin particles B-1 using a production apparatus equipped with an expansion process section shown in FIG. 3 according to the following procedure.

(Explanation of the foaming process section)
As shown in Figure 3, the foaming process section includes a centrally located gas inlet pipe (not shown) with a dispersion nozzle (11) at its outlet, an impingement plate (12) installed downstream of the dispersion nozzle (11), an overheating prevention tube (10) spaced apart around the gas inlet pipe, and a hot air nozzle (8) spaced apart around the overheating prevention tube (10). In this foaming process section, a gaseous fluid (13) containing thermally expandable resin particles flows in the direction of the arrow in the gas inlet pipe. A gas flow (14) for improving the dispersibility of the thermally expandable resin particles and preventing overheating of the gas inlet pipe and the impingement plate flows in the direction of the arrow in the space formed between the gas inlet pipe and the overheating prevention tube (10). Furthermore, a hot air flow for thermal expansion flows in the direction of the arrow in the space formed between the overheating prevention tube (10) and the hot air nozzle (8). Here, the hot air flow (15), the gaseous fluid (13), and the gas flow (14) usually flow in the same direction. Inside the superheat prevention tube (10), a refrigerant flow (9) flows in the direction of the arrow for cooling.

(Manufacturing equipment operation)
In the injection process, a gaseous fluid (13) containing thermally expandable resin particles is made to flow through a gas introduction pipe having a dispersion nozzle (11) at the outlet and installed inside a hot air flow (15), and the gaseous fluid (13) is injected from the dispersion nozzle (11).
In the dispersion step, the gaseous fluid (13) is caused to collide with an impingement plate (12) installed downstream of the dispersion nozzle (11), and the thermally expandable resin particles are operated so as to be evenly dispersed in the hot air flow (15). Here, the gaseous fluid (13) coming out of the dispersion nozzle (11) is guided toward the impingement plate (12) together with the gas flow (14) and collides with it.
In the expansion step, the dispersed thermally expandable resin particles are expanded by heating them to a temperature equal to or higher than the expansion initiation temperature in a hot air flow (15). Thereafter, the resulting resin particles are recovered by passing them through a cooling section or the like.

(Expansion conditions and results)
Resin particles B-9 obtained in Production Example 9 were obtained using the production apparatus shown in Figure 3 under expansion conditions of a raw material supply rate of 0.8 kg/min, a raw material dispersion gas amount of 0.35 m/min, a hot air flow rate of 9.0 m/min, and a hot air temperature of 250°C. The physical properties of the obtained resin particles B-9 are shown in Table 2.

<Production Examples 10 to 13>
The hot air treatment temperature was set to 250°C for resin particles B-3 obtained in Production Example 3, 280°C for resin particles B-4 obtained in Production Example 4, 300°C for resin particles B-5 obtained in Production Example 5, and 310°C for resin particles B-6 obtained in Production Example 6, to obtain expanded resin particles B-10 to B-13, respectively. The physical properties of the obtained resin particles are shown in Table 2.

<Comparative Example 1>
A conductive paste composition was prepared by mixing 125 parts by weight of polytetrafluoroethylene (PTFE, manufactured by Daikin Industries, Ltd.), 100 parts by weight of furnace black (Vulcan xc-72, average molecular weight 1000-3000, arithmetic mean particle size: 20-80 nm, manufactured by Cabot Corporation), 25 parts by weight of polyoxyethylene alkylene alkyl ether (Emulgen MS-110, manufactured by Kao Corporation), and 500 parts by weight of water. The performance of the prepared conductive paste composition was measured and evaluated by the method described below. The results are shown in Table 3.

Example 1
A conductive paste composition was prepared by adding 10 parts by weight of resin particles B-1 to the conductive paste composition described in Comparative Example 1 and uniformly mixing them. The performance of the prepared conductive paste composition was measured and evaluated in the same manner as in Comparative Example 1. The results are shown in Table 3.

<Examples 2 to 15>
In Examples 2 to 15, conductive paste compositions were prepared in the same manner as in Example 1, except that the resin particles and the amounts added were changed as shown in Table 3. The performance of each of the prepared conductive paste compositions was measured and evaluated in the same manner as in Comparative Example 1. The results are shown in Table 3.

<Comparative Example 2>
A conductive paste composition was prepared in the same manner as in Example 1, except that 10 parts by weight of JSR-SX8 (polystyrene-acrylonitrile copolymer particles, average particle size 0.4 μm, _d1 / _d2 0.66, manufactured by JSR Corporation) was added instead of resin particles B-1 as shown in Table 3. The performance of the prepared conductive paste composition was measured and evaluated in the same manner as in Comparative Example 1. The results are shown in Table 3.

[Evaluation of Dispersion Stability of Conductive Paste Composition]
The prepared conductive paste composition was placed in a 100 ml centrifuge tube and allowed to stand at room temperature for 24 hours, after which the weights of the sediment and the floating matter were measured, and the weight ratio (wt%) of the total amount of the sediment and the floating matter to 100 wt% of the nonvolatile content of the conductive paste composition was calculated. The dispersion stability was evaluated using the calculated weight ratio value according to the following evaluation criteria. The nonvolatile content of the conductive paste composition was determined by heating the conductive paste composition at 100°C and measuring the residue when it reached a constant weight.
⊚: The weight ratio of the total amount of sediment and floating matter is less than 10% by weight, and the dispersion stability is excellent.
Good: The weight ratio of the total amount of sediment and floating matter is 10% by weight or more and less than 20% by weight, and the dispersion stability is somewhat excellent.
Δ: The weight ratio of the total amount of sediment and floating matter is 20% by weight or more and less than 30% by weight, and the dispersion stability is somewhat poor.
×: The weight ratio of the total amount of sediment and floating matter is 30% by weight or more, and the dispersion stability is poor.

[Evaluation of Coatability of Conductive Paste Composition]
The prepared conductive paste composition was applied to a porous substrate, dried in the air at 95 ° C. for 20 minutes, and then fired in the air at 300 ° C. for 2 hours to obtain a porous substrate coated with the fired product of the conductive paste composition. The coverage area of the fired product of the conductive paste composition on the surface of the obtained porous substrate was measured, and the coating properties of the conductive paste composition were evaluated according to the following criteria.
The porous substrate was prepared by immersing carbon paper (TGP-H-120, manufactured by Toray Industries, Inc.) in a polytetrafluoroethylene aqueous dispersion (Polyflon PTFED-210C, 60% solids, manufactured by Daikin Industries, Ltd.) for 5 minutes, drying at 95 ° C. for 30 minutes in the air, and then baking at 350 ° C. for 30 minutes in the air to subject the substrate to a water-repellent treatment. Hereinafter, this porous substrate may be simply referred to as porous substrate A.
◯: The coverage area is 95% or more, there is no cracking of the coating, and the coating is excellent.
×: The coverage area is less than 95%, cracks occur in the coating, and the coating properties are poor.

[Measurement of Surface Tension of Conductive Paste Composition]
The surface tension of the prepared conductive paste composition was measured using an automatic surface tensiometer (CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.) and the porous substrate A, adjusting the temperature of the paste composition to 25°C, and using a plate method.

[Measurement of Contact Angle of Conductive Paste Composition with Substrate]
Using an automatic contact angle measuring device (OCA20, manufactured by Eiko Seiki Co., Ltd.), a droplet of about 1 microliter of the prepared conductive paste composition was dropped onto the surface of the porous substrate A, and the contact angle was measured 30 seconds after the dropping.

<Production of Conductive Film Composition>
The conductive paste compositions prepared in Examples 1 to 15 and Comparative Examples 1 and 2 were applied to a PTFE sheet, dried in the air at 95°C for 10 minutes, and then dried at 200°C for 10 minutes, and then peeled off from the PTFE sheet to produce conductive film compositions each having a thickness of 1 mm. The performance of the produced conductive film compositions was measured and evaluated using the method described below. The results are shown in Table 4.

[Evaluation of uniformity of conductive film composition]
The thickness of the produced conductive film composition was measured at 10 random points, and the uniformity of the conductive film composition was evaluated according to the following criteria.
○: The deviation of the maximum or minimum thickness from the average value is 5% or less. ×: The deviation of the maximum or minimum thickness from the average value is 5% or more.

[Measurement of Contact Angle of Conductive Film Composition with Water]
Using an automatic contact angle measuring instrument (OCA20, manufactured by Eiko Seiki Co., Ltd.), a water droplet of about 1 microliter was dropped onto the surface of the prepared conductive film composition, and the contact angle was measured 30 seconds after the drop.

[Measurement of specific gravity of conductive film composition]
The produced conductive film composition was cut into pieces of an appropriate size, and the cut pieces were measured for true specific gravity _Dm of the conductive film composition in the same manner as in the measurement of the true specific gravity of the resin particles (B) described above.

[Calculation of porosity of conductive film composition]
The produced conductive film composition was cut to an arbitrary size to prepare a test piece. The weight ( _WA ) of this test piece was weighed. The true volume (V) of the test piece was calculated from the weighed _WA and the conductive composition _Dm using the following calculation formula (9). Furthermore, the porosity (S) of the conductive film composition was calculated from the apparent volume ( _VA ) obtained from the external dimensions of the test piece and the true volume (V) of the test piece using the following calculation formula (10).
V=W _A /D _m (9)
S=(1-V/ _VA )×100 (10)

<Fuel cell manufacturing>
Fuel cells were manufactured using the conductive paste compositions of Examples 1 to 15 and Comparative Examples 1 and 2 in the following manner. The performance of the manufactured fuel cells was measured and evaluated in the manner described below. The results are shown in Tables 5 and 6.

(Preparation of catalyst coating composition)
An anode catalyst coating composition for forming an anode catalyst layer and a cathode catalyst coating composition for forming a cathode catalyst layer were prepared by blending 4 g of platinum catalyst-supported carbon particles (TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo K.K.), 40 g of a polymer conductive electrolyte solution (DE-520, Nafion 5 wt % solution, manufactured by DuPont), 12 g of distilled water, 20 g of n-butanol, and 20 g of t-butanol and stirring and mixing them using a disperser.

(Preparation of Coating Composition for Current Collecting Layer)
A mixture of Ketjenblack EC (manufactured by Lion Corporation), Teflon (registered trademark) dispersion PTFE31-J (manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and Nafion 117 solution (manufactured by DuPont) in a solids weight ratio of 80:10:10 was prepared, to which water and 2-propanol were added and the mixture was uniformly dispersed using ultrasonic waves to prepare a coating composition for a current collecting layer.

(Preparation of electrolyte membrane)
Styrene/divinylbenzene polymer particles with an average particle size of 500 nm and colloidal silica with a primary particle size of 50 nm were stirred and dispersed in a 50:50 volume ratio in water containing a surfactant using a high-speed homogenizer. The mixture was then filtered through a membrane filter with a pore size of 0.025 μm using a vacuum suction filter manufactured by Advantec Co., Ltd. The sample obtained on the filter paper was dried and then placed in a thermostatic box at 1000°C for firing to produce an inorganic porous substrate.
Separately, 2-acrylamido-2-methylpropanesulfonic acid as a monomer, N,N'-methylenebisacrylamide as a crosslinking agent, and AIBN (N,N'-azobisisovaleronitrile) as a polymerization initiator were mixed in a weight ratio of 100:20:1 in isopropyl alcohol:water = 4:1. The resulting mixture was poured into an inorganic porous substrate prepared under low vacuum. After returning to normal pressure, the inorganic porous substrate into which the mixture had been poured was slowly heated and maintained at 80°C for 2 hours to prepare an electrolyte membrane. The membrane thickness of the prepared electrolyte membrane was 150 μm.

(Manufacturing of Diffusion Layer)
Each of the conductive paste compositions of Examples 1 to 15 and Comparative Examples 1 and 2 was applied to a porous substrate A so that the thickness after sintering was 40 μm, and the applied coating was dried at 95° C. in an air atmosphere for 20 minutes, and then fired at 300° C. in an air atmosphere for 2 hours to produce a porous substrate A coated with a fired product of the conductive paste composition as a diffusion layer.

(Preparation of electrolyte membrane-catalyst layer stack)
The prepared anode coating composition and cathode coating composition were each applied to a transfer substrate (material: polyethylene terephthalate film) using an applicator, and dried at 95°C for about 30 minutes to form a catalyst layer, thereby preparing a transfer sheet for forming an anode catalyst layer and a transfer sheet for forming a cathode catalyst layer. The coating amount of the catalyst layer was such that the platinum loading amount for both the anode catalyst layer and the cathode catalyst layer was about 0.45 mg/ ^cm2 .
Next, the prepared transfer sheet for forming an anode catalyst layer and the prepared transfer sheet for forming a cathode catalyst layer were used to perform heat pressing on each side of the prepared composite membrane made of the inorganic porous substrate, and then only the transfer substrates were peeled off to prepare an electrolyte membrane-catalyst layer laminate.

(Fuel cell manufacturing)
Diffusion layers produced using the conductive paste compositions of Examples 1 to 15 and Comparative Examples 1 and 2 were laminated on both sides of the prepared electrolyte membrane-catalyst layer laminate so that the fired pastes were in contact with the catalyst layers (anode catalyst layer or cathode catalyst layer), thereby preparing respective electrolyte membrane-electrode assemblies (MEA).
Furthermore, the current collecting layer coating composition was applied to the inside of an acrylic separator having a thickness of 3 mm so as to give a film thickness of 20 μm after drying, thereby forming a current collecting layer, thereby producing an acrylic separator with a current collecting layer.
The electrolyte membrane-electrode assembly was fitted and fixed into the separator so that the diffusion layer of the electrolyte membrane-electrode assembly and the current collecting layer of the acrylic separator with current collecting layer were electrically connected, thereby producing fuel cells.

[Evaluation of fuel cell performance]
The cell performance of the manufactured fuel cell was evaluated under the following conditions: The cell voltage was measured while varying the load current from 1.25 to 25 A, and the measurement was performed at 1000 mA/ ^cm² , where the effect of gas diffusion is most pronounced.
Cell temperature: 80°C
Humidification temperature: cathode 80°C, anode 70°C
Gas utilization rate: cathode 40%, anode 70%

Details of the raw materials used in the above manufacturing examples, working examples, and comparative examples are shown in Table 7.

As can be seen from Tables 1 to 4, the conductive paste compositions described in the examples are conductive paste compositions containing a polymer component (A), resin particles (B), a conductive material (C), and a liquid medium (D). Because the resin particles (B) are composed of an outer shell made of a thermoplastic resin and an organic compound encapsulated therein, the compositions exhibit excellent dispersion stability and coatability, and the conductive film composition, which is the dried product of the conductive paste composition, also exhibits excellent uniformity. On the other hand, the conductive paste composition of Comparative Example 1, which does not contain resin particles (B), and the conductive paste composition of Comparative Example 2, which contains resin particles not encapsulating an organic compound, exhibit poor dispersion stability and coatability, and the conductive film composition, which is the dried product of the conductive paste composition, also exhibits poor uniformity.

REFERENCE SIGNS LIST 1 Electrolyte membrane 2 Anode catalyst layer 3 Cathode catalyst layer 4, 5 Diffusion layer 6, 7 Current collecting layer 8 Hot air nozzle 9 Coolant flow 10 Overheat protection tube 11 Dispersion nozzle 12 Collision plate 13 Gaseous fluid containing heat-expandable microspheres 14 Gas flow 15 Hot air flow 16 Outer shell made of thermoplastic resin 17 Organic compound

Claims (9)

A conductive paste composition comprising a polymer component (A), resin particles (B), a conductive material (C), and a liquid medium (D),
The conductive paste composition is used in a secondary battery or a fuel cell,
the particles (B) are composed of an outer shell made of a thermoplastic resin and an organic compound encapsulated therein,
the material (C) is at least one selected from furnace black, acetylene black, ketjen black, carbon nanofibers, carbon nanotubes, graphite, and graphene;
the content of the resin particles (B) is 0.5 to 10 parts by weight based on 100 parts by weight of the component (A),
The conductive paste composition has a content of the material (C) of 30 to 500 parts by weight relative to 100 parts by weight of the component (A). The conductive paste composition according to claim 1, wherein the thermoplastic resin is a polymer of a polymerizable component containing a nitrile-based monomer. The conductive paste composition according to claim 1 or 2, wherein the ratio (d ₁ /d ₂ ) of the inner diameter (d ₁ ) to the outer diameter (d ₂ ) of the particles (B) is 0.1 or more and 0.999 or less. The conductive paste composition according to any one of claims 1 to 3, wherein the organic compound is in gaseous and/or liquid form. The conductive paste composition according to any one of claims 1 to 4 , wherein the component (A) is at least one selected from the group consisting of an acrylic polymer, a fluorine-containing polymer, a diene-containing polymer, a vinyl-containing polymer, and a cellulose-containing polymer. The conductive paste composition according to any one of claims 1 to 4 , wherein the component (A) is a fluorine-containing polymer. A conductive film composition comprising a dried product of the conductive paste composition according to any one of claims 1 to 6 . A secondary battery comprising the conductive film composition of claim 7 . A fuel cell comprising at least one selected from the conductive film composition according to claim 7 and a fired product thereof.