Conductive material dispersion and conductive film made using the same

Abstract

To provide a conductive material dispersion having superior dispersibility, and to provide a thick conductive film having a sufficiently formed conductive network.SOLUTION: A conductive material dispersion comprises a carbon material (A), a dispersant (B), and an organic solvent (C), wherein the carbon material (A) comprises graphite (A-1) and a carbon material other than graphite (A-2), the graphite (A-1) comprises flake graphite, the content of the carbon material (A) is 50 mass% or more based on total solids of the conductive material dispersion, and the content of the graphite (A-1) is 65 to 99 mass% based on 100 mass% of the carbon material (A).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive material dispersion and a conductive film obtained using the same.

Background Art

[0002] In recent years, the development of electronics has been remarkable, and various efforts have been made for conductive materials used in various electronic devices, such as miniaturization, weight reduction, and cost reduction of products. As conductive materials, carbon-based conductive materials have been widely studied because of their high heat resistance, light resistance, corrosion resistance, light weight, relatively low cost, or high conductivity. However, in terms of conductivity, they are still insufficient compared to metals.

[0003] As higher-conductive carbon materials, conductive materials with low volume resistivity such as various graphites and carbon nanotubes have been studied so far. However, many carbon materials with excellent conductivity have a large specific surface area and are difficult to be uniformly mixed and dispersed in resins and solvents. Therefore, in the conductive films obtained from these conductive compositions, poor contact occurs between the carbon materials in the film, and the problem is that their conductivity cannot be sufficiently exhibited. (Patent Documents 1 to 3)

[0004] Therefore, Patent Documents 4 to 5 disclose conductive compositions using a combination of graphite and carbon black in order to develop a conductive network of carbon materials in a coating film.

[0005] Also, Patent Document 6 discloses a conductive composition using a combination of carbon fibers.

[0006] In addition, from the viewpoints of reducing the sheet resistance to a low resistance, and light shielding properties and shielding properties when combined with a transparent substrate, a thick film of a conductive film may be required. Patent Document 7 describes a thick film conductive film using carbon nanotubes. Patent Document 8 describes a thick film conductive film using conductive particles in which silver particles are coated with carbon.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 3-7740 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2001-60413 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2002-20515 [Patent Document 4] Japanese Unexamined Patent Application Publication No. 1-184901 [Patent Document 5] Japanese Unexamined Patent Application Publication No. 2-284968 [Patent Document 6] Japanese Unexamined Patent Application Publication No. 2004-221071 [Patent Document 7] Japanese Unexamined Patent Application Publication No. 2021-015726 [Patent Document 8] International Publication No. 200 / 016148 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] However, in the methods described in Patent Documents 1 to 6, the conductivity is insufficient, or the film thickness cannot be said to be sufficiently thick. Regarding thick film formation, in Patent Document 7, the coating film thickness in a single coating cannot be said to be sufficiently thick, and repeated coating is mentioned. When thick film formation is performed by repeated coating, interfacial resistance of the coating film occurs, so sufficient conductivity cannot be exhibited. In Patent Document 8, although formation of a highly conductive thick film can be achieved, from the viewpoints of corrosion resistance and cost reduction of the conductive film, it is insufficient because silver particles are used. As a result of intensive studies by the present inventors, it has been found that due to insufficient dispersibility of the carbon material, an appropriate conductive network cannot be constructed, the conductivity cannot be sufficiently exhibited, or due to insufficient sizing by dispersion, a decrease in stability such as thickening due to high concentration or poor film-forming properties during thick film coating occurs.

[0009] Accordingly, an object of the present invention is to provide a conductive material dispersion having good dispersibility and to provide a thick conductive film while sufficiently constructing a conductive network.

Means for Solving the Problems

[0010] As a result of further studies to solve the above problems, the present inventors have found that by using flaked graphite and other carbon materials in appropriate contents and further using a dispersant, it is possible to provide a conductive material dispersion having excellent dispersibility even at a high concentration.

[0011] That is, the present invention includes the following embodiments. The embodiments of the present invention are not limited to the following.

[0012] 〔1〕A conductive material dispersion containing a carbon material (A), a dispersant (B), and an organic solvent (C), wherein the carbon material (A) includes graphite (A-1) and a carbon material other than graphite (A-2), the graphite (A-1) includes flaked graphite, the content of the carbon material (A) is 50% by mass or more in the total solid content of the conductive material dispersion, and the content of the graphite (A-1) is 65 to 99% by mass in 100% by mass of the carbon material (A). A conductive material dispersion characterized by the above.

[0013] 〔2〕The conductive material dispersion according to 〔1〕, wherein the carbon material (A-2) other than the graphite contains carbon fiber.

[0014] 〔3〕The dispersant (B) includes a polymer type dispersant (B-1) or a low molecular type dispersant (B-2), and the polymer type dispersant (B-1) includes a vinyl resin or a polylactone resin. The conductive material dispersion according to 〔1〕 or 〔2〕.

[0015] 〔4〕A conductive film obtained by using the conductive material dispersion according to any one of 〔1〕 to 〔3〕.

[0016] 〔5〕A carbon material (A), a dispersant (B), and an organic solvent (C), wherein the carbon material (A) includes graphite (A-1) and a carbon material other than graphite (A-2), the graphite (A-1) includes flaky graphite, the content of the carbon material (A) is 50% by mass or more in the total solid content of the conductive material dispersion, and the content of the graphite (A-1) is 65 to 99% by mass in 100% by mass of the carbon material (A). A method for producing a conductive material dispersion, comprising a step of dispersing by applying at least one selected from the group consisting of shear stress, shear stress, frictional force, and impact force.

Advantages of the Invention

[0017] According to an embodiment of the present invention, it is possible to provide a conductive material dispersion in which two types of carbon materials are sufficiently dispersed and have good dispersibility, and to provide a conductive film with high conductivity, a thick film, and excellent adhesion.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the carbon material (A), the dispersant (B), the organic solvent (C), the conductive material dispersion, and the conductive film, which are embodiments of the present invention, will be described in detail. The present invention is not limited to the following embodiments, and the present invention also includes embodiments implemented within a range not changing the gist of the present invention.

[0019] <Carbon material (A)> The carbon material (A) of the present invention is characterized by including graphite (A-1) and a carbon material other than graphite (A-2), and further characterized in that the content of the carbon material (A) in the total solid content of the conductive material dispersion is 50% by mass or more. More preferably, it is 70% by mass or more, and still more preferably, it is 70% by mass or more and 99% by mass or less. By setting it within the above range, in the conductive film, components other than the carbon material can form a film without inhibiting the conductive network between the carbons, so that the conductivity is further improved.

[0020] <Graphite (A-1)> Examples of the graphite (A-1) of the present invention include artificial graphite and natural graphite. Artificial graphite is obtained by artificially orienting the orientation of fine graphite crystals with an irregular arrangement by heat-treating amorphous carbon, and is generally manufactured using petroleum coke or coal-based pitch coke as the main raw material. As natural graphite, flake graphite, massive graphite, earthy graphite, exfoliated graphite, spherical natural graphite, etc. can be used. Further, expanded graphite (also referred to as expandable graphite) obtained by chemically treating flake graphite or the like, or expanded graphite obtained by heat-treating expanded graphite to expand it and then obtaining it by micronization or pressing can also be used. The graphite (A-1) includes flaky graphite such as flake graphite, expanded graphite, and exfoliated graphite. The graphite (A-1) may be used alone with flaky graphite or in combination with flaky graphite and other graphite. Since flaky graphite has a thin plate-like structure, the contact area between the surfaces when the graphite particles are laminated is large, and the conductivity in the thickness direction can be dramatically improved. The content of flaky graphite is preferably 70% or more, particularly preferably 80% or more, in 100% by mass of the graphite (A-1).

[0021] The surfaces of these graphites may be subjected to surface treatments such as epoxy treatment, urethane treatment, silane coupling treatment, and oxidation treatment in order to increase the affinity with the polymer-type dispersant (B-1) as long as the properties of the conductive composition of the present invention are not impaired.

[0022] Also, the average particle size of the graphite is preferably 2 to 100 μm, particularly preferably 10 to 50 μm. When it is in the above range, the graphite particles are more likely to contact each other in a plane rather than at a point, so that a good conductive network is formed. Also, when it is in the above range, the dispersibility is good and sedimentation after dispersion is less likely to occur.

[0023] The average particle size referred to in the present invention is the particle size (D50) at which 50% is reached when the volume ratio of the particles is integrated from the finer particle sizes in the volume particle size distribution, and is measured by a general particle size distribution meter, for example, a particle size distribution meter of the dynamic light scattering method (Microtrac UPA manufactured by Nikkiso Co., Ltd.).

[0024] Examples of commercially available flaky graphite include CMX, UP-5, UP-10, UP-20, UP-35N, CSSP, CSPE, CSP, CP, CB-150, CB-100, ACP, ACP-1000, ACB-50, ACB-100, ACB-150, SP-10, SP-20, J-SP, SP-270, HOP, GR-60, LEP, F#1, F#2, F#3 manufactured by Nippon Graphite Industries Co., Ltd.; CX-3000, FBF, BF, CBR, SSC-3000, SSC-600, SSC-3, SSC, CX-600, CPF-8, CPF-3, CPB-6S, CPB, 96E, 96L, 96L-3, 90L-3, CPC, S-87, K-3, CF-80, CF-48, CF-32, CP-150, CP-100, CP, HF-80, HF-48, HF-32, SC-120, SC-80, SC-60, SC-32, BF15-AK manufactured by Chugoku Graphite Co., Ltd.; EC1500, EC1000, EC500, EC300, EC100, EC50 manufactured by Ito Graphite Industries Co., Ltd.; 10099M, PB-99 manufactured by Nishimura Graphite Co., Ltd., etc.

[0025] Examples of other commercially available graphite include spherical natural graphite such as CGC-20, CGC-50, CGB-20, CGB-50 manufactured by Nippon Graphite Industries Co., Ltd.; earthy graphite such as Blue P, AP, AOP, P#1 manufactured by Nippon Graphite Industries Co., Ltd.; APR, S-3, AP-6, 300F manufactured by Chugoku Graphite Co., Ltd.; artificial graphite such as PAG-60, PAG-80, PAG-120, PAG-5, HAG-10W, HAG-150 manufactured by Nippon Graphite Industries Co., Ltd.; RA-3000, RA-15, RA-44, GX-600, G-6S, G-3, G-150, G-100, G-48, G-30, G-50 manufactured by Chugoku Graphite Co., Ltd.; SGP-100, SGP-50, SGP-25, SGP-15, SGP-5, SGP-1, SGO-100, SGO-50, SGO-25, SGO-15, SGO-5, SGO-1, SGX-100, SGX-50, SGX-25, SGX-15, SGX-5, SGX-1 manufactured by SEC Carbon Co., Ltd.

[0026] Further, the content of graphite (A-1) in the conductive material dispersion of the present invention is characterized in that it is 65% to 99% by mass in 100% by mass of the carbon material (A). The content of graphite (A-1) is preferably 65.0% to 99.0% by mass, particularly preferably 75% to 90% by mass in 100% by mass of the carbon material (A). By setting it within the above range, the contact area between the surfaces when the flaky graphite particles are stacked increases, and the voids are filled with a carbon material (A-2) other than graphite, so that a conductive network can be sufficiently formed and the conductivity can be dramatically improved. In addition, the flaky graphite with a plate-like structure spreads on the surface while taking a laminated structure, so that the surface of the coating film becomes smoother and the film-forming property during thick film coating is improved.

[0027] <Carbon material (A-2) other than graphite> The carbon material (A-2) other than graphite of the present invention is not particularly limited, but from the viewpoint of improving the conductivity by forming a conductive network, it is particularly preferable to contain carbon fibers. In addition, carbon black, fullerene, etc. may be used alone or in combination of two or more.

[0028] As the carbon fiber, those obtained by firing from a petroleum-derived raw material are good, but those obtained by firing from a plant-derived raw material can also be used. Carbon fibers include vapor-grown carbon fibers and carbon nanotubes (hereinafter referred to as CNTs). From the viewpoints that they are less likely to break the laminated structure of the flaky graphite and less likely to reduce the adhesion, and that the fibrous structure bridges between the surfaces of the flaky graphite to construct a conductive network and improve the conductivity, it is particularly preferable to contain CNTs.

[0029] CNT includes a shape in which planar graphite is wound into a cylindrical shape, single-layer CNT, and multi-layer CNT, and these may be mixed. In addition, CNTs with different diameters may be mixed. Single-layer CNT has a structure in which one layer of graphite is wound. Multi-layer CNT has a structure in which two or more layers of graphite are wound. Also, the side wall of the CNT does not have to be a graphite structure. Further, for example, CNTs having a side wall with an amorphous structure are also CNTs in this specification.

[0030] The shape of the CNT is not limited. Such shapes include various shapes such as needle-like, cylindrical tube-like, fishbone-like (fishbone or cup stacking type), trump-like (platelet), and coil-like. In the present embodiment, the shape of the CNT is preferably needle-like or cylindrical tube-like among others. The CNT may be in a single shape or a combination of two or more shapes.

[0031] Examples of the form of the CNT include graphite whiskers, filamentous carbon, graphite fibers, ultra-thin carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. The CNT may have these single forms or a form combined with two or more of them.

[0032] When using the CNT, the average outer diameter of the CNT is preferably 1 nm or more. Also, it is preferably 30 nm or less. By setting the average outer diameter within the above range, the number of CNTs that can contact between the planes of the flaky graphite increases, and a dense conductive network can be formed, so the conductivity is improved. The average outer diameter can be calculated as follows. First, observe and image the CNT with a transmission electron microscope. Next, in the observation photograph, select any 300 CNTs and measure their respective outer diameters. Next, calculate the average outer diameter (nm) of the CNT as the number average of the outer diameters. The value obtained by dividing the average fiber length of the CNT by the average outer diameter is called the aspect ratio. From the viewpoint of the conductivity, the aspect ratio of the CNT is preferably 20 or more, and more preferably 50 or more. The average fiber length used for calculating the aspect ratio can be calculated as follows. First, observe and image the CNT with a scanning electron microscope. Next, in the observation photograph, select any 300 CNTs and measure their respective fiber lengths. Next, calculate the average fiber length of the CNT as the number average of the fiber lengths. The average fiber length of the CNT is preferably 0.3 μm or more, more preferably 0.5 μm or more, preferably 5.0 μm or less, and more preferably 2.0 μm or less in order to form an efficient conductive network.

[0033] Examples of commercially available carbon fibers include vapor-grown carbon fibers such as VGCF manufactured by Showa Denko K.K., single-walled CNTs such as EC1.0, EC1.5, EC2.0, EC1.5-P manufactured by Meijo NanoCarbon Co., Ltd., TUBALL manufactured by OCSiAl, and TNSR manufactured by Timesnano, and multi-walled CNTs such as FloTube9000, FloTube9100, FloTube9110, FloTube9200 manufactured by CNano, NC7000 manufactured by Nanocyl, 100T manufactured by Knano, BT1003M, LUCANBT1003M manufactured by LGchemLtd., and JENOTUBE10B, 6A manufactured by JEIO.

[0034] Examples of carbon black include acetylene black, furnace black, hollow carbon black, channel black, thermal black, and ketjen black. The carbon black may be neutral, acidic, or basic, and oxidized carbon black or graphitized carbon black may be used.

[0035] When using carbon black, the primary particle diameter is preferably 0.005 to 1 μm. By setting the particle diameter within this range, carbon black can enter the gaps between the graphite and increase the contact points, thereby improving the conductivity. However, the primary particle diameter referred to here is the average of the particle diameters measured by an electron microscope or the like.

[0036] Examples of commercially available carbon blacks include Tokablack #4300, #4400, #4500, #5500 manufactured by Tokai Carbon Co., Ltd., Printex L manufactured by Degussa AG, Raven 7000, 5750, 5250, 5000 ULTRAIII, 5000 ULTRA, Conductex SC ULTRA, Conductex 975 ULTRA, PUERBLACK 100, 115, 205 manufactured by Columbian Chemicals Company, #2350, #2400B, #2600B, #3050B, #3030B, #3230B, #3350B, #3400B, #5400B manufactured by Mitsubishi Chemical Corporation, MONARCH 1400, 1300, 900, Vulcan XC-72R, Black Pearls 2000 manufactured by Cabot Corporation, Ensaco 250G, Ensaco 260G, Ensaco 350G, Super P-Li, etc. manufactured by TIMCAL, Ketjenblack EC-300J, EC-600JD, etc. manufactured by Lion Corporation, DENKABLACK Li-100, Denka Black Li-400, FX-35, etc. manufactured by Denka Company Limited, and acetylene blacks.

[0037] <Dispersant (B)> In the present invention, the dispersant is used to disperse the carbon material in the conductive paste. Examples of the dispersant include resin-type dispersants, surfactants, silane coupling agents, and metal chelates. Among them, since the adsorptive power to the carbon material is strong and good dispersibility can be obtained, it is particularly preferable to contain one or more of the following polymer-type dispersants (B-1) or low-molecular-type dispersants (B-2).

[0038] <Polymer-type dispersant (B-1)> The polymer-type dispersant has a carbon material affinity site having a property of adsorbing to the carbon material and a site compatible with the carbon material carrier, and functions to adsorb to the carbon material and stabilize the dispersion in the colorant carrier. As the polymer-type dispersant, known polymer-type dispersants can be used. Also, the polymer-type dispersants can be used alone or in admixture of two or more.

[0039] The molecular weight of the polymer type dispersant (B-1) is not particularly limited, but the weight average molecular weight is preferably in the range of 2,000 to 500,000, and more preferably in the range of 3,000 to 200,000. When it is in the above range, the balance between the adsorptivity to the object to be dispersed and the affinity to the dispersion medium can be achieved, and the stability of the dispersion is improved.

[0040] In the present invention, as a preferable example of the polymer type dispersant, it is particularly preferable to contain a vinyl resin or a polylactone resin. By using these resins, the polymerization sites of vinyl groups or lactone groups with high affinity for the carbon material are sufficiently adsorbed, and better dispersibility can be obtained. Furthermore, since the resin is sufficiently adsorbed to the carbon material, it also contributes to the improvement of the adhesion.

[0041] (Vinyl resin) The vinyl resin is a general term for resins obtained by polymerizing polymerizable monomers having vinyl groups.

[0042] Examples of the vinyl resin having a basic functional group include those containing an amino group including a cyclic structure and a skeleton in which part or all of the amino groups are neutralized, or a quaternary ammonium salt, such as homopolymers of polymerizable monomers such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, methylethylaminoethyl (meth) acrylate, dimethylaminostyrene, diethylaminostyrene, or copolymers with other polymerizable monomers and their acid neutralization products.

[0043] Examples of the vinyl resin having an acidic functional group include those containing a carboxyl group, a sulfo group, a phosphate group, and a backbone obtained by partially or completely neutralizing these groups. For example, polymerizable monomers having a carboxyl group such as maleic acid, fumaric acid, itaconic acid, citraconic acid, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, etc., polymerizable monomers having a sulfo group such as vinylsulfonic acid, (meth)allylsulfonic acid, styrenesulfonic acid, (meth)acryloyloxyethylsulfonic acid, isoprenesulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, allyloxybenzenesulfonic acid, etc., polymerizable monomers having a phosphate group such as mono(2-acryloyloxyethyl) acid phosphate, mono(2-methacryloyloxyethyl) acid phosphate, diphenyl(2-acryloyloxyethyl) phosphate, diphenyl(2-methacryloyloxyethyl) phosphate, phenyl(2-acryloyloxyethyl) phosphate, acid phosphooxyethyl methacrylate, methacryloyloxyethyl acid phosphate monoethanolamine salt, 3-chloro-2-acid phosphooxypropyl methacrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate, acid phosphooxypolyoxypropylene glycol methacrylate, (meth)acryloyloxyethyl acid phosphate, (meth)acryloyloxypropyl acid phosphate, (meth)acryloyloxy-2-hydroxypropyl acid phosphate, (meth)acryloyloxy-3-hydroxypropyl acid phosphate, (meth)acryloyloxy-3-chloro-2-hydroxypropyl acid phosphate, allyl alcohol acid phosphate, etc., homopolymers of these polymerizable monomers, or copolymers with other polymerizable monomers and their alkali neutralization products.

[0044] The vinyl resin having a basic functional group and an acidic functional group means those containing both the basic backbone and the acidic backbone, and examples include copolymers of styrene-maleic acid-N,N-dimethylaminoethyl (meth)acrylate.

[0045] The nonionic vinyl resin is a resin other than the vinyl resin having the basic functional group, the vinyl resin having the acidic functional group, and the vinyl resin having the basic functional group and the acidic functional group, and examples thereof include polyvinylpyrrolidone, polyvinyl alcohol, polyacrylamide, poly-N-vinylacetamide, polyvinyl chloride, polyvinyl acetate, polyvinyl acetal, polyvinyl butyral, polyacrylonitrile, polyacrylate ester, polystyrene, butadiene rubber, acrylonitrile butadiene rubber, and the like.

[0046] Further, the nonionic resin may be a copolymer composed of a plurality of polymerizable monomers exemplified below.

[0047] Examples of the polymerizable monomer having an aromatic ring include styrene, α-methylstyrene, or benzyl (meth)acrylate.

[0048] Specific examples of the polymerizable monomer having a chain saturated hydrocarbon group include alkyl (meth)acrylates having 1 to 22 carbon atoms such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate, preferably alkyl group-containing acrylates or corresponding methacrylates having an alkyl group having 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms. These alkyl groups may be branched, and specific examples include isopropyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-butylhexyl (meth)acrylate, and the like. In addition, vinyl fatty acid compounds such as vinyl acetate, vinyl butyrate, vinyl propionate, vinyl hexanoate, vinyl caprylate, vinyl laurate, vinyl palmitate, and vinyl stearate are included. Furthermore, α-olefin compounds such as 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, and 1-hexadecene are included.

[0049] Examples of the polymerizable monomer having a cyclic saturated hydrocarbon group include isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, 1-adamantyl (meth)acrylate, and the like.

[0050] Examples of the polymerizable monomer having a polyoxyalkylene structure include monoacrylates or monomethacrylates having a hydroxyl group at the terminal and a polyoxyalkylene chain such as diethylene glycol mono (meth)acrylate, polyethylene glycol mono (meth)acrylate, polypropylene glycol mono (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and the like, and monoacrylates or corresponding monomethacrylates having an alkoxy group at the terminal and a polyoxyalkylene chain. Examples of the alkyl vinyl ether compound include butyl vinyl ether and ethyl vinyl ether. Also, cyclic compounds such as glycidyl (meth)acrylate and tetrahydrofurfuryl (meth)acrylate may be used.

[0051] Examples of the polymerizable monomer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol mono (meth)acrylate, 4-hydroxystyrene, vinyl alcohol, allyl alcohol, and the like.

[0052] Examples of nitrogen-containing polymerizable monomers include monoalkylol (meth)acrylamides such as N-vinyl-2-pyrrolidone, (meth)acrylamide, N-vinylacetamide, N-methylol (meth)acrylamide, and N-methoxymethyl-(meth)acrylamide; N,N-di(methylol)acrylamide, N-methylol-N-methoxymethyl (meth)acrylamide, N,N-di(methoxymethyl)acrylamide, and the like.

[0053] Furthermore, examples of other monomers include perfluoroalkylalkyl (meth)acrylates having a perfluoroalkyl group with 1 to 20 carbon atoms such as perfluoromethylmethyl (meth)acrylate, perfluoroethylmethyl (meth)acrylate, 2-perfluorobutylethyl (meth)acrylate, and 2-perfluorohexylethyl (meth)acrylate; perfluoroalkyl group-containing vinyl monomers such as perfluorobutylethylene, perfluorohexylethylene, perfluorooctylethylene, and perfluorodecylethylene, alkylene perfluoroalkyls, etc.; silanol group-containing vinyl compounds and their derivatives such as vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and γ-(meth)acryloxypropyltrimethoxysilane. A plurality of these can be used from these groups.

[0054] Examples of ethynyl compounds include acetylene, ethynylbenzene, ethynyltoluene, 1-ethynyl-1-cyclohexanol, and the like. These can be used alone or in combination of two or more.

[0055] Further, the vinyl resin may be modified. For example, by adding the hydroxyl groups in a vinyl polymer having two hydroxyl groups at one end to a tetracarboxylic anhydride, polymer dispersants described in WO2008 / 007776, JP-A-2008-029901, JP-A-2009-155406, JP-A-2010-185934, JP-A-2011-157416, JP-A-2009-251481, JP-A-2007-23195, JP-A-1996-143651, JP-A-2007-140487, etc. can also be used.

[0056] From the viewpoints of the adsorption ability to carbon materials and dispersibility, vinyl resins such as polyvinyl acetal, hydrogenated acrylonitrile-butadiene rubber, and a dispersant obtained by adding the hydroxyl groups in a vinyl polymer having two hydroxyl groups at one end described in WO2008 / 007776 to a tetracarboxylic anhydride are preferable.

[0057] Examples of commercially available polyvinyl acetal resins include Esrec BL-S, BL-1, BL-10, BM-1, BH-3, Esrec BX-1, BX-L, KS-10 (manufactured by Sekisui Chemical Co., Ltd.), Denka Butyral #3000-1, #3000-K, #4000-2 (manufactured by Denka Co., Ltd.), Mobital LPB16H, B20H, B30T, B30H, B30HH, B45M (manufactured by Kuraray Co., Ltd.), etc., but are not limited thereto.

[0058] Examples of commercially available hydrogenated acrylonitrile-butadiene rubbers include Zetpol0020, 1010, 2001, 2010, 2010H (manufactured by Zeon Corporation), Zhanber ZN28255, 35156, 43056, etc. (manufactured by Zannan Corporation), Therban3406, 3446, 3607, LT2007, LT2568, LT1707, etc. (manufactured by ARLANXEO Corporation), etc., but are not limited thereto.

[0059] (Poly lactone resin) The polycaprolactone-based resin is a general term for resins having a polycaprolactone skeleton with lactone as a monomer. Specific examples of lactone, which is the monomer constituting the polycaprolactone-based resin, include β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, δ-caprolactone, ε-caprolactone, and alkyl-substituted ε-caprolactone. Among these, δ-valerolactone, ε-caprolactone, alkyl-substituted ε-caprolactone, etc. can be mentioned. Homopolymers of these, copolymers of two or more of these, or mixtures of these can be mentioned. However, the monomers are not limited to these.

[0060] Examples of the polycaprolactone-based resin include polycaprolactone polyol and a dispersant obtained by adding the hydroxyl groups in a polycaprolactone having two hydroxyl groups at one end, as described in Japanese Patent No. 4020150, to a tetracarboxylic anhydride.

[0061] Specific examples of the polycaprolactone-based resin include SOLSPERSE 24000, 28000 (weight average molecular weight: 3,400), 32000 (weight average molecular weight: 3,900), 33000, 39000 (manufactured by Lubrizol Corporation), AJISPER PB821, PB822 (weight average molecular weight: 7,600), PB824, PB827 (manufactured by Ajinomoto Fine-Techno Co., Inc.), etc.

[0062] The content of the polymer type dispersant (B-1) is preferably 1% to 50% by mass, more preferably 1% to 30% by mass, in the total solid content of the conductive material dispersion. When it is within the above range, it is possible to achieve both good dispersibility and conductivity.

[0063] <Low molecular weight dispersant (B-2)> The low molecular weight dispersant is a substance that improves the affinity between carbon and the polymer type dispersant or the solvent, and functions to promote dispersion or stabilize the dispersion. As the low molecular weight dispersant, for example, a dye derivative or the like can be used. Also, the low molecular weight dispersant can be used alone or in combination of two or more.

[0064] As the dye derivative used in the present invention, known dye derivatives having an acidic group, a basic group, a neutral group, etc. in the organic dye residue can be used. For example, compounds having an acidic substituent such as a sulfo group, a carboxy group, a phosphate group, etc. and amine salts thereof, compounds having a basic substituent such as a sulfonamide group or a tertiary amino group at the terminal, and compounds having a neutral substituent such as a phenyl group or a phthalimidoalkyl group can be mentioned. Examples of the organic dye include diketopyrrolopyrrole-based pigments, anthraquinone-based pigments, quinacridone-based pigments, dioxazine-based pigments, perinone-based pigments, perylene-based pigments, thiazine indigo-based pigments, triazine-based pigments, benzimidazolone-based pigments, indole-based pigments such as benzisoindole, isoindoline-based pigments, isoindolinone-based pigments, quinophthalone-based pigments, naphthol-based pigments, threne-based pigments, metal complex-based pigments, azo-based pigments such as azo, disazo, polyazo, etc.

[0065] Specifically, examples of diketopyrrolopyrrole-based pigment derivatives include those described in JP-A-2001-220520, WO2009 / 081930 pamphlet, WO2011 / 052617 pamphlet, WO2012 / 102399 pamphlet, JP-A-2017-156397; examples of phthalocyanine-based pigment derivatives include those described in JP-A-2007-226161, WO2016 / 163351 pamphlet, JP-A-2017-165820, Patent No. 5753266; examples of anthraquinone-based pigment derivatives include those described in JP-A-63-264674, JP-A-09-272812, JP-A-10-245501, JP-A-10-265697, JP-A-2007-079094, WO2009 / 025325 pamphlet; examples of quinacridone-based pigment derivatives include those described in JP-A-48-54128, JP-A-03-9961, JP-A-2000-273383; examples of dioxazine-based pigment derivatives include those described in JP-A-2011-162662; examples of thiazine indigo-based pigment derivatives include those described in JP-A-2007-314785; examples of triazine-based pigment derivatives include those described in JP-A-61-246261, JP-A-11-199796, JP-A-2003-165922, JP-A-2003-168208, JP-A-2004-217842, JP-A-2007-314681; examples of benzoisoindole-based pigment derivatives include those described in JP-A-2009-57478; examples of quinophthalone-based pigment derivatives include those described in JP-A-2003-167112, JP-A-2006-291194, JP-A-2008-31281, JP-A-2012-226110; examples of naphthol-based pigment derivatives include those described in JP-A-2012-208329, JP-A-2014-5439; examples of azo-based pigment derivatives include those described in JP-A-2001-172520, JP-A-2012-172092; examples of acidic substituents include those described in JP-A-2004-307854; examples of basic substituents include those described in JP-A-2002-201377, JP-A-2003-171594, JP-A-2005-181383, JP-A-2005-213404, and the like. Known pigment derivatives described therein can be mentioned.Although these documents may describe the dye derivatives as derivatives, dye derivatives, dispersants, pigment dispersants, or simply compounds, etc., a compound having a substituent such as an acidic group, a basic group, or a neutral group in the above-described organic dye residue is synonymous with a dye derivative.

[0066] More specifically, the use of a triazine derivative represented by the following general formula (1) is preferred.

[0067] General formula (1)

Chemical formula

[0068] General formula (2)

Chemical formula

[0069] In the formula of general formula (1), M represents one equivalent of a cation with a valence of 1 to 3, and represents, for example, any one of a hydrogen atom (proton), a metal cation, and a quaternary ammonium cation. When there are two or more Ms in the dispersant structure, M may be only any one of a proton, a metal cation, and a quaternary ammonium cation, or a combination thereof. Examples of the metal include lithium, sodium, potassium, calcium, barium, magnesium, aluminum, nickel, cobalt, etc.

[0070] The quaternary ammonium cation is a single compound or a mixture having a structure represented by general formula (3).

[0071] General formula (3)

Chemical formula

[0072] R5, R6, R7, and R8 in general formula (3) may be the same or different. When R5, R6, R7, and R8 have carbon atoms, the number of carbon atoms is 1 to 40, preferably 1 to 30, more preferably 1 to 20. When the number of carbon atoms exceeds 40, the conductivity of the electrode may decrease.

[0073] Specific examples of quaternary ammonium include, but are not limited to, dimethylammonium, trimethylammonium, diethylammonium, triethylammonium, hydroxyethylammonium, dihydroxyethylammonium, 2-ethylhexylammonium, dimethylaminopropylammonium, octylammonium, laurylammonium, stearylammonium, etc.

[0074] Specific examples of the triazine derivative include the low molecular weight dispersants (a) to (d) described in Table 1.

[0075] [Table 1]

[0076] The content of the low molecular weight dispersant (B-2) is preferably 0.2% to 50% by mass, more preferably 0.2% to 30% by mass, and still more preferably 0.2% to 10% by mass in the total solid content of the conductive material dispersion. When within the above range, it is possible to achieve both dispersibility and conductivity.

[0077] <Organic solvent (C)> The organic solvent (C) of the present invention is not particularly limited and can be appropriately used. Examples of the organic solvent include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, ethylene glycol methyl ether, and diethylene glycol methyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; glycol ethers such as tetrahydrofuran, dioxane, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; and acetate esters of these monoethers, etc., hydrocarbons such as hexane, heptane, and octane; aromatics such as benzene, toluene, xylene, and cumene; esters such as ethyl acetate and butyl acetate. An appropriate one can be used according to the composition of the conductive material dispersion. Also, two or more solvents may be used. From the viewpoints of resin solubility and handleability, etc., alcohols such as isopropanol, n-butanol, and isobutanol, ketones such as methyl ethyl ketone, acetate esters of glycol ethers such as propylene glycol monomethyl ether acetate, and carboxylic acid esters such as butyl butyrate are preferred.

[0078] <Other components> In the conductive material dispersion of the present invention, if necessary, various additives such as fillers, thixotropy imparting agents, anti-aging agents, antioxidants, antifouling agents, preservatives, leveling agents, curing agents, thickeners, silane coupling agents, defoaming agents, inorganic bases, inorganic metal salts, and organic bases may be added within a range that does not interfere with the present invention.

[0079] <Conductive material dispersion> The conductive material dispersion in the present invention contains a carbon material (A), a dispersant (B), and an organic solvent (C). The conductive material dispersion can be used in applications such as electrodes for power generation and storage devices such as secondary batteries, conductive aids, antistatic materials for IC trays and molded bodies of electronic component materials for plastic and rubber products, electronic components, replacement of transparent electrodes (ITO films), electromagnetic shielding, conductive films, etc. However, from the viewpoint of improving conductivity by the formation of a laminated structure of graphite, it is particularly preferably used for applications for carbon electrodes formed by molding the conductive material dispersion into a conductive film. The carbon electrodes include, for example, electrodes for electric double layer capacitors, electrodes for non-aqueous electrolyte capacitors, electrodes for organic transistors, electrodes for power generation and storage devices such as redox flow batteries and fuel cells, electrodes for photoelectric conversion elements such as solar cells, electrodes for actuators, electrodes for electrochemical sensors, electrodes for carbon dioxide separation, recovery, and immobilization systems, etc. In particular, it can be suitably used for carbon electrodes for perovskite solar cells.

[0080] <Dispersion method> The conductive material dispersion of the present invention is preferably produced by subjecting a composition containing a dispersant, a carbon material, and a solvent to a dispersion treatment using a dispersion device to finely disperse it. Note that the dispersion treatment may arbitrarily adjust the addition timing of the materials used and may be a multi-stage treatment of two or more times.

[0081] The conductive material dispersion of the present invention preferably includes a step of dispersing by applying at least one selected from shear stress, shear stress, frictional force, and impact force. For example, methods of applying shear stress, shear stress, and frictional force, etc. by a rotating body such as a kneader or a roll mill, methods of applying shear stress, shear stress, frictional force, or impact force by a bead mill, etc., methods of applying shear stress by a high-pressure homogenizer, etc. Among them, a bead mill or a high-pressure homogenizer is preferable.

[0082] As a dispersion device utilizing the above method, a disperser commonly used for pigment dispersion or the like can be used. For example, a kneader, a two-roll mill, a three-roll mill, a planetary mixer, a ball mill, a horizontal sand mill, a vertical sand mill, an annular bead mill, an attritor, a high-shear mixer, a disper, or a high-pressure homogenizer, etc. can be mentioned. When using a high-pressure homogenizer, the pressure is preferably 60 to 150 MPa, and more preferably 60 to 120 MPa.

[0083] Dispersion methods using a dispersion device include batch dispersion, pass dispersion, circulation dispersion, etc. Any method may be used, and two or more methods may be combined. Batch dispersion is a method of performing dispersion only with the dispersion device main body without using piping or the like. Since it is easy to handle, it is preferable when producing a small quantity. Pass dispersion is a dispersion method in which the dispersion device main body is provided with a tank for supplying the liquid to be dispersed through a pipe and a tank for receiving the liquid to be dispersed, and the liquid to be dispersed is passed through (passed) the dispersion device main body. Also, circulation dispersion is a method of performing dispersion while returning the liquid to be dispersed that has passed through the dispersion device main body to the tank for supplying the liquid to be dispersed and circulating it. Since dispersion progresses as the processing time is lengthened in any of them, it is only necessary to repeat passing or circulation until the desired dispersion state is achieved, and the throughput can be increased by changing the size of the tank or the processing time. Pass dispersion is preferable in that it is easy to make the dispersion state uniform compared to circulation dispersion. Circulation dispersion is preferable in that the work and manufacturing equipment are simpler compared to pass dispersion. In the dispersion process, the crushing of aggregated particles, the loosening of the conductive material, wetting, stabilization, etc. proceed sequentially or simultaneously, and the final dispersion state differs depending on the way of progress. Therefore, it is preferable to manage the dispersion state in each dispersion process using various evaluation methods. For example, it can be managed by the method described in the examples.

[0084] As specific dispersing devices, for example, mixers such as a disper, a homomixer, or a planetary mixer; homogenizers such as "ClearMix" manufactured by M Technique Co., Ltd. or "Filmix" manufactured by PRIMIX Corporation; media type dispersers such as a paint conditioner (manufactured by Red Devil Co., Ltd.), a ball mill, a sand mill (such as "Dynomill" manufactured by Shinmaru Enterprises Co., Ltd.), an attritor, a pearl mill (such as "DCP Mill" manufactured by Eriez Co., Ltd.), or a coball mill; media-less dispersers such as a wet jet mill (such as "Genius PY" manufactured by Genius Co., Ltd., "Starburst" manufactured by Sugino Machine Co., Ltd., or "Nanomizer" manufactured by Nanomizer Co., Ltd.), "Clear SS-5" manufactured by M Technique Co., Ltd., or "MICROS" manufactured by Nara Machinery Co., Ltd.; or other roll mills, etc. may be mentioned, but it is not limited thereto.

[0085] For example, when using a media type disperser, it is preferable to use a disperser in which an agitator and a vessel are made of ceramic or resin, or a disperser in which a metal agitator and the surface of the vessel are treated by tungsten carbide spraying or resin coating, etc. And as the media, it is preferable to use glass beads, or ceramic beads such as zirconia beads or alumina beads. The dispersing device may use only one type, or may be used in combination with a plurality of types of devices.

[0086] <Conductive film> The conductive film in the present invention can be formed on a substrate using a conductive material dispersion. The conductive film can be suitably used as a carbon electrode such as the above-described electrode for a power generation / storage device, an electrode for a photoelectric conversion element, an electrode for an actuator, an electrode for an electrochemical sensor, an electrode for a carbon dioxide separation / recovery / immobilization system, etc.

[0087] <Substrate> The substrate used for forming the conductive film is not particularly limited, and examples include metal substrates and metal foil substrates using metals such as stainless steel, aluminum, nickel, titanium, gold, silver, copper, etc. or alloys thereof; plastic-based substrates such as polyvinyl chlorides, polyesters, polycarbonates, acrylates, etc.; glass substrates such as soda-lime glass, low-alkali borosilicate glass, and alkali-free aluminoborosilicate glass, etc.

[0088] <Coating method> As a method for coating the conductive material dispersion on the substrate, there is no particular limitation and known methods can be used. Specifically, examples include die coating method, dip coating method, roll coating method, doctor coating method, knife coating method, spray coating method, gravure coating method, screen printing method, or electrostatic coating method, etc. As drying methods, examples include air drying, or drying using a blower dryer, hot air dryer, infrared heater, far-infrared heater, etc., but it is not particularly limited thereto.

[0089] After coating, rolling treatment may be performed using a flat plate press, calendar roll, etc. The thickness of the formed film is, for example, 1 μm or more and 500 μm or less, preferably 10 μm or more and 50 μm or less.

Examples

[0090] Examples are given below to explain the present invention more specifically. The present invention is not limited to the following examples as long as it does not exceed the gist thereof. Unless otherwise specified, "parts" represents "parts by mass" and "%" represents "% by mass".

[0091] <Synthesis of polymer type dispersant (B-1)> (Synthesis Example 1) (Synthesis of polymer type dispersant (B-1-1)) Into a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, 85 parts of methyl methacrylate, 10 parts of tert-butyl methacrylate, 5 parts of cyclohexyl acrylate, and 25 parts of propylene glycol monomethyl ether acetate were charged and replaced with nitrogen gas. The inside of the reaction vessel was heated and stirred at 50 °C, and 6 parts of 3-mercapto-1,2-propanediol were added. The temperature was raised to 90 °C, and a solution prepared by adding 0.1 part of 2,2'-azobisisobutyronitrile to 45 parts of propylene glycol monomethyl ether acetate was added while reacting for 7 hours. It was confirmed by solid content measurement that 95% had reacted, and a vinyl polymer having two hydroxyl groups at one end was obtained. 9.5 parts of pyromellitic dianhydride, 25 parts of propylene glycol monomethyl ether acetate, and 0.4 part of 1,8-diazabicyclo-[5.4.0]-7-undecene as a catalyst were added and reacted at 100 °C for 7 hours. It was confirmed by acid value measurement that 98% or more of the acid anhydride was half-esterified, and the reaction was terminated. Propylene glycol monomethyl ether acetate was added for dilution so that the solid content became 50% by solid content measurement, and a polymeric dispersant (B-1-1) with an acid value of 42 mgKOH / g and a weight average molecular weight of 8500 was obtained. The polymeric dispersant (B-1-1) is a dispersant obtained by adding the hydroxyl groups in a vinyl polymer having two hydroxyl groups at one end to a tetracarboxylic dianhydride.

[0092] (Synthesis Example 2) (Synthesis of polymeric dispersant (B-1-2)) Into a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, 62.6 parts of 1-dodecanol, 287.4 parts of ε-caprolactone, and 0.1 part of monobutyltin(IV) oxide as a catalyst were charged, replaced with nitrogen gas, and then heated and stirred at 120 °C for 4 hours. It was confirmed by solid content measurement that 98% had reacted, and the first step was completed. The number average molecular weight of this reaction product was 1350, and the weight average molecular weight was 1890.

[0093] To the above reaction product, 36.6 parts of pyromellitic dianhydride were added and reacted at 100 °C for 5 hours. By measuring the acid value, it was confirmed that 97% or more of the acid anhydride was half-esterified, and the second step was completed. The obtained dispersant had a number average molecular weight of 2430, a weight average molecular weight of 3590, and an acid value of 49 mg KOH / g.

[0094] The resin was evaluated as follows. (Weight average molecular weight (Mw) of the resin) The weight average molecular weight (Mw) of the resin was the weight average molecular weight (Mw) in terms of polystyrene measured using a GPC (HLC-8120GPC, manufactured by Tosoh Corporation) equipped with an RI detector and using TSKgel columns (manufactured by Tosoh Corporation) with THF as the eluent.

[0095] (Acid value of the resin) To 0.5 - 1.0 part of the resin solution, 80 ml of acetone and 10 ml of water were added and stirred until uniformly dissolved. Using a 0.1 mol / L aqueous KOH solution as the titrant and an automatic titrator (AT-710S, manufactured by Kyoto Electronic Industry Co., Ltd.), the acid value of the resin solution was measured. Then, from the acid value of the resin solution and the solid content concentration of the resin solution, the acid value per solid content of the resin was calculated.

[0096] (Preparation of conductive material dispersion) (Example 1-1) 19.0 parts of A-1-1 as graphite, 1.0 part of A-2-1 as a carbon material other than graphite, 0.5 part of B-1-3 as a dispersant, and 79.5 parts of C-1 as an organic solvent were put into a mixer and mixed, and then put into a bead mill for dispersion to obtain a conductive material dispersion (D-1). The obtained conductive material dispersion was evaluated by the following method. The evaluation results are shown in Table 1.

[0097] (Examples 1-2 to 1-65, Comparative Examples 1-1 to 1-10) According to the compositions shown in Table 2, in the same manner as in Example 1-1, each conductive material dispersion (D-2 to D-75) was obtained.

[0098] (Method for evaluating the dispersibility of the conductive material dispersion) As an evaluation of the dispersibility of the conductive material, the viscosity value was measured. The measurement of the viscosity value was carried out immediately at a B-type viscometer rotor rotation speed of 50 rpm after sufficiently stirring the CNT dispersion with a spatula at a temperature of 25 °C of the CNT dispersion using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., "BL"). The rotor used for the measurement was No. 1 when the viscosity value was less than 100 mPa·s, No. 2 when it was 100 or more and less than 500 mPa·s, No. 3 when it was 500 or more and less than 2,000 mPa·s, and No. 4 when it was 2,000 or more and less than 10,000 mPa·s. The lower the viscosity, the better the dispersibility, and the higher the viscosity, the worse the dispersibility. Those in which the obtained dispersion was clearly separated or sedimented were regarded as having poor dispersibility. Judgment criteria ◎: Less than 300 mPa·s 〇: 300 mPa·s or more and less than 700 mPa·s △: 700 mPa·s or more and less than 1500 mPa·s ×: 1500 mPa·s or more, sedimentation or separation

[0099]

Table 2

[0100]

Table 2

[0101] The raw materials described in Table 2 are as follows. <Carbon material (A)> (Graphite (A-1)) · A-1-1: UP-20 (manufactured by Nippon Graphite Co., Ltd., flaky graphite, average particle size 20 μm) · A-1-2: UP-5 (manufactured by Nippon Graphite Co., Ltd., flaky graphite, average particle size 5 μm) · A-1-3: CB-100 (manufactured by Nippon Graphite Co., Ltd., flaky graphite, average particle size 80 μm) · A-1-4: BF15-AK (manufactured by Chogetsu Graphite Co., Ltd., flaky graphite, average particle size 15 μm) · A-1-5: CGB-20 (manufactured by Nippon Graphite Co., Ltd., spherical graphite, average particle size 20 μm) (Carbon materials other than graphite (A-2)) · A-2-1: JENOTUBE10B (manufactured by JEIO, multi-walled CNT, average outer diameter 10 nm) · A-2-2: JENOTUBE6A (manufactured by JEIO, multi-walled CNT, average outer diameter 6 nm) · A-2-3: TUBALL (manufactured by OCSiAl, single-walled CNT, average outer diameter 1.7 nm) · A-2-4: VGCF-H (manufactured by RESONAC, vapor-grown carbon fiber, average outer diameter 6 nm) · A-2-5: EC-600JD (manufactured by Lion Specialty Chemicals, Ketjen black, average particle size 34 nm) · A-2-6: Denka black Li-400 (manufactured by Denka, acetylene black, average particle size 48 nm) · A-2-7: #3050B (manufactured by Mitsubishi Chemical, furnace black, average particle size 50 nm) <Dispersant (B)> (Polymeric dispersant (B-1)) · B-1-3: Esrec BL-S (manufactured by Sekisui Chemical Co., Ltd., polyvinyl acetal resin) · B-1-4: PVP K30 (manufactured by Nippon Shokubai, polyvinyl pyrrolidone) · B-1-5: Therban #1707 (manufactured by ARLANXEO, hydrogenated acrylonitrile butadiene rubber resin) · B-1-6: DISPERBYK-161 (manufactured by BYK-Chemie, polyurethane resin) (Low-molecular-weight dispersant (B-2)) · (B-2-1): Dispersant (a) · (B-2-2): Dispersant (b) · (B-2-3): Dispersant (c) · (B-2-4): Dispersant (d) <Resins other than dispersant (B)> · Comparative resin: Novatec LLUJ580 (manufactured by Nippon Polyethylene Co., Ltd., polyethylene resin) <Organic solvent (C)> · C-1: Isopropyl alcohol · C-2: n-Butyl alcohol · C-3: Isobutyl alcohol ·C-4: Butyl butyrate ·C-5: Propylene glycol monomethyl ether acetate ·C-6: Methyl ethyl ketone

[0102] <Fabrication of conductive film> (Example 2-1) The conductive material dispersion (D-1) was coated on a glass substrate with a thickness of 1.1 mm using an applicator. Next, the substrate was dried on a hot plate at 80 °C for 60 minutes to fabricate a conductive film (E-1) with a film thickness of 20 μm. The thickness of the conductive film was calculated by subtracting the film thickness of the glass substrate from the average value measured at three points in the conductive film using a film thickness gauge (manufactured by NIKON, DIGIMICROMH-15M).

[0103] (Examples 2-2 to 2-65, Comparative Examples 2-1 to 2-10) According to the compositions shown in Table 3, each conductive film (E-2 to E-75) was obtained in the same manner as in Example 2-1.

[0104]

Table 3

[0105]

Table 3

[0106] (Method for evaluating conductivity of conductive film) The surface resistivity (Ω / □) of the conductive film fabricated above was measured using Loresta GP, MCP-T610 manufactured by Mitsubishi Chemical Analytech Co., Ltd. Three samples of the same conductive film were fabricated and measured, and the surface resistivity (Ω / □) at a film thickness of 20.0 μm was calculated by regression analysis of the film thickness and the surface resistivity (Ω / □), and judged according to the following criteria. ◎: Less than 15.0 Ω / □ (excellent) ○: 15.0 Ω / □ or more and less than 20.0 Ω / □ (good) △: 20.0 Ω / □ or more and less than 30.0 Ω / □ (practically applicable) ×: 30.0 Ω / □ or more (defective)

[0107] (Method for Evaluating Adhesion of Conductive Film) The adhesion of the conductive film prepared above to the substrate of the coating film was evaluated by an adhesion (cross-cut method) test according to JIS K5600-5-6, and 25 cuts with a width of 1 mm were made in a grid pattern. An adhesive tape was attached to these cuts and immediately peeled off, and the number of peeled-off conductive film pieces was counted and judged according to the following criteria. ◎: Number of peeled-off grid squares is 0 (excellent) 〇: Number of peeled-off grid squares is 1 or more and less than 5 (good) △: Number of peeled-off grid squares is 5 or more and less than 10 (practically acceptable) ×: Number of peeled-off grid squares is 10 or more (defective)

[0108] (Method for Evaluating Thick Film Coating Property of Conductive Film) (Residual Film Ratio) The thickness of the conductive film prepared above was measured using a film thickness gauge (manufactured by NIKON, DIGIMICROM H-15M), and the film thickness was calculated by subtracting the film thickness of the glass substrate from the average value measured at three points in the conductive film. The residual film ratio was calculated by dividing the obtained film thickness by the coating film thickness of the applicator used (corresponding to the wet film thickness of the conductive film before drying), and judged according to the following criteria. The higher the residual film ratio, the more possible it is to apply a thicker film when compared at the same wet film thickness. Good: 6% or more Practically acceptable: 3% or more and less than 6% Defective: 3% or less (Appearance Evaluation) Furthermore, the appearance was evaluated according to the following criteria. Good: No cracks, unevenness, roughness, coating unevenness, etc. are visible on the appearance, and the whole is smooth. Practically acceptable: Cracks, unevenness, roughness, coating unevenness, etc. partially occur on the appearance. Defective: Cracks, unevenness, roughness, coating unevenness, etc. occur on the whole appearance. (Thick Film Coating Property) As the thick film coating property, both results of the residual film ratio and the appearance evaluation were combined and judged according to the following criteria. ◎: Both the residual film ratio and the appearance evaluation are good (excellent) 〇: Residual film ratio is practically acceptable, appearance evaluation is good (good) △: Good residual film rate, appearance evaluation practical (practical acceptable) ×: Poor in both residual film rate and appearance evaluation (poor)

[0109] As shown in Table 3, a conductive material dispersion comprising a carbon material (A), a dispersant (B), and an organic solvent (C), which is a feature of the present invention, wherein the carbon material (A) includes graphite (A-1) and a carbon material other than graphite (A-2), the graphite (A-1) includes flaky graphite, the content of the carbon material (A) is 50% by mass or more in the total solid content of the conductive material dispersion, and the content of the graphite (A-1) is 65 to 99% by mass in 100% by mass of the carbon material (A). The conductive film obtained using the conductive material dispersion is excellent in conductivity and shows good results in both adhesion and thick film coating properties.

[0110] As described above, in the conductive material dispersion characterized by containing the carbon material (A), the dispersant (B), and the organic solvent (C) of the present invention and the conductive film obtained using the same, by selectively controlling the content of the carbon material, a highly conductive and thick film conductive film excellent in adhesion can be provided.

Claims

1. A conductive material dispersion containing a carbon material (A), a dispersant (B), and an organic solvent (C), wherein the carbon material (A) includes graphite (A-1) and a carbon material other than graphite (A-2), the graphite (A-1) includes flaky graphite, the content of the carbon material (A) is 50% by mass or more in the total solid content of the conductive material dispersion, and the content of the graphite (A-1) is 65 to 99% by mass in 100% by mass of the carbon material (A). A conductive material dispersion characterized by the above.

2. The conductive material dispersion according to claim 1, wherein the carbon material (A-2) other than graphite includes carbon fibers.

3. The conductive material dispersion according to claim 1, wherein the dispersant (B) includes a polymer-type dispersant (B-1) or a low-molecular-type dispersant (B-2), and the polymer-type dispersant (B-1) includes a vinyl-based resin or a polylactone-based resin.

4. The conductive material dispersion according to claim 1, which is for a carbon electrode.

5. A conductive film obtained by using the conductive material dispersion according to any one of claims 1 to 4.

6. A method for producing a conductive material dispersion, comprising a step of dispersing a composition containing a carbon material (A), a dispersant (B), and an organic solvent (C), wherein the carbon material (A) includes graphite (A-1) and a carbon material other than graphite (A-2), the graphite (A-1) includes flaky graphite, the content of the carbon material (A) is 50% by mass or more in the total solid content of the conductive material dispersion, and the content of the graphite (A-1) is 65 to 99% by mass in 100% by mass of the carbon material (A), by applying at least one selected from the group consisting of shear stress, shear stress, frictional force, and impact force.

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