Conductive composition and conductive film

Abstract

To provide a conductive composition that has excellent dispersibility and can form an excellent conductive network, offering excellent conductivity and durability, and to provide a conductive film.SOLUTION: A conductive composition contains a conductive carbon material and a binder resin. The conductive carbon material contains a conductive material, and a conduction aid having a greater specific surface area than that of the conductive material. The conduction aid contains a boron-containing carbon material. The conductive composition can be used to form a coating film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a conductive composition and a conductive film, and more particularly to a conductive composition containing a boron-containing carbon material as a conductive additive, and a conductive film obtained using the same. [Background technology]

[0002] Recent advances in electronics have been remarkable, and the conductive materials used in various electronic devices are also required to be smaller, lighter, and less expensive, while also offering longer lifespans in a variety of operating environments. For example, when manufacturing the wiring for electronic device substrates or the wiring that connects electronic devices, conductive compositions with good conductivity are required. However, conductive compositions that use metal fillers such as silver or copper are commonly used, posing significant challenges in terms of cost and durability. Meanwhile, various studies have been conducted on conductive compositions that use metal-free conductive carbon materials, but due to their insufficient conductivity, their use has been limited to semiconductive applications such as antistatic applications.

[0003] Furthermore, regarding conductive carbon materials, various conductive materials with low volume resistivity, such as graphite and carbon nanotubes, have been investigated to date. The volume resistivity of these conductive carbon materials is 10 -2 Although carbon materials exhibit high electrical conductivity of less than Ω·cm, many of these highly conductive carbon materials have a large specific surface area, making them difficult to uniformly mix and disperse in resins and solvents. As a result, poor contact occurs between the carbon materials in coatings and molded articles obtained from conductive compositions containing conductive carbon materials, resins, solvents, etc., and the electrical conductivity is not fully realized (Patent Documents 1 to 3). To solve this problem, a conductive composition has been disclosed in which a conductive network between carbon materials in a coating film is developed and graphite and carbon black are used together and dispersed in a binder (Patent Document 4). However, this method has the problem that the conductivity of carbon black, which acts as a conductive additive, is low compared to graphite, and the large specific surface area of carbon black makes mixing and dispersion difficult, making it difficult to obtain a coating film with good conductivity and durability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-7740 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-60413 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-20515 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-238881 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a conductive composition that has excellent dispersibility and is capable of forming a good conductive network, and a conductive film that has excellent conductivity and durability. [Means for solving the problem]

[0006] That is, the present invention relates to a conductive composition comprising a conductive carbon material (A) and a binder resin (B), wherein the conductive carbon material (A) comprises a conductive material and a conductive assistant having a larger specific surface area than the conductive material, and the conductive assistant comprises a boron-containing carbon material (A-1).

[0007] The present invention also relates to the conductive composition according to claim 1, which contains 0.1 to 50 mass % of the boron-containing carbon material (A-1) relative to 100 mass % of the conductive carbon material (A).

[0008] The present invention also provides a boron-containing carbon material (A-1) having a specific surface area of 5 to 700 m 2 / g.

[0009] The present invention also relates to the electrically conductive composition, wherein the boron-containing carbon material (A-1) has an average d002 interplanar spacing of 0.34 nm or more as determined by X-ray diffraction.

[0010] The present invention also relates to the aforementioned conductive composition, wherein the boron content of the boron-containing carbon material (A-1) is 0.005 to 15 mol %.

[0011] The present invention also relates to the conductive composition, wherein the conductive material comprises a carbon material (A-2), and the carbon material (A-2) comprises graphite.

[0012] The present invention also relates to the conductive composition, wherein the carbon material (A-2) contains boron.

[0013] The present invention also relates to the conductive composition, wherein the carbon material (A-2) has a boron content of 0.005 to 15 mol %.

[0014] The present invention also relates to a conductive film obtained by using the conductive composition. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a conductive composition that has excellent dispersibility and is capable of forming a good conductive network, and a conductive film that has excellent conductivity and durability. DETAILED DESCRIPTION OF THE INVENTION

[0016] The conductive composition of the present invention comprises a conductive carbon material (A) and a binder resin (B), wherein the conductive carbon material (A) comprises a conductive material and a conductive assistant having a larger specific surface area than the conductive material, and the conductive assistant comprises a boron-containing carbon material (A-1). By using a combination of the conductive material and the conductive assistant that contains a boron-containing carbon material and has a larger specific surface area than the conductive material, a resin composition with excellent mixing and dispersibility can be obtained, and at the same time, it is possible to strengthen the conductive network between the carbon materials in the coating film and improve packing, thereby achieving excellent conductivity and durability. The present invention will be described in detail below.

[0017] <Conductive carbon material (A)> The conductive carbon material (A) comprises a conductive material and a conductive auxiliary having a larger specific surface area than the conductive material. In this specification, the conductive material refers to a carbon material (conductive filler) that contributes to conductivity, and the conductive auxiliary refers to a conductive filler having a larger specific surface area than the conductive material, which, when used together with the conductive material, improves the contact and bonding of the conductive material and contributes to high conductivity of the coating film. The conductive material and conductive assistant are not particularly limited as long as they are conductive carbon materials and satisfy the above requirements.

[0018] <Conductive additive> [Boron-containing carbon materials (A-1)] The conductive additive contains a boron-containing carbon material (A-1). The boron-containing carbon material (A-1) is a carbon material whose basic skeleton is a hexagonal carbon network in which carbon atoms are covalently bonded in a hexagonal network pattern to form a network plane, and which has physical and chemical interactions (bonds) between its structural units, is doped with boron to substitute for at least a portion of the carbon, and may contain hetero elements such as nitrogen and phosphorus, or base metal elements.

[0019] As will be described later, the boron-containing carbon material (A-1) has improved carrier density and / or mobility by being doped with boron, and therefore the volume resistivity of the powder is lower than that of a carbon material that is not doped with boron. Furthermore, compared with carbon materials that are not doped with boron, the boron-containing carbon material (A-1) exhibits a change in surface condition, resulting in, for example, higher wettability with resins and solvents and a smaller specific surface area. This not only improves the electrical conductivity of the raw material itself, but also results in a resin composition with excellent mixing and dispersibility, which is believed to strengthen the conductive network between the carbon materials in the coating film. Furthermore, the improved wettability is believed to change the interaction with the binder resin, exposing the boron-containing carbon material (A-1), which acts as a conductive additive, to the resin surface, thereby reducing the contact resistance of the conductive material. Due to these effects, the use of the boron-containing carbon material (A-1) as a conductive additive is believed to enable the formation of a coating film with extremely excellent electrical conductivity. Furthermore, as described above, the boron-containing carbon material (A-1) has improved wettability to resins and solvents, which improves the dispersibility of conductive additives with a large specific surface area, which are particularly difficult to disperse, and allows the formation of a resin composition in which the conductive additives are uniformly dispersed. This is thought to further improve the uniformity of the coating film and the packing of the conductive additive (the conductive additive is densely packed), thereby improving durability.

[0020] Changes in the surface state of the boron-containing carbon material (A-1) can be confirmed, for example, by changes in the zeta potential. In the case of a composition obtained by mixing the carbon material (A-1), a resin, and a solvent, it is believed that the wettability of the resin and the solvent increases as the zeta potential decreases (the absolute value of the negative potential increases) due to boron doping. The zeta potential can be determined by a method in accordance with JIS Z8836:2017.

[0021] From the viewpoints of electrical conductivity and durability, the content of the boron-containing carbon material (A-1) is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 10 to 30 mass %, based on 100 mass % of the conductive carbon material (A).

[0022] When the mass ratio of the boron-containing carbon material (A-1) is 0.1 mass% or more, a conductive network is sufficiently formed, resulting in excellent conductivity and durability.When the mass ratio of the boron-containing carbon material (A-1) is 50 mass% or less, contact between the carbon materials (A-2) is not inhibited, resulting in excellent conductivity.

[0023] The boron-containing carbon material (A-1) is not particularly limited, and examples thereof include carbon black, activated carbon, graphite, conductive carbon fibers (carbon nanotubes, carbon nanofibers, etc.), carbon nanohorns, graphene, graphene nanoplatelets, nanoporous carbon, etc. From the viewpoints of specific surface area and particle size, carbon black is preferred.

[0024] The specific surface area of the boron-containing carbon material (A-1) is specifically the specific surface area (BET) calculated from the amount of nitrogen adsorbed, and is preferably 5 m 2 / g or more, 700m 2 / g or less, more preferably 20m 2 / g or more, 500m 2 / g or less, more preferably 20m 2 / g or more, 300m 2 / g or less, particularly preferably 110m 2 / g or more, 300m 2 / g or less. The specific surface area is 5m 2 When the solubility is 700m / g or more, sufficient conductivity can be obtained in the coating film. 2 When the content is 0.01 to 0.1g, mixing and dispersion are facilitated, and a coating film having good conductivity and durability can be obtained. In addition, when the content is within the above range, the effect of improving wettability to resins and solvents due to boron doping can be easily obtained.

[0025] (X-ray diffraction measurement) In X-ray diffraction (XRD) measurements of boron-doped carbon materials obtained using CuKα radiation as an X-ray source, the (002) diffraction peak, which appears at a diffraction angle (2θ) of approximately 24.0 to 27.0°, confirms that the material is a carbon material with a hexagonal carbon mesh plane as its basic skeleton. Furthermore, the average interplanar distance d002 calculated from the obtained peak is preferably 0.33 nm or greater, more preferably 0.34 nm or greater. While the smaller the average interplanar distance d002 of typical carbon materials, the better their electrical conductivity. When using a boron-containing carbon material as a conductive additive, the optimal average interplanar distance d002 is 0.33 nm or greater, particularly 0.34 nm or greater. Increasing the average interplanar distance d002 suppresses graphitization of the carbon material, improves its dispersibility in resins and solvents, and allows for the production of coating films with excellent electrical conductivity.

[0026] The boron content in the boron-containing carbon material (A-1) (the boron content in the entire carbon material) is not particularly limited, but is preferably 0.005 to 15 mol%, more preferably 0.01 to 10 mol%, and particularly preferably 0.1 to 5 mol%. When the boron content is 0.005 mol% or more, the boron doping effect is enhanced, while when the boron content is 15 mol% or less, the electron transfer due to excess boron is not inhibited, and a decrease in conductivity is suppressed. Therefore, when the boron content is in the range of 0.005 to 15 mol%, good conductivity can be exhibited. The boron content in the boron-containing carbon material (A-1) can be determined by methods such as ICP atomic emission spectroscopy and ICP mass spectroscopy. Examples include a measurement method conforming to JIS-R7223. The mol% boron content can be calculated by calculating the number of moles using the atomic weight of each element from the mass of each element contained in the carbon material, and then calculating the mol% from the molar ratio of each element. In addition, for boron-containing carbon materials containing elements that cannot be measured by ICP atomic emission spectroscopy, the masses of the contained elements and carbon elements can be measured in combination with measurements such as elemental analysis, and the molar ratio and mol% can be calculated from the atomic weight of each element. Typically, boron-containing carbon materials obtained by high-temperature heat treatment at 1000°C or higher volatilize or decompose almost all elements except for metals, which are difficult to volatilize or decompose. Therefore, the mol% of elements other than those detected by ICP atomic emission spectroscopy can be calculated as carbon elements.

[0027] The form of boron in the boron-containing carbon material is not particularly limited, and examples thereof include substitutional boron (BC3 type) in which boron is substituted at the position of a carbon element in a carbon skeleton, boron carbide type and boron cluster type boron (BC type, Bc type), and fully or partially oxidized boron oxide type boron (BC2O type, BCO2 type, BO3 type).

[0028] The electrical conductivity of the boron-containing carbon material (A-1) is expressed by the following formula. σ=μ×n×e (Equation 1) μ: mobility, n: carrier density, e: elementary charge (constant) According to the above formula (1), improving the conductivity requires improving the mobility and / or carrier density. By doping a carbon material with boron, the carrier density and / or mobility are improved, resulting in a carbon material with high conductivity.

[0029] (Manufacturing method) The method for producing the boron-containing carbon material (A-1) of the present invention is not particularly limited, but is preferably a method comprising the steps of mixing a carbon-based raw material (carbon source) with a boron-containing compound (boron source) and heat-treating the mixture at a high temperature of 1000°C or higher.

[0030] The raw material composition ratio of the carbonaceous raw material and the boron-containing compound for producing the boron-containing carbon material (A-1) is not particularly limited, but the ratio of the boron-containing compound to 100 parts by mass of the carbonaceous raw material is preferably 0.01 to 300 parts by mass, and more preferably 0.1 to 100 parts by mass.

[0031] The method for preparing the mixture may be any method as long as it contains at least a carbonaceous raw material and a boron-containing compound, and examples of the mixing method include dry mixing and wet mixing. As the mixing device, the following dry mixing device or wet mixing device can be used.

[0032] Examples of dry mixing devices include roll mills such as two-roll and three-roll devices, high-speed mixers such as Henschel mixers and super mixers, fluid energy mills such as micronizers and jet mills, attritors, particle composite devices manufactured by Hosokawa Micron Corporation such as "Nanocure," "Nobilta," and "Mechanofusion," and powder surface modification devices manufactured by Nara Machinery Manufacturing Co., Ltd. such as "Hybridization System," "Mechano Micros," and "Miraro."

[0033] When using a dry mixer, two or more raw materials may be directly mixed in powder form, but to prepare a more uniform mixture, one or more raw materials may be dissolved or dispersed in a small amount of solvent beforehand and then mixed. Furthermore, to improve processing efficiency, heating may be used.

[0034] Examples of wet mixing devices include mixers such as a Disper, Homomixer, or Planetary Mixer; homogenizers such as the "Clearmix" manufactured by M-Technique or the "Filmix" manufactured by PRIMIX; sand mills such as Red Devil paint conditioners, ball mills, and Shinmaru Enterprises' "Dynomill"; media-type dispersers such as an Attritor or Coball Mill; wet jet mills such as the "Genus PY" manufactured by Genus, the "Starburst" manufactured by Sugino Machine, and the "Nanomizer" manufactured by Nanomizer; media-less dispersers such as the "Clear SS-5" manufactured by M-Technique or the "Micros" manufactured by Nara Machinery Manufacturing Co., Ltd.; and other roll mills, kneaders, etc., but are not limited to these. It may be preferable to use wet mixing devices that have been treated to prevent metal contamination from the device.

[0035] For example, when using a media-type disperser, it is preferable to use a disperser whose agitator and vessel are made of ceramic or resin, or a disperser whose metallic agitator and vessel surfaces are treated with tungsten carbide thermal spraying or resin coating. It is also preferable to use ceramic beads such as glass beads, zirconia beads, or alumina beads as media. Also, when using a roll mill, it is preferable to use a ceramic roll. Only one type of dispersing device may be used, or multiple types of devices may be used in combination.

[0036] Furthermore, when the raw materials are not uniformly dissolved, a general dispersant may be added together to disperse and mix the raw materials in order to improve the wettability and dispersibility of each raw material in the solvent.

[0037] The dispersant functions effectively as a dispersant for each raw material and can reduce the aggregation thereof. There are no particular limitations on the dispersant as long as it has the effect of reducing aggregation, and any conventionally known dispersant can be used. For example, dispersants such as resin-type dispersants, surfactants, and pigment derivatives can be used.

[0038] Examples of resin-type dispersants include polyvinyl resins, polyurethanes, polyesters, polyethers, cellulose resins such as carboxymethyl cellulose, formalin condensates, silicones, and composite polymers thereof. Furthermore, two or more of these resin-type dispersants may be used in combination. Polyvinylpyrrolidone, polyvinyl alcohol, polystyrene sulfonic acid, polyacrylic acid, carboxymethyl cellulose, etc. are preferred.

[0039] In the method of heat treating the mixture, the heating temperature is preferably 1,000 to 3,200°C, more preferably 1,500 to 3,000°C, although this varies depending on the type and amount of the carbonaceous raw material and the boron-containing compound used as raw materials.

[0040] The heating time is not particularly limited, but is usually preferably from 30 minutes to 10 hours.

[0041] The atmosphere in the heat treatment step is preferably an inert gas atmosphere such as nitrogen or argon, or a vacuum atmosphere, in order to prevent oxidation of the raw materials.

[0042] Furthermore, the heat treatment step may not only be carried out in one stage under a fixed atmosphere and temperature, but may also be carried out in multiple stages by changing the atmosphere and temperature each time.

[0043] (carbon-based raw materials) Inorganic carbonaceous raw materials are preferred as carbonaceous raw materials for producing the boron-containing carbon material of the present invention. Specific examples of inorganic carbonaceous raw materials include carbon black (furnace black, acetylene black, ketjen black, medium thermal carbon black), activated carbon, graphite, carbon nanotubes, carbon nanofibers, carbon nanohorns, graphene, graphene nanoplatelets, nanoporous carbon, carbon fibers, and charcoal. Among the above carbonaceous raw materials, the size and lamination structure of the carbon hexagonal mesh plane vary depending on the type and manufacturer. Various physical properties, such as crystallinity, particle size, shape, BET specific surface area, pore volume, pore size, bulk density, DBP oil absorption, surface acidity, surface hydrophilicity, and electrical conductivity, as well as cost, vary. Therefore, an optimal material can be selected depending on the intended use and required performance. While the carbonaceous material is not particularly limited, carbon black is more preferred in terms of particle size and specific surface area, for example. In addition, conductive carbon fibers (carbon nanotubes, carbon nanofibers, carbon fibers), fullerenes, graphene, graphene nanoplatelets, etc. can be used alone or in combination of two or more kinds.

[0044] Carbon black can be produced singly or in combination of two or more types, including furnace black, which is produced by continuously pyrolyzing a gaseous or liquid raw material in a reactor, particularly ketjen black, which is made from ethylene heavy oil, channel black, which is produced by burning a raw material gas and then quenching it by applying the flame to the bottom surface of a channel steel, and thermal black, which is obtained by periodically repeating combustion and pyrolysis of a gas raw material, particularly acetylene black, which is made from acetylene gas. Conventional oxidation-treated carbon black and hollow carbon can also be used.

[0045] Carbon oxidation is a process that involves treating carbon at high temperatures in air or secondary treatment with nitric acid, nitrogen dioxide, ozone, etc., to directly introduce (covalently bond) oxygen-containing polar functional groups, such as phenol groups, quinone groups, carboxy groups, and carbonyl groups, onto the carbon surface, and is commonly performed to improve the dispersibility of carbon. However, since the conductivity of carbon generally decreases as the amount of functional groups introduced increases, it is preferable to use carbon that has not been subjected to oxidation treatment.

[0046] The specific surface area of carbon black is 20m 2 / g or more, 1500m 2 / g or less, preferably 50m 2 / g or more, 1500m 2 / g or less, more preferably 100m 2 / g or more, 1500 m 2 It is desirable to use a material with a specific surface area of 20m / g or less. 2 When carbon black with a conductivity below 1500m / g is used, it may be difficult to obtain sufficient conductivity. 2 / Carbon black exceeding this value may be difficult to obtain as a commercially available material.

[0047] The particle size of the carbon black used is preferably 0.005 to 1 μm, particularly preferably 0.01 to 0.2 μm, in terms of primary particle size, where the primary particle size is the average particle size measured with an electron microscope or the like.

[0048] Examples of commercially available carbon black include Tokablack #4300, #4400, #4500, and #5500 manufactured by Tokai Carbon Co., Ltd., Printex L manufactured by Degussa Corporation, and Raven 7000, 5750, 5250, 5000ULTRAIII, and 500 manufactured by Colombian. 0ULTRA, Conductex SCULTRA, Conductex 975ULTRA, PUERBLACK 100, 115, 205, Mitsubishi Chemical Corporation #2350, #2400B, #2600B, #3050B, #3030B, #3230B, #3350B, #3400B, #5400B, Cabot Corporation MONARCH 1400, 1300, 900, Vulcan XC-72R, BlackPearls 2000 and furnace blacks such as Ensaco 250G, Ensaco 260G, Ensaco 350G, and Super P-Li manufactured by TIMCAL Corporation), ketjen blacks such as EC-300J and EC-600JD manufactured by Lion Corporation, and acetylene blacks such as Denka Black, Denka Black HS-100, and FX-35 manufactured by Denki Kagaku Kogyo Co., Ltd., but are not limited to these, and two or more types may be used in combination.

[0049] Conductive carbon fibers are preferably obtained by firing petroleum-derived raw materials, but those obtained by firing plant-derived raw materials can also be used. Carbon nanotubes are classified into single-walled carbon nanotubes, which have a single graphene sheet and a diameter in the nanometer range, and multi-walled carbon nanotubes, which have multiple graphene sheets. Therefore, the diameter of multi-walled carbon nanotubes is larger, at 30 nm, compared to the 0.7-2.0 nm of typical single-walled carbon nanotubes.

[0050] Examples of commercially available conductive carbon fibers and carbon nanotubes include vapor grown carbon fibers such as VGCF manufactured by Showa Denko K.K., single-walled carbon nanotubes such as EC1.0, EC1.5, EC2.0, and EC1.5-P manufactured by Meijo Nano Carbon Co., Ltd., FloTube9000, FloTube9100, FloTube9110, and FloTube9200 manufactured by CNano, NC7000 manufactured by Nanocyl, and 100T manufactured by CNano. Commercially available graphene-based carbons include, but are not limited to, graphene nanoplatelets xGnP-C-300, xGnP-C-500, xGnP-C-750, xGnP-M-5, xGnP-M-15, xGnP-M-25, xGnP-H-5, xGnP-H-15, and xGnP-H-25 manufactured by XG Sciences. Among these, carbon black is preferred as a commercially available carbonaceous raw material from the viewpoints of conductivity and cost.

[0051] The carbonaceous raw material for producing the boron-containing carbon material of the present invention can be not only inorganic carbonaceous raw materials but also organic carbonaceous raw materials that become carbon particles after heat treatment. Specific organic materials include phenolic resins, polyimide resins, polyamide resins, polyamideimide resins, polyacrylonitrile resins, polyaniline resins, phenol-formaldehyde resins, polyimidazole resins, polypyrrole resins, polybenzimidazole resins, melamine resins, pitch, coke, lignite, polycarbodiimide, biomass, proteins, humic acid, and derivatives thereof. Among these, coke and pitch, which are also used as raw materials for graphite, are preferred.

[0052] (Boron-containing compounds) Next, a boron-containing compound used in the production of a boron-containing carbon material will be described. The boron-containing compound is not particularly limited, but may be BC (B 12 C3), B 12 boron carbides such as C2(BC); boron oxides such as BCO, BCO2, BO2, BO3, BO3, and BO5; boron nitrides such as BN; metal borides such as AlB2, CoB, FeB, MgB2, NiB, and TiB2; boron oxoacids such as orthoboric acid, metaboric acid, and tetraboric acid; boranes such as monoborane, diborane, and decaborane; boric acid esters such as trimethyl borate and triethyl borate, substituted boranes such as triethylborane and triphenylborane, and boron acids such as phenylboronic acid and phenylboronic acid esters.

[0053] [Carbon materials (A-2)] The conductive material as the conductive carbon material (A) preferably contains a carbon material (A-2). The carbon material (A-2) is not particularly limited, but examples thereof include carbon black (furnace black, acetylene black, ketjen black, medium thermal carbon black), activated carbon, graphite, carbon nanotubes, carbon nanofibers, carbon nanohorns, graphene, graphene nanoplatelets, nanoporous carbon, and carbon fibers, with graphite being preferred. From the viewpoints of electrical conductivity and durability, the content of the carbon material (A-2) is preferably in the range of 50 to 99.9 mass %, and more preferably in the range of 70 to 90 mass %, based on 100 mass % of the conductive carbon material (A).

[0054] In addition, the carbon material (A-2) has a specific surface area of 100 m 2 / g or less, and 2 / g or less is more preferable, and 2 / g or less is even more preferable. By using a carbon material (A-2) having a small specific surface area in combination with a boron-containing carbon material (A-1) having a larger specific surface area, the contact and adhesion of the carbon material (A-2) are improved, and a coating film with excellent conductivity can be obtained.

[0055] From the viewpoint of electrical conductivity, the carbon material (A-2) preferably contains boron. The boron content in the carbon material (A-2) (the boron content in the entire carbon material) is not particularly limited, but is preferably 0.005 to 15 mol%, more preferably 0.01 to 10 mol%, and particularly preferably 0.1 to 5 mol%. A boron content of 0.005 mol% or more enhances the boron doping effect, while a boron content of 15 mol% or less prevents the excessive boron from inhibiting electron transfer and suppresses a decrease in electrical conductivity. Therefore, a boron content in the range of 0.005 to 15 mol% can exhibit good electrical conductivity.

[0056] <Binder resin (B)> The mass ratio of the conductive material (A) to the binder resin (B) is preferably 95:5 to 60:40, and more preferably 80:20 to 60:40. When the mass ratio of the binder resin is 5 or more, the conductive film has excellent adhesion. On the other hand, when the mass ratio of the binder resin is 40 or less, contact between the carbon materials in the conductive film is not inhibited, resulting in excellent conductivity.

[0057] The binder resin may include one or more selected from the group consisting of polyurethane resins, polyamide resins, acrylonitrile resins, acrylic resins, butadiene resins, polyvinyl resins, polyvinyl butyral resins, polyolefin resins, polyester resins, polystyrene resins, EVA resins, polyvinylidene fluoride resins, polytetrafluoroethylene resins, silicone resins, polyether resins, and cellulose resins such as carboxymethyl cellulose. However, the binder resin is not limited to these resins. One type of binder resin may be used alone, or two or more types may be used in combination. From the viewpoints of volume resistivity, adhesion to the substrate, and durability, the binder resin preferably contains at least one resin selected from the group consisting of polyurethane-based, polyamide-based, and polyester-based resins, and polyurethane-based resins are more preferred. Furthermore, the binder resin is preferably one that softens or flows appropriately when the conductive composition is printed or coated on the substrate and then pressed or hot-pressed (hereinafter referred to as "hot" pressing). By using such a resin, the resin flows in the thickness direction while substantially maintaining the planar pattern shape of the conductive film, reducing voids in the conductive film and increasing the number of contact points between the conductive carbon materials (A), resulting in a conductive film with low volume resistivity.

[0058] [Polyurethane resin] The polyurethane resin may be synthesized by any method, including, but not limited to, reacting a polyol compound (a) with a diisocyanate (b), reacting a polyol compound (a), a diisocyanate (b), and a diol compound (c) having a carboxy group to obtain a urethane prepolymer (d) having an isocyanate group, further reacting the urethane prepolymer (d) with a polyamino compound (e), or, in the above three cases, adding a reaction terminator as needed.

[0059] As the polyol compound (a), various polyether polyols, polyester polyols, polycarbonate polyols, polybutadiene glycols, or mixtures thereof, which are generally known as polyol components constituting polyurethane resins, can be used.

[0060] Examples of polyether polyols include polymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran, and the like. Examples of polyester polyols include saturated and unsaturated low molecular weight diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, and dimer diol, as well as n-butyl glycidyl ether, 2-ethyl glycidyl ether, and the like. Examples of the polyester polyols include polyester polyols obtained by dehydration condensation of alkyl glycidyl ethers of hexyl glycidyl ethers, monocarboxylic acid glycidyl esters such as versatic acid glycidyl ester, and dicarboxylic acids such as adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid, or anhydrides thereof, and polyester polyols obtained by ring-opening polymerization of cyclic ester compounds. Examples of polycarbonate polyols that can be used include 1) reaction products of diols or bisphenols with carbonate esters, and 2) reaction products of diols or bisphenols with phosgene in the presence of an alkali. Examples of carbonate esters that can be used include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, and propylene carbonate. Examples of diols include ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 3,3'-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, octanediol, butylethylpentanediol, 2-ethyl-1,3-hexanediol, cyclohexanediol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl), 2,2,8,10-tetraoxospiro[5.5] undecane, etc. Examples of bisphenols include bisphenol A, bisphenol F, and bisphenols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to bisphenols.

[0061] The number average molecular weight (Mn) of the polyol compound is determined appropriately taking into consideration the solubility of the polyurethane resin when producing the conductive composition, the durability of the conductive film formed, and the adhesive strength to the substrate, but is usually preferably in the range of 580 to 8,000, and more preferably 1,000 to 5,000. The polyol compounds may be used alone or in combination of two or more. Furthermore, a portion of the polyol compound may be replaced with low molecular weight diols, such as the various low molecular weight diols used in producing the polyol compound, as long as the performance of the polyurethane resin is not impaired.

[0062] The diisocyanate compound (b) may be an aromatic diisocyanate, an aliphatic diisocyanate, an alicyclic isocyanate, or a mixture thereof, with isophorone diisocyanate being particularly preferred. Examples of aromatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-benzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, and xylylene diisocyanate.

[0063] Examples of the aliphatic diisocyanate include butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. Examples of the alicyclic diisocyanate include cyclohexane-1,4-diisocyanate, isophorone diisocyanate, norbornane diisocyanate methyl, bis(4-isocyanatocyclohexyl)methane, 1,3-bis(isocyanatomethyl)cyclohexane, and methylcyclohexane diisocyanate.

[0064] Examples of the diol compound (c) having a carboxy group include dimethylolalkanoic acids such as dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, and dimethylolpentanoic acid, dihydroxysuccinic acid, and dihydroxybenzoic acid. Dimethylolpropionic acid and dimethylolbutanoic acid are particularly preferred from the standpoints of reactivity and solubility. The conditions for reacting a polyol compound (a), a diisocyanate (b), and a diol compound (c) having a carboxy group to obtain a urethane prepolymer (d) having an isocyanate group are not particularly limited except that an excess of isocyanate groups is used, but the equivalent ratio of isocyanate groups to hydroxyl groups is preferably within the range of 1.05 / 1 to 3 / 1, and more preferably 1.2 / 1 to 2 / 1. The reaction is usually carried out between room temperature and 150°C, and preferably between 60 and 120°C in terms of production time and control of side reactions.

[0065] The polyamino compound (e) functions as a chain extender, and in addition to ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and norbornanediamine, amines having a hydroxyl group such as 2-(2-aminoethylamino)ethanol, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, and di-2-hydroxypropylethylenediamine can also be used. Of these, isophoronediamine is preferably used.

[0066] When synthesizing a polyurethane resin by reacting a urethane prepolymer (d) having an isocyanate group with a polyamino compound (e), a reaction terminator can be used in combination to adjust the molecular weight of the resulting polyurethane resin. Examples of reaction terminators that can be used include dialkylamines such as di-n-butylamine, dialkanolamines such as diethanolamine, and alcohols such as ethanol and isopropyl alcohol.

[0067] The conditions for reacting the urethane prepolymer (d) having an isocyanate group with the polyamino compound (e) and, if necessary, a reaction terminator are not particularly limited, but when the free isocyanate groups at both ends of the urethane prepolymer are taken as 1 equivalent, the total equivalent of the amino groups in the polyamino compound (e) and the reaction terminator is preferably within a range of 0.5 to 1.3, more preferably 0.8 to 0.995. The weight average molecular weight of the polyurethane resin is preferably in the range of 5,000 to 200,000 from the viewpoint of coatability and handling.

[0068] [Polyamide resin] Polyamide resin is a general term for polymers having amide bonds obtained by various reactions such as polycondensation of dibasic acids and diamines, polycondensation of aminocarboxylic acids, or ring-opening polymerization of lactams. It includes various modified polyamides and those produced from partially hydrogenated reaction products, and can also be used as polymers partially copolymerized with other monomers or mixtures of other substances such as various additives. The polyamide resin is not particularly limited, but a dimer acid-modified polyamide resin obtained by condensation polymerization of a dibasic acid containing dimer acid as the main component and a polyamine is preferred. Dimer acids obtained by polymerizing natural monobasic unsaturated fatty acids contained in tall oil fatty acids, soybean oil fatty acids, etc., are widely used industrially as dimer acids for producing dimer acid-modified polyamide resins. However, in principle, various dicarboxylic acids, such as saturated aliphatic, unsaturated aliphatic, alicyclic, or aromatic, may also be used. Commercially available dimer acids include Haridimer 200 and 300 (manufactured by Harima Chemicals), VersaDim 228 and 216, and Empol 1018, 1019, 1061, and 1062 (manufactured by Cognis). Furthermore, hydrogenated dimer acids can also be used. Commercially available hydrogenated dimer acids include Pripol 1009 (manufactured by Croda Japan Co., Ltd.) and Empol 1008 (manufactured by Cognis). In addition to the dimer acids, various dicarboxylic acids can be used as dibasic acids to obtain polyamide resins with appropriate flexibility. Specific examples of dicarboxylic acids that can be used include oxalic acid, malonic acid, succinic acid (anhydride), maleic acid (anhydride), glutaric acid, adipic acid, vimelic acid, suberic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, 1,3- or 1,4-cyclohexanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, and 1,16-hexadecanedicarboxylic acid.

[0069] Furthermore, dibasic acids having phenolic hydroxyl groups can also be used. By using dibasic acids having phenolic hydroxyl groups, phenolic hydroxyl groups can be introduced into the side chains of the polyamide resin, making them available for reaction with the curing agent. Examples of dibasic acids having a phenolic hydroxyl group include hydroxyisophthalic acids such as 2-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, and 5-hydroxyisophthalic acid; dihydroxyisophthalic acids such as 2,5-dihydroxyisophthalic acid, 2,4-dihydroxyisophthalic acid, and 4,6-dihydroxyisophthalic acid; dihydroxyterephthalic acids such as 2-hydroxyterephthalic acid, 2,3-dihydroxyterephthalic acid, and 2,6-dihydroxyterephthalic acid; hydroxyphthalic acids such as 4-hydroxyphthalic acid and 3-hydroxyphthalic acid; and dihydroxyphthalic acids such as 3,4-dihydroxyphthalic acid, 3,5-dihydroxyphthalic acid, 4,5-dihydroxyphthalic acid, and 3,6-dihydroxyphthalic acid. Furthermore, acid anhydrides and ester derivatives such as polybasic acid methyl esters of these acids are also included. Of these, 5-hydroxyisophthalic acid is preferred from the viewpoints of copolymerizability and ease of availability.

[0070] Furthermore, in order to obtain a polyamide resin with suitable fluidity when heated, various monocarboxylic acids are used as needed, such as propionic acid, acetic acid, caprylic acid (octanoic acid), stearic acid, and oleic acid. Examples of polyamines used as reactants in producing the dimer acid-modified polyamide resin include various aliphatic, alicyclic, and aromatic diamines, triamines, and polyamines. Specific examples of the diamines include ethylenediamine, propanediamine, butanediamine, triethylenediamine, tetraethylenediamine, hexamethylenediamine, p- or m-xylenediamine, 4,4'-methylenebis(cyclohexylamine), 2,2-bis-(4-cyclohexylamine), polyglycoldiamine, isophoronediamine, 1,2-, 1,3-, or 1,4-cyclohexanediamine, 1,4-bis-(2'-aminoethyl)benzene, N-ethylaminopiperazine, and piperazine. Examples of triamines include diethylenetriamine, and examples of polyamines include triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, etc. Furthermore, dimer diamines obtained by converting a dimerized aliphatic nitrile group and reducing it with hydrogen can also be used.

[0071] Furthermore, examples of polyamine compounds include compounds in which the carboxyl group of a polybasic acid compound having a cyclic or acyclic hydrocarbon group having 20 to 48 carbon atoms is converted to an amino group. Examples of commercially available products include "Priamine 1071," "Priamine 1073," "Priamine 1074," and "Priamine 1075" manufactured by Croda Japan Co., Ltd., and "Versamine 551" manufactured by Cognis Japan Co., Ltd. The diamine may be used in combination with an alkanolamine. Examples of alkanolamines include ethanolamine, propanolamine, diethanolamine, butanolamine, 2-amino-2-methyl-1-propanol, and 2-(2-aminoethoxy)ethanol. Polyether diamines having oxygen in the skeleton can also be used. The polyether is General formula: H2N-R1-(RO)n-R2-NH2 (In the formula, n is 2 to 100, R1 and R2 are alkyl groups or alicyclic hydrocarbon groups having 1 to 14 carbon atoms, and R is an alkyl group or alicyclic hydrocarbon group having 1 to 10 carbon atoms. The alkyl group may be linear or branched.) The ether diamine can be expressed by the formula: (a) (b) (c) (d) (e) (f) (g) (g) (h) (i) (j ...

[0072] [Polyester resin] Polyester resins are polymers composed of polycarboxylic acids and polyhydric alcohols as monomers. Known polyester resins can be used. Specifically, from the viewpoint of ensuring the cohesive strength of the resin, it is preferable that the weight-average molecular weight is 1,000 to 100,000. Furthermore, from the viewpoint of adhesion, it is preferable that the glass transition temperature is -10°C to 200°C. Examples of polycarboxylic acid components include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, unsaturated dicarboxylic acids, and trivalent or higher carboxylic acids. One or more of these can be selected and used. Examples of polyhydric alcohol components include aliphatic glycols, ether glycols, and trivalent or higher polyalcohols. One or more of these can be selected and used. Commercially available polyester resins include Vylon (manufactured by Toyobo Co., Ltd., "Vylon" is a registered trademark), Polyester (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., "Polyester" is a registered trademark), and Teslac (manufactured by Hitachi Chemical Polymer Co., Ltd., "Teslac" is a registered trademark).

[0073] From the viewpoints of fluidity during heating, volume resistivity, adhesion to the substrate, and durability, it is also preferable for the binder resin to contain a vinyl polymer having at least one structure selected from polyether, polyester, polycarbonate, and polybutadiene, which has a functional group reactive with an isocyanate group, in the side chain. The method for introducing the side chain is not particularly limited, and the binder resin can be obtained by various synthesis methods.

[0074] Examples of functional groups reactive with isocyanate groups include hydroxyl groups, amino groups, carboxyl groups, epoxy groups, N-methylol groups, and N-alkoxymethyl groups, with hydroxyl groups being preferred in terms of reactivity. The functional groups reactive with isocyanate groups can be introduced into the side chains or main chains of the vinyl polymer, and the introduction method is not particularly limited and they can be introduced by various synthesis methods. For applications requiring high toughness and durability, it is desirable to directly introduce the functional groups reactive with isocyanate into the main chain of the vinyl polymer, thereby improving the crosslink density of the resin.

[0075] The weight average molecular weight of the vinyl polymer, in terms of polystyrene, is preferably 5,000 to 500,000, and more preferably 10,000 to 100,000. When the weight average molecular weight of the polymer (A1) is 500,000 or less, the solubility in solvents is improved, and when it is 5,000 or more, sufficient coating strength is obtained after (hot) pressing.

[0076] The binder resin may be a curable resin that undergoes a curing (crosslinking) reaction after being applied to a substrate. The crosslinking agent used in the curable resin is not particularly limited, but examples thereof include polyisocyanate compounds having two or more isocyanate groups. Although the polyisocyanate compound is not particularly limited, when used outdoors, it is preferable to use only alicyclic or aliphatic compounds in order to prevent deterioration of the coating film over time. Examples of the alicyclic polyisocyanate compound include isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated 4,4'-diphenylmethane diisocyanate. Examples of the aliphatic polyisocyanate compound include trimethylhexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate. Examples of aromatic polyisocyanate compounds include diphenylmethane diisocyanate, toluylene diisocyanate, naphthylene-1,5-diisocyanate, o-xylene diisocyanate, m-xylene diisocyanate, p-xylene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate. As the polyisocyanate compound, adducts of the above compounds with glycols or diamines, both ends of which are isocyanate-terminated, biuret-modified compounds, and isocyanurate-modified compounds may also be used. In particular, when the polyisocyanate compound contains an isocyanurate-modified compound, particularly an isocyanurate ring-containing triisocyanate, sufficient coating film strength can be obtained after heat pressing, which is preferable. Specific examples of the isocyanurate ring-containing triisocyanate include isocyanurate-modified isophorone diisocyanate (e.g., Desmodur Z4470 manufactured by Sumitomo Bayer Urethane Co., Ltd.), isocyanurate-modified hexamethylene diisocyanate (e.g., Sumidur N3300 manufactured by Sumitomo Bayer Urethane Co., Ltd.), and isocyanurate-modified toluylene diisocyanate (e.g., Sumidur FL-2, FL-3, FL-4, HLBA manufactured by Sumitomo Bayer Urethane Co., Ltd.). Depending on the required performance, the polyisocyanate compound may be used alone or in a mixture of two or more kinds, in such a ratio that the total number of isocyanate groups is preferably 0.1 to 5.0 times, more preferably 0.5 to 3.0 times, and particularly preferably 0.8 to 2.0 times, relative to the total number of functional groups of the binder resin.

[0077] The binder resin may be in the form of either a soluble resin that dissolves in a solvent, or a dispersion-type resin fine particle (emulsion) that does not dissolve in a solvent and exists in the state of fine particles.

[0078] The particle structure of the dispersion-type resin microparticles can also be a multilayer structure, i.e., a core-shell particle. For example, by localizing a resin primarily polymerized from a monomer having a functional group in the core or shell, or by creating differences in Tg and composition between the core and shell, the curability, drying property, film-forming property, and mechanical strength of the binder can be improved. From the viewpoint of binding ability and particle stability, the average particle diameter of the resin microparticles is preferably 10 to 1,000 nm, and more preferably 10 to 300 nm. Furthermore, since the inclusion of a large number of coarse particles exceeding 1 μm impairs particle stability, it is preferable that the content of coarse particles exceeding 1 μm be at most 5%. Note that the average particle diameter in this invention refers to the volume-average particle diameter, which can be measured by dynamic light scattering. Measurement of the average particle diameter by dynamic light scattering can be performed as follows. Depending on the solid content of the resin microparticles, the dispersion liquid is diluted 200 to 1,000 times with the same dispersion medium. Approximately 5 ml of the diluted dispersion is poured into the cell of a measuring device (Nanotrac, manufactured by Nikkiso Co., Ltd.), and the refractive index conditions of the dispersion medium and resin appropriate for the sample are input, after which measurement is performed. The measurement can be performed based on the peak of the volume particle size distribution data (histogram) obtained at this time. The dispersed resin particles preferably contain crosslinked resin particles. Crosslinked resin particles refer to resin particles having an internal crosslinked structure (three-dimensional crosslinked structure), and it is important that the particles are crosslinked internally. Furthermore, the crosslinked resin particles contain specific functional groups, which can contribute to adhesion to the substrate. Furthermore, by adjusting the crosslinked structure and the amount of functional groups, a coating film with excellent durability can be obtained.

[0079] From the viewpoint of environmental load, etc., a water-soluble resin and aqueous resin microparticles that can be used in an aqueous solvent, preferably water, are preferred. Furthermore, from the viewpoint of the slurry stability and coatability of the resin composition, it is more preferred to use a water-soluble resin and aqueous resin microparticles in combination.

[0080] (Water-soluble resin) A water-soluble resin is a resin that can be completely dissolved in water without separation or precipitation after 1 g of resin is added to 99 g of water at 25°C, stirred, and left to stand at 25°C for 24 hours. The water-soluble resin has the effect of increasing the dispersibility of the carbon material, so that a stable composition can be obtained with a small amount of resin. Water-soluble resins are broadly classified into anionic resins, cationic resins, amphoteric resins that have both anionic and cationic properties, and other nonionic resins, and the resins may be composed of multiple monomers. Furthermore, the water-soluble resins may be used alone or in combination of two or more types. Examples of anionic resins include resins containing a skeleton containing a carboxy group, a sulfo group, a phosphate group, or a partially or completely neutralized skeleton of any of these groups. Examples include homopolymers of polymerizable monomers such as (meth)acrylic acid, itaconic acid, fumaric acid, maleic acid, 2-sulfoethyl methacrylate, and 2-methacryloyloxyethyl acid phosphate, copolymers thereof with other polymerizable monomers, carboxymethyl cellulose, and alkali-neutralized products thereof. The cationic resins include those containing cyclic amino groups and those in which some or all of the amino groups are neutralized. Examples include resins containing a quaternary ammonium salt or a polymer with a structure similar to that of N,N-diamine. Examples thereof include homopolymers of polymerizable monomers such as methylaminoethyl (meth)acrylate, N,N-diethyl (meth)acrylate, and vinylpyridine, or copolymers with other polymerizable monomers, and acid-neutralized products thereof. Examples of amphoteric resins include resins containing both the anionic skeleton and the cationic skeleton. An example thereof is a copolymer of styrene-maleic acid-N,N-dimethylaminoethyl (meth)acrylate. Nonionic resins are resins other than the above-mentioned anionic, cationic and amphoteric resins. Examples include polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl butyral, polyacrylamide, poly-N-vinylacetamide, and polyalkylene glycol. The molecular weight of the water-soluble resin is not particularly limited, but the mass average molecular weight is preferably 5,000 to 2,500,000.The mass average molecular weight (Mw) refers to the molecular weight in terms of polyethylene oxide measured by gel permeation chromatography (GPC).

[0081] (Aqueous resin fine particles) Aqueous resin microparticles (aqueous emulsions) are dispersed resin microparticles in which the resin does not dissolve in water but exists in the form of fine particles, and examples include (meth)acrylic emulsions, nitrile emulsions, urethane emulsions, polyolefin emulsions, fluorine-based emulsions (such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE)), and diene-based emulsions (such as styrene-butadiene rubber (SBR)). Note that (meth)acrylic refers to either methacrylic or acrylic. When a coating film is formed from a resin composition containing aqueous resin microparticles, it has excellent adhesion between particles and to a substrate, and can provide a coating film with high strength. Furthermore, because of the excellent adhesion, only a small amount of aqueous resin microparticles is required, resulting in improved conductivity of the resin composition. To achieve the above-mentioned effects, (meth)acrylic emulsions and urethane emulsions, which have excellent inter-particle adhesion and flexibility (film flexibility), are preferred as aqueous resin microparticles.

[0082] The (meth)acrylic emulsion is an emulsion polymer containing 10 parts by mass or more, preferably 20 parts by mass or more, and more preferably 30 parts by mass or more, of a monomer having a (meth)acryloyl group. The monomer having an acryloyl group has excellent reactivity, so that resin microparticles can be produced relatively easily. Therefore, the (meth)acrylic emulsion is particularly preferred as the aqueous resin microparticles.

[0083] <Solvent (dispersion medium)> The conductive composition of the present invention contains a conductive material (A), a binder resin (B), and, if necessary, a solvent. When the carbon material and the binder are mixed uniformly, a solvent can be appropriately used. Such a solvent is not particularly limited as long as it can dissolve the resin and stably disperse the resin particle emulsion, and examples thereof include water and organic solvents.

[0084] The organic solvent may be selected from alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether, and diethylene glycol methyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; hydrocarbons such as hexane, heptane, and octane; aromatics such as benzene, toluene, xylene, and cumene; and esters such as ethyl acetate and butyl acetate, depending on the composition of the conductive composition. The solvent may be a mixture of water and an organic solvent, or two or more organic solvents.

[0085] When a water-soluble resin or aqueous resin particles are used, it is preferable to use water as a solvent from the viewpoint of solubility and dispersibility, and a liquid medium compatible with water may be added as necessary. As the liquid medium compatible with water, an alcohol-based solvent having 4 or less carbon atoms is preferred. Furthermore, various additives such as ultraviolet absorbers, ultraviolet stabilizers, radical scavengers, fillers, thixotropy-imparting agents, antioxidants, antioxidants, antistatic agents, flame retardants, thermal conductivity improvers, plasticizers, anti-sagging agents, antifouling agents, preservatives, disinfectants, antifoaming agents, leveling agents, antiblocking agents, curing agents, thickeners, dispersants, and silane coupling agents may be added to the resin composition of the present invention, as needed, within the scope of not impairing the effects of the present invention.

[0086] The viscosity of the conductive composition depends on the method of applying the conductive composition, but is generally preferably 10 mPa·s or more and 30,000 mPa·s or less. The viscosity of a dispersion containing a boron-containing carbon material as a conductive additive tends to be lower than that of a dispersion prepared using a boron-free carbon material as a conductive additive because the surface condition of the conductive additive changes as described above, and this results in easier handling of the dispersion. The viscosity can be measured, for example, using a B-type viscometer.

[0087] (Dispersing machine / mixing machine) As the apparatus used to obtain the conductive composition, a disperser or mixer that is generally used for dispersing pigments or the like can be used.

[0088] For example, mixers such as a Disper, Homomixer, or Planetary Mixer; homogenizers such as M-Technique's "Clearmix" or PRIMIX's "Filmix"; media-type dispersers such as a paint conditioner (Red Devil), ball mill, sand mill (Shinmaru Enterprises' "Dynomill," etc.), attritor, pearl mill (Eirich's "DCP Mill," etc.), or Coball mill; media-less dispersers such as wet jet mills (Genus' "Genus PY," Sugino Machine's "Starburst," Nanomizer's "Nanomizer," etc.), M-Technique's "Clear SS-5," or Nara Machine's "MICROS"; or other roll mills, etc., can be mentioned, but are not limited to these.

[0089] For example, when using a media-type disperser, it is preferable to use a disperser whose agitator and vessel are made of ceramic or resin, or a disperser whose metal agitator and vessel surfaces are treated with tungsten carbide thermal spraying or resin coating. Furthermore, it is preferable to use ceramic beads such as glass beads, zirconia beads, or alumina beads as media. Only one type of dispersing device may be used, or multiple types of devices may be used in combination.

[0090] <Conductive film> The conductive film of the present invention has a conductive film formed from a conductive composition on a substrate.

[0091] (base material) The shape of the substrate used for forming the conductive film is not particularly limited, but is preferably a sheet. Also, an insulating resin film is preferred, and a substrate suitable for various applications can be selected appropriately.

[0092] For example, materials include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), polyimide, polyvinyl chloride, polyamide, nylon, OPP (oriented polypropylene), CPP (unoriented polypropylene), etc., but are not particularly limited.

[0093] As for the shape, a flat film is generally used, but substrates with a roughened surface, those treated with a primer, those with holes, and those in a mesh shape can also be used.

[0094] The method for applying the conductive composition onto the substrate is not particularly limited, and any known method can be used.

[0095] Specific examples of the coating method include die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, and electrostatic painting. Drying methods that can be used include, but are not limited to, standing to dry, air blowing, hot air drying, infrared heating, and far-infrared heating.

[0096] After coating, the conductive film may be rolled using a lithographic press or a calendar roll, and may be heated to soften the film and make it easier to press. The thickness of the conductive film is generally 0.1 μm or more and 1 mm or less, and preferably 1 μm or more and 200 μm or less.

[0097] (Volume resistivity of conductive film) The volume resistivity of the conductive film of the present invention is 5×10 -3 Preferably less than 3×10 Ω·cm -3 It is more preferable that the volume resistivity is less than 5×10 -3 With a resistivity of less than Ω·cm, the resin composition has extremely high conductivity and can be used for battery electrodes, current collectors, and wiring in batteries and electronic devices. [Example]

[0098] The present invention will be described in more detail below with reference to examples, but the following examples do not limit the scope of the invention in any way. In the examples and comparative examples, "parts" and "%" represent "parts by mass" and "% by mass".

[0099] <Boron content in carbon materials> The content of boron element in the carbon material was measured using ICP emission spectroscopy (SPECTROARCOS FHS12 manufactured by SPECTRO Inc.) The obtained value indicates the amount of boron element contained in the entire carbon material.

[0100] <Specific surface area> Nitrogen adsorption was measured using a gas adsorption measurement device (Microtrack-Bel BELSORP-mini), and the specific surface area was calculated by the BET method.

[0101] <002 inter-surface distance> Measurement was performed using an X-ray diffractometer (Smartlab manufactured by Rigaku Corporation) using CuKα radiation as an X-ray source, and the peak half-width of the (002) plane appearing in the vicinity of 2θ=24.0 to 27.0° was determined.

[0102] <Weight average molecular weight (Mw)> The Mw was measured using a GPC (gel permeation chromatography) "HPC-8020" manufactured by Tosoh Corporation. GPC is a liquid chromatography that separates and quantifies substances dissolved in a solvent (THF; tetrahydrofuran) based on differences in their molecular size. The measurement in this invention was carried out using two "LF-604" columns (Showa Denko K.K.: GPC column for rapid analysis: 6 mm ID x 150 mm size) connected in series, at a flow rate of 0.6 ml / min and a column temperature of 40°C, and the weight-average molecular weight was determined in polystyrene equivalent.

[0103] <Acid value> Accurately weigh approximately 1 g of sample into a stoppered Erlenmeyer flask and dissolve in 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2 / 1). Add phenolphthalein TS as an indicator and hold for 30 seconds. Then, titrate with 0.1 N alcoholic potassium hydroxide solution until the solution turns a pale pink color. The acid value was calculated using the following formula (unit: mgKOH / g). Acid value (mgKOH / g) = (5.611 × a × F) / S, where S: Amount of sample collected (g) a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml) F: Potency of 0.1N alcoholic potassium hydroxide solution

[0104] <Hydroxyl value> The hydroxyl value is the amount of hydroxyl groups contained in 1 g of a hydroxyl-containing resin, expressed as the amount (mg) of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl groups when the hydroxyl groups are acetylated. The hydroxyl value was measured in accordance with JIS K0070. In the present invention, the hydroxyl value is calculated taking into account the acid value, as shown in the following formula: Approximately 1 g of sample was precisely weighed into a stoppered Erlenmeyer flask and dissolved in 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2 / 1). Exactly 5 ml of an acetylating agent (25 g of acetic anhydride dissolved in pyridine to a volume of 100 ml) was then added and stirred for approximately 1 hour. Phenolphthalein TS was added as an indicator and the mixture was stirred for 30 seconds. The solution was then titrated with 0.1 N alcoholic potassium hydroxide solution until it turned a pale pink color. The hydroxyl value was calculated using the following formula (unit: mgKOH / g). Hydroxyl value (mgKOH / g) = [{(ba) × F × 28.05} / S] + D however, S: Amount of sample collected (g) a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml) b: Amount of 0.1N alcoholic potassium hydroxide solution consumed in the blank experiment (ml) F: Potency of 0.1N alcoholic potassium hydroxide solution D: Acid value (mgKOH / g)

[0105] <Method for measuring glass transition temperature> The binder resin from which the solvent had been dried was measured using a Mettler-Toledo DSC-1, raising the temperature from -80 to 150°C at a rate of 2°C / min.

[0106] <Conductive additive: production of boron-containing carbon material (A-1)> [Production Example 1] Boron-containing carbon material (1) Ketjenblack EC300J (Lion Specialty Chemicals) and boric acid (Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out to a mass ratio of 95 / 5 (Ketjenblack / boric acid) and mixed and composited using a particle compositer, Mechanofusion (Hosokawa Micron Corporation). The mixture was filled into a graphite crucible and heat-treated in a firing furnace under an argon atmosphere at 2050°C for 1 hour to obtain boron-containing carbon material (1).

[0107] [Production Example 2] Boron-containing carbon material (2) Ketjenblack EC300J (Lion Specialty Chemicals) and boric acid (Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out to a mass ratio of 79 / 21 (Ketjenblack / boric acid) and mixed and composited using a particle compositer, Mechanofusion (Hosokawa Micron Corporation). The mixture was filled into a graphite crucible and heat-treated in a firing furnace under an argon atmosphere at 2050°C for 1 hour to obtain boron-containing carbon material (2).

[0108] [Production Example 3] Boron-containing carbon material (3) Furnace black VULCAN XC-72R (Cabot Corporation), boric acid (Fujifilm Wako Pure Chemical Industries, Ltd.), and ethanol were weighed out to a mass ratio of 95 / 5 / 300 (furnace black / boric acid / ethanol), mixed using a disperser, dried in an oven at 80°C under atmospheric pressure, and then mixed and composited using a particle compositer, Mechanofusion (Hosokawa Micron Corporation), to obtain a mixture. The mixture was filled into a graphite crucible and heat-treated in a firing furnace under an argon atmosphere at 2050°C for 1 hour to obtain a boron-containing carbon material (3).

[0109] [Production Examples 4 and 6] Boron-containing carbon materials (4) and (6) Using the carbon- and boron-containing compounds shown in Table 1, boron-containing carbon materials (4) and (6) were obtained in the same manner as in Production Example 1.

[0110] [Production Example 5] Boron-containing carbon material (5) A boron-containing carbon material (5) was obtained in the same manner as in Production Example 2 using the compounds containing carbon and boron shown in Table 1.

[0111] [Production Example 7] Boron-containing carbon material (7) 740 g of zirconia beads with a diameter of 5 mm were placed in a 500 mL container, and flake graphite (UP-20, manufactured by Nippon Graphite Co., Ltd.) was added thereto, and the flake graphite was pulverized for 10 minutes using a planetary ball mill (manufactured by Fritsch GmbH) at a rotation speed of 100 rpm to refine the flake graphite. Thereafter, the obtained carbon material was subjected to the same operation as in Production Example 1 to obtain a boron-containing carbon material (7).

[0112] <Conductive material: Production of carbon material (A-2)> [Production Example 8] Boron-containing carbon material (8) Using flake graphite (UP-20 manufactured by Nippon Graphite Co., Ltd.), the same procedure as in Production Example 1 was carried out to obtain a boron-containing carbon material (8). The specific surface area was 4 m 2 / g, and the boron content was 0.62 mol%.

[0113] [Production Example 9] Boron-containing carbon material (9) Using multi-walled carbon nanotubes (NTP3003, manufactured by Shenzhen Nanotech Port Co., Ltd.), the same procedure as in Production Example 1 was carried out to obtain a boron-containing carbon material (9). The specific surface area was 187 m 2 / g, and the boron content was 0.69 mol%.

[0114] [Production Example 12] Boron-containing carbon material (20) Ketjenblack EC600JD (Lion Specialty Chemicals), boric acid (Fujifilm Wako Pure Chemical Industries, Ltd.), and ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed to a mass ratio of 99.5 / 0.5 / 400 (Ketjenblack / boric acid / ethanol), mixed in a planetary mixer, and then dried in an oven. Next, the mixture was mixed and composited using a Mechanofusion particle compositer (Hosokawa Micron Corporation) to obtain a mixture. The mixture was then filled into a graphite crucible and heat-treated in a firing furnace under an argon atmosphere at 1650°C for 1 hour to obtain the boron-containing carbon material (20).

[0115] [Production Example 13] Boron-containing carbon material (21) Ketjenblack EC600JD (Lion Specialty Chemicals) and boron carbide (Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed to a mass ratio of 98.8 / 1.2 (Ketjenblack / boron carbide) and mixed and composited using a particle compositer, Mechanofusion (Hosokawa Micron Corporation). The mixture was filled into a graphite crucible and heat-treated in a firing furnace under an argon atmosphere at 1500 °C for 1 hour to obtain the boron-containing carbon material (21).

[0116] [Production Example 4] Boron-containing carbon material (22) Ketjenblack EC600JD (Lion Specialty Chemicals) and boric acid (Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out to a mass ratio of 95 / 5 (Ketjenblack / boric acid) and mixed and composited using a particle compositer, Mechanofusion (Hosokawa Micron Corporation). The mixture was filled into a graphite crucible and heat-treated in a firing furnace under an argon atmosphere at 1700 °C for 1 hour to obtain the boron-containing carbon material (22).

[0117] [Production Example 15] Boron-containing carbon material (23) Ketjenblack EC600JD (Lion Specialty Chemicals), boric acid (Fujifilm Wako Pure Chemical Industries, Ltd.), and ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed to a mass ratio of 97 / 3 / 400 (Ketjenblack / boric acid / ethanol), mixed in a planetary mixer, and then dried in an oven. Next, the mixture was mixed and composited using a Mechanofusion particle compositer (Hosokawa Micron Corporation) to obtain a mixture. The mixture was then filled into a graphite crucible and heat-treated in a firing furnace under an argon atmosphere at 1650 °C for 1 hour to obtain the boron-containing carbon material (23).

[0118] [Production Example 16] Boron-containing carbon material (24) Multi-walled carbon nanotubes (NTP3003, manufactured by Shenzhen Nanotech Port Co., Ltd.) and boric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out to a mass ratio of 95 / 5 (carbon nanotubes / boric acid) and mixed and composited using a particle compositer, Mechanofusion (manufactured by Hosokawa Micron Corporation) to obtain a mixture. The mixture was filled into a graphite crucible and heat-treated in a firing furnace under an argon atmosphere at 1700°C for 1 hour to obtain a boron-containing carbon material (24).

[0119] [Boron-free carbon materials (A-2)] The following material was used as the boron-free carbon material (A-2). Flaky graphite: UP-20 (Nippon Graphite Co., Ltd., specific surface area 4m 2 / g) Spherical graphite: CGB-50 (Nippon Graphite Co., Ltd., specific surface area 2m 2 / g) Scaly graphite: F#2 (Nippon Graphite Co., Ltd., specific surface area 1 m 2 / g)

[0120] <For comparison: carbon material not containing boron> The following materials were used as boron-free carbon materials (10) to (14). Carbon material (10): Ketjenblack EC-300J (Lion Specialty Chemicals) Carbon material (11): Ketjenblack EC-600JD (Lion Specialty Chemicals) Carbon material (12): Furnace Black VULCAN XC-72R (manufactured by Cabot Corporation) Carbon material (13): Acetylene black HS-100 (manufactured by Denka Co., Ltd.) Carbon material (14): Graphene nanoplatelets xGNP-C750 (manufactured by XG Sciences)

[0121] The carbon materials obtained are listed below.

[0122] [Table 1]

[0123] <Volume resistivity of carbon materials> The volume resistivity of the carbon material was measured using a powder resistivity measurement system MCP-PD51 manufactured by Nitto Seiko Analytech Co., Ltd. Measurement was performed using a four-point probe method with a low-resistivity powder probe, and the volume resistivity value was measured when a load of 20 kN was applied to the sample. The volume resistivity of carbon material (1) was 7.4 × 10 -3 Ω·cm, and the volume resistivity of carbon material (10) is 2.3×10 -2 This confirmed that the volume resistivity of the carbon material was reduced by doping with boron. The volume resistivity of carbon material (3) is 8.3 × 10 -3 Ω·cm, and the volume resistivity of carbon material (4) is 7.4×10 -3 Ω·cm, and the volume resistivity of carbon material (5) is 6.8×10 -3 Ω·cm, and there was almost no difference in the volume resistivity of the powder depending on the type of carbon black.

[0124] <Wettability and zeta potential of carbon materials> The wettability of carbon materials (4) and (11) with water was evaluated. When 0.1 g of carbon material was mixed with 1 g of water, carbon material (11) was not miscible with water, whereas carbon material (4) was easily miscible with water. This confirmed that the surface condition of the carbon material was changed by boron doping. Zeta potential measurements were also carried out on carbon materials (4) and (11). 3 g of carbon material (4) or (11) was mixed with 35 g of the urethane resin solution described below (7 g of resin solids) and 87 g of toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) as a solvent, and the resin composition was subjected to zeta potential measurement. The zeta potential of the resin composition of carbon material (4) was -34 mV, and the zeta potential of the resin composition of carbon material (11) was -19 mV.

[0125] <Synthesis of binder resin (B)> [Production Example 10] Polyurethane resin solution A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube was charged with 455.5 parts of a polyester polyol obtained from terephthalic acid, adipic acid, and 3-methyl-1,5-pentanediol ("Kuraray Polyol P-2011" manufactured by Kuraray Co., Ltd., Mn=2011), 16.5 parts of dimethylolbutanoic acid, 105.2 parts of isophorone diisocyanate, and 140 parts of toluene, and the mixture was reacted at 90°C for 3 hours under a nitrogen atmosphere. 360 parts of toluene was then added to the mixture to obtain a urethane prepolymer solution having isocyanate groups. Next, 969.5 parts of the obtained urethane prepolymer solution having isocyanate groups was added to a mixture of 19.9 parts of isophoronediamine, 0.63 parts of di-n-butylamine, 294.5 parts of 2-propanol, and 335.5 parts of toluene (the total equivalent of amino groups relative to the free isocyanate groups at both ends of the urethane prepolymer was 0.98), and the mixture was reacted at 50°C for 3 hours and then at 70°C for 2 hours.The mixture was then diluted with 126 parts of toluene and 54 parts of 2-propanol to obtain a polyurethane resin solution with Mw=61,000 and an acid value=10 mgKOH / g. The resulting solution was diluted with toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) to prepare a polyurethane resin solution with a solid content of 20%.

[0126] [Production Example 11] Polyamide resin solution A four-neck flask equipped with a stirrer, reflux condenser, nitrogen inlet, inlet tube, and thermometer was charged with 156.2 g of Pripol 1009 (a polybasic acid compound), 5.5 g of 5-hydroxyisophthalic acid, 146.4 g of Priamine 1074 (a polyamine compound), and 100 g of ion-exchanged water. The mixture was stirred until the exothermic temperature stabilized. Once the temperature stabilized, the mixture was heated to 110°C. After confirming the outflow of water, the temperature was raised to 120°C after 30 minutes. The dehydration reaction was then continued by increasing the temperature by 10°C every 30 minutes. After the temperature reached 230°C, the reaction was continued at this temperature for 3 hours, then held under a vacuum of approximately 2 kPa for 1 hour, after which the temperature was lowered. Finally, an antioxidant was added, yielding a polyamide resin with a weight-average molecular weight of 24,000, an acid value of 13.2 mgKOH / g, a hydroxyl value of 5.5 mgKOH / g, and a glass transition temperature of -32°C. The obtained resin was diluted with toluene / 2-propanol (mass ratio: 2 / 1) to prepare a polyamide resin solution with a solid content of 20%.

[0127] [Polyester resin solution] Vylon 200 (a polyester resin manufactured by Toyobo Co., Ltd.) was diluted with toluene / methyl ethyl ketone (mass ratio: 1 / 1) to obtain a polyester resin solution with a solid content of 20%.

[0128] <Conductive composition and conductive film> (Example 1) Conductive composition (1) Among the conductive carbon materials (A), 10 parts of carbon material (1) were used as the boron-containing carbon material (A-1), and 10 parts of flaky graphite (manufactured by Nippon Graphite Co., Ltd., UP-20, specific surface area: 4 m) were used as the carbon material (A-2). 260 parts of a urethane resin solution (30 parts resin solids), 150 parts of a urethane resin solution (30 parts resin solids), and 137 parts of a toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) solvent were mixed in a mixer and further dispersed in a sand mill to obtain a conductive composition (1). This conductive composition (1) was then applied using a doctor blade to a 100 μm thick PET film serving as a sheet substrate, and then heated and dried to obtain a conductive film having a thickness of 30 μm. The proportion of the boron-containing carbon material (A-1) in the conductive carbon material (A) was 14 mass%. The obtained conductive film was evaluated by the following methods, and the evaluation results are shown in Table 2.

[0129] (Volume resistivity of conductive film) The volume resistivity of the conductive film was measured by the four-terminal method (JIS-K7194) using a Loresta GP (manufactured by Nitto Seiko Analytech Co., Ltd.) and judged according to the following criteria. ◎: Volume resistivity is 3×10 -3 Less than Ω·cm (very good) ○: Volume resistivity is 3×10 -3 Ω cm or more, 5×10 -3 Less than Ω cm (good) ○△: Volume resistivity is 5×10 -3 Ω cm or more, 5×10 -2 Less than Ω cm (usable) △: Volume resistivity is 5×10 -2 Ω cm or more, 1×10 -1 Less than Ω·cm (poor) ×: Volume resistivity is 1×10 -1 Ω·cm or more (very poor)

[0130] (Durability of conductive film) The durability of the conductive film prepared above was evaluated by scratch hardness (pencil method) using a pencil with HB hardness (in accordance with JIS K5600-5-4:1999 method). 〇: No plastic deformation or cohesive failure occurs (good) △: Plastic deformation or cohesive failure occurs (bad) ×: Plastic deformation and cohesive failure occurred (very poor)

[0131] (Examples 2 to 6, 12 to 15, Comparative Examples 1 to 6, 8) Conductive compositions (2) to (6), (12) to (15), (a) to (f), (h) A conductive composition was obtained in the same manner as for conductive composition (1), except that the formulation was changed to that shown in Table 2. A conductive film was then formed and evaluated in the same manner as for conductive composition (1).

[0132] (Example 7) Conductive composition (7) Among the conductive materials (A), 10 parts of carbon material (4) as the boron-containing carbon material (A-1), 60 parts of carbon material (8) as the other carbon material (A-2), 10 parts of the water-soluble resin PVP K-30 (polyvinylpyrrolidone, manufactured by ISP Japan Co., Ltd.) as the binder resin, and 237 parts of water were mixed in a mixer and further dispersed in a sand mill to obtain a dispersion. To this dispersion, 40 parts (20 parts of resin solids) of polyacrylic emulsion W-168 (50% solids by mass, manufactured by Toyochem Co., Ltd.) as the binder resin was further added as a binder resin to obtain a conductive composition (7). This conductive composition (7) was then applied using a doctor blade to a 100 μm-thick PET film serving as a sheet substrate, followed by heat drying and adjusting the thickness of the conductive film to 30 μm. The resulting conductive film was evaluated.

[0133] (Comparative Example 7) Conductive resin composition (g) A conductive resin composition was prepared in the same manner as in Example 7, except that carbon material (11) was used instead of carbon material (4), and a conductive film was formed and evaluated in the same manner as in the conductive composition (1).

[0134] (Example 8) Conductive composition (8) In the same manner as in Example 1, 5 parts of the carbon material (4) were used as the boron-containing carbon material (A-1) of the conductive material (A), and spherical graphite (manufactured by Nippon Graphite Co., Ltd., CGB-50, specific surface area 2 m) was used as the other carbon material (A-2). 2A conductive composition (8) was prepared using 75 parts of a polyethylene terephthalate (PEG-100 / g), 100 parts of a polyurethane resin solution (20 parts resin solids), and 177 parts of toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) as a solvent, and a conductive film was formed and evaluated in the same manner as for the conductive composition (1). The proportion of the boron-containing carbon material (A-1) in the conductive carbon material (A) was 6 mass%.

[0135] (Example 9) Conductive composition (9) In the same manner as in Example 1, 30 parts of the carbon material (5) was used as the boron-containing carbon material (A-1) of the conductive material (A), and flaky graphite (manufactured by Nippon Graphite Co., Ltd., F#2, specific surface area 1 m) was used as the other carbon material (A-2). 2 A conductive composition (9) was prepared using 40 parts of a polyethylene terephthalate (PEG-100 / g), 150 parts of a polyurethane resin solution (30 parts resin solids), and 137 parts of toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) as a solvent, and a conductive film was formed and evaluated in the same manner as for the conductive composition (1). The proportion of the boron-containing carbon material (A-1) in the conductive carbon material (A) was 43 mass%.

[0136] (Example 10) Conductive composition (10) In the same manner as in Example 1, a conductive composition (10) was prepared using 30 parts of carbon material (7) as the boron-containing carbon material (A-1) of the conductive material (A), 60 parts of flaky graphite as the other carbon material (A-2), 50 parts of a polyurethane resin solution (10 parts resin solids), and 217 parts of toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) as a solvent, and a conductive film was formed and evaluated in the same manner as in the conductive composition (1). The proportion of the boron-containing carbon material (A-1) in the conductive carbon material (A) was 33 mass%.

[0137] (Example 11) Conductive composition (11) Conductive composition (11) was prepared using 10 parts of carbon material (4) as the boron-containing carbon material (A-1) of the conductive material (A), 50 parts of carbon material (9) as the other carbon material (A-2), 200 parts of a polyurethane resin solution (40 parts resin solids), and 97 parts of toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) as a solvent in the same manner as in Example 1, and a conductive film was formed and evaluated in the same manner as in conductive composition (1). The proportion of boron-containing carbon material (A-1) in the conductive carbon material (A) was 17 mass%.

[0138] (Example 16) Conductive composition (16) In the same manner as in Example 1, a conductive composition (16) was prepared using 7 parts of carbon material (22) as the boron-containing carbon material (A-1), 63 parts of flaky graphite as the other carbon material (A-2), 150 parts of a polyurethane resin solution (30 parts resin solids), and 137 parts of toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) as a solvent, among the conductive materials (A), and a conductive film was formed and evaluated in the same manner as in conductive composition (1). The proportion of the boron-containing carbon material (A-1) in the conductive carbon material (A) was 10 mass%.

[0139] (Example 17) Conductive composition (17) In the same manner as in Example 1, a conductive composition (17) was prepared using 14 parts of carbon material (22) as the boron-containing carbon material (A-1) of the conductive material (A), 56 parts of flaky graphite as the other carbon material (A-2), 150 parts of a polyurethane resin solution (30 parts resin solids), and 137 parts of toluene / methyl ethyl ketone / 2-propanol (mass ratio: 1 / 1 / 1) as a solvent, and a conductive film was formed and evaluated in the same manner as in the conductive composition (1). The proportion of the boron-containing carbon material (A-1) in the conductive carbon material (A) was 20 mass%.

[0140] (Example 18) Conductive composition (18) A conductive composition (18) was prepared using 20 parts of carbon material (4) as the boron-containing carbon material (A-1) of the conductive material (A), 55 parts of flaky graphite as the other carbon material (A-2), 125 parts of a polyamide resin solution (25 parts resin solids), and 157 parts of toluene / 2-propanol (mass ratio: 2 / 1) as a solvent in the same manner as in Example 1, and a conductive film was formed and evaluated in the same manner as in the conductive composition (1). The proportion of the boron-containing carbon material (A-1) in the conductive carbon material (A) was 26.7 mass%.

[0141] (Examples 19 to 22, Comparative Examples 9 to 11) A conductive resin composition was prepared in the same manner as in Example 18, except that the blending composition was changed to that shown in Table 2, and a conductive film was formed and evaluated in the same manner as in the conductive composition (1).

[0142] [Table 2]

[0143] As shown in Table 2, the conductive film of the present invention was able to achieve both improved durability and conductivity compared to conventional films. Furthermore, Examples 1 to 6 and Comparative Examples 1 to 6 show that the use of a boron-containing carbon material (A-1) as a conductive additive improved the conductivity and durability of the coating film. Compared to carbon materials that are not doped with boron, the boron-containing carbon material (A-1) tends to have higher wettability with resins and solvents and a smaller specific surface area. Therefore, in addition to improving the conductivity of the raw material itself, a resin composition with excellent mixability and dispersibility is obtained, which is thought to strengthen the conductive network between the carbon materials in the coating film. Furthermore, improved wettability is thought to change the interaction with the binder resin, exposing the boron-containing carbon material (A-1), which serves as a conductive additive, to the resin surface, thereby reducing the contact resistance of the conductive material. These effects are thought to enable the formation of a coating film with extremely excellent conductivity by using the boron-containing carbon material (A-1) as a conductive additive. Furthermore, as described above, the boron-containing carbon material (A-1) has improved wettability to resins and solvents, which improves the dispersibility of conductive additives with a high specific surface area, which are difficult to disperse, and allows the formation of a resin composition in which the conductive additives are uniformly dispersed. This is thought to further improve the uniformity of the coating film and the packing of the conductive additive (the conductive additive is densely packed), thereby improving durability.

[0144] In Example 7, a boron-containing carbon material was used as the carbon material (A-2), which not only had high wettability with water, but also had a coating film with extremely excellent conductivity and durability due to the use of a carbon material with a similar surface condition as a conductive material. On the other hand, in Comparative Example 7, a carbon material with a large specific surface area was used as (A-1), which had low wettability with water, making dispersion very difficult and resulting in a coating film with poor appearance.

[0145] In addition, from Examples 1 to 22, the specific surface area is 20 m 2 When a boron-containing carbon material (A-1) with a specific surface area of 0.34 nm or more or a 002 interplanar distance of 0.34 nm or more was used, a coating film with excellent conductivity was obtained. This is thought to be because a high specific surface area generally tends to result in a low particle density, and the number of conductive additive particles relative to the conductive material increases. Therefore, it is thought that the higher the specific surface area, the stronger the conductive network between the carbon materials can be. Furthermore, it is thought that the conductive additive's dispersibility in resins and solvents is improved by suppressing graphitization. These effects resulted in a coating film with excellent conductivity.

[0146] Furthermore, even though the volume resistivity of the powder is similar, the specific surface area is 110m 2 When a boron-containing carbon material (A-1) having a specific surface area of 110 m / g or more was used, a coating film with particularly excellent conductivity and durability was obtained. 2 This is thought to be because the improved resin adsorption rate compared to boron-containing carbon materials with an adsorption rate of less than 1 / g allows more of the conductive additive to be exposed on the resin surface, thereby reducing the resistance due to contact between the conductive carbon material (A-2) and the binder resin.

[0147] On the other hand, when Examples 18 to 22 and Comparative Examples 9 to 11 are compared, when a carbon material not containing boron is used as the conductive additive, the larger the specific surface area, the better the conductivity tends to be. However, when a boron-containing carbon material (A-1) is used as the conductive additive, the larger the specific surface area, the lower the conductivity tends to be. Thus, differences in the behavior of the conductive compositions when made into conductive compositions were observed depending on the boron content of the conductive additive.

[0148] As described above, the conductive composition containing the boron-containing carbon material (A-1) as a conductive additive has improved wettability to resins and solvents, thereby improving the dispersibility of the conductive additive and resulting in a resin composition in which the conductive additive is uniformly dispersed. This further improves the uniformity of the coating film and the packing of the conductive material, and it has been found that the resulting resin composition exhibits excellent conductivity and durability.

Claims

1. A conductive composition comprising a conductive carbon material (A) and a binder resin (B), wherein the conductive carbon material (A) comprises a conductive material and a conductive assistant having a specific surface area larger than that of the conductive material, the conductive assistant comprising a boron-containing carbon material (A-1), and the specific surface area of the boron-containing carbon material (A-1) is 110 to 500 m ２ / g, and the average interplanar spacing d002 of the boron-containing carbon material (A-1) as determined by X-ray diffraction is 0.34 nm or more; the content of the boron-containing carbon material (A-1) is 10 to 30 mass% relative to 100 mass% of the conductive carbon material (A); A conductive composition, wherein the conductive material contains a carbon material (A-2), and the specific surface area of the carbon material (A-2) is 100 m 2 / g or less.

2. 2. The conductive composition according to claim 1, wherein the boron-containing carbon material (A-1) has a boron content of 0.005 to 15 mol %.

3. The conductive composition according to claim 1 or 2, wherein the carbon material (A-2) contains graphite.

4. The conductive composition according to any one of claims 1 to 3, wherein the carbon material (A-2) contains boron.

5. 5. The conductive composition according to claim 4, wherein the carbon material (A-2) has a boron content of 0.005 to 15 mol %.

6. A conductive film obtained by using the conductive composition according to any one of claims 1 to 5.

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