Conductive paper, method for producing same, metal bonded body, and method for producing same

Abstract

The present invention relates to a conductive paper, a method for producing the same, a metal bonded body, and a method for producing the same, the conductive paper comprising: a paper base material containing at least carbon fibers and fibrillated fibers, the content of the fibrillated fibers being 10-120 mass% with respect to the carbon fibers; and a cured product of a thermosetting resin, at least a part of which is impregnated in the paper substrate. Further, the present invention relates to a method for producing conductive paper, in which a slurry is prepared that contains carbon fibers and fibrillated fibers, the content of the fibrillated fibers being 10-120 mass% relative to the carbon fibers, the slurry is made into paper to obtain a paper base material, the paper base material is impregnated with a thermosetting resin, and the thermosetting resin is impregnated with a thermosetting resin to obtain the conductive paper. And heating the paper base impregnated with the thermosetting resin to cure the thermosetting resin.

Description

Technical Field

[0001] The present invention relates to conductive paper and a method for manufacturing the same, a metal bonded body and a method for manufacturing the same.

[0002] This application claims priority based on Japanese Patent Application No. 2024-071548 filed in Japan on April 25, 2024, and incorporates its content herein. Background Art

[0003] Conductive paper containing a conductive material such as carbon fiber is used for energization between product constituent members. Since it can utilize the characteristics of paper to impart functions other than conductivity, it can be used for various purposes such as ground brushes with complex shapes, diaphragms for fuel cells, gas diffusion electrode materials, and electromagnetic wave absorption materials.

[0004] Patent Document 1 discloses a porous conductive sheet and an electrode material using the porous conductive sheet, which is a porous conductive sheet obtained by papermaking a slurry containing conductive particles having a particle size of less than 1 μm, conductive particles having a particle size of 5 to 100 μm, carbon fiber, and organic fiber.

[0005] Patent Document 2 discloses a fuel cell separator, which is a fuel cell separator obtained by sandwiching a resin composition containing an ethylene-vinyl alcohol copolymer and a conductive material between a plurality of composite sheets obtained by papermaking a slurry containing polyolefin resin fibers, particulate conductive materials, and fibrous conductive materials, and performing fusion integration.

[0006] In recent years, with the continuous progress of the practical application of electric vehicles, a potential difference and current sometimes occur between a rotating member such as a shaft and a fixed member such as a housing, causing problems. For example, an electric motor that is usually driven by an inverter generates an axial voltage caused by the potential difference between the stator and the rotor. When the current derived from the axial voltage passes through the rolling bearing that supports the shaft, it will damage the rolling bearing, resulting in a problem called "electro-erosion". In addition, there may also be an electromagnetic compatibility problem in which voltage and current are generated as noise components such as switches from various electronic control parts located near the rotating member, and affect other electronic control parts via the rotating member.

[0007] The above problems are all caused by the lack of a conductive path between the rotating member and the fixed member. As a countermeasure, in addition to using high-strength materials such as metal materials and cross-linked rubber materials, the use of conductive paper as a paper material has also been studied. Conductive paper has high flexibility and processability. In addition, it is thin in thickness, so its mounting property is excellent and it can be mounted on members of various shapes. In addition, due to its low hardness, when there is a differential rotational speed with the opposing surface (metal member), wear of the opposing surface can be suppressed. Its own abrasion resistance is also high. In addition, due to its porosity, it can exclude the oil film and exhibit conductivity, so it is also suitable for members lubricated with oil.

[0008] However, the conductivity of conventional conductive paper is significantly inferior to that of metal members. Therefore, in order to ensure sufficient conductivity, it is necessary to increase the area and the load. Increasing the area and the load will lead to an increase in drag torque and a decrease in durability.

[0009] In addition, the conductive path between the rotating member and the fixed member is also required to have strength to cope with shear deformation caused by the differential rotational speed with the opposing surface and heat resistance to withstand sliding heat, but conventional conductive paper does not meet these requirements. For example, the porous conductive sheet of Patent Document 1 and the fuel cell separator of Patent Document 2 are strengthened with resin, but since the resin is a thermoplastic resin, it will soften due to sliding heat, resulting in a decrease in strength. Moreover, the fuel cell separator of Patent Document 2 sandwiches a resin composition between composite sheets, so its oil film exclusion property is poor and its conductivity in an oil environment is poor.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014 - 103030

[0013] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2020 - 145014 Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] The present invention has been completed in view of the above circumstances, and its object is to provide a conductive paper excellent in conductivity, strength, and heat resistance, a manufacturing method thereof, a metal bonded body using the conductive paper, and a manufacturing method thereof.

[0016] Means for Solving the Problems

[0017] The present invention has the following aspects.

[0018] [1] A conductive paper, which contains: a paper substrate containing at least carbon fibers and fibrillated fibers, the content of the fibrillated fibers being 10 to 120% by mass relative to the carbon fibers; and a cured product of a thermosetting resin, at least a part of which is impregnated in the paper substrate.

[0019] [2] The conductive paper according to [1] above, wherein the proportion of the carbon fibers contained in the paper substrate is 35 to 90% by mass.

[0020] [3] The conductive paper according to [1] or [2] above, wherein the proportion of the cured product of the thermosetting resin contained in the conductive paper is 10 to 55% by mass.

[0021] [4] A method for manufacturing a conductive paper, wherein a slurry is prepared: containing at least carbon fibers and fibrillated fibers, the content of the fibrillated fibers being 10 to 120% by mass relative to the carbon fibers, the slurry is formed into a paper substrate by papermaking, a thermosetting resin is impregnated in the paper substrate, and the paper substrate impregnated with the thermosetting resin is heated to cure the thermosetting resin.

[0022] [5] The method for manufacturing a conductive paper according to [4] above, wherein the proportion of the carbon fibers contained in the paper substrate is 35 to 90% by mass.

[0023] [6] The method for manufacturing a conductive paper according to [4] or [5] above, wherein the proportion of the cured product of the thermosetting resin contained in the conductive paper is 10 to 55% by mass.

[0024] [7] A metal bonded body, which includes: a metal member; and the conductive paper according to any one of [1] to [3], chemically or mechanically bonded to the surface of the metal member.

[0025] [8] A method for manufacturing a metal bonded body, wherein the conductive paper according to any one of [1] to [3] is chemically or mechanically bonded to the surface of a metal member.

[0026] Advantages of the Invention

[0027] According to the present invention, it is possible to provide a conductive paper excellent in conductivity, strength and heat resistance, a method for manufacturing the same, a metal bonded body using the conductive paper, and a method for manufacturing the same. Detailed Embodiments

[0028] Hereinafter, embodiments of the present invention will be described. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

[0029] In this specification, "~" indicating a numerical range means that the numerical values described before and after it are included as the lower limit value and the upper limit value.

[0030] [[Conductive paper]]

[0031] The conductive paper according to an embodiment of the present invention contains a paper substrate and a cured product of a thermosetting resin. At least a part of the cured product of the thermosetting resin is impregnated in the paper substrate.

[0032] <Paper substrate>

[0033] The paper substrate contains at least carbon fibers and fibrillated fibers.

[0034] The carbon fiber is a fibrous carbonaceous material.

[0035] The carbon fibers constitute the skeleton of the paper substrate. In addition, the carbon fibers form a conductive network in the paper substrate, exhibiting electrical conductivity.

[0036] The fiber length of the carbon fibers in the paper substrate is preferably 0.1 mm to 6.5 mm, more preferably 0.3 mm to 2.0 mm. When the fiber length is equal to or greater than the lower limit value, the carbon fibers are likely to form a mesh structure in the paper substrate, and there is a tendency to improve the electrical conductivity of the conductive paper. When the fiber length is equal to or less than the upper limit value, the reinforcing effect of the fibrillated fibers increases, and there is a tendency to improve the strength of the conductive paper.

[0037] The fiber length of the carbon fibers of the paper substrate and the conductive paper is measured by the following method: The carbon fibers are taken out by thermal decomposition and stirring, and the taken-out fibers are subjected to image analysis.

[0038] The fiber diameter of the carbon fibers is preferably 6 to 15 μm, more preferably 7 to 10 μm. When the fiber diameter is equal to or greater than the lower limit value, the amount of electric charge that can move within a single fiber increases, and there is a tendency for the electrical conductivity of a single fiber to be excellent. When the fiber diameter is equal to or less than the upper limit value, the number of carbon fibers contained in the paper substrate increases relative to the weight of the carbon fibers, and there is a tendency for the conductive network property to be excellent. The preferred fiber diameter range of the carbon fibers is determined based on the balance between the improvement of the electrical conductivity of a single fiber and the improvement of the conductive network property.

[0039] The fiber diameter is measured by microscopically observing the cross section of the carbon fibers generated by laser or the like using an electron microscope or the like. In the case of fibers with a flat cross section, the average value of the major axis and the minor axis is set as the fiber diameter.

[0040] Examples of the carbon fibers used in the present embodiment include: polyacrylonitrile (PAN)-based carbon fibers, pitch-based carbon fibers, phenolic-based carbon fibers, rayon-based carbon fibers, and the like.

[0041] The carbon fibers may be used alone or in combination of two or more.

[0042] The proportion of carbon fibers contained in the paper substrate is preferably 35 to 90% by mass, more preferably 50 to 80% by mass, relative to the total mass of the paper substrate. When the proportion of carbon fibers is at or above the lower limit value, the electrical conductivity network property of the carbon fibers increases, and the electrical conductivity of the conductive paper tends to be more excellent. When the proportion of carbon fibers is at or below the upper limit value, the proportion of fibrillated fibers that can be incorporated increases, and the proportion of fibrillated fibers incorporated increases. As a result, the strengthening effect of the fibrillated fibers is improved, and the strength of the conductive paper tends to be more excellent.

[0043] Fibrillated fibers refer to fibers obtained by beating organic fibers so that the fibril components of the fibers are in a fluffy state.

[0044] Fibrillated fibers and carbon fibers together constitute the framework of the paper substrate. In addition, since the paper substrate contains fibrillated fibers, the fibrillated fibers increase the entanglement between the fibers, and the strength of the paper substrate and the conductive paper is improved. In addition, the paper substrate contains fibrillated fibers, which reduces the content of carbon fibers in the paper substrate. However, due to the entanglement improvement effect brought by the fibrillated fibers, the contact points between the carbon fibers increase. Therefore, the electrical conductivity network property of the paper substrate is improved instead, and the electrical conductivity of the conductive paper is improved.

[0045] The fibrillation degree of fibrillated fibers is numerically valued according to the drainage degree and specific surface area. In particular, numerical valuation based on the drainage degree is simple and becomes a substitute index for the ease of entanglement, so it is often used to evaluate the fibrillation degree.

[0046] The drainage degree of fibrillated fibers is preferably 50 to 700 mL, more preferably 150 to 600 mL. The drainage degree is one of the indexes of fibrillation. When the drainage degree is at or below the upper limit value, the fibers are sufficiently entangled with each other, and the strength and electrical conductivity of the conductive paper tend to be more excellent. When the drainage degree is at or above the lower limit value, the oil film exclusion property is maintained, and the electrical conductivity under oil lubrication tends to be more excellent.

[0047] The drainage degree is the Canadian standard drainage degree measured according to JIS P8121-2:2012.

[0048] As the organic fibers in the fibrillated fibers, any fibers that can be fibrillated can be used. For example, cellulose fibers, aramid fibers, acrylic fibers, and polyolefin fibers can be cited.

[0049] As cellulose fibers, for example, plant cellulose fibers classified as seed hair fibers, bast fibers, and leaf vein fibers with natural plants such as cotton and hemp as the main raw materials; regenerated cellulose fibers obtained by extracting cellulose from trees and wood and subjecting it to chemical treatment; and semi-synthetic fibers such as acetate obtained by acetylating a part or all of the hydroxyl groups in cellulose through a chemical reaction with cellulose can be cited.

[0050] As aramid fibers (aromatic polyamide fibers), examples include: poly-p-phenylene terephthalamide, copoly-p-phenylene-3,4'-oxydiphenylene terephthalamide, poly-m-phenylene isophthalamide.

[0051] As acrylic fibers, examples include: polyacrylonitrile, acrylonitrile polymer, acrylonitrile copolymer.

[0052] As polyolefin fibers, examples include: polyethylene, polypropylene, ethylene-propylene copolymer, polycycloolefin, polymethylpentene.

[0053] As organic fibers, from the viewpoint of heat resistance, aramid fibers, acrylic fibers, and polyolefin fibers are preferred.

[0054] The fibrillated fiber can be used alone or in combination of two or more.

[0055] The content of the fibrillated fiber is 10 to 120% by mass, more preferably 30 to 100% by mass, relative to the carbon fiber. When the content of the fibrillated fiber is at or above the lower limit value, the fibers are sufficiently entangled with each other, and the conductive paper has excellent strength and conductivity. When the content of the fibrillated fiber is at or below the upper limit value, the conductive network of the carbon fiber can be sufficiently ensured, and the conductivity is excellent.

[0056] Within the range not hindering the object of the present invention, the paper substrate may further contain other components other than carbon fiber and fibrillated fiber.

[0057] As other components, examples include: fiber dispersant, paper strength agent, coagulant, thermoplastic resin having the function of a so-called binder component, fibrous or granular organic compound, fibrous or granular inorganic compound.

[0058] Other components can be used alone or in combination of two or more.

[0059] <Cured product of thermosetting resin>

[0060] The cured product of the thermosetting resin functions as a reinforcing material for strengthening the paper substrate. At least a part of the cured product of the thermosetting resin is impregnated in the paper substrate, whereby the conductive paper has excellent strength. In addition, the cured product of the thermosetting resin has excellent heat resistance compared with the thermoplastic resin. Therefore, even when the temperature rises due to sliding heat or the like, the strength of the conductive paper is not easily reduced, and the conductive paper has excellent heat resistance.

[0061] As the thermosetting resin, any substance that is in a varnish state capable of being impregnated and undergoes thermal curing can be used. Examples include: phenolic resin, modified phenolic resin, epoxy resin, modified epoxy resin, polyimide resin, silicone resin, polyester resin, polyurethane resin, rubber resin.

[0062] As the modifying components of modified phenolic resins and modified epoxy resins, examples thereof include oils, rubbers, cashews, acrylics, and components of natural origin.

[0063] As the rubber resin, a cured product of liquid rubber is suitable. As the liquid rubber, for example, liquid butadiene rubber, liquid isoprene rubber, liquid styrene-butadiene rubber, liquid fluororubber, liquid silicone rubber, and liquid urethane rubber can be cited. For the curing of the liquid rubber, in addition to using crosslinking agents such as isocyanates, various agents for promoting the crosslinking reaction can also be used.

[0064] Within the range not hindering the object of the present invention, components other than the resin component can also be added to the thermosetting resin. As components other than the resin component, for example, surface tension adjusters for improving the impregnation property contained or added in the resin solution, fibrous or particulate organic compounds or inorganic compounds can be cited.

[0065] As the thermosetting resin, from the perspectives of heat resistance, oil resistance, and strength, phenolic resins and modified phenolic resins are preferred.

[0066] The thermosetting resin can be used alone or in combination of two or more.

[0067] The proportion of the cured product of the thermosetting resin contained in the conductive paper is preferably 10 to 55% by mass, more preferably 20 to 40% by mass, relative to the total mass of the conductive paper. When the proportion of the cured product of the thermosetting resin is at least the lower limit value, there is a tendency for the strength to be more excellent. When the proportion of the cured product of the thermosetting resin is at most the upper limit value, there is a tendency for the conductivity and oil film removal property to be more excellent.

[0068] <Properties of the conductive paper>

[0069] The porosity of the conductive paper is preferably 30 to 95%, more preferably 50 to 90%. When the porosity is at most the upper limit value, the strength and conductivity are more excellent. When the porosity is at least the lower limit value, the oil film removal property is improved and the conductivity under oil lubrication is more excellent.

[0070] The porosity is a value measured by a mercury porosimeter.

[0071] The conductive paper of the present embodiment is preferably a conductive paper capable of withstanding the differential rotational speed with a rotating member, and as an index of its strength, shear strength can be cited.

[0072] The shear strength of the conductive paper is preferably 0.1 MPa or more, more preferably 0.2 MPa or more. When the shear strength is at least the lower limit value, the load on the conductive paper can be increased, so it is useful in applications requiring high conductivity.

[0073] The thickness of the conductive paper is preferably 0.2 to 1.5 mm, more preferably 0.3 mm to 1.0 mm. When the thickness of the conductive paper is above the lower limit value, the durability life determined by abrasion and collapse is more excellent. When the thickness is below the upper limit value, the distance of current conduction in the thickness direction of the conductive paper becomes shorter, so the conductivity in the thickness direction of the conductive paper is more excellent.

[0074] <Manufacturing method of conductive paper>

[0075] The conductive paper of this embodiment can be manufactured by, for example, the following method.

[0076] Prepare the following slurry: containing at least carbon fiber and fibrillated fiber, the content of the fibrillated fiber is 10 to 120% by mass relative to the carbon fiber, make paper from the slurry to obtain a paper substrate, impregnate the paper substrate with a thermosetting resin, and heat the paper substrate impregnated with the thermosetting resin to cure the thermosetting resin.

[0077] (Preparation of slurry)

[0078] The slurry can be prepared by dispersing carbon fiber, fibrillated fiber, and other components as needed in water.

[0079] Carbon fiber, fibrillated fiber, and other components can each be commercially available or manufactured by known methods. The fibrillated fiber is obtained, for example, by fibrillating the fiber by a known method. As the fibrillating method, for example, the method of beating the fiber using a beater, refiner, etc. can be cited.

[0080] The dispersion method is not particularly limited, and the methods used in the past for preparing pulp slurry in paper manufacturing can be applied. For example, it can be carried out using a dissociator (pulper), beater, refiner, etc.

[0081] (Paper making)

[0082] The paper making (wet paper making) of the slurry can be carried out by a known method. For example, it can be carried out using a fourdrinier-type or cylinder-type paper machine.

[0083] If necessary, in order to improve the strength of the paper substrate, the solution of the thermoplastic resin can also be impregnated into the paper formed by paper making by coating or impregnation to obtain the paper substrate.

[0084] In addition, within the scope not hindering the purpose of the present invention, the solution of the thermoplastic resin can also contain components other than the resin component. As components other than the resin component, for example, a surface tension adjuster for improving impregnation property, fibrous or particulate organic compounds or inorganic compounds contained or added in the resin solution can be cited.

[0085] (Impregnation with thermosetting resin)

[0086] As a method of impregnating a thermosetting resin into a paper substrate, a method of impregnating a varnish containing a thermosetting resin and a solvent into the paper substrate by coating or impregnation and then drying (removing the solvent) is preferred. By impregnating the thermosetting resin in this way, the entire paper substrate can be uniformly strengthened by the thermosetting resin compared to the case where the thermosetting resin is internally added to the paper substrate.

[0087] As the solvent of the varnish, any solvent that can dissolve the thermosetting resin can be used. In order to improve the impregnation property into the paper substrate, a solvent with a low viscosity is preferred, and in order to easily remove the solvent, a solvent with a high volatility is preferred.

[0088] Within the scope not hindering the object of the present invention, the varnish may also contain components other than the resin component. As components other than the resin component, for example, a surface tension adjuster for improving the impregnation property contained or added in the resin solution, a fibrous or particulate organic compound or inorganic compound can be cited.

[0089] As a method of impregnating the varnish into the paper substrate, for example, a method of coating the varnish on one or both sides of the paper substrate, or a method of immersing the paper substrate in the varnish can be cited.

[0090] For drying, as long as the solvent of the varnish can be removed, it can be heat drying or air drying. The temperature of heat drying is, for example, 50 to 200 °C.

[0091] (Curing)

[0092] Regarding the heating conditions for the paper substrate impregnated with the thermosetting resin, as long as the thermosetting resin can be cured, it can be appropriately selected according to the thermosetting resin used. In the case of a phenolic resin, it is generally about 10 to 100 minutes at 120 to 300 °C.

[0093] After curing, surface grinding, additional heating, compression molding, hot press bonding, chemical or mechanical bonding with metal or non-metal members, etc. can be performed as needed.

[0094] <Uses of conductive paper>

[0095] The conductive paper of the present embodiment is excellent in conductivity, strength, and heat resistance. Therefore, it is preferably used for applications that require these properties.

[0096] As a preferred example of the use of the conductive paper of the present embodiment, the formation of a conductive path between a rotating member and a fixed member can be cited. Among them, the formation of a conductive path for preventing electrolytic corrosion of a bearing that supports an inverter-controlled motor is preferred.

[0097] In applications of conductive paths, for example, conductive paper is chemically or mechanically bonded to the surface of a metal member to form a metal bonded body. In this metal bonded body, the conductive paper can be used as a conductive path. For example, metal members having a potential difference can be grounded through the conductive paper.

[0098] The metal member is not particularly limited. For example, as a rotating member, examples include: bearings, shafts, housings, shaft accessories, and housing accessories.

[0099] The metal bonded body of the present embodiment can be manufactured by a method of chemically or mechanically bonding the conductive paper of the present embodiment to the surface of a metal member.

[0100] As a method of chemically or mechanically bonding the conductive paper, for example, examples include: a method of bonding the conductive paper to the metal member through a chemical reaction with an adhesive; a method of chemically adsorbing and bonding the conductive paper to the metal member through the adhesive component of a tape; a method of mechanically fixing and bonding the conductive paper to the metal member through riveting or unevenness.

[0101] [Examples]

[0102] The present invention will be specifically described below by way of examples, but the present invention is not limited to the following description.

[0103] (Manufacture of Conductive Paper)

[0104] First, conductive papers of Example 1 and Comparative Examples 1 to 3 were manufactured.

[0105] Example 1 satisfies all of the following conditions: the condition of the content of fibrillated fibers in the paper substrate relative to carbon fibers in the present invention; the condition of the proportion of carbon fibers contained in the paper substrate; the condition of the proportion of the cured product of the thermosetting resin in the conductive paper obtained from the same paper substrate; the condition of the manufacturing method of obtaining a paper substrate by papermaking of a slurry, impregnating the thermosetting resin therein, and curing it. Specifically, in the conductive paper of Example 1, the content of fibrillated fibers in the paper substrate is 43% by mass relative to carbon fibers, the content ratio of carbon fibers in the paper substrate is 66% by mass, and the content ratio of the cured product of the thermosetting resin in the conductive paper is 20% by mass. In addition, in the manufacturing method of the conductive paper of Example 1, a slurry is prepared: containing carbon fibers, fibrillated fibers, and other components, the content of fibrillated fibers is 43% by mass relative to carbon fibers, a paper substrate is obtained by papermaking of the slurry, the varnish of the thermosetting resin is impregnated in the paper substrate, and the thermosetting resin is cured by heating the paper substrate impregnated with the thermosetting resin.

[0106] Comparative Example 1 does not satisfy the condition of the content of fibrillated fibers relative to carbon fibers in the present invention, and the paper substrate does not contain fibrillated fibers. Specifically, in the conductive paper of Comparative Example 1, the content of fibrillated fibers in the paper substrate is 0% by mass relative to carbon fibers, the content ratio of carbon fibers in the paper substrate is 95% by mass, and the content ratio of the cured product of the thermosetting resin in the conductive paper is 20% by mass. In addition, in the manufacturing method of the conductive paper of Comparative Example 1, a slurry containing carbon fibers and other components is prepared, the slurry is sheeted to obtain a paper substrate, the varnish of the thermosetting resin is impregnated in the paper substrate, and the paper substrate impregnated with the thermosetting resin is heated to cure the thermosetting resin.

[0107] Comparative Example 2 does not satisfy the condition of the content of fibrillated fibers relative to carbon fibers in the present invention, and the content of fibrillated fibers in the paper substrate is less than that relative to carbon fibers. Specifically, in the conductive paper of Comparative Example 2, the content of fibrillated fibers in the paper substrate is 5% by mass relative to carbon fibers, the content ratio of carbon fibers in the paper substrate is 90% by mass, and the content ratio of the cured product of the thermosetting resin in the conductive paper is 20% by mass. In addition, in the manufacturing method of the conductive paper of Comparative Example 2, a slurry is prepared as follows: containing carbon fibers, fibrillated fibers and other components, the content of fibrillated fibers is 5% by mass relative to carbon fibers, the slurry is sheeted to obtain a paper substrate, the varnish of the thermosetting resin is impregnated in the paper substrate, and the paper substrate impregnated with the thermosetting resin is heated to cure the thermosetting resin.

[0108] Comparative Example 3 does not satisfy the condition of the content of fibrillated fibers relative to carbon fibers in the present invention, and the content of fibrillated fibers in the paper substrate is more than that relative to carbon fibers. Specifically, in the conductive paper of Comparative Example 3, the content of fibrillated fibers in the paper substrate is 156% by mass relative to carbon fibers, the content ratio of carbon fibers in the paper substrate is 37% by mass, and the content ratio of the cured product of the thermosetting resin in the conductive paper is 20% by mass. In addition, in the manufacturing method of the conductive paper of Comparative Example 3, a slurry is prepared as follows: containing carbon fibers, fibrillated fibers and other components, the content of fibrillated fibers is 156% by mass relative to carbon fibers, the slurry is sheeted to obtain a paper substrate, the varnish of the thermosetting resin is impregnated in the paper substrate, and the paper substrate impregnated with the thermosetting resin is heated to cure the thermosetting resin.

[0109] That is, Comparative Examples 1 to 3 are conductive papers produced by the same manufacturing method as in Example 1, but do not satisfy the condition of the content of fibrillated fibers in the paper substrate relative to carbon fibers, and are outside the scope of the present invention.

[0110] The raw materials used in Example 1 and Comparative Examples 1 to 3 were exactly the same. PAN-based carbon fiber with a fiber diameter of 7 μm and a fiber length of 2 mm in a paper substrate was used as the carbon fiber, and aramid fiber with a drainage degree of 300 mL was used as the fibrillation fiber. Thermoplastic resin, paper strength agent, and coagulant were used as other components in the same amounts by composition and with a total content ratio in the paper substrate of 5% by mass.

[0111] In addition, the thickness of the conductive paper in Example 1 and Comparative Examples 1 to 3 was set to 0.5 mm.

[0112] (Evaluation of conductive paper)

[0113] Next, the strength and conductivity of the conductive papers in Example 1 and Comparative Examples 1 to 3 were evaluated. The results are shown in Table 1.

[0114] The strength was evaluated by measuring the shear strength of the conductive paper. The shear strength measurement was carried out by the following method: The front and back surfaces of the conductive paper were fixed to iron plates respectively, and the iron plates were moved in the shear direction, that is, in the direction perpendicular to the thickness direction of the conductive paper, and the iron plates on the front and back surfaces were moved in opposite directions, thereby causing the conductive paper to shear deform, and the maximum value of the shear stress until the conductive paper was sheared and damaged was taken as the shear strength.

[0115] The size of the conductive paper during the shear strength measurement was carried out with a diameter of Φ3 mm.

[0116] The conductivity was evaluated in the following manner: A ring-shaped conductive paper with an inner diameter of φ38.5 mm and an outer diameter of φ55.8 mm was made. The inner diameter side of the front and back surfaces of the ring-shaped conductive paper was clamped by a ring-shaped copper plate with an inner diameter of φ33 mm and an outer diameter of φ45 mm, and the outer diameter side of the front and back surfaces of the ring-shaped conductive paper was clamped by a ring-shaped copper plate with an inner diameter of φ49 mm and an outer diameter of 61 mm. A conductive path from the copper plate on the inner diameter side of the conductive paper to the copper plate on the outer diameter side of the conductive paper was formed on the conductive paper, and the resistance value, that is, the impedance, of the alternating current of this conductive path was measured. Here, the clamping pressure of the copper plate was set to 50 N on the inner diameter side and the outer diameter side of the conductive paper respectively. In addition, the conductivity was evaluated by taking the reciprocal of the measured impedance.

[0117] Regarding the evaluation results of strength and conductivity, the relative values of the shear strength and the reciprocal of the impedance were respectively expressed using the value of Comparative Example 1 as 100. When the evaluation value was greater than 100, it was judged that the performance was improved.

[0118] [Table 1]

[0119]

[0120] As can be seen from Table 1, in Example 1, the evaluation values of strength and conductivity are greater than 100 and are the highest compared to Comparative Examples 1 to 3. Compared with Comparative Example 1, the performance of Comparative Example 2 is improved, but the effect is not sufficiently increased. Compared with Comparative Example 1, the conductivity of Comparative Example 3 is decreased. Therefore, the conductive paper of Example 1 can sufficiently improve strength and conductivity.

Claims

1. A conductive paper, wherein: contain: A paper substrate comprising at least carbon fibers and fibrillated fibers, wherein the content of the fibrillated fibers is 10 to 120% by mass relative to the carbon fibers; and A cured product of a thermosetting resin is at least partially impregnated in the paper substrate. The ratio of the cured product of the thermosetting resin contained in the conductive paper is 10 to 55% by mass.

2. The conductive paper according to claim 1, wherein: The ratio of the carbon fibers contained in the paper substrate is 35 to 90% by mass.

3. A method for manufacturing conductive paper, wherein: The following slurry is prepared: the slurry contains at least carbon fibers and fibrillated fibers, wherein the content of the fibrillated fibers is 10 to 120% by mass relative to the carbon fibers. The slurry is subjected to papermaking to obtain a paper substrate, impregnating the paper substrate with a thermosetting resin, The paper base material impregnated with the thermosetting resin is heated to cure the thermosetting resin, and the ratio of the cured product of the thermosetting resin contained in the conductive paper is 10 to 55% by mass.

4. The method for producing conductive paper according to claim 3, wherein: The ratio of the carbon fibers contained in the paper substrate is 35 to 90% by mass.

5. A metal bond, wherein: have: Metal components; and Conductive paper is chemically or mechanically bonded to the surface of the metal component. The conductive paper contains: A paper substrate comprising at least carbon fibers and fibrillated fibers, wherein the content of the fibrillated fibers is 10 to 120% by mass relative to the carbon fibers; and At least a part of the cured product of the thermosetting resin is impregnated in the paper base material.

6. A metal bond, wherein: have: Metal components; and The conductive paper according to claim 1 or 2 is chemically or mechanically bonded to the surface of the metal member.

7. A method for producing a metal bond, wherein: Bond the conductive paper chemically or mechanically to the surface of the metal component. The conductive paper contains: A paper substrate comprising at least carbon fibers and fibrillated fibers, wherein the content of the fibrillated fibers is 10 to 120% by mass relative to the carbon fibers; and At least a part of the cured product of the thermosetting resin is impregnated in the paper base material.

8. A method for producing a metal bond, wherein: The conductive paper according to claim 1 or 2 is chemically or mechanically bonded to the surface of a metal member.

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