Conductive paper, production method thereof, metallic adherend and production method thereof

Abstract

To provide conductive paper with excellent electrical conductivity, strength, and heat resistance, and a method for producing the same.SOLUTION: The conductive paper comprises: a paper substrate containing at least a carbon fiber and a fibrillated fiber, and in which an amount of the fibrillated fiber is from 10 to 120 mass% with respect to the carbon fiber; and a cured product of a thermosetting resin at least partially impregnated into the paper substrate. The method for producing conductive paper comprises the steps of: preparing a slurry containing a carbon fiber and a fibrillated fiber, and in which an amount of the fibrillated fiber is from 10 to 120 mass% with respect to the carbon fiber; obtaining a paper substrate by subjecting the slurry to a papermaking process; impregnating the paper substrate with a thermosetting resin; and heating the paper substrate impregnated with the thermosetting resin to cure the thermosetting resin.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Conductive paper, which contains conductive materials such as carbon fiber, is used to conduct electricity between product components. Its properties as paper can be used to give it functions other than conductivity, so it is used in a variety of applications, such as complex-shaped grounding brushes, fuel cell separators, gas diffusion electrode materials, and electromagnetic wave absorbers. Patent Document 1 discloses a porous conductive sheet made by papermaking a slurry containing conductive particles with a particle diameter of less than 1 μm, conductive particles with a particle diameter of 5 to 100 μm, carbon fibers, and organic fibers, and an electrode material using the same. Patent Document 2 discloses a fuel cell separator in which a resin composition containing an ethylene vinyl alcohol copolymer and a conductive material is sandwiched between multiple composite sheets made by papermaking a slurry containing polyolefin resin fibers, a particulate conductive material, and a fibrous conductive material, and the sheets are welded together. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-103030 [Patent Document 2] Japanese Patent Publication No. 2020-145014 Summary of the Invention [Problem to be solved by the invention]

[0004] As electric vehicles have become more widely used in recent years, potential differences and currents can arise between rotating components such as shafts and fixed components such as housings, which can cause problems. For example, in electric motors that are typically inverter-driven, a shaft voltage is generated due to the potential difference between the stator and rotor. When current from the shaft voltage passes through the rolling bearings that support the shaft, it can damage the rolling bearings, causing a problem known as "electrolytic corrosion." Furthermore, various electronic control components located near the rotating components can generate voltages and currents as switching noise components, which can affect other electronic control components via the rotating components, resulting in electromagnetic compatibility problems. Both problems arise from the lack of a conductive path between the rotating and fixed components, and as a solution, the use of conductive paper, a paper material, is being considered in addition to high-strength materials such as metals and cross-linked rubber. Conductive paper is flexible, easy to process, and thin, making it easy to attach to components of various shapes. Its low hardness also helps prevent wear on the mating surface (metallic component) when there is differential rotation. Its own wear resistance is also high. Furthermore, its porosity allows it to eliminate oil films and demonstrate conductivity, making it suitable for use in components that require oil lubrication.

[0005] However, the conductivity of conventional conductive paper is significantly inferior to that of metal materials. Therefore, in order to ensure sufficient conductivity, it is necessary to increase the area and load. Increasing the area and load increases the drag torque and reduces durability. Furthermore, the conductive path between the rotating and fixed members must be strong enough to withstand shear deformation caused by differential rotation with respect to the opposing surfaces, and heat resistance sufficient to withstand sliding heat; however, conventional conductive paper does not meet these requirements. For example, the porous conductive sheet in Patent Document 1 and the fuel cell separator in Patent Document 2 are reinforced with resin, but because the resin is a thermoplastic resin, it softens due to sliding heat and loses strength. Furthermore, the fuel cell separator in Patent Document 2 has a resin composition sandwiched between composite sheets, resulting in poor oil film removal and poor conductivity in an oily environment.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide conductive paper with excellent conductivity, strength, and heat resistance, a method for manufacturing the same, and a metal adhesive using this conductive paper and a method for manufacturing the same. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A paper substrate containing 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; a cured product of a thermosetting resin at least partially impregnated into the paper substrate; A conductive paper comprising: [2] The conductive paper according to [1], wherein the proportion of the carbon fiber contained in the paper base material is 35 to 90 mass %. [3] The conductive paper according to [1] or [2], wherein the proportion of the cured thermosetting resin contained in the conductive paper is 10 to 55 mass %. [4] Preparing a slurry containing at least carbon fibers and fibrillated fibers, in which 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; The paper substrate is impregnated with a thermosetting resin; A method for producing conductive paper, comprising heating the paper base material impregnated with the thermosetting resin to cure the thermosetting resin. [5] The method for producing conductive paper according to [4] above, wherein the carbon fiber content of the paper base material is 35 to 90 mass %. [6] The method for producing conductive paper according to [4] or [5], wherein the proportion of the cured thermosetting resin contained in the conductive paper is 10 to 55 mass %. [7] A metal bonded body comprising a metal member and the conductive paper according to any one of [1] to [3] above, chemically or mechanically bonded to the surface of the metal member. [8] A method for producing a metal bonded body, comprising chemically or mechanically bonding the conductive paper according to any one of [1] to [3] above to the surface of a metal member. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide conductive paper having excellent conductivity, strength, and heat resistance, a method for manufacturing the same, and a metal bonded body using the conductive paper and a method for manufacturing the same. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments described below, and various modifications are possible without departing from the gist of the present invention. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] [Conductive paper] The conductive paper according to one embodiment of the present invention contains a paper substrate and a cured thermosetting resin, with at least a portion of the cured thermosetting resin impregnating the paper substrate.

[0011] <Paper base material> The paper substrate contains at least carbon fibers and fibrillated fibers.

[0012] Carbon fiber is a fibrous carbon-based material. The carbon fibers form the skeleton of the paper substrate, and also form a conductive network within the paper substrate, thereby providing electrical conductivity.

[0013] 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. If the fiber length is equal to or greater than the lower limit, the carbon fibers tend to form a mesh structure within the paper substrate, which tends to improve the conductivity of the conductive paper. If the fiber length is equal to or less than the upper limit, the reinforcing effect of the fibrillated fibers becomes greater, which tends to improve the strength of the conductive paper. The fiber length of the carbon fibers in the paper substrate and conductive paper is measured by extracting the carbon fibers through pyrolysis and stirring, and then analyzing the images of the extracted fibers.

[0014] The fiber diameter of the carbon fiber 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, the amount of charge that can move within a single fiber increases, and the conductivity of the single fiber tends to be excellent. When the fiber diameter is equal to or less than the upper limit, the number of carbon fibers relative to the weight of carbon fibers contained in the paper base material increases, and the conductive network properties tend to be excellent. The preferred fiber diameter range of the carbon fiber is determined by the balance between improving the conductivity of the single fiber and improving the conductive network properties. The fiber diameter is measured by microscopic observation of the cross section of carbon fiber formed by laser etc. using an electron microscope etc. In the case of a fiber with a flat cross section, the average value of the major axis and the minor axis is taken as the fiber diameter.

[0015] Examples of carbon fibers used in this embodiment include polyacrylonitrile (PAN)-based carbon fibers, pitch-based carbon fibers, phenol-based carbon fibers, and rayon-based carbon fibers. Only one type of carbon fiber may be used, or two or more types may be used in combination.

[0016] The proportion of carbon fiber contained in the paper base material is preferably 35 to 90 mass% and more preferably 50 to 80 mass% relative to the total mass of the paper base material. When the proportion of carbon fiber is equal to or greater than the lower limit, the conductive network properties of the carbon fiber are enhanced, and the conductive paper tends to have better conductivity. When the proportion of carbon fiber is equal to or less than the upper limit, the proportion of fibril fiber that can be incorporated increases, and as the proportion of fibril fiber incorporated increases, the reinforcing effect of the fibril fiber is enhanced, and the conductive paper tends to have better strength.

[0017] Fibrillated fibres refer to fibres in a state in which organic fibres have been beaten to fluff the fibril components of the fibres. The fibrillated fibers, together with the carbon fibers, form the skeleton of the paper substrate. Furthermore, when the paper substrate contains fibrillated fibers, the fibrillated fibers increase the entanglement between the fibers, improving the strength of the paper substrate and the conductive paper. Furthermore, although the inclusion of fibrillated fibers in the paper substrate reduces the carbon fiber content of the paper substrate, the increased entanglement effect of the fibrillated fibers increases the number of contact points between the carbon fibers, thereby improving the conductive network properties of the paper substrate and improving the conductivity of the conductive paper.

[0018] The degree of fibrillation of fibrillated fibers is quantified by freeness and specific surface area. In particular, freeness is often used to evaluate the degree of fibrillation because it is simple and serves as an alternative index for the ease of entanglement. The freeness of the fibrillated fiber is preferably 50 to 700 mL, more preferably 150 to 600 mL. The freeness is one of the indicators of fibrillation. When the freeness is below the upper limit, the fibers are sufficiently entangled with each other, and the strength and conductivity of the conductive paper tend to be superior. When the freeness is above the lower limit, the oil film removal ability is maintained, and the conductivity under oil lubrication tends to be superior. The freeness is the Canadian standard freeness measured in accordance with JIS P 8121-2:2012.

[0019] The organic fiber in the fibrillated fiber may be any fiber that can be fibrillated, and examples thereof include cellulose fiber, aramid fiber, acrylic fiber, and polyolefin fiber. Examples of cellulose fibers include plant cellulose fibers, which are primarily made from natural plants such as cotton and hemp and are classified into seed hair fibers, bast fibers, and leaf vein fibers; regenerated cellulose fibers, which are obtained by extracting cellulose from trees and wood and subjecting it to chemical treatment; and semi-synthetic fibers, which are acetates obtained by chemically acetylating some or all of the hydroxyl groups in cellulose. Examples of aramid fibers (aromatic polyamide fibers) include polyparaphenylene terephthalamide, copolyparaphenylene-3,4'oxydiphenylene-terephthalamide, and polymetaphenylene isophthalamide. Examples of acrylic fibers include polyacrylonitrile, acrylonitrile polymers, and acrylonitrile copolymers. Examples of polyolefin fibers include polyethylene, polypropylene, ethylene-propylene copolymer, polycycloolefin, and polymethylpentene. As the organic fiber, aramid fiber, acrylic fiber, and polyolefin fiber are preferred from the viewpoint of heat resistance.

[0020] The fibrillated fibers may be used alone or in combination of two or more kinds. The content of fibrillated fibers is 10 to 120% by mass, more preferably 30 to 100% by mass, relative to the carbon fibers. When the content of fibrillated fibers is equal to or greater than the lower limit, the fibers are sufficiently entangled, resulting in excellent strength and conductivity of the conductive paper. When the content of fibrillated fibers is equal to or less than the upper limit, the conductive network properties of the carbon fibers can be sufficiently ensured, resulting in excellent conductivity.

[0021] The paper substrate may further contain other components in addition to the carbon fibers and fibrillated fibers, as long as the object of the present invention is not impaired. Examples of other components include fiber dispersants, paper strength agents, flocculants, thermoplastic resins that act as so-called binder components, fibrous or particulate organic compounds, and fibrous or particulate inorganic compounds. The other components may be used alone or in combination of two or more.

[0022] <Cured thermosetting resin> The cured thermosetting resin functions as a reinforcing material that reinforces the paper substrate. The paper substrate is impregnated with at least a portion of the cured thermosetting resin, resulting in excellent strength of the conductive paper. Furthermore, since the cured thermosetting resin has better heat resistance than thermoplastic resin, the strength of the conductive paper is less likely to decrease even when the temperature rises due to heat from sliding, etc., resulting in excellent heat resistance of the conductive paper.

[0023] The thermosetting resin may be any resin that can be impregnated into a varnish and can be thermoset, and examples thereof include phenolic resin, modified phenolic resin, epoxy resin, modified epoxy resin, polyimide resin, silicone resin, polyester resin, polyurethane resin, and rubber resin. Modified components of modified phenolic resins and modified epoxy resins include oil, rubber, cashew, acrylic, and naturally occurring components. The rubber resin corresponds to a liquid rubber cured product. Examples of liquid rubber include liquid butadiene rubber, liquid isoprene rubber, liquid styrene butadiene rubber, liquid fluororubber, liquid silicone rubber, and liquid urethane rubber. In addition to a crosslinking agent such as isocyanate, various agents for accelerating the crosslinking reaction may be used to cure the liquid rubber. The thermosetting resin may contain components other than the resin component as long as the object of the present invention is not impaired. Examples of components other than the resin component include a surface tension adjuster for improving impregnation, and a fibrous or particulate organic or inorganic compound contained in or added to the resin solution. Of these, phenol resins and modified phenol resins are preferred as thermosetting resins from the various viewpoints of heat resistance, oil resistance, and strength. The thermosetting resins may be used alone or in combination of two or more.

[0024] The proportion of the cured thermosetting resin contained in the conductive paper is preferably 10 to 55 mass %, more preferably 20 to 40 mass %, relative to the total mass of the conductive paper. When the proportion of the cured thermosetting resin is equal to or greater than the lower limit, the strength tends to be better. When the proportion of the cured thermosetting resin is equal to or less than the upper limit, the conductivity and oil film removability tend to be better.

[0025] <Characteristics of conductive paper> The porosity of the conductive paper is preferably 30 to 95%, more preferably 50 to 90%. When the porosity is equal to or less than the upper limit, the strength and conductivity are superior. When the porosity is equal to or more than the lower limit, the oil film removal is enhanced and the conductivity under oil lubrication is superior. The porosity is a value measured by a mercury porosimeter.

[0026] The conductive paper of this embodiment is preferably one that can withstand the differential rotation with the rotating member, and an index of its strength is its shear strength. 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 equal to or greater than the lower limit, the load applied to the conductive paper can be increased, making it useful for applications requiring high conductivity.

[0027] The thickness of the conductive paper is preferably 0.2 to 1.5 mm, and more preferably 0.3 to 1.0 mm. When the thickness of the conductive paper is equal to or greater than the lower limit, the durability life determined by wear and settling is better. When the thickness is equal to or less than the upper limit, the distance through which electricity flows in the thickness direction of the conductive paper is shorter, resulting in better conductivity in the thickness direction of the conductive paper.

[0028] <Conductive paper manufacturing method> The conductive paper of this embodiment can be manufactured, for example, by the following method. A method comprising preparing a slurry containing at least carbon fibers and fibrillated fibers, with the fibrillated fibers being present in an amount of 10 to 120% by mass relative to the carbon fibers, making a paper base from the slurry, impregnating the paper base with a thermosetting resin, and heating the paper base impregnated with the thermosetting resin to cure the thermosetting resin.

[0029] (Preparation of Slurry) The slurry can be prepared by dispersing the carbon fibers, fibrillated fibers, and optionally other ingredients in water. The carbon fiber, fibrillated fiber, and other components may be commercially available or may be produced by a known method. The fibrillated fiber can be obtained, for example, by fibrillating fibers by a known method. Examples of the fibrillation method include beating fibers using a beater, refiner, or the like. The dispersion method is not particularly limited, and any method conventionally used for preparing pulp slurries in paper manufacturing can be applied, for example, using a disintegrator (pulper), beater, refiner, etc.

[0030] (Papermaking) Papermaking from the slurry (wet papermaking) can be carried out by a known method, for example, using a Fourdrinier or cylinder papermaking machine.

[0031] If necessary, the paper product formed by papermaking may be impregnated with a thermoplastic resin solution by coating or immersion to obtain a paper base material in order to improve the strength of the paper base material. The thermoplastic resin solution may contain components other than the resin component, provided that the object of the present invention is not impaired. Examples of components other than the resin component include a surface tension adjuster for improving impregnation properties and a fibrous or particulate organic or inorganic compound contained in or added to the resin solution.

[0032] (Thermosetting resin impregnation) A preferred method for impregnating a paper substrate with a thermosetting resin is to impregnate the paper substrate with a varnish containing a thermosetting resin and a solvent by coating or immersing the paper substrate in the varnish, and then drying (removing the solvent). By impregnating the paper substrate with the thermosetting resin in this manner, the entire paper substrate can be reinforced evenly with the thermosetting resin, compared to when the thermosetting resin is internally added to the paper substrate. The solvent for the varnish may be any solvent capable of dissolving the thermosetting resin, and preferably has low viscosity to enhance impregnation into the paper substrate, and high volatility to facilitate removal of the solvent. The varnish may contain components other than the resin component as long as the object of the present invention is not impaired. Examples of components other than the resin component include a surface tension adjuster for improving impregnation, and a fibrous or particulate organic or inorganic compound contained in or added to the resin solution. Methods for impregnating the paper substrate with the varnish include, for example, a method of applying the varnish to one or both sides of the paper substrate, and a method of immersing the paper substrate in the varnish. The drying may be performed by heat drying or air drying, as long as it can remove the solvent from the varnish. The temperature for heat drying is, for example, 50 to 200°C.

[0033] (hardening) The heating conditions for the paper substrate impregnated with the thermosetting resin can be selected appropriately depending on the thermosetting resin used, as long as the thermosetting resin can be cured. In the case of phenolic resin, the heating conditions are generally 120 to 300°C for 10 to 100 minutes.

[0034] After curing, the composition may be subjected to treatments such as surface polishing, additional heating, compression molding, thermocompression bonding, and chemical or mechanical bonding to metal or non-metallic members, if necessary.

[0035] <Uses of conductive paper> The conductive paper of this embodiment has excellent conductivity, strength, and heat resistance, and is therefore preferably used in applications where these properties are required. A preferred example of the use of the conductive paper of this embodiment is the formation of a conductive path between a rotating member and a fixed member, particularly for preventing electrolytic corrosion of bearings that support inverter-controlled motors. For conductive path applications, for example, conductive paper is chemically or mechanically bonded to the surface of a metal component to form a metal bonded assembly. In such a metal bonded assembly, the conductive paper can be used as a conductive path. For example, metal components with a potential difference can be grounded via the conductive paper.

[0036] The metal member is not particularly limited, but examples of the rotating member include bearings, shafts, housings, shaft accessories, and housing accessories.

[0037] The metal bonded body of this embodiment can be produced by a method of chemically or mechanically bonding the conductive paper of this embodiment to the surface of a metal member. Methods for chemically or mechanically bonding conductive paper include, for example, bonding the conductive paper to the metal member through a chemical reaction with an adhesive, bonding the conductive paper to the metal member by chemically adsorbing them using the adhesive components of the tape, and mechanically fixing and bonding the conductive paper to the metal member using crimping or unevenness. [Example]

[0038] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0039] (Preparation of conductive paper) First, conductive papers of Example 1 and Comparative Examples 1 to 3 were produced.

[0040] Example 1 satisfies all of the conditions of the present invention regarding the content of fibrillated fibers relative to the carbon fibers in the paper substrate, the condition regarding the ratio of carbon fibers contained in the paper substrate, the condition regarding the ratio of cured thermosetting resin in conductive paper obtained from the same paper substrate, and the conditions for the manufacturing method in which a paper substrate is obtained by papermaking a slurry, and then the paper substrate is impregnated with and cured with a thermosetting resin. Specifically, the conductive paper of Example 1 has a fibrillated fiber content of 43% by mass relative to the carbon fibers in the paper substrate, a carbon fiber content of 66% by mass in the paper substrate, and a cured thermosetting resin content of 20% by mass in the conductive paper. In addition, the manufacturing method for the conductive paper of Example 1 involves preparing a slurry containing carbon fibers, fibrillated fibers, and other components, with the fibrillated fiber content being 43% by mass relative to the carbon fibers, papermaking the slurry to obtain a paper substrate, impregnating the paper substrate with a thermosetting resin varnish, and heating the thermosetting resin-impregnated paper substrate to cure the thermosetting resin.

[0041] Comparative Example 1 does not satisfy the condition of the present invention for the content of fibrillated fibers relative to the carbon fibers, and the paper base material does not contain fibrillated fibers. Specifically, the conductive paper of Comparative Example 1 has a fibrillated fiber content of 0% by mass relative to the carbon fibers in the paper base material, a carbon fiber content of 95% by mass in the paper base material, and a cured thermosetting resin content of 20% by mass in the conductive paper. In addition, the conductive paper of Comparative Example 1 is manufactured by preparing a slurry containing carbon fibers and other components, papermaking the slurry to obtain a paper base material, impregnating the paper base material with a thermosetting resin varnish, and heating the paper base material impregnated with the thermosetting resin to cure the thermosetting resin.

[0042] Comparative Example 2 does not satisfy the condition of the fibrillated fiber content relative to the carbon fiber of the present invention, and the content of fibrillated fiber relative to the carbon fiber in the paper base material is low. Specifically, the conductive paper of Comparative Example 2 has a fibrillated fiber content of 5% by mass relative to the carbon fiber in the paper base material, a carbon fiber content of 90% by mass in the paper base material, and a cured thermosetting resin content of 20% by mass in the conductive paper. In addition, the conductive paper of Comparative Example 2 is manufactured by preparing a slurry containing carbon fiber, fibrillated fiber, and other components, with a fibrillated fiber content of 5% by mass relative to the carbon fiber, papermaking the slurry to obtain a paper base material, impregnating the paper base material with a thermosetting resin varnish, and heating the paper base material impregnated with the thermosetting resin to cure the thermosetting resin.

[0043] Comparative Example 3 does not satisfy the condition of the present invention for the content of fibrillated fibers relative to carbon fibers, and the content of fibrillated fibers relative to carbon fibers in the paper base material is high. Specifically, the conductive paper of Comparative Example 3 has a fibrillated fiber content of 156% by mass relative to the carbon fibers in the paper base material, a carbon fiber content of 37% by mass in the paper base material, and a cured thermosetting resin content of 20% by mass in the conductive paper. In addition, the conductive paper of Comparative Example 3 is manufactured by preparing a slurry containing carbon fibers, fibrillated fibers, and other components, with a fibrillated fiber content of 156% by mass relative to the carbon fibers, papermaking the slurry to obtain a paper base material, impregnating the paper base material with a thermosetting resin varnish, and heating the paper base material impregnated with the thermosetting resin to cure the thermosetting resin.

[0044] In other words, Comparative Examples 1 to 3 are conductive papers produced by the same manufacturing method as Example 1, but do not satisfy the conditions regarding the content of fibrillated fibers relative to carbon fibers in the paper base material, and are therefore outside the scope of the present invention.

[0045] The raw materials used were all the same in Example 1 and Comparative Examples 1 to 3. The carbon fibers used were PAN-based carbon fibers with a fiber diameter of 7 μm and a fiber length of 2 mm in the paper substrate, the fibrillated fibers were aramid fibers with a freeness of 300 mL, and the other components were a thermoplastic resin, a paper strength agent, and a flocculant, each in the same amount so that the total content in the paper substrate was 5% by mass. The thickness of the conductive paper in Example 1 and Comparative Examples 1 to 3 was all set to 0.5 mm.

[0046] (Evaluation of conductive paper) Next, the strength and conductivity were evaluated for the conductive papers of Example 1 and Comparative Examples 1 to 3. The results are shown in Table 1. Strength was evaluated by measuring the shear strength of the conductive paper. The shear strength measurement was carried out by fixing the front and back sides of the conductive paper to iron plates, and shearing the conductive paper by moving the iron plates in the shear direction, i.e., perpendicular to the thickness direction of the conductive paper, and moving the front and back iron plates in opposite directions, and taking the maximum shear stress until the conductive paper was shear-broken as the shear strength. When measuring shear strength, the conductive paper used is 3 mm in diameter. Conductivity was evaluated by preparing a doughnut-shaped conductive paper with an inner diameter of 38.5 mm and an outer diameter of 55.8 mm, sandwiching the inside and outside of the doughnut-shaped conductive paper between two doughnut-shaped copper plates with an inner diameter of 33 mm and an outer diameter of 45 mm, and sandwiching the outside and inside of the doughnut-shaped conductive paper between two doughnut-shaped copper plates with an inner diameter of 49 mm and an outer diameter of 61 mm. A conductive path was formed using the conductive paper from the copper plate on the inside of the conductive paper to the copper plate on the outside of the conductive paper, and measuring the resistance value of this conductive path in an AC current, i.e., impedance. The pressure applied to the copper plates was set to 50 N on both the inside and outside of the conductive paper. Conductivity was evaluated using the reciprocal of the measured impedance. Regarding the evaluation results of strength and conductivity, the reciprocal values ​​of shear strength and impedance are shown as relative values ​​with the value of Comparative Example 1 set to 100, and an evaluation value greater than 100 is considered to indicate improved performance.

[0047] [Table 1]

[0048] From Table 1, it can be seen that Example 1 had evaluation values ​​for strength and conductivity greater than 100, and was the highest compared to Comparative Examples 1 to 3. Comparative Example 2 had improved performance compared to Comparative Example 1, but the effect was not sufficiently great. Comparative Example 3 had decreased conductivity compared to Comparative Example 1. Therefore, the conductive paper of Example 1 was able to sufficiently improve strength and conductivity.

Claims

1. 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; a cured product of a thermosetting resin at least partially impregnated into the paper substrate; A conductive paper comprising:

2. The conductive paper according to claim 1, wherein the proportion of the carbon fiber contained in the paper base material is 35 to 90 mass %.

3. The conductive paper according to claim 1, wherein the proportion of the cured thermosetting resin contained in the conductive paper is 10 to 55 mass %.

4. A slurry containing at least carbon fibers and fibrillated fibers is prepared, in which 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; The paper substrate is impregnated with a thermosetting resin; A method for producing conductive paper, comprising heating the paper base material impregnated with the thermosetting resin to cure the thermosetting resin.

5. The method for producing conductive paper according to claim 4, wherein the proportion of the carbon fiber contained in the paper base material is 35 to 90 mass %.

6. The method for producing conductive paper according to claim 4 or 5, wherein the proportion of the cured thermosetting resin contained in the conductive paper is 10 to 55 mass %.

7. A metal bonded body comprising a metal member and the conductive paper according to any one of claims 1 to 3 chemically or mechanically bonded to the surface of the metal member.

8. A method for producing a metal bonded body, comprising chemically or mechanically bonding the conductive paper according to any one of claims 1 to 3 to the surface of a metal member.

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