Conductive film

Abstract

To provide a conductive film that is relatively lightweight and has a relatively low electrical resistance value.SOLUTION: A conductive film includes a binder resin, graphite, and carbon black. The graphite has an average particle diameter of 5 μm or more and 35 μm or less. The carbon black has a specific surface area of 1000 m2 / g or more and 1500 m2 / g or less. The total content of the graphite and the carbon black is 50 wt.% or more and 80 wt.% or less. The value calculated by dividing the content of the graphite by the content of the carbon black is 4 or more and 19 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a conductive film. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2021-136085 (Patent Document 1) discloses a transparent conductive film. This transparent conductive film includes a substrate and a transparent conductive layer, and the transparent conductive layer contains a metal filler (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-136085 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the transparent conductive film disclosed in the above Patent Document 1, the conductivity is ensured by the metal filler. However, when the conductive film contains the metal filler, the weight of the conductive film increases. In addition, the metal filler contained in the conductive film may corrode, thereby increasing the electrical resistance value of the conductive film.

[0005] The present invention has been made to solve such problems, and an object of the present invention is to provide a conductive film which is relatively light in weight and has a relatively low electrical resistance. [Means for solving the problem]

[0006] The conductive film according to the present invention includes a binder resin, graphite, and carbon black. The average particle size of the graphite is 5 μm or more and 35 μm or less. The specific surface area of ​​the carbon black is 1000 m 2 / g or more, 1500m 2 / g or less. The total content of graphite and carbon black is 50wt% or more and 80wt% or less. The graphite content divided by the carbon black content is 4 or more and 19 or less.

[0007] In this conductive film, the conductivity is ensured mainly by graphite and carbon black. This conductive film can be made lighter in weight than a conductive film in which the conductivity is ensured by a metal. The inventors have also found that (1) the average particle size of the graphite is 5 μm or more and 35 μm or less, and (2) the specific surface area of ​​the carbon black is 1000 m 2 / g or more, 1500m 2 / g or less, (3) the sum of the contents of graphite and carbon black is 50 wt% or more and 80 wt% or less, and (4) the value obtained by dividing the graphite content by the carbon black content is 4 or more and 19 or less, the electrical resistance value of the conductive film is sufficiently low. With this conductive film, the above conditions (1) to (4) are satisfied, and therefore the electrical resistance value can be sufficiently low. Thus, with this conductive film, the weight of the conductive film can be made sufficiently light, and the electrical resistance value of the conductive film can be sufficiently low.

[0008] In the conductive film, the graphite may have an average particle size of 10 μm or more.

[0009] The inventors have found that when the average particle size of the graphite contained in the conductive film is 10 μm or more, the electrical resistance value of the conductive film is further reduced. Since the average particle size of the graphite contained in the conductive film is 10 μm or more, the electrical resistance value of the conductive film can be further reduced.

[0010] In the conductive film, the graphite may be exfoliated graphite.

[0011] The inventor(s) found that when the graphite contained in the conductive film is exfoliated graphite, the electrical resistance value of the conductive film is further reduced. With this conductive film, since the graphite contained in the conductive film is exfoliated graphite, the electrical resistance value of the conductive film can be further reduced.

[0012] In the conductive film, the value obtained by dividing the graphite content by the carbon black content may be 9 or less.

[0013] The present inventor(s) found that the electrical resistance value of the conductive film is further reduced when the value obtained by dividing the graphite content by the carbon black content is not more than 9. With this conductive film, the value obtained by dividing the graphite content by the carbon black content is not more than 9, and therefore the electrical resistance value of the conductive film can be further reduced.

[0014] In the conductive film, the binder resin may be a phenoxy resin.

[0015] The present inventors have found that when the binder resin contained in the conductive film is a phenoxy resin, the conductive film is less likely to crack. With this conductive film, the binder resin contained in the conductive film is a phenoxy resin, so that the occurrence of cracks in the conductive film can be suppressed.

[0016] The conductive film may have a thickness of 30 μm or less. Effect of the Invention

[0017] According to the present invention, it is possible to provide a conductive film which is relatively lightweight and has a relatively low electrical resistance. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a diagram illustrating a cross section of a conductive film. [Diagram 2]1 is a flowchart showing a manufacturing procedure of a conductive film. [Diagram 3] FIG. 1 is a table summarizing the composition and other information of each conductive film in Examples 1 to 13. [Figure 4] FIG. 1 is a table summarizing the composition and other information of the conductive films of Comparative Examples 1 to 6. [Diagram 5] FIG. 1 is a table summarizing the test results for each conductive film of Examples 1 to 13. [Figure 6] FIG. 1 is a table summarizing the test results for each of the conductive films of Comparative Examples 1 to 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated. Also, each drawing is drawn in a schematic manner with objects appropriately omitted or exaggerated for ease of understanding.

[0020] [1. Conductive film composition] Fig. 1 is a schematic diagram showing a cross section of a conductive film 10 according to the present embodiment. Referring to Fig. 1, the conductive film 10 is, for example, a single-layer film. The thickness of the conductive film 10 is, for example, 5 µm or more and 100 µm or less, and preferably 10 µm or more and 30 µm or less. The conductive film 10 is produced, for example, by a so-called solution casting method, the details of which will be described later.

[0021] The conductive film 10 is used, for example, as a charging film or a static eliminating film for copiers, printers, etc., and various other functional films for electric / electronic devices and parts. The conductive film 10 may or may not be subjected to surface treatment such as corona, plasma, coating, or sputtering.

[0022] The conductive film 10 contains a binder resin, graphite, and carbon black (CB). The conductive film 10 may further contain some or all of additives such as a dispersant, an antioxidant, an antiblocking agent, and an ultraviolet protection agent.

[0023] The content of the binder resin in the conductive film 10 is, for example, 20 wt% or more and 50 wt% or less, and more preferably 23 wt% or more and 47 wt% or less. If the content of the binder resin is too small, the conductive film 10 becomes difficult to manufacture due to increased viscosity, and if the content of the binder resin is too large, the electrical resistance value of the conductive film 10 exceeds the allowable range.

[0024] The graphite content in the conductive film 10 is, for example, 40 wt% or more and 76 wt% or less, preferably 40 wt% or more and 72 wt% or less, and more preferably 45 wt% or more and 72 wt% or less. If the graphite content is too low, the electrical resistance value of the conductive film 10 exceeds the allowable range, and if the graphite content is too high, the binder resin content becomes low and the viscosity increases, making it difficult to manufacture the conductive film 10.

[0025] The carbon black content in the conductive film 10 is, for example, 4 wt% or more and 16 wt% or less, and preferably 5 wt% or more and 16 wt% or less. If the carbon black content is too low, the electrical resistance value of the conductive film 10 exceeds the allowable range, whereas if the carbon black content is too high, the viscosity increases, making it difficult to manufacture the conductive film 10.

[0026] An example of the binder resin is a phenoxy resin. The phenoxy resin is not particularly limited, but examples thereof include bisphenol A type, bisphenol F type, bisphenol A / bisphenol F copolymer type, biphenol type, and biphenyl type. Examples of commercially available phenoxy resins include bisphenol A type phenoxy resins such as jER-1256 (manufactured by Mitsubishi Chemical Corporation), YP-50 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), PKFE, and PKHH (manufactured by Gabriel Performance Products Co., Ltd.), and bisphenol A / bisphenol F copolymer type phenoxy resins such as jER-4275 (manufactured by Mitsubishi Chemical Corporation) and YP-70 (manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0027] Examples of graphite include artificial graphite and natural graphite. Artificial graphite is made by artificially orienting irregularly arranged micrographite crystals by heat treatment of amorphous carbon, and is generally manufactured using petroleum coke or coal-based pitch coke as the main raw material. Examples of natural graphite include flake graphite, lump graphite, and earthy graphite. In addition, expanded graphite, expanded graphite, or exfoliated graphite manufactured by subjecting natural graphite to various treatments may be used. From the viewpoint of electrical conductivity, it is preferable to use exfoliated graphite. In order to increase the affinity with the binder resin, the surface of these graphites may be subjected to a surface treatment such as an epoxy treatment, a urethane treatment, a silane coupling treatment, or an oxidation treatment.

[0028] The average particle diameter of the graphite is 5 μm or more and 35 μm or less, and preferably 10 μm or more and 35 μm or less. If the average particle diameter of the graphite is too small, the electrical resistance value of the conductive film 10 exceeds the allowable range, and if the average particle diameter of the graphite is too large, problems occur in the smoothness of the conductive film 10. The average particle diameter refers to the particle diameter (D50) at which the volume ratio of particles is 50% when the volume ratio of particles is accumulated from the finest particle diameter in the volume particle size distribution, and is measured with a general particle size distribution meter, for example, a dynamic light scattering type particle size distribution meter (Microtrack UPA manufactured by Nikkiso Co., Ltd.).

[0029] Examples of commercially available graphite include, for example, flake graphite (e.g., flake graphite, expanded graphite, and exfoliated graphite), such as CMX, UP-5, UP-10, UP-20, UP-35N, CSSP, CSPE, CSP, CP, CB-150, CB-100, ACP, ACP-1000, ACB-50, ACB-100, ACB-150, SP-10, SP-20, J-SP, SP-270, HOP, GR-60, LEP, F#1, F#2, and F#3 manufactured by Nippon Graphite Industries Co., Ltd., and CX-3000, FBF, BF, CBR, and SSC-3 manufactured by Chuetsu Graphite Co., Ltd. 000, SSC-600, SSC-3, SSC, CX-600, CPF-8, CPF-3, CPB-6S, CPB, 96E, 96L, 96L-3, 90L-3, CPC, S-87, K-3, CF-80, CF-48, CF-32, CP-150, CP-100, CP, HF-80, HF-48, HF-32, SC-120, SC-80, SC-60, SC-32, EC1500, EC1000, EC500, EC300, EC100, EC50 manufactured by Ito Graphite Industries Co., Ltd., 10099M and PB-99 manufactured by Nishimura Graphite Co., Ltd., and the like. Examples of amorphous graphite include Blue P, AP, AOP, and P#1 manufactured by Nippon Graphite Industries Co., Ltd., and APR, S-3, AP-6, and 300F manufactured by Chuetsu Graphite Co., Ltd. Examples of artificial graphite include PAG-60, PAG-80, PAG-120, PAG-5, HAG-10W, and HAG-150 manufactured by Nippon Graphite Industries Co., Ltd.; RA-3000, RA-15, RA-44, GX-600, G-6S, G-3, G-150, G-100, G-48, G-30, and G-50 manufactured by Chuetsu Graphite Co., Ltd.; and SGP-100, SGP-50, SGP-25, SGP-15, SGP-5, SGP-1, SGO-100, SGO-50, SGO-25, SGO-15, SGO-5, SGO-1, SGX-100, SGX-50, SGX-25, SGX-15, SGX-5, and SGX-1 manufactured by SEC Carbon Co., Ltd.

[0030] Examples of carbon black include acetylene black, ketjen black, furnace black, channel black, and thermal lamp black. Examples of commercially available carbon black include PRINTEX XE2B manufactured by Orion Engineered Carbons, BLACK PEARLS2000 manufactured by Cabot, and Ketjen Black EC600JD and Lionite CB manufactured by Lion Specialty Chemicals. The specific surface area of ​​carbon black is 1000 m2. 2 / g or more, 1500m 2 The specific surface area is measured by the BET method using nitrogen adsorption.

[0031] In the conductive film 10, the total content of graphite and carbon black is 50 weight percent (wt%) or more and 80 weight percent (wt%) or less, preferably 50 wt% or more and 65 wt% or less, and more preferably 50 wt% or more and 60 wt% or less.

[0032] In addition, in the conductive film 10, the ratio of graphite to carbon black is 8:2-9.5:0.5, and preferably 8:2-9:1. That is, in the conductive film 10, the value obtained by dividing the graphite content by the carbon black content is 4 or more and 19 or less, and preferably 4 or more and 9 or less.

[0033] [2. Manufacturing method of conductive film] FIG. 2 is a flowchart showing a manufacturing procedure of the conductive film 10. Referring to FIG. 2, an operator prepares a conductive resin solution (step S100). Specifically, the operator obtains the conductive resin solution by mixing a binder resin, graphite, carbon black, and an organic solvent. The operator applies the conductive resin solution obtained in step S100 to, for example, a PET film (release film) that has been subjected to a release treatment (step S110). The operator places the release film applied with the conductive resin solution in a dryer and dries the release film applied with the conductive resin solution (step S120). After the drying is completed, the operator peels off the release film portion from the release film on which the conductive film 10 is formed on the upper surface (step S130). As a result, the conductive film 10 is obtained.

[0034] [3. Features] As described above, the conductive film 10 according to the present embodiment contains a binder resin, graphite, and carbon black. The average particle size of the graphite is 5 μm or more and 35 μm or less. The specific surface area of ​​the carbon black is 1000 m 2 / g or more, 1500m 2 / g or less. The total content of graphite and carbon black is 50 wt% or more and 80 wt% or less. The value obtained by dividing the graphite content by the carbon black content is 4 or more and 19 or less. In the conductive film 10, the conductivity is ensured mainly by the graphite and carbon black. According to the conductive film 10, the weight of the conductive film can be reduced compared to a conductive film in which the conductivity is ensured by a metal. The present inventors have also found that (1) the average particle size of the graphite is 5 μm or more and 35 μm or less, and (2) the specific surface area of ​​the carbon black is 1000 m 2 / g or more, 1500m 2 / g or less, and (3) the total content of graphite and carbon black is 50 wt% or more and 80 wt% or less, and (4) the value obtained by dividing the graphite content by the carbon black content is 4 or more and 19 or less, the electrical resistance value of the conductive film is sufficiently low. According to the conductive film 10, the above conditions (1) to (4) are satisfied, and therefore the electrical resistance value can be sufficiently low. Thus, according to the conductive film 10, the weight of the conductive film can be made sufficiently light, and the electrical resistance value of the conductive film can be sufficiently low.

[0035] Furthermore, in the conductive film 10, the binder resin may be a phenoxy resin. The present inventor(s) have found that when the binder resin contained in the conductive film is a phenoxy resin, the conductive film is less likely to crack. According to the conductive film 10, when the binder resin contained in the conductive film is a phenoxy resin, the occurrence of cracks in the conductive film 10 can be suppressed.

[0036] The above describes the embodiments of the present invention by way of example. That is, the detailed description and the accompanying drawings are disclosed for the purpose of illustrative description. Therefore, some components described in the detailed description and the accompanying drawings may be non-essential components for solving the problem. Therefore, just because the non-essential components are described in the detailed description and the accompanying drawings, it should not be immediately determined that the non-essential components are essential.

[0037] Moreover, the above-described embodiments are merely examples of the present invention in every respect. Various improvements and modifications of the above-described embodiments are possible within the scope of the present invention. For example, at least a part of the configuration of any of the embodiments may be combined with at least a part of the configuration of any of the other embodiments. In other words, in implementing the present invention, specific configurations can be appropriately adopted according to the embodiment. EXAMPLES

[0038] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0039] [1. Examples and Comparative Examples] Each conductive film of Examples 1-13 and Comparative Examples 1-6 was obtained according to the procedure described below. A binder resin, graphite, carbon black (in the ratio shown in Fig. 3 and Fig. 4 described later) and an organic solvent were mixed, and zirconia beads (diameter 5 mm) of the same mass as the solution were added to the solution, and dispersion was performed for 6 hours using a paint shaker. Then, the zirconia beads were removed to obtain a conductive resin solution. Using an applicator, the obtained conductive resin solution was applied to a release-treated PET film ("SP3000, 50 μm thickness" manufactured by Toyo Cross Co., Ltd.) so that the film thickness after drying would be 30 μm. Then, the applied conductive resin solution was dried at 160°C for 1 hour, and the PET film was peeled off to obtain a conductive film. In each of Examples 1-13 and Comparative Examples 1-4 and 1-6, the mixed organic solvent was methyl ethyl ketone (200 parts). In Comparative Example 5, the mixed organic solvent was toluene (150 parts).

[0040] FIG. 3 is a table showing the composition of each conductive film of Examples 1-13. FIG. 4 is a table showing the composition of each conductive film of Comparative Examples 1-6. Referring to FIG. 3 and FIG. 4, the item "resin" indicates the type and content of binder resin contained in the conductive film. The item "graphite" indicates the type and content of graphite contained in the conductive film. The item "average particle size of graphite" indicates the average particle size of graphite contained in the conductive film. The item "CB" indicates the content of carbon black contained in the conductive film. The item "specific surface area of ​​CB" indicates the specific surface area of ​​carbon black contained in the conductive film. The item "total weight % of graphite and CB" indicates the sum (sum) of the weight % of graphite in the conductive film and the weight % of carbon black in the conductive film. The item "weight % of graphite / weight % of CB" indicates the value obtained by dividing the weight % of graphite in the conductive film by the weight % of carbon black in the conductive film. The item "film thickness" indicates the thickness of the conductive film. In Comparative Examples 3 and 4, films could not be produced due to an increase in viscosity.

[0041] [2.Various Tests] The conductive films of Examples 1 to 13 and Comparative Examples 1 to 6 were subjected to measurement of surface resistivity and evaluation of bending resistance. The specific methods for each were described below.

[0042] <2-1. Measurement of surface resistivity> The surface resistivity of each conductive film was measured using a low resistivity meter Loresta-GP MCP-T610 manufactured by Mitsubishi Chemical Analytech Co., Ltd. in accordance with JIS-K-7194 "Test method for resistivity of conductive plastics using the four-probe method."

[0043] <2-2. Evaluation of bending resistance> The bending resistance of each conductive film was evaluated in accordance with JIS K5600-5-1 "Bending resistance (cylindrical mandrel)" by bending the conductive film to a diameter of 2 mm and checking whether any cracks occurred in the conductive film.

[0044] [3. Test Results] Fig. 5 is a table showing the test results for each conductive film of Examples 1-13. Fig. 6 is a table showing the test results for each conductive film of Comparative Examples 1-6. Referring to Figs. 5 and 6, the surface resistivity of each conductive film of Examples 1-13 was lower than that of each conductive film of Comparative Examples 1-6. In addition, while each conductive film of Comparative Examples 5 and 6 was cracked, each conductive film of Examples 1-13 was not cracked.

[0045] In addition, with respect to Example 1-13, the surface resistivity of each of the conductive films of Examples 1-10 and 12-13 was lower than that of the conductive film of Example 11. In addition, with respect to Examples 1-10 and 12-13, the surface resistivity of the conductive films of Examples 1-10 and 12 was lower than that of the conductive film of Example 13. In addition, with respect to Examples 1-10 and 12, the surface resistivity of the conductive film of Example 1-10 was lower than that of the conductive film of Example 12. [Explanation of symbols]

[0046] 10 Conductive film

Claims

1. Contains a binder resin, graphite, and carbon black, The average particle size of the graphite is 5 μm or more and 35 μm or less, The specific surface area of ​​the carbon black is 1000 m ２ / g or more, 1500m ２ / g or less, The total content of the graphite and the carbon black is 50 wt % or more and 80 wt % or less, A conductive film, wherein a value obtained by dividing a content of the graphite by a content of the carbon black is 4 or more and 19 or less.

2. The conductive film according to claim 1 , wherein the graphite has an average particle size of 10 μm or more.

3. The conductive film according to claim 1 or 2, wherein the graphite is exfoliated graphite.

4. The conductive film according to claim 3 , wherein a value obtained by dividing the graphite content by the carbon black content is 9 or less.

5. The conductive film according to claim 1 or 2, wherein the binder resin is a phenoxy resin.

6. The conductive film according to claim 1 or 2, wherein the conductive film has a thickness of 30 μm or less.

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