Conductive sheet

Abstract

To provide a conductive sheet which is excellent in conductivity and cushion property, and can suppress warpage to a surface layer side and dust generation.SOLUTION: A conductive sheet 1 is formed by laminating a surface layer 12, an intermediate layer 14, and a back layer 16. The surface layer 12, the intermediate layer 14, and the back layer 16 are composed of a conductive thermoplastic resin composition containing a thermoplastic resin. The conductive sheet 1 contains conductive carbon. In the conductive sheet 1, an amount of a plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 is 29 to 47 pts.mass with respect to 100 pts.mass of the thermoplastic resin. The conductive thermoplastic resin composition constituting the surface layer 12 contains a vinyl chloride-based resin having a degree of polymerization according to JIS K 6720-2 of 1,300 or more as a matrix, and a ratio of thickness of the surface layer 12 to the thickness of the whole conductive sheet is 10-40%. A thickness of the back layer 16 is equal to or less than the thickness of the surface layer 12, and hardness of the whole conductive sheet 1 is 75 to 95.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] It is known that dust has a significant impact on the quality of products in clean rooms where electronic devices, pharmaceuticals, etc. are manufactured. Therefore, dust generation in clean rooms must be suppressed as much as possible. For example, conductive sheets used on floors, shelves, workbenches, etc. in clean rooms must be highly dust-resistant. Therefore, conductive sheets must have improved abrasion resistance and suppress dust generation from their surfaces. On the other hand, when conductive sheets are used as flooring materials, they must not warp on the surface and must have good cushioning properties.

[0003] As a conductive sheet for the purpose of suppressing dust generation, the following Patent Document 1 describes a conductive sheet having a volume resistivity of 1×10 on the surface side. 6 ~1×10 10 It has a dust-proof synthetic resin layer with a resistance of 1×10 Ω·cm on the back side. 0 ~1×10 4 It has a conductive base layer of Ω·cm, and the volume resistivity of the laminate having the synthetic resin layer and the base layer is 1×10 6 ~1×10 10 Patent Document 1 discloses an antistatic laminate sheet characterized by a resistance to wear of Ω·cm. The technology disclosed in this document claims to improve abrasion resistance by setting the thickness of the synthetic resin layer within a certain range, but since changing the thickness of the synthetic resin layer does not change the abrasion resistance of the synthetic resin layer itself, there is a problem in that abrasion resistance sufficient to suppress dust generation cannot be obtained. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 63-67141 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a conductive sheet that has excellent conductivity and cushioning properties and can suppress warping and dust generation on the surface layer side. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the "conductive sheet" according to the present invention is characterized by the following (1) to (7). (1) A conductive sheet comprising at least a surface layer, an intermediate layer, and a back layer, the surface layer, the intermediate layer, and the back layer are made of a conductive thermoplastic resin composition containing a thermoplastic resin, the conductive sheet contains conductive carbon; the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer is 29 to 47 parts by mass relative to 100 parts by mass of the thermoplastic resin; the thermoplastic resin in the conductive thermoplastic resin composition constituting the surface layer has a degree of polymerization based on JIS K6720-2 of 1300 or more; The ratio of the thickness of the surface layer to the thickness of the entire conductive sheet is 10 to 40%; The thickness of the back layer is equal to or less than the thickness of the surface layer, and The hardness of the entire conductive sheet is 75 to 95. It is a conductive sheet. (2) In the conductive sheet described in (1) above, The conductive thermoplastic resin composition has a vinyl chloride resin matrix. (3) In the conductive sheet according to (1) or (2), The surface resistance between two points measured in accordance with NFPA99 is 2.5 x 10 4 Ω~1.0×10 7 Being Omega. (4) In the conductive sheet according to any one of (1) to (3), The resistance between the top and bottom measured in accordance with NFPA99 is 2.5 x 10 4 Ω~1.0×10 7 Being Omega. (5) In the conductive sheet according to any one of (1) to (4), The amount of wear in the abrasion resistance test conforming to JIS A1454 is less than 0.05 mm. (6) In the conductive sheet according to any one of (1) to (5), The warpage toward the surface layer in the warpage test conforming to JIS A1454 is 0 mm. (7) In the conductive sheet according to any one of (1) to (6), The amount of dent measured in accordance with JIS A1454 must be 0.3 mm or more at 23°C and 1.5 mm or less at 45°C.

[0007] According to the conductive sheet having the configuration (1) above, a conductive sheet is provided which is formed by laminating a surface layer, an intermediate layer, and a back layer each made of a conductive thermoplastic resin composition, and which contains conductive carbon. The amount of plasticizer in the conductive thermoplastic resin composition of the surface layer, the degree of polymerization of the thermoplastic resin contained in the conductive thermoplastic resin composition, the thickness ratio of the surface layer, the thickness conditions of the back layer, and the hardness of the conductive sheet are specified, so that a conductive sheet can be provided which has excellent conductivity and cushioning properties and can suppress warping and dust generation toward the surface layer side.

[0008] According to the conductive sheet having the above configuration (2), since the conductive thermoplastic resin composition has a vinyl chloride resin as a matrix, it is possible to provide a conductive sheet that can further enhance cushioning properties and further suppress warping and dust generation toward the surface layer side.

[0009] According to the conductive sheet having the above configuration (3), the surface resistance between two points measured in accordance with NFPA99 is within a specific range, and therefore a conductive sheet having excellent conductivity can be provided.

[0010] According to the conductive sheet having the above configuration (4), the resistance between the top and bottom measured in accordance with NFPA99 is within a specific range, so that a conductive sheet having excellent conductivity can be provided.

[0011] According to the conductive sheet having the above configuration (5), the amount of abrasion in the abrasion resistance test in accordance with JIS A1454 is less than 0.05 mm, so that a conductive sheet that can further suppress dust generation can be provided.

[0012] According to the conductive sheet having the configuration (6) above, the warp toward the surface layer side in the warp test in accordance with JIS A1454 is 0 mm, so that a conductive sheet can be provided in which the warp toward the surface layer side is significantly suppressed.

[0013] According to the conductive sheet having the configuration (7) above, the amount of depression measured in accordance with JIS A1454 is 0.3 mm or more at 23°C and 1.5 mm or less at 45°C, so that a conductive sheet with even better cushioning properties can be provided. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a conductive sheet that has excellent conductivity and cushioning properties and is capable of suppressing warping and dust generation on the surface layer side.

[0015] The present invention has been briefly described above. The details of the present invention will become clearer by reading the following detailed description of the invention (hereinafter referred to as "embodiments") with reference to the accompanying drawings. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view of a conductive sheet according to this embodiment. [Figure 2]FIG. 2 is a cross-sectional view of the conductive sheet according to this embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the conductive sheet according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of a conductive sheet according to the present invention will be described with reference to the drawings.

[0018] The conductive sheet 1 according to this embodiment is formed by laminating a surface layer 12, an intermediate layer 14, and a back layer 16. The conductive sheet 1 according to this embodiment also contains conductive carbon. The conductive carbon may be contained as the conductive carbon layer 13, or may be contained in any of the layers (conductive thermoplastic resin composition) of the surface layer 12, the intermediate layer 14, and the back layer 16. That is, as shown in FIGS. 1 and 2, the conductive sheet 1 according to this embodiment may be formed by laminating the surface layer 12, the conductive carbon layer 13, the intermediate layer 14, and the back layer 16. Alternatively, as shown in FIG. 3, the conductive sheet 1 may be formed by laminating the surface layer 12, the intermediate layer 14, and the back layer 16, and the conductive carbon may be contained in any of the layers (for example, the back layer). Note that, hereinafter, a mode in which conductive carbon is contained as the conductive carbon layer 13 will be mainly described, but the conductive sheet according to this embodiment is not limited to this mode.

[0019] The characteristics of each layer are described below. The surface layer 12 is a layer located on the surface of the sheet and has abrasion resistance, scratch resistance, and contamination resistance. Here, the layer located on the surface of the sheet means the layer located on the top when the conductive sheet is installed. The conductive carbon layer 13 is located between the surface layer and the back layer, and is a layer that enhances the conductivity of the sheet, and contains conductive carbon. The intermediate layer 14 is all the layers between the surface layer and the back layer, and is a layer that contributes to the physical properties (cushioning properties, dimensional stability) of the entire sheet. The back layer 16 is the layer located at the bottom of the sheet and prevents the sheet from warping toward the surface layer. To enhance conductivity, it may contain conductive carbon. Here, the layer located at the bottom of the sheet means the layer located at the bottom when the conductive sheet is installed.

[0020] The surface layer 12, the conductive carbon layer 13, the intermediate layer 14 and the back layer 16 are made of a conductive thermoplastic resin composition. The conductive thermoplastic resin composition includes a thermoplastic resin such as a vinyl chloride resin, polyester, polyamide, polyolefin, acrylic resin, epoxy resin, or phenolic resin. The conductive thermoplastic resin composition includes the thermoplastic resin as a matrix, and a conductive material is mixed into the matrix. Examples of the conductive material include metal powder, carbon powder, graphite powder, ferrite powder, a conductive plasticizer, and an antistatic agent.

[0021] Among these, from the viewpoint of achieving excellent cushioning properties and suppressing warping and dust generation toward the surface layer side, vinyl chloride resin is preferred as the matrix of the conductive thermoplastic resin composition, and it is even more preferred that the surface layer 12, conductive carbon layer 13, intermediate layer 14, and back layer 16 are all made of a conductive thermoplastic resin composition having a vinyl chloride resin matrix (hereinafter also referred to as a conductive vinyl chloride resin composition). Below, an example will be described in which the surface layer 12, conductive carbon layer 13, intermediate layer 14, and back layer 16 are all sheets made of a conductive vinyl chloride resin composition, but the present invention is not limited to this form.

[0022] First, the conductive vinyl chloride resin composition used to prepare the sheet of the surface layer 12 will be described. The vinyl chloride resin used in the conductive vinyl chloride resin composition is not particularly limited, but examples thereof include a homopolymer of vinyl chloride, a copolymer of a vinyl chloride monomer and another monomer copolymerizable with the vinyl chloride monomer, and a graft copolymer in which a polymer other than a polyvinyl chloride resin is graft-copolymerized with a vinyl chloride monomer. The polyvinyl chloride resins may be used alone or in combination of two or more.

[0023] Examples of other monomers copolymerizable with the vinyl chloride monomer include α-olefins such as ethylene, propylene, and butylene; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as butyl vinyl ether and cetyl vinyl ether; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl acrylate; aromatic vinyls such as styrene and α-methylstyrene; and N-substituted maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide. One type of the other monomers may be used alone, or two or more types may be used in combination.

[0024] The vinyl chloride resin must have an average degree of polymerization based on JIS K6720-2 of 1300 or more. If the average degree of polymerization is less than 1300, the abrasion resistance decreases and the amount of dust generated increases. The average degree of polymerization is preferably 1300 to 2500, and more preferably 1300 to 2000.

[0025] Furthermore, examples of plasticizers used in vinyl chloride resins include high molecular weight plasticizers such as phthalate esters {e.g., dioctyl phthalate (DOP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), diundecyl phthalate (DUP), etc.}, trimellitate esters {e.g., trioctyl trimellitate (TOTM), tri-normal-octyl trimellitate (TnOTM)}, adipate esters {e.g., diisobutyl adipate (DIBA), diisodecyl adipate (DIDA)}, phosphates {e.g., triethyl phosphate, tricresyl phosphate}, and epoxy polyesters {e.g., epoxidized soybean oil}.

[0026] Examples of conductive materials that impart conductivity to vinyl chloride resins include metal powder, carbon powder, graphite powder, ferrite powder, conductive plasticizers, and antistatic agents. Examples of metal powders include powders of silver, nickel, copper, gold, aluminum, iron, graphite, and the like. Examples of carbon powder include carbon black. Examples of the conductive plasticizer include phthalate ester-based conductive plasticizers and adipic acid ester-based conductive plasticizers. Examples of antistatic agents include anionic antistatic agents (e.g., alkyl sulfate type, alkyl aryl sulfate type, alkyl phosphate type, alkylamine sulfate type, etc.), cationic antistatic agents (e.g., quaternary ammonium salt type, quaternary ammonium resin type, imidazoline type, etc.), nonionic agents (e.g., sorbitan type, ether type, amine and amide type, ethanolamide type, etc.), betaines, etc.

[0027] The amount of the conductive material to be mixed is preferably 10 to 55 parts by mass, and more preferably 20 to 50 parts by mass, per 100 parts by mass of the vinyl chloride resin.

[0028] Furthermore, the vinyl chloride resin composition may further contain known inorganic fine particles (calcium carbonate, calcined clay, talc, silica, etc.), stabilizers, lubricants, flame retardants, crosslinking agents, processing aids, colorants, etc., as needed. The amounts of these additives may also be arbitrary as long as they do not impair the effects of the present invention.

[0029] The vinyl chloride resin composition can be easily prepared by kneading the various materials described above using a known kneader.

[0030] In the present invention, the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 must be 29 to 47 parts by mass per 100 parts by mass of thermoplastic resin. If the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 is less than 29 parts by mass per 100 parts by mass of thermoplastic resin, the abrasion resistance decreases, the amount of dust generated increases, and the cushioning properties deteriorate. Conversely, if the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 exceeds 47 parts by mass per 100 parts by mass of thermoplastic resin, the abrasion resistance decreases and the amount of dust generated increases. The amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 is more preferably 33 to 43 parts by mass relative to 100 parts by mass of the thermoplastic resin.

[0031] The surface layer 12 can be formed by applying a conventionally known method such as extrusion molding, injection molding, calendar molding, or press molding.

[0032] Next, the conductive vinyl chloride resin composition used to prepare the sheets of the intermediate layer 14 and the back layer 16 will be described.

[0033] The conductive vinyl chloride resin composition used to prepare the sheet for the intermediate layer 14 is the same as the conductive vinyl chloride resin composition used to prepare the sheet for the surface layer 12, but preferably contains a larger amount of filler to improve dimensional stability. The composition preparation method and molding method are the same as those for the surface layer 12.

[0034] The conductive vinyl chloride resin composition used to prepare the sheet for the back layer 16 is the same as the conductive vinyl chloride resin composition used to prepare the sheet for the surface layer 12, but to increase flexibility, it preferably contains a larger amount of plasticizer than the surface layer 12. The composition preparation method and molding method are the same as those for the surface layer 12.

[0035] The conductive vinyl chloride resin composition used to prepare the sheet for the conductive carbon layer 13 is the same as the conductive vinyl chloride resin composition used to prepare the sheet for the surface layer 12, but differs in that it contains conductive carbon to enhance conductivity. The composition preparation method and molding method are the same as those for the surface layer 12.

[0036] Preferred types of conductive carbon include carbon black, graphite, carbon fiber, etc. The proportion of the conductive carbon contained in the conductive carbon layer 13 is more preferably 10 to 30 mass %.

[0037] The thickness of the surface layer 12 is preferably 0.2 mm to 0.8 mm, and more preferably 0.3 mm to 0.7 mm. The thickness of the intermediate layer 14 is preferably 0.6 mm to 1.6 mm, and more preferably 0.8 mm to 1.4 mm. The thickness of the back layer 16 is preferably 0.1 mm to 0.8 mm, and more preferably 0.2 mm to 0.7 mm. The thickness of the conductive carbon layer 13 is preferably 0.1 mm to 0.4 mm, and more preferably 0.2 mm to 0.3 mm.

[0038] In the present invention, the ratio of the thickness of the surface layer 12 to the thickness of the entire conductive sheet must be 10 to 40%. The thickness of the back layer 16 must be equal to or less than the thickness of the surface layer 12 . By specifying the thickness ratio of the surface layer 12 and the thickness of the back layer 16 as described above, it is possible to enhance cushioning properties, improve abrasion resistance, and reduce dust generation.

[0039] The thickness ratio of the surface layer 12 is more preferably 15 to 30%.

[0040] As described above, the conductive sheet 1 according to this embodiment may be formed by laminating a surface layer 12, a conductive carbon layer 13, an intermediate layer 14, and a back layer 16, as shown in Figures 1 and 2. Alternatively, the conductive sheet 1 may be formed by laminating a surface layer 12, an intermediate layer 14, and a back layer 16 containing conductive carbon, as shown in Figure 3. There are no particular limitations on the lamination method, and examples include a method in which each layer is calender-molded and then laminated. The overall thickness of the conductive sheet 1 of the present invention is preferably 1.0 mm to 3.0 mm, and more preferably 1.5 mm to 2.5 mm.

[0041] Furthermore, the conductive sheet 1 of the present invention must have a hardness measured in accordance with JIS K7215 of 75 to 95. By making the hardness of the conductive sheet 1 75 to 95, it is possible to enhance cushioning properties, improve abrasion resistance, and reduce the amount of dust generated. The hardness is more preferably 80 to 90.

[0042] In a preferred embodiment of the present invention, the conductive sheet 1 of the present invention has a two-point surface resistance measured in accordance with NFPA99 of 2.5×10 4 Ω~1.0×10 7 Ω, preferably 1.0×10 5 Ω~1.0×10 6 In this embodiment, a conductive sheet having excellent conductivity can be provided.

[0043] In a preferred embodiment of the present invention, the conductive sheet 1 of the present invention has a resistance between the top and bottom measured in accordance with NFPA99 of 2.5×10 4 Ω~1.0×10 7 Ω, preferably 1.0×10 5 Ω~1.0×10 6 In this embodiment, a conductive sheet having excellent conductivity can be provided.

[0044] In a preferred embodiment of the present invention, the conductive sheet 1 of the present invention has an abrasion loss of less than 0.05 mm, and more preferably 0.03 mm or less, in an abrasion resistance test in accordance with JIS A 1454. In this embodiment, a conductive sheet that further suppresses dust generation can be provided.

[0045] In a preferred embodiment of the present invention, it is more preferable that the warpage of the conductive sheet 1 of the present invention toward the surface layer side is 0 mm in a warpage test in accordance with JIS A 1454. In this embodiment, a conductive sheet can be provided in which warpage toward the surface layer side of the conductive sheet 1 is significantly suppressed.

[0046] In a preferred embodiment of the present invention, the conductive sheet 1 of the present invention has a depression amount measured in accordance with JIS A1454 of preferably 0.3 mm or more, more preferably 0.5 mm or more, at 23° C. Furthermore, the depression amount measured in accordance with JIS A1454 is preferably 1.5 mm or less, more preferably 1.2 mm or less, at 45° C. In this embodiment, a conductive sheet with even improved cushioning properties can be provided.

[0047] The hardness of the surface layer 12 can be adjusted by adjusting the degree of polymerization of the vinyl chloride resin and the amount of plasticizer.

[0048] The conductive sheet 1 of the present invention is particularly suitable for use as flooring, shelves, workbenches, etc. in clean rooms. [Example]

[0049] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0050] Examples 1 to 8, Comparative Examples 1 to 16 In Examples 1 to 8, based on the materials and blending amounts shown in Table 1 below, each component was kneaded in a kneader to prepare a vinyl chloride resin composition for a surface layer, a vinyl chloride resin composition for a conductive carbon layer, a vinyl chloride resin composition for an intermediate layer, and a vinyl chloride resin composition for a back layer, respectively. For Comparative Examples 1 to 16, the same materials as in Examples 1 to 8 were used, and the blending amounts were appropriately changed to prepare a vinyl chloride resin composition for the surface layer, a vinyl chloride resin composition for the conductive carbon layer, a vinyl chloride resin composition for the intermediate layer, and a vinyl chloride resin composition for the back layer, respectively.

[0051] [Table 1]

[0052] PVC (polyvinyl chloride resin): S1003 (Kaneka Corporation, average degree of polymerization based on JIS K6720-2 = 1300) TK-2000E (Shin-Etsu Chemical Co., Ltd., average degree of polymerization based on IS K6720-2 = 2000) Plasticizer: Diisononyl phthalate (DINP) (manufactured by J-Plus Co., Ltd.) Conductive plasticizer: C-1000 (manufactured by New Japan Chemical Co., Ltd.) Antistatic agent: LV-70 (ADEKA Corporation) Stabilizer: NPS-500 (ADEKA Corporation) Calcium carbonate: Escalon #1500 (manufactured by Sankyo Seifun Co., Ltd.) Conductive carbon: EC600JD (manufactured by Lion Specialty Chemicals)

[0053] Next, each composition was calendered to form the surface layer 12, conductive carbon layer 13, intermediate layer 14 and back layer 16 in this order, to produce conductive sheets having the thicknesses shown in Tables 4 to 6 below.

[0054] The various conductive sheets thus produced were measured for the following physical properties. Conductive sheet hardness (measured in accordance with JIS K7215) - Surface resistance between two points on a conductive sheet (measured in accordance with NFPA99) Resistance between the top and bottom of the conductive sheet (measured in accordance with NFPA99) Abrasion resistance of conductive sheet (measured in accordance with JIS A1454) Warping of the conductive sheet toward the surface (measured in accordance with JIS A1454) - Conductive sheet dent amount (measured in accordance with JIS A1454)

[0055] The results are shown in Tables 2 to 4 below.

[0056] [Table 2]

[0057] [Table 3]

[0058] [Table 4]

[0059] From the results of Examples 1 to 8, it was found that the conductive sheets of the examples were formed by laminating a surface layer 12, an intermediate layer 14, and a back layer 16, and that the surface layer 12, the intermediate layer 14, and the back layer 16 were composed of a conductive thermoplastic resin composition, the conductive sheet contained conductive carbon, the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 was 29 to 47 parts by mass per 100 parts by mass of thermoplastic resin, the conductive thermoplastic resin composition constituting the surface layer 12 had a matrix of vinyl chloride resin with a degree of polymerization of 1300 or more, the ratio of the thickness of the surface layer 12 to the thickness of the entire conductive sheet was 10 to 40%, the thickness of the back layer 16 was less than the thickness of the surface layer 12, and the hardness of the entire conductive sheet 1 was 75 to 95, so that the conductive sheet had excellent conductivity and cushioning properties and could suppress warping and dust generation toward the surface layer side.

[0060] In Comparative Example 1, the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 was 49 parts by mass per 100 parts by mass of thermoplastic resin, which exceeded the upper limit specified in the present invention, and therefore, a decrease in abrasion resistance and an increase in the amount of dust generated were expected. In Comparative Example 2, the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 was 27 parts by mass per 100 parts by mass of thermoplastic resin, which is less than the lower limit specified in the present invention, and therefore the cushioning properties were deteriorated. In Comparative Examples 3 and 4, the hardness of the conductive sheet 1 was outside the range specified by the present invention, and therefore the cushioning properties were poor. In Comparative Examples 5 and 6, the ratio of the thickness of the surface layer 12 to the thickness of the entire conductive sheet was outside the range specified in the present invention, and therefore the cushioning properties were deteriorated. In Comparative Examples 7 and 8, the thickness of the back layer 16 exceeded the thickness of the surface layer 12, so that the conductive sheet 1 warped toward the surface layer 12 side. In Comparative Example 9, the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 was 49 parts by mass per 100 parts by mass of the thermoplastic resin, and the degree of polymerization of the vinyl chloride resin in the conductive thermoplastic resin composition was 1000, which is below the lower limit specified in the present invention, so that a decrease in abrasion resistance and an increase in the amount of dust generation were expected. In Comparative Example 10, the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer 12 was 27 parts by mass per 100 parts by mass of thermoplastic resin, which is less than the lower limit specified in the present invention, and the degree of polymerization of the thermoplastic resin in the conductive thermoplastic resin composition was 1000, which is less than the lower limit specified in the present invention, so that a decrease in abrasion resistance and an increase in the amount of dust generated were expected. In Comparative Example 11, the hardness of the conductive sheet 1 was 72, which is below the lower limit specified in the present invention, and the degree of polymerization of the thermoplastic resin in the conductive thermoplastic resin composition was 1000, which is below the lower limit specified in the present invention, so that the abrasion resistance was reduced, the amount of dust generated was expected to increase, and the cushioning properties were deteriorated. In Comparative Example 12, the hardness of the conductive sheet 1 was 97, which exceeded the upper limit specified in the present invention, and the degree of polymerization of the thermoplastic resin in the conductive thermoplastic resin composition was 1000, which was below the lower limit specified in the present invention, so that a decrease in abrasion resistance and an increase in the amount of dust generation were expected. In Comparative Example 13, the ratio of the thickness of the surface layer 12 to the thickness of the entire conductive sheet was less than the lower limit specified in the present invention, and the degree of polymerization of the thermoplastic resin in the conductive thermoplastic resin composition was 1000, which is less than the lower limit specified in the present invention, so that the abrasion resistance was reduced, the amount of dust generated was expected to increase, and the cushioning properties were deteriorated. In Comparative Example 14, the ratio of the thickness of the surface layer 12 to the thickness of the entire conductive sheet exceeded the upper limit specified in the present invention, and the degree of polymerization of the thermoplastic resin in the conductive thermoplastic resin composition was 1000, which is less than the lower limit specified in the present invention, so that a decrease in abrasion resistance and an increase in the amount of dust generated were expected. In Comparative Examples 15 to 16, the thickness of the back layer 16 exceeded the thickness of the surface layer 12, and the degree of polymerization of the thermoplastic resin in the conductive thermoplastic resin composition was 1000, which is below the lower limit specified in the present invention. As a result, the abrasion resistance was reduced, the amount of dust generated was expected to increase, and warping occurred toward the surface layer 12 side of the conductive sheet 1.

[0061] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. are possible as appropriate. In addition, the material, shape, dimensions, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as the present invention can be achieved.

[0062] Here, the features of the above-described embodiments of the conductive sheet according to the present invention will be briefly summarized and listed below in (1) to (7). (1) A conductive sheet (1) comprising at least a surface layer (12), an intermediate layer (14), and a back layer (16) laminated together, The surface layer (12), the intermediate layer (14), and the back layer (16) are made of a conductive thermoplastic resin composition containing a thermoplastic resin, The conductive sheet (1) contains conductive carbon, the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer (12) is 29 to 47 parts by mass relative to 100 parts by mass of the thermoplastic resin, The degree of polymerization of the thermoplastic resin in the conductive thermoplastic resin composition constituting the surface layer (12) based on JIS K6720-2 is 1300 or more, The ratio of the thickness of the surface layer (12) to the total thickness of the conductive sheet is 10 to 40%, The thickness of the back layer (16) is equal to or less than the thickness of the surface layer (12), and The hardness of the entire conductive sheet (1) is 75 to 95. Conductive sheet. (2) In the conductive sheet of (1), The conductive sheet is one in which the conductive thermoplastic resin composition has a vinyl chloride resin matrix. (3) In the conductive sheet of (1) or (2), The surface resistance between two points measured in accordance with NFPA99 is 2.5 x 10 4 Ω~1.0×10 7 Ω, conductive sheet. (4) In any one of the conductive sheets (1) to (3), The resistance between the top and bottom measured in accordance with NFPA99 is 2.5 x 10 4 Ω~1.0×10 7 Ω, conductive sheet. (5) In any one of the conductive sheets (1) to (4), A conductive sheet whose abrasion amount in an abrasion resistance test conforming to JIS A1454 is less than 0.05 mm. (6) In any one of the conductive sheets (1) to (5), A conductive sheet in which the warpage toward the surface layer side is 0 mm in a warpage test in accordance with JIS A1454. (7) In any one of the conductive sheets (1) to (6), A conductive sheet whose depression measured in accordance with JIS A1454 is 0.3 mm or more at 23°C and 1.5 mm or less at 45°C. [Explanation of symbols]

[0063] 1 Conductive sheet 12 Surface layer 13 Conductive carbon layer 14 Middle Class

Claims

1. A conductive sheet comprising at least a surface layer, an intermediate layer, and a back layer, the surface layer, the intermediate layer, and the back layer are made of a conductive thermoplastic resin composition containing a thermoplastic resin, the conductive sheet contains conductive carbon; the amount of plasticizer in the conductive thermoplastic resin composition constituting the surface layer is 29 to 47 parts by mass relative to 100 parts by mass of the thermoplastic resin; the thermoplastic resin in the conductive thermoplastic resin composition constituting the surface layer has a degree of polymerization based on JIS K6720-2 of 1300 or more; The ratio of the thickness of the surface layer to the thickness of the entire conductive sheet is 10 to 40%; The thickness of the back layer is equal to or less than the thickness of the surface layer, and The hardness of the entire conductive sheet is 75 to 95. Conductive sheet.

2. The conductive sheet according to claim 1 , wherein the conductive thermoplastic resin composition has a vinyl chloride resin matrix.

3. The surface resistance between two points measured in accordance with NFPA99 is 2.5 x 10 ４ Ω ~ 1.0 x 10 ７ The conductive sheet according to claim 1 or 2, wherein the resistance is Ω.

4. The resistance between the top and bottom measured in accordance with NFPA99 is 2.5 x 10 ４ Ω ~ 1.0 x 10 ７ The conductive sheet according to any one of claims 1 to 3, wherein the resistance is Ω.

5. 5. The conductive sheet according to claim 1, wherein the amount of wear in an abrasion resistance test in accordance with JIS A1454 is less than 0.05 mm.

6. The conductive sheet according to any one of claims 1 to 5, wherein the warpage toward the surface layer side in a warpage test in accordance with JIS A1454 is 0 mm.

7. 7. The conductive sheet according to claim 1, wherein the amount of depression measured in accordance with JIS A1454 is 0.3 mm or more at 23°C and 1.5 mm or less at 45°C.

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