Conductive film

Abstract

The invention provides a conductive film. The conductive film includes a first layer, a second layer, and an intermediate layer. The intermediate layer is formed between the first layer and the second layer. The first layer and the second layer each contain a first resin and a conductive filler. The intermediate layer contains a resin having higher flexibility than the first resin and a conductive filler. The ratio of the thickness of the intermediate layer to the thickness of the conductive film is greater than 0.2 and less than 0.7. The conductive film has a volume resistivity of 40 [Omega] cm or less.

Description

Technical Field

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

[0002] Japanese Patent Publication No. 2019-179732 (Patent Document 1) discloses a conductive film comprising a crystalline olefin resin, a thermoplastic elastomer, and a conductive filler. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Publication No. 2019-179732 Summary of the invention Technical Problems to be Solved by the Invention

[0004] In the conductive film disclosed in the above-mentioned Patent Document 1, if the amount of conductive filler added is increased, the conductivity is improved. However, if the amount of conductive filler added is increased, the conductive film becomes brittle. For example, at least one of the tensile elongation at break and the tear strength of the conductive film is reduced.

[0005] The present invention has been made to solve the above problems, and an object of the present invention is to provide a conductive film containing a conductive filler, the conductive film having sufficient properties in terms of both tensile elongation at break and tear strength. Technical solutions for solving technical problems

[0006] The conductive film of the present invention comprises a first layer, a second layer and an intermediate layer. The intermediate layer is formed between the first layer and the second layer. Each of the first layer and the second layer comprises a first resin and a conductive filler. The intermediate layer comprises a second resin having higher flexibility than the first resin and a conductive filler. The ratio of the thickness of the intermediate layer to the thickness of the conductive film is greater than 0.2 and less than 0.7. The volume resistivity of the conductive film is less than 40Ω·cm.

[0007] In this conductive film, since the first layer and the second layer contain the first resin, sufficient tear strength is ensured, and since the intermediate layer contains the second resin having higher softness than the first resin, sufficient tensile elongation at break is ensured. In particular, since the ratio of the thickness of the intermediate layer to the thickness of the entire conductive film is greater than 0.2 and less than 0.7, for the conductive film, sufficient characteristics are ensured from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film is less than 40Ω·cm, sufficient conductivity is ensured. That is, according to this conductive film, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0008] In the above conductive film, the conductive filler may include a conductive carbon filler.

[0009] In the above conductive film, the first resin and the second resin may include at least one selected from olefin resins, polyamide resins, polyester resins, polystyrene resins, and elastomers thereof.

[0010] In the above conductive film, the second resin may be LDPE (low-density polyethylene), LLDPE (linear low-density polyethylene), or an elastomer.

[0011] In the above conductive film, the concentration of the conductive filler in the intermediate layer may be lower than the concentration of the conductive filler in each of the first layer and the second layer.

[0012] In the intermediate layer of the conductive film, the resin may be contained in an amount of 5 wt % or more in the entire composition constituting the intermediate layer. Effects of the Invention

[0013] According to the present invention, there can be provided a conductive film containing a conductive filler and having sufficient characteristics from the viewpoints of both tensile elongation at break and tear strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram schematically showing a cross section of the conductive film according to the first embodiment. Figure 2 It is a diagram schematically showing a conductive film production apparatus. Figure 3 This is a diagram schematically showing a cross section of a conductive film according to the second embodiment. Figure 4 This is a diagram schematically showing a cross section of a conductive film according to the third embodiment. Figure 5 This is a diagram for explaining the method for producing the conductive film according to the third embodiment. DETAILED DESCRIPTION

[0015] The following is a detailed description of an embodiment of one aspect of the present invention (hereinafter also referred to as "this embodiment") using the accompanying drawings. In addition, the same or corresponding parts in the figures are marked with the same reference numerals, and their descriptions are not repeated. In addition, for easy understanding, each figure appropriately omits or exaggerates the schematic depiction of the object.

[0016] [1. Implementation Method 1] <1-1. Configuration of Conductive Film> Figure 1 Schematic diagram of the cross section of the conductive film 10 of the first embodiment. Figure 1As shown, the conductive film 10 includes a first layer 100 , a second layer 110 , and an intermediate layer 120 formed between the first layer 100 and the second layer 110 .

[0017] One of the first layer 100 and the second layer 110 is a surface layer including the surface of the conductive film 10, and the other of the first layer 100 and the second layer 110 is a back layer including the back side of the conductive film 10. Each of the first layer 100 and the second layer 110 includes, for example, polypropylene 130 and a conductive carbon filler 132. Each of the first layer 100 and the second layer 110 may further include a part or all of additives such as a dispersant, an antioxidant, an anti-blocking agent, and an ultraviolet light blocking agent.

[0018] Examples of the polypropylene 130 include homopolypropylene, random polypropylene, block polypropylene, polypropylene having a long-chain branch structure, and acid-modified polypropylene.

[0019] In addition, examples of the conductive carbon filler 132 include graphite, carbon black (acetylene black, Ketjen black, furnace black, channel black, hot lamp black, etc.), carbon nanotubes, and mixtures thereof.

[0020] The intermediate layer 120 is sandwiched between the first layer 100 and the second layer 110. The intermediate layer 120 includes, for example, LDPE (low-density polyethylene) 134 and a conductive carbon filler 132. The intermediate layer 120 may also include a part or all of additives such as a dispersant, an antioxidant, an anti-blocking agent, and an ultraviolet light blocking agent, as well as at least one of other resins. LDPE 134 has higher flexibility than polypropylene 130. For example, LDPE 134 has at least one of a high tensile strength at break and a high tensile elongation at break compared to polypropylene 130. In the intermediate layer 120, the proportion of LDPE 134 in the entire composition constituting the intermediate layer 120 may be 5 wt% or more, preferably 10 wt% or more.

[0021] In the conductive film 10, the ratio of the thickness of the intermediate layer 120 to the thickness of the conductive film 10 is preferably greater than 0.2 and less than 0.7. In addition, the ratio of the thickness of the intermediate layer 120 to the thickness of the conductive film 10 is more preferably greater than 0.25 and less than 0.45, and more preferably greater than 0.25 and less than 0.4. In addition, the volume resistivity of the conductive film 10 is less than 40 Ω·cm.

[0022] In addition, the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120 may be greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120 may be greater than 1. In the conductive film 10, since the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120 is greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120 is greater than 1, sufficient tear strength is ensured by the first layer 100 and the second layer 110, and sufficient tensile elongation at break is ensured by the intermediate layer 120.

[0023] In addition, the result obtained by dividing the tensile elongation at break of the intermediate layer 120 by the tensile elongation at break of the first layer 100 may be greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120 by the tensile elongation at break of the second layer 110 may be greater than 1. In the conductive film 10, since the result obtained by dividing the tensile elongation at break of the intermediate layer 120 by the tensile elongation at break of the first layer 100 is greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120 by the tensile elongation at break of the second layer 110 is greater than 1, sufficient tensile elongation at break is ensured by the intermediate layer 120, and sufficient tear strength is ensured by the first layer 100 and the second layer 110.

[0024] In this way, in the conductive film 10, the intermediate layer 120 is provided between the first layer 100 and the second layer 110. Such a configuration is adopted in order to ensure sufficient characteristics in terms of both tensile elongation at break and tear strength.

[0025] In the conductive film 10, the first layer 100 and the second layer 110 contain polypropylene 130. The polypropylene 130 has high tear strength, and since the first layer 100 and the second layer 110 contain polypropylene 130, sufficient tear strength is ensured in the conductive film 10. In addition, in the conductive film 10, the intermediate layer 120 contains LDPE 134. LDPE 134 has high tensile elongation at break, and since the intermediate layer 120 contains LDPE 134, sufficient tensile elongation at break is ensured in the conductive film 10.

[0026] In addition, in the conductive film 10, the ratio of the thickness of the intermediate layer 120 to the thickness of the conductive film 10 is, for example, greater than 0.2 and less than 0.7. Since the ratio of the thickness of the intermediate layer 120 to the thickness of the conductive film 10 is within an appropriate range, the conductive film 10 has sufficient characteristics from the perspectives of both tensile elongation at break and tear strength. In addition, in the conductive film 10, since the volume resistivity of the conductive film 10 is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10 of the first embodiment, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0027] <1-2. Method for producing conductive film> Figure 2 2 is a diagram schematically showing a manufacturing apparatus 200 for the conductive film 10. Figure 2 As shown, the manufacturing device 200 includes a T-die 210 and raw material input parts 220 , 230 , and 240 .

[0028] The raw material for forming the first layer 100 is put into the raw material input part 220. For example, polypropylene 130 and conductive carbon filler 132 are put into the raw material input part 220. The raw material for forming the second layer 110 is put into the raw material input part 240. For example, polypropylene 130 and conductive carbon filler 132 are put into the raw material input part 240. The raw material for forming the intermediate layer 120 is put into the raw material input part 230. For example, LDPE 134 and conductive carbon filler 132 are put into the raw material input part 230.

[0029] The T-die 210 is configured to co-extrude the raw materials fed through the raw material feeding parts 220, 230, and 240, so that the melts of the raw materials fed through the raw material feeding parts are fused together to form an integrated film. That is, the T-die 210 is configured to produce the conductive film 10 based on the raw materials fed through the raw material feeding parts 220, 230, and 240. In this way, for example, the conductive film 10 is produced by laminating the first layer 100, the intermediate layer 120, and the second layer 110 using the manufacturing apparatus 200.

[0030] <1-3. Features> As described above, in the conductive film 10 of the first embodiment, since the first layer 100 and the second layer 110 contain polypropylene 130 (an example of the first resin), sufficient tear strength is ensured, and since the intermediate layer 120 contains LDPE 134 (an example of the second resin) having higher flexibility than the polypropylene 130, sufficient tensile elongation at break is ensured. In particular, since the ratio of the thickness of the intermediate layer 120 to the thickness of the entire conductive film 10 is greater than 0.2 and less than 0.7, sufficient tear strength is ensured. In addition, since the volume resistivity of the conductive film 10 is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10 of the first embodiment, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0031] In addition, in the conductive film 10 of the present embodiment 1, the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120 may be greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120 may be greater than 1. In this case, sufficient tear strength is ensured by the first layer 100 and the second layer 110, and sufficient tensile elongation at break is ensured by the intermediate layer 120. In particular, since the ratio of the thickness of the intermediate layer 120 to the thickness of the entire conductive film 10 is greater than 0.2 and less than 0.7, in the conductive film 10, sufficient characteristics are ensured from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10 is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0032] In addition, in the conductive film 10 of the present embodiment 1, the result obtained by dividing the tensile elongation at break of the intermediate layer 120 by the tensile elongation at break of the first layer 100 may be greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120 by the tensile elongation at break of the second layer 110 may be greater than 1. In this case, sufficient tensile elongation at break is ensured by the intermediate layer 120, and sufficient tear strength is ensured by the first layer 100 and the second layer 110. In particular, since the ratio of the thickness of the intermediate layer 120 to the thickness of the entire conductive film 10 is greater than 0.2 and less than 0.7, sufficient characteristics are ensured in the conductive film 10 in terms of tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10 is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0033] [2. Implementation Method 2] In the conductive film 10 of the first embodiment, the intermediate layer 120 is composed of LDPE 134 and conductive carbon filler 132. However, the structure of the intermediate layer 120 is not limited thereto. In the conductive film 10A of the second embodiment, the intermediate layer 120A has a structure different from the intermediate layer 120 of the conductive film 10 of the first embodiment. The conductive film 10A of the second embodiment is described below. In addition, the following mainly describes the differences from the first embodiment, and the common parts with the first embodiment are not repeated.

[0034] <2-1. Configuration of Conductive Film> Figure 3 Schematically shows a cross section of the conductive film 10A according to the second embodiment. Figure 2 As shown, the conductive film 10A includes a first layer 100, a second layer 110, and an intermediate layer 120A formed between the first layer 100 and the second layer 110. The configurations of the first layer 100 and the second layer 110 are the same as those of the first embodiment described above.

[0035] The middle layer 120A is sandwiched between the first layer 100 and the second layer 110. The middle layer 120A includes, for example, polypropylene 130, LDPE 134, and conductive carbon filler 132. The middle layer 120A may also include a part or all of additives such as a dispersant, an antioxidant, an anti-blocking agent, and an ultraviolet light blocking agent, and at least one of other resins. In the middle layer 120A, the proportion of the content of LDPE 134 in the entire composition constituting the middle layer 120A may be 5 wt% or more, preferably 10 wt% or more.

[0036] In the conductive film 10A, the ratio of the thickness of the intermediate layer 120A to the thickness of the conductive film 10A is preferably greater than 0.2 and less than 0.7. In addition, the ratio of the thickness of the intermediate layer 120A to the thickness of the conductive film 10A is more preferably greater than 0.25 and less than 0.45, and more preferably greater than 0.25 and less than 0.4. In addition, the volume resistivity of the conductive film 10A is less than 40Ω·cm.

[0037] In addition, the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120A may be greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120A may be greater than 1. In the conductive film 10A, since the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120A is greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120A is greater than 1, sufficient tear strength is ensured by the first layer 100 and the second layer 110, and sufficient tensile elongation at break is ensured by the intermediate layer 120A.

[0038] In addition, the result obtained by dividing the tensile elongation at break of the intermediate layer 120A by the tensile elongation at break of the first layer 100 may be greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120A by the tensile elongation at break of the second layer 110 may be greater than 1. In the conductive film 10A, since the result obtained by dividing the tensile elongation at break of the intermediate layer 120A by the tensile elongation at break of the first layer 100 is greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120A by the tensile elongation at break of the second layer 110 is greater than 1, sufficient tensile elongation at break is ensured by the intermediate layer 120A, and sufficient tear strength is ensured by the first layer 100 and the second layer 110.

[0039] In the conductive film 10A, since the first layer 100 and the second layer 110 contain polypropylene 130, sufficient tear strength is ensured, and since the intermediate layer 120A contains LDPE 134 having higher flexibility than polypropylene 130, sufficient tensile elongation at break is ensured. In particular, since the ratio of the thickness of the intermediate layer 120A to the thickness of the entire conductive film 10A is greater than 0.2 and less than 0.7, the conductive film 10A has sufficient characteristics from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10A is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10A of the second embodiment, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0040] <2-2. Method for producing conductive film> For example, through Figure 2 The manufacturing apparatus 200 shown in the figure manufactures the conductive film 10A. Figure 2, the raw material for forming the first layer 100 is put into the raw material input part 220. For example, polypropylene 130 and conductive carbon filler 132 are put into the raw material input part 220. The raw material for forming the second layer 110 is put into the raw material input part 240. For example, polypropylene 130 and conductive carbon filler 132 are put into the raw material input part 240. The raw material for forming the intermediate layer 120 is put into the raw material input part 230. For example, polypropylene 130, LDPE 134 and conductive carbon filler 132 are put into the raw material input part 230.

[0041] The T-die 210 is configured to co-extrude the raw materials input through the raw material input parts 220, 230, and 240, so that the melts of the raw materials input through the raw material input parts are fused together to form an integrated film. That is, the T-die 210 is configured to produce the conductive film 10A based on the raw materials input through the raw material input parts 220, 230, and 240. In this way, for example, the conductive film 10A is produced by laminating the first layer 100, the intermediate layer 120A, and the second layer 110 using the manufacturing apparatus 200.

[0042] <2-3. Features> As described above, in the conductive film 10A of the second embodiment, since the first layer 100 and the second layer 110 contain the polypropylene 130, sufficient tear strength is ensured, and since the intermediate layer 120A contains the LDPE 134 having higher flexibility than the polypropylene 130, sufficient tensile elongation at break is ensured. In particular, since the ratio of the thickness of the intermediate layer 120A to the thickness of the entire conductive film 10A is greater than 0.2 and less than 0.7, the conductive film 10A has sufficient characteristics from the viewpoints of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10A is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10A of the second embodiment, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0043] In addition, in the conductive film 10A of the second embodiment, the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120A may be greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120A may be greater than 1. In this case, sufficient tear strength is ensured by the first layer 100 and the second layer 110, and sufficient tensile elongation at break is ensured by the intermediate layer 120A. In particular, since the ratio of the thickness of the intermediate layer 120A to the thickness of the entire conductive film 10A is greater than 0.2 and less than 0.7, in the conductive film 10A, sufficient characteristics are ensured from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10A is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10A, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0044] In addition, in the conductive film 10A of the second embodiment, the result obtained by dividing the tensile elongation at break of the intermediate layer 120A by the tensile elongation at break of the first layer 100 may be greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120A by the tensile elongation at break of the second layer 110 may be greater than 1. In this case, sufficient tensile elongation at break is ensured by the intermediate layer 120A, and sufficient tear strength is ensured by the first layer 100 and the second layer 110. In particular, since the ratio of the thickness of the intermediate layer 120A to the thickness of the entire conductive film 10A is greater than 0.2 and less than 0.7, in the conductive film 10A, sufficient characteristics are ensured from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10A is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10A, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0045] [3. Implementation Method 3] In the intermediate layer 120A of the conductive film 10A of the second embodiment, polypropylene 130, LDPE 134, and conductive carbon filler 132 are mixed together. However, the structure of the intermediate layer is not limited to this. In the conductive film 10B of the third embodiment, the intermediate layer 120B has a structure different from the intermediate layer 120A of the conductive film 10A of the second embodiment. The conductive film 10B of the third embodiment is described below. In addition, the differences from the second embodiment are mainly described below, and the parts common to the second embodiment are not repeated.

[0046] <3-1. Configuration of Conductive Film> Figure 4Schematic diagram of a cross section of a conductive film 10B according to the third embodiment. Figure 4 , the middle layer 120B of the conductive film 10B has a so-called sea-island structure. The sea portion of the sea-island structure (hereinafter also referred to as the "sea portion") is mainly composed of polypropylene 130 and conductive carbon filler 132. The island portion of the sea-island structure (hereinafter also referred to as the "island portion") is mainly composed of LDPE 134. In the middle layer 120B, the content of polypropylene 130 is greater than the content of LDPE 134. In addition, since the middle layer 120B is manufactured by the "two-stage manufacturing method" described later, the middle layer 120B has such a sea-island structure.

[0047] In the middle layer 120B, since the island portion contains almost no conductive carbon filler 132 and the concentration of the conductive carbon filler 132 in the sea portion is maintained at a high concentration, the conductivity of the middle layer 120B is relatively high. For example, the volume resistivity of the middle layer 120B is less than 10 to the sixth power. In addition, since the island portion contains almost no conductive carbon filler 132 and the tensile elongation at break of the island portion is maintained at a large state, the tensile elongation at break of the middle layer 120B is also maintained at a high level.

[0048] In addition, the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120B may be greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120B may be greater than 1. In the conductive film 10B, since the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120B is greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120B is greater than 1, sufficient tear strength is ensured by the first layer 100 and the second layer 110, and sufficient tensile elongation at break is ensured by the intermediate layer 120B.

[0049] In addition, the result obtained by dividing the tensile elongation at break of the intermediate layer 120B by the tensile elongation at break of the first layer 100 may be greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120B by the tensile elongation at break of the second layer 110 may be greater than 1. In the conductive film 10B, since the result obtained by dividing the tensile elongation at break of the intermediate layer 120B by the tensile elongation at break of the first layer 100 is greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120B by the tensile elongation at break of the second layer 110 is greater than 1, sufficient tensile elongation at break is ensured by the intermediate layer 120B, and sufficient tear strength is ensured by the first layer 100 and the second layer 110.

[0050] In the conductive film 10B, since the first layer 100 and the second layer 110 contain polypropylene 130, sufficient tear strength is ensured, and since the island portion of the intermediate layer 120B is composed of LDPE 134, sufficient tensile elongation at break is ensured. In particular, since the ratio of the thickness of the intermediate layer 120B to the thickness of the entire conductive film 10B is greater than 0.2 and less than 0.7, the conductive film 10B has sufficient characteristics from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10B is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10B of the third embodiment, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0051] <3-2. Method for producing conductive film> Figure 5 10B is a diagram for explaining a method for manufacturing the conductive film 10B. Figure 5 , a raw material for forming the first layer 100 is fed into the raw material feeding part 220. For example, polypropylene 130 and a conductive carbon filler 132 (for example, carbon black (CB)) are fed into the raw material feeding part 220. A raw material for forming the second layer 110 is fed into the raw material feeding part 240. For example, polypropylene 130 and a conductive carbon filler 132 are fed into the raw material feeding part 240.

[0052] The raw material for forming the intermediate layer 120 is fed into the raw material feeding part 230. For example, a masterbatch and LDPE 134 are fed into the raw material feeding part 230. For example, the masterbatch is prepared in advance by melt-kneading the crushed polypropylene 130 and the conductive carbon filler 132. For example, the polypropylene 130 and the conductive carbon filler 132 are fed into a twin-screw extruder, and melt-kneaded in the twin-screw extruder to prepare the masterbatch.

[0053] The T-die 210 is configured to co-extrude the raw materials fed through the raw material feeding parts 220, 230, and 240, so that the melts of the raw materials fed through the raw material feeding parts are fused together to form an integrated film. That is, the T-die 210 is configured to produce the conductive film 10B based on the raw materials fed through the raw material feeding parts 220, 230, and 240. In this way, for example, the conductive film 10B is produced by laminating the first layer 100, the intermediate layer 120B, and the second layer 110 using the manufacturing apparatus 200.

[0054] In the conductive film 10B manufactured in this way, the intermediate layer 120B has a sea-island structure as described above. The intermediate layer 120B is manufactured through a first step of manufacturing a masterbatch using polypropylene 130 and conductive carbon filler 132, and a second step of mixing LDPE 134 with the masterbatch. In this way, the intermediate layer 120B is manufactured through a two-stage process. Hereinafter, such a method of manufacturing an intermediate layer through a two-stage process is also referred to as a "two-stage method". On the other hand, for example, a method of manufacturing an intermediate layer by simultaneously feeding polypropylene 130, LDPE 134, and conductive carbon filler 132 into a raw material feeding part 230 is also referred to as a "one-stage method".

[0055] <3-3. Features> As described above, in the conductive film 10B of the third embodiment, since the first layer 100 and the second layer 110 contain the polypropylene 130, sufficient tear strength is ensured, and since the island portion of the intermediate layer 120B is composed of the LDPE 134, sufficient tensile elongation at break is ensured. In particular, since the ratio of the thickness of the intermediate layer 120B to the thickness of the entire conductive film 10B is greater than 0.2 and less than 0.7, the conductive film 10B has sufficient characteristics from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10B is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10B of the third embodiment, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0056] In addition, in the conductive film 10B of the present embodiment 3, the result obtained by dividing the Young's modulus of the first layer 100 by the Young's modulus of the intermediate layer 120B may be greater than 1, and the result obtained by dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120B may be greater than 1. In this case, sufficient tear strength is ensured by the first layer 100 and the second layer 110, and sufficient tensile elongation at break is ensured by the intermediate layer 120B. In particular, since the ratio of the thickness of the intermediate layer 120B to the thickness of the entire conductive film 10B is greater than 0.2 and less than 0.7, in the conductive film 10B, sufficient characteristics are ensured from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10B is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10B, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0057] In addition, in the conductive film 10B of the present embodiment 3, the result obtained by dividing the tensile elongation at break of the intermediate layer 120B by the tensile elongation at break of the first layer 100 may be greater than 1, and the result obtained by dividing the tensile elongation at break of the intermediate layer 120B by the tensile elongation at break of the second layer 110 may be greater than 1. In this case, sufficient tensile elongation at break is ensured by the intermediate layer 120B, and sufficient tear strength is ensured by the first layer 100 and the second layer 110. In particular, since the ratio of the thickness of the intermediate layer 120B to the thickness of the entire conductive film 10B is greater than 0.2 and less than 0.7, in the conductive film 10B, sufficient characteristics are ensured from the perspectives of both tensile elongation at break and tear strength. In addition, since the volume resistivity of the conductive film 10B is 40Ω·cm or less, sufficient conductivity is ensured. That is, according to the conductive film 10B, sufficient conductivity can be ensured and both tensile elongation at break and tear strength can be ensured.

[0058] [4. Other embodiments] The concept of the above-described embodiment is not limited to the above-described embodiment. Hereinafter, an example of another embodiment to which the concept of the above-described embodiment can be applied will be described.

[0059] <4-1> In each of the above-mentioned embodiments 1 to 3, the intermediate layer contains LDPE 134. However, the resin contained in the intermediate layer does not necessarily have to be LDPE 134. For example, the intermediate layer may contain an elastomer, LLDPE (linear low-density polyethylene) or HDPE (high-density polyethylene) instead of LDPE 134. In short, the resin contained in the intermediate layer can be any resin as long as it has higher flexibility than polypropylene.

[0060] <4-2> In addition, in each of the above-mentioned embodiments 1-3, polypropylene 130 is included in each layer of the first layer 100 and the second layer 110. However, the resin included in each layer of the first layer 100 and the second layer 110 is not limited to polypropylene 130. Each layer may also include at least one selected from olefin resins, polyamide resins, polyester resins, polystyrene resins and their elastomers. As an olefin resin, polypropylene, polymethylpentene or cyclic polyolefin is preferably included, as a polyamide resin, polyamide 6, polyamide 66 or polymeta-xylyleneadipamide is preferably included, and as a polyester resin, polyethylene terephthalate or polybutylene terephthalate is preferably included. In addition, the resin included in each layer is preferably not an elastomer.

[0061] Here, the cyclic polyolefin (cyclic olefin resin) contains a cyclic olefin component as a copolymer component, and there is no particular limitation as long as it is a polyolefin resin containing a cyclic olefin component in the main chain. As an example of a cyclic polyolefin, an addition polymer of a cyclic olefin or its hydrogenated product, an addition copolymer of a cyclic olefin and an α-olefin or its hydrogenated product, etc. can be cited. In addition, as a cyclic polyolefin, it includes a substance obtained by further grafting and / or copolymerizing an unsaturated compound having a hydrophilic group to the above-mentioned polymer.

[0062] As the polar group, for example, carboxyl, anhydride, epoxy, amino, amide, ester, hydroxyl, sulfonic acid, phosphonyl, phosphino, etc. can be cited. As the unsaturated compound having a polar group, (meth) acrylic acid, maleic acid, maleic anhydride, itaconic anhydride, glycidyl (meth) acrylate, (meth) alkyl acrylate (carbon number 1 to 10), maleic acid alkyl (carbon number 1 to 10), (meth) acrylamide, (meth) acrylate-2-hydroxyethyl, etc. can be cited. Preferably, carboxyl, anhydride, epoxy, amino, amide, ester, hydroxyl, sulfonic acid, phosphonyl, phosphino are cited. As the cyclic olefin resin, an addition copolymer of a cyclic olefin and an α-olefin or a hydrogenated product thereof is preferred.

[0063] <4-3> In each of the above-mentioned embodiments 1 to 3, each of the first layer 100, the second layer 110, and the intermediate layer contains a conductive carbon filler 132. However, each layer does not necessarily need to contain a conductive carbon filler 132. Each layer only needs to contain a conductive filler. In addition, the types of conductive fillers contained in each layer do not necessarily need to be the same. As an example of a conductive filler, a metal conductive filler, a carbon conductive filler, a metal oxide conductive filler, and a conductive filler composed of a metal plating layer can be cited.

[0064] As an example of the shape of the metal conductive filler, powder, fiber and foil can be cited. As an example of the powdery metal conductive filler, silver, copper, nickel, tin and silver-plated copper powder can be cited. As an example of the fibrous metal conductive filler, copper, stainless copper, aluminum, brass and iron fiber can be cited. As an example of the foil-shaped metal conductive filler, aluminum and zinc foil can be cited.

[0065] Examples of the shape of the carbon-based conductive filler include powder and fiber. Examples of the powdered carbon-based conductive filler include carbon black and graphite. In addition, examples of the fibrous carbon-based conductive filler include nanotubes and carbon fibers.

[0066] As an example of the shape of the metal oxide conductive filler, powder can be cited. As an example of the powdered metal oxide conductive filler, tin oxide, indium oxide and zinc oxide powder can be cited. As an example of the shape of the conductive filler composed of metal plating, powder and fiber can be cited. As an example of the powdered conductive filler composed of metal plating, filler obtained by plating glass beads and filler obtained by plating mica powder can be cited. As an example of the fibrous conductive filler composed of metal plating, filler obtained by plating glass fibers and filler obtained by plating carbon fibers can be cited.

[0067] The embodiments of the present invention are described above by way of example. That is, for the purpose of illustrative description, the detailed description and the drawings are disclosed. Therefore, the components recorded in the detailed description and the drawings sometimes include components that are not necessary for solving the problem. Therefore, although those non-essential components are recorded in the detailed description and the drawings, it should not be immediately determined that those non-essential components are essential.

[0068] In addition, the above-mentioned embodiment is merely an illustration of the present invention in all aspects. The above-mentioned embodiment can be variously improved and changed within the scope of the present invention. That is, when implementing the present invention, a specific configuration can be appropriately adopted according to the embodiment.

[0069] [5. Example] <5-1. Examples and Comparative Examples> Each conductive film of Examples 1 to 3 was manufactured by coextrusion. The first layer and each layer of the second layer of each conductive film of Examples 1 to 3 were formed using polypropylene and carbon black. The middle layer of each conductive film of Examples 1 to 3 was formed using LDPE and carbon black. The thickness of the middle layer of each conductive film of Examples 1 to 3 was different from each other. The thickness of the middle layer of each conductive film of Examples 1 to 3 is shown later.

[0070] Each conductive film of Examples 4-6 was manufactured by coextrusion. The first layer and each layer of the second layer of each conductive film of Examples 4-6 were formed using polypropylene and carbon black. The intermediate layer of each conductive film of Examples 4-6 was formed using polypropylene, LDPE and carbon black. In each conductive film of Examples 4-6, the intermediate layer was formed by the above-mentioned 1-stage method. The thickness of the intermediate layer of each conductive film of Examples 4-6 is different from each other. The thickness of the intermediate layer of each conductive film of Examples 4-6 is shown later.

[0071] The conductive film of Example 7 was manufactured by coextrusion. The first layer and the second layer of the conductive film of Example 7 were formed by polypropylene and carbon black. The intermediate layer of the conductive film of Example 7 was formed by polypropylene, LDPE and carbon black. The intermediate layer was formed by the above-mentioned two-step method. That is, a masterbatch was once manufactured by polypropylene and carbon black, and then the masterbatch was mixed with LDPE to form the intermediate layer.

[0072] The weight percentage concentration (wt%) of each material of each conductive film of Examples 1 to 7, the total thickness (μm) of the conductive film, the thickness (μm) of the intermediate layer, and the ratio of the thickness of the intermediate layer to the total thickness are shown in the following Table 1. In addition, in each conductive film of Examples 4 to 7, the concentration of carbon black in the intermediate layer is lower than the concentration of carbon black in each of the first layer and the second layer.

[0073] [Table 1]

[0074] The conductive film of Comparative Example 1 was manufactured by extrusion molding. The conductive film of Comparative Example 1 is a single-layer film. The conductive film of Comparative Example 1 was formed using polypropylene and carbon black.

[0075] The conductive film of Comparative Example 2 was manufactured by extrusion molding. The conductive film of Comparative Example 2 is a single-layer film. The conductive film of Comparative Example 2 was formed using LDPE and carbon black.

[0076] The conductive film of Comparative Example 3 was manufactured by extrusion molding. The conductive film of Comparative Example 3 is a single-layer film. The conductive film of Comparative Example 3 was formed using polypropylene, LDPE, and carbon black.

[0077] The conductive films of Comparative Examples 4 and 5 were manufactured by coextrusion. The first layer and the second layer of the conductive films of Comparative Examples 4 and 5 were formed by polypropylene and carbon black. The intermediate layer of the conductive films of Comparative Examples 4 and 5 was formed by polypropylene, LDPE and carbon black. In the conductive films of Comparative Examples 4 and 5, the intermediate layer was formed by the above-mentioned one-stage manufacturing method.

[0078] The conductive film of Comparative Example 6 was manufactured by extrusion molding. The conductive film of Comparative Example 6 is a single-layer film. The conductive film of Comparative Example 6 was formed using polypropylene, PP elastomer, and carbon black.

[0079] The values ​​of the weight percentage concentration (wt %) of each material of each conductive film of Comparative Examples 1-6, the total thickness (μm) of the conductive film, the thickness of the intermediate layer (μm), and the ratio of the thickness of the intermediate layer to the total thickness are shown in Table 2 below.

[0080] [Table 2]

[0081] <5-2. Various measurements> For each conductive film of Examples 1-7 and Comparative Examples 1-6, the Young's modulus (GPa) of each layer, the tensile elongation at break (%) in MD (machine direction) of each layer, the volume resistivity (Ω·cm), the tensile strength at break (MPa) in MD, the tensile elongation at break (%) in MD, and the right-angle tear strength (N / mm) in MD were measured.

[0082] The Young's modulus of each layer was measured by the method according to JIS K 7127. Specifically, a single-layer film of 50 μm corresponding to each layer was prepared using the raw materials formulated for each layer, and the Young's modulus of each single-layer film was measured by the method according to JIS K 7127, thereby measuring the Young's modulus of each layer. In addition, the Young's modulus of each layer can also be measured in the following manner: each layer is separated from the conductive film by a physical or chemical method, and each separated layer is re-melted to prepare a single-layer film corresponding to each layer, and the Young's modulus of each single-layer film is measured by the method according to JIS K 7127.

[0083] The tensile elongation at break in MD of each layer was measured by the method according to JIS K 7127. Specifically, a 50 μm monolayer film corresponding to each layer was prepared using the raw materials formulated for each layer, and the tensile elongation at break in MD of each monolayer film was measured by the method according to JIS K 7127, thereby measuring the tensile elongation at break in MD of each layer. In addition, the tensile elongation at break in MD of each layer can also be measured, for example, in the following manner: each layer is separated from the conductive film by a physical or chemical method, and each separated layer is remelted to prepare a monolayer film corresponding to each layer, and the tensile elongation at break in MD of each monolayer film is measured by the method according to JIS K 7127.

[0084] The volume resistivity was measured by a method according to JIS K 7194. The tensile breaking strength was measured by a method according to JIS K 7127. The tensile breaking elongation was measured by a method according to JIS K 7127. The right-angle tear strength was measured by a method according to JIS-K7128-3.

[0085] <5-3. Results> The measurement results regarding each conductive film of Examples 1 to 7 are shown in Table 3 below.

[0086] [Table 3]

[0087] The measurement results of each conductive film of Comparative Examples 1 to 6 are shown in Table 4 below.

[0088] [Table 4]

[0089] As shown in Tables 3 and 4, sufficient values ​​were obtained for each measurement item in each conductive film of Examples 1 to 7. On the other hand, sufficient results were not obtained for at least one measurement item in each conductive film of Comparative Examples 1 to 6. For example, in Table 4, sufficient results were not obtained for the highlighted items. Description of Reference Numerals

[0090] 10, 10A, 10B: conductive film; 100: first layer; 110: second layer; 120, 120A, 120B: middle layer; 130: polypropylene; 132: conductive carbon filler; 134: LDPE; 200: manufacturing device; 210: T-die; 220, 230, 240: raw material input part.

Claims

1. A conductive film, characterized in that: The conductive film comprises: First floor; Second level; and an intermediate layer formed between the first layer and the second layer, The first layer and the second layer respectively contain a first resin and a conductive filler, The intermediate layer includes a second resin having higher flexibility than the first resin and the conductive filler, The ratio of the thickness of the intermediate layer to the thickness of the conductive film is greater than 0.2 and less than 0.7, The volume resistivity of the conductive film is 40 Ω·cm or less.

2. The conductive film according to claim 1, wherein The conductive filler includes a conductive carbon filler.

3. The conductive film according to claim 1 or 2, characterized in that: The first resin and the second resin include at least one selected from olefin resins, polyamide resins, polyester resins, polystyrene resins, and elastomers thereof.

4. The conductive film according to claim 1 or 2, characterized in that: The second resin is LDPE (low density polyethylene), LLDPE (linear low density polyethylene) or an elastomer.

5. The conductive film according to claim 1 or 2, characterized in that: The concentration of the conductive filler in the intermediate layer is lower than the concentration of the conductive filler in each of the first layer and the second layer.

6. The conductive film according to claim 1 or 2, characterized in that In the intermediate layer, the content of the second resin in the entire composition constituting the intermediate layer is 5 wt % or more.

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