conductive film

Abstract

To provide a conductive film which contains a conductive filler and has sufficient characteristics in terms of both tensile elongation at break and tear strength.SOLUTION: 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. Each of the first layer and the second layer contains a first resin and a conductive filler. The intermediate layer contains a second resin and the conductive filler. A result obtained by dividing the Young's modulus of the first layer by the Young's modulus of the intermediate layer is greater than 1. A result obtained by dividing the Young's modulus of the second layer by the Young's modulus of the intermediate layer is greater than 1. 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 Ω cm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Japanese Patent Application Laid-Open No. 2019-179732 (Patent Document 1) discloses a conductive film. This conductive film contains a crystalline olefin resin, a thermoplastic elastomer, and a conductive filler.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conductive film as disclosed in Patent Document 1 above, when the addition amount of the conductive filler increases, the conductivity increases. However, when the addition amount of the conductive filler increases, the conductive film becomes brittle. For example, at least one of the tensile elongation at break and the tear strength of the conductive film decreases.

[0005] The present invention has been made to solve such problems, and an object thereof is to provide a conductive film containing a conductive filler, which has sufficient properties from the viewpoints of both the tensile elongation at break and the tear strength.

Means for Solving the Problems

[0006] A conductive film according to 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 and second layers contains a first resin and a conductive filler. The intermediate layer contains a second resin and a conductive filler. The result of dividing the Young's modulus of the first layer by the Young's modulus of the intermediate layer is greater than 1. The result of dividing the Young's modulus of the second layer by the Young's modulus of the intermediate layer is greater than 1. 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.

[0007] In this conductive film, the result of dividing the Young's modulus of the first layer by the Young's modulus of the intermediate layer is greater than 1, and the result of dividing the Young's modulus of the second layer by the Young's modulus of the intermediate layer is greater than 1. Therefore, sufficient tear strength is ensured by the first and second layers, and sufficient tensile elongation at break is ensured by the intermediate layer. In particular, since the ratio of the thickness of the intermediate layer to the total thickness of the conductive film is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film in terms of both tensile elongation at break and tear strength. Furthermore, since the volume resistivity of the conductive film is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, this conductive film makes it possible to ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

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

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

[0010] In the conductive film described above, the second resin may be LDPE (Low Density Polyethylene), LLDPE (Linear Low Density Polyethylene), or an elastomer.

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

[0012] In the intermediate layer of the conductive film described above, the proportion of the resin content in the total composition constituting the intermediate layer may be 5 wt% or more. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a conductive film containing a conductive filler that has sufficient properties in terms of both tensile break elongation and tear strength. [Brief explanation of the drawing]

[0014] [Figure 1] This figure schematically shows a cross-section of a conductive film according to Embodiment 1. [Figure 2] This is a schematic diagram showing a manufacturing apparatus for conductive films. [Figure 3] This figure schematically shows a cross-section of a conductive film according to Embodiment 2. [Figure 4] This figure schematically shows a cross-section of a conductive film according to Embodiment 3. [Figure 5] This is a diagram illustrating a method for manufacturing a conductive film according to Embodiment 3. [Modes for carrying out the invention]

[0015] Hereinafter, an embodiment relating to one aspect of the present invention (hereinafter also referred to as "this embodiment") will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated. Furthermore, each drawing is schematically depicted with parts omitted or exaggerated as appropriate for ease of understanding.

[0016] [1. Embodiment 1] <1-1. Composition of the conductive film> FIG. 1 is a diagram schematically showing a cross section of a conductive film 10 according to Embodiment 1. As shown in FIG. 1, 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 surface 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. In each of the first layer 100 and the second layer, some or all of additives such as a dispersant, an antioxidant, an antiblocking agent, and an ultraviolet absorber may be further included.

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

[0019] Examples of the conductive carbon filler 132 include, for example, graphite, carbon black (acetylene black, ketjen black, furnace black, channel black, thermal 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 contains, for example, LDPE (Low Density Polyethylene) 134 and conductive carbon filler 132. In the intermediate layer 120, some or all of additives such as a dispersant, an antioxidant, an anti-blocking agent, and an ultraviolet light absorber, and at least one of other resins may be further contained. LDPE 134 has higher flexibility than polypropylene 130. For example, LDPE 134 has at least one of high tensile breaking strength and high tensile breaking elongation as compared with polypropylene 130. In the intermediate layer 120, the proportion of the content 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. Further, the ratio of the thickness of the intermediate layer 120 to the thickness of the conductive film 10 is more preferably 0.25 or more and 0.45 or less, and even more preferably 0.25 or more and 0.4 or less. Also, the volume resistivity of the conductive film 10 is 40 Ω·cm or less.

[0022] Further, the result of 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 of dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120 is greater than 1. In this conductive film 10, since the result of 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 of 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 breaking elongation is ensured by the intermediate layer 120.

[0023] Furthermore, the result of dividing the tensile elongation of the intermediate layer 120 by the tensile elongation of the first layer 100 may be greater than 1, and the result of dividing the tensile elongation of the intermediate layer 120 by the tensile elongation of the second layer 110 may also be greater than 1. In this conductive film 10, the result of dividing the tensile elongation of the intermediate layer 120 by the tensile elongation of the first layer 100 is greater than 1, and the result of dividing the tensile elongation of the intermediate layer 120 by the tensile elongation of the second layer 110 is greater than 1, so sufficient tensile elongation is ensured by the intermediate layer 120, and sufficient tear strength is ensured by the first layer 100 and the second layer 110.

[0024] Thus, in the conductive film 10, an intermediate layer 120 is provided between the first layer 100 and the second layer 110. This configuration is adopted to ensure sufficient properties in terms of both tensile break elongation and tear strength.

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

[0026] Furthermore, 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. Because 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 properties in terms of both tensile elongation at break and tear strength. In addition, the conductive film 10 has a volume resistivity of 40 Ω·cm or less, so sufficient conductivity is ensured. In other words, the conductive film 10 according to this embodiment 1 can ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

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

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

[0029] The T-die 210 is configured to fuse the molten raw materials introduced through the raw material input sections 220, 230, and 240 together to form a single, integrated film by co-extruding the raw materials introduced through each section. In other words, the T-die 210 is configured to produce a conductive film 10 based on the raw materials introduced through the raw material input sections 220, 230, and 240. Thus, the conductive film 10 is manufactured, for example, by the manufacturing apparatus 200, which laminates a first layer 100, an intermediate layer 120, and a second layer 110.

[0030] <1-3. Features> As described above, in the conductive film 10 according to this embodiment 1, the result of 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 of dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120 is greater than 1. Therefore, 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 total thickness of the conductive film 10 is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10 in terms of both tensile elongation at break and tear strength. Furthermore, since the volume resistivity of the conductive film 10 is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, with this conductive film 10, it is possible to ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

[0031] Furthermore, in the conductive film 10 according to this embodiment 1, the result of dividing the tensile elongation of the intermediate layer 120 by the tensile elongation of the first layer 100 may be greater than 1, and the result of dividing the tensile elongation of the intermediate layer 120 by the tensile elongation of the second layer 110 may also be greater than 1. In this case, sufficient tensile elongation 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 total thickness of the conductive film 10 is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10 in terms of both tensile elongation and tear strength. In addition, since the volume resistivity of the conductive film 10 is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, the conductive film 10 makes it possible to ensure both tensile elongation and tear strength while ensuring sufficient conductivity.

[0032] Furthermore, in the conductive film 10 according to this embodiment 1, sufficient tear strength is ensured because the first layer 100 and the second layer 110 contain polypropylene 130 (an example of the first resin), and sufficient tensile elongation at break is ensured because the intermediate layer 120 contains LDPE 134 (an example of the second resin), which has higher flexibility than polypropylene 130. In particular, since the ratio of the thickness of the intermediate layer 120 to the total thickness of the 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 40 Ω·cm or less, sufficient conductivity is ensured. In other words, the conductive film 10 according to this embodiment 1 can ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

[0033] [2. Embodiment 2] In the conductive film 10 according to Embodiment 1 described above, the intermediate layer 120 was composed of LDPE 134 and conductive carbon filler 132. However, the composition of the intermediate layer 120 is not limited to this. In the conductive film 10A according to Embodiment 2, the intermediate layer 120A has a different composition from the intermediate layer 120 in the conductive film 10 according to Embodiment 1 described above. The conductive film 10A according to Embodiment 2 will be described below. In the following, the differences from Embodiment 1 will be mainly described, and parts common to Embodiment 1 will not be repeated.

[0034] <2-1. Composition of the conductive film> Figure 3 is a schematic diagram showing a cross-section of the conductive film 10A according to Embodiment 2. As shown in Figure 2, 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 Embodiment 1 described above.

[0035] The intermediate layer 120A is sandwiched between the first layer 100 and the second layer 110. The intermediate layer 120A contains, for example, polypropylene 130, LDPE 134, and conductive carbon filler 132. The intermediate layer 120A may further contain some or all of the additives such as dispersants, antioxidants, antiblocking agents, and UV inhibitors, as well as at least one of the other resins. In the intermediate layer 120A, the proportion of LDPE 134 in the total composition constituting the intermediate 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. Furthermore, the ratio of the thickness of the intermediate layer 120A to the thickness of the conductive film 10A is more preferably 0.25 or more and 0.45 or less, and even more preferably 0.25 or more and 0.4 or less. In addition, the volume resistivity of the conductive film 10A is 40 Ω·cm or less.

[0037] Furthermore, the result of 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 of dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120A is greater than 1. In this conductive film 10A, since the result of 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 of 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] Furthermore, the result of 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 of dividing the tensile elongation at break of the intermediate layer 120A by the tensile elongation at break of the second layer 110 may also be greater than 1. In this conductive film 10A, the result of 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 of 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. Therefore, 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, sufficient tear strength is ensured because the first layer 100 and the second layer 110 contain polypropylene 130, and sufficient tensile elongation at break is ensured because the intermediate layer 120A contains LDPE 134, which has higher flexibility than polypropylene 130. In particular, since the ratio of the thickness of the intermediate layer 120A to the total thickness of the conductive film 10A is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10A in terms of both tensile elongation at break and tear strength. Furthermore, since the volume resistivity of the conductive film 10A is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, according to the conductive film 10A of this embodiment 2, it is possible to ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

[0040] <2-2. Method for manufacturing conductive film> The conductive film 10A is manufactured, for example, by the manufacturing apparatus 200 shown in Figure 2. Referring again to Figure 2, raw materials for forming the first layer 100 are fed into the raw material input section 220. For example, polypropylene 130 and conductive carbon filler 132 are fed into the raw material input section 220. Raw materials for forming the second layer 110 are fed into the raw material input section 240. For example, polypropylene 130 and conductive carbon filler 132 are fed into the raw material input section 240. Raw materials for forming the intermediate layer 120 are fed into the raw material input section 230. For example, polypropylene 130, LDPE 134, and conductive carbon filler 132 are fed into the raw material input section 230.

[0041] The T-die 210 is configured to fuse the molten raw materials introduced through the raw material input sections 220, 230, and 240 together to form a single, integrated film by co-extruding the raw materials introduced through each section. In other words, the T-die 210 is configured to produce a conductive film 10A based on the raw materials introduced through the raw material input sections 220, 230, and 240. Thus, the conductive film 10A is manufactured, for example, by the manufacturing apparatus 200, which laminates a first layer 100, an intermediate layer 120A, and a second layer 110.

[0042] <2-3. Features> As described above, in the conductive film 10A according to this second embodiment, the result of 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 of dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120A is greater than 1. Therefore, 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 total thickness of the conductive film 10A is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10A in terms of both tensile elongation at break and tear strength. Furthermore, since the volume resistivity of the conductive film 10A is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, with this conductive film 10A, it is possible to ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

[0043] Furthermore, in the conductive film 10A according to this second embodiment, the result of dividing the tensile elongation of the intermediate layer 120A by the tensile elongation of the first layer 100 may be greater than 1, and the result of dividing the tensile elongation of the intermediate layer 120A by the tensile elongation of the second layer 110 may also be greater than 1. In this case, sufficient tensile elongation 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 total thickness of the conductive film 10A is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10A in terms of both tensile elongation and tear strength. In addition, since the volume resistivity of the conductive film 10A is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, the conductive film 10A makes it possible to ensure both tensile elongation and tear strength while ensuring sufficient conductivity.

[0044] Furthermore, in the conductive film 10A according to this second embodiment, sufficient tear strength is ensured because the first layer 100 and the second layer 110 contain polypropylene 130, and sufficient tensile elongation at break is ensured because the intermediate layer 120A contains LDPE 134, which has higher flexibility than polypropylene 130. In particular, since the ratio of the thickness of the intermediate layer 120A to the total thickness of the conductive film 10A is greater than 0.2 and less than 0.7, the conductive film 10A has sufficient properties in terms of both tensile elongation at break and tear strength. In addition, sufficient conductivity is ensured because the volume resistivity of the conductive film 10A is 40 Ω·cm or less. In other words, the conductive film 10A according to this second embodiment can ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

[0045] [3. Embodiment 3] In the intermediate layer 120A of the conductive film 10A according to Embodiment 2 described above, polypropylene 130, LDPE 134, and conductive carbon filler 132 were integrally mixed together. However, the configuration of the intermediate layer is not limited to this. In the conductive film 10B according to Embodiment 3, the intermediate layer 120B has a different configuration from the intermediate layer 120A in the conductive film 10A according to Embodiment 2 described above. The conductive film 10B according to Embodiment 3 will be described below. Note that the following will mainly describe the differences from Embodiment 2 described above, and the parts common to Embodiment 2 will not be repeated.

[0046] <3-1. Composition of the conductive film> Figure 4 is a schematic diagram showing a cross-section of the conductive film 10B according to this embodiment 3. Referring to Figure 4, the intermediate layer 120B in the conductive film 10B has a so-called sea-island structure. The sea portion of the sea-island structure (hereinafter also simply 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 simply referred to as the "island portion") is mainly composed of LDPE 134. In the intermediate layer 120B, the content of polypropylene 130 is greater than the content of LDPE 134, and since the intermediate layer 120B is manufactured by the "two-stage manufacturing method" described later, the intermediate layer 120B has such a sea-island structure.

[0047] In the intermediate layer 120B, the conductive carbon filler 132 is hardly present in the island portions, while the concentration of conductive carbon filler 132 in the ocean portions remains high, resulting in relatively high conductivity of the intermediate layer 120B. For example, the volume resistivity of the intermediate layer 120B is 10 to the power of 6 or less. Furthermore, because the conductive carbon filler 132 is hardly present in the island portions, and the tensile elongation at break in the island portions remains high, the tensile elongation at break of the intermediate layer 120B is also maintained at a high level.

[0048] Furthermore, the result of 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 of dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120B may also be greater than 1. In this conductive film 10B, the result of 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 of dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120B is greater than 1. Therefore, 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] Furthermore, the result of 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 of dividing the tensile elongation at break of the intermediate layer 120B by the tensile elongation at break of the second layer 110 may also be greater than 1. In this conductive film 10B, the result of 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 of 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. Therefore, 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, sufficient tear strength is ensured because the first layer 100 and the second layer 110 contain polypropylene 130, and sufficient tensile elongation at break is ensured because the island portions of the intermediate layer 120B are composed of LDPE 134. In particular, since the ratio of the thickness of the intermediate layer 120B to the total thickness of the conductive film 10B is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10B in terms of both tensile elongation at break and tear strength. Furthermore, since the volume resistivity of the conductive film 10B is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, the conductive film 10B according to this embodiment 3 can ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

[0051] <3-2. Method for manufacturing conductive film> Figure 5 is a diagram illustrating the manufacturing method of the conductive film 10B. Referring to Figure 5, raw materials for forming the first layer 100 are introduced into the raw material input section 220. For example, polypropylene 130 and conductive carbon filler 132 (for example, carbon black (CB)) are introduced into the raw material input section 220. Raw materials for forming the second layer 110 are introduced into the raw material input section 240. For example, polypropylene 130 and conductive carbon filler 132 are introduced into the raw material input section 240.

[0052] Raw materials for forming the intermediate layer 120 are fed into the raw material input section 230. For example, a masterbatch and LDPE 134 are fed into the raw material input section 230. The masterbatch is manufactured in advance, for example, by melt-kneading crushed polypropylene 130 and conductive carbon filler 132. For example, polypropylene 130 and conductive carbon filler 132 are fed into a twin-screw extruder, where melt-kneading is performed to produce the masterbatch.

[0053] The T-die 210 is configured to fuse the molten raw materials introduced through the raw material input sections 220, 230, and 240 together to form a single, integrated film by co-extruding the raw materials introduced through each section. In other words, the T-die 210 is configured to produce a conductive film 10B based on the raw materials introduced through the raw material input sections 220, 230, and 240. Thus, the conductive film 10B is manufactured, for example, by the manufacturing apparatus 200, which laminates the first layer 100, the intermediate layer 120B, and the second layer 110.

[0054] In the conductive film 10B manufactured in this manner, 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. Thus, the intermediate layer 120B is manufactured through a two-step process. This two-step process for manufacturing the intermediate layer will also be referred to as the "two-step manufacturing method" below. On the other hand, for example, manufacturing the intermediate layer by adding polypropylene 130, LDPE 134, and conductive carbon filler 132 to the raw material input section 230 all at once will also be referred to as the "one-step manufacturing method" below.

[0055] <3-3. Features> As described above, in the conductive film 10B according to this third embodiment, the result of 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 of dividing the Young's modulus of the second layer 110 by the Young's modulus of the intermediate layer 120B is greater than 1. Therefore, 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 total thickness of the conductive film 10B is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10B in terms of both tensile elongation at break and tear strength. Furthermore, since the volume resistivity of the conductive film 10B is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, with this conductive film 10B, it is possible to ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

[0056] Furthermore, in the conductive film 10B according to this third embodiment, the result of dividing the tensile elongation of the intermediate layer 120B by the tensile elongation of the first layer 100 may be greater than 1, and the result of dividing the tensile elongation of the intermediate layer 120B by the tensile elongation of the second layer 110 may also be greater than 1. In this case, sufficient tensile elongation 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 total thickness of the conductive film 10B is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10B in terms of both tensile elongation and tear strength. In addition, since the volume resistivity of the conductive film 10B is 40 Ω·cm or less, sufficient conductivity is ensured. In other words, the conductive film 10B makes it possible to ensure both tensile elongation and tear strength while ensuring sufficient conductivity.

[0057] Furthermore, in the conductive film 10B according to this third embodiment, sufficient tear strength is ensured because the first layer 100 and the second layer 110 contain polypropylene 130, and sufficient tensile elongation at break is ensured because the island portions of the intermediate layer 120B are composed of LDPE 134. In particular, since the ratio of the thickness of the intermediate layer 120B to the total thickness of the conductive film 10B is greater than 0.2 and less than 0.7, sufficient properties are ensured in the conductive film 10B in terms of both tensile elongation at break and tear strength. In addition, sufficient conductivity is ensured because the volume resistivity of the conductive film 10B is 40 Ω·cm or less. In other words, the conductive film 10B according to this third embodiment makes it possible to ensure both tensile elongation at break and tear strength while ensuring sufficient conductivity.

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

[0059] <4-1> In each of the embodiments 1-3 described above, the intermediate layer contained LDPE134. However, the resin contained in the intermediate layer does not necessarily have to be LDPE134. For example, the intermediate layer may contain an elastomer, LLDPE (Linear Low Density Polyethylene), or HDPE (High Density Polyethylene) instead of LDPE134. In short, the resin contained in the intermediate layer can be any resin that has higher flexibility than polypropylene.

[0060] <4-2> Furthermore, in each of the embodiments 1-3 described above, polypropylene 130 was included in both the first layer 100 and the second layer 110. However, the resin included in each of the first layer 100 and the second layer 110 is not limited to polypropylene 130. Each layer may contain at least one selected from, for example, olefin resins, polyamide resins, polyester resins, polystyrene resins, or elastomers thereof. Preferably, the olefin resin includes polypropylene, polymethylpentene, or cyclic polyolefin; preferably the polyamide resin includes polyamide 6, polyamide 66, or polymetaxylylene adipamide; and preferably the polyester resin includes polyethylene terephthalate or polybutylene terephthalate. In addition, it is preferable that the resin included in each layer is not an elastomer.

[0061] Here, cyclic polyolefins (cyclic olefin resins) are those that contain a cyclic olefin component as a copolymer component, and are not particularly limited as long as they are polyolefin resins that contain a cyclic olefin component in the main chain. Examples of cyclic polyolefins include addition polymers of cyclic olefins or their hydrogenated products, addition copolymers of cyclic olefins and α-olefins or their hydrogenated products, etc. Furthermore, cyclic polyolefins include those obtained by grafting and / or copolymerizing the above polymers with an unsaturated compound having a hydrophilic group.

[0062] Examples of polar groups include carboxyl groups, acid anhydride groups, epoxy groups, amino groups, amide groups, ester groups, hydroxyl groups, sulfo groups, phosphono groups, and phosphino groups. Examples of unsaturated compounds having polar groups include (meth)acrylic acid, maleic acid, maleic anhydride, itaconic anhydride, glycidyl (meth)acrylate, alkyl (meth)acrylate (1-10 carbon atoms) esters, alkyl (1-10 carbon atoms) maleate esters, (meth)acrylamide, and 2-hydroxyethyl (meth)acrylate. Preferably, carboxyl groups, acid anhydride groups, epoxy groups, amino groups, amide groups, ester groups, hydroxyl groups, sulfo groups, phosphono groups, and phosphino groups are used. As for cyclic olefin resins, addition copolymers of cyclic olefins and α-olefins or hydrogenated versions thereof are preferred.

[0063] <4-3> Furthermore, in each of the embodiments 1-3 described above, the conductive carbon filler 132 was included in the first layer 100, the second layer 110, and the intermediate layer, respectively. However, it is not necessary for each layer to contain the conductive carbon filler 132. Each layer only needs to contain a conductive filler. Also, the types of conductive fillers included in each layer do not necessarily have to be the same. Examples of conductive fillers include metal-based conductive fillers, carbon-based conductive fillers, metal oxide-based conductive fillers, and conductive fillers composed of metal plating.

[0064] Examples of metallic conductive fillers in various forms include powders, fibers, and foils. Examples of powdered metallic conductive fillers include silver, copper, nickel, tin, and silver-plated copper powder. Examples of fibrous metallic conductive fillers include copper, stainless steel, aluminum, brass, and iron fibers. Examples of foil-type metallic conductive fillers include aluminum and zinc foils.

[0065] Examples of carbon-based conductive fillers in various forms include powders and fibers. Examples of powdered carbon-based conductive fillers include carbon black and graphite. Examples of fibrous carbon-based conductive fillers include nanotubes and carbon fibers.

[0066] One example of the form of a metal oxide-based conductive filler is powder. Examples of powdered metal oxide-based conductive fillers include tin oxide, indium oxide, and zinc oxide powder. Examples of the form of a conductive filler composed of metal plating include powder and fibers. Examples of powdered conductive fillers composed of metal plating include glass beads that have been plated and mica powder that has been plated. Examples of fibrous conductive fillers composed of metal plating include glass fibers that have been plated and carbon fibers that have been plated.

[0067] Embodiments of the present invention have been described illustratively above. That is, a detailed description and accompanying drawings have been disclosed for illustrative purposes. Therefore, some of the components described in the detailed description and accompanying drawings may not be essential for solving the problem. Consequently, the mere fact that these non-essential components are described in the detailed description and accompanying drawings does not mean that they should be immediately assumed to be essential.

[0068] Furthermore, the above embodiments are merely illustrative in every respect of the present invention. The above embodiments can be improved or modified in various ways within the scope of the present invention. That is, in carrying out the present invention, specific configurations can be appropriately adopted depending on the embodiment.

[0069] [5. Examples] <5-1. Examples and Comparative Examples> The conductive films of Examples 1-3 were manufactured by co-extrusion. The first and second layers of each conductive film of Examples 1-3 were formed using polypropylene and carbon black. The intermediate layers of each conductive film of Examples 1-3 were formed using LDPE and carbon black. The intermediate layers of each conductive film of Examples 1-3 differed from one another. The intermediate layer thicknesses of each conductive film of Examples 1-3 will be shown later.

[0070] Each conductive film of Example 4-6 was manufactured by co-extrusion. The first and second layers of each conductive film of Example 4-6 were formed using polypropylene and carbon black. The intermediate layer of each conductive film of Example 4-6 was formed using polypropylene, LDPE, and carbon black. In each conductive film of Example 4-6, the intermediate layer was formed by the one-step manufacturing method described above. Each conductive film of Example 4-6 had a different intermediate layer thickness. The intermediate layer thicknesses of each conductive film of Example 4-6 will be shown later.

[0071] The conductive film of Example 7 was manufactured by co-extrusion. The first and second layers of the conductive film of Example 7 were formed using polypropylene and carbon black, respectively. The intermediate layer of the conductive film of Example 7 was formed using polypropylene, LDPE, and carbon black. The intermediate layer was formed by the two-step manufacturing method described above. That is, a masterbatch was first manufactured using polypropylene and carbon black, and then the intermediate layer was formed by mixing the masterbatch with LDPE.

[0072] Table 1 below shows the following for each conductive film in Examples 1-7: the weight percentage concentration (wt%) of each material, the total thickness of the conductive film (μm), the thickness of the intermediate layer (μm), and the ratio of the thickness of the intermediate layer to the total thickness. In Examples 4-7, the concentration of carbon black in the intermediate layer was lower than the concentration of carbon black in the first and second layers, respectively.

[0073] [Table 1]

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

[0075] A conductive film of Comparative Example 2 was manufactured by extrusion molding. The conductive film of Comparative Example 2 was 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 was a single-layer film. The conductive film of Comparative Example 3 was formed from polypropylene, LDPE, and carbon black.

[0077] The conductive films of Comparative Examples 4 and 5 were manufactured by co-extrusion. The first and second layers of each conductive film of Comparative Examples 4 and 5 were formed using polypropylene and carbon black, respectively. The intermediate layers of each conductive film of Comparative Examples 4 and 5 were formed using polypropylene, LDPE, and carbon black. In each conductive film of Comparative Examples 4 and 5, the intermediate layers were formed by the one-step manufacturing method described above.

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

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

[0080] [Table 2]

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

[0082] The Young's modulus of each layer was measured according to the method conforming to JIS K 7127. Specifically, a 50 μm single-layer film corresponding to each layer was formed using raw materials formulated for each layer, and the Young's modulus of each single-layer film was measured according to the method conforming to JIS K 7127 to determine the Young's modulus of each layer. Alternatively, the Young's modulus of each layer may be measured by, for example, separating each layer from the conductive film by physical or chemical means, remelting each separated layer, forming a single-layer film corresponding to each layer, and measuring the Young's modulus of each single-layer film according to the method conforming to JIS K 7127.

[0083] The tensile elongation at break (MD) of each layer was measured according to the method conforming to JIS K 7127. Specifically, a 50 μm single-layer film corresponding to each layer was formed using raw materials formulated for each layer, and the tensile elongation at break of each single-layer film was measured according to the method conforming to JIS K 7127. Alternatively, the measurement of the tensile elongation at break of each layer may be performed, for example, by separating each layer from the conductive film by physical or chemical means, remelting each separated layer, forming a single-layer film corresponding to each layer, and measuring the tensile elongation at break of each single-layer film according to the method conforming to JIS K 7127.

[0084] Volume resistivity was measured according to the method conforming to JIS K 7194. Tensile breaking strength was measured according to the method conforming to JIS K 7127. Tensile breaking elongation was measured according to the method conforming to JIS K 7127. Right-angle tear strength was measured according to the method conforming to JIS-K 7128-3.

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

[0086] [Table 3]

[0087] The measurement results for each conductive film in Comparative Examples 1-6 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 1-7. On the other hand, in each conductive film of Comparative Examples 1-6, sufficient results were not obtained for at least one measurement item. For example, in Table 4, the highlighted items did not yield sufficient results. [Explanation of Symbols]

[0090] 10, 10A, 10B Conductive film, 100 First layer, 110 Second layer, 120, 120A, 120B Intermediate layer, 130 Polypropylene, 132 Conductive carbon filler, 134 LDPE, 200 Manufacturing equipment, 210 T-die, 220, 230, 240 Raw material input section.

Claims

1. A conductive film, The first layer, The second layer, The facility comprises an intermediate layer formed between the first layer and the second layer, Each of the first and second layers comprises a first resin and a conductive filler. The intermediate layer comprises the second resin and the conductive filler. The result of dividing the Young's modulus of the first layer by the Young's modulus of the intermediate layer is greater than 1. The result of dividing the Young's modulus of the second layer by the Young's modulus of the intermediate layer is greater than 1. 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. A conductive film having a volume resistivity of 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 claim 2, wherein the first resin and the second resin each comprise at least one selected from olefin resins, polyamide resins, polyester resins, polystyrene resins, or elastomers thereof.

4. The conductive film according to claim 1 or claim 2, wherein 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 claim 2, wherein the concentration of the conductive filler in the intermediate layer is lower than the concentration of the conductive filler in each of the first and second layers.

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

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