Conductive film manufacturing method and conductive film

Abstract

The invention provides a conductive film manufacturing method and a conductive film. The method for producing a conductive film comprises the steps of: producing a master batch by melt-kneading a thermoplastic first resin and a conductive carbon filler; and producing a conductive film by mixing a second resin that is incompatible with the first resin with the master batch.

Description

Technical Field

[0001] The present invention relates to a method for producing a conductive film and the conductive film. Background Art

[0002] Japanese Patent Application Laid-Open No. 63-130644 (Patent Document 1) discloses a conductive film comprising carbon black and a thermoplastic resin. Prior art literature Patent Literature

[0003] Patent document 1: Japanese Patent Publication No. 63-130644 Summary of the invention Technical Problems to be Solved by the Invention

[0004] In the conductive film disclosed in Patent Document 1, for example, if the content of carbon black (an example of conductive carbon filler) increases, the conductivity increases. However, if the content of carbon black increases, the conductive film becomes brittle and brittle fracture easily occurs in the conductive film.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing a conductive film having sufficient conductivity and capable of suppressing brittle fracture, and a conductive film. Technical solutions for solving technical problems

[0006] A method for producing a conductive film according to one aspect of the present invention comprises the steps of: producing a masterbatch by melt-kneading a first thermoplastic resin and a conductive carbon filler; and producing a conductive film by mixing a second resin incompatible with the first resin and the masterbatch.

[0007] In the method for manufacturing the conductive film, a masterbatch containing a first resin and a conductive carbon filler is temporarily manufactured, and then a conductive film is manufactured by mixing a second resin and the masterbatch. The inventor(s) discovered that the conductive film manufactured by such a two-stage molding has an island structure. The sea portion is composed of, for example, a first resin and a conductive carbon filler, and the island portion is composed of, for example, a second resin. The island portion contains almost no conductive carbon filler, and the concentration of the conductive carbon filler in the sea portion is maintained at a high concentration, so the conductivity of the conductive film becomes relatively high. In addition, the island portion contains almost no conductive carbon filler, and the tensile elongation of the island portion is maintained at a large state, so that brittle failure of the conductive film can be suppressed. Therefore, according to the method for manufacturing the conductive film, a conductive film having sufficient conductivity and capable of suppressing brittle failure can be manufactured.

[0008] In the above conductive film, a ratio of a content of the second resin in a total content of the first resin and the second resin may be greater than 0 wt % and less than 50 wt %.

[0009] According to this method for producing a conductive film, since the content of the second resin is less than that of the first resin, a conductive film having a sea-island structure in which the sea portion is composed of the first resin and the conductive carbon filler and the island portion is composed of the second resin can be produced.

[0010] In the above conductive film, the content of the second resin in the entire composition constituting the conductive film may be greater than 0 wt % and less than 40 wt %.

[0011] In the above method for producing a conductive film, the first resin may be a polypropylene resin, and the second resin may be a polyethylene resin.

[0012] According to this method for producing a conductive film, the second resin is a polyethylene resin having higher flexibility than the first resin (polypropylene resin), and therefore a conductive film capable of further suppressing brittle fracture can be produced.

[0013] In the above-mentioned method for producing a conductive film, the polyethylene resin may be LDPE (low-density polyethylene) or LLDPE (linear low-density polyethylene).

[0014] According to the method for producing a conductive film, the second resin is LDPE or LLDPE, which has higher flexibility, and thus it is possible to produce a conductive film in which brittle fracture can be further suppressed.

[0015] The conductive film of another aspect of the present invention has a sea-island structure. The sea portion of the sea-island structure is composed of a thermoplastic first resin and a conductive carbon filler. The island portion of the sea-island structure is composed of a second resin that is incompatible with the first resin.

[0016] In the conductive film, the sea portion is composed of the first resin and the conductive carbon filler, and the island portion is composed of the second resin. The island portion contains almost no conductive carbon filler, and the concentration of the conductive carbon filler in the sea portion is maintained at a high concentration, so the conductivity of the conductive film becomes relatively high. In addition, the island portion contains almost no conductive carbon filler, and the tensile elongation of the island portion is maintained at a large state, so brittle failure can be suppressed for the conductive film. That is, according to the conductive film, the conductivity can be maintained at a relatively high level and brittle failure can be suppressed. Effects of the Invention

[0017] According to the present invention, a method for producing a conductive film having sufficient conductivity and capable of suppressing brittle fracture, and a conductive film can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flowchart showing the manufacturing procedure of the conductive film. Figure 2 This is a diagram schematically showing a cross section of a conductive film produced by the conductive film production method according to the embodiment. Figure 3 This is a diagram schematically showing a cross section of a conductive film produced by a one-step production method. DETAILED DESCRIPTION

[0019] Hereinafter, an embodiment of one aspect of the present invention will be described in detail using the accompanying drawings. In addition, the same or corresponding parts in the figures are given the same reference numerals and their descriptions are not repeated. In addition, for easy understanding, each of the accompanying drawings appropriately omits or exaggerates the schematic depiction of the object.

[0020] [1. Method for producing conductive film] Figure 1 1 is a flowchart showing the manufacturing procedure of the conductive film 10. For example, an operator performs each step shown in the flowchart by using an apparatus.

[0021] Reference Figure 1 First, a masterbatch is manufactured by melt-kneading a first thermoplastic resin and a conductive carbon filler (step S100). For example, the first resin and the conductive carbon filler are put into a twin-shaft extruder, and melt-kneaded in the twin-shaft extruder to manufacture a masterbatch. In addition, the first resin used in step S100 may be crushed in advance or not. For example, when the first resin is crushed in advance, the dispersion and mixing of the first resin and the conductive carbon filler becomes good. In step S100, part or all of additives such as dispersants, antioxidants, anti-blocking agents, and UV inhibitors may also be used.

[0022] Examples of the first resin include polypropylene (PP), polyethylene terephthalate (PET), and polyamide (PA). Examples of polypropylene include homopolypropylene, random polypropylene, block polypropylene, polypropylene having a long chain branch structure, and acid-modified polypropylene.

[0023] Examples of the conductive carbon filler include graphite, carbon black (acetylene black, Ketjen black, furnace black, channel black, hot lamp black, etc.), carbon nanotubes, and mixtures thereof.

[0024] Then, a conductive film is manufactured by mixing a second resin incompatible with the first resin and the masterbatch manufactured in step S100 (step S110). For example, the second resin and the masterbatch are put into a uniaxial extruder, the second resin and the masterbatch are mixed in the uniaxial extruder, and the conductive film is manufactured by extrusion molding.

[0025] The second resin has, for example, a higher tensile elongation than the first resin. That is, the second resin has, for example, a higher softness than the first resin. As an example of the second resin, polyethylene (PE), polymethylpentene (PMP), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyamide (PA), polylactic acid (PLA), modified polyphenylene ether (PPE) and acrylonitrile-butadiene-styrene copolymer (ABS) can be cited. As an example of polyethylene, LDPE (low-density polyethylene), LLDPE (linear low-density polyethylene) and HDPE (high-density polyethylene) can be cited.

[0026] When the first resin is PET, for example, since PMP, PP, and PS are incompatible with PET, the second resin may be, for example, any one of PMP, PP, and PS. In addition, when the first resin is PP, for example, since PS, PE, PMP, PA, PC, and PLA are incompatible with PP, the second resin may be, for example, any one of PS, PE, PMP, PA, PC, and PLA. In addition, when the first resin is PA, for example, since PPE and AB are incompatible with PA, the second resin may be, for example, any one of PPE and AB.

[0027] In addition, in the conductive film 10, the proportion of the second resin content in the total content of the first resin and the second resin is greater than 0wt% and less than 50wt%. In addition, in the conductive film 10, the proportion of the second resin content in the total content of the first resin and the second resin may be greater than 0wt% and less than 40wt%. In addition, in the conductive film 10, the proportion of the second resin content in the total content of the first resin and the second resin may be greater than 0wt% and less than 30wt%.

[0028] In addition, in the conductive film 10, the proportion of the second resin in the entire composition constituting the conductive film 10 (including the first resin, the second resin, the conductive carbon filler, and the additive) may be greater than 0 wt% and less than 40 wt%. In addition, in the conductive film 10, the proportion of the second resin in the entire composition constituting the conductive film 10 may be greater than 0 wt% and less than 30 wt%.

[0029] Thus, in the method for producing a conductive film of the present embodiment, a first step of producing a masterbatch using a first resin and a conductive carbon filler, and a second step of producing a conductive film using a second resin and a masterbatch are performed. That is, in the method for producing a conductive film of the present embodiment, the conductive film 10 is produced through two steps. Hereinafter, such a method for producing the conductive film 10 through two steps is also referred to as a "two-stage method". The reason for producing the conductive film 10 through the two-stage method will be described in detail later.

[0030] [2. Configuration of Conductive Film] Figure 2 Schematically shows a cross section of a conductive film 10 manufactured by the method for manufacturing a conductive film according to the present embodiment. Figure 2 The conductive film 10 is polymer-alloyed by mixing the above-mentioned masterbatch and the second resin.

[0031] The conductive film 10 has a so-called sea-island structure, including a sea portion 11 and an island portion 12. The sea portion 11 is mainly composed of a first resin and a conductive carbon filler. The island portion 12 is mainly composed of a second resin. As described above, this is because the content of the first resin in the conductive film 10 is greater than the content of the second resin.

[0032] In the conductive film 10, the island portion 12 contains almost no conductive carbon filler, and the concentration of the conductive carbon filler in the sea portion 11 is maintained at a high concentration, so the conductivity of the conductive film 10 is relatively high. For example, the volume resistivity of the conductive film 10 is 10 to the sixth power or less. In addition, the island portion 12 contains almost no conductive carbon filler, and the tensile elongation of the island portion 12 is maintained at a large state, so brittle fracture of the conductive film 10 can be suppressed. That is, according to the conductive film 10, the conductivity can be maintained at a relatively high level and brittle fracture can be suppressed.

[0033] [3. Reasons for using the two-step method] Hereinafter, the method of manufacturing a conductive film by melt-kneading the first resin, the second resin, and the conductive carbon filler at the same time and then extruding the mixture is referred to as a "one-stage method". In the two-stage method, a first step of manufacturing a masterbatch using the first resin and the conductive carbon filler and a second step of manufacturing a conductive film using the second resin and the masterbatch are performed, whereas in the one-stage method, only a step of manufacturing a conductive film using the first resin, the second resin, and the conductive carbon filler is performed.

[0034] Figure 3 1 is a diagram schematically showing a cross section of a conductive film 10X manufactured by a one-step manufacturing method. Figure 3 , in the conductive film 10X, the first resin and the conductive carbon filler are sufficiently mixed, and the second resin and the conductive carbon filler are also sufficiently mixed.

[0035] Therefore, in the conductive film 10X, the conductive film 10 ( Figure 2 ) The concentration of the conductive carbon filler in the portion 11X corresponding to the sea portion 11 is lower than that of the conductive film 10. As a result, the conductivity of the conductive film 10X is lower than that of the conductive film 10.

[0036] In addition, in the conductive film 10X, the concentration of the conductive carbon filler in the portion 12X corresponding to the island portion 12 of the conductive film 10 is higher than that of the conductive film 10. As a result, the tensile elongation of the conductive film 10X is lower than that of the conductive film 10. Therefore, according to the conductive film 10X manufactured by the one-stage manufacturing method, it is impossible to maintain the conductivity at a relatively high level and suppress brittle fracture (for example, the tensile elongation at break of the conductive film is 10% or more).

[0037] On the other hand, as described above, according to the conductive film 10 manufactured by the two-step method, it is possible to maintain relatively high conductivity and suppress brittle fracture. Therefore, the two-step method is used to manufacture the conductive film 10.

[0038] [4. Features] As described above, in the method for manufacturing a conductive film of the present embodiment, a masterbatch containing a first resin and a conductive carbon filler is temporarily manufactured, and then a conductive film 10 is manufactured by mixing a second resin with the masterbatch. The inventors have found that the conductive film 10 manufactured by such two-stage molding has a sea-island structure. The sea portion 11 is composed of, for example, a first resin and a conductive carbon filler, and the island portion 12 is composed of, for example, a second resin. The island portion 12 contains almost no conductive carbon filler, and the concentration of the conductive carbon filler in the sea portion 11 is maintained at a high concentration, so the conductivity of the conductive film 10 becomes relatively high. In addition, the island portion 12 contains almost no conductive carbon filler, and the tensile elongation of the island portion 12 is maintained at a large state, so that brittle failure of the conductive film 10 can be suppressed. Therefore, according to the method for manufacturing a conductive film, a conductive film 10 having sufficient conductivity and capable of suppressing brittle failure can be manufactured.

[0039] In addition, according to the method for manufacturing a conductive film of this embodiment, since the content of the second resin is less than the content of the first resin, it is possible to manufacture a conductive film 10 having a sea-island structure in which the sea portion 11 is composed of the first resin and the conductive carbon filler and the island portion 12 is composed of the second resin.

[0040] Furthermore, according to the method for producing a conductive film of the present embodiment, since the second resin is polyethylene resin, for example, which has higher flexibility than the first resin (polypropylene resin), the conductive film 10 capable of further suppressing brittle fracture can be produced.

[0041] Furthermore, according to the method for producing a conductive film of the present embodiment, the second resin is LDPE, which has higher flexibility, and thus it is possible to produce a conductive film 10 in which brittle fracture can be further suppressed.

[0042] [5. Other embodiments] The concept of the above-described embodiment is not limited to the above-described embodiment. An example of another embodiment to which the concept of the above-described embodiment can be applied will be described below.

[0043] In the above embodiment, an example is described in which a twin-shaft extruder is used in the first process of manufacturing a masterbatch using a first resin and a conductive carbon filler, and a single-shaft extruder is used in the second process of manufacturing a conductive film using a second resin and a masterbatch. However, the devices used in each process are not limited to this. For example, a twin-shaft extruder may be used in each of the first process and the second process, and a single-shaft extruder may be used in each of the first process and the second process. In addition, a single-shaft extruder may be used in the first process and a twin-shaft extruder may be used in the second process.

[0044] In addition, the film manufactured by the manufacturing method of the conductive film of the above embodiment is not limited to a single-layer film. For example, a part of a film having multiple layers can also be manufactured by the manufacturing method of the conductive film of the above embodiment. For example, a part or all of the layers of a film having multiple layers can also be manufactured by a two-stage manufacturing method.

[0045] 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.

[0046] 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.

[0047] [6. Example] <6-1. Examples and Comparative Examples> In each of Examples 1 to 6 and Comparative Example 3, a conductive film was produced by the above-mentioned two-step production method. In each of Examples 1 to 3 and Comparative Example 3, in the first step, a masterbatch was produced by melt-kneading polypropylene (PP) and carbon black (CB). In the second step, the masterbatch and LDPE were mixed and extruded to produce a conductive film.

[0048] In each of Examples 4 to 6, in the first step, a masterbatch was produced by melt-kneading polypropylene (PP) and carbon black (CB), and in the second step, the masterbatch and LLDPE were mixed and extruded to produce a conductive film.

[0049] In Comparative Example 1, a conductive film was produced by the above-mentioned one-step production method. In Comparative Example 1, a conductive film was produced by melt-kneading polypropylene and carbon black and extruding them.

[0050] In Comparative Example 2, a conductive film was produced by the above-mentioned one-step production method. In Comparative Example 2, a conductive film was produced by melt-kneading polypropylene, carbon black, and LDPE and extruding them.

[0051] The weight percentage concentration (wt%) of each material in Examples 1-6 and Comparative Examples 1-3 is shown in Table 1 below. In addition, the weight percentage concentration (wt%) of each resin relative to the entire resin in Examples 1-6 and Comparative Examples 1-3 is shown in Table 2 below.

[0052] [Table 1] [Table 2]

[0053] <6-2. Various measurements> For each conductive film of Examples 1-6 and Comparative Examples 1-3, the film thickness (μm), tensile strength (MPa), yield strength (MPa), tensile elongation (%), tear strength (N / mm), surface resistivity (Ω / □) and volume resistivity (Ω·cm) were measured. The film thickness of each conductive film was measured by using a film thickness meter (Digimatic Micrometer manufactured by Mitutoyo). The tensile strength (tensile breaking strength) was measured by a method in accordance with JIS K 7127. The yield strength was measured by a method in accordance with JIS K 7127. The tensile elongation (tensile breaking elongation) was measured by a method in accordance with JIS K7127. The tear strength (tear strength) was measured by a method in accordance with JIS-K 7128-3. The surface resistivity was measured by a method in accordance with JIS K 7194. The volume resistivity was measured by a method in accordance with JIS K7194.

[0054] <6-3. Results> The results of various measurements are shown in Table 3 below.

[0055] [Table 3]

[0056] As shown in Table 3, sufficient tensile elongation could not be obtained in Comparative Examples 1 and 2. In addition, the surface resistivity and volume resistivity could not be sufficiently reduced in Comparative Example 3. On the other hand, in each of Examples 1 to 6, each resistivity was suppressed sufficiently low (for example, the volume resistivity was 10 to the sixth power or less) and sufficient tensile elongation could be obtained. Description of reference numerals:

[0057] 10, 10X: conductive film; 11: sea part; 11X, 12X: part; 12: island part.

Claims

1. A method for producing a conductive film, characterized in that: The steps include: A masterbatch is manufactured by melt-kneading a thermoplastic first resin and a conductive carbon filler; The conductive film is produced by mixing the second resin incompatible with the first resin and the master batch.

2. The method for producing a conductive film according to claim 1, wherein: In the conductive film, a ratio of the content of the second resin in the total content of the first resin and the second resin is greater than 0 wt % and less than 50 wt %.

3. The method for producing a conductive film according to claim 1, wherein: In the conductive film, a content ratio of the second resin in the entire composition constituting the conductive film is greater than 0 wt % and less than 40 wt %.

4. The method for producing a conductive film according to any one of claims 1 to 3, characterized in that: The first resin is a polypropylene resin, and the second resin is a polyethylene resin.

5. The method for producing a conductive film according to claim 4, wherein: The polyethylene resin is LDPE (low density polyethylene) or LLDPE (linear low density polyethylene).

6. A conductive film, characterized in that: The conductive film has a sea-island structure, The sea portion of the sea-island structure is composed of a first thermoplastic resin and a conductive carbon filler. The island portions of the sea-island structure are composed of a second resin that is incompatible with the first resin.

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