Conductive film and method for producing conductive film

Abstract

To provide a conductive film with superior conductivity.SOLUTION: A conductive film contains a resin, a conductive filler, and a dispersant with a polyethylene skeleton, used to disperse the conductive filler in the resin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a conductive film and a method for manufacturing a conductive film. [Background technology]

[0002] JP 2013-234290 A (Patent Document 1) discloses a conductive film. This conductive film contains a thermoplastic resin, carbon black as a conductive filler, and a dispersant that disperses the carbon black in the thermoplastic resin. The dispersant used is silicone rubber particles in which dimethylpolysiloxane is crosslinked two-dimensionally. By using this blending, Patent Document 1 improves the dispersibility of the carbon black, which is a conductive filler, suppresses the generation of agglomerates of the conductive filler, and improves the surface smoothness of the conductive film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-234290 A Summary of the Invention [Problem to be solved by the invention]

[0004] A conductive filler uniformly dispersed in a resin can increase the conductivity of a conductive film. In this regard, the conductive film disclosed in the above-mentioned Patent Document 1 can be said to have excellent conductivity because the conductive filler has high dispersibility, but depending on the application, further improvement in conductivity may be desired.

[0005] The present invention has been made to solve such problems, and an object of the present invention is to provide a conductive film having excellent conductivity and a method for manufacturing the conductive film. [Means for solving the problem]

[0006] A conductive film according to an aspect of the present invention includes a resin, a conductive filler, and a dispersant having a polyethylene skeleton that disperses the conductive filler in the resin.

[0007] The present inventors have found that adding a dispersant having a polyethylene skeleton to disperse a conductive filler in a resin reduces the electrical resistance of the conductive film. Therefore, according to the above aspect of the present invention, the presence of a dispersant having a polyethylene skeleton reduces the electrical resistance, making it possible to provide a conductive film with excellent electrical conductivity.

[0008] In the conductive film, the resin may be a resin incompatible with polyethylene.

[0009] In the conductive film, the resin may be a polyolefin resin.

[0010] The conductive film may have a volume resistivity of 160 Ω·cm or less.

[0011] In the conductive film, the amount of the dispersant added may be 1.0 wt % or more and 10 wt % or less.

[0012] In the conductive film, the conductive filler may be a carbon filler.

[0013] A method for producing a conductive film according to another aspect of the present invention includes the steps of producing a molten material by heating and melting a resin, a conductive filler, and a dispersant having a polyethylene skeleton that disperses the conductive filler in the resin, and producing a conductive film by extruding the molten material. Effect of the Invention

[0014] According to the present invention, a conductive film having excellent conductivity can be provided. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a schematic cross-sectional view of a conductive film according to an embodiment. [Diagram 2] FIG. 1 is a diagram illustrating a schematic configuration of a conductive film manufacturing apparatus according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated. Also, each drawing is drawn in a schematic manner with objects appropriately omitted or exaggerated for ease of understanding.

[0017] [1. Embodiment] <1-1. Structure of conductive film> Fig. 1 is a schematic cross-sectional view of a conductive film 10 according to the present embodiment. As shown in Fig. 1, the conductive film 10 is a single-layer film. The thickness of the conductive film 10 is, for example, not less than 25 µm and not more than 100 µm.

[0018] The conductive film 10 is used, for example, as a charging film or a static eliminating film for copiers, printers, etc., and various other functional films for electric / electronic devices and parts. The conductive film 10 may or may not be subjected to surface treatment such as corona, plasma, coating, or sputtering.

[0019] The conductive film 10 contains a resin as a main component, and further contains a conductive filler and a dispersant as additives. The conductive filler and the dispersant are dispersed in the resin. The conductive filler dispersed in the resin imparts conductivity to the conductive film 10. The dispersant serves to uniformly disperse the conductive filler in the resin, thereby increasing the dispersibility of the conductive filler in the resin and improving the conductivity of the conductive film 10. In addition to the conductive filler and the dispersant, the resin may further contain some or all of additives such as an antioxidant, an antiblocking agent, and an ultraviolet protection agent dispersed therein.

[0020] The dispersant contained in the conductive film 10 is composed of a polymeric material having a polyethylene skeleton. This is based on the findings obtained by the present inventors through experiments that will be disclosed below as examples. That is, the present inventors have found that using a dispersant having a polyethylene skeleton as a raw material for the conductive film reduces the electrical resistance value of the conductive film and improves the conductivity of the conductive film.

[0021] Preferred examples of the dispersant having a polyethylene skeleton include styrene-modified polyethylene and maleic anhydride-modified polyethylene.

[0022] From the viewpoint of increasing the dispersibility of the conductive filler and improving the conductivity, the amount of dispersant added to the entire conductive film 10 (mass percent concentration) is preferably 1.0 wt% or more. On the other hand, if the amount of dispersant added is too large, the conductive filler may become overdispersed, and the conductivity of the conductive film 10 may decrease. From this viewpoint, therefore, the amount of dispersant added to the entire conductive film 10 (mass percent concentration) is preferably 10 wt% or less. The dispersant contained in the conductive film 10 may be only one type, or a mixture of two or more types.

[0023] The conductive film 10 is made mainly of resin, and is therefore excellent in terms of moldability, chemical resistance, and the like. The type of resin contained in the conductive film 10 is not particularly limited, and any resin can be used. The resin contained in the conductive film 10 may be only one type, or a mixture of two or more types.

[0024] Preferable examples of the resin contained in the conductive film 10 include polyolefin resin, polyamide resin, polyester resin, and polystyrene resin. Examples of the polyolefin resin include polypropylene, polyethylene, polymethylpentene, and cyclic polyolefin. Examples of the polyamide resin include polyamide 6, polyamide 66, and polymetaxylylene adipamide. Examples of the polyester resin include polyethylene terephthalate and polybutylene terephthalate.

[0025] Among polyolefin resins, polypropylene is preferred from the viewpoints of moisture-proof properties and mechanical strength. Examples of polypropylene include homopolypropylene, random polypropylene, block polypropylene, polypropylene having a long-chain branched structure, and acid-modified polypropylene.

[0026] The cyclic polyolefin (cyclic olefin resin) contains a cyclic olefin component as a copolymer component, and is not particularly limited as long as it is a polyolefin resin containing a cyclic olefin component in the main chain. Preferred examples of the cyclic polyolefin include an addition polymer of a cyclic olefin or a hydrogenated product thereof, and an addition copolymer of a cyclic olefin and an α-olefin or a hydrogenated product thereof. In addition, the cyclic polyolefin includes the above-mentioned polymer further grafted and / or copolymerized with an unsaturated compound having a hydrophilic group.

[0027] Preferred examples of the polar group include a carboxyl group, an acid anhydride group, an epoxy group, an amino group, an amide group, an ester group, a hydroxyl group, a sulfo group, a phosphono group, and a phosphino group, and examples of the unsaturated compound having a polar group include (meth)acrylic acid, maleic acid, maleic anhydride, itaconic anhydride, glycidyl (meth)acrylate, (meth)acrylic acid alkyl ester (having 1 to 10 carbon atoms), maleic acid alkyl ester (having 1 to 10 carbon atoms), (meth)acrylamide, and (meth)acrylate-2-hydroxyethyl.

[0028] It is preferable that the resin contained in the conductive film 10 is incompatible with polyethylene. In this case, it is generally expected that the dispersing agent having a polyethylene skeleton is less likely to mix with the resin, and therefore the dispersibility of the conductive filler is reduced, and the conductivity of the conductive film is reduced. However, the present inventors have discovered that this actually reduces the electrical resistance value of the conductive film 10 and improves the conductivity of the conductive film 10.

[0029] Examples of resins incompatible with polyethylene include polyolefin resins other than polyethylene, polyamide resins, polyester resins, and polystyrene resins. Among these examples, polyolefin resins other than polyethylene are particularly preferred. Among polyolefin resins other than polyethylene, polypropylene is preferred. Polyethylene can be broadly classified into low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE), each of which is an incompatible resin. Therefore, for example, when the resin contained in the conductive film 10 is low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) is an incompatible resin.

[0030] Examples of the conductive filler contained in the conductive film 10 include a conductive carbon filler, a metal filler, a metal oxide filler, and a conductive filler formed by metal plating (hereinafter referred to as a metal-plated filler). Note that the conductive filler contained in the conductive film 10 may be only one type, or a mixture of two or more types.

[0031] Examples of the conductive carbon filler include graphite, carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.), carbon nanotubes, and carbon fibers. Examples of the shape of the conductive carbon filler include powder and fiber. A particularly preferred example is powdered carbon black.

[0032] Examples of the metal filler include platinum, gold, silver, copper, SUS (Stainless Used Steel), nickel, titanium, tin, aluminum, brass, iron and zinc. Examples of the shape of the metal filler include powder, fiber and foil.

[0033] Examples of metal oxide fillers include tin oxide, indium oxide, and zinc oxide, and examples of the form of the fillers include powder. Examples of metal plated fillers include plated glass beads, plated mica powder, plated glass fiber, and plated carbon fiber, and examples of the form of the fillers include powder and fiber.

[0034] Various combinations of resins and conductive fillers may be used in the conductive film 10. One preferred combination is one in which the resins are all olefin resins (particularly, polypropylene) and the conductive filler is a conductive carbon filler (particularly, carbon black).

[0035] The volume resistivity of the conductive film 10 is preferably 160 Ω·cm or less, more preferably 130 Ω·cm or less, and even more preferably 100 Ω·cm or less. When these numerical conditions are satisfied, an increase in the electrical resistance value of the conductive film 10 is suppressed, and the conductive film 10 exhibits excellent conductivity.

[0036] <1-2. Manufacturing method of conductive film> 2 is a diagram illustrating a schematic configuration of a manufacturing apparatus 20 for the conductive film 10 according to the present embodiment. As shown in FIG. 2, the manufacturing apparatus 20 includes a T-die 200, casting rolls 210 and 220, and a take-up roll 230.

[0037] In the T-die 200, resin, conductive filler, and a dispersant for dispersing the conductive filler in the resin are charged as raw materials for the conductive film 10. A polymeric material having a polyethylene skeleton is charged as the dispersant. The T-die 200 is configured to produce a molten material by heating and melting the charged material including the resin, conductive filler, and dispersant, and to extrude the molten material. This results in extrusion molding of the molten material. The cast rolls 210 and 220 are configured to cool the molten material extruded from the T-die 200 and send it downstream. The winding roll 230 is configured to pull and wind the molten material cooled by the cast rolls 210 and 220 at a predetermined speed. As described above, a roll of the conductive film 10 is produced through the manufacturing process in the manufacturing device 20.

[0038] <1-3.Features> As described above, a dispersant having a polyethylene skeleton is added to the conductive film 10 according to the present embodiment, which results in a reduced electrical resistance value of the conductive film 10 and excellent conductivity.

[0039] [2. Modifications] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0040] For example, in the above embodiment, the conductive film 10 is a single-layer film, but is not limited thereto and may be a multilayer film. In this case, it is preferable that the resin, conductive filler, and dispersant constituting at least one layer are configured similarly to the above embodiment. It is more preferable that the resin, conductive filler, and dispersant constituting two or more layers (including some layers or all layers) constituting the multilayer film are configured similarly to the above embodiment. EXAMPLES

[0041] 3. Working Examples Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0042] The conductive films of Examples 1 to 3 and Comparative Examples 1 and 2 were manufactured using a manufacturing apparatus 20 shown in FIG. 2. More specifically, in all of Examples 1 to 3 and Comparative Examples 1 and 2, carbon black and a dispersant were added to polypropylene and kneaded to manufacture a single-layer conductive film having a thickness of 50 μm. The types and acid values ​​of the dispersants added in Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1 below. The amounts of the dispersants added in Examples 1 to 3 and Comparative Examples 1 and 2 (weight percent concentration of the dispersant relative to the entire conductive film) were all 5 wt%. The amounts of the carbon black added in Examples 1 to 3 and Comparative Examples 1 and 2 (weight percent concentration of carbon black in the entire conductive film) were all 25 wt%.

[0043] The volume resistivity was measured for each of the conductive films produced as described above in Examples 1 to 3 and Comparative Examples 1 and 2. The results are also shown in Table 1.

[0044] [Table 1]

[0045] The volume resistivity was measured by the following method. First, the surface resistivity of the conductive film was measured. Specifically, the surface resistivity was measured by the four-point probe method using a portable low resistance meter Loresta FP manufactured by Mitsubishi Chemical Corporation. A PS probe was used as the probe. Next, the value obtained by dividing the surface resistivity thus measured by the film thickness (cm) was determined as the volume resistivity (Ω·cm).

[0046] From the results in Table 1, it was confirmed that the conductive films of Examples 1 to 3 had lower volume resistivities than the conductive films of Comparative Examples 1 and 2. In other words, it was found that the volume resistivity of the conductive film was lower when a dispersant having a polyethylene skeleton, such as maleic anhydride-modified polyethylene or styrene-modified polyethylene, was used (Examples 1 to 3) than when a dispersant having a polypropylene skeleton, such as maleic anhydride-modified polypropylene, was used (Comparative Examples 1 and 2). In other words, it was found that the conductivity of the conductive film was improved by using a dispersant having a polyethylene skeleton (Examples 1 to 3).

[0047] In addition, in the conductive films of Examples 1 to 3 and Comparative Examples 1 and 2, the type of resin that is the main component was polypropylene. That is, the dispersants of Examples 1 to 3 were incompatible with this, and the dispersants of Comparative Examples 1 and 2 were compatible with this. In general, when the resin and dispersant contained in the conductive film are incompatible, it is expected that the two are difficult to mix, so that the dispersibility of the conductive filler decreases and the conductivity of the conductive film decreases. However, from the results of Table 1, it was found that when the resin and dispersant contained in the conductive film are incompatible with each other, this rather reduces the volume resistivity of the conductive film and improves the conductivity. [Explanation of symbols]

[0048] 10 Conductive film, 20 Manufacturing equipment, 200 T die, 210, 220 Cast roll, 230 Winding roll

Claims

1. Resin and A conductive filler; a dispersant having a polyethylene skeleton for dispersing the conductive filler in the resin; A conductive film comprising:

2. The conductive film according to claim 1 , wherein the resin is incompatible with polyethylene.

3. The conductive film according to claim 2 , wherein the resin is a polyolefin resin.

4. The conductive film according to any one of claims 1 to 3, which has a volume resistivity of 160 Ω·cm or less.

5. 4. The conductive film according to claim 1, wherein the amount of the dispersant added is 1.0 wt % or more and 10 wt % or less.

6. The conductive film according to any one of claims 1 to 3, wherein the conductive filler is a carbon filler.

7. A step of producing a molten material by heating and melting a resin, a conductive filler, and a dispersant having a polyethylene skeleton that disperses the conductive filler in the resin; producing a conductive film by extruding the molten material; A method for producing a conductive film comprising the steps of:

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