Conductive film and conductive film manufacturing method

Abstract

The invention provides a conductive film with excellent conductivity and a method for manufacturing the conductive film. The conductive film includes a resin, a conductive filler, and a dispersant having a polyethylene skeleton in which the conductive filler is dispersed in the resin.

Description

Technical Field

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

[0002] Japanese Patent Publication No. 2013-234290 (Patent Document 1) discloses a conductive film. The conductive film comprises a thermoplastic resin, carbon black as a conductive filler, and a dispersant for dispersing the carbon black in the thermoplastic resin. As the dispersant, silicone rubber particles obtained by two-dimensionally crosslinking dimethyl polysiloxane are used. Patent Document 1 improves the dispersibility of carbon black as a conductive filler, suppresses the generation of agglomerates of the conductive filler, and improves the surface smoothness of the conductive film through such a combination.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2013-234290

[0004] The conductive filler uniformly dispersed in the resin can improve the conductivity of the conductive film. In this regard, the conductive film disclosed in Patent Document 1 has improved dispersibility of the conductive filler, so it can be said that the conductivity is excellent, but depending on the application, there is a case where further improvement of the conductivity is desired. Summary of the invention

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a conductive film having excellent conductivity and a method for producing the conductive film.

[0006] A conductive film according to one aspect of the present invention comprises: a resin; a conductive filler; and a dispersant having a polyethylene skeleton, wherein the conductive filler is dispersed in the resin.

[0007] The present inventors have found that if a dispersant having a polyethylene skeleton is added to disperse a conductive filler in a resin, the resistance value of the conductive film is reduced. Therefore, according to the above aspect of the present invention, a conductive film can be provided, which has a reduced resistance value and excellent conductivity due to the presence of a dispersant having a polyethylene skeleton.

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

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

[0010] In the conductive film, the volume resistivity may be 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 above conductive film, the conductive filler may be a carbon filler.

[0013] According to another aspect of the present invention, a method for manufacturing a conductive film includes: a step of manufacturing a molten material by heating and melting a resin, a conductive filler, and a dispersant having a polyethylene skeleton in which the conductive filler is dispersed in the resin; and a step of manufacturing a conductive film by extruding the molten material.

[0014] According to the present invention, a conductive film having excellent conductivity can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram schematically showing a cross section of a conductive film according to one embodiment. Figure 2 It is a diagram schematically showing the structure of a conductive film manufacturing apparatus according to one embodiment. DETAILED DESCRIPTION

[0016] Hereinafter, an embodiment of one aspect of the present invention (hereinafter also referred to as "this embodiment") is described in detail with reference to the accompanying drawings. In addition, the same or corresponding parts in the figures are marked with the same reference numerals and their descriptions are not repeated. In addition, for easy understanding, each figure appropriately omits or exaggerates the schematic depiction of the object.

[0017] [1. Implementation Method] <1-1. Structure of conductive film> Figure 1 Schematic diagram of a cross section of the conductive film 10 according to this embodiment. Figure 1 As shown, the conductive film 10 is a single-layer film. The thickness of the conductive film 10 is, for example, 25 μm or more and 100 μm or less.

[0018] The conductive film 10 is used as a charged film or a static-eliminating film for a copier, a printer, etc., and various functional films for other electrical and electronic devices or parts. In addition, the conductive film 10 may or may not be subjected to surface processing such as corona, plasma, coating, or sputtering.

[0019] The conductive film 10 contains a resin as a main component, and also 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 plays a role in uniformly dispersing the conductive filler in the resin, thereby improving the dispersibility of the conductive filler in the resin and improving the conductivity of the conductive film 10. In addition, in addition to the conductive filler and the dispersant dispersed in the resin, part or all of additives such as an antioxidant, an anti-blocking agent, and an anti-ultraviolet agent may also be further dispersed.

[0020] The dispersant contained in the conductive film 10 is composed of a polymer material having a polyethylene skeleton. This is based on the knowledge obtained by the inventors through experiments disclosed below as examples. That is, the inventors have obtained the following knowledge: if a dispersant having a polyethylene skeleton is used as a raw material for the conductive film, the resistance value of the conductive film is reduced and the conductivity of the conductive film is improved.

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

[0022] From the viewpoint of improving the dispersibility of the conductive filler and improving the conductivity, the amount of the dispersant added relative to the entire conductive film 10 (mass percentage concentration) is preferably 1.0 wt% or more. On the other hand, if the amount of the dispersant added is excessively increased, the dispersion state of the conductive filler becomes over-dispersed, and the conductivity of the conductive film 10 may also decrease. Therefore, from such a viewpoint, the amount of the dispersant added relative to the entire conductive film 10 (mass percentage concentration) is preferably 10 wt% or less. In addition, the dispersant contained in the conductive film 10 may be only one kind or a mixture of two or more kinds.

[0023] Since the conductive film 10 is mainly composed of resin, it is excellent in terms of molding processability and chemical resistance. The type of resin contained in the conductive film 10 is not particularly limited, and all resins can be used. In addition, the resin contained in the conductive film 10 may be only one type or a mixture of two or more types.

[0024] Preferred examples of the resin contained in the conductive film 10 include polyolefin resins, polyamide resins, polyester resins, and polystyrene resins. Examples of polyolefin resins include polypropylene, polyethylene, polymethylpentene, and cyclic polyolefins. Examples of polyamide resins include polyamide 6, polyamide 66, and polymeta-xylylene adipamide. Examples of polyester resins include polyethylene terephthalate and polybutylene terephthalate.

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

[0026] 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 cyclic polyolefins include addition polymers of cyclic olefins or hydrogenated products thereof, and addition copolymers of cyclic olefins and α-olefins or hydrogenated products thereof. In addition, cyclic polyolefins include cyclic polyolefins obtained by further grafting and / or copolymerizing unsaturated compounds having a hydrophilic group with the above polymers.

[0027] Preferred examples of polar groups include carboxyl groups, acid anhydride groups, epoxy groups, amino groups, amide groups, ester groups, hydroxyl groups, sulfonic groups, phosphonyl 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 (carbon number 1 to 10), alkyl maleate (carbon number 1 to 10), (meth)acrylamide and 2-hydroxyethyl (meth)acrylate.

[0028] The resin contained in the conductive film 10 is preferably incompatible with polyethylene. In this case, since the dispersant having a polyethylene skeleton is generally difficult to mix with the resin, it is expected that the dispersibility of the conductive filler will decrease and the conductivity of the conductive film will decrease. However, the present inventors have found that such a method can actually reduce the resistance value of the conductive film 10 and improve the conductivity of the conductive film 10.

[0029] Examples of resins incompatible with polyethylene include polyolefin resins, polyamide resins, polyester resins, and polystyrene resins except for polyethylene. Among these examples, polyolefin resins except for polyethylene are particularly preferred. In addition, among the polyolefin resins except for polyethylene, polypropylene is preferred. In addition, polyethylene can be roughly divided into low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE), which are incompatible resins. Therefore, for example, in the case where the resin contained in the conductive film 10 is low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) becomes an incompatible resin.

[0030] Examples of the conductive filler included in the conductive film 10 include conductive carbon fillers, metal fillers, metal oxide fillers, and conductive fillers composed of metal plating (hereinafter also referred to as metal plating fillers). The conductive filler included in the conductive film 10 may be one type or a mixture of two or more types.

[0031] Examples of conductive carbon fillers include graphite, carbon black (acetylene black, ketjen black, furnace black, channel black, heat lamp black, etc.), carbon nanotubes, and carbon fibers. Examples of the shape of the conductive carbon filler include powder and fiber. As a particularly preferred example, powdered carbon black can be cited.

[0032] Examples of the metal filler include platinum, gold, silver, copper, SUS (stainless 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 their shapes include powders. Examples of metal-plated fillers include fillers obtained by plating glass beads, fillers obtained by plating mica powder, fillers obtained by plating glass fibers, and fillers obtained by plating carbon fibers, and examples of their shapes include powders and fibers.

[0034] Various combinations of the resin and conductive filler contained in the conductive film 10 are conceivable. Among them, as an example of a preferred combination, all the resins may be olefin resins (especially polypropylene) and the conductive filler may be a conductive carbon filler (especially 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 further preferably 100 Ω·cm or less. When such numerical conditions are satisfied, the increase in the resistance value of the conductive film 10 is suppressed, and the conductive film 10 exhibits excellent conductivity.

[0036] <1-2. Method for producing conductive film> Figure 2 2 is a diagram schematically showing the structure of a manufacturing apparatus 20 for a conductive film 10 according to the present embodiment. Figure 2 As shown, the manufacturing device 20 includes a T-die 200 , casting rolls 210 , 220 , and a take-up roll 230 .

[0037] A resin, a conductive filler, and a dispersant for dispersing the conductive filler in the resin are fed into a T-die 20 as raw materials for the conductive film 10. A polymer material having a polyethylene skeleton is fed as a dispersant. The T-die 200 is configured to produce a molten material by heating and melting the materials containing the resin, the conductive filler, and the dispersant fed therein, and to extrude the molten material. Thus, the molten material is extruded and molded. The casting 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 up the molten material cooled by the casting rolls 210 and 220 at a predetermined speed. Thus, after the manufacturing process of the manufacturing device 20, a winding body of the conductive film 10 is manufactured.

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

[0039] [2. Modifications] An embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment, and various modifications can be made 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 it is not limited to this and may be a multi-layer film. In this case, it is preferred that the resin, conductive filler and dispersant constituting at least one layer are configured in the same manner as in the above embodiment. In addition, it is preferred that the resin, conductive filler and dispersant forming two or more layers (including the case of a part of the layers and the case of all the layers) for constituting the multi-layer film are configured in the same manner as in the above embodiment. [Example]

[0041] [3. Example] Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the following examples.

[0042] use Figure 2The manufacturing device 20 shown was used to manufacture the conductive films of Examples 1 to 3 and Comparative Examples 1 and 2. More specifically, in any one 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 conductive film with a single-layer structure having a thickness of 50 μm. The types of dispersants added in Examples 1 to 3 and Comparative Examples 1 and 2 and their acid values ​​are shown in Table 1 below. In addition, the amount of dispersant added in Examples 1 to 3 and Comparative Examples 1 and 2 (the weight percentage concentration of the dispersant relative to the entire conductive film) was all 5 wt%. In addition, the amount of carbon black added in Examples 1 to 3 and Comparative Examples 1 and 2 (the weight percentage concentration of carbon black in the entire conductive film) was all 25 wt%.

[0043] The volume resistivity of each of the conductive films of Examples 1 to 3 and Comparative Examples 1 and 2 produced as described above was measured. 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 a four-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 taken as the volume resistivity (Ω·cm).

[0046] According to the results in Table 1, it was confirmed that the volume resistivity of the conductive films of Examples 1 to 3 was lower than that of the conductive films of Comparative Examples 1 and 2. That is, it was found that the volume resistivity of the conductive film was lowered when the dispersant having a polyethylene skeleton such as maleic anhydride-modified polyethylene and styrene-modified polyethylene (Examples 1 to 3) was used compared with the dispersant having a polypropylene skeleton such as maleic anhydride-modified polypropylene (Comparative Examples 1 and 2). That is, it was found that the conductivity of the conductive film was improved by using the 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 is polypropylene. That is, the dispersants of Examples 1 to 3 are incompatible with polypropylene, and the dispersants of Comparative Examples 1 and 2 are compatible with polypropylene. Generally, when the resin and dispersant contained in the conductive film are incompatible, the two become difficult to mix, so it is expected that the dispersibility of the conductive filler will decrease and the conductivity of the conductive film will decrease. However, according to the results of Table 1, it is found that when the resin and dispersant contained in the conductive film are incompatible, the volume resistivity of the conductive film is reduced and the conductivity is improved. Description of Reference Numerals

[0048] 10 conductive film, 20 manufacturing device, 200 T-type die head, 210, 220 casting rollers, 230 winding roller.

Claims

1. A conductive film, characterized in that: Include: Resin; Conductive fillers; and The dispersant having a polyethylene skeleton disperses the conductive filler in the resin.

2. The conductive film according to claim 1, wherein The resin is a resin that 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, characterized in that The volume resistivity is 160Ω·cm or less.

5. The conductive film according to any one of claims 1 to 3, characterized in that The added amount of the dispersant is 1.0 wt % or more and 10 wt % or less.

6. The conductive film according to any one of claims 1 to 3, characterized in that The conductive filler is a carbon filler.

7. A method for producing a conductive film, characterized in that: include: A step of preparing a molten material by heating and melting a resin, a conductive filler, and a dispersant having a polyethylene skeleton for dispersing the conductive filler in the resin; as well as A step of manufacturing a conductive film by extrusion molding the molten material.

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