Conductive composite film transfer sheet, conductive member, and manufacturing method thereof

Abstract

To provide a conductive composite film transfer sheet capable of easily transferring a conductive film having excellent conductivity, smoothness, and film strength, and provide a conductive film excellent in conductivity, smoothness and film strength, and a conductive member comprising the conductive film.SOLUTION: This embodiment provides a conductive composite film transfer sheet including: a first release sheet made of a liquid-permeable sheet; and a conductive composite membrane precursor supported on a first main surface of the first release sheet and comprising conductive fibers and modified cellulose nanofibers modified with at least one anionic group. In the conductive composite film transfer sheet, the first release sheet and the conductive composite film precursor contain a first liquid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a conductive composite film transfer sheet, a conductive member, a method for producing the same, and a conductive film. Here, the term "conductive film" is a concept that includes a conductive composite film. [Background technology]

[0002] The transparent conductive layer can be used as an antistatic layer, a transparent planar heating element, a plasma display panel electrode, a liquid crystal electrode, an organic electroluminescence (EL) electrode, a touch panel, an electromagnetic wave shielding film, and the like.

[0003] Currently, transparent conductive films are mainly manufactured by the sputtering method. The advantage of the sputtering method is that it can form conductive films with low surface resistance even over a relatively large area. However, it has the disadvantage of requiring large-scale equipment and a slow film formation speed. In addition, because the film is formed by heating the conductive material in a vacuum device, the materials used are limited to those that can withstand such an environment.

[0004] Attempts have also been made to produce transparent conductive films using coating methods. In conventional coating methods, a conductive coating in which conductive particles are dispersed in a binder solution is applied to a substrate, dried, and cured to form a conductive film. Coating methods have the advantages of being easy to form large-area conductive films, requiring simple equipment and high productivity, and producing conductive films at lower cost than sputtering. In coating methods, electrical paths are formed when conductive particles come into contact with each other, thereby exhibiting conductivity. However, conductive films produced using conventional coating methods have the disadvantage that the conductive particles do not come into contact with each other sufficiently due to the presence of the binder, resulting in high electrical resistance (poor conductivity), which limits their applications.

[0005] In the coating method, it is possible to use conductive fibers such as carbon nanotubes, which are relatively easy to form contacts with compared to conductive microparticles. However, due to issues with the thickness of the coating film when forming the conductive film and the strength of the film after formation, a small amount of binder is generally mixed in before application, which reduces the conductivity.

[0006] Patent Document 1 discloses a method for producing a transparent conductive substrate having a transparent conductive film by transfer printing.

[0007] Patent Document 2 discloses a conductive film for transfer for transferring a transparent conductive layer onto the surface of an object as a transfer recipient. The transparent conductive layer provided in the conductive film for transfer is formed by compressing conductive fine particles.

[0008] Patent Document 3 discloses several methods using ultrafine conductive fibers as methods for producing a conductive molded article having a conductive layer on the surface of a substrate. One of these methods involves applying a dispersion of ultrafine conductive fibers onto a release film, drying the resulting layer, and then pressing the layer onto the substrate surface via an adhesive layer, which is then peeled off to transfer the layer. However, there is no detailed explanation of the transfer method, such as no specific explanation of the adhesive layer.

[0009] Patent Document 4 describes a method for producing a conductive film for transfer, which comprises a conductive layer formed by applying a coating liquid containing ultrafine conductive fibers thickened by mixing a volatile solvent with a resin binder onto a release film and then drying the coating liquid, and then laminating an adhesive layer made of an ultraviolet-curable resin composition on the conductive layer.

[0010] Non-Patent Document 1 describes a method for producing a conductive film of carbon nanotubes. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 6-103839 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-347150 [Patent Document 3] Patent No. 3903159 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-269569 [Non-patent literature]

[0012] [Non-Patent Document 1] Surface Chemistry, P587, Vol.64, No.11, 2013 Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention aims to provide a conductive composite film transfer sheet that can easily transfer a conductive film having excellent conductivity, smoothness, and film strength. Another object of the present invention is to provide a conductive film having excellent conductivity, smoothness, and film strength, and a conductive member having the conductive film. [Means for solving the problem]

[0014] As a result of intensive research conducted by the inventors to solve the above-mentioned problems, they discovered that by applying a dispersion liquid containing carbon nanotubes and modified cellulose nanofibers modified with specific groups onto a release sheet made of a liquid-permeable sheet and producing a conductive composite film transfer sheet that contains part of the dispersion solvent of the dispersion liquid, it is possible to efficiently and easily transfer a conductive film that has excellent conductivity, smoothness, and film strength, regardless of the material or shape (curved, flat, etc.) of the substrate to be transferred, and thus completed the present invention.

[0015] According to a first aspect of the present invention, there is provided a conductive composite film transfer sheet comprising a first release sheet made of a liquid-permeable sheet and a conductive composite film precursor supported on a first main surface of the first release sheet and comprising conductive fibers and modified cellulose nanofibers modified with at least one type of anionic group, wherein the first release sheet and the conductive composite film precursor contain a first liquid.

[0016] According to a second aspect of the present invention, there is provided a conductive composite film transfer sheet according to the first aspect, further comprising a second release sheet, wherein the conductive composite film precursor is sandwiched between the first release sheet and the second release sheet, and the second release sheet contains a second liquid.

[0017] According to a third aspect of the present invention, there is provided a method for producing a conductive composite film transfer sheet according to the first aspect, comprising: forming a coating film by applying a dispersion in which the conductive fibers and the modified cellulose nanofibers are dispersed in the first liquid onto the first main surface of the first release sheet; and forming the conductive composite film precursor by removing a portion of the first liquid from a second main surface side of the first release sheet, the second main surface being the opposite side of the first main surface; A method for producing a conductive composite film transfer sheet is provided.

[0018] According to a fourth aspect of the present invention, there is provided a method for producing a conductive composite film transfer sheet according to the second aspect, comprising the steps of: forming a coating film by applying a dispersion in which the conductive fibers and the modified cellulose nanofibers are dispersed in the first liquid onto the first main surface of the first release sheet; forming the conductive composite film precursor by removing a portion of the first liquid from a second main surface side, which is the backside of the first main surface of the first release sheet; and laminating the second release sheet containing the second liquid on the conductive composite film precursor, thereby sandwiching the conductive composite film precursor between the first release sheet and the second release sheet; A method for producing a conductive composite film transfer sheet is provided.

[0019] According to a fifth aspect of the present invention, there is provided a conductive member comprising a substrate and a conductive composite membrane formed on the substrate, wherein the conductive composite membrane comprises conductive fibers and modified cellulose nanofibers modified with at least one type of anionic group.

[0020] According to a sixth aspect of the present invention, there is provided a method for producing a conductive member comprising a substrate and a conductive composite film on the substrate, the method comprising: bringing the conductive composite film precursor contained in the conductive composite film transfer sheet according to the first aspect into contact with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; and Peeling off the first release sheet. A method for manufacturing a conductive member is provided, comprising:

[0021] According to a seventh aspect of the present invention, there is provided a method for producing a conductive member comprising a substrate and a conductive composite film on the substrate, the method comprising: Peeling off the second release sheet from the conductive composite film transfer sheet according to the second aspect; contacting the conductive composite film precursor with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; and Peeling off the first release sheet. A method for manufacturing a conductive member is provided, comprising:

[0022] According to an eighth aspect of the present invention, there is provided a conductive composite membrane comprising conductive fibers and modified cellulose nanofibers modified with at least one type of anionic group.

[0023] According to a ninth aspect of the present invention, there is provided a conductive member comprising a substrate and a conductive film on the substrate, the conductive film including carbon nanotubes and having a surface resistance value of 0.1 to 10,000 Ω / cm. 2 The conductive member has a thickness of 10 μm or less and a surface roughness of 0.5 μm or less in arithmetic mean height.

[0024] According to a tenth aspect of the present invention, there is provided a method for producing a conductive member comprising a substrate and a conductive film including conductive fibers formed on the substrate, the method comprising: bringing the conductive composite film precursor contained in the conductive composite film transfer sheet according to the first aspect into contact with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; peeling off the first release sheet; and Removing the modified cellulose nanofibers. A method for manufacturing a conductive member is provided, comprising:

[0025] According to an eleventh aspect of the present invention, there is provided a method for producing a conductive member comprising a substrate and a conductive film including conductive fibers formed on the substrate, the method comprising: Peeling off the second release sheet from the conductive composite film transfer sheet according to the second aspect; contacting the conductive composite film precursor with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; peeling off the first release sheet; and removing the modified cellulose nanofibers. A method for manufacturing a conductive member is provided, comprising:

[0026] According to a twelfth aspect of the present invention, there is provided a method for manufacturing a carbon nanotube-based composite material having a surface resistance of 0.1 to 10,000 Ω / cm. 2 The conductive film has a thickness of 10 μm or less and a surface roughness of 0.5 μm or less in arithmetic mean height. [Effects of the Invention]

[0027] According to the present invention, there are provided a conductive composite film transfer sheet that can easily transfer a conductive film that is excellent in conductivity, smoothness, and film strength, a conductive film that is excellent in conductivity, smoothness, and film strength, and a conductive member that includes the above-mentioned conductive film. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a cross-sectional view schematically showing an example of a conductive composite film transfer sheet according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a cross-sectional view schematically showing an example of a conductive composite film transfer sheet according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view schematically showing an example of a conductive member according to a third embodiment of the present invention. [Figure 4]FIG. 10 is a cross-sectional view schematically showing an example of a conductive member according to a fourth embodiment of the present invention. [Figure 5] 1 is an image obtained by observing the conductive composite film provided on the conductive member produced in Example 1 using an electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present embodiment will be described below with reference to the drawings. Elements having the same or similar functions are designated by the same reference numerals, and redundant description will be omitted.

[0030] [First embodiment] Fig. 1 is a cross-sectional view schematically showing an example of a conductive composite film transfer sheet according to a first embodiment of the present invention. The conductive composite film transfer sheet 10 shown in Fig. 1 comprises a first release sheet 1 made of a liquid-permeable sheet, and a conductive composite film precursor 4a supported on one main surface 1a (hereinafter referred to as the "first main surface") of the first release sheet 1 and containing conductive fibers 2 and modified cellulose nanofibers 3, and the first release sheet 1 and the conductive composite film precursor 4a contain a liquid (hereinafter referred to as the "first liquid") (not shown)

[0031] The first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is a dispersion solvent for the dispersion of conductive fibers and modified cellulose nanofibers (hereinafter also referred to as the "composite dispersion") used to form the conductive composite film precursor 4a, and the first release sheet 1 and the conductive composite film precursor 4a are wetted with the first liquid. The first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a plays an important role in the transferability of the conductive composite film precursor 4a to the transfer target. As will be described in detail later, the first liquid is removed from the conductive composite film transfer sheet 10 by heating or drying during transfer, and as a result, the transfer target and the conductive composite film are firmly bonded together by van der Waals forces generated.

[0032] The amount of the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is appropriately set in consideration of the film-forming properties of the conductive composite film precursor 4a and the transferability of the conductive composite film precursor 4a to a transfer recipient, etc. In one embodiment, the total mass of the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is preferably 50 mass% or more, more preferably 50 mass% or more and 200 mass% or less, even more preferably 100 mass% or more and 180 mass% or less, and particularly preferably 120 mass% or more and 170 mass% or less, based on the mass of the first release sheet.

[0033] (Conductive composite film precursor) The conductive composite film precursor 4a contains conductive fibers, modified cellulose nanofibers, and a first liquid. The conductive composite film precursor 4a is formed by removing a portion of the first liquid from a coating made of a composite dispersion in which conductive fibers and modified cellulose nanofibers are dispersed. The first liquid is removed by suction from the backside 1b (hereinafter referred to as the "second main surface") of the first release sheet 1, opposite the first main surface 1a. The thickness of the conductive composite film precursor 4a is not particularly limited and is appropriately adjusted depending on the application of the conductive composite film precursor 4a. In one embodiment, the thickness of the conductive composite film precursor 4a is appropriately set so that the thickness of the conductive composite film 4b, which is a transfer film and will be described later, is 10 μm or less. The thickness of the conductive composite film precursor 4a can be adjusted by the amount of composite dispersion applied, the concentration of the conductive fibers and modified cellulose nanofibers in the composite dispersion, and the like.

[0034] (Conductive fiber) Examples of conductive fibers used in this embodiment include carbon nanotubes (CNTs), carbon nanohorns, carbon nanowires, carbon nanofibers, carbon fibers made of graphite fibrils, metal fibers made of platinum, gold, silver, nickel, or silicon, metal fibers made of nanotubes or nanowires, and metal oxide fibers made of zinc oxide, such as metal oxide nanotubes or metal oxide nanowires. The diameter of the conductive fibers is preferably 0.3 nm to 100 nm, and the length is preferably 0.1 μm to 20 μm, more preferably 0.1 μm to 10 μm. Among these conductive fibers, carbon nanotubes are particularly thin, with a diameter of 0.3 to 80 nm and a large aspect ratio. Therefore, they rarely impede light transmission, making them preferable for obtaining a transparent conductive composite film. Furthermore, carbon nanotubes have excellent conductivity, which can reduce the surface resistance of the conductive composite film. In this embodiment, one type of conductive fiber may be used, or two or more types may be used.

[0035] The carbon nanotubes mentioned above include multi-walled carbon nanotubes (MWNT) and single-walled carbon nanotubes (SWNT). Single-walled carbon nanotubes have lower electrical resistance than multi-walled carbon nanotubes and are therefore more preferred.

[0036] Multi-walled carbon nanotubes (MWNTs) comprise a number of cylindrical carbon-walled tubes of different diameters that are concentrically arranged around a central axis. The carbon walls are formed in a hexagonal mesh structure. Some multi-walled carbon nanotubes have multiple layers of carbon walls that are spirally wound. Multi-walled carbon nanotubes that can be used in this embodiment have, in one example, 2 to 30 carbon wall layers stacked together, and in another example, 2 to 15 carbon wall layers stacked together. Typically, multi-walled carbon nanotubes are dispersed, with each carbon nanotube separated from the others. In some cases, two- or three-walled carbon nanotubes form bundles and are dispersed as described above.

[0037] Single-walled carbon nanotubes (SWNTs) have a single layer of carbon walls that are cylindrically closed around a central axis. As mentioned above, single-walled carbon nanotubes have a lower resistance value than multi-walled carbon nanotubes, making them more preferable. The carbon walls are formed in a hexagonal mesh structure. It is difficult to disperse these single-walled carbon nanotubes individually. Two or more tubes form bundles, and the bundles are entangled with each other. However, these bundles do not aggregate or become intricately entangled with each other. The bundles simply cross each other, contact each other at the intersections, and are uniformly dispersed on the surface. A preferred bundle of single-walled carbon nanotubes is a collection of 10 to 50 tubes. However, single-walled carbon nanotubes that are separated from each other and dispersed individually can also be suitably used in this embodiment.

[0038] (Modified cellulose nanofiber) The modified cellulose nanofibers used in this embodiment are modified cellulose nanofibers into which at least one type of anionic group has been introduced.

[0039] Examples of cellulose that can be used as a raw material include wood pulp obtained from softwood or hardwood trees, recycled paper pulp, and cotton, and it is preferable that the cellulose has a fiber shape derived from a microfibril structure. Cellulose nanofibers can be, for example, cellulose fibers in wood that have been refined to such an extent that at least one side of the structure is on the order of nanometers. Because such cellulose nanofibers have excellent strength and specific surface area, they are also expected to be used as fillers for reinforcing resins and adsorbents. In one embodiment, the cellulose nanofibers have a fiber width (average) of preferably 1 nm to 1,000 nm, more preferably 1 nm to 200 nm, and a fiber length (average) of preferably 100 nm to 3,000 nm, more preferably 100 nm to 1,000 nm.

[0040] The modified cellulose nanofibers used in this embodiment are anion-modified cellulose nanofibers into which at least one anionic group has been introduced, as described above. Examples of the anionic group include a group selected from a carboxyl group, a sulfonic acid group, a phosphate ester group, and derivatives thereof. By introducing the anionic groups into the cellulose nanofibers, these anionic groups repel each other in water, improving dispersibility in water. The carboxyl group, sulfonic acid group, and phosphate ester group may be in either an acid form or a salt form. Specific examples of derivatives include groups derived from carboxyl groups, such as an aldehyde group, an ester group, or an amide group represented by -COO-NR2 (where R represents a hydrogen atom, an alkyl group, a benzyl group, a phenyl group, a hydroxyalkyl group, or the like, and the two Rs may be the same or different).

[0041] The modified cellulose nanofibers used in this embodiment can be produced by known methods. For example, carboxyl group-containing cellulose nanofibers can be obtained through a modification step in which the raw material cellulose is oxidized, and a micronization step in which the oxidized cellulose is micronized. Furthermore, phosphate ester group-containing cellulose nanofibers can be produced using the phosphate esterification treatment described in Non-Patent Document 2 below. Non-Patent Document 2 discloses a method for selectively phosphate esterifying the surface of cellulose microfibers. Non-patent literature 2: Noguchi Y, Homma I, Matsubara Y. Complete nanofibrillation of cellulose prepared by phosphorylation. Cellulose. 2017;24:1295.10.1007 / s10570-017-1191-3

[0042] Commercially available modified cellulose nanofibers can be used. For example, carboxyl group-containing cellulose nanofibers can be manufactured under the TEMPO-oxidized cellulose nanofiber "CELLENPIA" (registered trademark) manufactured by Nippon Paper Industries Co., Ltd., and sulfonic acid group-containing cellulose nanofibers can be manufactured under the "STELLAFINE" (registered trademark) manufactured by Marusumi Paper Co., Ltd. One of these can be used alone, or two or more can be used in combination.

[0043] The amount of the modifying group (anionic group) introduced into the modified cellulose nanofiber is, for example, preferably in the range of 0.1 to 3.5 mmol / g. From the viewpoint of ease of production, it is more preferably in the range of 1.0 to 2.0 mmol / g. Here, the amount of the modifying group introduced can be measured by conductometric titration using a 0.5 N aqueous sodium hydroxide solution.

[0044] Modified cellulose nanofibers with these anionic groups are well dispersed in dispersions containing conductive fibers such as carbon nanotubes, maintaining their repulsion even during the drying process, preventing aggregation of the cellulose nanofibers themselves and the dispersed conductive fibers. As a result, the conductive composite film (described below), which is a transfer film of the conductive composite film precursor 4a formed from the composite dispersion, has excellent smoothness and a consistent appearance. This conductive composite film also has excellent conductivity. While the reason for this is still unclear, it is believed that the anionic groups act as electron donors, stably maintaining the conductivity of the conductive fibers. The conductive composite film, which is a transfer film of the conductive composite film precursor 4a, exhibits surface resistance values ​​nearly equivalent to those of a film made of conductive fibers alone, demonstrating excellent conductivity, even when the compounding ratio of the modified cellulose nanofibers is higher than that of the conductive fibers.

[0045] In one form, the modified cellulose nanofibers may be TEMPO-oxidized cellulose nanofibers. TEMPO-oxidized cellulose nanofibers are carboxyl group-containing cellulose fibers obtained by a method (TEMPO oxidation reaction) in which the surface of cellulose microfibers is selectively oxidized using the relatively stable N-oxyl compound 2,2,6,6-tetramethylpiperidinyl-1-oxyl radical (TEMPO) as a catalyst. The TEMPO oxidation reaction is an environmentally friendly chemical modification that proceeds in an aqueous system at room temperature and pressure. When applied to cellulose in wood, the reaction does not proceed inside the crystals, and only the alcoholic primary carbons in the cellulose molecular chains on the crystal surface can be selectively converted to carboxyl groups.

[0046] These TEMPO-oxidized cellulose nanofibers are known to have a lower decomposition temperature than modified cellulose nanofibers obtained by other manufacturing methods. That is, while modified cellulose nanofibers obtained by other manufacturing methods have a decomposition temperature of approximately 300°C, decomposition of TEMPO-oxidized cellulose nanofibers begins at 260°C. Therefore, it is preferable to use TEMPO-oxidized cellulose nanofibers when it is necessary to obtain the conductive film 4c included in the conductive member 40 according to the fourth embodiment of Figure 4, which will be described later, by thermally decomposing and removing the modified cellulose nanofibers contained in the conductive composite film, which is a transfer film.

[0047] The compounding ratio of the conductive fiber and the modified cellulose nanofiber contained in the conductive composite film precursor 4a is set to 10,000 Ω / cm. 2 To achieve a surface resistivity equal to or less than that of a conductive film made of carbon nanotubes, the amount of modified cellulose nanofibers is preferably 100 parts by mass or less per 1 part by mass of conductive fiber. From the viewpoint of maintaining a surface resistivity equivalent to that of a conductive film made of carbon nanotubes alone, the amount of modified cellulose nanofibers is more preferably 20 parts by mass or less per 1 part by mass of conductive fiber. Furthermore, from the viewpoints of smoothness and transferability, the amount of modified cellulose nanofibers is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 1 part by mass of conductive fiber.

[0048] (1st liquid) The first liquid is not particularly limited as long as it is a solvent capable of dispersing the conductive fibers and modified cellulose nanofibers, and any can be used. In this embodiment, when carbon nanotubes are used as the conductive fibers, the first liquid may be water, acetone, methyl ethyl ketone, methanol, ethanol, isopropanol, or a mixed solvent of two or more selected from these. Of these, water or alcohol is preferred, and a mixed solvent of these is also acceptable. As the alcohol, one with high polarity is preferred, and examples thereof include methanol, ethanol, isopropyl alcohol, and the like.

[0049] (Conductive assistant) In this embodiment, the conductive composite film precursor 4a may contain a conductive additive to improve conductivity and film strength. Examples of such conductive additives include conductive polymers such as PEDOT / PSS, polypyrrole, and polyaniline, and conductive metals such as gold, silver, and copper fine particles or fibers. Examples of metal fibers include silver nanowires. When a conductive additive is used, it is preferable that the blending ratio of the conductive additive in the conductive composite film precursor 4a does not exceed the blending ratio of the conductive fibers. If the blending ratio of the conductive additive is greater than the blending ratio of the conductive fibers, the film may not peel off from the first release sheet during transfer, potentially preventing transfer.

[0050] (surfactant) In this embodiment, the conductive composite film precursor 4a may contain a surfactant, provided that it can be removed together with the first liquid when removing the first liquid from the conductive composite film transfer sheet. If the surfactant remains in the conductive composite film as a transfer film, the conductivity may decrease. By removing the surfactant together with the first liquid, the conductivity of the conductive fibers can be enhanced. In one embodiment, a composite dispersion in which the conductive fibers and modified cellulose nanofibers are uniformly dispersed can be obtained by mixing a dispersion of conductive fibers previously dispersed with a surfactant with a modified cellulose nanofiber dispersion and subjecting the mixture to ultrasonic treatment or the like.

[0051] Specific examples of surfactants include sodium dodecyl sulfate; naphthalenesulfonic acid-formalin condensate salts such as the sodium salt of naphthalenesulfonic acid-formalin condensate (manufactured by Kao Corporation under the names "Demol N," "Demol RN," and "Mighty 150") and the NH salt of naphthalenesulfonic acid-formalin condensate (manufactured by Kao Corporation under the name "Demol AS"); methylnaphthalenesulfonic acid-formalin condensate salts such as the sodium salt of methylnaphthalenesulfonic acid-formalin condensate (manufactured by Kao Corporation under the name "Demol MS"); sodium salt of butylnaphthalene / naphthalenesulfonic acid-formalin condensate (manufactured by Kao Corporation under the name "Demol SNB"); sodium salt of naphtholmethylenesulfonic acid-formalin condensate (manufactured by Kao Corporation under the name "Demol SSL"); and sodium salt of creosote oil sulfonic acid-formalin condensate (manufactured by Kao Corporation under the name "Demol C"). Also included are ligninsulfonates, which are natural polycondensation sulfonates. Examples of polymeric aromatic surfactants include sodium polystyrene sulfonate ("sodium polystyrene sulfonate PS-1, PS-35, PS-50, PS-100" manufactured by Toyo Soda Co., Ltd.).

[0052] (First release sheet) The first release sheet 1 is a liquid-permeable sheet. The liquid-permeable sheet that can be used in this embodiment is any sheet that has permeability that allows the first liquid to be removed from a composite dispersion of conductive fibers and modified cellulose nanofibers while leaving the conductive fibers and modified cellulose nanofibers on the sheet. Specific examples include various porous membrane filters and nonwoven fabric filters. The pore size of the first release sheet 1 is appropriately determined based on the above-mentioned considerations. For example, a liquid-permeable sheet having an appropriate pore size may be selected depending on the length of the conductive fibers. In this embodiment, the pore size of the first release sheet is preferably, for example, 0.05 μm to 5.0 μm, and more preferably 0.1 μm to 2.0 μm. The pore size here is a value measured using a method conforming to the bubble point test method specified in JIS K3832.

[0053] Examples of materials for the first release sheet 1 include PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), PVDC (polyvinylidene chloride), PP (polypropylene), PE (polyethylene), cellulose, cellulose acetate, polycarbonate, etc., with PTFE, PVDF, and cellulose being preferred, and PTFE being more preferred. The first release sheet 1 may be a sheet made of a single material selected from these, or a sheet made of a mixture of two or more materials. There are no particular limitations on the thickness of the first release sheet 1, and it may be, for example, 10 to 200 μm.

[0054] (Manufacturing method) In this embodiment, the conductive composite film transfer sheet 10 according to the first embodiment shown in FIG. 1 is obtained, for example, as follows. First, a composite dispersion in which conductive fibers 2 and modified cellulose nanofibers 3 are dispersed in a first liquid is applied to the first main surface 1a of the first release sheet 1 to obtain a coating of the composite dispersion. The composite dispersion can be prepared, for example, by adding a modified cellulose nanofiber dispersion in the first liquid as a dispersion solvent to a conductive fiber dispersion in the first liquid as a dispersion solvent while maintaining a uniform dispersion. The concentration of the conductive fibers in the composite dispersion may be, for example, in the range of 0.001% to 0.5% by mass, and the concentration of the modified cellulose nanofibers may be, for example, in the range of 0.001% to 0.5% by mass. The two dispersions are mixed so that the conductive fibers and modified cellulose meet the above-mentioned blend ratio. The method for applying the composite dispersion is not particularly limited; the composite dispersion may be directly poured onto the first main surface 1a, or known application methods such as spraying can be used.

[0055] Next, a conductive composite film precursor 4a of a desired thickness is formed by removing a portion of the first liquid from the second main surface 1b, which is the reverse side of the first main surface 1a of the first release sheet 1 on which the composite dispersion coating has been formed. Removing a portion of the first liquid from the second main surface 1b of the first release sheet 1 improves adhesion between the conductive fibers, between the conductive fibers and the modified cellulose nanofibers, and between the modified cellulose nanofibers, thereby forming the conductive composite film precursor 4a on the first release sheet 1. At this time, the first release sheet 1 and the conductive composite film precursor 4a are wet due to the remaining first liquid. If these components are dry rather than wet, or if the amount of the first liquid contained is too small, problems such as failure to transfer the conductive composite film precursor 4a or partial transfer failure may occur. The preferred range of the total mass of the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is as described above.

[0056] Here, we will discuss the case where, instead of the composite dispersion, the conductive fiber dispersion and the modified cellulose nanofiber dispersion before mixing are used separately. That is, when comparing the present embodiment, which uses a composite dispersion, with the case where a conductive fiber dispersion is first applied to a first release sheet 1 to form a coating film, and then a modified cellulose nanofiber dispersion is applied to this coating film to form a coating film, the present embodiment, which uses a composite dispersion, is particularly superior in transferability and smoothness. In other words, by using a composite dispersion to form a conductive composite film precursor 4a containing conductive fibers 2 and modified cellulose nanofibers 3, transferability and smoothness are improved (see Examples 1 and 2 below). Furthermore, if the order of application of the two dispersions is reversed, transfer failure is likely to occur, making it difficult to obtain a transferred film (see Reference Example 3 below).

[0057] The first liquid is suitably removed all at once from the second main surface 1b side of the first release sheet 1 by suctioning the first liquid. Examples of suction methods include reduced pressure suction using an aspirator or the like, or a method in which a water-absorbent or oil-absorbent material is brought into contact with the second main surface 1b to absorb the first liquid.

[0058] In transfer using the conductive composite film transfer sheet 10, some recipients may have poor affinity with the first liquid contained in the conductive composite film precursor 4a, which may result in problems such as failure to transfer or partial transfer failure. In this case, the first liquid contained in the first release sheet 1 of the conductive composite film transfer sheet 10 and the conductive composite film precursor 4a may be replaced with a liquid that has good affinity with the recipient. The replacement of the first liquid contained in the conductive composite film transfer sheet 10 with another liquid may be performed, for example, as follows.

[0059] Here, we will explain the case where the "other liquid" that has a good affinity with the transfer target is a liquid that is miscible with the first liquid (hereinafter referred to as the "second liquid"). Here, "miscible" means that when the first liquid and the second liquid are mixed, they do not separate and no interface is formed.

[0060] To replace the first liquid contained in the conductive composite film transfer sheet 10 with a second liquid compatible with the first liquid, first, the second liquid is applied to the conductive composite film precursor 4a of the conductive composite film transfer sheet 10 containing the first liquid obtained by the method described above. The second liquid is applied to the conductive composite film precursor 4a in such a manner that the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is washed away with the second liquid, and the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is replaced with the second liquid. Next, a portion of the second liquid is removed from the second main surface 1b side of the first release sheet 1. This replaces the first liquid contained in the conductive composite film transfer sheet 10 with the second liquid, resulting in a conductive composite film transfer sheet 10 in which the first release sheet 1 and the conductive composite film precursor 4a are wetted with the second liquid. Here, the second liquid can be applied in the same manner as the dispersion liquid application method described above, and the liquid can be removed from the second main surface 1b side of the first release sheet 1 in the same manner as the first liquid removal described above.

[0061] [Second embodiment] Fig. 2 is a cross-sectional view schematically showing an example of a conductive composite film transfer sheet according to a second embodiment of the present invention. The conductive composite film transfer sheet 20 shown in Fig. 2 is the conductive composite film transfer sheet 10 according to the first embodiment shown in Fig. 1 further provided with a second release sheet 5, and a conductive composite film precursor 4a is sandwiched between the first release sheet 1 and the second release sheet 5.

[0062] The second release sheet 5 contains the same first liquid as the first release sheet 1 and the conductive composite film precursor 4a. In the conductive composite film transfer sheet 20, the second release sheet 5 is arranged to sandwich the conductive composite film precursor 4a together with the first release sheet 1, with the aim of preventing the conductive film transfer sheet from drying out and maintaining stable transferability for a long period of time. This ensures the storage stability of the conductive film transfer sheet 20 and improves its convenience.

[0063] The material of the second release sheet 5 is not particularly limited, as long as it can sufficiently absorb and retain the same liquid as the first liquid so as to prevent the conductive composite film precursor 4a containing the first liquid from drying out when it is attached to the conductive composite film precursor 4a. For example, when water is used as the dispersion solvent (first liquid) for dispersing the conductive fibers 2 and the modified cellulose nanofibers 3, a water-absorbent gel sheet of sodium polyacrylate, polyacrylamide, agar, carrageenan, or the like, or water-absorbent paper can be used. When alcohol is used as the dispersion solvent (first liquid), various oil-absorbent polymer sheets that absorb and retain the alcohol can be used.

[0064] In addition, in the conductive film transfer sheet 20, when the first liquid contained in the first release layer 1 and the conductive composite film precursor 4a is replaced with the second liquid by the above-mentioned method, the liquid to be contained in the second release sheet 5 is the same as the second liquid after replacement.

[0065] The conductive composite film transfer sheet 20 shown in Fig. 2 can be obtained by laminating the conductive composite film transfer sheet 10 shown in Fig. 1 obtained by the above-mentioned method with a second release sheet 5 sufficiently soaked in the first liquid on the surface of the conductive composite film precursor 4a that is not in contact with the first release sheet 1. As described above, the second release sheet 5 is used to prevent the conductive composite film precursor 4a, which serves as the transfer layer of the conductive composite film transfer sheet, from drying and fixing until it is transferred to the transfer recipient. Therefore, when laminating the second release sheet 5 onto the conductive composite film precursor 4a, it is important that the conductive composite film precursor 4a be kept wet.

[0066] In the conductive composite film transfer sheet 20, the total mass of the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a when the second release sheet 5 is peeled off is preferably approximately the same as the total mass of the content of the first liquid described in the conductive composite film transfer sheet 10 according to the first embodiment. That is, it may be 50% by mass or more and 200% by mass or less, 100% by mass or more and 180% by mass or less, or 120% by mass or more and 170% by mass or less, relative to the mass of the first release sheet 1.

[0067] In addition, in both embodiment 1 and embodiment 2, the conductive composite film transfer sheet of this embodiment is preferably stored in a storage bag such as an aluminum laminate pouch or a sealed case that can be completely sealed until use in order to maintain the moist state of the first release sheet 1 and the conductive composite film precursor 4a.

[0068] [Third embodiment] Fig. 3 is a cross-sectional view schematically showing an example of a conductive member according to a third embodiment of the present invention. The conductive member 30 shown in Fig. 3 comprises a substrate 6 as a transfer recipient, and a conductive composite film 4b, which is a film transferred from the conductive composite film transfer sheet 10 or 20 according to this embodiment, on the substrate 6. The conductive composite film 4b contains conductive fibers 2 and modified cellulose nanofibers 3.

[0069] The conductive member 30 shown in FIG. 3 is obtained, for example, as follows. When the conductive composite film transfer sheet is the conductive composite film transfer sheet 20 according to the second embodiment, the second release sheet 5 is first peeled off from the conductive composite film transfer sheet 20. Next, the surface of the conductive composite film precursor 4a from which the second release sheet 5 was peeled off is brought into contact with the substrate 6. At this time, it is preferable to press the conductive composite film precursor 4a against the substrate 6 to prevent air bubbles from being trapped between the substrate 6 and the conductive composite film precursor 4a. Next, the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is removed by heating or drying. The van der Waals forces generated by the removal of the first liquid firmly bond the substrate 6 and the conductive composite film 4b. Heating methods include, for example, applying hot air to the second main surface 1b of the first release sheet 1 using a dryer or heating from below using a heater. After removing the first liquid, the first release sheet 1 is peeled off, completing the transfer of the conductive composite film 4b to the substrate 6 and obtaining the conductive member 30.

[0070] As described above, the conductive composite film transfer sheet according to this embodiment has excellent transferability, and the conductive composite film 4b can be easily transferred by evaporating the liquid contained in the sheet with hot air from a dryer or the like without using any special equipment. Therefore, the conductive composite film 4b can be easily formed even if the substrate 6 is a substrate with low heat resistance.

[0071] In this embodiment, the thickness of the conductive composite film 4b is preferably 10 μm or less, more preferably 100 nm or more and 10 μm or less, and even more preferably 100 nm or more and 1 μm or less.

[0072] The conductive composite film obtained from the conductive composite film transfer sheet according to this embodiment is a composite film of conductive fibers and modified cellulose nanofibers, but has a surface resistance equivalent to that of a film made of carbon nanotubes alone, and has excellent conductivity. In one embodiment, the conductive composite film transfer sheet according to this embodiment achieves a surface resistance of 0.1 to 10,000 Ω / cm. 2A conductive member comprising such a highly conductive composite film can be used as an antistatic body, a transparent surface heating body, a plasma display panel electrode, a liquid crystal electrode, an organic EL electrode, a touch panel, an electromagnetic wave shielding film, etc., and according to this embodiment, such a conductive member can be obtained by a simple method.

[0073] The conductive composite film obtained from the conductive composite film transfer sheet according to this embodiment also has excellent smoothness. In one embodiment, the conductive composite film transfer sheet according to this embodiment can provide a conductive composite film having a surface roughness of 0.5 μm or less in arithmetic mean height (Sa).

[0074] The conductive composite film obtained from the conductive composite film transfer sheet according to this embodiment also has excellent transmittance. The transmittance can be adjusted, for example, by adjusting the compounding ratio of the conductive fibers. By transferring a conductive composite film with high transmittance to a transparent film or transparent glass, it can be used as a transparent conductive film or transparent conductive glass in various displays, etc.

[0075] Furthermore, since the conductive composite film obtained from the conductive composite film transfer sheet according to this embodiment contains conductive fibers and modified cellulose nanofibers, it is more resistant to deformation such as repeated bending than inorganic conductive films such as ITO and tin oxide, and can be used as a flexible conductor.

[0076] [Fourth embodiment] Fig. 4 is a cross-sectional view schematically illustrating an example of a conductive member according to a fourth embodiment of the present invention. The conductive member 40 shown in Fig. 4 comprises a substrate 6 as a transfer recipient, and a conductive film 4c, which is a film transferred from the conductive composite film transfer sheet according to this embodiment, on the substrate 6. The conductive film 4c contains conductive fibers 2 but does not contain modified cellulose nanofibers.

[0077] The conductive member 40 shown in FIG. 4 can be obtained, for example, by removing modified cellulose nanofibers from the conductive composite film 4b included in the conductive member 30 according to the third embodiment. The modified cellulose nanofibers can be removed from the conductive composite film 4b by known methods. For example, the conductive member 40 can be heated to the thermal decomposition temperature of the modified cellulose nanofibers to thermally decompose and remove the modified cellulose nanofibers. In this case, by using a modified cellulose nanofiber with a low decomposition temperature, such as the TEMPO-oxidized cellulose nanofiber described above, the limitations on the substrate 6, which is the transfer target, can be alleviated. Another example of a method for removing the modified cellulose nanofibers from the conductive composite film 4b is to immerse the conductive member 40 in a predetermined solvent (e.g., a nitric acid aqueous solution) to dissolve and remove the modified cellulose nanofibers.

[0078] The conductive film 4c provided in the conductive member 40 of this embodiment has almost the same performance in terms of conductivity, transmittance, smoothness, and film strength as the conductive composite film 4b provided in the conductive member 30 of the third embodiment described above, and can be used in the various fields described above.

[0079] Thus, with the conductive composite film transfer sheet of this embodiment, regardless of the material or type of the substrate to be transferred, by adhering the transfer sheet to the shape of the substrate, such as a curved surface or unevenness, it is possible to form a highly conductive film on substrates of a wide variety of shapes. Furthermore, the conductive film obtained from the conductive composite film transfer sheet according to this embodiment is a self-supporting film with high film strength that can maintain its shape even without a support. Therefore, the conductive composite transfer sheet according to this embodiment can be applied even when the transfer target is a substrate with a hollow center or a frame-shaped substrate. By transferring the conductive composite film to such a substrate, a conductive film can be obtained that is partially or mostly not in contact with the substrate, and can be used as a standalone conductive film. For example, a protective film or the like can also be produced using the conductive composite film transfer sheet according to this embodiment. Furthermore, the use of the conductive film according to this embodiment is not limited to applications requiring conductivity. As such, the conductive composite film transfer sheet according to this embodiment can be used in a variety of fields. [Example]

[0080] The present invention will be explained in more detail below with reference to test examples. [Preparation of carboxyl group-containing cellulose nanofiber dispersion] As the modified cellulose nanofibers, a dispersion of carboxyl group-containing cellulose nanofibers was prepared as follows. (1) Modification process A suspension of 30 g of bleached softwood kraft pulp was prepared in 1800 g of distilled water. Separately, a solution of 0.3 g of 2,2,6,6-tetramethylpiperidinyl-1-oxygen radical (TEMPO) and 3 g of sodium bromide was prepared in 200 g of distilled water. This solution was added to the suspension and the temperature was adjusted to 20°C. To this suspension, 220 g of sodium hypochlorite solution (concentration 2 mol / L, density 1.15 g / mL) adjusted to pH 10 with 1 N HCl aqueous solution was added dropwise to initiate the oxidation reaction, introducing carboxyl groups into the cellulose. The temperature of the system was maintained at 20°C. The pH decreased during the reaction, but was maintained at 10 by adding 0.5 N sodium hydroxide aqueous solution.

[0081] When the amount of sodium hydroxide consumed per 1 g of cellulose reached 2.5 mmol, it was determined that the desired amount of carboxyl groups had been introduced (based on a pre-prepared calibration curve), and a sufficient amount of ethanol was added to stop the reaction. Hydrochloric acid was then added until the pH reached 3, and the mixture was then repeatedly washed with distilled water to obtain the modified cellulose.

[0082] The modified cellulose was weighed out in an amount of 0.1 g as a solid content mass and dispersed in water to a concentration of 1% by mass, and hydrochloric acid was added to adjust the pH to 3. The amount of carboxy groups in this liquid was then determined by conductometric titration using a 0.5 N aqueous solution of sodium hydroxide, and was found to be 1.6 mmol per 1 g of modified cellulose (cellulose whose surface is modified with carboxy groups), i.e., 1.6 mmol / g.

[0083] (2) Refinement process 4 g of the modified cellulose obtained in the above (1) modification step was dispersed in 396 g of distilled water, and an aqueous sodium hydroxide solution was added to adjust the pH to 10. This liquid was then subjected to a micronization treatment using a mixer for 60 minutes to obtain a dispersion of carboxyl group-containing cellulose nanofibers (carboxyl group-containing cellulose nanofiber concentration: 1% by mass).

[0084] The carboxyl groups of the carboxyl group-containing cellulose nanofibers in this dispersion were in the salt form (sodium). The carboxyl group-containing cellulose nanofibers contained in dispersion (A) had an average fiber width of 3.5 nm and an average fiber length of 800 nm. The average fiber width and fiber length were measured using an atomic force microscope (AFM) on 20 samples.

[0085] [Example 1] <Production of the conductive composite film transfer sheet according to the first embodiment> A 0.2% by mass aqueous dispersion of commercially available single-walled carbon nanotubes (CNTs) with a diameter of 1 to 3 nm was diluted with water to 0.02% by mass to prepare dispersion (A) for conductive fiber 2. The carboxyl group-containing cellulose nanofiber dispersion prepared above was diluted with water to 0.02% by mass to prepare dispersion (B) for modified cellulose nanofiber (CNF) 3. Dispersions (A) and (B) were mixed so that the mass ratio of carbon nanotubes to carboxyl group-containing cellulose nanofibers (CNT:CNF) was 1:10. Ultrasonication was then performed for approximately 1 minute to prepare a uniform composite dispersion (C).

[0086] Next, this composite dispersion (C) was sprayed onto a PTFE sheet (first release sheet 1; diameter 47 mm, film thickness 65 μm, sheet pore size 0.2 μm) using an airbrush with a nozzle diameter of 0.3 mm, and the back side was aspirated with an aspirator to remove some of the water, thereby obtaining a conductive composite film transfer sheet 10 having a conductive composite film precursor 4a on the PTFE sheet. The liquid content of the obtained conductive composite film transfer sheet 10, represented by formula (1), was 160 mass%.

[0087] [(total mass of the liquid contained in the first release sheet and the conductive film) / mass of the first release sheet] × 100 (%) Formula (1)

[0088] <Production of the conductive member according to the third embodiment> The surface of the conductive composite film precursor 4a of the obtained conductive composite film transfer sheet 10 was laminated to a PET film 6 with a thickness of approximately 100 μm with moderate pressure to avoid trapping air bubbles. The PET film side of the obtained laminate was then placed in contact with a hot plate at approximately 90°C to thoroughly dry off the moisture. The PTFE sheet was then slowly peeled off from the edge to obtain a conductive member 30 having a conductive composite film 4b (transferred product) on the PET film 6. Figure 5 shows an electron microscope image of the conductive composite film 4b included in the obtained conductive member 30.

[0089] [Example 2] A conductive member 30 was produced under the same conditions as in Example 1, except that the carboxyl group-containing cellulose nanofibers were replaced with sulfonic acid group-containing cellulose nanofibers. Here, the sulfonic acid group-containing cellulose nanofibers used were a commercially available aqueous dispersion of sulfonic acid group-containing cellulose nanofibers (Stellafine (registered trademark), manufactured by Marusumi Paper Co., Ltd.) diluted to 0.02 mass %.

[0090] [Example 3] A conductive member 30 was produced under the same conditions as in Example 1, except that the carboxyl group-containing cellulose nanofibers were replaced with phosphate ester group-containing cellulose nanofibers. Here, the phosphate ester group-containing cellulose nanofibers used were prepared by diluting an aqueous dispersion prepared by the method described in Non-Patent Document 2 to 0.02% by mass.

[0091] [Example 4] <Production of conductive composite film transfer sheet according to the second embodiment> Under the same conditions as in Example 1, a conductive composite film transfer sheet 10 according to the first embodiment was obtained, in which a conductive composite film precursor 4a was formed on a PTFE sheet (first release sheet 1). Next, commercially available cellulose qualitative filter paper (diameter 50 mm, thickness 0.5 mm) was immersed in pure water and removed when sufficiently moistened. This was then used as the second release sheet 5 and attached to the conductive composite film precursor 4a to produce a conductive composite film transfer sheet 20 according to the second embodiment. This conductive composite film transfer sheet 20 according to the second embodiment was stored in an aluminum laminate bag with a zipper to prevent the sheet from drying out. After the time indicated in the "Time until transfer" column in Table 1, the sheet was removed from the aluminum laminate bag and used as a transfer sheet in the following transfer test.

[0092] <Production of the conductive member according to the third embodiment> After a predetermined time, the conductive composite film transfer sheet 20 was removed from the aluminum laminate bag. Next, the second release sheet 5 was peeled off, and the surface of the conductive composite film precursor 4a was attached to a 100 μm-thick PET film 6 with moderate pressure to avoid trapping air bubbles. Next, the PET film 6 side of the resulting laminate was contacted with a hot plate at approximately 90°C to thoroughly dry out the moisture. Next, the PTFE sheet 1, the first release sheet, was slowly peeled off from an edge to obtain a conductive member 30 having the conductive composite film 4b transferred onto the PET film 6.

[0093] [Example 5] <Production of conductive composite film transfer sheet according to the second embodiment> A conductive composite film transfer sheet 10 according to the first embodiment was obtained, in which a conductive composite film precursor 4a was formed on a PTFE sheet (first release sheet 1) under the same conditions as in Example 1. Next, ethanol was sprayed onto the conductive composite film precursor 4a with an airbrush, and excess ethanol was removed while the back surface 1b of the PTFE sheet 1 was aspirated with an aspirator, thereby obtaining a conductive composite film transfer sheet 10 according to the first embodiment, in which the water contained in the conductive composite film precursor 4a and the PTFE sheet 1 was completely replaced with ethanol.

[0094] Next, commercially available cellulose qualitative filter paper (diameter 50 mmφ, film thickness 0.5 mm) was immersed in ethanol, removed when sufficiently saturated with ethanol, and used as the second release sheet 5 to be attached onto the conductive composite film precursor 4a to produce a conductive composite film transfer sheet 20 according to the second embodiment. This conductive composite film transfer sheet 20 was stored in the same aluminum laminate bag with a zipper as in Example 4 to prevent the sheet from drying out.

[0095] <Production of the conductive member according to the third embodiment> After the time shown in "Time until transfer" in Table 1, the conductive composite film transfer sheet was taken out of the aluminum laminated bag, and the conductive member 30 was produced under the same conditions as in Example 4.

[0096] [Example 6] <Production of conductive composite film transfer sheet according to the second embodiment> A 0.02 mass% aqueous dispersion of silver nanowires (average diameter: 50 nm) was added to the composite dispersion (C) containing carbon nanotubes and carboxyl group-containing cellulose nanofibers prepared in Example 1 so that the mass ratio of carbon nanotubes:cellulose nanofibers:silver nanowires was 1:10:1, to prepare a uniform composite dispersion (D).

[0097] Next, this composite dispersion (D) was sprayed onto the PTFE sheet 1 using an airbrush with a nozzle diameter of 0.3 mm, and the back surface 1b was aspirated with an aspirator to remove some of the water, thereby obtaining a conductive composite film transfer sheet 10 according to the first embodiment, which has a conductive composite film precursor 4a containing carbon nanotubes, carboxyl group-containing cellulose nanofibers, and silver nanowires (not shown) on the PTFE sheet 1.

[0098] Next, a conductive composite film transfer sheet 20 according to the second embodiment was produced by laminating a moist cellulose qualitative filter paper as a second release sheet 5 onto the conductive composite film precursor 4a in the same manner as in Example 4. This conductive composite film transfer sheet 20 was stored in the same aluminum laminate bag with a zipper as in Example 4 to prevent the sheet from drying out.

[0099] <Production of the conductive member according to the third embodiment> After the time shown in "Time until transfer" in Table 1, the conductive composite film transfer sheet was taken out of the aluminum laminated bag, and the conductive member 30 was produced under the same conditions as in Example 4.

[0100] [Example 7] A conductive composite film transfer sheet 10 according to the first embodiment was obtained in the same manner as in Example 1, except that the PTFE sheet 1 was replaced with a PTFE sheet measuring 3 cm x 3 cm. In producing a conductive member 40 according to the fourth embodiment, a conductive composite film 4b was transferred in the same manner as in Example 1, except that a glass plate (4 cm x 4 cm, 0.7 mm thick) was used as the transfer substrate 6 instead of the PET film, thereby obtaining a conductive member 30 according to the third embodiment. The obtained conductive member 30 was then baked at 260°C for 30 minutes to remove the carboxyl group-containing cellulose nanofibers. This resulted in a conductive member 40 according to the fourth embodiment, which includes a conductive film 4c made of carbon nanotubes.

[0101] [Example 8] A conductive composite film transfer sheet 10 according to the first embodiment was obtained in the same manner as in Example 1, except that the PTFE sheet 1 was replaced with a PTFE sheet measuring 3 cm × 3 cm. In producing a conductive member 40 according to the fourth embodiment, a conductive composite film 4b was transferred in the same manner as in Example 1, except that a glass plate (4 cm × 4 cm, 0.7 mm thick) was used as the transfer substrate 6 instead of the PET film, thereby obtaining a conductive member 30 according to the third embodiment. The obtained conductive member 30 was then immersed in a 3M aqueous nitric acid solution at 60°C for 30 minutes to remove the carboxyl group-containing cellulose nanofibers, thereby obtaining a conductive member 40 according to the fourth embodiment, which includes a conductive film 4c made of carbon nanotubes. After immersion in the nitric acid solution, the member was washed with ethanol and then dried.

[0102] [Example 9] A conductive composite film transfer sheet 10 according to the first embodiment was obtained in the same manner as in Example 1, except that the PTFE sheet 1 was changed to a PTFE sheet measuring 3 cm × 3 cm. In producing a conductive member 30 according to the third embodiment, a glass plate (4 cm × 4 cm, 0.7 mm thick) with a hole of approximately 10 mm diameter in the center was used instead of the PET film as the transfer recipient 6, and the conductive composite film 4b was transferred in the same manner as in Example 1, thereby obtaining a conductive member 30 having a single film made of the conductive composite film 4b formed in the center.

[0103] [Comparative Example 1] A conductive composite film transfer sheet prepared in the same manner as in Example 1 was left at room temperature for 3 hours. Visual inspection of the transfer sheet revealed that it was dry. When this conductive composite film transfer sheet was subjected to a transfer test in the same manner as in Example 1, no conductive composite film was transferred to the PET film.

[0104] [Reference example 1] A conductive composite film transfer sheet was produced in the same manner as in Example 1, except that dispersion (A) containing single-walled carbon nanotubes at a concentration of 0.02 mass % used in preparing dispersion (C) was used instead of dispersion (C) containing carbon nanotubes and carboxyl group-containing cellulose nanofibers. A conductive composite film transfer sheet was produced in the same manner as in Example 1, using this conductive composite film transfer sheet.

[0105] [Reference example 2] A transfer sheet was prepared in the same manner as in Example 1, except that instead of the composite dispersion (C) containing carbon nanotubes and carboxyl group-containing cellulose nanofibers, the unmixed carbon nanotube dispersion (A) and the carboxyl group-containing cellulose nanofiber dispersion (B) were sprayed separately in that order onto a PTFE sheet, and then a conductive member was prepared.

[0106] [Reference example 3] A transfer sheet was prepared in the same manner as in Reference Example 2, except that the order in which the carbon nanotube dispersion (A) and the carboxyl group-containing cellulose nanofiber dispersion (B) were sprayed onto the PTFE sheet was reversed, and then a conductive member was prepared.

[0107] <Evaluation> The surface resistance, transmittance, and surface roughness of the conductive composite film or conductive film provided on each conductive member were measured by the following methods, and the transferability was evaluated based on the following criteria. The results are shown in Table 1. The film thickness of the conductive films obtained in Examples 1 to 9 was all within the range of 100 nm to 500 nm.

[0108] (Method for measuring surface resistance) The surface resistance was measured by a four-terminal method using a resistivity meter Loresta GP MCP-T610 (Mitsubishi Chemical Analytech Co., Ltd.).

[0109] (Transmittance measurement method) The transmittance was measured using a spectrophotometer U-4100 (Hitachi High-Technologies Corporation) for light transmittance at a wavelength of 550 nm, including the conductive composite film and the PET substrate.

[0110] (Method for measuring surface roughness (Sa)) Surface roughness (Sa) is the average of the absolute values ​​of the heights of each point relative to the average plane of the surface, and refers to the arithmetic mean height (Sa) specified in ISO 25178 Surface Texture (Surface Roughness Measurement). Surface roughness (Sa) was measured using a 3D measuring laser microscope OLS4000 (manufactured by Olympus Corporation).

[0111] (Method for measuring film thickness) The cross section was observed using a scanning electron microscope (SEM) and the film thickness was measured.

[0112] (Transferability) A: Complete transcription was possible (100% of the transcription area). B: Almost complete transcription (90% to less than 100% of the transcription area). C: More than half was transferred. (50% to less than 90% of the transferable region) D: Partial transcription was possible (more than 0% and less than 50% of the transcriptionable region). E: No transcription at all (0% of transcriptional region).

[0113] [Table 1]

[0114] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention. [Explanation of symbols]

[0115] DESCRIPTION OF SYMBOLS 1 First release sheet, 1a First main surface, 1b Second main surface, 2 Conductive fiber, 3 Modified cellulose nanofiber, 4a Conductive composite film precursor, 4b Conductive composite film, 4c Conductive film, 5 Second release sheet, 6 Substrate (receiving body), 10 Conductive composite film transfer sheet (first embodiment), 20 Conductive composite film transfer sheet (second embodiment), 30 Conductive member (third embodiment), 40 Conductive member (fourth embodiment) The inventions described in the original claims of this application are set forth below. [1] A conductive composite film transfer sheet comprising a first release sheet made of a liquid-permeable sheet and a conductive composite film precursor supported on a first main surface of the first release sheet and containing conductive fibers and modified cellulose nanofibers modified with at least one type of anionic group, wherein the first release sheet and the conductive composite film precursor contain a first liquid. [2] A conductive composite film transfer sheet according to appendix [1], wherein the total mass of the first release sheet and the first liquid contained in the conductive composite film precursor is 50 mass% or more relative to the mass of the first release sheet. [3] The conductive composite film transfer sheet according to appendix [1] or [2], wherein the first liquid contained in the first release sheet and the conductive composite film precursor is a dispersion solvent for a dispersion containing the conductive fiber and the modified cellulose nanofiber used in forming the conductive composite film precursor. [4] The conductive composite film transfer sheet according to any one of appendices [1] to [3], wherein the first liquid contains water or an alcohol. [5] A conductive composite film transfer sheet according to any one of appendices [1] to [4], wherein the amount of anionic groups introduced into the modified cellulose nanofibers is in the range of 0.1 to 3.5 mmol / g. [6] The conductive composite film transfer sheet according to any one of appendices [1] to [5], wherein the conductive fibers include at least carbon nanotubes. [7] The conductive composite film transfer sheet according to appendix [6], wherein the carbon nanotubes are single-walled carbon nanotubes. [8] The conductive composite film transfer sheet according to any one of appendices [1] to [7], wherein the first release sheet is a porous sheet having a pore size in the range of 0.05 μm to 5 μm. [9] The conductive composite film transfer sheet according to any one of appendices [1] to [8], wherein the first release sheet contains polytetrafluoroethylene.

[10] A conductive composite film transfer sheet according to any one of appendices [1] to [9], further comprising a second release sheet, the conductive composite film precursor being sandwiched between the first release sheet and the second release sheet, and the second release sheet containing a second liquid.

[11] The conductive composite film transfer sheet according to appendix

[10] , wherein the second liquid is the same as the first liquid.

[12] A method for producing a conductive composite film transfer sheet according to any one of appendices [1] to [9], forming a coating film by applying a dispersion in which the conductive fibers and the modified cellulose nanofibers are dispersed in the first liquid onto the first main surface of the first release sheet; and forming the conductive composite film precursor by removing a portion of the first liquid from a second main surface side of the first release sheet, the second main surface being the opposite side of the first main surface; A method for producing a conductive composite film transfer sheet comprising the steps of:

[13] A method for producing the conductive composite film transfer sheet according to appendix

[10] or

[11] , forming a coating film by applying a dispersion in which the conductive fibers and the modified cellulose nanofibers are dispersed in the first liquid onto the first main surface of the first release sheet; forming the conductive composite film precursor by removing a portion of the first liquid from a second main surface side of the first release sheet, the second main surface being the opposite side of the first main surface; and the second release sheet containing the second liquid is laminated on the conductive composite film precursor, thereby sandwiching the conductive composite film precursor between the first release sheet and the second release sheet; A method for producing a conductive composite film transfer sheet comprising the steps of:

[14] A method for manufacturing a conductive composite film transfer sheet according to appendix

[12] or

[13] , in which the first liquid is removed from the second main surface side of the first release sheet by suctioning the second main surface side.

[15] A conductive member comprising a substrate and a conductive composite membrane on the substrate, the conductive composite membrane comprising conductive fibers and modified cellulose nanofibers modified with at least one type of anionic group.

[16] The conductive member according to appendix

[15] , wherein the amount of the anionic group introduced into the modified cellulose nanofiber is in the range of 0.1 to 3.5 mmol / g.

[17] The conductive member according to appendix

[15] or

[16] , wherein the conductive fibers include at least carbon nanotubes.

[18] The conductive member according to appendix

[17] , wherein the carbon nanotubes are single-walled carbon nanotubes.

[19] A conductive member comprising a substrate and a conductive composite film on the substrate, wherein the conductive composite film is a transferred film of the conductive composite film precursor contained in the conductive composite film transfer sheet described in any one of appendices [1] to

[11] .

[20] A conductive member according to appendix

[19] , wherein the substrate and the conductive composite film are bonded by van der Waals forces generated by the removal of the first liquid when the conductive composite film precursor is transferred from the conductive composite film transfer sheet to the substrate.

[21] The conductive composite film contains the conductive fiber and the modified cellulose nanofiber in a compounding ratio of 0.5 to 100 parts by mass of the modified cellulose nanofiber to 1 part by mass of the conductive fiber, and has a surface resistance of 0.1 to 10,000 Ω / cm 2 The conductive member according to any one of appendices

[15] to

[20] , having a thickness of 10 μm or less.

[22] The conductive member according to any one of appendices

[15] to

[21] , wherein the surface roughness of the conductive composite film is an arithmetic mean height of 0.5 μm or less.

[23] The conductive member according to any one of appendices

[15] to

[22] , wherein the conductive composite film is a free-standing film and has a region supported by the substrate and a region not supported by the substrate.

[24] A method for producing a conductive member comprising a substrate and a conductive composite film on the substrate, the method comprising: Contacting the conductive composite film precursor contained in the conductive composite film transfer sheet according to any one of appendices [1] to [9] with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; and Peeling off the first release sheet. A method for manufacturing a conductive member, comprising:

[25] A method for producing a conductive member comprising a substrate and a conductive composite film on the substrate, the method comprising: Peeling off the second release sheet from the conductive composite film transfer sheet according to appendix

[10] or

[11] ; contacting the conductive composite film precursor with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; and Peeling off the first release sheet. A method for manufacturing a conductive member, comprising:

[26] A conductive composite membrane comprising conductive fibers and modified cellulose nanofibers modified with at least one anionic group.

[27] The conductive composite membrane according to appendix

[26] , wherein the amount of the anionic group introduced into the modified cellulose nanofiber is in the range of 0.1 to 3.5 mmol / g.

[28] The conductive composite film according to appendix

[26] or

[27] , wherein the conductive fibers include at least carbon nanotubes.

[29] The conductive composite film according to appendix

[28] , wherein the carbon nanotubes are single-walled carbon nanotubes.

[30] A conductive composite film which is a transferred film of the conductive composite film precursor contained in the conductive composite film transfer sheet according to any one of appendices [1] to

[11] .

[31] The conductive fiber and the modified cellulose nanofiber are contained in a compounding ratio of 0.5 to 100 parts by mass of the modified cellulose nanofiber to 1 part by mass of the conductive fiber, and the surface resistance value is 0.1 to 10,000 Ω / cm 2 The conductive composite film according to any one of appendices

[26] to

[30] , having a thickness of 10 μm or less.

[32] The conductive composite film according to any one of appendices

[26] to

[31] , wherein the conductive composite film has a surface roughness of 0.5 μm or less in arithmetic mean height.

[33] A conductive member comprising a substrate and a conductive film on the substrate, the conductive film containing carbon nanotubes and having a surface resistance of 0.1 to 10,000 Ω / cm. 2 and the thickness is A conductive member having a surface roughness of 0.5 μm or less in arithmetic mean height and a surface roughness of 10 μm or less.

[34] The conductive member according to appendix

[33] , wherein the conductive film is a free-standing film and has an area supported by the substrate and an area not supported by the substrate.

[35] A method for producing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, the method comprising: Contacting the conductive composite film precursor contained in the conductive composite film transfer sheet according to any one of appendices [1] to [9] with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; peeling off the first release sheet; and removing the modified cellulose nanofibers. A method for manufacturing a conductive member, comprising:

[36] A method for producing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, the method comprising: Peeling off the second release sheet from the conductive composite film transfer sheet according to appendix

[10] or

[11] ; contacting the conductive composite film precursor with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; peeling off the first release sheet; and removing the modified cellulose nanofibers. A method for manufacturing a conductive member, comprising:

[37] A method for producing a conductive member according to appendix

[35] or

[36] , in which the modified cellulose nanofibers are removed by thermal decomposition or by dissolution in a solvent.

[38] Carbon nanotubes are included, and the surface resistance is 0.1 to 10,000 Ω / cm. 2 A conductive film having a thickness of 10 μm or less and a surface roughness of 0.5 μm or less in arithmetic mean height.

Claims

1. The conductive composite membrane comprises a first release sheet made of a liquid-permeable sheet, and a conductive composite membrane precursor supported on a first main surface of the first release sheet and including conductive fibers and modified cellulose nanofibers modified with at least one anionic group; A conductive composite film transfer sheet in which the first release sheet and the conductive composite film precursor contain a first liquid, the total mass of the first liquid contained in the first release sheet and the conductive composite film precursor is 50 mass% or more relative to the mass of the first release sheet, and the first liquid contains water, ethanol, or a mixed solvent thereof.

2. The conductive composite film transfer sheet according to claim 1, wherein the first liquid contained in the first release sheet and the conductive composite film precursor is a dispersion solvent of a dispersion containing the conductive fiber and the modified cellulose nanofiber used in forming the conductive composite film precursor.

3. The conductive composite film transfer sheet according to claim 1 or 2, wherein the amount of the anionic group introduced into the modified cellulose nanofiber is in the range of 0.1 to 3.5 mmol / g.

4. The conductive composite film transfer sheet according to claim 1 , wherein the conductive fibers contain at least carbon nanotubes.

5. The conductive composite film transfer sheet according to claim 4, wherein the carbon nanotubes are single-walled carbon nanotubes.

6. 6. The conductive composite film transfer sheet according to claim 1, wherein the first release sheet is a porous sheet having pores with a diameter ranging from 0.05 [mu]m to 5 [mu]m.

7. 7. The conductive composite film transfer sheet according to claim 1, wherein the first release sheet contains polytetrafluoroethylene.

8. A conductive composite film transfer sheet described in any one of claims 1 to 7, further comprising a second release sheet, the conductive composite film precursor being sandwiched between the first release sheet and the second release sheet, and the second release sheet containing a second liquid.

9. The conductive composite film transfer sheet according to claim 8 , wherein the second liquid is the same as the first liquid.

10. A method for producing the conductive composite film transfer sheet according to any one of claims 1 to 7, comprising: forming a coating film by applying a dispersion in which the conductive fibers and the modified cellulose nanofibers are dispersed in the first liquid onto the first main surface of the first release sheet; and forming the conductive composite film precursor by removing a portion of the first liquid from a second main surface side of the first release sheet, the second main surface being the opposite side of the first main surface; A method for producing a conductive composite film transfer sheet comprising the steps of:

11. A method for producing the conductive composite film transfer sheet according to claim 8 or 9, comprising: forming a coating film by applying a dispersion in which the conductive fibers and the modified cellulose nanofibers are dispersed in the first liquid onto the first main surface of the first release sheet; forming the conductive composite film precursor by removing a portion of the first liquid from a second main surface side of the first release sheet, the second main surface being the opposite side of the first main surface; and the second release sheet containing the second liquid is laminated on the conductive composite film precursor, thereby sandwiching the conductive composite film precursor between the first release sheet and the second release sheet; A method for producing a conductive composite film transfer sheet comprising the steps of:

12. The method for producing a conductive composite film transfer sheet according to claim 10 or 11, wherein the first liquid is removed from the second main surface side of the first release sheet by suctioning the second main surface side.

13. A conductive member comprising a substrate and a conductive composite film on the substrate, wherein the conductive composite film is a free-standing film having an area supported by the substrate and an area not supported by the substrate, and is a transferred film of the conductive composite film precursor contained in the conductive composite film transfer sheet described in any one of claims 1 to 9.

14. The conductive member described in claim 13, wherein the substrate and the conductive composite film are bonded by van der Waals forces generated by the removal of the first liquid when the conductive composite film precursor is transferred from the conductive composite film transfer sheet to the substrate.

15. The conductive composite film contains the conductive fibers and the modified cellulose nanofibers in a compounding ratio of 0.5 to 100 parts by mass of the modified cellulose nanofibers to 1 part by mass of the conductive fibers, and has a surface resistance of 0.1 to 10,000 Ω / cm ２ and the thickness is The conductive member according to claim 13 or 14, having a thickness of 10 μm or less.

16. 16. The conductive member according to claim 13, wherein the conductive composite film has a surface roughness of 0.5 [mu]m or less in terms of arithmetic mean height.

17. A method for producing a conductive member comprising a substrate and a conductive composite film on the substrate, the method comprising: contacting the conductive composite film precursor contained in the conductive composite film transfer sheet according to any one of claims 1 to 7 with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; and Peeling off the first release sheet. A method for manufacturing a conductive member, comprising:

18. A method for producing a conductive member comprising a substrate and a conductive composite film on the substrate, the method comprising: Peeling off the second release sheet from the conductive composite film transfer sheet according to claim 8 or 9; contacting the conductive composite film precursor with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; and Peeling off the first release sheet. A method for manufacturing a conductive member, comprising:

19. A method for manufacturing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, the method comprising: contacting the conductive composite film precursor contained in the conductive composite film transfer sheet according to any one of claims 1 to 7 with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; peeling off the first release sheet; and removing the modified cellulose nanofibers. A method for manufacturing a conductive member, comprising:

20. A method for manufacturing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, the method comprising: Peeling off the second release sheet from the conductive composite film transfer sheet according to claim 8 or 9; contacting the conductive composite film precursor with the substrate; removing the first liquid contained in the first release sheet and the conductive composite film precursor by heating or drying; peeling off the first release sheet; and removing the modified cellulose nanofibers. A method for manufacturing a conductive member, comprising:

21. The method for producing a conductive member according to claim 19 or 20, wherein the modified cellulose nanofibers are removed by thermal decomposition or dissolution in a solvent.

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