Conductive composite film transfer sheet, method for manufacturing the same, and method for manufacturing a conductive member

Abstract

To provide: a conductive composite film transfer sheet capable of easily transferring a conductive film having excellent conductivity, smoothness and film strength; a conductive film having excellent conductivity, smoothness and film strength; and a conductive member including the conductive film.SOLUTION: An embodiment of the invention provides a conductive composite film transfer sheet including a first release sheet composed of a liquid permeable sheet, and a conductive composite film precursor that is supported on a first main surface of the first release sheet and contains a conductive fiber and a micronized cellulose. The first release sheet and the conductive composite film precursor contain a first liquid in the conductive composite film transfer sheet.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a conductive composite film transfer sheet, a conductive member, methods for producing the same, and a conductive film. Here, the term "conductive film" is a concept encompassing conductive composite films. [Background Art]

[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 produced by a sputtering method. The sputtering method is excellent in that it can form a conductive film with a low surface resistance even for a relatively large area. However, it has the drawbacks of requiring large-scale equipment and having a low film formation rate. In addition, since film formation is performed by heating a conductive material in a vacuum apparatus, it is limited to materials that can withstand such an environment.

[0004] Attempts have also been made to produce transparent conductive films by a coating method. In the conventional coating method, a conductive coating in which conductive fine particles are dispersed in a binder solution is applied onto a substrate, dried, and cured to form a conductive film. The coating method has advantages in that it easily forms a large-area conductive film, requires simple equipment, has high productivity, and can produce a conductive film at a lower cost than the sputtering method. In the coating method, conductive fine particles contact each other to form electrical paths, thereby developing conductivity. However, in a conductive film produced by a conventional coating method, the presence of the binder results in insufficient contact between the conductive fine particles, which causes the drawback that the obtained conductive film has a high electrical resistance value (poor conductivity), thus limiting its applications.

[0005] In the coating method, conductive fibers such as carbon nanotubes, which relatively more easily form contacts than conductive fine particles, can also be used. However, generally, a small amount of binder is mixed into the coating for the purposes of controlling the coating thickness during conductive film formation and ensuring the film strength after formation, which results in reduced conductivity.

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

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

[0008] Patent Document 3 discloses several methods for manufacturing a conductive molded article having a conductive layer on the surface of a substrate, using ultrafine conductive fibers. One of these methods involves applying a dispersion of ultrafine conductive fibers onto a release film, drying the layer, pressing it onto the substrate surface via an adhesive layer, and then peeling off the release film to transfer the material. However, there is no specific description of the adhesive layer, and the transfer method itself is not described in detail.

[0009] Patent Document 4 describes a method for manufacturing a transfer conductive film, comprising a conductive layer formed by applying a coating solution containing ultrafine conductive fibers, which is thickened by mixing a resin binder with a volatile solvent, onto a release film and drying it, and an adhesive layer made of an ultraviolet-curable resin composition laminated on this conductive layer.

[0010] Non-patent document 1 describes a method for manufacturing 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 Publication No. 2002-347150 [Patent Document 3] Patent No. 3903159 [Patent Document 4] Japanese Patent Publication No. 2010-269569 [Non-patent literature]

[0012] [Non-Patent Document 1] Surface Chemistry, P587, Vol.64, No.11, 2013 [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention aims to provide a conductive composite film transfer sheet that allows for the easy transfer of conductive films with excellent conductivity, smoothness, and film strength. Furthermore, the present invention aims to provide a conductive film with excellent conductivity, smoothness, and film strength, and a conductive member comprising the above-mentioned conductive film. [Means for solving the problem]

[0014] As a result of diligent research to solve the above problems, the present inventors have discovered that by applying a dispersion containing carbon nanotubes and finely milled cellulose onto a release sheet made of a liquid-permeable sheet, and creating a conductive composite film transfer sheet containing a portion of the dispersion solvent of the dispersion, a conductive film with excellent conductivity, smoothness, and film strength can be efficiently and simply transferred regardless of the material or shape (curved surface, flat surface, etc.) of the substrate to be transferred, thus completing the present invention.

[0015] According to a first aspect of the present invention, a conductive composite film transfer sheet is provided, comprising a first release sheet made of a liquid-permeable sheet, and a conductive composite film precursor supported on the first main surface of the first release sheet and containing conductive fibers and finely milled cellulose, 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, a conductive composite film transfer sheet is provided, wherein the conductive composite film transfer sheet according to the first aspect further comprises a second release sheet, 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 the third aspect of the present invention, there is provided a method for producing a conductive composite film transfer sheet according to the first aspect, which comprises forming a coating film by applying a dispersion liquid, in which the conductive fibers and the micronized cellulose are dispersed in a first liquid, onto the first main surface of the first release sheet, and forming the conductive composite film precursor by removing part of the first liquid from the second main surface side that is the back surface of the first main surface of the first release sheet, a method for producing a conductive composite film transfer sheet comprising the above steps is provided.

[0018] According to the fourth aspect of the present invention, there is provided a method for producing a conductive composite film transfer sheet according to the second aspect, which comprises forming a coating film by applying a dispersion liquid, in which the conductive fibers and the micronized cellulose are dispersed in a first liquid, onto the first main surface of the first release sheet, forming the conductive composite film precursor by removing part of the first liquid from the second main surface side that is the back surface of the first main surface of the first release sheet, and laminating the second release sheet containing the second liquid onto the conductive composite film precursor, so as to sandwich 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 above steps is provided.

[0019] According to the fifth aspect of the present invention, there is provided a conductive member comprising a base material and a conductive composite film on the base material, wherein the conductive composite film comprises conductive fibers and micronized cellulose.

[0020] According to the sixth aspect of the present invention, there is provided a method for producing a conductive member comprising a base material and a conductive composite film on the base material, 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 base material, 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 including the above is provided.

[0021] According to a seventh aspect of the present invention, a method for manufacturing a conductive member comprising a substrate and a conductive composite film on the substrate, Peeling the second release sheet from the conductive composite film transfer sheet relating to the second side surface, bringing the conductive composite film precursor into contact with the substrate, The first liquid contained in the first release sheet and the conductive composite film precursor is removed by heating or drying, and Remove the first release sheet mentioned above. A method for manufacturing a conductive member including the above is provided.

[0022] According to the eighth aspect of the present invention, a conductive composite film comprising conductive fibers and finely milled cellulose is provided.

[0023] According to the ninth aspect of the present invention, the conductive member comprises a substrate and a conductive film on the substrate, wherein the conductive film contains carbon nanotubes and has a surface resistance of 0.1 to 10000 Ω / cm². 2 A conductive member is provided that is within the range, has a thickness of 10 μm or less, and has a surface roughness of 0.5 μm or less in arithmetic mean height.

[0024] According to a tenth aspect of the present invention, a method for manufacturing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, The conductive composite film precursor contained in the conductive composite film transfer sheet relating to the first side surface is brought into contact with the substrate. The first liquid contained in the first release sheet and the conductive composite film precursor is removed by heating or drying. To peel off the first release sheet mentioned above, and Remove the above-mentioned finely ground cellulose. A method for manufacturing a conductive member including the above is provided.

[0025] According to an eleventh aspect of the present invention, a method for manufacturing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, Peeling the second release sheet from the conductive composite film transfer sheet relating to the second side surface, bringing the conductive composite film precursor into contact with the substrate, The first liquid contained in the first release sheet and the conductive composite film precursor is removed by heating or drying. To peel off the first release sheet mentioned above, and Removing the aforementioned finely ground cellulose A method for manufacturing a conductive member including the above is provided.

[0026] According to the twelfth aspect of the present invention, the material contains carbon nanotubes and has a surface resistance of 0.1 to 10000 Ω / cm². 2 A conductive film is provided that is within the specified range, has a thickness of 10 μm or less, and has a surface roughness of 0.5 μm or less in arithmetic mean height. [Effects of the Invention]

[0027] According to the present invention, a conductive composite film transfer sheet is provided that allows for the easy transfer of a conductive film having excellent conductivity, smoothness, and film strength; a conductive film having excellent conductivity, smoothness, and film strength; and a conductive member comprising the above-mentioned conductive film is provided. [Brief explanation of the drawing]

[0028] [Figure 1] A schematic cross-sectional view showing an example of a conductive composite film transfer sheet according to the first embodiment of the present invention. [Figure 2] A schematic cross-sectional view showing an example of a conductive composite film transfer sheet according to a second embodiment of the present invention. [Figure 3] A schematic cross-sectional view showing an example of a conductive member according to a third embodiment of the present invention. [Figure 4] A schematic cross-sectional view showing an example of a conductive member according to the fourth embodiment of the present invention. [Figure 5] Image of the conductive composite film on the conductive component manufactured in Example 1, observed under an electron microscope. [Modes for carrying out the invention]

[0029] This embodiment will be described below with reference to the drawings. Elements having similar or identical functions will be given the same reference numerals, and redundant descriptions will be omitted.

[0030] [First Embodiment] Figure 1 is a schematic cross-sectional view showing an example of a conductive composite film transfer sheet according to the first embodiment of the present invention. The conductive composite film transfer sheet 10 shown in Figure 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 (hereinafter referred to as the "first main surface") 1a of the first release sheet 1, and containing conductive fibers 2 and finely milled cellulose 3. 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 the dispersion solvent for the dispersion of conductive fibers and finely ground cellulose (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 moistened with the first liquid. This 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 van der Waals forces generated when the first liquid is removed from the conductive composite film transfer sheet 10 by heating or drying during transfer firmly bond the transfer target and the conductive composite film.

[0032] The amount of the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is set appropriately from the viewpoint of the film-forming properties of the conductive composite film precursor 4a and the transferability of the conductive composite film precursor 4a to the transfer target. 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% by mass or more, more preferably 50% by mass or more and 200% by mass or less, even more preferably 100% by mass or more and 180% by mass or less, and particularly preferably 120% by mass or more and 170% by mass or less, relative to the mass of the first release sheet.

[0033] (Conductive composite film precursor) The conductive composite film precursor 4a contains conductive fibers, finely milled cellulose, and a first liquid. The conductive composite film precursor 4a is formed by removing a portion of the first liquid from a coating film consisting of a composite dispersion in which conductive fibers and finely milled cellulose are dispersed in the first liquid. The removal of the first liquid is performed by suctioning the first liquid from the back surface (hereinafter referred to as the "second main surface") 1b side of the first main surface 1a of the first release sheet 1. There are no particular restrictions on the film thickness of the conductive composite film precursor 4a, and it is adjusted as appropriate depending on the application of the conductive composite film precursor 4a. In one embodiment, the film thickness of the conductive composite film precursor 4a is set as appropriate so that the film thickness of the conductive composite film 4b, which is a transfer film and will be described later, is 10 μm or less. The film thickness of the conductive composite film precursor 4a can be adjusted by the amount of composite dispersion applied, the concentration of conductive fibers and finely milled cellulose in the composite dispersion, etc.

[0034] (Conductive fiber) Examples of conductive fibers used in this embodiment include carbon nanotubes (CNTs), carbon nanohorns, carbon nanowires, carbon nanofibers, and graphite fibril carbon fibers; metal nanotubes and nanowires of platinum, gold, silver, nickel, and silicon; and metal oxide nanotubes and nanowires of zinc oxide. The diameter of the conductive fiber is preferably 0.3 nm to 100 nm, and the length is preferably 0.1 μm to 20 μm, and more preferably 0.1 μm to 10 μm. Among these conductive fibers, carbon nanotubes are particularly preferable because they have an extremely small diameter of 0.3 to 80 nm and a large aspect ratio. Therefore, they do not significantly hinder light transmission, making them preferable from the viewpoint of obtaining a transparent conductive composite film. Furthermore, because carbon nanotubes have excellent conductivity, the surface resistance of the conductive composite film can also be reduced. 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 (MWNTs) and single-walled carbon nanotubes (SWNTs). Single-walled carbon nanotubes have lower resistance values ​​compared to multi-walled carbon nanotubes and are therefore more preferable.

[0036] Multiwalled carbon nanotubes (MWNTs) are concentrically arranged tubes consisting of numerous cylindrical carbon walls of different diameters that are closed around a central axis. The carbon walls are formed in a hexagonal network structure. In some multiwalled carbon nanotubes, the carbon walls are spirally arranged to form multiple layers. In this embodiment, multiwalled carbon nanotubes that can be used have, in one example, 2 to 30 layers of carbon walls, and in another example, 2 to 15 layers of carbon walls. Typically, in multiwalled carbon nanotubes, each carbon nanotube is dispersed separately from one another. In other cases, 2 to 3 layers of carbon nanotubes may form bundles and be dispersed as described above.

[0037] Single-walled carbon nanotubes (SWNTs) have a single layer of carbon wall that is cylindrically closed around a central axis. As mentioned above, single-walled carbon nanotubes are more preferable than multi-walled carbon nanotubes because they have a lower resistance. This carbon wall is formed in a hexagonal network structure. It is difficult to disperse these single-walled carbon nanotubes individually. Two or more tubes form bundles, and these bundles are intertwined with each other. However, these bundles do not aggregate, nor are they intricately intertwined with each other. The bundles simply cross each other, contact at their intersections, and are uniformly dispersed on the surface. A preferred bundle of single-walled carbon nanotubes consists of 10 to 50 tubes. However, single-walled carbon nanotubes that are separated and dispersed individually can also be suitably used in this embodiment.

[0038] (Finely processed cellulose) The micronized cellulose used in this embodiment refers to cellulose in which at least one side of its structure is on the order of nanometers, and there are no particular limitations on its raw materials or preparation methods. Typically, micronized cellulose has a fibrous shape derived from a microfibril structure and is a concept that includes cellulose nanofibers (CNF). In one form, the micronized cellulose is preferably cellulose nanofibers, and its average fiber diameter is, in one example, 1 nm to 1000 nm, and in another example, 1 nm to 200 nm, and its average fiber length is, in one example, 100 nm to 10 mm, in another example, 100 nm to 3000 nm, and in yet another example, 100 nm to 1000 nm. Here, the average fiber diameter and average fiber length can be obtained by averaging the fiber diameter (fiber width) and fiber length obtained from observing each fiber (20 measurement samples) using an atomic force microscope (AFM).

[0039] The finely milled cellulose is uniformly dispersed in a composite dispersion containing conductive fibers such as carbon nanotubes, thereby suppressing the aggregation of the conductive fibers while enabling three-dimensional contact between them. As a result, the conductive composite film described later, which is a transfer film of the conductive composite film precursor 4a formed from this composite dispersion, has improved smoothness and a superior appearance compared to a film made solely of conductive fibers, and also exhibits superior conductivity even when the proportion of finely milled cellulose is higher than the proportion of conductive fibers.

[0040] The micronized cellulose may be modified micronized cellulose in which a modifying group has been introduced to one or more hydroxyl groups in the molecule, or it may be unmodified micronized cellulose in which no modifying group has been introduced to any hydroxyl groups in the molecule. Examples of modifying groups introduced in modified micronized cellulose include cationic groups, anionic groups, and hydrophobic groups. In this embodiment, one type selected from modified micronized cellulose and unmodified micronized cellulose may be used alone, or two or more types may be used in combination.

[0041] The modified cationic group may be, for example, a group containing onium, such as ammonium, phosphonium, or sulfonium, and is usually a group with a molecular weight of about 10,000 or less. Specifically, examples of cationic groups include ammonium such as primary ammonium, secondary ammonium, tertiary ammonium, and quaternary ammonium, phosphonium, sulfonium, or groups containing any of these. By introducing the above cationic group into the micronized cellulose, the dispersibility in water is further improved. The micronized cellulose may be, for example, a cationic modified cellulose nanofiber in which at least one of the above-mentioned cationic groups is introduced into one or more hydroxyl groups in the molecule.

[0042] Examples of anionic groups that can be used as modifying groups include carboxyl groups, sulfonic acid groups, phosphate ester groups, or groups selected from derivatives thereof. By introducing the above anionic groups into the micronized cellulose, the dispersibility in water is further improved as these anionic groups repel each other in water. The carboxyl groups, sulfonic acid groups, and phosphate ester groups may be in acid form or salt form. Specific examples of derivatives include, for example, aldehyde groups, ester groups, or amide groups represented by -COO-NR2 (where R represents a hydrogen atom, alkyl group, benzyl group, phenyl group, hydroxyalkyl group, etc., and the two Rs may be the same or different) as groups derived from carboxyl groups. The micronized cellulose may be, for example, an anionically modified cellulose nanofiber in which at least one of the above-mentioned anionic groups is introduced into one or more hydroxyl groups in the molecule.

[0043] As the raw material for micronized cellulose, for example, wood pulp obtained from coniferous or broad-leaved trees, recycled paper pulp, cotton, etc., can be used. Unmodified micronized cellulose and modified micronized cellulose can be produced by known methods.

[0044] Unmodified finely cellulose can be obtained, for example, by mechanical defibration using known high mechanical shear forces such as blenders and grinders on cellulose raw materials such as pulp. It has been reported that this method has yielded unmodified cellulose nanofibers with an average fiber diameter in the range of 10 nm to 50 nm and an average fiber length in the range of 1 μm to 10 mm.

[0045] Modified micronized cellulose can be obtained, for example, by introducing modified groups such as cationic or anionic groups into the cellulose raw material through chemical modification treatment to make it easier to micronize, followed by a low-energy mechanical defibrillation process similar to that of a household mixer. By introducing anionic or cationic groups into the hydroxyl groups contained in the cellulose, solvents can more easily penetrate between the cellulose microfibril structures due to osmotic pressure, significantly reducing the energy required to micronize the cellulose raw material.

[0046] Modified micronized cellulose may, in one form, be TEMPO-oxidized cellulose nanofibers. TEMPO-oxidized cellulose nanofibers are carboxyl group-containing cellulose nanofibers obtained by selectively oxidizing the surface of cellulose microfibers using 2,2,6,6-tetramethylpiperidinyl-1-oxy radical (TEMPO), a relatively stable N-oxyl compound, as a catalyst (TEMPO oxidation reaction). The TEMPO oxidation reaction allows for environmentally friendly chemical modification that proceeds in an aqueous system at room temperature and atmospheric pressure. When applied to cellulose in wood, the reaction does not proceed inside the crystal, and only the alcoholic primary carbon atoms of the cellulose molecular chains on the crystal surface can be selectively converted to carboxyl groups.

[0047] This TEMPO-oxidized cellulose nanofiber is known to have a lower decomposition temperature compared to anion-modified micronized cellulose obtained by other manufacturing methods. Specifically, while anion-modified cellulose nanofiber obtained by other manufacturing methods decomposes at approximately 300°C, TEMPO-oxidized cellulose nanofiber begins to decompose at 260°C. Therefore, when it is necessary to obtain the conductive film 4c provided in the conductive member 40 according to the fourth embodiment shown in Figure 4, described later, by thermal decomposition and removal of the modified micronized cellulose contained in the conductive composite film, which is a transfer film, it is preferable to use TEMPO-oxidized cellulose nanofiber.

[0048] The average fiber diameter and average fiber length of micronized cellulose can be adjusted by the mechanical defibrillation and / or chemical modification treatments described above. Modified micronized cellulose is subjected to mechanical defibrillation after being made more easily micronized by introducing modification groups (i.e., after chemical modification treatment), as described above, so that the average fiber diameter can be reduced to, for example, 3 nm to 4 nm. For this reason, modified micronized cellulose nanofibers with introduced cationic or anionic groups have better dispersibility than unmodified micronized cellulose nanofibers. For this reason, conductive composite films formed using a composite dispersion of modified micronized cellulose have better smoothness and conductivity than conductive composite films using unmodified micronized cellulose. Furthermore, when anionic modified micronized cellulose with introduced anionic groups is used, conductivity is further improved. This is presumed to be because the anionic groups act as electron donors, allowing the conductivity of the conductive fibers to be stably maintained.

[0049] Commercially available micronized cellulose can be used. As unmodified cellulose nanofibers, for example, the ELLEX®-S series from Daio Paper Corporation and the Celish® series from Daicel Mirise Co., Ltd. can be used. As modified micronized cellulose, for example, as carboxyl group-containing cellulose nanofibers, Nippon Paper Industries Ltd.'s TEMPO-oxidized cellulose nanofiber "Selenpia" (registered trademark) and as sulfonic acid group-containing cellulose nanofibers, Marusumi Paper Co., Ltd.'s "Stellafine" (registered trademark) can be used. Furthermore, as quaternary group-containing cellulose nanofibers, cationic cellulose nanofibrils sold by Cellulose Lab Inc. can be used.

[0050] The degree of cation substitution per glucose unit of cation-modified micronized cellulose is preferably 0.01 or higher, more preferably 0.02 or higher, and even more preferably 0.03 or higher. The upper limit is preferably 0.40 or lower, more preferably 0.30 or lower, and even more preferably 0.20 or lower. Here, the degree of cation substitution can be measured by the nitrogen content determined by elemental analysis.

[0051] In anionically modified micronized cellulose, the amount of anionic groups introduced is preferably in the range of 0.1 to 3.5 mmol / g, for example. From the viewpoint of ease of manufacture, it is more preferably in the range of 1.0 to 2.0 mmol / g. Here, the amount of modified groups introduced can be measured by conductivity titration using a 0.5N sodium hydroxide aqueous solution.

[0052] The mixing ratio of conductive fibers and finely milled cellulose contained in conductive composite film precursor 4a is such that the conductivity of the conductive composite film is 10,000 Ω / cm². 2To achieve the following, it is preferable that the amount of finely milled cellulose be 100 parts by mass or less per 1 part by mass of conductive fiber. From the viewpoint of maintaining a surface resistance equivalent to that of a conductive film which is a single film of carbon nanotubes, it is more preferable that the amount of finely milled cellulose be 20 parts by mass or less per 1 part by mass of conductive fiber. Furthermore, from the viewpoint of smoothness and transferability, it is preferable that the amount of finely milled cellulose be 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 1 part by mass of conductive fiber.

[0053] (1st liquid) The first liquid is not particularly limited as long as it is a solvent that can disperse conductive fibers and finely milled cellulose, and any of them can be used. In this embodiment, when carbon nanotubes are used as conductive fibers, the first liquid can be water, acetone, methyl ethyl ketone, methanol, ethanol, isopropanol, etc., and may be a mixture of two or more solvents selected from these. Water or alcohol is preferred, and a mixture of these solvents may also be used. As for alcohols, highly polar ones are preferred, such as methanol, ethanol, and isopropyl alcohol.

[0054] (Conductive additive) In this embodiment, the conductive composite film precursor 4a may contain conductive additives for the purpose of improving conductivity and film strength. Examples of such conductive additives include conductive polymers such as PEDOT / PSS, polypyrrole, and polyaniline, and conductive metals such as fine particles or fibers of gold, silver, and copper. Examples of metal fibers include silver nanowires. When using conductive additives, it is preferable that the proportion of conductive additives in the conductive composite film precursor 4a does not exceed the proportion of conductive fibers. If the proportion of conductive additives is greater than the proportion of conductive fibers, the film may not peel off the first release sheet during transfer, and transfer may not be possible.

[0055] (Surfactants) 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, it is possible to bring out the conductivity of the conductive fibers. In one embodiment, a composite dispersion in which conductive fibers and finely ground cellulose are uniformly dispersed can be obtained by mixing a dispersion of conductive fibers pre-dispersed with a surfactant with a dispersion of finely ground cellulose and subjecting it to ultrasonic treatment or the like.

[0056] Specific examples of surfactants include sodium dodecyl sulfate; naphthalene sulfonic acid formalin condensate salts such as the sodium salt of naphthalene sulfonic acid formalin condensate (Kao Corporation's "Demol N", "Demol RN", and "Mighty 150") and the NH3 salt of naphthalene sulfonic acid formalin condensate (Kao Corporation's "Demol AS"); methylnaphthalene sulfonic acid formalin condensate salts such as the sodium salt of methylnaphthalene sulfonic acid formalin condensate (Kao Corporation's "Demol MS"); butylnaphthalene / naphthalene sulfonic acid formalin condensate sodium salt (Kao Corporation's "Demol SNB"); naphthol methylene sulfonic acid formalin condensate sodium salt (Kao Corporation's "Demol SSL"); and creosote oil sulfonic acid formalin condensate sodium salt (Kao Corporation's "Demol C"). In addition, lignin sulfonates, which are naturally occurring polycondensed sulfonates, can be mentioned. Examples of polymer-based aromatic surfactants include sodium polystyrene sulfonate (such as "Sodium Polystyrene Sulfonate PS-1, PS-35, PS-50, and PS-100" manufactured by Toyo Soda Co., Ltd.).

[0057] (First release sheet) The first release sheet 1 is a liquid permeable sheet. Any liquid permeable sheet that can be used in this embodiment is one that has permeability to remove the first liquid from a composite dispersion of conductive fibers and finely milled cellulose while leaving the conductive fibers and finely milled cellulose on the sheet. Specific examples include various porous membrane filters and nonwoven fabric filters. The pore size of the first release sheet 1 is set appropriately from the above viewpoint, and for example, a liquid permeable sheet with a suitable pore size can be selected according to the length of the conductive fibers. In this embodiment, the pore size of the first release sheet is preferably 0.05 μm to 5.0 μm, and more preferably 0.1 μm to 2.0 μm. Here, the pore size is a value measured by a method in accordance with the bubble point test method specified in JIS K3832.

[0058] 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, and polycarbonate, 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 restrictions on the thickness of the first release sheet 1; for example, a thickness of 10 to 200 μm can be used.

[0059] (Manufacturing method) The conductive composite film transfer sheet 10 according to the first embodiment shown in Figure 1 can be obtained, for example, as follows. First, a composite dispersion film is obtained by applying a composite dispersion in which conductive fibers 2 and finely ground cellulose 3 are dispersed in a first liquid onto the first main surface 1a of the first release sheet 1. The composite dispersion can be prepared, for example, by adding a finely ground cellulose dispersion, with the first liquid as the dispersion solvent, to a dispersion of conductive fibers, with the first liquid as the dispersion solvent, while maintaining a uniform dispersion state. The concentration of 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 finely ground cellulose may be, for example, in the range of 0.001% to 0.5% by mass, and the two dispersions are mixed so that the conductive fibers and modified cellulose are in the above-mentioned mixing ratio. The method of applying the composite dispersion is not particularly limited, and the composite dispersion may be poured directly onto the first main surface 1a, or known application methods such as spray application can be used.

[0060] Next, a portion of the first liquid is removed from the second main surface 1b side, which is the back surface of the first main surface 1a of the first release sheet 1 on which the composite dispersion coating film is formed, thereby forming a conductive composite film precursor 4a of any thickness. By removing a portion of the first liquid from the second main surface 1b side of the first release sheet 1, adhesion is achieved between the conductive fibers 2, between the conductive fibers 2 and the finely milled cellulose 3, and among the finely milled cellulose 3, and the conductive composite film precursor 4a can be obtained on the first release sheet 1. At this time, the first release sheet 1 and the conductive composite film precursor 4a are in a wet state due to the first liquid that remains without being removed. If these components are dry and not wet, or if the amount of first liquid contained is too small, problems such as inability to transfer the conductive composite film precursor 4a or partial transfer failure may occur. The preferred range for 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.

[0061] Furthermore, let's consider the case where the conductive fiber dispersion and the micronized cellulose dispersion are used separately before mixing, instead of using the composite dispersion. Specifically, when comparing the case where the conductive fiber dispersion is first applied to the first release sheet 1 to form a coating film, and then the micronized cellulose dispersion is applied on this coating film to form a coating film, with the embodiment using the composite dispersion, the embodiment is particularly superior in terms of transferability and smoothness. In other words, by using the composite dispersion and forming a conductive composite film precursor 4a containing conductive fibers 2 and micronized cellulose 3, transferability and smoothness are improved (see Example 1 and Reference Example 2 below). Also, if the order in which the two dispersions are applied is reversed, transfer failure is likely to occur, and it is difficult to obtain a transfer film (see Reference Example 3 below).

[0062] The removal of the first liquid from the second main surface 1b side of the first release sheet 1 is appropriately performed all at once by suctioning the first liquid. Examples of suction methods include vacuum suction using an aspirator or a method of absorbing the first liquid by bringing a water-absorbing or oil-absorbing material into contact with the second main surface 1b.

[0063] In transfers using the conductive composite film transfer sheet 10, depending on the material to be transferred, poor affinity with the first liquid contained in the conductive composite film precursor 4a may occur, potentially resulting in failure to transfer or partial transfer defects. In this case, the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a of the conductive composite film transfer sheet 10 can be replaced with a liquid that has good affinity with the material to be transferred. The replacement of the first liquid contained in the conductive composite film transfer sheet 10 with another liquid can be carried out, for example, as follows.

[0064] This section describes the case where the "other liquid" with good affinity to the transfer target is a liquid that is compatible with the first liquid (hereinafter referred to as the "second liquid"). Here, "compatible" means that when the first liquid and the second liquid are mixed, they do not separate and no interface is formed.

[0065] As a method for replacing the first liquid contained in the conductive composite film transfer sheet 10 with a second liquid that is compatible with the first liquid, first, the second liquid is applied onto 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 application of the second liquid onto the conductive composite film precursor 4a is carried out in a manner that washes away the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a with the second liquid, and replaces the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a 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. As a result, the first liquid contained in the conductive composite film transfer sheet 10 is replaced with the second liquid, and a conductive composite film transfer sheet 10 can be obtained in which the first release sheet 1 and the conductive composite film precursor 4a are wetted with the second liquid. Here, the application of the second liquid can be carried out in the same manner as the application method for the dispersion described above, and the removal of the liquid from the second main surface 1b side of the first release sheet 1 can be carried out in the same manner as the removal of the first liquid described above.

[0066] [Second Embodiment] Figure 2 is a schematic cross-sectional view 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 Figure 2 is the conductive composite film transfer sheet 10 according to the first embodiment shown in Figure 1, further comprising a second release sheet 5, with the conductive composite film precursor 4a sandwiched between the first release sheet 1 and the second release sheet 5.

[0067] The second release sheet 5 contains the same liquid as the first release sheet 1 and the first liquid contained in the conductive composite film precursor 4a. In the conductive composite film transfer sheet 20, the second release sheet 5 is positioned to sandwich the conductive composite film precursor 4a together with the first release sheet 1 in order to prevent the conductive film transfer sheet from drying out in order to maintain stable transferability over a long period of time. This ensures the storage stability of the conductive film transfer sheet 20 and improves its convenience.

[0068] 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 that the conductive composite film precursor 4a containing the first liquid does not dry out when laminated with 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 finely ground cellulose 3, absorbent gel sheets such as sodium polyacrylate, polyacrylamide, agar, or carrageenan, or absorbent paper can be used. When alcohol is used as the dispersion solvent (first liquid), various oil-absorbing polymer sheets that absorb and retain the alcohol can be used.

[0069] Furthermore, in the conductive film transfer sheet 20, if the first liquid contained in the first release sheet 1 and the conductive composite film precursor 4a is replaced with the second liquid by the method described above, the liquid contained in the second release sheet 5 will also be the same liquid as the second liquid after replacement.

[0070] The conductive composite film transfer sheet 20 shown in Figure 2 is obtained by laminating a second release sheet 5, which has been thoroughly impregnated with the first liquid beforehand, onto the conductive composite film transfer sheet 10 shown in Figure 1, obtained by the method described above, on the side 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 drying and hardening during the transfer of the conductive composite film precursor 4a, which serves as the transfer layer of the conductive composite film transfer sheet, to the object to be transferred. Therefore, when laminating the second release sheet 5 onto the conductive composite film precursor 4a, it is essential to ensure that the conductive composite film precursor 4a remains wet during the lamination process.

[0071] In the conductive composite film transfer sheet 20, it is preferable that 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 approximately the same as the total mass of the first liquid content 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.

[0072] Furthermore, in both Embodiment 1 and Embodiment 2, the conductive composite film transfer sheet according to this embodiment is preferably stored in a sealed bag or case, such as an aluminum laminate pouch, 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.

[0073] [Third Embodiment] Figure 3 is a schematic cross-sectional view showing an example of a conductive member according to a third embodiment of the present invention. The conductive member 30 shown in Figure 3 comprises a substrate 6 as a transfer subject and a conductive composite film 4b on the substrate 6, which is a transfer film from a conductive composite film transfer sheet 10 or 20 according to this embodiment. The conductive composite film 4b contains conductive fibers 2 and finely milled cellulose 3.

[0074] The conductive member 30 shown in Figure 3 can be obtained, for example, as follows. If the conductive composite film transfer sheet is the conductive composite film transfer sheet 20 according to the second embodiment, first, the second release sheet 5 is peeled off from the conductive composite film transfer sheet 20. Next, the side 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 substrate 6 and the conductive composite film precursor 4a together so that no air bubbles are trapped between them. 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. As a heating means, for example, the second main surface 1b side of the first release sheet 1 may be heated by applying hot air with a dryer or the like, or it may be heated from below with a heater or the like. After removing the first liquid, the first release sheet 1 is peeled off to complete the transfer of the conductive composite film 4b to the substrate 6, and the conductive member 30 can be obtained.

[0075] 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 such as a hair dryer without using special equipment. Therefore, even if the substrate 6 is a substrate with low heat resistance, the conductive composite film 4b can be easily formed.

[0076] 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.

[0077] The conductive composite film according to this embodiment, despite being a composite film of conductive fibers and finely milled cellulose, achieves surface resistance values ​​equivalent to those of a carbon nanotube-only film in some regions, demonstrating excellent conductivity. In one embodiment, the conductive composite film transfer sheet according to this embodiment achieves a surface resistance value of 0.1 to 10,000 Ω / cm². 2A conductive composite film is obtained. Conductive members having such a highly conductive composite film can be used as antistatic bodies, transparent surface heating elements, plasma display panel electrodes, liquid crystal electrodes, organic EL electrodes, touch panels, electromagnetic wave shielding films, etc. According to this embodiment, such conductive members can be obtained by a simple method.

[0078] The conductive composite film according to this embodiment also exhibits excellent smoothness. In one embodiment, a conductive composite film with a surface roughness of 0.5 μm or less in arithmetic mean height (Sa) can be obtained using the conductive composite film transfer sheet according to this embodiment.

[0079] The conductive composite film according to this embodiment allows for easy adjustment of its transmittance, enabling the creation of a conductive composite film with a desired transmittance depending on the application. For example, by using cation-modified or anion-modified finely milled cellulose as the finely milled cellulose, or by increasing the proportion of conductive fibers, a conductive composite film with high transmittance can be obtained. 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. Furthermore, by using unmodified finely milled cellulose as the finely milled cellulose, a conductive composite film with low transmittance can be obtained. A conductive composite film with low transmittance can be applied to conductive films, surface electrode materials, surface heating elements, or applications utilizing light scattering.

[0080] Furthermore, because the conductive composite film according to this embodiment contains conductive fibers and finely milled cellulose, it is more resistant to deformation such as repeated bending compared to inorganic conductive films such as ITO and tin oxide, and can be used as a flexible conductor.

[0081] [Fourth Embodiment] Figure 4 is a schematic cross-sectional view showing an example of a conductive member according to the fourth embodiment of the present invention. The conductive member 40 shown in Figure 4 comprises a substrate 6 as a transfer subject and a conductive film 4c on the substrate 6, which is a transfer film from a conductive composite film transfer sheet according to this embodiment. The conductive film 4c contains conductive fibers 2 but does not contain finely milled cellulose.

[0082] The conductive member 40 shown in Figure 4 can be obtained, for example, by removing the finely milled cellulose 3 from the conductive composite film 4b provided in the conductive member 30 according to the third embodiment shown in Figure 3. Known methods can be used to remove the finely milled cellulose 3 from the conductive composite film 4b. For example, one method involves heating the conductive member 30 to the thermal decomposition temperature of the finely milled cellulose 3, thereby thermally decomposing and removing it. In this case, by using modified finely milled cellulose with a low decomposition temperature, such as the TEMPO-oxidized cellulose nanofibers mentioned above, the limitations on the substrate 6, which is the transfer target, can be relaxed. Another example of a method for removing the finely milled cellulose 3 from the conductive composite film 4b is to dissolve and remove the finely milled cellulose 3 by immersing the conductive member 30 in a predetermined solvent (e.g., an aqueous nitric acid solution).

[0083] The conductive film 4c provided by the conductive member 40 according to this embodiment has substantially the same performance in terms of conductivity, transmittance, smoothness, and film strength as the conductive composite film 4b provided by the conductive member 30 according to the third embodiment described above, and can be used in the various fields described above.

[0084] As described above, the conductive composite film transfer sheet according to this embodiment allows for the formation of highly conductive films on substrates of various shapes by adhering the transfer sheet to the substrate's shape, such as curved surfaces or uneven surfaces, regardless of the substrate's material or type. 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 film transfer sheet according to this embodiment can be applied even when the substrate is hollow in the center or frame-shaped. By transferring the conductive composite film to such a substrate, a conductive film can be obtained that is partially or entirely in contact with the substrate, making it usable as a standalone conductive film. For example, protective films can be manufactured using the conductive composite film transfer sheet according to this embodiment. Moreover, the applications of the conductive film according to this embodiment are not limited to applications requiring conductivity. Thus, the conductive composite film transfer sheet according to this embodiment can be used in a variety of fields. [Examples]

[0085] The present invention will be described in more detail below with reference to test examples. [Preparation of TEMPO-oxidized CNF dispersion] As the finely milled cellulose, a dispersion of TEMPO-oxidized cellulose nanofibers (carboxyl group-containing cellulose nanofibers) was prepared as follows.

[0086] (1) Modification process A suspension was prepared by suspending 30 g of bleached coniferous kraft pulp in 1800 g of distilled water. Separately, a solution was prepared by dissolving 0.3 g of 2,2,6,6-tetramethylpiperidinyl-1-oxyradical (TEMPO) and 3 g of sodium bromide in 200 g of distilled water. This solution was added to the aforementioned suspension, and the temperature was adjusted to 20°C. To this suspension, 220 g of an aqueous sodium hypochlorite solution (concentration 2 mol / L, density 1.15 g / mL), adjusted to pH 10 with a 1 N HCl aqueous solution, was added dropwise to initiate the oxidation reaction, introducing carboxyl groups into the cellulose. The temperature in the system was maintained at 20°C. During the reaction, the pH decreased; however, a 0.5 N sodium hydroxide aqueous solution was added to maintain the pH at 10.

[0087] When the amount of sodium hydroxide consumed reached 2.5 mmol per 1 g of cellulose, it was determined that the desired amount of carboxyl groups had been introduced (based on a previously prepared calibration curve), and a sufficient amount of ethanol was added to stop the reaction. Subsequently, hydrochloric acid was added until the pH reached 3, and then the mixture was repeatedly washed with distilled water to obtain modified cellulose.

[0088] Furthermore, 0.1 g of modified cellulose was weighed as solid content and dispersed in water to a concentration of 1% by mass, and hydrochloric acid was added to adjust the pH to 3. Next, the amount of carboxyl groups in this solution was determined by conductivity titration using a 0.5 N sodium hydroxide aqueous solution, and it was found to be 1.6 mmol per 1 g of modified cellulose (cellulose whose surface is modified with carboxyl groups), i.e., 1.6 mmol / g.

[0089] (2) Refinement process Four g of the modified cellulose obtained in step (1) above was dispersed in 396 g of distilled water, and an aqueous sodium hydroxide solution was added to adjust the pH to 10. Then, this liquid was micronized using a mixer for 60 minutes to obtain a TEMPO-oxidized cellulose nanofiber dispersion (TEMPO-oxidized cellulose nanofiber concentration 1% by mass).

[0090] The carboxyl groups of the TEMPO-oxidized cellulose nanofibers in this dispersion are of the salt type (sodium). Furthermore, the average fiber diameter (fiber width) of the TEMPO-oxidized cellulose nanofibers contained in dispersion (A) was 3.5 nm, and the average fiber length was 800 nm. Here, the average fiber diameter and average fiber length are the average values ​​obtained from atomic force microscopy (AFM) observations of 20 measurement samples.

[0091] [Example 1] <Preparation of a conductive composite film transfer sheet according to the first embodiment> As conductive fiber 2, a dispersion (A) was prepared by diluting a commercially available 0.2 mass% aqueous dispersion of single-walled carbon nanotubes (CNTs) with a diameter of 1-3 nm with water to 0.02 mass%. As finely milled cellulose 3, a dispersion (B) was prepared by diluting the TEMPO-oxidized cellulose nanofiber dispersion prepared above with water to 0.02 mass%. These dispersions (A) and (B) were mixed so that the mass ratio of carbon nanotubes to TEMPO-oxidized cellulose nanofibers (CNT:CNF) was 1:10. At this time, ultrasonic treatment was performed for about 1 minute to prepare a uniform composite dispersion (C).

[0092] Next, this composite dispersion (C) was sprayed onto a PTFE sheet (first release sheet 1; diameter 47 mmφ, film thickness 65 μm, sheet pore size 0.2 μm) using an airbrush with a nozzle diameter of 0.3 mm, and some of the water was removed by suctioning the back surface with an aspirator, 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% by mass.

[0093] [(Total mass of liquid contained in the first release sheet and conductive film) / Mass of the first release sheet] × 100 (%) ... Formula (1)

[0094] <Fabrication of conductive member according to the third embodiment> The conductive composite film precursor 4a side of the obtained conductive composite film transfer sheet 10 was bonded to a PET film 6 with a thickness of approximately 100 μm under appropriate pressure to avoid trapping air bubbles. Next, the PET film side of the resulting laminate was brought into contact with a hot plate at approximately 90°C to thoroughly dry out any moisture. Then, by slowly peeling the PTFE sheet from the edge, a conductive member 30 with the conductive composite film 4b, which is the transfer material, was obtained on the PET film 6. Figure 5 is an image of the conductive composite film 4b on the conductive member 30 obtained here, observed under an electron microscope.

[0095] [Example 2] The conductive member 30 was fabricated under the same conditions as in Example 1, except that the TEMPO-oxidized cellulose nanofibers used in Example 1 were replaced with unmodified cellulose that had not undergone chemical modification. Here, as the unmodified cellulose nanofibers, a commercially available aqueous dispersion of cellulose nanofibers (ELLEX-S (mechanical pulp), manufactured by Daio Paper Corporation) was used, diluted to 0.02% by mass. The fiber width of these unmodified cellulose nanofibers ranged from 20 nm to several hundred nm (product label value).

[0096] [Example 3] Conductive member 30 was fabricated under the same conditions as in Example 1, except that the TEMPO-oxidized cellulose nanofibers used in Example 1 were replaced with cation-modified cellulose nanofibers as the finely milled cellulose. Here, the cation-modified cellulose nanofibers used were a commercially available aqueous dispersion of quaternary ammonium group-containing cellulose nanofibers (cation-modified cellulose nanofibrils, manufactured by Cellulose Lab. Inc.) diluted to 0.02% by mass. The fiber width of these cation-modified cellulose nanofibers was 50 nm and the fiber length was several hundred μm (product label values).

[0097] [Example 4] <Preparation of a 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, a commercially available cellulose qualitative filter paper (diameter 50 mmφ, film thickness 0.5 mm) was immersed in pure water and removed when it was sufficiently moist. This was then used as the second release sheet 5 and laminated 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 according to the second embodiment was stored in a resealable aluminum laminate bag to prevent the sheet from drying out. After the time indicated in "Time until transfer" in Table 1, it was removed from the aluminum laminate bag and used as a transfer sheet in the following transfer tests.

[0098] <Fabrication of 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 side of the conductive composite film precursor 4a was bonded to the 100 μm thick PET film 6 with appropriate pressure to avoid trapping air bubbles. Next, the PET film 6 side of the resulting laminate was brought into contact with a hot plate at approximately 90°C to thoroughly dry out any moisture. Then, the first release sheet, the PTFE sheet 1, was slowly peeled off from the edge to obtain a conductive member 30 with the conductive composite film 4b, which is the transfer material, on the PET film 6.

[0099] [Example 5] <Preparation of a 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, ethanol was sprayed onto the conductive composite film precursor 4a with an airbrush, and the excess ethanol was removed while sucking the back surface 1b of the PTFE sheet 1 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.

[0100] Next, a commercially available cellulose qualitative filter paper (50 mm in diameter, 0.5 mm thick) was immersed in ethanol, removed when it was sufficiently saturated with ethanol, and this was used as the second release sheet 5. This was then laminated onto the conductive composite film precursor 4a to produce the conductive composite film transfer sheet 20 according to the second embodiment. This conductive composite film transfer sheet 20 was stored in the same resealable aluminum laminate bag as in Example 4 to prevent the sheet from drying out.

[0101] <Fabrication of conductive member according to the third embodiment> After the time indicated in "Time until transfer" in Table 1, the conductive composite film transfer sheet was removed from the aluminum laminate bag and used to manufacture the conductive member 30 under the same conditions as in Example 4.

[0102] [Example 6] <Preparation of a conductive composite film transfer sheet according to the second embodiment> A composite dispersion (C) containing carbon nanotubes and carboxyl group-containing cellulose nanofibers prepared in Example 1 was to be mixed with a 0.02 mass% aqueous dispersion of silver nanowires (average diameter: 50 nm) in such a mass ratio of carbon nanotubes:cellulose nanofibers:silver nanowires as 1:10:1 to prepare a homogeneous composite dispersion (D).

[0103] Next, the composite dispersion (D) was sprayed onto the PTFE sheet 1 using an airbrush with a nozzle diameter of 0.3 mm, and some of the water was removed by suctioning the back surface 1b with an aspirator, 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.

[0104] Next, a conductive composite film transfer sheet 20 according to the second embodiment was prepared by laminating a moisture-containing cellulose qualitative filter paper as a second release sheet 5 onto the conductive composite film precursor 4a using the same method as in Example 4. This conductive composite film transfer sheet 20 was stored in the same resealable aluminum laminate bag as in Example 4 to prevent the sheet from drying out.

[0105] <Fabrication of conductive member according to the third embodiment> After the time indicated in "Time until transfer" in Table 1, the conductive composite film transfer sheet was removed from the aluminum laminate bag and used to manufacture the conductive member 30 under the same conditions as in Example 4.

[0106] [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 changed to a PTFE sheet with dimensions of 3 cm x 3 cm. In the preparation of the conductive member 40 according to the fourth embodiment, the 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 instead of a PET film as the transfer body 6, thereby obtaining a conductive member 30 according to the third embodiment. Next, the obtained conductive member 30 was fired at 260°C for 30 minutes to remove the carboxyl group-containing cellulose nanofibers. This obtained a conductive member 40 according to the fourth embodiment equipped with a conductive film 4c made of carbon nanotubes.

[0107] [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 changed to a PTFE sheet with dimensions of 3 cm x 3 cm. In the preparation of the conductive member 40 according to the fourth embodiment, the 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 instead of a PET film as the transfer body 6, thereby obtaining a conductive member 30 according to the third embodiment. Next, the obtained conductive member 30 was immersed in a 3M nitric acid aqueous solution at 60°C for 30 minutes to remove carboxyl group-containing cellulose nanofibers, thereby obtaining a conductive member 40 according to the fourth embodiment equipped with a conductive film 4c made of carbon nanotubes. After immersion in the nitric acid aqueous solution, it was washed with ethanol and then dried.

[0108] [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 with dimensions of 3 cm x 3 cm. In the production of the conductive member 30 according to the third embodiment, a glass plate (4 cm x 4 cm, 0.7 mm thick) with a hole of approximately 10 mm in diameter in the center was used as the transfer body 6 instead of a PET film, and a conductive composite film 4b was transferred in the same manner as in Example 1 to obtain a conductive member 30 in which a single film made of the conductive composite film 4b was formed in the center.

[0109] [Comparative Example 1] A conductive composite film transfer sheet, prepared using the same method as in Example 1, was left at room temperature for 3 hours. Visual inspection of the transfer sheet revealed that it was dry. When a transfer test was performed on this conductive composite film transfer sheet in the same manner as in Example 1, the conductive composite film was not transferred to the PET film at all.

[0110] [Reference example 1] A conductive composite film transfer sheet was prepared in the same manner as in Example 1, except that a dispersion (A) containing the single-walled carbon nanotubes used in the preparation of dispersion (C) was used instead of dispersion (C) containing carbon nanotubes and carboxyl group-containing cellulose nanofibers. A conductive member was obtained using this conductive composite film transfer sheet in the same manner as in Example 1.

[0111] [Reference example 2] A transfer sheet was prepared in the same manner as in Example 1, except that instead of a 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 onto a PTFE sheet in that order. A conductive member was then fabricated.

[0112] [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. A conductive member was then fabricated.

[0113] <Rating> For each conductive component, the conductive composite film or conductive film was subjected to the following measurements of surface resistance, transmittance, and surface roughness. Transferability was also evaluated based on the following criteria. The results are shown in Table 1. The film thicknesses of the conductive films obtained in Examples 1 to 9 were all within the range of 100 nm to 500 nm.

[0114] (Method for measuring surface resistance) Surface resistance was measured using a four-terminal resistivity meter, Rolester GP MCP-T610 (Mitsubishi Chemical Analytec Co., Ltd.).

[0115] (Method for measuring transmittance) The transmittance was measured using a U-4100 spectrophotometer (Hitachi High-Technologies Corporation) to determine the light transmittance at a wavelength of 550 nm, including the conductive composite film and the PET substrate.

[0116] (Method for measuring surface roughness (Sa)) Surface roughness (Sa) is the average of the absolute heights of each point relative to the average surface area, and represents the arithmetic mean height (Sa) as defined in ISO 25178 Surface properties (surface roughness measurement). Surface roughness (Sa) was measured using a 3D measuring laser microscope OLS4000 (manufactured by Olympus Corporation).

[0117] (Method for measuring film thickness) Cross-sectional observation was performed using a scanning electron microscope (SEM) to measure the film thickness.

[0118] (Transferable) A: Completely transferred. (100% of the transferable area) B: Almost completely transcribed. (90% to less than 100% of the transcribable area) C: More than half was transcribed. (50% to less than 90% of the transcribable region) D: Partially transcribed. (More than 0% but less than 50% of the transcribable area) E: No transcription occurred at all. (0% of the transcribable region)

[0119] [Table 1]

[0120] It should be noted that the present invention is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. Furthermore, each embodiment may be combined as appropriate, and in that case, the combined effects can be obtained. Moreover, the above embodiments include various inventions, and various inventions can be extracted by selecting combinations from the multiple constituent elements disclosed. For example, if the problem can be solved and effects obtained even if some constituent elements are deleted from all the constituent elements shown in the embodiment, then the configuration with these deleted constituent elements can be extracted as an invention. [Explanation of symbols]

[0121] 1...First release sheet, 1a...First main surface, 1b...Second main surface, 2...Conductive fiber, 3...Finely processed cellulose, 4a...Conductive composite film precursor, 4b...Conductive composite film, 4c...Conductive film, 5...Second release sheet, 6...Substrate (transfer target), 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 invention described in the original claims of this application is listed 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 finely milled cellulose, wherein the first release sheet and the conductive composite film precursor contain a first liquid. [2] The 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% by mass or more of 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 fibers and the finely milled cellulose used in the formation of the conductive composite film precursor. [4] A conductive composite film transfer sheet according to any one of the appendices [1] to [3], wherein the first liquid is water or alcohol. [5] A conductive composite film transfer sheet according to any one of the appendices [1] to [4], comprising at least one selected from cation-modified micronized cellulose into which cationic groups have been introduced and unmodified micronized cellulose as the micronized cellulose. [6] A conductive composite film transfer sheet according to any one of the appendices [1] to [5], comprising at least carbon nanotubes as the conductive fibers. [7] The conductive composite film transfer sheet as described in Appendix [6], wherein the carbon nanotubes are single-walled carbon nanotubes. [8] The conductive composite film transfer sheet according to any one of the 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 first release sheet is a conductive composite film transfer sheet according to any one of the appendices [1] to [8], comprising polytetrafluoroethylene.

[10] A conductive composite film transfer sheet according to any one of the appendices [1] to [9], 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.

[11] The conductive composite film transfer sheet as described in Appendix

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

[12] A method for manufacturing a conductive composite film transfer sheet as described in any of the appendices [1] to [9], A coating film is formed on the first main surface of the first release sheet by applying a dispersion in which the conductive fibers and the finely ground cellulose are dispersed in the first liquid, and The conductive composite film precursor is formed by removing a portion of the first liquid from the second main surface side, which is the back surface of the first main surface of the first release sheet. A method for producing a conductive composite film transfer sheet containing [the specified component].

[13] A method for manufacturing a conductive composite film transfer sheet as described in Appendix

[10] or

[11] , A coating film is formed on the first main surface of the first release sheet by applying a dispersion in which the conductive fibers and finely ground cellulose are dispersed in the first liquid. The conductive composite film precursor is formed by removing a portion of the first liquid from the second main surface side, which is the back surface of the first main surface of the first release sheet, and By laminating the second release sheet containing the second liquid onto the conductive composite film precursor, the conductive composite film precursor is sandwiched between the first release sheet and the second release sheet. A method for producing a conductive composite film transfer sheet containing [the specified component].

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

[12] or

[13] , wherein the first liquid is removed from the second main surface side of the first release sheet by suction of the second main surface side.

[15] A conductive member comprising a substrate and a conductive composite film on the substrate, wherein the conductive composite film comprises conductive fibers and finely milled cellulose.

[16] The conductive member according to the appendix

[15] , wherein the finely milled cellulose comprises at least one selected from cation-modified finely milled cellulose into which cationic groups have been introduced and unmodified finely milled cellulose.

[17] The conductive member according to Appendix

[15] or

[16] , comprising at least carbon nanotubes as the conductive fibers.

[18] The conductive member described in Appendix

[17] , wherein the carbon nanotube is a single-walled carbon nanotube.

[19] A conductive member comprising a substrate and a conductive composite film on the substrate, wherein the conductive composite film is a transfer film of the conductive composite film precursor included in any of the conductive composite film transfer sheets described in Appendix [1] to

[11] .

[20] The conductive member according to Appendix

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

[21] The conductive composite film contains the conductive fibers and the finely milled cellulose in a blending ratio of 0.5 to 100 parts by mass of finely milled cellulose per 1 part by mass of conductive fibers, and has a surface resistance of 0.1 to 10000 Ω / cm². 2 A conductive member as described in any of the appendices

[15] to

[20] , which is within the range and has a thickness of 10 μm or less.

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

[15] to

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

[23] The conductive composite film is a self-supporting film and has a region supported by the substrate and a region not supported by the substrate, as described in any of the appendices

[15] to

[22] .

[24] A method for manufacturing a conductive member comprising a substrate and a conductive composite film on the substrate, Bringing the conductive composite film precursor contained in the conductive composite film transfer sheet described in any of the appendices [1] to [9] 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 To peel off the first release sheet. A method for manufacturing a conductive member containing [a specific component].

[25] A method for manufacturing a conductive member comprising a substrate and a conductive composite film on the substrate, The second release sheet is peeled off from the conductive composite film transfer sheet described in Appendix

[10] or

[11] . The conductive composite film precursor is brought 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 To peel off the first release sheet. A method for manufacturing a conductive member containing [a specific component].

[26] A conductive composite film comprising conductive fibers and finely milled cellulose.

[27] The conductive composite film according to Appendix

[26] , comprising at least one selected from cation-modified cellulose nanofibers into which cationic groups have been introduced and unmodified finely milled cellulose as the finely milled cellulose.

[28] The conductive composite film according to Appendix

[26] or

[27] , comprising at least carbon nanotubes as the conductive fibers.

[29] The conductive composite film as described in Appendix

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

[30] A conductive composite film which is a transfer film of the conductive composite film precursor included in the conductive composite film transfer sheet described in any of the appendices [1] to

[11] .

[31] The conductive fiber and the finely milled cellulose are present in a blending ratio of 0.5 to 100 parts by mass of finely milled cellulose per 1 part by mass of the conductive fiber, and the surface resistance is 0.1 to 10000 Ω / cm². 2 A conductive composite film as described in any of the appendices

[26] to

[30] , which is within the range and has a thickness of 10 μm or less.

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

[26] to

[31] , wherein the surface roughness is 0.5 μm or less in arithmetic mean height.

[33] A conductive member comprising a substrate and a conductive film on the substrate, wherein the conductive film contains carbon nanotubes and has a surface resistance of 0.1 to 10000 Ω / cm² 2 A conductive member that is within the specified range, has a thickness of 10 μm or less, and has a surface roughness of 0.5 μm or less in arithmetic mean height.

[34] The conductive member according to Appendix

[33] , wherein the conductive film is a self-supporting film and has a region supported by the substrate and a region that is not supported by the substrate.

[35] A method for manufacturing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, The conductive composite film precursor contained in the conductive composite film transfer sheet described in any of the appendices [1] to [9] is brought into contact with the substrate. The first liquid contained in the first release sheet and the conductive composite film precursor is removed by heating or drying. To peel off the first release sheet, and Removing the aforementioned finely ground cellulose A method for manufacturing a conductive member containing [a specific component].

[36] A method for manufacturing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, The second release sheet is peeled off from the conductive composite film transfer sheet described in Appendix

[10] or

[11] . The conductive composite film precursor is brought into contact with the substrate. The first liquid contained in the first release sheet and the conductive composite film precursor is removed by heating or drying. To peel off the first release sheet, and Removing the aforementioned finely ground cellulose A method for manufacturing a conductive member containing [a specific component].

[37] A method for manufacturing a conductive member according to Appendix

[35] or

[36] , wherein the removal of the finely ground cellulose is performed by thermal decomposition or dissolution in a solvent.

[38] Contains carbon nanotubes and has a surface resistance of 0.1 to 10000 Ω / cm 2 A conductive film that is within the specified range, has a thickness of 10 μm or less, and has a surface roughness of 0.5 μm or less in arithmetic mean height.

Claims

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 finely ground cellulose, wherein the first release sheet and the conductive composite film precursor contain a first liquid, and the total mass of the first liquid contained in the first release sheet and the conductive composite film precursor is 50% by mass or more of the mass of the first release sheet.

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 for a dispersion containing the conductive fibers and the finely milled cellulose used in the formation of the conductive composite film precursor.

3. The conductive composite film transfer sheet according to claim 1 or 2, wherein the first liquid comprises water or alcohols.

4. The conductive composite film transfer sheet according to any one of claims 1 to 3, wherein the finely milled cellulose comprises at least one selected from cation-modified finely milled cellulose into which cationic groups have been introduced and unmodified finely milled cellulose.

5. A conductive composite film transfer sheet according to any one of claims 1 to 4, wherein the conductive fibers include at least carbon nanotubes.

6. The conductive composite film transfer sheet according to claim 5, wherein the carbon nanotube is a single-walled carbon nanotube.

7. The conductive composite film transfer sheet according to any one of claims 1 to 6, wherein the first release sheet is a porous sheet having a pore size in the range of 0.05 μm to 5 μm.

8. The conductive composite film transfer sheet according to any one of claims 1 to 7, wherein the first release sheet comprises polytetrafluoroethylene.

9. The conductive composite film transfer sheet according to any one of claims 1 to 8, 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.

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

11. A method for manufacturing a conductive composite film transfer sheet according to any one of claims 1 to 8, A coating film is formed on the first main surface of the first release sheet by applying a dispersion in which the conductive fibers and the finely ground cellulose are dispersed in the first liquid, and The conductive composite film precursor is formed by removing a portion of the first liquid from the second main surface side, which is the back surface of the first main surface of the first release sheet. A method for producing a conductive composite film transfer sheet containing [the specified component].

12. A method for manufacturing a conductive composite film transfer sheet according to claim 9 or 10, A coating film is formed on the first main surface of the first release sheet by applying a dispersion in which the conductive fibers and finely ground cellulose are dispersed in the first liquid. The conductive composite film precursor is formed by removing a portion of the first liquid from the second main surface side, which is the back surface of the first main surface of the first release sheet, and By laminating the second release sheet containing the second liquid onto the conductive composite film precursor, the conductive composite film precursor is sandwiched between the first release sheet and the second release sheet. A method for producing a conductive composite film transfer sheet containing [the specified component].

13. A method for manufacturing a conductive composite film transfer sheet according to claim 11 or 12, wherein the removal of the first liquid from the second main surface side of the first release sheet is performed by suction of the second main surface side.

14. A method for manufacturing a conductive member comprising a substrate and a conductive composite film on the substrate, Bringing the conductive composite film precursor contained in the conductive composite film transfer sheet according to any one of claims 1 to 8 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 To peel off the first release sheet. A method for manufacturing a conductive member containing [a specific component].

15. A method for manufacturing a conductive member comprising a substrate and a conductive composite film on the substrate, The second release sheet is peeled off from the conductive composite film transfer sheet according to claim 9 or 10. The conductive composite film precursor is brought 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 To peel off the first release sheet. A method for manufacturing a conductive member containing [a specific component].

16. A method for manufacturing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, Bringing the conductive composite film precursor contained in the conductive composite film transfer sheet according to any one of claims 1 to 8 into contact with the substrate, The first liquid contained in the first release sheet and the conductive composite film precursor is removed by heating or drying. Peeling off the first release sheet, and Removing the aforementioned finely ground cellulose A method for manufacturing a conductive member containing [a specific component].

17. A method for manufacturing a conductive member comprising a substrate and a conductive film containing conductive fibers on the substrate, The second release sheet is peeled off from the conductive composite film transfer sheet according to claim 9 or 10. The conductive composite film precursor is brought into contact with the substrate. The first liquid contained in the first release sheet and the conductive composite film precursor is removed by heating or drying. Peeling off the first release sheet, and Removing the aforementioned finely ground cellulose A method for manufacturing a conductive member containing [a specific component].

18. The method for manufacturing a conductive member according to claim 16 or 17, wherein the removal of the finely ground cellulose is performed by thermal decomposition or dissolution in a solvent.

Images