Method for manufacturing conductive substrate, method for manufacturing electronic device, method for manufacturing electromagnetic wave shielding film, method for manufacturing planar heating element, and conductive substrate

Abstract

Provided is a method for producing a conductive base material, comprising: 1) a lamination step for forming a conductive particle-containing layer on the surface of a base material using a conductive composition containing conductive particles, thereby obtaining a laminate provided with a base material layer and the conductive particle-containing layer; (2) a penetration step in which a component (X) from which an oxide film on the surface of the conductive particles can be removed is penetrated into the conductive particle-containing layer; and (3) a conductive film formation step for forming a conductive film by at least pressurizing the conductive particle-containing layer impregnated with the component (X).

Description

Technical Field

[0001] The present invention relates to a method for producing a conductive substrate, a method for producing an electronic device, a method for producing an electromagnetic wave shielding film, a method for producing a planar heating element, and a conductive substrate. Background Art

[0002] There is known a technique of applying a conductive composition containing conductive particles on a substrate to provide a conductive particle-containing layer, and heating, pressing, etc. the conductive particle-containing layer to form a conductive substrate having a conductive film.

[0003] As an example, the following contents are described in the embodiment of Patent Document 1: silver microparticles having an average primary particle size of 7 nm are dispersed in water / ethylene glycol, the obtained solution is coated on a PET film to form a coating film, the coating film is heated and pressurized at 150° C.; and a conductive layer is formed through such a process.

[0004] As another example, the following is described in the embodiment of patent document 2: a coating film is formed by spin coating copper particles (copper nanoparticles) having a median particle size of about 40 nm, a dispersion medium and a dispersant (copper nano-ink) on a glass substrate, and then a conductive film is formed by firing.

[0005] As another example, Patent Document 3 describes the following: a conductive ink composition containing (A) a hydroxycarboxylic acid, (B) a nitrogen-containing compound, (C) copper particles, and (D) a dispersion medium is applied onto a substrate to form a coating film, and the coating film is treated to form a conductive layer.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 6181608

[0009] Patent Document 2: Japanese Patent Application Publication No. 2021-044308

[0010] Patent Document 3: Japanese Patent Application Publication No. 2017-191723 Summary of the invention

[0011] When a conductive film is formed using a conductive composition containing conductive particles, it is preferred that the resistivity of the formed conductive film be as low as possible. However, for conductive films obtained by conventional production methods such as those disclosed in Patent Documents 1 to 3, there is still room for further reducing the resistivity.

[0012] Based on the above circumstances, the present inventors have conducted various studies with the aim of producing a conductive substrate having a conductive film having a low resistivity using a conductive composition containing conductive particles.

[0013] The present inventors have completed the invention provided below and solved the above-mentioned problems.

[0014] The present invention is as follows.

[0015] 1. A method for manufacturing a conductive substrate, comprising:

[0016] a lamination step of forming a conductive particle-containing layer on a surface of a substrate using a conductive composition containing conductive particles to obtain a laminate having a substrate layer and a conductive particle-containing layer;

[0017] a permeating step of allowing the component (X) capable of removing the oxide film on the surface of the conductive particles to permeate into the conductive particle-containing layer; and

[0018] In the conductive film forming step, the conductive particle-containing layer impregnated with the component (X) is at least pressurized to form a conductive film.

[0019] 2. The method for producing a conductive substrate according to 1, wherein:

[0020] A pressurizing step is included between the laminating step and the impregnating step, and at least the conductive particle-containing layer is pressurized.

[0021] 3. The method for producing a conductive substrate according to 2, wherein:

[0022] The pressure applied to the conductive particle-containing layer in the pressurizing step is denoted as P1.

[0023] When the pressure applied to the conductive particle-containing layer in the conductive film forming step is P2,

[0024] P1<P2.

[0025] 4. The method for producing a conductive substrate according to any one of 1 to 3, wherein:

[0026] In the infiltration step, the liquid in which the component (X) is dissolved or dispersed is infiltrated into the conductive particle-containing layer.

[0027] 5. The method for producing a conductive substrate according to 4, wherein:

[0028] The above liquid includes water.

[0029] 6. The method for producing a conductive substrate according to 4 or 5, wherein:

[0030] Between the lamination step and the impregnation step, a liquid in which the component (X) is dissolved or dispersed is supplied at least to the surface of the conductive particle-containing layer by any method such as dropping, spraying or immersion.

[0031] 7. The method for producing a conductive substrate according to any one of 1 to 3, wherein:

[0032] In the impregnation step, the sheet containing the component (X) is brought into contact with the conductive particle-containing layer, thereby allowing the component (X) to penetrate into the conductive particle-containing layer.

[0033] 8. The method for producing a conductive substrate according to any one of 1 to 7, wherein:

[0034] In the conductive film forming step, the conductive particle-containing layer is pressurized while being heated.

[0035] 9. The method for producing a conductive substrate according to any one of 1 to 8, wherein:

[0036] In the conductive film forming step, after covering the surface of the laminated body on which the conductive particle-containing layer is provided with a film-like material, at least the conductive particle-containing layer is pressurized.

[0037] 10. The method for producing a conductive substrate according to any one of 1 to 9, wherein:

[0038] The above-mentioned impregnation step and the above-mentioned conductive film forming step are performed simultaneously.

[0039] 11. The method for producing a conductive substrate according to any one of 1 to 9, wherein:

[0040] After the above-mentioned infiltration step, the above-mentioned conductive film forming step is performed.

[0041] 12. The method for producing a conductive substrate according to any one of 1 to 11, wherein:

[0042] After the conductive film forming step, a removing step is included to remove the component (X) remaining on the surface or inside of the conductive film.

[0043] 13. The method for producing a conductive substrate according to any one of 1 to 12, wherein:

[0044] The component (X) includes at least one selected from the group consisting of an organic acid, an oxyacid of phosphorus, and hydrazine or a derivative thereof.

[0045] 14. The method for producing a conductive substrate according to any one of 1 to 13, wherein:

[0046] The conductive composition includes one or both of a resin and a binder.

[0047] 15. The method for producing a conductive substrate according to any one of 1 to 13, wherein:

[0048] The conductive composition contains substantially no resin and substantially no binder.

[0049] 16. The method for producing a conductive substrate according to any one of 1 to 15, wherein:

[0050] The above-mentioned substrate has flexibility.

[0051] 17. The method for producing a conductive substrate according to any one of 1 to 16, wherein:

[0052] The substrate is at least one selected from polyester, polyolefin, polyimide and paper.

[0053] 18. The method for producing a conductive substrate according to any one of 1 to 17, wherein:

[0054] The impregnation step is performed by applying pressure to the conductive particle-containing layer using a pressing member.

[0055] 19. The method for producing a conductive substrate according to any one of 1 to 18, wherein:

[0056] The impregnation step is performed in any one of the following ways (i) to (iii).

[0057] (i) The stacked body is sandwiched between two opposing rolls and conveyed between the two rolls.

[0058] (ii) The laminate is placed on a flat plate or on the flat surface of a table having a flat surface, and a roller is brought into contact with the laminate from above to apply pressure to the laminate while rotating the roller.

[0059] (iii) The stacked body is sandwiched between the first flat surface of a first pressing member having a first flat surface and the second flat surface of a second pressing member having a second flat surface.

[0060] 20. The method for producing a conductive substrate according to any one of 1 to 19, wherein:

[0061] The conductive film has a pattern structure.

[0062] 21. A method for producing an electronic device, comprising producing an electronic device using a conductive substrate obtained by the method for producing a conductive substrate according to any one of 1 to 20.

[0063] 22. The method for manufacturing an electronic device according to 21, wherein:

[0064] The above-mentioned electronic device is an RF tag.

[0065] 23. A method for producing an electromagnetic wave shielding film, comprising producing an electromagnetic wave shielding film using a conductive substrate obtained by the method for producing a conductive substrate according to any one of 1 to 20.

[0066] 24. A method for producing a planar heat generating body, comprising producing the planar heat generating body using a conductive substrate obtained by the method for producing a conductive substrate according to any one of 1 to 20.

[0067] 25. A conductive substrate comprising a substrate and a conductive film, wherein the conductive film is provided on at least a portion of a surface of the substrate using a conductive composition containing conductive particles.

[0068] A component (X) capable of removing an oxide film on the surface of the conductive particles exists on the surface or inside the conductive film.

[0069] According to the present invention, a conductive film having a low resistivity can be formed using a conductive composition containing conductive particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a figure for demonstrating the manufacturing method of a conductive base material. DETAILED DESCRIPTION

[0071] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0072] In all the drawings, the same components are denoted by the same reference numerals, and their description is appropriately omitted.

[0073] In order to avoid duplication of description, when there are a plurality of identical components in the same drawing, only one of them may be given a reference numeral instead of all of them.

[0074] The drawings are for explanation purposes only, and the shapes, dimensional ratios, etc. of the components in the drawings do not necessarily correspond to actual products.

[0075] In this specification, unless otherwise specified, the notation "X to Y" in describing a numerical range means greater than or equal to X and less than or equal to Y. For example, "1 to 5 mass %" means "greater than or equal to 1 mass % and less than or equal to 5 mass %".

[0076] The term "(meth)acrylic acid" in this specification represents a concept including both acrylic acid and methacrylic acid. The same applies to similar terms such as "(meth)acrylate".

[0077] <Method for producing conductive substrate>

[0078] The method for manufacturing a conductive substrate of this embodiment includes:

[0079] a lamination step of applying a conductive composition containing conductive particles on the surface of a substrate to obtain a laminate having a substrate layer and a conductive particle-containing layer;

[0080] a permeation step of allowing the component (X) capable of removing the oxide film on the surface of the conductive particles to permeate into the conductive particle-containing layer; and

[0081] In the conductive film forming step, at least the conductive particle-containing layer impregnated with the component (X) is pressurized to form a conductive film.

[0082] According to the findings of the present inventors, when a conductive film is formed by a conventionally known production method using a conductive composition containing conductive particles, the resistivity of the obtained conductive film tends to be high due to an oxide film present on the surface of the conductive particles.

[0083] Based on this, the present inventors have found that when a conductive film is formed using a conductive composition containing conductive particles, the resistivity of the resulting conductive film can be reduced by removing at least a portion of the oxide film on the surface of the conductive particles using a component (X) capable of removing the oxide film on the surface of the conductive particles.

[0084] Hereinafter, an example of the method for producing the conductive substrate according to the present embodiment will be described in detail with reference to the drawings.

[0085] [Lamination step: Film formation using a conductive composition ( Figure 1 A), and film drying ( Figure 1 B)]

[0086] In the lamination process, for example, first Figure 1 As shown in A, a film 3 is formed on the surface of a substrate 1 using a conductive composition containing conductive particles.

[0087] When the conductive composition contains a volatile solvent, the volatile solvent in the film 3 is volatilized to form a conductive particle-containing layer 3B (dried film). In this way, a laminate having a substrate 1 (substrate layer) and a conductive particle-containing layer 3B can be obtained. Of course, the lamination step is not limited to the following steps as long as a laminate having a substrate 1 and a conductive particle-containing layer 3B can be obtained. Figure 1 The methods shown in A and B.

[0088] The substrate 1 is usually in the form of a film, a sheet or a plate. From the viewpoint of industrial productivity, the shape of the substrate 1 is preferably any of these.

[0089] The substrate 1 is preferably flexible. By using the flexible substrate 1, a flexible printed circuit (FPC) can be manufactured.

[0090] In addition, by using the flexible substrate 1 , it becomes easy to form a conductive film using a “roller” in the conductive film forming step described later. This is preferable from the viewpoint of mass productivity.

[0091] To be more specific, the substrate 1 may be a rigid substrate without flexibility.

[0092] Considering the cost and the final use, the substrate 1 is preferably selected from polyesters such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate); polyolefins such as polyethylene and polypropylene; polyimide and paper. Here, the paper may be coated paper (paper whose surface is coated with a coating agent), or may be ordinary paper instead of coated paper. In addition, the substrate 1 is not limited to PET and the like, and a general resin film may be used.

[0093] In this embodiment, in the conductive film forming step, even in the absence of heating or relatively low temperature heating, a conductive film with sufficiently low resistivity can be obtained. Therefore, a substrate 1 with low heat resistance such as polyester, polyolefin, paper, etc. can also be suitably used as a substrate. In addition, when a substrate 1 with high heat resistance such as polyimide is used, the resistivity can be further reduced by performing high temperature heating in the conductive film forming step.

[0094] The method of forming a film using the conductive composition is not particularly limited, and various coating and printing techniques can be applied as the method of forming a film.

[0095] The film 3 and / or the conductive particle-containing layer 3B may be disposed on the entire surface of the substrate 1 or only on a portion of the surface of the substrate 1. In the former case, the film 3 can be formed by coating using a knife coater, an air knife coater, a knife coater, a roll coater, a bar coater (rod coater), a curtain coater or the like. In the latter case, the film 3 can be formed by various printing methods, such as screen printing, gravure printing, relief printing, lithographic printing (offset printing), inkjet printing, transfer printing, etc. By appropriately designing the "pattern" during printing, a substrate can be manufactured, and the substrate has a pattern structure such as a conductive film (circuit pattern) that can function as a circuit, a grid pattern having electromagnetic wave shielding ability, etc. In the case where the conductive composition is disposed only on a portion of the surface of the substrate 1, the printed "pattern" is preferably appropriately designed according to the purpose of the conductive film finally obtained.

[0096] In order to prevent the film 3 from being formed at a position other than a desired position in the substrate 1, for example, a film having holes may be placed on the substrate 1, the conductive composition may be applied or printed thereon, and then the film may be removed.

[0097] The amount of the conductive composition used can be appropriately adjusted from the viewpoint of obtaining sufficient conductivity when forming a conductive film and from the viewpoint of easy coating or printing. Specifically, the thickness of the film 3 or the thickness of the conductive particle-containing layer 3B is preferably 5 to 100 μm, more preferably 10 to 50 μm.

[0098] In particular, when the conductive composition contains a solvent, it is preferred to perform a heat treatment for drying the solvent so that the film 3 is a conductive particle-containing layer 3B (dried film). The conditions for the heat treatment are not particularly limited as long as the solvent is sufficiently dried, but can be adjusted from the perspective of sufficient drying of the solvent and suppressing the deterioration of the conductive particles due to excessive heating. The temperature of the heat treatment is preferably 50 to 150° C., more preferably 80 to 120° C. The time of the heat treatment is preferably 1 to 60 minutes, more preferably 3 to 30 minutes.

[0099] The heat treatment for drying the solvent can be performed, for example, by blowing hot air to the film 3. Of course, the heat treatment can also be performed by other methods.

[0100] The specific embodiment of the conductive composition will be described later.

[0101] [Pressure process ( Figure 1 C)]

[0102] In the present embodiment, it is preferable to include a pressurizing step, and to pressurize at least the conductive particle-containing layer 3B between the above-mentioned lamination step and the impregnation step described later.

[0103] It is optional whether to perform the pressurization step, but by performing this step, it becomes easy to maintain the shape of the conductive particle-containing layer 3B in the subsequent steps (especially the impregnation step). In particular, in the impregnation step, when the liquid in which the component (X) is dissolved or dispersed is impregnated into the conductive particle-containing layer 3B, it becomes easy to suppress deformation or collapse of at least a part of the conductive particle-containing layer 3B due to the liquid.

[0104] Particularly when a conductive composition substantially containing no resin or binder is used, the conductive particle-containing layer 3B before forming a conductive film is likely to be deformed or collapsed, and therefore, it is preferable to perform a pressurizing step.

[0105] On the other hand, when a conductive composition containing a resin and a binder is used, the conductive particle-containing layer 3B is less likely to deform or collapse than a conductive composition substantially containing no resin or binder. Therefore, the shape of the conductive particle-containing layer 3B may be sufficiently maintained even without performing the pressurization step.

[0106] The pressurization process is, for example, Figure 1 As shown in FIG. 3C , the laminate including the substrate 1 and the conductive particle-containing layer 3B is sandwiched between two opposing rollers 10A and 10B while being conveyed between the two rollers.

[0107] In the pressurization process, Figure 1 As shown in C, part or all of the surface of the laminate on which the conductive particle-containing layer 3B is provided may be covered with a film 5A, and on this basis, pressure may be applied to the conductive particle-containing layer 3B by applying a roller 10A from above the film 5A.

[0108] Since the film 5A is used, the roller 10A can be prevented from directly contacting the conductive particle-containing layer 3B, and thus it is easy to suppress the undesired deformation and collapse of the conductive particle-containing layer 3B. In addition, the film 5A functions as a "buffer material", which makes it easy to apply pressure evenly to the conductive particle-containing layer 3B. Applying pressure evenly to the conductive particle-containing layer 3B is related to the uniform penetration of the component (X) into the conductive particle-containing layer 3B in the impregnation process, so it is preferred. In addition, by using the film 5A, it is sometimes possible to prevent a part or all of the conductive particle-containing layer 3B from peeling off and adhering to the roller 10A.

[0109] From one perspective, the material of the film 5A may be the same as that of the base material 1. That is, the film 5A may be a polyester film such as a PET film.

[0110] As another viewpoint, from the viewpoint of suppressing the peeling and damage of the conductive particle-containing layer 3B, a release film can be preferably used as the film-like object 5A. The release film is usually a film formed by coating a release agent on at least one side of a resin film, and the types of the release agent include silicon-based, fluorine-based, and non-silicon-based. The release film can be obtained, for example, from Fujimori Industries, Ltd.

[0111] Furthermore, from another viewpoint, the film 5A may be made of a non-resin material such as paper or aluminum foil.

[0112] Incidentally, in order to prevent part or all of the conductive particle-containing layer 3B from being peeled off and adhering to the roller 10A, a film made of a silicone, fluorine, non-silicone or other release agent may be formed on the main body of the roller 10A instead of using the film 5A.

[0113] From the perspective of "making it easy to maintain the shape of the conductive particle-containing layer 3B in the subsequent steps (particularly the impregnation step), it is preferred that the pressure in the pressurizing step be high. On the other hand, from the perspective of making it easy for the component (X) to penetrate into the conductive particle-containing layer 3B in the impregnation step, it is preferred that the pressure in the pressurizing step be not too high, and that appropriate "gaps" remain in the conductive particle-containing layer 3B.

[0114] Specifically, when the pressure applied to the conductive particle-containing layer 3B in the pressurizing step is set to P1, and the pressure applied to the conductive particle-containing layer 3B in the conductive film forming step described later is set to P2, preferably P1<P2. More specifically, P1 is preferably 0.9 times or less of P2, more preferably 0.75 times or less, and further preferably 0.6 times or less. In other words, the pressure in the pressurizing step is preferably sufficiently smaller than the pressure required to compact or sinter the conductive particles in the conductive film forming step.

[0115] From various viewpoints, it is preferable to optimize each value of P1 and P2.

[0116] P1 is preferably 1 to 500 MPa, more preferably 10 to 200 MPa, and further preferably 20 to 100 MPa. By making P1 1 MPa or more, it is easy to reliably and sufficiently obtain the effect of easily maintaining the morphology of the conductive particle-containing layer 3B in the subsequent process (especially the impregnation process). In addition, by making P1 500 MPa or less, the "gap" for the penetration of component (X) is easy to fully remain in the conductive particle-containing layer 3B.

[0117] In addition, P2 is preferably 10 MPa or more, more preferably 10 to 5000 MPa, further preferably 20 to 300 MPa, and particularly preferably 30 to 250 MPa. By making P2 10 MPa or more, the resistivity of the obtained conductive film can be further reduced. In addition, by making the pressure 5000 MPa or less, damage to the substrate 1 and the conductive particle-containing layer 3B can be suppressed. By the way, if the strength of the substrate 1 is sufficient, the pressure can be increased to further reduce the resistivity of the conductive film.

[0118] To be cautious, the pressurization process can be carried out by Figure 1 The stacking is carried out by other means than the means described in C in which the stacked body is sandwiched and transported by the two rollers 10A and 10B.

[0119] As an example, the pressurizing step can be performed by placing the laminate on a flat plate or a flat surface of a table having a flat surface, contacting a roller from above, and applying pressure to the laminate while the roller rotates. As another example, the pressurizing step can also be performed by clamping the laminate by a first flat surface of a first pressing member having a first flat surface and a second flat surface of a second pressing member having a second flat surface. In these examples, the pressurizing step can also be performed by contacting the laminate with a roller from above. Figure 1 The film corresponding to the membrane 5A of C applies pressure to the laminated body.

[0120] In short, in the pressurizing step, any method may be used as long as pressure can be applied to the conductive particle-containing layer 3B before the infiltration step.

[0121] In the pressurizing step, heat is preferably applied to the conductive particle-containing layer 3B. This is presumably related to the surface treatment of commercially available conductive particles. Specifically, sometimes a portion of the surface of commercially available conductive particles is surface-treated with an organic substance, and by applying heat to the conductive particle-containing layer 3B, the organic substance on the surface of the conductive particles is removed or moved. There is a possibility that this promotes contact between the conductive particles.

[0122] In the pressurizing step, when heat is applied to the conductive particle-containing layer 3B, the temperature is, for example, in the range of 50 to 150° C., more preferably 70 to 140° C., and further preferably 70 to 130° C., and it is preferable to set a temperature at which the substrate 1 does not substantially deteriorate (soften, melt, etc.). However, when the heating time is short, heating at a temperature higher than this may be permitted.

[0123] Of course, heat does not need to be applied to the conductive particle-containing layer 3B in the pressurizing step.

[0124] When the film 5A is used in the pressurizing step, the film 5A is usually peeled off from the substrate 1 and the conductive particle-containing layer 3B before the subsequent steps are performed.

[0125] [Permeation step and conductive film forming step ( Figure 1 D)]

[0126] In the impregnation step, the component (X) capable of removing the oxide film on the surface of the conductive particles is impregnated into the conductive particle-containing layer 3B. In the conductive film forming step, the conductive particle-containing layer 3B impregnated with the component (X) is at least pressurized to form a conductive film.

[0127] To be cautious, although Figure 1 Although not shown in the figure, it is necessary to supply the component (X) to the conductive particle-containing layer 3B before the impregnation step. The specific means of supplying is not particularly limited, and for example, it may be dripping, spraying, dipping, etc. as described later.

[0128] In terms of the ease of process implementation and the ease with which component (X) can penetrate into the conductive particle-containing layer 3B, it is preferred that a liquid in which component (X) is dissolved or dispersed is penetrated into the conductive particle-containing layer 3B in the penetration step. It is more preferred that water in which component (X) is dissolved or dispersed is penetrated into the conductive particle-containing layer 3B in the penetration step. It is preferred to use "water" in which component (X) is dissolved or dispersed from the perspective of reducing environmental load and process safety (non-ignition). Of course, an organic solvent in which component (X) is dissolved or dispersed can also be used.

[0129] In the impregnation step, when the liquid in which the component (X) is dissolved or dispersed is impregnated into the conductive particle-containing layer 3B, the method for supplying the liquid to at least the surface of the conductive particle-containing layer 3B is not particularly limited. Specific methods include dripping, spraying, and immersion.

[0130] When the film 5B described later is used, at least a portion of the upper surface of the film 5B may be first wetted with a liquid in which the component (X) is dissolved or dispersed, and then the conductive particle-containing layer 3B of the laminate may be brought into contact (wet contact) with the upper surface of the film 5B.

[0131] Of course, the method of supplying the liquid at least to the surface of the conductive particle-containing layer 3B is not limited to the method specifically described here.

[0132] exist Figure 1 In D, the impregnation step and the conductive film formation step are performed simultaneously. Figure 1 In D, the pressure of the rollers 10C and 10D is used to promote the penetration of the liquid 50 containing the component (X) into the conductive particle-containing layer 3B. At the same time, the pressure of the rollers 10C and 10D is used to pressurize the conductive particle-containing layer 3B and change it into a conductive film.

[0133] In the case where the impregnation step includes a step of applying pressure to the conductive particle containing layer 3B in some form, the impregnation step and the conductive film forming step can be performed simultaneously. That is, by the pressure from the outside, the component (X) penetrates into the conductive particle containing layer 3B to remove the oxide film on the surface of the conductive particles, and at the same time, the interface of the conductive particles is bonded to each other, and the conductive particle containing layer 3B is changed into a conductive film.

[0134] Incidentally, the specific degree of pressurization here is as in the numerical range indicated by the above-mentioned "P2".

[0135] One or both of the impregnation step and the conductive film formation step may be performed by applying pressure to the conductive particle-containing layer 3B using a pressing member. More specifically, the impregnation step and the conductive film formation step may be performed in any of the following modes (i) to (iii).

[0136] (i)If Figure 1 As shown in FIG. 2D , the laminate including the substrate 1 and the conductive particle-containing layer 3B is sandwiched between two opposing rollers 10C and 10D while being conveyed between the two rollers.

[0137] (ii) The laminate is placed on a flat plate or a flat surface of a table having a flat surface, a roller is brought into contact with the laminate from above, and pressure is applied to the laminate while the roller is rotated.

[0138] (iii) The stacked body is sandwiched between a first flat surface of a first pressing member having a first flat surface and a second flat surface of a second pressing member having a second flat surface.

[0139] In the above description, although the case where the impregnation step and the conductive film forming step are performed simultaneously is described, it is of course possible to perform the conductive film forming step after the impregnation step.

[0140] As an example, first, a liquid containing the component (X) is supplied to at least the surface of the conductive particle-containing layer 3B by any method such as dropping, spraying, or immersion, and the liquid containing the component (X) is allowed to penetrate into the conductive particle-containing layer 3B under normal pressure or under pressure. Then, a conductive film forming step is performed.

[0141] As another example, by exposing at least a portion of the conductive particle-containing layer 3B in the laminate to a "gas" containing the component (X), the component (X) is infiltrated into the conductive particle-containing layer 3B, and then the conductive film forming step is performed. In this case, if the component (X) is a gas at room temperature and pressure, the infiltration step can be performed at room temperature and pressure. In addition, when the component (X) is a liquid or solid at room temperature and pressure, the component (X) is heated and vaporized, and the vaporized component (X) can be brought into contact with the conductive particle-containing layer 3B.

[0142] The specific form of the conductive film forming step after the impregnation step in these examples can be performed, for example, in the above-mentioned forms (i) to (iii).

[0143] When the conductive film forming step is performed after the permeation step, the component (X) that has not permeated into the conductive particle-containing layer 3B in the permeation step may or may not be removed before the conductive film forming step is performed.

[0144] Incidentally, when the conductive film forming step is performed after the infiltration step, it is also possible that a part of the oxide film is removed by the component (X) in the conductive film forming step.

[0145] When the conductive film forming step is performed after the impregnation step, in the impregnation step, in order to prevent the oxide film from being re-formed on the surface of the conductive particles from which the oxide film is removed, the time between the impregnation step and the conductive film forming step is preferably short. Specifically, when the conductive film forming step is performed after the impregnation step, the time from the end of the impregnation step to the start of the conductive film forming step is preferably 1 hour or less, more preferably 30 minutes or less, further preferably 10 minutes or less, and particularly preferably 1 minute or less.

[0146] Alternatively, in order to prevent the oxide film from being re-formed on the surface of the conductive particles from which the oxide film is removed in the impregnation step, the stacked body after the impregnation step and before the conductive film forming step can be temporarily stored in an atmosphere of an inert gas such as a rare gas or nitrogen, or in a reducing atmosphere, or in a vacuum or reduced pressure.

[0147] In one or both of the impregnation step and the conductive film formation step, it is preferred that Figure 1 As shown in D, a part or all of the surface of the laminated body provided with the conductive particle-containing layer 3B is covered with a film 5B, and on this basis, at least the conductive particle-containing layer 3B is pressurized. By adopting such a pressurization process, especially when using a liquid in which component (X) is dissolved or dispersed, the liquid cannot escape, and pressurization (and heating as needed) can be performed while maintaining the dense state of the liquid, which is preferred.

[0148] In terms of mass production suitability, it is preferred that the entire surface of the laminated body on which the conductive particle-containing layer 3B is provided is covered with the film 5B, and that at least the conductive particle-containing layer 3B is pressurized.

[0149] Of course, as long as a conductive film can be obtained in the end, the conductive particle-containing layer 3B may be pressed without using the film-like object 5B.

[0150] The material of the film 5B can be the same as that of the film 5A. That is, the material of the film 5B can be the same as that of the substrate 1. In addition, as the film 5B, a peeling film can be preferably used. In addition, the film 5B can also be a film made of a non-resin material such as paper or aluminum foil.

[0151] As the membrane 5B, the membrane 5A can be used. That is, the membrane 5B and the membrane 5A can be the same membrane. Of course, the membrane 5B can also be different from the membrane 5A.

[0152] The material of the membrane 5B may be the same as or different from that of the membrane 5A.

[0153] By covering the conductive particle-containing layer 3B with the film 5B and applying pressure to the conductive particle-containing layer 3B, the film 5B functions as a buffer material and easily applies uniform pressure to the conductive particle-containing layer 3B. Thus, a homogeneous conductive film can be easily obtained.

[0154] In addition, by pressing the conductive particle-containing layer 3B after covering it with the film-like material 5B, it is possible to suppress the pressing of the component (specifically, Figure 1 By the way, from the perspective of suppressing corrosion and degradation of the extrusion component, instead of using the film 5B, a film based on a release agent such as a silicon-based, fluorine-based, or non-silicon-based release agent may be formed on at least a portion of the surface of the extrusion component (specifically, the main body of the roller 10A).

[0155] Moreover, in particular, when the liquid in which the component (X) is dissolved or dispersed is impregnated into the conductive particle containing layer 3B, the presence of the film 5B can suppress the liquid from "escaping" due to pressure, and a sufficient amount of the component (X) becomes easy to penetrate into the conductive particle containing layer 3B, so it is preferred. In this regard, the film 5B is preferably a material (non-liquid-permeable) that is impermeable to the liquid in which the component (X) is dissolved or dispersed. Specifically, the film 5B is not paper that can easily penetrate liquid, and is usually preferably a resin film that does not allow liquid to penetrate. Of course, if a conductive film with a small resistivity can be obtained, the film 5B can be a film (a liquid-permeable film) that can be permeated by the liquid in which the component (X) is dissolved or dispersed. By making the film 5B liquid-permeable, it is possible to promote the discharge and removal of excess liquid.

[0156] The specific form of the film 5B may be the same as that of the substrate 1. However, the film 5B as described above is preferably a resin film.

[0157] In the conductive film forming step, it is preferred to apply pressure while heating the conductive particle-containing layer 3B.

[0158] The temperature of "heating" here can be appropriately set according to the heat resistance of the substrate 1, the type of conductive particles used, etc. For example, when the substrate 1 is composed of a raw material with low heat resistance such as polyester, polyolefin, paper, etc., the heating temperature is preferably considered the heat resistance temperature of the substrate used, for example, in the range of 50 to 200°C, more preferably 70 to 180°C, further preferably 70 to 150°C, and particularly preferably 80 to 125°C, and the substrate is substantially not deteriorated (softened, welded, etc.). However, when the heating time is short, heating at a higher temperature (for example, 400°C) is sometimes allowed.

[0159] On the other hand, when the substrate 1 is made of a highly heat-resistant raw material such as polyimide, the heating temperature may be 50 to 400° C. That is, when the conductive particle-containing layer 3B is heated, the temperature is preferably appropriately adjusted to 400° C. or less.

[0160] Incidentally, as shown in the examples described later, the higher the heating temperature, the better. Even if the heating temperature is increased, the resistivity of the conductive film obtained may not decrease, or may increase. Although it is only a guess, if the heating temperature is too high, the component (X) may deteriorate, or the conductive particles whose oxide film is removed by the component (X) may be rapidly oxidized again due to heat, and the resistivity of the conductive film obtained may not simply decrease.

[0161] The heating time can also be appropriately set according to the heat resistance of the substrate 1, the type of conductive particles used, etc. The heating time is, for example, 0.01 to 1 second, preferably 0.04 to 0.6 seconds. Incidentally, the "heating time" refers to the time when the conductive particle-containing layer 3B is pressurized and heated by the roller 10C when a roller press is used in the conductive film forming process. As an example, if the contact width of the two rollers rotating oppositely is set to 1 mm and the speed at which the substrate passes between the two rollers is set to v, then the heating time (equal to the time of being pressurized) is 0.59 seconds when v = 0.1 m / min, 0.04 seconds when v = 1.5 m / min, 0.06 seconds when v = 1.0 m / min, and 0.012 seconds when v = 5.0 m / min.

[0162] In the conductive film forming process, the Figure 1 In the case of extrusion by rollers such as shown in D, since the conductive particle-containing layer 3B is heated and pressurized at the same time, it is preferred to heat at least the roller 10C close to the conductive particle-containing layer 3B of the two rollers. As described above, the heating temperature of roller 10C can be appropriately set below 400°C according to the heat resistance of the substrate 1, the type of conductive particles used, etc. In addition, the heating time can be adjusted by changing the rotation speed (i.e., the conveying speed) of rollers 10C and 10D. Regarding the conveying speed, for example, between 0.1 and 10 m / min, it is appropriately adjusted in consideration of fully ensuring the heating and pressing time, mass productivity, etc.

[0163] In order to achieve uniform heating and shorten the heating time, not only the roller 10C but also the roller 10D may be heated.

[0164] On the other hand, if a conductive film with sufficiently low resistivity can be obtained, the roller 10C and the roller 10D may not be heated. Depending on the type of conductive composition used, a conductive film with sufficiently low resistivity may be obtained by simply applying pressure without heating.

[0165] If a conductive film with sufficiently low resistivity can be obtained, the conductive particle-containing layer 3B need not be heated in the conductive film forming step. In particular, when particles containing silver as a main component are used as conductive particles, a conductive film with sufficiently low resistivity can be easily obtained simply by applying pressure.

[0166] In the above, the method of making the "liquid" in which the component (X) is dissolved or dispersed penetrate into the conductive particle-containing layer 3B is mainly described, and in addition, the method in the case where the component (X) is a gas is briefly mentioned. As another method other than this, a sheet containing the component (X) is brought into contact with the conductive particle-containing layer 3B, and preferably the component (X) can be penetrated into the conductive particle-containing layer 3B by applying pressure.

[0167] Specific examples of the "sheet" herein include paper and nonwoven fabric containing the component (X), and a resin sheet on the surface of which the component (X) is coated or printed.

[0168] The specific embodiment of the component (X) will be described later.

[0169] [Processes that can be added]

[0170] The method for producing a conductive substrate according to the present embodiment may include steps other than the above-mentioned steps.

[0171] As an example, when the film-like object 5B is used in the conductive film forming step, the film-like object 5B is removed after the conductive film forming step is completed.

[0172] As another example, after the conductive film forming step, a removal step may be performed to remove the component (X) remaining on the surface or inside of the obtained conductive film. Specifically, there may be a step of immersing the obtained conductive substrate in a liquid (water, organic solvent) capable of dissolving or dispersing the component (X), a step of "washing" the residual component (X) by applying a liquid (water, organic solvent) on the surface of the conductive film, etc. In addition, a step of "gasifying and flying out" the residual component (X) by heating the obtained conductive substrate at a temperature that does not damage the substrate 1 may also be considered.

[0173] [Supplement to the overall manufacturing method]

[0174] The above-mentioned production steps may be performed continuously or discontinuously. From the viewpoint of mass productivity, it is preferable to perform the production steps continuously.

[0175] For example, it is preferred to use a manufacturing device that combines an appropriate conveying device and a pressurizing device (roller press, etc.) to continuously perform the following series of steps (i) to (viii). Incidentally, in the following series of steps, the penetration of the component (X) into the conductive particle-containing layer 3B may be performed through part or all of (v) to (vii).

[0176] (i) placing a laminate including a substrate 1 and a conductive particle-containing layer 3B on a production device;

[0177] (ii) covering at least the surface of the laminate having the conductive particle-containing layer 3B with the film 5A;

[0178] (iii) performing a pressurizing step using a pressurizing device;

[0179] (iv) peeling off the membrane 5A;

[0180] (v) supplying a liquid in which the component (X) is dissolved or dispersed to at least the surface of the conductive particle-containing layer 3B;

[0181] (vi) covering at least the surface of the laminate having the conductive particle-containing layer 3B (the surface to which the liquid is supplied) with the film 5B;

[0182] (vii) performing a conductive film forming step using a pressurizing device;

[0183] (viii) Peel off the film 5B.

[0184] [About conductive composition]

[0185] The conductive composition contains at least conductive particles.

[0186] From the viewpoint of easy availability and good conductivity, the conductive particles preferably contain at least one element selected from the group consisting of silver and copper.

[0187] Specifically, the conductive particles preferably include at least one selected from particles containing silver as the main component and particles containing copper as the main component. Here, the expression "containing silver as the main component" means that the proportion of silver elements in all constituent elements in the particles is preferably 50 mol% or more, more preferably 75 mol% or more, further preferably 90 mol% or more, and particularly preferably 95 mol% or more. Similarly, the expression "containing copper as the main component" means that the proportion of copper elements in all constituent elements in the particles is preferably 50 mol% or more, more preferably 75 mol% or more, further preferably 90 mol% or more, and particularly preferably 95 mol% or more.

[0188] To be careful, the conductive particles may contain elements other than silver and copper as long as the desired conductivity can be obtained. Examples of elements other than silver and copper include gold, aluminum, platinum, palladium, iridium, tungsten, nickel, tantalum, lead, and zinc.

[0189] The conductive particles may contain two or more elements. For example, conductive particles (silver-coated copper particles) coated with silver on the surface of copper particles are preferably used in this embodiment. Silver-coated copper particles are particles with copper as the main component, for example, with the total mass of the particles as the reference, and the surface of the copper particles is coated with silver in an amount of up to 35% by mass.

[0190] In the volume-based cumulative particle size distribution curve obtained when the particle size of the conductive particles is measured by the laser diffraction scattering method, the particle size D having a cumulative frequency of 50% is 50 It is preferably 0.5 to 100 μm, more preferably 0.6 to 50 μm, further preferably 0.7 to 30 μm, and particularly preferably 0.7 to 20 μm.

[0191] By making D50 When the diameter is appropriately large, the number of grain boundaries between the conductive particles per unit volume can be reduced, which is considered to lead to a further reduction in the resistivity of the resulting conductive film.

[0192] By making D 50 When the diameter is too large, the "gaps" between the conductive particles become smaller, which is considered to lead to a further decrease in the resistivity of the conductive film obtained.

[0193] The conductive particles that can be used in the present embodiment can be purchased from, for example, DOWA Electronic Technology Co., Ltd., Fukuda Metal Foil Powder Industry Co., Ltd., and the like.

[0194] For the purpose of adjusting and optimizing the particle size distribution or other purposes, two or more different types of conductive particles may be mixed and used.

[0195] From the viewpoint of further reducing the resistivity of the conductive film obtained, the proportion of conductive particles in the conductive composition is preferably larger. Specifically, the proportion of conductive particles in the total non-volatile components of the conductive composition is preferably 95% by mass or more, more preferably 97% by mass or more, further preferably 98% by mass or more, and particularly preferably 99% by mass or more. In other words, from the viewpoint of further reducing the resistivity of the conductive film obtained, it is preferred that the conductive composition does not substantially contain a resin, and further, it is preferred that it does not substantially contain a binder. Here, "substantially not containing" a resin or a binder means: it does not contain a resin or a binder at all, or although it contains a resin or a binder, its content is a small amount (in the total non-volatile components of the conductive composition, for example, 1% by mass or less, specifically, 0.5% by mass or less) to the extent that the expected effect (specifically, described below) cannot be obtained by the use of a resin or a binder.

[0196] The conductive composition may not contain a resin or a binder as long as a desired conductive film is obtained.

[0197] On the other hand, from the viewpoint of making it easy to maintain the morphology of the conductive particle-containing layer 3B in the impregnation step, specifically, from the viewpoint of suppressing deformation or collapse of at least a portion of the conductive particle-containing layer 3B due to the liquid when the liquid in which the component (X) is dissolved or dispersed is impregnated into the conductive particle-containing layer 3B in the impregnation step, the conductive composition preferably contains one or both of a resin and a binder. The conductive composition may contain both of a resin and a binder, or may contain only one of a resin and a binder without containing the other.

[0198] In addition, the pressurization process is omitted ( Figure 1In order to simplify the manufacturing process of the conductive substrate, a conductive composition containing one or both of a resin and a binder can be used. That is, since the conductive particle-containing layer 3B formed using a conductive composition containing one or both of a resin and a binder is unlikely to be deformed or collapsed by the liquid containing component (X), even if the pressurization step ( Figure 1 C), it is easy to maintain the morphology of the conductive particle-containing layer 3B. And it is easy to obtain the final desired conductive film.

[0199] When the conductive composition contains one or both of a resin and a binder, the content thereof is preferably 1 to 5% by mass, more preferably 2 to 5% by mass, in the total nonvolatile components of the conductive composition, from the viewpoint of easily maintaining the morphology of the conductive particle-containing layer 3B and reducing the resistivity of the obtained conductive film.

[0200] Specific examples of the resin or binder include preferably polyvinyl pyrrolidone, polyester, epoxy resin, (meth)acrylic resin, polyvinyl acetal resin, cellulose resin (eg, ethyl cellulose), phenol resin, and the like.

[0201] The conductive composition may contain a solvent. The conductive composition contains a solvent to improve the coating or printing properties on the substrate of the conductive composition. The solvent typically contains an organic solvent. The solvent may contain water if it can appropriately disperse the conductive particles.

[0202] The type of solvent is not particularly limited, and any solvent may be used as long as it does not substantially alter the properties of the components in the conductive composition.

[0203] The amount of the solvent used can be appropriately adjusted according to the coating and printing method of the conductive composition, etc. The amount of the solvent used is, for example, 3 to 30 mass %, preferably 5 to 25 mass %, and more preferably 10 to 20 mass % of the entire conductive composition.

[0204] The conductive composition may or may not contain various additive components of conventional ink compositions and conductive pastes.

[0205] [About ingredient (X)]

[0206] The component (X) is not particularly limited as long as it is a component that can remove the oxide film on the surface of the conductive particles.

[0207] In this specification, “removal” of the oxide film includes not only the removal of the oxide itself present on the surface of the conductive particle but also the return of the oxide to a non-oxide through chemical changes (reduction, etc.).

[0208] According to the findings of the present inventors, it is preferred that at least one selected from an organic acid, an oxyacid of phosphorus, and hydrazine or a derivative thereof be contained. These are particularly preferred when the conductive particles contain copper or silver.

[0209] Examples of the organic acid include carboxylic acids such as citric acid, formic acid, acetic acid, malonic acid, malic acid, tartaric acid, ascorbic acid, succinic acid, fumaric acid, and propionic acid.

[0210] Specific examples of the phosphorus oxygen acid include phosphinic acid, phosphonic acid, phosphorous acid, phosphoric acid, diphosphoric acid, triphosphoric acid, and methyl triphosphoric acid. Among these, phosphinic acid is particularly preferred.

[0211] Examples of hydrazine or its derivatives include hydrazine itself; hydrazines such as hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrobromide, and hydrazine sulfate; and other compounds having a -NH-NH2 structure.

[0212] In addition, in order to remove the oxide film, a compound with a small pKa in water can be used as component (X). Specifically, a compound with a pKa in water of -5.0 to 5.0 is preferably used as component (X), and a compound with a pKa of -4.0 to 4.5 is more preferably used as component (X). Incidentally, when component (X) is a polyacid, the smallest pKa among the plurality of pKas is preferably within the above range.

[0213] Considering only the small pKa and the removability of the oxide film, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid may be used as component (X). However, considering the problem of residues in the conductive particle-containing layer 3B, organic acids are preferred as component (X).

[0214] The pKa value here may be a value at room temperature (eg, 25° C.), but from the viewpoint of oxide film removability in an actual process, it may be said that it is preferable to use a pKa value at the temperature of the penetration step or the conductive film forming step.

[0215] In addition, any compound that can return the oxide film to a non-oxidized state by a reduction reaction can also be used as component (X). For example, a compound having an aldehyde group can be used as component (X) because it can reduce an oxide in some cases.

[0216] Furthermore, a compound having a small pKa in water and capable of returning the oxide film to a non-oxidized state by a reduction reaction is also preferably used as component (X). As such a compound, formic acid can be cited, for example. Formic acid has the advantage of being volatile and unlikely to remain in the conductive film.

[0217] In addition to the above, examples of component (X) include pyrogallol, phenidone, hydroquinone, o-aminophenol, etc. These are substances known to function as reducing agents in the field of silver salt photography.

[0218] In the case where a certain compound A is impregnated into the conductive particle-containing layer 3B, and in the case where it is not impregnated, if the former can obtain a conductive film having a further lower resistivity, the compound A can be adopted as the component (X).

[0219] In the impregnation step, when the liquid in which the component (X) is dissolved or dispersed is impregnated into the conductive particle-containing layer 3B, the concentration of the component (X) in the liquid can be appropriately adjusted. The concentration is adjusted from the viewpoint of allowing a sufficient amount of the component (X) to penetrate into the conductive particle-containing layer 3B, and from the viewpoint of reducing the amount of the residual component (X) to suppress corrosion and degradation of the conductive film.

[0220] The concentration of the component (X) in the liquid is, for example, 0.05 to 50 mol / L, preferably 0.1 to 40 mol / L, more preferably 0.1 to 30 mol / L, further preferably 0.1 to 10 mol / L, and particularly preferably 0.15 to 5.0 mol / L. Of course, a liquid containing the component (X) at a concentration lower than the concentration indicated here may be used, and a liquid containing the component (X) at a concentration higher than the concentration indicated here (e.g., saturated concentration) may also be used.

[0221] <About conductive substrate>

[0222] The conductive film of the conductive substrate obtained as described above has good electrical conductivity.

[0223] The conductive film of the conductive substrate obtained as described above is not necessarily the same, but may contain component (X) on the surface or inside of the conductive film due to the preparation method. That is, in this embodiment, the conductive substrate includes a substrate and a conductive film (formed using a conductive composition containing conductive particles) disposed on at least a portion of the surface of the substrate, and component (X) may be present on the surface or inside of the conductive film.

[0224] The component (X) present on the surface or inside of the conductive film can be confirmed by various measurement and observation methods. For example, by observing the conductive film using an electron microscope, it is sometimes possible to observe the salt generated by the reaction of the conductive particles and the component (X). In addition, sometimes the component (X) present on the surface or inside of the conductive film can be detected by methods such as transmission electron microscopy, X-ray diffraction, nuclear magnetic resonance, infrared spectroscopy, ultraviolet visible absorption spectroscopy, and Raman spectroscopy.

[0225] <Method for manufacturing electronic device>

[0226] The conductive substrate obtained as described above can be used to manufacture electronic devices. For example, in the case where the film 3 is formed only on a portion of one side of the substrate 1 by printing in the lamination process, by appropriately designing the printed "pattern", a substrate having a conductive film (circuit pattern) that can function as a circuit can be manufactured. Then, by combining the substrate with other electronic components, electronic devices can be manufactured.

[0227] Here, several examples of “electronic devices” are described. Of course, the electronic devices including the conductive substrate obtained by the method for producing a conductive substrate of the present embodiment are not limited to these.

[0228] Sensor: For example, the conductive substrate obtained by the method for producing a conductive substrate of the present embodiment can be applied to conductive components and circuits in sensors such as pressure-sensitive sensors and life sensors.

[0229] Solar cell: For example, the conductive substrate obtained by the method for producing a conductive substrate of the present embodiment can be applied to a current collecting wiring of a solar cell.

[0230] Membrane switch: A membrane switch is a switch formed by printing a circuit and contacts on a thin sheet-shaped film and then stacking them. To form the circuit and contacts, the method for producing a conductive substrate of this embodiment can be applied.

[0231] Touch sensor / touch panel: For example, the method for manufacturing a conductive substrate of this embodiment can be applied to form lead wiring in a touch sensor / touch panel. In addition, the method for manufacturing a conductive substrate of this embodiment can also be applied to form a transparent electrode of a touch sensor / touch panel.

[0232] Flexible substrate: Conventionally, a metal film is first applied to the entire surface of a flexible film, and then an unnecessary portion of the metal film is removed using a chemical to form a circuit. Instead of such conventional methods, the method for manufacturing a conductive substrate of this embodiment can be used to form a circuit.

[0233] In particular, in electronic devices in which a circuit is conventionally formed using a conductive paste, by forming a circuit using the method for producing a conductive substrate of the present embodiment, it can be expected that the resistivity of the circuit will be reduced and the performance of the electronic device will be improved.

[0234] In particular, a preferred electronic device is an RF tag. That is, in order to manufacture a conductive circuit such as an antenna portion of an RF tag, the method for manufacturing a conductive substrate of this embodiment is preferably used.

[0235] For the specific structure of the RF tag, for example, Japanese Patent Application Laid-Open No. 2003-332714, Japanese Patent Application Laid-Open No. 2020-46834, etc. can be referred to.

[0236] <Method for producing electromagnetic wave shielding film>

[0237] As other applications besides electronic devices, the method for manufacturing a conductive substrate according to the present embodiment is considered to manufacture an electromagnetic wave shielding film. Specifically, in the lamination process, the pattern when printing the conductive composition is used as a pattern (grid pattern, etc.) unique to the electromagnetic wave shielding film, thereby being able to manufacture the electromagnetic wave shielding film.

[0238] <Method for producing planar heating element>

[0239] As another application, it is conceivable to manufacture a planar heating element by the manufacturing method of the conductive substrate of this embodiment. A planar heating element refers to a planar heating element that generates heat by providing electrical wiring on a substrate and passing current through the wiring. As a specific example of a planar heating element, for example, a planar heating element used for anti-fogging and anti-cold, such as a rear window glass of a car, can be cited.

[0240] The embodiments of the present invention have been described above, which are examples of the present invention, and various configurations other than the above can be adopted. In addition, the present invention is not limited to the above-mentioned embodiments, and modifications and improvements within the scope that can achieve the purpose of the present invention are also included in the present invention.

[0241] Example

[0242] Embodiments of the present invention will be described in detail based on Examples and Comparative Examples. However, the present invention is not limited to the Examples.

[0243] In the following, exponential notation may be represented by the symbol "E". For example, 1.3E-06 means 1.3×10 －6 .

[0244] <Preparation of Conductive Composition>

[0245] 77 parts by mass of conductive particles and 23 parts by mass of an organic solvent were stirred using a planetary mixer. Thus, a uniform paste-like conductive composition was obtained. Copper powder (D 200 %) obtained from Fukuda Metal Foil Powder Co., Ltd. was used as the conductive particles. 50 :4.5μm).

[0246] To be more specific, the conductive composition does not contain a resin or a binder.

[0247] <Manufacturing of conductive substrate>

[0248] (Lamination process)

[0249] The conductive composition obtained in the above-mentioned <Preparation of conductive composition> was used to form a film (solid film) having a size of 15 mm×5 mm on a PET film.

[0250] Specifically, first, 3M's Scotch tape is attached to the PET film to set an "opening" of 15 mm x 5 mm. Then, the conductive composition is applied to the opening using a scraper to fill the opening. Then, the Scotch tape is peeled off. The thickness of the film (undried) at this time is about 40 μm.

[0251] The PET film provided with the above film was placed in a hot air circulation type atmospheric oven and heated at 100° C. for 15 minutes to volatilize the solvent.

[0252] As described above, a laminated body in which the conductive particle-containing layer was provided on the PET film was obtained.

[0253] (Pressure process)

[0254] A polyimide film was placed on the conductive particle-containing layer of the laminate obtained in the lamination step, and then the laminate and the polyimide film were rolled under the following conditions using a load-adjustable roll press ("SA-602" manufactured by Tester Industries, Ltd., equipped with a pair of rollers rotating oppositely).

[0255] Roller temperature: 110℃ for both upper and lower rollers

[0256] Pressure: 60MPa

[0257] Conveying speed: 0.1m / min

[0258] The roll temperature is supplemented. Although the roll press is equipped with a non-contact temperature sensor, this time the roll temperature was measured using a contact-type thermometer for more accurate temperature measurement.

[0259] In addition, the pressure was obtained by the following calculation.

[0260] Roller width: 165mm, contact width between rollers: 1mm, the area of ​​pressure applied is 165×1=165mm 2 Calculate. In addition, the pressure is 10kN. At 165mm 2 A force of 10 kN is applied to the area, so according to 10 kN ÷ 165 mm 2 Calculation shows that the pressure is 60.6MPa.

[0261] After the pressurization step was completed, the polyimide film was peeled off.

[0262] (Permeation step and conductive film forming step)

[0263] First, a 1 mL pipette is used to drip 1 drop of a liquid having a composition described in Table 1 described later (in which component (X) is dissolved or dispersed) onto the polyimide film to wet it. The laminate is placed in such a way that the conductive particle-containing layer after the above-mentioned pressurization process contacts the wetted portion. Furthermore, the laminate is placed together with the polyimide film on a roller press, heated and pressurized. Thus, component (X) is impregnated into the conductive particle-containing layer, and the conductive particle-containing layer is rolled using the same device as the pressurization process as a roller press. The processing conditions are the following conditions.

[0264] Roller temperature: 110℃ for both upper and lower rollers

[0265] Pressure: 121MPa

[0266] Conveying speed: 0.1m / min

[0267] After the treatment with the roll press described above, the polyimide film was peeled off.

[0268] As described above, a conductive substrate provided with a conductive film is produced.

[0269] <Measurement of resistivity>

[0270] The resistance value of the conductive film of the obtained conductive substrate is measured with a 4-terminal resistance measuring device, and the film thickness is measured with a film thickness meter. The resistivity is calculated from the measured resistance value and film thickness. The resistivity value is preferably smaller.

[0271] The above contents are summarized in Table 1.

[0272] Table 1

[0273]

[0274] The resistivity of the conductive film obtained in Examples 1-1 to 10 is lower than the resistivity of the conductive film obtained in the comparative example. From this, it can be understood that when a conductive film is formed using a conductive composition containing conductive particles, the resistivity of the conductive film obtained can be reduced by removing at least a portion of the oxide film on the surface of the conductive particles using the component (X) capable of removing the oxide film on the surface of the conductive particles.

[0275] Looking at the examples in more detail, in Examples 6-1 to 10, when pyrogallol, phenidone, hydroquinone or o-aminophenol was used as the component (X), the resistivity of the conductive film obtained was 10 －5 Ω·cm order of magnitude.

[0276] On the other hand, when various organic acids, phosphinic acid (phosphorus oxygen acid) or hydrazine of Examples 1-1 to 5 were used, a 10-fold－5 Ω·cm is smaller than 10 －6 Conductive film with resistivity of the order of Ω·cm.

[0277] From the comparison between these examples, it can be understood that various organic acids, phosphorus oxygen acids, hydrazine or derivatives thereof are preferred as component (X).

[0278] In addition, from the results of Examples 1-1 to 1-6, 3-1 to 3-4, and 4-1 to 4-4, it is not necessarily the case that the higher the concentration of the component (X), the smaller the resistivity of the obtained conductive film becomes. By increasing the concentration of the component (X), a tendency can be read as a slight increase in resistivity. It is presumed that this is due to the antagonism between the result of increasing the removal of the oxide film by increasing the concentration of the component (X) and the result of increasing the resistance due to a part of the high concentration of the component (X) remaining in the conductive film.

[0279] <Example of changing the pressure in the pressurization process>

[0280] In Examples 3-1 and 3-2 in Table 1, the pressure in the (pressing step) was changed from 60 MPa to 90 MPa (1.5 times) or 120 MPa (2 times) to obtain a conductive film. The resistivity was measured in the same manner as in <Measurement of Resistivity>. The results are shown in Table 2.

[0281] Table 2

[0282]

[0283] As shown in Table 2, especially when the concentration of component (X) (phosphinic acid) is low, if the pressure of the pressurizing process is increased, it can be seen that the resistivity of the obtained conductive film tends to increase slightly. On the contrary, the side with a relatively small pressure in the pressurizing process can obtain a conductive film with a lower resistivity. It is speculated that this is because when the pressure of the pressurizing process is relatively small, an appropriate "gap" remains in the conductive particle containing layer, so in the penetration process, component (X) easily penetrates into the inside of the conductive particle containing layer.

[0284] <Example of changing not only the pressure in the pressurization process but also the temperature>

[0285] In Example 3-2 in Table 1, a conductive film was obtained in which not only the pressure was changed (pressing step) but also the temperature was changed from 110°C to room temperature (25°C). The resistivity was measured in the same manner as in the above <Measurement of Resistivity>. The results are shown in Table 3.

[0286] Table 3

[0287]

[0288] As shown in Table 3, in the pressurizing step, when the pressure is the same, a conductive film having a lower resistivity can be obtained by processing at a high temperature (110° C.) compared to processing at room temperature (25° C.).

[0289] This is presumably because organic matter on the surface of the conductive particles (copper powder) used this time was removed or moved by heating, thereby promoting contact between the conductive particles.

[0290] <Example of Changing the Pressure in the Conductive Film Formation Step>

[0291] In Example 3-2 in Table 1, the pressure in (the impregnation step and the conductive film forming step) was changed from 121 MPa to the values ​​shown in Table 4 to obtain a conductive film. Then, the resistivity was measured in the same manner as in the above <Measurement of Resistivity>. The results are shown in Table 4.

[0292] Table 4

[0293]

[0294] As shown in Table 4, when the pressure in the conductive film forming step is set lower than 121 MPa in Example 3-2, the resistivity of the conductive film obtained increases slightly. However, even when the pressure is 36 MPa, the resistivity of the conductive film obtained is sufficiently lower than that of the comparative example in Table 1.

[0295] <Example of Changing the Temperature in the Conductive Film Formation Step>

[0296] In Examples 3-1 and 3-2 in Table 1, the temperature in the impregnation step and the conductive film forming step was changed from 110°C to the values ​​shown in Table 5 to obtain conductive films. The resistivity was then measured in the same manner as in <Measurement of Resistivity>. The results are shown in Table 5.

[0297] Table 5

[0298]

[0299] It can be understood from Table 5 that, from the perspective of further reducing the resistivity of the conductive film, the heating temperature of the conductive film forming process is preferably not too high. However, even at relatively high temperatures such as 150°C and 200°C, a conductive film with a resistivity sufficiently lower than that of the comparative example in Table 1 can be obtained.

[0300] <Example in which a polyimide film is not used in the impregnation step and the conductive film formation step>

[0301] In Example 4-2 of Table 1, a conductive film is obtained without using a polyimide film (film-like material) in the (impregnation process and conductive film forming process). Specifically, first, 1 drop of a liquid containing component (X) is directly added to the conductive particle-containing layer of the laminate obtained in the (lamination process) using a 1 mL pipette, and then the laminate is placed on a roller press, heated and pressurized. Then, a conductive substrate is obtained. Then, the resistivity is measured by performing the same operation as in the above <Measurement of resistivity>.

[0302] In this example, a roll subjected to a mold release treatment is used as the roll of the roll press because, when no polyimide film (film-like material) is used, the conductive film adheres to the roll and is easily peeled off.

[0303] The result of the resistivity measurement was 3.67E-6Ω·cm. That is, even if a film-like material is not used in the infiltration step and the conductive film formation step, a conductive film having a resistivity of the same order of magnitude as that in the case of using a film-like material can be formed.

[0304] <Example of using paper containing component (X) instead of liquid containing component (X) to allow component (X) to permeate into conductive particle-containing layer>

[0305] In the above (impregnation step and conductive film forming step), instead of using the polyimide film and the liquid of the composition described in Table 1, a paper containing a 1.5 mol / L formic acid aqueous solution was brought into contact with the conductive particle-containing layer, and heating and pressurization were performed using a roller press. Then, the resistivity of the resulting conductive film was measured by the same operation as in the above <Measurement of Resistivity>.

[0306] The resistivity of the obtained conductive film was 4.36E-6Ω·cm. That is, even if a "sheet" containing the component (X) is brought into contact with the conductive particle-containing layer instead of a liquid containing the component (X), a conductive film with a low resistivity can be obtained.

[0307] <Example of Changing the Conductive Composition and Not Performing the Pressing Step>

[0308] In Example 4-2 in Table 1, the following two points were changed to obtain a conductive substrate. Then, the resistivity of the conductive film was measured by the same operation as in the above <Measurement of Resistivity>.

[0309] Change point 1

[0310] As the conductive composition, a conductive composition containing a resin was used. Specifically, the following conductive composition was used: conductive particles (copper powder obtained from Fukuda Metal Foil Powder Co., Ltd., D 50: 4.5 μm), 79 parts by mass of a commercially available polyester resin, and 2 parts by mass of an organic solvent are stirred to obtain a uniform paste-like conductive composition.

[0311] Change point 2

[0312] That is, the laminated body obtained in the (laminating step) is directly subjected to the (infiltration step and conductive film forming step).

[0313] In this example, a conductive film having a resistivity of 5.75E-6 Ω·cm can be obtained. That is, by using a conductive composition containing a resin, a good conductive film can be obtained even without performing a pressurization step.

[0314] <Observation of the component (X) remaining in the conductive film>

[0315] The conductive film obtained in Example 4-4 was observed using a scanning electron microscope. In this observation, the presence of a substance believed to be a salt formed by copper ions and formic acid was confirmed. That is, at least the conductive substrate obtained in Example 4-4 includes a substrate and a conductive film disposed on at least a portion of the surface of the substrate, and component (X) (formic acid) exists on the surface or inside of the conductive film.

[0316] This application claims the benefit of priority based on Japanese Patent Application No. 2022-199931, filed on December 15, 2022, the disclosure of which is incorporated herein in its entirety.

[0317] Explanation of symbols

[0318] 1. Substrate

[0319] 3 Membrane

[0320] 3B Conductive particle containing layer

[0321] 5A Membrane

[0322] 5B membrane

[0323] 10A Roller

[0324] 10B Roller

[0325] 10C Roller

[0326] 10D Roller

[0327] 50 Liquid containing ingredient (X)

Claims

1. A method for manufacturing a conductive substrate, comprising: a lamination step of forming a conductive particle-containing layer on a surface of a substrate using a conductive composition containing conductive particles to obtain a laminate having a substrate layer and a conductive particle-containing layer; a permeating step of allowing the component (X) capable of removing the oxide film on the surface of the conductive particles to permeate into the conductive particle-containing layer; and The conductive film forming step is to form a conductive film by at least pressing the conductive particle-containing layer impregnated with the component (X).

2. The method for producing a conductive substrate according to claim 1, wherein: A pressurizing step is included between the laminating step and the impregnating step, and at least the conductive particle-containing layer is pressurized.

3. The method for producing a conductive substrate according to claim 2, wherein: When the pressure applied to the conductive particle-containing layer in the pressurizing step is represented by P1 and the pressure applied to the conductive particle-containing layer in the conductive film forming step is represented by P2, P1<P2.

4. The method for producing a conductive substrate according to claim 1 or 2, wherein: In the infiltration step, the liquid in which the component (X) is dissolved or dispersed is infiltrated into the conductive particle-containing layer.

5. The method for producing a conductive substrate according to claim 4, wherein: The liquid comprises water.

6. The method for producing a conductive substrate according to claim 4, wherein: Between the lamination step and the impregnation step, a liquid in which the component (X) is dissolved or dispersed is supplied at least to the surface of the conductive particle-containing layer by any method of dropping, spraying or immersion.

7. The method for producing a conductive substrate according to claim 1 or 2, wherein: In the infiltration step, a sheet containing the component (X) is brought into contact with the conductive particle-containing layer, thereby allowing the component (X) to infiltrate the conductive particle-containing layer.

8. The method for producing a conductive substrate according to claim 1 or 2, wherein: In the conductive film forming step, the conductive particle-containing layer is pressurized while being heated.

9. The method for producing a conductive substrate according to claim 1 or 2, wherein: In the conductive film forming step, after covering the surface of the laminated body on which the conductive particle-containing layer is provided with a film-like material, at least the conductive particle-containing layer is pressurized.

10. The method for producing a conductive substrate according to claim 1 or 2, wherein: The infiltration step and the conductive film formation step are performed simultaneously.

11. The method for producing a conductive substrate according to claim 1 or 2, wherein: After the infiltration step, the conductive film forming step is performed.

12. The method for producing a conductive substrate according to claim 1 or 2, wherein: After the conductive film forming step, a removing step of removing the component (X) remaining on the surface or inside of the conductive film is included.

13. The method for producing a conductive substrate according to claim 1 or 2, wherein: The component (X) contains at least one selected from the group consisting of an organic acid, an oxyacid of phosphorus, and hydrazine or a derivative thereof.

14. The method for producing a conductive substrate according to claim 1 or 2, wherein: The conductive composition includes one or both of a resin and a binder.

15. The method for producing a conductive substrate according to claim 1 or 2, wherein: The conductive composition contains substantially no resin and substantially no binder.

16. The method for producing a conductive substrate according to claim 1 or 2, wherein: The substrate has flexibility.

17. The method for producing a conductive substrate according to claim 1 or 2, wherein: The substrate is at least any one selected from polyester, polyolefin, polyimide and paper.

18. The method for producing a conductive substrate according to claim 1 or 2, wherein: The infiltration step is performed by applying pressure to the conductive particle-containing layer using a pressing member.

19. The method for producing a conductive substrate according to claim 1 or 2, wherein: The impregnation step is performed in any of the following ways (i) to (iii): (i) while sandwiching the laminated body between two opposing rollers, the laminated body is transported between the two rollers; (ii) placing the laminate on a flat plate or the flat surface of a table having a flat surface, contacting a roller from above, and applying pressure to the laminate while rotating the roller; (iii) The stacked body is sandwiched between the first flat surface of a first pressing member having a first flat surface and the second flat surface of a second pressing member having a second flat surface.

20. The method for producing a conductive substrate according to claim 1 or 2, wherein: The conductive film has a pattern structure.

21. A method for producing an electronic device, comprising producing an electronic device using a conductive substrate obtained by the method for producing a conductive substrate according to claim 1 or 2.

22. The method for manufacturing an electronic device according to claim 21, wherein: The electronic device is an RF tag. 23 . A method for producing an electromagnetic wave shielding film, comprising producing an electromagnetic wave shielding film using a conductive substrate obtained by the method for producing a conductive substrate according to claim 1 or 2.

24. A method for producing a planar heating element, comprising producing the planar heating element using a conductive substrate obtained by the method for producing a conductive substrate according to claim 1 or 2.

25. A conductive substrate comprising a substrate and a conductive film, wherein the conductive film is provided on at least a portion of a surface of the substrate using a conductive composition containing conductive particles, A component (X) capable of removing an oxide film on the surface of the conductive particles exists on the surface or inside the conductive film.

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