JP4273702B2 - Manufacturing method of conductive film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light-transmitting electrode and a light-transmitting electromagnetic wave shielding film such as various display devices and various window materials and packaging materials, and a conductive film useful as a transparent electrode for a solar cell and a method for producing the same. Specifically, the present invention relates to a conductive film that can be manufactured without using a plate, a mask, or the like by using a crack generated when a wet-coated layer is formed, and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, as a technique for forming a conductive mesh, a technique using a conductive fiber fabric such as a metal wire, a technique for forming a thin metal plate, a deposited metal thin film, a metal plating film, or the like, a conductive paste, etc. are screened. A technique of printing in a mesh form by a printing method, a technique of printing a catalyst on a base material in a mesh form and forming it by an electroless plating method, and the like have been used.
[0003]
However, when using a woven fabric of conductive fibers such as a metal wire, it is difficult to handle the woven fabric because the woven fabric easily expands and contracts. Also, in general, the fiber having a large wire diameter is coarse and the thin one is fine, so in applications requiring translucency, a thin wire diameter that is difficult to visually confirm and good It is very difficult to achieve a good aperture ratio.
[0004]
Regarding the technology for forming a conductive mesh by etching a thin metal plate, vapor-deposited metal thin film, metal plating film, etc., the manufacturing process is often complicated due to the use of a photolithography method, and furthermore, regarding the vapor deposition process and the plating process. However, since the manufacturing process is complicated, it involves low productivity and high manufacturing cost.
[0005]
Regarding a technique for forming a conductive mesh by printing a conductive paste or the like in a mesh shape by a screen printing method, a line width of about 20 μm is a limit in the current technique, and has not reached a level where visual confirmation is difficult.
[0006]
Regarding the technology for printing the catalyst on the base material in the form of a mesh and forming a conductive mesh by the electroless plating method, a fine pattern forming method using the micro contact printing method has been developed, but it has not been established as a production technology. In addition, the complexity of the electroless plating process is accompanied by low productivity and high manufacturing cost.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of such conventional problems, and intends to provide a conductive film that can be manufactured easily and inexpensively, is difficult to visually confirm, and has translucency, and a method for manufacturing the same. Is.
[0008]
[Means for Solving the Problems]
Although it is generally known that cracks occur in the coating film under various conditions, the inventor has the possibility that the cracks may be formed in a mesh shape, and that the conductive material is formed inside the groove of the cracks. By filling the substance, it has been found that a conductive mesh can be formed without using various plates and masks for patterning, and the above problems have been solved.
[0015]
The invention according to claim 1 is a mesh having a groove width of 10 μm or less by applying a coating liquid containing fine particles having a particle size of 10 μm or less on a substrate by a wet coating method, followed by drying and / or curing. Forming a crack layer having a crack in the shape of a crack, and then applying a solution, dispersion or paste containing a conductive substance to the crack layer surface by wet application, drying and / or curing, thereby forming a mesh shape of the crack layer And a step of filling the inside of the crack with a conductive substance.
[0016]
The invention according to claim 2 is a mesh having a groove width of 10 μm or less by applying a coating liquid containing fine particles having a particle diameter of 10 μm or less on a substrate by drying and / or curing. Forming a crack layer having a crack in the shape of a crack, and then applying a solution, dispersion or paste containing a conductive substance to the crack layer surface by wet application, drying and / or curing, thereby forming a mesh shape of the crack layer And a step of physically and / or chemically removing the conductive material other than the inside of the groove after filling the inside of the groove of the crack with the conductive material.
[0017]
The invention according to claim 3, wherein the substrate, the solvent absorption amount per unit area, is the method for producing a conductive film according to claim 1 or 2, characterized in that 1 cc / m ² or more .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below.
[0019]
As described above, the present invention relates to translucent electrodes such as various display devices, various window materials and packaging materials, translucent electromagnetic wave shielding films, and conductive films useful as transparent electrodes for solar cells. At that time, in order to achieve that it is difficult to confirm visually, the groove width of the crack, that is, the line width of the conductive portion made of the filled conductive material is preferably 10 μm or less, preferably 5 μm or less. More preferably, it is more preferably 1 μm or less. Further, in order to efficiently obtain solar energy as display contents from various display devices, visual information outside and inside various window materials and packaged visual information, and solar cell electrodes, the visible light transmittance is 30%. It is preferable that it is above, and it is more preferable that it is 50% or more.
[0020]
Next, an embodiment of the conductive film according to the present invention will be specifically described with reference to FIGS. However, this embodiment does not limit the content of the invention.
[0021]
1 and 2 are schematic views showing that a crack layer 2 having a mesh-like crack is formed on a base material 3, and that a conductive substance 1 is filled inside the groove of the crack.
[0022]
The base material 3 is not particularly limited as long as it has a conductive film and has a visible light transmittance of 30% or more and an appropriate mechanical strength. Specific examples include a glass plate, an acrylic plate, a polyester film, a polyethylene film, a polypropylene film, a triacetyl cellulose film, a polycarbonate film, a nylon film, and a cellophane film.
[0023]
In addition, the base material 3 is a conductive film and has a visible light transmittance of 30% or more and has an appropriate mechanical strength. It may be a multilayer structure composed of one or more functional layers provided on the substrate. Specific examples of functional layers include the formation of a conductive mesh and then adhesion to other sheets, a hard coat layer to protect the back of the conductive mesh surface, and improved adhesion between the substrate and crack layer And an easy-adhesion layer.
[0024]
Specific examples of the adhesive layer include a diene adhesive, an acrylic ester adhesive, a vinyl ether adhesive, and a urethane adhesive. Examples of the hard coat layer include acrylic resins and epoxy resins.
[0025]
The easy-adhesion layer is selected depending on the crack layer composition and the type of solvent used for the crack layer coating solution, and is generally used for the material having good adhesion to the crack layer composition and / or the crack layer coating solution. It is preferable to include a material having an affinity for the solvent. Specifically, when the crack layer contains a urethane resin, an acrylic resin, an epoxy resin or a polyvinyl alcohol resin, as a component to be included in the easy-adhesion layer, the same kind of resin as them, or urethane having good adhesion to them An example of selecting an acrylate resin is given. Moreover, when the solvent used for the crack layer coating liquid contains an aromatic solvent, an example of selecting a polystyrene resin or a polycarbonate resin as a component to be included in the easy-adhesion layer, or the solvent used for the crack layer coating liquid is an aqueous system. When a solvent is included, an example in which a polyvinyl alcohol resin or a polyvinyl acetate resin is selected as a component to be contained in the easy-adhesion layer can be given.
[0026]
Moreover, it is preferable that the base material 3 is a porous material or the base material which provided the porous layer on the support body. Examples of the porous material include porous glass and plastic foam, and examples of the porous layer include a layer that is porous by containing silicon oxide fine particles or aluminum oxide fine particles, and glass. Examples thereof include a layer that is porous by containing fibers. The substrate may be composed of a plurality of layers.
[0027]
Moreover, when the electroconductive substance 1 mentioned later contains a metal and / or metal oxide microparticles | fine-particles, it is preferable that the base material 3 is a porous material or the base material which provided the porous layer on the support body. The reason is as follows.
[0028]
By applying a solution containing metal and / or metal oxide fine particles to the porous material or porous layer, rapid penetration of the solvent into the porous material or porous layer occurs. Accordingly, the solution containing the metal and / or metal oxide fine particles is concentrated to cause aggregation of the fine particles. When the aggregated metal and / or metal oxide fine particles are larger than the pores of the porous material or the porous layer, the solvent, the dispersant dissolved in the solvent, the metal and / or metal oxide fine particles The adsorbing dispersant and the like selectively permeate into the pores. In contrast, aggregates of metal and / or metal oxide fine particles are selectively deposited on or near the surface of the porous material or the porous layer, and further compared with metal and / or metal oxide fine particles. Since the amount of the dispersing agent or the like is sufficiently reduced, the contact area between the metal and / or metal oxide fine particles is increased, the number of conduction paths is increased in proportion thereto, and the conductive layer having good conductivity is formed into the porous material. Alternatively, it is formed near the surface of the porous layer. In the case where the pore diameter of the porous material or the porous layer is smaller than that of the metal and / or metal oxide fine particles, the agglomeration of the metal and / or metal oxide fine particles due to concentration of the solution or the like may occur even if the aggregation does not occur. A favorable conductive layer is selectively formed on the surface of the porous material or the porous layer depending on the phenomenon.
[0029]
Furthermore, the amount of solvent absorption of the porous material and the porous layer with respect to the solvent used in the solution containing metal and / or metal oxide fine particles is preferably 1 cc / m ² or more. This is due to the following reason. In the case where 20% by volume or more of metal and / or metal oxide fine particles are dispersed with respect to the entire solution, a large amount of a dispersant, for example, a comb polymer must be contained, and a general concentration is 20% by volume. It is as follows. In addition, when a solution containing 20% by volume or more of metal and / or metal oxide fine particles is used, even if the solution is applied to the porous material or the porous layer having a very good solvent absorption capacity, a large amount of Since a conductive path is hardly obtained by the dispersant and good conductivity cannot be obtained, it is inappropriate as a solution for obtaining a conductive film. As a conductive film having good conductivity, a film thickness of 100 nm or more is preferable, and a coating amount of a solution having a metal and / or metal oxide fine particle concentration of 20% by volume or less is preferably 1 cc / m ² or more.
[0030]
Furthermore, the amount of solvent absorption of the porous material and the porous layer with respect to the solvent used in the solution containing the metal and / or metal oxide fine particles is ² cc / m ² to realize rapid solvent absorption. More preferably, the solution in which the metal and / or metal oxide fine particles are 20% by volume or more often has poor storage stability, and a dilute solution is often used. The solvent absorption capability of the porous material or the porous layer is preferably 5 cc / m ² or more.
[0031]
Further, in order to promote aggregation of metal and / or metal oxide fine particles, the porous material and the porous layer have a function of ionically neutralizing the surface charge of the metal and / or metal oxide fine particles. May be. Specifically, when the surface charge of the metal and / or metal oxide fine particles is negative, an example in which cationic silicon oxide fine particles or aluminum oxide fine particles are added to the porous material and the porous layer can be given.
[0032]
The crack layer 2 has a visible light transmittance of 30% or more in the state of a conductive film, and after applying the crack layer coating liquid, a drying and / or curing step is performed, and the groove width is 10 μm or less. There is no particular limitation as long as a mesh-like crack is formed.
[0033]
As a composition of the crack layer 2, it is preferable to contain 50% by weight or more of fine particles having a particle size of 10 μm or less. This is because cracks are likely to occur during drying and / or curing after the coating liquid for crack layer is applied by containing fine particles of 50% by weight or more, and cracks are caused by fine particles having a particle size of 10 μm or less. This is because the groove width becomes fine and a level difficult to confirm visually is achieved.
[0034]
The fine particles contained in the crack layer 2 are not particularly limited as long as the particle diameter is 10 μm or less, but those having transparency are preferable. Specific examples include silicon oxide fine particles, aluminum oxide fine particles, titanium oxide fine particles, resin fine particles containing acrylic resin, and resin fine particles containing styrene resin. Further, those having transparency and conductivity are preferable, and specific examples thereof include indium / tin oxide fine particles, zinc oxide fine particles, and antimony oxide fine particles.
[0035]
Although it does not specifically limit as another component contained in the crack layer 2, In order to give film | membrane intensity | strength, the resin component may be contained. Specific examples include acrylic resins, epoxy resins, urethane resins, and polyvinyl alcohol resins.
[0036]
As a coating liquid for forming the crack layer 2 (hereinafter referred to as crack layer forming solution), after applying the crack layer forming solution, through a drying and / or curing step, a mesh-like crack having a groove width of 10 μm or less is formed. If it does, it will not specifically limit. However, for the reasons described above, a coating liquid having a fine particle concentration such that the formed layer contains fine particles of 50% by weight or more is preferable. Further, the fine particles are silicon oxide fine particles, aluminum oxide fine particles, titanium oxide fine particles, resin fine particles containing acrylic resin, resin fine particles containing styrene resin, indium / tin oxide fine particles, zinc oxide fine particles, antimony oxide fine particles. preferable. The coating liquid may contain an acrylic resin or a precursor thereof, an epoxy resin or a precursor thereof, a urethane resin or a precursor thereof, or a polyvinyl alcohol resin.
[0037]
The crack layer forming solution may contain a solvent. The solvent is not particularly limited, but when the coating liquid contains fine particles, a solvent that improves the dispersion of the fine particles, and when the coating liquid contains a resin or a resin precursor, a solvent that can dissolve them is preferable. . Specifically, examples include using hexane when containing silicon oxide fine particles coated with alkyl groups, and using water when using a polyvinyl alcohol resin.
[0038]
Moreover, when the resin precursor is contained in the crack layer forming solution, a polymerization initiator having an effect of polymerizing the resin precursor may be contained in the coating liquid. Specifically, when the resin precursor is an acrylic monomer, an example including a benzophenone photopolymerization initiator is given.
[0039]
The coating method of the crack layer forming solution is not particularly limited, and gravure coating method, spin coating method, ink jet method, roll coating method, spray coating method, bar coating method, comma coating method, curtain coating method, dip coating. And a screen printing method.
[0040]
Moreover, you may perform the post-process after apply | coating the coating liquid for forming the crack layer 2. FIG. For example, when an ultraviolet curable resin precursor or an electron beam curable resin precursor is contained, ultraviolet or electron beam irradiation may be performed. Moreover, when the solvent which is not volatile at normal temperature, a thermosetting resin, or a resin precursor is contained in the coating liquid, drying by heating may be performed. When not performed, the crack layer can be formed by natural drying at room temperature.
[0041]
The film thickness of the crack layer 2 is not particularly limited as long as the groove width is 10 μm or less and the film has a mesh-like crack. However, if it is too thin, cracks are unlikely to occur during drying and / or curing after coating the crack layer coating solution, and if it is too thick, the crack groove width will be widened, so generally 0.5 μm to 50 μm. The range of is preferable.
[0042]
The crack shape and cracks of the crack layer 2 can be obtained by applying tension with a coating machine or a rewinding machine or stretching with a stretching machine after coating and / or after coating and / or after the post-treatment for forming the crack layer 2. The groove width may be controlled according to the purpose.
[0043]
The conductive substance 1 is not particularly limited as long as it has conductivity, and can be appropriately selected from metals, metal oxides, conductive polymers, and the like. Specifically, one selected from the group consisting of Fe, Co, Ni, Cr, Al, In, Zn, Pd, Sb, Sn, Pb, Cu, Pt, Ag, and Au, or an oxide thereof, or 2 Examples of such alloys include thiophene polymers, phenylene vinylene polymers, fluorene polymers, and the like.
[0044]
The method for filling the conductive substance 1 into the crack groove of the crack layer 2 is not particularly limited as long as it is a filling method. Specifically, a method in which fine particles of the conductive material are imprinted in the crack groove by a dry method, a solution in which the conductive material is dissolved, or a method in which a solution containing the fine particles of the conductive material is wet applied Is exemplified.
[0045]
Examples of the method for producing the fine particles of the conductive material include a gas phase method represented by a gas or metal oxide evaporation method, a liquid phase method represented by a reduction method in a metal salt dispersant solution, and a conductive method. It can be manufactured relatively easily by a number of known techniques such as a pulverization method for pulverizing a mass of a substance.
[0046]
As a more specific example of the method of imprinting fine particles of the conductive material into the crack groove by a dry method, iron powder is discharged onto the surface of the crack layer 2 with a powder discharger, and the iron powder is discharged into the crack groove with a cloth or the like. There is a method of imprinting.
[0047]
A more specific example of the method of wet-coating a solution in which the conductive material is dissolved includes a method of applying a chloroform solution of a thiophene polymer by a spin coating method.
[0048]
A more specific example of the method of wet-coating a solution containing fine particles of the conductive substance is a method of applying an aqueous dispersion of gold fine particles by an ink jet method.
[0049]
When fine particles of the conductive material are included, the particle size of the fine particles is preferably 10 μm or less for the reason described above. Therefore, in consideration of filling efficiency, 5 μm or less is preferable, and more preferably 1 μm or less is preferable.
[0050]
In the case of using a wet coating method of a solution containing fine particles of the conductive substance, the solvent used in the solution is not particularly limited as long as it has an effect of dispersing the fine particles of the conductive substance. Specifically, when silicon oxide fine particles whose surfaces are coated with alkyl groups are used as the fine particles of the conductive substance, hexane is exemplified.
[0051]
In the case of using a method of wet-coating a solution containing fine particles of the conductive material, the solution may contain components other than the fine particles of the conductive material and the solvent. Specifically, a dispersant such as sodium citrate, a binder such as polyvinyl acetate, a thermosetting resin such as urethane resin, a curable monomer such as an acrylic monomer, and various polymerization initiators can be used.
[0052]
In the case of using a method in which a solution in which the conductive substance is dissolved is wet-coated, the solvent used in the solution is not particularly limited as long as it dissolves the conductive substance. Specifically, when a thiophene polymer is used as the conductive substance, chloroform is exemplified.
[0053]
In the case of using a method in which a solution in which the conductive substance is dissolved is wet-coated, the solution may contain components other than the conductive substance and the solvent. Specifically, antifoaming agents such as silicone and doping agents such as iodine are exemplified.
[0054]
Further, post-processing after applying a coating liquid containing a conductive substance may be performed. Further, when an ultraviolet curable resin precursor or an electron beam curable resin precursor is contained, ultraviolet ray or electron beam irradiation may be performed. Moreover, when the solvent which is not volatile at normal temperature, a thermosetting resin, or a resin precursor is contained in the coating liquid, drying by heating may be performed. When not performed, the conductive substance is fixed inside the groove of the crack by natural drying.
[0055]
The method for removing the conductive material other than the crack groove of the crack layer 2 is not particularly limited as long as it is a removable method. Specific examples include a sand blasting method, a squeegee method, a wiping method using a cloth, a dissolving method using an acid aqueous solution, a peeling method using an adhesive, and the like.
[0056]
The timing for removing the conductive material other than the crack groove of the crack layer 2 is not particularly limited as long as it is removable, and the post-treatment after applying the coating liquid containing the conductive material, It may be before or after.
[0057]
Further, after the conductive material 3 is filled inside the crack groove of the crack layer 2, one or more various functional layers may be provided as an upper layer. Specific examples of the functional layer include a hard coat layer, an adhesive layer, an antireflection functional layer, an antiglare functional layer, and an antifouling layer.
[0058]
【Example】
(A. Preparation of aqueous silver fine particle solution)
A silver fine particle-dispersed aqueous solution was prepared by the method (Am. J. Sci., Vol. 37, pp. 491, 1889) published by Carey-Lea in 1889. The average primary particle diameter was about 7 nm by TEM observation. Furthermore, it diluted with distilled water and prepared so that Ag density | concentration might be 7 weight%.
[0059]
(B. Preparation of coating solution for forming porous layer)
20 parts by weight of an aqueous silica sol solution (Snowtex Ak, manufactured by Nissan Chemical Industries, 20% by weight of silica), 10 parts by weight of an aqueous solution of 10% by weight of polyvinyl alcohol (PVA217 manufactured by Kuraray), and 30 parts by weight of distilled water A mixed solution was prepared by stirring for 30 minutes.
[0060]
(C. Preparation of coating solution (a) for forming a crack layer)
10 parts by weight of silica sol aqueous solution (Snowtex C, manufactured by Nissan Chemical Industries, silica content 20% by weight), 1 part by weight of 10% by weight aqueous solution of polyvinyl alcohol (PVA217 made by Kuraray), and 11 parts by weight of distilled water A mixed solution was prepared by stirring for 30 minutes.
[0061]
(D. Preparation of coating solution (b) for forming a crack layer)
7 parts by weight of an aqueous solution of antimony double oxide fine particles (CX-Z300H manufactured by Nissan Chemical Industries, 30% by weight of antimony double oxide), 1 part by weight of a 10% by weight aqueous solution of polyvinyl alcohol (PVA217 made by Kuraray), and distilled water A solution prepared by mixing 10 parts by weight was prepared by stirring for 30 minutes.
[0062]
(E. Evaluation method)
The surface resistance was measured using a surface resistance meter Loresta AP (MCP-T400) manufactured by Mitsubishi Chemical Corporation. The visible light transmittance was measured using a reflection / transmittance meter (HR-100, manufactured by Murakami Color Research Laboratory).
[0063]
<Example 1>
On a polyethylene terephthalate (PET) film (A4300 manufactured by Toyobo Co., Ltd.), a coating solution for forming a porous layer is applied by a dip coating method so that the film thickness after drying becomes 20 μm, and dried at 120 ° C. for 1 minute, and porous. A quality layer was formed. The solvent absorption of this porous layer was 10 cc / m ² . On this porous layer, the crack layer forming coating solution (a) was applied by dip coating so that the film thickness after drying was 4 μm, and dried at 120 ° C. for 1 minute to form a crack layer. When the surface of this crack layer was observed with an optical microscope, it was found that the entire coated surface had cracks with a line width of 0.5 to 1.0 μm and an opening of 30 μm × 30 μm to 70 μm × 70 μm. Further, a silver fine particle aqueous solution was applied on the crack layer by a wire bar coating method to a wet film thickness of 7 μm, dried at 120 ° C. for 1 minute, and then wiped with a cotton cloth to provide a conductive mesh. A translucent sheet could be created. The translucent sheet with the conductive mesh had a surface resistance value of 30Ω / □ and a visible light transmittance of 80%. Further, the mesh structure could not be confirmed visually.
[0064]
<Example 2>
On a polyethylene terephthalate (PET) film (A4300 manufactured by Toyobo Co., Ltd.), a coating solution for forming a porous layer is applied by a dip coating method so that the film thickness after drying becomes 20 μm, and dried at 120 ° C. for 1 minute, and porous. A quality layer was formed. The solvent absorption of this porous layer was 10 cc / m ² . On this porous layer, a crack layer forming coating solution (b) was applied by a dip coating method so that the film thickness after drying was 6 μm, and dried at 120 ° C. for 1 minute to form a crack layer. When the surface of this crack layer was observed with an optical microscope, it was found that the entire coated surface had cracks with a line width of 2.0 to 3.0 μm and an opening of 50 μm × 50 μm to 100 μm × 100 μm. Further, a silver fine particle aqueous solution was applied on the crack layer by a wire bar coating method to a wet film thickness of 7 μm, dried at 120 ° C. for 1 minute, and then wiped with a cotton cloth to provide a conductive mesh. A translucent sheet could be created. The translucent sheet with the conductive mesh had a surface resistance value of 5Ω / □ and a visible light transmittance of 50%. Further, the mesh structure could not be confirmed visually.
[0065]
【The invention's effect】
According to the present invention, it is possible to provide a conductive film that has good conductivity and is difficult to see because the mesh-shaped conductive portion is fine, that is, good visibility and good visible light permeability. Furthermore, it is possible to provide an inexpensive and simple manufacturing method for the conductive film.
[0066]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a conductive film of the present invention.
FIG. 2 is a plan view showing an example of a conductive film of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conductive substance 2 Crack layer 3 Base material 3a Support body 3b Porous layer

Claims (3)

  A crack layer having a mesh-like crack with a groove width of 10 μm or less is formed on a substrate by applying a coating liquid containing fine particles having a particle size of 10 μm or less by a wet coating method, followed by drying and / or curing. And then applying a solution, dispersion or paste containing a conductive substance to the crack layer surface by wet application, drying and / or curing, so that the conductive substance is placed inside the mesh-shaped crack groove of the crack layer. And a step of filling the conductive film.   A crack layer having a mesh-like crack with a groove width of 10 μm or less is formed on a substrate by applying a coating liquid containing fine particles having a particle size of 10 μm or less by a wet coating method, followed by drying and / or curing. And then applying a solution, dispersion or paste containing a conductive substance to the crack layer surface by wet application, drying and / or curing, so that the conductive substance is placed inside the mesh-shaped crack groove of the crack layer. And a step of physically and / or chemically removing the conductive material other than the inside of the groove after filling. The substrate, the solvent absorption amount per unit area, the manufacturing method of the conductive film according to claim 1 or 2, characterized in that 1 cc / m ² or more.

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