JP5341544B2 - Transparent conductive substrate, transparent conductive substrate for dye-sensitized solar cell, and method for producing transparent conductive substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent conductive substrate which is excellent on transparency at low resistance and flatness, and a manufacturing method capable of inexpensively manufacturing the transparent conductive substrate. <P>SOLUTION: In the transparent conductive substrate, a metal minute particle dispersed solution is applied to a substrate 2 and is dried up, a first conductive layer 3 is completely covered by a highly transparent adhesive layer 7 after forming a mesh-shaped first conductive layer 3 on the substrate 2, and the substrate 2 is exfoliated after pasting the substrate 2 and a transferred substrate 8 together. Thus, the first conductive layer 3 and the adhesive layer 7 are thermally transferred integrally to the transferred substrate 8. Then, the surface 15 of the thermally-transferred first conductive layer 3 is etched, etched holes 21 are plated. Consequently, the transparent conductive substrate 1 which is excellent in transparency at low resistance can be attained. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a transparent conductive substrate having low resistance and excellent transparency and a method for producing the same, and in particular, a transparent conductive substrate suitable for a dye-sensitized solar cell having excellent solvent resistance and corrosion resistance to an electrolyte solution. The present invention relates to a conductive substrate and a manufacturing method thereof.

  In recent years, solar cells, an energy creation method using sunlight, have been against the backdrop of environmental problems such as soaring and depleting fossil fuels, increasing power consumption accompanying economic growth in Asian countries, and increasing carbon dioxide from fossil fuels. It is attracting attention and active research and development.

  Among them, solar cells using crystalline silicon or amorphous silicon are the mainstream. However, a large amount of energy is required to produce crystalline silicon and the like, and the use of silicon is contrary to the original intention of the solar cell in order to save energy. In addition, since silicon is also a basic material for integrated circuits, there is a shortage of silicon due to an increase in silicon demand and an increase in the price of silicon.

  For these reasons, attention has been given to dye-sensitized solar cells that can be manufactured with lower energy and can be manufactured at lower costs than silicon solar cells.

  A typical dye-sensitized solar cell has a transparent oxide electrode (ITO: composite oxide of tin oxide and indium oxide) formed on one side of a glass substrate, and a porous oxide containing the dye on it. Titanium is formed, an electrolyte solution containing iodine and an iodine compound is used as an electrolyte, and a counter electrode (platinum electrode or platinum-carbon electrode) is disposed thereon.

  In general, a glass substrate is used as the substrate, but by using a transparent resin substrate, a light-weight and flexible dye-sensitized solar cell can be produced. It can be enlarged.

The reason why iodine and an iodine compound are used for the electrolyte is that I ⁻ / I ₃ ⁻ is used as a bearer of the redox reaction during power generation. The iodine system is generally used because it is efficient as an electrolyte, but there is a problem that the metal electrode is corroded when a metal material having a lower resistance is used instead of the transparent oxide. Therefore, in order to protect the corroded metal material, a method of plating with a corrosion-resistant metal or a method of protecting with a conductive resin has been studied (for example, see Patent Document 1). In addition, although not limited to a conductive substrate for a dye-sensitized solar cell, a method for producing a transparent conductive substrate by plating on a mesh-shaped conductive portion has been proposed (for example, Patent Documents). 2).

JP 2008-66212 A JP 2007-227906 A

  The technique described in Patent Document 1 is a configuration in which a conductive resin is formed so as to cover the network-like first conductive portion, and in this configuration, the total light transmittance is reduced due to an excessive conductive resin. At the same time, since a conductive resin that hardly contributes to conductivity is required, it is difficult to say a technique for obtaining a low-cost substrate.

  Patent Document 2 discloses a method of performing plating on a mesh-like conductive portion made of metal fine particles. Although the patent document 2 does not particularly mention a conductive substrate for a dye-sensitized solar cell, it is possible to perform a plating process having corrosion resistance on the electrolyte. FIG. 2 is a diagram schematically showing a transparent conductive substrate obtained by the method described in Patent Document 2. As shown in FIG. In the preferable method for forming the mesh-like conductive portion 26 described in Patent Document 2, the conductive portion 26 is formed in a convex shape with respect to the substrate 25 as shown in FIG. When laminating a semiconductor layer such as titanium oxide corresponding to the power generation layer of the dye-sensitized solar cell, a problem remains in terms of flatness. Furthermore, when the conductive portion 26 is subjected to the plating 27 treatment (FIG. 2B), the width of the conductive portion 26 is widened by the plating treatment as the flatness is deteriorated, and there is a concern that the transmittance is lowered.

  Further, in the above-mentioned Patent Document 2, a method of digging a mesh-like groove in a substrate, which is a method described as another method for forming a mesh-like conductive portion, and embedding metal fine particles therein, is a photolithography method or laser etching. For example, a method for obtaining a conductive substrate for a dye-sensitized solar cell having a large area at low cost remains.

  Furthermore, in order to obtain high conductivity using the technique described in Patent Document 1 or Patent Document 2, sufficient heat treatment or chemical treatment is required after coating or printing, whether it is a metal fine particle dispersion solution or a conductive paste. It is. Therefore, there remains a problem that only a substrate excellent in heat resistance and chemical resistance can be used.

  An object of the present invention is to provide a transparent conductive substrate having low resistance, excellent transparency and excellent flatness, and a production method capable of manufacturing the transparent conductive substrate at low cost.

The present invention according to claim 1 is a method for manufacturing a transparent conductive substrate, wherein the transparent conductive substrate is manufactured by the following manufacturing steps 1 to 5.
1. A metal fine particle dispersion solution is applied on a substrate and dried, and a first conductive layer forming step 2 for forming a network-like first conductive layer on the substrate. The first conductive layer is completely covered. Adhesive layer laminating step 3 for laminating a transparent adhesive layer, the adhesive layer surface and the substrate to be transferred are bonded together, heated and pressed, then the substrate is peeled off, and the first conductive layer and the adhesive layer are integrated. A thermal transfer step 4 for thermally transferring the transferred layer to the substrate to be transferred, an etching step 5 for etching the surface of the thermally transferred first conductive layer, and plating the holes formed by the etching to laminate a second conductive layer. Second conductive layer formation process

According to a second aspect of the present invention, in the method for manufacturing a transparent conductive substrate, the transparent conductive substrate is manufactured by the following manufacturing steps 1 to 5.
1. A metal fine particle dispersion solution is applied on a substrate and dried to form a first conductive layer having a mesh shape on the substrate. 2. A transparent adhesive layer is formed on the substrate to be transferred. Laminating adhesive layer laminating step 3, the first conductive layer surface and the substrate to be transferred are bonded, heated and pressed, then the substrate is peeled off, and the transfer layer in which the first conductive layer and the adhesive layer are integrated A thermal transfer process 4 for thermally transferring the surface of the substrate to the transfer substrate, an etching process 5 for etching the surface of the thermally transferred first conductive layer, and a second conductive layer for plating the hole formed by the etching and laminating the second conductive layer. Layer formation process

  According to a third aspect of the present invention, in the first conductive layer forming step, the metal fine particle paste is printed on the substrate and dried to form a network-like first conductive layer on the substrate. 3. The method for producing a transparent conductive substrate according to claim 1, wherein the transparent conductive substrate is a conductive layer forming step.

  According to a fourth aspect of the present invention, in the first conductive layer forming step, after a metal salt solution, which is a precursor of metal fine particles, is applied to a substrate and dried, the precursor of the metal fine particles is heated. Alternatively, the transparent conductive layer according to claim 1 or 2, wherein the transparent conductive layer is a first conductive layer forming step in which a net-like first conductive layer is formed on a substrate by reduction deposition with ultraviolet irradiation or a reducing gas. It is a manufacturing method of a conductive substrate.

  The present invention according to claim 5 includes a step of performing heat treatment and / or chemical treatment on the first conductive layer between the first conductive layer forming step and the adhesive layer laminating step. The method for producing a transparent conductive substrate according to any one of claims 1 to 4, wherein:

  The present invention described in claim 6 is characterized in that the substrate is subjected to a surface treatment before the metal fine particle dispersion solution, the metal fine particle paste or the metal salt solution is applied to the substrate. Item 6. The method for producing a transparent conductive substrate according to any one of Items 1 to 5.

  The present invention according to claim 7 is characterized in that the thickness of the adhesive layer is higher than the height of the first conductive layer, and the first conductive layer does not contact the transfer substrate. It is a manufacturing method of the transparent conductive substrate of any one of 1-6.

  In the present invention described in claim 8, a third conductive layer is further laminated on the surface of the transparent conductive substrate obtained by the method for manufacturing a transparent conductive substrate according to any one of claims 1 to 7. It is a manufacturing method of the transparent conductive substrate of any one of Claim 1 to 7 provided with a 3rd conductive layer formation process.

  The present invention according to claim 9 is a transparent conductive substrate obtained by the method for producing a transparent conductive substrate according to any one of claims 1 to 8.

  The present invention according to claim 10 is characterized in that the maximum step between the first conductive layer and the adhesive layer is 300 nm or less, and the surface resistance value of the surface is 5 Ω / □ or less. It is a transparent conductive substrate of description.

  The present invention described in claim 11 is characterized in that the adhesive layer contains at least one adhesive selected from the group consisting of an acrylic adhesive and a polyester adhesive. This is a transparent conductive substrate.

  The present invention described in claim 12 is the transparent conductive substrate according to any one of claims 9 to 11, wherein the second conductive layer and the third conductive layer are in contact with an electrolyte solution. It is a transparent conductive substrate for dye-sensitized solar cells, characterized by having resistance.

  According to the method for producing a transparent conductive substrate according to the present invention, the first conductive layer is formed by applying or printing a metal fine particle dispersion solution, a metal fine particle paste, or a metal salt solution that is a precursor of metal fine particles. Therefore, a large-area network-like first conductive layer can be formed at low cost. Furthermore, by using a heat-resistant base material, heat treatment sufficient for sintering the metal fine particles can be performed, and a low-resistance first conductive layer can be obtained. Subsequently, the surface of the transfer layer in which the first conductive layer and the adhesive layer are integrated is flattened by interposing a highly transparent adhesive layer and thermally transferring the first conductive layer onto a desired transfer target substrate. It becomes. Furthermore, the surface of the transfer layer is etched by chemical treatment such as acid or alkali to form a hole only on the conductive part, and then metal or metal alloy plating is applied to the hole while paying attention to flatness. Moreover, since it is excellent in flatness, and further, it is possible to prevent the conductive part width from being expanded by plating, a transparent conductive substrate having low resistance and excellent transparency can be obtained.

  Further, by making the thickness of the adhesive layer higher than the height of the first conductive layer, the adhesive layer can be brought into contact with the entire surface of the substrate, and the adhesive force is improved.

  Further, according to the method for producing a transparent conductive substrate according to the present invention, a high transmittance and a low resistance are satisfied at the same time, and the flatness of the surface of the transparent conductive substrate is high. If a metal alloy is used as a plating material, it can be suitably used as a transparent conductive substrate for a dye-sensitized solar cell.

It is a figure which shows typically the manufacturing method of the transparent conductive substrate 1 as one Embodiment of this invention. It is a figure which shows typically the manufacturing method of the conventional transparent conductive substrate.

  The method for producing a transparent conductive substrate according to the present invention generally comprises applying a metal fine particle dispersion solution or metal fine particle paste on a substrate, printing, and drying to form a network-like first conductive layer, and then After performing heat treatment and / or chemical treatment as necessary, the network-like first conductive layer is thermally transferred onto another substrate (transfer target substrate) through a highly transparent adhesive layer, and thermal transfer is performed. The surface of the subsequent first conductive layer is etched by chemical treatment such as acid treatment, and then the second conductive layer is formed on the first conductive layer in the hole formed by etching by plating treatment. This is a method for manufacturing a conductive substrate. Further, the surface is coated with a conductive resin as necessary.

  FIG. 1 is a diagram schematically showing a method for manufacturing a transparent conductive substrate 1 as one embodiment of the present invention. Hereinafter, the manufacturing method will be described using the transparent conductive substrate 1 for a dye-sensitized solar cell as an example.

  First, a dispersion solution of metal fine particles is applied on the substrate 2 and dried to form the first conductive layer 3 made of a network structure on the substrate 2. Further, heat treatment and / or chemical treatment is performed on the first conductive layer 3 as necessary. Thereby, the base material 2 on which the first conductive layer 3 made of a network structure is laminated can be obtained. FIG. 1A shows a base material 2 on which a first conductive layer 3 is laminated.

  The metal fine particle dispersion solution that can be used here forms a network structure by self-organization after coating and drying on the base material 2, and heat treatment and chemical treatment of the laminated base material as necessary. Any metal fine particle dispersion solution may be used as long as the network structure exhibits low resistance and high transmittance by performing the treatment or any treatment. Further, instead of the metal fine particle dispersion solution, a fine metal paste may be used to print on the substrate 2 to form a network structure. Furthermore, instead of the metal fine particle dispersion solution, a solution of a metal salt which is a precursor of metal fine particles capable of forming a network structure (hereinafter, may be referred to as a metal fine particle precursor solution) may also be used. In the case of a metal fine particle precursor solution, after applying to the substrate 2 having heat resistance and / or chemical resistance and drying, the metal fine particle precursor is reduced or precipitated by heating, ultraviolet irradiation or a reducing gas. A shaped structure can be obtained.

  The metal fine particles contained in the metal fine particle dispersion liquid, metal fine particle paste or metal fine particle precursor solution are Au, Ag, Cu, Ni, Co, Fe, Cr, Zn, Al, Sn, Pd, Ti, Ta, W, Metal fine particles such as Mo, In, Pt, Ru, metal alloy fine particles, metal oxide fine particles, metal sulfide fine particles, carbon fine particles containing carbon, so-called nanocarbon materials such as carbon nanotubes, fullerenes, carbon nanohorns, or silicon. Silicon fine particles or silicon alloy fine particles of silicon and other metals, silicon oxide fine particles, silicon carbide fine particles, or silicon nitride fine particles can be used. In consideration of obtaining an oxidation resistance and a low-cost conductive substrate, a metal fine particle dispersion of Au, Ag, a metal fine particle paste or a metal fine particle precursor solution is preferable.

  Methods for preparing fine metal particles include conventional gas phase methods (evaporation in gas, etc.), liquid phase methods (liquid phase reduction methods using metal salts and reducing agents), and thermal decomposition methods (thermal decomposition of metal complexes). Or the like) can be used.

  The average particle size of the metal fine particles is preferably 10 nm or more and 1 μm or less, more preferably 10 nm to 500 nm, still more preferably 50 nm to 200 nm. When the average particle diameter exceeds 1 μm or less than 10 nm, a well-developed network structure is difficult to obtain, and as a result, low resistance and high transmittance are difficult to obtain.

As the metal fine particle dispersion solution, the metal fine particle paste or the metal fine particle precursor solution as described above, for example, a metal fine particle dispersion solution, a metal fine particle paste or a metal fine particle precursor solution prepared with reference to Patent Documents 3 to 5 may be used. I can do it.
JP 2007-234299 A JP 2005-530005 Gazette Japanese Patent Laid-Open No. 10-312715

  The base material 2 is one in which a metal fine particle dispersion solution, a metal fine particle paste, or a metal fine particle precursor solution is applied or printed to stably form a network structure, and the metal fine particle dispersion solution, the metal fine particle paste, or the metal fine particle precursor is formed. If it does not corrode or dissolve in the organic solvent contained in the body solution, and the electrical properties (resistance value) and optical properties (transmittance) of the network structure are not deteriorated by subsequent heat treatment or chemical treatment There is no particular limitation. In addition, after apply | coating and drying a metal fine particle precursor solution on the base material 2, when carrying out reduction | restoration precipitation of the metal fine particle precursor with heating, ultraviolet irradiation, or a reducing gas, it has resistance to these operation. It goes without saying that there must be.

  Further, the smoothness of the surface 6 is important for the substrate 2. Since the first conductive layer 3 made of a network structure formed on the base material 2 is thermally transferred onto the transfer substrate 8 via the adhesive layer 7, the first conductive layer on the base material 2 The bottom surface 9 becomes the surface 15 on the transfer substrate 8. For this reason, if the smoothness of the surface 6 of a base material is low, the smoothness of the surface 11 of the transparent conductive substrate 1 finally obtained will become low.

  Further, on the surface of the substrate 2 on which the metal fine particle dispersion solution, the metal fine particle paste or the metal fine particle precursor solution is applied or printed, the metal fine particles, the metal fine particle paste or the metal fine particle precursor form a network structure with good reproducibility in advance. Therefore, it is preferable to perform a primer treatment, a corona treatment, an acid / alkali treatment or the like. Although the said method is not specifically limited, It is preferable to perform the process suitable for each metal fine particle dispersion solution, metal fine particle paste, or metal fine particle precursor solution.

  In addition, it is preferable to provide a weak release layer (not shown) in advance on the base material 2 so that the first conductive layer 3 on the base material 2 is smoothly transferred to the transfer substrate 8 without being broken. The release layer is formed by coating with a dry thickness of 0.01 to 1.0 μm as a coating liquid such as a silicone polymer or a fluorine polymer. The release layer is treated to such an extent that a network structure of metal fine particles, metal fine particle paste or metal fine particle precursor is formed with good reproducibility.

  As the base material 2, it is preferable to use a less expensive resin film industrially. Specifically, a resin film of polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyphenylene sulfide, or the like can be used. In consideration of operability during thermal transfer, the substrate 2 preferably has flexibility. The substrate 2 can be used repeatedly. As for the thickness of the base material 2, 6-200 micrometers is preferable. Further, preferably, a thickness of 12 to 150 μm is used. Particularly preferably, one having a thickness of 25 to 125 μm is used.

  As a method for applying the metal fine particle dispersion solution or the metal fine particle precursor solution onto the base material 2, a known coating method such as a bar coater, a dip coater, a spray coater, a die coater, or a spin coater can be used.

  A known screen printing method can be used as a method for printing the metal fine particle paste on the substrate 2.

  After the application, it is possible to use a stationary drying method, a method of drying while passing a gas such as air at a constant flow rate, or a method of combining heating.

  After applying and drying the metal fine particle dispersion solution, or after printing and drying the metal fine particle paste, or in the case of a metal fine particle precursor solution, the metal fine particle precursor is reduced or precipitated by heating, ultraviolet irradiation or a reducing gas. It is preferable to heat-process and / or chemically-process the made network structure. The main purpose of chemical treatment is to remove the dispersant, resin, etc. contained in the metal fine particles, and to lower the resistance value of the network structure, and it is immersed in an organic solvent and an inorganic or organic acid. It is preferable to do. Examples of the organic solvent include ketones such as acetone and methyl ethyl ketone, and alcohols such as methanol, ethanol and isopropanol. Ketones such as acetone are preferred. Examples of the inorganic acid or organic acid include hydrochloric acid, nitric acid, formic acid, and acetic acid, and hydrochloric acid or formic acid is preferable. After the immersion, it is preferable to rinse with pure water or ethanol and then dry by standing drying or heat drying.

  Furthermore, it is more preferable to perform heat treatment for the purpose of promoting the sintering of the metal fine particles and lowering the resistance value. Although heat processing temperature changes with the base materials 2 to be used, in order to obtain sufficient electroconductivity, the range of 100-300 degreeC is preferable. More preferably, it is 100-200 degreeC.

  In the case of reducing the metal fine particle precursor, heating, light irradiation such as ultraviolet rays or radiation, or a reducing gas method can be combined.

  The total light transmittance of the first conductive layer 3 made of the network structure is 70% or more, more preferably 80% or more.

  Next, in order to thermally transfer the first conductive layer 3 made of a network structure formed on the base material 2 to a desired transfer target substrate 8, as shown in FIG. The entire surface of the laminated base material 2 is covered with a highly transparent adhesive to form the adhesive layer 7. At this time, it is important to fill all the openings 12 of the first conductive layer 3 with an adhesive and bury the openings 12 with the adhesive. Since the first conductive layer 3 is thermally transferred integrally with the adhesive layer 7 in the next step, the surface of the first conductive layer which is the bottom surface 9 on the substrate 2 becomes the surface after the thermal transfer. (FIGS. 1C and 1D). For this reason, if the opening 12 of the first conductive layer 3 is not completely embedded with an adhesive, the surface 14 of the transfer layer 10 (the first conductive layer and the adhesive layer) after the thermal transfer is locally perforated. Opened. In the subsequent steps, the surface 15 of the first conductive layer 3 after the thermal transfer is etched, and the etching portion is plated to form the second conductive layer 5, but the perforated portion is not plated. Since it remains as it is, the surface 11 of the transparent conductive substrate 1 is not preferable because it does not become flat. Further, even when a resin containing a conductive resin is applied so as to cover the surface 17 of the second conductive layer 5 and the third conductive layer 18 connected to the second conductive layer 5 is formed, the transfer layer 10 has a hole locally, the surface 19 of the third conductive layer 18 does not become flat, and the resin forming the third conductive layer 18 enters the hole, and the transmittance is increased. It is not preferable because it lowers.

  Further, the thickness of the adhesive layer 7 is set to a height slightly exceeding the height of the first conductive layer 3. In the present invention, the height of the first conductive layer 3 refers to the maximum height in the first conductive layer 3. The adhesive layer 7 is thermally transferred integrally with the first conductive layer 3 to the transfer substrate 8 in the next step. For this reason, the surface 13 of the adhesive layer 7 which is the surface on the base material 2 becomes a surface in contact with the substrate to be transferred 8 after thermal transfer. Therefore, if the first conductive layer 3 on the substrate 2 is not completely covered with the adhesive layer 7, sufficient adhesive strength cannot be obtained after thermal transfer. If the height of the adhesive layer 7 is the same as the height of the first conductive layer 3, it is not preferable because a portion where no adhesive is locally present on the adhesive surface with the substrate 8 to be transferred after thermal transfer. On the other hand, if the thickness of the adhesive layer 7 is increased more than necessary, the transmittance decreases, which is not preferable.

  The adhesive layer 7 may be provided on one surface of the transfer substrate 8 instead of being provided on the substrate 2 side.

  In addition to being highly transparent, the adhesive forming the adhesive layer 7 must be selected with the following points in mind. After the first conductive layer 3 is thermally transferred to the transfer substrate 8, the surface 15 of the first conductive layer 3 is etched using an acid solution or the like in the next step. Further, after the etching step, a plating operation for closing the hole 21 formed by etching with a plating film is performed. By these operations, the adhesive layer 7 comes into contact with the chemical and is placed in the environment of the etching operation and the plating operation. Therefore, it is necessary to select a chemical used in the etching process and the plating process and a material resistant to the environment.

  Various adhesives can be used as the adhesive used for the adhesive layer 7. Adhesive materials include polyvinyl chloride, polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyvinyl butyral, polyvinyl acetal, polyphenylene oxide, polybutadiene, poly (N-vinylcarbazole), polyvinyl pyrrolidone, hydrocarbon Resin, ketone resin, phenoxy resin, polyamide, chlorinated polypropylene, polyimide, urea, cellulose, vinyl acetate, ABS resin, polyurethane, phenol resin, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin, silicone resin and these Examples include at least one of the group consisting of copolymers, and / or any mixture thereof. Moreover, it is also possible to add conventionally well-known hardening | curing agents, such as an isocyanate type, a melamine type, and an epoxy type, in order to acquire the high tolerance with respect to the electrolyte solution of the transparent conductive substrate finally obtained.

  Moreover, an ultraviolet absorber, a color pigment, an antistatic agent, an antioxidant, a silane coupling agent, and the like can be appropriately used as necessary for the adhesive layer 7 as additives.

  As a method of forming the adhesive layer 7, a coating agent in which the above-mentioned adhesive material is dissolved in an organic solvent or water or dispersed in water to adjust the viscosity is prepared, and applied and dried by a conventionally known coating method such as gravure coating or spin coating. Can be used. The thickness of the adhesive layer 7 is preferably 0.5 to 50 μm, more preferably 1 to 30 μm. When the thickness of the adhesive layer 7 is less than 0.5 μm, the opening 12 of the first conductive layer 3 is not completely embedded with an adhesive, and the surface 14 of the transfer layer 10 after thermal transfer is locally perforated. It becomes. In the subsequent steps, the surface 15 of the first conductive layer 3 after the thermal transfer is etched, and the etching portion is plated to form the second conductive layer 5, but the perforated portion is not plated. Since it remains as it is, the surface 11 of the transparent conductive substrate 1 is not preferable because it does not become flat. Further, even when a resin containing a conductive resin is applied so as to cover the surface 17 of the second conductive layer 5 and the third conductive layer 18 connected to the second conductive layer 5 is formed, the transfer layer 10 has a hole locally, the surface 19 of the third conductive layer 18 does not become flat, and the resin forming the third conductive layer 18 enters the hole, and the transmittance is increased. Since it lowers, it is not preferable. Moreover, since the transmittance | permeability of the transparent conductive substrate 20 will fall when the thickness of the contact bonding layer 7 is thicker than 50 micrometers, it is unpreferable.

  Next, as shown in FIG. 1C, after the base material 2 and the transfer substrate 8 are bonded together, heat treatment, pressure treatment, and the like are performed, the base material 2 is peeled off, and the first conductive layer 3 is removed. Is transferred to the transfer substrate 8 through the adhesive layer 7. As the thermal transfer method, a known thermal transfer method can be used, and it may be appropriately selected according to the material of the base material 2 and the substrate to be transferred 8 and the adhesive layer. For example, a thermal transfer method using a hot laminator, a thermal transfer method using a hot press machine, a thermal transfer method using a thermal head, or the like can be used.

  The surface of the transfer layer 10 on the transfer substrate 8 obtained as described above is very flat because the substrate 2 is peeled after the substrate 2 and the transfer substrate 8 are bonded together. (FIG. 1 (d)), the step difference between the first conductive layer 3 and the adhesive layer 7 after thermal transfer is 300 nm or less so that the surface resistance value of the surface of the transfer layer 10 is 5 Ω / □ or less. . It is preferable to perform thermal transfer so that the increase rate of the surface resistance value after thermal transfer is 10% or less with respect to the surface resistance value of the first conductive layer 3 prepared by the above-described manufacturing method. When the rate of increase in the surface resistance value after thermal transfer is 10% or more, the adhesive layer 7 is inserted between the first conductive layer 3 and the second conductive layer 5 and includes the second conductive layer 5. Further, the surface resistance value of the transparent conductive substrate 1 is increased, which is not preferable.

  Even when the adhesive layer 7 is provided on the transferred substrate 8 instead of the base material 2 and the first conductive layer 3 is thermally transferred to the transferred substrate 8, the first conductive layer surface of the base material 2 and the transferred substrate 8 The first conductive layer 3 is embedded in the adhesive layer 7 with the bottom surface 9 of the first conductive layer 3 left, and after the thermal transfer, the base material 2 is peeled off, whereby the adhesive layer is adhered to the base material 2. The same state as when 7 is provided can be obtained.

  The substrate 8 to be transferred can be selected widely depending on each application. However, the following points need to be selected carefully. The surface 15 of the first conductive layer 3 after the thermal transfer is etched using an acid solution in the next step. Further, after the etching step, a plating operation for closing the hole 21 formed by etching with a plating film is performed. By these operations, the substrate 8 to be transferred comes into contact with the chemical and is placed in the environment of the etching operation and the plating operation. Therefore, it is necessary to select the chemical used in the etching process and the plating process and a material having resistance to the environment. Examples of the substrate 8 to be transferred include glass, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyphenylene sulfide, polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polycarbonate, acrylic resin, Si base material, and porous material. Examples thereof include ceramics. Among these, it is preferable to use a resin film such as polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyphenylene sulfide and the like because it can be produced at low cost by roll-to-roll.

  Next, as shown in FIG. 1E, the surface 15 of the first conductive layer 3 after the thermal transfer is etched. The etching method can be performed by wet etching using a chemical solution.

  The type and concentration of the etching solution used for the etching may be appropriately selected depending on the type of metal fine particles forming the first conductive layer 3. In the case of Ag, nitric acid, liquid for mixing phosphoric acid and nitric acid, ferric nitrate, mixed solution of ferric nitrate and sodium chlorite, mixed solution of sulfuric acid and ferric sulfate, ferric sulfate, etc. Can be given. For other metals, it is preferable to use an etching solution mainly composed of ferric chloride in the case of Cu or Ni. Moreover, the etching solution containing various surfactant etc. may be sufficient. Or what is marketed may be used. In consideration of the ease of etching and cost, a combination of Ag and a solution for mixing ferric nitrate-nitric acid or Cu and a solution for mixing hydrochloric acid or hydrochloric acid-ferric chloride is preferable. When the metal fine particles are amphoteric elements such as Al or Sn, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used as the alkaline solution. In the case of etching using an acid or alkali solution, it is preferable to carry out the etching under the condition that the adhesive layer 7 is not modified or deformed.

  The etching is performed by immersing the transfer substrate 8 on which the mesh-like first conductive layer 3 is laminated in the etching solution or spraying the etching solution on the surface 14 of the transfer layer 10 and then for a predetermined time. Let stand, and then wash with pure water. The degree of etching (depth) can be appropriately optimized in consideration of the resistance and conductivity of the dye-sensitized solar cell conductive substrate to the electrolyte.

  Next, as shown in FIG. 1F, plating is performed so as to close the hole 21 of the first conductive layer 3 formed by etching in the previous etching step. By this plating operation, the second conductive layer 5 that is electrically connected to the first conductive layer 3 is formed. As the metal for the plating treatment, a metal having corrosion resistance to the electrolyte is used, and includes one or more kinds of metals such as Ni, Zn, Au, Pt, Cr, Al, Cd, W, Sn, Co, and Fe, and the above metals. Alloys are preferred.

  As the plating method, electroless plating or electrolytic plating can be used. When electroless plating is performed, a catalyst such as Pd or Pd—Sn can be used as the catalyst. The plating conditions are preferably optimized so that only the holes 21 of the first conductive layer 3 are filled, and a step is generated between the surface 17 of the second conductive layer and the surface 16 of the adhesive layer. It is preferable not to do so. The thickness of the second conductive layer 5 is 0.1 to 10 μm, preferably 0.1 to 5 μm. If the thickness of the second conductive layer 5 is less than 0.1 μm, sufficient corrosion resistance cannot be obtained. If it exceeds 10 μm, the flatness deteriorates.

  The transparent conductive substrate 1 for a dye-sensitized solar cell obtained by the above production method is dye-sensitized because the second conductive layer 5 is resistant to an electrolyte solution, and has low resistance and excellent transparency. It can be suitably used as a transparent conductive substrate for a solar cell. Further, since the flatness of the surface 11 of the transparent conductive substrate 1 is excellent, this point is also advantageous as a transparent conductive substrate for a dye-sensitized solar cell.

  Further, as shown in FIG. 1 (g), a resin containing a conductive resin is applied to the surface 11 of the transparent conductive substrate 1 for further corrosion resistance and prevention of electrode localization on the transparent conductive substrate 1. Then, the third conductive layer 18 may be formed (FIG. 1 (g)).

  The third conductive layer 18 is preferably formed by applying and drying a coating liquid containing a conventionally known conductive polymer as a main component. Although there is no restriction | limiting in particular in the kind of electrically conductive polymer, Polythiophene, polyaniline, polypyrrole, its derivative (s), and mixtures thereof can be mentioned as a preferable electrically conductive polymer. Among them, a complex of poly (3,4-dialkoxythiophene) and polyanion is particularly preferable because of its excellent transparent conductivity. The solvent or dispersion medium contained in the conductive polymer coating solution is not particularly limited as long as it can dissolve or disperse the conductive polymer, and any of water, aqueous solvents, and organic solvents can be used.

  As a method for applying and drying the conductive polymer, a coating agent in which the above adhesive material is dissolved in an organic solvent or water or dispersed in water to prepare a viscosity is prepared and applied by a conventionally known coating method such as gravure coating or spin coating. A drying method can be used.

  In the case of an aqueous solvent, a mixed solvent of water and an organic solvent miscible with water can be used. The organic solvent miscible with water is not particularly limited, and examples thereof include the following solvents: alcohols such as methanol, ethanol, 2-propanol, 1-propanol, n-butanol; ethylene glycol, diethylene glycol, triethylene Ethylene glycols such as glycol and tetraethylene glycol; glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether and diethylene glycol dimethyl ether; ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, Glycol ethers such as diethylene glycol monobutyl ether acetate Acetates; propylene glycols such as propylene glycol, dipropylene glycol, tripropylene glycol; propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, propylene glycol dimethyl ether, dipropylene glycol Propylene glycol ethers such as dimethyl ether, propylene glycol diethyl ether, dipropylene glycol diethyl ether; propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether Propylene glycol ether acetates such as Tate; N- methylformamide, N, N- dimethylformamide, N- methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, acetone, acetonitrile and their blends.

  When the solvent or dispersion medium is an organic solvent system, the above-mentioned solvents that are miscible with water and the solvents that are immiscible with water may be mentioned. The latter includes toluene, xylene (o-, m-, or p-xylene). ), Benzene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, diethyl ether, diisopropyl ether, methyl-t-butyl ether, hexane, heptane, and the like. Normally, when the conductive polymer and the additive contained as necessary are completely dissolved in the solvent, the solvent is a “solvent” and any component is not dissolved but is dispersed. The case is described as “dispersion medium”.

  When the third conductive layer 18 of the present invention is a conductive polymer, a conductivity improver can be contained for the purpose of improving the conductivity. As such a conductivity improver, an organic solvent miscible with water is used. For example, ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, catechol, cyclohexanediol, diethylene glycol monoethyl Examples include ether, cyclohexanedimethanol, glycerin, dimethyl sulfoxide, N-methylpyrrolidone, N-methylformamide, N, N-dimethylformamide, γ-butyrolactone, isophorone, propylene carbonate, and cyclohexanone. These may be used individually by 1 type and may use 2 or more types together. These organic solvents may be used also as a solvent or a dispersion medium. When the conductivity improver is contained, the amount is not particularly limited, but it is usually contained in the composition at a ratio of 95% by mass or less.

The conductive polymer coating liquid preferably contains a binder because scratch resistance and surface hardness of the coating film are increased, and resistance to the electrolyte solution is improved.
The binder may be a thermosetting resin or a thermoplastic resin. For example, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyimides; polyamide imides; polyamides such as polyamide 6, polyamide 6, 6, polyamide 12, and polyamide 11; polyvinylidene fluoride, polyvinyl fluoride, polytetrafluoroethylene Fluoropolymers such as ethylene tetrafluoroethylene copolymer and polychlorotrifluoroethylene; vinyl resins such as polyvinyl alcohol, polyvinyl ether, polyvinyl butyral, polyvinyl acetate, and polyvinyl chloride; epoxy resins; xylene resins; aramid resins; Polyurea; polyurea; melamine resin; phenol resin; polyether; acrylic resin and copolymers thereof. These binders may be dissolved in an organic solvent, may be provided with a functional group such as a sulfonic acid group or a carboxylic acid group, may be formed into an aqueous solution, or may be dispersed in water such as emulsification.

  The content of the binder is preferably 0.1 to 1000 times, more preferably 1 to 100 times the amount of the conductive polymer. When the content of the binder is less than the lower limit, the film strength of the resulting conductive coating film tends to be low. When the content exceeds the upper limit, there is a decrease in conductivity due to a decrease in the conductive polymer concentration. May happen.

  The thickness of the third conductive layer 18 is preferably 0.1 to 10 μm, more preferably 0.2 to 3.5 μm. When it is less than 0.1 μm, iodine resistance is lowered. If it exceeds 10 μm, the transparency deteriorates.

  The transparent conductive substrate 22 obtained by the above manufacturing method is transparent for a dye-sensitized solar cell because the third conductive layer 18 is resistant to an electrolyte solution, and has low resistance and excellent transparency. It can be suitably used as a substrate.

  The measurement of the electrical resistance of the transparent conductive substrate was measured in accordance with JIS-K-7194 using a series 4-probe probe (ASP) in Loresta-GP (manufactured by Dia Instruments, model number: MCP-T610). The four-terminal four-probe method was used.

  The optical transmittance was evaluated as the total light transmittance. The transparent conductive substrate was measured according to JIS K-7105 using a haze meter (model number: NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

  The iodine electrolyte solution used for evaluation was the content of a commercially available dye-sensitized solar cell production kit (manufactured by Nishinoda Electric Co., Ltd.). The iodine electrolyte solution was applied onto the produced transparent conductive substrate, and allowed to stand in the dark at room temperature for 24 hours. The iodine electrolyte solution was washed with pure water and ethanol and then dried, and the surface resistance value was compared after the transparent conductive substrate was produced and after the iodine resistance test.

Example 1
<Preparation method of silver fine particles 1>
The liquid phase reduction preparation method of silver fine particles will be described as an example of the metal fine particles, but the type and production method of the metal fine particles are not limited.
40 g of silver nitrate, 37.9 g of butylamine, and 200 mL of methanol were added and stirred for 1 hour to prepare solution A. Separately, 62.2 g of isoascorbic acid was taken, 400 mL of water was added and dissolved by stirring, and then 200 mL of methanol was added to prepare solution B. B liquid was stirred well and A liquid was dripped at B liquid over 1 hour and 20 minutes. After completion of the dropwise addition, stirring was continued for 3 hours and 30 minutes.
After completion of stirring, the mixture was allowed to stand for 30 minutes to precipitate the solid. After removing the supernatant by decantation, 500 mL of water was newly added, and the supernatant was removed by stirring, standing, and decantation. This purification operation was repeated three times. The settled solid was dried in a dryer at 40 ° C. to remove moisture. Furthermore, 20 g of the obtained silver fine particles and 0.2 g of DISPERBYK-106 (manufactured by Big Chemie Japan) were mixed in a mixed solution of 100 mL of methanol and 5 mL of pure water, mixed for 1 hour, and then 100 mL of pure water was added. After filtering the slurry, the slurry was dried in a dryer at 40 ° C. to obtain silver fine particles 1. Silver fine particles had an average primary particle diameter of 60 nm as observed with an electron microscope.

<Preparation of silver fine particle dispersion 2>
The dispersion of silver fine particles was prepared with reference to Patent Document 4 (prepared with reference to JP 2005-530005 A).
That is, 4 g of the silver fine particles 1, 30 g of toluene, and 0.2 g of BYK-410 (manufactured by Big Chemie Japan) were mixed, and subjected to a dispersion treatment for 1.5 minutes with an ultrasonic disperser with an output of 180 W to obtain 15 g of pure water. Was added, and the obtained emulsion was subjected to a dispersion treatment for 30 seconds with an ultrasonic disperser with an output of 180 W to prepare a silver fine particle dispersion solution 2.

<Method for forming first conductive layer>
The silver fine particle dispersion 2 was coated on a polyethylene terephthalate substrate having a thickness of 100 μm using a bar coater. Subsequently, by spontaneous drying in the air, the silver fine particles formed a network structure by the self-organization phenomenon. Next, after heating at 150 ° C. for 2 minutes, each was immersed in acetone and 1N hydrochloric acid, and then heated and dried at 150 ° C. for 5 minutes to form a first conductive layer. After the first conductive layer was formed on the substrate, the total light transmittance was 85%, and the surface resistance value was 4.5Ω / □.

<Formation of adhesive layer>
The thickness after drying the following adhesive layer coating solution 1 on the first conductive layer surface side of the substrate on which the first conductive layer is formed is 5.1 μm (Example 1), 6.0 μm (Example 2). , 6.5 μm (Example 3), and dried at a temperature of 100 ° C. for 5 minutes to form an adhesive layer.

<Adhesive layer coating solution 1>
An adhesive resin coating solution 1 was prepared by adding 8.5 g of an acrylic resin (manufactured by Mitsubishi Rayon, Dianar BR83) +1.5 g of a polyester resin (byron 200, Byron 200) +75 g of toluene + 15 g of methyl ethyl ketone and stirring.

<Thermal transfer>
A hot laminator (manufactured by Taisei Laminator, Taisei First Laminator) is made to face the surface of the polyethylene terephthalate substrate having a thickness of 100 μm on which the surface of the 125 μm thick polyethylene terephthalate substrate is formed and the first conductive layer and the adhesive layer are formed. VAII-700) was used for heat pressure welding at 180 ° C. and left to cool to room temperature, and then the polyethylene terephthalate substrate was peeled off, and the first conductive layer and the adhesive layer were thermally transferred onto the polyethylene terephthalate substrate.

<Formation of second conductive layer>
A mixed aqueous solution of 10 wt% ferric nitrate-14 wt% nitric acid was prepared as an etching solution. The transparent conductive substrate produced by the transfer operation is immersed in the etching solution, and 0.8 μm (Example 1), 1.0 μm (Example 2), and 1.5 μm (Example 3) from the substrate surface. The etching process was performed under the condition that etching can be performed at a depth of 5 mm.
Subsequently, a Ni—Zn electroless plating solution was prepared, and the plating treatment was performed under conditions of film thicknesses of 0.8 μm (Example 1), 1.0 μm (Example 2), and 1.5 μm (Example 3). Then, a second conductive layer of Ni—Zn was formed in the etching hole.
The produced transparent conductive substrate has a surface resistance of 0.08Ω / □ (Example 1), 0.08Ω / □ (Example 2), 0.05Ω / □ (Example 3), and a total light transmittance of 85. % (Examples 1 to 3).

<Iodine resistance evaluation results>
The evaluation results of iodine resistance are shown in Table 1. The transparent conductive substrates prepared in Examples 1 to 3 and Comparative Examples 1 and 2 had iodine resistance. On the other hand, the transparent conductive substrate of Comparative Example 2 did not have sufficient iodine resistance because the plating film was thin.

Comparative Example 1
The first conductive layer was formed on the polyethylene terephthalate substrate by the method of Example 1. Subsequently, a Ni—Zn electroless plating solution was prepared, and a plating process was performed under the condition of a film thickness of 1.5 μm to form a second conductive layer.
The surface resistance value of the produced transparent conductive substrate was 0.05Ω / □, the total light transmittance was 65%, and the surface resistance value was lowered by the plating treatment, but the width of the conductive portion in the network structure was widened. The total light transmittance has decreased.

Comparative Example 2
The first conductive layer was formed on the polyethylene terephthalate substrate by the method of Example 1. Subsequently, a Ni—Zn electroless plating solution was prepared, and a plating process was performed under the condition of a film thickness of 0.05 μm to form a second conductive layer.
When the iodine resistance test of the produced transparent conductive substrate was performed, the conductive portion was dissolved in the iodine electrolyte solution, and the surface resistance value could not be measured.

  The transparent conductive substrate according to the present invention is not limited to a dye-sensitized solar cell electrode substrate, but is also applied to a transparent conductive substrate requiring corrosion resistance and weather resistance, such as a conductive film for a touch panel and an electromagnetic shielding film. I can do it. Further, even if the transparent conductive substrate is not particularly required to have corrosion resistance or the like, the transparent conductive substrate according to the present invention has a low resistance and a high transmittance and also has an excellent flatness on the upper surface of the substrate. It can be suitably used as a conductive substrate.

DESCRIPTION OF SYMBOLS 1 Transparent conductive substrate 2 Base material 3 1st conductive layer 5 2nd conductive layer 7 Adhesive layer 8 Transferred substrate 10 Transfer layer 11 Surface of transparent conductive substrate 12 Opening 14 Surface of transfer layer 15 1st after heat transfer Surface of one conductive layer 16 Surface of adhesive layer after thermal transfer 17 Surface of second conductive layer 18 Third conductive layer 21 Hole

Claims (12)

In the manufacturing method of a transparent conductive substrate, it manufactures in the manufacturing process of the following 1 to 5, The manufacturing method of the transparent conductive substrate characterized by the above-mentioned.
1. A metal fine particle dispersion solution is applied on a substrate and dried, and a first conductive layer forming step 2 for forming a network-like first conductive layer on the substrate. The first conductive layer is completely covered. Adhesive layer laminating step 3 for laminating a transparent adhesive layer, the adhesive layer surface and the substrate to be transferred are bonded together, heated and pressed, then the substrate is peeled off, and the first conductive layer and the adhesive layer are integrated. A thermal transfer step 4 for thermally transferring the transferred layer to the substrate to be transferred, an etching step 5 for etching the surface of the thermally transferred first conductive layer, and plating the holes formed by the etching to laminate a second conductive layer. Second conductive layer formation process In the manufacturing method of a transparent conductive substrate, it manufactures in the manufacturing process of the following 1 to 5, The manufacturing method of the transparent conductive substrate characterized by the above-mentioned.
1. A metal fine particle dispersion solution is applied on a substrate and dried to form a first conductive layer having a mesh shape on the substrate. 2. A transparent adhesive layer is formed on the substrate to be transferred. Laminating adhesive layer laminating step 3, the first conductive layer surface and the substrate to be transferred are bonded, heated and pressed, then the substrate is peeled off, and the transfer layer in which the first conductive layer and the adhesive layer are integrated A thermal transfer process 4 for thermally transferring the surface of the substrate to the transfer substrate, an etching process 5 for etching the surface of the thermally transferred first conductive layer, and a second conductive layer for plating the hole formed by the etching and laminating the second conductive layer. Layer formation process   The first conductive layer forming step is a first conductive layer forming step in which a metal fine particle paste is printed on a substrate and dried to form a network-like first conductive layer on the substrate. A method for producing a transparent conductive substrate according to claim 1 or 2.   In the first conductive layer forming step, a solution of a metal salt, which is a precursor of metal fine particles, is applied to a substrate and dried, and then the metal fine particle precursor is reduced or precipitated by heating, ultraviolet irradiation or a reducing gas. 3. The method for producing a transparent conductive substrate according to claim 1, wherein the method is a first conductive layer forming step of forming a network-like first conductive layer on a base material.   5. The method according to claim 1, further comprising a step of performing heat treatment and / or chemical treatment on the first conductive layer between the first conductive layer forming step and the adhesive layer laminating step. The manufacturing method of the transparent conductive substrate of any one of Claims 1.   The surface treatment is applied to the base material before applying the metal fine particle dispersion solution, the metal fine particle paste, or the metal salt solution to the base material. The manufacturing method of the transparent conductive substrate of description.   The thickness of the adhesive layer is higher than the height of the first conductive layer, and the first conductive layer is not in contact with the substrate to be transferred. Manufacturing method of transparent conductive substrate.   A third conductive layer forming step of further laminating a third conductive layer on the surface of the transparent conductive substrate obtained by the method for producing a transparent conductive substrate according to claim 1. The manufacturing method of the transparent conductive substrate of any one of Claim 1 to 7 characterized by these.   The transparent conductive substrate obtained by the manufacturing method of the transparent conductive substrate of any one of Claim 1 to 8.   The transparent conductive substrate according to claim 9, wherein a maximum step between the first conductive layer and the adhesive layer is 300 nm or less, and a surface resistance value of the surface is 5Ω / □ or less.   The transparent conductive substrate according to claim 9 or 10, wherein the adhesive layer contains at least one adhesive selected from the group consisting of an acrylic adhesive and a polyester adhesive.   The transparent conductive substrate according to any one of claims 9 to 11, wherein the second conductive layer and the third conductive layer are resistant to an electrolyte solution. Transparent conductive substrate for sensitive solar cells.

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