JP4951832B2 - Method for producing transparent conductive film - Google Patents

Description

【００５８】
上記表１の結果から、溶媒浸透層と凝集促進層の積層体上に銀微粒子水溶液を塗布することにより、ＰＥＴ基材のみ、溶媒浸透層のみ及び凝集促進層のみの積層体上に銀微粒子水溶液を塗布する場合に比べて、銀微粒子の凝集状態がほどよく制御され、良好な表面抵抗と可視光線透過率を示した。
【００５９】
【発明の効果】
本発明の透明導電膜は、金属微粒子凝集層の下側に、凝集促進層、好ましくは、さらに凝集促進層の下側に、溶媒の浸透を促進させる溶媒浸透層を設けることにより、金属微粒子の凝集が制御され、良好な表面抵抗と可視光線透過率を両立したものとなる。
また、上記構成から成るので、金属微粒子凝集層を形成するための塗布液を、全面に塗布、形成しても、網目状等の部分的に金属微粒子凝集層を形成することができる。
【図面の簡単な説明】
【図１】 本発明の透明導電膜の１例を示す断面図である。
【符号の説明】
１ 金属微粒子凝集層
２ 凝集促進層
３ 溶媒浸透層
４ 透明基材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic wave shielding film for various display devices such as EL, PDP, CRT, and LCD, a transparent electrode, or a transparent 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 transparent conductive film that can be heat-treated at a low temperature and can be applied to a wider range of substrates, and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, a transparent conductive film has been generally obtained by forming a thin film made of a conductive oxide such as tin-doped indium oxide (ITO) or a metal such as silver by a dry process such as sputtering or vapor deposition. Since the dry process is performed in a high vacuum, there is an essential problem that the film forming process is complicated and expensive.
[0003]
On the other hand, in recent years, a wet process typified by wet coating has been actively attempted as a low-cost method for forming a transparent conductive layer. As a wet coating material, a material obtained by dispersing a conductive material such as ITO fine particles or metal fine particles in a dispersion medium together with a binder and a dispersion stabilizer is generally used.
[0004]
Among these, the transparent conductive film using ITO fine particles has a surface resistance that can be achieved due to the intergranular resistance between the fine particles in the coating layer, which is at least 1000Ω / □ to 10,000Ω / □. The required level of conductivity cannot be obtained. Moreover, although resistance reduction is also possible by performing high temperature heat processing at 350 to 400 degreeC or more, a base material will be limited to glass.
[0005]
On the other hand, the metal fine particles have a volume specific resistivity smaller than that of the conductive oxide in the order of 1/100, and in addition to the conductive oxide fine particles, or the bulk state of the metal fine particles. In general, it is known that fusion of particles occurs at a low temperature.
For this reason, when the metal fine particles are used as a transparent conductive material for wet coating, it is possible to obtain a level of conductivity necessary for the above-mentioned application by heat treatment at a relatively low temperature. Recently, as a transparent conductive material, Attention has been paid.
[0006]
[Problems to be solved by the invention]
However, even when the metal fine particles are used, the temperature required to develop the level of conductivity required for the application is 150 to 200 ° C. or higher. It cannot be said that the temperature can be treated, and the problem that the usable substrate is limited has not been solved.
In addition, when using a coating liquid containing metal fine particles, mixing the metal fine particles and a compound other than a solvent increases the coating suitability, but the metal fine particles tend to agglomerate, and the stability of the coating liquid is poor. Generally, the conductivity is lowered.
However, a solution containing only metal fine particles and a solvent has extremely poor suitability for application to a general substrate.
[0007]
The present invention has been made in view of this problem, and it is possible to use a solution containing only metal fine particles and a solvent, and further, a transparent material exhibiting conductivity necessary for the use of the conductive film at a low heat treatment temperature. An object is to provide a conductive film.
[0008]
[Means for Solving the Problems]
The invention according to claim 1, after forming a solvent permeation layer containing one or more types of inorganic oxide fine particles on a transparent substrate , laminating an aggregation promoting layer containing one or more types of inorganic oxide fine particles, Coating and drying a metal fine particle solution comprising metal fine particles and a solvent to form a metal fine particle aggregated layer in which the metal fine particles are aggregated, and the kind and composition ratio of the inorganic oxide fine particles contained in the solvent permeation layer are The method for producing a transparent conductive film is characterized in that the kind and / or composition ratio of the inorganic oxide fine particles contained in the aggregation promoting layer is different .
[0010]
The invention according to claim 2, wherein the coagulation promoting layer is a method for producing a transparent conductive film according to claim 1, wherein the total content of the inorganic oxide fine particles is 20 weight% or more.
[0012]
The invention according to claim 3, wherein the solvent permeation layer is a manufacturing method according to claim 1 or 2 transparent conductive film, wherein the total content of the inorganic oxide fine particles is 20 wt% or more .
[0019]
The invention according to claim 4 is the method for producing a transparent conductive film according to any one of claims 1 to 3 , wherein the thickness of the aggregation promoting layer is provided in a range of 10 to 10,000 nm.
[0020]
The invention according to claim 5 is the method for producing a transparent conductive film according to any one of claims 1 to 4 , wherein the film thickness of the solvent permeation layer is provided in a range of 1 to 100 μm.
[0021]
The invention according to claim 6 is any one of Ag, Al, Cu, Au, Pt, Pd, or a combination or alloy of two or more thereof as the metal fine particles forming the metal fine particle aggregated layer. A method for producing a transparent conductive film according to any one of claims 1 to 5 .
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below.
[0024]
First, as shown in FIG. 1, in the present invention, one or more aggregation promoting layers 2 containing inorganic oxide fine particles are formed on a transparent substrate 4, and only metal fine particles and a solvent are formed on the aggregation promoting layer 2. It is the transparent conductive film in which the metal fine particle aggregation layer 1 which consists of this was formed.
Here, the aggregation promoting layer 2 may be formed on the entire surface or partially.
[0025]
Thus, by applying a solution consisting only of metal fine particles and a solvent on the aggregation promoting layer, the solvent selectively permeates mainly into the pores formed by the gaps between the inorganic oxide fine particles and the inorganic oxide fine particles, Accordingly, the aggregation of the metal fine particles is promoted in a portion close to the surface, and an appropriate metal fine particle aggregate layer can be formed at a low heat treatment temperature.
[0026]
Hereinafter, the layer configuration in the case where one solvent permeation layer 3 and one aggregation promoting layer 2 are provided will be described, but the present invention is not limited to this configuration.
[0027]
Here, the transparent substrate 4 in the present invention is not particularly limited, and may be appropriately selected from known transparent plastic films or sheets having appropriate mechanical rigidity including various glass substrates. it can. Specific examples include films of polyester, polyethylene, polypropylene, triacetyl cellulose, diacetyl cellulose and the like.
[0028]
In addition, the metal fine particles preferably have a primary particle size of 50 nm or less from the viewpoint of transparency. When the primary particle size is 50 nm or more, not only the transparency is lowered but also haze is likely to occur, leading to deterioration of visibility. Further, examples of the metal species of the metal fine particles used in the metal fine particle aggregated layer 1 include Ag, Au, Cu, Al, Pd, and the like, but those mainly composed of Ag are preferable from the viewpoint of conductivity and transparency. Further, in order to improve color tone and chemical stability, those two or more alloys, particularly an alloy containing Ag is preferable.
[0029]
The fine metal particles can be prepared relatively easily by a number of known techniques represented by the method published by Carey-Lea in 1889 (Am. J. Sci., Vol. 37, pp. 491, 1889). Is possible.
[0030]
In addition to the solvent, the metal fine particle solution includes a dispersing agent such as citric acid used during preparation, a reducing agent that has not been completely washed out, and other additives, but the metal dispersion performance in the solution. Since it may cause deterioration or conductivity deterioration after application, it is preferable not to add other additives.
[0031]
As described above, it is desirable not to add an additive to the metal fine particle solution. However, a dispersion stabilizer or a binder is added for the purpose of improving the dispersibility of metal fine particles, improving the coating suitability, and improving the coating film strength. May be.
[0032]
Examples of the additive include carboxylic acids such as citric acid, stearic acid, lauric acid, and oleic acid, sulfonic acids such as phenyldiazosulfonic acid and dodecylbenzenesulfonic acid, and water-soluble substances such as polyvinyl alcohol, polyvinylpyrrolidone, and polyethylene glycol. It is preferable to use a polymer compound.
[0033]
Solvents used for the metal fine particle solution include water; alcohols such as methanol, ethanol, propanol, butanol, diacetone alcohol, ethylene glycol, and hexylene glycol; esters such as acetic acid methyl ester and ethyl acetate; diethyl ether; Examples include ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether; ketones such as acetone, methyl ethyl ketone, acetylacetone, and acetoacetate. These may be used singly or in combination of two or more.
[0034]
The aggregation promoting layer 2 can achieve the purpose by containing 20% or more of inorganic oxide fine particles, and the higher the content, the more preferable.
[0035]
The inorganic oxide fine particles contained in the solvent permeation layer 3 have almost no gaps between the particles when the particle size is too small. On the other hand, when the particles are too large, the gaps between the particles become large and proper solvent penetration occurs. Since it becomes difficult and appropriate aggregation of the metal fine particles in the aggregation promoting layer is difficult to occur, the particle diameter is preferably in the range of 10 nm to 100 μm, and more preferably in the range of 100 nm to 10 μm.
The structure of the inorganic oxide fine particles is preferably a flake shape, a feather shape, or a shape close to a plate shape.
[0036]
The inorganic oxide species of the inorganic oxide fine particles contained in the solvent permeation layer 3 is not particularly limited, and general silicon oxide fine particles and aluminum oxide fine particles can be used.
[0037]
The other component contained in the solvent-penetrating layer 3 preferably contains a binder and / or a binder precursor monomer from the viewpoints of coating suitability and coating strength, and the binder is water-soluble such as polyvinyl alcohol or polyethylene glycol. Examples include, but are not limited to, polymers, thermosetting resins and monomers, and photocurable resins and monomers.
[0038]
As the content of the binder and / or binder precursor monomer contained in the solvent permeation layer 3, if it is too large, there will be no gap between the inorganic oxide fine particles, and if it is too small, the coating suitability and the coating strength will be poor. Therefore, the amount is preferably in the range of 1 to 100 parts by weight, more preferably in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the inorganic oxide fine particles.
[0039]
The thickness of the solvent permeation layer 3 is preferably in the range of 100 nm to 100 μm, more preferably in the range of 1 μm to 50 μm.
[0040]
As the inorganic oxide fine particles contained in the aggregation promoting layer 2, when the particle size is too small, there are almost no gaps between the particles, and when the particle size is too large, the gaps between the particles become large and appropriate aggregation of the metal fine particles occurs. Since it becomes difficult, the particle diameter is preferably in the range of 1 nm to 10 μm, more preferably in the range of 10 nm to 1 μm, and further preferably a shape close to a sphere.
[0041]
The inorganic oxide species of the inorganic oxide fine particles contained in the aggregation promoting layer 2 is not particularly limited, and general silicon oxide fine particles and aluminum oxide fine particles can be used.
[0042]
The other component contained in the aggregation promoting layer 2 preferably contains a binder and / or a binder precursor monomer from the viewpoint of coating suitability and coating strength, and the binder is water-soluble such as polyvinyl alcohol or polyethylene glycol. Examples include, but are not limited to, polymers, thermosetting resins and monomers, and photocurable resins and monomers.
[0043]
When the content of the binder and / or binder precursor monomer contained in the aggregation promoting layer 2 is too large, there is no gap between the inorganic oxide fine particles, and when it is too small, the coating suitability and the coating strength are poor. Therefore, the amount is preferably in the range of 1 to 100 parts by weight, more preferably in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the inorganic oxide fine particles.
[0044]
The film thickness of the aggregation promoting layer 2 is preferably in the range of 5 nm to 10 μm, more preferably in the range of 10 nm to 2 μm.
[0045]
As a coating method of the metal fine particle solution, the solvent permeation layer, and the aggregation accelerating layer for forming the metal fine particle agglomerated layer, usual film formation such as spin coating method, ink jet method, roll coating method, spray method, bar coating method, dip method, etc. The method can be used.
[0046]
After forming the metal fine particle aggregated layer, various overcoat layers can be further provided on the upper layer to impart various functions.
[0047]
【Example】
A. Preparation of Silver Fine Particle Aqueous Solution A silver fine particle dispersed aqueous solution was prepared by a 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%.
[0048]
B. Preparation of coating solution for forming solvent permeation layer 25 parts by weight of flaky alumina sol aqueous solution (Alumina sol 520 manufactured by Nissan Chemical Industries, 20% by weight of alumina) and 5 parts by weight of 10% by weight aqueous solution of polyvinyl alcohol (PVA217 manufactured by Kuraray) A solution prepared by mixing distilled water at a ratio of 100 parts by weight was prepared by stirring for 30 minutes.
[0049]
C. Preparation of a coating solution for forming an aggregation promoting layer 25 parts by weight of a spherical silica sol aqueous solution (Snowtex Ak, manufactured by Nissan Chemical Industries, silica content 20% by weight) and 5 parts by weight of a 10% by weight aqueous solution of polyvinyl alcohol (PVA217, manufactured by Kuraray) And the solution which mixed distilled water in the ratio of 100 weight part was prepared by stirring for 30 minutes.
[0050]
D. 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 for each transparent substrate.
[0051]
Example 1
On a polyethylene terephthalate (PET) film (A4300 manufactured by Toyobo Co., Ltd.), a coating solution for forming a solvent permeation layer was applied by a wire bar coating method so that the film thickness after drying was 10 μm, and dried at 120 ° C. for 1 minute. A solvent permeation layer was formed. On this solvent permeation layer, a coating solution for forming an aggregation promoting layer was applied by wire bar coating so that the film thickness after drying was 0.1 μm, and dried at 120 ° C. for 1 minute to form an aggregation promoting layer. . Further, a silver fine particle aqueous solution was applied on the aggregation promoting layer by a wire bar coating method so as to have a wet film thickness of 1 μm, and then dried at 120 ° C. for 1 minute to form a film.
[0052]
(Comparative Example 1)
An aqueous silver fine particle solution was applied onto a PET film (A4300 manufactured by Toyobo Co., Ltd.) by a wire bar coating method so as to have a wet film thickness of 1 μm, and then dried at 120 ° C. for 1 minute to prepare a target film.
[0053]
(Comparative Example 2)
On a PET film (Toyobo A4300), a coating solution for forming an aggregation promoting layer is applied by a wire bar coating method so that the film thickness after drying is 0.1 μm, and dried at 120 ° C. for 1 minute to promote aggregation. A layer was formed. Further, a silver fine particle aqueous solution was applied on the aggregation promoting layer by a wire bar coating method so as to have a wet film thickness of 1 μm, and then dried at 120 ° C. for 1 minute to form a film.
[0054]
(Comparative Example 3)
On the PET film (Toyobo A4300), a coating solution for forming an aggregation promoting layer was applied by a wire bar coating method so that the film thickness after drying was 10 μm, and dried at 120 ° C. for 1 minute to form an aggregation promoting layer. Formed. A silver fine particle aqueous solution was applied on the aggregation promoting layer by a wire bar coating method to a wet film thickness of 1 μm, and then dried at 120 ° C. for 1 minute to form a film.
[0055]
(Comparative Example 4)
On the PET film (Toyobo A4300), a coating solution for forming a solvent osmotic layer was applied by a wire bar coating method so that the film thickness after drying was 10 μm, and dried at 120 ° C. for 1 minute. Formed. A silver fine particle aqueous solution was applied on the solvent permeation layer by a wire bar coating method to a wet film thickness of 1 μm, and then dried at 120 ° C. for 1 minute to form a film.
[0056]
The characteristics of the produced conductive film are shown in Table 1 below.
[0057]
[Table 1]

[0058]
From the results of Table 1 above, by applying the silver fine particle aqueous solution on the laminate of the solvent permeation layer and the aggregation promoting layer, the silver fine particle aqueous solution is formed on the laminate of only the PET base material, only the solvent permeation layer and only the aggregation promoting layer. Compared with the case of coating, the agglomeration state of the silver fine particles was moderately controlled, and good surface resistance and visible light transmittance were exhibited.
[0059]
【Effect of the invention】
The transparent conductive film of the present invention is provided with an aggregation promoting layer below the metal fine particle agglomerated layer, preferably a solvent permeation layer for promoting solvent penetration below the aggregation promoting layer. Aggregation is controlled to achieve both good surface resistance and visible light transmittance.
Moreover, since it consists of the said structure, even if the coating liquid for forming a metal fine particle aggregate layer is apply | coated and formed on the whole surface, a metal fine particle aggregate layer can be formed partially, such as mesh shape.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a transparent conductive film of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal particulate aggregation layer 2 Aggregation promotion layer 3 Solvent penetration layer 4 Transparent base material

Claims (6)

After forming a solvent permeation layer containing one or more types of inorganic oxide fine particles on a transparent substrate, an aggregation promoting layer containing one or more types of inorganic oxide fine particles is laminated, and then metal fine particles composed of metal fine particles and a solvent. Applying and drying the solution to form a metal fine particle aggregated layer in which the metal fine particles are aggregated,
The method for producing a transparent conductive film, wherein the kind and composition ratio of the inorganic oxide fine particles contained in the solvent permeation layer are different from the kind and / or composition ratio of the inorganic oxide fine particles contained in the aggregation promoting layer .   The method for producing a transparent conductive film according to claim 1, wherein the aggregation promoting layer has a total content of inorganic oxide fine particles of 20% by weight or more.   The method for producing a transparent conductive film according to claim 1, wherein the solvent permeation layer has a total content of inorganic oxide fine particles of 20 wt% or more.   The method for producing a transparent conductive film according to any one of claims 1 to 3, wherein the aggregation promoting layer has a thickness of 10 to 10,000 nm.   The method for producing a transparent conductive film according to claim 1, wherein a film thickness of the solvent permeation layer is provided in a range of 1 to 100 μm.   6. The metal fine particles forming the metal fine particle aggregated layer are Ag, Al, Cu, Au, Pt, Pd, or a combination or alloy of two or more kinds thereof. Any manufacturing method of the transparent conductive film.

Images