JPH09194233A - Transparent conductive film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an inexpensive transparent conductive film low in resistance, with the characteristic fluctuation reduced even in an high-temp. and high-humidity environment and excellent in reliability from an ITO fine particle by this method. SOLUTION: An ITO fine particle is dispersed in resin and org. solvent, and the dispersion is applied on a substrate 11, dried and calcined to form a film 12 consisting of the ITO fine particle. A soln. of a metallic compd. is applied thereon, dried and calcined to form a metal oxide 13 filling the pore of the film 12, and a transparent conductive film 14 which is hardly affected by gas and moisture and excellent in reliability is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive film composed of indium tin oxide (hereinafter referred to as ITO) fine particles and a method for manufacturing the same.

[0002]

2. Description of the Related Art A transparent conductive film is widely used as an electrode of a display element such as a touch panel, an EL element and a liquid crystal display, and a resistance heating element for preventing fogging or icing of window glass of an aircraft, an automobile or the like. .

Such transparent conductive films are classified as follows according to the manufacturing method. (1) A method of depositing tin oxide or the like directly on a substrate (2) A method of depositing ITO or the like as a target by sputtering (3) A CVD method using a metal alkoxide (4) A substrate of an organic salt of tin or indium Method of applying and thermally decomposing on (5) Method of printing / applying ink containing fine particles of ITO etc. According to the method of (5) above, it is the most inexpensive and has a large area without complicated steps. ITO easily on the substrate
A transparent conductive film can be manufactured. At present, there is proposed a method of forming an ITO transparent conductive film by printing / applying a paste-like ink in which ITO powder is dispersed in a resin or an organic solvent on a substrate, drying and baking it (for example, JP-A-4-26
768).

[0004]

However, in the transparent conductive film produced by printing / coating and baking the above ITO powder, volatile components and thermal decomposition components escape from the film during drying and baking. After the removal, the pores remain and become a porous film. In addition, since the bond between the substrate and the ITO powder and the ITO powder is weak, the strength as a film is insufficient. Due to the above factors, there are drawbacks that the conductivity is lower than the transparent conductive film formed by sputtering or CVD, and the abrasion resistance and reliability are poor (especially, the resistance value change is large in a high temperature and high humidity environment).

In order to solve the above-mentioned problems, the present invention provides a transparent conductive film having high conductivity and less reliability even in a high temperature and high humidity environment and excellent in reliability, and a method for manufacturing the same. With the goal.

[0006]

In order to achieve the above-mentioned object, the transparent conductive film of the present invention comprises a film composed of ITO fine particles and a metal oxide filling the pores in the film.

With the above structure, a transparent conductive film having high conductivity and excellent reliability can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is composed of a film composed of ITO fine particles and a metal oxide for filling pores in the film, and is not easily affected by gas and moisture. The transparent conductive film has excellent reliability.

According to the second aspect of the present invention, the metal oxide film covers the film made of the ITO fine particles, whereby the reliability and abrasion resistance can be made excellent.

According to the third aspect of the invention, the metal oxide film contains silicon oxide, and the strength, transparency,
It has excellent gas barrier properties.

In the invention according to claim 4, the metal oxide film contains tin oxide, and the film can have a lower resistance.

According to a fifth aspect of the present invention, the first step of forming a film made of ITO fine particles by applying ITO fine particles dispersed in a resin and an organic solvent onto a substrate, drying and firing the film is formed. And a second step of applying a solution of a metal compound thereon, drying, and then firing to form a metal oxide so as to fill the pores of the film. It is possible to obtain a transparent conductive film having low resistance and excellent reliability by a low cost and simple process.

The invention according to claim 6 is a method of forming a film made of a metal oxide in the second step so as to cover the film made of the ITO fine particles formed in the first step, which is abrasion resistant. A transparent conductive film having excellent properties can be obtained.

The invention according to claim 7 is a method of filling voids by using a metal compound containing a silicon compound, and it is possible to obtain a material excellent in strength transparency and gas barrier property.

Further, according to the invention described in claim 8, a metal compound containing a tin compound is used to fill voids to obtain a lower resistance.

According to the ninth aspect of the present invention, the step of firing the metal compound is performed in an inert atmosphere or a reducing atmosphere, and a film having lower resistance and high transparency can be obtained. You can

Further, the invention according to claim 10 is ITO.
The step of baking fine particles dispersed in a resin and an organic solvent is sequentially performed in the air, and subsequently in an inert atmosphere or a reducing atmosphere to obtain a better film.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 1 is a sectional view showing an embodiment of the transparent conductive film of the present invention, and FIG. 2 is an enlarged view of the vicinity of the surface of the transparent conductive film. Silica-coated glass substrate 1
A transparent conductive film 14 is composed of a film 12 made of ITO fine particles 15 and a metal oxide 13 filling the holes in the film.

FIG. 3 is a view for explaining the method of manufacturing the transparent conductive film of the present invention. In the first step, a substrate 21 made of glass or the like is prepared (FIG. 3A), and a substance 22 in which ITO fine particles are dispersed in a resin and an organic solvent is applied or printed on the substrate 21 made of glass or the like ( FIG. 3B).
After drying until the solvent is dry, a baking process is performed and ITO
A film 23 made of fine particles is obtained (FIG. 3C).

When soda glass is used as the substrate, the sodium component eluted from the soda glass adversely affects the characteristics of the transparent conductive film, so it is desirable to use a silica coating for preventing sodium elution.

ITO fine particles having an average particle diameter of 50 nm or less are used. As a resin for dispersing the ITO fine particles, a resin having good dispersibility such as butyral, acryl, polyester or the like is preferable. Further, as the solvent, for example, a high boiling point solvent such as butyl cellosolve, isophorone, terpineol, etc. is used. It is also possible to mix the high boiling point solvent with a low boiling point solvent such as alcohol to adjust the drying rate.

10 fine particles of ITO are added to these resins and solvents.
Add about 60 wt% and disperse it sufficiently using a dispersing means with high shearing force such as paint shaker, printing method such as screen, gravure, intaglio, flat plate offset, dip coating, spin coating, flow coating, etc. Method is applied on the substrate.

The firing step is carried out at a temperature above the temperature at which the resin and solvent are completely pyrolyzed. At the time of firing, it is first necessary to perform firing in air (atmosphere containing oxygen) in order to thermally decompose the resin.

When baked in air, the absorption of blue light by ITO increases, and the resulting transparent conductive film becomes slightly yellowish. On the other hand, if the film is baked in an inert atmosphere such as nitrogen or argon, or in a reducing atmosphere such as a mixed gas of nitrogen and hydrogen, the ITO is not colored and a highly transparent film having a low resistance can be formed. Therefore, it is desirable that the firing process be sequentially performed in air, and subsequently in an inert atmosphere or a reducing atmosphere.

Next, in the second step, the metal compound solution 24 is applied onto the film 23 composed of the ITO fine particles obtained in the first step (FIG. 3 (d)), followed by a baking step after drying. Then, the holes of the film 23 are filled with the metal oxide 25 to obtain the transparent conductive film 26 (FIG. 3E).

The characteristics of the transparent conductive film of the present invention can be exhibited only by filling the voids in the film 23 with the metal oxide 25. However, even if the metal oxide 25 is further formed so as to cover the film 23. Well, in that case, abrasion resistance and reliability are further improved.

Examples of the metal compound include hydroxides, oxides, nitrates, sulfates and sulfides of various metals which are inorganic compounds, or alkoxides and organic acid salts of various metals which are organic compounds containing a metal in the structure. , Organic metal compounds, organic complexes and the like. These may be used alone or in combination of two or more.

When silicon oxide is formed using a compound containing silicon among these compounds,
A transparent conductive film having high strength and excellent moisture resistance is preferable.

Further, it is preferable to use a compound containing tin to form a structure containing tin oxide in the transparent conductive film because a film having lower resistance can be obtained.

Examples of the method of applying the solution of the metal compound include dip coating, spin coating and flow coating.

The firing step is performed at a temperature above the temperature at which the metal compound is thermally decomposed into a metal oxide and below the temperature at which the substrate is not adversely affected.

When fired in air, the transparent conductive film becomes slightly yellowish as in the first firing step. Therefore, an inert atmosphere such as nitrogen or argon or a mixed gas of nitrogen and hydrogen may be used. Baking in a reducing atmosphere is desirable. As a result, the ITO is not colored and can be a highly transparent film having a low resistance.

Next, a concrete embodiment will be described. The step of forming a film made of ITO fine particles was performed as follows.

100 g of ITO fine particles (average particle size 25 nm, tin content 5%), 80 g of butyl cellosolve, 80 g of isophorone, acrylic resin (Dianal LR.16)
7: 40 g of Mitsubishi Rayon Co., Ltd. product name) was mixed and dispersed for 12 hours with a paint shaker (manufactured by Red Devil Co.). The obtained dispersion was applied to a silica-coated soda glass substrate (thickness 1.1 mm) using a bar coater. After air-drying for 10 minutes, it was dried in a drying oven at 120 ° C. for 1 hour. The coating film was cured and adhered to the substrate so that it was not peeled off even when lightly rubbed with a finger. Next, in the firing process,
Substrate in a tube furnace in an air atmosphere from room temperature to 200 ° C / h
After increasing the temperature to 550 ° C for 30 minutes and holding for 20 minutes,
It was cooled to room temperature at a rate of 0 ° C./h and taken out. The obtained fired film was colored slightly yellow, and was peeled off by rubbing it with a finger for a while. The thickness of the fired film is about 800
was nm.

The step of filling the holes of the film made of the ITO fine particles or forming the metal oxide covering the film was performed as described in the following first to seventh embodiments.

(Embodiment 1) A coating liquid prepared by adjusting silicon ethoxide to 3 wt% in ethanol is prepared, and a pulling rate of 60 cm /
It was dip coated in minutes. This substrate was heated from room temperature to 550 ° C. at a rate of 200 ° C./h in a nitrogen atmosphere and held for 30 minutes, and then cooled to a room temperature at a rate of 200 ° C./h to obtain a transparent conductive film.

(Embodiment 2) A coating solution prepared by adjusting silicon ethoxide to 1 wt% in ethanol is prepared, and a pulling speed of 60 cm /
It was dip coated in minutes. This substrate was heated from room temperature to 550 ° C. at a rate of 200 ° C./h in a nitrogen atmosphere and held for 30 minutes, and then cooled to a room temperature at a rate of 200 ° C./h to obtain a transparent conductive film.

(Embodiment 3) A solution prepared so that 4 wt% of silicon ethoxide and 4 wt% of organic acid tin is prepared in 96 wt% of ethanol, and the pulling rate is 60 cm / min onto the film made of the ITO fine particles. I did a dip coat. This substrate is heated from room temperature to 200 ° C / in a nitrogen atmosphere.
After raising the temperature to 550 ° C at the speed of h for 30 minutes and holding, 2
A transparent conductive film was obtained by cooling to room temperature at a rate of 00 ° C / h.

(Embodiment 4) Silicon ethoxide 1.5 wt% and organic acid tin 1.5 w in ethanol 97 wt%.
A solution prepared to have a concentration of t% was prepared, and dip-coated on the film made of the ITO fine particles at a pulling rate of 60 cm / min. This substrate is heated from room temperature to 2 in a nitrogen atmosphere.
The temperature was raised to 550 ° C. at a rate of 00 ° C./h and held for 30 minutes, and then cooled to room temperature at a rate of 200 ° C./h to obtain a transparent conductive film.

(Embodiment 5) Silicon ethoxide 0.5 wt% and organic acid tin 0.5 w in ethanol 99 wt%.
A solution prepared to have a concentration of t% was prepared, and dip-coated on the film made of the ITO fine particles at a pulling rate of 60 cm / min. This substrate is heated from room temperature to 2 in a nitrogen atmosphere.
The temperature was raised to 550 ° C. at a rate of 00 ° C./h and held for 30 minutes, and then cooled to room temperature at a rate of 200 ° C./h to obtain a transparent conductive film.

(Embodiment 6) Silicon ethoxide 1.5 wt% and organic acid tin 1.5 w in ethanol 97 wt%.
A solution prepared to have a concentration of t% was prepared, and dip-coated on the film made of the ITO fine particles at a pulling rate of 60 cm / min. This substrate is heated in a mixed gas atmosphere of 90% nitrogen and 10% hydrogen from room temperature to 200 ° C./h at a rate of 55.
After raising the temperature to 0 ° C. and holding it for 30 minutes, it was cooled to room temperature at a rate of 200 ° C./h to obtain a transparent conductive film.

(Embodiment 7) In the first baking step for forming a film made of ITO fine particles, the temperature is raised from room temperature to 550 ° C. at a rate of 200 ° C./h and kept for 30 minutes in an air atmosphere, and then in a nitrogen atmosphere. Instead, it was cooled to room temperature at a rate of 200 ° C./h. The obtained baked film was almost colorless and transparent, but it was in a state of being peeled off with a little rubbing with a finger. A metal oxide was formed on this fired film under the same conditions as in Embodiment 4 to obtain a transparent conductive film.

As a comparative example, the following film made of ITO fine particles (having no hole filling with metal oxide) was prepared.

(Comparative Example 1) First of the first to sixth embodiments
A film made of ITO fine particles fired in an air atmosphere formed in the above step was set as Comparative Example 1.

Comparative Example 2 A film made of ITO fine particles that was formed in the first step of the above-mentioned Embodiment 7 and subsequently baked in a nitrogen atmosphere was used as Comparative Example 2.

Evaluation results of the transparent conductive films of the embodiment and the comparative example produced as described above are shown (Table 1).
Shown in The total light transmittance was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.), and the sheet resistance was measured using a 4-probe resistivity meter (Hiresta manufactured by Yuka Denshi Co., Ltd.).

[0047]

[Table 1]

As is clear from (Table 1), the embodiment of the present invention (the one in which the pores of the film made of ITO fine particles are filled to form the metal oxide) is a comparative example (no metal oxide is formed). It has a lower resistance than that of high temperature and high humidity environment (6
The change in resistance value after standing for 1000 hours at 0 ° C. and 95% RH was very small and stable. Further, in the comparative example, the surface of the film was scratched or the film was peeled off only by lightly rubbing it with the finger, but in all of the embodiments, even if the finger was strongly rubbed with the finger, it was not scratched at all.

As described above, according to the embodiment of the present invention, by filling the pores of the film made of the ITO fine particles with the metal oxide, the film is highly resistant to the influence of gas and moisture and has excellent reliability. . Further, since the strength of the film is increased, abrasion resistance can be improved.

[0050]

As described above, according to the present invention, by forming a transparent conductive film with a film composed of ITO fine particles and a metal oxide that fills the pores in the film or covers the film, it is possible to prevent gas and moisture. Realized a highly reliable film that is not easily affected by
Further, the strength of the film is increased to improve the abrasion resistance.

When the metal oxide contains a silicon oxide, a film excellent in strength, transparency and gas barrier property can be obtained, and when the metal oxide contains a tin oxide, a film having a lower resistance can be obtained.

The method for producing a transparent conductive film of the present invention is to produce a transparent conductive film having low resistance and excellent reliability by a low cost and simple process of coating and baking a solution.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of the main part.

3A to 3E are process conceptual diagrams used for explaining an embodiment of the present invention.

[Explanation of symbols]

11, 21 Substrate 12, 23 Film composed of ITO fine particles 13, 25 Metal oxide 14, 26 Transparent conductive film 15 ITO fine particle 22 ITO fine particle dispersed in resin and organic solvent 24 Metal compound solution

Claims (10)

[Claims] 1. A transparent conductive film composed of a film made of indium tin oxide fine particles and a metal oxide filling voids in the film. 2. A transparent conductive film comprising a film made of fine particles of indium tin oxide and a metal oxide film which fills voids in the film and further covers the film. 3. The transparent conductive film according to claim 1, wherein the metal oxide contains a silicon oxide. 4. The metal oxide comprises a tin oxide.
The transparent conductive film described. 5. A substrate in which fine particles of indium tin oxide are dispersed in a resin and an organic solvent are applied and dried,
The first step of forming a film composed of fine particles of indium tin oxide by baking, and applying a solution of a metal compound on the film, drying and baking the metal oxide so as to fill the pores of the film. A method for manufacturing a transparent conductive film, which comprises performing a second step of forming a product. 6. A substrate in which fine particles of indium tin oxide are dispersed in a resin and an organic solvent are applied and dried,
The first step of forming a film of indium tin oxide fine particles by baking, and applying a solution of a metal compound thereon, drying and baking to fill the pores of the film, and And a second step of forming a metal oxide film so as to cover the film. 7. The method for producing a transparent conductive film according to claim 5, wherein the metal compound contains a silicon compound. 8. The method for producing a transparent conductive film according to claim 7, wherein the metal compound contains a tin compound. 9. The firing of the metal compound is performed in an inert atmosphere or a reducing atmosphere.
7. The method for producing a transparent conductive film as described in 7 or 8. 10. The transparent composition according to claim 9, wherein the step of firing a dispersion of indium tin oxide fine particles in a resin and an organic solvent is sequentially carried out in the air and subsequently in an inert atmosphere or a reducing atmosphere. Method for manufacturing conductive film.