JPS623046A - Formation of silicon oxide film - Google Patents

Abstract

PURPOSE:To obtain a silicon oxide film suitable as an undercoating of a transparent electrically conductive film on electrically conductive glass substrates for solar cells, by coating a glass substrate surface with a specific solution forming the silicon oxide film and keeping the resultant film in an atmosphere at a specific humidity. CONSTITUTION:A glass substrate surface is coated with a solution for forming silicon oxide films containing an alkoxysilane compound, water and alcohol, and the resultant coated glass substrate is then kept in an atmosphere at 50-100%, more preferably 85-75% relative humidity for a given time to form the aimed silicon oxide films having an uneven surface on the glass substrate surface. The time for keeping the substrate in the above-mentioned atmosphere is preferably about 0.1-60min due to the relation between the hydrolytic reaction and the occurrence of the uneven surface. As methods for coating the glass substrate surface with the above-mentioned solution, especially the dipping and pulling up method is optimum, because a uniform film quality and film thickness can be obtained and the film can be exposed to an atmosphere at a constant humidity while pulling up the film at a constant speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a silicon oxide film, particularly to a method for forming a silicon oxide film that is optimal as an undercoat for a transparent conductive film on a conductive glass substrate for a solar cell. It is something.

[Prior Art] Today, coating the glass surface with a silicon oxide film is widely practiced. For example, when alkali-containing glass, such as soda lime glass, is used as a glass substrate for liquid crystal display panels or solar cells. The glass surface is coated with a silicon oxide film to prevent alkali precipitation from the glass surface. A transparent conductive coating of indium oxide or tin oxide is then formed on the surface of this silicon oxide coating. Conventionally, methods for forming a silicon oxide film as an undercoat include vacuum evaporation, sputtering, and C.
There are VD methods, CLD methods, etc., but all of them produce transparent silicon oxide films with flat surfaces.

For example, in conductive glass substrates for solar cells, a silicon oxide undercoat is coated with a transparent conductive tin oxide film as an electrode, but the reflectance in the visible light range is low in order to improve conversion efficiency. It is required to form appropriate irregularities on the surface of the transparent conductive tin oxide film so as to reduce the roughness. Such an uneven surface can scatter sunlight and reduce reflection from the surface, thereby increasing conversion efficiency. Since the silicon oxide film as an undercoat formed by the conventional method has a flat surface, by controlling the conditions for forming the transparent conductive tin oxide film, it is possible to obtain an appropriate unevenness on the surface of the tin oxide film. I was trying to make it possible. However, forming an uneven surface under the conditions for forming a tin oxide film not only controls the conditions for generating the uneven state, but also allows the desired resistance value, optical properties, film thickness, etc. of the tin oxide film to be obtained. The problem was that the conditions had to be controlled in such a way that it was extremely difficult to form a film.

[Problems to be Solved by the Invention] An object of the present invention is to solve the above-mentioned problems, and instead of forming an uneven state on the surface by controlling the film forming conditions of a transparent conductive tin oxide film. In addition, the present invention attempts to form an uneven state on the surface of a silicon oxide film using conditions for forming a silicon oxide film, which were hitherto unknown.

[Means for Solving the Problems] The present invention was invented as a result of research based on the above object, and the gist thereof is to provide a silicon oxide film forming solution containing an alkoxysilane compound, water and alcohol on the surface of a glass substrate. After coating.

This coated glass substrate was heated to a relative humidity of 50 to 100 $.
The present invention relates to a method for forming a silicon oxide film, which comprises holding the glass substrate in an atmosphere for a predetermined period of time to form a silicon oxide film having an uneven surface on the glass substrate surface.

According to the present invention, since a moderately uneven surface is formed on the surface of the silicon oxide film formed as an undercoat on a glass substrate, a transparent conductive film can be simply formed on this by a normal method. Due to the uneven surface of the silicon oxide film, the surface of the transparent conductive film also becomes uneven, making it possible to provide an optimal substrate for solar cells.

In forming a silicon oxide film according to the present invention, first, an alkoxysilane compound as a raw material for silicon oxide is mixed with water for hydrolyzing the alkoxysilane compound,
A silicon oxide film forming solution containing an alkoxysilane compound and an alcohol as a water-compatible solvent is prepared. Examples of the alkoxysilane compound include tetramethoxysilane (methyl silicate), tetraethoxysilane (ethyl silicate), tetrapropoxysilane (propyl silicate), and tetrabutoxysilane (butysilicate).

Monomethyltriethoxysilane, monoethyltriethoxysilane, tetraphenoxysilane, other higher alkoxysilanes, or partial hydrolysates of these alkoxysilanes can be used, among which tetraethoxysilane or partial hydrolysates of tetraethoxysilane can be used. is the most representative because of its ease of use, storage stability, and availability.

Further, as the alcohol added to the silicon oxide film forming solution, ethanol, butanol, impropatol, ethyl cellosolve, and mixtures thereof can be used.
It is preferable to use a mixed alcohol solution of ethanol and butanol in order to stably promote the storability of the coating liquid and the hydrolysis after pulling it up.

Furthermore, polyhydric alcohols such as ethylene glycol and propylene glycol, and chelate-forming compounds such as diacetone alcohol and acetylacetone can be added to the alcohol solution.

Furthermore, a basic catalyst or an acidic catalyst can be added to speed up the hydrolysis reaction. In addition, concentration adjusting agents, surfactants, etc. can also be added as necessary.

Such a silicon oxide film forming solution contains 50 to 110 mol% of alcohol per 1 mol of the alkoxysilane compound.
A typical example is one containing a predetermined amount of water necessary for the hydrolysis reaction.

A method for coating the glass substrate surface with the above-mentioned silicon oxide film forming solution is a dipping and pulling method.

Various coating methods such as a roll coater method, a meniscus coater method, and a printing method can be used. Among these, the immersion-pulling method is most suitable as a coating method in the present invention because it can obtain uniform film quality and thickness, and can be exposed to a constant humidity atmosphere while pulling at a constant speed.

The glass substrate temperature during this coating is optimally 20 to 23°C, and the temperature/degree of the silicon oxide film forming solution is 20 to 25°C.
°C is appropriate.

The glass substrate coated with the silicon oxide film forming solution is maintained for a predetermined time in an atmospheric atmosphere with a relative humidity of 50-100 $, more preferably 65-75 $.

By holding the coated glass substrate in such an atmosphere, the hydrolysis reaction of the coated silicon oxide film forming solution is controlled, and a silicon oxide film having an uneven surface can be obtained. In addition, if the humidity of the atmosphere in which the coated glass substrate is held is too high than the above range, a hydrolysis reaction will occur rapidly, resulting in the formation of a cloudy film with an uneven shape, which is undesirable. This is not preferable because the hydrolysis reaction is not promoted and a flat and transparent film is formed.

The retention time of the coated glass substrate in the above atmosphere is 0.1 due to the relationship between the hydrolysis reaction and the occurrence of surface irregularities.
About 80 minutes, particularly preferably about 1 minute to 5 minutes.
Note that the temperature of this atmosphere is preferably in the range of 20 to 25°C from the viewpoint of controlling the hydrolysis reaction.

The thickness of the silicon oxide film formed according to the present invention is not particularly limited, but from the viewpoint of creating suitable unevenness on the surface of the silicon oxide film, it is optimally about 1000 to 2000 thickness.

The degree of unevenness and film thickness of the silicon oxide film can be determined arbitrarily depending on the concentration of the alkoxysilane compound in the silicon oxide film forming solution, the atmospheric humidity, the atmospheric temperature, the holding time, and the pulling speed in the case of a coating method using a pulling method. can be controlled.

The degree of unevenness generated on the surface of the silicon oxide film according to the present invention can be measured, for example, by measuring the haze. According to the results measured with a haze meter of C light source, it is 3.0 to 2.
It was 5.0%. Note that the optimum level of unevenness for forming a transparent conductive film for solar cells is about 3.5 to 10.0% when expressed in terms of haze.

In the present invention, the glass substrate on which the silicon oxide film is formed includes an alkali-containing glass plate from which alkali elutes, such as a soda lime glass plate, but in order to prevent such alkali elution, a silicon oxide film is formed as an undercoat. Even if the plate is a low-alkali or alkali-free glass plate that does not require oxidation, these glasses may of course be used if a silicon oxide coating having an uneven surface is required.

The glass substrate with a silicon oxide film of the present invention has irregularities formed on one surface, so it is optimal as a glass substrate for forming a transparent conductive film for solar cells, but the silicon oxide film has irregularities and has a scattering effect. Since it has low reflectivity, it can also be used for anti-glare and various other applications.

Example 1 Ethanol 380 tQ, butanol 3Hm (2, diacetone alcohol 130 taQ, ethyl silicate 80
mQ, hydrochloric acid 7.5 yaQ, hexylene glycol 5■
Q.

Propylene glycol 5 Otori Q, surfactant 1 QlcS
Prepare a silicon oxide film forming solution by placing it in a US304 container and stirring for about 10 minutes. Then, after thorough cleaning, the size is 100 x 100m/ai and the thickness is 1.1
Soda lime glass of rI/m was immersed in the silicon oxide film forming container for 3 minutes, then pulled up at a constant speed of 20 cm/in, then held in an atmosphere with a relative humidity of 89% for 5 minutes, and dried. When heated at 500° C. for 10 minutes, a cloudy silicon oxide film having a film thickness of 1450 mm and a haze ratio of 3.6z and having an uneven surface was obtained.

Example 2 390 rsQ of ethanol, 390 rsQ of butanol, 80 Q of ethyl silicate, 7.5 taQ of hydrochloric acid, 5 mQ of hexylene glycol, 1 mQ of surfactant in 5IJS3
Soda lime glass with a size of 100 x 100 + s/layer thickness of 1.1 cm/shoe was prepared by placing it in a 04 container and stirring for about 10 minutes to prepare a silicon oxide film forming solution. 3 in the above silicon oxide film forming container.
After soaking for minutes, pull at a constant speed of 20cm/in.
After drying, the film was lifted into an atmosphere with a relative humidity of 75X and held for 1 minute, and then heated at 500℃ for 10 minutes.The film thickness was 1B00 and the haze rate was 12.82. A silicon oxide film was obtained.

Comparative Example 1 Koyu/-)L' 390 mQ, Buta/-L 390
taQ, diacetone alcohol 130 mQ, ethyl silicate) 80 intestinal Q, hydrochloric acid 7.5 mQ, hexylene glycol 5mf2, propylene glycol 5IIQ,
Pour 1 mQ of surfactant into a 5IIS304 container and add approximately 1 mQ of surfactant.
A silicon oxide film forming solution was prepared by stirring for 0 minutes. Next, a soda lime glass having a size of 1.1 mm/layer and a thickness of 1.1 layers/m after being thoroughly washed was placed in the silicon oxide film forming container. 20cm/ after 3 minutes immersion in
It was pulled up at a constant speed of sin, then pulled up into an atmosphere with a relative humidity of 48 cm, immediately dried, and then heated at 500°C for 10 minutes.
When heated for 1 minute, the film thickness was 1250 people and the haze rate was 0.3.
A transparent silicon oxide film with a smooth surface was obtained.

Comparative Example 2 Ethanol 390 layer Q, phthanol 380 layer Q, diacetone alcohol 130 rxQ, ethyl silicate 8°rsQ, hydrochloric acid 7.5 taQ, hexylene glycol 5
IIQ, propylene glycol 5m12, surfactant L
A silicon oxide film forming solution was prepared by placing taQ in a 511S304 container and stirring for about 10 minutes.Then, a soda lime with a size of 100 x 100 pieces/m and a thickness of 1.1rn/m was thoroughly washed. The glass was immersed in the silicon oxide film forming container for 3 minutes, then pulled up at a constant speed of 20 cm/sin, held in boiling steam for 1 minute, dried, and heated at 500°C for 10 minutes, resulting in a film thickness of 7000.
A cloudy silicon oxide film with cracks and a human haze rate of 20.9 dollars was obtained.

[Operations and Effects of the Invention] As described above, according to the present invention, after coating a glass substrate surface with a silicon oxide film forming solution containing an alkoxysilane compound, water, and alcohol, the relative humidity is 50 to 100%.
By holding the film in an atmosphere for a predetermined period of time, the hydrolysis reaction can be controlled, thereby making it possible to obtain a cloudy silicon oxide film with an uneven surface and a scattering effect. By coating a transparent conductive film on the silicon oxide film having an uneven surface, it becomes a transparent conductive film having an uneven surface. The substrate is extremely useful in creating solar cells with high conversion efficiency.

In addition, using the silicon oxide coated glass substrates obtained in Example 1 and Comparative Example 1, simulated solar cells were created as follows, and each was evaluated.

A tin oxide film was coated as a transparent conductive film on a soda lime glass substrate having an uneven surface and a cloudy silicon oxide film formed in Example 1 and having a haze ratio of 3H. A simulated solar cell (sample 1) was created by coating 2,000 pieces of aluminum on top of the coating.

When the spectral reflectance of this simulated solar cell was measured using an integrating sphere, the maximum reflectance in the visible light range of 340 to 700 square meters was about 14%. On the other hand, a simulated solar cell (Sample 2) was prepared on a soda lime glass substrate formed in Comparative Example 1 and coated with a smooth and transparent silicon oxide film with a haze rate of 0.3z.
), the maximum reflectance was about 28%. The results of measuring the spectral reflection characteristics of Sample 1 and Sample 2 are shown in FIG. In addition, in FIG. 1, curve 1 shows the spectral reflection curve of Sample 1, and curve 2 shows the spectral reflection curve of Sample 2. This shows that the soda lime glass coated with the cloudy silicon oxide film formed according to the present invention is When used to create a simulated solar cell, it has the excellent effect of significantly reducing reflectance in the visible light region.

Furthermore, according to the present invention, since the glass surface can be made uneven, it can also be used as a non-glare glass substrate.

[Brief explanation of drawings]

FIG. 1 is a spectral characteristic diagram showing the spectral reflection characteristics of an integrating sphere for a simulated solar cell. -/l! L table λ(π, M) Fig. 1

Claims (4)

[Claims] (1) After coating the glass substrate surface with a silicon oxide film forming solution containing an alkoxysilane compound, water, and alcohol, the coated glass substrate is heated to a relative humidity of 50 to 10
A method for forming a silicon oxide film, the method comprising: maintaining the silicon oxide film in a 0% atmosphere for a predetermined time to form a silicon oxide film having an uneven surface on the glass substrate surface. (2) The method for forming a silicon oxide film according to claim 1, wherein the coated glass substrate is held in an atmosphere with a relative humidity of 65 to 75%. (3) The method for forming a silicon oxide film according to claim 1, wherein the method is maintained in an atmosphere with a relative humidity of 50 to 100% for 0.1 to 60 minutes. (4) A claim characterized in that after a glass substrate is immersed in a silicon oxide film forming solution, it is pulled up at a constant speed into an atmosphere with a relative humidity of 50 to 100% and held in this atmosphere for a predetermined period of time. 2. The method for forming a silicon oxide film according to item 1.