JPS60243280A - Formation of transparent electrode - Google Patents

Abstract

PURPOSE:To form a transparent electrode low in resistance by coating a transparent electrode forming liquid contg. an organic metallic comp., an organic binder and solvent on a base plate and calcining it in the oxygen-enriched atmosphere for the first half and in the oxygen-deficient atmosphere for the latter half. CONSTITUTION:The transparent electrode forming liquid consisting of about 3- 8wt% unhydrolized organic metallic comp. contg. In and Sn or the like, about 1-25wt% organic binder such as nitrocellulose, solvent such as benzyl alcohol and methyl ethyl ketone and the balance is coated on a base plate with screen printing and a dipping method or the like. Then, the base plate is calcined at the temp. of 400-600 deg.C in the oxygen-enriched atmosphere for the first half and in the oxygen-deficient atmosphere for the latter half. In the first half of the above- mentioned calcination, the atmosphere is air and in the latter half, the atmosphere is preferably regulated to N2:O2=9:1 by mixing air with equivalent nitrogen. Thereby, the transparent electrode which is low in resistance and has uniform film quality and film thickness is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a transparent electrode forming method in which a transparent electrode forming liquid containing an organometallic compound is applied to a substrate such as glass and then baked.

"Archived technology and its problems" Oxide films made of indium oxide, tin oxide, cadmium oxide, etc. formed on substrates such as glass and ceramics are known to be transparent and have good conductivity, and are used for liquid crystal display. It is used as an electrode for display elements, semiconductor elements, etc., and as an electrode for preventing dew condensation on window glass.

Methods for forming such transparent electrodes include vacuum evaporation, in which a metal oxide is directly coated on a substrate to form a film, and a transparent electrode forming liquid containing an organometallic compound is applied to the substrate and baked to form a film. Screen printing methods, dipping methods, and the like are known. The vacuum evaporation method makes it easy to obtain transparent electrodes with relatively low resistance, but requires special equipment and
Since it is a batch type, it has the drawback of not being suitable for mass production. On the other hand, screen printing methods and dipping methods do not require relatively large-scale equipment and are suitable for mass production, but have the disadvantage that it is difficult to obtain transparent electrodes with low resistance.

"Object of the Invention" An object of the present invention is to enable a transparent electrode with low resistance to be obtained in a transparent electrode forming method in which a transparent electrode forming liquid is applied to a substrate and fired. "Structure of the Invention" The present invention The method for forming transparent electrodes involves applying a transparent electrode forming liquid containing an organometallic compound, an organic binder, and a solvent to a substrate and firing it. This method is carried out in an atmosphere lacking in

In this way, by changing the oxygen content between the first half and the second half of firing, it is possible to control the oxidation of the organic metal and form a low-resistance transparent electrode.

The transparent electrode forming liquid used in the present invention preferably has a composition consisting of a non-hydrolyzable organometallic compound containing indium and tin, an organic binder, and a solvent.

Examples of non-hydrolyzable organometallic compounds containing indium and tin include trisacetylacetonatoindium In-(acac), 1, bisacetylacetonatodibutyltin 5nBu2 (acac)2, and the like. In this case, the tin component is contained in the organometallic compound in 7.
5 to 15% by weight is suitable. The content of the organometallic compound is preferably 3 to 8% by weight in the total composition.

As the organic binder, cellulose compounds such as nitrocellulose, ethylcellulose, and benzylcellulose can be used. The appropriate content of the organic binder is 5 to 25% by weight in the total composition in the case of a screen printing paste, and 1 to 4% by weight in the total composition in the case of a dipping liquid.

As the solvent, for screen printing pastes, high boiling point solvents such as benzyl alcohol, dipropylene glycol, and benzyl acetate are mainly used, and for dipping liquids, low boiling point solvents such as methyl ethyl ketone are mainly used. . In order to adjust the boiling point, a trace amount of a low boiling point solvent may be added in the case of a paste for screen printing, or a trace amount of a high boiling point solvent may be added in the case of a dipping liquid.

These solvents constitute the remaining main components except for the organometallic compound and organic binder.

Then, the transparent electrode forming liquid as described above is applied to the substrate by screen printing or dipping. In this case, when a non-hydrolyzable organometallic compound as described above is used, there is no need to particularly limit the humidity conditions, and the shelf life of the transparent electrode forming solution is also improved.

In a preferred embodiment of the present invention, after applying the transparent electrode forming liquid, ultraviolet rays are irradiated. As the ultraviolet rays, those having a wavelength peak between 184.9n and 253.7n are preferably used, and this is, for example, 3.5 minutes/4 mw.
Ozone (
03) performs organic chain decomposition and forced oxidation, making the organic components more flammable. This makes the film quality uniform.

Note that this ultraviolet irradiation is not necessarily necessary in the present invention, and baking may be performed directly after applying the transparent electrode forming liquid to the substrate as described above.

In the present invention, firing can be carried out using various heating means, and a suitable heating temperature is 400 to 800°C. In a more preferred embodiment of the present invention, the baking is performed by irradiating the substrate with near-infrared rays. Here, near-infrared rays are infrared rays close to visible light, and have a wavelength of about 0.8 to 2.5 rays. As expected, near-infrared irradiation heats the substrate directly by radiation or radiation, and the heating rate (
The time it takes for the temperature of the substrate surface to rise from 100°C to 500°C is shortened. As a result, the volatilization of the solvent and organic binder component and the thermal decomposition of the organometallic compound proceed almost simultaneously, and the film quality and thickness are further made uniform. It is preferable to adjust the heating rate between 0.5 and 3 minutes; if the heating rate is less than 0.5 minutes, there is a risk that the substrate will break if a substrate such as glass is used; if the heating rate exceeds 3 minutes, the substrate may break. If this happens, the effect of making the thickness of the transparent electrode uniform becomes poor.

In the present invention, the first half of the firing process is performed in an oxygen-rich atmosphere, and the second half of the firing process is performed in an oxygen-poor atmosphere. Firing in an oxygen-rich atmosphere can be carried out, for example, in air. Firing in an oxygen-poor atmosphere can be carried out, for example, in a gas of N2:O2=9:1. In this case, N2: 02
= 8:l, since air contains 80% N2, the ratio of air:nitrogen = 1:I may be used. In this way, by changing the oxygen content between the first half and the second half of the firing process, it is possible to control the oxidation of the organic metal and form a low-resistance transparent electrode.

Note that in the latter half of the firing, it is preferable to gradually lower the temperature.

"Example of the invention" Tris acetylacetonate indium 87.5% by weight
, 5.5% by weight of an organometallic compound consisting of 12.5% by weight of dibutyltin bisacetylacetonate, 2.5% by weight of nitrocellulose, 2.0% by weight of benzyl alcohol,
A transparent electrode forming liquid containing 90.0% by weight of methyl ethyl ketone was prepared.

A glass substrate was immersed in this liquid and pulled up, and the liquid was applied to the glass substrate.

Next, the substrate was irradiated with ultraviolet rays at a rate of 3.5 minutes/4 mw/ctn''.

Furthermore, firing was performed by irradiating near infrared rays.

In that case, the heating rate was 2 minutes, and after the temperature rose, the temperature was kept at 500°C for the first 20 minutes, and the temperature was gradually lowered for the latter 15 minutes. This situation is shown in Figure 1. In the figure, A is the heating rate time, B is the first half firing time, and C is the second half firing time. The first half B is fired in air, and the second half C is fired at N2:02=
It is carried out in a gas of 1:1.

The transparent electrode thus obtained had uniform film quality and thickness, and good transparency. The film thickness was 300 mm, and the sheet resistance was IKΩ/mouth.

"Effects of the Invention" As explained above, according to the present invention, when a transparent electrode forming liquid is applied to a substrate and fired, the first half of the firing is performed in an oxygen-rich atmosphere, and the second half of the firing is performed in an oxygen-rich atmosphere. Since the process is carried out in a poor atmosphere, it is possible to control the oxidation of the organic metal and form a transparent electrode with low resistance.

[Brief explanation of drawings]

FIG. 1 is a chart showing firing temperatures and times in Examples of the present invention. Figure 1 a#

Claims (1)

[Claims] (1) In a transparent electrode forming method in which a transparent electrode forming liquid containing an organometallic compound, an organic binder, and a solvent is applied to a substrate and then fired, the first half of the firing is performed in an atmosphere rich in oxygen, and the second half of the firing is performed in an oxygen-rich atmosphere. A transparent electrode forming method characterized in that it is carried out in an atmosphere lacking in . (2. The transparent electrode forming method according to claim 1, wherein the first half of the firing is performed in air, and the second half of the firing is performed in an atmosphere of nitrogen:oxygen = 8:1.