JPS60175316A - Method of producing conductive transparent thin film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Technical field).

The present invention relates to a method for manufacturing an electrically conductive transparent thin film in which a film containing tungsten and its oxide as a main component is formed on a substrate.

(Prior art) Demand for transparent conductive thin films formed on transparent substrates such as glass or plastic is increasing for use in electro-optical devices such as liquid crystal display elements and solar cells, as well as anti-fog glass and antistatic materials. ing.

As a method for obtaining a transparent conductive film that is transparent and has high electrical conductivity in the visible region, 1, for example, Publication [Surface] V
ol 18. N[L8, p. 440, "Transparent Conductive Film J (1980)" describes the following methods: ■ method of depositing a very thin metal film such as gold or palladium; Methods for coating oxide semiconductors are known.The metal thin film deposition method (2) has good conductivity but poor transparency.The method (2) for coating oxide semiconductors has good conductivity but poor transparency.

Furthermore, there are methods of spraying an aqueous solution of tin halide or the like onto the substrate as a conductivity imparting agent, and methods of vacuum evaporating tin oxide, indium oxide, etc. (Japanese Patent Publication No. 51-37667, Japanese Patent Publication No. 49-18447). be. After titanium is vapor-deposited, it is forcibly oxidized.

A method for obtaining a titanium oxide film with an appropriate resistance value is also known. However, it is difficult to form a uniform conductive film using the aqueous solution spraying method. Furthermore, even in the vacuum deposition method, since the deposition conditions are unstable and the process is complicated, it is extremely difficult to produce a film with excellent transparency and conductivity with good reproducibility. In addition, indium oxide and the like also have the disadvantage of being expensive.

(Objective of the Invention) An object of the present invention is to provide a method for producing a thin film having excellent conductivity and transparency. Another object of the present invention is to provide a method for manufacturing a transparent thin film that is inexpensive and has uniform conductivity. Still another object of the present invention is to provide a method for forming a thin film having excellent conductivity and transparency on a substrate surface without going through complicated steps.

(Structure of the Invention) The present invention was completed based on the inventor's knowledge that a thin film formed on a substrate by evaporating metallic tungsten in an appropriate reduced pressure steam atmosphere is transparent and exhibits high conductivity. . therefore.

The method for producing a conductive transparent thin film of the present invention includes heating and evaporating metallic tungsten in an M-pressure steam atmosphere to form a film containing tungsten and its oxides as main components on a substrate. The above objective is achieved.

Examples of substrates used in the present invention include transparent glass and transparent plastic. However, the material is not limited to this, and various materials such as ceramic, cloth, and paper may be used. Tungsten metal is heated and evaporated onto these substrates while introducing water vapor.

Forms a transparent thin film. Specifically, the substrate is placed in a vacuum chamber, and while the vacuum chamber is evacuated by a vacuum pump, metal tungsten is heated by a known heating method such as resistance heating or electron gun heating. In the resistance heating method, tungsten atoms can be evaporated at any degree of vacuum by directly applying current to the tungsten wire. This method is suitable because the apparatus is simple. In the method using electron gun heating, the degree of vacuum is preferably greater than 5 x 10-'Torr. In such a high vacuum region, the deposition rate becomes faster. However, if the temperature is lower than this, electric discharge occurs and the filament is severely consumed, making heating impossible. Although the substrate does not require any particular heating.

Heating tends to increase the conductivity of the deposited thin film.

It is presumed that a portion of the metallic tungsten vapor generated by heating reacts with the water vapor, and a thin film containing tungsten and its oxides as main components is formed on the substrate. At this time, it is sufficient that the main partial pressure of the atmospheric gas is water, and other gases such as oxygen, nitrogen, and hydrogen may also be mixed to some extent. For example, the interior of a vapor deposition apparatus such as a Pelger is brought to a high vacuum of about 10-5 Torr in advance, and water is introduced from the outside to create an appropriate degree of vacuum. If a predetermined degree of vacuum is achieved using a vacuum pump such as a rotary pump or an oil diffusion pump, most of the residual gas will be water vapor.

Therefore, it is not necessary to particularly introduce water vapor. However, in order to control the water vapor pressure at a constant level, water vapor can be introduced from the outside as necessary during the vapor deposition process.

The partial pressure of water vapor in the tank has a large effect on the transparency and conductivity of the deposited film. Normally 2X10-'~I
It is set to 10””Torr. The degree of vacuum is lXl0-
When the temperature exceeds 'Torr, the deposited film is colored blue and the conductivity decreases. When the value is less than 2 x 10-'Torr, transparency improves, but conductivity extremely decreases. If a resistance heating method is used at this time, the deposition rate will be extremely slow.

The thickness of the deposited film is usually selected in the range of 500 to 2000. The thickness of the film is appropriately selected depending on the purpose of use.

If the film is too thick, the surface resistance will be low but the transparency will be reduced.

If the film is too thin, it will have excellent transparency but will have a high surface resistance. The obtained vapor deposited film has a surface resistance value of 0.1 to 10 Ω/a.
d. In addition, the total light transmittance in the visible region is 7
It is 5% or more, and by selecting the production conditions, it is also possible to obtain a deposited film with a total light transmittance of 85% or more.

The adhesion of the vapor deposited film obtained in the present invention to the substrate is J1.
It has been confirmed that it is good in a test based on S DO202.

(Example) The present invention will be described below with reference to Examples.

Large facility ↓ The cleaned glass plate was placed in a vacuum chamber. After evacuating the inside of the tank to I x 10-'Torr in advance,
Water vapor at 0-'Torr was introduced, and tungsten was heated with electricity to deposit it to a thickness of 500 mm at a rate of 100 mm/IIkin. The temperature of the glass plate at this time was 100°C. The surface resistance value of the glass plate on which the vapor deposited film was formed is 3.
Ω/cnl, and the total light transmittance at 600 nm was 85%. The total light transmittance of the glass plate before vapor deposition was 96%.

The process is the same as in Example 1 except that water vapor of 10-'' Torr was introduced.The surface resistance value of the glass plate on which the vapor-deposited film was formed was 1.5Ω/ail, and the total light beam was Transmittance was 75%.

The procedure was the same as in Example 1 except that the Inusato charcoal and glass plate was heated to 200° C. with an infrared heater. The surface resistance value of the glass plate on which the vapor deposited film was formed was 0.8 KΩ/cot.

The total light transmittance was 80%.

Charcoal↓ 1×1O−2 in the tank using a rotary pump in advance
The procedure was the same as in Example 1 except that the exhaust gas was evacuated to Torr and no water vapor was introduced. The surface resistance value of the glass plate on which the vapor deposited film was formed is 5Ω/ad, and the total light transmittance is 75.
%Met.

The procedure was the same as in Example 1 except that 8 x 10 Torr of oxygen was introduced. The surface resistance value of the glass plate on which the vapor deposited film was formed was 10'Ω/cd or more, and the total light transmittance was 95%.

The operation was carried out in the same manner as in Example 1 except that nitrogen of 8 x 10-' Torr was introduced, but the growth rate of the film was slow.
Vapor deposition could not be performed at a rate of 0.00 people/min. A deposited film with a thickness of 300 layers was formed at a rate of 10 layers/min.

The surface resistance value of the glass plate on which the vapor deposited film was formed was 108Ω/
and the total light transmittance was 95% or more.

This J2U was the same as Comparative Example 2 except that hydrogen was introduced instead of nitrogen. The surface resistance value of the glass plate on which the vapor deposited film was formed was 108Ω/e11! The total light transmittance was 95% or more.

The washed glass plate was placed in a vacuum chamber. After evacuating the inside of the tank to I x 10-'Torr in advance,
Water vapor at 0-'' Torr was introduced, and tin was heated in a tungsten boat and deposited to a thickness of 500 mm at a rate of 100 mm/min. At this time, the temperature of the glass plate was 10 mm.
It was 0°C. The deposited film formed was opaque and had a total light transmittance of 10% or less. The total light transmittance of the glass plate before vapor deposition was 96%. The adhesion of the deposited film to the glass plate was also poor, and it easily peeled off from the glass plate when rubbed with fingers.

(Effects of the Invention) According to the present invention, a vapor-deposited thin film exhibiting high conductivity and excellent transparency can be obtained. The deposited layer is uniform and therefore the conductivity is also uniform. It also has excellent adhesion to the substrate. Furthermore, the tungsten used does not necessarily have to be of high purity; commercially available tungsten wire can be used. Therefore, thin films can be prepared at low cost.

Further, no complicated operations are required. This conductive transparent thin film can be effectively used not only as electro-optical elements and heating elements, but also as drip-proof and anti-fog glass.

Claims (1)

[Claims] (2) A method for producing a conductive transparent thin film, which includes heating and evaporating metallic tungsten in a reduced pressure steam atmosphere to form a film containing tungsten and its oxides as main components on a substrate.