JPS6065708A - Formation of coating film of metal oxide - Google Patents

Abstract

PURPOSE:A substrate is coated with an organometallic compound and sintered in an atomsphere containing ozone to oxidize the organometallic compound whereby coating films of the matal oxide is formed at relatively lower temperatures. CONSTITUTION:The substrate coated with an organometallic compound is placed in a furnace and sintered as a gas containing about 1vol% of ozone is allowed to flow at about 500 deg.C to from coating films of the metal oxides on the substrate. Thus, oxide coating films of high density, high light transmission and high optical refraction are obtained in an arbitrary thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to improvements in the method for forming metal oxide films, and is particularly suitable for forming optical thin films made of metal oxides.

[Technical background of the invention and its problems]

For example, vacuum evaporation, sputtering, chemical vapor deposition, and the like have been conventionally used to obtain metal oxide films such as titanium oxide thin films constituting optical interference films. However, this method has the disadvantage that the equipment is complicated and the workability is poor.

In recent years, a method of applying and oxidizing an organometallic compound solution has been developed as a means to overcome these drawbacks. In this method, a solution of an organometallic compound is applied to a substrate and fired in air to transform it into a metal oxide. However, this method requires a high firing temperature in order to completely remove organic components present in the sample before firing or to completely oxidize the metal. In this case, many heat sources are inevitably required, and the heating device also becomes large.

[Purpose of the invention]

An object of the present invention is to provide a method for forming a metal oxide film that can be fired at a relatively low temperature.

[Summary of the invention]

By firing a substrate coated with an organometallic compound in an atmosphere containing ozone, the organometallic compound is oxidized at a low temperature by utilizing the strong acidity of ozone.

[Embodiments of the invention]

A plate-shaped quartz substrate was immersed in an organic solvent solution of an organic titanium compound, such as titanium alkoxide, containing 3% by weight of titanium calculated as rio2m, and was pulled up at a speed of 220 mm/min to coat the organic titanium compound.

Next, air containing 1% by volume of ozone was introduced from an ozone generator at a flow rate of 100ml/min into an electric furnace, and the substrate coated with the organic titanium compound was heated at 500°C in this furnace.
It was baked for 10 minutes at a temperature of . Then, the applied organic titanium compound was oxidized and transformed into a thin film made of titanium oxide. This thin film is dense, has excellent light transmittance, and has a large optical refractive index. Then.

In this formation method, the film thickness can be adjusted arbitrarily by adjusting the concentration and viscosity of the organic titanium compound solution or the pulling rate of the substrate.

Next, the characteristics of the product were compared between the sample manufactured using this method and a comparative example fired in air.

The results are shown in the table below.

This table also shows that even at a firing temperature of 500°C, the method of this example provides properties equivalent to those of the conventional firing temperature of 700°C.

Note that if the ozone concentration is high, the oxidation reaction may be too strong and the resulting film may have a coarse structure. According to experiments, if the film is preliminarily fired in air at 50°C and then fired in air containing ozone, a dense and high-quality film can be obtained, and there is no particular risk of defects. in this case,
Baking time can be shortened by increasing the ozone concentration.

Furthermore, in the present invention, the μL waiting time can be shortened by increasing the ozone concentration continuously or discontinuously during firing. In this case, the ozone concentration is set to O at the beginning of the force formation, and thereafter the ozone concentration is increased continuously or discontinuously, which is particularly suitable when the coating is thick.

Although the above-mentioned embodiment describes a method for forming a titanium oxide film, the present invention is not limited to this, and can be applied to film formation of other metals such as silica, tin oxide, zirconium oxide, etc. to achieve similar effects. There is. The atmosphere containing ozone is not limited to the above-mentioned air containing ozone, but may also be a non-oxidizing gas such as nitrogen or carbon dioxide containing ozone.

Further, the coating method is not limited to the dipping/pulling method, but may be any known method such as a spinner method or a spray method.

Furthermore, in the present invention, there is no limitation on the desired thickness of the coating, and its use is also free. Furthermore, the present invention can also be used when multiple thin films of different types are layered, such as an optical interference film.
It can be applied to the formation of one or all of these types of thin films. Thus, there are no restrictions on the type or shape of the substrate.

〔Effect of the invention〕

In the method for forming a metal oxide film of the present invention, a substrate coated with an organometallic compound is fired in an atmosphere containing ozone to oxidize the organometallic compound and form a film made of the metal oxide, so the temperature is low. A good oxide film can also be obtained by firing with.

Claims (3)

[Claims] (1) A metal oxide coating characterized in that an organic metal compound is applied to a substrate and fired in an atmosphere containing ozone to oxidize the organic metal compound to form a coating made of an oxide of the metal. Formation method. (2) Formation of a metal oxide film according to claim 1, characterized in that the substrate coated with the organometallic compound is preliminarily fired in air and then fired in an atmosphere containing ozone. Method. (3) A method for forming a metal oxide coating according to claim 1 or 2, characterized in that the ozone concentration in the atmosphere is gradually increased during firing.