JPH0891839A - Formation of thin titanium dioxide film - Google Patents

Abstract

PURPOSE: To profitably form a thin titanium dioxide film excellent in photocatalytic activity on the surface of a body having a large area, a body of a complex shape or a body having a small particle diameter. CONSTITUTION: When a thin titanium dioxide film is formed on a substrate by coating and thermal decomposition, a soln. of titanium salt of an org. acid is used as a precursor of titanium dioxide and the objective thin titanium dioxide film is formed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for forming a titanium dioxide thin film having excellent photocatalytic activity.

[0002]

2. Description of the Related Art Titanium dioxide thin films are used in photocatalysts, sensors, ferroelectrics, etc. because of their excellent semiconductor properties. It is also used as an optical thin film for preventing light reflection on the glass surface, absorbing and transmitting light having a specific wavelength. As a method for forming the titanium dioxide thin film, CVD is used.
Although a sputtering method, a sputtering method, a vacuum deposition method, etc. are known, the equipment is expensive and complicated, and thus the workability is poor. Further, it is not possible to form a thin film on the surface of a complicated shape or a large area. Therefore, there is a coating pyrolysis method as an alternative method. As the coating thermal decomposition method, there is known a sol-gel method utilizing hydrolysis of metal alkoxide. Further, as the coating method, a dipping method, a spray method, a spin coating method and the like are known.

[0003]

The titanium dioxide thin film precursor solution using a metal alkoxide as a starting material, which is used in the conventional coating pyrolysis method, has poor storage stability. For example, it is sealed after preparation. 12 ~
There is only 16 days of life. In addition, there are drawbacks such as difficulty in forming a film, drying, and cracking during heat treatment. It is known that ultrafine particles of titanium oxide are suspended in water as a product with improved storage stability.However, precipitates are formed during storage, and the thin film produced using this adheres to the substrate. There are drawbacks such as poor sex.

[0004]

In order to solve the problems of the above-mentioned coating pyrolysis method, the present invention has been intensively studied, and as a result, in a titanium dioxide thin film forming method by the conventional coating pyrolysis method,
As a titanium dioxide thin film precursor, an organic acid titanium salt solution,
Alternatively, by using a liquid in which ultrafine titanium dioxide is dispersed in an organic acid titanium salt solution, it is possible to obtain a uniform and crack-free titanium dioxide thin film that has no selectivity of the coating method and has excellent adhesion to any substrate. It was found and completed.

That is, the present invention is a method for forming a titanium dioxide thin film on a substrate by a coating pyrolysis method, characterized in that a titanium dioxide precursor solution is used as a titanium dioxide precursor solution. . The method for forming a titanium dioxide thin film by the coating pyrolysis method of the present invention is spin coating, dipping, spraying, brush coating, roll coating, or other method in which the organic acid titanium salt solution is easily applied to the substrate. After application, the organic solvent is volatilized, that is, at room temperature to 200 ° C.
After being dried for 60 minutes and then baked in an air or oxygen atmosphere at 400 to 800 ° C. for 5 to 10 minutes or more using an electric furnace, good adhesion to the substrate, a transparent and uniform 0.
This is a method for obtaining a thin film having a thickness of 1 to 0.3 μm.

When it is desired to obtain a thin film having a thickness of 1 to 5 μm by a single coating pyrolysis, organic acid titanium salt solutions 60 to 9 are used.
5 parts by weight of 5 to 40 parts by weight of titanium dioxide having a thickness of 0.1 to 1 μm is applied by a ball mill, a sand mill, or another dispersing method to obtain a slurry by coating and pyrolyzing the slurry to obtain good opacity. A uniform thin film can be obtained.

The organic acid titanium salt solution of the present invention is a 1500 peculiar to the organic acid metal salt in infrared absorption spectrum analysis.
It is a solution prepared by dissolving an organic acid titanium salt consisting of an organic acid and titanium having an absorption peak of ˜1600 ^{cm −} in an organic solvent such as mineral spirit, toluene or xylene. There are many types of organic acids depending on the type of organic acid, and any organic acid titanium salt that is soluble in an organic solvent can be used. Specific examples thereof include titanium naphthenate salt solution, titanium octylate solution, tall oil fatty acid titanium salt solution, and the like, but are not limited thereto.

When the Ti content in the organic acid titanium salt solution of the present invention is from 5 to 10% by weight, cracks occur even when coating and pyrolyzing in that state, resulting in poor adhesion to the substrate. Therefore, a solvent in which the organic acid titanium salt is dissolved, for example, but not limited to, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, ketone solvents, ester solvents, solvents such as ether solvents It is desirable to use one kind alone or a mixture of two or more kinds, and dilute the Ti content to 3% by weight or less before use.

The organic solvent used for the organic acid titanium salt solution is
Other than the above-mentioned ones, there is no particular limitation, and any one in which an organic acid titanium salt is soluble can be used. However, it is desirable to select one or more solvents from the viewpoints of coating workability, safety, stability of solution, uniformity of titanium dioxide thin film, economical efficiency, and the like.

For the purpose of obtaining a uniform titanium dioxide thin film, ethyl cellulose, polyvinyl butyral resin or the like may be blended with the organic acid titanium salt solution of the present invention, or a cissing inhibitor may be added if necessary. .

Further, since the organic acid titanium salt solution of the present invention does not select the shape, material and surface polarity of the article to be coated such as a substrate, a conical dryer or a fluidized bed drier can be used to form a flat surface such as a substrate. However, the titanium dioxide thin film can be formed on the surface of a small granular material, that is, by coating the surface of an inorganic material such as sand, glass beads, or a pigment, and by firing.

[0012]

【Example】

Example 1 Quartz glass (60 mm × 60 × 3) was spin-coated with a titanium octylate solution (titanium content 5.0 wt%) and xylene mixed and diluted at a ratio of 1: 1 (weight ratio), After drying at 70 ° C. for 5 minutes, it was baked at 550 ° C. in an electric furnace for 60 minutes. As a result, a 0.2 μm transparent thin film firmly adhered to the quartz glass surface was obtained. The film was judged to be titanium dioxide from the result of composition analysis.

Example 2 A titanium naphthenate solution (titanium content of 4.0% by weight) and xylene were mixed and diluted at a ratio of 1: 1 (weight ratio) and spun on quartz glass (60 mm × 60 × 3). After coating and drying at 70 ° C. for 5 minutes, it was baked for 60 minutes in an electric furnace at 700 ° C. As a result, a 0.2 μm transparent thin film firmly adhered to the quartz glass surface was obtained. The film was judged to be titanium dioxide from the result of composition analysis.

Example 3 A titanium octylate solution (titanium content of 5.0% by weight) and xylene were mixed and diluted at a ratio of 1: 1 (weight ratio), and spun on quartz glass (60 mm × 60 × 3). It was coated, dried at 70 ° C. for 5 minutes, and then baked in an electric furnace at 550 ° C. for 60 minutes. The operation was repeated once more. As a result, a slightly opaque thin film of 0.4 μm firmly adhered to the surface of the quartz glass was obtained. The film was judged to be titanium dioxide from the result of composition analysis.

Example 4 Titanium octylate solution (titanium content 5.0% by weight)
And 10c. p. A mixture obtained by mixing and diluting a 10 wt% xylene liquid of ethyl cellulose at a ratio of 1: 1 (weight ratio) was applied, dried and baked in the same manner as in Example 1, and as a result, 0.18 μm firmly adhered to the surface of the quartz glass was obtained. A transparent thin film of was obtained. The film was judged to be titanium dioxide from the result of composition analysis.

Example 5 100 g of glass beads having a diameter of 1 mm were placed in a fluidized bed dryer having a volume of 800 ml, and fluidized at 60 to 70 ° C.
Titanium naphthenate solution (titanium content 2.25% by weight)
10 g was added dropwise over 10 minutes, and fluidized and dried for another 10 minutes. The coated glass beads were transferred to a magnetic crucible and baked in an electric furnace at 500 ° C. for 60 minutes, then gradually cooled and brought to room temperature for 2 hours. As a result, a transparent thin film was obtained on the flat surface of the glass beads. From the result of compositional analysis, the film was judged to be titanium dioxide.

Example 6 Titanium octylate solution (titanium content 5% by weight) 50
g, ultrafine titanium dioxide 50g, xylene 50g 4
It was put in a 50 ml glass bottle, 150 g of glass beads having a diameter of 1 mm was further put, and titanium dioxide was dispersed for 30 minutes by a quick mill. The solution was applied, dried and baked in the same manner as in Example 1 to obtain an opaque thin film having a thickness of 0.6 μm. From the result of compositional analysis, it was determined to be titanium dioxide.

Comparative Example 1 50 g of a medium oily alkyd resin liquid (solid content 50% by weight),
30 g of titanium dioxide with a particle size of 0.2 μm, 20 g of xylene
In the same manner as in Example 6, titanium dioxide was dispersed, and coating, drying and firing were performed in the same manner as in Example 1. As a result, a thin film of titanium dioxide was formed on the glass surface, but the adhesion to the glass surface was poor when it could be wiped off with a laboratory paper waste.

Comparative Example 2 A commercially available nitric acid-acidified (pH 1.5) titanium dioxide solution was applied, dried and baked in the same manner as in Example 1, but a thin film was not formed.

[0020]

EFFECTS OF THE INVENTION By using an organic acid titanium salt solution or a solution of organic acid titanium solution in which ultrafine particles of titanium dioxide are dispersed, a surface having a large area, a complicated shape, and a small particle size can be obtained. In addition, a thin film of titanium dioxide excellent in photocatalytic activity has been economically obtained.

Claims (1)

[Claims] 1. A method for forming a titanium dioxide thin film on a substrate by a coating pyrolysis method, which comprises using an organic acid titanium salt solution as a titanium dioxide precursor.