JPS63293168A - Formation of thin titanium oxide film - Google Patents

Abstract

PURPOSE:To shorten baking time and to improve the optical characteristics of a formed thin titanium oxide film by heating a substrate having a film of an organotitanium compd. at a specified heating rate to bake the film at a specified temp. CONSTITUTION:A substrate is dipped in a soln. of an organotitanium compd., pulled up and dried to form a film of the organotitanium compd. The substrate having the film is heated at >=300 deg.C/min heating rate and the film is baked at >=600 deg.C to decompose the organotitanium compd. and to form a thin film of titanium oxide. This thin titanium oxide film has superior optical characteristics including refractive index and transmissivity, little unevenness in the characteristics and stable quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object 1] (Industrial Application Field) The present invention relates to a method for forming a titanium oxide thin film, and is particularly suitable for forming an optical thin film.

(Prior Art) Conventionally, a titanium oxide thin film has been formed by immersing a substrate in a solution of an organic titanium compound such as a metal alkoxide, pulling it up, drying it, and then baking it in a furnace at a temperature of 500° C. or more for 10 minutes or more. Such titanium oxide thin films are used for anti-glare films, interference films, filter films, etc., and are also used in various multi-interference films such as visible light transmitting infrared reflective films by being alternately layered with silica thin films.

(Problems to be solved by the invention) In the conventional forming method, not only does the firing process require a lot of time, but also the optical properties of the obtained titanium oxide thin film, such as refractive index and transmittance, vary widely, resulting in poor quality. It has the disadvantage of being difficult to stabilize.

[Structure of the invention]

(Means for Solving the Problems) The present invention heats a substrate having an organic titanium compound coating film and increases the temperature at a rate of 300°C/min or more to achieve a firing time of 600°C or more. and the optical properties of the obtained titanium oxide thin film.

This will improve the performance and reduce the variation.

(Function) Usually, a stabilizer, a vitrification agent, etc. are added to such an organic titanium compound solution for forming a titanium oxide thin film in order to improve the film-forming properties and stability of the solution. However, although such additives are small in quantity, they are stable, and therefore the decomposition and firing temperature is generally higher than that of the solvent in the film, making them difficult to decompose.

Therefore, if the temperature is gradually increased, these additives will remain undecomposed and dispersed in the film in the intermediate stage, and even if the temperature is increased further, the effects of these undecomposed additives will cause the firing to fail. Various problems occur, such as the film becoming almost sponge-like, or variations in film quality due to residual carbon produced by the decomposition of these additives.

In order to eliminate the negative effects of such additives, the substrate with the organic titanium compound coating is rapidly heated at a temperature increase rate of 300"07 minutes or more to decompose or evaporate the above-mentioned additives. This prevents undecomposed substances from remaining, and provides a titanium oxide thin film that is dense, has excellent optical properties, and has little variation.

(Example) The details of the present invention will be explained by referring to an example. First, the following 3
A seed organic titanium compound solution was prepared.

(A) Organic titanium compound A solution tetrane propoxy titanium (Ti (OiPr)4)
42.6 g of Ti(OjPr) was dissolved in 234 g of ethanol, and 30 g of acetylacetone was added and reacted to obtain an ethanol solution containing 54.6 g of organotitanium compound A in which a part of the -0iPr group of Ti(OjPr) was replaced with an acetylacetone residue. I got it. Here, iPr represents an isopropyl group (the same applies hereinafter) (B) Organic titanium compound polymer B solution tetraisopropoxytitanium (Ti(OiPr)) 56.8 g
was dissolved in 350 g of ethanol, and 3.0 g of water was added with stirring.
2g was gradually added and polymerized. Next, 40 g of acetylacetone was added to this solution while stirring, and -0i
Organotitanium compound polymer B in which a part of the Pr group is substituted with 7 cetyl acetone residues and has a degree of polymerization n = 10 is 60.8
An ethanol solution containing g was obtained.

(C) Coating solution for forming a titanium oxide thin film 30 g of the ethanol solution of the organic titanium compound (A) prepared above and 400 g of the ethanol solution of the organic titanium compound polymer B are mixed, and if necessary, pentoxide is added as a vitreous forming material. Rin (
P□0. ) Added 0.4 g of organic titanium compound A and organic titanium compound polymer B converted to TiO□, and adjusted the mixing ratio of both solutions A and B so that the mixture efficiency was 3.6% by weight. A coating solution for forming a titanium thin film was obtained.

Using each of the three solutions A, B, and C prepared in this manner, a quartz plate is immersed in the solution, pulled up at a constant speed, dried, and then fired using various methods described below to form the organic titanium compound. was decomposed to form a titanium oxide thin film.

The above-described firing process was carried out in an air atmosphere at various temperature increase rates, at various processing humidities, and for a typical processing time, for example, about 5 minutes, to obtain a large number of test specimens. The optical properties of the test pieces thus obtained were then compared.

Figure 1 shows the optical refractive index of a test product using the above-mentioned organic titanium compound A solution, where the horizontal axis shows the firing temperature in °C, and the vertical axis shows the temperature increase rate in °C/min. Something x
The mark indicates a refractive index n<2.0. Δ mark is 2.0≦n<2.1.0
The mark indicates 2.1≦n<2.2. The mark 0 indicates a test product with 2.2≦n. From this figure 1, any product heated at a rate of 300°C/min or higher and fired at a temperature of 500°C or higher has a refractive index n of 2.1 or higher. It is understandable that

Figure 2 shows the light transmittance of the test product using the above-mentioned organic titanium compound A solution, where the horizontal axis shows the firing temperature in °C, and the vertical axis shows the temperature increase rate in °C/min. The X mark indicates a test product where the transmittance T is 85%, the Δ mark is 85%≦T<90%, the Q mark is 90%≦T95%, and the ◎ mark is a test product with a transmittance of 95%≦T. From FIG. 2, it can be seen that the transmittance T is 90 or more for all of the materials that were heated at a rate of 300° C./min or more and fired at a temperature of 600° C. or more.

Figure 3 shows the optical refractive index of a test product using the organic titanium compound polymer B solution described above, with the firing temperature in degrees Celsius on the horizontal axis and the heating rate in degrees Celsius/minute on the vertical axis. The X mark indicates the refractive index n (2,0°; the Δ mark indicates 2.0≦n<2.1
．． Q mark indicates 2.1≦n (2,2, O mark indicates test product with 2.2≦n. From this figure 3, the temperature was increased at a rate of 300°C/min or more and baked at a temperature of 600°C or more. It can be seen that all of these have a refractive index n of 2.1 or more.

Figure 4 shows the light transmittance of a test product using the organic titanium compound polymer B solution described above, with the firing temperature in degrees Celsius on the horizontal axis and the temperature increase rate in degrees Celsius/minute on the vertical axis. The x mark indicates a transmittance T of 85%.

Δ mark indicates 85%≦T<90%, 0 mark indicates 90%≦T<95%
.

The O mark indicates a test product with 95%≦T.From this figure 4, 30
It can be seen that all the materials that were heated at a rate of 0° C./min or higher and fired at a temperature of 400° C. or higher had a transmittance T of 90 or higher.

Figure 5 shows the optical refractive index of a test product using the coating solution for forming a titanium oxide thin film described above, with the firing temperature in °C on the horizontal axis and the temperature increase rate in °C/min on the vertical axis. What I took,
The x mark indicates the refractive index n (2,0, and the Δ mark indicates 2.0≦n<2.1.
0 mark means 2.1≦n<2.2. The @ mark indicates a test product with 2.2≦n. In this figure, the temperature was raised at a rate of 300'C/min or more to 600'C or more (heating rate 5o).

It can be seen that in the case of 500°C or higher in the case of 500°C per minute, the refractive index n of all those fired at a temperature of 2.1 or higher is 2.1 or higher.

Figure 6 shows the light transmittance of a test product using the coating solution for forming a titanium oxide thin film described above, with the firing temperature plotted on the horizontal axis in degrees Celsius and the heating rate in degrees Celsius/min on the vertical axis. x
Mark indicates transmittance T〈85%, Δ mark indicates transmittance T〈85%, 0
The mark indicates a test item with 90%≦T<95%, and the 0 mark indicates a test item with 95%≦T. As shown in Figure 6: Raise the temperature at a rate of SOO℃ or higher to 500℃ or higher (if the heating rate is 300℃) is 600℃
The transmittance T of all those fired at temperatures above) is 90.
The above is understandable.

In this way, no matter which of the three solutions mentioned above is used,
Although there were small differences, good results were obtained with rapid heating and heat treatment at high temperatures, and the characteristic values were also excellent, with less variation.

In particular, increase the temperature to 600'C at a rate of 300°C/min or more.
Products fired at temperatures above are excellent in characteristic values and their dispersion, and can be used for the same purposes as conventional ones, such as anti-glare films, interference films, filter films, etc. as a single layer film, or interference filter films formed by alternately layering with silica thin films. It is highly effective when used for such purposes.

In addition, the heat source in the above-mentioned baking step is preferably an infrared light bulb, a gas bulb, a light emitting laser, a xenon lamp, or the like.

Thus, in the present invention, any substrate on which a thin film is to be formed may be used.

〔Effect of the invention〕

As described above, the method for forming a titanium oxide thin film of the present invention is a method in which a substrate is immersed in an organic titanium compound solution, pulled up and dried, and then fired to decompose the organic titanium compound and form a thin film made of titanium oxide. , the firing process is 30
Since the temperature is raised at a rate of 0° C./min or higher and the heat treatment is performed at a humidity of 600° C. or higher, the obtained titanium oxide thin film has excellent properties such as optical refractive index and optical transmittance, and has little variation.

It has the advantage of stable quality.

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing the correlation between the processing conditions and optical properties of the first embodiment of the method for forming a titanium oxide thin film of the present invention, and FIGS. Graphs showing the correlation between processing conditions and optical characteristics. FIGS. 5 and 6 are graphs showing the correlation between processing conditions and optical characteristics in the third embodiment. Agent Patent Attorney Inoue - Man XXXXX No. 3
Figure 0 4t>o BOO/200 mq° ;2=to-3('C)

Claims (1)

[Claims] In a method in which a substrate is immersed in an organic titanium compound solution, pulled up and dried, and then fired to decompose the organic titanium compound and form a thin film made of titanium oxide, the firing step involves heating the substrate having the coating film. 1. A method for forming a titanium oxide thin film, which comprises heating at a rate of 300° C./min or more and heat-treating at a temperature of 600° C. or more.