JP2913257B2 - Method for producing titania-silica and transparent thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a titania-silica solution,
The present invention relates to a method for producing titania-silica such as titania-silica flakes and a method for producing a transparent thin film.

[0002]

2. Description of the Related Art Titania-silica, which is a composite oxide of titanium, is known as a material having excellent corrosion resistance, heat resistance and abrasion resistance, and has high thermal stability, low thermal expansion coefficient, high refractive index and the like. Therefore, it is used for the exterior of space vehicles and the thin film coating of reflection telescope mirrors. Here, by increasing the visible light transparency of the titania-silica thin film, application to an optical laser or a coloring material can be expected. Therefore, a titania-silica thin film (transparent thin film) having high visible light transparency is required. ing.

As a conventional method for preparing titania-silica, for example, as shown in the flowchart of FIG. 5, titanium tetraisopropoxide (Ti (OC ₃ H ₇ ) ₄ : T
IP), tetraethyl orthosilicate ((C ₂ H
₅ O) ₄ Si: TEOS), ethanol (C ₂ H ₅ O)
After mixing H) at a predetermined molar ratio, a mixture of water (H ₂ O) and ethanol is added to carry out hydrolysis and polycondensation, and then the mixture is left in a 303K incubator. Gelled, and the gelled
There is known a method of obtaining a titania-silica molded body by performing through-flow drying at 3K for 50 hours and at 373K until the weight becomes constant.

[0004]

However, the titania-silica molded article prepared by the above-described method has low transparency, which is considered to be due to the fact that titania-silica easily causes phase separation and the composition uniformity is low. However, when the transparency is low as described above, when the thin-film coating of the reflecting telescope mirror is performed with the titania-silica as described above, the original function of the substrate is deteriorated, such as a decrease in the reflectance of the mirror. There was a problem of letting them do.

The present invention has been made under such circumstances, and an object of the present invention is to provide a method for producing titania-silica suitable for obtaining a transparent thin film having high visible light transparency, and a method for producing the titania-silica. An object of the present invention is to provide a method for manufacturing a transparent thin film used.

[0006]

According to a first aspect of the present invention, there is provided a process of mixing an amorphous titania, an acidic solution, and an organic silicate, and then allowing the mixture to stand to form a gel, and adding the acidic solution to the gel. And obtaining a titania-silica solution.

[0007] The invention of claim 2 is an amorphous titania.
, Acid solution and organic silicate
Forming a gel body by applying heat treatment to the gel body.
Obtaining titania-silica flakes by heating.
It is characterized by.

[0008] The invention of claim 3 is the invention according to claim 1 or 2.
In the invention, amorphous titania is titanium tetra
Alkoxides and alcohols corresponding to the alkoxides
, And further water is added, followed by solid-liquid separation,
Amole obtained by drying the obtained solid component
It is characterized by being fast titania fine particles.

According to a fourth aspect of the present invention, in the first, second or third aspect, the acidic solution is made of a hydrogen peroxide solution.

The invention of claim 5 is characterized in that the titania-silica solution according to claim 1 or 3 is applied and / or impregnated on a substrate.

[0011]

Effect: A mixture of amorphous titania, an acidic solution, and an organic silicate is gelled, and the resulting gel is dissolved again in an acidic solution to obtain a titania having high visible light transparency.
A silica solution is produced. The reason for obtaining a titania-silica solution having high visible light transparency in this way is thought to be that the aggregation of titania is dispersed by dissolving amorphous titania in an acidic solution, the composition becomes uniform, and no grain boundaries are formed. Can be In addition, a thin film can be obtained by subjecting the gel body to a heat treatment or applying and / or impregnating the substrate with the titania-silica solution. The thin film also has high visible light transparency.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to obtain a titania-silica thin film having high transparency to visible light, the present inventors first made the thin film transparent by eliminating impurities that absorb light and grain boundaries that scatter light. Since it is necessary, attention was paid to an amorphous material having no grain boundaries. Therefore, when the amorphous titania fine particles were manufactured by the method described later, the fine particles were white despite being amorphous, and the cause of this white was considered to be due to aggregation of the fine particles, and a method of redispersing the fine particles was examined. did. As a result, they found a method of dissolving the amorphous titania fine particles in an acidic solution and then gelling again, and completed the present invention. Hereinafter, the method for producing the titania-silica and the transparent thin film of the present invention will be described.

The titania-silica solution of the present invention is produced using amorphous titanium oxide, for example, amorphous titania fine particles as a raw material. The amorphous titania fine particles are produced, for example, by the method shown in the flowchart of FIG. That is, titanium tetraalkoxide such as titanium tetraisopropoxide (Ti (OC ₃ H ₇ ) ₄ : T
And IP), alcohols such as isopropanol for this alkoxide _{(iso-C 3 H 7 OH} : IPA)
And a predetermined molar ratio, for example, TIP / IPA / H ₂ O = 1 /
The mixture can be obtained by mixing at 10/4, further reacting by adding a mixed solution of a corresponding alcohol, for example, isopropanol and water, and subjecting the white suspension obtained by this reaction to solid-liquid separation and drying.

The titania-silica solution of the present invention is
For example, it is manufactured by the method shown in the flowchart of FIG. That is, amorphous titania fine particles and an acidic solution such as hydrogen peroxide solution are mixed at a ratio of, for example, 20 ml of 31% hydrogen peroxide water to 1 g of the amorphous titania fine particles, and an organic silicate such as tetraethylorthosilicate ((C ₂ H ₅₎ O) ₄ Si: TEOS) is mixed so as to have a predetermined molar ratio, for example, Ti / Si = 1/0 to 1/9, and this mixed solution is stirred at a temperature of, for example, 293 K for 2 hours. Is obtained. If, for example, Ti / Si = 1/1, the solution is left at room temperature, for example, at a temperature of 300 K, for example, for 1 week to 10 days to gel, and a yellow gel body is formed. When a predetermined amount of an acidic solution, for example, 31% hydrogen peroxide solution is added to the gel and stirred for 1 hour at a temperature of, for example, 293 K, a yellow transparent titania-silica solution is obtained.

Here, the acidic solution is a solution using ozone, oxygen, sodium hypochlorite, hypochlorous acid, sodium chlorate, chlorine dioxide or the like as an oxidizing agent in addition to the above-mentioned hydrogen peroxide solution. It is preferable, but if an acid component remains or impurities are mixed after the treatment, a problem occurs in purity. Therefore, it is preferable to use hydrogen peroxide water, ozone, oxygen, or the like. The organic silicate is a silicon component supply source, and any organic silicate containing no metal other than tetraethyl orthosilicate, for example, Si ₄ C ₈ H
₂₄ O ₄ and Si ₄ C ₄ H ₁₆ O ₄ can also be used.

When the above-mentioned yellow gel body of titania-silica is subjected to a heat treatment, for example, by sintering in an electric furnace placed in an air atmosphere, a plate-like colorless and transparent titania is obtained.
Silica flakes are obtained, and the yellow transparent titania-silica solution is coated on the surface of a substrate made of, for example, metal, ceramic, glass, or the like, and then baked in an electric furnace in an atmosphere, for example, for 3 hours.
When heat treatment is performed for 0 minutes, a titania-silica thin film having high visible light transparency is formed on the surface of the substrate. The coating of the titania-silica solution on the substrate is performed, for example, by applying the titania-silica solution to the substrate or by immersing the substrate in the titania-silica solution and impregnating the substrate with the solution. The application or impregnation of the solution may be performed repeatedly.

Titania-silica flakes and titania-silica thin films produced by such a method have high thermal stability, high refractive index, low thermal expansion, corrosion resistance, heat resistance, heat resistance, which are general properties of titania-silica. Titanium-silica flakes and titania-silica thin films having abrasion and high visible light transparency have such properties, for example, utilizing the optical field utilizing high refractive index and reflection properties, corrosion resistance. It can be used in many fields such as a corrosion prevention film, a refractory and heat-resistant material focusing on a low coefficient of thermal expansion, and a photocatalyst design utilizing light transmittance and surface activity. The titania-silica flake may be used by suspending it in a coating solution.

Next, an experiment was conducted to confirm the effect of the method of the present invention, and the titania produced by the method of the present invention was used.
An experimental example performed to study the properties of silica flake will be described. 31% hydrogen peroxide solution as an acidic solution,
TEOS was used as the alkyl silicate, and the mixed amount of TEOS was adjusted so that the Ti / Si ratio was 1 / 0.5, 1/1 and 1 /.
The resulting mixture was adjusted to 9 to prepare a titania-silica solution, and heat-treated titania-silica flakes were obtained at a temperature of 1273 K for 1 hour. The visible light transmittance of this flake was measured by ultraviolet-visible diffuse reflection spectroscopy (UV-Vis DRS), and it was found that any flake having a different titania-silica composition ratio had high visible light transmittance. Therefore, by dissolving the amorphous titania fine particles in the acidic solution, the fine particles that have been aggregated are re-dispersed, and subsequently gelled, thereby eliminating the grain boundaries that hinder the transparency and increasing the visible light transparency. confirmed.

When these flakes were analyzed by infrared diffuse reflection analysis (FT-IR DRS), the measurement results of the absorption spectrum shown in FIG. 3 were obtained.
The spectrum includes 960-970 cm ^-1 and 770 m
Near c ⁻¹ , an absorption peak not present in the spectra of silica and titania alone was observed. Even in amorphous titania, Ti = 0 near 960-990 cm ^-1.
Although an absorption peak considered to be attributed to the bond appears, it is difficult to distinguish it from the absorption peak.
The peak height decreases as the ratio of
It is unlikely that this peak is due to titania. Therefore titania - absorption peak around 960～970Cm ^-1 and 770 cm ^-1 appearing in FT-IR DRS silica flakes were determined to be those attributable to the expansion and contraction of the Ti-O-Si bonds.

This spectrum also suggested that most of the titania did not form a titania-silica bond but existed as titania. Therefore, the titania-silica flake was analyzed by UV-Vis DRS. The Ti / Si ratio is 1/0.
Titania as 5, 1 / 0.7, 1/1 and 1/9
The silica solution was prepared and heat treatment was performed at 773K and 1273K. The results are shown in FIG. 4, where TiOx means amorphous titania fine particles.

As shown in FIG. 4, the basic absorption edge shifts to a higher energy side as the silica content increases. However, since the degree of the shift is not so large, it is considered that the basic absorption edge is governed by the absorption of titania, whereby it is presumed that most of the titania is present without forming a Ti—O—Si bond. You.

From the above experimental results, it was confirmed that according to the method of the present invention, a thin film having high visible light transmittance could be obtained with a wide range of titania-silica composition ratio. FT-IR DRS and UV-Vis for titania-silica flakes
From the results of the analysis by DRS, the titania-silica produced by the method of the present invention shows that a part of titania is Ti—O—S
The i-bond is formed, and the remaining part is present in such a manner that the transparent titania film burrows the silica network, so that phase separation does not occur and no grain boundary is formed, so that visible light transparency is improved. It is estimated to be higher.

[0023]

According to the first, second and fourth aspects of the present invention, amorphous titania is dissolved and dispersed in an acidic solution, then gelled, and the gel is dissolved in the acidic solution again. Therefore, a titania-silica solution having high visible light transparency can be produced. According to the third and fifth aspects of the present invention, the gel body is subjected to a heat treatment, or the titania-silica solution is applied and / or impregnated on a substrate to form a thin film. High titania-silica flakes and thin films.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method for producing amorphous titania fine particles.

FIG. 2 is a flowchart showing a method for producing a titania-silica solution.

FIG. 3. FT-IR DR of titania-silica flakes
It is a figure showing an S measurement result.

FIG. 4. UV-Vis D of titania-silica flakes
It is a figure showing RS measurement result.

FIG. 5 is a flowchart showing a conventional method for producing a titania-silica molded body.

Claims (5)

(57) [Claims] 1. A step of mixing an amorphous titania, an acidic solution and an organic silicate and then leaving the mixture to form a gel, and a step of adding an acidic solution to the gel to obtain a titania-silica solution. A method for producing titania-silica, comprising: 2. Amorphous titania, acidic solution and organic
After mixing with the silicate, the mixture is left to form a gel.
That step and, titania subjected to heat treatment in the gel body - Shirikafure - click
Method for producing a silica - titania which comprises the the steps of obtaining a. 3. Amorphous titania is obtained by mixing titanium tetraalkoxide and an alcohol corresponding to the alkoxide, further adding water, and then performing solid-liquid separation.
2. An amorphous titania fine particle obtained by drying the obtained solid component.
Or the method for producing titania-silica according to item 2 . 4. The method for producing titania-silica according to claim 1, wherein the acidic solution comprises a hydrogen peroxide solution. 5. A method according to claim 1 or 3 titania according - method for producing a transparent thin film, characterized in that to the coating and / or impregnating a silica solution to the substrate.