JPH0615407B2 - Optical semiconductor and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an optical semiconductor in which a silica-based film is carried on the surface of a titanium oxide substrate and a method for producing the same.

This optical semiconductor can be used not only as a photobactericidal agent in cosmetics, pharmaceuticals, packaging materials and sensors, but also as a photodeodorant and sewage treatment. Also,
It can also be used as a photocatalyst for hydrogen generation by the decomposition of water and for the synthesis of amino acids and peptides.

[Conventional technology]

Titanium dioxide itself is an optical semiconductor, and when irradiated with light having an energy higher than its band gap, electrons are generated in the conduction band and holes are generated in the valence band. The electron transfer reaction caused by the energy-rich electrons and holes can exhibit a bactericidal effect or cause various chemical reactions. Particularly in the case of titanium dioxide, it is known that the photocatalytic activity is remarkably improved by forming fine particles to support platinum or ruthenium oxide.

[Problems to be solved by the invention]

However, the photocatalytic activity of the conventionally used optical semiconductors such as platinum black / titanium dioxide is certainly improved, but the color becomes black, the cost is high, and the activity decreases over time. However, there were problems such as insufficient safety. Therefore, although it can be used for catalytic reaction and the like, it is almost impossible to use it for daily necessities. For example, if you try to adjust the amount of makeup that suppresses acne,
When a drug is mixed as a component that inactivates the acne bacterium existing on the skin, its physiological action may adversely affect the skin. On the other hand, the white fungus black / titanium dioxide-based optical semiconductor cannot be mixed in a large amount in powder white powder because of its black color, and there is also a problem with the safety of platinum itself to the skin.
It was difficult to use.

Therefore, it is an object of the present invention to provide a white optical semiconductor that can be safely used for daily necessities and the like.

[Means for solving problems]

According to the present invention, the above object can be achieved by an optical semiconductor in which a silica-based coating is carried on the surface of a titanium oxide substrate.

That is, the first aspect of the present invention is an optical system in which a titanium oxide base material has a surface on which 0.1 to 30% by weight (based on the weight of an optical semiconductor) of a silica-based film having a film thickness of 4 to 500 Å and containing a silicon-titanium composite oxide is carried. It is a semiconductor.

As used herein, the term "photosemiconductor" refers to a semiconductor whose electrical conductivity is between that of a metal and an insulator, and which produces a light effect when the surface is irradiated with light in an electrolytic solution and is oxidized under photoexcitation conditions. It means a substance that causes a reduction reaction or an electrode reaction.

The titanium oxide base material used in the present invention comprises titanium dioxide, low order titanium oxide or a mixture thereof. Titanium dioxide may be any of anatase type, rutile type, brookite type, or a mixture thereof. Low-order titanium oxide refers to TiOn in which n is less than 2. The shape of the titanium oxide base material can be arbitrary, but a powder base material is generally used. The particle diameter of the preferable base powder is 0.08 to 10 µ, and particularly 0.01 to 1 µ.

The silica-based film for coating the surface of the optical semiconductor of the present invention is essentially composed of silicon oxide which is essentially composed of silicon and oxygen, or silicon, oxygen and titanium which are further bonded to titanium oxide on the surface of the substrate. It is composed of a silicon-titanium composite oxide. Furthermore, the silicon-carbon composite containing Si-C may be included. The molar ratio of silicon: oxygen in the silicon oxide is 1: about (1.5 to 2.5), and the molar ratio of silicon: titanium: oxygen in the silicon / titanium composite oxide is 1: about (0.1 to 9.0). : It is about (1.5 to 20). In general, the silica-based coating has the boundary surface with the substrate made of the silicon-titanium composite oxide and the other portions made of silicon oxide. The thickness of the film is 4 to 500Å, preferably 4Å to 100Å. Further, the silica-based film is supported on the optical semiconductor in an amount of about 0.1 to 30% by weight, preferably 1.0 to 10.0% by weight, based on the weight of the optical semiconductor. The supported amount varies depending on the specific surface area of the titanium oxide base material, and the larger the specific surface area, the larger the supported amount.
When the content is% by weight, the amount supported is small and the effect does not appear. Again 3
If it is 0% by weight or more, the silica-based coating becomes thick, and the effect is similarly lost.

Since the optical semiconductor according to the present invention is white and highly safe for humans, it can be used for medicines, cosmetics and the like. The bactericidal effect when irradiated with light is effective against various bacteria such as Escherichia coli and acne bacteria, and this action enables sterilization of the application site. Further, it can be selectively oxidized also as a photocatalytic action and can be used as a catalyst.

A second aspect of the present invention is a method for producing the above-described optical semiconductor, which comprises the steps of coating the surface of a titanium oxide device with a silicon compound and then firing the coated silicon compound.

In the method of the present invention, a silicon compound coating layer is first formed on the surface of a titanium oxide substrate. The coating layer is formed by bringing the silicon compound into contact with the titanium oxide base material in the solid phase, liquid phase or gas phase. It is preferable to use a method capable of forming a uniform and thin coating layer.

An inorganic silicon compound such as water glass can be used as the silicon compound. However, it is preferred to use organosilicon compounds. As the organosilicon compound, silanes such as chlorosilane and alkoxysilane, and cycloxane having various functional groups can be used. As the siloxane, for example, hydroxy-modified, amino-modified, carboxyl-modified, epoxy-modified, methacryloxy-modified, fluorine-modified, mercapto-modified, alkyl-modified, phenyl-modified siloxanes can be used. Among these, the present inventors have found that polysiloxane having Si-H forms a uniform coating layer on a titanium oxide substrate. That is, as a silicon compound, the formula (In the formula, R is a monovalent organic group, a is 1 or 2, and b is 0, 1 or 2, provided that the sum of a and b does not exceed 3.) When an organohydrogenpolysiloxane having at least one unit represented by the formula (1) in one molecule is used, Si—H groups are crosslinked on the base material to form a Si—O—Si bond to obtain a silicone polymer. . According to the findings of the present inventors, the cross-linking between Si—H groups proceeds by the action of active sites existing on the surface of the titanium oxide base material.
No catalyst addition is necessary at all. When the titanium oxide substrate having a silicone coating layer thus formed is fired, an optical semiconductor carrying a uniform and thin silica-based film can be obtained.
In the present invention, it is most preferable to cover the entire surface of the substrate with a thin and uniform silica coating. In order to form a thin and uniform silica-based coating on the entire surface of the base material, the conventional method of coating the base material with water glass and then firing is not sufficient. The most effective method is to first treat the substrate with a silicon compound to form a uniform coating layer of the silicon compound on the substrate, and then to bake it. As a method for uniformly coating the silicon compound on the titanium oxide substrate, Or expression (In the above formulas, R _{1 to} R ₈ may be the same or different from each other, and are a hydrogen atom, an alkyl group or an aryl group,
Each of k and n is a positive integer, provided that 3 ≦ k ≦ 100 and 1 ≦ n ≦ 100 are satisfied.) Titanium oxide using one or more silicone compounds represented by There is a method of polymerizing on a substrate. In this case, the ring-opening polymerization of the siloxane bond is sufficient for the polymerization, but as described above, the polymerization having the Si—H group is more favorable.

Examples of the compound of the formula (B) include dihydrohexamethylcyclotetrasiloxane, trihydropentamethylcyclotetracycloxane, tetrahydrotetramethylcyclotetrasiloxane, dihydrootamethylcyclopentasiloxane, trihydroheptamethylcyclopentasiloxane, It is desirable that one molecule has two or more hydrogen atoms, such as tetrahydrohexamethylcyclopentasiloxane and pentahydropentamethylcyclopentasiloxane. Further, when the number of hydrogen atoms is too large, it is difficult to obtain silicon atoms because two hydrogen atoms bond to silicon atoms.

The compound of the formula (C) also has two or more hydrogen atoms in one molecule, for example, a compound of the formula And the like are desirable.

The treatment of the substrate with the compound of the above formula (B) or the formula (C) can be carried out not only in the liquid phase but also in the solid phase using a ball mill. In the case of the solid phase, the particle system or the like changes. May be necessary and requires attention.

The most preferable treatment method is as follows. One or more volatile cyclic silicones of the formula (B) with k = 3 to 7 and / or one or more volatile linear silicones of the formula (C) with n = 0 to 6 and titanium oxide. Putting and in separate open containers, and leaving these containers in a common closed system, volatile silicone is adsorbed on the titanium oxide surface in a molecular form. The gas phase treatment of the substrate with volatile silicone can also be carried out in an open system. In this case, it is preferred to carry the volatile silicone on a substrate with a suitable carrier gas.

In this state, the volatile silicone volatilizes with the partial pressure at that temperature, and maintains adsorption equilibrium on titanium oxide. Here, if the surface of the base material has no polymerization activity, the base material returns to the original surface if the volatile silicone is desorbed when the base material is taken out.
However, if there is polymerization activity, the silicone compound will polymerize on the substrate. When the polymerization is carried out, the partial pressure of the volatile silicone on the surface of the base material is lowered, so that the volatile silicone in the container is further volatilized and supplied onto the base material.

In order to cause polymerization on the surface, heat is generally used or a polymerization catalyst is used. However, according to the knowledge obtained by the present inventors, the surface of titanium oxide is formed by crosslinking Si—H groups with each other.
It was found to have a catalytic action to form O-Si bonds. That is, the volatile silicone adsorbed on the surface of titanium oxide forms a sequentially cross-linked knitted silicone resin due to this surface activity. When the surface of the base material is coated with the silicone resin in this way, the surface active sites on the titanium oxide surface are blocked, and the subsequent adsorption and crosslinking reactions do not proceed and the formation of the coating layer stops. Then, by degassing, the unreacted volatile silicone is removed, and a titanium oxide base material that is volatilized only by the silicone resin is obtained.

The titanium oxide base material having the silicon compound coating layer thus obtained is then subjected to a firing step to form a silica-based film on the surface of the base material. The firing temperature is 300 to 1100 ° C, preferably
400 to 800 ° C. At 300 ° C or lower, organic groups such as methyl groups remain, and at 1100 ° C or higher, aggregation of the base material occurs, which is not preferable. The firing time is 2 to 24 hours. The firing atmosphere is air, vacuum, nitrogen stream, ammonia stream,
Either in a hydrogen stream may be used. The base material becomes titanium dioxide when fired in an air stream. Low-order titanium oxide is produced in a case other than in the air stream, and titanium nitride or silicon nitride may be partially formed in the ammonia stream, but in either case, the firing product is used as an optical semiconductor. Can be used.

The component constitution of the optical semiconductor of the present invention thus obtained can be estimated by X-ray photoelectron spectroscopy analysis, infrared spectroscopy analysis, X-ray diffraction and the like.

The optical semiconductor of the present invention is white, has excellent photobactericidal action, photocatalytic action, and the like, and is less deteriorated with time as compared with platinum-supported titanium dioxide.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Production Example 1 (1) 100 g of titanium dioxide fine particles (0.025 μm) and 20 g of tetrahydrotetramethylcyclotetrasiloxane were placed in separate small containers, and the small containers were left at room temperature in a closed container. After 96 hours, the titanium dioxide fine particles were taken out and weighed to obtain 107.85 g of silicone-treated titanium oxide fine particles, and further left in a dryer at 50 ° C. for 24 hours to obtain silicone-treated titanium dioxide fine particles.
4.80 g were obtained.

When the silicone-treated titanium dioxide fine particles were baked in an electric furnace in the presence of air at 500 ° C. for 120 minutes, 104.50 g of titanium dioxide fine particles having a silica-based coating was obtained.

(2) The composition of the product at each process step of Production Example 1 (1) was analyzed by an X-ray photoelectron spectroscopy analyzer.

ESCA-5300 manufactured by ULVAC-PHI, Inc.
15KV dual anode Mg 300 as X-ray source
W is a hemispherical electrostatic analyzer (SC
A) and PSD (position sensitive detector) were used as detectors. The binding energy was corrected with the value of C _1S as a standard, and measured in the range of 0 to 1000 eV.

The results of the X-ray photoelectron spectroscopy analysis are shown in Table 1. In FIG. 1, (a) shows the measurement results of titanium dioxide. Ti Auger (Ti _A ), Ti _2S Orbital and Ti _2P Orbital Binding Energy and O Auger (O _A ) and O
_The binding energy showing the _1S orbital was observed, which shows that titanium oxide, that is, titanium oxide is present on the surface. FIG. 1 (b) shows the measurement results of the silicon-treated titanium dioxide before firing, and (c) shows the measurement results of the product fired at 500 ° C. In any case Ti
The Si _2s orbit and the Si _2P orbit are observed in addition to the binding energy due to O and O, indicating that the Si compound exists on the surface. In both (b) and (c), the Si _{2 P} orbital shows 102.3 eV and no difference is observed.

When the compositional ratio of (b) and (c) was determined from the photoelectron spectrum, it was found that Ti = 14.58, O = 52.54, C =
24.09 Si = 8.08, (c) Ti = 14.78, O = 57.4
9, C = 20.67, Si = 7.06, and it was found that C decreased and O increased by firing. This is (b)
The Si-CH ₃ group of the silicone in
This seems to indicate that the bond was changed to -O.

(3) An infrared spectrophotometer was used to examine the product of each process step of Production Example 1 (1).

As the infrared spectrophotometer, FTS-15C manufactured by Disilab was used. The measurement was carried out under the following conditions by uniformly mixing 100 mg of the sample and 900 mg of KBr powder and filling the cell in a diffuse reflectance spectrum measurement.

Resolution: 1 cm ^-1 Number of integrations: 100 times Figure 2 shows the infrared absorption spectrum. (A) shows the spectrum of titanium dioxide, (b) shows the spectrum of the silicone-coated titanium dioxide before baking. In (b),
(A) due to the Si-H groups of the absorption and 2170 cm ^-1 attributable to Si-CH ₃ of Never 1270 cm ^-1 that seen to be absorbed Sotoshin. From this, the fine particles before firing of (b) are Si-CH.
_It can be seen that it is reliably coated with silicone having ₃ and Si-H groups.

On the other hand, in (c) showing the spectrum of the calcined product, the absorptions due to Si—CH ₃ and Si—H both disappear, and instead the absorptions at 3700 to 3800 cm ⁻¹ appear. This absorption is believed to be due to Si-OH. Therefore, from the result of the photoelectron spectrum of (2) above, it is known that Si is surely present on the surface of the baked product, so that SiO ₂ which is an inorganic Si compound is formed on the surface of the baked product. It is presumed that

(4) X-ray diffraction studies were conducted on the fine particles at each step of the above Production Example 1 (1).

For the X-ray diffraction, JRX-12X-A manufactured by JEOL Ltd. was used, and the target was Cu (Kα ray) at 40 KV and 100 mA. The filter is a monochromator, the dictator is S
C was used. FIG. 3 shows the X-ray diffraction result of the baked product. From this result, it is understood that the main component of the baked product of Example 1 (1) is titanium dioxide, and the anatase type is more than the rutile type. This X-ray diffraction pattern is the same for untreated titanium dioxide and pre-calcined silicone-coated titanium dioxide, indicating that the original anatase: rutile ratio did not change upon calcining at 500 ° C. Further, since the silica-based compound produced by firing was not observed by X-ray diffraction, it can be seen that the amount was very small.

From the above, it can be presumed that the fired product of Example 1 (1) has titanium dioxide (anatase type> rutile type) as a main component and has a thin silica-based coating on the surface.

Bactericidal activity test example (a) Photobactericidal activity against Escherichia coli Escherichia coli (Esherichia coli ATCC8739) pre-cultured in a broth medium (pH 7) for 24 hours in advance was suspended in 0.1 M phosphate buffer (pH 7) to obtain 3.5 ×. A cell suspension of 10 ³ cells / ml was prepared. On the other hand, in a 100 ml Erlenmeyer flask, titanium dioxide fine particles (0.025 μm) or the above Production Example 1 (1)
50 mg of the photo-semiconductor particles of the present invention prepared in the above was added, and 30 ml of the above cell suspension was added. Light irradiation was performed with a halogen lamp (about 10,000 lux) while gently shaking these Erlenmeyer flasks, and the number of viable cells after 180 minutes was measured by the colony method. These experiments were performed at room temperature. The results are shown in Table 1 below.

As is clear from Table 1, 180 minutes was observed both when the cell suspension containing no additive was irradiated with light and when the calcined product of Production Example 1 (1) was added and not irradiated with light. Subsequent viable cell counts have hardly changed. On the other hand, when the titanium dioxide fine particles were added and light irradiation was performed, the viable cell count was clearly reduced, and when the baked product of Production Example 1 (1) was added and light was irradiated, the viable cell count was decreased. It can be seen that the number is further reduced. From this, it is clear that the semiconductor according to the present invention exhibits effective bactericidal activity when exposed to light.

(B) Photobactericidal activity against Acne bacterium Acne bacterium (Propionibacterium acnes ATCC11827) pre-cultured in GAM agar medium (pH 7.3) for 48 hours in advance was suspended in M / 15 phosphate buffer (pH 7.2) to give 8 .3 ×
A cell suspension of 10 ⁵ cells / ml was prepared. On the other hand, 100
Into a ml Erlenmeyer flask, 10 mg of titanium oxide fine particles (0.025 μm) or the optical semiconductor particles of the present invention prepared in the above Production Example 1 (1) were placed, and 30 ml of the above cell suspension was placed.
While gently shaking these Erlenmeyer flasks, irradiate with fluorescence (about 6000 lux), and after 30 minutes,
The viable cell counts after 60 minutes and 90 minutes were measured by the colony method. These experiments were performed at 37 ° C. The results are shown in Table 2 below.

As is clear from Table 2, the same results as in the case of Escherichia coli were obtained in the case of P. acnes. However, the difference from titanium dioxide is larger than that of E. coli, and it can be seen that the photobactericidal action is stronger than that of untreated titanium dioxide.

[Brief description of drawings]

FIG. 1 is a graph showing the results of X-ray photoelectron spectroscopy analysis.
The figure is a graph showing an infrared absorption spectrum, and FIG. 3 is a graph showing the results of X-ray diffraction.

Claims (8)

[Claims] 1. A silica-based film having a thickness of 4 to 500 Å containing a silicon-titanium composite oxide on the surface of a titanium oxide base material, 0.1 to 30.
An optical semiconductor that carries a weight percentage (based on the weight of the optical semiconductor). 2. The optical semiconductor according to claim 1, wherein the titanium oxide base material is fine particles having a particle diameter of 0.008 to 10 μm. 3. The optical semiconductor according to claim 1, wherein the titanium oxide base material comprises low-order titanium oxide, anatase, rutile, brookite or a mixture thereof. 4. The optical semiconductor according to claim 1, wherein the silica-based coating contains silicon carbide. 5. A titanium oxide substrate is coated with a silicon compound on the surface thereof and then baked to obtain a film thickness of 4 on the surface of the substrate.
~ 500 Å Silica-based film 0.1 ~ 30 wt% (based on the weight of the optical semiconductor) A method of manufacturing an optical semiconductor. 6. A silicon compound of the formula (In the formula, R is a monovalent organic group, a is 1 or 2, and b is 0, 1 or 2, provided that the sum of a and b does not exceed 3.) The method according to claim 5, wherein an organohydrogenpolysiloxane having at least one unit represented by the formula (1) in one molecule is used. 7. A silicon compound of the formula Or expression (In the above formulas, R _{1 to} R ₈ may be the same or different from each other, and are a hydrogen atom, an alkyl group or an aryl group,
k and n are respectively positive integers, provided that the values of 3 ≦ k ≦ 100 and 1 ≦ n ≦ 100 are satisfied). Method. 8. The method according to claim 5, wherein the firing temperature is 300 ° C. to 1100 ° C.