JPS62260717A - Optical semiconductor and production thereof - Google Patents

Abstract

PURPOSE:To make it possible to obtain a white semiconductor safely usable for living goods, etc., by supporting a silica based film on the surface of a titanium oxide substrate. CONSTITUTION:The surface of titanium oxide is coated with a silicon compound and fired to form a silica based film thereon and give the aimed optical semiconductor without problems in safety for the skin. Since the color of the semiconductor is white, a large amount thereof can be blended in face powder and the activity is hardly deteriorated with time. The above-mentioned optical semiconductor is produced by putting, e.g. given amounts of fine titanium oxide particles and tetrahydrotetramethylcyclotetrasiloxane into separate small containers and allowing the small containers to stand in a hermetically sealed container at room temperature. The resultant fine titanium oxide particles treated with the silicone are then fired in an electric furnace in the absence of air under given condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Graduation field of application] The present invention relates to an optical semiconductor having a silica-based film supported on the surface of a titanium oxide base material and a method for producing the same.

This optical semiconductor can be used not only as a photosterilizer in cosmetics, pharmaceuticals, packaging materials, and sensors, but also as a photodeodorizer and in sewage treatment. Also,
It can also be used as a photocatalyst to generate hydrogen by decomposing water and to synthesize amino acids and peptides.

[Conventional technology]

Titanium dioxide itself is an optical semiconductor, and when it is irradiated with light with an energy higher than its band gap, electrons are generated in the conduction band and holes are generated in the valence band. Electron transfer reactions caused by these energetic electrons and holes can exhibit sterilizing effects and cause various chemical reactions. Particularly in the case of titanium dioxide, it is known that the photocatalytic ability of titanium dioxide is significantly improved if it is formed into fine particles and supported with platinum or ruthenium oxide.

[Problem that the invention seeks to solve]

However, conventionally used photosemiconductors such as platinum black/titanium dioxide type have certainly improved photocatalytic ability, but they have problems such as darkening of the color, high cost, and decrease in activity over time. However, there were problems such as insufficient safety. Therefore, although it could be used for catalytic reactions, it was almost impossible to use it for household products. For example, when preparing an acne-suppressing cosmetic,
When a drug is added as an ingredient to inactivate acne bacteria present on the skin, its physiological effects may have an adverse effect on the skin. On the other hand, platinum black/titanium dioxide-based photosemiconductors are black in color, so they cannot be incorporated in large quantities into white powder, and platinum itself has safety issues for the skin, making it difficult to use. Met.

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

Means for Solving Problem C] According to the present invention, the above object can be achieved by an optical semiconductor in which a silica-based film is supported on the surface of a titanium oxide base material.

That is, the first aspect of the present invention is an optical semiconductor comprising a titanium oxide base material with a silica-based film supported on its surface.

In this specification, the term "photosemiconductor" refers to a semiconductor whose electrical conductivity is between that of metals and insulators, which generates a light effect when its surface is irradiated with light in an electrolytic solution, and which undergoes oxidation under photoexcitation conditions. It means something that causes reduction reactions, electrode reactions, etc.

The titanium oxide base material used in the present invention is made of titanium dioxide, lower titanium oxide, or a mixture thereof.

The crystal form of titanium dioxide may be anatase type, rutile type, brutzite type, or a mixture thereof. Low-order titanium oxide refers to Ti0n in which n is less than 2. Although the shape of the titanium oxide base material can be arbitrary, a powder base material is generally used. , the preferred particle size of the base powder is 0.08 to 10μ, particularly 0.
．． O1-1μ.

The silica-based film coating the optical semiconductor surface of the present invention is composed of silicon oxide essentially consisting of silicon and oxygen, or essentially composed of silicon, oxygen, and titanium further combined with titanium oxide on the base material surface. It consists of silicon and titanium composite oxide. Furthermore, a silicon/carbon composite containing 5i-C may be included. The molar ratio of silicon:oxygen in the silicon oxide is 1:about θ, 5 to 2.5), and the molar ratio of silicon:titanium:oxygen in the silicon-titanium composite oxide is 1:about (0 , 1-9.02: Approximately (1,
5 to 20). Generally, in the silica-based film, the interface with the base material is made of the silicon-titanium composite oxide, and the other parts are made of silicon oxide. The thickness of the coating is 500 Å or less, preferably 4 to 100 Å.

In addition, the silica-based film is based on the weight of the optical semiconductor.
It 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. 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.
Even in a base material with a diameter of 0μ or less, if the amount is 0.1% by weight, the supported amount is too small to produce any effect. Moreover, if the weight exceeds 30%, the silica-based film becomes thick, so that the effect is similarly lost.

The optical semiconductor according to the present invention is white and highly safe for the human body, so it can be used in medicines, cosmetics, etc. The bactericidal effect when irradiated with light is effective against various types of bacteria such as Escherichia coli and acne scars, and this action makes it possible to sterilize the area where it is applied. In addition, selective oxidation can be performed as a photocatalyst, and it can also be used as a catalyst.

The second aspect of the present invention is a manufacturing method for obtaining the optical semiconductor described above, which comprises coating the surface of a titanium oxide base material with a silicon compound and then firing it.

In the method of the present invention, a coating layer of a silicon compound is first formed on the surface of a titanium oxide base material. The coating layer is formed by contacting the titanium oxide base material with a silicon compound in a solid, liquid or gas phase. It is preferable to use a method that can form a uniform and thin coating layer.

Inorganic silicon compounds such as water glass can be used as the silicon compound. However, preference is given to using organosilicon compounds. As the organosilicon compound, silanes such as chlorosilane and alkoxysilane, and siloxanes having various functional groups can be used. As the siloxanes, for example, hydroxy-modified, amino-modified, carboxyl-modified, epoxy-modified, methacryloxy-modified, fluorine-modified, mercapto-modified, alkyl-modified, and phenyl-modified siloxanes can be used. Among these, the present inventors have found that polysiloxane having 5i-H forms a uniform coating layer on a titanium oxide substrate.

That is, as a silicon compound, the formula (wherein R is a monovalent organic group, a is 1 or 2, and b is Oll or 2, provided that the sum of a and b does not exceed 3) If an organohydrodiene polysiloxane having at least one unit represented by is obtained. According to the findings of the present inventors, 5i
Since the crosslinking between =H groups proceeds by the action of active sites present on the surface of the titanium oxide base material, the addition of a catalyst is completely unnecessary. When the titanium oxide substrate with the silicone coating layer thus formed is fired, an optical semiconductor carrying a uniform and thin silica-based film is obtained. In the present invention, it is most preferable to cover the entire surface of the substrate with a thin and uniform silica-based film. In order to form a thin and uniform silica-based film over the entire surface of a substrate, the conventional method of coating the substrate with water glass and then firing it is insufficient. 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, followed by firing it. As a method for uniformly coating a silicon compound on a titanium oxide substrate, the formula or formula (in each of the above formulas, R1 to RIl may be the same or different from each other and are a hydrogen atom, an alkyl group, or an aryl group, and k and n are positive integers, provided that they satisfy the following values: 3≦≦100 and 1≦n≦100). There is a method of polymerizing on a substrate. In this case, a certain degree of polymerization is possible only by ring-opening polymerization of siloxane bonds, but as mentioned above, polymerization occurs more favorably with those having a 5i-H group.

Examples of the compound of formula (B) include dihydrohexamethylcyclotetrasiloxane, trihydropentamethylcyclotetrasiloxane, tetrahydrotetramethylcyclotetrasiloxane, dihydrooctamethylcyclopentasiloxane, trihydroheptamethylcyclopentasiloxane, tetra Those having two or more hydrogen atoms in one molecule are desirable, such as hydrohexamethylcyclopentasiloxane and pentahydropentamethylcyclopentasiloxane. Furthermore, if there are too many hydrogen atoms, two hydrogen atoms bond to a silicon atom, making it difficult to obtain.

Similarly, the compound of formula (C) is preferably one in which two or more hydrogen atoms are present in one molecule, such as a compound of the formula.

The treatment of the substrate with the compound of formula (B) or formula (C) above can be carried out not only in liquid phase but also in solid phase using a ball mill, but in the case of solid phase, the particle shape etc. may change. Caution is required.

The most preferred treatment method is the following method. Formula (B)
One or more volatile cyclic silicones with n = 3 to 7 and/or one or two or more volatile linear silicones with formula (C) where n = O to 6 and titanium oxide, respectively. When the titanium oxide is placed in an open container and these containers are left in a common closed system, volatile silicone will be adsorbed in molecular form on the surface of the titanium oxide.

The gas phase treatment of the substrate with volatile silicone can also be carried out in an open system. In this case, it is preferable to carry the volatile silicone onto the substrate with a suitable carrier gas.

In this state, volatile silicone volatilizes due to the partial pressure at that temperature and maintains an adsorption equilibrium on titanium oxide. If there is no polymerization activity on the surface of the base material, when the base material is removed, the volatile silicone will be desorbed and the base material will return to its original surface. However, if there is polymerization activity, the silicone compound will polymerize on the substrate. Upon polymerization, the partial pressure of the volatile silicone on the surface of the substrate decreases, so that the volatile silicone in the container is further volatilized and delivered onto the substrate - heat is generally used to cause polymerization on the surface, or Alternatively, a polymerization catalyst is used, but according to the knowledge obtained by the present inventors, 5i-H groups are cross-linked to each other on the titanium oxide surface.
It was found that it has a catalytic effect to generate a 0-3i bond. That is, the volatile silicone adsorbed on the surface of titanium oxide forms a mesh-like silicone resin that is successively crosslinked by this surface activity. When the surface of the substrate is coated with the silicone resin in this manner, the surface active sites on the titanium oxide surface are blocked, and subsequent adsorption and crosslinking reactions do not proceed, stopping the formation of the coating layer.

Thereafter, by degassing, unreacted volatile silicone is removed, and a titanium oxide base material coated only with silicone resin is obtained.

The titanium oxide base material having the silicon compound coating layer thus obtained is then subjected to a firing process to form a silica-based film on the surface of the base material. The firing temperature is 300-1100°C, preferably 400-800°C.

At temperatures below 300°C, organic groups such as methyl and groups remain, and 11
Temperatures of 00° C. or higher are not preferable because agglomeration of the base material occurs.

Firing time is 2 to 24 hours. The firing atmosphere is in the air.
It may be in a vacuum, in a nitrogen stream, in an ammonia stream, or in a hydrogen stream. When fired in a stream of air, the base material becomes titanium dioxide. Low-order titanium oxide is generated when not in an air stream, and titanium nitride or silicon nitride may be partially formed in an ammonia stream, but in either case, the fired product cannot be used as an optical semiconductor. Can be used.

The composition of the optical semiconductor of the present invention thus obtained can be estimated by X-ray photoelectron spectroscopy, infrared spectroscopy, X-ray diffraction, or the like.

The optical semiconductor of the present invention is white, has excellent photosterilizing action, photocatalytic action, etc., and is less likely to deteriorate over time than platinum-supported titanium dioxide.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Production example 1 (1) Titanium dioxide fine particles (0,025am) 100g
and tetrahydrotetramethylcyclotetrasiloxane 2
0 g were placed in separate small containers, and the small containers were left in a closed container at room temperature. After 96 hours, the titanium dioxide fine particles were taken out and weighed, and 107.85 g of silicone-treated titanium oxide fine particles were obtained.
When the mixture was left in a dryer for 24 hours, 104.80 g of silicone-treated titanium dioxide fine particles were obtained.

When the silicone-treated titanium dioxide fine particles were fired at 500°C for 120 minutes in the presence of air in an electric furnace, the titanium dioxide fine particles with a silica-based film were found to have a silica-based coating.
0 g was obtained.

(2) The structure of the product at each process step in Production Example 1 (1) was analyzed using an X-ray photoelectron spectrometer.

The analyzer is ESCA-5 manufactured by ULVAC-PHI.
300, and 15KV dual anode M as the X-ray source.
g300W, a hemispherical electrostatic analyzer (SCA) as an energy analyzer, and a PSD (position sensitive detector) as a detector. The binding energy was determined by correcting the value of CtS as a standard.
Measurements were performed in the range of 0 to 1000 eV.

The results of X-ray photoelectron spectroscopy are shown in FIG. In FIG. 1, (a) shows the measurement results for titanium dioxide. Ti Auger (T iA), T izs orbit and Ti2
．． A bond energy indicating an orbital, a zero Auger (OA), and a bond energy indicating a zero orbit were observed, indicating that an oxide of titanium, that is, titanium oxide, is present on the surface.

FIG. 1(b) shows the measurement results for silicone-treated titanium dioxide before firing, and FIG. 1(C) shows the measurement results for the product fired at 500°C. In any case, Si□ orbital and 5iZF orbital were observed in addition to the bond energy due to Ti and O, and Si compound.

It shows that it exists on the surface. In (b) and (c), the 5izp orbital both showed 102.3 eV, and no difference was observed.

When the composition ratio of (b) and (c) was determined from the photoelectron spectrum, (b) had T i =14.58, 0 =5
2.54, C=24.09 S i =8.08
．． (c) is Ti=14.78, O=57.4
9, C=20.67, S i=7.06, and it was found that C decreased and 0 increased by firing. This is the 5iC of silicone in (b)
This seems to indicate that the Hz group was changed into a 5i-0 bond by firing.

(3) The products of each process step in Production Example 1 (1) were examined using an infrared spectrophotometer.

The infrared spectrophotometer is FTS-1 manufactured by Disilab.
5G was used. The measurement was carried out under the following conditions by uniformly mixing 100 mg of the sample and -900 mg of KBrFA powder, filling it in a diffuse reflection spectrum measurement cell.

Resolution: 1 cm-' Number of integrations = 100 Figure 2 shows the infrared absorption spectrum. (a) shows the spectrum of titanium dioxide, and (b) shows the spectrum of silicone-coated titanium dioxide before firing. In (b), (
Absorption caused by 5iCH3 at 1270 cm-' and absorption caused by 5i-H% at 2170 cm-', which are not seen in a), are observed. From this, it can be seen that the fired curved fine particles of (b) are reliably coated with silicone having 5iCH:+ and 5i-H.

On the other hand, in (c) showing the spectrum of the calcined product, both the absorptions due to 3iCHt and 5i-H disappear, and absorption at 3700 to 3800 cm-' appears instead. This absorption is believed to be due to 5i-OH.

Therefore, from the photoelectron svector results in (2) above, it is known that Si is definitely present on the surface of the fired product, so SiO□, an inorganic St compound, is present on the surface of the fired product. It is estimated that this is generated.

(4) The fine particles at each step of the process in Production Example 1 (1) were examined by XvA diffraction.

For X-ray diffraction, JRX-12V-A manufactured by JEOL Ltd. was used, and the target was Cu (KCl ray) at 40 KV and 100 mA.
I went there. A monochromator was used as a filter, and an SC was used as a detector. FIG. 3 shows the results of X-ray diffraction of the fired product. This result shows that the main component of the fired product of Example 1 (1) is titanium dioxide, and the anatase type is more abundant than the rutile type. This X-ray diffraction pattern is the same for the untreated titanium dioxide and the silicone-coated titanium dioxide before firing, indicating that the original anatase-niltile ratio does not change after firing at 500°C. Further, since the silica-based compound produced by the calcination was not observed by X-ray diffraction, it can be seen that the amount was very small.

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

Bactericidal activity test example (a) Photophyte bacterium activity against Escherichia coli Escherichia coli (Escherichia coli ATCC8) precultured in broth medium (all 7) for 24 hours
739) in 0.1M phosphate buffer (pH 7),
3.5. A cell suspension of X 10' cells/ml was prepared. On the other hand, titanium dioxide fine particles (0,025 μm) or the above Production Example 1 were placed in a 100 m Erlenmeyer flask.
50 mg of the photosemiconductor particles of the present invention prepared in (1) were added, and 30 ml of the above cell suspension was added. These Erlenmeyer flasks were irradiated with light using a halogen lamp (approximately 10,000 lux) while being shaken gently, and the number of viable bacteria was measured after 180 minutes by the colony method. These experiments were conducted at room temperature. The results are shown in Table 1 below.

Table 1: Production Example 1 (1) Even when the baked product was added and no light was irradiated, the number of viable bacteria after 180 minutes hardly changed. On the other hand, when titanium dioxide fine particles were added and irradiated with light, the number of viable bacteria clearly decreased, and when the baked product of Production Example 1 (1) was added and irradiated with light, the number of viable bacteria decreased. It can be seen that it has further decreased significantly. From this, it is clear that the optical semiconductor according to the present invention exhibits effective bactericidal activity when irradiated with light.

(b) Photosterilizing activity against P. acnes P. acnes (Erium acnes A) pre-cultured on CAM agar medium (pH 7.3) for 48 hours
TCC11827) in M/15 phosphate buffer (pH 7,
2), 8.3 x 105 cells/mA!
A cell suspension was prepared. On the other hand, in a 100 mA Erlenmeyer flask, 10 m of titanium oxide fine particles (0,025 μm) or the photosemiconductor particles of the present invention prepared in Production Example 1 (1) were placed.
g, and 30 ml of the above cell suspension was added thereto. These Erlenmeyer flasks were irradiated with light using a fluorescent light (approximately 6,000 lux) while being shaken gently, and after 30 minutes, 6
The number of viable bacteria was measured after 0 minutes and after 90 minutes using the colony method. These experiments were conducted at 37°C. The results are shown in Table 2 below.

Margin 2 below: Effect of acne (unit: cells/mJ) As is clear from Table 2, results similar to those for Escherichia coli were obtained in the case of P. acnes. However, the difference with titanium dioxide is larger than in the case of E. coli, indicating that the photosterilization effect is stronger than that of untreated titanium dioxide.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. An optical semiconductor comprising a silica-based film supported on the surface of a titanium oxide base material. 2. The optical semiconductor according to claim 1, wherein the titanium oxide base material is fine particles with a particle size of 0.008 to 10 μm. 3. The light guide according to claim 1, wherein the titanium oxide base material is composed of lower titanium oxide, anatase, rutile, brookite, or a mixture thereof. 4. The optical semiconductor according to claim 1, wherein the silica-based film is a silicon-titanium composite oxide. 5. The optical semiconductor according to claim 1, wherein the silica-based film contains silicon carbide. 6. A method for producing an optical semiconductor, which comprises coating the surface of a titanium oxide base material with a silicon compound and then firing it to form a silica-based film on the surface of the base material. 7. As silicon compounds, there are formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ (A) (wherein R is a monovalent organic group, a is 1 or 2, and b is 0, 1 or 2 However, the sum of a and b shall not exceed 3. Method. 8. As silicon compounds, there are formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ (B) or formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ (C) (In each of the above formulas, R_1 to R_8 may be the same or different. may be a hydrogen atom, an alkyl group, or an aryl group, and k and n are each positive integers, provided that the following values are satisfied: 3≦k≦100 and 1≦n≦100) 7. A method according to claim 6, which uses a compound comprising: 9. The method according to claim 6, wherein the firing temperature is 300°C to 1100°C.