Photocatalytic material having high orientation titanium oxide crystal-oriented film

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a photocatalytic material having a crystal alignment film made of titanium dioxide on the surface of various base materials such as metal, glass, ceramics, ceramics and plastics. The photocatalytic material having the titanium dioxide crystal alignment film of the present invention has excellent properties such as antibacterial action, antifouling action, and superhydrophilic action, and has excellent properties such as cooking utensils, tableware, kitchen utensils such as refrigerators, medical utensils, and toilets. It is widely used for toilet materials, air conditioner filters, electronic parts, building materials, road-related materials, etc.

【0002】

[Problems to be solved by conventional techniques and inventions]

It has been conventionally known that a titanium dioxide thin film has various functions by a photocatalytic reaction, and a titanium dioxide thin film is formed on the surface of various base materials such as a metal material, a semiconductor element, and a plastic material to form an antireflection material, a sensor material, and the like. It is also known to be used as an insulating material or the like. Further, as a method for forming a titanium dioxide thin film on the surface of these base materials, a coating method, a dipping method, a sputtering method, a thermal CVD method in which a metal vapor heated and evaporated in an oxygen gas atmosphere is introduced and reacted, and the like are used. Are known.

【0003】

Among these conventional titanium dioxide thin film forming methods, the titanium dioxide crystal alignment film cannot be obtained by the coating method or the dipping method, and it is difficult to control the crystal structure of the obtained thin film by the sputtering method. Further, in the conventional thermal CVD method, in order to form a crystalline titanium dioxide thin film on the surface of the base material, the base material is usually heated to a high temperature of about 500 to 800 ° C, and the thin film formation is sealed. It had to be done under reduced pressure in the plating chamber. With this conventional thermal CVD method, the deposition rate of the titanium dioxide thin film is extremely slow, it is difficult to control the crystal structure of the obtained thin film, and it is not possible to obtain a crystal alignment film oriented in a specific direction. ..

【0004】

The present inventors have a titanium dioxide crystal alignment film on the surface of the base material obtained by spraying the previously vaporized titanium alkoxide together with an inert gas as a carrier onto the surface of the base material heated under atmospheric pressure. We have found that the material exhibits excellent photocatalytic properties and proposed it as Japanese Patent Application Laid-Open No. 10-152396. As a result of further studying the photocatalytic properties of the titanium dioxide crystal alignment film, the present inventors have found that a material having a titanium dioxide crystal alignment film oriented in a specific direction on the surface of the substrate has another titanium dioxide crystal alignment film. The present invention has been completed by finding that it exhibits remarkably excellent photocatalytic properties as compared with materials. That is, an object of the present invention is to provide a photocatalytic material having remarkably excellent photocatalytic properties such as antibacterial action, antifouling action, and superhydrophilic action.

【0005】

[Means for solving problems]

The photocatalytic material having the highly oriented titanium dioxide crystal alignment film of the present invention has the following constitution. 1. A photocatalytic material having a titanium dioxide crystal alignment film oriented in the (112) direction perpendicular to the crystal surface on the surface of the substrate. 2. The photocatalytic material according to 1, wherein the thickness of the crystal alignment film is 0.1 μm or more. 3. The photocatalytic material according to 1 or 2, wherein the crystal grain size of the crystals forming the crystal alignment film is 0.01 to 10 μm, and the particle size distribution is substantially an average value of ± 100%. 4. The photocatalytic material according to any one of 1 to 3, wherein the crystal alignment film has a network structure. 5. The photocatalytic material according to any one of 1 to 4, wherein the base material is a metal. 6. The photocatalytic material according to any one of 1 to 4, wherein the base material is glass, ceramics, ceramics, or plastic. 7. The photocatalytic material according to any one of 1 to 6, wherein the base material is a material having a single crystal alignment film. An electronic component composed of the photocatalytic material described in 8.7.

【0006】

In the present invention, the titanium dioxide crystal alignment film means an alignment film made of a single crystal of titanium dioxide and an alignment film made of polycrystals. Here, the single crystal alignment film is not limited to a film in which the entire alignment film is composed of a single crystal, as is usually used in the field of materials science, and the alignment films have the same crystal orientation in the three-dimensional direction. It also includes those composed of a large number of crystals. The material having the titanium dioxide crystal alignment film oriented in a specific direction of the present invention is prepared by using vaporized titanium alkoxide (raw material complex) on the surface of a base material heated under atmospheric pressure together with an inert gas as a carrier. It can be manufactured by spraying.

【0007】

BEST MODE FOR CARRYING OUT THE INVENTION

The base material used for the material having the titanium dioxide crystal alignment film of the present invention is not particularly limited, and any material that can withstand heating during spraying of titanium dioxide can be used, but usually metal, glass, or the like. Use ceramics, ceramics, plastics, etc. Suitable materials include, for example, metals such as stainless steel and iron, Si single crystals, sintered bodies of silicon nitride and silicon carbide, strontium titanate, and oxide single crystals such as magnesium oxide and sapphire. When a base material having a single crystal alignment film such as Si single crystal, strontium titanate single crystal, or oxide single crystal such as magnesium oxide or sapphire is used as the base material, the superconducting characteristics are improved and laser oscillation is performed. It has favorable properties as an electronic component material such as sapphire. Commercially available products can be used as the base material having these single crystal alignment films.

【0008】

As a raw material for forming a titanium dioxide crystal alignment film, the general formula Ti (OR) is used.₄Titanium alkoxide represented by is used. (In the formula, R represents an alkyl group having 2 to 10 carbon atoms.) Among these titanium alkoxides, Ti (OC)₂H₅)₄(Hereafter, abbreviated as "TTE"), Ti (OiC₃H₇)₄(Hereafter, abbreviated as "TTIP"), Ti (OnC₄H₉)₄(Hereinafter, abbreviated as "TTNB") is preferable, and among them, TTIP is a particularly preferable raw material because the deposition rate of titanium dioxide is high and the crystal structure of the obtained alignment film can be easily controlled.

【0009】

In the present invention, the raw material complex is vaporized by a vaporizer and sprayed together with an inert gas as a carrier onto the surface of a base material heated under atmospheric pressure to form a crystal alignment film of titanium dioxide on the surface of the base material. The inert gas used as a carrier is not particularly limited, and any of commonly used inert gases such as nitrogen, helium, and argon can be used, but nitrogen gas is preferably used from the viewpoint of economic efficiency and the like. Of these, it is particularly preferable to use nitrogen gas from which water has been removed through liquid nitrogen. The vaporization temperature of the raw material complex is adjusted according to the type of raw material, but in the case of TTE, TTIP, and TTNB, for example, it is preferably 70 to 150 ° C.

【0010】

When spraying the raw material complex carried by the inert gas carrier onto the surface of the base material heated under atmospheric pressure, the base material 20 is placed on the heating table 11 in the heating furnace 10 as shown in FIG. Place it and spray it onto the substrate from the slit-shaped nozzle 9. Further, when the base material is placed on a carrier such as a roller, a belt, or a chain and moved in the heating furnace, the raw material complex is sprayed on the surface of the base material moving from the slit type nozzle. A crystal alignment film of titanium dioxide can be continuously formed on the surface of a long base material such as a rod shape, a rod shape, a pipe shape, or a base material preformed into various shapes such as a dish and a tray. It will be possible. The raw material complex ejected from the nozzle together with the inert carrier gas into the air is hydrolyzed by water in the air to form a titanium dioxide crystal alignment film on the surface of the heated substrate.

【0011】

The photocatalytic material having a titanium dioxide crystal alignment film oriented in the (112) direction perpendicular to the crystal surface on the surface of the base material of the present invention is the type and temperature of the base material, the type and vaporization temperature of the raw material, and the carrier gas. By adjusting the flow rate and the like, it is possible to have a desired film thickness, crystal particle size and particle size distribution. It has been found that the photocatalytic material of the present invention is remarkably superior in the following photocatalytic action as compared with those having a titanium dioxide crystal alignment film oriented in other directions.

【0012】

(1) It has a remarkable antibacterial action (bactericidal action and sterilization action), and can decompose the products of dead bacteria and bacteria such as toxins, so it prevents stains and exerts a long-lasting antibacterial action. To do. (2) Prevents the adhesion of dirt, decomposes the attached dirt, and easily removes it by natural rain or washing with water to maintain the gloss of the surface. (3) Decomposes substances that cause odors and has deodorizing and deodorizing effects. (4) Irradiation with ultraviolet rays reduces the contact angle with water and approaches 0 degrees, so that it does not repel water. Therefore, water droplets are not formed on the surface and a uniform water film is formed, which can prevent fogging. (5) Decompose nitrogen oxides (NOx) and sulfur oxides (S0x) in the air to purify the air. (6) Purify water by decomposing pollutants in water such as organic halogen compounds and oils. Therefore, the material having the titanium dioxide crystal alignment film oriented in a specific direction on the surface makes the best use of the above characteristics, such as medical utensils, tableware, cooking utensils, refrigerators, refrigerated vehicles, washrooms and kitchen utensils, interior materials, and exteriors. It can be widely used as a material for various building materials, road-related materials, air conditioner filters, electronic parts, etc.

【0013】

According to the present invention, the film thickness of the crystal alignment film formed on the surface of the substrate can be desired, but by setting the film thickness to 0.1 μm or more, the substrate has various antibacterial properties and the like. Since the above characteristics can be imparted, it is usually 0.1 to 10 μm, preferably 0.2 to 2.0 μm. Further, when the particle size of the crystals forming the alignment film is set to the same level as the wavelengths of visible light and ultraviolet rays, those having particularly excellent photocatalytic properties such as antibacterial properties can be obtained, and in particular, crystals having a uniform particle size distribution. The effect is remarkable when it is used as an alignment film. Therefore, it is preferable to use a crystal alignment film having a crystal particle size of 0.1 to 10 μm and a particle size distribution of substantially an average value of ± 100%, and a crystal alignment film having an average value of ± 50%. Is particularly preferred. The particle size distribution of the crystal in the present invention is calculated as follows according to a conventional method in the field of materials science. That is, as shown in FIG. 2, in a histogram drawn with the particle size (maximum diameter) of each crystal constituting the alignment film on the horizontal axis and the number of crystals on the vertical axis, the maximum value Y on the vertical axis.₁The average value of the crystal grain size and the grain size distribution are calculated for 50% or more of the crystals (shaded area in Fig. 2). Further, as another preferable material, a material in which the crystal alignment film of titanium dioxide has a network structure can be mentioned. As these materials, if necessary, those which have been subjected to an annealing treatment in an oxygen atmosphere after forming a crystal alignment film of titanium dioxide on the surface of the base material can be used. In the present invention, the crystal alignment film having a network structure means a state in which needle-shaped crystals are crossed or a state in which needle-shaped crystals are arranged in a honeycomb shape. Then, annealing treatment in an oxygen atmosphere means heating a crystal alignment film made of titanium dioxide under atmospheric pressure in an oxygen stream using an electric furnace at an arbitrary temperature of 300 ° C to 600 ° C for several hours. Means.

【0014】

[Example]

Next, the present invention will be described with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. FIG. 1 is a schematic view showing an atmospheric pressure open type thermal CVD apparatus used in the following examples. In FIG. 1, reference numeral 1 is a nitrogen gas supply source such as a cylinder, reference numeral 2 is a flow meter, reference numeral 3 is a trap containing liquid nitrogen, and reference numerals 4, 5 and 6 are valves provided in a pipe. Reference numeral 7 is a vaporizer of titanium alkoxide 8 as a raw material, reference numeral 9 is a slit type nozzle having a slit having a predetermined width at the bottom, reference numeral 10 is a heating furnace (electric furnace), and reference numeral 11 is a substrate 20. Represents a heating table. The nitrogen gas supplied from the nitrogen gas supply source 1 is sent to the trap 3 containing liquid nitrogen through the flow meter 2, and after removing the water, is sent to the valves 4 and 6. The nitrogen gas that has passed through the valve 4 is released as bubbles into the liquid titanium alkoxide 8 in the vaporizer 7 to help vaporize the titanium alkoxide. The mixed gas of vaporized titanium alkoxide and nitrogen gas is mixed with the nitrogen gas sent from the valve 6 via the valve 5, sent to the slit type nozzle 9, and heated on the heating table 11 in the heating furnace 10. The surface of the base material 20 is sprayed to form a titanium dioxide crystal alignment film.

【0015】

(Example 1) TTIP was used as a raw material complex, and TTIP was vaporized at a vaporizer temperature of 120 ° C. and a nitrogen gas flow rate of 1.5 l / min. As a base material, a quartz glass base material having a thickness of 0.5 mm and a thickness of 20 mm × 20 mm was placed at a position of 20 mm under a blowout slit in a heating furnace heated to 350 ° C, and vaporized TTIP was sprayed. TTIP reacts with water in the atmosphere to form titanium dioxide, which is deposited on a quartz glass substrate, and the priority orientation is (112) in the direction perpendicular to the crystal surface. Anatase-type titanium dioxide crystal with a film thickness of 1 μm. An alignment film was formed. The grain size of the crystals of this alignment film was 0.05 to 0.25 μm, and the grain size distribution was 0.15 ± 0.10 μm. The result of X-ray diffraction of this alignment film is shown in Fig. 3, and the SEM photograph of the surface is shown in Fig. 4.

【0016】

(Comparative Example 1) Anatase-type titanium dioxide crystal alignment film was formed on a quartz glass substrate in the same manner as in Example 1 except that the vaporizer temperature was 100 ° C and the heating furnace temperature was 400 ° C. The preferential orientation direction of this crystal alignment film was (110) in the direction perpendicular to the crystal surface.

【0017】

(Comparative Example 2) Anatase-type titanium dioxide crystal alignment film was formed on a quartz glass substrate in the same manner as in Example 1 except that the vaporizer temperature was 130 ° C and the heating furnace temperature was 400 ° C. The preferential orientation direction of this crystal alignment film was the (001) direction perpendicular to the crystal surface.

【0018】

(Comparative Example 3) Anatase-type titanium dioxide crystal alignment film was formed on a quartz glass substrate in the same manner as in Example 1 except that the vaporizer temperature was 60 ° C and the heating furnace temperature was 500 ° C. The preferential orientation direction of this crystal alignment film was (100) in the direction perpendicular to the crystal surface.

【0019】

(Methylene blue reduction test) To prepare 10 mm × 10 mm test pieces from the photocatalytic material obtained in each of the above examples and forming a titanium dioxide crystal alignment film on the surface of the substrate, and measure the photocatalytic activity as follows. The reduction test of methylene blue was carried out. It is generally understood that the faster the reduction rate of methylene blue, the greater the photocatalytic activity. A methylene blue aqueous solution having a concentration of 1 mmol / l was dropped into a Pyrex glass cell having an internal dimension of 10 mm in length, 10 mm in width, and 1 mm in depth, and each test piece was sealed. A spacer with a diameter of 8 mm and a thickness of 25 μm is placed on each test piece, and the amount of methylene blue solution present on each test piece is 1.25 mm.³And said. This cell was irradiated with an ultraviolet fluorescent lamp having a center wavelength of 352 nm from a distance of 30 mm. UV intensity on the test piece is 1 mW / cm²Met. Table 1 shows the results of calculating the relative absorbance of each test piece by measuring the absorbance of methylene blue at a wavelength of 580 nm after unirradiated and 5 minutes irradiation with a color difference meter and setting the relative absorbance when methylene blue is completely reduced to 0. It was. For comparison, the relative absorbance of the quartz glass substrate itself on which the titanium dioxide crystal alignment film was not formed was calculated and shown in Table 1.

【0020】

[table 1]

<img file="JP2001219072A_D0001.tif" />【0021】

(Antibacterial test) From the photocatalytic material obtained in each of the above examples, in which a titanium dioxide crystal alignment film was formed on the surface of the base material, 20 mm × 20 mm test pieces were prepared, and the antibacterial test was performed as follows. It was. Preliminarily enriched and measured liquid-cultured general bacteria (Bacillus subtilis), 10⁵Apply to each of the above test pieces to order, and irradiate this with black light at a distance of 30 mm for 3 hours. UV intensity on the test piece is 1 mW / cm²Met. Then, 9 ml of physiological saline was added, mixed well, and cultured and measured at 35 ° C for 48 hours in a quantitative standard agar medium according to a conventional method (hygiene test method: 1980 edition edited by the Pharmaceutical Society of Japan). For comparison, the stainless steel test piece and the quartz glass substrate test piece having no titanium dioxide crystal alignment film were treated in the same manner, and the number of bacteria was measured. The results are shown in Table 2.

【0022】

[Table 2]

<img file="JP2001219072A_D0002.tif" />【0023】

(Oil decomposition test 1) From the photocatalytic materials obtained in each of the above examples, test pieces of 10 mm × 10 mm were prepared, and after fingerprinting the thumb on the surface, an ultraviolet fluorescent lamp with a center wavelength of 352 nm was used from a distance of 30 mm. Table 3 shows the results of irradiating and visually observing the disappearance of fingerprints. For comparison, Table 3 shows the results of the same treatment and observation of the stainless steel test piece and the quartz glass substrate test piece having no titanium dioxide crystal alignment film.

【0024】

[Table 3]

<img file="JP2001219072A_D0003.tif" />【0025】

(Oil decomposition test 2) After applying 0.1 mg of commercially available salad oil to each test piece similar to the above oil decomposition test 1 and irradiating with an ultraviolet fluorescent lamp for 24 hours in the same manner as in the oil decomposition test 1, Table 4 shows the results of measuring the residual amount of salad oil.

【0026】

[Table 4]

<img file="JP2001219072A_D0004.tif" />【0027】

According to the results of each of the above tests, the photocatalytic material having a titanium dioxide crystal alignment film oriented in the (112) direction perpendicular to the crystal surface on the surface of the base material of the present invention has a photocatalytic action oriented in another direction. It can be seen that it is remarkably superior to the one having a titanium dioxide crystal alignment film.

【0028】

(Example 2) A commercially available base material having a thickness of 0.5 mm and a single crystal sapphire (0001) surface of 20 mm × 20 mm was used as a base material, and the vaporizer temperature was set to 100 ° C and the heating furnace temperature was set to 450 ° C. Other than that, an anatase-type titanium dioxide crystal alignment film was formed on the substrate in the same manner as in Example 1. The preferential orientation direction of this crystal alignment film is the (112) direction perpendicular to the crystal surface, the film thickness is 1 μm, the crystal grain size is 0.1 to 0.6 μm, and the grain size distribution is 0.35 ± 0.25 μm. It was. The result of X-ray diffraction of this alignment film is shown in Fig. 5, and the SEM photograph of the surface is shown in Fig. 6. The photocatalytic material having this crystal alignment film showed excellent photocatalytic activity similar to that of Example 1.

[Simple explanation of drawings]

[Figure 1]

It is a schematic diagram which shows the atmospheric pressure open type thermal CVD apparatus used for manufacturing the photocatalyst material which has the titanium dioxide crystal alignment film of this invention.

[Figure 2]

It is a figure explaining the calculation method of the particle size distribution of a crystal.

[Fig. 3]

It is an X-ray diffraction pattern of an example of the titanium dioxide polycrystalline alignment film formed on the surface of the photocatalyst material having the titanium dioxide crystal alignment film of this invention.

[Fig. 4]

It is an SEM photograph of an example of the titanium dioxide polycrystalline alignment film formed on the surface of the photocatalyst material having the titanium dioxide crystal alignment film of this invention.

[Fig. 5]

It is an X-ray diffraction pattern of another example of the titanium dioxide polycrystalline alignment film formed on the surface of the photocatalyst material having the titanium dioxide crystal alignment film of this invention.

[Fig. 6]

It is an SEM photograph of another example of the titanium dioxide polycrystalline alignment film formed on the surface of the photocatalyst material having the titanium dioxide crystal alignment film of this invention.

[Explanation of symbols]

4, 5, 6 Valves installed in the piping of thermal CVD equipment 7 Vaporization room 8 Liquid titanium alkoxide 9 Slit type nozzle 10 heating furnace 11 Heating table 20 base material