JPH1171138A - Formation of photocatalyst thin film, mold for forming photocatalyst thin film and photocatalytic thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming photocatalyst thin film, capable of controlling the surface shape of thin film and size of a photocatalyst exposed and fixed. SOLUTION: This method for forming photocatalyst thin film comprises applying fine particles having 1 nm to 500 μm particle diameter to die material surface to form fine particle layer, applying photocatalyst particles and/or a photocatalyst precursor onto space of the fine particle layer and fine particles, as necessary, converting the photocatalyst precursor to photocatalyst particles, arranging a substrate onto the surface to which the photocatalyst particles and/or photocatalyst precursor is applied, releasing the die material from the fine particle layer, dissolving a part of mold release surface of fine particle layer and exposing the photocatalyst which exists in space of the fine particle layer to the outside air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel method for forming a photocatalytic thin film and a mold for forming a photocatalytic thin film.

[0002]

2. Description of the Related Art Semiconductor photocatalysts such as titanium oxide generate conduction electrons and holes when irradiated with light due to their semiconducting properties and exhibit a redox function. Water splitting, water purification,
Antimicrobial, deodorant, antifouling by organic matter decomposition, NOx and SO
It is proposed to be applicable to decomposition and removal of harmful substances such as x and carbon dioxide, synthesis of organic substances such as phenol and methane, and metal plating. The most typical use of the photocatalyst is to immobilize a thin film on the surface of an article or member. As this method, a spray coat method, a spin coat method, a dip coat method, a mold transfer method (Japanese Patent Laid-Open No.
157743) has been proposed.

[0003]

However, although there are proposals for a method for sufficiently exhibiting the oxidation-reduction function in the conventional proposals, the oxidation-reduction reaction is stopped halfway, or only a specific oxidation-reduction reaction is selectively performed. There is no proposal for controlling the reaction such as causing the oxidation-reduction reaction to proceed to a higher degree than ever before. As one method of such reaction control, a method of controlling the surface microstructure can be considered. However, in the conventional thin film forming method, the possibility of forming a photocatalytic thin film having a texture as a thin film such as abrasion resistance and corrosion resistance is considered. Almost no mention is made of the above-mentioned surface microstructure control.

[0004]

Therefore, in the present invention, as one proposal of a method for controlling a surface microstructure, a particle size of 1 nm to 1 μm is proposed.
forming fine particle layers by applying fine particles of m to the surface of the mold material; applying photocatalyst particles and / or a photocatalyst precursor to the gaps between the fine particle layers and on the fine particles; Converting into photocatalyst particles, arranging a substrate on the surface to which the photocatalyst particles and / or photocatalyst precursor is applied, releasing the mold from the fine particle layer, and releasing the fine particle layer Removing a part of the surface to expose the photocatalyst present in the gap between the fine particle layers to the outside air, and a fine particle layer having a particle diameter of 1 nm to 500 μm on the surface of the mold material. And the photocatalyst particles and / or
Alternatively, there is provided a mold for forming a photocatalyst thin film, wherein a photocatalyst precursor is present, and a photocatalyst particle and / or a photocatalyst precursor-containing layer is formed on the fine particle layer. By forming a photocatalytic thin film by the above method,
The surface of the photocatalytic thin film is a thin film with a structure in which the photocatalyst is fixed between the fine particles. At the same time, the size and distribution of the particle gaps of the fine particles to which the photocatalyst is fixed are controlled by selecting the fine particle diameter of the starting material It is possible to do. The particle size of the fine particles is 1 nm to 500 μm, preferably 1 nm.
By setting the particle size to 400 nm, a particle gap (concave portion) of fine particles having substantially the same size as the fine particle diameter is generated, and the photocatalyst is fixed there. That is, a thin film is formed on the substrate surface, and the thin film has a photocatalyst and a particle size of 1 nm to 500 nm.
μm (1 nm to 400 nm in a preferred embodiment) and a fine particle gap of 1 nm to 500 μm (1 nm to 400 nm in a preferred embodiment) having a concave surface, and a photocatalyst is fixed to the concave surface. Is formed. Then, since such a minute concave curved surface has a large free energy, it can be expected that various substances are easily concentrated in order to minimize the free energy, thereby acting as a unique chemical reaction field. .

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Fine particles having a particle size of 1 nm to 500 μm are not particularly limited in material, but may be silica, alumina, zirconia, titania, ceria, tin oxide, calcia, magnesia, chromia, ferrite, zinc oxide, etc. Inorganic oxide particles, polystyrene, acrylate, fluoropolymer, silicone and other polymers, micelles and reverse micelles with lipids and surfactants, natural compounds such as metals and pollen, phosphates and silicates Etc. are available.
In particular, silica or polymer latex which can be easily monodispersed in a solvent in a coating solution can be suitably used. The shape is not particularly limited, but is spherical, plate-like, needle-like, angular, star-like,
An amorphous type or the like can be used. In particular, a spherical shape is preferable because it is easily monodispersed and a uniform concave portion is easily formed at the time of forming a coating film.

[0006] The material of the mold is not particularly limited either.
Ceramics such as zirconia, mullite, and silicon carbide, glass, metals, plastics, electrode materials, magnetic materials, and water absorbing materials can be used.

[0007] The method of applying the fine particles to the surface of the molding material includes spray coating, spin coating, flow coating, dip coating, roll coating, gravure coating, brush coating, sponge coating, and the like. General coating methods can be used. The mold material may be oxidized by a method such as atmospheric oxidation or anodic oxidation to form oxide fine particles on the surface. Fine particles may be applied by electrolytic reaction or electrophoresis by immersing the electrode material in a coating solution using a mold material. When the fine particles are a magnetic material such as ferrite, the fine particles may be applied by magnetic force using a magnetic material as a mold material. Further, fine particles may be applied by a slip casting method using a water-absorbing material such as gypsum as a molding material.

As the photocatalyst, anatase type titanium oxide, rutile type titanium oxide, zinc oxide, strontium titanate, tin oxide, tungsten trioxide, bismuth trioxide, ferric oxide, zirconia and the like can be used.

To fix the photocatalyst in the gaps between the fine particle layers and on the fine particles, photocatalyst particles and / or a photocatalyst precursor are applied.

To apply the photocatalyst particles, it is preferable to use a sol in which the photocatalyst particles are dispersed. That is, the sol in which the photocatalyst particles are dispersed is spray-coated, spin-coated, flow-coated, dip-coated,
It is applied by a general coating method such as roll coating, gravure coating, brush coating, and sponge coating.
When the photocatalyst is zinc oxide, it can be applied at the same time as generating the photocatalyst particles by the anodic oxidation method.

As the photocatalyst precursor, for example, when the photocatalyst is crystalline titanium oxide, organic titanium such as amorphous titanium oxide, titanium chelate, alkyl titanate, titanium acetate and titanium acetylacetonate; Inorganic titanium such as titanium chloride and titanium sulfate can be used. When a photocatalyst precursor is applied, the same method as that of the above-described sol can be used. When the photocatalyst precursor is amorphous titanium oxide, titanium oxide, titanium metal, etc.
Get, electron beam evaporation, sputtering, PV
It can also be applied by D, CVD, ion beam evaporation or the like.

The step of converting the photocatalyst precursor into photocatalyst particles is, for example, a step of finally converting the photocatalyst precursor into crystalline titanium oxide when the photocatalyst is crystalline titanium oxide. When the photocatalyst precursor is amorphous titanium oxide,
This is a step of crystallizing the amorphous titanium oxide into an anatase type titanium oxide or a rutile type titanium oxide by a method such as heating. The photocatalyst precursor is titanium chelate or alkyl titanate.
In the case of organic titanium such as titanium, titanium acetate and titanium acetylacetonate, and inorganic titanium such as titanium tetrachloride and titanium sulfate, amorphous titanium oxide is generated by hydrolysis, polycondensation, etc., and then heated. The amorphous titanium oxide is crystallized into an anatase type titanium oxide or a rutile type titanium oxide by the method described above.

Although the substrate to which the present invention can be applied is not particularly limited, glass, ceramic, plastic, wood, metal, a composite thereof, a laminate thereof, a coating thereof, and the like can be used. By applying to the above substrate, various functions as a photocatalyst, that is, water decomposition, antimicrobial, deodorization,
Antifouling by decomposition of organic substances, decomposition and removal of harmful substances such as NOx, SOx and carbon dioxide, water purification, surface hydrophilicity, maintenance of antifogging, improvement of water washability, self-cleaning by rainfall, organic substances such as phenol and methane Functions such as synthesis and metal plating can be exhibited.

In order to easily release the mold material from the fine particle layer, a mold release agent may be applied to the surface of the mold material. As the release agent, a silicone-based release agent is preferable from the viewpoint of light corrosion resistance.

The steps of removing a part of the release surface of the fine particle layer include chemically removing a part of the release surface of the fine particle layer and physically removing a part of the release surface of the fine particle layer. Both steps. As a step of chemically removing a part of the release surface of the fine particle layer, methods such as dissolution, vaporization, and decomposition are considered. As a step of physically removing a part of the release surface of the fine particle layer, a method such as sputtering, grinding, or polishing can be considered. It is also conceivable to remove them by a mechanochemical process. Since the fine particles have a particle size of 1 nm to 1 μm,
Of these, chemical removal methods such as dissolution, vaporization, and decomposition are preferred.

The surface of the photocatalytic thin film produced in the present invention preferably has an irregularity of about 0.4 μm or less. Then, the photocatalytic thin film is less likely to cause interference color and cloudiness,
It becomes easier to ensure transparency.

Further, at least one substance selected from the group consisting of silver, copper, platinum, palladium, nickel, iron, cobalt, zinc and compounds thereof may be fixed to the photocatalytic thin film by a method such as photoreduction. Then, the redox effect of the photocatalyst can be further enhanced. Further, among the above compounds, one selected from the group consisting of silver, copper, zinc and their compounds
It is preferable to fix more than one kind of substance because it is possible to obtain antibacterial properties in a dark place to some extent.

[0018]

EXAMPLE A monodispersed silica particle (Nippon Shokubai, Seahoster, KE-P) having a particle size of 0.1 to 0.5 μm was fixed on a glass mold base to form a silica particle film. Next, 0.05M titanyl acetylacetonate (Tokyo Kasei) dispersed in ethanol was sprayed onto these silica particle membranes by spray pyrolysis to form a film having a thickness of 400 to 500.
C., and anatase-type titanium oxide is fixed on the gaps in the silica particle film and on the silica particle film, and # 1A to # 1C
A sample was obtained. Here, for the # 1A sample, the silica particle diameter fixed to the mold base is 0.5 μm, the firing temperature is 450 ° C., and the # 1B
In Example 1, the silica particle diameter fixed to the mold substrate was 0.5 μm and the firing temperature was 430 ° C., and in # 1C, the silica particle diameter fixed to the mold substrate was 0.1 μm and the firing temperature was 450 ° C. In each case, the thickness of the anatase-type titanium oxide on the silica particle film was 1-2 μm. Then # 1 on the glass substrate
After setting the sample upside down and releasing the mold base made of glass, the release surface was immersed in a 55% hydrogen fluoride solution and dried to obtain # 2A to # 2C samples. FIG. 1 shows a process chart until manufacturing of # 2A to # 2C.

FIGS. 2A to 2C show the results of observation of secondary electron images of the sample surfaces # 2A to # 2C with a scanning electron microscope (JSM-5400, JEOL). FIG. 2 (A)
~ From FIG. 2 (C), the surface of the # 2 sample is submicron
It can be seen that the surface structure of the Dar having the open pores with uniform pore diameters is maintained. Further, a comparison between FIG. 2A and FIG. 2C shows that the size of the open pores can be controlled by the silica particle diameter fixed to the mold base material. Further, FIG.
2B shows that the size of the open pores can be controlled also by the firing temperature.

Next, the surface of the # 2A sample was immersed in a 50 mM silver nitrate aqueous solution, and irradiated with ultraviolet rays having a wavelength of 365 nm for 30 minutes. The titanium oxide is dried, and then dried with a scanning electron microscope.
The secondary electron image and the reflected electron image were observed. Fig. 3 shows the results.
(A) and FIG. 3 (b). From FIG. 3A, it can be seen that even if silver is photoreduced and precipitated on the surface, the microstructure of the thin film surface does not change. Further, it can be seen from FIG. 3 (b) that the silver (white portion) deposited by photoreduction on the surface is mainly deposited on the open pores on the surface. This indicates that the photocatalytic titanium oxide is present particularly in the fine open pores on the surface. In addition, it is presumed that it functions as a chemical reaction field for the main photoreduction reaction.

The thin film having titanium oxide in the fine open pores obtained by the above method has various functions as a photocatalyst, namely, water decomposition, antimicrobial, deodorization, antifouling by decomposition of organic substances, NOx and Functions such as decomposition and removal of harmful substances such as SOx and carbon dioxide, water purification, surface hydrophilicity, maintenance of anti-fog, improvement of water washability, self-cleaning by rainfall, synthesis of organic substances such as phenol and methane, metal plating, etc. It is thought that it can be used as a molecular-selective material and an energy-converting material in addition to being able to exert its effects.

[0022]

According to the present invention, since the particle gap of the fine particles having substantially the same size as the particle diameter is generated, the size of the particle gap can be controlled. Then, the size of the photocatalyst that is exposed and fixed in the concave portion between the particles can also be controlled. Further, since the gap is a curved surface with a minute concave portion and a large free energy, various substances are easily concentrated in order to minimize the free energy, so that the gap acts as a unique chemical reaction field. Can be expected.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for forming a photocatalytic thin film according to an embodiment of the present invention.

FIG. 2 is a diagram showing the results of surface observation of a photocatalytic thin film formed based on the method of the example of the present invention. (A) Silica particles fixed to a mold substrate having a diameter of 0.5 μm and a sintering temperature of 450 ° C. (B) A product prepared under the conditions that the silica particle diameter fixed to the mold substrate is 0.5 μm and the firing temperature is 430 ° C. (C) A silica particle fixed to the mold substrate having a diameter of 0.1 μm and a firing temperature of 450 ° C.

FIG. 3 is a view showing the results of surface observation of a product obtained by photoreducing and depositing silver on a photocatalytic thin film formed based on the method of the example of the present invention. (A) Secondary electron image. (B) Backscattered electron image.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 35/02 B01J 35/02 J C03C 17/27 C03C 17/27

Claims (9)

[Claims] 1. A step of applying fine particles having a particle size of 1 nm to 500 μm to the surface of a mold material to form a fine particle layer, and applying photocatalyst particles and / or a photocatalyst precursor to the gaps between the fine particle layers and the fine particles. Converting the photocatalyst precursor into photocatalyst particles if necessary;
Or a step of disposing a substrate on the surface to which the photocatalyst precursor is applied, and a step of releasing the mold from the fine particle layer,
Removing a part of the release surface of the fine particle layer to expose the photocatalyst existing in the gap between the fine particle layers to the outside air. 2. The method according to claim 1, wherein the fine particles have a particle size of 1 nm to 400 nm. 3. A fine particle layer having a particle size of 1 nm to 500 μm is formed on the surface of a mold, and photocatalyst particles and / or a photocatalyst precursor are present in gaps between the fine particle layers. A photocatalyst thin film forming die, wherein a layer containing particles and / or a photocatalyst precursor is formed. 4. The mold for forming a photocatalytic thin film according to claim 3, wherein the fine particles have a particle size of 1 nm to 400 nm. 5. A photocatalytic thin film formed by the method according to claim 1. 6. A thin film is formed on a surface of a substrate, said thin film comprising a photocatalyst and fine particles having a particle diameter of 1 nm to 500 μm, and having a concave fine particle gap of 1 nm to 500 μm. A photocatalyst thin film, wherein a photocatalyst is fixed on the thin film. 7. A thin film is formed on the surface of a substrate, said thin film comprising a photocatalyst and fine particles having a particle size of 1 nm to 400 nm, and having a concave fine particle gap of 1 nm to 400 nm. A photocatalyst thin film, wherein a photocatalyst is fixed on the thin film. 8. The photocatalytic thin film, wherein at least one substance selected from the group consisting of silver, copper, platinum, palladium, nickel, iron, cobalt, zinc and a compound thereof is fixed by photoreduction. The photocatalytic thin film according to claim 5. 9. The photocatalyst thin film according to claim 5, wherein the photocatalyst is titanium oxide.