Photocatalyst and its production

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a photocatalyst having an excellent photocatalytic function, a method for producing the same, and a photocatalytic composition used therein.

【0002】

[Conventional technology]

When a semiconductor is irradiated with light having a wavelength equal to or higher than the band gap, a redox reaction occurs. Such a semiconductor is called a photocatalytic semiconductor, or simply a photocatalyst. The photocatalyst may be used as a powder suspended in a solution, or may be supported on some substrate. From the viewpoint of photocatalytic activity, the former is generally more active due to its large surface area, but from a practical point of view, the latter has to be adopted rather than the former because of its ease of handling. In many cases, it is not obtained. In order to support the photocatalyst on the substrate, a method of sintering and supporting the photocatalyst particles at a high temperature on the substrate is adopted. In addition, a method of supporting a photocatalyst on a substrate using a certain fluorine-based polymer as a binder has also been proposed. For example, Japanese Patent Application Laid-Open No. 4-284851 describes a method of laminating and pressure-bonding a mixture of photocatalytic particles and a fluorine-based polymer, and Japanese Patent Application Laid-Open No. 4-334552 describes heat-sealing photocatalytic particles to a fluorine-based polymer. The method is described. Further, Japanese Patent Application Laid-Open No. 7-171408 describes a method of adhering photocatalytic particles on a substrate via a persistent binder composed of an inorganic system such as water glass and an organic system such as a silicon polymer, and on the substrate. A method for producing a photocatalyst body is described in which a persistent binder is provided as a first layer, and a second layer composed of a persistent binder and photocatalytic particles is provided on the first layer. Further, Japanese Patent Application Laid-Open No. 5-309267 describes a method of using a metal oxide generated from a metal oxide sol as a supporting and fixing material for a photocatalyst powder, and the metal oxide sol is a metal as used in the sol-gel method. There is a description that it can be obtained by hydrolyzing a metal-organic compound such as alkoxide, acetylacetonate, or carboxylate, or an alcohol solution of chloride such as titanium tetrachloride in the presence of an acid or alkali catalyst.

【0003】

PROBLEM TO BE SOLVED: To solve a problem

Recently, there have been attempts to decompose, purify, and sterilize harmful substances, malodorous components, oils, etc. generated in the daily living environment using photocatalysts, and the range of application of photocatalysts is rapidly expanding. Along with this, there is a demand for a method of supporting photocatalytic particles on any substrate firmly and for a long period of time without impairing the photocatalytic function. In particular, when a titanium oxide sol having an excellent photocatalytic function is used as a photocatalyst, the binder function to the substrate is weak, and therefore improvement in its adhesiveness has been particularly required. However, in the above-mentioned conventional method, the adhesive strength is not sufficient, and there are few products that can be carried for a long period of time. There was a problem of lowering. When a substrate made of an organic polymer resin is used, the photocatalytic reaction proceeds even with rutile-type titanium oxide, which is said to have a weaker photocatalytic function than the anatase-type, and the photochemistry of the organic polymer resin itself. Combined with the reaction, it deteriorates and decomposes after long-term use. Further, when an organic polymer resin is used as a substrate, it has been considered to be coated in advance with a silica sol or the like, but cracks and vacancies are generated in the process of aggregation and drying of the silica sol, and it is used as a binder. There was a performance problem.

【0004】

[Means for solving problems]

In order to solve the above problems, as a result of searching for a method of supporting photocatalytic particles on any substrate firmly and for a long period of time without impairing the photocatalytic function, an amorphous titanium peroxide sol is used as a binder. Surprisingly, we have found that the photocatalytic particles can be supported on any substrate firmly and for a long period of time without impairing the photocatalytic function, and have completed the present invention.

【0005】

That is, the present invention is a method for producing a photocatalyst in which a photocatalyst is supported and fixed on a substrate, a method for producing a photocatalyst using a photocatalyst such as titanium oxide and an amorphous titanium peroxide sol, and an amorphous type photocatalyst on the substrate. A photocatalyst body prepared by providing a first layer having no phototactile function prepared using a titanium oxide sol and providing a second layer prepared by using a photocatalyst and an amorphous titanium peroxide sol on the first layer. The present invention, the photocatalyst body produced by these methods, and the photocatalyst composition used for the production thereof.

【0006】

The amorphous titanium peroxide sol used in the present invention can be produced, for example, as follows. Titanium tetrachloride TiCl₄Ammonia water or alkali hydroxide such as sodium hydroxide is added to the aqueous titanium salt solution such as. The resulting pale bluish white, amorphous titanium hydroxide Ti (OH)₄Is orthotitanium acid H₄TiO₄Also called, when this titanium hydroxide is washed and separated and then treated with hydrogen peroxide solution, the amorphous titanium peroxide solution of the present invention can be obtained. This amorphous titanium peroxide sol has a pH of 6.0 to 7.0 and a particle size of 8 to 20 nm, and its appearance is a transparent yellow liquid, which is stable even when stored at room temperature for a long period of time. The sol concentration is usually adjusted to 1.40 to 1.60%, but the concentration can be adjusted as needed. When using at a low concentration, dilute with distilled water or the like before use.

【0007】

In addition, this amorphous titanium peroxide sol is amorphous at room temperature and has not yet crystallized into anatase-type titanium oxide, so it is possible to create a uniform and flat thin film with excellent adhesion and film formation. It can be formed, and the dry film has the property of being insoluble in water. When the amorphous titanium peroxide sol is heated at 100 ° C or higher, it becomes an anatase type titanium oxide sol, and when the amorphous titanium peroxide sol is coated on the substrate and then dried and fixed, the anatase is heated at 250 ° C or higher. It becomes a type titanium oxide.

【0008】

The photocatalyst that can be used in the present invention is Ti0.₂, ZnO, SrTiO₃, CdS, Cd0, CaP, InP, In₂O₃, CaAs, BaTiO₃, K₂NbO₃, Fe₂O₃, Ta₂O₅, WO₃, SaO₂, Bi₂O₃, NiO, Cu₂O, SiC, SiO₂, MoS₂, MoS₃, InPb, RuO₂, CeO₂Among these, titanium oxide is preferable, and titanium oxide is used in the form of particles or powder, or in the form of sol.

【0009】

The sol-like titanium oxide, that is, the titanium oxide sol, can be produced by heating the amorphous titanium peroxide sol at a temperature of 100 ° C. or higher as described above, but the properties of the titanium oxide sol are slightly different depending on the heating temperature and the heating time. The amorphous titanium oxide sol, which changes and is produced by treatment at 100 ° C. for 6 hours, has a pH of 7.5 to 9.5 and a particle size of 8 to 20 nm, and its appearance is a yellow-suspended liquid. This titanium oxide sol is stable even when stored at room temperature for a long period of time, but precipitation may occur when mixed with an acid or an aqueous metal solution, and the presence of Na ions may impair photocatalytic activity and acid resistance. is there. The sol concentration is usually adjusted to 2.70 to 2.90%, but the concentration can be adjusted and used as needed. It is desirable to use the above-mentioned titanium oxide sol as the photocatalyst, but commercially available "ST-01" (manufactured by Ishihara Sangyo Co., Ltd.) and "ST-31" (manufactured by Ishihara Sangyo Co., Ltd.) can also be used.

【0010】

In the present invention, as the substrate, an inorganic material such as ceramics or glass, an organic material such as plastic, rubber, wood or paper, or a metal material such as aluminum or steel can be used. Among these, application to organic polymer resin materials such as acrylonitrile resin, vinyl chloride resin, polycarbonate resin, methyl methacrylate resin (acrylic resin), polyester resin, and polyurethane resin is particularly effective. Further, the size and shape are not limited, and a honeycomb shape, a fiber shape, a filtration sheet shape, a bead shape, a foam shape, or a product obtained by accumulating them may be used. Further, a photocatalyst can be applied to the inner surface of a substrate that allows ultraviolet rays to pass through, and it can also be applied to painted articles.

【0011】

In the present invention, the binder that is not decomposed by a photocatalyst is, for example, an inorganic polymer such as water glass, colloidal silica, cement, a fluorine polymer, or a silicon polymer as described in JP-A-7-171408. It means a binder that is not easily decomposed by a photocatalyst composed of organic materials such as.

【0012】

Next, there are several methods for preparing the composition for producing the photocatalyst of the present invention. First, a method of using a titanium oxide powder uniformly suspended in an amorphous titanium peroxide sol can be mentioned. It is advantageous to use ultrasonic waves after mechanical agitation for uniform turbidity.

【0013】

Next, the titanium oxide sol and the amorphous titanium peroxide sol are mixed to prepare a mixed sol. The mixing ratio of the two is determined by the product site to which the photocatalyst of the present invention is applied and the usage conditions of the equipment. At that time, the adhesion and formation of the photocatalyst prepared using the mixed sol to the substrate are formed. Membrane properties, corrosion resistance, cosmetic properties, etc. are taken into consideration. Then, it can be roughly divided into the following three categories. For example, interior tiles, sanitary ware, various unit products, tableware, building interior / exterior materials, automobile interior materials, etc., which are likely to come into contact with people or require visual cosmeticity. Lighting fixtures, underpasses, roads, tunnels, civil engineering materials, electrical fixture exterior panels, etc. that are not in contact with humans but require visual cosmeticity. Normally, people do not touch or see, and utilize the organic matter decomposition function based on the photocatalytic function and the properties of the semiconductor metal itself, septic tanks, various wastewater treatment devices, water heaters, bath kettles, air conditioners, range hoods. Internal and other parts incorporated in the equipment. For the above classification, a photocatalyst formed by using a mixed sol in which titanium oxide sol is mixed at a ratio of 30% by weight or less with respect to the total amount of titanium oxide sol and amorphous titanium peroxide sol is suitable. Products using this are sufficient for sterilization, pollution prevention, and residual odor decomposition in daily life, and the film surface is hard, there is no wear or dirt due to cleaning, etc., and it is difficult for fingerprints to adhere due to contact. I understood it. Further, in septic tanks belonging to the above categories, for example, high photocatalytic activity is the most important performance required as a photocatalyst used in order to reduce the residual organic matter (BOD) value of the final wastewater treatment water. It was found that the photocatalyst formed by using a mixed sol in which the titanium oxide sol was mixed at a ratio of 70% by weight or more with respect to the total amount of the titanium oxide sol and the amorphous titanium peroxide sol was optimal. Although this photocatalyst is inferior in cosmeticity, it has been found that the problem that humans normally do not touch or see in this category and that some residue adheres can be solved by regular removal and cleaning. It was. Further, for the above classification, a photocatalyst formed by using a mixed sol obtained by mixing 20 to 80% by weight of titanium oxide sol with respect to the total amount of titanium oxide sol and amorphous titanium peroxide sol is suitable. I understood. This photocatalyst exhibits intermediate properties between the former two in terms of hardness, adhesion of miscellaneous substances, photocatalytic activity, and the like.

【0014】

For coating the substrate with a titanium oxide sol, an amorphous titanium peroxide sol, a mixed sol or the like, or by spraying, for example, known methods such as dipping, spray spraying, and coating can be used. In coating, it is often good to repeat the application multiple times.

【0015】

After coating by coating or spraying as described above, the photocatalyst of the present invention can be obtained by drying and solidifying, but the photocatalyst of the present invention is sintered and solidified at around 200 ° C to 400 ° C. You can also do it. In addition, since the photocatalytic function of titanium oxide is reduced by sodium ions, when an organic polymer resin that is easily decomposed by the photocatalyst is used as the substrate, a substance containing sodium ions such as a sodium hydroxide solution is used prior to coating. It is advantageous to allow the sodium source to exist by cleaning the resin surface with. When the amorphous titanium peroxide sol is used as the first layer, when it is heated to 250 ° C or higher, it becomes crystals of anatase-type titanium oxide and a photocatalytic function is generated. Therefore, it is dried and solidified at a lower temperature, for example, 80 ° C or lower. .. Further, in this case, sodium ions can be added to the titanium peroxide sol for the same reason as described above.

【0016】

Before molding, particles made of a material of a spontaneous ultraviolet radiation material or a phosphorescent ultraviolet radiation material or particles mixed with these radiation materials can be mixed together with a photocatalyst. Spontaneous ultraviolet radiation material (spontaneous light emitting ceramic) is a material that consumes internal energy and emits light by itself. It utilizes the radiation decay of radium and promethium, and has an ultraviolet region for light emission. At present, crushed particles obtained by re-crushing a solidified rock refined powder containing such a component are used. A phosphorescent ultraviolet radiating material (phosphorescent luminescent ceramic) is a material that emits light while taking in external energy and emitting that amount, and has an ultraviolet region for light emission. "Luminova" (trade name: Nemoto & Co., Ltd.) and "Kiplus" (trade name: Next Eye Co., Ltd.) are commercially available. These are strontium aluminate (SrAl) containing components such as high-purity alumina, strontium carbonate, europium, and dysprosium.₂O₄) Is the main component. The maximum point of the absorption spectrum is at 360 nm, and the particle size is 20 μm to 50 μm. However, the crushed state before crushing can be obtained as it is as crushed particles. If any of these commercially available products whose performance deteriorates significantly when it absorbs moisture, it can be used by encapsulating it in a transparent organic polymer resin such as glass or polycarbonate in advance. , It can be mixed in the substrate or attached to the surface of the substrate for use.

【0017】

When a photocatalyst is prepared by mixing such spontaneous light emitting ceramics, phosphorescent light emitting ceramic particles, or particles formed by mixing fine particles of these ceramics (hereinafter referred to as mixed particles) with a photocatalyst, ultraviolet rays to the photocatalyst body are obtained. Even if the irradiation of the photocatalyst is interrupted, the photocatalyst semiconductor of the photocatalyst is excited by the ultraviolet rays emitted from the spontaneously emitting ceramic particles or the ultraviolet rays emitted by the particles of the phosphorescent luminescent ceramic by consuming the energy accumulated up to that point. , Sustains photocatalytic function. In addition, since the particles of the spontaneous-emitting ceramic or the phosphorescent ceramic usually emit green, blue, or orange visible light, they can be used for decoration or guidance in the dark.

【0018】

In addition, the photocatalytic semiconductor has an ultraviolet wavelength (absorption band), that is, excitation, which is required for exerting the catalytic function by adjusting its composition (addition of inorganic pigments and metals) and adjusting the heat treatment in the manufacturing process. The wavelength can be changed. For example, TiO₂CrO₃When a small amount of is added, the absorption band is displaced to the long wavelength side. As a result, the photocatalyst side can be matched with the emission spectrum characteristics of the spontaneous ultraviolet radiation material or the phosphorescent ultraviolet radiation material, and the photocatalyst semiconductor suitable for the wavelength of the supplied ultraviolet rays can be selected.

【0019】

On the other hand, on the contrary, the emission spectral characteristics of the spontaneous ultraviolet radiation material or the phosphorescent ultraviolet radiation material can be matched with the excitation wavelength of the photocatalytic semiconductor. For example, the excitation wavelength of titanium oxide is 180 nm to 400 nm, but there is no phosphorescent ultraviolet radiation material currently on the market that matches it. As a commercially available phosphorescent ceramic that has a long-term afterglow, there is "N Luminous" from Nemoto & Co., Ltd., and some have an afterglow time of more than 1000 minutes. This is made from strontium carbonate and calcium carbonate as the main raw material, alumina is added, and urobium and dysprosium are added as activators, and lantern, cerium, placeodium, samarium, cadnium, terbium, holmium, erbium, thulium, ytterbium, lutetium, manganese, etc. One of the elements tin and bismus and boric acid as a flax are added and heat-treated at 1300 ° C to produce a phosphorescent ceramic with afterglow for a long time. In this mixed production method, it is a blue illuminant having a peak of 440 nm even at the shortest wavelength. In order to make this an emission wavelength of 400 nm or less, which is the excitation wavelength of titanium oxide, it is necessary to bring the absorption wavelength having a peak of 360 nm and the emission wavelength of 440 nm, which are possessed by the above-mentioned "N phosphorescence", close to each other. If the added metal element is added, or if the blue emission of around 450 nm, which is the original phosphorescent wavelength characteristic of minerals such as strontium, potassium, and borosand, does not generate an emission wavelength of 440 nm or less, the phosphorescent color does not emit. It is possible to develop a phosphorescent ultraviolet radiation material by purifying a mineral element having an emission wavelength of 400 nm or less, which has a shorter wavelength than that of strontium and does not develop color, and formulating and processing it.

【0020】

The photocatalytic semiconductor is supported only on the surface of the unit particles in advance, or is supported on the entire surface after the unit particles are mixed with spontaneous light emitting ceramic or phosphorescent ceramic particles or mixed particles to form a molded product. There is. In the former case, the photocatalytic semiconductor does not adhere to the surface of the particles of the spontaneous light emitting ceramic or the phosphorescent light emitting ceramic or the mixed particles, and the amount of ultraviolet rays emitted from these particles is large. Further, in the case of phosphorescent type luminescent ceramic particles, ultraviolet rays from the outside can be efficiently absorbed.

【0021】

Photocatalyst function auxiliary addition metals (Pt, Ag, Rh, RuO, Nb, Cu, Sn, NiO, etc.) may be added to the photocatalyst during the manufacturing process. well known. [0022]

[Example]

Hereinafter, the present invention will be described in more detail with reference to Reference Examples and Examples, but the scope of the present invention is not limited to these examples.

【0023】

Reference Example 1 (Manufacturing of amorphous titanium peroxide sol) Titanium tetrachloride TiCl₄50% solution (Sumitomo Citics Co., Ltd.) diluted 70 times with distilled water and ammonium hydroxide NH₄A 25% solution of OH (Takasugi Pharmaceutical Co., Ltd.) diluted 10-fold with distilled water is mixed at a volume ratio of 7: 1 to carry out a neutralization reaction. After the neutralization reaction, adjust the pH to 6.5 to 6.8, leave it for a while, and then discard the supernatant. Remaining Ti (OH)₄Add about 4 times the amount of distilled water in the gel, stir well and leave. Check with silver nitrate and repeat washing with water until no chloride ions are detected in the supernatant. Finally, discard the supernatant and leave only the gel. In some cases, dehydration can be performed by centrifugation. This pale bluish white Ti (OH)₄To 3600 ml, 210 ml of 35% hydrogen peroxide solution is added in two portions every 30 minutes, and the mixture is stirred at about 5 ° C overnight to obtain about 2500 ml of a yellow transparent amorphous titanium peroxide sol. In the above steps, if heat generation is not suppressed, water-insoluble substances such as metatitanic acid may precipitate, so it is desirable to suppress heat generation in all steps.

【0024】

Reference Example 2 (Manufacturing of titanium oxide sol from amorphous titanium peroxide sol) When the amorphous titanium peroxide sol is heated at 100 ° C., anatase-type titanium oxide is produced after about 3 hours, and when it is heated for about 6 hours, anatase-type titanium oxide sol is obtained. In addition, when heated at 100 ° C for 8 hours, it becomes pale yellow and slightly suspended fluorescence, and when concentrated, a yellow opaque substance is obtained, and when heated at 100 ° C for 16 hours, a very pale yellow substance is obtained. The degree of dry adhesion is slightly lower than that of the above-mentioned one heated at 100 ° C for 6 hours. Since this titanium oxide sol has a lower viscosity than the amorphous titanium peroxide, it is concentrated to 2.5% by weight for easy dipping.

【0025】

Example 1 The decomposition test of the organic substance based on the mixing ratio of the amorphous titanium peroxide sol and the titanium oxide sol was carried out as follows. For the substrate, a Keramit decorative board (manufactured by Clay Burn Ceramics Co., Ltd.) with a length and width of 150 x 220 mm and a thickness of 4 mm was used. This substrate was coated with a mixed sol of various mixing ratios to a thickness of about 2 μm by a spray method, dried at 70 ° C from room temperature, sintered at about 400 ° C for 30 minutes, and carried a photocatalyst on the substrate5. Various photocatalysts were obtained. These test photocatalysts were placed in a test container, and then a colored solution of an organic substance to be decomposed was poured into the container to a depth of 1 cm. This coloring solution is obtained by diluting Poluk Red PM-R (manufactured by Sumika Color Co., Ltd.), which is an aqueous dispersion (red liquid substance) of monoazo red, 30 times. Next, in order to prevent evaporation of the coloring solution in the container, the container was covered with a float glass (wavelength of 300 nm or less was cut). Two ultraviolet radiators (20w blue color fluorescent tubes) were installed 5 cm above the test container and 9.5 cm from the substrate at a distance of 13 cm, and various photocatalysts were irradiated. It is assumed that the decomposition of organic matter has been completed. The results are as follows. When the substrate was made of 100% titanium oxide sol, the color disappeared 72 hours after the start of the test, and while the resolution of the organic substance, that is, the photocatalytic function was excellent, there were many decomposition residues. On the other hand, the amorphous type 100% titanium oxide sol disappears in 150 hours, and the resolution of the organic substance, that is, the photocatalytic function is inferior to that of the above 100% titanium oxide sol, but the adhesion / film forming property and corrosion resistance , It was excellent in cosmetics. In addition, the mixture ratio of amorphous titanium peroxide sol and titanium oxide sol 1: 3 is 78 hours, and the mixture ratio 1: 1 is 102 hours, and the mixing ratio is 3: 1. One of 1 was 120 hours and each color disappeared. From the above experiments, it was found that the photocatalytic function is inversely proportional to the adhesion / film-forming property, corrosion resistance, and cosmetic property. From these facts, it was found that according to the present invention, it can be used for various purposes (product application site, use conditions) by changing the mixing ratio.

【0026】

Example 2 An acrylic resin plate and a methacrylic resin plate were used as the substrates. These resin plates are immersed in a 2% sodium hydroxide solution at 80 ° C. for 30 minutes, washed with water, and then dried. As the first layer, a titanium peroxide sol prepared in Reference Example 1 to which 0.5% of a surfactant was added was applied to this resin plate 3 to 4 times by dipping. Drying was performed at 70 ° C for 10 minutes. As the second layer, the same as in Example 1, 5 kinds of amorphous titanium peroxide sol and titanium oxide sol compounding ratios were applied 3 to 4 times by dipping. Drying and solidification was completed at 120 ° C for 3 minutes for the acrylic resin plate and when the temperature of the dryer rose to 119 ° C for the methacrylic resin plate. The photocatalyst function was the same as in Example 1, but the first layer was significantly superior in terms of adhesion to the resin plate and difficult decomposition of the resin plate by the photocatalyst.

【0027】

Example 3 As a substrate, a commercially available tile having high water absorption was used. First, it was washed with a neutral detergent, dried, and then coated with a surface active agent. As a photocatalyst composition, by weight ratio, add 1 part of titanium oxide powder "ST-01" (manufactured by Ishihara Sangyo Co., Ltd.) to 50 parts of titanium peroxide sol (pH 6.4) made in Reference Example 1 for about 15 minutes. After mechanically stirring, the one that was stirred using ultrasonic waves was used so as not to form lumps. Dipped at a rate of 0.3-0.5 cm per second and dried overnight at 30 ° C. This product was calcined at 400 ° C. for 30 minutes to produce a photocatalyst. This photocatalyst was firmly adhered to the tile surface for a long period of time. On the other hand, when the tile was coated with titanium oxide powder dispersed in distilled water, it could not be adhered well.

【0028】

Example 4 The surface of the float glass treated with a degreasing / surfactant was coated with a suspension of glass beads several times with a spray gun. This was dried at 40 ° C and then calcined at 700 ° C for 30 minutes. The photocatalyst composition used in Example 3 was coated on the float glass on which the glass beads were fixed, dried, and then fired at 400 ° C. for 30 minutes to produce a photocatalyst. This photocatalyst was firmly adhered to the glass beads fixed to the float glass for a long period of time.

【0029】

Example 5 Amorphous titanium peroxide sol is mixed with phosphorescent ultraviolet radiation material "Kiplus" (trade name: Next Eye Co., Ltd.) at a ratio of 25% by weight with respect to titanium peroxide in the sol, and stirred to make Keramit makeup as a substrate. It is sprayed onto a plate, dried at room temperature, fired at 400 ° C for 30 minutes, cooled, and then a titanium oxide sol whose excitation wavelength is adjusted to the emission wavelength of the above-mentioned radioactive material is sprayed and dried to a thickness of 1 μm, and then 4 O °. Bake in C for 30 minutes. Even if the irradiation of the photocatalyst with ultraviolet rays is interrupted, the photocatalyst maintains the photocatalytic action by the ultraviolet rays emitted by the ultraviolet radiating material.

【0030】

[Effect of the invention]

According to the present invention, there is provided a method for producing a photocatalyst that can be carried and fixed on a substrate without deteriorating the photocatalytic function of the photocatalyst and can be used for a long period of time. When titanium oxide and amorphous titanium peroxide sol are used, they can be applied to products for various purposes by changing the mixing ratio. Furthermore, by mixing particles made of a spontaneous ultraviolet radiation material or a phosphorescent ultraviolet radiation material or particles mixed with these radiation materials together with a photocatalyst, the photocatalyst function is continuously exhibited outdoors without an ultraviolet radiator. Can be made to.