Stainproof plate

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an antifouling plate such as a kitchen bag that is placed around a kitchen stove and receives oil stains scattered from cooked foods on the stove. In particular, the present invention relates to an antifouling plate that easily removes adhered dirt.

【0002】

[Conventional technology]

On a kitchen stove, when cooking with a frying pan, dirt such as oil scatters around. The wall surface around the stove, which is exposed to the scattered dirt, is made of a material that is easy to remove (clean) the attached dirt. Alternatively, a tsuitate is set up around the stove to catch the scattering of dirt. In the present specification, members such as these wall surfaces and counters that are arranged around a device (stove) that causes stains and receive the stains are referred to as antifouling plates. The antifouling plate is made of tile or the like because it is desirable that the antifouling plate has a property of easily removing the attached dirt.

【0003】

[Problems to be Solved by the Invention]

However, even with tile antifouling boards, it is difficult to remove strong oil stains. In particular, when the adhered oil is polymerized and solidified to form glue, it becomes a difficult task to remove this stain. An object of the present invention is to provide an antifouling plate that can easily remove attached oil stains and the like. Furthermore, it is an object of the present invention to provide an antifouling plate having an action of decomposing attached oil stains and the like.

【0004】

[Means for solving problems]

In order to solve the above problems, the antifouling plate of the present invention is an antifouling plate that is arranged around an apparatus that causes stain emission and receives the stain; it has a surface layer containing an optical semiconductor, and the light It is characterized in that the surface exhibits hydrophilicity in response to photoexcitation of a semiconductor. If the surface of the antifouling plate shows sufficient hydrophilicity, the dirt adhering to the surface can be easily removed.

【0005】

In the present invention, it is further preferable that the photosemiconductor oxidatively decomposes the dirt adhering to the antifouling plate by its photooxidizing action. It is possible to prevent the oil from polymerizing and solidifying to form glue.

【0006】

BEST MODE FOR CARRYING OUT THE INVENTION

In the antifouling plate of the present invention, it is preferable that the surface layer containing the photosemiconductor contains anatase-type titanium oxide and silica, or anatase-type titanium oxide and silicone in which at least a part is silanolized. These provide a hydrophilic surface with an extremely high degree of hydrophilicity. The degree of hydrophilicity is remarkable when the contact angle with water is 10 ° or 3 ° or less. In addition, since anatase-type titanium oxide has a high bandgap energy, it has a strong oxidative decomposition action on dirt. Here, the content of titanium oxide in the surface layer is preferably 5 to 90% by volume. This is because the hydrophilicity and the activity of the redox reaction are good in this range. Further, it is preferable to further add any metal of Ag, Pt, Pd, Ru, Os, and Ir because the redox property can be further activated without impairing the hydrophilic performance.

【0007】

Next, the relationship between hydrophilicity and optical semiconductors will be described. The present inventor has discovered that when a photosemiconductor is photoexcited, the surface of the photosemiconductor becomes highly hydrophilic. That is, when light semi-conducting titania is photoexcited with ultraviolet rays, the surface becomes highly hydrophilic to the extent that the contact angle with water is 10 ° or less, more specifically 5 ° or less, especially about 0 °. It was discovered that the high degree of hydrophilicity is maintained and restored by irradiation with light, and that the highly hydrophilic state is maintained even in the dark for 3 weeks or more under specific conditions.

【0008】

When light having a wavelength higher than the band gap energy of the optical semiconductor is irradiated with sufficient illuminance for a sufficient time, the surface of the optical semiconductor-containing layer becomes hydrophilic. At present, the surface hydrophilization phenomenon caused by photoexcitation of photosemiconductors cannot always be clearly explained. It seems that the hydrophilization phenomenon by a photosemiconductor is not necessarily the same as the photodecomposition of a substance by a photocatalytic redox reaction conventionally known in the field of application of a photosemiconductor to a chemical reaction. In this regard, the conventional theory regarding photocatalytic redox reactions is that electron-hole pairs are generated by photoexcitation, and the generated electrons reduce surface oxygen to superoxide ions (O).₂^-), The holes oxidize the surface hydroxyl groups to generate hydroxide radicals ( OH), and these highly reactive reactive oxygen species (O)₂^-The substance was decomposed by the redox reaction of OH).

【0009】

However, the hydrophilization phenomenon by photosemiconductors is inconsistent with the conventional knowledge about photocatalytic decomposition of substances in at least two points. First, according to the conventional wisdom, photosemiconductors such as rutyl and tin oxide do not have a sufficiently high energy level of the conductor, so that the reduction reaction does not proceed, and as a result, the electrons photoexcited by the conductor. Was excessive, and it was thought that the electron-hole pairs generated by photoexcitation recombine without participating in the redox reaction. On the other hand, it was confirmed that the hydrophilization phenomenon caused by optical semiconductors also occurs in optical semiconductors such as rutile and tin oxide.

【0010】

Secondly, conventionally, it is considered that decomposition of a substance by a photocatalytic redox reaction does not occur unless the film thickness of the photosemiconductor layer is at least 100 nm or more. On the other hand, it was observed that the hydrophilicity by the photosemiconductor occurs even when the film thickness of the photocatalyst-containing layer is on the order of several nm.

【0011】

Therefore, although it cannot be clearly concluded, the hydrophilization phenomenon by photosemiconductors is considered to be a phenomenon slightly different from the photodecomposition of substances by photocatalytic redox reaction. However, it was confirmed that surface hydrophilicity does not occur unless light with an energy higher than the bandgap energy of the optical semiconductor is irradiated. Presumably, the conduction electrons and holes generated by the excitation of the photo-semiconductor impart polarity to the surface of the photo-semiconductor-containing layer, and water becomes a hydroxyl group (OH).^- ) Is chemically adsorbed, and a physically adsorbed aqueous layer is formed on the chemisorbent, and the surface becomes hydrophilic.

【0012】

Once the surface of the photo-semiconductor-containing layer is highly hydrophilic by photoexcitation, the surface hydrophilicity persists for some period of time even when the substrate is held in the dark. When pollutants are adsorbed on the surface hydroxyl groups with the passage of time and the surface gradually loses its hydrophilicity, the hydrophilicity is restored by photoexcitation again.

【0013】

In order to first hydrophilize the optical semiconductor-containing layer, an arbitrary light source having a wavelength having an energy higher than the bandgap energy of the optical semiconductor can be used. In the case of an optical semiconductor whose photoexcitation wavelength is located in the ultraviolet region such as titania, the ultraviolet rays contained in the sunlight are preferably used under the condition that the substrate coated with the optical semiconductor-containing layer is exposed to sunlight. be able to. An optical semiconductor can be photoexcited by an artificial light source indoors or at night. As will be described later, when the optical semiconductor-containing layer is made of silica-blended titania, it can be easily hydrophilized even with weak ultraviolet rays contained in a fluorescent lamp.

【0014】

Once the surface of the opto-semiconductor-containing layer is hydrophilized, the hydrophilicity can be maintained or restored by relatively weak light. For example, in the case of titania, the maintenance and restoration of hydrophilicity can be sufficiently performed even with weak ultraviolet rays contained in indoor lighting such as fluorescent lamps.

【0015】

The photosemiconductor-containing layer exhibits hydrophilicity even if it is very thin, and in particular, the photocatalytic semiconductor material made of a metal oxide has sufficient hardness, so that the photosemiconductor-containing layer has sufficient durability and abrasion resistance.

【0016】

Base material In the present invention, the substrate includes, for example, metal, ceramics, glass, plastics, wood, stone, cement, concrete, combinations thereof, laminates thereof, and coating on them. The surface of the base material is covered with an optical semiconductor-containing layer.

【0017】

When the base material is made of a non-heat resistant material such as plastics or the base material is painted with a paint, a photooxidizing paint containing a photosemiconductor is applied to the surface as described later. The photosemiconductor-containing layer can be formed by curing.

【0018】

Optical semiconductor The optical semiconductor used in the present invention is titania (TiO).₂ ) Is the most preferable. Titania is harmless, chemically stable, and inexpensively available. Furthermore, titania has a high bandgap energy, and therefore requires ultraviolet rays for photoexcitation and does not absorb visible light in the process of photoexcitation, so that color development due to complementary color components does not occur.

【0019】

Both anatase and rutile can be used as titania. The advantage of anatase-type titania is that a sol in which very fine particles are dispersed is easily available on the market, and a very thin thin film can be easily formed. Although rutile-type titania has a lower conduction band level than anatase-type, it can be used for the purpose of hydrophilization by photosemiconductors. When the base material is coated with a photosemiconductor-containing layer made of titania and titania is photoexcited by ultraviolet rays, water becomes a hydroxyl group (OH).^- ) Is chemically adsorbed on the surface, and a physically adsorbed aqueous layer is formed on the surface, and as a result, the surface is considered to be hydrophilic.

【0020】

Other optical semiconductors that can be used in the present invention include ZnO and SnO.₂ , SrTiO₃, WO₃ , Bi₂ O₃ , Fe₂ O₃ There are metal oxides such as. Similar to titania, these metal oxides have metal elements and oxygen on their surface, so they have surface hydroxyl groups (OH).^- ) Is considered to be easily adsorbed. Further, the particles of the optical semiconductor may be mixed with a metal oxide that is not an optical semiconductor such as silica. In particular, when an optical semiconductor is blended with silica or tin oxide, the surface can be highly hydrophilic.

【0021】

As an example of a method for producing an optical semiconductor layer made of such silica-blended titania, precursors of atypical silica (for example, tetraethoxysilane, tetraisopropoxysilane, tetran-propoxysilane, tetrabutoxysilane, tetramethoxysilane, etc. Tetraalkoxysilanes such as; silanols, which are their hydrolyzates; or polysiloxanes with an average molecular weight of 3,000 or less) are applied to the surface of the substrate and hydrolyzed as necessary to obtain silanols. After the formation, the silanol is subjected to dehydration-condensation polymerization at room temperature or, if necessary, by heating to form a photo-semiconductor layer in which titania is bound with atypical silica.

【0022】

Formation of photocatalyst layer by firing amorphous titania When the base material is made of a heat-resistant material such as metal, ceramics, or glass, an optical semiconductor with excellent wear resistance that exhibits a high degree of hydrophilicity with a contact angle with water of 0 °. One of the preferred methods for forming the containing layer is to first coat the surface of the substrate with amorphous titania and then calcin the amorphous titania to crystalline titania (anatase or rutyl). Any of the following methods can be adopted for the formation of amorphous titania.

【0023】

(1) Hydrolysis and dehydration polycondensation of organic titanium compounds Hydrolysis inhibitors such as hydrochloric acid or ethylamine are added to titanium alkoxides such as tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, and such as ethanol and propanol. After diluting with alcohol and then partially or completely hydrolyzing, the mixture is applied to the substrate by spray coating, flow coating, spin coating, dip coating, roll coating or other coating method. Apply to the surface of and dry at a temperature of 200 ° C from room temperature. Drying completes the hydrolysis of the titanium alkoxide to produce titanium hydroxide, and the dehydration polycondensation of titanium hydroxide forms a layer of amorphous titania on the surface of the substrate. Instead of the titanium alkoxide, other organic titanium compounds such as titanium chelates or titanium acetates may be used.

【0024】

(2) Formation of amorphous titania by inorganic titanium compound Inorganic titanium compounds such as TiCl₄ Or Ti (SO)₄)₂ The acidic aqueous solution of the above is applied to the surface of the base material by spray coating, flow coating, spin coating, dip coating, and roll coating. The inorganic titanium compound is then subjected to hydrolysis and dehydration polycondensation by drying at a temperature of about 100-200 ° C to form a layer of amorphous titania on the surface of the substrate. Or TiCl₄Amorphous titania may be formed on the surface of the base material by chemical vapor deposition of.

【0025】

(3) Formation of amorphous titania by sputtering Metallic titanium or TiO₂ Amorphous titania is adhered to the surface of the base material by irradiating the target with an electron beam in an oxidizing atmosphere.

【0026】

(4) Baking temperature The amorphous titania is calcined at a temperature at least higher than the crystallization temperature of anatase. Amorphous titania can be converted to anatase-type titania by firing at a temperature of 400 to 500 ° C or higher. Amorphous titania can be converted to rutile-type titania by firing at a temperature of 600 to 700 ° C or higher.

【0027】

Photocatalytic layer made of silica-blended titania Another preferred method for forming a wear-resistant photosemiconductor-containing layer that exhibits a high degree of hydrophilicity such that the contact angle with water is 0 ° is a photosemiconductor-containing layer made of a mixture of titania and silica. It is to be formed on the surface of the base material. The ratio of silica to the total of titania and silica can be 5 to 90 mol%, preferably 10 to 70 mol%, more preferably 10 to 50 mol%. Any of the following methods can be adopted for forming the optical semiconductor-containing layer made of silica-blended titania.

【0028】

(1) A suspension containing anatase-type or rutile-type titania particles and silica particles is applied to the surface of the base material, and sintered at a temperature below the softening point of the base material. (2) Tetraalkoxysilanes such as precursors of amorphous silica (for example, tetraethoxysilane, tetraisopropoxysilane, tetran-propoxysilane, tetrabutoxysilane, tetramethoxysilane, etc.; silanols which are hydrolysates thereof; Alternatively, a mixture of (polysiloxane) with an average molecular weight of 3,000 or less) and crystalline titania sol is applied to the surface of the substrate and hydrolyzed as necessary to form silanol, and then heated at a temperature of about 100 ° C or higher. By subjecting silanol to dehydration-condensation polymerization, titania forms a photo-semiconductor-containing layer bound with amorphous silica. In particular, if the dehydration polycondensation temperature of silanol is carried out at a temperature of about 200 ° C. or higher, the degree of polymerization of silanol can be increased and the alkali resistance performance of the optical semiconductor-containing layer can be improved.

【0029】

(3) Amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate, or acetate, or TiCl₄ Or Ti (SO)₄)₂ A suspension of silica particles dispersed in a solution of an inorganic titanium compound such as) is applied to the surface of the substrate, and the titanium compound is subjected to hydrolysis and dehydration polycondensation at a temperature of 200 ° C from room temperature. Therefore, a thin film of amorphous titania in which silica particles are dispersed is formed. Next, the amorphous titania is phase-changed into crystalline titania by heating to a temperature equal to or higher than the crystallization temperature of titania and below the softening point of the substrate.

【0030】

(4) Amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate, or acetate, or TiCl₄ Or Ti (SO)₄)₂ Inorganic titanium compounds such as tetraalkoxysilanes such as atypical silica precursors (eg, tetraethoxysilane, tetraisopropoxysilane, tetran-propoxysilane, tetrabutoxysilane, tetramethoxysilane, etc.); The hydrolyzate silanol; or polysiloxane with an average molecular weight of 3,000 or less) is mixed and applied to the surface of the substrate. These precursors are then subjected to hydrolysis and dehydration polycondensation to form a thin film consisting of a mixture of amorphous titania and amorphous silica. Next, the amorphous titania is phase-changed into crystalline titania by heating to a temperature equal to or higher than the crystallization temperature of titania and below the softening point of the substrate.

【0031】

Optical semiconductor layer made of tin oxide-blended titania Yet another preferred method for forming a wear-resistant photosemiconductor-containing layer that exhibits a high degree of hydrophilicity with a contact angle of 0 ° with water is a photosemiconductor containing a mixture of titania and tin oxide. The layer is to be formed on the surface of the substrate. The ratio of tin oxide to the total of titania and tin oxide can be 1 to 95% by weight, preferably 1 to 50% by weight. Any of the following methods can be adopted for forming the optical semiconductor-containing layer made of tin oxide-containing titania.

【0032】

(1) A suspension containing anatase-type or rutile-type titania particles and tin oxide particles is applied to the surface of the base material, and sintered at a temperature below the softening point of the base material. (2) Amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate, or acetate, or TiCl₄ Or Ti (SO)₄)₂ A suspension of tin oxide particles dispersed in a solution of an inorganic titanium compound such as) is applied to the surface of the substrate, and the titanium compound is subjected to hydrolysis and dehydration polycondensation at a temperature of 200 ° C from room temperature. As a result, a thin film of amorphous titania in which tin oxide particles are dispersed is formed. Next, the amorphous titania is phase-changed into crystalline titania by heating to a temperature equal to or higher than the crystallization temperature of titania and below the softening point of the substrate.

【0033】

Silicone paint containing optical semiconductor Yet another preferred method of forming a photosemiconductor layer with a high degree of hydrophilicity such that the contact angle with water is 0 ° is uncured or partially cured silicone (organopolysiloxane) or a precursor of silicone. It is to use a composition in which particles of an optical semiconductor are dispersed in a coating film forming element composed of a body. When this composition is applied to the surface of the base material, the coating film-forming element is cured, and then the photosemiconductor is photoexcited, the organic group bonded to the silicon atom of the silicone molecule is replaced with a hydroxyl group by the action of the photosemiconductor, resulting in light. The surface of the semiconductor-containing layer is made hydrophilic.

【0034】

This approach has several advantages. Since the opto-semiconductor-containing silicone paint can be cured at room temperature or relatively low temperature, it can be applied to non-heat-resistant materials such as plastics and organic substances. This coating composition containing an opto-semiconductor can be applied to an existing substrate that requires surface hydrophilicity at any time by dipping, brush coating, spray coating, roll coating, or the like. Hydrophilization of an optical semiconductor by photoexcitation can be easily performed even with a light source such as sunlight.

【0035】

Further, when a coating film is formed on a plastically processable base material such as a steel sheet, the steel sheet can be easily plastically worked after the coating film is cured and before being photoexcited. Prior to photoexcitation, organic groups are bonded to the silicon atoms of the silicone molecule, and therefore the coating film has sufficient flexibility to easily plastically process the steel sheet without damaging the coating film. Can be done. After the plastic processing, if the photosemiconductor is photoexcited, the organic group bonded to the silicon atom of the silicone molecule is replaced with a hydroxyl group by the photosemiconductor action, and the surface of the coating film is made hydrophilic.

【0036】

Since the photosemiconductor-containing silicone composition has a siloxane bond, it has sufficient resistance to the photooxidizing action of the photosemiconductor (photosemiconductor). Yet another advantage of the photo-semiconductor-containing layer made of photo-semiconductor-containing silicone paint is that once the surface is hydrophilic, it remains hydrophilic for a long period of time even when kept in the dark, and is like a fluorescent lamp. It is to restore hydrophilicity even with the light of indoor lighting.

【0037】

The coating film-forming elements include methyltrichlorosilane, methyltribromsilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltrit-butoxysilane; ethyltrichlorosilane, ethyltribromsilane, and ethyltrimethoxy. Silane, ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltri t-butoxysilane; n-propyltrichlorosilane, n-propyltribromsilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltri Isopropoxysilane, n-propyltrit-butoxysilane; n-hexyltrichlorosilane, n-hexyltribromsilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-hexyltriisopropoxysilane, n- Hexyltri t-butoxysilane; n-decyltrichlorosilane, n-decyltribromsilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n-decyltriisopropoxysilane, n-decyltri t-butoxysilane; n -Octadecyltrichlorosilane, n-octadecyltribromsilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltriisopropoxysilane, n-octadecyltri t-butoxysilane; Silane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltrit-butoxysilane; tetrachlorosilane, tetrabromsilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane; Didimethyldichlorosilane, dimethyldibromosilane, dimethyldimethoxysilane, dimethyldiethoxysilane; diphenyldichlorosilane, diphenyldiblomsilane, diphenyldimethoxysilane, diphenyldiethoxysilane;Phenylmethyldichlorosilane, phenylmethyldibromsilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane; trichlorohydrosilane, tribromhydrosilane, trimethoxyhydrosilane, triethoxyhydrosilane, triisopropoxyhydrosilane, trit-butoxyhydrosilane; vinyl Trichlorosilane, Vinyltribromsilane, Vinyltrimethoxysilane, Vinyltriethoxysilane, Vinyltriisopropoxysilane, Vinyltrit-butoxysilane; Trifluoropropyltrichlorosilane, Trifluoropropyltribromsilane, Trifluoropropyltrimethoxysilane, Trifluoropropyltriethoxysilane, trifluoropropyltriisopropoxysilane, trifluoropropyltrit-butoxysilane; γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxy Propyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxysilane, γ-glycidoxypropyltri t-butoxysilane; γ-methacryloxipropylmethyldimethoxysilane, γ- Metaacryloxypropylmethyldiethoxysilane, γ-metaacryloxypropyltrimethoxysilane, γ-metaacryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-methacryloxypropyltri t-butoxy Silane; γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropyltrit -Butoxysilane;γ-Mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltri t-butoxy Silanes; β- (3,4-epylcyclohexyl) ethyltrimethoxysilane, β- (3,4-epylcyclohexyl) ethyltriethoxysilane; and partial hydrolysates thereof; and mixtures thereof can be used. it can.

【0038】

In order to ensure good hardness and smoothness of the silicone coating film, it is preferable to contain 10 mol% or more of the three-dimensional crosslinked siloxane. Further, in order to provide sufficient flexibility of the coating film while ensuring good hardness and smoothness, it is preferable to contain 60 mol% or less of the two-dimensional crosslinked siloxane. Further, in order to increase the rate at which the organic group bonded to the silicon atom of the silicone molecule is replaced with the hydroxyl group by photoexcitation, a silicone in which the organic group bonded to the silicon atom of the silicone molecule is composed of an n-propyl group or a phenyl group is used. Is preferable. It is also possible to use an organopolysilazane compound having a silazane bond instead of the silicone having a siloxane bond.

【0039】

Addition of antibacterial enhancer The opto-semiconductor-containing layer can be doped with metals such as Ag, Cu, and Zn. In order to doped a photosemiconductor with Ag, Cu, or Zn, a soluble salt of these metals can be added to a suspension of photosemiconductor particles, and the obtained solution can be used to form a photosemiconductor-containing layer. it can. Alternatively, after forming the photosemiconductor-containing layer, soluble salts of these metals may be applied and photoreduced and precipitated by light irradiation.

【0040】

Photosemiconductor-containing layers doped with Ag, Cu, or Zn can kill bacteria attached to the surface. Furthermore, this photosemiconductor-containing layer suppresses the growth of microorganisms such as mold, algae and moss. Therefore, the surface of the member can be kept clean for a long period of time.

【0041】

Addition of photoactivity enhancer The opto-semiconductor-containing layer can be further doped with platinum group metals such as Pt, Pd, Rh, Ru, Os and Ir. Similarly, these metals can be doped into photosemiconductors by photoreduction precipitation or addition of soluble salts. Doping a photosemiconductor with a platinum group metal can enhance the redox activity of the photosemiconductor and decompose contaminants adhering to the surface.

【0042】

Photoexcitation / UV irradiation In the present invention, it is preferable to form the optical semiconductor-containing layer with an optical semiconductor having a high bandgap energy and being photoexcited only by ultraviolet rays, such as titania. Then, the visible light is not absorbed by the optical semiconductor-containing layer, and the member is not colored by the complementary color component. Anatase-type titania can be photoexcited with ultraviolet rays having a wavelength of 387 nm or less, rutile-type titania having a wavelength of 431 nm or less, tin oxide having a wavelength of 344 nm or less, and zinc oxide having a wavelength of 387 nm or less.

【0043】

As the ultraviolet light source, indoor lighting such as a fluorescent lamp, an incandescent lamp, a metal halide lamp, and a mercury lamp can be used. Under conditions of exposure to sunlight, the optical semiconductor is naturally photoexcited by the ultraviolet rays contained in the sunlight.

【0044】

Photoexcitation can be performed or allowed to occur until the surface contact angle with water is about 10 ° or less, preferably about 5 ° or less, particularly about 0 °. Generally 0.001 mW / cm²If it is photoexcited with the ultraviolet illuminance of, it can be hydrophilized until the contact angle with water becomes about 0 ° in a few days. The illuminance of ultraviolet rays contained in the sunlight falling on the surface of the earth is about 0.1 to 1 mW / cm.²Therefore, the surface can be hydrophilized in a shorter time by exposing it to sunlight.

【0045】

When the photosemiconductor-containing layer is made of titania-containing silicone, it is preferable to photoexcite the photocatalyst with sufficient illuminance so that the surface organic groups bonded to the silicon atoms of the silicone molecule are replaced with hydroxyl groups in a sufficient amount. .. The most advantageous way to do this is to use sunlight. Once the surface is highly hydrophilic, the hydrophilicity persists even at night. Hydrophilicity is restored and maintained each time it is exposed to sunlight again.

【0046】

When providing the member of the present invention to the user, it is desirable to make the member hydrophilic in advance.

【0047】

In the present invention, an intermediate layer may be provided between the base material and the optical semiconductor-containing layer. As a result, the adhesion to the base material is increased and the wear resistance is improved.

【0048】

[Example]

Examples of the present invention will be described. Example 1 A surface layer composed of 70 parts of anatase-type titanium oxide, 30 parts of silica, and 1 part of platinum was formed on the base tile by the following method. First, anatase-type titania sol (Ishihara Sangyo, Osaka, STS-11), colloidal silica sol (Nissan Chemical, Snowtex O), and chloroplatinic acid hexahydrate are mixed, and a 15 cm square glazed tile (Toto, AB02E01) The surface was coated by a spray coating method and calcined at a temperature of 800 ° C. for 1 hour to obtain a sample coated with a coating composed of titania and silica. The film thickness was 0.5 μm. The contact angle with water immediately after firing was 5 °. The contact angle with water after leaving the sample in the dark for 1 week was still 5 °. 0.03 mW / cm on the surface of the sample using a BLB fluorescent lamp²After irradiating with ultraviolet rays for one day at the illuminance of ultraviolet rays, the contact angle with water became 0 °.

【0049】

Example 2 A surface layer composed of 50 parts of anatase-type titanium oxide, 50 parts of silica, and 1 part of palladium was formed on the base tile by the following method. TiO₂ After mixing (Nissan Chemical, TA-15), tetraethoxysilane and palladium chloride aqueous solution, it was applied to the surface of a 15 cm square glazed tile and heated at 150 ° C to obtain a sample. The film thickness was 0.5 μm. 0.03 mW / cm after leaving the sample in the dark for 1 week²When the BLB lamp was irradiated, the contact angle with water became 0 °.

【0050】

Comparative example The above tiles were used as they were.

【0051】

Evaluation of contact angle with water Next, 0.5 mW / cm was used for this sample using a BLB fluorescent lamp.²It was irradiated with ultraviolet rays for one day at the illuminance of. The contact angle of the surface of this sample with water was measured with a contact angle measuring device (CA-X150). Examples 1 and 2 had a contact angle of 0 °. On the other hand, the comparative example had a contact angle of 30 °.

【0052】

Oleic acid underwater release test Oleic acid was applied to the surfaces of the samples of Examples and Comparative Examples, and each sample was immersed in water filled in a water tank while keeping the sample surface in a horizontal position. In the comparative sample, oleic acid remained attached to the surface of the sample. On the other hand, in the sample of the example, the oleic acid curled up into oil droplets, which were released from the surface of the sample and surfaced. When the surface of the base material is coated with the photocatalytic top coat in this way, the surface of the base material is maintained hydrophilic, and oily stains can be easily released from the surface in water to clean the surface. confirmed. In this embodiment, for example, if an optical semiconductor coating is provided on the surface of a member and the optical semiconductor is excited by ultraviolet rays, the surface of the member contaminated with oil can be easily cleaned by simply flushing it with water without using a detergent. Shown.

【0053】

BLB irradiation after application of triolein acid glyceride Apply 2.5 mg of trioleic acid glyceride to the surface of the base material, 0.5 mW / cm²When the weight loss after irradiating the BLB lamp at 70% humidity for 1 week was measured, the weight loss was reduced by 2.5 mg in Examples 1 and 2. The applied trioleic acid glyceride is completely CO₂ And H₂ It is thought that it was decomposed into O. On the other hand, in the comparative example, almost no weight loss was observed.

【0054】

[Effect of the invention]

As is clear from the above description, the present invention can provide an antifouling plate that can easily remove attached oil stains and the like. Further, it is possible to provide an antifouling plate having an action of decomposing attached oil stains and the like.