JPH09225388A - Stainproofing member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop color by the photoreduction of iron by a method in which a surface layer containing photocatalyst particles is formed on the surface of a member and is brought into contact with water containing iron ion. SOLUTION: The photoreduction capacity of a surface layer which indicates a hydrophilic property is controlled by the irradiation of ultraviolet rays etc. To express practically by the change in color difference (ΔE), when a member is immersed in water containing 2ppm of iron ion, and the surface layer is irradiated with light having energy higher than the band gap energy of photocatalyst particles in conditions in which photon density per unit time is 1×10<15> /sec.cm<2> , and accumulated photon density is 8×10<19> /cm<2> , ΔE<1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tiles, concrete, glass, bricks, plastics, ceramics, or composite members thereof.

[0002]

2. Description of the Related Art Conventionally, it has been considered that stains are less likely to adhere by making the surface of a member water repellent. However, when it is made water-repellent, muddy water or the like remains as water droplets on the surface of the base material, and when it dries, it becomes difficult to drop it. Also, black stripe-like stains will become noticeable over time on the tiles and the like attached to the outer wall. The dirt is composed of a hydrophobic substance such as carbon black which is a combustion product. Since the hydrophobic substance is more easily adapted to a hydrophobic base material than water, it is hard to be washed away by rainwater and stays on the surface of the material.

Therefore, recently, it has been proposed in the literature ("Polymer" 1995, Vol. 44) to exert an automatic cleaning effect by applying a hydrophilic resin coating to the surface of a base material. That is, by imparting hydrophilicity to the surface of the base material, a thin water film is formed on the surface to make it difficult for dirt components to adhere and to easily wash away dirt with rainwater or the like.

Therefore, it has been proposed to coat the building with a hydrophilic graft polymer (Chemical Industry Daily 19
January 30, 1995). Further, recently, many hydrophilic paints such as acrylic resin and acrylic silicone resin are commercially available.

Examples of hydrophilic coating materials include acrylic silicone resins, water-based silicone coating agents, graft polymers of silicone resins and acrylic resins, block polymers of silicone resins and acrylic resins, acrylic resins, acrylic-styrene resins, sorbitan fatty acid ethylene. There are cross-linked urethanes composed of oxides, urethane acetates, sorbitan fatty acid esters, polycarbonate diols and / or polyisocyanates, polyacrylic acid alkyl ester cross-linked products, and the like.

[0006]

As described above, even when the surface of the base material is made hydrophilic by the resin coating, the contact angle with water can be reduced to about 30 to 40 ° at most, and this is common. It is larger than the contact angle of water (about 20 °) on the tile surface, and the automatic cleaning effect is no better than the tile.

Further, since combustion products and city dust are basically hydrophobic, when the contact angle of the base material with water increases, the base material having the same hydrophobicity easily adheres to the surface of the base material and stains are conspicuous. Like Further, dirt such as combustion products and sludge other than urban dust exhibits hydrophilicity with a contact angle with water of about 20 ° to 50 °. Therefore, when the contact angle of the surface of the substrate with water is 20 ° to 50 °, the surface of the base material and the stain exhibit similar hydrophilicity, and they easily adhere to each other and show the peak value of the stain.

On the contrary, the contact angle of the surface of the substrate with water is 20 ° or less, preferably 10 ° or less, more preferably 1
When the temperature is less than °, the affinity for water becomes higher than the affinity for inorganic substances (dirt), and the water preferentially adhering to the surface inhibits the adhesion of the inorganic substances, and at the same time tries to adhere or try to adhere. The resulting inorganic substance is easily washed away with water, but no technique has been developed for keeping the contact angle of the surface of the substrate with water at 10 ° or less for a long period of time.

On the other hand, Japanese Unexamined Patent Publication No. 6-278241 and Japanese Unexamined Patent Publication No. 7-51646 propose to decompose dirt by the redox action of a photocatalyst. Decomposing action based on the redox reaction of the photocatalyst particles is irradiated with ultraviolet rays or the like to the photocatalyst particles, electrons by photoexcitation - hole pairs are generated, superoxide ion electron pairs is by reducing the surface oxygen ^- the (O ₂₎ generated, holes oxidize surface hydroxyl groups to produce the hydroxyl radical (· OH), these highly active species highly reactive ^- attached to the surface by an oxidation-reduction reaction of (O ₂ or · OH) malodor It is to decompose the components.

[0010]

According to the present invention, in order to impart the property that dirt is not easily attached to the surface of a member and to have a self-cleaning effect on the member itself, the contact angle to water is more preferable than making the surface water repellent. The fact that it is more effective to make it less hydrophilic. Further, the present inventors have found that photocatalyst particles such as titanium oxide have a function of hydrophilizing (superhydrophilizing) the surface of an article in addition to the function of decomposing dirt and the like by a conventionally known redox reaction. The present invention has been made based on the facts independently discovered by.

Here, the theoretical basis of the hydrophilization action of the photocatalyst newly discovered by the present inventors has not been completely elucidated, but the photocatalytic effect causes a hydroxyl group (OH ⁻ ).
Are chemically adsorbed on the surface of photocatalyst particles, or hydroxyl groups (O
H ^-) is replaced with an organic group, further the hydroxyl (OH ^-) water molecules in the air is physically adsorbed, the hydrophilic surface is increased by physically adsorbed water increases, super hydrophilic surface is achieved I think so.

As a specific example, a case where the surface layer is made of a silicone resin having a Si--O bond will be described. Before the photocatalyst particles are irradiated with light, as shown in FIG.
Since the alkyl group (R) is bonded to the atom, the surface layer exhibits hydrophobicity. However, when the surface layer is irradiated with light having an energy higher than the band gap energy of the photocatalyst particles, as shown in FIG. the substitution (chemisorption), further the hydroxyl group - ^(OH) alkyl group (R) is a hydroxyl group by photocatalytic effect - exhibit hydrophilic water molecules in the air are physically adsorbed ^(OH).

Further, titanium oxide (Ti
O ₂ ) will be described. The state shown in FIG. 2A before the light irradiation is changed to the state shown in FIG. 2A when the light is irradiated, as shown in FIG. 2B. hydroxyl group constituting the (OH ^-) is a Ti atom, a hydrogen atom (H ⁺⁾ is chemically adsorbed to the oxygen atom (O), further the hydroxyl - water molecules and in the air a hydrogen atom (H ^{+) (OH)} Exerts hydrophilicity by physical adsorption.

[0014] In the above description, it is apparent that the decomposition and hydrophilization effect of a substance is completely different, if Shimese concrete examples, TiO ₂ anatase even TiO ₂ oxidation-reduction reaction However, rutile-type TiO ₂ shows almost no decomposition action of the substance based on the redox reaction. Also, among the photocatalysts, tin oxide does not show a decomposition effect of a substance based on a redox reaction. In these photocatalyst particles, the energy level of the conduction band is not sufficiently high, so that the reduction reaction does not proceed. As a result, the electrons excited by the photoexcitation in the conduction band become excessive, and the electron-hole pairs generated by the photoexcitation are oxidized and reduced. It is believed that they recombine without participating in the reaction. However, both rutile TiO ₂ and tin oxide exhibit a hydrophilizing action. Further, the photocatalytic layer needs to have a thickness of at least 100 nm in order to exhibit the decomposing action of the substance, but it is possible for the photocatalytic layer to exhibit a hydrophilizing action if it has a thickness of several nm or more. From these facts, it can be said that the decomposition action of the substance by the photocatalyst and the hydrophilization action are completely different.

As described above, the decomposition action of the substance by the photocatalyst is caused by the electron-hole pair generated by photoexcitation, and when the surface layer containing such photocatalyst comes into contact with water containing iron ions. , Causes a photoreduction reaction of iron that can occur by transfer of less electrons, and the member is colored. That is, the redox action of the photocatalyst particles has an advantage of decomposing the dirt component, but has a disadvantage of coloring the member.

Therefore, in the antifouling member according to the present invention, a surface layer composed of photocatalyst particles or a surface layer containing photocatalyst particles is formed on the surface, and this surface layer has an energy higher than the band gap energy of the photocatalyst particles. When the surface of the photocatalyst has a bandgap energy of 2 ppm by immersing the member in water containing 2 ppm of iron ions, the surface of the photocatalyst exhibits hydrophilicity when it is exposed to light and the photoreduction capacity of the surface layer is represented by a color difference change (ΔE). ΔE ≦ 1 when light of higher energy is irradiated at a cumulative photon density of 8 × 10 ¹⁹ / cm ^{2 under the} condition that the photon density per unit time is 1 × 10 ¹⁵ / sec · cm ^2. I did it.

One of the means for suppressing the photoreduction ability is to reduce the amount of photocatalyst per unit area. As described above, the redox reaction and the hydrophilization action of the photocatalyst are different actions. A large amount of photocatalyst particles per unit area is required for the redox reaction, but the hydrophilization action is exhibited even with a small amount of photocatalyst particles. It For this reason, the content of photocatalyst particles is preferably 10 μmol / cm ² or less per unit area. By doing so, only the hydrophilizing action can be selected.

As another means for suppressing the photoreduction ability,
For example, at least one of alkali metal, alkaline earth metal, alumina, silica, zirconia, antimony oxide, amorphous titanium oxide, hydrous titanium oxide, aluminum, and manganese is added to the surface layer itself, or a base layer of the surface layer. Alternatively, it is added to the coating layer formed on the surface layer.

In the present invention, the change in color difference (ΔE) was selected as an index showing how much the photoreduction ability was suppressed. Specifically, the member is immersed in water containing 2 ppm of iron ions, and light having an energy higher than the band gap energy of the photocatalyst particles is applied to the surface layer at a photon density (p) of 1 × 10 ¹⁵ / sec. · cm ² become the condition, color difference change when the 8 × 10 ¹⁹ / cm ² were irradiated with integrated photon density (P) (ΔE) was set to be 1 or less.

Here, the photon density (p) per unit time is expressed by p = (Aλ) / (hc).
Where A is ultraviolet illuminance (W / cm ² ), λ is ultraviolet wavelength (cm), h is Planck's constant, and c is speed of light (cm / se).
c) If there is a wavelength distribution, p = Σ (Ai · λi) /
It is represented by (h · c). However, Ai is the illuminance of the wavelength λi.

On the other hand, the integrated photon density (P) is P =
It is represented by (A · λ · t) / (h · c). However, t
Is the irradiation time (sec) of ultraviolet rays. When there is a wavelength distribution, p = Σ (Ai · λi · t) / (h · c)
Is represented by

Titanium oxide is most preferable as the photocatalyst particles, but in addition to this, ZnO, SnO ₂ , SrTiO ₃ ,
Examples thereof include metal oxides such as WO ₃ , Bi ₂ O ₃ and Fe ₂ O ₃ . Since metal elements and oxygen exist on the surface of these, it is considered that hydroxyl groups (OH −) are easily adsorbed on the surface and therefore hydrophilicity is easily exhibited.

As a method of forming a hydrophilic surface layer containing photocatalyst particles, taking titania (titanium oxide) as an example, the formation of amorphous titania, the application of silica-containing titania, the application of tin oxide-containing titania, the inclusion of titania Examples thereof include application of silicone paint.

The formation of amorphous titania is a method in which the surface to be coated is first coated with amorphous titania and then fired to change the phase to crystalline titania, and any of the following methods can be adopted. . (1) Hydrolysis and dehydration condensation polymerization of an organic titanium compound An alkoxide of titanium, for example, tetraethoxytitanium, tetraisopropoxytitanium, tetra-n-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, or a hydrochloride such as hydrochloric acid or ethylamine After adding a decomposition inhibitor and diluting with an alcohol such as ethanol or propanol, the mixture is applied after partially or completely promoting the hydrolysis, and then the mixture is applied, and the temperature is from room temperature to 200 ° C. And dry. By drying, the hydrolysis of the alkoxide of titanium is completed to form titanium hydroxide, and a layer of amorphous titania is formed by dehydration-condensation polymerization of titanium hydroxide. Instead of titanium alkoxide,
Other organic titanium compounds such as titanium chelates or titanium acetate may be used. (2) Formation of amorphous titania by inorganic titanium compound Inorganic titanium compound such as TiCl ₄ or Ti (S
Hydrolysis and dehydration polycondensation are performed by applying an acidic aqueous solution of O ₄ ) ₂ and drying at a temperature of 100 to 200 ° C.
Form a layer of amorphous titania. Or it may form a layer of amorphous titania on the surface to be coated by chemical vapor deposition of TiCl _4. (3) Formation of Amorphous Titania by Sputtering A target of metallic titanium or titanium oxide is irradiated with an electron beam in an oxidizing atmosphere to form a layer of amorphous titania on the surface to be coated.

Application of silica-containing titania is to form a layer of a mixture of titania and silica on the surface to be coated. The ratio of silica to the total of titania and silica is 5 to 90 mol%, preferably 10 to 70 mol%, more preferably 10 to 50 mol%. The following method can be employed for forming the surface layer made of silica-containing titania. (1) A suspension containing particles of anatase type or rutile type titania and particles of silica is applied to a surface to be coated, and fired at a temperature equal to or lower than the softening point of the substrate (object to be coated). (2) Based on a mixture of a precursor of amorphous silica (for example, tetraalkoxysilane such as tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, etc.) and crystalline titania sol After applying to the surface of the material and hydrolyzing it as necessary to form silanol, heating at a temperature of about 100 ° C. or more and subjecting the silanol to dehydration polycondensation, the titania is bound with amorphous silica. Obtained surface layer (photocatalytic coating). In particular, if the dehydration condensation polymerization of silanol is performed 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 photocatalytic coating can be improved. (3) Dispersing silica particles in a solution of amorphous titania precursor (organic titanium compound such as alkoxide, chelate or acetate of titanium, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) Is applied to the surface of the base material, and the titanium compound is cooled to room temperature for 20 minutes.
By subjecting it to hydrolysis and dehydration polycondensation at a temperature of 0 ° C.,
A thin film of amorphous titania in which silica particles are dispersed is formed. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate. (4) Amorphous titania precursor (organic titanium compound such as alkoxide, chelate or acetate of titanium, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) in a solution of amorphous titania precursor (For example, tetraalkoxysilanes such as tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, etc., silanols which are hydrolysates thereof, or polysiloxanes having an average molecular weight of 3000 or less) And apply to the surface of the substrate. Next, these precursors are subjected to hydrolysis and dehydration condensation polymerization to form a thin film composed of a mixture of amorphous titania and amorphous silica. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate.

The application of titania containing tin oxide is to form a layer of a mixture of titania and tin oxide on the surface to be coated. The ratio of tin oxide to the total of titania and tin oxide is 1 to 95 mol%, preferably 1 to 50 mol%. The following method can be adopted as a method for forming a surface layer made of titania mixed with tin oxide. (1) A suspension containing particles of anatase type or rutile type titania and particles of tin oxide is applied to a surface to be coated, and fired at a temperature equal to or lower than the softening point of the substrate (object to be coated). (2) Dispersion of tin oxide particles in a solution of a precursor of amorphous titania (organic titanium compound such as titanium alkoxide, chelate or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) The resulting suspension is applied to the surface of the substrate, and the titanium compound is heated to room temperature for 20 minutes.
By subjecting it to hydrolysis and dehydration polycondensation at a temperature of 0 ° C.,
A thin film of amorphous titania in which tin oxide particles are dispersed is formed. Next, the amorphous titania is changed into crystalline titania by heating to a temperature higher than the crystallization temperature of titania and lower than the softening point of the substrate.

The titania-containing silicone coating is applied by using a coating in which titania (photocatalyst particles) is dispersed in a coating film-forming element made of uncured or partially cured silicone (organopolysiloxane) or a precursor of silicone. . Specifically, after the above coating material is applied to the surface of the base material, and after the film-forming element is cured, when the photocatalyst 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 photocatalyst. Then, the contact angle of the surface with water becomes close to 0 °, and the surface becomes hydrophilic (super-hydrophilic). This method can cure the film forming element at a relatively low temperature, and can be applied as many times as necessary,
In addition, there is an advantage that it can be easily made hydrophilic even by sunlight. The following resins can be used as the resin. Methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltri-t-butoxysilane, ethyltrichlorosilane, ethyltribromosilane, ethyltrimethoxysilane, ethyltriethoxysilane, Ethyltriisopropoxysilane, ethyltri-t-butoxysilane, n-propyltrichlorosilane, n-propyltribromosilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltriisopropoxysilane, n-
Propyltri-t-butoxysilane, n-hexyltrichlorosilane, n-hexyltribromosilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-hexyltriisopropoxysilane, n-hexyltrit-butoxysilane, n-decyltrichlorosilane, n-decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n-
Decyltriisopropoxysilane, n-decyltri-t-
Butoxysilane, n-octadecyltrichlorosilane,
n-octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltriisopropoxysilane, n
-Octadecyltri-t-butoxysilane, phenyltrichlorosilane, phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltri-t-butoxysilane, tetrachlorosilane, tetrabromosilane, tetramethoxy Silane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane, dimethyldichlorosilane,
Dimethyldibromosilane, dimethyldimethoxysilane,
Dimethyldiethoxysilane, diphenyldichlorosilane, diphenyldibromosilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenylmethyldichlorosilane, phenylmethyldibromosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, triethoxyhydrosilane , Tribromohydrosilane, trimethoxyhydrosilane, isopropoxyhydrosilane, tri-t-butoxyhydrosilane, vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltrit-butoxysilane, Trifluoropropyltrichlorosilane, trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane , Trifluoropropyltriethoxysilane, trifluoropropyltriisopropoxysilane, trifluoropropyltri-t-butoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycid Xypropyltrimethoxysilane, γ
-Glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxysilane, γ-glycidoxypropyltri-t-butoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldi Ethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-
Methacryloxypropyltri-t-butoxysilane, γ
-Aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropyltrit-butoxysilane , Γ-
Mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltrit-
Butoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and their partial hydrolysates or mixtures thereof can be used. .

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

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1) Ammonia peptization type titanium oxide sol (STS-11 manufactured by Ishihara Sangyo) was applied on the surface of the glazed tile in an amount of 5.6 μmo.
It was applied at 1 / cm ² and baked at 880 ° C.

Example 2 Ammonia deflocculating titanium oxide sol (STS-11 manufactured by Ishihara Sangyo) and silica sol were mixed at a solid content weight ratio of 80:20 on the surface of the glazed tile, and 5.6 μmol of this mixture was added. / Cm ² application, 880 ℃
It was baked in.

Example 3 Ammonia deflocculating titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied on the surface of the glazed tile at 10.0 μmol / cm ² and baked at 880 ° C.

Example 4 11.2 μmol / cm ² of ammonia-peptized titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied to the surface of the glazed tile and baked at 880 ° C. Then, a calcium metal concentration of 5 on the titanium oxide film.
An aqueous calcium nitrate solution of 0 μmol / g was applied to fix calcium.

(Example 5) 11.2 μmol / cm ² of an ammonia-peptizing titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied to the surface of the glazed tile and baked at 880 ° C. Then, potassium was fixed instead of calcium in Example 4.

(Example 6) 11.2 μmol / cm ² of ammonia peptization type titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied to the surface of the glazed tile and baked at 880 ° C. Then, sodium was fixed instead of calcium in Example 4.

(Example 7) 11.2 μmol / cm ² of ammonia peptization type titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied to the surface of the glazed tile and baked at 880 ° C. Then, magnesium was fixed instead of calcium in Example 4.

(Example 8) Ammonia deflocculating titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied on the surface of the glazed tile in an amount of 11.2 µmol / cm ² and baked at 880 ° C. Then, lithium was fixed instead of calcium in Example 4.

(Example 9) 11.2 μmol / cm ² of ammonia-peptized titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied to the surface of the glazed tile and baked at 880 ° C. Then, instead of calcium in Example 4, zinc was fixed.

(Example 10) Ammonia deflocculating titanium oxide sol (STS-11 manufactured by Ishihara Sangyo) was applied to the surface of the glazed tile.
Was applied at 1.0 μmol / cm ² and baked at 880 ° C.

(Comparative Example 1) 11.2 μmol / cm ² of ammonia peptization type titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied to the surface of the glazed tile and baked at 880 ° C.

(Comparative Example 2) 11.2 μmol / cm ² of ammonia peptization type titanium oxide sol (STS-11 manufactured by Ishihara Sangyo Co., Ltd.) was applied on the surface of the glazed tile and baked at 880 ° C. After this, copper acetate is applied and B of 0.5 mW / cm2 is applied.
It was fixed by photoreduction with an LB lamp.

Iron ion colorability (color difference ΔE), contact angle with water, maintainability of contact angle with water in each of the above Examples and Comparative Examples,
The results of the tests for hydrophobic stain removability and hydrophilic stain removability are shown in the following (Table). The iron ion coloring property is 0.5.
The change in color difference was measured before irradiation with the mW / cm ² BLB lamp and after irradiation for 10 days.

[0042]

【table】

[0043]

As described above, according to the present invention, since the surface layer containing the photocatalyst particles is formed on the surface of the member, the surface layer exhibits hydrophilicity only by being irradiated with ultraviolet rays or the like, and as a result, the member is formed. It is difficult for dirt to adhere to the surface. In addition, the attached dirt can be easily removed by washing with water, and the self-cleaning effect due to rain can be expected. Then, according to the present invention, the amount of the photocatalyst particles added to the surface layer per unit area is limited, or a substance that suppresses the photoreduction ability of the surface layer without inhibiting the hydrophilicity of the photocatalyst is added. In addition, hydrophilicity can be maintained while preventing coloration due to reaction with iron ions.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a process of imparting hydrophilicity to the surface of a silicone resin containing photocatalyst particles.

FIG. 2 is a diagram illustrating a process of imparting hydrophilicity to a surface layer made of photocatalytic particles.

Claims (6)

[Claims] 1. A surface layer comprising photocatalyst particles or a surface layer containing photocatalyst particles is formed on the surface of a member, and the surface layer is hydrophilic by irradiating with light having an energy higher than the bandgap energy of the photocatalyst particles. And the photoreduction ability of the surface layer is represented by a color difference change (ΔE), 2p
By immersing the member in water containing iron ions of pm, the surface layer is irradiated with light having an energy higher than the band gap energy of the photocatalyst particles at a photon density of 1 × 10 ¹⁵ / se.
8 × 10 in integrated photon density under the condition of c · cm ^2.
An antifouling member, wherein ΔE ≦ 1 when irradiated with ¹⁹ / cm ² . 2. The antifouling member according to claim 1,
The antifouling member, wherein the photocatalyst particles are titanium oxide, and the light having energy higher than the bandgap energy of the photocatalyst particles is ultraviolet rays having a wavelength of 400 nm or less. 3. The antifouling member according to claim 1 or 2, wherein the antifouling member contains a substance that inhibits the photoreduction ability of the surface layer without inhibiting the hydrophilicity of the surface layer. An antifouling member characterized by being added. 4. The antifouling member according to claim 3,
The substance that suppresses the photoreduction ability of the surface layer is at least one of alkali metal, alkaline earth metal, alumina, silica, zirconia, antimony oxide, amorphous titanium oxide, hydrous titanium oxide, aluminum and manganese. An antifouling member characterized by. 5. The antifouling member according to claim 3 or 4, wherein the substance that suppresses the photoreduction ability of the surface layer is added to the surface layer itself, or an underlayer or surface of the surface layer. An antifouling member, which is added in a coating layer formed on a layer. 6. The antifouling member according to claim 1, wherein the content of the photocatalyst particles in the surface layer is 10 μmol / cm ² or less per unit area. Element.