Member capable of obtaining hydrophilic nature in accordance with photoexcitation of optical semiconductor and manufacturing method thereof

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a technique for making the surface of a substrate highly hydrophilic and maintaining it. More specifically, the present invention prevents the surface from becoming dirty by highly hydrophilicizing the surface of buildings, windowpanes, machinery, and articles, or self-cleans or easily cleans the surface. Regarding the technology to do.

【0002】

[Conventional technology]

When the surface of the base material is hydrophilized, the adhered water droplets spread uniformly on the surface of the base material, so that combustion products such as carbon black contained in the exhaust gas of urban dust and automobiles, fats and oils, and sealants are eluted. Hydrophobic pollutants such as components do not easily adhere, and even if they adhere, they can be easily removed by rainfall or washing with water, which is convenient.

【0003】

Under these circumstances, hydrophilic resins have been conventionally proposed, especially in the field of exterior antifouling paints (for example, Jitsukaihei 5-68006, "Polymer", Vol. 44, May 1995, p. .307). In addition, a surface treatment method for hydrophilization has also been proposed (for example, Jitsukaihei 3-129357).

【0004】

However, the previously proposed hydrophilic resin is hydrophilic only up to about 30 to 50 ° in terms of contact angle with water, and the adhesion of pollutants made of inorganic clay, rainfall, and cleanliness by washing with water are sufficient. Not. Further, in the conventionally proposed surface treatment method for hydrophilization (etching treatment, plasma treatment, etc.), even if it can be temporarily highly hydrophilized, the state cannot be maintained for a long period of time.

【0005】

In PCT / JP96 / 00733, the present inventor invented that when an optical semiconductor-containing layer is formed on the surface of a base material, the surface becomes highly hydrophilic in response to photoexcitation of the optical semiconductor, and this technique is applied to glass. It has been proposed that when applied to various composite materials such as lenses, mirrors, exterior materials, and water-related members, these composite materials can be provided with excellent antifogging and antifouling functions. According to this method, adhesion of pollutants composed of hydrophobic pollutants and inorganic clays, precipitation, and cleanliness by washing with water are dramatically improved. In addition, the hydrophilic state is maintained and restored in response to the photoexcitation of the photosemiconductor.

【0006】

[Problems to be Solved by the Invention]

However, when a layer made of only an optical semiconductor having substantially excellent abrasion resistance is directly applied to a substrate having a smooth surface such as a glazed tile substrate or a glass substrate by the optical semiconductor sol coating method and fired. Is not hydrolyzed to about 10 ° or less in response to photoexcitation of the photosemiconductor. Further, for example, in order to form a layer made of only photosemi-conducting titanium oxide on a glass substrate, an amorphous titanium oxide layer is formed by an alkoxide method, a sputtering method or the like, and then fired to crystallize the amorphous titanium oxide. If it is a method of making it hydrophilic, it will be hydrophilic to about 10 ° or less according to the photoexcitation of the optical semiconductor, but in this case as well, it is thought that higher antifogging and antifouling performance will be exhibited if the hydrophilicity is further advanced. Be done. Therefore, in the present invention, as compared with a layer made of only an optical semiconductor, a member that becomes more highly hydrophilic in response to photoexcitation of the optical semiconductor, more specifically, more pollutants are less likely to adhere and precipitation occurs. It is an object of the present invention to provide an antifouling member having excellent cleanliness by washing with water and a member having a surface that is easier to dry.

【0007】

[Means for solving problems]

In the present invention, in order to solve the above problems, in order to solve the above-mentioned problems, in a hydrophilic member, an antifogging member, an antifouling member, and an easy-to-dry member whose surface is made hydrophilic in response to photoexcitation of an optical semiconductor, A layer containing an opto-semiconductor and at least one selected from one group of alkali metals, alkaline earth metals, zinc, aluminum, ruthenium, alumina, zirconia, ceria, and itria was formed. In a preferred embodiment of the present invention, the surface of the member is hydrophilized to 10 ° or less, more preferably 5 ° or less in terms of contact angle with water in response to photoexcitation of the photosemiconductor. By doing so, it becomes a member which is dramatically excellent in the adhesion prevention property of pollutants and the cleanliness by rainfall and washing with water.

【0008】

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the components of the present invention will be described. The photosemiconductor referred to here refers to the surface of a base material by forming an adsorbed aqueous layer, probably by imparting polarity to the surface by a reaction via holes or conduction electrons generated by excitation of electrons in the valence band. Refers to those that can be made hydrophilic, and more specifically, anatase-type titanium oxide, rutile-type titanium oxide, tin oxide, zinc oxide, dibismuth trioxide, tungsten trioxide, ferric oxide, strontium titanate, etc. are used. it can.

【0009】

The term "hydrophilicization" as used herein refers to a change in a state in which water wettability is improved. Combustion products such as carbon black contained in exhaust gas of urban dust and automobiles, and hydrophobic pollutants such as oils and fats and sealant elution components are hard to adhere, and even if they adhere, they can be easily removed by rainfall or washing with water. In order to do so, the surface of the base material should be hydrophilized to about 50 ° or less, more preferably about 30 ° or less in terms of the contact angle with water. Furthermore, in order to prevent inorganic clay pollutants from adhering, and to make it easy to remove by rainfall or washing with water, the surface of the base material should be 20 ° or less, preferably 10 °, in terms of contact angle with water. Below, it is more preferable to make it hydrophilic to about 5 ° or less.

【0010】

The base material that can be used in the present invention includes, for example, metals, ceramics, glass, plastics, wood, stones, cement, concrete, fibers, fabrics, papers, and combinations thereof in outdoor applications where self-purification due to rainfall can be expected. These laminates, their coatings, etc. More specifically, building exteriors such as exterior walls and roofs; window frames; exteriors and paintings of vehicles such as automobiles, railroad vehicles, aircraft, ships, bicycles, motorcycles; windowpanes; signs, traffic signs, soundproof walls, Vinyl house, glass, vehicle cover, tent material, reflector, window door, net door, solar cell cover, heat collector cover such as solar water heater, street light, roof, outdoor lighting, artificial waterfall / artificial fountain stone / Tiles, bridges, greenhouses, exterior wall materials, wall-to-wall and glass sealers, guard rails, verandas, vending machines, air conditioner outdoor units, outdoor benches, various display devices, shutters, toll booths, toll boxes, roof gutters, vehicle lamps. Includes protective covers, dustproof covers and paints, paints on machinery and articles, exteriors and paints on billboards, structural members, and films that can be attached to those articles.

【0011】

As the base material that can be used in the present invention, for applications that can be expected to be cleaned by washing with water, for example, metals, ceramics, glass, plastics, wood, stones, cement, concrete, fibers, fabrics, papers, combinations thereof, and their combinations. Laminates, their coatings, etc. More specifically, in addition to the above-mentioned outdoor use members, building interior materials, window glass, housing equipment, toilet bowls, bathtubs, washstands, lighting fixtures, kitchen utensils, tableware, tableware dryers, etc. Includes sinks, cooking ranges, kitchen hoods, ventilators, window rails, window frames, tunnel interior walls, tunnel interior lighting, and films that can be attached to these items.

【0012】

The base material that can be used in the present invention includes, for example, window sashes, heat exchanger fins, sashes, bathroom mirrors, vanities, greenhouse ceilings, and their articles in applications that can be expected to promote drying. Includes affixable films and the like.

【0013】

In addition to the above, the base material that can be used in the present invention can be used for preventing snow accretion, preventing bubble adhesion, improving biocompatibility, and the like. Snow accretion prevention is particularly excellent when a surface layer with a surface roughness of 1 μm or less is provided. For example, a group containing a roofing material for snowy countries, an antenna, a power transmission line, a film that can be attached to those articles, and the like. Applicable to materials.

【0014】

Photoexcitation of an optical semiconductor is performed by irradiating the optical semiconductor with light having an energy (that is, a short wavelength) larger than the energy gap between the conduction electron band and the valence band of the optical semiconductor crystal. More specifically, when the optical semiconductor is anatase-type titanium oxide, the wavelength is 387 nm or less, when rutyl titanium oxide is 413 nm or less, when tin oxide is 344 nm or less, and when zinc oxide is zinc oxide, the wavelength is 387 nm or less. Irradiate with light rays containing the following light. In the case of the above-mentioned optical semiconductor, since it is photoexcited by an ultraviolet light source, the light sources include fluorescent lamps, incandescent lamps, metal halide lamps, indoor lighting such as mercury lamps, sunlight, and those light sources are guided by low-loss fibers. You can use the light source etc. The illuminance of light required to photoexcite an optical semiconductor, which is required to make the surface of a composite material hydrophilic, is 0.001 mW / cm.²Above, more preferably 0.01 mW / cm²That is all.

【0015】

In the present invention, when alumina or yttria is selected as a substance to be added to the surface of the base material other than the optical semiconductor, 0.01 mW / cm.²Hydrophilicity retention under weak excitation light irradiation of less than less than or in a dark place will be better exhibited.

【0016】

Further, in a more preferable embodiment of the present invention, silica and / or a silicone resin in which at least a part of the organic group bonded to the silicon atom is replaced with a hydroxyl group is further added to the photosemiconductor-containing layer. To do so. By doing so, the hydrophilicity of the surface of the composite material generated in response to the photoexcitation of the photosemiconductor becomes higher, and the hydrophilicity is maintained for a long period of time even when the once hydrophilic composite material is left in a dark place. Will be done.

【0017】

The film thickness of the optical semiconductor-containing layer is preferably 0.2 μm or less. By doing so, it is possible to prevent color development of the optical semiconductor-containing layer due to light interference. Further, the thinner the film thickness of the optical semiconductor-containing layer, the more transparent the base material can be ensured. Further, if the film thickness is reduced, the wear resistance of the optical semiconductor-containing layer is improved. A wear-resistant or corrosion-resistant protective layer or other functional film that can be hydrophilized may be further provided on the opto-semiconductor-containing layer.

【0018】

The refractive index of the optical semiconductor-containing layer should be smaller than or not so large as that of the base material. For example, when the base material is a glass base material (refractive index 1.5), the refractive index of the optical semiconductor-containing layer is preferably 2 or less. By doing so, it is possible to prevent reflection of visible light on the surface of the composite material, which is useful for ensuring visibility in the transparent material and preventing glare in the design exterior or painting. To reduce the refractive index of the optical semiconductor-containing layer to 2 or less, for example, when the optical semiconductor is a substance having a refractive index exceeding 2 such as anatase-type titanium oxide (refractive index 2.5), the refractive index is 2 in addition to the optical semiconductor. Add less than a substance. As a substance having a refractive index of less than 2, for example, alumina (refractive index 1.6), silica (refractive index 1.5), tin oxide (refractive index 1.9), and at least a part of organic groups bonded to silicon atoms are replaced with hydroxyl groups. Silicone resin (refractive index 1.4 to 1.6) can be preferably used.

【0019】

There are the following methods for forming a layer containing an optical semiconductor and other metals such as alkali metal, alkaline earth metal, zinc, aluminum, platinum, palladium, and ruthenium on the surface of the base material. (1) After forming the optical semiconductor particle layer on the surface of the base material, the above metal-containing material is applied and dried and fixed. (2) After forming the optical semiconductor particle layer on the surface of the base material, the above metal-containing material is applied, and the metal is reduced and fixed by photoexcitation of the optical semiconductor. (3) Photo-semiconductor particles and the above metal-containing material are applied to the surface of the base material and then fired. (4) After applying the photo-semiconductor particles, the metal-containing material, and a curable binder that can be made hydrophilic by photoexcitation of the photo-semiconductor on the surface of the substrate, the curable binder is cured, and further photo-excitation of the photo-semiconductor Makes the binder hydrophilic.

【0020】

Examples of the method for forming the optical semiconductor particle layer include a sol coating firing method, an alkoxide method, and a sputtering method. The sol coating and firing method is a method in which an optical semiconductor sol is applied to a substrate surface by a spray coating, spin coating, dip coating, roll coating, flow coating or other coating method and fired. The alkoxide method is, for example, when the optical semiconductor is crystalline titanium oxide, the alkoxide of titanium (for example, tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium) is added to hydrochloric acid. Alternatively, a hydrolysis inhibitor such as ethylamine is added, diluted with a diluent such as ethanol or propanol, and then the mixture is spray-coated with partial or complete hydrolysis. It is applied to the surface of the substrate by spin coating, dip coating, roll coating, flow coating or other coating method and dried to form an atypical titanium oxide layer, and then atypical titanium oxide is fired to form an anatase type titanium oxide. Alternatively, it is a method of converting to rutile type titanium oxide. Instead of titanium alkoxide, other organic titanium compounds such as titanium chelate or titanium acetate may be used. In the sputtering method, for example, when the optical semiconductor is crystalline titanium oxide, metallic titanium or titanium oxide is targeted, an amorphous titanium oxide layer is formed on the surface of the base material in an oxygen atmosphere, and then the amorphous titanium oxide is formed by firing. This is a method for converting titanium oxide into anatase-type titanium oxide or rutile-type titanium oxide.

【0021】

The metal-containing substance is, for example, a metal compound such as alkali metal, alkaline earth metal, zinc, aluminum, platinum, palladium, or ruthenium (lithium chloride, sodium nitrate, potassium chloride, magnesium chloride dihydrate, calcium nitrate, chloride. A solution containing strontium hexahydrate, zinc chloride, aluminum chloride, platinum chloride hexahydrate, palladium chloride, ruthenium chloride hydrate, etc.) as a solute.

【0022】

Examples of the curable binder that can be hydrophilized by photoexcitation of the photo-semiconductor include silicone resin, organosilanol that becomes a silicone resin by dehydration polycondensation, and organoalkoxysilane that becomes a silicone resin by hydrolysis / dehydration polycondensation. .. The method of hydrophilizing the binder can be performed by photoexcitation of a photosemiconductor.

【0023】

There are the following methods for forming a layer containing an optical semiconductor and other oxides such as alumina, zirconia, ceria, and yttria on the surface of the base material. (5) Photo-semiconductor particles and the above oxide are applied to the surface of the base material and then fired. (6) After coating the precursor of the optical semiconductor and the above oxide on the surface of the base material, the precursor of the optical semiconductor is converted into the optical semiconductor by a method such as firing. (7) After applying the photo-semiconductor particles, the above oxide, and a curable binder that can be made hydrophilic by photoexcitation of the photo-semiconductor on the surface of the substrate, the curable binder is cured, and further by photo-excitation of the photo-semiconductor. Hydrolyzes the binder.

【0024】

The precursor of the optical semiconductor is, for example, when the optical semiconductor is crystalline titanium oxide, an alkoxide of titanium (for example, tetraethoxytitanium, tetraisopropoxytitanium, tetran-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium). , Titanium chelate or other organic titanium compounds such as titanium acetate may be used. Converting the precursor of an optical semiconductor to an optical semiconductor means that when the optical semiconductor is crystalline titanium oxide, it is converted to anatase-type titanium oxide or rutile-type titanium oxide by processes such as hydrolysis, dehydration polycondensation, and firing. The method.

【0025】

[Example]

Comparative Example 115 cm square glazed tile (manufactured by Toto, AB02E01) was coated with ammonia-freezing type titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) by spray coating method and fired at 800 ° C. A sample was obtained. The film thickness of the titanium oxide layer at this time was set to 0.3 μm. The contact angle of the sample surface immediately after firing with water was measured with a contact angle measuring device (manufactured by Kyowa Interface Science, model CA-X150). The contact angle was measured 30 seconds after dropping water droplets on the sample surface from the microsyringe. The contact angle of the sample surface with water immediately after firing was 8 °. When this sample was left in a dark place for 1 week and then the contact angle of the sample surface with water was measured again, it increased to 21 °. This rise is considered to be due to the detachment of adsorbed water from the sample surface and the adhesion of pollutants in the atmosphere. Ultraviolet illuminance 0.3mW / cm for this sample²After irradiating with the BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) for 2 days, the contact angle with water was measured. As a result, the sample surface became hydrophilic only up to 15 ° in response to photoexcitation.

【0026】

Example 1 (calcium addition, post-addition) A titanium oxide layer-coated glazed tile sample having a film thickness of 0.3 μm was obtained in the same manner as in Comparative Example 1. After applying 0.3 g of calcium nitrate aqueous solution with calcium metal concentration of 50 μmol / g to the surface of this sample, 0.4 mW / cm²A sample was obtained by irradiating the BLB fluorescent lamp of the above for 10 minutes. The contact angle of the sample surface with water immediately after preparation of this sample was 38 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 22 °. Furthermore, this sample has an ultraviolet illuminance of 0.3 mW / cm.²After irradiating with the BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 5 ° in response to photoexcitation.

【0027】

Example 2 (calcium addition, mixed addition) Ammonia sinter type titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) 18 g and calcium nitrate aqueous solution 27 g with a calcium metal concentration of 77 μmol / g are mixed and applied to the surface of a 15 cm square glazed tile by a spray coating method. Then, it was calcined at 800 ° C to obtain a sample. The film thickness of the titanium oxide layer at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after preparation of this sample was 22 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 25 °. Furthermore, this sample has an ultraviolet illuminance of 0.15 mW / cm.²After irradiating with the BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 8 ° in response to photoexcitation.

【0028】

Example 3 (potassium addition, post-addition) A titanium oxide layer-coated glazed tile sample having a film thickness of 0.3 μm was obtained in the same manner as in Comparative Example 1. After applying 0.3 g of potassium chloride aqueous solution with a potassium metal concentration of 50 μmol / g to the surface of this sample, 0.4 mW / cm²A sample was obtained by irradiating the BLB fluorescent lamp of the above for 10 minutes. The contact angle of the sample surface with water immediately after preparation of this sample was 37 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 27 °. Furthermore, this sample has an ultraviolet illuminance of 0.15 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 8 ° in response to photoexcitation.

【0029】

Example 4 (addition of sodium, post-addition) A titanium oxide layer-coated glazed tile sample having a film thickness of 0.3 μm was obtained in the same manner as in Comparative Example 1. After applying 0.3 g of sodium nitrate aqueous solution with a sodium metal concentration of 50 μmol / g to the surface of this sample, 0.4 mW / cm²A sample was obtained by irradiating the BLB fluorescent lamp of the above for 10 minutes. The contact angle of the sample surface with water immediately after preparation of this sample was 37 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 26 °. Furthermore, this sample has an ultraviolet illuminance of 0.3 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 7 ° in response to photoexcitation.

【0030】

Example 5 (sodium addition, mixed addition) Ammonia sinter type titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) 18 g and 27 g sodium nitrate aqueous solution with a sodium metal concentration of 77 μmol / g are mixed and applied to the surface of a 15 cm square glazed tile by a spray coating method. Then, it was calcined at 800 ° C to obtain a sample. The film thickness of the titanium oxide layer at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after preparation of this sample was 17 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 22 °. Furthermore, this sample has an ultraviolet illuminance of 0.15 mW / cm.²After irradiating with the BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 6 ° in response to photoexcitation.

【0031】

Example 6 (magnesium addition, post-addition) A titanium oxide layer-coated glazed tile sample having a film thickness of 0.3 μm was obtained in the same manner as in Comparative Example 1. After applying 0.3 g of magnesium chloride dihydrate aqueous solution with magnesium metal concentration of 50 μmol / g to the surface of this sample, 0.4 mW / cm²A sample was obtained by irradiating the BLB fluorescent lamp of the above for 10 minutes. The contact angle of the sample surface with water immediately after preparation of this sample was 37 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 22 °. Furthermore, this sample has an ultraviolet illuminance of 0.3 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 8 ° in response to photoexcitation.

【0032】

Example 7 (magnesium addition, mixed addition) 18 g of ammonia deflated titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) and 27 g of magnesium chloride dihydrate aqueous solution with sodium metal concentration of 77 μmol / g are mixed and spray-coated on the surface of a 15 cm square glazed tile. And fired at 800 ° C to obtain a sample. The film thickness of the titanium oxide layer at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after preparation of this sample was 20 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 25 °. Furthermore, this sample has an ultraviolet illuminance of 0.15 mW / cm.²After irradiating with the BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 7 ° in response to photoexcitation.

【0033】

Example 8 (addition of lithium, post-addition) A titanium oxide layer-coated glazed tile sample having a film thickness of 0.3 μm was obtained in the same manner as in Comparative Example 1. After applying 0.3 g of a lithium chloride aqueous solution with a lithium metal concentration of 50 μmol / g to the surface of this sample, 0.4 mW / cm²A sample was obtained by irradiating the BLB fluorescent lamp of the above for 10 minutes. The contact angle of the sample surface with water immediately after preparation of this sample was 36 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 28 °. Furthermore, this sample has an ultraviolet illuminance of 0.3 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 8 ° in response to photoexcitation.

【0034】

Example 9 (Zinc addition, post-addition) A titanium oxide layer-coated glazed tile sample having a film thickness of 0.3 μm was obtained in the same manner as in Comparative Example 1. After applying 0.3 g of zinc chloride aqueous solution with zinc metal concentration of 50 μmol / g to the surface of this sample, 0.4 mW / cm²A sample was obtained by irradiating the BLB fluorescent lamp of the above for 10 minutes. The contact angle of the sample surface with water immediately after preparation of this sample was 43 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 23 °. Furthermore, this sample has an ultraviolet illuminance of 0.15 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 8 ° in response to photoexcitation.

【0035】

Example 10 (addition of strontium, post-addition) A titanium oxide layer-coated glazed tile sample having a film thickness of 0.3 μm was obtained in the same manner as in Comparative Example 1. After applying 0.3 g of an aqueous solution of strontium chloride hexahydrate having a strontium metal concentration of 50 μmol / g on the surface of this sample, 0.4 mW / cm²A sample was obtained by irradiating the BLB fluorescent lamp of the above for 10 minutes. The contact angle of the sample surface with water immediately after preparation of this sample was 33 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 23 °. Furthermore, this sample has an ultraviolet illuminance of 0.3 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 7 ° in response to photoexcitation.

【0036】

Example 11 (Strontium addition, mixed addition) 18 g of ammonia deflated titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) and 27 g of strontium chloride hexahydrate aqueous solution with a strontium metal concentration of 77 μmol / g are mixed and spray-coated on the surface of a 15 cm square glazed tile. And fired at 700 ° C to obtain a sample. The film thickness of the titanium oxide layer at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after preparation of this sample was 8 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 14 °. Furthermore, this sample has an ultraviolet illuminance of 0.15 mW / cm.²After irradiating with the BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 5 ° in response to photoexcitation.

【0037】

Example 12 (ruthenium addition, mixed addition) 18 g of ammonia-freezing titanium oxide sol (manufactured by Ishihara Sangyo Co., Ltd., STS-11) and 27 g of ruthenium chloride hydrate aqueous solution with a ruthenium metal concentration of 77 μmol / g are mixed and spray-coated on the surface of a 15 cm square glazed tile. And fired at 700 ° C to obtain a sample. The film thickness of the titanium oxide layer at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after preparation of this sample was 15 °. When this sample was left in a dark place for one week and then the contact angle of the sample surface with water was measured again, it was 18 °. Furthermore, this sample has an ultraviolet illuminance of 0.15 mW / cm.²After irradiating with the BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) for 0.2 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 7 ° in response to photoexcitation.

【0038】

Example 13 (Aluminum addition, mixed addition) Ammonia deflated titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) and an aqueous solution of aluminum chloride with an aluminum metal concentration of 50 μmol / g are mixed so that the molar ratio of titanium oxide to the amount of aluminum metal is 87:13. , A 15 cm square glazed tile surface was coated by a spray coating method and fired at 700 ° C to obtain a sample. The film thickness of the titanium oxide layer at this time was set to 0.7 μm. The contact angle of the sample surface with water immediately after preparation of this sample was 11 °. When this sample was left in a dark place for one day and then the contact angle of the sample surface with water was measured again, it was 13 °. Furthermore, this sample has an ultraviolet illuminance of 0.15 mW / cm.²After irradiating with the BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) for 1 day, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 3 ° in response to photoexcitation.

【0039】

Example 14 (addition of yttria) Titanium oxide sol (manufactured by Ishihara Sangyo Co., Ltd., CS-N) and yttrium oxide sol (manufactured by Taki Chemical Co., Ltd., solute concentration 15% by weight, average crystallite diameter 4 nm, pH 7.6) are combined with titanium oxide. After mixing so that the molar ratio with yttrium oxide was 88:12, it was applied to the surface of a 15 cm square glazed tile by a spray coating method and baked at 800 ° C. for 1 hour to obtain a sample. The film thickness at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after firing was 21 °. The obtained sample was left in the dark for 2 weeks. After that, when the contact angle of the sample surface with water was measured again, it was 25 °. After that, the ultraviolet illuminance is 0.3 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 13 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 2 ° in response to photoexcitation. After that, the ultraviolet illuminance is 0.004 mW / cm.²The white light of No. 1 was irradiated for 4 days, and the hydrophilicity retention under indoor lighting was examined. As a result, the sample surface was maintained at about 9 °.

【0040】

Example 15 (Alumina added) Titanium oxide sol (manufactured by Ishihara Sangyo Co., Ltd., CS-C) and aluminum oxide sol (manufactured by Nissan Chemical Industries, Ltd., alumina sol-100) were mixed so that the molar ratio of titanium oxide and aluminum oxide was 88:12. After that, it was applied to the surface of a 15 cm square glazed tile by a spray coating method, and baked at 800 ° C. for 1 hour to obtain a sample. The film thickness at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after firing was 2 °. The obtained sample was left in the dark for 2 weeks. After that, when the contact angle of the sample surface with water was measured again, it was 20 °. After that, the ultraviolet illuminance is 0.3 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 13 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 2 ° again in response to photoexcitation. After that, the ultraviolet illuminance is 0.004 mW / cm.²The white light of No. 1 was irradiated for 2 days, and the hydrophilicity retention under indoor lighting was examined. As a result, the sample surface was maintained at about 9 °.

【0041】

Example 16 (addition of zirconia) Ammonia glutinous titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) and zirconium oxide sol, manufactured by Insan Kagaku, NZS-30B) were mixed so that the molar ratio of titanium oxide to zirconium oxide was 88:12. After that, it was applied to the surface of a 15 cm square glazed tile by a spray coating method and fired at 800 ° C. for 1 hour to obtain a sample. The film thickness at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after firing was 23 °. The obtained sample was left in the dark for 1 week. After that, when the contact angle of the sample surface with water was measured again, it was 35 °. After that, the ultraviolet illuminance is 0.3 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 13 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 4 ° in response to photoexcitation.

【0042】

Example 17 (addition of ceria) After mixing ammonia-freezing titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) and cerium oxide sol (manufactured by Taki Chemical Co., Ltd. W-15) so that the molar ratio of titanium oxide and cerium oxide is 88:12. , A 15 cm square glazed tile surface was coated by a spray coating method and baked at 800 ° C. for 1 hour to obtain a sample. The film thickness at this time was set to 0.3 μm. The contact angle of the sample surface with water immediately after firing was 22 °. The obtained sample was left in the dark for 1 week. After that, when the contact angle of the sample surface with water was measured again, it was 38 °. After that, the ultraviolet illuminance is 0.3 mW / cm.²After irradiating the sample with the BLB fluorescent lamp for 13 days, the contact angle with water was measured. As a result, the sample surface was hydrophilized to 6 ° in response to photoexcitation.

【0043】

Example 18 (Relationship between contact angle with water and antifouling property) Various samples were subjected to the sludge test shown below. The samples examined are the # 1 to # 6 samples shown below. # 1 Sample: A mixture of anatase-type titanium oxide sol (manufactured by Ishihara Sangyo, STS-11) and colloidal silica sol (Snowtex 20) (silica ratio in solid content is 10% by weight) is only 4.5 mg in terms of solid content, 15 cm. It was applied to a square glazed tile (manufactured by Toto, AB02E01) and fired at a temperature of 880 ° C for 10 minutes to obtain a # 0 sample. 0.5mW / cm for this # 0 sample using a BLB fluorescent lamp²A # 1 sample was obtained by irradiating with ultraviolet rays for 3 hours at the ultraviolet illuminance of. # 2 sample: After applying 0.3 g of a copper acetate monohydrate aqueous solution with a copper concentration of 50 μmol / g to the # 0 sample, 0.4 mW / cm using a BLB fluorescent lamp.²The copper was fixed by irradiating with the ultraviolet illuminance of the above for 10 minutes. After that, 0.5mW / cm using BLB fluorescent lamp²A # 2 sample was obtained by irradiating with ultraviolet rays for 3 hours at the ultraviolet illuminance of. # 3 Sample: Glazed tile (manufactured by Toto, AB02E01). # 4 Sample: Acrylic resin (PMMA) board. # 5 Sample: Artificial marble plate (manufactured by Toto, ML03). # 6 Sample: Polytetrafluoroethylene (PTFE) plate. The sludge test was conducted as follows. First, the sludge slurry was prepared as follows. That is, a powder mixture containing 64.3% by weight of yellow ocher, 21.4% by weight of calcined Kanto loam, 4.8% by weight of hydrophobic carbon black, 4.8% by weight of silica powder, and 4.7% by weight of hydrophilic carbon black was mixed with water at a concentration of 1.05 g / liter. A slurry suspended in was prepared. 150 ml of the above slurry was allowed to flow down and dried for 15 minutes on # 1 to # 6 samples tilted at 45 degrees, and then 150 ml of distilled water was allowed to flow down and dried for 15 minutes, and this cycle was repeated 25 times. The change in color difference and the change in glossiness before and after the test were investigated. The color difference change was determined by subtracting the color difference of the sample surface before the test from the color difference of the sample surface after the test. For the color difference, ΔE * display was used according to Japanese Industrial Standards (JIS) H0201. The glossiness was measured according to the provisions of Japanese Industrial Standards (JIS) Z8741, and the change in glossiness was determined by dividing the glossiness of the sample surface after the test by the glossiness of the sample surface before the test. The results are shown in Table 1.

【0044】

[table 1]

<img file="JP2001089752A_D0001.tif" />【0045】

Furthermore, outdoor fouling acceleration tests were performed on # 1, # 3, # 4, # 6, and # 7 samples shown below. # 7 Sample: Silica sol (manufactured by Japan Synthetic Rubber, Grasca A solution) and trimethoxysilane (manufactured by Japan Synthetic Rubber, Glasca B solution) were mixed on a 10 cm square aluminum substrate so that the weight ratio was 3: 1. A liquid material was applied and cured at 150 ° C. to obtain a silicone-coated plate (# 7 sample) having a thickness of 3 μm. The outdoor dirt acceleration test was conducted as follows. That is, the outdoor dirt acceleration test equipment shown in Fig. 1 (a) and Fig. 1 (b) was installed on the roof of the building located in Chigasaki City. With reference to FIGS. 1 (a) and 1 (b), the device comprises an inclined sample support surface 22 supported by a frame 20 and is adapted to mount the sample 24. A roof 26 that slopes forward is fixed to the top of the frame. The roof is made of corrugated plastic plates, and the collected rain flows down in a streak on the surface of the sample 24 attached to the sample support surface 22. The above # 1, # 3, # 4, # 6, and # 7 samples were attached to the sample support surface 22 of this device and exposed outdoors for one month. The adhesion of dirt in this test tends to cause a large amount of dirt to adhere to the vertical streaks, which are the flow paths in rainy weather. Therefore, the degree of stain on the sample surface was evaluated by subtracting the color difference before the test from the color difference of the vertical streak stain portion after the test. The results are shown in Table 2.

【0046】

[Table 2]

<img file="JP2001089752A_D0002.tif" />【0047】

For ease of understanding, the contact angles and color difference changes with water shown in Tables 1 and 2 are plotted in the graph of FIG. In the graph of Fig. 2, curve A shows the relationship between the color difference change due to combustion products such as carbon black in the atmosphere and dirt such as urban dust in the dirt acceleration test and the contact angle with water, and curve B is the sludge test. The relationship between the color difference change due to sludge and the contact angle with water is shown. As can be clearly seen from the curve A, as the contact angle of the base material with water increases, the contamination by combustion products and urban dust becomes more noticeable, referring to the graph in FIG. This is because pollutants such as combustion products and urban dust are basically hydrophobic and therefore tend to adhere to hydrophobic surfaces. On the other hand, curve B shows that sludge stains peak in the range of 20 ° to 50 ° in contact with water. This is because inorganic substances such as mud and soil originally have hydrophilicity with a contact angle of about 20 to 50 ° with water, and easily adhere to a surface having similar hydrophilicity. Therefore, the surface should be hydrophilic with a contact angle of 20 ° or less with water, or the contact angle with water should be 60 °. It can be seen that if it is made more hydrophobic, it is possible to prevent the adhesion of inorganic substances to the surface. When the contact angle with water is 20 ° or less, the dirt caused by sludge is reduced. When the surface becomes highly hydrophilic with the contact angle with water of 20 ° or less, the affinity for water is more than the affinity for inorganic substances. This is because water that preferentially adheres to the surface hinders the adhesion of inorganic substances, and the inorganic substances that are about to adhere are easily washed away by water. From the above, in order to prevent both hydrophobic and hydrophilic stains from adhering to the surface of buildings, etc., or to prevent the stains accumulated on the surface from being washed away by rainfall and self-cleaning the surface. It can be seen that the contact angle of the surface with water should be 20 ° or less, preferably 10 ° or less, and more preferably 5 ° or less. In all of the above Examples 1 to 17, since the contact angle with water becomes 10 ° or less in response to photoexcitation, it is considered that excellent cleanliness by rainfall or washing with water is exhibited.

【0048】

[Effect of the invention]

By forming a layer containing at least one of alkali metal, alkaline earth metal, zinc, aluminum, ruthenium, alumina, zirconia, ceria, and itria on the surface of the base material in addition to optical semiconductors, a sol coating firing method can be used. Even when an optical semiconductor-containing layer is formed on the surface of the base material, it becomes hydrophilic to 10 ° or less in response to photoexcitation of the optical semiconductor by a light source commonly used in daily life such as sunlight and indoor lighting. Further, even when the optical semiconductor-containing layer is formed on the surface of the base material by a method other than the sol coating firing method, such as an alkoxide method, a sputtering method, or a method using curing of a binder such as silica or silicone, the optical semiconductor is photoexcited. It can be expected that the hydrophilic performance will be improved according to the above.

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows the outdoor dirt acceleration test apparatus, (a) is a front view, (b) is a side view (the unit of dimensional numerical value is millimeter).

[Figure 2]

The figure which shows the degree to which the surface with different hydrophilicity is contaminated by urban dust and sludge.