Photocatalitic hydrophilic coating composition

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention has a coating composition in which the surface of the coating film exhibits a high degree of hydrophilicity in response to irradiation with light having a wavelength at which the photocatalytic particles can be excited by applying or spraying the coating film on a transparent substrate. Regarding things. More specifically, by highly hydrophilicizing the surface of a mirror, glass, lens, prism or other transparent base material, anti-fog for forming a coating film capable of preventing fogging or formation of water droplets on the base material. Regarding sex paint compositions. The present invention can also prevent the surface from becoming dirty or clean the surface with water by making the surface of buildings, windowpanes, machinery, vehicles and articles highly hydrophilic. The present invention relates to an easy-to-clean coating composition for forming a coating film. The present invention also relates to an easily drying coating composition for forming a coating film capable of accelerating the drying of adhered water droplets by making the surface of an automobile body or the like highly hydrophilic.

【0002】

[Conventional technology]

It is often experienced that the windshields and windows of automobiles and other vehicles, the windows of buildings, the lenses of eyeglasses, and the cover glass of various instrument panels become cloudy with condensed moisture in cold weather. It is also common to see the mirrors and eyeglass lenses in bathrooms and washrooms become cloudy with steam. The surface of the article becomes cloudy because when the surface is placed at a temperature below the dew point of the atmosphere, the moisture in the atmosphere condenses and condenses on the surface. If the condensed water droplets are fine enough and their diameter is about half the wavelength of visible light, the water droplets scatter the light, the glass and mirrors become apparently opaque, and visibility is lost. If the condensation of the wet matter progresses further and the fine condensed water droplets fuse with each other to grow into larger discrete water droplets, the surface will be squeezed by the refraction of light at the interface between the water droplets and the surface and the interface between the water droplets and the air. Blurred or cloudy. As a result, the perspective image is distorted and the transparency is lowered in a transparent article such as glass, and the reflected image is disturbed in a mirror. In addition, when the windshield and window glass of vehicles, window glass of buildings, back mirrors of vehicles, lenses of eyeglasses, masks and helmet shields are exposed to rainfall and spray, and a large number of scattered water droplets adhere to the surface, they. The surface of the glass is frosted, blurred, or cloudy, and also loses visibility. The term "anti-fog" used here broadly means a technique for preventing such optical damage due to fogging, growth of condensed water droplets, and adhesion of water droplets. Needless to say, anti-fog technology has a profound effect on safety and efficiency of various tasks. For example, if the windshield, window glass, or back mirror of a vehicle becomes cloudy or holds, the safety of the vehicle or traffic will be impaired. Fogging of endoscopic lenses and dental dentistry interferes with accurate diagnosis, surgery, and treatment. If the cover glass of the instrument panel becomes cloudy, it becomes difficult to read the data.

【0003】

On the other hand, in the field of construction and paint, pollution of building exterior materials, outdoor buildings and their coating films has become a problem due to environmental pollution. Dust and particles floating in the atmosphere accumulate on the roof and outer walls of buildings in fine weather. Sediment is washed away by rainwater as it rains, and flows down the outer wall of the building. Furthermore, in rainy weather, floating dust is carried by the rain and flows down the outer walls of buildings and the surface of outdoor buildings. As a result, contaminants adhere to the surface along the rainwater path. When the surface dries, striped stains appear on the surface. Dirt on building exterior materials and coatings consists of combustion products such as carbon black and pollutants of inorganic substances such as urban dust and clay particles. It is thought that such diversity of pollutants complicates antifouling measures (Yoshinori Tachibana, "Test Method for Accelerating Contamination of Exterior Wall Finishing Materials", Architectural Institute of Japan, Structural Papers, No. 404, October 1989, p.15-24). Conventional wisdom has been that water-repellent paints such as polytetrafluoroethylene (PTFE) are preferable to prevent stains on the exterior of buildings, but recently, urban dust containing a large amount of hydrophobic components. Therefore, it is considered that the surface of the coating film should be made as hydrophilic as possible (Polymer, Vol. 44, May 1995, p.307). Therefore, the hydrophilic graft polymer- It has been proposed to paint the building in (Newspaper "Chemical Industry Daily", January 30, 1995). According to reports, this coating film exhibits hydrophilicity of 30 to 40 ° in terms of contact angle with water. However, the contact angle of inorganic dust represented by clay minerals with water is 20 to 50 °, and it has an affinity for graft polymers with a contact angle of 30 to 40 ° with water, and its surface. It is considered that the coating film of this graft polymer cannot prevent stains due to inorganic dust because it easily adheres to the clay.

【0004】

[Problems to be Solved by the Invention]

An object of the present invention is to provide a hydrophilic coating composition capable of forming a coating film capable of making a surface highly hydrophilic and maintaining the surface. Another object of the present invention is to provide a hydrophilic coating composition having excellent dispersion stability. Another object of the present invention is to provide a hydrophilic coating composition which can easily realize transparent and uniform coating. Another object of the present invention is to provide a hydrophilic coating composition which has a certain degree of adhesiveness and is easy to peel off so that a user can easily re-form a coating film. Another object of the present invention is to provide a hydrophilic coating composition that can be realized by applying a coating film having the above properties at room temperature, drying the coating film, and irradiating light having a specific wavelength as needed.

【0005】

Another object of the present invention is to provide an anti-fog coating composition capable of forming a semi-permanent anti-fog coating film. Another object of the present invention is to provide an antifogging coating composition having excellent dispersion stability. Another object of the present invention is to provide an antifogging coating composition which can easily realize coating without impairing the transparency of the substrate. Another object of the present invention is to provide an antifogging coating composition which prevents reflection by a coating film and has excellent visible light transmission. Another object of the present invention is to provide an antifogging coating composition which has a certain degree of adhesiveness and is easy to peel off so that a user can easily re-form a coating film. Another object of the present invention is to provide an antifogging coating composition that can be realized by applying a coating film having the above properties at room temperature, drying the coating film, and irradiating light of a specific wavelength as necessary. is there.

【0006】

Another object of the present invention is to provide an easy-to-clean coating composition capable of forming a semi-permanent easy-to-clean coating film. Another object of the present invention is to provide an easy-to-clean coating composition having excellent dispersion stability. Another object of the present invention is to provide an easy-to-clean coating composition capable of easily realizing coating without impairing the transparency of the substrate. Another object of the present invention is to provide an easy-to-clean coating composition which prevents reflection by a coating film and has excellent visible light transmission. Another object of the present invention is to provide an easy-to-clean coating composition which has a certain degree of adhesiveness and is easy to peel off so that a user can easily re-form a coating film. Another object of the present invention is to provide an easy-to-clean coating composition which can be realized only by applying a coating film having the above-mentioned properties at room temperature, drying the coating film, and irradiating light of a specific wavelength as necessary. is there.

【0007】

Another object of the present invention is to provide an easy-to-dry coating composition capable of forming a semi-permanent easy-drying coating film. Another object of the present invention is to provide an easy-to-dry coating composition having excellent dispersion stability. Another object of the present invention is to provide an easily drying coating composition capable of easily realizing coating without impairing the transparency of the substrate. Another object of the present invention is to provide an easy-to-dry coating composition which prevents reflection by a coating film and has excellent visible light transmission. Another object of the present invention is to provide an easy-to-dry coating composition which has a certain degree of adhesiveness and is easy to peel off so that a user can easily re-form a coating film. Another object of the present invention is to provide an easy-to-dry coating composition which can be realized by applying and drying a coating film having the above-mentioned properties at room temperature and irradiating light of a specific wavelength as needed. is there.

【0008】

[Means for solving problems]

The present invention is based on the discovery that when a photocatalyst is photoexcited in a substrate on which a surface layer containing a photocatalyst is formed, the surface of the substrate becomes highly hydrophilic. This phenomenon is considered to proceed by the mechanism shown below. That is, when the photocatalyst is irradiated with light having an energy equal to or greater than the energy gap between the upper end of the valence band and the lower end of the conduction band of the photocatalyst, the electrons in the valence band of the photocatalyst are excited to generate conduction electrons and holes. It is produced, and the action of either or both imparts polarity (possibly electron attraction) to the surface. As a result, the chemical bond with the pollutant chemically adsorbed on the surface is broken, water is chemically adsorbed, and a physically adsorbed aqueous layer is formed on the water layer to increase the amount. As a result, the surface becomes highly hydrophilic with a water wetting angle of 5 ° or less.

【0009】

The present invention provides a photocatalytic hydrophilic coating composition composed of photocatalytic particles made of a metal oxide, a dispersant containing almost no hydrophobic functional groups, and a solvent. By containing the dispersant in the constituent elements, it is possible to provide an antifogging coating composition having excellent dispersion stability, and at the same time, it is possible to form a uniform coating film. Here, since the dispersant also appears on the surface of the coating film, from the viewpoint of forming a hydrophilic surface from the initial stage of the coating film, a dispersant containing almost no hydrophobic functional groups, more preferably silica or It is preferable that it is a silicon-based dispersant such as tetraalkoxysilane which is a precursor thereof, an alkylsilicate having a structure similar to that of silica, or a silicate compound such as water glass. In addition, since the surface of the coating film contains almost no hydrophobic functional groups, the coating film exhibits hydrophilicity from the initial stage of the coating film only by applying and drying at room temperature, and exhibits hydrophilicity in response to photoexcitation of the photocatalyst. Will be obtained. When the dispersant is a silicon-based dispersant, the following effects are further added. That is, since the silicon-based dispersant has water storage, the contact angle with water does not easily increase even when left in a dark place, and a high degree of hydrophilicity can be maintained for a long time, and the light that excites the photocatalyst is emitted for a short time. It becomes hydrophilic just by irradiating it. By containing the solvent in the constituent elements, it is possible to provide an antifogging coating composition having excellent dispersion stability, and at the same time, it is possible to form a uniform coating film. Further, the film thickness of the coating film can be controlled according to the amount. Here, the solvent is preferably alcohol or water.

【0010】

In a preferred embodiment of the present invention, the average crystallite diameter of the photocatalytic particles is 100 nm or less. By setting the average crystallite diameter of the photocatalytic particles to 100 nm or less, it is possible to prevent devitrification of the base material due to scattering by visible light particles when forming a coating film, and at the same time, adhesion to the base material due to the surface energy possessed by the photocatalyst particles Will be able to be secured to some extent. However, since this energy-based bonding does not have the strength of a bond based on a curing polymerization reaction or a sintering reaction, it is possible to ensure ease of peeling so that the user can easily re-form the coating film.

【0011】

In a preferred embodiment of the present invention, the weight of the solvent with respect to 1 part by weight of the photocatalyst particles is 100 parts by weight or more and less than 10,000 parts by weight, more preferably 100 parts by weight or more and 1000 parts by weight or less. The present invention is based on the discovery of the fact that the photocatalytic surface hydrophilization reaction is essentially different from the conventionally known photocatalytic redox reactions. That is, in the conventional redox reaction using a photocatalyst, for example, as described in JP-A-8-164334, the redox effect is not exhibited unless the solid content concentration in the liquid is 5% or more, whereas the surface using a photocatalyst is used. In the hydrophilization reaction of, the weight of the solvent with respect to 1 part by weight of the photocatalyst particles is 10,000 parts by weight, that is, the weight of the solvent with respect to 1 part by weight of the photocatalyst particles exceeds about 0.01% in the solid content concentration of titanium oxide in the liquid, more preferably 1000 parts by weight. The hydrophilic effect is exhibited in parts by weight, that is, at a concentration of titanium oxide solids in the liquid of about 0.1%. By reducing the weight of the solvent to 1 part by weight of the photocatalyst particles to less than 10000 parts by weight, more preferably 1000 parts by weight or less, a thin film exhibiting a high degree of hydrophilicity can be easily formed. By setting the weight of the solvent with respect to 1 part by weight of the photocatalyst particles to 100 parts by weight or more, it becomes possible to prevent devitrification of the base material due to scattering by visible light particles. Therefore, by reducing the weight of the solvent to 1 part by weight of the photocatalyst particles to 100 parts by weight or more and less than 10,000 parts by weight, it becomes possible to form a transparent and uniform thin film exhibiting a high degree of hydrophilicity by photoexcitation of the photocatalyst.

【0012】

In a preferred embodiment of the present invention, an antibacterial metal or a compound thereof is further included. As a result, antibacterial properties are exhibited at the same time as anti-fog properties.

【0013】

In a preferred embodiment of the present invention, the photocatalytic particles are anatase-type titanium oxide. Anatase-type titanium oxide is preferable because a sol in which very fine fine particles are dispersed can be easily obtained by a hydrothermal method or the like.

【0014】

In a preferred embodiment of the present invention, a substance having a refractive index of 2 or less is further added. By setting the refractive index of the added substance to 2 or less, it is possible to prevent reflection of visible light by the coating film when the coating film is formed.

【0015】

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the components of the present invention will be described. The photocatalytic particles made of metal oxides referred to here are those that form an adsorbed aqueous layer by imparting polarity to the surface by a reaction via holes or conduction electrons generated by the excitation of electrons in the valence band. , A material that can make the surface of the base material hydrophilic, more specifically, anatase-type titanium oxide, rutile-type titanium oxide, tin oxide, zinc oxide, dibismuth trioxide, tungsten trioxide, ferric oxide. , Strontium titanate, etc. can be used.

【0016】

Dispersants containing almost no hydrophobic functional groups include dispersants containing no hydrophobic functional groups such as silica, alkyl silicate, water glass, phosphoric acid, and sodium phosphate, and tetramethoxysilane, tetraethoxysilane, and tetra. Dispersants that do not contain hydrophobic side chains with more than 4 carbon atoms, such as propoxysilane, tetrabutoxysilane, methacrylic acid, acetic acid, sodium methacrylate, sodium polycarboxylic acid, ammonium methacrylate, ammonium polycarboxylic acid, polyethylene glycol, etc. Including both.

【0017】

As the solvent, water, ethanol, propanol, butanol, pentanol, ethylene glycol and the like can be preferably used.

【0018】

The average crystallite diameter of the photocatalyst particles is a value obtained by obtaining the integral width of the strongest peak of the photocatalyst crystal obtained by the powder X-ray diffraction method and calculating it by the Sherah equation.

【0019】

The silicon-based dispersant is a dispersant containing Si, and includes methyl silicate, ethyl silicate, water glass, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane, silica and the like. It can be preferably used.

【0020】

Antibacterial metal or its compound refers to silver, copper, zinc and compounds containing those metals (silver nitrate, copper nitrate, zinc nitrate, copper acetate, silver chloride, copper chloride, zinc chloride, silver phosphate, etc.). ..

【0021】

Substances with a refractive index of 2 or less include silica (refractive index 1.5), tin oxide (1.9), calcium carbonate (1.6), calcium hydroxide (1.6), magnesium carbonate (1.5), and strontium carbonate (1.5). ), Dolomite (1.7), Calcium Fluoride (1.4), Magnesium Fluoride (1.4), Alumina (1.6), Silica (1.6), Zeolite (1.5), Montmorillonite (1.5), Kaolin (1.6), sericite (1.6), ferric oxide (1.8), yttrium oxide (1.9) and the like can be preferably used.

【0022】

As shown in PCT / JP96 / 00733, if the surface of the substrate is 10 ° or less, more preferably 5 ° or less in terms of contact angle with water, moisture and steam in the air will condense. Even so, the tendency of the condensed water to form a uniform water film without forming individual water droplets becomes remarkable. Similarly, when windowpanes, vehicle back mirrors, vehicle windshields, eyeglass lenses, and helmet shields are exposed to rainfall or splashes, they are highly visible and visible without the formation of scattered, obtrusive water droplets. The effect of ensuring the sexuality, guaranteeing the safety of vehicles and traffic, and improving the efficiency of various tasks and activities is dramatically improved. Similarly, as shown in PCT / JP96 / 00733, if the surface of the base material is 10 ° or less, more preferably 5 ° or less in terms of contact angle with water, urban dust and automobiles Combustion products such as carbon black contained in exhaust gas such as carbon black, hydrophobic pollutants such as oils and fats and sealant elution components, and inorganic clay pollutants are difficult to adhere to, and even if they adhere, it will cause rainfall. It can be easily removed by washing with water.

【0023】

If the surface of the member exhibits the above-mentioned high degree of hydrophilicity and maintains that state, in addition to the above-mentioned antifogging effect and surface cleaning effect, a drying promoting effect, an antistatic effect, a dust adhesion preventing effect, and a heat insulating effect, The effect of preventing bubble adhesion in water, the effect of improving efficiency in a heat exchanger, the effect of improving biocompatibility, etc. will be exhibited.

【0024】

The base material to which the present invention can be applied is a transparent base material when an antifogging effect is expected, and glass, plastic, or the like can be preferably used as the material. Applicable substrates include bathroom or washroom mirrors, vehicle back mirrors such as door mirrors and fender mirrors in automobiles and back mirrors in motorcycles, dental dentistry, road mirrors, etc. Mirrors; spectacle lenses, optical lenses, camera lenses, copying machine lenses, endoscopic lenses, lighting lenses, semiconductor manufacturing lenses, vehicle rear-view camera lenses-like lenses; prisms; of buildings and surveillance towers Window glass; window glass for vehicles such as automobiles, railroad vehicles, aircraft, ships, submersibles, snow vehicles, ropeway gondola, amusement park gondola, spacecraft; automobiles, railroad vehicles, aircraft, ships, submersibles Windshields for vehicles such as snow vehicles, snow vehicles, auto-buy, ropeway gondola, amusement park gondola, spacecraft; protective or sports goggles or masks (for diving) Shield (including mask); Helmet shield; Glass for frozen food display case, Glass for display case of heat-retaining food such as Chinese buns; Cover of measuring equipment, Rear confirmation camera lens for vehicles Covers, lasers, focusing lenses for dental treatment devices, inter-vehicle distance sensors, etc. lasers-light detection sensors-covers, infrared sensors-covers, camera filters-and their article surfaces Includes films, sheets, seals, etc. that can be attached to.

【0025】

As a base material to which the present invention can be applied, when a cleaning effect is expected, the material thereof is, for example, metal, ceramic, glass, plastic, wood, stone, cement, concrete, fiber, cloth, and the like. Combinations of these, and their laminates can be preferably used. Applicable base materials include building materials, building exteriors, building interiors, window frames, windowpanes, structural members, vehicle exteriors and paints, machinery and article exteriors, dustproof covers and paints, traffic signs, etc. Various display devices, advertising towers, signs, sound insulation walls for roads, sound insulation walls for railways, bridges, exterior and painting of guard rails, tunnel interior and painting, porcelain, solar cell cover, solar water heater heat collector cover, vinyl -Le House, vehicle lighting cover, housing equipment, toilet bowl, tub, wash basin, lighting equipment, lighting cover-, kitchen utensils, tableware, dishwasher, dish dryer, sink, cooking range, kitchen hood , Ventilation fan, and films, sheets, seals, etc. that can be attached to the surface of the article.

【0026】

When the drying promoting effect is expected as the base material to which the present invention can be applied, the materials thereof are, for example, metal, ceramic, glass, plastic, wood, stone, cement, concrete, fiber, cloth, and the like. Combinations and laminates thereof can be preferably used. Applications of applicable substrates include automobile bodies, windows, pavements, and films, sheets, seals, etc. that can be attached to the surface of the article.

【0027】

When the antistatic effect is expected as the base material to which the present invention can be applied, the materials thereof are, for example, metal, ceramic, glass, plastic, wood, stone, cement, concrete, fiber, cloth, and the like. Combinations of these, and their laminates can be preferably used. Applicable base materials include brown tubes, magnetic recording media, optical recording media, optical magnetic recording media, audio tapes, video tapes, analog records, OHP sheets, household electrical products. Housing, parts, exterior and painting, housing, parts, exterior and painting of OA equipment products, building materials, building exterior, building interior, window frame, window glass, structural members, exterior and painting of vehicles, exterior of machinery and articles , Dustproof cover and coating, and films, sheets, seals, etc. that can be attached to the surface of the above-mentioned articles.

【0028】

The hydrophilic coating composition is used as a spray agent, wax or paint for imparting antifogging property to the transparent substrate.

【0029】

The above hydrophilic coating composition is applied to a base material by a method such as spray, roll printing, gravure printing, sponge impregnation coating, float, transfer, etc., and the surface is made hydrophilic by photoexcitation of a photocatalyst. Let me use it. Here, the photocatalyst is photoexcited by irradiating the photocatalyst with light having an energy larger than the energy gap between the conduction electron band and the valence band of the photocatalyst crystal (that is, a short wavelength). More specifically, when the photocatalyst is anatase-type titanium oxide, the wavelength is 387 nm or less, when the photocatalyst is rutile-type titanium oxide, the wavelength is 413 nm or less, when tin oxide is used, the wavelength is 344 nm or less, and when zinc oxide is used. Irradiate light containing light with a wavelength of 387 nm or less. In the case of the above photocatalyst, since it is photoexcited by an ultraviolet light source, the light source is a fluorescent lamp, an incandescent lamp, a metal halide lamp, indoor lighting such as a mercury lamp, sunlight, or a low-loss fiber for those light sources. An induced light source or the like can be used. The illuminance of light required to photoexcitate the photocatalyst, which is required to make the coating film surface hydrophilic, is 0.001 mW / cm.² Above, more preferably 0.01 mW / cm²That is all.

【0030】

[Example]

Example 1. (Effect of silicon-based dispersant and solvent ratio) Photocatalytic sol (manufactured by Ishihara Sangyo, ST-K01, solid content 10% by weight, solid content consists of 8 parts by weight of anatase-type titanium oxide and 2 parts by weight of alkyl silicate), further 10 times with ethanol, 100 It was diluted 5-fold and 1000-fold to obtain # 1 sample, # 2 sample, and # 3 sample, respectively. These samples were left for 3 days, but no aggregation was observed. Samples # 1 to 3 were applied to a 10 cm square soda lime glass substrate and dried at room temperature for 18 hours. As a result, a transparent and uniform coating film was obtained in all of the # 1 to 3 samples. However, interference fringes were also observed in the coating film obtained with the # 1 sample. Next, the ultraviolet illuminance of 0.25 mW / cm was applied to the coating film obtained from each of the # 1 to 3 samples.²The light source (Sankyo Denki, BLB (black light bull) fluorescent lamp) was irradiated for 1 hour, and the antifogging property of the coating film was measured thereafter. The evaluation criteria for measurement are shown below. : It does not become cloudy even if you blow on it. : It becomes a little cloudy when you blow on it, but the transmitted image is clearly visible. Δ: When blown, the transmitted image becomes cloudy to the extent that the transmitted image cannot be clearly seen, although it is not as much as the base glass. ×: When blown, it becomes cloudy like the base glass. As a result, it was in the # 1 sample and the # 2 sample, and × in the # 3 sample. Next, for the # 1 sample and the # 2 sample, the ultraviolet illuminance of 025 mW / cm was applied to the coating film obtained for each.² The contact angle of the coating film surface with water was measured after irradiating the light source (Sankyo Denki, BLB (black light bull) fluorescent lamp) for 1 hour. The contact angle with water was examined by using a contact angle measuring device (Kyowa Interface Science, CA-X150) and measuring 30 seconds after dropping water droplets on the sample surface from a microsyringe. As a result, both the # 1 sample and the # 2 sample were superhydrophilicized to 0 ° at the contact angle with water. Next, for the # 1 sample, the adhesiveness of the coating film to the substrate and the ease of peeling from the substrate were evaluated. Here, the adhesiveness to the substrate was evaluated by the number of times until peeling occurred by sliding with a Kimwipe soaked in water. On the other hand, the ease of peeling from the base material was evaluated by the number of slides until the coating film was completely peeled off when sliding with a plastic eraser. Each test was performed 3 times. As a result, regarding the adhesiveness to the base material, peeling did not occur even after sliding 20 times. On the other hand, regarding the ease of peeling from the base material, the coating film was completely peeled off after a few sliding times. The following can be seen from the above experimental facts. (1) Titanium oxide sol ST-K01 in which anatase-type titanium oxide having a particle size of about 20 nm is dispersed by a silicon-based dispersant (alkyl silicate), and the weight of the solvent is 10,000 parts by weight with respect to 1 part by weight of titanium oxide particles. By diluting to less than, more preferably 1000 parts by weight or less, it becomes hydrophilic to 5 ° or less in terms of contact angle with water, and exhibits excellent antifogging property. (2) A transparent and uniform coating film was produced by using the titanium oxide sol ST-K01 in which anatase-type titanium oxide having a particle size of about 20 nm was dispersed with a silicon-based dispersant (alkyl silicate). (3) Titanium oxide sol ST-K01 in which anatase-type titanium oxide having a particle size of about 20 nm is dispersed with a silicon-based dispersant (alkyl silicate), and the weight of the solvent is 100 parts by weight with respect to 1 part by weight of titanium oxide particles. By diluting as described above, the appropriate adhesiveness of the coating film to the substrate and the ease of peeling from the substrate were exhibited. (4) By using titanium oxide sol ST-K01 in which anatase-type titanium oxide having a particle size of about 20 nm was dispersed with a silicon-based dispersant (alkyl silicate), it was left for 3 days, but no aggregation was observed. It showed good dispersibility.

【0031】

Example 2. (Effect of copper) To 10 g of a photocatalytic sol (manufactured by Ishihara Sangyo, ST-K01, solid content 10% by weight), 100 μl of a copper sulfate aqueous solution having a copper concentration of 1 g / liter was added, and the mixture was further diluted 100-fold with etanol. Although this diluted solution was left to stand for 3 days, no aggregation was observed and good dispersibility was shown. Therefore, even if copper, which is an antibacterial metal, is added, the performance as a coating liquid does not change, and it is considered that it can be used in the same manner as in Example 1.

【0032】

Example 3. (Effect of silica) Titanium oxide sol (Nissan Chemical Industries, Ltd., TA-15) was diluted with ethanol to obtain a coating solution having a concentration of titanium oxide particles of 0.5% by weight. On the other hand, after mixing silica sol (Nippon Synthetic Rubber, Glasca A solution) with titanium oxide sol (Nissan Chemical Industries, Ltd., TA-15), dilute with ethanol, the concentration of titanium oxide particles is 0.5% by weight, and the concentration of silica particles is 0.5. A coating solution of% by weight was obtained. Each coating solution was applied to a 10 cm square soda lime glass substrate, held at 50 ° C. for 1 hour, and allowed to cool for 15 minutes to obtain # 4 sample and # 5 sample, respectively. When observing the coatings of the # 4 and # 5 samples, the # 4 sample had strong visible light reflectivity and felt glaring, while the # 5 sample had almost no visible light reflectivity and was good. It showed excellent visible light transmission. For # 4 and # 5 samples, UV illuminance of 0.25 mW / cm²The light source (BLB fluorescent lamp) was irradiated for 2 hours, and then the antifogging property of the coating film was measured. As a result, all the samples showed good anti-fog property as . From the above, it was found that by adding silica having a refractive index lower than that of titania, it exhibits excellent antifogging property while maintaining the visible light transmittance of the surface.

【0033】

Example 4. (Effect of surfactant type) Titanium oxide sol (Nissan Chemical Industries, Ltd., TA-15) is mixed with silica sol (Nippon Synthetic Rubber, Glasca A solution) and diluted with ethanol to make titanium oxide particles 0.5% by weight and silica particles 0.5% by weight. The coating liquid of was obtained. Titanium oxide sol (Nissan Chemical Industries, Ltd., TA-15) is mixed with silica sol (Nippon Synthetic Rubber, Grasca A solution) and polyethylene glycol (molecular weight 3000) as a surfactant, diluted with ethanol, and titanium oxide. A coating liquid having a particle concentration of 0.5% by weight, a silica particle concentration of 0.5% by weight, and a polyethylene glycol concentration of 0.2% by weight was obtained. Titanium oxide sol (Nissan Kagaku, TA-15) is mixed with silica sol (Nippon Synthetic Rubber, Grasca A solution) and modified silicone (Shinetsu Kagaku, KF-351, polyester type) as a surfactant, and then etano. Diluted with a solution to obtain a coating liquid having a concentration of titanium oxide particles of 0.5% by weight, a concentration of silica particles of 0.5% by weight, and a concentration of modified silicone particles of 0.2% by weight. On the other hand, after mixing titanium oxide sol (Nissan Kagaku, TA-15) with silica sol (Nippon Synthetic Rubber, Glasca A solution) and modified silicone (Shinetsu Kagaku, KF-945, polyester type) as a surfactant. , Diluted with ethanol to obtain a coating liquid having a concentration of titanium oxide particles of 0.5% by weight, a concentration of silica particles of 0.5% by weight, and a concentration of modified silicone particles of 0.2% by weight. Each coating solution was applied to a 10 cm square soda lime glass substrate, held at 50 ° C. for 1 hour, and allowed to cool for 15 minutes to obtain # 6 to # 8 samples, respectively. For # 6 to # 9 samples, UV illuminance of 0.25 mW / cm² The light source (BLB fluorescent lamp) was irradiated, and the change in the antifogging property of the coating film with respect to the irradiation time was measured. The results are shown in Figure 1. As a result, the # 6 sample showed good anti-fog property in 2 hours, whereas the # 7 sample showed good anti-fog property in 3 hours, and the # 8 sample showed 4 hours. It takes more than 20 hours for the # 9 sample, and it can be seen that the more a surfactant having a strong influence on the hydrophobic part is added, the more ultraviolet rays must be irradiated in order to show antifogging property.

【0034】

Example 5. (Application to automobile side mirror) Photocatalyst sol (manufactured by Ishihara Sangyo, ST-K01, solid content 10% by weight, solid content consists of 4 parts by weight of anatase-type titanium oxide and 1 part by weight of alkyl silicate) and photocatalyst sol (manufactured by Ishihara Sangyo) , ST-K03, solid content 10% by weight, solid content consists of 1 part by weight of anatase type titanium oxide and 1 part by weight of alkyl silicate) Mix 1 part by weight and dilute further 20 times with isopropanol. Then, a # 10 sample was obtained. After impregnating the non-woven fabric with # 10 sample, it was applied to the side mirror of an automobile (Nissan Motor, Sani) on October 25, 1996. At the same time, a commercially available water-repellent coating agent (manufactured by Kinnodo, Superrain X) was applied to the remaining half of the automobile side mirror in the same manner. After that, it was used every day in Kayagasaki for about 2 months. When not in use, such as at night, the car was parked in a garage with no roof and poor sunlight. When water was sprayed on December 24, 1996, polka-dot-like water droplets remained on the surface coated with the water-repellent coating, whereas the water spread uniformly on the surface coated with the # 10 sample. No water droplets could be confirmed by. In addition, when comparing the appearance, rain streak stains became noticeable on the water-repellent coat coating surface from around the end of November, about one month later, while on the # 10 sample coating surface, noticeable stains. Was not observed.

【0035】

Example 6. (Application to automobile side window glass) After impregnating the non-woven fabric with the # 10 sample of Example 5, it was applied to the outer half surface of the side window glass of an automobile (Nissan Motor Co., Ltd.) on October 25, 1996. At the same time, a commercially available water-repellent coating agent (manufactured by Kinnodo, Super Rain X) was similarly applied to the remaining half of the outside of the side window glass of the automobile. After that, it was used every day in Kayagasaki for about 2 months. When not in use, such as at night, the car was parked in a garage with no roof and poor sunlight. When water was sprayed on December 24, 1996, polka-dot-like water droplets remained on the surface coated with the water-repellent coating, whereas the water spread uniformly on the surface coated with the # 10 sample. No water droplets could be confirmed by. In addition, when comparing the appearance, rain streak stains became noticeable on the water-repellent coat coating surface from around the end of November, about one month later, while on the # 10 sample coating surface, noticeable stains. Was not observed.

【0036】

Example 7. (Application to automobile rear glass) After impregnating the non-woven fabric with the # 10 sample of Example 5, it was applied to the outer half surface of the rear glass of an automobile (Nissan Motor Co., Ltd., Sani) on October 25, 1996. At the same time, a commercially available water-repellent coating agent (manufactured by Kinnodo, Superrain X) was similarly applied to the remaining half of the outer surface of the rear glass of the automobile. After that, it was used every day near Kayagasaki for about 2 months. When not in use, such as at night, the car was parked in a garage with no roof and poor sunlight. When water was sprayed on December 24, 1996, polka-dot-like water droplets remained on the surface coated with the water-repellent coating, whereas the water spread uniformly on the surface coated with the # 10 sample. No water droplets could be confirmed by. In addition, when comparing the appearance, rain streaks became noticeable on the water-repellent coating surface from around the end of November, about one month later, while on the # 10 sample-coated surface, the stains became noticeable. Was not observed.

【0037】

Example 8. (Application to automobile body) Photocatalytic sol (manufactured by Ishihara Sangyo, ST-K01, solid content 10% by weight, solid content consists of 4 parts by weight of anatase-type titanium oxide and 1 part by weight of alkyl silicate) is further increased by 20 times with isopropanol. Dilution gave # 11 sample. The # 11 sample was applied to the vertical surface of the passenger seat side of an automobile (Nissan Motor Co., Ltd., Sani) on December 8, 1996 by the spray coating method. At the same time, a commercially available solid wax was applied to adjacent positions. When showering was applied to the entire vehicle immediately after application, polka dot-like water droplets remained on the solid wax application surface, whereas the water spread uniformly on the # 11 sample application surface and could be visually confirmed. Was not recognized. After that, when the # 11 sample-coated surface was left to stand for a while, the solid wax-coated surface was observed, but it was observed that polka-dot-shaped water droplets still remained. It rained on December 10, 1996, and the next day (sunny), after the car body dried, each coated surface was observed. As a result, polka dot-like stains were observed on the solid wax-coated surface, whereas such stains were not observed on the # 11 sample-coated surface.

【0038】

Example 9. (Application to Carb Mira) The # 11 sample of Example 8 was applied to an acrylic carve mirror on December 8, 1996 by the spray coating method. When water was sprayed immediately after application, the water spread uniformly on the # 11 sample application surface, and no visually recognizable water droplets were observed.

【0039】

[Effect of the invention]

According to the present invention, a transparent and uniform coating film can be formed while maintaining excellent dispersion stability of the coating composition, and the surface of the coating film can be permanently kept hydrophilic.

[Simple explanation of drawings]

[Figure 1]

The figure which shows the change of the antifogging property of a coating film with respect to the ultraviolet irradiation time which concerns on Example of this invention.