JP2002284910A - Photocatalytic hydrophilic member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalytic hydrophilic member applicable to an organic substrate without causing the corrosion of the substrate or generating a delamination at the boundary of the substrate and a photocatalytic coating layer and sufficiently durable to the use subjected to the antifogging treatment, cleaning with rain, cleaning by washing with water and acceleration of drying. SOLUTION: The photocatalytic hydrophilic member has a layer comprising antimony-containing tin oxide particles on the surface of a substrate having an organic resin surface. The surface of the layer exhibits a hydrophilicity of <=20 deg. in terms of the contact angle with water according to the photo- excitation of the photocatalyst by the irradiation of solar light or ultraviolet rays of <=10 mW/cm<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrophilic member capable of maintaining a high degree of hydrophilicity by the photoexciting action of a photocatalyst, and more particularly to a photocatalytic hydrophilic member having excellent weather resistance and excellent hydrophilicity in a dark place.

[0002]

2. Description of the Related Art The present inventor has previously proposed a method for highly hydrophilizing the surface of an article by photoexcitation of a semiconductor photocatalyst (WO 96/29375). According to this method,
The surface of the article is coated with a coating of a semiconductor photocatalyst such as an anatase type titanium oxide. This you
When the photocatalytic coating made of titanium oxide is irradiated with ultraviolet light to excite the photocatalyst with sufficient illuminance for a sufficient time, the surface of the photocatalytic coating has a contact angle with water of about 0 degrees. Highly hydrophilized. As disclosed in WO 96/29375,
The photocatalytic coating which can be highly hydrophilized as described above can be applied to various articles for various purposes such as anti-fogging, purification by rainfall, purification by washing, promotion of drying, and the like. For example, when a transparent article such as a windshield of a vehicle, a door mirror, a window glass of a building, a lens of an eyeglass, or a mirror is coated with a photocatalytic coating, the surface of the coating is accompanied by photoexcitation of the photocatalyst. It is highly hydrophilized, so that the article is prevented from fogging with condensed moisture or steam and from being overshadowed by adhering water droplets. Alternatively, when a building or an article placed outdoors is covered with a photocatalytic coating, hydrophobic dust and contaminants adhering to the hydrophilic surface are washed away by rainwater every rainfall and the surface is purified. Is done.

However, anatase-type titanium oxide has a strong redox activity as a photocatalyst and oxidizes and decomposes organic matter. For this reason, after directly applying photocatalytic anatase-type titanium oxide to an organic resin substrate and then irradiating ultraviolet rays such as sunlight, the substrate is eroded or peeling occurs at the interface between the substrate and the anatase-type titanium oxide coating. In some cases.

Accordingly, in order to support anatase-type titanium oxide on a substrate such as an organic resin, a hardly decomposable intermediate layer such as a silica-based binder is provided to protect the substrate, or the anatase-type titanium oxide is coated on the substrate. A method has been adopted in which a hydrophilic silica binder is added, the amount thereof is increased, and the content ratio of anatase type titanium oxide is reduced to suppress the photocatalytic activity.

However, in the method of protecting the substrate by providing the intermediate layer, the number of steps is increased, so that the operation is complicated and the manufacturing cost is increased.

In the method of adding a hydrophilic silica binder to the anatase-type titanium oxide coating and increasing the amount thereof, the presence of the anatase-type titanium oxide on the substrate surface varies, and the anatase-type oxidation occurs. The portion without titanium does not recover hydrophilicity even when irradiated with light, so that there is a problem that the stain remaining on the portion when washed by rainfall or washing with water is rather conspicuous.

On the other hand, tin oxide, which has been conventionally known as a photocatalyst, has a low oxidative decomposition power of organic substances, and when applied to an organic substrate, the substrate is eroded or peels off at the interface between the substrate and the tin oxide coating. Although it does not occur, it has been considered that it is difficult to apply it to antifogging, purification by rainfall, purification by washing, promotion of drying, and the like, because the effect of hydrophilicity by ultraviolet irradiation is weak.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to prevent the substrate from being eroded when applied to an organic substrate, and to prevent delamination at the interface between the substrate and the photocatalyst coating, and to provide an anti-fogging film. It is an object of the present invention to provide a photocatalytic hydrophilic member that can sufficiently withstand application to purification by rainfall, purification by washing with water, promotion of drying, and the like.

In the present invention, in order to solve the above-mentioned problems, a layer containing tin oxide particles containing antimony is formed on the surface of a substrate having an organic resin surface, and the layer is made of sunlight or 10 mW / cm ^2. Provided is a photocatalytic hydrophilic member, wherein the surface of the layer exhibits hydrophilicity of 20 ° or less in terms of a contact angle with water in response to photoexcitation of the photocatalyst by irradiation of ultraviolet rays described below. In this aspect, since tin oxide having a weak oxidative decomposition power is used, the substrate is not eroded, and peeling does not occur at the interface between the substrate and the photocatalyst coating. Further, by containing antimony, it is possible to sufficiently withstand applications to antifogging, purification by rainfall, purification by washing, promotion of drying, and the like. The reason is considered below. Photocatalytic hydrophilic member is anti-fog, purification by rainfall,
Equilibrium is determined by the rate of hydrophilicity by UV irradiation and the rate of hydrophobicity by adsorption of organic substances in air, etc. Is determined by Therefore U
Even if the rate of hydrophilization by V is low, if the rate of hydrophobization can be suppressed, the photocatalytic hydrophilic member can be highly hydrophilized. That is, the hydrophilicity maintenance property in a dark place may be improved. In particular, when using sunlight, it is important to suppress the rate of hydrophobicity in a dark place because ultraviolet light is not radiated at night, and its importance increases in winter when the sunshine time is short. The present inventor has found that, by adding antimony to tin oxide, the rate of hydrophobization can be suppressed without affecting the ability of tin oxide to decompose organic substances and the rate of hydrophilization. Hydroxyl groups on the surface of general tin oxide particles are Lewis bases compared to silicon oxide, so they react quickly with impurities in the air and thus become hydrophobic earlier, but containing antimony suppresses the reaction. It is thought that we can do it.

In a preferred aspect of the present invention, the layer is directly fixed on the surface of the organic resin. By doing so, it is possible to enjoy the above-mentioned effects without increasing the number of steps.

[0011] In a preferred embodiment of the present invention, the content of the tin oxide particles in the layer is 50% by weight or more. By doing so, variation in the manner of existence of tin oxide is less likely to occur, and the photocatalyst is uniformly present on the surface of the organic resin.

In a preferred aspect of the present invention, the content of antimony in the tin oxide particles is 1 to 30% by weight based on the total amount of tin oxide and antimony oxide in terms of the amount of antimony oxide. To When the content is 1% by weight or more, the effect of maintaining hydrophilicity in a dark place based on the addition of antimony is sufficient, and when the content is 30% by weight or less, coloring accompanying the addition of antimony is prevented.

In a preferred aspect of the present invention, the tin oxide particles have a particle size of 20 nm or less, preferably 7 nm.
Hereinafter, it is more desirably 3 nm or less. This is because the smaller the particle size, the stronger and uniform the thin film can be formed.
In particular, when the thickness is 3 nm or less, particles enter fine irregularities on the surface, so that a thin film that cannot be easily peeled off without a binder can be formed.

[0014]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, terms used in the present invention will be described in more detail. In the present invention, the organic resin is, for example, cellulose, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyacrylonitrile, polyacrylamide, polyalcohol, allyl polyacetate, polyoxymethylene, poly-n-butyl. Isocyanate, polyethylene oxide, 6-nylon, poly-β-oxypropionate, phenolic resin, urea resin, melamine resin, alkyd melamine resin, epoxy resin, unsaturated polyester resin, silicone resin having an organic functional group, etc. Is mentioned.

In the present invention, the substrate is an organic resin or a laminate or a coating having an organic resin surface. Speaking of applicable substrates, when anti-fogging and drip-proof effects are expected, transparent organic resins or laminates or coatings having an organic resin surface, specifically, for example, vehicles Rear view mirrors, mirrors for bathrooms, bathroom mirrors, dental mirrors, mirrors such as road mirrors; spectacle lenses, optical lenses, illumination lenses, semiconductor lenses, copier lenses, rear view camera lenses for vehicles Lenses such as; prisms; windows of buildings and watchtowers; windows of vehicles such as cars, railway vehicles, aircraft, ships, submersibles, snowmobiles, gondolas in lowways, gondolas in amusement parks, and spaceships Windshields for vehicles such as cars, motorbikes, railway vehicles, aircraft, ships, submersibles, snowmobiles, snowmobiles, gondolaes in lowways, gondolas in amusement parks, and spaceships; -Guru, Sport-
Goggles for shoes, shield for protective mask, shield for sports mask, shield for helmet, glass for frozen food display case, display case for warm food such as Chinese bun Glass; cover of measuring instrument, cover of camera lens for rear view confirmation, cover lens of laser, dental treatment device, etc., cover of laser light detecting sensor, such as inter-vehicle distance sensor,
Cover of infrared sensor; filter for camera, and film, sheet, or sheet for attaching to the surface of the article
And emblems. When expecting a self-purifying effect by rainfall or washing, specifically, for example, building materials, building exterior, building interior, window frames, window glass, structural members,
Exterior and painting of vehicles, Exterior of machinery and goods, Dust cover and painting, Traffic signs, Various display devices, Advertising towers, Sound insulation walls for roads, Railway sound insulation walls, Bridges, Gard rail exterior and painting, Tunnels Interior and paint, insulators, solar cell cover,
Solar water heater heat collection cover, vinyl house, vehicle lighting cover, housing equipment, toilet bowl, bathtub, wash basin, lighting fixture, lighting cover, kitchenware, tableware, dishwasher, dish dryer, Sinks, cooking ranges, kitchen hoods, ventilation fans, and films, sheets, etc. for attaching to the surface of the article;
Seals, patches and the like. When the drying promotion effect is expected, specifically, for example, an automobile body, a window,
Films, sheets, seals, emblems, and the like for sticking to pavements and the surface of the above-mentioned articles are exemplified. If the surface exhibits the above-mentioned high hydrophilicity and keeps its state, in addition to the anti-fogging effect and the surface cleaning effect, the anti-static effect (dust adhesion preventing effect), the heat insulating effect, the bubbles in water The effect of preventing adhesion, the effect of improving efficiency in the heat exchanger, the effect of improving biocompatibility, and the like are exhibited. When an antistatic effect is expected, specifically, for example, a cathode ray tube, a magnetic recording medium, an optical recording medium, a magneto-optical recording medium, an audio tape, a video tape, and an analog record
Housing, parts, exterior and painting of household electrical appliances, housing, parts, exterior and painting of OA equipment products,
Building materials, building exteriors, building interiors, window frames, window glasses, structural members, vehicle exteriors and coatings, exteriors of machinery and articles, dustproof covers and coatings, and films and sheets for sticking to the surface of the articles And seals, patches and the like.

The contact angle with water is preferably 20 ° or less. By doing so, as disclosed in Example 31 of WO96 / 29375, the self-purifying property by rainfall or washing is improved.

The layer containing tin oxide particles containing antimony according to the present invention can contain arbitrary components in addition to the tin oxide particles. According to a preferred embodiment of the present invention, the composition according to the present invention may comprise a substance having a refractive index of tin oxide of less than 1.9. The addition of a substance with a refractive index of less than 1.9 has the advantage that the reflection of visible light on the applied surface can be effectively prevented. Substances having a refractive index of less than 1.9 that can be added to the composition according to the present invention include:
Silica (refractive index 1.5), calcium carbonate (1.
6), calcium hydroxide (1.6), magnesium carbonate (1.5), strontium carbonate (1.5), dolomite (1.7), calcium fluoride (1.
4), magnesium fluoride (1.4), alumina (1.6), silica sand (1.6), zeolite (1.
5), montmorillonite (1.5), kaolin (1.6), sericite (1.6), ferric oxide (1.8) and the like.

In a preferred embodiment of the present invention, the layer containing tin oxide particles containing antimony according to the present invention may contain an antibacterial metal such as Ag, Cu, Zn or the like and a compound thereof. When the metal is added, the surface layer formed by the coating film can kill bacteria and fungi attached to the surface even in a dark place, and even after application, molds, algae, and moss on the surface. The growth of microorganisms can be suppressed.

The thickness of the surface layer formed by the coating film on the member surface is preferably 0.6 μm or less. Then, cloudiness due to irregular reflection of light can be prevented, and the surface layer becomes substantially transparent. Further, the thickness of the surface layer is set to 0.
It is more preferable that the thickness be 2 μm or less. Then, it is possible to prevent the surface layer from being colored by light interference. Also, the thinner the surface layer, the better its transparency. Furthermore,
When the film thickness is reduced, the wear resistance of the surface layer is improved.

When a thin film containing tin oxide containing antimony is formed on the surface of the member, the surface of the member becomes hydrophilic in response to photoexcitation of tin oxide, which is an optical semiconductor.
Here, in order for the surface of the base material to be highly hydrophilized by photoexcitation of the optical semiconductor, practically, sunlight or 10 mW /
Irradiation with light containing ultraviolet rays of cm ² is sufficient, and the ultraviolet rays hardly adversely affect the organic resin. However, needless to say, even stronger ultraviolet light may be applied by a xenon lamp, a high-pressure sodium lamp, a metal halide lamp, a BLB lamp, a germicidal lamp or the like according to the purpose. The illuminance of the excitation light is 0.01 mW / cm2
While the above is sufficient to cause photocatalytic hydrophilic action, it is preferably 0.1 mW / cm2 or more, and 1 mW / c or more.
More preferably, it is at least m2. As the light source, sunlight, indoor lighting, a fluorescent lamp, a mercury lamp, and an incandescent lamp can be suitably used.

However, when a thin film having a thickness of 0.1 μm or less is used, even a thin film having a good absorbency of 250 to 350 nm is used.
It is preferable that a large amount of short-wavelength light (preferably about 300 to 340 nm) is contained.

[0022]

EXAMPLE 13.3 g of tin oxide sol S-8 (particle size: 2 nm, no antimony) manufactured by Taki Kagaku KK was added to 1.56 g of water.
g, 9.55 g of isopropanol, and then 0.50 g of surfactant Surfynol GA was added to obtain a coating solution. This liquid was applied by flow coating to a white coated steel sheet whose surface was a melamine alkyd resin to prepare a comparative example.

To 1.25 g of antimony-containing tin oxide sol F-10 (containing 2 nm of antimony) manufactured by Taki Kagaku, diluted with 13.70 g of water and 9.55 g of isopropanol, 0.50 g of surfactant Surfynol GA was added. Thus, a coating liquid was obtained. This liquid was applied to a white coated steel sheet whose surface was a melamine alkyd resin by flow coating to prepare an example.

When the comparative example and the example were horizontally exposed outdoors, the initial contact angle with water was 29.4 degrees in the comparative example and 9.4 degrees in the example. Is 26.
Although it was 8 degrees, the example was 11.7 degrees. As for the degree of adhesion of dirt, in the comparative example, dust adhered here and there, resulting in a mottled pattern. After the exposure, the surfaces of the comparative example and the example were observed with an optical microscope (2500 times), and no crack or peeling due to deterioration of both coated surfaces was observed.

[0025]

According to the present invention, when applied to an organic substrate, the substrate is not eroded or peeled off at the interface between the substrate and the photocatalyst coating. It is possible to provide a photocatalytic hydrophilic member which can sufficiently withstand application to purification by washing with water, promotion of drying, and the like.

Claims (7)

[Claims] Claims: 1. A surface of a substrate having an organic resin surface,
A layer containing tin oxide particles containing antimony is formed, and the surface of the layer is converted into a contact angle with water in response to photoexcitation of the photocatalyst by irradiation of sunlight or ultraviolet rays of 10 mW / cm ² or less. A photocatalytic hydrophilic member having a hydrophilicity of 20 ° or less. 2. The photocatalytic hydrophilic member according to claim 1, wherein the layer is directly fixed on the surface of the organic resin. 3. The layer according to claim 1, wherein the content of the tin oxide particles in the layer is 50% by weight or more.
3. The photocatalytic hydrophilic member according to 1.). 4. The method according to claim 1, wherein the content of antimony in the tin oxide particles is 1 to 30% by weight, based on the total amount of tin oxide and antimony oxide, in terms of the amount of antimony oxide. 4. The photocatalytic hydrophilic member according to any one of 1 to 3. 5. The photocatalytic hydrophilic member according to claim 1, wherein the tin oxide particles have a particle size of 20 nm or less. 6. The thickness of the layer containing tin oxide particles is 2-6.
The photocatalytic hydrophilic member according to claim 1, wherein the thickness is about 00 nm. 7. The photocatalytic hydrophilic member according to claim 1, wherein the substrate is an automobile having a painted surface.