JP3266526B2 - Photocatalytic hydrophilic member and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for making a member surface highly hydrophilic and maintaining it. More specifically, the present invention relates to an anti-fog technology for preventing the fogging and water droplets from forming on a mirror, lens, glass, prism or other transparent member by making the surface of the member highly hydrophilic. The present invention also prevents the surface from being stained by highly hydrophilizing the surface of a building, a window glass, a mechanical device or an article,
Alternatively, the present invention relates to a technique of self-cleaning (self-cleaning) or easily cleaning a surface.

[0002]

2. Description of the Related Art It is often experienced that in cold weather, windshields and glazings of automobiles and other vehicles, glazings of buildings, lenses of glasses, and cover glasses of various instrument panels are fogged by condensed moisture. . In addition, mirrors and eyeglass lenses in bathrooms and washrooms are often fogged by steam. Furthermore,
Vehicle windshields and windows, building windows, vehicle back mirrors, eyeglass lenses, masks and helmet shields are subjected to rainfall and splashes, and when a large number of discrete water droplets adhere to the surface, the Can be dark, blurred, mottled, or cloudy, again losing visibility. Needless to say, the above "clouding" has a profound effect on safety and efficiency of various operations. For example, if the windshield or window glass of the vehicle or the back mirror of the vehicle is overcast or cloudy in cold weather or rainy weather, it is difficult to secure a view, and traffic safety is impaired. Fogging of the endoscope lens and the dental dentoscope hinders accurate diagnosis, surgery, and treatment. If the cover glass of the instrument panel becomes fogged, it becomes difficult to read the data.

It has been proposed to make the surface hydrophilic in order to eliminate the "clouding". For example, 3-1
No. 29357 discloses a method in which a polymer layer is provided on the surface of a base material, and this layer is irradiated with ultraviolet rays and then treated with an aqueous alkali solution to generate high-density acidic groups, whereby the surface of the polymer layer becomes hydrophilic. A mirror anti-fogging method is disclosed. However, with such acidic groups, the surface polarity is not sufficient and the surface loses hydrophilicity over time due to contaminants adhering to the surface,
It is considered that the anti-fog performance is gradually lost.

[0004] On the other hand, in the fields of construction and paints, stains on building exterior materials, outdoor buildings and their coatings have become a problem with environmental pollution. Dust and particles suspended in the air 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 building's outer walls. Furthermore, in the rain, the floating dust is carried by the rain and flows down on the outer wall of the building or the surface of the outdoor building. As a result, pollutants adhere to the surface along the path of rainwater. 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 inorganic pollutants such as urban dust and clay particles. It is thought that such a variety of contaminants complicates antifouling measures (Yoshinori Tachibana, "Method for Accelerated Testing of Contamination of Exterior Wall Finishing Materials", Proc. No., October 1989, p.
5-24).

According to conventional wisdom, in order to prevent dirt on the building exterior and the like, polytetrafluoroethylene (PT) is used.
Although water-repellent paints such as FE) were considered preferable, recently it has been considered that it is desirable to make the surface of the paint film as hydrophilic as possible for urban dust containing a large amount of hydrophobic components. (Polymer, Vol. 44, May 1995, p. 307). Therefore, a hydrophilic graft polymer
It has been proposed to paint a building at (Chemical Industry Daily, January 30, 1995). According to reports, this coating exhibits a hydrophilicity of 30 to 40 ° in contact angle with water. However, the contact angle of inorganic dust typified by clay minerals with water is from 20 ° to 50 °, and has an affinity for a graft polymer having a contact angle of 30 to 40 ° with water. It is thought that the coating of the graft polymer cannot prevent contamination by inorganic dust because it easily adheres.

[0006]

As described above, by making the surface of the member hydrophilic, it is possible to prevent the member from fogging or forming water droplets, and also to prevent the surfaces of buildings, window glasses, mechanical devices and articles from becoming dirty. Although there are proposals that can prevent blemishes or clean the surface by self-cleaning or can be easily cleaned, the effect was not sufficient because the surface could not be maintained at a high degree of hydrophilicity for a long time. In view of the above circumstances, an object of the present invention is to provide a member capable of maintaining a surface with a high degree of hydrophilicity for a long period of time.

[0007]

SUMMARY OF THE INVENTION The present invention is based on the discovery that, in a member having a surface layer containing a photocatalyst, the surface of the member is highly hydrophilized when the photocatalyst is photoexcited. This phenomenon is considered to proceed by the following mechanism. That is, when light having energy equal to or greater than the energy gap between the upper end of the valence band and the lower end of the conduction electron band of the photocatalyst is irradiated on the photocatalyst, the electrons in the valence band of the photocatalyst are excited to cause conduction electrons and holes. Are produced, and one or both of them may possibly impart a polarity to the surface and collect polar components such as water and hydroxyl groups. Then, one or both of the conduction electrons and holes and the above-mentioned polar components cooperate to cut the chemical bond between the adsorption surface and the contaminant chemically adsorbed on the surface, and the chemically adsorbed water on the surface. It adsorbs and a physisorbed water layer is formed on it.

In the present invention, a surface layer containing a photocatalytic titanium oxide and an oxide complex of molybdenum and titanium is formed, or a layer containing a photocatalytic titanium oxide is formed, and further, molybdenum and titanium are formed thereon. Provided is a photocatalytic hydrophilic member, on which a surface layer containing the oxide composite of (1) is formed. When the surface layer contains an oxide composite of molybdenum and titanium, the surface of the oxide composite has a large electron-accepting property or a proton-donating property. It becomes an extremely large state. Therefore, it is easier to selectively adsorb a water molecule which is a polar molecule than a hydrophobic molecule. Therefore, a stable physically adsorbed water layer is easily formed, and even if the layer is kept in a dark place, the hydrophilicity of the surface can be maintained at a high level for a considerably long period. Furthermore, since the photocatalytic oxide is contained in the surface layer, even when the hydrophilicity of the surface has been lost due to long-term storage in a dark place, etc., the superhydrophilicity is increased according to the photoexcitation of the photocatalytic oxide. Will be presented.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first embodiment of the present invention, as shown in FIG. 1, a surface layer containing a photocatalytic titanium oxide and an oxide complex of molybdenum and titanium is formed on a substrate surface. To have been. In the second embodiment of the present invention, as shown in FIG. 2, a photocatalytic titanium oxide-containing layer is formed on a substrate surface, and a surface layer containing a molybdenum-titanium oxide composite is further formed thereon. To be formed.

The term “highly hydrophilic” in the present invention means a state exhibiting water wettability of 10 ° or less, preferably 5 ° or less in terms of a contact angle with water. PCT / JP96 / 007
As shown in No. 33, if the surface of the member is less than 10 ° in terms of the contact angle with water, condensed water forms individual water droplets even if moisture or steam in the air is dewed. Without this, the tendency to form a uniform water film becomes remarkable. Therefore, the tendency that light scattering fogging does not occur on the surface becomes remarkable. Similarly, when a window glass, a vehicle back mirror, a vehicle windshield, an eyeglass lens, or a shield of a helmet is subjected to rainfall or splashing, discrete unsightly water droplets are not formed, and high visibility and visibility are achieved. As a result, the effects of ensuring safety, ensuring the safety of vehicles and traffic, and improving the efficiency of various tasks and activities are greatly improved. Also, as shown in PCT / JP96 / 00733, if the surface of the member is in a state of 10 ° or less, preferably 5 ° or less in terms of a contact angle with water, urban dust,
Combustion products such as carbon black contained in exhaust gas from automobiles, hydrophobic contaminants such as oils and fats, sealant-eluting components, and inorganic clay contaminants are unlikely to adhere, and even if they do adhere, it will rain. It can be easily dropped by washing with water.

If the surface of the member can maintain the above-mentioned high degree of hydrophilicity, in addition to the above-mentioned anti-fogging effect and surface cleaning effect, it also has an anti-static effect (dust-preventing effect), a heat-insulating effect, an effect of preventing air bubbles from adhering in water, The effect of improving the efficiency of the vessel, the effect of biocompatibility, and the like are exhibited.

The substrate to which the present invention can be applied is a transparent member in the case where the above antifogging effect is expected, and glass, plastic, or the like can be suitably used as the material. Speaking of applicable base materials, mirrors such as vehicle back mirrors, bathroom mirrors, toilet mirrors, dental mirrors, road mirrors; spectacle lenses, optical lenses, camera lenses, endoscope lenses, Lenses such as illumination lenses, semiconductor lenses, and copier lenses; prisms; windows of buildings and towers; automobiles, railway vehicles, aircraft, ships, submersibles, snowmobiles, lowway gondolas, and amusement parks. Windowpanes for vehicles such as gondola and spacecraft; cars, railcars, aircraft, ships, submarines,
Windshields for vehicles such as snowmobiles, snowmobiles, motorcycles, lowway gondola, amusement park gondola, spaceships; protective goggles, sports goggles, protective Includes mask shield, sports mask shield, helmet shield, frozen food display case glass; measuring instrument cover glass; and film for attaching to the surface of the article. . When the surface cleaning effect is expected as a substrate to which the present invention can be applied, the material is, for example, metal, ceramics, glass, plastic, wood, stone, cement, concrete, fiber, cloth, Combinations thereof and laminates thereof can be suitably used. Speaking of applicable base materials, building materials, building exteriors, building interiors, window frames, window glasses, structural members, vehicle exteriors and coatings,
Exterior of machinery and equipment, dust cover and paint, traffic signs, various display devices, advertising towers, road sound barriers, railway sound barriers, bridges, exterior and paint of garlands, tunnel interior and paint, Insulators, solar cell covers, solar water heater heat collection covers, vinyl houses, vehicular lighting covers, housing equipment, toilets, bathtubs, washbasins, lighting fixtures, lighting covers, kitchenware, tableware, tableware Includes washer, dish dryer, sink, cooking range, kitchen hood, ventilator, and film for application to the surface of the article. When the antistatic effect is expected as a substrate to which the present invention can be applied, the material is, for example, metal, ceramics, glass, plastic, wood, stone, cement, concrete, fiber, cloth,
Combinations thereof and laminates thereof can be suitably used.
Speaking of applicable base materials, cathode ray tubes, magnetic recording media, optical recording media, magneto-optical recording media,
Diode tapes, video tapes, analog records, housing and parts and exteriors and paintings for household electrical appliances, housings and parts and exteriors and paintings for OA equipment products, building materials, building exteriors, building interiors, window frames, windows It includes glass, structural members, vehicle exteriors and coatings, exteriors of machinery and articles, dustproof covers and paintings, and films to be attached to the article surfaces.

[0013] A photocatalytic oxide is formed by irradiating light (excitation light) having energy (ie, shorter wavelength) larger than the energy gap between the conduction electron band and the valence band of an oxide crystal. An oxide capable of generating conduction electrons and holes by the excitation of electrons (photoexcitation) in the valence band, including anatase-type titanium oxide, rutile-type titanium oxide, tin oxide, zinc oxide, bismuth trioxide, Tungsten trioxide, ferric oxide, strontium titanate and the like can be suitably used. The light source used for photoexcitation of the photocatalytic oxide is, for example, indoor lighting such as a fluorescent lamp, an incandescent lamp, a metal halide lamp, or a mercury lamp, the sun, or a light source that guides light from the light source through a low-loss fiber. Can be suitably used. In order for the substrate surface to be highly hydrophilized by photoexcitation of the photocatalytic oxide, the illuminance of the excitation light is 0.001 m
W suffices / cm ² or more, but preferably that it 0.01 mW / cm ² or more, and more preferably it 0.1 mW / cm ² or more.

It is preferable that the thickness of the surface layer be 0.2 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 more transparent the member can be. Further, when the film thickness is reduced, the wear resistance of the surface layer is improved. The surface of the surface layer may be further provided with a wear-resistant or corrosion-resistant protective layer capable of being made hydrophilic and other functional films. Preferably, the surface layer does not have a very high refractive index as compared to the substrate. Preferably, the refractive index of the surface layer is 2 or less. Then, light reflection at the interface between the base material and the surface layer can be suppressed. When the substrate is a glass or glazed tile containing an alkali network modifying ion such as sodium, an intermediate layer such as silica may be formed between the substrate and the surface layer. Then, the diffusion of the alkali network modifying ions from the base material to the surface layer during the firing is prevented, and the photocatalytic function is more effectively exhibited. Metals such as Ag, Cu, and Zn can be added to the surface layer. The surface layer to which the metal is added can kill bacteria adhering to the surface. Furthermore, this surface layer inhibits the growth of microorganisms such as molds, algae and moss. Therefore, adhesion of dirt on the member surface due to microorganisms can be more effectively suppressed. The surface layer has P
Platinum group metals such as t, Pd, Rh, Ru, Os, Ir can be added. The surface layer to which the metal is added can enhance the oxidizing activity of the photocatalyst, and promote the decomposition of contaminants attached to the member surface. In addition, the addition of the platinum group metal improves the electron accepting property or the proton donating property of the oxide complex of molybdenum and titanium, so that the hydrophilicity is also improved. Mo may be added to the surface layer. Also in this case, the electron-accepting property or the proton-donating property of the oxide composite of molybdenum and titanium is improved, so that the hydrophilicity retention property is improved.

The method for forming the hydrophilic member shown in FIG. 1 includes, for example, applying a mixture of a photocatalytic titanium oxide sol and a basic solution containing molybdic acid onto a substrate surface by spray coating, flow coating, or the like. After coating by spin coating, dip coating, roll coating, etc., it is fired at a temperature of 400 to 800 ° C. at which an oxide complex of molybdenum and titanium is formed, and the surface layer is fixed to the substrate. I do.

In the method of forming the hydrophilic member shown in FIG. 2, for example, a sol in which photocatalytic titanium oxide particles are
After coating and drying by a method such as spray coating, flow coating, spin coating, dip coating, roll coating, and the like, a basic solution containing molybdic acid is further added to any of the above. And calcined at a temperature of 400 to 800 ° C. at which an oxide complex of molybdenum and titanium is formed, to fix the surface layer to the base material. In another method for forming the hydrophilic member shown in FIG. 2, for example, tetraalkoxytitanium such as tetraethoxytitanium, tetramethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium; titanium chelate, acetate titanium; A precursor of a photocatalytic titanium oxide such as a soluble inorganic titanium compound such as titanium chloride; titanium hydroxide; and amorphous titanium oxide is sprayed on a substrate surface.
After coating and drying by methods such as coating, flow coating, spin coating, dip coating, roll coating, and electron beam evaporation, a basic solution containing molybdic acid is further applied thereon. To a temperature above the temperature at which the precursor of the photocatalytic titanium oxide changes to a photocatalytic oxide (the crystallization temperature of the anatase-type titanium oxide), and the oxidation of molybdenum and titanium. Is baked at a temperature of 500 to 800 ° C. at which the product complex is formed, and the surface layer is fixed to the substrate. In the hydrophilic member shown in FIG. 2, it is preferable that the photocatalytic oxide layer has a thickness of 10 nm or more, because the photocatalytic oxide is particularly excellent in hydrophilicity by photoexcitation.

[0017]

EXAMPLE A 10 cm square soda lime glass plate was immersed in a 3.5% by weight tetraethoxysilane solution (diluent: ethanol, hydrolysis inhibitor: ethanolamine), and then immersed in a 24 cm / min. The solution was pulled up at a speed, and the solution was applied to the surface of a glass plate by a dip coating method and dried. Through the steps so far, tetraethoxysilane was hydrolyzed to be silanol first, and then a thin film of amorphous silica was formed on the surface of the glass plate by dehydration-condensation polymerization of silanol. Next, after immersing in a 3.5% by weight tetraethoxytitanium solution (diluent: ethanol, hydrolysis inhibitor: ethanolamine), the solution is pulled up at a speed of 24 cm / min, and the solution is subjected to dip coating. ,
The sample was applied to the surface and dried to obtain a # 1 sample. Through the steps so far, tetraethoxytitanium is hydrolyzed to titanium hydroxide first, and then a thin film of amorphous titanium oxide (about 50 nm thick) is formed on the surface by dehydration-condensation polymerization of titanium hydroxide. . Next, 0.875% by weight of 7
2 minutes per minute after immersion in 6 ammonium molybdate hydrate solution
The solution was pulled up at a speed of 4 cm, and the solution was applied to the surface by dip coating, baked at 500 ° C., and # 2
A sample was obtained. Amorphous titanium oxide was crystallized by the calcination to form an anatase type titanium oxide, and an oxide complex of titanium and molybdenum was formed. Oleic acid was applied to the surface of # 2 sample immediately after firing, rubbed with a neutral detergent, rinsed with tap water and distilled water, and then dried at 50 ° C.
For 30 minutes to intentionally contaminate the surface. As a result, the contact angle with water increased to 55 °. Here, the contact angle with water is measured using a contact angle measuring instrument (Kyowa Interface Science, C
AX150), a water drop was dropped with a microsyringe, and the value 30 seconds later was measured. Next, light source B
LB lamp (Sankyo Electric, Black Light Bull-Lamp)
And irradiated with ultraviolet light having an illuminance of 0.3 mW / cm ² per day. As a result, the contact angle of the sample surface with water was reduced to 5 °. Next, the sample was left in a dark place for 6 hours, and the change in the contact angle of the sample surface with water was measured. As a result, the value was maintained as low as 9 °.

[0018]

According to the present invention, a layer comprising an oxide composite of photocatalytic titanium oxide and titanium and molybdenum is formed, or a layer containing a photocatalytic titanium oxide is formed, and the oxidation of titanium and molybdenum is further formed thereon. By forming a layer consisting of a compound complex, the surface becomes highly hydrophilic in response to the photoexcitation of the photocatalytic titanium oxide, so that the surface is permanently maintained at a high degree of hydrophilicity And at the same time, by the action of the oxide complex of titanium and molybdenum, the polarity of the surface probably increases, and the surface that once exhibited a high degree of hydrophilicity maintains the hydrophilicity during light shielding for a long time Will be done.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 shows a second embodiment of the present invention.

────────────────────────────────────────────────── ─── Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B01J 21/00-38/74 JICST file (JOIS) WPI / L (QUESTEL)

Claims (4)

(57) [Claims] 1. A photocatalytic titanium oxide layer comprising: a photocatalytic titanium oxide-containing layer formed on a surface of a substrate; and a surface layer containing an oxide composite of molybdenum and titanium formed thereon. Hydrophilic member. 2. A step of coating the surface of the substrate with a layer containing a photocatalytic titanium oxide particle, a step of coating it further with a liquid material containing molybdic acid, and baking at 400 to 800 ° C. to form an oxide of titanium and molybdenum. A method for producing a photocatalytic hydrophilic member, comprising a step of forming a composite. 3. A step of coating the surface of the substrate with an amorphous titanium oxide-containing layer, a step of coating the substrate surface with a liquid material containing molybdic acid, and baking at 400 to 800 ° C. to crystallize the amorphous titanium oxide. A method for producing a photocatalytic hydrophilic member, comprising a step of forming an oxide composite of titanium and molybdenum, together with a step of forming an oxide composite of titanium and molybdenum. 4. The method for producing a photocatalytic hydrophilic member according to claim 2, wherein the liquid containing molybdic acid is a basic solution.