JPH09227159A - Front and rear window glass of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stain removability, non-fogging properties and abrasion resistance with keeping the visual field owing to no optical refraction at water drop interfaces by bonding a transparent layer containing an optically catalytic semiconductor material to the surface of a base material. SOLUTION: A layer in which particles of an optically catalytic semiconductor material are uniformly dispersed and having <=0.2μm thickness is formed on a base material consisting of front and rear window glasses 12, 4, 11 of a vehicle 11 by coating a coating solution containing an optically catalytic semiconductor material comprising one metal oxide selected from TiO2 , ZnO, SnO2 , SrTiO3 , WO3 , Bi2 O3 and Fe2 O3 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to front and rear or front and rear windows of a vehicle.

[0002]

2. Description of the Related Art When a window glass of a vehicle is exposed to rain or splashes and a large number of discrete water drops adhere to the glass surface, refraction of light at the interface between the water drop and the glass surface and the interface between the water drop and the air causes these water drops to be scattered. The surface is wrinkled, blurred, mottled, or cloudy and the perspective image is distorted, reducing visibility. It is also common to experience fog in vehicle windows due to condensed moisture during cold weather. The reason why the surface of the window glass becomes cloudy is that when the surface is placed at a temperature lower than the dew point of the atmosphere, the moisture in the atmosphere condenses and condenses on the surface. If the condensed water droplets are sufficiently fine and their diameter is about ½ of the wavelength of visible light, the water droplets scatter light and the window glass becomes apparently opaque and loses visibility. Then, when the condensation of moisture further progresses and fine condensed water droplets fuse with each other to grow into larger discrete water droplets, refraction of light at the interface between the water droplet and the glass surface and the interface between the water droplet and air causes Wings, blurry, mottled, or cloudy, again reducing visibility. In particular, the reduction of visibility in the front and rear windows has a great influence on driving and traffic safety. Conventionally, in order to secure a view in cold weather or rainy weather, for example, a windshield or a windshield of an automobile is equipped with a wiper or a defrosting device, and a rear windshield or a rear window glass is equipped with a wiper. Or the heating wire is embedded. The wiper wipes water droplets off the glass surface and smoothes the interface between the water droplets and the glass surface and the interface between the water droplets and the air to prevent light refraction and secure the field of view. Further, the defrosting device and the heating wire raise the temperature of the glass surface and its surroundings, and reduce the condensation of moisture in the atmosphere to secure the visibility. The visibility can also be secured by applying a hydrophilic compound such as polyethylene glycol or a water repellent compound such as silicone to the surface.

[0003]

However, in the wiper, the wiping is completely uneven due to the uneven wiping, the range that the wiper cannot reach, and the fact that the wiper obstructs the view. Is difficult to secure. Also, in the defrosting device and heating wire, it is necessary to fully secure the field of view due to the fact that it takes time for the temperature to rise and a sufficient field of view is secured, and there is unevenness due to a partial temperature rise. Is difficult Further, the method of applying the hydrophilic compound or the water-repellent compound is only a temporary method, and it is easily removed by washing with water or contact, and there is a drawback that the effect is lost early.

Accordingly, it is an object of the present invention to provide a front and rear window glass for a vehicle and a method for manufacturing the same, which can secure a field of view even in cold weather or rain.

[0005]

The front and rear glazing of a vehicle according to claim 1 is characterized in that it comprises a layer of substantially transparent photocatalytic semiconductor material bonded to the surface of the substrate. .

The front and rear window glass for a vehicle according to a second aspect is the front and rear window glass for a vehicle according to the first aspect, wherein the base material is tempered glass.

The vehicle front and rear window glass according to claim 3 is the vehicle front and rear window glass according to claim 1, wherein the base material is laminated glass.

A front and rear window glass for a vehicle according to claim 4 is the front and rear window glass for a vehicle according to any one of claims 1 to 3, wherein the surface of the layer is in contact with water upon photoexcitation. It exhibits water wettability of about 10 ° or less in terms of angle.

A front and rear window glass for a vehicle according to claim 5 is the front and rear window glass for a vehicle according to any one of claims 1 to 3, wherein the surface of the layer is in contact with water upon photoexcitation. It exhibits water wettability of about 5 ° or less in terms of angle.

A front and rear window glass for a vehicle according to claim 6 is the front and rear window glass for a vehicle according to any one of claims 1 to 5, wherein the photocatalytic semiconductor material is TiO ₂ , ZnO. , SnO ₂ , SrTiO ₃ , WO ₃ ,
It contains one kind of oxide selected from the group consisting of Bi ₂ O ₃ and Fe ₂ O ₃ .

The front and rear window glass for a vehicle according to claim 7 is the front and rear window glass for a vehicle according to any one of claims 1 to 6, wherein the photocatalytic semiconductor material is anatase-type titania. .

A front and rear window glass for a vehicle according to claim 8 is the front and rear window glass for a vehicle according to claim 6 or 7, wherein the layer further comprises SiO ₂ or SnO ₂ .

A front and rear window glass for a vehicle according to claim 9 is the front and rear window glass for a vehicle according to any one of claims 1 to 8, wherein the layer has uniform particles of a photocatalytic semiconductor material. It is formed by a coating film dispersed in.

A front and rear window glass for a vehicle according to claim 10 is the front and rear window glass for a vehicle according to any one of claims 1 to 9, wherein the layer has a thickness of about 0.
2 μm or less.

A method for manufacturing a front and rear window glass for a vehicle according to claim 11 is characterized in that the surface of a transparent substrate is coated with a layer which is substantially transparent and contains a photocatalytic semiconductor material.

According to a twelfth aspect of the present invention, there is provided a vehicle front / rear window glass manufacturing method according to the eleventh aspect, wherein the coating film is formed of silicone and the surface thereof is silicone. It is formed of a silicone derivative in which an organic group bonded to a silicon atom of a molecule is at least partially substituted with a hydroxyl group by photocatalytic action of a photocatalytic material in response to photoexcitation.

According to a thirteenth aspect of the present invention, there is provided a vehicle front / rear window glass producing method according to the eleventh or twelfth aspect of the present invention, wherein the base material is an alkaline network modifying ion. A thin film is formed between the substrate and the layer to prevent the ions from diffusing from the substrate into the layer.

According to a fourteenth aspect of the present invention, there is provided a front and rear window glass for a vehicle according to the thirteenth aspect, wherein the thin film is a silica thin film.

[0019]

The present inventor discovered for the first time in the world that the surface of a photocatalyst is highly hydrophilized when the photocatalyst is photoexcited.
Surprisingly, when photocatalytic titania was photoexcited with ultraviolet rays, the surface was highly hydrophilized so that the contact angle with water was 10 ° or less, more specifically 5 ° or less, especially about 0 °. Was discovered. The present invention is based on such a new discovery, and the present invention provides a front and rear window glass of a vehicle having a highly hydrophilic surface, and a manufacturing method thereof. When light having a wavelength higher than the band gap energy of the photocatalytic semiconductor is irradiated with sufficient illuminance for a sufficient time, the surface of the photocatalytic coating becomes superhydrophilic. As used herein, "superhydrophilic (superhyd
or “super hydrophilic” (sup)
The term "erhydrophilic" means a high degree of hydrophilicity (ie water wettability) of about 10 ° or less, preferably about 5 ° or less in terms of contact angle with water. superhydrophilificati
on) ”or“ superhydrophilic ”
The term "hilify)" means that the surface has a high degree of hydrophilicity in terms of contact angle with water of about 10 ° or less, preferably about 5 ° or less. Superhydrophilicity of the surface caused by photoexcitation of the photocatalyst. At present, it is not always possible to clearly explain the photocatalytic phenomenon.The superhydrophilization phenomenon by a photocatalyst is not necessarily the same as the photolysis of a substance by a photocatalytic redox reaction known in the field of photocatalyst. In this regard, the conventional theory regarding the photocatalytic redox reaction is that an electron-hole pair is generated by photoexcitation, and the generated electron reduces surface oxygen to generate a superoxide ion (O _2- ). generated, holes oxidize surface hydroxyl groups to produce the hydroxyl radical (· OH), these highly reactive oxygen species - by redox reaction (O ₂ or · OH) However, the photocatalytic superhydrophilization phenomenon is inconsistent with the conventional findings on the photocatalytic decomposition of substances in at least two respects. In photocatalysts such as tin oxide and tin oxide, the energy level of the conductor is not high enough, so the reduction reaction does not proceed, and as a result, the photoexcited electrons in the conductor become excessive, and the electrons generated by photoexcitation are positive. It was thought that the pore pair would recombine without participating in the redox reaction, whereas it was confirmed that the photocatalytic superhydrophilization phenomenon also occurs in photocatalysts such as rutile and tin oxide, as described later. Secondly, conventionally, it is considered that the decomposition of the substance by the photocatalytic redox reaction does not occur unless the thickness of the photocatalytic layer is at least 100 nm or more. It was observed that photocatalytic superhydrophilization occurs even when the film thickness of the photocatalytic coating is on the order of several nm.Therefore, although it cannot be clearly concluded, the superhydrophilization phenomenon by photocatalyst is caused by photocatalytic redox reaction. It is considered that this is a phenomenon that is slightly different from the photodecomposition of substances. Probably, the surface of the photocatalytic coating becomes superhydrophilic by the chemisorption of water in the form of hydroxyl groups (OH-) on the surface of the photocatalytic coating by the photocatalytic action of the photocatalyst. If highly hydrophilicized, the hydrophilicity of the surface will continue for some time, even if the substrate is kept in the dark. When the contaminant is adsorbed on the surface hydroxyl groups with the passage of time and the surface gradually loses the superhydrophilic property, the superhydrophilic property is restored by photoexcitation again. Any light source having a wavelength of energy higher than the bandgap energy of the photocatalyst can be utilized to initially superhydrophilize the photocatalytic coating. In the case of a photocatalyst whose photoexcitation wavelength is located in the ultraviolet region, such as titania, under the condition that sunlight hits the substrate coated with the photocatalytic coating, it is possible to suitably use the ultraviolet rays contained in the sunlight. it can. The photocatalyst can be photoexcited with an artificial light source indoors or at night. As will be described later, when the photocatalytic coating is made of silica-containing cyania, it can be easily hydrophilized even with the weak ultraviolet rays contained in the fluorescent lamp. Once the surface of the photocatalytic coating has been made superhydrophilic, it can be maintained or restored with relatively weak light. For example, in the case of titania, the maintenance and restoration of superhydrophilicity can be sufficiently performed even with the weak ultraviolet rays contained in an interior lighting lamp such as a fluorescent lamp. The photocatalytic coating exhibits superhydrophilicity even when it is very thin, and in particular, the photocatalytic semiconductor material made of a metal oxide has sufficient hardness, so that the photocatalytic coating has sufficient durability and abrasion resistance. From the above, on the surface of the window glass of a vehicle that has been made highly hydrophilic, the water droplets that have adhered due to rainfall or splashes immediately become a water film, and the refraction of light at the interface between the water droplet and the surface and at the interface between the water droplet and air is performed. It is possible to prevent the surface from crawling, blurring, forming a patchy pattern, or clouding, and distorting the perspective image to reduce the visibility. Similarly, the condensed water droplets generated by dew condensation,
Since it does not immediately form a water film and grow into large water droplets,
Visibility is prevented from decreasing.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a front and rear window glass for a vehicle and a method for manufacturing the same according to the present invention will be described based on Examples.

As a first embodiment of the present invention, an automobile windshield having a photocatalytic semiconductor material composed of anatase type titania as a surface layer and a method for producing the same will be described. First, the manufacturing method will be described in the order of circled numbers, and then the resulting product will be described. A glass base plate (not shown) is processed into a shape that fits the front window 12 of the automobile 11 shown in FIG. 1, and as shown in FIG. 3 later, it is laminated with the HRP film 3 sandwiched as a laminated glass structure. In order to be able to do so, the glass plate 1 on the outdoor side and the glass plate 2 on the indoor side are prepared. Tetraethoxy titanium Ti (OC ₂ H ₅ ) ₄ (Mer
ck) 0.1 part by weight of 36% hydrochloric acid as a hydrolysis inhibitor was added to a mixture of 1 part by weight and 9 parts by weight of ethanol to prepare a titania coating solution, and the solution was dried on the surface of the glass plate 1 in dry air. Was applied by the flow coating method. The coating amount is 45 μg / cm ² converted to titania
And Since the hydrolysis rate of tetraethoxytitanium is extremely high, a part of tetraethoxytitanium was hydrolyzed at the coating stage, and titanium hydroxide Ti (OH) ₄ began to be produced. By holding this glass plate 1 at a temperature of about 150 ° C. for 1 to 10 minutes, the hydrolysis of tetraethoxytitanium is completed, and the produced titanium hydroxide is subjected to dehydration polycondensation to form amorphous titania. It was Further, this was fired at a temperature of 500 ° C. to convert the amorphous titania into anatase titania and form a surface layer of anatase titania on the glass plate 1. Here, the firing temperature may be increased to form the surface layer of rutile type titania. Similarly, a surface layer of anatase type titania was formed on the glass plate 2. Finally, the HRP film 3 is provided between the glass plate 1 and the glass plate 2.
By sandwiching the above with each other, a windshield 4 having a laminated glass structure having anatase-type titania as a surface layer on its inner and outer surfaces was obtained.

Windshield 4 manufactured in this way
First, light irradiation was carried out for 24 hours at an ultraviolet intensity of 0.3 W / cm ² to develop hydrophilicity by photoexcitation, and the contact angle of the water droplets after irradiation was about 1 ° which is the measurement limit. The ordinary laminated glass had an angle of about 20 °. The thickness of the surface layer was 0.2 μm. In fact, as a result of traveling in the rain in an automobile 11 equipped with this windshield 4, raindrops adhere to a normal windshield structure without a wiper to form a convex lens shape, which hinders the visibility. It was confirmed that in the windshield 4, water drops adhering to the glass surface spread quickly due to the influence of wind on the glass surface and running, and the visibility was maintained without the wiper. Further, even when it was cold, the inner surface was hardly fogged while the defrosting device was not operated. In addition, as a result of observing the vehicle housed indoors after running, it was found that the water was in a water droplet state and the water did not adhere to the vehicle, so that the water was dried quickly and no trace of water droplets often seen after the drying was observed. In addition, the hydrophilicity of the surface layer is gradually lost with the passage of time when stored in a dark place for a long time, but the hydrophilicity is restored again when the automobile is exposed to sunlight by traveling outdoors. Further, when the titania is used as the surface layer, the hydrophilicity can be maintained / recovered sufficiently even with weak ultraviolet rays contained in a fluorescent lamp or the like.

As a second embodiment of the present invention, an automobile windshield having a photocatalytic semiconductor material composed of anatase-type titania as a surface layer and a silica thin film interposed between the glass and the surface layer, and the same The manufacturing method will be described. Similar to the first embodiment, the outer glass plate 1 and the indoor glass plate 2 shown in FIG. 1 are prepared. 86 parts by weight of ethanol solvent, 6 parts by weight of tetraethoxysilane Si (OC ₂ H ₅ ) ₄ (Wako Pure Chemical Industries, Osaka), 6 parts by weight of pure water, and 2 parts by weight of 36% hydrochloric acid as a hydrolysis inhibitor of tetraethoxysilane. Parts were added and mixed to prepare a silica coating solution. Since the solution generated heat by mixing, the mixed solution was left to cool for about 1 hour. This solution is applied to the surface of the glass plate 1 by the flow coating method,
Dried at a temperature of ° C. As it was dried, tetraethoxysilane was hydrolyzed and silanol Si (OH) ₄
Then, a thin film of amorphous silica was formed on the surface of the glass plate 1 by dehydration condensation polymerization of silanol. After that, the windshield 4 having a laminated glass structure having a surface layer made of anatase-type titania on its inner and outer surfaces was obtained in the same manner as in the first example.

Windshield 4 manufactured in this way
First, the sample was irradiated with light at an ultraviolet intensity of 0.3 W / cm ² for 24 hours to develop hydrophilicity by photoexcitation, and the contact angle of water droplets after irradiation was smaller than the measurement limit of 1 °.
The contact angle was smaller than that of the first embodiment because the amorphous titania coating was coated with amorphous silica in the lower layer, so that it was like the sodium in the glass plate during firing. It is considered that this is because the alkali network modifying ions did not diffuse from the glass substrate into the titania coating. In other respects, the same effect as in the first embodiment was obtained, but the spread of water droplets was more rapid,
Visibility was maintained even without the wiper, and in particular, no clouding of the inner surface occurred during cold weather.

As a third embodiment of the present invention, an automobile windshield having a surface layer of a photocatalytic semiconductor material made of titanium oxide and a method for manufacturing the same will be described. Similar to the first embodiment, an outdoor glass plate 1 and an indoor glass plate 2 shown in FIG. 1 are prepared. A coating solution for undercoat is prepared by mixing silicon alkoxide, ethanol and hydrochloric acid. This solution was applied to the surface of glass by flow coating. A top coat solution was prepared by mixing titanium alkoxide, ethanol and hydrochloric acid. Apply this solution to both sides of the glass by flow coating and after drying 5
Heat treatment was performed at 00 ° C. The HRP film 3 was sandwiched between the glass plate 1 and the glass plate 2 and bonded to each other to obtain a windshield 4 having a laminated glass structure including a photocatalytic semiconductor material made of titanium oxide as a surface layer.

The thus manufactured windshield was first irradiated with light having an ultraviolet intensity of 0.3 W / cm ² for 24 hours to develop hydrophilicity by photoexcitation, and the contact angle of water droplets after irradiation was about 1 °. Therefore, the same effect as that of the first embodiment can be obtained.

As a fourth embodiment of the present invention, an automobile windshield having a photocatalytic semiconductor material made of titanium oxide as a surface layer and a method for manufacturing the same will be described. In this embodiment, first, as shown in FIG. 4, a glass plate 1 obtained by processing a glass base plate into a shape that fits the front window 12.
Then, the glass plate 2 is prepared, and the HRP film 3 is sandwiched between the glass plate 2 and the glass plate 2, and the front glass 4 having a laminated glass structure is manufactured first. A coating solution was prepared by mixing titanium oxide sol, tetraethoxysilane, ethanol and water. The composition was such that the molar amounts of titania and silica were equal, and the solid content was 1% by weight. This solution was applied to the surface of the windshield 4 by flow coating, dried and then heat-treated at 150 ° C. to obtain a windshield 4 having a laminated glass structure having a photocatalytic semiconductor material made of titanium oxide as a surface layer. .

Windshield 4 manufactured in this way
Was exposed to ultraviolet light of 0.3 W / cm ² for 24 hours to develop hydrophilicity by photoexcitation, and the contact angle of water droplets after irradiation was about 1 °, which was the same effect as in the first embodiment. I was able to get

As a fifth embodiment of the present invention, an automobile windshield having a silicone layer containing a photocatalytic semiconductor material composed of anatase type titania as a surface layer and a method for producing the same will be described. As shown in FIG. 5, the glass blank is attached to the front window 12
A windshield 4 having a tempered glass structure is manufactured by heat-treating a material processed into a shape suitable for "Glaska", a composition for paint of Japan Synthetic Rubber (Tokyo)
Solution A (silica sol) and solution B (trimethoxymethylsilane) are mixed so that the ratio of the weight of silica to the weight of trimethoxymethylsilane is 3, and this mixed solution is applied to the surface of the windshield 4, It is cured at a temperature of 150 ° C. to form a silicone coating with a thickness of 3 μm. Anatase type titania sol (Nissan Kagaku, TA-15) and the above-mentioned "grasca" solution A (silica sol) are mixed and diluted with ethanol, and then the above-mentioned "grasca" solution B is added to obtain a titania-containing coating composition. It was adjusted. The composition of the coating composition was 3 parts by weight of silica, 1 part by weight of trimethoxymethylsilane, and 4 parts by weight of titania. This coating composition is applied to the surface of the windshield 4 and cured at a temperature of 150 ° C. to obtain a windshield 4 having a tempered glass structure having a surface layer in which anatase-type titania particles are dispersed in a silicone coating film. Was given.

The thus-produced windshield was first irradiated with light having an ultraviolet intensity of 0.3 W / cm ² for 24 hours to develop hydrophilicity by photoexcitation, and the contact angle of water droplets after irradiation was at the measurement limit. It was about 3 °. Also,
When the silicone layer contains a photocatalytic semiconductor material,
Since it can be effected at room temperature or relatively low temperature,
It can be formed by applying it to an existing windshield by brush coating, spray coating, roll coating or the like. Further, superhydrophilization by photoexcitation can be easily performed by sunlight, and its maintenance / recovery can be sufficiently performed by light of an indoor illumination lamp such as a fluorescent lamp.

The present invention is not limited to the above embodiment. For example, in the embodiment, the windshield of an automobile has been described, but it goes without saying that it can be applied to a rear windshield.
It can be applied to front and rear window glasses of all vehicles such as ships and covered scooters, that is, the window glass of the portion where the driver's view is most desired in the forward and backward direction of the vehicle. Of course, it may be applied to other side window glass.

[0032]

According to the present invention, there are the following excellent effects. (B) Even if the windshield receives water droplets due to rainfall, it forms a uniform water film, so that the visibility is secured without refraction of light at the interface of the water droplets. Therefore, it is not necessary to operate a device that secures a field of view such as a wiper. Therefore, the reciprocating motion of the windshield wiper is eliminated, which facilitates driving. In addition, a device such as a wiper can be simplified as an auxiliary device for removing a large amount of dirt if it should occur. Further, for example, the wiper of the rear window glass of the automobile can be omitted. (B) Water droplets are not formed due to dew condensation or the like, and a uniform water film is formed. Therefore, it is not necessary to operate devices such as the defrosting device and the heating wire. So, for example, in the driver's seat of a car,
There is no unpleasant warm air on your face during the rainy season. The heating wire on the rear window glass of the car can be omitted. (C) Dirt adhering to the window glass during fine weather is easily removed by spraying water or by rainfall, so cleaning is easy. (D) Since no water droplets are formed, no water droplets remain on the windshield surface that has dried after being wet. (E) Since the surface layer provided on the glass has excellent abrasion resistance, the effect is semipermanently maintained only by periodically irradiating light. (F) Since the surface layer can be provided even on the existing windshield, the same effect as that provided in advance can be expected.

[Brief description of drawings]

FIG. 1 is a plan view of an automobile having a windshield according to the present invention.

FIG. 2 is a side view of an automobile having a windshield according to the present invention.

FIG. 3 is an exploded sectional view of a windshield (laminated glass structure) according to the present invention.

FIG. 4 is a sectional view of a windshield (laminated glass structure) according to the present invention.

FIG. 5 is a sectional view of a windshield (tempered glass structure) according to the present invention.

[Explanation of symbols]

 1, 2 Glass plate 3 HRP film 4 Windshield 11 Automobile 12 Front window

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Senkoku 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu City Tohoku Kikai Co., Ltd. (72) Inventor Atsushi Kitamura 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu City No. 1 Totoki Co., Ltd. (72) Inventor Toshiya Watanabe 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu City Totoki Co., Ltd.

Claims (14)

[Claims] 1. A front and rear glazing of a vehicle comprising a layer of substantially transparent, photocatalytic semiconductor material bonded to a surface of a substrate. 2. The front and rear window glass for a vehicle according to claim 1, wherein the base material is tempered glass. 3. The front and rear window glass for a vehicle according to claim 1, wherein the base material is laminated glass. 4. The front and rear window of a vehicle according to claim 1, wherein the surface of the layer exhibits a water wettability of about 10 ° or less when converted to a contact angle with water when excited by light. Glass. 5. The front-rear window of a vehicle according to claim 1, wherein the surface of the layer exhibits a water wettability of about 5 ° or less when converted to a contact angle with water when excited by light. Glass. 6. The photocatalytic semiconductor material is TiO ₂ , Z
nO, SnO ₂ , SrTiO ₃ , WO ₃ , Bi ₂ O ₃ , F
The front and rear window glass for a vehicle according to any one of claims 1 to 5, comprising one kind of oxide selected from the group consisting of e ₂ O ₃ . 7. The front and rear window glass for a vehicle according to claim 1, wherein the photocatalytic semiconductor material is made of anatase type titania. 8. The front and rear glazing of a vehicle according to claim 6 or 7, wherein said layer further comprises SiO ₂ or SnO ₂ . 9. A front and rear window glass for a vehicle according to claim 1, wherein the layer is formed by a coating film in which particles of a photocatalytic semiconductor material are uniformly dispersed. 10. The vehicle front and rear window glass according to claim 1, wherein the layer has a thickness of about 0.2 μm or less. 11. A method for manufacturing a front and rear window glass for a vehicle, which comprises coating the surface of a transparent substrate with a layer which is substantially transparent and contains a photocatalytic semiconductor material. 12. A silicone derivative in which the coating film is formed of silicone and the surface of which organic groups bonded to silicon atoms of silicone molecules are at least partially substituted with hydroxyl groups by photocatalytic action of a photocatalytic material in response to photoexcitation. The method for manufacturing a front and rear window glass of a vehicle according to claim 11, which is formed by. 13. The substrate is formed of glass containing alkaline network modifying ions, and a thin film is interposed between the substrate and the layer to prevent the ions from diffusing from the substrate into the layer. The method for manufacturing a front and rear window glass of a vehicle according to claim 11 or 12. 14. A thin film of silica as the thin film.
4. The method for manufacturing a front and rear window glass for a vehicle according to item 3.