Nonfogging and stainproof glass articles

Details Nonfogging and stainproof glass articles Nonfogging and stainproof glass articles

1999-07-16

2002-04-30

Jones, Deborah (Department: 1775)

Stock material or miscellaneous articles

Structurally defined web or sheet

Continuous and nonuniform or irregular surface on layer or...

C428S325000, C428S432000, C428S447000, C428S429000

Reexamination Certificate

active

06379776

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an anti-fogging and stain-prevented glass article, and in particular relates to an anti-fogging and stain-prevented sheet glass for buildings, and an anti-fogging and stain-prevented glass article used for glasses, mirrors, lenses, showcases, etc.
BACKGROUND OF THE INVENTION
There has been a strong need for anti-fogging and stain-prevented glass plate mainly in the fields of automobiles and buildings since ever. In particular, as regards automobiles, it becomes an important theme to give anti-fogging and stain preventing properties to window glass in view of safe driving.
Conventionally, various kinds of anti-fogging and stain preventing coatings have been studied with respect to glass articles. For example, there are organic or inorganic thin film coating containing a surface-active agent (Japanese Laid-open Patent Publication No. 117202 of 1995, Method 1), hydrophilic polymer coating (Japanese Patent Publication No. 1344292, Method 2) and organic/inorganic composite film coating containing a hydrophilic organic functional group (Japanese Laid-Open Patent Publication No. 220428-1994, Method 3), etc.
Recently, anti-fogging and stain-prevented glass having a titanium oxide thin film, which acts as an photocatalytic film, coated on its surface has been proposed (For example, “Ceramics” 31, 837-840 (1996), published by Japan Ceramics Association Inc., Method 4). This utilizes that titanium oxide on the surface of glass absorbs ultra violet light, and the absorbed ultra violet light energy efficiently oxidizes and decomposes organic articles adsorbed on the glass surface, thereby causing a clean surface having a remarkably hydrophilicity to be obtained.
Furthermore, the anti-fogging and stain-prevented glass having the abovementioned titanium oxide thin film coated on its glass surface is composed of inorganic substances and is excellent in the mechanism strength, wherein as far as light is given thereto once stains are adhered thereto, the surface can be purified again to cause a hydrophilic surface to be restored. If the surface sustains hydrophilicity, city type lipophilic black stains are hardly adhered, and furthermore if adhered stains are easily eliminated by precipitation of rain (For example, “Painting Technique” published by Riko Publishing Co., Ltd., January, 1995, 94-99(1995), “Novel stain fogging type paint” prepared by Toshiki Komatsusawa and Toshikazu Nakaiye; “Painting Technique” 1996, October Special Issue, 95-102 (1995), “Contamination deterioration and Contamination-resisting painting technique” (Industrial Paint) prepared by Shoichi Tanaka). That is, the surface sustaining hydrophilicity has a self-cleaning property and such glass materials can be used as a stain preventing material.
Although the abovementioned method 1 is excellent in the initial performance, there is such a problem where the service life is short since the surface-active agent is gradually consumed. Furthermore, the abovementioned method 2 can not be applicable to glass for which a comparatively mechanical strength is required for automobiles and buildings although the same is an effective means in some cases. Furthermore, although method 3 is devised in order to meet the anti-fogging property and mechanical strength at the same time, the same has a limitation in both aspects. Still furthermore, in a case where stains are once adhered, there is such a problem where the anti-fogging property is remarkably lowered. Furthermore, although method 4 has in principle some features which can not be achieved by the other methods, with this method, anti-fogging and stain-prevented glass articles which can be used in practical aspects can not be achieved yet since the intensity of ultraviolet light in automobiles and buildings is very weak.
It is therefore an object of the invention to provide an anti-fogging and stain-prevented glass article, having excellent long-term anti-fogging and stain preventing properties, which can be used for window glass of automobiles and buildings, and for glasses.
DISCLOSURE OF THE INVENTION
The present invention provides an anti-fogging and stain-prevented glass article in which an alkali shut-off film and an photocatalytic film are laminated on the surface of glass substrate in the order, wherein the glass article has dents and projections, the arithmetical mean roughness (Ra) of which is 1.5 to 80 nm, and the mean interval (Sm) of which is 4 to 300 nm, formed on the photocatalytic film surface.
The invention provides an anti-fogging and stain-prevented glass article in which an alkali shut-off film, an photocatalytic film, and silicon oxide layer or an organic substance adhering preventing layer consisting of a layer of organosilane or its hydrolyzed substance having at least one functional group selected from groups consisting of polyalkylene oxide group, alkyl group, alkenyl group and aryl group in its molecule are laminated on its glass article in the order.
It is necessary to meet the three requirements at the same time in order to obtain excellent anti-fogging and stain preventing properties using an photocatalytic film; the first of which is to efficiently oxidize and decompose organic substances which will be cause of fogs and stains adsorbed on the surface of an photocatalytic film (that is, high photocatalytic activation), the second of which is that organic substances are hardly adsorbed on the surface (adsorption preventing property), and third of which is to reduce the apparent contact angle when water drops are adhered although necessary to secure an anti-fogging property (small contact angle). If the abovementioned three requirements are satisfied, it is possible to achieve excellent anti-fogging and stain preventing properties for a longer period of time.
In the invention, TiO
2
, ZnO, ZnS, WO
3
, Fe
2
O
3
, GaAs, CdSe, GaAsP, Cds, SrTiO
3
, GaP, In
2
O
3
or MoO
3
, etc. may be used as a photocatalyst. TiO
2
is photocatalyst which is most widely utilized at present in view of high photocatalytic activation and chemical stability, which can be favorably used in the invention. Hereinafter, a description is given of titanium oxide as a representative example.
Even though an photocatalytic film such as titanium oxide film is directly coated on the surface of glass substrate, high photocatalytic activation can not be obtained. This is because alkali metal ions such as Na ions, which come out from and are diffused from the glass substrate containing alkali metal in heat treatment, lowers the crystalization of the titanium oxide film. In order to prevent the crystalization of the titanium oxide film from being lowered, in the invention, a silicon oxide film or other alkali shut-off film is provided on the glass subtrate, and an photocatalytic film consisting of titanium oxide or an photocatalytic film containing titanium oxide is coated thereon. In a case where a film containing titanium oxide as an photocatalytic film is used, it is preferable that the content of titanium oxide is 10 or more percent by weight. If the content of titanium oxide is less than 10 percent by weight, the photocatalytic activation on the surface is lowered too much and this is not practical.
An anti-fogging and stain-prevented glass according to the invention has excellent anti-fogging and stain preventing properties and their sustainability and is excellent in mechanical strength, the same can be favorably used for automobiles, buildings and glasses.
Hereinafter, a description is given of the respective components of the invention.
[Alkali shut-off film]
As the abovementioned alkali shut-off film, a monocomponent or multicomponent composition selected from a group of silica oxide, aluminium oxide, titanium oxide, zirconium oxide and cerium oxide may be preferably used. Of them, a monocomponent of silica oxide or a multicomponent having silica oxide as its main component is preferable, and a two-component metal oxide consisting of silica oxide and zirconium oxide is further preferable. Since a metal oxide having sili

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