Water-repellent glass and process for preparing same

Details Water-repellent glass and process for preparing same Water-repellent glass and process for preparing same

1998-12-31

2001-04-03

Le, H. Thi (Department: 1773)

Coating processes

Solid particles or fibers applied

Uniting particles to form continuous coating with...

C427S204000, C427S301000, C427S419200, C428S331000, C428S428000, C428S429000

Reexamination Certificate

active

06210750

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for the preparation of a water-repellent glass having excellent durability and hardness; and to a water-repellent glass prepared by said process.
BACKGROUND OF THE INVENTION
Water-repellent glass used in such applications as vehicular and architectural window glasses are generally prepared by coating a water-repellent agent having a low surface energy on the surface of a glass substrate to impart a water-repellent property to the substrate, thereby improving the vision through the windows.
However, a single coating of a water-repellent agent on the surface of a glass substrate is not desirable since an alkaline components of glass migrates to the surface thereof and weakens the bonding between the glass surface and the water-repellent agent, deteriorating the water repellency in course of time. Accordingly, it is required to block such effect caused by the alkaline component for an extended lifetime of a water-repellent glass.
To solve the above problem and also to impart improved durability to a water-repellent coating layer, there have been suggested methods of forming on a glass substrate a silica film preferably having a rough surface. Such film provides an increased surface area which serves to bring a water-repellent agent into better contact with the surface thereof.
For example, Japanese Laid-open Patent Publication No. 213633/1993 and 267684/1995 disclose the use of a coating solution containing at least two silicon polymers having different average molecular weights to form a silica film having microscopically rough surface. However, this method has disadvantages in that the preparation of a coating solution containing two different silicon polymers is not easy, and the coated layer must be heat-treated at a high temperature of 400° C. or higher in order to achieve desired surface roughness. Accordingly, it is difficult to apply this method to vehicular safety glasses such as laminated or tempered glass plates.
Japanese Laid-open Patent Publication No. 132433/1997 suggests a method of preparing a coating solution by mixing two separate silicon polymers obtained from two alkoxysilanes having different alkyl groups. However, this method still requires a high temperature heat treatment step for achieving a suitable surface roughness on the silica film.
SUMMARY OF THE INVENTION
It is, therefore, an objective of the present invention to provide a simple process for preparing a water-repellent glass comprising a silica film having good uniformity, optical transparency, durability and hardness, which does not require a high temperature heat treatment step.
In accordance with an aspect of the present invention, there is provided a process for the preparation of a water-repellent glass which comprises:
(a) preparing a colloidal silica suspension by hydrolyzing and polycondensing an alkoxysilane in an organic solvent under a basic condition in the presence of water, and then treating the colloidal silica suspension under an acidic condition, to obtain a silica dispersion containing cross-linked spherical silica particles and linear polysiloxane,
(b) combining the silica dispersion with a mixed solvent composed of acetic acid and an alcohol to obtain a coating composition,
(c) applying the coating composition on the surface of a glass substrate to form a silica layer therefrom,
(d) heat treating the silica layer to provide a silica film on the glass substrate, and
(e) applying a water-repellent agent on the silica film to provide the water-repellent glass.


REFERENCES:
patent: 5523161 (1996-06-01), Goodwin
patent: 5651921 (1997-07-01), Kaijou
patent: 5674625 (1997-10-01), Takahashi et al.
patent: 5707740 (1998-01-01), Goodwin
patent: 5814397 (1998-09-01), Cagliostro et al.
patent: 5856016 (1999-01-01), Takahashi et al.

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