Coated glass

DETAILED DESCRIPTION OF THE INVENTION Electron donating compounds are compounds which contain, either in bonds or as lone pair electrons, electrons which can be donated into the electronic structure of suitable acceptor molecules.
Examples of electron donating compounds which contain the donor electrons in bonds are unsaturated hydrocarbons, especially olefins (alkenes) and acetylenes (alkynes), for example ethylene, butadiene, pentene, difluoroethylene, and acetylene (C.
sub.
2 H.
sub.
2), and aromatic hydrocarbons, for example benzene and xylene.
Examples of electron donating compounds which contain their donor electrons in lone pairs are ethers, amines, aldehydes, ketones, alcohols, hydrides of nitrogen, carbon monoxide and carbon dioxide.
It is preferred, for reasons of convenience, to use electron donating compounds which are gaseous under ambient conditions, but other electron donating compounds can be used without undue difficulty provided they have a vapour pressure of at least 5 KPa at 60.
degree.
C.
The use of the electron donating compound is found to result, in a manner not understood, in the incorporation of oxygen from the glass with silicon from the silane to form the transparent barrier coating on the glass.
Although the mechanism is not understood, it is believed to involve adsorption of the electron donating compound on the glass surface.
Thus, although the pyrolysis may be carried out in the absence of any oxygen containing gases, a transparent coating containing silicon and oxygen derived from the glass is obtained and not a reflecting silicon coating.
The rate of migration of oxygen containing species from the glass depends on the glass temperature, and the coating is therefore deposited at a glass temperature above 600.
degree.
C.
in order to increase the availability of oxygen-containing species from the glass.
The oxygen in the transparent barrier coatings is not necessarily all derived from the glass, but may be derived in part from the electron donating compound and some further oxidation may occur when the coated glass is exposed to atmospheric oxygen after the coating operation