Coating silicate glass surfaces with hard, partially reflective layer - with silicate surface pre-treated to reduce alkali content and increase silicate network forming agents leading to improved wear and corrosion resistance in final coating

摘要

The surface of a silicate glass object to be coated with a partially reflective, wear and corrosion resistant hard layer of Ti, Zr or Ti-Al alloy nitrides and/or carbides is treated in such a way as to reduce its alkali content and increase its content of metal oxides which form network changing or network building agents for the silicate glass. The oxides are at least one from Al, Mg, Ti, Cr, Zn, Zr, Fe, Be, Ni, Co, Pd. The process is simple and economic and the final coating has improved hardness, wear and corrosion resistance compared with prior art processes. The silicate glass surface is treated to reduce its hydroxyl ion content. The affected surface layer has a thickness of 1-10, pref. 1-5 nm and the hard coating is pref. TiN with a degree of nitriding between 0.55-1.16. The surface treatment is carried out by a low pressure plasma process in an electric DC field. During the treatment the alkali ions are reduced and the surface enriched with the required oxides. The process uses cathodes made mainly of Al or Ti. The cathode may be a binary alloy of Al-Mg or an Al-Mg mixture with additives of Ti or Cr. Alternatively a ternary alloy of Al-Zn-Mg with Cr additive may be used. USE/ADVANTAGE - In making car windscreen and welding protection glasses.