OPTICAL GLASS COATINGS

摘要

The present invention provides a method of producing a substantially crack-free optical quality glass coating on a substantially high temperature-stable substrate, which glass coating has a glass coating layer thickness of from 1 to 15 νm and a desired refractive index value of from 1.44 to 1.70, comprising the steps of: (1) providing a sol comprising colloidal silica and at least 14 wt % of an organic binder material relative to the silica content, wherein from 0 to 25 mole % of said colloidal silica is derived from a first, non-hydrolytically removable group containing, precursor of the formula Rx-SiA4-x wherein, R represents at least one organic moiety which is hydrolytically non-removable from the Si, A represents at least one hydrolysable moiety, and x = 1,2 or 3; (2) coating a substrate with said sol to form a sol-coated substrate; (3) drying the sol-coated substrate so as to produce a gel-coated substrate; (4) doping the gel-coating of said gel coated substrate by contacting said gel-coating with a selected gas phase dopant material at an elevated temperature below a temperature at which densification of said gel-coating occurs, so as to change the refractive index of the resulting glass coating to said desired refractive index value; and (5) densifying the doped gel-coating by heat treatment thereof at a temperature not less than the densification temperature of said gel-coating.