Method of forming a transparent reflection reducing coating on glass and the articleresulting therefrom

Claim 1

THE METHOD FORMING A TRANSPARENT REFLECTION-REDUCING COATING ON THE SURFACE OF A GLASS ARTICLE HAVING A REFRACTIVE INDEX GREATER THAN UNITY WHICH METHOD COMPRISES, COATING THE SAID SURFACE OF THE ARTICLE WITH A SUSPENSION COMPRISING TRANSPARENT COLLOIDAL SILICA PARTICLES DISPERSED IN A LIQUID DISPERSION MEDIUM HAVING IN SOLUTION THEREWITH FROM APPROXIMATELY A HALF TO A FEW PER CENT BY WEIGHT OF A METALLIC SALT DECOMPOSABLE INTO FREE METAL AT A TEMPERATURE BELOW THE SOFTENING TEMPERATURE OF THE GLASS ARTICLE, THE SAID METAL BEING ABSORBABLE INTO THE GLASS OF THE ARTICLE WHEN THE LATTER IS IN A HEATED CONDITION AT A TEMPERATURE JUST BELOW ITS SOFTENING POINT, AND THEN HEATING THE COATED ARTICLE AT A TEMPERATURE OF FROM ABOUT 500* TO 700* C., WHICH IS ABOVE THE DECOMPOSITION TEMPERATURE OF THE SAID METALLIC SALT BUT BELOW THE SOFTENING TEMPERATURE OF THE GLASS ARTICLE FOR A SUFFICIENT TIME TO DECOMPOSE THE SAID METALLIC SALT INTO FREE METAL AND CAUSE ABSORPTION OF THE LATTER INTO THE SAID SURFACE OF THE GLASS ARTICLE AT THE AREAS WHERE THE SILICA PARTICLES CONTACT THE SURFACE OF THE GLASS WHEREBY TO ATTACH THE SAID COLLOIDAL SILICA PARTICLES TO SAID SURFACE.