Method of making photosensitive colored glasses exhibiting alterable photo-anisotropic effects

Claim 1

A method for making a photosensitive colored glass article exhibiting alterable photo-anisotropic effects consisting of a body portion and an integral hydrated surface layer of a thickness about 1-500 microns having Ag-AgCl-containing crystals therein, at least a portion of which exhibits photo-dichroic and birefringent properties, which comprises contacting an anhydrous glass body consisting essentially, in mole percent of the oxide basis, of about 70-82% SiO 2 , 10-17% Na 2 O and/or K 2 O, 5-15% ZnO, 0.5-5% Al 2 O 3 , and and 0.1-3% Cl with an aqueous solution containing Ag + ions and acidified to a pH less than about 2, this contact being made at a temperature in excess of 200° C. and at a pressure in excess of 225 psig. for a period of time sufficient to hydrate a surface layer thereon having a thickness of about 1-500 microns, to cause the replacement of Na + and/or K + ions with Ag + ions in said hydrated glass, the proportion of Na + and/or K + ions in said hydrated glass being less with a corresponding increase in Ag + ions, and to cause a reaction between Ag + ions and Cl - ions in said hydrated glasses to form Ag-AgCl-containing crystals therein, and thereafter to expose said surface layer to ultraviolet radiation at an intensity and for a time sufficient to develop photo-dichroic and birefringent properties in at least a portion thereof.

Claim 2

A method for making a photosensitive colored glass article exhibiting alterable photo-anisotropic effects consisting of a body portion and an integral hydrated surface layer of a thickness about 1-500 microns having Ag-AgCl-containing crystals therein, at least a portion of which exhibits photo-dichroic and birefringent properties, which comprises contacting an anhydrous glass body consisting essentially, in mole percent of the oxide basis, of about 70-82% SiO 2 , 10-17% Na 2 O and/or K 2 O, 5-15% ZnO, 0.5-5% Al 2 O 3 , and and 0.1-3% Cl with an aqueous solution containing Ag + ions and acidified to a pH less than about 2, this contact being made at a temperature in excess of 200° C. and at a pressure in excess of 225 psig. for a period of time sufficient to hydrate a surface layer thereon having a thickness of about 1-500 microns, to cause the replacement of Na + and/or K + ions with Ag + ions in said hydrated glass, the proportion of Na + and/or K + ions in said hydrated glass being less with a corresponding increase in Ag + ions, and to cause a reaction between Ag + ions and Cl - ions in said hydrated glasses to form Ag-AgCl-containing crystals therein, and thereafter to expose said surface layer to ultraviolet radiation at an intensity and for a time sufficient to develop photo-dichroic and birefringent properties in at least a portion thereof.