Method for producing a metal coated glass-ceramic article

Claim 1

IN A METHOD OF PRODUCING A METAL COATED GLASS-CERAMIC ARTICLE BY: MELTING A GLASS-FORMING BATCH CONTAINING SILICA AND ALUMINA AS MAIN COMPONENTS, A NUCLEATING AGENT, AND 0.05 TO 5 PERCENT BY WEIGHT, CALCULATED AS THE METAL BASED ON THE TOTAL WEIGHT OF THE GLASS-FORMING COMPOSITION, OF AT LEAST ONE METAL COMPOUND SELECTED FROM COPPER AND SILVER, FORMING THE MELT INTO A GLASS ARTICLE OF THE DESIRED CONFIGURATION, AND HEATING THE FORMED GLASS ARTICLE IN A REDUCING ATMOSPHERE TO DEVITRIFY THE GLASS, WHILE CAUSING THE METALLIC IONS GENERATED FROM SAID METAL COMPOUND TO MIGRATE THROUGH THE GLASS MATRIX, DIFFUSE TO THE SURFACE OF SAID DEVITRIFIED GLASS ARTICLE AND TO REDUCE TO THE STATE OF METALLIC PARTICLES AT THE SURFACE, THE IMPROVEMENT COMPRISING: A. COVERING THE RESULTING GLASS ARTICLE PRIOR TO THE HEATING STEP IN A REDUCING ATMOSPHERE, WITH A SUBSTANCE CONSISTING ESSENTIALLY OF A. AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF COPPER, SILVER, AND COMPOUNDS THEREOF, PRESENT IN AT LEAST 5% METAL WEIGHT BASED ON THE TOTAL METAL WEIGHT OF THE COVERING SUBSTANCE, AND B. AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF METALS OTHER THAN COPPER AND SILVER, AND COMPOUNDS THEREOF, HAVING A MELTING POINT HIGHER THAN THE TEMPERATURE OF THE HEATING STEP, PRESENT IN FROM 0 TO 95% METAL WEIGHT BASED ON THE TOTAL METAL WEIGHT OF THE COVERING SUBSTANCE, AND B. HEATING THE COVERED GLASS ARTICLE IN A REDUCING ATMOSPHERE, WHEREBY THE METALLIC PARTICLES FORMED BY METALLIC ION DIFFUSION TO THE SURFACE ARE COMBINED WITH METALLIC PARTICLES OF THE COVERING SUBSTANCE, THEREBY FORMING A METALLIC LAYER OF INCREASED THICKNESS WHICH IS INTEGRALLY INCORPORATED WITH THE SURFAE OF THE GLASSCERAMIC ARTICLE.