GLASS FOR PRESSED LENS AND PRODUCTION OF PRESSED LENS

• Main Author: HIROTA SHINICHIRO
• Format: Patent
• Language: English
• Published: 24.12.1987
• Subjects: CHEMISTRY; GLASS; MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES; METALLURGY; MINERAL OR SLAG WOOL

PURPOSE:To produce a glass for the molding of pressed lens preventing the fusion of the glass to a mold in compression molding, by coating a surface of an inner glass with a surface glass layer having higher glass transition temperature than the inner glass. CONSTITUTION:A disk-shaped inner glass 1 containing large amount of e.g. PbO is preformed and its upper and lower surfaces are coated with glass surface layers 2 by vacuum evaporation method to obtain a glass 3 for pressed lens. In the above process, the glass of the surface layer 2 has a glass transition temperature higher than that of the inner glass by 15-700 deg.C. The glass 3 is inserted between an upper and a lower molds 4, 5, heated together with the molds 4, 5, 6 in an inert atmosphere by induction heating coil 10 to soften the inner glass 1 and compression molded by lowering a press rod 7 while maintaining the surface layer 2 in unsoftened state. The compression-molded product is slowly cooled to obtain a lens 3' finished to the state of final product. The use of a glass surface layer having higher glass transition temperature than the inner glass is effective in preventing the welding of the glass to the mold and the reduction of PbO in the glass, if any.