Production manner of the glass material for press molding and production manner of the glass press molding item, the process melting the production mannered

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a glass material, in which a transparent and high quality press molded article can be produced even from glass that tends to easily loose transparency by reheat press molding, and to provide a method for producing the press molded article.;SOLUTION: The method for producing the glass material for press molding comprises the steps of melting the glass, molding the glass and annealing. The molten glass has a composition which (1) provides a glass that has a scattering coefficient at wavelengths of 400-2,500 nm of less than 0.005 cm^-1 or contains a crystal in an amount less than 10^-6 by volume fraction when quenched to room temperature; and (2) provides a glass that has a scattering coefficient at at least one wavelength in wavelengths of 400-2,500 nm of 0.01 cm^-1 or more, or contains a crystal in an amount more than 10^-5 by volume fraction when quenched to room temperature after maintained at a temperature 10°C higher than the glass transition temperature for 3 hours and then maintained at a temperature in which the molten glass exhibits a viscosity of 10^4.5-10^3.5 dPa-s for 10 minutes. The molded glass is subjected to the annealing at a temperature less than the glass transition temperature.;COPYRIGHT: (C)2003,JPO