Optical glass, glass material for press molding, optical element, and method of manufacturing same

Abstract

A method of making a press-moldable glass, including melting starting materials, forming a melt, and annealing a formed glass, wherein the melt has a composition such that, (1) when rapidly cooled to room temperature, it becomes glass that has a scattering coefficient of less than 0.005 cm-1 at wavelengths of from 400 to 2,500 nm or comprises crystals with a volumetric ratio of less than 10-6, and (2) when maintained for three hours at a temperature 10° C. higher than the glass transition temperature, maintained for 10 min at a temperature yielding a viscosity of 104.5 to 103.5 dPa·s, and then rapidly cooled to room temperature, (3) the resulting glass has (a) a scattering coefficient of at least one wavelength from 400 to 2,500 nm of greater than 0.01 cm-1 or (b) crystals with a volumetric ratio of greater than 10-5. A temperature for annealing is lower than for glass transition.

Dependencies are inferred from the claim text.