Patent ID: 6713419
Filing Date: 2004-03-30
Classification: C03C,Y10S

Abstract:
An optical glass for precision press molding consisting of a lanthanum borosilicate system glass having:optical constants of refractive index (nd) within a range from 1.65 to 1.73 and Abbe number (&ngr;d) within a range from 50 to 60; and a glass transformation point (Tg) within a range of 480-580Â° C.; wherein the devitrification temperature of the glass is less than the temperature at which the glass has a viscosity, &eegr;, in poise corresponding to log &eegr;=2.5; in which the devitrification temperature is defined as the temperature at which crystallite occurs on at least one of the surface of the glass or within the glass after the glass is cooled from a temperature in which the melt is transparent; and the optical glass is free from F2 component.