Optical glass, press-molding preform, process for the production thereof, optical element and process for the production thereof

Abstract

A low-dispersion optical glass suitable for producing a quality preform from a molten glass and suitable for precision press-molding, which is a fluorophosphate glass containing, as essential cationic components, P5+, Al3+, at least two members selected from Mg2+, Ca2+, Sr2+ and Ba2+ as divalent cationic components (R2+) and Li+ and containing, by cationic %, 10 to 45% of P5+, 5 to 30% of Al3+, 0 to 20% of Mg2+, 0 to 25% of Ca2+, 0 to 30% of Sr2+, 0 to 33% of Ba2+, 1 to 30% of Li+, 0 to 10% of Na+, 0 to 10% of K+, 0 to 5% of Y3+, and 0 to 15% of B3+, the molar ratio of the content of F− to the total content of F− and O2−, F−/(F−+O2−) being 0.25 to 0.85, the optical glass having a refractive index (Nd) of 1.40 to 1.58 and an Abbe's number (νd) of 67 to 90.

Dependencies are inferred from the claim text.