Patent Number: 6,251,813

Title: Optical glass and its use

Abstract: An optical glass having properties of a high refractive index and low dispersion and having both a low sag temperature T.sub.s and a low liquidus temperature L.T., is provided. The optical glass comprises, by % by weight, 25 to 42% of B.sub.2 O.sub.3, 14 to 30% of La.sub.2 O.sub.3, 2 to 13% of Y.sub.2 O.sub.3, 2 to 20 of SiO.sub.2, greater than 2% and 9% or less of Li.sub.2 O, 0.5 to 20% of CaO, 2 to 20% of ZnO, 0 to 8% of Gd.sub.2 O.sub.3, 0 to 8% of ZrO.sub.2, Gd.sub.2 O.sub.3 +ZrO.sub.2 being 0.5 to 12%, the total content thereof being at least 90%, and optionally contains 0 to 5% of Na.sub.2 O, 0 to 5% of K.sub.2 O, 0 to 5% of MgO, 0 to 5% of SrO, 0 to 10% of SrO, 0 to 10% of BaO, 0 to 5% of Ta.sub.2 O, 0 to 5% of Al.sub.2 O.sub.3, 0 to 5% of Yb.sub.2 O.sub.3, 0 to 5% of Nb.sub.2 O.sub.5, 0 to 2% of As.sub.2 O.sub.3 and 0 to 2% of Sb.sub.2 O.sub.3.

Inventors: Sato; Kouichi (Tokyo, JP)

Assignee: Hoya Corporation

International Classification: C03C 3/068 (20060101); C03C 3/062 (20060101); C03C 003/066 (); C03C 003/068 ()

Expiration Date: 06/26/2018