Acidproof, hydrolysis-resistant optical and ophathalmic glass of low density

Abstract

An improved optical glass having an index of refraction of .gtoreq.1.69, an Abbe number of .gtoreq.38, and a density of .ltoreq.3.25 g/cm.sup.3, represents a further development of another optical glass recently provided by the same inventors. The new glass has improved suitability for continuous-tank manufacture and increased acidproofness and differs from the other glass in its content of 0.5-4.0% by weight of P.sub.2 O.sub.5 ; its sum total of SiO.sub.2 +B.sub.2 O.sub.3 +Al.sub.2 O.sub.3 +P.sub.2 O.sub.5 being 38.5-41.5% by weight; and its sum total of MgO+CaO being 13-17.5% by weight. The full glass composition, e.g. is in % by weight: ______________________________________ SiO.sub.2 26.0-32.5 B.sub.2 O.sub.3 6.0-12.0 Al.sub.2 O.sub.3 0-3.0 P.sub.2 O.sub.5 0.5-4.0 SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 + P.sub.2 O.sub.5 = 38.5-41.5 Li.sub.2 O 0-5 Na.sub.2 O 0-6 K.sub.2 O 0-8 Li.sub.2 O + Na.sub.2 O + K.sub.2 O = 4.5-12.0 MgO 0-8 CaO 9-16 MgO + CaO = 13-17.5 SrO 0-6 BaO 0-5 ZnO 0-7 PbO 0-4 SrO + BaO + ZnO + PbO = 0-7 MgO + CaO + SrO + BaO + ZnO + PbO = 17-24 La.sub.2 O.sub.3 6-11 ZrO.sub.2 5-8 La.sub.2 O.sub.3 + ZrO.sub.2 = 13.5-17.5 TiO.sub.2 5-9 Nb.sub.2 O.sub.5 6-11 WO.sub.3 0-4 TiO.sub.2 + Nb.sub.2 O.sub.5 + WO.sub.3 = 14-18 La.sub.2 O.sub.3 + ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 + WO.sub.3 = 28-33 ZrO.sub.2 + TiO.sub.2 + Nb.sub.2 O.sub.5 = 20-26 ______________________________________

Dependencies are inferred from the claim text.