High refractive index low density glass - based on silica, titania and alkali metal and alkaline earth metal oxide(s)

摘要

Glass having refractive index 1.675-1.720, density 3.1-3.4 g/cc., Abbe no. 33-36.5 wt. loss in an acid bath (AO test) 0.010 mg/sq. cm and viscosity at liquidus temp. >=220 poise, pref. >=250 poise, has compsn (by wt.)% 40-46% SiO2, 0-3% Al2O3, 40-46% (SiO2 + Al2O3), 13-17% TiO2, 4-11% ZrO2, 0-2% MgO, 8-16% CaO, 0-4% SrO, 4-8% (CaO + MgO), 15-25% (CaO +baO + SrO), 2-10% Nb2O5, 0-3% Li2O, 2-7% Na2O, 3-8% K2O and 5-12% (Li2O + Na2O + K2O). Used in high correction spectacle lenses and in optical instruments, where min. is important; glass can be produced on an industrial scale in a continuous furnace and then machine moulded.