Lithium-containing aluminoborosilicate glass used in the manufacture of optical elements with a refractive index gradient

摘要

PROBLEM TO BE SOLVED: To provide a lithium-containing silicate glass capable of providing high performance optical element with desired refractive index gradient while suppressing deterioration of glass itself or facility.SOLUTION: A lithium-containing silicate glass is a lithium-containing aluminoborosilicate glass used for manufacturing optical elements having refractive index gradient, contains SiO:50 to 70 mol%, BO:3 to 15 mol%, AlO:5 to 15 mol%, LiO:3 to 25 mol% and NaO:0 to 22 mol% with total of LiO and NaO of 15 to 25 mol%, no alkaline earth metal, no TiO, no NbOand satisfying the following formula:(Y+2×Z)/X0.5, where mol% of total of SiOand AlOis X, mol% of BOis Y and mol% of total of LiO and NaO is Z.SELECTED DRAWING: Figure 1