High refractive index glasses of limited specific gravity for distance and near vision spectacle lenses

摘要

Optical glasses having high refractive indexes and low specific gravities are provided for use as both distant and near vision spectacle lenses. The glasses consist essentially of low molecular weight cationic oxides, alkali metal oxides and divalent oxides to promote the crystallization stability of the glass. They have good chemical resistance, chemical hardenability and a thermal expansion coefficient between 93 and 99x10-7/ DEG C. in the range of 20 DEG -300 DEG C. Optical lenses can be continuously produced due to the high crystallization stability of the glasses and the resultant spectacle lenses have high dioptric values even with thinner edge or center thicknesses.