Improvements introduced in the manufacture of lenses to reduce incomodidad.procedente of aphasia and eye diseases Cer- tas

摘要

A photochromic glass article which is especially suitable for spectacle lenses having an integral colored surface layer and exhibiting near-zero transmittance of radiations having wavelengths shorter than a selected cutoff wavelength ranging between 440-550 nm, said glass consisting essentially, expressed in weight percent on the oxide basis, of 0-2.5% Li2O, o-9%Na2O,0-17%K2O,0-6%Cs2O,8-20%Li2O + Na2O + K2O + Cs2O, 14-23% B2O3, 5-25% Al2O3, 0-25% P2O5, 20-65% SiO2, 0.004-0.02% CuO, 0.15-0.3% Ag, 0.1-0.25% Cl, and 0.1-2% Br, wherein the molar ratio of alkali metal oxides: B2O3 varies between about 0.55-0.85 and the weight ratio Ag: (Cl+Br) ranges between 0.65-0.95. …??Such glasses are suitable for use as spectacle lenses for aphakics or for persons subject to photoretinitis or retinitis pigmentosa. …??The integral colored layers is developed on the surface by exposure to a strongly reducing atmosphere at a temperature of 350 to 520 DEG C for at least 12 hours.