Spectacle lenses to reduce discomfort from aphakia and certain eye diseases
AssigneeCorning Glass Works
InventorBrent M. Wedding
Life of this patent
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Abstract
This invention is concerned with producing glasses suitable for use as spectacle lenses for aphakics or for persons subject to photoretinitis or retinitis pigmentosa. The glasses exhibit near-zero transmittance of radiations having wavelengths shorter than a selected cutoff wavelength ranging about 440-550 nm and the transmittance of the remainder of the visible spectrum is adjusted through the glass demonstrating photochromic behavior. The inventive method contemplates exposing photochromic glass within a narrowly-defined composition range to a strongly-reducing atmosphere at temperatures between about 350.degree.-520.degree. C. for a period of time of at least 12 hours to develop an integral colored surface layer on the glass.
Claims17
A photochromic glass article 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 about 440-550 nm, said glass consisting essentially, expressed in weight percent on the oxide basis, of about 0-2.5% Li.sub.2 O, 0-9% Na.sub.2 O, 0-17% K.sub.2 O, 0-6% Cs.sub.2 O, 8-20% Li.sub.2 O+Na.sub.2 O+K.sub.2 O+Cs.sub.2 O, 14-23% B.sub.2 O.sub.3, 5-25% Al.sub.2 O.sub.3, 0-25% P.sub.2 O.sub.5, 20-65% SiO.sub.2, 0.004-0.02% CuO, 0.15-0.3% Ag, 0.1-0.25% Cl, and 0.1-0.2% Br, wherein the molar ratio of alkali metal oxides:B.sub.2 O.sub.3 varies between about 0.55-0.85 and the weight ratio Ag:(Cl+Br) ranges between about 0.65-0.95.
A method for making a photochromic glass article 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 about 440-550 nm which comprises subjecting a photochromic glass consisting essentially, expressed in weight percent on the oxide basis, of about 0-2.5% Li.sub.2 O, 0-9% Na.sub.2 O, 0-17% K.sub.2 O, 0-6% Cs.sub.2 O, 8-20% Li.sub.2 O+Na.sub.2 O+K.sub.2 O+Cs.sub.2 O, 14-23% B.sub.2 O.sub.3, 5-25% Al.sub.2 O.sub.3, 0-25% P.sub.2 O.sub.5, 20-65% SiO.sub.2, 0.004-0.02% CuO, 0.15-0.3% Ag, 0.1-0.25% Cl, and 0.1-0.2% Br, wherein the molar ratio of alkali metal oxide:B.sub.2 O.sub.3 varies between about 0.55-0.85 and the weight ratio Ag:(Cl+Br) ranges between about 0.65-0.95, to a strongly reducing atmosphere at a temperature between about 350.degree.-520.degree. C. for a period of time of at least 12 hours to develop an integral colored surface layer therein.
Dependencies are inferred from the claim text.