Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1975-08-20
1977-03-15
Rubin, David H.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
351166, 351177, 65 30E, 106 47Q, G02C 702
Patent
active
040121313
ABSTRACT:
An ophthalmic glass lens can be prepared by exposing an alkali metal silicate glass to an ion exchange process in which the glass is chemically strengthened by an exchange of potassium ions for sodium ions in the surface layer of the lens at a temperature either above or below the strain point of the glass. The glasses prepared are essentially free of alumina, have adequate strength and substantially increased depth of pentration of the neutral zone even when up to about 6 percent lime is utilized in the preparation of the glass. The effect of lime as a diffusion-retarding agent during the ion exchange process can be overcome (1) by use of an appropriate amount of zinc or magnesium oxide or mixtures thereof so as to maintain an adequate rate of diffusion during ion exchange or (2) by preparation of the glass essentially free of alumina.
REFERENCES:
patent: 3287200 (1966-11-01), Hess et al.
patent: 3357876 (1967-12-01), Rinehart
patent: 3477834 (1969-11-01), Morris
patent: 3697242 (1972-10-01), Shonebarger
patent: 3741739 (1973-06-01), Baker
patent: 3743491 (1973-07-01), Poole et al.
patent: 3790260 (1974-02-01), Boyd et al.
Deeg Emil W.
Graf Robert E.
Krohn David A.
American Optical Corporation
Berkenstock, Jr. H. R.
Nealon William C.
Rubin David H.
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