The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 15, 1977
Filed:
Aug. 20, 1975
David A Krohn, Southbridge, MA (US);
Emil W Deeg, Woodstock, CT (US);
Robert E Graf, Southeridge, MA (US);
American Optical Corporation, Southbridge, MA (US);
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.