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:
Apr. 20, 1976
Filed:
Nov. 29, 1974
Richard John Parry, Southport, EN;
Reginald Dunning, Parbold, Nr. Wigan, EN;
Pilkington Brothers Limited, St. Helens, EN;
Abstract
Ophthalmic glass compositions suitable for toughening by the known ion-exchange process have a composition in weight percentages of: SiO.sub.2 58 to 67% Al.sub.2 O.sub.3 4.5 to 8.0% Na.sub.2 O 8.5 to 17% K.sub.2 O 2 to 11% ZnO 0 to 10% ZrO.sub.2 0 to 6.5% TiO.sub.2 0 to 5.0% As.sub.2 O.sub.3 0 to 1% Sb.sub.2 O.sub.3 0 to 1% B.sub.2 O.sub.3 0 to 6% The total of the foregoing constituents amounting to at least 95% of the composition and the balance, if any, being composed of compatible constituents; the composition including an effective amount of either one or both of ZnO and ZrO.sub.2, to promote ion penetration in an ion-exchange toughening process, either one or both of ZrO.sub.2 and TiO.sub.2 being present; the total of Na.sub.2 O + K.sub.2 O being not more than 22%; B.sub.2 O.sub.3 being present when the total of Al.sub.2 O.sub.3 + ZrO.sub.2 exceeds 10%; and the total of ZrO.sub.2 + TiO.sub.2, when TiO.sub.2 is present, being not more than 5.5%. Refractive index n.sub.d is close to the standard value of 1.523 and good penetration of the ion exchange is achieved in toughening, while the expansion coefficient makes the glass compatible with a standard flint glass in fused bi-focal lenses.