Photochromic glass compositions for lightweight lenses

US4608349A · kind A · utility

Assignee

• Corning Glass Works · US

Inventors

• David J. Kerko · Corning, US
• David W. Morgan · London, GB
• David L. Morse · Tampa, US

Key dates

• Filing date: Nov 28, 1985
• Grant date: Aug 26, 1986
• Expiry date: Nov 28, 2005

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C03C4/06
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Photochromic glass compositions for thin refractive-index-corrected lens elements consisting essentially of about: ______________________________________ SiO.sub.2 54-58% B.sub.2 O.sub.3 18-22% Al.sub.2 O.sub.3 7-8% Li.sub.2 O 3.75-4.5% Na.sub.2 O 0-1% K.sub.2 O 5.5-7.5% TiO.sub.2 0-2% ZrO.sub.2 2-4.5% Ag 0.20-0.33% Cl 0.30-0.50% Br 0.04-0.12% CuO 0.007-0.012% PbO 0-0.08% Sb.sub.2 O.sub.3 0-0.20% ______________________________________ having a Li.sub.2 O:Na.sub.2 O molar ratio of at least 9:1 and exhibiting good darkening, fast fading, good chemical strengthenability and neutral dark-state coloration at thicknesses on the order of 1 mm, are described.