Strengthening glass by ion exchange
First Claim
1. In a method of strengthening a silicate glass article by developing compressive stress in a surface layer on the article through an exchange of alkali metal ions in the surface layer at an elevated temperature below the glass strain point, the step of minimizing stress relaxation by carrying out the ion exchange in the silicate glass containing less than 1% non-bridging oxygen atoms.
1 Assignment
0 Petitions
Accused Products
Abstract
A method of strengthening a glass article by developing compressive stress in a surface layer on the article through an exchange of alkali metal ions in the surface layer at an elevated temperature below the glass strain point, the step of minimizing stress relaxation by carrying out the ion exchange in a glass essentially free from non-bridging oxygen atoms. Glasses having particular utility contain alumina in their compositions in such amount that the number of aluminum atoms in a glass are at least equal to the number of alkali metal ions, or contain both alumina and boric oxide in such amounts that the formula ##EQU1## is satisfied.
-
Citations
15 Claims
- 1. In a method of strengthening a silicate glass article by developing compressive stress in a surface layer on the article through an exchange of alkali metal ions in the surface layer at an elevated temperature below the glass strain point, the step of minimizing stress relaxation by carrying out the ion exchange in the silicate glass containing less than 1% non-bridging oxygen atoms.
- 6. A method of minimizing stress relaxation in a silicate glass article having compressive stress developed by exchange of alkali metal ions in a surface layer on the article which comprises carrying out the ion exchange on the silicate glass containing less than 1% non-bridging oxygen atoms.
- 11. An ion-exchange strengthened silicate glass article composed of a glass selected from a group consisting of R2 O--Al2 O3 --SiO2 glasses having compositions containing alumina in such amount that the number of aluminum atoms in the glass are at least equal to the number of alkali metal atoms in the glass, and R2 O--Al2 O3 --B2 O3 --SiO2 glasses having compositions containing both alumina and boric oxide in such amounts that the formula ##EQU9## is satisfied, and wherein the non-bridging oxygen content is less than 1% of the total oxygen content.
Specification