DOUBLE ION EXCHANGE METHOD FOR STRENGTHENING GLASS ARTICLES

• US 3,798,013 A
• Filed: 04/24/1972
• Issued: 03/19/1974
• Est. Priority Date: 04/26/1971
• Status: Expired due to Term

• Current Assignee: Jun Hasegawa, Nobuyoshi Ohsato, Touru Inoue
• Original Assignee: Jun Hasegawa, Nobuyoshi Ohsato, Touru Inoue
• Inventors: Ohsato, Nobuyoshi, Hasegawa, Jun, Inoue, Touru
• Primary Examiner(s): Lindsay, Jr., Robert L.
• Application Number:
  US05/246,815
• Time in Patent Office: 694 Days
• Field of Search: 65/30
• US Class Current: 65/30.14
• CPC Class Codes: C03C 21/002 to perform ion-exchange between alkali ions C03C21/005 takes precedence

Abstract

A process for increasing the strength of a glass article by subjecting a glass article containing alkali metal ion A to a treatment of exchanging the ion A with an alkali metal ion B having a larger ion radius than the ion A, wherein the exchanging treatment is performed in two successive stages, and the secondstage exchanging treatment is carried out under milder treating conditions using a treating salt having a larger ion B content than in the first-stage treatment.

Claims

2. The method of claim 1, wherein the treatment temperature is from 50*C. below the strain point to 100*C. below the strain point.

3. The method of claim 1, wherein the content of the alkali metal ion B is 60 to 80 mol percent based on the sum of the alkali metal ions A and B.

4. The method of claim 1, wherein the second-stage treatment is carried out in a plurality of stages wherein the proportion of the alkali metal ion B in one stage is equal to, or larger than, that in the preceding stage and also the ion-exchange reaction conditions in one stage are milder than those in the preceding stage.