Method for producing a chemically pretensioned glass body

US5876472A · kind A · utility

Assignee

• Schott Glaswerke · DE

Inventors

• Oliver Gros · Rheinböllen, DE
• Sabine Melson · Mainz, DE
• Roland Leroux · Stadecken-Elsheim, DE
• Otmar Becker · Langen, DE
• Dietrich Busch · Simmern, DE

Key dates

• Filing date: Oct 27, 1997
• Grant date: Mar 2, 1999
• Expiry date: Oct 27, 2017

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C03C3/093
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

The invention is directed to a method of producing a chemically pretensioned glass body. In the method, a glass body is provided having a composition in percent by weight on oxide basis: SiO.sub.2 70-85; B.sub.2 O.sub.3 8-15; Na.sub.2 O 1-5; K.sub.2 O 1-<5; Al.sub.2 O.sub.3 1-5; MgO 0-3; SrO+BaO 0-2; CaO 0-3; ZnO 0-3; with CaO+ZnO 2-6; and, ZrO.sub.2 0-3.5. The glass body is placed in an ion exchange salt bath containing at least 90% by weight of potassium salts. The salt bath is maintained at a temperature below the transformation point Tg of the glass defined by the glass composition for a duration of at least 2.0 hr causing potassium ions from the salt bath to migrate into the surface region of the glass body to thereby produce the chemically pretensioned glass body.