Use of a glass body for the production of a chemical tempered glass body

Die Erfindung betrifft die Verwendung eines Glaskörpers mit einer Zusammensetzung (in Gew.-% auf Oxidbasis) von SiO2 70 - 85; B2O3 8 - 15; Na2O 1 - 5; K2O 1 - < 5; Al2O3 1 - 5; CaO 0 - 3; MgO 0 - 3; SrO + BaO 0 - 2; ZnO 0 - 3; ZrO2 0 - 3,5 mit CaO + ZnO 2 - 6 zur Erzeugung eines chemisch vorgespannten Glaskörpers in einem Ionenaustauschverfahren unterhalb von Tg. The use of a glass body of the following composition, for producing a chemically toughened glass by a conventional ion exchange method below the glass transition temperature. The glass has the composition (by wt., on oxide basis) 70-85% SiO2, 8-15% B2O3, 1-5% Na2O, 1 to less than 5% K2O, 1-5% Al2O3, 0-3% MgO, 0-2% SrO + BaO, 0-3% CaO, 0-3% ZnO, 2-6% CaO + ZnO, 0-3.5% ZrO2 and optionally usual amounts of refiners. Preferably, ion exchange is carried out at 400-550 degrees C for 2-25 h in a bath containing ≥ 90 wt.% potassium salts.