Chemically toughened glasses
AssigneePilkington plc
InventorsJohn Michael Bradshaw, Ian Heaton Smith, Ashley Carl Torr, Stanley Lythgoe
Life of this patent
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Abstract
A glass composition capable of being chemically strengthened by ion-exchange within 100 hours to provide a glass with a surface compressive stress of greater then 400 MPa and an ion-exchange depth greater then 200 microns comprising: SiO2 58% to 70% (by weight), Al2O3 5% to 15%, Na2O 12% to 18%, K2O 0.1% to 5%, MgO 4% to 10%, CaO 0% to 1% with the provisos that the total of the Al2O3 and MgO is in excess of 13%, the total of the amounts of Al2O3 plus MgO divided by the amount of K2O is at least 3 and that the sum of the amounts of Na2O, K2O and MgO is at least 22%.
Claims12
A boron-free float glass having a density which is less than 2.48 g/cm3 and a composition capable of being chemically strengthened over a period of less than 100 hours to exhibit a surface stress of at least 400 Mpa with a depth of ion penetration greater than 200 microns comprising:
- SiO2 58% to 70% (by weight) Al2O3 5% to 15% Na2O 12% to 18% K2O 0.1% to 5% MgO 4% to 10% CaO 0% to 1%
- with the provisos that the sum of the Al2O3 and MgO exceeds 13%, that the sum of the amounts of Al2O3 plus MgO divided by the amount of K2O exceeds 3 and that the sum of the Na2O plus K2O plus MgO exceeds 22%.
Dependencies are inferred from the claim text.