Chemically toughened glasses

• US 6,518,211 B1
• Filed: 09/14/2000
• Issued: 02/11/2003
• Est. Priority Date: 03/20/1998
• Status: Expired due to Term

• Current Assignee: GKN Aerospace Services Limited (Melrose Industries Plc)
• Original Assignee: Pilkington PLC
• Inventors: Smith, Ian Heaton, Bradshaw, John Michael, Lythgoe, Stanley, Torr, Ashley Carl
• Primary Examiner(s): SAMPLE, DAVID R
• Application Number:
  US09/646,240
• Time in Patent Office: 880 Days
• Field of Search: 501/64, 501/69, 501/70, 501/71, 501/72, 428/410
• US Class Current: 501/69
• CPC Class Codes: C03C 21/002 to perform ion-exchange between alkali ions C03C21/005 takes precedence
• CPC Class Codes: C03C 3/085 containing an oxide of a divalent metal
• CPC Class Codes: Y10T 428/315 Surface modified glass [e.g., tempered, strengthened, etc.]

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%.

Claims

1. 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:

2. A composition as claimed in claim 1 additionally containing Fe₂O₃ in an amount of from 0.2% to 4% by weight, the ferrous state being at least 20%.

3. A composition as claimed in claim 1 additionally containing Fe₂O₃ in an amount of less than 0.2% by weight.

4. A composition as claimed in claim 3 additionally including cerium oxide in an amount of from 0.05% to 0.5% by weight.

5. A composition as claimed in claim 3 wherein the ferrous state is less than 20%.

6. A composition as claimed in claim 1 additionally containing TiO₂ in an amount of up to 1% by weight.

7. A composition as claimed in claim 1 additionally containing sulphate in an amount of from 0.1% to 0.4% by weight.

8. A composition as claimed in claim 2 additionally including a colorant for neturalising the green colour produced by the Fe₂O₃.

9. A composition as claimed in claim 8 wherein the colorant is selected from cobalt oxide, nickel oxide or selenium or mixtures thereof.

10. A composition as claimed in claim 1 in which the Al₂O₃ is present in an amount in excess of 6% by weight and the MgO is present in an amount of from 4% to 8% by weight.

11. A composition as claimed in claim 1 in which the MgO is present in an amount in excess of 8% by weight and the Al₂O₃ is present in an amount of from 5% to 9% by weight.

12. A composition as claimed in claim 1 in which the K₂O is present in an amount of from 0.5% to 3.5% by weight and the Al₂O₃ is present in an amount of from