Damage resistant glass with high coefficient of thermal expansion
Ion exchangeable glasses having coefficients of thermal expansion (CTE) at least about 90×10 −7 ° C. −1 . The glasses undergo rapid ion exchange, for example, in a molten KNO 3 salt bath to a depth of layer of greater than 30 microns in less than 2 hours at temperatures of 370° C. to 390° C. When ion-exchanged to a depth of layer between 30 to 50 microns, the glasses exhibit a Vickers median/radial crack initiation threshold exceeding 30 kilograms force (kgf). The glasses are fusion formable and, in some embodiments, compatible with zircon.
1. A glass, the glass comprising SiO 2 , from 6 mol % to 17 mol % Al 2 O 3 , greater than 5 mol % P 2 O 5 , and greater than 1 mol % K 2 O, wherein
R 2 O+R′O is greater than 18 mol %, where R is at least one alkali metal and R′ is at least one alkaline earth oxide,
the glass is substantially free of B 2 O 3 , and
the glass has a coefficient of thermal expansion of greater than 95×10 −7 ° C. −1 .
2. The glass of claim 1 , wherein the glass is ion exchanged and has a Vickers crack initiation threshold in a range from greater than 20 kgf to 50 kgf.
3. The glass of claim 2 , wherein the Vickers crack initiation threshold is in a range from 30 kgf up to 50 kgf.
4. The glass of claim 2 , wherein the glass has a compressive layer extending from a surface of the glass to a depth of layer of at least 30 μm.
5. The glass of claim 4 , wherein the depth of layer is in a range from 30 μm up to 50 μm.
6. The glass of claim 4 , wherein the compressive layer has a compressive stress of at least 800 MPa.
7. The glass of claim 4 , wherein the glass has been ion exchanged in an ion exchange bath comprising KNO 3 at a temperature in a range from 370° C. to 390° C. for up to two hours.
8. The glass of claim 1 , wherein the glass has a liquidus temperature T L , a 160 kP temperature T 160kP , a 35 kP temperature T 35kP , and a zircon breakdown temperature T breakdown , wherein T L <T 160kP and T breakdown >T 35kP .
9. The glass of claim 1 , wherein the glass comprises from 57 mol % to 75 mol % SiO 2 ; from 6 mol % to 17 mol % Al 2 O 3 ; from greater than 5 mol % to 7 mol % P 2 O 5 ; from 14 mol % to 17 mol % Na 2 O; and from greater than 1 mol % to 5 mol % K 2 O.
10. The glass of claim 9 , comprising from 0 mol % to 2 mol % MgO.
11. The glass of claim 9 , wherein the glass comprises from 57 mol % to 59 mol % SiO 2 ; from greater than 13 mol % to 17 mol % Al 2 O 3 ; from greater than 5 mol % to 7 mol % P 2 O 5 ; from 16 mol % to 17 mol % Na 2 O; and from 1 mol % to 5 mol % K 2 O.
12. The glass of claim 1 , wherein the glass comprises at least 13 mol % Al 2 O 3 .
13. The glass of claim 1 , wherein the glass is substantially free of MgO.
14. The glass of claim 1 , wherein the glass, when ion exchanged for one hour at 390° C. in a KNO 3 bath, has a Vickers crack initiation threshold of greater than 20 kgf.
15. An appliance, comprising the glass of claim 1 .
16. The appliance of claim 15 , further comprising a display.
17. An ion exchanged glass, the ion exchanged glass comprising SiO 2 , from 6 mol % to 17 mol % Al 2 O 3 , greater than 5 mol % P 2 O 5 , greater than 1 mol % K 2 O, wherein R 2 O+R′O is greater than 18 mol %, where R is at least one alkali metal and R′ is at least one alkaline earth oxide, and the glass is substantially free of B 2 O 3 , and wherein the glass has a coefficient of thermal expansion of greater than 95×10 −7 ° C. −1 and has a Vickers crack initiation threshold in a range from greater than 20 kgf to 50 kgf.
18. The ion exchanged glass of claim 17 , wherein the Vickers crack initiation threshold is in a range from 30 kgf up to 50 kgf.
19. The ion exchanged glass of claim 17 , wherein the glass has a compressive layer extending from a surface of the glass to a depth of layer of at least 30 μm.
20. The ion exchanged glass of claim 19 , wherein the depth of layer is in a range from 30 μm up to 50 μm.
21. The ion exchanged glass of claim 19 , wherein the compressive layer has a compressive stress of at least 800 MPa.
22. The ion exchanged glass of claim 19 , wherein the ion exchanged glass has been ion exchanged in an ion exchange bath comprising KNO 3 at a temperature in a range from 370° C. to 390° C. for up to two hours.
23. The ion exchanged glass of claim 17 , wherein the ion exchanged glass has a liquidus temperature T L , a 160 kP temperature T 160kP , a 35 kP temperature T 35kP , and a zircon breakdown temperature T breakdown , wherein T L <T 160P and T breakdown >T 35kP .
24. The ion exchanged glass of claim 17 , wherein the ion exchanged glass comprises from 57 mol % to 59 mol % SiO 2 ; from greater than 13 mol % to 17 mol % Al 2 O 3 ; from greater than 5 mol % to 7 mol % P 2 O 5 ; from 16 mol % to 17 mol % Na 2 O; and from greater than 1 mol % to 5 mol % K 2 O.
25. The ion exchanged glass of claim 24 , further comprising up to 2 mol % MgO.
26. The ion exchanged glass of claim 17 , wherein the ion exchanged glass comprises at least 13 mol % Al 2 O 3 .
27. The ion exchanged glass of claim 17 , wherein the ion exchanged glass is substantially free of MgO.
28. An appliance, comprising the ion exchanged glass of claim 17 .
29. The appliance of claim 28 , further comprising a display.
30. A method of ion exchanging a glass, the method comprising:
a. providing a glass, the glass comprising SiO 2 , from 6 mol % to 17 mol % Al 2 O 3 , greater than 5 mol % P 2 O 5 , and greater than 1% K 2 O, wherein R 2 O+R′O is greater than 18 mol %, where R is at least one alkali metal and R′ is at least one alkaline earth oxide, the glass being substantially free of B 2 O 3 and having a coefficient of thermal expansion of greater than 95×10 −7 ° C. −1 ;
b. providing an ion exchange bath, wherein the ion exchange bath comprises KNO 3 and is at a temperature in a range from 370° C. to 390° C.; and
c. ion exchanging the glass in the ion exchange bath for a time period of up to two hours, wherein the ion exchanged glass has a layer under a compressive stress, the layer extending from a surface of the glass to a depth of layer of at least 30 μm.
31. The method of claim 30 , wherein the ion exchanged glass has a Vickers crack initiation threshold of at least 4-5 in a range from 20 kgf to 50 kgf.
32. The method of claim 31 , wherein the Vickers crack initiation threshold is in a range from 30 kgf up to 50 kgf.
33. The method of claim 30 , wherein the depth of layer is in a range from 30 μm up to 50 μm.
34. The method of claim 30 , wherein the compressive stress is at least 800 MPa.
35. The method of claim 30 , wherein the ion exchanged glass comprises from 57 mol % to 59 mol % SiO 2 ; from greater than 13 mol % to 17 mol % Al 2 O 3 ; greater than 5 mol % to 7 mol % P 2 O 5 ; from 16 mol % to 17 mol % Na 2 O; and greater than 1 mol % to 5 mol % K 2 O.
36. The method of claim 35 , further comprising up to 2 mol % MgO.
37. The method of claim 30 , wherein the ion exchanged glass comprises at least 13 mol % Al 2 O 3 .