STRENGTHENED GLASS SUBSTRATE AND PROCESS FOR PRODUCING THE SAME

• US 20100087307A1
• Filed: 06/03/2008
• Published: 04/08/2010
• Est. Priority Date: 06/07/2007
• Status: Active Grant

• Current Assignee: Nippon Electric Glass Company Limited
• Original Assignee: Nippon Electric Glass Company Limited
• Inventors: Yamazaki, Hiroki, Murata, Takashi
• Granted Patent: US 8,349,454 B2
• Time in Patent Office: Days
• US Class Current: 501/67
• 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: G02F 1/133302 Rigid substrates, e.g. inorganic substrates
• CPC Class Codes: G02F 1/133331 Cover glasses
• CPC Class Codes: Y10T 428/315 Surface modified glass [e.g., tempered, strengthened, etc.]

Abstract

An object of the invention is to obtain a glass substrate having high mechanical strength by reconciling suitability for ion exchange and devitrification proof in a glass. The strengthened glass substrate of the invention is a strengthened glass substrate having a compression stress layer in the surface thereof, the glass substrate having a glass composition including, in terms of % by mass, 40-70% of SiO₂, 12-25% of Al₂O₃, 0-10% of B₂O₃, 0-8% of Li₂O, 6-15% of Na₂O, 0-10% of K₂O, 13-20% of Li₂O+Na₂O+K₂O, 0-3.9% of MgO, 0-5% of CaO, 0-5% of ZnO, 0-6% of ZrO₂, and 0-5% of SrO+BaO, the value of (MgO+ZrO₂+ZnO)/(MgO+ZrO₂+ZnO+Al₂O₃) in terms of mass proportion being from 0.25 to 0.45. The above-mentioned strengthened glass can be produced by melting raw glass materials mixed together so as to result in the given glass composition, forming the melt into a sheet by an overflow downdraw process, and then conducting an ion exchange treatment to form a compression stress layer in the glass sheet surface.

Claims

1. A strengthened glass substrate having a compression stress layer in the surface thereof, said glass substrate having a glass composition comprising, in terms of % by mass, 40-70% of SiO₂, 12-25% of Al₂O₃, 0-10% of B₂O₃, 0-8% of Li₂O, 6-15% of Na₂O, 0-10% of K₂O, 13-20% of Li₂O+Na₂O+K₂O, 0-3.9% of MgO, 0-5% of CaO, 0-5% of ZnO, 0-6% of ZrO₂, and 0-5% of SrO+BaO, the value of (MgO+ZrO₂+ZnO)/(MgO+ZrO₂+ZnO+Al₂O₃) in terms of mass proportion being from 0.25 to 0.45.

2. The strengthened glass substrate according to claim 1, which is a strengthened glass substrate having a compression stress layer in the surface thereof and having a glass composition comprising, in terms of % by mass, 40-70% of SiO₂, 12-25% of Al₂O₃, 0-10% of B₂O₃, 0-8% of Li₂O, 6-15% of Na₂O, 0-10% of K₂O, 13-20% of Li₂O+Na₂O+K₂O, 0-3.9% of MgO, 0-5% of CaO, 0-5% of ZnO, 0-5.5% of ZrO₂, and 0-5% of SrO+BaO, the value of (MgO+ZrO₂+ZnO)/(MgO+ZrO₂+ZnO+Al₂O₃) in terms of mass proportion being from 0.25 to 0.45.

3. The strengthened glass substrate according to claim 1, which has been chemically strengthened.

4. The strengthened glass substrate according to claim 1, which has a compressive stress of the surface thereof of 100 MPa or higher and a depth of the compression stress layer of 1 μ

m or larger.

5. The strengthened glass substrate according to claim 1, which has an unpolished surface.

6. The strengthened glass substrate according to claim 1, which is composed of a glass having a liquidus temperature of 1,050°

C. or lower.

7. The strengthened glass substrate according to claim 1, which is composed of a glass having a liquidus viscosity of 10^4.0 dPa·

s or higher.

8. The strengthened glass substrate according to claim 1, which is for use in a touch panel display.

9. The strengthened glass substrate according to claim 1, which is for use as the cover glass of a portable telephone.

10. The strengthened glass substrate according to claim 1, which is for use as the cover glass of a solar cell.

11. The strengthened glass substrate according to claim 1, which is for use as a protective member in a display.

12. A glass having a glass composition comprising, in terms of % by mass, 40-70% of SiO₂, 12-25% of Al₂O₃, 0-10% of B₂O₃, 0-8% of Li₂O, 6-15% of Na₂O, 0-10% of K₂O, 13-20% of Li₂O+Na₂O+K₂O, 0-3.9% of MgO, 0-5% of CaO, 0-5% of ZnO, 0-6% of ZrO₂, and 0-5% of SrO+BaO, the value of (MgO+ZrO₂+ZnO)/(MgO+ZrO₂+ZnO+Al₂O₃) in terms of mass proportion being from 0.25 to 0.45.

13. A process for producing a strengthened glass substrate, which comprises:

melting raw glass materials mixed together so as to result in a glass composition comprising, in terms of % by mass, 40-70% of SiO₂, 12-25% of Al₂O₃, 0-10% of B₂O₃, 0-8% of Li₂O, 6-15% of Na₂O, 0-10% of K₂O, 13-20% of Li₂O+Na₂O+K₂O, 0-3.9% of MgO, 0-5% of CaO, 0-5% of ZnO, 0-6% of ZrO₂, and 0-5% of SrO+BaO, the value of (MgO+ZrO₂+ZnO)/(MgO+ZrO₂+ZnO+Al₂O₃) in terms of mass proportion being in the range of from 0.25 to 0.45;

forming the melt into a sheet; and

then conducting an ion exchange treatment to form a compression stress layer in the glass surface.

14. The process for producing a strengthened glass substrate according to claim 13, wherein the melt is formed into a sheet by a downdraw process.

15. The process for producing a strengthened glass substrate according to claim 13, wherein the melt is formed into a sheet by an overflow downdraw process.