Glass sheets with improved mechanical strength

Patent metadata

Field	Value
Publication number	US-9434633-B2
Application number	US-201113170675-A
Country	US
Kind code	B2
Filing date	Jun 28, 2011
Priority date	Jun 29, 2010
Publication date	Sep 6, 2016
Grant date	Sep 6, 2016

Abstract

Transparent glass sheets having increased mechanical strength include an inner layer surrounded by surface compressive layers wherein the difference of the coefficient of thermal expansion of the inner layer and the surface compressive layer is greater than 50×10 −7 ° C. −1 and wherein the surface compressive layer has a compressive stress of at least about 300 MPa.

First claim

What is claimed is:

1. A transparent glass sheet comprising a surface compressive layer and an inner layer adjacent to the surface compressive layer,
wherein between 0° C. and 300° C. a difference between a coefficient of thermal expansion of the inner layer and a coefficient of thermal expansion of the surface compressive layer is greater than 50×10 −7 ° C. −1 , and
wherein the surface compressive layer has a compressive stress of at least about 300 MPa and the inner layer has a tensile stress of at least 29 MPa.

2. The transparent glass sheet according to claim 1 , wherein between 0° C. and 300° C. a ratio of the coefficient of thermal expansion of the inner layer to the coefficient of thermal expansion of the surface compressive layer is greater than 2.5.

3. The transparent glass sheet according to claim 1 , wherein the transparent glass sheet has a thickness and the inner layer has a thickness, and a ratio of the thickness of the inner layer to the thickness of the transparent glass sheet is at least about 0.8.

4. The transparent glass sheet according to claim 1 , wherein the transparent glass sheet has a thickness ranging from about 0.3 mm to about 3 mm.

5. The transparent glass sheet according to claim 1 , wherein the softening point of the surface compressive layer is at least 40° C. below a softening point of the inner layer.

6. The transparent glass sheet according to claim 1 , wherein the ratio of the viscosity of the surface compressive layer to a viscosity of the inner layer in a range of the softening point of the inner layer ±200° C. is from about 0.1 to about 0.9.

7. The transparent glass sheet according to claim 1 , wherein the inner layer comprises in weight percent on an oxide basis: (i) 50≦SiO 2 ≦65%; (ii) 10≦Al 2 O 3 ≦20%; (iii) 0≦MgO≦5%; (iv) 10≦Na 2 O≦20%; (iv) 0≦K 2 O≦5%; and (v)≧0 and ≦1% of at least one of B 2 O 3 , CaO, ZrO 2 and Fe 2 O 3 .

8. The transparent glass sheet according to claim 1 , wherein the surface compressive layer has a compressive stress of at least about 500 MPa.

9. The transparent glass sheet according to claim 1 , wherein no layer of the transparent glass sheet has been subjected to an in situ crystallization process.

10. The transparent glass sheet according to claim 1 , wherein less than 10 ppm of any layer in the glass sheet is in a crystalline state.

11. The transparent glass sheet according to claim 1 , wherein no layer of the transparent glass sheet has been subjected to an ion exchange process.

12. The transparent glass sheet according to claim 1 , wherein between 0° C. and 300° C. a ratio of the coefficient of thermal expansion of the inner layer to the coefficient of thermal expansion of the surface compressive layer is greater than 3.

13. The transparent glass sheet according to claim 1 , wherein between 0° C. and 300° C. the difference of the coefficient of thermal expansion of the inner layer and the coefficient of thermal expansion of the surface compressive layer is greater than 75×10 −7 ° C. −1 .

14. The transparent glass sheet according to claim 1 , wherein the transparent glass sheet has a thickness and the inner layer has a total thickness, and a ratio of the total thickness of the inner layer to the thickness of the transparent glass sheet is at least about 0.9.

15. The transparent glass sheet according to claim 1 , wherein between 0° C. and 300° C. a ratio of the coefficient of thermal expansion of the inner layer to the coefficient of thermal expansion of the surface compressive layer is greater than 4.

16. The transparent glass sheet according to claim 1 , wherein between 0° C. and 300° C. the difference between the coefficient of thermal expansion of the inner layer and the coefficient of thermal expansion of the surface compressive layer is greater than 90×10 −7 ° C. −1 .

17. The transparent glass sheet according to claim 1 , wherein the surface compressive layer has a compressive stress of at least about 700 MPa.

18. The transparent glass sheet according to claim 1 , wherein the inner layer has a tensile stress of at least about 57 MPa.

19. The transparent glass sheet according to claim 1 , wherein the inner layer comprises an alkali aluminosilicate glass.

20. The transparent glass sheet according to claim 1 , wherein the surface compressive layer comprises in weight percent on an oxide basis: (i) 65≦SiO 2 ≦75%; (ii) 7≦Al 2 O 3 ≦13%; (iii) 5≦B 2 O 3 ≦15%; (iv) 5≦CaO≦15%; (v) 0≦BaO≦5%; (vi) 0≦MgO≦3%; and (vii) 0≦SrO≦5%.

21. The transparent glass sheet according to claim 20 , wherein the surface compressive layer is essentially free of BaO.

22. The transparent glass sheet according to claim 1 , wherein a ratio of a thickness of the inner layer to a thickness of the transparent glass sheet is less than or equal to 0.9.

23. The transparent glass sheet according to claim 1 , wherein the inner layer has a tensile stress of at least about 42 MPa.

24. A transparent glass sheet comprising a surface compressive layer and an inner layer adjacent to the surface compressive layer, wherein between 0° C. and 300° C. the difference between the coefficient of thermal expansion of the inner layer and the coefficient of thermal expansion of the surface compressive layer is greater than 50×10 −7 ° C. −1 , the surface compressive layer has a compressive stress of at least about 300 MPa, and a ratio of a thickness of the inner layer to a thickness of the transparent glass sheet is less than or equal to 0.9.

Assignees

• Bookbinder Dana Craig
• House Keith Leonard
• Tandon Pushkar
• Corning Inc

Inventors

• Bookbinder Dana Craig
• House Keith Leonard
• Tandon Pushkar

Classifications

• C03B17/064 Primary

  by the overflow downdraw fusion process; Isopipes therefor · CPC title

• Y10T428/2495

  Thickness [relative or absolute] · CPC title

• C03C3/093

  containing zinc or zirconium · CPC title

• C03C3/091

  containing aluminium · CPC title

• C03B17/068

  Means for providing the drawing force, e.g. traction or draw rollers · CPC title