METHOD OF SEPARATING STRENGTHENED GLASS

• US 20100210442A1
• Filed: 02/19/2009
• Published: 08/19/2010
• Est. Priority Date: 02/19/2009
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Abramov, Anatoli Anatolyevich, Gomez, Sinue, Tsuda, Sergio
• Granted Patent: US 8,347,651 B2
• Time in Patent Office: Days
• US Class Current: 501/66
• CPC Class Codes: C03B 27/0413 Stresses, e.g. patterns, values or formulae for flat or bent glass sheets
• CPC Class Codes: C03B 33/091 using at least one focussed radiation beam, e.g. laser beam C03B33/0955 takes precedence

Abstract

A method is provided for separating or dividing strengthened glass articles, particularly strengthened glass sheets, into at least two pieces, one of which has a predetermined shape and/or dimension. A flaw is initiated in the glass at a depth that is greater than the depth of the strengthened surface layer of the glass, and a vent extending from the flaw is created at a vent depth that is greater than the depth of and outside the strengthened surface layer to at least partially separate the glass. In one embodiment, the vent is generated by treating the glass with a laser to heat the glass to a temperature in a range from about 50° C. below the strain point of the glass up to a temperature between the strain point and the anneal point of the glass. A glass article having at least one strengthened surface and at least one edge having an average edge strength of at least 200 MPa is also described.

Claims

1. A method of separating a strengthened glass sheet into at least two pieces, the method comprising:

a. providing the strengthened glass sheet, the strengthened glass sheet having a strain point, an anneal point, a thickness, and a first surface and a second surface that are substantially parallel to each other and joined by a plurality of edges, wherein at least one of the first surface and the second surface has a strengthened surface layer under a compressive stress, the strengthened surface layer extending from the surface to a depth of layer;

b. initiating a flaw at a flaw depth within the strengthened glass sheet, wherein the flaw depth is greater than and outside the depth of layer; and

c. forming a vent in the strengthened glass sheet to at least partially separate the strengthened glass sheet into the at least two pieces, wherein the vent originates at the flaw and extends from the flaw in a separation direction along the strengthened glass sheet at a vent depth that is greater than or equal to the depth of layer.

2. The method of claim 1, wherein the step of forming the vent in the strengthened glass sheet comprises irradiating the strengthened glass sheet with a laser beam and heating the strengthened glass sheet along a vent direction at the vent depth to a temperature in a range of at least 50°

below the strain point up to a temperature between the strain point and the anneal point of the strengthened glass sheet to form the vent.

3. The method of claim 2, wherein the step of irradiating the strengthened glass sheet with a laser beam and heating the strengthened glass sheet along the vent direction at the vent depth to a temperature in a range from about 50°

C. below the strain point up to a temperature between the strain point and the anneal point of the strengthened glass sheet comprises irradiating and heating the strengthened glass sheet through the entire thickness to separate the strengthened glass sheet along the vent into the at least two pieces.

4. The method of claim 2, wherein the temperature is between the strain point and the anneal point of the strengthened glass.

5. The method of claim 2, wherein the laser beam has a wavelength of 10.6 μ

m and is generated by CO₂ laser.

6. The method of claim 2, wherein the laser beam is an elongated elliptical beam.

7. The method of claim 6, wherein the strengthened glass sheet has a length, and wherein the elongated elliptical bean has a length that is greater than or equal to the length of the strengthened glass sheet.

8. The method of claim 6, wherein the elongated elliptical laser beam has a length of at least about 300 mm.

9. The method of claim 2, further including the step of translating the laser beam across one of the first surface and the second surface.

10. The method of claim 2, wherein the laser beam is translated across one of the first surface and the second surface at a rate of up to 750 mm/s.

11. The method of claim 2, further including irradiating the strengthened glass sheet with a second elongated elliptical laser beam to preheat the strengthened glass sheet.

12. The method of claim 2, wherein the laser beam has one of an S mode profile, a D mode profile and a flat top profile.

13. The method of claim 1, further comprising the step of creating a stress to separate the strengthened glass sheet along the vent into the plurality of pieces.

15. The method of claim 1, wherein the glass is an alkali aluminosilicate glass.

16. The method of claim 15, wherein the alkali aluminosilicate glass comprises:

60-70 mol % SiO₂;

6-14 mol % Al₂O₃;

0-15 mol % B₂O₃;

0-15 mol % Li₂O;

0-20 mol % Na₂O;

0-10 mol % K₂O;

0-8 mol % MgO;

0-10 mol % CaO;

0-5 mol % ZrO₂;

0-1 mol % SnO₂;

0-1 mol % CeO₂;

less than 50 ppm As₂O₃; and

less than 50 ppm Sb₂O₃;

wherein 12 mol %≦

Li₂O+Na₂O+K₂₀≦

20 mol % and 0 mol %≦

MgO+CaO≦

10 mol %.

17. The method of claim 16, wherein the alkali aluminosilicate glass comprises:

64 mol %≦

SiO₂≦

68 mol %;

12 mol %≦

Na₂₀≦

16 mol %;

8 mol %≦

Al₂O₃≦

12 mol %;

0 mol %≦

B₂O₃≦

3 mol %;

2 mol %≦

K₂₀≦

5 mol %;

4 mol %≦

MgO≦

6 mol %; and

0 mol %≦

CaO≦

5 mol %, wherein;

66 mol %≦

SiO₂+B₂O₃+CaO≦

69 mol %;

Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>

10 mol %;

5 mol %≦

MgO+CaO+SrO≦

8 mol %;

(Na₂O+B₂O₃)−

Al₂O₃≦

2 mol %;

2 mol %≦

Na₂O−

Al₂O₃≦

6 mol %; and

4 mol %≦

(Na₂O+K₂O)−

Al₂O₃≦

10 mol %, and wherein the glass has a liquidus viscosity of at least 130 kpoise.

18. The method of claim 16, wherein the alkali aluminosilicate glass is substantially free of lithium.

19. The method of claim 16, wherein the alkali aluminosilicate glass is substantially free of arsenic, antimony, and barium.

20. The method of claim 1, wherein the strengthened glass sheet is strengthened by ion exchange.

21. The method of claim 20, wherein the strengthened glass sheet has a depth of layer of at least about 20 μ

m, a compressive stress of at least about 200 MPa, and a central tension less than or equal to about 100 MPa.

14. The method of claim 14, wherein the step of creating a stress to separate the strengthened glass sheet along the vent into the plurality of pieces comprises quenching a portion of the strengthened glass sheet with a fluid after irradiating the strengthened glass sheet with the laser beam.

22. A method of forming a vent in a strengthened glass sheet, the strengthened glass sheet having a strain point and an anneal point, a central region under a tensile stress, and a strengthened surface layer that is under a compressive stress and extends from the surface to a depth of layer, the method comprising:

a. initiating a flaw at a flaw depth within the strengthened glass sheet, wherein the flaw depth is greater than and outside the depth of layer; and

b. irradiating the strengthened glass sheet with a laser beam and heating the glass along a vent direction at a vent depth to a temperature in a range from about 50°

C. below the strain point up to a temperature between the strain point and the anneal point to form the vent, wherein the vent depth is greater than or equal to the depth of layer, and wherein the vent originates at and extends from the flaw.

23. The method of claim 22, wherein the laser beam has a wavelength of 10.6 μ

m and is generated by CO₂ laser.

24. The method of claim 22, wherein the laser beam is an elongated elliptical beam.

25. The method of claim 24, wherein the strengthened glass sheet has a length, and wherein the elongated elliptical bean has a length that is greater than or equal to the length of the strengthened glass sheet.

26. The method of claim 24, wherein the laser beam has one of an S mode profile, D mode profile and a flat top profile.

27. A strengthened glass article, wherein the strengthened glass article has a central region under a tensile stress, and at least one strengthened surface layer that is under a compressive stress and extends from the surface to a depth of layer, and at least one edge, wherein the at least one edge has an average edge strength of at least 200 MPa.

28. The strengthened glass article of claim 27, wherein the at least one edge is a laser cut edge.

29. The strengthened glass article of claim 28, wherein the laser cut edge is formed by:

a. providing a strengthened glass sheet, the strengthened glass sheet having a strain point and an anneal point;

b. initiating a flaw at a flaw depth within a strengthened glass sheet, wherein the flaw depth is greater than the depth of layer and within the central region; and

c. irradiating the strengthened glass article with a laser beam and heating the strengthened glass article at a vent depth to a temperature in a range from about 50°

C. below the strain point up to a temperature between the strain point and the anneal point to form a vent extending from the flaw and separate the strengthened glass sheet to form the strengthened glass article, wherein the at least one edge is formed by separating the strengthened glass sheet.

30. The strengthened glass article of claim 27, wherein the strengthened glass article is an alkali aluminosilicate glass.

31. The strengthened glass article of claim 30, wherein the alkali aluminosilicate glass comprises:

wherein the alkali aluminosilicate glass comprises;

64 mol %≦

SiO₂≦

68 mol %;

12 mol %≦

Na₂₀≦

16 mol %;

8 mol %≦

Al₂O₃≦

12 mol %;

0 mol %≦

B₂O₃≦

3 mol %;

2 mol %≦

K₂₀≦

5 mol %;

4 mol %≦

MgO≦

6 mol %; and

0 mol %≦

CaO≦

5 mol %, wherein;

66 mol %≦

SiO₂+B₂O₃+CaO≦

69 mol %;

Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>

10 mol %;

5 mol %≦

MgO+CaO+SrO≦

8 mol %;

(Na₂O+B₂O₃)−

Al₂O₃≦

2 mol %;

2 mol %≦

Na₂O−

Al₂O₃≦

6 mol %; and

4 mol %≦

(Na₂O+K₂O)−

Al₂O₃≦

10 mol %, and wherein the glass has a liquidus viscosity of at least 130 kpoise.

32. The strengthened glass article of claim 30, wherein the strengthened glass article is chemically strengthened by ion exchange.

33. The strengthened glass article of claim 27, wherein the strengthened glass article is one of a cover plate for a mobile communication or entertainment device and a screen for a portable computer.