GLASS LAMINATE HAVING INCREASED STRENGTH

• US 20170210662A1
• Filed: 04/07/2017
• Published: 07/27/2017
• Est. Priority Date: 10/07/2014
• Status: Active Application

• Current Assignee: Schott AG (Carl-Zeiss-Stiftung)
• Original Assignee: Schott AG (Carl-Zeiss-Stiftung)
• Inventors: WAGNER, Fabian, ORTNER, Andreas
• Application Number:
  US15/482,256
• Publication Number:
  US 20170210662A1
• Time in Patent Office: Days
• CPC Class Codes: B32B 17/06 comprising glass as the main or only constituent of a layer, next to another layer of a specific material
• CPC Class Codes: B32B 2250/03 3 layers
• CPC Class Codes: B32B 2250/40 Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
• CPC Class Codes: C03B 23/037 by drawing
• CPC Class Codes: C03B 23/047 by drawing C03B23/091 , C03B37/025 takes precedence
• CPC Class Codes: C03B 23/20 Uniting glass pieces by fusing without substantial reshaping
• CPC Class Codes: C03B 23/207 Uniting glass rods, glass tubes, or hollow glassware C03B23/24 takes precedence
• CPC Class Codes: C03B 27/012 by heat treatment, e.g. for crystallisation; Heat treatment of glass products before tempering by cooling C03B27/008, C03B27/016 take precedence
• CPC Class Codes: C03C 1/004 Refining agents refining C03B5/225
• CPC Class Codes: C03C 21/002 to perform ion-exchange between alkali ions C03C21/005 takes precedence
• CPC Class Codes: C03C 3/078 containing an oxide of a divalent metal, e.g. an oxide of zinc
• CPC Class Codes: C03C 3/085 containing an oxide of a divalent metal
• CPC Class Codes: C03C 3/087 containing calcium oxide, e.g. common sheet or container glass
• CPC Class Codes: C03C 3/091 containing aluminium
• CPC Class Codes: C03C 3/093 containing zinc or zirconium
• CPC Class Codes: C03C 3/095 containing rare earths
• CPC Class Codes: C03C 3/097 containing phosphorus, niobium or tantalum
• CPC Class Codes: C03C 3/112 containing fluorine
• CPC Class Codes: C03C 3/118 containing aluminium

Abstract

A method for producing a glass article having a compressive stress zone close to the surface by redrawing a preform having a rectangular cross section is provided. The preform includes at least a first and a second glass, wherein both glasses are not connected to each other in the preform in a force-fitting manner. The second glass has a higher thermal expansion coefficient than the first glass and is located in the preform in the interior of the glass tube of the first glass. A glass laminate having increased strength is also provided, which is composed as an at least three-layer composite material of at least two different glasses. The individual layers of the layer composite are connected to each other over the entire area and in a non-positive manner, in particular by melting, and the glass laminate has a thermally stable compressive stress zone in the areas close to the surface of the layer composite and a tensile stress zone in the inner region of the layer composite.

Claims

1. A method for producing a glass article that has a compressive stress zone close to the surface by redrawing, comprising at least the steps of:

providing a preform comprising at least a first glass and a second glass, the second glass having a higher thermal expansion coefficient than the first glass, the first glass being a glass tube of a length (L) with two sides extending over a width (B), and the second glass is located inside the glass tube; and

redrawing the preform so that the preform passes through a hot zone to form a drawing onion and is subsequently reshaped by application of mechanical force.

3. The method as claimed in claim 1, wherein the glass tube has two plane-parallel sides extending over the width and arranged with a spacing (d₁) therebetween, wherein the length is larger than the width and the width is larger than the spacing.

4. The method as claimed in claim 1, wherein the preform has a rectangular or ovaloid cross-sectional shape.

5. The method as claimed in claim 1, wherein the second glass is a sheet glass.

6. The method as claimed in claim 1, wherein the first and second glasses are not connected in force-fitted manner to each other in the preform.

7. The method as claimed in claim 1, wherein the first glass is glass selected from the group consisting of a borosilicate glass, a glass ceramic, and an alkali silicate glass, and/or wherein the second glass is a glass selected from the group consisting of a soda-lime glass, a waterglass, and an alkali silicate glass.

8. The method as claimed in claim 1, further comprising applying a vacuum to the preform.

9. The method as claimed in claim 1, wherein the step of providing the preform comprises:

providing a flat preform;

producing an angular or ovaloid glass tube made of the first glass;

sealing one end of the tube by fusing the tube; and

introducing the second glass into the glass tube at an end opposite the sealed one end.

10. The method as claimed in claim 1, wherein the step of redrawing comprises connecting an upper end of the preform to a vacuum generating device.

11. The method as claimed in claim 9, wherein the glass tube is produced by a laser-based reshaping process which comprises hot-forming a sheet glass made of the first glass.

12. The method as claimed in claim 1, wherein, subsequent to the redrawing step, the method further comprises applying a coating to the glass article on one or both sides thereof.

13. The method as claimed in claim 12, wherein the coating is selected from the group consisting of a scratch resistance coating, a sapphire glass coating, an easy-to-clean coating, an anti-fingerprint coating, an anti-glare coating, an anti-reflective coating, an anti-bacterial coating, and combinations thereof.

14. The method as claimed in claim 1, further comprising, subsequent to the redrawing step, the method further comprises the step of thermally and/or chemically tempered the glass article.

15. The method as claimed in claim 1, wherein the redrawing step comprises reshaping the preform into a sheet glass having a thickness of <

3 mm.

16. The method as claimed in claim 1, wherein the first glass has a coefficient of thermal expansion in a range from −

0.1*10<sup>−

6</sup>/K to 12*10<sup>−

6</sup>/K and/or wherein the second glass has a coefficient of thermal expansion in a range from 0*10<sup>−

6</sup>/K to 12.1*10<sup>−

6</sup>/K.

17. The method as claimed in claim 1, wherein the thermal expansion coefficients of the second and first glasses have a ratio (r_α

) that is greater than 1, and wherein the ratio has an absolute value of less than 125.

18. The method as claimed in claim 1, wherein the thermal expansion coefficients between the second glass and the first glass have a difference (Δ

_α

) that is 0.1 to 12*10<sup>−

6</sup>/K.

19. The method as claimed in claim 1, wherein the step of providing the preform further comprises providing a third glass in the form of a different glass tube having a rectangular cross-sectional shape and wherein the different glass tube is disposed inside the glass tube, and wherein the second glass is disposed inside the different glass tube.

2. A method for producing a glass article that has a compressive stress zone close to the surface by redrawing, comprising at least the steps of:

providing a preform comprising at least a first glass and a second glass, the second glass has a higher thermal expansion coefficient than the first glass, the first glass has a length (L) with two sides extending over a width (B), and the second glass is located between the two sides of the first glass, the first glass has lateral portions extending beyond the second glass at lateral sides thereof;

redrawing the preform so that the preform passes through a hot zone to form a drawing onion and is subsequently reshaped by application of mechanical force, wherein during the redrawing the lateral portions of the first glass form a laterally sealed body that encloses the second glass.

20. A glass laminate with increased strength, comprising:

a layer composite with at least three layers made of two different glasses,

wherein the at least three layers are connected to each other over an entire surface area and in a non-positive manner, the layer composite having a compressive stress zone in regions close to a surface of the layer composite and by a tensile stress zone in an inner region of the layer composite,

wherein the layer composite has outer layers made of a first glass and an inner layer disposed between the outer layers that is made of a second glass,

wherein the first glass has a first coefficient of thermal expansion and the second glass has a second coefficient of thermal expansion,

wherein the first coefficient of thermal expansion is smaller than the second coefficient of thermal expansion, and

wherein the compressive stress zone is thermally stable.

23. The glass laminate as claimed in claim 20, comprising a compressive stress of not more than 800 MPa.

24. The glass laminate as claimed in claim 20, wherein the first glass contains alkali ions.

25. The glass laminate as claimed in claim 20, comprising a ratio of layer thicknesses of the first and second glasses of 3:

2.

21. A glass laminate with increased strength, comprising:

a layer composite with at least three layers made of two different glasses,

wherein the at least three layers are connected to each other over an entire surface area and in a non-positive manner, the layer composite having a compressive stress zone in regions close to a surface of the layer composite and by a tensile stress zone in an inner region of the layer composite,

wherein the layer composite has outer layers that are made of a first glass and an inner layer that is disposed between the outer layers that is made of a second glass,

wherein the first glass has a first coefficient of thermal expansion and the second glass has a second coefficient of thermal expansion,

wherein the first coefficient of thermal expansion is smaller than the second coefficient of thermal expansion, wherein, in a viscosity range from 10⁴ to 10⁵ dPa·

s, the first glass and/or the second glass exhibits a crystallization rate of >

0.5 μ

m/min, and

wherein the compressive stress zone is thermally stable.

22. A glass laminate with increased strength, comprising:

a layer composite with at least five layers made of three different glasses, wherein the at least five layers are connected to each other over an entire surface area and in a non-positive manner,

wherein the layer composite has the outer layers that are made of a first glass, an innermost layer that is made of a second glass, a layer made of a third glass disposed between each of the outer layers and the innermost layer,

wherein the layer composite has a compressive stress zone in regions of the layer composite close to a surface of the layer composite and by a tensile stress zone in an inner region of the layer composite,

wherein the outer layers are made of a first glass, the layer that is disposed between the outer layers and the inner most layer is made of a second glass,

wherein the first glass has a first coefficient of thermal expansion and the second glass has a second coefficient of thermal expansion,

wherein the first coefficient of thermal expansion is smaller than the second coefficient of thermal expansion, and

wherein the compressive stress zone is thermally stable.

26. The glass laminate as claimed in claim 22, wherein the third glass has a third coefficient of thermal expansion that is smaller than the second coefficient of thermal expansion and greater than the first coefficient of thermal expansion.