Low CTE alkali-free boroaluminosilicate glass compositions and glass articles comprising the same

• US 9,764,981 B2
• Filed: 02/28/2013
• Issued: 09/19/2017
• Est. Priority Date: 02/29/2012
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Mauro, John Christopher
• Primary Examiner(s): Sample, David
• Assistant Examiner(s): Gugliotta, Nicole T
• Application Number:
  US14/380,164
• Publication Number:
  US 20150037553A1
• Time in Patent Office: 1,664 Days
• Field of Search: None
• CPC Class Codes: C03B 17/02 Forming molten glass coated with coloured layers; Forming molten glass of different compositions or layers; Forming molten glass comprising reinforcements or inserts
• CPC Class Codes: C03B 17/064 by the overflow downdraw fusion process; Isopipes therefor
• CPC Class Codes: C03C 3/091 containing aluminium
• CPC Class Codes: C03C 3/093 containing zinc or zirconium
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/24983 Hardness

Abstract

Low CTE glass compositions and glass articles formed from the same are described. In one embodiment, a glass composition includes from about 60 mol. % to about 66 mol. % SiO₂; from about 7 mol. % to about 10 mol. % AI₂O₃; and from about 14 mol. % to about 18 mol. % B₂O₃ as glass network formers. The glass composition may further include from about 9 mol. % to about 16 mol. % alkaline earth oxide. The alkaline earth oxide includes at least CaO. The CaO may be present in the glass composition in a concentration from about 3 mol. % to about 12 mol. %. The glass composition is free from alkali metals. The glass composition has a coefficient of thermal expansion which is less than or equal to 40×10⁻⁷/° C. averaged over the temperature range from about 20° C. to 300° C. The glass composition is particularly well suited for use as a glass cladding layer in a laminated glass article.

Claims

1. A glass composition comprising:

from about 60 mol. % to about 66 mol. % SiO₂;

from about 7 mol. % to about 10 mol. % Al₂O₃;

from about 14 mol. % to about 18 mol. % B₂O₃; and

from about 9 mol. % to about 16 mol. % alkaline earth oxide, wherein the alkaline earth oxide comprises from about 3 mol. % to about 12 mol. % CaO, from 2 mol. % to 4 mol. % MqO, and from 1 mol. % to 4 mol. % SrO; and

wherein the glass composition is substantially free from alkali metals and compounds containing alkali metals, is free from heavy metals, and has a liquidus viscosity of greater than or equal to 50 kPoise and a liquidus temperature of less than or equal to 1040°

C.

2. The glass composition of claim 1, wherein:

the glass composition comprises;

from about 63 mol. % to about 65 mol. % SiO₂;

from 16 mol. % to about 17 mol. % B₂O₃.

3. The glass composition of claim 1, wherein the glass composition has a coefficient of thermal expansion which is less than or equal to 40×

10<sup>−

7</sup>/°

C. averaged over a temperature range from 20°

C. to 300°

C.

4. The glass composition of claim 1, wherein the glass composition has a Young'"'"'s modulus less than or equal to 10.5 Mpsi.

5. A glass article comprising:

a glass core layer disposed between a first glass cladding layer and a second glass cladding layer, wherein the first glass cladding layer and the second glass cladding layer are formed from a glass composition comprising;

from about 60 mol. % to about 66 mol. % SiO₂;

from about 7 mol. % to about 10 mol. % Al₂O₃;

from about 14 mol. % to about 18 mol. % B₂O₃;

from about 9 mol. % to about 16 mol. % alkaline earth oxide,

wherein the alkaline earth oxide comprises from about 3 mol. % to about 12 mol. % CaO, from 2 mol. % to 4 mol. % MqO, and from 1 mol. % to 4 mol. % SrO; and

wherein the glass composition is substantially free from alkali metals and compounds containing alkali metals, is free from heavy metals, and has a liquidus viscosity of greater than or equal to about 50 kPoise and a liquidus temperature of less than or equal to 1040°

C.

6. The glass article of claim 5, wherein the first glass cladding layer and the second glass cladding layer comprise from about 11 mol. % to about 12 mol. % alkaline earth oxide.

7. The glass article of claim 5, wherein the first glass cladding layer and the second glass cladding layer comprise:

from about 63 mol. % to about 65 mol. % SiO₂; and

from about 16 mol. % to about 17 mol. % B₂O₃.

8. The glass article of claim 5, wherein:

the glass core layer has an average core coefficient of thermal expansion CTE_core;

the first glass cladding layer and the second glass cladding layer have an average cladding coefficient of thermal expansion CTE_clad which is less than the average core coefficient of thermal expansion CTE_core; and

the first glass cladding layer and the second glass cladding layer are compressively stressed.

9. The glass article of claim 8, wherein the average cladding coefficient of thermal expansion CTE_clad is less than or equal to 40×

10<sup>−

7</sup>/°

C. in a temperature range from 20°

C. to 300°

C.

10. The glass article of claim 5, wherein the glass core layer comprises alkali ions.

11. The glass article of claim 5, wherein the first glass cladding layer and the second glass cladding layer have a Young'"'"'s modulus less than or equal to 10.5 Mpsi.

12. The glass article of claim 5, wherein a first surface of the glass core layer is directly adjacent the first glass cladding layer, and wherein a second surface of the glass core layer is directly adjacent the second glass cladding layer.

13. The glass article of claim 5, wherein a diffusive layer is disposed between the first glass cladding layer or the second glass cladding layer and the glass core layer, and the average coefficient of thermal expansion of the diffusive layer has a value between that of an average core coefficient of thermal expansion of the core and an average cladding coefficient of thermal expansion of the first glass cladding layer or the second glass cladding layer.