Alkali-free glass and method for producing the same

Patent metadata

Field	Value
Publication number	US-10730786-B2
Application number	US-201916392714-A
Country	US
Kind code	B2
Filing date	Apr 24, 2019
Priority date	Nov 2, 2016
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

The present invention relates to an alkali-free glass and a method for producing the same. More specifically, the present invention relates to an alkali-free glass suitable as a glass for substrates of various displays such as liquid crystal display, and a method for producing the same. According to the present invention, an alkali-free glass suitable as a glass for display substrates, in which inclusion of bubbles is greatly reduced by virtue of containing a refining agent and suppressing the stirring reboil, is obtained.

First claim

The invention claimed is:

1. An alkali-free glass having a strain point of 680° C. or more, an average thermal expansion coefficient at from 50 to 350° C. of from 30×10 −7 to 45×10 −7 /° C., a temperature T 2 at which a glass viscosity reaches 10 2 dPa·s of 1,730° C. or less, a temperature T 4 at which a glass viscosity reaches 10 4 dPa·s of 1,350° C. or less, and a Young's modulus of 80 GPa or more, comprising, in terms of wt % on the basis of oxides,
SiO 2 : from 54 to 66%,
Al 2 O 3 : from 10 to 25%,
B 2 O 3 : from 0 to 5%,
MgO: from 0 to 10%,
CaO: from 0 to 15%,
SrO: from 0 to 10%,
BaO: from 0 to 10%, and
SnO 2 : from 0.05 to 1%,
provided that MgO+CaO+SrO+BaO is from 8 to 24%, and
having a total sulfur content in terms of SO 3 of from 0.5 to 16 ppm by weight,
wherein the alkali-free glass is produced by heating raw materials to obtain a molten glass, by stirring the molten glass, and then by cooling the molten glass, and
wherein the molten glass is stirred at least at a temperature of 1,500 to 1,800° C., and the molten glass has a S 2− content in terms of SO 3 of 3 ppm or less by weight during the stirring, where the S 2− content is measured after cooling from 1,500 to 1,800° C. to 600° C. or less within 1 minute.

2. The alkali-free glass according to claim 1 , wherein:
the strain point is 690° C. or more;
the average thermal expansion coefficient is from 35×10 −7 to 43×10 −7 /° C.;
the temperature T 2 is 1,700° C. or less;
the alkali-free glass comprises, in terms of wt % on the basis of oxides,
SiO 2 : from 57 to 63%,
Al 2 O 3 : from 18 to 22%,
B 2 O 3 : from 1 to 4%,
MgO: from 0 to 7%,
CaO: from 3 to 10%,
SrO: from 0 to 6%,
BaO: from 2 to 8%, and
SnO 2 : from 0.1 to 0.5%,
provided that MgO+CaO+SrO+BaO is from 12 to 20%;

the total sulfur content in terms of SO 3 of the alkali-free glass is from 0.5 to 16 ppm by weight; and
the S 2− content in terms of SO 3 of the molten glass during the stirring is 2.5 ppm by weight or less.

3. The alkali-free glass according to claim 1 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 1 to 16 ppm by weight.

4. The alkali-free glass according to claim 1 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 3 to 16 ppm by weight.

5. The alkali-free glass according to claim 1 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 8 to 16 ppm by weight.

6. The alkali-free glass according to claim 1 , wherein the S 2− content in terms of SO 3 of the molten glass during the stirring is 2.0 ppm by weight or less.

7. The alkali-free glass according to claim 1 , wherein the S 2− content in terms of SO 3 of the molten glass during the stirring is 1.5 ppm by weight or less.

8. A method for producing an alkali-free glass, the method comprising:
melting a glass raw material to obtain a molten glass,
stirring the molten glass; and
cooling the molten glass to form an alkali-free glass,
the alkali-free glass comprising, in terms of wt % on the basis of oxides,
SiO 2 : from 54 to 66%,
Al 2 O 3 : from 10 to 25%,
B 2 O 3 : from 0 to 10%,
MgO: from 0 to 10%,
CaO: from 0 to 15%,
SrO: from 0 to 10%,
BaO: from 0 to 10%, and
SnO 2 : from 0.05 to 1%,
provided that MgO+CaO+SrO+BaO is from 8 to 24%, and
having a total sulfur content in terms of SO 3 of from 1 to 16 ppm by weight;

wherein the molten glass is stirred at least at a temperature of 1,500 to 1,800° C., and the molten glass has a S 2− content in terms of SO 3 of 3 ppm or less by weight during the stirring, where the S 2− content is measured after cooling from 1,500 to 1,800° C. to 600° C. or less within 1 minute.

9. The method for producing an alkali-free glass according to claim 8 , wherein:
the alkali-free glass comprises, in terms of wt % on the basis of oxides,
SiO 2 : from 57 to 63%,
Al 2 O 3 : from 18 to 22%,
B 2 O 3 : from 1 to 9%,
MgO: from 0 to 7%,
CaO: from 3 to 10%,
SrO: from 0 to 6%,
BaO: from 2 to 8%, and
SnO 2 : from 0.1 to 0.5%,
provided that MgO+CaO+SrO+BaO is from 12 to 20%; and

the total sulfur content in terms of SO 3 of the alkali-free glass is from 2 to 16 ppm by weight.

10. The method for producing an alkali-free glass according to claim 8 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 3 to 16 ppm by weight.

11. The method for producing an alkali-free glass according to claim 8 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 5 to 16 ppm by weight.

12. The method for producing an alkali-free glass according to claim 8 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 8 to 16 ppm by weight.

13. The method for producing an alkali-free glass according to claim 8 , wherein the S 2− content in terms of SO 3 of the molten glass during the stirring is 2.0 ppm by weight or less.

14. The method for producing an alkali-free glass according to claim 8 , wherein the S 2− content in terms of SO 3 of the molten glass during the stirring is 1.5 ppm by weight or less.

15. An alkali-free glass having a strain point of 680° C. or more, an average thermal expansion coefficient at from 50 to 350° C. of from 30×10 −7 to 45×10 −7 /° C., a temperature T 2 at which a glass viscosity reaches 10 2 dPa·s of 1,730° C. or less, a temperature T 4 at which a glass viscosity reaches 10 4 dPa·s of 1,350° C. or less, and a Young's modulus of 80 GPa or more, comprising, in terms of wt % on the basis of oxides,
SiO 2 : from 54 to 66%,
Al 2 O 3 : from 10 to 25%,
B 2 O 3 : from 0 to 5%,
MgO: from 0 to 10%,
CaO: from 0 to 15%,
SrO: from 0 to 10%,
BaO: from 0 to 10%, and
SnO 2 : from 0.05 to 1%,
provided that MgO+CaO+SrO+BaO is from 8 to 24%, and
having a total sulfur content in terms of SO 3 of from 0.5 to 16 ppm by weight, and a S 2− content in terms of SO 3 of 3 ppm or less by weight, where the S 2− content is measured by heating the alkali-free glass to a temperature range of from 1,500 to 1,800° C. to remelt the alkali-free glass and then by cooling the molten alkali-free glass to 600° C. or less within 1 minute.

16. The alkali-free glass according to claim 15 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 1 to 16 ppm by weight.

17. The alkali-free glass according to claim 15 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 3 to 16 ppm by weight.

18. The alkali-free glass according to claim 15 , wherein the total sulfur content in terms of SO 3 of the alkali-free glass is from 8 to 16 ppm by weight.

19. The alkali-free glass according to claim 15 , wherein the S 2− content in terms of SO 3 of the alkali-free glass is 2.0 ppm by weight or less.

20. The alkali-free glass according to claim 15 , wherein the S 2− content in terms of SO 3 of the alkali-free glass is 1.5 ppm by weight or less.

Assignees

• Agc Inc

Inventors

• Tokunaga Hirofumi
• Ono Kazutaka
• Hirose Motoyuki

Classifications

• C03C3/091 Primary

  containing aluminium · CPC title

• C03C3/087

  containing calcium oxide, e.g. common sheet or container glass · CPC title

• C03C3/083 Primary

  containing aluminium oxide or an iron compound · CPC title

• C03B5/18

  Stirring devices; Homogenisation {(mixing in general B01F)} · CPC title

• C03C2203/10

  Melting processes · CPC title