Alkali-free glass and alkali-free glass plate using same
View Patent ↗The present invention relates to an alkali-free glass having a strain point of from 680 to 735° C., an average thermal expansion coefficient at from 50 to 350° C. of from 30×10 −7 to 43×10 −7 /° C., and a specific gravity of 2.60 or less, and containing, indicated by mol % on the basis of oxides, SiO 2 65 to 69%, Al 2 O 3 11.5 to 14%, B 2 O 3 3 to 6.5%, MgO 1 to 5%, CaO 7.5 to 12%, SrO 0 to 1%, BaO 0.5 to 6%, and ZrO 2 0 to 2%.
1. An alkali-free glass having a strain point of from 685 to 735° C., an average thermal expansion coefficient at from 50 to 350° C. of from 35×10 −7 to 43×10 −7 /° C., a specific gravity of 2.60 or less, a temperature T 2 at which viscosity η reaches 10 2 poise (dPa.s) of 1,710° C. or lower, and a photoelastic constant of 30 nm/MPa/cm or less, and comprising, indicated by mol % on the basis of oxides,
SiO 2 65 to 69%,
Al 2 O 3 11.5 to 14%,
B 2 O 3 3 to 6.5%,
MgO 1 to 5%,
CaO 7.5 to 12%,
SrO 0 to 1%,
BaO 0.5 to 6%, and
ZrO 2 0 to 2%.
2. An alkali-free glass having a strain point of from 680 to 735° C., an average thermal expansion coefficient at from 50 to 350° C. of from 35×10 −7 to 43×10 −7 /° C., and a specific gravity of 2.60 or less, and comprising, indicated by mol % on the basis of oxides,
SiO 2 65 to 69%,
Al 2 O 3 11.5 to 14%,
B 2 O 3 3 to 6.5%,
MgO 1 to 5%,
CaO 7.5 to 12%,
SrO from greater than 1% to 3%,
BaO 0.5 to 4%, and
ZrO 2 0 to 2%.
3. The alkali-free glass according to claim 1 , having a viscosity at a devitrification temperature of 10 4.5 poise or more.
4. The alkali-free glass according to claim 1 , having an average cooling rate around a glass transition point acquired by a rate cooling method of 100° C./min or higher.
5. An alkali-free glass plate made of the alkali-free glass according to claim 1 ,
wherein a plate thickness is 0.4 mm or less, and
at least one surface has been subjected to a hydrofluoric acid (HF) etching treatment by a depth of 5μm or more from the surface.
6. The alkali-free glass according to claim 2 , having a photoelastic constant of 31 nm/MPa/cm or less.
7. The alkali-free glass according to claim 2 , having a viscosity at a devitrification temperature of 10 4.5 poise or more.
8. The alkali-free glass according to claim 2 , having an average cooling rate around a glass transition point acquired by a rate cooling method of 100° C./min or higher.
9. An alkali-free glass plate made of the alkali-free glass according to claim 2 ,
wherein a plate thickness is 0.4 mm or less, and
at least one surface has been subjected to a hydrofluoric acid (HF) etching treatment by a depth of 5μm or more from the surface.
10. The alkali-free glass according to claim 1 , comprising from 8 to 12% of CaO, indicated by mol % on the basis of oxides.
11. The alkali-free glass according to claim 2 , comprising from 8 to 12% of CaO, indicated by mol % on the basis of oxides.
12. The alkali-free glass according to claim 1 , comprising from 8.3 to 12% of CaO, indicated by mol % on the basis of oxides.
13. The alkali-free glass according to claim 2 , comprising from 8.3 to 12% of CaO, indicated by mol % on the basis of oxides.
14. The alkali-free glass according to claim 2 , comprising from 1.5 to 3% of SrO, indicated by mol % on the basis of oxides.
15. The alkali-free glass according to claim 1 , comprising from 3 to 5.5% of B 2 O 3 .
16. The alkali-free glass according to claim 1 , comprising from 1 to 6% of BaO.
17. The alkali-free glass according to claim 1 , wherein the average thermal expansion coefficient at from 50 to 350° C. of from 35×10 −7 to 40×10 −7 /° C.
18. The alkali-free glass according to claim 2 , wherein the average thermal expansion coefficient at from 50 to 350° C. of from 35×10 −7 to 40×10 −7 /° C.
19. The alkali-free glass according to claim 1 , wherein the strain point is from 690 to 735° C.
20. The alkali-free glass according to claim 2 , wherein the strain point is from 690 to 735° C.
21. The alkali-free glass according to claim 1 , wherein the temperature T 2 is from 1700° C. or lower.
22. The alkali-free glass according to claim 2 , wherein the temperature T 2 is from 1700° C. or lower.
23. The alkali-free glass according to claim 1 , wherein the total content of MgO, CaO, SrO, and BaO is 14 mol % or more.
24. The alkali-free glass according to claim 2 , wherein the total content of MgO, CaO, SrO, and BaO is 14 mol % or more.