Alkali-free glass
To provide an alkali-free glass, of which the compaction is low, the strain point is high, and the ultraviolet transmittance is high, and which is easy to melt. An alkali-free glass, which comprises, as represented by mol % based on oxides, SiO 2 from 65 to 75, Al 2 O 3 from 9 to 15, B 2 O 3 from 0 to 3, MgO from 0 to 12, CaO from 0 to 8, SrO from 0 to 6, and BaO from 0 to 5, wherein MgO+CaO+SrO+BaO is from 12 to 22, and 4.84[Fe 2 O 3 ]+5.65[Na 2 O]+4.03[K 2 O]+4.55[SnO 2 ] is at most 0.55, and of which the compaction is at most 80 ppm.
1. An alkali-free glass, comprising, as represented by mol % based on oxides,
SiO 2
from 65 to 75,
Al 2 O 3
from 9 to 15,
B 2 O 3
from 0 to 3,
MgO
from 5 to 12,
CaO
from 3 to 8,
SrO
from 1 to 6,
BaO
from 0 to 5,
Fe 2 O 3
from 0.001 to 0.03,
Na 2 O
from 0.003 to 0.06,
K 2 O
from 0 to 0.02,
SnO 2
from 0 to 0.12, and
ZrO 2
from 0 to 2,
wherein MgO+CaO+SrO+BaO is from 12 to 22, MgO/(MgO+CaO+SrO+BaO) is at least 0.33, MgO/(MgO+CaO) is at least 0.40, MgO/(MgO+SrO) is at least 0.45, and 4.84[Fe 2 O 3 ]+5.65[Na 2 O]+4.03[K 2 O]+4.55[SnO 2 ] is at most 0.55, and
wherein an average thermal expansion coefficient at from 50 to 350° C. is from 30×10 −7 to 45×10 −7 /° C.
2. The alkali-free glass according to claim 1 , wherein the alkali-free glass has a strain point of at least 690° C., a temperature T 2 at which a glass viscosity becomes 10 2 dPa·s of at most 1,710° C., and a temperature T 4 at which the glass viscosity becomes 10 4 dPa·s of at most 1.350° C.
3. The alkali-free glass according to claim 1 , wherein a strain point of the alkali-free glass is at least 725° C.
4. The alkali-free glass according to claim 1 , wherein a glass transition point of the alkali-free glass is at least 750° C.
5. The alkali-free glass according to claim 1 , wherein a compaction is at most 50 ppm.
6. The alkali-free glass according to claim 1 , wherein a compaction is at most 80 ppm.
7. The alkali-free glass according to claim 1 , wherein an ultraviolet transmittance of the alkali-free glass at the wavelength of 300 nm in the plate thickness of 0.5 mm is at least 40%.
8. The alkali-free glass according to claim 1 , of wherein a photoelastic constant of the alkali-free glass is at most 31 nm/MPa/cm.
9. The alkali-free glass according to claim 1 , wherein a β-OH value of the alkali-free glass is at most 0.45 mm −1 .
10. The alkali-free glass according to claim 1 , wherein a dielectric constant of the alkali-free glass is at least 5.6.
11. The alkali-free glass according to claim 1 , wherein a Young's modulus of the alkali-free glass is at least 82 GPa.
12. The alkali-free glass according to claim 1 , which is a substrate glass for displays.
13. A substrate glass for displays, comprising:
the alkali-free glass of claim 1 , and
a thin film of a metal or oxide on at least one surface.
14. The alkali free substrate glass according to claim 13 , wherein the substrate glass is used for a liquid crystal display device, an organic EL device, or a lighting device.