Alkali-free glass substrate and method for producing same
The present invention relates to an alkali-free glass substrate, having a strain point of 680° C. or higher, a Young's modulus of 78 GPa or greater, an UV transmittance at a wavelength of 300 nm of from 40% to 85% in terms of 0.5 mm thickness, an in-plane distribution of the UV transmittance at a wavelength of 300 nm in a G6-sized substrate of 1% or less in terms of 0.5 mm thickness, an average cooling rate around the glass transition point obtained according to a rate cooling method of 400° C./min or lower, and an in-plane distribution of the average cooling rate of 40° C./min or less.
1. An alkali-free glass substrate, having a strain point of 680° C. or higher, a Young's modulus of 78 GPa or greater, an UV transmittance at a wavelength of 300 nm of from 40% to 85% in terms of 0.5 mm thickness,
wherein, at an average cooling rate around a glass transition point obtained according to a rate cooling method of 400° C./min or lower, the alkali-free glass substrate has an in-plane distribution of the UV transmittance at a wavelength of 300 nm in a substrate size of 1850 mm×1500 mm of 1% or less in terms of 0.5 mm thickness, and an in-plane distribution of the average cooling rate in the substrate size of 1850 mm×1500 mm of 40° C./min or less,
the alkali-free glass substrate comprising, on a mass percentage basis in terms of oxides:
SiO 2
50 to 73;
Al 2 O 3
10.5 to 24;
B 2 O 3
0 to 5;
MgO
0 to 10;
CaO
0 to 14.5;
SrO
0 to 24;
BaO
0 to 20;
ZrO 2
0 to 5;
SnO 2
0.01 to 1; and
Fe 2 O 3
0.005 to 0.1,
wherein MgO+CaO+SrO+BaO is from 8 to 29.5.
2. The alkali-free glass substrate according to claim 1 , comprising, on a mass percentage basis in terms of oxides:
SiO 2
56 to 67;
Al 2 O 3
14.5 to 23;
B 2 O 3
0 to 4;
MgO
0 to 7;
CaO
0 to 8.5;
SrO
0 to 10.5;
BaO
0 to 13.5;
ZrO 2
0 to 1;
SnO 2
0.01 to 0.5; and
Fe 2 O 3
0.005 to 0.045,
wherein MgO+CaO+SrO+BaO is from 13 to 22.
3. The alkali-free glass substrate according to claim 1 , having an in-plane distribution of a content of Fe of from 0.001% to 0.003% on a mass percentage basis in terms of Fe 2 O 3 .
4. The alkali-free glass substrate according to claim 1 , wherein the amount of Fe 2 O 3 is from 0.005% to 0.017%, on a mass percentage basis in terms of oxide.
5. The alkali-free glass substrate according to claim 1 , comprising a total amount of a halogen element of from 0.001% to 1%, on a mass percentage basis in terms of oxides.
6. The alkali-free glass substrate according to claim 1 , comprising a total amount of a halogen element of from 0.03% to 1%, on a mass percentage basis in terms of oxides.
7. The alkali-free glass substrate according to claim 1 , comprising 0.03 to 0.15 mass % of fluorine.
8. The alkali-free glass substrate according to claim 1 , comprising 0.01 to 0.35 mass % of chlorine.
9. The alkali-free glass substrate according to claim 1 , wherein the average cooling rate around a glass transition point obtained according to a rate cooling method is 300° C./min or lower.
10. The alkali-free glass substrate according to claim 1 , having the UV transmittance at a wavelength of 300 nm of from 45% to 85% in terms of 0.5 mm thickness.
11. The alkali-free glass substrate according to claim 1 , having the Young's modulus of 80 GPa or greater.
12. The alkali-free glass substrate according to claim 1 , having the strain point of 710° C. or higher.