Alkali-free glass substrate and method for producing same

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, an in-plane distribution of the 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, and 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,

and wherein the alkali-free glass substrate is obtained by managing temperature conditions at the time of forming and annealing such that an average cooling rate around the glass transition point obtained according to a rate cooling method is 400° C./min or lower, an in-plane distribution of the average cooling rate is 40° C./min or less, and an in-plane distribution of the UV transmittance at a wavelength of 300 nm in a G6-sized substrate is 1% or less in terms of 0.5 mm thickness.

2. 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 .

3. The alkali-free glass substrate according to claim 1 , having a strain point of 690° C. or higher, a Young's modulus of 80 GPa or greater, an UV transmittance at a wavelength of 300 nm of from 45% to 80% 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 0.5% 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 350° C./min or lower, and an in-plane distribution of the average cooling rate of 30° C./min or less, and comprising, on a mass percentage basis in terms of oxides:

SiO 2 56 to 70;

Al 2 O 3 16.5 to 22;

B 2 O 3 0.5 to 5;

MgO 3 to 7;

CaO 1 to 10;

SrO 1.5 to 9;

BaO 0 to 6;

ZrO 2 0 to 5;

SnO 2 0.03 to 0.3; and

Fe 2 O 3 0.008 to 0.05,

wherein MgO+CaO+SrO+BaO is from 8 to 29.5.

4. The alkali-free glass substrate according to claim 1 , having a total amount of a halogen element is from 0.001% to 1%, on a mass percentage basis in terms of oxides.

5. The alkali-free glass substrate according to claim 4 , 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 .

6. A method of producing an alkali-free glass substrate according to claim 1 , having a SiO 2 —Al 2 O 3 —RO (RO is one or more kinds of MgO, CaO, BaO, and, SrO)-based composition, comprising:

a process of preparing glass raw materials so as to make alkali-free glass having a strain point of 680° C. or higher, a Young's modulus of 78 GPa or greater and an UV transmittance at a wavelength of 300 nm of from 40% to 85% in terms of 0.5 mm thickness, and 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; and

a process of managing temperature conditions at the time of forming and annealing such that an average cooling rate around the glass transition point obtained according to a rate cooling method is 400° C./min or lower, an in-plane distribution of the average cooling rate is 40° C./min or less, and an in-plane distribution of the UV transmittance at a wavelength of 300 nm in a G6-sized substrate is 1% or less in terms of 0.5 mm thickness.

7. The method of producing an alkali-free glass substrate according to claim 6 , wherein an in-plane distribution of a content of Fe is from 0.001% to 0.003% on a mass percentage basis in terms of Fe 2 O 3 .

8. The method of producing an alkali-free glass substrate according to claim 6 , wherein a total amount of a halogen element is from 0.001% to 1% on a mass percentage basis in terms of oxides.

9. The method of producing an alkali-free glass substrate according to claim 8 , wherein an in-plane distribution of a content of Fe is from 0.001% to 0.003% on a mass percentage basis in terms of Fe 2 O 3 .