High-transparency glass

1. A glass comprising 1 to 30 ppm of a total iron oxide (t-Fe 2 O 3 ) in terms of Fe 2 O 3 , having a redox of 0% or more and 25% or less, comprising, as expressed by mass percentage based on oxides:

SiO 2 50 to 81%,

Al 2 O 3 1 to 20%,

B 2 O 3 0 to 5%,

Li 2 O+Na 2 O+K 2 O 5 to 20%, and

MgO+CaO+SrO+BaO 5 to 27%,

wherein the redox is a ratio of divalent iron in terms of Fe 2 O 3 to a total of divalent iron and trivalent iron in terms of Fe 2 O 3 ([divalent iron (Fe 2+ ) in terms of Fe 2 O 3 ]/[total (Fe 2+ +Fe 3+ ) of divalent iron (Fe 2+ ) and trivalent iron (Fe 3+ ) in terms of Fe 2 O 3 ]),

a bubble disappearance-starting temperature (TD) of the glass is 1485° C. or lower, and

the glass has a minimum value of an inner transmittance along light path length of 200 mm in a wavelength range of 400 to 700 nm of 85% or more, and a difference between a maximum value and the minimum value of the inner transmittance is 13% or less.

2. A glass comprising 1 to 30 ppm of a total iron oxide (t-Fe 2 O 3 ) in terms of Fe 2 O 3 , comprising, as expressed by mass percentage based on oxides:

SiO 2 50 to 81%,

Al 2 O 3 1 to 20%,

B 2 O 3 0 to 5%,

Li 2 O Na 2 O+K 2 O 5 to 20%, and

MgO+CaO+SrO+BaO 5 to 27%,

wherein a value of D represented by the following expression (1) of the glass is 0 or more, and a bubble disappearance-starting temperature (TD) of the glass is 1485° C. or lower:

D =4×[SiO 2 ]+8×[Al 2 O 3 ]+2×[MgO]−1×[CaO]−2×[SrO]−2×[BaO]−8×[Na 2 O]−12×[K 2 O]−180  (1)

wherein, as expressed by mass percentage based on oxides,

[SiO 2 ] is the content of SiO 2 ,

[Al 2 O 3 ] is the content of Al 2 O 3 ,

[MgO] is the content of MgO,

[CaO] is the content of CaO,

[SrO] is the content of SrO,

[BaO] is the content of BaO,

[Na 2 O] is the content of Na 2 O, and

[K 2 O] is the content of K 2 O, and

the glass has a minimum value of an inner transmittance along light path length of 200 mm in a wavelength range of 400 to 700 nm of 85% or more, and a difference between a maximum value and the minimum value of the inner transmittance is 13% or less.

3. A glass comprising 1 to 30 ppm of a total iron oxide (t-Fe 2 O 3 ) in terms of Fe 2 O 3 , comprising, as expressed by mass percentage based on oxides:

SiO 2 50 to 81%,

Al 2 O 3 1 to 20%,

B 2 O 3 0 to 5%,

Li 2 O+Na 2 O+K 2 O 5 to 20%, and

MgO+CaO+SrO+BaO 5 to 27%,

wherein when a bubble density B is defined as that in a glass body obtained by melting glass raw materials at a temperature of 1550° C., followed by forming into a sheet and then annealing, the bubble density B of the glass is 10 pieces/kg or less, and

the glass has a minimum value of an inner transmittance along light path length of 200 mm in a wavelength range of 400 to 700 nm of 85% or more, and a difference between a maximum value and the minimum value of the inner transmittance is 13% or less.

4. The glass according to claim 3 , wherein a ratio (B/A) of the bubble density B to a bubble density A is 10 −3 or less, wherein the bubble density A is defined as that in a glass body obtained by melting glass raw materials at a temperature of 1350° C., followed by forming into a sheet and then annealing.

5. The glass according to claim 1 , wherein a content of divalent iron (Fe 2+ ) in terms of Fe 2 O 3 in the glass is 50 ppm or less.

6. The glass according to claim 1 , wherein a content of Al 2 O 3 as expressed by mass percentage is 1 to 10%.

7. The glass according to claim 1 , wherein a content of Li 2 O+Na 2 O+K 2 O is 5 to 15%.

8. The glass according to claim 1 , wherein a content of MgO+CaO+SrO+BaO is 13 to 27%.

9. The glass according to claim 1 , comprising, as expressed by mass percentage based on oxides:

SiO 2 50 to 81%,

Al 2 O 3 1 to 10%,

B 2 O 3 0 to 5%,

Li 2 O 0 to 5%,

Na 2 O 5 to 15%,

K 2 O 0 to 7.5%,

MgO 0 to 15%,

CaO 0 to 15%,

SrO 0 to 15%,

BaO 0 to 15%,

Li 2 O+Na 2 O+K 2 O 5 to 15%, and

MgO+CaO+SrO+BaO 13 to 27%.

10. The glass according to claim 1 , wherein the glass is substantially free from B 2 O 3 .

11. The glass according to claim 1 , further comprising more than 0% and 0.5% or less of SO 3 as expressed by mass percentage.

12. The glass according to claim 1 , wherein a content of SnO 2 as expressed by mass percentage is 1% or less.

13. The glass according to claim 1 , wherein a total content of Sb 2 O 3 and As 2 O 3 as expressed by mass percentage is 0.5% or less.

14. The glass according to claim 1 , wherein a content of CeO 2 as expressed by mass percentage is 0.05% or less.

15. The glass according to claim 1 , wherein the glass has a temperature (T2) at which a viscosity of a glass melt reaches 10 2 dPa·s of 1550° C. or lower.

16. The glass according to claim 1 , wherein a difference (Tc-T4) between a devitrification temperature (Tc) of the glass and a temperature (T4) at which a viscosity of a glass melt reaches 10 4 dPa·s is 100° C. or lower.

17. A glass sheet comprising the glass according to claim 1 .

18. The glass sheet according to claim 17 , wherein the glass sheet has a length of at least one side thereof of 200 mm or more and a thickness of 0.5 mm or more.

19. A method for producing the glass sheet according to claim 17 , comprising:

melting glass materials to obtain a molten glass; and

forming the molten glass by using any one forming method selected from the group consisting of a float process, a roll-out process, a pulling-up process, and a fusion process to obtain a glass sheet, wherein a maximum melting temperature in melting the glass raw materials is in a range of the bubble disappearance-starting temperature (TD) of the glass to TD+150° C.

20. The glass according to claim 1 , wherein a value of D represented by the following expression (1) of the glass is 20.8 or more:

D =4×[SiO 2 ]+8×[Al 2 O 3 ]+2×[MgO]−1×[CaO]−2×[SrO]−2×[BaO]−8×[Na 2 O]−12×[K 2 O]−180  (1)

wherein, as expressed by mass percentage based on oxides,

[SiO 2 ] is the content of SiO 2 ,

[Al 2 O 3 ] is the content of Al 2 O 3 ,

[MgO] is the content of MgO,

[CaO] is the content of CaO,

[SrO] is the content of SrO,

[BaO] is the content of BaO,

[Na 2 O] is the content of Na 2 O, and

[K 2 O] is the content of K 2 O.