High-transparency glass
View Patent ↗The present invention provides a high-transparency glass having a high fining action at a low temperature and capable of achieving redox lowering more than before. The present invention relates to a glass containing 1 to 500 ppm of a total iron oxide (t-Fe 2 O 3 ) in terms of Fe 2 O 3 , having a redox ([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 ]) of 0% or more and 25% or less, containing, as expressed by mass percentage based on oxides, 50 to 81% of SiO 2 , 1 to 20% of Al 2 O 3 , 0 to 5% of B 2 O 3 , 5 to 20% of Li 2 O+Na 2 O+K 2 O, and 5 to 27% of MgO+CaO+SrO+BaO, and having a bubble disappearance-starting temperature (TD) of 1485° C. or lower.
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 , comprising, as expressed by mass percentage based on oxides:
SiO 2 50 to 81%,
Al 2 O 3 1 to 12.9%,
MgO 0 to 5%,
CaO 0 to 5.0%,
B 2 O 3 0 to 5%, and
Li 2 O+Na 2 O+K 2 O 5 to 20%,
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 in a wavelength range of 400 to 700 nm under a condition of a light path length of 200 mm being 80% or more, and
a difference between a maximum value and the minimum value of the inner transmittance being 15% or less.
2. The glass according to claim 1 , wherein a ratio (B/A) of the bubble density B of the glass to a bubble density A of the glass 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.
3. The glass according to claim 1 , comprising 0 to 30 ppm of divalent iron (Fe 2+ ) in terms of Fe 2 O 3 .
4. The glass according to claim 1 , wherein a content of Al 2 O 3 as expressed by mass percentage is 1 to 10%.
5. The glass according to claim 1 , wherein the content of Li 2 O+Na 2 O+K 2 O is 5 to 15%.
6. The glass according to claim 1 , wherein a content of MgO as expressed by mass percentage based on oxides is 0.8 to 4.6%.
7. 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 12.9%,
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 5%,
CaO 0 to 5.0%,
SrO 0 to 6%,
BaO 0 to 6%, and
Li 2 O+Na 2 O+K 2 O 5 to 15%.
8. 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 12.9%,
MgO 0 to 5%,
CaO 0 to 5.0%,
B 2 O 3 0 to 5%, and
Li 2 O+Na 2 O+K 2 O 5 to 20%,
wherein the glass has a value of D represented by expression (1) of 23.3 or more,
the glass has a minimum value of an inner transmittance in a wavelength range of 400 to 700 nm under a condition of a light path length of 200 mm being 80% or more, and
a difference between a maximum value and the minimum value of the inner transmittance being 15% or less:
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.
9. The glass according to claim 8 , wherein a ratio (B/A) of a bubble density B of the glass to a bubble density A of the glass is 10 −3 or less, wherein the 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, and 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.
10. The glass according to claim 8 , comprising 0 to 30 ppm of divalent iron (Fe 2+ ) in terms of Fe 2 O 3 .
11. The glass according to claim 8 , wherein a content of Al 2 O 3 as expressed by mass percentage is 1 to 10%.
12. The glass according to claim 8 , wherein the content of Li 2 O+Na 2 O+K 2 O is 5 to 15%.
13. The glass according to claim 8 , wherein a content of MgO as expressed by mass percentage based on oxides is 0.8 to 4.6%.
14. The glass according to claim 8 , comprising, as expressed by mass percentage based on oxides:
SiO 2 50 to 81%,
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 5%,
CaO 0 to 5.0%,
SrO 0 to 6%,
BaO 0 to 6%, and
Li 2 O+Na 2 O+K 2 O 5 to 15%.
15. The glass according to claim 1 , wherein the glass is substantially free from B 2 O 3 .
16. The glass according to claim 1 , wherein a content of SnO 2 is 1% or less as expressed by mass percentage.
17. The glass according to claim 1 , wherein a content of CeO 2 is 0.05% or less as expressed by mass percentage.
18. A glass sheet made of the glass according to claim 1 .
19. The glass sheet according to claim 18 , 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.