Glass plate and process for its production
View Patent ↗A glass plate made of soda lime silica glass containing at least MgO, CaO, Na 2 O and Al 2 O 3 produced by a float process or a downdraw method, wherein [MgO] is at least 4.5%, [MgO]/[CaO] is larger than 1, and Q=([MgO]/[CaO])×([CaO]+[Na 2 O]−[Al 2 O 3 ]) is at least 20, wherein [MgO] is the content of MgO, [CaO] is the content of CaO, [Na 2 O] is the content of Na 2 O, and [Al 2 O 3 ] is the content of Al 2 O 3 (each being as represented by mass percentage based on oxide) and a process for the glass plate.
1. A glass plate, comprising:
soda lime silica glass that comprises MgO, CaO, Na 2 O, and Al 2 O 3 ,
wherein the glass plate is obtained by a float process or a downdraw method,
a content of MgO in the glass plate is at least 4.5% by mass percentage based on oxide,
a content of Na 2 O in the glass plate is from 10 to 20% by mass percentage based on oxide,
a ratio of the content of MgO by mass percentage based on oxide, to a content of CaO by mass percentage based on oxide, ([MgO]/[CaO]), is larger than 1,
a value Q obtained by formula (1) is at least 20:
Q =([MgO]/[CaO])×([CaO]+[Na 2 O]−[Al 2 O 3 ]) (1),
[MgO] is the content of MgO by mass percentage based on oxide,
[CaO] is the content of CaO by mass percentage based on oxide,
[Na 2 O] is a content of Na 2 O by mass percentage based on oxide,
[Al 2 O 3 ] is a content of Al 2 O 3 by mass percentage based on oxide, and
a content of B 2 O 3 if present by mass percentage based on oxide is at most 1%.
2. The glass plate according to claim 1 ,
wherein the ratio of the content of MgO by mass percentage based on oxide, to the content of CaO by mass percentage based on oxide, ([MgO]/[CaO]), is larger than 1 and not larger than 30, and
the value Q obtained by formula (1) is at least 20 and at most 400.
3. The glass plate according to claim 1 , which comprises by mass percentage based on oxides,
SiO 2 : from 60 to 75%,
Al 2 O 3 : more than 0%,
Na 2 O: from 10 to 20%,
MgO: at least 4.5%, and
CaO: from 1 to 10%.
4. The glass plate according to claim 1 , which comprises by mass percentage based on oxides,
SiO 2 : from 60 to 75%,
Al 2 O 3 : more than 0% and at most 4.5%,
Na 2 O: from 10 to 20%,
MgO: from 4.5 to 15%,
CaO: from 1 to 10%, and
total iron calculated as Fe 2 O 3 : from 0 to 0.1%.
5. The glass plate according to claim 1 , which comprises by mass percentage based on oxides,
SiO 2 : from 60 to 75%,
Al 2 O 3 : more than 0% and at most 4.5%,
Na 2 O: from 10 to 20%,
K 2 O: from 0 to 5%,
MgO: from 4.5 to 10%,
CaO: from 1 to 10%, and
total iron calculated as Fe 2 O 3 : from 0 to 0.1%.
6. The glass plate according to claim 1 , which comprises by mass percentage based on oxides,
SiO 2 : from 60 to 75%,
Al 2 O 3 : more than 0% and at most 4.5%,
Na 2 O: from 10 to 20%,
MgO: from 4.5 to 15%,
CaO: from 1 to 10%, ZrO 2 : from 0 to 3%,
total iron calculated as Fe 2 O 3 : from 0 to 0.1%,
CeO 2 : from 0 to 0.1%, and
Sb 2 O 3 : from 0 to 0.5%.
7. The glass plate according to claim 1 , which comprises by mass percentage based on oxides,
SiO 2 : from 60 to 74.5%,
Al 2 O 3 : from 0.5 to 3.5%,
Na 2 O: from 10 to 20%,
K 2 O: from 0 to 5%,
MgO: from 4.5 to 13%,
CaO: from 1 to 10%,
total iron calculated as Fe 2 O 3 : from 0 to 0.1%,
CeO 2 : from 0 to 0.05%, and
Sb 2 O 3 : from 0 to 0.5%.
8. The glass plate according to claim 1 , which comprises by mass percentage based on oxides,
SiO 2 : from 60 to 74%,
Al 2 O 3 : from 0.5 to 2.5%,
Na 2 O: from 10 to 20%,
K 2 O: from 0 to 3%,
MgO: from 4.5 to 10%, CaO: from 1 to 10%,
total iron calculated as Fe 2 O 3 : from 0.005 to 0.06%.
Sb 2 O 3 : from 0 to 0.1%, and
ZrO 2 : from 0 to 3%,
and which does not substantially contain CeO 2 .
9. The glass plate according to claim 1 , wherein as calculated in a thickness of 4 mm of the glass plate, a visible light transmittance (Tv) is at least 80%, and a solar transmittance (Te) is at least 80%.
10. A process for producing a glass plate, the process comprising:
melting glass raw material, followed by
forming the glass plate by a float process or a downdraw method,
wherein the glass plate comprises a soda lime silica glass, which comprises MgO, CaO, Na 2 O, and Al 2 O 3 ,
a content of MgO in the glass plate is at least 4.5% by mass percentage based on oxide,
a content of Na 7 O in the glass plate is from 10 to 20% by mass percentage based on oxide,
a ratio of the content of MgO by mass percentage based on oxide, to a content of CaO by mass percentage based on oxide, ([MgO]/[CaO]), is larger than 1,
a value Q obtained by formula (1) is at least 20:
Q =([MgO]/[CaO])×([CaO]+[Na 2 O]−[Al 2 O 3 ]) (1),
[MgO] is the content of MgO by mass percentage based on oxide,
[CaO] is the content of CaO by mass percentage based on oxide,
[Na 2 O] is a content of Na 2 O by mass percentage based on oxide,
[Al 2 O 3 ] is a content of Al 2 O 3 by mass percentage based on oxide, and
a content of B 2 O 3 if present by mass percentage based on oxide is at most 1%.
11. The glass plate of claim 1 , wherein B 2 O 3 is not present.
12. The glass plate of claim 1 , wherein B 2 O 3 is present only as an impurity.
13. The process of claim 10 , wherein the glass plate does not comprise B 2 O 3 .
14. The process of claim 10 , wherein the glass plate comprises B 2 O 3 only as an impurity.
15. The glass plate of claim 1 , wherein a content of CaO present in the glass plate is from 1 to 10% by mass percentage based on oxide.
16. The glass plate of claim 1 , wherein a content of SiO 2 present in the glass plate is at least 71% by mass percentage based on oxide.
17. The glass plate of claim 1 , wherein the content of MgO present in the glass plate is at least 6.4% by mass percentage based on oxide.
18. The process of claim 10 , wherein a content of CaO present in the glass plate is from 1 to 10% by mass percentage based on oxide.
19. The process of claim 10 , wherein a content of SiO 2 present in the glass plate is at most 71% by mass percentage based on oxide.
20. The process of claim 10 , wherein the content of MgO present in the glass plate is at least 6.4% by mass percentage based on oxide.