To provide a glass plate which can be made to have higher Te than conventional glass plates when its iron content is substantially the same as the conventional glass plates, to have substantially the same level of Te as conventional glass plates when its iron content is larger than the conventional glass plates, or to have very high Te when its iron content is smaller than conventional glass plates, and which presents good productivity. A glass plate which comprises, as represented by mol percentage based on oxides, SiO 2 : from 57 to 71%, Al 2 O 3 : from 0 to 6%, B 2 O 3 : from 0 to 5%, Na 2 O: from 10 to 16%, MgO: from 7.5 to 19.8%, and CaO: from 1.6 to 11%, provided that S-value represented by MgO+Al 2 O 3 +B 2 O 3 —Na 2 O (as represented by mol percentage) is from −10 to 10.5%, and the ratio of the content of MgO, as represented by mol percentage based on oxide, to the content of CaO, as represented by mol percentage based on oxide, ([MgO]/[CaO]), is from 0.8 to 10.
1. A glass plate which comprises, as represented by mol percentage based on oxides,
SiO 2 : 57 to 71%,
Al 2 O 3 : 0.5 to 6%,
B 2 O 3 : 0 to 5%,
Na 2 O: 10 to 16%,
MgO: 7.5 to 19.8%, and
CaO: 1.6 to 8.0%,
provided that S-value represented by MgO+Al 2 O 2 +B 2 O 3 —Na 2 O (as represented by mol percentage) is −10 to 10.5%, and
the ratio of the content of MgO, as represented by mol percentage based on oxide, to the content of CaO, as represented by mol percentage based on oxide, ([MgO]/[CaO]), is 0.9375 to 10.
2. The glass plate according to claim 1 , wherein the S-value is −2 to 10.5%.
3. The glass plate according to claim 1 , wherein the S-value is 0 to 10.5%.
4. The glass plate according to claim 1 , wherein the mol percentage of B 2 O 3 is
B 2 O 3 : 3 to 5%.
5. The glass plate according to claim 1 , wherein the ratio of [MgO]/[CaO] is 0.9375 to 1.5.
6. The glass plate according to claim 1 , which comprises, as represented by mol percentage based on oxides:
SiO 2 : 60 to 69%,
Al 2 O 3 : 0.5 to 3.0%,
B 2 O 3 : 0%,
Na 2 O: 11 to 15%,
MgO: 9 to 18%, and
CaO: 3.2 to 5%,
provided that S-value represented by MgO+Al 2 O 3 +B 2 O 3 —Na 2 O (as represented by mol percentage) is −3.0 to 2.2%, and
the ratio of the content of MgO, as represented by mol percentage based on oxide, to the content of CaO, as represented by mol percentage based on oxide, ([MgO]/[CaO]), is 1.8 to 4.
7. The glass plate according to claim 1 , which comprises, as represented by mol percentage based on oxides:
SiO 2 : 65 to 68%,
Al 2 O 3 : 0.8 to 3.0%,
B 2 O 3 : 0%,
Na 2 O: 14.0 to 15.0%,
MgO: 10.5 to 12.8%, and
CaO: 3.8 to 5%,
K 2 O: 0 to 0.7%,
provided that S-value represented by MgO+Al 2 O 3 +B 2 O 3 —Na 2 O (as represented by mol percentage) is −0.5 to 1.4%, and
the ratio of the content of MgO, as represented by mol percentage based on oxide, to the content of CaO, as represented by mol percentage based on oxide, ([MgO]/[CaO]), is 2.1 to 4.
8. The glass plate according to claim 1 , wherein a content of total iron calculated as Fe 2 O 3 is 0 to 0.06% as represented by mass percentage based on oxide.
9. The glass plate according to claim 1 , wherein
the Te of the glass plate is at least 80%, and
the Tv of the glass plate is at least 80%,
each as calculated a thickness of 4 mm by measuring transmittance by a spectrophotometer in accordance with JIS R3106.
10. The glass plate according to claim 1 , wherein
the Te of the glass plate is at least 82.7%, and
the Tv of the glass plate is at least 82%,
each as calculated in a thickness of 4 mm by measuring transmittance by a spectrophotometer in accordance with JIS R3106.
11. The glass plate according to claim 6 , wherein a content of total iron calculated as Fe 2 O 3 is 0 to 0.06% as represented by mass percentage based on oxide.
12. The glass plate according to claim 6 , wherein
the Te of the glass plate is at least 80%, and
the Tv of the glass plate is at least 80%,
each as calculated in a thickness of 4 mm by measuring transmittance by a spectrophotometer in accordance with JIS R3106.
13. The glass plate according to claim 6 , wherein
the Te of the glass plate is at least 82.7%, and
the Tv of the glass plate is at least 82%,
each as calculated in a thickness of 4 mm by measuring transmittance by a spectrophotometer in accordance with JIS R3106.
14. The glass plate according to claim 7 , wherein a content of total iron calculated as Fe 2 O 3 is 0 to 0.06% as represented by mass percentage based on oxide.
15. The glass plate according to claim 7 , wherein
the Te of the glass plate is at least 80%, and
the Tv of the glass plate is at least 80%,
each as calculated in a thickness of 4 mm by measuring transmittance by a spectrophotometer in accordance with JIS R3106.
16. The glass plate according to claim 7 , wherein
the Te of the glass plate is at least 82.7%, and
the Tv of the glass plate is at least 82%,
each as calculated in a thickness of 4 mm by measuring transmittance by a spectrophotometer in accordance with JIS R3106.
17. A solar cell or a light collecting mirror comprising the glass plate according to claim 1 .
18. A solar cell or a light collecting mirror comprising the glass plate according to claim 6 .
19. A solar cell or a light collecting mirror comprising the glass plate according to claim 7 .