Glasses
Glasses are disclosed having a composition comprising the following oxides (in weight %): SiO 2 61 to 70%, Al 2 O 3 0 to 9%, Na 2 O 10 to 13%, K 2 O 0 to 1%, MgO 2 to 6%, CaO 6 to 16%, SrO 0 to 1%, ZrO 2 0 to 1%, TiO 2 2 to 15%, the glasses having a strain point greater than 570° C. The glasses have good dimensional stability at high temperatures, making them suitable for fire protection glazings and substrates which are processed at elevated temperatures, e.g. substrates for display panels, information storage discs and semiconductor devices, including photovoltaic cells. Physical properties of the glasses, such as thermal expansion coefficient, density and refractive index, are disclosed, as are the melting and liquidus temperatures. The glasses are suitable for manufacture by the float process, yielding flat glass in the form of sheets.
1. A soda lime silica glass having a strain point greater than 570° C., comprising the following oxides (in weight %):
SiO 2
61 to 69%
Al 2 O 3
3 to 8%
Na 2 O
10 to 13%
K 2 O
0 to 1%
MgO
2 to 6%
CaO
7 to 13%
SrO
0 to 1%
ZrO 2
0 to 1%
TiO 2
3 to 12%
B 2 O 3
0 to 1%.
2. The glass as claimed in claim 1 , comprising from 3 to 11% TiO 2 .
3. The glass as claimed in claim 1 , comprising from 4 to 10% TiO 2 .
4. The glass as claimed in claim 1 , comprising from 4 to 6% TiO 2 .
5. The glass as claimed in claim 1 having a strain point greater than 580° C.
6. The glass as claimed in claim 1 having a melting temperature (at which viscosity=log 2 poise) less than 1500° C.
7. The glass as claimed in claim 1 having a liquidus temperature less than 1200° C.
8. The glass as claimed in claim 1 having a working range (defined as T log 4 poise minus the liquidus temperature) greater than −100° C.
9. The glass as claimed in claim 1 having a coefficient of thermal expansion from 70 to 90×10 −7 ° C. −1 (50-350° C.).
10. The glass as claimed in claim 1 having a density from 2.50 to 2.70 g cm −3 at 25° C.
11. The glass as claimed in claim 1 having a refractive index from 1.50 to 1.62.
12. A sheet of glass formed from glass as claimed in claim 1 .
13. A glass substrate comprising glass as claimed in claim 1 .
14. A photovoltaic cell comprising the glass substrate of claim 13 .
15. A flat glass produced by an on-line float glass process, having a strain point greater than 570° C., comprising the following oxides (in weight %):
SiO 2
61 to 69%
Al 2 O 3
3 to 8%
Na 2 O
10 to 13%
K 2 O
0 to 1%
MgO
2 to 6%
CaO
7 to 13%
SrO
0 to 1%
ZrO 2
0 to 1%
TiO 2
3 to 12%.
16. A glass substrate for a photovoltaic cell comprising the flat glass as claimed in claim 15 .
17. A flat glass substrate having a strain point greater than 570° C., comprising the following oxides (in weight %):
SiO 2
61 to 69%
Al 2 O 3
0 to 8%
Na 2 O
10 to 13%
K 2 O
0 to 1%
MgO
2 to 6%
CaO
9.2 to 13%
SrO
0 to 1%
ZrO 2
0 to 1%
TiO 2
3 to 13%
B 2 O 3
0 to 1%.
18. A photovoltaic cell comprising the flat glass substrate of claim 17 .