High strain point glass
The present invention relates to a glass composition that includes: 57 to 75 percent by weight of SiO 2 ; 3 to 11 percent by weight of Al 2 O 3 ; 6 to 11 percent by weight of Na 2 O; 16 to 21 percent by weight of CaO; 0.01 to 0.1 percent by weight of Li 2 O; and less than 0.05 percent by weight of K 2 O. Each percent by weight is based on total weight of the glass composition. Glass products are also provided that have a bulk glass composition as described above. The glass products, such as flat glass products and glass substrates, have a strain point of at least 590° C. and a thermal expansion of at least 7.4 ppm/° C. The present invention also relates to magnetic recording articles and photovoltaic cells that include a glass substrate that has a bulk glass composition as described above.
1. A glass composition comprising:
SiO 2 57 to 75 percent by weight;
Al 2 O 3 3 to 11 percent by weight;
Na 2 O 8.24 to 9.29 percent by weight;
CaO 16 to 18.40 percent by weight; and
K 2 O less than 0.05 percent by weight;
wherein the source of alumina is alumina hydrate;
wherein the glass composition is free of zirconium;
wherein each percent by weight is based on total weight of said glass composition, and
wherein a glass product prepared from said glass composition has, (i) a strain point in the range of 590° C. and 635° C., and (ii) a coefficient of thermal expansion of at least 7.4 ppm/° C. and less than 8.5 ppm/° C.
2. The glass composition of claim 1 wherein, Al 2 O 3 is present in an amount of 4 to 10 percent by weight.
3. The glass composition of claim 1 wherein, Al 2 O 3 is present in an amount of 4.5 to 9.5 percent by weight.
4. The glass composition of claim 1 wherein, a weight ratio of Al 2 O 3 to Na 2 O is from 0.5 to 1.0.
5. The glass composition of claim 1 wherein, a weight ratio of Al 2 O 3 to CaO is from 0.2 to 0.5.
6. The glass composition of claim 1 wherein, a weight ratio of Na 2 O to CaO is from 0.46 to 0.5.
7. The glass composition of claim 1 wherein,
a weight ratio of Al 2 O 3 to Na 2 O is from 0.5 to 1.0,
a weight ratio of Al 2 O 3 to CaO is from 0.2 to 0.5.
8. A glass product having a bulk glass composition comprising:
SiO 2 57 to 75 percent by weight;
Al 2 O 3 3 to 11 percent by weight;
Na 2 O 8.24 to 9.29 percent by weight;
CaO 16 to 18.40 percent by weight; and
K 2 O less than 0.05 percent by weight;
wherein the source of alumina is alumina hydrate;
wherein the bulk glass composition is free of zirconium;
wherein each percent by weight is based on total weight of said bulk glass composition, and
wherein said glass product has, (i) a strain point in the range of 590° C. to 635° C. and (ii) a coefficient of thermal expansion of at least 7.4 ppm/° C. and less than 8.5 ppm/° C.
9. The glass product of claim 8 wherein said glass product is a flat glass product.
10. A magnetic recording article comprising a glass substrate, wherein said glass substrate has a bulk glass composition comprising:
SiO 2 57 to 75 percent by weight;
Al 2 O 3 3 to 11 percent by weight;
Na 2 O 8.24 to 9.29 percent by weight;
CaO 16 to 18.40 percent by weight; and
K 2 O less than 0.05 percent by weight;
wherein the source of alumina is alumina hydrate;
wherein the bulk glass composition is free of zirconium;
wherein each percent by weight is based on total weight of said bulk glass composition, and
wherein said glass substrate has, (i) a strain point in the range of 590° C. to 635° C., and (ii) a coefficient of thermal expansion of at least 7.4 ppm/° C. and less than 8.5 ppm/° C.
11. A photovoltaic cell comprising a glass substrate and at least one semiconductor layer over said glass substrate, wherein said glass substrate has a bulk glass composition comprising:
SiO 2 57 to 75 percent by weight;
Al 2 O 3 3 to 11 percent by weight;
Na 2 O 8.24 to 9.29 percent by weight;
CaO 16 to 18.40 percent by weight; and
K 2 O less than 0.05 percent by weight;
wherein the source of alumina is alumina hydrate;
wherein the bulk glass composition is free of zirconium;
wherein each percent by weight is based on total weight of said bulk glass composition, and
wherein said glass substrate has, (i) a strain point in the range of 590° C. to 635° C., and (ii) a coefficient of thermal expansion of at least 7.4 ppm/° C. and less than 8.5 ppm/° C.
12. The photovoltaic cell of claim 11 wherein at least one semiconductor layer comprises at least one of cadmium and telluride.
13. The glass composition of claim 1 further comprising 0.14 weight percent of MgO.
14. The glass composition of claim 1 further comprising 0.082 weight percent of SO 3 .
15. The glass composition of claim 1 wherein the Al 2 O 3 is present in an amount of 5.32 weight percent.
16. The glass composition of claim of claim 13 further comprising 0.082 weight percent of SO 3 , wherein the glass composition comprises:
SiO 2 68.66 percent by weight;
Al 2 O 3 5.32 percent by weight;
Na 2 O 8.65 percent by weight;
CaO 17.1 percent by weight;
Li 2 O 0.03 percent by weight;
K 2 O 0.013 percent by weight; and
Fe 2 O 3 0.0076 percent by weight.
17. The glass composition of claim 8 further comprising 0.14 weight percent of MgO.
18. The glass composition of claim 8 further comprising 0.082 weight percent of SO 3 .
19. The glass composition of claim 8 wherein the Al 2 O 3 is present in an amount of 5.32 weight percent.
20. The glass composition of claim 10 further comprising 0.14 weight percent of MgO.
21. The glass composition of claim 1 , wherein the glass composition has a visible light transmittance (Lta) of at least 75% in a glass composition having a thickness of at least 5 mm.