Laminated glass article with low compaction and method for forming the same
A strengthened glass article ( 100 ), such as a substrate for a p-Si based transistors, includes first and second glass cladding layers ( 104, 106 ) and a glass core layer ( 102 ) disposed therebetween. A coefficient of thermal expansion [CTE] of each cladding layer ( 104, 106 ), which can be made of the same glass, is at least 1×10 −7 ° C. −1 less than that of the core layer ( 102 ). Each of the core and cladding layers has a strain point less than 700° C. A compaction of the glass article ( 100 ) is at most about 20 ppm [see FIG. 1 ]. A method includes forming a glass article and/or heating a glass article to a first temperature of at least about 400° C. The glass article has a glass core layer ( 102 ) and a glass cladding layer ( 104, 106 ) adjacent to the core layer. The glass article is maintained at a temperature within a range of from 400° C. to 600° C. for a holding period from 30 to 90 minutes and subsequently cooled to a temperature of at most 50° C. over a cooling period from 30 seconds to 5 minutes. The glass article ( 100 ) for heat strengthening may have been produced by the fusion overflow down draw process, e.g. as depicted in FIG. 3.
1. A strengthened glass article comprising:
a first glass cladding layer;
a second glass cladding layer; and
a glass core layer disposed between the first glass cladding layer and the second glass cladding layer;
wherein a coefficient of thermal expansion (CTE) of each of the first glass cladding layer and the second glass cladding layer is at least 1×10 7 ° C. −1 less than a CTE of the glass core layer;
wherein each of the glass core layer and the glass cladding layer comprises a strain point of less than 650° C.;
wherein each of the first glass cladding layer and the second glass cladding layer comprises a compressive stress of at least about 20 MPa; and
wherein a compaction of the glass article is at most about 20 ppm.
2. The glass article of claim 1 , wherein at least one of the glass cladding layers is substantially free of BaO.
3. The glass article of claim 1 , wherein at least one of the glass cladding layers comprises from about 60 mol % to about 70 mol % SiO 2 , from about 6 mol % to about 18 mol % Al 2 O 3 , from about 6 mol % to about 21 mol % B 2 O 3 , from about 0.2 mol % to about 5 mol % MgO, and from about 8 mol % to about 12 mol % CaO.
4. The glass article of claim 1 , wherein the glass cladding layer is substantially free of alkali metal.
5. The glass article of claim 1 , wherein the glass cladding layer is substantially free of As 2 O 3 .
6. The glass article of claim 1 , wherein the glass core layer comprises from about 50 mol % to about 80 mol % SiO 2 , from about 5 mol % to about 20 mol % Al 2 O 3 , and from about 1 mol % to about 8 mol % MgO.
7. The glass article of claim 1 , wherein the compaction of the glass article is at most about 3 ppm.
8. The glass article of claim 1 , wherein the compaction of the glass article is at most about 1 ppm.
9. The glass article of claim 1 , further comprising a poly-crystalline silicon (p-Si) electronic device formed on a surface of the glass article.
10. The glass article of claim 9 , wherein the p-Si electronic device comprises a thin-film-transistor (TFT).
11. A display device comprising the glass article of claim 1 .
12. A method comprising:
forming a glass article comprising a glass core layer and a glass cladding layer adjacent to the glass core layer;
maintaining the glass article within a hold temperature range from about 400° C. to about 600° C. for a holding period from about 30 minutes to about 90 minutes; and
cooling the glass article to a quench temperature of at most about 50° C. over a cooling period from about 30 seconds to about 5 minutes subsequent to the maintaining step.
13. The method of claim 12 , further comprising cooling the glass article to a cool temperature of about 200° C. at a cooling rate from about 1° C./minute to about 7° C./minute subsequent to the maintaining step and prior to the cooling the glass article to the quench temperature step.
14. The method of claim 12 , wherein the glass cladding layer comprises a first glass cladding layer and a second glass cladding layer, and the glass core layer is disposed between the first glass cladding layer and the second glass cladding layer.
15. The method of claim 12 , further comprising forming a poly-crystalline silicon (p-Si) electronic device on a surface of the glass article.
16. The method of claim 12 , wherein the forming the glass article comprises contacting the glass core layer in a viscous state with the glass cladding layer in a viscous state using an overflow distributor.
17. A method comprising:
heating a glass article to a first temperature of at least about 400° C., the glass article comprising a glass core layer and a glass cladding layer adjacent to the glass core layer;
maintaining the glass article within a temperature range from about 400° C. to about 600° C. for a holding period from about 30 minutes to about 90 minutes; and
cooling the glass article to a second temperature of at most about 50° C. over a cooling period from about 30 seconds to about 5 minutes subsequent to the maintaining step.
18. The method of claim 17 , further comprising cooling the glass article to an intermediate temperature of about 200° C. at a cooling rate from about 1° C./minute to about 7° C./minute subsequent to the maintaining step and prior to the cooling the glass article to the second temperature step.
19. The method of claim 17 , wherein the glass cladding layer comprises a first glass cladding layer and a second glass cladding layer, and the glass core layer is disposed between the first glass cladding layer and the second glass cladding layer.
20. The method of claim 17 , further comprising forming a poly-crystalline silicon (p-Si) electronic device on a surface of the glass article.
21. The method of claim 12 , wherein subsequent to the cooling step, a compaction of the glass article is at most about 20 ppm.
22. The method of claim 17 , wherein subsequent to the cooling step, a compaction of the glass article is at most about 20 ppm.
23. A glass article made by the method of claim 12 .