Glass compositions and strengthened glass laminate articles comprising the same
A glass composition includes from 60 mol % to 76 mol % SiO 2 ; from 7 mol % to 16 mol % Al 2 O 3 ; from 0 mol % to 12 mol % B 2 O 3 ; and from 0 mol to 14 mol % Na 2 O. (R 2 O+RO)/Al 2 O 3 in the glass composition may be greater than or equal to 1. A glass laminate article includes a core glass layer having a low temperature coefficient of thermal expansion (LTCTE core ) and a high temperature coefficient of thermal expansion (HTCTE core ): a clad glass layer laminated to a surface of the core glass layer, the clad glass layer having a low temperature coefficient of thermal expansion (LTCTE clad ) and a high temperature coefficient of thermal expansion (HTCTE clad ); and a thickness t.
1. A method of manufacturing a strengthened glass article, comprising:
increasing by at least 20 MPa compressive stress of a clad glass in a laminate comprising a core glass fused to the clad glass by heating up the laminate from below 100° C. to above 100° C. but below 600° C. and having the laminate above 100° C. but below 600° C. for longer than an hour,
wherein curves of coefficient of thermal expansion (y-axis) as a function of temperature (x-axis) of the core and clad glasses intersect one another above 100° C. but below 600° C.
2. The method of claim 1 , wherein at least some of the heating occurs with the laminate outside of a salt bath.
3. The method of claim 2 , wherein the at least some of the heating occurs in a gaseous environment comprising greater than 70% nitrogen and greater than 15% oxygen by volume.
4. The method of claim 1 , wherein the increasing is by at least 50 MPa.
5. The method of claim 4 , wherein the increasing is by at least 100 MPa.
6. The method of claim 5 , further comprising additionally increasing compressive stress of the clad glass by ion-exchange chemical tempering.
7. The method of claim 1 , wherein the hour is continuous as opposed to broken up into segments that add to longer than an hour in aggregate.
8. A method of manufacturing a strengthened glass article, comprising:
relaxing stresses, in a laminate comprising a core glass fused to a clad glass, corresponding to differences in high-temperature coefficients of thermal expansion of the clad and core glasses while preserving stresses corresponding to differences in low-temperature coefficients of thermal expansion of the clad and core glasses to apply a compressive stress on the clad glass,
wherein the compressive stress applied by the relaxing is at least 20 MPa.
9. The method of claim 8 , wherein the relaxing comprises heating up the laminate.
10. The method of claim 8 , further comprising additionally increasing compressive stress of the clad glass by ion-exchange chemical tempering.
11. The method of claim 8 , wherein curves of coefficient of thermal expansion (y-axis) as a function of temperature (x-axis) of the core and clad glasses intersect one another above 200° C. but below a 10 11 poise temperature of both the core and clad glasses if the 10 11 poise temperature of at least one of the core and clad glasses is less than 600° C.
12. A method of manufacturing a strengthened glass article, comprising:
forming a glass-to-glass laminate by fusing clad and core glasses to one another, wherein the clad glass has a greater high-temperature coefficient of thermal expansion (HTCTE) than the core glass, but a lesser low-temperature coefficient of thermal expansion (LTCTE) than the core glass;
cooling the glass-to-glass laminate to impart stresses through contraction mismatch between the clad and core glasses,
wherein stresses in the glass-to-glass laminate from differences in the HTCTE of the clad and core glasses at least partially offset stresses in the glass-to-glass laminate from differences in the LTCTE of the clad and core glasses;
after the cooling, modifying geometry of the laminate;
after the modifying, relaxing at least some of the stresses in the glass-to-glass laminate from differences in the HTCTE of the clad and core glasses such that the stresses in the glass-to-glass laminate from differences in the LTCTE of the clad and core glasses change stresses in the clad glass by at least 20 MPa.
13. The method of claim 12 , wherein the modifying increases compressive stresses in the clad glass by at least 20 MPa.
14. The method of claim 13 , further comprising exchanging ions of the clad glass with larger ions to further increase compressive stress of the clad glass beyond the relaxing.
15. The method of claim 14 , wherein at least a portion of the relaxing occurs after the exchanging ions.
16. The method of claim 14 , wherein at least a portion of the relaxing occurs in a gaseous environment.
17. The method of claim 12 , wherein the modifying comprises cutting the laminate.
18. The method of claim 17 , wherein the modifying further comprises polishing edges of the laminate.
19. The method of claim 12 , wherein the relaxing comprises having the laminate above 300° C. and below 600° C. for at least an hour.
20. The method of claim 19 , wherein the relaxing further comprises heating up the laminate from below 100° C. to above 300° C.
21. The method of claim 19 , wherein aggregate time having the laminate above 300° C. and below 600° C. is greater than 21 hours.