Damage-resistant glass articles and method
A strengthened glass article has opposing first and second compressively stressed surface portions bound to a tensilely stressed core portion, with the first surface portion having a higher level of compressive surface stress than the second surface portion for improved resistance to surface damage, the compressively stressed surface portions being provided by lamination, ion-exchange, thermal tempering, or combinations thereof to control the stress profiles and limit the fracture energies of the articles.
1. A glass article comprising:
a glass core layer;
first and second glass surface layers fused to the glass core layer to form a laminated article, each of the first and second glass surface layers having a lower thermal expansion than the glass core layer; and
an asymmetric stress profile resulting at least partially from subjecting the laminated article to an ion-exchange treatment at outer surfaces of the laminated article; and
a bending moment M as defined by the expression M=(1+ρ)(D 1 +D 2 +D 3 )/ρ of substantially zero, wherein D 1 , D 2 and D 3 correspond, respectively, to bending rigidities of the first glass surface layer, the glass core layer, and the second glass surface layer, and wherein ρ represents a common radius of curvature of the glass article.
2. The glass article of claim 1 , wherein at least one of the first or second glass surface layers comprises a surface compression of at least 300 MPa.
3. The glass article of claim 1 , wherein the glass core layer comprises a tensile stress not exceeding 20 MPa.
4. The glass article of claim 1 , wherein the thermal expansion of each of the first and second glass surface layers is less than or equal to 52×10 −7 /° C.
5. The glass article of claim 1 , wherein the thermal expansion of the glass core layer is greater than or equal to 74×10 −7 /° C.
6. The glass article of claim 1 , wherein each of the first and second glass surface layers comprises a compressively stressed surface portion of the glass article, and the glass core layer comprises a tensilely stressed core portion of the glass article.
7. The glass article of claim 1 , wherein one of the first or second glass surface layers comprises a higher surface compression than the other of the first or second glass surface layers.
8. The glass article of claim 1 , wherein the first glass surface layer comprises a different composition than the second glass surface layer.
9. The glass article of claim 1 , wherein the first glass surface layer comprises a different thermal expansion than the second glass surface layer.
10. The glass article of claim 1 , wherein the first glass surface layer comprises a different thickness than the second glass surface layer.
11. The glass article of claim 1 , wherein the thermal expansion of each of the glass core layer, the first glass surface layer, and the second glass surface layer is the thermal expansion at a set point of the respective layer.
12. The glass article of claim 1 , wherein:
at least one of the first or second glass surface layers comprises a surface compression of at least 300 MPa;
the thermal expansion of each of the first and second glass surface layers is less than or equal to 52×10 −7 /° C.; and
the thermal expansion of the glass core layer is greater than or equal to 74×10 −7 /° C.
13. The glass article of claim 1 , wherein the first glass surface layer comprises at least one of a different composition, a different thermal expansion, or a different thickness than the second glass surface layer.