Coated articles with optical coatings having residual compressive stress
A coated article includes a substrate having a major surface, and an optical coating disposed on the major surface of the substrate. At least a portion of the optical coating includes a residual compressive stress of about 50 MPa or more. The coated article has strain-to-failure of about 0.5% or more as measured by a Ring-on-Ring Tensile Testing Procedure. The coated article has an average photopic transmission of about 80% or greater.
1. A coated article comprising:
a substrate comprising a major surface;
an optical coating disposed on the major surface of the substrate and forming an air-side surface, the optical coating comprising one or more layers of deposited material;
wherein:
at least a portion of the optical coating comprises a residual compressive stress of more than about 50 MPa;
the optical coating comprises a strain-to-failure of about 0.4% or more as measured by a Ring-on-Ring Tensile Testing Procedure;
the optical coating comprises a maximum hardness of 12 GPa or more as measured on the air-side surface by a Berkovich Indenter Hardness Test along an indentation depth of about 50 nm and greater; and
the coated article comprises an average photopic transmission of about 80% or greater.
2. The coated article of claim 1 , wherein one of:
(i) the optical coating comprises: a thickness of from about 350 nm to less than about 600 nm; a strain to failure greater than about 0.65%; and a maximum hardness of 14 GPa or more; and
(ii) the optical coating comprises: a thickness of about 600 nm or more; a coating strain to failure greater than about 0.4%; and a maximum hardness of 13 GPa or more.
3. The coated article of claim 1 , wherein the portion of the optical coating comprising the residual stress further comprises a plurality of ion-exchangeable metal ions and a plurality of ion-exchanged metal ions, the ion-exchanged metal ions comprising an atomic radius larger than the atomic radius of the ion-exchangeable metal ions.
4. The coated article of claim 1 , wherein the residual compressive stress is imparted on the optical coating by mechanical blasting.
5. The coated article of claim 1 , wherein the at least a portion of the optical coating comprises a coefficient of thermal expansion and the substrate comprises a coefficient of thermal expansion, wherein the substrate comprises a greater coefficient of thermal expansion than does the at least a portion of the optical coating, wherein the coefficients of thermal expansion are measured over a temperature range of from about 20° C. to about 300° C.
6. The coated article of claim 5 , wherein the ratio of the coefficient of thermal expansion of the substrate to the coefficient of thermal expansion of the at least a portion of the optical coating is about 1.2:1 or more.
7. The coated article of claim 1 , wherein the optical coating exhibits a maximum hardness of about 14 GPa or greater.
8. The coated article of claim 1 , wherein the substrate comprises an amorphous substrate or a crystalline substrate.
9. A consumer electronic product, comprising:
a housing having a front surface, a back surface and side surfaces;
electrical components provided at least partially within the housing, the electrical components including at least a controller, a memory, and a display, the display being provided at or adjacent the front surface of the housing; and
a cover glass disposed over the display, wherein at least one of a portion of the housing or the cover glass comprises the coated article of claim 1 .
10. A method for making a coated article, the method comprising:
depositing an optical coating onto a major surface of a substrate, the optical coating forming an air-side surface and comprising one or more layers of deposited material;
wherein:
at least a portion of the optical coating comprises a residual compressive stress of more than about 50 MPa;
the optical coating comprises a strain-to-failure of about 0.4% or more as measured by a Ring-on-Ring Tensile Testing Procedure;
the optical coating comprises a maximum hardness of 12 GPa or more as measured on the air-side surface by a Berkovich Indenter Hardness Test along an indentation depth of about 50 nm and greater; and
the coated article comprises an average photopic transmission of about 80% or greater.
11. The method of claim 10 , wherein one of:
(i) the optical coating comprises: a thickness of from about 350 nm to less than about 600 nm; a strain to failure greater than about 0.65%; and a maximum hardness of 14 GPa or more; and
(ii) the optical coating comprises: a thickness of about 600 nm or more; a coating strain to failure greater than about 0.4%; and a maximum hardness of 13 GPa or more.
12. The method of claim 10 , further comprising imparting residual compressive stress on the optical coating by ion-exchange processing the deposited optical coating.
13. The method of claim 12 , wherein the ion-exchange processing comprises contacting the optical coating with an ionic salt bath.
14. The method of claim 12 , wherein the ion-exchange processing comprises field-assisted ion-exchange.
15. The method of claim 10 , further comprising imparting residual compressive stress on the optical coating by mechanical blasting.
16. The method of claim 10 , further comprising:
deforming the substrate under physical stress prior to the deposition of the optical coating; and
allowing the deformed substrate to reshape itself following the deposition of the optical coating;
wherein the optical coating is deposited onto a deformed substrate.
17. The method of claim 10 , further comprising disposing the at least a portion of the optical coating on the substrate, heating the substrate, and allowing the substrate to cool with the coating disposed thereon.
18. The method of claim 10 , wherein the coated article exhibits a maximum hardness of about 14 GPa or greater.