Articles having retained strength
One or more aspects of the disclosure pertain to an article including a film disposed on a glass substrate, which may be strengthened, where the interface between the film and the glass substrate is modified, such that the article retains its average flexural strength, and the film retains key functional properties for its application. Some key functional properties of the film include optical, electrical and/or mechanical properties. The bridging of a crack from one of the film or the glass substrate into the other of the film or the glass substrate can be prevented by inserting a crack mitigating layer between the glass substrate and the film.
1. An article, comprising:
a glass substrate having opposing major surfaces and a thickness from about 600 μm to about 5 mm, the substrate being chemically strengthened and having a surface compressive stress of at least 500 MPa and a compressive depth of layer 15 μm or greater;
a crack mitigating layer disposed on and directly in contact with the first major surface of the substrate, wherein the crack mitigating layer consists of a polyimide film having a thickness from about 0.04 μm to about 0.5 μm and a first critical strain energy release rate (G IC =K IC 2 /E); and
a second film disposed on and directly in contact with the crack mitigating layer having a thickness from about 0.01 μm to about 0.5 μm and having a second critical strain energy release rate (G IC =K IC 2 /E) that is less than the first critical strain energy release rate,
wherein the crack mitigating layer increases the average flexural strength of the article, when compared to an article comprising the glass substrate and the second film but not the crack mitigating layer, and
wherein the crack mitigating layer prevents cracks originating in one of the second film or the glass substrate from bridging to the other of the second film or the glass substrate, and
further wherein the second film is exposed.
2. The article of claim 1 , wherein the second film has a fracture toughness of less than about 10 MPa·m 1/2 and the crack mitigating layer has a fracture toughness of 1 MPa·m 1/2 or greater.
3. The article of claim 1 , wherein the second film comprises one or more layers selected from transparent conductive oxide layers, IR reflecting layers, UV reflecting layers, conducting layers, semiconducting layers, electronics layers, thin film transistor layers, anti-reflection layers, anti-glare layers, dirt-resistant layers, self-cleaning layers, scratch-resistant layers, barrier layers, passivation layers, hermetic layers, diffusion-blocking layers, and fingerprint-resistant layers.
4. The article of claim 3 , wherein the second film comprises one or more transparent conductive oxide layers, the one or more transparent conductive oxide layers comprising indium-tin-oxide.
5. The article of claim 1 , further exhibiting an average strain-to-failure that is greater than the average strain-to-failure of an article comprising the glass substrate and the second film but not the crack mitigating layer.
6. The article of claim 1 , wherein the glass substrate has a first refractive index, the crack mitigating layer has a second refractive index greater than the first refractive index, and the second film has a third refractive index greater than the second refractive index.
7. The article of claim 1 , wherein the article has a total reflectivity of about 10.0% or less over the visible wavelength range from about 450 nm to about 650 nm.
8. The article of claim 1 , wherein the glass substrate has an average strain-to-failure in the range from about 0.5% to about 2%.
9. An article, comprising:
a glass substrate having opposing major surfaces and a thickness from about 600 μm to about 5 mm, the substrate being chemically strengthened and having a first average strain-to-failure that is greater than about 0.5%, a surface compressive stress of at least 500 MPa and a compressive depth of layer 15 μm or greater;
a crack mitigating layer disposed on and directly in contact with the first major surface of the substrate, wherein the crack mitigating layer consists of a polyimide film having a thickness from about 0.04 μm to about 0.5 μm; and
a second film disposed on and directly in contact with the crack mitigating layer and having a thickness from about 0.01 μm to about 0.5 μm,
wherein the crack mitigating layer prevents cracks originating in one of the second film or the glass substrate from bridging to the other of the second film or the glass substrate, and
further wherein the second film is exposed.
10. The article of claim 9 , wherein the crack mitigating layer has a second average strain-to-failure, and the second film has a third average strain-to-failure, and wherein the first average strain-to-failure and the second average strain-to-failure are greater than the third average strain-to-failure.
11. The article of claim 9 , wherein the second film comprises functional properties selected from one or more of optical properties, electrical properties and mechanical properties.
12. The article of claim 9 , further exhibiting a greater average flexural strength and lower average reflectance over a wavelength range from 450-650 nm than an article comprising the glass substrate and the second film but not the crack mitigating layer.
13. The article of claim 9 , wherein the second film comprises more than one layer, wherein the more than one layer comprise one or more of optical interference layers, barrier layers, surface modifying layers, insulating layers, passivation layers, seeding layers, hermetic layers, and diffusion-blocking layers.
14. The article of claim 9 , further exhibiting at least one of an average flexural strength that is greater than the average flexural strength of an article comprising the glass substrate and the second film but without the crack mitigating layer or an average strain-to-failure that is greater than the average strain-to-failure of an article comprising the glass substrate and the second film but without the crack mitigating layer.
15. The article of claim 9 , further exhibiting at least one of an average flexural strength that is substantially the same as the average flexural strength of the glass substrate or an average strain-to-failure that is substantially the same as the average strain-to-failure of the glass substrate.
16. The article of claim 9 , wherein the second film comprises a single layer or a plurality of layers forming the second thickness, and wherein the crack mitigating layer comprises a first thickness that is less than or equal to about 10 times the second thickness.
17. The article of claim 16 , wherein the first thickness is less than or equal to about 5 times the second thickness.
18. The article of claim 16 , wherein the second thickness and the first thickness are each less than about 10 micrometers.
19. A touch-sensing device comprising the article of claim 9 .
20. An information display device comprising the article of claim 9 .