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 having a first average strain-to-failure of 0.5% or greater 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 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 having a second average strain-to-failure that is less than the first average strain-to-failure and having at least one of a modulus of at least 25 GPa and a hardness of at least 1.75 GPa,
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 comprises functional properties selected from one or more of optical properties, electrical properties and mechanical properties, and wherein the second film retains substantially the same functional properties when the crack mitigating layer is disposed between the glass substrate and the second film.
3. The article of claim 2 , 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, EMI shielding 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 1 , wherein the crack mitigating layer exhibits a first critical strain energy release rate (G IC =K IC 2 /E) and the second film exhibits a second critical strain energy release rate (G IC =K IC 2 /E) that is less than the first critical strain energy release rate.
5. The article of claim 4 , wherein the first critical strain energy release rate (G IC =K IC 2 /E) is about 0.1 kJ/m 2 or greater, and wherein the second critical strain energy release rate (G IC =K IC 2 /E) is less than about 0.1 kJ/m 2 .
6. The article of claim 1 , wherein the crack mitigating layer has a third average strain-to-failure, and wherein the second average strain-to-failure is less than the first average strain-to-failure and the third average strain-to-failure.
7. The article of claim 6 , wherein the crack mitigating layer has a yield stress of less than about 500 MPa.
8. The article of claim 1 , wherein the crack mitigating layer has an elastic modulus of about 50 GPa or less.
9. The article of claim 8 , wherein the second film has an elastic modulus of about 25 GPa or more.
10. The article of claim 9 , wherein the second film has a hardness of about 2 GPa or more.
11. The article of claim 1 , wherein the glass substrate has an average flexural strength that is maintained when the crack mitigating layer is disposed on the first major surface and the film is disposed on the crack mitigating layer.
12. 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 film has a third refractive index greater than the second refractive index.
13. The article of claim 1 , wherein the article has a total reflectivity of 10.0% or less over the visible wavelength range from about 450 nm to about 650 nm.
14. An article, comprising:
a glass substrate having opposing major surfaces having a first average strain-to-failure of 0.5% or greater and a thickness from about 600 μm to about 5 μm, 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, wherein the crack mitigating layer consists of an aminosilane-based adhesion promoter disposed on and directly in contact with the first major surface of the substrate and a polyimide film having a thickness from about 0.04 μm to about 0.5 μm disposed directly on and in contact with the aminosilane-based adhesion promoter; 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, having a second average strain-to-failure that is less than the first average strain-to-failure and having at least one of a modulus of at least 25 GPa and a hardness of at least 1.75 GPa,
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 film or the glass substrate,
wherein the second film comprises indium-tin-oxide, and
further wherein the second film is exposed.