Multilayer Polymer Film
In a first aspect, a multilayer polymer film includes a first substantially transparent polymer layer having a first elastic modulus and a second substantially transparent polymer layer having a second elastic modulus. The first elastic modulus is different from the second elastic modulus and the first and second substantially transparent polymer layers are bonded by consolidation. In a second aspect, a cover window includes the multilayer polymer film of the first aspect and a layer of a transparent material. The layer of a transparent material has a speed of sound of at least 2000 m/s. In a third aspect, an electronic device includes the cover window of the second aspect.
1 . A multilayer polymer film comprising:
a first substantially transparent polymer layer having a first elastic modulus; and
a second substantially transparent polymer layer having a second elastic modulus, wherein:
the first elastic modulus is different from the second elastic modulus; and
the first and second substantially transparent polymer layers are bonded by consolidation.
2 . The multilayer polymer film of claim 1 , wherein a Mode I interlaminar fracture toughness (G lc ) between the first and second substantially transparent polymer layers is at least 500 J/m 2 .
3 . The multilayer polymer film of claim 1 , wherein a difference between the elastic moduli of the first and second substantially transparent polymer layers is at least 5%.
4 . The multilayer polymer film of claim 1 , wherein the first substantially transparent polymer layer, the second substantially transparent polymer layer, or both the first and second substantially transparent polymer layers have a speed of sound of at least 1300 m/s.
5 . The multilayer polymer film of claim 1 , wherein the first substantially transparent polymer layer, the second substantially transparent polymer layer, or both the first and second substantially transparent polymer layers further comprise sub-micron fillers.
6 . The multilayer polymer film of claim 1 , wherein the polymer of the first substantially transparent polymer layer is cross-linked, the polymer of the second substantially transparent polymer layer is cross-linked, or the polymers of both the first and second substantially transparent polymer layers are cross-linked.
7 . The multilayer polymer film of claim 1 , wherein the first substantially transparent polymer layer, the second substantially transparent polymer layer, or both the first and second substantially transparent polymer layers comprise a polyimide, a polyamide imide, a block copolymer of a polyimide or a block copolymer of a polyamide imide.
8 . The multilayer polymer film of claim 7 , wherein the first substantially transparent polymer layer, the second substantially transparent polymer layer, or both the first and second substantially transparent polymer layers further comprise an imidization catalyst.
9 . The multilayer polymer film of claim 1 , further comprising a third substantially transparent polymer layer having a third elastic modulus, wherein:
the second substantially transparent polymer layer is positioned between the first and third substantially transparent polymer layers; and
the second and third substantially transparent polymer layers are bonded by consolidation.
10 . The multilayer polymer film of claim 9 , wherein: (i) the second elastic modulus is smaller than the first elastic modulus and the third elastic modulus is greater than the second elastic modulus, or (ii) the second elastic modulus is greater than the first elastic modulus and the third elastic modulus is greater than the second elastic modulus, or (iii) the second elastic modulus is smaller than the first elastic modulus and third elastic modulus smaller than the second elastic modulus.
11 . A cover window comprising the multilayer polymer film of claim 1 and a layer of a transparent material, wherein the layer of a transparent material has a speed of sound of at least 2000 m/s.
12 . The cover window of claim 11 , wherein the transparent material is selected from the group consisting of polyimide, polyamide imide, poly(methyl methacrylate), polyether ketone, polystyrene, polycarbonate, polyester and particle reinforced polymer.
13 . The cover window of claim 11 , further comprising an additional layer of a transparent material with a speed of sound of at least 2000 m/s, such that the multilayer polymer film is positioned between the two layers of transparent material with a speed of sound of at least 2000 m/s.
14 . The cover window of claim 11 further comprising an adhesive layer.
15 . The cover window of claim 11 , wherein a minimum Mode I interlaminar fracture toughness (G lc ) between any adjacent layers in the cover window is at least 100 J/m 2 .
16 . The cover window of claim 11 , wherein the cover window has a haze of less than 2%.
17 . The cover window of claim 11 , wherein the cover window has a b* of less than 2.
18 . The cover window of claim 11 , wherein the cover window has a transmittance of at least 80%.
19 . An electronic device comprising the cover window of claim 11 .