Transparent, flexible, impact resistant, multilayer film comprising polycarbonate copolymers

1. A multilayer film comprising:

(a) a plurality of layers, comprising,

a polymer A layer comprising a polycarbonate copolymer wherein the polycarbonate copolymer comprises at least one of:

a copolymer of polycarbonate and iso- and terephthalate esters of resorcinol at a weight ratio of the iso- and terephthalate esters of resorcinol to the polycarbonate of 20/80; or

copolymer comprising bisphenol A carbonate units and 2-phenyl-3,3′-bis(4-hydroxyphenyl) phthalimidine carbonate units; and

a polymer B layer comprising a semi-crystalline polyester used to form the film;

(b) an interdiffusion region between each polymer A and polymer B;

wherein a differential solubility parameter of polymer A towards polymer B (Δδ AB ) is

2.6 MPa 1/2 ≤Δδ AB ≤3.0 MPa 1/2 ; and

wherein the multilayer film has an average impact dent depth of less than or equal to 15 μm as determined in accordance with an impact dent depth test and measured using an optical profiler having a 5×objective lens, 1×scan, white illumination, 0.5% threshold, 20 μm backscan length, and 20 μm scan length;

wherein the impact dent depth test comprises impacting the multilayer film comprising a polymer A outer layer with a ball point pen tip from a height of 12 cm between the ball point pen tip and the multilayer film, by dropping a 5.4 g polymer foam guider comprising the ball point pen tip onto the polymer A outer layer of the multilayer film to form an impact dent, wherein the average impact dent depth is an average of six measurements at different locations on the sample, wherein the ball point pen tip has a 1.0 mm ball tip diameter;

wherein the multilayer film has a dynamic flexure of greater than or equal to 200,000 cycles, as determined by bending 180° on a 10 mm radius cylinder at a rate of 1 hertz; and

wherein the multilayer film, without any skin layers or masking films, has a total thickness of 40 μm to 70 μm;

wherein the multilayer film has a transmission at a wavelength of 360 nm to 750 nm of greater than or equal to 89% at the thickness of the multilayer film, as measured according to ASTM D1003-00, under D65 illumination, with a 10 degrees observer; and

wherein the multilayer film has a haze of less than or equal to 1% at the thickness of the multilayer film, as measured according to ASTM D1003-00, under D65 illumination, with a 10 degrees observer.

2. The multilayer film of claim 1 , wherein the dynamic flexure, determined by bending 180°, 1 Hz, on a 2 mm radius cylinder, is greater than or equal to 200,000 cycles.

3. The multilayer film of claim 1 , wherein a total thickness of the multilayer film is 40 μm to 60 μm.

4. The multilayer film of claim 1 , further comprising a skin layer attached to a side of the multilayer film.

5. The multilayer film of claim 4 , wherein the skin layer has a thickness of 1 to 10 μm.

6. The multilayer film of claim 1 , comprising a coating, wherein the coating has a hardness (H) and a modulus (E) determined via nano-indentation, and wherein a ratio of hardness to modulus (H/E) is 0.03 to 0.1, wherein the coating can be located on at least one of a skin layer, opposing skin layers, on an outermost layer of the multilayer film, or on opposing outermost surfaces of the multilayer film.

7. The multilayer film of claim 1 , wherein the semi-crystalline polyester is poly(ethylene terephthalate) formed from terephthalic acid and a combination of ethylene glycol and diethylene glycol.

8. The multilayer film of claim 1 , wherein the multilayer film, minus any skin layers and any mask films has a total thickness of 40 to 70 μm.

9. An article comprising the multilayer film of claim 1 .

10. The article of claim 9 , wherein the article is at least one of a five-wire resistive touch screen, a surface capacitive touch screen, a projected capacitive touch screen, a surface acoustic wave touch screen, an optical imaging touch screen, or an infrared touch screen.

11. The article of claim 9 , wherein the article is a display article with curvature or flexure.

12. The article of claim 9 , wherein the article is a cellular phone or a tablet.

13. A method for producing the multilayer film of claim 1 , comprising:

(i)

coextruding polymer A and polymer B;

splitting the coextruded polymer A and polymer B to obtain two or more sub-streams;

repositioning the sub-streams in an overlapping manner, and contacting the sub-streams to obtain alternating layers of polymer A and polymer B; and

repeating the preceding steps until the desired number of layers has been attained; and

passing the stream through a die to produce the multilayer film; or

(ii)

separately extruding polymer A and polymer B to form individual polymer streams A and B;

splitting the individual polymer streams A and B into more than 3 sub-streams, and

recombining the sub-streams to form a recombined stream, alternating between the A and B sub-streams; and

passing the recombined stream through a die to produce the multilayer film.

14. The method of claim 13 , further comprising adding a skin layer to the recombined stream prior to passing it through a die.

15. An electronic device comprising the multilayer film of claim 1 , wherein the electronic device has a dynamic flexure of greater than or equal to 200,000 cycles, as determined by bending 180° on a 10 mm radius cylinder at a rate of 1 hertz.

16. The multilayer film of claim 1 , wherein the polymer A layer comprises the copolymer comprising bisphenol A carbonate units and 2-phenyl-3,3′-bis(4-hydroxyphenyl) phthalimidine carbonate units.

17. The multilayer film of claim 1 , wherein the multilayer film comprises 4 layers to 128 layers.

18. The article of claim 9 , wherein the article is a flexible wristwatch, clothing with integrated display, curved vehicle display, or rollable screen.