Transparent composite film with hard coating, method for forming the same and flexible display device including the same
Described herein are articles and methods of making articles, including a transparent composite film having a fiber filler embedded in a polymer network and further including a hard coating. The polymer network of the film is a cured, cross-linked matrix. The hard coating is a cross-linked aromatic urethane acrylate oligomer and a photoinitiator and provides a flexible protective layer that maintains good hardness, puncture-resistance and scratch-resistance.
1. A flexible transparent composite film comprising:
a film of a composite composition, the composite composition comprising a cross-linked polymer network, a fiber filler embedded in the cross-linked polymer network, and an optional photoinitiator; and
a hard coating provided on one or both sides of the composite composition film, the hard coating comprising a cross-linked hard coating composition, the hard coating composition comprising an aromatic urethane acrylate oligomer and a photoinitiator;
wherein the flexible transparent composite film comprises a bend radius of less than about 5 mm and a Pencil Hardness greater than or equal to about 5 H.
2. The flexible transparent composite film of claim 1 , wherein the aromatic urethane acrylate oligomer is a multifunctional aromatic urethane acrylate oligomer.
3. The flexible transparent composite film of claim 1 , wherein the aromatic urethane acrylate oligomer comprises a number average molecular weight (MW) of from about 750 to about 2500.
4. The flexible transparent composite film of claim 1 , wherein a minimum number of acrylate functional groups (F) in the aromatic urethane acrylate oligomer follows the following equation:
F =MW/250,
wherein MW is a number average molecular weight of the aromatic urethane acrylate oligomer.
5. The flexible transparent composite film of claim 1 , wherein the hard coating composition further comprises a second aromatic urethane acrylate oligomer.
6. The flexible transparent composite film of claim 1 , wherein the cross-linked polymer network comprises one or more functional group.
7. The flexible transparent composite film of claim 6 , wherein the one or more functional group comprises acrylate, ester, ether, hydroxyl, or combinations thereof.
8. The flexible transparent composite film of claim 1 , wherein the photoinitiator is present in the hard coating and optionally present in the composite composition, in an amount from about 2 weight percent to about 6 weight percent, based on the weight of each of the hard coating and the composite composition.
9. The flexible transparent composite film of claim 8 , wherein the photoinitiator is present in the hard coating, in an amount from about 3 weight percent to about 5 weight percent, based on the weight of the hard coating.
10. The flexible transparent composite film of claim 9 , wherein the photoinitiator is present in the hard coating, in an amount of about 5 weight percent, based on the weight of the hard coating.
11. The flexible transparent composite film of claim 1 , wherein the hard coating comprises a coefficient of thermal expansion, at a temperature that is from 25° C. to 300° C., that is less than a coefficient of thermal expansion of the composite composition film.
12. The flexible transparent composite film of claim 1 , wherein the bend radius is less than about 2 mm.
13. The flexible transparent composite film of claim 1 , wherein the Pencil Hardness is greater than or equal to about 8 H.
14. The flexible transparent composite film of claim 1 , wherein the fiber filler comprises glass fibers.
15. The flexible transparent composite film of claim 1 , wherein the hard coating comprises an average thickness of less than or equal to about 25 μm.
16. The flexible transparent composite film of claim 1 , wherein the composite composition film comprises an average thickness of less than or equal to about 200 μm.
17. The flexible transparent composite film of claim 16 , wherein the composite composition film has an average thickness of less than or equal to about 55 μm.
18. The flexible transparent composite film of claim 1 , wherein the hard coating is provided on both sides of the composite composition film.
19. The flexible transparent composite film of claim 1 , wherein the fiber filler is a woven fiber fabric.
20. A consumer electronic product, comprising:
a housing comprising a front surface, a back surface and side surfaces;
electrical components at least partially within the housing, the electrical components comprising at least a controller, a memory, and a display, the display at or adjacent the front surface of the housing; and
a cover material disposed over the display,
wherein at least one of a portion of the housing or the cover material comprises the flexible transparent composite film of claim 1 .
21. A method for making a flexible transparent composite film comprising:
applying a resin composition onto a fiber filler, the resin composition comprising one or more acrylate-functionalized monomers and an optional photoinitiator;
at least partially curing the resin composition to form a film of a composite composition, the composite composition comprising an at least partially cross-linked polymer network, the fiber filler embedded in the at least partially cross-linked polymer network, and the optional photoinitiator;
applying a hard coating composition to one side of the composite composition film, the hard coating composition comprising one or more aromatic urethane acrylate oligomers and a photoinitiator;
at least partially curing the hard coating composition to form a first hard coating;
optionally applying the hard coating composition to the other side of the composite composition film, and at least partially curing the hard coating composition to form a second hard coating; and
finally curing the flexible transparent composite film;
wherein the flexible transparent composite film comprises a bend radius of less than about 5 mm and a Pencil Hardness greater than or equal to about 5 H.