| CPC C08J 7/042 (2013.01) [C08J 7/044 (2020.01); G02B 1/14 (2015.01); G06F 1/1652 (2013.01); C08J 2367/00 (2013.01); C08J 2433/14 (2013.01)] | 5 Claims |
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1. A composite film, which comprises a base film; a hard coating layer disposed on one side of the base film; and an elastic layer disposed on the other side of the base film,
wherein the ΔE′ value according to the following Equation (1) is 2 to 300:
ΔE′=E′[−30° C.]/E′[50° C.] (1)
in which E′[−30° C.] is the storage modulus (Pa) of the elastic layer at −30° C., and E′[50° C.] is the storage modulus (Pa) of the elastic layer at 50° C., and
wherein the composite film has an Hy increase (N/mm2) of 2.0 N/mm2 or more as calculated by the following Equation (2) and a recovery increase of 1.5% or more as calculated by the following Equation (3):
HV increase(N/mm2)=HV1(N/mm2)−HV2(N/mm2) (2)
Recovery increase(%)=Recovery1(%)−Recovery2(%) (3)
in which HV1 is the Vickers hardness (HV) (N/mm2) of the composite film, HV2 is the Vickers hardness (HV) (N/mm2) of a film having a layer structure excluding the elastic layer from the composite film,
Recovery1 is the recovery (%) of the composite film, and Recovery2 is the recovery (%) of a film having a layer structure excluding the elastic layer from the composite film,
wherein the composite film has a Vickers hardness (HV) of 30 N/mm2 or more when measured for the surface of the hard coating layer by a nanoindentation test according to the ISO 14577-1: 2002 (E) standard and a recovery of 69% or more as calculated by the following equation:
Recovery(%)=[(hmax−hp)/hmax]×100
in which hmax is the maximum indentation depth (μm) during which the surface of the hard coating layer is pressed downward for 15 seconds at a force of 30 mN and held for 5 seconds, and hp is the depth (μm) of the indentation that remains unrecovered even after the force is released,
wherein the ratio of the storage modulus of the elastic layer to the storage modulus of the base film (elastic layer/base film) is 0.5 or less at 25° C.,
wherein the elastic layer comprises a UV-curable urethane acrylate-based oligomer having 2 to 8 functional groups, and
wherein the hard coating layer comprises at least one selected from the group consisting of a urethane acrylate-based compound, an acrylic ester-based compound, and an epoxy acrylate-based compound.
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