LAMINATED FILM HAVING IMPROVED SURFACE HARDNESS AND RESTORATION PROPERTIES AND DISPLAY DEVICE COMPRISING SAME
In a laminated film according to an embodiment, an elastic layer containing polyether-block-amide and a hard coating-treated base film are laminated. Due to the layer configuration in which different materials are compounded, the surface hardness and restoration properties and elasticity can be improved at the same time, and also, excellent optical properties can be implemented.
1 . A laminate 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 elastic layer comprises a polyether-block-amide.
2 . The laminate film of claim 1 , wherein the laminate film has a Vickers hardness (HV) of 48 N/mm 2 or more and an indentation hardness (H IT ) of 505 N/mm 2 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.
3 . The laminate film of claim 1 , wherein the laminate film has a recovery of 76% 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 the recovery is calculated by the following equation:
Recovery
(
%
)
=
[
(
h
max
(
at
30
mN
)
-
h
p
)
/
h
max
(
at
30
mN
)
]
×
100
wherein h max (at 30 mN) 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 (crept) for 5 seconds, and h p is the depth (μm) of the indentation that remains unrecovered even after the force is released.
4 . The laminate film of claim 1 , wherein the laminate film has:
an average visible light transmittance of 80% or more when measured according to the ISO 13468 standard,
a haze of 4% or less when measured according to the ISO 14782 standard, and
a transmittance increase of 2% or more as calculated by the following equation:
Transmittance
increase
(
%
)
=
TT
1
(
%
)
-
TT
2
(
%
)
wherein TT1 is the average visible light transmittance (%) of the laminate film, TT2 is the average visible light transmittance (%) of a film having a layer structure excluding the hard coating layer from the laminate film, and the average visible light transmittance is measured under the same conditions according to the ISO 13468 standard.
5 . The laminate film of claim 1 , wherein the laminate film has a yellow index of 1.5 or less when measured at 10° using a D65 light source according to the ASTM-E313 standard and a yellow index decrease of 0.5 or more as calculated by the following equation:
Yellow
index
decrease
=
YI
2
-
YI
1
wherein YI1 is the yellow index of the laminate film, YI2 is the yellow index of a film having a layer structure excluding the hard coating layer from the laminate film, and the yellow index is measured under the same conditions at 10° using a D65 light source according to the ASTM-E313 standard.
6 . The laminate film of claim 1 , wherein the laminate film has an L* value of 92 or more, an a* value of −2 to 1, and a b* value of −1 to 2 of transparent color in the CIE Lab color coordinates when measured using a D65 light source.
7 . The laminate film of claim 1 , wherein the base film comprises a polymer film or ultra-thin glass (UTG).
8 . The laminate film of claim 1 , wherein the base film comprises a polyester-based resin.
9 . The laminate film of claim 8 , wherein the laminate film has a Martens hardness (HM) of 175 N/mm 2 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.
10 . The laminate film of claim 8 , wherein the laminate film has an indentation modulus (E IT ) of 2,900 MPa 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.
11 . The laminate film of claim 8 , wherein the laminate film has a recovery relation (η IT ) of 63.6% 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.
12 . The laminate film of claim 8 , wherein the laminate film has an indentation creep (C IT ) of 3.5% 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.
13 . The laminate film of claim 8 , wherein the laminate film has a recovery of 65% 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 the recovery is calculated by the following equation:
Recovery
(
%
)
=
[
(
h
m
ax
(
at
30
mN
)
-
h
p
)
/
h
m
ax
(
at
30
mN
)
]
×
100
wherein h max (at 30 mN) 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 h p is the depth (μm) of the indentation that remains unrecovered even after the force is released.
14 . The laminate film of claim 8 , wherein the laminate film has an average visible light transmittance of 85% or more when measured according to the ISO 13468 standard and a transmittance increase of 3% or more as calculated by the above equation:
Transmittance
increase
(
%
)
=
TT
1
(
%
)
-
TT
2
(
%
)
wherein TT1 is the average visible light transmittance (%) of the laminate film, TT2 is the average visible light transmittance (%) of a film having a layer structure excluding the hard coating layer from the laminate film, and the average visible light transmittance is measured under the same conditions according to the ISO 13468 standard.
15 . The laminate film of claim 1 , 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, an acrylate-based compound, and an epoxy acrylate-based compound.
16 . The laminate film of claim 15 , wherein the hard coating layer further comprises a fluorine-based compound.
17 . A display device, which comprises a display panel; and a cover window disposed on the front side of the display panel,
wherein the cover window 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, and
the elastic layer comprises a polyether-block-amide.
18 . The display device of claim 17 , wherein the base film comprises a polyester-based resin.
19 . The laminate film of claim 8 , 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, an acrylate-based compound, and an epoxy acrylate-based compound.