POLARIZING PLATE AND OPTICAL DISPLAY APPARATUS
A polarizing plate for an optical display apparatus includes: a polarizer; and a retardation layer laminated on one surface of the polarizer, wherein the retardation layer includes a retardation film satisfying nx>nz>ny at a wavelength of 550 nm (Here, nx, ny, and nz refer to a refractive index of the retardation film in a slow axis direction, a refractive index of the retardation film in a fast axis direction, and a refractive index of the retardation film in a thickness direction at a wavelength of 550 nm.), an orientation direction of a main chain of a resin contained in the retardation film is about −5° to about +5° relative to a light absorption axis of the polarizer, and the retardation film has a degree of biaxiality of about 0.3 to about 0.7 at a wavelength of 550 nm.
1 . A polarizing plate comprising:
a polarizer; and
a retardation layer on a first surface of the polarizer,
wherein the retardation layer comprises a retardation film satisfying nx>nz>ny at a wavelength of 550 nm, nx, ny, and nz being a refractive index of the retardation film in a slow axis direction, a refractive index of the retardation film in a fast axis direction, and a refractive index of the retardation film in a thickness direction, at a wavelength of 550 nm, respectively,
an orientation direction of a main chain of a resin contained in the retardation film is about −5° to about +5° relative to a light absorption axis of the polarizer, and
the retardation film has a degree of biaxiality of about 0.3 to about 0.7 at a wavelength of 550 nm.
2 . The polarizing plate as claimed in claim 1 , wherein the retardation film is a single-layer retardation film.
3 . The polarizing plate as claimed in claim 1 , wherein the retardation film has an in-plane retardation of about 220 nm to about 300 nm at a wavelength of 550 nm.
4 . The polarizing plate as claimed in claim 1 , wherein in the retardation film, a value of Expression 1 is about 0.8 to about 1.2, and a value of Expression 2 is about 0.9 to about 1.1,
Re
(
450
nm
)
/
Re
(
550
nm
)
Expression
1
Re
(
650
nm
)
/
Re
(
550
nm
)
Expression
2
in Expression 1 and Expression 2, Re (450 nm), Re (550 nm), and Re (650 nm) being in-plane retardations (units: nm) of the retardation film at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.
5 . The polarizing plate as claimed in claim 1 , wherein a slow axis of the retardation film is about −5° to about +5° relative to a light transmission axis of the polarizer.
6 . The polarizing plate as claimed in claim 1 , wherein a slow axis of the retardation film is parallel to a transverse direction of the retardation film.
7 . The polarizing plate as claimed in claim 1 , wherein the retardation film is stretched in a machine direction (MD).
8 . The polarizing plate as claimed in claim 1 , wherein (nx−ny) is about 0.0022 to about 0.0075, and (nx−nz) is about 0.00066 to about 0.00525.
9 . The polarizing plate as claimed in claim 1 , wherein nx is about 1.500 to about 1.710, ny is about 1.480 to about 1.700, and nz is about 1.500 to about 1.705.
10 . The polarizing plate as claimed in claim 1 , wherein the resin is a main component of the retardation film.
11 . The polarizing plate as claimed in claim 1 , wherein the resin is a cellulose ester-based resin.
12 . The polarizing plate as claimed in claim 11 , wherein in the cellulose ester-based resin, hydrogen of at least a part among hydroxyl groups (OH) of each of C2, C3, and C6 of cellulose is regioselectively substituted with one or more selected from among a plurality of aromatic-CO-groups as a substituent and a plurality of first unsaturated or saturated (C 1-6 )alkyl-CO-groups as a substituent.
13 . The polarizing plate as claimed in claim 12 , wherein the cellulose ester-based resin has a degree of substitution for a hydroxy group of about 0.2 to about 2.0, a degree of substitution at C2 of about 0.15 to about 0.8, a degree of substitution at C3 of about 0.05 to about 0.6, and a degree of substitution at C6 of about 0.05 to about 0.6, and a total degree of substitution of about 0.25 to about 2.5.
14 . The polarizing plate as claimed in claim 1 , wherein the retardation layer consists of the retardation film.
15 . The polarizing plate as claimed in claim 1 , wherein the retardation layer has a thickness of about 40 μm to about 100 μm.
16 . The polarizing plate as claimed in claim 1 , wherein a protective layer is on a second surface of the polarizer opposite the first surface of the polarizer.
17 . An optical display apparatus comprising the polarizing plate as claimed in claim 1 .