POLARIZING PLATE AND OPTICAL DISPLAY DEVICE
A polarizing plate and an optical display device comprising same are provided, the polarizing plate comprising: a polarizer; and a phase difference layer laminated on the lower surface of the polarizer, wherein in the phase difference layer, the maximum value of the ratio expressed by formula 1 is 1.1 to 1.8 and the minimum value is 0.3 to 0.7. [Formula 1] Ratio B/A (A is the front surface phase difference (unit:nm) of the phase difference layer at wavelength of 550 nm, and B is an inclined phase difference (unit:nm) measured at wavelength of 550 nm with rotation of the phase difference layer by +60° or −60° about a fast axis of the phase difference layer as the rotational axis.
1 . A polarizing plate comprising: a polarizer; and a retardation layer stacked on a lower surface of the polarizer,
wherein the retardation layer has a maximum ratio of 1.1 to 1.8 and a minimum ratio of 0.3 to 0.7, as calculated according to Equation 1:
[
[
Ratio
]
]
ratio
_
=
B
/
A
,
[
Equation
1
]
in the Equation 1,
A is a front retardation of the retardation layer (unit:nm) at a wavelength of 550 nm; and
B is an oblique retardation of the retardation layer (unit:nm), as measured at the wavelength of 550 nm with the retardation layer rotated at an angle of +60° or −60° about a fast axis of the retardation layer as a rotational axis.
2 . The polarizing plate according to claim 1 , wherein the retardation layer has an A value of 110 nm to 170 nm in Equation 1.
3 . The polarizing plate according to claim 1 , wherein the retardation layer has a maximum B value of 120 nm to 310 nm and a minimum B value of 20 nm to 120 nm in Equation 1.
4 . The polarizing plate according to claim 1 , wherein the retardation layer has a difference of 45 nm or more between a maximum oblique retardation and a minimum oblique retardation, as measured at the wavelength of 550 nm with the retardation layer rotated at the angle of +60° or −60° about the fast axis of the retardation layer as the rotational axis.
5 . The polarizing plate according to claim 1 , wherein the retardation layer has an oblique retardation of 130 nm to 240 nm, as measured at the wavelength of 550 nm with the retardation layer rotated at an angle of +60° or −60° about a slow axis of the retardation layer as the rotational axis.
6 . The polarizing plate according to claim 1 , wherein the retardation layer has negative wavelength dispersion.
7 . The polarizing plate according to claim 1 , wherein the retardation layer has an asymmetrical relative value in a graph where an x-axis denotes a rotational angle (°) of a retardation meter and a Y-axis denotes a relative value of oblique retardation (nm) to front retardation (nm) (oblique retardation/front retardation), the oblique retardation being measured with the fast axis of the retardation layer set as the rotational axis.
8 . The polarizing plate according to claim 1 , wherein the retardation layer has a symmetrical relative value in a graph where an x-axis denotes a rotational angle (°) of a retardation meter and a Y-axis denotes a relative value of oblique retardation (nm) to front retardation (nm) (oblique retardation/front retardation), the oblique retardation being measured with a slow axis of the retardation layer set as the rotational axis.
9 . The polarizing plate according to claim 1 , wherein a slow axis of the retardation layer is tilted at an angle of 40° to 50° with respect to a light transmission axis of the polarizer, assuming that the light transmission axis of the polarizer is set to 0°.
10 . The polarizing plate according to claim 1 , wherein the retardation layer comprises an O-plate liquid crystal retardation layer.
11 . The polarizing plate according to claim 10 , wherein, assuming that one surface of the O-plate liquid crystal retardation layer in a thickness direction thereof is a top surface and the other surface thereof opposite the top surface is a bottom surface, the O-plate type liquid crystal retardation layer has a greater liquid crystal tilt angle on the top surface than on the BOTTOM-bottom surface.
12 . The polarizing plate according to claim 11 , wherein the O-plate liquid crystal retardation layer has a liquid crystal tilt angle of 30° to 90° on the top surface and a liquid crystal tilt angle of 0° to 10° on the bottom surface.
13 . The polarizing plate according to claim 11 , wherein the top surface is closer to the polarizer than the BOTTOM-bottom surface.
14 . The polarizing plate according to claim 11 , wherein an absolute difference between the liquid crystal tilt angle on the top surface and the liquid crystal tilt angle on the bottom surface ranges from 30° to 90°.
15 . The polarizing plate according to claim 10 , wherein the O-plate liquid crystal retardation layer is a nematic liquid crystal layer.
16 . The polarizing plate according to claim 10 , wherein the retardation layer comprises the O-plate liquid crystal retardation layer alone.
17 . The polarizing plate according to claim 10 , wherein the retardation layer comprises the O-plate liquid crystal retardation layer and a first protective layer.
18 . The polarizing plate according to claim 17 , wherein the first protective layer has a front retardation of 10 nm or less at the wavelength of 550 nm.
19 . The polarizing plate according to claim 1 , further comprising:
at least one of a second protective layer on an upper surface of the polarizer or a third protective layer on the lower surface of the polarizer.
20 . An optical display apparatus comprising the polarizing plate according to claim 1 .