POLARIZING PLATE AND OPTICAL DISPLAY DEVICE
Provided are a polarizing plate and an optical display device comprising same, wherein the polarizing plate comprises: a polarizer; and a phase retardation layer laminated on a lower surface of the polarizer, the phase retardation layer including a negative C layer, a negative A layer, and a positive A layer, which are sequentially laminated from the lower surface of the polarizer, wherein the negative C layer has a thickness-dependent phase retardation of 20 nm to 60 nm at a wavelength of 550 nm.
1 . A polarizing plate comprising: a polarizer; and a retardation layer stacked on a lower surface of the polarizer,
wherein the retardation layer comprises a negative C layer, a negative A layer and a positive A layer sequentially stacked on the lower surface of the polarizer, and the negative C layer has an out-of-plane retardation of 20 nm to 60 nm at a wavelength of 550 nm.
2 . The polarizing plate according to claim 1 , wherein the negative C layer has a front in-plane retardation of 0 nm to 10 nm at a wavelength of 550 nm.
3 . The polarizing plate according to claim 1 , wherein the negative C layer has a ratio of 0.0005 nm/nm to 0.003 nm/nm, as calculated according to Equation 1:
A
/
B
,
(
1
)
where A is an out-of-plane retardation of the negative C layer at a wavelength of 550 nm and B is a thickness of the negative C layer, a unit of A is nm, and a unit of B is nm.
4 . The polarizing plate according to claim 1 , wherein the negative C layer has a water vapor transmission rate of 400 g/m 2 ·day or less.
5 . The polarizing plate according to claim 1 , wherein the negative C layer is a film or coating layer comprising a polymer exhibiting positive inherent birefringence.
6 . The polarizing plate according to claim 1 , wherein the negative C layer is formed of a triacetylcellulose (TAC), cyclic olefin polymer (COP) or cyclic olefin copolymer (COC) resin.
7 . The polarizing plate according to claim 1 , wherein a thickness ratio of a laminate of the negative C layer, the negative A layer and the positive A layer to the retardation layer is 95% or more.
8 . The polarizing plate according to claim 1 , wherein a laminate of the negative A layer and the positive A layer has negative wavelength dispersion characteristics.
9 . The polarizing plate according to claim 1 , wherein a laminate of the negative A layer and the positive A layer has a linear retardation of 120 nm to 180 nm at a wavelength of 550 nm.
10 . The polarizing plate according to claim 1 , wherein the positive A layer has a lower front in-plane retardation at a wavelength of 550 nm than the negative A layer.
11 . The polarizing plate according to claim 10 , wherein the positive A layer has a front in-plane retardation of 100 nm to 140 nm at a wavelength of 550 nm and the negative A layer has a front in-plane retardation of 200 nm to 280 nm at a wavelength of 550 nm.
12 . The polarizing plate according to claim 1 , wherein a slow axis of the positive A layer is slanted at an angle of 55° to 65° with respect to a slow axis of the negative A layer.
13 . The polarizing plate according to claim 1 , wherein a slow axis of the positive A layer is slanted at an angle of 70° to 85° with respect to a light transmission axis of the polarizer and a slow axis of the negative A layer is slanted at an angle of 10° to 25° with respect to the light transmission axis of the polarizer.
14 . The polarizing plate according to claim 1 , wherein each of the positive A layer and the negative A layer is a liquid crystal layer.
15 . The polarizing plate according to claim 14 , wherein the positive A layer is a nematic liquid crystal layer and the negative A layer is a discotic liquid crystal layer.
16 . The polarizing plate according to claim 1 , further comprising:
a second protective layer stacked on an upper surface of the polarizer.
17 . An optical display apparatus comprising the polarizing plate according to claim 1 .