Polarizing plate and optical display apparatus
A polarizing plate and an optical display apparatus are disclosed. A polarizing plate includes a polarizer and a stack of retardation layers on a surface of the polarizer, and the stack of retardation layers includes a second retardation layer and a first retardation layer stacked on the polarizer in sequence from the surface of the polarizer, the second retardation layer being a non-liquid crystal layer, and the stack of retardation layers has an out-of-plane retardation of −40 nm or more to less than 0 nm at a wavelength of 550 nm and satisfies Relation 1.
1 . A polarizing plate comprising: a polarizer; and a stack of retardation layers on a surface of the polarizer,
wherein the stack of retardation layers comprises a second retardation layer and a first retardation layer stacked on the polarizer in sequence from the surface of the polarizer,
the second retardation layer being a non-liquid crystal layer, and
wherein the stack of retardation layers has an out-of-plane retardation of −40 nm or more to less than 0 nm at a wavelength of 550 nm and satisfies the following
1
.
1
≤
R
t
h
(
4
50
)
/
Rt
h
(
5
5
0
)
≤
1
.
5
,
Relation
1
where Rth(450) and Rth(550) are out-of-plane retardations (unit: nm) of the stack of retardation layers at wavelengths of 450 nm and 550 nm, respectively.
2 . The polarizing plate as claimed in claim 1 , wherein the stack of retardation layers has an out-of-plane retardation of −25 nm to −5 nm at a wavelength of 550 nm.
3 . The polarizing plate as claimed in claim 1 , wherein the stack of retardation layers satisfies the following Relations 3 and 4:
R
t
h
(
4
50
)
/
Rt
h
(
5
5
0
)
>
R
e
(
4
50
)
/
R
e
(
550
)
;
Relation
3
R
e
(
650
)
/
R
e
(
5
5
0
)
>
R
t
h
(
6
50
)
/
Rth
(
5
50
)
,
Relation
4
where Re(450), Re(550), and Re(650) are in-plane retardations (unit: nm) of the stack of retardation layers at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.
4 . The polarizing plate as claimed in claim 1 , wherein the stack of retardation layers satisfies the following Relation 5:
1
<
R
e
(
4
50
)
/
R
e
(
5
5
0
)
≤
1.1
,
where Re(450) and Re(550) are in-plane retardations (unit: nm) of the stack of retardation layers at wavelengths of 450 nm and 550 nm, respectively.
5 . The polarizing plate as claimed in claim 1 , wherein the stack of retardation layers satisfies the following Relation 2:
0
.
1
≤
Rth
2
(
650
)
/
Rth
(
550
)
≤
1.
,
where Rth(650) and Rth(550) are out-of-plane retardations (unit: nm) of the stack of retardation layers at wavelengths of 650 nm and 550 nm, respectively.
6 . The polarizing plate as claimed in claim 1 , wherein the second retardation layer satisfies the following Relation 8:
1
.
0
≤
R
t
h
2
(
4
50
)
/
Rth
2
(
5
5
0
)
≤
1
.
1
,
where Rth2(450) and Rth2(550) are out-of-plane retardations (unit: nm) of the second retardation layer at wavelengths of 450 nm and 550 nm, respectively.
7 . The polarizing plate as claimed in claim 1 , wherein the second retardation layer has a water vapor transmission rate of 1 g/m 2 /day or greater.
8 . The polarizing plate as claimed in claim 1 , wherein the second retardation layer has a glass transition temperature of 130° C. or greater.
9 . The polarizing plate as claimed in claim 1 , wherein the second retardation layer comprises at least one selected from among a cellulose based compound and a polystyrene based compound.
10 . The polarizing plate as claimed in claim 9 , wherein each of the cellulose based compound and the polystyrene based compound contains fluorine.
11 . The polarizing plate as claimed in claim 1 , wherein the second retardation layer is a +C layer, and the first retardation layer is a +A layer.
12 . The polarizing plate as claimed in claim 1 , wherein a slow axis of the first retardation layer is slanted at an angle of −5 to 5° with respect to a light absorption axis of the polarizer.
13 . The polarizing plate as claimed in claim 1 , wherein the first retardation layer has an in-plane retardation with a short wavelength dispersion (Re(450)/Re(550)) of 1.0 to 1.1.
14 . The polarizing plate as claimed in claim 1 , wherein the first retardation layer has a degree of biaxiality of 0.9 to 1.1 at a wavelength of 550 nm.
15 . The polarizing plate as claimed in claim 1 , wherein the first retardation layer is a non-liquid crystal film.
16 . The polarizing plate as claimed in claim 15 , wherein the first retardation layer comprises a cyclic olefin polymer (COP) based or cyclic olefin polymer copolymer (COC) based film.
17 . The polarizing plate as claimed in claim 1 , wherein the second retardation layer is directly formed on the first retardation layer.
18 . The polarizing plate as claimed in claim 1 , wherein the first retardation layer is adhered to the second retardation layer via an adhesive layer.
19 . The polarizing plate as claimed in claim 18 , wherein a surface of the first retardation layer contacting the adhesive layer has a water contact angle of 60° or less at 25° C., and the adhesive layer has a glass transition temperature of −40° C. or less.
20 . An optical display apparatus comprising the polarizing plate as claimed in claim 1 .