POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY DEVICE INCLUDING SAME
The present invention provides a polarizing plate and a liquid crystal display device comprising same, the polarizing plate comprising: a polarizer; and a first retardation layer and a second retardation layer formed on one surface of the polarizer, wherein the first retardation layer has a thickness direction retardation (Rth) of about −75 nm to about −130 nm at a wavelength of about 550 nm, the second retardation layer satisfies Relations 1 and 2, a laminated body of the first retardation layer and the second retardation layer has a thickness direction retardation (Rth) of about −70 nm to about 0 nm at a wavelength of about 550 nm, and the first retardation layer includes a coating layer formed of a composition containing a cellulose ester-based compound.
1 . A polarizing plate comprising a polarizer and first and second retardation layers formed on one surface of the polarizer, wherein:
the first retardation layer has an out-of-plane retardation Rth of about −130 nm to about −75 nm at a wavelength of about 550 nm;
the second retardation layer satisfies Relations 1 and 2;
a laminate of the first retardation layer and the second retardation layer has an out-of-plane retardation Rth of about −70 nm to about 0 nm at a wavelength of about 550 nm; and
the first retardation layer comprises a coating layer formed of a composition comprising a cellulose ester compound:
about 0.8 ≤Re (450)/ Re (550)≤about 1.05 [Relation 1]
about 0.95 ≤Re (650)/ Re (550)≤about 1.10 [Relation 2]
where Re(450), Re(550), and Re(650) denote in-plane retardations Re (unit: nm) of the second retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.
2 . The polarizing plate according to claim 1 , wherein the first retardation layer and the second retardation layer are sequentially stacked in the stated sequence from the polarizer.
3 . The polarizing plate according to claim 1 , wherein, assuming that an absorption axis of the polarizer is about 0°, an angle between a slow axis of the second retardation layer and the absorption angle of the polarizer ranges from about −5° to about +5°.
4 . The polarizing plate according to claim 1 , wherein the second retardation layer has an in-plane retardation Re of about 100 nm to about 150 nm at a wavelength of about 550 nm.
5 . The polarizing plate according to claim 1 , wherein the second retardation layer has an out-of-plane retardation Rth of about 40 nm to about 120 nm at a wavelength of about 550 nm.
6 . The polarizing plate according to claim 1 , wherein the second retardation layer is an MD uniaxially stretched film.
7 . The polarizing plate according to claim 1 , wherein the second retardation layer comprises a fluorene retardation layer.
8 . The polarizing plate according to claim 7 , wherein the fluorene retardation layer comprises a compound represented by Formula 1:
where Z is an aromatic hydrocarbon group; R 1 and R 2 are each independently a substituent group; R 3 is a C 1 to C 10 alkylene group; n is an integer of 0 or more; k is an integer of 0 to 4; m is an integer of 0 or more, and p is an integer of 1 or more.
9 . The polarizing plate according to claim 1 , wherein the first retardation layer has an in-plane retardation Re of about 10 nm or less at a wavelength of about 550 nm.
10 . The polarizing plate according to claim 1 , wherein the first retardation layer is formed of a composition for the first retardation layer comprising the cellulose ester compound and an aromatic fused ring-containing additive.
11 . The polarizing plate according to claim 10 , wherein the aromatic fused ring-containing additive is present in an amount of about 0.1 wt % to about 30 wt % in the first retardation layer.
12 . The polarizing plate according to claim 1 , wherein the cellulose ester compound comprises at least one selected from among cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate.
13 . The polarizing plate according to claim 10 , wherein the aromatic fused ring-containing additive comprises at least one selected from among naphthalene, anthracene, phenanthrene, pyrene, Structure 1, Structure 2, 2-naphthyl benzoate, 2,6-naphthalene dicarboxylic acid diester of Structure 3, and an abietic acid ester of Structure 4:
where R is a C 1 to C 20 alkyl or a C 6 to C 20 aryl, and n is an integer of 0 to 6
where R is a C 1 to C 20 alkyl or a C 6 to C 20 aryl.
14 . The polarizing plate according to claim 1 , wherein the first retardation layer is directly formed on the second retardation layer.
15 . The polarizing plate according to claim 1 , wherein the first retardation layer has a thickness of about 2 μm to about 10 μm.
16 . The polarizing plate according to claim 1 , wherein the laminate satisfies Relations 6 and 7:
about 0.9 ≤Rth (450)/ Rth (550)≤about 1.3 [Relation 6]
about 0.8 ≤Rth (650)/ Rth (550)≤about 1.1 [Relation 7]
where Rth(450), Rth(550), and Rth(650) denote out-of-plane retardations Rth (unit: nm) of the laminate at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.
17 . The polarizing plate according to claim 1 , wherein the laminate has an in-plane retardation Re of about 100 nm to about 150 nm at a wavelength of about 550 nm.
18 . The polarizing plate according to claim 1 , wherein the laminate has a degree of biaxiality (NZ) of about −0.1 to about 0.5 at a wavelength of about 550 nm.
19 . The polarizing plate according to claim 1 , further comprising: a protective film on the other surface of the polarizer.
20 . A liquid crystal display device comprising the polarizing plate according to claim 1 .