Polarizing plate and optical display device comprising same
Provided are a polarizing plate and an optical display device comprising same, the polarizing plate comprising: a polarizer; and a first phase difference layer, a second phase difference layer and a third phase difference layer which are sequentially stacked on the lower surface of the polarizer. The first phase difference layer comprises a positive C phase difference layer. The second phase difference layer has positive wavelength dispersibility and an in-plane phase difference of approximately 200 nm to 280 nm in a wavelength of 550 nm. The third phase difference layer has positive wavelength dispersibility and an in-plane phase difference of approximately 80 nm to 145 nm in a wavelength of 550 nm. When the absorption axis of the polarizer is 0°, the angle formed by the slow axis of the second phase difference layer is approximately +14° to +24° or approximately −24° to −14°, and the angle formed by the slow axis of the third phase difference layer is approximately +79° to +89° or approximately −89° to −79°.
1. A polarizing plate comprising:
a polarizer; and
a first retardation layer, a second retardation layer and a third retardation layer sequentially stacked on a lower surface of the polarizer,
wherein the first retardation layer is a positive C retardation layer;
the second retardation layer exhibits positive dispersion and has an in-plane retardation of about 220 nm to about 280 nm at a wavelength of 550 nm;
the third retardation layer exhibits positive dispersion and has an in-plane retardation of about 80 nm to about 145 nm at a wavelength of 550 nm; and
assuming an absorption axis of the polarizer is tilted at an angle of 0°, the second retardation layer has a slow axis tilted at an angle θ2 of about +14° to about +24° or of about −24° to about −14° with respect to the absorption axis of the polarizer and the third retardation layer has a slow axis tilted at an angle θ3 of about +79° to about +89° or of about −89° to about −79° with respect to the absorption axis of the polarizer.
2. The polarizing plate according to claim 1 , wherein the angle θ2 ranges from about +14° to about +24° and the angle θ3 ranges from about +79° to about +89°.
3. The polarizing plate according to claim 1 , wherein the angle θ2 ranges from about −24° to about −14° and the angle θ3 ranges from about-89° to about-79°.
4. The polarizing plate according to claim 1 , wherein an angle θ1 defined between the slow axis of the second retardation layer and the slow axis of the third retardation layer ranges from about 61° to about 67°.
5. The polarizing plate according to claim 1 , wherein a laminate of the first retardation layer, the second retardation layer and the third retardation layer has a degree of biaxiality of about 0.4 to about 1.0 at a wavelength of 550 nm.
6. The polarizing plate according to claim 1 , wherein one of the second retardation layer and the third retardation layer satisfies Relation 3 and the other retardation layer satisfies Relation 6:
nx>ny≈nz, [Relation 3]
where nx, ny, and nz are indexes of refraction of the retardation layer in a slow axis direction, a fast axis direction and a thickness direction at a wavelength of 550 nm, respectively;
nx≈nz>ny, [Relation 6]
where nx, ny, and nz are indexes of refraction of the retardation layer in the slow axis direction, the fast axis direction and the thickness direction at a wavelength of 550 nm, respectively.
7. The polarizing plate according to claim 1 , wherein a laminate of the second retardation layer and the third retardation layer exhibits negative dispersion.
8. The polarizing plate according to claim 1 , wherein the second retardation layer satisfies Relation 1 and Relation 2:
about 1.0<Re(450)/Re(550)≤about 1.1 [Relation 1]
about 0.9≤Re(650)/Re(550)<about 1.0, [Relation 2]
where Re(450), Re(550), and Re(650) are in-plane retardations (unit: nm) of the second retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.
9. The polarizing plate according to claim 8 , wherein the second retardation layer has a smaller Re(450)/Re(550) than the third retardation layer and a greater Re(650)/Re(550) than the third retardation layer.
10. The polarizing plate according to claim 1 , wherein the third retardation layer satisfies Relation 4 and Relation 5:
about 1.0<Re(450)/Re(550)≤about 1.2 [Relation 4]
about 0.9≤Re(650)/Re(550)<about 1.0, [Relation 5]
where Re(450), Re(550), and Re(650) are in-plane retardations (unit: nm) of the third retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.
11. The polarizing plate according to claim 1 , wherein the first retardation layer has an index of refraction (nx) of about 1.5 to about 1.6, an index of refraction (ny) of about 1.5 to about 1.6, and an index of refraction (nz) of about 1.6 to about 1.7 at a wavelength of 550 nm, where nx, ny, and nz are indexes of refraction of the retardation layer in the slow axis direction, the fast axis direction and the thickness direction at a wavelength of 550 nm, respectively.
12. The polarizing plate according to claim 1 , wherein the first retardation layer has an out-of-plane retardation of about −150 nm to about 0 nm at a wavelength of 550 nm.
13. The polarizing plate according to claim 1 , wherein the second retardation layer comprises a cyclic olefin polymer film and the third retardation layer comprises a polystyrene coating layer.
14. The polarizing plate according to claim 1 , further comprising:
a protective layer stacked on an upper surface of the polarizer or between the polarizer and the first retardation layer.
15. The polarizing plate according to claim 1 , further comprising:
an adhesive layer or a bonding layer formed on a lower surface of the third retardation layer.
16. An optical display device comprising the polarizing plate according to claim 1 and one of a liquid crystal display or a light emitting diode display.