Polarizing plate and optical display device

Abstract

A polarizing plate and an optical display device are disclosed. The polarizing plate includes a polarizer and a retardation layer stacked on the surface of the polarizer. The retardation layer includes a retardation film satisfying the relationship nx > nz > ny, where nx, ny, and nz are the refractive indices of the retardation film in the slow axis direction, fast axis direction, and thickness direction, respectively, at a wavelength of 550 nm. The orientation direction of the main chain of the resin contained in the retardation film relative to the light transmission axis of the polarizer is within the range of -5° to +5°, and the retardation film has a biaxiality of 0.2 to 0.6 at a wavelength of 550 nm.

Claims

1. A polarizing plate, comprising: polarizer; A retardation layer is stacked on the surface of the polarizer, wherein the retardation layer comprises a retardation film satisfying the relationship nx > nz > ny, where nx, ny, and nz are the refractive indices of the retardation film at a wavelength of 550 nm in the slow axis direction, fast axis direction, and thickness direction of the retardation film, respectively. The orientation direction of the main chain of the resin contained in the retardation film relative to the optical transmission axis of the polarizer is in the range of -5° to +5°. The resin is a cellulose ester resin, comprising a cellulose ester resin selectively substituted with a plurality of first unsaturated or saturated (C1-6) alkyl-CO- groups as substituents and a plurality of hydroxyl positions. The retardation film has an in-plane retardation of 220 nm to 300 nm at a wavelength of 550 nm, (nx-ny) is in the range of 0.0022 to 0.0075, and (nx-nz) is in the range of 0.00044 to 0.0045. The retardation film has a biaxiality of 0.2 to 0.6 at a wavelength of 550 nm.

2. The polarizing plate as claimed in claim 1, wherein the retardation film is a single-layer retardation film.

3. The polarizing plate as claimed in claim 1, wherein in the retardation film, the value of the following Equation 1 is in the range of 0.8 to 1.2, and the value of the following Equation 2 is in the range of 0.9 to 1.1: Equation 1 Re(450 nm) / Re(550 nm); Equation 2 Re(650 nm) / Re(550 nm), wherein in Equations 1 and 2, Re(450 nm), Re(550 nm), and Re(650 nm) are the in-plane retardations of the retardation film at wavelengths of 450 nm, 550 nm, and 650 nm, respectively, and the unit of in-plane retardation is nm.

4. The polarizing plate as claimed in claim 1, wherein the slow axis of the retardation film is within the range of -5° to +5° relative to the light absorption axis of the polarizer.

5. The polarizing plate as claimed in claim 1, wherein the slow axis of the retardation film is parallel to the mechanical direction of the retardation film.

6. The polarizing plate as claimed in claim 1, wherein the retardation film is a retardation film stretched in the transverse direction.

7. The polarizing plate as claimed in claim 1, wherein nx is in the range of 1.500 to 1.710, ny is in the range of 1.480 to 1.700, and nz is in the range of 1.500 to 1.

705.

8. The polarizing plate as claimed in claim 1, wherein the resin is the main component of the retardation film.

9. The polarizing plate as claimed in claim 1, wherein in the cellulose ester resin, the degree of hydroxyl substitution is in the range of 0.2 to 2.0, the degree of C2 substitution is in the range of 0.15 to 0.8, the degree of C3 substitution is in the range of 0.05 to 0.6, the degree of C6 substitution is in the range of 0.05 to 0.6, and the total degree of substitution is in the range of 0.25 to 2.

5.

10. The polarizing plate as claimed in claim 1, wherein the retardation layer is formed solely of the retardation film.

11. The polarizing plate as claimed in claim 1, wherein the retardation film has a thickness of 40 μm to 100 μm.

12. The polarizing plate as claimed in claim 1, further comprising a protective layer laminated on another surface of the polarizer.

13. An optical display device comprising a polarizing plate as described in claim 1.

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