Polarizing plate, method for manufacturing same and liquid-crystal display device comprising same
The present invention relates to a polarizing plate including a polarizer and a polyester film formed on an upper side of the polarizer, wherein the polyester film has a maximum thermal shrink angle of about 10° or less, and any one of a refractive index of x-axis direction nx at a wavelength of 550 nm and a refractive index of y-axis direction ny at a wavelength of 550 nm of about 1.65 or more; a method of preparing the polarizing plate; and a liquid crystal display apparatus comprising the polarizing plate.
1. A polarizing plate comprising:
a polarizer; and
a polyester film formed on an upper side of the polarizer,
wherein the polyester film has a maximum thermal shrink angle of about 10° or less, a refractive index of x-axis direction (nx) at a wavelength of 550 nm of about 1.65 or more, a refractive index of y-axis direction (ny) at a wavelength of 550 nm of less than about 1.65, a front retardation (Ro) of about 5,000 to about 15,000 nm at a wavelength of 550 nm, a degree of biaxiality (NZ) of about 1.8 or less at a wavelength of 550 nm, as represented by Equation 1, and a retardation in a thickness direction (Rth) of 8,000 nm to 13,000 nm at a wavelength of 550 nm, as calculated by Equation 2:
NZ =( nx−nz )/( nx−ny ) [Equation 1]
R th={( nx+ny )/2− nz}×d [Equation 2]
where in Equations 1 and 2, nx, ny and nz are refractive indices in an x-axis direction, a y-axis direction and a z-axis direction of the polyester film at a wavelength of 550 nm, respectively, and d is a thickness of the film in nm, and
wherein the x-axis direction is a transverse direction (TD) of the polyester film and the y-axis direction is a machine direction (MD) of the polyester film.
2. The polarizing plate according to claim 1 , wherein an absolute value of nx-ny is about 0.1 to about 0.2.
3. The polarizing plate according to claim 1 , wherein the nx is about 1.65 to about 1.75, and the ny is about 1.45 to about 1.60.
4. The polarizing plate according to claim 1 , wherein the ny is about 1.56 or less.
5. The polarizing plate according to claim 1 , wherein the front retardation (Ro) is about 5,000 to about 12,000 nm.
6. The polarizing plate according to claim 1 , wherein the polyester film has a maximum thermal shrinkage of about 0.8% or less.
7. The polarizing plate according to claim 1 , wherein the polyester film has an absolute value of molecular orientation angle (θr) of a polyester molecule based on a TD of about 5° or less.
8. The polarizing plate according to claim 1 , wherein the polyester film has a thickness of about 25 μm to about 115 μm.
9. The polarizing plate according to claim 1 , wherein the polyester film is a TD drawn film.
10. The polarizing plate according to claim 1 , wherein the polyester film is a film formed of at least one of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polybutylene naphthalate.
11. The polarizing plate according to claim 1 , wherein an optical film is further formed on a lower side of the polarizer.
12. The polarizing plate according to claim 11 , wherein the optical film has a front retardation (Ro) of about 40 to about 60 nm at a wavelength of 550 nm.
13. The polarizing plate according to claim 12 , wherein the optical film is a film formed of at least one of cellulose, polyester, cyclic polyolefin, polycarbonate, polyether sulfone, polysulfone, polyamide, polyimide, polyolefin, polyacrylate, polyvinyl alcohol, polyvinyl chloride, and polyvinylidene chloride resins.
14. The polarizing plate according to claim 1 , wherein the polarizing plate has a polarization degree of about 99.99% or more, and a transmittance of about 40% or more.
15. A liquid crystal display apparatus comprising the polarizing plate according to claim 1 .
16. A polarizing plate comprising:
a polarizer; and
a polyester film formed on an upper side of the polarizer,
wherein the polyester film has a refractive index of x-axis direction (nx) at a wavelength of 550 nm of about 1.65 or more, a refractive index of y-axis direction (ny) at a wavelength of 550 nm of less than about 1.65, a degree of biaxiality (NZ) of about 1.8 or less at a wavelength of 550 nm, as represented by Equation 1, and a retardation in a thickness direction (Rth) of 8,000 nm to 13,000 nm at a wavelength of 550 nm, as calculated by Equation 2:
NZ =( nx−nz )/( nx−ny ) [Equation 1]
R th={( nx+ny )/2− nz}×d [Equation 2]
where in Equations 1 and 2, nx, ny and nz are refractive indices in an x-axis direction, a y-axis direction and a z-axis direction of the polyester film at a wavelength of 550 nm, respectively, and d is a thickness of the film in nm, and
wherein the x-axis direction is a transverse direction (TD) of the polyester film and the y-axis direction is a machine direction (MD) of the polyester film.
17. The polarizing plate according to claim 16 , wherein the polyester film has a maximum thermal shrink angle of about 10° or less.
18. The polarizing plate according to claim 16 , wherein the polyester film has an absolute value of molecular orientation angle (θr) of a polyester molecule based on a TD of about 5° or less.
19. The polarizing plate according to claim 16 , wherein the polyester film has a thickness of about 25 μm to about 115 μm.
20. A liquid crystal display apparatus comprising the polarizing plate according to claim 16 .