Polarizing plate, liquid crystal display comprising the same and method for preparing polarizing plate
A polarizing plate includes a polarizer and a polyester film formed on at least one surface of the polarizer. The polyester film includes a polyester base film and a primer layer formed on at least one surface of the polyester base film. The polyester film contains about 0.1 wt % to about 5 wt % of a UV absorbent. In addition, a liquid crystal display includes the polarizing plate. A method of fabricating a polarizing plate includes preparing a multilayer film containing about 0.1 wt % to about 5 wt % of a UV absorbent, stretching the multilayer film to about 2 to about 10 times its initial length in a transverse direction (TD) to prepare a polyester film, and attaching the polyester film to at least one surface of a polarizer. The multilayer film comprises a polyester base film and a primer layer on at least one surface of the polyester base film.
1. A polarizing plate comprising a polarizer and a polyester film on at least one surface of the polarizer,
wherein the polyester film comprises a polyester base film, and a primer layer on at least one surface of the polyester base film, and the polyester film contains about 0.1 wt % to about 5 wt % of a UV absorbent, and
wherein the polyester film has:
a variation rate in retardation of about 0% to about 5%, as calculated using Equation 1
Variation rate of retardation=| B−A|/A× 100 (1)
wherein A is an initial retardation at a wavelength of 550 nm of the polyester film, and B is a retardation at a wavelength of 550 nm of the polyester film after being left at 85° C. for 1000 hours or after being left at 60° C./RH 95% for 1000 hours; and/or
a variation rate in haze of about 0% to about 5%, as calculated using Equation 2:
Variation rate of haze=| D−C|/C× 100 (2)
wherein C is an initial haze percentage at a wavelength of 550 nm of the polyester film, and D is a haze percentage at a wavelength of 550 nm of the polyester film after being left at 85° C. for 1000 hours; and/or
a variation rate in transmittance of about 0% to about 5%, as calculated using Equation 3:
Variation rate of transmittance=| F−E|/E× 100 (3)
wherein E is an initial transmittance percentage at a wavelength of 370 nm of the polyester film, and F is a transmittance percentage at a wavelength of 370 nm of the polyester film after being subjected to UV irradiation at 120 W·sec/m 2 for 1000 hours.
2. The polarizing plate according to claim 1 , wherein the UV absorbent is contained in at least one of the polyester base film and the primer layer.
3. The polarizing plate according to claim 1 , wherein the polyester film has an index of refraction of about 1.67 to about 1.75.
4. The polarizing plate according to claim 1 , wherein the UV absorbent comprises at least one of a phenol, a benzotriazole, a salicylic acid, a benzophenone, a triazine, and/or a oxamide UV absorbent.
5. The polarizing plate according to claim 1 , wherein the polyester film has an in-plane retardation (Ro) at a wavelength of 550 nm of about 5,000 nm to about 15,000 nm.
6. The polarizing plate according to claim 1 , wherein the polyester film has a thickness direction retardation (Rth) at a wavelength of 550 nm of about 15,000 nm or less.
7. The polarizing plate according to claim 1 , wherein the polyester film has the variation rate in retardation of about 0% to about 5%, as calculated using Equation 1:
Variation rate of retardation=| B−A|/A× 100 (1)
wherein A is the initial retardation at a wavelength of 550 nm of the polyester film, and B is the retardation at a wavelength of 550 nm of the polyester film after being left at 85° C. for 1000 hours or after being left at 60° C./RH 95% for 1000 hours.
8. The polarizing plate according to claim 1 , wherein the polyester film has the variation rate in haze of about 0% to about 5%, as calculated using Equation 2:
Variation rate of haze=| D−C|/C× 100 (2)
wherein C is the initial haze percentage at a wavelength of 550 nm of the polyester film, and D is the haze percentage at a wavelength of 550 nm of the polyester film after being left at 85° C. for 1000 hours.
9. The polarizing plate according to claim 1 , wherein the polyester film has the variation rate in transmittance of about 0% to about 5%, as calculated using Equation 3:
Variation rate of transmittance=| F−E|/E× 100 (3)
wherein E is the initial transmittance percentage at a wavelength of 370 nm of the polyester film, and F is the transmittance percentage at a wavelength of 370 nm of the polyester film after being subjected to UV irradiation at 120 W·sec/m 2 for 1000 hours.
10. The polarizing plate according to claim 1 , wherein the polyester film has an absolute value (|nx−ny|) of a difference between an index of refraction at a wavelength of 550 nm in an x-axis direction (nx) of the polyester film and an index of refraction at a wavelength of 550 nm in a y-axis direction (ny) of the polyester film of about 0.1 to about 0.2.
11. The polarizing plate according to claim 1 , wherein the primer layer adjoins the polarizer.
12. The polarizing plate according to claim 1 , further comprising: an optical film on another surface of the polarizer.
13. A liquid crystal display comprising the polarizing plate according to claim 1 .
14. A method of fabricating a polarizing plate, comprising:
preparing a multilayer film containing about 0.1 wt % to about 5 wt % of a UV absorbent;
stretching the multilayer film to about 2 to about 10 times an initial length thereof in a transverse direction (TD) to prepare a polyester film; and
attaching the polyester film to at least one surface of a polarizer,
wherein the multilayer film comprises a polyester base film and a primer layer formed on at least one surface of the polyester base film, wherein the multilayer film has:
a variation rate in retardation of about 0% to about 5%, as calculated using Equation 1
Variation rate of retardation=| B−A|/A× 100 (1)
wherein A is an initial retardation at a wavelength of 550 nm of the multilayer film, and B is a retardation at a wavelength of 550 nm of the multilayer film after being left at 85° C. for 1000 hours or after being left at 60° C./RH 95% for 1000 hours; and/or
a variation rate in haze of about 0% to about 5%, as calculated using Equation 2:
Variation rate of haze=| D−C|/C× 100 (2)
wherein C is an initial haze percentage at a wavelength of 550 nm of the multilayer film, and D is a haze percentage at a wavelength of 550 nm of the multilayer film after being left at 85° C. for 1000 hours; and/or
a variation rate in transmittance of about 0% to about 5%, as calculated using Equation 3:
Variation rate of transmittance=| F−E|/E× 100 (3)
wherein E is an initial transmittance percentage at a wavelength of 370 nm of the multilayer film, and F is a transmittance percentage at a wavelength of 370 nm of the multilayer film after being subjected to UV irradiation at 120 W·sec/m 2 for 1000 hours.
15. The method according to claim 14 , wherein the multilayer film is stretched only in the TD without machine direction (MD) stretching.
16. The method according to claim 14 , further comprising: before attaching the polyester film to the polarizer, performing tension-relaxation to anneal the polyester film.