Polarizing plate, method of preparing the same, and liquid crystal display apparatus including the same

Patent metadata

Field	Value
Publication number	US-9358768-B2
Application number	US-201314108272-A
Country	US
Kind code	B2
Filing date	Dec 16, 2013
Priority date	Dec 17, 2012
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

A polarizing plate, a method of preparing the same and a liquid crystal display apparatus including the same are disclosed. The polarizing plate includes a polarizer and a polyester film formed on a surface of the polarizer, wherein the polyester film has a ratio of an elongation ratio in a machine direction to an elongation ratio in a transverse direction of about 1:0.8 to about 1:1.2, an in-plane retardation (Re) of about 500 nm or less at a wavelength of 550 nm, and an out-of-plane retardation (Rth) of about 10,000 nm or less at a wavelength of 550 nm.

First claim

What is claimed is:

1. A polarizing plate comprising:
a polarizer; and
a polyester film on a surface of the polarizer, and
an optical film on an other surface of the polarizer, the optical film having an angle of axis distortion of a fast axis of the optical film with respect to an absorption axis of the polarizer of about +0.03° or greater and less than about +0.2°;
the polyester film having a ratio of an elongation ratio in a machine direction to an elongation ratio in a transverse direction of about 1:0.8 to about 1:1.2, an in-plane retardation (Re) of about 500 nm or less at a wavelength of 550 nm as calculated by Equation 1, and an out-of-plane retardation (Rth) of about 1,000 nm to about 10,000 nm at a wavelength of 550 nm as calculated by Equation 2:
Re =( nx−ny )× d   Equation 1

Rth =(( nx+ny )/2 −nz )× d   Equation 2

wherein mc is a refractive index at a wavelength of 550 nm in an x-axis direction of the polyester film, ny is a refractive index of the polyester film at a wavelength of 550 nm in a y-axis direction of the polyester film, nz is a refractive index at a wavelength of 550 nm in a z-axis direction of the polyester film, and d is a thickness of the polyester film in nm.

2. The polarizing plate according to claim 1 , wherein the ratio of the elongation ratio in the machine direction to the elongation ratio in the transverse direction of the polyester film is about 1:1.

3. The polarizing plate according to claim 1 , wherein the polyester film has a degree of biaxiality (NZ) of about 1 or greater as represented by Equation 3:
NZ =( nx−nz )/( nx−ny )  Equation 3

wherein nx is the refractive index at a wavelength of 550 nm in the x-axis direction of the polyester film, ny is the refractive index of the polyester film at a wavelength of 550 nm in the y-axis direction of the polyester film, and nz is the refractive index at a wavelength of 550 nm in the z-axis direction of the polyester film.

4. The polarizing plate according to claim 1 , wherein the polyester film has a difference of nx−ny of about 0 to about 0.1, and the polyester film has a degree of biaxiality (NZ) of about 15 or greater as represented by Equation 3:
NZ =( n−nz )/( nx−ny )  Equation 3

wherein nx is the refractive index at a wavelength of 550 nm in the x-axis direction of the polyester film, ny is the refractive index of the polyester film at a wavelength of 550 nm in the y-axis direction of the polyester film, and nz is the refractive index at a wavelength of 550 nm in the z-axis direction of the polyester film.

5. The polarizing plate according to claim 1 , wherein the polyester film is non-birefringent.

6. The polarizing plate according to claim 1 , wherein the polyester film comprises polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and/or polybutylene naphthalate resins.

7. The polarizing plate according to claim 1 , wherein the optical film is a retardation film.

8. The polarizing plate according to claim 1 , wherein the optical film comprises cellulose, polyester, cyclic polyolefin, polycarbonate, polyether sulfone, polysulfone, polyamide, polyimide, polyolefin, polyacrylate, polyvinyl alcohol, polyvinyl chloride, and/or polyvinylidene chloride resins.

9. A liquid crystal display apparatus comprising the polarizing plate according to claim 1 .

10. A method of preparing a polarizing plate, comprising:
preparing a polyester film by concurrent elongation of a melt-extruded polyester resin in machine and transverse directions in a ratio of an elongation ratio in a machine direction to an elongation ratio in a transverse direction of about 1:0.8 to about 1:1.2;
bonding the polyester film to a surface of a polarizer; and
bonding an optical film to an other surface of the polarizer, the optical film being bonded to the polarizer such that an angle of axis distortion of a fast axis of the optical film with respect to an absorption axis of the polarizer is about +0.03° or greater and less than about +0.2°.

11. The method according to claim 10 , wherein the polyester film has an in-plane retardation (Re) of about 500 nm or less at a wavelength of 550 nm as represented by Equation 1, and an out-of-plane retardation (Rth) of about 10,000 nm or less at a wavelength of 550 nm as represented by Equation 2:
Re =( nx−ny )× d   Equation 1

Rth =(( nx +ny )/2 −nz )× d   Equation 2

wherein nx is a refractive index at a wavelength of 550 nm in an x-axis direction of the polyester film, ny is a refractive index of the polyester film at a wavelength of 550 nm in a y-axis direction of the polyester film, nz is a refractive index at a wavelength of 550 nm in a z-axis direction of the polyester film, and d is a thickness of the film in nanometers.

12. The method according to claim 10 , wherein the polyester film has a degree of biaxiality (NZ) of 15 or greater as represented by Equation 3:
NZ =( nx−nz )/( nx−ny )  Equation 3

wherein nx is a refractive index at a wavelength of 550 nm in an x-axis direction of the polyester film, ny is a refractive index of the polyester film at a wavelength of 550 nm in a y-axis direction of the polyester film, and nz is a refractive index at a wavelength of 550 nm in a z-axis direction of the polyester film.

13. The method according to claim 10 , wherein the polyester resin comprises polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and/or polybutylene naphthalate.

14. The method according to claim 10 , wherein the ratio of the elongation ratio in the machine direction to the elongation ratio in the transverse direction of the polyester film is about 1:1.

Assignees

• Cheil Ind Inc
• Samsung Sdi Co Ltd

Inventors

• Shin Kwang Ho
• Park Eun Su
• Shin Dong Yoon
• Eun Jong Hyuk
• Chung Hae Ryong
• Kim Ae Kyoung
• Kang Han Saem
• Kim Han Su
• Jo A Ra

Classifications

• B32B2367/00

  Polyesters, e.g. PET, i.e. polyethylene terephthalate · CPC title

• B32B2038/0028

  Stretching, elongating · CPC title

• G02B5/3083

  Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001) · CPC title

• B32B38/0012 Primary

  Mechanical treatment, e.g. roughening, deforming, stretching · CPC title

• B32B2307/42

  Polarizing, birefringent, filtering · CPC title