BI-AXIAL RETARDATION COMPENSATION FILM AND VERTICALLY ALIGNED LIQUID CRYSTAL DISPLAY USING THE SAME

• US 20110032463A1
• Filed: 07/20/2010
• Published: 02/10/2011
• Est. Priority Date: 01/28/2003
• Status: Active Grant

• Current Assignee: LG Chem Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: JEON, Byoung-kun, Belyaev, Sergey, Yu, Jeong-su
• Granted Patent: US 8,237,898 B2
• Time in Patent Office: Days
• US Class Current: 349/117
• CPC Class Codes: G02F 1/133634 the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis
• CPC Class Codes: G02F 1/133637 characterised by the wavelength dispersion
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence

Abstract

The present invention relates to a vertically aligned LCD (VA-LCD) employing a bi-axial retardation compensation film, in which an in-plain refractive index (n_x, n_y) and a thickness refractive index (n_z) of the film is n_x>n_y>n_z. The film has a reversed wavelength dispersion in which retardation is increased in proportion to the increase of a wavelength in the range of visible rays and has a normal wavelength dispersion in which an absolute value of the thickness retardation is decreased in proportion to the increase of a wavelength in the range of visible rays. The VA-LCD cell having a retardation compensation characteristic is comprised by arranging a bi-axial retardation compensation film between the vertically aligned panel and a upper and lower polarizing plate. The VA-LCD of the present invention improves contrast characteristics on a front surface and at a tilt angle and minimizes coloring in a black state according to the tilt angle.

Claims

1. A bi-axial retardation compensation film having n_x>

n_y>

n_z, R_in=(n_x−

n_y)×

d>

0 and R_th=(n_z−

n_y)×

d<

0, wherein n_x and n_y are in-plane refractive indexes, n_z is a thickness refractive index, R_in is a in-plane retardation, R_th is a thickness retardation and d is a thickness.

2. The bi-axial retardation compensation film according to claim 1, wherein a wavelength dispersion (R_in,400/R_in,550) is in the range of 0.4˜

0.9 at wavelengths of 400 nm and 550 nm, and a wavelength dispersion (R_in,700/R_in,550) is in the range of 1.1˜

1.8 at wavelengths of 700 nm and 550 nm, wherein R_in,400, R_in,550 and R_in,700 are in-plane retardations at wavelengths of 400 nm, 550 nm and 700 nm.

3. The bi-axial retardation compensation film according to claim 1, wherein a in-plane retardation (R_in) is in the range of 30˜

150 nm at a wavelength of 550 nm.

4. The bi-axial retardation compensation film according to claim 1, wherein a wavelength dispersion (R_th,400/R_th,550) is in the range of 1.05˜

1.4 at wavelengths of 400 nm and 550 nm, and a wavelength dispersion (R_th,700/R_th,550) is in the range of 0.5˜

0.95 at wavelengths of 700 nm and 550 nm, wherein R_th,400, R_th,550 and R_th,700 are thickness retardations at wavelengths of 400 nm, 550 nm and 700 nm.

5. The bi-axial retardation compensation film according to claim 1, wherein a thickness retardation (R_th) is in the range of −

50˜

−

500 nm at 550 nm.

6. The bi-axial retardation compensation film according to claim 1, wherein said bi-axial retardation compensation film is manufactured by elongating a polymer prepared with co-polymerization of a first monomer and a second monomer, wherein the first monomer has a characteristic positive of a double refraction and the second monomer has a characteristic negative of a double refraction.

7. The bi-axial retardation compensation film according to claim 1, wherein said bi-axial retardation compensation film is manufactured by elongating a polymer prepared by mixing a first monomer and a second monomer, wherein the first monomer has a characteristic positive of a double refraction and the second monomer has a characteristic negative of a double refraction.

8. The bi-axial retardation compensation film according to claim 1, wherein said bi-axial retardation compensation film is prepared by laminating more than two sheets having different dependability of a in-plane retardation (R_in) and a thickness retardation (R_th).

10. The vertically aligned LCD according to claim 2, wherein a liquid crystal cell is prepared by arranging the bi-axial retardation compensation film at one place of between the vertically aligned panel and upper polarizing plate, or between the vertically aligned panel and lower polarizing plate.

9. (canceled)

11-18. -18. (canceled)