[WIDE VIEWING ANGLE LIQUID CRYSTAL DISPLAY]

• US 20040223104A1
• Filed: 04/30/2004
• Published: 11/11/2004
• Est. Priority Date: 05/08/2003
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Chang, Ting-Jui
• Granted Patent: US 7,253,860 B2
• Time in Patent Office: Days
• US Class Current: 349/118
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• 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 1/1395 Optically compensated birefringence [OCB]- cells or PI- cells

Abstract

A wide viewing angle liquid crystal display comprises a back light unit, an optical compensation circular polarizer unit, a liquid crystal panel and an optical compensation circular analyzer unit. The optical compensation circular polarizer unit is set over the back light unit. The liquid crystal panel is set over the optical compensation circular polarizer unit. The optical compensation circular analyzer unit is set over the liquid crystal panel. The liquid crystal display operates using circularly polarized light to improve uniformity of viewing angle properties and contrast ratio, and prevent gray level inversion due to wide-angle viewing.

Claims

1. A wide viewing angle liquid crystal display, comprising:

a back light unit;

an optical compensation circular polarizer unit set over the back light unit;

an optically self-compensated birefringence liquid crystal panel set over the optical compensation circular polarizer unit; and

an optical compensation circular analyzer set over the liquid crystal panel.

2. The liquid crystal display of claim 1, wherein the optical compensation circular polarizer unit further comprises:

a polarizer plate; and

a first biaxial compensation film sandwiched between the polarizer plate and the liquid crystal panel.

3. The liquid crystal display of claim 2, wherein the first biaxial compensation film has principal refractive indices nx, ny and nz that satisfies the following inequality relations:

nx>

ny>

nz and 4>

(nx−

nz)/(nx−

ny)>

2, and the principal axis with the refractive index nx forms an included angle between 40°

to 75°

with the alignment direction of the liquid crystal panel.

4. The liquid crystal display of claim 2, wherein the optical compensation circular analyzer unit further comprises:

an analyzer plate, wherein the absorption axis of the analyzer plate is perpendicular to the absorption axis of the polarizer plate, and the absorption axis of the polarizer plate forms an included angle between 40°

to 75°

with the liquid crystal panel;

a uniaxial quarter-wave plate sandwiched between the analyzer plate and the liquid crystal panel, wherein the optical axis of the second uniaxial quarter-wave plate forms an included angle of about 45°

with the absorption axis of the analyzer plate; and

a second biaxial compensation film sandwiched between the second uniaxial quarter-wave plate and the liquid crystal panel.

5. The liquid crystal display of claim 4, wherein the second biaxial compensation film has principal refractive indices nx′

, ny′ and

nz′

that satisfy the following inequality relations;

nx′

>

ny′

>

nz′ and

(nx′

−

nz′

)/(nx′

−

ny′

)>

6, and the principal axis with the refractive index nx′

is perpendicular to the alignment direction of the liquid crystal panel.

6. The liquid crystal display of claim 1, wherein the optical compensation circular polarizer unit further comprises:

a polarizer plate;

a first uniaxial quarter-wave plate sandwiched between the polarizer plate and the liquid crystal panel, wherein the optical axis of the first uniaxial quarter-wave plate and an absorption axis of the polarizer plate form an included angle of about 45°

; and

a first biaxial compensation film sandwiched between the first uniaxial quarter-wave plate and the liquid crystal panel.

7. The liquid crystal display of claim 6, wherein the first biaxial compensation film has principal refractive indices nx, ny and nz that satisfy the following inequality relations:

nx>

ny>

nz and (nx−

nz)/(nx−

ny)>

6, and the principal axis with the refractive index nx is perpendicular to the alignment direction of the liquid crystal panel.

8. The liquid crystal display of claim 6, wherein the optical compensation circular analyzer unit further comprises:

an analyzer plate, wherein the absorption axis of the analyzer plate is perpendicular to the absorption axis of the polarizer plate, and the polarizer plate form an included angle of between 40°

to 75°

with the alignment direction of the liquid crystal panel; and

a second biaxial compensation film sandwiched between the analyzer plate and the liquid crystal panel.

9. The liquid crystal display of claim 8, wherein the second biaxial compensation film has principal refractive indices nx′

, ny′ and

nz′

that satisfy the following inequality relations;

nx′

>

ny′

>

nz′ and

4>

(nx′

−

nz′

)/(nx′

−

ny′

)>

2, and the principal axis with the refractive index nx′

forms an included angle of between 20°

to 50°

with the alignment direction of the liquid crystal panel.

10. The liquid crystal display of claim 6, wherein the optical compensation circular analyzer unit further comprises:

an analyzer plate, wherein the absorption axis of the analyzer plate is perpendicular to the absorption axis of the polarizer plate, and the polarizer plate form an included angle of between 40°

to 50°

with the alignment direction of the liquid crystal panel;

a second uniaxial quarter-wave plate sandwiched between the analyzer plate and the liquid crystal panel, wherein the optical axis of the second uniaxial quarter-wave plate forms an included angle of about 45°

with the absorption axis of the analyzer plate; and

a second biaxial compensation film sandwiched between the second uniaxial quarter-wave plate and the liquid crystal panel.

11. The liquid crystal display of claim 10, wherein the second biaxial compensation film has principal refractive indices nx′

, ny′ and

nz′

that satisfy the following inequality relations;

nx′

>

ny′

>

nz′ and

4>

(nx′

−

nz′

)/(nx′

−

ny′

)>

2, and the principal axis with the refractive index nx″

is perpendicular to the alignment direction of the liquid crystal panel.

12. A wide viewing angle liquid crystal display, comprising:

a back light unit;

an optical compensation circular polarizer unit set over the back light unit;

a liquid crystal panel set over the optical compensation circular polarizer unit;

an optical compensation circular analyzer set over the liquid crystal panel;

a cholesteric liquid crystal layer; and

a first biaxial compensation film sandwiched between the cholesteric liquid crystal layer and the liquid crystal panel, wherein the first biaxial compensation film has principal refractive indices nx, ny and nz that satisfy the following inequality relations;

nx>

ny>

nz, and the principal axis with the refractive index nx is perpendicular to the alignment direction of the liquid crystal panel.

13. The liquid crystal display of claim 12, wherein the optical compensation circular analyzer unit furthermore comprises:

an analyzer plate, wherein the absorption axis of the analyzer plate is perpendicular to the absorption axis of the polarizer plate, and the polarizer plate forms an included angle of between 15°

to 50°

with the alignment direction of the liquid crystal panel;

a uniaxial quarter-wave plate sandwiched between the analyzer plate and the liquid crystal panel, wherein the optical axis of the uniaxial quarter-wave plate forms an included angle of about 45°

with the absorption axis of the analyzer plate; and

a second biaxial compensation film sandwiched between the uniaxial quarter-wave plate and the liquid crystal panel, wherein the second biaxial compensation film has principal refractive indices nx′

, ny′ and

nz′

that satisfy the following inequality relations;

nx′

>

ny′

>

nz′

, and the principal axis with the refractive index nx′

is perpendicular to the alignment direction of the liquid crystal panel.

14. The liquid crystal display of claim 12, wherein the optical compensation circular analyzer unit furthermore comprises:

an analyzer plate, wherein the absorption axis of the analyzer plate is perpendicular to the absorption axis of the polarizer plate, and the polarizer plate forms an included angle of between 15°

to 50°

with the alignment direction of the liquid crystal panel; and

a second biaxial compensation film sandwiched between the analyzer plate and the liquid crystal panel, wherein the second biaxial compensation film has principal refractive indices nx′

, ny′ and

nz′ and

the principal axis with the refractive index nx′

forms an included angle of between 20°

to 50°

with the alignment direction of the liquid crystal panel.