Optical compensator and liquid crystal display

• US 5,337,174 A
• Filed: 04/14/1993
• Issued: 08/09/1994
• Est. Priority Date: 06/17/1991
• Status: Expired due to Term

• Current Assignee: Fujimori Kogyo Company Limited, Seiko Epson Corporation (Seiko Group)
• Original Assignee: Fujimori Kogyo Company Limited, Seiko Epson Corporation (Seiko Group)
• Inventors: Yamada, Takashi, Okumura, Osamu, Wada, Hiroshi, Hashimoto, Kenji, Wada, Shinji, Ichikawa, Rinjiro
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/969,156
• Time in Patent Office: 482 Days
• Field of Search: 359/63, 359/73, 359/102, 359/106
• US Class Current: 349/119
• CPC Class Codes: G02B 5/3083 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 Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133637 characterised by the wavelength dispersion
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2413/02 Number of plates being 2
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation

Abstract

There is provided a laminate consisting of a first oriented film (1) obtainable by drawing, at least in one direction, a polymer film having a refractive index of n_D ≧1.60, an Abbe number of ν_D ≧30.0 and a glass transition temperature of Tg=60° to 160° C. and a second oriented film (2) obtainable by drawing, at least in one direction, a polymer film having a refractive index of n_D <1.60. The laminate has a retardation value R of 60-1000 nm and a wavelength dispersion value ν_RF of not less than 1.10. This oriented film either as it is or as laminated with an optically isotropic film at least on one side is used to fabricate an optical compensator for color compensation in a liquid crystal panel. In this manner, there can be obtained a liquid crystal display panel which solves the long-standing problems of coloration and low contrast ratio.

Claims

1. An optical compensator comprising a laminate, wherein the laminate comprises:

(1) at least one oriented film of a first type obtained by stretching, in at least one axis, a polymer film having a refractive index n_D ≧

1.60, an Abbe number ν

_D ≦

30.0 and a glass transition temperature Tg=60°

to 160°

C., and

(2) at least one oriented film of a second type laminated to said oriented film of the first type, said oriented film of the second type being obtained by stretching, in at least one axis, a polymer film having a refractive index n_D <

1.60,

wherein the oriented film of the first type has at least one axis of orientation which is parallel to an axis of orientation of the oriented film of the second type.

2. The optical compensator of claim 1, wherein the laminate film has a retardation value R=60 to 1000 nm, and the oriented film of the first type has a wavelength dispersion value ν

_RF of not less than 1.10, wherein ν

_RF is defined by the following equation;

##EQU1## wherein Δ

n is the refractive index of the oriented film of the first type and d is the thickness of the oriented film of the first type.

3. The optical compensator of claim 1, wherein the laminate has a structure represented by (1)/(2), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

4. The optical compensator of claim 1, wherein the laminate has a structure represented by (1)/(2)/(1), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

5. The optical compensator of claim 1, wherein the laminate has a structure represented by (1)/(1)/(2), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

6. The optical compensator of claim 1, wherein the laminate has a structure represented by (2)/(1)/(2), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

7. The optical compensator of claim 1, wherein the laminate has a structure represented by (2)/(1)/(2)/(2), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

8. The optical compensator of claim 1, wherein the laminate has a structure represented by (1a)/(2a)/(1b), wherein (1a) is an oriented film of the first type, (1b) is an oriented film of the first type, and (2a) is an oriented film of the second type.

9. The optical compensator of claim 1, wherein the laminate has a structure represented by (1a)/(2a)/(1b)/(2b), wherein (1a) is an oriented film of the first type, (1b) is an oriented film of the first type, (2a) is an oriented film of the second type, and (2b) is an oriented film of the second type.

10. The optical compensator of claim 1, wherein the laminate has a structure represented by (1a)/(1b)/(2a)/(2b), wherein (1a) is an oriented film of the first type, (1b) is an oriented film of the first type, (2a) is an oriented film of the second type, and (2b) is an oriented film of the second type.

11. A liquid crystal display comprising:

(a) a liquid crystal cell,

(b) a pair of polarizers disposed on respective sides of said liquid crystal cell; and

(c) at least one optical compensator interposed between said liquid crystal cell and one polarizer of said pair of polarizers, said optical compensator comprising a laminate which comprises;

(1) at least one oriented film of a first type obtained by stretching, in at least one axis, a polymer film having a refractive index n_D ≧

1.60, an Abbe number ν

_D ≦

30.0 and a glass transition temperature Tg=60°

to 160°

C., and

(2) at least one oriented film of a second type laminated to said oriented film of the first type, said oriented film of the second type being obtained by stretching, in at least one axis, a polymer film having a refractive index n_D <

1.60,

wherein the oriented film of the first type has at least one axis of orientation which is parallel to an axis of orientation of the oriented film of the second type.

12. The liquid crystal display of claim 11, wherein the laminate film has a retardation value R=60 to 1000 nm, and the oriented film of the first type has a wavelength dispersion value ν

_RF of not less than 1.10, wherein ν

_RF is defined by the following equation;

##EQU2## wherein Δ

n is the refractive index of the oriented film of the first type and d is the thickness of the oriented film of the first type.

13. The liquid crystal display of claim 12, wherein the laminate has a structure represented by (1)/(2), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

14. The liquid crystal display of claim 12, wherein the laminate has a structure represented by (1)/(2)/(1), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

15. The liquid crystal display of claim 12, wherein the laminate has a structure represented by (1)/(1)/(2), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

16. The liquid crystal display of claim 12, wherein the laminate has a structure represented by (2)/(1)/(2), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

17. The liquid crystal display of claim 12, wherein the laminate has a structure represented by (2)/(1)/(2)/(2), wherein (1) is an oriented film of the first type and (2) is an oriented film of the second type.

18. The liquid crystal display of claim 12, wherein the laminate has a structure represented by (1a)/(2a)/(1b), wherein (1a) is an oriented film of the first type, (1b) is an oriented film of the first type, and (2a) is an oriented film of the second type.

19. The liquid crystal display of claim 12, wherein the laminate has a structure represented by (1a)/(2a)/(1b)/(2b), wherein (1a) is an oriented film of the first type, (1b) is an oriented film of the first type, (2a) is an oriented film of the second type, and (2b) is an oriented film of the second type.

20. The liquid crystal display of claim 12, wherein the laminate has a structure represented by (1a)/(1b)/(2a)/(2b), wherein (1a) is an oriented film of the first type, (1b) is an oriented film of the first type, (2a) is an oriented film of the second type, and (2b) is an oriented film of the second type.