LIQUID CRYSTAL DISPLAY DEVICE

• US 20060274229A1
• Filed: 05/31/2006
• Published: 12/07/2006
• Est. Priority Date: 06/01/2005
• Status: Abandoned Application

• Current Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Inventors: ITO, Hideki, TAGO, Chigusa, HISATAKE, Yuuzo, MURAYAMA, Akio
• Application Number:
  US11/421,305
• Publication Number:
  US 20060274229A1
• Time in Patent Office: Days
• US Class Current: 349/96
• CPC Class Codes: G02F 1/133541 Circular polarisers
• 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 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence

Abstract

A liquid crystal display device includes a circular polarizer structure, a circular analyzer structure and a variable retarder structure. The circular polarizer structure includes a uniaxial third retardation plate with a refractive index anisotropy of nx≅ny<nz and a uniaxial fourth retardation plate with a refractive index anisotropy of nx>ny≅nz, which are disposed for optical compensation of the circular polarizer structure. The circular analyzer structure includes a uniaxial fifth retardation plate with a refractive index anisotropy of nx≅ny<nz and a uniaxial sixth retardation plate with a refractive index anisotropy of nx>ny≅nz, which are disposed for optical compensation of the circular analyzer structure. The variable retarder structure includes a uniaxial seventh retardation plate with a refractive index anisotropy of nx≅ny>nz, which is disposed for optical compensation of the variable retarder structure.

Claims

1. A liquid crystal display device which is configured such that a dot-matrix liquid crystal cell, in which a liquid crystal layer is held between two electrode-equipped substrates, is disposed between a first polarizer plate that is situated on a light source side and a second polarizer plate that is situated on an observer side, a first retardation plate is disposed between the first polarizer plate and the liquid crystal cell such that a slow axis of the first retardation plate forms an angle of about 45°

with respect to an absorption axis of the first polarizer plate, and a second retardation plate is disposed between the second polarizer plate and the liquid crystal cell such that a slow axis of the second retardation plate forms an angle of about 45°

with respect to an absorption axis of the second polarizer plate, the liquid crystal display device comprising;

a circular polarizer structure including the first polarizer plate and the first retardation plate;

a variable retarder structure including the liquid crystal cell; and

a circular analyzer structure including the second polarizer plate and the second retardation plate,

wherein the variable retarder structure has an optically positive normal-directional phase difference in a black display state,

each of the first retardation plate and the second retardation plate is a uniaxial ¼

wavelength plate which provides a phase difference of a ¼

wavelength between light rays of a predetermined wavelength that travel along a fast axis and the slow axis thereof,

the circular polarizer structure includes a first optical compensation layer which is disposed for optical compensation of the circular polarizer structure between the first polarizer plate and the first retardation plate, the first optical compensation layer including a uniaxial third retardation plate with a refractive index anisotropy of nx≅

ny<

nz and a uniaxial fourth retardation plate with a refractive index anisotropy of nx>

ny≅

nz, the fourth retardation plate being disposed such that a slow axis of the fourth retardation plate is substantially perpendicular to the absorption axis of the first polarizer plate,

the circular analyzer structure includes a second optical compensation layer which is disposed for optical compensation of the circular analyzer structure between the second polarizer plate and the second retardation plate, the second optical compensation layer including a uniaxial fifth retardation plate with a refractive index anisotropy of nx≅

ny<

nz and a uniaxial sixth retardation plate with a refractive index anisotropy of nx>

ny≅

nz, the sixth retardation plate being disposed such that a slow axis of the sixth retardation plate is substantially perpendicular to the absorption axis of the second polarizer plate and is substantially perpendicular to the slow axis of the fourth retardation plate, and

the variable retarder structure includes a third optical compensation layer which is disposed for optical compensation of the variable retarder structure between the first retardation plate and the second retardation plate, the third optical compensation layer including a uniaxial seventh retardation plate with a refractive index anisotropy of nx≅

ny>

nz.

2. The liquid crystal display device according to claim 1, wherein at least one of a) the first optical compensation layer, b) the second optical compensation layer, c) a combination of the first retardation plate and the third retardation plate and d) a combination of the second retardation plate and the fifth retardation plate is composed of a single optical film in which two liquid crystal films are stacked, each of the two liquid crystal films being configured such that liquid crystal polymer molecules, which exhibit positive uniaxiality in a major plane, are nematic-hybrid-aligned along a normal direction.

3. The liquid crystal display device according to claim 2, wherein directors of liquid crystal polymer molecules in the two liquid crystal films, which constitute the optical film, are parallel in the major plane and perpendicular to each other in a cross section along the normal direction.

4. The liquid crystal display device according to claim 3, wherein the directors of the liquid crystal polymer molecules in the two liquid crystal films, which constitute the optical film, are substantially perpendicular to a bonding interface between the two liquid crystal films in the vicinity of the bonding interface and are substantially parallel to the bonding interface in the vicinity of outer surfaces of the respective liquid crystal films.

5. The liquid crystal display device according to claim 1, wherein the first optical compensation layer further includes a uniaxial eighth retardation plate with a refractive index anisotropy of nx≅

ny<

nz, and

the second optical compensation layer further includes a uniaxial ninth retardation plate with a refractive index anisotropy of nx≅

ny<

nz.

6. The liquid crystal display device according to claim 5, wherein at least one of the first optical compensation layer and the second optical compensation layer is composed of a single optical film in which two liquid crystal films are stacked, each of the two liquid crystal films being configured such that liquid crystal polymer molecules, which exhibit positive uniaxiality in a major plane, are nematic-hybrid-aligned along a normal direction.

7. The liquid crystal display device according to claim 6, wherein directors of liquid crystal polymer molecules in the two liquid crystal films, which constitute the optical film, are parallel in the major plane and perpendicular to each other in a cross section along the normal direction.

8. The liquid crystal display device according to claim 7, wherein the directors of the liquid crystal polymer molecules in the two liquid crystal films, which constitute the optical film, are substantially parallel to a bonding interface between the two liquid crystal films in the vicinity of the bonding interface and are substantially perpendicular to the bonding interface in the vicinity of outer surfaces of the respective liquid crystal films.

9. The liquid crystal display device according to claim 5, wherein at least one of a) a combination of the first retardation plate and the third retardation plate, b) a combination of the fourth retardation plate and the eighth retardation plate, c) a combination of the second retardation plate and the fifth retardation plate and d) a combination of the sixth retardation plate and the ninth retardation plate is composed of a single optical film in which two liquid crystal films are stacked, each of the two liquid crystal films being configured such that liquid crystal polymer molecules, which exhibit positive uniaxiality in a major plane, are nematic-hybrid-aligned along a normal direction.

10. The liquid crystal display device according to claim 9, wherein directors of liquid crystal polymer molecules in the two liquid crystal films, which constitute the optical film, are parallel in the major plane and perpendicular to each other in a cross section along the normal direction.

11. The liquid crystal display device according to claim 10, wherein the directors of the liquid crystal polymer molecules in the two liquid crystal films, which constitute the optical film, are substantially perpendicular to a bonding interface between the two liquid crystal films in the vicinity of the bonding interface and are substantially parallel to the bonding interface in the vicinity of outer surfaces of the respective liquid crystal films.

12. The liquid crystal display device according to claim 1, wherein the seventh retardation plate comprises a first segment layer, which is disposed between the first retardation plate and the liquid crystal cell, and a second segment layer, which is disposed between the second retardation plate and the liquid crystal cell.

13. The liquid crystal display device according to claim 12, wherein the first segment layer is formed on the first retardation plate such that a total optical function is equivalent to a biaxial refractive index anisotropy of nx>

ny>

nz.

14. The liquid crystal display device according to claim 12, wherein the second segment layer is formed on the second retardation plate such that a total optical function is equivalent to a biaxial refractive index anisotropy of nx>

ny>

nz.

15. The liquid crystal display device according to claim 1, wherein the liquid crystal cell has a vertical alignment mode in which liquid crystal molecules in a pixel are aligned substantially vertical to a major surface of the substrate in a voltage-off state.

16. The liquid crystal display device according to claim 15, wherein the liquid crystal cell has a multi-domain vertical alignment mode in which liquid crystal molecules in the pixel are controlled and oriented in at least two directions in a voltage-on state.

17. The liquid crystal display device according to claim 15, wherein such a domain is formed that an orientation direction of liquid crystal molecules in the pixel in a voltage-on state is substantially parallel to the absorption axis or a transmission axis of the first polarizer plate in at least half an opening region of each pixel.

18. The liquid crystal display device according to claim 1, wherein the third retardation plate and the fifth retardation plate are formed of a nematic liquid crystal polymer having a normal-directional optical axis.

19. A liquid crystal display device which is configured such that a first retardation plate is disposed between a dot-matrix liquid crystal cell, in which a liquid crystal layer is held between two electrode-equipped substrates and a reflective layer is provided on each of pixels, and a polarizer plate such that a slow axis of the first retardation plate forms an angle of about 45°

with respect to an absorption axis of the polarizer plate, the liquid crystal display device comprising;

a circular polarizer/analyzer structure including the polarizer plate and the first retardation plate; and

a variable retarder structure including the liquid crystal cell,

wherein the variable retarder structure has an optically positive normal-directional phase difference in a black display state,

the first retardation plate is a uniaxial ¼

wavelength plate which provides a phase difference of a ¼

wavelength between light rays of a predetermined wavelength that travel along a fast axis and the slow axis thereof,

the circular polarizer/analyzer structure includes a first optical compensation layer which is disposed for optical compensation of the circular polarizer/analyzer structure between the polarizer plate and the first retardation plate, the first optical compensation layer including a uniaxial second retardation plate with a refractive index anisotropy of nx≅

ny<

nz and a uniaxial third retardation plate with a refractive index anisotropy of nx>

ny≅

nz, the third retardation plate being disposed such that a slow axis of the third retardation plate is substantially perpendicular to the absorption axis of the polarizer plate, and

the variable retarder structure includes a second optical compensation layer which is disposed for optical compensation of the variable retarder structure between the first retardation plate and the liquid crystal cell, the second optical compensation layer including a fourth retardation plate with a refractive index anisotropy of nx≅

ny>

nz.

20. The liquid crystal display device according to claim 19, wherein the first optical compensation layer further includes a uniaxial fifth retardation plate with a refractive index anisotropy of nx≅

ny<

nz.