Liquid crystal display device

• US 20060203162A1
• Filed: 03/06/2006
• Published: 09/14/2006
• Est. Priority Date: 03/08/2005
• Status: Abandoned Application

• Current Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Inventors: Ito, Hideki, Murayama, Akio, Hisatake, Yuuzo, Tago, Chigusa
• Application Number:
  US11/367,338
• Publication Number:
  US 20060203162A1
• Time in Patent Office: Days
• US Class Current: 349/117
• CPC Class Codes: G02F 1/133541 Circular polarisers
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• 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
• CPC Class Codes: G02F 2413/04 Number of plates greater than or equal to 4

Abstract

A circular-polarization-based vertical alignment mode liquid crystal display device includes a circular polarizer structure, a variable retarder structure and a circular analyzer structure. The circular polarizer structure includes a first optical compensation layer for optical compensation thereof, the first optical compensation layer including a uniaxial retardation plate with a refractive index anisotropy of nx≈ny<nz. The circular analyzer structure includes a second optical compensation layer for optical compensation thereof, the second optical compensation layer including a uniaxial retardation plate with a refractive index anisotropy of nx≈ny<nz. The variable retarder structure includes a third optical compensation layer for optical compensation thereof, the third optical compensation layer including a uniaxial retardation plate with a refractive index anisotropy of nx≈ny>nz.

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, and a second retardation plate is disposed between the second polarizer plate and the liquid crystal cell, 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 predetermined wavelengths that travel along a fast axis and a 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,

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 fourth retardation plate with a refractive index anisotropy of nx≈

ny<

nz, 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 fifth retardation plate with a refractive index anisotropy of nx≈

ny>

nz.

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

ny≈

nz, a slow axis of the sixth retardation plate being disposed to be substantially parallel to a transmission axis of the first polarizer plate, and

the second optical compensation layer includes a uniaxial seventh retardation plate with a refractive index anisotropy of nx<

ny≈

nz, a slow axis of the seventh retardation plate being disposed to be substantially parallel to a transmission axis of the second polarizer plate.

3. The liquid crystal display device according to claim 2, wherein the first optical compensation layer is formed of an optical device in which a total optical function is equivalent to a biaxial refractive index anisotropy of nx<

ny<

nz.

4. The liquid crystal display device according to claim 2, wherein the second optical compensation layer is formed of an optical device in which a total optical function is equivalent to a biaxial refractive index anisotropy of nx<

ny<

nz.

5. The liquid crystal display device according to claim 1, wherein the fifth retardation plate is formed on one of the first retardation plate and the second retardation plate such that a total optical function is equivalent to a biaxial refractive index anisotropy of nx>

ny>

nz.

6. The liquid crystal display device according to claim 1, wherein the fifth 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.

7. The liquid crystal display device according to claim 6, 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.

8. The liquid crystal display device according to claim 6, 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.

9. 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.

10. The liquid crystal display device according to claim 9, 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.

11. The liquid crystal display device according to claim 9, 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 an absorption axis or a transmission axis of the first polarizer plate in at least half an opening region of each pixel.

12. The liquid crystal display device according to claim 10, wherein a protrusion for forming a multi-domain structure is provided within the pixel.

13. The liquid crystal display device according to claim 10, wherein a slit for forming a multi-domain structure is provided in the electrode.

14. The liquid crystal display device according to claim 10, wherein alignment films, which are subjected to an alignment treatment for forming a multi-domain structure, are provided on those surfaces of the two substrates, which sandwich the liquid crystal layer.

15. The liquid crystal display device according to claim 1, wherein the first retardation plate and the second retardation plate are formed of a resin selected from the group consisting of ARTON resin, a polyvinyl alcohol resin, ZEONOR resin, a triacetyl cellulose resin and a denatured polycarbonate resin.

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

17. The liquid crystal display device according to claim 1, wherein the fifth retardation plate is formed of one of a chiral nematic liquid crystal polymer, a cholesteric liquid crystal polymer and a discotic liquid crystal polymer.

18. The liquid crystal display device according to claim 2, wherein the sixth retardation plate and the seventh retardation plate are formed of a discotic liquid crystal polymer having an in-plane optical axis.

19. The liquid crystal display device according to claim 2, wherein when a normal-directional phase difference of each of the third retardation plate and the fourth retardation plate is R(1), a normal-directional phase difference of the fifth retardation plate is R(2) and an in-plane phase difference of each of the sixth retardation plate and the seventh retardation plate is R(3), the following condition is satisfied:

−

6/5×

R(1)−

244≦

R(2)≦

−

6/5×

R(1)−

172,
and
20≦

R(2)≦

80, and
−

40≦

R(3)≦

0.

20. The liquid crystal display device according to claim 2, wherein when a normal-directional phase difference of each of the third retardation plate and the fourth retardation plate is R(1), a normal-directional phase difference of the fifth retardation plate is R(2) and an in-plane phase difference of each of the sixth retardation plate and the seventh retardation plate is R(3), the following condition is satisfied:

−

230≦

R(1)≦

−

210, and
40≦

R(2)≦

60, and
−

40≦

R(3)≦

0.

21. The liquid crystal display device according to claim 1, wherein the liquid crystal cell includes a reflective layer on at least a part of the pixel, or in at least a part of the display region.

22. 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, 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 predetermined wavelengths that travel along a fast axis and a 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

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 third retardation plate with a refractive index anisotropy of nx≈

ny>

nz.

23. The liquid crystal display device according to claim 22, wherein the first optical compensation layer includes a uniaxial fourth retardation plate with a refractive index anisotropy of nx<

ny≈

nz, a slow axis of the fourth retardation plate being disposed to be substantially parallel to a transmission axis of the polarizer plate.

24. The liquid crystal display device according to claim 23, wherein the first optical compensation layer is formed of a single optical device in which a total optical function is equivalent to a biaxial refractive index anisotropy of nx<

ny<

nz.

25. The liquid crystal display device according to claim 22, wherein the third retardation plate 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.

26. The liquid crystal display device according to claim 22, wherein the liquid crystal cell has a vertical alignment mode in which liquid crystal molecules in the pixel are aligned substantially vertical to a major surface of the substrate in a voltage-off state.

27. The liquid crystal display device according to claim 26, 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.

28. The liquid crystal display device according to claim 26, 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 an absorption axis or a transmission axis of the polarizer plate in at least half an opening region of each pixel.

29. The liquid crystal display device according to claim 27, wherein a protrusion for forming a multi-domain structure is provided within the pixel.

30. The liquid crystal display device according to claim 27, wherein a slit for forming a multi-domain structure is provided in the electrode.

31. The liquid crystal display device according to claim 27, wherein alignment films, which are subjected to an alignment treatment for forming a multi-domain structure, are provided on those surfaces of the two substrates, which sandwich the liquid crystal layer.

32. The liquid crystal display device according to claim 22, wherein the first retardation plate is formed of a resin selected from the group consisting of ARTON resin, a polyvinyl alcohol resin, ZEONOR resin, a triacetyl cellulose resin and a denatured polycarbonate resin.

33. The liquid crystal display device according to claim 22, wherein the second retardation plate is formed of a nematic liquid crystal polymer having a normal-directional optical axis.

34. The liquid crystal display device according to claim 22, wherein the third retardation plate is formed of one of a chiral nematic liquid crystal polymer, a cholesteric liquid crystal polymer and a discotic liquid crystal polymer.

35. The liquid crystal display device according to claim 23, wherein the fourth retardation plate is formed of a discotic liquid crystal polymer having an in-plane optical axis.

36. The liquid crystal display device according to claim 23, wherein when a normal-directional phase difference of the second retardation plate is R(1), a normal-directional phase difference of the third retardation plate is R(2) and an in-plane phase difference of the fourth retardation plate is R(3), the following condition is satisfied:

−

6/5×

R(1)−

244≦

R(2)≦

−

6/5×

R(1)−

172,
and
20≦

R(2)≦

80, and
−

40≦

R(3)≦

0.

37. The liquid crystal display device according to claim 23, wherein when a normal-directional phase difference of the second retardation plate is R(1), a normal-directional phase difference of the third retardation plate is R(2) and an in-plane phase difference of the fourth retardation plate is R(3), the following condition is satisfied:

−

230≦

R(1)≦

−

210, and
40≦

R(2)≦

60, and
−

40≦

R(3)≦

0.