LIQUID CRYSTAL DISPLAY DEVICE

• US 20070076152A1
• Filed: 10/02/2006
• Published: 04/05/2007
• Est. Priority Date: 10/04/2005
• 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:
  US11/537,860
• Publication Number:
  US 20070076152A1
• Time in Patent Office: Days
• US Class Current: 349/117
• CPC Class Codes: G02F 1/133528 Polarisers
• 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 1/133634 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 1/136222 Colour filters incorporated in the active matrix substrate
• 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
• CPC Class Codes: G02F 2413/12 Biaxial compensators
• CPC Class Codes: G02F 2413/13 Positive birefingence
• CPC Class Codes: G02F 2413/14 Negative birefingence

Abstract

A circular polarizer structure, which is included in a liquid crystal display device, includes a uniaxial third retardation plate for optical compensation of the circular polarizer structure between a first polarizer plate and a first retardation plate, the uniaxial third retardation plate having a refractive index anisotropy of nx≃nz>ny. A circular analyzer structure includes a uniaxial fourth retardation plate for optical compensation of the circular analyzer structure between a second polarizer plate and a second retardation plate, the uniaxial fourth retardation plate having a refractive index anisotropy of nx≃nz>ny. A variable retarder structure includes a fifth retardation plate for optical compensation of the variable retarder structure between the first retardation plate and the second retardation plate, the fifth retardation plate having 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 uniaxial 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 uniaxial 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 ¼

wavelength plate which provides a phase difference of a ¼

wavelength between light rays of a predetermined wavelength that pass through 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 third retardation plate with a refractive index anisotropy of nx≃

nz>

ny, the third retardation plate being disposed such that a slow axis thereof 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 fourth retardation plate with a refractive index anisotropy of nx≃

nz>

ny, the fourth retardation plate being disposed such that a slow axis thereof is substantially perpendicular to the absorption axis of the second polarizer 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 fifth retardation plate with a refractive index anisotropy of nx≃

ny>

nz.

2. 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.

3. The liquid crystal display device according to claim 2, wherein at least one of a combination of the first segment layer and the first retardation plate and a combination of the second segment layer and the second retardation plate is formed of a single biaxial retardation plate which has such a total optical function as to impart a phase difference of ¼

wavelength between light rays of a predetermined wavelength that pass through a fast axis and a slow axis thereof, and to be equivalent to a biaxial refractive index anisotropy of nx>

ny>

nz.

4. 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.

5. The liquid crystal display device according to claim 4, 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.

6. The liquid crystal display device according to claim 5, wherein an orientation direction of liquid crystal molecules in the pixel in the voltage-on state is controlled to be 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.

7. The liquid crystal display device according to claim 5, wherein the liquid crystal display device includes at least one of a protrusion for multi-domain control, which is provided in the pixel, and a slit for multi-domain control, which is provided in the electrode.

8. The liquid crystal display device according to claim 5, wherein alignment films, which are subjected to an alignment process for multi-domain control, are provided on those surfaces of the two substrates, which hold the liquid crystal layer.

9. The liquid crystal display device according to claim 1, wherein a combination of the second retardation plate and the fifth retardation plate is formed of a single biaxial retardation plate which has such a total optical function as to impart a phase difference of ¼

wavelength between light rays of a predetermined wavelength that pass through a fast axis and a slow axis thereof, and to be equivalent to a biaxial refractive index anisotropy of nx>

ny>

nz.

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

11. The liquid crystal display device according to claim 1, wherein the third retardation plate and the fourth retardation plate are formed of one of a norbornene resin, a denatured polycarbonate resin and a discotic liquid crystal polymer.

12. 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.

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

14. The liquid crystal display device according to claim 1, wherein an in-plane phase difference and an normal-directional phase difference of the third retardation plate and fourth retardation plate are greater than 30 nm and less than 160 nm.

15. The liquid crystal display device according to claim 1, wherein an normal-directional phase difference of the fifth retardation plate is greater than −

180 nm and less than −

145 nm.

16. A liquid crystal display device including a uniaxial first retardation plate, which 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 in 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 ¼

wavelength plate which provides a phase difference of a ¼

wavelength between light rays of a predetermined wavelength that pass through 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 second retardation plate with a refractive index anisotropy of nx≃

nz>

ny, the second retardation plate being disposed such that a slow axis thereof 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 third retardation plate with a refractive index anisotropy of nx≃

ny>

nz.