Circular polarizing plate and liquid crystal display device

• US 20040257498A1
• Filed: 05/18/2004
• Published: 12/23/2004
• Est. Priority Date: 11/19/2001
• Status: Abandoned Application

• Current Assignee: Nippon Oil Corporation (ENEOS Holdings, Inc.)
• Original Assignee: Nippon Oil Corporation (ENEOS Holdings, Inc.)
• Inventors: Ogasawara, Toyokazu, Uesaka, Tetsuya, Yoda, Eiji
• Application Number:
  US10/495,853
• Publication Number:
  US 20040257498A1
• Time in Patent Office: Days
• US Class Current: 349/98
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133541 Circular polarisers
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 1/133632 with refractive index ellipsoid inclined relative to the LC-layer surface
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 2203/09 transflective
• CPC Class Codes: G02F 2413/105 with varying inclination in thickness direction, e.g. hybrid oriented discotic LC

Abstract

A circular polarizer comprises at least a polarizer and an optical anisotropic element having an optical retardation of about ¼ wavelength in a visible light region, wherein the optical anisotropic element comprises at least a 50 μm or less thick liquid crystal film (A) obtained by fixing a liquid crystal substance exhibiting an optically positive uniaxiality, in a nematic hybrid orientation with an average tilt angle of 5 to 35 degrees, formed when the substance is in a liquid crystal state, thereby providing a favorable circular polarization characteristics with a decreased thickness. The use of this circular polarizer makes it possible to produce a transflective type liquid crystal device which is capable of providing bright display images of high contrast and is less dependent on the viewing angle.

Claims

1. A circular polarizer comprising at least a polarizer and an optical anisotropic element having an optical retardation of about ¼

wavelength in a visible light region, wherein the optical anisotropic element comprises at least a 50 μ

m or less thick liquid crystal film (A) obtained by fixing a liquid crystal substance exhibiting an optically positive uniaxiality, in a nematic hybrid orientation with an average tilt angle of 5 to 35 degrees, formed when the substance is in a liquid crystal state.

2. The circular polarizer according to claim 1 wherein said optical anisotropic element comprises at least the liquid crystal film (A) and a polymeric stretched film.

3. The circular polarizer according to claim 1 wherein said optical anisotropic element comprises at least the liquid crystal film (A) and a 50 μ

m or less thick liquid crystal film (B) obtained by fixing a liquid crystal substance exhibiting an optically positive uniaxiality, in a nematic orientation formed when the substance is in a liquid crystal state.

4. The circular polarizer according to any of claims 1 to 3 wherein said liquid crystal film (A) is a liquid crystal film obtained by allowing a liquid crystal substance exhibiting an optically positive uniaxiality, in a liquid crystal state, to be aligned in a nematic hybrid orientation and by cooling the aligned substance to be fixed in a glassy state.

5. The circular polarizer according to any of claims 1 to 3 wherein said liquid crystal film (A) is a liquid crystal film obtained by allowing a liquid crystal substance exhibiting an optically positive uniaxiality, in a liquid crystal state, to be aligned in a nematic hybrid orientation and by fixing the aligned substance by cross-linking.

6. A liquid crystal display device comprising a liquid crystal cell in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode, and the circular polarizer defined in claim 1.

7. A transflective type liquid crystal display device comprising a liquid crystal display device provided with a liquid crystal cell wherein a liquid crystal layer is sandwiched between a first substrate with a transparent electrode and a second substrate with a transflective electrode;

at least one optical retardation compensator disposed on the surface, opposite to the surface facing to the liquid crystal layer, of the first substrate; and

one polarizer disposed on the optical retardation compensator, wherein the circular polarizer defined in claim 1 is disposed on the surface, opposite to the surface facing the liquid crystal layer, of the second substrate.

8. A transflective type liquid crystal display device comprising a liquid crystal display device provided with a liquid crystal cell wherein a liquid crystal layer is sandwiched between a first substrate with a transparent electrode and a second substrate with a transflective electrode;

at least one optical retardation compensator disposed on the surface, opposite to the surface facing to the liquid crystal layer, of the second substrate; and

one polarizer disposed under the optical retardation compensator, wherein the circular polarizer defined in claim 1 is disposed on the surface, opposite to the surface facing the liquid crystal layer, of the first substrate.

9. A transflective type liquid crystal display device comprising a liquid crystal display device provided with a liquid crystal cell wherein a liquid crystal layer is sandwiched between a first substrate with a transparent electrode and a second substrate with a transflective electrode, wherein the circular polarizers defined in claim 1 are disposed on both sides of the liquid crystal cell.

10. The liquid crystal display device according to any of claims 6 to 9, wherein the liquid crystal layer is of a twisted nematic mode.

11. The liquid crystal display device according to any of claims 6 to 9, wherein the liquid crystal layer is of a super twisted nematic mode.

12. The liquid crystal display device according to any of claims 6 to 9, wherein the liquid crystal layer is of an ECB mode.

13. The liquid crystal display device according to any of claims 6 to 9, wherein the liquid crystal layer is of a HAN mode.