Rotatory polarization plate, optical element, light condensation backlight system and liquid crystal display

• US 7,326,451 B2
• Filed: 10/21/2004
• Issued: 02/05/2008
• Est. Priority Date: 10/23/2003
• Status: Expired due to Fees

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Hara, Kazutaka, Takahashi, Naoki, Takeda, Kentarou, Shiraogawa, Miki
• Primary Examiner(s): Dye; Rena
• Assistant Examiner(s): Hon; Sow-Fun
• Application Number:
  US10/969,055
• Publication Number:
  US 20050088740A1
• Time in Patent Office: 1,202 Days
• Field of Search: 428/1.1, 428/1.3, 428/1.31, 349/18, 349/96, 349 98- 99, 349102-103, 349/115, 349/185
• US Class Current: 428/1.31
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
• CPC Class Codes: C09K 2323/031 Polarizer or dye
• CPC Class Codes: G02B 5/3016 involving passive liquid crystal elements optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one

Abstract

A rotatory polarization plate capable of extracting an emission polarized light from an incident polarized light and rotating an azimuth angle of an polarization axis of the incident polarized light, wherein a rotatory polarization angle of the azimuth angle is changed by an incidence angle of the incident polarized light, is useful for an optical element capable of condensing and collimating incident light from a light source in a specific direction.

Claims

1. A rotatory polarization plate, capable of extracting a polarized light from an incident polarized light and rotating an azimuth angle of a polarization axis of the incident polarized light, wherein a rotatory polarization angle of the azimuth angle is changed by an incidence angle of the incident polarized light, wherein the azimuth angle of the polarization axis of linearly polarized light is rotated by about 90°

when, in the normal direction, the linearly polarized light passes through the rotatory polarization plate, and being rotated by about 0°

when, at the incidence angle larger than 30°

, the linearly polarized light passes through the rotatory polarization plate, wherein the rotatory polarization plate is formed with a cholesteric liquid crystal layer, and wherein all of a selective reflection wavelength band of the rotatory polarization plate is in a wavelength region longer than 610 nm.

2. An optical element comprising:

a linearly polarizing element (A) and the rotatory polarization plate (B) according to claim 1.

3. The optical element according to claim 2,

comprising:

the rotatory polarization plate (B) according to claim 1; and

two or more linearly polarizing elements (A), wherein the rotatory polarization plate (B) is disposed between two adjacent linearly polarizing elements (A).

4. The optical element according to claim 2, wherein the linearly polarizing element (A) is a linearly polarized light reflection polarizer.

5. The optical element according to claim 2, wherein the linearly polarizing element (A) is a linearly polarized light absorption polarizer.

6. The optical element according to claim 2, wherein the linearly polarizing element (A) is a polarized light emitting element.

7. The optical element according to claim 2, wherein each of layers is laminated with a light translucent adhesive or pressure-sensitive adhesive.

8. A light condensation backlight system comprising at least:

a light source and the optical element according to claim 2.

9. A liquid crystal display comprising at least:

a liquid crystal cell and the light condensation backlight system according to claim 8.

10. The liquid crystal display according to claim 9, further comprising a diffusion plate having substantially neither backscattering nor polarization cancellation laminated on a viewer side of the liquid crystal cell.