Polarizing element, optical element, and liquid crystal display

• US 20030067582A1
• Filed: 10/05/2001
• Published: 04/10/2003
• Est. Priority Date: 10/05/2001
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Hara, Kazutaka
• Granted Patent: US 6,661,482 B2
• Time in Patent Office: Days
• US Class Current: 349/194
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence

Abstract

A polarizing element and an optical element are provided that can form a semitransparent or other type of liquid crystal display which is excellent in contrast in a reflective display mode and also is excellent in luminance in a transmissive display mode utilizing a reflective polarizing plate. A polarizing element comprising a reflective polarizing plate and an absorptive polarizer, wherein the reflective polarizing plate separates an incident natural light into a reflected light and a transmitted light each comprising a polarized light, and the absorptive polarizer is arranged on one side of the reflective polarizing plate so as to transmit a polarized light comprising the transmitted light. Also, an optical element comprising this polarizing element; and (a) a quarter wavelength plate or (b) an absorptive polarizing plate and a quarter wavelength plate arranged on the side of the absorptive polarizer in the polarizing element, wherein the absorptive polarizing plate has an axial relation so as to transmit a polarized light transmitted through the absorptive polarizer. While accomplishing the function as a semitransparent reflective polarizer utilizing the reflective polarizing plate, in a transmissive display mode, high luminance display can be achieved with high contrast, and in a reflective display mode, unnecessary reflected light (returned light) of an external light can be absorbed and cut off efficiently.

Claims

1. A polarizing element, comprising:

a reflective polarizing plate; and

an absorptive polarizer,

wherein the reflective polarizing plate separates an incident natural light into a reflected light and a transmitted light each comprising a polarized light; and

the absorptive polarizer is arranged on one side of the reflective polarizing plate so as to transmit a polarized light comprising the transmitted light.

2. The polarizing element according to claim 1, wherein:

the reflective polarizing plate comprises a linearly polarized light separation plate; and

the absorptive polarizer comprises an absorptive polarizing plate arranged so that a transmission axis with respect to the transmitted light comprising a linearly polarized light is in parallel with the polarizing direction of the linearly polarized light.

3. The polarizing element according to claim 2, wherein the linearly polarized light separation plate comprises a dielectric multilayer film.

4. The polarizing element according to claim 2, wherein the linearly polarized light separation plate comprises a laminate of multiple thin films different in refractive index anisotropy.

5. The polarizing element according to claim 2, wherein the linearly polarized light separation plate and the absorptive polarizing plate are fixed with each other through an acrylic adhesive layer.

6. The polarizing element according to claim 1, wherein:

the reflective polarizing plate comprises a circularly polarized light separation plate; and

the absorptive polarizer comprises a circularly polarizing plate arranged so that its rotating direction with respect to the transmitted light comprising a circularly polarized light is the same as the rotating direction of the circularly polarized light.

7. The polarizing element according to claim 6, wherein the circularly polarized light separation plate comprises an oriented film of a cholesteric liquid crystal polymer.

8. The polarizing element according to claim 6, wherein the circularly polarized light separation plate comprises a sheet in which an oriented liquid crystal layer of a cholesteric liquid crystal polymer is supported on a film substrate.

9. The polarizing element according to claim 6, wherein the circularly polarized light separation plate and the circularly polarizing plate are fixed with each other through an acrylic adhesive layer.

10. The polarizing element according to claim 6, wherein the circularly polarizing plate comprises a quarter wavelength plate and an absorptive polarizing plate.

11. The polarizing element according to claim 10, wherein the quarter wavelength plate comprises at least two optical retardation layers.

12. The polarizing element according to claim 11, wherein the quarter wavelength plate comprises a stretched film of a polymer.

13. The polarizing element according to claim 2 or 10, wherein the absorptive polarizing plate comprises a polarizing film obtained by adsorbing iodine and/or dichromatic dye on a hydrophilic polymer film and stretching the hydrophilic polymer film.

14. The polarizing element according to claim 13, wherein a transparent protective layer is formed on one or both sides of the polarizing film.

15. An optical element comprising:

a polarizing element, the polarizing element comprising a reflective polarizing plate and an absorptive polarizer; and

(a) a quarter wavelength plate or (b) an absorptive polarizing plate and a quarter wavelength plate, arranged on the side of the absorptive polarizer in the polarizing element,

wherein the reflective polarizing plate separates an incident natural light into a reflected light and a transmitted light each comprising a polarized light; and

the absorptive polarizer is arranged on one side of the reflective polarizing plate so as to transmit a polarized light comprising the transmitted light.

16. The optical element according to claim 15, wherein the absorptive polarizing plate has an axial relation so as to transmit a polarized light transmitted through the absorptive polarizer.

17. The optical element according to claim 15, wherein:

the reflective polarizing plate comprises a linearly polarized light separation plate; and

the absorptive polarizer comprises an absorptive polarizing plate arranged so that its transmission axis with respect to the transmitted light comprising a linearly polarized light is in parallel with the polarizing direction of the linearly polarized light.

18. The optical element according to claim 15, wherein:

the reflective polarizing plate comprises a circularly polarized light separation plate; and

the absorptive polarizer comprises a circularly polarizing plate arranged so that its rotating direction with respect to the transmitted light comprising a circularly polarized light is the same as the rotating direction of the circularly polarized light.

19. The optical element according to claim 18, wherein the circularly polarizing plate comprises a quarter wavelength plate and an absorptive polarizing plate.

20. The optical element according to claim 15, wherein the reflective polarizing plate, the absorptive polarizer, and (a) the quarter wavelength plate or (b) the absorptive polarizing plate and the quarter wavelength plate are fixed with one another through an acrylic adhesive layer.

21. A semitransparent liquid crystal display, comprising:

a liquid crystal cell; and

(A) a polarizing element or (B) an optical element;

(A) the polarizing element comprising a reflective polarizing plate and an absorptive polarizer;

(B) the optical element comprising a polarizing element, the polarizing element comprising a reflective polarizing plate and an absorptive polarizer, and the optical element further comprising (a) a quarter wavelength plate or (b) an absorptive polarizing plate and a quarter wavelength plate, arranged on the side of the absorptive polarizer in the polarizing element; and

(A) the polarizing element or (B) the optical element being arranged on at least one side of the liquid crystal cell;

wherein the reflective polarizing plate separates an incident natural light into a reflected light and a transmitted light each comprising a polarized light; and

the absorptive polarizer is arranged on one side of the reflective polarizing plate so as to transmit a polarized light comprising the transmitted light.