Polarizing element, optical element, and liquid crystal display

• US 6,661,482 B2
• Filed: 10/05/2001
• Issued: 12/09/2003
• Est. Priority Date: 10/05/2001
• Status: Expired due to Fees

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Hara, Kazutaka
• Primary Examiner(s): Tsai, Jey
• Application Number:
  US09/972,029
• Publication Number:
  US 20030067582A1
• Time in Patent Office: 795 Days
• Field of Search: 349/96, 349/98, 349/69-71, 349/117, 349/112-113, 349/9, 349/64, 349/115
• US Class Current: 349/96
• 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 display comprising a liquid crystal cell and a polarizing element, the 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;

the absorptive polarizer is arranged on a side of the reflective polarizing plate opposed to the liquid crystal plate so as to transmit a polarized light comprising the transmitted light, and

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

2. The display according to claim 1, wherein the reflective polarizing plate comprises a linearly polarized light separation plate.

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

4. The display 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 display 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 display 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 cf the circularly polarized light.

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

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

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

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

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

22. The display of claim 1, wherein the display is a semitransparent liquid crystal display.

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 opposed to the reflective polarizing plate 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;

(B) 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 opposed to the reflective polarizing plate 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.

23. 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;

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

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.

24. A semitransparent liquid crystal display comprising the polarizing element of claim 23, wherein the absorptive polarizer is disposed on a side of the reflective polarizing plate opposed to a display side of the display.

25. A semitransparent liquid crystal display comprising the polarizing element of claim 23.

26. A semitransparent liquid crystal display comprising the polarizing element of claim 24.