Dark state light recycling film and display

• US 20060055844A1
• Filed: 09/13/2004
• Published: 03/16/2006
• Est. Priority Date: 09/13/2004
• Status: Abandoned Application

• Current Assignee: Rohm and Haas Denmark Finance A/S
• Original Assignee: Eastman Kodak Company
• Inventors: Mi, Xiang-Dong
• Application Number:
  US10/939,656
• Publication Number:
  US 20060055844A1
• Time in Patent Office: Days
• US Class Current: 349/96
• CPC Class Codes: G02F 1/133507 Films for enhancing the luminance
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133562 on the viewer side
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 2203/66 Normally white display, i.e. the off state being white

Abstract

A liquid crystal device display (20) has a backlight unit (56) for providing substantially unpolarized illumination, a rear polarizer (50b) disposed proximate the backlight unit (56) for receiving the incident substantially unpolarized illumination and transmitting substantially polarized illumination, a liquid crystal spatial light modulator for forming a display beam by selective, pixel-wise modulation of the polarization of the substantially polarized illumination, and a reflective polarizer (52a) disposed between the liquid crystal spatial light modulator and a front polarizer (50a), the reflective polarizer (52a) reflecting a portion of dark state light back toward the backlight unit (56).

Claims

1. A liquid crystal display comprising:

(a) a backlight unit for providing substantially unpolarized illumination;

(b) a rear polarizer disposed proximate the backlight unit for receiving the incident substantially unpolarized illumination and transmitting substantially polarized illumination;

(c) a liquid crystal spatial light modulator for forming a display beam by selective, pixel-wise modulation of the polarization of the substantially polarized illumination; and

,

(d) a reflective polarizer disposed between the liquid crystal spatial light modulator and a front polarizer, the reflective polarizer reflecting a portion of dark state light back toward the backlight unit.

2. A liquid crystal display according to claim 1 wherein the reflective polarizer is coupled to the surface of the liquid crystal spatial light modulator.

3. A liquid crystal display according to claim 1 wherein the transmittance of the reflective polarizer is greater than 75%.

4. A liquid crystal display according to claim 1 further comprising an additional reflective polarizer disposed between the rear polarizer and the backlight unit.

5. A liquid crystal display according to claim 1 further comprising a collimating film disposed between the rear polarizer and the backlight unit.

6. A liquid crystal display according to claim 1 further comprising a compensation film.

7. A liquid crystal display according to claim 1 wherein the respective transmission axes of the front and rear polarizers are parallel to each other within ±

10 degrees.

8. A liquid crystal display according to claim 1 wherein the respective transmission axes of the front and rear polarizers are orthogonal to each other within ±

10 degrees.

9. A liquid crystal display according to claim 1 wherein the respective transmission axes of the front and reflective polarizers are parallel to each other within ±

10 degrees.

10. A liquid crystal display according to claim 1 wherein the reflective polarizer is a wire grid polarizer.

11. A liquid crystal display according to claim 1 wherein the reflective polarizer comprises a multilayer interference-based polarizer.

12. A liquid crystal display according to claim 1 wherein the reflective polarizer comprises a circular polarizer with a quarter wave retarder.

13. A liquid crystal display according to claim 1 wherein the backlight unit comprises at least one light source with an output that can be controlled.

14. A liquid crystal display according to claim 13 wherein the light source comprises one or more light emitting diode.

15. A liquid crystal display comprising:

(a) a backlight unit providing substantially unpolarized illumination;

(b) a first reflective polarizer, having a transmission axis, for

(i) transmitting that portion of light from the substantially unpolarized backlight unit illumination that has polarization parallel to the transmission axis; and

,

(ii) reflecting light having a polarization orthogonal to the transmission axis;

(c) a rear polarizer for receiving the polarized light transmitted from the first reflective polarizer;

(d) a liquid crystal spatial light modulator for forming an image by selective, pixel-wise modulation of polarization of the polarized illumination; and

,

(e) a second reflective polarizer disposed between the liquid crystal spatial light modulator and a front polarizer for reflecting a portion of dark state light from the liquid crystal spatial light modulator back toward the backlight unit.

16. A liquid crystal display according to claim 15 wherein the second reflective polarizer is coupled to the surface of the LC spatial light modulator.

17. A liquid crystal display according to claim 15 wherein the transmittance of the second reflective polarizer is greater than 75%.

18. A liquid crystal display according to claim 15 further comprising a collimating film disposed between the rear polarizer and the backlight unit.

19. A liquid crystal display according to claim 15 further comprising a compensation film.

20. A liquid crystal display according to claim 15 wherein the respective transmission axes of the front and rear polarizers are parallel to each other within ±

10 degrees.

21. A liquid crystal display according to claim 15 wherein the respective transmission axes of the front and rear polarizers are orthogonal to each other within ±

10 degrees.

22. A liquid crystal display according to claim 15 wherein the respective transmission axes of the front polarizer and second reflective polarizer are parallel to each other within ±

10 degrees.

23. A liquid crystal display according to claim 15 wherein the first reflective polarizer is a wire grid polarizer.

24. A liquid crystal display according to claim 15 wherein the second reflective polarizer is a wire grid polarizer.

25. A liquid crystal display according to claim 15 wherein the second reflective polarizer comprises a multilayer interference-based polarizer.

26. A liquid crystal display according to claim 15 wherein the second reflective polarizer comprises a circular polarizer with a quarter wave retarder.

27. A liquid crystal display according to claim 15 wherein the backlight unit comprises at least one light source with an output that can be controlled.

28. A liquid crystal display according to claim 27 wherein the light source comprises one or more light emitting diode.

29. A method for adjusting display brightness comprising:

a) providing backlight illumination to a transmissive liquid crystal display component;

b) forming an image beam by pixel-wise modulation of the polarization of the backlight illumination according to image data;

c) disposing a reflective polarizer in the path of the image beam;

d) determining, based on the image data, the relative proportion of dark pixels to light pixels; and

,

e) modulating the backlight illumination brightness level based on the relative proportion of dark to light pixels for the displayed image.

30. A method according to claim 29 wherein the step of modulating the backlight illumination brightness level comprises the step of varying the drive current to a light source that can be controlled.

31. A method according to claim 29 wherein the light source comprises one or more LEDs.