Light recycling film and display

• US 20060055838A1
• Filed: 10/10/2005
• Published: 03/16/2006
• Est. Priority Date: 09/13/2004
• Status: Abandoned Application

• Current Assignee: Rohm and Haas Denmark Finance A/S (Dow, Inc.)
• Original Assignee: Eastman Kodak Company
• Inventors: Mi, Xiang-Dong, Nothhard, Gary E.
• Application Number:
  US11/247,880
• Publication Number:
  US 20060055838A1
• Time in Patent Office: Days
• US Class Current: 349/30
• CPC Class Codes: G02F 1/133507 Films for enhancing the luminance
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133531 characterised by the arrangement of polariser or analyser axes
• 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 1/133567 on the back side
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/1397 the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells
• CPC Class Codes: G02F 2203/66 Normally white display, i.e. the off state being white
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

A liquid crystal device display (20) has a backlight unit (56) for providing illumination, a rear polarizer (50b) disposed proximate the backlight unit (56) for receiving the incident 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).

Claims

1. A liquid crystal display comprising:

(a) a backlight unit for providing illumination;

(b) a rear polarizer disposed proximate the backlight unit for receiving the incident 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.

2. A liquid crystal display according to claim 1 wherein the reflective polarizer reflects a portion of dark state light back toward the backlight unit.

3. A liquid crystal display according to claim 1 wherein the reflective polarizer reflects a portion of gray state light back toward the backlight unit.

4. A liquid crystal display according to claim 1 wherein the reflective polarizer reflects a portion of white state light back toward the backlight unit.

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

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

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

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

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

10. 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.

11. 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.

12. 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.

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

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

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

16. 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.

17. A liquid crystal display according to claim 16 wherein the light source comprises one or more light emitting diode.

18. A liquid crystal display according to claim 1 wherein the liquid crystal spatial light modulator is taken from the group consisting of an super twisted nematic, an in-plane switching, a twisted nematic, a vertically aligned, and an optically compensated bend liquid crystal spatial light modulator.

19. A liquid crystal display according to claim 1 wherein the transmission axis of the front polarizer is oriented at an angle of between 5 and 85 degrees with respect to the transmission axis of the rear polarizer.

20. A liquid crystal display according to claim 1 wherein the transmission axis of the reflective polarizer is oriented at an angle of between 5 and 85 degrees with respect to the transmission axis of the rear polarizer.

21. A liquid crystal display according to claim 1 wherein the backlight unit provides substantially unpolarized illumination.

22. A liquid crystal display according to claim 1 wherein the backlight unit provides polarized illumination.

23. A liquid crystal display comprising:

(a) a backlight unit providing illumination;

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

(i) transmitting that portion of light from the incident 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 illumination 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 light from the liquid crystal spatial light modulator back toward the backlight unit.

24. A liquid crystal display according to claim 23 wherein the second reflective polarizer is coupled to the surface of the LC spatial light modulator.

25. A liquid crystal display according to claim 23 wherein the transmittance of the second reflective polarizer is greater than 75%.

26. A liquid crystal display according to claim 23 further comprising a collimating film disposed between the rear polarizer and the backlight unit.

27. A liquid crystal display according to claim 23 further comprising a compensation film.

28. A liquid crystal display according to claim 23 wherein the respective transmission axes of the front and rear polarizers are parallel to each other within ±

10 degrees.

29. A liquid crystal display according to claim 23 wherein the respective transmission axes of the front and rear polarizers are orthogonal to each other within ±

10 degrees.

30. A liquid crystal display according to claim 23 wherein the respective transmission axes of the front polarizer and second reflective polarizer are parallel to each other within ±

10 degrees.

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

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

33. A liquid crystal display according to claim 23 wherein the second reflective polarizer comprises a multilayer interference-based polarizer.

34. A liquid crystal display according to claim 23 wherein the second reflective polarizer comprises a circular polarizer with a quarter wave retarder.

35. A liquid crystal display according to claim 23 wherein the backlight unit comprises at least one light source with an output that can be controlled.

36. A liquid crystal display according to claim 23 wherein the light source comprises one or more light emitting diode.

37. A liquid crystal display according to claim 23 wherein the second reflective polarizer reflects a portion of dark state light back toward the backlight unit.

38. A liquid crystal display according to claim 23 wherein the second reflective polarizer reflects a portion of gray state light back toward the backlight unit.

39. A liquid crystal display according to claim 23 wherein the second reflective polarizer reflects a portion of white state light back toward the backlight unit.

40. A liquid crystal display according to claim 23 wherein the transmission axis of the front polarizer is oriented at an angle of between 5 degrees and 85 degrees with respect to the transmission axis of the rear polarizer.

41. A liquid crystal display according to claim 23 wherein the liquid crystal spatial light modulator is taken from the group consisting of an super twisted nematic, an in-plane switching, a twisted nematic, a vertically aligned, and an optically compensated bend liquid crystal spatial light modulator.

42. A liquid crystal display according to claim 23 wherein the transmission axis of the front polarizer is oriented at an angle of between 5 and 85 degrees with respect to the transmission axis of the rear polarizer.

43. A liquid crystal display according to claim 23 wherein the transmission axis of the first reflective polarizer is oriented at an angle of between 5 and 85 degrees with respect to the transmission axis of the rear polarizer.

44. A liquid crystal display according to claim 23 wherein the backlight unit provides substantially unpolarized illumination.

45. A liquid crystal display according to claim 23 wherein the backlight unit provides polarized illumination.

46. 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.

47. A method according to claim 46 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.

48. A method according to claim 46 wherein the light source comprises one or more LEDs.

49. A liquid crystal display comprising:

(a) a backlight unit for providing illumination;

(b) a rear polarizer having a transmission axis, the rear polarizer disposed proximate the backlight unit for receiving the incident illumination and transmitting substantially polarized illumination in alignment with its transmission axis;

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

(d) a front polarizer having a transmission axis for transmitting the portion of the modulated beam having polarization in alignment with its transmission axis; and

,

(e) a reflective polarizing element disposed between the liquid crystal spatial light modulator and the front polarizer, the reflective polarizing element reflecting a portion of light back toward the backlight unit;

wherein the transmission axis of the front polarizer is oriented at an angle of between 5 degrees and 85 degrees with respect to the transmission axis of the rear polarizer.

50. A liquid crystal display according to claim 49 wherein the liquid crystal spatial light modulator is of a super twisted nematic type.

51. A liquid crystal display according to claim 49 wherein the reflective polarizing element is a wire grid polarizer.

52. A liquid crystal display according to claim 49 wherein the transmission axis of the reflective polarizer is oriented at an angle of greater than 5 degrees with respect to the transmission axis of the front polarizer.

53. A liquid crystal display according to claim 49 wherein the backlight unit provides substantially unpolarized illumination.

54. A liquid crystal display according to claim 49 wherein the backlight unit provides polarized illumination.

55. A liquid crystal display according to claim 49 further comprising a control logic processor for adjusting brightness according to an area of interest identified in the displayed image.