Transflective liquid crystal device with bright reflective display

• US 6,285,422 B1
• Filed: 05/14/1998
• Issued: 09/04/2001
• Est. Priority Date: 09/17/1996
• Status: Expired due to Term

• Current Assignee: Japan Display West Incorporated (Japan Display Incorporated)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Maeda, Tsuyoshi, Okumura, Osamu
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): NGUYEN, FRANCIS N
• Application Number:
  US09/068,661
• Time in Patent Office: 1,209 Days
• Field of Search: 345/87, 345/102, 345/83, 345/76, 345/77, 345/44, 349/68, 349/96, 349/71, 349/61-62, 349/69-70, 349/97, 349/101, 349/113, 349/114, 349/98, 349/86, 349/64-65, 349/104, 359/495, 359/497-498, 359/501, 359/483, 359/487, 362/84, 362/19
• US Class Current: 349/96
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/133567 on the back side
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one

Abstract

A polarizer 14 is provided on the upper side of a liquid crystal panel 10, and a light scattering member 15 and a polarized light separator 16 are provided in turn on the lower side of the liquid crystal panel 10. Of light incident on the upper side of the polarized light separator 16, a linearly polarized light component parallel to the drawings is transmitted, a linearly polarized light component perpendicular to the drawings is reflected, and for light incident on the lower side thereof, a linearly polarized light component parallel to the drawings can be emitted upward. When the switch is off, the external light incident on the display device is reflected by the polarized light separator 16 to obtain a bright display, and when the switch is on, the incident external light is transmitted through the polarized light separator 16 to obtain a dark display. When the switch is off, light from a light source 17 is transmitted through the polarized light separator 16 and absorbed by the polarizer 12 to obtain dark display, and when the switch is on, the light is transmitted through the polarized light separator 16 and through the polarizer 14 to obtain a bright display.

Claims

1. A display device, comprising:

a polarization changing element that changes a transmission polarization axis;

a first polarized light separator and a second polarized light separator disposed on opposite sides of the polarization changing element;

a light absorber that substantially absorbs external light; and

a light source disposed on a side of the second polarized light separator opposite the polarization changing element that emits colored light,

the first polarized light separator transmitting a linearly polarized light component in a first predetermined direction, the first polarized light separator not transmitting a linearly polarized light component in a second direction different from the first direction, and

the second polarized light separator transmitting a linearly polarized light component in a third predetermined direction and reflecting a linearly polarized light component in a fourth predetermined direction different from the third predetermined direction.

2. The display device according to claim 1, the first polarized light separator comprising a polarizer.

3. The display device according to claim 1, the polarization changing element comprising a liquid crystal element.

4. The display device according to claim 3, the polarization changing element comprising one of a TN liquid crystal element, an STN liquid crystal element, an F-STN liquid crystal element and an ECB liquid crystal element.

5. The display device according to claim 1, the light source comprising at least one EL element that emits light in a predetermined wavelength region.

6. The display device according to claim 5, the light source comprising:

a first EL element that emits light in a third predetermined wavelength region, and

a second EL element that emits light in a fourth predetermined wavelength region different from the third predetermined wavelength region.

7. The display device according to claim 1, a color of display with the light from the light source is different from a color of display with incident light from a polarizer side.

8. A display device, comprising:

a liquid crystal panel that changes a polarization transmission polarization axis;

a polarizer disposed on one side of the liquid crystal panel;

a reflective polarizer disposed on a side opposite to the polarizer with respect to the liquid crystal panel;

a light absorber that substantially absorbs external light; and

a light source, disposed on a side opposite to the liquid crystal panel with respect to the reflective polarizer, that emits colored light, the light source comprising a first light element that emits light in a first predetermined wavelength region, and a second a first light element that emits light in a second predetermined wavelength region different from the first predetermined wavelength region.

9. The display device according to claim 8, the first light element comprising a first LED that emits light in the first predetermined wavelength region, and the second light element comprising a second LED that emits light in the second predetermined wavelength region different from the first predetermined wavelength region.

10. The display device according to claim 8, the light source comprising a light guide plate that comprises:

a first light guide region where light in the first predetermined wavelength region is incident from the first light element and emitted to a reflective polarizer side;

a second light guide region where light in the second predetermined wavelength region is incident from the second light element and emitted to the reflective polarizer side; and

a light shield provided between the first light guide region and the second light guide region.

11. A display device, comprising:

a liquid crystal panel having liquid crystal sandwiched between a pair of substrates;

a polarizer disposed on one side of the liquid crystal panel;

a reflective polarizer disposed on a side opposite to the polarizer with respect to the liquid crystal panel;

a light source disposed on a side opposite to the liquid crystal panel with respect to the reflective polarizer, and

a light absorber provided between the reflective polarizer and the light source, that substantially absorbs external light from a reflective polarizer side and transmitting light from the light source.

12. The display device according to claim 11, the light absorber having an opening.

13. The display device according to claim 11, the light absorber being translucent.

14. The display device according to claim 11, the light absorber being a light scattering member.

15. The display device according to claim 11, the light absorber comprising a polarizer having a transmission axis shifted from that of the reflective polarizer.

16. A display device, comprising:

a liquid crystal panel comprising liquid crystal and a pair of substrates provided with the liquid crystal therebetween, the liquid crystal panel changing a polarization transmission polarization axis;

a polarizer disposed on one side of the liquid crystal panel;

a reflective polarizer disposed on a side opposite to the polarizer with respect to the liquid crystal panel;

a light absorber that substantially absorbs external light; and

a light source, disposed on a side opposite to the liquid crystal panel with respect to the reflective polarizer.

17. The display device according to claim 16, the reflective polarizer transmitting a linearly polarized light component in the third predetermined direction for light over substantially the entire wavelength range of the visible light spectrum, and reflecting a linearly polarized light component in the fourth predetermined direction for light over substantially the entire wavelength range of the visible light spectrum.

18. The display device according to claim 16, the reflective polarizer comprising multilayer films laminated in a plurality of layers, and refractive indexes of adjacent layers in the plurality of layers being the same in the third predetermined direction and different in the fourth predetermined direction.

19. The display device according to claim 16, a surface color of the light source being darkened.

20. The display device according to claim 16, the light absorber being an optical element provided between the reflective polarizer and the light source that absorbs light from a reflective polarizer side, and transmits light from the light source to the reflective polarizer side.

21. The display device according to claim 20, optical element absorbs light over substantially the entire wavelength range of the visible light spectrum.

22. The display device according to claim 21, the optical element comprising a black light absorber.

23. The display device according to claim 20, the optical element having an opening.

24. The display device according to claim 23, an area ratio of the opening to the optical element being limited.

25. The display device according to claim 23, a distance between the optical element and the light source being larger than a diameter of the opening.

28. The display device according to claim 20, the optical element comprising a light scattering member that changes a state of polarization of light incident on the optical element and emitted from the optical element.

29. The display device according to claim 20, the optical element comprising a polarizer having a transmission axis shifted from that of the reflective polarizer.

30. The display device according to claim 20, further comprising a light converging device that converges light from the light source toward a front of the optical element.

31. The display device according to claim 30, the light converging device being disposed between the light source and the reflective polarizer.

32. The display device according to claim 16, further comprising a light diffuser between the liquid crystal panel and the reflective polarizer.

33. The display device according to claim 16, the light source comprising at least one LED that emits light in a predetermined wavelength region to a reflective polarizer side.

34. The display device according to claim 33, the light source comprising:

a light guide plate that emits light in the predetermined wavelength region, which is incident from the LED, to the reflective polarizer side.

35. An electronic apparatus, comprising the display device according to claim 16 as a display unit.

36. The display device according to claim 16, the light source comprising an EL element that emits light in a predetermined wavelength region to a reflective polarizer side.

26. The display device according to the optical element comprising a light absorber in a gray translucent state.

27. The display device according to the light absorber in the translucent state having a transmittance of 10 to 80% for light over substantially the entire visible wavelength spectrum.

37. A display device, comprising:

a liquid crystal panel comprising a liquid crystal and a pair of substrates provided with the liquid crystal therebetween, the liquid crystal panel;

a polarizer disposed on one side of the liquid crystal panel;

a reflective polarizer disposed on a side opposite to the polarizer with respect to the liquid crystal panel;

a light absorber that substantially absorbs external light; and

a light source, disposed on a side opposite to the liquid crystal panel with respect to the reflective polarizer, that emits colored light,

the liquid crystal panel comprising one of a TN liquid crystal element, an STN liquid crystal element, an F-STN liquid crystal element and an ECB liquid crystal element.

38. The display device according to claim 37, further comprising an optical element provided between the reflective polarizer and the light source that absorbs light from a reflective polarizer side, and transmits light from the light source to the reflective polarizer side.

39. The display device according to claim 38, the optical element absorbs light over substantially the entire wavelength range of the visible light spectrum.

40. The display device according to claim 39, the optical element comprising a black light absorber.

41. The display device according to claim 38, the optical element having an opening.

42. The display device according to claim 41, an area ratio of the opening to the optical element being limited.

43. The display device according to claim 41, a distance between the optical element and the light source being larger than a diameter of the opening.

44. The display device according to claim 38, the optical element comprising a light absorber in a gray translucent state.

45. The display device according to claim 44, the light absorber in the translucent state having a transmittance of 10 to 80% for light over substantially the entire visible wavelength spectrum.

46. The display device according to claim 38, the optical element comprising a light scattering member that changes a state of polarization of light incident on the optical element and emitted from the optical element.

47. The display device according to claim 38, the optical element comprising a polarizer having a transmission axis shifted from that of the reflective polarizer.

48. The display device according to claim 38, further comprising a light converging device that converges light from the light source toward a front of the optical element.

49. The display device according to claim 48, the light converging device being disposed between the light source and the reflective polarizer.

50. The display device according to claim 37, further comprising a light diffuser between the liquid crystal panel and the reflective polarizer.

51. The display device according to claim 37, the light source comprising at least one LED that emits light in a predetermined wavelength region to a reflective polarizer side.