Combined cholesteric liquid crystal display and solar cell assembly device

• US 6,518,944 B1
• Filed: 10/25/1999
• Issued: 02/11/2003
• Est. Priority Date: 10/25/1999
• Status: Expired due to Term

• Current Assignee: Kent Displays Incorporated
• Original Assignee: Kent Displays Incorporated
• Inventors: Doane, J. William, Miller, Nick M. IV, Davis, Donald James
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): NGUYEN, FRANCIS N
• Application Number:
  US09/427,137
• Time in Patent Office: 1,205 Days
• Field of Search: 345/87, 345/204-205, 345/211, 345/94-95, 349/115, 349/116, 349/175, 349/179, 349/169, 349/113, 126/595, 353/122
• US Class Current: 345/87
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal
• CPC Class Codes: G09G 2330/02 Details of power systems and of start or stop of display operation

Abstract

The present invention is directed to an integrated, reflective bistable, cholesteric liquid crystal display and solar cell assembly providing electrical energy to power display electronics. The liquid crystal display includes the layer of cholesteric liquid crystal material sandwiched between first and second transparent substrates. An inner surface of the first substrate and an inner surface of the second substrate bound the layer of liquid crystal material and the first substrate is closest to a viewer of the display. A first set of conductive electrodes is disposed on the inner surface of the first substrate and a second set of conductive electrodes is disposed on the inner surface of the second substrate. Display driver circuitry is electrically coupled to the first and the second sets of conductive electrodes for generating desired voltage differentials between electrodes of the first set of conductive electrodes and electrodes of the second set of conductive electrodes. A solar cell assembly that is provided includes a solar cell or solar panel positioned behind the second substrate and electrically coupled to a rechargeable energy storage device, such as a rechargeable battery. The solar cell receives illumination passing through the first substrate, liquid crystal material and the second substrate and converts the illumination incident on the solar cell to electrical energy to supply power to the rechargeable energy storage device. The cholesteric liquid crystal material permits transmission of incident light regardless of the configuration of the liquid crystal material.

Claims

1. A liquid crystal display comprising:

a) a layer of reflective chiral nematic liquid crystal material;

b) first substrate and a spaced apart second substrate, an inner surface of the first substrate and an inner surface of the second substrate bounding said liquid crystal material layer, the first substrate being closer than the second substrate to a viewer of the display,

c) a first set of conductive electrodes disposed on the inner surface of the first substrate and a second set of conductive electrodes spaced apart from the first set of electrodes and disposed on the inner surface of the second substrate bounding said liquid crystal material layer;

d) display driver circuitry electrically coupled to the first and the second set of conductive electrodes for generating desired voltage differentials between electrodes of the first set of conductive electrodes and electrodes of the second set of conductive electrodes; and

e) a solar cell assembly including a solar cell positioned adjacent said second substrate and electrically coupled to the display driver circuitry, the solar cell receiving illumination passing through the first substrate and said liquid crystal material and converting said illumination to electrical energy to supply power to an energy storage device.

2. The liquid crystal display of claim 1 wherein the energy storage device is electrically coupled to the display driver circuitry and power supplied to the energy storage device is used to provide power to the display driver circuitry.

3. The liquid crystal display of claim 1 wherein the solar cell is disposed adjacent an outer surface of the second substrate.

4. The liquid crystal display of claim 3 wherein a layer of index matching optical material is provided between the solar cell and the second substrate.

5. The liquid crystal display of claim 1 wherein the solar cell is comprised of single crystalline material.

6. The liquid crystal display of claim 2 wherein the solar cell assembly includes a diode disposed between the solar cell and the energy storage device such that electrical current flows only in a direction from the solar cell to the energy storage device.

7. The liquid crystal display of claim 1 wherein the first and second substrates are comprised of glass.

8. The liquid crystal display of claim 1 wherein a layer of infrared radiation absorbing material is disposed between the solar cell and the outer surface of the second substrate.

9. The liquid crystal display of claim 1 wherein said first set of electrodes comprise a plurality of substantially parallel electrode segments and said second set of electrodes comprise a plurality of substantially parallel electrode segments, said first set of electrodes extending transverse to said second set of electrodes.

10. The liquid crystal display of claim 1 wherein the energy storage device is a rechargeable battery.

11. The liquid crystal display of claim 1 wherein the solar cell assembly includes a DC/DC voltage converter to increase a magnitude of voltage output to the drive circuitry.

17. The liquid crystal display of claim 1 wherein the solar cell is comprised of a single crystalline material.

12. A liquid crystal display comprising:

a) a layer of reflective chiral nematic liquid crystal material;

b) first substrate and a spaced apart second substrate, an inner surface of the first substrate and an inner surface of the second substrate bounding said liquid crystal material layer, the first substrate being closer than the second substrate to a viewer of the display;

c) a first set of conductive electrodes disposed on the inner surface of the first substrate and a second set of conductive electrodes spaced apart from the first set of electrodes and disposed on the inner surface of the second substrate bounding said liquid crystal material layer;

d) display driver circuitry electrically coupled to the first and the second set of conductive electrodes for generating desired voltage differentials between electrodes of the first set of conductive electrodes and electrodes of the second set of conductive electrodes; and

e) a solar cell assembly including a solar cell at least of portion of which is positioned on a side of the liquid crystal material away from the first substrate and electrically coupled to the display driver circuitry, the solar cell receiving illumination passing through the first substrate and said liquid crystal material and converting said illumination to electrical energy to supply power to an energy storage device.

13. The liquid crystal display of claim 12 wherein the energy storage device is electrically coupled to the display driver circuitry and power supplied to the energy storage device is used to provide power to the display driver circuitry.

14. The liquid crystal display of claim 12 wherein said portion of the solar cell is disposed adjacent the second substrate.

15. The liquid crystal display of claim 14 wherein the solar cell is disposed adjacent an outer surface of the second substrate.

16. The liquid crystal display of claim 15 wherein a layer of index matching optical material is provided between the solar cell and the second substrate.

18. The liquid crystal display of claim 12 wherein the solar cell assembly includes a diode disposed between the solar cell and the energy storage device such that current flows only in a direction from the solar cell to the energy storage device.

19. The liquid crystal display of claim 12 wherein the first and second substrates are comprised of glass.

20. The liquid display of claim 12 wherein a layer of infrared radiation absorbing material is disposed between the solar cell and the outer surface of the second substrate.

21. The liquid crystal display of claim 12 wherein said first set of electrodes comprise a plurality of substantially parallel electrode segments and said second set of electrodes comprise a plurality of substantially parallel electrode segments, said first set of electrodes extending transverse to said second set of electrodes.

22. The liquid crystal display of claim 12 wherein the energy storage device is a rechargeable battery.

23. The liquid crystal display of claim 12 wherein the solar cell assembly includes a DC/DC voltage converter to increase a magnitude of voltage output to the drive circuitry.

24. A liquid crystal display device comprising chiral nematic liquid crystal material, cell wall structure communicating with said liquid crystal material to form focal conic and reflective planar textures that are stable in the absence of an electric field, a solar cell device for converting electromagnetic radiation that has passed through said liquid crystal material into electrical energy, and means for applying an electrical field to said liquid crystal material to place at least a portion thereof into at least one of the focal conic and planar textures.

25. The display device of claim 24 wherein said cell wall structure comprises substrates between which said liquid crystal material is disposed.

26. The display device of claim 25 wherein said solar cell device comprises a panel composed of silicon disposed adjacent and downstream one of said substrates relative to a direction of incident radiation through said liquid crystal material.

27. The display device of claim 26 comprising a layer of at least one of visible light absorbing and infrared transmissive material disposed between said one substrate and said panel.

28. The display device of claim 27 wherein said layer allows the passage of infrared radiation therethrough.

29. The display device of claim 24 where said liquid crystal material has a pitch length effective to reflect visible light.

30. The display device of claim 29 wherein said liquid crystal material has a pitch length effective to reflect infrared radiation.

31. The display device of claim 24 wherein said cell wall structure bounds a first region of liquid crystal material having a pitch length effective to reflect visible light and a second region of liquid crystal material having a pitch length effective to reflect infrared radiation.

32. The display device of claim 25 comprising at least two layers of said liquid crystal material disposed between said substrates and isolated from communication with one another.

33. The display device of claim 32 wherein said liquid crystal material in said layers has a pitch length effective to reflect visible light.

34. A liquid crystal display comprising:

a) a layer of reflective chiral nematic liquid crystal material;

b) first substrate and a spaced apart second substrate, an inner surface of the first substrate and an inner surface of the second substrate bounding said liquid crystal material layer, the first substrate being closer than the second substrate to a viewer of the display;

c) display driver circuitry for changing a reflective state of selected image pixels of the display, the image pixels associated with respective different regions of the liquid crystal material layer; and

e) the second substrate comprising at least one solar cell electrically coupled to the display driver circuitry, the at least one solar cell receiving illumination passing through the first substrate and said liquid crystal material and converting said illumination to electrical energy to supply power to the display driver circuitry.

35. The liquid crystal display of claim 34 further including an energy storage device coupled to and providing power to said display driver circuitry, the at least one solar cell electrically coupled to and supplying power to said energy storage device.

36. The liquid crystal display of claim 34 wherein the display further includes a first set of conductive electrodes disposed on the inner surface of the first substrate and a second set of conductive electrodes spaced apart from the first set of electrodes and disposed on the inner surface of the second substrate bounding said liquid crystal material layer and the display driver circuitry is electrically coupled to the first and the second set of conductive electrodes for generating desired voltage differentials between electrodes of the first set of conductive electrodes and electrodes of the second set of conductive electrodes, the image pixels being defined by regions of the liquid crystal material layer adjacent intersections of the first set of conductive electrodes and the second set of conductive electrodes, a reflective state of an image pixel being dependent upon a voltage differential between an electrode of the first set of conductive electrodes and an electrode of the second set of conductive electrodes associated with the image pixel.

37. The liquid crystal display of claim 34 wherein the first and second substrates are comprised of glass.

38. The liquid crystal display of claim 36 wherein said first set of electrodes comprise a plurality of substantially parallel electrode segments and said second set of electrodes comprise a plurality of substantially parallel electrode segments, said first set of electrodes extending transverse to said second set of electrodes.

39. A liquid crystal display comprising:

a) a plurality of layers of reflective chiral nematic liquid crystal material;

b) a plurality of spaced apart substrates bounding the plurality of liquid crystal material layers, a back substrate being positioned furthest from a viewer of the display;

c) display driver circuitry for changing a reflective state of aligned portions of the plurality of liquid crystal material layers comprising an image pixel; and

d) a solar cell assembly including a solar cell disposed on the back substrate and electrically coupled to the display driver circuitry, the solar cell receiving illumination passing through the plurality of spaced apart substrates and the plurality of liquid crystal material layers and converting said illumination to electrical energy to supply power to the display driver circuitry.

40. A liquid crystal display device comprising:

chiral nematic liquid crystal material;

cell wall structure confining said liquid crystal material;

display driver circuitry for generating voltage differentials across said liquid crystal material effective to place said liquid crystal material into at least one of focal conic and planar textures; and

a photovoltaic cell positioned so as to receive electromagnetic radiation passing through said liquid crystal material for converting said radiation into electrical energy.

41. The liquid crystal display device of claim 40 wherein said display device has no polarizer.

42. The liquid crystal display device of claim 41 wherein said display device has no reflector.

43. The liquid crystal display device of claim 40 comprising a layer of material disposed between said liquid crystal material and said photovoltaic cell which restricts reflection toward said liquid crystal material while permitting passage of electromagnetic radiation to said photovoltaic cell.

44. The liquid crystal display device of claim 40 comprising a plurality of electrodes disposed on said cell wall structure and bounding said liquid crystal material, said electrodes being electrically coupled to said display driver circuitry.

45. The liquid crystal display of claim 40 comprising a plurality of electrodes and transistors disposed on said cell wall structure and bounding said liquid crystal material, said electrodes and said transistors being electrically coupled to said display driver circuitry.

46. The liquid crystal display device of claim 40 comprising an energy storage device electrically coupled to said photovoltaic cell for receiving the electrical energy generated by said photovoltaic cell.

47. A liquid crystal display device comprising:

chiral nematic liquid crystal material;

cell wall structure confining said liquid crystal material, said cell wall structure communicating with said liquid crystal material to form focal conic and planar textures that are stable In the absence of an electric field, said cell wall structure comprising a transparent front substrate near an external front surface of said display device;

display driver circuitry for generating voltage differentials across said liquid crystal material effective to form an image that is displayed through said transparent front substrate to a viewer; and

a photovoltaic cell positioned behind said liquid crystal material so as not to occupy the external front surface of said display device effective to receive electromagnetic radiation passing through said liquid crystal material for converting said radiation into electrical energy.

48. The liquid crystal display device of claim 47 wherein said display device has no polarizer.

49. The liquid crystal display device of claim 47 comprising a layer of material disposed between said liquid crystal material and said photovoltaic cell which restricts reflection toward said liquid crystal material while permitting passage of electromagnetic radiation to said photovoltaic cell.

50. The liquid crystal display device of claim 47 comprising an energy storage device electrically coupled to said photovoltaic cell for receiving the electrical energy generated by said photovoltaic cell.