Liquid crystal color display and method

• US 4,878,741 A
• Filed: 12/16/1986
• Issued: 11/07/1989
• Est. Priority Date: 09/10/1986
• Status: Expired due to Fees

• Current Assignee: Manchester R & D Partnership
• Original Assignee: Manchester R & D Partnership
• Inventors: Fergason, James L.
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US06/942,548
• Time in Patent Office: 1,057 Days
• Field of Search: 350/339 F, 350/334, 350/336, 350/349, 350/332
• US Class Current: 349/79
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
• CPC Class Codes: G02F 1/13475 in which at least one liquid crystal cell or layer is doped with a pleochroic dye, e.g. GH-LC cell G02F1/13476 takes precedence

Abstract

A liquid crystal color display (20) provides a transmitted light output of one or more colors, black, and/or white, as a function of incident light and controlled energization or not of respective optically serially positioned liquid crystal color layers (2, 3, 4) and/or multicolor composite liquid crystal color layer(s) in the display. Plural optically serially arranged volumes (21) of operationally nematic liquid crystal material (25) having different optical characteristics, e.g. being dyed with different pleochroic dyes (28), may be selectively aligned or not with respect to an electric field to determine optical output of the device in a subtractive color mode. Exemplary colors of pleochroic dye include yellow, cyan and magenta, and black dye may be used to control saturation or hue. Non-pleochroic dye also may be used in one or more layers of the liquid crystal color display to filter or to color light transmitted therethrough thereby to cooperate with the pleochroic dye to provide a final color output. Additionally, individual pixel-like areas (72, 73, 74) of the liquid crystal color display may be so positioned in proximity to each other to operate in a color additive mode. Techniques for discriminating voltage and/or frequency enable a multicolor response using only a single pair of electrodes. Using cross over liquid crystal material having positive and negative dielectric anisotropy characteristics as a function of frequency of applied signal, multiplex driving of the liquid crystal color display is facilitated.

Claims

1. An optical device, comprising an assemblage of plural groups of volumes of liquid crystal material, a plurality of said volumes comprising discrete capsules formed by containment medium of isolating polymer containing therein said liquid crystal material, the liquid crystal material in at least one of said groups comprising nematic or operationally nematic liquid crystal, the device being formed in such a way to maintain adequate resistivity to obtain a field across the liquid crystal material in response to an applied voltage to cause alignment of said liquid crystal material with respect to such field, said resistivity being obtained by purifying at least part of the containment medium prior to formation of the device.

2. An optical device, comprising plural groups of volumes of liquid crystal in a containment medium, a plurality of such groups containing in the volumes thereof respective pleochroic dye to color light transmitted therethrough, said volumes being arranged relative to each other in generally optically serial relation to affect color of light transmitted therethrough in a subtractive color operation, and at least one of such groups containing in the volumes thereof black pleochroic dye operative selectively to attenuate light incident thereon.

3. The device of claim 2, said group containing in the volumes thereof black pleochroic dye being operative to control brightness of light transmitted through the device.

4. The device of claim 2, said groups of volumes being responsive to application of a prescribed input to be substantially optically transmissive with minimum filtering of light transmitted therethrough, thereby to produce a substantially white output.

5. The device of claim 2, wherein each group of plural volumes is in a separate layer separated from one or more relatively adjacent layers by electrode means, said electrode means being operative for applying electric field to respective layers as a prescribed input to affect the alignment of liquid crystal structure and dye structure in such volumes.

6. The device of claim 5, wherein at least one layer is more proximately exposed to a source of external optical radiation than another layer, and the liquid crystal in said more proximately exposed layer includes pleochroic dye that removes at least a substantial amount of ultraviolet optical radiation from such optical radiation emitted by such source prior to passing such optical radiation to a less proximately exposed layer.

7. The device of claim 5, wherein said volumes distort the natural structure of the liquid crystal in the absence of an electric field, and in the presence of such electric field the liquid crystal structure tends to align with respect to such field.

8. The device of claim 7, such alignment in the presence of a field being generally parallel or perpendicular to the field.

9. The device of claim 5, wherein the liquid crystal material in at least one group of plural volumes comprises nematic or operationally nematic liquid crystal.

10. The device of claim 5, wherein said electrode means comprises plural strip-like electrodes on one side of one layer and plural strip-like electrodes on the other side of one layer to effect a crossed-electrode pattern thereby to define individual pixel-like areas between each pair of crossed electrodes.

11. The device of claim 10, wherein each of said electrode means comprises plural strip-like electrodes thereby to form crossed electrode patterns for each layer of plural volumes.

12. The device of claim 11, wherein there are four layers of plural volumes, three of such layers comprising color pleochroic dye, and a fourth such layer comprising black plepchroic dye, and said electrode means comprises five layers of electrodes, one layer at each side of each layer of liquid crystal volumes.

13. The device of claim 2, wherein there are four layers of plural volumes, three of such layers comprising color pleochroic dye, and a fourth such layer comprising black pleochroic dye, and said liquid crystal material in such three color layers having a relatively low difference between the ordinary and extraordinary indices of refraction and such indices being substantially matched to the index of refraction of such containment medium.

14. The device of claim 13, said liquid crystal material in such fourth black layer having a relatively high difference between the ordinary and extraordinary indices of refraction and the ordinary index of refraction of such liquid crystal material being substantially matched to the index of refraction of said containment medium of such group.

15. The device of claim 14, said electrode means comprises five layers of electrodes, one layer at each side of each layer of liquid crystal volumes.

16. The device of claim 15, wherein at least one layer is more proximately exposed to a source of external optical radiation than another layer, and the liquid crystal in said more proximately exposed layer includes pleochroic dye that removes at least a substantial amount of ultraviolet optical radiation from such optical radiation emitted by such source prior to passing such optical radiation to a less proximately exposed layer.

17. An optical device, comprising plural groups of volumes of liquid crystal in a containment medium, a plurality of such groups containing in the volumes thereof respective pleochroic dye to color light transmitted therethrough, said volumes being arranged relative to each other in generally optically serial relation to affect color of light transmitted therethrough in a subtractive color operation, and at least one of such groups containing in the volumes thereof black pleochroic dye operative selectively to attenuate light incident thereon, wherein each group of plural volumes is in a separate layer separated from one or more relatively adjacent layers by electrode means, said electrode means being operative for applying electric field to respective layers as a prescribed input to affect the alignment of liquid crystal structure and dye structure in such volumes, wherein at least one layer is more proximately exposed to a source of external optical radiation than another layer, and the liquid crystal in said more proximately exposed layer includes pleochroic dye that removes at least a substantial amount of ultraviolet optical radiation from such optical radiation emitted by such source prior to passing such optical radiation to a less proximately exposed layer, and wherein said volumes distort the natural structure of the liquid crystal in the absence of an electric field, and in the presence of such electric field the liquid crystal structure tends to aling with respect to such field.

18. A liquid crystal device, comprising a first plurality of volumes of a first liquid crystal material and a second plurality of volumes of a second liquid crystal material, said volumes being formed by containment medium means for tending to distort the natural structure of the liquid crystal material in the absence of a prescribed input, said second liquid crystal material having dielectric anisotropy that is frequency dependent so as to undergo a change in sign, whereby the optical transmission characteristics of the device are a function of the magnitude and frequency of prescribed input applied to said liquid crystal materials.

19. The device of claim 18, at least one of said liquid crystal materials being nematic or operationally nematic.

20. The device of claim 18, wherein in response to an applied electric field as such as prescribed input, at relatively low frequency the threshold level of said second liquid crystal material at which such liquid crystal structure aligns generally in parallel with respect to such field is lower than the threshold level of said first liquid crystal material, and at relatively high frequency the dielectric anisotropy of said second liquid crystal material changes sign, whereby the same becomes aligned relatively perpendicular generally with respect to such electric field.

21. The device of claim 18, further comprising pleochroic dye in said volumes of liquid crystal material, whereby at least one of the color, intensity, saturation or hue of light transmitted through said volumes of liquid crystal material and pleochroic dye is a function of alignment of such liquid crystal material and dye therein.

22. The device of claim 21, wherein the pleochroic dye in said first liquid crystal material is one color and the pleocroic dye in said second liquid crystal material is another color.

23. The device of claim 21, wherein in response to an applied electric field as such prescribed input, at relatively low frequency the threshold level of said second liquid crystal material at which such liquid crystal structure aligns generally in parallel with respect to such field is lower than the threshold level of said first liquid crystal material, and at relatively high frequency the dielectric anisotropy of said second liquid crystal material changes sign, whereby the same becomes aligned relatively perpendicular generally with respect to such electric field.

24. The device of claim 23, further comprising a third plurality of volumes of a liquid crystal material having a further pleochroic dye therein.

25. The device of claim 24, further comprising a fourth plurality of volumes of a liquid crystal material therin having a black pleochroic dye therein.

26. The device of claim 23, at least one of said liquid crystal materials being nematic or operationally nematic.

27. The device of claim 18, said first plurality of volumes comprising a plurality of isolating capsules of a containment medium containing said first liquid crystal material.

28. The device of claim 27, said isolating capsules being arranged in a first layer, and said second plurality of volumes of second liquid crystal material being arranged in a layer substantially separate and optically serially related to said first layer.

29. The device of claim 28, wherein said second plurality of volumes of second liquid crystal material comprises an emulsion of said second liquid crystal material and a second containment medium.

30. The device of claim 28, further comprising a single pair of electrode means for applying electric field to both said first layer and said second layer as such prescribed input thereto.

31. The device of claim 30, at least one of said electrode means comprises plural electrode strips.

32. The device of claim 31, wherein both pairs of electrode means comprises plural electrode strips respectively arranged on opposite sides of said layers in a crossed electrode pattern to form plural pixel-like areas therebetween.

33. The device of claim 32, said isolating capsules being arranged in a first layer, and said second plurality of volumes of second liquid crystal material comprising a plurality of volumes of said second liquid crystal material distributed within the plurality of isolating capsules, whereby plural volumes of said first and second pluralities thereof are arranged in generally optical serial relation.

34. The device of claim 33, said second plurality of volumes comprising a plurality of isolating capsules of a containment medium containing said second liquid crystal material.

35. A liquid crystal device, comprising a first plurality of volumes of a first liquid crystal material and a second plurality of volumes of a second liquid crystal material, said volumes being formed by containment medium means for tending to distort the natural structure of the liquid crystal material in the absence of a prescribed input, said second liquid crystal material having dielectric anisotropy that is frequency dependent, whereby the optical transmission characteristics of the device are a function of the magnitude and frequency of prescribed input applied to said liquid crystal materials, and said first plurality of volumes comprising a plurality of isolating capsules of a containment medium containing said first liquid crystal material, said isolating capsules being arranged in a first layer, and said second plurality of volumes of second liquid crystal material being arranged in a layer substantially separate and optically serially related to said first layer, and, wherein at least one layer is more proximately exposed to a source of external optical radiation than another layer, and the liquid crystal in said more proximately exposed layer includes pleochroic dye that removes at least a substantial amount of ultraviolet optical radiation from such optical radiation emitted by such source prior to passing such optical radiation to a less proximately exposed layer.

36. A liquid crystal device, comprising a first plurality of volumes of a first liquid crystal material and a second plurality of volumes of a second liquid crystal material, said volumes being formed by containment medium means for tending to distort the natural structure of the liquid crystal material in the absence of a prescribed input, said second liquid crystal material having dielectric anisotropy that is frequency dependent, whereby the optical transmission characteristics of the device are a function of the magnitude and frequency of prescribed input applied to said liquid crystal materials, and, wherein at least one of said liquid crystal materials has a cross-over with respect to frequency of the dielectric anisotropy.

37. The device of claim 36, wherein both liquid crystal materials have a cross-over with respect to frequency of the dielectric anisotropy.

38. The device of claim 37, wherein such cross-over frequencies are different.

39. The device of claim 38, further comprising input means for supplying as a prescribed input to said volumes of liquid crystal material first and second electrical signals, each having a relatively low and a relatively high frequency component that are respectively additive to apply a resultant field to such volumes of liquid crystal material.

40. The device of claim 39, wherein said input means comprises circuit means for applying first and second electrical signals to said liquid crystal material such that the amplitude of each alone is less than the amplitude required to effect a responsive alignment function of liquid structure with respect thereto.

41. The device of claim 39, wherein said circuit means includes means for shifting the phase relation of at least one of the high and low frequency components of one electrical signal relative to the phase of the respective high and low frequency component of the other electrical signal.

42. Apparatus for signal discrimination, comprising plural volumes of liquid crystal material in a containment medium, said liquid crystal material having has a positive dielectric anisotropy in one frequency domain and a negative dielectric anisotropy in a second frequency domain, the effect of which is to discriminate between applied electrical inputs, and electrical input means for applying such electrical inputs to said liquid crystal material, and wherein said containment medium comprises a containment medium means for containing said liquid crystal material, said containment medium means including surface means for distorting the natural structure of the liquid crystal material in the absence of a prescribed electrical input, and such liquid crystal being responsive to an applied electric field in said one frequency domain to align generally in parallel with respect to such field and being responsive to an applied electric field in said second frequency domain to undergo non-alignment with respect thereto as a function of different polarity dielectric anisotropy of said liquid crystal.

43. The apparatus of claim 42, said liquid crystal comprising nematic of operationally nematic liquid crystal material.

44. The apparatus of claim 42, further comprising pleochroic dye in the liquid crystal material, whereby the color or brightness of light transmitted through said liquid crystal material is a function of such electrical inputs.

45. The apparatus of claim 44, further comprising a second plurality of volumes of a liquid crystal material, said second plurality of volumes having a different optical characteristic from the optical characteristic of said first plural volumes of liquid crystal and pleochroic dye, and said second plurality of volumes having a different electrical response characteristic to an applied electric field than the response characteristic of said first plural volumes of liquid crystal and pleochroic dye further to effect discrimination of electrical input.

46. The apparatus of claim 45, said second plurality of volumes of liquid crystal including pleochroic dye, and said different optical characteristic being a function of said pleochroic dye.

47. A liquid crystal device, comprising plural volumes of liquid crystal material, said liquid crystal material having a natural structure which in the absence of a prescribed input is distorted by surface means defining said volumes, whereby in response to such distortion said volumes of liquid crystal material at least one of scatter or absorb light, and further comprising input means for supplying as a prescribed input to said volumes of liquid crystal material first and second electrical signals, each having a relatively low and a relatively high frequency component that are respectively additive to apply a resultant field to such volumes of liquid crystal material, and wherein said liquid crystal material comprises cross over liquid crystal material having two different dielectric anisotropy characteristics as a function of frequency of input electrical signal thereto, and said input means comprises a circuit means for applying such first and second electrical signals such that the amplitude of each alone is less than the amplitude required to effect a responsive alignment function of liquid structure with respect thereto.

48. The device of claim 47, wherein said circuit means includes means for shifting the phase relation of at least one of the high and low frequency components of one electrical signal relative to the phase of the respective high and low frequency component of the other electrical signal.

49. The device of claim 47, further comprising pleochroic dye in said liquid crystal material, said dye being optically absorbing when said liquid crystal structure is aligned in generally distorted condition out of generally parallel alignment with an applied electric field;

and said dye being generally optically transmissive and less absorbing when said liquid crystal structure is aligned generally in parallel with respect to an applied electric field.

50. The device of claim 47, said plural volumes being arranged in a first layer, and further comprising a second layer of plural volumes of liquid crystal material having a natural structure which in the absence of a prescribed input is distorted by surface means defining said volumes, whereby in response to such distortion said volumes of liquid crystal material at least one of scatter or absorb light, at least one of said liquid crystal materials comprising cross over liquid crystal material.

51. The device of claim 50, wherein said input means is operative to apply such electrical signals to both layers of volumes of liquid crystal material.

52. The device of claim 50, further comprising electrode means for applying such electrical signals to said layers of volumes of liquid crystal material, said electrode means including a scan electrode between said layers and respective signal electrodes on opposite sides of said layers relative to said scan electrode.

53. The device of claim 52, wherein each of said electrodes comprises plural electrode strips oriented such that said scan electrode strips are generally crossed relative to the signal electrode strips to define pixel-like areas of respective layers of volumes of liquid crystal material.

54. A liquid crystal color display, comprising a layer of plural volumes of operationally nematic liquid crystal in a containment medium, electrode means for applying electric field to said layer or to parts thereof, a power supply means for applying a prescribed input to said layer selectively to effect parallel alignment of the liquid crystal, and pleochroic dye in plural volumes of said liquid crystal and non-pleochroic dye in at least one of said liquid crystal and containment medium.

55. The display of claim 54, wherein said pleochroic dye has a structure that follows the liquid crystal structure so as to absorb or to color light when distorted or not aligned generally in parallel generally with respect to the direction of propagation of light therethrough and to reduce the amount of such absorption when the dye structure aligns generally in the direction of light propagation.

56. The display of claim 55, wherein said pleochroic dye and non-pleochroic dye are complementary colors.

57. A method of controlling light, comprising directing light to a liquid crystal device having a layer of plural volumes of operationally nematic liquid crystal in a containment medium, pleochroic dye in said liquid crystal and non-pleochroic dye in at least one of the containment medium and liquid crystal, such containment medium having surface means for distorting the natural structure of the liquid crystal in the absence of a prescribed input, when no prescribed input is applied allowing both the pleochroic dye and the non-pleochroic dye will tend to affect light incident thereon, and selectively applying a prescribed input to such liquid crystal material to reduce the coloring effect of the pleochroic dye while permitting the coloring effect of the non-pleochroic dye to continue coloring light.

58. The method of claim 57, further comprising selecting such dyes to be complementary colors to provide a black light output in the absence of such prescribed input and to provide a color output due to the non-pleochroic dye in the presence of such prescribed input.

59. A liquid crystal device, comprising plural volumes of liquid crystal material, said liquid crystal material having a natural structure which in the absence of a prescribed input is distorted by surface means defining said volumes, whereby in response to such distortion said volumes of liquid crystal material at least one of scatter or absorb light, and further comprising input means for supplying as a prescribed input to said volumes of liquid crystal material first and second electrical signals, each having at least one of a relatively low and a relatively high frequency component that is respectively additive to apply a resultant field to such volumes of liquid crystal material.

60. The device of claim 59, in which each signal alone is of inadequate amplitude to effect a responsive alignment of liquid crystal structure.

61. The device of claim 60, wherein said input means includes phase shifting means for shifting the phase of at least one of said signals relative to the phase of the other of said signals.

62. The device of claim 59, further comprising one color pheochroic dye in a first plurality of said volumes of liquid crystal material.

63. The device of claim 62, further comprising a different color pleochroic dye in a second plurality of said volumes of liquid crystal material, at least some of said volumes of said first and second pluralities of volumes being optically serially aligned for subtractive color operation.

64. A liquid crystal apparatus comprising a composite layer containing two or more liquid crystal compositions that respond differently to a prescribed input, and input means for applying such prescribed input, said different response being a sign of dielectric anisotropy.

65. The apparatus of claim 64, said different response being absorption of light.

66. A liquid crystal apparatus comprising two or more liquid crystal compositions placed in intimate but non-mixing relation such that the liquid crystal compositions function in optical serial relation without parallax, said liquid crystal compositions being operative to discriminate at least one characteristic of such prescribed input, wherein a plurality of said liquid crystal compositions respectively have different size volumes of liquid crystal in a containment medium and are capable of discriminating as a function of such size.

67. A liquid crystal apparatus comprising a composite layer containing two or more liquid crystal compositions that respond differently to a prescribed input, and input means for applying such prescribed input, said different response being a sign of dielectric anisotropy, said input means comprising electrodes.

68. The apparatus of claim 67, said input means comprising a single pair of electrodes for addressing substantially all parts of said composite layer.

69. The apparatus of claim 67, said electrodes comprising one electrode on one side of said composite layer, one electrode on the other side of said composite layer, and one electrode between said composite layers for cooperating with both of said first-mentioned electrodes to apply electric field to respective liquid crystal compositions.

70. In combination, at least three groups of volumes of liquid crystal, each group comprising liquid crystal material, pleochroic dye of a respective color and a containment medium for containing therein said liquid crystal material and pleochroic dye, said volumes being aligned in optical series, and means for applying a prescribed input to at least some of said volumes to affect the filtering of light by the pleochroic dye therein, and wherein said groups are arranged in relatively close proximity to each other to achieve substantially parallax-free operation.

71. The combination of claim 70, wherein said dyes are cyan, magenta and yellow, respectively.

72. A liquid crystal device, comprising plural volumes of liquid crystal material and pleochroic dye in a containment medium, and non-pleochroic dye in at least one of said liquid crystal material and containment medium;

said pleochroic dye and said non-pleochroic dye being complementary colors.

73. The device of claim 72, said liquid crystal material having comprising operationally nematic liquid crystal having a natural structure that in the absence of a prescribed input is distorted by a surface of said volumes whereupon said pleochroic dye and non-pleochroic dye cooperate to produce a black output;

and said liquid crystal material being responsive to a prescribed input to undergo generally parallel alignment to reduce the affect of the pleochroic dye, whereby primary coloring of light transmitted through the device is a function of the color of said non-pleochroic dye.

74. A multicolor display comprising plural picture elements formed of the device of claim 73.

75. The device of claim 74, further comprising electrical means for selectively providing electric field to selected picture elements.

76. An optical switch, comprising plural volumes of liquid crystal material in a containment medium, pleochroic dye in said liquid crystal, and non-pleochroic dye in at least one of said liquid crystal and containment medium, said dyes being of complementary colors, and input means for applying a prescribed input to said liquid crystal material to determine the transmission of light by the switch.

77. An optical device, comprising plural groups of volumes of liquid crystal in a containment medium, a plurality of such groups containing in the volumes thereof respective pleochroic dye to color light transmitted therethrough, said volumes being arranged relative to each other in generally optically serial relation to affect color of light transmitted therethrough in a substractive color operation, and further comprising a layer of a plurality of volumes of liquid crystal and pleochroic dye, said layer being more proximately exposed to a source of external optical radiation than another said other groups of volumes of liquid crystal in a containment medium, and the liquid crystal in said more proximately exposed layer includes pleochroic dye that removes at least a substantial amount of ultraviolet optical radiation from such optical radiation emitted by such source prior to passing such optical radiation to other groups of volumes.

78. An optical device, comprising plural groups of volumes of liquid crystal in a containment medium, a plurality of such groups containing in the volumes thereof respective pleochroic dye to color light transmitted therethrough, said volumes being arranged relative to each other in generally optically serial relation to affect color of light transmitted therethrough in a subtractive color operation, and wherein said liquid crystal material in a plurality of said groups having a relatively low difference between the ordinary and extraordinary indices of refraction and such indices being substantially matched to the index of refraction of such containment medium.

79. The device of claim 78, wherein one group of volumes includes black pleochroic dye, and said liquid crystal material in said one group has a relatively high difference between the ordinary and extraordinary indices of refraction and the ordinary index of refraction of such liquid crystal material being substantially matched to the index of refraction of said containment medium of such group.