Fluorescent colored encapsulated liquid crystal apparatus using enhanced scattering

• US 4,856,876 A
• Filed: 06/23/1986
• Issued: 08/15/1989
• Est. Priority Date: 03/30/1983
• Status: Expired due to Term

• 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): Gallivan, Richard F.
• Application Number:
  US06/877,109
• Time in Patent Office: 1,149 Days
• Field of Search: 350/334, 350/339 F, 350/347 V, 350/350 F, 350/351
• US Class Current: 349/66
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/1335 Structural association of cells with optical devices, e.g. polarisers or reflectors
• CPC Class Codes: G02F 2202/04 dye

Abstract

The present invention relates to use of liquid crystal material encapsulated in a containment medium to produce a controlled colored output, for example, in response to the application, removal and variation in an electric field. In one embodiment a non-pleochroic dye is in the containment medium itself and in another embodiment the non-pleochroic dye is in the liquid crystal material itself; and in both cases the dye preferably is fluorescent or a combination of fluorescent and non-fluorescent, and the object is to color light and/or to whiten or to brighten the light emitted out from a display embodying the invention. Incident light impinging on the encapsulated liquid crystal material, which is mounted on, in, or with respect to a support medium, is isotropically scattered in the absence of an electric field, and using the principle of total internal reflection (or optical interference or both) a relatively large part of the isotropically scattered light in the support medium is reflected back to illuminate the scattering liquid crystal material, which isotropically scatters such light again, thus increasing the optical path through the dyed material and, therefore, the coloring, whitening and/or brightening of the light traveling such increased path. Light scattered back to the viewing direction out of the support medium causes the liquid crystal material to appear relatively bright and colored as compared to the background where there is no liquid crystal material or where the liquid crystal material is in parallel alignment in field-on condition, i.e. aligned with respect to an electric field, and, thus, substantially transmissive.

Claims

1. A liquid crystal apparatus, comprising liquid crystal material, surface means for distorting the natural structure of said liquid crystal material in the absence of a prescribed input to cause scattering of light, said liquid crystal being responsive to a prescribed input to reduce the amount of such scattering, and fluorescent means for fluorescing during such scattering of light.

2. The apparatus of claim 1, wherein said liquid crystal material is operationally nematic liquid crystal.

3. The apparatus of claim 2, wherein said liquid crystal material has positive dielectric anisotropy.

4. The apparatus of claim 1, said fluorescent means comprises fluorescent dye.

5. The apparatus of claim 4, said dye being responsive to incident light and to scattered light to re-radiate light at a relatively lower wavelength.

6. The apparatus of claim 4, said dye being operative to effect brightening of light emitted by the apparatus in the absence of an electric field.

7. The display of claim 1, said dye being in said liquid crystal.

8. The apparatus of claim 1, further comprising a containment medium means for containing said liquid crystal material in volumes, said dye being contained in said containment medium means, and said surface means comprising a wall formed by said containment medium means.

9. The apparatus of claim 8, further comprising a support medium means for supporting said contained liquid crystal, said support medium means being capable of total internal reflection.

10. The apparatus of claim 9, further comprising a further medium means cooperative with said support medium means to form an interface effective to cause such total internal reflection of light impinging on such interface at an angle exceeding a predetermined angle with respect to normal.

11. The apparatus of claim 10, said further medium comprising a layer of air.

12. The apparatus of claim 10, wherein the index of refraction of said support medium means exceeds the index of refraction of said further medium means.

13. The apparatus of claim 12, further comprising a tuned dielectric interference layer of material for effecting selective constructive and destructive interference with respect to light transmitted through a surface of said support medium means.

14. The apparatus of claim 13, said support medium means having a viewing surface through which light may be transmitted in both directions and an opposite surface, and said tuned dielectric interference layer comprising a layer of material on said opposite surface.

15. The apparatus of claim 9, said support medium means having a viewing surface through which light may be transmitted in both directions and an opposite surface, said viewing surface being substantially totally internally reflective as to light in said support medium means impinging thereon at an angle to normal greater than a predetermined magnitude.

16. The apparatus of claim 9, further comprising optical absorbing means for absorbing light transmitted through said support medium means.

17. The apparatus of claim 9, said liquid crystal and containment medium means comprising encapsulated liquid crystal material.

18. The apparatus of claim 17, said support medium means being capable of total internal reflection to cause reflection of light therein along relatively long path lengths through said dye to color such light.

19. The apparatus of claim 1, further comprising means for selectively changing the ordered or random alignment of such liquid crystal to effect, respectively, optical transmission or isotropic scattering of light incident on such liquid crystal.

20. The apparatus of claim 1, said surface means comprising a cross linked containment medium means for containing said liquid crystal material.

21. The apparatus of claim 20, said containment medium means being formed of a mixture of polyvinyl alcohol and Gantrez, on the one hand, and said liquid crystal material, on the other hand.

22. The apparatus of claim 1, further comprising housing means for containing said liquid crystal material surface means and fluorescent means, input means for providing radiation input to said liquid crystal material and fluorescent means, and output means for emitting light in response to fluorescence by said fluorescent means.

23. The apparatus of claim 22, further comprising radiation means for generating such radiation input, said radiation means being positioned out of line of sight of said output means to prevent direct transmission of radiation from said radiation means to said output means.

24. The apparatus of claim 23, further comprising means for providing a prescribed input to said liquid crystal material to align the same so as to reduce scattering of light and to reduce fluoresced radiation.

25. A liquid crystal display comprising liquid crystal means for selectively isotropically scattering light or transmitting light, substantially transparent support medium means for supporting said liquid crystal means, and dye colorant in said support medium means for coloring light isotropically scattered in said support medium means, said dye comprising fluorescent material.

26. The display of claim 25, said support medium means being capable of total internal reflection of light isotropically scattered therein by said liquid crystal means, said dye coloring light isotropically scattered and totally internally reflected in said support medium means.

27. The display of claim 25, said support medium means at least substantially fully enclosing said liquid crystal means on all sides as a containment medium.

28. The display of claim 25, said liquid crystal means comprising encapsulated liquid crystal, said support medium being a water base material and said dye being water soluble.

29. The display of claim 28, further comprising means for selectively changing the alignment of such liquid crystal between distorted and ordered alignment to effect isotropic scattering and transmission of light, respectively.

30. The display of claim 25, said liquid crystal means being positioned in at least one layer in said support medium means in a pattern to display predetermined information.

31. The display of claim 25, said support medium means comprising a containment medium means for containing quantities of liquid crystal means in capsule-like environments as encapsulated liquid crystal and support means for supporting said encapsulated liquid crystal.

32. Liquid crystal apparatus comprising liquid crystal means for selectively primarily scattering or transmitting light in response to a prescribed input, a support medium means for holding therein such liquid crystal means, said support medium means having a characteristic of total internal reflection, and dye means in at least one of said liquid crystal means and said support medium means for coloring ligh transmitted therein, said support medium means comprising a containment medium means for forming with said liquid crystal means encapsulated liquid crystal and a support means for supporting said encapsulated liquid crystal, said support means having a viewing surface and an opposite side, the index of refraction of said support means being greater than the index of refraction of at least one of the media respectively at such viewing and opposite sides forming an interface therewith to effect total internal reflection of light in said support means incident on such interface at an angle exceeding a predetermined cone of light angle at which light would be transmitted through such interface, said dye comprising fluorescent dye material.

33. The apparatus of claim 32, said dye comprising non-pleochroic dye dissolved in said containment medium means.

34. The apparatus of claim 32, said dye comprising non-pleochroic dye dissolved in said liquid crystal means.

35. The apparatus of claim 32, said dye further comprising a water soluble pigmented dye dissolved in said containment medium.

36. The apparatus of claim 32, wherein said viewing side emits light transmitted in said support means to impinge on said viewing side at an angle less than a predetermined angle with respect to normal as colored illumination when said liquid crystal means is in random alignment.

37. A method of making a liquid crystal apparatus comprising placing an encapsulated liquid crystal material in or on a support medium, and placing a fluorescent dye in at least one of such encapsulated liquid crystal material and support medium.

38. The method of claim 37, comprising forming a plurality of volumes of liquid crystal in a containment medium to make such encapsulated liquid crystal.

39. The method of claim 38, said forming comprising mixing such liquid crystal and containment medium to form volumes of liquid crystal with surface means for distorting the natural structure of the liquid crystal in the absence of a prescribed input.

40. The method of claim 37, said placing a dye comprising placing a non-pleochroic dye in such encapsulated liquid crystal material.

41. The method of claim 37, said placing a dye comprising placing a non-pleochroic dye.

42. The method of claim 37, wherein such support medium has a substantial internal reflection characteristic, and further comprising providing a further medium at an interface with such support medium and selecting the index of refraction of such support medium to be greater than the index of refraction of such further medium, whereby total internal reflection of light will occur in such support medium with respect to light impinging on such interface at an angle less than a predetermined angle with respect to normal.

43. The method of claim 42, further comprising applying a light absorbing material beyond such further medium for absorbing light transmitted through such further medium.

44. The method of claim 37, further comprising applying a tuned dielectric interference layer to a surface of such support medium opposite the surface at which such support medium ordinarily is viewed.

45. The method of claim 37, comprising mixing a water soluble dye in a water base containment medium for encapsulating liquid crystal material.

46. The combination of operationally nematic liquid crystal material contained in a generally spherical capsule of encapsulating medium, said encapsulating medium having a wall, the ordinary index of refraction of said liquid crystal material being approximately the same as the index of refraction of the encapsulating medium, and non-pleochroic fluorescent dye in at least one of said liquid crystal material and encapsulating medium.

47. The combination of claim 46, said containment medium comprising a water base material, and said dye comprising a water soluble dye dissolved in said containment medium.

48. The combination of claim 46, said liquid crystal material comprising an oil base material, and said dye comprising an oil soluble dye dissolved in said liquid crystal material.

49. An optical apparatus for providing a color output comprising an operationally nematic liquid crystal, containment medium means for containing said liquid crystal, support medium means for supporting said containment medium means and liquid crystal, and non-pleochroic dye, said liquid crystal means having positive dielectric anisotropy and having an ordinary index of refraction substantially matched to that of said containment medium means to maximize optical transmission in the presence of an electric field and to effect scattering in the absence of an electric field, said dye comprising fluorescent material.

50. The apparatus of claim 49, said dye being responsive to incident light and to scattered light to re-radiate light at a relatively lower wavelength.

51. The apparatus of claim 49, said dye being operative to effect brightening of light emitted by the apparatus in the absence of an electric field.

52. The apparatus of claim 49, wherein the dielectric constant of said support medium means is at least about as large as the lower dielectric constant of said liquid crystal.

53. The apparatus of claim 49, said support medium means having a viewing side and an opposite side, respective media at said viewing and opposite sides, and the index of refraction of said support medium means being greater than the index of refraction of the medium at one of respectively such viewing and opposite sides, and reflecting means for reflecting light and comprising an interface of such one of said sides with the medium thereat to effect total internal reflection of light in said support medium means incident on such interface at an angle exceeding a predetermined cone of light angle at which light would be transmitted through such interface.

54. The apparatus of claim 49, said liquid crystal and said containment means comprising a layer of encapsulated liquid crystal, and further comprising electrode means positioned between said support medium means and said layer of encapsulated liquid crystal for applying an electric field to align said liquid crystal with respect thereto.

55. The apparatus of claim 49, said liquid crystal comprising an emulsion of liquid crystal material and said containment medium means, said liquid crystal material and said containment medium means being operative to effect substantially isotropic scattering in the absence of an electric field.

56. The apparatus of claim 49, further comprising light director means for directing incident light into said support medium means.

57. The apparatus of claim 56, said director means comprising a louvered light control film.

58. The apparatus of claim 56, said director means comprising means for directing such incident light into said support medium means at a direction substantially out of the usual viewing line of sight from said viewing side.

59. The apparatus of claim 49, said support medium means having a viewing side and an opposite side, and further comprising a tuned dielectric interference layer on said opposite side of said support medium means for effecting optical constructive interference of at least some of the light in said support medium means incident on said interference layer or the interface thereof with said support medium means at an angle exceeding a predetermined cone angle and destructive interference of light incident at an angle within such cone angle.

60. The apparatus of claim 49, said liquid crystal and containment medium means comprising an emulsion of said liquid crystal and said containment medium means.

61. The apparatus of claim 60, further comprising additive means in said operationally nematic liquid crystal material for expediting such distorting and return to random alignment upon the removal of such electric field.

62. The apparatus of claim 60, said support medium means further comprising a substantially optically transparent support.

63. The apparatus of claim 62, further comprising electrode means for applying an electric field to said liquid crystal to cause the latter to change from a random alignment condition distorted in configuration or shape by the wall of respective capsule-like volumes in such emulsion for scattering light incident thereon to generally parallel alignment condition to transmit light incident thereon.

64. The apparatus of claim 60, further comprising chloroform.

65. The apparatus of claim 60, further comprising a surfactant.

66. The apparatus of claim 65, said surfactant comprising a non-ionic surfactant.

67. A display device formed of the liquid crystal apparatus of claim 49.

68. The display of claim 67, said liquid crystal comprising at least one layer of liquid crystal material in said containment medium means that tends to distort at least some of the liquid crystal material to align generally with respect to a wall of such containment medium means when in the absence of an electric field, and said liquid crystal material being responsive to an electric field to tend to align with respect thereto.

69. An optical shutter formed of the liquid crystal apparatus of claim 49.

70. The apparatus of claim 60, further comprising an aligning means at least partly reactive with said containment medium means to align in relatively fixed position with respect thereto, and said aligning means being so positioned with respect to walls of volumes formed in said emulsion and with respect to said liquid crystal to align at least part of at least some of the latter substantially normal with respect to said wall.

71. The apparatus of claim 70, said aligning means comprising a chrome alkyl complex.

72. A display device formed of a liquid crystal apparatus for providing a color output comprising an operationally nematic liquid crystal in a support medium and a non-pleochroic dye, said liquid crystal comprising at least one layer of liquid crystal material in a containment medium that tends to distort at least some of the liquid crystal to align generally with respect to a wall of such containment medium when in the absence of an electric field, and said liquid crystal being responsive to an electric field to tend to align with respect thereto, said dye comprising fluorescent material.

73. An optical display for displaying a color output, comprising liquid crystal, a non-pleochroic dye, and a containment medium means for containing said liquid crystal in volumes, said dye being contained in said containment medium means, said liquid crystal and containment medium means comprising at least one layer of liquid crystal material in a containment medium that tends to distort the natural structure of at least some of the liquid crystal material relative to a wall of such containment medium when in the absence of an electric field, said dye comprising a fluorescent material.

74. The display of claim 73, wherein said containment medium comprises a water base material, said containment medium tends to align the structure of at least some of the liquid crystal material generally parallel to a wall of the containment medium when in the absence of an electric field, and said dye comprises a water soluble dye.

75. A liquid crystal display comprising liquid crystal means for selectively generally isotropically scattering light or transmitting light, substantially transparent support medium means for supporting said liquid crystal means, and dye colorant in said support medium means for coloring light isotropically scattered in said support medium means, said support medium means comprising a containment medium means for containing quantities of liquid crystal means in capsule-like environments as encapsulated liquid crystal and support means for supporting said encapsulated liquid crystal, said dye comprising a fluorescent material.

76. An optical device for producing a colored optical output, including a containment medium comprising a non-pleochroic dye means for coloring light and a polymer base, said containment medium having a total internal reflection angle and being operative to effect total internal reflection of light impinging on a surface thereof at an angle exceeding such total internal reflection angle, and liquid crystal material in said containment medium, said liquid crystal material being cooperative with said containment medium in the absence of electric field to scatter a substantial amount of light at an angle greater than the total internal reflection angle for said medium substantially independently of wavelength, said dye comprising fluorescent material.

77. The optical device of claim 76, said containment medium comprising means for defining volumes for containing said liquid crystal material therein.

78. The device of claim 77, said support medium further comprising support means for supporting said containment medium and said liquid crystal material.

79. The device of claim 78, wherein the ordinary index of refraction of said liquid crystal material is substantially matched to the index of refraction of said support medium, and the extraordinary index of refraction of said liquid crystal material is different from the index of refraction of said support medium to effect refraction and scattering of light in the absence of an electric field.

80. The device of claim 79, the device having a viewing surface and an opposite surface, and further comprising an optical absorber means positioned beyond said opposite surface of said support medium to absorb light transmitted therethrough.

81. The device of claim 76, wherein the ordinary index of refraction of said liquid crystal material is substantially matched to the index of refraction of said support medium, and the extraordinary index of refraction of said liquid crystal material is different from the index of refraction of said support medium to effect refraction and scattering of light in the absence of an electric field.

82. The device of claim 76, the device having a viewing surface and an opposite surface, and further comprising an optical absorber means positioned beyond said opposite surface of said support medium to absorb light transmitted therethrough.

83. The device of claim 76, wherein said containment medium defines volumes for containing liquid crystal material therein, said volumes having wall means for distorting the natural structure of the liquid crystal material in the absence of a prescribed electric field applied to said liquid crystal material, and further comprising electrode means for applying electric field to liquid crystal material in volumes thereof to effect alignment of such liquid crystal material structure with respect to such field.

84. The device of claim 83, further comprising circuit means for applying electric energy to said electrode means to effect selective application of electric field to said liquid crystal material.

85. A method of making a liquid crystal apparatus comprising placing an encapsulated liquid crystal material in or on a support medium, and placing a dye in at least one of such encapsulated liquid crystal material and support medium, wherein such support medium has a substantial internal reflection characteristic, providing a further medium at an interface with such support medium, and selecting the index of refraction of such support medium to be greater than the index of refraction of such further medium, whereby total internal reflection of light will occur in such support medium with respect to light impinging on such interface at an angle less than a predetermined angle with respect to normal and applying a light absorbing material beyond such further medium for absorbing light transmitted through such further medium.

86. A method of displaying a colored character or other information on a background using liquid crystal in a containment medium supported with respect to a support medium, such liquid crystal being operationally nematic and having positive dielectric anisotropy, comprising isotropically scattering light incident on such liquid crystal material, totally internally reflecting such isotropically scattered light in such support medium back to such liquid crystal material, whereby said scattering and reflecting substantially increase the path length of light in such support medium, and coloring light transmitted along such substantially increased path length in such support medium by dye contained in such support medium.

87. A display device formed of a liquid crystal apparatus for providing a color output comprising an operationally nematic liquid crystal in a support medium and a non-pleochroic dye, said liquid crystal means comprising at least one layer of liquid crystal material in a containment medium that tends to distort at least some of the liquid crystal material to align generally with respect to a wall of such containment medium when in the absence of an electric field, and said liquid crystal material being responsive to an electric field to tend to align with respect thereto.

88. An optical device for producing a colored optical output, including a containment medium comprising a non-pleochroic dye means for coloring light and a polymer base, said containment medium having a total internal reflection angle and being operative to effect total internal reflection of light impinging on a surface thereof at an angle exceeding such total internal reflection angle, and liquid crystal material in said containment medium, said liquid crystal material being cooperative with said containment medium in the absence of electric field to scatter a substantial amount of light at an angle greater than the total internal reflection angle for said medium substantially independently of wavelength, said dye comprising fluorescent dye.

89. The optical device of claim 88, wherein said liquid crystal material is operative in the absence of an electric field to scatter light in said containment medium thereby to increase the path length of light in said containment medium, and wherein the coloring of light by said non-pleochroic dye increases substantially with increased path length of light during such scattering.

90. The optical device of claim 88, said containment medium comprising means for defining volumes for containing said liquid crystal material therein.

91. The device of claim 90, said support medium further comprising support means for supporting said containment medium and said liquid crystal material.

92. The device of claim 91, wherein the ordinary index of refraction of said liquid crystal material is substantially matched to the index of refraction of said support medium, and the extraordinary index of refraction of said liquid crystal material is different from the index of refraction of said support medium to effect refraction and scattering of light in the absence of an electric field.

93. The device of claim 92, the device having a viewing surface and an opposite surface, and further comprising an optical absorber means positioned beyond said opposite surface of said support medium to absorb light transmitted therethrough.

94. The device of claim 88, wherein the ordinary index of refraction of said liquid crystal material is substantially matched to the index of refraction of said support medium, and the extraordinary index of refraction of said liquid crystal material is different from the index of refraction of said support medium to effect refraction and scattering of light in the absence of an electric field.

95. The device of claim 88, the device having a viewing surface and an opposite surface, and further comprising an optical absorber means positioned beyond said opposite surface of said support medium to absorb light transmitted therethrough.

96. The device of claim 88, wherein said containment medium defines volumes for containing liquid crystal material therein, said volumes having wall means for distorting the natural structure of the liquid crystal material in the absence of a prescribed electric field applied to said liquid crystal material, and further comprising electrode means for applying electric field to liquid crystal material in volume thereof to effect alignment of such liquid crystal material structure with respect to such field.

97. The device of claim 96, further comprising circuit means for applying electric energy to said electrode means to effect selective application of electric field to said liquid crystal material.

98. A method of making a fluorescent liquid crystal apparatus, compriing forming a plurality of volumes of liquid crystal in a containment medium that distorts the natural structure of such liquid crystal absent a prescribed input to effect scattering of light, such liquid crystal being responsive to such prescribed input to align with respect thereto to reduce the amount of such scattering, and combining with at least one of such liquid crystal and containment medium a fluorescent dye.

99. The method of claim 98, comprising forming a cross linked containment medium for containing volumes of liquid crystal.