Encapsulated liquid crystal and method

• US 4,435,047 A
• Filed: 09/16/1981
• Issued: 03/06/1984
• Est. Priority Date: 09/16/1981
• Status: Expired due to Term

• Current Assignee: Manchester R & D Partnership
• Original Assignee: Manchester R & D Partnership
• Inventors: Fergason, James L.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Gallivan, Richard F.
• Application Number:
  US06/302,780
• Time in Patent Office: 902 Days
• Field of Search: 252/316, 428/1, 350/331 R, 350/334, 350/349, 350/350 R, 350/347 V, 350/340, 350/341
• US Class Current: 349/86
• 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 2202/043 pleochroic

Abstract

Briefly, according to one aspect of the invention, liquid crystal material, and especially nematic material, is encapsulated; according to another aspect the encapsulated liquid crystal material is used in liquid crystal devices, such as relatively large size visual display devices; and according to further aspects there are provided methods for encapsulating liquid crystal material and for making a liquid crystal device using such encapsulated liquid crystal material.

Claims

1. A liquid crystal apparatus, comprising liquid crystal material having positive dielectric anisotropy, and surface means for affecting the natural structure of said liquid crystal material to induce a distorted alignment thereof in the absence of an electric field to reduce optical transmission independent of polarization, said liquid crystal material being responsive to the presence of an electric field to increase such optical transmission.

3. An electro-optic display comprising the apparatus of claim 1 or 2, and further comprising electrical means for applying such electric field.

2. A liquid crystal apparatus, comprising liquid crystal material having positive dielectric anisotropy, surface means for affecting the natural structure of said liquid crystal material to induce a distorted alignment thereof in the absence of an electric field to reduce optical transmission independent of polarization, said liquid crystal material being responsive to the pesence of an electric field to increase such optical transmission, and pleochroic dye contained in said liquid crystal material.

4. Liquid crystal material and a medium for containing discrete quantities of said liquid crystal material, said material having positive dielectric anisotropy, said medium having dielectric constant that is no less than the lower dielectric constant value of said material, and wherein when exposed to an electric field the electrical impedance of said medium and liquid crystal material exposed to such field along an electrical path through both said medium and liquid crystal material are related such that the electrical impedance of said medium is less than the electrical impedance of said liquid crystal material exposed to such field.

5. An electro-optic display comprising the material of claim 4, and further comprising electrical means for applying such electric field.

7. An electro-optic display comprising the material and medium of claim 4 or 6, and further comprising electrical means for applying such electric field.

6. Liquid crystal material and a medium for containing discrete quantities of said liquid crystal material, said material having positive dielectric anisotropy, said medium having a dielectric constant that is no less than the lower dielectric constant value of said material, wherein said medium is an encapsulating medium for said liquid crystal material, and wherein said liquid crystal material and said encapsulating medium have electrical properties such that upon application of an electric field across a capsule along an electrical path through said encapsulating medium and liquid crystal material there is a greater voltage drop across said liquid crystal material than across said encapsulating medium.

8. A material comprising a containment medium having an index of refraction, and optically anisotropic liquid crystal means contained in said containment medium and having an ordinary index of refraction in the presence of an electric field substantially equal to the index of refraction of said containment medium for maximizing optical transmission in the presence of an electric field.

9. A method of making encapsulated nematic liquid crystals, comprising mixing at least an encapsulating medium, a nematic liquid crystal material, and a pleochroic dye.

10. A method of making encapsulated nematic liquid crystals, comprising mixing at least an encapsulating medium and a nematic liquid crystal material, and further comprising selecting such liquid crystal material and such encapsulating medium such that the liquid crystal material has a positive dielectric anisotropy and the dielectric constant of such encapsulating medium is at least as great as the lower dielectric constant of such liquid crystal material.

11. The method of claim 10, said selecting further comprising selecting such liquid crystal material and such encapsulating medium such that the liquid crystal material has an ordinary index of refraction substantially the same as the index of refraction of the encapsulating medium.

15. The method of claims 9, 10, 12 or 14, wherein such encapsulating medium comprises polyvinyl alcohol.

16. The method of claims 9, 10, 12 or 14, further comprising mixing a carrier material with such encapsulating medium and liquid crystal material to form an emulsion therewith, such liquid crystal material and encapsulating medium being insoluble in such carrier material.

17. The method of claim 16, further comprising removing such carrier material from such emulsion and curing such encapsulating medium.

18. The method of claim 17, such carrier material comprising water, and said removing comprising drying.

19. The method of claim 16, said mixing further comprising mixing in a colloid mill to obtain particles suspended in such emulsion of substantially uniform size.

20. The method of claim 16, further comprising forming capsules from such emulsion of a size on the order of from about 2 microns to about 25 microns.

22. The method of claims 9, 10, 12 or 14, said encapsulating medium forming plural capsules of such nematic liquid crystal material, and further comprising applying the plural capsules of such encapsulated liquid crystal material to a substrate or to an electrode thereof.

23. The method of claim 22, further comprising applying a further electrode on the side of the encapsulated liquid crystal material relatively remote from such substrate.

24. The method of claim 23, further comprising applying a protective coating over such second mentioned electrode.

25. The method of claim 23, further comprising forming at least one of such electrodes in a preestablished pattern and forming both of such electrodes to be substantially optically transparent to electromagnetic radiation in at least a portion of the visible range.

39. The invention of claim 23, said containment means comprising a containment medium that tends to align at least some of the liquid crystal material generally parallel to a wall of such medium when in the absence of an electric field.

12. A method of making encapsulated nematic liquid crystals, comprising mixing at least an encapsulating medium and a nematic liquid crystal material, and further comprising selecting such liquid crystal material and such encapsulating medium such that the liquid crystal material has an ordinary index of refraction substantially the same as the index of refraction of the encapsulating medium.

13. The method of claim 12, further comprising selecting such liquid crystal material and encapsulating medium such that the liquid crystal material has an extraordinary index of refraction that is different from the index of refraction of the encapsulating medium.

14. A method of making encapsulated nematic liquid crystals, comprising mixing at least an encapsulating medium and a nematic liquid crystal material, and further comprising causing such liquid crystal material to perform substantially independently of the optical polarization direction of incident light, including confining such liquid crystal material in a capsule formed by such encapsulating medium that causes distortion of the direction of the liquid crystal molecules when no electric field is applied thereto.

21. The method of claim 14, the nematic liquid crystal material comprising from about 5 to about 20% by volume, the encapsulating medium comprising from about 5 to about 20% by volume, and the remainder of the material mixed comprising water.

26. A method of causing nematic liquid crystal material to perform substantially independently of the optical polarization direction of incident light, comprising confining such nematic liquid crystal material in a capsule which causes distortion of the direction of the liquid crystal material.

27. An article made in accordance with the preceding claim.

58. The apparatus of claim 27, wherein such prescribed input is an electric field, and said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that there is a greater voltage drop across the liquid crystal material than across the containment means.

69. The invention of claims 27, 60, 61, 62, 64, or 68, said liquid crystal material consisting essentially of nematic liquid crystal material.

71. The invention of claims 27, 60, 61, 62, 64, 68, 70 or 29, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

72. The invention of claims 27, 60, 61, 62, 64, 68 or 70, further comprising means for applying an electric field to said liquid crystal material to affect the alignment thereof and at least one of the absorbence and scattering of light thereby.

73. The invention of claim 72, said means for applying comprising electrode means for applying the electric field across said liquid crystal material.

74. The invention of claim 73, said means for applying further comprising circuit means for providing electrical energy to said electrode means to create such electric field.

83. The invention of claims 27, 70, 78, 81, or 82, said liquid crystal material having positive dielectric anisotropy.

28. A method of causing liquid crystal material to perform substantially independently of the optical polarization direction of incident light, comprising combining pleochroic dye with the liquid crystal material and confining such dyed liquid crystal material as a suspension in a confining medium.

29. Liquid crystal apparatus, comprising liquid crystal material, and containment means for inducing a distorted alignment of said liquid crystal material which in response to such alignment at least one of scatters and absorbs light and which in response to a prescribed input reduces the amount of such scattering or absorption.

30. The invention of claim 29, said liquid crystal material consisting essentially of nematic liquid crystal material.

31. The invention of claim 30, said liquid crystal material comprising nematic NM8250 liquid crystal material.

32. The invention of claim 29, said liquid crystal material being reversible.

33. The invention of claim 29, wherein such containment means forms a capsule containing such liquid crystal material, and wherein the size of such capsules is from about 2 microns to about 25 microns.

34. The invention of claim 29, said containment means comprising resin or polymer.

35. The invention of claim 34, said containment means being selected from the group comprising gelatin, Carbopole, Gantrez and polyvinyl alcohol.

36. The invention of claim 35, said containment means comprising polyvinyl alcohol.

37. The invention of claim 29, wherein said containment means forms a generally spherical capsule for containing such liquid crystal material.

38. The invention of claim 37, wherein the dielectric constant of the wall of such capsule results in a capacitance in a radial direction that does not drop the voltage appreciably relative to the voltage drop across the liquid crystal material upon application of an electric field across the capsule.

40. The invention of claim 29, said containment means comprising an encapsulating medium that distorts the internal structure of the liquid crystal material in the absence of an electric field.

41. The invention of claim 29, further comprising substrate means for supporting the combination of said liquid crystal material and containment means.

42. The invention of claim 41, further comprising means for adhering the combination of said liquid crystal material and containment means to said substrate means.

43. The invention of claim 41, further comprising electrode means on said substrate means for applying an electric field to said liquid crystal material.

44. The invention of claim 43, further comprising means for adhering the combination of said liquid crystal material and containment means to said electrode means.

45. The invention of claim 29, said containment means forming discrete curved volumes containing discrete quantities of liquid crystal material, and said distorted alignment comprising alignment at least partly paralleling the curvature of such volumes.

46. The invention of claim 29, said liquid crystal material having positive dielectric anisotropy.

47. The invention of claim 29, said liquid crystal material having optical anisotropy.

48. The invention of claim 29, the combination of said liquid crystalmaterial and containment means forming a plurality of encapsulated liquid crystals, and further comprising substrate means for supporting said plurality of encapsulate liquid crystals.

49. The invention of claim 29, further comprising electrode means for applying an electrical field to said liquid crystal material as such prescribed input.

50. The invention of claim 49, further comprising circuit means for applying electrical energy to said electrode means to enable the same to apply such electric field.

51. The invention of claim 29, wherein such prescribed input is an electric field, and further comprising means for applying such electric field to such liquid crystal material.

52. The apparatus of claim 29, further comprising pleochroic dye in combination with said liquid crystal material.

53. The apparatus of claim 29, said liquid crystal material and containment means being cooperative at least one of to absorb and to scatter light independently of the polarization of the light incident thereon.

54. The apparatus of claim 29, said liquid crystal material and said containment means having substantially matched indices of refraction in the presence of such prescribed input.

55. The apparatus of claim 54, said liquid crystal material and said containment means having different indices of refraction in the absence of such prescribed input.

56. The apparatus of claim 29, wherein such prescribed input is an electric field, and said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that the electrical impedance of the containment means exposed to such field is less than the electrical impedance of the liquid crystal material exposed to such field.

57. The apparatus of claim 56, wherein said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that there is a greater voltage drop across the liquid crystal material than across the containment means.

59. The invention of clim 29, said containment means comprising means for containing discrete quantities of such liquid crystal material causing the structure of such material to fold in on itself creating storage of elastic energy in such structure.

60. Liquid crystal material and a medium for containing discrete quantities of said liquid crystal material, said liquid crystal material having positive dielectric anisotropy, and wherein when exposed to an electric field the electrical impedance of said medium and liquid crystal material exposed to such field along an electrical path through both said medium and liquid crystal material are related such that the electrical impedance of said medium is less than the electrical impedance of said liquid crystal material exposed to such field.

61. Liquid crystal material and a medium for containing discrete quantities of said liquid crystal material, said liquid crystal material having positive dielectric anisotropy, wherein said medium is an encapsulating medium for said liquid crystal material, and wherein said liquid crystal material and said encapsulating medium have electrical properties such that upon application of an electric field across a capsule along an electrical path through said encapsulating medium and liquid crystal material there is a greater voltage drop across said liquid crystal material than across said encapsulating medium.

62. Liquid crystal material and a medium for containing discrete quantities of such liquid crystal material, said material having positive dielectric anisotropy, and mixed with the liquid crystal material a pleochroic dye that is soluble in the liquid crystal material.

63. The invention of claim 62, said pleochroic dye being selected from the group consisting of indophenol blue, Sudan black, Sudan 3 and Sudan 2.

64. Liquid crystal material and a medium for containing discrete quantities of such liquid crystal material, said material having positive dielectric anisotropy, said liquid crystal material having an ordinary index of refraction substantially the same as the index of refraction of said medium.

65. The invention of claim 64, said liquid crystal material having an extraordinary index of refraction that is different from the index of refraction of said medium.

66. Liquid crystal material and a medium for containing discrete quantities of such liquid crystal material, said material having positive dielectric anisotropy, said liquid crystal material comprising nematic liquid crystal material, and said medium comprising means for aligning the liquid crystal material to achieve a substantially maximum absorption of light energy under a no field condition.

67. The invention of claim 66, further comprising pleochroic dye in said liquid crystal material.

68. Liquid crystal material and a medium for containing discrete quantities of said liquid crystal material, said material comprising nematic liquid crystal material having positive dielectric anisotropy, said medium having a dielectric constant that is no less than the lower dielectric constant value of said material.

70. The combination of nematic liquid crystal material contained in a generally spherical capsule of encapsulating medium, said encapsulating medium having a wall, and wherein the ordinary index of refraction of said liquid crystal material is approximately the same as the index of refraction of the encapsulating medium.

75. The invention of claim 70, wherein the extraordinary index of refraction of such liquid crystal material is different from the index of refraction of the encapsulating medium.

76. The invention of claim 75, wherein said encapsulating medium aligns the liquid crystal material substantially parallel to at least a portion of the direction of a proximate wall portion of such encapsulating medium, thereby distorting the internal structure of the liquid crystal material.

77. Liquid crystal material and a medium for containing discrete quantities of such liquid crystal material, said material comprising an operationally nematic material having positive dielectric anisotropy, and said medium comprising means for tending physically to align said liquid crystal material with respect to said medium, said medium comprising encapsulating means for substantially encapsulating said material in substantially spherical capsules, and said means for tending physically to align comprising wall means of said capsules for tending to align said liquid crystal material generally in parallel with said wall means in the absence of an electric field.

78. An operationally nematic liquid crystal material and a containment means for containing discrete quantities of such liquid crystal material causing said material to fold in on itself creating storage of elastic energy in said material.

79. A display device comprising a substrate and supported thereby encapsulated liquid crystal which is operationally nematic and has a positive dielectric anisotropy.

80. The device of claim 79, said encapsulated liquid crystal comprising plural encapsulated liquid crystals, each capsule including liquid crystal material and an encapsulating medium, electrode means for applying an electric field across at least some of said encapsulated liquid crystals, and means for adhering said encapsulated liquid crystal to at least one of said electrode means and said substrate.

81. A liquid crystal apparatus comprising an operationally nematic liquid crystal material contained in discrete quantities by a matrix formed of an emulsion of such liquid crystal material and a further medium.

82. A display device formed of the liquid crystal apparatus of claim 81.

84. Liquid crystal apparatus, comprising liquid crystal material, and containment means for inducing a distorted alignment of said liquid crystal material which in response to such alignment absorbs light and which in response to a prescribed input reduces the amount of such absorption.

85. The invention of claim 84, said liquid crystal material having positive dielectric anisotropy.

86. The invention of claim 84, further comprising substrate means for supporting the combination of said liquid crystal material and containment means.

87. The invention of claim 86, further comprising means for adhering the combination of said liquid crystal material and containment means to said substrate means.

88. The invention of claim 86, further comprising electrode means on said substrate means for applying an electric field to said liquid crystal material.

89. The invention of claim 88, further comprising means for adhering the combination of said liquid crystal material and containment means to said electrode means.

90. The invention of claim 84, said containment means forming discrete curved volumes containing discrete quantities of liquid crystal material, and said distorted alignment comprising alignment at least partly paralleling the curvature of such volumes.

91. The invention of claim 84, said liquid crystal material having positive dielectric anisotropy.

92. The invention of claim 84, said liquid crystal material having optical anisotropy.

93. The invention of claim 84, the combination of said liquid crystal material and containment means forming a plurality of encapsulated liquid crystals, and further comprising substrate means for supporting said plurality of encapsulated liquid crystals.

94. The invention of claim 84, further comprising electrode means for applying an electrical field to said liquid crystal material as such prescribed input.

95. The invention of claim 94, further comprising circuit means for applying electrical energy to said electrode means to enable the same to apply such electric field.

96. The invention of claim 84, wherein such prescribed input is an electric field, and further comprising means for applying such electric field to such liquid crystal material.

97. The apparatus of claim 84, further comprising pleochroic dye in combination with said liquid crystal material.

98. The apparatus of claim 84, said liquid crystal material and containment means being cooperative to absorb light independently of the polarization of the light incident thereon.

99. The apparatus of claim 84, said liquid crystal material and said containment means having substantially matched indices of refraction in the presence of such prescribed input.

100. The apparatus of claim 99, said liquid crystal material and said containment means having different indices of refraction in the absence of such prescribed input.

101. The apparatus of claim 84, wherein such prescribed input is an electric field, and said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that the electrical impedance of the containment means exposed to such field is less than the electrical impedance of the liquid crystal material exposed to such field.

102. The apparatus of claim 84, wherein such prescribed input is an electric field, and said liquid crystal material and said containment means have substantially related dielectric constants in the presence of an electric field such that there is a greater voltage drop across the liquid crystal material than across the containment means.

103. The invention of claim 84, said liquid crystal material consisting substantially of operationally nematic liquid crystal material.

104. A liquid crystal device comprising liquid crystal material and containment means, said containment means forming a plurality of capsules each having a curved interior wall surface, said capsules containing said liquid crystal material;

which liquid crystal material in the absence of an applied electric field at least one of scatters or absorbs incident light independently of the polarization of said light, and which device in the presence of an applied electric field displays decreased scattering or absorption at least in the direction of the applied electric field.

105. The device of claim 104 wherein the liquid crystal material consists essentially of nematic liquid crystal material having a positive dielectric anisotropy.

106. The device of claim 104 wherein the liquid crystal material contains a pleochroic dye.

107. The device of claim 104 wherein the liquid crystal material is optically anisotropic and the ordinary refractive index of the liquid crystal is substantially the same as the refractive index of the containment means.

108. The device of claim 104 which further comprises electrodes for applying such electric field.

109. The device of claim 108 which further comprises a substrate means for supporting said electrodes, liquid crystal material and containment means.

110. The device of claim 108 which further comprises circuit means for energizing said electrodes to apply such electric field.

111. Liquid crystal apparatus, comprising nematic liquid crystal material having positive dielectric anisotropy, and a plurality of containment means with curved surfaces for inducing a distorted alignment of said liquid crystal material which in response to such distortion at least one of scatters and absorbs light when pleochroic dye is present in the liquid crystal material and which in response to a prescribed input reduces the amount of such scattering or absorption.