Pixelized liquid crystal display materials including chiral material adopted to change its chirality upon photo-irradiation

• US 5,668,614 A
• Filed: 05/01/1995
• Issued: 09/16/1997
• Est. Priority Date: 05/01/1995
• Status: Expired due to Term

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Doane, Joseph William, Chien, Liang-Chy
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): MILLER, CHARLES LELAND
• Application Number:
  US08/431,540
• Time in Patent Office: 869 Days
• Field of Search: 359/91, 359/105, 252/299.7, 349/115, 349/176
• US Class Current: 349/115
• CPC Class Codes: C09K 19/02 characterised by optical, electrical or physical properties of the components, in general
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: G02F 1/133362 Optically addressed liquid crystal cells G02F1/135 takes precedence
• CPC Class Codes: G02F 1/13345 Network or three-dimensional gels
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal

Abstract

An improvement in a light modulating chiral nematic liquid crystal adapted to form focal conic and twisted planar textures and a liquid crystal device employing such a material, the improvement wherein the liquid crystal material includes a plurality of essentially distinct regions within which the liquid crystal has different pitch lengths, whereby the liquid crystal can be made to reflect different wavelengths of light in different regions. The regions are created by including in the chiral nematic liquid crystal composition, a chiral material adapted to change its chirality upon photo-irradiation, in an amount effective to change the pitch length of the liquid crystal composition upon photo-irradiation. By exposing different regions of the material to increasing amounts of photo-irradiation, the pitch length of each region can be selectively tuned to reflect light of a different wavelength.

Claims

1. A light modulating chiral nematic liquid crystal material including a chiral material adapted to change chirality upon application of an energy input, wherein said liquid crystal material includes a plurality of essentially distinct regions within which the liquid crystal has different pitch lengths, whereby said liquid crystal material can be made to reflect different wavelengths of light in different regions.

2. The material according to claim 1 including a plurality of essentially distinct region types, each of said region types having a pitch length effective to reflect a different color in the visible spectrum from the other of said region types.

3. The material according to claim 1 including three essentially distinct region types, each of said three region types having a pitch length effective to reflect a different color in the visible spectrum.

4. The material according to claim 1, 2 or 3, wherein said regions are distributed within said material in a pattern effective to produce images of any desired color or combination of colors.

5. The material according to claim 1 wherein said liquid crystal material is interspersed with a solidified polymer matrix.

6. In a light modulating chiral nematic liquid crystal composition, the improvement comprising a cleavable chiral material adapted to change its chirality upon photo-irradiation, said material being present in an amount effective to change the pitch length of the liquid crystal composition upon said photo-irradiation, and wherein said chiral material includes a chiral carbon whereby upon photo-irradiation the chiral carbon is rendered achiral by cleavage of a moiety from said chiral material.

7. The composition according to claim 6 wherein said chiral material includes a chiral carbon having a photo-cleavable leaving group directly bound thereto, whereby upon photo-irradiation the chiral carbon is rendered achiral.

8. The composition according to claim 6 wherein said chiral material includes a chiral carbon that is cleavable from said material upon photo-irradiation, whereupon the chiral carbon is rendered achiral.

9. The composition according to claim 6 wherein the chiral nematic liquid crystal and said chiral material have the same handedness of chirality.

10. The composition according to claim 6 wherein the chiral nematic liquid crystal and the chiral material have opposite handedness of chirality.

11. In a light modulating chiral nematic liquid crystal composition, the improvement comprising a chiral material adapted to change its chirality upon photo-irradiation, said material being present in an amount effective to change the pitch length of the liquid crystal composition upon said photo-irradiation, wherein said chiral material has as its dominant reaction product upon photo-irradiation a racemic mixture.

13. The composition according to any one of claims 6, 7, 8, 11 or 12 further including a polymer matrix forming material.

12. In a light modulating chiral nematic liquid crystal composition, the improvement comprising a chiral material adapted to change its chirality upon photo-irradiation, said material being present in an amount effective to change the pitch length of the liquid crystal composition upon said photo-irradiation, wherein said chiral material has as its dominant reaction product upon photo-irradiation a structural isomer with chirality opposite that of said chiral material.

14. In a light modulating chiral nematic liquid crystal composition, the improvement comprising a chiral material, having at least one polymerizable double bond, adapted to change its chirality upon photo-irradiation, said material being present in an amount effective to change the pitch length of the liquid crystal composition upon said photo-irradiation, including a polymer matrix forming material having at least one double bond that is polymerizable with at least one polymerizable double bond of said chiral material.

15. In a light modulating chiral nematic liquid crystal composition, the improvement comprising a chiral material adapted to change its chirality upon photo-irradiation, said material being present in an amount effective to change the pitch length of the liquid crystal composition upon said photo-irradiation, wherein said chiral material is selected from the group consisting of an arylcyano acetic acid, an aryloxy acetic acid, an aryl ketone, a binaphthol, a binaphthalene or combination thereof.

16. In a light modulating liquid crystal device comprising chiral nematic liquid crystal material adapted to form focal conic and twisted planar textures and cell wall structure confining said liquid crystal, the improvement wherein said liquid crystal material includes a chiral material adapted to change chirality upon application of an energy input, and a plurality of essentially distinct regions within which the liquid crystal has different pitch lengths, whereby said liquid crystal can be made to reflect different wavelengths of light in different regions.

17. The device according to claim 16 including a plurality of essentially distinct region types, each of said region types having a pitch length effective to reflect a different color in the visible spectrum from the other of said region types.

18. The device according to claim 17 comprising electrodes on said cell wall structure arranged in a manner adapted to simultaneously address the liquid crystal in at least two adjacent region types independently of the liquid crystal in other said region types, whereby the addressed regions appear white.

19. The device according to claim 16 including three essentially distinct region types, each of said three region types having a pitch length effective to reflect a different color in the visible spectrum.

20. The device according to claim 16, 17 or 19, wherein said regions are distributed within said material in a pattern effective to produce images of any desired color or combination of colors.

21. The device according to claim 16 wherein said liquid crystal material is interspersed with a solidified polymer matrix.

22. The device according to claim 16 wherein said cell wall structure is treated to align the liquid crystal.

23. The device according to claim 16 wherein said cell wall structure is treated to promote homeotropic alignment of said liquid crystal.

24. The device according to claim 16 comprising electrodes on said cell wall structure arranged in a manner adapted to electrically address said liquid crystal in each of said regions independently of the liquid crystal in each other of said regions.

25. A method of preparing a light modulating liquid crystal cell comprising the steps of:

a) disposing between a pair of cell walls, a light modulating chiral nematic liquid crystal composition including a chiral material adapted to change its chirality upon irradiation, said material being present in an amount effective to change the pitch length of the liquid crystal composition upon said irradiation;

b) masking at least a portion of said liquid crystal from an irradiation source; and

,

c) irradiating said liquid crystal composition to change the pitch length of the unmasked portion of said liquid crystal

wherein said masking and photo-irradiation steps are preformed so as to create a plurality of essentially distinct regions within which the liquid crystal has different pitch lengths effective to reflect different colors in the visible spectrum.

26. The method according to claim 25 wherein said portion of said liquid crystal is masked by an electrically addressable liquid crystalline light shutter.

27. The method according to claim 25 further comprising disposing electrodes on said cell walls in a manner adapted to electrically address said liquid crystal in each of said regions independently of the liquid crystal in each other of said regions.

28. The method according to claim 25 further comprising disposing electrodes on said cell walls in a manner adapted to electrically address said liquid crystal in a plurality of said regions simultaneously, and independently of the liquid crystal in other said regions.

29. The method of claim 25 wherein said chiral material includes polymerizable double bonds, and said material is polymerized prior to said masking step.

30. The method of claim 25 further comprising disposing a polymerizable material between said cell walls and polymerizing said material to create a polymerized polymer network prior to said masking step.