Four domain pixel for liquid crystalline light modulating device

• US 6,141,074 A
• Filed: 12/18/1997
• Issued: 10/31/2000
• Est. Priority Date: 05/19/1995
• Status: Expired due to Fees

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Chen, Jianmin, Johnson, David L., Vithana, Hemasiri K., Bos, Philip J.
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US08/993,912
• Time in Patent Office: 1,048 Days
• Field of Search: 349/123, 349/125, 349/128, 349/129, 349/132, 349/134, 349/136, 349/130, 349/179, 349/186, 349/86
• US Class Current: 349/129
• CPC Class Codes: G02F 1/133753 with different alignment orientations or pretilt angles on a same surface, e.g. for grey scale or improved viewing angle
• CPC Class Codes: G02F 1/133757 with different alignment orientations
• CPC Class Codes: G02F 1/13775 Polymer-stabilized liquid crystal layers

Abstract

A liquid crystalline light modulating pixel includes first and second cell wall structures and nematic liquid crystal disposed therebetween. The first and second cell wall structures cooperate with the liquid crystal to form four liquid crystal domains within the pixel. The liquid crystal in each of the domains exhibits a twisted nematic liquid crystal structure and the orientation of the liquid crystal director of the liquid crystal adjacent one of the cell wall structures in at least two domains is different.

Claims

1. A liquid crystalline light modulating pixel comprising first and second cell wall structures and nematic liquid crystal disposed therebetween, said first and second cell wall structures cooperating with said liquid crystal to form four polymer-stabilized liquid crystal domains within said pixel, wherein the liquid crystal in each of said domains exhibits a twisted nematic liquid crystal structure and the orientation of the liquid crystal director of the liquid crystal adjacent one of said cell wall structures in at least two domains is different in the absence of chiral additives.

2. The liquid crystalline pixel according to claim 1 wherein said liquid crystal has positive dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect thereto from 0.5°

-30°

.

3. The liquid crystalline pixel according to claim 1 wherein said liquid crystal has negative dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect to a normal to said cell wall structures from 0.1°

-10°

.

4. The liquid crystalline pixel according to claim 1 wherein the orientation of the liquid crystal director in all four domains adjacent one of said cell wall structures is different.

5. The liquid crystalline pixel according to claim 1 wherein the liquid crystal director in two domains has right hand rotation and the liquid crystal director in the remaining domains has left hand rotation.

6. A liquid crystalline light modulating pixel comprising first and second cell wall structures and nematic liquid crystal disposed therebetween, said first and second cell wall structures cooperating with said liquid crystal to form four polymer-stabilized liquid crystal domains within said pixel, wherein the liquid crystal in each of said domains exhibits a twisted nematic liquid crystal structure and the orientation of the liquid crystal director of the liquid crystal in at least two domains adjacent each of said cell wall structures is different in the absence of chiral additives.

7. The liquid crystalline pixel according to claim 6 wherein said liquid crystal has positive dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect thereto from 0.5°

-30°

.

8. The liquid crystalline pixel according to claim 6 wherein said liquid crystal has negative dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect to a normal to said cell wall structures from 0.1°

-10°

.

9. The liquid crystalline pixel according to claim 6 wherein the orientation of the liquid crystal director in all four domains adjacent one of said cell wall structures is different.

10. The liquid crystalline pixel according to claim 6 wherein the liquid crystal director of the liquid crystal in two domains adjacent one of the cell wall structures is rotated 180°

about the cell wall normal with respect to the liquid crystal director in the remaining two domains adjacent said one cell wall structure.

11. The liquid crystalline pixel according to claim 6 wherein the liquid crystal director in two domains has right hand rotation and the liquid crystal director in the remaining domains has left hand rotation.

12. The liquid crystalline pixel according to claim 6 wherein at a middle plane of the pixel substantially midway between and parallel to said first and second cell wall structures the liquid crystal director in one domain is orthogonal to the liquid crystal director in two other domains.

13. The liquid crystalline pixel according to claim 6 wherein each of the cell wall structures includes a rubbed polyimide layer.

14. The liquid crystalline pixel according to claim 6 wherein each of the cell wall structures includes a layer of vacuum oblique evaporated material.

15. A liquid crystalline light modulating device including first and second cell wall structures with nematic liquid crystal disposed therebetween and means for electrically addressing the liquid crystal, the improvement comprising at least one liquid crystalline light modulating pixel comprising four polymer-stabilized liquid crystal domains within said pixel formed by cooperation of said first and second cell wall structures with said liquid crystal, wherein the liquid crystal in each of said domains exhibits a twisted nematic liquid crystal structure and the orientation of the liquid crystal director of the liquid crystal adjacent one of said cell wall structures in at least two domains is different in the absence of chiral additives.

16. The light modulating device according to claim 15 wherein said liquid crystal has positive dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect thereto from 0.5°

-30°

.

17. The light modulating device according to claim 15 wherein said liquid crystal has negative dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect to a normal to said cell wall structures from 0.1°

-10°

.

18. The light modulating device according to claim 15 wherein the orientation of the liquid crystal director in all four domains adjacent one of said cell wall structures is different.

19. The light modulating device according to claim 15 wherein the liquid crystal director in two domains has right hand rotation and the liquid crystal director in the remaining domains has left hand rotation.

20. The light modulating device according to claim 15 further comprising two polarizers between which the cell wall structures are located, wherein a polarization orientation passed by one polarizer is parallel to a polarization orientation passed by the other polarizer.

21. The light modulating device according to claim 15 further comprising two polarizers between which the cell wall structures are located, wherein a polarization orientation passed by one polarizer is orthogonal to a polarization orientation passed by the other polarizer.

22. A method of producing a four domain liquid crystalline pixel for a light modulating device comprising the steps of

providing first and second cell wall structures,

treating at least a first region on said cell wall structures to promote a liquid crystal orientation in one direction,

treating at least a second region on said cell wall structures to promote a liquid crystal orientation in a different direction than in said first region,

spacing apart the cell wall structures and providing a polymer and a nematic liquid crystal therebetween, and

inducing polymerization,

wherein the treatment of said first and second regions produces four polymer-stabilized domains in which the liquid crystal has twisted nematic liquid crystal structure extending between said first and second cell wall structures and the orientation of the liquid crystal director of the liquid crystal adjacent one of said cell wall structure in at least two domains is different in the absence of chiral additives.

23. The method according to claim 22 further comprising orienting the cell wall structures such that the orientation of the liquid crystal director of the liquid crystal in one domain adjacent one of the cell wall structures is orthogonal to the orientation of the liquid crystal director of the liquid crystal in said one domain adjacent the other cell wall structure.

24. The method according to claim 22 wherein the treatment of said first and second regions of said first and second cell wall structures comprises forming a layer of material on said cell wall structures, rubbing said layer in one direction, forming a mask on said layer to cover one of said first and second regions and leave the other uncovered, rubbing said layer in said first and second regions in a different direction, and removing said mask.

25. The method according to claim 24 wherein the rubbing direction of the first region is opposite to the rubbing direction of the second region.

26. The method according to claim 22 wherein the treatment of said first and second regions of said first and second cell wall structures comprises forming a first layer of material on the cell wall structures by vacuum oblique evaporation, forming a mask on said first layer to cover one of said first and second regions and leave the other uncovered, rotating the cell wall structures, forming a second layer of material on the first and second regions by vacuum oblique evaporation, and removing said mask.

27. The method according to claim 26 wherein the cell wall structures are rotated 180°

.

28. A method of producing a polymer stabilized four domain liquid crystalline pixel for a light modulating device, comprising the steps of

providing first and second cell wall structures,

rotating the cell wall structures,

depositing a first layer of liquid crystal alignment material onto the rotating cell wall structures by vacuum oblique evaporation,

stopping rotation of the cell wall structures opposite to an intended pretilt orientation of a liquid crystal director of liquid crystal adjacent the cell wall structures,

depositing a second layer of liquid crystal alignment material onto the fixed cell wall structures by vacuum oblique evaporation,

masking the cell wall structures in an alternating striped pattern,

rotating the cell wall structures a predetermined angle,

depositing a third layer of liquid crystal alignment material onto the cell wall structures by vacuum oblique evaporation,

removing said mask, and

spacing said first and second cell wall structures apart and providing a polymer and a nematic liquid crystal therebetween and inducing polymerization in the absence of chiral additives.

29. The method according to claim 28 further comprising orienting the cell wall structures such that the striped pattern on the first cell wall structure is orthogonal to the striped pattern on the second cell wall structure.

30. The method according to claim 28 wherein the liquid crystal alignment material is SiO_x.

31. The method according to claim 28 wherein said predetermined angle is 180°

.

32. A liquid crystalline light modulating pixel comprising first and second cell wall structures and nematic liquid crystal disposed therebetween, said first and second cell wall structures cooperating with said liquid crystal to form four liquid crystal domains within said pixel, wherein the liquid crystal in each of said domains exhibits a twisted nematic liquid crystal structure and the orientation of the liquid crystal director of the liquid crystal adjacent one of said cell wall structures in at least two domains is different in the absence of chiral additives and wherein a pretilt angle in all liquid crystal domains is the same, and wherein the first and second cell wall structures are treated to promote liquid crystal orientation.

33. The liquid crystalline pixel according to claim 32 wherein said liquid crystal has positive dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect thereto from 0.5°

-30°

.

34. The liquid crystalline pixel according to claim 32 wherein said liquid crystal has negative dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect to a normal to said cell wall structures from 0.1°

-10°

.

35. The liquid crystalline pixel according to claim 32 wherein the orientation of the liquid crystal director in all four domains adjacent one of said cell wall structures is different.

36. The liquid crystalline pixel according to claim 32 wherein the liquid crystal director in two domains has right hand rotation and the liquid crystal director in the remaining domains has left hand rotation.

37. A liquid crystalline light modulating pixel comprising first and second cell wall structures and nematic liquid crystal disposed therebetween, said first and second cell wall structures cooperating with said liquid crystal to form four liquid crystal domains within said pixel, wherein the liquid crystal in each of said domains exhibits a twisted nematic liquid crystal structure and the orientation of the liquid crystal director of the liquid crystal in at least two domains adjacent each of said cell wall structures is different in the absence of chiral additives and wherein a pretilt angle in all liquid crystal domains is the same, and wherein the first and second cell wall structures are treated to promote liquid crystal orientation.

38. The liquid crystalline pixel according to claim 37 wherein said liquid crystal has positive dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect thereto from 0.5°

-30°

.

39. The liquid crystalline pixel according to claim 37 wherein said liquid crystal has negative dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect to a normal to said cell wall structures from 0.1°

-10°

.

40. The liquid crystalline pixel according to claim 37 wherein the orientation of the liquid crystal director in all four domains adjacent one of said cell wall structures is different.

41. The liquid crystalline pixel according to claim 37 wherein the liquid crystal director of the liquid crystal in two domains adjacent one of the cell wall structures is rotated 180°

about the cell wall normal with respect to the liquid crystal director in the remaining two domains adjacent said one cell wall structure.

42. The liquid crystalline pixel according to claim 37 wherein the liquid crystal director in two domains has right hand rotation and the liquid crystal director in the remaining domains has left hand rotation.

43. The liquid crystalline pixel according to claim 37 wherein at a middle plane of the pixel substantially midway between and parallel to said first and second cell wall structures the liquid crystal director in one domain is orthogonal to the liquid crystal director in two other domains.

44. The liquid crystalline pixel according to claim 37 wherein each of the cell wall structures includes a rubbed polyimide layer.

45. The liquid crystalline pixel according to claim 37 wherein each of the cell wall structures includes a layer of vacuum oblique evaporated material.

46. A liquid crystalline light modulating device including first and second cell wall structures with nematic liquid crystal disposed therebetween and means for electrically addressing the liquid crystal, the improvement comprising at least one liquid crystalline light modulating pixel comprising four liquid crystal domains within said pixel formed by cooperation of said first and second cell wall structures with said liquid crystal, wherein the liquid crystal in each of said domains exhibits a twisted nematic liquid crystal structure and the orientation of the liquid crystal director of the liquid crystal adjacent one of said cell wall structures in at least two domains is different in the absence of chiral additives and wherein a pretilt angle in all liquid crystal domains is the same, and wherein the first and second cell wall structures are treated to promote liquid crystal orientation.

47. The light modulating device according to claim 46 wherein said liquid crystal has positive dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect thereto from 0.5°

-30°

.

48. The light modulating device according to claim 46 wherein said liquid crystal has negative dielectric anisotropy and the liquid crystal adjacent said cell wall structures is tilted with respect to a normal to said cell wall structures from 0.1°

-10°

.

49. The light modulating device according to claim 46 wherein the orientation of the liquid crystal director in all four domains adjacent one of said cell wall structures is different.

50. The light modulating device according to claim 46 wherein the liquid crystal director in two domains has right hand rotation and the liquid crystal director in the remaining domains has left hand rotation.

51. The light modulating device according to claim 46 further comprising two polarizers between which the cell wall structures are located, wherein a polarization orientation passed by one polarizer is parallel to a polarization orientation passed by the other polarizer.

52. The light modulating device according to claim 46 further comprising two polarizers between which the cell wall structures are located, wherein a polarization orientation passed by one polarizer is orthogonal to a polarization orientation passed by the other polarizer.

53. A method of producing a four domain liquid crystalline pixel for a light modulating device, comprising the steps of

providing first and second cell wall structures,

treating at least a first region on said cell wall structures to promote a liquid crystal orientation in one direction,

treating at least a second region on said cell wall structures to promote a liquid crystal orientation in a different direction than in said first region,

spacing apart the cell wall structures and providing a nematic liquid crystal therebetween,

wherein the treatment of said first and second regions produces four domains in which the liquid crystal has a twisted nematic liquid crystal structure extending between said first and second cell wall structures and the orientation of the liquid crystal director of the liquid crystal adjacent one of said cell wall structures in at least two domains is different in the absence of chiral additives and wherein a pretilt angle in all liquid crystal domains is the same.

54. The method according to claim 53 further comprising orienting the cell wall structures such that the orientation of the liquid crystal director of the liquid crystal in one domain adjacent one of the cell wall structures is orthogonal to the orientation of the liquid crystal director of the liquid crystal in said one domain adjacent the other cell wall structure.

55. The method according to claim 53 wherein the treatment of said first and second regions of said first and second cell wall structures comprises forming a layer of material on said cell wall structures, rubbing said layer in one direction, forming a mask on said layer to cover one of said first and second regions and leave the other uncovered, rubbing said layer in said first and second regions in a different direction, and removing said mask.

56. The method according to claim 53 wherein the rubbing direction of the first region is opposite to the rubbing direction of the second region.

57. The method according to claim 53 wherein the treatment of said first and second regions of said first and second cell wall structures comprises forming a first layer of material on the cell wall structures by vacuum oblique evaporation, forming a mask on said first layer to cover one of said first and second regions and leave the other uncovered, rotating the cell wall structures, forming a second layer of material on the first and second regions by vacuum oblique evaporation, and removing said mask.

58. The method according to claim 57 wherein the cell wall structures are rotated 180°

.

59. A method of producing a four domain liquid crystalline pixel for a light modulating device, comprising the steps of

providing first and second cell wall structures,

rotating the cell wall structures,

depositing a first layer of liquid crystal alignment material onto the rotating cell wall structures by vacuum oblique evaporation,

stopping rotation of the cell wall structures opposite to an intended pretilt orientation of a liquid crystal director of liquid crystal adjacent the cell wall structures,

depositing a second layer of liquid crystal alignment material onto the fixed cell wall structures by vacuum oblique evaporation,

masking the cell wall structures in an alternating striped pattern,

rotating the cell wall structures a predetermined angle,

depositing a third layer of liquid crystal alignment material onto the cell wall structures by vacuum oblique evaporation,

removing said mask, and

spacing said first and second cell wall structures apart and providing a nematic liquid crystal therebetween in the absence of chiral additives and wherein a pretilt angle in all liquid crystal domains is the same.

60. The method according to claim 59 further comprising orienting the cell wall structures such that the striped pattern on the first cell wall structure is orthogonal to the striped pattern on the second cell wall structure.

61. The method according to claim 59 wherein the liquid crystal alignment material is SiO_x.

62. The method according to claim 59 wherein said predetermined angle is 180°

.