Polymer stabilized four domain twisted nematic liquid crystal display

• US 5,831,700 A
• Filed: 05/15/1996
• Issued: 11/03/1998
• Est. Priority Date: 05/19/1995
• Status: Expired due to Fees

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Li, Jianlin, Chen, Jianmin, Bos, Philip J.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/644,962
• Time in Patent Office: 902 Days
• Field of Search: 349/88, 349/93, 349/94, 349/125, 349/129, 349/134, 349/136
• US Class Current: 349/88
• 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 within a UV cured polymer network 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. The polymer network stabilizes the four domain structure at both high field and zero field conditions.

Claims

1. A liquid crystalline light modulating pixel comprising first and second cell wall structures and nematic liquid crystal within a UV cured polymer network disposed herebetween, 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.

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 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.

6. The liquid crystalline pixel according to claim 1 wherein the four domain structure is stable at both high field and zero field conditions.

7. 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.

8. The liquid crystalline pixel according to claim 1 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.

9. The liquid crystalline pixel according to claim 1 wherein each of the cell wall structures includes a rubbed polyimide layer.

10. The liquid crystalline pixel according to claim 1 wherein each of the cell wall structures includes a layer of vacuum oblique evaporated material.

11. 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 and a UV curable monomer therebetween, and,

curing the cell by UV exposure while applying a field, 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.

12. The method according to claim 11 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.

13. The method according to claim 11 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.

14. The method according to claim 11 wherein the rubbing direction of the first region is opposite to the rubbing direction of the second region.

15. The method according to claim 11 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.

16. The method according to claim 15 wherein the cell wall structures are rotated 180°

.

17. The method according to claim 11 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°

.

18. The method according to claim 11 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°

.

19. The method according to claim 11 wherein the orientation of the liquid crystal director in all four domains adjacent one of said cell wall structures is different.

20. The method according to claim 11 wherein the liquid crystal director of the liquid in two domains adjacent one of the cell wall structures is rotated 120°

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

21. The method according to claim 11 wherein the four domain structure is stable at both high field and zero field conditions.

22. The method according to claim 11 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.

23. The method according to claim 11 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.

24. The method according to claim 11 wherein each of the cell wall structures includes a rubbed polyimide layer.

25. The method according to claim 11 wherein each of the cell wall structures includes a layer of vacuum oblique evaporated material.