Bistable liquid crystal display device using polymer stabilization

• US 6,583,838 B1
• Filed: 02/22/2000
• Issued: 06/24/2003
• Est. Priority Date: 05/10/1996
• Status: Expired due to Term

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Hoke, Charles D., Bos, Philip J., Li, Jianlin
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): LEE, HWA S
• Application Number:
  US09/507,954
• Time in Patent Office: 1,218 Days
• Field of Search: 349/134, 349/135, 349/88, 349/156, 349/133, 349/125
• US Class Current: 349/134
• CPC Class Codes: G02F 1/13775 Polymer-stabilized liquid crystal layers
• CPC Class Codes: G02F 1/1391 Bistable or multi-stable liquid crystal cells G02F1/141 takes precedence
• CPC Class Codes: G02F 1/1397 the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells

Abstract

A liquid crystal display device including a polyimide alignment layer, having a bistable liquid crystal material and a polymer stabilizer in an amount effective to stabilize the liquid crystal the liquid crystal preferably having a low or medium pretilt angle to eliminate undesired states and stripe tendency and to increase hysteresis. The device has a low driving voltage, low power consumption and fast switching.

Claims

1. A liquid crystal display device including a polyimide alignment layer, having a bistable liquid crystal material and a polymer stabilizer in an amount from about 1% to about 15% based on the total weight of polymer and liquid crystal material, wherein the liquid crystal provides a twist angle from 0°

to 360°

.

2. The liquid crystal display device of claim 1 wherein the polymer stabilizer stabilizes the state of the liquid crystal in the absence of an applied field, and permits the liquid crystal to change states in the presence of an applied field.

3. The liquid crystal display device of claim 1 wherein the polymer stabilizer is present in an amount of from about 1% to less than 4% based on the total weight of polymer and liquid crystal material.

4. The liquid crystal display device of claim 1 wherein the polymer stabilizer is present in an amount of from greater than 4% to about 15% based on the total weight of polymer and liquid crystal material.

5. The liquid crystal display device of claim 1, wherein the liquid crystal has a low pretilt angle.

6. The liquid crystal display device of claim 1, wherein the liquid crystal has a medium pretilt angle.

7. The liquid crystal display device of claim 1 wherein the liquid crystal material is a chiral nematic liquid crystal, including chiral material in an amount effective to form twist angles of φ

and φ

+360°

, wherein φ

is an angle from about 0°

to about 180°

.

8. The liquid crystal display device of claim 1 wherein the liquid crystal material is a chiral nematic liquid crystal, including chiral material in an amount effective to form a twist angle of 360°

.

9. The liquid crystal display device of claim 7 having a cell thickness to pitch ratio of greater than or equal to about 0.5 to less than or equal to about 1.25.

10. The liquid crystal display device of claim 8 having a thickness to pitch ratio of about 0.6 to about 0.9.

11. The liquid crystal display device of claim 1 wherein the surface pretilt angle is about 5°

.

12. The liquid crystal display device of claim 1 wherein the polyimide alignment layers are antiparallelly rubbed on opposing substrates.

13. The liquid crystal display device of claim 11, wherein the substrates are transparent substrates selected from the group consisting of glass and plastic.

14. The liquid crystal display device of claim 1, wherein the polymer stabilizer is a polymerizable monomer that dissolves into and is aligned with the liquid crystal.

15. The liquid crystal display device of claim 1, wherein the polymer stabilizer is a UV curable acrylate.

16. The liquid crystal display device of claim 14, wherein the acrylate is a diacrylate.