Conductive absorption layer for flexible displays

• US 7,630,029 B2
• Filed: 02/16/2005
• Issued: 12/08/2009
• Est. Priority Date: 02/16/2005
• Status: Expired due to Fees

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Freedman, Gary S., Allen, Delaina A., Majumdar, Debasis, Bauer, Charles L.
• Primary Examiner(s): Dudek, James A
• Application Number:
  US11/059,270
• Publication Number:
  US 20060181658A1
• Time in Patent Office: 1,756 Days
• Field of Search: 349/86, 349/113, 349/158, 428/1.1
• US Class Current: 349/86
• CPC Class Codes: G02F 1/13476 in which at least one liquid crystal cell or layer assumes a scattering state
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal

Abstract

The present invention relates to a bistable reflective display and a method for making the display comprising a substrate, an electrically modulated imaging layer, and a coatable color contrast conductive layer comprising an electronically conductive polymer and colorant.

Claims

1. A bistable reflective display comprising a substrate, an electrically modulated imaging layer, and a coatable color contrast conductive layer comprising an electronically conductive polymer and colorant, wherein the ratio of said polymer to said colorant is in the range from about 95:

5 to about 40;

60.

2. The bistable reflective display of claim 1 wherein said substrate is flexible.

3. The bistable reflective display of claim 1 wherein said substrate comprises polyester.

4. The bistable reflective display of claim 1 wherein said substrate comprises cellulose triacetate, also known as triacetylcellulose or TAC.

5. The bistable reflective display of claim 1 wherein said electrically modulated imaging layer comprises a light modulating material.

6. The bistable reflective display of claim 5 wherein said light modulating material is a chiral nematic liquid crystal material.

7. The bistable reflective display of claim 5 wherein said electrically modulated imaging layer comprises a polymer dispersed cholesteric liquid crystal layer.

8. The bistable reflective display of claim 7 wherein said polymer within which said cholesteric liquid crystal is dispersed is gelatin.

9. The bistable reflective display of claim 7 wherein said polymer within which said cholesteric liquid crystal is dispersed is water soluble.

10. The bistable reflective display of claim 1 wherein said electronically conductive polymer is polythiophene.

11. The bistable reflective display of claim 10 wherein said polythiophene is present in a cationic form with a polyanion.

12. The bistable reflective display of claim 1 wherein said color contrast conductive layer has a surface electrical resistivity of less than 10⁴ ohms/sq.

13. The bistable reflective display of claim 1 wherein said color contrast conductive layer has a thickness less than 1.0 micron.

14. The bistable reflective display of claim 1 wherein the thickness of said color contrast conductive layer is less than 25% of the said electrically modulated imaging layer.

15. The bistable reflective display of claim 1 wherein said color contrast conductive layer has visual light transmission of ≦

10%.

16. The bistable reflective display of claim 1 wherein said colorant comprises carbon.

17. The bistable reflective display of claim 1 wherein said color contrast conductive layer provides a background that is substantially neutral to the human eye.

18. The bistable reflective display of claim 1 wherein said color contrast conductive layer provides a background that provides a substantially neutral optical density such that there is variability of less than +/−

20% from the mean optical density over at least 80% of the visible spectrum from 400 to 700 nm.

19. The bistable reflective display of claim 1 wherein said color contrast conductive layer comprises a combination of at least two nonconductive colorants which have different hues.

20. The bistable reflective display of claim 1 wherein said color contrast conductive layer comprises cyan, magenta, and yellow nonconductive colorants.

21. The bistable reflective display of claim 20 wherein said colorant comprises a pigment particle having a median particle diameter of less than 50 percent of the thickness of said color contrast conductive layer.

22. The bistable reflective display of claim 1 wherein said color contrast conductive layer further comprises a conductivity enhancing agent (CEA).

23. The bistable reflective display of claim 1 further comprising a transparent electrically conductive layer, wherein said electrically modulated imaging layer is between said color contrast conductive layer and said transparent electrically conductive layer.

24. A method for making a bistable reflective display comprising providing a substrate, applying a transparent conductive layer, applying an electrically modulated imaging layer to said substrate and said transparent conductive layer, and adding a color contrast conductive layer comprising an electronically conductive polymer and colorant, wherein the ratio of the electrically conductive polymer to the colorant is in the range from about 95:

5 to about 40;

60.

25. A bistable reflective display comprising a substrate, an electrically modulated imaging layer, and a coatable color contrast conductive layer comprising an electronically conductive polymer and colorant, wherein said color contrast conductive layer has visual light transmission of ≦

10%.

26. The bistable reflective display of claim 25, wherein said color contrast conductive layer provides a background that provides a substantially neutral optical density such that there is variability of less than +/−

20% from the mean optical density over at least 80% of the visible spectrum from 400 to 700 nm.

27. A bistable reflective display comprising a substrate, an electrically modulated imaging layer, and a coatable color contrast conductive layer comprising an electronically conductive polymer and colorant, wherein said color contrast conductive layer provides a background that provides a substantially neutral optical density such that there is variability of less than +/−

20% from the mean optical density over at least 80% of the visible spectrum from 400 to 700 nm.