Liquid crystal switching mechanism

• US 6,824,837 B2
• Filed: 09/04/2002
• Issued: 11/30/2004
• Est. Priority Date: 09/04/2001
• Status: Expired due to Term

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Luk, Yan-Yeung, Abbott, Nicholas Lawrence
• Primary Examiner(s): WU, SHEAN CHIU
• Application Number:
  US10/234,449
• Publication Number:
  US 20030071949A1
• Time in Patent Office: 818 Days
• Field of Search: 252/299.01, 252/299.5, 252/299.3, 252/399.4, 428/1.1, 428/1.3, 428/1.4, 349/41, 349/123
• US Class Current: 428/1.1
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
• CPC Class Codes: C09K 2323/03 Viewing layer characterised by chemical composition
• CPC Class Codes: C09K 2323/04 Charge transferring layer characterised by chemical composition, i.e. conductive
• CPC Class Codes: G02F 1/133719 with coupling agent molecules, e.g. silane
• CPC Class Codes: G02F 1/133769 comprising an active, e.g. switchable, alignment layer

Abstract

The invention provides liquid crystal switching devices, liquid crystal cells made from the switching devices, and electrooptical cells made from the switching devices. The invention further provides methods for methods for changing the orientation of a liquid crystal in a liquid crystal switching device. The liquid crystal switching devices are constructed from a redox-active material supported by a substrate and a liquid crystal having a salt dispersed therein disposed atop the redox-active material.

Claims

1. A liquid crystal switching device comprising:

(a) a first substrate having a first surface;

(b) a redox-active material disposed on a first portion of the first surface, the redox-active material comprising at least one redox-active group;

(c) a liquid crystal disposed above the redox-active material; and

(d) a salt dispersed in the liquid crystal, wherein the liquid crystal changes from a first orientation to a second orientation with respect to the first surface of the substrate when an oxidation state of the at least one redox-active group is changed from a first oxidation state to a second oxidation state.

2. The liquid crystal switching device of claim 1, wherein the liquid crystal changes from the second orientation back to the first orientation when the oxidation state of the at least one redox-active group is changed from the second oxidation state back to the first oxidation state.

3. The liquid crystal switching device of claim 1, wherein the first surface comprises at least one electrically conducting region.

4. The liquid crystal switching device of claim 3, wherein the at least one electrically conducting region is a metallized region.

5. The liquid crystal switching device of claim 4, wherein the metallized region comprises a metal selected from the group consisting of gold, silver, copper, nickel, palladium, platinum, and combinations thereof.

6. The liquid crystal switching device of claim 3, wherein the at least one electrically conducting region comprises an electrically conducting polymer or an electrically conducting metal oxide.

7. The liquid crystal switching device of claim 1, wherein the first surface comprises a semiconducting material or a non-electrically conducting material.

8. The liquid crystal switching device of claim 1, wherein the at least one redox-active group comprises a monocyclic or polycyclic aromatic group.

9. The liquid crystal switching device of claim 8, wherein the at least one redox-active group is selected from the group consisting of ferrocenes, derivatized ferrocenes, viologens, pyridines, bipyridines, metal meso porphyrins, quinones, hydroquinones, anthracenes, and combinations thereof.

10. The liquid crystal switching device of claim 1, wherein the at least one redox-active group is a ferrocene.

11. The liquid crystal switching device of claim 1, wherein the redox-active material comprises a polymer and the redox-active groups are pendant groups on the polymer.

12. The liquid crystal switching device of claim 11 wherein the polymer comprises poly(vinylferrocene).

13. The liquid crystal switching device of claim 1, wherein the redox-active material is a self-assembled monolayer comprising a plurality of molecules comprising the at least one redox-active group.

14. The liquid crystal switching device of claim 13 wherein the first surface comprises at least one metallized region and the self-assembled monolayer is formed by contacting a compound of the formula Fc—

(CH₂)n—

SH with the at least one metallized region, wherein Fc is ferrocene and n has a value ranging from 1 to 20.

15. The liquid crystal switching device of claim 1, wherein the first surface of the first substrate comprises a second portion and a second redox-active material is disposed on the second portion of the first surface, and further wherein the second redox-active material and the redox-active material possess different redox potentials.

16. The liquid crystal switching device of claim 1, wherein the liquid crystal is a nematic liquid crystal.

17. The liquid crystal switching device of claim 1, wherein the liquid crystal comprises 4-cyano-4′

-pentylbiphenyl.

18. The liquid crystal switching device of claim 1, wherein the salt is a tetraalkylammonium salt, a metal halide salt, or an organic-inorganic hybrid salt comprising an organic encapsulated metal.

19. The liquid crystal switching device of claim 1, further comprising an oxidizing agent or a redox mediator dispersed in the liquid crystal.

20. The liquid crystal switching device of claim 1, further comprising, a second substrate having a second surface, wherein the second surface is disposed above the redox-active material to form a gap between the redox-active material and the second surface, and further wherein the liquid crystal is located within the gap.

21. The liquid crystal switching device of claim 20, further comprising a spacing material disposed between the first and the second substrates.

22. The liquid switching device of claim 21, wherein the spacing material comprises a polymeric film or microparticles.

23. The liquid crystal switching device of claim 20, wherein the second surface comprises at least one electrically conducting region.

24. The liquid crystal switching device of claim 23, wherein the at least one electrically conducting region of the second surface is a metallized region.

25. The liquid crystal switching device of claim 24, wherein the metallized region of the second surface comprises a metal selected from the group consisting of gold, silver, copper, nickel, palladium, platinum, and combinations thereof.

26. The liquid crystal switching device of claim 23, wherein the at least one electrically conducting region of the second surface comprises an electrically conducting polymer or an electrically conducting metal oxide.

27. The liquid crystal switching device of claim 20, wherein the second surface comprises a semiconducting material or a non-electrically conducting material.

28. The liquid crystal switching device of claim 1, wherein the first surface comprises at least one electrically conducting region, and further wherein the at least one electrically conducting region of the first surface provides a first working electrode, the liquid crystal device further comprising a counter electrode comprising an electrically conducting material.

29. The liquid crystal switching device of claim 28, wherein the counter electrode is disposed on the first surface of the first substrate.

30. The liquid crystal switching device of claim 29, wherein the first surface comprises at least a second electrically conducting region, and further wherein the second electrically conducting region provides a second working electrode, and still further wherein a redox-active material comprising at least one redox-active group is disposed on the second working electrode.

31. A method of changing the orientation of a liquid crystal in a liquid crystal switching device, comprising:

oxidizing or reducing redox-active groups in a liquid crystal switching device, wherein the liquid crystal switching device comprises;

(a) a first substrate having a first surface;

(b) a redox-active material disposed on at least a portion of the first surface of the first substrate, the redox-active material comprising the redox-active groups;

(c) a liquid crystal disposed above the redox active material; and

(d) a salt dispersed in the liquid crystal,

wherein the orientation of the liquid crystal in the liquid crystal switching device is changed when the redox-active groups are oxidized or reduced.

32. The method of claim 31, wherein the first surface comprises at least one electrically conducting region, and further wherein the at least one electrically conducting region of the first surface provides a first working electrode and further wherein the liquid crystal device further comprises a counter electrode comprising an electrically conducting material.

33. The method of claim 32, wherein the redox-active groups are oxidized or reduced by applying an electric potential to the working electrode or the counter electrode.

34. The method of claim 33, wherein the electric potential is applied to the working electrode and further wherein the electric potential is less than 350 mV relative to the counter electrode.

35. The method of claim 31, wherein an oxidizing agent or a redox mediator is dispersed in the liquid crystal and the redox-active groups are oxidized or reduced by exposing the redox-active groups to the oxidizing agent or the redox mediator.

36. A method of manufacturing a liquid crystal switching device comprising:

(a) depositing a material having one or more redox-active groups on a surface of a substrate;

(b) disposing a liquid crystal over the material having the redox-active groups; and

(c) dispersing a salt in the liquid crystal.

37. The method of claim 36, wherein the salt is dispersed in the liquid crystal before the liquid crystal is disposed over the material having the redox-active groups.

38. A kit for manufacturing a liquid crystal device comprising:

(a) a substrate having a surface;

(b) a material comprising one or more redox-active groups;

(c) a liquid crystal; and

(d) a salt.