LIQUID CRYSTAL PAPER

• US 20130070184A1
• Filed: 09/17/2012
• Published: 03/21/2013
• Est. Priority Date: 09/16/2011
• Status: Active Grant

• Current Assignee: Kent Displays Incorporated
• Original Assignee: Kent Displays Incorporated
• Inventors: GREEN, Albert, MORRIS, Hunter
• Granted Patent: US 9,651,813 B2
• Time in Patent Office: Days
• US Class Current: 349/88
• CPC Class Codes: G02F 1/1313 specially adapted for a particular application
• CPC Class Codes: G02F 1/132 Thermal activation of liquid crystals exhibiting a thermo-optic effect
• CPC Class Codes: G02F 1/133305 Flexible substrates, e.g. plastics, organic film
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/13345 Network or three-dimensional gels
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal

Abstract

Disclosed is liquid crystal paper and an erasing device that is not permanently connected to the liquid crystal paper. A sheet of liquid crystal paper includes flexible polymeric substrates. A polymer network or a spacer network, in which bistable cholesteric reflective liquid crystal material is dispersed, is disposed between two of the substrates. Optional alignment layers or optional electrically conductive layers sandwich the liquid crystal material therebetween. An optional layer of light absorbing material is disposed near one of the substrates. Application of pressure to an upper substrate changes a focal conic nonreflective texture of the liquid crystal material to a reflective planar texture. The erasing device applies a voltage or heat for erasing the paper by changing the reflective planar texture to the focal conic nonreflective texture.

Claims

1. Liquid crystal paper in combination with a separate erasing device for erasing the liquid crystal paper comprising:

a sheet of liquid crystal paper comprising;

flexible polymeric substrates;

a polymer network or spacer network in which bistable cholesteric reflective liquid crystal material is dispersed, disposed between two of said substrates;

alignment layers or electrically conductive layers that sandwich said liquid crystal material therebetween, said alignment layers favoring formation of a focal conic nonreflective texture in said liquid crystal material;

wherein application of pressure to an upper said substrate changes said focal conic nonreflective texture of said liquid crystal material to a reflective planar texture; and

an erasing device for erasing said liquid crystal paper that is not permanently connected to said liquid crystal paper, said erasing device including a source of voltage or a source of heat for erasing said liquid crystal paper by changing said reflective planar texture to said focal conic nonreflective texture.

2. The liquid crystal paper and separate erasing device of claim 1 comprising a layer of light absorbing material disposed near one of said substrates.

3. The liquid crystal paper and separate erasing device of claim 2 wherein all of said substrates that are upstream of said light absorbing layer in a direction of incident light are transparent.

4. The liquid crystal paper and separate erasing device of claim 1 wherein said polymer network in which said liquid crystal material is dispersed is in the form of a liquid crystal layer.

5. The liquid crystal paper and separate erasing device of claim 4 comprising at least two of said liquid crystal layers.

6. The liquid crystal paper and separate erasing device of claim 5 wherein each of said liquid crystal layers is sandwiched by said electrically conductive layers.

7. The liquid crystal paper and separate erasing device of claim 6 wherein at least one of said substrates is disposed between adjacent said electrically conductive layers.

8. The liquid crystal paper and separate erasing device of claim 4 wherein said liquid crystal layer has a thickness ranging from 2 to 10 microns.

9. The liquid crystal paper and separate erasing device of claim 1 wherein each said substrate has a thickness ranging from 12.5 μ

m to 200 μ

m.

10. The liquid crystal paper and separate erasing device of claim 1 wherein application of pressure to said upper substrate creates gray scale caused by a presence of a combination of said focal conic nonreflective texture and said reflective planar texture.

11. The liquid crystal paper and separate erasing device of claim 1 comprising a stylus for applying said pressure that is untethered to said liquid crystal paper or to said erasing device, said stylus containing no lead or ink.

12. Liquid crystal paper in combination with a separate erasing device for electrically erasing the liquid crystal paper comprising:

a sheet of liquid crystal paper comprising;

flexible polymeric substrates;

a polymer network or spacer network in which bistable cholesteric reflective liquid crystal material is dispersed, disposed between two of said substrates;

electrically conductive layers that sandwich said liquid crystal material therebetween;

a layer of light absorbing material disposed near one of said substrates;

electrically conductive leads extending from said electrically conductive layers so as to be exposed exterior to said substrates;

wherein application of pressure to an upper said substrate changes a focal conic nonreflective texture of said liquid crystal material to a reflective planar texture; and

an erasing device for erasing said liquid crystal paper that is not permanently connected to said liquid crystal paper, said erasing device comprising a housing including electrical contacts that detachably connect with said electrically conductive leads, and drive electronics that apply a voltage to said contacts for erasing said liquid crystal paper by changing said reflective planar texture to said focal conic nonreflective texture.

13. The liquid crystal paper and separate erasing device of claim 12 wherein all of said substrates that are upstream of said light absorbing layer in a direction of incident light are transparent.

14. The liquid crystal paper and separate erasing device of claim 12 wherein said polymer network in which said liquid crystal material is dispersed is in the form of a liquid crystal layer.

15. The liquid crystal paper and separate erasing device of claim 14 comprising at least two of said liquid crystal layers.

16. The liquid crystal paper and separate erasing device of claim 15 wherein each of said liquid crystal layers is sandwiched by said electrically conductive layers.

17. The liquid crystal paper and separate erasing device of claim 16 wherein at least one of said substrates is disposed between adjacent said electrically conductive layers.

18. The liquid crystal paper and separate erasing device of claim 14 wherein said liquid crystal layer has a thickness ranging from 2 to 10 microns.

19. The liquid crystal paper and separate erasing device of claim 12 wherein each said substrate has a thickness ranging from 12.5 μ

m to 200 μ

m.

20. The liquid crystal paper and separate erasing device of claim 12 wherein said erasing device includes a switch enabling said voltage from said drive electronics to be applied to said contacts and to erase said liquid crystal paper.

21. The liquid crystal paper and separate erasing device of claim 12 wherein application of pressure to said upper substrate creates gray scale caused by a presence of a combination of said focal conic nonreflective texture and said reflective planar texture.

22. The liquid crystal paper and separate erasing device of claim 12 comprising a stylus for applying said pressure that is untethered to said liquid crystal paper or to said erasing device, said stylus containing no lead or ink.

23. The liquid crystal paper and separate erasing device of claim 12 comprising a plurality of said sheets of said liquid crystal paper and a document feeder that feeds individual said sheets to said erasing device.

24. The liquid crystal paper and separate erasing device of claim 12 wherein said erasing device includes sockets in which said contacts are disposed, said sockets being configured and arranged to receive said leads.

25. The liquid crystal paper and separate erasing device of claim 12 comprising a casing in contact with said substrates that ruggedizes said liquid crystal paper.

26. Liquid crystal paper in combination with a separate erasing device for erasing the liquid crystal paper with heat comprising:

a sheet of liquid crystal paper comprising;

flexible polymeric substrates;

a polymer network or a spacer network in which bistable cholesteric reflective liquid crystal material is dispersed, disposed between two of said substrates;

a layer of light absorbing material disposed near one of said substrates;

wherein application of pressure to an upper said substrate changes a focal conic nonreflective texture of said liquid crystal material to a reflective planar texture; and

an erasing device for erasing said liquid crystal paper that is not permanently connected to said liquid crystal paper, said erasing device applying heat effective to cause said liquid crystal material to reach a clearing temperature such that after said liquid paper cools it returns to said focal conic nonreflective texture.

27. The liquid crystal paper and separate erasing device of claim 26 wherein all of said substrates that are upstream of said light absorbing layer in a direction of incident light are transparent.

28. The liquid crystal paper and separate erasing device of claim 26 wherein said polymer network in which said liquid crystal material is dispersed is in the form of a liquid crystal layer.

29. The liquid crystal paper and separate erasing device of claim 28 comprising at least two of said liquid crystal layers.

30. The liquid crystal paper and separate erasing device of claim 28 wherein said liquid crystal layer has a thickness ranging from 2 to 10 microns.

31. The liquid crystal paper and separate erasing device of claim 26 comprising alignment layers that sandwich said liquid crystal material therebetween, said alignment layers favoring formation of a focal conic nonreflective texture in said liquid crystal material.

32. The liquid crystal paper and separate erasing device of claim 31 wherein said alignment layers are part of said polymer network.

33. The liquid crystal paper and separate erasing device of claim 26 wherein there is no alignment layer favoring formation of said focal conic nonreflective texture in said liquid crystal material.

34. The liquid crystal paper and separate erasing device of claim 26 wherein each said substrate has a thickness ranging from 12.5 μ

m to 200 μ

m.

35. The liquid crystal paper and separate erasing device of claim 26 comprising a stylus for applying said pressure that is untethered to said liquid crystal paper or to said erasing device, said stylus containing no lead or ink.

36. The liquid crystal paper and separate erasing device of claim 26 comprising a plurality of said sheets of said liquid crystal paper and a document feeder that feeds individual said sheets to said erasing device.