Liquid crystal paper

• US 9,651,813 B2
• Filed: 09/17/2012
• Issued: 05/16/2017
• Est. Priority Date: 09/16/2011
• Status: Active Grant

• Current Assignee: Kent Displays Incorporated
• Original Assignee: Kent Displays Incorporated
• Inventors: Morris, Hunter, Green, Albert
• Primary Examiner(s): Glick, Edward
• Assistant Examiner(s): Chung, David
• Application Number:
  US13/621,367
• Publication Number:
  US 20130070184A1
• Time in Patent Office: 1,702 Days
• Field of Search: 349 12, 349 58, 349158, 345173, 345174
• 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 bistable dispersion layer including a polymer network or spacer network in which cholesteric reflective liquid crystal material is dispersed, disposed between two of said substrates;

electrically conductive layers that sandwich said dispersion layer therebetween;

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;

wherein said liquid crystal paper is flexible and includes no casing that ruggedizes said liquid crystal paper;

wherein a through hole is in said liquid crystal paper which internally exposes said electrically conductive layers; 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 for erasing said liquid crystal paper by changing said reflective planar texture to said focal conic nonreflective texture;

wherein said erasing device comprises a post and electrically conductive contacts disposed on said post that detachably connect with said exposed electrically conductive layers, wherein said drive electronics apply said voltage to said electrically conductive contacts for erasing said liquid crystal paper.

2. The liquid crystal paper and separate erasing device of claim 1 comprising a spring mechanism for outwardly urging said electrically conductive contacts.

3. The liquid crystal paper and separate erasing device of claim 1,

wherein each of said substrates has a thickness of not more than 50 microns.

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

5. The liquid crystal paper and separate erasing device of claim 4 wherein all of said substrates that are upstream of said light absorbing layer in a direction of incident light are transparent.

6. The liquid crystal paper and separate erasing device of claim 1 wherein said dispersion layer includes said polymer network in which said liquid crystal material is dispersed.

7. The liquid crystal paper and separate erasing device of claim 6 comprising at least two of said dispersion layers.

8. The liquid crystal paper and separate erasing device of claim 7 wherein each of said dispersion layers is sandwiched by said electrically conductive layers.

9. The liquid crystal paper and separate erasing device of claim 8 wherein at least one of said substrates is disposed between adjacent said electrically conductive layers.

10. The liquid crystal paper and separate erasing device of claim 6 wherein said dispersion layer has a thickness ranging from 2 to 10 microns.

11. The liquid crystal paper and separate erasing device of claim 3 wherein each said substrate has a thickness of at least 12.5 μ

m.

12. 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.

13. 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.

14. The liquid crystal paper and separate erasing device of claim 1 comprising a seal around a periphery of said liquid crystal paper formed by laser singulation.

15. The liquid crystal paper of claim 1 wherein said electrically conductive layers comprise unpatterned conductors.

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

electrically conductive layers that sandwich said dispersion layer 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;

wherein said liquid crystal paper is flexible; 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 sockets including internal electrical contacts that detachably connect with said electrically conductive leads, and drive electronics that apply a voltage to said internal contacts for erasing said liquid crystal paper by changing said reflective planar texture to said focal conic nonreflective texture.

17. The liquid crystal paper and separate erasing device of claim 16 wherein all of said substrates that are upstream of said light absorbing layer in a direction of incident light are transparent.

18. The liquid crystal paper and separate erasing device of claim 16 wherein said dispersion layer includes said polymer network in which said liquid crystal material is dispersed.

19. The liquid crystal paper and separate erasing device of claim 18 comprising at least two of said dispersion layers.

20. The liquid crystal paper and separate erasing device of claim 19 wherein each of said dispersion layers is sandwiched by said electrically conductive layers.

21. The liquid crystal paper and separate erasing device of claim 20 wherein at least one of said substrates is disposed between adjacent said electrically conductive layers.

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

23. The liquid crystal paper and separate erasing device of claim 16 wherein each said substrate has a thickness up to 50 μ

m.

24. The liquid crystal paper and separate erasing device of claim 16 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.

25. The liquid crystal paper and separate erasing device of claim 16 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.

26. The liquid crystal paper and separate erasing device of claim 16 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.

27. The liquid crystal paper and separate erasing device of claim 16 comprising a seal around a periphery of said liquid crystal paper formed by laser singulation.

28. The liquid crystal paper and separate erasing device of claim 23 wherein each of said substrates has a thickness of at least 12.5 microns.

29. The liquid crystal paper of claim 16 wherein said electrically conductive layers comprise unpatterned conductors.