Electrophoretic media and processes for the production thereof

• US 7,375,875 B2
• Filed: 05/02/2007
• Issued: 05/20/2008
• Est. Priority Date: 05/15/2001
• Status: Expired due to Term

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Whitesides, Thomas H., Wilcox, Russell J., Zhou, Qingye
• Primary Examiner(s): Ben; Loha
• Application Number:
  US11/743,204
• Publication Number:
  US 20070201124A1
• Time in Patent Office: 384 Days
• Field of Search: 359/296, 359/452, 345/55, 345/107, 204/450, 204/600, 204/601, 204/606, 204/616, 430/32, 430/34, 430/38, 427/212, 427/216, 349/86, 252/583
• US Class Current: 359/296
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01P 2002/88 by thermal analysis data, e.g. TGA, DTA, DSC
• CPC Class Codes: C01P 2004/32 Spheres
• CPC Class Codes: C01P 2004/51 Particles with a specific particle size distribution
• CPC Class Codes: C01P 2004/61 Micrometer sized, i.e. from 1-100 micrometer
• CPC Class Codes: C01P 2004/62 Submicrometer sized, i.e. from 0.1-1 micrometer
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2004/82 two phases having the same anion, e.g. both oxidic phases
• CPC Class Codes: C01P 2004/84 one phase coated with the other
• CPC Class Codes: C01P 2006/10 Solid density
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C01P 2006/60 Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: C01P 2006/80 Compositional purity
• CPC Class Codes: C01P 2006/90 Other properties not specified above
• CPC Class Codes: C09B 67/0013 with polymeric coatings
• CPC Class Codes: C09B 68/41 Polymers attached to the pigment surface C09B68/444, C09B68/446 take precedence
• CPC Class Codes: C09B 68/44 Non-ionic groups, e.g. halogen, OH or SH
• CPC Class Codes: C09C 1/00 Treatment of specific inorganic materials other than fibrous fillers tenebrescent materials C09K9/00; luminescent materials C09K11/00; Preparation of carbon black
• CPC Class Codes: C09C 1/24 Oxides of iron
• CPC Class Codes: C09C 1/343 containing silicon or associated with silicon containing material, except when silicon only occurs in a thin coating of the particles
• CPC Class Codes: C09C 3/10 : Treatment with macromolecular organic compounds C09C3/006 takes precedence
• CPC Class Codes: G01N 27/44747 : Composition of gel or of carrier mixture
• CPC Class Codes: G02F 1/167 : by electrophoresis
• CPC Class Codes: G02F 2001/1678 : characterised by the composition or particle type
• CPC Class Codes: G02F 2202/022 : polymeric
• CPC Class Codes: Y10T 428/2991 : Coated

Abstract

A first electrophoretic medium comprises an electrically charged particle suspended in a suspending fluid, the particle having a polymeric shell having repeating units derived from at least one monomer the homopolymer of which is incompatible with the suspending fluid. A second, similar electrophoretic medium comprises a suspending fluid, and first and second types of electrically charged particle suspended in the suspending fluid, the two types of particle having differing optical characteristics but both having polymeric shells. The polymeric shells are arranged such that homoaggregation of the two types of particles is thermodynamically favored over heteroaggregation.

Claims

1. An electrophoretic medium comprising an electrically charged particle disposed in a fluid, the particle having a polymeric shell having repeating units derived from at least one monomer the homopolymer of which is incompatible with the fluid.

2. An electrophoretic medium according to claim 1 wherein the polymeric shell further comprises repeating units derived from at least one monomer the homopolymer of which is compatible with the fluid.

3. An electrophoretic medium according to claim 2 wherein the at least one monomer forming the compatible homopolymer comprises from about 15 to about 99 percent by weight of the polymer shell.

4. An electrophoretic medium according to claim 3 wherein the at least one monomer forming the compatible homopolymer comprises from about 50 to about 99 percent by weight of the polymer shell.

5. An electrophoretic medium according to claim 2 wherein the monomer forming the compatible homopolymer comprises lauryl methacrylate and the monomer forming the incompatible homopolymer comprises any one or more or styrene, t-butyl methacrylate and N-vinylpyrrolidone.

6. An electrophoretic medium according to claim 1 wherein the fluid comprises a hydrocarbon.

7. An electrophoretic medium according to claim 1 wherein the monomer forming the incompatible homopolymer comprises any one or more of acrylates and methacrylates formed from alcohols containing not more than about eight carbon atoms, said alcohols optionally containing hydroxyl or fluoro substitutents;

acrylamides and methacrylamides;

N,N-dialkylacrylamides;

N-vinylpyrrolidone;

styrene and derivatives thereof;

vinyl esters;

vinyl halides;

polyfluoroaromatic molecules containing a polymerizable functional group; and

silicone-containing molecules containing a polymerizable functional group.

8. An electrophoretic medium according to claim 7 wherein the monomer forming the incompatible homopolymer comprises any one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, trifluoroethyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, acrylamide, acrylic acid, acrylonitrile, methyl vinyl ketone, methacrylamide, N-vinylpyrrolidone, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, and pentafluorostyrene.

9. An electrophoretic medium according to claim 1 wherein the fluid and the particles are retained within a plurality of capsules or cells.

10. An electrophoretic display comprising an electrophoretic medium according to claim 1 and at least one electrode disposed adjacent the electrophoretic medium and arranged to apply an electric field thereto.

11. An electrophoretic particle comprising a pigment particle having a polymeric shell having repeating units derived from at least one monomer the homopolymer of which is incompatible with n-hexane.

12. An electrophoretic particle according to claim 11 wherein the polymeric shell further comprises repeating units derived from at least one monomer the homopolymer of which is compatible with n-hexane.

13. An electrophoretic particle according to claim 12 wherein the at least one monomer forming the compatible homopolymer comprises from about 15 to about 99 percent by weight of the polymer shell.

14. An electrophoretic particle according to claim 13 wherein the at least one monomer forming the compatible homopolymer comprises from about 50 to about 99 percent by weight of the polymer shell.

15. An electrophoretic particle according to claim 12 wherein the monomer forming the compatible homopolymer comprises lauryl methacrylate and the monomer forming the incompatible homopolymer comprises any one or more or styrene, t-butyl methacrylate and N-vinylpyrrolidone.

16. An electrophoretic particle according to claim 11 wherein the monomer forming the incompatible homopolymer comprises any one or more of acrylates and methacrylates formed from alcohols containing not more than about eight carbon atoms, said alcohols optionally containing hydroxyl or fluoro substitutents;

acrylamides and methacrylamides;

N,N-dialkylacrylamides;

N-vinylpyrrolidone;

styrene and derivatives thereof;

vinyl esters;

vinyl halides;

polyfluoroaromatic molecules containing a polymerizable functional group; and

silicone-containing molecules containing a polymerizable functional group.

17. An electrophoretic particle according to claim 11 wherein the monomer forming the incompatible homopolymer comprises any one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, trifluoroethyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, acrylamide, acrylic acid, acrylonitrile, methyl vinyl ketone, methacrylamide, N-vinylpyrrolidone, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, and pentafluorostyrene.

18. An electrophoretic particle according to claim 11 wherein the pigment particle comprises any one or more of titania, carbon black and copper chromite.

19. An electrophoretic particle comprising a pigment particle having a polymeric shell having repeating units derived from at least one monomer the homopolymer of which is incompatible with perfluorodecalin.

20. An electrophoretic particle comprising a pigment particle having a polymeric shell having repeating units derived from at least one monomer the homopolymer of which is incompatible with polydimethylsiloxane 200, viscosity 0.65 centistokes.