Electrophoretic particles, and processes for the production thereof

• US 7,002,728 B2
• Filed: 02/09/2004
• Issued: 02/21/2006
• Est. Priority Date: 08/28/1997
• Status: Expired due to Term

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Albert, Jonathan D., Comiskey, Barrett, Whitesides, Thomas H., Honeyman, Charles H., Pullen, Anthony Edward
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): CHOI, WILLIAM C
• Application Number:
  US10/708,130
• Publication Number:
  US 20050000813A1
• Time in Patent Office: 743 Days
• Field of Search: 359/228, 359/296, 359/321, 106/493, 106/499, 106/502, 106/504, 428/402, 428/403, 428/405, 345/107, 252/570, 252/572, 505/472, 526/934, 430/32, 430/34, 430/114
• US Class Current: 359/296
• CPC Class Codes: B41J 3/4076 printing on rewritable, bistable "electronic paper" by a focused electric or magnetic field
• 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 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 2006/12 Surface area
• 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 67/0097 Dye preparations of special physical nature; Tablets, films, extrusion, microcapsules, sheets, pads, bags with dyes
• 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 1/34 : Compounds of chromium C09C1/0009, C09C1/0015, C09C1/0078, C09C1/08, C09C1/20 take precedence
• CPC Class Codes: C09C 3/006 : Combinations of treatments provided for in groups C09C3/04 - C09C3/12
• CPC Class Codes: C09C 3/10 : Treatment with macromolecular organic compounds C09C3/006 takes precedence
• CPC Class Codes: C09C 3/12 : Treatment with organosilicon compounds C09C3/006 takes precedence
• CPC Class Codes: C23C 18/1212 : Zeolites, glasses
• CPC Class Codes: C23C 18/1229 : Composition of the substrate
• CPC Class Codes: C23C 18/1295 : with after-treatment of the deposited inorganic material
• CPC Class Codes: C25D 13/02 : with inorganic material
• CPC Class Codes: G02B 26/026 : based on the rotation of particles under the influence of an external field, e.g. gyricons, twisting ball displays based on orientable dipolar particles G02F1/172; based on electrophoresis G02F1/167
• CPC Class Codes: G02F 1/133305 : Flexible substrates, e.g. plastics, organic film
• CPC Class Codes: G02F 1/133348 : Charged particles addressed liquid crystal cells, e.g. controlled by an electron beam
• CPC Class Codes: G02F 1/13336 : Combining plural substrates to produce large-area displays, e.g. tiled displays
• CPC Class Codes: G02F 1/1334 : based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/1343 : Electrodes reflective electrodes G02F1/133553
• CPC Class Codes: G02F 1/1345 : Conductors connecting electrodes to cell terminals
• CPC Class Codes: G02F 1/135 : Liquid crystal cells structurally associated with a photoconducting or a ferro-electric layer, the properties of which can be optically or electrically varied G02F1/133348 takes precedence
• CPC Class Codes: G02F 1/1365 : in which the switching element is a two-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 1/167 : by electrophoresis
• CPC Class Codes: G02F 1/172 : based on a suspension of orientable dipolar particles, e.g. suspended particles displays
• CPC Class Codes: G02F 2001/1678 : characterised by the composition or particle type
• CPC Class Codes: G02F 2202/12 : photoconductor
• CPC Class Codes: G02F 2202/28 : Adhesive materials or arrangements
• CPC Class Codes: G03G 17/02 : with electrolytic development
• CPC Class Codes: G03G 17/04 : using photoelectrophoresis
• CPC Class Codes: G03G 17/06 : Apparatus therefor
• CPC Class Codes: G06K 19/07703 : the interface being visual
• CPC Class Codes: G09F 9/302 : characterised by the form or geometrical disposition of the individual elements
• CPC Class Codes: G09F 9/372 : the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: H01L 27/12 : the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H10K 10/462 : Insulated gate field-effect transistors [IGFETs]
• CPC Class Codes: H10K 10/466 : Lateral bottom-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 19/00 : Integrated devices, or assemblies of multiple devices, comprising at least one organic element specially adapted for rectifying, amplifying, oscillating or switching, covered by group H10K10/00
• CPC Class Codes: H10K 85/113 : Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• CPC Class Codes: H10K 85/114 : Poly-phenylenevinylene; Derivatives thereof
• CPC Class Codes: H10K 85/20 : Carbon compounds, e.g. carbon nanotubes or fullerenes
• CPC Class Codes: H10K 85/30 : Coordination compounds
• CPC Class Codes: H10K 85/311 : Phthalocyanine
• CPC Class Codes: H10K 85/60 : Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence
• CPC Class Codes: H10K 85/611 : Charge transfer complexes
• CPC Class Codes: H10K 85/615 : Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: Y10T 428/2991 : Coated
• CPC Class Codes: Y10T 428/2998 : including synthetic resin or polymer

Abstract

Copper chromite particles can advantageously be used as black particles in electrophoretic media and displays. Preferably, the copper chromite particles are coated with a silica coating and a polymer coating.

Claims

1. An electrophoretic medium comprising at least one electrically charged particle suspended in a suspending fluid and capable of moving through the fluid on application of an electrical field to the fluid, wherein the at least one electrically charged particle comprises copper chromite.

2. An electrophoretic medium according to claim 1 wherein the at least one electrically charged particle has an average diameter of from about 0.25 to about 2 μ

m.

3. An electrophoretic medium according to claim 1 wherein the at least one electrically charged particle is coated with silica.

4. An electrophoretic medium according to claim 3 wherein the at least one particle has a polymer chemically bonded to the silica coating.

5. An electrophoretic medium according to claim 1 wherein the at least one electrically charged particle has a polymer chemically bonded to, or cross-linked around, the at least one particle.

6. An electrophoretic medium according to claim 5 wherein the polymer is chemically bonded to the at least one particle.

7. An electrophoretic medium according to claim 6 wherein the polymer comprises from about 5 to about 500 mg m⁻

2 of the surface area of the at least one particle.

8. An electrophoretic medium according to claim 7 wherein the polymer comprises from about 10 to about 100 mg m⁻

2 of the surface area of the at least one particle.

9. An electrophoretic medium according to claim 8 wherein the polymer comprises from about 20 to about 100 mg m⁻

2 of the surface area of the at least one particle.

10. An electrophoretic medium according to claim 9 wherein the polymer comprises amino groups.

11. An electrophoretic medium according to claim 7 wherein the polymer comprises from about 2 to about 8 percent by weight of the at least one particle.

12. An electrophoretic medium according to claim 6 wherein the polymer comprises charged or chargeable groups.

13. An electrophoretic medium according to claim 6 wherein the polymer comprises a main chain and a plurality of side chains extending from the main chain, each of the side chains comprising at least about four carbon atoms.

14. An electrophoretic medium according to claim 6 wherein the polymer is formed from an acrylate or a methacrylate.

15. An electrophoretic medium according to claim 6 wherein the polymer is bonded to the at least one particle via a residue of a functionalization agent.

16. An electrophoretic medium according to claim 15 wherein the functionalization agent comprises a silane.

17. An electrophoretic medium according to claim 15 wherein the residue of the functionalization agent comprises charged or chargeable groups.

18. An electrophoretic medium according to claim 1 further comprising at least one second particle having at least one optical characteristic differing from that of the copper chromite particle(s), the at least one second particle also having an electrophoretic mobility differing from that of the copper chromite particle(s).

19. An electrophoretic medium according to claim 18 wherein the copper chromite particle(s) and the second particle(s) bear charges of opposite polarity.

20. An electrophoretic medium according to claim 18 wherein the second particle(s) are substantially white.

21. An electrophoretic medium according to claim 20 wherein the second particle(s) comprise titania.

22. An electrophoretic medium according to claim 1 wherein the suspending fluid comprises a hydrocarbon, or a mixture of a hydrocarbon and a halogenated hydrocarbon.

23. An electrophoretic medium according to claim 1 further comprising a capsule wall within which the suspending fluid and the at least one particle are retained.

24. An electrophoretic medium according to claim 23 comprising a plurality of capsules each comprising a capsule wall and the suspending fluid and at least one particle retained therein, the medium further comprising a polymeric binder surrounding the capsules.

25. An electrophoretic display comprising an electrophoretic medium according to claim 1 and at least one electrode disposed adjacent the electrophoretic medium for applying an electric field to the medium.

26. An electrophoretic display according to claim 25 wherein the electrophoretic medium comprises a plurality of capsules.

27. An electrophoretic display according to claim 25 wherein the electrophoretic medium comprises a plurality of droplets comprising the suspending fluid and a continuous phase of a polymeric material surrounding the droplets.

28. An electrophoretic display according to claim 25 wherein the electrophoretic medium comprises a substrate having a plurality of sealed cavities formed therein, and the suspending fluid and the copper chromite particles are retained within the sealed cavities.