Electrophoretic displays using nanoparticles

• US 6,323,989 B1
• Filed: 05/05/2000
• Issued: 11/27/2001
• Est. Priority Date: 07/19/1996
• Status: Expired due to Term

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Drzaic, Paul S., Jacobson, Joseph M., Morrison, Ian D.
• Primary Examiner(s): Dang, Hung Xuan
• Application Number:
  US09/565,417
• Time in Patent Office: 571 Days
• Field of Search: 345/107, 345/86, 359/296, 359/529, 359/530, 359/536, 359/538, 359/539, 359/541, 349/86, 349/89
• US Class Current: 359/296
• CPC Class Codes: B41J 2/01 Ink jet
• CPC Class Codes: B41J 2/02 generating a continuous ink jet
• CPC Class Codes: B41J 3/4076 printing on rewritable, bistable "electronic paper" by a focused electric or magnetic field
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: C09D 11/30 Inkjet printing inks
• CPC Class Codes: C09D 11/50 Sympathetic, colour changing or similar inks
• 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 1/13336 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 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/16757 Microcapsules
• CPC Class Codes: G02F 2202/28 Adhesive materials or arrangements
• CPC Class Codes: G03G 15/2057 relating to the chemical composition of the heat element and layers thereof
• CPC Class Codes: G04B 47/00 Time-pieces combined with other articles which do not interfere with the running or the time-keeping of the time-piece clockwork cases for special purposes G04B37/12; clocks with magnifying glass built in the face G04B39/00; time-pieces in which parts or cases produce special effects, e.g. aesthetic effects, G04B45/00, particularly with inscriptions or pictures moved by hand G04B45/003, with specially shaped cases or parts G04B45/0069; combination of writing or drawing implements with devices for indicating time B43K29/087; combined with cameras, projectors, or photographic printing apparatus G03B29/00
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: H05K 1/097 Inks comprising nanoparticles and specially adapted for being sintered at low temperature H05K1/095 takes precedence
• CPC Class Codes: H05K 3/105 by conversion of non-conductive material on or in the support into conductive material, e.g. by using an energy beam
• CPC Class Codes: H05K 3/1241 by ink-jet printing or drawing by dispensing
• CPC Class Codes: H10K 10/46 : Field-effect transistors, e.g. organic thin-film transistors [OTFT] H10K10/43 takes precedence
• CPC Class Codes: H10K 10/462 : Insulated gate field-effect transistors [IGFETs]
• CPC Class Codes: H10K 85/30 : Coordination compounds
• CPC Class Codes: H10K 85/60 : Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence

Abstract

An electrophoretic display comprises a fluid and a plurality of nanoparticles having diameters substantially less the wavelengths of visible light such that, when the nanoparticles are in a dispersed state and uniformly dispersed throughout the fluid, the fluid presents a first optical characteristic, but when the nanoparticles are in an aggregated state in which they are gathered into aggregates substantially larger than the individual nanoparticles, the fluid presents a second optical characteristic different from the first optical characteristic. The electrophoretic display further comprises at least one electrode arranged to apply an electric field to the nanoparticle-containing fluid and thereby move the nanoparticles between their dispersed and aggregated states.

Claims

1. An electrophoretic display comprising a fluid and a plurality of nanoparticles having diameters substantially less than the wavelengths of visible light such that, when the nanoparticles are in a dispersed state and uniformly dispersed throughout the fluid, the fluid presents a first optical characteristic, but when the nanoparticles are in an aggregated state in which they are gathered into aggregates substantially larger than the individual nanoparticles, the fluid presents a second optical characteristic different from the first optical characteristic, the electrophoretic display further comprising at least one electrode arranged to apply an electric field to the nanoparticle-containing fluid and thereby move the nanoparticles between their dispersed and aggregated states.

2. An electrophoretic display according to claim 1 wherein the nanoparticles have an average diameter not in excess of about 200 nm.

3. An electrophoretic display according to claim 2 wherein the nanoparticles have an average diameter not in excess of about 100 nm.

4. An electrophoretic display according to claim 3 wherein the nanoparticles have an average diameter not in excess of about 50 nm.

5. An electrophoretic display according to claim 1 wherein the nanoparticles comprise at least one insulator.

6. An electrophoretic display according to claim 5 wherein the nanoparticles comprise titanium dioxide.

7. An electrophoretic display according to claim 5 wherein the nanoparticles comprise any one or more of zinc oxide, a clay and magnesium silicate.

8. An electrophoretic display according to claim 1 wherein the first optical characteristic is a low level of light scattering and the second optical characteristic is a substantially increased level of light scattering.

9. An electrophoretic display according to claim 1 wherein the nanoparticles comprise at least one conductor.

10. An electrophoretic display according to claim 9 wherein the nanoparticles comprise silver or gold.

11. An electrophoretic display according to claim 1 wherein the nanoparticles comprise at least one semiconductor.

12. An electrophoretic display according to claim 11 wherein the nanoparticles comprise cadmium selenide.

13. An electrophoretic display according to claim 1 wherein the first and second optical characteristics are differing colors.

14. An electrophoretic display according to claim 1 wherein the fluid and the nanoparticles are encapsulated within at least one capsule.

15. An electrophoretic display according to claim 14 wherein the fluid and the nanoparticles are encapsulated within a plurality of microcapsules having diameters in the range of from about 10 to about 500 μ

m.

16. An electrophoretic display according to claim 1 wherein the fluid is colored.

17. An electrophoretic display according to claim 1 wherein the fluid comprises a hydrocarbon.

18. An electrophoretic display according to claim 1 comprising at least two different species of nanoparticles having different electrophoretic mobilities.

19. An electrophoretic display according to claim 18 wherein the two different species of nanoparticles have charges of opposite polarity.

20. An electrophoretic display according to claim 1 wherein at least some of the nanoparticles are in the form of units each comprising a plurality of nanoparticles attached to a single substrate, such that upon application of an electric field to the units, the distances between nanoparticles within the unit will change, thereby changing the optical characteristic displayed by the unit.

21. An electrophoretic display according to claim 20 wherein the unit comprises at least two nanoparticles connected by a flexible filament.

22. An electrophoretic display according to claim 20 wherein the unit comprises an elongate flexible filament having one end attached to a fixed body and having an electrically charged body affixed at or adjacent its opposed end, the filament having a plurality of nanoparticles fixed thereto at spaced intervals between the fixed body and the electrically charged body, such that upon application of an electric field to the unit, the spacing between the fixed body and the electrically charged body will change, thereby changing the distances between the nanoparticles.

23. An electrophoretic display according to claim 20 wherein the unit comprises an elongate flexible filament having one end attached to a first electrically charged body and its opposed end attached to a second electrically charged body bearing a charge of opposite polarity to the first electrically charged body, the filament having a plurality of nanoparticles fixed thereto at spaced intervals between the two electrically charged bodies, such that upon application of an electric field to the unit, the spacing between the two electrically charged bodies will change, thereby changing the distances between the nanoparticles.

24. An electrophoretic display according to claim 1 wherein at least some of the nanoparticles bear an electrical charge and are attached via flexible filaments to a fixed body, such that upon application of an electrical field to the nanoparticles the spacing between the nanoparticles and the fixed body will vary.

25. An electrophoretic display according to claim 1 having a viewing surface through which the nanoparticle-containing fluid can be viewed, and on the opposed side of the display from the viewing surface, a light source arranged to pass light through the nanoparticle containing fluid, and wherein the first optical characteristic is a low level of light scattering and the second optical characteristic is a substantially increased level of light scattering, so that the nanoparticle-containing fluid acts as a light valve.

26. An electrophoretic display according to claim 1 having a viewing surface through which the nanoparticle-containing fluid can be viewed, and on the opposed side of the display from the viewing surface, a reflective or colored surface, and wherein the first optical characteristic is a low level of light scattering and the second optical characteristic is a substantially increased level of light scattering, so that when the nanoparticles are in their dispersed state an observer viewing the viewing surface of the display will see the reflective or colored surface, whereas when the nanoparticles are in their aggregated state such a viewer will see the color of the aggregated nanoparticles.

27. An electrophoretic display according to claim 1 having two electrodes disposed on opposed sides of the nanoparticle-containing fluid, at least one of the electrodes being substantially transparent.

28. An electrophoretic display according to claim 1 having two electrodes disposed on the same side of the nanoparticle-containing fluid, so that the opposed side of the nanoparticle-containing fluid constitutes a viewing surface through which the nanoparticle-containing fluid can be viewed.