Electrophoretic displays and systems for addressing such displays

• US 6,445,489 B1
• Filed: 03/18/1999
• Issued: 09/03/2002
• Est. Priority Date: 03/18/1998
• Status: Expired due to Fees

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Jacobson, Joseph M., Comiskey, Barrett, Wilcox, Russell J., Drzaic, Paul, Morrison, Ian
• Primary Examiner(s): Ben, Loha
• Application Number:
  US09/272,716
• Time in Patent Office: 1,265 Days
• Field of Search: 359/296, 345/105, 345/107, 345/108, 204/450, 204/600, 204/606
• 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: 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 1/1334 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 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1677 Structural association of cells with optical devices, e.g. reflectors or illuminating devices
• CPC Class Codes: G02F 2202/12 photoconductor
• CPC Class Codes: G02F 2202/28 Adhesive materials or arrangements
• 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: 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

Electrophoretic displays include a light-emitting layer, a photoconductive layer, and an electrophoretic layer. The light-emitting layer may be an organic, light-emitting material, or organic, light-emitting diode, which is addressable using a multiplex addressing drive scheme. The impedance of the photoconductive layer is lowered when struck by light from the light-emitting layer. As a result of the lowered impedance of the photoconductive layer, the electrophoretic layer, which itself cannot be multiplexed, is addressed at a lower, subthreshold voltage.

Claims

1. An electrophoretic display, comprising:

(a) an organic, light-emitting layer;

(b) a photoconductive layer adjacent said organic, light-emitting layer; and

(c) an electrophoretic layer adjacent said photoconductive layer, wherein light from said organic, light-emitting layer reduces an impedance of said photoconductive layer, permitting an applied electric field to address said electrophoretic layer at a predetermined point on said electrophoretic layer.

2. The display of claim 1, wherein said organic light-emitting layer comprises an organic material disposed on a clear substrate.

3. The display of claim 2, wherein said clear substrate is selected from the group consisting of a glass substrate, a plastic substrate, and a polyester substrate.

4. The display of claim 2, wherein said organic material is selected from the group consisting of organic compounds, organometallic compounds, oligomers and polymers.

5. The display of claim 2, wherein said organic material is tris-(8-hydroxyquinoline) aluminum.

6. The display of claim 2, wherein said organic material further comprises a dispersion of inorganic semiconductors.

7. The display of claim 6, wherein said inorganic semiconductors are CdSe.

8. The display of claim 1, wherein said light-emitting layer comprises an electroluminescent layer.

9. The display of claim 8, wherein said electroluminescent layer comprises a dispersion of ZnS particles in a polymer binder disposed on a clear substrate.

10. The display of claim 9, wherein said clear substrate is selected from the group consisting of a glass substrate, a plastic substrate, and a polyester substrate.

11. The display of claim 1, wherein said photoconductive layer comprises a photoconductive material disposed on a clear substrate.

12. The display of claim 11, wherein said clear substrate is selected from the group consisting of a glass substrate, a plastic substrate, and a polyester substrate.

13. The display of claim 11, wherein said photoconductive material is selected from the group consisting of organic photoconductive polymers, dye-aggregate photoreceptors, and pigment-based photoconductors.

14. The display of claim 11, wherein said photoconductive material is 2,4,7-trinitro-9-fluorenone complexed with poly(N-vinylcarbazole).

15. The display of claim 1, wherein said photoconductive layer comprises a first photoconductive material and a second photoconductive material, said first photoconductive material being sensitive to a different variable of light than said second photoconductive material.

16. The display of claim 15, wherein said variable of light is selected from the group consisting of a wavelength of said light, an intensity of said light, and a duration of said light.

17. The display of claim 1, wherein said electrophoretic layer is selected from the group consisting of an encapsulated electrophoretic layer and a dielectrophoretic layer.

18. The display of claim 17, wherein said encapsulated electrophoretic layer comprises a plurality of particles dispersed in a suspending fluid and encapsulated in a polymer matrix.

19. The display of claim 1, further comprising a dielectrophoretic layer disposed adjacent said photoconductive layer.

20. The display of claim 1, further comprising a reflective substrate for directing light from said organic, light-emitting layer to said photoconductive layer.

21. The display of claim 1, further comprising a capacitor disposed adjacent said photoconductive layer.

22. The display of claim 1, wherein said display is flexible.

23. The display of claim 1, further comprising a clear electrode in electrical communication with said photoconductive layer.

24. The display of claim 23, wherein said clear electrode comprises a clear substrate coated with indium tin oxide.

25. The display of claim 1, further comprising an optical barrier layer disposed over said photoconductive layer for blocking a quantity of light from at least a portion of said photoconductive layer.

26. The display of claim 25, wherein said optical barrier layer comprises a dispersion of opaque conductive particles in a polymer matrix.

27. An emissive display, comprising:

(a) an organic, light-emitting layer addressable at a first predetermined voltage, a first fraction of said first predetermined voltage dropping across said organic, light-emitting layer; and

(b) a photoconductive layer disposed under said organic, light-emitting layer, a second fraction of said first predetermined voltage dropping across said photoconductive layer, wherein light from said organic, light-emitting layer strikes said photoconductive layer, thereby lowering an impedance of said photoconductive layer and thereby reducing said second fraction of said voltage and thereby increasing said first fraction of said voltage,

whereby said organic, light-emitting layer is subsequently addressable at a second predetermined voltage, said second predetermined voltage being lower than said first predetermined voltage.

28. The display of claim 27, further comprising a fenestrated dielectrophoretic layer disposed between said organic, light-emitting layer and said photoconductive layer, said fenestrated dielectrophoretic layer for modulating an amount of light striking said photoconductive layer.

29. The display of claim 27, wherein said organic, light-emitting layer comprises an organic material disposed on a clear substrate.

30. The display of claim 29, wherein said clear substrate is selected from the group consisting of a glass substrate, a plastic substrate, and a polyester substrate.

31. The display of claim 29, wherein said organic material is a material selected from the group consisting of organic compounds, organometallic compounds, oligomers, and polymers.

32. The display of claim 29, wherein said organic material is tris-(8-hydroxyquinoline) aluminum.

33. The display of claim 30, wherein said organic material further comprises a dispersion of inorganic semiconductors.

34. The display of claim 33, wherein said inorganic semiconductors are CdSe.

35. The display of claim 27, wherein said photoconductive layer comprises a photoconductive material disposed on a clear substrate.

36. The display of claim 35, wherein said clear substrate is selected from the group consisting of a glass substrate, a plastic substrate, and a polyester substrate.

37. The display of claim 35, wherein said photoconductive material is selected from the group consisting of organic photoconductive polymers, dye-aggregate photoreceptors, and pigment-based photoconductors.

38. The display of claim 35, wherein said photoconductive material is 2,4,7-trinitro-9-fluorenone complexed with poly(N-vinylcarbazole).

39. The display of claim 27, further comprising a clear electrode in electrical communication with said photoconductive layer.

40. The display of claim 39, wherein said clear electrode comprises a clear substrate coated with indium tin oxide.

41. The display of claim 40, wherein said clear substrate is selected from the group consisting of a glass substrate, a plastic substrate, and a polyester substrate.

42. The display of claim 27, wherein said display is flexible.