Method and apparatus for determining properties of an electrophoretic display

• US 6,995,550 B2
• Filed: 08/27/2003
• Issued: 02/07/2006
• Est. Priority Date: 07/08/1998
• Status: Expired due to Fees

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: O'Neil, Steven J., Jacobson, Joseph M., Gates, Holly G., Drzaic, Paul, Abramson, Justin
• Primary Examiner(s): HOLLINGTON, JERMELE M
• Application Number:
  US10/649,370
• Publication Number:
  US 20050099672A1
• Time in Patent Office: 895 Days
• Field of Search: 324/71.1, 324/96, 359/296, 359/290, 204/606, 204/450
• US Class Current: 324/71.1
• 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 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1685 Operation of cells; Circuit arrangements affecting the entire cell
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 3/344 based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167
• CPC Class Codes: H10K 10/462 Insulated gate field-effect transistors [IGFETs]
• 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 85/30 Coordination compounds
• CPC Class Codes: H10K 85/60 Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence

Abstract

A method for sensing the state of an electrophoretic display includes the steps of applying an electrical signal to a display element, measuring an electrical response for the display element, and deducing the state of the display element from the measured electrical response. Also, the parameters of the display materials are determined using the encapsulated electrophoretic display media as a sensor, either alone or in conjunction with other sensors.

Claims

1. A method for determining properties of an encapsulated electrophoretic display medium, comprising the steps of:

(a) providing an encapsulated electrophoretic display medium comprising a plurality of voids dispersed in a polymeric matrix, wherein at least one of said plurality of voids contains an electrophoretic contrast medium phase that includes at least one particle and a suspending fluid;

(b) providing a first electrode and a second electrode, said first and second electrodes lying adjacent said plurality of voids;

(c) applying a first electrical signal to said first electrode;

(d) applying a second electrical signal to said second electrode; and

(e) measuring a first electrical characteristic of said encapsulated electrophoretic display medium, said first electrical characteristic generated in response to said applied first and second electrical signals.

2. The method of claim 1, wherein step (e) comprises measuring a first electrical characteristic represented by a time constant.

3. The method of claim 1, wherein step (e) comprises measuring a first electrical characteristic represented by a current.

4. The method of claim 1, wherein step (e) comprises measuring a first electrical characteristic represented by a voltage.

5. The method of claim 1, wherein step (e) comprises measuring a first electrical characteristic represented by a capacitance.

6. The method of claim 1 further comprising deducing a second electrical characteristic of said encapsulated electrophoretic display medium based on said measured first electrical characteristic.

7. The method of claim 6 wherein said second electrical characteristic is resistivity of said encapsulated electrophoretic display medium.

8. The method of claim 7 further comprising measuring a first environmental factor of said encapsulated electrophoretic display medium using an external sensor.

9. The method of claim 8 further comprising determining a second environmental factor of said encapsulated electrophoretic display medium based on said resistivity and said measured first environmental factor.

10. The method of claim 9 wherein one of said first and second environmental factors is temperature and the other is humidity.

11. A method for determining properties of an encapsulated electrophoretic display medium, comprising the steps of:

(a) providing an encapsulated electrophoretic display medium comprising a plurality of pixels, each pixel comprising at least one void dispersed in a polymeric matrix, wherein said at least one void contains an electrophoretic contrast medium phase that includes at least one particle and a suspending fluid;

(b) providing a first electrode, said first electrode common to and adjacent each of said plurality of pixels;

(c) providing at least one measurement pixel of said plurality of pixels, said at least one measurement pixel having a measurement electrode adjacent thereto;

(d) applying a first electrical signal to said first electrode;

(e) applying a second electrical signal to said measurement electrode; and

(f) measuring a first electrical characteristic of said at least one measuring pixel, said first electrical characteristic generated in response to said applied first and second electrical signals.

12. The method of claim 11, wherein step (f) comprises measuring a first electrical characteristic represented by a time constant.

13. The method of claim 11, wherein step (f) comprises measuring a first electrical characteristic represented by a current.

14. The method of claim 11, wherein step (f) comprises measuring a first electrical characteristic represented by a voltage.

15. The method of claim 11, wherein step (f) comprises measuring a first electrical characteristic represented by a capacitance.

16. The method of claim 11 further comprising calculating an aggregate first electrical characteristic of said encapsulated electrophoretic display medium using measured first electrical characteristics of each of said at least one measurement pixel.

17. The method of claim 11 further comprising deducing a second electrical characteristic of said at least one measurement pixel based on said measured first electrical characteristic.

18. The method of claim 17, wherein said second electrical characteristic is resistivity of said at least one measurement pixel.

19. The method of claim 17 further comprising calculating an aggregate second electrical characteristic of said encapsulated electrophoretic display medium using deduced second electrical characteristics of each of said at least one measurement pixel.

20. The method of claim 17 further comprising measuring a first environmental factor of said encapsulated electrophoretic display medium using an external sensor.

21. The method of claim 20 further comprising determining a second environmental factor of said encapsulated electrophoretic display medium based on said resistivity and said measured first environmental factor.

22. The method of claim 21 wherein one of said first and second environmental factors is temperature, and the other is humidity.

23. A method for detecting a change in an electrical characteristic of an encapsulated electrophoretic display medium, comprising the steps of:

(a) providing an encapsulated electrophoretic display medium comprising a plurality of pixels, each pixel comprising at least one void dispersed in a polymeric matrix, wherein said at least one void contains an electrophoretic contrast medium phase that includes at least one particle and a suspending fluid;

(b) providing a first electrode, said first electrode being common to and adjacent each of said plurality of pixels;

(c) providing at least one measurement pixel of said plurality of pixels, said at least one measurement pixel having a measurement electrode adjacent thereto;

(d) applying a first electrical signal to said first electrode;

(e) applying a second electrical signal to said measurement electrode;

(f) measuring a first electrical characteristic of said at least one measuring pixel, thereby obtaining a first value of said electrical characteristic, said first electrical characteristic being generated in response to said applied first and second electrical signals;

(g) repeating steps (d)–

(f), thereby obtaining a second value of said electrical characteristic; and

(h) comparing said first and second values of said electrical characteristic thereby detecting a change therein.

24. An apparatus for determining properties of an encapsulated electrophoretic display medium, said encapsulated electrophoretic display medium comprising a plurality of voids dispersed in a polymeric matrix, wherein at least one of said plurality of voids contains an electrophoretic contrast medium phase that includes at least one particle and a suspending fluid, and two electrodes adjacent to said plurality of voids;

said apparatus comprising;

(a) a signal generator for applying electrical signals to said two electrodes; and

(b) a detection circuit for measuring a first electrical characteristic of said encapsulated electrophoretic display medium generated in response to said electrical signals.

25. The apparatus of claim 24, further comprising a processor for deducing a second electrical characteristic of said encapsulated electrophoretic display medium based on said measured first electrical characteristic.

26. The apparatus of claim 25 wherein said second electrical characteristic is resistivity of said encapsulated electrophoretic display medium.

27. The apparatus of claim 26 further comprising measuring a first environmental factor of said encapsulated electrophoretic display medium using an external sensor.

28. The apparatus of claim 27 further comprising determining a second environmental factor of said encapsulated electrophoretic display medium based on said resistivity and said measured first environmental factor.

29. The apparatus of claim 28 wherein one of said first and second environmental factors is temperature, and other is humidity.

30. The apparatus of claim 24 wherein said detection circuit comprises a capacitance bridge.

31. The apparatus of claim 24 wherein said detection circuit comprises a circuit capable of measuring time constants.

32. The apparatus of claim 24 wherein said detection circuit comprises a circuit capable of measuring frequency.

33. The apparatus of claim 24 wherein said detection circuit comprises a circuit capable of measuring voltage.

34. An electrophoretic display comprising an encapsulated electrophoretic display medium comprising a plurality of pixels, each pixel comprising at least one void dispersed in a polymeric matrix, wherein said at least one void contains an electrophoretic contrast medium phase that includes at least one particle and a suspending fluid, said electrophoretic display comprising:

(a) a first electrode, said first electrode common to and adjacent each of said plurality of pixels;

(b) at least one measurement pixel of said plurality of pixels, said at least one measurement pixel having a measurement electrode adjacent thereto;

(c) a signal generator for applying electrical signals to said first electrode and said measurement electrode; and

(d) a detection circuit for measuring a first electrical characteristic of said at least one measurement pixel, said first electrical characteristic generated in response to said applied electrical signals.

35. The electrophoretic display of claim 34 further comprising a processor for deducing a second electrical characteristic of said at least one measurement pixel based on said measured first electrical characteristic.

36. The electrophoretic display of claim 34 wherein said second electrical characteristic comprises resistivity of said at least one measurement pixel.

37. The electrophoretic display of claim 36 further comprising measuring a first environmental factor of said encapsulated electrophoretic display medium using an external sensor.

38. The electrophoretic display of claim 37 further comprising determining a second environmental factor of said encapsulated electrophoretic display medium based on said resistivity and said measured first environmental factor.

39. The electrophoretic display of claim 38 wherein one of said first and second environmental factors is temperature, and the other is humidity.

40. The electrophoretic display of claim 34 wherein said detection circuit comprises a capacitance bridge.

41. The electrophoretic display of claim 34 wherein said detection circuit comprises a circuit capable of measuring time constants.

42. The electrophoretic display of claim 34 wherein said detection circuit comprises a circuit capable of measuring frequency.

43. The electrophoretic display of claim 34 wherein said detection circuit comprises a circuit capable of measuring voltage.

44. An input device, comprising

(a) an encapsulated electrophoretic display medium, said encapsulated electrophoretic display medium comprising a plurality of pixels, each pixel comprising at least one void dispersed in a polymeric matrix, wherein said at least one void contains an electrophoretic contrast medium phase that includes at least one particle and a suspending fluid, each pixel having a pixel electrode adjacent thereto;

(b) a first electrode, said first electrode common to and adjacent each of said plurality of pixels;

(c) a signal generator for applying electrical signals to said first electrode and each of said pixel electrodes;

(d) a detection circuit for measuring a first electrical characteristic of each of said plurality of pixels, said first electrical characteristic generated in response to said applied electrical signals;

(e) a discriminator circuit for detecting a change in said first electrical characteristic of at least one pixel of said plurality of pixels; and

(f) a response generator for generating a response to said change and identifying said at least one pixel.

45. The input device of claim 44 wherein said first electrical characteristic is a voltage or capacitance.

46. The input device of claim 44, further comprising a processor for deducing a second electrical characteristic of said at least one pixel based on said measured first electrical characteristic.

47. The input device of claim 46 wherein said second electrical characteristic is resistivity.