Display medium, display device and display method

• US 20080112040A1
• Filed: 06/04/2007
• Published: 05/15/2008
• Est. Priority Date: 11/10/2006
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Inventors: Machida, Yoshinori, Shigehiro, Kiyoshi, Suwabe, Yasufumi, Tatsuura, Satoshi, Abe, Masaaki
• Granted Patent: US 7,656,576 B2
• Time in Patent Office: Days
• US Class Current: 359/296
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1685 Operation of cells; Circuit arrangements affecting the entire cell

Abstract

A display medium includes at least: a pair of substrates, at least one of the substrates having optical transparency; a dispersion medium positioned in a gap between the pair of substrates; one or more kinds of electrophoretic particles or two or more kinds of electrophoretic particles different in color from each other, included in the dispersion medium; and a holder disposed between the pair of substrates, the holder having a function of holding the electrophoretic particles and a function of controlling, by an external voltage, a movement amount of the electrophoretic particles on the holder.

Claims

1. A display medium, comprising at least:

a pair of substrates, at least one of the substrates having optical transparency;

a dispersion medium positioned in a gap between the pair of substrates;

one or more kinds of electrophoretic particles or two or more kinds of electrophoretic particles different in color from each other, included in the dispersion medium; and

a holder disposed between the pair of substrates, the holder having a function of holding the electrophoretic particles and a function of controlling, by an external voltage, a movement amount of the electrophoretic particles on the holder.

2. The display medium of claim 1, wherein an absolute value of a threshold value of an electric field at which the electrophoretic particles in a state of being held by the holder are detached from the holder and moved in the dispersion medium is in the range of about 100 V/cm to 30 kV/cm.

3. The display medium of claim 1, wherein the electrophoretic particles are charged with a positive or negative polarity, and the holder is at least partially charged with a polarity opposite to that of all kinds of the electrophoretic particles.

4. The display medium of claim 1, wherein the holder includes two or more particulate members.

5. The display medium of claim 1, wherein the holder has a color different from that of all kinds of the electrophoretic particles.

6. The display medium of claim 1, wherein the holder includes an aggregate of fibers.

7. The display medium of claim 1, wherein the holder includes a non-woven fabric.

8. The display medium of claim 1, wherein the function of holding the electrophoretic particles of the holder varies continuously or stepwise in a direction in which the pair of substrates face each other.

9. The display medium of claim 1, wherein the function of holding the electrophoretic particles of the holder decreases continuously or stepwise as a distance from at least one of the pair of substrates increases in a direction in which the pair of substrates face each other.

10. The display medium of claim 1, wherein the holder includes a porous body having gaps through which the electrophoretic particles pass.

11. The display medium of claim 1, wherein the holder has a white color.

12. The display medium of claim 1, wherein the electrophoretic particles include two or more kinds of electrophoretic particles different from each other in color and in an absolute value of a threshold value of an electric field at which the electrophoretic particles in a state of being held by the holder are detached from the holder and moved in the dispersion medium.

13. The display medium of claim 1, wherein the electrophoretic particles include two or more kinds of electrophoretic particles different from each other in a volume average primary particle diameter.

14. The display medium of claim 1, wherein the electrophoretic particles include two or more kinds of electrophoretic particles different from each other in a color formed in a state of being dispersed in the dispersion medium and in an absolute value of a threshold value of an electric field at which the electrophoretic particles in a state of being held by the holder are detached from the holder and moved in the dispersion medium.

15. A display device, comprising at least:

a pair of substrates, at least one of the substrates having optical transparency;

a dispersion medium positioned in a gap between the pair of substrates;

one or more kinds of electrophoretic particles or two or more kinds of electrophoretic particles different in color from each other, included in the dispersion medium;

a light-modulating layer disposed between the pair of substrates and including a holder having a function of holding the electrophoretic particles;

a pair of electrodes respectively disposed on one substrate side and the other substrate side of the pair of substrates; and

an electric field applicator that is connected to the pair of electrodes and applies an electric field to the dispersion medium, the electric field applicator controlling a movement amount of the electrophoretic particles on the holder.

16. The display device of claim 15, wherein

an absolute value of a threshold value of an electric field at which the electrophoretic particles in a state of being held by the holder are detached from the holder and moved in the dispersion medium is in the range of about 100 V/cm to 30 kV/cm;

the electric field applicator applies, to the dispersion medium, an electric field having a voltage waveform having cycles each including a first interval where an electric field is continuously applied at a voltage where an absolute value of the voltage is equal to or higher than an absolute value of a threshold voltage corresponding to the threshold value of the electric field and a second interval where an electric field is continuously applied at a voltage where an absolute value of the voltage is less than an absolute value of a threshold voltage corresponding to the threshold value of the electric field; and

in the first interval in at least any one of the cycles, the following formula (1) is satisfied;

Ep<

Emax  

 

Formula (1)

wherein Ep denotes a value represented by the following formula (2), and Emax denotes a product of voltage·

time (V·

s) necessary for varying a display density from the maximum density to the minimum density or from the minimum density to the maximum density when an electric field is continuously applied to the light-modulating layer at a voltage where an absolute value of the voltage is equal to or higher than the absolute value of the threshold voltage

E_p=∫

₀^tpV(t)dt  

 

Formula (2)

wherein t denotes any time (s) within the first interval in the at least any one of the cycles, tp denotes a time (s) from a start to an end of the first interval in the at least any one of the cycles, and V(t) denotes a voltage (V) at the time t.

17. The display device of claim 15, wherein the electrophoretic particles are charged with a positive or negative polarity, and the holder is at least partially charged with a polarity opposite to that of all kinds of the electrophoretic particles.

18. The display device of claim 15, wherein the holder includes two or more particulate members.

19. The display device of claim 15, wherein the holder has a color different from that of all kinds of the electrophoretic particles.

20. The display device of claim 15, wherein the holder includes an aggregate of fibers.

21. The display device of claim 15, wherein the holder includes a non-woven fabric.

22. The display device of claim 15, wherein the function of holding the electrophoretic particles of the holder varies continuously or stepwise in a direction in which the pair of substrates face each other.

23. The display device of claim 15, wherein the function of holding the electrophoretic particles of the holder decreases continuously or stepwise as a distance from at least one of the pair of substrates increases in a direction in which the pair of substrates face each other.

24. The display device of claim 15, wherein the holder includes a porous body having gaps through which the electrophoretic particles pass.

25. The display device of claim 15, wherein the holder has a white color.

26. The display device of claim 15, wherein the electrophoretic particles include two or more kinds of electrophoretic particles different from each other in color and in an absolute value of a threshold value of an electric field at which the electrophoretic particles in a state of being held by the holder are detached from the holder and moved in the dispersion medium.

27. The display device of claim 15, wherein the electrophoretic particles include two or more kinds of electrophoretic particles different from each other in a volume average primary particle diameter.

28. The display device of claim 15, wherein the electrophoretic particles include two or more kinds of electrophoretic particles different from each other in a color formed in a state of being dispersed in the dispersion medium and in an absolute value of a threshold value of an electric field at which the electrophoretic particles in a state of being held by the holder are detached from the holder and moved in the dispersion medium.

29. A display method of switching a display by carrying out the following processes in any order, the method comprising:

applying an electric field to a light-modulating layer that includes a dispersion medium, one or more kinds of electrophoretic particles or two or more kinds of electrophoretic particles different in color from each other, included in the dispersion medium, and a holder having a function of holding the electrophoretic particles, the electric field forming a potential gradient and moving the electrophoretic particles via the holder, to localize the electrophoretic particles at one side of the light-modulating layer, thereby displaying a color due to the electrophoretic particles at the one side of the light-modulating layer at a maximum density;

applying an electric field to the light-modulating layer, the electric field forming a potential gradient and moving the electrophoretic particles via the holder, to localize the electrophoretic particles at the other side of the light-modulating layer, thereby displaying a color due to the electrophoretic particles at the one side of the light-modulating layer at a minimum density; and

applying an electric field to the light-modulating layer, the electric field forming a potential gradient and moving the electrophoretic particles via the holder, to localize the electrophoretic particles between the one side and the other side of the light-modulating layer, thereby displaying a color due to the electrophoretic particles at the one side of the light-modulating layer at a density smaller than the maximum density but larger than the minimum density.

30. The display method of claim 29, wherein an absolute value of a threshold value of an electric field at which the electrophoretic particles in a state of being held by the holder are detached from the holder and moved in the dispersion medium is in the range of about 100 V/cm to 30 kV/cm.

31. The display method of claim 29, wherein

a voltage waveform of the electric field applied to the light-modulating layer has cycles each including

a first interval where an electric field is continuously applied at a voltage where an absolute value of the voltage is equal to or higher than an absolute value of a threshold voltage corresponding to a threshold value of an electric field at which the electrophoretic particles in a state of being held by the holder are detached from the holder and moved in the dispersion medium, and

a second interval where an electric field is continuously applied at a voltage where an absolute value of the voltage is less than an absolute value of a threshold voltage corresponding to the threshold value of the electric field,

in the first interval in at least any one of the cycles, the following formula (3) being satisfied:

Ep<

Emax  

 

Formula (3)

wherein Ep denotes a value represented by the following formula (4), and Emax denotes a product of voltage·

time (V·

s) necessary for varying a display density from the maximum density to the minimum density or from the minimum density to the maximum density when an electric field is continuously applied to the light-modulating layer at a voltage where an absolute value of the voltage is equal to or higher than the absolute value of the threshold voltage

E_p=∫

₀^tpV(t)dt  

 

Formula (4)

wherein t denotes any time (s) within the first interval in the at least any one of the cycles, tp denotes a time (s) from a start to an end of the first interval in the at least any one of the cycles, and V(t) denotes a voltage (V) at the time t.