Display medium, display device and display method
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.
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, charged with a positive or negative polarity and included in the dispersion medium; and
a holder disposed between the pair of substrates and at least partially charged with a polarity opposite to that of all the kinds of the electrophoretic particles, the holder having a function of holding the electrophoretic particles.
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 about 30 kV/cm.
3. The display medium of claim 1 , wherein the holder further comprises at least two particulate members.
4. The display medium of claim 1 , wherein the holder has a color different from that of all the kinds of the electrophoretic particles.
5. The display medium of claim 1 , wherein the holder further comprises an aggregate of fibers.
6. The display medium of claim 1 , wherein the holder further comprises a non-woven fabric.
7. 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.
8. 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.
9. The display medium of claim 1 , wherein the holder further comprises a porous body having gaps through which the electrophoretic particles pass.
10. The display medium of claim 1 , wherein the holder has a white color.
11. The display medium of claim 1 , wherein the electrophoretic particles further comprises at least two 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 are detached from the holder and moved in the dispersion medium.
12. The display medium of claim 1 , wherein the electrophoretic particles further comprises at least two kinds of electrophoretic particles different from each other in a volume average primary particle diameter.
13. The display medium of claim 1 , wherein the electrophoretic particles further comprises at least two 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 are detached from the holder and moved in the dispersion medium.
14. The display medium of claim 1 , wherein the electrophoretic particles are moved, by an external voltage, at least from a state of being held in an arbitrary region on a surface of the holder to another region on a surface of the holder.
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, charged with a positive or negative polarity and included in the dispersion medium;
a light-modulating layer disposed between the pair of substrates and including a holder at least partially charged with a polarity opposite to that of all the kinds of the electrophoretic particles, the 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.
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 about 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
t
p
V
(
t
)
ⅆ
t
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 holder further comprises at least two particulate members.
18. The display device of claim 15 , wherein the holder has a color different from that of all the kinds of the electrophoretic particles.
19. The display device of claim 15 , wherein the holder further comprises an aggregate of fibers.
20. The display device of claim 15 , wherein the holder further comprises a non-woven fabric.
21. 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.
22. 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.
23. The display device of claim 15 , wherein the holder further comprises a porous body having gaps through which the electrophoretic particles pass.
24. The display device of claim 15 , wherein the holder has a white color.
25. The display device of claim 15 , wherein the electrophoretic particles further comprises at least two 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 are detached from the holder and moved in the dispersion medium.
26. The display device of claim 15 , wherein the electrophoretic particles further comprises at least two kinds of electrophoretic particles different from each other in a volume average primary particle diameter.
27. The display device of claim 15 , wherein the electrophoretic particles further comprises at least two 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 are detached from the holder and moved in the dispersion medium.
28. The display device of claim 15 , wherein the electrophoretic particles are moved, by an electric field applied by the electric field applicator, at least from a state of being held in an arbitrary region on a surface of the holder to another region on a surface of the holder.
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, at least one kind of electrophoretic particles or at least two 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 about 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
t
p
V
(
t
)
ⅆ
t
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.
32. 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;
at least one kind of electrophoretic particles or at least two 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 including a non-woven fabric and having a function of holding the electrophoretic particles.
33. The display medium of claim 32 , 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.
34. The display medium of claim 32 , 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.
35. The display medium of claim 32 , wherein the electrophoretic particles are moved by, an external voltage, at least from a state of being held in an arbitrary region on a surface of the holder to another region on a surface of the holder.
36. 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;
at least one kind of electrophoretic particles or at least two 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 including a non-woven fabric, the 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.
37. The display device of claim 36 , 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.
38. The display device of claim 36 , 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.
39. The display device of claim 36 , wherein the electrophoretic particles are moved, by an electric field applied by the electric field applicator, from a state of being held on an arbitrary region on a surface of the holder to another region on a surface of the holder.