Electrophoretic display element with filler particles
First Claim
1. An electrophoretic display element, the display element having a viewing surface and comprising at least one droplet of an electrophoretic phase and a wall surrounding the droplet, the droplet comprising:
- a fluid;
a plurality of first particles disposed in the fluid and having a first optical characteristic and a first electrophoretic mobility;
a plurality of second particles disposed in the fluid and having a second optical characteristic different from the first optical characteristic and a second electrophoretic mobility of opposite polarity to the first electrophoretic mobility; and
a plurality of third particles disposed in the fluid and having a third optical characteristic different from the first and second optical characteristics, the third particles not undergoing electrophoretic motion in an electric field,the electrophoretic display element having a first display state in which the viewing surface displays the first optical characteristic, a second display state in which the viewing surface displays the second optical characteristic, and a third display state in which the viewing surface displays the third optical characteristic.
1 Assignment
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Accused Products
Abstract
The invention relates to methods and materials for controlling stability and color intensity in an electrophoretic display element. Filler particles in the electrophoretic display element, serves as a medium that the electrophoretic particles must travel through during switching between optical states of the display. The filler particles provide improved control over the color intensity of the electrophoretic display element. In addition, the filler particles create resistance to the migration of the electrophoretic particles, thereby improving the bistability of the electrophoretic displays and inhibiting settling of the electrophoretic particles. Also, migration resistance provided by the filler particles can enable threshold addressing of an electrophoretic display.
576 Citations
24 Claims
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1. An electrophoretic display element, the display element having a viewing surface and comprising at least one droplet of an electrophoretic phase and a wall surrounding the droplet, the droplet comprising:
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a fluid; a plurality of first particles disposed in the fluid and having a first optical characteristic and a first electrophoretic mobility; a plurality of second particles disposed in the fluid and having a second optical characteristic different from the first optical characteristic and a second electrophoretic mobility of opposite polarity to the first electrophoretic mobility; and a plurality of third particles disposed in the fluid and having a third optical characteristic different from the first and second optical characteristics, the third particles not undergoing electrophoretic motion in an electric field, the electrophoretic display element having a first display state in which the viewing surface displays the first optical characteristic, a second display state in which the viewing surface displays the second optical characteristic, and a third display state in which the viewing surface displays the third optical characteristic. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12)
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11. A method of driving an electrophoretic display element, the display element having a viewing surface and comprising at least one droplet of an electrophoretic phase and a wall surrounding the droplet, the droplet comprising
a fluid; -
a plurality of first particles disposed in the fluid and having a first optical characteristic and a first electrophoretic mobility; a plurality of second particles disposed in the fluid and having a second optical characteristic different from the first optical characteristic and a second electrophoretic mobility of opposite polarity to the first electrophoretic mobility; and a plurality of third particles disposed in the fluid and having a third optical characteristic different from the first and second optical characteristics, the third particles not undergoing electrophoretic motion in an electric field, the method comprising; applying an electric field of one polarity to the droplet, thereby causing the first particles to approach the viewing surface and the second particles to become spaced from the viewing surface, so that the viewing surface displays the first optical characteristic; applying an electric field of the opposite polarity to the droplet, thereby causing the second particles to approach the viewing surface and the first particles to become spaced from the viewing surface, so that the viewing surface displays the second optical characteristic; and applying to the droplet an electric field of such polarity and duration that both the first and second particles are hidden by the third particles, so that the viewing surface displays the third optical characteristic.
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13. An electrophoretic display element, the display element comprising at least one droplet of an electrophoretic phase and a wall surrounding the droplet, the droplet comprising:
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a fluid; a plurality of first particles disposed in the fluid and having an optical characteristic and an electrophoretic mobility; and a plurality of second particles disposed in the fluid and forming a filler therein through which the first particles can move, the second particles not undergoing electrophoretic motion in an electric field, wherein in the absence of an electric field, the first particles are attracted to the second particles. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. An electrophoretic medium comprising a fluid;
- a plurality of a first type of particle having a first optical characteristic and a charge of one polarity; and
a plurality of a second type of particle having a second optical characteristic different from the first optical characteristic and a charge of the opposite polarity, the first and second types of particles being dispersed in the fluid, the electrophoretic medium displaying essentially zero conductivity on application of an electric field below a threshold, and a non-zero conductivity on application of an electric field above the threshold. - View Dependent Claims (23)
- a plurality of a first type of particle having a first optical characteristic and a charge of one polarity; and
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24. A method of varying the optical state of an electrophoretic medium, the medium comprising a fluid;
- a plurality of a first type of particle having a first optical characteristic and a charge of one polarity; and
a plurality of a second type of particle having a second optical characteristic different from the first optical characteristic and a charge of the opposite polarity, the first and second types of particles being dispersed in the fluid, the electrophoretic medium exhibiting a non-linear response to an applied electric field, the method comprising applying to the electrophoretic medium in an initial optical state a first drive pulse having a first voltage and a first duration and thereafter applying to the electrophoretic medium a second drive pulse having a second voltage and a second duration such that the algebraic sum of the impulses applied by the two drive pulses is zero, thereby driving the electrophoretic to a final optical state different from the initial optical state.
- a plurality of a first type of particle having a first optical characteristic and a charge of one polarity; and
Specification