Colored electrophoretic displays
First Claim
1. An electrophoretic medium comprising a fluid and first, second, third and fourth particles (1-4) dispersed in the fluid, the medium being characterized in that:
- (a) the plurality of first (1) and the plurality of fourth (4) particles bear charges of opposite polarity and each have a polymer coating comprising at least about 60 per cent by weight of an acrylate or methacrylate ester monomer comprising a hydrocarbon chain comprising at least about six carbon atoms, one of the first (1) and fourth (4 particles being a light-scattering particle and the other of the first (1) and fourth (4 particles being a substantially non-light-scattering particle having a subtractive primary color;
(b) the plurality of second particles (2) bear charges of the same polarity as the fourth particles, have a polymer coating comprising at least about 60 per cent by weight of a polydimethylsiloxane-containing monomer, and have a subtractive primary color different from the substantially non-light-scattering one of the first (1) and fourth (4) particles; and
(d) the plurality of third particles (3) bear charges of the same polarity as the first particles, are substantially non-light scattering and have a subtractive primary color different from the substantially non-light-scattering one of the first (1) and fourth (4) particles and different from that of the second particles (2), andwherein the first and second particles (1,
2) carry polymer coatings such that the volume fraction of polymer in the particles is at least about 25 percent, while the third and fourth particles (3,
4) either have no polymer shell or a polymer shell such that the volume fraction of polymer in the particles does not exceed about 15 percent.
1 Assignment
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Accused Products
Abstract
An electrophoretic medium comprises a fluid, a first, light scattering particle (typically white) and second, third and fourth particles having three subtractive primary colors (typically magenta, cyan and yellow); at least two of these colored particles being non-light scattering. The first and second particles bear polymer coatings such that the electric field required to separate an aggregate formed by the third and the fourth particles is greater than that required to separate an aggregate formed from any other two types of particles. Methods for driving the medium to produce white, black, magenta, cyan, yellow, red, green and blue colors are also described.
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Citations
20 Claims
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1. An electrophoretic medium comprising a fluid and first, second, third and fourth particles (1-4) dispersed in the fluid, the medium being characterized in that:
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(a) the plurality of first (1) and the plurality of fourth (4) particles bear charges of opposite polarity and each have a polymer coating comprising at least about 60 per cent by weight of an acrylate or methacrylate ester monomer comprising a hydrocarbon chain comprising at least about six carbon atoms, one of the first (1) and fourth (4 particles being a light-scattering particle and the other of the first (1) and fourth (4 particles being a substantially non-light-scattering particle having a subtractive primary color; (b) the plurality of second particles (2) bear charges of the same polarity as the fourth particles, have a polymer coating comprising at least about 60 per cent by weight of a polydimethylsiloxane-containing monomer, and have a subtractive primary color different from the substantially non-light-scattering one of the first (1) and fourth (4) particles; and (d) the plurality of third particles (3) bear charges of the same polarity as the first particles, are substantially non-light scattering and have a subtractive primary color different from the substantially non-light-scattering one of the first (1) and fourth (4) particles and different from that of the second particles (2), and wherein the first and second particles (1,
2) carry polymer coatings such that the volume fraction of polymer in the particles is at least about 25 percent, while the third and fourth particles (3,
4) either have no polymer shell or a polymer shell such that the volume fraction of polymer in the particles does not exceed about 15 percent. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An electrophoretic medium comprising a fluid and first, second, third and fourth particles (1-4) dispersed in the fluid, the medium being characterized in that:
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(a) the plurality of first (1) and the plurality of fourth (4) particles bear charges of opposite polarity and each have a polymer coating comprising at least about 60 per cent by weight of an acrylate or methacrylate ester monomer comprising a hydrocarbon chain comprising at least about six carbon atoms, one of the first (1) and fourth (4) particles being a light-scattering particle and the other of the first (1) and fourth (4) particles being a substantially non-light-scattering particle comprising a pigment having a subtractive primary color selected from the group consisting of cyan, yellow, and magenta; (b) the plurality of second particles (2) bear charges of the same polarity as the fourth particles, have a polymer coating comprising at least about 60 per cent by weight of a polydimethylsiloxane-containing monomer, and comprise a pigment having one of the subtractive primary colors different from the substantially non-light-scattering one of the first (1) and fourth (4) particles; and (d) the plurality of third particles (3) bear charges of the same polarity as the first particles, are substantially non-light scattering and comprise a pigment having one of the subtractive primary colors different from the substantially non-light-scattering one of the first (1) and fourth (4) particles and different from that of the second particles (2), and wherein the yellow, magenta, and cyan pigments exhibit diffuse reflectances at 650, 650 and 450 nm, respectively, measured over a black background, of less than 2.5% when the pigment is approximately isotropically distributed at 15% by volume in a layer of thickness 1 μ
m comprising the pigment and a liquid of refractive index less than 1.55. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification