Color organic pigments and electrophoretic display media containing the same
An electrophoretic display medium includes a front and a rear electrode, at least one of the front and rear electrodes being transparent, and an encapsulated dispersion fluid containing a plurality of pigments positioned between the front and rear electrode. The plurality of pigments includes a first and a second type of organic pigment particle. The first type of organic pigment particle has a first color and a first charge polarity. The second type of organic pigment particle has a second color different from the first color and a second charge polarity the same as the first charge polarity. At least one of the first and second types of organic pigment particle includes a silica coating and a polymeric stabilizer covalently bonded to the silica coating.
1. An electrophoretic display comprising:
a front and a rear electrode, at least one of the front and rear electrodes being transparent; and
a dispersion fluid containing a plurality of pigments positioned between the front and rear electrode, the plurality of pigments comprising a first, a second, and third type of organic pigment particle, and a fourth type of inorganic pigment particle;
the first type of organic pigment particle having a first color and a first charge polarity, the first type of organic pigment particle including a silica coating and a polymeric stabilizer, wherein the polymeric stabilizer is covalently bonded to a silane coupling group covalently bonded to the silica coating, and wherein the first type of organic pigment particles contains from about 4 to about 15 percent polymeric stabilizer by weight of the organic pigment particle;
the second type of organic pigment particle having a second color and the first charge polarity, the second color being different than the first color;
the third type of organic pigment particle having a third color and a second charge polarity, the third color being different than the first and second color, and the second charge polarity being opposite from the first charge polarity;
the fourth type of inorganic pigment particle having a fourth color and the second charge polarity, the fourth color being different than the first, second, and third color.
2. The electrophoretic display of claim 1 , wherein the dispersion fluid contains a fifth type of pigment particle.
3. The electrophoretic display of claim 1 , wherein the second type of organic pigment particle has a surface treatment formed via dispersion polymerization.
4. The electrophoretic display of claim 1 , wherein the first, second and third types of organic pigment particle comprise an organic pigment independently selected from the group consisting of PB15:1, PB15:2, PB15:3, PB15:4, PR 254, PR122, PR149, PG36, PG58, PG7, PY138, PY150, PY151, PY154 and PY20.
5. The electrophoretic display of claim 1 , wherein the first, second, and third types of organic pigment particle are independently colored red, green, blue, cyan, magenta, or yellow.
6. The electrophoretic display of claim 1 , wherein the fourth type of inorganic pigment particle is black.
7. The electrophoretic display of claim 6 , wherein the fourth type of inorganic pigment particle is selected from the group consisting of metal oxides, manganese ferrite black, copper chromite lack spinel, carbon black, and combinations thereof.
8. The electrophoretic display of claim 1 , wherein the fourth type of inorganic pigment particle is white.
9. The electrophoretic display of claim 8 , wherein the fourth type of inorganic pigment particle is selected from the group consisting of TiO 2 , ZrO 2 , ZnO, ZnS, Al 2 O 3 , Sb 2 O 3 , BaSO 4 , and PhSO 4 .
10. The electrophoretic display of claim 1 , wherein the polymeric stabilizer is derived from a monomer or macromonomer.
11. The electrophoretic display of claim 10 , wherein the monomer is selected from the group consisting of styrene, alpha methyl styrene, methyl acrylate, methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, vinyl pyridine, n-vinyl pyrrolidone, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hexyl acrylate, hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, n-octadecyl acrylate, n-octadecyl methacrylate, 2-perfluorobutylethyl acrylate, 2,2,2 trifluoroethyl methacrylate, 2,2,3,3 tetrafluoropropyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate.
12. The electrophoretic display of claim 10 , wherein the macromonomer contains a terminal functional group selected from the group consisting of an acrylate group, a vinyl group, or combinations thereof.
13. The electrophoretic display of claim 10 , wherein the macromonomer is an acrylate terminated polysiloxane.
14. The electrophoretic display of claim 10 , wherein the macromonomer comprises polyethylene oxide.
15. The electrophoretic display of claim 10 , wherein the polymer stabilizer is formed using random graft polymerization, ionic random graft polymerization, or atom transfer radical polymerization.
16. The electrophoretic display of claim 10 , wherein the silica coating of the first type of organic pigment particle is 0.5 to 10 nm thick.
17. The electrophoretic display of claim 1 , wherein the dispersion fluid is encapsulated.
18. The electrophoretic display of claim 17 , wherein the dispersion fluid is encapsulated within a microcapsule.
19. The electrophoretic display of claim 17 , wherein the dispersion fluid is encapsulated within a microcell.
20. The electrophoretic display of claim 17 , wherein the dispersion fluid is encapsulated within a polymer matrix.