Particles for electrophoretic displays
This invention relates to colored polymer particles preferably with surface functionality for charge retention, a process for their preparation, the use of these particles for the preparation of an electrophoretic device, color electrophoretic displays comprising such particle, and new water-soluble dyes.
1. An electrophoretic fluid comprising colored polymer particles, which comprise monomer units of at least one polymerizable dye, at least one monomer, optionally at least one charged co-monomer, and optionally at least one crosslinking co-monomer,
wherein the polymerizable dye is a dye of Formula 2 or a dye of formula 3
wherein
R5, R7=alkyl,
R6, R8=H or CH 3 , and
Hal=halogen.
2. An electrophoretic fluid according to claim 1 , wherein the colored polymer particles have been prepared by a process, which comprises
a) reacting the at least one polymerizable dye, at least one monomer, at least one initiator, and optionally at least one charged co-monomer, and optionally
b) washing and drying the colored polymer particles.
3. An electrophoretic fluid according to claim 1 , wherein the dye is a water-insoluble dye.
4. An electrophoretic fluid according to claim 1 , wherein the dye is a water-soluble dye.
5. An electrophoretic fluid according to claim 1 , wherein the polymerizable dye is of Formula 3
wherein
R7=alkyl, and
R8=H or CH 3 .
6. An electrophoretic fluid according to claim 1 , wherein the polymer particles have been prepared from a composition comprising the polymerizable dye, a monomer, a crosslinker, an ionic co-monomer, and an initiator by surfactant-free emulsion copolymerization in a batch process.
7. An electrophoretic fluid according to claim 1 , wherein the colored polymer particles have been prepared by a process, which is a mini-emulsion polymerization.
8. An electrophoretic fluid according to claim 1 , wherein the polymer particles have a diameter of 50-1000 nm.
9. An electrophoretic fluid according to claim 1 , wherein the colored polymer particles comprise monomer units of the at least one polymerizable dye, at least one monomer, at least one charged co-monomer, and at least one crosslinking co-monomer.
10. A mono, bi or polychromal electrophoretic device, comprising an electrophoretic fluid according to claim 1 .
11. An electrophoretic display device comprising an electrophoretic fluid according to claim 1 .
12. An electrophoretic fluid according to claim 1 , wherein the polymerizable dye is a compound of Formula 2
wherein
R5=alkyl,
R6=H or CH 3 , and
Hal=halogen.
13. An electrophoretic fluid according to claim 1 , wherein the polymerizable dye is a compound of Formula 2 in which Hal=Cl, and R5 and R6=CH 3 .
14. An electrophoretic fluid according to claim 1 , wherein the polymer particles have a diameter of 150-600 nm.
15. An electrophoretic fluid according to claim 1 , wherein the polymerizable dye is a compound of Formula 3 in which R7=C 2 H 5 and R8=CH 3 .