Coloured 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, and to color electrophoretic displays comprising such particles.
1. A process for the preparation of coloured polymer particles for use in electrophoretic devices, comprising the steps of
a) preparing polymer particles, comprising sites of charging and/or of stabilisation,
b) colouring the polymer particles by incorporation of at least one pre-polymerised dye, and
c) washing and drying the coloured polymer particles.
2. A process according to claim 1 , wherein the pre-polymerised dye is a homo-polymerised dye and/or co-polymerised dyes.
3. A process according to claim 1 , wherein the pre-polymerised dye is an uncharged dye.
4. A process according to claim 1 , wherein the pre-polymerised dye contains a chromophore, one or more polymerised groups, optional linker groups, optional groups to modify physical properties and optionally charged group(s).
5. A process according to claim 1 , wherein the pre-polymerised dye comprises at least one azo group, anthraquinone group or phthalocyanine group.
6. A process according to claim 1 , wherein the pre-polymerised dye is Poly(Disperse red 1 methacrylate) and/or Poly(Methyl methacrylate)-co-(Disperse Red 1 methacrylate).
7. A process according to claim 1 , wherein the polymer particles of step a) are prepared from a composition comprising a monomer, a crosslinker, an ionic monomer, and an initiator by surfactant-free emulsion copolymerisation in a batch process.
8. A process according to claim 1 , wherein the colouring of the polymer particles is done by solvent swelling with at least one pre-polymerised dye at a temperature range from 30-60° C.
9. A process according to claim 1 , wherein the coloured polymer particles have a diameter of 50-1000 nm.
10. Coloured polymer particles obtained by a process according to claim 1 .
11. A process according to claim 1 , wherein the coloured polymer particles have a diameter of 150-600 nm.
12. Coloured polymer particles comprising a polymeric framework and at least one pre-polymerised dye.
13. A mono, bi or polychromal electrophoretic device, comprising coloured polymer particles according to claim 12 .
14. Electrophoretic fluid comprising coloured polymer particles according to claim 12 .
15. Colour electrophoretic display device comprising coloured polymer particles according to claim 12 .