Particles for electrophoretic displays
This invention relates to particles comprising a pigment core particle encapsulated by a polymer, a process for their preparation, electrophoretic fluids comprising such particles, and electrophoretic display devices comprising such fluids.
1. Particles comprising a single organic or inorganic pigment core particle encapsulated by a polymer having monomer units of at least one polymerisable steric stabiliser, at least one co-monomer, optionally at least one charged co-monomer, and optionally at least one crosslinking co-monomer, and the particles comprise at least one surfactant, wherein the amount of surfactant is from 1-10% by weight based on the weight of the pigment.
2. The particles according to claim 1 , wherein a single organic or inorganic pigment core particle is coated with at least one surfactant and encapsulated by a polymer.
3. The particles according to claim 1 , wherein the pigment core particle is titanium dioxide in the rutile, anatase, or amorphous modification or carbon black.
4. The particles according to claim 1 , wherein the surfactant is soluble in non-polar organic solvents.
5. The particles according to claim 1 , wherein the polymerisable steric stabiliser is a poly(dimethylsiloxane) macromonomer with at least one polymerisable group and a molecular weight in the range of 1000-50000.
6. The particles according to claim 1 , wherein the polymerisable steric stabiliser is a mono-methacrylate terminated poly-dimethylsiloxane.
7. The particles according to claim 1 , wherein the percentage of polymerisable steric stabiliser is at least 5% by weight based on the weight of the particle.
8. The particles according to claim 1 , wherein the particles have a diameter of 400-1000 nm.
9. An optical, electrooptical, electronic, electrochemical, electrophotographic, electrowetting, electrophoretic display or device comprising the particles according to claim 1 .
10. An electrophoretic fluid comprising particles according to claim 1 .
11. An electrophoretic display device comprising an electrophoretic fluid according to claim 10 .
12. An electrophoretic display device according to claim 11 , wherein the electrophoretic fluid is applied by a technique selected from inkjet printing, slot die spraying, nozzle spraying, and flexographic printing, or any other contact or contactless printing or deposition technique.