Modification Of White And Blue Electrophoretic Particles For Electrophoretic Displays Application

In this paper, we modified cooper phthalocyanine （CuPc） particles and titaniumdioxide （TiO₂） particles as electrophoretic particles for the application of microcupEPDs and microencapsulated EPDs, which had been got good electropforeticproperties in the electric ink microcapsules.We used titanium dioxide particles as the white electrophoretic particles. In orderto change its surface from hydrophilic to hydrophobic and lower its density, TiO₂wasgrafted by γ-Methacryloxypropyl trimethoxy silane making the surface fromhydrophilic to hydrophobic, and then coated with poly（methyl methacrylate） via adispersion polymerization method prior to being used for an electronic ink material.In order to improve their mobility, a charge control agent was also added to thesuspension of synthesized nanoparticles in the dielectric medium.We use CuPc particles as the blue electrophoretic particles. In order to makecrystal transfer of CuPc particles happen, which is going to lower its size, therecrystallization process through acid-leaching method has been used. Then we coatedthem with a layer of silica as a protective shell and a substrate for next step. Finallywe couple them with KH-550. Or, coating with poly（methyl methacrylate） via adispersion polymerization method prior to being used for an electronic ink material isgoing which could improve the charged ability. In order to improve their mobility, thecharge control agents stearic acid and T-151were respectively added to thesuspension of synthesized nanoparticles in the dielectric medium.Good dispersion stability and surface charges of the modified particles in solventwere achieved in the presence of hyperdispersants and charge control agents. And thecolor displays were successfully achieved by the dual-particle systems ofelectrophoretic slurry containing blue-white pigment particles. Stable, elastic, andoptically transparent gelatin-gum arabic microcapsules containing modified particlesand dielectric media as core materials were prepared by a coacervation process. Themodified pigment particles had good electrophoretic properties in the electric inkmicrocapsules. The colored microcapsules were coated on indium tin oxide （ITO）film by using a home-made coating machine. After natural drying, the coating microcapsules were bonded on a patterned electrode. The prototype of coloredmicroencapsulated EPDs was obtained and the goal of color display was achieved.