Modification Of Colored Electrophoretic Particles And Characterization Of Electrophoretic Suspensions

In this paper, the yellow organic pigments and red organic pigments were chosen as electrophoretic particles. They were modified by encapsulating polymers in the surface. The modified pigment particles were used in electrophoretic displays (EPDs) and performed good electrophoretic properties.Pigment yellow13(PY13) particles were encapsulated by polystyrene (PS) via a mini-emulsion polymerization procedure. The effects of dispersion methods, monomer concentration, emulsifier concentration and rotate speed on reaction were investigated. The modified composite particles were spherical, and the surface was smooth. The particle size was about500nm, and the distribution was narrow. We use the composite particles as electrophoretic particles, and optimized the electrophoretic fluids recipe. The contrast ratio of yellow-white EPDs was1.26. In addition, PY13were encapsulated by St-AM co-polymerization and St-MMA co-polymerization to raise the surface charge.PY13particles were modified by encapsulating polymethyl methacrylate (PMMA) through a mini-emulsion polymerization procedure because PMMA has good light transmission. The effects of monomer concentration, emulsifier concentration, initiator concentration and rotate speed on reaction were investigated. The morphology of PMMA-modified composite particles was regular. The particles size was about400nm, and the size distribution was narrow. Compared with PMMA-modified particles, the shape of PS-modified particles was spherical and the surface was smoother. Both particles have higher surface charges. PMMA-encapsulated particles were used as yellow electrophoretic particles, and the effects of hyper dispersant CH-5and charge control additive on suspension properties were investigated. The contrast ration of yellow-white dual-color EPDs was1.24.Pigment Red254(PR254), Pigment Red48:2(PR48:2), Pigment Red146(PR146) particles were chosen as red particles. They were encapsulated by PS through a mini-emulsion polymerization procedure. The effect of pigment chemical structures on encapsulation procedure was investigated, and the results showed that PR146particles were completely encapsulated by PS. The effects of different reaction conditions were studied. The modified composite particles were spherical and the surface was smooth. The particle size was about500nm and the size distribution was narrow. The modified particles were used as red electrophoretic particles, and the electrophoretic properties of electrophoretic fluids in C2Cl4system and Isopar M system were studied. The electrophoretic mobility in Isopar M system was higher and the contrast ratio of red-white EPDs was1.59.