Preparation and Characterization of Acrylic-Based Electronic Inks by In Situ Emulsifier-Free Emulsion Polymerization for Electrophoretic Displays

Attempts were made to prepare monodispersed electronic ink particles by a new procedure, in situ emulsifier-free emulsion polymerization. Highly monodispersed poly(methyl methacrylate-co-ethylene glycol dimethacrylate) electronic ink particles containing blue dyes and charge control additives (E-81) were successfully prepared both in aqueous medium and in a mixture of water and methanol by emulsifier-free emulsion polymerization. On increasing either the concentration of oil blue N or E-81, the particle size decreased initially but then increased in the absence of methanol, whereas particle size progressively increases in the presence of methanol. The addition of methanol in the polymerization also influences the polymerization kinetic and the charge density of electronic ink particles. The resulting electronic inks were found to be smooth on the surfaces and particle sizes were 300-700 nm with a coefficient of variation of 0.3%. Electrophoretic mobility of the resulting electronic ink was -2.08 to -5.28 × 10^-5 cm^2/V·s in the presence of charge control additives.