Microencapsulation of Electrophoretic TiO2 Nanoparticles for E-INK application

초록

Microencapsulation of electrophoretic dispersion is one of the key steps in developing the portable electrophoretic display technique such as electronic papers. In this study, TiO2 nanoparticles were used as electrophoretic particles due to their chemical stability and whiteness as well as unique optical and electrical properties. TiO2 particles were uniformly dispersed in a dielectric medium of halocarbon oil and the TiO2 based core material was emulsified using a polymeric surfactant of poly(sodium 4-styrenesulfonic acid)(PSSA). After the colloid particles were stabilized, urea/melamine formaldehyde prepolymer was introduced as the wall material and the microencapsulation of the core materials was accomplished by the polycondensation of the amino prepolymer. Average diameter of the microcapsules was about 50 um and their thermal properties were measured by both DSC and TGA. Molar ratio of urea/melamine and formaldehyde were varied and the surface morphology of the microcapsule was dependent on the molar ratio. Meanwhile, the effect of deionized water on the stability of the microcapsule was also investigated. As the water content decreased, more stable microcapsules were obtained.