(358h) The Preparation of Environmental Friendly Gelatin-Gum Arabic Microcapsule for Electrophoretic Display

The Preparation of Environmental Friendly Gelatin-Gum Arabic Microcapsule for Electrophoretic Display

Hongli Liu ,Shirong Wang,Xianggao Li ,Yin Xiao*

(School of Chemical Engineering and Technology, Tianjin University, Tianjin,300072, China)

Abstract Electrophoretic display (EPD),which present images as the result of the particles with opposite charges moving in the electric field ,is know as the technology to relize the reflective display.And it has attracted more and more attention due to its low cost, low weight, good flexibility, wide viewing angles and low power consumption.

In order to get high response rate and contrast ratio electrophoretic display,the black/white particles together with charge control agent and dispersant et al.were coated in the gelatin-gum arabic microcapsule. Microencapsulated electrophoretic ink possesses the merits of flexibility,bistablity, extremely low power consumption, high contrast and reflectivity, as well as wide view angle. So it was successfully used in the preparation of electronic paper.

the choice of dispersion medium is especially critical for the electrophoretic fluid . At present, tetrachlorethylene is commonly used as dispersion medium, while it is not only harmful to human beings because of the effect of stimulation and anesthesia but also contaminates the environment by polluting underground water. In this article, isopar L ,which is isoparaffin,was selected as the dispersion medium instead of tetrachlorethylene. It is not only nearly non-toxic to human beings but also environmental friendly because of its low aromatic concentration and volatility.

The electrophoretic microcapsules containing carbon black and TiO₂ particles dispersed in isopar L were prepared by complex coacervation between gelatin and acacia. Carbon black and TiO₂  particles in the electrophoretic microcapsules were prepared by ball milling. Various factors affecting the properties of the prepared microcapsules, such as the ratio of gelatin and gum arabic to electrophoretic fluid , pH value and curing process, dispersion time and rate ,were experimentally investigated. And the result showed that the optimum conditions are as followsFthe ratio of gelatin and gum arabic to electrophoretic fluid was 1:4(w:w), the microcapsule wall should be cured for 70 min at pH 8 to 11 (T=45°C) ,the time and rate to disperse the electrophoretic fluid was 20 min and 800 rpm,respectively.The particle size of the electrophoretic microcapsule prepared in such conditions was well-distributed in 30`60μm. it is found that the particles represent electrophoretic behavior when the field strength was 4000V·m^-1. The electrophoretic display devices composed of these prepared microcapsules have good display properties when driven by the active or passive matrix driving.