Preparation Of Microcapsule For Electrophoretic Display

Electrophoretic display (EPD), realized by electrophoresis of particles in microcapsules under an electric field, is a kind of new display technology, with such features, as low cost, high brightness, full-view, low power consumption and high flexibility. Compared to other types of microcapsules, the ones for EPD require smooth surface, superior transparence as well as good strength and flexibility. According to above requirements, in this thesis microcapsules were fabricated and applied in EPD with superior performance.Microcapsules were prepared through single coacervation and complex coacervation method, with gelatin, gelatin-gum Arabic and chitosan-polyacrylic acid as wall material, and tetrachloroethylene as core material. It was found that microcapsules with gelatin-gum Arabic as wall material had smooth surface, superior transparence and encapsulation efficiency high to 91.2%. It was also found that strength of microcapsules increased significantly and broken rate of microcapsules decreased to 51.2% from 100% after slight toluene-2, 4-diisocyanate (TDI) was added into wall material.Microcapsules were prepared through two-step and one-step in situ polymerization method, with urea-formaldehyde as wall material, and tetrachloroethylene as core material. It was found that one-step in situ polymerization method was easy to utilize and had good repeatability, and that microcapsules prepared by this method had fairly smooth surface and superior transparence, as well as encapsulation efficiency high to 96.6%. We also tried to combine complex coacervation and in situ polymerization method together: Surface of urea-formaldehyde microcapsules was encapsulated by another layer of gelatin to form a kind of double-layer microcapsule, which had thicker wall, better strength and flexibility, and broken rate decreased to 15.1% from 98.1%.Microcapsules were prepared by interfacial polymerization, with adipoyl chloride-triethylenetetramine as wall material, and tetrachloroethylene as core material. It was found that this method could be utilized easily and quickly and that prepared microcapsules, with 93.3% encapsulation efficiency and 48.3% broken rate, had smooth surface, superior transparence and satisfied strength. Strength and flexibility of this kind of microcapsules could be further improved to decrease broken rate to 36.2% by using triethylenetetramine modified by glutaraldehyde.Electrophoretic particles were prepared by milling, with hansa yellow 10G as particles, with Span 80 as surfactant, and p-methoxyaniline as charge control agent. It was found that dispersibility of this kind of particles was 82.4% and electrophoretic mobility was -0.118cm2V-1s-1. Hansa yellow 10G was applied in EPD via above preparation methods, and it was found that electrophoresis was reversible and responding time was 1~3s at the condition of 30V/mm.