Prepration And Display Performance Of Gelatin Modified Urea-formaldehyde Resin Microcapsule

Electrophoretic displays have the advantages of high brightness and contrast, wideviewing angles, state bistablity, and low power consumption. Microcapsuleselectrophoretic display is the commercialized technique. In this paper,Urea-formaldehyde resin microcapsules modified by gelatin were prepared via in situpolymerization. The surface topography of UF resin microcapsules was improvedsignificantly compared to those prepared by the traditional method. And the modifiedmicrocapsules possess good sphericity, smooth surface and excellent displayproperties.The preparation conditions of gelatin-UF resin electrophoretic microcapsules werestudied in this paper, the selection of emulsifier and curing agents. The results showthat the optimum processing conditions of UF resin microcapsule modified by gelatinwere: the mole ratio of formaldehyde to urea was1.8:1. the pH and temperature ofaddition reaction was9.0~9.5and75℃respectively, the condensationpolymerization reaction was at55℃and pH3.0~3.5. The addition amount of thegelatin was0.5%,0.8%of sodium lauryl sulfate was used as emulsifier, resorcinoland ammonium chloride were used as curing agent, and the weight ratio of the curingagent resorcinol and urea was10%. The microcapsules with good sphericity, smoothsurface, high strength, uniform distribution of particle size and good electrophoreticproperties were abtained and could be used to fabricate display devices.The coating technology of gelatin modified urea-formaldehyde resin microcapsulesalso was studied in this paper. The optimum conditions were: using polyurethanes611as binders, the concentration of the thickening agent was2.0%, the capsule weremixed with binder with the mass ratio of10:1, the range of microcapsule diameterwas35~70μm and coating thickness was0.50mm. The electrophoretic microcapsulesfilm has the characteristic of smooth surface, high contrast ratio, and fast responsebehavior.The display device of eight-section clock display and active matrix was prepared.At the electric field of15V, the contrast of the eight-section clock display device was9.0, the response time of black and white state was387ms and560ms respectively.The contrast of active matrix display device was7.5and the response time is less than1s. The device shows excellent display performance.