Preparation Of Red And Yellow Electrophoretic Particles For Electrophoretic Displays Application

In this paper,the organic pigment red particles and organic pigment yellow particles were selected as the electrophoretic display particles.The surface of the particles was modified to get satisfied performance of electrophoresis.P.R.48:2,P.R.57:1 and P.R.254 were selected as red electrophoretic particles.And the surface of particles was coated by polyethylene with different density and different structure through the method of in-situ polymerization.Then the electrophoretic properties of modified particles in Isopar L:C2Cl4=1:1 were studied,as well as the effect of pigment structure and polyethylene on the preparation of composite particles.The results showed that the effect of P.R.48:2 and P.R.254 was better than that of P.R.57:1,and the properties of P.R.48:2 particles coated with high density polyethylene were the best.The particle size distribution index decreased from 0.325 to 0.272,and charge quantity increased from 4.675×10-6 cm2v-1s-1 to 19.29×10-6 cm2v-1s-1.Besides,the lightness increased from 20.35 to 28.98,and the contrast ratio reached 2.67 which was measured by a simple electrophoresis display of red and white.All these results indicated that polyethylene with straight chains,high crystallinity and density was more suitable to be used as coating material,and red pigment particles with electron withdrawing groups were more suitable for electrophoretic particles.In our study,nonionic surfactants Span 80,Tween 80 and OP-10 were selected to modify the pigment yellow PY110.The results showed that the coating effect of Span 80 was the best and we got the modified pigment yellow PY110-S with smaller particle size,and better dispersion in the solvent.Then the PY110-S was coated with PS through the method of mini-emulsion polymerization.What's more,we studied the effects of surfactants,assistant surfactants and the amount of pigment particles on the preparation of composite particles.Under optimal conditions,yellow electrophoretic particles with the particle size of 434.4 nm,smooth surface,uniform dispersion and excellent spherical degree.The modified yellow particles PS/PY110-S were used in yellow electrophoretic display with the contrast ratio of 1.46,which was measured through a simple yellow and white dual color display device.When the modified red particles PS/PR146 were doped in PS/PY110-S,the contrast ratio reached 1.58.