Study On Modification Of Electrophoretic Particles And Formulation Of Display Solution

Electrophoretic display combines the advantages of traditional paper and smart displays,becoming the most promising new type of flexible display.High-quality electrophoretic particles and display fluid formulations are the key to improve electrophoretic display performance.However,there are few electrophoretic particles based on electrophoretic display technology,and the display solution formulation is complex.In this paper,Fe-Mn black nanoparticles for electrophoretic display were obtained by surface modification technology,the display liquid formulation was studied,and a prototype device with good display effect was obtained.TiO₂ nanoparticles were prepared by sol-gel method.After surface modification with silane coupling agent（KH570）,the surface lipophilicity and charge amount of the modified TiO₂particles were improved.Zeta potential（ζ）has increased from15.39mV to 57.73mV,it helps to accelerate the electrophoretic migration rate of TiO₂,improve contrast and response time of devices.And the average particle size is about230nm,which meets the particle size requirements of electrophoretic display particles.The dispersion particle size and surface charge properties of three kinds of black particles in iso-dodecane（Isopar L）were analyzed.It was found that the particle size distribution of Fe-Mn black was more uniform than that of Cu-Cr black,the average particle size of Fe-Mn black was 110nm and 165nm,respectively.The charge of Fe-Mn black was higher than that of carbon black,and theζvalues were-97.72mV and-80.73mV,respectively.Therefore,the Fe-Mn black particles used in electrophoretic display were further studied.Four active agents,cetyltrimethylammonium bromide（CTAB）,sodium lauryl sulfate（SDS）,sorbitan trioleate（Span 85）and（N-tetraethylene tetramine）polyisobutylene monosuccinimide（T151）were selected,and the Fe-Mn black was treated by a mixed ball milling process.The particle size distribution and surface charging properties of Fe-Mn black particles in Isopar L were studied.T151 has the best modification effect.The average particle size of the original Fe-Mn black is 1μm.After T151 modification,the average particle size is 110nm,and theζvalue is-96.71mV.The prepared display device has good electrophoretic response.Researches on the particle size and conductivity of the electrophoretic particles,the chain length of the isoparaffin of the dispersion medium,and the type and amount of additives showed the influence of the liquid formulation on the performance of the device.In Isopar L medium,the additives were T151 and superdispersant（A4300）with mass fraction of 1.5%～2.5%,when the particle sizes of the two particles with strong dielectric properties are between 50nm and 100nm,the performance of the display liquid is the best.The contrast of the prepared device is 7.46,a white state and a black state response times are 950ms and 670ms respectively,steady state time can reach 24h.