Optical and Electrical Characterization of Electrophoretic Displays

The operational optical and electrical characteristics of an electrophoretic display based on anatase TiO 2 suspended in a dyed dielectric fluid are described. Optical response times as low as 10 msec were obtained with this system. The optical response of the device is related to the TiO 2 particle mobility and to the dynamics of removal of a charged particle from a conducting electrode. The electric field threshold was found to be controlled by the particle‐electrode interaction forces which are in the 10 −10 N range. The electrical conductivity of the system results mainly from charge control agent (which dissociates into ions) remaining in solution. Despite this ionic conduction, electrical resistivities of the order of 10 10 Ωcm and switching energy densities of 3 μJ/cm 2 were obtained. The optimal performance of this type of display device is predicted. The response time, electric field threshold, and electrical conductivity limitations of the electrophoretic display are outlined. Possible improvements in the materials package and cell fabrication techniques to overcome some of these drawbacks are suggested.