Electrophoretic image display (EPID) panel

A new reflective-type electrophoretic image display (EPID) panel is described which is based on electrophoresis. In the EPID panel, a suspension is mainly composed of pigment particles and a suspending liquid. A dc voltage applied across a suspension layer changes the reflective color of the suspension as a result of the electrophoretic migration of the particles. The precipitation of the particles in the suspension is prevented by making the densities of the pigment particles and the suspending liquid equal. Color combinations of both the pigment particles and the suspending liquid can be used to achieve a desired color display. A reversal between the colors of the displayed pattern and its background can be obtained by changing the polarities of the applied dc voltage. The EPID panel has a memory function because of the deposition of the pigment particles on the electrode surface. A reflective contrast ratio of 40:1 at 75 V dc is demonstrated with experimental EPID panels. Rise and fall times of the panels are 20 ms and 10 ms, respectively, at 100 V ac. Power dissipation of the panel is about 7.5 mW for displaying a numeral "8" (107 by 59 mm²).