Bbc Brown, Boveri & Company, Limited

Andreas Zimmermann

Klaus Muller

An electrophoretic display including a cell having two plates spaced apart and provided at least regionally with electrodes, where at least one plate and an associated electrode facing the observer are transparent. The cell contains a suspension consisting of an inert dielectric liquid phase and a dispersed solid phase which at least in part are optically discriminable electrophoretic particles. The individual electrophoretic particles each are of practically the same density as the liquid phase, and at least part of the electrophoretic particles are pigment particles provided with a coating of organic material which is solid at the cell operating temperature but which melts at higher temperatures. The coating material contains at least one charge control agent. The charge control agent, preferably a salt of a divalent metal or metal of higher valency and of an organic acid, imparts a well-defined, uniform surface charge and a well defined, uniform surface potential to the particles.

Electrophoretic display

A method and apparatus for operating an electrophoretic indicating element driven by a drive signal, wherein the drive signal is modulated by an alternating voltage signal superimposed on the drive signal and having a frequency sufficiently high to prevent observation thereof. The modulating signal can have either a sinusoidal, triangular, or rectangular wave shape, or can be a succession of individual wave trains wherein the duration of each wave train is selected in accordance with the composition of the electrophoretic switching element.

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Emmenbrucke, Switzerland

Andreas Zimmermann