Physical mechanisms of dc switching in a liquid‐crystal bistable boundary layer display

We discuss two mechanisms proposed to explain dc switching of a bistable liquid‐crystal boundary layer display. These are (1) biasing by double layer fields that arise from charge of one sign preferentially adsorbed at the walls, and (2) asymmetry in the transient depletion layer fields which result from a difference in mobility of the positive and negative ions. By a quantitative discussion, we argue that both mechanisms are plausible, but crucial parameters remain unknown. For the double layer mechanism the surface density of adsorbed charge is estimated as 8×10−10 C/cm2 from published measurements of the thickness dependence of the resistivity. For a numerical example of the differential mobility mechanism, we arbitrarily take μ−=3μ+=9×10−6 cm2/V sec. Either mechanism may be made dominant by the choice of material and surface properties. For fast switching, it may prove advantageous to choose interfaces to exploit the double layer mechanism because it begins to act immediately upon application of the v...