Recent experimental and theoretical results that link the phenomenon of dielectric relaxation in nematic liquid
crystals (NLCs) to their dynamics and fast electro-optical switching are presented. Namely, we illustrate that the
dielectric torque acting on the uniaxial nematic liquid crystal depends not only on the present value of the field and
the present orientation of the director, but also on the prehistory of these two parameters. The resulting "dielectric
memory" effect leads to a spectacular but counter-intuitive effect: director relaxation during the "switch-off" stage
can be accelerated if instead of the abrupt vertical back edge, one uses a voltage pulse with a non-instantaneously
vanishing back edge. The acceleration effect can be enhanced with a short high voltage pulse at the end of the
"switch on" process.
The dielectric dispersion in uniaxial nematic liquid crystals creates a "dielectric memory" effect whereby
the polarization induced by the electric field decays exponentially with time rather than instantaneously, as in
materials without dispersion. The induced polarization couples linearly with the electric field. This linear coupling
allows one to accelerate the director relaxation towards the "off" state by a specially designed electric pulse of a
proper polarity and duration We show theoretically and experimentally the possibility of electrically driving the
director towards the off state, thereby decreasing the switching time.
Cholesteric liquid crystal display (Ch-LCD) are lightweight, low power, sunlight readable displays. In addition, they can serve a dual function as pen-input device switch no additional hardware. Because of the unique properties of this technology, Ch-LCDs can be made with plastic substrates thus making the displayed extremely lightweight, compact and unbreakable. We discuss in this paper cent advances in merging Ch-LCD technology with conducting polymer electrodes. Conducting polymer provides potential benefits over the use of the standard display electrode materials, indium tin oxide, by improving the reliability of the display. Furthermore, the potential to print the conducting polymer electrodes could significantly increase manufacturing volume and decrease display cost. We report on scaling display size and resolution by demonstrating a 1/8 VGA Ch-LCD using polypyrrole as the conducting polymer. We fabricated these displays using either a vacuum fill or polymer wall/lamination approach and we discus subsequent failure analysis to determine the cause for the line-outs observed on these displays. We present initial results in determining the suitability for using Ch-LCD technology as a pen-input device. Finally, we discuss initial work towards printing the conducting polymer electrodes to determine the feasibility of printing electrodes on plastic substrates in a roll-to-roll, high volume, low cost process.