Lateral ion transport in nematic liquid-crystal devices

Liquid crystals used in electronic displays usually contain small amounts of ions that move under the influence of the varying applied electric field. It is well known that the motion of ions perpendicular to the substrates may lead to modified electric fields resulting in image sticking effects. During operation, the modulation in the director tilt angle can also lead to a net residual lateral component of the ion motion, parallel with the glass plates. A sustained ac driving voltage will accumulate the lateral ion motion and may result in image sticking effects near the pixel edge. Such effects have indeed been observed in supertwisted nematic cells.