Changes of twisted nematic liquid-crystal layers by frequency switching of applied electric fields

Abstract Electric fields of low and high frequency were applied successively to a twisted nematic layer consisting of a material with a dielectric anisotropy whose sign depends on the frequency. Six different areas have been observed which are found to have twist angles of ± π /2, ±3 π /2 and ±5 π /2. The formation process of these regions is described in some detail.