Asymmetric electro-optical switching of a nematic cell controlled by a corona poled ferroelectric polymer layer

A polar asymmetry of electro-optical behavior has been studied for a liquid-crystal cell, one electrode of which is covered by a thin film of a ferroelectric polymer. A well-known copolymer PVF2-TrFE (70:30) previously poled by a corona discharge has been used to modify the quadratic electro-optical response of the nematic mixture in a hybrid cell. The voltage for the onset of switching becomes polarity dependent. A simple model of an internal electric field created by a poled ferroelectric and built in the nematic layer is discussed, which is consistent with the sign and general features of the effect. (C) 1998 American Institute of Physics. [S0003-6951(98)03425-1].