Electrical response of a liquid crystal cell: The role of Debye's layer

The authors investigate the effect of the surface treatment on the electrical response of a nematic liquid crystal cell. The theoretical analysis is performed by describing, from the electrical point of view, the liquid crystal and the surface treatment by means of the dielectric constants and the electrical conductivities. The predictions of the model are compared with the measurements performed on a nematic cell submitted to an external voltage steplike or linear in time. They show that to correctly interpret the experimental data it is necessary to take into account the surface layer of Debye, connected with the presence of the ions, responsible for the electrical conduction in nematics.