Electron beam irradiation induced transformations in the electro-optical and dielectric properties of a twisted-nematic display material 4′-pentyl-4-cyanobiphenyl (5CB)

Abstract

Changes in the electro-optical and dielectric properties of 4′-pentyl-4-cyanobiphenyl (5CB) due to electron beam irradiation up to 20 kGy dose have been studied. Dielectric spectroscopy for planar and homeotropic aligned samples has been carried out in the frequency range 100 Hz–35 MHz. Threshold and switching voltages, dielectric anisotropy, relaxation frequency, dielectric strength, distribution parameter and activation energy of an observed relaxation mode have been determined as a function of the irradiation dose. The electro-optical experiments show that the steepness of the transmission–voltage curve improves due to irradiation. The dielectric anisotropy decreases linearly with the irradiation dose. The dielectric relaxation study of the homeotropic aligned samples shows that the relaxation frequency and the activation energy corresponding to the flip-flop motion of the molecules about their short axes increase due to irradiation.