Dispersive Ion Generation in Nematic Liquid Crystal Displays

Ion generation and recombination have been characterized in nematic liquid crystal displays. A model for dispersive generation may explain the time dependency of the leakage current through the cell. This current leads to the build-up of a charge layer near the electrodes depending on the resistivity of the alignment layer (a.l.) used. The amount of transported charge can then be calculated and related to a compensating voltage, which gives rise to image retention problems. Agreement between the results of theoretical analysis and experiments was reached when the capacitances of the a.l. and the diffusion layer were taken into account. Furthermore, the gradual removal of the charge layer during a short circuit was analyzed. This effect, depending on the type of a.l. used, is related to the diffusion and recombination of the ions involved.