Actual capacitance function of nematic liquid crystal cell

Liquid crystals (LCs) used in electronic displays usually contain many ions that come either from the raw material itself or from impurities during fabrication. The ions form an electrical double layer (EDL) at the surface, causes some image retention problems, and also influence the optical or electrical measurements in LC cells. The time response of the capacitance measurement in nematic LC cells under various external DC voltages is discussed. The actual applied DC voltage drop at the liquid crystal is modified by taking the EDL effect into account. To obtain a more exact solution, a constant displacement vector is applied instead of the simple assumption that the electric field intensity in the LC cell is constant. Consequently, the voltage- and time-dependent capacitance function of the nematic LC cell is expressed, and simulations with this function agree qualitatively with the measured results.