The flicker minimizing method has been proposed in order to measure the residual DC voltage. However the flicker minimizing method has some problems; A)measurement results vary by test person, B)difficult to obtain good reproduction in measurement results even by single test person. We proposed the dielectric absorption method in order to measure the residual DC voltage in 1996. We found that the residual DC voltage depended on the thickness of alignment layers. The dielectric absorption method is a very simple measurement method. We have confirmed a strong correlation between the results of the flicker minimizing method and those of the dielectric absorption method.