Patent ID: 7626645

Claim:
An optical modulation method for a liquid crystal layer, in reference to a reference liquid crystal layer characterized by having one retardation through application of a predetermined high voltage and an other retardation through application of a predetermined low voltage, whereby a predetermined difference between the one and the other retardations can provide predetermined dark and bright states, comprising: making a thickness of the liquid crystal layer and/or a pre-tilt angle of liquid crystal molecules of the liquid crystal layer to be greater than that of the reference liquid crystal layer, the same value of the predetermined difference in retardation is obtained by a first retardation obtained by applying the liquid crystal layer with a modified high voltage lower than the predetermined high voltage and a second retardation obtained by applying the liquid crystal layer with a modified low voltage equal to or higher than the predetermined low voltage, or by a first retardation obtained by applying the liquid crystal layer with a modified high voltage equal to or lower than the predetermined high voltage and a second retardation obtained by applying the liquid crystal layer with a modified low voltage higher than the predetermined low voltage.