Electro-Optical Characteristics of Quasi-Homogeneous Cell in Twisted Nematic Mode

A liquid crystal (LC) director distribution was numerically analyzed in 90-degree twisted nematic (TN) LC cells with a symmetric and an asymmetric azimuthal anchoring strength of the alignment substrate and the influence of anchoring strength on the electro-optical property of the TN cell was evaluated. The twist angle decreased with decreasing azimuthal anchoring strength and the LC orientation changed to a homogeneous orientation with the twist angle of 0 degrees in the LC cell with asymmetric azimuthal anchoring strength, specifically with the strong anchoring substrate and the weak anchoring substrate below a critical strength. The asymmetric anchoring LC cell was fabricated by using a poly (vinyl cinnamate) alignment substrate as the weak anchoring surface and a polyimide alignment substrate as the strong anchoring surface. The LC cell performed the dark–bright–dark switching of the transmittance in the crossed polarizers, since the homogeneous LC orientation changed to the TN orientation again with increasing the applied voltage. Therefore, it was experimentally confirmed that LC molecules rotated at 90 degrees in the plane on the alignment surface by the electric field perpendicular to the weak anchoring substrate.