Achromatic supertwisted nematic LCD using birefringent film

A novel achromatic supertwisted nematic (STN) cell with birefringent film, which is used to compensate the rotational dispersion of the STN-cell, is proposed, and optical properties of the cell are discussed. It is found from the numerical analysis using Oseen-Frank elastic theory and Berreman's 4*4 matrix method that there are several solutions that yield high contrast ratio and color-tree background. This result is confirmed by experiment. The advantages of the cell are its light weight and good contrast ratio.>