Polymer negative birefringence films for compensation of twisted nematic devices

Compensation of the liquid crystal layer within twisted nematic displays operating in normally white and normally black modes was examined. Studies of commercially available compensation films allowed us to develop the optimum compensating configuration for normally white displays including negative C-plates, discotic splay layers and A-plates. The optimum compensation of the normally black display mode was achieved using a stack of A-plates. The compensation provides a wide viewing cone and no gray-scale inversion in the most important viewing directions for both optimized display types. The compensated devices exhibit an achromatic dark state.