The effect of surface orientation on the operation of multiplexed twisted-nematic devices

The voltage and angular dependence of the electro-optic transfer characteristic of a twisted-nematic display are strongly affected by the average orientation (tilt bias) of the liquid-crystal molecules at the solid surfaces enclosing the fluid. A cell made with low tilt bias of the liquid-crystal molecules has a much sharper threshold in its electro-optic transfer curve and much better viewability when operated in a multiplexed mode than a display with a high tilt bias of the liquid-crystal molecules. As an example, a four-digit multiplexed twisted-nematic display of low tilt bias is viewable over a solid angle of about II/2 sr; whereas a high tilt-bias twisted-nematic device operating under the same multiplexing conditions is only viewable over a solid angle of about 0.50 sr.