Pulse-Length Modulation Achieves Two-Phase Writing in Matrix-Addressed Liquid-Crystal Information Displays

Matrix-addressed liquid-crystal information displays exhibiting the bistability effect require either special performance of display and cell configuration or a two-phase dynamic erase, writing, and driving scheme. Two-phase operation is done by pulse-length modulation thus providing the required different rms voltage levels for erasing, writing, and sustaining the information. Controlling these levels can easily be done by logic operation. Configuration for an integrated circuit is given by serial input shift register with parallel outputs feeding high-voltage drivers and may be universally used for driving x and y lines. Data for a 82 000-dot array system are presented.