Control and elimination of disclinations in twisted nematic liquid-crystal displays

A method for controlling and eliminating reverse-twist and reverse-tilt disclinations in twisted nematic cells without using cholesterics has been developed both theoretically and experimentally. Pretilt angle and tilting direction as well as twist angle and sense have been correlated with the appearance of disclinations. It is shown that for practical twisted nematic cells having a special sense of pretilt, the disclination free cells are realized by adopting the pretilt angle of 1°-5° and the twist angle of 80°-85°.