We present a novel surface-controlled bistable nematic liquid crystal display. This black and white device uses simple monostable planar anchorings and a dielectrically positive nematic. The two bistable textures are, respectively, quasiuniform U and almost half-turn twisted T. Short electric pulses break the surface anchorings. Hydrodynamically coupled breaking of both anchorings creates T. U is obtained by breaking only one anchoring. Write and erase times for high resolution video are achieved at voltages compatible with the usual drivers.

2014 Nous décrivons un nouvel effet flexoélectrique de volume en champ électrique homogène, dans la phase nématique du MBBA. Une texture de flexion-divergence est créée entre deux plaques de verre, traitées pour induire des orientations antagonistes homéotrope et planaire. Il en résulte une polarisation flexoélectrique en volume. Un champ électrique continu transverse induit une torsion de la texture, mesurée par une rotation de la polarisation de la lumière en mode guide d'onde. La constante flexoélectrique de volume e1-e3 vaut + 1,0 ± 0,2 10-4 ues à 20 °C. La rotation de polarisation de la lumière, continûment contrôlable sur une amplitude ~ ± 45°, peut être utile pour des applications. Abstract 2014 We describe a new flexoelectric volume effect in homogeneous electric field, in the nematic phase of MBBA. An initial splay-bend texture is created by strong antagonistic planar and homeotropic anchoring on two glass plates. This results in a volume flexoelectric polarization. A transverse DC electric field creates a twist of the texture, which can be measured by the resulting wave guided rotation of light polarization. We obtain the volume flexoelectric constant e1-e3 = + 1.0 ± 0.2 10-4 stat C/cm at 20 °C. The continuously controllable light polarization rotation on a total amplitude ~ ± 45° may be useful for applications.

Weak anchoring of liquid crystals on solid substrates is usually dominated by the surface memory. We show that the memory can be removed by surface passivation by silane molecules. We realize planar, azimuthally degenerated, and memory-free anchorings without pretilt.