Distortion of the cholesteric planar texture in liquid crystals with a negative dielectric anisotropy

2014 A study is made of the formation of new planar regions during the electrohydrodynamic distortion of the cholesteric planar texture in liquid crystals with a negative dielectric anisotropy. With increasing voltage successive planar regions are observed which are associated with an increasing number of helices across the layer with steady planar boundary conditions. The resulting pitch contraction occurs via discontinuities which can be related to S = (1) disclinations. The stability of the new planar regions if favoured by a large negative dielectric anisotropy. The threshold voltage for the square grid perturbation of these induced textures is much larger than that predicted theoretically by Helfrich and Hurault, whose theory only holds for cholesteric planar layers in which the natural pitch P0 occurs. LE JOURNAL DE PHYSIQUE ’ TOME 39, AVRIL 1978,