Alignment of nematic liquid crystals by photo-oriented layers

In the present work the optical anisotropy of various azodyes used as orienting layers for liquid crystals (LC) was investigated, The anisotropy was induced by linearly polarised light, It was experimentally shown that the orientation by photo-oriented layers is in some cases better than the one obtained by routine rubbing. The dyes investigated were either introduced into polymer films or used as single substances. It was shown that the value of pretilt angle depends on various factors but mainly on the nature and the treatment of the orienting layers. Angles from 0 up to 7 degrees were obtained, The value of the angle can be imposed by the proper choice of the film-preparation process.