Electrically induced uniform planar alignment of S*C liquid crystals on homeotropically treated plates

Chevron textures of SC* films are usually obtained with the conventional procedure where a planar alignment coating (e.g., buffed polyimide) is used. We describe a new technique which enables us to obtain uniform bookshelf textures which show bistability and can be switched with low fields (∼1 V/μm). This is achieved with a homeotropic surface coating. With a homeotropic coating the samples form a uniform texture with horizontal layers on cooling. The homeotropic texture becomes unstable under sufficiently strong electric fields and transforms to a birefringent texture with smectic layers oriented vertically. Without an additional bias the texture has domains of different layer orientations. By simultaneous application of a vertical field and horizontal shear stable uniform bookshelf textures can be obtained. Here we show that it is possible to obtain uniform bookshelf alignment by the simultaneous action of a horizontal field gradient and ac fields. The horizontal gradient leads to a more or less well-defined propagating front of the texture transformation. It results in a biased domain texture with vertical layers. The effect of the strong ac field (∼100 Hz) is to smooth out the domain texture.