Surface topography and alignment of liquid crystals on rubbed oxide surfaces

For several nematic liquid crystals (LC’s), the relation between alignments of the LC’s on rubbed oxide surfaces and rubbing pressures of the substrates is given. When the LC’s take a parallel alignment to the surfaces, good homogeneous alignment is achieved at low pressures. High pressure rubbing also produces good homogeneous alignment of LC’s, although alignment is perpendicular to the nonrubbed surfaces. Fine stripes of deposited cloth fibers can be observed on the cloth-rubbed oxide surfaces. The stripes consist of asymmetric projections ranging in the rubbed direction. On the basis of the asymmetric structure formed on the surface, the tilt direction of LC’s and their tilt angles are interpreted.