Surface TiIt Distributions of Homogeneously Aligned Liquid Crystals

Abstract

The dielectric axes of surface molecules in a homogeneously aligned, nematic liquid crystal cell, have characteristic non-zero tilt orientations, δθ, with respect to the bounding surface. An experimental technique is described which allows direct measurement of the average value of δθ, <δθ>, as well as the distribution about <δθ> over a finite surface area. A theoretical treatment of threshold behavior of a homogeneously aligned cell with a surface tilt boundary condition in the presence of a vertical electric field and a non-vertical magnetic field is presented which allows the quantitative interpretation of the experimental measurements. “Good” surfaces utilizing conventional rubbing techniques have sharp Gaussian distributions which are characteristic of the type of liquid crystal. surface composition and orientation technique. This procedure leads to a useful, quantitative technique to evaluate processing and orientation techniques as well as a means to study surface phenomena.