Spacers with alignment effect and substrates having a weak alignment effect

Claim 1

An optical modulation device comprising chiral smectic liquid crystal between a pair of parallel base plates oppositely spaced from each other, said chiral smectic liquid crystal forming a plurality of molecular layers substantially perpendicular to said pair of parallel base plates, wherein: at least one of said pair of parallel base plates is provided with a first coating and a socond coating, the first coating having a unidirectional orientation effect for orienting the liquid crystal molecules preferentially in one direction, and the second coating being disposed on the first coating for orienting the liquid crystal molecules substantially parallel to said base plates and suppressing the unidirectional orientation effect of the first coating, said unidirectional orientation effect being provided by rubbing or oblique vapor deposition; at least one of said pair of parallel base plates is provided with a plurality of ridges arranged in striped form with a pitch of from 10 microns for 2 mm so as to extend in one direction and having side walls with a wall effect for orienting the liquid crystal molecular layers substantilly perpendicular to the direction in which said redges extend, the chiral smectic liquid crystal is placed in a non-spiral structure even in the absence of an electric field to provide a bistability condition wherein the liquid crystal molecules are oriented to either one of a first state and a second state thereof, and said ridges include a bar of trapezoid-shape in cross section.