Utilization of dyes for liquid crystal displays

Abstract

In a cholesteric guest-host liquid crystal composition having a positive dielectric anisotropy and consisting of a nematic host component with a dye incorporated as a guest component therein and an optically active (cholesteric) component, the improvement consisting of a substantially stable and water insoluble azo dye guest component having a pleochroic ratio a.sub.1 /a.sub.2 of at least 6.5 and an absorption maximum in the range of from 350 to 700 nm, said azo dye being a compound of the formula (1) X -- A -- N .dbd. N -- B -- Y (I) wherein A is selected from the group consisting of 1,4-phenylene, 2-hydroxy-1,4-naphthylene and 2-hydroxy-8-amino-1,4-naphthylene; B is selected from the group consisting of 1,4-phenylene, 1,5-naphthylene and 5-substituted benzothiazo-(1,3)-2-yl; X is selected from the group consisting of nitro, nitrile, dimethylamino, di(hydroxyethyl)-amino, phenyl and straight chain C.sub.1 -C.sub.10 alkyl, and Y is a monovalent organic radical that does not promote water solubility in the dye molecule.

Dependencies are inferred from the claim text.