Novel yellow azo dyes and dichroic liquid crystal compositions made therewith

摘要

Novel yellow azo dye compositions and a liquid crystal composition containing the yellow azo dye composition are disclosed. The yellow azo dye composition, having terminal ester groups, has the general formula: wherein R and R' are acyl groups having the formula: and R2 is an alkyl or substituted alkyl wherein the alkyl has at least 4 carbon atoms, or R2 is an aryl, arylalkyl, substituted aryl or substituted arylalkyl. When the yellow azo dichroic dyes are used alone, or in combination with other dyes, as a guest in a host liquid crystal material, they form a novel liquid crystal composition for use in liquid crystal displays. The disclosure also embraces a method of improving the black color of dichroic dyes for use in black liquid crystal displays, wherein a dye composition having a mixture of dichroic dyes of various colors and containing at least one yellow azo dichroic dye, as described above, is added to a host liquid crystal material. The mixture of dichroic dyes of various colors must be one which absorbs radiation in the spectral range of about 400-700 nm to produce the substantially black color for use in black liquid crystal displays.