Dichroic dyes having a plurality of azo bonding groups

A dichroic liquid crystal composition for use in a liquid crystal display, comprising:

• a host liquid crystal material of positive dielectric anisotropy;
• and
• a guest dichroic dye dissolved in said liquid crystal material, said dichroic dye being a penta-azo dichroic dye having a general chemical formula ##STR15## wherein the substituents at bonds U,U', V, V', W, X, Y, and Z are coordinately selected for a desired set of an approximate order parameter and an approximate wavelength of maximum absorption in accordance with the following table:
• ______________________________________ DYE U U' V V' W ______________________________________ A CH.sub.3 CH.sub.3 H H H B CH.sub.3 CH.sub.3 H H OH C CH.sub.3 CH.sub.3 H H H D H CH.sub.3 CH.sub.3 H H E H CH.sub.3 CH.sub.3 H H ______________________________________ S max..sup.(nm.) DYE X Y Z (approx.) (approx.) ______________________________________ A (CH.sub.3).sub.2 N H H 0.73 525 ##STR16## 0.70 545 C ##STR17## 0.65 590-620 D ##STR18## ##STR19## 0.80 595 E ##STR20## H H 0.80 595 ______________________________________
• the approximate order parameter and approximate wavelength of maximum absorption being measured with said dye dissolved in a host material consisting of a mixture of 70% by weight of p-pentylphenyl-2-chloro-4-(p-pentyl-benzoyloxy) benzoate, and 30% by weight of an ester mixture composed approximately 50-60% by weight of 4'-n-pentylphenyl ester of anisic acid, 25-35% by weight of 4'-n-pentylphenyl ester of 4-hexyloxybenzoic acid, and 10-15% by weight (2'-cyano-4'-butylphenyl) ester of 4-(hexanoyloxybenzoyloxy)-benzoic acid.