Abstract: Dichroic liquid crystal compositions for use in displays are mixtures of a liquid crystal host material and at least one of a plurality of dyes each having a plurality of azo (--N.dbd.N--) bonding groups and a high order parameter. The dichroic liquid crystal compositions each provide a contrast ratio on the order of 10:1.

Abstract: A method for improving the decay time of a display device utilizing a twisted nematic liquid crystal composition by the addition of a controlled amount of optically active material to produce a natural pitch, under field-free conditions, shorter than four times the thickness of the display device cell.

Abstract: Dichroic liquid crystal compositions, for use in liquid crystal displays, have a host liquid crystal material in which is dissolved one of a plurality of guest dichroic dyes, each having at least one Schiff-base ##STR1## bonding group. The dichroic liquid crystal compositions have a high order parameter, for providing contrast ratios on the order of 10:1 and imparting a yellow color to the display.

Abstract: Dichroic liquid crystal compositions for use in displays are mixtures of a liquid crystal host material and at least one of a plurality of dyes each having a plurality of azo (--N.dbd.N--) bonding groups and a high order parameter. The dichroic liquid crystal compositions each provide a contrast ratio on the order of 10:1.

Abstract: Dichroic dyes of the 4,4'-Bis-(substituted naphthylazo)azobenzene type, each having three azo (--N.dbd.N--) bonding groups, provide a high order parameter in excess of 0.70, when dissolved in liquid crystal mixtures to provide contrast ratios on the order of 10:1.

Abstract: Dichroic liquid crystal compositions for use in displays are mixtures of a liquid crystal host material and at least one of a plurality of stilbene-derivative dichroic dyes each having a vinylidene (--CH.dbd.CH--) group and a high order parameter. The dichroic liquid crystal compositions each provide a contrast ratio on the order of 10:1.

Abstract: Non-liquid crystal additives to negative dielectric anisotropy liquid crystals produce a positive dielectric anisotropy. Criteria for empirically determining suitable additives are disclosed. The general structure of suitable compounds is: ##SPC1##Wherein Z is a divalent radical, n is an integer having a value of 1 to 2; X, X', Y, Y' occupy only meta- and para-positions; X and X' are either electron withdrawing polar groups or hydrogen; Y and Y' are either electron repelling polar groups or hydrogen; at least one of X, X', Y and Y' is a polar group and, when only one of X, X', Y and Y' is a polar group, it occupies the para-position.