Abstract: A transmissive liquid crystal display actuatable to provide each of a plurality of different colors utilizes at least one parallel-nematic or twisted-nematic liquid crystal cell each having a dichroic dye dissolved therein for absorbing light each of a different color. The cells are sequentially arranged between a pair of polarizing elements have their axes of polarization perpendicular to one another. The polarizing element nearest an observer contains a dichroic dye for absorbing an additional wavelength (color) of visible light and may be selectively actuatable. By energizing different combinations of the cells from their quiescent to active conditions, different combinations of visible light wavelengths are absorbed to change the color of light transmitted through the display. Maximum-color displays, providing up to 2.sup.

Abstract: A liquid crystal composition of highly positive dielectric anisotropy comprises a mixture of a substantial fraction of substituted cyanophenylbenzoates and at least one (non-nitrile bearing) substituted phenyl benzoate, which may be a single and/or double ester. The large proportion of cyanophenylbenzoates causes the high positive dielectric anisotropy, and the use of a plurality of compounds reduces the melting point by eutectic action, also increasing the mesophase operating temperature range. The use of solely esters ensures high chemical stability, and the mixture is colorless.

Abstract: Nematic liquid crystal mixtures characterized by a selectively variable anisotropy and a mesophase including room temperatures are described. The mixtures comprise a negative dielectric anisotropic nematic liquid crystal material and a small percentage of a positive dielectric anisotropic nematic liquid crystal present in an amount effective to increase the dielectric anisotropy of the mixture. The further addition of a small percentage of a cholesteric material produces a mixture characterized by a helicoidal structure having a pitch greater than the wavelength of visible light and a cholesteric-nematic transition phenomenon induced by an electric field.

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.

Abstract: Nematic liquid crystal mixtures characterized by a homogeneous boundary condition are prepared by the addition of soluble compounds having at least two polar groups to nematic liquid crystals of either positive or negative dielectric anisotropy. Between approximately 0.5 and 5 percent by weight of compounds such as dicarboxylic acids, aliphatic diamines, aliphatic dinitriles, diols, polyalkylene glycol, alkanol amines, e.g., ethanolamine, diethanolamine, triethanolamine and diethylene triamine, for example, when dissolved in a nematic material produce spontaneous homogeneous boundary conditions therein.