Abstract: Pleochroic fluorescent dyes of the general formula I: ##STR1## in which R is hydrogen or an aliphatic hydrocarbon radical containing not more than 20 carbon atoms and --CH.sub.2 -- between carbon atoms or adjacent to the bicyclo[2.2]octane residue may be replaced by --O-- may be dissolved in liquid crystal host material to form displays which are caused to fluoresce by incident low-energy ultraviolet initially absorbed by the liquid cyrstal host material and then internally transferred to the fluorophor. These dyes have greater stability to ultraviolet than other perylenedicarboxylic diesters while possessing good fluorescent properties and satisfactory order parameters. In formula I, R is preferably a straight or branched alkyl, and/or cycloalkyl group having 3 to 10 carbon atoms, preferably 5 to 7 carbon atoms. The liquid cyrstal host material preferably contains an energy-transfer agent such as a 4-substituted 4"-cyanoterphenyl. The 4-pentyl- and 4-propyl- bicyclo[2.2.

Abstract: A display device is described which comprises a liquid crystal host material and an anisotropically emitting fluorescent guest material dissolved in the host material such that the molecules of the guest material align with the molecules of the host material. An electric field applied across the host material causes the direction of radiation emitted by the guest material incident on an interface between two materials of different refractive index to vary so as to control the amount of radiation emitted by the display.