Guest-host type liquid crystal composition and liquid crystal display device using the same

In a liquid crystal composition comprising at least one host liquid crystal and at least one pleochroic dye dissolved as a guest in said at least one host liquid crystal, said host liquid crystal being a nematic liquid crystal, wherein said at least one pleochroic dye includes at least one anthraquinone dye represented by the formula:

• ##STR207## wherein X is an oxygen atom, and R' is a cycloalkyl group or an aryl group each having one or more substituents, each of said substituents having 1 to 18 carbon atoms.

In a liquid crystal composition comprising at least one host liquid crystal and at least one pleochroic dye dissolved as a guest in said at least one host liquid crystal, said host liquid crystal being a nematic liquid crystal, wherein said at least one pleochroic dye includes at least one anthraquinone dye represented by the formula:

• ##STR208## wherein X is an oxygen atom, and R' is a cycloalkyl group or an aryl group each having one or more substituents, each of said substituents having 1 to 24 carbon atoms.

A liquid crystal display device comprising a pair of base plates at least one of which is transparent, transparent electrodes for driving the liquid crystal formed on the opposite surface of said base plates facing each other, a liquid crystal layer held between said plates via the transparent electrodes, and a means for applying an electric field for driving the liquid crystal via the aforesaid transparent electrodes, characterized in that the aforesaid liquid crystal layer comprises at least one host liquid crystal and at least one pleochroic dye dissolved as a guest in said at least one host liquid crystal, said host liquid crystal being a nematic liquid crystal, wherein said at least one pleochroic dye includes at least one anthraquinone dye represented by the formula:

• ##STR209## wherein R is OH or NH.sub.2, provided that (a) when R is OH, Y is selected from the group consisting of COXR' in which X is an oxygen atom, and R' is a cycloalkyl group or an aryl group each having one or more substituents, and (b) when R is NH.sub.2, Y is COXR' in which X and R' are as defined above, and wherein said substituents have 1 to 18 carbon atoms when R is OH, and 1 to 24 carbon atoms when R is NH.sub.2.