A liquid crystal device includes a sheet of plastic material having an open pore structure in which a liquid crystal material has been introduced. The liquid crystal material may be dichroic and contain one or more dyes which may be dichroic. The liquid crystal material may be nematic or cholesteric or a mixture of these two or a smectic material. Protective layers of plastic or glass may be arranged to enclose the sheet and the protective layer may carry electrodes. The liquid crystal may be applied to selected portions only of the sheet and the remaining parts of the sheet filled with a non-mesomorphic material.