Bistable nematic liquid crystal device

A bistable liquid crystal device comprising:

• a first cell wall and a second cell wall enclosing a layer of nematic liquid crystal material;
• electrodes on at least one cell wall for applying an electric field across at least some of the liquid crystal material;
• a grating alignment structure on the inner surface of the first cell wall;
• a coating of a polymeric material on the said grating alignment structure, the polymeric material being in contact with the liquid crystal material and substantially insoluble therein;
• the arrangement being such that two stable molecular configurations can exist within the nematic layer after suitable electrical signals have been applied to the electrodes.

A bistable liquid crystal display device comprising a first cell wall and a second cell wall enclosing a layer of nematic liquid crystal material;

• electrodes on both cell walls for applying an electric field across at least some of the liquid crystal material;
• substantially identical grating alignment structures formed on the inner surface of both cell walls;
• and
• a coating of a polymeric material on the alignment structure of the first cell wall but not on the alignment structure of the second cell wall, and in contact with the liquid crystal material;
• the arrangement being such that two stable molecular configurations can exist within the nematic layer after suitable electrical signals have been applied to the electrodes.

A bistable liquid crystal display device comprising a first cell wall and a second cell wall enclosing a layer of nematic liquid crystal material;

• electrodes on both cell walls for applying an electric field across at least some of the liquid crystal material;
• a grating alignment structure formed on the inner surface of the first cell wall;
• and
• a coating of a polymeric material on the alignment structure of the first cell wall and in contact with the liquid crystal material, the polymeric material being crystalline or glassy at the operating temperature range of the device;
• the arrangement being such that two stable molecular configurations can exist within the nematic layer after suitable electrical signals have been applied to the electrodes.

A method of manufacturing a bistable liquid crystal device, the method comprising:

• initially forming a cell from first and second opposed spaced-apart cell walls enclosing a layer of nematic liquid crystal material having a photopolymerisable polymer precursor dissolved therein;
• wherein electrodes are provided on the inner surface of both cell walls for applying an electric field across at least some of the liquid crystal material;
• and
• wherein the inner surfaces the cell walls are each provided with a substantially identical grating alignment structure;
• and then illuminating the cell through the first cell wall with suitable light to effect photopolymerisation of the polymer precursor close to the first cell wall and deposition of the resulting polymeric material as a coating on the grating alignment structure on the first cell wall;
• thereby producing an asymmetric device wherein two stable molecular configurations can exist within the nematic layer after suitable electrical signals have been applied to the electrodes.