Optically switching ferroelectric liquid crystal light valve

Claim 1

A liquid crystal device of multi-layer structure with front and rear faces, having two optically different stable states and switchable therebetween by a bias voltage, the device comprising: a liquid crystal layer composed of ferroelectric liquid crystal composition; a pair of front and rear alignment layers sandwiching therebetween the liquid crystal layer to establish the two optically different stable states in the liquid crystal layer, each alignment layer comprising an obliquely evaporated silicon monoxide film evaporated at an evaporation angle between 75 to 85 degrees and having a tilted micro column structure effective to establish the bistable state in the liquid crystal layer; a front electrode layer adjacent to the front alignment layer; an optically reflecting layer adjacent to the rear alignment layer; a photoconductive layer comprising a hydrogenated amorphous silicon film disposed on the optically reflecting layer and responsive to the incident light incident from the rear face to increase its electroconductivity; a rear electrode layer disposed on the photoconductive layer and cooperative with the front electrode layer to apply the bias voltage between the multi-layer structure including the liquid crystal layer and the photo-conductive layer such that an effective bias voltage is applied across the liquid crystal layer through the increased electroconductivity portion of the photoconductive layer to thereby effect the switching between the two stable states; and a pair of front and rear transparent substrates for sandwiching therebetween the multi-layer structure.

Claim 4

A method for driving a liquid crystal device having a multi-layer structure composed of a photoconductive layer and a ferroelectric liquid crystal layer having two optically different stable states, the method comprising the steps of: A. presetting said liquid crystal device to one stable state of said two stable states by one of applying a DC voltage, greater than a first threshold voltage value effective to switch between said two stable states under a bright condition, to said multi-layer structure under an irradiation of light and applying a DC voltage, greater than a second threshold voltage value effective to switch between said two stable states under a dark condition, to said multilayer structure under said dark condition, and B. writing an image into said liquid crystal device by applying a bias DC voltage, which has a polarity opposite to said presetting DC voltages and a magnitude greater than said first threshold voltage value and smaller than said second threshold voltage value, to said multi-layer structure under irradiation of light having image information.

Claim 5

A method for driving a liquid crystal device having a multi-layer structure composed of a photoconductive layer and a ferroelectric liquid crystal layer having two optically different stable states, the method comprising the steps of: A. presetting said liquid crystal device to one stable state of said two stable states by one of applying a DC voltage, greater than a first threshold voltage value effective to switch between said two stable states under a bright condition, to said multi-layer structure under an irradiation of light and applying a DC voltage, greater than a second threshold voltage value effective to switch between said two stable states under a dark condition, to said multilayer structure under said dark condition, and B. writing an image into said liquid crystal device by applying a bias DC voltage, which has a polarity opposite to said presetting DC voltages and a magnitude greater than said first threshold voltage value and smaller than said second threshold voltage value, to said multi-layer structure under irradiation of light having image information.