Optical writing type liquid crystal light valve and writing apparatus

Abstract

A liquid crystal light valve has a photoconductive layer between a pair of electrodes, and a liquid crystal layer. The resistivity of the photoconductive layer at the portion which is irradiated with light is reduced by partial light irradiation. By applying a voltage between the electrodes in this state, the voltage is applied to the liquid crystal layer in the portion which is irradiated with light and the crystalline structure at this portion is changed, thereby enabling image data writing. The photoconductive layer is a laminate of an amorphous Si film and an inorganic insulating film disposed on the electrode side, which structure suppresses the carrier injection from the electrode to the amorphous Si film. The polarity of a voltage for writing image data into the liquid crystal light valve is inverted for every horizontal scanning operation. That is, writing of black portions on a white background and writing of white portions on a black background are alternately executed. It is therefore possible to write data on one line and erase the data on the next line by a voltage of one polarity. By periodically setting a period in which no voltage is applied during writing, writing error caused by stored charges is prevented.