Variable grating mode imaging method

Abstract

A novel projection imaging method. An imaging member is utilized comprising between two electrodes a negative photoconductor in contact with an about 1 to about 6 micron thick layer of nematic liquid crystalline material which, in the absence of an electrical field is provided in the homogeneous texture, and of negative dielectric anisotropy. A d.c. voltage above the parallel variable grating mode threshold for the nematic liquid crystalline material is applied between the two electrodes of the imaging member and the entire nematic layer goes into the parallel variable grating mode. While the voltage is applied, the negative photoconductor is exposed to imagewise configured actinic electromagnetic radiation and becomes more resistive in exposed areas. The actinic radiation causes the voltage to decrease across portions of the nematic liquid crystalline layer in contact with regions of the negative photoconductor exposed to the actinic radiation. The decrease in voltage across these portions of the liquid crystalline material is sufficient to cause cylindrical, vortical domains of molecules of the nematic liquid crystalline material in the parallel variable grating mode to disappear in imagewise configuration. Conventional Schlieren readout utilizing light linearly polarized in a direction orthogonal to the major axes of the vortical domains prevents unwanted exposure of the negative photoconductor while simultaneously maintaining the resistance of the negative photoconductor in imagewise configuration. Selective write and erase capabilities are provided.