HOLDING FIELD TO IMPROVE THE IMAGE RETENTION OF A CHOLESTERIC NEMATIC PHASE TRANSITION LIQUID CRYSTAL IMAGING SYSTEM

摘要

An imaging system including an imaging layer comprising cholesteric liquid crystalline material in an electrical field capable of having field strengths in the cholesteric nematic phase transition field strength range or the Grandjean to focal-conic texture transformation field strength range of the liquid crystalline imaging material. The imaging material is typically imaged by placing an imagewise phase-transition or texture-transformation inducing electrical field across a layer of imaging material. The present invention controls such an imaging system by maintaining a substantially uniform holding field across the entire surface of the imaging material, said holding field typically being maintained across the imaging material after it has been imaged. The holding field may be applied in the form of various phenomena. The particular type of holding field applied has field strengths below the cholesteric-nematic phase transition or the Grandjean to focal-conic texture transformation field strength thresholds of the imaging material. The imaging system, and especially its image memory and image relaxation characteristics are controlled by varying the strength of the holding field, and by applying field pulses in imagewise configuration to image the liquid crystalline imaging material, or by pulsing the field uniformly across the entire surface of the imaging material to field strengths above the phase-transition threshold or the texture transformation threshold, thereby enhancing the image already formed in the imaging material.