Relationship between spatial resolution and electrooptic thresholding in polymer-dispersed liquid crystals

We have studied the dependence of the spatial resolution of polymer-dispersed liquid crystal cells with finely patterned transparent electrodes on their electrooptic threshold properties. In a numerical simulation of the electrical potential based on the finite element method, the slit-patterned transparent electrodes induced a nonuniform electric field distribution in the cell and the spatial change of the electric field intensity significantly decreased with increasing spatial resolution of the slit width. It was estimated that spatial resolutions of 50 lines pairs (lp)/mm and 100 lp/mm would lead to saturation/threshold voltage ratios of 2 and 1.5, respectively, in the electrooptic property. When uniform and small liquid crystal droplets were formed by controlling photopolymerization-induced phase separation phenomena, the voltage ratio was decreased from 1.73 to 1.5. The measured limiting resolution reached more than 100 lp/mm, when small slit images displayed by a cell driven by the approximate applied voltage were magnified and sensed using a video camera. The experimental results confirmed the validity of the above resolution simulation results.