Free energy in vertically aligned liquid crystal mode

Abstract

ABSTRACTVertical alignment (VA) is a widely applied operation mode for liquid crystal displays. To achieve optimum brightness, the electrode of VA is often patterned with fish-bone fine slits to generate fringe field, so the negative liquid crystal aligns along the fine slits when the electric field is applied. VA is usually simply modelled by the bend geometry along the cell gap. However, defects, domain boundaries and periodical splay induced by the fine slits also exist in real pixels and disturb the liquid crystal alignment. Polymer-stabilised VA test cells with various fine slit pitches which lead to various strength of fringe field were fabricated to observe the deformation of liquid crystal. Then the models of liquid crystal deformation nearby the defects and in the fine slit area were proposed to calculate the electromagnetic (fEM) and elastic free energy (felastic). The results show that the key factor to regulate fEM and felastic is the pitch of the fine slits, and the optimum liquid crystal alignment is obtained when fEM and felastic are equal. The models are useful for further investigation on the dynamics of liquid crystal alignment and applications in industrial products.