Columnar liquid crystal as a unique ferroelectric liquid crystal

A recently discovered ferroelectric columnar liquid crystal (LC) is reviewed. Particular attention is paid to differentiate it from conventional ferroelectric LCs such as the smectic-C*-type and bent-core LCs from the symmetry point of view. After reviewing ferroelectric smectic LCs (FSLCs), a ferroelectric columnar LC (FCLC) is introduced as a unique ferroelectric LC. FSLCs have a polarization parallel to the layer plane and have arbitrariness in the polarization direction within the two-dimensional plane. Hence surface constraints are generally indispensable for fixing the polarization direction. In contrast, FCLC has an Ising polarization along the column axis, which is very stable once poling is performed and convertible by applying an opposite electric field. In this sense, FCLC is the first genuine ferroelectric LC. Poling and switching can be achieved using spin-coated FCLC films with an open surface as well as conventional sandwich cells. Hence the FCLCs are more suitable for applications such as piezoelectric devices and ultrahigh-density memory devices, whereas only an application to fast display devices is proposed for FSLCs.