Impact of twisted alignment on the smectic layer structure of ferroelectric liquid crystal

Abstract

The twisted aligned cell of ferroelectric liquid crystal is assessed through electro-optical and dielectric spectroscopy and a comparison is made with antiparallel planar aligned cells of the same thickness around 8 μm. The study has been carried in two types of twisted aligned samples, one is natural cooled sample in the heating chamber and another is slow cooled at the rate of 0.05 °C/min. The influential distinct results have been observed in natural cooled twisted cells. In natural cooled cells, the helicoidal structure at the surface and in the bulk of the cell is distinct and contributes separately to the response of the cell. On the other hand, at the same cooling condition in twisted cell, the smectic layers are in a twisted state resulting into a non-uniform helical structure, therefore, the partial helicoidal unwound structure at the surface and in the bulk of the cell are not observed contributing to the dielectric permittivity separately unlike in planar aligned cell. The twisted cell is found to induce the restoring force within the sample. However, the slow cooling cycles on the twisted cell changes to the strain free equilibrium state, whereas the behavior of the planar sample cell remains unchanged. The studies are significant for the display devices based on twisted alignment of FLC cells.