INVESTIGATIONS ON THE FIELD-INDUCED SWITCHING BEHAVIOR IN AN ANTIFERROELECTRIC LIQUID-CRYSTAL

The switching currents and field-induced apparent tilt angles in an an tiferroelectric liquid crystal, (R)-MHPOBC, were measured. The structu ral differences among different smectic C subphases may sensitively r eflect the field or temperature dependence of the apparent tilt angle. In a thin cell, the apparent tilt angle was found to change in two st eps as a function of field strength in the SmCalpha and SmC* phases: a steep increase at lower fields and a small linear increase at higher fields. The steep increase in apparent tilt angle is divided into two parts via a plateau in the ferrielectric SmCgamma phase. Stepwise ch ange with a plateau is also seen in the relation of apparent tilt angl e versus temperature under various electric fields. Moreover, the appa rent tilt angle in the vicinity of the plateau is almost temperature- and field-independent, implying a preferred orientation of the molecul es in the ferrielectric state. The influence of the cell thickness on the structural changes was also investigated.