抄録
One of the central quantities in determining the response times of liquid crystal display devices based on nematic is the rotational viscosity coefficient γ_1 which is related to changes in the director orientation. A particularly relevant method with which to determine γ_1 is to generate a non-equilibrium state by applying a field at some orientation to the director and then to monitor this as the system returns to equilibrium. In experimental investigations of field-induced director dynamics it is usual to employ a high frequency electric field, typically several kHz, to ensure that disruption of the director orientation by conductive motion of ions is eliminated. However, in the torque-balance equation used to predict the director dynamics, the electric field is taken to be constant. Clearly in the low frequency, the periodic variation in the square of the electric field will influence the director dynamics. In our experiment, a nematic cell was set in an NMR spectrometer. By applying the magnetic and periodic electric field, the director orientation fluctuates. We call this motion a pendulum effect. The values of the maximum and minimum angle due to a fluctuation of the director orientation give information on dynamic properties. Here, we consider this pendulum effect both theoretically and experimentally.
