Light-emitting liquid-crystal cells with polarization switching function: Electrochemiluminescent method

A unique light-emitting liquid-crystal (LC) cell that emits polarized light is developed by an electrochemiluminescent (ECL) method; sandwich-type LC cells filled with a nematic LC doped with an organic fluorescent dye are constructed. Luminance and current density characteristics as a function of an applied voltage are investigated under different sample preparation conditions such as mixing temperature and time. It is shown that luminance strongly depends on the abovementioned conditions. From the results of ECL and photoluminescent measurements, we conclude that a significant increase in luminance by heating is attributed to an increase in the molecularly dissolved rubrene concentration. Furthermore, attempts were made to develop a dynamic polarization switch by introducing a pair of crossed interdigitated electrodes. As a result, although a not so high polarization ratio smaller than 2 was obtained, the polarization direction of the emitted light was switched by changing the direction of the in-plane electric field.