Light Transmission and Texture Changes of Mixed Liquid Crystals by Temperature Variations

The changes in liquid-crystal light transmission caused by temperature variations are investigated in connection with texture changes. Materials under investigation are the nematic-cholesteric and the smectic-cholesteric mixed liquid crystals. In the nematic-cholesteric mixed liquid crystal, the light scattering centers produced by the temperature variation from the liquid phase to the cholesteric phase cannot disappear with the applied voltage of 1 kHz. On the contrary, the light scattering centers produced in the dynamic scattering mode can disappear with the applied voltage of 1 kHz. In the cholesteric phase of a smectic-cholesteric mixed liquid crystal, the planar texture appears in a heating process but the focal conic texture in a cooling process. This texture difference causes the difference in the light transmission between the heating and the cooling processes. Further, the difference in the light transmission of a planar texture depends on the mesh area: as the area is larger, the transmission is greater.