Thermally tunable light filter composed of cholesteric liquid crystals with different temperature dependence

A thermally tunable light filter by using cholesteric liquid crystals as a reflective type of optical device is proposed for an advanced thermo-driven light controller to realize the efficient control of solar-rays without losing the outdoor view and mounting the additional films. The cholesteric liquid crystals (CLCs) are fabricated to control the temperature dependence of selective transmittance spectra by using the composites of chiral dopants with different magnitude and sign of helical twisting power (HTP). The effects of chiral dopants on temperature dependence of selective wavelength are explained by the theoretical equation introduced for the mixture of chiral dopants. The optical properties for polymer stabilized cholesteric liquid crystal are also investigated by the spectroscopic measurements at different temperature in the various polymer concentrations. The optical performance of the tunable light filter formed by the combination of CLCs with different temperature dependence is demonstrated for the application as a reflective thermo-driven solar-ray controller.