Haze-Suppressed Wideband Light Shutter from Near Ultraviolet to Infrared Rays Utilizing Electrophoretic Carbon Black Particles

Carbon black (CB) particles that can absorb from near ultraviolet to infrared rays are well dispersed into an isotropic dielectric liquid and their optical properties can be kept even under exposure to sunlight over a long time. The shutter which controls the position of CB particles by electrophoretic force can be applied to switchable light shutters for windows in buildings and automobiles for the purpose of energy savings. Here, a wideband light shutter with three terminal electrodes is proposed, exhibiting excellent dark (transmittance approximate to 1.4%) and transparent state (transmittance >60%). The device operates at a low field intensity of about 1 V mu m(-1) to obtain transparent state and its wide temperature range operation from -50 to 120 degrees C is confirmed while conventional liquid crystal-based shutter cannot perform such levels due to a limited temperature range in the nematic phase. In addition, haze is minimized in a transparent state by adopting an insulation layer over electrodes and a solution is found to keep a transparent state without applying power. It is believed that the proposed broadband shutter with fast response time could open a new chapter in switchable windows owing to its low power consumption and working in a wide temperature range.