| dc.description.abstract | With the continuous growth of liquid crystal (LC) technology, the developments of LC devices have been being paid much attention by scientists. Among them, scattering mode LC light shutter is one of the popular techniques, such as polymer dispersed LCs (PDLCs). One of the scattering mechanisms is based on the formation of LC droplets by means of the polymerization induced phase separation of pre-polymer and LCs. Moreover, the scattering state and transparent state can be switched between each other by applying an external voltage. It should be noted that the continuously applied voltage is required to keep the transparent state. Restated, the transparent state will be switched back to scattering state when the applied voltage is turned off. Regarding the energy saving, the bistable scattering mode LC light shutters are the great candidates to save power, and to replace the devices with the disadvantage of high power consumption. Briefly, the bistable LC devices, which do not require real-time information update and do consume power when the displayed image content needs to be changed. One can apply an external voltage to switch the scattering mode LC light shutter to transparent state, and can also apply another external voltage to switch the transparent LC light shutter back to scattering state.
In this study, mesoporous silica nanoparticles (MSNs)-doped nematic LCs are adopted to demonstrate light scattering. Such an approach provides the advantages of low-cost, environmental protection, and simple fabrication processes. Moreover, the dual frequency LCs doped with MSNs present a bistable scattering mode LC light shutter. It is also demonstrated that the scattering and transparent states can be switched with each other by changing the frequency of the applied voltage. After the applied voltage is turned off, the transmission can be kept stable. The following four topics will be discussed in this thesis, including (1) the effect of various LC materials doped with MSNs onto the transmission and stability performances; (2) the effect of various surface alignment layers onto the scattering mode LC device; (3) the effect of concentration of MSNs onto the scattering mode LC device; and (4) the effect of MSNs onto the existing temperature of blue phase LCs.
Considering the mechanism of light scattering based on MSNs-doped LCs, it can be understood that the doped mesoporous will affect the orientation of LCs so that the LC domains can be generated in the LC cell. Hence, the incident light can be scattered by the LC domains due to the mismatch and the discontinuousness of refractive indices of LC and MSNs. Importantly, we infer that the orientation of the rod-like MSNs will be rotated by the torque produced by the application of external voltage onto the LCs due to the molecular interaction force between the doped MSNs and LCs. To demonstrate the bistable scattering mode LC light shutter, dual-frequency LCs doped with MSNs are employed to obtain the stable scattering and transparent states. Briefly, such a LC device can be switched to transparent (scattering) state by the application of external voltage having relative low (high) frequency since the dual-frequency LCs present positive (negative) dielectric anisotropic LCs with the application of external voltage having relative low (high) frequency. Moreover, we infer that the LCs will distribute around the MSNs so that the MSNs do not be aggregated with each other. Once the orientation of the rod-like MSNs, caused by the LCs, is parallel to the direction of the applied voltage, the stable transparent state can be obtained due to the scales of LCs and MSNs. As the result, the bistable scattering mode LC light shutter reported in this thesis possesses many advantages, such as low power consumption (environmental protection), simply fabrication processes, and so on. We believe that such a bistable LC light shutter has huge potential for application of electronics in the near future. | en_US |