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|Title: ||中孔洞奈米粒子摻雜液晶之光電特性及其應用之研究;Studies of the electro-optical properties of mesoporous-doped liquid crystals and their applications|
|Keywords: ||散射;雙穩態;中孔洞材料;配向膜;scattering;bistable;mesoporous;alignment layer|
|Issue Date: ||2016-10-13 13:15:08 (UTC+8)|
|Abstract: ||隨著液晶技術的日趨成熟，液晶元件的研究更是蓬勃發展，而液晶散射光閥便是其中之一。目前最廣受應用的液晶散射光閥為聚合物分散液晶(polymer dispersed liquid crystal, PDLC)，可利用其混合物之單體聚合反應引致液晶與高分子相分離而產生散射，並藉由外加電壓改變此液晶元件的散射態以及穿透態。此外，一般的散射光閥需對元件持續施加電壓方能維持其穿透狀態，在提倡綠色能源的時代持續耗電的元件將陸續被改良，取而代之的便是雙穩態的散射光閥，在利用電壓切換狀態之後，即便關閉其施加電壓亦能維持著穿透狀態，且能利用外加另一電壓而使該穿透態切換回散射態。|
;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.
|Appears in Collections:||[光電科學研究所] 博碩士論文|
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