低操作電壓高分子分散型液晶及其應用之研究;Studies of low-operating-voltage polymer-dispersed liquid crystals and their applications

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题名:	低操作電壓高分子分散型液晶及其應用之研究;Studies of low-operating-voltage polymer-dispersed liquid crystals and their applications
作者:	梁哲源;Liang, Zhe-Yuang
贡献者:	光電科學與工程學系
关键词:	液晶;高分子分散型;光閥;liquid crystals;PDLC;polymer-dispersed liquid crystals
日期:	2017-07-24
上传时间:	2017-10-27 17:17:53 (UTC+8)
出版者:	國立中央大學
摘要:	本論文主要研究主題分為三部分，第一部分主要研究液晶(E7)與聚合物單體(P107)以特定比例混合後，經由照射紫外光製成的PDLC (polymer dispersed liquid crystal)光閥擁有低操作電壓、未施加電壓之起始低穿透度等特性。另本實驗亦探討紫外光照射強度及液晶盒厚度對該液晶光閥之影響，最佳參數為1.0 mW/cm2之紫外光強度照射60分鐘，且該液晶盒間隙厚度為7 μm。另探討不同聚合物單體混合液晶(E7)製成不同之PDLC光閥之性能比較，並以錨定強度的原理分析其操作電壓高低，即利用比較其閥值電壓與液晶微滴大小的關係，可得到液晶微滴的邊界錨定強度，若為弱錨定強度之液晶盒，則更容易使施加電場後的液晶分子轉動。第二部分是利用橫向電場IPS (In Plane-Switching, IPS)基板，製作三電極與四電極之PDLC光閥。利用IPS基板可施加的平行於基板方向電場之特性製作偏振選擇性的PDLC光閥，在液晶盒前方置入一個可旋轉的線偏振片，在PDLC光閥上施加電場，若光線通過液晶分子材料時所感受到的液晶折射率為ne，此時會因液晶折射率ne與聚合物折射率np的不匹配而散射光線。反之，若旋轉線偏振片，且在PDLC光閥上施加入電場，若光線通過液晶分子材料時所感受到的液晶折射率為no，則因液晶折射率no與聚合物折射率np匹配而使入射光穿透。第三部分將染料(Methyl Red)添加入液晶與聚合物單體的混合溶液中經由照光製作PDLC光閥，可發現於摻雜染料的PDLC光閥中施加交流電壓，經一段時間後關閉電場，其可維持一段時間的穿透態；而當加入直流電壓一段時間後關閉電場，則會馬上轉換為散射態。推測可利用此特性製作雙穩態的PDLC光閥。;In this thesis, a kind of monomer, P107, for fabricating polymer dispersed liquid crystal (PDLC) light shutters with low-operating-voltage has been investigated. The research herein can be divided into three parts. The first is to investigate the surface anchoring of the interfaces between LCs and polymer matrixes, and the transmittance versus voltage (T-V) curves in the PDLC. The experimental results show that the surface anchoring provided by P107 is weak so that such a PDLC light shutter shows low threshold voltage. The second is to investigate polarization-selective PDLC light shutters using crossed interdigitated electrodes. The interdigitated electrodes on the upper and bottom substrates can generate an electric field parallel to x- and y-axis, respectively. The incident linearly polarized light with linear polarization direction along y (x)-axis cannot (can) pass through the PDLC light shutter because the incident light does (does not) encounter obviously refractive index difference of LCs and polymers in the PDLC light shutter as the electrical field, whose direction is parallel to x (y)-axis, is applied onto the upper (bottom) substrate. The third is to study the temporarily stable state in dye-doped PDLCs (DDPDLCs). After turning off the applied AC field, the DDPDLCs can temporarily remain in transparent state for a short time. We proposed that the internal field, generated by the applied AC field, could result in the temporarily stable state. It can be used to approach a bistable PDLC shutter. Moreover, regarding the effect of the application of DC voltage, the DDPDLCs can be quickly switched back to scattering state after the applied DC voltage is switched off. It indicates that no temporarily stable state can be observed in this case.
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