| 摘要: | 非接觸式液晶配向技術近年來越發盛行，利用此技術可避免機械摩擦 或高溫烘烤等所產生的損耗。於西元 2005 年，夏普公司發現將奈米離子 Polyhedral Oligomeric Slisesquioxanes (POSS)摻雜於液晶中可得到液晶分子 垂直配向排列，自此開始，許多研究團隊便著手研究此類型液晶配向材料， 欲將成本降低並提高其均勻度。
本論文中所使用的離子性材料(C-R8NOH)與 POSS 同樣擁有以低濃度 混入液晶中，並注入表面僅有 ITO 導電膜的液晶空盒中即可得液晶垂直配 向排列的特性。研究中根據液晶材料的物性，可利用不同濃度及注入溫度得 到不同液晶分子排列的液晶盒，論文中使用不同種類的液晶材料，以該實驗 結果推測 C-R8NOH 之擴散型態，且因摻雜濃度較低，故不將 C-R8NOH 對 整體材料物性的影響加入討論。經多次實驗得知，在混合物溫度控制於超過 該液晶相變溫度時注入液晶空盒，注入過程中混合物之擴散係數相對較高， 故 C-R8NOH 易雜亂堆疊於基板上使液晶盒產生散射態;若將混合物溫度控 制於未達該液晶相變溫度時，則因擴散係數相對較低，C-R8NOH 可均勻地 吸附於基板上，故較容易得到液晶均勻的垂直配向排列。此外，於基板上塗 佈不同表面配向材料(如 PI, PVA 等)製成液晶空盒，將摻雜 C-R8NOH 的液 晶混合物注入該液晶空盒，將由於 C-R8NOH 於不同配向材料上的表現不 同，故所得結果不同。值得一提的是若將上述配向膜進行摩擦配向，當利用
I
溫度控制混合物處於低擴散係數時注入該液晶空盒，則 C-R8NOH 會平行於 摩擦配向方向吸附在配向膜上，另因其 3D 結構的影響而提供液晶分子排列 偏離原水平配向膜 10o。有關 C-R8NOH 離子性材料的電性，經實驗發現在 施加適當直流電壓後可將 C-R8NOH 分離為正離子及負離子，並分別吸附在 負電極與正電極上，且因該離子之長鏈結構，故使液晶分子隨之排列成垂直 配向。;The mechanical rubbing process is a common approach to obtain homogeneous alignment for liquid crystals (LCs) because of its simplicity, thermal stability and low-cost. However, the mechanical damages could be generated through such a contact process to degrade the display performances and production yields. Hence, in the past decades, several non-contact alignment techniques have been studied and developed widely. In 2005, Sharp has successfully demonstrated a non- contact solution to align LCs vertically in a nanoparticle doped LCs (NPdLCs). The NPs can spontaneously adhere onto the substrates to generate vertical alignment anchoring due to their special structures. The manufactures can omit the LC alignment processes to enhance the production rate.
In this thesis, the feasibility to approach a variety of LC alignments in ionic nanoparticle doped LCs (INPdLCs) has been successfully demonstrated. The LC alignments generated by INPs are strongly dependent on the concentration of the INPs and the temperature of INPdLCs. As the sample of INPdLCs is heated to the temperature higher than its clearing temperature, the diffusion rate of INPs toward the indium-tin-oxide (ITO)-coated substrates is relatively high because of the low viscosity of the LC mixture. Accordingly, considerable INPs do randomly adhere onto the ITO-coated substrates to produce random alignment anchoring. The LC multi-domains generate due to the massive accumulation of disordered INPs adhered onto the ITO-coated substrates. Hence, the incident lights are scattered because they encounter different refractive indices of each LC domain through whole LC bulk. On the other hand, as the temperature of the INPdLCs sample is lower than its clearing temperature, the diffusion rate of INPs toward the substrates is relatively low. The INPs can homogeneously adhere onto the ITO-
III
coated substrates and produce uniformly vertical alignment anchoring.
Furthermore, different LC alignments can be obtained as the INPs adhere onto different coatings, such as polyimide, PVA, etc., onto the ITO-coated substrates. The INPs generate the homogeneous alignment force as they adhere onto the substrates coated with unidirectionally rubbed polyimide. Interestingly, the angle between the homogeneous alignment anchoring and the rubbing direction of polyimide/PVA was experimentally measured to be about 10o. A model will be given to elucidate the experimental results in this thesis. Moreover, the electrochemistry of the INPdLCs was also investigated. Each INP is composed of one positive ion and one negative ion. They can be separated as a suitable DC voltage is applied. The positive (negative) ions diffuse across the bulk and adhere onto the negative (positive) electrode to produce vertical alignment anchoring, generated by the long side-chain of the positive and negative ions. In other words, the initially homogeneous LC alignment can be electrically switched to vertical one. The proposed results have also been confirmed according to the direct evidences obtained by mass spectrometry. |
