從物理系統之自發擾動行為探討其低激發態特性

Abstract

古典統計力學的擾動耗散定理闡明了「低維激發態所引起的自發擾動行為存在所有凝態物理系統中」，本論文之研究主旨即在探討特定凝態材料-液晶的分子動態擾動現象。 液晶分子與液晶盒基板間的錨定作用力大小與表面配向處理的方法有關。本論文由動態光散射理論出發，輔以液晶指向矢流體動力方程式與特定邊界條件，推得經液晶散射之光訊號其特徵相關時間與錨定能係數間之關係式，並以實際合成不同表面配向處理的向列型液晶盒為實驗樣本，由動態光散射實驗得到符合理論預測之結果，即液晶顯示器工業常使用的摩擦配向法所造成的錨定作用力，大於光配向法所造成的錨定作用力，其錨定能係數相差約兩個數量級；並且，於配向層上沉積液晶聚合物確能有效提升液晶分子排列品質。 表面穩定型鐵電相液晶元件具有高應答速度、寬視角範圍等優點，然鐵電相結構因不易完美排列而產生缺陷的缺點，限制了其在工業應用方面的發展。參雜氧化鋅奈米晶體的表面穩定型鐵電相液晶元件由於奈米晶體引致的分子束縛效應有效地提升了鐵電相液晶分子的排列品質；本論文觀察到因排列品質的提升使得部份鐵電相液晶分子脫離表面錨定作用力影響的現象。

The fluctuation-dissipation theorem of classical statistical mechanics reveals that there always exist spontaneous fluctuation behaviors induced by low-level excitations in all condensed matter physical systems. The main theme of this thesis study lay in the discussion about the dynamical molecular fluctuations of specific condensed matter material – liquid crystal (LC). The anchoring strength of a LC cell is relevant to the surface treatment methods. In this thesis, we began the derivations from the dynamic light scattering theory, together with the hydrodynamic equation of LC director and certain specific boundary conditions. We finally obtained the relationship between the correlation time of the scattering light scattered by LC and the anchoring energy coefficient of the cell. After measuring the scattering light coming from various nematic cells with different surface treatments, the results obtained from dynamic light scattering technique confirmed the theoretical predictions well, that is, the anchoring energy coefficient produced by mechanical rubbing method that is often used in liquid crystal display industry is larger than that produced by photoalignment method by around two order of magnitude; moreover, depositing liquid crystal polymer on the photoalignment layer of the cell does improve the LC alignment quality. Surface-stabilized ferroelectric liquid crystal devices have merits of fast response speed and wide viewing angle. However, the tendency toward defect formation owing to imperfect molecular alignment restrains their development in industrial applications. Doping ZnO nanocrystals into ferroelectric liquid crystal host can improve the quality of liquid crystal molecular alignment by virtue of the molecular binding effect. In this thesis, we observed a novel phenomenon that a portion of the liquid crystal molecules got rid of the influence of surface anchoring because of the improvement of doping-induced orientational order.