摻二氧化鈦向列液晶受紫外光曝照之電學特性

Abstract

本論文旨在探討將二氧化鈦奈米粒子摻入向列型液晶所產生之電學特性。本實驗將兩者均勻混合製作成液晶盒樣品，利用介電頻譜術量測觀察離子電荷對於介電特性之影響。搭配可調整輸出功率之紫外光設備，對液晶盒進行不同強度紫外光照射，再藉由電壓保持率量測探討在不同光強照射下，液晶盒中的離子抑制效果。 實驗結果顯示，受紫外光照射影響下；液晶盒會有離子濃度增加、電壓保持率降低及電學性能下降等不良反應，利用二氧化鈦奈米粒子光化學反應及離子吸收能力的特性，透過適當濃度二氧化鈦奈米粒子的摻雜，有助於降低液晶中離子雜質濃度，提升液晶盒的介電特性，增強和延長液晶在陽光下的電學性能和壽命。

The effect of ultraviolet (UV) exposure on electrical and ionic characteristics of nematic liquid crystals (NLCs) doped with anatase nanoparticles (TiO2 NPs) was investigated by means of dielectric spectroscopy as well as the voltage holding ratio (VHR) measurement. In this study, experimental samples were prepared by mixing NLCs and TiO2 NPs at appropriate concentrations. For cell samples with UV exposure, the exposure time and the intensity of UV light were set as variables. The irradiation of UV light to a LC cell leads to the increase in ionic concentration and the reduction in VHR, presumably due to the dissociation of the LC material and photoinduced desorption and injection of impurity ions. Increasing either the intensity of light or exposure time results in the promotion of the ionic effect in the cell. Specifically, experimental results demonstrate that the influence of UV light on ion density and VHR of a NLC cell can be suppressed by doping a proper amount of TiO2 NPs because of the ion-trapping ability of doped TiO2 associated with the photochemical reaction of TiO2 with irradiated UV light. As a result, our proposed TiO2/NLC system is a potential approach to enhancing the electro-optical performance and extend the lifetime of a LC display under sunlight.