可控制液晶預傾角的高分子配向應用在光學補償彎曲模式之光電特性研究

The Electro-optical Characteristics of Optically Compensated Bend Liquid Crystal Display Mode with Controllable Pretilt Angle by Photo-curable Monomer

吳聲明(Sheng-Ming Wu)

指導教授 ： 陳殿榮 ； 吳俊傑

國立臺北科技大學/電資學院/光電工程系研究所/碩士(2007年)

摘要

在本論文中，我們將照光可垂直配向的單體材料，以適當的比例混合並注入空OCB液晶盒中，在曝曬紫外光的同時施加Vuv電壓輔助配向，並使單體聚合成高分子，藉由控制實驗條件參數，可使液晶分子穩定在不同預傾角狀態，達到不同的初始排列，進而形成彎曲排列(bend)或是扭轉(twist)排列以縮短暖機時間。並且分成四個部份針對實驗中不同的參數來做探討與分析。此外，由於此材料的特性是照光時會往上下兩基板方向作聚合，在液晶層整體(bulk layer)中的高分子網極少，高分子叢集大部分只存在於兩邊界部份，因此本研究之樣品皆無散射光的產生，能夠維持良好的對比度水準。
　　實驗中，我們利用偏光顯微鏡的觀察，以及穿透率曲線(T-V curve)、相位延遲量、動態響應時間以及水平視角曲線等量測，來探討實驗樣品的結構與光電特性，並與經由模擬軟體DimMos所得到的結果驗證之。而實驗結果發現，在適當的範圍與同樣的條件下，curing時間愈久、Vuv愈大以及單體濃度愈高的樣品，其液晶層的相位延遲會愈小，即預傾角會愈高，將愈容易穩定在bend或是接近垂直配向的排列結構。此外，也探討了twist-π的光電特性以及實驗結果，雖然實驗結果不如預期，但也證實了此單體材料的確具有可將液晶分子重新穩定排列在不同預傾角狀態的潛力，進而形成splay、twist 以及bend等排列。

關鍵字

光學補償彎曲模式 ； 高分子配向 ； 紫外光曝曬 ； Bend ； Twist-π

並列摘要

In this study, the photo-curable monomer, which was used to form vertical alignment, was doped into liquid crystal (E7) at various proper concentrations and injected into empty parallel-aligned cell, so called “OCB Cell” or “π-cell”. In order to accomplish the initial bend or twist configuration to reduce the “Warm Up Time” of the π-cell, it was suffered from UV irradiation to stabilized at high pretilt angle. Four parts were presented to discuss. Besides, due to the characteristics of the polymer, the polymer bundles mostly existed near the substrate. Therefore, there is good optical contrast because of light scattering free.
We study the LC molecular alignment and electro-optical characteristics by observing the polarizing optical microscopy, voltage to transmission curve, phase retardation, response time and horizontal viewing angle. In addition, we verified the experimental results by simulation software “DIMOS”. We found that the higher pretilt angle could be accomplished by more curing time, larger curing voltage and higher polymer concentration. And we also discuss the electro-optical characteristics of the twist-π configuration. Although the experimental result were not we expected, it proved that LC molecules could be stabilized at various alignment configuration, including splay, twist and bend state.

並列關鍵字

OCB Mode ； photo-curable ； UV irradiation ； bend ； twist-π

參考文獻

[2] Dwight. W. Berreman, J. Appl. Phys. 46, p.3746 (1975)

[5] Tatsuo Uchida, Kazuyoshi Saitoh, Tetsuya Miyasita and Makoto Suzuki, SID Int. Symp. Dig. Tech. Papers, P.37.(1997)

[7] Seo Hern Lee and Kyoung-Ho Park, Appl. Phys. Lett. , 82, 4215 (2003).

[8] X. j. Yu and H. S. Kwok, Appl. Phys. Lett. 85, 3711 (2004).

[9] Sang Ho Kang, Chul Gyu Jhun, Seong Lyong Lee, Jae Chang Kim, and Tae-Hoon Yoon, IDW, LCT p1-12. (2004)