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研究生:徐嘉均
研究生(外文):Chia-Chun Hsu
論文名稱:利用液晶指向矢模型模擬和分析高分子穩定藍相液晶之光電特性
論文名稱(外文):Using the Director Model to Simulate and Analyze the Electro-Optics of Polymer-Stabilized Blue Phase Liquid Crystal
指導教授:吳俊傑吳俊傑引用關係陳殿榮
口試委員:黃俊誠徐芝珊
口試日期:2012-06-29
學位類別:碩士
校院名稱:國立臺北科技大學
系所名稱:光電工程系研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2012
畢業學年度:100
語文別:英文
論文頁數:52
中文關鍵詞:液晶指向矢模型藍相液晶克爾效應
外文關鍵詞:director modelblue phase liquid crystaKerr effect
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最近,無論在學術或產業界正興起一種很有前途的新技術--藍相液晶(BPLC)。液晶的藍相介於各向同性及膽固醇相之間,其存在於一個很窄的溫度範圍內(1~2 ℃)。由於藍相液晶所存在的溫度範圍過於狹窄,此應用上較為困難。然而,經由高分子化之後,藍相液晶穩定的溫度範圍可以被擴展至超過60 ℃,使得藍相液晶成為顯示器應用中強大的競爭者,特別是在場序式驅動的液晶顯示器。基本上,藍相液晶是一個擁有單位晶格結構的高手徵性液晶分子系統,其光電機制是由電場所誘發的雙折射,通常叫作克爾效應。在克爾效應中,誘發雙折射與電場強度的平方呈線性正比關係。然而,這種線性關係只有在低電場下符合,當電場增加時,所誘發的雙折射不可能無限期地增加,也就是說,它會逐漸地飽和。顯然,克爾效應是無法描述這種行為。此外,由克爾效應要得到藍相液晶盒的反應時間亦是相當困難的。

在本篇論文中,我們提出一個「液晶指向矢模型」來模擬和解釋藉由垂直電場和水平電場驅動的高分子穩定藍相液晶盒(PS-BPLC)之光電特性。對於一個高分子穩定藍相液晶盒而言,照光後的高分子聚合物會排列在液晶之晶格內,此現象用現今的液晶理論「指向矢」來描述藍相液晶系統是有意義地。因此,我們藉由推疊一定數量的向列型液晶(NLC)來模擬高分子藍相液晶盒,為了要模擬和解析實驗結果,我們調整液晶盒的厚度(dbp)和電壓的倍數(M)來貼合實驗結果,此模擬結果與實驗結果相當符合。另一方面,我們所提出之理論模型是將液晶分子的導軸視為連續性分布,並發現隨著電場的增加,藍相液晶之折射率的變化和液晶分子在電場方向平均的餘弦值呈線性關係,此結果顯示藍相液晶之折射率的變化與電位能有很大的關聯。比較克爾效應或延伸克爾效應,我們的計算結果更加精準,這樣的理論和結果將有助於未來在設計藍相液晶相關的應用上有極大的幫助。

Recently, a promising new technology involving blue phase liquid crystal (BPLC) is emerging. BPLC exists in a very narrow temperature range (1~2℃) between the chiral-nematic and isotropic phases. But their mesogenic temperature range was always too narrow for practical applications. However after polymerization, the stable temperature range has been extended to over 60 °C, which makes BPLC a strong candidate for display applications, especially for color sequential displays. Basically, BPLC is a highly chiral liquid crystal system with a crystal-like structure. The electro-optical mechanism of BPLC is the electric-field-induced birefringence known as the Kerr effect. In the Kerr effect the induced birefringence is linearly proportional to E2, where E is the electric field intensity. However, this linear relationship is valid only in the low field region. As E increases, the induced birefringence cannot increase indefinitely, i.e., it will gradually saturate. Apparently the model cannot describe this behavior. Furthermore, the model has difficulty to obtain the response time of a BPLC cell.

In this dissertation, we propose a director model to simulate and explain the observed electro-optical properties of polymer-stabilized blue phase liquid crystal (PS-BPLC) with vertical-field-switching and in-plane-switching cell. Due to liquid crystal molecules are constrained by the polymer in crystal lattices, it is meaningful to describe a BPLC system by the “director (n)” used in the current liquid crystal theory. Thus, we model the BPLC cell by the stacking of a number of nematic liquid crystal (NLC) layers. To simulate and analyze the experimental results, we adjusted the value of the BPLC thickness (dbp) and the voltage multiplier (M) to fit the experimental results, which are in fair agreement with the experimental results can be obtained. On the other hand, the director model treats LC molecules as directors in the continuous distribution. We found that the refractive index change of the BPLC is linearly related to the averaged direction cosine on the electric field direction in any magnitude of the field. At the same time, we accurately calculate the saturated refractive index change. This result showed that the refractive index change of the BPLC and the electric potential energy have considerable extent relationship. Compared to the Kerr effect or the extended Kerr effect, our results are more accurate. The concept and results presented here will pave the way to designing a PS-BPLC device for photonics and display applications.

摘 要..................................................i
ABSTRACT................................................iii
Acknowledgement.........................................v
Content.................................................vi
List of Figure..........................................viii
Chapter 1 Introduction..................................1
1.1 Blue Phase Liquid Crystals.....................2
1.1.1 History...................................2
1.1.2 Structure of Blue Phases..................2
1.1.3 Defects...................................4
1.1.4 Expanding the Stable Temperature Range of
Blue Phases...............................6
1.2 Organization of this dissertation..............8
Chapter 2 Polymer-Stabilized Blue Phase Liquid Crystal
(PS-BPLC).....................................10
2.1 The Principle of PS-BPLC.......................10
2.2 Kerr effect of PS-BPLC.........................11
2.3 Blue Phase Liquid Crystal Display (BP-LCD).....12
2.3.1 Display Principle of BP-LCD................12
2.3.2 First Blue Phase Liquid Crystal Display....13
2.3.3 Issue of Blue Phase Liquid Crystal Display.14
Chapter 3 Director Model for Blue Phase Liquid Crystal..15
3.1 Introduction...................................15
3.2 Theory.........................................16
3.2.1 Theoretical Key Elements...................16
3.2.2 Theoretical Calculations...................16
3.2.3 Response Time..............................23
3.3 Simulation Results and Discussion..............23
3.3.1 Simulation Results.........................23
3.3.2 Discussions................................25
3.4 Summary........................................26
Chapter 4 Simulation of Blue Phase Liquid Crystal Cell
Driven by In-Plane Electric Field.............27
4.1 Introduction...................................27
4.2 Simulation Principle...........................28
4.3 Simulation Results and Discussions.............32
4.4 Summary........................................34
Chapter 5 The Essentials of Kerr Effect for Blue Phase
Liquid Crystal................................36
5.1 Introduction...................................36
5.2 Simulation Principle...........................37
5.3 Simulation Results and Discussions.............39
5.4 Summary........................................43
Chapter 6 Conclusion and Future Scope...................44
6.1 Conclusion.....................................44
6.2 Future Scope...................................45

Reference ...............................................47
Appendix
A Techwiz LCD......................................50
B BPLC Sample......................................51
Publication List........................................52

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