臺灣博碩士論文加值系統

本論文研究封閉式柱形線狀液晶樣品於外加電場下的導向矢排列穩定性及
其光學特性。我們針對內含負性介電各向異性線狀液晶的錐柱腔及正圓柱
腔來討論，同時邊界上的液晶指向矢皆成垂直腔壁之狀態。理論上我們預
測在錐柱腔中受外加電場及液晶彈性常數的影響。可以有五類分子場轉換
序列存在。在正圓柱腔中受外加電場及外觀參數的影響，線狀液晶MBBA會
有三類分子場轉換序列存在。實驗上，我們製備了錐柱腔含負性介電各向
異性的線狀液晶樣品，並使液晶分子垂直於腔壁。在正交偏光顯微鏡下觀
察記錄外加電壓對光學圖像的影響，並與理論預測相互驗證。

We report the study on the director-field transition induced by
electric field in a closed cylindrical cavity of nematic liquid
crystal (NLC) with negative dielectric anisotropy. The closed
conical cavity and the closed regular cylindrical cavity are
used to demonstrate the stability of director fields and
optical properties. The directors of NLC are forced to be
strong anchoring on the boundaries of cavity. The electric
potential is applied along the symmetry axis of the cylindrical
cavity. The dependency of the stability and transition sequence
of sequence of director field on bulk elastic constants are
demonstrated in the case of closed conical cavity. The
dependency of the stability of director field and the
transition voltage on the aspect ratio are also investigated in
closed regular cylindrical cavity and closed conical cavity. In
experiment, we have prepared the closed conical cavities of
NLCs. Using the polarizing microscope, we observe the
transitions of optical patterns induced by electric field as
the prediction of theory.

Cover
Chapter I Introduction
I.I NLCs confined in spherical droplets
1.2 NLSx confined in cylindrical cavities
1.3 Aims of this research
Chapter 2 Theory
2.1 Continuum theory
2.1.1 Free energy andEuler-Lagrange equations
2.1.2 Boundary conditions
2,2 Numerical method
2,2,1 The finite difference method and the relaxation method.
2.2.2 The strategy of finding the most stable director field
Chapter 3 Simulations of Optical Patterns
3.1 Jones matrix formulation
3.2 Optical patterns of white light
Chapter 4 Theoretical Results and Discussion
4.1 Analytical studies on one-elastic-constant case
4.1.1 Closed regular cavity
4,1.2 Closed conical cavity
4.2 Numerical studies on three-elastic-constants case
4.2.1 Electric field induced transitions of the director fields
4.2.1.1
4.2.1.2
4.2.2 Dependency of the transition sequence on K11/K-33
4.2.3 Dependency of the transition sequence on K22/K33
4.2.4 Dependency of the transition on eO△E/K33
4.2.5 Dependency of the transition on the aspect ratio
4.3 Topological considerations
Chapter 5 Experimental Results and Discussion
5.1 Sample preparation
5.2 Observation and discussion
5.2.1 Observation method
5.2.2 Electric field induced variations of textures
5.2.3 Cylindrical symmetry of the director fields
5.2.4 Brightness and color of textures
5.2.5 Observation in cavities with different aspect ratios
5.2.6 Degenerate states of textures
Chapter 6 Conclusions
References
Appendix 1 Flow chart of numerical simulation of director field
Appendix 2 Program of numerical simulation of optical patterns
Appendix 3 Physical properties ofZL114627
Appendix 4 Physical properties of MBBA