前瞻薄膜電晶體藍相液晶顯示器指向矢物理建模及克爾電光效應特性分析

Prospective Blue Phase Liquid Crystal Display (BP-LCD) Development Using Physical Director Model for Electro-Optical Properties of Kerr Effect

紀承諭(Cheng-Yu Chi)

指導教授 ： 楊英杰

共同指導教授 ： 吳俊傑

國立臺灣大學/電機資訊學院/電子工程學研究所/博士(2017年)

https://doi.org/10.6342/NTU201702545

摘要

無資料

關鍵字

半導體元件 ； 薄膜電晶體 ； 光電顯示器 ； 指向矢模型 ； 藍相液晶模擬 ； 克爾效應 ； 高分子穩定藍相液晶 ； 材料分析

並列摘要

Blue phase liquid crystal is the liquid crystal molecule with the lattice structure of double twist cylinder. When an electric field is applied, its electro-optical effect induces birefringence-the so-called Kerr effect. We start discussion of Kerr constant changes caused by liquid crystal cell thickness from experiment, which is also an important reference and assistance in the improvement of both the electro-optical properties of blue phase liquid crystal, and furthermore the development of the relevant components of blue phase liquid crystal displays in the next generation. In this study, we take the blue phase liquid crystal cells of different thicknesses to measure the dependency between its phase (φ) and voltage (V) under irradiation of oblique incident light by the driving of the applied vertical electric field. Besides, we use phase formulas to find out birefringence (δ_n) and sort out the formulas related to the Kerr effect. After that, it can be seen that at low electric field, birefringence (δ_n) is linearly related to applied electric field square (E2) so it can be confirmed that theoretical values and experimental data are consistent. Therefore, it is realized that different liquid crystal cell thicknesses also affect Kerr constant changes. Also, this study proposed the director model of blue phase liquid crystal to interpret and analyze the electro-optical properties of the polymer stabilized blue phase liquid crystal (PS-BPLC). Herein, it also simulated by stacking a specific number of nematic liquid crystal and decided the stacked layers of nematic liquid crystal (M_z) fitting to experimental results through regulating the multiple of voltage (M) in this research. This simulation results almost perfectly fit experimental results. The research went on to explore the electro-optical characteristics of the liquid crystal cell in the established models. In addition to the known relationship between induced birefringence and the electric field which can be described by the Kerr effect, it can also be explained by proposed director model. We further discover refractive index changes are linearly related to the angle between liquid crystal molecules, and the direction of the electric field after taking the cosine square. We got the shown electro-optical characteristics under the influence of the Kerr effect in the use of the blue phase simulation software. Through a series of controls of the result and the director model, it is found that the proposed director model is more in line with the actual values. This mathematical physics model can be applied to the development of blue phase displays, which is helpful to the next generation of displays of blue phase liquid crystal and thin film transistor (TFT-BPLC) in the early-stage display design development and pre-verification of new materials; also, it can substantially save the cost of investment in the development of the semiconductor optoelectronic display industry and improve the development efficiency.

並列關鍵字

semiconductor devices ； thin film transistor (TFT) ； electro-optical display ； director model ； blue phase liquid crystal simulation ； Kerr effect ； polymer-stabilized blue phase liquid crystal (PS-BPLC) ； material analysis

參考文獻

[1] Masahito Oh‐e and Katsumi Kondo, “Electro-optical characteristics and switching behavior of the in-plane switching mode,” Appl. Phys. Lett., 1995, 67, pp.3895–3897.

[2] Lee, S.H, Lee, S.L, Kim, H.Y, “Electro-optic characteristics and switching principle of a nematic liquid crystal cell controlled by fringe-field switching,” Appl. Phys. Lett.,1998, 73, pp. 2881–2883.

[5] S. Yoon, M. Kim, M-S Kim, B-G Kang, M-K Kim, A-K Srivastava, S-H Lee, Z. Ge, L. Rao, S. Gauza and S-T Wu, “Optimisation of electrode structure to improve the electro-optic characteristics of liquid crystal display based on the Kerr effect,” Liquid Crystals, 2010, Vol. 37, No. 2 , 201–208.

[8] F. Reinitzer, “Beiträge zur kenntnis des cholesterins,” Monatshefte für Chemie, vol. 9, 1888, pp. 421–441.

[9] J. Cohen, “The blue phase of cholesteric liquid crystals,” 2007. (http://guava.physics.uiuc.edu/~nigel/courses/569/Essays_2002/files/cohen.pdf)