液晶因各向相異性使其大量應用於光學元件上，但倘若液晶排列混亂，則調控光場的優勢將消失，因此液晶須秩序性排列方可呈現出各向相異性，所以對液晶進行配向為製作元件一大要件。本研究在不需配向膜的製程下，再藉由摩擦配向法給定指向性的空液晶盒中，將接有八支偶氮染料(azo dye)的多面體低聚倍半矽氧烷(Polyhedral Oligomeric Silsesquioxane, POSS)奈米分子摻入向列型液晶中並灌入液晶盒，探討azo-POSS於向列型液晶中的特性，並藉由照射不同UV光(λ=365nm)及藍光(λ=450nm)強度比例達到控制偶氮染料順式(cis-)與反式(trans-)結構分子比例，使奈米分子於液晶中分散性改變，當奈米分子因分散性改變析出於基板，使得基板上分子密度提高，此時將使液晶傾角提高，反之，若基板上奈米分子密度低，此時液晶受奈米粒子影響較小，因此排列偏向原本水平配向排列，使得液晶傾角降低，因此可藉由照光控制奈米分子析出量，調控液晶傾角以調控光相位，且此元件的相位穩定性、切換次數與解析度具有相當高的表現。因此我們成功製作出具高可調性及灰階穩定性的光控相位調變器，同時演示經過照射不同UV光能量的偶氮奈米分子元件，利用元件中不同順反式分子比例，經由溫度控制分子分散性製作出溫控相位調變器。

Liquid crystal is applied for numerous devices due to its anisotropy. However, if liquid crystal has chaos order, it will be regarded as an isotropic material. Therefore, surface alignment is crucial for almost all liquid-crystal applications. In this study, we use polyhedral oligosilsesquioxane (POSS) linked with eight group of azo-benzene mesogens to control the pretilt angle of liquid crystal. Under ultraviolet irradiation (λ = 365 nm), the Azo-POSS undergoes multiple configurational transformation from the fully-trans state (8 trans azobenzenes) through an intermediate (trans-cis-mixed) state to the fully-cis state, while the back-isomerization process can be activated by blue irradiation (λ = 450 nm). Under ultraviolet-blue dichromatic illumination, the Azo-POSS can be stabilized at any of the aforementioned states depending on the light-mixing ratio, thereby determining the dispersion behavior of the Azo-POSS nanoparticles in a nematic liquid crystal. As the result, we can control the pretilt angle of liquid crystal ranging from 0° to 90°. Furthermore, the optical phase modulator made of azo-POSS has high stability. It can remain a phase for 50 minutes and switch up to 50 times. The resolution of the device is 30μm. Hence, a photo-tunable and high-stability phase modulator was demonstrated. In addition, the temperature dependence of pretilt angle has been examined at different illumination conditions.

第一章 緒論 1
第二章 液晶簡介 2
2-1 液晶的發現 2
2-2 液晶介紹 2
2-3 液晶分類 4
2-3.1 向列相 (Nematic phase) 5
2-3.2 層列相 (Smectic phase) 6
2-3.3 膽固醇相 (Cholesteric phase) 8
2-4 液晶的物理特性 11
2-4.1 秩序參數 (Order Parameter) 11
2-4.2 折射率異向性 (Birefringence) 12
2-4.3 介電係數異向性 (Dielectric anisotropy) 14
2-4.4 連續彈性理論 15
2-4.5 黏滯係數(Viscosity) 16
第三章 理論介紹 17
3-1 偶氮染料光致同素異構化 17
3-2 奈米粒子摻雜於向列型液晶引致配向改變 20
第四章 實驗樣品製備 24
4-1. 材料介紹 24
4-2 元件製作 26
第五章 實驗結果與討論 30
5-1 無配向膜水平配向照光配向變化 30
5-2 機制探討 32
5-2.1染料吸收推測液晶方向 32
5-2.2 照光偏振相依性 37
5-2.3 溫度對POSS-BAFKP分散性影響 44
5-3 相位調變器應用 54
5-3.1 光控相位調變器 54
5-3.2 溫控相位調變器 61
第六章 結論與未來展望 63
參考文獻 64

[1] M. O’Neill, and S. M. Kelly, “Photoinduced surface alignment for liquid crystal diplays,” J. Phys. D: Appl. Phys. 33, R67-R84 (2000)
[2] Y. Yu, and T. Ikeda, “Alignment modulation of azobenzene-containing liquid crystal systems by photochemical reactions,” J. Photoch. Photobio. C: Photochemistry Review 5, 247-265 (2004)
[3] M. M. Chrzanowski, J. Zielinski, M. Olifierczuk, L. Kedzierski, and E. Nowinowski-Kruszelnicki, “Photoalignment - an alternative aligning technique for liquid crystal displays,” Journal of Achievements in Materials and Manufacturing Engineering 45(1), 7-13 (2011)
[4] O. Yaroshchuk, and Y. Reznikov, “Photoalignment of liquid crystals: basics and current trends,” J. Mater. Chem. 22, 286-300 (2012)
[5] V. G. Chigrinov, “Photoaligning and photopattering—a new challenge in liquid crystal photonics,” Crystals 3, 149-162 (2013)
[6] C. J. Hsu, B. L. Chen, and C. Y. Huang, “Controlling liquid crystal pretilt angle with photocurable prepolymer and vertically aligned substrate,” Opt. Express 24(2), 1463-1471 (2016)
[7] H. Akiyama, T. Kawara, H. Takada, H. Takatsu, V. Chigrinov, E. Prudnikova, V. Kozenkov, and H. Kwok, “Synthesis and properties of azo dye aligning layers for liquid crystal cells,” Liq. Cryst. 29(10), 1321-1327 (2002).
[8] K. Yu, and W. Lee, “Voltage-assisted photoaligning effect of an azo dye doped in a liquid crystal with negative dielectric anisotropy,” Opt. Express 18(19), 19914-19919 (2010).
[9] S. Singh, and D. A. Dunmur, Liquid Crystal:Fundamentals, World Scientific,
Singapore, (1990)
[10] P. J. Collings and M. Hird, Introduction to Liquid Crystals Chemistry and Physics, Taylor & Francis Ltd, Hampshire (1997)
[11] I. C. Khoo and S. T. Wu, Optics and Nonlinear Optics of Liquid Crystals, World Scientific, Singapore (1993)
[12] K. Ichimura, Y. Hayashi, H. Akiyama, and N. Ishizuki, “Photoregulation of in-plane reorientation of liquid crystals by azobenzenes laterally attached to substrate surfaces,” Langmuir 9(11), 3298-3304 (1993).
[13] S. R. Nersisyan, N. V. Tabiryan, D. M. Steeves, B. R. Kimball, V. G. Chigrinov, and H. S. Kwok, “Study of azo dye surface command photoalignment material for photonics applications,” Appl. Opt. 49(10), 1720-1727 (2010).
[14] K. Ichimura, Y. Suzuki, T. Seki, A. Hosoki, and K. Aoki, “Reversible change in alignment mode of nematic liquid crystals regulated photochemically by command surfaces modified with an azobenzene monolayer,” Langmuir 4(5), 1214-1216 (1988).
[15] C. R. Lee, J. D. Lin, B. Y. Huang, T. S. Mo, and S. Y. Huang, “All-optically controllable random laser based on a dye-doped liquid crystal added with a photoisomerizable dye,” Opt. Express 18(25), 25896-25905 (2010).
[16] H. Qi, and T. Hegmann, “Multiple alignment modes for nematic liquid crystals doped with alkylthiol-capped gold nanoparticles,” J. Am. Chem. Soc. 1(8), 1731-1738 (2009).
[17] O. Buchnev, A. Dyadyusha, M. Kaczmarek, V. Reshetnyak, and Y. Reznikov, “Enhanced two-beam coupling in colloids of ferroelectric nanoparticles in liquid crystals,” J. Opt. Soc. Am. B 24(7), 1512-1516 (2007).
[18] S. J. Hwang, S. C. Jeng, C. Y. Yang, C. W. Kuo, and C. C. Liao, “Characteristics of nanoparticle-doped homeotropic liquid crystal devices,” J. Phys. D: Appl. Phys. 42(2), 025102-025108 (2009).
[19] S. C. Jeng, S. J. Hwang, T. A. Chen1, H. S. Liu, and M. Z. Chen, “Controlling the alignment of liquid crystals by nanoparticle-doped and UV-treated polyimide alignment films,” Proc. of SPIE 8279, 827912-827920 (2012).
[20] W. Z. Chen, Y. T. Tsai and T. H. Lin, “Photoalignment effect in a liquid-crystal film doped with nanoparticles and azo-dye.” Appl. Phys. Lett. 94, 201114-201118 (2009).
[21] M. Urbanski, “On the impact of nanoparticle doping on the electro-optic response of nematic hosts,” Liquid Crystals Today 24(4), 102-115 (2015).
[22] A. Miniewicz, J. Girones, P. Karpinski, B. Mossety-Leszczak, H. Galinab, and M. Dutkiewiczc, “Photochromic and nonlinear optical properties of azo-functionalized POSS nanoparticles dispersed in nematic liquid crystals,” J. Mater. Chem. C 2(3), 432-440 (2014).
[23] M. Draper, I. M. Saez, S. J. Cowling, P. Gai, B. Heinrich, B. Donnio, D. Guillon, and J. W. Goodby, “Self-assembly and shape morphology of liquid crystalline gold metamaterials,” Adv. Funct. Mat. 21(7), 1260–1278 (2011).
[24] W. M. Gibbons, P. J. Shannon, S. T. Sun, and B. J. Swetlin, “Surface-mediated alignment of nematic liquid crystals with polarized laser light,” Nature 351(6321), 49-50 (1991).
[25] Y. Kawanishi, T. Tamaki, T. Seki, M. Sakuragi, and K. Ichimura, “Nematic homogeneous alignment regulated by the polarization photochromism of surface azobenzenes,” Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. A 218(1), 153-158 (1992).