臺灣博碩士論文加值系統

高分子分散型液晶(PDLC)晶胞為一由微米大小的液晶滴與聚合物基材組成的複合型晶胞，可經由外加電場來進行液晶分子的調控，進而產生電光調制的效應，此特性可應用在與光折變晶體組成全光調控的高解析度空間光學調制器。為進一步完善此器件的功能，在本論文中，我們研究氧化石墨烯奈米粒子摻雜對PDLC晶胞電光調制特性的影響。實驗時，我們選擇三種氧化石墨烯奈米粒子，分別是：多層(記作:ML-GO)、功能基化的單層(SL-GO)、以及還原氧化(r-GO)等型態進行研究。首先，我們提出濕式球磨技術來打破粒子團聚現象，並進一步縮小粒子的大小至兩百奈米左右，使其能更均勻的摻雜到PDLC晶胞中，然後，經由拉曼光譜量測驗證這個概念。完成樣品製成後，我們量測各型態的PDLC晶胞樣品的電壓-穿透率曲線，藉以研究樣品晶胞的電光調制性質。我們發現三種奈米粒子都能有效地降低PDLC晶胞的臨界電壓與驅動電壓，且對同一系列樣品，這兩個電壓也隨摻雜的濃度增加而減小。其中，摻雜r-GO奈米微粒的PDLC樣品晶胞，電光特性的改進最為明顯，其臨界電壓與未摻雜PDLC晶胞樣品相比，約降低了三倍。為了解各型態晶胞效能改進的機制，我們以穿透式電子顯微鏡量測PDLC樣品晶胞型態，發現液晶微滴的大小隨著摻雜濃度增加，這與PDLC晶胞的理論中樣品的驅動電壓與液晶微滴大小成反比相符，另外，摻雜r-GO奈米微粒的最佳改進效果可能其可增加聚合物基材的導電率有關。未來研究若能研究摻雜奈米粒子到PDLC中對其聚合物的導電性與液晶介電率的影響程度，當可更清楚了解晶胞改進的機制。
總結來說，我們發現氧化石墨烯與還原氧化石墨烯的奈米粒子對降低PDLC的驅動電壓的成果，將可給我們更多PDLC研究與應用的可能。

Polymer-dispersed liquid crystals (PDLCs) are composite cells that consist of submicron-size droplets of liquid crystal randomly dispersed in a polymer matrix. They can modulate through application of external electric field. This e/o modulation property can apply with photorefractive crystals in all optically controlled high-resolution spatial light modulator. In order to improve this hybrid structure’s features, in this thesis, we study the effect of e/o modulation that Graphene Oxide nanoparticles doped into PDLC. In our experiment, we choose three types of Graphene Oxide nanoparticles which are multilayer (named ML-GO) and single layer (named SL-GO, functionalized, thickness almost 1 atomic layer) and Reduced Graphene Oxide respectively to study. First, we used wet ball milling method to avoid aggregation and reduce the nanoparticles size close to two hundred nanometers to achieve uniformly dispersion when they doped into PDLC cells. We use Raman analysis to ensure this method. After finished samples, we measure these samples voltage-transmittance curve to study their e/o modulation. We found that both GO and r-GO lower the threshold voltage and driving voltage in comparison with non-doped PDLC and these two voltages lower in the increasing of concentration in same series samples. The r-GO shows stronger effect by reducing the threshold voltage 3 times in comparison with non-doped PDLC. To understand the characteristics improvement mechanism, we measuring the PDLC morphology using Scanning Electron Microscopy (SEM). We found the size of LC droplets is inversely proportional to the concentration and threshold voltage, which is the same relation to PDLC theory. Furthermore, doping r-GO nanoparticles shows the best improvement may come from that it enhances conductivity of the polymer matrix. Further study of effect of nanoparticles addition on polymer conductivity and dielectric permittivity change of LC will give complete understanding of the physical phenomena inside the PCLD compound.
As a conclusion, we found that both Graphene Oxide and Reduced Graphene Oxide nanoparticles reduce the driving voltage of PDLC and give perspectives for further study and practical applications.

摘要 i
Abstract ii
致謝 iiv
目錄 v
表目錄 vi
圖目錄 vii
符號說明 ix
第一章 緒論 1
1.1. 前言 1
1.2. 文獻回顧 2
1.3. 論文章節架構 8
第二章 高分子分散型液晶晶胞製備與量測原理 9
2.1. 高分子分散型液晶晶胞的工作原理 9
2.2. 濕式研磨分散技術 13
2.3. 摻雜氧化石墨烯奈米顆粒高分子分散型液晶晶胞樣品製作 18
2.3.1. 實驗藥品資料 19
2.3.2. 摻雜不同GO之PDLC晶胞樣品製作 22
2.4. 電光效應量測光學系統與實驗 24
第三章 實驗結果與討論 29
3.1. 摻雜GO之PDLC晶胞的拉曼光譜實驗 29
3.2. PDLC摻雜GO型態與光電特性影響 32
第四章 結論 43
參考文獻 45
附錄一:實驗與儀器操作步驟 48
Part 1 氧化石墨烯分散液製作 48
Part 2 白金濺鍍機 50
Part 3 穿透式電子顯微鏡 52
Part 4 拉曼光譜儀 55
附錄二:儀器規格 57
Part 1 樣品製備 57
Part 2 樣品量測 59
A. SEM量測 59
B. Raman量測 60
C. V-T 曲線 60

[1] Kelker, H. "Survey of the Early History of Liquid Crystals." Molecular Crystals and Liquid Crystals Incorporating Nonlinear Optics 165(1): 1-43, 1988.

[2] Hoogboom, J., et al. "LCD alignment layers. Controlling nematic domain properties." Journal of Materials Chemistry 16(14): 1305-1314, 2006.

[3] Heilmeier, G. H. and L. A. Zanoni. "GUEST‐HOST INTERACTIONS IN NEMATIC LIQUID CRYSTALS. A NEW ELECTRO‐OPTIC EFFECT." Applied Physics Letters 13(3): 91-92, 1968.

[4] Yeh, P. and Gu, C., Optics of liquid crystal display, Wiley Interscience, New York, 2010.

[5] Liu, R. C., et al. "Near-infrared sensitive photorefractive device using polymer dispersed liquid crystal and BSO:Ru hybrid structure." Optics Letters 39(11): 3320-3323, 2014.

[6] Gospodinova, V. M., et al.. “All-optically controlled light valve assembled by photorefractive crystal and PDLC hybrid structure. “SPIE Optics+ Optoelectronics, International Society for Optics and Photonics.

[7] Li, W., et al. "Studies on electro-optical properties of polymer matrix/LC/SiO2 nanoparticles composites." Journal of Applied Polymer Science 111(3): 1449-1453, 2009.

[8] Hinojosa, A. and S. C. Sharma. "Effects of gold nanoparticles on electro-optical properties of a polymer-dispersed liquid crystal." Applied Physics Letters 97(8): 081114, 2010.

[9] Hsu, C.-C., et al. "Low switching voltage ZnO quantum dots doped polymer-dispersed liquid crystal film." Optics Express 24(7): 7063-7068, 2016.

[10] Jamil, M., et al. "Nanoparticle-doped polymer-dispersed liquid crystal display." Current Science(Bangalore) 101(12): 1544-1552, 2011.

[11] Geim, A. K. and K. S. Novoselov. "The rise of graphene." Nat Mater 6(3): 183-191, 2007.

[12] Al-Zangana, S., et al. "Properties of a Thermotropic Nematic Liquid Crystal Doped with Graphene Oxide." Advanced Optical Materials 4(10): 1541-1548, 2016.

[13] Basu, R., et al. "Graphene and liquid crystal mediated interactions." Liquid Crystals 43(13-15): 2375-2390, 2016.

[14] Griggs, C. S. and Medina, V. F. "Graphene and graphene oxide membranes for water treatment.” AccessScience, McGraw-Hill Education, 2016.

[15] Zhu, Y., et al. "Graphene and Graphene Oxide: Synthesis, Properties, and Applications." Advanced Materials 22(35): 3906-3924, 2010.

[16] Ito, J., et al. "Semiconducting nature of the oxygen-adsorbed graphene sheet." Journal of Applied Physics 103(11): 113712, 2008.

[17] Coates, D. "Polymer-dispersed liquid crystals." Journal of Materials Chemistry 5(12): 2063-2072, 1995.

[18] Kim, Y., et al. "Flexible polymer dispersed liquid crystal film with graphene transparent electrodes.", Current Applied Physics 16(3): 409-414, 2016.

[19] Amundson, K. "Electro-optic properties of a polymer-dispersed liquid-crystal film: Temperature dependence and phase behavior." Physical Review E 53(3): 2412-2422, 1996.

[20] Wu, B.-G., et al. "Response times and voltages for PDLC light shutters." Liquid Crystals 5(5): 1453-1465, 1989.

[21] Gudarzi, M. M. "Colloidal Stability of Graphene Oxide: Aggregation in Two Dimensions." Langmuir 32(20): 5058-5068, 2016

[22] 徐敬添等撰，奈米微分散技術與材料應用，奈米技術專刊，工研院化學工業研究所，應用化學組，p140~141，2001.

[23] Spruce, G. and R. D. Pringle "Polymer dispersed liquid crystal (PDLC) films." Electronics & Communication Engineering Journal 4(2): 91-100, 1992.

[24] Marinova, V., et al. "Graphene oxide doped PDLC films for all optically controlled light valve structures." Proc. SPIE 9970, 2016.