臺灣博碩士論文加值系統

液晶顯示器具有非常廣泛的應用，如手機、電視、電腦螢幕、汽車導航系統等。由於輕薄可攜式，適合隨時隨地使用，然而他仍有需要改進的地方，如耗電、明暗對比、殘影等，這些都是急需改善的目標。藉由添加奈米粒子使得液晶的彈性係數降低及提高介電係數，進而縮短響應時間和降低臨界電壓，來達到更好的畫質和節能的效果。在本研究中，硝酸銀為前驅物，乙醇為溶劑與還原劑，紫外光為能量來源，並分別以聚乙烯?咯烷酮(Polyvinylpyrrolidone, PVP)和4''-正戊基-4-氰基聯苯(4-Cyano-4''-pentylbiphenyl, 5CB)做為保護劑，在批式與循環製程下，製備膠體銀奈米粒子；接著將膠體銀奈米粒子加入5CB液晶中，並利用含有透明加熱板之偏光顯微鏡(POM)觀察膠體銀奈米粒子對液晶相的影響。在實驗過程中，使用紫外光-可見光光譜儀(UV-Vis)、傅里葉轉換紅外光譜儀(FTIR)、X光繞射分析儀(XRD)、穿透式電子顯微鏡(TEM)、能量散佈分析儀(EDS)、離子選擇電極(ISE)，分別來鑑定膠體銀奈米粒子成長、保護劑官能基與銀粒子的鍵結、銀粒子晶相、銀粒子形貌、元素組成、銀粒子的轉化率。本實驗經由紫外光強度為85mW/cm2及照射時間為60分鐘，獲得以下重要成果：
(1) 透過光化學合成法製備膠體銀奈米粒子，由UV-Vis測得銀奈米粒子引起的表面電漿共振效應吸收波長位於440~450nm。XRD於(1 1 1)出現吸收峰，為銀奈米粒子的面心立方結構；並由FTIR證實銀奈米粒子與保護劑產生鍵結，PVP膠體銀奈米粒子C=O官能基由1662cm-1位移到1652cm-1，5CB膠體銀奈米粒子C≡N官能基2225cm-1旁多出2246cm-1的吸收峰。
(2) 在批式製程及室溫情況下，當保護劑/前驅物莫耳濃度比分別為1，30，及60時，發現保護劑濃度越高則有較小的銀粒子，其中，PVP膠體銀粒子粒徑由6.4±3.5nm變為4.2±1.3nm及5CB膠體銀粒子大小由4.5±2.4 nm變為3.7±0.8nm。
(3) 在循環製程及室溫情況下，當保護劑/前驅物莫耳濃度比分別為1，30，及60時，發現保護劑濃度越高則有較小的銀粒子，其中，PVP膠體銀粒子粒徑由5.5±1.8nm變為3.2±0.8nm及5CB膠體銀粒子大小由3.6±0.9 nm變為3.3±0.7nm，此相較於批式製程，雖然轉化率差異不大(約3%)，但循環製程所製備的銀粒子大小及均一性較佳，其原因為溶液流動使得照光時間較短，還原出的銀顆粒較小且隨即被保護劑所包覆而無法繼續成長。
(4) 當5CB液晶中添加膠體銀奈米粒子從0.01wt%到1wt%時，PVP和5CB膠體銀奈米粒子分別使清晰點溫度下降為33.5°C到31.9°C及33.7°C到33.3°C，此差異為PVP膠體銀奈米粒子於各向同性的液體溶解度較高及5CB膠體銀奈米粒子造成液晶的方向性降低所致。

Liquid crystal display (LCD) was widely applied for smartphone, television, computer screen, car navigation system and so on, because it’s thin and portable. However, LCD still needs improvement, such as power consumption, contrast, motion blur, etc. To achieve better image quality and energy saving, nanoparticles were added into the liquid crystal, reducing the elastic constants and increasing the dielectric constants to shorten the response time and lower the threshold voltage. In this research, firstly, we used polyvinylpyrrolidone (PVP) and 4-cyano-4''-pentylbiphenyl (5CB) as protecting agents and then the colloidal silver particles were synthesized by ultraviolet irradiation of an ethanol solution of silver nitrate (AgNO3) through batch and cycle process respectively; finally, we doped as-fabricated colloidal silver nanoparticles into the 5CB to observe the influence of colloidal silver nanoparticles on the liquid crystal phase by polarized optical microscopy (POM). We applied ultraviolet-visible absorption spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and ion selective electrode (ISE), to identify the growth of colloidal silver nanoparticles, protecting agent''s functional group bonding with silver particles, crystal structure of silver particles, silver particles morphology, elemental composition, and conversion of the silver particles from silver ions, respectively. By means of ultraviolet irradiation with 85mW/cm2 and exposure time of 60min, this study summarized the following significant remarks:
(1) The UV-Vis spectrum of the as-prepared silver nanoparticles shown a surface plasmon resonance at 440~450nm; and FTIR confirmed that the silver nanoparticles bonding with protecting agents, PVP colloidal silver nanoparticles C=O was shifted from 1662cm-1 to 1652cm-1, but 5CB colloidal silver nanoparticles got a new absorption peak at 2246cm-1 near group of C≡N.
(2) As the ratio of protecting agent to precursor with room temperature in batch process was varied from 1 to 60, mean diameter of PVP and 5CB colloidal silver nanoparticles decreased from 6.4±3.5nm to 4.2±1.3nm and from 4.5±2.4nm to 3.7±0.8nm.
(3) When the ratio of protecting agent to precursor with room temperature in cycle process was varied from 1 to 60, average diameter of PVP and 5CB colloidal silver nanoparticles decreased from 5.5±1.8nm to 3.2±0.8nm and from 3.6±0.9nm to 3.3±0.7nm. The size and distribution of synthesized silver particle from the cycle process were smaller and narrower than that from the batch process. This result was attributed to the reacting flow fluid, causing to reduce the exposure time, therefore, the synthesized silver particles were coated with protecting agent immediately and then prevented particles growth.
(4) As 5CB added colloidal silver nanoparticles from 0.01wt% to 1wt%, PVP and 5CB colloidal silver nanoparticles caused clearing point of 5CB from 33.5°C to 31.9°C and from 33.7°C to 33.3°C respectively. This difference between PVP and 5CB colloidal silver nanoparticles were because of the particles had a better solubility in isotropic solution and the particles caused the liquid crystal to reduce the directivity respectively.

摘要 i
Abstract iii
目錄 v
圖目錄 vii
表目錄 xii
第一章 緒論 1
1-1 前言 1
1-2 研究動機與方法 2
1-3 論文架構 4
第二章 文獻回顧 5
2-1 奈米材料 5
2-1-1 奈米材料簡介 5
2-1-2 奈米材料製備 7
2-1-3 奈米粒子的團聚與分散 12
2-2 液晶材料 14
2-2-1 液晶的簡介 14
2-2-2 液晶的物理 16
2-2-3 液晶的光電特性 19
第三章 研究方法 22
3-1 膠體銀奈米粒子製備 22
3-2 液晶清晰點(clearing point)量測 24
3-3 儀器分析 25
3-4 實驗材料與儀器設備 32
3-4-1 材料規格 32
3-4-2 實驗裝置示意圖 34
3-4-3 儀器設備 35
第四章 結果與討論 36
4-1 膠體銀奈米粒子的製備 36
4-1-1 紫外光-可見光光譜儀分析 36
4-1-2 XRD分析 38
4-1-3 EDS分析 39
4-1-4 FTIR分析 41
4-2 批式製程 43
4-2-1 保護劑添加量的影響 43
4-2-2 溫度的影響 49
4-2-3 光化學合成機制 56
4-3 批式與循環製程的比較 58
4-3-1對膠體銀奈米粒子的影響 58
4-3-2轉化率比較 71
4-4 添加膠體銀奈米粒子對液晶的影響 75
第五章 結論與未來方向 80
5-1 結論 80
5-2 未來延續工作 82
參考文獻 83

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