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研究生:李學文
研究生(外文):Hsueh-Wen Li
論文名稱:穩定型橫向螺旋膽固醇液晶光柵之研究
論文名稱(外文):Study of stable uniformly lying helix cholesteric liquid crystal grating
指導教授:林宗賢林宗賢引用關係
指導教授(外文):Tsung-Hsien Lin
學位類別:碩士
校院名稱:國立中山大學
系所名稱:光電工程學系研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2012
畢業學年度:100
語文別:中文
論文頁數:75
中文關鍵詞:膽固醇液晶手紋結構光柵橫向螺旋
外文關鍵詞:gratingcholesteric liquid crystaluniform lying helix
相關次數:
  • 被引用被引用:12
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  • 下載下載:64
  • 收藏至我的研究室書目清單書目收藏:0
橫向螺旋結構擁有周期性折射率分佈的特性,使其可作為一光柵,且在橫向螺旋結構下,膽固醇液晶之周期可藉由電控改變,得到更多元的應用,如可調控週期之光柵與布拉格反射鏡。膽固醇液晶橫向螺旋結構一般是在d/p<2,且良好的配向下,由膽固醇液晶平面螺旋態(planar)加上特定電場驅動而得到,若將電壓停止,橫向螺旋結構會回到平面螺旋態。
本論文主要研究穩定型橫向螺旋結構(uniform lying helix, ULH);在一般的狀況下ULH不是一個穩態,需要持續的電場來維持其結構,我們發現d/p較大的情形下,可以在停止外加電壓後得到較穩定的橫向螺旋結構,但過大的d/p會使橫向螺旋結構無法排列方向不均勻。我們藉由在電場下升降溫、以及在電場下對樣品施加應力兩種方法,使較大的d/p樣品也可以排列成整齊的橫向螺旋結構。藉著這樣的改善技術,我們研究各種不同d/p對ULH穩定程度影響,發現在d/p大於10之後,ULH的穩定性大幅增加。最後我們比較不同配向錨定能對ULH穩定的影響,發現使用錨定能較弱的光配向,會使表面配向力更不容易將橫向螺旋拉回平面螺旋,能得到在24小時後依然全部穩固在橫向螺旋的樣品。
最後利用上述研究結果,我們利用12 um厚的液晶盒,製作了一個螺距可調控在1030 nm~1410 nm之間的ULH光柵,且在無外加電壓下,依然維持光柵結構的可調週期光柵。

關鍵字:膽固醇液晶、手紋結構、橫向螺旋、光柵。
Uniform lying helix(ULH) is a cholesteric LC structure with helical axix lying on the substrate. This structure has a periodic refractive index profile characteristics, so that it can be used as a phase grating. The ULH period can be tuned with different electric fields which provide with various applications.
However, ULH is not a steady state in general, once the electric field shutdown, ULH texture will transform to planar texture. Generally, the ULH exist only under a few conditions: well homogeneous alignment and cell the ratio of gap to pitch smaller than 2 , in case the ratio more than 2, the ULH won’t align well. We use two methods to make ULH align well at large cell gap pitch ratio; cooling down from isotropic temperature under electric field and putting mechanical stress on the sample, therefore we can get a well alignment and more stable ULH.
We discuss the influence of different boundary conditions to the stability of ULH, and we discover that when d/p large than 10, the stability of ULH improved significantly. Then we study the influence in different alignment anchoring, we find stronger anchoring energy makes ULH transform to planar easily. So we use photo alignment to get weaker anchoring energy, and the ULH using photo alignment stable more than 24 hours.
Finally we use a large d/p ULH as tunable phase grating, the pitch length can be tuned about 380nm with low power consumption, and it still have grating function when the field shutdown .
Keyword: cholesteric liquid crystal、uniform lying helix、grating
摘要 .................................................................................................................................. i
Abstract ............................................................................................................................. ii
目錄 ................................................................................................................................. 1
圖目錄 .............................................................................................................................. 3
表目錄 .............................................................................................................................. 5
第一章 簡介 .................................................................................................................. 6
1-1 液晶介紹 ........................................................................................................... 6
1-2 液晶的分類 ....................................................................................................... 7
1-3 液晶的物理特性 .............................................................................................. 11
1-3-1. 液晶的秩序參數 (order parameter) ................................................... 11
1-3-2. 液晶的光學異向性 ............................................................................. 11
1-3-3. 液晶的介電異向性 ............................................................................ 14
1-3-4. 連續彈性體理論 ................................................................................ 15
1-3-5. 溫度對向列型液晶的影響 ................................................................ 16
第二章 理論介紹 ........................................................................................................ 18
2-1 膽固醇液晶介紹 ............................................................................................. 18
2-1-1. 膽固醇液晶的平面螺旋結構及布拉格反射 .................................... 19
2-1-2. 膽固醇液晶的Focal conic 與Homeotropic ..................................... 22
2-1-3. 膽固醇液晶在電場下的排列結構 .................................................... 23
2-2.手紋結構(fingerprint texture)與橫向螺旋(Uniform lying helix) ................... 24
2-2-1. Developable-Modulation type (DM type) fingerprint ......................... 25
2-2-2. Growing-Modulation type (GM type) fingerprint ............................... 26
2-2-3. 橫向螺旋結構(Uniform lying helix) .................................................. 29
2-2-4. 膽固醇液晶相位光柵 ........................................................................ 30
2-3. 光配向(photo alignment )理論 ...................................................................... 31
2-3-1. 光引致染料分子轉向 ........................................................................ 31
2-3-2. 激發偶氮染料同素異構化 ................................................................ 32
2-3-3. 吸附效應 ............................................................................................ 32
第三章 實驗過程與方法 ............................................................................................ 33
3-1. 材料介紹 ...................................................................................................... 33
3-1-1 膽固醇液晶 ........................................................................................ 33
3-1-2 .偶氮染料 Methyl Red .................................................................... 35
2
3-1-3 .配向膜PVA(Polyvinyl alcohol) ....................................................... 36
3-2. 儀器介紹 ...................................................................................................... 37
3-3. 樣品製備 ...................................................................................................... 40
3-3-1. 膽固醇液晶的配製 .......................................................................... 40
3-3-2. 光配向膽固醇液晶藥品的配製 ...................................................... 40
3-3-3.玻璃基板準備與配向 ........................................................................ 41
3-3-4.樣品盒(CELL)製作 ............................................................................ 42
3-3-5. 光配向樣品的製作 .......................................................................... 44
3-4. 實驗觀察與量測 .......................................................................................... 45
3-4-1.樣品型態觀察 .................................................................................... 45
3-4-2.膽固醇ULH 穩定度測量 .................................................................. 45
3-4-3.膽固醇手紋結構光柵繞射 ................................................................ 48
第四章 實驗結果與討論 ............................................................................................ 49
4-1. 不同cell gap 下的膽固醇液晶橫向螺旋排列情形 ................................ 49
4-1-1.d/p < 2 之ULH ................................................................................ 49
4-1-2. d/p >5 之ULH ................................................................................ 51
4-2. 膽固醇液晶橫向螺旋的穩定存在現象 ...................................................... 56
4-2-1.不同cell gap 下的穩定現象 .......................................................... 56
4-2-2.不同螺距下的穩定現象 .................................................................... 59
4-2-2.相同d/p 下的穩定現象 .................................................................... 60
4-2-3.光配向ULH 樣品的穩定現象 .......................................................... 61
4-3. 電控膽固醇液晶光柵 .................................................................................. 63
第五章 結論與未來展望 ............................................................................................ 67
參考文獻 ........................................................................................................................ 68
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