玻璃面板之抗反射沸石膜; Zeolitic Anti-Reflective Coating on Glass Substrate

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题名:	玻璃面板之抗反射沸石膜;Zeolitic Anti-Reflective Coating on Glass Substrate
作者:	黎孝怡;Shiao-yi Li
贡献者:	化學工程與材料工程研究所
关键词:	透明;抗反射;沸石;沸石膜;Transparent;Anti-Reflective;Zeolitic film;Zeolite
日期:	2007-06-27
上传时间:	2009-09-21 12:28:10 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	於玻璃基板上塗佈一層抗反射(AR)膜可以提高光的穿透度，其應用範圍如濾光片、光電元件、窗戶、眼鏡或螢幕等。抗反射膜可以使用化學蝕刻、物理氣相沈積(PVD)、濺鍍(sputtering)與溶-凝膠(sol-gel)等多種方法來製作。對於折射率為1.52的玻璃基板而言，理想的抗反射層折射率為1.23。要做出此低折射率的薄膜，最簡單的方法就是使用孔隙性材料。以二氧化矽為例，其空隙率至少要超過60%才能達到抗反射的需求，只是擁有這樣高孔隙率的同時常會犧牲掉膜層的機械性質。本論文的研究目的是：使用微孔結晶性材料--沸石，製作出抗反射膜。沸石為多孔性材料，具有低折射率的性質，而因為是結晶，故有良好機械性質。為了要達到理想的透明性，必須使用小於60nm的沸石結晶來製作鍍膜，以避開可見光之散射。本實驗使用浸鍍技術在玻璃基材的雙面塗佈抗反射膜，而塗佈液是由沸石溶膠、界面活性劑與溶劑共同組成。本研究所探討的變因群有三：鍍膜液配方、鍍膜參數與成膜後的熱處理條件。鍍膜液配方影響薄膜的折射率，因此會(1)添加不同種類的界面活性劑、(2)改變界面活性劑對沸石的比例、(3)使用不同時期的沸石前趨物、(4)混合沸石前趨物與奈米結晶等改變來做探討。鍍膜操作參數主要是影響薄膜的厚度，故研究目的在於(1)找出最合適的鍍膜濃度、(2)調整鍍膜時的拉升速度。而熱處理條件會同時影響薄膜的折射率與厚度，因此要找出一個最佳的煆燒溫度與加熱時程。對於最後成品，我們除了光學性質之測試外，還測試了薄膜在實際應用上需要考量的機械強度。我們用來製作鍍膜的沸石溶膠有兩種。一種是濃縮的沸石前驅物(CP)，一種是已經結晶的奈米沸石分散液(NC)。因為沸石前趨物溶膠粒子表面具有比較多的-OH基，粒子間的黏著度較佳，因此膜層結構較緊密，而具有比較強的機械性質。只是膜層的折射率始終偏高，需要外加界面活性劑當作產生孔隙之模板，才能降低折射率。可是孔隙路率高時，機械強度就無法保持。結晶的奈米沸石粒子內部有微孔(30% porosity)，可以降低材料折射率。結晶粒子本身的機械強度也較高。故使用沸石奈米結晶鍍膜可以有效降低薄膜折射率。只是奈米沸石粒子表面-OH基較少，粒子間的黏著性不佳。因此若使用純奈米沸石溶膠來鍍膜，對基材的附著力很差。要達到降低折射率又同時保持機械強度與對基材之附著性，解決方法是在奈米沸石鍍膜液中添加黏著力較好的前趨物溶膠作為黏著劑，幫助奈米沸石粒子附著在基材上，也可作為沸石粒子間的連接介質，因此發展出CP/NC混合鍍膜液。目前我們已經可以用CP/NC混合鍍膜液製作出反射率小於1%的抗反射膜，且膜層的機械性質也能符合商業上的需求。而膜層的表面性質屬於超親水性。 Antireflection (AR) coating is needed on glass substrate to improve light transmission, which benefits applications such as optical filters, photovoltaics, windows, eye-wear, and display screens. AR coatings have been produced by chemical etching, physical vapor deposition, sputtering and by sol-gel method. For a glass substrate (ns=1.52), an ideal homogeneous AR layer would require a refractive index of 1.23. The easiest way to achieve such a low index is a porous coating. Taking Silica as the matrix (ns=1.5), this would mean a porosity higher than 60%, which usually leads to a degraded mechanical strength. The objective of this research is to fabricate AR coatings with microporous crystalline material, zeolite, which is known to have a refractive index ~1.3. Since it is a crystalline material, the mechanical strength would be strong. To reach the desired refractive index of 1.23, inter-particle void below scattering limit can be introduced by using <60 nm nanocrystals. In this research, AR layer was prepared on both sides of glass substrates by dip- coating with sols made form a combination of fully dispersed zeolite nanocrystals, concentrated zeolite precursors, surfactant template for inter-particle void and appropriate solvents. The major variables investigated were the recipe (type of surfactants, the surfactant to zeolite ratio, Aging time of zeolite precursor and the zeolite to precursor ratio), the dip coating parameters (sol concentration, pulling rate), and the heat treatment conditions after coating. The reflectivity of the obtained coatings was measured to identify the best recipe and procedures, along with critical issues such as adhesion strength, scratch resistance, durability in harsh environment and anti-soil ability. The AR film formed using precursor sol (CP) along is comparatively dense and mechanically strong due to the excessive hydroxyl sites on precursor particles, but the associated reflective index is high. To reduce its refractive index, one has to add surfactant as pore forming template, but this quickly diminishes the original mechanical strength. Zeolite nanocrystals, on the other hand, from a film with very low refractive index, thanks to its > 60% intercrystal and intracrystal porosity. However, fully crystalized particles have practically no surface hydroxyl group to bond with the substrate, and the adhesion of the film is very weak. The obvious next step is to combine the reactive precursor as glue and the nanocrystals as porous brieck to form a strong and porous AR layer. Under the best combination tested so far, we were able to prepare coating that has less than 1% average reflection in the visible range. The adhesion strength, scratch resistance of the coating were also comparable to commercial requirements. The coating prepared currently is super-hydrophilic in nature, but can be easily made hydrophobic by reacting with flourosilane.
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