Fabrication and Characterization of Multi-Scale Micro Lens Arrays with Anti-reflection and Diffusion Properties

由目前研究文獻中，二維次波長週期性錐形結構已經被提出可以有效地降低不同介質之交界面的反射率。雖然目前此種技術主要還是被傳統抗反射鍍膜支配著，但未來在我們必須微小化一些光學元件時，這種次波長抗反射結構的應用將會成為更合適的方法來取代傳統薄膜抗反射處理。然而已有研究指出蒼蠅複眼具有同時提升視角與增加光萃取量的特性。因此可預期此種整合微米及奈米之複層結構有潛力成為多功光學元件並且應用在LCD以及LED的光萃取等光電產業上。 在此論文中，我們將會利用雙光干涉微影術定義次波長結構。並且利用在離子蝕刻機(RIE)中蝕刻擋罩縮小的機制簡單地將錐形次波長結構製作在平面玻璃基材上。此外，我們利用光微影術及耦合式電漿離子機(ICP)於矽基材上製作微米結構。而後，我們將利用此兩種尺度的微/奈米模具於可撓性基材上製作複層結構。而我們所提出的方法主要是結合奈米壓印微影術及傳統熱擠出成型技術將含有次波長結構的平面轉換至微透鏡陣列上。因此這種方法是非常簡單且可重複製作人工複眼結構的技術。而且我們利用自行組裝的反射儀，來確定將次波長結構整合到微透鏡上後，抗反射效果仍然是有作用的。 最後我們在利用熱壓成型技術將可撓性基材上的複層結構轉印至直下式導光板的毫米半球曲面上。並且利用感光耦合元件相機與積分球來量測此含有複層結構導光板的穿透率與擴散率也驗證了這多功元件應用於背光模組的潛力。It has been reported that two dimensional taper-shaped sub-wavelength periodic structures could reduce the reflectivity at the interface of different materials effectively. Though this technique is not widely used to replace traditional thin film coating presently, it is expected to become a more suitable solution when applied to ever smaller optical elements. It has been pointed out that compound eyes of flies have the ability to enhance both viewing angle and to increase light extraction efficiency simultaneously. Therefore, we expect such a compound integration of micro and nano structures can have the potential to become a multi-function optical element and will be applied in LCD and LED light extraction industries. In this thesis, we would utilize two-beam interference lithography to define the sub-wavelength structures (SWS), and use the mechanism of reducing etching mask to easily fabricate taper-shaped SWS on a SiO2 substrate in a reactive ion etching (RIE) system. In addition, we would fabricate micro structures on a Si substrate by utilizing photolithography and inductive couple plasma (ICP) etching. After that, we would use these two-scale micro/nano molds to fabricate compound eye structures on a flexible substrate. Then we transferred SWS from the flat surfaces to the curved surfaces of micro lens arrays by combining nanoimprint and hot-extrusion technique. Thus it is a very simple and reproducible method to fabricate artificial compound eye structures. Furthermore, we would measure the reflectivity of a single micro lens to confirm the effect of anti-reflection by utilizing our homemade reflectometer. Finally, we would transfer the compound structures from the flexible substrate to the millimeter hemisphere of an LGP by utilizing hot-embossing process. Then we would measure the transmittance and diffusibility of an LGP with compound structures by utilizing a CCD camera and an integrating sphere, respectively. The measurement results show that the multi-function optical element has potential to be applied in back light units