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標題: Development of Asymmetric Light Control Film Microlens Array Using Lithography Process
作者: Tung-Yu Chang
關鍵字: lithography;asymmetric microlens array;light control films;proximity exposure;lift-off method;thermal reflow;微影;非對稱性微透鏡陣列;光控膜;近接式曝光;舉離法;熱熔法
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The study utilizes the lithography process to develop an asymmetric microlens array which is applied to light control films and has two principal functions. The first function is to use it on an unprocessed plane screen surface to scatter light at different angles rather than a fixed one. This helps the anti-glare function of a display. The second function is to solve the insufficient brightness problem among most reflective liquid-crystal displays. The asymmetric microlens array of light control films is capable of collecting incident light from various angles to compensate for what is lacking, as mentioned above. The study develops three processes for producing the asymmetrical microlens array. The first one utilizes the proximity exposure to incline the base which changes the conventional vertical exposure into a canted one, enabling the lens to tilt. Based on the different distances between photomask and photoresistance, the asymmetric microlens array with a tilt angle of 46.9° can be determined without the traditional procedure of thermal reflow for microlens. The second process is the offset positioning process, which is produced by adopting two photomasks of different diameters with round patterns. Exposure, development, hard bake and copper plating are initially performed on the smaller photomask, so as to attain the first level photo spacer through the lift-off method. Subsequently, the larger photomask is used for transferring toward one direction and covering the first-layer metal column for the second exposure and development. Thus, the framework of the round photoresistance column can be obtained and the tilt thermal reflow can be executed. Through this process, a canted lens array with an inclined angle of 56.3° can be determined. The last process utilizes two photoresistances with different melting temperatures for producing incanted microlens. First of all, coating, exposure and development are performed for two photoresistances with different glass transition temperatures AZ 5214E and AZ 4620 before the tilt thermal reflow is processed. When the temperature of thermal reflow becomes higher than the glass transition temperature of AZ 4620, but lower than that of AZ 5214E; the upper AZ 4620 will be restricted by the round base of the lower AZ 5214E. An incanted lens array can be produced after hot melting. All three processes mentioned above are capable of producing an asymmetric microlens array.

本研究利用微影製程開發出一種應用於光控膜上的非對稱性微透鏡陣列,此非對稱性微透鏡陣列具有兩大項功能,第一項功能,應用在未經處理的顯示器平整表面,透過此非對稱性微透鏡陣列,使照在上面的光線散射到各個角度,而不會集中在某一個特定角度,提升顯示器抗眩功能,第二項功能為多數的反射式液晶顯示器有亮度不足的問題。使用非對稱性光控膜微透鏡陣列,可聚集多種角度之環境入射光,改善上述的缺失。本研究開發出三種不同製程來製作非對稱性微透鏡陣列,第一種製程利用近接式曝光時,將基座傾斜,實驗結果顯示可藉由光罩與光阻間距的不同,省略傳統微透鏡之熱熔步驟便可成功製作出傾斜角度為46.9°之非對稱性微透鏡陣列,第二種製程為偏移對位製程,使用兩種不同直徑尺寸之圓形圖案光罩製作,先將小尺寸之圓形光罩進行曝光、顯影,硬烤,濺鍍一層銅後,使用舉離(Lift-Off)法可獲得第一層光阻柱。再來使用大尺寸之圓形偏移一方向並覆蓋第一層金屬圓柱來進行第二次的曝光與顯影,便可獲得圓柱光阻柱之結構,然後進行傾斜熱熔,即可製作出斜角56.3°的斜透鏡陣列。第三種製程為變異熔點溫度光阻進行傾斜微透鏡陣列製造,先將兩個不同玻璃轉移溫度的光阻AZ 5214E 與AZ 4620進行塗佈、曝光、顯影,然後進行倒置式傾斜熱熔,當熱熔溫度提升至高於AZ 4620玻璃轉移溫度,低於AZ 5214E玻璃轉移溫度之間時,上層AZ 4620由於被下層的AZ 5214E圓形底座限制住,熱熔後將可製造出傾斜角31.8°的斜透鏡陣列。上述三種製程中皆成功製作出非對稱性微透鏡陣列。
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