微鏡片薄膜改進背光模組出光效率

Abstract

微透鏡(microlens)有很多應用，如光通訊用的聚光元件，成像系統，藉以增加發光元件的出光效率。但是一般常用的光阻熱流方法(Photoresist thermal reflow process)卻可能遇到瓶頸。首先，一般常用的正光阻會遇到覆蓋率低的問題，因為UV光對較厚的光阻曝光與光罩將會有落差。但若是使用負光阻，則會因為負光阻材質被UV光照射後產生的化學鍵，不容易在經由加熱方式改變其圓柱型態。因此我們發展改良式熱流方式來製造微鏡片或是壓印微鏡片的母模。 隨著LCD顯示科技的蓬勃發展，背光模組扮演重要角色，因顯示器出光亮度效率優劣取決於背光模組的好壞，在背光模組中，提升亮度效率的關鍵零組件為稜鏡片(Prism sheets)，又稱為增亮膜(Brightness Enhancement Film，BEF)，它可以使通過擴散片(Diffuser)的光重新聚集藉以提升亮度，兩片BEF可以使亮度提升達120%。但是目前有關BEF的專利大都掌握在3M公司，所以本論文的目的是利用實驗室製作的微鏡片陣列薄膜(Microlens Array Thin Film)提升背光模組的出光效率。 製程結果顯示，比起傳統方式，利用改良式熱流方法，可以得到一個精確的微鏡片尺寸，可以在模擬上精準估計背光源的效率。 實驗結果則顯示，微鏡片薄膜加在背光模組上，可以有效的提升出光效率1.21倍，與模擬所預估相去不遠，而在背光模組視角也明顯提升。故微鏡片陣列適合應用於背光模組中。

Microlens has many applications. We can use microlens thin film to improve external efficiency of many optical systems, for example, the focusing device of optical communication, imaging system, the backlight unit of LCD panel. The most general fabrication method of microlens is Photoresist thermal reflow process. But this method maybe face some problems. First of all, positive photoresist may cause low fill factor because of UV light diffraction. Second, if we cannot control reflow time precisely, the adjacent photoresist would combine together. Finally, if we change photoresist from positive to negative, after exposing UV light, the chemical bond of negative photoresist is difficult to change the cylindrical form to spherical form. Thus we develop new method to fabricate microlens and metal mold. With the development of LCD, back light unit (BLU) plays an important role. The brightness and efficiency depend on the performance of BLU. The critical optical film to improve brightness and efficiency is prism sheets. It can re-converge the light penetrate through diffuser to increase efficiency. If we use two layers BEF, the brightness will increase 120%. But the patents of BEF almost belong to 3M. Therefore, this thesis we use microlens array thin film to improve the external efficiency of BLU. The process results show that the size of microlens fabricated by new process would define precisely better than traditional process. The advantage is that we can simulate accurately. The experiment results show that microlens thin film can increase efficiency 1.21 times efficiency of BEF, it is close to simulation results. And the view angle is wilder than BEF. Therefore, microlens would have the potential to apply in BLU.