反轉式氣輔UV壓印製程應用於大面積微結構之複製

Abstract

本研究致力於大面積壓印技術之開發，將結合紫外光固化成型技術、反轉式壓印成型技術及氣體輔助壓印製程，進行大面積之微結構複製，並搭配改良式的壓印機構來改善紫外光固化壓印成型最常見的氣泡問題，提供ㄧ個室溫、低壓、快速的大面積微結構複製技術。紫外光固化成型技術的運用，使整個壓印製程能夠在室溫低壓下進行，減少了升降溫所造成之變形及殘留應力等問題；運用反轉式壓印成型技術，壓印模具上之微結構模穴將被UV樹脂先充填完全，再進行壓印複製，可有效提高微結構之轉寫性；氣體輔助壓印技術其氣體施壓等向、等壓之特性使壓印壓力在整個大面積壓印區域能夠均勻分布，同時也能提高在各位置之微結構的複製成型均勻性。 實驗結果顯示，利用本研究所開發之大面積反轉式氣體輔助紫外光固化壓印製程能夠成功於大面積(230 mm × 203 mm)之壓克力基板上複製出微結構，而複製出之微結構具相當良好的複製均勻性與轉寫性，所製作出的大尺寸壓印成品沒有明顯的殘留應力與翹曲現象發生，成功結合紫外光固化壓印成型與氣體輔助壓印成型的機制與製程特性。另外，針對大面積壓印氣泡缺陷問題，本研究利用反轉式壓印技術結合彈簧式基板載具以改善壓印製程中抽真空的效率，實驗結果也証明能夠成功消除大面積壓印的氣泡缺陷問題，提供ㄧ個操作簡單且低成本的氣泡缺陷改善技術。而反轉式壓印技術的導入，並改良其壓印機制，更可有效提高整個大面壓印具區域的微結構高度轉寫率達99%以上，不受壓印製程參數所影響。本研究結合紫外光固化壓印成型、氣體輔助壓印成型以及改良式反轉式壓印成型技術，成功開發出一大面積微結構光學元件製作技術，預期可運用於大面積薄型導光板、擴散板、微透鏡陣列等光學元件之製作。

This study is devoted to developing a process for effective fabrication of large-area microstructures at room temperature and with low imprinting pressure. This process integrates the ultraviolet-curing (UV-curing) imprinting process, the gas-assisted imprinting process, and the reversal imprinting process to fabricate the microstructures onto the large area substrate. The UV-curing imprinting enables the process to perform without heating and cooling and under low pressure, while the gas-assisted embossing provides the uniform pressing pressure over the whole large area. By using gas-assisted and UV-curing mechanisms, the high temperature and high pressure can be avoided. With the reversal imprinting mechanism, the UV resin is coated onto the stmaper with microstructures cavity rather than the substrate, and is completely filled into the cavity then imprinting. In addition, in this study the reversal imprinting is incorporated with a gap-retained substrate holder to overcome the problem of air bubble defects. The experimental results show that the microstructures can be successfully fabricated onto the whole large area (230 mm × 203 mm) substrate with high replication uniformity and negligible residual stress by using the proposed process. The imprinting results also show the negligible air bubble defects, demonstrating the effectiveness of air bubble removing using reversal imprinting technique and gap-retained substrate holder. In addition, the modified reversal imprinting mechanism can effectively enhance the height transcription of microstructures without the control of imprinting processing parameters. In summary, this study has successfully developed a large area gas-assisted UV-curing reversal imprinting process for the large area fabrication of microstructures, which shows the potential of being applied to the large-area optical elements such as ultra-thin light guide plates, diffusers, large array of microlens, etc.