墨水溶劑的調配對噴印圖案品質之影響

Abstract

運用溶液製程與印刷技術於可撓曲之基材上塗佈精微圖樣後，在常溫常壓下，因溶劑的揮發導致圖樣體積的減少進而使得邊界的內縮造成原來噴塗的圖樣損壞。為了維持噴塗圖樣之品質不受到溶劑去除過程的邊界移動效應影響，本研究發展了一套墨水組成方法改善此問題。墨水組成採用兩種溶劑成分，利用乙二醇（EG）和聚乙二醇（PEG）幾近不揮發與後退角接近零度的特性，加入水溶液中混溶以維持圖樣的接觸線固定不動。為了觀察及了解液膜邊界移動行為，利用噴墨製程製造圓形液膜，並用接觸角儀將蒸發液膜的外型紀錄下來並分析之。實驗結果顯示，當乙二醇/聚乙二醇濃度較低時，液膜三相接觸線會於蒸發過程中向內縮；當提高乙二醇/聚乙二醇的濃度(~10 wt%)，液膜邊界維持固定，使原來的圖樣不改變。在本論文中提出一套液膜邊界的後退機制來解釋不同組成之液膜接觸線行為，並能有效地預測墨水之臨界組成，作為蒸發液膜邊界是否固定不動之依據。當水蒸發後，透過加熱去除剩餘不易揮發之乙二醇/聚乙二醇，溶質便可平整地沉積於原來噴塗圖樣之位置。本研究提出的墨水調配方法具.有簡單與方便之特性，可應用於多種塗佈製程，例如噴墨印刷(inkjet printing)、凹版印刷(gravure）與平版印刷（Offset printing）等。

For printed micro-patterns on plastic substrates, the decreasing volume due to solvent evaporation frequently leads to contact line receding and changes the original printed pattern. To prevent printing quality deterioration caused by contact line motions, an ink formulation method was developed in this study. A nearly non-volatile solvent (ethylene glycol, EG；polyethylene glycol, PEG) with low receding angle on polyethylene terephthalate (PET) sheets was added in water to hold the contact line. To obtain fundamental information about the contact line motion when water evaporated, the geometrical evolution of circular liquid films under evaporation was recorded and analyzed. The results showed at low EG/PEG concentrations, the contact line receded as water evaporated, but remain pinned at high EG/PEG concentration (~10 wt%). A model was proposed to explain the dewetting phenomena and can successfully predict the critical PEG concentration, beyond which the contact lines will be unconditionally pinned. After water evaporation, PEG was then removed by thermal evaporation. Uniform thin films of remaining nanoparticles were then deposited with the original shapes. This method can be directly applied to many pattern coating applications, such as inkjet printing, gravure, and offset printing.