壓電式噴墨頭異常噴射研析

現今顯示器工業當中，高可靠度的(DOD)墨水噴墨頭扮演著重要的角色，然而在噴墨列印的過程中，噴嘴孔平板邊緣潤濕與空氣泡阻塞噴嘴出口都將導致噴射異常現象發生。本研究目的在於透過改變壓電驅動噴墨頭噴嘴四周平板構造與壁面接觸角，改善潤濕層沈積減緩異常噴射現象發生。於數值計算分析過程當中，基於求解三維質量守恆與動量守恆方程式進行數值模型計算，其中液體與氣體邊界之表面張力計算則採用連續表面張力(CSF)法，液滴輪廓於整體噴射過程中透過CFD-ACE+a所提供之完整VOF-PLIC模組進行數值計算，整體數值模組準確性與工作頻率為200-μs Picojeta噴墨頭運行過程的微影像進行驗證比對並獲得良好一致性，之後延伸計算此數值模型對於噴嘴出口平板四周潤濕對於印刷過程中異常噴射現象之交互關係研究，結果顯示透過良好的噴嘴出口平板幾何結構、親疏水性、將有效減緩噴嘴出口平板潤濕層沈積，改善壓電式墨水噴墨頭在印刷過程中，墨水液滴的異常噴射現象發生。

關鍵字

壓電式噴墨頭；液滴噴射過程；異常噴射

並列摘要

A highly reliable drop-on-demand (DOD) printhead plays a decisive role in the display industry. However, during inkjet printing, anomalous ejection can happen frequently owing to wetting on the nozzle plate and air bubbles encumbered at the nozzle exit. This research aims to investigate the influence of nozzle configuration on the anomalous ejection flowfield for evasion of misfiring by mending nozzle structures of a piezo-driven inkjet printhead. In the analyses, the theoretical approach was based on the transient three-dimensional conservation equations of mass and momentum. The surface tension effect at the gas-liquid boundary was treated by the continuous surface force (CSF) method. The complex droplet ejection process was simulated using an integrated volume-of-fluid and piecewise linear interface construction (VOF-PLIC) technique implemented in a commercial computational fluid dynamics software CFD-ACE+a. To validate the present theoretical model and numerical mesh, the predicted droplet topology and breakup length/time through the ejection sequence were compared with micro-photographed images for a 200-μs actuating cycle of a PicojetR printhead. Simulations were extended to elucidate the nozzle-ink wetting interaction for probing the mechanism of anomalous ejections in the printing process. The predictions also showed an effective solution via modification of the nozzle design and the hydrophilic property of coating materials over the surface of the nozzle exit to evade the occurrence of anomalous ejections of a printhead.

並列關鍵字

Piezoelectric printhead ； Droplet ejection process ； Anomalous ejection

參考文獻

[1] Paul K E, Wong W S, Ready S E and Street R A 2003 Additive jet printing of polymer thin-film transistors Appl Phys Lett.83 2070-2.

[2] Singh M, Haverinen H M, Dhagat P and Jabbour G E 2010 Inkjet printing-process and its applications Adv Mater.22 673-85.

[3] Lee F C, Mills R N and Talke F E 1984 The Application of Drop-on-Demand Ink Jet Technology to Color Printing IBM J Res Dev.28 307-13.

[4] Le H P 1998 Progress and trends in ink-jet printing technology J Imag Sci Tech.42 49-62.

[5] Carnahan R D and Hou S L 1977 Ink Jet Technology IEEE Trans Ind Appl.IA-13 95-104.

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壓電式噴墨頭異常噴射研析

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