本研究利用CCD攝影機建立流場觀測技術，研究不同形狀之凹槽對塗佈之影響，實驗可改變之操作條件為：(1)塗佈間隙(2)塗佈滾輪速率(3)塗液物性(4)凹槽形狀。流場觀測技術的主要架構是使用CCD從塗佈方向的側面拍攝，CCD相較於傳統顯微鏡可以提供較為清晰的放大影像，並且可以將塗佈過程輸出到電腦上建構影片，然而因為塗佈速度的限制，要了解機制的詳細運作過程，需要更精密的影像處理，本研究採用CASIO EX-F1高速相機進行影片的同步拍攝，以取得更短時間間距的照片、影片，進而了解機制的詳細情況與一般放映速度下不易觀察得知的關鍵處。
目前己取得之實驗成果顯示，塗佈過程並未如一般預期在凹槽邊界內形成穩定之塗佈液橋，取而代之的是液體先行被拉出凹槽，形成在外部與滾輪接觸之變動液橋，而後進行塗佈。
本研究針對此現象進行分析，找出影響轉移率之關鍵因素主要是凹槽形狀、塗液性質、塗佈速度、塗佈間隙等。結果顯示塗佈液珠斷裂的位置與時間影響轉移率最大，當塗佈速度與塗液黏度上升時，液珠顯得容易斷裂，導致塗液被拉出凹槽的量減少，因而降低了轉移率；凹槽形狀決定了邊界阻礙液珠運動的效應，隨著各凹槽邊界效應的大小，轉移率在各凹槽也有所變化，其中三角形凹槽的轉移率最大，梯形居次，長條形最小；塗佈間隙則是影響液珠在凹槽內斷裂的的位置點與凹槽外液橋的穩定性，塗佈間隙越高，液珠斷裂的位置越偏上層，液珠在凹槽外維持穩定的難度變高，液珠容易往塗佈方向拉遠，並且較易斷裂而殘留一部分液體在凹槽邊界外，使得轉移率變低。

A flow visualization technique was applied to observe the liquid emptying from scaled-up gravure cells of different shapes. Dilute Newtonian poly(vinyl)alcohol solutions were used as tested fluid. The emptying process depends on the stability of the liquid bridge that connects the moving roller and the gravure cell. It was found that the downstream free surface of the liquid bridge first extends in the coating direction after the moving roller contacts the coating solution and then the position of the free surface remains unchanged until the upstream free surface position is adjusted and fixed, then the liquid bridge shrinks as coating starts until the bridge breaks up. The adjustments of the upstream free surface depends strongly on the fluid viscosity. Two limiting cases can demonstrate how the upstream free surface varies; for a low-viscosity solution with a smaller coating gap, the position of the upstream free surface is fixed until the downstream free surface reaches a steady position before coating starts. However, for a high-viscosity solution with a larger coating gap, the upstream free surface will even pass the gravure cell and the liquid bridge is out of the gravure cell. Variation of the upstream free surfaces are between these two limiting cases. Other factors such as the departing angle of the gravure cell, the gap between the moving roller and the gravure cell, and capillary number will also influence the fluid motion of the gravure cell.

1. 劉大佼“高分子加工原理與應用” （1997）
2. 吳平耀“超薄塗佈技術簡介－精密的製造師”, 工業材料雜誌第 194期（2003）
3. Booth, G. L. “Coating Equipment and Processes”, Lockwood, New York（1970）
4. Chuang, H. K., Lee, C. C., Liu, T. J. “An experimental study on the pickout of scale-up gravure cells”, International Polymer Processing, 23, 216-222. (2008).
5. Pritchard, E. J., Finkle, W.“Ink transfer in gravure printing and its effect on halftone reproduction. In: Banks, W. H.（Ed.）”, Advances in Printing Science and Technology, vol. 3. Pergamon Press, Oxford, pp. 263-281（1964）
6. Pritchard, E. J.“What do we know about gravure”, The British Ink Maker（May）, 147-157 （1965）
7. Joyce, E., Fuchs, G. L.“Study of gravure ink transfer”,TAGA Proceeding, 294-311（1966）
8. Bery, Y. A.“Gravure printing on non-absorbing materials”,TAGA Proceeding, 207-220（1976）
9.康耀庭“滾筒表面特性與轉動方向對塗佈工程之影響”,國立清華大學化學工程研究所碩士論文（1990）
10. Patel, R., Benkreira, H.“Gravure roll coating of Newtonian liq-uids”, Chemical Engineering Science 46, 751-756（1991）
11. Benkreira, H., Patel, R.“Direct gravure roll coating”, Chemical Engineering Science 48, 2329-2335（1993）
12. Benkreira, H., Cohu, O.“Direct forward gravure coating on un-supported web”, Chemical Engineering Science 53, 1223-1231（1998）
13. Kapur, N., Gaskell, P. H., Bates, A.“A parametric study of offset gravure coating”,Chemical Engineering Research and Design: Transactions of the Institution of Chemical Engineers 79A, 41-50（2001）
14. Schwartz, L.W., Moussalli, P., Campbell, P., Eley, R. R.“Numerical modelling of liquid withdrawal from gravure cavities in coating operations”,Chemical Engineering Research and Design: Transactions of the Institution of Chemical Engineers 76A, 22-28（1998）
15. Schwartz, L. W.“Numerical modeling of liquid withdrawal from gravure cavities in coating operations; the effect of cell pattern”,Journal of Engineering Mathematics 42, 243-253（2002）
16. Powell, C. A., Savage, M. D., Gaskell, P. H.“Modelling the meniscus evacuation problem in direct gravure coating”, Chemical Engineering Research and Design: Transactions of the Institution of Chemical Engineers 78A, 61-67（2000）
17. Yin, X., Kumar, S.“Lubrication flow between a cavity and a
flexible wall”, Physics of Fluids 17, 063101-13（2005）
18. Yin, X., Kumar, S.“Flow visualization of the liquid-emptying process in scaled-up gravure grooves and cells”, Chemical Engi-neering Science 61, 1146-1156（2006）