Analysis of the Occurring of the Un-uniform Regions in Slot Coating
|關鍵字:||狹縫式塗佈;三維數值模型;膜厚均勻性;Slot coating;3D numerical model;Uniformity of film thickness|
本研究旨在利用計算流體力學軟體POLYFLOW建立狹縫塗佈製程的數值模擬方法，並探討製程參數對於薄膜塗佈特性的影響，輔助分析狹縫塗佈時邊緣不均勻區的發生原因和特性。首先透過實驗取得非牛頓流體塗料的流變特性和表面張力等物性資料，並將其建置於模擬軟體內，進行二維黏彈性流體以及三維黏性高分子材料的流變模型擬合。其次，分別建立二維及三維狹縫塗佈製程模型，並使用軟體內的有限元素法Arbitrary Lagrangian-Eulerian Method (ALE法)進行計算。由模擬結果發現：二維黏彈性材料方面，表面張力會與塗佈長度呈負相關，而鬆弛時間內的控制值以及基板速度則會與塗佈長度呈正相關，但速度過快也會導致缺陷的產生；在三維黏性高分子材料方面，推估塗佈前緣的不穩定，會致使之後自動生成的網格變形不均勻而產生更多不良網格，應是計算中止的重要原因；而塗佈參數間並無絕對趨勢，取平衡才是最佳。
Although the slot coating process in the production of polymer films has a wide range of applications, the process is difficult to be systemized, and un-uniform regions often occur on the edges of the slot coating film, so this study developed a solution for the problem of non-uniform regions on the edges of slot coating film. This research aims to use the CFD software POLYFLOW to aid the analysis of the cause and characterstics of the un-uniform regions on slot coating films. First, the non-Newtonian rheological properties and surface tension of the coating material were acquired through experiments. The measurement data were imported to the simulation software for mathematical modeling. Then, 2D and 3D numerical model of the slot coating process were created. Arbitrary Lagrangian-Eulerian (ALE) calculation methods were used in the POLYFLOW software for simulation. The results of 2D simulation show that surface tension will decreases the coating length. Substrate speed and relaxation time increase coating length, but excessive substrate speed causes defects. The 3D simulation results show that unsteady phenomena at the flow front generate uneven deformation grids, which cause a divergence in the calculation. Balancing the system parameters can improve the results. Additionally, moderately increasing the length of the coating lip increases the uniformity of the flow rate in the x-direction, and helps to minimize un-uniform areas of the slot coating. An additional trench on the coating lip usually does not improve the flow rate in the x-direction. However, the simulation of a 0.5*0.1*2.5 mm3 trench achieved good results, which were consistent with the experimental results. This research provides a reference for improved mold design.