摘要
本研究之主題為條紋塗佈之分析，乃藉由狹縫式模具進行條紋塗佈，所研究的流道寬度範圍在1mm~10cm之間，塗液為低黏度(μ<50mPas)之牛頓流體，同時藉由實驗及理論兩方面探討影響成膜寬度之成因，並以流場觀測及數值模擬分析其缺陷產生機制。 首先比較一般狹縫式塗佈與條紋塗佈的差異，實驗結果顯示，窄膜塗佈具有較高之塗速上限，但其膜寬變化與寬膜塗佈相近，相較之下，膜寬變化對窄膜塗佈的影響相當明顯，因此本研究由多項變因分析其對於窄膜塗佈的影響，結果顯示，塗液之表面張力、黏滯力及狹縫出口處的慣性力均與成膜寬度相關，經由無因次分析及步進回歸，可得一無因次膜厚對Re*及Bo之關係式，由此可預測條紋塗佈之成膜寬度。本研究尚藉由流場觀測及數值模擬分析條紋塗佈的缺陷機制，同時探討寬膜與窄膜塗佈二者於速度上限有所差異的原因。 為了避免塗佈液珠之下游彎月面爬上模具斜邊而導致渦流發生，並因塗液揮發變質而導致斷膜與刮膜缺陷，本研究藉由套裝軟體FLOW-3D進行理論模擬，分析諸多變因對潤溼線位置的影響，其結果顯示，增加模唇邊角之角度或使塗液在模具表面之接觸角增大均可助於避免液珠之下游潤溼線爬上模具，且若對上述兩項設計進行適當調整，能助於進一步提高塗速上限。
並列摘要
The fluid mechanics of narrow stripe coating for low-viscosity Newtonian solutions were investigated. It was found that the coating solution will expand laterally after emanating from the slot die channel at low coating speeds. As coating speed increases, the stripe width will contract until it is close to the slot channel width, then coating failure would appear. Three slot channel widths were tested, coating failure such as ribbing appears at high speeds for two larger slot channel widths. However, for the smallest channel width, the critical speed for coating failure to appear is much higher and the coating failure is not ribbing but the narrow stripe breaks periodically. The effects of each parameter on the coating width variation were examined and a universal correlation which involves modified Reynolds and Bond number was established to predict the coating width. A flow visualization technique was applied to observe the mechanism on how a narrow stripe breaks at high coating speeds. 2-D and 3-D numerical simulations on coating flows were examined for a better understanding on the stability of narrow stripe coating. For certain operating conditions, the downstream contact line of the coating bead may climb on the die shoulder, which may cause vortices near the downstream region. Since most of the coating solutions in industry are volatile, vortices in the flow fields should be avoided to prevent the coating solutions from degradation. Otherwise, some coating defects such as bead-break in stripe coating or rivulet in conventional slot-die coating would take place. To avoid the contact lines from climbing on the die shoulder, many factors such as viscosity of the coating solutions, film thickness, and die geometry were tested with software package FLOW-3D. Among all the factors, designing the dies by adopting smaller angles at the die edge or by increasing the contact angles of the coating solutions on the die can effectively pin the positions of the downstream contact lines at the die edge, and suppress the formations of vortices as well. Besides, the stability of the coating beads was also analyzed. With appropriate adjustments, higher coating speeds can be reached by the use of the newly-designed slot die.