Mechanism and Control of the Trailing Edge in Intermittent Slot Die Coating

Intermittent slot die coating is widely used to create the structured coating layer in the flexible electronics production but is inevitable to engender trailing edge of uneven coating thickness. Herein, we established a validated two-dimensional model to analyze the mechanism of the trailing edge and discussed the method to control its length. We found that the tail length was greatly depending on the capillary number (Ca), and it could be divided into three regions as Ca increased. The tail length reduced gradually in the tail length reduction region, was stable, and could be well controlled in the stable region while increased rapidly and irregularly in the unstable region. Meanwhile, a higher viscous and smaller static contact angle could control the tail length by postponing the tail length unstable region. Furthermore, a criterion within ±18% accuracy was proposed for a quick prediction of the tail length stable region in the industrial production.