Ink Fluidic Behaviors during R2R Slot Die Coating on Quality Thin Film Formation

Abstract

Abstract High throughput slot die coating is a desired fabrication method for flexible display, solar cell, Li-ion battery pack, intelligent package and wearable electronics. In this study, the stability of the thin film formation by slot die coating is investigated through theoretical, experimental and numerical studies with the combined effects of the fluid and substrate surface characteristics. The theoretical model based on the viscous capillary theory reveals fluid upstream and downstream distribution patterns and associated parameters that descript the coating layer stability. A 3D model based on the volume of fluid method (VOF) is developed to illustrate the coating process affecting the coating quality by the substrate velocity and flow rate. The numerical and experimental results agree that higher viscosity fluid is more prone to trap air bubbles and/or to create de-wetting areas while as the lower viscosity fluid were responsible for upstream liquid dripping. Boundary by the fluid, substrate, and operating parameters, our numerical study has developed the coating operation window to minimize or eliminate coating defects which has been confirmed by the experiments. These study results could lead high yield coating processes and efficiency in large area functional coating production.