Pattern Formation in Slot-Die Coating

Abstract

We experimentally study the occurrence of pattern formation during the slot-die coating of lowviscosity nearly Newtonian liquids onto Polyethylenterephthalat (PET)-substrates. In particular, it is demonstrated that with increase of the coating speed a homogeneous coating becomes unstable with respect to periodic stripe patterns. Thereby, depending on the liquid viscosity, the stripes can be oriented parallel or perpendicular with respect to the coating direction. Mixed states do also occur. The spatial period of perpendicular [parallel] stripes increases [decrease] with the coating speed. The dependence of the effect on various control parameters of slot-die coating is investigated.Finally, a simple theoretical model based on the hydrodynamics of thin films of partially wetting liquids is analysed. Comparing the results to the experiments, conclusions are drawn regarding the acting instability and pattern formation mechanisms.

Modelling and Simulation of Transverse Homogeneity of Slotted Coating Process

“…However, because the mechanisms of slotted coating are still poorly understood, the research and development costs are very high, and the coating quality and accuracy are very difficult to control. Therefore, it is urgent to carry out mechanical modelling and simulation research on the coating process, to provide theoretical support for the design of slotted die and the precise control of the coating process [1][2][3].…”