Unpublished

Figure 1: Sketch of the bead break-up from the upstream meniscus, which marks the onset of the low-flow limit in slot coating process. Slot coating is commonly used in the manufacturing of many different products. The coating liquid is pumped to a coating die, is distributed across the width of a narrow slot in a distribution chamber and, as it exits the slot, the liquid fills the gap between the die and the moving substrate. The liquid in the gap, bounded upstream and downstream by gas-liquid interfaces, or menisci, forms the coating bead. The competition among viscous, capillary and pressure forces, and in some cases inertial and elastic forces, sets the range of operating parameters in which the viscous free surface flow of the liquid can be two-dimensional and steady. The region in the operating parameters of a coating process where the delivered liquid layer is adequately uniform is usually referred to as coating window. Knowledge of coating windows of different coating methods in needed in 167 order to predict whether a particular method can be used to coat a given substrate at a prescribed production rate. Romero et al. (2004) reviews the different analyses of slot coating flows and predictions of the coating window of the process for both Newtonian and non Newtonian liquids. The main contributions for Newtonia