Apparatus and method of coating a web

Abstract

An apparatus and method of bead coating a web using a coating die. The method comprises forming one or more layers of coating material using the coating die and allowing the one or more layers to impinge on the web as the web and die move relative to each other. The web surface has an average peak to peak roughness as defined by DIN 4768, ISO4287 or BS1134 between 2 μm and 20 μm. The layer of coating material forming a wetting layer adjacent to the web has a viscosity of between 35 mPas and 200 mPas measured at a shear rate of substantially 10,000 s−1. An electrostatic field is provided at the point at which the layers impinge on the web to stabilize the layers of coating material. The method enables the web being coated to be conveyed at a speed greater than 400 cm/s relative to the coating die whilst avoiding the problem of air entrainment.

Dependencies are inferred from the claim text.