Operative limits of curtain coating due to edges

Multilayer curtain coating has been used for more than 50 years in photographic industry for large volume production. The leading experts in multilayer curtain coating technology of the photographic industry have looked in detail at a high number of operative limits, in order to assure the efficiency, productivity and quality of their production. The study of the coating window gives the basic knowledge needed to establish the specifications for a multilayer curtain plant. The knowledge of possible coating defects is the second step required to successfully use a multilayer curtain coating line. The use of a coating line for a wide range of products, having a large spectrum of rheology properties and coating thicknesses, is very often the case. Often the edges and their design are neglected or were forgotten. Even if long term experiences did show that edge effects strongly influence the productivity of such a coating line by creating quality problems and inducing running stop's, the knowledge on edge effects are often poor. Theory on edge profile of curtain coating is summarized and methods to analyse edge issues in production are presented. An example of real industrial edge issue in production is highlighted.