Curl Effects in Roll‐to‐Roll Operations

Summary

One very distinct shape distortion, commonly observed in roll‐to‐roll (R2R)‐based products, is manifested as curl or curvature in the nominally flat product and is typically associated with the core‐set curl effect. This chapter reviews the phenomenology and mechanism of core‐set curl and discusses ways to mitigate and control its deleterious effect on film planarity. The phenomenology of core‐set curl (bending recovery) is observed to a greater or lesser extent in most polymeric films. Film products are often stored in roll form for extended times, either before the R2R operation or after the operation and before or after various finishing steps. The chapter considers the effect of aging time on the evolution of the instantaneous core‐set curl with winding time for a polyethylene terephthalate (PET) film. In order to minimize curling effects in film products, it is necessary to first identify the underlying curling mechanism that drives the deviations from planarity.