Production of multilayer laminated polymer substrates e.g. smart cards avoiding distortion

摘要

Practically-distortionless, laminated polymer substrates are made from polymer films, each having non-zero intrinsic and thermal stressing. The films are stacked, with at least three sheets to a multilayer, the second and third sheets outside the first, and having identical stressing. The multilayer is then laminated, which produces a distortion-free result. Also claimed are distortion-free laminates, produced by this manner.. Second and third films are polyethylene terephthalate (PET) and have the same tensile strength, same shrinkage index, and same expansion factor. The several layers each have a machine-worked direction, which are all laid parallel, as well as being parallel to the length of the substrate.