Influence of Molecular Orientation on The Curling Phenomenon in Laminated Films

—A Curl Control Method of “Communication Paper”—

Abstract

Recently, plastic films have been widely applied to manufacture “communication paper”, such as direct thermal films (or paper) and dye diffusion thermal transfer sheets. In these applications, the biaxially drawn films are used, and their molecular chain orientation causes “curl phenomena”, particularly in laminated films.
We found that the curl-value (ΔK) of plastic films clearly related to the difference of the thermal expansion coefficients of each ply in laminated films, and the thermal expansion coefficient could be predicted by measuring the degree of molecular chain orientation (MOR-value) determined by the transmitted microwave intensity method.
Based on these findings, we propose that quantitative curl prediction is possible by employing an approximate formula derived from the lamination theory.