Techniques to suppress the lift-off peel of films at the edge of an adherend based on the energy release rate

Lift-off peel is a phenomenon that occurs at the edge of an adherend when a film with an adhesive is pressed and laminated onto the adherend, potentially compromising the bonding quality. This study investigates this phenomenon and proposes methods to suppress it. When laminating a functional layer onto a brittle substrate with a complex geometry, one approach involves vacuum-forming a film coated with the functional layer so that it conforms precisely to the substrate shape. During this process, gaps between the substrate and mold cause the film to sink under the applied pressure. Consequently, the film may peel and lift at the edges, resulting in incomplete lamination. This lift-off peel represents a configuration in which separation occurs opposite to the applied load, which acts perpendicular to the bonding surface; however, this phenomenon has rarely been analyzed. In this study, the film behavior during lift-off peel was formulated using principles of classical solid mechanics. The conditions required to prevent lift-off were identified based on the derived energy release rate. The experimental measurements from the custom-built apparatus demonstrated strong agreement with the predicted deflection curve. The findings of this study indicate that the energy release rate, governed by parameters such as film stiffness, mold inclination, applied pressure, and gap distance, serves as the critical threshold for suppressing peeling. The proposed criterion provides practical guidelines for mitigating defects in film lamination processes.