Thermo-mechanical analysis of laser peeling of ultrathin glass for removing edge flaws in web processing applications

Abstract

For efficient production of display and touch sensing components of modern tablets and mobile communication devices, the bending strength of ultrathin glass must be enhanced for efficient processing in roll-to-roll process. Laser peeling is an effective method for enhancing the strength by removing edge defects on glass using irradiating CO2 laser pulses on glass edges to peel off a thin layer containing edge defects. However, this process involves complicated interaction in various fields such as heat transfer, stress, fracture, and phase change, as well as possible material properties variations. Without carefully selection of the processing conditions, the process can lose of control easily. To guide the process design for optimizing the laser peeling process and prevent failure, the mechanism of this material removal process is investigated individually, including the heat transfer model for analyzing transient temperature variation in a substrate being peeled and thermal stress induced structure fracture. Subsequently, essential parametric studies are performed later to characterize the influence of individual processing parameters. It was found that the depth of the heat affective zone has a strong impact on the peeling performance and the simulation results agree with that from experimental observations. Finally, by means of fracture mechanics and using the strain energy release rate as the measure, this work successfully explains the observed features and provide engineering basis for possible future process improvements. The laser peeling process is also successfully modelled as a moving temperature source for simulating the crack propagation during peeling using the extended finite element method. It is believed that through this study, the fundamental mechanism of laser peeling can be clearly understood, which would be vital for conducting subsequent process optimization and related glass packaging applications.