Clarification of Crack Curvature Mechanism and Estimation of Crack Shape in Laser Scribing of Glass

Laser scribing generates a shallow crack on a glass surface as a pre-processing for division. It utilizes thermal stress caused by heating with the laser beam and by cooling with the water jet. In the laser scribing, a crack curves when there is a gap along the scribing line between the centers of the heated area and cooled one. In this study, we conducted some experiments of laser scribing under such asymmetric processing conditions and observed the crosssectional crack shapes. As a result, it was found that the crack propagates quasi-steadily even in assymmetric stress distribution. We proposed a crack propagation analysis method for such quasi-steady crack propagation using a boundary element method. The present analysis needs only static stress distribution at a quasi-steady state. The entire crack shape was obtained by repeating a calculation with a constant and small number of elements. The crack shape obtained from the analysis agreed relatively well with the experimental results. Therefore, the validity and usefulness of the analysis method were verified.