Suitable processing conditions determined from the standpoint of residual strain in laser scribing of glass

Abstract

Laser scribing is one of non-contact pre-processing for division of glass. A shallow crack which is origin of the division is formed, utilizing thermal stress caused by heating with the laser beam and by cooling with the water jet. By this process microcracks on a scribed surface can be avoided, resulting in higher edge strength of divided glass. However, it has been cleared by our previous study that even low external force on the laser beam irradiated area sometimes allows formation of secondary cracks. In this study, we have conducted the laser scribing experiments under a variety of the laser beam shape, the laser power, and the scanning velocity, and then examined in which case the secondary cracks are formed. In order to estimate the suitable processing conditions where the secondary cracks are not formed, we have conducted a two-dimensional thermo-elastic analysis by the finite element method. Obtained conclusions are as follows: Secondary cracks are generated due to the residual stress induced by the laser heating. Generation of secondary cracks can be estimated experimentally by measuring the retardation and analytically by investigating the maximum shear stress.Laser scribing is one of non-contact pre-processing for division of glass. A shallow crack which is origin of the division is formed, utilizing thermal stress caused by heating with the laser beam and by cooling with the water jet. By this process microcracks on a scribed surface can be avoided, resulting in higher edge strength of divided glass. However, it has been cleared by our previous study that even low external force on the laser beam irradiated area sometimes allows formation of secondary cracks. In this study, we have conducted the laser scribing experiments under a variety of the laser beam shape, the laser power, and the scanning velocity, and then examined in which case the secondary cracks are formed. In order to estimate the suitable processing conditions where the secondary cracks are not formed, we have conducted a two-dimensional thermo-elastic analysis by the finite element method. Obtained conclusions are as follows: Secondary cracks are generated due to the residual stress induced by ...