Three dimensional thermal stress analysis on laser scribing of glass

Abstract

In the laser scribing of glass a thermal stress is induced into a glass plate by means of a CO2 laser irradiation. The glass plate is then rapidly cooled down by water jet immediately after the irradiation. For the purpose of theoretical clarification of the factors ruling the crack depth and the scribable condition, the crack depth and the crack profile were observed for various values of the distance between heating area and cooling area. Furthermore, scribable conditions were acquired in laser irradiation experiments using a soda-lime glass plate having a thickness of 0.7mm. On the. basis of the scribable conditions obtained from the experiments, the thermal elasticity analysis was conducted by the finite element method, allowing the following findings to be obtained. The crack depth in laser scribing depends on the surface tensile stress in the cooling area and the compressive stress field immediately under the area. The scribable condition can be estimated from the maximum surface tensile stress in the cooling area and the maximum surface temperature.