Thermal stress analysis on laser cross scribe of glass

In CO2 laser scribe processing of glass, an initial crack on the start edge of the glass is indispensable. When carrying out laser cross scribe, there is no initial crack on the edge of the first scribed line. However, the second scribe progresses across the first scribed line. In this research, in order to clarify the phenomena of laser cross scribe, the laser irradiation experiments were carried out at various velocities of the second scribing. Using the same conditions as the experiments, three-dimensional thermal stress analyses were conducted by a finite element method. As a result, two kinds of forms were found in the progresses of the second scribe. One is a form that the first scribed crack surfaces are bonded by strong compression at high temperature in the heating area during the second scribing. The other is a form that the tensile stress in the cooling area which makes the second scribe progress is transmitted by the frictional force generated in the first scribed crack surface. Consequently the second scribe progresses across the first scribed line although there is no initial crack on the edge of the first scribed line.