Influence of thermal expansion coefficient in laser scribing of glass

Aluminosilicate glass, which has a relatively low thermal expansion coefficient, is used as a glass substrate in liquid crystal displays, whereas soda-lime glass is generally used for such items as windows. The aim of this study was to clarify the influence of the thermal expansion coefficient on the glass substrate during laser scribing with crack propagation produced by laser heating and followed by quick quenching. The laser scribe conditions with aluminosilicate glass and fused silica were obtained in laser irradiation experiments to compare the difference of glass materials. Two-dimensional thermal elasticity analysis was then conducted with a finite element method based on the experimental results. The laser scribable condition of aluminosilicate glass can be estimated by combining the upper limit of the maximum surface temperature and the lower limit of the maximum tensile stress in the cooling area. The tensile stress generated in the cooling area decreases as the thermal expansion coefficient decreases. Therefore, fused silica, whose thermal expansion is much lower than aluminosilicate glass, is rarely applicable in laser scribing for separation.