Diamond scribing and laser breaking for LCD glass substrates

This paper investigates diamond scribing and laser breaking for LCD glass substrates. A scoring tool was used to generate a groove-crack along the cutting path in a glass surface. The glass substrate was then separated by applying a defocused laser beam along the scribed line to drive the groove-crack through the thickness of the glass. The laser source was a CO2 laser. The relationships between the scribing force, groove depth, median crack depth, and the cutting speed were obtained. Diamond scribing can enhance cutting speed during the cutting process. The scribed groove-crack can determine the direction of crack propagation. The glass substrate separates exactly along the scribing path during the laser-breaking process. The separation process was examined by detecting the extending crack and analyzing the acoustic emission signals. There are two types of glass separation: in one type, the crack tip lags behind the laser spot; in the other, the crack moves ahead of the laser spot. The finite element software ANSYS was employed to calculate the temperature and stress distributions to explain the scribing effect. It was found that the maximum tensile stress of the scribed glass is about twice as high as that of un-scribed glass. Thus, the scribed glass is much easier to separate than un-scribed glass.