Laser cutting with controlled fracture and pre-bending applied to LCD glass separation

In this study, a laser beam, a water jet coolant and a pre-bending device were used to produce tensile stress along the cutting path that causes the material to separate along the moving path of the laser beam. The fracture mechanism and the machining parameters of laser cutting with controlled fracture were studied. The specimen materials were LCD glass substrates and the laser source was a CO2 laser. The relationships between laser power, cutting speed, and bending deflection were obtained from experimental analyses. The separation of glass substrates is similar to crack propagation. The extension of the crack tip lags behind the laser spot at a non-uniform lagging distance. The acoustic emission signals generated during the fracture process were analyzed to obtain the stages of fracture growth. It was found that the three types of breaking, namely delay breaking, nick breaking, and ahead breaking, are all dominated by the moving speed of the laser beam. The breaking surface shows no micro-cracks and the surface quality is much better than that obtained by mechanical breaking.