The Reserch Of Edge Chipping On LCD Glass With Thermal-controlled Method Of Laser Cutting

High transmittance glass has been widely used in office equipment,portable devices and wearable devices.As an important protective material of display screens,the associativity of glass and display materials had increased with the costs.Small piece of glass was used on portable devices,due to the larger area of first-made glass,the glass sheet needs to be processed in a high efficiency,low cost,high yield segmentation way.During the thermal-controlled cutting process of LCD glass substrates,due to changes of cutting parameter settings or environmental factors,the cutting edge would have a great probability of inducing edge micro-cracks,and in the subsequent period,temperature change effect gradually influenced the micro-crack tip to expand and join,finally lead to chipping and low processing quality of the cutting edge.According to the experimental observation,the glass substrate material does not contain defects such as air pockets before cutting.The laser head was observed with white matter during cutting process,the white matter was generated during the gasification process of the glass surface.And the white mater was attached to the laser head after it leave the radiation area.The cavitation defect was formed under the surface of laser irradiation region.Based on the above background,the main work of this article was list as follows:(1)Finite element method was used in the analysis of laser scanning process on glass substrate in transient heat conduction.Heat flux field was acquired and multi-crack propagation was analyzed according to thermal elastic plane stress theory and the theory of multi-crack propagation.Micro-cracks crack propagation was determined by fracture criterion of micro-cracks.Crack branching angle was calculated according to the crack bifurcation criteria.Using this method,the symmetrical cutting process was analyzed,micro-cracks generate mechanism was researched as crack formation and expansion of the edge chipping phenomenon.(2)This article presents a segmentation iterative algorithm according to the simulation and micro-crack propagation direction of the laser scanning process.By observing the micro-cracks,extended model micro-cracks extended period of each micro-cracks were proposed in accordance with the maximum circumferential stress criterion(MTS)to predict its propagation direction.Propagation angle was calculated on the basis of previous extended period.(3)Computer graphics method was used to analysis the image of cutting edge chipping micro-cracks.The captured images were processed by graying,binarization,corrosion algorithm to acquire the image pixel coordinates.The maximum width algorithm and actual length extraction method were used in image processing.The efficiency and accuracy of the experimental data have been improved.Numerical results presented in this article shows the micro-crack initiate around the midpoint of the glass edge cavitation or pits arc,and extended to the interior of the glass at the midpoint of the arc pit,the tilt direction of cracks were in contrast of the laser scanning direction.Due to the crack tip SIF have reached the critical stress intensity factor,bifurcation was occurred at the caudal crack.During the cooling process,and micro-cracks continue to expand and link,final result in edge chipping.