LASER BEAM MACHINING METHOD

摘要

To provide a laser processing method which can highly accurately cut a planar object to be processed having an irregular surface as an entrance surface for processing laser light. This laser processing method irradiates a planar object to be processed with laser light while locating a light-converging point within the object, thereby forming modified regions 71 to 77 to become a starting point region for cutting along lines to cut 5. The entrance surface r for the laser light in the object is an irregular surface. The lines to cut 5 extend over a depressed area surface r2 and a protruded area surface r1 in the entrance surface r. The modified region 71 is formed inside by a predetermined distance from the depressed area surface r2. At the time of irradiation with laser light along a part 51a on the protruded area surface r1, the light-converging point is located on the outside of the object. The modified region 72 is formed inside by a predetermined distance from the protruded area surface r1. At the time of irradiation with laser light along a part 51 b on the depressed area surface r2, the light-converging point is located on the outside of the object.