Abstract: The invention relates to a method for cutting a strengthened glass sheet 10, and the strengthened glass sheet 10 including a front surface layer 13 and a rear surface layer 15 which have a residual compressive stress, and an intermediate layer 17 which is formed between the front surface layer 13 and the rear surface layer 15 and has an inside residual tensile stress is cut by moving an irradiation region 22 of the laser beam. In addition, when initiating the cutting of the strengthened glass sheet 10, a thermal stress which induces the generation of a crack is exerted on a cutting initiation location, the extension of the crack is suppressed simultaneously with the generation of the crack at the cutting initiation location, and then the strengthened glass sheet 10 is cut while suppressing the extension of a crack caused by the inside residual tensile stress in the intermediate layer 17.

Abstract: A method of cutting a strengthened glass including a front surface layer and a back surface layer in each of which a compression stress remains, respectively, and an intermediate layer formed between the front surface layer and the back surface layer, in which a tensile stress remains, the method includes: cutting the strengthened glass plate by heating the intermediate layer at an irradiation area of a laser beam at a temperature less than or equal to an annealing point while transmitting 70.0% to 99.8% of the laser beam having a wavelength between 800 to 1100 nm injected into the front surface and moving the irradiation area of the laser beam at a speed greater than or equal to 1.0 mm/sec, so that a crack, which penetrates the strengthened glass plate in a thickness direction of the strengthened glass plate, follows the irradiation area.

Abstract: A method of cutting a strengthened glass including, a front surface layer and a back surface layer each having a remaining compression stress, respectively, and an intermediate layer formed between the front surface layer and the back surface layer, having an internal remaining tensile stress, the method includes heating the intermediate layer at an irradiation area of a laser beam at a temperature less than or equal to an annealing point to generate a tensile stress less than a value of the internal remaining tensile stress of the intermediate layer or a compression stress at the center of the irradiation area for suppressing the propagation of the crack.