Method of cutting brittle material, device for cutting brittle material, method of manufacturing cut brittle material and cut brittle material

A method of cutting a glass plate, the method comprising:

• a conveyance cutting step having a first step of converging and irradiating a near-infrared ray on a surface of a glass plate of soda lime silicate with a thickness of 2 to 25 mm linearly along an intended cut line using a near-infrared line heater while moving at a first speed the near-infrared line heater relative to the glass plate in a direction along the intended cut line in a state where a portion immediately beneath the intended cut line in a lower surface of the glass plate is exposed to air, thereby extending an initial crack throughout an entire glass plate thickness induced at a front end of the intended cut line of the glass plate to a position short of a terminal region of the glass plate along the intended cut line,
• wherein the first step is performed by moving the near-infrared line heater relative to the glass plate in a direction along the intended cut line, without blowing gas or water;
• and
• wherein the conveyance cutting step comprises a cooling step of jetting a fluid ahead of a front end of the crack to cool the terminal region for cutting in the glass plate, allowing the crack to extend on a front surface of the glass plate on the intended cut line, to subsequently extend in a side at an end of the glass plate, and to further extend in a back surface at the end of the glass plate when cuttinq the terminal region after the first step.