Heat treatment furnace

A heat treatment furnace comprising:

• a furnace body including an entrance, an exit and a processing chamber disposed between the entrance and the exit;
• a conveyor configured to convey a sheet-shaped object from the entrance through the processing chamber to the exit, the object extending from the entrance to the exit;
• and
• a heating device disposed in a space in the processing chamber in which the object is conveyed and configured to heat the object being conveyed by the conveyor,
• wherein
• the heating device comprises one or more heaters each including a heating part configured to radiate infrared electromagnetic waves to the object,
• the one or more heaters are disposed along a conveying path of the object,
• the heating part is disposed parallel to a front or back surface of the object, and extends in a width direction of the object orthogonal to the conveying path, and
• when a widthwise dimension of the object is Wd and a widthwise dimension of the heating part is Hd, Wd/Hd is in a range of 0.20 to 0.80.