Zipper strap structure, packaging bag comprising zipper strap structure, and manufacturing method for zipper strap structure

A manufacturing method for a zipper strap structure, comprising:

• molding a first strap and an internal coupling unit to have a uniform cross section by extrusion molding, the internal coupling unit including a column portion which projects from the first strap and is extended in a length direction of the first strap and a head portion which has a pair of latching protrusions formed to expand in a width direction of the first strap from an end of the column portion and to be extended in the length direction of the first strap and a central separation groove that is formed by concavely indenting an outer end surface of the column portion between the latching protrusions and is extended in the length direction of the first strap;
• and
• repeatedly pressing parts of the head portion and deform a cross section of the internal coupling unit by a pressurizing device, where pressure is applied to the central separation groove to pressurize and expand the latching protrusions of the head portion toward both sides and first head portions and the second head portions are alternately arranged in the length direction of the first strap, the first head portions being disposed to have a first height with respect to the first strap, the second head portions being disposed to have a second height which is lower than the first height with respect to the first strap.