Method for producing opening detection sheet, opening detection sheet, and packaging material

A method for producing an opening detection sheet, comprising:

• a first resin applying step of applying, using gravure printing, a first resin having an insulation property onto a metal foil layer made of a metal containing aluminum to form a first resin layer;
• a circuit pattern printing step of printing, using gravure printing, a circuit pattern onto the first resin layer with use of an ink containing a conductive substance;
• and
• a second resin applying step of applying, using gravure printing, a second resin onto the first resin layer so as to cover at least a part of the circuit pattern to form a second resin layer,
• said method further comprising a step of applying, using gravure printing, a third resin onto a surface of the metal foil layer that faces away from the first resin layer to form a third resin layer having thermal fusibility,
• wherein the gravure printing comprises:
• (1) a step of immersing a part of a gravure printing cylinder provided with recesses on a plate surface thereof in a resin reservoir in which the first resin, the second resin, the ink, or the third resin is reserved, so that the recesses are filled with the first resin, the second resin, the ink, or the third resin;
• (2) a step of lifting the gravure printing cylinder from the resin reservoir while rotating the gravure printing cylinder;
• (3) a step of removing, with a blade, the resin adhering to areas other than the recesses on the plate surface of the gravure printing cylinder;
• (4) a step of passing the metal foil between a pressure roller and the gravure printing cylinder, so that the resin in the recesses is transferred to the metal foil;
• and
• (5) a step of drying the resin transferred to the metal foil,
• wherein a dry weight per unit area of the first resin layer is not less than 1.48 g/m2 and not more than 3.70 g/m2,
• wherein the first resin contains, as a main component, at least one of vinyl chloride and vinyl acetate, and
• wherein a dry weight per unit area of the second resin layer is not less than 0.8 g/m2 and not more than 2.0 g/m2.