PURPOSE: To provide a sealed container which can withstand an increase in the internal pressure at the time of sterilization in a retort and which has such peel strength that a lid is easily openable by hand from the outside of the container, by a method wherein a heat sealing part is sealed in the forms of a flat shape, a shape of the teeth of a comb and a net-like shape from the outer portion of a flange of the container toward the inner portion thereof.
CONSTITUTION: In an upper heating platen 10 for heat-sealing a flange part 41 of a cup-like container 40 and a lid material 30, an inner edge portion of a printing face is formed into a shape of a net type recess and protrusion portion 12 for embossing the flange part and the lid material into a net shape, and an outer edge portion side is formed into a flat face 13 for performing flat sealing, while a printing face of a lower heating platen 20 is formed into a flat shape. Recesses and protrusions 14 formed into an inwardly almost parallel wave- like recess and protrusion shape i.e., a shape of the teeth of a comb are projected between the flat face 13 and the net type recess and protrusion portion 12. When heat sealing is performed by using the upper and the lower heating platens 10, 11, the recesses and protrusions 12 by embossing can be formed at the inner edge portion of a sealing part 31 of a sealed container and, if a distance between the upper and the lower heating platens 15 made shorter on the inner edge side, the depth of sealing becomes gradually deeper toward the inner edge portion. Accordingly, seal strength becomes stronger toward the inner edge portion of the flange.
AYA TETSUYA
NARITA HISAYA
MITSUBISHI CHEM CORP