Patent ID: 8465817

Claim:
A polyester container, comprising: a trunk portion; a flange integrally formed with the trunk portion and having a flat upper surface; and a heat sealing structure integrally formed with the flange and adapted to form a hermetic heat seal between the container and a cover member, the heat sealing structure comprising a projecting portion projecting from the flat upper surface of the flange, wherein the projecting portion is formed at a center or an outer peripheral side of the flat upper surface relative to a width direction of the flat upper surface so that at least a portion of the projecting portion which becomes a heat-sealing-face of the heat seal comprises an amorphous portion or a lowly crystallized portion, and which has a crystallinity lower than that of a rest of the flange except for the at least the portion of the projecting portion which becomes the heat-sealing-face.