Patent ID: 8608895

Claim:
A manufacturing method of an easy-open container including a container body having an opening and a flange extending from a circumference of the opening; and a lid for covering the opening, in which a surface layer of the container body exposed on the flange and a seal layer of the lid are heat-sealed to form the easy-open container and the lid can be opened by a cohesive failure occurring in the surface layer of the container body and/or the seal layer of the lid, the method comprising: superposing the lid on an upper side of the flange of the container body; pressing a circular sealing board onto the upper side of the flange from above the lid, the sealing board including a curved surface with a curved cross section provided on an inner circumferential edge of the sealing board; an inclined surface provided on an outer circumferential edge to be continuous with the curved surface; and a tip at which the curved surface and the inclined surface meet, the tip being provided close to the inner circumferential edge in a width direction of the cross section of the circular sealing board, the sealing board being pressed to the upper side of the flange so that the curved surface touches the lid later than the tip; and heat-sealing the surface layer exposed on the flange of the container body and the seal layer of the lid while forming a swelling gathered resin part formed of respective resin components of the surface layer of the container body, a layer adjacent to the surface layer and the seal layer of the lid, the gathered resin part being formed in a vicinity of a position on the flange which the inner edge of the circular sealing board touches, wherein a radius of the cross section of the curved surface is not less than 0.2 mm and not more than 0.5×H mm, where H is a width of the circular sealing board, an angle of the inclined surface relative to the flange from the inner circumferential edge to the outer circumferential edge is in a range from 2° to 20°, and the surface layer of the container body and the seal layer of the lid are continuously heat-sealed from the outer circumferential edge toward the inner circumferential edge of the flange.