The closure device comprises a closure cap (1) which can be screwed onto the threaded connection of a container, said closure cap forming a fillable capsule (2) that is open at the bottom, on which a seal (15) directed downward is sealed. The upper side of the part of the closure cap which forms the capsule (2) is designed to be deformable and can be pressed axially downward. A press element (38) is moulded on this cover of the closure cap (1) at the bottom. By pressing the cover downward, the downward-directed seal (15) of the capsule (2) is broken open by the press element (38). As a special feature, the seal (15) is made from a laminate comprising a carrier material (30) with a thickness of at least 0.5 mm. Subsequently, a barrier film (31), for example, an aluminium or EVOH film as an oxygen, UV, and moisture barrier, is sprayed or laminated on said carrier material, externally in relation to the capsule (2), and a sealing layer (32) in the form of a paint or a PE laminate layer is sprayed or laminated on this barrier film (31), said sealing layer crimping over the seal (15) at the outer edge thereof, around the edge of the barrier film (31) and the edge of the carrier material (30). The crimping forms a circumferential edge, by means of which the seal (15) can be sealed to the capsule edge, on the inner side of the carrier material (30), with respect to the capsule (13), and resting on same. The carrier material (30) has notches in the form of cuts, which approximately cut through the carrier material (30) yet leave the attached films (31, 32) intact.