Composite membranes, caps, and covered containers used to contain contained substances

Abstract

The invention proposes a composite film, a lid formed from a composite film, and a lidded container for the purpose of containing the contents* in which a hole can be made in the lid in which a hole can be made at the part of the peeling before the full opening of the lid, in which the composite film restricts the occurrence of defects such as tearing or incomplete perforation during the peeling process to form the hole, and obtains a peel strength that allows for reliable peeling. In the composite film forming the cover element, the peelable resin layer and the polyester films are arranged on both surfaces of the peelable resin layer in a specific structure. Specifically, composite film 1 consists of a first polyester film layer Sa, a peelable resin layer 10, and a second polyester film layer 8b in this order. The first polyester film layer 8a is not treated with corona treatment on either of its surfaces. The second polyester film layer 8b is treated with corona treatment on at least the surface in contact with the peelable resin layer 10. The components and compositions of the peelable resin layer are within a specific range.