Patent ID: 7045190

Claim:
A packaging material suitable for use as a substrate for packaging bags or packaging containers employed in heat treatment or thermal sterilization processes, said packaging material comprising a film laminate in which a heat sealing agent with a low melting point is coated on a prescribed zone of an oriented film made of a synthetic resin, a cutting line is cut in the oriented film in the form of a solid or broken line passing through the zone coated with the heat sealing agent, and a cast film made of a synthetic resin and having heat sealing properties is affixed to the oriented film, wherein when the packaging material is subjected to stress acting in a direction perpendicular to the cutting line in the zone coated with the heat sealing agent, the cast film extends and expands in the direction of the stress and when the cast film is incapable of further extension and expansion, a small hole forms therein at both ends of the cutting line, each of said small holes being capable of elastically expanding and shrinking.