Film, package, and contents-containing package

Abstract

A film is used in a package in which the internal pressure of a container increases when heated in a microwave oven, and the internal pressure is reduced by releasing internal steam. The film includes: an outer layer film molecularly oriented by biaxial stretching; an inner layer film that is laminated to the outer layer film and heat-sealable; one or more orientation relaxation portions formed in the outer layer film, and a breaking portion provided at a position which the one or more orientation relaxation portions face with a predetermined distance and configured to rupture when the internal pressure of the container is increased in the microwave oven. At least the breaking portion omits a printed layer between the outer layer film and the inner layer film.

What is claimed is: 
     
         1 . A film used for a package in which an internal pressure of a container increases when heated in a microwave oven, and steam is released to reduce the internal pressure, the film comprising:
 an outer layer film molecularly oriented by biaxial stretching;   an inner layer film laminated to the outer layer film and capable of being heat-sealed;   one or more orientation relaxation portions formed in the outer layer film; and   a breaking portion formed at a position which the one or more orientation relaxation portions faces with a predetermined distance, and configured to rupture when the internal pressure of the container increases during microwave heating,   wherein at least in the breaking portion, a printed layer is omitted between the outer layer film and the inner layer film.   
     
     
         2 . The film according to  claim 1 , wherein the printed layer is provided between the outer layer film and the inner layer film in at least part of a region excluding the breaking portion. 
     
     
         3 . The film according to  claim 1 , wherein the printed layer is provided on an outer surface side of the outer layer film. 
     
     
         4 . The film according to  claim 3 , wherein the printed layer provided on the outer surface side of the outer layer film is located in a region excluding the breaking portion. 
     
     
         5 . The film according to  claim 1 , wherein the printed layer between the outer layer film and the inner layer film is omitted in the breaking portion and the orientation relaxation portions. 
     
     
         6 . A package wherein the film as recited in  claim 1  is used as at least part of a packaging material. 
     
     
         7 . The package according to  claim 6 , wherein the printed layer is provided between the outer layer film and the inner layer film in at least part of a region excluding the breaking portion. 
     
     
         8 . The package according to  claim 6 , wherein the printed layer is provided on an outer surface side of the outer layer film. 
     
     
         9 . The package according to  claim 8 , wherein the printed layer provided on the outer surface side of the outer layer film is located in a region excluding the breaking portion. 
     
     
         10 . The package according to  claim 6 , wherein the printed layer between the outer layer film and the inner layer film is omitted in the breaking portion and the orientation relaxation portions. 
     
     
         11 . The package according to  claim 6 , wherein inner layer films are heat-sealed together to form a bag-like structure for accommodating contents, and the orientation relaxation portions and the breaking portion are disposed in a region that constitutes the bag-like structure. 
     
     
         12 . The package according to  claim 6 , comprising:
 the film, and   a container body including a flange around an opening and configured to contain contents,   wherein the inner layer film of the film is heat-sealed to the flange to cover the opening, and the orientation relaxation portions and the breaking portion are arranged at a position facing the opening.   
     
     
         13 . A contents-containing package comprising:
 the package as recited in  claim 6 , and   contents contained within the package.