Easy-to-open tubular sealed casing

An easy-to-open tubular sealed casing for packaging a content therein, the casing comprising:

• a base film comprising a composite plastic film with at least three film layers including an outer layer film which forms an outer surface when the composite plastic film is formed into a tubular form, an intermediate layer film which forms an intermediate layer and an inner layer film, said composite plastic film being formed into a tubular form by bending said base film, overlaying two edges of said base film;
• and
• a heat seal section formed by heat-sealing the overlaid section to heat seal together a portion of the outer layer film to a portion of the inner layer film so that a not heat-sealed section will be left along an edge of the film, with a notch provided man edge of said not-sealed section, a peel strength between said outer layer film and said intermediate layer film being set to a lower level as compared to a peel strength between said inner layer film and said intermediate layer film, whereby a pulling of said not-sealed section adjacent to said notch causes said outer layer film to be disrupted and then peeled from said intermediate film layer starting adjacent to said heat sealed section to open casing.