| 摘要 |
PROBLEM TO BE SOLVED: To prevent the application of unbalanced stress to a container when a film is extended over the container and then heat shrunken by setting lateral primary and secondary shrinking stresses A and (a) and longitudinal primary and secondary stresses B and (b) that are produced when a film is heat shruken to fall within a range expressed by specific equations. SOLUTION: In order to relax a drastic increase in shrink stress produced at the time of heat shrink, the constituent of a film is composed of, in addition to polyetylene terephtalate, a composition compounded with at least one kind or two more kinds of polyester resins constituted by di-carboxylate constituent and diol constituent each having a low glass transition point. Lateral primary shrinking stress A and secondary shrinking stress (a) and longitudinal primary shrinking stress B and secondary shrinking stress (b) all produced at the time of heat shrink are set to fall within a range expressed by equation (1) 0<=|A-B|<=100 and equation (2) 0<=|a-b|<=100. This results in a packaging container that finishes beautiful and provides very little deformation. |
