| 摘要 |
PURPOSE:To make beautiful and tight covering package and tying package possible, by providing a polyester film having such a heat shrinkability that its heat shrinkage factor in a direction of principal shrinkage has at lest a specified value and that the one in a direction perpendicular to the direction of principal shrinkage has the min. value at a specified temp. CONSTITUTION:A heat-shrinkable polyester film has such a heat shrinkability that is heat shrinkage factor at 80 deg.C is 30% or above, that the one at 100 deg.C is 50% or above and that the one in a direction perpendicular to the above direction of principal shrinkage has the min. value in a temp. region of 80+ or -25 deg.C. To obtain these film characteristics, it is desirable to use these film chracteristics, it is desirable to use a mixture of at least two polyesters, wherein the residue of an arom. dicarboxylic acid accounts for 30-90mol% of the mixture, or a copolyester. It is desirable that a difference heat shrinkage factor between the direction of principal shrinkage of the film and the direction perpendicular to said direction is 15% or below and a coefficient of planar orientation is 100-10<-3> or below. |
