Patent ID: 9527266
Filing Date: 2016-12-27
CPC Classification: B32B,G02B,Y10T

Claim Text:
1. A multi-layer laminated film comprising layers composed of a crystalline thermoplastic resin A (A layers) and layers composed of a non-crystalline thermoplastic resin B as a major component (B layers), which A layers and B layers are alternately laminated in 51 or more layers, wherein the multi-layer laminated film is biaxially stretched in the longitudinal and transverse directions at a temperature from 80° C. to 120° C. with a draw ratio of 2 to 6 for each direction, heat-treating the film at a temperature from 160° C. to 220° C., and subjecting the heat-treated film to cooling at a temperature that is 80° C. of higher; and wherein said film has: a heat shrinkage stress of not less than 0.5 MPa and not more than 5 MPa at 150° C. in longitudinal and width directions of said film; and a heat shrinkage stress kick-off temperature of 110° C. or lower in both the longitudinal and width directions of said film, said heat shrinkage stress kick-off temperature being defined as, in a heat shrinkage stress curve determined under a condition where temperature is 25° C. to 200° C. and a heating rate is 5° C./min, the temperature at an intersection between a baseline preceding an initial rise of said heat shrinkage stress curve and a tangent line drawn at a point where said heat shrinkage stress curve has a maximum slope after said initial rise.