| 摘要 |
PURPOSE:To obtain a film which can be cut off manually, easily and linearly and is superior in productivity, tenacity and heat resistance by a method wherein the value of birefringence of a biaxially oriented polyester film mainly composed of polyethylene terephthalate is made 0.04-0.10 and a thickness of the same is made 2-75mu by satisfying a specific formula. CONSTITUTION:An index of birefringence, tensile break strength in a main orientation tear direction (Tm), tensile break elongation in an auxiliary orientation direction of a biaxially oriented polyester film are established respectively as 0.04-0.10, 15-35kg/mm<2> and 5%-70%. Then as the tensile break elongation (Em) in a main orientation direction is 80-170% and the tensile break strength in the auxiliary orientation direction is 4-20kg/mm<2>, manual tear properties are improved. In addition, as stress (Fs) at the time of elongation of 5% in the auxiliary orientation direction exceeds break strength (Ts), the film is superior in productivity and tenacity. Thus the film which can be torn easily, linearly and manually can be obtained. |
