| 摘要 |
PURPOSE:To obtain a biaxially stretched PE terephthalate film which has small shrinkage and is hardly susceptible to deformation strain when exposed to a high temp. by specifying the strain modulus and thermal shrinkage in the longitudinal direction of the film and specifying the axial orientation ratio thereof. CONSTITUTION:The strain modulus G2 (Newton/square meter) in the longitudinal direction of the biaxially stretched PE terephthalate film having a thickness (d) (micronmeter) and the thermal shrinkage sigmab(%) in the longitudinal direction of the film are specified to (1.84-sigmab)dG2>=1.48X10<11>, 1<=d<=15, sigmab>0 and the axial orientation ratio thereof is specified to >=1.5, >=3.0. The polyester of the biaxially stretched polyester film may be any polyester as far as said polyester consists essentially of linear polyester. A substantial decease in the magnetic recording density is resulted and is undesirable if the thickness (d) exceeds 15mum. The polyester film no longer functions as the supporting film for the magnetic recording medium with the dynamic characteristics there of if the (d) is below 1mum. |
