| 摘要 |
PURPOSE:To obtain a magnetic recording medium with no curl and superior planeness by using a biaxially oriented poly-p-phenylene sulfide film having specified characteristics as a principal constituent layer. CONSTITUTION:A biaxially oriented poly-p-phenylene sulfide (PPS) film contg. units represented by structural formula I by >=90mol% of the repeating units is used as the principal constituent layer of a base film, and a ferromagnetic layer is formed on at least one side of the PPS film. The characteristics of the base film are allowed to satisfy an equation 2X10<-7=AXC<=5X10<-5> in all directions in the surface. In the equation, A is the coefft. ( deg.C<-1>) of thermal expansion at 120 deg.C, and B is the rate (%) of thermal shrinkage at 120 deg.C. PPS used is required to contain >=90mol% repeating units represented by structural formula II. In case of <90mol%, the crystallizability of the polymer is reduced, so the mechanical characteristics of the resulting film are unsatisfactory. Units of m- phenylene sulfide, ether or the like account for the remaining <=10mol%. PPS is melted and molded into a sheet, and this sheet is biaxially stretched and heat treated to obtain said biaxially oriented PPS film. The preferred thickness is 5-100mum. |
