| 摘要 |
PURPOSE:The titled film made of specific polyether ester which is superior in stability in size and shock-resistant performance and having favorable running performance as a magnetic tape. CONSTITUTION:Polyether ester containing more than 85mol% polyethylene alpha,beta- bis (2-chlorinated phenoxin) ethane 4, 4'-dicarboxylite is extruded through a slitlike die in a molten state at a temperature of 275-320 deg.C, coold suddently at a temperature of 10-80 deg.C and unextended film whose density is 1.42-1.45 is obtained. Then bi-axial extension of the film is made so that extension magnification alpha in the lognitudinal direction and extension magnification beta in the direction of width satisfy the formula I , desirably the formula II, and a bi- axial extension film whose total of refractive indexes in the longitudinal direction and in the direction of width is 3.295-3.410 is obtained. Then the film is extended so that extension magnification gamma in the longitudinal direction and extension magnification delta in the direction of width satisfy the formula III, desirably IV, and the film, whose total of refractive indexes in the longitudinal direction and in the direction of width is 3.305-3.420 and difference is -0.20- 0.20 and the total of Young's moduluese in the longitudinal direction and in the direction of width is more than 1,500kg/nm<2>, is obtained. |
