| 摘要 |
PURPOSE:To obtain high dimension accuracy, long life of a belt and better adhesion with an electrical conductivity layer or the like by manufacturing a seamless belt constituted of a biaxially oriented thermoplastic polyester resin having a given value of dry heat shrinkage factor at a given temperature and a given value of breaking extension in the driving direction. CONSTITUTION:Thermoplastic resin is extruded in the form of a tubular film 1 through a tubular die and cooled, and then heated up to the temperature to be oriented by a ring-shaped sheathed heater 4 between two couples of nip rolls 2 and 3 positioned on the upper and lower sections of said film, and a biaxially oriented tubular film 5 is prepared by orienting the film vertically and laterally at the same time by means of the difference of peripheral speed between the pressure (infration method) generated by the air enclosed in the tubular film and two couples of nip rolls. As said seamless belt is of high dimension accuracy, provided with a long life of belt and of good adhesion with an electrical conductivity layer, dry heat shrinkable factor should be 2% or less at 80 deg.C of the belt temperature and breaking extension should be 95% or less. |
