| 摘要 |
PURPOSE:To even the thickness of a film with high precision by a method wherein the melt viscosities of the thicker and thinner portions of the film are adjusted contactlessly and locally in a zone where a resin is in softened state. CONSTITUTION:A resin molten in an extruder 1 is extruded from a circular die 2 to form an unsolidified softened tubular resin film A', which is then cooled by water through a cooling ring 3 to form a solidified tubular film A. The thickness distribution of the periphery of the film A or A' is measured with naked eye or by a measuring instrument; thicker portions are irradiated with infrared rays by an infrared heater 5 having a slit 5' between itself and the resin, while thinner portions are subjected to a cold blast fed from a cooling nozzle 4. As for the nozzle 4 and the heater 5, plural units are arranged at fixed positions in the circumferential direction, or a single unit is arranged movably in the circumferential direction. The film thus evened in thickness is further drawn to be a uniform drawn film. |
