| 摘要 |
PURPOSE:To provide an automatic control method for especially preventing the non-uniformity of the thickness of a side end part when a thermoplastic resin is extruded from an extrusion die to form a membrane. CONSTITUTION:When a thermoplastic resin is extruded from an extrusion die to form a membrane alone or to form the same on at least one surface of a support, the thickness of the membrane is controlled by the heater die bolts 2 arranged in the lateral direction of the extrusion die 1. In this method, an objective thickness pattern is applied to the heater die bolts 2 so as to contain a part gradually becoming thin toward the side end part 5 of the membrane in the vicinity of the inside of the side end part 5. Further, the objective thickness pattern of the heater die bolts 2 is corrected using the deviation of the output of a film thickness measuring device 4 provided after the membrane is formed from an objective value. As the film thickness measuring device 4, one due to an optical spot is used and the effective size in the lateral direction of a spot at the measuring point thereof is set to the range of 1/50-1/3 the pitch in the lateral direction of the heater die bolts. |
