| 摘要 |
PURPOSE:To enhance the accuracy of thickness distribution after stretching by a method wherein the thickness distribution of a stretched film in the lateral direction is measured and the heating in the biaxially stretching part of a tubular film is controlled in a state divided in the peripheral direction of the tubular film corresponding to the measured thickness distribution. CONSTITUTION:The set temps. of the respective infrared heat generators 25A of an infrared heating cylindrical furnace 25 are controlled in a divided state on the basis of the respective detection outputs outputted from respective temp. detectors 25B and a thickness distribution detector 6 or 8 and 10 so as to uniformize the thickness distributions of all of a bubble like stretched film A3 and films B1, B2 after stretching. This dividing temp. control of the cylindrical furnace 25 is automatically performed by a control part 12 or manually performed. Prior to manufacturing a film, the thickness change rates of the films B1, B2 after stretching corresponding to the temp. change quantities per unit temp. of the respective parts of the heating furnace 25 are preliminarily calculated and, at the time of the actual production of the films, the temp. of the heating furnace 25 to be controlled is calculated from the masured thickness distributions of the films B1, B2 after stretching to perform control so as to obtain said temp. |
