| 摘要 |
PROBLEM TO BE SOLVED: To obtain a superior uniformity of thickness and printing and traveling properties without impairing excellent mechanical characteristics by allowing the unevenness of thickness in the longitudinal direction to be in a range of a specific value. SOLUTION: After heating, thermoplastic polymer is fed to an ordinary extruder to be cheated at a melting point, and then it is spouted from a T-die metal piece quantitatively to subsequently be adhesion solidified to a cooling drum while, applying high voltage for forming an unoriented film. The unoriented films is heated and oriented in the longitudinal direction before cooling. Herein, the unevenness of a ribbon in the longitudinal direction obtained finally is restrained to be in a range of 0.3-5% or lower. When the unevenness of thickness exceeds 5%, heat conductivity becomes greatly different in the thick part and thin part of the thickness during the printing period by external heating; also, unevenness of physical properties is generated due to the thickness of the film. For this reason, it is not preferable that the unevenness of printing takes place and the finish becomes not clear. In addition, one having the unevenness of thickness of less than 0.3% is not needed feasibly in particular. |
