| 摘要 |
PROBLEM TO BE SOLVED: To provide a simultaneously coaxially stretched polyamide film having excellent quality stability and uniformity by eliminating the presence of a thickness irregularity cycle specific to a tenter clip interval generated in a simultaneous biaxial stretching process. SOLUTION: The amplitude component of a simultaneous biaxial stretching tenter clip interval cycle, which is analyzed by a linear spectrum obtained by the fast Fourier transform of a thickness irregularity fluctuating waveform in a longitudinal direction, is 8 dB or less with respect to the overall value of a total periodic band. When the diameter of each of tenter clips performing simultaneous biaxial stretching is set to D and the distance between the clips grasping a film at first is set to P, stretching is performed so that the ratio NCI/NMD of the mechanical longitudinal draw ratio NCI of the interval P-D between the side end of a certain clip and the side end of the adjacent clip with a longitudinal draw ratio NMD becomes 1.3-2.3. |
