| abstract |
The present invention relates to a porous polyolefin film in which the peak temperature of tan δ of the dynamic viscoelasticity thereof measured at a frequency of 1 Hz, a temperature increase rate of 5°C/minute, and a strain rate of 0.1%/second is 105°C or greater in at least one of the MD direction (machine direction) and the TD direction (transverse direction). This porous polyolefin film is not prone to short circuiting due to foreign matter even when reduced in thickness, and also has excellent shape stability against high temperature or high tension. |