| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous film having small stretching unevenness and high homogeneity even in the film manufactured from a resin composition containing much thermoplastic resin having a high melt viscosity and a low melt elongation. SOLUTION: The method for manufacturing the porous film comprises the steps of stretching twice to ten times a film-like material F made of the resin formed of a thermoplastic resin composition containing a filler of 10 to 300 pts.wt. in a TD direction under a condition 1 of T1/T2>1.05, a condition 2 of 1.5>T3/T2>1.2 and a condition 3 of Tm>T3>(Tm-5), wherein T1 is a preheating temperature of a preheating part A at a stretching time, T2 is a stretching temperature at a stretched part B, T3 is a heat setting temperature at the heat treating part C, and Tm is a melting point of the thermoplastic resin, by using a stretching unit having a preheating part, a stretching part and a heat treating part.
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