| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method of a microporous film having excellent transmissivity while suppressing generation of wrinkles.SOLUTION: The production method of a microporous film includes steps in the following order: a film formation step of obtaining a monolayer raw film comprising at least one type of polypropylene resin selected from the group consisting of a polypropylene resin (A) having a pentad fraction of 90 to 97% and a polypropylene resin (B) having a propylene content of 98 to 99.5 mol%, or obtaining a laminated raw film having a layer comprising at least one type of polypropylene resin selected from the group consisting of the above polypropylene resin (A) and the polypropylene resin (B) as an outermost layer; a stretching step of overlapping two or more of the above monolayer raw films or the above laminated raw films obtained in the film formation step and stretching the overlapped films in at least one direction with a magnification of 1.05 times to 5.0 times while maintaining the films at 90°C to 160°C to obtain a laminate; and a coating step of coating both surfaces of the laminate obtained in the stretching step with a dispersion liquid of an inorganic filler, and then peeling layers of the laminate to obtain at least two microporous films each having one surface coated with the inorganic filler. |
