To improve the strength of a porous film and to prevent the film from being hurt or broken.
The porous film 3 is composed of a web 12 as a reinforcing sheet-shaped member and a honeycomb structure layer 8 as a porous layer formed on the upper surface of the web 12. The honeycomb structure layer 8 is formed through a casting process in which a polymer solution is cast on the web 12 to form a cast film, a bedewing process in which liquid droplets are formed in the cast film, and a solvent evaporation process in which voids are formed by evaporating the liquid droplets in the cast film. The honeycomb structure layer 8 with the entire surface reinforced by the web 12 is prevented from being hurt or broken even when laminated.
COPYRIGHT: (C)2008,JPO&INPIT
YAMAZAKI HIDEKAZU
Shigeru Iijima
Kobayashi Hideyoshi
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