Patent ID: 7866487

Claim:
An aromatic polyamide porous film comprising an aromatic polyamide polymer having repeating units of formula (1) and/or formula (2): wherein Ar 1 , Ar 2 and Ar 3 are aromatic rings independently selected from the group consisting of wherein X and Y are independently selected from the group consisting of —O—, —CH 2 —, —CO—, —CO 2 —, —S—, —SO 2 —, and —C(CH 3 ) 2 —; wherein the aromatic rings may be substituted with one or more substituents selected from the group consisting of fluoro, bromo, chloro, nitro, methyl, ethyl, propyl, methoxy, ethoxy, and propoxy groups; and wherein 80 mol % or more of the aromatic rings have a para orientation; wherein the aromatic polyamide porous film has an Open Cell structure in which a fibrous material composed of the aromatic polyamide polymer is connected through three- or more forked intersections to form a three-dimensionally spreading network; and where use of an atomic force microscope to measure a range of S μm 2 at least on one surface, the sectional area S (10) μm 2 at a depth of 10 nm from the surface and the sectional area S (20) μm 2 at a depth of 20 nm from the surface results in these measured values satisfying the following formulae simultaneously: 0.01≦ S (10)/ S≦ 0.3 5≦ S (20)/ S (10)≦20,