Porous polyether sulfone film and production method therefor

A porous polyethersulfone film having a surface layer (a), a surface layer (b), and a macrovoid layer sandwiched between the surface layer (a) and the surface layer (b),

• wherein the macrovoid layer has a partition wall bonded to the surface layers (a) and (b);
• and a plurality of macrovoids surrounded by the partition wall and the surface layers (a) and (b), the macrovoids having an average pore diameter in a film plane direction of 10 μm to 500 μm;
• wherein the partition wall of the macrovoid layer has a thickness of 0.1 μm to 50 μm;
• wherein each of the surface layers (a) and (b) has a thickness of 0.1 μm to 50 μm;
• wherein one of the surface layers (a) and (b) has a plurality of fine pores having an average pore diameter of more than 5 μm and not more than 200 μm, while the other has a plurality of fine pores having an average pore diameter of not less than 0.01 μm and not more than 200 μm;
• wherein a surface opening ratio of one of the surface layers (a) and (b) is not less than 15%, while the surface opening ratio of the other surface layer is not less than 10%;
• wherein the fine pores in the surface layers (a) and (b) communicate with the plurality of macrovoids;
• and
• wherein the porous polyethersulfone film has a total film thickness of 5 μm to 500 μm, and a porosity of 50% to 95%.