Water-proof air-permeable filter and use of the same
A water-proof air-permeable filter ( 1 ) includes: a resin film ( 2 ) having formed therein a plurality of through pores ( 21 ); and a treated layer ( 3 ) having hydrophobicity and oil repellency, and formed on at least one of both surfaces in the thickness direction of the resin film ( 2 ) such that the treated layer ( 3 ) has openings ( 31 ) at positions corresponding to the through pores ( 21 ). The through pores ( 21 ) each have a predetermined size larger than or equal to 0.01 μm and smaller than or equal to 10 μm, and are uniformly distributed such that a density of the through pores falls within specific limits included in a range from 10 to 1×10 8 pores/mm 2 .
1. A water-proof air-permeable filter for ensuring ventilation and also preventing entry of water, the water-proof air-permeable filter comprising:
a non-porous resin film having formed therein a plurality of through pores extending through the resin film in a thickness direction; and
a treated layer having hydrophobicity and oil repellency, and formed on at least one of both surfaces in the thickness direction of the resin film such that the treated layer has openings at positions corresponding to the plurality of through pores,
wherein the plurality of the through pores each have a size larger than or equal to 0.01 μm and smaller than or equal to 10 μm, and
the plurality of the through pores are uniformly distributed such that a density of the plurality of the through pores falls within a range from 10 to 1×10 8 pores/mm 2 ,
the treated layer coats an inner surface of the through pores so as to form an inner part of the treated layer located inside the through pores, and
a material forming the treated layer is different from a material forming the resin film.
2. The water-proof air-permeable filter according to claim 1 , wherein a porosity of the resin film is 50% or less.
3. The water-proof air-permeable filter according to claim 1 , wherein a ratio of a thickness of the resin film to the size of the plurality of the through pores is 1 or more and 10000 or less.
4. The water-proof air-permeable filter according to claim 1 , wherein the resin film is made of a resin that is decomposed with at least one solution selected from the group consisting of an alkali solution, an oxidant solution, and an alkali solution containing an oxidant.
5. The water-proof air-permeable filter according to claim 4 , wherein the resin is at least one material selected from the group consisting of polyethylene terephthalate, polycarbonate, polyimide, polyethylene naphthalate, and polyvinylidene fluoride.
6. The water-proof air-permeable filter according to claim 1 , further comprising an air-permeable supporting member laminated to the resin film.
7. The water-proof air-permeable filter according to claim 1 , wherein a water pressure resistance measured according to JIS L1092-A (low water pressure method) or JIS L1092-B (high water pressure method) is 1 kPa or more and 1000 kPa or less.
8. A method of closing an opening of a housing, comprising applying the water-proof air-permeable filter according to claim 1 so as to cover the opening of the housing and to eliminate a pressure difference between inside of the housing and outside of the housing via the water-proof air-permeable filter.
9. The water-proof air-permeable filter according to claim 1 , wherein the treated layer has a higher waterproof property than a waterproof property of the resin film.
10. The water-proof air-permeable filter according to claim 1 , wherein the resin film is made of at least one resin selected from the group consisting of polyethylene terephthalate, polyimide, and polyethylene naphthalate.
11. The water-proof air-permeable filter according to claim 10 , wherein the treated layer is formed of a fluorine-based agent by applying the fluorine-based agent to the non-porous resin film having the through pores and drying the fluorine-based agent.
12. The water-proof air-permeable filter according to claim 1 , wherein
the through pores are straight pores extending linearly through the resin film when viewed in a cross-section of the resin film, and
a size of the opening of the treated layer is smaller than a size of an opening of the respective through pore corresponding to the opening of the treated layer by a thickness of the inner part of the treated layer when viewed in the thickness direction of the resin film.