Film for membrane structure

A film for a membrane structure, wherein the film comprises:

• a film substrate;
• a photocatalyst layer;
• and
• an interlayer interposed between the film substrate and the photocatalyst layer,
• wherein the film substrate comprises at least one fluororesin selected from the group consisting of an ethylene/tetrafluoroethylene copolymer, a tetrafluoroethylene/hexafluoropropylene copolymer, a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, a polyvinyl fluoride and a polyvinylidene fluoride,
• wherein the interlayer comprises a zirconia curing agent and an organic-inorganic hybrid polymer obtained by hydrolyzing/co-condensing at least one member selected from the group consisting of an organosilane, a hydrolysate of an organosilane and a condensate of an organosilane, and a silyl group-containing organic polymer, wherein the mass remaining ratio of the organic-inorganic hybrid polymer is from 50% to 80% at 500° C. measured by thermogravimetric analysis,
• wherein the photocatalyst layer comprises a zirconia curing agent and a photocatalyst,
• wherein the film substrate exhibits a surface tension of at least 38 mN/m as a result of having been subjected to a corona discharge surface treatment,
• wherein adhesion between the film substrate and the interlayer is at least 85% as measured by a cross-cut method in accordance with JIS K5600,
• wherein the water contact angle on a surface of the photocatalyst layer is at most 5° as measured after the following weather resistance test, and
• wherein the change in haze is at most 3% as measured before and after the following weather resistance test:
• weather resistance test:
• while the film is irradiated with ultraviolet rays at a wavelength of from 300 nm to 400 nm at an intensity of 100 mW/cm2, a cycle comprising (i) irradiation with ultraviolet rays at a temperature of 63° C. at a relative humidity of 50% RH for 10 hours, (ii) a shower for 20 seconds, (iii) moisture condensation for 2 hours, and (iv) a shower for 20 seconds, is repeatedly carried out for 200 hours.