Novel perfluoropolyether-modified silanes are improved in water/oil repellency, parting properties, chemical resistance, lubricity, durability, antifouling properties and fingerprint wipe-off. An antireflection filter is also provided comprising an inorganic antireflection layer including a surface layer in the form of a silicon dioxide-base inorganic layer, and an antifouling layer, preferably of the perfluoropolyether-modified silane, on the surface layer. The antifouling layer has a sliding angle of oleic acid of up to 5.degree., a change of the sliding angle after solvent washing relative to the sliding angle before solvent washing being up to 10%.