Patent attributes
An object of the present invention is to provide an antireflection film and an optical device having excellent antireflection characteristics against a light beam having a wide wavelength range at a wide range of an incident angle, and also having practically sufficient durability. To achieve the above object, the present invention adopts an antireflection film having an optical two-layer structure composed of an intermediate layer provided on a base material and a low refractive index layer provided on a surface of the intermediate layer, wherein the low refractive index layer is a layer obtained by binding hollow silica by a binder, a refractive index n(1) thereof is between 1.15 and 1.24 inclusive, and a refractive index n(2) of the intermediate layer satisfies a relation in the expression (1) below assuming a refractive index of the base material n(sub).n(1)×√{square root over (n(sub))}×0.930≦n(2)≦n(1)×√{square root over (n(sub))}×0.985 (1).
