| 摘要 |
PROBLEM TO BE SOLVED: To provide an antireflection film having low reflectance for a wide incident angle range of rays and to provide an optical element and an aligner mounting the element. SOLUTION: The antireflection film formed on a substrate which is transparent for light in the wavelength range of 150 nm is obtained by laminating a low refractive index layer consisting of a material having a refractive index lower than the refractive index of the substrate, a high refractive index layer consisting of a material having a refractive index higher than that of the substrate, and a medium refractive index layer having a refractive index in the range between those of the low refractive index layer and the high refractive index layer. The layers each having the optical film thickness according to the designed wavelength λ0 are, successively from the substrate side, the medium refractive index layer having 0.30 to 0.40λ0 optical film thickness, high refractive index layer having 0.10 to 0.15λ0 optical film thickness, medium refractive index layer having 0.30 to 0.40λ0 optical film thickness, low refractive index layer having 0.25 to 0.35λ0 optical film thickness, medium refractive index layer having 0.25 to 0.35λ0 , and low refractive index layer having 0.25 to 0.30λ0 optical film thickness. |
