Patent ID: 7773301

Claim:
An antireflection film disposed on a substrate, the antireflection film comprising: first to eighth layers that are stacked sequentially from an opposite side to the substrate, wherein: the first and fourth layers are made of a low-refractive index material exhibiting a refractive index of 1.35 to 1.50 with respect to the d-line, the third and fifth layers are made of an intermediate-refractive index material exhibiting a refractive index of 1.55 to 1.85 with respect to the d-line, and the second and sixth layers are made of a high-refractive index material exhibiting a refractive index that is in a range from 1.70 to 2.50 with respect to the d-line, and that is higher than the refractive index of the intermediate-refractive index material; wherein the antireflection film satisfies following conditional expressions (1) to (6): 0.25×λ0 ≦N 1 ·d 1≦0.27×λ0 (1) 0.48×λ0 ≦N 2 ·d 2≦0.50×λ0 (2) 0.20×λ0 ≦N 3 ·d 3≦0.23×λ0 (3) 0.08×λ0 ≦N 4 ·d 4≦0.09×λ0 (4) 0.27×λ0 ≦N 5 ·d 5≦0.30×λ0 (5) 0.41×λ0 ≦N 6 ·d 6≦0.60×λ0 (6) where λ0: center wavelength, N1 to N6: refractive indices of the first to sixth layers with respect to the center wavelength λ0, and d1 to d6: physical thicknesses of the first to sixth layers.