Patent ID: 7379244

Claim:
An anti-reflection film that has three component layers overlying a substrate and deposited one over another in the order as denoted by ordinal numbers, 1st to 3rd where, at an arbitrary design basis wavelength λ within a wavelength range in and near visible band, a refractive index ‘n’ and an optical film thickness (spectrometric wavelength) ‘nd’ are given as follows for each of the substrate and the component layers deposited on the same: Refractive Index ‘n’ Optical Film thickness ‘nd’ Substrate 1.90 ≦ n s ≦ 2.10 1st Layer 1.54 ≦ n 1 ≦ 2.00 0.465λ ≦ n 1 d 1 ≦ 0.575λ 2nd Layer 1.95 ≦ n 2 ≦ 2.63 0.490λ ≦ n 2 d 2 ≦ 0.508λ 3rd Layer 1.35 ≦ n 3 ≦ 1.55 0.245λ ≦ n 3 d 3 ≦ 0.255λ.