Patent ID: 10168452

Abstract:
The antireflection coating is a multi-layer film to be formed on a surface of a substrate. The film includes multiple layers including an uppermost layer most distant from the substrate among the multiple layers, and a lower layer including at least one layer other than the uppermost layer. A refractive index nm of the uppermost layer for a wavelength of λ (nm) satisfies a condition of 1.11≤nm≤1.3. An optical admittance Y of the lower layer is expressed by Y=a+ib, and a and b in the optical admittance satisfy conditions of (a−1.13)2+(b−0.24)2≤0.452 for λ=430, (a−1.33)2+(b+0.05)2≤0.252 for λ=900 and (a−1.14)2+(b+0.25)2≤0.292 for λ=1800.