Patent ID: 8125714

Claim:
An anti-reflection coating comprising first to seventh layers formed on a substrate in this order, said first layer being an alumina-based layer, said seventh layer being a porous, silica-based layer, and in a wavelength range of 400-700 nm, said substrate having a refractive index of 1.45-1.72, said first layer having an optical thickness of 25.0-250.0 nm, said second layer having a refractive index of 1.95-2.23 and an optical thickness of 27.5-52.5 nm, said third layer having a refractive index of 1.33-1.50 and an optical thickness of 37.5-54.0 nm, said fourth layer having a refractive index of 2.04-2.24 and an optical thickness of 45.0-62.5 nm, said fifth layer having a refractive index of 1.33-1.50 and an optical thickness of 77.5-102.5 nm, said sixth layer having a refractive index of 1.85-2.40 and an optical thickness of 16.0-26.5 nm, and said seventh layer having an optical thickness of 112.5-162.5 nm.