Patent ID: 8263172

Claim:
A method for producing an optical element having a multi-layered film in which a layer made of a low-refractive-index material and a layer made of a high-refractive-index material are alternately formed on a plastic substrate, the optical element being used for light in a wavelength range of 300 nm to 450 nm, the optical element producing method comprising: forming alternately the layer made of the low-refractive-index material and the layer made of the high-refractive-index material on the plastic substrate to produce the optical element while plasma or ionized gas is generated by a generation source in forming at least the layer made of the high-refractive-index material under predetermined producing conditions, wherein the predetermined producing conditions are determined such that the oxygen permeability coefficient of the produced optical element is equal to or less than 30 cm3×mm/(m2×24 hr×atm) such that transmittance of the light in a wavelength range of 300 nm to 450 nm of the optical element is substantially maintained after being irradiated with the light for 1000 hours.