| 摘要 |
PURPOSE:To eliminate the change of refractive index with the lapse of time and to improve the adhesion of a reflection reducing coating by forming a first layer consisting of SiO2, a second layer consisting of Al2O3, and a third layer consisting of CeO2, on the surface of a plastic optical parts, providing thus respectively specified refractive index and optical film thickness. CONSTITUTION:A first layer consisting of SiO2 to the outermost air side, a second layer consisting of Al2O3, and a third layer consisting of CeO2 are formed in the order on the surface of a plastic optical parts. Further, relations between n1 (the refractive index of the first layer), n2 (the refractive index of the second layer), n3 (the refractive index of the third layer), n1d1 (the optical film thickness of the first layer), n2d2 (the optical film thickness of the second layer), n3d3 (the optical film thickness of the third layer), and lambda0 (designed principal wavelength) are defined by the formulas: n1=1.47; 0.20lambda0<=n1d1<=0.32lambda0; 1.50<=n2<=1.62; 0.02lambda0<=n2d2<=0.15lambda0; 1.92<=n3<=2.10; 0.02lambda0<=n3d3<=0.50lambda0. By this constitution, there is no fear for causing change of the refractive index with the lapse of time, and the adhesion to the substrate is improved. |
