| 摘要 |
PURPOSE:To provide superior water resistance and durability to an antireflection film formed on the surface of a synthetic resin lens, to reduce the change of the film with the passage of time, and to enhance the spectral reflectance by coating the uppermost layer of the film with a metallic nitride. CONSTITUTION:An SiO2 layer 14 as the uppermost layer of an antireflection film is coated with a metallic nitride 21. The metallic nitride is very stable to water, causes no yellowing by water and has no hydroscopicity, so it undergoes no change with the passage of time. The preferred metallic nitride 21 is silicon nitride (Si3N4), titanium nitride (Ti3N4), tantalum nitride (Ta3N5) or aluminum nitride (AlN). The metallic nitride layer 21 having about 0.01-0.03lambda optical thickness is a colorless transparent film and has about 2.0-2.7 high refractive index eta, yet because of the small thickness, the layer 21 exerts a slight influence on the spectral reflectance. |
