| 摘要 |
PROBLEM TO BE SOLVED: To improve the reflectance of a mirror without using silver or gold. SOLUTION: The backside reflecting mirror formed on a substrate having 1.85 to 1.92 refractive index has a reflectance Rv in the wavelength region from 420 nm to 650 nm for the light incident from the substrate side at an angle from 45 deg. to 55 deg. of >=82%. The mirror consists of the following layers, wherein the refractive index and the film thickness are measured atλ=550 nm. The layers are, from the substrate side, the first layer having 1.35 to 1.48 refractive index and 15 to 272 nm optical film thickness, the second layer having 1.85 to 2.30 refractive index and 20 to 138 nm optical film thickness, the third layer having 1.35 to 1.48 refractive index and 105 to 450 nm optical film thickness, the fourth layer having 1.85 to 2.30 refractive index and 27 to 123 nm optical film thickness, the fifth layer having 1.35 to 1.48 refractive index and 120 to 450 nm optical film thickness, the sixth layer having 1.85 to 2.30 refractive index and 43 to 98 nm optical film thickness, and the seventh layer made of metal aluminum having 50 to 200 nm physical film thickness. A protective film is applied in the air side of the seventh layer.
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