| 摘要 |
PROBLEM TO BE SOLVED: To obtain moisture resistance and to maintain good reflection characteristics in 150 to 300 nm UV ray region by specifying the structure of a dielectric multilayered film layer. SOLUTION: This mirror for UV region layer is produced by successively forming at least a first dielectric multilayered film layer 4a consisting of alternately deposited layer of low refractive index layers 3, 6 and high refractive index layers 2, 5, and a protective dielectric multilayered film layer 4b on a substrate 1. The first dielectric multilayered film layer 4a has the structure of H1/[L1/H1]x from the substrate 1 side, while the protective dielectric multilayered film layer 4b has the structure of L2/[H2/L2]y or H2/[L2/H2]y from the substrate 1 side. The optical film thickness of each layer is defined as H1=0.25λto 0.35λ, H2=0.25λto 1.0λ, L1=0.25λto 0.35λ, L2=0.25λto 1.0λ, whereinλis the designed center wavelength, H1, H2, L1 and L2 represent the first and second high (low) refractive index layers, respectively, and (x) and (y) satisfy x>=3 and Y=1 to 3. Moreover, the difference in the refractive index between the first high refractive index layer and the first low refractive index layer is specified to be >=0.27.
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