| 摘要 |
PROBLEM TO BE SOLVED: To realize an antireflection coating having high antireflection characteristics in the visible region. SOLUTION: A multilayer film having ten layers in total consists of a first layer 11 and a seventh layer 17 of Al2O3 which are intermediate refractive index layers having refractive indexes of 1.50 to 1.80, a second, fourth, sixth and ninth layers 12, 14, 16 and 19 which are high refractive index layers having refractive indexes of 2.00 or more, and a third, a fifth, an eighth and tenth layers 13, 15, 18 and 20 which are low refractive index layers having refractive indexes of 1.46 or less, is provided on an optical substrate 10. By optimizing the optical film thickness of each layer within a prescribed range, the reflectance by a simulation is made to 0.1% or less, and the reflectance in real characteristics including a manufacturing error is made to 0.2% or less in the whole visible region.
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