| 摘要 |
PROBLEM TO BE SOLVED: To almost permanently maintain an antimold effect and to efficiently suppress production of mold by forming a thin film containing a heavy metal compd. on an optical member. SOLUTION: A thin film having antimold characteristics is directly formed as a multilayered antireflection film on the surface of a substrate. The antireflection film has a four-layer structure in which the first layer consists of a low refractive index material having 1.35-1.5 refractive index, the second layer consists of a medium refractive index material containing a heavy metal compd. and having 1.5-1.8 refractive index, the third layer consists of a high refractive index material having 1.8-2.6 refractive index and containing a heavy metal compd., and the fourth layer consists of a low refractive index material having 1.35-1.5 refractive index. The heavy metal compd. is oxides or fluorides of metals in the VI group in the periodical table, for example, barium fluoride, hafnium oxide, tantalum oxide, lanthanum fluoride, cerium fluoride, neodymium fluoride, gadolinium fluoride, dysprosium fluoride, and ytterbium fluoride. |
