| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain an ND filter reduced in the spectral reflectivity of a visible wavelength region, in the low-density region of about 3.0 or lower in density. <P>SOLUTION: An ND film 2, having a gradation gradient changing continuously in density at maximum density, is formed on a PET substrate 1 and an MgF<SB>2</SB>film of a single layer is formed on the outermost surface layer. Furthermore, antireflection films 4 comprising of multilayered films are formed in the low-density region which is relatively high in the spectral reflectivity of the visible wavelength region of the ND film 2, for example, in the region of 0.3 or lower in density for improving the anti-reflection function. The antireflection films 4 consist of a five-layered configuration alternately laminated with SiO<SB>2</SB>films and TiO<SB>2</SB>films, have an approximately fixed film thickness, are partially masked and are formed by vacuum deposition method. <P>COPYRIGHT: (C)2007,JPO&INPIT |
