Patent ID: 7940462

Claim:
An antireflective structure comprising: a substantially flat layer having a surface; a fine structure layer including: a myriad of truncated fine protrusions each including: a head end part, and a base face which is at least one of: a substantially circular base face of a truncated cone, the circular base face having a diameter D of a circle, and a substantially polygonal base face of a truncated pyramid, the polygonal base face having a diameter D of a circumscribing circle of the polygonal base face, the truncated fine protrusions being arranged on the surface of the flat layer in such a manner as to define a pitch, wherein, with a first reflective face formed in the head end part of each of the truncated fine protrusions, and a second reflective face formed between the truncated fine protrusions on the surface of the flat layer: each of the diameter D of the circle and the diameter D of the circumscribing circle is smaller than a wavelength λ of an incident electromagnetic wave, the wavelength λ being a wavelength of visible light, and the pitch is smaller than the wavelength λ of the incident electromagnetic wave, a ratio is in a range of 0.2 to 2, where the ratio is given by dividing: a first occupancy of the first reflective faces, by a second occupancy of the second reflective faces, and a height H of each of the fine protrusions is given by the following expression (1): H=A ×(λ/2 n ) expression (1) where n denotes an average refractive index of parts forming the fine protrusions and A denotes an arbitrary value in a range of 0.6 to 1.4, each of the diameter D of the circle and the diameter D of the circumscribing circle is less than or equal to 380 nm, the pitch is less than or equal to 380 nm, and the height H of each of the fine protrusions is in a range of 160 nm to 350 nm.