Antireflection structure and manufacturing method thereof

An antireflection structure comprising:

• a transparent substrate (B) having a plurality of holes (Hn) with U-shaped or V-shaped cross-sectional shapes in a direction perpendicular to a flat surface portion thereof, and
• a metal oxide film disposed on a surface portion (S) of the transparent substrate (B) and in space portions (Cn) formed in an upward direction from bottom portions of the holes (Hn) of the transparent substrate (B),
• wherein each of the holes (Hn) has a geometry in which an average diameter (m) of openings of the holes (Hn) is 50 nm to 300 nm, an average distance (k) between center points of the openings of adjacent holes (Hn) is 100 nm to 400 nm, and a depth (dn) of each hole (Hn) from the surface portion (S) is 80 nm to 250 nm,
• a thickness (tn) of the metal oxide film disposed in each of the space portions (Cn) increases as the depth (dn) of each of the holes (Hn) becomes larger so that differences in depth (fn) between the respective holes (Hn) from an uppermost surface portion (Sm) of the metal oxide film disposed on the surface portion (S) to a surface portion of the metal oxide film in the space portion (Cn) are reduced, and
• the metal oxide film disposed on the surface portion (S) of the substrate (B) is a thin film, and the metal oxide film disposed in the space portion (Cn) in an upper direction from the bottom of each hole (Hn) is a fibrous columnar film.