TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: In the optical element: a hydrophilic surface layer is provided on the main surface of the base, where the hydrophilic surface layer contains at least one of a hydrophilic resin and a metal oxide having hydrophilicity; the thickness of the hydrophilic surface layer is equal to or less than an arrangement pitch of the structures; and the hydrophilic surface layer is formed by curing a polysilazane compound. The hydrophilic resin is a compound having at least one hydrophilic group and at least one of methacryloyl group, where the hydrophilic group is hydroxyl, carboxyl, cyano or amide group. The metal oxide is at least one of silica, titania, zinc oxide and strontium titanate.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: In the optical element: the structures are arranged to form many rows of tracks on the main surface of the base and form a hexagonal lattice pattern, a quasi-hexagonal lattice pattern, a tetragonal lattice pattern, or a quasi-tetragonal lattice pattern; each of the structures have an elliptical cone shape or a truncated elliptical cone shape, and the major axis direction of the structures is a direction in which the tracks extend; a filling factor of the structures to the main surface of the base is greater than or equal to 65%; when an arrangement pitch of the structures in the same track is represented by P1 and the diameter of the bottom surface of each of the structures in a direction in which the tracks extend is represented by 2r, the ratio ((2r/P1) x 100) of the diameter 2r to the arrangement pitch P1 is greater than or equal to 85% and the ratio (((2 x 2r)/P1) x 100) of the double of the diameter 2r to the arrangement pitch P1 is greater than or equal to 127%; a contact angle of the main surface of the base to oleic acid is less than or equal to 30 degrees ; the main surface of the base is subjected to a corona treatment or a plasma treatment; the structures are arranged to form many rows of linear tracks and form a quasi-hexagonal lattice pattern, and a height or a depth of each of the structures in the direction in which the tracks extend is smaller than a height or a depth of each of the structures in a row direction of the tracks; the structures are arranged to form many rows of linear tracks and form a tetragonal lattice pattern or a quasi-tetragonal lattice pattern, and a height or a depth of each of the structures in an arrangement direction that is slanted with respect to the direction in which the tracks extend is smaller than a height or a depth of each of the structures in the direction in which the tracks extend; the structures form a hexagonal lattice pattern or a quasi-hexagonal lattice pattern on the main surface of the base, and when an arrangement pitch of the structures in the same track is represented by P1 and an arrangement pitch of the structures between two adjacent tracks is represented by P2, the ratio P1/P2 is greater than 1 to 1.1; the structures form a tetragonal lattice pattern or a quasi-tetragonal lattice pattern on the main surface of the base, then the ratio P1/P2 is greater than 1.4 to 1.5; and an arrangement pitch P1 of the structures in the same track is longer than an arrangement pitch P2 of the structures between two adjacent tracks. EXAMPLE - Glass roll master having an outer diameter of 126 mm was prepared. Photoresist was diluted to 1/10 with a thinner, and the diluted resist was then applied onto the columnar surface of the glass roll master by dipping so as to have a thickness of 130 nm to form a film of the resist. Then, the glass master serving as a recording medium was transferred to the roll master exposure apparatus and the resist was exposed, thus patterning latent images in the resist, where the latent images were arranged in the form of a single spiral and forming a hexagonal lattice pattern in three adjacent tracks. Specifically, an area where the hexagonal lattice pattern was to be formed was irradiated with a laser beam of 0.5 mW/m and thus forming a recess-shaped hexagonal lattice pattern. Then, development treatment was performed on the resist formed on the glass roll master to dissolve the resist located in the exposed portions, thus conducting development. Then, a resist glass master having a resist layer in which openings were formed in a hexagonal lattice pattern was prepared and the plasma etching was conducted in a trifluoromethane gas atmosphere using roll plasma etching. Then, on the surface of the glass roll master, the etching proceeded in only portions of the hexagonal lattice pattern exposed from the resist layer, and the other areas were not etched because the photoresist functioned as a mask. Thus, recesses each having an elliptical cone shape were obtained. Then, the photoresist was completely removed by oxygen ashing to prepare a moth-eye glass roll master having a recess-shaped hexagonal lattice pattern. An acrylic sheet onto which an ultraviolet-curable resin was applied was brought into close contact with the moth-eye glass roll master, and was then detached while conducting curing by applying ultraviolet light, to give an optical element in which an irregular surface having structures (surface having a moth-eye structure) was formed on its main surface.