A segmented core (1) for molding of an impeller (12), especially a pump impeller, includes at least three segments (2). All of the segments (2) have the same form and each segment (2) has connecting devices (3, 3) for connecting the segment (2) with the adjacent segments (2). A method for molding an impeller (12) includes the steps of: providing a molding tool (14), providing a core (1) including at least three identical segments (2), which include the connection portions (3, 3) for connecting the segment (2) with the adjacent segments (2); assembling of the core (1); placing the core (1) in the molding tool (14); molding the impeller (12), ejecting the core (1) and the impeller (12) out of the molding tool (14); and removing the core (1) from the impeller (12).

A fine concavo-convex structure product (10) is provided with an etching layer (11), and a resist layer (12) comprised of a heat-reactive resist material for dry etching provided on the etching layer (11), a concavo-convex structure associated with opening portions (12a) formed in the resist layer (12) is formed in the etching layer (11), a pattern pitch P of a fine pattern of the concavo-convex structure ranges from 1 nm to 10 m, a pattern depth H of the fine pattern ranges from 1 nm to 10 m, and a pattern cross-sectional shape of the fine pattern is a trapezoid, a triangle or a mixed shape thereof. The heat-reactive resist material for dry etching has, as a principal constituent element, at least one species selected from the group consisting of Cu, Nb, Sn, Mn, oxides thereof, nitrides thereof and NiBi.

A fine concavo-convex structure product (10) is provided with an etching layer (11), and a resist layer (12) comprised of a heat-reactive resist material for dry etching provided on the etching layer (11), a concavo-convex structure associated with opening portions (12a) formed in the resist layer (12) is formed in the etching layer (11), a pattern pitch P of a fine pattern of the concavo-convex structure ranges from 1 nm to 10 m, a pattern depth H of the fine pattern ranges from 1 nm to 10 m, and a pattern cross-sectional shape of the fine pattern is a trapezoid, a triangle or a mixed shape thereof. The heat-reactive resist material for dry etching has, as a principal constituent element, at least one species selected from the group consisting of Cu, Nb, Sn, Mn, oxides thereof, nitrides thereof and NiBi.

A fine concavo-convex structure product (10) is provided with an etching layer (11), and a resist layer (12) comprised of a heat-reactive resist material for dry etching provided on the etching layer (11), a concavo-convex structure associated with opening portions (12a) formed in the resist layer (12) is formed in the etching layer (11), a pattern pitch P of a fine pattern of the concavo-convex structure ranges from 1 nm to 10 m, a pattern depth H of the fine pattern ranges from 1 nm to 10 m, and a pattern cross-sectional shape of the fine pattern is a trapezoid, a triangle or a mixed shape thereof. The heat-reactive resist material for dry etching has, as a principal constituent element, at least one species selected from the group consisting of Cu, Nb, Sn, Mn, oxides thereof, nitrides thereof and NiBi.