Abstract: Projection row (2) and recess row (3) are alternately and successively formed in a direction (Y-direction) perpendicular to a direction (X-direction) of their rows, thereby forming a corrugated cross-sectional shape of a cross-sectional wave shape. Between projection row (2) and recess row (3), there is provided inclined wall surface (4) having a wave shape in plan view. Each of projection row (2) and recess row (3) has a shape in a cross-section along X-direction that is formed into a corrugated cross-sectional shape of a wave shape. Pitch and height difference between valley portion (5) and crest portion (6) in the corrugated cross-sectional shape along this X-direction are smaller, as compared with a relationship between projection row (2) and recess row (3) in the corrugated cross-sectional shape along Y-direction.

Abstract: Projection row (2) and recess row (3) are alternately and successively formed in a direction (Y-direction) perpendicular to a direction (X-direction) of their rows, thereby forming a corrugated cross-sectional shape of a cross-sectional wave shape. Between projection row (2) and recess row (3), there is provided inclined wall surface (4) having a wave shape in plan view. Each of projection row (2) and recess row (3) has a shape in a cross-section along X-direction that is formed into a corrugated cross-sectional shape of a wave shape. Pitch and height difference between valley portion (5) and crest portion (6) in the corrugated cross-sectional shape along this X-direction are smaller, as compared with a relationship between projection row (2) and recess row (3) in the corrugated cross-sectional shape along Y-direction.