| 摘要 |
<p>Within an area of substantially regular hexagons arranged at regular intervals on an imaginary reference plane, a concave-convex section 20 has a basic pattern in which one first region A1 is surrounded by six second regions A2 and the basic pattern repeats in regular intervals in lateral and longitudinal directions on the plane. The concave-convex section 20 has a shape that provides first protruding portions 21 and second protruding portion 22, which protrude in opposite directions from each other in the thickness direction in the first regions and the second regions, respectively. The first protruding portions 21 have a hexagonal pyramidal shape or a truncated hexagonal pyramidal shape, which protrudes on one side in the thickness direction with an outer contour line of the first region on the reference plane serving as a base portion, and the second protruding portions 22 have a hexagonal pyramidal shape or a truncated hexagonal pyramidal shape, which protrudes on the other side in the thickness direction with an outer contour line of the second region on the reference plane serving as a base portion.</p> |
