| 摘要 |
A triangular pyramidal cube corner retroreflection sheet improved in a high- intensity property, an optical characteristic desired for the sheet, and in a wide angle property such as an observation angle characteristic, an incident angle characteristic and a rotation angle characteristic, wherein an inclined surface (c-surface) using as one side thereof a bottom side (x) of opposing triangular pyramidal reflection elements which share one bottom side (x) on a bottom surface (X-X') and are disposed in a closest packing manner on the bottom surface forms a pentagonal or triangular shape, and other two surfaces (a-surface, b-surface) sharing one ridge line starting at the apex (H) of the triangular pyramidal reflection element form a quadrangular shape, characterized in that, when a height from the apex (H) to the bottom surface (X-X') is (h), a height up to a substantially horizontal surface (Z-Z') including the bottom sides (z, w) of the other two surfaces (a-surface, b- surface) is (h0) and an angle formed by an optical axis of the triangular pyramidal reflection element and a plane (Y-Y') including the bottom side (x) and perpendicular to the bottom surface (X-X') is (.theta.), h and h0 are not substantially equal and h/h0 and .theta. satisfy a specific relational expression.
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