Patent ID: 6390629
Filing Date: 2002-05-21
Classification: G02B

Abstract:
A triangular-pyramidal cube-corner retroreflective sheeting characterized in that triangular-pyramidal cube-corner retro-reflective elements protruded beyond a common base plane (X-Xâ€²) are faced each other and arranged on the base plane (X-Xâ€²) in the closest-packed state by sharing one base edge on the base plane (X-Xâ€²), the base plane (X-Xâ€²) is a common plane including many base edges (x, x, . . . ) shared by the triangular-pyramidal reflective elements, the two triangular-pyramidal reflective elements faced each other constitute an element pair having substantially same shape faced so as to be respectively substantially symmetric to planes (Y-Yâ€², Y-Yâ€², . . . ) vertical to the base plane (X-Xâ€²) including many shared base edges (x, x, . . . ) on the base plane (X-Xâ€²), the triangular-pyramidal reflective elements are constituted of substantially same hexagonal or triangular lateral faces (prism faces) (faces c1 and c2) using the shared base edges (x, x, . . . ) as one sides and substantially same quadrangular lateral faces (faces a1 and b1 and faces a2 and b2) substantially orthogonal to the face c1 or the face c2 by using two upper sides of the face c1 or c2 starting with apexes (H1 and H2) of the triangular-pyramidal reflective elements as one sides and sharing one ridge line of the triangular-pyramidal reflective elements and using the ridge line as one side, and when assuming the height from the apexes (H1 and H2) of the triangular-pyramidal reflective elements up to the base plane (X-Xâ€²) including the base edges (x, x, . . . ) of the hexagonal or triangular lateral faces (faces c1 and c2) of the triangular-pyramidal reflective elements as (h), the height from the apexes (H1 and H2) of the triangular-pyramidal reflective elements up to a substantially horizontal plane (Z-Zâ€²) including base edges (z and w) of other lateral faces (faces a1 and b1 and faces a2 and b2) of the triangular-pyramidal reflective elements as (h0), the intersection between a vertical line from the apexes (H1 and H2) of the triangular-pyramidal reflective elements to the base plane (X-Xâ€²) and the base plane (X-Xâ€²) as P, the intersection between an optical axis passing through the apexes (H1 and H2) and the base plane (X-Xâ€²) as Q, and moreover, expressing distances from the intersections (P) and (Q) up to planes (Y-Yâ€², Y-Yâ€², . . . ) including the base edges (x, x, . . . ) shared by the triangular-pyramidal reflective elements and vertical to the base plane (X-Xâ€²) as p and q, and assuming the angle formed between the optical axis and the vertical plane (Y-Yâ€²) as (&thgr;), the above h and h0 are not substantially equal and meet the following expression (1) 0.5&it;â€ƒ&it;R&LessFullEqual;hh0&LessFullEqual;1.5&it;â€ƒ&it;R(1)(In the above expression, R has a value defined by the following expression.) R=sin&it;(35.2644*-Î¸)+1.2247&it;sin&it;â€ƒ&it;Î¸sin&it;(35.2644*-Î¸)(In the above expression, it is assumed that when the value of the above (pâˆ’q) is negative, &thgr; takes a negative (âˆ’) value).