Patent ID: 6883921

Claim:
A retroreflective device in which a large number of complex cube-corner retroreflective elements are arranged in closest-packed state, each of said complex cube-corner retroreflective elements having a first and second triangular-pyramidal retroreflective units and at least one tetrahedral retroreflective unit, characterized in that the three reflective lateral faces (a 1 , b 1 , c 1 and a 2 , b 2 , c 2 ) of each of the first and second triangular-pyramidal retroreflective units form mutually perpendicular cube-corner reflective surfaces, respectively, the first reflective lateral face (f 11 ), the second reflective lateral face (e 11 ) and the third reflective lateral face (g 11 ) of said at least one tetrahedral retroreflective unit form a mutually perpendicular cube-corner reflective surfaces, said first reflective lateral face (a 1 ) of the first triangular-pyramidal retroreflective unit is on the same plane with the first lateral face (f 11 ) of said tetrahedral retroreflective unit, said second reflective lateral face (b 1 ) of the first triangular-pyramidal retroreflective unit is on the same plane with the second lateral face (e 11 ) of said tetrahedral retroreflective unit, said complex cube-corner retroreflective element has a quadrangular circumference defined by mutually parallel y-lines and mutually parallel z-lines, said complex cube-corner retroreflective element has a substantially symmetrical V-shaped groove with its center line x-x′ passing through the points of intersection of said parallel y-lines and parallel z-lines, the third reflective lateral face (c 1 ) of said first triangular-pyramidal retroreflective unit is parallel to one of the two lateral faces (g 11 ) forming said V-shaped groove, the third reflective lateral face (c 2 ) of said second triangular-pyramidal retroreflective unit is identical with, or parallel to, the other (g 21 ) of the two faces forming said V-shaped groove, and the third reflective lateral face (g 11 ) of said tetrahedral retroreflective unit is same as one of the two faces forming said V-shaped groove.