Retroreflective sheet comprising microspheres, the diameter and refractive index of which being specifically related to the refractive indices of layers directly in contact therewith

Abstract

A retroreflective sheet capable of exhibiting an excellent decorative effect during both daytime and nighttime, and particularly an excellent rainbow-colored decorative effect. The sheet comprises, in order, a binder in the back side of which a plurality of microspheres, arranged in a monolayer, are partially embedded, a focusing layer underlying some of the microspheres, and a reflective layer underlying the focusing layer and underlying microspheres which do not have a focusing layer therebehind. The focusing layer has a film thickness selection coefficient x in the range of 0.16 to 0.95 as defined by equation (II) of the following equations (I) and (II): ##EQU1## wherein f is the coefficient for the optimum layer thickness of the layer, d is the diameter of the microspheres, h is the thickness of the focusing layer, n.sub.b is the refractive index of the binder layer, n.sub.g is the refractive index of the microspheres, and n.sub.s is the refractive index of the focusing layer.

Dependencies are inferred from the claim text.