Method of making retrochromic beads and kit thereof

#The present invention relates generally to retroreflective beads that cause a change in color of retroreflected light, methods of making same, and articles containing same.

#“Retroreflectivity” means the ability, if engaged by a beam of light, to reflect that light substantially back in the direction of the light source. Films, for example, transparent adhesive-backed overlay films, having covert retroreflective patterns have been used to authenticate security articles (e.g., passports, identification badges). Typically, such overlay films have covert retroreflective patterns that are not readily legible under conditions of diffuse illumination, but become readily legible if viewed in retroreflective mode (e.g., with a flashlight or specialized device such as a retroviewer).

#Depending on the application, the addition of covert color to retroreflective articles may provide additional security features (e.g., as in the case of authentication of passports or identification badges), or novel visual effects (e.g., as used in the design and production of graphic articles).

#FIG. 1 is a cross-sectional representation of a Type I retrochromic bead depicting exemplary paths of retroreflected light.

#FIG. 2 is a flow diagram of an exemplary process, according to the present invention, for making Type I retrochromic beads.

#Intrinsically retrochromic beads may, for example, be of at least two types, referred to herein as Type I and Type II intrinsically retrochromic beads.

#Type I Intrinsically Retrochromic Beads

#Referring now to FIG. 1, a Type I intrinsically retrochromic bead 100 comprises a transparent substantially spherical core 110 having thereon a concentric optical interference layer 120 having an exterior surface 125. Core 110 contacts optical interference layer 120 at interface 115.