PLANCHETTES CONTAINING INCONSTANT PIGMENT OR DYE FOR SECURE ARTICLE

摘要

The present invention describes planchettes incorporated into the substrate of secure articles, such as bank notes, passports and tax stamps. These planchettes may take various forms (such as fibers), regular shapes (such as circles), irregular shapes (such as polygons) or as threads or stripes running throughout the length of the document and are colored with an ultra color inconstant pigment or dye, or a non-color inconstant pigment or dye, or combination thereof. Ultra color inconstant pigments and dyes appear as markedly different colors under light sources with differing spectral distributions. The planchettes are coated with an ink containing a color inconstant pigment and function as a method of authenticating the document. When the light source that the article is viewed under is changed, the planchettes change color at the same time. The effect is striking and proves the document to be genuine. This allows for facile authentication without the need of complex or costly equipment. The bulk of the substrate may also be colored to match the appearance of the planchettes under one illuminant, so that they only become visible when the spectral characteristics of the light source are changed.