Luminescent taggant compositions, luminescent materials including the same, and articles including the same

A luminescent material comprising:

• a medium;
• a first luminescent taggant disposed in the medium and comprising a first emitting ion, wherein the first luminescent taggant produces a first emission in a first taggant emission band when exposed to excitation energy;
• a second luminescent taggant disposed in the medium and comprising a second emitting ion different from the first emitting ion, wherein the second luminescent taggant produces a second emission in a second taggant emission band that is different from the first taggant emission band when exposed to excitation energy;
• and
• a third luminescent taggant disposed in the medium and comprising the first emitting ion and the second emitting ion;
• wherein the first luminescent taggant is substantially free of the second emitting ion and the second luminescent taggant is substantially free of the first emitting ion;
• wherein the first emitting ion and the second emitting ion are independently chosen from neodymium, ytterbium, erbium, thulium, or holmium;
• and
• wherein each luminescent taggant includes at least a host material, the respective emitting ion(s), and optionally a sensitizing ion, whereby production of radiation by the luminescent taggants is accomplished by absorption of incident radiation by the emitting ion(s) or by either or both the host material and the optional sensitizing ion(s). energy transfer from the host material/sensitizing ion(s) to the emitting ion(s), and radiation of the transferred energy by the emitting ion(s).

An article comprising:

• a substrate;
• and
• an authentication feature on a surface of the substrate or integrated within the substrate, wherein the authentication feature comprises:
• a first luminescent taggant comprising a first emitting ion, wherein the first luminescent taggant produces a first emission in a first taggant emission band when exposed to excitation energy;
• a second luminescent taggant comprising a second emitting ion different from the first emitting ion, wherein the second luminescent taggant produces a second emission in a second taggant emission band that is different from the first taggant emission band when exposed to excitation energy;
• and
• a third luminescent taggant comprising the first emitting ion and the second emitting ion;
• wherein the first luminescent taggant is substantially free of the second emitting ion and the second luminescent taggant is substantially free of the first emitting ion;
• wherein the first emitting ion and the second emitting ion are independently chosen from neodymium, ytterbium, erbium, thulium, or holmium;
• and
• wherein each luminescent taggant includes at least a host material, the respective emitting ion(s), and optionally a sensitizing ion, whereby production of radiation by the luminescent taggants is accomplished by absorption of incident radiation by the emitting ion(s) or by either or both the host material and the optional sensitizing ion(s), energy transfer from the host material/sensitizing ion(s) to the emitting ion(s), and radiation of the transferred energy by the emitting ion(s).