| 摘要 |
A security document ( 1 ) comprises a substrate ( 10 ) including at least one layer of. polymeric material ( 12, 26 ) and containing an upconverting fluorescent material ( 18 ), and at least one coating ( 14 ) containing a refractive pigment applied to the substrate ( 10 ). When the security document is exposed to electromagnetic radiation of a particular wavelength, e.g. infra-red, the upconverting material ( 18 ) emits a signal of electromagnetic radiation of a shorter wavelength, e.g. visible light, and the coating ( 14 ) containing the refractive pigment enhances the signal. |
