The Post Office

Berkeley Michael Ferro

Aubrey Douglas Walker

Rodney Edwin Spratling

A credential, such as a passport or an identification card, is provided, for example by impregnation or coating, with a phosphorescent composition which includes at least two phosphorescence activators which exhibit different emission characteristics both with respect to wavelength and lifetime so that, when the composition is irradiated, the initial afterglow changes color, for example from green to blue.

Identification matter

A method of rendering a surface, especially a paper surface, phosphorescent, in which a composition comprising a phosphorescence activator and a soluble condensation product of formaldehyde and an amino compound is applied to the surface and is allowed to react in situ to form a phosphorescent insoluble condensation product. The composition may, for example, be in the form of a printing ink or a paper-coating mix.

Phosphorescent materials

Phosphorescent materials and solutions suitable for their preparation, the solutions comprising a phosphorescence activator and a soluble condensation product capable of further reaction to form an insoluble condensation product, the latter being one that does not absorb ultraviolet radiation in the absorption range of the activator.

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Barnehurst, United Kingdom

Berkeley Michael Ferro