LUMINESCING INKS AND USE OF SUCH INKS IN CODING AND OTHER MARKING OPERATIONS

摘要

Coding of items of mail is achieved to good effect irrespective of the moisture content of the mail and/or ambient relative humidity by applying to at least one part of the surface a composition comprising both phosphorescence activation means and fluorescence activation means such that exposure of the surface to ultraviolet light will lead to an emission of detectable phosphorescence to an extent which will depend upon the amount of moisture at the surface. Fluorescence will be activated irrespective of moisture content. Preferably red phosphorescence and red fluorescence are manifested.