Developer powder for magnetographic printing

摘要

Developer powder comprising fine dry particles each having a magnetic core coated with a substance having a defined m.pt. in a first range of around 120 deg C, a powdered fluidising agent and a luminescent pigment which luminesces in a desired colour upon exposure to UV. The pigment has a m.pt. in a second range of around 120 deg C. Pref. the final material contains 5-80 wt. % magnetic particles and 40-60 wt. % thermoplastic resin. Pref. the fluidising agent is silica used in an amt. of 0.01-10 wt. %; the lubricant is pref. PTFE used in an amt. of 0.01-10 wt. %; and the conductive and contrasting agent is eg carbon black or SnO2 used in an amt. of 0.01-10 wt. %.