Laser drilling of banknote substrates

Abstract

In banknote production, several security features are introduced into banknotes, including perforation of organic substrates like paper, polymer or their composites. This paper describes a comparative study about efficiency and quality aspects of laser drilling processes of organic substrates with different laser systems. The substrates investigated are cotton-based paper, Guardian™ (Biaxially Oriented Polypropylene) and two composite substrates composed of cotton paper and polymer (Durasafe™ and Hybrid™). The used laser wavelengths are 515 nm, 1060/1070 nm and 2940 nm. Laser systems with pulse durations covering the ultra-short pulse regime (ps), nanosecond pulses (ns) and microsecond pulses (µs) were used. This article gives an overview of this topic, deals with the tasks and challenges in this special field of laser manufacturing and compares different laser systems with respect to drilling quality and energy specific volume.