Increasing the marking speed is of growing importance for the packaging industry. For this reason it was necessary to investigate the potential of micro mirror devices (MMDs) in combination with well absorbed and short-pulsed UV-excimer laser beams.
The advantage of this new marking technique in comparison with conventional processes is the ability to generate the finest markings by one laser pulse so the marking speed is only limited by the pulse frequency of the laser. Computer-controlled micro mirror arrays bring highest flexibility into the marking process: within only one laser pulse (typical 30 … 40 ns), up to millions of pixels can be transferred to the material.
The Fraunhofer Institute for Material and Beam Technology (Fh IWS) in Dresden / Germany has developed a laser marking process on the basis of a phase-shifting micro mirror device from Fraunhofer Institute for Microelectronic Circuits and Systems (Fh IMS) and a 308nm excimer laser. We have devised an optical system for applying the mask projection technique in combination with the MMD a as reflective mask. The technique was tested on different materials relevant for the packaging industry such as paper and plastic foil.
Although the available fluence is limited by the MMD specifications we obtained clear high- contrast and high-accuracy markings due to matched projection demagnification factor.
Our studies lead us to the result that using MMDs in combination with short wavelength and short pulse lasers is a suitable and reasonable method for very fast direct marking of packaging relevant materials.