Direct Laser Synthesis of Functional Coatings by FEL Treatments

Abstract

The printing industry is a growing market for laser applications with a wide spectrum of different kinds of lasers having been established. This paper focuses on the precise micro structuring of gravure, flexo, and embossing print forms by direct laser ablation. The principle of gravure printing is the direct ink transfer from an ink source to the print substrate by small 3-dimensional cells engraved into the surface of a cylinder. Direct laser engraving into metallic cylinders is performed with a high power Q-switched Nd:YAG laser system tuned for high reproducibility and stability of the mean pulse energy (σ 2  < 1%). An exact modulation technique allows fast variation and precise calibration of the energy of each single laser pulse as well as active modulation of the intensity profile of the beam. This method permits to set diameter and depth of each cell independently from pulse to pulse at a rate of 70 kHz. The aspect ratio and the shape of each single cell can therefore be defined freely for each laser pulse controlled by digital image data. Thus the cell shape can be optimized for the best ink transfer characteristic on different print substrates.