Product Code: ICA10_P139

Color Change in Laser Cutting of Paper Material
Authors:
Alexander Stepanov, Lappeenranta University of Technology, Faculty of Technology, Laser Processing Research Group (Laboratory of Welding Technology and Laser Processing); Lappeenranta Finland
Heidi Piili, Lappeenranta University of Technology, Faculty of Technology, Laser Processing Research Group (Laboratory of Welding Technology and Laser Processing); Lappeenranta Finland
Antti Salminen, Lappeenranta University of Technology, Faculty of Technology, Laser Processing Research Group (Laboratory of Welding Technology and Laser Processing); Lappeenranta Finland
Presented at ICALEO 2010

Laser technology has been developed for cutting of paper materials in the middle of 1970s. Because of high cost of equipment and maintenance and complicity of the systems the laser technology has been applied in paper industry only in 1990s. During its development in the field of processing with different wood-based materials laser technology was confronted with problem of color change in the area of interaction between laser beam and paper material.

The main problems in laser cutting of paper are yellowing and carbonization of the cutting edge. It is commonly known from paper technology that lignin is the main cause of color change. Due to its optical characteristics lignin is a good absorber of light compared to other wood compounds like cellulose and hemicelluloses. But structure of lignin is still unresolved nowadays and only few studies has concentrated on the phenomena of interaction between laser beam and paper material.

The aim of this study was to clarify the nature of color change of the samples which were exposed to influence of light with different wavelength after cutting. CO2 laser was employed to carry out cutting of paper material samples. This choice was caused by its high suitability for cutting of wood based materials. CO2 laser operated with wavelength of 10.6 nm which can be easily absorbed by paper material. The experimental part covers measurement of optical characteristics of the samples after laser treatment as well as during 21 day storage time. The effect of laser parameters, such as laser power and cutting speed, was considered.