Product Code: ICAL09_P112

Interaction Between Laser Beam and Paper Materials
Authors:
Heidi Piili, Lappeenranta University of Technology, Laser Processing Research Group (Laborato; Lappeenranta Finland
Antti Salminen, Lappeenranta University of Technology, Laser Processing Research Group (Laboratory of Welding Technology and Laser Processing), Lappeenranta, Finland; Lappeenranta Finland
Veli Kujanpää, Lappeenranta University of Technology, VTT Industrial Systems; Lappeenranta Finland
Presented at ICALEO 2009

It is commonly known that laser beam is suitable for cutting of paper materials. Even tough laser technology has been applied to paper material cutting since 1970s, there exists quite little published research work about issue. Purpose of this literature review is to give comprehensive point of view about interaction between laser beam and paper materials by examining the issue from different aspects:
Optical phenomena of interaction
Absorption phenomena of interaction
Thermo-chemical phenomena of interaction

When realised that paper materials is a miniature 3D net structure consisting fibres, pores and small pigment particles, it can be foreseen that there are many optical boundaries and surfaces inside material that seems to have even smooth surface for outside observer. Actually paper is optically much more complicated than a metal surface. That is why interaction of laser light can transmit, reflect, scatter, refract, diffract, absorb etc., when it interacts with paper material and the phenomena happens both on surface and inside the structure. There exist only a few articles of laser absorption of paper materials. Problem is that they concentrate in visible wavelength range and usually the used power is low. Based on literature, it was found that paper materials have absorption maximum in wavelength ranges of around 3 µm and 8-10 µm. It is also important to understand what happens to paper material in high temperatures. Chemical mechanism of thermal decomposition of cellulose (basic component of paper materials) in laser processing is called pyrolysis; solid cellulose decomposes in high temperatures and absence of oxygen into small volatile compounds, like COx, water and furanes.