Optimization of Paper Discoloration via Pyrolysis Using Lasers

Abstract

Printing ink is a main component of the modern printer, and it has always been throughout the history of printing. Ink and toners are expensive replaceable components that inkjet and laser printers cannot function without. The digital printing industry, which is majorly composed of monochrome printing, is expected to increase by 225% by 2024 from a 2013 baseline (Smithers et al., 2014). Expenses aside, toner cartridges and ink cartridges pose an overlooked threat to the environment. Manufacturing, packaging, transporting, and waste disposal of printer ink and toners result in carbon dioxide emissions. The complete elimination of ink in monochrome printing is potentially viable with the patented new discoloration technique. The patent studies a discoloration method by carbonizing a paper’s surface (Alhashem et al., 2015). The printing method optimizes surface paper pyrolysis via laser heating. The aim is obtaining the darkest possible shade without compromising paper quality. The challenge is in creating a printed area from the paper material itself, rather than depositing ink on paper.

A 75-watt CO2 laser engraving machine emitting a 10.6 μm wavelength beam for heating is used with low power settings to carbonize a fraction of the paper surface. The carbonization is essentially a combustion reaction. Solid fuel burns in three stages: drying, devolatilization (pyrolysis, or distillation phase), and lastly, the char (charcoal) combustion. These stages are driven by heat from the CO2 laser. Moving the laser rapidly above the paper surface arrests the reaction at the second stage, after the formation of blackened char. The control variables in the experimental method are laser power, speed, and the vertical position that affects the laser intensity. Computer software controls these variables. The discoloration of paper is quantified by measuring the light absorptivity using a UV-Vis-IR Spectrometer.