The Identification Of Laser Printer Toner

Laser print has been widely used nowadays for it is convenient, formal, neat and clear.The printer files have replaced writing files in many fields such as contracts,agreements, bills, certificates. However, the printer is illegally used sometimesthrough changing or forging documents and so on. Therefore, it is necessary toanalyze and inspect the computer-printed documents to find out its source, printedtime and relevant information as an evidence of suspect or commit.Toner is the main substance on the printer paper, so identification of toner componentson paper is the most important content of the document examination. Ramanmicro-spectroscopy(Raman), infrared spectroscopy(IR), scanning electron microscopecombined with electron spectroscopy (SEM/EDS) and pyrolysis-gaschromatography/mass spectrometry (Py-GC/MS) are performed to detect the33kindsof powder samples, including23popular brands of laser printer special toner and10brands of universal toner.The results showed that the23special toners could be classified into11categoriesand10universal toners could not be distinguished by Raman in785nm because of arelatively weak signal response of the toner in Raman. By IR the23samples could beclassified into6categories and10universal toners could be classified into twocategories according to their characteristics infrared absorption, in addition, itindicated that one of the toner composition is a hot melt resin material, includingpolystyrene resin, acrylate, or epoxy through searching the IR spectrum library. Themicroscopic structure of the toner particles on the paper can be observed by SEM/EDS and there are no evident structure difference among all the samples while all the33samples can be distinguished from each other through qualitative and quantitativedetermination of the elements composition of the toner. The Py-GC/MS can provide alot of information about the toner by detecting its pyrolysis products. Around74%ofthe special toners and80%of the universal toner can be distinguished by Py-GC/MS.The four methods are all effective with little sample consume, Raman and SEM/EDScan also supply a non-destructive determination of toners on documents. The fourmethods were combined to distinguish all the toner samples in the paper.