A laser printer is a common type of printer which is most often seen in offices. A laser printer produces a high quality finish and can print many pages quickly. Colour printers normally use xerographic printing processes, just like a photocopier does.

The page to be printed is stored in the laser printer’s memory. An electrostatic charge is applied onto the photoconductor unit in the laser printer. A laser is then aimed at the photoreceptor in the form of the image that needs to be printed. Where the light falls, the charge is reversed on the photoconductor unit. This creates an electrostatic image on the photoreceptor surface.

Laser printer toner has a negative charge. When applied to the photoreceptor surface, it sits in the pattern of the image thanks to the laws of attraction and repulsion in electrostatic forces. The photoreceptor is then pressed onto a sheet of new paper, thus transferring the image. Heat and pressure is then applied to melt the toner so that it bonds to the paper. The photoreceptor is then cleaned with a soft, plastic blade and the laser printer is then ready to start printing the next sheet of paper.

Colour laser printers add coloured toner in three additional passes. These additional stages mean that printing with a laser printer can sometimes cause slight misalignments between the printer passes, which can make the image slightly blurred or streaked.

Modern laser printers leave a near-invisible pattern of dots on every sheet of paper they print. These dots are yellow and are around 0.1mm in size. These dots are to help uniquely identify each laser printer in case counterfeits are found. The dots are said to encode printing date, time and serial number in binary format.

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