How Laser Printers Work

A laser printer is one of the most common printers used today, especially within businesses small and large due to its capability to rapidly produce high quality text and graphics. But while you know what a laser printer is, do you know how it actually works? There are a few basic scientific principles behind the laser printing process and they explain the great advantages to using a laser printer.

A laser printer obviously uses a laser to print, but how does it get the image on a sheet of paper? Laser printers use the process of electro photography whose primary principle at work is static electricity. Since oppositely charged atoms are attracted to each other, objects with opposite static electricity will cling together. Laser printers use a revolving drum, or photoreceptor, made out of highly photoconductive material that is discharged by light photons. The photoconductor, a photosensitive surface, is uniformly charged by a wire with an electrical current running through it, called the charge corona wire, with static electricity. The printer then beams a laser across the surface of the drum and projects an image of the page to discharge certain points. The laser is essentially "drawing" the letters and images to be printed as a pattern of electrical charges.

Afterwards, the toner, a fine powder, is spread over the surface of the drum and only adheres to the charged areas, which is how the latent design or image becomes visible. Next, the sheet of paper rolls along a belt and is given a negative charge by the corona wire. The paper is charged opposite to the toner since the toner has a positive charge. With the toner powder affixed, the drum rolls over a sheet of paper. The negative charge of the paper is strong enough to pull the toner pattern away. Also, since the paper and the drum move at the same speed, the image pattern is picked up exactly as it was "written." In order to keep the paper from clinging to the drum, it is discharged by the detac corona wire right after picking up the toner.

To permanently fix the transferred image to the paper, the toner is fused with pressure and heat. To do this the paper is quickly passed through the fuser, which is a pair of heated rollers. The printer then cleans all of the excess toner and electrostatic charges from the photoconductor to make it ready for the next print job. The printer cleans itself through the heat actually melting loose toner powder away and by passing the paper through the discharge lamp which exposes the entire photoreceptor thereby erasing the electrical image. After these steps, the paper then rolls out onto the output tray ready for pick up.

Due to the unique method of exposition and formation, laser printers and color laser printers have many significant advantages over other types of printers. Laser printers offer the best print quality and highest resolution and have the ability to print up to 200 monochrome pages per minute. Laser printer speed depends upon the printer model and the graphic intensity of the job being printed. However, the bottom line is that laser printers are much faster than inkjet printers due to their unique process. This makes them ideal for users with heavy printing needs, whether they are monochrome text documents or multiple-page documents loaded with text, charts and images.

The first commercial implementation of a laser printer was by IBM with the model 3800 in 1976, but the first mass market laser printer was through the combined efforts of HP and Canon. While HP printers and Canon printers were first to the laser printer consumer market, Brother printers, IBM printers and others quickly followed and overtime dropped significantly in price.