xerografiamenetelmää

Xerography is a dry copying process in which electrostatically charged powder adheres to areas of an electrostatically charged surface that have been exposed to light. This process is the basis for most modern photocopiers and laser printers. The term "xerography" is derived from the Greek words xeros (dry) and graphein (to write).

The xerographic process begins with a light-sensitive drum or belt coated with a photoconductive material, typically selenium or a similar compound. This surface is initially given a uniform electrostatic charge. When an image is projected onto the photoconductive surface, the areas exposed to light become conductive, and the electrostatic charge in these areas dissipates. The areas that remain in shadow retain their charge, forming an electrostatic image.

Next, a fine, dry powder called toner, which is oppositely charged to the drum's initial charge, is cascaded over the surface. The toner particles are attracted to and adhere to the charged areas of the electrostatic image, creating a visible toner image on the drum.

This toner image is then transferred to a sheet of paper, which is also given an electrostatic charge to attract the toner. Finally, the toner is fused onto the paper using heat and pressure, creating a permanent copy. The photoconductive drum is then cleaned and recharged for the next cycle. Xerography revolutionized document reproduction by offering a faster, cleaner, and more convenient method compared to older wet-inking or carbon-copying techniques.