electrophotographic

Electrophotography is a method of forming images by using electrostatic charges on a photoconductive surface, typically a drum or belt. The process was invented by Chester Carlson in 1938 and later commercialized by the Haloid Company (which became Xerox), contributing to the development of modern office copiers and laser printers.

Core components include a photoconductor, a charging device, exposure optics or a scanning laser/LED, developer units with toner, transfer apparatus, and fusing equipment. Operation begins with uniformly charging the surface. Next, the surface is exposed to light that encodes the desired image; in light-exposed areas the photoconductor becomes conductive and loses the charge, forming a latent electrostatic image.

The latent image is developed by applying charged toner particles that adhere to the negatively charged areas, producing a visible powder image. The image is transferred to paper and fixed by heat and pressure in the fusing stage. The photoconductor is then cleaned to remove residual toner and recharged for the next cycle.

In color electrophotography, multiple color toners are used, either with multiple drums or a tandem system employing an intermediate transfer belt. Color devices may perform several passes or use simultaneous development to produce full-color prints. Common photoconductor materials have evolved from selenium to organic photoconductors in modern equipment.

Applications and impact include widespread use in laser printers, photocopiers, and some digital presses, offering high-speed, non-impact printing with good image quality. The field integrates principles of electrostatics, photoconductivity, and materials science to enable rapid, repeatable image formation.