Electrostatic Printing - What is electrostatic printing?
A method of printing; this process creates an image by using static electricity to attract toner to specific areas of a substrate and is one of the earliest dry printing processes to be invented. The substrate is usually paper that has been coated to improve its dielectric strength and given a negative (or positive) charge.
Electrostatic printing involves two steps; first, a latent image is created on the substrate (an “invisible” image that is created by exposing a photosensitive material to light) and then the latent image is processed (toner is applied and bonded in place) to create the finished image.
The paper substrate is photoconductive, meaning that it becomes more conductive of electricity when exposed to light. To create a latent image, light is passed through or reflected off a document that is being copied or is used to project an original image onto the photoconductive paper. In the copied document, the “content” of the image will block or absorb light while the “non-content” (blank, white areas) will allow light to pass through or reflect light onto the paper. In the original image, a negative of the image is projected so that the “non-content” is projected directly onto the paper. Where light falls onto the paper, the negative (or positive) charge is discharged, creating a latent image of the original made up of negatively (or positively) charged areas of the substrate.
To process the latent image into a visual finished image, the paper will then pass a toner cartridge; the toner particles have a positive (or negative) charge, meaning that they will be attracted to the charged areas of the paper. The toner is then bonded in place using heat and pressure generated by a fuser unit.
Electrostatic printing can be used to create monochromatic images (one toner is used to create images made up of different shades of that one colour, usually black) or colour images (there are four toners - one for each of the four process colours - which are applied in sequence, with the process of charging and discharging specific areas of the paper being repeated before each colour is applied).
Electrostatic printing was invented in 1778; today, there are still some electrostatic printers available but the process is more commonly used as one part of other, more modern, printing methods such as xerography and laser printing.Go Back to Glossary