Xerography

Printing with Electrostatics

What are Electrostatics?

Electrostatics are the study of stationary electric charges, and electric charges at rest. From static electricity objects can become positively or negatively charged in a method. Static charge is the method by which when two objects rub against each other, they both become charged; one becomes positively charged and the other becomes negatively charged. One can determine the charge an object will have when rubbed with another object by observing the electrostatic series. This is a chart that determines the hold and strength an object has on its electrons, and is used in the process of observing a charge on an object, through static charge.

What is Xerography?

Xerography, also known as electrophotography is a printing and photocopying technique that works on the basis of electrostatic charges. It is the process of reproducing images and printing computer data, which is used in photocpiers, laser printers, and fax machines. Originally, the first xerography process only allowed for the reproduction of grayscale images. The first commercial use of the machines was of a flat photosensor (an electronic component which detects the presence of visible light) with a copy camera and a separate processing unit to produce offset lithographic plates. However, later the machines allowed for the production of printing colour. Eventually, Xerography may supplement for traditional printing for the production of books and magazines.

The Xerography Process

Stage 1: Charging

-An electrostatic charge of 600 volts is uniformly distributed over the surface of the drum by a corona discharge or with the use of a contact roller with a charge applied to it

-A corona discharge is generated by a narrow wire 1/4 to 1/2 inch apart from the photoconductor.

-A negative charge is placed on the wire, which will ionize the space between the wire and conductor, therefore making the electrons repel the wire and push onto the conductor


Stage 2: Exposure

-A bright lamp illuminates the original document, and the white areas of the original document reflect the light onto the surface of the photoconductive drum

-The areas of the drum that are exposed become conductive, and discharge to the ground

-The area of the drum not exposed to light remains negatively charged

-This results in an electrical image on the surface of the drum


Stage 3: Developing

-The toner is positively charged

-When it is applied to the drum to develop the image,it is attracted (unlike charges attract) and sticks to the areas of the drum that are negatively charged


Stage 4: Transfer

-The toner image on the surface of the drum is transferred onto a piece of paper with a higher negative charge than the drum

Everyday Use of Xerography

Xerography is a very important tool, and is used in an everyday world. It create copies and photocopies of documents, photos, or images. It is necessary because many people need to reproduce a file or document, without the hassle of writing it out or creating a new one.

Xerography Principle

Xerography principle, Rate My Science

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