Photocopiers look complex however they operate on two fairly basic pieces of science.
The basis of the photocopier is a rotating drum equipped with a unique photo-conductive coating. The bright light shines across the paper and white areas become positively charged, while black areas remain negatively charged. The drum attracts toner that sticks to it, creating an printed image on the paper.
Xerography
The basic technology of most current copy machines is called xerography, which is a process that makes use of electrostatic charge. Basically, it operates by transferring opposing electrical static charges the ‘ink’ (a black powder referred to as toner) followed by applying heat to get them to adhere to the paper.
Chester Carlson invented the xerographic method in his home lab in 1938. It revolutionized our work by making it possible to produce massive quantities of copies. While some big companies did not like the idea at the time, he managed to turn it into one of the biggest office inventions of the 20th century.
The sheet of paper which is being photocopied is lit by a bright light. The areas of the paper that have been printed on or branded with a symbol reflect the light, while the unmarked parts do. This causes electrons close to the edge of the drum to radiate downwards leaving behind a lingering electrostatic image of the paper.
Next, you need to add a negative charge on the toner particles. This is done by sending the ‘ink’ into an electric field created by corona wires. The toner’s negative charge is drawn to the electrical reflection of the photoconductor and produces an inked replica of the original. The paper on the opposite side of the belt then gets a positive charge from an incline, and this draws the toner that is positively charged. The paper and toner are melted under high temperatures. The result is that the copy the appearance of a permanent copy.
Photocopying technology
Photocopiers print documents on paper by using an electric charge, instead of ink. The charge is produced by a rotating drum containing a reservoir containing black powder called toner. The drum has one type of charge electrically and the toner has another – opposing charges draw each other. The drum is coated by a special chemical that can pick up the toner particles and deposit them on a blank piece of paper.
You insert the document you wish to copy onto the slot on the top of the machine. The bright light scans the document looking for black areas. The radiation from the scanner bounces off the dark areas, and creates an “electrical shadow” of the page.
A photoconductor consists of a cylindrical object with a photoconductive coating. The drum is charged with positive charge through the laser inside a printer or scanning system in scanner. Drums are also subjected to a reservoir containing carbon toner particles which carry an opposite charge. Toner adheres to exposed drum areas that are heated before being combined with the paper. The static electricity could cause the paper to become jammed if it is still on the copied copy. It is crucial to wash the surface of your copy machine frequently.
Photocopier components
The glass tray on which you put your document is the most visible element of a photocopier. Next, there’s the lamp, which shines a light on the document. Then there’s the drum, which is a rotating belt covered in a photo-conductive coating. The photoconductor used in the early copiers was a type of the rare metal selenium, and later models used enhanced selenium telluride alloys. The material converts light into electricity by taking electrons from photo-conductive atoms. When you shine a bright light across the original document more light bounces off of the areas of white that have not been printed than off the black inked areas making an electrical shadow of the initial page the photoconductor.
The optical scanner generates an image that is then passed to the printing section of the photocopier through the RIP. This section also produces static electricity and uses the same process as a photocopier. The printer prints every line of the document by using the drum, which heats to make the ink set.
Static electricity is one the two tricks in science that make a photocopier work as it should, and is something you’ve probably come across previously. Static electricity is what happens when you put a balloon in your clothes and then stick it to the wall. The other trick involves the fact that some substances are more conductive once they absorb light (photoconductivity). This is the way xerography works, and it’s what makes most modern photocopiers the reliable and efficient machines they are.
Electrophotography
A charge electrostatic that forms in the drum or other surface is essential to photocopying. This charge originates from corona wires that are exposed to high voltages in order to create an electrical field that is created between the drum and the paper. The toner particles are positively charged and draw the negative charges on the paper. This creates an image.
The basic operating principle behind the operation of all laser and digital copiers printers is known as electrophotography (or xerography). Chester Carlson invented the process in 1937 and collaborated together with Battelle Memorial Institute on developing the technology into a product that could be used that could be used commercially. He founded Haloid Corporation which became Xerox Corporation in the year 1961.
Thue may photocopy hcm uses two natural phenomena, which is that substances with opposite electrical charges draw each other and some materials can conduct better electricity after exposure to light. Carlson developed a procedure in six steps to transfer images from one surface onto another using these natural phenomenon.
First, the document is exposed to a photoreceptor. It is typically a special drum covered with a semiconductor which conducts only in a vertical direction. After placing the document on top of a photoreceptor shining light is reflected on it. The light reflects off the white areas of the document and is then is transmitted through mirrors to light the dark areas. The reflected light passes through the photoreceptor, and releases its electric charge into the illuminated areas. Latent images are the patterns of electrical charges that appear on the photoreceptor.
