Laser Printers-An application of Elctrostatics
The Laser printer was invented in 1969 by Gary Starkweather while he was working at Xerox. It uses the principle of electrostatics electricity where the positively charged ink toner is attracted to a negatively charged image on the photoreceiver drum.
Inside the laser printer when electricity flows through a corona wire, this gives the revolving drum a positive charge. The drum is also called a photoreceptor as the text or image that is being printed will be temporarily copied onto the drum. There is a tiny laser beam that negatively charges certain areas on the drum, thus creating an exact electrostatic image or text to be printed on the photoreceptor. The background of the drum that has not been lasered remains positively charged. As the drum revolves the positively charged toner particles are attracted to the negatively charged image created on the photoreceptor. The printer paper just before it makes contact with the revolving drum is given a negative charge by a corona wire. The paper has a stronger negative charge compared to the revolving drum and so the positively charged toner particles are attracted to the paper. This is the process of how the ink gets onto the paper as it goes through the machine. Finally the paper passses through a pair of heated rollers called the fuser. The heated rollers baked the toner into the fibres in the paper so that the toner cannot come loose. This is the reason why the paper from a laser printer is warm when it exits the printer.
Some advantages of having a laser printer is that it makes it possible to complete a large volume of work in a short period of time. This is why many offices and workspaces use at least 1 laser printer when printing large quantities. Also the inkjet ink cartridges run out faster and it could be expensive to replace. Laser Printers use toner which has a much longer shelf life, and comes in larger containers so therefore lasts a long time and costs less.
Color Printing involves the same process, but requires more repetitions as the ink is applied one color at a time. After the image is printed out on the paper, the drum inside the printer is erased by a discharger that wipes out the final charge and then the drum is charged again with a positive electrostatic charge so it is ready to go again.