Laser printer works on a principle called the static electricity. A charge is built up on any object that can be a balloon, your body etc. we know that atom with opposite charge attracts each other and the objects bind with the others having atoms of opposite static electricity.
There is a drum present in the printer which turns slowly. With the turning of this drum it gets positively charged by the wire or sometimes by another roller. This drum is made up of the material that is very much photoconductive which is given out by photons of light. Now with the revolving of drum a shinny small laser beam of light is seen across the surface this is to discharge some points. By this, laser had made all the words and images to get printed as an electrical charge. So we can say that we will get the negatively charged image on the positively charged background. This can be reversed by using the positively charged image on negatively charged background.
After this, the drum covers itself with a toner i.e. black fine powder which is positively charged. The toner only clings to these parts of the drum that are negatively charged and leave the positively charged parts. This process is something like if we write with liquid glue on a rolling can and then role over some powdery substance then that substance will clings only to the parts where there is glue.
Almost the basic process is over now and we have only to get the letters on the paper. The paper is charged negatively with wire or the other roller then the drum rolls over this charged paper which is also moving below along the belt. The toner is now pulled by the paper because it has more strong negative charge than the electrostatic image. Both paper and drum are moving at the same speed so we are getting the images on the paper. After this the detac corona wire immediately discharges the paper so that it will not cling to drum. Finally the paper is passed through heated rollers where the loose toner in powdered form melts and fusing in the paper fibers. This is the reason why paper is hot after coming out from the laser printer. The process of printing is now over and paper comes out from the printer in an output tray.
Paper never burns while passing through heated rollers because it moves at a very high speed from these rollers.
