Laser

Printing Process

Laser printing works using an electrically-charged powder called toner. Toner particles contain pigment and a waxy plastic. This provides some advantages over liquid ink. The primary advantage is that it will bind to the fibers of any kind of paper and won't smudge or bleed. [Laser]

picture from: [Laser]

The printer uses static electricity and a revolving photoconductive drum to get the toner onto the paper. As the drum spins, it is first given a total positive charge by a charge corona wire. Next a laser beam shines on the drum using a system of spinning mirrors to move the beam across the width of the drum, one line at a time. For a printer with a 600dpi vertical resolution, the drum will rotate 1/600th of an inch for each line. As the beam moves, the laser is rapidly turned on and off based on the image being printed. The speed at which the laser cycles will determine the horizontal resolution of the printer. When the beam is on, the charge at that point becomes negative. Thus the drum is left with negative charge where the page should be black and positive charge for the white background. [Laser, PCTech]

picture from: [Laser]

Next, the drum passes the positively charged toner with the help of a developer roller. Where the drum is negatively charged, black toner particles will adhere to the drum. Toner will be repelled by the positively charged areas which will remain white on the printed page. At the same time, the paper is given a negative charge by the transfer corona wire. As the paper moves along the drum, the toner will move to the paper since it has a stronger charge. After picking up the toner, the paper is discharged by the detac corona wire to prevent it from sticking to the drum. [Laser, PCTech]

picture from: [Laser]

Next, the paper passed through a pair of heated rollers called the fuser to melt the toner in place. If you've ever taken a jammed page out of a laser printer, you may have noticed how the image will be on the page but can simply be wiped off with a towel, your hands, or your clothes because it hasn't been fused yet.

Finally, the drum passes a discharge lamp which exposes the entire surface to erase the electrical image and prepare the drum to be charged again for the next pass. [Laser, PCTech]