Image Developing
The developing process changes the latent electrostatic image into a visible
image by depositing negatively charged toner particles on the exposed areas
of the drum. The developing station is located inside the toner cartridge
and consists of a metallic cylinder that rotates around a fixed magnetic core.
The developing cylinder is charged with an AC current that is centered around a
negative DC bias. The AC current improves density and contrast by decreasing
the attraction between the toner particles and the magnetic core of the cylinder.
This increases the repelling action of the toner against the areas of the drum not
exposed to laser light. The negative DC bias applied to the developing cylinder is
also changed according to the Print Density setting. Both the primary charging
roller and developing cylinder DC bias voltages are changed in response to the
density setting. These changes in DC bias cause either more or less toner to be
attracted to the drum, thus increasing or decreasing print density.
The toner is a powdery substance made of black plastic resin bound to iron
particles. The toner particles are attracted to the magnetic core of the
developing cylinder. A rubber blade “brushes” the toner on the developing
cylinder to a uniform thickness.
The toner particles obtain a negative static charge by rubbing against the
developing cylinder which is charged with a negative DC bias. The negatively
charged toner is attracted to the discharged (exposed, more positive) areas of
the drum, and repelled from the negatively charged (non-exposed) areas.
Image Development
Figure 5-11
5Functional
Overview
Functional Overview 5-17