Oki OKIPAGE 12i Series, Service Handbook

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2.3.2 Electrophotographic Process
The electrophotographic processing is outlined below. The electrophotographic printing process
is shown in Figure 2-4.
1 Charging
The surface of the image drum is charged uniformly with a negative charge by applying the
negative voltage to the charge roller.
2 Exposure
Light emitted from the LED head irradiates the negatively charged surface of the image drum.
The surface potential of the irradiated portion of the image drum surface becomes lower,
forming the electrostatic latent image associated with the print image.
3 Developing and toner recovery
When the negatively charged toner is brought into contact with the image drum, it is attracted
to the electrostatic latent image by static electricity, making the image visible.
At the same time, the residual toner on the image drum is attracted to the developing roller
by static electricity.
4 Transfer
When paper is placed over the image drum surface, the positive charge which is opposite
in polarity to that of the toner, is applied to the reverse side of the paper by the transfer roller.
The toner is attracted by the positive charge and is transferred onto the paper. This results
in the transfer of the toner image formed on the image drum onto the paper.
5 Temporary cleaning
Residual toner which remains on the image drum without being transferred is evened out by
the cleaning roller and is temporarily attracted to the cleaning roller by static electricity.
6 Fusing
The toner image transferred onto the paper is fused to the paper by heat and pressure.
An electrophotographic process timing chart is shown in Figure 2-5.