In this step, CPU applies DC bias onto the toner that was not charged by frictional electrification. Here, the toner becomes uniformed negative potential. The printer

charges the uncharged toner by applying DC bias onto the blade inside the toner cartridge.

The DC bias is also used as developing bias.

Step 4: Development

The toner is adhered onto an electrostatic latent image on the photosensitive drum in this step.

The toner is insulators, and acquires a negative charge by friction due to the rotating cylinder and the blade.

When the negatively charged toner makes contact with the drum, exposed areas on the drum are more positively charged than that on the cylinder. Then the toner

charged about the same as the cylinder adheres onto the exposed areas on the drum. The latent image on the drum becomes visible.

Although the charges on the exposed area on the drum are shown as positive in follow, in actuality, they are negative. However, they are more positive than the

charges on the cylinder.

2.3.1.5 Transfer Block

This block comprises three steps, which transfers the toner image on the drum surface onto paper.

Step 5: Primary transfer

The toner on the drum is transferred onto the ITB in this step.

A DC positive bias is applied to the primary transfer roller opposite to the drum in order to charge the ITB positively. Then the negatively charged toner on the

drum is transferred onto the positively charged ITB. This procedure is repeated for each color (Y, M, C, Bk).

In full-color printing, as toners in four colors are piled up on the ITB, the holding force of the toner weakens as the transfer process progresses for the 1st color, 2nd

color... Therefore, after transferring the first color, the DC positive bias is increased for each color in order to supplement the holding force of the toner.

2-10

Stirrer

DC bias

-V

Time (t)

Blade

Photosensitive

drum

Developing

cylinder

DC bias

F-2-17