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(11) | EP 2 088 474 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Image forming apparatus and image forming method |
| (57) An image forming apparatus includes image bearing members (20), transfer members
(12), and pressing units (18). The image bearing members (20) include a black image
bearing member (20K) for forming black image and other image bearing members (20Y,20M,20C)
for forming other color images. The toner image from the image bearing members is
transferred with the transfer member. The pressing units (18) press the transfer member
(12) to the image bearing members (20) with a given pressure. The toner has a sunken
rate of additives of 40% or more. The sunken rate of additives X% = { (A-B) / A }
× 100. "A (m2/g)" is a BET specific surface of toner matrix before sinking additives in toner,
and "B (m2/g)" is a BET specific surface of the toner after sinking additives in toner. The
pressing unit (18K) for the black image bearing member (20K) presses the transfer
member (12K) with a pressure set smaller compared to other pressing units (18) for
the other image bearing members (20).
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