Image forming apparatus with plural developing devices

Details Image forming apparatus with plural developing devices Image forming apparatus with plural developing devices

1988-01-19

1991-02-12

Bralin, Fred L.

Photocopying

Contact printing

Light boxes

355272, 355273, 355319, G03G 1506

Patent

active

049928317

ABSTRACT:
In an image forming apparatus having two developers, toner deposition parameters in the second developing device are larger than the first developing device. Here, the toner deposition parameter is represented by an amount of electric charge of the toner particles, an amount of developer particles constituting a foggy background, an amount of carrier particles deposited on the image bearing member, or any combination of these parameters. The amount of the fog developer particles is determined first by a ratio of the total area occupied by the fog developer particles to the entire background area, second by a ratio of the fog developer particles having large particle sizes to the entire fog developer particles, third by a particle size at which a number of the fog developer particles accumulated in the large size side of a number/particle size distribution graph reaches a predetermined percentage to the entie number of fog developer particles, and fourth by a number of fog developer particles per unit area. By this arrangement of the developing devices, failure of transfer material separation from the image bearing member and retransfer of the image can be avoided when the toner image formed by the second developer is transferred.

REFERENCES:
patent: 3267840 (1966-08-01), Honma et al.
patent: 4187774 (1980-02-01), Iwasa et al.
patent: 4251154 (1981-02-01), Russel
patent: 4539281 (1985-09-01), Tanaka et al.
patent: 4572651 (1986-02-01), Komatsu et al.
patent: 4609280 (1986-09-01), Queener

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