Photocopying – Contact printing – Light boxes
Patent
1989-05-23
1990-09-04
Pendegrass, Joan H.
Photocopying
Contact printing
Light boxes
355225, 355266, 355268, 3461531, G03G 1506, G03G 1502
Patent
active
049548433
ABSTRACT:
An image forming apparatus wherein a photosensitive layer arranged to rotate in one direction is charged by a charger, and a negative electrostatic latent image is formed thereon by an exposure unit and then is subjected to reversal development by a developing device so that a positive noticeable image can be attained. The apparatus has a scorotoron charger for charging the negative latent image which has just been formed by the exposure unit with the opposite polarity thereof. A grid of the scorotoron charger is constituted to be impressed with a voltage with the same polarity as the latent image and a value lower than that of the surface potential, and by the scorotoron charger, the potential of the non-imaged portions of the latent image is lowered around the grid voltage. Further, the developing device is constituted to be impressed with a developing bias voltage with the same polarity as the latent image and a value lower than that of the surface potential but higher than a developing threshold value, whereby toner charged with the same polarity as that charged by the charger sticks to the imaged portions with potential lower than the developing bias voltage, resulting in a positive toner image with sharp line widths.
REFERENCES:
patent: 3967891 (1976-07-01), Rippstein
patent: 4794062 (1988-12-01), Oka et al.
patent: 4821076 (1989-04-01), Toyoshi et al.
Oka Tateki
Toda Kunio
Toyoshi Naoki
Minolta Camera Kabushiki Kaisha
Pendegrass Joan H.
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