Electrophotography – Image formation – Transfer
Patent
1999-08-09
2000-10-31
Lee, Susan S. Y.
Electrophotography
Image formation
Transfer
399299, G03G 1522, G03G 1501
Patent
active
061415235
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to an electrographic printer device, particularly a printer or a copier, comprising at least two essentially identical printing units with a transfer printing location each between which a carrier web to be printed is conducted. The invention is also directed to a method for the operation of a printer device.
BACKGROUND OF THE INVENTION
In a traditional printer device, a latent image is applied onto a toner image carrier with the assistance of an electrographic process, for example by exposing a photoconductor or by magnetization of a magnetically sensitive layer. Toner agglomerates at the latent image according to the image-related distribution of the electrical charges or of the magnetic poles. The toner is then transferred onto a carrier material, generally a paper web, at the transfer printing location. The toner image is later fixed on the carrier material.
There is a demand in modern printing technology that a single device print the carrier material on both sides with high speed. This operating mode is generally referred to as duplex printing. Further, there is a demand for the operating mode of spot color printing or two-color printing wherein printing is carried out in two colors on at least one side. Moreover, there is a need for a full-color printing with the four process colors. In order, for example, to realize the operating mode of duplex printing, it is known to initially print the continuous carrier web on one side, to then turn the carrier web over and to print the second side with the same printing unit. A web turn-over means is required given this solution. The conveying path of the carrier web through the printer is relatively long and requires a complicated conveyor mechanism for the carrier material that, thus, is also susceptible to malfunction.
A further disadvantage of the known printer is comprised therein that the toner image can smear when it has not yet been fixed on the one side of the carrier web and, thus, the printing quality is diminished or, respectively, a reject is produced. In order to avoid this, an intermediate fixing of the toner image can ensue, as a result whereof, however, the technical outlay becomes great. Moreover, the carrier web must traverse the fixing process a second time after being printed on the second side, as a result whereof is thermally highly stressed, shrinkage problems occur and the registration of the print is diminished. Due to the long conveying path between the first transfer printing location for the first transfer printing of a toner image and the second transfer printing location, adherence to a high registration of the carrier web can only be assured with great technological outlay.
The aforementioned problems also occur given what is referred to as a "twin system" wherein two identical printers are connected in series with one another in order to realize a two-sided printing, i.e. the duplex printing, while turning the carrier web over. In addition to the high costs for two printers, it is also disadvantageous that a large basement surface must be made available and the apparatus control of the two printers must be adapted to one another with relatively high technological outlay.
EP 0 629 931 A1 (Applicant: XEIKON) discloses an electrostatic printer wherein a carrier web is conducted through between a plurality of toner image carrier in vertical direction. Each toner image carrier has a means that generates a toner image. The toner is transferred onto the carrier web at a respective transfer printing location of the toner image carriers. As a result of the both-sided arrangement of toner image carriers along the vertically proceeding carrier web, duplex printing with different toner colors is possible. The known apparatus has a complicated structure, a complicated carrier material guidance and is bulky.
EP 0 433 444 B1 (Applicant: Eastman Kodak Company) discloses a printer wherein a plurality of developer stations are arranged along a photoconductive band as toner image carrie
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Bergmann Peter
Eggerstorfer Vilmar
Lee Susan S. Y.
Oce Printing Systems GmbH
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