Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1999-12-14
2003-07-15
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108100, C430S111400, C430S109100
Reexamination Certificate
active
06593051
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to toner for use in an image forming apparatus such as a copier, a printer, and a facsimile, and an electrophotographic method.
2. Description of the Related Art
In electrophotographic copiers, printers, and the like, printing is performed by the following process. First, a photoreceptor is charged for forming an image. As a method for charging a photoreceptor, a corona electrical charger conventionally has been used. Recently, uniformly charging the surface of a photoreceptor by a contact type charging method has been put into practical use for the purpose of reducing the generation of ozone. According to the contact type charging method, a conductive roller is directly pressed onto a photoreceptor. In the case of a copier, after a photoreceptor is charged, an original for copying is irradiated with light. Then, the photoreceptor is irradiated with light reflected from the original through a lens system. In the case of a printer, an image signal is transmitted to a light-emitting diode, a laser diode, or the like as an exposure light source, and a latent image is formed on a photoreceptor by ON-OFF control of light. When a latent image (level of a surface potential) is formed on the photoreceptor, the latent image is developed with toner (diameter: about 5 &mgr;m to about 15 &mgr;m), which is previously charged coloring powder. Toner adheres to the surface of the photoreceptor in accordance with the level of a surface potential thereof, and thereafter is electrically transferred to a copying sheet. More specifically, toner is previously charged positively or negatively, and the back side of the copying sheet is charged with a polarity opposite to that of the toner, whereby the toner is attracted to the copying sheet. Hitherto, a corona electrical charger has been widely used for providing charge to the copying sheet in the same way as in charging a photoreceptor. However, in order to reduce generation of ozone, recently, a transfer apparatus using a conductive roller has been put into practical use. During transfer, all the toner on a photoreceptor is not transferred to a copying sheet. The toner partially remains on the photoreceptor. The remaining toner is scraped off by a cleaning blade or the like in a cleaning section to become waste toner. Conventionally, according to electrophotography, waste toner has been discarded without being recycled. Careless discarding should be avoided from the viewpoint of environmental protection. Recycling of waste toner poses a significant problem.
In a color copier, a photoreceptor is charged by a corona electrical charger. Thereafter, a latent image of each color is provided to the photoreceptor as a light signal, whereby an electrostatic latent image of each color is formed thereon. Then, the electrostatic latent image is developed with the first color (e.g., yellow toner) so as to become visible.
Thereafter, a transfer material charged with a polarity opposite to that of the yellow toner is brought into contact with the photoreceptor, whereby the yellow toner image formed on the photoreceptor is transferred to the transfer material. The toner remaining on the photoreceptor after transfer is cleaned, and the photoreceptor is discharged. Thus, development and transfer of the first color toner are completed.
Thereafter, the same process as that of yellow toner is repeated with respect to toner of magenta, cyan, and the like, and toner images of the respective colors are overlapped on the transfer material to form a color image. These overlapped toner images are transferred and fixed to a sheet charged with a polarity opposite to that of the toner images, whereby copying is completed.
A method for forming a color image generally includes a transfer drum method and a continuous overlapping method. According to the transfer drum method, a toner image of each color is successively formed on a single photoreceptor. Then, a transfer material wound around a transfer drum is rotated so as to repeatedly face the photoreceptor. A toner image of each color which is successively formed is transferred to the photoreceptor so as to overlap each other. According to the continuous overlapping method, a plurality of image forming sections is arranged. Then, each image forming section is passed through a transfer material transported by a belt. Thus, a toner image of each color is successively transferred to the transfer material in such a manner that color images overlap each other.
As an example using the above-mentioned transfer drum method, Japanese Laid-open Publication No. 1-252982 discloses a color image forming apparatus.
FIG. 3
is a schematic view of an entire structure of the conventional example. Hereinafter, the structure and operation thereof will be described briefly.
In
FIG. 3
, reference numeral
501
denotes a photoreceptor. A charger
502
, a developing section
503
, a transfer drum
504
, and a cleaner
505
are provided so as to face the photoreceptor
501
. The developing section
503
includes a Y developing unit
506
for forming a yellow toner image, an M developing unit
507
for forming a magenta toner image, a C developing unit
508
for forming a cyan toner image, and a Bk developing unit
509
for forming a black toner image. All the developing units are rotated in such a manner that each developing unit successively faces the photoreceptor
501
. Thus, each developing unit becomes ready for development. During operation, the transfer drum
512
and the photoreceptor
501
are rotated at a constant speed in respective arrow directions while facing each other. Reference numeral
518
denotes a toner hopper for supplying toner to a developing unit.
When an image forming operation is started, the photoreceptor
501
is rotated in the arrow direction, and the surface thereof is uniformly charged by the charger
502
. Thereafter, the surface of the photoreceptor
501
is irradiated with a laser beam
510
which has been modulated with a signal for forming an image of the first color (yellow), and a latent image is formed on the surface of the photoreceptor
501
. Then, the latent image is first developed by the Y developing unit
506
, which faces the photoreceptor
501
, to form a yellow toner image. By the time when the yellow toner image formed on the photoreceptor
501
moves to a position facing the transfer drum
504
, an end of a transfer material (i.e., sheet transported from a sheet supply section
511
) has been trapped by a hook
512
and wound around an outer periphery of the transfer drum
504
. Thus, timing is provided in such a manner that the yellow toner image on the photoreceptor
501
faces a predetermined position of the sheet.
After the yellow toner image on the photoreceptor
501
is transferred to the sheet by a transfer charger
513
, the surface of the photoreceptor
501
is cleaned by the cleaner
505
, so that the surface is ready to receive a subsequent color image. Then, toner images of magenta, cyan, and black are similarly formed. At this time, the developing section
503
allows each developing unit used in accordance with color to face the photoreceptor
501
, whereby each developing unit becomes ready for development. The transfer drum
504
has a size sufficient for allowing the longest sheet to wind around it and allowing developing units to be exchanged between images of respective colors.
The laser beam
510
for forming an image of each color is radiated in such a manner that a toner image of each color on the photoreceptor
501
faces a toner image which has been transferred to the sheet on the transfer drum
504
with their positions matched with each other during rotation. In this manner, toner images of four colors are overlapped and transferred to the sheet on the transfer drum
504
, whereby a color image is formed on the sheet. After the toner images of all the colors are transferred, the sheet is peeled off from the transfer drum
504
by a peeling hook
514
. Then, the sheet is passed through a tra
Hirota Noriaki
Maeda Masahisa
Tatematsu Hideki
Yuasa Yasuhito
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Rodee Christopher
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