Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-09-07
2004-02-24
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S308000
Reexamination Certificate
active
06697595
ABSTRACT:
CROSS-REFERENCE TO A RELATED APPLICATION
This document claims priority and contains subject matter related to Japanese Patent Application No. 2000-272196, filed on Sep. 7, 2000, the entire contents which are incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for image formation, and more particularly to a method and an apparatus that can form a high quality image by suppressing an occurrence of toner scatter and a partial omission of a toner image.
2. Discussion of the Background
An image forming apparatus, in which a toner image is formed on a seamless image bearing belt and the toner image is transferred onto a transfer medium by a transfer device, such as a copying machine, a printer, a facsimile, or a multifunctional apparatus having at least the above-described two functions is commonly known. The image bearing member includes, for example, a photoconductive belt on a surface of which a toner image is formed or an intermediate transfer belt onto which the toner image is transferred from a photoconductive element, according to a type of a developing device.
FIG. 10
is a schematic drawing illustrating a construction of a transfer section of a conventional image forming apparatus in which an intermediate transfer belt is used as an image bearing member. As shown, an intermediate transfer belt
1
A is spanned around a plurality of rollers including a roller
2
A and other rollers (not shown), and is driven in a direction indicated by an arrow “A.” Each toner image of different colors is transferred onto the surface of the intermediate transfer belt
1
A from a photoconductive element (not shown) one after another while being superimposed on each other. A transfer roller
3
A, as an example of a transfer device, is provided at a position opposed to the roller
2
A via the intermediate transfer belt
1
A.
As illustrated in
FIG. 10
, the transfer roller
3
A press-contacts with the roller
2
A via the intermediate transfer belt
1
A when a toner image formed on the surface of the intermediate transfer belt
1
A is transferred onto a recording medium including a transfer medium
4
A. At this time, the transfer roller
3
A rotates in a direction indicated by an arrow, and the transfer medium
4
A is conveyed in a direction indicated by an arrow “B” to pass through a nip
5
A. As described above, the transfer roller
3
A press-contacts with the roller
2
A via the intermediate transfer belt
1
A and the transfer medium
4
A. At this time, a transfer voltage with a reverse polarity of toner image formed on the surface of the intermediate transfer belt
1
A is applied to the transfer roller
3
A.
The toner image formed on the surface of the intermediate transfer belt
1
A is then transferred onto the surface of the transfer medium
4
A which is conveyed in the direction indicated by the arrow “B” while contacting the surface of the intermediate transfer belt
1
A. The transfer medium
4
A, which has been conveyed through the nip
5
A formed between the roller
2
A and the transfer roller
3
A, is conveyed to a fixing device so that the toner image transferred onto the surface thereof is fixed.
As explained above, the transfer medium
4
A is conveyed to the nip
5
A from an inlet side “I.” A wedge-shaped gap “G” is formed between the intermediate transfer belt
1
A and the transfer medium
4
A in a region in the inlet side “I.” Further, a portion of the transfer medium
4
A, which is placed adjacent to the nip
5
, is charged with the reverse polarity of the toner image because the above-described transfer voltage has been applied to the transfer roller
3
A. Thus, toner on the surface of the intermediate transfer belt
1
A electrostatically flies and adheres to the surface of the transfer medium
4
A as indicated by the arrows “C.” Such a phenomenon is called “toner scatter.” When toner scatter occurs, the scattered toner appears around the image transferred onto the transfer medium
4
A, which has passed through the nip
5
A, in a blotted condition resulting in a degradation in the quality of the toner image.
The above-described inconvenience is also caused when the image bearing belt includes a photoconductive belt or a dielectric belt and the transfer medium includes an intermediate transfer element or a recording medium. The intermediate transfer belt
1
A generally has a volume resistivity of, for example, 10
8
&OHgr; cm to 10
13
&OHgr; cm. The above-described toner scatter frequently occurs when the intermediate transfer belt
1
A is used. A reason for the frequent occurrence of toner scatter is because a force of toner that electrostatically adheres to the surface of the intermediate transfer belt
1
A is less than a force of the toner that electrostatically adheres to an insulator. Therefore, the toner adheres to the surface of the intermediate transfer belt
1
A in a state that the toner is comparatively easy to move.
Further, toner in an upper-most layer is easily moved when each toner color image is formed on the surface of the intermediate transfer belt
1
A while superimposed on each other, because an amount of the toner per unit area on the surface of the intermediate transfer belt
1
A is increased. In addition, when the surface of the intermediate transfer belt
1
A (on which the toner adheres in the state that it can easily move) is opposed to the charged transfer medium
4
A with the minute gap “G” therebetween, the toner on the surface of the intermediate transfer belt
1
A easily flies onto the surface of the transfer medium
4
A electrostatically, resulting in the frequent occurrence of the toner scatter phenomenon.
As illustrated in
FIG. 11
, a roller
7
A is provided to approximately parallelize a portion of the intermediate transfer belt
1
A (which is positioned between the roller
2
A opposed to the transfer roller
3
A and the roller
7
A supporting the intermediate transfer belt
1
A) with the conveying direction “B” of the transfer medium
4
A conveyed to the nip
5
. With this configuration, the transfer medium
4
A starts to contact the surface of the intermediate transfer belt
1
A at a position substantially upstream from the nip
5
in a moving direction of the intermediate transfer belt
1
A. Thus, when a portion
8
A of the transfer medium
4
A conveyed to a vicinity of the nip
5
A is charged by a voltage applied to the transfer roller
3
A, the toner on the surface of the intermediate transfer belt
1
A does not fly onto the surface of the portion
8
A of the transfer medium
4
A or a very small amount of the toner flies thereon. Therefore, an occurrence of the toner scatter is suppressed.
In addition, when the diameter of the rollers
2
A and
7
A supporting the intermediate transfer belt
1
A is too small, the intermediate transfer belt
1
A passing over the rollers tends to curl. Thus, an uneven transfer of an image to the transfer medium
4
A from the intermediate transfer belt
1
A arises, resulting in a degenerated toner image. Further, when the diameter of the roller
2
A opposed to the transfer roller
3
A is too small, a length of the nip
5
A (i.e., the nip width) in the conveying direction of the transfer medium
4
A is decreased, resulting in a reduction of a transfer efficiency of the toner image. Therefore, the diameter of rollers
2
A and
7
A cannot be decreased very much.
In addition, when the diameter of the rollers
2
A and
7
A is increased, a length “D” of the transfer medium
4
A, in which the transfer medium
4
A contacts the surface of the intermediate transfer belt
1
A before the transfer medium
4
A reaches the nip
5
, is increased. Thus, the transfer medium
4
A starts to contact the surface of the intermediate transfer belt
1
A at a position substantially upstream from the nip
5
in a moving direction of the transfer medium
4
A.
A portion
9
A of the transfer medium
4
A, which is an upstream side portion of the transfer medium
4
A in the conveying direction of the transfer medium
4
A, is positioned substantially away
Kawagoe Katsuya
Kayahara Shin
Motohashi Toshiaki
Ogiyama Hiromi
Ono Hiroshi
Grainger Quana M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
LandOfFree
Method and apparatus for forming an image with no degradation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for forming an image with no degradation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for forming an image with no degradation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3319286