Electrophotography – Image formation – Transfer
Reexamination Certificate
2002-09-09
2004-10-26
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Transfer
Reexamination Certificate
active
06810228
ABSTRACT:
The present disclosure relates to the subject matter contained in Japanese Patent Application No.283734 filed on Sep. 10, 2002, which are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to an electrophotographic type image forming apparatus such as a copy machine, a printer, and a facsimile, and also related to a fixing apparatus thereof. Precisely speaking, the present invention is directed to a simultaneous image-transferring/fixing type image forming apparatus and a fixing apparatus thereof.
2. Description of the Related Art
Conventionally, image forming methods have been widely utilized by which electrostatic latent images are formed on photosensitive drums, these electrostatic latent images are developed by using dry type toners, and thereafter, the toner images are transferred onto recording media in electrostatic manners so as to be fixed thereon. In these conventional image forming methods, since concave/convex portions of a surface of paper corresponding to the recording media are present, this paper cannot be completely made in close contact with such a photosensitive drum, so that ununiform gaps may be produced. Therefore, there is such a problem that a transfer electric field is disturbed. Also, since Coulomb's repulsion may occur among the toners, there is another problem that images are disturbed.
To solve this problem, an image forming method of forming a color copy in the below-mentioned manner, and another image forming method has been proposed. That is, when a plurality of toner images having different colors are transferred onto an intermediate transfer member in a multiple manner, an electrostatic field is utilized, whereas when a multi-colored toner image transferred onto the intermediate transfer member is again transferred onto a recording medium, heat is utilized in order that the melted multi-colored toner image on the intermediate transfer member is transferred onto the recording medium and, at the same time, is fixed on this recording medium, and thus, such a color copy may be produced. On the other hand, in the latter image forming method, while a toner image formed on an endless belt-shaped photosensitive drum is heated so as to be melted, the melted toner image is transferred onto a recording medium so as to be fixed thereon.
In these image forming methods, since the toner images are transferred onto the recording media, these image transfer operations are carried out by utilizing heat in a non-electrostatic manner, deteriorations of image qualities which are caused by the disturbance of transfer electric fields and the Coulomb's repulsion can hardly occur.
Furthermore, in the above-described non-electrostatic image forming methods by such a simultaneous image transferring/fixing method, U.S. Pat. No. 2,990,278, JP-A-5-19642, JP-A-5-107950, and JP-A-5-249798 have described the following methods. That is, in order to transfer a toner image formed on an image carrier such as an intermediate transfer member and a photosensitive drum onto a recording medium under better condition, while the image carrier is made in close contact to a recording medium, heat and pressure are applied to this image carrier. Thereafter, both the image carrier and the recording medium are cooled while this image carrier is made in contact with the recording medium, so that a toner image sandwiched between the image carrier and the recording medium is made solid, and also, this solidified toner image is fixed on the recording medium. Then, the toner image fixed on this recording medium is exfoliated from the image carrier.
In accordance with this method, after cohesive power produced among the mutual toners which are penetrated into the recording medium becomes larger than adhesive power produced between the toners and the image carrier, since the toners are separated from the image carrier, a so-called “offset” (namely, a portion of toners are left on image carrier) can be prevented, oilless toner separations can be realized, and furthermore, the transfer efficiency of these toners can be increased, so that the images having better color balance can be obtained. In addition, since the toners are made solid along the surface of the image carrier, such high-quality images having high-class feelings can be produced, while unform glossy feelings can be realized and superior transparent characteristics of the toners can be obtained.
However, in order to obtain such a high-quality image, even after the toner image has been simultaneously transferred/fixed to/on the recording medium, cooling operations of both the intermediate transfer member and the recording medium are required while this intermediate transfer member is made in close contact to the recording medium. When the recording medium is exfoliated from the intermediate transfer member before the toners sandwiched between the recording medium and the intermediate transfer member are cooled to be solidified, the toners of an exfoliated portion of this recording medium are not made solid along either the surface of the intermediate transfer member or the surface of the photosensitive drum, but concave/convex portions are formed. As a result, the glossy feelings are deteriorated. Therefore, there is a difference in the glossy feelings between the close-contacted portion and the exfoliated portion, and fluctuations in the glossy feelings may occur as the entire image, so that the image quality is considerably deteriorated. More specifically, in the case that a breathability of a recording medium is low, that is, an air permeability of a recording medium is high, for example, double-sided coated paper for printing, this exfoliation may occur. The reason why such an exfoliation occurs is given as follows. That is, water components contained in the coated paper are heated to be vaporized and expanded, and then, the vapor components pass through the coated layer to fall out from the coated paper. The water vapor which has been penetrated into the space in the side of the intermediate transfer member is stayed between this intermediate transfer member and the coated layer of the coated paper. Thus, the coated paper is eventually exfoliated from the intermediate transfer member by this water vapor pressure. This phenomenon will be referred to as an “exfoliation blister” hereinafter.
FIG. 1
is a diagram for illustratively showing an occurrence condition of an exfoliation blister.
In
FIG. 1
, four sets of rectangle-shaped toner images
110
are arranged in such a manner that these four toner images
110
are separated from each other in a slight interval. An exfoliation blister
111
occurs while a non-image portion (namely, paper portion) corresponding to a center portion of the four arranged toner images
110
is positioned as a center.
FIG.
2
and
FIG. 3
are diagrams for illustratively showing a mechanism by which the exfoliation blister occurs.
As indicated in
FIG. 2
, while paper
112
is overlapped with an intermediate transfer belt
113
which carries thereon the toner image
110
, heat and pressure are applied to this paper
112
in a heat/pressure-applying unit (not shown). As a result, water components
114
contained inside this paper
112
are heated to be vaporized.
As indicated in
FIG. 3
, vaporized water components (namely, water vapor)
114
a
will fall out from the internal portion of this paper
112
to an external area. At this time, when this paper
112
corresponds to such a paper whose air permeability is small and which can easily penetrate therethrough air, the vaporized water components
114
a
may fall out from the rear surface of this paper. However, in the case of such a paper whose air permeability is large, for example, double-sided coated paper for printing, water vapor
114
a
may relatively gently fall out from the both surfaces of this paper
112
. As a result, such water vapor
114
a
which has fallen out on the side of the intermediate transfer belt
113
is stayed at a region where the toner
Fukuda Yuichi
Inoue Tohru
Kiuchi Yutaka
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