Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
2002-08-30
2004-09-21
Grainger, Quana (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
C399S066000, C399S302000, C399S308000
Reexamination Certificate
active
06795667
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process cartridge and an electrophotographic apparatus, and in particular to an intermediate transfer belt-electrophotographic photosensitive member integrated process cartridge and an electrophotographic apparatus having the process cartridge.
2. Related Background Art
An image forming apparatus of an electrophotographic system (electrophotographic apparatus) using a belt-shaped intermediate transferring member (intermediate transfer belt) is effective as a color electrophotographic apparatus and as a multi-color image forming apparatus which brings a plurality of component color images of color image information or multi-color image information into sequential lamination transfer so as to output image formed matter synthesized and reproduced from color images and multicolor images.
Compared with a conventional color electrophotographic apparatus (for example, Japanese Patent Application Laid-Open No. 63-301960, etc.) of a system in which images are transferred from an electrophotographic photosensitive member to a transfer material fastened or attracted onto a transferring drum, a color electrophotographic apparatus using an intermediate transfer belt does not require any processing or control (for example, prehension to a gripper or absorbing, giving curvature, etc.) on the transfer material but can transfer images from the intermediate transfer belt, and therefore has an advantage that various kinds of transfer material can be selected regardless of wideness
arrowness of the width or the longness/shortness of the length to cover thin paper (40 g/m
2
paper) to thick paper (200 g/m
2
paper) such as envelopes, postcards, and label forms, etc.
In addition, compared with such a case where an intermediate transfer member (intermediate transfer drum) in a rigid drum shape is used, adopting an intermediate transfer belt shape for the intermediate transfer member, freedom for disposing inside an electrophotographic apparatus increases, giving rise to an advantage that miniaturization or cost reduction of the main body of the electrophotographic apparatus can be implemented by efficiently utilizing spaces.
In addition, as a photoconductive material used for the electrophotographic photosensitive member which the electrophotographic apparatus comprises, inorganic materials such as zinc oxide, selenium and cadmium sulfide, etc. are known.
As compared with inorganic materials, organic materials such as polyvinyl carbazole, phthalocyanine, and azo pigment have advantages such as high production efficiency or pollution-free performance, and in particular are superior in photoconductivity. Organic electrophotographic photosensitive members using such organic materials are widely used for electrophotographic apparatuses.
An intermediate transfer belt repeatedly receives bending stress and contact with or rubbing from various kinds of drive members and transfer members, etc., every time it rotates, and with a high potential being applied, its life is shorter than the main body of an electrophotographic apparatus, and replacement is indispensable under the current state.
Likewise, the electrophotographic photosensitive member is also repeatedly affected by electrification, exposure, development, transfer, cleaning, and dielectrification, and therefore requires various chemical or physical endurance, and thus an organic electrophotographic photosensitive member needs to be replaced as well.
Otherwise, waste toner having collected residual toner on an intermediate transfer belt needs treatment, and a lot of components such as an electrophotographic photosensitive member, developing means and toner, etc. need replacement and maintenance.
As a method to unitize these replacement components and attach to/remove from the main body of an electrophotographic apparatus easily, Japanese Patent Application Laid-Open No. 8-137181 proposes to dispose an intermediate transfer belt and an electrophotographic photosensitive member as respectively independent units detachably mountable to the main body of an electrophotographic apparatus without difficulty.
However, these means involve a number of replacement units to make the user's operation complicated. Moreover, the intermediate transfer unit and the electrophotographic photosensitive member unit are respectively designed and disposed independently, thereby causing such a problem that the main body of the electrophotographic apparatus becomes larger or costs increase.
As a means to solve this problem, replacing means to cause the intermediate transfer belt and the electrophotographic photosensitive member (replacement parts) to be supported integrally as one body in one unit, and to be constructed so as to cause it to be simultaneously removed from/attached to the main body of the electrophotographic apparatus are suitable, and are proposed in Japanese Patent Application Laid-Open No. 6-110261, Japanese Patent Application Laid-Open No.10-177329, and Japanese Patent Application Laid-Open No. 11-30944.
However, the method to construct the intermediate transfer belt and the electrophotographic photosensitive member as one-body unit to become an intermediate transfer belt-electrophotographic photosensitive member integrated process cartridge that is detachably mountable to the main body of the electrophotographic apparatus gives rise to several problems originated from the intermediate transfer belt.
In particular, what causes a big problem is a characteristic abnormality of the electrophotographic photosensitive member and the intermediate transfer belt that takes place when the intermediate transferring member and the electrophotographic photosensitive member are left to stand for a long time while they are integrally provided under a state of one body.
The electrophotographic photosensitive member as well as the intermediate transfer belt contain various materials being mixed in order to obtain required functions, and among those materials some may affect adversely each other by being left for a long time.
For example, in case when a material permeating into constructing components, such as a binder resin, to make it plastic or a material influencing movement of electric charges, are attached, in particular, an organic electrophotographic photosensitive member is apt to be influenced thereby.
In the case of matter influencing movements of electric charges being attached to the electrophotographic photosensitive member, the difference in sensitivity characteristic is brought about in that portion, giving rise to a density difference from the neighborhood at the time of printing to provide an abnormal image.
Also, as for the intermediate transfer belt, partial changes in electric characteristics such as resistance or capacity will result in transfer unevenness, which will appear in the image.
The most serious problem is the case where a crack occurs in the photosensitive layer due to the matter having migrated from the intermediate transfer belt. Such a crack is remarkable in the thickest layer among the layers constituting the photosensitive layer, and is apt to occur in the photosensitive layer and in the charge transport layer in case of lamination type photosensitive layers.
Such a phenomenon that a crack occurs in the electrophotographic photosensitive member or a shift in matter influencing movements of electric charges takes place remarkably in a portion (contact part) where the intermediate transfer belt and electrophotographic photosensitive member are brought into contact, but in case of the matter in question being volatile, not only the contact part but also the neighborhood is affected so that unevenness in the image density is caused to take place.
Accordingly, even if the intermediate transfer belt and the electrophotographic photosensitive member are not always brought into contact, in case of an intermediate transfer belt-electrophotographic photosensitive member integrated process cartridge which is disposed in the same housing, leaving the in
Ashibe Tsunenori
Kobayashi Hiroyuki
Kusaba Takashi
Matsuda Hidekazu
Nakazawa Akihiko
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grainger Quana
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