Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2000-03-24
2002-06-04
Dote, Janis L. (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S065000, C430S066000, C430S069000, C430S096000, C430S970000
Reexamination Certificate
active
06399262
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrophotographic photoreceptor (hereinafter occasionally referred simply to as a photoreceptor), and a processing cartridge as well as an image forming apparatus using said photoreceptor.
BACKGROUND OF THE INVENTION
In recent years, as electrophotographic photoreceptors, organic photoreceptors comprising organic photoconductive materials have been most widely employed. The organic photoreceptors are superior to other photoreceptors in such a manner that it is easier to develop materials in response to various types of exposure light sources ranging from visible light to infrared light; it is possible to select materials which result in no environmental pollution; the production cost is lower; and the like. However, only one problem of the organic photoreceptors is mechanically weak and during copying a large volume as well as during printing, the photoreceptor surface results in degradation as well as abrasion.
Such photoreceptors are generally prepared employing the following method. A charge generating layer is prepared by vacuum-evaporating organic charge generating materials onto an electrically conductive support which is comprised of aluminum or an aluminum alloy, or by applying a coating composition prepared by mixing organic charge generating materials with organic polymeric resins as the binding agent onto said support. Subsequently, a charge transport layer is formed by applying a coating composition, prepared by mixing organic charge transport materials and organic polymeric resins as the binding agent with a solvent onto the resulting charge generating layer.
In recent years, demand for electrophotographic image forming apparatuses has become more stringent in regard to image quality. Specifically, for reversal development type printers such as LD and LED printers and the like, still higher printing quality is desired. For instance, it is desired to eliminate minute black points (so-called black spots), which are formed on white backgrounds, and the like.
Generally, in electrophotographic copiers utilizing the Carlson method, after uniformly charging a photoreceptor, the resulting charge is eliminated imagewise by exposure to form an electrostatic latent image, which is developed employing toner and visualized. Subsequently, the toner is transferred onto paper and the like, and then fixed.
However, all toner on the photoreceptor is not transferred and a small portion of the toner remains on the photoreceptor. When images are repeatedly formed in such a state, the residual toner adversely affects the formation of the latent images. As a result, it is impossible to obtain high quality image copies without staining. Therefore, it is required to remove the residual toner. Representative cleaning means include a fur brush, a magnetic brush, a blade, and the like. Of these, a blade is mainly employed from the viewpoint of the performance, constitution, and the like. As the blade member, a plate-shaped rubber elastic body is generally employed.
As described above, electrical and external mechanical forces are directly applied to the surface of the electrophotographic photoreceptor through the charging unit, the development unit, the transfer means, the cleaning unit, and the like. Accordingly, durability against these processes is essential. Specifically, mechanical durability is required to counter the wear and abrasion of the photoreceptor surface due to sliding, as well as film peeling and the like, due to impact and the like, during corrective action to remove foreign matter and undo paper jams. Of these, durability similar to inorganic photoreceptors is strongly demanded against flaws due to impact, as well as film peeling.
In order to realize the various desired properties as described above, heretofore, various items have been investigated.
In order to improve the aforementioned image quality, proposed is a photoreceptor in which an alumite layer as a boundary blocking layer, which retards charge injection to the photosensitive layer, is formed on the surface of the aluminum base plate as the electrically conductive support. When such an alumite layer is employed, image quality, due to reduction of black spots and the like, is improved. However, since its close adhesion with the photosensitive layer decreases, durability of the photosensitive layer surface against external mechanical force also decreases. As a result, problems such as flaws, as well as film peeling, occur. It has been difficult to dissolve such problems of the film peeling caused by decrease of close adhesion with the photosensitive layer.
As far as the durability against mechanical force concerns, it is reported that wear resistant properties of the surface, as well as toner filming properties, are improved by employing BPZ polycarbonate as the binder (a binding resin) on the surface of the organic photoreceptor. Further, Japanese Patent Publication Open to Public Inspection No. 6-118681 discloses colloidal silica containing hardenable silicone resin employed as the protective surface layer of a photoreceptor.
However, a photoreceptor comprising the bisphenol Z type polycarbonate binder exhibits insufficient wear resistant properties and also does not exhibit sufficient durability. On the other hand, improved are wear resistant properties of the surface layer comprised of the colloidal silica containing hardenable silicone resin. However, electrophotographic properties are unsatisfactory during repeated use, and background staining as well as blurred images tends to occur. Thus, this method does not exhibit sufficient durability. Namely durability is not insufficient in each case, particularly it is difficult to prevent peeling due to deterioration of sdhesion of alumite layer and the photosensitive layer.
Japanese Patent Publication Open to Public Inspection Nos. 9-124943 and 9-190004 disclose a photoreceptor having as the surface layer, a resin layer in which an organic silicone modified positive hole transport compound is bonded to a hardenable organic silicone based polymer. However, said resin layer tends to form background staining as well as blurred images at a relatively high humid ambiance. Thus sufficient durability is not obtained. Further, said hardenable organic silicone compound film exhibits high wear resistant properties. However, since said film tends to suffer from flaws due to external impact and tends to peel, its strength, as well as adhesion, is not sufficient.
Further, accompanying the recent progress of digital technology, in the image forming methods employing electrophotography, image exposure utilizing an interfering light source has been the main process. Thus, desired has been the development of a photoreceptors which are suitable for such an interfering light source and do not form an interference moire; exhibit high wear resistance, and neither suffer from flaws nor peel due to external impact; and further does not form blurred images.
SUMMARY OF THE INVENTION
It is an object of the present invention to dissolve problems caused by decrease of close adhesion of the photosensitive layer with alumite layer. For this purpose, it is the object to provide a photoreceptor having high surface hardness. It is an object of the present invention to provide, while overcoming the problems described above, an electrophotographic photoreceptor which exhibits high surface hardness, high wear resistance, and high flaw resistance; exhibits consistent electrophotographic properties at high temperature and humidity during repeated use, and accordingly, repeatedly produces excellent images, and does not form a moire during the formation of digital images employing a laser beam and the like, and further to provide a processing cartridge as well as an image forming apparatus employing said photoreceptor.
The inventors of the present invention have endeavored to overcome the problems described above, in particular to maintain close adhesion of the photosensitive layer even when alumite is employed. As a result, it was discovered
Itami Akihiko
Kitahara Yohko
Kurachi Masahiko
Oshiba Takeo
Sakimura Tomoo
Bierman, Muserlian and Lucas
Dote Janis L.
Konica Corporation
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