Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
1999-11-24
2001-04-17
Martin, Roland (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S067000
Reexamination Certificate
active
06218064
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic apparatus, and more particularly to an electrophotographic apparatus with an improved light receiving member.
2. Related Background Art
There have been known many electrophotographic methods, for example, as described in U.S. Pat. No. 2,297,692, Japanese Patent Publication No. 42-23910, and Japanese Patent Publication No. 43-24748. It is common practice to utilize a light receiving member, form an electric latent image on the light receiving member by various means, then develop the latent image with a developing agent (developer), electrically transfer the developer image onto a transfer medium such as paper as occasion demands, and thereafter fix the image by heat, pressure, heat and pressure, or solvent vapor or the like to obtain a copy.
In the above steps, since the residual developer remains on the surface of the light receiving member even after the developer image has been transferred onto the transfer medium, a cleaning blade, used as a means for removing the residual developer, is put in contact with the surface of the light receiving member to scrape the residual developer therefrom and discharge the untransferred developer to the outside of the system.
As the materials for the light receiving member used as an electrophotographic photosensitive member, a variety of materials are proposed, including inorganic materials such as selenium, cadmium sulfide, zinc oxide, and amorphous silicon (hereinafter referred to as a-Si), organic materials, and so on. Of these materials, non-monocrystalline deposited films containing silicon atoms as a main component, typified by a-Si, for example amorphous deposited films of a-Si or the like containing hydrogen and/or halogen (for example, fluorine, chlorine, etc.) (for example, compensating for hydrogen or dangling bonds), are suggested as high-performance, high-durability, and nonpolluting photosensitive members and some of them are practically used. U.S. Pat. No. 4,265,991 discloses the technology of the electrophotographic photosensitive member the photoconductive layer of which is formed mainly of a-Si. Further, as techniques for enhancing water repellency and wear resistance, Japanese Patent Application Laid-Open No. 60-12554 (U.S. Pat. No. 4,559,289) discloses a surface layer containing carbon and halogen atoms in the surface of a photoconductive layer comprised of amorphous silicon containing silicon atoms, and Japanese Patent Application Laid-Open No. 2-111962 discloses a photosensitive member having a surface protecting-lubricating layer provided on an a-Si:H or a-C:H photosensitive layer. However, these publications include no description concerning the relationship between the electrophotographic process and the scraping property of the surface layer.
Since the a-Si base photosensitive members, typified by a-Si, have excellent properties that they demonstrate high sensitivity to light of long wavelengths such as semiconductor lasers (770 nm to 800 nm) and have little deterioration recognized after repetitive use, they are widely used as photosensitive members for electrophotography, for example, in high-speed copying machines, LBPs (laser beam printers), and so on.
As the methods for forming the silicon base non-monocrystalline deposited films, there are many known methods, including the sputtering method, the method of decomposing a source gas by heat (thermal CVD method), the method of decomposing a source gas by light (photo CVD method), the method of decomposing a source gas by plasma (plasma CVD method), and so on. Of these methods, the plasma CVD method, which is a method of decomposing a source gas by a glow discharge or the like generated by direct current, high frequency (RF or VHF), or microwave to form a deposited film on a desired substrate such as glass, quartz, a heat-resistant synthetic resin film, stainless steel, or aluminum are now under way to practical use, including not only the method of forming the amorphous silicon deposited films for electrophotography, but also methods for forming deposited films for the other uses, and there are also proposed various apparatuses for such methods.
For the light receiving members, there are recently required improvement in the electrophotographic characteristics matching with high-speed operation and vivider image quality. Therefore, in addition to the improvement in the characteristics of the photosensitive member, the grain diameters of the developer are being decreased and there are frequently used those developers having the weight average grain diameter of 5 to 8 &mgr;m measured by a coulter counter or the like.
As the charging and decharging means for the conventional light receiving members including the a-Si type light receiving member, there has been utilized in most cases the corona charger (corotron, scorotron) containing a wire electrode (a metal wire such as a gold plated tungsten wire of 50 to 100 &mgr;m&phgr;) and a shield plate as main components. That is, the charging and decharging of the light receiving member using the corona charger is carried out by applying a high voltage (about 4 to 8 kV) to the wire electrode to generate a corona current and allowing the corona current to act on the light receiving member. The corona charger is excellent in uniform charging and decharging.
However, the corona discharge is accompanied by generation of ozone (O
3
). The ozone oxidizes nitrogen in the air to form nitrogen oxides (NOx). Further, the nitrogen oxides react with water in the air to form nitric acid and other products.
The products due to the corona discharge such as the nitrogen oxides, nitric acid, etc., adhere to and are deposited on the surface of the light receiving member and peripheral devices. Since the corona discharge products have a strong hygroscopic property, deposition of the corona discharge products on the surface of the light receiving member results in reduction of the resistance of the surface due to moisture absorption of the corona discharge products to substantially decrease the charge retaining capability of the light receiving member throughout or in part of the surface, which may cause the image defect called image smearing (the charge in the surface of the light receiving member leaks in the plane directions to destroy or fail to form an electrostatic latent image pattern).
Further, the corona discharge products adhering to the internal surface of a shield plate of the corona charger are evaporated and liberated not only during operation of the electrophotographic apparatus but also during quiescent periods of the apparatus, e.g. during the nighttime, and they then adhere to the surface of the light receiving member at a part thereof corresponding to the discharge aperture region of the charger and absorb moisture to decrease the resistance of the surface of the light receiving member.
As a result, it becomes easier to cause the image smearing in the first image or subsequent several images outputted when restarting the operation of the electrophotographic apparatus, at the region corresponding to the aperture portion of the charger.
Further, the a-Si type light receiving member has a surface hardness extremely higher than those of the other light receiving members. Therefore, the corona discharge product adhering to the surface of the light receiving member can not be removed by the ordinary cleaning step of the light receiving member surface, so that the corona discharge product is likely to remain on the light receiving member surface.
Thus, hitherto, it has been sometimes practiced to provide a heater for directly heating the light receiving member or to send hot air to the light receiving member by a hot air sending device to heat the light receiving member surface (at 30 to 50° C.) to thereby maintain the dry state, thus preventing the corona discharge products adhering to the light receiving member surface from absorbing moisture to substantially lower the resistance of the light receiving member surface
Hashizume Junichiro
Okamura Ryuji
Ueda Shigenori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Martin Roland
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