Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1998-12-22
2001-02-06
Chapman, Mark (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C399S350000
Reexamination Certificate
active
06183930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, an electrophotographic apparatus, and an electrophotographic method and, more particularly, to an electrophotographic photosensitive member, which is a light receiving member, an electrophotographic apparatus, and an electrophotographic method capable of providing high-quality images stably throughout a long period of time without image unfocussing or image smearing.
2. Related Background Art
Hitherto, 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 suggested, 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. Japanese Patent Application Laid-Open No. 60-12554 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. These all are techniques for enhancing water repellency and wear resistance and 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 which demonstrate their 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 proceeding 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. There are also proposed various apparatuses for such methods.
Further, in the field of the application to the electrophotographic photosensitive members, demands for improvement in quality of film and processing performance are becoming stronger and stronger in recent years and a variety of ideas are also under study.
Particularly, the plasma processes using high-frequency power are used because of their various advantages including high stability of discharge, the capability of being also used for formation of insulating materials such as oxide films or nitride films, and so on.
For the light receiving members, there are recently required improvement in the electrophotographic characteristics matching with high-speed operation and more vivid 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 a weight average grain diameter of 5 to 8 &mgr;m measured by a Coulter counter or the like.
Since the a-Si base light receiving members have surface hardnesses much higher than those of the other photosensitive members, a blade-type cleaning method with high cleaning ability is popularly used as a cleaning means.
However, in such a blade-type cleaning method, differences occur in the amounts of the developer remaining on the blade surface because of differences in character patterns in an original chart. Further, uneven scraping may occur in the surface layer of the light receiving member. When such uneven scraping occurs, sensitivity irregularities appear as electrophotographic characteristics and result in density irregularities in an image. This phenomenon becomes more prominent particularly as the grain diameters of the developer decrease. In recent years, because the decrease of the grain diameters of the developer is being advanced in order to meet the demands for higher quality of image characteristics, such density irregularities occur more readily.
Further, the decrease of grain diameters of the developer improves the quality of image on one hand while tending to increase scrubbing force on the other hand. This increase of scrubbing force causes the developer (toner) to slip through the cleaning blade because of chatter or the like of the cleaning blade and this slipping of the developer may cause a black-line-like cleaning failure. When the copying step is repeated in this state, fine particles of the developer and additives (strontium titanate, silica, etc.) contained in the developer may be scattered in a corona charger to adhere to a wire electrode of the corona charger (hereinafter referred to as a charger wire), thereby causing discharge irregularities. When the discharge irregularities due to the contamination of the charger wire are caused, in the case of positive development (a method of developing unexposed portions of the surface of the light receiving member), the quality of output image may be lowered by appearance of linear blank area portions on the image, scale-like black fog spreading over the entire image, local black dots (0.1 to 0.3 mm&phgr;) without periodicity, and so on.
Further, when the contamination of the charger wire is caused, abnormal discharge may be induced between the contaminated portion and the light receiving member, thus damaging the surface of the photosensitive member and causing image defects.
In addition, when the frictional resistance is high, friction heat is built up between the light receiving member and the cleaning blade, and this friction heat may cause a fusion phenomenon in which the developer used for thermal fixatio
Aoki Makoto
Hashizume Junichiro
Ueda Shigenori
Canon Kabushiki Kaisha
Chapman Mark
Fitzpatrick ,Cella, Harper & Scinto
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