Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2002-06-27
2004-12-14
Goodrow, John L (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S059600, C430S096000, C430S126200, C430S132000, C399S159000
Reexamination Certificate
active
06830858
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrophotographic photosensitive member used for a image forming apparatus such as copy machine, electrostatic printing, facsimile, laser printer and electrostatic recording, a preparation method thereof, an image forming process, an apparatus and a process cartridge using the electrophotographic photosensitive member. More specifically the present invention relates to an electrophotographic photosensitive member used for an image forming apparatus, a preparation method thereof, an image forming apparatus which is capable of forming high quality of images with high speed operation for a long period of repeated use time.
DESCRIPTION OF THE RELATED ART
There are corona charging method and contact charging method used in electrophotograpy, those both have been used as electric charging method to make the photosensitive member electrically charged. The corona charging method contains corotron charging method and scotron charging method having a grid, those are a method in which AC potential or DC-overlapped AC potential is applied to the charging wire such as tungsten wire or nickel wire and so forth which being stretched on the central position of a housing shielded by metal plate, thereby corona discharge is induced which makes electrically charged photosensitive member.
However in this kind of method a high voltage is applied to the charging wire thus occurs ozone and nitrogen oxides products. And it has been known that such oxidant products affect bad influences upon, not only environmental aspect, but also the photosensitive member from the viewpoint of their durability and characteristics of produced image.
In recent years, instead of above described method using the charging wire for corona discharging, the contact charging method has been used in practice for the purpose of obtaining a lowered or an eliminated generation of ozone and a lowered consumption of electric power. The contact charging method is a method in which AC potential or DC-overlapped AC potential is applied to a charging member having electric resistance from 10
2
to 10
10
&OHgr;·cm degree, which is pressed to contact with the surface of an electrophotographic photosensitive member, thereby the electrophotographic photosensitive member is electrically charged. This charging method, which is subjected Paschen's law, is effectuated by a discharge emitted from the charging member toward the photosensitive member as charge-receiving member, therefore the charging of the photosensitive member is initiated by applying electric potential more than threshold level of voltage. In the execution of the contact charging method, an electric potential level to be applied may be lowered in comparison with that of corona charging method, but the method accompanies with an inevitable discharging, thus generates small amount of ozone and nitrogen oxides.
And the contact charging method causes a contact of charging member with the surface of the electrophotographic photosensitive member (hereinafter may also be referred as photoreceptor), therefore there is a problem that the abrasion of the surface of the electrophotographic photosensitive member is increased.
In the field of electrophotographic apparatus the demands such as higher quality image reproduction, higher tolerance, lower running cost and full-color imaging have been growing large in market in recent years. Particularly a full-color duplication has been popularized by the commercial diffusion of color printer and color copier, thus a demand for duplicating full-color image with almost same high speed as that of mono-color printing has growing. For satisfying this demand an attention has been paid to so called tandem type of full-color image forming apparatus. The tandem type of full-color image forming apparatus includes a plurality of photosensitive members arranged in parallel and equipped with developing unit respectively, and respective single colors formed on each photosensitive member are transferred and overlaid one by one onto the surface of recording member to make composed color image. This tandem type of full-color image forming apparatus is capable of significant time saving for printing action, in comparison with that of so called one drum type of image forming apparatus which employs only one photosensitive member and thereon are repeated a plurality of image forming actions (usually four times of action) to form full-color image. However such tandem type of full-color image forming apparatus has a plurality of image forming sections independent each other, therefore becomes large in apparatus scale, thus is apt to be expensive.
At the present time, with a demand for obtaining high quality of color image by color printer or color copier, as light sources for such photo-printers, the application of laser diodes (LDs) and light emitting diodes (LEDs) both which have smaller light beam diameter capable of high power emission so as to make itself capable of a finer dot recording has been prevailingly be trended in the field of image forming apparatus. Meantime, thicker CTL (charge transfer layer) of photosensitive member causes more decreased straight passages in the CTL for electric charges which are injected into the CTL and arrive to the surface of the CTL to neutralize the surface charges having opposite polarity, hence occurs blurring of images formed, therefore it is required to shorten the thickness of CTL.
Generally speaking, in Carlson process, the CTL is abraded and decreases its thickness by its repeated uses. Accordingly, for the purposes of avoiding the generation of smearing in back ground area of printed image or avoiding the decrease of the image density which are caused by decrease in electric charge potential and decrease in photosensitivity of the photosensitive member, it is thought to shorten the thickness of the CTL, but such shortening of the CTL thickness was disadvantageous from the point of view to attain high durability of the photosensitive member.
There is a tendency to require a higher sensitivity and a higher responsibility of the photosensitive member in accompanying with an achievement of high speed electrophotographic apparatus, a smaller photosensitive member in accompanying with an achievement of down sized apparatus, thus requiring a higher tolerance of the photosensitive member. For such requirements Japanese patent No 2838891 considered the quantum efficiency in dependence on the strength of electric field in photosensitive member, and discloses a photosensitive member which is achieved a high sensitivity, compatible with an improved durability, by the combination of a CTL having relatively large value of 25 to 60 &mgr;m in thickness and a CGL (charge generating layer) having quantum efficiency depended slightly upon the strength of electric field. However there was a shown drawback with this photosensitive member that it reveals the decease in sensitivity pursuant to the decrease in thickness of CTL caused by abrasions of the layer in the photosensitive member used repeatedly.
Hereupon, an electrophotographic photosensitive member has been designed and used in real which has an improved anti-abrasion nature by providing a protection layer on the photosensitive layer.
For instances Japanese Patent Laid-open Publication of Tokkai Shou 63-91666 discloses a technique to provide a protection layer made of silicone material on the photosensitive layer, Japanese Patent Laid-open Publication of Tokkai Hei 03-155558 discloses a technique to provide a protection layer made of curable silicone resin, Japanese Patent Laid-open Publication of Tokkai Shou 60-3639 discloses a technique to make a protection layer made of a composed mixture of a curable resin and an acrylic resin, Japanese Patent Laid-open Publication of Tokkai Shou 57-176057 discloses a technique to provide an insulate protection layer made of a fluoride resin dispersing therein powder of hard particles onto the photosensitive layer, Japanese Patent Laid-open Publication of Tokkai Shou 63-18354
Sugino Akihiro
Suzuki Yasuo
Goodrow John L
RICOH Company, Ltd.
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