Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
1998-04-09
2001-11-27
Rodee, Christopher (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S067000, C430S132000, C399S159000
Reexamination Certificate
active
06322943
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light-receiving member, an image forming apparatus having the member, and an image forming method utilizing the member, and more particularly to a light-receiving member with excellent characteristics free from causing drawbacks such as a faint image or a smeared image regardless of the ambient conditions and without heating the light-receiving member, and capable of maintaining such characteristics, also an image forming apparatus having such light-receiving member and an image forming method utilizing such light-receiving member.
2. Related Background Art
For the element member employed for a light-receiving member such as an electrophotographic photosensitive member, there have been proposed various materials such as selenium, cadmium sulfide, zinc oxide, phthalocyanine, amorphous silicon (hereinafter abbreviated as a-Si), etc. Among these materials, non-single-crystal deposited films containing silicon atoms as the main component, as represented by a-Si, for example amorphous deposited films such as a-Si compensated with hydrogen and/or halogen (for example fluorine or chlorine), have been proposed as the photosensitive member of high performance, high durability and no ecological problem, and some deposited films have been practically used. U.S. Pat. No. 4,265,991 discloses an electrophotographic photosensitive member of which a photoconductive layer is mainly composed of a-Si.
The a-Si photosensitive member has a high surface hardness, a high sensitivity to the light of long wavelength region such as of a semiconductor laser (770 nm to 800 nm) and exhibits little deterioration even after repeated use, and is widely employed as the electrophotographic photosensitive member for high-speed copying machines and laser beam printers (LBP).
For forming such deposited films, there have been known various methods such as sputtering, thermal CVD, photo CVD, plasma CVD, etc. Among these methods, the plasma CVD in which a raw material gas is decomposed by glow discharge caused by a DC current, a high frequency (RF, VHF) or a microwave to form a thin deposited film on a substrate such as glass, quartz, a heat-resistant plastic film, stainless steel or aluminum has been particularly advanced, for example, for the formation of an amorphous silicon deposited film for practical use in electrophotography, and various apparatus have also been proposed for executing such formation.
Also in recent years, there have been made various considerations for meeting the increasing demands for an improved film quality and for a higher throughput.
In particular, the plasma process utilizing the high frequency power has been adopted because of various advantages such as stability of discharge and applicability in the formation of insulating films such as an oxide film and a nitride film. Also recently a report on the plasma CVD method employing a high frequency power source of 50 MHz or higher in a plasma CVD apparatus with parallel flat electrodes (Plasma Chemistry and Plasma Processing, Vol. 7, No. 3 (1987), pp. 267-373) has shown a possibility of improving the deposition rate, without deteriorating the properties of the deposited film, by elevating the discharge frequency beyond the conventionally employed frequency of 13.56 MHz. Such elevation in the discharge frequency has also been tried in sputtering processes and is being investigated widely.
In applying the a-Si photosensitive member, produced by such methods, to an image forming apparatus employing so-called electrophotographic technology, a corona charger (corotron or scorotron) is mostly employed as the charging and charge eliminating means for the photosensitive member. Such corona discharge generates ozone (O
3
) which oxidizes nitrogen in the air to generate corona discharge products such as nitrogen oxides (NO
x
), and thus generated nitrogen oxides etc. react with the moisture in the air to generate nitric acid or the like. Such corona discharge products, for example nitrogen oxides and nitric acid, are deposited on the photosensitive member and surrounding devices and contaminate the surfaces thereof. As the corona discharge products exhibit a low electrical resistance by moisture absorption, the charge retaining ability is substantially lowered over the entire area or in local areas, leading to image defects such as a faint image or a smeared image (due to deformation or no formation of the electrostatic latent image by the charge on the photosensitive member leaking along the surface thereof).
Also the corona discharge products deposited on the internal surface of a shield plate of the corona charger evaporate and are liberated not only while the image forming apparatus is in operation but also while the apparatus is stopped—for example, during the night. The evaporated products deposit on the surface of the photosensitive member corresponding to the aperture of the corona charger and absorb moisture, whereby the surface of the photosensitive member is reduced in electrical resistance. For this reason, the first copy (output) or several copies at the initial stage when the apparatus is started after a pause tend to show a faint image or a smeared image in an area which is opposed to the aperture of the corona charger while the apparatus is stopped. Such image smear, appearing like the trace of the charger, is often called the charger trace smear. Such defect becomes conspicuous when the corona charger is an AC corona charger.
The faint image and the smeared image induced by the corona discharge products become more serious when the photosensitive member is an a-Si photosensitive member. In comparison with other photosensitive members, the a-Si photosensitive member tends to exhibit a lower efficiency of charging and charge elimination, so that the charging and the charge elimination by corona discharge to the a-Si photosensitive member are conducted with a higher voltage for applying to the charger in order to significantly increase the charging current in comparison with the cases of other photosensitive members. Since the amount of ozone generation is proportional to the corona charging current, a configuration employing an a-Si photosensitive member in combination with a corona charger particularly generates a large amount of ozone, thereby eventually enhancing the faint image and the smeared image resulting from the corona discharge products. Also in the case of the a-Si photosensitive member, due to the adverse effect of the very high surface hardness thereof, the corona discharge products deposited thereon tend to remain firmly for a long time.
For preventing such faint image or smeared image, there have been contemplated the following two methods.
The first method consists of reducing the relative humidity by heating (30° C. to 50° C.) the surface of the photosensitive member by use of a heater incorporated into the photosensitive member or by blowing warm air to the photosensitive member by use of a warm air blower. This method is capable of evaporating the corona discharge products and the moisture deposited on the surface of the photosensitive member, thereby substantially avoiding the reduction in resistance of the photosensitive member surface.
The second method consists of increasing the water repellent property of the surface of the photosensitive member, thereby rendering the deposition of the corona discharge products more difficult and thus preventing the smeared image. For example, the Japanese Patent Application Laid-Open No. 61-289354 discloses an a-C surface layer subjected to plasma treatment with a fluorine-containing gas. Also the Japanese Patent Application Laid-Open No. 60-12554 discloses an electrophotographic photosensitive member having a surface layer composed of an amorphous material containing carbon and halogen atoms, and a producing method therefor. Furthermore, the Japanese Patent Application Laid-Open No. 63-65447 discloses the technology on a fluorine-containing organic polymer film defined by the relations
Aoki Makoto
Hashizume Junichiro
Ueda Shigenori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Rodee Christopher
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