Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2002-12-09
2004-10-19
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, C430S058650, C430S058800, C399S159000
Reexamination Certificate
active
06806009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member. More particularly, it relates to an electrophotographic photosensitive member having on a cylindrical support a photosensitive layer and a protective layer in this order, which cylindrical support has an outer diameter of less than 30 mm; and a process cartridge and an electrophotographic apparatus which have such an electrophotographic photosensitive member.
2. Related Background Art
With achievement of high image quality and high-speed and high-durability image formation in recent years, organic electrophotographic photosensitive members making use of organic photoconductive materials are also required to be more improved in mechanical durability.
In recent years, electrophotographic apparatus such as printers, copying machines and facsimile machines making use of electrophotographic photosensitive members have also come into wide use in various fields, and are more severely required to provide images which are always stable even in more various environments.
Electrophotographic photosensitive members, to which electrical and mechanical external forces are directly applied, are required to have durabilities to such forces. Stated specifically, they are required to have durability to the occurrence of surface wear and scratches due to friction and durability to the deterioration of surface layer that is caused by adhesion of active substances such as ozone and nitrogen oxides generated at the time of charging.
In addition, electrophotographic photosensitive members are repeatedly put to steps of charging, exposure, development, transfer, cleaning and charge elimination. An electrostatic latent image formed upon charging and exposure is made into a toner image by the use of a toner. This toner image is further transferred to a transfer material such as paper by a transfer means, where it is not that the toner of the toner image is all transferred but that it remains partly on the surface of the photosensitive member as a transfer residual toner.
If this transfer residual toner is in a large quantity, i.e., any faulty transfer occurs, the image on the transfer material comes into an image with what is called crumbling blank areas. This not only results in lack of image uniformity but also may cause a problem that the melt adhesion of toner or filming occurs on the electrophotographic photosensitive member. To solve such a problem, it is required to improve the releasability of the surface layer of the electrophotographic photosensitive member.
To meet such requirements, it has been attempted to provide protective layers of various types. Among various attempts, protective layers composed chiefly of resins have been proposed in a large number. For example, as disclosed in Japanese Patent Application Laid-Open No. 57-30846, a protective layer is proposed which is formed of a binder resin to which a metal oxide is added as conductive particles so that its volume resistivity can be controlled.
As also disclosed in Japanese Patent Application Laid-Open No. 6-82223, it is proposed to use a curable phenolic resin as a resin for protective layers. However, in an electrophotographic photosensitive member disclosed in this publication, carbon fluoride is dispersed in its protective layer, and hence the resin of the protective layer has a low transparency to make images have a poor one-dot reproducibility.
The metal oxide is dispersed in the protective layer of an electrophotographic photosensitive member chiefly in order to control the volume resistivity of the protective layer itself to prevent residual potential from increasing in the photosensitive member as the electrophotographic process is repeated. It is known that suitable volume resistivities of protective layers for electrophotographic photosensitive members are 10
10
to 10
15
&OHgr;·cm.
However, where the volume resistivity is within the above range, the volume resistivity of the protective layer tends to be affected by ion conduction, and hence the volume resistivity tends to undergo great changes depending on environmental changes. In particular, in the case when the metal oxide is dispersed in the protective layer, the metal oxide surface has so high water absorption properties that it has hitherto been very difficult to keep the volume resistivity of the protective layer within the above range in every environment and besides in the repetition of the electrophotographic process. Especially in an environment of high humidity, the volume resistivity may gradually lower with leaving and the active substances such as ozone and nitrogen oxides generated at the time of charging may repeatedly adhere to the surface. These may cause a decrease in volume resistivity of the electrophotographic photosensitive member surface layer and a lowering of releasability of toner from the surface layer, bringing about problems that defects such as what is called smeared images and blurred images may occur and that an insufficient image uniformity may result.
Where particles are dispersed in the protective layer as commonly done, it is preferable for the particles to have a particle diameter which is smaller than the wavelength of incident light, i.e., 0.3 &mgr;m or less.
However, metal oxide particles usually tend to agglomerate in a resin solution and may uniformly be dispersed with difficulty. Even if they have once been dispersed, they tend to cause secondary agglomeration or sedimentation. Accordingly, it has been very difficult to stably produce films in which fine particles of 0.3 &mgr;m or less in particle diameter are dispersed in a good state.
In addition, from the viewpoint of improving the transparency and conduction uniformity of the protective layer, it is preferable to disperse ultrafine particles having especially small particle diameter (0.1 &mgr;m or less in primary particle diameter), but such ultrafine particles tend to have poorer dispersibility and dispersion stability.
In order to compensate the above disadvantage, for example, Japanese Patent Application Laid-Open No. 1-306857 discloses a protective layer to which a fluorine-atom-containing silane coupling agent, a titanate coupling agent or a compound such as C
7
F
15
NCO has been added; Japanese Patent Application Laid-Open No. 62-295066, a protective layer in a binder resin of which fine metal particles or fine metal oxide particles improved in dispersibility and moisture resistance by water-repellent treatment have been dispersed; and Japanese Patent Application Laid-Open No. 2-50167, a protective layer in a binder resin of which fine metal oxide particles surface-treated with any of a titanate coupling agent, a fluorine-atom-containing silane coupling agent and an acetoalkoxyaluminum diisopropionate have been dispersed.
An example in which a charge-transporting material having a hydroxyl group is contained in the protective layer is also disclosed in, e.g., Japanese Patent Application Laid-Open Nos. 10-228126 and 10-228127.
An example in which a phenolic resin is used as the binder resin used in the protective layer is also disclosed in, e.g., Japanese Patent Application Laid-Open No. 5-181299.
Under existing circumstances, however, even these protective layers have not achieved any durability and releasability against various impact to surface and against wear and scratching, which are high enough to be able to meet the high durability and high image quality required in recent years.
In addition, there is an increasing need for space saving, and it is driven by necessity to make small the size of the main body of an electrophotographic apparatus. Accordingly, it is necessary to manufacture electrophotographic photosensitive members adapted to the size of the main body, and it is essential to make electrophotographic photosensitive members have a small diameter.
However, in an attempt to make achievement both for manufactu
Ikezue Tatsuya
Morikawa Yosuke
Nakata Kouichi
Tanaka Daisuke
Yoshimura Kimihiro
Canon Kabushiki Kaisha
Goodrow John L
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