Electrophotography – Image formation – Charging
Reexamination Certificate
1999-07-19
2001-02-06
Martin, Roland (Department: 1753)
Electrophotography
Image formation
Charging
C430S066000, C430S067000, C430S059600
Reexamination Certificate
active
06185398
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to an electrophotographic photosensitive member, particularly an electrophotographic photosensitive member having a surface layer comprising a specific (polyester) resin, a process cartridge including the photosensitive member, and an electrophotographic apparatus using the photosensitive member.
In recent years, there have been developed electrophotographic photosensitive members utilizing various organic photoconductive compounds.
Such organic photoconductive compounds have different sensitive wavelength regions depending on the compounds used. In this regard, Japanese Laid-Open Patent Applications (JP-A) 61-272754 and 56-167759 disclose azo pigments showing a high (photo-)sensitivity in a visible (wavelength) region. Further, JP-A 57-19576 and JP-A 61-228453 disclose compounds showing a sensitive wavelength region extending in an infrared (wavelength) region. Of these compounds (pigments), those showing a sensitivity also in the infrared region are suitable for use in laser beam printers and LED (light-emitting diode) printers and have more frequently been employed in recent years.
The photosensitive member is generally required to have good characteristics in terms of sensitivity, electrical characteristics, mechanical characteristics and optical characteristics. Particularly, when the photosensitive member is repetitively used, electrical and mechanical external forces are directly exerted on a surface layer of the photosensitive member during a sequence of, e.g., charging-exposure-developing-transfer-cleaning in an ordinary electrophotographic process. As a result, the surface layer of the photosensitive member is required to have durabilities against such external forces, such as a durability against a deterioration due to ozone and nitrogen oxides generated in the charging step and a durability against electrical and mechanical deteriorations due to surface abrasion and/or mars caused by charging (discharging) and/or cleaning.
Particularly, an organic photosensitive member uses a softer organic photoconductive compound (substance) in many cases when compared with an inorganic photosensitive member, and thus is required to improve its durability against mechanical deterioration.
Further, in recent years, there has been mainly used, as a charging scheme, a contact (or direct) charging scheme wherein a photosensitive member is charged by applying a voltage to a charging member disposed in contact with the photosensitive member as described in JP-A 57-17826 and JP-A 58-40566.
The contact charging scheme has the advantages of less ozone generation and high charging efficiency when compared with the case of a corona discharge scheme using scorotron liable to cause ozone generation and inefficient charging due to a large amount of current passing through a shield (ca. 80% based on that of current to be supplied to a charger), thus resulting in a very economical and effective charging scheme.
The contact charging scheme is used in contact with a photosensitive member. Accordingly, the photosensitive member is required to have a further improved mechanical strength.
Further, the use of a contact (direct) charging scheme utilizing a DC (direct-current) voltage superposed with an AC (alternating-current) voltage has been proposed in order to enhance charging stability (JP-A 63-149668).
However, while the contact charging scheme (as described in JP-A 63-149668) can improve charging stability, it is accompanied by a problem such that an amount of current passing through a photosensitive member is liable to be remarkably increased due to the use of the AC voltage which results in a larger amount of abrasion of the photosensitive member.
As described above, the electrophotographic photosensitive member is required to have not only mechanical strength but also electrical strength.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electrophotographic photosensitive member having solved the above-mentioned problems and providing excellent mechanical and electrical strengths even in repetitive use for a long period of time.
Another object of the present invention is to provide a process cartridge including the photosensitive member and an electrophotographic apparatus including the photosensitive member.
According to the present invention, there is provided an electrophotographic photosensitive member, comprising: a support and a photosensitive layer disposed on the support, wherein
said electrophotographic photosensitive member has a surface layer comprising a polyester resin having a recurring unit represented by the following formula (1):
wherein A
1
represents a substituted or unsubstituted divalent aliphatic hydrocarbon group.
According to the present invention, there is also provided a process cartridge detachably mountable to an electrophotographic apparatus main body, comprising the above-mentioned electrophotographic photosensitive member and at least one means selected from the group consisting of charging means, developing means and cleaning means.
According to the present invention, there is further provided an electrophotographic apparatus comprising the above-mentioned electrophotographic photosensitive member, charging means, exposure means, developing means and transfer means.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawing.
REFERENCES:
patent: 4284699 (1981-08-01), Berwick et al.
patent: 4551403 (1985-11-01), Miyakawa et al.
patent: 4769304 (1988-09-01), Kondo et al.
patent: 5258252 (1993-11-01), Sakai et al.
patent: 5538826 (1996-07-01), Anitoya et al.
patent: 5876890 (1999-03-01), Kitamura
patent: 3215646 (1982-11-01), None
patent: 56-167759 (1981-12-01), None
patent: 57-017826 (1982-01-01), None
patent: 57-019576 (1982-02-01), None
patent: 58-040566 (1983-03-01), None
patent: 61-228453 (1986-10-01), None
patent: 61-272754 (1986-12-01), None
patent: 63-149668 (1988-06-01), None
Hirano Hidetoshi
Tanaka Takakazu
Uesugi Hirotoshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Martin Roland
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