Electrophotography – Supplemental electrophotographic process – Exposure or charging
Reexamination Certificate
1999-04-29
2001-05-29
Grimley, Arthur T. (Department: 2852)
Electrophotography
Supplemental electrophotographic process
Exposure or charging
C399S127000, C399S177000
Reexamination Certificate
active
06240269
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic process and an electrophotographic apparatus and, more particularly, to an electrophotographic process using an amorphous silicon base photosensitive member (a-Si photosensitive member) and an electrophotographic apparatus having the photosensitive member.
2. Related Background Art
The a-Si photosensitive members have characteristics of high surface hardness, high sensitivity to long-wavelength light of semiconductor lasers (770 nm to 800 nm) etc., little deterioration after repetitive use, and so on and are commercially used as photosensitive members for electrophotography, particularly, for high-speed copying machines, LBPs (laser beam printers), and so on.
FIG. 1
is a schematic, structural view for explaining an example of the image forming process in an electrophotographic apparatus using the a-Si photosensitive member, in which around a photosensitive member
401
arranged to rotate in the direction of arrow R
1
there are provided a primary charger
402
, an electrostatic latent image forming section
403
, a developing unit
405
, a transfer sheet supplying system
406
, a transfer charger
407
a
, a separation charger
407
b
, a cleaner
409
, a conveying system
410
, a charge-eliminating light source
411
, and so on. Normally, a corona charger excellent in uniform charging is widely used as the primary charger
402
.
The image forming process will be described below with the above example. The photosensitive member
401
is uniformly charged by the primary charger
402
to which the high voltage of +6 to 8 kV is applied. Light is guided from the electrostatic latent image forming section
403
to be projected onto the photosensitive member
401
to form an electrostatic latent image thereon. A negative toner is supplied from the developing unit
405
onto the latent image to form a toner image. On the other hand, a transfer sheet P is supplied through the transfer sheet supplying system
406
to the photosensitive member and a positive electric field, which is of a polarity opposite to the polarity of the toner, is applied thereto from the back in a gap between the photosensitive member
401
and the transfer charger
407
a
to which the high voltage of +7 to 8 kV is applied. This causes the negative toner image on the surface of the photosensitive member to be transferred onto the transfer sheet P. The transfer sheet P is separated by the separation charger
407
b
to which the high AC voltage of 12 to 14 kvp-p and 300 to 600 Hz is applied and it is conveyed through the transfer sheet conveying system
410
to a fixing device (not illustrated), in which the toner image is fixed. The transfer sheet P is then discharged out of the apparatus.
In the electrophotography, a photoconductive material for forming the photosensitive layer in the photosensitive member needs to have the following characteristics; high sensitivity, high SN ratio [photocurrent (Ip)/dark current (Id)], an absorption spectrum compatible with spectral characteristics of electromagnetic waves to be radiated thereto, quick optical response, and desired dark resistance, and harmlessness to the human body during use, and so on. Particularly, in the case of the photosensitive members for image-forming apparatus incorporated in the image-forming apparatus used as business machines in offices, a nonpolluting property during the aforementioned use is a significant point. One of the photoconductive materials demonstrating excellent properties in the aforementioned aspects is hydrogenated amorphous silicon (which will be referred to as “a-Si:H”). For example, Japanese Patent Publication No. 60-35059 describes an application thereof to the photosensitive member for image-forming apparatus.
The photosensitive members for image-forming apparatus using a-Si:H are generally made by heating a conductive support at 50° C. to 400° C. and forming a photoconductive layer comprised of a-Si on the support by a film forming method such as a vacuum evaporation method, a sputtering method, an ion plating method, a thermal CVD method, a photo CVD method, a plasma CVD method, or the like. Among them the plasma CVD method, which is a method for decomposing a source gas by direct current or high-frequency or microwave glow discharge to form an a-Si deposited film on the support, is practically used as a preferred method.
For example, Japanese Patent Application Laid-Open No. 54-83746 suggests the photosensitive member for image-forming apparatus comprised of an electroconductive support and a photoconductive layer made of a-Si containing halogen atoms as a constituent (hereinafter referred to as “a-Si:X”). This application describes that when a-Si contains 1 to 40 atomic % halogen atoms, the photoconductive layer has high heat resistance and good electrical and optical characteristics as a photoconductive layer of the photosensitive member for image-forming apparatus.
Japanese Patent Application Laid-Open No. 57-11556 describes the technology of forming a surface layer of a non-photoconductive amorphous material containing silicon atoms and carbon atoms, on the photoconductive layer of an amorphous material containing silicon atoms as a matrix in order to improve the electrical, optical, and photoconductive properties including the dark resistance, photosensitivity, optical response, and so on, operating environment characteristics such as humidity resistance and the like, and temporal stability of the photoconductive member having the photoconductive layer comprised of the a-Si deposited film.
Further, Japanese Patent Application Laid-Open No. 60-67951 describes the technology of the photosensitive member in which a light transmissive insulating overcoat layer comprised of amorphous silicon containing carbon, oxygen, and fluorine is stacked, and Japanese Patent Application Laid-Open No. 62-168161 describes the technology using an amorphous material containing silicon atoms, carbon atoms, and 41 to 70 atomic % hydrogen atoms, as a surface layer.
Further, Japanese Patent Application Laid-Open No. 57-158650 describes that the photosensitive member for image-forming apparatus with high sensitivity and high resistance can be obtained by using a photoconductive layer comprised of a-Si:H containing 10 to 40 atomic % hydrogen, wherein the absorption coefficient ratio of absorption peaks at 2100 cm
−1
and at 2000 cm
−1
in an infrared absorption spectrum is 0.2 to 1.7.
On the other hand, Japanese Patent Application Laid-Open No. 60-95551 discloses the technology for preventing lowering in surface resistance due to adsorption of water in the surface of the photosensitive member and image smearing occurring therewith by carrying out the image forming process including charging, exposure, development, and transfer while maintaining the temperature of the vicinity of the surface of the photosensitive member at 30° C. to 40° C. in order to improve the quality of image of the amorphous silicon photosensitive member.
These technologies improved the electrical, optical, and photoconductive characteristics and the operating environment characteristics of the photosensitive members for image-forming apparatus and also improved the image quality therewith.
Further, in order to prevent and eliminate the aforementioned image smearing of the photosensitive member at a high humidity, it is known to heat the photosensitive member by a heat source disposed on the internal surface side of the photosensitive member, for example, by an electric heater of a surface or rod shape disposed on the internal surface side of the cylindrical photosensitive member.
However, the continuous heating by the heater for prevention of the image smearing increases power consumption, as described above. Capacities of such heaters are normally approximately 15 W to 80 W, which do not always seem large electric energy. In most cases the apparatus is always powered throughout the day including the nighttime. The power consumption per
Ehara Toshiyuki
Karaki Tetsuya
Kawada Masaya
Kaya Takaaki
Nakayama Yuji
Canon Kabushiki Kaisha
Fitzpatrick, Cella, Harper and Scinto
Grimley Arthur T.
Ngo Hoang
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