Electrophotography – Image formation – Charging
Reexamination Certificate
2001-05-22
2003-10-21
Dote, Janis L. (Department: 1756)
Electrophotography
Image formation
Charging
C430S066000, C399S150000, C399S159000
Reexamination Certificate
active
06636715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosensitive member and an image forming apparatus, and more specifically a photosensitive member usable for electrophotography which is configured by consecutively laminating a photoconductive layer containing amorphous Si and a surface protective layer, and an image forming apparatus comprising the photosensitive member according to the present invention.
2. Related Background Art
An electrophotographic apparatus comprising an image forming apparatus such as a copier, a facsimile or a printer forms a copied image or the like by uniformly charging an outer circumferential surface of a photosensitive member having a substrate on a surface of which a photoconductive layer is disposed by charging means for roller charging, fur brush charging or magnetic brush charging, and then exposing an image to be copied of an object to be copied to reflected rays, a laser corresponding to a modulated signal or an LED to form an electrostatic latent image on the outer circumference of the above described photosensitive member, further adhering a toner to the above described photosensitive member to form a toner image and transferring the toner image to copying paper or the like.
After the image is formed by the electrophotographic apparatus as described above, the toner partially remains on the photosensitive member and it is necessary to remove the residual toner. It is general to remove such residual toner at a cleaning step using a cleaning blade, a fur brush, a magnet brush or the like.
By the way, there has recently been proposed and disclosed electrophotographic apparatuses which use no cleaning device so as to produce waste toner in a smaller amount of toner or no waste toner for solicitudes of environments. This type electrophotographic apparatuses are classified into those such as an apparatus disclosed by Japanese Patent Application Laid-Open No. 6-118741 which uses a direct charger such as a brush charger serving for both charging step and a cleaning step, those such as an apparatus disclosed by Japanese Patent Application Laid-Open No. 10-307455 which uses a developing apparatus serving for both a developing step and a cleaning step and others: any apparatus using a step of removing unwanted toner from a surface of a photosensitive member by rubbing the toner with the surface of the photosensitive member.
In recent years where toners which have average particle diameters smaller than conventional are used for enhancing qualities of printed images and toners which have fusion points lower than conventional are used for energy saving, however, it is difficult to remove the residual toner at a toner removing step which is proceeded simultaneously with another process, whereby a problem of toner adhesion may be posed that the above described residual toner interlocks with a surface of a photosensitive member as a result of repeated image formation, thereby producing an image defect of black spots or white spots.
As a measure to solve the above described problem, there has been proposed a method which uses a photosensitive member having amorphous Si as a photosensitive layer and preliminarily roughens, by cutting or with a rotary ball mill, a surface of an electrically conductive substrate on which the above described photosensitive layer is to be formed as disclosed by Japanese Patent Application Laid-Open No. 9-297420, and surface roughness of the substrate as measured with a surface roughness meter is specified on the order of micrometers.
In Japanese Patent Application Laid-Open No. 8-129266, a worked form of an electrically conductive substrate is specified as a value of an average inclination angle &thgr;a measured with a surface roughness meter in an evaluation length on the order of millimeters. Furthermore, the value corresponds to 0.0035 to 0.0524 in terms of an average inclination &Dgr;a.
Furthermore, progresses which have been made in digital electrophotographic apparatuses is forming a main stream of latent image formation with a light source emitting rays having a wavelength such as a laser, an LED or the like. As a result, the above described method which preliminarily cuts the substrate may pose a problem that exposing rays incident on the electrically conductive layer are different dependently on the form of the substrate, thereby forming stripe patterns (interference fringe) on a printed image. Furthermore, a cost is enhanced by newly adding a step of preliminarily roughening the surface of the electrically conductive substrate. When the substrate is worked to roughness within a range where the above described stripe patterns are not produced, in contrast, it may not possible to sufficiently the toner adhesion.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a photosensitive member and an image forming apparatus having the photosensitive member which are free from image degradation due to useless toner adhesion to a photosensitive member or a problem due to improper cleaning and capable of maintaining performance for image sharpness not only of an analog image but also of a digital image for a long time.
Furthermore, an object of the present invention is to provide a photosensitive member and an image forming apparatus which prevent a toner from adhering at a cleaning step, thereby providing a favorable image.
Another object of the present invention is to provide a photosensitive member which is composed by laminating a photosensitive layer containing at least amorphous Si and a surface protective layer consecutively on an electrically conductive substrate and has an average inclination &Dgr;a of 0.12 to 1.0 within a range of 10 &mgr;m×10 &mgr;m as well as an image forming apparatus which has the photosensitive member.
The present invention which accomplishes the above described objects is achieved on the basis of a finding that a toner adhesion preventing effect is not always determined by surface roughness of an electrically conductive substrate on the order of micrometers dependent on a worked form of the substrate as measured with a surface roughness meter, but largely dependent rather on microscopic surface roughness (specifically on the order of several nanometers to tens of nanometers) of amorphous Si film (film having a non-single crystal (preferably amorphous) material containing silicon as a parent body). Furthermore, the present invention is based on a finding of a significant correlation between an average inclination &Dgr;a calculated from this surface shape and the toner adhesion preventing effect.
The average inclination &Dgr;a within the range of 10 &mgr;m×10 &mgr;m indicates a result which is measured with an atomic force microscope (Q-SCOPE 250 (version 3.181) manufactured by Quesant Co.) and it is preferable to measure microscopic surface roughness within a measuring range of 10 &mgr;m×10 &mgr;m for obtaining a result with a high accuracy and a high repeatability. Furthermore, it is preferable to carry out correction (tilt removal) of a result obtained with Q-SCOPE 250 manufactured by Quesant Co. to prevent an error from being involved due to curvature and an inclination of a sample. Specifically, a correction (parabolic) for flattening curvature of an AFM image is carried out by fitting the image to a parabolic curve and a correction (line by line) for flattening an inclination is carried out. This technique is preferable for the photosensitive member which is cylindrical. It is possible to appropriately correct an inclination of a sample within a range where data is not distorted as described above.
By controlling the average inclination &Dgr;a of the amorphous Si photosensitive member measured as described above, it is possible to provide an electrophotographic photosensitive member which is capable of effectively preventing toner adhesion and forming an image which has extremely high quality.
In addition, it is more preferable that the above described average inclination &Dgr;a has a value within a range of 0.1
Ehara Toshiyuki
Karaki Tetsuya
Kawada Masaya
Kawamura Kunimasa
Owaki Hironori
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