JPH07234608A - Electrophotographic photosensitive drum unit - Google Patents

Abstract

PURPOSE:To prevent vibration sound of a photosensitive drum and dielectric breakdown of a photosensitive layer by contact electrostatic charge by providing this drum unit with a photoreceptor formed with the photosensitive layer on a stainless steel substrate specified in surface roughness and an electrostatic charging device in contact with this photoreceptor. CONSTITUTION:An electrostatic charging roll 2 is disposed on the surface of the photosensitive drum 1 in such a manner that this roll comes into contact therewith. DC voltage superposed with an AC components is impressed on the core material 3 of this electrostatic charging roll 2 formed with a layer consisting of a conductive elastic material for the core material 3. The conductive substrate made of a stainless steel pipe is used for this photosensitive drum 1 and its surface roughness Rmax is adjusted to >=2.0mum by grinding. The photosensitive layer is formed on such conductive substrate. Further, the surface roughness Rmax is preferably >=0.1mum in order to prevent generation of interference fringe patterns to be generated at the time of irradiation with a laser beam. As a result, the photosensitive layer less generates abnormal discharge and the discharge breakdown of the photosensitive layer is prevented when the photosensitive drum is subjected to contact electrostatic charge. The vibration sound generated by contact or sliding is thus prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive drum unit for electrophotography using a conductive support made of stainless steel, and particularly to preventing electrostatic charge damage to the photosensitive drum due to contact charging and generation of vibration noise during charging. The present invention relates to a photosensitive drum unit for electrophotography.

[0002]

2. Description of the Related Art Conventionally, a non-contact type corona discharge device has been generally used as a charging device in an electrophotographic apparatus using a photosensitive drum. However, in recent years, since the power source can be reduced in voltage and ozone is generated in an extremely small amount, there are advantages such as a roller type, a blade type, and a brush type charging member to which a voltage is applied. A contact charger using is being used. When charging by a contact charger, there are a method of applying a direct current and a method of applying an oscillating voltage in which an alternating current is superimposed on a direct current. By the way, when the above-described oscillating voltage is applied to the charging roller to charge the photosensitive drum, cycle unevenness in the circumferential direction of the photosensitive drum tends to occur as the peripheral speed of the photosensitive drum increases, and this is prevented. Therefore, the frequency of the vibration voltage applied to the charging roller must be increased. However, the frequency is about 200H
If z is exceeded, there is a problem in that a so-called charging noise is increased due to vibration of the photosensitive drum and the charging roller. In addition, there is a problem that sliding noise is generated due to friction with the cleaning blade. Such charging noise and sliding noise (hereinafter referred to as vibration noise) are generated when the base of the photosensitive drum has a thickness of 2 mm or less. However, it is especially likely to occur with thin-walled aluminum pipes. In order to prevent the generation of such vibration noise, for example, JP-A-3-105348 and JP-A-5-34936 are used.
In Japanese Patent Laid-Open Publication No. 2003-242242, it is proposed to put a filler inside the photosensitive drum to reduce vibration noise of the photosensitive drum.

[0003]

On the other hand, if a pipe other than an aluminum pipe, for example, a pipe made of stainless steel is used, no vibrating noise is generated without inserting a filler.
However, when contact charging is applied to a photosensitive drum using a stainless steel pipe as a substrate, there is a problem that the photosensitive layer is easily broken by abnormal discharge during charging.
This phenomenon is considered to be due to the following reasons.
That is, in the case of the contact charger, the current capacity is larger than that of the corona charger, so if there is a weak withstand voltage in the photosensitive layer, the current concentrates there and the current flows until discharge breakdown occurs. Occurs. In the case of charging by a corona charger, the current capacity is small, so that the current does not flow in a concentrated manner as described above and the photosensitive layer is not destroyed unless otherwise noted. When the photosensitive layer is destroyed, not only the electric charge is not applied to that portion and an image defect is caused, but also the charging member may be destroyed by an abnormal current, and as a result, uniform charging can be almost expected. Disappear. The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to prevent generation of vibration noise of a photosensitive drum due to contact charging, and
It is an object of the present invention to provide a photosensitive drum unit for electrophotography, which can prevent electrostatic charge damage to the photosensitive layer that occurs during charging.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that, in an electrophotographic apparatus for contact-charging a photosensitive drum using a stainless steel pipe, electrostatic breakdown is caused by abnormal protrusions on the substrate surface. It was That is, since the stainless steel pipe has a higher hardness than the aluminum pipe, the protrusions existing on the surface are less likely to be smooth, and moreover, the protrusions are left in an acute angle state, so that abnormal discharge is likely to occur. Therefore, by smoothing the surface of the stainless steel pipe,
We were able to achieve the above objectives. The photosensitive drum unit for electrophotography of the present invention comprises a conductive support made of stainless steel having a surface roughness Rmax of 2.0 μm or less,
It is characterized by comprising a photoconductor having a photoconductive layer formed thereon and a contact charger for charging the photoconductor by contacting the photoconductor. In the present invention, it is preferable that the charging member of the contact charger is configured so that a DC voltage on which an AC component is superimposed is applied.

Further, due to the recent miniaturization of electrophotographic apparatus, a photosensitive drum having a diameter of 30 mm or less is widely used. In order to apply such a photosensitive drum, a stainless steel pipe is used in the present invention. The diameter is 30 mm or less, and in that case, the wall thickness is preferably 0.4 mm or more. Thickness is 0.4m
When the thickness is less than m, the effect of preventing vibration noise becomes insufficient. Also, if the wall thickness becomes too thick, the weight will increase,
Since it becomes difficult to use, it is preferably 2 mm or less.

The present invention will be described below with reference to the drawings.
FIG. 1 is a schematic perspective view of an example of the electrophotographic photosensitive drum unit of the present invention. In the figure, the charging roll 2 is disposed so as to contact the surface of the photosensitive drum 1. As the charging roll, one having a structure in which a layer made of a conductive elastic material is formed on the core material 3 is used. A direct current voltage on which an alternating current component is superimposed is applied to the core material 3 from a power source (not shown).

In the present invention, the conductive support is produced by grinding the surface of a stainless steel pipe so that the surface roughness Rmax is 2.0 μm or less. However, Ra is preferably 0.1 μm or more in order to prevent the occurrence of an interference fringe pattern that occurs when the laser beam is irradiated. The surface of the stainless steel pipe can be ground with a rotating grindstone, sandpaper, a polishing belt, or the like.

FIG. 4 is a schematic diagram of a centerless grinding apparatus for grinding the surface of a stainless steel pipe.
The centerless grinding apparatus is composed of three sets of grindstones consisting of a pair of opposing rotary grindstones, namely grindstones 5 and 5, grindstones 6 and 6, grindstones 7 and 7, and grindstones 5 and 6,
It consists of fine abrasive grains in the order of 7. The pair of rotating grindstones facing each other are installed so that the rotating speeds thereof are different from each other, whereby the stainless steel pipe 4 placed thereon is rotated. In addition, the intervals of the respective rotating grindstones facing each other can be adjusted, whereby the stainless steel pipes are moved from the grindstones 5, 5 to the grindstone 6,
6, then to the grindstones 7, 7. In this grinding machine, the stainless steel pipe 4 is
It is placed on two rotating grindstones 5 and 5, and is ground while rotating, and is sequentially grinded by grindstones 6 and 6 and grindstones 7 and 7. FIG. 5 is a schematic configuration diagram of another grinding apparatus for grinding the surface of a stainless steel pipe. in this case,
The grinding film 9 coated with polishing powder is used, and the roll 1
Rotating stainless steel pipe 4 sent from 0
Is pressed against the surface of the sheet by a pressing roller 8 with an appropriate pressure. The grinding film is taken up by the take-up roll 11.

[0009]

In the present invention, the surface of the conductive substrate has a surface roughness Rmax of 2.0 μm or less, and since there are no high protrusions, when contact charging is performed, the photosensitive layer causes abnormal discharge. It is possible to prevent discharge breakdown of the photosensitive layer and to uniformly charge the photosensitive layer. This will be described with reference to FIGS. 2 and 3. FIG. 2 shows the result of measuring the surface roughness of the stainless steel pipe.
High protrusions exceeding 2 μm are observed here and there.
The surface roughness Rmax is 3.5 μm. If such a stainless steel pipe is used as it is, the problems as described in the above-mentioned conventional technique occur. On the other hand, in the present invention, the surface roughness Rmax is 2. because the stainless steel pipe is ground.
It is less than 0 μm. FIG. 3 shows an example thereof, and shows the result of measuring the surface roughness of a ground stainless steel pipe. As is clear from FIG. 3, no protrusion exceeding 2 μm is observed, and the surface roughness Rmax is 2.0 μm or less. Note that Rmax is preferably 0.1 μm or more in order to prevent the generation of an interference fringe pattern that occurs when the laser beam is irradiated. As described above, in the present invention, the conductive support made of stainless steel is used, and the surface roughness Rmax is 2.0.
Since the thickness is less than μm, when the photosensitive layer formed thereon is subjected to contact charging, abnormal discharge of the photosensitive layer is less likely to occur, discharge breakdown of the photosensitive layer can be prevented, and uniform charging is performed. be able to. Further, in the present invention, since the conductive substrate is made of stainless steel having a higher specific gravity than aluminum, the vibration noise generated by the contact or sliding by the contact charger or the cleaning blade is used. Can be prevented.

[0010]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 and Comparative Example 1 30 mmφ × 253 mmL × 0.4 mmt SUS30
4 pipes were prepared, and the surfaces of the pipes were ground by the centerless grinding device shown in FIG. What was taken out at the stage of rough cutting had a surface roughness Rmax = 3.
It was 5 μm and Ra = 0.40 μm (Comparative Example 1). What was ground with a finer grindstone had the surface roughness shown in FIG. 3, where Rmax = 1.8 μm and Ra = 0.22 μ.
m (Example 1). These pipes were used as a conductive substrate, and a surface of the pipe was coated with a methanol / butanol mixed solution of type 8 nylon resin (trade name: Toresin F30, manufactured by Teikoku Chemical Co., Ltd.) to form an undercoat layer having a thickness of 1 μm.
Then, a solution of X-type metal-free phthalocyanine dispersed in a solution of polyvinyl butyral resin (trade name: S-REC BM1, manufactured by Sekisui Chemical Co., Ltd.) at a weight ratio of 3: 1 was applied, and a charge having a film thickness of 0.25 μm was applied. A generator layer was formed. Furthermore, N, N'-diphenyl-N, N'-bis (m
-Tolyl) benzidine and polycarbonate Z resin 3
A coating liquid composed of a mixture containing a ratio of 6:64 was applied to form a charge transport layer having a film thickness of 18 μm to obtain a photosensitive drum. A charging roll was attached to this photosensitive drum to produce a photosensitive drum unit. The charging roll used was as follows. That is, an elastic layer made of polyether-based polyurethane rubber with conductivity added by adding 0.5% of lithium perchlorate to the outer circumference of a 5 mmφ stainless steel shaft was used.
Formed to have a diameter of 5 mm, and 0.001% on the surface.
The coating liquid consisting of the polyester-based polyurethane emulsion resin aqueous solution to which the methylphenyl silicone leveling agent was added is applied by the dip coating method, and the coating liquid is applied at 120 ° C. for 20
It was used for the drying for a minute to form a coating layer having a film thickness of 20 μm.

An image writing device using a semiconductor laser, a one-component toner developing device,
The image was evaluated by mounting it on a printer equipped with a transfer device and a cleaning device equipped with a urethane rubber blade. A direct current component of -600 V and an alternating current component of 400 Hz and a superimposed voltage of 1800 V were applied to the charging roll to charge the photosensitive drum. As a result, the surface potential is −
It became 600V. Then, reverse image exposure was performed and the print image was evaluated. As a result, in the case of the photoconductor drum of Example 1, an image of good quality without interference fringe patterns and image defects such as black and white dots was obtained. On the other hand, Comparative Example 1
In the case of No. 2, an abnormal current flowed during contact charging, and many black spots appeared when the image was viewed. This is because the photosensitive layer was destroyed by the abnormal discharge and no electric potential was applied to that portion, and it appeared as a black dot because it was an inverted image.
When the surface of the photosensitive drum corresponding to the black spots was examined, it was found that the metal was exposed and that the abnormal protrusion on the surface of the substrate was the cause.

Example 2 In the above Example 1, when the grinding was further finely finished and the surface roughness was set to Rmax = 0.5 μm and Ra = 0.08 μm, a photosensitive drum unit was prepared in the same manner as described above, and When the image was evaluated, black spots were not recognized, but an interference fringe pattern was generated in the halftone image. However, when used in a printer that does not output a halftone image, no problems occurred.

Example 3 A photosensitive drum unit was produced in the same manner as in Example 1 except that a stainless steel pipe having a wall thickness of 0.2 mm was used. When I attached this to the printer,
An image with good image quality without interference fringe patterns and image defects such as black and white dots was obtained. However, a small charging noise called peen was generated during contact charging.

Comparative Example 2 As a conductive substrate, 30 mmφ × 253 mmL × 0.8
An mmt aluminum pipe was used. The surface roughness was Rmax = 1.8 μm and Ra = 0.15 μm. A photosensitive drum unit was produced in the same manner as in Example 1 except that this was used. When this was mounted on the printer, a charging sound called peening was generated during contact charging.

[0015]

Since the electrophotographic photosensitive drum unit of the present invention uses a conductive substrate formed of stainless steel having a specific gravity higher than that of aluminum, contact charging is performed by applying a DC voltage with an AC component superimposed. Even if it goes, no vibration noise is generated from the photosensitive drum. Further, since the abnormal protrusions are ground away on the surface of the conductive substrate and Rmax is 2.0 μm or less, electrostatic damage of the photosensitive layer does not occur and image defects such as black and white spots occur. It is possible to obtain an image of excellent quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an electrophotographic photosensitive drum unit of the present invention.

FIG. 2 is a diagram showing a state of a surface of a conductive substrate for comparison.

FIG. 3 is a diagram showing a state of a surface of a conductive substrate in Example 1.

FIG. 4 is a schematic configuration diagram of an example of a centerless grinding device.

FIG. 5 is a schematic configuration diagram of another example of a grinding device.

[Explanation of symbols]

1 ... Photosensitive drum, 2 ... Charging roll, 3 ... Core material, 4 ... Stainless steel pipe, 5, 6 and 7 ... Grinding stone, 8 ... Pressing roll, 9 ... Grinding film, 10 ... Roll, 11 ... Winding roll .

Claims (4)

[Claims] 1. A photoconductor having a photosensitive layer formed on a conductive support made of stainless steel having a surface roughness Rmax of 2.0 μm or less, and a contact charger for charging the photoconductor by contacting the photoconductor. A photosensitive drum unit for electrophotography, comprising: 2. The photosensitive drum unit for electrophotography according to claim 1, wherein the conductive support is formed by grinding the surface of a stainless steel pipe to have a surface roughness Rmax of 2.0 μm or less. 3. The electrophotographic photosensitive drum unit according to claim 1, wherein the contact charger comprises a charging member to which a DC voltage having an AC component superimposed is applied. 4. The photosensitive drum unit for electrophotography according to claim 1, wherein the conductive support is a stainless steel pipe having a diameter of 30 mm or less and a wall thickness of 0.4 mm or more.