JP2021043358A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can prevent high humidity deletion while achieving power saving, and can reduce unevenness in sensitivity of a photoreceptor.SOLUTION: An image forming apparatus has a cylindrical photoreceptor 201, a heater 209 that heats the photoreceptor 201, and air flow generation means that generates an air flow in the longitudinal direction of the photoreceptor 201. The length of the heater 209 in the longitudinal direction of the photoreceptor 201 is shorter than the length of an area 1 that is an image forming area in the longitudinal direction of the photoreceptor 201. The arithmetic average roughness of an outside surface of the photoreceptor 201 in JISB0601:2001 gradually increases from a first end of the area 1 that is the image forming area of the photoreceptor 201 toward a second end. The photoreceptor 201 is arranged such that the end (second end) with a larger arithmetic average roughness of the outside surface is the upstream side of the air flow, and the end (first end) with a smaller arithmetic average roughness of the outside surface is the downstream side of the air flow.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus equipped with a heater for heating a photoconductor.

An electrophotographic method and an image forming apparatus using the same are widely and generally used as a copier, a facsimile apparatus, and a printer. In such an image forming apparatus, an electrostatic latent image is formed on the surface of the photoconductor by uniformly charging the surface of the photoconductor provided with the photoconducting layer and exposing the photoconductor with a laser or LED corresponding to the image information. Form. Then, a toner image is formed on the surface of the photoconductor by adhering the toner to the formed electrostatic latent image, and the toner image is transferred to a transfer material such as paper to form an image.

As a photoconductor that can be suitably used in such an image forming apparatus, a photoconductor having a photoconducting layer formed of a non-single crystal material containing a silicon atom as a main component (hereinafter, abbreviated as a-Si photoconductor). To do.) Can be mentioned. The a-Si photoconductor has a Vickers hardness of 1000 kgf / mm ² or more, which is extremely hard, and is excellent in durability, heat resistance, and environmental stability. Therefore, it is particularly preferable for high-speed machines that require high reliability.

In an image forming apparatus using an a-Si photoconductor, image defects such as blurring of characters in a high humidity environment or white spots without printing the characters may occur. Hereinafter, these image defects will be abbreviated as "high humidity flow". It is recognized that one of the causes of the high humidity flow is the moisture adsorbed on the surface of the electrophotographic photosensitive member (hereinafter, also simply referred to as “photoreceptor”). Conventionally, in order to suppress a high humidity flow, the photoconductor has been heated to reduce or remove the water adsorbed on the surface of the photoconductor. Various methods are known as means for heating such a photoconductor, and for example, a method in which a heater is provided inside the photoconductor to heat the photoconductor is known. As another method, there is known a method in which a heater for heating the photoconductor is provided outside the photoconductor to heat the photoconductor from the outside (Patent Document 1).

JP-A-2017-015759

In recent years, power saving has been desired in image forming apparatus from the viewpoint of preserving the natural environment. The above-mentioned heaters are also required to reduce power consumption, and there is room for further improvement in order to suppress high humidity flow while achieving power saving.
When an a-Si photoconductor is used as the photoconductor, the outer surface may be oxidized due to ozone generated in the charging process of the image forming process and the applied current voltage. When an oxide film is formed on the outer surface, the oxide film functions as an antireflection layer, so that the amount of light entering the film changes depending on the thickness of the oxide film, the sensitivity of the photoconductor changes, and the photoconductor's sensitivity changes. It has been found that it may affect the potential. If the oxide film is formed uniformly, the effect on the image is small, but if the oxide film is formed non-uniformly, it leads to uneven sensitivity of the photoconductor, resulting in uneven potential and eventually density on the image. This is because it may lead to unevenness. Therefore, in order to form the oxide film more uniformly and reduce the sensitivity unevenness, there is room for further improvement.

According to one aspect of the invention
Cylindrical photoconductor and
A heating means for heating the photoconductor and
An airflow generating means for generating airflow in the longitudinal direction of the photoconductor, and
A charging means for charging the surface of the photoconductor and
An exposure means for irradiating the surface of the photoconductor with exposure light,
A developing means for forming a toner image on the surface of the photoconductor, and
A transfer means for transferring the toner image to a transfer material,
A cleaning means for removing toner on the surface of the photoconductor, and
In the image forming apparatus having
The length of the heating means in the longitudinal direction of the photoconductor is shorter than the length of the image forming region in the longitudinal direction of the photoconductor.
The arithmetic mean roughness of the outer surface of the photoconductor in JIS B0601: 2001 gradually increases from the first end of the image forming region of the photoconductor toward the second end of the image forming region. ,
An image forming apparatus is provided in which the first end portion is on the downstream side of the air flow from the second end portion.

According to the present invention, it is possible to provide an image forming apparatus capable of achieving power saving, suppression of high humidity flow, and reduction of sensitivity unevenness.

It is a figure explaining the composition of the arithmetic mean roughness of a photoconductor and its outer surface, a heater, and an air flow. It is a schematic diagram which shows an example of the schematic structure of the image forming apparatus which concerns on this invention. It is a schematic diagram which showed an example of the layer structure of the photoconductor which concerns on this invention. It is a graph which shows the measurement result of the arithmetic mean roughness of the Example of this invention and the comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Electrophotophotoreceptor)
3 (a) to 3 (c) are schematic views showing an example of a layer structure of a photoconductor that can be manufactured by the manufacturing method of the present invention.
The photoconductor 300 shown in FIG. 3A is composed of a substrate 301, a photoconducting layer 302 sequentially formed on the substrate 301, and a surface layer 303.
As shown in FIG. 3B, a lower charge injection blocking layer 304 is provided on the substrate 301 to prevent charge injection from the substrate side, and a photoconducting layer is provided on the lower charge injection blocking layer 304. A layer structure in which the 302 and the surface layer 303 are sequentially provided may be used.
As shown in FIG. 3C, the layer structure is such that an upper charge injection blocking layer 305 is provided between the photoconducting layer 302 and the surface layer 303 in order to prevent charge injection from the surface side. May be good.
If necessary, the photoconducting layer 302 may have a two-layer structure including a first layer region on the substrate 301 side and a second layer region on the surface layer 303 side. Further, the interface between the photoconducting layer 302 and the surface layer 303 may be continuously changed to perform interface control to suppress interfacial reflection.

As the photoconductor, various photoconductors can be used, and for example, an amorphous silicon photoconductor (a-Si photoconductor) can be used. The a-Si photoconductor is formed on a substrate by a generally known film deposition method such as a vacuum vapor deposition method, a sputtering method, an ion plating method, a thermal CVD method, an optical CVD method, or a plasma CVD method. An a-Si photoconductor having a layer structure as shown in (1) may be produced. Among them, an a-Si photoconductor is suitably produced by using a plasma CVD method in which high-frequency power in the RF band or VHF band is applied to the raw material gas and decomposed by glow discharge to form a deposited film on the substrate. be able to. Examples of the raw material gas include the following. Material gases such as silane (SiH ₄ ), disilane (Si ₂ H ₆ ), methane (CH ₄ ), ethane (C ₂ H ₆ ), nitrogen monoxide (NO), diborane (B ₂ H ₆ ), phosphine (PH) Doping gas such as _{3 ), diluted gas such as hydrogen (H 2} ), helium (He), argon (Ar).

The present invention is characterized in that the arithmetic mean roughness of the outer surface of the photoconductor in JIS B0601: 2001 gradually increases from the first end portion to the second end portion of the photoconductor. In order to achieve this, it is preferable to roughen the surface of the substrate 301. As a specific method for roughening the surface, for example, known methods such as wet blasting, dry lasting, wet etching, dry etching, polishing, and cutting can be used.

The outer surface of the photoconductor can also be roughened by roughening the surface of the substrate and forming the layer structure shown in FIG. 3 on the surface of the roughened substrate.
That is, in order to gradually increase the arithmetic mean roughness of the outer surface from the first end to the second end of the photoconductor,
The arithmetic mean roughness of the surface of the substrate may be gradually increased from the first end to the second end.
In order to gradually increase the arithmetic mean roughness of the surface of the substrate from the first end to the second end,
The treatment conditions for roughening the surface of the substrate may be changed from the first end to the second end or from the second end to the first end.
More specifically, when the surface of the substrate is roughened by wet blasting, the moving speed of the blast head in the longitudinal direction is changed according to the position of the blast head with respect to the work (base).
Change the pressure of the air that projects the abrasive from the blast head to the work,
This can be achieved by changing the distance (interval) between the work and the blast head.

Further, as another method of roughening the outer surface of the photoconductor, the outer surface of the surface layer 303 may be roughened after forming each layer of FIG. Specific methods for roughening the surface in this case include drive lasting, polishing, and pressure contact of a mold having a fine uneven shape to transfer the fine uneven shape to the outer surface on the outer surface. Examples include a method of roughening the surface.
In order to gradually increase the arithmetic mean roughness of the outer surface from the first end to the second end of the photoconductor, when the outer surface is roughened, the arithmetic mean roughness is first. The processing conditions may be changed so as to gradually increase from the end of 1 to the second end.
Similar to the case of roughening the surface of the substrate, when the outer surface is roughened by the blasting treatment, the moving speed of the blast head in the longitudinal direction is changed according to the position of the blast head with respect to the work.
Change the pressure at which the abrasive is projected from the blast head to the work,
This can be achieved by changing the distance (interval) between the work and the blast head.

(Image forming device)
FIG. 2 is a diagram illustrating a schematic configuration of the image forming apparatus of the present invention. The photoconductor 201 is rotationally driven at a predetermined peripheral speed (process speed) in the direction indicated by the arrow X in FIG. 2, and is charged to a predetermined polarity and potential by the primary charger 202 during the rotation process. Next, it receives the image exposure light 203 irradiated from the exposure means (not shown), whereby an electrostatic latent image corresponding to the target image is formed on the surface of the photoconductor 201. Next, the electrostatic latent image is developed using the toner supplied from the developer 204, and the toner image is formed on the surface of the photoconductor 201.

Then, by applying the primary transfer bias to the primary transfer roller 205 from the bias power supply (not shown), the toner image formed on the surface of the photoconductor 201 is first transferred to the intermediate transfer belt 206. After that, the surface of the photoconductor 201 is cleaned by the photoconductor cleaner unit 207 having a cleaning blade, and the static electricity is removed by the static elimination means 208. Further, a heater 209 is provided between the photoconductor cleaner unit 207 and the static elimination means 208 as a heating means for heating the photoconductor 201 from the outside.

FIG. 1 is a diagram illustrating the configuration of the arithmetic mean roughness of the photoconductor 201 and its outer surface, the heater 209, and the air flow. The image forming apparatus has an airflow generating means (not shown) that generates airflow in the longitudinal direction of the photoconductor in order to remove ozone generated by the primary charger 202. The arrow 101 in FIG. 1 indicates the direction of the airflow generated from the airflow generating means.

Area 1 in FIG. 1 shows an image forming region in the longitudinal direction of the photoconductor 201, and area 2 shows a region to be heated facing the heater 209 in the longitudinal direction of the photoconductor 201. As shown in FIG. 1, the image forming apparatus of the present invention is characterized in that the length of the heater 209 for heating the electrophotographic photosensitive member 201 is shorter than the length of the image forming region in the longitudinal direction of the electrophotographic photosensitive member 201. To do.

As described above, the arithmetic mean roughness of the outer surface of the photoconductor gradually increases from the first end portion of the image forming region toward the second end portion. In the image forming apparatus of the present invention, as shown in FIG. 1, a photoconductor whose outer surface arithmetic mean roughness gradually increases is arranged so that the first end portion is on the downstream side of the airflow from the second end portion. It is characterized by being done.
That is, the end having the larger arithmetic mean roughness on the outer surface (the second end) is the upstream side of the airflow, and the end having the smaller arithmetic mean roughness on the outer surface (the first end). ) Is placed on the downstream side of the airflow.

The present inventors consider the reason why the high humidity flow can be suppressed while achieving power saving by the above configuration as follows. First, by making the length of the heater that heats the photoconductor shorter than the length of the image forming region in the longitudinal direction of the photoconductor, it is possible to reduce the power consumption and achieve the power saving.
Area 1 in FIG. 1 indicates an image forming area, area 2 indicates an area facing the heater, and areas 3a and 3b indicate areas of area 1 that are not area 2. With respect to the high humidity flow, the area 2 is heated by the heater to reduce or remove the water adsorbed on the photoconductor, so that the high humidity flow can be suppressed.

Regarding areas 3a and 3b, it has been found that high humidity flow can be suppressed by the following mechanism.
As is clear from FIG. 1, the area 3a is located on the upstream side of the airflow, so that the discharge products such as nitrogen oxides, which are the causative substances of the high humidity flow, are relatively small, and the area 3a is high due to the effect of the airflow. It has been found that it is easy to suppress the wet flow.
It is presumed that the area 3b is configured to increase the contact area between the photoconductor and the cleaning blade by reducing the arithmetic mean roughness of the outer surface of the photoconductor. By increasing the contact area, the rubbing force of the cleaning blade on the outer surface of the photoconductor can be increased, discharge products such as nitrogen oxides can be easily scraped off, and high humidity flow can be suppressed. It has become clear that the configuration is easy to use.

As described above, the length of the heater is shortened, and in addition to this, the distribution of the arithmetic mean roughness of the outer surface of the photoconductor and the direction of the air flow are configured as shown in FIG. 1 to save power. And the high humidity flow suppression can be achieved at the same time, and the present invention has been completed.

Let A be the length of the heating means (heater 209) in the longitudinal direction of the photoconductor.
When the length of the image forming region (area 1) in the longitudinal direction of the photoconductor is B,
It is preferable that A is B / 3 or more and 2B / 3 or less.
When A is B / 3 or more, the above-mentioned effect of heating the heater, the effect of air flow, and the effect of rubbing force are more efficiently exhibited, and the effect of easily suppressing high humidity flow over the entire drum is more remarkable. It is demonstrated in.
When A is 2B / 3 or less, it is more preferable from the viewpoint of power saving.

Further, as described above, when an a-Si photoconductor is used as the photoconductor, an oxide film is formed due to ozone generated in the charging process and the applied current voltage, resulting in uneven density on the image. May be connected. The oxide film at this time is formed by the balance between the force oxidized by the electric discharge and the force removed by rubbing with the cleaning blade, and proceeds as an oxide film. Regarding the force to be oxidized by the electric discharge, since a large amount of ozone generated by the electric discharge remains on the downstream side of the air flow, the structure is such that it is easily oxidized as it goes to the downstream side of the air flow. On the other hand, by distributing the outer surface of the photoconductor so that the arithmetic mean roughness gradually increases and arranging the one with the smaller arithmetic mean roughness on the downstream side of the airflow, the rubbing force of the cleaning blade can be reduced. The configuration is such that it becomes stronger toward the downstream of the airflow. As a result, since the distribution of ozone and the distribution of rubbing force in the longitudinal direction of the photoconductor are balanced, the progress of the oxide film can be made more uniform, and the sensitivity unevenness caused by the oxide film can be further reduced. It was found to have a further effect. "The distribution of ozone and the distribution of rubbing force are balanced" means that the rubbing force is weak on the upstream side of the airflow with low ozone and strong on the downstream side of the airflow with high ozone. To do. As a result, on the upstream side of the airflow, less oxide film is produced and less is removed, while on the downstream side of the airflow, more oxide film is produced and less oxide film is removed. There are many.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples.

[Example 1]
As the cylindrical substrate 301 shown in FIG. 3, an aluminum photoconductor 300 having an outer diameter of 84 mm, an inner diameter of 78 mm, a length of 381 mm, and a wall thickness of 3 mm was used, and an a-Si photoconductor 300 was prepared as follows.
The outer surface of the substrate 301 was subjected to mirror cutting and wet blasting, and the substrate 301 was washed at the end of each processing.

First, as a mirror cutting process, in order to suppress the vibration of the cylindrical base 301, a urethane rubber cylinder is inserted inside the base 301 so as to be in close contact with the inside of the base 301, and the inner circumference of the base 301 is centered with the spindle yatoi. It was installed on the cutting device by sandwiching it from the left and right with the tapered surface of the rubber. Then, the substrate 301 was rotated at a high speed of 3000 rpm, the feed pitch per rotation to the substrate 301 was set to 0.12 mm, the depth of cut of the diamond bite was set, and the diamond bite was pressed against the substrate for cutting. When the cutting was completed, the substrate 301 was removed from the cutting device, moved to a washing machine, and degreased and washed.

Next, the substrate 301 was installed in a wet blasting apparatus while holding both ends of the inner surface of the substrate 301. Then, the substrate 301 was rotated at 15 rpm, and a solution of a mixture of an abrasive made of alumina and water was mixed with compressed air on the surface of the substrate 301 so that the concentration of the abrasive was 10 Vol% from the projection nozzle. It was projected onto the outer surface of the substrate 301. The moving speed of the projection nozzle at this time was set to 5 mm / sec, and the air pressure at the time of projection was changed in the range of 0.10 to 0.30 MPa. Then, the air pressure was gradually reduced from the wet blasting start end portion of the substrate 301 to the opposite end portion to change the arithmetic mean roughness of the outer surface of the substrate 301. When the wet blasting process was completed, the substrate 301 was removed from the wet blasting apparatus, moved to a washing machine, and washed using pure water and ultrasonic waves.

After that, the lower charge injection blocking layer 304, the photoconducting layer 302, the upper charge injection blocking layer 305, and the surface layer 303 are placed on the cylindrical substrate 301 so as to have the layer structure shown in FIG. 3C. Was formed to prepare an a-Si photoconductor 300.
The prepared a-Si photoconductor was evaluated for "arithmetic mean roughness", "high humidity flow", and "sensitivity unevenness" according to the following procedure.

"Arithmetic Mean Roughness"
In the present invention, the arithmetic mean roughness Ra was measured using a surface roughness measuring machine (manufactured by Mitutoyo Co., Ltd., Foam Tracer SV-C4000S4) conforming to JIS B0651: 2001. The shape of the stylus used was in accordance with JIS B0651: 2001. That is, the shape of the stylus was a cone having a spherical tip, the radius of the spherical tip was 2 μm, the taper angle of the cone was 60 °, and the measuring force was 0.75 mN. The setting of the reference length, the evaluation length, the λs contour curve filter, and the λc contour curve filter was in accordance with JIS B0633: 2001 and JIS B0651: 2001. The scanning speed was 0.1 mm / sec, the measurement environment was an air temperature of 25 ° C., and a relative humidity of 65%. Other conditions not specifically described were all based on JIS B0601: 2001, JIS B0633: 2001, and JIS B0651: 2001. In addition, all the measurement procedures by the specific foam tracer SV-C4000S4 were performed according to the instruction manual attached to the device.

The measurement positions of the photoconductor in the axial direction were measured at 9 locations (-160 mm, -120 mm, -80 mm, -40 mm, 0 mm, 40 mm, 80 mm, 120 mm, 160 mm) up to ± 160 mm at 40 mm intervals with the center as 0 mm. .. The plus and minus of the measurement position are described so as to be the same as the direction of the air flow when placed in the image forming apparatus described later, and the minus side indicates the upstream side of the air flow and the plus side indicates the downstream side of the air flow. ing. The measurement result is shown in FIG.

"High humidity flow"
The evaluation of the image flow was carried out by a modified machine obtained by modifying an office multifunction device (imageRUNNER ADVANCE 8585III manufactured by Canon Inc.) so as to have the configuration shown in FIG. More specifically, a heater capable of heating the photoconductor having the configuration shown in FIG. 1 from the outside was installed, and the charging polarity of the charger was modified to be a negative charging method. The length (A) of the heater was set to 200 mm, and the length (B) of the maximum image forming region of this image forming apparatus was set to 330 mm.
That is, the length A (200 mm) of the heater, which is the heating means, is
It is 1/3 (110 mm) or more of the length B (330 mm) of the image forming region and 2/3 (220 mm) or less of the length B (330 mm) of the image forming region.
Further, the length of the area 3a is 65 mm, and the length of the area 3b is also 65 mm.

The prepared a-Si photoconductor was placed in the modified image forming apparatus. At this time, the orientation of the a-Si photoconductor was arranged as follows so as to have the configuration shown in FIG.
The larger the arithmetic mean roughness is, the upstream side of the airflow.
The smaller the arithmetic mean roughness is, the downstream side of the airflow.
Then, in an environment of a temperature of 23 ° C. and a relative humidity of 50%, a full-face character chart (4 pt, printing rate of 4%) was output on A3 size paper (330 mm × 483 mm) to obtain an initial image. At this time, the heater was turned on, and an image was output under the condition that the surface of the a-Si photoconductor was kept at a temperature of about 40 ° C.

Then, a continuous paper passing test was carried out in a high temperature and high humidity environment. More specifically, the environment is set to a temperature of 30 ° C. and a relative humidity of 80%, and using an A4 test pattern with a printing rate of 1%, a continuous paper passing test of 25,000 sheets per day is performed for 20 days, for a cumulative total of 500,000. I went up to the sheet. After the continuous paper passing test was completed, the image was output using the same chart as the initial image in a state where the temperature was 30 ° C. and the relative humidity was 80%.

The initial output image and the image output after the continuous paper passing test were digitized into a PDF file under binary conditions of monochrome 300 dpi using an office multifunction device (Canon Co., Ltd., imageRUNNER ADVANCE 8585III). .. The ratio of pixels displayed in black within the range of the image area (length 263.9 mm) for one circumference of the photoconductor using image editing software (Photoshop (registered trademark) manufactured by Adobe) for the digitized image. (Hereinafter referred to as "black ratio") was measured. More specifically, an image having a range of 40 mm × 263.9 mm was cut out at a position on the image corresponding to the areas 2, 3a, and 3b shown in FIG. 1, and the black ratio was calculated by image editing software. The measured black ratio was evaluated by the ratio of the black ratio of the image after the continuous paper passing test to the black ratio of the initial image.
A: 0.95 or more B: 0.85 or more, less than 0.95 C: less than 0.85 In this evaluation method, the larger the value, the less the high humidity flow and the better the evaluation result. The evaluation results are shown in Table 1.

"Sensitivity unevenness"
Using the same image forming apparatus as the high humidity flow evaluation described above, the produced a-Si photoconductor was installed in the image forming apparatus in the same manner as in the high humidity flow evaluation, and the image forming apparatus having the configuration shown in FIG. 1 was prepared. ..
Then, in an environment of a temperature of 23 ° C. and a relative humidity of 50%, a full-face halftone image having a pixel density of 25%, 37.5%, and 50% is output on A3 size paper (330 mm × 483 mm), and the image is combined with the initial image. did. At this time, the heater was turned on, and an image was output under the condition that the surface of the a-Si photoconductor was kept at a temperature of about 40 ° C.

Then, the continuous paper passing test was carried out in an environment of a temperature of 23 ° C. and a relative humidity of 50% while maintaining the environment. More specifically, using an A4 test pattern with a printing rate of 1%, a continuous paper passing test of 25,000 sheets per day was carried out for 20 days, up to a total of 500,000 sheets. Every time 100,000 sheets pass during the continuous paper passing test, and after the continuous paper passing test of 500,000 sheets is completed, the environment of the temperature of 23 ° C. and the relative humidity of 50% is maintained, and the initial image is displayed. The same image was output.

Then, using the images output so far, the uniformity of the image density was measured and the sensitivity unevenness was evaluated. As described above, when the a-Si photoconductor is used, an oxide film may be formed due to ozone generated in the charging process and the applied current voltage, which may lead to density unevenness on the image. Therefore, the uniformity of the image density was measured and the sensitivity unevenness was evaluated.

The output image was measured for image density uniformity using a reflection densitometer (manufactured by X-Rite, 504 spectrodensitometer). More specifically, in the short side direction of the output paper, the center is 0 mm and 17 places up to ± 160 mm at 20 mm intervals, and in the long side direction, the image tip is 0 mm and 14 up to 260 mm at 20 mm intervals. Image densities were measured at a total of 238 locations. Calculate the standard deviation of the measured values at these 238 locations, and standardize the standard deviation of the comparative image sample as 1 so that slight density unevenness can be confirmed by visually observing. , Evaluated relatively according to the following criteria.
A: Less than 1.10 B: 1.10 or more, less than 1.30 C: 1.3 or more In this evaluation method, the smaller the value, the smaller the sensitivity unevenness, indicating that the evaluation result is good. Table 1 shows the evaluation results with the largest numerical values among the initial evaluation values, the evaluation values during the continuous paper passing test, and the evaluation values after the continuous paper passing test is completed.

[Comparative Example 1]
In Comparative Example 1, an a-Si photoconductor similar to the a-Si photoconductor produced in Example 1 was produced under the same conditions as in Example 1.
Unlike the first embodiment, the produced a-Si photoconductor was placed in the image forming apparatus so that the orientation in the longitudinal direction was opposite to the configuration shown in FIG. That is, in Comparative Example 1, the a-Si photoconductor was placed in the image forming apparatus as shown below.
The smaller the arithmetic mean roughness is, the upstream side of the airflow.
The larger the arithmetic mean roughness is, the downstream side of the airflow.
Other than that, "arithmetic mean roughness", "high humidity flow", and "sensitivity unevenness" were evaluated by the same method as in Example 1. The measurement results of the arithmetic mean roughness are shown in FIG. 4, and the evaluation results of high humidity flow and sensitivity unevenness are shown in Table 1.

[Comparative Example 2]
In Comparative Example 2, the air pressure condition in the wet blasting process during the production of the a-Si photoconductor was changed from the processing start end to the opposite end, unlike in Example 1. Wet blasting was performed at a constant pressure. An a-Si photoconductor was prepared under the same conditions as in Example 1 except for the wet blasting processing conditions.
The prepared a-Si photoconductor was evaluated for "arithmetic mean roughness", "high humidity flow", and "sensitivity unevenness" in the same manner as in Example 1. The measurement results of the arithmetic mean roughness are shown in FIG. 4, and the evaluation results of high humidity flow and sensitivity unevenness are shown in Table 1.

As shown in FIG. 4, the arithmetic mean roughness of the a-Si photoconductor of Example 1 is
It gradually increases from the positive side to the negative side in the longitudinal direction.
It can be confirmed that the airflow of the image forming apparatus gradually increases from the downstream side to the upstream side.
There is a fairly strong correlation between the arithmetic mean roughness and the position in the longitudinal direction, and the arithmetic mean roughness changes by about 0.1 nm per 1 mm of length in the longitudinal direction. Further, the average value in the measurement range of the arithmetic mean roughness is about 0.05 μm, and it can be seen that the arithmetic mean roughness at the position corresponding to the area 3b on the downstream side of the airflow is less than the above-mentioned average value. ..

As shown in FIG. 4, the arithmetic mean roughness of the a-Si photoconductor of Comparative Example 1 is opposite to that of Example 1.
It gradually increases from the negative side in the longitudinal direction to the positive side.
It can be confirmed that the airflow of the image forming apparatus gradually increases from the upstream side to the downstream side.
The correlation between the arithmetic mean roughness and the position in the longitudinal direction is the same as in Example 1, and there is a fairly strong correlation, and the arithmetic mean roughness changes by about 0.1 nm per 1 mm of length in the longitudinal direction.
Regarding the a-Si photoconductor shown in Comparative Example 2, the arithmetic mean roughness is substantially constant, and it can be confirmed that there is almost no correlation between the arithmetic mean roughness and the longitudinal position.

As is clear from Table 1, it can be seen that the image forming apparatus of the present invention shown in Example 1 has obtained good evaluation results of high humidity flow in all of the area 2, the area 3a, and the area 3b. That is, it can be confirmed that the high humidity flow is good not only in the area 2 which is advantageous for the high humidity flow by heating by the heater, but also in all the image forming regions including the areas 3a and 3b where the heating of the heater is difficult to reach.
On the other hand, in the image forming apparatus of Comparative Example 1 and Comparative Example 2, an image flow was generated in the area 3b on the downstream side of the air flow, resulting in a decrease in the evaluation rank of the high humidity flow.

It is presumed that the reason why the evaluation of the high humidity flow was good in the area 3b in the image forming apparatus of the first embodiment is as follows. That is, it is presumed that by reducing the arithmetic mean roughness of the area 3b, the rubbing force of the cleaning blade can be increased, and the discharge products such as nitrogen oxides can be easily scraped off efficiently. ..
From the above results, it was confirmed that in the image forming apparatus of the present invention, the high humidity flow could be suppressed while reducing the power consumption by shortening the length of the heater.

In addition, the image forming apparatus of the present invention shown in Example 1 also obtained good evaluation results in the evaluation of sensitivity unevenness. On the other hand, in the image forming apparatus of Comparative Example 1 and Comparative Example 2, very slight density unevenness was confirmed by visual observation, and the evaluation rank was lowered.
It is presumed that the reason why the evaluation of sensitivity unevenness was good with respect to the image forming apparatus of Example 1 is as follows. That is, because the structure is such that the rubbing force on the downstream side of the airflow in which a large amount of ozone remains is increased, the distribution of ozone and the rubbing force can be balanced, and the progress of the oxide film can be made more uniform. I'm guessing.
From the above results, it was confirmed that the image forming apparatus of the present invention can make the progress of oxidation more uniform and reduce sensitivity unevenness.

201 ... Photoreceptor 202 ... Primary charger 203 ... Image exposure light 204 ... Developer 205 ... Primary transfer roller 206 ... Intermediate transfer belt 207 ... Photoreceptor cleaner unit 208 ... Static elimination means 209 ... Heater

Claims (3)

Cylindrical photoconductor and
A heating means for heating the photoconductor and
An airflow generating means for generating airflow in the longitudinal direction of the photoconductor, and
A charging means for charging the surface of the photoconductor and
An exposure means for irradiating the surface of the photoconductor with exposure light,
A developing means for forming a toner image on the surface of the photoconductor, and
A transfer means for transferring the toner image to a transfer material,
A cleaning means for removing toner on the surface of the photoconductor, and
The length of the heating means in the longitudinal direction of the photoconductor is shorter than the length of the image forming region in the longitudinal direction of the photoconductor.
The arithmetic mean roughness of the outer surface of the photoconductor in JIS B0601: 2001 gradually increases from the first end of the image forming region of the photoconductor toward the second end of the image forming region. ,
An image forming apparatus characterized in that the first end portion is on the downstream side of the air flow with respect to the second end portion. The length of the heating means in the longitudinal direction of the photoconductor is A.
The length of the image forming region in the longitudinal direction of the photoconductor is B.
The image forming apparatus according to claim 1, wherein A is B / 3 or more and 2B / 3 or less. The image forming apparatus according to any one of claims 1 or 2, wherein the photoconductor is an amorphous silicon photoconductor.

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