JP2014219484A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress unevenness in the amount of an external additive in the longitudinal direction on the surface of a cleaning roller to suppress the uneven wear in the longitudinal direction of an electrophotographic photoreceptor, and thereby suppressing density unevenness of output images considered to be due to the uneven wear in the longitudinal direction of the electrophotographic photoreceptor.SOLUTION: A plurality of conveyance paths through which toner is conveyed by a conveyance mechanism are present in the longitudinal direction of an electrophotographic photoreceptor inside a cleaning unit.

Description

  The present invention relates to an electrophotographic apparatus.

  Electrophotographic apparatuses are widely used as copying machines, facsimiles, printers, and the like.

  FIG. 2 is a diagram illustrating an example of the configuration of the electrophotographic apparatus. An example of an image forming process (electrophotographic process) by an electrophotographic apparatus will be described with reference to FIG.

  The electrophotographic photosensitive member 2001 is rotated, and the surface of the electrophotographic photosensitive member 2001 is charged by charging means (charging roller) 2002. Thereafter, image exposure light is irradiated from the image exposure unit 2003 to the surface of the electrophotographic photosensitive member 2001 to form an electrostatic latent image on the surface of the electrophotographic photosensitive member 2001. Thereafter, toner is supplied from the developing unit 2004 to the surface of the electrophotographic photosensitive member 2001 to develop the electrostatic latent image formed on the surface of the electrophotographic photosensitive member 2001.

  As a result, a toner image is formed on the surface of the electrophotographic photoreceptor 2001.

  Next, a toner image formed on the surface of the electrophotographic photosensitive member 2001 is transferred to a transfer material 2006 by a transfer unit (transfer charger) 2005.

  On the other hand, a part of the toner remains on the surface of the electrophotographic photoreceptor 2001 after the toner image is transferred to the transfer material 2006. Hereinafter, this is also referred to as “transfer remaining toner”. A part of the transfer residual toner is removed by a cleaning roller 2008 inside a cleaning unit (cleaning unit) 2007. The toner remaining on the surface of the electrophotographic photoreceptor 2001 without being removed is then removed by the cleaning blade 2009 inside the cleaning means (cleaning unit) 2007. 2011 is a conveyance screw which is a conveyance mechanism.

  Thereafter, the pre-exposure unit 2010 irradiates the surface of the electrophotographic photoreceptor 2001 with pre-exposure light, and the surface of the electrophotographic photoreceptor 2001 is neutralized.

  By repeating the above series of steps, image formation is continuously performed.

  An electrophotographic apparatus is required to maintain high quality of an output image even when used repeatedly for a long time.

  However, in a system that employs an electrophotographic process having a cleaning process as described above, wear of the electrophotographic photosensitive member due to contact with a cleaning blade, a cleaning roller, or the like occurs due to repeated use over a long period of time. In particular, during repeated use over a long period of time, the state of the toner carried on the surface of the cleaning roller may differ in the longitudinal direction of the electrophotographic photosensitive member. Therefore, unevenness (uneven wear) is likely to occur in the degree of wear of the electrophotographic photosensitive member. Hereinafter, the longitudinal direction of the electrophotographic photosensitive member and the same direction are also simply referred to as “longitudinal direction”. When uneven wear occurs on the surface of the electrophotographic photosensitive member, unevenness occurs in the amount of light transmitted through the surface of the electrophotographic photosensitive member, and thus unevenness (sensitivity unevenness) is likely to occur in sensitivity (photosensitivity). When unevenness of sensitivity occurs in the electrophotographic photosensitive member, unevenness of potential on the surface of the electrophotographic photosensitive member (potential unevenness) is likely to occur during image formation. When potential unevenness occurs, unevenness (density unevenness) tends to occur in the density of the output image, and it may be impossible to maintain the high quality of the output image.

  Japanese Patent Application Laid-Open No. 2004-133830 discloses a technique for making the thickness of the toner carried on the surface of the cleaning roller uniform by a toner regulating member, suppressing the cleaning blade from curling and squeaking, and suppressing uneven wear on the surface of the electrophotographic photosensitive member. It is disclosed.

JP 2012-226124 A

  However, there are cases where uneven wear on the surface of the electrophotographic photosensitive member cannot be sufficiently suppressed by simply equalizing the thickness of the toner carried on the surface of the cleaning roller as in the prior art. As a result of the study, the present inventors have come to consider that the reason is as follows.

  That is, the toner generally contains an external additive such as strontium titanate, titanium dioxide, or silicon dioxide (silica) in order to adjust the chargeability and fluidity. These external additives may be peeled off from the toner particles (the base material carrying the external additive) during the electrophotographic process or in the process of transporting the untransferred toner removed from the surface of the electrophotographic photosensitive member. is there. As a result, the amount of external additives tends to increase on the downstream side of the conveyance path.

  FIG. 5 is a diagram illustrating an example of a configuration of a conventional cleaning unit.

  In the conventional cleaning unit, the untransferred toner removed from the surface of the electrophotographic photosensitive member is conveyed from one end in the longitudinal direction of the cleaning roller 1002 to the other end by a conveying mechanism (conveying screw) 1003. The Conventionally, since this conveyance path is long, the amount of the external additive attached to the surface of the cleaning roller 1002 in the longitudinal direction of the cleaning roller 1002 may be uneven. Since the amount of wear on the surface of the electrophotographic photosensitive member is likely to depend on the amount of the external additive that contacts the surface of the electrophotographic photosensitive member, the amount of the external additive on the surface of the cleaning roller 1002 may cause unevenness. Wear unevenness may be caused in the longitudinal direction of the surface.

  The object of the present invention is to suppress unevenness in the amount of external additive in the longitudinal direction of the surface of the cleaning roller, to suppress uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member, and in the longitudinal direction of the surface of the electrophotographic photosensitive member. It is to suppress the density unevenness of the output image which is considered to be due to the uneven wear of the toner.

  As a result of intensive studies by the present inventors, uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member due to unevenness in the amount of external additive on the surface of the cleaning roller is caused by the length of the toner conveyance path by the conveyance mechanism. It turned out to be dependent on. Specifically, it was found that the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member becomes more prominent as the toner conveyance path becomes longer.

  Therefore, the present inventors divide the toner conveyance path into a plurality of parts in the longitudinal direction and shorten the length per one conveyance path, thereby reducing the amount of the external additive adhering to the surface of the cleaning roller. Tried to suppress unevenness. As a result, it has been found that uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member can be suppressed, and uneven density in the output image can be suppressed, and the present invention has been completed.

That is, the present invention
A cylindrical electrophotographic photoreceptor;
Transfer means for transferring a toner image formed on the surface of the electrophotographic photosensitive member to a transfer material;
A cleaning roller and a cleaning blade for removing the transfer residual toner on the surface of the electrophotographic photosensitive member disposed in contact with the surface of the electrophotographic photosensitive member; a transport mechanism for transporting the removed toner; And an electrophotographic apparatus having a cleaning unit having a toner discharge port for discharging the toner,
The toner includes toner particles and an external additive externally added to the toner particles;
The cleaning roller, the cleaning blade, and the transport mechanism are disposed inside the cleaning unit,
The electrophotographic apparatus is characterized in that a plurality of transport paths of the toner by the transport mechanism in the cleaning unit exist in a longitudinal direction of the electrophotographic photosensitive member.

  According to the present invention, the unevenness in the amount of the external additive in the longitudinal direction of the surface of the cleaning roller is suppressed, the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member is suppressed, and the longitudinal direction of the surface of the electrophotographic photosensitive member is suppressed. It is possible to suppress the density unevenness of the output image that is considered to be due to the uneven wear of the toner.

It is a figure which shows an example of a structure of the cleaning unit used for the electrophotographic apparatus of this invention. It is a figure which shows an example of a structure of an electrophotographic apparatus. 1 is a schematic cross-sectional view of an electrophotographic photoreceptor that can be used in the present invention. It is a figure which shows an example of a structure of the cleaning unit used for the electrophotographic apparatus of this invention. It is a figure which shows an example of a structure of the conventional cleaning unit. It is a graph showing the longitudinal direction distribution of the amount of wear of an electrophotographic photosensitive member according to a continuous sheet passing test of 1 million sheets. It is a graph showing the longitudinal direction distribution of the amount of wear of an electrophotographic photosensitive member according to a continuous sheet passing test of 1 million sheets.

  FIG. 1 is a diagram showing an example of the configuration of a cleaning unit used in the electrophotographic apparatus of the present invention.

  The cleaning unit 1000 shown in FIG. 1 is roughly composed of a cleaning blade 1001, a cleaning roller 1002, a transport screw 1003 that is a transport mechanism for transporting toner, and a toner discharge port 1004. A cleaning blade 1001 and a cleaning roller 1002 for removing toner remaining after transfer on the surface of the electrophotographic photosensitive member are disposed in contact with the surface of the electrophotographic photosensitive member. As described above, the untransferred toner is toner that remains on the surface of the electrophotographic photosensitive member even after the toner image is transferred from the surface of the electrophotographic photosensitive member to the transfer material. Further, the toner discharged from the toner discharge port 1004 is sent to the toner box 1006 through the duct 1005.

  As described above, the external additive may be peeled off from the toner particles in the step of transporting the untransferred toner removed from the surface of the electrophotographic photosensitive member. Therefore, the longer the toner conveyance path in the conveyance mechanism (conveyance screw 1003), the greater the chance of peeling off from the toner particles. Further, the longer the time during which the transport mechanism is transported, the easier the external additive is peeled off from the toner particles. Accordingly, it is considered that the amount of the external additive that peels off from the toner particles increases as the conveying path becomes longer. Further, it is considered that the amount of the external additive peeled off from the toner particles is larger on the downstream side than on the upstream side of the conveyance path. That is, in the longitudinal direction, it is considered that the amount of the external additive peeled off from the toner particles varies. The external additive that has peeled off easily adheres to the surface of the cleaning roller 1002, and the amount of the external additive that has peeled off varies in the longitudinal direction. Therefore, it is considered that the amount of the external additive attached to the surface of the cleaning roller 1002 varies in the longitudinal direction, that is, the amount of the external additive attached is uneven. As described above, since the cleaning roller 1002 is disposed in contact with the surface of the electrophotographic photosensitive member, the surface of the electrophotographic photosensitive member is worn by the external additive attached to the cleaning roller 1002. The portion of the surface of the electrophotographic photosensitive member that is in contact with the portion where the amount of the external additive adhering to the cleaning roller 1002 is large increases and the portion that is in contact with the portion where the amount is small. The amount of wear is reduced. That is, if the unevenness of the amount of the external additive adhering to the surface of the cleaning roller 1002 is suppressed, it is considered that the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member can be suppressed. For this purpose, it is effective to shorten the length of the toner conveyance path in the conveyance mechanism (conveyance screw 1003).

  Therefore, in the present invention, in order to shorten the length of the toner transport path, the conventional toner transport path extending from one end of the cleaning roller to the other end is divided into a plurality of parts in the longitudinal direction. doing. The more the toner conveyance paths are divided, that is, the greater the number of toner conveyance paths, the shorter the length per conveyance path.

  In the cleaning unit 1000 of FIG. 1, there are a plurality of toner transport paths depending on the structure of the transport screw 1003. In the case of the example shown in FIG. 1, the conveyance path from the left end in FIG. 1 in the longitudinal direction of the cleaning roller 1002 toward the center, and the right end in FIG. 1 in the longitudinal direction of the cleaning roller 1002 in the center. There are two transport paths in total, one transport path toward Both of the toners that have passed through the two transport paths are discharged from the toner discharge port 1004 and are sent to the toner box 1006 through the duct 1005.

  Also in the cleaning unit 1000 in FIG. 4A, there are a plurality of toner conveyance paths depending on the structure of the conveyance screw 1011. In the case of the example shown in FIG. 4A, the conveyance path from the central portion in the longitudinal direction of the cleaning roller 1002 toward the left end in FIG. 4A and the central portion in the longitudinal direction of the cleaning roller 1002 are shown in FIG. (A) There are a total of two transport paths that are directed toward the right end in FIG. The toner that has passed through the former conveyance path is discharged from the toner discharge port 1004 on the left side in FIG. 4A and is sent to the toner box 1006 through the duct 1005. The toner that has passed through the latter conveyance path is discharged from the toner discharge port 1004 on the right side in FIG. 4A and is sent to the toner box 1006 through the duct 1005.

  Also in the cleaning unit 1000 in FIG. 4B, there are a plurality of toner conveyance paths depending on the structure of the conveyance screw 1012. In the case of the example shown in FIG. 4B, there are a total of four transport paths. The arrows in FIG. 4B indicate the direction (conveyance direction) in which the toner passes through each conveyance path. The same applies to the arrows in FIG. 1 and FIG.

  As a method of making a plurality of toner transport paths, as shown in FIG. 1 and FIGS. 4A and 4B, the number of transport paths is two or four, as well as three or five or more. There is a way to do it. The length of each conveyance path may be the same or different. It is preferable to make the length of the conveyance path the same because the effect of suppressing uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member is excellent. Further, the toner discharge ports corresponding to a plurality of transport paths may be shared as shown in FIG. 1, or the toner discharge ports corresponding to the plurality of transport paths may be provided respectively as shown in FIG. Also good. It is preferable to use a common toner discharge port corresponding to a plurality of conveyance paths because the number of toner discharge ports is small and the configuration is simplified. In the example shown in FIG. 4B, the toner discharge ports corresponding to the second and third transport paths from the left in FIG. 4B are shared.

  Further, as the number of transport paths increases, the length per transport path becomes shorter, which is advantageous in suppressing uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member. As the number increases, the number of necessary toner outlets tends to increase. Therefore, the number of transport paths may be selected in consideration of the balance between the use / required performance and cost of the electrophotographic apparatus.

  Examples of the cleaning roller that can be used in the present invention include a magnet roller and a brush roller.

  Examples of the cleaning blade that can be used in the present invention include a urethane rubber blade.

  The toner that can be used in the present invention may be a magnetic toner or a non-magnetic toner. When a magnet roller is used as the cleaning roller, magnetic toner is preferable. Further, the developer may be a one-component developer containing a magnetic toner, or a two-component developer containing a non-magnetic toner and a magnetic carrier.

  The toner used in the present invention includes toner particles and external additives externally added to the toner particles. Examples of the external additives include strontium titanate, titanium dioxide, and silicon dioxide (silica). It is done.

  The electrophotographic photoreceptor that can be used in the present invention may be an inorganic photoreceptor using an inorganic photoconductive material such as amorphous silicon, or an organic photoreceptor using an organic photoconductive material. Also good.

  FIG. 3 is a diagram showing an example of a layer structure of an amorphous silicon photoconductor (a-Si photoconductor) which is one type of inorganic photoconductor.

  In FIG. 3, a charge injection blocking layer 3002, a photoconductive layer 3003, and a surface layer 3004 are laminated in this order on a conductive substrate 3001. The charge injection blocking layer 3002 is a layer that plays a role of blocking charge injection from the substrate 3001 to the photoconductive layer 3003 and the surface layer 3004. The photoconductive layer 3003 is a layer that plays a role of generating charges and transporting them to the surface layer 3004. The surface layer 3004 is a layer that plays a role of protecting the photoconductive layer 3003 and the charge injection blocking layer 3002.

  Next, the reason for the occurrence of uneven density in the output image due to uneven wear in the longitudinal direction of the surface of the electrophotographic photoreceptor will be described using the a-Si photoreceptor shown in FIG. 3 as an example.

  Image exposure light irradiated to form an electrostatic latent image passes through the surface layer 3004 and generates a charge in the photoconductive layer 3003. The generated charge varies depending on the amount of image exposure light incident on the photoconductive layer 3003. The amount of image exposure light incident on the photoconductive layer 3003 is affected by the amount of light absorbed by the surface layer 3004. The light absorption amount of the surface layer 3004 is mainly determined by the film thickness and the absorption coefficient of the surface layer 3004. The occurrence of uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member means that uneven wear in the longitudinal direction of the surface of the surface layer 3004 occurs. When uneven wear in the longitudinal direction of the surface of the surface layer 3004 occurs, unevenness occurs in the amount of image exposure light incident on the photoconductive layer 3003, and unevenness in the sensitivity and surface potential of the electrophotographic photosensitive member during image formation ( (Potential unevenness) occurs. Due to potential unevenness on the surface of the electrophotographic photosensitive member, the density of the output image is uneven.

  Hereinafter, the present invention will be described in detail by way of examples and comparative examples.

[Example 1]
In Example 1, an electrophotographic apparatus including a cylindrical electrophotographic photosensitive member, a charging unit, an image exposing unit, a developing unit, a transfer unit, and a cleaning unit was used. Specifically, a copying machine (trade name: iR-ADV6275) manufactured by Canon Inc. was used as the electrophotographic apparatus. However, as described later, the cleaning unit of each example was used as the cleaning unit.

  As the electrophotographic photosensitive member, an a-Si photosensitive member having the layer structure shown in FIG. 3 was used. As the cleaning unit, the cleaning unit having the configuration shown in FIG. 1 was used. A magnet roller was used as the cleaning roller. A urethane rubber blade was used as the cleaning blade. Magnetic toner was used as the toner, and silicon dioxide (silica) was used as the external additive contained in the magnetic toner.

  Using the electrophotographic apparatus having the above configuration, a continuous sheet passing test of 1 million sheets was carried out, and the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member and the uneven density of the output image were evaluated.

[Example 2]
In Example 2, an electrophotographic apparatus having the same configuration as that of Example 1 was used except that the cleaning unit having the configuration shown in FIG. 4A was used as the cleaning unit. The cleaning roller and the cleaning blade in the cleaning unit were the same as those in Example 1. Then, in the same manner as in Example 1, a continuous paper passing test of 1,000,000 sheets was performed, and the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member and the uneven density of the output image were evaluated.

Example 3
In Example 3, an electrophotographic apparatus having the same configuration as that of Example 1 was used except that the cleaning unit having the configuration shown in FIG. 4B was used as the cleaning unit. The cleaning roller and the cleaning blade in the cleaning unit were the same as those in Example 1. Then, in the same manner as in Example 1, a continuous paper passing test of 1,000,000 sheets was performed, and the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member and the uneven density of the output image were evaluated.

[Comparative Example 1]
In Comparative Example 1, an electrophotographic apparatus having the same configuration as that of Example 1 was used except that the cleaning unit having the configuration shown in FIG. 5 was used as the cleaning unit. The cleaning roller and the cleaning blade in the cleaning unit were the same as those in Example 1. Then, in the same manner as in Example 1, a continuous paper passing test of 1,000,000 sheets was performed, and the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member and the uneven density of the output image were evaluated.

  A method for evaluating the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member and the uneven density of the output image is shown below.

[Evaluation method of wear unevenness in the longitudinal direction of the surface of the electrophotographic photoreceptor]
The film thickness of the surface layer of the electrophotographic photosensitive member was measured at 60 points in total, 15 points in the longitudinal direction and 4 points in 90 ° increments in the circumferential direction. The measurement points in the longitudinal direction are 0 mm (center portion), ± 20 mm, ± 40 mm, ± 60 mm, ± 80 mm, ± 100 mm, ± 120 mm, ± 140 mm in total, with reference to the central portion in the longitudinal direction of the electrophotographic photosensitive member. Is a point.

  After measuring the film thickness of the surface layer of the electrophotographic photosensitive member, the electrophotographic photosensitive member and the cleaning unit of each example were installed in the electrophotographic apparatus, and a continuous paper passing test was performed. Specifically, using an A4 test pattern with a printing rate of 1%, paper was continuously fed to output 1 million images. After the continuous sheet passing test for 1 million sheets was completed, the electrophotographic photosensitive member was taken out from the electrophotographic apparatus. The film thickness of the surface layer of the removed electrophotographic photosensitive member was measured at the same position as before the continuous paper passing test. And the difference of the film thickness of the surface layer before a continuous paper passing test and after a continuous paper passing test was calculated | required, and it was set as the amount of wear in a continuous paper passing test. The obtained difference in wear amount was averaged at four points in the circumferential direction having the same longitudinal direction. And the value which divided the value of the position where the amount of wear was the largest in the longitudinal direction by the value of the position where the amount of wear was the smallest was made into the evaluation value. And Examples 1-3 and the comparative example 1 were compared by the relative value when the evaluation value of the comparative example 1 was set to 1.00. It means that the smaller the relative value of the evaluation value is, the better, and when the relative value of the evaluation value is 0.95 or less, it was judged that the effect of the present invention was obtained. The results are shown in Table 1.

  Further, graphs showing the distribution of the wear amount in the longitudinal direction of the surface of the electrophotographic photosensitive member are shown in FIGS. The vertical axis of the graph represents the amount of wear on the surface of the electrophotographic photosensitive member. In Comparative Example 1, the wear amount value at the point of least wear (position where the distance from the center of the electrophotographic photosensitive member in FIG. 7A is −140 mm) is 1, and the relative value is plotted. . The horizontal axis of the graph represents the distance from the center of the surface of the electrophotographic photosensitive member. 6 (a) shows the results of Example 1, FIG. 6 (b) shows the results of Example 2, FIG. 6 (c) shows the results of Example 3, and FIG. 7 (a) shows a comparative example. 1 result.

[Method for measuring film thickness of surface layer of electrophotographic photosensitive member]
First, a reference electrophotographic photosensitive member in which only a charge injection blocking layer and a photoconductive layer were formed on a substrate was manufactured, and a central portion in the longitudinal direction (circumferential direction was arbitrary) was cut into a 15 mm square to produce a reference sample. .

  Next, the electrophotographic photosensitive member on which the charge injection blocking layer, the photoconductive layer, and the surface layer were formed was cut out in the same manner to prepare a measurement sample.

  The reference sample and the measurement sample were measured by spectroscopic ellipsometry (manufactured by JA Woollam: high-speed spectroscopic ellipsometry M-2000) to determine the refractive index of the surface layer.

  Specific measurement conditions for spectroscopic ellipsometry are incident angles: 60 °, 65 ° and 70 °, measurement wavelengths: 195 nm to 700 nm, and beam diameter: 1 mm × 2 mm.

  First, the relationship between the wavelength, the amplitude ratio Ψ and the phase difference Δ was determined for each reference angle of the reference sample by spectroscopic ellipsometry.

  Next, using the measurement result of the reference sample as a reference, the relationship between the wavelength, the amplitude ratio ψ, and the phase difference Δ was determined at each incident angle by spectroscopic ellipsometry in the same manner as the reference sample.

  In addition, a layer structure having a charge injection blocking layer, a photoconductive layer, and a surface layer sequentially formed on a substrate and having a roughness layer in which the surface layer and the air layer coexist on the outermost surface was used as a calculation model. Then, the volume ratio between the surface layer of the roughness layer and the air layer was changed by analysis software, and the relationship between the wavelength at each incident angle, the amplitude ratio Ψ, and the phase difference Δ was obtained by calculation. With this selected calculation model, the refractive index of the surface layer was calculated, and the obtained value was used as the refractive index of the surface layer. The analysis software is J.I. A. WVASE32 (trade name) manufactured by Woollam was used. The volume ratio of the surface layer to the air layer of the roughness layer was calculated by changing the ratio of the air layer in the roughness layer by 1 from 10: 0 to 1: 9 in the surface layer: air layer. In the a-Si photoreceptor used in Example 1, when the volume ratio of the surface layer of the roughness layer to the air layer is 8: 2, the relationship between the wavelength obtained by calculation, the amplitude ratio Ψ, and the phase difference Δ And the mean square error between the measured wavelength and the relationship between the amplitude ratio ψ and the phase difference Δ was minimized. This means that the accuracy of the calculated value is high when the volume ratio of the surface layer of the roughness layer to the air layer is 8: 2. Therefore, the refractive index was calculated using this volume ratio.

  Next, the surface of the electrophotographic photosensitive member is irradiated with light perpendicularly with a spot diameter of 2 mm, and the reflected light is spectroscopically measured using a spectrometer (trade name: MCPD-2000, manufactured by Otsuka Electronics Co., Ltd.). It was. The film thickness of the surface layer was calculated based on the obtained reflection waveform. At this time, the wavelength range was 500 nm to 750 nm, the refractive index of the photoconductive layer was 3.30, and the refractive index of the surface layer was a value obtained from the above-described spectroscopic ellipsometry measurement.

[Method for evaluating density unevenness in output image]
The electrophotographic photosensitive member after the continuous paper passing test was installed in the above-described electrophotographic apparatus, and three halftone images with an image ratio of 50% were output on A3 paper using the text mode. The density was measured by a reflection densitometer (manufactured by X-Rite Inc, trade name: 504 spectral densitometer) at a location corresponding to the position where the film thickness of the surface layer of the electrophotographic photosensitive member was measured on the output image. The average value of image density was determined at each measurement location. The difference between the highest image density value and the lowest image density was defined as the density unevenness of the output image. Examples 1 to 3 and Comparative Example 1 were compared with relative values when the image density unevenness value of Comparative Example 1 was set to 100. It means that the smaller the number of the relative value is, the better, and when the number of the relative value is 90 or less, it was judged that the effect of the present invention was obtained. The results are shown in Table 1.

  From Table 1, it can be seen that in Examples 1 to 3, compared to Comparative Example 1, uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member is suppressed, and uneven density in the output image is suppressed.

  6 and 7, in each of Examples 1 to 3 and Comparative Example 1, the amount of wear on the surface of the electrophotographic photosensitive member on the side close to the toner discharge port is large, and the wear amount is further away from the toner discharge port. Resulted in less. From this, it can be seen that the length of one toner conveyance path affects the abrasion of the surface of the electrophotographic photosensitive member.

  When the first and second embodiments are compared, the length of the conveyance path itself is the same, and thus the same effect is obtained. However, in the first embodiment, since only one toner discharge port can be formed, the apparatus is This is preferable from the viewpoint of simplifying the configuration. In Example 3, an effect superior to that in Examples 1 and 2 was obtained. From this, it can be seen that the greater the conveyance path, the better the effect.

Example 4
In Example 4, an electrophotographic apparatus having the same configuration as that of Example 1 was used except that a brush roller was used as the cleaning roller. Then, in the same manner as in Example 1, a continuous paper passing test of 1,000,000 sheets was performed, and the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member and the uneven density of the output image were evaluated. The results are shown in Table 2. FIG. 6D is a graph showing the distribution of the wear amount in the longitudinal direction of the surface of the electrophotographic photosensitive member.

[Comparative Example 2]
In Comparative Example 2, an electrophotographic apparatus similar to Comparative Example 1 was used except that a brush roller was used as the cleaning roller. Then, in the same manner as in Example 1, a continuous paper passing test of 1,000,000 sheets was performed, and the uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member and the uneven density of the output image were evaluated. The results are shown in Table 2. FIG. 7B is a graph showing the distribution of the wear amount in the longitudinal direction of the surface of the electrophotographic photosensitive member.

  From Table 2 and FIGS. 6 (d) and 7 (b), in Example 4, as compared with Comparative Example 2, uneven wear in the longitudinal direction of the surface of the electrophotographic photosensitive member is suppressed, and uneven density in the output image is reduced. It turns out that it is suppressed. That is, it can be seen that the effect of the present invention can be obtained even when a brush roller is used as the cleaning roller.

1001 Cleaning blade 1002 Cleaning roller 1003 Conveying screw (conveying mechanism)
1004 Toner discharge port 1011 Conveying screw (conveying mechanism)
1012 Conveying screw (conveying mechanism)
2001 Electrophotographic photosensitive member 2002 Charging means (charging roller)
2003 Image exposure means 2004 Development means 2005 Transfer means (transfer charger)
2006 Transfer material 2007 Cleaning unit 2008 Cleaning roller 2009 Cleaning blade 2010 Pre-exposure means 2011 Conveying screw (conveying mechanism)
3001 substrate 3002 charge injection blocking layer 3003 photoconductive layer 3004 surface layer

Claims (10)

A cylindrical electrophotographic photoreceptor;
Transfer means for transferring a toner image formed on the surface of the electrophotographic photosensitive member to a transfer material;
A cleaning roller and a cleaning blade for removing the transfer residual toner on the surface of the electrophotographic photosensitive member disposed in contact with the surface of the electrophotographic photosensitive member; a transport mechanism for transporting the removed toner; And an electrophotographic apparatus having a cleaning unit having a toner discharge port for discharging the toner,
The toner includes toner particles and an external additive externally added to the toner particles;
The cleaning roller, the cleaning blade, and the transport mechanism are disposed inside the cleaning unit,
An electrophotographic apparatus comprising a plurality of toner transport paths in the longitudinal direction of the electrophotographic photosensitive member by the transport mechanism inside the cleaning unit.   There are two transport paths for the toner by the transport mechanism, and each of the two transport paths is a transport path for transporting toner in the direction from the end in the longitudinal direction of the electrophotographic photosensitive member toward the center. The electrophotographic apparatus according to claim 1.   The electrophotographic apparatus according to claim 2, wherein toner discharge ports corresponding to the two conveyance paths are shared.   The electrophotographic apparatus according to claim 1, wherein the cleaning roller is a magnet roller or a brush roller.   The electrophotographic apparatus according to claim 4, wherein the cleaning roller is a magnet roller.   The electrophotographic apparatus according to claim 5, wherein the toner is a magnetic toner.   The electrophotographic apparatus according to claim 1, wherein the external additive is at least one selected from the group consisting of strontium titanate, titanium dioxide, and silicon dioxide.   The electrophotographic apparatus according to claim 7, wherein the external additive is silicon dioxide.   The electrophotographic apparatus according to claim 1, wherein the electrophotographic photosensitive member is an amorphous silicon photosensitive member.   The electrophotographic apparatus according to claim 1, wherein the transport mechanism is a transport screw.

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