JP2021005078A - Electrophotographic photoreceptor, process cartridge, and electrophotographic apparatus - Google Patents

Abstract

To provide an electrophotographic photoreceptor that can prevent discharge streaks occurring at an end.SOLUTION: An electrophotographic photoreceptor has a cylindrical support, a charge generating layer, and a charge transport layer in this order. When an area between the middle position in an axial direction of the electrophotographic photoreceptor and a 90% position located at 90% of the length from the middle position of the electrophotographic photoreceptor to one end is an area X, and an area from the 90% position to the one end of the electrophotographic photoreceptor is an area Z, the average film thicknesses of respective areas obtained by dividing the area X into five equal parts and respective areas obtained by dividing the area Z into three equal parts satisfy specific relationships.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to an electrophotographic photosensitive member, a process cartridge having the electrophotographic photosensitive member, and an electrophotographic apparatus.

In recent years, semiconductor lasers have become the mainstream of exposure means used in electrophotographic apparatus. The laser light emitted from a normal light source is scanned by a laser scanning writing device in the axial direction of a cylindrical electrophotographic photosensitive member (hereinafter, also simply referred to as “photoreceptor”). The light amount distribution is controlled so that the amount of light applied to the photoconductor is uniform with respect to the axial direction of the photoconductor by an optical system such as a polygon mirror used at this time and various electrical correction means. There is.

The cost of the polygon mirror has been reduced, and the optical system has become smaller due to improvements in electrical correction technology. Laser beam printers for personal use using electrophotographic methods have also been used, but these days the cost has been further reduced. And miniaturization is required.

The laser light scanned by the laser scanning writing device has a bias in the amount of light distribution with respect to the axial direction of the photoconductor unless the optical system is devised or electrically corrected. In particular, since the laser beam is scanned by a polygon mirror or the like, it has a region in which the amount of light decreases from the central portion in the axial direction of the photoconductor toward the end portion. If such a bias of the light amount distribution is made uniform by control by an optical system or electrical correction, the cost increases and the size increases.

Therefore, conventionally, for a photoconductor, the exposure potential distribution in the axial direction of the photoconductor is made uniform by providing a sensitivity distribution with respect to the axial direction of the photoconductor so as to cancel the bias of the light amount distribution. ..

As a method of providing an appropriate sensitivity distribution to the photoconductor, it is conceivable to give an appropriate distribution to the capacitance of the photosensitive layer in the single-layer photoconductor and the charge transport layer in the laminated photoconductor. The smaller the capacitance, the smaller the amount of canceling charge required to reduce the exposure potential to a specified potential, so that the exposure potential tends to decrease with respect to the amount of light, and the sensitivity improves. As a method of giving an appropriate distribution to the capacitance, it is known to change the film thickness of the photosensitive layer or the charge transport layer.

However, when there is a capacitance distribution in the axial direction of the photoconductor, the distribution also occurs in phenomena such as a fog phenomenon and a ghost phenomenon that change due to a change in the capacitance of the photoconductor. As a result, there is a problem that it becomes difficult to suppress these phenomena over the entire axial direction of the photoconductor in the entire electrophotographic system.

Therefore, as a method of providing an appropriate sensitivity distribution to the photoconductor, it is effective to give an appropriate distribution to the photoelectric conversion efficiency of the charge generation layer in the laminated photoconductor.

In Patent Document 1, a deviation is provided in the film thickness of the charge generation layer of the photoconductor due to the speed control during immersion coating, thereby causing a deviation in the adhesion amount of the trisazo pigment used as the charge generation substance. Techniques for changing the value of Macbeth concentration are described. By providing a deviation in the distribution of Macbeth concentration in the axial direction of the photoconductor, the amount of light absorption of the charge generation layer is changed in the axial direction of the photoconductor, and an appropriate distribution is provided for the photoelectric conversion efficiency.

In Patent Document 2, two types of droplet ejection heads are used at the time of inkjet coating, and the ratio of the charge generating substance to the resin in the coating liquid for the charge generating layer discharged from each droplet ejection head (P / B ratio). By controlling the scanning conditions of each droplet ejection head, the chlorogallium phthalocyanine pigment used as the charge generating substance is contained while keeping the film thickness of the charge generating layer constant in the axial direction of the photoconductor. Techniques for increasing the amount from the center to both ends are described. By giving an appropriate distribution to the content per unit volume of the charge generating substance while keeping the film thickness of the charge generating layer constant, the light absorption amount of the charge generating layer is changed while suppressing the ghost phenomenon, and the photoelectric The conversion efficiency has an appropriate distribution.

Japanese Unexamined Patent Publication No. 2001-305838 Japanese Unexamined Patent Publication No. 2008-076657

In an electrophotographic apparatus, when a charging roller is used as a charging means and a DC bias is applied to output an image, innumerable streak-shaped discharge marks (hereinafter, "charged streaks") are formed in the axial direction of the photoconductor of the output image. Also referred to as) may occur. It is known that this phenomenon is likely to occur when the film thickness of the charge generation layer of the photoconductor is thick. Further, if the film thickness of the charge transport layer is reduced in that state, the charge streaks tend to disappear. Regarding the mechanism of generation of the charge streaks, the discharge state in the vicinity of the charge roller changes due to the influence of the thickening of the charge generation layer and the increase of dark attenuation and the effect of the thinning of the charge transport layer and the increase in capacitance. I think it is because of this, but the details are not clear. However, there is a relationship between the discharge light near the charging roller and the generation behavior of the charging streaks, and if the film thickness of the charge generation layer is thin, the discharge is completed near the upstream of the charging roller and the film thickness of the charge generation layer becomes thick. It was known that an electric discharge also occurs downstream of the charging roller and a charging streak is generated.

On the other hand, when the film thickness of the charge transport layer is reduced, the discharge downstream of the charging roller becomes stable and the generation of charge streaks is suppressed. It is considered that there is a correlation between the phenomenon that the discharge position shifts from the upstream to the downstream and the generation of the charging streaks, and the generation of the charging streaks can be suppressed by stabilizing the discharge behavior.

Conventionally, in order to compensate for the insufficient amount of light at the axial end of the photoconductor, the film thickness of the charge generation layer has been increased from the center to the end. Therefore, since the charge generation layer at the end is thickened, the condition is such that charge streaks are likely to occur at the end. Therefore, in the present disclosure, in order to compensate for the insufficient amount of light at the axial end of the photoconductor, even if the film thickness of the charge generation layer is increased from the center to the end, the electrograph that suppresses the charge streaks generated at the end is suppressed. Provide a photoconductor.

According to one aspect of the present disclosure, it has a cylindrical support, a charge generation layer, and a charge transport layer, from an axially central position of the electrophotographic photosensitive member and from the central position of the electrophotographic photosensitive member. When the region between the 90% positions located at 90% of the length to one end is defined as the region X and the region between the 90% position and the one end of the electrophotographic photosensitive member is defined as the region Z, the region is defined as the region. The region in which X is divided into five equal parts is designated as X1, X2, X3, X4, and X5 in order from the central position, and the region in which the region Z is divided into three equal parts is referred to as Z1, Z2, and Z3 in the order closer to the central position. Then, the average film thickness of the charge generation layer in the X1, X2, X3, X4, X5, Z1, Z2, and Z3 is represented by DgX1, DgX2, DgX3, DgX4, DgX5, DgZ1, DgZ2, and DgZ3. , X1, X2, X3, X4, X5, Z1, Z2, and Z3, respectively, represented by the average thickness of the charge transport layer DtX1, DtX2, DtX3, DtX4, DtX5, DtZ1, DtZ2, and DtZ3. If so, an electrophotographic photosensitive member is provided that satisfies DgX1 <DgX2 <DgX3 <DgX4 <DgX5 and DtX5> DtZ1.

According to the present disclosure, the insufficient amount of light at the axial end of the photoconductor is dealt with by increasing the film thickness of the charge generating layer from the center to the end, and also reducing the film thickness of the charge transport layer at the end. By doing so, it is possible to suppress the discharge streaks generated at the ends.

It is a figure which shows an example of the schematic structure of the electrophotographic apparatus provided with the process cartridge which has the electrophotographic photosensitive member of this disclosure. It is a figure which shows an example of the schematic structure about the exposure means of the electrophotographic apparatus provided with the electrophotographic photosensitive member of this disclosure. It is sectional drawing of the laser scanning apparatus of the electrophotographic apparatus provided with the electrophotographic photosensitive member of this disclosure. It is a graph which shows the relationship between the scanning characteristic coefficient B in the formula (E6), and the geometric feature θ _max of a laser scanning apparatus. It is a figure which shows each region of the electrophotographic photosensitive member of this disclosure. It is sectional drawing of the charge generation layer and charge transport layer of the electrophotographic photosensitive member of this disclosure.

Hereinafter, the present disclosure will be described in detail with reference to preferred embodiments.
[Electrophotophotoreceptor]
The electrophotographic photosensitive member of the present disclosure is characterized by having a charge generation layer and a charge transport layer.
Examples of the method for producing the electrophotographic photosensitive member of the present disclosure include a method in which a coating liquid for each layer described later is prepared, applied to a cylindrical support in the order of desired layers, and dried. At this time, examples of the coating liquid coating method include immersion coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, dip coating is preferable from the viewpoint of efficiency and productivity.

As shown in FIG. 5, the electrophotographic photosensitive member of the present disclosure is located at the center position in the axial direction of the electrophotographic photosensitive member and at the 90% position located at 90% of the length from the center position to one end of the electrophotographic photosensitive member. The region between them is defined as region X, and the region from the 90% position to one end of the electrophotographic photosensitive member is defined as region Z. The regions obtained by further dividing the region X into five equal parts are designated as X1, X2, X3, X4, and X5 in order from the central position. Further, the regions obtained by further dividing the region Z into three equal parts are designated as Z1, Z2, and Z3 in the order closer to the center. The average film thickness of the charge generation layer in each of the regions X1, X2, X3, X4, X5, Z1, Z2, and Z3 is represented by DgX1, DgX2, DgX3, DgX4, DgX5, DgZ1, DgZ2, and DgZ3. The average film thickness of the charge transport layer in each of the regions X1, X2, X3, X4, X5, Z1, Z2, and Z3 is represented by DtX1, DtX2, DtX3, DtX4, DtX5, DtZ1, DtZ2, and DtZ3.

In the electrophotographic photosensitive member of the present disclosure, the film thickness of the charge generation layer is formed so as to satisfy DgX1 <DgX2 <DgX3 <DgX4 <DgX5. Therefore, it is preferable that the coating method of the coating liquid for the charge generation layer is dip coating, and the film thickness of each region is controlled by changing the pulling speed of the dip coating. For example, the film thickness of each region can be controlled by setting the pulling speed for each of 10 arbitrary points in the axial direction of the photoconductor and smoothly changing the pulling speed between two adjacent points during immersion coating. Can be achieved. At that time, the 10 points for setting the pull-up speed do not need to be equally divided in the axial direction of the photoconductor, but rather, the charge is generated by selecting the pull-up speed setting points so that the value of the pull-up speed is evenly divided. This is preferable from the viewpoint of improving the accuracy of controlling the film thickness of each region of the layer.

In order to correct the light amount distribution in the axial direction of the photoconductor, it is necessary to satisfy DgX1 <DgX2 <DgX3 <DgX4 <DgX5. However, in order to maximize the film thickness DgX5 of the region X5 which is the end of the region X, the film thickness DgZ1 of the region Z1 on the more end side in the axial direction of the photoconductor may be made a thicker film. is necessary. This also becomes a de facto restriction, and is a factor that worsens the generation of charged streaks at the edges of the photoconductor. As described above, by setting the relationship between DgX5 and DgZ1 to DgX5 <DgZ1, the average film thickness of the charge generation layer that satisfactorily suppresses the generation of charge streaks can be obtained. Further, when the relationship between DgX5 and DgZ1 is DgX5 * 1.2 <DgZ1, the average film thickness of the charge generation layer that suppresses the generation of charge streaks can be obtained more satisfactorily.

Further, the potential on the photoconductor is affected by the film thickness of the charge transport layer in terms of the capacitance. The exposed potential is affected by the film thickness of the charge generation layer from the viewpoint of the amount of charge generation and by the film thickness of the charge transport layer from the viewpoint of capacitance. In the present disclosure, the amount of charge generated in the axial direction of the photoconductor is made uniform by adjusting the film thickness of the charge generation layer according to the distribution of the amount of light in the axial direction of the photoconductor of the electrophotographic apparatus as described above. Further, by making the film thickness of the charge transport layer uniform together with the charge generation layer, the surface potential becomes more uniform, and the density uniformity of the output image can be improved.

In addition, as a result of verification using several types of evaluation devices as a boundary for thinning the film thickness at the end of the charge transport layer, the inventors found that 90% of the length from the central position to one end of the electrophotographic photosensitive member was 90%. Found to be appropriate. If the boundary is set to the end side from 90%, the generation of charging streaks cannot be suppressed at the end, and if the boundary is set to the center side from 90%, the image density at the end becomes thin. Therefore, by reducing the film thickness of the end portion of the charge transport layer with the position of exactly 90% as a boundary, the generation of charge streaks can be effectively suppressed.

From the above, in the electrophotographic photosensitive member of the present disclosure, the charge transport is performed so that the relationship between the average film thicknesses DtX5, DtZ1, DtZ2, and DtZ3 of the charge transport layer satisfies DtX5 * 0.9> DtZ1 ≧ DtZ2 ≧ DtZ3. By forming the layer, it is possible to more effectively suppress the generation of charged streaks at the edges. The film thicknesses of DtZ1, DtZ2, and DtZ3 are 0, that is, the charge transport layer may not be formed in the region Z.

Further, by setting the standard deviation of the average thickness DtX1, DtX2, DtX3, DtX4, and DtX5 of the charge transport layer to 0.1 or less, the potential in the image region becomes uniform and the density uniformity of the output image is improved. Can be done.

[Process cartridge, electrophotographic equipment]
The process cartridge of the present disclosure integrally supports an electrophotographic photosensitive member and at least one means selected from the group consisting of charging means, developing means, and cleaning means, and is detachable to the main body of the electrophotographic apparatus. It is characterized by.

Further, the electrophotographic apparatus of the present disclosure is characterized by having an electrophotographic photosensitive member, a charging means, an exposure means, a developing means and a transfer means.

FIG. 1 shows an example of a schematic configuration of an electrophotographic apparatus having a process cartridge 11 provided with an electrophotographic photosensitive member.
The cylindrical electrophotographic photosensitive member 1 is rotationally driven at a predetermined peripheral speed in the direction of an arrow about a shaft 2. The surface of the electrophotographic photosensitive member 1 is charged to a predetermined positive or negative potential by the charging means 3. Although the roller charging method using the roller type charging member is shown in the figure, a charging method such as a corona charging method, a proximity charging method, or an injection charging method may be adopted. The surface of the charged electrophotographic photosensitive member 1 is irradiated with exposure light 4 from an exposure means (not shown), and an electrostatic latent image corresponding to the target image information is formed. The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1 is developed with the toner contained in the developing means 5, and the toner image is formed on the surface of the electrophotographic photosensitive member 1. The toner image formed on the surface of the electrophotographic photosensitive member 1 is transferred to the transfer material 7 by the transfer means 6. The transfer material 7 to which the toner image is transferred is conveyed to the fixing means 8, undergoes the fixing process of the toner image, and is printed out of the electrophotographic apparatus. The electrophotographic apparatus may have a cleaning means 9 for removing deposits such as toner remaining on the surface of the electrophotographic photosensitive member 1 after transfer. Further, a so-called cleanerless system may be used in which the cleaning means 9 is not separately provided and the deposits are removed by a developing means or the like. The electrophotographic apparatus may have a static elimination mechanism for statically eliminating the surface of the electrophotographic photosensitive member 1 with preexposure light 10 from a preexposure means (not shown). Further, in order to attach / detach the process cartridge 11 of the present disclosure to / from the main body of the electrophotographic apparatus, a guide means 12 such as a rail may be provided.

The electrophotographic photosensitive member of the present disclosure can be used for laser beam printers, LED printers, copiers, facsimiles, and multifunction devices thereof.

FIG. 2 shows an example of a schematic configuration of an exposure means of an electrophotographic apparatus provided with the electrophotographic photosensitive member of the present disclosure.
The laser driving unit 203 in the laser scanning device 204, which is a laser scanning means, emits laser scanning light based on the image signal output from the image signal generation unit 201 and the control signal output from the control unit 202. The electrophotographic photosensitive member 205 charged by a charging means (not shown) is scanned with a laser beam to form an electrostatic latent image on the surface of the electrophotographic photosensitive member 205. The transfer material having the toner image obtained from the electrostatic latent image formed on the surface of the electrophotographic photosensitive member 205 is transported to the fixing means 206, undergoes the fixing process of the toner image, and then goes out of the electrophotographic apparatus. It will be printed out.

FIG. 3 is a cross-sectional view of a laser scanning apparatus 204 of an electrophotographic apparatus provided with an electrophotographic photosensitive member according to one aspect of the present disclosure.
The laser light (light beam) emitted from the laser light source 208 is transmitted through the optical system and then reflected by the deflection surface (reflection surface) 209a of the polygon mirror (deflector) 209, and is transmitted through the imaging lens 210 to the surface of the photoconductor. It is incident on the surface to be scanned 211. The imaging lens 210 is an imaging optical element. In the laser scanning apparatus 204, the imaging optical system is composed of only a single imaging optical element (imaging lens 210). An image is formed on the surface to be scanned 211 on the surface of the photoconductor to which the laser light transmitted through the imaging lens 210 is incident, and a predetermined spot-like image (spot) is formed. By rotating at a constant angular velocity A ₀ by a driving unit (not shown) polygon mirror 209, the spot on the scan surface 211 of the photosensitive member surface is moved in the axial direction of the photosensitive member, the surface to be scanned of the photosensitive member surface 211 An electrostatic latent image is formed on the top.

The imaging lens 210 does not have the so-called fθ characteristic. That is, when the polygon mirror 209 is rotating at a constant angular velocity A _0, does not have the scanning characteristic as to move the spot of the laser light passing through the imaging lens 210 to a constant speed on the scan surface 211 .. In this way, by using the imaging lens 210 that does not have the fθ characteristic, the imaging lens 210 can be arranged close to the polygon mirror 209 (at a position where the distance D1 is small). Further, the imaging lens 210 having no fθ characteristic can be made smaller in terms of width LW and thickness LT than the imaging lens having fθ characteristic. Therefore, the laser scanning apparatus 204 can be miniaturized. Further, in the case of a lens having fθ characteristics, there may be a sharp change in the shape of the entrance surface and the exit surface of the lens, and if there is such a shape restriction, good imaging performance may not be obtained. There is. On the other hand, since the imaging lens 210 does not have the fθ characteristic, there are few sharp changes in the shapes of the incident surface and the exit surface of the lens, and good imaging performance can be obtained.

式（Ｅ３）では、ポリゴンミラー２０９による走査角度をθ、レーザ光の感光体表面の被走査面２１１上での感光体の軸方向の集光位置（像高）をＹ［ｍｍ］としている。また、軸上像高における結像係数をＫ［ｍｍ］、結像レンズ２１０の走査特性を決定する係数（走査特性係数）をＢとしている。なお、本開示において軸上像高は、光軸上の像高（Ｙ＝０＝Ｙ_ｍｉｎ）を指し、走査角度θ＝０に対応する。また、軸外像高は、中心光軸（走査角度θ＝０の時）よりも外側の像高（Ｙ≠０）を指し、走査角度θ≠０に対応している。さらに、最軸外像高とは、走査角度θが最大となる時の像高（Ｙ＝＋Ｙ’_ｍａｘ、−Ｙ’_ｍａｘ）を指す。なお、感光体表面の被走査面２１１上の潜像を形成可能な所定の領域（走査領域）の感光体の軸方向の幅である走査幅ＷはＷ＝｜＋Ｙ’_ｍａｘ｜＋｜−Ｙ’_ｍａｘ｜で表される。つまり、走査領域の中央位置が軸上像高で端位置が最軸外像高となる。また、走査領域は感光体の画像形成領域よりも大きい。 The scanning characteristics of the imaging lens 210 that does not have the fθ characteristic, which is effective in reducing the size and improving the imaging performance, are represented by the following equation (E3).

In the formula (E3), the scanning angle by the polygon mirror 209 is θ, and the axial focusing position (image height) of the photoconductor on the surface to be scanned of the photoconductor surface of the laser beam is Y [mm]. Further, the imaging coefficient at the axial image height is K [mm], and the coefficient for determining the scanning characteristic of the imaging lens 210 (scanning characteristic coefficient) is B. In the present disclosure, the on-axis image height refers to the on-axis image height (Y = 0 = Y _min ) and corresponds to the scanning angle θ = 0. The off-axis image height refers to an image height (Y ≠ 0) outside the central optical axis (when the scanning angle θ = 0), and corresponds to a scanning angle θ ≠ 0. Furthermore, the most off-axial image height refers image height when the scanning angle θ is maximum _{(Y = + Y 'max,} -Y' max) to. The scanning width W, which is the axial width of the photoconductor in a predetermined region (scanning region) on which a latent image can be formed on the surface to be scanned 211 on the surface of the photoconductor, is W = | + _Y'max | + | -Y. It is represented _by'max |. That is, the central position of the scanning region is the on-axis image height, and the end position is the most off-axis image height. Further, the scanning area is larger than the image forming area of the photoconductor.

Here, the imaging coefficient K is a coefficient corresponding to f at the scanning characteristic (fθ characteristic) Y = fθ when it is assumed that the imaging lens 210 has the fθ characteristic. That is, the imaging coefficient K is a proportional coefficient in the relational expression between the focusing position Y and the scanning angle θ as in the fθ characteristic when a light flux other than parallel light is incident on the imaging lens 210.

Supplementing the scanning characteristic coefficient, the equation (E3) when B = 0 is Y = Kθ, which corresponds to the scanning characteristic Y = fθ of the imaging lens used in the conventional optical scanning apparatus. Further, since the equation (E3) when B = 1 is Y = K · tan θ, it corresponds to the projection characteristic Y = f · tan θ of a lens used in an imaging device (camera) or the like. That is, in the equation (E3), by setting the scanning characteristic coefficient B in the range of 0 ≦ B ≦ 1, the scanning characteristic between the projection characteristic Y = f · tan θ and the scanning characteristic Y = fθ can be obtained. ..

Here, when the equation (E3) is differentiated by the scanning angle θ, the scanning speed of the laser beam on the surface to be scanned 211 on the surface of the photoconductor with respect to the scanning angle θ can be obtained as shown in the following equation (E4).

Further, when the equation (E4) is divided by the velocity Y / θ = K at the axial image height and the reciprocals of both sides are taken, the following equation (E5) is obtained.

Equation (E5) expresses the ratio of the reciprocal of the scanning speed of each off-axis image height to the reciprocal of the scanning speed of the on-axis image height. Since the total energy of the laser light is constant regardless of the scanning angle θ, the inverse of the scanning speed of the laser light on the surface to be scanned 211 on the surface of the photoconductor is the laser per unit area irradiated to the location of the scanning angle θ. It is proportional to the amount of light [μJ / cm ² ]. Therefore, the formula (E5) is applied to the scanned surface 211 of the photoconductor surface at the scanning angle θ ≠ 0 with respect to the amount of laser light per unit area irradiated to the scanned surface 211 of the photoconductor surface at the scanning angle θ = 0. It means the ratio of the amount of laser light per unit area. In the laser scanning apparatus 204, when B ≠ 0, the amount of laser light per unit area irradiated on the surface to be scanned 211 on the surface of the photoconductor differs between the on-axis image height and the off-axis image height.

When the above-mentioned distribution of the amount of laser light exists in the axial direction of the photoconductor, the present disclosure having a sensitivity distribution in the axial direction of the photoconductor can be preferably used. That is, if a sensitivity distribution that just cancels the distribution of the amount of laser light is realized by the configuration according to the present disclosure, the exposure potential distribution in the axial direction of the photoconductor becomes uniform. The sensitivity distribution shape obtained at that time is represented by the following equation (E6), which is the reciprocal of the above equation (E5).

Assuming that the scanning angle corresponding to the edge position of the image forming region of the photoconductor is θ = θ _max , the value of the equation (E6) at θ = θ _max is the photoconductor according to the above-mentioned laser scanning apparatus and one aspect of the present disclosure. Means the sensitivity ratio r required for the photoconductor when these are combined. Here, the sensitivity ratio r is the ratio of the photoelectric conversion efficiency at the edge position of the image forming region to the photoelectric conversion efficiency at the center position of the image forming region. If this sensitivity ratio r is determined, the geometrical feature θ _{max of the} laser scanning apparatus and the scanning characteristic coefficient B of the optical system, which are allowed to form a uniform exposure potential distribution in the axial direction of the photoconductor in the image forming region. Is decided. Specifically, when the condition of the following formula (E7) is satisfied, a uniform exposure potential distribution in the axial direction of the photoconductor can be formed in the image forming region of the photoconductor according to one aspect of the present disclosure. It is possible.

Solving equation (E7) for θ _max gives the following equation (E8).

A graph of the equation (E8) is shown in FIG. As can be seen from FIG. 4, for example, when a photoconductor with r = 1.2 and an imaging lens 210 having a scanning characteristic coefficient B = 0.5 are combined, the laser scanning device 204 should be designed so that θ _max = 48 °. Just do it. As a result, the exposure potential distribution can be made uniform in the image forming region of the photoconductor. On the other hand, consider, for example, a case where a photoconductor with r = 1.1 and an imaging lens 210 having a scanning characteristic coefficient B = 0.5 are combined. In this case, if the laser scanning apparatus 204 is designed so that θ _max = 48 °, the exposure potential distribution will be partially uneven in the image forming region of the photoconductor. At this time, θ _max = 35 ° is required to make the exposure potential distribution uniform in the image forming region of the photoconductor, and this value is smaller than θ _max = 48 °. The larger the θ _{max, the} shorter the optical path length D2 from the deflection surface 209a shown in FIG. 3 to the surface to be scanned 211 on the surface of the photoconductor, so that the laser scanning apparatus 204 can be miniaturized. Therefore, the larger the sensitivity ratio r between the central position of the image forming region and the edge position of the image forming region in the axial direction of the photoconductor, the smaller the size of the laser beam printer becomes possible when the photoconductor is used.

The cylindrical support and each layer constituting the electrophotographic photosensitive member according to one aspect of the present disclosure will be described in detail below.

<Cylindrical support>
In the present disclosure, the cylindrical support of the electrophotographic photosensitive member is preferably a conductive support having conductivity. Also, the support is solid or hollow. Further, the surface of the cylindrical support may be subjected to an electrochemical treatment such as anodization, a blast treatment, a cutting treatment or the like.
As the material of the cylindrical support, metal, resin, glass and the like are preferable.
Examples of the metal include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Above all, it is preferable that the support is made of aluminum using aluminum.
Further, the resin or glass may be imparted with conductivity by a treatment such as mixing or coating a conductive material.

<Conductive layer>
In the present disclosure, it is preferable to provide a conductive layer on the cylindrical support. By providing the conductive layer, scratches and irregularities on the surface of the cylindrical support can be concealed. In addition, by controlling the reflection of light on the surface of the cylindrical support, when the exposure laser incident on the photoconductor and passing through the charge generation layer of the present disclosure is reflected and incident on the charge generation layer again. The transmittance can be lowered. Therefore, the light absorption rate in the charge generation layer of the incident exposure laser is improved as compared with the case where the conductive layer is not provided, and the average film thickness of the charge generation layer can be made thinner, so that edge streaks can be generated more effectively. It can be suppressed.
The conductive layer preferably contains conductive particles and a resin.

Examples of the material of the conductive particles include metal oxides, metals, and carbon black. Examples of the metal oxide include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of the metal include aluminum, nickel, iron, nichrome, copper, zinc, silver and the like.
Among these, it is preferable to use a metal oxide as the conductive particles.
When a metal oxide is used as the conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or the like, or the metal oxide may be doped with an element or its oxide. Examples of the element to be doped and its oxide include phosphorus, aluminum, niobium, and tantalum.
Further, the conductive particles may have a laminated structure having core material particles and a coating layer covering the particles. Examples of the core material particles include titanium oxide, barium sulfate, zinc oxide and the like. Examples of the coating layer include metal oxides such as tin oxide and titanium oxide.

Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, and alkyd resin.
Further, the conductive layer may further contain a hiding agent such as silicone oil, resin particles, and titanium oxide.

From the viewpoint of more effectively obtaining the sensitivity distribution in the axial direction of the photoconductor of the present disclosure, the thickness of the conductive layer is larger than 10 μm, the conductive layer contains a binder resin and metal oxide fine particles, and the metal oxide. The average diameter of the fine particles is preferably 100 nm or more and 400 nm or less. When the average diameter of the metal oxide fine particles is 100 nm or more and 400 nm or less, a laser in a submicron wavelength region used as an exposure light source of an electrophotographic apparatus in recent years is well scattered. When the thickness of the conductive layer is larger than 10 μm, the laser beam incident on the photoconductor passes through the conductive layer, is reflected by the cylindrical support, passes through the conductive layer again, and reaches the charge generation layer. It will run a distance of 20 μm or more. This distance is more than 20 times the wavelength of the exposure laser used, and the laser light traveling while being scattered over such a distance loses its coherency sufficiently. Therefore, the transmittance of the laser beam reflected and incident on the charge generation layer again with respect to the charge generation layer becomes low, and the laser light is well absorbed by the charge generation layer, so that the sensitivity of the photoconductor is substantially improved. By the above mechanism, the above-mentioned conductive layer configuration makes it possible to effectively obtain the sensitivity distribution of the present disclosure even with a thin charge generation layer film thickness.

Further, from the viewpoint of effectively obtaining the sensitivity distribution of the present disclosure as described above and further improving the image quality when the electrophotographic photosensitive member of the present disclosure is used, the metal contained in the conductive layer. It is more preferable that the oxide fine particles have a core material containing titanium oxide and a coating layer containing titanium oxide that coats the core material and is doped with niobium or tantalum. Titanium oxide has a higher refractive index than tin oxide, which is often used as a coating layer. Therefore, when both the core material and the coating layer of the metal oxide fine particles contain titanium oxide, the invasion into the conductive layer after passing through the charge generation layer of the exposure laser incident on the photoconductor is suppressed, and the conductivity is suppressed. It is easy to be reflected or scattered near the interface on the charge generation layer side of the layer. In the conductive layer, the more the exposure laser is scattered at a position farther from the interface on the charge generation layer side of the conductive layer, the wider the irradiation range of the exposure laser on the charge generation layer is substantially widened, and the finer the latent image is. It is considered that the property is lowered, and as a result, the fineness of the output image is lowered. By combining the conductive layer having the above structure with the charge generation layer of the present disclosure, it is possible to achieve both a substantial increase in sensitivity of the photoconductor due to scattering of the exposure laser and a prevention of a substantial expansion of the irradiation range in the charge generation layer of the exposure laser. However, it is possible to further improve the image quality by improving the fineness of the output image.

The conductive layer can be formed by preparing a coating liquid for a conductive layer containing each of the above-mentioned materials and a solvent, forming the coating film, and drying the coating film. Examples of the solvent used for the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents and the like. Examples of the dispersion method for dispersing the conductive particles in the coating liquid for the conductive layer include a method using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

The average particle size of the metal oxide fine particles in the present disclosure was determined as follows. That is, the particles to be measured are observed using a scanning electron microscope S-4800 manufactured by Hitachi, Ltd., the individual particle sizes of 100 particles are measured from the observed images, and the arithmetic averages thereof are calculated. The average diameter (average primary particle size) was used. The individual particle sizes were (a + b) / 2 when the longest side of the primary particle was a and the shortest side was b. In the case of needle-shaped titanium oxide particles or flaky titanium oxide particles, the average particle size was calculated for each of the major axis diameter and the minor axis diameter.

<Underlay layer>
In the present disclosure, an undercoat layer may be provided on the cylindrical support or the conductive layer. By providing the undercoat layer, the adhesive function between the layers is enhanced, and the charge injection blocking function can be imparted.

The undercoat layer preferably contains a resin. Further, an undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.

Resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinylphenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, and polyamide resin. , Polyamic acid resin, polyimide resin, polyamideimide resin, cellulose resin and the like.

The polymerizable functional group of the monomer having a polymerizable functional group includes an isocyanate group, a blocked isocyanate group, a methylol group, an alkylated methylol group, an epoxy group, a metal alkoxide group, a hydroxyl group, an amino group, a carboxyl group and a thiol group. Examples thereof include a carboxylic acid anhydride group and a carbon-carbon double bond group.

Further, the undercoat layer may further contain an electron transporting substance, a metal oxide, a metal, a conductive polymer and the like for the purpose of enhancing the electrical characteristics. Among these, it is preferable to use an electron transporting substance and a metal oxide.
Examples of the electron transporting substance include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, aryl halide compounds, silol compounds, and boron-containing compounds. .. An undercoat layer may be formed as a cured film by using an electron transporting substance having a polymerizable functional group as the electron transporting substance and copolymerizing it with the above-mentioned monomer having a polymerizable functional group.
Examples of the metal oxide include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, silicon dioxide and the like. Examples of the metal include gold, silver and aluminum.
Further, the undercoat layer may further contain an additive.

The average film thickness of the undercoat layer is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 40 μm or less, and particularly preferably 0.3 μm or more and 30 μm or less.

The undercoat layer can be formed by preparing a coating liquid for an undercoat layer containing each of the above-mentioned materials and solvents, forming this coating film, and drying and / or curing. Examples of the solvent used for the coating liquid include alcohol solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents and the like.

<Photosensitive layer>
The photosensitive layer of the electrophotographic photosensitive member of the present disclosure is a laminated photosensitive layer having a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance.

(1) Charge generating layer The charge generating layer preferably contains a charge generating substance and a resin.

In the present disclosure, the charge generating layer is a charge generating substance, which is described in JP-A-2000-137340, and has a Bragg angle of 2θ of 7.4 ° ± 0.3 ° and 28.2 ° ± 0 in CuKα characteristic X-ray diffraction. A hydroxygallium phthalocyanine crystal having a strong peak at .3 °, or a strong peak at 27.2 ° ± 0.3 ° of Bragg angle 2θ in CuKα characteristic X-ray diffraction described in JP-A-2000-137340. The titanyl phthalocyanine crystal or the spectral absorption spectrum described in US Pat. No. 9,720,337 has at least one peak in the wavelength range of 646 nm or more and 668 nm or less and the wavelength range of 782 nm or more and 809 nm or less, and is 646 nm or more and 668 nm or less. When the peak showing the maximum absorbance among the peaks existing in the wavelength range of 782 nm is set as the first peak, and the peak showing the maximum absorbance among the peaks existing in the wavelength range of 782 nm or more and 809 nm or less is set as the second peak. , Contains chlorogallium phthalocyanine crystals in which the absorbance of the first peak is greater than the absorbance of the second peak.

The content of the charge generating substance in the charge generating layer is preferably 40% by mass or more and 85% by mass or less, and more preferably 60% by mass or more and 80% by mass or less with respect to the total mass of the charge generating layer. preferable.

As the resin, polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin , Polyvinyl chloride resin and the like. Among these, polyvinyl butyral resin is more preferable.

Further, the charge generation layer may further contain additives such as an antioxidant and an ultraviolet absorber. Specific examples thereof include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

The film thickness of the charge generation layer is preferably 10 nm or more and 1000 nm or less, and more preferably 70 nm or more and 300 nm or less.

The average film thickness of the charge generation layer of the present disclosure was measured as follows.
First, a region X is defined as a region between the axial center position of the cylindrical electrophotographic photosensitive member of the present disclosure and the 90% position located at 90% of the length from the center position to one end of the electrophotographic photosensitive member. The region between the 90% position and the one end of the electrophotographic photosensitive member is defined as region Z. The region X is divided into five equal parts as X1, X2, X3, X4, and X5 in order from the central position, and the region Z is divided into three equal parts as Z1, Z2, and Z3 in the order closer to the central position. For the 32 divisions obtained by further dividing each region into 4 equal parts in the axial direction and 8 equal parts in the circumferential direction, the film thickness was measured at any measurement point in each division, and the average value thereof was used as the charge generation. The average film thickness of each region of the layer. The average film thickness in each region of X1, X2, X3, X4, X5, Z1, Z2, and Z3 is defined as DgX1, DgX2, DgX3, DgX4, DgX5, DgZ1, DgZ2, and DgZ3 [nm].

The film thickness distribution of the charge generation layer is as follows: when the light absorption coefficient of the charge generation layer is β [nm ^-1 ], the film thickness d ₀ [μm] of the charge generation layer at the center of the image formation region and X5. It is preferable that the film thickness d ₆ [μm] of the charge generation layer at the boundary position of Z1 satisfies the relationship represented by the formula (E1).

The light absorption coefficient β referred to here is defined by Lambert-Beer's law expressed by the equation (E9).

Here, I ₀ is the total energy of light incident on the film having a film thickness d [nm], and I is the energy of light absorbed by the film having a film thickness d [nm]. Further, d ₀ and d ₆ are average values of film thickness defined as follows. That is, first, consider a region having a width of Y _max / 20 [mm] in the axial direction and making one round in the circumferential direction, centered on the respective points of the center position of the image forming region and the end position of the image forming region. At this time, the film thickness of the charge generation layer is measured at an arbitrary measurement point in each of the 32 divisions obtained by dividing each region into 4 equal parts in the axial direction and 8 equal parts in the circumferential direction. Subsequently, the average value of the obtained measured values is obtained for each region and defined as d ₀ and d ₆ , respectively.

As is clear from the formula (E9), the numerator on the left side of the formula (E1) is the light absorption rate at the axial end of the image forming region end position, and the left side denominator is the light absorption rate at the axial center of the image forming region end position. Represents each. Therefore, the formula (E1) means that the edge position of the image forming region has a light absorption rate of 1.2 times or more with respect to the center position of the image forming region. As a result, a difference in sensitivity of at least 1.2 times can be provided in the image forming region in the axial direction of the photoconductor, so that a realistic light amount distribution generated by miniaturization of the optical system in the laser scanning system of the electrophotographic apparatus It is possible to flexibly deal with the deviation of. Further, the reason why the factor 2 is applied to the shoulder of the exponent in the formula (E1) is that the exposure laser that has passed through the charge generation layer is reflected by the support side of the photoconductor and passes through the charge generation layer again.

式（Ｅ２）中、Ｙは上述の像高Ｙと同一であり、Ｙ_ｍａｘは上述の最軸外像高Ｙ’_ｍａｘよりも小さい。 Further, the distance from the center position of the image forming region in the axial direction of the photoconductor is Y [mm], the value of Y at the edge position of the image forming region is Y = Y _max [mm], and the difference between d ₆ and d ₀ is Δ =. When d ₆ −d ₀ , the thickness distribution of the charge generation layer is d −0.2Δ for all Y of 0 ≦ Y ≦ Y _max with respect to d (Y) calculated by the equation (E2). It is more preferable that it is between and d + 0.2Δ.

Wherein (E2), Y is the same as the image height Y _{above, Y max} is less than the minimum off-axis image height Y _'max above.

The film thickness of the charge generation layer at all Y of 0 ≦ Y ≦ Y _max is measured as follows. That is, it has a width of Y _max / 20 [mm] in the axial direction of the photoconductor, centered on a point where the distance from the center position of the image forming region in the axial direction of the photoconductor is Y [mm], and is in the circumferential direction. When considering a region that makes one round, d (Y) is used as the average value when the film thickness of the charge generation layer is measured at 32 measurement points that divide the region into four equal parts in the axial direction and eight equal parts in the circumferential direction. ) Is defined.

By forming a charge generation layer having a film thickness distribution represented by a quadratic function such as the formula (E2), the exposure laser scans with an optical system having the characteristics represented by the formula (E3). The inventors have found that the axial light amount distribution of the body can be appropriately canceled and the axial exposure potential distribution of the photoconductor can be made uniform at a higher level. The mechanism will be described below.

As described above, in order to make the exposure potential distribution uniform with respect to the optical system having the characteristics represented by the formula (E3), the photoconductor must have the sensitivity distribution shape represented by the formula (E6). Just do it. In the present disclosure, since the sensitivity is determined by the photoelectric conversion efficiency calculated from the film thickness of the charge generation layer by Lambert-Beer's law, d ₅ is arbitrarily set to 0 ≦ Y ≦ Y _{max on} the left side of the equation (E1). The exposure potential distribution becomes uniform when the film thickness d (Y) of the charge generation layer in Y is equal to the right side of the equation (E6), that is, when the equation (E10) is satisfied.

By substituting the equation (E3) into the equation (E10) using the trigonometric function formula 1 + tan ² (x) = 1 / cos ² (x), the equation (E10) can be transformed like the equation (E11).

Here, by substituting Y = Y _max and d (Y) = d ₆ into the equation (E11) and transforming it, the equation (E12) is obtained.

式（Ｅ１３）中、上述したようにΔ＝ｄ_６−ｄ_０と定義し、ｌｎ（・）は自然対数関数を表す。 Substituting Eq. (E12) into Eq. (E11) and solving for d (Y) gives Eq. (E13).

In the equation (E13), Δ = d ₆ − d ₀ is defined as described above, and ln (・) represents a natural logarithm function.

The film thickness distribution d (Y) of the charge generation layer represented by the formula (E13) is the exact film thickness distribution required to make the axial exposure potential distribution of the photoconductor uniform at a higher level in the present disclosure. The solution.

のように変形し、（Ｙ^２／Ｙ_ｍａｘ ^２）について２次、および２βΔについて２次までを残すことによって、最終的な電荷発生層の膜厚分布を表す式（Ｅ２）が得られる。

The present inventors further considered expressing the equation (E13) as an approximate equation when it holds when Y ² / Y _max ² and 2βΔ are small. By doing so, the film thickness distribution shape of the charge generation layer suitable for the present disclosure becomes clearer, and it becomes easy to actually form the film thickness distribution by dip coating. Specifically, using ln (1-x) and Maclaurin expansion of ^{e -x,} wherein the (E13) the formula (E14)

By transforming as follows and leaving the second order for (Y ² / Y _max ² ) and the second order for 2βΔ, the equation (E2) representing the final film thickness distribution of the charge generation layer can be obtained.

The charge generation layer can be formed by preparing a coating liquid for a charge generation layer containing each of the above-mentioned materials and a solvent, forming the coating film, and drying the coating film. Examples of the solvent used for the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents and the like.

In order to determine the film thickness of the charge generation layer from the state of the electrophotographic photosensitive member, the charge generation layer of the electrophotographic photosensitive member may be taken out by the FIB method, and the SICE & View of FIB-SEM may be performed. The film thickness of the charge generation layer can be obtained from the cross-sectional SEM observation image of the FIB-SEM by Slice & View. Further, a method of obtaining the film thickness from the average specific gravity and weight of the charge generation layer can be used more simply. More simply, a method is also used in which a calibration curve of the Macbeth concentration of the electrophotographic photosensitive member and the film thickness of the charge generation layer is obtained in advance, and then the Macbeth concentration at each point of the photoconductor is measured and converted into the film thickness. be able to.

In the present disclosure, a calibration curve is obtained from a Macbeth concentration value measured by pressing a spectroscopic densitometer (trade name: X-Rite 504/508, manufactured by X-Rite) against the surface of a photoconductor, and a film thickness measurement value by observing a cross-sectional SEM image. Was obtained, and the Macbeth concentration value at each point of the photoconductor was converted using it to measure the average film thickness of the charge generation layer accurately and easily.

In the present disclosure, the light absorption coefficient β for each charge generating substance is determined as follows. First, the electrophotographic photosensitive member is processed so that the charge generation layer is exposed on the surface. For example, the layer above the charge generation layer may be peeled off using a solvent or the like. Then, the light reflectance in that state is measured. Subsequently, the charge generation layer is also peeled off in the same manner, and the light reflectance is measured for the state where the lower layer of the charge generation layer is exposed on the surface. The light absorption coefficient of the single layer of the charge generation layer is calculated using the two types of reflectances thus obtained. On the other hand, the film thickness of the charge generation layer is obtained by the above method. By connecting the data of the natural logarithmic value and the film thickness of the light absorption rate obtained by the above method with a straight line between the natural logarithmic value 0 of the light absorption rate and the point of the film thickness 0, the absorption coefficient can be obtained from the slope. can get.

The powder X-ray diffraction measurement and ¹ H-NMR measurement of the phthalocyanine pigment contained in the electrophotographic photosensitive member of the present disclosure were carried out under the following conditions.

(Powder X-ray diffraction measurement)
Measuring machine used: X-ray diffractometer RINT-TTRII manufactured by Rigaku Denki Co., Ltd.
X-ray tube: Cu
X-ray wavelength: Kα1
Tube voltage: 50KV
Tube current: 300mA
Scan method: 2θ scan Scan speed: 4.0 ° / min
Sampling interval: 0.02 °
Start angle 2θ: 5.0 °
Stop angle 2θ: 35.0 °
Goniometer: Rotor horizontal goniometer (TTR-2)
Attachment: Capillary rotating sample table Filter: None Detector: Scintillation counter Incident monochromator: Slit used: Variable slit (parallel beam method)
Counter monochromator: Unused divergence slit: Open divergence vertical limiting slit: 10.00 mm
Scattering slit: Open Light receiving slit: Open

( ^{1 1} H-NMR measurement)
Measuring instrument used: BRUKER, AVANCE III 500
Solvent: Bisulfuric acid (D ₂ SO ₄ )
Accumulation number: 2,000

(2) Charge transport layer The charge transport layer preferably contains a charge transport substance and a resin.

Examples of the charge transporting substance include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Be done. Among these, triarylamine compounds and benzidine compounds are preferable.
The content of the charge transporting substance in the charge transport layer is preferably 25% by mass or more and 70% by mass or less, and more preferably 30% by mass or more and 55% by mass or less, based on the total mass of the charge transport layer. preferable.

Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin and the like. Among these, polycarbonate resin and polyester resin are preferable. As the polyester resin, a polyarylate resin is particularly preferable.
The content ratio (mass ratio) of the charge transporting substance to the resin is preferably 4: 10 to 20:10, more preferably 5: 10 to 12:10.

Further, the charge transport layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipperiness imparting agent, and an abrasion resistance improving agent. Specifically, hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles. And so on.

The average film thickness of the charge transport layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

The charge transport layer can be formed by preparing a coating liquid for a charge transport layer containing each of the above-mentioned materials and a solvent, forming the coating film, and drying the coating film. Examples of the solvent used for the coating liquid include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents or aromatic hydrocarbon-based solvents are preferable.

The film thickness of the charge transport layer is measured as follows.
First, a region X is defined as a region between the axial center position of the cylindrical electrophotographic photosensitive member of the present disclosure and the 90% position located at 90% of the length from the center position to one end of the electrophotographic photosensitive member. The region between the 90% position and the one end of the electrophotographic photosensitive member is defined as region Z. The regions obtained by dividing the region X into five equal parts were designated as X1, X2, X3, X4, and X5 in order from the central position, and the regions obtained by dividing the region Z into three equal parts were designated as Z1, Z2, and Z3 in the order closer to the central position. The average film thickness in each region of X1, X2, X3, X4, X5, Z1, Z2, and Z3 is defined as DtX1, DtX2, DtX3, DtX4, DtX5, DtZ1, DtZ2, and DtZ3 [μm]. The film thickness is measured by facing the probe of the laser interference film thickness meter against the photoconductor, rotating the photoconductor in the circumferential direction while scanning in the axial direction, and measuring the film thickness at intervals of 1 mm pitch in both the axial direction and the circumferential direction. Can be measured. The obtained values are averaged for the defined regions of DtX1, DtX2, DtX3, DtX4, DtX5, DtZ1, DtZ2, and DtZ3, and the average film thickness of each region is obtained. As the laser interference film thickness meter, for example, a laser interference film thickness meter SI-T80 manufactured by KEYENCE CORPORATION can be used.

FIG. 6 shows an image of the cross-sectional shape of the charge generation layer and the charge transport layer of the electrophotographic photosensitive member of the present disclosure. In FIG. 6, the charge generation layer 21 is provided directly on the support 22, but as described above, a conductive layer and / or an undercoat layer is provided between the support 22 and the charge generation layer 21. May be charged. The charge generation layer 21 is provided with a sensitivity distribution in the axial direction of the photoconductor so as to cancel the bias of the light amount distribution. Further, the charge transport layer 20 has a thin end portion in order to suppress discharge streaks (in other words, charge streaks) generated at the end portions.

<Protective layer>
In the present disclosure, a protective layer may be provided on the photosensitive layer. Durability can be improved by providing a protective layer.

The protective layer preferably contains conductive particles and / or charge transporting material and a resin. When the protective layer has a charge transport material, in the present disclosure, the average thickness of the charge transport layer DtX1, DtX2, DtX3, DtX4, DtX5, DtZ1, DtZ2, and DtZ3 are X1, X2, X3, X4, X5, Z1, It is the sum of the average film thicknesses of the charge transport layer and the protective layer in each region of Z2 and Z3. In this case as well, the average film thickness of each region can be obtained in the same manner as in the method of obtaining the average film thickness of the charge transport layer.

Examples of the conductive particles include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide.

Examples of the charge transporting substance include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these, triarylamine compounds and benzidine compounds are preferable.

Examples of the resin include polyester resin, acrylic resin, phenoxy resin, polycarbonate resin, polystyrene resin, phenol resin, melamine resin, epoxy resin and the like. Of these, polycarbonate resin, polyester resin, and acrylic resin are preferable.

Further, the protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the reaction at that time include a thermal polymerization reaction, a photopolymerization reaction, and a radiation polymerization reaction. Examples of the polymerizable functional group contained in the monomer having a polymerizable functional group include an acrylic group and a methacrylic group. As the monomer having a polymerizable functional group, a material having a charge transporting ability may be used.

The protective layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipper-imparting agent, and an abrasion resistance improver. Specifically, hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles. And so on.

The average film thickness of the protective layer is preferably 0.5 μm or more and 10 μm or less, and preferably 1 μm or more and 7 μm or less.

The protective layer can be formed by preparing a coating liquid for a protective layer containing each of the above-mentioned materials and solvents, forming this coating film, and drying and / or curing it. Examples of the solvent used for the coating liquid include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

Hereinafter, the present disclosure will be described in more detail with reference to Examples and Comparative Examples. The present disclosure is not limited to any of the examples below, as long as it does not go beyond its gist. In the description of the following examples, the term "part" is based on mass unless otherwise specified.

[Synthesis Example 1]
Under a nitrogen flow atmosphere, 5.46 parts of orthophthalonitrile and 45 parts of α-chloronaphthalene were put into a reaction vessel and then heated to a temperature of 30 ° C. to maintain this temperature. Next, 3.75 parts of gallium trichloride was charged at this temperature (30 ° C.). The water concentration of the mixed solution at the time of charging was 150 ppm. Then, the temperature was raised to 200 ° C. The reaction was then carried out at a temperature of 200 ° C. for 4.5 hours under a nitrogen flow atmosphere, then cooled and the product was filtered when the temperature reached 150 ° C. The obtained filtrate was dispersed and washed with N, N-dimethylformamide at a temperature of 140 ° C. for 2 hours, and then filtered. The obtained filtrate was washed with methanol and then dried to obtain a chlorogallium phthalocyanine pigment in a yield of 71%.

[Synthesis Example 2]
4.65 parts of the chlorogallium phthalocyanine pigment obtained in Synthesis Example 1 was dissolved in 139.5 parts of concentrated sulfuric acid at a temperature of 10 ° C., dropped into 620 parts of ice water under stirring, and reprecipitated, and then filtered. Was filtered under reduced pressure using. At this time, as a filter, No. 5C (manufactured by Advantech Co., Ltd.) was used. The obtained wet cake (filter) was dispersed and washed with 2% aqueous ammonia for 30 minutes, and then filtered using a filter press. Next, the obtained wet cake (filter) was dispersed and washed with ion-exchanged water, and then filtration using a filter press was repeated three times. Finally, freeze-drying was carried out to obtain a hydroxygallium phthalocyanine pigment having a solid content of 23% (hydrous hydroxygallium phthalocyanine pigment) in a yield of 97%.

[Synthesis Example 3]
Using a hyper dry dryer (trade name: HD-06R, manufactured by Nippon Biocon, frequency (oscillation frequency): 2455 MHz ± 15 MHz), 6.6 kg of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 2 was used as follows. It was dried.

Place the above hydroxygallium phthalocyanine pigment on a special circular plastic tray in a lump state (water-containing cake thickness 4 cm or less) as it is taken out from the filter press, so that far infrared rays are turned off and the temperature of the inner wall of the dryer is 50 ° C. I set it. Then, at the time of microwave irradiation, the vacuum pump and the leak valve were adjusted, and the degree of vacuum was adjusted to 4.0 to 10.0 kPa.

First, as the first step, the hydroxygallium phthalocyanine pigment was irradiated with 4.8 kW microwaves for 50 minutes, then the microwaves were once turned off and the leak valve was temporarily closed to create a high vacuum of 2 kPa or less. The solid content of the hydroxygallium phthalocyanine pigment at this time was 88%. As the second step, the leak valve was adjusted and the degree of vacuum (pressure in the dryer) was adjusted within the above set value (4.0 to 10.0 kPa). Then, a 1.2 kW microwave was irradiated to the hydroxygallium phthalocyanine pigment for 5 minutes, and the microwave was once turned off and the leak valve was once closed to create a high vacuum of 2 kPa or less. This second step was repeated once more (twice in total). The solid content of the hydroxygallium phthalocyanine pigment at this time was 98%. Further, as the third step, microwave irradiation was performed in the same manner as in the second step except that the microwave output in the second step was changed from 1.2 kW to 0.8 kW. This third step was repeated once more (twice in total). Further, as a fourth step, the leak valve was adjusted to restore the degree of vacuum (pressure in the dryer) to within the above set value (4.0 to 10.0 kPa). Then, 0.4 kW microwave was irradiated to the hydroxygallium phthalocyanine pigment for 3 minutes, and the microwave was once turned off and the leak valve was temporarily closed to create a high vacuum of 2 kPa or less. This fourth step was repeated 7 more times (8 times in total). As described above, 1.52 kg of hydroxygallium phthalocyanine pigment (crystal) having a water content of 1% or less was obtained in a total of 3 hours.

[Synthesis Example 4]
10 parts of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 2 and 200 parts of hydrochloric acid having a concentration of 35% by mass and a temperature of 23 ° C. were mixed and stirred with a magnetic stirrer for 90 minutes. The amount of hydrochloric acid mixed was 118 mol of hydrogen chloride with respect to 1 mol of hydroxygallium phthalocyanine. After stirring, the mixture was added dropwise to 1000 parts of ion-exchanged water cooled with ice water, and the mixture was stirred with a magnetic stirrer for 30 minutes. This was filtered under reduced pressure. At this time, as a filter, No. 5C (manufactured by Advantech Co., Ltd.) was used. Then, the dispersion washing was carried out four times with ion-exchanged water having a temperature of 23 ° C. In this way, 9 parts of chlorogallium phthalocyanine pigment was obtained.

[Synthesis Example 5]
In 100 g of α-chloronaphthalene, 5.0 g of o-phthalodinitrile and 2.0 g of titanium tetrachloride were heated and stirred at 200 ° C. for 3 hours, cooled to 50 ° C., and the precipitated crystals were filtered off to obtain dichlorotitanium phthalocyanine. I got the paste. Next, this was stirred and washed with 100 mL of N, N-dimethylformamide heated to 100 ° C., and then washed twice with 100 mL of methanol at 60 ° C. and filtered off repeatedly. Further, the obtained paste was stirred in 100 mL of deionized water at 80 ° C. for 1 hour, and filtered off to obtain 4.3 g of a blue titanyl phthalocyanine pigment.

Next, this pigment was dissolved in 30 mL of concentrated sulfuric acid, dropped in 300 mL of deionized water at 20 ° C. under stirring, reprecipitated, filtered and thoroughly washed with water to obtain an amorphous titanyl phthalocyanine pigment. 4.0 g of this amorphous titanyl phthalocyanine pigment was suspended and stirred in 100 mL of methanol at room temperature (22 ° C.) for 8 hours, filtered and dried under reduced pressure to obtain a low crystalline titanyl phthalocyanine pigment.

[Milling example 1]
0.5 parts of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3, 9.5 parts of N, N-dimethylformamide (product code: D0722, manufactured by Tokyo Chemical Industry), and 15 parts of glass beads having a diameter of 0.9 mm were added to room temperature (product code: D0722, manufactured by Tokyo Chemical Industry). It was milled with a ball mill for 100 hours at 23 ° C.). At this time, a standard bottle (product name: PS-6, manufactured by Kashiwayo Glass) was used as the container, and the container was rotated 60 times per minute. The liquid treated in this manner was filtered through a filter (product number: N-NO.125T, manufactured by NBC Meshtec, pore size: 133 μm) to remove glass beads. After adding 30 parts of N, N-dimethylformamide to this solution, the mixture was filtered, and the filtrate on the filter was thoroughly washed with tetrahydrofuran. Then, the washed sample was vacuum dried to obtain 0.48 parts of hydroxygallium phthalocyanine pigment. The obtained pigment has peaks at 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° of Bragg angle 2θ in the X-ray diffraction spectrum using CuKα ray.

[Milling example 2]
80 parts of hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3, 9 parts of N-methylformamide (product code: F0059, manufactured by Tokyo Chemical Industry), and 15 parts of glass beads having a diameter of 0.9 mm at a cooling water temperature of 18 ° C. Milling treatment was carried out using a sand mill (trade name: K-800, manufactured by Igarashi Kikai Seisakusho (currently IMEX), disc diameter 70 mm, number of discs 5). At this time, the disc was rotated 400 times per minute. After adding 30 parts of N-methylformamide to the liquid treated in this manner, the mixture was filtered, and the filtrate on the filter was thoroughly washed with tetrahydrofuran. Then, the washed sample was vacuum dried to obtain 0.45 parts of hydroxygallium phthalocyanine pigment. The obtained pigment has strong peaks at 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° of Bragg angle 2θ in the X-ray diffraction spectrum using CuKα ray. ¹ The content of N-methylformamide in the hydroxygallium phthalocyanine crystal particles estimated by H-NMR measurement was 0.9% by mass with respect to the content of hydroxygallium phthalocyanine.

[Milling example 3]
In Milling Example 2, the hydroxygallium phthalocyanine pigment of Milling Example 3 was obtained in the same manner as in Milling Example 2 except that the milling treatment time was changed from 80 hours to 100 hours. The obtained pigment has strong peaks at 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° of Bragg angle 2θ in the X-ray diffraction spectrum using CuKα ray. ¹ The content of N-methylformamide in the hydroxygallium phthalocyanine crystal particles estimated by H-NMR measurement was 1.4% by mass with respect to the content of hydroxygallium phthalocyanine.

[Milling example 4]
0.5 parts of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3, 9.5 parts of N-methylformamide (product code: F0059, manufactured by Tokyo Chemical Industry), and 15 parts of glass beads having a diameter of 0.9 mm were added to room temperature (23 ° C.). ) Under the milling treatment with a ball mill for 100 hours. At this time, a standard bottle (product name: PS-6, manufactured by Kashiwayo Glass) was used as the container, and the container was rotated 60 times per minute. The liquid treated in this manner was filtered through a filter (product number: N-NO.125T, pore diameter: 133 μm, manufactured by NBC Meshtec) to remove glass beads. After adding 30 parts of N-methylformamide to this solution, the mixture was filtered, and the filtrate on the filter was thoroughly washed with tetrahydrofuran. Then, the washed sample was vacuum dried to obtain 0.45 parts of hydroxygallium phthalocyanine pigment. The obtained pigment has strong peaks at 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° of Bragg angle 2θ in the X-ray diffraction spectrum using CuKα ray. ¹ The content of N-methylformamide in the hydroxygallium phthalocyanine crystal particles estimated by H-NMR measurement was 2.1% by mass with respect to the content of hydroxygallium phthalocyanine.

[Milling example 5]
In Milling Example 3, the hydroxygallium phthalocyanine pigment of Milling Example 5 was obtained in the same manner as in Milling Example 3 except that the milling treatment time was changed from 100 hours to 7 hours. The obtained pigment has strong peaks at 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° of Bragg angle 2θ in the X-ray diffraction spectrum using CuKα ray. ¹ The content of N-methylformamide in the hydroxygallium phthalocyanine crystal particles estimated by H-NMR measurement was 2.9% by mass with respect to the content of hydroxygallium phthalocyanine.

[Milling example 6]
In Milling Example 3, the hydroxygallium phthalocyanine pigment of Milling Example 6 was obtained in the same manner as in Milling Example 3 except that the milling treatment time was changed from 100 hours to 5 hours. The obtained pigment has strong peaks at 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° of Bragg angle 2θ in the X-ray diffraction spectrum using CuKα ray. ¹ The content of N-methylformamide in the hydroxygallium phthalocyanine crystal particles estimated by H-NMR measurement was 3.1% by mass with respect to the content of hydroxygallium phthalocyanine.

[Milling example 7]
1.0 part of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3, 9.0 parts of N-methylformamide (product code: F0059, manufactured by Tokyo Chemical Industry Co., Ltd.), and 15 parts of glass beads having a diameter of 0.9 mm were added to room temperature (23 ° C.). ) Under the milling treatment with a ball mill for 4 hours. At this time, a standard bottle (product name: PS-6, manufactured by Kashiwayo Glass) was used as the container, and the container was rotated 60 times per minute. The liquid treated in this manner was filtered through a filter (product number: N-NO.125T, pore diameter: 133 μm, manufactured by NBC Meshtec) to remove glass beads. After adding 30 parts of N-methylformamide to this solution, the mixture was filtered, and the filtrate on the filter was thoroughly washed with tetrahydrofuran. Then, the washed sample was vacuum dried to obtain 0.44 parts of hydroxygallium phthalocyanine pigment. The obtained pigment has strong peaks at 7.4 ° ± 0.3 ° and 28.2 ° ± 0.3 ° of Bragg angle 2θ in the X-ray diffraction spectrum using CuKα ray. ¹ The content of N-methylformamide in the hydroxygallium phthalocyanine crystal particles estimated by H-NMR measurement was 3.9% by mass with respect to the content of hydroxygallium phthalocyanine.

[Milling example 8]
0.5 parts of the titanyl phthalocyanine pigment obtained in Synthesis Example 5, 10 parts of tetrahydrofuran, and 15 parts of glass beads having a diameter of 0.9 mm were placed in a sand mill (trade name: K-800, Igarashi Machinery) at a cooling water temperature of 18 ° C. for 48 hours. Milling treatment was carried out using manufacturing (currently IMEX), a disc diameter of 70 mm, and 5 discs). At this time, the disc was rotated 500 times per minute. The liquid treated in this manner was filtered through a filter (product number: N-NO.125T, pore diameter: 133 μm, manufactured by NBC Meshtec) to remove glass beads. After adding 30 parts of tetrahydrofuran to this solution, the mixture was filtered, and the filtrate on the filter was thoroughly washed with methanol and water. Then, the washed sample was vacuum-dried to obtain 0.45 parts of the titanyl phthalocyanine pigment. The obtained pigment has a strong peak at 27.2 ° ± 0.3 ° of Bragg angle 2θ in the X-ray diffraction spectrum using CuKα ray.

[Milling example 9]
Milling 0.5 parts of the chlorogallium phthalocyanine pigment obtained in Synthesis Example 4 and 10 parts of N, N-dimethylformamide (product code: D0722, manufactured by Tokyo Chemical Industry Co., Ltd.) at room temperature (23 ° C.) for 4 hours with a magnetic stirrer. Processed. The chlorogallium phthalocyanine pigment is taken out from the liquid treated in this manner using tetrahydrofuran, filtered through a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec), and the filtrate on the filter is sufficiently filtered with tetrahydrofuran. Washed. Then, the washed sample was vacuum dried to obtain 0.46 parts of a chlorogallium phthalocyanine pigment. In the spectral absorption spectrum by the method described above, the obtained pigment has a spectrum having a first peak at 659 nm and a second peak at 791 nm, and the absorbance of the second peak is that of the absorbance of the first peak. It was 0.79 times.

[Milling example 10]
0.5 parts of the chlorogallium phthalocyanine pigment obtained in Synthesis Example 4, 10 parts of N, N-dimethylformamide (product code: D0722, manufactured by Tokyo Chemical Industry), and 15 parts of glass beads having a diameter of 0.9 mm were added to room temperature (23 ° C.). ) For 48 hours, milling treatment was performed using a paint shaker (manufactured by Toyo Seiki Seisakusho). At this time, a standard bottle (product name: PS-6, manufactured by Kashiwayo Glass) was used as the container. The liquid treated in this manner was filtered through a filter (product number: N-NO.125T, pore diameter: 133 μm, manufactured by NBC Meshtec) to remove glass beads. After adding 30 parts of N, N-dimethylformamide to this solution, the mixture was filtered, and the filtrate on the filter was thoroughly washed with tetrahydrofuran. Then, the washed sample was vacuum dried to obtain 0.47 parts of a chlorogallium phthalocyanine pigment. In the spectral absorption spectrum by the method described above, the obtained pigment has a spectrum having a first peak at 643 nm and a second peak at 789 nm, and the absorbance of the second peak is that of the absorbance of the first peak. It was 0.74 times. Further, in the X-ray diffraction spectrum using CuKα rays, it has peaks at 7.4 °, 16.6 °, 25.5 ° and 28.3 ° at Bragg angles of 2θ ± 0.2 °.

[Production Example 1 of Titanium Oxide Particles]
Anatase-type titanium oxide having an average primary particle size of 200 nm was used as a substrate, and a titanium niobium sulfuric acid solution containing 33.7 parts of titanium in terms of TiO ₂ and 2.9 parts of niobium in terms of Nb ₂ O ₅ was prepared. .. 100 parts of the substrate was dispersed in pure water to form a suspension of 1000 parts, which was heated to 60 ° C. The titaniumniobium sulfuric acid solution and 10 mol / L sodium hydroxide were added dropwise over 3 hours so that the pH of the suspension became 2-3. After dropping the whole amount, the pH was adjusted to near neutral, and a polyacrylamide-based flocculant was added to precipitate the solid content. The supernatant was removed, filtered and washed, and dried at 110 ° C. to obtain an intermediate containing 0.1 wt% of organic matter derived from the flocculant in terms of C. This intermediate was calcined in nitrogen at 750 ° C. for 1 hour and then calcined in air at 450 ° C. to prepare titanium oxide particles 1. The obtained particles had an average particle size (average primary particle size) of 220 nm in the particle size measurement method using the scanning electron microscope described above.

[Example 1]
<Cylindrical support>
An aluminum cylinder (JIS-A3003, aluminum alloy) having a length of 257 mm and a diameter of 24 mm manufactured by a manufacturing method including an extrusion step and a drawing step was used as a cylindrical support.

<Conductive layer>
Next, a phenol resin (monomer / oligomer of phenol resin) as a binder material (trade name: Pryofen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g / cm ³ ) Fifty parts were dissolved in 35 parts of 1-methoxy-2-propanol as a solvent to obtain a solution.
75 parts of titanium oxide particles 1 obtained in Production Example 1 of titanium oxide particles were added to this solution, and this solution was placed in a vertical sand mill using 120 parts of glass beads having an average particle size of 1.0 mm as a dispersion medium to prepare a dispersion liquid. A dispersion treatment was carried out for 4 hours under the conditions of a temperature of 23 ± 3 ° C. and a rotation speed of 1500 rpm (peripheral speed 5.5 m / s) to obtain a dispersion solution. Glass beads were removed from this dispersion with a mesh. In the dispersion liquid after removing the glass beads, 0.01 part of silicone oil (trade name: SH28 PAINT ADDITIVE, manufactured by Dow Toray Co., Ltd.) as a leveling agent, and silicone resin particles (trade name) as a surface roughness imparting material. : KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average particle size: 2 μm, density: 1.3 g / cm ³ ) Add 8 parts, stir, and add using PTFE filter paper (trade name: PF060, manufactured by Advantech Toyo). A coating liquid for a conductive layer was prepared by pressure filtration. The coating liquid for the conductive layer prepared in this manner is immersed and coated on the above-mentioned cylindrical support under a normal temperature and humidity (23 ° C./50% RH) environment to form a coating film, and the coating film is formed at 170 ° C. A conductive layer having a film thickness of 25 μm was formed by heating and curing the mixture for 30 minutes.

<Underlay layer>
Next, 25 parts of N-methoxymethylated nylon 6 (trade name: Tredin EF-30T, manufactured by Nagase ChemteX) was dissolved in 480 parts of a methanol / n-butanol = 2/1 mixed solution (heat dissolution at 65 ° C.). The solution was cooled. Then, the solution was filtered through a membrane filter (trade name: FP-022, pore size: 0.22 μm, manufactured by Sumitomo Electric Industries, Ltd.) to prepare a coating liquid for the undercoat layer. The coating liquid for the undercoat layer prepared in this manner is immersed and coated on the above-mentioned conductive layer to form a coating film, and the coating film is heated and dried at a temperature of 100 ° C. for 10 minutes to achieve a film thickness of 0.5 μm. An undercoat layer was formed.

<Charge generation layer>
Next, 12 parts of the titanyl phthalocyanine pigment obtained in Milling Example 8, 10 parts of polyvinyl butyral (trade name: Eslek BX-1, manufactured by Sekisui Chemical Co., Ltd.), 139 parts of cyclohexanone, and 354 parts of glass beads having a diameter of 0.9 mm were cooled. Dispersion treatment was performed at a water temperature of 18 ° C. for 4 hours using a sand mill (trade name: K-800, manufactured by Igarashi Kikai Seisakusho (currently IMEX), disc diameter 70 mm, number of discs 5). At this time, the disc was rotated 1,800 times per minute. A coating solution for a charge generation layer was prepared by adding 326 parts of cyclohexanone and 465 parts of ethyl acetate to this dispersion.

The coating liquid for the charge generation layer was immersed and coated on the above-mentioned undercoat layer, and gradually changed as shown in Table 1 according to the distance of the liquid surface from the upper end of the support. The coating film thus obtained was heated and dried at 100 ° C. for 10 minutes to form a charge generation layer having an average film thickness shown in Table 2. The average film thickness of each region of the charge generation layer was determined by the above method using a spectrophotometer (trade name: X-Rite 504/508, manufactured by X-Rite).

式（Ｂ２）で示されるトリアリールアミン化合物１０部、

ポリカーボネート（商品名：ユーピロンＺ−２００、三菱エンジニアリングプラスチックス製）１００部をモノクロロベンゼン６３０部に溶解させることによって、電荷輸送層用塗布液を調製した。このようにして調製した電荷輸送層用塗布液を上述の電荷発生層上に浸漬塗布して塗膜を形成し、塗膜を温度１２０℃で１時間加熱乾燥することにより、表２に示す平均膜厚を持つ電荷輸送層を形成した。電荷輸送層の各領域の平均膜厚は、レーザー干渉膜厚計（商品名：ＳＩ−Ｔ８０、株式会社キーエンス社製）を用いて上記の方法で求めた。 <Charge transport layer>
Next, as a charge transporting substance, 70 parts of the triarylamine compound represented by the formula (B1),

10 parts of the triarylamine compound represented by the formula (B2),

A coating liquid for a charge transport layer was prepared by dissolving 100 parts of polycarbonate (trade name: Iupilon Z-200, manufactured by Mitsubishi Engineering Plastics) in 630 parts of monochlorobenzene. The coating liquid for the charge transport layer thus prepared was immersed and coated on the above-mentioned charge generation layer to form a coating film, and the coating film was heated and dried at a temperature of 120 ° C. for 1 hour to obtain an average shown in Table 2. A charge transport layer having a film thickness was formed. The average film thickness of each region of the charge transport layer was determined by the above method using a laser interference film thickness meter (trade name: SI-T80, manufactured by KEYENCE CORPORATION).

As described above, a cylindrical (drum-shaped) electrophotographic photosensitive member was manufactured. From the average film thickness of the obtained charge generation layer and charge transport layer, the difference between DtX5 and DtZ1 (DtX5-DtZ1), the difference between DgX5 and DgZ1 (DgX5-DgZ1), and the ratio of DtZ1 to DtX5 (DtZ1 / DtX5). ) And the ratio of DgZ1 to DgX5 (DgZ1 / DgX5) are shown in Table 3 for the upper and lower sides of the electrophotographic photosensitive member, respectively.

[Evaluation]
The electrophotographic photosensitive member produced above was evaluated as follows. The results are shown in Tables 2-4.

<Evaluation device>
A laser beam printer (trade name: Color Laser Jet CP3525dn) manufactured by Hewlett-Packard Co., Ltd. was prepared as an electrophotographic apparatus for evaluation, and was modified and used as follows.
Regarding the modification of the optical system, in addition to the default machine that does not change anything, the scanning characteristic coefficient B in the equation (E8) and the geometric feature θ _{max of the} laser scanning device are (B = 0.55, θ _max =). 55 °) was prepared.
In addition, the pre-exposure conditions, charging conditions, and laser exposure amount are made variable. Further, the manufactured electrophotographic photosensitive member was attached to the process cartridge for cyan color, and attached to the station of the process cartridge for cyan color. Process cartridges for other colors (magenta, yellow, black) can now be operated without being attached to the laser beam printer body.
When outputting the image, only the process cartridge for cyan color was attached to the main body of the laser beam printer, and a single color image using only cyan toner was output.

<Evaluation of solid image density unevenness>
The electrophotographic photosensitive members manufactured in Examples and Comparative Examples were mounted on the above laser beam printer under a normal temperature and humidity environment (temperature 23 ° C., relative humidity 50%), and at the center position of the image forming region of the electrophotographic photosensitive members. The pre-exposure amount, the charger and the exposure amount were set so that the initial dark part potential was −600 V and the bright part potential was −150 V. For the measurement of the surface potential of the electrophotographic photosensitive member at the time of setting the potential, a potential probe (trade name: model6000B-8, manufactured by Trek Japan) is attached to the developing position of the process cartridge, and the electrophotographic photosensitive member is used. The potential at the center of the image forming region was measured using a surface electrometer (trade name: model344, manufactured by Trek Japan).

A solid image was output under the above conditions, and the solid image was visually evaluated and ranked according to the following criteria, and is shown as "density uniformity" in Table 4. Ranks A to C are within an acceptable range as an effect of the present disclosure, since improvement in concentration uniformity can be confirmed as compared with the prior art. On the other hand, since rank D is the same result as the prior art, the effect of the present disclosure is unacceptable.
A: No uneven density is observed in the solid image.
B: Almost no uneven density is observed in the solid image.
C: Since the density near the edge of the solid image is dark or light, slight density unevenness is observed.
D: Since the density near the edge of the solid image is extremely low, uneven density is clearly observed.

<End charging streaks>
The electrophotographic photosensitive members produced in Examples and Comparative Examples were attached to the above laser beam printer in a normal temperature and humidity environment (temperature 23 ° C., relative humidity 50%), and evaluated as follows. The charging potential was set to −600 V, and the bright area potential after exposure was adjusted to be −150 V. Further, the development potential was adjusted to be −400 V. With this setting, each pixel of 600 dpi was lit with a light emission time of 40% on A4 size plain paper to output an image.

Next, the obtained evaluation images were ranked as follows, and are shown in Table 4 as "upper end charged horizontal streaks" and "lower end charged horizontal streaks". Ranks A to C are within an acceptable range as an effect of the present disclosure, as it can be confirmed that the generation of edge charging streaks is suppressed as compared with the prior art. On the other hand, since rank D is the same result as the prior art, the effect of the present disclosure is unacceptable.
A: No charged streaks are observed.
B: The charged streaks can be partially discriminated.
C: Charge streaks can be confirmed over the entire circumference.
D: Clear charging streaks can be confirmed over the entire circumference.

[Example 2]
In the formation of the charge transport layer of Example 1, when the coating film is formed by immersion coating, the speed of pulling up the cylindrical support immersed in the coating liquid from the coating liquid is reduced by slowing the speeds of the upper end and the lower end, respectively. , The film thickness at both ends was reduced. Then, the obtained coating film was heated and dried at 130 ° C. for 30 minutes to form a charge transport layer having an average film thickness shown in Table 2 to produce an electrophotographic photosensitive member. From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3.

[Examples 3 to 8]
In the formation of the charge transport layer of Example 1, when the coating film is formed by immersion coating, the speed of pulling up the cylindrical support immersed in the coating liquid from the coating liquid is reduced by slowing the speeds of the upper end and the lower end, respectively. , The film thickness at both ends was reduced. Then, the obtained coating film was heated and dried at 130 ° C. for 30 minutes to form a charge transport layer having an average film thickness shown in Table 2 to produce an electrophotographic photosensitive member. From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3.

[Example 9]
Using the electrophotographic photosensitive member manufactured in Example 7, a laser beam printer (trade name: Color LaserJet CP4525) manufactured by Hewlett-Packard Co., Ltd. was prepared as an electrophotographic apparatus for evaluation, and the amount of light on the drum surface was determined in Example 1. It was modified and used so that it had the same distribution as.

[Example 10]
Using the electrophotographic photosensitive member manufactured in Example 7, a laser beam printer (trade name: Color LaserJet M609) manufactured by Hewlett-Packard Co., Ltd. was prepared as an electrophotographic apparatus for evaluation, and the amount of light on the drum surface was determined in Example 1. It was modified and used so that it had the same distribution as.

[Example 11]
Using the electrophotographic photosensitive member manufactured in Example 7, a laser beam printer (trade name: Color LaserJet M552) manufactured by Hewlett-Packard Co., Ltd. was prepared as an electrophotographic apparatus for evaluation, and the amount of light on the drum surface was determined in Example 1. It was modified and used so that it had the same distribution as.

[Example 12]
In Example 1, the preparation of the coating liquid for the charge generating layer was changed as follows, and the immersion coating of the charge generating layer was carried out in the same manner as the above method so as to have the average film thickness of the charge generating layer shown in Table 2. An electrophotographic photosensitive member of Example 20 was produced in the same manner as in Example 1 except that it was changed.

Cooling water temperature of 30 parts of chlorogallium phthalocyanine pigment obtained in Milling Example 9, 10 parts of polyvinyl butyral (trade name: Eslek BX-1, manufactured by Sekisui Chemical Co., Ltd.), 253 parts of cyclohexanone, 643 parts of glass beads having a diameter of 0.9 mm. Dispersion treatment was performed at 18 ° C. for 4 hours using a sand mill (trade name: K-800, manufactured by Igarashi Kikai Seisakusho (currently IMEX), disc diameter 70 mm, number of discs 5). At this time, the disc was rotated 1,800 times per minute. A coating solution for a charge generation layer was prepared by adding 592 parts of cyclohexanone and 845 parts of ethyl acetate to this dispersion.

From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3.

[Example 13]
In the formation of the charge generation layer of Example 1, the hydroxygallium phthalocyanine pigment obtained in Milling Example 1 was changed to the hydroxygallium phthalocyanine pigment obtained in Milling Example 3, and immersion coating was carried out in the same manner as in Example 1. An electrophotographic photosensitive member was manufactured by changing the average thickness of the charge generation layer shown in 2. From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3.

[Example 14]
In the formation of the charge generation layer of Example 1, 20 parts of the hydroxygallium phthalocyanine pigment obtained in Milling Example 1, 10 parts of polyvinyl butyral (trade name: Eslek BX-1, manufactured by Sekisui Chemical Co., Ltd.), 190 parts of cyclohexanone, diameter 0. 482 parts of 4.9 mm glass beads are dispersed for 4 hours at a cooling water temperature of 18 ° C. using a sand mill (trade name: K-800, manufactured by Igarashi Kikai Seisakusho (currently IMEX), disc diameter 70 mm, number of discs 5). did. At this time, the disc was rotated 1,800 times per minute. A coating solution for a charge generation layer was prepared by adding 444 parts of cyclohexanone and 634 parts of ethyl acetate to this dispersion. An electrophotographic photosensitive member was produced by forming a charge transport layer having an average film thickness shown in Table 2 in the same manner as in Example 1 except that the coating liquid for the charge generation layer was used. From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3.

[Example 15]
In the formation of the charge generation layer of Example 1, 30 parts of the chlorogallium phthalocyanine pigment obtained in Milling Example 10, 10 parts of polyvinyl butyral (trade name: Eslek BX-1, manufactured by Sekisui Chemical Co., Ltd.), 253 parts of cyclohexanone, diameter 0. Disperse 643 parts of .9 mm glass beads at a cooling water temperature of 18 ° C. for 4 hours using a sand mill (trade name: K-800, manufactured by Igarashi Kikai Seisakusho (currently IMEX), disc diameter 70 mm, number of discs 5). did. At this time, the disc was rotated 1,800 times per minute. A coating solution for a charge generation layer was prepared by adding 592 parts of cyclohexanone and 845 parts of ethyl acetate to this dispersion. An electrophotographic photosensitive member was produced by forming a charge transport layer having an average film thickness shown in Table 2 in the same manner as in Example 1 except that the coating liquid for the charge generation layer was used. From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3.

[Example 16]
In the formation of the charge generation layer of Example 1, 20 parts of the disuazo compound represented by the formula (C1), 8 parts of polyvinyl butyral (trade name: Eslek BX-1, manufactured by Sekisui Chemical Co., Ltd.), 177 parts of cyclohexanone, 0.9 mm in diameter. 482 parts of the glass beads of No. 1 were dispersed in a sand mill (trade name: K-800, manufactured by Igarashi Kikai Seisakusho (currently IMEX), disk diameter 70 mm, number of disks 5) at a cooling water temperature of 18 ° C. for 4 hours. At this time, the disc was rotated 1,800 times per minute. A coating solution for a charge generation layer was prepared by adding 414 parts of cyclohexanone and 592 parts of ethyl acetate to this dispersion. An electrophotographic photosensitive member was produced by forming a charge transport layer having an average film thickness shown in Table 2 in the same manner as in Example 1 except that the coating liquid for the charge generation layer was used. From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3.

[Reference example 1]
In the formation of the charge transport layer of Example 1, only the division of the region for evaluating the film thickness of the charge transport layer is changed, and the center position and the center position of the electrophotographic photosensitive member to one end in the axial direction of the electrophotographic photosensitive member are changed. The region between the 85% positions located at 85% of the length was designated as X, and the region from the 85% position to the end of the electrophotographic photosensitive member was designated as Z. That is, in Table 2, the boundary position between X5 and Z1 in Reference Example 1 is 90% from the central position in the axial direction of the electrophotographic photosensitive member to one end in the charge generation layer, whereas it is 90% in the charge transport layer. The position is 85% from the central position in the axial direction of the electrophotographic photosensitive member to one end. When the charge transport layer is immersed and coated to form a coating film, the speed at which the cylindrical support immersed in the coating liquid is pulled up from the coating liquid is changed at the upper end and the lower end, respectively, and the charge transport layer is on both ends rather than the center side. The film thickness of was made thinner. Then, the obtained coating film was heated and dried at 130 ° C. for 30 minutes to form a charge transport layer having an average film thickness shown in Table 2 to produce an electrophotographic photosensitive member. From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3. As the electrophotographic apparatus for evaluation, the same apparatus as in Example 1 was used.

[Reference example 2]
The electrophotographic photosensitive member manufactured in Reference Example 1 was used, and the same apparatus as in Example 9 was used as the electrophotographic apparatus for evaluation.

[Reference example 3]
The electrophotographic photosensitive member manufactured in Reference Example 1 was used, and the same apparatus as in Example 10 was used as the electrophotographic apparatus for evaluation.

[Reference example 4]
The electrophotographic photosensitive member manufactured in Reference Example 1 was used, and the same apparatus as in Example 11 was used as the electrophotographic apparatus for evaluation.

[Reference example 5]
In the formation of the charge transport layer of Example 1, only the division of the region for evaluating the film thickness of the charge transport layer is changed, and the center position and the center position of the electrophotographic photosensitive member to one end in the axial direction of the electrophotographic photosensitive member are changed. The region between the 95% positions located at 95% of the length was designated as X, and the region from the 95% position to the one end of the electrophotographic photosensitive member was designated as Z. That is, in Table 2, the boundary position between X5 and Z1 in Reference Example 5 is 90% from the central position in the axial direction of the electrophotographic photosensitive member to one end in the charge generation layer, whereas it is 90% in the charge transport layer. It is a 95% position from the central position in the axial direction of the electrophotographic photosensitive member to one end. When the charge transport layer is immersed and coated to form a coating film, the speed at which the cylindrical support immersed in the coating liquid is pulled up from the coating liquid is changed at the upper end and the lower end, respectively, to increase the film thickness in the Z region rather than the X5 region. I made it thinner. Then, the obtained coating film was heated and dried at 130 ° C. for 30 minutes to form a charge transport layer having an average film thickness shown in Table 2 to produce an electrophotographic photosensitive member. From the average film thicknesses of the obtained charge generation layer and charge transport layer, DtX5-DtZ1 and DgX5-DgZ1, and DtZ1 / DtX5 and DgZ1 / DgX5 are obtained for the upper side and the lower side of the electrophotographic photosensitive member, respectively. Shown in 3. As the electrophotographic apparatus for evaluation, the same apparatus as in Example 1 was used.

[Reference example 6]
The electrophotographic photosensitive member manufactured in Reference Example 5 was used, and the same apparatus as in Example 9 was used as the electrophotographic apparatus for evaluation.

[Reference Example 7]
The electrophotographic photosensitive member manufactured in Reference Example 5 was used, and the same apparatus as in Example 10 was used as the electrophotographic apparatus for evaluation.

[Reference Example 8]
The electrophotographic photosensitive member manufactured in Reference Example 5 was used, and the same apparatus as in Example 11 was used as the electrophotographic apparatus for evaluation.

[Comparative Example 1]
In the formation of the charge transport layer of Example 1, when the coating film is formed by immersion coating, the speed at which the cylindrical support immersed in the coating liquid is pulled up from the coating liquid is not adjusted, and a substantially uniform film thickness distribution is obtained. It was formed as follows. Then, the obtained coating film was heated and dried at 130 ° C. for 30 minutes to form a charge transport layer having an average film thickness shown in Table 2 to produce an electrophotographic photosensitive member.

<Evaluation of electrophotographic photosensitive members of Examples 2 to 16, Reference Examples 1 to 8, and Comparative Example 1>
Density unevenness and density unevenness of solid images output using the electrophotographic photosensitive members manufactured in Examples 2 to 16, Reference Examples 1 to 8, and Comparative Example 1 in the same manner as the electrophotographic photosensitive member manufactured in Example 1. The charging streaks at the edges of the evaluation image were evaluated. The results are shown in Table 4.

As in Reference Examples 1 to 4, when the X region of the charge transport layer is the region between the central position and the 85% position located at 85% of the length from the central position to one end of the electrophotographic photosensitive member, the image Since the film thickness of the charge transport layer is reduced in the formation region, it is considered that the concentration uniformity at the end portion is reduced as shown in Table 4. On the other hand, as in Examples 1 to 16 and Reference Examples 5 to 8, the X region of the charge transport layer is located at the center position and 90% position located at 90% of the length from the center position to one end of the electrophotographic photosensitive member or When the region is between the 95% positions located at 95%, it is considered that the density uniformity is maintained because the film thickness of the charge transport layer is constant in the image forming region.

Further, as in Reference Examples 5 to 8, when the X region of the charge transport layer is set between the central position and the 95% position located at 95% of the length from the central position to one end of the electrophotographic photosensitive member. , The Z region of the charge transport layer is 5% of the end side, and even if the film thickness of the charge transport layer in the Z region is thinned, the change in capacitance is small and not sufficient, so that horizontal streaks of charge occur. It is thought that it was. On the other hand, as in Examples 1 to 16 and Reference Examples 1 to 4, the X region of the charge transport layer is located at the center position and 90% position located at 90% of the length from the center position to one end of the electrophotographic photosensitive member or In the case of the region between the 85% positions located at 85%, the capacitance was sufficiently increased by reducing the film thickness of the charge transport layer in the Z region, so that the charge lateral streaks did not occur or occurred. Even if it is, it is considered that it occurred partially.

1 Electrophotographic photosensitive member 2 Axis 3 Charging means 4 Exposure light 5 Developing means 6 Transfer means 7 Transfer material 8 Fixing means 9 Cleaning means 10 Pre-exposure light 11 Process cartridge 12 Guide means 20 Charge transport layer 21 Charge generation layer 22 Support 201 Image signal generation unit 202 Control unit 203 Laser drive unit 204 Laser scanning device 205 Electrophotograph photoconductor 206 Fixing means 208 Laser light source 209 Polygon mirror 209a Deflection surface 210 Imaging lens 211 Scanned surface A ₀ angular velocity on the surface of the photoconductor

Claims (7)

An electrophotographic photosensitive member having a cylindrical support, a charge generation layer, and a charge transport layer in this order.
The region between the axially central position of the electrophotographic photosensitive member and the 90% position located at 90% of the length from the central position to one end of the electrophotographic photosensitive member is defined as a region X, and the region X is defined from the 90% position. When the region between the one end of the electrophotographic photosensitive member is defined as the region Z,
The region obtained by dividing the region X into five equal parts is designated as X1, X2, X3, X4, and X5 in order from the central position.
When the regions obtained by dividing the region Z into three equal parts are designated as Z1, Z2, and Z3 in the order closer to the central position.
The average film thickness of the charge generation layer in each region of X1, X2, X3, X4, X5, Z1, Z2, and Z3 is determined by DgX1, DgX2, DgX3, DgX4, DgX5, DgZ1, DgZ2, and DgZ3. Represent,
The average film thickness of the charge transport layer in each region of X1, X2, X3, X4, X5, Z1, Z2, and Z3 is represented by DtX1, DtX2, DtX3, DtX4, DtX5, DtZ1, DtZ2, and DtZ3. if you did this,
An electrophotographic photosensitive member satisfying DgX1 <DgX2 <DgX3 <DgX4 <DgX5 and DtX5> DtZ1. The electrophotographic photosensitive member according to claim 1, wherein the DgX5 and the DgZ1 satisfy DgX5 <DgZ1. The electrophotographic photosensitive member according to claim 1 or 2, wherein the DgX5 and the DgZ1 satisfy DgX5 * 1.2 <DgZ1. The electrophotographic photosensitive member according to any one of claims 1 to 3, wherein the DtX5, the DtZ1, the DtZ2, and the DtZ3 satisfy DtX5 * 0.9> DtZ1 ≧ DtZ2 ≧ DtZ3. The electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the standard deviation of the DtX1, the DtX2, the DtX3, the DtX4, and the DtX5 is 0.1 or less. The electrophotographic apparatus main body integrally supports the electrophotographic photosensitive member according to any one of claims 1 to 5 and at least one means selected from the group consisting of charging means, developing means, and cleaning means. A process cartridge that can be attached and detached. An electrophotographic apparatus having the electrophotographic photosensitive member according to any one of claims 1 to 5, and a charging means, an exposure means, a developing means, and a transfer means.

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