Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus

Abstract

The present invention relates to electrophotographic photosensitive members, process cartridges, and electrophotographic apparatuses. Provided is an electrophotographic photosensitive member including a support, a charge generating layer on the support, and a charge transport layer on the charge generating layer and satisfying a regulation on an EV curve based on a measurement method of NESA-EV curve. The electrophotographic photosensitive member can exhibit high character quality in low line screen halftone and digital gradation while maintaining analog gradation in high speed processing.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrophotographic photosensitive member and a process cartridge and an electrophotographic apparatus using the same. BACKGROUND

[0002] An electrophotographic process related to an electrophotographic photosensitive member (hereinafter, also simply referred to as "photosensitive member") mainly includes four processes of charging, exposure, development, and transfer, and a process of cleaning and pre-exposure is added as necessary. Among them, the exposure process is a process of controlling the charge distribution of the photosensitive member and setting the surface of the photosensitive member to have a desired potential distribution, and is a process that is the core of forming an electrostatic latent image.

[0003] As a method of controlling the image density of an electrophotographic apparatus in the exposure process, there are two methods of an analog gradation method and a digital gradation method. The analog gradation method is a method of expressing the density gradation from a toner non-development part (so-called solid white) to a toner maximum development part (so-called solid black). In the analog gradation method, the exposure amount is adjusted. Thereby, the average potential of the surface of the photosensitive member is a multilevel value, and the toner development amount on the photosensitive member in the development process is controlled by adjustment. Meanwhile, in the digital gradation method, the density gradation is expressed by controlling the area rate of a solid black single dot. Therefore, in the digital gradation method, the single dot area irradiated with light is always solid black, and the toner development amount in the light irradiation part is always set to be the maximum by fixing the light amount at the time of emission to be the maximum and setting the photosensitive member surface potential of the light irradiation part to be the minimum.

[0004] Since the semiconductor laser used for the electrophotographic apparatus in recent years has a small spot diameter, the digital gradation method is mainstream. Meanwhile, the semiconductor laser generally has a clock-shaped spot diameter-light amount distribution. In addition, the 1 / e 2 diameter of the semiconductor laser is usually several tens of μm to 100 μm, and this is almost the same as the single dot length of 84 μm, 42 μm, and 21 μm in an image in which the resolution in the usual electrophotographic apparatus is 300 dpi, 600 dpi, and 1,200 dpi, respectively. Therefore, even if irradiation is performed with the maximum light amount, a part irradiated with a low light amount is formed in the single dot outside the 1 / e 2 diameter. Thereby, even when the digital gradation method is employed, both the digital gradation and the analog gradation are actually mixed, and the ratio of the two gradations depends on the number of lines (line number) at the time of image formation. The smaller the number of lines, the lower the image frequency and the relatively smaller the spot diameter. Therefore, the gradation becomes closer to the digital gradation. Meanwhile, the larger the number of lines, the higher the image frequency and the relatively larger the spot diameter. Therefore, the gradation becomes closer to the analog gradation.

[0005] An electrophotographic photosensitive member for an electrophotographic apparatus is generally a member in which various layers such as a photosensitive layer are formed on a support. Further, in recent years, from the viewpoint of low cost and high productivity, an organic photosensitive member in which the main component of the layer formed on the support is a resin is popular as an electrophotographic photosensitive member. Among such organic photosensitive members, due to the advantages of high sensitivity and versatility of material design, an organic photosensitive member in which the photosensitive layer is a laminated photosensitive layer is mainstream. A laminated organic photosensitive member is formed by stacking a charge generating layer containing a charge generating substance such as a photoconductive dye or a photoconductive pigment and a charge transport layer containing a charge transport substance such as a photoconductive polymer or a photoconductive small molecule with each other.

[0006] The charge transport layer of the laminated organic photosensitive member has a resin as the main component. However, since the resistance of the resin itself is generally high, the charge transport layer tends to trap the charges generated by exposure. Further, due to the potential barrier caused by the energy level difference between the two layers, the generated charges tend to be trapped at the interface between the charge transport layer and the charge generating layer. Therefore, the laminated organic photosensitive member generally has the following problem: even if the laminated organic photosensitive member is irradiated with light strong enough, the residual surface potential (hereinafter, referred to as "residual potential") is still high. This problem is confirmed in a graph (hereinafter, referred to as "EV curve") representing the relationship between the irradiation exposure amount I exp [μJ / cm 2 ] and the absolute value V exp [V] of the surface potential at the time of exposure. Further, the laminated organic photosensitive member has the following problem: the linearity of the EV curve tends to deteriorate around the exposure amount I 1 / 2 [μJ / cm 2 ] at which the charging potential is halved, also due to the aforementioned trapping.

[0007] As the residual potential becomes lower and closer to 0 [V], the concentration of the solid black single point in the digital gray scale becomes higher and more stable. At the same time, as the linearity of the EV curve becomes higher, the linearity of the relationship between the irradiation exposure amount and the surface average potential, that is, the relationship between the toner developing amount and the exposure amount becomes closer to a linear shape, and the analog gray scale is improved.

[0008] Therefore, it can be said that the aforementioned problems of the laminated organic photosensitive member, that is, the high residual potential and the poor linearity of the EV curve, are factors that impair the digital gray scale property and the analog gray scale property, respectively.

[0009] Furthermore, in recent years, pigment-dispersed charge-generating layers have been used to improve the sensitivity of organic photosensitive components. In pigment-dispersed charge-generating layers, the interface between the resin and the pigment dispersed in the resin further traps charges. Therefore, the aforementioned problems of laminated organic photosensitive components are particularly significant. Consequently, it is difficult to simultaneously satisfy low residual potential characteristics, linear EV curves, and high sensitivity characteristics in laminated organic photosensitive components.

[0010] As described above, to obtain good grayscale characteristics and character quality in the aforementioned electrophotographic devices that mix digital and analog grayscale, it is necessary to set the exposure amount that can achieve a good balance between digital and analog grayscale. In this case, setting such exposure amount is difficult unless the aforementioned three characteristics (sensitivity, residual potential, and linearity) are satisfied on the EV curve of the aforementioned stacked organic photosensitive element. In particular, when using space-saving optical systems and low-cost laser chips to meet the miniaturization and cost reduction requirements of electrophotographic devices, the exposure spot becomes larger and the analog grayscale becomes stronger. In such cases, it is difficult to improve character quality and digital grayscale at low line count halftones while maintaining analog grayscale, and this problem needs to be solved by improving the stacked organic photosensitive element.

[0011] Japanese Patent Application Publication No. 2014-197237 discloses a photosensitive component with high sensitivity and less susceptibility to humidity changes by forming a charge-generating layer with a film thickness of 400 nm using titanium dioxide phthalocyanine. Japanese Patent Application Publication No. 2014-197237 also discloses a photosensitive component with a wavelength of 780 nm and an intensity of 0.15 mW / cm². 2 When a photosensitive element is irradiated with light and charged to a potential of 700V, the photosensitive element has a small half-value exposure and the exposure potential changes little with humidity.

[0012] Japanese Patent Application Publication No. 2007-206349 discloses an image forming method and an image forming apparatus that determine the charging potential and image exposure based on the film thickness of the photosensitive layer, the linearity near the half-value exposure on the EV curve, and the surface potential value at an exposure of approximately twice the half-value exposure. The surface potential at an exposure of approximately twice the half-value exposure is close to the residual potential. Therefore, it can be said that the method described in Japanese Patent Application Publication No. 2007-206349 is a method for determining the appropriate image exposure by using equation (1) from the linearity of the EV curve and the residual potential. This technology enables photosensitive components that maintain high resolution and high-definition reproducibility from the start of use, even when the film thickness of the photosensitive layer is increased to extend its lifespan.

[0013] Japanese Patent Application Laid-Open No. 2003-195577 describes a photosensitive member with high linearity in the vicinity of a half-value exposure amount on an EV curve when the absolute value of a charging potential is 600 V. This technology enables each point of a digital latent image to be developed faithfully and enables high-quality images with excellent resolution and gradation characteristics to be output at high speed.

[0014] Japanese Patent Application Laid-Open No. 2002-072522 describes a photosensitive member in which a half-value exposure amount E 1 / 2 is divided by an exposure amount E 50 required to set a surface potential to -50 V is 0.25 or more. The lower the residual potential, the smaller E 50 becomes. In addition, the higher the linearity, the larger E 1 / 2 becomes. Therefore, this means that the residual potential is low and the linearity is high on the EV curve. As a result, excellent surface potential decay characteristics are obtained and the gradation characteristics of an image are improved.

[0015] Japanese Patent Application Laid-Open No. 2001-183852 describes a photosensitive member having high linearity in a range from a half-value exposure amount to 1 / 5 exposure amount on an EV curve. As a result, an electrostatic charge image of a single point pixel can be reproduced stably.

[0016] According to the research of the present inventors, none of the electrophotographic photosensitive members and image forming methods described in the aforementioned patent documents are optimized in terms of satisfying the three characteristics of sensitivity, residual potential, and linearity on an EV curve. In recent years, due to the demand for miniaturization and low cost of electrophotographic equipment, it is not possible to reduce the spot diameter of a laser. The problem of how to improve the character quality under low-line halftone and the digital gradation characteristics while maintaining analog gradation characteristics in high-speed processing to achieve high productivity in such cases has not been solved.

[0017] Therefore, an object of the present application is to provide an electrophotographic photosensitive member that exhibits high character quality under low-line halftone and digital gradation characteristics while maintaining analog gradation characteristics in high-speed processing. In addition, another object of the present application is to provide a process cartridge and an electrophotographic apparatus that use the electrophotographic photosensitive member. SUMMARY

[0018] The aforementioned objects are achieved by the present application described below. Specifically, the electrophotographic photosensitive member according to the present application is an electrophotographic photosensitive member including a support, a charge generation layer on the support, and a charge transport layer on the charge generation layer, in which the electrophotographic photosensitive member is an organic photosensitive member, and satisfies I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.370, and LR i ≤ 780 V-cm 2 / μJ, where a charging potential is V.d When it is 500V, it is obtained at a temperature of 23.5°C and a relative humidity of 50%RH according to the following <Measurement method of NESA-EV curve>, and the horizontal axis represents the irradiation exposure amount I exp and the vertical axis represents the absolute value V of the surface potential after exposure exp of I exp -V exp In the figure, V exp When it is 250V, the light quantity is represented by I 1 / 2 [μJ / cm 2 , in the figure, I exp =0.000~3.414·I 1 / 2 [μJ / cm 2 , the product S = I exp ·V exp of I within the range of exp ·V exp [V·μJ / cm 2 is represented by S max , in the figure, I exp =0.000~0.100·I 1 / 2 [μJ / cm 2 , the intersection point of the approximate straight line within the range of exp =(5·I 1 / 2 -0.100)~5·I 1 / 2 [μJ / cm 2 is represented by Q, the light quantity value at point Q is represented by I i [μJ / cm 2 [[ID=5,1]]], the potential value at point Q is represented by V i [V], and the product of I i and V i is represented by S i =I i ·V i [V·μJ / cm 2 , the ratio of S i to S max is represented by AR = S i / S max , and the value obtained by dividing V i by I i is represented by LR i =V i / I i [V·cm 2 / μJ],

[0019] In addition, in the electrophotographic photosensitive member according to the present invention, the above I 1 / 2 , AR = S i / S​​max and LR i = V i / I i satisfies I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.500 and LR i ≤ 520 V-cm 2 / μJ.

[0020] <Measurement method of NESA-EV curve>

[0021] (1) : The surface potential of the electrophotographic photosensitive member is set to 0 V,

[0022] (2) : The electrophotographic photosensitive member is charged for 0.005 seconds to make the absolute value of the surface potential of the electrophotographic photosensitive member V0 [V],

[0023] (3) : After the start of charging for 0.02 seconds, the charged electrophotographic photosensitive member is continuously exposed to light having a wavelength of 805 nm and an intensity of 25 mW / cm 2 for t seconds to make the exposure amount I exp [μJ / cm 2 ],

[0024] (4) : After the start of charging for 0.06 seconds, the absolute value of the surface potential of the exposed electrophotographic photosensitive member is measured and the measured value is represented by V exp [V],

[0025] (5) : While changing I 2 from 0.000 μJ / cm exp to 0.850 μJ / cm 2 at intervals of 0.001 μJ / cm 2 by changing t, operations (1) to (4) are repeated to obtain V exp corresponding to each value of I exp , and

[0026] (6) : V exp [V] in the case where t = 0 and I d = 0.000 μJ / cm d are set in the operation of (3) is called the charging potential V max [V], and V0 [V] is set in the case where the operation of (2) is performed to make the value of V 2 500 V.

[0027] Further features of the present application will become apparent from the following description of exemplary embodiments with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 、 Figure 1A and Figure 1B are conceptual diagrams each showing a barter relationship between analog gradation and digital gradation in an EV curve of a conventional photosensitive member.

[0029] Figure 2 is a conceptual diagram showing that both analog gradation and digital gradation can be achieved in good balance in an EV curve of a photosensitive member satisfying the provision of the EV curve in the present application.

[0030] Figure 3 is a conceptual diagram showing S max [V·μJ / cm 2 ] and S i [V·μJ / cm 2 ] in an EV curve of a conventional photosensitive member.

[0031] Figure 4 is a conceptual diagram showing S max [V·μJ / cm 2 ] and S i [V·μJ / cm 2 ] in an EV curve of a photosensitive member in the present application.

[0032] Figure 5A 、 Figure 5B 、 Figure 5C and Figure 5D are diagrams for explaining analog gradation and digital gradation and explaining a change in a mixing ratio of analog gradation and digital gradation in actual gradation due to a size relationship between the size of a single dot and the diameter of an exposure light spot.

[0033] Figure 6 is a diagram schematically showing an apparatus for measuring a NESA-EV curve.

[0034] Figure 7 is a diagram showing one example of a layer constitution of an electrophotographic photosensitive member in the present application.

[0035] Figure 8 is a diagram showing one example of a schematic constitution of an electrophotographic apparatus including a process cartridge provided with an electrophotographic photosensitive member and a charging unit.

[0036] Figure 9A 、 Figure 9B 、 Figure 9C 、 Figure 9D and Figure 9E are diagrams each showing an example of a gradation dither pattern used for evaluation in the present application.

[0037] Figure 10An example of an area ratio normalized concentration chart related to a line growth dither pattern of 32 gradations of line number 600 was measured at a processing speed of 300 [mm / s] for the photosensitive member production example 1 of the present application.

[0038] Figure 11 A graph for explaining the calculation method of "high light gradation property" and "shadow gradation property" on the area ratio normalized concentration chart for evaluation in the present application.

[0039] Figure 12 A graph of 1 dot 4 space halftone for showing evaluation in the present application. DETAILED DESCRIPTION

[0040] The present application is described in detail by using preferred embodiments. Note that in the present specification, voltage is expressed in absolute value.

[0041] The electrophotographic photosensitive member of the present application is an electrophotographic photosensitive member including a support, a charge generating layer on the support, and a charge transport layer on the charge generating layer. The electrophotographic photosensitive member of the present application is an organic photosensitive member and relates to an electrophotographic photosensitive member. It is assumed that, in the case where the charging potential is V d = 500 V, at a temperature of 23.5°C and a relative humidity of 50% RH, is obtained according to the following <Measurement method of NESA-EV curve> and in which the horizontal axis represents the irradiated exposure amount I exp and the vertical axis represents the absolute value of the surface potential after exposure V exp of I exp -V exp In the graph, the light amount at V exp = 250 V is represented by I 1 / 2 [μJ / cm 2 ], in the graph, I exp = 0.000 ~ 3.414 · I 1 / 2 [μJ / cm 2 ] in the range, the product S = I exp · V exp [V·μJ / cm exp ] of I exp and V 2 is represented by S max [V·μJ / cm 2 ], in the graph, I exp = 0.000 ~ 0.100 · I 1 / 2 [μJ / cm 2 ] in the range, the approximate straight line and I exp = (5 · I 1 / 2 - 0.100) ~ 5 · I 1 / 2[μJ / cm 2 范围内 of the approximate straight line is represented by Q, and the light quantity value at point Q is represented by I i [μJ / cm 2 . The potential value at point Q is represented by V i [V]. The product of I i and V i is represented by S i = I i ·V i [V·μJ / cm 2 . S i divided by S max is represented by AR = S i / S max . And the value obtained by dividing V i by I i is represented by LR i = V i / I i [V·cm 2 / μJ]. In this case, it satisfies I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.370, and LR i ≤ 780 V·cm 2 / μJ.

[0042] In addition, the electrophotographic photosensitive member according to the present invention relates to an electrophotographic photosensitive member in which the above I 1 / 2 , AR = S i / S max and LR i = V i / I i satisfy I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.500, and LR i ≤ 520 V·cm 2 / μJ.

[0043] <Measurement method of NESA - EV curve>

[0044] (1): Set the surface potential of the electrophotographic photosensitive member to 0 V,

[0045] (2): Charge the electrophotographic photosensitive member for 0.005 seconds so that the absolute value of the surface potential of the electrophotographic photosensitive member becomes V0 [V],

[0046] (3): After 0.02 seconds from the start of charging, continuously expose the charged electrophotographic photosensitive member to light with a wavelength of 805 nm and an intensity of 25 mW / cm 2 for t seconds so that the exposure amount becomes Iexp [μJ / cm 2 ],

[0047] (4) : After 0.06 seconds from the start of charging, the absolute value of the surface potential of the exposed electrophotographic photosensitive member is measured and the measured value is represented by V exp [V],

[0048] (5) : While changing I 2 from 0.000 μJ / cm exp to 0.850 μJ / cm 2 at intervals of 0.001 μJ / cm 2 , operations (1) to (4) are repeated to obtain V exp corresponding to each value of I exp , and

[0049] (6) : V exp [V] in the case where t = 0 and I 2 = 0.000 μJ / cm exp are set in the operation of (3) is called a charging potential V d [V], and V0 [V] set in the case where the operation of (2) is performed is set so that the value of V d becomes 500 V.

[0050] Further, the present application relates to a process cartridge which integrally supports the aforementioned electrophotographic photosensitive member and at least one unit selected from the group consisting of a charging unit, a developing unit, and a cleaning unit, and which is detachably attached to a main body of an electrophotographic apparatus.

[0051] Further, the present application relates to an electrophotographic apparatus which includes the aforementioned electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a transfer unit.

[0052] In the research conducted by the present inventors, the photosensitive member of the conventional art could not satisfy the three characteristics of sensitivity, residual potential, and linearity on the EV curve at a high level. In recent years, due to the requirements for miniaturization and low cost of electrophotographic apparatuses, it has not been possible to reduce the spot diameter of the laser. A technology which achieves both improvement in character quality in low line number halftone and digital gradability while maintaining analog gradability in high speed processing to achieve high productivity as described above has not been realized.

[0053] Further, in the conventional art, in view of the aforementioned object, a method prescribed in order to satisfy the three characteristics of sensitivity, residual potential, and linearity on the EV curve at a high level is insufficient. Further, the basic characteristic evaluation means for the measurement of the EV curve is insufficient for realizing high speed processing expected in recent years and in the future.

[0054] Therefore, the inventors have specified a balance between the three characteristics of sensitivity, residual potential, and linearity on the EV curve. Furthermore, the inventors have discovered that, for the aforementioned purposes, it is only necessary to appropriately measure the EV curve and specify, measure, and design the photosensitive element as follows to solve the aforementioned problems.

[0055] <Design of Photosensitive Components>

[0056] To achieve a good balance between analog and digital grayscale, photosensitive components need to achieve high sensitivity, low residual potential, and high linearity at a high level, while maintaining an optimal balance among these characteristics.

[0057] (The relationship between EV curves and the stability of analog and digital grayscale)

[0058] Figure 1 This illustrates the barter relationship between analog and digital grayscale in the EV curves of a conventional photosensitive element. To improve analog grayscale, it is necessary to make the change in surface potential under varying light intensity more linear. Therefore, in Figure 1 In the EV curve, you can choose (a) low light intensity as the image exposure. Figure 1A The low-light level (a) of the EV curve is shown in magnified view. From this magnified image, it can be observed that when the EV curve is divided into portions with a fixed image exposure (equal light intensity), the range of surface potentials corresponding to each portion is relatively uniform. Therefore, under low light intensity, the simulated grayscale is relatively improved. Meanwhile, Figure 1B The EV curve is shown in magnified form when (b) high light intensity is selected as the image exposure. From this magnified image, it can be observed that when the EV curve is divided into equal parts, the range of surface potentials corresponding to each part is far from uniform. Therefore, under high light intensity, grayscale degradation is simulated.

[0059] At the same time, to improve digital grayscale, individual pixels need to be dark and stable. Therefore, one can choose... Figure 1 The highlight amount in (b) of the EV curve is taken as the image exposure. In this case, such as Figure 1 As shown, due to the small absolute value of the slope of the EV curve, the surface potential change is stable relative to the change in light intensity, resulting in stability at a single point. Meanwhile, when (a) low light intensity is selected as the image exposure, as... Figure 1 As shown, the absolute value of the slope of the EV curve is large. Therefore, the surface potential is unstable relative to changes in light intensity, resulting in instability at a single point.

[0060] As mentioned above, based on the choice of which amount of light on the EV curve is used as the image exposure, analog grayscale and digital grayscale are usually in a barter relationship.

[0061] At the same time,Figure 1 In the EV curve of the conventional photosensitive member in the above (a) low light amount as the image exposure amount is selected, the linearity between the light amount and the surface potential is insufficient, and in (b) high light amount as the image exposure amount is selected, the stability of the surface potential variation with respect to the light amount is insufficient and the residual potential is high.

[0062] Next, Figure 2 The relationship between the analog gradation and the digital gradation in the EV curve of the photosensitive member of the present application is shown. Since the photosensitive member of the present application has a low residual potential and high linearity, the curvature in the case where the EV curve changes from the low light amount side to the high light amount side is steep. Therefore, it is possible to make Figure 1 The region of (a) low light amount which is favorable for the analog gradation and the region of (b) high light amount which is favorable for the digital gradation shown in the above are made closer. As Figure 2 In the EV curve where the two regions are close to each other as shown in the above, since the linearity of the EV curve is high in the region of low light amount, when the variation of the image exposure amount is equally divided, the variation of the corresponding surface potential is also divided into almost equal parts. Meanwhile, in the region of high light amount, the stability of the single point with respect to the light amount variation is high. Further, since the residual potential is low, the width between the upper and lower limits of the surface potential which can be used for the analog gradation (hereinafter, referred to as "latent image contrast") is increased, and this also contributes to the improvement of the analog gradation. Further, since the latent image contrast is increased and the single point density is high and stable, this also contributes to the improvement of the digital gradation.

[0063] The NESA-EV curve described later is measured for each photosensitive member and is independent of the process. However, the EV curve measured in a laser beam printer is dependent on the process. In particular, at a high processing speed, when the mobility of the photo-generated carrier in the photosensitive member is low, the EV curve deteriorates. Further, when the irradiation time of the image exposure light is short or the number of irradiations is small due to the increase of the processing speed and the adoption of multiple laser beams and the like, the density of the photo-generated carrier per unit time and unit area in the photosensitive member increases. Therefore, when there are many traps in the interface surface or the bulk, the EV curve deteriorates (this is referred to as the "reciprocity law failure" characteristic of the photosensitive member). In order to avoid these problems, it is necessary that the mobility of the photo-generated carrier is high and the number of such traps is small. The photosensitive member of high sensitivity satisfies these conditions. Therefore, in order to stably achieve both the analog gradation and the digital gradation in good balance in the high speed processing in recent years and in the future, in addition to the low residual potential and the high linearity on the EV curve, the photosensitive member of the present application also needs to satisfy the high sensitivity.

[0064] (Specification of the EV curve)

[0065] In the present application, the NESA-EV curve is used as the EV curve. The NESA-EV curve is obtained by the following measurement method of the NESA-EV curve. exp -V exp Figure. In the present application, each characteristic value is determined as follows. In the NESA-EV curve in the case where the charging potential is V d = 500 V, the light amount at the time when V exp = 250 V is indicated by I 1 / 2 [μJ / cm 2 ]. S is defined as S = I exp · V exp [V·μJ / cm 2 ]. The maximum value of S [V·μJ / cm exp ] in the range of I 1 / 2 = 0.000 ~ 3.414 · I 2 [μJ / cm 2 ] in the figure is indicated by S max [V·μJ / cm 2 ]. An approximate straight line in the range of I exp = 0.000 ~ 0.100 · I 1 / 2 [μJ / cm 2 ] in the figure is obtained. An approximate straight line in the range of I exp = (5 · I 1 / 2 - 0.100) ~ 5 · I 1 / 2 [μJ / cm 2 ] is obtained. The intersection point of these two approximate straight lines is indicated by Q. The light amount value at the point Q is indicated by I i [μJ / cm 2 ], the potential value at the point Q is indicated by V i [V], and the product of I i and V i is indicated by S i = I i · V i [V·μJ / cm 2 ]. AR = S i / S max is defined and LR i = V i / I i [V·cm 2 / μJ].

[0066] Figure 3 A conceptual diagram showing S max [V·μJ / cm 2 ] and S i [V·μJ / cm 2 ] in the EV curve of a conventional photosensitive member is shown.

[0067] S max means the maximum value of S [V μJ / cm exp ] calculated by S = I 1 / 2 · V 2 in the range of I exp = 0.000 ~ 3.414 · I exp [μJ / cm 2 ]. In this case, I 1 / 2 is the half-value exposure amount and V exp is the absolute value of the surface potential in the case of exposure with the light amount of I exp . The value "3.414" is explained as follows. Considering an arbitrary point (x, y) on a downward convex quadratic function, a vertex (x0, y0) of the quadratic function, and a point (x1, y1 = (y + y0) / 2) which takes the middle value of the y coordinate values of these two points on the quadratic function. In this case, the ratio of the distance from (x, 0) to (x1, 0) (corresponding to the half-value exposure amount) to the distance from (x, 0) to (x0, 0) (corresponding to the residual potential exposure amount) is 3.414. For any downward convex quadratic function, the ratio is always (x0 - x) / (x1 - x) = 2 / (2 - V2) « 3.414. Therefore, in the range of I exp = 0.000 ~ 3.414 · I 1 / 2 [μJ / cm 2 ], the lower the sensitivity and the residual potential and the higher the linearity, the larger S max becomes.

[0068] Meanwhile, S i is defined as follows. The intersection point of the approximate straight line in the range of I exp = 0.000 ~ 0.100 · I 1 / 2 [μJ / cm 2 ] and the approximate straight line in the range of I exp = (5 · I 1 / 2 - 0.100) ~ 5 · I 1 / 2 [μJ / cm 2 ] is denoted by Q. When the light amount value at the point Q is denoted by I i [μJ / cm 2 ] and the potential value at the point Q is denoted by V i [V], the product of I i and V i is S i . By this definition, the higher the sensitivity and the lower the residual potential, the smaller S i becomes.

[0069] Considering S max defined as described above and S iRatio: AR = S i / S max . The sensitivity affects S i and S max in the opposite direction. Therefore, the sensitivity has little effect on the size of AR. As a result, the lower the residual potential or the higher the linearity, the smaller AR is and the relatively smaller the effect of the sensitivity on AR. Furthermore, considering the aspect ratio of S i , LR i = V i / I i , from its definition, the lower the sensitivity and the residual potential and the higher the linearity, the smaller LR i is. In particular, the low residual potential strongly affects LR i .

[0070] The present inventors found that the foregoing I 1 / 2 , AR and LR i are optimal for achieving high sensitivity, low residual potential and high linearity at a high level, while maintaining the best balance for the purpose of achieving both analog gradation and digital gradation at a good balance, in satisfaction of the following set of regulations:

[0071] (A) I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.370 and LR i ≤ 780 V-cm 2 / μJ; or

[0072] (B) I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.500 and LR i ≤ 520 V-cm 2 / μJ.

[0073] Figure 4 A conceptual diagram showing the EV curve of the photosensitive member of the present application satisfying these regulations is shown. As is apparent from Figure 4 , when the low residual potential and high linearity are satisfied, both AR = S i / S max and LR i = V i / I i are small. Furthermore, it can be found that the effect of the low residual potential is large.

[0074] In comparison with the regulations of (B) I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.500 and LR i ≤ 520 V-cm 2 / μJ, (A) I 1 / 2≤ 0.170 μJ / cm 2 , AR ≤ 0.370 and LR i ≤ 780 V-cm 2 / μJ of the present application. Specifically, this means that, as described in (A) or (B), when a low residual potential and a high linearity complement each other while being balanced with a high sensitivity, the object of the present application can be achieved.

[0075] In a case where the laser spot diameter cannot be reduced due to a demand for miniaturization and low cost of electrophotographic apparatuses in recent years, as shown in Figure 5A to Figure 5D , the analog gradation property becomes stronger. Figure 5A to Figure 5C Each shows a pattern of 600 dpi in which a single dot is 42 μm x 42 μm. Figure 5A shows analog gradation (a case where control is performed by using the average potential of the macroscopic), Figure 5B shows digital gradation (a case where control is performed by using the area ratio of the microscopic), and Figure 5C shows an example of a pattern obtained when the laser spot diameter cannot be sufficiently controlled. Figure 5D is a schematic view of the spot diameter-light amount distribution of the laser. When the spot diameter is large, the analog gradation property is strong, and when the spot diameter is small, the digital gradation property is strong. In this case, LR i of the present application is particularly important for improving the character quality under low line halftone and the digital gradation property while maintaining the analog gradation property.

[0076] (Measurement method of NESA-EV curve)

[0077] The NESA-EV curve is obtained by the following measurement method. Note that, in this technical field, under specific process conditions, the EV curve is measured in a laser beam printer is relatively common. Meanwhile, the NESA-EV curve is not measured in a printer, but is measured for a photosensitive member under specific conditions as described below and is defined for each photosensitive member.

[0078] Under a temperature of 23.5°C and a relative humidity of 50% RH, with the charging potential set to V d = 500 V, the NESA-EV curve is measured as follows.

[0079] (1) : The surface potential of the electrophotographic photosensitive member is set to 0 V,

[0080] (2) : The electrophotographic photosensitive member is charged for 0.005 seconds to make the absolute value of the surface potential of the electrophotographic photosensitive member V0 [V],

[0081] (3): 0.02 seconds after the start of charging, the charged electrophotographic photosensitive component was continuously exposed to an atmosphere with a wavelength of 805 nm and an intensity of 25 mW / cm². 2 The light t seconds make the exposure amount I exp [μJ / cm 2 ],

[0082] (4): 0.06 seconds after the start of charging, measure the absolute value of the surface potential of the electrophotographic photosensitive component after exposure, and the measured value is determined by V. exp [V] indicates that,

[0083] (5): By changing t to 0.001 μJ / cm 2 The interval will I exp From 0.000 μJ / cm 2 Change to 0.850 μJ / cm 2 Simultaneously repeat operations (1) to (4) to obtain the corresponding I exp V values exp ,and

[0084] (6): In the operation of (3), set t=0 and I exp =0.000μJ / cm 2 V in the case exp [V] is called the charging potential. d [V], and set V0[V] in the case of performing operation (2) so that V d The value becomes 500V.

[0085] Describe a specific example of a measurement system for the NESA-EV curve. However, the measurement system is not limited to the following methods, as long as the measurement method for the NESA-EV curve can be implemented.

[0086] A transparent quartz glass (hereinafter referred to as "NESA glass") with its entire surface optically ground and a transparent ITO electrode deposited on the surface to form a thin-film resistance of less than 1,000 Ω / sq was prepared. Figure 6 As shown, the surface of the photosensitive element 201 is brought into close contact with NESA glass 202 on which a transparent ITO electrode 204 is deposited by vapor deposition. In this case, glycerin is provided between the NESA glass 202 and the photosensitive element 201 to ensure a truly tight contact between the two elements. Note that when the photosensitive element has a flat shape, a smooth NESA glass is used, and when the photosensitive element has a cylindrical shape, a smooth NESA glass is used. Figure 6 The image shows a curved NESA glass. Applying a voltage to the NESA glass using a high-voltage power supply 205 in this state can charge the surface of the photosensitive element. Furthermore, a voltage of 805 nm wavelength and 25 mW / cm² is applied from the lower surface of the NESA glass.2 When planar light shines on the surface of a photosensitive component, it can expose the surface of the photosensitive component to light 203 and cause light attenuation of the surface potential.

[0087] Using the aforementioned measurement system allows for measurement at only 25mW / cm 2 The light briefly illuminates the photosensitive component once, while charging and exposure are repeated at a cycle faster than that of electrophotographic equipment in recent years or anticipated in the future. 25mW / cm 2 The light intensity is greater than that used for irradiating photosensitive components in electrophotographic devices that are expected or anticipated in the future. This allows for a stable and easy acquisition of a spacing of 0.001 μJ / cm. 2 The system provides a large amount of data on light intensity and can obtain the NESA-EV curve of the photosensitive element of the present invention and the characteristic values ​​calculated from the NESA-EV curve. Furthermore, the aforementioned measurement method, implemented using this measurement system, can also be used to evaluate the characteristics of the photosensitive element when processing speeds increase in recent years or in the future and exposure times become shorter. In addition, the aforementioned measurement method can be used to evaluate the characteristics of the photosensitive element corresponding to the reduction in the number of exposures that occurs when the exposure method changes from the currently mainstream laser scanning optical system to an LED array. Specifically, considering the reciprocal failure characteristics of the photosensitive element, an intensity of 25 mW / cm² is used. 2 Furthermore, the light irradiation conditions of a single exposure over a short period of time are sufficiently stringent for future EV curve measurement methods.

[0088] [Electronic photographic sensor]

[0089] The electrophotographic photosensitive component of the present invention is an organic photosensitive component comprising a support, a charge-generating layer on the support, and a charge-transporting layer on the charge-generating layer. The charge-generating layer contains a charge-generating substance, and the charge-transporting layer contains a charge-transporting substance. An organic photosensitive component refers to a photosensitive component whose main component in the layer formed on the support is resin. Figure 7 This diagram illustrates an example of the layered structure of an electrophotographic photosensitive component. Figure 7 In the accompanying drawings, reference numeral 101 denotes a support, 102 denotes a base coating layer, 103 denotes a charge generating layer, 104 denotes a charge transport layer, and 105 denotes a photosensitive layer. In this invention, the base coating layer 102 can be omitted.

[0090] Furthermore, the photosensitive element of the present invention needs to meet the following requirements.

[0091] (A)I 1 / 2 ≤0.170μJ / cm 2 AR≤0.370 and LR i ≤780V·cm 2 / μJ; or

[0092] (B)I1 / 2 ≤0.170 μJ / cm 2 、AR ≤ 0.500 and LR i ≤520 V·cm 2 / μJ

[0093] where, at a temperature of 23.5 °C and a relative humidity of 50%RH, at a charging potential of V d = 500 V, obtained according to the aforementioned <Measurement method of NESA-EV curve> and where the horizontal axis represents I exp and the vertical axis represents V exp of the I exp -V exp in the figure,

[0094] the light quantity at V exp = 250 V in the figure is represented by I 1 / 2 [μJ / cm 2 ,

[0095] the maximum value of S[V·μJ / cm exp calculated from S = I 1 / 2 [μJ / cm 2 within the range of I exp ·V exp = 0.000 to 3.414·I 2 is represented by S max [V·μJ / cm 2 ,

[0096] the intersection point of the approximate straight line within the range of I exp = 0.000 to 0.100·I 1 / 2 [μJ / cm 2 and the approximate straight line within the range of I exp = (5·I 1 / 2 - 0.100) to 5·I 1 / 2 [μJ / cm 2 is represented by Q, the light quantity value at point Q is represented by I i [μJ / cm 2 , the potential value at point Q is represented by V i [V], and the product of I i and V i is represented by S i = I i ·V i [V·μJ / cm 2 ,

[0097] the ratio of S i to S max is represented by AR = S i / Smax indicates, and

[0098] by dividing V i by I i The value obtained is represented by LR i = V i / I i [V-cm 2 / μJ].

[0099] Further, from the viewpoint of improving both the image on the high light side where the dot area ratio is low and the image on the shadow side where the dot area ratio is high, the photosensitive member is preferably configured so that AR ≤ 0.370 and LR i ≤ 520 V-cm 2 / μJ to satisfy both (A) and (B) above. When AR ≤ 0.370 and LR i ≤ 520 V-cm 2 / μJ, the balance between low residual potential and high linearity is further improved in high-speed processing where the spot diameter of the laser is 80 μm and the printing speed is 100 ppm (500 mm / sec). As a result, the gradation on both the high light side and the shadow side is improved.

[0100] Further, from the viewpoint of improving the reproducibility of a hollow character with a small font size by further improving the image on the shadow side where the line number is high, it is more preferable that the aforementioned AR satisfy AR ≤ 0.100. When AR ≤ 0.100, the visibility of a 6-pt hollow character on the shadow side is improved in high-speed processing where the spot diameter of the laser is 80 μm and the printing speed is 100 ppm (500 mm / sec).

[0101] Meanwhile, from the viewpoint of improving the reproducibility of a normal character with a small font size by further improving the image on the high light side where the line number is low, it is more preferable that the aforementioned LR i satisfy LR i ≤ 60 V-cm 2 / μJ. When LR i ≤ 60 V-cm 2 / μJ, the visibility of a 3-pt normal character on the high light side is improved in high-speed processing where the spot diameter of the laser is 80 μm and the printing speed is 100 ppm (500 mm / sec).

[0102] Further, from the viewpoint of improving the reproducibility of a single isolated dot when the charging potential is set to a low level for the purpose of energy saving or the like, the aforementioned I exp -V exp on the graph I exp = 5 · I 1 / 2 [μJ / cm 2 ] is V exp .r V is preferably ≤ 70 V. More preferably, V r ≤ 10 V. When V r ≤ 70 V, V r ≤ 70 V, V d = 450 V, the reproducibility of isolated single dots is improved. When V r ≤ 10 V, the concentration of isolated single dot patterns becomes even higher.

[0103] The method of manufacturing the electrophotographic photosensitive member of the present application includes a method of preparing a coating liquid of each layer described later, coating and drying in the desired order of layers. In this case, the coating method of the coating liquid includes dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating, etc. Among them, dip coating is preferred from the viewpoint of efficiency and productivity.

[0104] The support and each layer are described below.

[0105] <Support>

[0106] In the present application, the electrophotographic photosensitive member includes a support. The support is preferably a conductive support having conductivity. Further, the shape of the support includes a cylindrical shape, a belt shape, and a sheet shape, etc., and, among them, a cylindrical support is preferred. Further, the surface of the support can be subjected to a sandblasting treatment or a cutting treatment, etc.

[0107] As the material of the support, a metal, a resin, or glass, etc. is preferred.

[0108] The metal includes aluminum, iron, nickel, copper, gold, stainless steel, and alloys of these metals. Among them, an aluminum support using aluminum is preferred.

[0109] When the material is a resin or glass, the support can be subjected to a treatment such as mixing or coating of a conductive material, etc. to impart conductivity thereto.

[0110] The support of the present application can be used in a case where the surface of the support is anodized in an acidic liquid containing an oxidizing agent. In this case, in the anodizing treatment, for example, inorganic acids such as sulfuric acid and chromic acid and organic acids such as oxalic acid and sulfonic acid, etc. can be used as an electrolyte. Conditions such as applied voltage, current density, treatment temperature, and time, etc. can be selected according to the film thickness and the kind of the aforementioned electrolyte. Further, the anodized surface used in the electrophotographic photosensitive member of the present application can be subjected to an electrolytic treatment and then to a sealing treatment. The sealing treatment can be a hot water treatment, a water vapor treatment, or a treatment using various sealing agents such as nickel acetate and nickel fluoride, etc. The treatment using nickel acetate which can effectively seal the fine pores is preferred.

[0111] <conductive layer>

[0112] In the present application, a conductive layer can be provided on the support. The provision of the conductive layer can cover scratches and unevenness on the surface of the support and enable control of light reflection on the surface of the support.

[0113] The conductive layer preferably contains conductive particles and a resin.

[0114] The material of the conductive particles includes metal oxides, metals, and carbon black, etc.

[0115] The metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide, etc. The metals include aluminum, nickel, iron, nickel-chromium alloy, copper, zinc, and silver, etc.

[0116] Among them, it is preferable to use a metal oxide as the conductive particles, and it is particularly preferable to use titanium oxide, tin oxide, and zinc oxide.

[0117] When a metal oxide is used as the conductive particles, the surface of the metal oxide can be treated with a silane coupling agent, or the metal oxide can be doped with an element such as phosphorus or aluminum, or an oxide thereof. The element or the oxide thereof for doping includes phosphorus, aluminum, niobium, and tantalum, etc.

[0118] Further, the conductive particles can have a layered structure including core particles and a coating layer covering the particles. The core particles include titanium oxide, barium sulfate, and zinc oxide, etc. The coating layer includes metal oxides such as tin oxide and titanium oxide, etc.

[0119] Further, when a metal oxide is used as the conductive particles, the volume average particle diameter thereof is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0120] The resin includes polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, and alkyd resin, etc.

[0121] Further, the conductive layer can further contain a masking agent such as silicone oil, resin particles, or titanium oxide, etc.

[0122] The average film thickness of the conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less.

[0123] The conductive layer can be formed by preparing a coating liquid for a conductive layer containing each of the aforementioned materials and a solvent, forming a coating film of the coating liquid on a lower layer or a support, and drying the coating liquid. The solvent used in the coating liquid includes alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents, and the like. The dispersion method for dispersing the conductive particles in the coating liquid for a conductive layer includes a method using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

[0124] <undercoat layer>

[0125] In the present application, an undercoat layer can be provided on the support or the conductive layer. The provision of the undercoat layer can improve the adhesion function between layers and provide a charge injection prevention function.

[0126] The undercoat layer preferably contains a resin. Furthermore, the undercoat layer can be formed into a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.

[0127] The resin includes a polyester resin, a polycarbonate resin, a polyvinyl acetal resin, an acrylic resin, an epoxy resin, a melamine resin, a polyurethane resin, a phenol resin, a polyvinyl phenol resin, an alkyd resin, a polyvinyl alcohol resin, a polyethylene oxide resin, a polypropylene oxide resin, a polyamide resin, a polyamide acid resin, a polyimide resin, a polyamide-imide resin, a cellulose resin, and the like.

[0128] The polymerizable functional group contained in 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, a thiol group, a carboxylic anhydride structure, a carbon-carbon double bond, and the like.

[0129] Furthermore, the undercoat layer can further contain an electron-transporting substance, a metal oxide, a metal, and a conductive polymer, or the like, to improve the electrical properties. Among them, an electron-transporting substance and a metal oxide are preferably used.

[0130] In particular, the selection of the electron-transporting substance, the metal oxide, the metal, the conductive polymer, and the resin, and the control of the compounding ratio thereof, or the like, is important. Such appropriate selection and control, and the appropriate selection of the photosensitive layer on the undercoat layer allow the photo-carriers generated in the charge generation layer to flow smoothly to the support, and a photosensitive member satisfying the prescribed EV curve of the present application can be obtained.

[0131] The electron-transporting substance includes quinone compounds, imide compounds, benzimidazole compounds, cyclopentadiene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyano vinyl compounds, aryl halides, thiopyryl compounds, and boron-containing compounds, and the like. The undercoat layer can be formed into a cured film by using an electron-transporting substance containing a polymerizable functional group as the electron-transporting substance and copolymerizing it with the aforementioned monomer having a polymerizable functional group.

[0132] The metal oxide includes indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide, and the like. The metal includes gold, silver, and aluminum, and the like. Among them, from the viewpoint of smoothly flowing the photo-carriers generated in the charge generation layer to the support, titanium oxide particles whose surface is subjected to silane treatment and whose crystal structure is rutile type or anatase type are preferable. In the surface silane treatment, it is preferable to use at least one compound selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldimethoxysilane. Providing hydrophobicity by performing the silane treatment can inhibit carrier transfer inhibition caused by moisture adsorption, and using titanium oxide particles of the rutile type or the anatase type can reduce carrier hydrazine. Furthermore, from the viewpoint of further inhibiting carrier transfer inhibition, the titanium oxide particles are more preferably rutile titanium oxide particles having low photocatalytic activity, and even more preferably titanium oxide particles having a rutilization rate of 90% or more. Furthermore, from the viewpoint of preventing the binder resin from damaging the conductivity of the titanium oxide particles, the volume ratio of the titanium oxide particles to the binder resin (the volume of the titanium oxide particles with respect to the volume of the binder resin) is preferably 0.2 or more. If the ratio is less than 0.2, the binder resin sometimes inhibits the smooth transfer of photo-carriers.

[0133] Furthermore, the undercoat layer can further contain an additive.

[0134] 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.

[0135] The undercoat layer can be formed by preparing a coating liquid for the undercoat layer containing the aforementioned materials and a solvent, forming a coating film of the coating liquid on the lower layer or the support, and drying and / or curing the coating liquid. The solvent used in the coating liquid includes alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents, and the like.

[0136] <Charge Generation Layer>

[0137] The charge generation layer needs to contain a charge generating substance and a resin.

[0138] Charge generating substances include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments, etc. Among them, from the viewpoint of easily obtaining high sensitivity required in the present application, phthalocyanine pigments are preferred.

[0139] In comparing phthalocyanine pigments and azo pigments as charge generating substances, azo pigments are of an interface type in which a charge generation site is at an interface between a charge generation layer and a charge transport layer, whereas phthalocyanine pigments are of a bulk type in which a charge generation site is in the bulk of a charge generation layer (reference: Minoru Umeda, "Extrinsic Photocarrier Generation Process and Kinetics of a Layered Organic Photoreceptor", Journal of the Chemical Society of Japan, 1996, No. 11, pp. 932-937). Therefore, when a phthalocyanine pigment is used as a charge generating substance, the amount of photo-generated carriers can be more easily increased by increasing the film thickness of the charge generation layer, as compared with azo pigments. As a result, when a phthalocyanine pigment is used as a charge generating substance, a photosensitive member having high sensitivity in the present application can be easily obtained.

[0140] Among phthalocyanine pigments, a titanium oxyphtalocyanine pigment or a gallium hydroxyphthalocyanine pigment is preferred because a high photosensitivity can be stably obtained. Further, a gallium hydroxyphthalocyanine crystal described in Japanese Patent Application Laid-Open No. 2000-137340 and having strong peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in CuKα characteristic X-ray diffraction or a titanium oxyphtalocyanine crystal described in Japanese Patent Application Laid-Open No. 2000-137340 and having a strong peak at a Bragg angle 2θ of 27.2°±0.3° in CuKα characteristic X-ray diffraction is more preferred. Among such crystals, a gallium hydroxyphthalocyanine crystal described in Examples of Japanese Patent Application Laid-Open No. 2018-189692 and containing 0.4 mass% or more and 3.0 mass% or less of a compound having a structure represented by the following formula (A1) in the crystal is particularly preferred.

[0141]

[0142] (R in the aforementioned formula (A1) 0 represents a methyl group, a propyl group, or a vinyl group)

[0143] This is based on the viewpoint of improving sensitivity while reducing residual potential by preventing the interface between a resin and a pigment dispersed in the resin from becoming a charge trap.

[0144] In the foregoing crystal, in a hydroxygallium phthalocyanine crystal containing 0.4 mass% or more and 3.0 mass% or less of a compound having a structure represented by the following formula (A1), the size of the crystal particles is made uniform to a size as large as the charge generation layer film thickness. The reason is also described in Japanese Patent Application Laid-Open No. 2018-189692. Therefore, both the quantum efficiency determined by Onsager's equation described in Japanese Patent Application Laid-Open No. 2018-189692 and the light absorption rate determined by Beer-Lambert equation can have high values. Therefore, it is not necessary to make the charge generation layer film thickness excessively large to improve the sensitivity, and the amount of interface traps between the charge generating substance (crystal particles) and the resin, which tends to increase as the film thickness increases, can be suppressed and the residual potential can be reduced.

[0145] The content of the charge generating substance in the charge generation layer is preferably 40% by mass or more and 85% by mass or less, more preferably 60% by mass or more and 80% by mass or less, relative to the total mass of the charge generation layer.

[0146] The resin includes polyester resins, polycarbonate resins, polyvinyl acetal resins, polyvinyl butyral resins, acrylic resins, silicone resins, epoxy resins, melamine resins, polyurethane resins, phenolic resins, polyvinyl alcohol resins, cellulose resins, polystyrene resins, polyvinyl acetate resins, and polyvinyl chloride resins, and the like. Among them, polyvinyl butyral resins are more preferable.

[0147] Further, the charge generation layer can further contain additives such as antioxidants and ultraviolet absorbers. Specifically, the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds, and the like.

[0148] The average film thickness of the charge generation layer is preferably 0.1 μm or more and 1 μm or less, more preferably 0.15 μm or more and 0.3 μm or less.

[0149] The charge generation layer can be formed by preparing a coating liquid for a charge generation layer containing the aforementioned materials and a solvent, forming a coating film of the coating liquid on a lower layer or a support, and drying the coating liquid. The solvent used in the coating liquid includes alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents, and the like.

[0150] <Charge transport layer>

[0151] The charge transport layer needs to contain a charge transport substance and a resin.

[0152] Examples of the charge-transporting substance include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, diphenylamine compounds, triarylamine compounds, and resins containing groups derived from these substances, and the like. Among them, triarylamine compounds and diphenylamine compounds are preferable.

[0153] The content of the charge-transporting substance in the charge-transporting layer is preferably 25 mass% or more and 70 mass% or less, more preferably 30 mass% or more and 55 mass% or less, with respect to the total mass of the charge-transporting layer.

[0154] The resin includes polyester resins, polycarbonate resins, acrylic resins, and polystyrene resins, and the like. Among them, polycarbonate resins and polyester resins are preferable. As the polyester resin, polyarylate resins are particularly preferable.

[0155] From the viewpoint of smoothly transferring the photo-carriers generated in the charge-generating layer to the charge-transporting layer, the charge-transporting layer preferably has an ionization potential close to that of the charge-generating layer. In particular, when titanium oxophthalocyanine or hydroxygallium phthalocyanine is used as the charge-generating substance, the ionization potential of the charge-transporting layer is preferably 5.2 eV or more and 5.5 eV or less, more preferably 5.3 eV or more and 5.4 eV or less. When the ionization potential is 5.2 eV or more and 5.5 eV or less, it is less likely that a trap is generated at the interface between the charge-generating layer and the charge-transporting layer, and the residual potential is reduced. When the ionization potential is less than 5.2 eV, the memory phenomenon is deteriorated in some cases. When the ionization potential is greater than 5.5 eV, the residual potential is increased in some cases.

[0156] Further, from the viewpoint of making the generated photo-carriers move rapidly in the charge-transporting layer, the charge-transporting layer preferably has a high mobility. Therefore, the content ratio (mass ratio) of the charge-transporting substance to the resin is preferably 6:10 to 20:10, more preferably 8:10 to 12:10. When the content ratio (mass ratio) of the charge-transporting substance to the resin is 8:10 to 12:10, it is less likely that a trap is generated in the bulk of the charge-transporting layer, and the residual potential is reduced. If the content ratio of the charge-transporting substance is higher than the above content ratio, the durability and the manufacturing stability of the photosensitive member are reduced.

[0157] Further, the charge-transporting layer can contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slip property-imparting agents, and wear resistance-improving agents, and specifically, the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, silicone-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles, and the like.

[0158] The average film thickness of the charge transport layer is preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more and 23 μm or less, and particularly preferably 14 μm or more and 20 μm or less.

[0159] The charge transport layer can be formed by preparing a coating liquid for a charge transport layer containing the aforementioned materials and a solvent, forming a coating film of the coating liquid on a lower layer, and drying the coating liquid. The solvent used in the coating liquid includes alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents, and the like. Among these solvents, ether-based solvents or aromatic hydrocarbon-based solvents are preferable.

[0160] <Protective Layer>

[0161] In the present application, a protective layer can be provided on the photosensitive layer. The provision of the protective layer can improve durability.

[0162] The protective layer preferably contains a resin and electrically conductive particles and / or a charge transport substance.

[0163] The electrically conductive particles include, for example, particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide.

[0164] The charge transport substance includes polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins containing groups derived from these substances, and the like. Among these, triarylamine compounds and benzidine compounds are preferable.

[0165] The resin includes polyester resins, acrylic resins, phenoxy resins, polycarbonate resins, polystyrene resins, phenol resins, melamine resins, and epoxy resins, and the like. Among these, polycarbonate resins, polyester resins, and acrylic resins are preferable.

[0166] Further, the protective layer can be formed into a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. The polymerization reaction in this case includes thermal polymerization, photopolymerization, radiation-induced polymerization, and the like. The polymerizable functional group included in the monomer having a polymerizable functional group includes acryloyl groups, methacryloyl groups, and the like. A material having a charge transport function can be used as the monomer having a polymerizable functional group.

[0167] The protective layer can contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slip imparting agents, and wear resistance improvers. Specifically, the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, silicone-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles, and the like.

[0168] 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.

[0169] The protective layer can be formed by preparing a coating liquid for the protective layer containing each of the aforementioned materials and a solvent, forming a coating film of the coating liquid on the lower layer, and drying and / or curing the coating liquid. The solvent used in the coating liquid includes alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0170] <Example satisfying I 1 / 2 ≤0.170 μJ / cm 2 , AR ≤ 0.370, and LR i ≤ 780 V·cm 2 / μJ in an electrophotographic photosensitive member>

[0171] In order for the electrophotographic photosensitive member to satisfy I 1 / 2 ≤0.170 μJ / cm 2 , AR ≤ 0.370, and LR i ≤ 780 V·cm 2 / μJ, each layer of the electrophotographic photosensitive member preferably has the following composition. Specifically, the electrophotographic photosensitive member preferably includes a charge generation layer including a hydroxygallium phthalocyanine crystal recited in the Examples of Japanese Patent Application Laid-Open No. 2018-189692 and containing 0.4 mass% or more and 3.0 mass% or less of a compound having the structure represented by the aforementioned formula (A1) in a crystal or a titanyl phthalocyanine crystal recited in Japanese Patent Application Laid-Open No. 2000-137340 and having a strong peak at a Bragg angle 2θ of 27.2° ± 0.3° in CuKα characteristic X-ray diffraction. Among them, the electrophotographic photosensitive member preferably includes a charge generation layer including a hydroxygallium phthalocyanine crystal recited in the Examples of Japanese Patent Application Laid-Open No. 2018-189692 and containing 0.4 mass% or more and 3.0 mass% or less of a compound having the structure represented by the aforementioned formula (A1) in a crystal. Further, the electrophotographic photosensitive member preferably includes a charge transport layer having an ionization potential of 5.2 eV or more and 5.5 eV or less, and more preferably includes a charge transport layer having an ionization potential of 5.3 eV or more and 5.4 eV or less.

[0172] Further, the electrophotographic photosensitive member preferably includes both the aforementioned charge generation layer and the charge transport layer.

[0173] This is based on the view that the photo-carriers generated in the pigments dispersed in the resin are smoothly flown to the charge transport layer by combining the charge generation layer that prevents the interface between the pigments and the resin from becoming a charge trap and the charge transport layer that hinders the generation of an interface trap between the charge generation layer and the charge transport layer.

[0174] Examples of the preferred configuration include an electrophotographic photosensitive member including a hydroxygallium phthalocyanine crystal containing a compound represented by the aforementioned formula (A1) as recited in the Examples of Japanese Patent Application Laid-Open No. 2018-189692 and 0.4 mass% or more and 3.0 mass% or less in the crystal and a charge transport layer having an ionization potential of 5.3 eV or more and 5.4 eV or less.

[0175] However, the above-described configuration example is merely an example and the electrophotographic photosensitive member of the present application is not limited to the aforementioned configuration example as long as it satisfies I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.370, and LR i ≤ 780 V·cm 2 / μJ.

[0176] <electrophotographic photosensitive member satisfying I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.500, and LR i ≤ 520 V·cm 2 / μJ>

[0177] Further, in order for the electrophotographic photosensitive member to satisfy I 1 / 2 ≤ 0.170 μJ / cm 2 , AR ≤ 0.500, and LR i ≤ 520 V·cm 2 / μJ. / μJ, and each layer of the electrophotographic photosensitive member preferably has the following constitution. The electrophotographic photosensitive member preferably includes a primer layer including titanium oxide particles whose surface is silane-treated and whose crystal structure is rutile type or anatase type. In such a primer layer, the electrophotographic photosensitive member preferably includes a primer layer including rutile-type titanium oxide whose rutilization rate is 90% or more and whose surface is silane-treated by using at least one compound selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldimethoxysilane, the primer layer being a layer in which the volume ratio of titanium oxide particles to binder resin (the volume of titanium oxide particles relative to the volume of binder resin) is 0.2 or more. Further, the electrophotographic photosensitive member preferably includes a charge generation layer including a hydroxygallium phthalocyanine crystal recited in the Examples of Japanese Patent Application Laid-Open No. 2018-189692 and containing 0.4% by mass or more and 3.0% by mass or less of a compound having the structure represented by the aforementioned formula (A1) in a crystal or an oxotitanium phthalocyanine crystal recited in Japanese Patent Application Laid-Open No. 2000-137340 and having a strong peak at a Bragg angle 2θ of 27.2° ± 0.3° in CuKα characteristic X-ray diffraction. Among them, the electrophotographic photosensitive member preferably includes a charge generation layer including a hydroxygallium phthalocyanine crystal recited in the Examples of Japanese Patent Application Laid-Open No. 2018-189692 and containing 0.4% by mass or more and 3.0% by mass or less of a compound having the structure represented by the aforementioned formula (A1) in a crystal. Further, the electrophotographic photosensitive member preferably includes a charge transport layer having an ionization potential of 5.2 eV or more and 5.5 eV or less, more preferably a charge transport layer having an ionization potential of 5.3 eV or more and 5.4 eV or less.

[0178] Further, the electrophotographic photosensitive member particularly preferably includes all of the above-described primer layer, charge generation layer, and charge transport layer.

[0179] This is based on the view that by combining a primer layer that causes the photo-carriers generated in the charge generation layer to flow smoothly toward the support, a charge generation layer that prevents the interface between the pigment and the resin from becoming a charge well, and a charge transport layer that hinders the generation of an interface well between the charge generation layer and the charge transport layer, one of the positive and negative photo-carriers generated in the pigment dispersed in the resin flows smoothly toward the charge transport layer and also the photo-carrier of the opposite polarity flows smoothly toward the support.

[0180] As one example of a preferred configuration, an electrophotographic photosensitive member including the following can be given: a primer layer containing rutile titanium oxide particles having a rutile rate of 90% or more and having a surface thereof treated with silane using at least one compound selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldimethoxysilane, the primer layer being a layer in which the volume ratio of the titanium oxide particles to the binder resin (the volume of the titanium oxide particles with respect to the volume of the binder resin) is 0.2 or more; a charge generation layer containing a hydroxygallium phthalocyanine crystal described in the Examples of Japanese Patent Application Laid-Open No. 2018-189692 and containing 0.4 mass% or more and 3.0 mass% or less of a compound having the structure represented by the aforementioned formula (A1) in the crystal; and a charge transport layer having an ionization potential of 5.3 eV or more and 5.4 eV or less. However, the aforementioned configuration example is merely an example, and the electrophotographic photosensitive member of the present application is not limited to the aforementioned configuration as long as it satisfies I 1 / 2 ≤0.170 μJ / cm 2 , AR ≤ 0.500, and LR i ≤ 520 V·cm 2 / μJ.

[0181] [Process cartridge and electrophotographic apparatus]

[0182] Figure 8 One example of a schematic configuration of an electrophotographic apparatus including a process cartridge provided with an electrophotographic photosensitive member is shown. In Figure 8 , reference numeral 1 denotes a cylindrical (drum-shaped) electrophotographic photosensitive member and the electrophotographic photosensitive member 1 is rotationally driven in the direction of the arrow around a shaft 2 at a predetermined peripheral speed (process speed).

[0183] The surface of the electrophotographic photosensitive member 1 is charged to a predetermined positive or negative potential by means of a charging unit 3 during rotation. Then, the surface of the charged electrophotographic photosensitive member 1 is irradiated with image exposure light 4 from an exposure unit (not shown) to form an electrostatic latent image corresponding to target image information. The image exposure light 4 is light output from an exposure unit such as a slit exposure or a laser beam scanning exposure, for example, and intensity-modulated in accordance with a time-series electric digital image signal of the target image information.

[0184] An electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1 is developed by using toner accommodated in the developing unit 5 (normal development or reverse development is performed), and a toner image is formed on the surface of the electrophotographic photosensitive member 1. The transfer unit 6 transfers the toner image formed on the surface of the electrophotographic photosensitive member 1 to the transfer material 7. In this case, a bias voltage having a polarity opposite to that of the charge held by the toner is applied to the transfer unit 6 from a bias power source (not shown). Further, when the transfer material 7 is paper, the transfer material 7 is taken out from a paper feed unit (not shown) and fed to a portion between the electrophotographic photosensitive member 1 and the transfer unit 6 in synchronization with the rotation of the electrophotographic photosensitive member 1.

[0185] The transfer material 7 onto which the toner image is transferred from the electrophotographic photosensitive member 1 is separated from the surface of the electrophotographic photosensitive member 1, and then conveyed to the fixing unit 8, a fixing process of the toner image is performed, and printed as an image formation (print, copy) to the outside of the electrophotographic apparatus. The cleaning unit 9 cleans the surface of the electrophotographic photosensitive member 1 after the toner image is transferred to the transfer material 7 by removing adherents such as residual toner (transfer residual toner) and the like. By using a cleanerless system developed in recent years, the transfer residual toner can be directly removed in a developing device or the like. Further, the surface of the electrophotographic photosensitive member 1 is subjected to a charge removing process by using pre-exposure light 10 from a pre-exposure unit (not shown) and then repeatedly used for image formation. Note that when the charging unit 3 is a contact charging unit using a charging roller or the like, the pre-exposure unit is not necessarily required. In the present application, a plurality of components among the aforementioned components such as the electrophotographic photosensitive member 1, the charging unit 3, the developing unit 5, and the cleaning unit 9 or the like can be accommodated in a container that is integrally supported and forms a process cartridge. Further, the process cartridge can be configured to be detachably mounted to a main body of the electrophotographic apparatus. For example, at least one selected from the group consisting of the charging unit 3, the developing unit 5, and the cleaning unit 9 can be integrally supported together with the electrophotographic photosensitive member 1 to form a cartridge. Further, the process cartridge 11 can be detachably mounted to the main body of the electrophotographic apparatus by using a guide unit 12 such as a guide rail or the like in the main body of the electrophotographic apparatus. When the electrophotographic apparatus is a copier or a printer, the image exposure light 4 can be reflected light or transmitted light on a document. Alternatively, the configuration can be such that a document is read by a sensor and converted into a signal, and the image exposure light 4 is light emitted by scanning of a laser beam, driving of an LED array, or driving of a liquid crystal shutter array according to the signal, or the like.

[0186] The electrophotographic photosensitive member 1 of the present application can be widely applied to the field of electrophotographic applications such as a laser beam printer, a CRT printer, an LED printer, a facsimile machine, a liquid crystal printer, and a laser lithography or the like.

[0187] [Examples]

[0188] The present application is described in further detail below by using examples and comparative examples. The present application is not limited by the following examples as long as the gist of the present application is not deviated. Note that in the description of the following examples, "parts" are based on mass unless otherwise specified.

[0189] The film thickness of each layer in the electrophotographic photosensitive member of the examples and comparative examples except for the charge generating layer was obtained by a method using a Fischerscope (trademark), manufactured by Fisher Instruments, or a method of specific gravity conversion based on the mass per unit area. The film thickness of the charge generating layer was obtained as follows. Specifically, a spectrodensitometer (product name: X-Rite 504 / 508, manufactured by X-Rite Inc.) was pressed against the surface of the photosensitive member to measure a Macbeth density value. The film thickness was calculated from the measured Macbeth density value by using a calibration curve obtained in advance from the Macbeth density value and the film thickness value measured by cross-sectional SEM observation.

[0190] <Preparation of coating liquid for conductive layer>

[0191] [Example of production of titanium oxide particles]

[0192] A titanium niobium sulfuric acid solution containing 33.7 parts of titanium in terms of Ti02and 2.9 parts of niobium in terms of Nb205as a base was prepared by using anatase titanium oxide having an average primary particle diameter of 200 nm. Then, 100 parts of the base was dispersed in pure water to produce 1000 parts of a suspension and heated to 60°C. The titanium niobium sulfuric acid solution and 10 mol / L sodium hydroxide were simultaneously added dropwise over 3 hours to make the pH of the suspension 2 to 3. After the total amount was dropped, the pH was adjusted to near neutral and a polyacrylamide-based flocculating agent was added to settle the solid components. The solution was subjected to removal of supernatant, and filtered, washed, and dried at 110°C to obtain an intermediate containing 0.1% by weight of organic matter derived from the flocculating agent in terms of C. The intermediate was calcined in nitrogen at 750°C for 1 hour, and then in air at 450°C to produce titanium oxide particles. The average particle diameter (average primary particle diameter) of the obtained particles was measured by the aforementioned particle diameter measurement method using a scanning electron microscope and was 220 nm.

[0193] [Preparation of coating liquid 1 for conductive layer]

[0194] A coating liquid for conductive layer was prepared by dispersing 50 parts of a phenol aldehyde resin (monomer / oligomer of phenol aldehyde resin) as a binding material (product name: Plyofen J-325, manufactured by DIC corporation, resin solid content: 60%, density after curing: 1.3 g / cm 2) was dissolved in 35 parts of 1-methoxy-2-propanol as a solvent to obtain a solution.

[0195] To the solution, 75 parts of the titanium oxide particles obtained in the production example of titanium oxide particles were added to produce a dispersion medium. The dispersion medium was put into a vertical sand mill using 120 parts of glass beads having an average particle diameter of 1.0 mm, and dispersion treatment was performed for 4 hours under conditions where the dispersion liquid temperature was 23 ± 3°C and the rotation speed was 1,500 rpm (circumferential speed 5.5 m / s) to obtain a dispersion liquid. The glass beads were removed from the dispersion liquid by using a screen. To the dispersion liquid from which the glass beads were removed, 0.01 parts of silicone oil (product name: SH28PAINT additive, manufactured by Dow Corning Toray Co., Ltd.) and 8 parts of silicone resin particles (product name: KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average particle diameter: 2 μm, density: 1.3 g / cm 3 ) were added as a leveling agent and a surface roughness imparting agent, and the dispersion liquid was stirred and dispersed. The dispersion liquid was pressure-filtered by using a PTFE filter paper (product name: PF060, Advantec Toyo Kaisha, Ltd.) to prepare a coating liquid 1 for a conductive layer.

[0196] [Preparation of Coating Liquid 2 for Conductive Layer]

[0197] A coating liquid 2 for a conductive layer was prepared by putting 60 parts of barium sulfate particles covered with tin oxide (product name: Passstran PC1, manufactured by Mitsui Mining & Smelting Co., Ltd.), 15 parts of titanium oxide particles (product name: TITANIX JR, manufactured by TAYCA Co., Ltd.), 43 parts of a resol-type phenol resin (product name: PHENOLITE J-325, manufactured by DIC corporation, solid content: 70 mass%), 0.015 parts of silicone oil (product name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.), 3.6 parts of silicone resin particles (product name: Tospearl 120, manufactured by Momentive Performance Materials Japan LLC), 50 parts of 2-methoxy-1-propanol, and 50 parts of methanol into a ball mill and performing dispersion treatment for 20 hours.

[0198] [Preparation of Coating Liquid 3 for Conductive Layer]

[0199] First, 100 parts of zinc oxide particles (average primary particle diameter: 50 nm, specific surface area: 19 m 2 / g, powder resistance: 1.0 x 10 7The surface-treated zinc oxide particles were obtained by mixing 100 parts of the aforementioned surface-treated zinc oxide particles, 12 parts of the aforementioned surface-treated titanium oxide particles, 30 parts of a blocked isocyanate compound represented by the following formula (A2) (product name: Sumidur 3175, solid content: 75 mass%, manufactured by Sumitomo Bayer Urethane Co., Ltd.), 15 parts of a polyvinyl butyral resin (product name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.), and 1 part of 2,3,4-trihydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) in a mixed solvent of 70 parts of methyl ethyl ketone and 70 parts of cyclohexanone to prepare a dispersion liquid.

[0200] Next, 100 parts of titanium oxide particles (product name: JR-405, average primary particle diameter: 210 nm, manufactured by TAYCA Co., Ltd.) were mixed with 500 parts of toluene and stirred, 0.75 parts of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane was added, and the mixture was stirred for 2 hours. Thereafter, the toluene was distilled off under reduced pressure and the mixture was dried at 120°C for 3 hours to obtain surface-treated titanium oxide particles.

[0201] Subsequently, 100 parts of the aforementioned surface-treated zinc oxide particles, 12 parts of the aforementioned surface-treated titanium oxide particles, 30 parts of a blocked isocyanate compound represented by the following formula (A2) (product name: Sumidur 3175, solid content: 75 mass%, manufactured by Sumitomo Bayer Urethane Co., Ltd.),

[0202]

[0203] 15 parts of a polyvinyl butyral resin (product name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.), and 1 part of 2,3,4-trihydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to a mixed solvent of 70 parts of methyl ethyl ketone and 70 parts of cyclohexanone to prepare a dispersion liquid.

[0204] The dispersion liquid was subjected to a dispersion treatment in a vertical sand mill at a rotation speed of 1,500 rpm for 3 hours in an atmosphere at 23°C by using glass beads having an average particle diameter of 1.0 mm. After the dispersion treatment, the glass beads were removed from the obtained dispersion liquid by using a screen, and 7 parts of crosslinked polymethyl methacrylate particles (product name: SSX-103, average particle diameter: 3 μm, Sekisui Chemical Co., Ltd.) and 0.01 parts of silicone oil (product name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.) were added, and the dispersion liquid was stirred to prepare a coating liquid 3 for a conductive layer.

[0205] [Preparation of coating liquid 4 for conductive layer]

[0206] First, 100 parts of zinc oxide (average primary particle diameter: 70 nm, specific surface area: 15 m 2 / g, manufactured by TAYCA Co., Ltd.) was mixed with 500 parts of toluene while stirring. To this mixture, 1.25 parts of a silane coupling agent (product name: KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a surface treatment agent and mixed for 2 hours while stirring. Thereafter, toluene was distilled off under reduced pressure, and the mixture was dried at 150°C for 2 hours to obtain surface-treated zinc oxide particles.

[0207] Then, 60 parts of the aforementioned surface-treated zinc oxide particles, 13.5 parts of a blocked isocyanate compound represented by the aforementioned formula (A2) (product name: Sumidur 3175, solid content: 75 mass%, manufactured by Sumitomo Bayer Urethane Co., Ltd.), and 15 parts of a polyvinyl butyral resin (product name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) were added to 85 parts of methyl ethyl ketone to prepare a dispersion liquid.

[0208] The dispersion liquid was subjected to dispersion treatment in a vertical sand mill at a rotation speed of 1,500 rpm for 2 hours under an atmosphere of 23°C by using glass beads having an average particle diameter of 1.0 mm. After the dispersion treatment, the glass beads were removed from the obtained dispersion liquid by using a screen, and 0.005 parts of dioctyltin dilaurate and 3.4 parts of silicone resin particles (product name: Tospearl 130, manufactured by GE Toshiba Silicones Co., Ltd.) were added as a catalyst to obtain a coating liquid 4 for conductive layer.

[0209] [Preparation of coating liquid 5 for conductive layer]

[0210] First, 50 parts of titanium oxide powder covered with tin oxide containing 10% antimony oxide, 25 parts of resol-type phenol resin, 20 parts of methyl cellosolve, 5 parts of methanol, and 0.002 parts of silicone oil (copolymer of polydimethylsiloxane and polyoxyalkylene, average molecular weight: 3,000) were subjected to dispersion treatment in a vertical sand mill at a rotation speed of 1,500 rpm for 2 hours under an atmosphere of 23°C by using glass beads having an average particle diameter of 1.0 mm. After the dispersion treatment, the glass beads were removed from the obtained dispersion liquid by using a screen, and a coating liquid 5 for conductive layer was prepared.

[0211] [Preparation of coating liquid for base coat layer]

[0212] Preparation of coating liquid 1 for primer layer

[0213] First, 100 parts of rutile titanium oxide particles (product name: MT-600B, average primary particle diameter: 50 nm, manufactured by TAYCA Co., Ltd.) were mixed with 500 parts of toluene and stirred, and 5.0 parts of vinyltrimethoxysilane (product name: KBM-1003, manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and the mixture was stirred for 8 hours. Thereafter, the toluene was distilled off under reduced pressure, and the mixture was dried at 120°C for 3 hours to obtain rutile titanium oxide particles surface-treated with vinyltrimethoxysilane.

[0214] Next, 18 parts of the aforementioned rutile titanium oxide particles surface-treated with vinyltrimethoxysilane, 4.5 parts of N-methoxymethylated nylon 6 (product name: TORESIN EF-30T, manufactured by Nagase Chemtex Corporation), and 1.5 parts of a copolymer nylon resin (product name: Amilan (trademark) CM8000, manufactured by Toray Industries, Inc.) were added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion liquid. The dispersion liquid was subjected to dispersion treatment in a vertical sand mill for 5 hours by using glass beads having a diameter of 1.0 mm to prepare coating liquid 1 for a primer layer.

[0215] Preparation of coating liquid 2 for primer layer

[0216] A solution obtained by dissolving 25 parts of N-methoxymethylated nylon 6 (product name: TORESIN EF-30T, manufactured by Nagase Chemtex Corporation) in 480 parts of a methanol / n-butanol = 2 / 1 mixed solution (heating dissolution at 65°C) was cooled. Thereafter, the solution was filtered by using a membrane filter (trade name: FP-022, pore diameter: 0.22 μm, manufactured by Sumitomo Electric Industries, Ltd.) to prepare coating liquid 2 for a primer layer.

[0217] Preparation of coating liquid 3 for primer layer

[0218] First, 1 part by mass of a compound represented by the following formula (A3),

[0219]

[0220] 0.2 parts by mass of a polyvinyl butyral resin (product name: S-LEC KS5, manufactured by Sekisui Chemical Co., Ltd.) and 0.0005 parts by mass of dioctyltin laurate were dissolved in a mixed solvent of 15 parts by mass of methoxypropanol and 15 parts by mass of tetrahydrofuran. A solid content equivalent to 1.3 parts by mass of a blocked isocyanate resin (product name: DURANATE SBN-70D, manufactured by Asahi Kasei Corporation) was added to the solution, and coating liquid 3 for a primer layer was prepared.

[0221] [Preparation of Coating Liquid 4 for a Primer Layer]

[0222] First, 1 part by mass of a compound represented by the following formula (A4),

[0223]

[0224] 0.2 parts by mass of a polyvinyl butyral resin (S-LEC KS5, manufactured by Sekisui Chemical Co., Ltd.) and 0.0005 parts by mass of dioctyltin laurate were dissolved in a mixed solvent of 15 parts by mass of methoxypropanol and 15 parts by mass of tetrahydrofuran. A solid content equivalent to 1.3 parts by mass of a blocked isocyanate resin (product name: DURANATE SBN-70D, manufactured by Asahi Kasei Corporation) was added to the solution, and coating liquid 4 for a primer layer was prepared.

[0225] [Preparation of Coating Liquid 5 for a Primer Layer]

[0226] A solution obtained by dissolving 5 parts of a 6-66-610-12 quaternary polyamide copolymer in 95 parts of a methanol / n-butanol = 14 / 5 mixed solution (heating dissolution was performed at 65°C) was cooled. Thereafter, the solution was filtered by using a membrane filter (trade name: FP-022, pore size: 0.22 μm, manufactured by Sumitomo Electric Industries, Ltd.) to prepare coating liquid 5 for a primer layer.

[0227] [Preparation of Coating Liquid 6 for a Primer Layer]

[0228] Coating liquid 6 for a primer layer was prepared by dissolving 30 parts of a titanium chelate (product name: TC-750, manufactured by Matsumoto Pharmaceutical Manufacture Co.) and 17 parts of a silane coupling agent (product name: KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) in 117 parts of 2-propanol.

[0229] Preparation of coating liquid for charge generation layer

[0230] [Synthesis Example 1]

[0231] In an atmosphere of nitrogen stream, 5.46 parts of phthalonitrile and 45 parts of α-chloronaphthalene were put into a reaction vessel, and then heated to a temperature of 30°C, and maintained at that temperature. Next, at that temperature (30°C), 3.75 parts of gallium trichloride was put into the reaction vessel. The moisture concentration of the mixed liquid at the time of putting was 150 ppm. Thereafter, the temperature was raised to 200°C. Next, the substances were allowed to react at 200°C for 4.5 hours in an atmosphere of nitrogen stream and then cooled, and when the temperature reached 150°C, the product was filtered. The obtained residue was subjected to dispersion washing at a temperature of 140°C for 2 hours by using N,N-dimethylformamide, and then filtered. The obtained residue was washed with methanol, and then dried, and a chlorogallium phthalocyanine pigment was obtained at a yield of 71%.

[0232] [Synthesis Example 2]

[0233] First, 4.65 parts of the chlorogallium phthalocyanine pigment obtained in Synthesis Example 1 was dissolved in 139.5 parts of concentrated sulfuric acid at 10°C, and the dissolved liquid was added dropwise to 620 parts of ice water with stirring to reprecipitate, and filtered under reduced pressure by using a filter press No. 5C (manufactured by Advantec Co. Ltd.) used as a filter in this case. The obtained wet cake (residue) was subjected to dispersion washing with 2% ammonia water for 20 minutes, and then filtered by using a filter press. Next, the obtained wet cake (residue) was subjected to dispersion washing with ion exchange water, and then repeatedly filtered three times by using a filter press. Finally, freeze drying was performed and a hydroxygallium phthalocyanine pigment (aqueous hydroxygallium phthalocyanine pigment) having a solid content of 23% was obtained at a yield of 97%.

[0234] [Synthesis Example 3]

[0235] First, 6.6 kg of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 2 was dried by using a super-dry dryer (product name: HD-06, frequency (oscillation frequency): 2,455 MHz ± 15 MHz, manufactured by Biocon Japan Ltd.) as follows.

[0236] The aforementioned hydroxygallium phthalocyanine pigment taken out from the filter press was placed as it was in a solid state (aqueous cake having a thickness of 4 cm or less) on a dedicated circular plastic tray, and the dryer was set so that the far infrared was turned off and the temperature of the inner wall of the dryer was 50°C. Then, at the time of microwave irradiation, the vacuum pump and the air release valve were adjusted to adjust the degree of vacuum to 4.0 to 10.0 kPa.

[0237] As a first process, the hydroxygallium phthalocyanine pigment was irradiated with 4.8 kW of microwaves for 50 minutes. Then, the microwaves were temporarily turned off and the exhaust valve was temporarily closed to achieve a high vacuum of 2 kPa or less. At this time, the solid content of the hydroxygallium phthalocyanine pigment was 88%. As a second process, the exhaust valve was adjusted to adjust the degree of vacuum (pressure in the drier) to a value within the aforementioned set value (4.0 to 10.0 kPa). Thereafter, the hydroxygallium phthalocyanine pigment was irradiated with 1.2 kW of microwaves for 5 minutes. The microwaves were temporarily turned off and the exhaust valve was temporarily closed to again achieve a high vacuum of 2 kPa or less. This second process was repeated once more (specifically, a total of twice). At this time, the solid content of the hydroxygallium phthalocyanine pigment was 98%. As a third process, the microwave irradiation was performed similarly to the second process, except that the output of the microwaves was changed from 1.2 kW in the second process to 0.8 kW. This third process was repeated once more (specifically, a total of twice). Further, as a fourth process, the exhaust valve was adjusted to return the degree of vacuum to a value within the aforementioned set value (4.0 to 10.0 kPa). Thereafter, the hydroxygallium phthalocyanine pigment was irradiated with 0.4 kW of microwaves for 3 minutes. The microwaves were temporarily turned off and the exhaust valve was temporarily closed to again achieve a high vacuum of 2 kPa or less. This fourth process was repeated 7 times (specifically, a total of 8 times). Thus, 1.52 kg of a hydroxygallium phthalocyanine pigment (crystals) having a water content of 1% or less was obtained in a total of 3 hours.

[0238] [Synthesis Example 4]

[0239] First, 5.0 g of phthalonitrile and 2.0 g of titanium tetrachloride were heated and stirred in 100 g of a-chloronaphthalene at 200°C for 3 hours, and then cooled to 50°C. The crystals precipitated thereby were filtered and a paste of dichlorotitanium phthalocyanine was obtained. Next, the paste was stirred and washed in 100 mL of N,N-dimethylformamide heated to 100°C, and then washed repeatedly twice with 100 mL of methanol at 60°C, and then filtered. The obtained paste was further stirred in 100 mL of deionized water at 80°C for 1 hour and filtered, and 4.3 g of a blue titanium oxide phthalocyanine pigment was obtained.

[0240] [Grinding Example 1]

[0241] The hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3, 9 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 subjected to a grinding treatment for 70 hours at a cooling water temperature of 18°C by using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now IMEX Co., Ltd.), disc diameter: 70 mm, number of discs: 5). The grinding treatment was performed under the condition that the discs were rotated at 400 times per minute. The liquid treated as described above was filtered with a filter (product number: N-NO. 125T, pore size: 133 μm, manufactured by NBC Meshtec Inc.) to remove the glass beads. Next, 30 parts of N-methylformamide were added to the liquid. Then, the liquid was filtered and the residue on the filter device was sufficiently washed with tetrahydrofuran. Next, the washed residue was vacuum-dried and 0.45 parts of a hydroxygallium phthalocyanine pigment was obtained. The obtained pigment had strong peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum using CuKα rays. The content of the amide compound (N-methylformamide) represented by the aforementioned formula (Al) in the presumed hydroxygallium phthalocyanine crystal particles was 0.8 mass% with respect to the content of the hydroxygallium phthalocyanine by H-NMR measurement. 1 The content of the amide compound (N-methylformamide) represented by the aforementioned formula (Al) in the presumed hydroxygallium phthalocyanine crystal particles was 0.8 mass% with respect to the content of the hydroxygallium phthalocyanine by H-NMR measurement.

[0242] [Grinding Example 2]

[0243] The titanium oxide phthalocyanine pigment obtained in Synthesis Example 4, 10 parts of tetrahydrofuran, and 15 parts of glass beads having a diameter of 0.9 mm were subjected to a grinding treatment for 48 hours at a cooling water temperature of 18°C by using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now IMEX Co., Ltd.), disc diameter: 70 mm, number of discs: 5). The grinding treatment was performed under the condition that the discs were rotated at 500 times per minute. The liquid treated as described above was filtered with a filter (product number: N-NO. 125T, pore size: 133 μm, manufactured by NBC Meshtec Inc.) to remove the glass beads. Next, 30 parts of tetrahydrofuran were added to the liquid. Then, the liquid was filtered and the residue on the filter device was sufficiently washed with methanol and water. The washed residue was vacuum-dried and 0.45 parts of a titanium oxide phthalocyanine pigment was obtained. The obtained pigment had a strong peak at a Bragg angle 2θ of 27.2°±0.3° in an X-ray diffraction spectrum using CuKα rays.

[0244] [Grinding Example 3]

[0245] By using a ball mill, 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 Co., Ltd.), and 15 parts of glass beads having a diameter of 0.9 mm were subjected to a grinding treatment for 100 hours at room temperature (23°C). In this case, a standard bottle (product name: PS-6, manufactured by Hakuyo Glass Co., Ltd.) was used as a container, and the treatment was performed under conditions in which the container was rotated at 60 times per minute. The liquid treated as described above was filtered with a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec Inc.) to remove the glass beads. Next, 30 parts of N,N-dimethylformamide were added to the liquid. Then, the liquid was filtered and the residue on the filter device was sufficiently washed with tetrahydrofuran. The washed residue was vacuum-dried and 0.48 parts of a hydroxygallium phthalocyanine pigment were obtained. The obtained pigment had peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum using CuKα rays.

[0246] [Preparation of Coating Liquid 1 for Charge Generation Layer]

[0247] By using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now IMEX Co., Ltd.), disc diameter: 70 mm, number of discs: 5), 20 parts of the hydroxygallium phthalocyanine pigment obtained in Grinding Example 1, 10 parts of polyvinyl butyral (product name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.), 190 parts of cyclohexanone, and 482 parts of glass beads having a diameter of 0.9 mm were subjected to a dispersion treatment for 4 hours at a cooling water temperature of 18°C. The dispersion treatment was performed under conditions in which the discs were rotated at 1,800 times per minute. After the glass beads were removed, 444 parts of cyclohexanone and 634 parts of ethyl acetate were added to the dispersion liquid and Coating Liquid 1 for a charge generation layer was prepared.

[0248] [Preparation of Coating Liquid 2 for Charge Generation Layer]

[0249] dispersion treatment was performed under the condition that the disc was rotated at 1,800 times per minute. After the glass beads were removed, 396 parts of cyclohexanone and 527 parts of ethyl acetate were added to the dispersion liquid and Coating Liquid 2 for a charge generation layer was prepared.

[0250] [Preparation of Coating Liquid 3 for a Charge Generation Layer]

[0251] dispersion treatment was performed under the condition that the disc was rotated at 1,800 times per minute. After the glass beads were removed, 396 parts of cyclohexanone and 527 parts of ethyl acetate were added to the dispersion liquid and Coating Liquid 2 for a charge generation layer was prepared.

[0252] [Preparation of Coating Liquid 4 for a Charge Generation Layer]

[0253] A grinding treatment was performed on 0.45 parts of polycarbonate (product name: Iupilon Z-200, manufactured by Mitsubishi Engineering-Plastics Corporation), 2.4 parts of the hydroxygallium phthalocyanine pigment obtained in Grinding Example 3, 56 parts of tetrahydrofuran, and 300 parts of stainless steel balls having a diameter of 3.2 mm at room temperature (23°C) in a ball mill in which the container was rotated at 120 times per minute, by using a standard bottle (product name: PS-6, manufactured by Hakuyo Glass Co., Ltd.). After the stainless steel balls were removed, 2.25 parts of polycarbonate (product name: Iupilon Z-200, manufactured by Mitsubishi Engineering-Plastics Corporation) was dissolved in 46.1 parts of tetrahydrofuran, and this solution was added to the aforementioned hydroxygallium phthalocyanine slurry. Then, a dispersion treatment was performed on 300 parts of this slurry and 450 parts of glass beads having a diameter of 0.9 mm at a cooling water temperature of 18°C for 10 minutes by using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now IMEX Co., Ltd.), disc diameter: 70 mm, number of discs: 5). The dispersion treatment was performed under conditions in which the discs were rotated at 1,800 times per minute. The glass beads were removed from the dispersion liquid and Coating Liquid 4 for a charge generation layer was prepared.

[0254] [Preparation of Coating Liquid 5 for a Charge Generation Layer]

[0255] A dispersion treatment was performed on 10 parts of a triazo pigment represented by the following formula (CGM-1),

[0256]

[0257] 5 parts of a phenoxy resin (product name: PKHH, manufactured by Union Carbide Corporation), 5 parts of a polyvinyl butyral resin (product name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.), 100 parts of cyclohexanone, and 200 parts of glass beads having a diameter of 0.9 mm at a cooling water temperature of 18°C for 24 hours by using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now IMEX Co., Ltd.), disc diameter: 70 mm, number of discs: 5). The dispersion treatment was performed under conditions in which the discs were rotated at 1,800 times per minute. After the glass beads were removed, 200 parts of 1,4-dioxane was added to the dispersion liquid and Coating Liquid 5 for a charge generation layer was prepared.

[0258] [Preparation of coating liquid 6 for charge generation layer]

[0259] By using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now IMEX Co., Ltd.), disc diameter: 70 mm, number of discs: 5), 9 parts of titanyl phthalocyanine having strong peaks at Bragg angles 2Θ of 9.6°±0.2°, 24.0°±0.2° and 27.2°±0.2° in an X-ray diffraction spectrum using CuKα line, 11 parts of polyvinyl butyral (product name: BX-55, manufactured by Sekisui Chemical Co., Ltd.), 90 parts of a mixed solvent of 2-butanone and cyclohexanone, and 200 parts of glass beads having a diameter of 0.9 mm were subjected to dispersion treatment for 4 hours at a cooling water temperature of 18°C. The dispersion treatment was performed under the condition that the discs were rotated at 1,800 times per minute. After the dispersion treatment, the glass beads were removed from the dispersion liquid and a coating liquid 6 for charge generation layer was prepared.

[0260] [Preparation of coating liquid 7 for charge generation layer]

[0261] By using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now IMEX Co., Ltd.), disc diameter: 70 mm, number of discs: 5), 6 parts of titanyl phthalocyanine having strong peaks at Bragg angles 2Θ of 9.6°±0.2°, 24.0°±0.2° and 27.2°±0.2° in an X-ray diffraction spectrum using CuKα line, 3 parts of titanyl phthalocyanine having strong peaks at Bragg angles 2Θ of 7.6°±0.2°, 25.3°±0.2° and 28.6°±0.2° in an X-ray diffraction spectrum using CuKα line, 11 parts of polyvinyl butyral (product name: BX-55, manufactured by Sekisui Chemical Co., Ltd.), 90 parts of a mixed solvent of 2-butanone and cyclohexanone, and 200 parts of glass beads having a diameter of 0.9 mm were subjected to dispersion treatment for 4 hours at a cooling water temperature of 18°C. The dispersion treatment was performed under the condition that the discs were rotated at 1,800 times per minute. After the dispersion treatment, the glass beads were removed from the dispersion liquid and a coating liquid 7 for charge generation layer was prepared.

[0262] [Preparation of coating liquid 1 for charge transport layer]

[0263] As the charge transport substance, 40 parts of a charge transport substance having an ionization potential of 5.4 eV and represented by the following formula (A5),

[0264]

[0265] 60 parts of a charge transporting substance having an ionization potential of 5.3 eV and represented by the following formula (A6),

[0266]

[0267] and 100 parts of polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering-Plastics Corporation) were dissolved in 225 parts of o-xylene / 375 parts of methyl benzoate / 150 parts of dimethoxymethane to prepare a coating solution 1 for a charge transporting layer.

[0268] [Preparation of a coating solution 2 for a charge transporting layer]

[0269] As the charge transporting substance, 100 parts of a charge transporting substance having an ionization potential of 5.5 eV and represented by the following formula (A7)

[0270]

[0271] and 100 parts of polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering-Plastics Corporation) were dissolved in 225 parts of o-xylene / 375 parts of methyl benzoate / 150 parts of dimethoxymethane to prepare a coating solution 2 for a charge transporting layer.

[0272] [Preparation of a coating solution 3 for a charge transporting layer]

[0273] As the charge transporting substance, 100 parts of a charge transporting substance having an ionization potential of 5.5 eV and represented by the following formula (A8)

[0274]

[0275] and 100 parts of polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering-Plastics Corporation) were dissolved in 225 parts of o-xylene / 375 parts of methyl benzoate / 150 parts of dimethoxymethane to prepare a coating solution 3 for a charge transporting layer.

[0276] [Preparation of a coating solution 4 for a charge transporting layer]

[0277] As the charge transporting substance, 100 parts of a charge transporting substance having an ionization potential of 5.5 eV and represented by the following formula (A9)

[0278]

[0279] and 100 parts of polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering-Plastics Corporation) were dissolved in 225 parts of o-xylene / 375 parts of methyl benzoate / 150 parts of dimethoxymethane to prepare a coating solution 4 for a charge transport layer.

[0280] [Preparation of Coating Solution 5 for Charge Transport Layer]

[0281] As the charge transport substance, 90 parts of a charge transport substance having an ionization potential of 5.35 eV and represented by the following formula (A10)

[0282]

[0283] and 100 parts of a polyarylate resin having a weight average molecular weight of 100,000 were dissolved in a mixed solvent of 300 parts of dimethoxymethane and 700 parts of chlorobenzene to prepare a coating solution 5 for a charge transport layer.

[0284]

[0285] and a structural unit represented by the following formula (A12)

[0286]

[0287] and 100 parts of polycarbonate (product name: Iupilon Z-200, manufactured by Mitsubishi Engineering-Plastics Corporation) were dissolved in 630 parts of monochlorobenzene to prepare a coating solution 6 for a charge transport layer.

[0288] [Preparation of Coating Solution 7 for Charge Transport Layer]

[0289] As the charge transport substance, 50 parts of a charge transport substance represented by the following formula (A14)

[0290]

[0291] and 100 parts of polycarbonate (product name: Iupilon Z-200, manufactured by Mitsubishi Engineering-Plastics Corporation) were dissolved in 630 parts of monochlorobenzene to prepare a coating solution 6 for a charge transport layer.

[0292] [Preparation of Coating Solution 7 for Charge Transport Layer]

[0293] As the charge transport substance, 50 parts of a charge transport substance represented by the following formula (A14)

[0294]

[0295] A polycarbonate resin having a terminal structural formula derived from p-tert-butylphenol, 100 parts, containing structural units represented by the following formula (A15)

[0296]

[0297] and structural units represented by the following formula (A16)

[0298]

[0299] A polycarbonate resin having a terminal structural formula derived from p-tert-butylphenol, 100 parts, containing structural units represented by the foregoing formula (A15) and structural units represented by the foregoing formula (A16) as repeating units in a ratio of 51 mol% / 49 mol% and 0.05 parts of a silicone oil (product name: KF96, manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 640 parts of a mixed solvent of tetrahydrofuran / toluene (mass ratio 8 / 2) to prepare a coating liquid 8 for a charge transport layer.

[0300] [Preparation of a coating liquid 8 for a charge transport layer]

[0301] As a charge transport substance, 25 parts of a charge transport substance represented by the foregoing formula (A6) and 25 parts of a charge transport substance represented by the following formula (A17)

[0302]

[0303] A polycarbonate resin having a terminal structural formula derived from p-tert-butylphenol, 100 parts, containing structural units represented by the foregoing formula (A15) and structural units represented by the foregoing formula (A16) as repeating units in a ratio of 51 mol% / 49 mol% and 0.05 parts of a silicone oil (product name: KF96, manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 640 parts of a mixed solvent of tetrahydrofuran / toluene (mass ratio 8 / 2) to prepare a coating liquid 8 for a charge transport layer.

[0304] [Preparation of a coating liquid 9 for a charge transport layer]

[0305] As a charge transport substance, 10 parts of a charge transport substance represented by the foregoing formula (A6) and 10 parts of a polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering-Plastics Corporation) were dissolved in 39 parts of tetrahydrofuran to prepare a coating liquid 9 for a charge transport layer.

[0306] [Preparation of a coating liquid 10 for a charge transport layer]

[0307] As a charge transporting substance, 30 parts of 4,4',4"-tris(5-tert-butyl-2- hydroxyphenyl)valeric acid, 30 parts of polycarbonate (product name: Iupilon Z-300, manufactured by Mitsubishi Engineering-Plastics Corporation) and 1 part of tin oxide fine particles were dissolved in 200 parts of dioxolane to prepare a coating solution 10 for a charge transporting layer.

[0308] [Preparation of a coating solution 11 for a charge transporting layer]

[0309] By dissolving 50 parts of a charge transporting substance represented by the following formula (A18),

[0310]

[0311] 50 parts of polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering-Plastics Corporation) and 1.5 parts of a dicyano compound represented by the following formula (A19)

[0312]

[0313] in 4 parts of di-t-butylhydroxytoluene and dichloromethane to prepare a coating solution 11 for a charge transporting layer.

[0314] [Preparation of a coating solution 12 for a charge transporting layer]

[0315] By dissolving 27.0 parts of DEH (p-diethylamino) benzaldehyde diphenylhydrazone), 37.9 parts of bisphenol A (Bayer AG) and 0.48 parts of azoxanthene in a mixed solvent of tetrahydrofuran and 1,4-dioxane, a coating solution 12 for a charge transporting layer was prepared.

[0316] [Preparation of a coating solution 1 for a single-layer photosensitive layer]

[0317] By using a paint shaker (manufactured by Toyo Seiki Seisaku-sho, Ltd.), 5 parts of a metal-free phthalocyanine, 10 parts of a charge transporting substance (hole transporting substance) represented by the following formula (A20),

[0318]

[0319] 3 parts of a charge transporting substance (electron transporting substance) represented by the following formula (A21),

[0320]

[0321] 10 parts of polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering-Plastics Corporation), 80 parts of tetrahydrofuran, and 250 parts of glass beads having a diameter of 0.9 mm were subjected to a grinding treatment for 10 hours. In this case, a standard bottle (product name: PS-6, manufactured by Hakuyo Glass Co., Ltd.) was used as the container. The liquid subjected to the grinding treatment as described above was filtered with a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec Inc.) to remove the glass beads and a coating liquid 1 for a single-layer photosensitive layer was prepared.

[0322] <Manufacture of electrophotographic photosensitive member>

[0323] (Photosensitive member production example 1)

[0324] An aluminum cylinder (JIS-A3003, aluminum alloy) having a length of 260.5 mm and a diameter of 30 mm was obtained as the support body by a manufacturing method including an extrusion process and a drawing process.

[0325] The coating liquid 1 for the conductive layer was dip-coated onto the support body to form a coating film, and the coating film was heat-dried at 150°C for 20 minutes to form a conductive layer having a film thickness of 19 μm.

[0326] Next, the coating liquid 1 for the undercoat layer was dip-coated onto the conductive layer to form a coating film, and the coating film was heat-dried at 100°C for 10 minutes to form an undercoat layer having a film thickness of 2.2 μm.

[0327] Then, the coating liquid 1 for the charge generation layer was dip-coated onto the undercoat layer to form a coating film, and the coating film was heat-dried at 100°C for 10 minutes to form a charge generation layer having a film thickness of 140 μm.

[0328] Next, the coating liquid 1 for the charge transport layer was dip-coated onto the charge generation layer to form a coating film, and the coating film was heat-dried at a temperature of 120°C for 60 minutes to form a charge transport layer having a film thickness of 17 μm.

[0329] The heat treatment of the coating film for each layer was performed by using an oven set to the respective temperatures. Thereby, a photosensitive member 1 in a cylindrical (drum) shape was manufactured.

[0330] I 1 / 2 [μJ·cm 2 ], AR, LR i and V r were obtained in the aforementioned method. The results together with the constitution of the photosensitive member production example 1 are shown in Table 1.

[0331] Note that in Tables 1 and 2, "CPL" means "conductive layer", "1", "2", "3", "4", and "5" in the CPL coating liquid No. mean "coating liquid for conductive layer 1", "coating liquid for conductive layer 2", "coating liquid for conductive layer 3", "coating liquid for conductive layer 4", and "coating liquid for conductive layer 5", respectively. Further, "UCL" means "undercoat layer" and "1", "2", "3", "4", "5", and "6" in the UCL coating liquid No. mean "coating liquid for undercoat layer 1", "coating liquid for undercoat layer 2", "coating liquid for undercoat layer 3", "coating liquid for undercoat layer 4", "coating liquid for undercoat layer 5", and "coating liquid for undercoat layer 6", respectively. "CGL" means "charge generation layer" and "1", "2", "3", "4", "5", "6", and "7" in the CGL coating liquid No. mean "coating liquid for charge generation layer 1", "coating liquid for charge generation layer 2", "coating liquid for charge generation layer 3", "coating liquid for charge generation layer 4", "coating liquid for charge generation layer 5", "coating liquid for charge generation layer 6", and "coating liquid for charge generation layer 7", respectively. "CTL" means "charge transport layer" and "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", and "12" in the CTL coating liquid No. mean "coating liquid for charge transport layer 1", "coating liquid for charge transport layer 2", "coating liquid for charge transport layer 3", "coating liquid for charge transport layer 4", "coating liquid for charge transport layer 5", "coating liquid for charge transport layer 6", "coating liquid for charge transport layer 7", "coating liquid for charge transport layer 8", "coating liquid for charge transport layer 9", "coating liquid for charge transport layer 10", "coating liquid for charge transport layer 11", and "coating liquid for charge transport layer 12", respectively. "Forming a film with a thickness of 38 μm by using single-layer photosensitive layer coating liquid 1" means forming "single-layer photosensitive layer coating liquid 1" on an aluminum cylinder with a film thickness of 38 μm.

[0332] Further, in the case of dip coating by using CPL coating liquid Nos. 1 to 5 in Tables 1 and 2, the drying temperature and drying time are as follows.

[0333] • CPL coating liquid No. 1: drying temperature 150°C, drying time 20 minutes

[0334] • CPL coating liquid No. 2: drying temperature 145°C, drying time 60 minutes

[0335] • CPL coating liquid No. 3: drying temperature 170°C, drying time 20 minutes

[0336] • CPL coating liquid No. 4: drying temperature 170°C, drying time 40 minutes

[0337] • CPL Coating Liquid No. 5: drying temperature 140°C, drying time 30 minutes

[0338] Further, the drying temperature and drying time in the case where dip coating is performed by using the UCL Coating Liquids Nos. 1 to 6 in Table 1 and Table 2 are as follows.

[0339] • UCL Coating Liquid No. 1: drying temperature 100°C, drying time 10 minutes

[0340] • UCL Coating Liquid No. 2: drying temperature 100°C, drying time 10 minutes

[0341] • UCL Coating Liquid No. 3: drying temperature 160°C, drying time 30 minutes

[0342] • UCL Coating Liquid No. 4: drying temperature 160°C, drying time 30 minutes

[0343] • UCL Coating Liquid No. 5: drying temperature 100°C, drying time 10 minutes

[0344] • UCL Coating Liquid No. 6: drying temperature 120°C, drying time 30 minutes

[0345] Further, the drying temperature and drying time in the case where dip coating is performed by using the CGL Coating Liquids Nos. 1 to 7 in Table 1 and Table 2 are as follows.

[0346] • CGL Coating Liquid No. 1: drying temperature 100°C, drying time 10 minutes

[0347] • CGL Coating Liquid No. 2: drying temperature 100°C, drying time 10 minutes

[0348] • CGL Coating Liquid No. 3: drying temperature 100°C, drying time 10 minutes

[0349] • CGL Coating Liquid No. 4: drying temperature 125°C, drying time 2 minutes

[0350] • CGL Coating Liquid No. 5: drying temperature 100°C, drying time 10 minutes

[0351] • CGL Coating Liquid No. 6: drying temperature 100°C, drying time 15 minutes

[0352] • CGL Coating Liquid No. 7: drying temperature 100°C, drying time 15 minutes

[0353] Further, the drying temperature and drying time in the case where dip coating is performed by using the CTL Coating Liquids Nos. 1 to 12 in Table 1 and Table 2 are as follows.

[0354] • CTL coating liquid No. 1: drying temperature 125°C, drying time 30 minutes

[0355] • CTL coating liquid No. 2: drying temperature 125°C, drying time 30 minutes

[0356] • CTL coating liquid No. 3: drying temperature 125°C, drying time 30 minutes

[0357] • CTL coating liquid No. 4: drying temperature 125°C, drying time 30 minutes

[0358] • CTL coating liquid No. 5: drying temperature 125°C, drying time 30 minutes

[0359] • CTL coating liquid No. 6: drying temperature 125°C, drying time 30 minutes

[0360] • CTL coating liquid No. 7: drying temperature 125°C, drying time 30 minutes

[0361] • CTL coating liquid No. 8: drying temperature 125°C, drying time 30 minutes

[0362] • CTL coating liquid No. 9: drying temperature 120°C, drying time 30 minutes

[0363] • CTL coating liquid No. 10: drying temperature 125°C, drying time 30 minutes

[0364] • CTL coating liquid No. 11: drying temperature 125°C, drying time 30 minutes

[0365] • CTL coating liquid No. 12: drying temperature 100°C, drying time 60 minutes

[0366] Further, the drying temperature and drying time in the case where dip coating was performed by using the "single-layer photosensitive layer coating liquid 1" in photosensitive member production example 79 of Table 2 were as follows.

[0367] • Drying temperature 130°C, drying time 30 minutes

[0368] Further, "-" in Table 1 and Table 2 means that the corresponding layer was not formed.

[0369] (Photosensitive member production examples 2 to 83)

[0370] The photosensitive members 2 to 83 were produced in the same manner as in Photosensitive Member Production Example 1, except that the conductive layer, the undercoat layer, the charge generation layer, and the charge transport layer were changed as shown in Tables 1 and 2 in Photosensitive Member Production Example 1. Note that the heating treatment of the coating films of the conductive layer, the undercoat layer, the charge generation layer, and the charge transport layer was performed individually by using an oven set to the respective temperatures for the respective times as described above.

[0371] Further, I 1 / 2 [μJ·cm 2 ], AR, LR i , and V r of the photosensitive members 2 to 83 were obtained in the same manner as in Photosensitive Member Production Example 1. The results thereof together with the constitution of the photosensitive members Production Examples 2 to 83 are shown in Tables 1 and 2.

[0372]

[0373]

[0374]

[0375]

[0376] [Assessment]

[0377] Examples 1 to 50 and Comparative Examples 1 to 33 were assessed by using the aforementioned Photosensitive Member Production Examples 1 to 83. The assessment was performed as follows. The results thereof are shown in Tables 3 and 4.

[0378] [Assessment Device]

[0379] A laser beam printer (product name: Laser Jet Enterprise M609dn) manufactured by Hewlett-Packard Company was prepared as an assessment electrophotographic device and was modified so that the processing speed, the voltage applied to the charging roller, the image exposure amount, and the voltage applied to the developing roller could be adjusted and measured.

[0380] With respect to the output of the image, each drum of the aforementioned Photosensitive Member Production Examples 1 to 83 was mounted to the aforementioned laser printer cartridge and a monochrome image was output.

[0381] [Confirmation of Whether the Analog Gray Scale Property Was Maintained]

[0382] The dark area potential was set to 450 V and an exposure amount was obtained which gave a surface potential after exposure of 225 V. The absolute value of the difference between the dark area potential 450 V and the surface potential in the case where the surface of the photosensitive member was irradiated with light at 10 times the aforementioned exposure amount was determined as ΔV. In order to make the gradation simulation on the EV curve consistent, an exposure amount which gave a surface potential after exposure of 450 - 0.99 ΔV was set as the image exposure amount. An apparatus in which a potential probe (product name: model 6000B-8, manufactured by Trek Japan) was installed to the developing position of the process cartridge was used for the measurement of the surface potential of the photosensitive member at the time of potential setting, and measurement was performed by using a surface potential meter (product name: model 344, manufactured by Trek Japan).

[0383] Next, evaluation dither patterns were prepared. Figure 9A to Figure 9E Examples in which the area ratio was 0% ( Figure 9A ), 25% ( Figure 9B ), 50% ( Figure 9C ), 75% ( Figure 9D ), and 100% ( Figure 9E ) in a line-growth dither pattern in which the resolution was 600 dpi and the line number was 150 lines were prepared. In actual measurement, an image of 32 gradations of area ratio (33 patterns including the case of solid white with an area ratio of 0%) was output by equally dividing the entire range of area ratio into 32 segments. In this case, step interpolation was performed to less than one pixel by using pulse width modulation (PWM). In addition to the line number of 150 lines, a similar line-growth dither pattern of 32 gradations was prepared for a line number of 600 lines.

[0384] When the image exposure amount set in the aforementioned method was fixed, the voltage applied to the charging roller and the developing roller was adjusted so that the absolute value V back of the difference between the dark area potential and the developing potential and the absolute value V cont of the difference between the developing potential and the exposure potential were V back = 200 V and V cont = 200 V, respectively, and the aforementioned line-growth dither pattern of 32 gradations of line number of 600 was output. The toner concentration of each gradation in the output image was measured by using a reflection densitometer (product name: RD-918, manufactured by Macbeth Corporation). The measured values were plotted in a graph in which the horizontal axis represents the area ratio and the vertical axis represents a value obtained by subtracting the concentration of the solid white part with an area ratio of 0% from the concentration data of each gradation and by normalizing the resulting value by using the concentration with an area ratio of 100%. Figure 10 ​​​​​​​​​​A graph in the case where measurement was performed at a processing speed of 300 mm / s for the aforementioned photosensitive member production example 1 was shown as an example. When the normalized concentration at an area ratio of 60% in the graph was within the range of 0.8 ± 0.05, it was judged that the analog gradation property was maintained. When the normalized concentration was higher than 0.85, the image exposure amount was reduced by about 10% and the area ratio normalized concentration graph was measured again. Meanwhile, when the normalized concentration was lower than 0.75, the image exposure amount was increased by about 10% and the area ratio normalized concentration graph was measured again. The aforementioned operation was repeated until the normalized concentration at an area ratio of 60% was within the range of 0.8 ± 0.05, and the final image exposure amount was determined.

[0385] <Evaluation of digital gradation property>

[0386] The processing speed was set to 200 mm / s, the dark area potential was set to 450 V, and the development potential was set to 250 V, and an image of a solid pattern was output at the aforementioned image exposure amount determined in the method in the <confirmation of whether the analog gradation property was maintained>. The concentration of the output image was determined as the concentration-normalized maximum concentration value determined for each photosensitive member production example to be evaluated.

[0387] Next, the processing speed was set to 300 mm / s, 400 mm / s, or 500 mm / s, the dark area potential was set to 450 V, and the development potential was set to 250 V, and an image of a line growth dither pattern of 32 gradations of the aforementioned line number of 150 was output at the image exposure amount determined in the aforementioned method. The toner concentration of each gradation in the output image was measured by using a reflection densitometer (product name: RD-918, manufactured by Macbeth Corporation). The measured values were shown in a graph in which the horizontal axis represents the area ratio, and the vertical axis represents a value obtained by subtracting the concentration of the solid white portion at an area ratio of 0% from the concentration data of each gradation and by normalizing the resulting value by using the aforementioned concentration-normalized maximum concentration value, and the following two numerical values were calculated.

[0388] (i) In the area ratio normalized concentration graph shown in Figure 11 , two points at area ratios of 0% and 50% were connected to each other by a straight line, and the difference from each piece of data of the 16 gradations in the range of 0% to 50% of the area ratio was obtained, and the average value thereof was taken as the "high light gradation property". The closer the value thus obtained to 0, the better the gradation property of the high light portion.

[0389] (ii) In the area ratio normalized concentration graph shown in Figure 11In the area ratio normalized concentration chart shown in the middle, two points of area 50% and 100% are connected to each other by a straight line, and the difference from each data segment of 16 gradations in the range of area ratio 50% to 100% is obtained, and the average thereof is taken as "shadow gradation property". The closer the value thus obtained to 0, the better the gradation property of the shadow portion.

[0390] Evaluation of 6pt hollow character visibility

[0391] The processing speed was set to 300 mm / s, 400 mm / s, or 500 mm / s, the dark area potential was set to 450 V, and the development potential was set to 250 V, and an image of a hollow Japanese kanji character "denkyo" of 6pt, MS Ming font was outputted with the aforementioned image exposure amount determined in <Confirmation of whether the analog gradation property was maintained>. The output image was visually observed, and the 6pt hollow character visibility was evaluated based on the following criteria.

[0392] • Grade A: The hollow "denkyo" character can be clearly read.

[0393] • Grade B: Blur was observed in the hollow "denkyo" character.

[0394] • Grade C: The hollow "denkyo" character was almost indistinguishable.

[0395] • Grade X: The solid black portion of the hollow "denkyo" character was lighter.

[0396] Grades A and B in the aforementioned evaluation were judged to be good 6pt hollow character visibility.

[0397] Evaluation of 3pt character visibility

[0398] The processing speed was set to 300 mm / s, 400 mm / s, or 500 mm / s, the dark area potential was set to 450 V, and the development potential was set to 250 V, and an image of a Japanese kanji character "denkyo" of 3pt, MS Ming font was outputted with the aforementioned image exposure amount determined in <Confirmation of whether the analog gradation property was maintained>. The output image was visually observed, and the 3pt character visibility was evaluated based on the following criteria.

[0399] • Grade A: The "denkyo" character can be clearly read.

[0400] • Grade B: Blur was observed in the "denkyo" character.

[0401] • Grade C: The "denkyo" character was lighter.

[0402] The 3 pt character visibility in which the grades A and B in the foregoing evaluation were judged to be good.

[0403] <Isolated single point reproducibility evaluation>

[0404] The processing speed was set to 300 mm / s, 400 mm / s, or 500 mm / s, the dark area potential was set to 450 V, and the development potential was set to 250 V, and the image exposure amount output in the foregoing in <Confirmation of whether the analog gradation property was maintained> was output Figure 12 The halftone image of 1 dot 4 space. The toner density of the output image was measured by using a reflection densitometer (product name: RD-918, manufactured by Macbeth Corporation), and the isolated single point reproducibility was evaluated based on the following standards.

[0405] • Grade A: The toner density was 0.084 or more.

[0406] • Grade B: The toner density was 0.076 or more and less than 0.084.

[0407] • Grade C: The toner density was 0.059 or more and less than 0.076.

[0408] • Grade D: The toner density was less than 0.059.

[0409] The isolated single point reproducibility in which the grades A and B in the foregoing evaluation were judged to be good.

[0410]

[0411]

[0412]

[0413]

[0414] In recent years, it has been impossible to reduce the laser spot diameter due to the demand for miniaturization and low cost of electrophotographic apparatuses, and it is also necessary to achieve both digital gradation property and analog gradation property in good balance. In such a case, the present application can provide an electrophotographic photosensitive member in which the character quality in low line number halftone and the digital gradation property are improved while maintaining the analog gradation property in high productivity high speed processing, and a process cartridge and an electrophotographic apparatus using the electrophotographic photosensitive member.

[0415] While the present application has been described with reference to example embodiments, it is to be understood that the application is not limited to the disclosed example embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all the modifications and equivalent structures and functions.

Claims

1. An electrophotographic photosensitive member comprising: a support; a primer layer on the support; a charge generating layer on the primer layer; and a charge transporting layer on the charge generating layer, characterized in that the electrophotographic photosensitive member is an organic photosensitive member, the primer layer contains titanium oxide particles whose surface is silane-treated and whose crystal structure is rutile or anatase, the charge generating layer contains an oxotitanium phthalocyanine pigment having a strong peak at a Bragg angle 2 theta of 27.2° ± 0.3° in Cu Kα characteristic X-ray diffraction, and Satisfy I 1 / 2 ≤0.170μJ / cm 2 AR≤0.370 and LR i ≤780V·cm 2 / μJ, where, at charging potential V d For V d The values ​​were obtained according to the NESA-EV curve measurement method at 500V, 23.5°C, and 50%RH relative humidity, where the horizontal axis represents the irradiation exposure I. exp The vertical axis represents the absolute value V of the surface potential after irradiation. exp I exp -V exp In the picture, V in the figure exp The light intensity at =250V is determined by I 1 / 2 express, The figure is in I exp =0.000~3.414·I 1 / 2 Within the range of I exp With V exp The product S=I exp ·V exp The maximum value is determined by S max express, The graph in I exp =0.000~0.100·I 1 / 2 The intersection of the approximate straight line in the range of I exp =(5·I 1 / 2 -0.100)~5·I 1 / 2 The light amount value at the point Q is represented by I i The potential value at the point Q is represented by V i The product of I i and V i is represented by S i =I i ·V i , S i The ratio of S max The ratio of S i / S max is represented by AR = S By dividing V i by I i , the value obtained is represented by LR i = V i / I i , and the measurement method of the NESA-EV curve is performed as follows: (1): the surface potential of the electrophotographic photosensitive member is set to 0 V, (2): the electrophotographic photosensitive member is charged for 0.005 seconds to make the absolute value of the surface potential of the electrophotographic photosensitive member V0, (3) : after 0.02 seconds from the start of charging, the electrified electrophotographic photosensitive member is continuously exposed to light having a wavelength of 805 nm and an intensity of 25 mW / cm 2 for t seconds to change the exposure amount to I exp , (4): The absolute value of the surface potential of the electrophotographic photosensitive member after exposure was measured 0.06 seconds after the start of charging and the measured value is represented by V exp , and the surface potential of the electrophotographic photosensitive member after exposure was measured 0.06 seconds after the start of charging and the measured value is represented by V exp . (5): The operation (1) to (4) is repeated while changing I from 0.000 μJ / cm 2 to 0.850 μJ / cm exp at intervals of 0.001 μJ / cm 2 by changing t, to obtain V 2 corresponding to each value of I exp , and exp ​ (6): V0= 0 and I0= 0 in the operation of (3) exp = 0.000 μJ / cm2 2 exp is called a charging potential V d , and V0is set so that the value of V d becomes 500 V in the case where the operation of (2) is performed,​ where V d , V exp , V i , V0is in V, I exp , I 1 / 2 , I i is in μJ / cm 2 , S, S i , S max is in V·μJ / cm 2 , LR i is in V·cm 2 / μJ.

2. The electrophotographic photosensitive member according to claim 1, wherein the AR and the LR i are AR < 0.370 and LR i ≤ 520 V-cm 2 / μJ.

3. The electrophotographic photosensitive member according to claim 1, wherein the AR is AR < 0.

100.

4. The electrophotographic photosensitive member according to claim 1, wherein the LR i is LR i ≤ 60 V-cm 2 / μJ.

5. The electrophotographic photosensitive member according to claim 1, wherein in the I exp -V exp the value V exp of V 1 / 2 when I exp = 5 · I r is V r ≤ 70 V.

6. The electrophotographic photosensitive member according to claim 5, wherein the V r is V r ≤ 10 V.

7. A process cartridge, characterized by, which integrally supports the electrophotographic photosensitive member according to any one of claims 1 to 6 and at least one unit selected from the group consisting of a charging unit, a developing unit, and a cleaning unit, and the process cartridge is detachably attached to a main body of an electrophotographic apparatus.

8. An electrophotographic apparatus, characterized by, which comprises: the electrophotographic photosensitive member according to any one of claims 1 to 6; a charging unit; an exposure unit; a developing unit; and a transfer unit.

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