Electrophotographic photoreceptor, process cartridge and electrophotographic device

Abstract

To provide an electrophotographic photoreceptor that can maintain an analog harmony in a rapid process and also can show the digital harmony characteristics of a low line number halftone or a high letter quality.SOLUTION: The electrophotographic photoreceptor includes: a supporting body; a charge generation layer on the supporting body; and a charge transfer layer on the charge generation layer, and satisfies the prescription in an EV curve based on a NESA-EV curve measurement technique.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus using the electrophotographic photosensitive member. [Background technology]

[0002] The electrophotographic process involving electrophotographic photoreceptors (hereafter simply referred to as "photoreceptors") mainly consists of four processes: charging, exposure, development, and transfer, with additional processes such as cleaning and pre-exposure added as needed. Among these, the exposure process is the key to forming an electrostatic latent image, as it controls the charge distribution on the photoreceptor and creates the desired potential distribution on the photoreceptor surface.

[0003] In this exposure process, electrophotographic devices use two methods for controlling image density: analog tone and digital tone. Analog tone is a method of expressing density gradations ranging from non-toner-developed areas (so-called solid white) to maximum toner-developed areas (so-called solid black). Analog tone involves adjusting the amount of exposure light to create a multi-level average potential on the photoconductor surface, controlling the amount of toner developed on the photoconductor during the development process. Digital tone, on the other hand, expresses density gradations by controlling the area ratio of a single solid black dot. Therefore, with digital tone, the area illuminated by light is always solid black, and the amount of light emitted is always fixed at its maximum. By minimizing the surface potential of the photoconductor in the illuminated area, the amount of toner developed in the illuminated area is maximized.

[0004] The semiconductor lasers used in recent electrophotographic devices have small spot diameters, so digital gradation methods are mainstream. On the other hand, semiconductor lasers generally have a bell-shaped spot diameter-light quantity distribution. And, 1 / e of the semiconductor laser 2 The diameter is typically several tens of μm to a hundred μm, which is equivalent to the length of one dot of 84 μm, 42 μm, and 21 μm in the images of typical electrophotographic devices with a resolution of 300 dpi, 600 dpi, and 1200 dpi, respectively. Therefore, even when irradiated with the maximum amount of light, there is only 1 / e 2There will be areas that are irradiated with low light intensity outside the diameter. Therefore, even if a digital gradation system is used, both digital gradation and analog gradation are actually mixed, and the relative importance of the two depends on the number of lines used to form the image. The lower the number of lines, the lower the image frequency and the relatively smaller the spot diameter, so it approaches digital gradation, and conversely, the higher the number of lines, the higher the image frequency and the relatively larger the spot diameter, so it approaches analog gradation.

[0005] Electrophotographic photoreceptors used in electrophotographic devices generally have various layers, such as a photosensitive layer, formed on a support. In recent years, organic photoreceptors, in which the main component of the layer formed on the support is a resin, have become popular as electrophotographic photoreceptors from the viewpoints of low cost and high productivity. Among these, organic photoreceptors with a laminated photosensitive layer are mainstream due to their advantages of high sensitivity and diverse material design. A laminated organic photoreceptor is constructed by laminating a charge generation layer containing a charge generation material, such as a photoconductive dye or a photoconductive pigment, and a charge transport layer containing a charge transport material, such as a photoconductive polymer or a photoconductive low-molecular-weight compound.

[0006] However, the charge transport layer of a laminated organic photoreceptor is mainly made of resin, and since the resin itself generally has high electrical resistance, the charge transport layer is likely to trap the charge generated by exposure. Furthermore, at the interface between the charge transport layer and the charge generation layer, the generated charge is also likely to be trapped due to a barrier caused by the difference in energy levels between the two layers. Therefore, laminated organic photoreceptors generally have the problem of a high residual surface potential (hereinafter referred to as "residual charge") even when irradiated with sufficiently strong light. This problem is caused by the amount of exposure I of the photoreceptor. exp [μJ / cm 2 ] and the absolute value of the surface potential at that time V exp This can be confirmed in the graph showing the relationship between the exposure dose I and the charge potential [V] (hereinafter referred to as the "EV curve"). Furthermore, due to the above trapping, in the case of a laminated organic photoreceptor, the exposure dose I when the charge potential is reduced by half is 1 / 2 [μJ / cm 2 ], the linearity of the EV curve is easily impaired in the vicinity.

[0007] The lower the residual voltage and the closer it is to 0V, the higher and more stable the density of a single black dot in digital gradation. On the other hand, the higher the linearity of the EV curve, the more linear the relationship between exposure adjustment and average surface potential becomes, meaning the relationship between toner development amount and exposure amount also approaches linearity, improving analog gradation. Therefore, the problems with the above-mentioned laminated organic photoreceptor, namely, the high residual charge and the poor linearity of the EV curve, can be said to be factors that impair digital gradation and analog gradation, respectively.

[0008] In recent years, pigment-dispersed charge generating layers have been used to increase the sensitivity of organic photoreceptors. In pigment-dispersed charge generating layers, the interface between the pigment dispersed in the resin and the resin further traps charge, making the above-mentioned problems with multilayer organic photoreceptors particularly pronounced. Therefore, it has been difficult for multilayer organic photoreceptors to satisfy all of the requirements of low residual current, linear EV curves, and high sensitivity.

[0009] As described above, to achieve good density gradation characteristics and character quality in the electrophotographic device, which combines digital and analog gradation, it is necessary to set the exposure light amount so that both digital and analog gradation are compatible. However, setting such an exposure light amount is difficult unless the three characteristics (sensitivity, residual voltage, and linearity) mentioned above are satisfied on the EV curve of the layered organic photoreceptor. In particular, when space-saving optical systems and inexpensive laser chips are used to meet the demand for smaller and lower-cost electrophotographic devices, the exposure spot becomes larger, resulting in stronger analog gradation. In such cases, it is difficult to improve low-line-count halftone digital gradation characteristics and character quality while maintaining analog gradation, and a solution is needed through improvements to the layered organic photoreceptor.

[0010] Patent Document 1 describes that a photoreceptor that is highly sensitive yet less susceptible to humidity changes was obtained by forming a charge generation layer using titanyl phthalocyanine with a film thickness of 400 nm. This photoreceptor was charged to a potential of 700 V in absolute value and had a wavelength of 780 nm and an intensity of 0.15 mW / cm. 2It is also described that when irradiated with light of

[0049] , the half-life of the exposure is small, and the change in the exposure potential with respect to the humidity change is small.

[0011] Patent Document 2 describes an image forming method and image forming apparatus that determines the charging potential and image exposure amount depending on the linearity of the EV curve near the half-life exposure, the surface potential value at an exposure amount approximately twice the half-life exposure, and the photosensitive layer thickness. The surface potential at an exposure amount approximately twice the half-life exposure is close to the residual voltage. Therefore, Patent Document 2 can be said to be a method that determines the appropriate image exposure amount using equation (1) in the document based on the linearity of the EV curve and the residual voltage. This allows for the realization of a photoreceptor that maintains high resolution and high-definition reproducibility over a long period of time from the start of use, even when the photosensitive layer thickness is increased for the purpose of extending its life.

[0012] Patent Document 3 describes a photoreceptor that has high linearity near the half-life exposure on the EV curve when the absolute value of the charging potential is 600 V. This allows faithful development of each dot that forms the digital latent image, enabling high-quality images with excellent resolution and gradation to be output at high speed.

[0013] Patent Document 4 describes the exposure dose E required to set the surface potential to -50 [V]. 50 Half-life exposure E 1 / 2 The photoconductors listed are those with a value of 0.25 or more when the residual charge is lower. 50 The smaller the value, the higher the linearity. 1 / 2 is large, which means that the residual voltage on the EV curve is low and highly linear. This results in good surface potential decay characteristics and improves the gradation of the image.

[0014] Patent Document 5 describes a photoreceptor that has high linearity in the range of half-life exposure to ⅕ exposure on the EV curve, which allows for stable reproduction of an electrostatic charge image of a single pixel. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-197237 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-206349 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-195577 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-072522 [Patent Document 5] Japanese Patent Application Laid-Open No. 2001-183852 Summary of the Invention [Problem to be solved by the invention]

[0016] According to the inventors' investigations, none of the electrophotographic photosensitive members and image forming methods described in Patent Documents 1 to 5 have been optimized to satisfy the three characteristics of sensitivity, residual voltage, and linearity on the EV curve. In recent years, due to demands for smaller and lower-cost electrophotographic devices, it has become impossible to reduce the laser spot diameter. Under these circumstances, the problem of how to improve low-screen halftone digital gradation characteristics and character quality while maintaining analog gradation characteristics even in high-speed processes aimed at achieving high productivity has not been solved.

[0017] Therefore, an object of the present invention is to provide an electrophotographic photoreceptor that exhibits low-line halftone digital gradation characteristics and high character quality while maintaining analog gradation characteristics in high-speed processes, and a process cartridge and an electrophotographic apparatus using the electrophotographic photoreceptor. [Means for solving the problem]

[0018] The above object can be achieved by the present invention, which comprises: support, Applicable On the support an undercoat layer, 1. An electrophotographic photoreceptor having a charge generating layer and a charge transport layer on the charge generating layer, the electrophotographic photoreceptor is an organic photoreceptor, the undercoat layer contains titanium oxide particles whose surfaces have been silane-treated and whose crystal structure is rutile or anatase, the charge generating layer is A hydroxygallium phthalocyanine crystal having strong peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in CuKα characteristic X-ray diffraction, and containing 0.4% by mass or more and 3.0% by mass or less of a compound having a structure represented by the following formula (A1): JPEG0007725286000001.jpg3371 (In the above formula (A1), R 0 represents a methyl group, a propyl group, or a vinyl group; Titanyl phthalocyanine crystals with a strong peak at 27.2°±0.3° of the Bragg angle 2θ in CuKα characteristic X-ray diffraction Including, the charge generating layer has an average film thickness of 150 nm or more and 300 nm or less; the charge transport layer contains a charge transport material and a resin, and the content ratio (mass ratio) of the charge transport material to the resin in the charge transport layer is 8:10 to 12:10; At a temperature of 23.5 [°C] and a relative humidity of 50 [%RH], when the charged potential is V d = 500 [V], the horizontal axis is I obtained according to the following <Measurement method of NESA-EV curve> exp and the vertical axis is V exp of I exp -V exp In the graph, the light quantity when V exp = 250 [V] is taken as I 1 / 2 [μJ / cm 2 , and in the range of I exp = 0.000~3.414·I 1 / 2 [μJ / cm 2 , S = I exp ·V exp is calculated as the maximum value of S [V·μJ / cm 2 and is denoted as S max [V·μJ / cm 2 . In the range of I exp = 0.000 [μJ / cm 2 ~0.100·I 1 / 2 [μJ / cm 2 , the intersection point of the approximate straight line and the approximate straight line in the range of I exp =(5·I 1 / 2 -0.100)[μJ / cm 2 ~5·I 1 / 2 [μJ / cm 2 is taken as Q, the light quantity value of point Q is I i [μJ / cm 2 , the potential value of point Q is V i [V], and the product of I i and V i is Si =I i ·V i [V·μJ / cm 2 and let S i and S max The ratio of is AR = S i / S max and let V i be divided by I i The value obtained is LR i =V i / I i [V·cm 2 / μJ]. When, I 1 / 2 ≦0.170, and AR≦0.370, and LR i ≦780, which is characterized by this.

[0019] Also, the electrophotographic photoreceptor according to the present invention has the above I 1 / 2 and AR = S i / S max and LR i =V i / I i wherein I 1 / 2 ≦0.170, and AR≦0.500, and LR i ≦520, which is characterized by this.

[0020] <Measurement method of NESA - EV curve> (1): Set the surface potential of the electrophotographic photoreceptor to 0 [V], (2): Charge the electrophotographic photoreceptor for 0.005 seconds so that the absolute value of the surface potential of the electrophotographic photoreceptor becomes V0 [V], (3): Starting from 0.02 seconds after the start of charging, expose the charged electrophotographic photoreceptor continuously for t seconds with light having a wavelength of 805 [nm] and an intensity of 25 [mW / cm exp [μJ / cm 2 so that the exposure amount becomes I 2 , (4): Measure the absolute value of the surface potential of the electrophotographic photoreceptor after exposure at 0.06 seconds after the start of charging and set it as V exp [V]. (5): By changing t, perform the operations of (1) to (4) so that I exp ranges from 0.000 [μJ / cm 2 to 0.850 [μJ / cm2 ] up to 0.001 [μJ / cm 2 ] and repeat the process. exp V corresponding to exp get. (6): By operating (3), t=0, I exp =0.000[μJ / cm 2 ], V exp [V] is the charged potential V d [V], and the V d Set V0 [V] when performing operation (2) so that the value is 500 [V]. [Effects of the Invention]

[0021] In recent years, due to the demand for smaller and lower-cost electrophotographic devices, it has become impossible to reduce the laser spot diameter, and a balance between digital and analog tonality is required. In this environment, the present invention makes it possible to provide an electrophotographic photosensitive member that has improved low-line halftone digital tonality and character quality while maintaining analog tonality even in high-speed processes for achieving high productivity, as well as a process cartridge and electrophotographic device using the electrophotographic photosensitive member. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a conceptual diagram showing the barter relationship between analog gradation and digital gradation in the EV curve of a conventional photoconductor. [Figure 2] FIG. 1 is a conceptual diagram showing that analog gradation and digital gradation can be achieved simultaneously in the EV curve of a photosensitive member that satisfies the EV curve specification of the present invention. [Figure 3] This is a conceptual diagram showing Smax [V·μJ / cm2] and Si [V·μJ / cm2] in the EV curve of a conventional photoconductor. [Figure 4] FIG. 2 is a conceptual diagram showing Smax [V·μJ / cm2] and Si [V·μJ / cm2] in the EV curve of the photoreceptor of the present invention. [Figure 5]This figure explains analogue gradation and digital gradation, and explains how the ratio of how analogue gradation and digital gradation are mixed in actual gradation changes depending on the relationship between the size of one dot and the exposure spot diameter. [Figure 6] FIG. 1 is a diagram showing an outline of the device used to measure the NESA-EV curve. [Figure 7] 1 is a diagram illustrating an example of a layer structure of an electrophotographic photoreceptor of the present invention. [Figure 8] 1 is a diagram showing an example of a schematic configuration of an electrophotographic apparatus having a process cartridge equipped with an electrophotographic photosensitive member and a charging unit. [Figure 9] FIG. 10 is a diagram showing an example of a gradation dither pattern used in evaluating the present invention. [Figure 10] For photoreceptor manufacturing example 1 of the present invention, an example of measurement of an area ratio-normalized density graph for a 32-tone line-grown dither pattern with a line count of 600 at a process speed of 300 [mm / s] is shown. [Figure 11] FIG. 10 is a diagram for explaining a method for calculating "highlight gradation" and "shadow gradation" on an area ratio-normalized density graph used in the evaluation of the present invention. [Figure 12] FIG. 1 is a diagram showing a 1-dot 4-space halftone used in evaluating the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in detail below with reference to preferred embodiments. In this specification, voltages are indicated as absolute values. The electrophotographic photoreceptor of the present invention comprises a support, Applicable On the support an undercoat layer, 1. An electrophotographic photoreceptor having a charge generating layer and a charge transport layer on the charge generating layer, the electrophotographic photoreceptor is an organic photoreceptor, the undercoat layer contains titanium oxide particles having a rutile or anatase crystal structure and having a silane-treated surface; and the charge generating layer contains hydroxygallium phthalocyanine crystals having strong peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in CuKα characteristic X-ray diffraction, the crystals containing 0.4% by mass or more and 3.0% by mass or less of a compound having a structure represented by formula (A1): JPEG0007725286000002.jpg3371 (In the above formula (A1), R 0 represents a methyl group, a propyl group, or a vinyl group; Titanyl phthalocyanine crystals with a strong peak at 27.2°±0.3° of the Bragg angle 2θ in CuKα characteristic X-ray diffraction Including, the charge generating layer has an average film thickness of 150 nm or more and 300 nm or less; the charge transport layer contains a charge transport material and a resin, and the content ratio (mass ratio) of the charge transport material to the resin in the charge transport layer is 8:10 to 12:10; At a temperature of 23.5 [°C] and a relative humidity of 50 [%RH], when the charging potential is V d = 500 [V], according to the following <Measurement method of NESA-EV curve>, the horizontal axis is I exp and the vertical axis is V exp of the I exp -V exp In the graph, the light quantity when V exp = 250 [V] is taken as I 1 / 2 [μJ / cm 2 , and in the range of I exp = 0.000~3.414·I 1 / 2 [μJ / cm 2 , S = I exp ·V exp is calculated as the maximum value of S [V·μJ / cm 2 and taken as S max [V·μJ / cm 2 . In the range of I exp = 0.000 [μJ / cm 2 ~0.100·I 1 / 2 [μJ / cm 2 , the intersection of the approximate straight line and the approximate straight line in the range of I exp =(5·I 1 / 2 -0.100)[μJ / cm 2 ~5·I 1 / 2 [μJ / cm 2 is taken as point Q. The light quantity value of point Q is I i [μJ / cm 2 , the potential value of point Q is V i [V], and the product of I i and V i is taken as S i = I i ·V i [V·μJ / cm 2 . The ratio of S i to S max is taken as AR = S i / S max , and the value obtained by dividing V i by I i is taken as LR i = V i / Ii [V·cm 2 / μJ], when I 1 / 2 ≦0.170, and AR≦0.370, and LR i ≦780, which relates to an electrophotographic photoreceptor characterized by the above.

[0024] In addition, the electrophotographic photoreceptor according to the present invention is the above I 1 / 2 and AR = S i / S max and LR i = V i / I i when I 1 / 2 ≦0.170, and AR≦0.500, and LR i ≦520, which relates to an electrophotographic photoreceptor characterized by the above.

[0025] <Measurement method of NESA - EV curve> (1): Set the surface potential of the electrophotographic photoreceptor to 0 [V], (2): Charge the electrophotographic photoreceptor for 0.005 seconds so that the absolute value of the surface potential of the electrophotographic photoreceptor becomes V0 [V], (3): Starting from 0.02 seconds after the start of charging, expose the charged electrophotographic photoreceptor continuously for t seconds with light having a wavelength of 805 [nm] and an intensity of 25 [mW / cm exp [μJ / cm 2 such that the exposure amount becomes I 2 , (4): Measure the absolute value of the surface potential of the exposed electrophotographic photoreceptor 0.06 seconds after the start of charging and set it as V exp [V]. (5): By changing t in the operations of (1) to (4), repeat the operations while changing I exp from 0.000 [μJ / cm 2 to 0.850 [μJ / cm 2 at an interval of 0.001 [μJ / cm 2 to obtain V exp corresponding to each I exp . (6): In the operation of (3), when t = 0, I exp = 0.000 [μJ / cm 2], V exp [V] is the charged potential V d It is called [V] and V d Set V0 [V] when performing operation (2) so that the value is 500 [V].

[0026] The present invention further relates to a process cartridge which integrally supports the above electrophotographic photosensitive member and at least one means selected from the group consisting of a charging means, a developing means, and a cleaning means, and is detachably mountable to the main body of an electrophotographic apparatus. The present invention further relates to an electrophotographic apparatus comprising the above electrophotographic photosensitive member, a charging means, an exposure means, a developing means and a transfer means.

[0027] The inventors' investigations revealed that conventional photoconductors do not satisfy the three characteristics of sensitivity, residual voltage, and linearity at a high level on the EV curve. In recent years, the demand for smaller and lower-cost electrophotographic devices has made it impossible to reduce the laser spot diameter. Even in such high-speed processes aimed at achieving high productivity, it has not been possible to improve low-screen halftone digital gradation characteristics and character quality while maintaining analog gradation characteristics. In light of the above objectives, the prior art did not adequately define the three characteristics of sensitivity, residual voltage, and linearity on the EV curve to achieve a high level.Furthermore, the basic characteristic evaluation means for measuring the EV curve were not satisfactory for achieving the high-speed processes expected in recent years and in the future.

[0028] Therefore, the inventors have determined the optimal balance between the three characteristics of sensitivity, residual voltage, and linearity on the EV curve. Furthermore, they have discovered that in order to properly measure the EV curve and solve the above problems, it is sufficient to determine, measure, and design the photoconductor as follows:

[0029] <Photoreceptor design> To achieve the goal of achieving both analog and digital gradation, the photoconductor needed to achieve high levels of the three characteristics of high sensitivity, low residual voltage, and high linearity while maintaining an optimal balance.

[0030] (Regarding the relationship between the EV curve and the stability of analog and digital gradation) Figure 1 shows the trade-off between analog and digital gradations in the EV curve of a conventional photoconductor. To improve analog gradations, it is necessary to make the change in surface potential as the light intensity varies more linear. This can be achieved by selecting (a) low light intensity as the image exposure in the EV curve in Figure 1. Figure 1(a) shows an enlarged version of the EV curve (a) low light intensity. This enlarged view reveals that when the EV curve is divided into equal parts for a given image exposure (equal light intensity), the corresponding surface potential is also divided into relatively equal parts. Therefore, analog gradations are relatively improved at low light intensity. In contrast, the EV curve when (b) high light intensity is selected as the image exposure is shown enlarged in (b). This enlarged view reveals that when the EV curve is divided into equal parts for the light intensity, the corresponding surface potential is divided into parts that are far from equal. Therefore, analog gradations deteriorate at high light intensity.

[0031] On the other hand, to improve digital gradation, it is necessary for each dot to be dense and stable. To achieve this, it is sufficient to select (b) high light intensity as the image exposure on the EV curve in Figure 1. In this case, as shown in Figure 1, the absolute value of the slope of the EV curve is small, so the change in surface potential is stable with respect to fluctuations in light intensity, resulting in a stable single dot. In contrast, if (a) low light intensity is selected as the image exposure, as shown in Figure 1, the absolute value of the slope of the EV curve is large, so the surface potential becomes unstable with respect to fluctuations in light intensity, resulting in an unstable single dot.

[0032] As mentioned above, when it comes to selecting which amount of light on the EV curve to use as the image exposure, analog gradation and digital gradation are generally in a trade-off relationship.

[0033] On the other hand, in the EV curve of the conventional photoconductor shown in Figure 1, (a) when the image exposure amount is low, the linearity of the relationship between the light amount and the surface potential is insufficient, and (b) when the image exposure amount is high, the stability of the surface potential against fluctuations in the light amount is insufficient, and the residual voltage is high.

[0034] Next, Figure 2 shows the relationship between analog and digital gradations in the EV curve of the photoreceptor of the present invention. Because the photoreceptor of the present invention has low residual voltage and high linearity, the EV curve bends sharply when it changes from low light intensity to high light intensity. Therefore, the (a) low-light-intensity region, which is advantageous for analog gradation, and the (b) high-light-intensity region, which is advantageous for digital gradation, shown in Figure 1, can be brought closer together. As shown in Figure 2, in an EV curve where these two regions are close together, the EV curve is highly linear in the low-light-intensity region, so when the change in image exposure is divided equally, the corresponding change in surface potential is also nearly equal. At the same time, in the high-light-intensity region, the stability of a single dot against fluctuations in light intensity is also high. Additionally, because the photoreceptor has low residual voltage, the upper and lower limits of the surface potential usable for analog gradation (hereinafter referred to as "latent image contrast") are widened, which also contributes to improved analog gradation. Furthermore, the contrast of the latent image is increased and the density of each dot is stabilized and high, which contributes to improving digital gradation.

[0035] While the NESA-EV curve, described below, is measured for each photoreceptor and is process-independent, the EV curve measured within a laser beam printer is process-dependent. In particular, at high process speeds, the EV curve deteriorates if the mobility of photogenerated carriers within the photoreceptor is slow. Furthermore, when the exposure time or number of exposures is shortened due to increased process speed or the use of multiple laser beams, the density of photogenerated carriers within the photoreceptor per unit time and per unit volume increases. Therefore, the EV curve deteriorates when there are many traps at the layer interface or in the bulk (this is called the "reciprocity law failure" characteristic of the photoreceptor). To avoid these problems, the mobility of photogenerated carriers must be fast and the number of such traps must be minimal. A highly sensitive photoreceptor satisfies these requirements. Therefore, to stably achieve both analog and digital gradation in recent and future high-speed processes, the photoreceptor of the present invention must have high sensitivity in addition to low residual current and high linearity on the EV curve.

[0036] (Regarding EV curve regulations) In the present invention, the NESA-EV curve is used as the EV curve. The NESA-EV curve is obtained by the following NESA-EV curve measurement method. exp -V exp In the present invention, the characteristic values are defined as follows: d In the NESA-EV curve at =500[V], the V exp = 250[V], the amount of light when 1 / 2 [μJ / cm 2 ]. S=I exp ·V exp The graph I exp =0.000~3.414 I 1 / 2 [μJ / cm 2 ] in the range of S[V·μJ / cm 2 ] maximum value of S max [V·μJ / cm 2 ]. I of the graph exp =0.000[μJ / cm 2 ]~0.100·I 1 / 2 [μJ / cm2 ] to find an approximate line in the range I exp =(5 I 1 / 2 -0.100) [μJ / cm 2 ]~5·I 1 / 2 [μJ / cm 2 ]. The intersection of these two approximate lines is Q. The light intensity value at point Q is I i [μJ / cm 2 ], the potential value at point Q is V i [V] and I i and V i The product of S i =I i ·V i [V·μJ / cm 2 ]. AR=S i / S max Then, LR i =V i / I i [V cm 2 / μJ].

[0037] Figure 3 shows the S in the EV curve of a conventional photoconductor. max [V·μJ / cm 2 ] and S i [V·μJ / cm 2 ] is shown in a conceptual diagram.

[0038] S max is the exposure I exp =0.000~3.414 I 1 / 2 [μJ / cm 2 ] range, S=I exp ·V exp S [V μJ / cm 2 ] means the maximum value of I 1 / 2 is the half-life exposure, and V exp I expis the absolute value of the surface potential when exposed to light of 1000 times the amount of light. "3.414" can be explained as follows. Consider an arbitrary point (x, y) and vertex (x0, y0) on a downward convex quadratic function, and a point (x1, y1 = (y + y0) / 2) that is the midpoint of the y coordinate values of those two points. In this case, the ratio of the distance from (x, 0) to (x1, 0) (corresponding to half-life exposure) to the distance from (x, 0) to (x0, 0) (corresponding to residual exposure) is 3.414. For any downward convex quadratic function, (x0-x) / (x1-x) = 2 / (2-√2) ≒ 3.414. Therefore, I exp =0.000~3.414 I 1 / 2 [μJ / cm 2 ] range, S max The lower the sensitivity, the higher the linearity, and the lower the residual voltage, the larger the value.

[0039] On the other hand S i is defined as follows: I exp =0.000[μJ / cm 2 ]~0.100·I 1 / 2 [μJ / cm 2 ] and the approximate line in the range of I exp =(5 I 1 / 2 -0.100) [μJ / cm 2 ]~5·I 1 / 2 [μJ / cm 2 The intersection of the approximated lines in the range of ] is Q. The light intensity value at point Q is I i [μJ / cm 2 ], the potential value at point Q is V i I when [V] i and V i The product of these is S i From this definition, S i The higher the sensitivity and the lower the residual charge, the smaller the value.

[0040] S defined in this way max and S i Ratio: AR=S i / S max The sensitivity is S i and S maxTherefore, the sensitivity does not have much effect on the magnitude of AR. Therefore, the lower the residual charge or the higher the linearity, the smaller the AR, and the effect of the sensitivity is relatively small. i Aspect ratio:LR i =V i / I i Considering this, from the definition, LR i The lower the sensitivity, the higher the linearity, and the lower the residual voltage, the smaller the σ. However, the effect of low residual voltage is particularly strong.

[0041] The present inventors have 1 / 2 and AR and LR i and the following provisions, (A)I 1 / 2 ≦0.170, and AR≦0.370, and LR i ≦780 or (B)I 1 / 2 ≦0.170, and AR≦0.500, and LR i It has been found that satisfying the condition AR=S≦520 is optimal for achieving the three characteristics of high sensitivity, low residual current, and high linearity at a high level while maintaining an optimal balance for the purpose of achieving both analog and digital gradation. A conceptual diagram of the EV curve of the photoconductor of the present invention, which satisfies this condition, is shown in FIG. 4. As is clear from FIG. 4, if low residual current and high linearity are satisfied, then AR=S i / S max and LR i =V i / I i It can also be seen that the influence of low residual battery is particularly large.

[0042] (A) I 1 / 2 ≦0.170, and AR≦0.370, and LR i The regulation of ≦780 is based on the fact that (B) contributes more to high linearity than to low residual power. 1 / 2 ≦0.170, and AR≦0.500, and LR i This is greater than the requirement that the residual current and high linearity are ≦520. In other words, the object of the present invention can be achieved if a balance is maintained between low residual current and high linearity, complementing each other, and high sensitivity, as shown in (A) or (B).

[0043] In recent years, with the demand for smaller and cheaper electrophotographic devices, in situations where the laser spot diameter cannot be reduced, analog gradation becomes stronger, as shown in Figure 5. In Figure 5, (a), (b), and (c) show patterns where one dot is 42 μm x 42 μm and 600 dpi. (a) shows analog gradation (when controlled by macroscopic average potential), (b) shows digital gradation (when controlled by microscopic area ratio), and (c) shows an example of a pattern obtained when the laser spot diameter cannot be sufficiently controlled. (d) is a schematic diagram of the laser spot diameter-light intensity distribution. When the spot diameter is large, analog gradation is strong, and when the spot diameter is small, digital gradation is strong. In this case, LR, which better reflects low residual current, is used. i The above provision is particularly important for improving the digital gradation characteristics and character quality of low-line halftones while maintaining analog gradation.

[0044] (NESA-EV curve measurement method) The NESA-EV curve is obtained by the following measurement method. Note that in this technical field, it is relatively common for EV curves to be measured inside a laser beam printer under specific process conditions. On the other hand, the NESA-EV curve is not measured inside the printer, but rather is measured under specific conditions for only the photoconductor, as will be explained below, and is determined for each photoconductor.

[0045] The NESA-EV curve is measured at a temperature of 23.5°C and a relative humidity of 50%RH, with the charge potential measured as V d =500[V] and proceed 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 so that the absolute value of the surface potential of the electrophotographic photosensitive member becomes V0 [V], (3): 0.02 seconds after the start of charging, the exposure amount is I exp [μJ / cm 2 ] so that the wavelength is 805 [nm] and the intensity is 25 [mW / cm 2the electrophotographic photosensitive member after charging is continuously exposed to light of (4): 0.06 seconds after the start of charging, the absolute value of the surface potential of the electrophotographic photosensitive member after exposure is measured and V exp Let's call it [V]. (5): By changing t in the operations (1) to (4), I exp to 0.000 [μJ / cm 2 ] to 0.850 [μJ / cm 2 ] up to 0.001 [μJ / cm 2 ] and repeat the process. exp V corresponding to exp get. (6): By operating (3), t=0, I exp =0.000[μJ / cm 2 ], V exp [V] is the charged potential V d It is called [V] and V d Set V0 [V] when performing operation (2) so that the value is 500 [V].

[0046] A specific example of a measurement system for the NESA-EV curve will be described below. However, as long as the NESA-EV curve measurement method can be performed, it is not necessarily limited to the following method.

[0047] A fully optically polished transparent quartz glass sheet is prepared (hereinafter referred to as "NESA glass"), with a transparent ITO electrode vapor-deposited on the surface to give a sheet resistance of 1,000 Ω / sq or less. As shown in FIG. 6, the surface of the photoconductor 201 is brought into close contact with the NESA glass sheet 202, with a transparent ITO electrode 204 vapor-deposited on its surface. At this time, glycerin is interposed between the NESA glass sheet 202 and the photoconductor 201 to ensure close contact. If the photoconductor is flat, smooth NESA glass is used, and if the photoconductor is cylindrical, curved NESA glass as shown in FIG. 6 is used. In this state, the surface of the photoconductor can be charged by applying a voltage to the NESA glass sheet using a high-voltage power supply 205. In addition, a voltage of 805 nm wavelength and 25 mW / cm intensity is applied from the underside of the NESA glass. 2], the surface of the photosensitive member is exposed 203, and the surface potential can be optically attenuated.

[0048] Using the above measurement system, 25 [mW / cm 2 ] light is irradiated onto the photosensitive member only once for a short time, while at the same time repeating charging and exposure in a cycle faster than the process speed of electrophotographic devices currently in use or expected in the future. 2 ] is stronger than the exposure light irradiated onto the photosensitive member in electrophotographic devices that are expected to be used in the future. 2 By stably and easily acquiring a large amount of data on the light amount in increments of 25 [mW / cm], it is possible to obtain the NESA-EV curve of the photoreceptor of the present invention and the characteristic values calculated therefrom. At the same time, the above measurement method realized using this measurement system makes it possible to evaluate the characteristics of photoreceptors even when the process speed has increased in recent years and in the future and the exposure irradiation time has become shorter. Furthermore, it is possible to evaluate the characteristics of photoreceptors even when the number of exposures has decreased due to the change in exposure method from the currently mainstream laser scanning optical system to an LED array. In particular, it is possible to evaluate the characteristics of photoreceptors when the intensity is 25 [mW / cm] 2 ] is a sufficiently strict EV curve measurement method that will remain in place for the future, even in light of the reciprocity law failure characteristics of photoconductors.

[0049] [Electrophotographic photoreceptor] The electrophotographic photoreceptor of the present invention is an organic photoreceptor having a support, a charge generation layer on the support, and a charge transport layer on the charge generation layer. The charge generation layer contains a charge generation material, and the charge transport layer contains a charge transport material. The organic photoreceptor refers to a photoreceptor in which the main component of the layer formed on the support is a resin. Figure 7 is a diagram showing an example of the layer structure of an electrophotographic photoreceptor. In Figure 7, 101 is a support, 102 is an undercoat layer, 103 is a charge generation layer, 104 is a charge transport layer, and 105 is a photosensitive layer. In the present invention, the undercoat layer 102 may be omitted.

[0050] Furthermore, the photoreceptor of the present invention has a charging potential of V at a temperature of 23.5°C and a relative humidity of 50%RH.d When it is = 500 [V], the horizontal axis obtained according to the above <Measurement method of EV curve> is I exp and the vertical axis is V exp of I exp -V exp In the graph, the V of this graph exp When it becomes = 250 [V], the light quantity is I 1 / 2 [μJ / cm 2 , and the I of this graph exp = 0.000~3.414·I 1 / 2 [μJ / cm 2 in the range of, S = I exp ·V exp is calculated as S [V·μJ / cm 2 , and the maximum value of S is S max [V·μJ / cm 2 , and the I of this graph exp = 0.000 [μJ / cm 2 ~0.100·I 1 / 2 [μJ / cm 2 in the range of the approximate straight line and I exp =(5·I 1 / 2 -0.100)[μJ / cm 2 ~5·I 1 / 2 [μJ / cm 2 in the range of the intersection point of the approximate straight line is set as Q, the light quantity value of point Q is I i [μJ / cm 2 , the potential value of point Q is V i [V], I i and V i The product of is S i = I i ·V i [V·μJ / cm 2 , and S i and S max The ratio of is AR = S i / S max , and V i divided by I i The value obtained is LR i = V i / I i [V·cm 2 / μJ], in the case of (A)I 1 / 2 ≦0.170, and AR≦0.370, and LR i ≦780, or (B)I 1 / 2 ≦0.170, and AR≦0.500, and LR i ≦520 It is necessary to do so.

[0051] In addition, from the viewpoint of improving both the highlight side image with a small dot area ratio and the shadow side image with a large dot area ratio, the AR is set to 0.370 and the LR is set to 0.370 so as to satisfy both (A) and (B) above. i It is preferable that AR≦0.370 and LR≦520. i When the value is ≦520, the balance between low residual current and high linearity is further improved even in a high-speed process equivalent to a laser spot diameter of 80 μm and a printing speed of 100 ppm (500 mm / sec). As a result, the gradation on both the highlight and shadow sides is improved.

[0052] Furthermore, from the viewpoint of further improving the image on the shadow side with high screen ruling and increasing the reproducibility of small font-size outline characters, it is more preferable to satisfy the above-mentioned AR≦0.100. When AR≦0.100, the visibility of 6 pt outline characters on the shadow side is improved even in a high-speed process equivalent to a laser spot diameter of 80 μm and a printing speed of 100 ppm (500 mm / sec).

[0053] On the other hand, in order to further improve the image on the highlight side of low screen frequency and increase the reproducibility of normal small font size characters, i It is more preferable that LR is ≦60. i When the value is ≦60, the visibility of 3 pt white characters on the highlight side is improved even in a high-speed process equivalent to a laser spot diameter of 80 μm and a printing speed of 100 ppm (500 mm / sec).

[0054] In addition, in order to improve the reproducibility of an isolated dot when the charging potential is set low for the purpose of energy saving, etc., exp -V expI on the graph exp =5 I 1 / 2 [μJ / cm 2 ] in V exp The value of V r [V] is V r It is preferable that V≦70. r It is more preferable that V is ≦10. r If the laser spot diameter is 80 μm and the printing speed is 100 ppm (500 mm / sec), the V d = 450[V], the reproducibility of an isolated dot is improved, and V r If it is ≦10, the density of the isolated one-dot pattern becomes even higher.

[0055] The method for producing the electrophotographic photoreceptor of the present invention includes a method in which a coating liquid for each layer described below is prepared, and the layers are coated in the desired order and dried. In this case, the coating liquid can be applied by dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, ring coating, etc. Among these, dip coating is preferred from the viewpoints of efficiency and productivity.

[0056] The support and each layer will be described below. <Support> In the present invention, the electrophotographic photoreceptor has a support. The support is preferably a conductive support having electrical conductivity. The shape of the support may be cylindrical, belt-like, sheet-like, or the like, and among these, a cylindrical support is preferred. The surface of the support may be subjected to blasting treatment, cutting treatment, or the like. The support is preferably made of a metal, a resin, or a glass. Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof, and among these, an aluminum support is preferred. Furthermore, when the material is resin or glass, conductivity may be imparted by processing such as mixing or coating with a conductive material.

[0057] The support of the present invention may be used by anodizing the surface of the support in an acidic liquid containing an oxidizing agent. In this case, for example, an inorganic acid such as sulfuric acid or chromic acid or an organic acid such as oxalic acid or sulfonic acid can be used as the electrolyte for the anodizing treatment. Conditions such as applied voltage, current density, treatment temperature, and time can be selected depending on the type of electrolyte and film thickness. In addition, the anodized surface used in the electrophotographic photoreceptor of the present invention may be subjected to a sealing treatment after electrolysis. The sealing treatment may be a hot water treatment, a steam treatment, or a treatment using various sealing agents such as nickel acetate or nickel fluoride, but a treatment using nickel acetate is preferred because it can efficiently seal micropores.

[0058] <Conductive layer> In the present invention, a conductive layer may be provided on the support. By providing the conductive layer, scratches and irregularities on the support surface can be concealed and light reflection on the support surface can be controlled. The conductive layer preferably contains conductive particles and a resin.

[0059] Examples of materials for the conductive particles include metal oxides, metals, and carbon black. Examples of metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, etc. Examples of metals include aluminum, nickel, iron, nichrome, copper, zinc, silver, etc. Among these, it is preferable to use metal oxides as the conductive particles, and it is particularly preferable to use titanium oxide, tin oxide, or zinc oxide. When metal oxides are used as conductive particles, the surfaces of the metal oxides may be treated with a silane coupling agent or the like, or the metal oxides may be doped with elements such as phosphorus or aluminum or oxides thereof, such as phosphorus, aluminum, niobium, and tantalum. The conductive particles may have a laminated structure including a core particle and a coating layer covering the core particle. Examples of the core particle include titanium oxide, barium sulfate, and zinc oxide. Examples of the coating layer include metal oxides such as tin oxide and titanium oxide. When metal oxide particles are used as the conductive particles, the volume average particle size is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0060] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, and alkyd resin. The conductive layer may further contain silicone oil, resin particles, a masking agent such as titanium oxide, and the like.

[0061] The average 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.

[0062] The conductive layer can be formed by preparing a coating solution for the conductive layer containing the above-mentioned materials and solvent, forming this coating film on an underlayer or a support, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Examples of dispersion methods for dispersing the conductive particles in the coating solution for the conductive layer include methods using a paint shaker, sand mill, ball mill, or liquid collision-type high-speed disperser.

[0063] <Undercoat layer> In the present invention, an undercoat layer may be provided on the support or the conductive layer. By providing an undercoat layer, the adhesion function between layers can be improved and a charge injection blocking function can be imparted. The undercoat layer preferably contains a resin. Alternatively, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinylphenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamideimide resin, and cellulose resin. Examples of the polymerizable functional group possessed by the monomer having a polymerizable functional group include 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, and a carbon-carbon double bond.

[0064] Furthermore, for the purpose of improving electrical properties, the undercoat layer may further contain an electron transporting substance, a metal oxide, a metal, a conductive polymer, etc. Among these, it is preferable to use an electron transporting substance or a metal oxide. In particular, it is important to select the electron transport material, metal oxide, metal, conductive polymer, and resin, and to control their compounding ratios, etc. By appropriately selecting and controlling these, and by appropriately selecting the photosensitive layer on the undercoat layer, it is possible to smoothly flow the photocarriers generated in the charge generation layer toward the support, thereby obtaining a photoreceptor that satisfies the EV curve specification of the present invention. Examples of the electron transport substance include a quinone compound, an imide compound, a benzimidazole compound, a cyclopentadienylidene compound, a fluorenone compound, a xanthone compound, a benzophenone compound, a cyanovinyl compound, an aryl halide compound, a silole compound, a boron-containing compound, etc. An electron transport substance having a polymerizable functional group may be used as the electron transport substance, and the undercoat layer may be formed as a cured film by copolymerizing the electron transport substance with a monomer having the polymerizable functional group. Examples of metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide. Examples of metals include gold, silver, and aluminum. Among these, titanium oxide particles with a rutile or anatase crystal structure whose surface is silane-treated are preferred from the viewpoint of smoothly transferring photocarriers generated in the charge generating layer of the present invention to the support side. The surface silane treatment is preferably carried out with at least one compound selected from vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldimethoxysilane. Silane treatment to impart hydrophobicity can suppress carrier migration inhibition due to moisture adsorption, and rutile or anatase titanium oxide particles can suppress carrier trapping. Furthermore, from the viewpoint of further suppressing carrier migration inhibition, the titanium oxide particles are more preferably rutile, which has weak photocatalytic activity, and preferably have a rutile content of 90% or more. In addition, in order to prevent the conductivity of the titanium oxide particles from being hindered by the binder resin, the volume ratio of the titanium oxide particles to the binder resin (volume of the titanium oxide particles relative to the volume of the binder resin) is preferably 0.2 or more. If it is less than 0.2, the binder resin may hinder the smooth movement of photocarriers. The undercoat layer may further contain additives.

[0065] The average thickness of the undercoat layer is preferably from 0.1 μm to 50 μm, more preferably from 0.2 μm to 40 μm, and particularly preferably from 0.3 μm to 30 μm.

[0066] The undercoat layer can be formed by preparing a coating solution for the undercoat layer containing the above-mentioned materials and solvent, forming a coating film of this on the underlayer or support, and drying and / or curing it. Examples of the solvent used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0067] <Charge generation layer> The charge generating layer must contain a charge generating material and a resin. Examples of the charge generating substance include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, phthalocyanine pigments, etc. Among these, phthalocyanine pigments are preferred from the viewpoint of easily obtaining the high sensitivity required in the present invention.

[0068] Comparing phthalocyanine pigments and azo pigments as charge-generating materials, azo pigments are interfacial, with charge generation occurring at the interface between the charge-generating layer and the charge-transport layer, whereas phthalocyanine pigments are bulk, with charge generation occurring in the bulk of the charge-generating layer (see Umeda, Minoru, "Extrinsic Photocarrier Generation Process and Its Kinetics in Laminated Organic Photoreceptors," Journal of the Chemical Society of Japan, 1996, No. 11, pp. 932-937). Therefore, when phthalocyanine pigments are used as charge-generating materials, it is easier to increase the amount of photogenerated carriers by increasing the thickness of the charge-generating layer compared to azo pigments. As a result, using phthalocyanine pigments as charge-generating materials facilitates the production of the highly sensitive photoreceptors of the present invention.

[0069] Among phthalocyanine pigments, titanyl phthalocyanine pigments or hydroxygallium phthalocyanine pigments are preferred because they provide stable, high photosensitivity. Also preferred are hydroxygallium phthalocyanine crystals described in JP 2000-137340 A, which have strong peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in CuKα characteristic X-ray diffraction, and titanyl phthalocyanine crystals described in JP 2000-137340 A, which have strong peaks at Bragg angles 2θ of 27.2°±0.3° in CuKα characteristic X-ray diffraction. Of these, particularly preferred is a hydroxygallium phthalocyanine crystal containing 0.4% by mass to 3.0% by mass of a compound having a structure represented by the following formula (A1) in the crystals, as described in the examples of JP 2018-189692 A: [ka] (In the above formula (A1), R 0 represents a methyl group, a propyl group, or a vinyl group. This is based on the viewpoint of increasing sensitivity while preventing the interface between the pigment dispersed in the resin and the resin from becoming a charge trap, thereby reducing residual charge.

[0070] In the hydroxygallium phthalocyanine crystals described above, the compound having the structure shown in formula (A1) is present in an amount of 0.4% by mass or more and 3.0% by mass or less, and the crystal grain size is uniform to the thickness of the charge-generating layer. The reason for this is also described in JP 2018-189692 A. This allows for high quantum efficiency, determined by the Onsager equation described in JP 2018-189692 A, and high light absorption, determined by the Beer-Lambert equation. Therefore, there is no need to increase the thickness of the charge-generating layer excessively to increase sensitivity. This suppresses the amount of interfacial trapping between the charge-generating material (crystal grains) and the resin, which tends to increase with increasing film thickness, thereby reducing residual charge.

[0071] The content of the charge generating material in the charge generating layer is preferably 40% by mass or more and 85% by mass or less, and more preferably 60% by mass or more and 80% by mass or less, based on the total mass of the charge generating layer.

[0072] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, polyvinyl chloride resin, etc. Among these, polyvinyl butyral resin is more preferred. The charge generating layer may further contain additives such as antioxidants and ultraviolet absorbers, etc. Specific examples of the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0073] The average thickness of the charge generating layer is preferably from 0.1 μm to 1 μm, and more preferably from 0.15 μm to 0.3 μm.

[0074] The charge generating layer can be formed by preparing a coating solution for the charge generating layer containing the above-mentioned materials and solvent, forming a coating film of this on an underlayer or a support, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0075] <Charge transport layer> The charge transport layer must contain a charge transport material and a resin.

[0076] Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these materials. Among these, triarylamine compounds and benzidine compounds are preferred. The content of the charge transport material in the charge transport layer is preferably 25% by mass to 70% by mass, and more preferably 30% by mass to 55% by mass, based on the total mass of the charge transport layer.

[0077] Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, etc. Among these, polycarbonate resin and polyester resin are preferred. As the polyester resin, polyarylate resin is particularly preferred.

[0078] The charge transport layer preferably has an ionization potential close to that of the charge generation layer, from the viewpoint of ensuring smooth transfer of photocarriers generated in the charge generation layer to the charge transport layer. In particular, when titanyl phthalocyanine or hydroxyphthalocyanine is used as the charge generation material, the ionization potential of the charge transport layer is preferably 5.2 eV to 5.5 eV, more preferably 5.3 eV to 5.4 eV. When the ionization potential is 5.2 eV to 5.5 eV, traps are less likely to occur at the interface between the charge generation layer and the charge transport layer, resulting in low residual charge. An ionization potential less than 5.2 eV may worsen the memory phenomenon, while an ionization potential greater than 5.5 eV may increase residual charge.

[0079] Furthermore, the charge transport layer preferably has high mobility in order to rapidly move generated photocarriers within the charge transport layer. Therefore, the content ratio (mass ratio) of the charge transport material 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 transport material to the resin is 8:10 to 12:10, traps are less likely to occur in the bulk of the charge transport layer, resulting in low residual charge. Increasing the content ratio of the charge transport material beyond this range may result in a decrease in the durability and manufacturing stability of the photoreceptor.

[0080] The charge transport layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slippage agents, and abrasion resistance improvers. Specific examples of the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0081] The average thickness of the charge transport layer is preferably from 5 μm to 50 μm, more preferably from 10 μm to 23 μm, and particularly preferably from 14 μm to 20 μm.

[0082] The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned materials and solvent, forming a coating film of this on the underlayer, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents and aromatic hydrocarbon-based solvents are preferred.

[0083] <Protective layer> In the present invention, a protective layer may be provided on the photosensitive layer, which can improve durability. The protective layer preferably contains conductive particles and / or a charge transport material, and a resin. Examples of conductive particles include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide. Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these materials. Among these, triarylamine compounds and benzidine compounds are preferred. Examples of the resin include polyester resin, acrylic resin, phenoxy resin, polycarbonate resin, polystyrene resin, phenol resin, melamine resin, epoxy resin, etc. Among these, polycarbonate resin, polyester resin, and acrylic resin are preferred.

[0084] The protective layer may also be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the polymerization reaction include thermal polymerization, photopolymerization, and radiation-induced polymerization. Examples of the polymerizable functional group of the monomer having a polymerizable functional group include an acryloyl group and a methacryloyl group. A material having charge transport capability may also be used as the monomer having a polymerizable functional group.

[0085] The protective layer may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slippage imparting agents, abrasion resistance improvers, etc. Specific examples of the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0086] The average thickness of the protective layer is preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 7 μm or less.

[0087] The protective layer can be formed by preparing a coating solution for the protective layer containing the above-mentioned materials and solvent, forming a coating film of this on the underlayer, and drying and / or curing it. Examples of the solvent used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0088] 1 / 2 ≦0.170, and AR≦0.370, and LR i Example of the structure of each layer of an electronic photoreceptor that satisfies ≦780> The electrophotographic photoreceptor is I 1 / 2 ≦0.170, and AR≦0.370, and LR i ​To satisfy the requirement of ≦780, each layer of the electrophotographic photoreceptor preferably has the following configuration. Specifically, the electrophotographic photoreceptor preferably has a charge generation layer containing hydroxygallium phthalocyanine crystals containing 0.4% by mass or more and 3.0% by mass or less of a compound having the structure represented by formula (A1) in the crystals, as described in the examples of JP 2018-189692 A, or titanyl phthalocyanine crystals having a strong peak at a Bragg angle 2θ of 27.2°±0.3° in CuKα characteristic X-ray diffraction. In particular, the electrophotographic photoreceptor preferably has a charge generation layer containing hydroxygallium phthalocyanine crystals containing 0.4% by mass or more and 3.0% by mass or less of a compound having the structure represented by formula (A1) in the crystals, as described in the examples of JP 2018-189692 A. The electrophotographic photoreceptor preferably has a charge transport layer having an ionization potential of 5.2 eV or more and 5.5 eV or less, and more preferably has a charge transport layer having an ionization potential of 5.3 eV or more and 5.4 eV or less. Furthermore, it is particularly preferable to have both the charge generating layer and the charge transport layer. This is based on the idea that by combining a charge generation layer that prevents the interface between the pigment dispersed in the resin and the resin from becoming a charge trap, and a charge transport layer that makes it difficult for interface traps to occur between the charge generation layer and the charge transport layer, photocarriers generated in the pigment can flow smoothly to the charge transport layer. An example of a preferred configuration is an electrophotosensitive body having a hydroxygallium phthalocyanine crystal containing 0.4% by mass or more and 3.0% by mass or less of a compound having the structure shown in formula (A1) in the crystal, as described in the examples of JP 2018-189692 A, and a charge transport layer having an ionization potential of 5.3 eV or more and 5.4 eV or less. However, the above-described configuration examples are merely examples, and the electrophotosensitive member of the present invention is not limited to I 1 / 2 ≦0.170, and AR≦0.370, and LR i As long as the condition ≦780 is satisfied, the configuration is not limited to the above example.

[0089] 1 / 2 ≦0.170, and AR≦0.500, and LR​i Example of the structure of each layer of an electrophotosensitive member that satisfies ≦520> In addition, the electrophotographic photoreceptor is I 1 / 2 ≦0.170, and AR≦0.500, and LR i To satisfy the requirement of ≦520, each layer of the electrophotographic photoreceptor preferably has the following configuration. The electrophotographic photoreceptor preferably includes an undercoat layer containing titanium oxide particles having a rutile or anatase crystal structure and having a silane-treated surface. In particular, the undercoat layer preferably includes rutile titanium oxide particles having a rutile content of 90% or more and having a silane-treated surface with at least one compound selected from vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldimethoxysilane, and in which the volume ratio of titanium oxide particles to binder resin (volume of titanium oxide particles relative to volume of binder resin) is 0.2 or more. The electrophotosensitive member preferably includes a charge generation layer containing hydroxygallium phthalocyanine crystals containing 0.4% to 3.0% by mass of a compound having the structure represented by formula (A1) in the crystals, as described in the examples of JP 2018-189692 A, or titanyl phthalocyanine crystals having a strong peak at a Bragg angle 2θ of 27.2°±0.3° in CuKα characteristic X-ray diffraction, as described in JP 2000-137340 A. In particular, the electrophotosensitive member preferably includes a charge generation layer containing hydroxygallium phthalocyanine crystals containing 0.4% to 3.0% by mass of a compound having the structure represented by formula (A1) in the crystals, as described in the examples of JP 2018-189692 A. The electrophotographic photoreceptor preferably has a charge transport layer having an ionization potential of 5.2 eV or more and 5.5 eV or less, and more preferably has a charge transport layer having an ionization potential of 5.3 eV or more and 5.4 eV or less. Furthermore, it is particularly preferable to have all of the above-mentioned undercoat layer, charge generating layer, and charge transport layer. This is based on the idea that by combining an undercoat layer that allows photocarriers generated in the charge generation layer to flow smoothly toward the support, a charge generation layer that prevents the interface between the pigment dispersed in the resin and the resin from becoming a charge trap, and a charge transport layer that makes it difficult for interface traps to occur between the charge generation layer and the charge transport layer, one of the positive and negative photocarriers generated in the pigment can flow smoothly to the charge transport layer, and photocarriers of the opposite polarity can also flow smoothly to the support. An example of a preferred configuration is an electrophotoreceptor having an undercoat layer containing rutile-type titanium oxide particles having a rutile content of 90% or more and whose surfaces have been silane-treated with at least one compound selected from vinyltrimethoxysilane, vinyltriethoxysilane, and vinylmethyldimethoxysilane, and in which the volume ratio of titanium oxide particles to binder resin (volume of titanium oxide particles relative to volume of binder resin) is 0.2 or more; a charge generation layer containing hydroxygallium phthalocyanine crystals containing 0.4% by mass to 3.0% by mass of a compound having the structure represented by formula (A1) in the crystals, as described in the examples of JP 2018-189692 A; and a charge transport layer having an ionization potential of 5.3 eV to 5.4 eV. However, the configuration examples described above are merely illustrative, and the electrophotoreceptor of the present invention can be used in a variety of applications. 1 / 2 ≦0.170, and AR≦0.500, and LR i As long as the condition ≦520 is satisfied, the configuration is not limited to the above example.

[0090] [Process cartridge and electrophotographic device] An example of the schematic configuration of an electrophotographic apparatus having a process cartridge equipped with an electrophotographic photosensitive member is shown in Figure 8. In Figure 8, reference numeral 1 denotes a cylindrical (drum-shaped) electrophotographic photosensitive member, which is driven to rotate around an axis 2 in the direction of the arrow at a predetermined peripheral speed (process speed). During rotation, the surface of the electrophotographic photosensitive member 1 is charged to a predetermined positive or negative potential by charging means 3. Next, the charged surface of the electrophotographic photosensitive member 1 is irradiated with image exposure light 4 from exposure means (not shown), and an electrostatic latent image corresponding to the target image information is formed. The image exposure light 4 is light whose intensity is modulated in accordance with a time-series electric digital image signal of the target image information, output from exposure means such as slit exposure or laser beam scanning exposure. The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1 is developed (normal development or reversal development) with toner contained in the developing means 5, and a toner image is formed on the surface of the electrophotographic photosensitive member 1. The toner image formed on the surface of the electrophotographic photosensitive member 1 is transferred to a transfer material 7 by a transfer means 6. At this time, a bias voltage of a polarity opposite to that of the charge held by the toner is applied to the transfer means 6 from a bias power supply (not shown). Furthermore, if the transfer material 7 is paper, the transfer material 7 is taken out from a paper feed unit (not shown) and fed between the electrophotographic photosensitive member 1 and the transfer means 6 in synchronization with the rotation of the electrophotographic photosensitive member 1.

[0091] The transfer material 7, onto which the toner image has been transferred from the electrophotographic photoreceptor 1, is separated from the surface of the electrophotographic photoreceptor 1 and transported to a fixing means 8, where the toner image is fixed and printed out as an image-formed product (print, copy) outside the electrophotographic device. After the toner image has been transferred to the transfer material 7, the surface of the electrophotographic photoreceptor 1 is cleaned by a cleaning means 9 to remove any remaining toner (residual toner), etc. Recently developed cleanerless systems also allow the residual toner to be removed directly by a developing device, etc. Furthermore, the surface of the electrophotographic photoreceptor 1 is neutralized with pre-exposure light 10 from a pre-exposure means (not shown) before being used for repeated image formation. Note that if the charging means 3 is a contact charging means using a charging roller or the like, the pre-exposure means is not necessarily required. In the present invention, a process cartridge can be formed by housing and integrally supporting multiple components, such as the electrophotographic photoreceptor 1, charging means 3, developing means 5, and cleaning means 9, in a container. Furthermore, this process cartridge can be configured to be detachable from the main body of the electrophotographic device. For example, at least one selected from the charging means 3, the developing means 5, and the cleaning means 9 can be integrally supported together with the electrophotographic photosensitive member 1 to form a cartridge. Furthermore, a process cartridge 11 can be formed that is detachably attachable to the main body of the electrophotographic apparatus using guide means 12 such as rails of the main body of the electrophotographic apparatus. When the electrophotographic apparatus is a copier or printer, the image exposure light 4 may be reflected light or transmitted light from an original. Alternatively, the image exposure light 4 may be light emitted by scanning a laser beam, driving an LED array, or driving a liquid crystal shutter array in accordance with a signal obtained by reading the original with a sensor and converting it into a signal.

[0092] The electrophotographic photoreceptor 1 of the present invention can be widely applied to electrophotographic application fields such as laser beam printers, CRT printers, LED printers, FAX machines, liquid crystal printers, and laser plate making. [Example]

[0093] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples without departing from the gist of the present invention. In the following examples, "parts" are by mass unless otherwise specified. The film thickness of each layer of the electrophotographic photoreceptors in the Examples and Comparative Examples, except for the charge generation layer, was determined using an eddy current film thickness meter (Fischerscope (trademark), manufactured by Fisher Instruments) or by converting the mass per unit area into specific gravity. The film thickness of the charge generation layer was determined as follows: That is, a spectrodensitometer (trade name: X-Rite504 / 508, manufactured by X-Rite) was pressed against the surface of the photoreceptor to measure the Macbeth density value. The film thickness was calculated from the measured Macbeth density value using a calibration curve previously obtained from the Macbeth density value and film thickness measurements obtained by observing cross-sectional SEM images.

[0094] <Preparation of Coating Solution for Conductive Layer> [Example of titanium oxide particle production] A titanium niobium sulfate solution containing 33.7 parts titanium (calculated as TiO2) and 2.9 parts niobium (calculated as Nb2O5) was prepared using anatase titanium dioxide (TiO2) as the substrate. 100 parts of the substrate were dispersed in pure water to prepare a 1000-part suspension, which was then heated to 60°C. The titanium niobium sulfate solution and 10 mol / L sodium hydroxide were simultaneously added dropwise over a period of 3 hours to adjust the pH of the suspension to 2-3. After the entire amount was added, the pH was adjusted to near neutral, and a polyacrylamide-based flocculant was added to settle the solids. The supernatant was removed, filtered, washed, and dried at 110°C to obtain an intermediate containing 0.1 wt% of organic matter derived from the flocculant (calculated as C). This intermediate was calcined in nitrogen at 750°C for 1 hour, followed by calcination in air at 450°C to produce titanium oxide particles. The obtained particles had an average particle size (average primary particle size) of 220 nm as determined by the particle size measurement method using a scanning electron microscope described above.

[0095] [Preparation of conductive layer coating solution 1] Phenolic resin (phenolic resin monomer / oligomer) as a binder (product name: Plyofen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g / cm 2 50 parts of the hydroxybenzoate was dissolved in 35 parts of 1-methoxy-2-propanol as a solvent to obtain a solution. To this solution, 75 parts of the titanium oxide particles obtained in the Titanium Oxide Particle Production Example were added, and this was used as a dispersion medium. The resulting solution was placed in a vertical sand mill using 120 parts of glass beads with an average particle size of 1.0 mm, and subjected to a dispersion treatment for 4 hours at a dispersion temperature of 23±3°C and a rotation speed of 1500 rpm (circumferential speed of 5.5 m / s), to obtain a dispersion. The glass beads were removed from this dispersion using a mesh. To the dispersion from which the glass beads had been removed, 0.01 parts of silicone oil (trade name: SH28 PAINT ADDITIVE, manufactured by Toray Dow Corning) as a leveling agent and silicone resin particles (trade name: KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average particle size: 2 μm, density: 1.3 g / cm) as a surface roughness imparting agent were added. 3 8 parts of the above-mentioned acrylic acid ester was added and stirred, and the mixture was filtered under pressure using PTFE filter paper (trade name: PF060, manufactured by Advantec Toyo Co., Ltd.) to prepare coating liquid 1 for conductive layer.

[0096] [Preparation of conductive layer coating solution 2] 60 parts of tin oxide-coated barium sulfate particles (trade name: Pastran PC1, manufactured by Mitsui Mining & Smelting Co., Ltd.), 15 parts of titanium oxide particles (trade name: TITANIX JR, manufactured by Teika Co., Ltd.), 43 parts of resol-type phenolic resin (trade name: Phenolite J-325, manufactured by DIC, solids content 70% by mass), 0.015 parts of silicone oil (trade name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.), 3.6 parts of silicone resin particles (trade name: Tospearl 120, manufactured by Momentive Performance Materials Japan Co., Ltd.), 50 parts of 2-methoxy-1-propanol, and 50 parts of methanol were placed in a ball mill and dispersed for 20 hours to prepare conductive layer coating solution 2.

[0097] [Preparation of Conductive Layer Coating Solution 3] Zinc oxide particles (average primary particle diameter: 50 nm, specific surface area: 19 m 2 / g, powder resistance: 1.0×10 7 One hundred parts of a sol-gel (Ω·cm, manufactured by Teika) was mixed with 500 parts of toluene while stirring. To this was added 0.75 parts of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (trade name: KBM-602, manufactured by Shin-Etsu Chemical Co., Ltd.) as a surface treatment agent, and the mixture was mixed with stirring 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 zinc oxide particles. Next, 100 parts of titanium oxide particles (trade name: JR-405, average primary particle diameter: 210 nm, manufactured by Teika) were mixed with 500 parts of toluene by stirring, and 0.75 parts of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane was added and 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. Next, 100 parts of the surface-treated zinc oxide particles, 12 parts of the surface-treated titanium oxide, and a mixture of the following formula (A2) [ka] A dispersion was prepared by adding 30 parts of a blocked isocyanate compound represented by the formula (trade name: Sumidur 3175, solid content: 75 mass%, manufactured by Sumika Bayer Urethane), 15 parts of a polyvinyl butyral resin (trade 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.) to a mixed solvent of 70 parts of methyl ethyl ketone and 70 parts of cyclohexanone. This dispersion was dispersed in a vertical sand mill using glass beads with an average particle size of 1.0 mm for 3 hours at 1,500 rpm in an atmosphere of 23°C. After dispersion, the glass beads were removed from the resulting dispersion using a mesh, and 7 parts of cross-linked polymethyl methacrylate particles (product name: SSX-103, average particle size: 3 μm, manufactured by Sekisui Chemical Co., Ltd.) and 0.01 parts of silicone oil (product name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.) were added and stirred to prepare coating solution 3 for the conductive layer.

[0098] [Preparation of Conductive Layer Coating Solution 4] Zinc oxide (average primary particle diameter: 70 nm, specific surface area: 15 m 2 100 parts of zinc oxide (1 / g, prototype manufactured by Teika) were mixed with 500 parts of toluene while stirring. 1.25 parts of a silane coupling agent (trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a surface treatment agent, and the mixture was mixed while stirring for 2 hours. Thereafter, the 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. Subsequently, 60 parts of the surface-treated zinc oxide particles, 13.5 parts of a blocked isocyanate compound represented by the formula (A2) above (trade name: Sumidur 3175, solid content: 75% by mass, manufactured by Sumika Bayer Urethane Co., Ltd.), and 15 parts of a polyvinyl butyral resin (trade name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) were added to 85 parts of methyl ethyl ketone to prepare a dispersion. This dispersion was dispersed in a vertical sand mill using glass beads with an average particle size of 1.0 mm for 2 hours at 1,500 rpm in an atmosphere of 23° C. After dispersion, the glass beads were removed from the resulting dispersion using a mesh, and 0.005 parts of dioctyltin dilaurate as a catalyst and 3.4 parts of silicone resin particles (product name: Tospearl 130, manufactured by GE Toshiba Silicones) were added to obtain coating solution 4 for conductive layer.

[0099] [Preparation of Conductive Layer Coating Solution 5] 50 parts of titanium dioxide powder coated with tin oxide containing 10% antimony oxide, 25 parts of resol-type phenolic resin, 20 parts of methyl cellosolve, 5 parts of methanol, and 0.002 parts of silicone oil (polydimethylsiloxane-polyoxyalkylene copolymer, average molecular weight 3,000) were dispersed in a vertical sand mill using glass beads with an average particle size of 1.0 mm at 23°C and 1,500 rpm for 2 hours. After dispersion, the glass beads were removed from the resulting dispersion using a mesh to prepare conductive layer coating solution 5.

[0100] <Preparation of coating solution for undercoat layer> [Preparation of Coating Solution 1 for Undercoat Layer] One hundred parts of rutile-type titanium dioxide particles (product name: MT-600B, average primary particle size: 50 nm, manufactured by Teika) were mixed with 500 parts of toluene and stirred, and 5.0 parts of vinyltrimethoxysilane (product name: KBM-1003, manufactured by Shin-Etsu Chemical) were added and stirred for 8 hours. The toluene was then removed by distillation under reduced pressure, and the mixture was dried at 120°C for 3 hours to obtain rutile-type titanium dioxide particles that had been surface-treated with vinyltrimethoxysilane. Next, 18 parts of the rutile-type titanium oxide particles that had been surface-treated with the vinyltrimethoxysilane, 4.5 parts of N-methoxymethylated nylon (product name: Toresin EF-30T, manufactured by Nagase ChemteX), and 1.5 parts of copolymer nylon resin (product name: Amilan™ CM8000, manufactured by Toray) were added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion. This dispersion was dispersed for 5 hours in a vertical sand mill using glass beads with a diameter of 1.0 mm to prepare coating solution 1 for the undercoat layer.

[0101] [Preparation of Coating Solution 2 for Undercoat Layer] A solution obtained by dissolving 25 parts of N-methoxymethylated nylon 6 (trade name: Toresin EF-30T, manufactured by Nagase ChemteX) in 480 parts of a 2 / 1 mixed solution of methanol and n-butanol (heated and dissolved at 65°C) was cooled, and then the solution was filtered through a membrane filter (trade name: FP-022, pore size: 0.22 μm, manufactured by Sumitomo Electric Industries, Ltd.) to prepare coating solution 2 for undercoat layer.

[0102] [Preparation of Coating Solution 3 for Undercoat Layer] The following formula (A3) [ka] 1 part by mass of a compound represented by the formula (I), 0.2 parts by mass of polyvinyl butyral resin (trade 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. To this solution was added a blocked isocyanate resin (trade name: Duranate SBN-70D, manufactured by Asahi Kasei Co., Ltd.) in an amount equivalent to 1.3 parts by mass of solids, to prepare coating solution 3 for undercoat layer.

[0103] [Preparation of Coating Solution 4 for Undercoat Layer] The following formula (A4) [ka] 1 part by mass of a compound represented by the formula (I), 0.2 parts by mass of polyvinyl butyral resin (trade 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. To this solution was added a blocked isocyanate resin (trade name: Duranate SBN-70D, manufactured by Asahi Kasei Co., Ltd.) in an amount equivalent to 1.3 parts by mass of solids, to prepare coating solution 4 for undercoat layer.

[0104] [Preparation of Coating Solution 5 for Undercoat Layer] A solution obtained by dissolving 5 parts of a 6-66-610-12 quaternary polyamide copolymer in 95 parts of a 14 / 5 mixed solution of methanol and n-butanol (heated and dissolved at 65°C) was cooled and then filtered through a membrane filter (product name: FP-022, pore size: 0.22 μm, manufactured by Sumitomo Electric Industries, Ltd.) to prepare coating solution 5 for undercoat layer.

[0105] [Preparation of Coating Solution 6 for Undercoat Layer] 30 parts of a titanium chelate compound (trade name: TC-750, manufactured by Matsumoto Pharmaceutical Co., Ltd.) and 17 parts of a silane coupling agent (trade name: KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 117 parts of 2-propanol to prepare coating solution 6 for undercoat layer.

[0106] <Preparation of Coating Solution for Charge Generating Layer> [Synthesis Example 1] Under a nitrogen flow atmosphere, 5.46 parts of orthophthalonitrile and 45 parts of α-chloronaphthalene were added to a reaction vessel, which was then heated to 30°C and maintained at that temperature. Next, 3.75 parts of gallium trichloride were added at this temperature (30°C). The water concentration of the mixed solution at the time of addition was 150 ppm. The temperature was then increased to 200°C. Next, under a nitrogen flow atmosphere, the mixture was reacted at 200°C for 4.5 hours, then cooled, and the product was filtered when the temperature reached 150°C. The resulting filtrate was dispersed and washed using N,N-dimethylformamide at 140°C for 2 hours, followed by filtration. The resulting filtrate was washed with methanol and dried, yielding a chlorogallium phthalocyanine pigment in a 71% yield.

[0107] [Synthesis Example 2] 4.65 parts of the chlorogallium phthalocyanine pigment obtained in Synthesis Example 1 above was dissolved in 139.5 parts of concentrated sulfuric acid at 10°C, and the solution was added dropwise to 620 parts of ice water with stirring to reprecipitate, followed by vacuum filtration using a filter press. A No. 5C filter (manufactured by Advantec Co., Ltd.) was used. The resulting wet cake (filtrate) was dispersed and washed with 2% aqueous ammonia for 30 minutes, and then filtered using a filter press. The resulting wet cake (filtrate) was then dispersed and washed with ion-exchanged water, followed by filtration using a filter press, which was repeated three times. Finally, freeze-drying was performed to obtain a hydroxygallium phthalocyanine pigment (hydrated hydroxygallium phthalocyanine pigment) with a solids content of 23% in a yield of 97%.

[0108] [Synthesis Example 3] 6.6 kg of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 2 above was dried using a Hyper Dry dryer (trade name: HD-06R, frequency (oscillation frequency): 2455 MHz±15 MHz, manufactured by Nippon Biocon) as follows. The hydroxygallium phthalocyanine pigment was placed on a dedicated circular plastic tray in the form of a lump (a wet cake thickness of 4 cm or less) just as it was removed from the filter press, the far infrared rays were turned off, and the temperature of the inner wall of the dryer was set to 50° C. Then, during microwave irradiation, the vacuum pump and leak valve were adjusted to adjust the degree of vacuum to 4.0 to 10.0 kPa. First, in the first step, a 4.8 kW microwave was irradiated onto the hydroxygallium phthalocyanine pigment for 50 minutes. Next, the microwave was turned off, the leak valve was closed, and a high vacuum of 2 kPa or less was created. At this point, the solid content of the hydroxygallium phthalocyanine pigment was 88%. In the second step, the leak valve was adjusted to adjust the vacuum level (pressure inside the dryer) to within the set value (4.0 to 10.0 kPa). Next, a 1.2 kW microwave was irradiated onto the hydroxygallium phthalocyanine pigment for 5 minutes. Then, the microwave was turned off, the leak valve was closed, and a high vacuum of 2 kPa or less was created. This second step was repeated once more (i.e., this step was performed twice in total). At this point, the solid content of the hydroxygallium phthalocyanine pigment was 98%. Furthermore, in the third step, microwave irradiation was performed in the same manner as in the second step, except that the microwave output in the second step was changed from 1.2 kW to 0.8 kW. This third step was repeated once more (i.e., this step was performed twice in total). Furthermore, in the fourth step, the leak valve was adjusted to restore the degree of vacuum (pressure inside the dryer) to the above-mentioned set value (4.0 to 10.0 kPa). After that, the hydroxygallium phthalocyanine pigment was irradiated with 0.4 kW microwaves for 3 minutes, and then the microwaves were turned off and the leak valve was closed to create a high vacuum of 2 kPa or less. This fourth step was repeated seven more times (i.e., this step was performed eight times in total). Over a total of three hours, 1.52 kg of hydroxygallium phthalocyanine pigment (crystals) with a moisture content of 1% or less was obtained.

[0109] [Synthesis Example 4] 5.0 g of o-phthalodinitrile and 2.0 g of titanium tetrachloride were heated and stirred in 100 g of α-chloronaphthalene at 200°C for 3 hours, then cooled to 50°C. The precipitated crystals were filtered off to obtain a paste of dichlorotitanium phthalocyanine. This was then washed with stirring in 100 mL of N,N-dimethylformamide heated to 100°C, followed by two repeated washes with 100 mL of methanol at 60°C and filtration. The resulting paste was then stirred in 100 mL of deionized water at 80°C for 1 hour and filtered to obtain 4.3 g of blue titanyl phthalocyanine pigment.

[0110] [Milling example 1] One part of 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 with a diameter of 0.9 mm were milled for 70 hours at a cooling water temperature of 18°C using a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing Co., Ltd. (now Imex), disk diameter 70 mm, number of disks: 5). The milling was carried out at a disk rotation speed of 400 revolutions per minute. The resulting solution was filtered through a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec) to remove the glass beads. Thirty parts of N-methylformamide were added to the solution, followed by filtration. The filter cake was thoroughly washed with tetrahydrofuran. The washed filter cake was then vacuum dried to obtain 0.45 parts of hydroxygallium phthalocyanine pigment. The obtained pigment had strong peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in its X-ray diffraction spectrum using CuKα radiation. 1 The content of the amide compound (N-methylformamide) represented by the above formula (A1) in the hydroxygallium phthalocyanine crystal particles estimated by H-NMR measurement was 0.8 mass % relative to the content of hydroxygallium phthalocyanine.

[0111] [Milling example 2] 0.5 parts of the titanyl phthalocyanine pigment obtained in Synthesis Example 4, 10 parts of tetrahydrofuran, and 15 parts of glass beads with a diameter of 0.9 mm were milled for 48 hours using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now Imex), disk diameter 70 mm, number of disks: 5) at a cooling water temperature of 18°C. The milling was performed at 500 disk revolutions per minute. The resulting solution was filtered through a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec) to remove the glass beads. 30 parts of tetrahydrofuran were added to the solution, followed by filtration. The filtered product was thoroughly washed with methanol and water. The washed product was then vacuum dried to obtain 0.45 parts of titanyl phthalocyanine pigment. The resulting pigment exhibited a strong peak at a Bragg angle 2θ of 27.2°±0.3° in its X-ray diffraction spectrum using CuKα radiation.

[0112] [Milling example 3] 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 with a diameter of 0.9 mm were milled in a ball mill at room temperature (23°C) for 100 hours. A standard bottle (product name: PS-6, manufactured by Kakuyo Glass Co., Ltd.) was used for milling, and the milling was carried out at 60 revolutions per minute. The resulting solution was filtered through a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec Co., Ltd.) to remove the glass beads. 30 parts of N,N-dimethylformamide was added to the solution, followed by filtration. The filter cake was thoroughly washed with tetrahydrofuran. The washed filter cake was then dried under vacuum to obtain 0.48 parts of hydroxygallium phthalocyanine pigment. The obtained pigment had peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in its X-ray diffraction spectrum using CuKα radiation.

[0113] [Preparation of Coating Solution 1 for Charge Generating Layer] 20 parts of the hydroxygallium phthalocyanine pigment obtained in Milling 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 with a diameter of 0.9 mm were dispersed in a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now Imex), disk diameter 70 mm, number of disks: 5) at a cooling water temperature of 18°C for 4 hours. The disks were rotated at 1,800 revolutions per minute. After removing the glass beads, 444 parts of cyclohexanone and 634 parts of ethyl acetate were added to the dispersion to prepare Coating Solution 1 for the CGL.

[0114] [Preparation of Coating Solution 2 for Charge Generating Layer] 12 parts of the titanyl phthalocyanine pigment obtained in Milling Example 2, 10 parts of polyvinyl butyral (product name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.), 158 parts of cyclohexanone, and 402 parts of glass beads with a diameter of 0.9 mm were dispersed in a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now Imex Co., Ltd.), 70 mm disk diameter, 5 disks) at a cooling water temperature of 18°C for 4 hours at a disk rotation speed of 1,800 revolutions per minute. After removing the glass beads, 369 parts of cyclohexanone and 527 parts of ethyl acetate were added to this dispersion to prepare Coating Solution 2 for the CGL.

[0115] [Preparation of Coating Solution 3 for Charge Generating Layer] 20 parts of the hydroxygallium phthalocyanine pigment obtained in Milling Example 3, 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 with a diameter of 0.9 mm were dispersed in a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now Imex), disk diameter 70 mm, number of disks: 5) at a cooling water temperature of 18°C for 4 hours. The disks were rotated at 1,800 revolutions per minute. After removing the glass beads, 444 parts of cyclohexanone and 634 parts of ethyl acetate were added to the dispersion to prepare Coating Solution 3 for the CGL.

[0116] [Preparation of Coating Solution 4 for Charge Generating Layer] 0.45 parts of polycarbonate (trade name: Iupilon Z-200, manufactured by Mitsubishi Engineering Plastics), 2.4 parts of the hydroxygallium phthalocyanine pigment obtained in Milling Example 3, 56 parts of tetrahydrofuran, and 300 parts of 3.2 mm diameter stainless steel balls were milled in a standard bottle (trade name: PS-6, manufactured by Kakuyo Glass) at room temperature (23°C) for 24 hours at 120 revolutions per minute. After removing the stainless steel balls, 2.25 parts of polycarbonate (trade name: Iupilon Z-200, manufactured by Mitsubishi Engineering Plastics) was dissolved in 46.1 parts of tetrahydrofuran, and this was added to the above-mentioned hydroxygallium phthalocyanine slurry. Next, 300 parts of this slurry and 450 parts of glass beads with a diameter of 0.9 mm were dispersed in a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing (now Imex), disk diameter 70 mm, number of disks 5) for 10 minutes at a cooling water temperature of 18°C. The disks were rotated at 1800 revolutions per minute. The glass beads were removed from this dispersion to prepare Coating Solution 4 for the charge generating layer.

[0117] [Preparation of Coating Solution 5 for Charge Generating Layer] The following formula (CGM-1) [ka] A mixture of 10 parts of a trisazo pigment represented by the formula (I), 5 parts of a phenoxy resin (product name: PKHH, manufactured by Union Carbide), 5 parts of a polyvinyl butyral resin (product name: S-LEC BX-1, manufactured by Sekisui Chemical), 100 parts of cyclohexanone, and 200 parts of 0.9 mm diameter glass beads was dispersed in a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now Imex), 70 mm diameter, 5 disks) at a cooling water temperature of 18°C for 24 hours at a disk rotation speed of 1,800 revolutions per minute. After removing the glass beads, 200 parts of 1,4-dioxane was added to the dispersion to prepare Coating Solution 5 for the CGL.

[0118] [Preparation of Coating Solution 6 for Charge Generating Layer] 9 parts of titanyl phthalocyanine, which exhibits strong peaks at Bragg angles 2θ of 9.6±0.2°, 24.0±0.2°, and 27.2±0.2° in its X-ray diffraction spectrum using CuKα radiation, 11 parts of polyvinyl butyral (trade name: BX-55, manufactured by Sekisui Chemical Co., Ltd.), 90 parts of a mixed solvent of 2-butanone and cyclohexanone, and 200 parts of 0.9 mm diameter glass beads were dispersed in a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now Imex Co., Ltd.), 70 mm diameter disk, 5 disks) for 4 hours at a cooling water temperature of 18°C. The disks were rotated at 1,800 revolutions per minute. After dispersion, the glass beads were removed from the dispersion to prepare CGL Coating Solution 6.

[0119] [Preparation of Coating Solution 7 for Charge Generating Layer] Six parts of titanyl phthalocyanine (6 parts) exhibiting peaks at Bragg angles 2θ of 9.6±0.2°, 24.0±0.2°, and 27.2±0.2° in its X-ray diffraction spectrum using CuKα radiation, three parts of titanyl phthalocyanine (3 parts) exhibiting peaks at Bragg angles 2θ of 7.6±0.2°, 25.3±0.2°, and 28.6±0.2° in its X-ray diffraction spectrum using CuKα radiation, 11 parts of polyvinyl butyral (trade name: BX-55, manufactured by Sekisui Chemical Co., Ltd.), 90 parts of a mixed solvent of 2-butanone and cyclohexanone, and 200 parts of 0.9 mm diameter glass beads were dispersed in a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now Imex Co., Ltd.), 70 mm diameter disk, five disks) at 1,800 rotations per minute for four hours under cooling water temperature of 18°C. After the dispersion treatment, the glass beads were removed from the dispersion to prepare Coating Solution 7 for Charge Generating Layer.

[0120] [Preparation of Coating Solution 1 for Charge Transport Layer] As the charge transport material, a compound represented by the following formula (A5) [ka] 40 parts of a charge transport material having an ionization potential of 5.4 eV, The following formula (A6) [ka] 60 parts of a charge transport material having an ionization potential of 5.3 eV, Charge transport layer coating solution 1 was prepared by dissolving 100 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) in 225 parts of orthoxylene / 375 parts of methyl benzoate / 150 parts of dimethoxymethane.

[0121] [Preparation of Coating Solution 2 for Charge Transport Layer] As the charge transport material, the following formula (A7) [ka] 100 parts of a charge transport material having an ionization potential of 5.5 eV, Charge transport layer coating solution 2 was prepared by dissolving 100 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) in 225 parts of orthoxylene / 375 parts of methyl benzoate / 150 parts of dimethoxymethane.

[0122] [Preparation of Coating Solution 3 for Charge Transport Layer] As the charge transport material, the following formula (A8) [ka] 100 parts of a charge transport material having an ionization potential of 5.5 eV, Charge transport layer coating solution 3 was prepared by dissolving 100 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) in 225 parts of orthoxylene / 375 parts of methyl benzoate / 150 parts of dimethoxymethane.

[0123] [Preparation of Coating Solution 4 for Charge Transport Layer] As the charge transport material, the following formula (A9) [ka] 100 parts of a charge transport material having an ionization potential of 5.5 eV, Charge transport layer coating solution 4 was prepared by dissolving 100 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) in 225 parts of ortho-xylene / 375 parts of methyl benzoate / 150 parts of dimethoxymethane.

[0124] [Preparation of Coating Solution 5 for Charge Transport Layer] As the charge transport material, a compound represented by the following formula (A10) [ka] 90 parts of a charge transport material having an ionization potential of 5.35 eV, The following formula (A11) [ka] and a structural unit represented by The following formula (A12) [ka] and structural units represented by the following formula (1) in a ratio of 5 / 5 and having a weight average molecular weight of 100,000 was dissolved in a mixed solvent of 300 parts of dimethoxymethane and 700 parts of chlorobenzene to prepare coating solution 5 for charge transport layer.

[0125] [Preparation of Coating Solution 6 for Charge Transport Layer] 70 parts of a triarylamine compound represented by the formula (A10) as a charge transport material, The following formula (A13) [ka] 10 parts of a triarylamine compound represented by the following formula: and 100 parts of polycarbonate (trade name: Iupilon Z-200, manufactured by Mitsubishi Engineering Plastics) were dissolved in 630 parts of monochlorobenzene to prepare coating solution 6 for charge transport layer.

[0126] [Preparation of Coating Solution 7 for Charge Transport Layer] As a charge transport material, 50 parts of a charge transport material represented by the following formula (A14): [ka] The following formula (A15) [ka] and a structural unit represented by The following formula (A16) [ka] and a structural unit represented by the following formula: 100 parts of a polycarbonate resin having a terminal structural formula derived from butylphenol, 8 parts of 2,6-di-t-butyl-4-methylphenol, Charge transport layer coating solution 7 was prepared by dissolving 0.03 parts of silicone oil (trade name: KF96, manufactured by Shin-Etsu Chemical Co., Ltd.) in 640 parts of a mixed solvent of tetrahydrofuran / toluene (weight ratio 8 / 2).

[0127] [Preparation of Coating Solution 8 for Charge Transport Layer] 25 parts of the charge transport material represented by formula (A6) as the charge transport material; The following formula (A17) [ka] 25 parts of a charge transport material represented by the formula: 100 parts of a polycarbonate resin having a repeating unit of the structural unit represented by the formula (A15) and a repeating unit of the structural unit represented by the formula (A16) in a ratio of 51 mol % / 49 mol % and having a terminal structural formula derived from pt-butylphenol, Charge transport layer coating solution 8 was prepared by dissolving 0.05 parts of silicone oil (trade name: KF96, manufactured by Shin-Etsu Chemical Co., Ltd.) in 640 parts of a mixed solvent of tetrahydrofuran / toluene (weight ratio 8 / 2).

[0128] [Preparation of Coating Solution 9 for Charge Transport Layer] 10 parts of the charge transport material represented by formula (A6) as the charge transport material; Charge transport layer coating solution 9 was prepared by dissolving 10 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) in 39 parts of tetrahydrofuran.

[0129] [Preparation of Coating Solution 10 for Charge Transport Layer] 30 parts of (4-methoxy-4'-(4-methyl-α-phenylstyryl)triphenylamine) as a charge transport material, 30 parts polycarbonate (product name: Iupilon Z-300, manufactured by Mitsubishi Engineering Plastics) Charge transport layer coating solution 10 was prepared by dissolving 1 part of tin oxide fine particles in 200 parts of dioxolane.

[0130] [Preparation of Coating Solution 11 for Charge Transport Layer] The following formula (A18) [ka] 50 parts of a charge transport material represented by 50 parts polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) The following formula (A19) [ka] 1.5 parts of a dicyano compound represented by the following formula was dissolved in 4 parts of di-tert-butylhydroxytoluene and dichloromethane to prepare a coating solution 11 for a charge transport layer.

[0131] [Preparation of Coating Solution 12 for Charge Transport Layer] DEH (p-(diethylamino)benzaldehyde diphenylhydrazone) 27.0 parts, Bisphenol-A (Bayer AG) 37.9 parts, 0.48 parts of acetosol yellow was dissolved in a mixed solvent of tetrahydrofuran and 1,4-dioxane to prepare coating solution 12 for charge transport layer.

[0132] [Preparation of Coating Solution 1 for Single-Layer Photosensitive Layer] Metal-free phthalocyanine 5 parts, The following formula (A20) [ka] 10 parts of a charge transport material (hole transport material) represented by the formula: The following formula (A21) [ka] 3 parts of a charge transport material (electron transport material) represented by 10 parts of polycarbonate (product name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics), 80 parts of tetrahydrofuran, and 250 parts of glass beads with a diameter of 0.9 mm were milled for 10 hours at room temperature (23°C) using a paint shaker (manufactured by Toyo Seiki Seisakusho). A standard bottle (product name: PS-6, manufactured by Kakuyo Glass) was used as the container. The milled solution was filtered through a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec) to remove the glass beads, preparing Coating Solution 1 for a single-layer photosensitive layer.

[0133] <Production of electrophotographic photoreceptors> (Photoreceptor manufacturing example 1) An aluminum cylinder (JIS-A3003, aluminum alloy) having a length of 260.5 mm and a diameter of 30 mm was obtained as a support by a manufacturing method including an extrusion step and a drawing step. The conductive layer coating liquid 1 was dip-coated onto this support to form a coating film, and the coating film was dried by heating at 150° C. for 20 minutes to form a conductive layer with a film thickness of 19 μm. Next, the undercoat layer coating liquid 1 was dip-coated onto the conductive layer to form a coating film, and the coating film was dried by heating at 100° C. for 10 minutes to form an undercoat layer with a thickness of 2.2 μm. Next, the undercoat layer was dip-coated with Coating Solution 1 for Charge Generating Layer to form a coating film, and the coating film was dried by heating at 100°C for 10 minutes to form a charge generating layer with a thickness of 140 nm. Next, the charge transport layer coating liquid 1 was dip coated onto the charge generation layer to form a coating film, and the coating film was dried by heating at a temperature of 120°C for 60 minutes to form a charge transport layer with a thickness of 17 μm. The heat treatment of the coating film of each layer was carried out using an oven set to the respective temperature. In this manner, a cylindrical (drum-shaped) photoreceptor 1 was produced.

[0134] The characteristic value of the photoconductor obtained at this time is I 1 / 2 [μJ·cm 2 ], AR, LR i , and V r The results are shown in Table 1 together with the structure of Photoreceptor Production Example 1.

[0135] In Tables 1 and 2, "CPL" means "conductive layer," and the CPL coating liquid numbers "1," "2," "3," "4," and "5" respectively mean "conductive layer coating liquid 1," "conductive layer coating liquid 2," "conductive layer coating liquid 3," "conductive layer coating liquid 4," and "conductive layer coating liquid 5." Furthermore, "UCL" means "undercoat layer," and the UCL coating liquid numbers "1," "2," "3," "4," "5," and "6" respectively mean "undercoat layer coating liquid 1," "undercoat layer coating liquid 2," "undercoat layer coating liquid 3," "undercoat layer coating liquid 4," "undercoat layer coating liquid 5," and "undercoat layer coating liquid 6." "CGL" refers to "charge generation layer," and the CGL coating liquid numbers "1," "2," "3," "4," "5," "6," and "7" refer to "charge generation layer coating liquid 1," "charge generation layer coating liquid 2," "charge generation layer coating liquid 3," "charge generation layer coating liquid 4," "charge generation layer coating liquid 5," "charge generation layer coating liquid 6," and "charge generation layer coating liquid 7," respectively. "CTL" refers to "charge transport layer." The CTL coating liquid numbers "1," "2," "3," "4," "5," "6," "7," "8," "9," "10," "11," and "12" refer to "charge transport layer coating liquid 1," "charge transport layer coating liquid 2," "charge transport layer coating liquid 3," "charge transport layer coating liquid 4," "charge transport layer coating liquid 5," "charge transport layer coating liquid 6," "charge transport layer coating liquid 7," "charge transport layer coating liquid 8," "charge transport layer coating liquid 9," "charge transport layer coating liquid 10," "charge transport layer coating liquid 11," and "charge transport layer coating liquid 12." "A film thickness of 38 μm was formed using coating solution 1 for single-layer photosensitive layer" means that "coating solution 1 for single-layer photosensitive layer" was applied to the aluminum cylinder to form a film with a thickness of 38 μm.

[0136] The drying temperatures and drying times when CPL coating solutions Nos. 1 to 5 in Tables 1 and 2 were dip-coated were as follows. CPL Coating Solution No. 1: Drying temperature 150°C, drying time 20 minutes CPL coating solution No. 2: Drying temperature 145°C, drying time 60 minutes CPL coating solution No. 3: Drying temperature 170°C, drying time 20 minutes CPL coating solution No. 4: Drying temperature 170°C, drying time 40 minutes CPL coating solution No. 5: Drying temperature 140°C, drying time 30 minutes

[0137] The drying temperatures and drying times when UCL coating solutions Nos. 1 to 6 in Tables 1 and 2 were dip-coated were as follows. UCL Coating Solution No. 1: Drying temperature 100°C, drying time 10 minutes UCL Coating Solution No. 2: Drying temperature 100°C, drying time 10 minutes UCL Coating Solution No. 3: Drying temperature 160°C, drying time 30 minutes UCL Coating Solution No. 4: Drying temperature 160°C, drying time 30 minutes UCL Coating Solution No. 5: Drying temperature 100°C, drying time 10 minutes UCL Coating Solution No. 6: Drying temperature 120°C, drying time 30 minutes

[0138] The drying temperatures and drying times when CGL coating solutions Nos. 1 to 7 in Tables 1 and 2 were dip-coated were as follows. CGL Coating Solution No. 1: Drying temperature 100°C, drying time 10 minutes CGL Coating Solution No. 2: Drying temperature 100°C, drying time 10 minutes CGL Coating Solution No. 3: Drying temperature 100°C, drying time 10 minutes CGL Coating Solution No. 4: Drying temperature 125°C, drying time 2 minutes CGL Coating Solution No. 5: Drying temperature 100°C, drying time 10 minutes CGL Coating Solution No. 6: Drying temperature 100°C, drying time 15 minutes CGL Coating Solution No. 7: Drying temperature 100°C, drying time 15 minutes

[0139] The drying temperatures and drying times when CTL coating solutions Nos. 1 to 12 in Tables 1 and 2 were dip-coated were as follows. CTL coating solution No. 1: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 2: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 3: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 4: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 5: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 6: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 7: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 8: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 9: Drying temperature 120°C, drying time 30 minutes CTL coating solution No. 10: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 11: Drying temperature 125°C, drying time 30 minutes CTL coating solution No. 12: Drying temperature 100°C, drying time 60 minutes

[0140] Furthermore, the drying temperature and drying time when "single layer drying coating liquid 1" in Photoreceptor Production Example 79 in Table 2 was dip coated were as follows. Drying temperature: 130°C, drying time: 30 minutes Furthermore, "-" in Tables 1 and 2 means that the corresponding layer was not formed.

[0141] (Photoreceptor manufacturing examples 2 to 83) Photoreceptors 2 to 83 were produced in the same manner as in Photoreceptor Production Example 1, except that the conductive layer, undercoat layer, charge generation layer, and charge transport layer in Photoreceptor Production Example 1 were changed as shown in Tables 1 and 2. However, the heat treatment of the coating films of the conductive layer, undercoat layer, charge generation layer, and charge transport layer was carried out for the respective times using ovens set at the respective temperatures as described above.

[0142] In addition, in the same manner as in Photoreceptor Manufacturing Example 1, the characteristic values of photoreceptors 2 to 83, I 1 / 2 [μJ·cm 2 ], AR, LR i , and V r The results are shown in Tables 1 and 2 together with the configurations of Photoreceptor Production Examples 2 to 83.

[0143] [Table 1]

[0144] [Table 2]

[0145] [evaluation] Using the above photoreceptor manufacturing examples 1 to 83, evaluations were carried out for Examples 1 to 50 and Comparative Examples 1 to 33. The evaluations were carried out as follows. The results are shown in Tables 3 and 4.

[0146] <Evaluation equipment> A laser beam printer (product name: Laser Jet Enterprise M609dn) manufactured by Hewlett-Packard was prepared as the electrophotographic device for evaluation, and was modified so that the process 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. When outputting an image, the drums of the above-mentioned Photoreceptor Production Examples 1 to 83 were attached to the process cartridge of the above-mentioned laser beam printer, and a monochrome image was output.

[0147] <Checking whether analog tone is maintained> The dark potential was set to 450 [V], and the exposure dose was determined so that the surface potential after exposure was 225 [V]. The absolute value of the difference between the surface potential when irradiated with 10 times the light intensity and the dark potential of 450 [V] was defined as ΔV. To ensure consistent analog gradation on the EV curve, the exposure dose was set so that the surface potential after exposure was 450 - 0.99 ΔV. To measure the photoreceptor surface potential during potential setting, a potential probe (product name: model 6000B-8, Trek Japan) was attached to the development position of the process cartridge, and measurements were taken using a surface potential meter (product name: model 344, Trek Japan). Next, dither patterns were prepared for evaluation. Figure 9 shows examples of line-growing dither patterns with 150 lines at a resolution of 600 dpi, with area ratios of (a) 0%, (b) 25%, (c) 50%, (d) 75%, and (e) 100%. In actual measurements, 32 gradations (33 patterns, including a solid white pattern with an area ratio of 0%) were produced by dividing the area ratio into 32 equal parts. Step interpolation to less than one pixel was performed using pulse width modulation (PWM). A similar 32-gradation line-growing dither pattern was also prepared for a 600-line frequency, in addition to the 150-line frequency. When the image exposure amount set by the above method is fixed, the absolute value V of the difference between the dark potential and the development potential back [V] and the absolute value of the difference between the development potential and the exposure potential V cont [V] is V back = 200 [V] and V back The voltage applied to the charging roller and developing roller was adjusted so that the line density was 200 V, and the 32-level, 600-line-count, line-growth dither pattern was output. The toner density at each level of this output image was measured using a reflection densitometer (product name: RD-918, manufactured by Macbeth). The measured values were normalized by the density at an area ratio of 100% after subtracting the density of the solid white area with an area ratio of 0% from the density data for all levels of gradation. The vertical axis represents the measured value, and the horizontal axis represents the area ratio. Figure 10 shows an example of a graph obtained by measuring the above-mentioned photoreceptor manufacturing example 1 at a process speed of 300 mm / s. On this graph, if the normalized density at an area ratio of 60% was within 0.8 ± 0.05, it was determined that analog gradation was maintained. If the normalized density at an area ratio of 60% was above 0.85, the image exposure was reduced by approximately 10% and the area ratio vs. normalized density graph was remeasured. On the other hand, if the result is below 0.75, the image exposure is increased by about 10% and the area ratio-normalized density graph is measured again. This process is repeated until the normalized density at an area ratio of 60% falls within 0.8±0.05, and the final image exposure is determined.

[0148] <Evaluation of digital tonality> The process speed was set to 200 mm / s, the dark potential to 450 V, and the development potential to 250 V, and a solid pattern was output at the image exposure determined by the method described above in <Confirmation of whether analog gradation is maintained>. The density of this output image was taken as the maximum density value for density normalization determined for each photoreceptor manufacturing example to be evaluated. Next, the process speed was set to 300 [mm / s], 400 [mm / s], or 500 [mm / s], the dark potential was set to 450 [V], the development potential was set to 250 [V], and the image exposure determined by the method above was used to output the above-mentioned 32-level 150-line-fiber-count dither pattern. The toner density of each level of this output image was measured using a reflection densitometer (product name: RD-918, manufactured by Macbeth). The measured values were normalized by the maximum density value for density normalization described above, after subtracting the density of the solid white area with an area ratio of 0 [%] from the density data for all levels. The vertical axis represents the density, and the horizontal axis represents the area ratio. The following two values were calculated. (i) In the area ratio vs. normalized density graph shown in Figure 11, the two points of area ratio 0[%] and 50[%] are connected with a straight line, and the difference with the data for 16 gradations in the area ratio range of 0 to 50[%] is calculated and averaged to determine the "highlight gradation." The closer this value is to 0, the better the gradation in the highlight area is. (ii) In the area ratio vs. normalized density graph shown in Figure 11, the two points of area ratio 50[%] and 100[%] were connected with a straight line, and the difference with the data for 16 gradations in the area ratio range of 50-100[%] was calculated and averaged to determine the "shadow gradation." The closer this value is to 0, the better the gradation in the shadow area.

[0149] <Evaluation of visibility of 6pt white characters> The process speed was set to 300 [mm / s], 400 [mm / s], or 500 [mm / s], the dark potential to 450 [V], the development potential to 250 [V], and the image exposure determined in the above <Confirmation of whether analog gradation is maintained> was used to output an image of the white "Denkyo" character in MS Mincho font with a font size of 6 pt. The output image was visually observed, and the visibility of the 6 pt white character was evaluated according to the following criteria. Rank A: The white "Denkyo" characters are clearly readable. Rank B: The white "Denkyo" characters are faded. Rank C: The white "Denkyo" characters are starting to get crushed. Rank X: The solid black part of the white "Denkyo" character has faded. In the above evaluation, ranks A and B were determined to be good visibility of 6 pt white characters.

[0150] <Evaluation of visibility of 3pt characters> The process speed was set to 300 [mm / s], 400 [mm / s], or 500 [mm / s], the dark potential was set to 450 [V], the development potential was set to 250 [V], and the character "Denkyo" in MS Mincho font with a font size of 3 pt was output as an image at the image exposure determined in the above <Confirmation of whether analog gradation is maintained>. This output image was visually observed, and the visibility of the 3 pt characters was evaluated according to the following criteria. Rank A: The "Denkyo" character can be read clearly. Rank B: The characters "Denkyo" are faint. Rank C: The "Denkyo" characters are faded. In the above evaluation, ranks A and B were determined to be good visibility of 3pt characters.

[0151] <Evaluation of isolated single dot reproducibility> The process speed was set to 300 [mm / s], 400 [mm / s], or 500 [mm / s], the dark potential was set to 450 [V], the development potential was set to 250 [V], and the image exposure amount determined in <Confirming whether analog gradation is maintained> above was used to output a 1 dot 4 space halftone image shown in Figure 12. The toner density of this output image was measured with a reflection densitometer (product name: RD-918, manufactured by Macbeth), and the isolated 1 dot reproducibility was evaluated according to the following criteria. Rank A: Toner density 0.084 or higher. Rank B: Toner density 0.076 or more but less than 0.084. Rank C: Toner density 0.059 or more but less than 0.076. Rank D: Toner density less than 0.059. In the above evaluation, ranks A and B were judged to be good in terms of isolated dot reproducibility.

[0152] [Table 3]

[0153] [Table 4] [Explanation of symbols]

[0154] 101:Support 102: Undercoat layer 103: Charge generating layer 104: Charge transport layer 105: Photosensitive layer 1: Electrophotographic photoreceptor 2: Axis 3: Charging means 4: Image exposure light 5: Developing method 6: Transfer means 7: Transfer material 8: Image fixing means 9: Cleaning means 10: Pre-exposure light 11: Process cartridge 12: Guidance means 201: Photoreceptor 202: NESA Glass 203: Exposure 204: Transparent ITO electrode 205: High voltage power supply

Claims

1. 1. An electrophotographic photoreceptor having a support, an undercoat layer on the support, a charge generating layer on the undercoat layer, and a charge transport layer on the charge generating layer, the electrophotographic photoreceptor is an organic photoreceptor, the undercoat layer contains titanium oxide particles whose surfaces have been silane-treated and whose crystal structure is rutile or anatase, the charge generating layer is A hydroxygallium phthalocyanine crystal having strong peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in CuKα characteristic X-ray diffraction, and containing 0.4% by mass or more and 3.0% by mass or less of a compound having a structure represented by the following formula (A1): (In the above formula (A1), R 0 represents a methyl group, a propyl group, or a vinyl group), or Titanyl phthalocyanine crystals having a strong peak at the Bragg angle 2θ of 27.2°±0.3° in CuKα characteristic X-ray diffraction Including, the average film thickness of the charge generating layer is 150 nm or more and 300 nm or less; the charge transport layer contains a charge transport material and a resin, and the content ratio (mass ratio) of the charge transport material to the resin in the charge transport layer is 8:10 to 12:10; At a temperature of 23.5°C and a relative humidity of 50%RH, the charge potential is V ｄ = 500 [V], the horizontal axis obtained according to the following <NESA-EV curve measurement method> is I ｅｘｐ The vertical axis is V ｅｘｐ I ｅｘｐ -V ｅｘｐ In the graph, V of the graph ｅｘｐ When the light intensity becomes I = 250 [V], １／２ [μJ / cm ２ ]year, I of the graph ｅｘｐ =0.000~3.414・I １／２ [μJ / cm ２ ] in the range of S = I ｅｘｐ ・V ｅｘｐ S [V μJ / cm ２ ] is the maximum value of S ｍａｘ [V μJ / cm ２ ]year, I of the graph ｅｘｐ =0.000[μJ / cm ２ ]~0.100・I １／２ [μJ / cm ２ ] and the approximate line in the range of I ｅｘｐ = (5 I １／２ -0.100) [μJ / cm ２ ]~5・Ⅰ １／２ [μJ / cm ２ ] is the intersection point of the approximate line in the range of Q, and the light intensity value of point Q is I ｉ [μJ / cm ２ ], the potential value at point Q is V ｉ [V], I ｉ and V ｉ The product of S ｉ =I ｉ ・V ｉ [V μJ / cm ２ ]year, S ｉ and S ｍａｘ The ratio of AR = S ｉ / S ｍａｘ year, V ｉ I ｉ The value divided by LR ｉ =V ｉ / I ｉ [V cm ２ / μJ], I １／２ ≦0.170, and AR≦0.370, and LR ｉ ≦780, An electrophotographic photoreceptor characterized by the above-mentioned. <Method for measuring NESA-EV curve> (1): The surface potential of the electrophotographic photosensitive member is set to 0 [V], (2): The absolute value of the surface potential of the electrophotographic photosensitive member is V ０ The electrophotographic photosensitive member is charged for 0.005 seconds to a voltage of [V]. (3): 0.02 seconds after the start of charging, the exposure amount is I ｅｘｐ [μJ / cm ２ ], the wavelength is 805 [nm] and the intensity is 25 [mW / cm ２ the electrophotographic photosensitive member after charging is continuously exposed to light of (4): 0.06 seconds after the start of charging, the absolute value of the surface potential of the electrophotographic photosensitive member after exposure is measured. ｅｘｐ Let it be [V]. (5): By changing t in the operations (1) to (4), I ｅｘｐ to 0.000 [μJ / cm ２ ] to 0.850 [μJ / cm ２ ] up to 0.001 [μJ / cm ２ ] and repeat the process. ｅｘｐ V corresponding to ｅｘｐ get. (6): By operating (3), t = 0, I ｅｘｐ =0.000[μJ / cm ２ ]When V ｅｘｐ [V] is the charging potential V ｄ It is called [V] and V ｄ When performing the operation (2) so that the value of V is 500 [V] ０ Set [V].

2. 1. An electrophotographic photoreceptor having a support, an undercoat layer on the support, a charge generating layer on the undercoat layer, and a charge transport layer on the charge generating layer, the electrophotographic photoreceptor is an organic photoreceptor, the undercoat layer contains titanium oxide particles whose surfaces have been silane-treated and whose crystal structure is rutile or anatase, the charge generating layer is A hydroxygallium phthalocyanine crystal having strong peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in CuKα characteristic X-ray diffraction, and containing 0.4% by mass or more and 3.0% by mass or less of a compound having a structure represented by the following formula (A1): (In the above formula (A1), R 0 represents a methyl group, a propyl group, or a vinyl group), or Titanyl phthalocyanine crystals having a strong peak at the Bragg angle 2θ of 27.2°±0.3° in CuKα characteristic X-ray diffraction Including, the average film thickness of the charge generating layer is 150 nm or more and 300 nm or less; the charge transport layer contains a charge transport material and a resin, and the content ratio (mass ratio) of the charge transport material to the resin in the charge transport layer is 8:10 to 12:10; At a temperature of 23.5°C and a relative humidity of 50%RH, the charge potential is V ｄ = 500 [V], the horizontal axis obtained according to the following <NESA-EV curve measurement method> is I ｅｘｐ The vertical axis is V ｅｘｐ I ｅｘｐ -V ｅｘｐ In the graph, V of the graph ｅｘｐ When the light intensity becomes I = 250 [V], １／２ [μJ / cm ２ ]year, I of the graph ｅｘｐ =0.000~3.414・I １／２ [μJ / cm ２ ] in the range of S = I ｅｘｐ ・V ｅｘｐ The maximum value of S [V μJ / cm2] calculated by ｍａｘ [V μJ / cm ２ ]year, I of the graph ｅｘｐ =0.000[μJ / cm ２ ]~0.100・I １／２ [μJ / cm ２ ] and the approximate line in the range of I ｅｘｐ = (5 I １／２ -0.100) [μJ / cm ２ ]~5・Ⅰ １／２ [μJ / cm ２ ] is the intersection point of the approximated line in the range of Q, and the light intensity value of point Q is I ｉ [μJ / cm ２ ], the potential value at point Q is V ｉ [V], I ｉ and V ｉ The product of S ｉ =I ｉ ・V ｉ [V μJ / cm ２ ]year, S ｉ and S ｍａｘ The ratio of AR = S ｉ / S ｍａｘ year, V ｉ I ｉ The value divided by LR ｉ =V ｉ / I ｉ [V cm ２ / μJ], I １／２ ≦0.170, and AR≦0.500, and LR ｉ ≦520 An electrophotographic photoreceptor characterized by the above-mentioned. <Method for measuring NESA-EV curve> (1): The surface potential of the electrophotographic photosensitive member is set to 0 [V], (2): The absolute value of the surface potential of the electrophotographic photosensitive member is V ０ The electrophotographic photosensitive member is charged for 0.005 seconds to a voltage of [V]. (3): 0.02 seconds after the start of charging, the exposure amount is I ｅｘｐ [μJ / cm ２ ], the wavelength is 805 [nm] and the intensity is 25 [mW / cm ２ the electrophotographic photosensitive member after charging is continuously exposed to light of (4): 0.06 seconds after the start of charging, the absolute value of the surface potential of the electrophotographic photosensitive member after exposure is measured. ｅｘｐ Let it be [V]. (5): By changing t in the operations (1) to (4), I ｅｘｐ to 0.000 [μJ / cm ２ ] to 0.850 [μJ / cm ２ ] up to 0.001 [μJ / cm ２ ] and repeat the process. ｅｘｐ V corresponding to ｅｘｐ get. (6): By operating (3), t = 0, I ｅｘｐ =0.000[μJ / cm ２ ]When V ｅｘｐ [V] is the charging potential V ｄ It is called [V] and V ｄ When performing the operation (2) so that the value of V is 500 [V] ０ Set [V].

3. The AR and the LR ｉ AR≦0.370 and LR ｉ 3. The electrophotographic photoreceptor according to claim 1, wherein the average molecular weight of the electrophotographic photoreceptor is 520 or less.

4. 4. The electrophotographic photoreceptor according to claim 1, wherein the AR satisfies AR≦0.

100.

5. The LR ｉ But, LR ｉ 5. The electrophotographic photoreceptor according to claim 1, wherein the average molecular weight of the electrophotographic photoreceptor is ≦60.

6. I ｅｘｐ -V ｅｘｐ I on the graph ｅｘｐ = 5 I １／２ [μJ / cm ２ ] in V ｅｘｐ 6. The electrophotographic photoreceptor according to claim 1, wherein the value Vr [V] satisfies Vr≦70.

7. 7. The electrophotographic photoreceptor according to claim 6, wherein Vr is equal to or less than 10.

8. 8. A process cartridge which integrally supports the electrophotographic photosensitive member according to claim 1 and at least one means selected from the group consisting of a charging means, a developing means, and a cleaning means, and is detachably mountable to a main body of an electrophotographic apparatus.

9. 8. An electrophotographic apparatus comprising the electrophotographic photosensitive member according to claim 1, a charging unit, an exposure unit, a developing unit, and a transfer unit.

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