Electrophotographic photoreceptor, process cartridge and electrophotographic device

Abstract

To provide an electrophotographic photoreceptor that prevents the generation of memory and maintains high contrast through the durable use.SOLUTION: An electrophotographic photoreceptor has a charge generating layer and a charge transport layer having a film thickness of 0.2 μm or more. At 23.5°C and 50%RH, when the photoreceptor is (1) made to have a surface potential of 0 V and (2) is electrified for 0.005 seconds to adjust the absolute value of the surface potential to be Vd[V], (3) the photoreceptor after the electrification is exposed with light having a wavelength of 805 nm and a quantity of light of Iexp[μJ / cm2] after 0.02 seconds from the start of electrification, and (4) the absolute value obtained through measurement after 0.06 seconds from the start of electrification is Vexp[V], in the relational expression between an electric field intensity E and a recoupling constant Pe obtained from a specific graph generated by repeatedly performing operations and measurement in (1) to (4) while changing Iexp from 0.000 to 1.000μJ / cm2 at an interval of 0.001μJ / cm2, the absolute value of the inclination α of a primary approximation straight line at an electric field intensity E of 10 to 40 V / μm is 4×10-3 or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Electrophotographic photoreceptors used in electrophotographic devices such as copiers and laser beam printers are required to have sufficient sensitivity to image exposure light. Azo pigments and phthalocyanine pigments used as charge transport materials are known to exhibit high sensitivity to light over a wide range of wavelengths. In addition, in recent years, there has been a demand for higher image quality, as exemplified by colorization. This trend has led to an increase in halftone images and solid images, such as photographs, and the quality of these images is improving year by year.

[0003] In order to achieve higher image quality, a desired function of an electrophotographic photosensitive member is to maintain high contrast from the initial stage to the end of its service life. From the viewpoint of increasing the sensitivity of an electrophotographic photoreceptor, it is desirable to design the charge generating layer to have a large thickness, but in this case, the resulting electrophotographic photoreceptor has the drawback of generating a memory. Also, from the viewpoint of increasing the sensitivity of a charge transport layer, it is desirable to design the layer to have a large thickness, but in this case, the resulting electrophotographic photoreceptor has the drawback of increasing the residual charge and also tends to have a worsening of the memory.

[0004] On the other hand, energy saving is desired to reduce the environmental load, and from that perspective, it is conceivable to reduce the voltage applied to the charger in the electrophotographic apparatus. However, when the applied voltage is reduced, the electric field strength applied to the electrophotographic photosensitive member is reduced, and this further worsens the memory caused by the charge generation layer.

[0005] Patent Document 1 describes an electrophotographic photoreceptor having excellent durability and sensitivity, which is achieved by combining a charge generation layer and a charge transfer layer in which η has a sufficiently weak electric field dependency in the relationship between the quantum efficiency η and the electric field E as an electrophotographic photoreceptor, and by having a specific charge transfer layer film thickness.

[0006] Patent Document 2 describes an electrophotographic device that measures the surface potential on an image carrier when exposed with varying exposure energy, and sets the device to irradiate with an exposure energy J that makes the surface potential 1.3 times or more the theoretical value based on the light attenuation characteristics of the image carrier. In this electrophotographic device, by controlling the recombination rate, i.e., by increasing the amount of charge (carrier) generated in the image carrier and increasing carrier recombination, the decrease in latent image potential is controlled and the amount of toner on the image carrier is regulated, thereby enabling the formation of images with high image quality and excellent gradation.

[0007] Patent Document 3 describes the discovery that the increase in dark decay that occurs when a charge generating layer using a phthalocyanine pigment is formed as a thick film is correlated with the degree of alignment of the phthalocyanine pigment in the π-stacking direction and the molecular axis direction, i.e., the ratio of the crystal correlation length, and dark decay. The ratio of the crystal correlation length is a parameter obtained from an X-ray diffraction spectrum, and it is described that dark decay can be suppressed by setting it to a specific value. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 10-115939 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-091882 [Patent Document 3] Japanese Patent Application Publication No. 2018-189957 Summary of the Invention [Problem to be solved by the invention]

[0009] According to the investigations of the present inventors, the electrophotographic photoreceptor described in Patent Document 1 exhibited good sensitivity with low electric field dependency in the relationship between quantum efficiency η and electric field E, but memory occurred. This was attributed to the charge generation layer having a thickness of 0.4 μm in the configuration disclosed in the examples, which caused charges to accumulate in the charge generation layer. Furthermore, because the thickness of the charge transport layer was 25 μm or more, the electric field strength decreased as the thickness of the charge transport layer increased, and the memory phenomenon became more pronounced.

[0010] Patent Document 2 discloses that increasing the amount of charge (carrier) generated in the image carrier and increasing carrier recombination suppresses the decrease in latent image potential and reduces toner consumption. However, when focusing on the memory phenomenon, there is a problem that carrying out durability testing in a state where carrier recombination is increased causes carrier generation and recombination to be repeated, which increases the rate at which charges remain in the charge generating layer, and therefore increases the memory phenomenon due to the durability history.

[0011] Patent Document 3 discloses that dark decay can be suppressed by using a phthalocyanine pigment that exhibits specific properties even when the thickness of the charge generation layer is greater than 200 nm. However, particularly in situations where the electric field strength is low, charges remain in the charge generation layer, and this does not sufficiently reduce the memory phenomenon.

[0012] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an electrophotographic photoreceptor that does not generate memory and maintains high contrast throughout its life. Another object of the present invention is to provide a process cartridge and an electrophotographic apparatus having an electrophotographic photosensitive member that does not generate memory and maintains high contrast throughout its life. [Means for solving the problem]

[0013] The above object can be achieved by the present invention as follows. That is, the electrophotographic photoreceptor according to the present invention is an electrophotographic photoreceptor having a support, a charge generating layer on the support, and a charge transport layer on the charge generating layer, wherein the thickness of the charge generating layer is 0.2 μm or more, The electrophotographic photoreceptor was subjected to the following test at a temperature of 23.5°C and a relative humidity of 50%RH. (1) setting the surface potential of the electrophotographic photosensitive member to 0 [V]; (2) charging the electrophotographic photosensitive member for 0.005 seconds so that the absolute value of the surface potential of the electrophotographic photosensitive member becomes Vd [V]; (3) 0.02 seconds after the start of charging, the wavelength is 805 [nm] and the light intensity is I exp [μJ / cm 2 the electrophotographic photosensitive member after charging is 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 When [V] is used, (1) to (4) operations and measurements exp to 0.000 [μJ / cm 2 ] to 1.000 [μJ / cm 2 ] up to 0.001 [μJ / cm 2 The horizontal axis is the amount of exposure light I exp The vertical axis is the absolute value of the surface potential V exp In the relationship between the recombination constant Pe and the electric field strength E obtained from the graph, the absolute value of the gradient α of the linear approximation line when the electric field strength E is 10 to 40 V / μm shown in the following formula (1) is 4 × 10 -3 Below is the law of nature, the charge generating layer contains a charge generating material, the charge generating material is a hydroxygallium phthalocyanine pigment, the hydroxygallium phthalocyanine pigment has peaks at 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum (Bragg angle 2θ) using CuKα radiation, The angle θ1 [°] and integral width β of the peak at 7.4° ± 0.3° 1 [°], the angle θ2 [°] of the peak at 28.2° ± 0.3° and the integral width β 2 A calculated from equation (4) is 0.8 or less. The charge transport layer contains a charge transport material represented by the following formula (B-1) and having an ionization potential of 5.4 eV, and a charge transport material represented by the following formula (B-2) and having an ionization potential of 5.3 eV. The electrophotographic photoreceptor is characterized in that Pe=α×E+γ (1) In the above formula (1) and the following formula (2), Pe and Vr are the V expWhen the quantum efficiency obtained using the following formula (3) from the data points on the graph in the range until Vd drops to Vd / 2 is defined as η0, the recombination constant and residual charge are obtained from the following formula (2), and E represents the electric field strength V / μm obtained from Vd and the film thickness of the charge transport layer.

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[0014] According to the present invention, it is possible to provide an electrophotographic photoreceptor that is free from memory and can maintain high contrast throughout its durability. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing an example of a schematic configuration of an electrophotographic apparatus equipped with a process cartridge having an electrophotographic photosensitive member of the present invention. [Figure 2] FIG. 1 is a powder X-ray diffraction pattern of hydroxygallium phthalocyanine crystal. [Figure 3] This is an example of a graph where the horizontal axis is Iexp and the vertical axis is Vexp, created by repeatedly changing Iexp from 0.000 [μJ / cm2] to 1.000 [μJ / cm2] in intervals of 0.001 [μJ / cm2] when Vd was 500V. [Figure 4]1 is an example of a graph showing the recombination constant Pe obtained on the vertical axis and the gradient α of a linear approximation line of the electric field strength E at an electric field strength of 10 to 40 V / μm on the horizontal axis. [Figure 5] 1A is a diagram illustrating a ghost evaluation image used in ghost image evaluation, and FIG. 1B is a diagram illustrating a one-dot knight pattern image. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below with reference to preferred embodiments. The above object can be achieved by the present invention, which provides an electrophotographic photoreceptor having a support, a charge generating layer on the support, and a charge transport layer on the charge generating layer, the charge generating layer having a thickness of 0.2 μm or more, The electrophotographic photoreceptor was subjected to the following test at a temperature of 23.5°C and a relative humidity of 50%RH. (1) setting the surface potential of the electrophotographic photosensitive member to 0 [V]; (2) charging the electrophotographic photosensitive member for 0.005 seconds so that the absolute value of the surface potential of the electrophotographic photosensitive member becomes Vd [V]; (3) 0.02 seconds after the start of charging, the wavelength is 805 [nm] and the light intensity is I exp [μJ / cm 2 the electrophotographic photosensitive member after charging is 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 When [V] is used, (1) to (4) operations and measurements exp to 0.000 [μJ / cm 2 ] to 1.000 [μJ / cm 2 ] up to 0.001 [μJ / cm 2 The horizontal axis is the amount of exposure light I exp The vertical axis is the absolute value of the surface potential V exp In the relationship between the recombination constant Pe obtained from the graph and the electric field strength E, the absolute value of the gradient α of the linear approximation line when the electric field strength E is 10 to 40 V / μm shown in the following formula (1) is 4 × 10-3 Below is the law of nature, the charge generating layer contains a charge generating material, the charge generating material is a hydroxygallium phthalocyanine pigment, the hydroxygallium phthalocyanine pigment has peaks at 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum (Bragg angle 2θ) using CuKα radiation, The angle θ1 [°] and integral width β of the peak at 7.4° ± 0.3° 1 [°], the angle θ2 [°] of the peak at 28.2° ± 0.3° and the integral width β 2 A calculated from equation (4) is 0.8 or less. The charge transport layer contains a charge transport material represented by the following formula (B-1) and having an ionization potential of 5.4 eV, and a charge transport material represented by the following formula (B-2) and having an ionization potential of 5.3 eV. The electrophotographic photoreceptor is characterized by the Pe=α×E+γ (1) In the above formula (1) and the following formula (2), Pe and Vr respectively represent the recombination constant and residual charge obtained from the following formula (2) when the quantum efficiency obtained from the slope of the range until Vd on the above graph decreases to Vd / 2 is defined as η0, and E represents the electric field strength V / μm obtained from Vd and the film thickness of the charge transport layer.

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[0017] The procedure for determining the slope α to derive equation (1) and for determining Vr (residual charge), η0 (quantum efficiency), and Pe (recombination constant) from equation (2) is as follows: Step 1: Set an arbitrary Vd at several points between 10 and 40 V (Vd = electric field strength E × photoconductor film thickness). exp to 0.000 [μJ / cm 2 ] to 1.000 [μJ / cm 2 ] up to 0.001 [μJ / cm 2] and the horizontal axis is the amount of exposure light I exp The vertical axis is the absolute value of the surface potential V exp Create a graph where Figure 3 shows the I when Vd was 500V. exp to 0.000 [μJ / cm 2 ] to 1.000 [μJ / cm 2 ] up to 0.001 [μJ / cm 2 ] and the horizontal axis is the amount of exposure light I exp The vertical axis is the absolute value of the surface potential V exp is an example of a graph where Step 2: The quantum efficiency η in equation (2) is V exp The range of I until it drops to Vd / 2 exp -V exp The data points of the graph are determined by fitting using the following equation (3) with η0 as the fitting parameter.

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[0018] Figure 4 shows the recombination constant P e1 is an example of a graph showing the gradient α of a linear approximation line at electric field intensities of 10 to 40 V / μm, with electric field intensity E on the horizontal axis. Increasing the thickness of the charge generation layer causes a memory phenomenon, and providing a durability history further increases the memory. As a result of our investigation, we found that the memory phenomenon became more pronounced when the thickness of the charge generation layer was increased and when the electric field strength was reduced. We speculate that the charge remaining in the charge generation layer is the cause of the memory phenomenon.

[0019] Ideally, even if the charge generation layer is thick, charge separation occurs quickly after exposure, and positive and negative charges are smoothly injected into the charge transport layer and undercoat layer, resulting in EV curve characteristics with a low recombination rate and low residual charge.

[0020] The amount of charge remaining in the charge generating layer is thought to have a strong correlation with the recombination rate, and attention was focused on the recombination constant shown in formula (2). However, a low recombination constant does not necessarily suppress the occurrence of the memory phenomenon. -3 It was necessary that the following was true: Electric field dependence α is 4×10 -3 The reason why the memory phenomenon is small when the value is 0.01 or less is presumed to be as follows. The retained charges that cause memory are charges that remain in the charge generating layer without recombining, and whether they are injected, recombined, or retained depends on the magnitude of the driving force, which depends on the magnitude of the electric field.

[0021] Therefore, the recombination constant P e The small electric field dependence of means that the injected charge does not increase when the electric field is strengthened, and the rate of change is small even when a durable history is given. e There is a correlation between the electric field dependence of and the memory phenomenon.

[0022] Furthermore, the effect of the present invention is even more pronounced in low electric fields. The absolute value of the electric field dependence α is 2×10 -3It is more preferable that the density is 2×10 or less. -3 If the value is larger, the rate of change may not be sufficiently reduced when a durability history is applied. It is more preferable that the recombination constant Pe shown by formula (2) is 0.7 or less at an electric field strength of 15 V / μm. If it is more than 0.7, the effect of reducing the initial memory may not be sufficiently obtained in a low electric field. It is more preferable that the quantum efficiency η0 shown by the formula (2) is 0.4 or more at an electric field strength of 15 V / μm. If it is less than 0.4, the effect of reducing the initial memory may not be sufficiently obtained in a low electric field. At an electric field strength of 15 V / μm, the residual voltage Vr shown in formula (2) is more preferably 20 V or less. If it is more than 20 V, the effect of reducing the initial memory may not be sufficiently obtained in a low electric field.

[0023] In the present invention, the memory phenomenon caused by the amount of charge remaining in the charge generating layer can be evaluated as a ghost phenomenon (a phenomenon in which, when a portion irradiated with light becomes a halftone image in the next rotation of the electrophotographic photosensitive member during the formation of an image, the density of only the portion irradiated with light appears different).

[0024] [Electrophotographic photoreceptor] The electrophotographic photoreceptor of the present invention is characterized by having a charge generating layer and a charge transporting layer. 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. The support and each layer will be described below.

[0025] <Support> In the present invention, the electrophotographic photoreceptor has a support. The support is preferably conductive (conductive support). The shape of the support may be cylindrical, belt-like, sheet-like, or the like. Of these, a cylindrical support is preferred. The surface of the support may be subjected to electrochemical treatment such as anodization, blasting, cutting, 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, among which an aluminum support using aluminum is preferred. Furthermore, the resin or glass may be made conductive by mixing or coating it with a conductive material.

[0026] <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 surface of the support can be concealed and light reflection on the surface of the support can be controlled. The conductive layer preferably contains conductive particles and a resin.

[0027] 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 the conductive particles, the surface 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. The conductive particles may have a layered 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 a metal oxide such as tin 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.

[0028] 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.

[0029] 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.

[0030] 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 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.

[0031] <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.

[0032] 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 group, and a carbon-carbon double bond group. Among these, polyamide resins are preferred, and polyamide resins soluble in alcohol-based solvents are preferred. For example, ternary (6-66-610) copolymer polyamides, quaternary (6-66-610-12) copolymer polyamides, N-methoxymethylated nylon, polymerized fatty acid polyamides, polymerized fatty acid polyamide block copolymers, and copolymer polyamides containing diamine components are preferably used.

[0033] For the purpose of improving electrical properties, the undercoat layer may further contain an electron transport material, a metal oxide, a metal, a conductive polymer, etc. Among these, the use of an electron transport material or a metal oxide is preferred because it can extract charges from the charge generating layer even in a low electric field. 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 the above-mentioned monomer having the polymerizable functional group. Examples of metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, silicon dioxide, etc. Examples of metals include gold, silver, aluminum, etc. Among these, titanium oxide is preferred, and from the viewpoint of suppressing charge accumulation, the crystal structure is preferably rutile or anatase, and rutile, which has weaker photocatalytic activity, is more preferred. If the crystal structure is rutile, the rutile content is preferably 90% or more. The shape of the titanium oxide particles is preferably spherical, and from the viewpoints of suppressing charge accumulation and achieving uniform dispersibility, the average primary particle size is preferably 10 nm or more and 100 nm or less, and more preferably 30 nm or more and 60 nm or less. From the viewpoint of achieving uniform dispersibility, the titanium oxide particles may be treated with a silane coupling agent or the like. Titanium oxide particles that have been surface-treated with vinylsilane are preferred because they can extract charges from the charge generating layer even in a low electric field. The undercoat layer may further contain an additive.

[0034] The average thickness of the undercoat layer is preferably from 0.1 μm to 10 μm, more preferably from 0.2 μm to 5 μm, and particularly preferably from 0.3 μm to 3 μm.

[0035] The undercoat layer can be formed by preparing a coating solution for the undercoat layer containing the above-mentioned materials and solvent, forming the coating film on the support or the conductive layer, and drying and / or curing the coating film. 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.

[0036] <Charge generation layer> The charge generating layer preferably contains a charge generating material and a resin. Examples of the charge generating material include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, phthalocyanine pigments are preferred. Among phthalocyanine pigments, hydroxygallium phthalocyanine pigments are preferred.

[0037] Among hydroxygallium phthalocyanine pigments, those having crystal particles with a crystal type that exhibits peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum using CuKα radiation are preferred. Figure 2 shows an example of the X-ray diffraction spectrum of a hydroxygallium phthalocyanine pigment. In particular, to achieve high sensitivity in a thick film and reduce the amount of charge remaining in the charge generating layer under a low electric field, it is preferable to use a hydroxygallium phthalocyanine pigment in which A, calculated using the peak angle θ1 [°] and integral width β1 [°] at 7.4°±0.3° and the peak angle θ2 [°] and integral width β2 [°] at 28.2°±0.3°, using the following formula (4), is 0.8 or less.

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[0038] Furthermore, it is more preferable that the hydroxygallium phthalocyanine pigment has crystal particles that contain an amide compound represented by the following formula (A1): Examples of the amide compound represented by formula (A1) include N-methylformamide, N-propylformamide, and N-vinylformamide. [ka] In the above formula (A1), R 1 represents a methyl group, a propyl group, or a vinyl group.

[0039] Furthermore, the content of the amide compound represented by formula (A1) contained within the crystal particles is preferably 0.1% by mass or more and 3.0% by mass or less, and more preferably 0.1% by mass or more and 1.4% by mass or less, relative to the content of the crystal particles. By setting the content of the amide compound to 0.1% by mass or more and 3.0% by mass or less, the crystal particles can be made to have an appropriate uniform size. A phthalocyanine pigment containing the amide compound represented by formula (A1) within its crystal particles can be obtained by a step of converting the crystal structure of a phthalocyanine pigment obtained by an acid pasting method and the amide compound represented by formula (A1) by a wet milling process.

[0040] When a dispersant is used in the milling treatment, the amount of the dispersant is preferably 10 to 50 times the mass of the phthalocyanine pigment. Examples of the solvent that can be used include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, the compound represented by formula (A1), N-methylacetamide, and N-methylpropioamide, halogenated solvents such as chloroform, ether solvents such as tetrahydrofuran, and sulfoxide solvents such as dimethyl sulfoxide. The amount of the solvent used is preferably 5 to 30 times the mass of the phthalocyanine pigment.

[0041] The powder X-ray diffraction measurement of the phthalocyanine pigment contained in the electrophotographic photosensitive member of the present invention was carried out under the following conditions. (Powder X-ray diffraction measurement) Measuring equipment used: Rigaku Electric Co., Ltd., X-ray diffraction equipment RINT-TTRII X-ray tube:Cu X-ray wavelength: Kα1 Tube voltage: 50KV Tube current: 300mA Scanning method: 2θ scan Scan speed: 4.0° / min Sampling interval: 0.02° Starting angle (2θ): 5.0° Stop angle (2θ): 35.0° Goniometer: Rotor horizontal goniometer (TTR-2) Attachment: Capillary rotating sample stage Filter: None Detector: Scintillation counter Incident Monochrome: Use Slit: Variable slit (parallel beam method) Counter monochromator: Not used Divergence slit: open Divergence vertical limit slit: 10.00 mm Scattering slit: open Receiving slit: open

[0042] The content of the charge generating material in the charge generating layer is preferably 50% by mass or more and 85% by mass or less, and more preferably 65% ​​by mass or more and 75% by mass or less, based on the total mass of the charge generating layer. If the content of the charge generating material in the charge generating layer is less than 50% by mass, contact between particles of the charge generating material will be reduced, resulting in insufficient charge transfer, particularly under a low electric field. If the content is more than 85% by mass, there will not be enough binder resin between the particles of the charge generating material, which may create points where charges accumulate, and this may increase the slope α of the linear approximation line that represents the electric field strength dependence.

[0043] 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 include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0044] The average thickness of the charge generating layer of the present invention is 0.2 μm or more. 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 the coating film on the support, conductive layer, or undercoat layer, 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.

[0045] <Charge transport layer> The charge transport layer preferably contains a charge transport material and a resin.

[0046] Examples of charge transport materials 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, to achieve the effects of the present invention, it is preferable that the ionization potential is 5.2 eV or more and 5.4 eV or less. If the ionization potential is less than 5.2 eV, the α, which represents the electric field strength dependency, becomes large, and the memory phenomenon may worsen after endurance testing. If the ionization potential is more than 5.4 eV, the residual charge may increase. The ionization potential was measured by measuring the threshold energy for emitting electrons using an atmospheric photoelectron spectrometer (trade name: AC-2) manufactured by Riken Keiki Co., Ltd. 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.

[0047] 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. The content ratio (mass ratio) of the charge transport material to the resin is preferably 4:10 to 20:10, and more preferably 5:10 to 12:10.

[0048] The charge transport layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipping agents, and abrasion resistance improvers. Specific examples of such 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.

[0049] The average thickness of the charge transport layer is preferably from 5 μm to 50 μm, more preferably from 8 μm to 40 μm, and particularly preferably from 10 μm to 30 μm.

[0050] 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 this coating film on the charge generation layer, 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.

[0051] <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.

[0052] 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.

[0053] 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.

[0054] 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 reaction include thermal polymerization, photopolymerization, and radiation-induced polymerization. Examples of the polymerizable functional group possessed by the monomer having a polymerizable functional group include an acrylic group and a methacrylic group. A material having charge transport capability may also be used as the monomer having a polymerizable functional group.

[0055] The protective layer may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipping agents, and abrasion resistance improvers. Specific examples of such 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.

[0056] 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.

[0057] The protective layer can be formed by preparing a coating solution for the protective layer containing the above-mentioned materials and solvent, forming the coating film on the photosensitive layer, and drying and / or curing the coating film. 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.

[0058] [Process cartridges, electrophotographic devices] The process cartridge of the present invention is characterized in that it integrally supports the electrophotographic photosensitive member described above and at least one means selected from the group consisting of a charging means, a developing means, a transfer means and a cleaning means, and is detachably mountable to the main body of the electrophotographic apparatus. The electrophotographic apparatus of the present invention is characterized by comprising the electrophotographic photosensitive member, charging means, exposure means, developing means and transfer means described above.

[0059] FIG. 1 shows an example of a schematic configuration of an electrophotographic apparatus having a process cartridge equipped with an electrophotographic photosensitive member. Reference numeral 1 denotes a cylindrical electrophotographic photoreceptor, which is driven to rotate around shaft 2 in the direction of the arrow at a predetermined peripheral speed. The surface of electrophotographic photoreceptor 1 is charged to a predetermined positive or negative potential by charging means 3. While FIG. 1 shows a roller charging method using a roller-type charging member, other charging methods, such as corona charging, proximity charging, and injection charging, may also be used. Exposure light 4 is irradiated onto the charged surface of electrophotographic photoreceptor 1 from exposure means (not shown), forming an electrostatic latent image corresponding to the desired image information. The electrostatic latent image formed on the surface of electrophotographic photoreceptor 1 is developed with toner contained in developing means 5, forming a toner image on the surface of electrophotographic photoreceptor 1. The toner image formed on the surface of electrophotographic photoreceptor 1 is transferred to transfer material 7 by transfer means 6. The transfer material 7 to which the toner image has been transferred is transported to fixing means 8, where the toner image is fixed and printed out from the electrophotographic device. The electrophotographic apparatus may have cleaning means 9 for removing deposits such as toner remaining on the surface of the electrophotographic photosensitive member 1 after transfer. Alternatively, a so-called cleanerless system may be used in which the deposits are removed by the developing means or the like without providing a separate cleaning means. The electrophotographic apparatus may have a charge-removing mechanism for removing charge from the surface of the electrophotographic photosensitive member 1 by pre-exposure light 10 from pre-exposure means (not shown). Also, guide means 12 such as rails may be provided for mounting and demounting the process cartridge 11 of the present invention to the main body of the electrophotographic apparatus.

[0060] The electrophotographic photoreceptor of the present invention can be used in laser beam printers, LED printers, copying machines, facsimiles, and multifunction machines thereof. [Example]

[0061] 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 description of the examples, "parts" are by mass unless otherwise specified. In the following description, Examples 4, 14 to 17, and 28 are reference examples.

[0062] [Synthesis of phthalocyanine pigments] [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.

[0063] [Synthesis Example 2] 4.65 parts of the chlorogallium phthalocyanine pigment obtained in Synthesis Example 1 was dissolved in 139.5 parts of concentrated sulfuric acid at 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, and then filtered three times using a filter press. Finally, the solution was freeze-dried to obtain a hydroxygallium phthalocyanine pigment (hydrated hydroxygallium phthalocyanine pigment) with a solids content of 23% in a yield of 97%.

[0064] [Synthesis Example 3] 6.6 kg of the hydrous hydroxygallium phthalocyanine pigment obtained in Synthesis Example 2 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) as it was removed from the filter press, and the far infrared rays were turned off, with the temperature of the inner wall of the dryer set to 50° C. 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, 4.8 kW microwaves were irradiated onto the hydroxygallium phthalocyanine pigment for 50 minutes. Next, the microwaves were turned off, the leak valve was closed, and a high vacuum of 2 kPa or less was created. At this point, the solids 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, 1.2 kW microwaves were irradiated onto the hydroxygallium phthalocyanine pigment for 5 minutes. Then, the microwaves were 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 (twice in total). At this point, the solids content of the hydroxygallium phthalocyanine pigment was 98%. Furthermore, in the third step, microwave irradiation was carried out in the same manner as in the second step, except that the microwave output in the second step was changed from 1.2 kW to 0.8 kW. This third step was repeated once more (twice in total). In the fourth step, the leak valve was adjusted to restore the vacuum (pressure inside the dryer) to the set value (4.0 to 10.0 kPa). The hydroxygallium phthalocyanine pigment was then irradiated with 0.4 kW microwaves for 3 minutes, and the microwaves were then 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 (for a total of eight times). Over a total of three hours, 1.52 kg of hydroxygallium phthalocyanine pigment (crystals) with a moisture content of 1% or less was obtained.

[0065] [Synthesis Example 4] 30 parts of 1,3-diiminoisoindoline and 9.1 parts of gallium trichloride were added to 230 parts of dimethyl sulfoxide and reacted with stirring at 160°C for 6 hours to obtain a reddish purple pigment. The obtained pigment was washed with dimethyl sulfoxide, then washed with ion-exchanged water, and dried to obtain 28 parts of a chlorogallium phthalocyanine pigment.

[0066] [Synthesis Example 5] A solution of 10 parts of the chlorogallium phthalocyanine pigment obtained in Synthesis Example 4 in 300 parts of sulfuric acid (concentration: 97%) heated to 60°C was added dropwise to a mixed solution of 600 parts of 25% aqueous ammonia and 200 parts of ion-exchanged water. The precipitated pigment was collected by filtration, washed with N,N-dimethylformamide and ion-exchanged water, and dried to obtain 8 parts of a hydroxygallium phthalocyanine pigment.

[0067] [Example 1] <Support> An aluminum cylinder having a diameter of 24 mm and a length of 257 mm was used as a support (conductive cylindrical support).

[0068] <Conductive layer> 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 as the substrate, with a primary particle size of 200 nm. One hundred parts of the substrate was dispersed in pure water to prepare a 1,000-part suspension, which was then heated to 60°C. The titanium niobium sulfate solution and 10 mol / L sodium hydroxide were added dropwise over three 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 one hour, followed by calcination in air at 450°C to produce titanium oxide particles 1. The particles obtained had an average particle size (average primary particle size) of 220 nm as determined by a particle size measurement method using a scanning electron microscope. Next, a phenolic resin (phenolic resin monomer / oligomer) (trade name: Plyofen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g / cm) was used as a binder. 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, 60 parts of titanium oxide particles 1 were added, and the mixture was placed in a vertical sand mill using 120 parts of glass beads with an average particle size of 1.0 mm as a dispersion medium. The mixture was dispersed 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), yielding a dispersion. The glass beads were removed from the dispersion using a mesh. After removing the glass beads, the dispersion was mixed with 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. 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 a coating liquid for the conductive layer. The conductive layer coating solution thus prepared was dip-coated onto the above-mentioned support to form a coating film, and the coating film was heated at 150°C for 20 minutes to harden, thereby forming a conductive layer with a film thickness of 15 μm.

[0069] <Undercoat layer> One hundred parts of rutile-type titanium dioxide particles (average primary particle size: 50 nm, manufactured by Teika) were mixed with 500 parts of toluene and stirred, to which 3.0 parts of vinyltrimethoxysilane (trade name: KBM-1003, manufactured by Shin-Etsu Chemical) was added, followed by stirring 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 surface-treated with vinyltrimethoxysilane. A dispersion was prepared by dispersing 18 parts of the rutile titanium dioxide particles surface-treated with 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 Industries, Inc.) in a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol. This dispersion was subjected to a dispersion treatment for 6 hours in a vertical sand mill using glass beads with a diameter of 1.0 mm to prepare a coating solution for an undercoat layer. The coating solution for the undercoat layer was dip-coated onto the conductive layer to form a coating film, and the coating film was dried by heating at a temperature of 100° C. for 10 minutes to form an undercoat layer with a thickness of 1 μm.

[0070] <Charge generation layer> Next, 0.5 parts of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3, 9.5 parts of N-methylformamide (product code: F0059, manufactured by Tokyo Chemical Industry Co., Ltd.), and 15 parts of glass beads with a diameter of 0.9 mm were milled at room temperature (23°C) for 6 hours using a paint shaker (manufactured by Toyo Seiki Seisakusho) (first stage). A standard bottle (product name: PS-6, manufactured by Hakuyo Glass Co., Ltd.) was used as the container. The milled liquid was then filtered through a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec Co., Ltd.) to remove the glass beads. This liquid was then milled in a ball mill at room temperature (23°C) for 40 hours (second stage). A standard bottle (product name: PS-6, manufactured by Hakuyo Glass Co., Ltd.) was used as the container, and the milling was carried out at 120 rotations per minute. No media such as glass beads were used in this milling process. To the solution thus treated, 30 parts of N-methylformamide was added, followed by filtration, and the residue on the filter was thoroughly washed with tetrahydrofuran and then vacuum dried to obtain 0.46 parts of a hydroxygallium phthalocyanine pigment. The X-ray diffraction spectrum of the obtained hydroxygallium phthalocyanine pigment using CuKα radiation shows peaks at Bragg angles 2θ of 7.4°±0.3°, 9.9°±0.3°, 16.2°±0.3°, 18.6°±0.3°, 25.2°±0.3°, and 28.2°±0.3°. The crystal correlation lengths estimated from the peaks at 7.4°±0.3° and 28.2°±0.3°, which are the most intense diffraction peaks in the 5° to 35° range, are r1 = 31 nm and r2 = 19 nm, respectively. Therefore, the value of A calculated from equation (4) is 0.60. Next, 20 parts of the hydroxygallium phthalocyanine pigment obtained by the milling process, 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 Co., Ltd.), 70 mm disk diameter, 5 disks) at a cooling water temperature of 18°C ​​for 4 hours. The dispersion was run at 1,800 revolutions per minute. A charge generation layer coating solution was prepared by adding 444 parts of cyclohexanone and 634 parts of ethyl acetate to the dispersion. This charge generation layer coating solution was dip-coated onto the undercoat layer to form a coating film, which was then dried by heating at 100°C for 10 minutes to form a charge generation layer with a thickness of 0.23 μm.

[0071] <Charge transport layer> As a charge transport material, 6 parts of a charge transport material having an ionization potential of 5.4 eV and represented by the following formula (B-1): [ka] 4 parts of a charge transport compound having an ionization potential of 5.3 eV and represented by the following formula (B-2): [ka] A coating solution for the charge transport layer was prepared by dissolving 10 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) in a mixed solvent of 25 parts of orthoxylene, 25 parts of methyl benzoate, and 25 parts of dimethoxymethane. The charge transport layer coating liquid thus prepared 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 30 minutes to form a charge transport layer with a thickness of 25 μm.

[0072] Using the electrophotographic photoreceptor thus prepared, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the following memory evaluation method. The results are shown in Table 1.

[0073] (Memory evaluation) A laser beam printer (trade name: Laser Jet Enterprise M653) manufactured by Hewlett-Packard was prepared as the electrophotographic device for evaluation, and was modified to eliminate pre-exposure and to allow adjustment of the process speed, the voltage applied to the charging roller, and the amount of image exposure. The modifications were to change the process speed to 200 mm / s, set the dark area potential to -500 V, and make the amount of exposure light (image exposure light) variable. Details are as follows: In an environment with a temperature of 23°C and a humidity of 50% RH, a cyan process cartridge for the above-mentioned laser beam printer was modified, a potential probe (model 6000B-8, manufactured by Trek Japan Co., Ltd.) was attached to the development position, and an electrophotographic photosensitive member for evaluating positive ghost and potential fluctuations was attached, and the potential at the center of the electrophotographic photosensitive member was measured using a surface potentiometer (model 344, manufactured by Trek Japan Co., Ltd.). The exposure light intensity was set so that the surface potential of the electrophotographic photosensitive member was -500V for the dark potential (Vd) and -100V for the light potential (Vl).

[0074] Next, the electrophotographic photosensitive member described above was installed in a cyan process cartridge of the laser beam printer, and the process cartridge was installed in the station for the cyan process cartridge, and images were output. First, one solid white image, five images for evaluating ghosting, one solid black image, and five images for evaluating ghosting were output consecutively in this order. The ghost evaluation image was created by creating a square "solid image" in a "white image" at the beginning of the image as shown in Figure 5(A), and then creating a "halftone image with a one-dot knight pattern" as shown in Figure 5(B). Note that the "ghost" part in Figure 5(A) is the part where ghosts due to the "solid image" may appear.

[0075] Positive ghosting was evaluated by measuring the difference in density between the image density of a halftone image with a one-dot knight's horse pattern and the image density of the ghost area. Using a spectrodensitometer (trade name: X-Rite504 / 508, manufactured by X-Rite Corporation), the density difference was measured at 10 points within one ghost evaluation image. This procedure was repeated for all 10 ghost evaluation images, and the average of a total of 100 points was calculated. The evaluation criteria for memory, based on the difference in image density between the halftone image and the ghost area, are as follows: Memory was evaluated based on the initial memory and the memory after durability testing following image output. In the present invention, the effects of the present invention were obtained when the evaluation was A, B, or C. The evaluation results are shown in Table 1. A: Density difference is 0.00 or more but less than 0.01. No visible difference. B: Density difference 0.01 or more but less than 0.03, almost no difference in appearance C: Density difference 0.03 or more but less than 0.05. There is a slight difference in appearance. D: Density difference 0.05 or more but less than 0.08 There is a clear difference in appearance E: Density difference of 0.08 or more. There is a large difference in appearance.

[0076] [Example 2] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that in the preparation of the charge generating layer coating liquid in Example 1, the milling treatment in the second stage ball mill was changed from 40 hours to 100 hours. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50% RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1. The value A of the obtained phthalocyanine pigment, calculated from formula (4), was 0.7.

[0077] [Example 3] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that in the preparation of the coating liquid for the charge generating layer of Example 1, the milling treatment was changed as follows. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods in an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0078] (Preparation of Coating Solution for Charge Generating Layer) One part of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3 was dried under reduced pressure to obtain a pigment with a water content of 6000 ppm. Next, the obtained pigment was milled with 9 parts of N-methylformamide (product code: F0059, manufactured by Tokyo Chemical Industry Co., Ltd.) and 15 parts of 0.9 mm diameter glass beads at a cooling water temperature of 18°C ​​for 43 hours using a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing Co., Ltd. (now Imex), disk diameter 70 mm, number of disks: 5). This milling was performed at 200 disk revolutions per minute. The water content of the N-methylformamide before addition was 1000 ppm, so the water content in the system was 1550 ppm. 30 parts of N-methylformamide was added to the resulting solution, which was then filtered. 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 value of A of the obtained phthalocyanine pigment calculated from formula (4) was 0.8.

[0079] [Example 4] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that in the preparation of the coating liquid for the charge generating layer of Example 1, the step of obtaining the hydroxygallium phthalocyanine pigment was changed as follows. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0080] (Preparation of Coating Solution for Charge Generating Layer) 0.5 parts of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 5 and 8 parts of N,N-dimethylformamide (product code: D0722, manufactured by Tokyo Chemical Industry Co., Ltd.) were milled with a magnetic stirrer at 30°C for 24 hours (first stage). A standard bottle (product name: PS-6, manufactured by Kakuyo Glass Co., Ltd.) was used, and the rotor was rotated at 1,500 revolutions per minute. 30 parts of N,N-dimethylformamide was added to the resulting solution, which was then filtered. The residue was thoroughly washed with ion-exchanged water. The washed residue was then vacuum-dried to obtain 0.45 parts of hydroxygallium phthalocyanine pigment. Subsequently, 0.5 parts of the resulting hydroxygallium phthalocyanine pigment and 5 parts of zirconia beads with a diameter of 5.0 mm were milled at room temperature (23°C) for 5 minutes using a small vibration mill (model MB-0, manufactured by Chuo Kakoki Co., Ltd.) (second stage). An alumina pot was used as the container. 0.48 parts of hydroxygallium phthalocyanine pigment was thus obtained. The value of A calculated from formula (4) of the obtained phthalocyanine pigment was 0.83.

[0081] [Example 5] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that in the preparation of the coating liquid for the charge generating layer of Example 1, the step of obtaining the hydroxygallium phthalocyanine pigment was changed as follows. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0082] (Preparation of Coating Solution for Charge Generating Layer) 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 0.9 mm diameter glass beads 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 rate of 400 revolutions per minute. After adding 30 parts of N-methylformamide to the resulting solution, the mixture was filtered, and the residue collected on the filter was thoroughly washed with tetrahydrofuran. The washed residue was then vacuum dried to obtain 0.45 parts of hydroxygallium phthalocyanine pigment. The value of A calculated from formula (4) of the resulting phthalocyanine pigment was 0.5.

[0083] [Example 6] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the amount of hydroxygallium phthalocyanine pigment obtained by milling in the preparation of the coating liquid for the charge generating layer in Example 1 was changed from 20 parts to 25 parts. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0084] [Examples 7 to 9] Electrophotographic photoreceptors were prepared in the same manner as in Example 1, except that the amount of hydroxygallium phthalocyanine pigment obtained by milling in the preparation of the coating liquid for the charge generating layer in Example 1 was changed from 20 parts to 30 parts, 18 parts, and 15 parts, respectively. Using the prepared electrophotographic photoreceptors, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptors were evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0085] [Examples 10 to 13] Electrophotographic photoreceptors were prepared in the same manner as in Example 1, except that the thickness of the charge generating layer in Example 1 was changed from 0.23 μm to 0.20 μm, 0.25 μm, 0.30 μm, and 0.40 μm. Using the prepared electrophotographic photoreceptors, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5° C. and a relative humidity of 50% RH, and the electrophotographic photoreceptors were evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0086] [Example 14] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the charge transport layer coating liquid of Example 1 was prepared as follows. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0087] (Coating liquid for charge transport layer) As a charge transport material, 10 parts of a charge transport material having an ionization potential of 5.5 eV and represented by the following formula (B-3): [ka] A coating solution for the charge transport layer was prepared by dissolving 10 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) in a mixed solvent of 50 parts of ortho-xylene and 25 parts of THF.

[0088] [Example 15] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the charge transport layer coating liquid of Example 1 was prepared as follows. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0089] (Coating liquid for charge transport layer) As a charge transport material, 10 parts of a charge transport material having an ionization potential of 5.5 eV and represented by the following formula (B-4): [ka] A coating solution for the charge transport layer was prepared by dissolving 10 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering Plastics) in a mixed solvent of 25 parts of orthoxylene, 25 parts of methyl benzoate, and 25 parts of dimethoxymethane.

[0090] [Example 16] An electrophotographic photoreceptor was prepared in the same manner as in Example 15, except that the charge transport material (B-4) in Example 15 was replaced with the charge transport material (B-1). Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0091] [Example 17] An electrophotographic photoreceptor was prepared in the same manner as in Example 15, except that the charge transport material (B-4) in Example 15 was replaced with the charge transport material (B-2). Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0092] [Example 18] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that in the preparation of the coating solution for the undercoat layer in Example 1, the amount of rutile-type titanium oxide particles surface-treated with vinyltrimethoxysilane was changed from 12 parts to 18 parts. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0093] [Example 19] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the coating liquid for the undercoat layer in Example 1 was prepared as follows. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0094] (Coating liquid for undercoat layer) One hundred parts of rutile-type titanium dioxide particles (average primary particle size: 15 nm, manufactured by Teika) were mixed with 500 parts of toluene and stirred, to which 9.6 parts of vinyltrimethoxysilane (trade name: KBM-1003, manufactured by Shin-Etsu Chemical) was added, followed by stirring 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 methyldimethoxysilane. A dispersion was prepared by adding 6 parts of the methyldimethoxysilane-surface-treated rutile-type titanium dioxide particles, 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) to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol. This dispersion was then dispersed for 6 hours in a vertical sand mill using 1.0 mm diameter glass beads. The sand mill-dispersed solution was then further dispersed for 1 hour in an ultrasonic disperser (UT-205, manufactured by Sharp) to prepare a coating solution for the undercoat layer.

[0095] [Example 20] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that in the preparation of the coating liquid for the undercoat layer in Example 1, vinyltrimethoxysilane was changed to methyldimethoxysilane ("TSL8117" manufactured by Toshiba Silicones Co., Ltd.), and using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods in an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0096] [Example 21] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the undercoat layer of Example 3 was prepared as follows. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0097] (Preparation of coating solution for undercoat layer) A coating solution for the undercoat layer was prepared by dissolving 4.5 parts of N-methoxymethylated nylon (trade name: Toresin EF-30T, manufactured by Nagase ChemteX) and 1.5 parts of copolymer nylon resin (trade name: Amilan CM8000, manufactured by Toray) in a mixed solvent of 65 parts of methanol and 30 parts of 1-butanol. The coating solution for the undercoat layer was dip-coated onto the conductive layer to form a coating film, and the coating film was dried by heating at a temperature of 100° C. for 10 minutes to form an undercoat layer with a thickness of 0.4 μm.

[0098] [Examples 22 to 27] Electrophotographic photoreceptors were prepared in the same manner as in Example 1, except that the thickness of the charge transport layer in Example 1 was changed from 25 μm to 15 μm, 20 μm, 23 μm, 30 μm, 35 μm, and 40 μm. Using the prepared electrophotographic photoreceptors, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5° C. and a relative humidity of 50% RH, and the electrophotographic photoreceptors were evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0099] [Example 28] An electrophotographic photoreceptor was prepared in the same manner as in Example 17, except that in the preparation of the charge transport layer coating liquid of Example 17, 10 parts of polycarbonate was replaced with a polyester resin having structural units represented by the following formulas (C-1) and (C-2), in which the molar ratio of (C-1) to (C-2) was 5 / 5 and the weight average molecular weight was 120,000. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1. [ka] [ka]

[0100] [Comparative Example 1] In the preparation of the coating liquid for the charge transport layer of Example 21, 5 parts of the charge transport material (B-1) and 5 parts of the charge transport material (B-2) were replaced with 7 parts of a charge transport material having an ionization potential of 5.5 eV and represented by the following formula (B-5): [ka] One part of a charge transport material having an ionization potential of 5.6 eV and represented by the following formula (B-6): [ka] An electrophotographic photoreceptor was prepared in the same manner as in Example 21, except that the above-mentioned conditions were changed. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0101] Comparative Example 2 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the thickness of the charge generating layer in Example 1 was changed from 0.23 μm to 0.15 μm, and the charge transport layer coating liquid was prepared using 5 parts of charge transport material (B-5) and 5 parts of charge transport material (B-6). Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5° C. and a relative humidity of 50% RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0102] Comparative Example 3 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the undercoat layer, charge generating layer, and charge transport layer of Example 2 described in JP-A-09-114120 were formed on the support described in Example 1. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods in an environment of a temperature of 23.5°C and a relative humidity of 50% RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0103] Comparative Example 4 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the undercoat layer, charge generating layer, and charge transport layer of Example 1 described in JP-A-10-069109 were formed on the support described in Example 1. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods in an environment of a temperature of 23.5° C. and a relative humidity of 50% RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0104] Comparative Example 5 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the undercoat layer, charge generating layer, and charge transport layer of Example 2 described in JP-A-11-184119 were formed on the support described in Example 1. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods in an environment of a temperature of 23.5° C. and a relative humidity of 50% RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0105] Comparative Example 6 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the undercoat layer, charge generating layer, and charge transport layer of Example 2 described in JP-A-10-1415939 were formed on the support described in Example 1. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods in an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0106] Comparative Example 7 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the charge generating layer and charge transport layer of Example 3 described in JP-A-05-080544 were prepared on the support described in Example 1. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50% RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0107] [Comparative Example 8] An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the intermediate layer, charge generating layer, and charge transport layer of Formulation 1 described in JP-A No. 2001-183852 were prepared on the support described in Example 1. Using the prepared electrophotographic photoreceptor, Pe, α, η0, and Vr were measured by the above-mentioned methods under an environment of a temperature of 23.5°C and a relative humidity of 50%RH, and the electrophotographic photoreceptor was evaluated based on the above-mentioned memory evaluation method. The results are shown in Table 1.

[0108] [Table 1] [Explanation of symbols]

[0109] 1. Electrophotographic photoreceptor 2-axis 3. Charging means 4 Exposure light 5. Developing method 6 Transfer Method 7 Transfer material 8 Fixing Method 9 Cleaning Method 10 Pre-exposure light 11 Process cartridge 12 Guidance means

Claims

1. An electrophotographic photoreceptor comprising a support, a charge generating layer on the support, and a charge transport layer on the charge generating layer, the charge generating layer having a thickness of 0.2 μm or more, The electrophotographic photosensitive member was subjected to the following test at a temperature of 23.5° C. and a relative humidity of 50% RH: (1) The surface potential of the electrophotographic photosensitive member is set to 0 [V], (2) charging the electrophotographic photosensitive member for 0.005 seconds so that the absolute value of the surface potential of the electrophotographic photosensitive member becomes Vd [V]; (3) 0.02 seconds after the start of charging, the wavelength is 805 [nm] and the light intensity is I ｅｘｐ [μJ / cm ２ the electrophotographic photosensitive member after charging is 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 When [V] is used, The operations and measurements (1) to (4) are ｅｘｐ to 0.000 [μJ / cm ２ ] to 1.000 [μJ / cm ２ ] up to 0.001 [μJ / cm ２ The horizontal axis represents the amount of exposure light I ｅｘｐ The vertical axis is the absolute value of the surface potential V ｅｘｐ In the relationship between the recombination constant Pe obtained from the graph and the electric field strength E, the absolute value of the gradient α of the linear approximation line when the electric field strength E is 10 to 40 V / μm shown in the following formula (1) is 4×10 －３ is as follows: the charge generating layer contains a charge generating material, the charge generating material is a hydroxygallium phthalocyanine pigment, the hydroxygallium phthalocyanine pigment has peaks at 7.4°±0.3° and 28.2°±0.3° in an X-ray diffraction spectrum (Bragg angle 2θ) using CuKα radiation, A calculated by equation (4) from the angle θ1 [°] and integral width β1 [°] of the peak at 7.4°±0.3° and the angle θ2 [°] and integral width β2 [°] of the peak at 28.2°±0.3° is 0.8 or less, The charge transport layer contains a charge transport material having an ionization potential of 5.4 eV and represented by the following formula (B-1) and a charge transport material having an ionization potential of 5.3 eV and represented by the following formula (B-2): An electrophotographic photoreceptor characterized by the above-mentioned. Pe=α×E+γ (1) (In the above formula (1) and the following formula (2), Pe and Vr are the V ｅｘｐ The quantum efficiency obtained using the following formula (3) from the data points of the graph in the range until Vd / 2 is reached is η ０ represents the recombination constant and residual charge obtained from the following formula (2) when Vd is 0.01 and E represents the electric field strength V / μm obtained from Vd and the film thickness of the charge transport layer. [Equation 1] [Equation 2] (In the above formulas (2) and (3), e is the elementary charge, d is the film thickness of the photosensitive layer, η ０ is the quantum efficiency, ε ０ is the dielectric constant of a vacuum, ε ｒ is the relative dielectric constant, h is Planck's constant, and ν is the frequency of the irradiated light. [Equation 3] 【number】 【number】

2. The absolute value of the gradient α of the linear approximation is 2×10 －３ 2. The electrophotographic photoreceptor according to claim 1, wherein:

3. 3. The electrophotographic photosensitive member according to claim 1, wherein the recombination constant Pe obtained from the formula (2) when the electric field strength is 15 V / .mu.m is 0.7 or less.

4. The quantum efficiency η obtained from the above formula (2) when the electric field strength is 15 V / μm ０ 4. The electrophotographic photoreceptor according to claim 1, wherein the value of the ρ is 0.4 or more.

5. 5. The electrophotographic photoreceptor according to claim 1, wherein the residual voltage Vr obtained from the formula (2) when the electric field strength is 15 V / μm is 20 V or less.

6. 6. The electrophotographic photoreceptor according to claim 1, wherein the charge generating material accounts for 65% by mass or more and 75% by mass or less of the total mass of the charge generating layer.

7. the electrophotographic photoreceptor has an undercoat layer directly under the charge generating layer, The undercoat layer contains titanium oxide that has been surface-treated with vinylsilane. The electrophotographic photoreceptor according to any one of claims 1 to 6.

8. The hydroxygallium phthalocyanine pigment has crystal particles containing an amide compound represented by the following formula (A1) within the particles, The content of the amide compound represented by the following formula (A1) contained in the crystal particles is 0.1% by mass or more and 3.0% by mass or less with respect to the content of the crystal particles. The electrophotographic photoreceptor according to any one of claims 1 to 6. 【Chemistry 3】 (In the formula (A1), R 1 represents a methyl group, a propyl group, or a vinyl group.)

9. 9. 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, a transfer means and a cleaning means, and is detachably mountable to a main body of an electrophotographic apparatus.

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

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