Electrophotographic photoreceptor, processing cartridge and image formation device

Abstract

To provide an electrophotographic photoreceptor that has superior electric characteristics and hardly generates a dotted image defect.SOLUTION: An electrophotographic photoreceptor comprises a conductive base, a charge generation layer, a charge transport layer, and an inorganic protection layer. and the charge transport layer has one or two or more layers, wherein at least one layer contains a filler, and the outermost layer of the charge transport layer having the one or two or more layers is arranged in the inorganic protection layer. Further, the outermost transport layer contains a solvent of 80°C or lower in boiling point, the ratio of the solvent of 80°C in boiling point to the outermost charge transport layer is 0.1 to 0.3 mass%, and an outer peripheral surface of the outermost charge transport layer has a mathematically average roughness Ra (JIS B0601:2013) of 0.013 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses an electrophotographic photoreceptor including a conductive substrate, a charge transport layer provided on the conductive substrate and containing a charge transport material, a binder resin, and silica particles, an inorganic protective layer provided on the charge transport layer, and a crack suppression layer sandwiched between the charge transport layer and the inorganic protective layer and suppressing cracks on the surface of the inorganic protective layer facing the charge transport layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-159181 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure has an object to provide an electrophotographic photoreceptor which has superior electrical characteristics and is less susceptible to dot-like image defects, compared to an electrophotographic photoreceptor in which the proportion of a solvent having a boiling point of 80°C or less in the outermost charge transport layer is less than 0.1 mass % or exceeds 0.3 mass %, or an electrophotographic photoreceptor in which the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer exceeds 0.013 μm. [Means for solving the problem]

[0005] Specific means for solving the above problems include the following aspects. <1> The electroconductive substrate includes a charge generating layer, a charge transport layer, and an inorganic protective layer, the charge transport layer is one or more layers, and at least one layer contains a filler; the inorganic protective layer is disposed in contact with an outermost charge transport layer of the one or more charge transport layers; the outermost charge transport layer contains a solvent having a boiling point of 80° C. or less; the ratio of the solvent having a boiling point of 80° C. or less in the outermost charge transport layer is 0.1% by mass or more and 0.3% by mass or less; The arithmetic average roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer is 0.013 μm or less. Electrophotographic photoreceptor. <2> the outermost charge transport layer contains a solvent having a boiling point of 60° C. or more and 70° C. or less; the proportion of the solvent having a boiling point of 60° C. or more and 70° C. or less in the outermost charge transport layer is 0.1% by mass or more and 0.3% by mass or less; <1> The electrophotographic photoreceptor according to claim 1. <3> The filler comprises silica particles. <1> or <2> The electrophotographic photoreceptor according to claim 1. <4> the outermost charge transport layer comprises a filler; When the outermost charge transport layer is divided into an outer peripheral side and an inner peripheral side with a thickness ratio of 20:80, a filler volume ratio Vo on the outer peripheral side and a filler volume ratio Vi on the inner peripheral side satisfy 5≦(Vo-Vi)≦50. <1> ~ <3> 13. The electrophotographic photoreceptor according to claim 12, <5> The filler volume ratio Vo on the outer peripheral surface side and the filler volume ratio Vi on the inner peripheral surface side satisfy 10≦(Vo-Vi)≦30. <4> The electrophotographic photoreceptor according to claim 1. <6> the charge transport layer is one layer, and the ratio of the filler in the one charge transport layer is 60% by volume or more and 70% by volume or less; <4> or <5> The electrophotographic photoreceptor according to claim 1. <7> The charge transport layer has two or more layers, the outermost charge transport layer does not contain or contains a filler, The ratio of the filler in the outermost charge transport layer is 0% by volume or more and 30% by volume or less. <1> ~ <3> 13. The electrophotographic photoreceptor according to claim 12, <8> The thickness of the outermost charge transport layer is more than 0.8 μm and not more than 5 μm. <7> The electrophotographic photoreceptor according to claim 1. <9> the charge transport layer is a two-layered layer, and the ratio of the filler in the two-layered charge transport layer is 30% by volume or more and 50% by volume or less; <7> or <8> The electrophotographic photoreceptor according to claim 1. <10> <1> ~ <9> The electrophotographic photoreceptor according to any one of the above items is provided, A process cartridge that is detachably attached to an image forming apparatus. <11> <1> ~ <9> and an electrophotographic photoreceptor according to any one of the above items. a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising: Effect of the Invention

[0006] <1> or <3> According to this, an electrophotographic photoreceptor is provided that has excellent electrical characteristics and is less susceptible to dot-like image defects, as compared to an electrophotographic photoreceptor in which the proportion of solvents with a boiling point of 80°C or less in the outermost charge transport layer is less than 0.1 mass % or exceeds 0.3 mass %, or an electrophotographic photoreceptor in which the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer exceeds 0.013 μm. <2> According to the present invention, an electrophotographic photoreceptor is provided which is excellent in electrical properties and is less susceptible to dot-like image defects, as compared with an electrophotographic photoreceptor in which the proportion of a solvent having a boiling point of 60° C. or more and 70° C. or less in the outermost charge transport layer is less than 0.1 mass % or exceeds 0.3 mass %. <4> According to the present invention, compared with electrophotographic photoreceptors having a (Vo-Vi) of less than 5 or more than 50, an electrophotographic photoreceptor having excellent electrical properties and less susceptible to dot-like image defects is provided. <5> According to this, compared with electrophotographic photoreceptors having a (Vo-Vi) of less than 10 or more than 30, an electrophotographic photoreceptor is provided which is excellent in electrical properties and is less susceptible to dot-like image defects. <6> According to this, an electrophotographic photoreceptor is provided which has excellent electrical properties and is less susceptible to dot-like image defects, as compared with electrophotographic photoreceptors in which the proportion of filler in the entire charge transport layer is less than 60 volume % or more than 70 volume %. <7> According to this, an electrophotographic photoreceptor is provided which is excellent in electrical properties and less prone to dot-like image defects, as compared with an electrophotographic photoreceptor in which the proportion of filler in the outermost charge transport layer exceeds 30% by volume. <8> According to this, an electrophotographic photoreceptor is provided which is excellent in electrical characteristics and less susceptible to dot-like image defects, as compared with electrophotographic photoreceptors in which the thickness of the outermost charge transport layer is 0.8 μm or less or exceeds 5 μm. <9> According to this, an electrophotographic photoreceptor is provided which is excellent in electrical properties and less susceptible to dot-like image defects, as compared with electrophotographic photoreceptors in which the proportion of filler in the entire charge transport layer is less than 30 volume % or more than 50 volume %. <10> According to this, a process cartridge is provided that is equipped with an electrophotographic photoreceptor that has excellent electrical characteristics and is less susceptible to dot-like image defects, compared to an electrophotographic photoreceptor in which the proportion of solvents with a boiling point of 80°C or less in the outermost charge transport layer is less than 0.1 mass % or more than 0.3 mass %, or an electrophotographic photoreceptor in which the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer exceeds 0.013 μm. <11> According to this, an image forming apparatus is provided that is equipped with an electrophotographic photoreceptor that has superior electrical characteristics and is less susceptible to dot-like image defects, compared to an electrophotographic photoreceptor in which the proportion of solvents with a boiling point of 80°C or less in the outermost charge transport layer is less than 0.1 mass % or more than 0.3 mass %, or an electrophotographic photoreceptor in which the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer exceeds 0.013 μm. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a partial cross-sectional view showing an example of a layer structure of the electrophotographic photoreceptor according to the present embodiment. [Diagram 2] FIG. 4 is a partial cross-sectional view showing another example of the layer structure of the electrophotographic photoreceptor according to the present embodiment. [Diagram 3] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are merely illustrative of the embodiments, and are not intended to limit the scope of the embodiments.

[0009] In the present disclosure, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.

[0010] In the present disclosure, the term "step" includes not only an independent step, but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0011] When an embodiment of the present disclosure is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the size of the members in each drawing is conceptual, and the relative relationship between the sizes of the members is not limited to this.

[0012] In the present disclosure, each component may contain multiple types of corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified. In the present disclosure, the particles corresponding to each component may include multiple types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0013] In the present disclosure, unless otherwise specified, the alkyl group and the alkylene group include any of straight-chain, branched, and cyclic groups. In the present disclosure, a hydrogen atom in an organic group, an aromatic ring, a linking group, an alkyl group, an alkylene group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, and the like may be substituted with a halogen atom. In the present disclosure, when a compound is shown by a structural formula, the symbols (C and H) representing carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain may be omitted.

[0014] In the present disclosure, the term "structural unit" of a copolymer or resin is synonymous with a monomer unit.

[0015] In the present disclosure, the "axial direction" of an electrophotographic photosensitive member means the direction in which the rotation axis of the electrophotographic photosensitive member extends, and the "circumferential direction" of an electrophotographic photosensitive member means the rotation direction of the electrophotographic photosensitive member.

[0016] <Electrophotographic photoreceptor> The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment includes a conductive substrate, a charge generation layer, a charge transport layer, and an inorganic protective layer, and the charge transport layer is one or more layers, and the inorganic protective layer is disposed in contact with the outermost charge transport layer of the one or more charge transport layers. In the photoreceptor according to this embodiment, the charge generation layer and the charge transport layer constitute a photosensitive layer (so-called function-separated photosensitive layer).

[0017] Fig. 1 is a partial cross-sectional view showing an example of the layer structure of the photoreceptor according to the present embodiment. The photoreceptor 10A shown in Fig. 1 has a structure in which an undercoat layer 2, a charge generation layer 3, a charge transport layer 4, and an inorganic protective layer 6 are laminated in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute a photosensitive layer 5. The photoreceptor 10A has a single charge transport layer, and the inorganic protective layer 6 is disposed in contact with the charge transport layer 4. The photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The undercoat layer 2 may or may not be present.

[0018] Fig. 2 is a partial cross-sectional view showing another example of the layer structure of the photoreceptor according to the present embodiment. The photoreceptor 10B shown in Fig. 2 has a structure in which an undercoat layer 2, a charge generation layer 3, a charge transport layer 4a, a charge transport layer 4b, and an inorganic protective layer 6 are laminated in this order on a conductive substrate 1, and the charge generation layer 3, the charge transport layer 4a, and the charge transport layer 4b constitute a photoreceptor layer 5. The photoreceptor 10B has two charge transport layers, and the inorganic protective layer 6 is disposed in contact with the charge transport layer 4b. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The undercoat layer 2 may or may not be present.

[0019] Conventionally, it is known to dispose an inorganic protective layer on the photosensitive layer of a photoreceptor in order to suppress wear of the photosensitive layer. The inorganic protective layer is hard but has poor toughness, so that cracks may occur due to localized impact. Therefore, it is known to harden the photosensitive layer by adding a filler (e.g., inorganic particles such as silica particles) to the photosensitive layer, thereby reducing the deformation amount of the photosensitive layer and suppressing cracking of the inorganic protective layer.

[0020] In the photoreceptor according to the present embodiment, from the viewpoint of increasing the hardness of the photosensitive layer in order to suppress cracking of the inorganic protective layer due to local impact, at least one layer among one or more charge transport layers contains a filler. As the filler of the charge transport layer, from the viewpoint of hardness, inorganic particles are preferable, for example, silica particles, boron nitride particles, titanium oxide particles, etc. can be mentioned, and among them, silica particles are preferable.

[0021] In the photoreceptor according to the present embodiment, the outermost charge transport layer (i.e., the charge transport layer in contact with the inorganic protective layer) contains a solvent having a boiling point of 80° C. or less, and the proportion of the solvent having a boiling point of 80° C. or less in the outermost charge transport layer is 0.1% by mass or more and 0.3% by mass or less. In the present disclosure, a solvent having a boiling point of 80° C. or less is referred to as a "low boiling point solvent." The charge transport layer is generally formed by applying a coating liquid and drying the coating film. The fact that the charge transport layer contains a low boiling point solvent means that the solvent of the coating liquid used to form the charge transport layer is a low boiling point solvent. If the boiling point of the solvent constituting the coating solution is low, the time required for drying the coating film is relatively short, i.e., the time for the coating film to flow is relatively short, so that the surface of the charge transport layer is less likely to become rough. As a result, there are fewer irregularities on the outer peripheral surface of the outermost charge transport layer that can become the starting point for cracks in the inorganic protective layer, and point-like image defects are less likely to occur. The mass ratio of the low boiling point solvent in the outermost charge transport layer is 0.1 mass % or more, preferably 0.15 mass % or more, from the viewpoint of not exposing the charge transport layer to a dry environment for a long period of time so as not to roughen the surface of the charge transport layer. The mass ratio of the low boiling point solvent in the outermost charge transport layer is 0.3 mass % or less, and preferably 0.25 mass % or less, from the viewpoint of providing excellent electrical characteristics to the layer.

[0022] From the viewpoint of shortening the time required for drying the coating film that becomes the outermost charge transport layer, the low boiling point solvent preferably has a boiling point of 78° C. or less, more preferably a boiling point of 75° C. or less, and even more preferably a boiling point of 70° C. or less. The low-boiling point solvent preferably has a boiling point of 50° C. or higher, more preferably 55° C. or higher, and even more preferably 60° C. or higher, from the viewpoint of being less volatile at room temperature.

[0023] The low boiling point solvent is preferably a solvent having a boiling point of 60° C. to 70° C. Therefore, in the photoreceptor according to this embodiment, the outermost charge transport layer (i.e., the charge transport layer in contact with the inorganic protective layer) contains a solvent having a boiling point of 60° C. to 70° C., and the proportion of the solvent having a boiling point of 60° C. to 70° C. in the outermost charge transport layer is preferably 0.1% by mass to 0.3% by mass.

[0024] Examples of the low boiling point solvent include tetrahydrofuran (boiling point 66° C.), ethyl acetate (boiling point 77° C.), etc. The low boiling point solvent may be one type or two or more types.

[0025] The amount of solvent contained in the outermost charge transport layer is determined using a gas chromatograph-mass spectrometer. A solvent used for preparing a coating liquid for forming the outermost charge transport layer is prepared in advance, and the retention time when the solvent is heated and vaporized at 300° C. is measured to prepare a calibration curve. The outermost charge transport layer is peeled off from the conductive substrate, cut into a 1 cm x 1 cm square, and precisely weighed. This square charge transport layer is placed in a vial and heated at 300°C, and the retention time of the volatile components is measured. The amount of solvent is calculated based on the peak area of ​​the corresponding component that appears in the chromatograph and the calibration curve. The mass percentage (%) of the solvent in the 1 cm x 1 cm charge transport layer is calculated.

[0026] In the photoreceptor according to this embodiment, the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer is 0.013 μm or less. This means that the outer peripheral surface of the outermost charge transport layer has few irregularities that can become starting points for cracks in the inorganic protective layer, and therefore, with the photoreceptor according to this embodiment, point-like image defects are unlikely to occur. From the viewpoint of suppressing dot-like image defects, the value of the arithmetic mean roughness Ra is preferably 0.011 μm or less, more preferably 0.009 μm or less, and even more preferably 0.007 μm or less, and the smaller the value, the more preferable. The lower limit of the arithmetic mean roughness Ra is, but is not limited to, for example, 0.005 μm or more.

[0027] The arithmetic mean roughness Ra (JIS B0601:2013) of the peripheral surface of the outermost charge transport layer is determined by the following measurement method. A release agent is applied to the photoconductor to soften the inorganic protective layer and remove it. A sodium hydroxide solution is used as the release agent. The sodium hydroxide solution contains sodium hydroxide at a concentration of 0.01 mol / L in water as a solvent, and is a liquid with a pH of 12 or higher. The temperature of the release agent is room temperature. The roughness of the outer peripheral surface of the exposed charge transport layer is measured using a contact surface roughness measuring instrument (Surfcom 570A, Tokyo Seimitsu Co., Ltd.) in an environment with a temperature of 23°C and a relative humidity of 55%. The photoconductor is scanned in the axial direction at a scanning speed of 0.5 mm / sec, a measurement length of 2.5 mm, and a cutoff value of 0.8 mm. The measuring probe is a cone with an apex angle of 90°, a tip curvature radius of 5 μm, and a tip material of diamond. Three measurement points are taken: the center in the axial direction and both ends of the image forming area. A roughness curve according to JIS B0601:2013 is derived from the measurements at the three points, and the arithmetic average roughness Ra is calculated.

[0028] Preferred embodiments of the photoreceptor according to the present embodiment include a first embodiment and a second embodiment. In the present disclosure, when matters common to the first embodiment and the second embodiment are described, both embodiments are collectively referred to as the present embodiment.

[0029] In the photoreceptor according to the first embodiment, the outermost charge transport layer contains a filler, and when the outermost charge transport layer is divided into an outer peripheral side and an inner peripheral side with a thickness ratio of 20:80, the filler volume ratio Vo on the outer peripheral side and the filler volume ratio Vi on the inner peripheral side satisfy 5≦(Vo-Vi)≦50. In the photoconductor according to the first embodiment, since the filler is unevenly distributed on the outer peripheral surface side in the outermost charge transport layer, the area directly below the inorganic protective layer is harder, so that cracks in the inorganic protective layer are suppressed and dot-like image defects are unlikely to occur. However, from the viewpoint of the electrical properties of the photoconductor, it is preferable that the filler is not too unevenly distributed on the outer peripheral surface side of the outermost charge transport layer. From the above viewpoints, it is preferable that 5≦(Vo-Vi)≦50, it is more preferable that 8≦(Vo-Vi)≦40, and it is further preferable that 10≦(Vo-Vi)≦30.

[0030] The filler can be unevenly distributed on the outer peripheral surface side of the outermost charge transport layer by using a low boiling point solvent for the coating solution used to form the layer. The coating film dries relatively quickly, which increases the filler density on the outer peripheral surface side.

[0031] The volume fraction of the filler contained in the charge transport layer is determined by cross-sectional analysis. Using the cryomicrotome method, the photoreceptor is cut in the thickness direction along the axial direction to prepare slice samples. Three slice samples are prepared: the central part in the axial direction and both ends of the image formation area. The slice samples are imaged using a scanning electron microscope. The area for image analysis is the total thickness of the charge transport layer x 50 μm in the axial direction for each slice sample. The filler and binder resin are distinguished by their shades of color. The area percentage of the filler is calculated from the three slice samples, and this area percentage is taken as the volume percentage.

[0032] The photoreceptor according to the first embodiment preferably has a single charge transport layer. In this case, from the viewpoint of excellent electrical properties and less occurrence of dot-like image defects, the ratio of the filler to the entire charge transport layer is preferably 50% by volume or more and 80% by volume or less, more preferably 55% by volume or more and 75% by volume or less, and even more preferably 60% by volume or more and 70% by volume or less. In the above embodiment, the filler is preferably inorganic particles, more preferably silica particles, and the volume ratio of the inorganic particles (particularly silica particles) to the entire charge transport layer is preferably within the above range.

[0033] In the first embodiment, the thickness of the outermost charge transport layer is preferably 10 μm or more and 50 μm or less, and more preferably 15 μm or more and 30 μm or less.

[0034] In this embodiment, the thickness of each layer of the photoreceptor is the arithmetic average of values ​​measured with an electromagnetic film thickness meter, and the measurements were taken at four locations at 90° intervals around the circumferential direction from the axial center of the photoreceptor.

[0035] The photoreceptor according to the second embodiment has two or more charge transport layers, the outermost charge transport layer does not contain or contains a filler, and the proportion of the filler in the outermost charge transport layer is 0% by volume or more and 30% by volume or less. The photoreceptor according to the second embodiment does not contain a filler in the outermost charge transport layer, or if it does contain a filler, the amount is relatively small. Therefore, the outermost charge transport layer is a smooth layer, cracking of the inorganic protective layer is suppressed, and point-like image defects are less likely to occur.

[0036] In the second embodiment, the thickness of the outermost charge transport layer is preferably greater than 0.8 μm and less than or equal to 5 μm. By making the thickness of the outermost charge transport layer more than 0.8 μm, the smoothness immediately below the inorganic protective layer is maintained. From this viewpoint, the thickness of the outermost charge transport layer is more preferably 1 μm or more. By making the thickness of the outermost charge transport layer 5 μm or less, the hardness of the entire photosensitive layer is maintained and cracking of the inorganic protective layer is suppressed. From this viewpoint, the thickness of the outermost charge transport layer is more preferably 3 μm or less, and further preferably 2 μm or less.

[0037] The photoreceptor according to the second embodiment preferably has a charge transport layer of two layers. In this case, from the viewpoint of excellent electrical properties and less occurrence of dot-like image defects, the ratio of the filler to the entire two-layer charge transport layer is preferably 30 volume % or more and 70 volume % or less, more preferably 30 volume % or more and 60 volume % or less, and even more preferably 30 volume % or more and 50 volume % or less. In the above embodiment, the filler is preferably inorganic particles, more preferably silica particles, and the volume ratio of the inorganic particles (particularly silica particles) to the entire two-layer charge transport layer is preferably within the above range. In the above embodiment, the thickness of the charge transport layer on the inner periphery side is preferably 10 μm or more and 50 μm or less, and more preferably 15 μm or more and 30 μm or less.

[0038] In the present embodiment, the filler contained in the charge transport layer is preferably silica particles. Examples of the silica particles include dry silica particles and wet silica particles.

[0039] Examples of dry silica particles include combustion silica (fumed silica) obtained by burning a silane compound, and deflagration silica obtained by explosively burning metallic silicon powder. Examples of wet silica particles include wet silica particles obtained by a neutralization reaction between sodium silicate and a mineral acid (precipitation method silica synthesized and agglomerated under alkaline conditions, gel method silica particles synthesized and agglomerated under acidic conditions), colloidal silica particles (silica sol particles) obtained by making acidic silicic acid alkaline and polymerizing it, and sol-gel method silica particles obtained by hydrolysis of an organic silane compound (e.g., alkoxysilane). As the silica particles, from the viewpoint of suppressing image defects due to deterioration of electrical properties, combustion method silica (fumed silica) having few silanol groups on the surface and a poor void structure is preferable.

[0040] The average particle size of the silica particles is preferably 20 nm to 200 nm, more preferably 30 nm to 180 nm, and even more preferably 40 nm to 150 nm, from the viewpoint of suppressing cracking of the inorganic protective layer and from the viewpoint of light transmittance of the photosensitive layer.

[0041] The average particle size of the silica particles is determined by the following measurement method. The silica particles are extracted from the photosensitive layer. For example, the photosensitive layer peeled off from the photoreceptor is immersed in an organic solvent that dissolves the binder resin to extract the silica particles; the photosensitive layer peeled off from the photoreceptor is heated to about 800°C to remove the binder resin and extract the silica particles. Silica particles are observed under a scanning electron microscope, the circular equivalent diameters of 100 randomly selected primary particles are determined, and the arithmetic mean of the circular equivalent diameters is taken as the average particle size.

[0042] From the viewpoint of dispersibility in the coating liquid for forming the photosensitive layer, the silica particles are preferably surface-treated with a hydrophobic treatment agent, such as known silane compounds such as chlorosilane, alkoxysilane, and silazane. The hydrophobic treatment agent is preferably a silane compound having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group, that is, the silica particles preferably have a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group on the surface. Examples of silane compounds having a trimethylsilyl group include trimethylchlorosilane, trimethylmethoxysilane, 1,1,1,3,3,3-hexamethyldisilazane, etc. Examples of silane compounds having a decylsilyl group include decyltrichlorosilane, decyltrichlorosilane, decyldimethylchlorosilane, decyltrimethoxysilane, etc. Examples of silane compounds having a phenyl group include triphenylmethoxysilane, triphenylchlorosilane, etc.

[0043] Each layer of the photoreceptor will now be described in detail.

[0044] [Conductive substrate] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Examples of conductive substrates include paper, resin films, belts, etc. coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. Here, "conductive" refers to a material having a volume resistivity of 1×10 13 This means that the resistance is less than Ωcm.

[0045] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiating with laser light. When non-interfering light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for extending the life of the conductive substrate since it suppresses the occurrence of defects due to unevenness on the surface.

[0046] Examples of methods for roughening the surface include wet honing, which involves spraying an abrasive suspended in water onto the conductive substrate; centerless grinding, in which the conductive substrate is pressed against a rotating grindstone and continuously ground; and anodizing.

[0047] As a method for roughening the surface, there can be mentioned a method in which, without roughening the surface of the conductive substrate, a conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the surface is roughened by the particles dispersed in the layer.

[0048] In the roughening treatment by anodization, an oxide film is formed on the surface of a conductive substrate made of metal (e.g., aluminum) by anodizing the substrate in an electrolyte solution using the substrate as the anode. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodization is chemically active in its original state, easily contaminated, and has a large resistance variation depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, in which the micropores of the oxide film are filled by volume expansion caused by hydration reaction in pressurized steam or boiling water (metal salts such as nickel may be added) to change the film into a more stable hydrated oxide.

[0049] The thickness of the anodic oxide film is preferably, for example, from 0.3 μm to 15 μm. If the thickness is within this range, the film tends to exhibit a barrier property against injection and tends to suppress an increase in residual potential due to repeated use.

[0050] The conductive substrate may be subjected to a treatment with an acidic treatment solution or a boehmite treatment. Treatment with an acid treatment liquid is carried out, for example, as follows. First, an acid treatment liquid containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acid treatment liquid are, for example, in the range of 10% by mass to 11% by mass for phosphoric acid, 3% by mass to 5% by mass for chromic acid, and 0.5% by mass to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% by mass to 18% by mass. The treatment temperature is preferably, for example, 42° C. to 48° C. The film thickness of the coating is preferably 0.3 μm to 15 μm.

[0051] The boehmite treatment is carried out, for example, by immersing the material in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the material with heated steam at 90°C to 120°C for 5 to 60 minutes. The thickness of the coating is preferably 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution having low coating solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, or citrates.

[0052] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0053] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ωcm or more 1×10 11 Examples of such particles include inorganic particles with a particle size of Ωcm or less. Among these, examples of inorganic particles having the above-mentioned resistance value include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and zinc oxide particles are particularly preferred.

[0054] The specific surface area of ​​inorganic particles by the BET method is, for example, 10 m 2 / g or higher is preferable. The volume average particle size of the inorganic particles is, for example, from 50 nm to 2000 nm (preferably from 60 nm to 1000 nm).

[0055] The content of the inorganic particles is, for example, preferably from 10% by mass to 80% by mass, more preferably from 40% by mass to 80% by mass, based on the binder resin.

[0056] The inorganic particles may be surface-treated. Two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0057] Examples of the surface treatment agent include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, etc. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0058] Examples of silane coupling agents having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0059] Silane coupling agents may be used in combination of two or more kinds. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0060] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

[0061] The amount of the surface treatment agent to be used is preferably, for example, 0.5% by mass or more and 10% by mass or less based on the inorganic particles.

[0062] Here, it is preferable that the undercoat layer contains an electron accepting compound (acceptor compound) together with the inorganic particles, from the viewpoints of improving the long-term stability of electrical properties and carrier blocking properties.

[0063] Examples of the electron-accepting compound include electron-transporting substances such as quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; and benzophenone compounds. In particular, the electron-accepting compound is preferably a compound having an anthraquinone structure. Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds, and more specifically, anthraquinone, alizarin, quinizarin, anthrarufin, and purpurin.

[0064] The electron accepting compound may be contained in the undercoat layer in a dispersed state together with the inorganic particles, or may be contained in a state of being attached to the surfaces of the inorganic particles.

[0065] The method for attaching the electron accepting compound to the surface of the inorganic particles may be, for example, a dry method or a wet method.

[0066] The dry method is, for example, a method in which an electron-accepting compound is attached to the surface of inorganic particles by dropping an electron-accepting compound directly or dissolved in an organic solvent or spraying it together with dry air or nitrogen gas while stirring inorganic particles with a mixer or the like that exerts a large shearing force. The dropping or spraying of the electron-accepting compound is preferably performed at a temperature below the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be performed at 100° C. or higher. The temperature and time of baking are not particularly limited as long as electrophotographic properties can be obtained.

[0067] The wet method is a method in which, for example, an electron-accepting compound is added while dispersing inorganic particles in a solvent by stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, etc., and the inorganic particles are stirred or dispersed, and then the solvent is removed to attach the electron-accepting compound to the surface of the inorganic particles. The solvent is removed, for example, by filtration or distillation. After the solvent is removed, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as electrophotographic properties are obtained. In the wet method, moisture contained in the inorganic particles may be removed before adding the electron-accepting compound, and examples of such methods include a method of removing the moisture while stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

[0068] The attachment of the electron accepting compound may be carried out before or after the inorganic particles are subjected to a surface treatment with a surface treatment agent, or the attachment of the electron accepting compound and the surface treatment with the surface treatment agent may be carried out simultaneously.

[0069] The content of the electron accepting compound is, for example, from 0.01% by mass to 20% by mass, and preferably from 0.01% by mass to 10% by mass, based on the inorganic particles.

[0070] Examples of the binder resin used in the undercoat layer include known materials such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents. Examples of the binder resin used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline, etc.), and the like.

[0071] Among these, the binder resin used in the undercoat layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and in particular, a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins, with a curing agent is preferred. When two or more of these binder resins are used in combination, the mixing ratio is set as necessary.

[0072] The undercoat layer may contain various additives for improving electrical properties, environmental stability, and image quality. Examples of the additives include known materials such as polycyclic condensation and azo-based electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, silane coupling agents, etc. As described above, silane coupling agents are used for surface treatment of inorganic particles, and may also be added to the undercoat layer as an additive.

[0073] Examples of silane coupling agents as additives include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and the like.

[0074] Examples of the zirconium chelate compound include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0075] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0076] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0077] These additives may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0078] The undercoat layer preferably has a Vickers hardness of 35 or more. The surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to between 1 / (4n) (n is the refractive index of the upper layer) and 1 / 2 of the wavelength λ of the exposure laser used in order to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. The surface of the undercoat layer may be polished to adjust the surface roughness. Examples of the polishing method include buffing, sandblasting, wet honing, grinding, and the like.

[0079] The formation of the undercoat layer is not particularly limited, and a known formation method can be used. For example, the undercoat layer can be formed by forming a coating film of a coating solution for forming the undercoat layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary.

[0080] Examples of the solvent for preparing the coating liquid for forming the undercoat layer include known organic solvents, such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include ordinary organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0081] Examples of the method for dispersing the inorganic particles when preparing the coating liquid for forming the undercoat layer include known methods such as those using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0082] Examples of the method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, knife coating, and curtain coating.

[0083] The thickness of the undercoat layer is preferably set to 15 μm or more, and more preferably within the range of 20 μm to 50 μm.

[0084] [Middle layer] The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, and melamine resins. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in the intermediate layer may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0085] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0086] The formation of the intermediate layer is not particularly limited, and a known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of a coating solution for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary. The intermediate layer can be formed by any of the usual coating methods, such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating and curtain coating.

[0087] The thickness of the intermediate layer is preferably set in the range of 0.1 μm to 3 μm. The intermediate layer may be used as an undercoat layer.

[0088] [Charge generation layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. The charge generation layer may also be a vapor deposition layer of the charge generation material. The vapor deposition layer of the charge generation material is suitable for use with a non-coherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array.

[0089] Examples of the charge generating material include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0090] Among these, in order to accommodate laser exposure in the near infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material, specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, or titanyl phthalocyanine.

[0091] On the other hand, in order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include condensed aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments.

[0092] The above charge generating materials may be used when using incoherent light sources such as LEDs and organic EL image arrays that emit light at a central wavelength of 450 nm to 780 nm, but from the viewpoint of resolution, when using a thin photosensitive layer of 20 μm or less, the electric field strength in the photosensitive layer becomes high, and a decrease in charging due to charge injection from the substrate, so-called black spots, is likely to occur as an image defect. This becomes more noticeable when using charge generating materials that are p-type semiconductors such as trigonal selenium and phthalocyanine pigments and are prone to generating dark current.

[0093] In contrast, when n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge generating materials, dark current is unlikely to occur, and image defects called black spots can be suppressed even in thin films. The n-type is determined by the polarity of the flowing photocurrent using the commonly used time-of-flight method, and those that are more likely to pass electrons as carriers than holes are considered to be n-type.

[0094] The binder resin used in the charge generating layer may be selected from a wide range of insulating resins, and may also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, polysilane, and the like. Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (polycondensation product of bisphenols and aromatic dicarboxylic acid, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin, etc. Here, "insulating" means a material having a volume resistivity of 10 13 These binder resins are used alone or in combination of two or more.

[0095] The compounding ratio of the charge generating material to the binder resin is preferably within a range of 10:1 to 1:10 by mass.

[0096] The charge generating layer may contain other known additives.

[0097] The formation of the charge generation layer is not particularly limited, and a known formation method is used, for example, by forming a coating film of a coating solution for forming the charge generation layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary. The formation of the charge generation layer may be performed by vapor deposition of the charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0098] Examples of the solvent for preparing the coating liquid for forming the charge generating layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene, etc. These solvents may be used alone or in combination of two or more.

[0099] As a method for dispersing particles (e.g., charge generating material) in the coating liquid for forming a charge generating layer, for example, a media dispersing machine such as a ball mill, a vibration ball mill, an attritor, a sand mill, or a horizontal sand mill, or a media-less dispersing machine such as an agitator, an ultrasonic dispersing machine, a roll mill, or a high-pressure homogenizer, may be used. Examples of high-pressure homogenizers include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion is dispersed by penetrating a fine flow path under high pressure. During dispersion, it is effective to set the average particle size of the charge generating material in the coating liquid for forming a charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0100] Examples of methods for applying the coating liquid for forming the charge generating layer onto the undercoat layer (or onto the intermediate layer) include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, knife coating, and curtain coating.

[0101] The thickness of the charge generating layer is preferably set within the range of 0.1 μm or more and 5.0 μm or less, and more preferably 0.2 μm or more and 2.0 μm or less.

[0102] [Charge transport layer] The charge transport layer is, for example, a layer containing a charge transport material, a binder resin, a filler, and a low boiling point solvent. The charge transport layer may be a layer containing a polymer charge transport material.

[0103] Examples of the charge transport material include electron transporting compounds such as quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. Examples of the charge transport material include hole transporting compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination, but are not limited to these.

[0104] As the charge transport material, from the viewpoint of charge mobility, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferred.

[0105] [ka]

[0106] In structural formula (a-1), Ar T1 , Ar T2 , and Ar T3 each independently represents a substituted or unsubstituted aryl group; 6 H 4 -C(R T4 )=C(R T5 )(R T6 ), or -C 6 H 4 -CH=CH-CH=C(R T7 )(R T8 ) is shown. T4 , R T5 , R T6 , R T7 , and R T8 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Examples of the substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0107] [ka]

[0108] In structural formula (a-2), R T91 and R T92 R each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. T101 , R T102 , R T111 and R T112 each independently represents a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, an amino group substituted with an alkyl group having from 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ) and R T12 , R T13 , R T14 , R T15 and R T16 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, ​​Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less. Examples of the substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0109] Among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), in particular, 6 H 4-CH=CH-CH=C(R T7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 ) is preferable from the viewpoint of charge mobility.

[0110] As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester polymer charge transport materials are particularly preferred. The polymer charge transport material may be used alone or in combination with a binder resin.

[0111] Examples of the binder resin used in the charge transport layer include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polysilane, etc. Among these, polycarbonate resin or polyarylate resin is suitable as the binder resin. These binder resins are used alone or in combination of two or more. The compounding ratio of the charge transport material to the binder resin is preferably from 10:1 to 1:5 by mass.

[0112] The charge transport layer may contain other known additives.

[0113] The charge transport layer is preferably formed by coating. A preferred example of the coating method includes dissolving or dispersing a binder resin, a charge transport material, and a filler in a low boiling point solvent to prepare a coating liquid for forming the charge transport layer, coating the coating liquid for forming the charge transport layer on the surface of the charge generating layer to form a coating film, and drying the coating film.

[0114] The coating liquid used to form the outermost charge transport layer contains a low boiling point solvent (a solvent having a boiling point of 80° C. or less). The low boiling point solvent may be one type or two or more types. The coating liquid used to form the outermost charge transport layer may contain a solvent other than the low boiling point solvent (i.e., a solvent having a boiling point of more than 80° C.). However, the proportion of the low boiling point solvent in the total amount of solvent is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 100% by mass.

[0115] The filler can be dispersed in the charge transport layer forming coating liquid using, for example, a media dispersing machine such as a ball mill, a vibration ball mill, an attritor, a sand mill, or a horizontal sand mill, or a medialess dispersing machine such as an agitator, an ultrasonic dispersing machine, a roll mill, or a high-pressure homogenizer.

[0116] Examples of the coating method for applying the coating liquid for forming the charge transport layer onto the charge generating layer include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, knife coating and curtain coating.

[0117] The drying temperature of the coating film for the outermost charge transport layer is adjusted according to the boiling point of the solvent used in preparing the coating solution so that the amount of solvent contained in the layer after drying is 0.1% by mass or more and 0.3% by mass or less.

[0118] In order to obtain the photoconductor according to the first embodiment, it is preferable to smooth the outer peripheral surface of the outermost charge transport layer so that the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer is adjusted to 0.013 μm or less. The smoothing treatment may be, for example, a heating treatment in which a heating member is brought into contact with the outermost charge transport layer, or a polishing treatment in which the outermost charge transport layer is precisely polished. The surface temperature of the heating member used in the heating treatment is preferably equal to or higher than the glass transition temperature of the binder resin constituting the outermost charge transport layer. For the polishing treatment, a sheet-like or film-like precision polishing material (so-called lapping film) is preferably used.

[0119] The thickness of the outermost charge transport layer is preferably within the range described above in each of the first and second embodiments.

[0120] The total thickness of all the charge transport layers is preferably from 10 μm to 50 μm, and more preferably from 15 μm to 30 μm.

[0121] [Inorganic protective layer] The inorganic protective layer is an inorganic material layer. Examples of inorganic materials include metal oxides such as gallium oxide, aluminum oxide, zinc oxide, titanium oxide, indium oxide, tin oxide, and boron oxide; metal nitrides such as gallium nitride, aluminum nitride, zinc nitride, titanium nitride, indium nitride, tin nitride, and boron nitride; carbon-based and silicon-based inorganic materials such as diamond-like carbon, amorphous carbon, hydrogenated amorphous carbon, hydrogenated / fluorinated amorphous carbon, amorphous silicon carbide, hydrogenated amorphous silicon carbide, amorphous silicon, and hydrogenated amorphous silicon; and mixed crystals thereof.

[0122] From the viewpoint of wear resistance and electrical properties of the photoconductor, the inorganic protective layer is preferably a layer containing a metal oxide, more preferably a layer containing a Group 13 element and an oxygen element, and further preferably a layer containing gallium oxide or a layer containing aluminum oxide. The metal oxide contained in the inorganic protective layer may be one type or two or more types.

[0123] The volume resistivity of the inorganic protective layer is set to 1.0×10 10 It is preferable that the resistance is Ω·cm or more, and 1.0×10 11 It is more preferable that the resistivity is Ω·cm or more.

[0124] In the present disclosure, the method for measuring the volume resistivity of the inorganic protective layer is as follows. The inorganic protective layer is peeled off from the photoconductor to prepare a sample. The sample is clamped in the sample holder of an impedance analyzer (Toyo Corporation), and the resistance is measured at an AC voltage of 1V and a frequency of 100Hz, and calculated based on the electrode area and the thickness of the sample.

[0125] Examples of methods for forming the inorganic protective layer include known vapor phase film formation methods such as plasma CVD (Chemical Vapor Deposition), metalorganic vapor phase epitaxy, molecular beam epitaxy, deposition, sputtering, etc. For example, the inorganic protective layer can be formed by applying the plasma CVD film formation apparatus and film formation conditions described in JP 2014-191179 A.

[0126] From the viewpoint of the abrasion resistance and electrical properties of the photoreceptor, the thickness of the inorganic protective layer is preferably from 0.2 to 10 μm, more preferably from 0.4 to 8 μm, and even more preferably from 0.6 to 6 μm.

[0127] <Image forming apparatus, process cartridge> The image forming apparatus according to the present embodiment includes an electrophotographic photoreceptor, a charging device that charges the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, and a transfer device that transfers the toner image to the surface of a recording medium. The electrophotographic photoreceptor according to the present embodiment is applied as the electrophotographic photoreceptor.

[0128] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus including a fixing device that fixes a toner image transferred onto the surface of a recording medium; an apparatus of a direct transfer type that directly transfers a toner image formed on the surface of an electrophotographic photosensitive member onto a recording medium; an apparatus of an intermediate transfer type that primarily transfers a toner image formed on the surface of an electrophotographic photosensitive member onto the surface of an intermediate transfer member, and then secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus including a cleaning device that cleans the surface of an electrophotographic photosensitive member before charging after the transfer of a toner image; an apparatus including a static elimination device that irradiates the surface of an electrophotographic photosensitive member with static elimination light to eliminate static electricity before charging after the transfer of a toner image; and an apparatus including an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

[0129] In the case of an intermediate transfer type device, the transfer device is configured to have, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer device which primarily transfers the toner image formed on the surface of an electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer device which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0130] The image forming apparatus according to the present embodiment may be either a dry development type image forming apparatus or a wet development type image forming apparatus (a development type using a liquid developer).

[0131] In the image forming apparatus according to the present embodiment, for example, a portion including an electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to the present embodiment is preferably used. The process cartridge may include, in addition to the electrophotographic photosensitive member, at least one selected from the group consisting of a charging device, an electrostatic latent image forming device, a developing device, and a transfer device.

[0132] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Principal parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0133] FIG. 3 is a schematic diagram showing an example of an image forming apparatus according to the present embodiment. As shown in FIG. 3, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 via the intermediate transfer body 50, and the intermediate transfer body 50 is disposed with a part of it in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer device.

[0134] 3 supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a cleaning device) integrally within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is disposed so as to come into contact with the surface of the electrophotographic photoreceptor 7. The cleaning member may not be in the form of the cleaning blade 131, but may be a conductive or insulating fibrous member, which may be used alone or in combination with the cleaning blade 131.

[0135] FIG. 3 shows an example of an image forming apparatus including a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of the electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists in cleaning, which are arranged as needed.

[0136] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0137] -Charging device- As the charging device 8, for example, a contact type charger using a conductive or semiconductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. Also, a non-contact type roller charger, a scorotron charger or corotron charger that utilizes corona discharge, or other chargers known per se, can be used.

[0138] -Exposure equipment- The exposure device 9 may be, for example, an optical device that exposes the surface of the electrophotographic photoreceptor 7 with light such as semiconductor laser light, LED light, or liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. The wavelength of the semiconductor laser is mainly near infrared light having an oscillation wavelength of about 780 nm. However, it is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a blue laser having an oscillation wavelength of 400 nm to 450 nm may also be used. In addition, a surface-emitting laser light source capable of outputting multiple beams is also effective for forming a color image.

[0139] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contacting or non-contacting a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected according to the purpose. For example, it may be a known developing device that has a function of attaching a one-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, roller, or the like. Among them, it is preferable to use a developing roller that holds a developer on its surface.

[0140] The developer used in the developing device 11 may be a one-component developer containing only toner, or may be a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Known developers are used.

[0141] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131. In addition to the cleaning blade type, a fur brush cleaning type or a simultaneous development and cleaning type may also be adopted.

[0142] -Transfer device- Examples of the transfer device 40 include known transfer chargers such as a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0143] -Intermediate transfer body- A belt-like intermediate transfer belt containing semiconductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. is used as the intermediate transfer body 50. The intermediate transfer body may be in the form of a drum other than a belt.

[0144] FIG. 4 is a schematic diagram showing another example of the image forming apparatus according to the present embodiment. 4 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one electrophotographic photosensitive body is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type. EXAMPLES

[0145] Hereinafter, the embodiments of the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are by mass. In the following description, unless otherwise specified, synthesis, production, processing, measurement, etc. were carried out at room temperature (25° C.±3° C.).

[0146] First Embodiment <Example 1> [Formation of undercoat layer] As a conductive substrate, an aluminum cylindrical tube having an outer diameter of 30 mm, a length of 250 mm, and a wall thickness of 1 mm was prepared.

[0147] Zinc oxide (average particle size 70 nm, specific surface area 15 m 2 100 parts of a silane coupling agent (trade name: KBM603, Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) was added and stirred for 2 hours. The toluene was then distilled off under reduced pressure, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0148] 110 parts of the surface-treated zinc oxide was mixed with 500 parts of tetrahydrofuran by stirring, and a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added thereto, followed by stirring for 5 hours at 50° C. Next, the solid content was filtered off by reduced pressure filtration and dried under reduced pressure at 60° C. to obtain zinc oxide with alizarin added thereto.

[0149] 100 parts of a solution of 60 parts of alizarin-added zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, product name: Sumidur 3175, Sumitomo Bayer Urethane Co., Ltd.), and 15 parts of butyral resin (product name: S-LEC BM-1, Sekisui Chemical Co., Ltd.) dissolved in 68 parts of methyl ethyl ketone was mixed with 5 parts of methyl ethyl ketone, and dispersed for 2 hours in a sand mill using glass beads with a diameter of 1 mm to obtain a dispersion. 0.005 parts of dioctyltin dilaurate as a catalyst and 4 parts of silicone resin particles (product name: Tospearl 145, Momentive Performance Materials Co., Ltd.) were added to the dispersion to obtain a coating liquid for forming an undercoat layer. The coating liquid for forming an undercoat layer was applied to the outer peripheral surface of a conductive substrate by dip coating, and dried and cured at 170°C for 40 minutes to form an undercoat layer with a thickness of 20 μm.

[0150] [Formation of charge generation layer] A mixture of 15 parts of hydroxygallium phthalocyanine (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in the X-ray diffraction spectrum using CuKα characteristic X-rays) as a charge generating material, 10 parts of vinyl chloride-vinyl acetate copolymer resin (product name: VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using glass beads with a diameter of 1 mm for 4 hours. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion and stirred to obtain a coating solution for forming a charge generating layer. The coating solution for forming a charge generating layer was dip-coated on the undercoat layer and dried at room temperature to form a charge generating layer with a layer thickness of 0.25 μm.

[0151] [Formation of charge transport layer] Binder resin: Polycarbonate resin (PC1) 4.7% by mass ·Charge transport material: CTM-1 3.1% by mass Silica particles hydrophobized with 1,1,1,3,3,3-hexamethyldisilazane (average particle size 80 nm) 20.2% by mass Tetrahydrofuran (boiling point 66°C) 64.8% by mass Toluene (boiling point 111°C) 7.2% by mass The above materials were mixed by stirring to obtain a coating solution for forming a charge transport layer, which was then dip-coated onto the charge generating layer and dried at 140° C. for 40 minutes to form a charge transport layer having a thickness of 20 μm. The chemical structures of the polycarbonate resin (PC1) and the charge transport material CTM-1 are as follows: The numerical values ​​in the following structural formulas are molar ratios.

[0152] [ka]

[0153] [ka]

[0154] [Formation of inorganic protective layer] Using trimethylgallium as the film-forming material, an amorphous layer containing gallium oxide was formed on the charge transport layer of the intermediate product by plasma CVD. The inorganic protective layer had a thickness of 2 μm. Thus, a photoreceptor was obtained in which the undercoat layer, the charge generating layer, the charge transport layer and the inorganic protective layer were disposed on the conductive substrate.

[0155] <Comparative Example 1> A photoreceptor was prepared in the same manner as in Example 1, except that in forming the charge transport layer, the solvent of the coating liquid was changed to cyclopentyl methyl ether (boiling point 106° C.).

[0156] <Comparative Examples 2 to 3> A photoreceptor was prepared in the same manner as in Example 1, except that the solvent of the coating liquid in forming the charge transport layer was changed as shown in Table 1.

[0157] <Examples 2 to 5> A photoreceptor was prepared in the same manner as in Example 1, except that the amount of hydrophobized silica particles used in forming the charge transport layer was changed so that the volume ratio of the particles to the charge transport layer was the value shown in Table 1.

[0158] <Example 6> A photoreceptor was prepared in the same manner as in Example 1, except that in forming the charge transport layer, the solvent of the coating liquid was changed from tetrahydrofuran to ethyl acetate (boiling point 77.1° C.).

[0159] <Example 7> A photoreceptor was prepared in the same manner as in Example 1, except that the film-forming material in forming the inorganic protective layer was changed to trimethylaluminum.

[0160] <Example 8> A photoreceptor was prepared in the same manner as in Example 1, except that in forming the charge transport layer, the hydrophobized silica particles were replaced with boron nitride particles (average particle size 500 nm) that had been hydrophobized with 1,1,1,3,3,3-hexamethyldisilazane. The amount of the hydrophobized boron nitride particles was adjusted so that the volume ratio of the charge transport layer was the value shown in Table 1.

[0161] <Example 9> A photoreceptor was prepared in the same manner as in Example 1, except that in forming the charge transport layer, the hydrophobized silica particles were replaced with titanium oxide particles (average particle size 20 nm) that had been hydrophobized with 1,1,1,3,3,3-hexamethyldisilazane. The amount of the hydrophobized titanium oxide particles was adjusted so that the volume ratio of the charge transport layer was as shown in Table 1.

[0162] <Example 10> A photoreceptor was prepared in the same manner as in Example 1, except that the charge transport layer was subjected to the following smoothing treatment, and then an inorganic protective layer was formed.

[0163] [Smoothing treatment of the outer surface of the charge transport layer] The intermediate product on which the charge transport layer had been formed was brought into contact with a hot plate having a surface temperature of 140° C. while being rotated, to smooth the outer peripheral surface of the charge transport layer.

[0164] <Examples 11 to 14> A photoreceptor was prepared in the same manner as in Example 10, except that the amount of hydrophobized silica particles used in forming the charge transport layer was changed so that the volume ratio of the particles to the charge transport layer was the value shown in Table 1.

[0165] Second Embodiment <Example 21> [Formation of undercoat layer] An undercoat layer was formed in the same manner as in Example 1.

[0166] [Formation of charge generation layer] A charge generating layer was formed in the same manner as in Example 1.

[0167] [Formation of the first charge transport layer] A first charge transport layer was formed in the same manner as in Example 1, except that the amount of hydrophobized silica particles used was changed so that the volume ratio of the hydrophobized silica particles to the charge transport layer was 50 volume %.

[0168] [Formation of the second charge transport layer] Binder resin: Polycarbonate resin (PC1) 16.8% by mass ·Charge transport material: CTM-1 11.2% by mass Tetrahydrofuran (boiling point 66°C) 64.8% by mass Toluene (boiling point 111°C) 7.2% by mass The above materials were mixed by stirring to obtain a coating solution for forming a second charge transport layer. The coating solution for forming the second charge transport layer was dip-coated on the first charge transport layer and dried at 140° C. for 40 minutes to form a second charge transport layer having a thickness of 1 μm.

[0169] [Formation of inorganic protective layer] An inorganic protective layer was formed in the same manner as in Example 1. Thus, a photoreceptor was obtained in which the undercoat layer, the charge generating layer, the first charge transport layer, the second charge transport layer and the inorganic protective layer were disposed on the conductive substrate.

[0170] <Comparative Example 4> A photoreceptor was prepared in the same manner as in Example 21, except that in forming the second charge transport layer, the solvent of the coating liquid was changed to cyclopentyl methyl ether (boiling point 106° C.).

[0171] <Comparative Examples 5 to 6> A photoreceptor was prepared in the same manner as in Example 21, except that the solvent of the coating liquid in forming the second charge transport layer was changed as shown in Table 2.

[0172] <Examples 22 to 24> A photoreceptor was prepared in the same manner as in Example 21, except that the layer thickness of the second charge transport layer was changed as shown in Table 2.

[0173] <Examples 25 to 27> A photoreceptor was prepared in the same manner as in Example 21, except that silica particles (average particle size 80 nm) that had been hydrophobized with 1,1,1,3,3,3-hexamethyldisilazane were added to the coating solution in forming the second charge transport layer. The amount of the hydrophobized silica particles used was adjusted so that the volume ratio of the charge transport layer was the value shown in Table 2.

[0174] <Photoreceptor performance evaluation> [Electrical characteristics] A surface potential probe of a surface potential meter (Trek 334, manufactured by Trek Corporation) was placed at the axial center of the photoreceptor and 1 mm away from the surface of the photoreceptor. In an environment with a temperature of 25°C and a relative humidity of 55%, the photoconductor was charged to -700 V while rotating at a rotation speed of 40 rpm, and the exposure dose was 10 mJ / m 2 The surface potential of the photoconductor was measured and its absolute value was classified as follows. The evaluation results are shown in Tables 1 and 2. A: More than 200V, less than 250V B: More than 250V, less than 270V C: More than 270V, less than 290V D: More than 290V, less than 300V E: Over 300V

[0175] [Point-like image defects] The photoconductor was dropped once from a height of 10 cm onto a concrete surface with the axial direction of the photoconductor aligned in the direction of gravity. The photoconductor was also dropped once with the axial direction of the photoconductor reversed. The photoconductor was installed in a modified image forming apparatus DocuCentre-V C7775 (FUJIFILM Business Innovation Co., Ltd.). Under an environment of 25°C temperature and 55% relative humidity, a full-surface halftone image in cyan with an image density of 50% was formed on A3-size plain paper. The paper was visually observed to confirm the presence or absence of color spots. If color spots were found, their size was measured under a microscope and classified as follows. The evaluation results are shown in Tables 1 and 2. A: No color spots are observed. B: Color spots are observed, and the maximum diameter of the color spots is less than 50 μm. C: Color spots are observed, and the maximum diameter of the color spots is 50 μm or more and less than 80 μm. D: Color spots are observed, and the maximum diameter of the color spots is 80 μm or more and less than 100 μm. E: Color spots are observed, and the maximum diameter of the color spots is 100 μm or more.

[0176] The abbreviations listed in Tables 1 and 2 refer to the following compounds. THF: Tetrahydrofuran CPME: Cyclopentyl methyl ether

[0177] [Table 1]

[0178] [Table 2]

[0179] The electrophotographic photoreceptor, process cartridge, and image forming apparatus of the present disclosure include the following aspects.

[0180] (((1))) The electroconductive substrate includes a charge generating layer, a charge transport layer, and an inorganic protective layer, the charge transport layer is one or more layers, and at least one layer contains a filler; the inorganic protective layer is disposed in contact with an outermost charge transport layer of the one or more charge transport layers; the outermost charge transport layer contains a solvent having a boiling point of 80° C. or less; the ratio of the solvent having a boiling point of 80° C. or less in the outermost charge transport layer is 0.1% by mass or more and 0.3% by mass or less; The arithmetic average roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer is 0.013 μm or less. Electrophotographic photoreceptor. (((2))) the outermost charge transport layer contains a solvent having a boiling point of 60° C. or more and 70° C. or less; the proportion of the solvent having a boiling point of 60° C. or more and 70° C. or less in the outermost charge transport layer is 0.1% by mass or more and 0.3% by mass or less; The electrophotographic photoreceptor according to (((1))). (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein the filler comprises silica particles. (((4))) the outermost charge transport layer comprises a filler; When the outermost charge transport layer is divided into an outer peripheral side and an inner peripheral side with a thickness ratio of 20:80, a filler volume ratio Vo on the outer peripheral side and a filler volume ratio Vi on the inner peripheral side satisfy 5≦(Vo-Vi)≦50. The electrophotographic photoreceptor according to any one of (((1))) to (((3))). (((5))) The electrophotographic photoreceptor according to (((4))), wherein the filler volume ratio Vo on the outer circumferential surface side and the filler volume ratio Vi on the inner circumferential surface side satisfy 10≦(Vo-Vi)≦30. (((6))) The electrophotographic photoreceptor according to (((4))) or (((5))), wherein the charge transport layer is a single layer, and the filler accounts for 60 volume % or more and 70 volume % or less of the single charge transport layer. (((7))) The charge transport layer has two or more layers, the outermost charge transport layer does not contain or contains a filler, The ratio of the filler in the outermost charge transport layer is 0% by volume or more and 30% by volume or less. The electrophotographic photoreceptor according to any one of (((1))) to (((3))). (((8))) The electrophotographic photoreceptor according to (((7))), wherein the outermost charge transport layer has a thickness of more than 0.8 μm and not more than 5 μm. (((9))) The electrophotographic photoreceptor according to (((7))) or (((8))), wherein the charge transport layer is a two-layered structure, and the filler accounts for 30 volume % or more and 50 volume % or less of the two charge transport layers. (((10))) An electrophotographic photoreceptor according to any one of (((1))) to (((9))), A process cartridge that is detachably attached to an image forming apparatus. (((11))) An electrophotographic photoreceptor according to any one of (((1))) to (((9))), a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising:

[0181] According to (((1))) or (((3))), an electrophotographic photoreceptor is provided which is superior in electrical characteristics and less susceptible to dot-like image defects, as compared with an electrophotographic photoreceptor in which the proportion of a solvent having a boiling point of 80° C. or less in the outermost charge transport layer is less than 0.1 mass % or exceeds 0.3 mass %, or an electrophotographic photoreceptor in which the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer exceeds 0.013 μm. According to (((2))), an electrophotographic photoreceptor is provided which is excellent in electrical characteristics and is less susceptible to dot-like image defects, as compared with an electrophotographic photoreceptor in which the proportion of a solvent having a boiling point of 60° C. or more and 70° C. or less in the outermost charge transport layer is less than 0.1 mass % or more than 0.3 mass %. According to (((4))), compared with electrophotographic photoreceptors having a (Vo-Vi) of less than 5 or more than 50, an electrophotographic photoreceptor having excellent electrical characteristics and less susceptible to dot-like image defects is provided. According to (((5))), compared with electrophotographic photoreceptors having a (Vo-Vi) of less than 10 or more than 30, an electrophotographic photoreceptor having excellent electrical characteristics and less susceptible to dot-like image defects is provided. According to (((6))), an electrophotographic photoreceptor is provided which is excellent in electrical characteristics and less prone to dot-like image defects, as compared with electrophotographic photoreceptors in which the proportion of filler in the entire charge transport layer is less than 60 volume % or more than 70 volume %. According to (((7))), an electrophotographic photoreceptor is provided which is excellent in electrical characteristics and less prone to dot-like image defects, as compared with an electrophotographic photoreceptor in which the proportion of filler in the outermost charge transport layer exceeds 30 volume %. According to (((8))), an electrophotographic photoreceptor is provided which is excellent in electrical characteristics and less prone to dot-like image defects, as compared with electrophotographic photoreceptors having an outermost charge transport layer having a layer thickness of 0.8 μm or less or exceeding 5 μm. According to (((9))), an electrophotographic photoreceptor is provided which is excellent in electrical characteristics and less prone to dot-like image defects, compared to electrophotographic photoreceptors in which the proportion of filler in the entire charge transport layer is less than 30 volume % or more than 50 volume %. According to (((10))), there is provided a process cartridge equipped with an electrophotographic photoreceptor which has superior electrical characteristics and is less susceptible to dot-like image defects, compared to an electrophotographic photoreceptor in which the proportion of a solvent having a boiling point of 80°C or less in the outermost charge transport layer is less than 0.1 mass % or exceeds 0.3 mass %, or an electrophotographic photoreceptor in which the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer exceeds 0.013 μm. According to (((11))), an image forming apparatus is provided that is equipped with an electrophotographic photoreceptor that has superior electrical characteristics and is less susceptible to dot-like image defects, compared to an electrophotographic photoreceptor in which the proportion of a solvent having a boiling point of 80°C or less in the outermost charge transport layer is less than 0.1 mass % or exceeds 0.3 mass %, or an electrophotographic photoreceptor in which the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer exceeds 0.013 μm. [Explanation of symbols]

[0182] 1 conductive substrate, 2 subbing layer, 3 charge generation layer, 4 charge transport layer, 4a charge transport layer, 4b charge transport layer, 5 photosensitive layer, 6 inorganic protective layer, 10A photoreceptor, 10B photoreceptor

[0183] 7 electrophotographic photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll-shaped), 133 fibrous member (flat brush-shaped), 300 process cartridge

Claims

1. The electroconductive substrate includes a charge generating layer, a charge transport layer, and an inorganic protective layer, the charge transport layer is one or more layers, and at least one layer contains a filler; the inorganic protective layer is disposed in contact with an outermost charge transport layer of the one or more charge transport layers; the outermost charge transport layer contains a solvent having a boiling point of 80° C. or less; the ratio of the solvent having a boiling point of 80° C. or less in the outermost charge transport layer is 0.1% by mass or more and 0.3% by mass or less; the arithmetic mean roughness Ra (JIS B0601:2013) of the outer peripheral surface of the outermost charge transport layer is 0.013 μm or less; Electrophotographic photoreceptor.

2. The outermost charge transport layer contains a solvent having a boiling point of 60° C. or more and 70° C. or less, the ratio of the solvent having a boiling point of 60° C. or more and 70° C. or less in the outermost charge transport layer is 0.1% by mass or more and 0.3% by mass or less; The electrophotographic photoreceptor according to claim 1 .

3. The electrophotographic photoreceptor of claim 1 , wherein the filler comprises silica particles.

4. the outermost charge transport layer comprises a filler; When the outermost charge transport layer is divided into an outer peripheral side and an inner peripheral side with a thickness ratio of 20:80, a filler volume ratio Vo on the outer peripheral side and a filler volume ratio Vi on the inner peripheral side satisfy 5≦(Vo−Vi)≦50. The electrophotographic photoreceptor according to claim 1 .

5. 5. The electrophotographic photoreceptor according to claim 4, wherein the outer peripheral surface side filler volume ratio Vo and the inner peripheral surface side filler volume ratio Vi satisfy 10≦(Vo−Vi)≦30.

6. 5. The electrophotographic photoreceptor according to claim 4, wherein the charge transport layer is one layer, and the ratio of the filler in the one charge transport layer is 60 volume % or more and 70 volume % or less.

7. The charge transport layer has two or more layers, the outermost charge transport layer does not contain or contains a filler, the ratio of the filler in the outermost charge transport layer is 0% by volume or more and 30% by volume or less; The electrophotographic photoreceptor according to claim 1 .

8. 8. The electrophotographic photoreceptor according to claim 7, wherein the outermost charge transport layer has a thickness of more than 0.8 [mu]m and not more than 5 [mu]m.

9. 8. The electrophotographic photoreceptor according to claim 7, wherein the charge transport layer is a two-layered layer, and the ratio of the filler in the two-layered charge transport layer is 30% by volume or more and 50% by volume or less.

10. The electrophotographic photoreceptor according to any one of claims 1 to 9 is provided, A process cartridge that is detachably attached to an image forming apparatus.

11. The electrophotographic photoreceptor according to any one of claims 1 to 9, a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising:

Images