Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that is excellent in charging maintainability.SOLUTION: Provided are: an electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer provided on the conductive substrate and containing a binder resin and an electron transport material represented by the following general formula (P), and a photosensitive layer provided on the undercoat layer; a process cartridge; and an image forming apparatus. In the above-mentioned general formula (P), R1, R2, R3, R4, R5, R6, R7, and R8 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In an electrophotographic image forming apparatus, generally, the surface of an electrophotographic photoreceptor is charged to a predetermined polarity and potential by a charging means, and the surface of the electrophotographic photoreceptor after charging is selectively discharged by image exposure to form an electrostatic latent image, and then a developing means attaches toner to the electrostatic latent image, developing the latent image into a toner image. Then, the toner image is transferred to a transfer medium by a transfer means, and the image formed is discharged. In recent years, electrophotographic photoreceptors have the advantages of high speed and high print quality, and are therefore widely used in fields such as copying machines and laser beam printers.

[0003] Currently, in many cases, electrophotographic photoreceptors are manufactured by forming an undercoat layer on a conductive support layer such as an aluminum base material, and then successively forming, on the undercoat layer, a single-layer type photosensitive layer in which a charge generating agent and a charge transporting agent are contained in the same layer, or a so-called functionally separated type photosensitive layer in which a charge generating layer containing a charge generating agent and a charge transporting layer containing a charge transporting agent are laminated.

[0004] The undercoat layer is required to suppress charge injection into the photosensitive layer when a voltage is applied to the electrophotographic photoreceptor while concealing defects in the substrate, and to control the resistance. On the other hand, the undercoat layer is also required to suppress the charge generated in the photosensitive layer from being retained inside the photoreceptor, that is, to have charge transportability.

[0005] Patent Document 1 discloses an electrophotographic photoreceptor having a conductive support layer, a photosensitive layer containing a pigment, and an intermediate layer disposed between the conductive support layer and the photosensitive layer, the intermediate layer containing zinc oxide particles and a binder resin, the zinc oxide particles contained in the intermediate layer having a maximum primary particle diameter of less than 300 nm and an average particle diameter of 20 to 200 nm, and the intermediate layer having a thickness of 15 to 50 μm.

[0006] Patent Document 2 discloses an electrophotographic photoreceptor comprising a conductive support layer, a photosensitive layer containing a pigment, and an intermediate layer disposed between the conductive support layer and the photosensitive layer, the intermediate layer containing metal oxide particles coated with a coupling agent and a binder resin, the intermediate layer having a thickness greater than 20 μm and equal to or less than 50 μm, and the binder resin being a thermosetting resin.

[0007] Patent Document 3 discloses an electrophotographic photoreceptor having an intermediate layer and a photosensitive layer in this order on a support, characterized in that the intermediate layer contains a polymer of an electron transport material having a non-hydrolyzable polymerizable functional group. Patent Document 4 discloses an electrophotographic photoreceptor having an intermediate layer and a photosensitive layer in this order on a support, the intermediate layer containing a specific resin.

[0008] Patent Document 5 discloses an asymmetric imide compound having two differently structured substituents.

[0009] Patent Document 6 discloses a method for producing an electrophotographic photoreceptor, which comprises step (i) of forming an intermediate layer on a conductive support using an intermediate layer coating material containing polynaphthyldiimide particles, and step (ii) of forming a photosensitive layer on the intermediate layer, in which the polynaphthyldiimide particles are polynaphthyldiimide particles having a repeating unit containing a naphthyldiimide structure represented by the following general formula (2).

[0010] Patent Document 7 discloses an electrophotographic photoreceptor having an intermediate layer and a photosensitive layer provided in this order on a conductive support, the intermediate layer containing a polyolefin resin and an organic electron transport material, the polyolefin resin being a specific polyolefin resin, and the organic electron transport material being a compound selected from the group consisting of imide-based compounds, benzimidazole-based compounds, quinone-based compounds, cyclopentadienylidene-based compounds, azo-based compounds, and derivatives thereof.

[0011] Patent Document 8 describes an electrophotographic photoreceptor having an intermediate layer and a photosensitive layer on a support in this order, the photosensitive layer containing a charge generating material and a charge transport material, and an electrostatic latent image formed on the surface by a semiconductor laser, the intermediate layer containing a specific electron transport material, and the volume resistivity of the intermediate layer in an environment of 30° C. and 80% RH is 1×10 12 and the ratio (Rz / λ) of the ten-point average roughness (Rz) of the photosensitive layer side surface of the support to the wavelength (λ) of the semiconductor laser is 0.6 or more and 2.5 or less. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Patent No. 3991638 [Patent Document 2] JP 2003-091086 A [Patent Document 3] JP 2003-330209 A [Patent Document 4] JP 2003-345044 A [Patent Document 5] Patent No. 5147274 [Patent Document 6] Patent No. 4411232 [Patent Document 7] JP 2011-095665 A [Patent Document 8] Patent No. 3958154 Summary of the Invention [Problem to be solved by the invention]

[0013] In a conventional electrophotographic photoreceptor having a conductive substrate, an undercoat layer, and a photosensitive layer, a method of adjusting the charge retention is known, in which an undercoat layer containing a binder resin and an electron transport material (for example, the following electron transport material (A), (B), or (C) is included). However, there is a demand for the development of an electrophotographic photoreceptor having better charge retention. An object of the present disclosure is to provide an electrophotographic photoreceptor having excellent charge retention properties compared to an electrophotographic photoreceptor employing an undercoat layer containing a binder resin and a conventional electron transport material (for example, the following electron transport material (A), (B) or (C)). [ka] [Means for solving the problem]

[0014] Specific means for solving the above problems include the following aspects.

[0015] <1> A conductive substrate; an undercoat layer provided on the conductive substrate and containing a binder resin and an electron transport material represented by the following general formula (P); a photosensitive layer provided on the undercoat layer; An electrophotographic photoreceptor comprising: [ka] In the above general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. <2> In the general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R each independently represents a hydrogen atom or a halogen atom; <1> The electrophotographic photoreceptor according to claim 1. <3> In the general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 represents a hydrogen atom, <1> or <2> The electrophotographic photoreceptor according to claim 1. <4> The electron transport material has an average primary particle size of 1 μm or less. <1> ~ <3> 13. The electrophotographic photoreceptor according to claim 12. <5> The electron transport material has an average primary particle size of 0.03 μm or more and 1 μm or less. <4> The electrophotographic photoreceptor according to claim 1. <6> The content of the electron transporting material is less than 70% by mass based on the total solid content of the undercoat layer. <1> ~ <5> 13. The electrophotographic photoreceptor according to claim 12. <7> The thickness of the undercoat layer is 5 μm or more and 15 μm or less. <1> ~ <6> 13. The electrophotographic photoreceptor according to claim 12. <8> The binder resin is a thermosetting resin. <1> ~ <7> 13. The electrophotographic photoreceptor according to claim 12. <9> The thermosetting resin contains at least one resin selected from the group consisting of urethane resins, melamine resins, and benzoguanamine resins. <8> The electrophotographic photoreceptor according to claim 1. <10> The content of the metal oxide in the undercoat layer is 5% by mass or less based on the total solid content of the undercoat layer. <1> The electrophotographic photoreceptor according to claim 1. <11> <1> ~ <10> The electrophotographic photoreceptor according to any one of claims 1 to 5, A process cartridge that is detachably attached to an image forming apparatus. <12> <1> ~ <10> The 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; The electrostatic latent image formed on the surface of the electrophotographic photoreceptor is developed with a developer containing a toner. a developing device for forming a toner image by using the toner; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising: Effect of the Invention

[0016] <1> , <2> or <3> According to the present invention, there is provided an electrophotographic photoreceptor having excellent charge retention properties compared to a case in which an undercoat layer containing a binder resin and a conventional electron transport material (for example, the above-mentioned electron transport material (A), (B) or (C) etc.) is used. <4> According to the present invention, an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with a case where the average primary particle diameter of the electron transporting material exceeds 1 μm. <5> According to the present invention, an electrophotographic photoreceptor is provided which is excellent in film-forming properties and charge retention properties, as compared with the case where the average primary particle diameter of the electron transporting material is less than 0.03 μm or exceeds 1 μm. <6> According to the present invention, an electrophotographic photoreceptor is provided which is excellent in film-forming properties and charge retention properties, compared to a case in which the content of the electron transporting material is 70 mass % or more relative to the total solid content of the undercoat layer. <7> According to the present invention, an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with a case in which the thickness of the undercoat layer is less than 5 μm or exceeds 15 μm. <8> According to the present invention, an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with a case in which the binder resin is a thermoplastic resin. <9> According to the present invention, an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with a case where the thermosetting resin is nylon polyamide. <10> According to the present invention, an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with a case where the content of the metal oxide in the undercoat layer exceeds 5 mass % with respect to the total solid content of the undercoat layer. <11> or <12> According to the invention, there is provided a process cartridge or image forming apparatus equipped with an electrophotographic photoreceptor having excellent charge retention properties, compared to a process cartridge or image forming apparatus equipped with an electrophotographic photoreceptor employing an undercoat layer containing a binder resin and a conventional electron transport material (for example, the above-mentioned electron transport material (A), (B) or (C)). [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a schematic partial cross-sectional view showing an example of a layer structure of the electrophotographic photoreceptor according to the present embodiment. [Diagram 2] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 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.

[0019] In this specification, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively.

[0020] 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.

[0021] 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.

[0022] In this disclosure, the electrophotographic photoreceptor is also simply referred to as a photoreceptor.

[0023] <Electrophotographic photoreceptor> The electrophotographic photoreceptor according to the present embodiment includes a conductive substrate, an undercoat layer provided on the conductive substrate and containing a binder resin and an electron transport material represented by the following general formula (P), and a photosensitive layer provided on the undercoat layer. [ka] In the above general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.

[0024] The photoreceptor according to this embodiment includes a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer. Fig. 1 shows a schematic example of a layer structure of a photoreceptor according to this embodiment. Photoreceptor 7A shown in Fig. 1 has a structure in which an undercoat layer 1, a charge generation layer 2, and a charge transport layer 3 are laminated in this order on a conductive substrate 4. The charge generation layer 2 and the charge transport layer 3 constitute a photosensitive layer 5. Photoreceptor 7A may have a layer structure in which a protective layer is further provided on the charge transport layer 3.

[0025] In the photoreceptor according to this embodiment, the photosensitive layer may be a functionally separated type photosensitive layer in which a charge generation layer 2 and a charge transport layer 3 are separated, as in the photoreceptor 7A shown in FIG. 1, or may be a single-layer type photosensitive layer having a charge generation function and a charge transport function, instead of the charge generation layer 2 and the charge transport layer 3.

[0026] The electrophotographic photoreceptor according to this embodiment has an undercoat layer containing a binder resin and an electron transporting material represented by the above general formula (P).

[0027] In order to improve the charge retention of the electrophotographic photoreceptor, it is required to increase the electron transportability and decrease the hole transportability in the undercoat layer. As the conventional electron transport material, for example, the above-mentioned electron transport materials (A), (B) and (C) are adopted. However, these materials have high electron transportability but also have a property of moving holes slightly. Therefore, when a voltage is applied to the electrophotographic photoreceptor, holes move in the undercoat layer, and charge injection into the photosensitive layer may occur. As a result, the hole blocking property is insufficient, dark decay increases, and charge retention tends to decrease.

[0028] On the other hand, the electrophotographic photoreceptor according to the present embodiment contains an electron transporting material represented by general formula (P) in addition to a binder resin in the undercoat layer. As a result of intensive research, the present inventors have found that the electron transporting material represented by general formula (P) is a so-called perylene tetracarboxylic dianhydride, which has excellent electron transporting properties and low hole transporting properties as an electron transporting material to be blended in the undercoat layer. Thus, the electrophotographic photoreceptor according to the present embodiment is considered to have excellent charge retention properties because the undercoat layer has excellent electron transporting properties and reduces dark decay.

[0029] Each layer of the photoreceptor according to this embodiment will be described in detail below.

[0030] [Sublayer] The undercoat layer contains a binder resin and an electron transporting material represented by the following general formula (P). The undercoat layer may contain materials other than the binder resin and the electron transporting material represented by the following general formula (P).

[0031] [ka] In the above general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.

[0032] The electron transporting material represented by formula (P) has the property of excellent electron transporting property and low hole transporting property, and therefore, when the undercoat layer contains the electron transporting material represented by formula (P), the undercoat layer has excellent electron transporting property and reduces dark decay, which is considered to result in excellent charge retention.

[0033] In the general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 each independently preferably represents a hydrogen atom or a halogen atom, and more preferably represents a hydrogen atom. In general formula (P), R 1 ~R 8When is a hydrogen atom or a halogen atom (more preferably a hydrogen atom), the undercoat layer has better electron transport properties and further reduces dark decay, which is believed to result in better charge retention.

[0034] In general formula (P), R 1 ~R 8 The alkyl group represented by the formula (I) may be a substituted or unsubstituted alkyl group.

[0035] In general formula (P), R 1 ~R 8 Examples of the unsubstituted alkyl group represented by the formula (I) include a linear alkyl group having 1 to 20 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms), a branched alkyl group having 3 to 20 carbon atoms (preferably 3 to 10 carbon atoms), and a cyclic alkyl group having 3 to 20 carbon atoms (preferably 3 to 10 carbon atoms).

[0036] Examples of the linear alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, a tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-icosyl group.

[0037] Examples of the branched alkyl group having 3 to 20 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, an isododecyl group, a sec-dodecyl group, a tert-dodecyl group, a tert-tetradecyl group, and a tert-pentadecyl group.

[0038] Examples of the cyclic alkyl group having 3 to 20 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups formed by linking these monocyclic alkyl groups.

[0039] Among the above, as the unsubstituted alkyl group, a straight-chain alkyl group such as a methyl group or an ethyl group is preferable.

[0040] Substituents in the alkyl group include an alkoxy group, a hydroxy group, a carboxy group, a nitro group, and a halogen atom (such as a fluorine atom, a bromine atom, or an iodine atom). The alkoxy group that replaces the hydrogen atom in the alkyl group is R 1 ~R 8 Examples of the alkoxy group include the same as the unsubstituted alkoxy group represented by the following formula:

[0041] In general formula (P), R 1 ~R 8 The alkoxy group represented by the following formula (I) includes a substituted or unsubstituted alkoxy group.

[0042] In general formula (P), R 1 ~R 8 Examples of the unsubstituted alkoxy group represented by the formula (I) include linear, branched or cyclic alkoxy groups having 1 to 10 carbon atoms (preferably 1 to 6, more preferably 1 to 4).

[0043] Specific examples of linear alkoxy groups include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, and an n-decyloxy group. Specific examples of branched alkoxy groups include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, a tert-hexyloxy group, an isoheptyloxy group, a sec-heptyloxy group, a tert-heptyloxy group, an isooctyloxy group, a sec-octyloxy group, a tert-octyloxy group, an isononyloxy group, a sec-nonyloxy group, a tert-nonyloxy group, an isodecyloxy group, a sec-decyloxy group, and a tert-decyloxy group. Specific examples of the cyclic alkoxy group include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, a cyclononyloxy group, and a cyclodecyloxy group. Among these, the unsubstituted alkoxy group is preferably a linear alkoxy group.

[0044] Substituents in the alkoxy group include an aryl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a hydroxyl group, a carboxy group, a nitro group and a halogen atom (such as a fluorine atom, a bromine atom or an iodine atom). As the aryl group substituting the hydrogen atom in the alkoxy group, R 1 ~R 8 Examples of the unsubstituted aryl group include the same groups as the unsubstituted aryl group represented by the following formula: The alkoxycarbonyl group which replaces the hydrogen atom in the alkoxy group is, for example, 1 ~R 8 Examples of the alkoxycarbonyl group include the unsubstituted alkoxycarbonyl group represented by the following formula: The aryloxycarbonyl group which substitutes the hydrogen atom in the alkoxy group is, for example, 1 ~R 8 Examples of the aryloxycarbonyl group include the unsubstituted aryloxycarbonyl group represented by the following formula:

[0045] In general formula (P), R 1 ~R8 The aralkyl group represented by the following formula (I) includes a substituted or unsubstituted aralkyl group.

[0046] In general formula (P), R 1 ~R 8 The unsubstituted aralkyl group represented by the following formula is preferably an aralkyl group having 7 to 30 carbon atoms, more preferably an aralkyl group having 7 to 16 carbon atoms, and even more preferably an aralkyl group having 7 to 12 carbon atoms.

[0047] Examples of the unsubstituted aralkyl group having 7 to 30 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a 4-phenylbutyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, a phenylnonyl group, a naphthylmethyl group, a naphthylethyl group, an anthracylmethyl group, and a phenyl-cyclopentylmethyl group.

[0048] Substituents in the aralkyl group include an alkoxy group, an alkoxycarbonyl group, and a halogen atom (such as a fluorine atom, a bromine atom, an iodine atom, etc.). The alkoxy group which substitutes the hydrogen atom in the aralkyl group is, for example, 1 ~R 8 Examples of the alkoxy group include the same as the unsubstituted alkoxy group represented by the following formula: The alkoxycarbonyl group which substitutes a hydrogen atom in the aralkyl group is, for example, 1 ~R 8 Examples of the alkoxycarbonyl group include the unsubstituted alkoxycarbonyl group represented by the following formula:

[0049] In general formula (P), R 1 ~R 8 The aryl group represented by the formula (I) may be a substituted or unsubstituted aryl group.

[0050] In general formula (P), R 1 ~R 8The unsubstituted aryl group represented by the following formula is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 14 carbon atoms, and even more preferably an aryl group having 6 to 10 carbon atoms.

[0051] Examples of the aryl group having 6 to 30 carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, a 9-anthryl group, a 9-phenanthryl group, a 1-pyrenyl group, a 5-naphthacenyl group, a 1-indenyl group, a 2-azulenyl group, a 9-fluorenyl group, a biphenylenyl group, an indacenyl group, a fluoranthenyl group, an acenaphthylenyl group, an aceanthryllenyl group, a phenalenyl group, and a fluorenyl group. Examples of the anthryl group include anthryl, bianthracenyl, teranthracenyl, quaternary anthracenyl, anthraquinolyl, phenanthryl, triphenylenyl, pyrenyl, chrysenyl, naphthacenyl, pleiadenyl, picenyl, perylenyl, pentaphenyl, pentacenyl, tetraphenylenyl, hexaphenyl, hexacenyl, rubicenyl, and coronenyl groups. Of the above, the phenyl group is preferred.

[0052] Substituents in the aryl group include an alkyl group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a halogen atom (such as a fluorine atom, a bromine atom, an iodine atom, etc.). The alkyl group that substitutes the hydrogen atom in the aryl group is, for example, 1 ~R 8 Examples of the unsubstituted alkyl group include the same groups as the unsubstituted alkyl group represented by the following formula: The alkoxy group which substitutes the hydrogen atom in the aryl group is, in general formula (P), R 1 ~R 8 Examples of the alkoxy group include the same as the unsubstituted alkoxy group represented by the following formula: The alkoxycarbonyl group which substitutes the hydrogen atom in the aryl group is, in general formula (P), R 1 ~R 8 Examples of the alkoxycarbonyl group include the unsubstituted alkoxycarbonyl group represented by the following formula:

[0053] In general formula (P), R1 ~R 8 The alkoxycarbonyl group represented by the following formula (I) includes a substituted or unsubstituted alkoxycarbonyl group.

[0054] In general formula (P), R 1 ~R 8 The number of carbon atoms in the alkyl chain in the unsubstituted alkoxycarbonyl group represented by the following formula is preferably 1 or more and 20 or less, more preferably 1 or more and 15 or less, and even more preferably 1 or more and 10 or less.

[0055] Examples of the alkoxycarbonyl group having an alkyl chain carbon number of 1 to 20 include a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, an isopropoxycarbonyl group, an n-butoxycarbonyl group, a sec-butoxybutylcarbonyl group, a tert-butoxycarbonyl group, a pentaoxycarbonyl group, a hexaoxycarbonyl group, a heptoxycarbonyl group, an octaoxycarbonyl group, a nonaoxycarbonyl group, a decaoxycarbonyl group, a dodecaoxycarbonyl group, a tridecaoxycarbonyl group, a tetradecaoxycarbonyl group, a pentadecaoxycarbonyl group, a hexadecaoxycarbonyl group, a heptadecaoxycarbonyl group, an octadecaoxycarbonyl group, a nonadecaoxycarbonyl group, and an icosaoxycarbonyl group.

[0056] Substituents in the alkoxycarbonyl group include an aryl group, a hydroxy group and a halogen atom (such as a fluorine atom, a bromine atom, an iodine atom, etc.). The aryl group replacing the hydrogen atom in the alkoxycarbonyl group is, for example, 1 ~R 8 Examples of the unsubstituted aryl group include the same groups as the unsubstituted aryl group represented by the following formula:

[0057] In general formula (P), R 1 ~R 8 Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0058] Exemplary compounds of the electron transport material represented by general formula (P) are shown below, but the present embodiment is not limited thereto. Note that the following exemplary compound numbers are hereinafter expressed as exemplary compound (P-number).

[0059] [ka]

[0060] [ka]

[0061] The electron transporting material represented by general formula (P) preferably has an average primary particle size of 1 μm or less, more preferably from 0.03 μm to 1 μm, even more preferably from 0.03 μm to 0.8 μm, and particularly preferably from 0.05 μm to 0.7 μm. When the average primary particle size of the electron transporting material represented by formula (P) is 1 μm or less, the electron transporting material is less likely to localize in the undercoat layer and is more likely to exist with high dispersibility, resulting in better electron transporting properties and lower hole transporting properties.When the average primary particle size of the electron transporting material is 0.03 μm or more, the electron transporting material is less likely to aggregate and is more likely to exist with high dispersibility in the undercoat layer, resulting in better electron transporting properties and lower hole transporting properties.

[0062] The average primary particle size of the electron transporting material represented by general formula (P) is determined as follows. The undercoat layer is observed at a magnification of 100,000 times on a cross section of the laminate in the thickness direction of an electrophotographic photoreceptor using a SEM (scanning electron microscope), and the electron transporting material represented by general formula (P) is identified. Then, the particle diameters of any 10 particles present as primary particles among the electron transporting material represented by general formula (P) present in the obtained SEM image are determined. The arithmetic mean value of the obtained particle diameters is regarded as the average primary particle diameter of the electron transporting material.

[0063] The electron transporting material represented by formula (P) preferably has an aspect ratio of 1.0 or more and 5 or less, more preferably 1.1 or more and 3 or less, and even more preferably 1.2 or more and 2.5 or less. When the aspect ratio of the electron transporting material represented by formula (P) is 2.5 or less, the electron transporting material is likely to be present in the undercoat layer with high dispersibility, so that the electron transporting property is excellent and the hole transporting property is likely to be low.When the aspect ratio of the electron transporting material is 1.0 or more and 5 or less, the electron transporting material is likely to be present in the undercoat layer with high dispersibility, so that the electron transporting property is excellent and the charge retention is maintained.

[0064] The aspect ratio of the electron transporting material represented by general formula (P) means the ratio of the major axis length of the electron transporting material to the minor axis length of the electron transporting material (major axis length / minor axis length). The length of the electron transport material in the long axis direction refers to the longest linear distance when connecting one end to the other end of the electron transport material in the long axis direction, and the length of the electron transport material in the short axis direction refers to the longest linear distance when connecting one end to the other end of the electron transport material in the direction perpendicular to the long axis. The photosensitive layer (and protective layer, if necessary) is removed from the electrophotographic photoreceptor, and the undercoat layer is observed at 3,000 to 100,000 times magnification using a field emission scanning electron microscope (JEOL JSM-6700F) to identify the electron transport material represented by general formula (P). From the obtained micrograph, the major axis length and minor axis length are measured for any 10 points of the electron transport material, and the aspect ratio (major axis length / minor axis length) is determined for each. The arithmetic average value of each aspect ratio is taken as the aspect ratio of the electron transport material.

[0065] The method for adjusting the average primary particle size and aspect ratio of the electron transporting material represented by general formula (P) to fall within the above-mentioned ranges is not particularly limited, and examples thereof include a pulverization method using a ball mill, a bead mill, a mortar, a sand mill, a kneader, an attritor, or the like, and a method in which the material is dissolved in fluoroacetic acid, sulfuric acid, or the like and then brought into contact with water or a poor solvent to precipitate microcrystals.

[0066] The undercoat layer may further contain an electron transporting material other than the electron transporting material represented by general formula (P) within the range in which the effects of the present disclosure are achieved. The proportion of the electron transporting material represented by general formula (P) in the total amount of the electron transporting materials in the undercoat layer is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less.

[0067] The content of the electron transporting material represented by general formula (P) is preferably less than 70 mass %, more preferably from 45 mass % to less than 60 mass %, and even more preferably from 50 mass % to less than 60 mass %, based on the total solid content of the undercoat layer. In the past, the content of the electron transporting material represented by formula (P) in the undercoat layer was considered to be 70% by mass or more based on the total solid content of the undercoat layer from the viewpoint of ensuring both electron mobility and charge retention. In contrast, in the present embodiment, since the electron transporting material represented by formula (P) having excellent electron transportability and low hole transportability is contained, it is possible to achieve both electron mobility and charge retention even if the content of the electron transporting material is less than 70% by mass.

[0068] The content of the electron transporting material represented by the general formula (P) may be 60% by mass or more, or may be 60% by mass or more and 70% by mass or less, based on the total solid content of the undercoat layer. If the content of the electron transporting material is 70% by mass or less, the film quality becomes brittle, film formability decreases, and the occurrence of surface roughness of the undercoat layer is suppressed, resulting in better charge retention. On the other hand, if the content of the electron transporting material is 60% by mass or more, sufficient electron transport ability is provided, and better charge retention is provided.

[0069] , Examples of the binder resin include known polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, diallyl phthalate resins, polyamide resins, nylon resins, nylon polyamide resins, cellulose resins, gelatin, urethane resins, melamine resins, benzoguanamine resins (e.g., methylated benzoguanamine resins, etc.), 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, phenolic resins (e.g., resol-type phenolic resins, etc.), phenol-formaldehyde 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 (e.g., polyaniline, etc.), etc. The binder resin may be used alone or in combination of two or more. When two or more binder resins are used in combination, the mixing ratio is set as necessary.

[0070] In this specification, the term "binder resin" is a concept that encompasses resins obtained by reacting the above-mentioned resins with a curing agent, and resins obtained by reacting a curing agent.

[0071] In this specification, a resin obtained by reacting a urethane resin with a curing agent is referred to as a "curable urethane resin" for convenience.

[0072] The binder resin may be either a thermoplastic resin or a thermosetting resin, but is preferably a thermosetting resin, which is preferable because the binder resin does not cause dissolution or swelling of the film during the formation of the upper coating film.

[0073] Among these, the binder resin used in the undercoat layer is preferably a resin insoluble in the coating solvent of the upper layer, and is preferably a resin obtained by reacting at least one resin selected from the group consisting of diallyl phthalate resin, polyamide resin, nylon resin, urethane resin, melamine resin, benzoguanamine resin, and phenol resin with a curing agent, and more preferably contains at least one resin selected from the group consisting of urethane resin, melamine resin, and benzoguanamine resin. When the binder resin contains at least one resin selected from the above group, the hole blocking property is high and the charge retention is excellent.

[0074] The proportion of at least one resin selected from the group consisting of urethane resins, melamine resins, and benzoguanamine resins in the total amount of binder resins in the undercoat layer is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less.

[0075] The undercoat layer may further contain inorganic particles. As inorganic particles, for example, powder resistivity (volume resistivity) of 10 2 Ωcm or more 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.

[0076] The specific surface area of ​​inorganic particles by the BET method is, for example, 10 m 2 / g or more is preferable. The specific surface area is 10m 2 When the molecular weight is 1.0 or more, the decrease in electrostatic chargeability tends to be suppressed. 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).

[0077] The content of the inorganic particles is, for example, preferably from 0% by mass to 80% by mass, and more preferably from 0% by mass to 70% by mass, based on the total solid content of the undercoat layer.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] The silane coupling agent may be used in combination of two or more kinds. For example, The silane coupling agent may be used in combination with other silane coupling agents. Examples of the 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.

[0082] 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.

[0083] 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.

[0084] The dry method is, for example, a method in which a surface treatment agent is attached to the surface of inorganic particles by dropping a surface treatment agent 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 surface treatment agent is preferably performed at a temperature below the boiling point of the solvent. After dropping or spraying the surface treatment agent, 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.

[0085] The wet method is a method in which, for example, by stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, or the like, inorganic particles are dispersed in a solvent, a surface treatment agent is added, and the mixture is stirred or dispersed, and then the solvent is removed to attach the surface treatment agent 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 the addition of the surface treatment agent, 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.

[0086] The undercoat layer may further 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 transporting materials, 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0091] These additives may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0092] The volume resistivity of the undercoat layer is 1×10 10 Ωcm or more 1×10 12 It is preferable that the resistivity is Ωcm or less.

[0093] 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.

[0094] - Method for forming undercoat layer - The formation of the undercoat layer is not particularly limited, and a well-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.

[0095] 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.

[0096] 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. Since the electron transport material (particularly the electron transport material represented by the general formula (P)) is difficult to dissolve in an organic solvent, it is preferable to disperse it in the organic solvent. Examples of the dispersion method include known methods such as a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker. When metal oxide particles are blended in the undercoat layer, it is preferable to disperse the metal oxide particles in the organic solvent by the same dispersion method.

[0097] 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, air knife coating, and curtain coating.

[0098] The metal oxide content in the undercoat layer is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 0 mass% (i.e., no metal oxide) or 2 mass% or less, based on the total solid content of the undercoat layer. In general, metal oxides tend to have low resistance. Therefore, if the content of metal oxide in the undercoat layer is 5 mass% or less, the resistance of the undercoat layer is low, and the decrease in charging property is suppressed. In addition, it is preferable to reduce the content of metal oxide from the viewpoint of manufacturing aimed at reducing the environmental load.

[0099] From the viewpoint of achieving superior electrostatic retention, the thickness of the undercoat layer is preferably from 5 μm to 15 μm, more preferably from 7 μm to 14 μm, and even more preferably from 8 μm to 13 μm. The thickness of the undercoat layer may be 15 μm or more, or may be from 20 μm to 50 μm.

[0100] Conventional organic pigment-based electron transport materials have not only electron transport properties but also hole transport properties to a certain extent, and when used in an undercoat layer, holes are likely to be injected from the conductive substrate when the electrophotographic photoreceptor is charged, or into the charge generating layer above, which can lead to problems such as a decrease in chargeability and an increase in dark decay after charging, and a negative effect on image quality due to a deterioration in charge retention. This tendency is more pronounced the thicker the undercoat layer is. For this reason, it has been necessary to make the undercoat layer thin (for example, 5 μm or less) for practical use. However, if the undercoat layer is thin, when foreign matter from the outside (such as toner carriers and wear debris from plastic parts), particularly needle-like foreign matter such as carbon fiber, adheres to the surface of the photoreceptor during image formation, the foreign matter may penetrate the surface of the photoreceptor due to contact pressure with the intermediate transfer body, causing leakage current. In contrast, in this embodiment, the undercoat layer contains an electron transport material represented by general formula (P) that has excellent electron transport properties, low hole transport properties, and good charge retention properties, so the film thickness can be made thicker (for example, 5 μm or more) than that of a conventional undercoat layer that uses an organic pigment as the main component. Therefore, even if foreign matter penetrates from the surface of the electrophotographic photoreceptor to the undercoat layer, leakage current is unlikely to occur, and it is considered that the charge retention properties are excellent. When the thickness of the undercoat layer is at least 15 μm or less, sufficient electron transport properties are exhibited within the time of the electrophotographic photoreceptor process, and the bulk resistance of the undercoat layer can be maintained high, making it possible to maintain resistance to leakage due to foreign matter and charge retention over a long period of cycles.

[0101] [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 10 13 This means that the resistance is less than Ωcm.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] In the roughening treatment by anodization, a conductive substrate made of metal (e.g., aluminum) is used as the anode and anodized in an electrolyte solution to form an oxide film on the surface of the conductive substrate. Examples of electrolyte solutions include sulfuric acid solutions and oxalic acid solutions. 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 sealed 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] (Middle class) Although not shown, an intermediate layer may be further provided between the undercoat layer and the photosensitive 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.

[0110] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0111] The formation of the intermediate layer is not particularly limited, and a well-known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of a coating liquid for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it if 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.

[0112] The thickness of the intermediate layer is preferably set in the range of, for example, 0.1 μm to 3 μm. The intermediate layer may also be used as an undercoat layer.

[0113] (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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] In contrast, when an n-type semiconductor such as a fused aromatic pigment, a perylene pigment, or an azo pigment is used as the charge generating material, dark current is unlikely to occur, and image defects called black spots can be suppressed even when the material is made into a thin film. The n-type is determined by the polarity of the photocurrent that flows using the commonly used time-of-flight method, and those that easily pass electrons as carriers rather than holes are considered to be n-type.

[0119] 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 This means that the resistance is Ωcm or more. These binder resins may be used alone or in combination of two or more.

[0120] The mixing ratio of the charge generating material to the binder resin is in the range of 10:1 to 1:10 by mass. It is preferable that the temperature is within 100° C.

[0121] The charge generating layer may contain other well-known additives.

[0122] 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 a 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 a 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.

[0123] 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.

[0124] Examples of methods for dispersing particles (e.g., charge generating material) in the coating liquid for forming a charge generating layer include media dispersers such as ball mills, vibration ball mills, attritors, sand mills, and horizontal sand mills, and medialess dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. 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 liquid is dispersed by penetrating a fine flow path under high pressure. During this dispersion, it is effective to adjust the average particle size of the charge generating material in the coating liquid for forming the charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0125] Examples of a method 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, air knife coating, and curtain coating.

[0126] The thickness of the charge generating layer is set, for example, preferably in the range of 0.1 μm or more and 5.0 μm or less, and more preferably in the range of 0.2 μm or more and 2.0 μm or less.

[0127] (charge transport layer) The charge transport layer is, for example, a layer containing a charge transport material and a binder resin, and may be a layer containing a polymer charge transport material.

[0128] 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.

[0129] 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 preferable.

[0130] [ka]

[0131] In structural formula (a-1), Ar T1 , Ar T2 , and Ar T3 each independently represents a substituted or unsubstituted aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ), or -CH-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.

[0132] [ka]

[0133] 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 , RT13 , 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.

[0134] Among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), in particular, "-C6H4-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.

[0135] 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.

[0136] 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.

[0137] The charge transport layer may contain other well-known additives.

[0138] The formation of the charge transport layer is not particularly limited, and a known formation method can be used. For example, the charge transport layer can be formed by forming a coating film of a coating liquid for forming the charge transport layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0139] Examples of solvents for preparing the coating liquid for forming the charge transport layer include ordinary organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride, and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents may be used alone or in combination of two or more.

[0140] Examples of a coating method for coating the coating liquid for forming the charge transport layer on the charge generating layer include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating and curtain coating.

[0141] The thickness of the charge transport layer is set, for example, preferably in the range of 5 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

[0142] (protective layer) A protective layer is provided on the photosensitive layer as necessary for the purpose of, for example, preventing chemical changes in the photosensitive layer when the photosensitive layer is charged and further improving the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a layer composed of a cured film (crosslinked film) as the protective layer. Examples of such a layer include the following layers 1) and 2).

[0143] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton in the same molecule (i.e., a layer containing a polymer or crosslinked product of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition containing a non-reactive charge transport material and a reactive group-containing non-charge transport material having no charge transport skeleton and having a reactive group (i.e., a non-reactive charge A layer comprising a charge transport material and a polymer or crosslinked product of the reactive group-containing non-charge transport material.

[0144] The reactive group of the reactive group-containing charge transport material may be a chain polymerizable group, an epoxy group, -OH, -OR (wherein R represents an alkyl group), -NH2, -SH, -COOH, or -SiR. Q1 3-Qn (OR Q2 ) Qn [However, R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group; R Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group; Qn represents an integer of 1 to 3.

[0145] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, and is, for example, a functional group having a group containing at least a carbon double bond.Specific examples include a group containing at least one selected from a vinyl group, a vinyl ether group, a vinyl thioether group, a styryl group (vinyl phenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof.Among them, the chain polymerizable group is preferably a group containing at least one selected from a vinyl group, a styryl group (vinyl phenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof, because of its excellent reactivity.

[0146] The charge transporting skeleton of the reactive group-containing charge transporting material is not particularly limited as long as it is a known structure in electrophotographic photoreceptors, and examples thereof include a skeleton derived from a nitrogen-containing hole transporting compound such as a triarylamine compound, a benzidine compound, a hydrazone compound, etc., and a structure conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferred.

[0147] The reactive group-containing charge transport material having a reactive group and a charge transporting skeleton, the non-reactive charge transport material, and the reactive group-containing non-charge transport material may be selected from well-known materials.

[0148] The protective layer may contain other well-known additives.

[0149] The formation of the protective layer is not particularly limited, and a well-known formation method can be used. For example, the protective layer can be formed by forming a coating film of a coating liquid for forming the protective layer in which the above components are added to a solvent, drying the coating film, and, if necessary, subjecting it to a curing treatment such as heating.

[0150] Examples of solvents for preparing a coating solution for forming a protective layer include aromatic solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, ether solvents such as tetrahydrofuran and dioxane, cellosolve solvents such as ethylene glycol monomethyl ether, and alcohol solvents such as isopropyl alcohol and butanol. These solvents may be used alone or in combination of two or more. The protective layer-forming coating liquid may be a solvent-free coating liquid.

[0151] Examples of a method for applying the protective layer-forming coating liquid onto a photosensitive layer (e.g., a charge transport layer) include conventional methods such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating.

[0152] The thickness of the protective layer is set, for example, preferably in the range of 1 μm or more and 20 μm or less, and more preferably in the range of 2 μm or more and 10 μm or less.

[0153] [Single-layer photosensitive layer] The single-layer type photosensitive layer (charge generating / transporting layer) is, for example, a layer containing a charge generating material, a charge transporting material, and, if necessary, a binder resin and other well-known additives. The materials are similar to those described for the charge generating layer and the charge transport layer. The content of the charge generating material in the single-layer photosensitive layer is preferably 0.1% by mass to 10% by mass, more preferably 0.8% by mass to 5% by mass, based on the total solid content. The content of the charge transport material in the single-layer photosensitive layer is preferably 5% by mass to 50% by mass, based on the total solid content. The method for forming the single-layer type photosensitive layer is the same as the method for forming the charge generating layer and the charge transport layer. The thickness of the single-layer photosensitive layer is, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 40 μm or less.

[0154] [Image forming devices, process cartridges] The image forming apparatus according to the present embodiment includes an electrophotographic photoreceptor, a charging device for charging the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, a developing device for developing 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 for transferring the toner image to the surface of a recording medium. The electrophotographic photoreceptor according to the present embodiment is applied as the electrophotographic photoreceptor.

[0155] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus provided with 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 performs primary transfer of a toner image formed on the surface of an electrophotographic photosensitive member onto the surface of an intermediate transfer member and secondary transfer of the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus provided with a cleaning device that cleans the surface of an electrophotographic photosensitive member before charging after the transfer of a toner image; an apparatus provided with 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 provided with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

[0156] 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.

[0157] 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).

[0158] In the image forming apparatus according to the present embodiment, for example, a portion including an electrophotographic photosensitive member may be a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge including an electrophotographic photosensitive member according to the present embodiment is preferably used. In addition to the electrophotographic photosensitive member, the process cartridge may include 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.

[0159] 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. Note that only the main parts shown in the drawings will be described, and descriptions of the rest will be omitted.

[0160] FIG. 2 is a schematic diagram showing an example of the image forming apparatus according to the present embodiment. As shown in Fig. 2, the image forming apparatus 100 according to this embodiment includes a process cartridge 300 having an electrophotographic photosensitive member 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (primary transfer device), and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photosensitive member 7 from the opening of the process cartridge 300, and the transfer device 40 is exposed to the electrophotographic photosensitive member 7 via the intermediate transfer member 50. The intermediate transfer body 50 is disposed at a position facing the electrophotographic photosensitive body 7, and a portion of the intermediate transfer body 50 is disposed in contact with the electrophotographic photosensitive body 7. Although not shown, the intermediate transfer body 50 also has a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 onto a recording medium (e.g., paper). The intermediate transfer body 50, transfer device 40 (primary transfer device), and secondary transfer device (not shown) correspond to an example of a transfer device.

[0161] 2 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.

[0162] FIG. 2 shows an example of an image forming apparatus equipped with a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists in cleaning, which may be arranged as needed.

[0163] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0164] -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.

[0165] -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.

[0166] -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.

[0167] 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. Well-known developers are used.

[0168] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131 . In addition to the cleaning blade system, a fur brush cleaning system or a simultaneous development and cleaning system may also be used.

[0169] -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.

[0170] -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.

[0171] FIG. 3 is a schematic diagram showing another example of the image forming apparatus according to the present embodiment. 3 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

[0172] The electrophotographic photoreceptor of the present disclosure will be described in more detail below with reference to examples. The materials, amounts, ratios, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present disclosure. Therefore, the scope of the electrophotographic photoreceptor of the present disclosure should not be interpreted as being limited by the specific examples shown below.

[0173] - Preparation of undercoat layer - (Preparation of Undercoat Layer 1) A solution of 15 parts by mass of a curable urethane resin (thermosetting resin, blocked isocyanate Coronate BI-301, manufactured by Tosoh Corporation, solid content 75%) and 6.3 parts by mass of a butyral resin (S-LEC BL-S, manufactured by Sekisui Chemical Co., Ltd.) dissolved in 170 parts by mass of methyl ethyl ketone was mixed with 32 parts by mass of an electron transport material (P-1), and the mixture was dispersed in a sand mill using 1 mmφ glass beads for 300 minutes to obtain a dispersion liquid. After filtering off the glass beads, 0.005 parts by mass of bismuth carboxylate (K-KAT XK-640) manufactured by King Industries was added as a catalyst to the obtained dispersion to obtain a coating solution for forming an undercoat layer. This coating solution was dip-coated onto an aluminum substrate by a dip coating method, and dried and cured at 160°C for 60 minutes to obtain a 10 μm-thick undercoat layer 1 containing a curable urethane resin and an electron transporting material represented by general formula (P).

[0174] (Preparation of Undercoat Layer 2) A solution of 15 parts by mass of resol type phenolic resin (thermosetting resin, PL-2215, manufactured by Gun-ei Chemical Industry Co., Ltd.) and 5.0 parts by mass of butyral resin (S-LEC BL-1, manufactured by Sekisui Chemical Co., Ltd.) dissolved in 120 parts by mass of methyl ethyl ketone and 60 parts by mass of isopropanol was mixed with 30 parts by mass of electron transport material (P-1), and the mixture was dispersed in a sand mill using 1 mmφ glass beads for 300 minutes to obtain a dispersion liquid. After filtering off the glass beads, 0.003 parts by mass of blocked sulfonic acid (Nacure 2500) manufactured by King Industries was added as a catalyst to the obtained dispersion to obtain a coating solution for forming an undercoat layer. This coating solution was dip-coated onto an aluminum substrate by a dip coating method, and dried and cured at 150°C for 60 minutes to obtain an undercoat layer 2 having a thickness of 10 μm, which contains a phenolic resin and an electron transporting material represented by general formula (P).

[0175] (Preparation of Undercoat Layer 3) 25 parts by mass of methylated benzoguanamine resin (thermosetting resin, BL-60, Sanwa Chemical Co., Ltd., solid content 60%) and 5 parts by mass of methylated melamine (MW-390, Sanwa Chemical Co., Ltd.) were dissolved in 120 parts by mass of methyl ethyl ketone and 60 parts by mass of isopropanol, and 30 parts by mass of electron transport material (P-1) were mixed and dispersed for 300 minutes in a sand mill using glass beads of 1 mmφ to obtain a dispersion. After filtering off the glass beads, 0.003 parts by mass of blocked sulfonic acid (Nacure 5225) manufactured by King Industries Co., Ltd. was added as a catalyst to the obtained dispersion to obtain a coating liquid for forming an undercoat layer. This coating liquid was dip-coated on an aluminum substrate by a dip coating method, and dried and cured at 150 ° C. for 60 minutes to obtain an undercoat layer 3 having a thickness of 10 μm, which contains a guanamine resin and an electron transport material represented by the general formula (P).

[0176] (Preparation of Undercoat Layer 4) 10 parts by mass of electron transport material (P-1) with a primary particle size of 1 μm, 10 parts by mass of sodium chloride, and 150 parts by mass of 0.3 mm zirconia beads were placed in a zirconia container and ground at 500 rpm for 1 hour using a planetary mill manufactured by Fritsch. The zirconia beads were filtered through a 50 μm mesh made of polypropylene and washed with methanol. The obtained crystals were repeatedly washed with distilled water and then dried in a freeze dryer for 48 hours to obtain 7.5 parts by mass of electron transport material (P-1). This process was repeated four times to obtain a total of 30 parts by mass of ground electron transport material (P-1). The average primary particle size of 10 crystals randomly selected from the SEM image was 0.08 μm. 30 parts by mass of the obtained electron transport material (P-1), 15 parts by mass of diallyl phthalate prepolymer (Daiso DAP (registered trademark) A, manufactured by Osaka Gas), 5.0 parts by mass of trimethylolpropane trimethacrylate, and 170 ml of methyl ethyl ketone were mixed, and dispersed for 180 minutes using glass beads of 1 mmφ in a paint shaker to obtain a dispersion. 1.0 part by mass of Perbutyl (registered trademark) Z (manufactured by NOF Corporation), a polymerization initiator, was added to the obtained dispersion to obtain a coating liquid for forming an undercoat layer. This coating liquid was dip-coated on an aluminum substrate by a dip coating method, and dried and cured at 160 ° C. for 60 minutes under a nitrogen atmosphere to obtain a 10 μm-thick undercoat layer 4 containing a diallyl phthalate resin (thermosetting resin) and an electron transport material represented by the general formula (P).

[0177] (Preparation of Undercoat Layer 5) 20 g of nylon polyamide (thermoplastic resin, CM8000, manufactured by Toray), a copolymer of nylon and polyamide, was dissolved in 200 ml of methanol, to which was added 30 g of the electron transporting material (P-1) pulverized in the same manner as for the undercoat layer 4, and the mixture was dispersed for 180 minutes using a paint shaker with 1 mmφ glass beads to obtain a dispersion. This coating liquid was dip-coated onto an aluminum substrate by a dip coating method, and dried at 150°C for 45 minutes in a nitrogen atmosphere to obtain a 10 μm-thick undercoat layer 5 containing nylon polyamide and the electron transporting material represented by general formula (P).

[0178] (Preparation of Undercoat Layer 6) An undercoat layer 6 was obtained in the same manner as in the undercoat layer 1, except that the electron transporting material (P-1) in the undercoat layer 1 was changed to the electron transporting material (P-3).

[0179] (Preparation of Undercoat Layer 7) Subcoat layer 7 was prepared in the same manner as for subcoat layer 1, except that the electron transporting material (P-1) in the subcoat layer 1 was changed to the electron transporting material (P-8).

[0180] (Preparation of Undercoat Layer 8) Subcoat layer 8 was obtained in the same manner as for subcoat layer 1, except that the electron transporting material (P-1) in the above-mentioned subcoat layer 1 was replaced with the electron transporting material (P-1) ground in the same manner as for subcoat layer 4.

[0181] (Preparation of Undercoat Layer 9) Subcoat layer 9 was obtained in the same manner as for subcoat layer 3, except that the methylated benzoguanamine resin in the above-mentioned subcoat layer 3 was changed to a melamine resin (thermosetting resin, product name MX-750, manufactured by Sanwa Chemical Co., Ltd.).

[0182] (Preparation of Undercoat Layers 10 to 14) Subcoat layers 10 to 14 were prepared in the same manner as for subcoat layer 1, except that the electron transporting material (P-1) in the above-mentioned subcoat layer 1 was changed to the electron transporting material shown in Table 1, thereby obtaining subcoat layers 10 to 14, respectively.

[0183] (Preparation of Undercoat Layers 15 to 16) Subcoat layers 15 to 16 were prepared in the same manner as subcoat layer 1, except that the thickness of the subcoat layer was changed to the thickness shown in Table 1, to obtain subcoat layers 15 to 16, respectively.

[0184] (Preparation of Undercoat Layer 17) Subcoat layer 17 was obtained in the same manner as subcoat layer 1, except that in the preparation of subcoat layer 1, the electron transporting material (P-1) was changed to the electron transporting material (P-1) having an average primary particle diameter of 0.01 μm obtained by increasing the grinding time to 4 hours in the preparation of subcoat layer 4.

[0185] (Preparation of Undercoat Layer 18) An undercoat layer 18 was obtained in the same manner as in the undercoat layer 1, except that the electron transporting material (P-1) in the undercoat layer 1 was changed to an electron transporting material (P-1) having a particle size of 1.2 μm obtained by recrystallization with sulfuric acid.

[0186] (Preparation of Undercoat Layer 19) A solution of 15 parts by mass of a curable urethane resin (thermosetting resin, blocked isocyanate Coronate BI-301, manufactured by Tosoh Corporation, solid content 75%) and 6.3 parts by mass of a butyral resin (S-LEC BL-S, manufactured by Sekisui Chemical Co., Ltd.) in 170 parts by mass of methyl ethyl ketone was added to the solution, and 32 parts by mass of an electron transport material (P-1) and zinc oxide fine particles (manufactured by Teika Co., Ltd., average particle diameter: 75 nm, specific surface area value: 14 m 2 The mixture was dispersed in a sand mill using 1 mmφ glass beads for 300 minutes to obtain a dispersion. After filtering off the glass beads, 0.005 parts by mass of bismuth carboxylate (K-KAT XK-640) manufactured by King Industries was added as a catalyst to the obtained dispersion to obtain a coating solution for forming an undercoat layer. This coating solution was dip-coated onto an aluminum substrate by a dip coating method, and dried and cured at 160°C for 60 minutes to obtain a 10 μm-thick undercoat layer 19 containing a curable urethane resin and an electron transporting material represented by general formula (P).

[0187] (Preparation of Undercoat Layer 20) An undercoat layer 20 was obtained in the same manner as in the undercoat layer 1, except that the content of the electron transporting material (P-1) in the total solid content of the undercoat layer was set to the amount shown in Table 1.

[0188] (Preparation of Comparative Sublayer 1) A comparative subcoat layer 1 was prepared in the same manner as the subcoat layer 1, except that the electron transporting material (P-1) in the subcoat layer 1 was changed to the following imide compound (A).

[0189] (Preparation of Comparative Sublayer 2) A comparative subcoat layer 2 was prepared in the same manner as the subcoat layer 1, except that the electron transporting material (P-1) in the subcoat layer 1 was changed to the following imide compound (B).

[0190] (Preparation of Comparative Sublayer 3) Comparative subcoat layer 3 was prepared in the same manner as subcoat layer 1, except that the electron transporting material (P-1) in subcoat layer 1 was changed to the following imide compound (C).

[0191] (Preparation of Comparative Sublayer 4) Comparative undercoat layer 4 was prepared in the same manner as undercoat layer 1, except that in undercoat layer 1, the electron transport material (P-1) was changed to the imide compound (C) below and the amount of imide compound (C) below was as shown in Table 1.

[0192] [ka]

[0193] <Examples 1 to 20 and Comparative Examples 1 to 4> (Formation of Charge Generation Layer) A mixture of 15 parts by mass of hydroxygallium phthalocyanine, which has diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.3°, 16.0°, 24.9°, and 28.0° in the X-ray diffraction spectrum using Cukα characteristic X-rays, 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts by mass of n-butyl acetate was stirred and dispersed in a sand mill using glass beads with a diameter of 1 mm for 4 hours. 175 parts by mass of n-butyl acetate and 180 parts by mass of methyl ethyl ketone were added to the obtained dispersion and stirred to obtain a coating liquid for forming a charge generation layer. This coating liquid for forming a charge generation layer was dip-coated on the outer peripheral surface of the undercoat layer of the type shown in Table 1, and dried at 150° C. for 15 minutes to form a charge generation layer with a thickness of 0.2 μm.

[0194] (Formation of charge transport layer) 38 parts by mass of the following charge transport material (HT-1), 10 parts by mass of the following charge transport material (HT-2), 52 parts by mass of the following polycarbonate resin (A) (viscosity average molecular weight: 46,000), and 0.3 parts by mass of a fluorine-containing graft polymer (manufactured by Toa Gosei: GF-500) as a dispersing aid were added and dissolved in 800 parts by mass of tetrahydrofuran, and 8 parts by mass of tetrafluoroethylene resin (manufactured by Daikin Industries: Lubron L5, average particle size 300 nm) were added, and the mixture was dispersed for 2 hours at 5500 rpm using a homogenizer (manufactured by IKA: Ultra Turrax) to obtain a coating liquid for forming a charge transport layer. This coating liquid was applied onto the charge generation layer, and dried at 140° C. for 40 minutes to form a charge transport layer with a film thickness of 30 μm. This was used as an electrophotographic photoreceptor.

[0195] [ka]

[0196] [ka]

[0197] <Evaluation> The electrophotographic photoreceptor of each of the Examples and Comparative Examples was mounted on a modified image forming apparatus DocuCentre C5570 manufactured by FUJIFILM Business Innovation Co., Ltd., and the following evaluations were carried out.

[0198] -Evaluation of charge retention- In an environment of 10°C and 15% RH, the electrophotographic photoreceptor was charged with an applied voltage of -710V, and the initial charge potential V1 (before image output) on the outer peripheral surface of the electrophotographic photoreceptor before image output and the charge potential V2 on the outer peripheral surface of the electrophotographic photoreceptor after printing 30,000 sheets of 50% halftone images were measured. The potential difference V1-V2 was then calculated and evaluated according to the following criteria. Incidentally, A to C are acceptable. A: Less than 20V. B: 20V or more and less than 25V. C: 25V or more and less than 30V. D: Between 30V and 35V, a problematic level. E: 35V or higher, a problematic level.

[0199] -Evaluation of foreign object penetration- When carbon fibers penetrate the photosensitive layer and the undercoat layer to reach the conductive substrate, a current flows and a dot-like image defect occurs. Using this phenomenon, the suppression of foreign matter penetration was evaluated. At this time, the charging potential was usually -700V. Carbon fibers (average diameter 7 μm, average length 30 μm) were mixed into the developer in an amount to give a concentration of 0.2 mass %, and 20,000 images with a concentration of 20% were continuously output on A4 paper. Next, 10 images with a concentration of 20% were output on A4 paper. The presence or absence of dot-like image defects in the 10th image was visually observed, and the degree of image defects was classified into the following A to D. The results are shown in Table 1.

[0200] A: There are no point-like image defects. B: Less than 5 point-like image defects. C: 5 to less than 10 point-like image defects. D: 10 or more point-like image defects.

[0201] [Table 1]

[0202] As shown in Table 1, it was found that the electrophotographic photoreceptors of Examples were superior in charge retention to the electrophotographic photoreceptors of Comparative Examples.

[0203] The present embodiment includes the following aspects. (((1))) A conductive substrate; an undercoat layer provided on the conductive substrate and containing a binder resin and an electron transport material represented by the following general formula (P); a photosensitive layer provided on the undercoat layer; An electrophotographic photoreceptor comprising: [ka] In the above general formula (P), R 1 , R 2, R 3 , R 4 , R 5 , R 6 , R 7 and R 8 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. (((2))) In the general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R each independently represents a hydrogen atom or a halogen atom. (((3))) In the general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 represents a hydrogen atom. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the electron transporting material has an average primary particle size of 1 μm or less. (((5))) The electrophotographic photoreceptor according to (((4))), wherein the electron transporting material has an average primary particle size of 0.03 μm or more and 1 μm or less. (((6))) The electrophotographic photoreceptor according to any one of (((1))) to (((5))), wherein the content of the electron transporting material is less than 70 mass % based on the total solid content of the undercoat layer. (((7))) The electrophotographic photoreceptor according to any one of (((1))) to (((6))), wherein the undercoat layer has a thickness of 5 μm or more and 15 μm or less. (((8))) The electrophotographic photoreceptor according to any one of (((1))) to (((7))), wherein the binder resin is a thermosetting resin. (((9))) The electrophotographic photoreceptor according to (((8))), wherein the thermosetting resin contains at least one resin selected from the group consisting of a urethane resin, a melamine resin, and a benzoguanamine resin. (((10))) The electrophotographic photoreceptor according to (((1))), wherein the metal oxide content in the undercoat layer is 5% by mass or less based on the total solid content of the undercoat layer. (((11))) The electrophotographic photoreceptor according to any one of (((1))) to (((10))) is provided, A process cartridge that is detachably attached to an image forming apparatus. (((12))) An electrophotographic photoreceptor according to any one of (((1))) to (((10))), 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; The electrostatic latent image formed on the surface of the electrophotographic photoreceptor is developed with a developer containing a toner. a developing device for forming a toner image by using the toner; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising:

[0204] The advantages of the above aspect are as follows. According to the invention related to (((1))), (((2))) or (((3))), an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with a case in which an undercoat layer containing a binder resin and a conventional electron transport material (for example, the above-mentioned electron transport material (A), (B) or (C) etc.) is employed. According to the invention related to (((4))), an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with a case in which the average primary particle diameter of the electron transporting material exceeds 1 μm. According to the invention related to (((5))), an electrophotographic photoreceptor is provided which is excellent in film-forming properties and charge-retaining properties, as compared with cases in which the average primary particle diameter of the electron transporting material is less than 0.03 μm or exceeds 1 μm. According to the invention related to (((6))), an electrophotographic photoreceptor is provided which is excellent in film-forming properties and charge-retaining properties, as compared with a case in which the content of the electron transporting material is 70 mass % or more relative to the total solid content of the undercoat layer. According to the invention related to (((7))), an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with cases in which the thickness of the undercoat layer is less than 5 μm or exceeds 15 μm. According to the invention related to (((8))), there is provided an electrophotographic photoreceptor which is excellent in charge retention properties compared to when the binder resin is a thermoplastic resin. According to the invention related to (((9))), an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with the case where the thermosetting resin is nylon polyamide. According to the invention related to (((10))), an electrophotographic photoreceptor having excellent charge retention properties is provided, as compared with a case in which the metal oxide content in the undercoat layer exceeds 5 mass % relative to the total solid content of the undercoat layer. According to the invention related to (((11))) or (((12))), there is provided a process cartridge or image forming apparatus equipped with an electrophotographic photoreceptor which is excellent in charge retention property, as compared with a process cartridge or image forming apparatus equipped with an electrophotographic photoreceptor employing an undercoat layer containing a binder resin and a conventional electron transport material (for example, the above-mentioned electron transport material (A), (B) or (C)). [Explanation of symbols]

[0205] 1 undercoat layer, 2 charge generation layer, 3 charge transport layer, 4 conductive substrate, 5 photosensitive layer, 7A electrophotographic photosensitive member, 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. A conductive substrate; an undercoat layer provided on the conductive substrate, the undercoat layer containing a binder resin and an electron transport material represented by the following general formula (P); a photosensitive layer provided on the undercoat layer; An electrophotographic photoreceptor comprising: 【Chemistry 1】 In the above general formula (P), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ and R ８ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.

2. In the general formula (P), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ and R each independently represent a hydrogen atom or a halogen atom.

3. In the general formula (P), R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ and R ８ The electrophotographic photoreceptor according to claim 1 , wherein represents a hydrogen atom.

4. 2. The electrophotographic photoreceptor according to claim 1, wherein the electron transporting material has an average primary particle size of 1 [mu]m or less.

5. 5. The electrophotographic photoreceptor according to claim 4, wherein the electron transporting material has an average primary particle size of 0.03 [mu]m or more and 1 [mu]m or less.

6. The electrophotographic photoreceptor according to claim 1 , wherein the content of the electron transporting material is less than 70% by mass based on the total solid content of the undercoat layer.

7. 2. The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer has a thickness of 5 [mu]m or more and 15 [mu]m or less.

8. 2. The electrophotographic photoreceptor according to claim 1, wherein the binder resin is a thermosetting resin.

9. The electrophotographic photoreceptor according to claim 8 , wherein the thermosetting resin contains at least one resin selected from the group consisting of a urethane resin, a melamine resin, and a benzoguanamine resin.

10. The electrophotographic photoreceptor according to claim 1 , wherein the content of the metal oxide in the undercoat layer is 5% by mass or less based on the total solid content of the undercoat layer.

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

12. An electrophotographic photoreceptor according to any one of claims 1 to 10, 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; The electrostatic latent image formed on the surface of the electrophotographic photoreceptor is developed with a developer containing a toner. a developing device for forming a toner image by using the toner; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising:

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