Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

The invention provides an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus. The electrophotographic photoreceptor includes: a conductive substrate; the lower coating layer is arranged on the conductive substrate; and a photosensitive layer provided on the undercoat layer, the undercoat layer containing a binder resin and an electron-transporting material having a crystal density of 1.62 g / cm3 or more, and the full width at half maximum (FWHM) of the maximum intensity peak in an X-ray diffraction spectrum measured from the thickness direction being 5.0 DEG or less.

Description

Technical Field

[0001] The present invention relates to an electronic photographic photosensitive body, a processing box and an image forming device. Background Art

[0002] In an image forming apparatus using an electrophotographic method, the surface of an electrophotographic photoreceptor is usually charged to a predetermined polarity and potential by a charging member, and the charged surface of the electrophotographic photoreceptor is selectively destaticized by image exposure, thereby forming an electrostatic latent image. Then, a toner is attached to the electrostatic latent image by a developing member, and the latent image is developed into a toner image. Then, the toner image is transferred to a transfer medium by a transfer member, and the image formation is discharged. In recent years, electrophotographic photoreceptors have the advantages of achieving high speed and high printing quality, and are therefore widely used in the fields of copiers and laser printers.

[0003] Currently, in many cases, an electrophotographic photoreceptor is prepared by forming an undercoat layer on a conductive support layer such as an aluminum substrate, and then forming a photosensitive layer on the undercoat layer.

[0004] The undercoat layer is required to conceal defects of the substrate, suppress charge injection into the photosensitive layer when voltage is applied to the electrophotographic photoreceptor, and control 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 transport properties.

[0005] Patent Document 1 discloses an electrophotographic photoreceptor, wherein an undercoat layer and a photosensitive layer are sequentially provided on a conductive support, wherein the undercoat layer contains dichlorotin phthalocyanine and a binder resin.

[0006] Patent Document 2 discloses an electrophotographic photoreceptor in which an undercoat layer, a charge generating layer, and a charge transporting layer are sequentially stacked on a conductive layer, wherein the undercoat layer contains a binder, an organic charge generating material, and a specific diphenylquinone derivative.

[0007] Patent document 3 discloses an electronic photographic photoreceptor, which is composed of a photosensitive layer containing a charge generating agent provided on a conductive support, wherein the charge generating agent is obtained by sublimation purification of a specific benzimidazole perylene pigment and dry pulverization, and in an X-ray diffraction measurement of the powder in a non-oriented state with CuKα rays as the light source, the photoreceptor has a crystal form with Bragg angles (2θ±0.2°) of 2θ=6.2°, 12.3°, and 26.8°, and a half width S(26.8°) of 26.8° of S(26.8°)≥0.5.

[0008] Patent Document 4 discloses an electrophotographic photoreceptor having an undercoat layer and a photosensitive layer laminated in this order on a conductive support, wherein the undercoat layer contains an organic pigment and a rosin compound in a polyamide resin.

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 11-202520

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 03-216662

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 05-249719

[0012] Patent Document 4: Japanese Patent Application Laid-Open No. 11-184129 Summary of the invention

[0013] In conventional electrophotographic photoreceptors including a conductive substrate, an undercoat layer, and a photosensitive layer, there is a tendency for charge retention to decrease when electron transport properties are improved.

[0014] Therefore, the present invention aims to provide a method for preparing a coating layer containing a binder resin and an electron transport material, wherein the full width at half maximum (FWHM) of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction of the undercoat layer containing a binder resin and an electron transport material exceeds 5.0° or the crystal density of the electron transport material is less than 1.62 g / cm 3 Compared with the case of , an electrophotographic photoreceptor with excellent electron transport properties.

[0015] Specific means for solving the above-mentioned problems include the following aspects.

[0016] <1> An electrophotographic photoreceptor comprising:

[0017] Conductive substrate;

[0018] A lower coating layer is disposed on the conductive substrate; and

[0019] A photosensitive layer is disposed on the lower coating layer,

[0020] The lower coating layer contains a bonding resin and a crystal density of 1.62 g / cm 3 The electron transporting material has a full width at half maximum (FWHM) of a maximum intensity peak in an X-ray diffraction spectrum measured in the thickness direction of 5.0° or less.

[0021] <2> The electrophotographic photoreceptor according to <1>, wherein

[0022] The electron transport material has an aspect ratio of 1.0 to 2.5.

[0023] <3> The electrophotographic photoreceptor according to <2>, wherein

[0024] The electron transport material has an aspect ratio of 1.5 to 2.3.

[0025] <4> The electrophotographic photoreceptor according to <1>, wherein

[0026] When the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction of the undercoat layer is defined as I1,

[0027] When the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured when the undercoat layer is in a powder state with a volume average particle size of 5 μm or less is defined as I2, the maximum value Nmax in the orientation index N represented by the following formula (1) is greater than or equal to 1.0 and less than or equal to 5.5.

[0028] [Formula 1]

[0029]

[0030] <5> The electrophotographic photoreceptor according to <1>, wherein

[0031] The LUMO energy level of the undercoat layer is 3.8 eV or more and 4.2 eV or less.

[0032] <6> The electrophotographic photoreceptor according to <1>, wherein

[0033] The electron transport material includes at least one of an electron transport material represented by the following general formula (P) and an electron transport material represented by the following general formula (Q).

[0034] [Chemical formula 1]

[0035]

[0036] 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.

[0037] In the above general formula (Q), R 51 and R 52 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.

[0038] <7> The electrophotographic photoreceptor according to <6>, wherein

[0039] In the 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 or a halogen atom.

[0040] <8> The electrophotographic photoreceptor according to <6>, wherein

[0041] In the general formula (Q), R 51 and R 52 Represents a hydrogen atom.

[0042] <9> The electrophotographic photoreceptor according to <1>, wherein

[0043] The electron transport material has an average primary particle size of 500 nm or less.

[0044] <10> The electrophotographic photoreceptor according to <1>, wherein

[0045] The content of the electron transport material is 60 mass % or more and 75 mass % or less relative to the total binder resin component of the undercoat layer.

[0046] <11> The electrophotographic photoreceptor according to <1>, wherein

[0047] The undercoat layer has a thickness of 5 μm or more and 15 μm or less.

[0048] <12> The electrophotographic photoreceptor according to <1>, wherein

[0049] The ratio of the metal oxide in the undercoat layer is 5 mass % or less relative to the total solid content of the undercoat layer.

[0050] <13> A process cartridge comprising the electrophotographic photoreceptor according to any one of <1> to <12>, wherein:

[0051] The process cartridge is attachable to and detachable from the image forming apparatus.

[0052] <14> An image forming apparatus comprising:

[0053] The electrophotographic photoreceptor according to any one of <1> to <12>;

[0054] A charging device for charging the surface of the electrophotographic photoreceptor;

[0055] An electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

[0056] a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and

[0057] The transfer device transfers the toner image to the surface of a recording medium.

[0058] Effects of the Invention

[0059] According to the invention of <1>, there is provided a case where the full width at half maximum (FWHM) of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction of the undercoat layer containing a binder resin and an electron transporting material exceeds 5.0° or the crystal density of the electron transporting material is less than 1.62 g / cm 3 Compared with the case of , an electrophotographic photoreceptor with excellent electron transport properties.

[0060] According to the invention as set forth in <2>, there is provided an electrophotographic photoreceptor having an excellent electron transport property compared to a case where the aspect ratio of the electron transport material exceeds 2.5.

[0061] According to the invention as set forth in <3>, there is provided an electrophotographic photoreceptor having an excellent electron transport property compared with a case where the aspect ratio of the electron transport material is less than 1.5 or exceeds 2.3.

[0062] According to the invention involved in <4>, there is provided an electronic photographic photosensitive body having excellent electron transport properties, compared with a case where the value of the maximum value Nmax in the orientation index N represented by the formula (1) is less than 1.0 or greater than 5.5, when the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured for the undercoat layer in the thickness direction is set to I1 and the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured with the undercoat layer in a powder state with a volume average particle size of less than 5 μm is set to I2.

[0063] According to the invention as set forth in <5>, there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the LUMO energy level of the undercoat layer is less than 3.8 eV or exceeds 4.2 eV.

[0064] According to the invention according to <6>, <7> or <8>, there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the electron transport material contains the following compound (D) or compound (E).

[0065] [Chemical formula 2]

[0066]

[0067] According to the invention as set forth in <9>, there is provided an electrophotographic photoreceptor having an excellent electron transport property compared with a case where the average primary particle size of the electron transport material exceeds 500 nm.

[0068] According to the invention <10>, there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the content of the electron transport material is less than 60 mass % or more than 75 mass % based on the total binder resin component of the undercoat layer.

[0069] According to the invention as set forth in <11>, there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the thickness of the undercoat layer is less than 5 μm or exceeds 15 μm.

[0070] According to the invention according to <12>, there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the ratio of the metal oxide in the undercoat layer exceeds 5% by mass based on the total solid content of the undercoat layer.

[0071] According to the invention of <13> or <14>, there is provided an electrophotographic photoreceptor having an undercoat layer containing a binder resin and an electron transporting material, wherein the full width at half maximum (FWHM) of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction exceeds 5.0°, or an electrophotographic photoreceptor having a crystal density of the electron transporting material of less than 1.62 g / cm 3 A process cartridge or an image forming apparatus including an electrophotographic photoreceptor having excellent electron transport properties is provided compared to a process cartridge or an image forming apparatus including an electrophotographic photoreceptor having excellent electron transport properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0073] Figure 1 is a schematic partial cross-sectional view showing an example of a layer structure of an electrophotographic photoreceptor according to the present embodiment;

[0074] Figure 2 is a schematic structural diagram showing an example of an image forming apparatus according to the present embodiment;

[0075] Figure 3 It is a schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment.

[0076] Explanation of symbols

[0077] 1-undercoat layer, 2-charge generating layer, 3-charge transporting layer, 4-conductive substrate, 5-photosensitive layer, 7A-photoreceptor, 7-electrophotographic photoreceptor, 8-charging device, 9-exposure device, 11-developing device, 13-cleaning device, 14-lubricant, 40-transfer device, 50-intermediate transfer body, 100-image forming device, 120-image forming device, 131-cleaning blade, 132-fibrous component (roller-shaped), 133-fibrous component (flat brush-shaped), 300-processing box. DETAILED DESCRIPTION

[0078] Hereinafter, embodiments of the present invention will be described. These descriptions and examples are intended to illustrate the embodiments and do not limit the scope of the embodiments.

[0079] In the numerical ranges recorded in stages in the present invention, the upper limit or lower limit recorded in one numerical range may also be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical ranges recorded in the present invention, the upper limit or lower limit of the numerical range may also be replaced by the value shown in the embodiment.

[0080] In the present invention, each component may also include a plurality of corresponding substances. In the present invention, when referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it indicates the total amount of the plurality of substances present in the composition.

[0081] In the present invention, LUMO is an abbreviation for "Lowest Unoccupied Molecular Orbital".

[0082] In the present invention, the electrophotographic photoreceptor is also simply referred to as a photoreceptor.

[0083] <Electronic Photographic Photoreceptor>

[0084] The electrophotographic photoreceptor according to the present embodiment comprises a conductive substrate, an undercoat layer provided on the conductive substrate, and a photosensitive layer provided on the undercoat layer, wherein the undercoat layer contains a binder resin and a crystal density of 1.62 g / cm 3 The electron transporting material has a full width at half maximum (FWHM) of a maximum intensity peak in an X-ray diffraction spectrum measured in the thickness direction of 5.0° or less.

[0085] The photoreceptor according to the present embodiment includes a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer.

[0086] Figure 1 An example of the layer structure of the photoreceptor according to the present embodiment is schematically shown. Figure 1 The photoreceptor 7A shown has a structure in which an undercoat layer 1, a charge generating layer 2, and a charge transporting layer 3 are sequentially stacked on a conductive substrate 4. The charge generating layer 2 and the charge transporting layer 3 constitute a photosensitive layer 5. The photoreceptor 7A may have a layer structure in which a protective layer is further provided on the charge transporting layer 3.

[0087] In the photoreceptor according to this embodiment, Figure 1 The photosensitive layer of the photoreceptor 7A shown may be a functional separation type photosensitive layer in which the charge generating layer 2 and the charge transporting layer 3 are separated, or may be a single layer photosensitive layer having charge generating capability and charge transporting capability instead of the charge generating layer 2 and the charge transporting layer 3 .

[0088] In order to improve the electron transport property of the electrophotographic photoreceptor, an electrophotographic photoreceptor having an undercoat layer is used. However, in the conventional electrophotographic photoreceptor having an undercoat layer, there is still room for improvement in the electron transport performance.

[0089] On the other hand, the electrophotographic photoreceptor according to the present embodiment has excellent electron transport properties due to the above-mentioned structure. The mechanism of this action is not clear, but can be estimated as follows.

[0090] The undercoat layer in the electrophotographic photoreceptor according to the present embodiment contains a crystal density of 1.62 g / cm 3 More than electron transport materials. That is, the crystal density of the electron transport material is larger than before. Usually, the crystal density represents the molecular weight in the unit grid / the volume of the crystal unit grid. The crystal density is large, so there is a tendency for the electron transport materials to exist close to each other in the lower coating. As a result, the overlap of the energy levels of the LUMO of the electron transport materials is easy to become larger, so that it is considered that the electron transport property is excellent.

[0091] Furthermore, in the lower coating layer in the electrophotographic photoreceptor involved in the present embodiment, the full width at half maximum (FWHM) of the maximum intensity peak in the X-ray diffraction spectrum measured from the thickness direction is 5.0° or less. Typically, the peak in the X-ray diffraction spectrum has a tendency to be observed more clearly with a high purity and a smaller lattice distortion without doping with impurities or crystals. That is, if the full width at half maximum (FWHM) of the maximum intensity peak is 5.0° or less, there is a tendency that the doping of multiple crystals is less and the configuration of the electron transport materials in the lower coating layer is not easy to be messy. As a result, it is believed that the electron transport property is more excellent.

[0092] Hereinafter, each layer of the photoreceptor according to the present embodiment will be described in detail.

[0093] [Undercoat]

[0094] The lower coating contains a binder resin and a crystal density of 1.62 g / cm3 The electron transporting material has a full width at half maximum (FWHM) of a maximum intensity peak in an X-ray diffraction spectrum measured in the thickness direction of 5.0° or less.

[0095] (Electron transport material)

[0096] The crystal density of the electron transport material is 1.62 g / cm 3 Above, for example, preferably 1.64 g / cm 3 Above and 3.00g / cm 3 Below, more preferably 1.66 g / cm 3 Above and 2.50g / cm 3 Below, more preferably 1.68 g / cm 3 Above 1.90g / cm 3 the following.

[0097] If the crystal density of the electron transport material is 1.62 g / cm 3 As described above, that is, the higher the crystal density, the more molecules tend to exist close to each other in the crystal structure. As a result, the overlap of the LUMO energy levels of the electron transporting materials is likely to increase, thereby further improving the electron transporting property.

[0098] If the crystal density of the electron transport material is 3.00 g / cm 3 Then, the molecules in the crystal structure are prevented from coming too close to each other. As a result, it is presumed that the energy repulsion between the molecules is easily suppressed, and the stability of the crystal structure is more excellent.

[0099] The crystal density of the electron transport material is determined as follows.

[0100] A solvent is used to remove the layer on the outer peripheral side of the electrophotographic photoreceptor, i.e., the photosensitive layer, leaving only the conductive substrate and the undercoat layer. Then, after the undercoat layer is peeled off from the conductive substrate, the volume average particle size of the electron transport material contained in the undercoat layer is adjusted to less than 5 μm, and an X-ray diffraction measurement (XRD measurement) is performed. The obtained X-ray diffraction profile is compared with a database (e.g., Cambridge Structural Database: CSD (Cambridge Structural Database), Crystallography Open Database: COD (Crystal Structure Database), etc.), and compounds consistent with the X-ray diffraction peak position are identified. When the electron transport material can be identified by comparison with the database, the crystal density is determined based on the CIF file of the electron transport material recorded in the database.

[0101] The obtained X-ray diffraction profile is compared with the database. When there is no corresponding X-ray diffraction profile, after clarifying the molecular structure of the electron transport material by chemical analysis (e.g., elemental analysis), a single crystal of the electron transport material is prepared, and the crystal structure is determined by single crystal X-ray structure analysis. Based on the obtained crystal structure data, the crystal density is calculated from the volume of the unit grid and the mass of the atoms contained in the unit grid.

[0102] There is no particular limitation on the method for setting the crystal density of the electron transport material within the above range, but examples include a method of using a molecular structure with less steric hindrance, a method of setting the electron transport material to a molecular structure with high three-dimensional planarity (for example, a method of setting it to have a skeleton that can achieve intermolecular interactions such as π-π stacking); a method of setting the type of electron transport material to a specification that includes at least one of the electron transport material represented by the general formula (P) described later and the electron transport material represented by the general formula (Q); etc.

[0103] In the electron transport material, for example, the average primary particle size is preferably 500 nm or more, more preferably 30 nm or more and 400 nm or less, and further preferably 50 nm or more and 200 nm or less.

[0104] If the average primary particle size of the electron transport material is 500 nm or less, the electron transport material is not easily localized in the lower coating layer, and is easily present with high dispersion, so the electron transport property is more excellent. If the average primary particle size of the electron transport material is 30 nm or more, the aggregation of the electron transport material is suppressed, and it is easy to exist with high dispersion in the lower coating layer, so the electron transport property is more excellent.

[0105] The average primary particle size of the electron transport material was determined as follows.

[0106] The cross section of the stack in the thickness direction of the electrophotographic photoreceptor is observed by SEM (scanning electron microscope) at a magnification of 5000 times to identify the electron transport material. Here, the electron transport material exists as a solid substance in the binder resin, and the outline can be identified by the small step difference at the interface between the binder resin and the electron transport material. The electron transport material is identified by identifying the outline.

[0107] Then, the equivalent circle diameters of particles existing as primary particles at any 10 points in the electron transport material present in the obtained SEM image are calculated, and the arithmetic mean of the obtained equivalent circle diameters is defined as the average primary particle size of the electron transport material.

[0108] In the electron transport material, for example, the aspect ratio is preferably 1.0 to 2.5, more preferably 1.2 to 2.4, and further preferably 1.5 to 2.3.

[0109] When the aspect ratio of the electron transport material is 2.5 or less, the electron transport material is less likely to be localized in the undercoat layer and is more likely to exist with high dispersion, so that the electron transport property is more excellent.

[0110] The aspect ratio of the electron transporting material refers to the ratio of the length of the major axis of the electron transporting material to the length of the minor axis of the electron transporting material (length of the major axis / length of the minor axis).

[0111] The length of the electron transport material in the long axis direction represents the longest straight line distance when connecting one end of the electron transport material in the long axis direction to the other end. The length of the electron transport material in the short axis direction represents the longest straight line distance when connecting one end of the electron transport material in the direction orthogonal to the long axis to the other end.

[0112] The aspect ratio of the electron transport material is calculated as follows.

[0113] The photosensitive layer is removed from the electrophotographic photoreceptor (and the protective layer is removed as needed), and the lower coating is observed at 3000 to 100000 times using a field emission scanning electron microscope (JEOL JSM-6700F) to identify the electron transport material. Here, the electron transport material exists as a solid substance in the binder resin, and the contour can be identified by the small step difference at the interface between the binder resin and the electron transport material. The electron transport material is identified by identifying the contour.

[0114] The lengths of the major axis and the minor axis of any 100 points of the electron transport material were measured from the obtained microscope photographs, and the aspect ratios (major axis length / minor axis length) were calculated. The arithmetic mean of the aspect ratios was defined as the aspect ratio of the electron transport material.

[0115] There is no particular limitation on the method for setting the average primary particle size and aspect ratio of the electron transport material within the above range, but examples include a method of crushing the electron transport material or a coating liquid for forming a lower coating layer containing the same using a ball mill, a bead mill, a mortar, a sand mill, a kneader, a grinder, or the like; a method of precipitating microcrystals by dissolving the material in fluoroacetic acid, sulfuric acid, or the like and then contacting the material with water or a poor solvent; and the like.

[0116] From the viewpoint of setting the crystal density to the aforementioned range and setting the full width at half maximum (FWHM) of the maximum intensity peak in the X-ray diffraction spectrum measured from the thickness direction to less than 5.0°, the electron transport material preferably contains at least one of the electron transport material represented by the following general formula (P) and the electron transport material represented by the general formula (Q), and more preferably contains the electron transport material represented by the general formula (P).

[0117] [Chemical formula 3]

[0118]

[0119] 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.

[0120] In the above general formula (Q), R 51 and R 52 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.

[0121] The electron transport material represented by the general formula (P) and the electron transport material represented by the general formula (Q) have the property of excellent electron transport and low hole transport. Therefore, it is believed that if the lower coating contains at least one of the electron transport material represented by the general formula (P) and the electron transport material represented by the general formula (Q), the electron transport property of the lower coating is excellent, and the dark attenuation is reduced, so the charge retention is excellent.

[0122] [Electron transport material represented by general formula (P)]

[0123] Hereinafter, the electron transport material represented by the general formula (P) will be described.

[0124] [Chemical formula 4]

[0125]

[0126] In the 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.

[0127] In the general formula (P), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 For example, each independently represents preferably a hydrogen atom or a halogen atom, and more preferably a hydrogen atom.

[0128] It is believed that when R in the general formula (P) 1 ~R 8 When it is a hydrogen atom or a halogen atom (for example, a hydrogen atom is more preferable), the electron transport property of the undercoat layer is more excellent, and the dark decay is further reduced, so the charge retention property is more excellent.

[0129] As R in the general formula (P) 1 ~R 8 The alkyl group represented by may be a substituted or unsubstituted alkyl group.

[0130] As R in the general formula (P) 1 ~R 8 The unsubstituted alkyl group represented by the present invention includes a straight-chain alkyl group having 1 to 20 carbon atoms (for example, preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms), a branched alkyl group having 3 to 20 carbon atoms (for example, preferably 3 to 10 carbon atoms), and a cyclic alkyl group having 3 to 20 carbon atoms (for example, preferably 3 to 10 carbon atoms).

[0131] Examples of the straight-chain alkyl group having 1 to 20 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, tridecyl, n-tetradecyl, n-pentadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, and n-eicosyl.

[0132] Examples of the branched alkyl group having 3 to 20 carbon atoms include isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, tert-hexyl, isoheptyl, sec-heptyl, tert-heptyl, isooctyl, sec-octyl, tert-octyl, isononyl, sec-nonyl, tert-nonyl, isodecyl, sec-decyl, tert-decyl, isododecyl, sec-dodecyl, tert-dodecyl, tert-tetradecyl, and tert-pentadecyl.

[0133] Examples of the cyclic alkyl group having 3 to 20 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups in which these monocyclic alkyl groups are linked.

[0134] Among the above, the unsubstituted alkyl group is preferably a linear alkyl group such as a methyl group or an ethyl group.

[0135] Examples of the substituent in the alkyl group include an alkoxy group, a hydroxyl group, a carboxyl group, a nitro group, and a halogen atom (a fluorine atom, a bromine atom, an iodine atom, etc.).

[0136] Examples of the alkoxy group substituting the hydrogen atom in the alkyl group include: 1 ~R 8 The same groups as the unsubstituted alkoxy groups represented.

[0137] As R in the general formula (P) 1 ~R 8 The alkoxy group represented by may be a substituted or unsubstituted alkoxy group.

[0138] As R in the general formula (P) 1 ~R 8 Examples of the unsubstituted alkoxy group represented by the above include linear, branched or cyclic alkoxy groups having 1 to 10 carbon atoms (for example, preferably 1 to 6, more preferably 1 to 4).

[0139] Specific examples of the linear alkoxy group 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.

[0140] Specifically, examples of the branched alkoxy group include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentyloxy, neopentyloxy, tert-pentyloxy, isohexyloxy, sec-hexyloxy, tert-hexyloxy, isoheptyloxy, sec-heptyloxy, tert-heptyloxy, isooctyloxy, sec-octyloxy, tert-octyloxy, isononyloxy, sec-nonyloxy, tert-nonyloxy, isodecyloxy, sec-decyloxy, and tert-decyloxy.

[0141] Specific examples of the cyclic alkoxy group include a cyclopropyloxy group, a cyclobutyloxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, a cyclononyloxy group, and a cyclodecyloxy group.

[0142] Among them, as the unsubstituted alkoxy group, for example, a linear alkoxy group is preferred.

[0143] Examples of the substituent in the alkoxy group include an aryl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a hydroxyl group, a carboxyl group, a nitro group, and a halogen atom (such as a fluorine atom, a bromine atom, and an iodine atom).

[0144] Examples of the aryl group that replaces the hydrogen atom in the alkoxy group include the following: 1 ~R 8 The same groups as those represented by the unsubstituted aryl groups.

[0145] Examples of the alkoxycarbonyl group that replaces the hydrogen atom in the alkoxy group include the following: 1 ~R 8 The same groups as the unsubstituted alkoxycarbonyl groups represented.

[0146] Examples of the aryloxycarbonyl group that replaces the hydrogen atom in the alkoxy group include the following: 1 ~R 8 The same groups as the unsubstituted aryloxycarbonyl groups represented.

[0147] As R in the general formula (P) 1 ~R 8 The aralkyl group represented by may be a substituted or unsubstituted aralkyl group.

[0148] As R in the general formula (P) 1 ~R 8 The unsubstituted aralkyl group represented is, for example, preferably an aralkyl group having 7 to 30 carbon atoms, more preferably an aralkyl group having 7 to 16 carbon atoms, and still more preferably an aralkyl group having 7 to 12 carbon atoms.

[0149] Examples of the unsubstituted aralkyl group having 7 to 30 carbon atoms include benzyl, phenylethyl, phenylpropyl, 4-phenylbutyl, phenylpentyl, phenylhexyl, phenylheptyl, phenyloctyl, phenylnonyl, naphthylmethyl, naphthylethyl, anthracenylmethyl, and phenyl-cyclopentylmethyl.

[0150] Examples of the substituent in the aralkyl group include an alkoxy group, an alkoxycarbonyl group, and a halogen atom (a fluorine atom, a bromine atom, an iodine atom, etc.).

[0151] Examples of the alkoxy group substituting the hydrogen atom in the aralkyl group include the following: 1 ~R 8 The same groups as the unsubstituted alkoxy groups represented.

[0152] Examples of the alkoxycarbonyl group that replaces the hydrogen atom in the aralkyl group include the following: 1 ~R 8 The same groups as the unsubstituted alkoxycarbonyl groups represented.

[0153] As R in the general formula (P) 1 ~R 8The aryl group represented by may be a substituted or unsubstituted aryl group.

[0154] As R in the general formula (P) 1 ~R 8 The unsubstituted aryl group represented by is, for example, preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 14 carbon atoms, and further preferably an aryl group having 6 to 10 carbon atoms.

[0155] Examples of the aryl group having 6 to 30 carbon atoms include phenyl, biphenyl, 1-naphthyl, 2-naphthyl, 9-anthryl, 9-phenanthryl, 1-pyrenyl, 5-naphthyl, 1-indenyl, 2-azulyl, 9-fluorenyl, biphenylene, indacenyl, fluoranthenyl, acenaphthyl, acenaphthylene, phenanthrenyl, fluorenyl, anthracenyl, anthracenyl, quaternary anthracenyl, anthraquinolyl, phenanthrenyl, triphenylene, pyrenyl, chrysenyl, naphthphenyl, pleiadenyl, picenyl, perylenyl, pentaphenyl, pentacene, tetraphenylene, hexaphenyl, hexacenyl, ruthenyl, and coronenyl. Among the above, for example, phenyl is preferred.

[0156] Examples of the substituent in the aryl group include an alkyl group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a halogen atom (a fluorine atom, a bromine atom, an iodine atom, etc.).

[0157] Examples of the alkyl group that replaces the hydrogen atom in the aryl group include the following: 1 ~R 8 The same groups as the unsubstituted alkyl groups represented.

[0158] Examples of the alkoxy group substituting the hydrogen atom in the aryl group include the following: 1 ~R 8 The same groups as the unsubstituted alkoxy groups represented.

[0159] Examples of the alkoxycarbonyl group substituting the hydrogen atom in the aryl group include the following: 1 ~R 8 The same groups as the unsubstituted alkoxycarbonyl groups represented.

[0160] As R in the general formula (P) 1 ~R 8 Examples of the alkoxycarbonyl group represented by include substituted or unsubstituted alkoxycarbonyl groups.

[0161] As R in the general formula (P) 1 ~R 8The number of carbon atoms in the alkyl chain of the unsubstituted alkoxycarbonyl group represented is, for example, preferably 1 or more and 20 or less, more preferably 1 or more and 15 or less, and further preferably 1 or more and 10 or less.

[0162] Examples of the alkoxycarbonyl group having an alkyl chain with a carbon number of 1 to 20 include methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, n-butoxycarbonyl, sec-butoxybutylcarbonyl, tert-butoxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl, heptyloxycarbonyl, octyloxycarbonyl, nonyloxy, decyloxycarbonyl, dodecyloxycarbonyl, tridecanyloxycarbonyl, tetradecanyloxycarbonyl, pentadecyloxycarbonyl, hexadecyloxycarbonyl, heptadecanyloxycarbonyl, hexadecyloxycarbonyl, heptadecanyloxycarbonyl, octadecyloxycarbonyl, and eicosyloxycarbonyl.

[0163] Examples of the substituent in the alkoxycarbonyl group include an aryl group, a hydroxyl group and a halogen atom (a fluorine atom, a bromine atom, an iodine atom, etc.).

[0164] Examples of the aryl group substituting the hydrogen atom in the alkoxycarbonyl group include the following: 1 ~R 8 The same groups as those represented by the unsubstituted aryl groups.

[0165] As R in the general formula (P) 1 ~R 8 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0166] Hereinafter, exemplary compounds of the electron transport material represented by the general formula (P) are shown, but the present embodiment is not limited thereto. In addition, the following exemplary compound numbers are denoted as exemplary compounds (P-numbers).

[0167] [Chemical formula 5]

[0168]

[0169] [Chemical formula 6]

[0170]

[0171] [Electron transport material represented by general formula (Q)]

[0172] Hereinafter, the electron transport material represented by the general formula (Q) will be described.

[0173] [Chemical formula 7]

[0174]

[0175] In the general formula (Q), R 51 and R 52Each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group or a halogen atom.

[0176] In the general formula (Q), R 51 and R 52 For example, each independently represents preferably a hydrogen atom or a halogen atom, and more preferably a hydrogen atom.

[0177] It is believed that when R in the general formula (P) 51 and R 52 When it is a hydrogen atom or a halogen atom (for example, a hydrogen atom is more preferable), the electron transport property of the undercoat layer is more excellent, and the dark decay is further reduced, so the charge retention property is more excellent.

[0178] As R in the general formula (Q) 51 and R 52 The alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group and halogen atom represented by the formula (P) include the same as R 1 ~R 8 The alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group and halogen atom represented are the same groups and atoms.

[0179] In the general formula (Q), R 51 and R 52 The alkyl, alkoxy, aralkyl, aryl and alkoxycarbonyl groups represented by the formula (P) may have the same 1 ~R 8 The substituents mentioned for the alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented are the same substituents.

[0180] In the general formula (Q), R 51 and R 52 Each of them can be independently represented by a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group.

[0181] Hereinafter, exemplary compounds of the electron transport material represented by the general formula (Q) are shown, but the present embodiment is not limited thereto. In addition, the following exemplary compound numbers are denoted as exemplary compounds (Q-numbers).

[0182] [Chemical formula 8]

[0183]

[0184] [Chemical formula 9]

[0185]

[0186] In addition, the abbreviations and the like in the above-mentioned exemplary compounds have the following meanings.

[0187] Ph: phenyl

[0188] ·OCH3:Methoxy

[0189] ·t-C4H9O: tert-butoxy

[0190] ·c-C6H 11 :Cyclohexyl

[0191] ·C6H5: phenyl

[0192] ·CH2C6H5: benzyl

[0193] ·3,5-(CH3)2-C6H3: 3,5-dimethylphenyl

[0194] ·3,5-Cl2-C6H3: 3,5-dichlorophenyl

[0195] Br: Bromine atom

[0196] Cl: chlorine atom

[0197] The undercoat layer may further contain an electron transporting material other than the electron transporting material represented by the general formula (P) and the electron transporting material represented by the general formula (Q) within a range in which the effects of the present invention can be exerted.

[0198] The proportion of the electron transport material represented by the general formula (P) and the electron transport material represented by the general formula (Q) in the total amount of the electron transport material in the lower coating layer is, for example, preferably greater than 80 mass % and less than 100 mass %, more preferably greater than 90 mass % and less than 100 mass %, and further preferably greater than 95 mass % and less than 100 mass %.

[0199] The content of the electron transport material is, for example, preferably 60 mass % or more, more preferably 60 mass % or more and 80 mass % or less, and further preferably 65 mass % or more and 75 mass % or less, based on the total binder resin component of the undercoat layer.

[0200] If the content of the electron transport material is 80% by mass or less, the film becomes brittle, the film-forming property is reduced, and the generation of surface roughness of the lower coating layer is suppressed, so that both the electron transport property and the charge retention property are more excellent. On the other hand, if the content of the electron transport material is 60% by mass or more, the generation of excess or deficiency in the electron transport energy is suppressed, so that both the electron transport property and the charge retention property are more excellent.

[0201] The content of the electron transport material may be less than 60 mass %, 45 mass % or more and less than 60 mass %, or 50 mass % or more and less than 60 mass % based on the total binder resin component of the undercoat layer.

[0202] In this embodiment, the crystal density is 1.62 g / cm 3 The above electron transport material has a full width at half maximum (FWHM) of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction of 5.0° or less, so even if the content of the electron transport material is less than 60% by mass, the electron transport property and charge retention property are excellent.

[0203] (Binder resin)

[0204] Examples of the binder resin used in the lower coating layer include acetal resins (e.g., polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, epoxy resins and other well-known polymer compounds; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; silane coupling agents and other well-known materials.

[0205] Examples of the binder resin used in the undercoat layer include a charge transporting resin having a charge transporting group, and a conductive resin (for example, polyaniline).

[0206] Among them, the binding resin used in the lower coating layer is preferably a resin that is insoluble in the coating solvent in the upper layer, and is particularly preferably a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenolic resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, epoxy resin, polyamide resin, polyester resin, polyether resin, methacrylic resin, acrylic resin, polyvinyl alcohol resin and polyvinyl acetal resin with a curing agent.

[0207] When two or more of these binder resins are used in combination, the mixing ratio is set as needed. In addition, in this specification, for convenience, the urethane resin obtained by the reaction between the resin and the curing agent is also referred to as a "curable urethane resin".

[0208] (Inorganic particles)

[0209] The undercoat layer may further contain inorganic particles.

[0210] Examples of inorganic particles include powder resistance (volume resistivity) of 10 2 Ω·cm or more and 10 11Inorganic particles with a particle size of less than Ω·cm.

[0211] Among them, as the inorganic particles having the above resistance value, for example, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles are preferred, and zinc oxide particles are particularly preferred.

[0212] The specific surface area of ​​the inorganic particles based on the BET method is preferably 10 m 2 / g or more. If the specific surface area is 10m 2 / g or more, there is a tendency that a decrease in charging properties is suppressed.

[0213] The volume average particle diameter of the inorganic particles is, for example, preferably 50 nm or more and 2000 nm or less (for example, preferably 60 nm or more and 1000 nm or less).

[0214] The content of the inorganic particles is, for example, preferably 0 mass % to 80 mass % and more preferably 0 mass % to 70 mass % with respect to the total solid content of the undercoat layer.

[0215] The inorganic particles may be subjected to surface treatment. Two or more inorganic particles having different surface treatments or particles having different particle sizes may be used in combination.

[0216] Examples of the surface treatment agent include silane coupling agents, titanate coupling agents, aluminum coupling agents, surfactants, etc. In particular, for example, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0217] Examples of the silane coupling agent 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.

[0218] Silane coupling agents can be mixed and used in two or more ways. For example, silane coupling agents with amino groups can be used in combination with other silane coupling agents. As other silane coupling agents, for example, vinyl trimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyl trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, vinyl triacetoxysilane, 3-mercaptopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, N-2- (aminoethyl) -3-aminopropyl trimethoxysilane, N-2- (aminoethyl) -3-aminopropyl methyl dimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyl triethoxysilane, 3-chloropropyl trimethoxysilane, etc. can be cited, but it is not limited thereto.

[0219] The surface treatment method using the surface treatment agent may be any method as long as it is a known method, and may be either a dry method or a wet method.

[0220] The treatment amount of the surface treatment agent is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0221] The dry method is, for example, a method in which a surface treatment agent dissolved in an organic solvent is directly dripped or added while stirring the inorganic particles by a mixer with a large shear force, and the surface treatment agent is sprayed together with dry air or nitrogen to make the surface treatment agent adhere to the surface of the inorganic particles. When the surface treatment agent is dripped or sprayed, for example, it can be carried out at a temperature below the boiling point of the solvent. After the surface treatment agent is dripped or sprayed, sintering can also be carried out at 100°C or above. There is no particular limitation on the sintering temperature and time as long as the electrophotographic characteristics can be obtained.

[0222] The wet method is, for example, a method in which inorganic particles are dispersed in a solvent by stirring, ultrasonic waves, a sand mill, a grinder, a ball mill, etc., and after adding a surface treatment agent and stirring or dispersing, the solvent is removed to attach the surface treatment agent to the surface of the inorganic particles. The solvent removal method is, for example, to remove the solvent by filtering or distilling. After removing the solvent, sintering can also be performed at a condition of 100° C. or above. Sintering is not particularly limited as long as the temperature and time are such that electronic photographic properties can be obtained. In the wet method, the water content of the inorganic particles can be removed before adding the surface treatment agent. As examples thereof, a method of removing the water content in the solvent while stirring and heating and a method of removing the water content by azeotropy with the solvent can be cited.

[0223] (Other materials)

[0224] In order to improve electrical characteristics, improve environmental stability, and improve image quality, various additives may be included in the undercoat layer.

[0225] As additives, there can be mentioned known materials such as polycyclic condensation type, azo type and other electron transporting pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, silane coupling agents, etc. As mentioned above, silane coupling agents are used for surface treatment of inorganic particles, but can also be added to the undercoat layer as an additive.

[0226] Examples of the silane coupling agent as an additive 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, and 3-chloropropyltrimethoxysilane.

[0227] Examples of the zirconium chelate compound include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, zirconium acetylacetonate butoxide, zirconium ethyl acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium methacrylate butoxide, zirconium stearate butoxide, and zirconium isostearate butoxide.

[0228] Examples of the titanium chelate compound include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, titanium polyacetylacetonate, titanium octanediol, ammonium lactate titanium, titanium lactate, ethyl lactate titanium, triethanolamine titanium, and polyhydroxystearate titanium.

[0229] Examples of the aluminum chelate compound include aluminum isopropoxide, monobutoxyaluminum diisopropoxide, aluminum butoxide, diethyl acetoacetate aluminum diisopropoxide, and tris(ethyl acetoacetate)aluminum.

[0230] These additives may be used alone or in the form of a mixture or polycondensate of a plurality of compounds.

[0231] - Characteristics of the bottom coating -

[0232] The full width at half maximum (FWHM) of the maximum intensity peak in X-ray diffraction measurement of the undercoat layer measured in the thickness direction is 5.0° or less, for example, preferably 3.0° or less, more preferably 1.0° or less, particularly preferably 0.7° or less.

[0233] When the full width at half maximum (FWHM) of the maximum intensity peak is 5.0° or less, there are fewer defects in the crystal structure and the crystals are orderly arranged, resulting in more excellent electron transport properties.

[0234] The method of adjusting the full width at half maximum of the maximum intensity peak to fall within the above range is not particularly limited, and examples thereof include a method of adjusting the full width at half maximum of the maximum intensity peak according to the average primary particle size, aspect ratio, etc. of the electron transport material in the undercoat layer.

[0235] When the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured for the lower coating layer in the thickness direction is set to I1, and the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured when the lower coating layer is in a powder state with a volume average particle size of less than 5 μm is set to I2, the value of the maximum value Nmax in the orientation index N represented by the following formula (1) is, for example, preferably greater than 1.0 and less than 5.5, more preferably greater than 3.0 and less than 5.3, and further preferably greater than 4.0 and less than 5.1.

[0236] [Formula 2]

[0237]

[0238] In the present invention, the “maximum intensity peak” refers to the strongest crystal diffraction peak in an X-ray diffraction spectrum measured when the undercoat layer is in a powder state having a volume average particle size of 5 μm or less.

[0239] In the present invention, the relative integrated intensity of the maximum intensity peak is defined as the intensity obtained by integrating the value obtained by subtracting the background intensity from the intensity of the maximum intensity peak, and the subtraction of the background intensity is performed by the Shirley method.

[0240] For example, the orientation index N represented by formula (1) in a certain maximum intensity peak A is the value of the relative integrated intensity of a certain peak A in the X-ray diffraction spectrum / the relative integrated intensity of all peaks divided by the value of the relative integrated intensity of a certain maximum intensity peak A in the X-ray diffraction spectrum measured when the undercoat layer is in a powder state with a volume average particle size of less than 5 μm / the relative integrated intensity of all peaks in the X-ray diffraction spectrum measured when the undercoat layer is in a powder state with a volume average particle size of less than 5 μm.

[0241] The maximum value among the orientation indexes N represented by the formula (1) obtained in each peak is the value of Nmax.

[0242] Furthermore, the lower coating layer is in a powder state with a volume average particle size of less than 5 μm, and it is inferred that the orientation state is random. Therefore, it is inferred that the maximum value Nmax of the orientation index N represented by the formula (1) is less than 5.5, that is, the smaller the value, the less the orientation of the crystals in the lower coating layer, and the configuration of the crystal direction of the electron transport material in the lower coating layer becomes random.

[0243] In the present invention, the full width at half maximum (FWHM) of the maximum intensity peak and the maximum value Nmax of the orientation index N are values ​​obtained by performing X-ray diffraction measurement under measurement conditions.

[0244] Measurement device: D8 DISCOVER manufactured by Bruker AXS Co., Ltd.

[0245] X-ray source: CuKα

[0246] ·Measurement method: 2θ / θ scanning

[0247] However, Cr, Fe, Co, and Mo may be used as X-ray sources in addition to these, and the measurement range must be set within a range in which all diffraction peaks derived from the electron transporting compound in a powder state can be detected.

[0248] As a method for making the lower coating layer in a powder state with a volume average particle size of less than 5 μm, a method of pulverizing using a ball mill, a bead mill, a mortar, a sand mill, a kneader, a grinder, etc. can be adopted; after being dissolved in fluoroacetic acid, sulfuric acid, etc., it is contacted with water or a poor solvent to precipitate microcrystals, and any other method. In addition, as the conditions for the above-mentioned pulverization treatment, any of the dry method and the wet method can be adopted. For example, when pulverizing, inorganic compounds such as salt and sodium sulfate or grinding media such as glass beads, steel balls, alumina beads, and zirconia beads are used, and the uniformity of the crystals is easily obtained, so it is preferred. In the case of the wet method, all processing solvents such as water, alcohol, and organic solvents can be used for the purpose of further controlling the crystal form or size of the particles.

[0249] The method of setting the value of the maximum value Nmax within the above range is not particularly limited, and examples thereof include a method of adjusting the value based on the average primary particle size, aspect ratio, etc. of the electron transport material in the undercoat layer.

[0250] In the undercoat layer, for example, the LUMO energy level is preferably 3.8 eV to 4.2 eV, more preferably 3.9 eV to 4.2 eV, and even more preferably 4.0 eV to 4.2 eV.

[0251] When the LUMO energy level of the undercoat layer is 4.2 eV or less, the charge retention property is more excellent. On the other hand, when the LUMO energy level of the undercoat layer is 3.8 eV or more, the electron injection property from the charge generation layer is more excellent.

[0252] There is no particular limitation on the method for setting the energy level of the LUMO of the lower coating layer to within the above range, but examples thereof include methods of adjusting the type of electron transporting material (for example, more preferably setting the specification so that the electron transporting material contains at least one of the electron transporting material represented by the general formula (P) and the electron transporting material represented by the general formula (Q)).

[0253] The LUMO energy level of the undercoat layer was determined as follows.

[0254] After cutting out the electrophotographic photoreceptor from the outer peripheral surface side in the stacking direction with a 2 cm square, the photosensitive layer is removed using a solvent such as THF to obtain a sample with only a conductive substrate and an undercoat layer. The prepared sample is measured from the outer peripheral surface side of the electrophotographic photoreceptor (i.e., from the undercoat layer side) at a wavelength of 500 nm using the atmospheric photoelectron absorption spectrometer AC-2 manufactured by RIKEN to measure the range of 4eV to 6.2eV, and obtain a spectrum with the horizontal axis set to the energy of the irradiated light and the vertical axis set to the electron coefficient rate. In this spectrum, the intersection of the baseline and the straight line drawn from the plotted rising part of the baseline is set to EHOMO. Next, the single film of the undercoat layer peeled off from the substrate was measured by transmission method using an ultraviolet visible near infrared (UV-Vis-NIR) spectrophotometer (model: Cary5000, manufactured by Agilent Technologies Japan, Ltd.) to a wavelength range of 200 nm to 800 nm, and the absorption end at a wavelength of 400 nm to 700 nm was calculated and set as an energy gap (HOMO-LUMO=energy difference ΔE). LUMO was obtained according to the following formula.

[0255] Formula: LUMO = HOMO - ΔE

[0256] The volume resistivity of the lower coating layer is preferably 1×10 10 Ω·cm or more and 1×10 12 Ω·cm or less.

[0257] The undercoat layer may have a Vickers hardness of 35 or more, for example.

[0258] In order to suppress interference moire images, the surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to, for example, 1 / (4n) (n is the refractive index of the upper layer) to 1 / 2 of the exposure laser wavelength λ used.

[0259] In order to adjust the surface roughness, resin particles or the like may be added to the undercoat layer. Examples of the resin particles include silicone resin particles and cross-linked polymethacrylate methyl resin particles. In addition, in order to adjust the surface roughness, the surface of the undercoat layer may be ground. Examples of the grinding method include polishing, sandblasting, wet grinding, grinding, and the like.

[0260] -Method for forming lower coating layer-

[0261] The formation of the undercoat layer is not particularly limited and can be performed by a known formation method. For example, the undercoat layer can be formed by forming a coating film of an undercoat layer-forming coating liquid prepared by adding the above-mentioned components to a solvent, drying the coating film, and heating as necessary.

[0262] Examples of the solvent used for preparing the coating solution for forming an undercoat layer include known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents, and ester solvents.

[0263] Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, and toluene.

[0264] Examples of a method for dispersing the inorganic particles when preparing the coating liquid for forming an undercoat layer include known methods such as a roll mill, a ball mill, a vibration ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0265] Electron transport materials (especially electron transport materials represented by general formula (P)) are difficult to dissolve in organic solvents, so for example, they are preferably dispersed in organic solvents. As the dispersion method, for example, known methods such as roller mills, ball mills, vibrating ball mills, grinders, sand mills, colloid mills, paint stirrers, etc. can be cited. When metal oxide particles are combined in the lower coating, for example, the metal oxide particles are preferably dispersed in the organic solvent by the same dispersion method.

[0266] Examples of a method for applying the coating liquid for forming an undercoat layer onto the conductive substrate include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0267] The content of the metal oxide in the undercoat layer is, for example, preferably 5 mass % or less, more preferably 3 mass % or less, further preferably 0 mass % (ie, containing no metal oxide) or 2 mass % or less, relative to the total solid content of the undercoat layer.

[0268] Generally, metal oxides have a tendency to have low resistance. Therefore, if the content of the metal oxide in the undercoat layer is less than 5% by mass, the resistance of the undercoat layer becomes low, and the reduction of electron transport or charge retention is suppressed. In addition, from the viewpoint of manufacturing for the purpose of low environmental load, for example, it is also preferred to reduce the content of the metal oxide.

[0269] The average thickness of the undercoat layer is, for example, preferably 5 μm or more and 15 μm or less, more preferably 7 μm or more and 14 μm or less, and further preferably 8 μm or more and 13 μm or less.

[0270] The thickness of the undercoat layer may be 15 μm or more, or 20 μm or more and 50 μm or less.

[0271] In addition to electron transport properties, existing electron transport materials also have a slight hole transport property. Therefore, by reducing the film thickness of the lower coating layer (for example, set to less than 5 μm), the image defects caused by the injection of charge from the conductive substrate to the photosensitive layer and the reduction of surface charge are suppressed. However, if the film thickness of the lower coating layer is thin, for example, when the needle-shaped foreign matter is mixed from the developing member (such as a developer, etc.) or the transfer member (such as an intermediate transfer body, etc.) during image formation, the needle-shaped foreign matter punctures the lower coating layer from the surface of the electrophotographic photoreceptor, so that the charge maintenance is sometimes reduced due to leakage current. In contrast, in the present embodiment, the lower coating layer contains an electron transport material represented by the general formula (P) with excellent electron transport properties and low hole transport properties, so that the film thickness can be made thicker than the existing lower coating layer (for example, set to more than 5 μm). Therefore, even in the case where the needle-shaped foreign matter punctures the lower coating layer from the surface of the electrophotographic photoreceptor, it is difficult to generate leakage current, so that the charge maintenance is excellent.

[0272] When the thickness of the undercoat layer is 15 μm or less, leakage current is generated in the body and the charge remaining in the undercoat layer increases, thereby suppressing dark decay. As a result, it is considered that the charge retention is more excellent.

[0273] [Conductive substrate]

[0274] As the conductive substrate, for example, 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.) can be cited. In addition, as the conductive substrate, for example, conductive compounds (such as conductive polymers, indium oxide, etc.); paper coated, vapor-deposited or laminated with metals (such as aluminum, palladium, gold, etc.) or alloys; resin films; belts, etc. Here, "conductive" means that the volume resistivity is less than 10 13 Ω·cm.

[0275] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to 0.04 μm or more and 0.5 μm or less in terms of center line average roughness Ra for the purpose of suppressing interference fringes generated when irradiating a laser beam. In addition, when incoherent light is used as a light source, roughening to prevent interference fringes is not particularly necessary, but the generation of defects caused by the unevenness of the conductive substrate surface is suppressed, so it is suitable for a longer life.

[0276] Examples of the roughening method include wet grinding in which an abrasive is suspended in water and sprayed onto the conductive substrate, centerless grinding in which the conductive substrate is pressed against a rotating grinding wheel and continuously ground, and anodizing.

[0277] As a method of roughening, there is also a method in which, without roughening the surface of the conductive substrate, conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and roughening is performed by particles dispersed in the layer.

[0278] The roughening treatment based on anodization is to use a metal (e.g., aluminum) conductive substrate as an anode and perform anodization in an electrolyte solution, thereby forming an oxide film on the surface of the conductive substrate. As an electrolyte solution, for example, sulfuric acid solution, oxalic acid solution, etc. can be cited. However, the porous anodized film formed by anodization has chemical activity in its original state, is easily contaminated, and the resistance change caused by the environment is also large. Therefore, for example, it is preferred that the porous anodized film is blocked by the volume expansion caused by water and reaction in pressurized water vapor or boiling water (metal salts such as nickel can be added) to change the micropores of the oxide film to the sealing treatment of a more stable hydrated oxide.

[0279] The film thickness of the anodized film is preferably, for example, 0.3 μm or more and 15 μm or less. When the film thickness is within the above range, the barrier property against injection tends to function and the increase in residual potential due to repeated use tends to be suppressed.

[0280] The conductive substrate may be subjected to a treatment using an acidic treatment liquid or a boehmite treatment.

[0281] The treatment based on the acidic treatment liquid is implemented, for example, in the following manner. First, an acidic treatment liquid containing phosphoric acid, chromic acid and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid and hydrofluoric acid in the acidic treatment liquid is, for example, in the range of 10 mass % or more and 11 mass % or less for phosphoric acid, in the range of 3 mass % or more and 5 mass % or less for chromic acid, and in the range of 0.5 mass % or more and 2 mass % or less for hydrofluoric acid, and the concentration of the total amount of these acids is, for example, preferably in the range of 13.5 mass % or more and 18 mass % or less. The treatment temperature is, for example, preferably in the range of 42° C. or more and 48° C. or less. The film thickness of the film is, for example, preferably in the range of 0.3 μm or more and 15 μm or less.

[0282] The boehmite treatment is carried out, for example, by immersing in pure water at 90°C to 100°C for 5 to 60 minutes or contacting in heated water vapor at 90°C to 120°C for 5 to 60 minutes. The film thickness of the film is preferably 0.1 μm to 5 μm. An anodizing treatment can be further performed using an electrolyte solution with low film solubility such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0283] (Middle layer)

[0284] Although not shown in the figure, an intermediate layer may be provided between the undercoat layer and the photosensitive layer.

[0285] The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include acetal resins (e.g., polyvinyl butyral), 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, melamine resins and other polymer compounds.

[0286] The intermediate layer may be a layer containing an organic metal compound. Examples of the organic metal compound used in the intermediate layer include organic metal compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.

[0287] The compounds used in the intermediate layer may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0288] Among them, the intermediate layer is preferably a layer containing an organic metal compound containing zirconium atoms or silicon atoms, for example.

[0289] The formation of the intermediate layer is not particularly limited and a known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of an intermediate layer-forming coating liquid prepared by adding the above components to a solvent, drying the coating film, and heating as necessary.

[0290] As a coating method for forming the intermediate layer, a common method such as a dip coating method, a push coating method, a wire bar coating method, a spray coating method, a blade coating method, an air knife coating method, a curtain coating method, etc. can be used.

[0291] The film thickness of the intermediate layer is preferably set within a range of, for example, 0.1 μm or more and 3 μm or less.

[0292] (Charge Generation Layer)

[0293] The charge generating layer is, for example, a layer containing a charge generating material and a binder resin. Furthermore, the charge generating layer may be a vapor-deposited layer of the charge generating material. The vapor-deposited layer of the charge generating material is suitable for the case where an incoherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array is used.

[0294] Examples of the charge generating material include azo pigments such as disazo and trisazo; condensed ring aromatic pigments such as dibromoanthraquinone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0295] Among them, in order to cope with laser exposure in the near-infrared region, metal phthalocyanine pigments or metal-free phthalocyanine pigments are preferably used as charge generating materials, and more specifically, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and oxytitanium phthalocyanine are more preferred.

[0296] On the other hand, in order to cope with laser exposure in the near-ultraviolet region, preferred charge generating materials include condensed ring aromatic pigments such as dibromoanthraquinone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and disazo pigments.

[0297] Even when using an incoherent light source such as an LED or an organic EL image array whose central wavelength of light emission is within the range of 450nm to 780nm, the above-mentioned charge generating material can be used. However, from the viewpoint of resolution, when a photosensitive layer is used as a thin film of 20μm or less, the electric field intensity in the photosensitive layer becomes high, and the charge is reduced due to the injection of charges from the substrate, which easily causes image defects called black spots. This becomes significant when using a charge generating material that easily generates dark current in a p-type semiconductor such as trigonal selenium and phthalocyanine pigments.

[0298] On the other hand, when an n-type semiconductor such as a condensed aromatic pigment, perylene pigment, or azo pigment is used as a charge generating material, dark current is less likely to be generated, and image defects called black spots can be suppressed even in a thin film.

[0299] The n-type is determined by using the commonly used time-of-flight method based on the polarity of the photocurrent flowing, and a semiconductor in which electrons flow more easily as carriers than holes is defined as the n-type.

[0300] The binder resin used in the charge generating layer can be selected from a wide range of insulating resins, and can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinyl anthracene, polyvinyl pyrene, and polysilane.

[0301] Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (condensation products of bisphenols and aromatic dicarboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, etc. Here, "insulation" means that the volume resistivity is 10 13 Ω·cm or more.

[0302] These binder resins may be used alone or in combination of two or more.

[0303] The mixing ratio of the charge generating material to the binder resin is preferably in the range of 10:1 to 1:10, for example, in terms of mass ratio.

[0304] Other well-known additives may be contained in the charge generating layer.

[0305] The formation of the charge generating layer is not particularly limited, and a known formation method can be used, but for example, it can be performed by forming a coating film of a charge generating layer-forming coating liquid in which the above-mentioned components are added to a solvent, drying the coating film, and heating as needed. In addition, the charge generating layer can be formed by vapor deposition of the charge generating material. The formation of the charge generating layer by vapor deposition is particularly suitable for the case where a condensed ring aromatic pigment or a perylene pigment is used as the charge generating material.

[0306] Examples of the solvent used for preparing the charge generating layer-forming coating solution 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, dichloromethane, chloroform, chlorobenzene, toluene, etc. These solvents may be used alone or in combination of two or more.

[0307] As a method for dispersing particles (e.g., charge generating material) in the coating liquid for forming the charge generating layer, for example, a medium disperser such as a ball mill, a vibrating ball mill, a grinder, a sand mill, a horizontal sand mill, or a stirrer, an ultrasonic disperser, a roll mill, a high-pressure homogenizer, or a medium-free disperser can be used. As a high-pressure homogenizer, for example, a collision method in which the dispersion is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion is dispersed by penetrating a fine flow path under high pressure, etc. can be cited.

[0308] In the dispersion, it is effective to set the average particle size of the charge generating material in the charge generating layer forming coating liquid to 0.5 μm or less, for example, preferably 0.3 μm or less, more preferably 0.15 μm or less.

[0309] Examples of a method for applying the charge generating layer forming coating liquid onto the undercoat layer (or the intermediate layer) include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0310] The film thickness of the charge generating layer is preferably set within the range of, for example, 0.1 μm to 5.0 μm, and more preferably within the range of 0.2 μm to 2.0 μm.

[0311] (Charge Transport Layer)

[0312] The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may be a layer containing a polymer charge transport material.

[0313] As charge transport materials, there can be cited quinone compounds such as p-benzoquinone, chloranil, tetrabromobenzoquinone, anthraquinone, etc.; tetracyanoterephthalene compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; anthrone compounds; benzophenone compounds; cyanoethylene compounds; vinyl compounds and other electron transport compounds. As charge transport materials, there can also be cited triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted vinyl compounds, stilbene compounds, anthracene compounds, hydrazone compounds and other hole transport compounds. These charge transport materials can be used alone or in combination of two or more, but are not limited thereto.

[0314] From the viewpoint of charge mobility, the charge transport material is preferably, for example, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2).

[0315] [Chemical formula 10]

[0316]

[0317] In the 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 -C6H4-CH=CH-CH=C(R T7 )(R T8 ). 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.

[0318] Examples of substituents of the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. In addition, examples of substituents of the above groups include substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms.

[0319] [Chemical formula 11]

[0320]

[0321] In the structural formula (a-2), RT91 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 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted by an alkyl group having 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 ), R T12 , R T13 , R T14 , R T15 and R T16 Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, ​​Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less.

[0322] Examples of substituents of the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. In addition, examples of substituents of the above groups include substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms.

[0323] Here, from the viewpoint of charge mobility, among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), for example, those having "-C6H4-CH=CH-CH=C(R T7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 )" benzidine derivatives.

[0324] As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinyl carbazole and polysilane can be cited. In particular, polyester-based polymer charge transport materials are particularly preferred. The polymer charge transport material can be used alone or in combination with a binder resin.

[0325] The binder resin used in the charge transport layer can be 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-vinyl carbazole, polysilane, etc. Among them, as a binder resin, for example, preferably polycarbonate resin or polyarylate resin. These binder resins are used alone or in combination of two or more.

[0326] The mixing ratio of the charge transport material to the binder resin is preferably, for example, 10:1 to 1:5 in terms of mass ratio.

[0327] Other well-known additives may be contained in the charge transport layer.

[0328] The charge transport layer can be formed by any known method without particular limitation, but can be formed by, for example, forming a coating film of a charge transport layer-forming coating liquid prepared by adding the above components to a solvent, drying the coating film, and heating as necessary.

[0329] As the solvent for preparing the coating solution for forming the charge transport layer, there can be mentioned aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and dichloroethane; cyclic or linear ethers such as tetrahydrofuran and diethyl ether, and other common organic solvents. These solvents can be used alone or in combination of two or more.

[0330] Examples of a coating method for coating the charge transport layer-forming coating liquid on the charge generating layer include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0331] The film thickness of the charge transport layer is preferably set within the range of, for example, 5 μm to 50 μm, and more preferably within the range of 10 μm to 30 μm.

[0332] (Protective layer)

[0333] The protective layer is provided on the photosensitive layer as required. The protective layer is provided, for example, to prevent chemical changes in the photosensitive layer during charging or to further improve the mechanical strength of the photosensitive layer.

[0334] Therefore, the protective layer may be, for example, a layer composed of a cured film (crosslinked film). Examples of these layers include the layers shown in the following 1) or 2).

[0335] 1) A layer consisting 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 a crosslinked body of the reactive group-containing charge transport material)

[0336] 2) A layer composed of a cured film of a composition comprising a non-reactive charge transport material and a non-charge transport material having a reactive group but not having a charge transport skeleton (i.e., a layer comprising a non-reactive charge transport material and a polymer or a crosslinked body of the non-charge transport material having a reactive group)

[0337] Examples of the reactive group of the charge transport material containing a reactive group include a chain polymerizable group, an epoxy group, -OH, -OR [wherein R represents an alkyl group], -NH2, -SH, -COOH, -SiR Q1 3-Qn (OR Q2 ) Qn [Among them, 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, a trialkylsilyl group, and Qn represents an integer of 1 to 3] and the like.

[0338] As a chain polymerizable group, there is no particular limitation as long as it is a functional group capable of free radical polymerization, and for example, it is a functional group having a group containing at least a carbon double bond. Specifically, there can be mentioned a group containing at least one selected from vinyl, vinyl ether, vinyl sulfide, styryl (vinyl phenyl), acryloyl, methacryloyl and their derivatives. Among them, due to its excellent reactivity, as a chain polymerizable group, for example, it is preferably a group containing at least one selected from vinyl, styryl (vinyl phenyl), acryloyl, methacryloyl and their derivatives.

[0339] The charge transport skeleton of the charge transport material containing a reactive group is not particularly limited as long as it is a known structure in an electrophotographic photoreceptor, and examples thereof include skeletons derived from nitrogen-containing hole transport compounds such as triarylamine compounds, benzidine compounds, and hydrazone compounds, and structures conjugated with nitrogen atoms. Among them, for example, a triarylamine skeleton is preferred.

[0340] The reactive group-containing charge transport material, the non-reactive charge transport material, and the reactive group-containing non-charge transport material having these reactive groups and charge transport skeletons may be selected from known materials.

[0341] Other well-known additives may be contained in the protective layer.

[0342] The protective layer can be formed by any known method without particular limitation, but can be formed by, for example, forming a coating film of a protective layer-forming coating liquid prepared by adding the above components to a solvent, drying the coating film, and performing a curing treatment such as heating as necessary.

[0343] Examples of the solvent used to prepare the protective layer-forming coating solution 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; alcohol solvents such as isopropyl alcohol and butanol, etc. These solvents may be used alone or in combination of two or more.

[0344] In addition, the protective layer-forming coating liquid may be a solvent-free coating liquid.

[0345] Examples of a method for applying the protective layer-forming coating liquid onto a photosensitive layer (eg, charge transport layer) include common methods such as dip coating, push coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating.

[0346] The film thickness of the protective layer is preferably set within the range of, for example, 1 μm to 20 μm, and more preferably within the range of 2 μm to 10 μm.

[0347] [Single-layer photosensitive layer]

[0348] The single-layer photosensitive layer (charge generation / charge transport layer) is, for example, a layer containing a charge generation material, a charge transport material, and, if necessary, a binder resin and other known additives. These materials are the same as those described for the charge generation layer and the charge transport layer.

[0349] In the single-layer photosensitive layer, the content of the charge generating material relative to the total solid content may be, for example, 0.1% by mass or more and 10% by mass or less, preferably 0.8% by mass or more and 5% by mass or less. In addition, in the single-layer photosensitive layer, the content of the charge transporting material relative to the total solid content may be, for example, 5% by mass or more and 50% by mass or less.

[0350] The method for forming the single-layer photosensitive layer is the same as the method for forming the charge generating layer or the charge transporting layer.

[0351] The film thickness of the single-layer photosensitive layer may be, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 40 μm or less.

[0352] [Image forming apparatus, process cartridge]

[0353] The image forming apparatus according to the present embodiment comprises 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 a toner to form a toner image, and a transfer device for transferring the toner image to the surface of a recording medium. As the electrophotographic photoreceptor, the electrophotographic photoreceptor according to the present embodiment is applied.

[0354] The image forming apparatus involved in this embodiment is applicable to the following well-known image forming apparatuses: an apparatus equipped with a fixing device for fixing a toner image transferred to the surface of a recording medium; an apparatus using a direct transfer method for directly transferring a toner image formed on the surface of an electrophotographic photosensitive body to a recording medium; an apparatus using an intermediate transfer method for transferring a toner image formed on the surface of an electrophotographic photosensitive body once to the surface of an intermediate transfer body, and for a second time transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium; an apparatus equipped with a cleaning device for cleaning the surface of the electrophotographic photosensitive body after transferring the toner image but before charging; an apparatus equipped with a static elimination device for removing static electricity by irradiating the surface of the electrophotographic photosensitive body with static elimination light after transferring the toner image and before charging; and an apparatus equipped with an electrophotographic photosensitive body heating component for increasing the temperature of the electrophotographic photosensitive body and lowering the relative temperature, etc.

[0355] In the case of an intermediate transfer type device, the transfer device, for example, is applicable to the following structure, which has an intermediate transfer body that transfers the toner image on the surface, a primary transfer device that transfers the toner image formed on the surface of the electronic photographic photosensitive body to the surface of the intermediate transfer body for the first time, and a secondary transfer device that transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium for the second time.

[0356] The image forming apparatus according to the present embodiment may be any of a dry developing system image forming apparatus and a wet developing system (development system using a liquid developer) image forming apparatus.

[0357] In addition, in the image forming apparatus according to the present embodiment, for example, the portion having the electrophotographic photosensitive body may be a box structure (processing box) that can be loaded and unloaded relative to the image forming apparatus. As the processing box, for example, a processing box having the electrophotographic photosensitive body according to the present embodiment is preferably used. In addition, in the processing box, in addition to the electrophotographic photosensitive body, for example, 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 may be provided.

[0358] Hereinafter, an example of the image forming apparatus according to the present embodiment is shown, but the present invention is not limited thereto. In addition, the main parts shown in the drawings are described, and the description of other parts is omitted.

[0359] Figure 2 It is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment.

[0360] like Figure 2 As shown, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 having an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In addition, in the image forming apparatus 100, the exposure device 9 is arranged at a position capable of exposing the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, and the transfer device 40 is arranged at a position opposed to the electrophotographic photoreceptor 7 with the intermediate transfer body 50 interposed therebetween, and the intermediate transfer body 50 is arranged so that a part thereof contacts the electrophotographic photoreceptor 7. Although not shown in the figure, a secondary transfer device is further provided for transferring the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). In addition, the intermediate transfer body 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown in the figure) correspond to an example of a transfer device.

[0361] Figure 2 The process box 300 in the embodiment integrally supports the electrophotographic photoreceptor 7, the charging device 8 (an example of a charging device), the developing device 11 (an example of a developing device), and the cleaning device 13 (an example of a cleaning device) in the housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is configured to contact the surface of the electrophotographic photoreceptor 7. In addition, the cleaning member may be a conductive or insulating fibrous member instead of the cleaning blade 131, and it may be used alone or in combination with the cleaning blade 131.

[0362] In addition, Figure 2 In the example shown, as the image forming apparatus, a fibrous member 132 (roller-shaped) for supplying lubricant 14 to the surface of electrophotographic photoreceptor 7 and a fibrous member 133 (flat brush-shaped) for assisting cleaning are provided, but these may be arranged as necessary.

[0363] Hereinafter, each structure of the image forming apparatus according to the present embodiment will be described.

[0364] -Electrified Devices-

[0365] As the charging device 8, for example, a contact type charging device such as a charging roller, a charging brush, a charging film, a charging rubber blade, a charging hose, etc. using conductive or semi-conductive charging can be used. In addition, a non-contact type roller charging device, a scorotron charging device or a corotron charging device using corona discharge, etc., which are known per se, can also be used.

[0366] -Exposure device-

[0367] As the exposure device 9, for example, there can be cited an optical system device that exposes semiconductor laser, LED light, liquid crystal shutter light, etc. on the surface of the electrophotographic photoreceptor 7 to a prescribed pattern. The wavelength of the light source is set within the spectral sensitivity region of the electrophotographic photoreceptor. As the wavelength of the semiconductor laser, near-infrared light with an oscillation wavelength near 780nm is the mainstream. However, it is not limited to this wavelength. As an oscillation wavelength laser or a blue laser in the 600nm band, a laser with an oscillation wavelength in the range of more than 400nm and less than 450nm can also be used. In addition, a surface-emitting laser light source of the type that can output multiple beams in order to form a color image is also effective.

[0368] -Developing device-

[0369] As the developing device 11, for example, a general developing device that develops by contact or non-contact with a developer can be cited. As the developing device 11, there is no particular limitation as long as it has the above-mentioned function, and it can be selected according to the purpose. For example, a known developer having a function of attaching a single-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, a roller, etc. can be cited. Among them, for example, a developer using a developing roller that holds the developer on the surface is preferred.

[0370] The developer used in the developing device 11 may be a single-component developer containing only a toner, or may be a two-component developer containing a toner and a carrier. Furthermore, the developer may be magnetic or non-magnetic. As these developers, well-known developers are applicable.

[0371] -Cleaning device-

[0372] The cleaning device 13 may be a cleaning blade type device including a cleaning blade 131 .

[0373] In addition to the cleaning blade method, a brush cleaning method and a simultaneous development and cleaning method may also be used.

[0374] -Transfer device-

[0375] Examples of the transfer device 40 include a contact transfer charger using a belt, a roller, a film, a rubber blade, etc.; a corotron transfer charger using corona discharge; a corotron transfer charger, etc., which are known per se.

[0376] -Intermediate transfer body-

[0377] As the intermediate transfer body 50, a belt-shaped transfer body (intermediate transfer belt) made of polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. imparted with semiconductivity can be used. In addition, as a form of the intermediate transfer body, a roller-shaped transfer body can be used.

[0378] Figure 3 It is a schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment.

[0379] Figure 3 The image forming apparatus 120 shown is a multi-color image forming apparatus of a tandem type equipped with four process cartridges 300. In the image forming apparatus 120, four process cartridges 300 are arranged on the intermediate transfer body 50, respectively, and a single electrophotographic photoreceptor is used for each color. In addition, the image forming apparatus 120 has the same structure as the image forming apparatus 100 except for the tandem type.

[0380] Example

[0381] The following examples are given to further specifically illustrate the electrophotographic photosensitive body of the present invention. The materials, usage amounts, ratios, processing steps, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the purpose of the present invention. Therefore, the scope of the electrophotographic photosensitive body of the present invention should not be interpreted in a restrictive manner by the specific examples shown below.

[0382] -Preparation of electron transport material-

[0383] (Preparation of Electron Transporting Material (1))

[0384] 6.4 parts by mass of the electron transport material represented by the general formula (P) having a crystal form of α-type (CCDC No.: CCDC196996), i.e., the exemplary compound (P-1: referred to as "P-1α" in the table), 72 parts by mass of zirconia beads with a diameter of 0.3 mm, and 1.0 parts by mass of sodium chloride were added to a zirconia container and pulverized at a rotation speed of 500 rpm for 2 hours using a planetary mill device (manufactured by Fritsch Co., Ltd.: P-7 CLASSICLINE). After pulverization, the zirconia beads were washed with 500 ml of distilled water while the particles were filtered and separated. The aqueous dispersion of the particles obtained by centrifugation was separated from the electron transport material by removing the water of the supernatant by decantation. The separated electron transport material was repeatedly washed with water until the conductivity became less than 10 μS / cm, and then dried in a freeze dryer for 48 hours to obtain an electron transport material (1) having the aspect ratio and average primary particle size shown in Table 1.

[0385] (Preparation of Electron Transporting Material (2))

[0386] In the preparation of the electron transport material (1), the electron transport material (2) was obtained by following the same steps except that the material used was changed from the exemplary compound (P-1) having an α-type crystal form to an exemplary compound (P-1: referred to as "P-1β" in the table) having a β-type crystal form (CCDC number: CCDC196997).

[0387] (Preparation of Electron Transporting Material (3))

[0388] In the preparation of the electron transporting material (1), the electron transporting material (3) was obtained by the same procedure except that the material used was changed to the crystal form (CCDC No.: CCDC798609) of the exemplary compound (Q-12).

[0389] (Preparation of Electron Transport Material (4))

[0390] In the preparation of the electron transport material (1), the pulverization step based on a planetary mill and the subsequent filtering and separation steps of the pulverized particles were omitted. Instead, the material was repeatedly washed with water until the conductivity became less than 10 μS / cm, and then dried in a freeze dryer for 48 hours. In addition, the same steps were followed to obtain the electron transport material (4).

[0391] (Preparation of Electron Transport Material (C1))

[0392] In the preparation of the electron transporting material (1), the electron transporting material (C1) was obtained by the same procedure except that the material used was changed to the following compound (D) having a crystal structure (COD number: COD8100240).

[0393] [Chemical formula 12]

[0394]

[0395] (Preparation of Electron Transport Material (C2))

[0396] In the preparation of the electron transporting material (1), an electron transporting material (C2) was obtained by the same procedure except that the material used was changed to the following compound (E) having a crystal structure (CCDC No.: CCDC1872270).

[0397] [Chemical formula 13]

[0398]

[0399] (Preparation of Electron Transport Material (C3))

[0400] In the preparation of the electron transporting material (4), the electron transporting material (C3) was obtained by the same procedure except that the material used was changed to the above-mentioned compound (D) having a crystal structure of COD8100240.

[0401] -Preparation of the bottom coating-

[0402] (Preparation of lower coating layer (1))

[0403] 60 parts of the electron transport material (1), 13.5 parts of a curing agent (blocked isocyanate, SUMIDUR 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.), 15 parts of a butyral resin (S-LECBM-1, manufactured by SEKISUI CHEMICAL CO., LTD.), and 85 parts of methyl ethyl ketone were mixed to obtain a mixed solution. 38 parts of the mixed solution was mixed with 25 parts of methyl ethyl ketone and the mixture was stirred for 2 hours. The glass beads were dispersed in a sand mill for 3 hours to obtain a dispersion.

[0404] 0.005 parts of dioctyltin dilaurate as a catalyst was added to the obtained dispersion to obtain an undercoat coating solution, which was applied to a cylindrical aluminum substrate by dip coating and dried and cured at 170° C. for 30 minutes to obtain an undercoat layer having a film thickness of 10 μm.

[0405] (Production of lower coating layer (2))

[0406] An undercoat layer (2) was obtained in the same manner as in the undercoat layer (1), except that the electron transporting material in the undercoat layer (1) was changed to the electron transporting material (2).

[0407] (Production of lower coating layer (3))

[0408] An undercoat layer (3) was obtained in the same manner as in the undercoat layer (1), except that the electron transporting material in the undercoat layer (1) was changed to the electron transporting material (3).

[0409] (Production of lower coating layer (4))

[0410] An undercoat layer (4) was obtained in the same manner as in the undercoat layer (1), except that the dispersion step using a sand mill in the undercoat layer (1) was changed to a dispersion step using a paint shaker for 2 hours.

[0411] (Production of lower coating layer (5))

[0412] An undercoat layer (5) was obtained in the same manner except that the electron transporting material (1) was changed to the electron transporting material (2) in the undercoat layer (4).

[0413] (Production of lower coating layer (6))

[0414] An undercoat layer (6) was obtained in the same manner except that the electron transporting material (1) was changed to the electron transporting material (3) in the undercoat layer (4).

[0415] (Production of lower coating layer (7))

[0416] An undercoat layer (7) was obtained in the same manner except that the electron transporting material (1) was changed to the electron transporting material (4) in the undercoat layer (4).

[0417] (Production of lower coating layers (8) to (9))

[0418] In the undercoat layer (1), except that the content of the electron transport material (1) relative to the total solid content of the undercoat layer was changed to the content shown in the table, undercoat layers (8) to (9) were obtained in the same manner.

[0419] (Production of lower coating layers (10) to (11))

[0420] In the undercoat layer (1), except that the thickness of the undercoat layer was changed to the thickness shown in the table, undercoat layers (10) to (11) were obtained in the same manner.

[0421] (Production of lower coating layer (12))

[0422] In the undercoat layer (1), an undercoat layer (12) was obtained in the same manner except that the specification was changed to 10% by mass in the ratio of the metal oxide.

[0423] (Preparation of Undercoat Layer (1) for Comparative Example)

[0424] In the undercoat layer (1), a comparative example undercoat layer (1) was obtained in the same manner except that the electron transporting material (1) was changed to the electron transporting material (C1).

[0425] (Preparation of Undercoat Layer (2) for Comparative Example)

[0426] In the undercoat layer (1), except that the electron transporting material (1) was changed to the electron transporting material (C2), a comparative example undercoat layer (2) was obtained in the same manner.

[0427] (Preparation of Undercoat Layer (3) for Comparative Example)

[0428] In the undercoat layer (1), a comparative example undercoat layer (3) was obtained in the same manner except that the electron transporting material (1) was changed to the electron transporting material (C3).

[0429] Table 1 shows the crystal density, FWHM, LUMO energy level and maximum value Nmax of the electron transport material in the undercoat layer, and the aspect ratio and average primary particle size of the electron transport material obtained by the above-mentioned measurement method.

[0430] In Table 1, the crystal density of the electron transporting material in the undercoat layer is referred to as “crystal density”.

[0431] In Table 1, the full width at half maximum of the maximum intensity peak in the X-ray diffraction spectrum of the undercoat layer measured in the thickness direction is referred to as “FWHM”.

[0432] In Table 1, "maximum value Nmax" refers to the value of the maximum value Nmax in the orientation index N represented by the above formula (1) when the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured from the thickness direction of the undercoat layer is set to I1, and the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured when the undercoat layer is in a powder state with a volume average particle size of less than 5 μm is set to I2.

[0433] In Table 1, "LUMO" refers to the energy level of LUMO of the undercoat layer.

[0434] In Table 1, the “content” in the item “electron transport material” refers to the content of the electron transport material relative to the total solid content of the undercoat layer.

[0435] In Table 1, “the ratio of the metal oxide” refers to the ratio of the metal oxide to the total solid content of the undercoat layer.

[0436] <Example 1 to Example 12 and Comparative Examples 1 to 3>

[0437] (Formation of Charge Generation Layer)

[0438] A mixture of 15 parts by mass of hydroxygallium phthalocyanine having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.3°, 16.0°, 24.9°, and 28.0° in an X-ray diffraction spectrum using Cukα characteristic X-rays as a charge generating material, 10 parts by mass of a vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar Company Limited) as a binder resin, and 200 parts by mass of n-butyl acetate was used as a diameter The glass beads were stirred in a sand mill for 4 hours to disperse them. 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 solution for forming a charge generation layer. The coating solution for forming a charge generation layer was dip-coated on the outer peripheral surface of the undercoat layer of the type shown in the table, and dried at 150° C. for 15 minutes to form a charge generation layer with a film thickness of 0.2 μm.

[0439] (Formation of Charge Transport Layer)

[0440] 38 parts by mass of the following charge transport agent (HT-1), 10 parts by mass of the following charge transport agent (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 fluorinated graft polymer (manufactured by TOAGOSEICO., LTD.: GF-500) as a dispersing aid were added to 800 parts by mass of tetrahydrofuran and dissolved, 8 parts by mass of tetrafluoroethylene resin (manufactured by DAIKIN INDUSTRIES, Ltd.: Luberon L5, average particle size 300 nm) were added, and a homogenizer (manufactured by IKA: ULTRA-TURRAX) was used to disperse at 5500 rpm for 2 hours to obtain a coating liquid for forming a charge transport layer. The coating liquid was applied to the charge generating layer and dried at 140°C for 40 minutes to form a charge transport layer with a film thickness of 30 μm. It was set as an electrophotographic photoreceptor.

[0441] [Chemical formula 14]

[0442]

[0443] [Chemical formula 15]

[0444]

[0445] In the formula, 15 and 85 represent molar ratios (mol %).

[0446] <Evaluation>

[0447] The electrophotographic photoreceptors of the examples or comparative examples were mounted on a modified image forming apparatus DocuCentre C5570 manufactured by FUJIFILM Business Innovation, and the following evaluations were performed.

[0448] -Evaluation of charge retention performance-

[0449] In an environment of temperature 20°C and relative humidity 40%, the photoreceptor was charged using a scorotron charger with a grid voltage of -800V, and 1 million images were output in a non-exposed state. Then, the photoreceptor was charged using a scorotron charger with a voltage of -800V and the potential was measured again 200msec later. The value (potential reduction) of the potential after 150msec was subtracted from the measured potential when the photoreceptor was charged at -800V initially was used as an index of charging property.

[0450] A: The measured potential exceeds -15V.

[0451] B: The measured potential is -15V or less and exceeds -18V.

[0452] C: The measured potential is -18 V or less and exceeds -20 V.

[0453] D: The measured potential is -20V or less and exceeds -22V.

[0454] E: The measured potential is -22 V or less.

[0455] -Evaluation of electron transport performance-

[0456] In an environment with a temperature of 20°C and a relative humidity of 40%, the photoreceptor was charged using a scorotron charger with a grid voltage of -700V and irradiated with a 780nm semiconductor laser at 4.0 erg / cm 2 After the light was applied, the potential was measured at a position corresponding to 70 msec after charging.

[0457] A: The potential after exposure exceeds -50 V.

[0458] B: The potential after exposure is -50 V or less and exceeds -57 V.

[0459] C: The potential after exposure is -57 V or less and exceeds -60 V.

[0460] D: The potential after exposure is -60 V or less and exceeds -65 V.

[0461] E: The potential after exposure is -65 V or less.

[0462]

[0463] As shown in Table 1, the electrophotographic photoreceptor of the example is found to have better electron transport properties than the electrophotographic photoreceptor of the comparative example. Also, the electrophotographic photoreceptor of the example is found to have better charge retention properties than the electrophotographic photoreceptor of the comparative example.

[0464] This embodiment includes the following aspects.

[0465] (1) An electrophotographic photoreceptor comprising:

[0466] Conductive substrate;

[0467] A lower coating layer is disposed on the conductive substrate; and

[0468] A photosensitive layer is disposed on the lower coating layer,

[0469] The lower coating layer contains a bonding resin and a crystal density of 1.62 g / cm 3 The electron transporting material has a full width at half maximum (FWHM) of a maximum intensity peak in an X-ray diffraction spectrum measured in the thickness direction of 5.0° or less.

[0470] (2) The electrophotographic photoreceptor according to (1), wherein

[0471] The electron transport material has an aspect ratio of 1.0 to 2.5.

[0472] (3) The electrophotographic photoreceptor according to (2), wherein

[0473] The electron transport material has an aspect ratio of 1.5 to 2.3.

[0474] (4) The electrophotographic photoreceptor according to (1), wherein

[0475] When the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction of the undercoat layer is defined as I1,

[0476] When the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured when the undercoat layer is in a powder state with a volume average particle size of 5 μm or less is defined as I2, the maximum value Nmax in the orientation index N represented by the following formula (1) is greater than or equal to 1.0 and less than or equal to 5.5.

[0477] [Formula 3]

[0478]

[0479] (5) The electrophotographic photoreceptor according to (1), wherein

[0480] The LUMO energy level of the undercoat layer is 3.8 eV or more and 4.2 eV or less.

[0481] (6) The electrophotographic photoreceptor according to (1), wherein

[0482] The electron transport material includes at least one of an electron transport material represented by the following general formula (P) and an electron transport material represented by the following general formula (Q).

[0483] [Chemical formula 16]

[0484]

[0485] 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.

[0486] In the above general formula (Q), R 51 and R 52 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.

[0487] (7) The electrophotographic photoreceptor according to (6), wherein

[0488] In the 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 or a halogen atom.

[0489] (8) The electrophotographic photoreceptor according to (6), wherein

[0490] In the general formula (Q), R 51 and R 52 Represents a hydrogen atom.

[0491] (9) The electrophotographic photoreceptor according to (1), wherein

[0492] The electron transport material has an average primary particle size of 500 nm or less.

[0493] (10) The electrophotographic photoreceptor according to (1), wherein

[0494] The content of the electron transport material is 60 mass % or more and 75 mass % or less relative to the total binder resin component of the undercoat layer.

[0495] (11) The electrophotographic photoreceptor according to (1), wherein

[0496] The undercoat layer has a thickness of 5 μm or more and 15 μm or less.

[0497] (12) The electrophotographic photoreceptor according to (1), wherein

[0498] The ratio of the metal oxide in the undercoat layer is 5 mass % or less relative to the total solid content of the undercoat layer.

[0499] (13) A process cartridge comprising the electrophotographic photoreceptor according to any one of (1) to (12), wherein:

[0500] The process cartridge is attachable to and detachable from the image forming apparatus.

[0501] (14) An image forming apparatus comprising:

[0502] The electrophotographic photoreceptor according to any one of (1) to (12);

[0503] A charging device for charging the surface of the electrophotographic photoreceptor;

[0504] An electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

[0505] a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and

[0506] The transfer device transfers the toner image to the surface of a recording medium.

[0507] According to the invention according to (1), there is provided a case where the full width at half maximum (FWHM) of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction of the undercoat layer containing a binder resin and an electron transporting material exceeds 5.0° or the crystal density of the electron transporting material is less than 1.62 g / cm3 Compared with the case of , an electrophotographic photoreceptor with excellent electron transport properties.

[0508] According to the invention as set forth in (2), there is provided an electrophotographic photoreceptor having an excellent electron transport property compared with a case where the aspect ratio of the electron transport material exceeds 2.5.

[0509] According to the invention as set forth in (3), there is provided an electrophotographic photoreceptor having an excellent electron transport property compared with a case where the aspect ratio of the electron transport material is less than 1.5 or exceeds 2.3.

[0510] According to the invention involved in (4), there is provided an electronic photographic photosensitive body having excellent electron transport properties, compared with a case where the value of the maximum value Nmax in the orientation index N represented by the formula (1) is less than 1.0 or greater than 5.5, when the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured for the undercoat layer in the thickness direction is set to I1 and the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured with the undercoat layer in a powder state with a volume average particle size of less than 5 μm is set to I2.

[0511] According to the invention as set forth in (5), there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the LUMO energy level of the undercoat layer is less than 3.8 eV or exceeds 4.2 eV.

[0512] According to the invention as set forth in (6), (7) or (8), there is provided an electrophotographic photoreceptor having an excellent electron transport property compared with a case where the electron transport material contains the following compound (D) or compound (E).

[0513] [Chemical formula 17]

[0514]

[0515] According to the invention as set forth in (9), there is provided an electrophotographic photoreceptor having an excellent electron transport property compared with a case where the average primary particle size of the electron transport material exceeds 500 nm.

[0516] According to the invention as set forth in (10), there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the content of the electron transport material is less than 60% by mass or more than 75% by mass based on the total binder resin component of the undercoat layer.

[0517] According to the invention as set forth in (11), there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the thickness of the undercoat layer is less than 5 μm or exceeds 15 μm.

[0518] According to the invention as set forth in (12), there is provided an electrophotographic photoreceptor having excellent electron transport properties compared with a case where the ratio of the metal oxide in the undercoat layer exceeds 5% by mass based on the total solid content of the undercoat layer.

[0519] According to the invention of (13) or (14), there is provided an electrophotographic photoreceptor having an undercoat layer containing a binder resin and an electron transporting material, wherein the full width at half maximum (FWHM) of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction exceeds 5.0°, or an electrophotographic photoreceptor having a crystal density of the electron transporting material of less than 1.62 g / cm 3 A process cartridge or an image forming apparatus including an electrophotographic photoreceptor having excellent electron transport properties is provided compared to a process cartridge or an image forming apparatus including an electrophotographic photoreceptor having excellent electron transport properties.

[0520] The above-mentioned embodiments of the present invention are provided for the purpose of illustration and description. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed methods. Obviously, various modifications and changes are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily understand the principles of the present invention and its application. Thus, other technicians in the art can understand the present invention through various variations optimized for specific uses assumed to be various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. An electrophotographic photoreceptor comprising: Conductive substrate; A lower coating layer is disposed on the conductive substrate; and A photosensitive layer is disposed on the lower coating layer, The lower coating layer contains a bonding resin and a crystal density of 1.62 g / cm 3 The electron transporting material has a full width at half maximum (FWHM) of a maximum intensity peak in an X-ray diffraction spectrum measured in the thickness direction of 5.0° or less.

2. The electrophotographic photoreceptor according to claim 1, wherein The electron transport material has an aspect ratio of 1.0 to 2.

5.

3. The electrophotographic photoreceptor according to claim 2, wherein The electron transport material has an aspect ratio of 1.5 to 2.

3.

4. The electrophotographic photoreceptor according to claim 1, wherein When the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured in the thickness direction of the undercoat layer is defined as I1, When the relative integrated intensity of the maximum intensity peak in the X-ray diffraction spectrum measured by making the undercoat layer in a powder state having a volume average particle size of 5 μm or less is defined as I2, the value of the maximum value Nmax in the orientation index N represented by the following formula (1) is 1.0 or more and 5.5 or less, [Formula 1] 5. The electrophotographic photoreceptor according to claim 1, wherein The LUMO energy level of the undercoat layer is 3.8 eV or more and 4.2 eV or less.

6. The electrophotographic photoreceptor according to claim 1, wherein The electron transport material includes at least one of an electron transport material represented by the following general formula (P) and an electron transport material represented by the following general formula (Q), [Chemical formula 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, In the above general formula (Q), R 51 and R 52 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.

7. The electrophotographic photoreceptor according to claim 6, wherein In the 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 or a halogen atom.

8. The electrophotographic photoreceptor according to claim 6, wherein In the general formula (Q), R 51 and R 52 Represents a hydrogen atom.

9. The electrophotographic photoreceptor according to claim 1, wherein The electron transport material has an average primary particle size of 500 nm or less.

10. The electrophotographic photoreceptor according to claim 1, wherein The content of the electron transport material is 60 mass % or more and 75 mass % or less relative to the total binder resin component of the undercoat layer.

11. The electrophotographic photoreceptor according to claim 1, wherein The undercoat layer has a thickness of 5 μm or more and 15 μm or less.

12. The electrophotographic photoreceptor according to claim 1, wherein The ratio of the metal oxide in the undercoat layer is 5 mass % or less relative to the total solid content of the undercoat layer.

13. A process cartridge comprising the electrophotographic photoreceptor according to any one of claims 1 to 12, wherein: The process cartridge is attachable to and detachable from the image forming apparatus.

14. An image forming apparatus comprising: The electrophotographic photoreceptor according to any one of claims 1 to 12; 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 charged surface of the electrophotographic photoreceptor; a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and The transfer device transfers the toner image to the surface of a recording medium.

Images