Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

An electrophotographic photoreceptor, a process cartridge, and an image forming apparatus, the electrophotographic photoreceptor including: a conductive substrate; an undercoat layer disposed on the conductive substrate; and a laminated photosensitive layer disposed on the undercoat layer and having a charge generation layer and a charge transport layer, the charge transport layer containing a charge transport material and a polyarylate resin, the polyarylate resin containing a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), the capacitance of the lower coating layer is 1.0 * 10 <-10 > F or more and 3.0 * 10 <-9 > F or less. [Chemical Formula 1] Formula (A) Formula (B)

Description

Technical Field

[0001] This invention relates to an electrophotographic photosensitive element, a processing cartridge, and an image forming apparatus. Background Technology

[0002] Patent Document 1 discloses an electrophotographic photosensitive material comprising: a support; a lower coating layer disposed on the support, comprising at least a binding resin, metal oxide particles, and an electron-receiving compound having an anthraquinone structure, wherein the electron-receiving compound comprises 0.5% by mass or more and 1.5% by mass or less relative to the metal oxide particles, and the contact angle of the metal oxide particles with water is 7 degrees or more and 12 degrees or less; and a photosensitive layer disposed on the lower coating layer.

[0003] Patent Document 2 discloses an electrophotographic photosensitive material comprising: a conductive substrate; a lower coating disposed on the conductive substrate and comprising a bonding resin, metal oxide particles and an electron-receiving compound having an anthraquinone skeleton represented by the following general formula (1A), wherein the reflectivity RL of light in the wavelength range of 470 nm and above and 510 nm and below is 2% and above and 5% and below; and a photosensitive layer disposed on the lower coating.

[0004] Patent document 3 discloses an electrophotographic photosensitive material comprising a conductive substrate, a lower coating layer disposed on the conductive substrate, a charge generating layer disposed on the lower coating layer, a charge transport layer disposed on the charge generating layer, and a protective layer disposed on the charge transport layer. The lower coating layer contains a conductive agent, and the number of primary particles of the conductive agent is 58% or less relative to the total number of primary and secondary particles of the conductive agent. The charge mobility μ(CTL) of the charge transport layer and the charge mobility μ(OCL) of the protective layer satisfy μ(CTL) ≥ 1.0 × 10⁻⁶. -5 (cm 2 / Vs) and μ(OCL)≥0.68×10 -5 (cm 2 / Vs).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-242483

[0006] Patent Document 2: Japanese Patent No. 6838324

[0007] Patent Document 3: Japanese Patent Application Publication No. 2024-043372 Summary of the Invention

[0008] The objective of this invention is to provide an electrophotographic photoreceptor in which the capacitance of the undercoat is less than 1.0 × 10⁻⁶, comprising a conductive substrate, an undercoat disposed on the conductive substrate, and a charge-generating layer and a charge-transfer layer disposed on the undercoat, wherein the charge-transfer layer contains a charge-transfer material and a polyaryl resin comprising a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B). -10 F or more than 3.0 × 10 -9 Compared to case F, an electrophotographic photoreceptor is provided in which potential changes after the formation of an electrostatic latent image are suppressed.

[0009] The specific means used to solve the problem include the following methods.

[0010] <1>

[0011] An electrophotographic photosensitive material, comprising:

[0012] Conductive substrate;

[0013] The lower coating layer is disposed on the conductive substrate; and

[0014] A stacked photosensitive layer is disposed on the lower coating layer and has a charge generation layer and a charge transport layer.

[0015] The charge transport layer contains a charge transport material and a polyarylate resin.

[0016] The polyaryl ester resin comprises a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B).

[0017] The electrostatic capacitance of the lower coating is 1.0 × 10⁻⁶. -10 F or higher and 3.0 × 10 -9 Below F,

[0018] [Chemical Formula 1]

[0019]

[0020] In equation (A), Ar A1 and Ar A2 Each is an aromatic ring that can have substituents, L A It is a single bond or a divalent linker, n A1 It can be 0, 1, or 2;

[0021] In equation (B), Ar B1 and Ar B2 Each is an aromatic ring that can have substituents, L B It is a single bond, an oxygen atom, a sulfur atom, or -C(Rb) 1 (Rb) 2)-,n B1 It can be 0, 1, or 2; Rb 1 and Rb 2 Rb is independently composed of hydrogen atoms, an alkyl group having 1 or more but less than 20 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an aralkyl group having 7 or more but less than 20 carbon atoms. 1 With Rb 2 They can bond together to form cyclic alkyl groups.

[0022] <2>

[0023] According to the electrophotographic photosensitive material described in <1>, wherein...

[0024] The relative permittivity of the charge transport layer is above 3.0 and below 5.0.

[0025] <3>

[0026] According to the electrophotographic photosensitive material described in <1> or <2>, wherein,

[0027] The ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat layer, i.e., the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat layer, is 0.010 or more and 0.400 or less.

[0028] <4>

[0029] According to any one of <1> to <3>, the electrophotographic photosensitive material, wherein,

[0030] The undercoat comprises zinc oxide particles imparting an electron-receiving compound, which are 62% by mass or more and 75% by mass or less relative to the undercoat.

[0031] <5>

[0032] According to the electrophotographic photosensitive material described in <4>, wherein...

[0033] The electron-accepting compound is an anthraquinone derivative having three OH groups or two OH groups and one alkoxy group.

[0034] <6>

[0035] According to the electrophotographic photosensitive material described in <5>, wherein...

[0036] The anthraquinone derivative is an alizarin derivative represented by formula (C).

[0037] [Chemical Formula 2]

[0038]

[0039] In formula (C), R represents a hydroxyl group or an alkoxy group with 1 or more but less than 10 carbon atoms.

[0040] <7>

[0041] According to any one of <1> to <6>, the electrophotographic photosensitive material, wherein,

[0042] The thickness of the lower coating layer is greater than 17 μm and less than 35 μm.

[0043] <8>

[0044] According to any one of <1> to <7>, the electrophotographic photosensitive material, wherein,

[0045] The charge transport layer also comprises polycarbonate resin.

[0046] The polyaryl ester resin and the polycarbonate resin each have structural units comprising biphenyl represented by the following formula (BP).

[0047] [Chemical Formula 3]

[0048]

[0049] In equation (BP), j is an integer greater than 0 and less than 4, and j are R... 1 Each is independently methyl or ethyl, k is an integer greater than or equal to 0 and less than or equal to 4, and k R's are independent of each other. 2 Each can be methyl or ethyl, independently.

[0050] <9>

[0051] A processing box comprising the electrophotographic photosensitive element as described in any one of <1> to <8>,

[0052] The processing box is mounted and dismounted from the image forming apparatus.

[0053] <10>

[0054] An image forming apparatus comprising: an electrophotographic photoreceptor as described in any one of <1> to <8>; a charging unit for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming unit for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing unit for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developing agent containing a toner to form a toner image; and a transfer unit for transferring the toner image onto the surface of a recording medium.

[0055] Invention Effects

[0056] According to the invention described in <1>, a laminated photosensitive layer comprises a conductive substrate, an undercoat disposed on the conductive substrate, and a charge generation layer and a charge transport layer disposed on the undercoat. The charge transport layer contains a charge transport material and a polyaryl ester resin. The polyaryl ester resin comprises a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B). The capacitance of the undercoat is less than 1.0 × 10⁻⁶. -10 F or more than 3.0 × 10 -9 Compared to case F, an electrophotographic photoreceptor is provided in which potential changes after the formation of an electrostatic latent image are suppressed.

[0057] According to the invention described in <2>, an electrophotographic photoreceptor is provided in which potential variations after the formation of an electrostatic latent image are suppressed, compared to cases where the relative permittivity of the charge transport layer is less than 3.0 or greater than 5.0.

[0058] According to the invention described in <3>, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed, compared to cases where the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat (relative permittivity of the charge transport layer / relative permittivity of the undercoat) is less than 0.010 or greater than 0.400.

[0059] According to the invention described in <4>, compared to the case where the undercoat contains zinc oxide particles endowed with electron-receptive compounds in an amount of less than 62% by mass or more than 75% by mass, an electrophotographic photoreceptor is provided in which potential variations after electrostatic latent image formation are suppressed.

[0060] According to the invention described in <5>, compared with the case where the electron-receiving compound is an anthraquinone derivative that does not have 3 OH groups or does not have 2 OH groups and has 1 alkoxy group, an electron photosensitive material is provided in which potential changes after electrostatic latent image formation are suppressed.

[0061] According to the invention described in <6>, compared with the case where the anthraquinone derivative is an alizarin derivative that does not satisfy the structure represented by formula (C), an electrophotographic photoreceptor is provided in which potential changes after the formation of an electrostatic latent image are suppressed.

[0062] According to the invention described in <7>, an electrophotographic photoreceptor is provided in which potential variations after electrostatic latent image formation are suppressed, compared to cases where the thickness of the undercoating layer is less than 17 μm or more than 35 μm.

[0063] According to the invention described in <8>, compared with the case where polyarylate resin and polycarbonate resin do not have structural units containing biphenyl, an electrophotographic photosensitive material is provided in which potential changes after electrostatic latent image formation are suppressed.

[0064] According to the invention described in <9> or <10>, a laminated photosensitive layer comprising a conductive substrate, an undercoat disposed on the conductive substrate, and a charge generation layer and a charge transport layer disposed on the undercoat, wherein the charge transport layer contains a charge transport material and a polyaryl ester resin, the polyaryl ester resin comprising a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), and the capacitance of the undercoat is less than 1.0 × 10⁻⁶. -10 F or more than 3.0 × 10 -9 Compared to case F, a processing box or image forming apparatus for an electrophotographic photoreceptor is provided that suppresses potential changes after electrostatic latent image formation. Attached Figure Description

[0065] The embodiments of the present invention will be described in detail with reference to the following figures.

[0066] Figure 1 This is a partial cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor according to this embodiment;

[0067] Figure 2 This is a schematic structural diagram illustrating an example of the image forming apparatus according to this embodiment;

[0068] Figure 3 This is a schematic structural diagram showing another example of the image forming apparatus according to this embodiment.

[0069] Symbol Explanation

[0070] 1-Conductive substrate, 2-Undercoat layer, 3-Charge generating layer, 4-Charge transport layer, 5-Photosensitive layer, 10A-Photosensitive material; 7-Electrophotographic photosensitive material, 8-Charging device, 9-Exposure device, 11-Developing device, 13-Cleaning device, 14-Lubricant, 40-Transfer device, 50-Intermediate transfer material, 100-Image forming device, 120-Image forming device, 131-Cleaning scraper, 132-Fiber component (roller), 133-Fiber component (flat brush), 300-Processing box. Detailed Implementation

[0071] The embodiments of the present invention will be described below. These descriptions and examples are illustrative and do not limit the scope of the embodiments.

[0072] In this invention, the numerical range represented by “~” indicates the range to be included by taking the values ​​before and after “~” as the minimum and maximum values, respectively.

[0073] In the numerical ranges described in stages in this invention, the upper or lower limit value of a numerical range can be replaced with the upper or lower limit value of other numerical ranges described in stages. Furthermore, within the numerical ranges described in this invention, the upper or lower limit value of that numerical range can be replaced with the values ​​shown in the embodiments.

[0074] In this invention, the term "process" includes not only independent processes, but also processes that can achieve their purpose, even if they cannot be clearly distinguished from other processes.

[0075] In this invention, when the embodiments are described with reference to the accompanying drawings, the structure of the embodiments is not limited to the structure shown in the drawings. Furthermore, the sizes of the components in the figures are conceptual, and the relative sizes of the components are not limited thereto.

[0076] In this invention, each component may contain multiple corresponding substances. When referring to the amount of each component in the composition in this invention, if multiple substances corresponding to each component are present in the composition, it refers to the total amount of the multiple substances present in the composition unless otherwise specified.

[0077] In this invention, a variety of particles corresponding to each component may be included. When a variety of particles corresponding to each component are present in the composition, unless otherwise specified, the particle size of each component represents a value relating to the mixture of the various particles present in the composition.

[0078] In this invention, unless otherwise specified, alkyl groups include straight-chain, branched-chain, and cyclic forms.

[0079] In this invention, regarding organic groups, aromatic rings, linking groups, alkyl groups, aryl groups, aralkyl groups, alkoxy groups, and aryloxy groups, the hydrogen atoms in the groups can be replaced by halogen atoms.

[0080] <Electronic Photoreceptor>

[0081] The electrophotographic photosensitive material (hereinafter also referred to as a photosensitive material) according to this embodiment includes a conductive substrate, a lower coating layer, and a stacked photosensitive layer having a charge generation layer and a charge transport layer. The lower coating layer is disposed on the conductive substrate. The stacked photosensitive layer is disposed above the lower coating layer. The charge transport layer includes a charge transport material and a polyarylate resin comprising a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B) described above. The capacitance of the lower coating layer is 1.0 × 10⁻⁶. -10 F or higher and 3.0 × 10 -9 Below F.

[0082] Furthermore, in the photoreceptor of this embodiment, the charge transport layer is the outermost layer.

[0083] The photoreceptor described in this embodiment, through the above-described structure, becomes a photoreceptor in which potential changes after the formation of an electrostatic latent image are suppressed. The reason for this is as follows.

[0084] To improve the charge-carrying capacity of the photoreceptor, it is effective to use a resin with a high dielectric constant in the charge transport layer. As one such resin, there is a polyarylate resin comprising a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B).

[0085] On the other hand, if a polyarylate resin with a high dielectric constant is used in the charge transport layer, the voltage applied to the charge transport layer decreases when the photoreceptor is charged, thus allowing trace amounts of charge carriers to remain. In particular, when images are repeatedly formed over a long period, potential fluctuations occur after the formation of an electrostatic latent image due to the influence of these trace amounts of residual charge carriers. These potential fluctuations cause image quality defects such as fogging (i.e., the formation of dot-like images in non-image areas) or ghosting (i.e., image retention due to the traces of previous images).

[0086] Therefore, in the photoreceptor according to this embodiment, in order to increase the voltage applied to the charge transport layer, the electrostatic capacity of the lower coating layer is increased.

[0087] In a multilayer photoreceptor, the voltage applied to each layer is calculated based on the reciprocal ratio of the capacitances of each layer. Therefore, increasing the capacitance of the lower layer increases the voltage applied to the charge transport layer.

[0088] Therefore, even when images are repeatedly formed over a long period of time, it is possible to suppress the residual trace carriers in the charge transport layer, thereby suppressing potential fluctuations after the formation of the electrostatic latent image.

[0089] Based on the above reasons, it is speculated that the photoreceptor involved in this embodiment is a photoreceptor in which potential changes after the formation of an electrostatic latent image are suppressed.

[0090] The following is a detailed description of the photoreceptor involved in this embodiment.

[0091] Figure 1 This is a partial cross-sectional view that schematically illustrates an example of the layer structure of the photoreceptor involved in this embodiment. Figure 1 The photoreceptor 10A shown has a stacked photosensitive layer. The photoreceptor 10A has a structure in which a lower coating layer 2, a charge generation layer 3, and a charge transport layer 4 are sequentially stacked on a conductive substrate 1. The charge generation layer 3 and the charge transport layer 4 constitute the photosensitive layer 5 (a so-called functionally separated photosensitive layer). The photoreceptor 10A may have an intermediate layer (not shown) between the lower coating layer 2 and the charge generation layer 3.

[0092] The following is a detailed description of each layer of the photoreceptor. Symbols are omitted in the description of each layer of the photoreceptor.

[0093] [Conductive substrate]

[0094] Examples of conductive substrates include metal plates, metal drums, and metal strips containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Furthermore, examples of conductive substrates include conductive compounds (e.g., conductive polymers, indium oxide, etc.); paper coated, vapor-deposited, or laminated with metals (e.g., aluminum, palladium, gold, etc.) or alloys; resin films; and tapes. Here, "conductivity" refers to a volume resistivity of less than 10 Ω·cm. 13 Ω·cm.

[0095] When an electrophotographic photosensitive material is used in a laser printer, to suppress interference fringes generated when the laser beam is irradiated, the surface of the conductive substrate is preferably roughened to, for example, 0.04 μm or more and 0.5 μm or less, based on the centerline average roughness Ra. Furthermore, when incoherent light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but suppressing defects caused by unevenness on the conductive substrate surface is beneficial for extending its lifespan.

[0096] Examples of roughening methods include wet grinding, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate onto a rotating grinding wheel and continuously grinding it; and anodizing.

[0097] As a roughening method, another example is a method in which conductive or semi-conductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate without roughening the surface of the conductive substrate, and roughening is achieved by the particles dispersed in the layer.

[0098] Anodizing-based roughening processes involve anolysing a conductive metallic substrate (e.g., aluminum) in an electrolyte solution, thereby forming an oxide film on the surface of the conductive substrate. Examples of electrolyte solutions include sulfuric acid and oxalic acid. However, the porous anodic oxide film formed by anodizing is chemically active in its original state, easily contaminated, and exhibits significant resistance variations due to environmental factors. Therefore, it is preferable, for example, to perform a sealing treatment on the porous anodic oxide film, blocking the micropores of the oxide film by volume expansion caused by water and reaction in pressurized steam or boiling water (with the addition of metal salts such as nickel), thereby transforming it into a more stable hydrated oxide.

[0099] The thickness of the anodic oxide film is preferably 0.3 μm or more and 15 μm or less. If the film thickness is within the above range, there is a tendency for it to exert a barrier effect relative to the implantation, and there is a tendency for the rise in residual potential caused by repeated use to be suppressed.

[0100] Conductive substrates can be treated with acidic solutions or boehmite.

[0101] The treatment based on the acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The proportions of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution are, for example, phosphoric acid in the range of 10% by mass or more and 11% by mass or less, chromic acid in the range of 3% by mass or more and 5% by mass or less, and hydrofluoric acid in the range of 0.5% by mass or more and 2% by mass or less. The concentration of their total acid content is preferably in the range of 13.5% by mass or more and 18% by mass or less. The treatment temperature is preferably, for example, 42°C or more and 48°C or less. The film thickness is preferably, for example, 0.3 μm or more and 15 μm or less.

[0102] Boehmite treatment can be performed, for example, by immersion in pure water at a temperature above 90°C and below 100°C for 5 to 60 minutes, or by contact in heated steam at a temperature above 90°C and below 120°C for 5 to 60 minutes. The film thickness is preferably, for example, 0.1 μm or more and 5 μm or less. Further anodizing can be performed using electrolyte solutions with low film solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, and citrates.

[0103] (Undercoat)

[0104] The undercoat layer may be, for example, a layer containing inorganic particles and a binding resin.

[0105] As inorganic particles, examples include powder resistance (volume resistivity) of 10. 2 Ω·cm or more and 10 11 Inorganic particles below Ω·cm.

[0106] Among them, inorganic particles having the above-mentioned resistance values ​​are preferably metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and zinc oxide particles are particularly preferred.

[0107] The specific surface area of ​​inorganic particles based on the BET method is preferably, for example, 10 m². 2 / g or more.

[0108] The volume average particle size of the inorganic particles is preferably 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

[0109] The content of inorganic particles, relative to the bonding resin, is preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less.

[0110] Inorganic particles can be used for surface treatment. Two or more types of inorganic particles with different surface treatments or different particle sizes can be mixed together.

[0111] Examples of surface treatment agents include silane coupling agents, titanate coupling agents, aluminum coupling agents, and surfactants. In particular, silane coupling agents are preferred, and silane coupling agents having an amino group are more preferred.

[0112] Examples of amino-containing silane coupling agents include 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, but are not limited to these.

[0113] Two or more silane coupling agents can be used in combination. For example, an amino-containing silane coupling agent can be used in combination with other silane coupling agents. Other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacryloyloxypropyltris(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.

[0114] Surface treatment methods based on surface treatment agents can be any known method, including either dry or wet methods.

[0115] The amount of surface treatment agent relative to the inorganic particles is preferably 0.5% by mass or more and 10% by mass or less.

[0116] From the viewpoint of setting the capacitance within the aforementioned range and suppressing potential fluctuations after the formation of an electrostatic latent image, zinc oxide particles are preferably used as the inorganic particles in the lower coating. In particular, zinc oxide particles endowed with electron-accepting compounds are preferred as the inorganic particles.

[0117] -Zinc oxide particles endowed with electron-accepting compounds-

[0118] The zinc oxide particles imparting the electron-accepting compound to the undercoat are preferably contained in an amount of 62% by mass or more and 75% by mass or less, more preferably in an amount of 65% by mass or more and 73% by mass or less, relative to the undercoat.

[0119] If the content of zinc oxide particles endowed with electron-accepting compounds is 62% by mass or more, the electrostatic capacity of the undercoat is increased, thereby making it easier to increase the voltage applied to the charge transport layer. As a result, potential fluctuations after the formation of electrostatic latent images are easily suppressed.

[0120] If the content of zinc oxide particles imparting electron-accepting compounds is below 75% by mass, the excessively high electrostatic capacitance of the undercoat can be suppressed. As a result, potential fluctuations after the formation of electrostatic latent images are easily suppressed.

[0121] By ensuring that the content of zinc oxide particles containing electron-receiving compounds meets the above-mentioned range, the dielectric constant of the lower coating of the photoreceptor is increased, the voltage applied to the charge transport layer is increased, and thus the potential variation after the formation of the electrostatic latent image is suppressed.

[0122] -Electron-receiving compounds-

[0123] Electron-accepting compounds are preferably anthraquinone derivatives having three OH groups or two OH groups and one alkoxy group.

[0124] Anthraquinone derivatives, for example, are preferably alizarin derivatives represented by formula (C).

[0125] When the above-mentioned compound is used as an electron-receiving compound, the electrostatic capacitance of the lower coating increases, and the voltage applied to the charge transport layer increases. As a result, potential fluctuations after the formation of the electrostatic latent image are suppressed.

[0126] The reasoning is as follows: Compared to anthraquinone or alizarin, when added in the same amount to the charge transport layer, the anthraquinone derivatives and the alizarin derivatives represented by formula (C) have a larger proportion in terms of both mass and volume in the undercoat due to differences in molecular weight. Therefore, the anthraquinone derivatives and the alizarin derivatives represented by formula (C) form charge-transfer complexes with zinc oxide particles over a wider range. Thus, it is speculated that the electrostatic capacitance of the undercoat is increased.

[0127] [Chemical Formula 4]

[0128]

[0129] In formula (C), R represents a hydroxyl group or an alkoxy group with 1 or more but less than 10 carbon atoms.

[0130] In formula (C), the number of carbon atoms of the alkoxy group represented by R is preferably 1 or more and 4 or less, and more preferably 1 or more and 2 or less.

[0131] Specifically, examples of electron-accepting compounds include rutin and the following compound (A). Among these, rutin and the following compound (A) are preferred as electron-accepting compounds.

[0132] In addition, other quinones, anthracene phenols, or their derivatives can be used as electron-accepting compounds.

[0133] [Chemical Formula 5]

[0134]

[0135] Methods for imparting electron-accepting compounds to inorganic particles (i.e., methods for attaching them to the surface of inorganic particles) include, for example, dry or wet methods.

[0136] A dry method, for example, involves directly adding an electron-accepting compound or an electron-accepting compound dissolved in an organic solvent while stirring inorganic particles using a mixer with high shear force, and then spraying it together with dry air or nitrogen, thereby causing the electron-accepting compound to adhere to the surface of the inorganic particles. When adding or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After adding or spraying the electron-accepting compound, sintering can be performed at a temperature above 100°C. There are no particular limitations on the temperature and time of sintering, as long as the electron photographic properties are obtained.

[0137] Wet processes, for example, involve dispersing inorganic particles in a solvent using a mixer, ultrasonic disperser, sand mill, grinder, or ball mill. An electron-accepting compound is added, and the mixture is stirred or dispersed. The solvent is then removed, allowing the electron-accepting compound to adhere to the surface of the inorganic particles. Solvent removal methods include filtration or evaporation. After solvent removal, sintering can be performed at temperatures above 100°C. The temperature and time for sintering are not particularly limited as long as the electron imaging properties are obtained. In wet processes, the moisture content of the inorganic particles can be removed before adding the electron-accepting compound. Examples include removing moisture while stirring and heating in a solvent, or removing it through azeotropic mixing with the solvent.

[0138] In addition, the attachment of electron-receiving compounds can be carried out before or after the surface treatment of inorganic particles based on surface treatment agents, or the attachment of electron-receiving compounds and surface treatment based on surface treatment agents can be carried out simultaneously.

[0139] The content (i.e., the amount of electron-accepting compound) relative to inorganic particles is preferably 0.01% by mass or more and 20% by mass or less, and more preferably 0.01% by mass or more and 10% by mass or less.

[0140] Examples of known polymeric compounds used as adhesive resins in the undercoat include acetal resins (such as polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic acid 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, phenolic-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organotitanium compounds; and silane coupling agents.

[0141] Examples of adhesive resins used in the undercoat include charge-transporting resins with charge-transporting groups and conductive resins (e.g., polyaniline).

[0142] The adhesive resin used in the lower coating layer is preferably a resin that is insoluble in the coating solvent, and more preferably a resin obtained by reacting a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenolic resin, phenolic-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin; polyamide resin, polyester resin, polyether resin, methacrylic resin, acrylic resin, polyvinyl alcohol resin, and polyvinyl alcohol acetal resin.

[0143] When using two or more adhesive resins in combination, the mixing ratio should be set as needed.

[0144] To improve electrical properties, environmental stability, and image quality, various additives can be included in the undercoat.

[0145] Examples of additives include polycyclic condensation pigments, azo pigments, zirconium chelates, titanium chelates, aluminum chelates, titanium alkoxides, organotitanium compounds, and silane coupling agents. As mentioned earlier, silane coupling agents are used for surface treatment of inorganic particles, but they can also be added as additives to undercoatings.

[0146] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacryloyloxypropyltris(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.

[0147] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetoacetate, zirconium triethanolamine, zirconium acetylacetone butoxide, zirconium 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.

[0148] Examples of titanium chelate compounds include tetraisopropyl titanate, tetrabutyl titanate, tetrabutyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetone, polyacetylacetone titanium, octanediol titanium, titanium ammonium lactate, titanium lactate, titanium ethyl lactate, titanium triethanolamine, and titanium polyhydroxystearate.

[0149] Examples of aluminum chelate compounds include aluminum isopropoxide, aluminum monobutoxydiisopropoxide, aluminum butoxide, aluminum diacetoacetate diisopropoxide, and aluminum triacetoacetate.

[0150] These additives can be used alone or as a mixture or condensation polymer of multiple compounds.

[0151] -Capacitance of the undercoat-

[0152] The electrostatic capacitance of the lower coating is 1.0 × 10⁻⁶. -10 F or higher and 3.0 × 10 -9 F or less. The electrostatic capacitance of the lower coating is more preferably 2.5 × 10⁻⁶. -10 F or higher and 2.0 × 10 -9 F below, is further preferably 5.3 × 10 -10 F or higher and 1.5 × 10 -9 Below F.

[0153] If the electrostatic capacitance of the undercoat is less than 1.0 × 10⁻⁶ -10 F, then the voltage applied to the charge transport layer is weakened, thus worsening the potential variation after the formation of the electrostatic latent image.

[0154] If the electrostatic capacitance of the undercoat exceeds 3.0 × 10⁻⁶-9 If F is too low, the voltage applied to the lower coating becomes excessively low, and similarly, the potential variation after the formation of the electrostatic latent image deteriorates.

[0155] As a method for setting the electrostatic capacitance of the undercoat to the above range, the following method can be used: as an electron-accepting compound, an alizarin derivative represented by the above formula (C) is used, and the film thickness of the undercoat is adjusted to be 17 μm or more and 35 μm or less.

[0156] The capacitance of the undercoat was set to a state where a single layer of the undercoat was adhered to the substrate after the charge transport layer and charge generation layer were removed by solvent. In this state, an Au electrode with a radius of 3 mm was formed on the surface of the undercoat. Using an impedance analyzer, the capacitance at an AC frequency of 1 Hz was measured with a DC voltage of 10 V and an AC voltage of 2 V applied from the conductive substrate and the Au electrode to the undercoat.

[0157] -Thickness of the lower coating layer-

[0158] The thickness of the lower coating is set in the range of 17 μm or more and 35 μm or less, and more preferably in the range of 18 μm or more and 26 μm or less.

[0159] If the thickness of the lower coating is 17 μm or more, the electrostatic capacity of the lower coating is increased, the voltage applied to the charge transport layer increases, and thus it is easier to suppress potential changes after the formation of electrostatic latent images.

[0160] If the thickness of the undercoat is less than 35 μm, it can suppress the excessive reduction of the voltage applied to the charge transport layer due to the excessive reduction of the electrostatic capacitance of the undercoat, thereby easily suppressing the potential changes after the formation of the electrostatic latent image.

[0161] By adjusting the thickness of the undercoat to achieve the aforementioned structure, the electrostatic capacitance of the undercoat of the photoreceptor increases, and the voltage applied to the charge transport layer also increases. Consequently, potential fluctuations after the formation of the electrostatic latent image are suppressed.

[0162] The undercoat is preferably coated with a Vickers hardness of 35 or higher.

[0163] To suppress interference ripples, the surface roughness (ten-point average roughness) of the lower coating is preferably adjusted to, for example, 1 / (4n) to 1 / 2 of the wavelength λ of the laser used for exposure (where n is the refractive index of the upper layer).

[0164] To adjust surface roughness, resin particles can be added to the undercoat. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. Furthermore, to adjust surface roughness, the surface of the undercoat can be ground. Examples of grinding methods include polishing, sandblasting, wet grinding, and grinding.

[0165] There are no particular limitations on the formation of the undercoat, and well-known formation methods can be used. However, for example, it can be carried out by forming a coating film of an undercoat forming liquid in which the above-mentioned components are added to a solvent, drying the coating film, and heating as needed.

[0166] As solvents used to prepare coating liquids for forming the undercoat, known organic solvents can be cited, such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketol solvents, ether solvents, ester solvents, etc.

[0167] Specifically, examples of these solvents include, for instance, 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, toluene, and other common organic solvents.

[0168] Methods for dispersing inorganic particles during the preparation of coating liquid for forming a lower coating include, for example, known methods such as roller mills, ball mills, vibratory ball mills, grinding mills, sand mills, colloid mills, and paint mixers.

[0169] Methods for applying a coating liquid for forming an undercoat onto a conductive substrate include, for example, scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, and curtain coating.

[0170] (Middle layer)

[0171] Illustrations omitted, but an intermediate layer can also be placed between the lower coating layer and the photosensitive layer.

[0172] The intermediate layer may be, for example, a layer containing resin. Examples of resins used in the intermediate layer include acetal resins (such as polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic acid resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenolic-formaldehyde resins, melamine resins, and other polymeric compounds.

[0173] The intermediate layer can be a layer containing an organometallic compound. Examples of organometallic compounds used as intermediate layers include those containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.

[0174] The compounds used in these intermediate layers can be used alone or as a mixture of multiple compounds or as condensation polymers.

[0175] The intermediate layer is preferably a layer containing an organometallic compound containing zirconium or silicon atoms.

[0176] There are no particular limitations on the formation of the intermediate layer, and well-known formation methods can be used. However, for example, a coating film of a coating liquid can be formed by forming an intermediate layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating as needed.

[0177] As a coating method for forming the intermediate layer, conventional methods such as dip coating, push coating, bar coating, spraying, scraper coating, air knife coating, and curtain coating can be used.

[0178] The thickness of the intermediate layer is preferably set in the range of 0.1 μm or more and 3 μm or less. Alternatively, the intermediate layer can be used as the lower coating layer.

[0179] (charge generation layer)

[0180] The charge generation layer is, for example, a layer comprising a charge generation material and a binding resin. Furthermore, the charge generation layer can be a vapor-deposited layer of the charge generation material. Vapor-deposited layers of charge generation material are suitable, for example, for use with incoherent light sources such as LED (Light Emitting Diode) and organic EL (Electro-Luminescence) image arrays.

[0181] Examples of charge-generating materials include azo pigments such as diazo and triazo; fused-ring aromatic pigments such as dibromoanthracene anthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0182] 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. Specifically, hydroxy gallium phthalocyanine, gallium chloride phthalocyanine, dichlorotin phthalocyanine, and titanium dioxide phthalocyanine are more preferred.

[0183] On the other hand, in order to cope with laser exposure in the near-ultraviolet region, the preferred charge-generating materials are, for example, fused-ring aromatic pigments such as dibromoanthracene; sulfur-indigo pigments; porphyrin compounds; zinc oxide; trigonal selenium; and diazo pigments.

[0184] The above-mentioned charge-generating materials can be used even when using incoherent light sources such as LEDs and organic EL image arrays with a center wavelength of light emission above 450nm and below 780nm.

[0185] When n-type semiconductors such as fused-ring aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark currents are not easily generated, and even when set as thin films, image defects known as black spots can be suppressed.

[0186] Furthermore, regarding the determination of n-type, the commonly used time-of-flight method is used, and the determination is made based on the polarity of the flowing photocurrent. Semiconductors that flow more easily than holes with electrons as charge carriers are defined as n-type.

[0187] The adhesive resin used in the charge generation layer is selected from a wide range of insulating resins, and the adhesive resin can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinyl anthracene, polyvinylpyrene, and polysilane.

[0188] Examples of adhesive resins include polyvinyl butyral resin, polyarylate resins (condensates of bisphenols and aromatic dicarboxylic acids, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin. Here, "insulation" refers to a volume resistivity of 10 Ω·cm. 13 Ω·cm or higher.

[0189] These adhesive resins can be used alone or in combination of two or more.

[0190] In addition, the mixing ratio of the charge-generating material to the adhesive resin is preferably in the range of 10:1 to 1:10 by mass, for example.

[0191] Other well-known additives may be included in the charge-generating layer.

[0192] There are no particular limitations on the formation of the charge-generating layer, and well-known formation methods can be used. For example, it can be achieved by forming a coating film of a charge-generating layer forming liquid in which the aforementioned components are added to a solvent, drying the coating film, and heating it as needed. Alternatively, the charge-generating layer can be formed by vapor deposition of a charge-generating material. Vapor deposition-based formation of the charge-generating layer is particularly suitable, for example, when using polycyclic aromatic pigments or perylene pigments as the charge-generating material.

[0193] Examples of solvents used in preparing coating solutions for forming charge-generating layers 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, and toluene. These solvents can be used alone or in combination of two or more.

[0194] As a method for dispersing particles (e.g., charge-generating materials) in a coating liquid for forming a charge-generating layer, media dispersers such as ball mills, vibratory ball mills, grinders, sand mills, and horizontal sand mills, or medialess dispersers such as mixers, ultrasonic dispersers, roller mills, and high-pressure homogenizers can be used. Examples of high-pressure homogenizers include collision methods that disperse the dispersion by liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods that disperse the dispersion through fine flow paths under high pressure.

[0195] In addition, when performing this dispersion, it is effective to set the average particle size of the charge-generating material in the coating liquid for forming the charge-generating layer to 0.5 μm or less, for example, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0196] Methods for applying a coating liquid for forming a charge generation layer onto an underlying layer (or an intermediate layer) include, for example, scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, curtain coating, and other common methods.

[0197] The thickness of the charge generation layer is preferably set in the range of 0.1 μm or more and 5.0 μm or less, and more preferably in the range of 0.2 μm or more and 2.0 μm or less.

[0198] [charge transport layer]

[0199] The charge transport layer is a layer containing a bonding resin and a charge transport material.

[0200] (charge transport materials)

[0201] Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloroquinone, tetrabromobenzoquinone, and anthraquinone; dimethyl compounds such as tetracyano-p-benzodiquinone; fluorenone compounds such as 2,4,7-trinitrofluorenone; anthrone compounds; benzophenone compounds; cyanoethylene compounds; and ethylene compounds, all of which are electron transport compounds. Examples of hole transport materials include triarylamine compounds, benzidine compounds, arylalkyl compounds, aryl-substituted ethylene compounds, piracene compounds, anthracene compounds, and hydrazone compounds, all of which are hole transport compounds. These charge transport materials can be used alone or in combination, but are not limited to this.

[0202] Examples of polymeric charge transport materials include well-known chemical substances with charge transport properties such as poly-N-vinylcarbazole and polysilanes. Polyester-based polymeric charge transport materials are preferred, for example. These polymeric charge transport materials can be used alone or in combination with binding resins.

[0203] Examples of charge transport materials or polymeric charge transport materials include polycyclic aromatic compounds, aromatic nitro compounds, aromatic amine compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds (especially triphenylamine compounds), diamine compounds, oxadiazole compounds, carbazole compounds, organopolysilane compounds, pyrazoline compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, cyanide compounds, benzofuran compounds, aniline compounds, butadiene compounds, and resins having groups derived from these substances. Specifically, examples include paragraphs 0078-0080 of Japanese Patent Application Publication No. 2021-117377, paragraphs 0046-0048 of Japanese Patent Application Publication No. 2019-035900, paragraphs 0052-0053 of Japanese Patent Application Publication No. 2019-012141, paragraphs 0122-0134 of Japanese Patent Application Publication No. 2021-071565, and paragraphs 0021-0 The compounds described in paragraphs 0101 to 0110 of Japanese Patent Application Publication No. 15223, paragraph 0116 of Japanese Patent Application Publication No. 2013-097300, paragraphs 0309 to 0316 of International Publication No. 2019 / 070003, paragraphs 0103 to 0107 of Japanese Patent Application Publication No. 2018-159087, and paragraphs 0102 to 0113 of Japanese Patent Application Publication No. 2021-148818.

[0204] From the viewpoint of charge mobility, the charge transport material preferably comprises at least one selected from the group consisting of a chemical substance (C1) represented by formula (C1), a chemical substance (C2) represented by formula (C2), a chemical substance (C3) represented by formula (C3), and a chemical substance (C4) represented by formula (C4).

[0205] [Chemical Formula 6]

[0206]

[0207] In equation (C1), Ar T1 Ar T2 and Ar T3 They are independently aryl and -C6H4-C(R) T4 )=C(R T5 (R) T6 ) or -C6H4-CH=CH-CH=C(R T7 (R) T8 R T4 R T5 R T6 R T7 and R T8Each is independently a hydrogen atom, alkyl group, or aryl group. When R... T5 and R T6 When it is aryl, the aryl groups can cross each other via -C(R) 51 (R) 52 - and / or -C(R) 61 )=C(R 62 The divalent group of )- is linked. R 51 R 52 R 61 and R 62 Each is independently an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms.

[0208] The groups in formula (C1) may be substituted by halogen atoms, alkyl groups having 1 or more but less than 5 carbon atoms, alkoxy groups having 1 or more but less than 5 carbon atoms, or substituted amino groups having 1 or more but less than 3 carbon atoms.

[0209] As a chemical substance (C1), from the viewpoint of charge mobility, it is preferred, for example, to have at least one aryl group or -C6H4-CH=CH-CH=C(R T7 (R) T8 The chemical substance is more preferably the chemical substance represented by the following formula (C'1).

[0210] [Chemical Formula 7]

[0211]

[0212] In equation (C'1), R T111 R T112 R T121 R T122 R T131 and R T132 Each of the following is independently a hydrogen atom, a halogen atom, an alkyl group (preferably an alkyl group having 1 or more and 3 or less carbon atoms), an alkoxy group (preferably an alkoxy group having 1 or more and 3 or less carbon atoms), a phenyl group, or a phenoxy group. Tj1, Tj2, Tj3, Tk1, Tk2, and Tk3 are independently 0, 1, or 2.

[0213] [Chemical Formula 8]

[0214]

[0215] In equation (C2), R T201 R T202 R T211 and R T212 Each of the following is independently a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, an alkoxy group having 1 or more but less than 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, or a -C(R) group.T21 )=C(R T22 (R) T23 ) or -CH=CH-CH=C(R T24 (R) T25 R T21 R T22 R T23 R T24 and R T25 Each can be independently a hydrogen atom, alkyl group, or aryl group. R T221 and R T222 Each of the following is independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, or an alkoxy group having 1 or more but less than 5 carbon atoms. Tm1, Tm2, ​​Tn1, and Tn2 are independently 0, 1, or 2, respectively.

[0216] The groups in formula (C2) may be substituted by halogen atoms, alkyl groups having 1 or more but less than 5 carbon atoms, alkoxy groups having 1 or more but less than 5 carbon atoms, or substituted amino groups having 1 or more but less than 3 carbon atoms.

[0217] As a chemical substance (C2), from the viewpoint of charge mobility, it is preferred, for example, to have at least one alkyl, aryl, or -CH=CH-CH=C(R) group. T24 (R) T25 The chemical substance, more preferably having at least two alkyl, aryl, or -CH=CH-CH=C(R) groups, is preferred. T24 (R) T25 ) chemical substances.

[0218] [Chemical Formula 9]

[0219]

[0220] In equation (C3), R T301 R T302 R T311 and R T312 Each of the following is independently a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, an alkoxy group having 1 or more but less than 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, or a -C(R) group. T31 )=C(R T32 (R) T33 ) or -CH=CH-CH=C(R T34 (R) T35 R T31 R T32 R T33 R T34 and R T35 Each can be independently a hydrogen atom, alkyl group, or aryl group. R T321 R T322and R T331 Each of the following is independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, or an alkoxy group having 1 or more but less than 5 carbon atoms. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are independently 0, 1, or 2, respectively.

[0221] The groups in formula (C3) may be substituted by halogen atoms, alkyl groups having 1 or more but less than 5 carbon atoms, alkoxy groups having 1 or more but less than 5 carbon atoms, or substituted amino groups having 1 or more but less than 3 carbon atoms.

[0222] [Chemical Formula 10]

[0223]

[0224] In equation (C4), R T401 R T402 R T411 and R T412 Each of the following is independently a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, an alkoxy group having 1 or more but less than 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, or a -C(R) group. T41 )=C(R T42 (R) T43 ) or -CH=CH-CH=C(R T44 (R) T45 R T41 R T42 R T43 R T44 and R T45 Each can be independently a hydrogen atom, alkyl group, or aryl group. R T421 R T422 and R T431 Each of the following is independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, or an alkoxy group having 1 or more but less than 5 carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are independently 0, 1, or 2, respectively.

[0225] The groups in formula (C4) may be substituted by halogen atoms, alkyl groups having 1 or more but less than 5 carbon atoms, alkoxy groups having 1 or more but less than 5 carbon atoms, or substituted amino groups having 1 or more but less than 3 carbon atoms.

[0226] The content of charge transport material contained in the charge transport layer relative to the total mass of the charge transport layer is preferably 20% by mass or more and 70% by mass or less.

[0227] [Adhesive Resin]

[0228] The bonding resin used in the charge transport layer comprises a dicarboxylic acid unit represented by formula (A) (hereinafter, "dicarboxylic acid unit (A)") and a diol unit represented by formula (B) (hereinafter, "diol unit (B)"), which are applicable. In this invention, the polyarylate resin is also referred to as polyarylate resin (PA).

[0229] The dicarboxylic acid unit (A) is the structural unit represented by the following formula (A).

[0230] [Chemical Formula 11]

[0231]

[0232] In equation (A), Ar A1 and Ar A2 Each is an aromatic ring that can have substituents, L A It is a single bond or a divalent linker, n A1 It can be 0, 1, or 2.

[0233] Ar A1 The aromatic ring can be any of a monocyclic or polycyclic aromatic ring. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0234] Ar A1 The hydrogen atoms on the aromatic ring can be replaced by alkyl, aryl, aralkyl, alkoxy, aryloxy, halogen atoms, etc. As Ar... A1 When the aromatic ring is substituted, the substituents are preferably alkyl groups having 1 or more and 10 or less carbon atoms, aryl groups having 6 or more and 12 or less carbon atoms, and alkoxy groups having 1 or more and 6 or less carbon atoms.

[0235] Ar A2 The aromatic ring can be any of a monocyclic or polycyclic aromatic ring. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0236] Ar A2 The hydrogen atoms on the aromatic ring can be replaced by alkyl, aryl, aralkyl, alkoxy, aryloxy, halogen atoms, etc. As Ar... A2 When the aromatic ring is substituted, the substituents are preferably alkyl groups having 1 or more and 10 or less carbon atoms, aryl groups having 6 or more and 12 or less carbon atoms, and alkoxy groups having 1 or more and 6 or less carbon atoms.

[0237] When L A When the linking group is divalent, examples of divalent linking groups include oxygen atoms, sulfur atoms, and -C(Ra). 1 (Ra) 2 )-。 Here, Ra 1 and Ra2 Ra is independently composed of hydrogen atoms, an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an aralkyl group having 7 or more but less than 20 carbon atoms. 1 With Ra 2 They can bond together to form cyclic alkyl groups.

[0238] Ra 1 and Ra 2 The alkyl group involving 1 or more and 10 or less carbon atoms can be any of straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and even more preferably 1 or 2.

[0239] Ra 1 and Ra 2 The aryl group involving 6 or more but less than 12 carbon atoms can be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more but less than 10, and more preferably 6.

[0240] Ra 1 and Ra 2 The alkyl group in the aralkyl group with 7 or more and 20 or less carbon atoms can be any one of straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group of the aralkyl group with 7 or more and 20 or less carbon atoms is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and even more preferably 1 or 2.

[0241] Ra 1 and Ra 2 The aryl group in the aralkyl group involving 7 or more and 20 or less carbon atoms can be any of a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6.

[0242] The dicarboxylic acid unit (A) preferably comprises at least one selected from the group consisting of dicarboxylic acid units (A1) represented by formula (A1), dicarboxylic acid units (A2) represented by formula (A2), dicarboxylic acid units (A3) represented by formula (A3), dicarboxylic acid units (A4) represented by formula (A4), and dicarboxylic acid units (A5). More preferably, the dicarboxylic acid unit (A) comprises at least one selected from the group consisting of dicarboxylic acid units (A2), dicarboxylic acid units (A3), and dicarboxylic acid units (A4), and even more preferably comprises a dicarboxylic acid unit (A2).

[0243] [Chemical Formula 12]

[0244]

[0245] In equation (A1), n 101n is an integer greater than 0 and less than 4. 101 Ra 101 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0246] n 101 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0247] [Chemical Formula 13]

[0248]

[0249] In equation (A2), n 201 and n 202 Each of the following is an independent integer greater than 0 and less than 4, n 201 Ra 201 and n 202 Ra 202 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0250] n 201 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0251] n 202 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0252] [Chemical Formula 14]

[0253]

[0254] In equation (A3), n 301 and n 302 Each of the following is an independent integer greater than 0 and less than 4, n 301 Ra 301 and n 302 Ra 302 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0255] n 301 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0256] n 302 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0257] [Chemical Formula 15]

[0258]

[0259] In equation (A4), n 401 n is an integer greater than 0 and less than 6. 401 Ra 401 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0260] n 401 For example, it is preferably an integer greater than or equal to 0 and less than or equal to 4, more preferably 0, 1 or 2, and even more preferably 0.

[0261] [Chemical Formula 16]

[0262]

[0263] In equation (A5), n 501 n 502 and n 503 Each of the following is an independent integer greater than 0 and less than 4, n 501 Ra 501 n 502 Ra 502 and n 503 Ra 503 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0264] n 501 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0265] n 502 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0266] n 503 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0267] Ra of formula (A1) 101 Ra of formula (A2) 201 and Ra 202 Ra of formula (A3) 301 and Ra 302 Ra of formula (A4) 401 And Ra of formula (A5) 501 Ra 502 and Ra 503 The specific form and preferred form are the same, therefore Ra will be described below.101 Ra 201 Ra 202 Ra 301 Ra 302 Ra 401 Ra 501 Ra 502 and Ra 503 We will refer to them collectively as "Ra" for explanation.

[0268] The alkyl group involved in Ra with 1 or more and 10 or less carbon atoms can be any of straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and even more preferably 1 or 2.

[0269] Examples of straight-chain alkyl groups with 1 or more but less than 10 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl.

[0270] Examples of branched alkyl groups with 3 or more but less than 10 carbon atoms include isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, tert-hexyl, isohexyl, sec-heptyl, tert-heptyl, isooctyl, sec-octyl, tert-octyl, isononyl, sec-nonyl, tert-nonyl, isodel, sec-decyl, and tert-decyl.

[0271] Examples of cyclic alkyl groups with 3 or more but less than 10 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups formed by linking these monocyclic alkyl groups.

[0272] The aryl group involved in Ra, which has 6 or more but less than 12 carbon atoms, can be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more but less than 10, and more preferably 6.

[0273] Examples of aryl groups with 6 or more but less than 12 carbon atoms include phenyl, biphenyl, 1-naphthyl, and 2-naphthyl.

[0274] The alkyl group in the alkoxy group involving Ra, which has 1 or more and 6 or less carbon atoms, can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group, which has 1 or more and 4 or less carbon atoms, is preferably 1 or more and 3 or less, and even more preferably 1 or 2.

[0275] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0276] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0277] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0278] The following examples of dicarboxylic acid units (A1-1) to (A1-9) are shown as specific examples of dicarboxylic acid units (A1). The dicarboxylic acid unit (A1) is not limited to these examples.

[0279] [Chemical Formula 17]

[0280]

[0281] The following examples of dicarboxylic acid units (A2-1) to (A2-3) are shown as specific examples of dicarboxylic acid units (A2). The dicarboxylic acid unit (A2) is not limited to these examples.

[0282] [Chemical Formula 18]

[0283]

[0284] Hereinafter, dicarboxylic acid units (A3-1) to (A3-2) are specifically shown as dicarboxylic acid units (A3). The dicarboxylic acid unit (A3) is not limited to these.

[0285] [Chemical Formula 19]

[0286]

[0287] Hereinafter, dicarboxylic acid units (A4-1) to (A4-3) are specifically shown as dicarboxylic acid units (A4). The dicarboxylic acid unit (A4) is not limited to these.

[0288] [Chemical Formula 20]

[0289]

[0290] Hereinafter, dicarboxylic acid units (A5-1) to (A5-4) are specifically shown as dicarboxylic acid units (A5). The dicarboxylic acid unit (A5) is not limited to these.

[0291] [Chemical Formula 21]

[0292]

[0293] As a dicarboxylic acid unit (A), it is preferred to include at least one selected from the group consisting of (A1-1), (A1-7), (A2-3), (A3-2) and (A4-3) of the above specific examples, more preferably to include at least one selected from the group consisting of (A2-3), (A3-2) and (A4-3), and even more preferably to include at least (A2-3).

[0294] The dicarboxylic acid unit (A) contained in polyaryl ester resin (PA) can be one or more.

[0295] The mass percentage of dicarboxylic acid unit (A) in polyarylate resin (PA) is preferably 15% by mass or more and 60% by mass or less.

[0296] If the mass percentage of dicarboxylic acid unit (A) is 15% by mass or more, the charge transport layer exhibits good wear resistance. From this perspective, the mass percentage of dicarboxylic acid unit (A) is more preferably 20% by mass or more, and even more preferably 25% by mass or more.

[0297] If the mass percentage of the dicarboxylic acid unit (A) is 60% by mass or less, the stripping of the charge transport layer can be suppressed. From this point of view, the mass percentage of the dicarboxylic acid unit (A) is more preferably 55% by mass or less, and even more preferably 50% by mass or less.

[0298] Polyaryl ester resins (PA) may contain dicarboxylic acid units other than the dicarboxylic acid unit (A). Examples of other dicarboxylic acid units include, for instance, aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citracic acid, itaconic acid, pentenic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid), alicyclic dicarboxylic acid units (e.g., cyclohexanedicarboxylic acid), and their lower (e.g., having 1 or more but less than 5 carbon atoms) alkyl ester units. The polyaryl ester resin (PA) may contain one or more of these dicarboxylic acid units.

[0299] The diol unit (B) is the structural unit represented by the following formula (B).

[0300] [Chemical Formula 22]

[0301]

[0302] In equation (B), Ar B1 and Ar B2 Each is an aromatic ring that can have substituents, L B It is a single bond, an oxygen atom, a sulfur atom, or -C(Rb) 1 (Rb) 2 )-,n B1 It can be 0, 1, or 2; Rb 1and Rb 2 Rb is independently composed of hydrogen atoms, an alkyl group having 1 or more but less than 20 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an aralkyl group having 7 or more but less than 20 carbon atoms. 1 With Rb 2 They can bond together to form cyclic alkyl groups.

[0303] Ar B1 The aromatic ring can be any of a monocyclic or polycyclic aromatic ring. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0304] Ar B1 The hydrogen atoms on the aromatic ring can be replaced by alkyl, aryl, aralkyl, alkoxy, aryloxy, halogen atoms, etc. As Ar... B1 When the aromatic ring is substituted, the substituents are preferably alkyl groups having 1 or more and 10 or less carbon atoms, aryl groups having 6 or more and 12 or less carbon atoms, and alkoxy groups having 1 or more and 6 or less carbon atoms.

[0305] Ar B2 The aromatic ring can be any of a monocyclic or polycyclic aromatic ring. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0306] Ar B2 The hydrogen atoms on the aromatic ring can be replaced by alkyl, aryl, aralkyl, alkoxy, aryloxy, halogen atoms, etc. As Ar... B2 When the aromatic ring is substituted, the substituents are preferably alkyl groups having 1 or more and 10 or less carbon atoms, aryl groups having 6 or more and 12 or less carbon atoms, and alkoxy groups having 1 or more and 6 or less carbon atoms.

[0307] Rb 1 and Rb 2 The alkyl group involving 1 or more and 20 or less carbon atoms can be any of straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 18 or less, more preferably 1 or more and 14 or less, and even more preferably 1 or more and 10 or less.

[0308] Rb 1 and Rb 2 The aryl group involving 6 or more but less than 12 carbon atoms can be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more but less than 10, and more preferably 6.

[0309] Rb 1 and Rb 2The alkyl group in the aralkyl group with 7 or more and 20 or less carbon atoms can be any one of straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group of the aralkyl group with 7 or more and 20 or less carbon atoms is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and even more preferably 1 or 2.

[0310] Rb 1 and Rb 2 The aryl group in the aralkyl group involving 7 or more and 20 or less carbon atoms can be any of a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6.

[0311] The diol unit (B) preferably comprises at least one selected from the group consisting of diol unit (B1) represented by formula (B1), diol unit (B2) represented by formula (B2), diol unit (B3) represented by formula (B3), diol unit (B4) represented by formula (B4), diol unit (B5) represented by formula (B5), diol unit (B6) represented by formula (B6), diol unit (B7) represented by formula (B7) and diol unit (B8) represented by formula (B8).

[0312] The diol unit (B) more preferably comprises at least one selected from the group consisting of diol units (B1) represented by formula (B1), diol units (B2) represented by formula (B2), diol units (B4) represented by formula (B4), diol units (B5) represented by formula (B5), and diol units (B6) represented by formula (B6).

[0313] Further preferably, it comprises at least one selected from the group consisting of diol units (B1) represented by formula (B1), diol units (B2) represented by formula (B2), diol units (B5) represented by formula (B5), and diol units (B6) represented by formula (B6).

[0314] More preferably, it comprises at least one selected from the group consisting of diol units (B1) represented by formula (B1), diol units (B2) represented by formula (B2), and diol units (B6) represented by formula (B6).

[0315] Most preferably, it comprises at least one of the groups consisting of diol units (B1) represented by formula (B1) and diol units (B2) represented by formula (B2).

[0316] [Chemical Formula 23]

[0317]

[0318] In equation (B1), Rb 101Branched alkyl groups with 4 or more but less than 20 carbon atoms, Rb 201 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 401 、Rb 501 、Rb 801 and Rb 901 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0319] Rb 101 The branched alkyl group involving 4 or more and 20 or less carbon atoms preferably has 4 or more and 16 or less carbon atoms, more preferably 4 or more and 12 or less, and even more preferably 4 or more and 8 or less. As Rb 101 Specific examples include isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, tert-hexyl, isohexyl, sec-heptyl, tert-heptyl, isooctyl, sec-octyl, tert-octyl, isononyl, sec-nonyl, tert-nonyl, isodel, sec-decyl, tert-decyl, isododecyl, sec-dodecyl, tert-dodecyl, tert-tetradecyl, tert-pentadecanyl, etc.

[0320] [Chemical Formula 24]

[0321]

[0322] In equation (B2), Rb 102 Rb is a straight-chain alkyl group with 4 or more but less than 20 carbon atoms. 202 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 402 、Rb 502 、Rb 802 and Rb 902 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0323] Rb 102 The linear alkyl group involving 4 or more and 20 carbon atoms preferably has 4 or more and 16 or less carbon atoms, more preferably 4 or more and 12 or less, and even more preferably 4 or more and 8 or less. As Rb 102 Specific examples include n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, tridecyl, n-tetradecyl, n-pentadecanyl, n-heptadecyl, n-octadecyl, n-nonadecanyl, n-eicosyl, etc.

[0324] [Chemical Formula 25]

[0325]

[0326] In equation (B3), Rb 113 and Rb 213 Each of the following is independently a hydrogen atom, a straight-chain alkyl group having 1 or more but less than 3 carbon atoms, an alkoxy group having 1 or more but less than 4 carbon atoms, or a halogen atom, where d is an integer between 7 and 15, and Rb 403 、Rb 503 、Rb 803 and Rb 903 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0327] Rb 113 and Rb 213 The number of carbon atoms in the straight-chain alkyl group involving 1 or more and 3 or less is preferably 1 or 2, more preferably 1. Specific examples of this group include methyl, ethyl, and n-propyl.

[0328] Rb 113 and Rb 213 The alkyl group in the alkoxy group with 1 or more and 4 or fewer carbon atoms can be any of the following: linear, branched, and cyclic. The alkyl group in the alkoxy group with 1 or more and 4 or fewer carbon atoms preferably has 1 or more and 3 or fewer carbon atoms, more preferably 1 or 2, and even more preferably 1. Specific examples of this group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy.

[0329] As Rb 113 and Rb 213 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0330] [Chemical Formula 26]

[0331]

[0332] In equation (B4), Rb 104 and Rb 204 Each is independently an alkyl group having 1 or more but less than 3 carbon atoms, Rb 404 、Rb 504 、Rb 804 and Rb 904 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0333] Rb 104The alkyl group involving 1 to 3 carbon atoms can be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, more preferably 1. As Rb 104 Specific examples include methyl, ethyl, n-propyl, isopropyl, and cyclopropyl.

[0334] [Chemical Formula 27]

[0335]

[0336] In equation (B5), Ar 105 Rb is an aryl group having 6 or more but less than 12 carbon atoms, or an aralkyl group having 7 or more but less than 20 carbon atoms. 205 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 405 、Rb 505 、Rb 805 and Rb 905 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0337] Ar 105 The aryl group involving 6 or more but less than 12 carbon atoms can be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more but less than 10, and more preferably 6.

[0338] Ar 105 The alkyl group in the aralkyl group having 7 or more and 20 or fewer carbon atoms can be any of straight-chain, branched, or cyclic. The alkyl group in the aralkyl group having 7 or more and 20 or fewer carbon atoms preferably has 1 or more and 4 or fewer carbon atoms, more preferably 1 or more and 3 or fewer carbon atoms, and even more preferably 1 or 2 carbon atoms. 105 The aryl group in the aralkyl group with 7 or more and 20 or less carbon atoms can be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6. Examples of aralkyl groups with 7 or more and 20 or less carbon atoms include benzyl, phenylethyl, phenylpropyl, 4-phenylbutyl, phenylpentyl, phenylhexyl, phenylheptyl, phenyloctyl, phenylnonyl, naphthylmethyl, naphthylethyl, anthraceneylmethyl, and phenyl-cyclopentylmethyl.

[0339] [Chemical Formula 28]

[0340]

[0341] In equation (B6), Rb 116 and Rb 216Each of the following is independently a hydrogen atom, a straight-chain alkyl group having 1 or more but less than 3 carbon atoms, an alkoxy group having 1 or more but less than 4 carbon atoms, or a halogen atom, where e is an integer of 4 or more but less than 6, and Rb 406 、Rb 506 、Rb 806 and Rb 906 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0342] Rb 116 and Rb 216 The number of carbon atoms in the straight-chain alkyl group involving 1 or more and 3 or less is preferably 1 or 2, more preferably 1. Specific examples of this group include methyl, ethyl, and n-propyl.

[0343] Rb 116 and Rb 216 The alkyl group in the alkoxy group with 1 or more and 4 or fewer carbon atoms can be any of the following: linear, branched, and cyclic. The alkyl group in the alkoxy group with 1 or more and 4 or fewer carbon atoms preferably has 1 or more and 3 or fewer carbon atoms, more preferably 1 or 2, and even more preferably 1. Specific examples of this group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy.

[0344] As Rb 116 and Rb 216 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0345] [Chemical Formula 29]

[0346]

[0347] In equation (B7), Rb 407 、Rb 507 、Rb 807 and Rb 907 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0348] [Chemical Formula 30]

[0349]

[0350] In equation (B8), Rb 408 、Rb 508 、Rb 808 and Rb 908Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0351] Rb in equation (B1) 201 Rb in equation (B2) 202 Rb in equation (B4) 204 and Rb of formula (B5) 205 The specific form and preferred form are the same, therefore, Rb will be referred to below. 201 、Rb 202 、Rb 204 and Rb 205 Collectively referred to as "Rb" 200 To explain.

[0352] Rb 200 The alkyl group involving 1 or more but less than 3 carbon atoms can be any of the following: straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or 2, and more preferably 1.

[0353] Examples of alkyl groups with 1 or more but less than 3 carbon atoms include methyl, ethyl, n-propyl, isopropyl, and cyclopropyl.

[0354] Rb in equation (B1) 401 Rb in equation (B2) 402 Rb in equation (B3) 403 Rb in equation (B4) 404 Rb in equation (B5) 405 Rb in equation (B6) 406 Rb in equation (B7) 407 and Rb of formula (B8) 408 The specific form and preferred form are the same, therefore, Rb will be referred to below. 401 、Rb 402 、Rb 403 、Rb 404 、Rb 405 、Rb 406 、Rb 407 and Rb 408 Collectively referred to as "Rb" 400 To explain.

[0355] Rb 400 The alkyl group involving 1 or more and 4 or less carbon atoms can be any of the following: straight-chain, branched, and cyclic. The alkyl group preferably has 1 or more and 3 or less carbon atoms, more preferably 1 or 2, and even more preferably 1.

[0356] Examples of straight-chain alkyl groups with 1 or more but less than 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl.

[0357] Examples of branched alkyl groups with 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl.

[0358] Examples of cyclic alkyl groups with 3 or 4 carbon atoms include cyclopropyl and cyclobutyl.

[0359] Rb 400 The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms preferably has 1 or more and 4 or less carbon atoms, more preferably 1 or more and 3 or less carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0360] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0361] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0362] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0363] As Rb 400 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0364] Rb in equation (B1) 501 Rb in equation (B2) 502 Rb in equation (B3) 503 Rb in equation (B4) 504 Rb in equation (B5) 505 Rb in equation (B6) 506 Rb in equation (B7) 507 and Rb of formula (B8) 508 The specific form and preferred form are the same, therefore, Rb will be referred to below. 501 、Rb 502 、Rb 503 、Rb 504 、Rb 505 、Rb 506 、Rb 507 and Rb 508 Collectively referred to as "Rb" 500 To explain.

[0365] Rb 500The alkyl group involving 1 or more and 4 or less carbon atoms can be any of the following: straight-chain, branched, and cyclic. The alkyl group preferably has 1 or more and 3 or less carbon atoms, more preferably 1 or 2, and even more preferably 1.

[0366] Examples of straight-chain alkyl groups with 1 or more but less than 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl.

[0367] Examples of branched alkyl groups with 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl.

[0368] Examples of cyclic alkyl groups with 3 or 4 carbon atoms include cyclopropyl and cyclobutyl.

[0369] Rb 500 The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms preferably has 1 or more and 4 or less carbon atoms, more preferably 1 or more and 3 or less carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0370] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0371] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0372] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0373] As Rb 500 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0374] Rb in equation (B1) 801 Rb in equation (B2) 802 Rb in equation (B3) 803 Rb in equation (B4) 804 Rb in equation (B5) 805 Rb in equation (B6) 806 Rb in equation (B7) 807 and Rb of formula (B8) 808 The specific form and preferred form are the same, therefore, Rb will be referred to below. 801 、Rb 802 、Rb 803 、Rb 804 、Rb805 、Rb 806 、Rb 807 and Rb 808 Collectively referred to as "Rb" 800 To explain.

[0375] Rb 800 The alkyl group involving 1 or more and 4 or less carbon atoms can be any of the following: straight-chain, branched, and cyclic. The alkyl group preferably has 1 or more and 3 or less carbon atoms, more preferably 1 or 2, and even more preferably 1.

[0376] Examples of straight-chain alkyl groups with 1 or more but less than 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl.

[0377] Examples of branched alkyl groups with 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl.

[0378] Examples of cyclic alkyl groups with 3 or 4 carbon atoms include cyclopropyl and cyclobutyl.

[0379] Rb 800 The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms preferably has 1 or more and 4 or less carbon atoms, more preferably 1 or more and 3 or less carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0380] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0381] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0382] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0383] As Rb 800 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0384] Rb in equation (B1) 901 Rb in equation (B2) 902 Rb in equation (B3) 903 Rb in equation (B4) 904 Rb in equation (B5) 905 Rb in equation (B6) 906 Rb in equation (B7)907 and Rb of formula (B8) 908 The specific form and preferred form are the same, therefore, Rb will be referred to below. 901 、Rb 902 、Rb 903 、Rb 904 、Rb 905 、Rb 906 、Rb 907 and Rb 908 Collectively referred to as "Rb" 900 To explain.

[0385] Rb 900 The alkyl group involving 1 or more and 4 or less carbon atoms can be any of the following: straight-chain, branched, and cyclic. The alkyl group preferably has 1 or more and 3 or less carbon atoms, more preferably 1 or 2, and even more preferably 1.

[0386] Examples of straight-chain alkyl groups with 1 or more but less than 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl.

[0387] Examples of branched alkyl groups with 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl.

[0388] Examples of cyclic alkyl groups with 3 or 4 carbon atoms include cyclopropyl and cyclobutyl.

[0389] Rb 900 The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms preferably has 1 or more and 4 or less carbon atoms, more preferably 1 or more and 3 or less carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0390] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0391] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0392] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0393] As Rb 900 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0394] Hereinafter, diol units (B1-1) to (B1-6) are specifically shown as diol units (B1). The diol unit (B1) is not limited to this.

[0395] [Chemical Formula 31]

[0396]

[0397] Hereinafter, diol units (B2-1) to (B2-11) are specifically shown as diol units (B2). The diol unit (B2) is not limited to these.

[0398] [Chemical Formula 32]

[0399]

[0400] Hereinafter, diol units (B3-1) to (B3-4) are specifically shown as diol units (B3). The diol unit (B3) is not limited to these.

[0401] [Chemical Formula 33]

[0402]

[0403] Hereinafter, diol units (B4-1) to (B4-7) are specifically shown as diol units (B4). The diol unit (B4) is not limited to this.

[0404] [Chemical Formula 34]

[0405]

[0406] Hereinafter, diol units (B5-1) to (B5-6) are specifically shown as diol units (B5). The diol unit (B5) is not limited to these.

[0407] [Chemical Formula 35]

[0408]

[0409] Hereinafter, diol units (B6-1) to (B6-4) are specifically shown as diol units (B6). The diol unit (B6) is not limited to these.

[0410] [Chemical Formula 36]

[0411]

[0412] Hereinafter, diol units (B7-1) to (B7-3) are specifically shown as diol units (B7). The diol unit (B7) is not limited to these.

[0413] [Chemical Formula 37]

[0414]

[0415] Hereinafter, diol units (B8-1) to (B8-3) are specifically shown as diol units (B8). The diol unit (B8) is not limited to these.

[0416] [Chemical Formula 38]

[0417]

[0418] The diol unit (B) contained in polyaryl ester resin (PA) can be one or more.

[0419] The mass percentage of the diol unit (B) in the polyaryl ester resin (PA) is preferably 25% by mass or more and 80% by mass or less.

[0420] If the mass percentage of the diol unit (B) is 25% by mass or more, the stripping of the charge transport layer can be suppressed. From this point of view, the mass percentage of the diol unit (B) is more preferably 30% by mass or more, and even more preferably 35% by mass or more.

[0421] If the mass percentage of the diol unit (B) is 80% by mass or less, the wear resistance can be improved by maintaining the solubility relative to the coating liquid used to form the charge transport layer. From this point of view, the mass percentage of the diol unit (B) is more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0422] Polyaryl ester resins (PA) may contain diol units other than the diol unit (B). Examples of other diol units include, for instance, aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) and alicyclic diols (e.g., cyclohexanediol, cyclohexanediol, hydrogenated bisphenol A). The polyaryl ester resin (PA) may contain one or more of these diol units.

[0423] The ends of polyarylate resins (PA) can be sealed or modified by end-capping agents or molecular weight regulators used during manufacturing. Examples of end-capping agents or molecular weight regulators include monohydric phenols, monohydric acyl chlorides, monohydric alcohols, and monohydric carboxylic acids.

[0424] Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m-phenylphenol, p-phenylphenol, and o-methoxyphenol. Phenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, 2-phenyl-2-(3-hydroxyphenyl)propane.

[0425] Examples of monoacyl chlorides include benzoyl chloride, benzoyl chloride, methanesulfonyl chloride, phenyl chloroformate, acetyl chloride, butyryl chloride, octanoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, phenylphosphonic chloride, and their substituted derivatives, which are all functional acid acyl halides.

[0426] Examples of monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenylethanol.

[0427] Examples of monocarboxylic acids include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, methylbenzoic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0428] The weight-average molecular weight of the polyaryl ester resin (PA) is preferably 30,000 or more and 300,000 or less, more preferably 40,000 or more and 250,000 or less, and even more preferably 50,000 or more and 200,000 or less.

[0429] The molecular weight of polyaryl ester resin (PA) is the molecular weight converted from polystyrene as determined by GPC (gel permeation chromatography). Tetrahydrofuran is used as the eluent in GPC.

[0430] Polyaryl ester resins (PA) are obtained by conventional methods involving the polycondensation of monomers containing dicarboxylic acid units (A), monomers containing diol units (B), and other monomers as needed. Examples of monomer polycondensation methods include interfacial polymerization, solution polymerization, and melt polymerization. Interfacial polymerization is a polymerization method that obtains polyesters by mixing a dicarboxyl halogen dissolved in a water-incompatible organic solvent and a diol dissolved in an alkaline aqueous solution. References related to interfacial polymerization include WMEARECKSON, J. Poly. Sci., XL399, 1959, Japanese Patent Publication No. 40-1959. Compared to solution polymerization, interfacial polymerization has a faster reaction rate, thus suppressing the hydrolysis of the dicarboxyl halogen, resulting in the production of high molecular weight polyaryl ester resins (PA).

[0431] The proportion of polyaryl ester resin (PA) in the total adhesive resin relative to the charge transport layer is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 75% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less.

[0432] (Other adhesive resins)

[0433] In addition to polyaryl ester resin (PA), polycarbonate resin can also be used as the binding resin in the charge transport layer. When both polyaryl ester resin (PA) and polycarbonate resin are used, the ester bonds in polycarbonate have higher symmetry and lower local polarity compared to the carbonate bonds in polyaryl ester resin. Therefore, it is presumed that, for example, fewer charge carriers are trapped in the charge transport layer compared to polyaryl ester resin alone, thus making it less likely to hinder charge transfer, which is therefore preferable.

[0434] The proportion of polyaryl ester resin (PA) in the total amount of polyaryl ester resin (PA) and polycarbonate resin contained in the charge transport layer is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 75% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less.

[0435] Polyaryl ester resins (PAs) improve the wear resistance of the charge transport layer by stacking aromatic rings, which binds the resin molecules together through intermolecular forces. For example, condensation polymers of bisphenols and aromatic dicarboxylic acids are preferred as polyaryl ester resins (PAs).

[0436] As a polycarbonate resin, a polycarbonate resin having a continuous structure of aromatic rings is preferred, for example. This polycarbonate resin, through the stacking of aromatic rings, allows resin molecules to be bonded together by intermolecular forces, thereby improving the wear resistance of the charge transport layer. Specifically, the polycarbonate resin disclosed in Japanese Patent Application Publication No. 2023-121553 can be cited as an example of a polycarbonate resin.

[0437] The combination of polyaryl ester resin (PA) and polycarbonate resin is preferably a combination of resins in which both have structural units containing biphenyl as represented by the following formula (BP). That is, for example, it is preferable that the polyaryl ester resin (PA) and the polycarbonate resin each have structural units containing biphenyl as represented by the following formula (BP). By including biphenyl in the polyaryl ester resin (PA) and the polycarbonate resin respectively, the orientation of the molecules towards each other becomes stronger. As a result, the dielectric constant of the charge transport layer becomes larger, and when the same amount of charge is trapped therein, the potential change is less likely to appear, thus easily suppressing potential fluctuations after the formation of an electrostatic latent image.

[0438] Furthermore, it is presumed that by having structural units containing biphenyl in both resins, the compatibility between polyaryl ester resin (PA) and polycarbonate resin is improved, and the charge trapping caused by the structure of each resin is reduced.

[0439] [Chemical Formula 39]

[0440]

[0441] In equation (BP), j is an integer greater than 0 and less than 4, and j are R... 1 Each is independently methyl or ethyl, k is an integer greater than or equal to 0 and less than or equal to 4, and k R's are independent of each other. 2 Each can be methyl or ethyl, independently.

[0442] The biphenyl represented by formula (BP) can be the entire structure obtained by removing ester bonds (-C(=O)O-) or carbonate bonds (-OC(=O)O-) from the structural unit containing the biphenyl represented by formula (BP), or it can be a part of the structure. In other words, the right and left ends of the biphenyl represented by formula (BP) can be directly bonded to ester bonds or carbonate bonds independently, or they can be bonded to ester bonds or carbonate bonds through other atoms or groups.

[0443] j is an integer greater than or equal to 0 and less than 4, preferably an integer greater than or equal to 0 and less than 3, more preferably an integer greater than or equal to 0 and less than 2, further preferably 0 or 1, and especially preferably 0.

[0444] When j is an integer greater than or equal to 1, j R 1 Each is independently methyl or ethyl, for example preferably methyl.

[0445] k is an integer greater than or equal to 0 and less than 4, preferably an integer greater than or equal to 0 and less than 3, more preferably an integer greater than or equal to 0 and less than 2, further preferably 0 or 1, and especially preferably 0.

[0446] When k is an integer greater than or equal to 1, k R 2 Each is independently methyl or ethyl, for example preferably methyl.

[0447] The biphenyl represented by formula (BP) is preferably linked at a 4,4'-biphenyl position in the main chain.

[0448] As a combination of polyaryl ester resin (PA) and polycarbonate resin, a combination of polyaryl ester resin (PA) having at least one of dicarboxylic acid unit (A2-3) and diol unit (B7-1) and polycarbonate resin having structural unit (Cb7-1) is particularly preferred.

[0449] [Chemical Formula 40]

[0450]

[0451] In addition to polyaryl ester resin (PA) and polycarbonate resin, the bonding resin used in the charge transport layer can also be methacrylic acid resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polysilane, and other resins.

[0452] The proportion of other resins in the adhesive resin is preferably 10% by mass or less, and more preferably 5% by mass or less.

[0453] Furthermore, the mixing ratio of the charge transport material to the binder resin is preferably 10:1 to 1:5 by mass, for example.

[0454] (Other additives)

[0455] Other known additives may be included in the charge transport layer.

[0456] For example, the charge transport layer can contain phenolic compounds.

[0457] Examples of phenolic compounds included in the charge transport layer include phenol, cresol, catechol, resorcinol, hydroquinone, naphthol, and bisphenols (bisphenol A, AP, AF, B, BP, C, C2, E, F, G, M, S, P, PH, TMC, Z). A single phenolic compound can be used, or two or more can be used simultaneously.

[0458] Hindered phenolic compounds can also be cited as phenolic compounds contained in the charge transport layer. From the viewpoint of suppressing the oxidative degradation of the charge transport layer, the phenolic compounds contained in the charge transport layer preferably include, for example, hindered phenolic compounds. Generally, hindered phenolic compounds are compounds in which at least one of the ortho positions of the hydroxyl groups of phenol is substituted with a bulky group, and they are known to exert an antioxidant effect on the composition.

[0459] Examples of hindered phenolic compounds include the following compounds.

[0460] Alkylated monophenol compounds and their derivatives: for example, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, octyl-3,5-di-tert-butyl-4-hydroxy-hydroxycinnamate.

[0461] Alkylated hydroquinone compounds and their derivatives: for example, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-pentylhydroquinone

[0462] Alkyl thiocresol compounds and their derivatives: for example, 2,4-dioctylthiomethyl-6-tert-butylphenol, 2,4-dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-docodecylthiomethyl-4-nonylphenol

[0463] Alkylene bisphenol compounds and their derivatives: for example, 4,4'-butyride bis(6-tert-butyl-3-methylphenol), 2,2'-methylene bis(6-tert-butyl-4-methylphenol), 2,2'-methylene bis(6-tert-butyl-4-ethylphenol), 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane

[0464] Commercially available hindered phenolic compounds include ADEKA CORPORATION's "ADKSTAB AO-80", "ADKSTAB AO-60", "ADKSTAB AO-50", "ADKSTAB AO-40", "ADKSTAB AO-30", "ADKSTAB AO-20", and "ADKSTAB AO-330"; BASF Japan Ltd.'s "Irganox 1010", "Irganox 245", "Irganox 1076", and "Irganox 1520"; and Sumitomo Chemical Co., Ltd.'s "Sumilizer GA-80", "Sumilizer GM", and "Sumilizer GS".

[0465] Hindered phenolic compounds can be used alone or in combination with two or more compounds.

[0466] The content of phenolic compounds contained in the charge transport layer is preferably 0.1% by mass or more and 20% by mass or less relative to the total mass of the charge transport layer, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less.

[0467] In the charge transport layer, the proportion of fluoropolymer particles in the layer is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass (i.e., it does not contain fluoropolymer particles).

[0468] Given the high likelihood of stricter restrictions on the manufacture and use of organofluorine compounds in the future, the content of fluoropolymer particles is preferably within the range described above.

[0469] -Relative permittivity of the charge transport layer-

[0470] The relative permittivity of the charge transport layer is preferably 3.0 or more and 5.0 or less, more preferably 3.0 or more and 4.0 or less, and even more preferably 3.1 or more and 3.3 or less.

[0471] If the relative permittivity of the charge transport layer is 3.0 or higher, then, for example, the ratio of the relative permittivity of the charge transport layer to that of the underlying layer becomes a preferred range, thus making it easier to suppress potential fluctuations after the formation of an electrostatic latent image.

[0472] If the relative permittivity of the charge transport layer is below 5.0, it will suppress the situation where the ratio of the relative permittivity of the charge transport layer to that of the underlying layer is too large, thereby making it easier to suppress potential changes after the formation of electrostatic latent images.

[0473] By ensuring that the relative permittivity of the charge transport layer meets the above range, the chargeability of the photoreceptor is improved.

[0474] As a method for setting the relative permittivity of the charge transport layer within the aforementioned range, there are methods that control it according to the structure of the resin used. For example, if a substance containing a large number of aromatic rings in its structure is used, or a substance with little twisting is used as the structural element, there is a tendency for the dielectric constant to easily increase due to molecular stacking. Furthermore, a method can be cited that obtains an intermediate value of their relative permittivity by mixing multiple resins.

[0475] - The ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlying coating layer-

[0476] The ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat (relative permittivity of the charge transport layer / relative permittivity of the undercoat) is preferably 0.010 or more and 0.400 or less, more preferably 0.02 or more and 0.2 or less, and even more preferably 0.03 or more and 0.1 or less.

[0477] If the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat is 0.01 or higher, then, for example, the relative permittivity of the undercoat relative to the charge transport layer is within a preferred range, thereby preventing the following situation: in order to increase the voltage of the charge transport layer, the voltage of the undercoat is excessively reduced, resulting in potential changes after the formation of an electrostatic latent image.

[0478] If the ratio of the relative permittivity of the charge transport layer to that of the underlying layer is 0.40 or less, then, for example, the relative permittivity of the underlying layer becomes a preferred range, thereby suppressing the voltage drop applied to the charge transport layer and easily suppressing potential changes after the formation of an electrostatic latent image.

[0479] When the ratio of the relative permittivity of the charge transport layer to that of the underlying layer satisfies the aforementioned range, the permittivity of the underlying layer of the photoreceptor increases, and the voltage applied to the charge transport layer increases. Consequently, potential fluctuations after the formation of the electrostatic latent image are suppressed.

[0480] The relative permittivity of the charge transport layer and the underlying coating was determined as follows.

[0481] First, the electrostatic capacitance (C) of the charge transport layer CT ) and the electrostatic capacitance of the underlying coating (C) UC The following methods are used to determine and calculate it.

[0482] A sample of appropriate size (i.e., a sample with a base coat, a charge generation layer, and a charge transport layer stacked on a conductive substrate) was cut from the photoreceptor of the test object. A 3 mm radius Au electrode was formed as the counter electrode using vacuum evaporation. Using an impedance analyzer, with a DC voltage of 10 V and an AC voltage of 2 V applied from the conductive substrate and the Au electrode to the base coat, the capacitance at an AC frequency of 1 Hz was measured. This capacitance was denoted as C. T .

[0483] Next, the sample was designed so that the charge transport layer and charge generation layer were removed using a solvent, leaving a single layer of the undercoat on the conductive substrate. In this state, an Au electrode with a radius of 3 mm was formed on the surface of the undercoat. Using an impedance analyzer, with a DC voltage of 10V and an AC voltage of 2V applied from the conductive substrate and the Au electrode to the undercoat, the capacitance of the undercoat at an AC frequency of 1Hz was measured. The capacitance of this undercoat was defined as C. UC .

[0484] The electrostatic capacity C of the charge transport layer CT According to the capacitance C T and the electrostatic capacitance C of the undercoat UC It can be obtained by the following formula.

[0485] Formula: C CT =(C T ×C UC ) / (C UC -C T )

[0486] Based on the electrostatic capacitance C of the charge transport layer CT and the electrostatic capacitance C of the undercoat UC The relative permittivity of the charge transport layer and the underlying layer is calculated using the following formula, based on the dielectric constant of vacuum, the area of ​​the Au electrode, and the film thickness of each layer.

[0487] Formula: Relative permittivity of the object layer = (C / S×d) / ε0

[0488] In the formula, C is the electrostatic capacitance of the target layer (F), and S is the capacitance of the Au electrode (m). 2 ), d is the film thickness of the target layer (m), ε0 is the dielectric constant of vacuum (=8.854×10 ) -12 )

[0489] -Thickness of each layer-

[0490] In addition, when the lower coating is set as a single layer, a cut is made in the film with a cutting tool or the like to expose the conductive substrate, and the depth of the exposed part is measured with a roughness gauge.

[0491] The thickness of the charge transport layer is calculated as follows: a cut is made in each layer below the charge transport layer with a cutting tool to expose the conductive substrate, and the depth of the exposed portion is measured with a roughness gauge. The thickness of the aforementioned lower coating layer is subtracted from the thickness of each layer below the charge transport layer.

[0492] There are no particular limitations on the formation of the charge transport layer, and known formation methods can be used. For example, a coating film can be formed by adding the above-mentioned components to a solvent for forming a charge transport layer, and the coating film can be dried and heated as needed.

[0493] Examples of solvents used in preparing coating solutions for charge transport layer formation include aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and vinyl chloride; and cyclic or linear ethers such as tetrahydrofuran and diethyl ether. These solvents can be used alone or in combination of two or more.

[0494] Common methods for applying a coating liquid for forming a charge transport layer onto a charge generation layer include scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, and curtain coating.

[0495] The thickness of the charge transport layer is preferably set in the range of 5 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

[0496] <Image forming apparatus, processing box>

[0497] The image forming apparatus according to this embodiment includes an electrophotographic photosensitive body, a charging device for charging the surface of the electrophotographic photosensitive body, an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive body, a developing device for forming a toner image by developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive body with a developing agent containing a toner, a transfer device for transferring the toner image onto the surface of a recording medium, and a cleaning device for cleaning the surface of the electrophotographic photosensitive body. Furthermore, the electrophotographic photosensitive body according to this embodiment is applicable.

[0498] In the image forming apparatus of this embodiment, the cleaning device has a cleaning blade that contacts the outer peripheral surface of the photoreceptor, and the cleaning blade cleans the surface of the photoreceptor after the toner image is transferred and before it is charged.

[0499] The image forming apparatus according to this embodiment is applicable to the following known image forming apparatuses: an apparatus having a fixing apparatus for fixing a toner image transferred to the surface of a recording medium; an apparatus for a direct transfer method that directly transfers a toner image formed on the surface of an electrophotographic photosensitive body to the recording medium; an apparatus for an intermediate transfer method that transfers a toner image formed on the surface of an electrophotographic photosensitive body to the surface of an intermediate transfer body in one step, and then transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium in a second step; an apparatus having an antistatic apparatus for irradiating the surface of an electrophotographic photosensitive body with antistatic light after the toner image is transferred but before it is charged to eliminate static electricity; and an apparatus having an electrophotographic photosensitive body heating member for raising the temperature of the electrophotographic photosensitive body and lowering the relative temperature, etc.

[0500] In the case of an intermediate transfer method apparatus, the transfer apparatus may have a structure that includes an intermediate transfer body for transferring a toner image onto a surface, a primary transfer apparatus for transferring a toner image formed on the surface of an electrophotographic photosensitive body to the surface of the intermediate transfer body in one step, and a secondary transfer apparatus for transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium in a second step.

[0501] The image forming apparatus described in this embodiment can be either a dry developing image forming apparatus or a wet developing image forming apparatus (a developing method that utilizes liquid developer).

[0502] In the image forming apparatus according to this embodiment, for example, the portion including the electrophotographic photosensitive element can be a cassette structure (processing cassette) that is detachable from the image forming apparatus. As the processing cassette, for example, a processing cassette including the electrophotographic photosensitive element according to this embodiment is preferably used. In addition to the electrophotographic photosensitive element, the processing cassette may also include at least one selected from the group consisting of a charging device, an electrostatic latent image forming apparatus, a developing apparatus, and a transfer apparatus.

[0503] The following describes an example of the image forming apparatus according to this embodiment, but it is not limited thereto. The main parts shown in the figures will be described, while the description of other parts will be omitted.

[0504] Figure 2 This is a schematic structural diagram illustrating an example of the image forming apparatus according to this embodiment.

[0505] like Figure 2As shown, the image forming apparatus 100 according to this embodiment includes a processing cartridge 300 having an electrophotographic photosensitive element 7, an exposure apparatus 9 (an example of an electrostatic latent image forming apparatus), a transfer apparatus 40 (a primary transfer apparatus), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure apparatus 9 is positioned to expose the electrophotographic photosensitive element 7 through the opening of the processing cartridge 300, and the transfer apparatus 40 is positioned opposite the electrophotographic photosensitive element 7 across the intermediate transfer body 50, with a portion of the intermediate transfer body 50 in contact with the electrophotographic photosensitive element 7. Although not shown, a secondary transfer apparatus is also included to transfer the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer apparatus 40 (a primary transfer apparatus), and the secondary transfer apparatus (not shown) are examples of transfer apparatuses.

[0506] Figure 2 The processing cartridge 300 integrally supports the electrophotographic photoreceptor 7, the charging device 8 (an example of the charging device), the developing device 11 (an example of the developing device), and the cleaning device 13 (an example of the cleaning device) within the housing. The cleaning device 13 has a cleaning blade (an example of a cleaning component) 131, which is configured to contact the surface of the electrophotographic photoreceptor 7. The cleaning component may be a conductive or insulating fibrous component instead of the cleaning blade 131, and may be used alone or in conjunction with the cleaning blade 131.

[0507] exist Figure 2 In the example shown, as an image forming apparatus, a fibrous component 132 (roller-shaped) is provided for supplying lubricant 14 to the surface of the electrophotographic photosensitive element 7, and a fibrous component 133 (flat brush-shaped) is provided for auxiliary cleaning, but they can be configured as needed.

[0508] The structure of the image forming apparatus according to this embodiment will be described below.

[0509] -Electrified devices-

[0510] The charging device 8 can be a contact-type charging device where the charged component is in contact with the peripheral surface of the photoreceptor, or a non-contact-type charging device where the charged component is not in contact with the peripheral surface of the photoreceptor. The effect of the image forming apparatus according to this embodiment (not easily contaminated by the charged component over a long period of time) is particularly significant in the contact-type charging device.

[0511] As the charging device 8, contact-type charging components that utilize conductive or semi-conductive materials, such as charging rollers, charging brushes, charging films, charging rubber scrapers, and charging hoses, can be used. Furthermore, non-contact roller belt chargers, grid corona tube belt chargers utilizing corona discharge, or corona tube belt chargers, and other known charging devices, can also be used.

[0512] -Exposure device-

[0513] Examples of exposure devices 9 include optical systems that expose semiconductor lasers, LED lights, liquid crystal shutter lights, etc., onto the surface of an electrophotographic photosensitive object 7 to form a predetermined pattern. The wavelength of the light source is set within the spectral sensitivity range of the electrophotographic photosensitive object. Near-infrared light with an oscillation wavelength around 780 nm is the most common wavelength for semiconductor lasers. However, it is not limited to this wavelength; lasers with an oscillation wavelength in the 600 nm band or blue lasers, or lasers with an oscillation wavelength in the range of 400 nm to 450 nm, can be used. Furthermore, surface-emitting laser sources capable of outputting multiple beams for forming color images are also effective.

[0514] -Developing apparatus-

[0515] As a developing apparatus 11, examples include conventional developing apparatuses that perform development by contact or non-contact with the developer. There are no particular limitations on the developing apparatus 11 as long as it possesses the aforementioned functions, and it can be selected according to the purpose. For example, known developing machines that use brushes, rollers, etc., to adhere single-component or two-component developers to the electrophotographic photosensitive element 7 can be cited. Among these, a developing machine that uses a developing roller to hold the developer on the surface is preferred, for example.

[0516] The developer used in the developing apparatus 11 can be a single-component developer containing only a toner, or a two-component developer containing both a toner and charge carriers. Furthermore, the developer can be magnetic or non-magnetic. Commonly known developers are acceptable.

[0517] -Cleaning Device-

[0518] The cleaning device 13 is a cleaning scraper device equipped with a cleaning scraper 131. In addition to the cleaning scraper method, a brush cleaning method or a simultaneous developing and cleaning method can also be used.

[0519] -Transfer Device-

[0520] As a transfer device 40, examples include contact transfer belt appliances that use belts, rollers, films, rubber squeegees, etc.; grid corona tube transfer belt appliances that utilize corona discharge; and corona tube transfer belt appliances, which are known in themselves.

[0521] -Intermediate Transfer Material-

[0522] As the intermediate transfer body 50, a strip-shaped transfer body (intermediate transfer tape) containing polyimide, polyamide-imide, polycarbonate, polyarylate, polyester, rubber, etc., which are endowed with semi-conductivity is used. Furthermore, in addition to the strip shape, a drum-shaped transfer body can also be used as the intermediate transfer body.

[0523] Figure 3 This is a schematic structural diagram showing another example of the image forming apparatus according to this embodiment.

[0524] Figure 3 The image forming apparatus 120 shown is a multicolor image forming apparatus equipped with four processing cartridges 300 arranged in series. In the image forming apparatus 120, four processing cartridges 300 are arranged side by side on the intermediate transfer body 50, and a structure is formed in which one electrophotographic photosensitive element is used for each color. Except for the series arrangement, the image forming apparatus 120 has the same structure as the image forming apparatus 100.

[0525] Example

[0526] The following describes the implementation of the invention in detail with reference to the embodiments, but the implementation of the invention is not limited to these embodiments in any way.

[0527] Unless otherwise specified, “parts” and “%” are quality standards in the following description.

[0528] Unless otherwise specified, the synthesis, processing, and manufacturing processes are carried out at room temperature (25℃±3℃).

[0529] <Example 1>

[0530] [Formation of the undercoat]

[0531] Zinc oxide particles (average particle size 70 nm, specific surface area 15 m²) were used. 2 100 parts of zinc oxide (manufactured by TAYCA CORPORATION) were mixed with 500 parts of toluene and stirred. 1.3 parts of a silane coupling agent (trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) were added, and the mixture was stirred for 2 hours. Then, the toluene was distilled under reduced pressure, and sintered at 120°C for 3 hours to obtain zinc oxide particles surface-treated with the silane coupling agent.

[0532] 110 parts of surface-treated zinc oxide particles were mixed with 500 parts of tetrahydrofuran to form an electron-accepting compound. A solution prepared by dissolving 0.6 parts of the above compound (A) in 50 parts of tetrahydrofuran was added, and the mixture was stirred at 50°C for 5 hours. Then, the solid components were filtered off by vacuum filtration and dried under reduced pressure at 60°C to obtain zinc oxide particles endowed with the electron-accepting compound.

[0533] A solution of 60 parts zinc oxide particles (a compound that imparts electron-accepting properties), 13.5 parts curing agent (terminated isocyanate, trade name: SUMIDUR3175, manufactured by Sumika Bayer Urethane Co., Ltd.), and 15 parts butyral resin (trade name: S-LEC BM-1, manufactured by SEKISUI CHEMICAL CO.,LTD.) dissolved in 68 parts methyl ethyl ketone and 5 parts methyl ethyl ketone was used. Glass beads were dispersed in a sand mill for 2 hours to obtain a dispersion. 0.005 parts of dioctyltin dilaurate and 4 parts of silicone resin particles (trade name: TOSPEARL145, manufactured by Momentive Performance Materials Inc.) were added to the dispersion as a catalyst to obtain a coating solution for forming the undercoat. The coating solution for forming the undercoat was applied to the outer peripheral surface of a conductive substrate by dip coating, and dried and cured at 170°C for 40 minutes to form an undercoat with a film thickness of 23.5 μm.

[0534] [Formation of the charge generation layer]

[0535] A mixture consisting of 15 parts of hydroxyl gallium phthalocyanine (which exhibits diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in X-ray diffraction spectra using Cukα characteristic X-rays), 10 parts of vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, manufactured by Nippon Unicar Company Limited) and 200 parts of n-butyl acetate was dispersed using glass beads with a diameter of 1 mm and milled in a sand mill for 4 hours. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion, and the mixture was stirred to obtain a coating solution for forming a charge-generating layer. The coating solution for forming the charge-generating layer was impregnated onto a lower coating layer and dried at room temperature (25°C±3°C) to form a charge-generating layer with a film thickness of 0.18 μm.

[0536] [Formation of the charge transport layer]

[0537] 35 parts of the following polyarylate resin (PA1) and 24 parts of the following polycarbonate resin (PC1) as binders, and 28.7 parts of CTM-1 and 12.3 parts of CTM-2 as charge transport materials were dissolved in 270 parts of tetrahydrofuran and 30 parts of toluene to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was impregnated onto a charge generation layer and dried at 143°C for 30 minutes to form a charge transport layer with a film thickness of 32 μm.

[0538] [Chemical Formula 41]

[0539]

[0540] The numbers marked on the structural units indicate the molar ratio.

[0541] [Chemical Formula 42]

[0542]

[0543] [Chemical Formula 43]

[0544]

[0545] The above process yields a photoreceptor.

[0546] <Example 2>

[0547] In the formation of the charge transport layer, the charge transport material was set to 41.0 parts of CTM-1 alone, and otherwise the photoreceptor was obtained in the same manner as in Example 1.

[0548] <Example 3>

[0549] In the formation of the lower coating, the mass percentage of zinc oxide particles imparting electron-receiving compounds was changed to 62% by mass, otherwise the photoreceptor was obtained in the same manner as in Example 1.

[0550] <Example 4>

[0551] In the formation of the lower coating, the mass percentage of zinc oxide particles imparting electron-receiving compounds was changed to 72% by mass, otherwise the photoreceptor was obtained in the same manner as in Example 1.

[0552] <Example 5>

[0553] In the formation of the charge transport layer, the ratio of the binder resin of the charge transport layer was changed to 17.7 parts of polyarylate resin and 41.3 parts of polycarbonate resin, and the charge transport material was set to 44 parts of CTM-1 alone. Otherwise, the photoreceptor was obtained in the same manner as in Example 1.

[0554] <Example 6>

[0555] In the formation of the charge transport layer, the binder resin of the charge transport layer was changed to 59.0 parts of polyarylate resin alone. As the charge transport material, CTM-1 was set to 26.4 parts and CTM-2 was set to 11.3 parts. Otherwise, the photoreceptor was obtained in the same manner as in Example 1.

[0556] <Example 7>

[0557] In the formation of the charge transport layer, the binder resin of the charge transport layer was changed to 59.0 parts of a polyarylate resin (PA2) with 50 mol% of dicarboxylic acid units (A2-3) and 50 mol% of diol units (B4-3). Otherwise, the photoreceptor was obtained in the same manner as in Example 1.

[0558] <Examples 8 and 9>

[0559] In the formation of the lower coating, the electron-receiving compound was changed to the compound described in Table 1, and otherwise the photoreceptor was obtained in the same manner as in Example 1.

[0560] <Example 10>

[0561] In the formation of the lower coating, the mass percentage of zinc oxide particles containing electron-accepting compounds in the lower coating was changed to 75% by mass. In the formation of the charge transport layer, the ratio of the binder resin in the charge transport layer was changed to 17.7 parts of polyarylate resin and 41.3 parts of polycarbonate resin. The charge transport material was set to 44 parts of CTM-1 alone. Otherwise, the photoreceptor was obtained in the same manner as in Example 1.

[0562] <Examples 11-14>

[0563] In the formation of the lower coating, the film thickness of the lower coating is changed to the film thickness recorded in Table 1, and the photoreceptor is otherwise obtained in the same manner as in Example 1.

[0564] <Example 15>

[0565] In the formation of the charge transport layer, the polycarbonate resin of the charge transport layer was changed to the polycarbonate resin (PC3) shown below, otherwise the photoreceptor was obtained in the same manner as in Example 1.

[0566] [Chemical Formula 44]

[0567]

[0568] <Example 16>

[0569] In the formation of the charge transport layer, the polyaryl ester resin of the charge transport layer was changed to a polyaryl ester resin (PA3) in which the dicarboxylic acid units consisted of 40 mol% (A3-2) and 10 mol% (A4-3) and the diol units consisted of 50 mol% (B6-4), and the polycarbonate resin was changed to the above-mentioned polycarbonate resin (PC3). Otherwise, the photoreceptor was obtained in the same manner as in Example 1.

[0570] <Example 17>

[0571] In the formation of the charge transport layer, the polyaryl ester resin of the charge transport layer was changed to a polyaryl ester resin (PA4) in which the dicarboxylic acid unit is composed of 50 mol% (A3-2) and the diol unit is composed of 50 mol% (B4-4), and the polycarbonate resin was changed to the above-mentioned polycarbonate resin (PC3). Otherwise, the photoreceptor was obtained in the same manner as in Example 1.

[0572] <Comparative Examples 1 and 4>

[0573] In the formation of the lower coating, the electron-receiving compound was changed to the compound described in Table 1, and otherwise the photoreceptor was obtained in the same manner as in Example 1.

[0574] <Comparative Example 2>

[0575] In the formation of the lower coating, the mass percentage of zinc oxide particles imparting electron-receiving compounds was changed to 76%, otherwise the photoreceptor was obtained in the same manner as in Example 1.

[0576] <Comparative Example 3>

[0577] In the formation of the charge transport layer, the binder resin of the charge transport layer was changed to 59 parts of polycarbonate resin (PC1), otherwise the photoreceptor was obtained in the same manner as in Example 1.

[0578] <Comparative Example 5>

[0579] In the formation of the lower coating, the mass percentage of zinc oxide particles containing electron-accepting compounds in the lower coating was changed to 77%. In the formation of the charge transport layer, the ratio of the binder resin in the charge transport layer was changed to 17.7 parts of polyarylate resin and 41.3 parts of polycarbonate resin. Otherwise, the photoreceptor was obtained in the same manner as in Example 1.

[0580] <Comparative Example 6>

[0581] In the formation of the lower coating, the mass percentage of zinc oxide particles containing electron-accepting compounds in the lower coating was changed to 61%. In the formation of the charge transport layer, the binder resin of the charge transport layer was changed to 59 parts of polyarylate resin (PA1) alone. As charge transport materials, CTM-1 was set to 26.4 parts and CTM-2 was set to 11.3 parts. Otherwise, the photoreceptor was obtained in the same manner as in Example 1.

[0582] <Various Measurements>

[0583] The following items were determined using the methods described above.

[0584] • Capacitance of the undercoat

[0585] • The ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlying layer

[0586] Additionally, in the table, "(value A)E-(value B)" is expressed as (value A)×10 -(数值B) The value of .

[0587] <Performance Evaluation of Photoreceptors>

[0588] [Electrical potential variation]

[0589] The potential changes after the formation of the electrostatic latent image in each photoreceptor were evaluated below.

[0590] The photoreceptor was mounted on an image forming apparatus (a modified version of the Apeos C7070 manufactured by FUJIFILM Business Innovation Corporation). A potentiometric probe was installed at the developer location. Under conditions of 350 nm / sec processing speed, 30°C temperature, and 75% humidity, the photoreceptor was charged to 700V, and then 4 mJ / m² of potentiometric radiation was imparted. -2 The exposure sequence was repeated 6400 times, and the potential changes during this time were classified as follows.

[0591] A: Less than 15V

[0592] B: 15V or higher and less than 17.5V

[0593] C: 17.5V or higher and less than 20V

[0594] D: 20V or higher and less than 22.5V

[0595] E: 22.5V and above but less than 25V

[0596] F: 25V or higher but less than 27.5V

[0597]

[0598] As can be seen from the above results, the potential variation after electrostatic latent image formation is suppressed in the photoreceptor of the embodiment compared with that of the comparative example.

[0599] This implementation includes the following methods. (1)

[0601] An electrophotographic photosensitive material comprises: a conductive substrate; a lower coating layer disposed on the conductive substrate; and a stacked photosensitive layer disposed on the lower coating layer and having a charge generating layer and a charge transport layer, the charge transport layer comprising a charge transport material and a polyaryl ester resin, the polyaryl ester resin comprising a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), and the lower coating layer having a capacitance of 1.0 × 10⁻⁶.-10 F or higher and 3.0 × 10 -9 Below F,

[0602] [Chemical Formula 45]

[0603]

[0604] In equation (A), Ar A1 and Ar A2 Each is an aromatic ring that can have substituents, L A It is a single bond or a divalent linker, n A1 It can be 0, 1, or 2;

[0605] In equation (B), Ar B1 and Ar B2 Each is an aromatic ring that can have substituents, L B It is a single bond, an oxygen atom, a sulfur atom, or -C(Rb) 1 (Rb) 2 )-,n B1 It can be 0, 1, or 2; Rb 1 and Rb 2 Rb is independently composed of hydrogen atoms, an alkyl group having 1 or more but less than 20 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an aralkyl group having 7 or more but less than 20 carbon atoms. 1 With Rb 2 They can bond together to form cyclic alkyl groups. (2)

[0607] According to the electrophotographic photosensitive material of (1), the relative permittivity of the charge transport layer is 3.0 or more and 5.0 or less. (3)

[0609] According to the electrophotographic photosensitive material of (1) or (2), the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat layer, i.e., the relative permittivity of the charge transport layer / the relative permittivity of the undercoat layer, is 0.010 or more and 0.400 or less. (4)

[0611] According to any one of (1) to (3), the electrophotographic photosensitive material comprises zinc oxide particles imparted with an electron-receiving compound, which are 62% by mass or more and 75% by mass or less relative to the undercoat. (5)

[0613] According to the electron photophotoreceptor described in (4), the electron-receiving compound is an anthraquinone derivative having 3 OH groups or 2 OH groups and 1 alkoxy group. (6)

[0615] According to the electrophotographic photoreceptor described in (5), the anthraquinone derivative is an alizarin derivative represented by formula (C).

[0616] [Chemical Formula 46]

[0617]

[0618] In formula (C), R represents a hydroxyl group or an alkoxy group with 1 or more but less than 10 carbon atoms. (7)

[0620] According to any one of (1) to (6), the electrophotographic photosensitive material has a film thickness of 17 μm or more and 35 μm or less. (8)

[0622] According to any one of (1) to (7), the electrophotographic photoreceptor, wherein the charge transport layer further comprises a polycarbonate resin, wherein the polyaryl ester resin and the polycarbonate resin each have a structural unit comprising biphenyl represented by the following formula (BP).

[0623] [Chemical Formula 47]

[0624]

[0625] In equation (BP), j is an integer greater than 0 and less than 4, and j are R... 1 Each is independently methyl or ethyl, k is an integer greater than or equal to 0 and less than or equal to 4, and k R's are independent of each other. 2 Each can be methyl or ethyl, independently. (9)

[0627] A processing cartridge comprising any one of (1) to (8) an electrophotographic photosensitive element, the processing cartridge being detachable from an image forming apparatus. (10)

[0629] An image forming apparatus comprising: an electrophotographic photoreceptor as described in any one of (1) to (8); a charging unit for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming unit for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing unit for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developing agent containing a toner to form a toner image; and a transfer unit for transferring the toner image onto the surface of a recording medium.

[0630] The effects of the above methods are as follows.

[0631] According to the invention described in (1), a laminated photosensitive layer comprising a conductive substrate, an undercoat disposed on the conductive substrate, and a charge generation layer and a charge transport layer disposed on the undercoat, wherein the charge transport layer contains a charge transport material and a polyaryl ester resin, the polyaryl ester resin comprising a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), and the electrostatic capacitance of the undercoat is less than 1.0 × 10⁻⁶. -10 F or more than 3.0 × 10 -9 Compared to case F, an electrophotographic photoreceptor is provided in which potential changes after the formation of an electrostatic latent image are suppressed.

[0632] According to the invention involved in (2), an electrophotographic photoreceptor is provided in which potential changes after the formation of an electrostatic latent image are suppressed, compared to cases where the relative permittivity of the charge transport layer is less than 3.0 or greater than 5.0.

[0633] According to the invention involved in (3), an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed, compared to cases where the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat (relative permittivity of the charge transport layer / relative permittivity of the undercoat) is less than 0.010 or greater than 0.400.

[0634] According to the invention involved in (4), an electrophotographic photoreceptor is provided in which potential changes after electrostatic latent image formation are suppressed, compared to the case where the undercoat contains zinc oxide particles endowed with electron-receptive compounds in an amount of less than 62% by mass or more than 75% by mass.

[0635] According to the invention involved in (5), compared with the case where the electron receiving compound is an anthraquinone derivative that does not have 3 OH groups or does not have 2 OH groups and has 1 alkoxy group, an electron photosensitive material is provided in which potential changes after electrostatic latent image formation are suppressed.

[0636] According to the invention involved in (6), compared with the case where the anthraquinone derivative is an alizarin derivative that does not satisfy the structure represented by formula (C), an electrophotographic photoreceptor is provided in which potential changes after the formation of an electrostatic latent image are suppressed.

[0637] According to the invention involved in (7), an electrophotographic photoreceptor is provided in which potential changes after electrostatic latent image formation are suppressed, compared with the case where the film thickness of the undercoat is less than 17 μm or more than 35 μm.

[0638] According to the invention involved in (8), compared with the case where polyarylate resin and polycarbonate resin do not have structural units containing biphenyl, an electrophotographic photosensitive material is provided in which potential changes after electrostatic latent image formation are suppressed.

[0639] According to the invention described in (9) or (10), a laminated photosensitive layer comprising a conductive substrate, an undercoat disposed on the conductive substrate, and a charge generation layer and a charge transport layer disposed on the undercoat, wherein the charge transport layer contains a charge transport material and a polyaryl ester resin, the polyaryl ester resin comprising a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), and the capacitance of the undercoat is less than 1.0 × 10⁻⁶. -10 F or more than 3.0 × 10 -9 Compared to case F, a processing box or image forming apparatus for an electrophotographic photoreceptor is provided that suppresses potential changes after electrostatic latent image formation.

[0640] The embodiments of the present invention described above are provided for illustrative purposes. Furthermore, these embodiments do not encompass the entirety of the invention, nor do they limit the invention to the disclosed methods. It will be apparent to those skilled in the art that various modifications and variations will be readily understood. These embodiments were chosen and described to most readily explain the principles and applications of the invention. Thus, those skilled in the art can understand the invention through various modifications that are assumed to be optimized for specific uses of various embodiments. The scope of the invention is defined by the foregoing claims and their equivalents.

Claims

1. An electrophotographic photosensitive material, comprising: Conductive substrate; The lower coating layer is disposed on the conductive substrate; and A stacked photosensitive layer is disposed on the lower coating layer and has a charge generation layer and a charge transport layer. The charge transport layer contains a charge transport material and a polyarylate resin. The polyaryl ester resin comprises a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B). The electrostatic capacitance of the lower coating is 1.0 × 10⁻⁶. -10 F or higher and 3.0 × 10 -9 Below F, [Chemical Formula 1] In equation (A), Ar A1 and Ar A2 Each is an aromatic ring that can have substituents, L A It is a single bond or a divalent linker, n A1 It can be 0, 1, or 2; In equation (B), Ar B1 and Ar B2 Each is an aromatic ring that can have substituents, L B It is a single bond, an oxygen atom, a sulfur atom, or -C(Rb) 1 (Rb) 2 )-,n B1 It can be 0, 1, or 2; Rb 1 and Rb 2 Rb is independently composed of hydrogen atoms, an alkyl group having 1 or more but less than 20 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an aralkyl group having 7 or more but less than 20 carbon atoms. 1 With Rb 2 They can bond together to form cyclic alkyl groups.

2. The electrophotographic photosensitive material according to claim 1, wherein, The relative permittivity of the charge transport layer is above 3.0 and below 5.

0.

3. The electrophotographic photosensitive material according to claim 1 or 2, wherein, The ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat layer, i.e., the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat layer, is 0.010 or more and 0.400 or less.

4. The electrophotographic photosensitive material according to any one of claims 1 to 3, wherein, The undercoat comprises zinc oxide particles imparting an electron-receiving compound, which are 62% by mass or more and 75% by mass or less relative to the undercoat.

5. The electrophotographic photosensitive material according to claim 4, wherein, The electron-accepting compound is an anthraquinone derivative having three OH groups or two OH groups and one alkoxy group.

6. The electrophotographic photosensitive material according to claim 5, wherein, The anthraquinone derivative is an alizarin derivative represented by formula (C). [Chemical Formula 2] In formula (C), R represents a hydroxyl group or an alkoxy group with 1 or more but less than 10 carbon atoms.

7. The electrophotographic photosensitive material according to any one of claims 1 to 6, wherein, The thickness of the lower coating layer is greater than 17 μm and less than 35 μm.

8. The electrophotographic photosensitive material according to any one of claims 1 to 7, wherein, The charge transport layer also comprises polycarbonate resin. The polyaryl ester resin and the polycarbonate resin each have structural units comprising biphenyl represented by the following formula (BP). [Chemical Formula 3] In equation (BP), j is an integer greater than 0 and less than 4, and j are R... 1 Each is independently methyl or ethyl, k is an integer greater than or equal to 0 and less than or equal to 4, and k R's are independent of each other. 2 Each can be methyl or ethyl, independently.

9. A processing cartridge comprising the electrophotographic photosensitive element as described in any one of claims 1 to 8. The processing box is mounted and dismounted from the image forming apparatus.

10. An image forming apparatus comprising: Electrophotographic photoresist according to any one of claims 1 to 8; The charging unit charges the surface of the electrophotographic photosensitive element. An electrostatic latent image forming unit forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor; The developing unit develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor using a developing agent containing a toner to form a toner image. and The transfer unit transfers the toner image onto the surface of the recording medium.

Images