JP7613049B2 - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus.

Electrophotographic photoreceptors are used as image carriers in electrophotographic image forming apparatuses (e.g., printers or multifunction machines). Electrophotographic photoreceptors have a photosensitive layer. Examples of electrophotographic photoreceptors that can be used include single-layer electrophotographic photoreceptors and multi-layer electrophotographic photoreceptors. Single-layer electrophotographic photoreceptors have a single photosensitive layer that has a charge generation function and a charge transport function. Multi-layer electrophotographic photoreceptors have a photosensitive layer that includes a charge generation layer that has a charge generation function and a charge transport layer that has a charge transport function.

Patent Document 1 describes an electrophotographic photoreceptor having a photosensitive layer. The binder resin of this photosensitive layer is a polyarylate resin containing a structure represented by the following formula:

JP 2003-322982 A

However, the inventors' investigations revealed that the electrophotographic photoreceptor described in Patent Document 1 is insufficient in terms of sensitivity characteristics, filming resistance, and scratch resistance.

The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an electrophotographic photoreceptor that has excellent sensitivity characteristics, filming resistance, and scratch resistance. Another object of the present invention is to provide a process cartridge and an image forming apparatus that can improve the sensitivity characteristics, filming resistance, and scratch resistance of the electrophotographic photoreceptor.

The electrophotographic photoreceptor of the present invention includes a conductive substrate and a photosensitive layer. The photosensitive layer is a single layer. The photosensitive layer contains a charge generating agent, a hole transport agent, an electron transport agent, a polyarylate resin, and a dispersion aid. The charge generating agent contains titanyl phthalocyanine. The polyarylate resin contains a repeating unit represented by formula (1), a repeating unit represented by formula (2), and a repeating unit represented by formula (3). The ratio n1/ _n2 of the number n1 of the repeating units represented by formula (1) to the number _n2 of the repeating units represented by formula ( ₂ ) is _1.0 or more. The dispersion aid contains a compound represented by formula (30) or (31).

In the formula (1), ^R1 and ^R2 each represent a methyl group, and ^R3 and ^R4 are bonded to each other to represent a cycloalkylidene group having 5 or 6 carbon atoms, or ^R1 and ^R2 each independently represent a hydrogen atom or a methyl group, ^R3 represents a methyl group, and ^R4 represents a hydrogen atom or an alkyl group having 2 or 3 carbon atoms.

The process cartridge of the present invention is equipped with the electrophotographic photoreceptor.

The image forming apparatus of the present invention includes an image carrier, a charging device that charges the surface of the image carrier, an exposure device that exposes the charged surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier, a developing device that supplies toner to the surface of the image carrier to develop the electrostatic latent image as a toner image, and a transfer device that transfers the toner image from the image carrier to a transfer recipient. The image carrier is the electrophotographic photoreceptor described above.

The electrophotographic photoreceptor of the present invention has excellent sensitivity characteristics, filming resistance, and scratch resistance. Furthermore, the process cartridge and image forming apparatus of the present invention can improve the sensitivity characteristics, filming resistance, and scratch resistance of the electrophotographic photoreceptor.

1 is a partial cross-sectional view of an electrophotographic photoreceptor according to a first embodiment of the present invention. 1 is a partial cross-sectional view of an electrophotographic photoreceptor according to a first embodiment of the present invention. 1 is a partial cross-sectional view of an electrophotographic photoreceptor according to a first embodiment of the present invention. FIG. 11 is a diagram illustrating an example of a configuration of an image forming apparatus according to a second embodiment of the present invention. FIG. 5 is a diagram showing an example of the configuration of the developing device shown in FIG. 4 .

The following describes in detail the embodiments of the present invention. However, the present invention is not limited to the following embodiments, and can be practiced with appropriate modifications within the scope of the purpose of the present invention. Note that, although the explanation may be omitted where appropriate for overlapping parts, the gist of the invention is not limited thereto. Hereinafter, the compound and its derivatives may be collectively referred to by adding "system" after the compound name. In addition, when the compound name is followed by "system" to express the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. In addition, general formulas and chemical formulas are collectively described as "formula". In addition, "independently" in the explanation of the formula means that it may represent the same group or different groups. In addition, each component described in this specification may be used alone or in combination of two or more types, unless otherwise specified. In addition, the viscosity average molecular weight is a value measured in accordance with JIS (Japanese Industrial Standards) K7252-1:2016, unless otherwise specified.

First, the substituents used in this specification will be described. Examples of halogen atoms (halogen groups) include fluorine atoms (fluoro groups), chlorine atoms (chloro groups), bromine atoms (bromo groups), and iodine atoms (iodo groups).

Unless otherwise specified, alkyl groups having 1 to 6 carbon atoms, alkyl groups having 1 to 5 carbon atoms, alkyl groups having 1 to 4 carbon atoms, alkyl groups having 1 to 3 carbon atoms, alkyl groups having 2 carbon atoms, and alkyl groups having 3 carbon atoms are each straight-chain or branched-chain and unsubstituted. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylpropyl group, a 2-ethylpropyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, an n-hexyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, a 3,3-dimethylbutyl group, a 1,1,2-trimethylpropyl group, a 1,2,2-trimethylpropyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, and a 3-ethylbutyl group. Examples of alkyl groups with 1 to 5 carbon atoms, alkyl groups with 1 to 4 carbon atoms, alkyl groups with 1 to 3 carbon atoms, alkyl groups with 2 carbon atoms, and alkyl groups with 3 carbon atoms are groups having the corresponding number of carbon atoms among the groups mentioned as examples of alkyl groups with 1 to 6 carbon atoms.

Alkoxy groups having 1 to 6 carbon atoms and alkoxy groups having 1 to 3 carbon atoms are linear or branched and unsubstituted unless otherwise specified. Examples of alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, 1-methylbutoxy, 2-methylbutoxy, 3-methylbutoxy, 1-ethylpropoxy, 2-ethylpropoxy, 1,1-dimethylpropoxy, 1,2-dimethylpropoxy, 2,2-dimethylpropoxy, n-hexyl ... Examples of alkoxy groups having 1 to 3 carbon atoms include alkoxy groups having the corresponding number of carbon atoms among the groups mentioned as examples of alkoxy groups having 1 to 6 carbon atoms.

Each of the aryl groups having 6 to 14 carbon atoms and the aryl groups having 6 to 10 carbon atoms is unsubstituted unless otherwise specified. Examples of aryl groups having 6 to 14 carbon atoms include phenyl, naphthyl, indacenyl, biphenylenyl, acenaphthylenyl, anthryl, and phenanthryl. Examples of aryl groups having 6 to 10 carbon atoms include phenyl and naphthyl.

Unless otherwise specified, an alkenyl group having 2 to 6 carbon atoms is linear or branched and unsubstituted. An alkenyl group having 2 to 6 carbon atoms has one to three double bonds. Examples of alkenyl groups having 2 to 6 carbon atoms include ethenyl, propenyl, butenyl, butadienyl, pentenyl, hexenyl, hexadienyl, and hexatriyl. The above describes the substituents used in this specification.

First embodiment: electrophotographic photoreceptor
The first embodiment relates to an electrophotographic photoreceptor (hereinafter, may be referred to as a photoreceptor). The structure of the electrophotographic photoreceptor according to the first embodiment of the present invention will be described below with reference to Figures 1 to 3. Each of Figures 1 to 3 shows a partial cross-sectional view of a photoreceptor 1.

As shown in FIG. 1, the photoreceptor 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 is a single layer. The photoreceptor 1 is a single-layer electrophotographic photoreceptor including a single photosensitive layer 3.

As shown in FIG. 2, the photoreceptor 1 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2 and the photosensitive layer 3. The intermediate layer 4 is provided between the conductive substrate 2 and the photosensitive layer 3. As shown in FIG. 1, the photosensitive layer 3 may be provided directly on the conductive substrate 2. Alternatively, as shown in FIG. 2, the photosensitive layer 3 may be provided on the conductive substrate 2 via the intermediate layer 4.

As shown in FIG. 3, the photoreceptor 1 may further include a protective layer 5 in addition to the conductive substrate 2 and the photosensitive layer 3. The protective layer 5 is provided on the photosensitive layer 3. As shown in FIG. 3, the protective layer 5 may be provided as the outermost layer of the photoreceptor 1. However, as shown in FIG. 1 and FIG. 2, it is preferable that the photosensitive layer 3 is provided as the outermost layer of the photoreceptor 1. By providing the photosensitive layer 3 containing the polyarylate resin (PA) and a dispersion aid described later as the outermost layer, the sensitivity characteristics, filming resistance, and scratch resistance of the photoreceptor 1 are further improved.

The thickness of the photosensitive layer 3 is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less. Above, the structure of the photoreceptor 1 has been described with reference to Figures 1 to 3.

The photoreceptor is further described below. The photosensitive layer of the photoreceptor contains a charge generating agent, a hole transport agent, an electron transport agent, a polyarylate resin, and a dispersion aid.

(Charge generating material)
The charge generating material contains titanyl phthalocyanine. Titanyl phthalocyanine is represented by formula (CG-1). When the photosensitive layer contains titanyl phthalocyanine and a specific dispersion aid described later, the sensitivity characteristics of the photoreceptor are improved. The reason for this will be described later in the explanation of the dispersion aid.

Titanyl phthalocyanine may be crystalline or non-crystalline. Examples of titanyl phthalocyanine crystals include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter, these may be referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively). As the titanyl phthalocyanine crystal, Y-type titanyl phthalocyanine is preferred.

In the CuKα characteristic X-ray diffraction spectrum, Y-type titanyl phthalocyanine has a main peak at, for example, a Bragg angle (2θ±0.2°) of 27.2°. The main peak in the CuKα characteristic X-ray diffraction spectrum is the peak with the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is 3° or more and 40° or less. In the CuKα characteristic X-ray diffraction spectrum, Y-type titanyl phthalocyanine does not have a peak at 26.2°.

The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, the sample (titanyl phthalocyanine) is loaded into the sample holder of an X-ray diffraction device (for example, Rigaku Corporation's "RINT (registered trademark) 1100"), and the X-ray diffraction spectrum is measured under the conditions of a Cu X-ray tube, a tube voltage of 40 kV, a tube current of 30 mA, and a wavelength of 1.542 Å for the CuKα characteristic X-rays. The measurement range (2θ) is, for example, 3° to 40° (start angle 3°, stop angle 40°), and the scanning speed is, for example, 10°/min. The main peak is determined from the obtained X-ray diffraction spectrum, and the Bragg angle of the main peak is read.

The photosensitive layer may contain only titanyl phthalocyanine as a charge generating agent, or may further contain other charge generating agents (hereinafter, sometimes referred to as other charge generating agents). Examples of other charge generating agents include phthalocyanine pigments other than titanyl phthalocyanine, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, indigo pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon), pyrylium pigments, anthanthrone pigments, triphenylmethane pigments, threne pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments.

The content of the charge generating agent is preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the binder resin.

(Binder resin)
The photosensitive layer contains a polyarylate resin as a binder resin. The polyarylate resin includes a repeating unit represented by formula (1), a repeating unit represented by formula (2), and a repeating unit represented by formula (3). The ratio _n1 / _n2 of the number of repeating units represented by formula ( ₁ ) to the number of repeating units represented by formula (2), _n2 , is 1.0 or more.

In formula (1), ^R1 and ^R2 each represent a methyl group, and ^R3 and ^R4 are bonded to each other to represent a cycloalkylidene group having 5 or 6 carbon atoms. Alternatively, in formula (1), ^R1 and ^R2 each independently represent a hydrogen atom or a methyl group, ^R3 represents a methyl group, and ^R4 represents a hydrogen atom or an alkyl group having 2 or 3 carbon atoms.

Hereinafter, the repeating units represented by formulas (1), (2), and (3) may be referred to as repeating units (1), (2), and (3), respectively. A polyarylate resin containing repeating units (1), (2), and (3) and having a ratio _n1 / _n2 of the number of repeating units (1 ₎ to the number of repeating units (2), _n2 , of 1.0 or more may be referred to as a polyarylate resin (PA).

The polyarylate resin (PA) contains a repeating unit (1) and repeating units (2) and (3) having an ether bond (-O- bond), and the ratio n ₁ /n ₂ is 1.0 or more. By containing a polyarylate resin (PA) having such a predetermined structure, the elastic modulus of the photosensitive layer is increased, and the external additives and paper powder of the toner are less likely to sink into the photosensitive layer. As a result, the external additives and paper powder attached to the photosensitive layer are suitably cleaned, and the filming resistance of the photoreceptor is improved. Note that filming of the photoreceptor is a defect in which the external additives and paper powder remaining on the surface of the photoreceptor after cleaning are fused to the surface of the photoreceptor. In addition, by containing a polyarylate resin (PA) having such a predetermined structure, the strength of the photosensitive layer is increased, and the scratch resistance of the photoreceptor is improved. In addition, by containing a polyarylate resin (PA) having such a predetermined structure, the sensitivity characteristics of the photoreceptor are improved.

In order to improve the filming resistance of the photoreceptor, it is preferable that R ¹ and R ² in formula (1) represent a methyl group.

Examples of the cycloalkylidene group having 5 or 6 carbon atoms represented by ^R3 and ^R4 in formula (1) bonded together include a cyclopentylidene group and a cyclohexylidene group. The cyclopentylidene group and the cyclohexylidene group are divalent groups represented by the following formulas (5) and (6), respectively. As the cycloalkylidene group having 5 or 6 carbon atoms, a cyclohexylidene group is preferred.

Examples of the alkyl group having 2 or 3 carbon atoms represented by ^R4 in formula (1) include an ethyl group, an n-propyl group, and an isopropyl group. As the alkyl group having 2 or 3 carbon atoms, an ethyl group or an isopropyl group is preferred.

Suitable examples of the repeating unit (1) include repeating units represented by formulae (1-1), (1-2), (1-3), (1-4), and (1-5). Hereinafter, the repeating units represented by formulae (1-1), (1-2), (1-3), (1-4), and (1-5) may be referred to as repeating units (1-1), (1-2), (1-3), (1-4), and (1-5), respectively. In order to improve the sensitivity characteristics, filming resistance, and scratch resistance of the photoreceptor, the repeating unit (1) is preferably the repeating unit (1-2), (1-4), or (1-5), and more preferably the repeating unit (1-5).

The ratio _n1 / _n2 of the number _n1 of the repeating units (1) contained in the polyarylate resin (PA) to the number _n2 of the repeating units (2) contained in the polyarylate resin (PA) is 1.0 or more. That is, the number _n1 of the repeating units (1) is equal to the number _n2 of the repeating units (2) or is greater than the number _n2 of the repeating units (2 ₎ . When the ratio _n1 / _n2 is 1.0 or more, the sensitivity characteristics, filming resistance, and scratch resistance of the photoconductor are improved. In order to improve the sensitivity characteristics, filming resistance, and scratch resistance of the photoconductor, the ratio _n1 /n2 is preferably 1.5 or more, and more preferably 2.0 or more. For the same reason, the ratio _n1 / _n2 is preferably 10.0 or less, more preferably 9.0 or less, even more preferably 6.0 or less, and particularly preferably 5.0 or less. For the same reason, it is also preferable that the ratio _n1 / _n2 is within a range of two values selected from 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 9.0, and 10.0. The ratio _n1 / _n2 can be calculated, for example, by measuring the ^1H -NMR spectrum of the polyarylate resin (PA) using a proton nuclear magnetic resonance spectrometer and calculating from the ratio of peaks characteristic of each repeating unit in the obtained ^1H -NMR spectrum.

As the polyarylate resin (PA), polyarylate resins (PA-a) to (PA-e) shown in the following Table 1 are preferred. As the polyarylate resin (PA), polyarylate resins (PA-1) to (PA-8) shown in the following Table 2 are more preferred. In Tables 1 and 2, "unit (1)", "unit (2)", and "unit (3)" represent repeating units (1), (2), and (3), respectively. In Tables 1 and 2, "n ₁ /n ₂ " represents the ratio n ₁ /n ₂ .

As the polyarylate resin (PA), polyarylate resins represented by formulae (R-1) to (R-8) (hereinafter, each may be referred to as polyarylate resin (R-1) to (R-8)) are more preferred. In formulae (R-1) to (R-8), the numbers on the bottom right of each repeating unit indicate the percentage (%) of the number of each repeating unit with respect to the total number of repeating units contained in the polyarylate resin. The total number of repeating units is the sum of the number of bisphenol-derived repeating units and the number of dicarboxylic acid-derived repeating units. For convenience of description, each of formulae (R-1) to (R-8) has two repeating units (3). However, the percentage of the number of repeating units (3) with respect to the total number of repeating units contained in each of polyarylate resins (R-1) to (R-8) is 50% (the sum of the numbers on the bottom right of the two repeating units (3)).

To improve filming resistance and scratch resistance, the polyarylate resin (PA) is preferably polyarylate resin (PA-b), (PA-c), or (PA-e), more preferably polyarylate resin (PA-2), (PA-3), (PA-5), or (PA-7), and particularly preferably polyarylate resin (R-2), (R-3), (R-5), or (R-7).

The polyarylate resin (PA) may contain only one type of repeating unit (1), or may contain two or more types of repeating units (1). The polyarylate resin (PA) may contain only repeating units (1), (2), and (3) as repeating units, or may further contain repeating units other than these. The photosensitive layer may contain only one type of polyarylate resin (PA), or may contain two or more types of polyarylate resin (PA).

In the polyarylate resin (PA), the bisphenol-derived repeating units and the dicarboxylic acid-derived repeating units are adjacent to each other and bonded to each other. The bisphenol-derived repeating units are, for example, repeating units (1) and (2). The dicarboxylic acid-derived repeating units are, for example, repeating units (3). The polyarylate resin (PA) may be, for example, a random copolymer, an alternating copolymer, a periodic copolymer, or a block copolymer.

The viscosity average molecular weight of the polyarylate resin (PA) is preferably 10,000 or more, more preferably 30,000 or more, and even more preferably 50,000 or more. When the viscosity average molecular weight of the polyarylate resin (PA) is 10,000 or more, the abrasion resistance of the photoreceptor is improved. On the other hand, the viscosity average molecular weight of the polyarylate resin (PA) is preferably 80,000 or less, and more preferably 70,000 or less. When the viscosity average molecular weight of the polyarylate resin (PA) is 80,000 or less, the polyarylate resin (PA) is easily dissolved in a solvent for forming the photosensitive layer.

The method for producing the polyarylate resin (PA) is not particularly limited. For example, the method for producing the polyarylate resin (PA) includes a method of polycondensing bisphenol for forming a bisphenol-derived repeating unit and dicarboxylic acid for forming a dicarboxylic acid-derived repeating unit. For polycondensation, a known synthesis method (for example, solution polymerization, melt polymerization, or interfacial polymerization) can be used.

Examples of bisphenols for constituting the bisphenol-derived repeating units include compounds represented by formulas (BP-1) and (BP-2) (hereinafter, these may be referred to as compounds (BP-1) and (BP-2) respectively). Examples of dicarboxylic acids for constituting the dicarboxylic acid-derived repeating units include compounds represented by formula (DC-3) (hereinafter, these may be referred to as compounds (DC-3)). R ¹ , R ² , R ³ , and R ⁴ in formula (BP-1) are synonymous with R ¹ , R ² , R ³ , and R ⁴ in formula (1), respectively. The ratio n ₁ /n 2 can be adjusted by changing the amount of compound (BP-1) and the amount of compound (BP-2) added when producing the polyarylate resin ( _PA ).

Bisphenols (e.g., compounds (BP-1) and (BP-2)) may be derivatized to aromatic diacetates before use. Dicarboxylic acids (e.g., compound (DC-3)) may be derivatized before use. Examples of dicarboxylic acid derivatives include dicarboxylic acid dichlorides, dicarboxylic acid dimethyl esters, dicarboxylic acid diethyl esters, and dicarboxylic acid anhydrides. Dicarboxylic acid dichlorides are compounds in which the two "-C(=O)-OH" groups of a dicarboxylic acid are each replaced with a "-C(=O)-Cl" group.

In the condensation polymerization of bisphenol and dicarboxylic acid, a base and/or a catalyst may be added. An example of the base is sodium hydroxide. Examples of the catalyst are benzyltributylammonium chloride, ammonium chloride, ammonium bromide, quaternary ammonium salts, triethylamine, and trimethylamine.

The photosensitive layer may contain only polyarylate resin (PA) as the binder resin, or may further contain other binder resins (hereinafter sometimes referred to as other binder resins). Other binder resins include, for example, thermoplastic resins (more specifically, polyarylate resins other than polyarylate resin (PA), polycarbonate resins, styrene-based resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, acrylic copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomers, vinyl chloride-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyvinyl acetal resins, and polyether resins), thermosetting resins (more specifically, silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins), and photocurable resins (more specifically, epoxy-acrylic acid-based resins, and urethane-acrylic acid-based copolymers).

(Dispersing agent)
The dispersing aid includes a compound represented by formula (30) or (31) (hereinafter, these may be referred to as dispersing aids (30) and (31), respectively).

The photosensitive layer contains titanyl phthalocyanine and a dispersion aid (30) or (31), which improves the sensitivity characteristics of the photoreceptor. The reason for this is presumed to be as follows. The dispersion aids (30) and (31) have electron-withdrawing groups (e.g., chloro groups and trifluoromethyl groups). The charge generating agent titanyl phthalocyanine has electron-donating sites (e.g., TiO sites). Therefore, the electron-withdrawing groups of the dispersion aids (30) and (31) are attracted to the electron-donating sites of the titanyl phthalocyanine. The attracted dispersion aids (30) and (31) then help disperse the titanyl phthalocyanine in the photosensitive layer. The favorable dispersion of titanyl phthalocyanine in the photosensitive layer improves the sensitivity characteristics of the photoreceptor.

The content of the dispersing aid is preferably 0.01 parts by mass or more and 10.00 parts by mass or less, more preferably 0.10 parts by mass or more and 5.00 parts by mass or less, and even more preferably 0.50 parts by mass or more and 3.00 parts by mass or less, relative to 100.00 parts by mass of the binder resin. The photosensitive layer may contain only one type of dispersing aid, or may contain two types of dispersing aids.

(Electron Transport Agent)
Examples of the electron transport agent include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Examples of the quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds.

Suitable examples of the electron transport agent include compounds represented by formulas (10), (11), (12), (13), (14), (15), and (16) (hereinafter, these may be referred to as electron transport agents (10), (11), (12), (13), (14), (15), and (16), respectively). When the photosensitive layer contains the electron transport agent (10), (11), (12), (13), (14), (15), or (16) together with the polyarylate resin (PA) and the dispersion aid, the sensitivity characteristics, filming resistance, and scratch resistance of the photoreceptor are further improved.

^Q1 and ^Q2 in formula (10), ^Q11 , ^Q12 , and ^Q13 in formula (11), ^Q21 , ^Q22 , ^Q23 , and ^Q24 in formula (12), ^Q31 and ^Q32 in formula (13), ^Q41 , ^Q42 , ^Q43 , and ^Q44 in formula (14), ^Q51 , ^Q52 , ^Q53 , ^Q54 , ^Q55 , and ^Q56 in formula (15), and ^Q61 and Q in formula (16). Each of ⁶² independently represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 2 to 6 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, or an aryl group having from 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms and a halogen atom. ^Y1 and ^Y2 in formula (15) independently represent an oxygen atom or a sulfur atom.

It is preferable that ^Q1 and ^Q2 in formula (10), ^Q11 to ^Q13 in formula (11), ^Q21 to ^Q24 in formula (12), ^Q31 and ^Q32 in formula (13), ^Q41 to ^Q44 in formula (14), ^Q51 to ^Q56 in formula (15), and ^Q61 and ^Q62 in formula (16) each independently represent a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, or an aryl group having from 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms and a halogen atom. It is preferable that ^Y1 and ^Y2 in formula (15) represent an oxygen atom.

The alkyl group having 1 to 6 carbon atoms represented by Q ¹ and Q ² in formula (10), Q ¹¹ to Q ¹³ in formula (11), Q ²¹ to Q ²⁴ in formula (12), Q ³¹ and Q ³² in formula (13), Q ⁴¹ to Q ⁴⁴ in formula (14), Q ⁵¹ to Q ⁵⁶ in formula (15), and Q ⁶¹ and Q ⁶² in formula (16) is preferably an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group, and particularly preferably a methyl group, an isopropyl group, a tert-butyl group, or a 1,1-dimethylpropyl group.

The aryl group having 6 to 14 carbon atoms represented by Q ¹ and Q ² in formula (10), Q ¹¹ to Q ¹³ in formula (11), Q ²¹ to Q ²⁴ in formula (12), Q ³¹ and Q ³² in formula (13), Q ⁴¹ to Q ⁴⁴ in formula (14), Q ⁵¹ to Q ⁵⁶ in formula (15), and Q ⁶¹ and Q ⁶² in formula (16) is preferably an aryl group having 6 to 10 carbon atoms, more preferably a phenyl group. The aryl group having 6 to 14 carbon atoms may be substituted with at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms and a halogen atom. The alkyl group having 1 to 6 carbon atoms as the substituent is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. The halogen atom as the substituent is preferably a fluorine atom, a chlorine atom, or a bromine atom, and particularly preferably a chlorine atom. When an aryl group having 6 to 14 carbon atoms is substituted with a substituent, the number of the substituents is preferably 1 to 5, and more preferably 1 or 2. The aryl group having 6 to 14 carbon atoms substituted with at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms and a halogen atom is preferably a chlorophenyl group, a dichlorophenyl group, or an ethylmethylphenyl group, and more preferably a 4-chlorophenyl group, a 2,5-dichlorophenyl group, or a 2-ethyl-6-methylphenyl group.

A suitable example of the electron transport agent (10) is a compound represented by formula (E-4). A suitable example of the electron transport agent (11) is a compound represented by formula (E-5). A suitable example of the electron transport agent (12) is a compound represented by formula (E-7). A suitable example of the electron transport agent (13) is a compound represented by formula (E-6). A suitable example of the electron transport agent (14) is a compound represented by formula (E-8). A suitable example of the electron transport agent (15) is a compound represented by formulas (E-2) and (E-3). A suitable example of the electron transport agent (16) is a compound represented by formula (E-1). Hereinafter, the compounds represented by formulas (E-1) to (E-8) may be referred to as electron transport agents (E-1) to (E-8), respectively.

The content of the electron transport agent is preferably 5 parts by mass or more and 150 parts by mass or less, more preferably 10 parts by mass or more and 100 parts by mass or less, and even more preferably 30 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the binder resin. The photosensitive layer may contain only one type of electron transport agent, or may contain two or more types of electron transport agents.

(Hole Transport Agent)
Examples of the hole transport agent include triphenylamine derivatives, diamine derivatives (e.g., N,N,N',N'-tetraphenylbenzidine derivatives, N,N,N',N'-tetraphenylphenylenediamine derivatives, N,N,N',N'-tetraphenylnaphthylenediamine derivatives, N,N,N',N'-tetraphenylphenanthrylenediamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazo Examples of the compound include aryl compounds, styryl compounds (e.g., 9-(4-diethylaminostyryl)anthracene), carbazole compounds (e.g., polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

Suitable examples of the hole transport agent include compounds represented by formulas (20), (21), (22), (23), and (24) (hereinafter, these may be referred to as hole transport agents (20), (21), (22), (23), and (24), respectively). When the photosensitive layer contains hole transport agent (20), (21), (22), (23), or (24) together with polyarylate resin (PA) and a dispersion aid, the sensitivity characteristics, filming resistance, and scratch resistance of the photoreceptor are further improved.

In formula (20), ^R11 , ^R12 , ^R13 , and ^R14 each independently represent an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. _a1 , _a2 , _a3 , and _a4 each independently represent an integer of 0 to 5.

In formula (20), when a ₁ represents an integer of 2 or more and 5 or less, multiple R ¹¹ may represent the same group or different groups. When a ₂ represents an integer of 2 or more and 5 or less, multiple R ¹² may represent the same group or different groups. When _{a 3} represents an integer of 2 or more and 5 or less, multiple R ¹³ may represent the same group or different groups. When _{a 4} represents an integer of 2 or more and 5 or less, multiple R ¹⁴ may represent the same group or different groups.

In formula (20), ^R11 , ^R12 , ^R13 , and ^R14 each independently preferably represent an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. _a1 , _a2 , _a3 , and _a4 each independently preferably represent an integer of 1 to 3, more preferably 1.

In formula (21), ^R21 , ^R22 , and ^R23 each independently represent an alkyl group having 1 to 6 carbon atoms. ^R24 , ^R25 , and ^R26 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. _b1 , _b2 , and _b3 each independently represent 0 or 1.

In formula (21), R ²¹ , R ²² , and R ²³ each independently preferably represent an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. R ²¹ , R ²² , and R ²³ are preferably bonded to the meta position of the phenyl group relative to the ethenyl group or butadienyl group. R ²⁴ , R ²⁵ , and R ²⁶ each preferably represent a hydrogen atom. b ₁ , b ₂ , and b ₃ each preferably represent 0 or 1.

In formula (22), R ³¹ , R ³² , and R ³³ each independently represent an alkyl group having 1 to 6 carbon atoms. ^{R 34} represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. d ₁ , d ₂ , and d ₃ each independently represent an integer of 0 to 5.

In formula (22), when _d1 is an integer of 2 or more and 5 or less, multiple ^R31 may represent the same group or different groups. When _d2 is an integer of 2 or more and 5 or less, multiple ^R32 may represent the same group or different groups. When _d3 is an integer of 2 or more and 5 or less, multiple ^R33 may represent the same group or different groups.

In formula (22), R ³⁴ preferably represents a hydrogen atom. d ₁ , d ₂ , and d ₃ each preferably represent 0.

In formula (23), R ⁴¹ , R ⁴² , R ⁴³ , R ⁴⁴ , R ⁴⁵ , and R ⁴⁶ each independently represent an alkyl group having 1 to 6 carbon atoms, or a phenyl group. R ⁴⁷ and R ⁴⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group. e ₁ , e ₂ , e ₃ , and e ₄ each independently represent an integer of 0 to 5. e ₅ and e ₆ each independently represent an integer of 0 to 4. e ₇ and e ₈ each independently represent 0 or 1.

In formula (23), when e ₁ represents an integer of 2 or more and 5 or less, the multiple R ⁴¹ may represent the same group or different groups. When e ₂ represents an integer of 2 or more and 5 or less, the multiple R ⁴² may represent the same group or different groups. When e ₃ represents an integer of 2 or more and 5 or less, the multiple R ⁴³ may represent the same group or different groups. When e ₄ represents an integer of 2 or more and 5 or less, the multiple R ⁴⁴ may represent the same group or different groups. When e ₅ represents an integer of 2 or more and 4 or less, the multiple R ⁴⁵ may represent the same group or different groups. When e ₆ represents an integer of 2 or more and 4 or less, the multiple R ⁴⁶ may represent the same group or different groups.

In formula (23), R ⁴¹ to R ⁴⁶ each independently preferably represent an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group or an ethyl group. R ⁴⁷ and R ⁴⁸ each independently preferably represent a hydrogen atom. e ₁ , e ₂ , e ₃ , and e ₄ each independently preferably represent an integer having 0 to 2, more preferably e ₁ and e ₂ represent 0 and e ₃ and e ₄ represent 2. e ₅ and e ₆ each preferably represent 0. e ₇ and e ₈ each preferably represent 0 or 1.

In formula (24), R ⁵⁰ and R ⁵¹ each independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group. R ⁵² , R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ , and R ⁵⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group which may be substituted with an alkyl group having 1 to 6 carbon atoms. f ₁ and f ₂ each independently represent an integer of 0 to 2. f ₃ and f ₄ each independently represent an integer of 0 to 5.

In formula (24), when _f3 is an integer of 2 or more and 5 or less, multiple ^R50 may represent the same group or different groups. When _f4 is an integer of 2 or more and 5 or less, multiple ^R51 may represent the same group or different groups.

In formula (24), R ⁵⁰ and R ⁵¹ each preferably independently represent an alkyl group having 1 to 6 carbon atoms. R ⁵² and R ⁵³ each preferably represent a phenyl group which may be substituted with a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R ⁵⁴ to R ⁵⁸ each preferably independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. _{f 1} and f ₂ each preferably represent 0, both preferably represent 1, or both preferably represent 2. f ₃ and f ₄ each preferably independently represent 0 or 1.

The alkyl group having 1 to 6 carbon atoms represented by R ⁵⁰ and R ⁵¹ is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. The phenyl group which may be substituted with an alkyl group having 1 to 6 carbon atoms represented by R ⁵² and R ⁵³ is preferably a phenyl group or a phenyl group substituted with an alkyl group having 1 to 3 carbon atoms. The phenyl group substituted with an alkyl group having 1 to 3 carbon atoms is preferably a methylphenyl group, more preferably a 4-methylphenyl group. The alkyl group having 1 to 6 carbon atoms represented by ^{R 54} to R ⁵⁸ is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group, an ethyl group, or an n-butyl group. The alkoxy group having 1 to 6 carbon atoms represented by R ⁵⁴ to R ⁵⁸ is preferably an alkoxy group having 1 to 3 carbon atoms, more preferably an ethoxy group.

Suitable examples of the hole transport agent (20) include compounds represented by formula (H-11). Suitable examples of the hole transport agent (21) include compounds represented by formulas (H-7) and (H-8). Suitable examples of the hole transport agent (22) include compounds represented by formula (H-6). Suitable examples of the hole transport agent (23) include compounds represented by formulas (H-9) and (H-10). Suitable examples of the hole transport agent (24) include compounds represented by formulas (H-1), (H-2), (H-3), (H-4), and (H-5). Hereinafter, the compounds represented by formulas (H-1) to (H-11) may be referred to as hole transport agents (H-1) to (H-11), respectively.

The content of the hole transport agent is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 30 parts by mass or more and 120 parts by mass or less, and even more preferably 50 parts by mass or more and 90 parts by mass or less, relative to 100 parts by mass of the binder resin. The photosensitive layer may contain only one type of hole transport agent, or may contain two or more types of hole transport agents.

(Additives)
The photosensitive layer may contain additives as necessary, such as ultraviolet absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, extenders, thickeners, waxes, donors, surfactants, plasticizers, sensitizers, and leveling agents.

(Material Combination)
In order to improve the sensitivity characteristics, filming resistance, and scratch resistance of the photoconductor, it is preferable that the polyarylate resin is each of the polyarylate resins (PA-a) to (PA-e), (PA-1) to (PA-8), and (R-1) to (R-8), and the dispersion aid is the dispersion aid (30). For the same reason, it is preferable that the polyarylate resin is each of the polyarylate resins (PA-a) to (PA-e), (PA-1) to (PA-8), and (R-1) to (R-8), and the dispersion aid is the dispersion aid (31). For the same reason, it is preferable that the combination of the electron transport agent and the polyarylate resin is each of the combinations No. a-1 to a-14, b-1 to b-17, and c-1 to c-17 shown in Table 3, and the dispersion aid is the dispersion aid (30) or (31). For the same reason, it is preferable that the combination of the hole transport agent and the polyarylate resin is each of the combinations No. a-1 to a-14, b-1 to b-17, and c-1 to c-17 shown in Table 4. d-1 to d-17, e-1 to e-20, and f-1 to f-20, and the dispersion aid is preferably the dispersion aid (30) or (31). For the same reason, the combination of the electron transport material, the hole transport material, and the polyarylate resin is preferably the combination No. g-1 to g-24, h-1 to h-27, and i-1 to i-27 shown in Table 5, and the dispersion aid is preferably the dispersion aid (30) or (31). For the same reason, the photosensitive layer preferably contains the materials of these combinations and the Y-type titanyl phthalocyanine, which is the charge generating agent. In Tables 3 to 5, "No." indicates "combination No.", "ETM" indicates "electron transport material", "HTM" indicates "hole transport material", and "resin" indicates "polyarylate resin".

(Conductive Substrate)
The conductive substrate is not particularly limited as long as it can be used as the conductive substrate of the photoreceptor. The conductive substrate may be made of a material having at least a surface portion having conductivity. An example of the conductive substrate is a conductive substrate made of a material having conductivity. Another example of the conductive substrate is a conductive substrate coated with a material having conductivity. Examples of the conductive material include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. Among these conductive materials, aluminum and aluminum alloys are preferred because they have good charge transfer from the photosensitive layer to the conductive substrate.

The shape of the conductive substrate is appropriately selected according to the structure of the image forming device. Examples of the shape of the conductive substrate include a sheet shape and a drum shape. The thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

(Middle class)
The intermediate layer (undercoat layer) contains, for example, inorganic particles and a resin (intermediate layer resin) used in the intermediate layer. The presence of the intermediate layer makes it possible to maintain an insulating state sufficient to suppress leakage, while smoothing the flow of current generated when the photoconductor is exposed to light, thereby suppressing an increase in resistance.

Inorganic particles include, for example, particles of metals (e.g., aluminum, iron, and copper), particles of metal oxides (e.g., titanium oxide, alumina, zirconium oxide, tin oxide, and zinc oxide), and particles of non-metal oxides (e.g., silica).

Examples of the resin for the intermediate layer are the same as the examples of other binder resins already mentioned. In order to form the intermediate layer and the photosensitive layer well, it is preferable that the resin for the intermediate layer is different from the binder resin contained in the photosensitive layer. The intermediate layer may contain additives. Examples of the additives contained in the intermediate layer are the same as the examples of the additives contained in the photosensitive layer.

(Method of Manufacturing Photoreceptor)
Next, an example of a method for manufacturing a photoreceptor will be described. The method for manufacturing a photoreceptor includes a photosensitive layer forming step. In the photosensitive layer forming step, a coating liquid for forming a photosensitive layer (hereinafter, sometimes referred to as a coating liquid for a photosensitive layer) is prepared. The coating liquid for a photosensitive layer is applied onto a conductive substrate. Then, at least a part of the solvent contained in the applied coating liquid for a photosensitive layer is removed to form a photosensitive layer. The coating liquid for a photosensitive layer contains, for example, a charge generating agent, a hole transporting agent, an electron transporting agent, a binder resin, a dispersion aid, and a solvent. The coating liquid for a photosensitive layer is prepared by dissolving or dispersing the charge generating agent, the hole transporting agent, the electron transporting agent, the binder resin, and the dispersion aid in a solvent.

The solvent contained in the coating solution for the photosensitive layer is not particularly limited as long as it can dissolve or disperse each component contained in the coating solution for the photosensitive layer. Examples of the solvent include alcohols (more specifically, methanol, ethanol, isopropanol, butanol, etc.), aliphatic hydrocarbons (more specifically, n-hexane, octane, cyclohexane, etc.), aromatic hydrocarbons (more specifically, benzene, toluene, xylene, etc.), halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, etc.), ethers (more specifically, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc.), ketones (more specifically, acetone, methyl ethyl ketone, cyclohexanone, etc.), esters (more specifically, ethyl acetate, methyl acetate, etc.), dimethylformaldehyde, dimethylformamide, and dimethylsulfoxide.

The coating solution for the photosensitive layer is prepared by mixing each component and dispersing it in a solvent. For example, a bead mill, a roll mill, a ball mill, an attritor, a paint shaker, a rod-shaped sonic oscillator, or an ultrasonic disperser can be used for mixing or dispersing.

The method for applying the coating liquid for the photosensitive layer is not particularly limited as long as it is a method that can apply the coating liquid for the photosensitive layer uniformly. Examples of the coating method include a dip coating method, a spray coating method, a spin coating method, and a bar coating method.

Methods for removing at least a portion of the solvent contained in the coating solution for the photosensitive layer include, for example, heating, reducing pressure, or a combination of heating and reducing pressure. More specifically, a method for heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer can be used. The temperature for the heat treatment is, for example, 40°C or higher and 150°C or lower. The time for the heat treatment is, for example, 3 minutes or higher and 120 minutes or lower.

The method for manufacturing the photoreceptor may further include a step of forming an intermediate layer, if necessary. The step of forming the intermediate layer may be appropriately selected from known methods.

Second embodiment: Image forming apparatus
Next, an image forming apparatus 100 according to a second embodiment of the present invention will be described with reference to Fig. 4. Fig. 4 is a diagram showing an example of the configuration of the image forming apparatus 100. The image forming apparatus 100 is, for example, a tandem type color printer.

As shown in FIG. 4, the image forming apparatus 100 includes a control unit 10, an operation unit 20, a paper feed unit 30, a conveying unit 40, a toner supply unit 50, an image forming unit 60, a transfer device 70, a fixing device 80, and a discharge unit 90.

The control unit 10 controls the operation of each unit of the image forming device 100. The control unit 10 includes a processor (not shown) and a memory unit (not shown). The processor includes, for example, a CPU (Central Processing Unit). The memory unit includes a memory such as a semiconductor memory, and may also include a HDD (Hard Disk Drive). The processor controls the operation of the image forming device 100 by executing a control program. The memory unit stores the control program.

The operation unit 20 accepts instructions from the user. When the operation unit 20 accepts an instruction from the user, it transmits a signal indicating the instruction from the user to the control unit 10. As a result, the image forming operation by the image forming device 100 is started.

The paper feed unit 30 has a paper feed cassette 31 and a paper feed roller group 32. The paper feed cassette 31 can accommodate multiple recording media P (e.g., paper). The paper feed roller group 32 feeds the recording media P accommodated in the paper feed cassette 31 one by one to the transport unit 40.

The transport unit 40 includes rollers and guide members. The transport unit 40 extends from the paper feed unit 30 to the discharge unit 90. The transport unit 40 transports the recording medium P from the paper feed unit 30 to the discharge unit 90, passing through the image forming unit 60 and the fixing device 80.

The toner supply unit 50 supplies toner to the image forming unit 60. The toner supply unit 50 includes a first mounting unit 51Y, a second mounting unit 51C, a third mounting unit 51M, and a fourth mounting unit 51K.

The first toner container 52Y is attached to the first mounting portion 51Y. Similarly, the second toner container 52C is attached to the second mounting portion 51C, the third toner container 52M is attached to the third mounting portion 51M, and the fourth toner container 52K is attached to the fourth mounting portion 51K.

The first toner container 52Y, the second toner container 52C, the third toner container 52M, and the fourth toner container 52K each contain toner. In the second embodiment, the first toner container 52Y contains yellow toner. The second toner container 52C contains cyan toner. The third toner container 52M contains magenta toner. The fourth toner container 52K contains black toner.

The image forming section 60 includes an exposure device 61, a first image forming unit 62Y, a second image forming unit 62C, a third image forming unit 62M, and a fourth image forming unit 62K.

Each of the first image forming unit 62Y to the fourth image forming unit 62K has a charging device 63, a developing device 64, an image carrier 65, a cleaning device 66, and a charge removing device 67.

The first image forming unit 62Y to the fourth image forming unit 62K are configured the same except for the type of toner supplied from the toner supply unit 50. Therefore, in FIG. 4, the reference numerals are omitted for the components of the second image forming unit 62C to the fourth image forming unit 62K.

The image carrier 65 is the photoreceptor 1 of the first embodiment. As described in the first embodiment, the photoreceptor 1 of the first embodiment has excellent sensitivity characteristics, filming resistance, and scratch resistance. Therefore, the image forming device 100 of the second embodiment can improve the sensitivity characteristics, filming resistance, and scratch resistance of the photoreceptor 1, which is the image carrier 65.

The charging device 63, the developing device 64, the cleaning device 66, and the charge removing device 67 are arranged along the circumferential surface of the image carrier 65. In the second embodiment, the image carrier 65 rotates in the direction indicated by the arrow R1 in FIG. 4 (clockwise direction).

The charging device 63 charges the surface (circumferential surface) of the image carrier 65. The charging device 63 uniformly charges the image carrier 65 to a predetermined polarity by discharging. In the second embodiment, the charging device 63 charges the image carrier 65 to a positive polarity. The charging device 63 is, for example, a charging roller.

The exposure device 61 exposes the surface of the charged image carrier 65. More specifically, the exposure device 61 irradiates the surface of the charged image carrier 65 with laser light. This forms an electrostatic latent image on the surface of the image carrier 65.

The developing device 64 is supplied with toner from the toner supply unit 50. The developing device 64 supplies the toner supplied from the toner supply unit 50 to the surface of the image carrier 65. As a result, the electrostatic latent image formed on the surface of the image carrier 65 is developed into a toner image.

In the second embodiment, the developing device 64 of the first image forming unit 62Y is connected to the first toner container 52Y. Therefore, the developing device 64 of the first image forming unit 62Y is replenished with yellow toner. Therefore, a yellow toner image is formed on the surface of the image carrier 65 of the first image forming unit 62Y.

Similarly, the developing device 64 of the second image forming unit 62C, the developing device 64 of the third image forming unit 62M, and the developing device 64 of the fourth image forming unit 62K are connected to the second toner container 52C, the third toner container 52M, and the fourth toner container 52K, respectively. Therefore, the developing device 64 of the second image forming unit 62C, the developing device 64 of the third image forming unit 62M, and the developing device 64 of the fourth image forming unit 62K are replenished with cyan toner, magenta toner, and black toner, respectively. Therefore, a cyan toner image, a magenta toner image, and a black toner image are formed on the surface of the image carrier 65 of the second image forming unit 62C, the surface of the image carrier 65 of the third image forming unit 62M, and the surface of the image carrier 65 of the fourth image forming unit 62K, respectively.

The cleaning device 66 has a cleaning member 661. After transfer by the primary transfer roller 71 described below, the cleaning device 66 collects the toner adhering to the surface of the image carrier 65. More specifically, the cleaning device 66 presses the cleaning member 661 against the surface of the image carrier 65 to collect the toner adhering to the surface of the image carrier 65. The cleaning member 661 is, for example, a cleaning blade.

The static elimination device 67 irradiates the surface of the image carrier 65 with static elimination light to eliminate static electricity from the surface of the image carrier 65.

The transfer device 70 transfers the toner image from the image carrier 65 to the recording medium P, which is the receiving medium. More specifically, the transfer device 70 transfers each toner image formed on the surface of each image carrier 65 of the first image forming unit 62Y to the fourth image forming unit 62K, superimposed on the recording medium P. In the second embodiment, the transfer device 70 transfers each toner image to the recording medium P, superimposed, by a secondary transfer method (intermediate transfer method). The transfer device 70 has four primary transfer rollers 71, an intermediate transfer belt 72, a drive roller 73, a driven roller 74, and a secondary transfer roller 75.

The intermediate transfer belt 72 is an endless belt stretched around four primary transfer rollers 71, a drive roller 73, and a driven roller 74. The intermediate transfer belt 72 is driven in response to the rotation of the drive roller 73. In FIG. 4, the intermediate transfer belt 72 rotates counterclockwise. The driven roller 74 is driven to rotate in response to the drive of the intermediate transfer belt 72.

The first image forming unit 62Y to the fourth image forming unit 62K are arranged facing the lower surface of the intermediate transfer belt 72. In the second embodiment, the first image forming unit 62Y to the fourth image forming unit 62K are arranged in this order from the upstream side to the downstream side of the driving direction D of the lower surface of the intermediate transfer belt 72.

Each primary transfer roller 71 is disposed opposite each image carrier 65 via the intermediate transfer belt 72 and is pressed against each image carrier 65. Therefore, the toner images formed on the surface of each image carrier 65 are sequentially transferred to the intermediate transfer belt 72 by each primary transfer roller 71. In the second embodiment, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are transferred and stacked in this order onto the intermediate transfer belt 72. Hereinafter, the toner image in which a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are stacked may be referred to as a "laminated toner image."

The secondary transfer roller 75 is disposed opposite the drive roller 73 via the intermediate transfer belt 72. The secondary transfer roller 75 is pressed against the drive roller 73. This forms a transfer nip between the secondary transfer roller 75 and the drive roller 73. When the recording medium P passes through the transfer nip, the secondary transfer roller 75 transfers the laminated toner image on the intermediate transfer belt 72 to the recording medium P. In the second embodiment, the yellow toner image, the cyan toner image, the magenta toner image, and the black toner image are transferred to the recording medium P in this order from top to bottom. The recording medium P to which the laminated toner image has been transferred is transported by the transport unit 40 toward the fixing device 80.

The fixing device 80 includes a heating member 81 and a pressure member 82. The heating member 81 and the pressure member 82 are arranged facing each other to form a fixing nip. The recording medium P conveyed from the image forming section 60 passes through the fixing nip and is pressurized while being heated at a predetermined fixing temperature. As a result, the laminated toner image is fixed to the recording medium P. The recording medium P is conveyed from the fixing device 80 to the discharge section 90 by the conveying section 40.

The discharge section 90 has a discharge roller pair 91 and a discharge tray 93. The discharge roller pair 91 transports the recording medium P to the discharge tray 93 through a discharge opening 92. The discharge opening 92 is formed in the upper part of the image forming device 100.

Next, the configuration of the developing device 64 will be described in detail with reference to FIG. 5. FIG. 5 is a diagram showing an example of the configuration of the developing device 64. In detail, FIG. 5 shows the developing device 64 of the first image forming unit 62Y. Note that in FIG. 5, the image carrier 65 is shown by a two-dot chain line for ease of understanding. In the second embodiment, the developing device 64 employs a two-component development method that uses a two-component developer and a touch-down development method.

As already described with reference to FIG. 4, the developing container 640 of the developing device 64 is connected to the first toner container 52Y. Therefore, yellow toner is replenished to the developing container 640 of the developing device 64 through the toner refill port 640h.

As shown in FIG. 5, the developing device 64 has a developing roller 641, a magnetic roller 642, a first stirring screw 643, a second stirring screw 644, and a blade 645 inside a developing container 640. In detail, the developing roller 641 is disposed opposite the magnetic roller 642. The magnetic roller 642 is disposed opposite the second stirring screw 644. The blade 645 is disposed opposite the magnetic roller 642.

The developing container 640 is divided into a first stirring chamber 640a and a second stirring chamber 640b by a partition wall 640c. The partition wall 640c extends in the axial direction of the developing roller 641. The first stirring chamber 640a and the second stirring chamber 640b are connected to each other on the outside of both longitudinal ends of the partition wall 640c.

A first stirring screw 643 is disposed in the first stirring chamber 640a. A carrier, which is a magnetic material, is accommodated in the first stirring chamber 640a. Toner, which is a non-magnetic material, is supplied to the first stirring chamber 640a through the toner supply port 640h. In the example shown in FIG. 5, yellow toner is supplied to the first stirring chamber 640a.

The second stirring chamber 640b is provided with a second stirring screw 644. The second stirring chamber 640b contains a carrier that is a magnetic material.

The yellow toner is mixed with the carrier by the first mixing screw 643 and the second mixing screw 644. As a result, a two-component developer containing the carrier and the yellow toner is formed.

The first stirring screw 643 and the second stirring screw 644 circulate and stir the two-component developer between the first stirring chamber 640a and the second stirring chamber 640b. As a result, the toner is charged to a predetermined polarity due to friction with the carrier. In the second embodiment, the toner is charged to a positive polarity.

The magnetic roller 642 is composed of a non-magnetic rotating sleeve 642a and a magnet body 642b. The magnet body 642b is fixedly disposed inside the rotating sleeve 642a. The magnet body 642b includes multiple magnetic poles. The two-component developer is attracted to the magnetic roller 642 by the magnetic force of the magnet body 642b. As a result, a magnetic brush is formed on the surface of the magnetic roller 642.

In the second embodiment, the magnetic roller 642 rotates in the direction indicated by the arrow R3 in FIG. 5 (counterclockwise direction). The magnetic roller 642 transports the magnetic brush to a position facing the blade 645 by rotating. The blade 645 is positioned so that a gap is formed between the magnetic roller 642 and the blade 645. Therefore, the thickness of the magnetic brush is determined by the blade 645. The blade 645 is positioned upstream in the rotation direction of the magnetic roller 642 from the position where the magnetic roller 642 and the developing roller 641 face each other.

A predetermined voltage is applied to the developing roller 641 and the magnetic roller 642. When a predetermined voltage is applied and a predetermined potential difference is created between the developing roller 641 and the magnetic roller 642, the yellow toner contained in the two-component developer is transferred to the developing roller 641. As a result, a thin toner layer made of yellow toner is formed on the surface of the developing roller 641.

The developing roller 641 rotates in the direction indicated by the arrow R2 in FIG. 5 (counterclockwise). This causes the thin layer of toner formed on the surface to be transported to a position facing the image carrier 65, where it adheres to the image carrier 65. In this way, the developing device 64 supplies the toner, which has been charged by friction with the carrier, to the surface of the image carrier 65.

The developing device 64 of the first image forming unit 62Y has been described above with reference to FIG. 5. The configuration of the developing device 64 of each of the first image forming unit 62Y to the fourth image forming unit 62K is the same except that the type of toner replenished from the toner replenishing section 50 is different. Therefore, a description of the configuration of the developing device 64 of the second image forming unit 62C to the fourth image forming unit 62K will be omitted.

Although an example of an image forming apparatus has been described above with reference to FIG. 4 and FIG. 5, the image forming apparatus is not limited to the image forming apparatus 100. The image forming apparatus 100 was a color image forming apparatus, but the image forming apparatus may be a monochrome image forming apparatus. In this case, the image forming apparatus may have only one image forming unit, for example. In addition, the image forming apparatus 100 employs a tandem system, but the image forming apparatus may employ, for example, a rotary system. Although the charging roller has been described as an example of the charging device 63, the charging device may be a charging device other than a charging roller (for example, a scorotron charger, a charging brush, or a corotron charger). The image forming apparatus 100 employs a two-component development system using a two-component developer, but the image forming apparatus may employ a one-component development system using a one-component developer. The image forming apparatus 100 employs a touch-down development system, but the image forming apparatus may employ a development system other than the touch-down development system (for example, a development system in which a magnetic roller also serves as a developing roller without a developing roller). Although the image forming apparatus 100 described above employs an intermediate transfer method, the image forming apparatus may employ a direct transfer method. When the image forming apparatus employs a direct transfer method, the toner image is directly transferred from the image carrier 65 to the recording medium P while the image carrier 65 is in contact with the recording medium P. Although a cleaning blade has been described as an example of the cleaning member 661, the cleaning member may be a cleaning roller. Also, the image forming apparatus may not be equipped with the cleaning device 66. Also, although the first image forming unit 62Y to the fourth image forming unit 62K described above are equipped with static eliminators, the image forming units may not be equipped with static eliminators.

Third Embodiment: Process Cartridge
Next, with continued reference to FIG. 4, a process cartridge according to a third embodiment of the present invention will be described. The process cartridge of the third embodiment corresponds to each of the first image forming unit 62Y to the fourth image forming unit 62K. The process cartridge includes an image carrier 65. The image carrier 65 is the photoreceptor 1 of the first embodiment. As described in the first embodiment, the photoreceptor 1 of the first embodiment is excellent in sensitivity characteristics, filming resistance, and scratch resistance. Therefore, the process cartridge of the third embodiment can improve the sensitivity characteristics, filming resistance, and scratch resistance of the photoreceptor 1, which is the image carrier 65.

In addition to the image carrier 65, the process cartridge further includes at least one (e.g., one or more and four or less) selected from the group consisting of a charging device 63, a developing device 64, a cleaning device 66, and a static eliminator 67. The process cartridge may further include a transfer device 70 (particularly, a primary transfer roller 71). The process cartridge may further include an exposure device 61. The process cartridge is designed to be detachable from the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and when the sensitivity characteristics of the image carrier 65 deteriorate, it can be easily and quickly replaced including the image carrier 65. The process cartridge of the third embodiment has been described above with reference to FIG. 4.

The present invention will be described in more detail below using examples. However, the present invention is not limited to the scope of the examples.

First, the following charge generating agent, electron transport agent, hole transport agent, binder resin, and dispersion aid were prepared as materials for forming the photosensitive layer of the photoreceptor.

(Charge generating material)
As the charge generating material, the Y-type titanyl phthalocyanine described in the first embodiment was prepared. Furthermore, as the charge generating material used in the comparative example, the X-type metal-free phthalocyanine represented by the following formula (CG-A) was prepared.

(Electron Transport Agent)
As the electron transport material, each of the electron transport materials (E-1) to (E-8) described in the first embodiment was prepared.

(Hole Transport Agent)
As the hole transport material, the hole transport materials (H-1) to (H-11) described in the first embodiment were prepared.

(Binder resin)
As the binder resin, the polyarylate resins (R-1) to (R-8) described in the first embodiment were prepared. The viscosity average molecular weight of the polyarylate resins (R-1) to (R-8) was 60,000.

In addition, polycarbonate resins (R-A) to (R-C) and polyarylate resins (R-D) to (R-G) were also prepared as binder resins for use in the comparative examples. The polycarbonate resins (R-A) to (R-C) and polyarylate resins (R-D) to (R-G) are each represented by the following formulas (R-A) to (R-G). The numbers to the lower right of each repeating unit indicate the percentage (unit: %) of the number of each repeating unit relative to the total number of repeating units contained in the resin. The viscosity average molecular weight of the polycarbonate resins (R-A) to (R-C) and polyarylate resins (R-D) to (R-G) was 60,000.

(Dispersing agent)
As the dispersion aids, the dispersion aids (30) and (31) described in the first embodiment were prepared.

<Production of photoreceptor>
(Production of Photoreceptor (A-1))
2.0 parts by mass of Y-type titanyl phthalocyanine as a charge generating agent, 1.6 parts by mass of dispersion aid (30), 70.0 parts by mass of hole transport agent (H-1), 50.0 parts by mass of electron transport agent (E-1), 100.0 parts by mass of polyarylate resin (R-1) as a binder resin, and 500.0 parts by mass of tetrahydrofuran as a solvent were mixed for 20 minutes using a rod-shaped ultrasonic oscillator to obtain a dispersion. The dispersion was filtered using a filter with a mesh size of 5 μm to obtain a coating liquid for a photosensitive layer. The coating liquid for a photosensitive layer was applied onto a conductive substrate (aluminum drum-shaped support) by a dip coating method, and dried with hot air at 120° C. for 50 minutes. In this way, a photosensitive layer (film thickness 30 μm) was formed on the conductive substrate to obtain a photoreceptor (A-1). In the photoreceptor (A-1), a single layer of photosensitive layer was directly provided on the conductive substrate.

(Production of Photoreceptors (A-2) to (A-27) and (B-3) to (B-11))
Photoreceptors (A-2) to (A-27) and (B-3) to (B-11) were each produced in the same manner as in the production of photoreceptor (A-1), except that the charge generating agent, dispersion aid, hole transport agent, electron transport agent, and binder resin shown in Tables 6 and 7 were used.

(Production of Photoreceptors (B-1) to (B-2))
Each of the photoreceptors (B-1) to (B-2) was produced in the same manner as in the production of the photoreceptor (A-1), except that no dispersion aid was used and that the charge generating material, hole transport material, electron transport material, and binder resin shown in Table 7 were used.

<Evaluation>
The photoreceptors (A-1) to (A-27) and (B-1) to (B-11) obtained were evaluated for their sensitivity characteristics, filming resistance, and scratch resistance by the following methods. For these evaluations, paper (Askul Multipaper Super Economy+ sold by Askul Corporation) was used. The photoreceptor was mounted on an evaluation machine. A modified image forming apparatus (FS-C5250DN manufactured by Kyocera Document Solutions Inc.) was used as the evaluation machine. This evaluation machine was equipped with a charging roller made of epichlorohydrin resin with conductive carbon dispersed therein as a charging device. The charging polarity of the charging roller was positive, and the applied voltage to the charging roller was a DC voltage. This evaluation machine also adopted a two-component development method and an intermediate transfer method. This evaluation machine also had a cleaning blade and a static elimination device.

<Evaluation of sensitivity characteristics>
The applied voltage of the charging roller was set so that the charging potential of the photoconductor was +570V. The exposure light of the exposure device was set to a wavelength of 780 nm, a half-width of 20 nm, and a light intensity of 1.16 μJ/ ^m2 . The photoconductor was charged and exposed using an evaluation machine under an environment of a temperature of 10° C. and a relative humidity of 15% RH. The surface potential of the exposed area (corresponding to the image area) was measured at the development position. The measured surface potential of the exposed area was taken as the post-exposure potential VL (unit: +V). VL is shown in Tables 6 and 7. Photoconductors with VL of +110V or less were evaluated as having good sensitivity characteristics, and photoconductors with VL of more than +110V were evaluated as having poor sensitivity characteristics.

<Evaluation of filming resistance and scratch resistance>
In an environment of a temperature of 23° C. and a relative humidity of 50% RH, an image I (a character image with a print rate of 5%) was continuously printed on 50,000 sheets of paper using an evaluation machine. Next, an image II (an image including a halftone image and a white background image) was printed on one sheet of paper using the evaluation machine, and the obtained image was used as a first evaluation image.

After obtaining the first evaluation image, the photoconductor was removed from the evaluation machine. The surface of the photoconductor was observed with the naked eye to check for scratches and filming on the surface of the photoconductor. After the naked eye observation, the photoconductor was loaded back into the evaluation machine.

Next, in an environment of 10°C temperature and 15% RH relative humidity, image I (a character image with a print rate of 5%) was continuously printed on 50,000 sheets of paper using the evaluation machine. Next, image II (an image including a halftone image and a white background image) was printed on one sheet of paper using the evaluation machine, and the resulting image was used as the second evaluation image.

The first evaluation image and the second evaluation image were observed to confirm the presence or absence of image defects due to filming. Image defects due to filming include, for example, dash marks and fog. Dash marks are black dots arranged parallel to the paper transport direction. The larger the area where filming occurs on the surface of the photoreceptor, the more fog occurs in the formed image starting from the dash marks. Based on the results of checking the surface of the photoreceptor and the results of checking the image defects of the first evaluation image and the second evaluation image, the filming resistance and scratch resistance were evaluated based on the following criteria. The evaluation results of filming resistance and scratch resistance are shown in Tables 6 and 7.

Evaluation A (particularly good): Neither scratches nor filming occurred on the surface of the photoconductor. In addition, no image defects occurred in either the first or second evaluation image.
Evaluation B (good): At least one of scratches and filming occurred on the surface of the photoconductor, but no image defects occurred in either the first or second evaluation image.
Evaluation C (poor): At least one of scratches and filming was observed on the surface of the photoconductor. Image defects were observed in the second evaluation image. However, no image defects were observed in the first evaluation image.
Evaluation D (particularly poor): At least one of scratches and filming occurred on the surface of the photoconductor. Also, image defects occurred in both the first evaluation image and the second evaluation image.

The meanings of the terms in Tables 6 and 7 are as follows: "CGM" indicates a charge generating material. "CG-1" indicates Y-type titanyl phthalocyanine. "CG-A" indicates X-type metal-free phthalocyanine. "HTM" indicates a hole transport material. "ETM" indicates an electron transport material. "Resin" indicates a binder resin. "VL" indicates the potential after exposure (unit: +V). "Filming/scratch" indicates the evaluation results of filming resistance and scratch resistance. "-" indicates that the corresponding material is not used.

As shown in Table 7, the photosensitive layer of photoreceptor (B-1) did not contain a dispersion aid. The photosensitive layer of photoreceptor (B-2) did not contain titanyl phthalocyanine or a dispersion aid. Photoreceptors (B-3) and (B-4) did not contain titanyl phthalocyanine. As a result, the post-exposure potential VL of photoreceptors (B-1) to (B-4) exceeded +110 V, and the sensitivity characteristics were poor.

As shown in Table 7, the photosensitive layers of photoreceptors (B-5) to (B-10) did not contain polyarylate resin (PA). For this reason, the evaluation results for the filming resistance and scratch resistance of photoreceptors (B-5) to (B-10) were C or D, and the filming resistance and scratch resistance were poor.

As shown in Table 7, the photosensitive layer of the photoreceptor (B-11) contained polyarylate resin (R-G), but polyarylate resin (R-G) was not a resin included in polyarylate resin (PA). As a result, the post-exposure potential VL of the photoreceptor (B-11) exceeded +110 V, and the sensitivity characteristics were poor.

On the other hand, as shown in Table 6, the photosensitive layers of the photoconductors (A-1) to (A-27) contained a charge generating agent, a hole transporting agent, an electron transporting agent, a polyarylate resin, and a dispersion aid. The charge generating agent contained titanyl phthalocyanine. The polyarylate resin was a polyarylate resin (PA) (more specifically, one of the polyarylate resins (R-1) to (R-8)). The dispersion aid contained dispersion aid (30) or (31). Therefore, the post-exposure potential VL of the photoconductors (A-1) to (A-27) was +110 V or less, and the sensitivity characteristics were good. In addition, the evaluation results of the filming resistance and scratch resistance of the photoconductors (A-1) to (A-27) were A or B, and the filming resistance and scratch resistance were excellent.

From the above, it has been shown that the photoreceptors of the present invention, including photoreceptors (A-1) to (A-27), have excellent sensitivity characteristics, filming resistance, and scratch resistance. Furthermore, since the process cartridge and image forming apparatus of the present invention are equipped with such photoreceptors, it is believed that the sensitivity characteristics, filming resistance, and scratch resistance of the photoreceptor can be improved.

The photoconductor and process cartridge of the present invention can be used in an image forming apparatus. The image forming apparatus of the present invention can be used to form an image on a recording medium.

1: Photoconductor (electrophotographic photoconductor)
2: conductive substrate 3: photosensitive layer 61: exposure device 63: charging device 64: developing device 65: image carrier 66: cleaning device 67: charge removing device 70: transfer device 100: image forming device P: recording medium

Claims (8)

A conductive substrate and a photosensitive layer are provided.
the photosensitive layer is a single layer,
the photosensitive layer contains a charge generating material, a hole transport material, an electron transport material, a polyarylate resin, and a dispersion aid;
The charge generating material includes titanyl phthalocyanine,
the polyarylate resin contains a repeating unit represented by formula (1-5), a repeating unit represented by formula (2), and a repeating unit represented by formula (3), and a ratio n1/ _n2 of the number _n1 of the repeating units represented by formula (1-5) to the number n2 of the repeating units represented by formula ( ₂ ) is _1.0 or more and 6.0 or less;
The dispersion aid comprises a compound represented by formula (30) or (31),
The electron transport agent includes a compound represented by formula (16),
The electrophotographic photoreceptor, wherein the hole transport agent comprises a compound represented by formula (24):

(Q ⁶¹ and Q ⁶² in the formula (16) each independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 2 to 6 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, or an aryl group having from 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms and a halogen atom.)

In the formula (24), R ⁵⁰ and R ⁵¹ each independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group; R ⁵² , R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ , and R ⁵⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group which may be substituted with an alkyl group having 1 to 6 carbon atoms; f ₁ and f ₂ each independently represent an integer of 0 to 2; and f ₃ and f ₄ each independently represent an integer of 0 to 5. 2. The electrophotographic photoreceptor according to claim 1 , wherein the electron transport agent comprises a compound represented by formula (E-1):

3. The electrophotographic photoreceptor according to claim 1, wherein the hole transport agent comprises a compound represented by formula (H-1), (H-2), (H-3), (H-4), or (H-5).

A process cartridge comprising the electrophotographic photoreceptor according to any one of claims 1 to 3. An image carrier;
a charging device for charging the surface of the image carrier;
an exposure device that exposes the charged surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier;
a developing device that supplies toner to the surface of the image carrier to develop the electrostatic latent image into a toner image;
a transfer device that transfers the toner image from the image carrier to a transfer medium,
An image forming apparatus, wherein the image bearing member is the electrophotographic photoreceptor according to any one of claims 1 to 3. The image forming apparatus according to claim 5, further comprising one or both of a cleaning device that collects the toner adhering to the surface of the image carrier and a charge eliminating device that eliminates charge from the surface of the image carrier. The image forming apparatus according to claim 5 or 6, wherein the charging device is a charging roller. The image forming apparatus according to any one of claims 5 to 7, wherein the developing device supplies the toner, which is charged by friction with the carrier, to the surface of the image carrier.

Images