Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that can prevent environmental dependency of sensitivity, and the occurrence of fogging in a high temperature and high humidity environment.SOLUTION: An electrophotographic photoreceptor comprises a conductive substrate, and a photosensitive layer. The photosensitive layer has a charge generating layer and a charge transport layer. The charge transport layer contains a binder resin, a hole transport agent, and a phthalocyanine pigment. The binder resin includes a specific polyarylate resin. The specific polyarylate resin has first to fourth repeating units represented by the general formulas (1) to (4), respectively.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Electrophotographic photoreceptors are required to have excellent sensitivity characteristics, abrasion resistance, and storage stability, as well as to suppress the occurrence of image memory and fogging. In response to such requirements, an electrophotographic photoreceptor has been proposed in which a polyarylate resin is added to the surface layer (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-020514 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with the electrophotographic photoreceptor described in Patent Document 1, it is difficult to satisfy all of the requirements of excellent sensitivity characteristics, abrasion resistance and storage stability, as well as suppression of image memory and fogging.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrophotographic photoreceptor which is excellent in sensitivity characteristics, abrasion resistance and storage stability, and which can suppress the occurrence of image memory and fogging. Another object of the present invention is to provide a process cartridge and an image forming apparatus equipped with such an electrophotographic photoreceptor. [Means for solving the problem]

[0006] The electrophotographic photoreceptor of the present invention includes a conductive substrate and a photosensitive layer provided directly or indirectly on the conductive substrate. The photosensitive layer has a charge generating layer and a charge transport layer. The charge transport layer contains a binder resin, a hole transport agent, and a phthalocyanine pigment. The binder resin includes a specific polyarylate resin. The specific polyarylate resin has a first repeating unit represented by the following general formula (1), a second repeating unit represented by the following chemical formula (2), a third repeating unit represented by the following chemical formula (3), and a fourth repeating unit represented by the following chemical formula (4). The ratio of the number of moles of the third repeating unit to the total number of moles of the first repeating unit and the third repeating unit is more than 0.0 mol% and less than 50.0 mol%. The ratio of the number of moles of the fourth repeating unit to the total number of moles of the second repeating unit and the fourth repeating unit is 30.0 mol% or more and less than 70.0 mol%.

[0007] [ka]

[0008] In the general formula (1), X represents a divalent group having 1 to 10 carbon atoms. 1 and R 2 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0009] The process cartridge of the present invention includes the above-mentioned electrophotographic photoreceptor.

[0010] The image forming apparatus of the present invention includes an image carrier, a charging device for charging the surface of the image carrier, an exposure device for exposing 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 for supplying toner to the surface of the image carrier to develop the electrostatic latent image into a toner image, and a transfer device for transferring the toner image from the image carrier to a transferee. The image carrier is the electrophotographic photoreceptor described above. Effect of the Invention

[0011] The electrophotographic photoreceptor of the present invention is excellent in sensitivity, wear resistance and storage stability, and can suppress the occurrence of image memory and fogging. The process cartridge of the present invention and the image forming apparatus of the present invention are excellent in sensitivity, wear resistance and storage stability, and can suppress the occurrence of image memory and fogging. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a partial cross-sectional view showing an example of an electrophotographic photoreceptor according to the first embodiment. [Diagram 2] FIG. 4 is a partial cross-sectional view showing another example of the electrophotographic photoreceptor according to the first embodiment. [Diagram 3] FIG. 13 is a diagram illustrating an example of an image forming apparatus according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments and can be practiced with appropriate modifications within the scope of the object of the present invention.

[0014] Acrylic and methacrylic may be collectively referred to as "(meth)acrylic". Acrylate and methacrylate may be collectively referred to as "(meth)acrylate". The number average primary particle diameter is the number average value of the circle equivalent diameter of primary particles (Heywood diameter: diameter of a circle having the same area as the projected area of ​​a primary particle) measured using a scanning electron microscope, unless otherwise specified. The number average primary particle diameter is, for example, the number average value of the circle equivalent diameter of 100 primary particles. The viscosity average molecular weight of a resin is measured according to JIS (Japanese Industrial Standards) K7252-1:2016. The compound name may be followed by "system" to collectively refer to the compound and its derivatives. In addition, when the compound name is followed by "system" to represent 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 formula" and "chemical formula" are collectively described as "formula". In the explanation of the formula, "independently" means that it may represent the same group or different groups. Unless otherwise specified, each component described in this specification may be used alone or in combination of two or more. For example, "at least one of A, B, and C" and "at least one of A, B, and C" are synonymous with "at least one selected from the group consisting of A, B, and C."

[0015] [First embodiment: electrophotographic photoreceptor] The first embodiment of the present invention relates to an electrophotographic photoreceptor (hereinafter, sometimes referred to as a photoreceptor). The photoreceptor of this embodiment includes a conductive substrate and a photosensitive layer provided directly or indirectly on the conductive substrate. The photosensitive layer has a charge generation layer and a charge transport layer. The charge transport layer contains a binder resin, a hole transport agent, and a phthalocyanine pigment. The binder resin includes a specific polyarylate resin. The specific polyarylate resin has a first repeating unit represented by the following general formula (1), a second repeating unit represented by the following chemical formula (2), a third repeating unit represented by the following chemical formula (3), and a fourth repeating unit represented by the following chemical formula (4). The ratio of the number of moles of the third repeating unit to the total number of moles of the first repeating unit and the third repeating unit (hereinafter, sometimes referred to as a ratio (3)) is more than 0.0 mol% and less than 50.0 mol%. The ratio of the number of moles of the fourth repeating unit to the total number of moles of the second repeating unit and the fourth repeating unit (hereinafter sometimes referred to as ratio (4)) is 30.0 mol % or more and less than 70.0 mol %.

[0016] [ka]

[0017] In the general formula (1), X represents a divalent group having 1 to 10 carbon atoms. 1 and R 2 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0018] The photoreceptor of the present embodiment has the above-mentioned configuration, and is excellent in sensitivity characteristics, wear resistance, and storage stability, and can suppress the occurrence of image memory and fogging. The reason is presumed to be as follows. In the photoreceptor of the present embodiment, the charge transport layer contains a specific polyarylate resin. The specific polyarylate resin has a first repeating unit to a fourth repeating unit. The first repeating unit imparts rigidity to the specific polyarylate resin. The second repeating unit and the third repeating unit impart flexibility to the specific polyarylate resin. The fourth repeating unit adjusts the balance of the physical properties of the specific polyarylate resin. The specific polyarylate resin has the first repeating unit to the fourth repeating unit, and the ratios (3) and (4) are set in specific ranges, thereby imparting excellent sensitivity characteristics, wear resistance, and storage stability to the photoreceptor of the present embodiment. In particular, the specific polyarylate resin can impart excellent wear resistance to the photoreceptor of the present embodiment by having the ratio (3) of the third repeating unit exceeding 0.0 mol %. Furthermore, when the specific polyarylate resin has a ratio (3) of the third repeating unit of less than 50.0 mol%, gelation of the coating liquid prepared for forming the charge transport layer can be suppressed. Furthermore, when the specific polyarylate resin has a ratio (4) of the fourth repeating unit of 30.0 mol% or more, excellent storage stability can be imparted to the photoreceptor of this embodiment. Furthermore, when the specific polyarylate resin has a ratio (4) of the fourth repeating unit of less than 70.0 mol%, excellent wear resistance can be imparted to the photoreceptor of this embodiment.

[0019] On the other hand, known photoreceptors using polyarylate resin as the binder resin of the charge transport layer tend to easily accumulate charges in the charge transport layer. In known photoreceptors, accumulation of charges in the charge transport layer causes image memory and fogging. In contrast, the charge transport layer of the photoreceptor of the present embodiment contains a phthalocyanine pigment. The pigment can cancel the charge accumulated in the charge transport layer and suppress the occurrence of fogging. Among the pigments, the phthalocyanine pigment can effectively cancel the charge accumulated in the charge transport layer and suppress the occurrence of fogging as well as the occurrence of image memory. The charge transport layer of the photoreceptor of the present embodiment contains a phthalocyanine pigment, so that the occurrence of image memory and fogging can be suppressed. The photoreceptor will be further described below.

[0020] The photoreceptor of this embodiment is, for example, a photoreceptor including a negatively charged laminated photoreceptor layer. Hereinafter, the structure of a photoreceptor 1, which is an example of the photoreceptor of this embodiment, will be described with reference to FIG. 1. FIG. 1 shows a partial cross-sectional view of the 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 includes a charge generation layer 3a and a charge transport layer 3b. That is, the photoreceptor 1 includes a conductive substrate 2, a charge generation layer 3a provided on the conductive substrate 2, and a charge transport layer 3b provided on the charge generation layer 3a.

[0021] The thickness of the charge generating layer 3a is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 3 μm or less. In the example shown in FIG. 1, the charge generating layer 3a has a single-layer structure. However, the charge generating layer 3a may have a multi-layer structure.

[0022] The thickness of the charge transport layer 3b is not particularly limited, but is preferably 2 μm to 100 μm, more preferably 5 μm to 50 μm. In the example shown in FIG. 1, the charge transport layer 3b has a single-layer structure. However, the charge transport layer 3b may have a multi-layer structure. The structure of the photoreceptor 1, which is an example of the photoreceptor of this embodiment, has been described above with reference to FIG. 1.

[0023] Next, the structure of a photoreceptor 11, which is another example of the photoreceptor of this embodiment, will be described with reference to FIG. 2. FIG. 2 shows a partial cross-sectional view of the photoreceptor 11. As shown in FIG. 2, the photoreceptor 11 includes, for example, a conductive substrate 12, an intermediate layer 14, and a photosensitive layer 13. The photosensitive layer 13 includes a charge generating layer 13a and a charge transport layer 13b. That is, the photoreceptor 11 shown in FIG. 2 includes a conductive substrate 12, an intermediate layer 14 provided on the conductive substrate 12, a charge generating layer 13a provided on the intermediate layer 14, and a charge transport layer 13b provided on the charge generating layer 13a.

[0024] The thickness of the intermediate layer 3 is preferably 1.0 μm or more and 20.0 μm or less, and more preferably 1.0 μm or more and 5.0 μm or less.

[0025] The conductive substrate 12, photosensitive layer 13, charge generation layer 13a, and charge transport layer 13b of the photoreceptor 11 shown in FIG. 2 are similar to the conductive substrate 2, photosensitive layer 3, charge generation layer 3a, and charge transport layer 3b of the photoreceptor 1 shown in FIG. 1, and therefore their description will be omitted.

[0026] The structure of the photoreceptor 1, which is an example of the photoreceptor of this embodiment, and the structure of the photoreceptor 11, which is another example, have been described above with reference to FIGS. 1 and 2. However, the structure of the photoreceptor of this embodiment may be different from that of FIGS. 1 and 2. In the photoreceptor of this embodiment, the charge transport layer is preferably the outermost layer. By using the charge transport layer as the outermost layer, the photoreceptor of this embodiment can maximize the excellent wear resistance of the charge transport layer due to the specific polyarylate resin. However, in the photoreceptor of this embodiment, the charge transport layer does not have to be the outermost layer. For example, the photoreceptor of this embodiment may further include a protective layer provided on the photoreceptor layer. Even when the photoreceptor of this embodiment further includes a protective layer, the photoreceptor of this embodiment can exhibit excellent wear resistance by satisfying the above-mentioned configuration. This is because when the protective layer is worn and the charge transport layer is exposed, the excellent wear resistance of the charge transport layer due to the specific polyarylate resin is exhibited. In addition, the photoreceptor of this embodiment may further include layers other than the intermediate layer, the photoreceptor, and the protective layer.

[0027] [Conductive substrate] The conductive substrate is not particularly limited, and at least the surface portion may be made of a material having electrical conductivity. An example of the conductive substrate is a conductive substrate made of a material having electrical conductivity. Another example of the conductive substrate is a conductive substrate coated with a material having electrical conductivity. Examples of the conductive material include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, and indium. Two or more conductive materials may be combined and used as an alloy (more specifically, aluminum alloy, stainless steel, brass, etc.). Since the charge transfer from the photosensitive layer to the conductive substrate is good, aluminum or an aluminum alloy is preferred as the conductive material. The shape of the conductive substrate is appropriately selected according to the structure of the image forming apparatus. 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.

[0028] [Photosensitive layer] The photosensitive layer is provided directly on the conductive substrate, or indirectly on the conductive substrate via another layer (for example, an intermediate layer). The photosensitive layer has a charge generating layer and a charge transport layer.

[0029] [Charge generation layer] The charge generation layer contains a charge generation agent. The charge generation layer may further contain a binder resin for the charge generation layer (hereinafter, may be referred to as a "base resin"). The charge generation layer may further contain additives as necessary.

[0030] (Charge generating material) Examples of the charge generating agent include phthalocyanine 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-based pigments, triphenylmethane-based pigments, threne-based pigments, toluidine-based pigments, and pyrazoline-based pigments.

[0031] The phthalocyanine pigment has a phthalocyanine structure. Examples of the phthalocyanine pigment include metal phthalocyanine and metal-free phthalocyanine. Examples of the metal phthalocyanine include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. The metal phthalocyanine is preferably titanyl phthalocyanine. Titanyl phthalocyanine is represented by formula (CG-1). Metal-free phthalocyanine is represented by formula (CG-2).

[0032] [ka]

[0033] The phthalocyanine pigment may be crystalline or non-crystalline. Examples of the metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter, may be referred to as X-type metal-free phthalocyanine). Examples of the titanyl phthalocyanine crystals include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter, may be referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively).

[0034] For example, a photoconductor having sensitivity in the wavelength region of 700 nm or more is preferably used in a digital optical image forming apparatus (for example, a laser beam printer or a facsimile using a light source such as a semiconductor laser). As the charge generating agent, a phthalocyanine pigment is preferable, titanyl phthalocyanine is more preferable, and Y-type titanyl phthalocyanine is even more preferable, because they have a high quantum yield in the wavelength region of 700 nm or more.

[0035] The Y-type titanyl phthalocyanine has a main peak at, for example, 27.2° of Bragg angle (2θ±0.2°) in the CuKα characteristic X-ray diffraction spectrum. The main peak in the CuKα characteristic X-ray diffraction spectrum is the peak having the first or second largest intensity in the range of Bragg angle (2θ±0.2°) from 3° to 40°. The Y-type titanyl phthalocyanine does not have a peak at 26.2° in the CuKα characteristic X-ray diffraction spectrum.

[0036] The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, a sample (titanyl phthalocyanine) is loaded into a sample holder of an X-ray diffractometer (for example, Rigaku Corporation's "RINT (registered trademark) 1100"), and the X-ray diffraction spectrum is measured under the conditions of an X-ray tube Cu, a tube voltage of 40 kV, a tube current of 30 mA, and a wavelength of CuKα characteristic X-ray of 1.542 Å. 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.

[0037] The content of the charge generating agent in the charge generating layer is preferably from 0.1 to 10.0 parts by weight, and more preferably from 1.0 to 4.0 parts by weight, per 100 parts by weight of the base resin.

[0038] (Base resin) Examples of the base resin include thermoplastic resin, thermosetting resin, and photocurable resin. Examples of the thermoplastic resin include polycarbonate resin, polyarylate resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic acid polymer, styrene-acrylic acid copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, urethane resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyester resin, polyvinyl acetal resin, and polyether resin. Examples of the thermosetting resin include silicone resin, epoxy resin, phenol resin, urea resin, and melamine resin. Examples of the photocurable resin include acrylic acid adduct of epoxy compound and acrylic acid adduct of urethane compound. The base resin is preferably polyvinyl acetal resin.

[0039] The content of the base resin in the charge generating layer is preferably from 10.0% by mass to 60.0% by mass, and more preferably from 20.0% by mass to 40.0% by mass.

[0040] (Additives) Examples of additives in the charge generating layer include anti-deterioration agents (e.g., antioxidants, radical scavengers, singlet quenchers, or ultraviolet absorbers), softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, acceptor compounds (e.g., electron acceptor compounds), donors, surfactants, plasticizers, sensitizers, and leveling agents. Examples of antioxidants include hindered phenol compounds, hindered amine compounds, thioether compounds, and phosphite compounds. Examples of leveling agents include dimethyl silicone oil.

[0041] [Charge transport layer] The charge transport layer contains a binder resin, a hole transport agent, and a phthalocyanine pigment. The charge transport layer may further contain an additive.

[0042] (binder resin) The binder resin includes a specific polyarylate resin. The binder resin may include a resin other than the specific polyarylate resin, but preferably includes only the specific polyarylate resin. The content of the specific polyarylate resin in the binder resin is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. The content of the binder resin in the charge transport layer is preferably 50.0% by mass or more and 90.0% by mass or less, and more preferably 60.0% by mass or more and 75.0% by mass or less.

[0043] (Specific polyarylate resin) The specific polyarylate resin is, for example, a polymer of a dicarboxylic acid monomer and a bisphenol compound monomer. The dicarboxylic acid monomer includes a dicarboxylic acid or a dicarboxylic acid derivative (e.g., dicarboxylic acid dichloride, dicarboxylic acid dimethyl ester, dicarboxylic acid diethyl ester, and dicarboxylic acid anhydride). The bisphenol compound monomer includes a bisphenol compound or a bisphenol compound derivative (e.g., aromatic diacetate derived from a bisphenol compound). In the specific polyarylate resin, the ratio of the total mole number of repeating units derived from the dicarboxylic acid monomer to the total mole number of repeating units derived from the bisphenol compound monomer is approximately 1:1.

[0044] The specific polyarylate resin has a first repeating unit represented by general formula (1), a second repeating unit represented by chemical formula (2), a third repeating unit represented by chemical formula (3), and a fourth repeating unit represented by chemical formula (4). The specific polyarylate resin may further have repeating units other than the first to fourth repeating units, but preferably has only the first to fourth repeating units. The total content of the first to fourth repeating units in all repeating units contained in the specific polyarylate resin is preferably 80.0 mol% or more, more preferably 95.0 mol% or more, and even more preferably 100.0 mol%.

[0045] (First repeat unit) The first repeating unit is represented by the general formula (1). In the total repeating units of the specific polyarylate resin, the content ratio of the first repeating unit is preferably 20.0 mol% or more and 45.0 mol% or less, and more preferably 35.0 mol% or more and 45.0 mol% or less. By making the content ratio of the first repeating unit 20.0 mol% or more, the photoreceptor of this embodiment can more effectively suppress gelation of the coating liquid prepared when forming the charge transport layer. By making the content ratio of the first repeating unit 45.0 mol% or less, the photoreceptor of this embodiment can exhibit even better wear resistance.

[0046] [ka]

[0047] In the general formula (1), X represents a divalent group having 1 to 10 carbon atoms. 1 and R 2 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0048] In the general formula (1), R 1 and R 2 The alkyl group having 1 to 6 carbon atoms represented by the formula (1) is preferably a methyl group, an ethyl group, or a propyl group, and more preferably a methyl group. 1and R 2 Preferably, each of them represents the same group, and more preferably, each of them represents a hydrogen atom or each of them represents a methyl group.

[0049] In general formula (1), the divalent group having 1 to 10 carbon atoms represented by X is preferably an alkanediyl group having 2 to 5 carbon atoms or a cycloalkanediyl group having 5 to 7 carbon atoms, and more preferably a group represented by chemical formula (X1) or (X2). In chemical formula (X1) or (X2), * represents a bond.

[0050] [ka]

[0051] The first repeating unit is preferably represented by chemical formula (1-1) or (1-2).

[0052] [ka]

[0053] The first repeating unit is derived from, for example, a compound represented by general formula (1a). In general formula (1a), R 1 , R 2 and X are the same as defined in formula (1).

[0054] [ka]

[0055] (Second repeat unit) The second repeating unit is represented by chemical formula (2). In the total repeating units of the specific polyarylate resin, the content ratio of the second repeating unit is preferably 10.0 mol% or more and 40.0 mol% or less, and more preferably 27.5 mol% or more and 37.5 mol% or less. By making the content ratio of the second repeating unit 10.0 mol% or more, the photoreceptor of this embodiment can exhibit even better abrasion resistance. By making the content ratio of the second repeating unit 40.0 mol% or less, the photoreceptor of this embodiment can exhibit even better storage stability and more effectively suppress the occurrence of fogging.

[0056] [ka]

[0057] The second repeating unit is derived from, for example, 4,4'-oxybisbenzoyl chloride.

[0058] (Third repeat unit) The third repeating unit is represented by chemical formula (3). The content ratio of the third repeating unit in all repeating units contained in the specific polyarylate resin is preferably 5.0 mol% or more and 30.0 mol% or less, and more preferably 5.0 mol% or more and 15.0 mol% or less. By making the content ratio of the third repeating unit 5.0 mol% or more, the photoreceptor of this embodiment can exhibit even better abrasion resistance. By making the content ratio of the third repeating unit 30.0 mol% or less, the gelation of the coating liquid prepared when forming the charge transport layer can be more effectively suppressed.

[0059] [ka]

[0060] The third repeat unit is derived, for example, from 4,4'-dihydroxydiphenyl ether.

[0061] (fourth repeat unit) The fourth repeating unit is represented by chemical formula (4). In the total repeating units of the specific polyarylate resin, the content ratio of the fourth repeating unit is preferably 10.0 mol% or more and 40.0 mol% or less, and more preferably 12.5 mol% or more and 22.5 mol% or less. By making the content ratio of the fourth repeating unit 10.0 mol% or more, the photoreceptor of this embodiment can more effectively suppress the occurrence of fogging while exhibiting more excellent storage stability. By making the content ratio of the fourth repeating unit 40.0 mol% or less, the wear resistance of the photoreceptor of this embodiment can be further optimized.

[0062] [ka]

[0063] The fourth repeat unit is derived from, for example, terephthalic acid dichloride.

[0064] In the specific polyarylate resin, the ratio (3) of the number of moles of the third repeating unit to the total number of moles of the first repeating unit and the third repeating unit is more than 0.0 mol% and less than 50.0 mol%, preferably 5.0 mol% or more and 45.0 mol% or less, and more preferably 15.0 mol% or more and 25.0 mol% or less.

[0065] In the specific polyarylate resin, the ratio (4) of the number of moles of the fourth repeating unit to the total number of moles of the second repeating unit and the fourth repeating unit is 30.0 mol% or more and less than 70.0 mol%, preferably 30.0 mol% or more and 67.0 mol% or less, and more preferably 30.0 mol% or more and 40.0 mol% or less.

[0066] It is preferable that, relative to all repeating units contained in the specific polyarylate resin, the content of the first repeating unit is 20.0 mol% or more and 45.0 mol% or less, the content of the second repeating unit is 10.0 mol% or more and 40.0 mol% or less, the content of the third repeating unit is 5.0 mol% or more and 30.0 mol% or less, and the content of the fourth repeating unit is 10.0 mol% or more and 40.0 mol% or less.

[0067] The content ratio of each repeating unit in the specific polyarylate resin was measured by using a proton nuclear magnetic resonance spectrometer. 1 The H-NMR spectrum was measured and 1 It can be calculated from the ratio of peaks characteristic of each repeating unit in the H-NMR spectrum.

[0068] The specific polyarylate resin may have a terminal group. Examples of the terminal group of the specific polyarylate resin include terminal groups represented by formulas (T-1) and (T-2). The terminal group represented by formula (T-1) is preferably a terminal group represented by formula (T-DMP) (hereinafter, sometimes referred to as terminal group (T-DMP)). The terminal group represented by formula (T-2) is preferably a terminal group represented by formula (T-PFH) (hereinafter, sometimes referred to as terminal group (T-PFH)).

[0069] [ka]

[0070] In formula (T-1), R 21 represents an alkyl group having 1 to 6 carbon atoms or a halogen atom, and p represents an integer of 0 to 5. 21 preferably represents an alkyl group having 1 to 6 carbon atoms, more preferably represents an alkyl group having 1 to 3 carbon atoms, and even more preferably represents a methyl group. p preferably represents an integer of 1 to 3, and more preferably represents 2.

[0071] In formula (T-2), R 22 represents an alkanediyl group having 1 to 6 carbon atoms. Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms. R 22Rf preferably represents an alkanediyl group having from 1 to 3 carbon atoms, and more preferably represents a methylene group. Rf preferably represents a perfluoroalkyl group having from 3 to 10 carbon atoms, more preferably a perfluoroalkyl group having from 5 to 7 carbon atoms, and even more preferably a perfluoroalkyl group having 6 carbon atoms.

[0072] The * in the formulae (T-1), (T-2), (T-DMP), and (T-PFH) represents a bond. The bond represented by the * in the formulae (T-1), (T-2), (T-DMP), and (T-PFH) is bonded to a repeating unit derived from a dicarboxylic acid monomer located at an end of the specific polyarylate resin (more specifically, the second repeating unit or the fourth repeating unit).

[0073] From the viewpoint of improving the filming resistance and scratch resistance of the photoreceptor of the present embodiment, the specific polyarylate resin preferably has a terminal group having a halogen atom.

[0074] An example of a terminal group having a halogen atom is R 21 represents a halogen atom. Another example of an end group having a halogen atom is the end group (T-2).

[0075] In the specific polyarylate resin, the repeating unit derived from the bisphenol compound monomer and the repeating unit derived from the dicarboxylic acid monomer are adjacent to each other and bonded to each other. The specific polyarylate resin may be, for example, a random copolymer, an alternating copolymer, a periodic copolymer, or a block copolymer.

[0076] The specific polyarylate resin is preferably polyarylate resins (a) to (d) shown in Table 1. In Table 1, the numerical range of each repeating unit indicates the numerical range of the content ratio of each repeating unit to all repeating units contained in the polyarylate resin. "1-1" and "1-2" of the type of first repeating unit indicate repeating units represented by chemical formula (1-1) or (1-2), respectively. For example, polyarylate resin (a) has a repeating unit represented by chemical formula (1-1) as the first repeating unit. With respect to all repeating units contained in polyarylate resin (a), the content ratio of the first repeating unit is 75.0 mol% or more and 85.0 mol% or less, the content ratio of the second repeating unit is 15.0 mol% or more and 25.0 mol% or less, the content ratio of the third repeating unit is 62.0 mol% or more and 68.0 mol% or less, and the content ratio of the fourth repeating unit is 32.0 mol% or more and 38.0 mol% or less. The polyarylate resins (a) to (d) may further have the above-mentioned terminal groups.

[0077] [Table 1]

[0078] As the specific polyarylate resin, resins represented by chemical formulas (pa-1) to (pa-4) (hereinafter, polyarylate resins (pa-1) to (pa-4)) are particularly preferred. In the chemical formulas (pa-1) to (pa-4), the numbers written to the lower right of each repeating unit indicate the content ratio of each repeating unit to the total repeating units contained in the polyarylate resins (pa-1) to (pa-4). The polyarylate resins (pa-1) to (pa-4) may further have the above-mentioned terminal groups in addition to the repeating units represented by the chemical formulas (pa-1) to (pa-4).

[0079] [ka]

[0080] The viscosity average molecular weight of the specific polyarylate resin is preferably 10,000 or more, more preferably 30,000 or more, even more preferably 35,000 or more, and particularly preferably 50,000 or more. When the viscosity average molecular weight of the specific polyarylate resin is 10,000 or more, the abrasion resistance of the photoreceptor of this embodiment can be further optimized. On the other hand, the viscosity average molecular weight of the specific polyarylate resin is preferably 80,000 or less, more preferably 70,000 or less, and even more preferably 60,000 or less. When the viscosity average molecular weight of the specific polyarylate resin is 80,000 or less, the solubility of the specific polyarylate resin in a solvent is improved. The viscosity average molecular weight of the specific polyarylate resin is measured according to JIS (Japanese Industrial Standards) K7252-1:2016.

[0081] Next, a method for producing the specific polyarylate resin will be described. As a method for producing the specific polyarylate resin, for example, a method of polycondensing a bisphenol compound monomer and a dicarboxylic acid monomer can be mentioned. For the polycondensation, a known synthesis method (for example, solution polymerization, melt polymerization, or interfacial polymerization) can be adopted. The bisphenol compound monomer includes a compound that forms the first repeat unit and the third repeat unit described above. The dicarboxylic acid monomer includes a compound that forms the second repeat unit and the fourth repeat unit described above.

[0082] In the polycondensation of bisphenol and dicarboxylic acid, a terminal terminator may be added. Examples of the terminal terminator include 2,6-dimethylphenol and 1H,1H-perfluoro-1-heptanol. By using 2,6-dimethylphenol as the terminal terminator, a terminal group (T-DMP) is formed. By using 1H,1H-perfluoro-1-heptanol as the terminal terminator, a terminal group (T-PFH) is formed.

[0083] In the polycondensation of the bisphenol compound monomer and the dicarboxylic acid compound monomer, a base and / or a catalyst may be added. An example of the base is sodium hydroxide. An example of the catalyst is benzyltributylammonium chloride, ammonium chloride, ammonium bromide, quaternary ammonium salt, triethylamine, and trimethylamine.

[0084] (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.

[0085] Examples of the hole transport material include compounds represented by general formulas (20), (23), (24), and (25) (hereinafter, these may be referred to as hole transport materials (20), (23), (24), and (25), respectively).

[0086] [ka]

[0087] In general formula (20), R 50 and R51 R each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group. 52 , R 53 , R 54 , R 55 , R 56 , R 57 , and R 58 each independently represents a phenyl group which may be substituted with an alkyl group having 1 to 6 carbon atoms, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. each independently represents an integer of 0 to 2. each independently represents an integer of 0 to 5.

[0088] In the general formula (20), when f3 represents an integer of 2 or more and 5 or less, a plurality of R 50 may represent the same group or different groups. When f4 represents an integer of 2 to 5, multiple R 51 may represent the same group or different groups.

[0089] In general formula (20), R 50 and R 51 R preferably each independently represents an alkyl group having 1 to 3 carbon atoms. 52 and R 53 R preferably represents a phenyl group which may be substituted with a methyl group, or a hydrogen atom. 54 ~R 58 each independently preferably represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms. each of f1 and f2 preferably represents 0 or 1. each of f3 and f4 preferably represents 0 or 1.

[0090] [ka]

[0091] In general formula (23), R 41 , R 42, R 43 , R 44 , R 45 , and R 46 R each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group. 47 and R 48 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group. e1, e2, e3, and e4 each independently represent an integer of 0 to 5. e5 and e6 each independently represent an integer of 0 to 4. e7 and e8 each independently represent 0 or 1.

[0092] In the general formula (23), when e1 to e6 represent an integer of 2 or more and 4 or less, a plurality of R 41 ~Multiple R's 46 may represent the same group or different groups.

[0093] In general formula (23), R 41 ~R 46 R preferably each independently represents an alkyl group having 1 to 3 carbon atoms. 47 and R 48 preferably represents a hydrogen atom. e1, e2, e5, and e6 preferably represent 0. e3 and e4 preferably represent 2. e7 and e8 preferably both represent 0 or both represent 1.

[0094] In general formula (24), R 11 , R 12 , R 13 , and R 14 each independently represents 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.

[0095] In the general formula (24), when a1 to a4 each represent an integer of 2 or more and 5 or less, a plurality of R 11 ~Multiple R's 14 may represent the same group or different groups.

[0096] In general formula (24), R 11 , R 12 , R 13 , and R 14 each independently preferably represents an alkyl group having from 1 to 3 carbon atoms. a1, a2, a3, and a4 each independently preferably represent 0 or 1.

[0097] [ka]

[0098] In general formula (25), R 60 R represents a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms, a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. 61 , R 62 , and R 63 Each of g1, g2, and g3 independently represents an integer of 0 to 5. g4 represents 0 or 1. R 60 R preferably represents a phenyl group. 61 , R 62 , and R 63 each independently preferably represents an alkyl group having 1 to 3 carbon atoms. g1 and g2 preferably represent 1. g3 preferably represents 0.

[0099] In the general formula (25), when g1 to g3 each represent an integer of 2 or more and 5 or less, a plurality of R 61 ~Multiple R's 63 may represent the same group or different groups.

[0100] As the hole transport agent, compounds represented by chemical formulas (H-1) to (H-5), general formula (H-6) and chemical formula (H-7) (hereinafter, each may be referred to as hole transport (H-1) to (H-7)), are preferable.

[0101] [ka]

[0102] [ka]

[0103] In general formula (H-6), R 100 ~R 103 each independently represents a hydrogen atom or a methyl group. 100 ~R 103 At least two of the represent methyl groups.

[0104] The hole transport material (H-6) is, in the general formula (H-6), 100 ~R 103 In the general formula (H-6), two of R represent a methyl group and the remaining two represent a hydrogen atom. 100 ~R 103 and a hole transport agent (H-6b) in which three of the R 100 ~R 103 In the present invention, a mixture of a hole transport agent (H-6c) in which four of the groups represent a methyl group (hereinafter, referred to as a hole transport agent (H-6 Mixture)) is preferred.

[0105] The total content of the hole transport agents (20) and (23) to (25) based on the total amount of the hole transport agents is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0106] In the charge transport layer, the content of the hole transport agent relative to 100 parts by weight of the binder resin is preferably 10 parts by weight to 200 parts by weight, more preferably 30 parts by weight to 60 parts by weight. By setting the content of the hole transport agent to 10 parts by weight to 200 parts by weight, the photoreceptor of this embodiment can more effectively suppress the occurrence of fogging.

[0107] (Phthalocyanine pigment) The phthalocyanine pigment contained in the charge transport layer has a phthalocyanine structure. For example, the phthalocyanine pigment may be the same compound as the compound exemplified as the charge generating agent contained in the charge generation layer. For the phthalocyanine pigment contained in the charge transport layer, metal-free phthalocyanine (compound represented by the above formula (CG-2)) or compound represented by general formula (P-1) (metal phthalocyanine) is preferred, titanyl phthalocyanine is more preferred, and Y-type titanyl phthalocyanine is even more preferred.

[0108] [ka]

[0109] In the general formula (P-1), M represents a metal atom which may have a ligand. The metal atom represented by M is preferably titanium which may have a ligand.

[0110] In the charge transport layer, the content of the phthalocyanine pigment is preferably 0.1 parts by mass or more and 0.5 parts by mass or less, and more preferably 0.2 parts by mass or more and 0.4 parts by mass or less, relative to 100.0 parts by mass of the binder resin. By making the content of the phthalocyanine pigment 0.1 parts by mass or more, the photoreceptor of this embodiment can more effectively suppress the occurrence of image memory and fogging. By making the content of the phthalocyanine pigment 0.5 parts by mass or less, the photoreceptor of this embodiment can further optimize the sensitivity characteristics.

[0111] (Additives) Examples of additives contained in the charge transport layer include ultraviolet absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, electron acceptor compounds, and leveling agents. Examples of the leveling agent include silicone oil, more specifically dimethyl silicone oil.

[0112] The charge transport layer preferably contains silicone oil, and in this case, the content of the silicone oil in the charge transport layer is preferably 0.01 parts by weight or more and 0.5 parts by weight or less with respect to 100 parts by weight of the binder resin.

[0113] The charge transport layer preferably contains only the specific polyarylate resin, the hole transport agent, the phthalocyanine pigment, and the additive (particularly, silicone oil). In the charge transport layer, the total content of the specific polyarylate resin, the hole transport agent, the phthalocyanine pigment, and the additive (particularly, silicone oil) is preferably 90% by mass or more, more preferably 100% by mass.

[0114] Table 2 shows preferred combinations of the type of polyarylate resin, the type and content of the hole transport agent, and the type and content of the pigment in the charge transport layer. In Table 2, the content indicates the content [parts by mass] of each component relative to 100.0 parts by mass of the binder resin. The numerical range of the content indicates the numerical range of the content ratio of each component. The phthalocyanine pigments "K-1" and "K-2" respectively indicate Y-type titanyl phthalocyanine and metal-free phthalocyanine. For example, in the case of combination 1, the charge transport layer contains only polyarylate resin (pa-1) as the binder resin, contains only hole transport agent (H-1) as the hole transport agent, contains only Y-type titanyl phthalocyanine pigment as the phthalocyanine pigment, the content ratio of the hole transport agent to 100.0 parts by mass of the binder resin is 40.0 parts by mass or more and 50.0 parts by mass or less, and the content ratio of the phthalocyanine pigment to 100.0 parts by mass of the binder resin is 0.05 parts by mass or more and 0.15 parts by mass or less. In the case of combination 1, the charge transport layer may further contain an additive.

[0115] [Table 2]

[0116] [Middle layer] The intermediate layer is disposed between the conductive substrate and the photosensitive layer. The intermediate layer contains, for example, an intermediate layer resin and inorganic particles. The presence of the intermediate layer makes it possible to maintain an insulating state sufficient to suppress leakage, while facilitating the flow of current generated when the photoreceptor of the present embodiment is exposed to light, thereby suppressing an increase in resistance.

[0117] Examples of the resin for the intermediate layer include the same resins as those exemplified as the base resin in the charge generating layer. The resin for the intermediate layer is preferably a polyamide resin, more preferably a tetrapolymer polyamide resin of nylon 6, nylon 12, nylon 66 and nylon 610.

[0118] In the intermediate layer, the content of the intermediate layer resin is preferably from 20.0% by mass to 50.0% by mass, and more preferably from 25.0% by mass to 40.0% by mass.

[0119] Inorganic particles include, for example, particles of metals (eg, aluminum, iron, or copper), metal oxides (eg, titanium oxide, alumina, zirconium oxide, tin oxide, or zinc oxide), and non-metal oxides (eg, silica).

[0120] In the intermediate layer, the content of the inorganic particles is preferably from 100 to 300 parts by mass, and more preferably from 150 to 250 parts by mass, per 100 parts by mass of the intermediate layer resin.

[0121] The intermediate layer may contain an additive. Examples of the additive contained in the intermediate layer are the same as the examples of the additive contained in the charge transport layer. However, it is preferable that the intermediate layer contains only the intermediate layer resin and inorganic particles. Specifically, the total content of the intermediate layer resin and inorganic particles in the intermediate layer is preferably 90% by mass or more, more preferably 99% by mass or more, and even more preferably 100% by mass.

[0122] [Photoreceptor manufacturing method] Next, an example of a method for manufacturing a photoreceptor according to the present embodiment will be described. The method for manufacturing a photoreceptor includes, for example, a photosensitive layer forming step. The photosensitive layer forming step includes, for example, a charge generating layer forming step and a charge transport layer forming step. The method for manufacturing a photoreceptor may further include an intermediate layer forming step before the photosensitive layer forming step.

[0123] (Intermediate layer formation process) In the intermediate layer forming step, a coating liquid for forming an intermediate layer (hereinafter, sometimes referred to as an intermediate layer coating liquid) is prepared. The intermediate layer coating liquid contains, for example, an intermediate layer resin, inorganic particles, and a solvent. Next, the intermediate layer coating liquid is applied onto a conductive substrate. Next, at least a part of the solvent contained in the applied intermediate layer is removed to form the intermediate layer.

[0124] (Charge generation layer forming process) In the charge generation layer forming step, a coating liquid for forming a charge generation layer (hereinafter, sometimes referred to as a charge generation layer coating liquid) is prepared. The charge generation layer coating liquid contains, for example, a charge generating agent, a base resin, a solvent, and optional components (for example, additives). The charge generation layer coating liquid is prepared by mixing the above-mentioned components. Next, the charge generation layer coating liquid is applied onto a conductive substrate or an intermediate layer. Next, at least a part of the solvent contained in the applied charge generation layer coating liquid is removed to form a charge generation layer.

[0125] (Charge transport layer formation process) In the charge transport layer forming step, a coating liquid for forming a charge transport layer (hereinafter, sometimes referred to as a charge transport layer coating liquid) is prepared. The charge transport layer coating liquid contains a hole transport agent, a binder resin, a phthalocyanine pigment, a solvent, and optional components (e.g., additives). The charge transport layer coating liquid is prepared by mixing the above-mentioned components. Next, the charge transport layer coating liquid is applied onto the charge generating layer. Next, at least a part of the solvent contained in the applied charge transport layer coating liquid is removed to form a charge transport layer.

[0126] The solvent contained in the coating liquid for the intermediate layer, the coating liquid for the charge generating layer, and the coating liquid for the charge transport layer (hereinafter, these may be collectively referred to as coating liquids) is not particularly limited as long as it can dissolve or disperse each component contained in the coating liquid. 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, methylene chloride, chloroform, ethylene chloride, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, etc.), ethers (more specifically, dioxane, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, diethylene glycol dimethyl ether, etc.), ketones (more specifically, acetone, methyl ethyl ketone, 2-butanone, cyclohexanone, etc.), esters (more specifically, ethyl acetate, methyl acetate, etc.), dimethylformaldehyde, dimethylformamide, and dimethylsulfoxide.

[0127] The coating liquid is prepared by mixing the respective components and dissolving or dispersing them in a solvent. For mixing, for example, a bead mill, a ball mill, a roll mill, a paint shaker, or an ultrasonic disperser can be used.

[0128] The method for applying the coating liquid is not particularly limited as long as the coating liquid can be uniformly applied. Examples of the coating method include a dip coating method, a spray coating method, a bead coating method, a blade coating method, and a roller coating method.

[0129] The method for removing at least a part of the solvent contained in the coating liquid for the intermediate layer, the coating liquid for the charge generating layer, and the coating liquid for the charge transport layer includes, 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 is included. 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 150 minutes or lower.

[0130] [Second embodiment: Image forming apparatus] The second embodiment of the present invention relates to an image forming apparatus. The image forming apparatus includes an image carrier, a charging device for charging the surface of the image carrier, an exposure device for exposing the surface of the charged image carrier to light to form an electrostatic latent image on the surface of the image carrier, a developing device for supplying toner to the surface of the image carrier to develop the electrostatic latent image into a toner image, and a transfer device for transferring the toner image from the image carrier to a transferee. The image carrier is the electrophotographic photoreceptor described in the first embodiment.

[0131] An image forming apparatus 110, which is an example of the image forming apparatus of this embodiment, will be described with reference to Fig. 3. Fig. 3 is a diagram showing an example of the configuration of the image forming apparatus 110. The image forming apparatus 110 is, for example, a tandem type color printer.

[0132] The image forming apparatus 110 shown in FIG. 3 includes a feed section 20, a conveying section 30, image forming units 40Y, 40M, 40C, and 40K, a transfer section 60, a belt cleaning section 70, a fixing section 80, and a paper discharge section 90.

[0133] The image forming apparatus 110 may further include a control device. The control device controls the operation of each part of the image forming apparatus 110 (more specifically, the feeding section 20, the conveying section 30, the image forming units 40Y, 40M, 40C, and 40K, the transfer section 60, the belt cleaning section 70, the fixing section 80, and the paper discharge section 90). The control device is disposed at an appropriate position in the main body housing. The control device includes, for example, a Central Processing Unit (CPU), a Random Access Memory (RAM), a Read Only Memory (ROM), and an input / output interface. The control device executes control by performing each arithmetic process based on the detection results of various sensors and a preset program.

[0134] The feeding unit 20 includes a cassette 22. The cassette 22 accommodates a plurality of recording media P. The feeding unit 20 feeds the recording media P from the cassette 22 to the transport unit 30. The recording media P is, for example, a sheet made of paper, cloth, or synthetic resin.

[0135] The conveying section 30 conveys the recording medium P to the image forming units 40Y, 40M, 40C, and 40K.

[0136] The image forming units 40Y, 40M, 40C, and 40K each include a corresponding image carrier 100Y, 100M, 100C, and 100K, a charging device 42Y, 42M, 42C, and 42K, an exposure device 44Y, 44M, 44C, and 44K, a developing device 46Y, 46M, 46C, and 46K, a cleaning device 48Y, 48M, 48C, and 48K, and a charge removing device 50Y, 50M, 50C, and 50K. Hereinafter, when there is no need to distinguish between them, the suffixes "Y", "M", "C", and "K" attached to each member of the image forming apparatus 110 will be omitted. For example, when there is no need to distinguish between them, each of the image forming units 40Y, 40M, 40C, and 40K will be described as an image forming unit 40.

[0137] The transfer unit 60 includes four transfer devices 62Y, 62M, 62C, and 62K, a drive roller 64, an endless transfer belt 66, a driven roller 67, and a tension roller 68. The transfer devices 62Y, 62M, 62C, and 62K are disposed on the inner periphery side of the transfer belt 66, and face the image carriers 100Y, 100M, 100C, and 100K via the transfer belt 66. The transfer belt 66 is stretched over the drive roller 64, the driven roller 67, and the tension roller 68. The transfer belt 66 rotates in the direction of the arrow (clockwise direction in FIG. 3) as the drive roller 64 rotates.

[0138] An image carrier 100 is provided at the center of the image forming unit 40. The image carrier 100 is provided so as to be rotatable in the direction of the arrow (counterclockwise in FIG. 3). Around the image carrier 100, a charging device 42, an exposure device 44, a developing device 46, a transfer device 62, a cleaning device 48, and a static elimination device 50 are provided in this order from the upstream side in the rotation direction of the image carrier 100.

[0139] Image carrier 100 is the photoreceptor described above (eg, photoreceptor 1 in FIG. 1).

[0140] The charging device 42 positively charges the surface (for example, the peripheral surface) of the image carrier 100. The charging device 42 is, for example, a scorotron charger.

[0141] The exposure device 44 exposes the charged surface of the image carrier 100. As a result, an electrostatic latent image is formed on the surface of the image carrier 100. The electrostatic latent image is formed based on image data input to the image forming device 110.

[0142] The developing device 46 supplies toner to the surface of the image carrier 100 and develops the electrostatic latent image into a toner image. The toner is a positively charged toner. The developing device 46 is in contact with the surface of the image carrier 100. That is, the image forming apparatus 110 employs a contact development method. The developing device 46 is, for example, a developing roller.

[0143] The developer is preferably a one-component developer. In this case, the developing device 46 supplies toner, which is a one-component developer, to the electrostatic latent image formed on the image carrier 100. However, the developer may be a two-component developer. In this case, the developing device 46 supplies toner, of the toner and carrier contained in the two-component developer, to the electrostatic latent image formed on the image carrier 100. The toner image formed by the supplied toner is carried by the image carrier 100.

[0144] The transfer belt 66 transports the recording medium P between the image carrier 100 and the transfer device 62. The transfer device 62 transfers the toner image developed by the developing device 46 from the surface of the image carrier 100 to the recording medium P, which is a receiving body. During transfer, the surface of the image carrier 100 and the recording medium P are in contact with each other. That is, the image forming apparatus 110 employs a direct transfer method. The transfer device 62 is, for example, a transfer roller.

[0145] Each of image forming unit 40Y and transfer device 62Y, image forming unit 40M and transfer device 62M, image forming unit 40C and transfer device 62C, and image forming unit 40K and transfer device 62K sequentially overlays toner images of multiple colors (for example, four colors: yellow, magenta, cyan, and black) on the recording medium P on the transfer belt 66 to form an unfixed toner image.

[0146] The cleaning devices 48Y, 48M, 48C, and 48K include corresponding housings 481Y, 481M, 481C, and 481K, and cleaning members 482Y, 482M, 482C, and 482K, respectively. The cleaning member 482 is disposed in the housing 481. The cleaning member 482 abuts against the surface of the image carrier 100. The cleaning member 482 polishes the surface of the image carrier 100, and collects the toner adhering to the surface of the image carrier 100 into the housing 481. In this manner, the cleaning device 48 collects the toner adhering to the surface of the image carrier 100. The cleaning member 482 is, for example, a cleaning roller or a cleaning brush.

[0147] The static eliminator 50 eliminates static electricity from the surface of the image carrier 100 .

[0148] The recording medium P on which the unfixed toner image has been formed is transported to a fixing unit 80. The fixing unit 80 includes a pressure member 82 and a heating member 84. The pressure member 82 and the heating member 84 apply pressure and heat to the recording medium P, thereby fixing the unfixed toner image to the recording medium P.

[0149] The recording medium P on which the toner image has been fixed is discharged from the paper discharge section 90.

[0150] An example of the image forming apparatus of the present embodiment has been described above, but the image forming apparatus of the present embodiment is not limited to the image forming apparatus 110, and may be further modified in the following ways, for example. The image forming apparatus 110 is a color image forming apparatus, but the image forming apparatus of the present embodiment may be a monochrome image forming apparatus. In this case, the image forming apparatus of the present embodiment may include, for example, only one image forming unit. In addition, the image forming apparatus 110 employs a tandem system, but the image forming apparatus of the present embodiment may employ, for example, a rotary system. Although a scorotron charger has been described as an example of the charging device 42, the charging device may be a charging device other than a scorotron charger (for example, a charging roller, a charging brush, or a corotron charger). The image forming apparatus 110 employs a contact development system, but the image forming apparatus may employ a non-contact development system. The image forming apparatus 110 employs a direct transfer system, but the image forming apparatus may employ an intermediate transfer system. In a known image forming apparatus of the direct transfer system, transfer damage is caused to the photoconductor when a toner image is transferred from the photoconductor to a recording medium. As a result, in known image forming apparatuses using a direct transfer method, image memory and fogging are likely to occur. In contrast, in the image forming apparatus of the present embodiment, since the image forming apparatus is provided with the photoconductor of the first embodiment, the occurrence of image memory and fogging can be effectively suppressed. The image forming apparatus of the present embodiment has been described above.

[0151] [Third embodiment: process cartridge] A third embodiment of the present invention relates to a process cartridge. The process cartridge of this embodiment includes the photoconductor of the first embodiment.

[0152] Continuing to refer to FIG. 3, the process cartridge of this embodiment will be described. The process cartridge of this embodiment corresponds to each of the image forming units 40Y, 40M, 40C, and 40K. The process cartridge includes an image carrier 100, which is the photoconductor of the first embodiment. As described in the first embodiment, the photoconductor of the first embodiment is excellent in sensitivity characteristics, wear resistance, and storage stability, and can suppress the occurrence of image memory and fogging. Therefore, the process cartridge of this embodiment is excellent in sensitivity characteristics, wear resistance, and storage stability of the photoconductor, and can suppress the occurrence of image memory and fogging.

[0153] The process cartridge may further include at least one (e.g., 1 to 7) selected from the group consisting of a charging device 42, an exposure device 44, a developing device 46, a transfer device 62, a cleaning member 482, and a static eliminator 50, in addition to the image carrier 100. The process cartridge is designed to be detachable from the image forming apparatus 110. Therefore, the process cartridge is easy to handle, and when the sensitivity characteristics or the like of the image carrier 100 deteriorates, it can be easily and quickly replaced including the image carrier 100. The process cartridge of this embodiment has been described above with reference to FIG. 3.

[0154] [Substituent] The substituents used in this specification will be described below. Examples of halogen atoms (halogen groups) include fluorine atoms (fluoro groups), chlorine atoms (chloro groups), bromine atoms (bromo groups), and iodine atoms (iodo groups).

[0155] The alkyl groups are linear or branched and unsubstituted unless otherwise specified. Examples of the alkyl group having 1 to 8 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 ... Examples of alkyl groups having different carbon atoms include alkyl groups, 3-methylpentyl groups, 4-methylpentyl groups, 1,1-dimethylbutyl groups, 1,2-dimethylbutyl groups, 1,3-dimethylbutyl groups, 2,2-dimethylbutyl groups, 2,3-dimethylbutyl groups, 3,3-dimethylbutyl groups, 1,1,2-trimethylpropyl groups, 1,2,2-trimethylpropyl groups, 1-ethylbutyl groups, 2-ethylbutyl groups, 3-ethylbutyl groups, linear and branched heptyl groups, and linear and branched octyl groups. Examples of alkyl groups having different carbon atom numbers include, for example, the above-mentioned alkyl groups having a predetermined number of carbon atoms.

[0156] The alkoxy group is linear or branched and unsubstituted unless otherwise specified. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, an n-pentoxy group, a 1-methylbutoxy group, a 2-methylbutoxy group, a 3-methylbutoxy group, a 1-ethylpropoxy group, a 2-ethylpropoxy group, a 1,1-dimethylpropoxy group, a 1,2-dimethylpropoxy group, a 2,2-dimethylpropoxy group, an n-hexyloxy group, a 1-methylbutoxy group, a 2 ... Examples of alkoxy groups having different carbon numbers include alkoxy groups having a specific number of carbon atoms among the above-mentioned alkoxy groups. The substituents used in this specification have been described above. EXAMPLES

[0157] The present invention will be described in more detail below using examples, but the present invention is not limited to the scope of the examples.

[0158] [Synthesis of polyarylate resin] Polyarylate resins (PA-1) to (PA-10) were synthesized by the following method. The monomers used in the synthesis of each polyarylate resin are shown in the chemical formulas (BisCZ), (BisB), (DHPE), (BisBP), (OBBOC), (1,4-NADOC), (2,6-NADOC) and (TPC) (hereinafter, the compounds represented by each chemical formula will be referred to as compounds (BisCZ), (BisB), (DHPE), (BisBP), (OBBOC), (1,4-NADOC), (2,6-NADOC) and (TPC), respectively).

[0159] [ka]

[0160] A three-neck flask equipped with a thermometer, a three-way cock, and a dropping funnel was used as the reaction vessel. Compound (BisCZ) (32.8 mmol), compound (DHPE) (8.2 mmol), 2,6-dimethylphenol (0.413 mmol) as a terminal terminator, sodium hydroxide (98 mmol), and benzyltributylammonium chloride (0.384 mmol) were placed in the reaction vessel. The air in the reaction vessel was replaced with argon gas. Water (300 mL) was added to the contents of the reaction vessel. The contents of the reaction vessel were stirred at 50°C for 1 hour. The contents of the reaction vessel were cooled to 10°C to obtain an alkaline aqueous solution SA. Of the bisphenol compounds contained in the alkaline aqueous solution SA, the proportion of compound (BisCZ) was 80.0 mol%, and the proportion of compound (DHPE) was 20.0 mol%.

[0161] Next, the compound (OBBOC) (20.8 mmol) and the compound (TPC) (11.2 mmol) were dissolved in chloroform (150 mL). This resulted in a chloroform solution SB. Of the dicarboxylic acid dichlorides contained in the chloroform solution SB, the proportion of the compound (OBBOC) was 65.0 mol %, and the proportion of the compound (TPC) was 35.0 mol %.

[0162] The chloroform solution SB was slowly dropped into the alkaline aqueous solution SA over 110 minutes using a dropping funnel. The contents of the reaction vessel were stirred for 4 hours while controlling the temperature (liquid temperature) of the contents of the reaction vessel to 15±5°C to allow the polymerization reaction to proceed. The upper layer (aqueous layer) of the contents of the reaction vessel was removed using a decant to obtain an organic layer. Next, ion-exchanged water (400 mL) was added to the Erlenmeyer flask. The obtained organic layer was further added to the Erlenmeyer flask. Chloroform (400 mL) and acetic acid (2 mL) were further added to the Erlenmeyer flask. The contents of the Erlenmeyer flask were stirred at room temperature (25°C) for 30 minutes. The upper layer (aqueous layer) of the contents of the Erlenmeyer flask was removed using a decant to obtain an organic layer. The obtained organic layer was washed with ion-exchanged water (1 L) using a separating funnel. Washing with ion-exchanged water was repeated five times to obtain a water-washed organic layer. Next, the water-washed organic layer was filtered to obtain a filtrate. The obtained filtrate was slowly dropped into methanol (1 L) to obtain a precipitate. The precipitate was collected by filtration and then vacuum dried at 70° C. for 12 hours. As a result, a polyarylate resin (PA-1) was obtained.

[0163] Each of the polyarylate resins (PA-2) to (PA-10) was synthesized in the same manner as the synthesis of the polyarylate resin (PA-1), except that the types and amounts of monomers shown in Table 3 were used. In the synthesis of the polyarylate resins (PA-2) to (PA-10), the total amount of the bisphenol compound was 41.0 mmol, and the total amount of the dicarboxylic acid dichloride was 32.0 mmol. In Table 3, "%" indicates mol%. In Table 3, "Ratio (3)" and "Ratio (4)" indicate ratio (3) and ratio (4), respectively.

[0164] The polyarylate resins (PA-1) to (PA-10) obtained were analyzed using a proton nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd., 600 MHz). 1 H-NMR spectrum was measured. Deuterated chloroform was used as the solvent. Tetramethylsilane (TMS) was used as the internal standard. 1From the chemical shifts read from the H-NMR spectrum, it was confirmed that the polyarylate resins (PA-1) to (PA-10) had repeating units represented by the chemical formulas (pa-1) to (pa-10), respectively. The content of repeating units derived from bisphenol compounds and the content of repeating units derived from dicarboxylic acid dichloride were approximately 50.0 mol % relative to the total repeating units contained in each of the polyarylate resins (PA-1) to (PA-10). Of the polyarylate resins (PA-1) to (PA-10), the polyarylate resins (PA-1) to (PA-4) were specific polyarylate resins.

[0165] [Table 3]

[0166] [ka]

[0167] [ka]

[0168] [Pigment] Compounds represented by the following chemical formulas (K-1) to (K-5) (hereinafter sometimes referred to as pigments (K-1) to (K-5)) were prepared as pigments to be added to the charge transport layer. Of the pigments (K-1) to (K-5), pigments (K-1) to (K-2) were phthalocyanine pigments. Pigment (K-1) was a Y-type titanyl phthalocyanine. Pigment (K-2) was a metal-free phthalocyanine.

[0169] [ka]

[0170] [ka]

[0171] <Production of photoconductors> Photoreceptors of Examples 1 to 13 and Comparative Examples 1 to 18, which are photoreceptors having a negatively charged laminated photosensitive layer, were manufactured by the following method.

[0172] [Example 1] (Middle layer formation) As the metal oxide particles, a prototype "SMT-A" manufactured by Teika Corporation was used. The metal oxide particles were particles (number average primary particle diameter 10 nm) in which a primary surface treatment using alumina and silica and a secondary surface treatment using methylhydrogenpolysiloxane were sequentially performed on titanium oxide particles. 2 parts by mass of the above-mentioned metal oxide particles, 1 part by mass of polyamide resin ("Amilan (registered trademark) CM8000" manufactured by Toray Industries, Inc., a copolymer of nylon 6, nylon 12, nylon 66 and nylon 610), 10 parts by mass of methanol, 1 part by mass of n-butanol and 1 part by mass of toluene were mixed. The resulting mixture was stirred for 5 hours with a bead mill to thoroughly disperse the titanium oxide particles in the solvent (a mixed organic solvent of methanol, n-butanol and toluene). The mixture after dispersion was filtered through a 5 μm filter. This prepared a coating liquid for the intermediate layer.

[0173] An aluminum drum-shaped support (diameter 30 mm) was used as the conductive substrate. The above-mentioned intermediate layer coating solution was applied to the conductive substrate by dip coating. Next, the conductive substrate after coating was heated and dried at 130° C. for 30 minutes. This formed an intermediate layer (film thickness: 1.5 μm) on the conductive substrate.

[0174] (Charge generation layer formation) 2.3 parts by mass of Y-type titanyl phthalocyanine, 1.0 part by mass of polyvinyl acetal resin ("S-LEC (registered trademark) BX-5" manufactured by Sekisui Chemical Co., Ltd.) as a base resin, 40.0 parts by mass of propylene glycol monomethyl ether, and 40.0 parts by mass of tetrahydrofuran were mixed to obtain a mixed liquid. The obtained mixed liquid was dispersed for 12 hours using a bead mill. The dispersed mixed liquid was filtered through a 3 μm filter. This resulted in a coating liquid for a charge generation layer. Next, the coating liquid for a charge generation layer was applied on the intermediate layer by a dip coating method. The applied coating liquid for a charge generation layer was dried at 50° C. for 5 minutes to form a charge generation layer (film thickness: 0.3 μm) on the intermediate layer.

[0175] (Formation of charge transport layer) 45.0 parts by mass of hole transport agent (H-1), 100.0 parts by mass of polyarylate resin (PA-1) as binder resin, 0.1 parts by mass of pigment (K-1), 0.05 parts by mass of silicone oil (Shin-Etsu Chemical Co., Ltd. "KF96-50CS", dimethyl silicone oil), 560.0 parts by mass of tetrahydrofuran, and 140.0 parts by mass of toluene were mixed to obtain a coating liquid for charge transport layer. Next, the coating liquid for charge transport layer was applied onto the charge generation layer by dip coating. The applied coating liquid for charge transport layer was dried at 120°C for 40 minutes to form a charge transport layer (film thickness: 20 μm) on the charge generation layer. This resulted in the photoreceptor of Example 1.

[0176] [Examples 2 to 13 and Comparative Examples 1 to 18] Photoreceptors of Examples 2 to 13 and Comparative Examples 1 to 18 were manufactured by the same method as that of the photoreceptor of Example 1, except for the following changes. In the manufacture of the photoreceptors of Examples 2 to 13 and Comparative Examples 1 to 18, the types of polyarylate resin and hole transport agent used in forming the charge transport layer, and the type and amount of pigment were changed as shown in Table 4. However, in the manufacture of the photoreceptor of Comparative Example 16, the coating liquid for the charge transport layer gelled, and the photoreceptor could not be manufactured. In addition, in the manufacture of the photoreceptor of Comparative Example 18, although the photoreceptor could be manufactured, the coating liquid for the charge transport layer became turbid.

[0177] [Table 4]

[0178] <Evaluation> The sensitivity characteristics, abrasion resistance, storage stability, image memory, and fogging of each photoreceptor were evaluated by the following methods. The evaluation results are shown in Table 5.

[0179] [Sensitivity characteristics] The sensitivity characteristics were evaluated in an environment of 23°C temperature and 50% RH using a photoconductor electrical characteristic inspection device (manufactured by GENTEC Co., Ltd.). In the evaluation of the sensitivity characteristics, two types of sensitivity characteristics (sensitivity characteristics A and B) were evaluated. A photoconductor that passed both sensitivity characteristics A and B was judged to have excellent sensitivity characteristics. On the other hand, a photoconductor that failed at least one of sensitivity characteristics A and B was judged to have insufficient sensitivity characteristics. Note that sensitivity characteristic B corresponds to the exposure conditions when expressing halftones. Therefore, a photoconductor that passed sensitivity characteristic B is judged to be excellent in expressing halftones.

[0180] (Sensitivity characteristic A) Using the above device, the surface potential of the photoconductor was charged to -500 V (charging potential). Next, using the above device, exposure light (wavelength 780 nm, exposure amount 0.30 μJ / cm 2 ) was applied to the surface of the photoconductor. 2 ) was irradiated. Next, the surface potential of the photoconductor 77 milliseconds after the exposure (post-exposure potential A) was measured. The obtained post-exposure potential A was taken as the measured value of sensitivity characteristic A. Sensitivity characteristic A was judged according to the following criteria.

[0181] (Standard for sensitivity characteristic A) A (pass): The absolute value of the post-exposure potential A is 100 V or less. B (Fail): The absolute value of the post-exposure potential A is greater than 100V.

[0182] (Sensitivity characteristic B) Using the above device, the surface potential of the photoconductor was charged to -500 V (charging potential). Next, using the above device, exposure light (wavelength 780 nm, exposure amount 0.15 μJ / cm 2 ) was applied to the surface of the photoconductor. 2) was irradiated. Next, the surface potential of the photoconductor 77 milliseconds after the exposure (post-exposure potential B) was measured. The obtained post-exposure potential B was taken as the measured value of sensitivity characteristic B. Sensitivity characteristic B was judged according to the following criteria.

[0183] (Standard for sensitivity characteristic B) A (pass): The absolute value of the post-exposure potential B is 250 V or less. B (Fail): The absolute value of the post-exposure potential B is greater than 250V.

[0184] [Wear resistance] In the evaluation of wear resistance, a color printer (Oki Electric Industry Co., Ltd. "C844dnw") was used as an evaluation machine. A cyan toner was filled into the toner cartridge of the evaluation machine. First, the thickness T1 of the charge transport layer of the photoreceptor to be evaluated was measured. Next, the photoreceptor to be evaluated was mounted in a cyan cartridge, and the cyan cartridge was mounted in the evaluation machine. Next, in a normal temperature and normal humidity environment (temperature 23°C and humidity 50% RH), an image I (a pattern image with a printing rate of 1%) was printed on 4,000 sheets of paper using the evaluation machine. Next, in a high temperature and high humidity environment (temperature 32°C and humidity 85% RH), an image I was printed on 4,000 sheets of paper using the evaluation machine. Next, in a low temperature and low humidity environment (temperature 10°C and humidity 15% RH: hereinafter, sometimes referred to as LL environment), an image I was printed on 4,000 sheets of paper using the evaluation machine. After printing in the LL environment, the evaluation machine was left to stand for 2 hours. Next, a solid image (image with 100% image density) was printed on one sheet of paper under LL environment. After that, the photoconductor to be evaluated was removed from the evaluation machine. Then, the film thickness T2 of the charge transport layer of the photoconductor was measured. Then, the amount of wear (T1-T2, unit: μm), which is the amount of change in film thickness of the charge transport layer before and after printing, was obtained. From the amount of wear, the wear resistance of the photoconductor was judged according to the following criteria.

[0185] (Abrasion resistance standard) A (good): The amount of wear is 2.0 μm or less. B (bad): The amount of wear is more than 2.0 μm.

[0186] [Image Memory] In the evaluation of image memory, a color printer (Oki Electric Industry Co., Ltd.'s "C844dnw") was used as the evaluation machine. The toner cartridge of the evaluation machine was filled with cyan toner. The photoconductor to be evaluated was attached to a cyan cartridge, and the cyan cartridge was attached to the evaluation machine. Next, the print media type (recording medium) of the evaluation machine was set to thick paper, and the paper feed direction was set to vertical feed. Next, 100 sheets of cyan solid images were printed on A4-sized recording media (Oji Paper Co., Ltd.'s "Laser Peach WETY-145") using the evaluation machine. Next, a cyan halftone image (image density 50%) was printed on A3-sized plain paper. The halftone image printed on the A3-sized plain paper was used as the evaluation image. When printing the cyan solid image, the photoconductor in the paper-passing area where the A4-sized recording medium had passed was indirectly damaged by transfer (accumulation of charge in the charge transport layer) through the recording medium. On the other hand, the photoconductor in the non-paper-passing area where the A4-sized recording medium had not passed was directly damaged by transfer. Therefore, in the evaluation image, a density difference may occur between the image of the portion formed by the paper passing area of ​​the photoconductor (paper passing area image) and the image of the portion formed by the non-paper passing area of ​​the photoconductor (non-paper passing area image). Specifically, the non-paper passing area image may be darker than the paper passing area image. In the evaluation of image memory, the density difference between the paper passing area image and the non-paper passing area image was visually compared. Then, a photoconductor with a small density difference is evaluated as being able to suppress the occurrence of image memory. Image memory was judged according to the following criteria.

[0187] (Image memory standard) Particularly good (A): No difference in image density is observed between the image in the paper passing area and the image in the non-paper passing area. Good (B): A slight difference in image density is observed between the image in the paper passing area and the image in the non-paper passing area. Poor (C): A clear difference in image density is observed between the image in the paper passing area and the image in the non-paper passing area.

[0188] [Focus] In the evaluation of fogging, a color printer ("C844dnw" manufactured by Oki Electric Industry Co., Ltd.) was used as an evaluation machine. A cyan toner was filled into the toner cartridge of the evaluation machine. The photoconductor to be evaluated was mounted in a cyan cartridge, and the cyan cartridge was mounted in the evaluation machine. At a temperature of 32°C and a humidity of 85% RH (under HH environment), an image I (a pattern image with a printing rate of 1%) was printed on 2,000 sheets of paper using the evaluation machine. Next, the evaluation machine was left to stand for 12 hours under HH environment. Next, a blank image was printed on one sheet of paper under HH environment. Next, the photoconductor was removed from the evaluation machine. Next, the toner attached to the surface of the photoconductor was collected with a tape ("Scotch (registered trademark) Mending Tape" manufactured by 3M Co., Ltd.). Next, the image density of the above tape was measured using a fluorescence spectrodensitometer ("FD-5" manufactured by Konica Minolta, Inc.). The fogging was judged according to the following criteria.

[0189] (Fog standard) A (particularly good): Image density is 1.3 or less. B (Good): Image density is greater than 1.3 and equal to or less than 1.6. C (poor): Image density is more than 1.6.

[0190] [Storability] The photoreceptor to be evaluated was mounted on an image drum (Oki Electric Industry Co., Ltd., "DR-C3BC"). Then, the charging roller of the image drum was brought into contact with a part of the peripheral surface of the photoreceptor. Hereinafter, the part of the peripheral surface of the photoreceptor that was brought into contact with the charging roller is referred to as the "member contact area". In addition, the area of ​​the photoreceptor other than the member contact area is referred to as the "non-member contact area". The image drum with the photoreceptor mounted thereon was left standing for 4 weeks in an environment with a temperature of 50°C and a humidity of 85% RH. Immediately after leaving it standing for 4 weeks, the image drum with the photoreceptor mounted thereon was mounted on the above-mentioned evaluation machine. Next, an image (a cyan halftone image with a printing rate of 50%) was printed on one sheet of paper using the evaluation machine. This image was used as the image for evaluation. In the member contact area of ​​the photoreceptor, the charge transport layer is subjected to pressure due to contact with the charging roller, and the components that bleed out from the charging roller are attached to the surface of the charge transport layer. As a result, in the evaluation image, the image density of the image (image A) formed by the member contact area of ​​the photoreceptor may be greater than the image density of the image (image B) formed by the non-member contact area of ​​the photoreceptor. However, in a photoreceptor with excellent storage stability, the above-mentioned difference in image density is unlikely to occur. In evaluating the storage stability of the photoreceptor, the difference in image density between images A and B was compared visually. Then, a photoreceptor with a small difference in the above-mentioned image density is evaluated as having excellent storage stability. The storage stability of the photoreceptor was judged according to the following criteria.

[0191] (Standards for shelf life) A (particularly good): No difference in image density between images A and B is observed. B (Good): A slight difference in image density between images A and B is observed. C (Poor): A clear difference in image density between images A and B is observed.

[0192] [Table 5]

[0193] As shown in Tables 3 to 5, the photoreceptors of Examples 1 to 13 included a conductive substrate and a photosensitive layer indirectly provided on the conductive substrate. The photosensitive layer included a charge generating layer and a charge transport layer. The charge transport layer included a binder resin, a hole transport agent, and a phthalocyanine pigment. The binder resin included a specific polyarylate resin. The specific polyarylate resin included a first repeating unit represented by general formula (1), a second repeating unit represented by chemical formula (2), a third repeating unit represented by chemical formula (3), and a fourth repeating unit represented by chemical formula (4). The ratio (3) of the number of moles of the third repeating unit to the total number of moles of the first repeating unit and the third repeating unit was more than 0.0 mol% and less than 50.0 mol%. The ratio (4) of the number of moles of the fourth repeating unit to the total number of moles of the second repeating unit and the fourth repeating unit was 30.0 mol% or more and less than 70.0 mol%. The photoreceptors of Examples 1 to 13 were excellent in sensitivity characteristics, abrasion resistance and storage stability, and were able to suppress the occurrence of image memory and fogging.

[0194] On the other hand, the photoreceptor of Comparative Example 1 did not contain a pigment in the charge transport layer. As a result, the photoreceptor of Comparative Example 1 had image memory and fogging. The photoreceptors of Comparative Examples 2 to 4 had charge transport layers containing pigments other than the phthalocyanine pigment. The photoreceptors of Comparative Examples 2 to 4 were able to suppress the occurrence of fogging compared to the photoreceptor of Comparative Example 1. However, the photoreceptors of Comparative Examples 2 to 4 were unable to suppress the occurrence of image memory.

[0195] The photoreceptors of Comparative Examples 5 to 9 used a polyarylate resin (PA-5) different from the specific polyarylate resin as the binder resin of the charge transport layer. The photoreceptors of Comparative Examples 4 and 6 to 9 did not contain a phthalocyanine pigment in the charge transport layer. As a result, the photoreceptors of Comparative Examples 4 and 6 to 9 had poor wear resistance and could not suppress the occurrence of image memory. The photoreceptor of Comparative Example 5 was able to suppress the occurrence of image memory by containing a phthalocyanine pigment in the charge transport layer. However, the photoreceptor of Comparative Example 5 also had poor wear resistance.

[0196] The photoreceptors of Comparative Examples 10 to 14 used a polyarylate resin (PA-6) different from the specific polyarylate resin as the binder resin of the charge transport layer. The photoreceptors of Comparative Examples 10 and 12 to 14 did not contain a phthalocyanine pigment in the charge transport layer. As a result, the photoreceptors of Comparative Examples 10 and 12 to 14 had poor storage stability and could not suppress the occurrence of image memory and fogging. The photoreceptor of Comparative Example 11 was able to suppress the occurrence of image memory by containing a phthalocyanine pigment in the charge transport layer. However, the photoreceptor of Comparative Example 5 also had poor storage stability and could not suppress the occurrence of fogging.

[0197] The photoconductor of Comparative Example 15 used a polyarylate resin (PA-7) different from the specific polyarylate resin as the binder resin of the charge transport layer. The polyarylate resin (PA-7) did not have a third repeating unit. As a result, the photoconductor of Comparative Example 15 had poor wear resistance.

[0198] In the production of the photoconductor of Comparative Example 16, a polyarylate resin (PA-8) different from the specific polyarylate resin was used as the binder resin of the charge transport layer. The polyarylate resin (PA-8) had a ratio (3) of 50.0 mol% or more. As a result, in the production of the photoconductor of Comparative Example 16, the photoconductor could not be produced due to gelation of the coating liquid for the charge transport layer.

[0199] The photoconductor of Comparative Example 17 used a polyarylate resin (PA-9) different from the specific polyarylate resin as the binder resin of the charge transport layer. The polyarylate resin (PA-9) did not have a fourth repeating unit. As a result, the photoconductor of Comparative Example 17 had poor storage stability.

[0200] The photoconductor of Comparative Example 18 used a polyarylate resin (PA-10) different from the specific polyarylate resin as the binder resin of the charge transport layer. The polyarylate resin (PA-10) had a ratio (4) of 70.0 mol% or more. As a result, the photoconductor of Comparative Example 18 had poor wear resistance. [Industrial Applicability]

[0201] The photoreceptor according to the present invention can be used in an image forming apparatus, and the process cartridge and image forming apparatus according to the present invention can be used to form an image on a recording medium. [Explanation of symbols]

[0202] 1, 11: Photoreceptor 2, 12: Conductive substrate 3, 13: Photosensitive layer 3a, 13a: Charge generating layer 3b, 13b: Charge transport layer 4: Middle class 42: Charging device 44: Exposure equipment 46: Developing device 62: Transcription device 100: Image carrier 110: Image forming apparatus

Claims

1. An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer provided directly or indirectly on the conductive substrate, the photosensitive layer has a charge generating layer and a charge transport layer, the charge transport layer contains a binder resin, a hole transport agent, and a phthalocyanine pigment; The binder resin contains a specific polyarylate resin, The specific polyarylate resin has a first repeating unit represented by the following general formula (1), a second repeating unit represented by the following chemical formula (2), a third repeating unit represented by the following chemical formula (3), and a fourth repeating unit represented by the following chemical formula (4), a ratio of the number of moles of the third repeat unit to the total number of moles of the first repeat unit and the third repeat unit is greater than 0.0 mol% and less than 50.0 mol%, a ratio of the number of moles of the fourth repeating unit to the total number of moles of the second repeating unit and the fourth repeating unit is 30.0 mol % or more and less than 70.0 mol %. 【Chemistry 1】 (In the general formula (1), X represents a divalent group having 1 to 10 carbon atoms, R 1 and R 2 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

2. The electrophotographic photoreceptor according to claim 1, wherein the first repeating unit is represented by the following chemical formula (1-1) or (1-2). 【Chemistry 2】

3. 3. The electrophotographic photoreceptor according to claim 1, wherein the phthalocyanine pigment comprises at least one of a metal-free phthalocyanine and a compound represented by the following general formula (P-1): 【Chemistry 3】 (In the general formula (P-1), M represents a metal atom which may have a ligand.)

4. 3. The electrophotographic photoreceptor according to claim 1, wherein the phthalocyanine pigment comprises titanyl phthalocyanine.

5. 3. The electrophotographic photoreceptor according to claim 1, wherein the content of the phthalocyanine pigment in the charge transport layer is from 0.1 parts by mass to 0.5 parts by mass with respect to 100.0 parts by mass of the binder resin.

6. With respect to all repeating units contained in the specific polyarylate resin, The content of the first repeating unit is 20.0 mol% or more and 45.0 mol% or less, The content of the second repeating unit is 10.0 mol % or more and 40.0 mol % or less, The content of the third repeating unit is 5.0 mol % or more and 30.0 mol % or less, The electrophotographic photoreceptor according to claim 1 or 2, wherein a content ratio of the fourth repeating unit is 10.0 mol % or more and 40.0 mol % or less.

7. 3. The electrophotographic photoreceptor according to claim 1, wherein the specific polyarylate resin contains at least one of resins represented by the following chemical formulas (pa-1) to (pa-4). 【Chemistry 4】

8. 3. The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer is an outermost layer.

9. 3. The electrophotographic photoreceptor according to claim 1, wherein the hole transport agent comprises at least one of compounds represented by the following general formulas (20), (23), (24) and (25): 【Chemistry 5】 【Chemistry 6】 【Chemistry 7】 【Chemistry 8】 (In general formula (20), R 50 and R 51 each independently represents an alkyl group having from 1 to 6 carbon atoms, an alkoxy group having from 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 represents a phenyl group which may be substituted with an alkyl group having from 1 to 6 carbon atoms, a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms; f 1 and f 2 each independently represents an integer of 0 to 2, f 3 and f 4 each independently represents an integer of 0 to 5, In general formula (23), R 41 , R 42 , R 43 , R 44 , R 45 , and R 46 each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group; R 47 and R 48 each independently represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, or a phenyl group; e 1 , e 2 , e 3 , and e 4 each independently represents an integer of 0 to 5, e 5 and e 6 each independently represents an integer of 0 to 4, e 7 and e 8 each independently represents 0 or 1; In general formula (24), R 11 , R 12 , R 13 , and R 14 each independently represents an alkyl group having from 1 to 6 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms; a 1 , a 2 , a 3 , and a 4 each independently represents an integer of 0 to 5, In general formula (25), R 60 represents a phenyl group which may be substituted with an alkyl group having from 1 to 8 carbon atoms, a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, or an alkoxy group having from 1 to 8 carbon atoms, R 61 , R 62 , and R 63 each independently represents an alkyl group having from 1 to 8 carbon atoms, or an alkoxy group having from 1 to 8 carbon atoms; g1, g2, and g3 each independently represent an integer of 0 to 5, g4 represents 0 or 1.

10. The electrophotographic photoreceptor according to claim 9, wherein the hole transport agent comprises at least one of compounds represented by the following chemical formulas (H-1) to (H-5), general formula (H-6), and chemical formula (H-7). 【Chemistry 9】 【Chemistry 10】 (In the general formula (H-6), R 100 ~R 103 each independently represents a hydrogen atom or a methyl group. 100 ~R 103 At least two of the groups represent methyl groups.

11. The electrophotographic photoreceptor according to claim 1 , wherein the charge generating layer contains a charge generating agent and a base resin.

12. 12. The electrophotographic photoreceptor of claim 11, wherein the charge generating agent comprises Y-type titanyl phthalocyanine.

13. A process cartridge comprising the electrophotographic photoreceptor according to claim 1 or 2.

14. 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, The image forming apparatus, wherein the image carrier is the electrophotographic photoreceptor according to claim 1 .

15. the transfer device is a direct transfer type transfer device, The image forming apparatus according to claim 14 , wherein the transfer medium is a recording medium.

Images