JP6741152B2 - Electrophotographic photoreceptor, image forming apparatus and process cartridge - Google Patents

Description

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

The electrophotographic photosensitive member is used as an image bearing member in an electrophotographic image forming apparatus (for example, a printer or a multifunction peripheral). The electrophotographic photosensitive member includes a photosensitive layer. Examples of the electrophotographic photosensitive member include a single-layer type electrophotographic photosensitive member and a laminated electrophotographic photosensitive member. The single-layer type electrophotographic photoreceptor includes a photosensitive layer having a charge generating function and a charge transporting function. The laminated electrophotographic photoreceptor includes a photosensitive layer including a charge generating layer having a charge generating function and a charge transporting layer having a charge transporting function.

Patent Document 1 describes an electrophotographic photoreceptor containing a polyarylate resin represented by the following chemical formula (RA).

JP, 10-288845, A

However, the electrophotographic photosensitive member described in Patent Document 1 has insufficient filming resistance.

The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic photosensitive member having excellent filming resistance. Another object of the present invention is to provide an image forming apparatus and a process cartridge that can suppress the occurrence of image defects.

The electrophotographic photoreceptor of the present invention comprises a conductive substrate and a photosensitive layer. The photosensitive layer has a charge generation layer and a charge transport layer. The charge generation layer contains a charge generation agent. The charge transport layer includes a hole transport material, a binder resin, and an electron acceptor compound. The binder resin includes a polyarylate resin having a repeating unit represented by the following general formula (1). The electron acceptor compound includes a compound represented by the following general formula (E1), general formula (E2), general formula (E3), or general formula (E4).

In the general formula (1), s represents a number of 1 or more and 100 or less. u represents a number of 0 or more and 99 or less. s+u=100. X and Y are each independently a divalent group represented by the following chemical formula (1A), chemical formula (1B), chemical formula (1C), chemical formula (1D), chemical formula (1E), or chemical formula (1F). ..

In the general formula (E1), R ¹ and R ² each independently represent an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. R ³ represents a halogen atom or a hydrogen atom.

In the general formula (E2), R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ may each independently have an alkyl group having 1 to 6 carbon atoms or a halogen atom. Aryl group having 6 to 14 carbon atoms, heterocyclic group having 3 to 14 carbon atoms, alkoxycarbonyl group having 2 to 7 carbon atoms, alkoxy group having 1 to 6 carbon atoms, 7 carbon atoms An aralkyl group having 20 to 20 carbon atoms, an acyl group having 1 to 7 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a hydrogen atom, a cyano group, a nitro group, a halogen Represents an atom, a hydroxyl group, an amino group, or a carboxyl group. G ¹ represents an oxygen atom, a sulfur atom, or ═C(CN) ₂ . G ² represents an oxygen atom or a sulfur atom.

In the general formula (E3), R ¹⁰ represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, and a carbon atom which may have alkyl group having 1 to 6 carbon atoms. It represents an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.

In the general formula (E4), R ¹¹ , R ¹² , R ¹³ and R ¹⁴ each independently have an alkyl group having 1 to 6 carbon atoms or an alkoxymethyl group having 2 to 7 carbon atoms. Optionally represents a phenyl group, an alkyl group having 1 to 6 carbon atoms, a hydrogen atom, or a halogen atom.

The image forming apparatus of the present invention includes an image carrier, a charging unit, an exposing unit, a developing unit, and a transfer unit. The image carrier is the electrophotographic photoreceptor described above. The charging unit charges the surface of the image carrier. The exposure unit exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier. The developing unit develops the electrostatic latent image as a toner image. The transfer unit transfers the toner image from the image carrier to the transfer target.

A process cartridge of the present invention includes the above-mentioned electrophotographic photosensitive member.

The electrophotographic photoreceptor of the present invention can improve filming resistance. Further, the image forming apparatus and the process cartridge of the present invention can suppress the occurrence of image defects.

FIG. 3 is a partial cross-sectional view showing an example of the structure of the electrophotographic photosensitive member according to the first embodiment of the present invention. FIG. 3 is a partial cross-sectional view showing an example of the structure of the electrophotographic photosensitive member according to the first embodiment of the present invention. FIG. 3 is a partial cross-sectional view showing an example of the structure of the electrophotographic photosensitive member according to the first embodiment of the present invention. It is a figure which shows an example of the image forming apparatus which concerns on 2nd embodiment of this invention. It is a figure which shows an example of a structure of a scratching device. It is sectional drawing in the IV-IV line of FIG. FIG. 6 is a side view of the fixing base shown in FIG. 5, a scratching needle, and an electrophotographic photosensitive member. It is a figure which shows the scratch which was formed in the surface of the photosensitive layer. ^{1 is} a ¹ H-NMR spectrum of a polyarylate resin represented by the chemical formula (R-3).

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention. It should be noted that the description of the overlapping description may be appropriately omitted, but the gist of the invention is not limited thereto. In the present specification, a compound and its derivative may be generically referred to by adding "system" after the compound name. When a "system" is added after the compound name to represent the polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative.

Hereinafter, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 14 carbon atoms, a heterocyclic group having 3 to 14 carbon atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms, a carbon atom C1 to C6 alkoxy group, C7 to C20 aralkyl group, C1 to C7 acyl group, C2 to C6 alkenyl group, C2 to C6 The alkynyl group, the cycloalkyl group having 3 to 10 carbon atoms, the alkoxymethyl group having 2 to 7 carbon atoms, and the halogen atom have the following meanings, respectively.

The alkyl group having 1 to 6 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 6 carbon atoms include, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, pentyl group, isopentyl group, neopentyl group. , And a hexyl group.

The aryl group having 6 to 14 carbon atoms is unsubstituted. Examples of the aryl group having 6 to 14 carbon atoms include an unsubstituted aromatic monocyclic hydrocarbon group having 6 to 14 carbon atoms, and an unsubstituted aromatic fused bicyclic ring having 6 to 14 carbon atoms. Examples thereof include a hydrocarbon group and an unsubstituted aromatic condensed tricyclic hydrocarbon group having 6 to 14 carbon atoms. Specific examples of the aryl group having 6 to 14 carbon atoms include a phenyl group, a naphthyl group, an anthryl group, and a phenanthryl group.

The heterocyclic group having 3 to 14 carbon atoms is unsubstituted and may be an aromatic compound or an aliphatic compound. Examples of the heterocyclic group having 3 to 14 carbon atoms include a 5- or 6-membered monocyclic heterocyclic group containing one or more (preferably 1 to 3) heteroatoms; A heterocyclic group in which monocycles are condensed; a heterocyclic group in which such a monocycle is condensed with a 5- or 6-membered hydrocarbon ring is included. Examples of the hetero atom include a nitrogen atom, a sulfur atom and an oxygen atom. Specific examples of the heterocyclic group having 3 to 14 carbon atoms include thiophenyl group, furanyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, isothiazolyl group, isoxazolyl group, oxazolyl group, oxolanyl group, thiazolyl group, flazanyl group, Pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, indolyl group, 1H-indazolyl group, isoindolyl group, chromeenyl group, quinolinyl group, isoquinolinyl group, purinyl group, pteridinyl group, triazolyl group, tetrazolyl group, 4H-quinolidinyl group, naphthyridinyl group Group, benzofuranyl group, 1,3-benzodioxolyl group, benzoxazolyl group, benzothiazolyl group and benzimidazolyl group.

The alkoxycarbonyl group having 2 to 7 carbon atoms is linear or branched and unsubstituted. Examples of the alkoxycarbonyl group having 2 to 7 carbon atoms include methoxycarbonyl group, ethoxycarbonyl group, n-propoxycarbonyl group, isopropoxycarbonyl group, n-butoxycarbonyl group, s-butoxycarbonyl group, t-butoxy group. Examples thereof include a carbonyl group, a pentyloxycarbonyl group, and a hexyloxycarbonyl group.

The alkoxy group having 1 to 6 carbon atoms is linear or branched and unsubstituted. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, s-butoxy group, t-butoxy group, pentyloxy group and iso Examples include a pentyloxy group, a neopentyloxy group, and a hexyloxy group.

The aralkyl group having 7 to 20 carbon atoms is a group in which one of the hydrogen atoms of an alkyl group having 1 to 6 carbon atoms is substituted with an aryl group having 6 to 14 carbon atoms. Examples of the aralkyl group having 7 to 20 carbon atoms include phenylmethyl group (benzyl group), 2-phenylethyl group (phenethyl group), 1-phenylethyl group, 3-phenylpropyl group, 4-phenylbutyl group. , Naphthylmethyl group, anthrylmethyl group and phenanthrylmethyl group.

The acyl group having 1 to 7 carbon atoms is linear or branched and unsubstituted. Examples of the acyl group having 1 to 7 carbon atoms include formyl group, methylcarbonyl group (acetyl group), ethylcarbonyl group, n-propylcarbonyl group, isopropylcarbonyl group, n-butylcarbonyl group, s-butylcarbonyl group. Group, t-butylcarbonyl group, pentylcarbonyl group, isopentylcarbonyl group, neopentylcarbonyl group, and hexylcarbonyl group.

The alkenyl group having 2 to 6 carbon atoms is linear or branched and unsubstituted. The alkenyl group having 2 to 6 carbon atoms has, for example, 1 to 3 carbon-carbon double bonds. Examples of the alkenyl group having 2 to 6 carbon atoms include vinyl group (ethenyl group), 1-propenyl group, allyl group, butenyl group, pentenyl group, pentadienyl group, hexenyl group, and hexadienyl group.

The alkynyl group having 2 to 6 carbon atoms is linear or branched and unsubstituted. The alkynyl group having 2 to 6 carbon atoms has, for example, 1 to 3 carbon-carbon triple bonds. Examples of the alkynyl group having 2 to 6 carbon atoms include ethynyl group, propynyl group, butynyl group, pentynyl group, and hexynyl group.

The cycloalkyl group having 3 to 10 carbon atoms is unsubstituted. Examples of the cycloalkyl group having 3 to 10 carbon atoms include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, and cyclodecyl group.

The alkoxymethyl group having 2 to 7 carbon atoms is linear or branched and unsubstituted. Examples of the alkoxymethyl group having 2 to 7 carbon atoms include methoxymethyl group, ethoxymethyl group, n-propoxymethyl group, isopropoxymethyl group, n-butoxymethyl group, s-butoxymethyl group, t-butoxy group. Examples include a methyl group, a pentyloxymethyl group, and a hexyloxymethyl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Further, in the following description, “may have a halogen atom” means that part or all of the hydrogen atoms of the functional group may be substituted with a halogen atom. The same applies to “may have an alkyl group having 1 to 6 carbon atoms” and “may have an alkoxymethyl group having 2 to 7 carbon atoms”.

<First Embodiment: Electrophotographic Photoreceptor>
The structure of the electrophotographic photosensitive member (hereinafter, also referred to as a photosensitive member) according to the first embodiment of the present invention will be described. FIGS. 1, 2 and 3 are partial cross-sectional views showing the structure of the photoconductor 1 which is an example of the first embodiment. As shown in FIG. 1, the photoconductor 1 includes 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.

As shown in FIG. 2, in the photoreceptor 1, the charge transport layer 3b may be provided on the conductive substrate 2, and the charge generation layer 3a may be provided on the charge transport layer 3b. However, since the thickness of the charge transport layer 3b is generally thicker than that of the charge generation layer 3a, the charge transport layer 3b is less likely to be damaged than the charge generation layer 3a. Therefore, in order to improve the wear resistance of the photoconductor 1, as shown in FIG. 1, the charge generation layer 3a is provided on the conductive substrate 2, and the charge transport layer 3b is provided on the charge generation layer 3a. It is preferable.

As shown in FIG. 3, the photoreceptor 1 may include a conductive substrate 2, a photosensitive layer 3, and an intermediate layer 4 (for example, an undercoat layer). The intermediate layer 4 is provided between the conductive substrate 2 and the photosensitive layer 3. A protective layer (not shown) may be provided on the photosensitive layer 3.

The thicknesses of the charge generation layer 3a and the charge transport layer 3b are not particularly limited as long as the functions of the respective layers can be sufficiently exhibited. The thickness of the charge generation layer 3a 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. The thickness of the charge transport layer 3b is preferably 2 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less. The structure of the photoreceptor 1 has been described above with reference to FIGS.

The elements (conductive substrate, photosensitive layer, and intermediate layer) of the photoreceptor according to this embodiment will be described below. Further, a method of manufacturing the photoconductor will be described.

[1. Conductive substrate]
The conductive substrate is not particularly limited as long as it can be used as the conductive substrate of the photoconductor. As the conductive substrate, it is possible to use a conductive substrate having at least a surface portion made of a material having conductivity. An example of the conductive substrate is a conductive substrate made of a material having conductivity (conductive material). Another example of a conductive substrate is a conductive substrate coated with a conductive material. Examples of the conductive material include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, and indium. Of these conductive materials, one kind may be used alone, or two or more kinds may be used in combination. Examples of the combination of two or more kinds include alloys (more specifically, aluminum alloys, stainless steel, brass, etc.). Among these conductive materials, aluminum and aluminum alloys are preferable.

The shape of the conductive substrate can be appropriately selected according to the structure of the image forming apparatus used. Examples of the shape of the conductive substrate include a sheet shape and a drum shape. Further, the thickness of the conductive substrate can be appropriately selected according to the shape of the conductive substrate.

[2. Photosensitive layer]
[Charge generation layer]
The charge generation layer contains a charge generation agent. Further, the charge generation layer may contain a binder resin for the charge generation layer (hereinafter sometimes referred to as a base resin) and various additives.

(Charge generating agent)
The charge generating agent is not particularly limited as long as it is a charge generating agent for a photoreceptor. Examples of the charge generating agent include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, indigo pigments, azurenium pigments, cyanines. Pigment, inorganic photoconductive material powder (more specifically, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, amorphous silicon, etc.), pyrylium pigment, anthanthrone pigment, triphenylmethane pigment, slene pigment , Toluidine pigments, pyrazoline pigments and quinacridone pigments. As the charge generating agent, one kind may be used alone, or two or more kinds may be used in combination.

Examples of the phthalocyanine-based pigment include metal-free phthalocyanine and metal phthalocyanine represented by the following chemical formula (C-1). Examples of the metal phthalocyanine include titanyl phthalocyanine, hydroxygallium phthalocyanine and chlorogallium phthalocyanine represented by the following chemical formula (C-2). The phthalocyanine-based pigment may be crystalline or non-crystalline. The crystal shape of the phthalocyanine-based pigment (for example, α type, β type, X type, Y type, V type and II type) is not particularly limited, and phthalocyanine type pigments having various crystal shapes are used.

Examples of the metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter, sometimes referred to as X-type metal-free phthalocyanine). Examples of the crystal of titanyl phthalocyanine 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). Examples of hydroxygallium phthalocyanine crystals include V-type crystals of hydroxygallium phthalocyanine.

For example, in a digital optical image forming apparatus (for example, a laser beam printer and a facsimile using a light source such as a semiconductor laser), it is preferable to use a photoconductor having sensitivity in a wavelength region of 700 nm or more. As the charge generating agent in this case, a phthalocyanine-based pigment is preferable, a metal-free phthalocyanine and titanyl phthalocyanine are more preferable, and an X-type metal-free phthalocyanine and a Y-type titanyl phthalocyanine are preferable because they have a high quantum yield in a wavelength region of 700 nm or more. Is more preferable.

The Y-type titanyl phthalocyanine has a main peak at 27.2° of the 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 a peak having the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is 3° or more and 40° or less.

An example of the method for measuring the CuKα characteristic X-ray diffraction spectrum will be described. A sample (titanyl phthalocyanine) is filled in a sample holder of an X-ray diffractometer (for example, "RINT (registered trademark) 1100" manufactured by Rigaku Corporation), and an X-ray tube Cu, a tube voltage of 40 kV, a tube current of 30 mA, and CuKα. An X-ray diffraction spectrum is measured under the condition that the characteristic X-ray wavelength is 1.542Å. The measurement range (2θ) is, for example, 3° or more and 40° or less (start angle 3°, stop angle 40°), and the scanning speed is, for example, 10°/min.

The content of the charge generating agent is, for example, preferably 5 parts by mass or more and 1000 parts by mass or less, and 30 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the base resin contained in the charge generating layer. Is more preferable.

(Base resin)
The base resin is not particularly limited as long as it is a resin for the charge generation layer. Examples of the base resin include thermoplastic resins, thermosetting resins, and photocurable resins. Examples of the thermoplastic resin include styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic acid copolymer, styrene-acrylic acid copolymer, polyethylene resin, ethylene-acetic acid. Vinyl copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, urethane resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl acetal Examples thereof include resins, polyvinyl butyral resins, polyether resins, polycarbonate resins, polyarylate resins and polyester resins. Examples of the thermosetting resin include silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, and other crosslinkable thermosetting resins. Examples of the photocurable resin include an epoxy-acrylic acid resin (acrylic acid adduct of epoxy compound) and a urethane-acrylic acid copolymer (acrylic acid adduct of urethane compound). A polyvinyl acetal resin is preferably used as the base resin. As the base resin, one kind may be used alone, or two or more kinds may be used in combination.

The base resin is preferably a resin different from the binder resin described later. This is because, for example, since the coating solution for the charge transport layer is applied onto the charge generation layer when the photoreceptor is produced, it is preferable that the charge generation layer is not dissolved in the solvent of the coating solution for the charge transport layer.

[Charge transport layer]
The charge transport layer contains a hole transport material, a binder resin, and an electron acceptor compound. The charge transport layer may contain various additives as required.

(Hole transfer agent)
Examples of the hole transfer agent include nitrogen-containing cyclic compounds and condensed polycyclic compounds. Examples of the nitrogen-containing cyclic compound and the condensed polycyclic compound include triphenylamine derivatives; diamine derivatives (more specifically, N,N,N′,N′-tetraphenylbenzidine derivatives, N,N,N ',N'-Tetraphenylphenylenediamine derivative, N,N,N',N'-tetraphenylnaphthylenediamine derivative, di(aminophenylethenyl)benzene derivative, N,N,N',N'-tetraphenyl Phenanthrylene diamine derivative, etc.); oxadiazole compound (more specifically, 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole, etc.); styryl compound (more Specifically, 9-(4-diethylaminostyryl)anthracene and the like); carbazole-based compound (more specifically, polyvinylcarbazole and the like); organic polysilane compound; pyrazoline-based compound (more specifically, 1-phenyl- 3-(p-dimethylaminophenyl)pyrazoline etc.); hydrazone compounds; indole compounds; oxazole compounds; isoxazole compounds; thiazole compounds; thiadiazole compounds; imidazole compounds; pyrazole compounds; triazole compounds Can be mentioned. These hole transport agents may be used alone or in combination of two or more.

From the viewpoint of efficiently transporting holes, the content of the hole transport agent is preferably 10 parts by mass or more and 200 parts by mass or less, and 10 parts by mass or more and 100 parts by mass or less, with respect to 100 parts by mass of the binder resin. Is more preferable.

(Binder resin)
The binder resin includes a polyarylate resin having a repeating unit represented by the following general formula (1) (hereinafter sometimes referred to as polyarylate resin (1)). The charge transport layer may contain one kind or two or more kinds of the polyarylate resin (1).

In general formula (1), s represents a number of 1 or more and 100 or less. u represents a number of 0 or more and 99 or less. s+u=100. X and Y are each independently a divalent group represented by the following chemical formula (1A), chemical formula (1B), chemical formula (1C), chemical formula (1D), chemical formula (1E), or chemical formula (1F). ..

In the general formula (1), at least one of X and Y is preferably a divalent group represented by the chemical formula (1A) or the chemical formula (1E), from the viewpoint of further improving the filming resistance. More preferably, it is a divalent group represented by (1A).

In the general formula (1), it is preferable that s and u each independently represent a number of 30 or more and 70 or less from the viewpoint of further improving the filming resistance. From the same viewpoint, X and Y are preferably different from each other. From the viewpoint of further improving the filming resistance, s and u each independently represent a number of 30 or more and 70 or less, X and Y are different from each other, and at least one of X and Y is represented by the chemical formula (1A). It is preferably a divalent group.

The polyarylate resin (1) includes, for example, a repeating unit represented by the following general formula (1-1) (hereinafter sometimes referred to as repeating unit (1-1)), and a general formula (1-2) below. ) And a repeating unit (hereinafter, sometimes referred to as a repeating unit (1-2)).

X in the general formula (1-1) and Y in the general formula (1-2) have the same meanings as X and Y in the general formula (1), respectively.

The polyarylate resin (1) may have a repeating unit other than the repeating units (1-1) and (1-2). The ratio (molar fraction) of the total amount of the repeating units (1-1) and (1-2) to the total amount of the repeating units in the polyarylate resin (1) is preferably 0.80 or more, 0.90 or more is more preferable, and 1.00 is still more preferable.

When u in the general formula (1) is not 0, the sequences of the repeating units (1-1) and (1-2) in the polyarylate resin (1) are not particularly limited. That is, the polyarylate resin (1) may be any copolymer such as a random copolymer, an alternating copolymer, a periodic copolymer or a block copolymer. Examples of the random copolymer include a copolymer in which the repeating unit (1-1) and the repeating unit (1-2) are randomly arranged. Examples of the alternating copolymer include a copolymer in which the repeating unit (1-1) and the repeating unit (1-2) are alternately arranged. Examples of the periodic copolymer include a copolymer in which one or more repeating units (1-1) and one or more repeating units (1-2) are periodically arranged. Examples of the block copolymer include a copolymer in which a block composed of a plurality of repeating units (1-1) and a block composed of a plurality of repeating units (1-2) are arranged.

In addition, s in the general formula (1) is the repeating unit (1-) with respect to the sum of the number of repeating units (1-1) and the number of repeating units (1-2) contained in the polyarylate resin (1). It represents the percentage of the number of 1). U in the general formula (1) is the repeating unit (1-2) with respect to the sum of the number of repeating units (1-1) and the number of repeating units (1-2) contained in the polyarylate resin (1). Represents the percentage of the number. Each of s and u in the general formula (1) is not a value obtained from one molecular chain, but a value obtained from the entire polyarylate resin (1) (a plurality of molecular chains) contained in the photosensitive layer. Is the average value of.

As the binder resin, only the polyarylate resin (1) may be used alone, or the polyarylate resin (1) and a resin (other resin) other than the polyarylate resin (1) may be used in combination. Examples of other resins include thermoplastic resins (polyarylate resins other than polyarylate resin (1), polycarbonate resins, styrene resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers). Polymer, styrene-acrylic acid copolymer, acrylic copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, vinyl chloride-vinyl acetate copolymer , Polyester resin, alkyd resin, polyamide resin, polyurethane resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, polyester resin, etc., thermosetting resin (silicone resin, epoxy resin, phenol resin, Examples thereof include urea resins, melamine resins, crosslinkable thermosetting resins other than these, and photocurable resins (epoxy-acrylic acid type resins, urethane-acrylic acid type copolymers, etc.). These may be used alone or in combination of two or more. The content of the polyarylate resin (1) is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass, based on the total amount of the binder resin.

The viscosity average molecular weight of the binder resin is preferably 10,000 or more, more preferably 20,000 or more, further preferably 30,000 or more, from the viewpoint of further improving the filming resistance. It is particularly preferably 40,000 or more. On the other hand, the viscosity average molecular weight of the binder resin is preferably 80,000 or less, more preferably 60,000 or less. When the viscosity average molecular weight of the binder resin is 80,000 or less, the binder resin is likely to be dissolved in the solvent at the time of forming the charge transport layer, and the charge transport layer tends to be easily formed.

The method for producing the binder resin is not particularly limited as long as the polyarylate resin (1) can be produced. Examples of the method for producing the binder resin include a method in which an aromatic diol for forming the repeating unit of the polyarylate resin (1) and an aromatic dicarboxylic acid are polycondensed. The method of polycondensing the aromatic diol and the aromatic dicarboxylic acid is not particularly limited, and known synthesis methods (more specifically, solution polymerization, melt polymerization, interfacial polymerization, etc.) can be adopted.

The aromatic dicarboxylic acid for producing the polyarylate resin (1) has two carboxyl groups and is represented by the following general formula (1-9) or general formula (1-10). X in the general formula (1-9) and Y in the general formula (1-10) have the same meanings as X and Y in the general formula (1), respectively.

As the aromatic dicarboxylic acid, for example, an aromatic dicarboxylic acid having two carboxyl groups bonded to an aromatic ring (more specifically, 4,4′-dicarboxydiphenyl ether, 4,4′-dicarboxybiphenyl, etc.) Is mentioned. The aromatic dicarboxylic acid can also be used as a derivative such as diacid chloride, dimethyl ester, diethyl ester and the like. Further, the aromatic dicarboxylic acid used in the polycondensation may contain other aromatic dicarboxylic acids in addition to the aromatic dicarboxylic acids represented by the general formulas (1-9) and (1-10).

The aromatic diol has two phenolic hydroxyl groups and is represented by the following chemical formula (1-11).

When synthesizing the polyarylate resin (1), the aromatic diol can also be used as a derivative such as diacetate. Further, the aromatic diol used for the condensation polymerization may contain other aromatic diol other than the aromatic diol represented by the chemical formula (1-11).

Examples of the polyarylate resin (1) include polyarylate resins represented by the following chemical formulas (R-1) to (R-8) (hereinafter, polyarylate resins (R-1) to (R-8), respectively). It may be mentioned).

Among the polyarylate resins (R-1) to (R-8), from the viewpoint of further improving the filming resistance, the polyarylate resins (R-2), (R-4), (R-5), (R-6) and (R-7) are preferable, and polyarylate resins (R-4), (R-5) and (R-6) are more preferable.

(Electron acceptor compound)
The charge transport layer contains an electron acceptor compound represented by the following general formula (E1), general formula (E2), general formula (E3), or general formula (E4). Hereinafter, the electron acceptor compounds represented by the general formulas (E1) to (E4) may be referred to as electron acceptor compounds (E1) to (E4), respectively. Further, the electron acceptor compounds (E1) to (E4) may be collectively referred to as the electron acceptor compound E. The charge transport layer contains one or more of the electron acceptor compounds (E1) to (E4).

In formula (E1), R ¹ and R ² each independently represent an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. R ³ represents a halogen atom or a hydrogen atom.

In formula (E2), R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are each independently an alkyl group having 1 to 6 carbon atoms or a carbon atom which may have a halogen atom. Aryl groups having 6 to 14 carbon atoms, heterocyclic groups having 3 to 14 carbon atoms, alkoxycarbonyl groups having 2 to 7 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and 7 or more carbon atoms Aralkyl group having 20 or less, acyl group having 1 to 7 carbon atoms, alkenyl group having 2 to 6 carbon atoms, alkynyl group having 2 to 6 carbon atoms, hydrogen atom, cyano group, nitro group, halogen atom Represents a hydroxyl group, an amino group, or a carboxyl group. G ¹ represents an oxygen atom, a sulfur atom, or ═C(CN) ₂ . G ² represents an oxygen atom or a sulfur atom.

In formula (E3), R ¹⁰ represents an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, and 6 carbon atoms which may have an alkyl group having 1 to 6 carbon atoms. It represents an aryl group having 14 to 14 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.

In formula (E4), R ¹¹ , R ¹² , R ¹³ and R ¹⁴ each independently have an alkyl group having 1 to 6 carbon atoms or an alkoxymethyl group having 2 to 7 carbon atoms. Represents a phenyl group, an alkyl group having 1 to 6 carbon atoms, a hydrogen atom, or a halogen atom.

The photoconductor of this exemplary embodiment has excellent filming resistance because the charge transport layer contains the electron acceptor compound E and the above-described polyarylate resin (1). The reason is presumed as follows.

It is considered that the electron acceptor compound E contained in the charge transport layer can improve the hole transport ability of the hole transport agent. Therefore, in the photoconductor according to this exemplary embodiment, holes tend to be quickly transported in the charge transport layer. As a result, the photoreceptor according to this exemplary embodiment tends to suppress the generation of residual charges in the charge transport layer.

Further, when the charge transport layer is formed, the polyarylate resin (1) and the electron acceptor compound E interact with each other in the coating liquid for the charge transport layer, so that the layer density of the charge transport layer formed tends to increase. There is. As a result, the surface of the photosensitive layer of the photoreceptor according to this exemplary embodiment tends to have high hardness.

As described above, in the photoconductor according to the exemplary embodiment, generation of residual charges in the charge transport layer is suppressed, and the hardness of the surface of the photoconductive layer tends to be high, which may cause filming on the surface of the photoconductive layer. Adhesion of the following components (more specifically, toner components, paper powder, etc.) tends to be suppressed. Therefore, the photoconductor according to the exemplary embodiment is considered to have excellent filming resistance.

In the general formula (E1), R ¹ and R ² each independently preferably represent an alkyl group having 1 to 6 carbon atoms, and 1 or more carbon atoms, from the viewpoint of further improving filming resistance. More preferably, it represents a branched chain alkyl group of 6 or less.

In the general formula (E1), R ³ is preferably a halogen atom, more preferably a chlorine atom, from the viewpoint of further improving the filming resistance.

As the electron acceptor compound (E1) represented by the general formula (E1), for example, a compound represented by the following chemical formula (E1-1) (hereinafter may be referred to as an electron acceptor compound (E1-1)). Is mentioned.

In the general formula (E2), it is preferable that R ⁴ , R ⁶ and R ⁸ each independently represent an alkyl group having 1 to 6 carbon atoms from the viewpoint of further improving filming resistance, and a carbon atom. It is more preferable to represent a branched alkyl group having a number of 1 or more and 6 or less.

In the general formula (E2), R ⁵ and R ⁷ preferably represent hydrogen atoms from the viewpoint of further improving the filming resistance.

In the general formula (E2), R ⁹ preferably represents an aryl group having 6 to 14 carbon atoms which may have a halogen atom, from the viewpoint of further improving filming resistance, and has a halogen atom. It may more preferably represent a phenyl group which may be present, more preferably represent a phenyl group having a chlorine atom, and particularly preferably represent a phenyl group having a plurality of chlorine atoms.

In the general formula (E2), it is preferable that G ¹ and G ² represent an oxygen atom from the viewpoint of further improving the filming resistance.

As the electron acceptor compound (E2) represented by the general formula (E2), for example, a compound represented by the following chemical formula (E2-1) (hereinafter, may be referred to as an electron acceptor compound (E2-1)). Is mentioned.

In the general formula (E3), R ¹⁰ preferably represents an alkyl group having 1 to 6 carbon atoms, which may have a halogen atom, from the viewpoint of further improving filming resistance, and has a chlorine atom. It is more preferable to represent an alkyl group having 1 to 6 carbon atoms.

As the electron acceptor compound (E3) represented by the general formula (E3), for example, a compound represented by the following chemical formula (E3-1) (hereinafter, may be referred to as an electron acceptor compound (E3-1)). Is mentioned.

In the general formula (E4), it is preferable that R ¹¹ , R ¹² , R ¹³ and R ¹⁴ each independently represent an alkyl group having 1 to 6 carbon atoms from the viewpoint of further improving the filming resistance. More preferably, it represents a branched alkyl group having 1 to 6 carbon atoms.

As the electron acceptor compound (E4) represented by the general formula (E4), for example, a compound represented by the following chemical formula (E4-1) (hereinafter, may be referred to as an electron acceptor compound (E4-1)). Is mentioned.

As the electron acceptor compound E, the electron acceptor compound (E4) is preferable, and the electron acceptor compound (E4-1) is more preferable, from the viewpoint of further improving the filming resistance.

The charge transport layer may contain an electron acceptor compound other than the electron acceptor compound E (other electron acceptor compound). Examples of other electron acceptor compounds include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds. Compounds, dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride and dibromomaleic anhydride, electron acceptor compounds Examples thereof include compounds having a structure different from that of E. The content of the electron acceptor compound E is preferably 80 mass% or more, more preferably 90 mass% or more, and more preferably 100 mass% with respect to the total amount of the electron acceptor compound contained in the charge transport layer. Is more preferable.

From the viewpoint of further improving the filming resistance, the content of the electron acceptor compound is preferably 1 part by mass or more and 10 parts by mass or less, and preferably 1 part by mass or more and 5 parts by mass or less, with respect to 100 parts by mass of the binder resin. Is more preferable, and more preferably 2 parts by mass or more and 4 parts by mass or less.

(Additive)
The charge transport layer may contain an additive, if necessary. Examples of the additives include deterioration inhibitors (more specifically, antioxidants, radical scavengers, quenchers, ultraviolet absorbers, etc.), softeners, surface modifiers, extenders, thickeners, dispersions. Examples include stabilizers, waxes, donors, surfactants, and leveling agents.

Examples of the antioxidant include hindered phenol compounds, hindered amine compounds, thioether compounds, and phosphite compounds. Among these antioxidants, hindered phenol compounds and hindered amine compounds are preferable.

(Combination of materials)
From the viewpoint of further improving the filming resistance, it is preferable that the binder resin and the electron acceptor compound are any of Combination Examples 1 to 11 shown in Table 1 below. From the same viewpoint, it is more preferable that the binder resin and the electron acceptor compound be any one of combination examples 1 to 11 shown in Table 1 below, and the hole transfer agent is the hole transfer agent (HTM-1). preferable. From the same viewpoint, it is more preferable that the binder resin and the electron acceptor compound are any of Combination Examples 1 to 11 shown in Table 1 below, and the charge generating agent is Y-type titanyl phthalocyanine. From the same viewpoint, the binder resin and the electron acceptor compound are any of Combination Examples 1 to 11 shown in Table 1 below, the hole transfer agent is the hole transfer agent (HTM-1), and the charge generation is performed. More preferably, the agent is Y-type titanyl phthalocyanine. The hole transport material (HTM-1) will be described later in Examples.

[3. Middle layer]
The photoreceptor according to the first embodiment may have an intermediate layer (for example, an undercoat layer). The intermediate layer contains, for example, inorganic particles and a resin used for the intermediate layer (intermediate layer resin). By interposing the intermediate layer, it is possible to smooth the flow of current generated when the photosensitive member is exposed and suppress an increase in electric resistance, while maintaining an insulating state to the extent that leakage can be suppressed.

Examples of the inorganic particles include particles of metal (more specifically, aluminum, iron, copper, etc.), metal oxides (more specifically, titanium oxide, alumina, zirconium oxide, tin oxide, zinc oxide, etc.). And particles of non-metal oxides (more specifically, silica and the like). These inorganic particles may be used alone or in combination of two or more. The inorganic particles may be surface-treated.

The intermediate layer resin is not particularly limited as long as it can be used as a resin forming the intermediate layer.

[4. Manufacturing Method of Photoreceptor]
The method for manufacturing the photoconductor of the present embodiment is not particularly limited as long as it is a method including a photosensitive layer forming step. The photosensitive layer forming step includes, for example, a charge generating layer forming step and a charge transporting layer forming step.

In the charge generation layer forming step, first, a charge generation layer coating liquid is prepared. Next, the charge generation layer coating liquid is applied onto the conductive substrate. Then, by drying by a suitable method, at least a part of the solvent contained in the applied charge generation layer coating liquid is removed to form a charge generation layer. The charge generation layer coating liquid contains, for example, a charge generation agent, a base resin, and a solvent. Such a charge generating layer coating liquid can be prepared by dissolving or dispersing a charge generating agent and a base resin in a solvent. Various additives may be added to the charge generation layer coating liquid, if necessary.

In the charge transport layer forming step, first, a charge transport layer coating liquid is prepared. Next, the charge transport layer coating liquid is applied onto the charge generation layer. Then, by drying by an appropriate method, at least a part of the solvent contained in the applied charge transport layer coating liquid is removed to form the charge transport layer. The charge transport layer coating solution contains, for example, a hole transport agent, a polyarylate resin (1) as a binder resin, an electron acceptor compound E, and a solvent. Such a charge transport layer coating liquid can be prepared by dissolving or dispersing the hole transport agent, the polyarylate resin (1), and the electron acceptor compound E in a solvent. If necessary, various additives may be added to the coating liquid for the charge transport layer.

The details of the photosensitive layer forming step will be described below. The solvent contained in the coating liquid for the charge generating layer and the coating liquid for the charge transporting layer (hereinafter, these may be collectively referred to as a coating liquid) is a solvent, if each component contained in the coating liquid can be dissolved or dispersed. It is not particularly limited. 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, o-xylene, m-xylene, p-xylene, etc., halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, etc.), ether (more Specifically, dimethyl ether, diethyl ether, tetrahydrofuran, 1,4-dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc.), ketone (more specifically, acetone, methyl ethyl ketone, cyclohexanone, etc.), ester (more specifically) , Ethyl acetate, methyl acetate, etc.), dimethylformaldehyde, dimethylformamide, and dimethylsulfoxide. These solvents may be used alone or in combination of two or more. Of these solvents, it is preferable to use a non-halogen solvent.

Further, as the solvent contained in the coating liquid for the charge transport layer, a solvent containing at least one selected from toluene, 1,4-dioxane and o-xylene is preferable from the viewpoint of further improving the filming resistance. More preferably, the solvent contains o-xylene. Hereinafter, toluene, 1,4-dioxane and o-xylene may be collectively referred to as a solvent Q. When a solvent containing the solvent Q is used, the content of the solvent Q with respect to the total weight of the solvent is preferably 5% by mass or more and 10% by mass or more and 30% by mass from the viewpoint of further improving the filming resistance. The following is more preferable. When a solvent containing the solvent Q is used, tetrahydrofuran (hereinafter sometimes referred to as THF) is preferable as the solvent other than the solvent Q.

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

The coating liquid may contain, for example, a surfactant in order to improve the dispersibility of each component.

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

The method for removing at least a part of the solvent contained in the coating liquid is not particularly limited as long as it is a method capable of evaporating at least a part of the solvent in the coating liquid. Examples of the method for removing include heating, depressurization, and combined use of heating and depressurization. More specifically, a method of heat treatment (hot air drying) using a high temperature dryer or a reduced pressure dryer can be mentioned. The heat treatment conditions are, for example, a temperature of 40° C. or higher and 150° C. or lower, and a time of 3 minutes or longer and 120 minutes or shorter.

The method for manufacturing the photoconductor may further include a step of forming an intermediate layer, etc., if necessary. A known method can be appropriately selected for the step of forming the intermediate layer.

The photoreceptor of the present exemplary embodiment described above has excellent filming resistance, and thus can be suitably used in various image forming apparatuses.

<Second embodiment: image forming apparatus>
Hereinafter, one aspect of the image forming apparatus according to the second embodiment will be described by taking a tandem type color image forming apparatus as an example. FIG. 4 is a diagram illustrating an example of the image forming apparatus according to the second embodiment. The image forming apparatus 100 according to the second embodiment includes an image carrier 30, a charging unit 42, an exposure unit 44, a developing unit 46, and a transfer unit 48. The image carrier 30 is the photoconductor according to the first embodiment. The charging unit 42 charges the surface of the image carrier 30. The exposure unit 44 exposes the charged surface of the image carrier 30 to form an electrostatic latent image on the surface of the image carrier 30. The developing unit 46 develops the electrostatic latent image as a toner image. The transfer unit 48 transfers the toner image from the image carrier 30 to the recording medium P that is a transfer target. The outline of the image forming apparatus 100 according to the second embodiment has been described above.

The image forming apparatus 100 according to the second embodiment can suppress the occurrence of image defects. The reason is presumed as follows. The image forming apparatus 100 according to the second embodiment includes the photoconductor according to the first embodiment as the image carrier 30. The photoreceptor according to the first embodiment has excellent filming resistance. Therefore, the image forming apparatus 100 according to the second embodiment can suppress the occurrence of image defects such as image defects due to filming.

Hereinafter, each unit of the image forming apparatus 100 will be described in detail with reference to FIG.

The image forming apparatus 100 includes image forming units 40a, 40b, 40c and 40d, a transfer belt 50, and a fixing unit 52. Hereinafter, when it is not necessary to distinguish them, each of the image forming units 40a, 40b, 40c, and 40d is referred to as an image forming unit 40.

The image forming unit 40 includes an image carrier 30, a charging unit 42, an exposing unit 44, a developing unit 46, and a transfer unit 48. The image carrier 30 is provided at the center of the image forming unit 40. The image carrier 30 is provided rotatably in the arrow direction (counterclockwise). Around the image carrier 30, a charging unit 42, an exposure unit 44, a developing unit 46, and a transfer unit 48 are provided in order from the upstream side in the rotation direction of the image carrier 30 with the charging unit 42 as a reference. .. The image forming unit 40 may further include one or both of a cleaning unit (not shown) and a charge eliminating unit (not shown).

Toner images of a plurality of colors (for example, four colors of black, cyan, magenta, and yellow) are sequentially superposed on the recording medium P on the transfer belt 50 by each of the image forming units 40a to 40d.

The charging unit 42 is a charging roller. The charging roller charges the surface of the image carrier 30 while contacting the surface of the image carrier 30. As described above, the image forming apparatus 100 which is an example of the second embodiment employs the contact charging method. Examples of other contact charging type charging units include a charging brush. The charging unit may be a non-contact type. Examples of the non-contact type charging unit include a corotron charging unit and a scorotron charging unit.

The voltage applied by the charging unit 42 is not particularly limited. Examples of the voltage applied by the charging unit 42 include a DC voltage, an AC voltage, and a superposed voltage (a voltage obtained by superposing the AC voltage on the DC voltage), and the DC voltage is preferable. The DC voltage has the following advantages over the AC voltage and the superimposed voltage. When the charging unit 42 applies only a DC voltage, the voltage value applied to the image carrier 30 is constant, so that the surface of the image carrier 30 is easily uniformly charged to a constant potential. Further, when the charging unit 42 applies only the DC voltage, the abrasion amount of the photosensitive layer tends to decrease. As a result, a suitable image can be formed.

The exposure unit 44 exposes the surface of the charged image carrier 30. As a result, an electrostatic latent image is formed on the surface of the image carrier 30. The electrostatic latent image is formed based on the image data input to the image forming apparatus 100.

The developing unit 46 supplies toner to the surface of the image carrier 30 to develop the electrostatic latent image as a toner image. The developing unit 46 may function as a cleaning unit that cleans the surface of the image carrier 30.

The transfer belt 50 conveys the recording medium P between the image carrier 30 and the transfer section 48. The transfer belt 50 is an endless belt. The transfer belt 50 is provided so as to be rotatable in the arrow direction (clockwise direction).

The transfer unit 48 transfers the toner image developed by the developing unit 46 from the surface of the image carrier 30 to the recording medium P. Examples of the transfer unit 48 include a transfer roller.

The fixing unit 52 heats and/or pressurizes the unfixed toner image transferred onto the recording medium P by the transfer unit 48. The fixing unit 52 is, for example, a heating roller and/or a pressure roller. The toner image is fixed on the recording medium P by heating and/or pressing the toner image. As a result, an image is formed on the recording medium P.

Although an example of the image forming apparatus according to the second embodiment has been described above, the image forming apparatus according to the second embodiment is not limited to the image forming apparatus 100 described above. For example, the image forming apparatus 100 described above is a tandem type image forming apparatus, but the image forming apparatus according to the second embodiment is not limited to this, and a rotary type or the like may be adopted. Further, the image forming apparatus according to the second embodiment may be a monochrome image forming apparatus. In this case, the image forming apparatus may include only one image forming unit, for example. Further, the image forming apparatus according to the second embodiment may employ an intermediate transfer method. When the image forming apparatus according to the second embodiment adopts the intermediate transfer method, the transfer target corresponds to the intermediate transfer belt.

<Third Embodiment: Process Cartridge>
The process cartridge according to the third embodiment includes the photoconductor according to the first embodiment as an image carrier. Next, with reference to FIG. 4, an example of the process cartridge according to the third embodiment will be described.

The process cartridge according to the third embodiment corresponds to, for example, each of the image forming units 40a to 40d (FIG. 4). These process cartridges include unitized parts. The unitized portion includes the image carrier 30. Further, the unitized portion may include at least one selected from the group consisting of the charging unit 42, the exposure unit 44, the developing unit 46, and the transfer unit 48, in addition to the image carrier 30. The process cartridge may further include one or both of a cleaning unit (not shown) and a charge eliminating unit (not shown). The process cartridge is designed to be attachable to and detachable from the image forming apparatus 100, for example. The process cartridge in this case is easy to handle, and when the sensitivity characteristic of the image carrier 30 is deteriorated, the process cartridge including the image carrier 30 can be replaced easily and quickly.

The process cartridge according to the third embodiment described above includes the photoconductor according to the first embodiment as an image carrier, and thus can suppress the occurrence of image defects.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the scope of the embodiments.

<Material for photoconductor>
The following hole transport agents, binder resins, and electron acceptor compounds were prepared as materials for manufacturing the photoconductor.

[Hole transfer agent]
A hole transfer material (HTM-1) represented by the following chemical formula (HTM-1) was prepared.

[Binder resin]
A polyarylate resin (R-9) was prepared in addition to the polyarylate resins (R-1) to (R-8) described in the first embodiment. The polyarylate resin (R-9) is represented by the following chemical formula (R-9).

[Method for synthesizing polyarylate resins (R-1) to (R-8)]
The method for synthesizing the polyarylate resins (R-1) to (R-8) will be described below.

(Method for synthesizing polyarylate resin (R-3))
A three-necked flask with a capacity of 1 L equipped with a thermometer, a three-way cock, and a dropping funnel was used as a reaction vessel. In a reaction vessel, 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane 12.2 g (41.3 mmol), t-butylphenol 0.06 g (0.41 mmol) and sodium hydroxide 3.9 g. (98 mmol) and 0.12 g (0.38 mmol) of benzyltributylammonium chloride were added. Then, the inside of the reaction vessel was replaced with argon. Then, 600 mL of water was further charged into the reaction vessel. The internal temperature of the reaction vessel was maintained at 20° C., and the contents of the reaction vessel were stirred for 1 hour. Next, the contents of the reaction container were cooled, and the internal temperature of the reaction container was lowered to 10°C. In this way, an alkaline aqueous solution was prepared.

On the other hand, 4.5 g (16.2 mmol) of 4,4′-biphenyldicarboxylic acid dichloride and 4.1 g (16.2 mmol) of 2,6-naphthalenedicarboxylic acid dichloride were dissolved in 300 g of chloroform to form a chloroform solution. Prepared.

Next, while maintaining the temperature of the alkaline aqueous solution at 10° C. and stirring the contents of the reaction vessel, the chloroform solution was added to the alkaline aqueous solution to start the polymerization reaction. The polymerization reaction was allowed to proceed for 3 hours while stirring the contents of the reaction vessel and maintaining the internal temperature of the reaction vessel at 13±3°C. Then, the upper layer (aqueous layer) was removed using a decant to obtain an organic layer.

Next, 500 mL of ion-exchanged water was added to a three-necked flask having a capacity of 2 L, and then the obtained organic layer was added. Further, 300 g of chloroform and 6 mL of acetic acid were added. The contents of the three-necked flask were stirred at room temperature (25°C) for 30 minutes. Then, the upper layer (water layer) in the contents of the three-necked flask was removed using a decant, and an organic layer was obtained. The obtained organic layer was washed with 500 mL of ion-exchanged water using a separating funnel. Washing with ion-exchanged water was repeated 8 times to obtain an organic layer washed with water.

Next, the organic layer washed with water was filtered to obtain a filtrate. 1.5 L of methanol was put into a 3 L Erlenmeyer flask. The obtained filtrate was slowly added dropwise to the Erlenmeyer flask to obtain a precipitate. The precipitate was filtered off by filtration. The obtained precipitate was vacuum dried at a temperature of 70° C. for 12 hours. As a result, a polyarylate resin (R-3) having a viscosity average molecular weight of 55,500 was obtained.

(Method for synthesizing polyarylate resin (R-1), (R-2) and (R-4) to (R-8))
4,4'-biphenyldicarboxylic acid dichloride and 2,6-naphthalenedicarboxylic acid dichloride are starting materials for polyarylate resins (R-1), (R-2) and (R-4) to (R-8). Polyarylate resins (R-1), (R-2), and (R-4) to (R-8) were respectively prepared in the same manner as the polyarylate resin (R-3) except that the aryloyl halide was used. Synthesized. The total amount of the halogenated aryloyl in each synthesis of the polyarylate resin (R-1), (R-2) and (R-4) to (R-8) is the same as that of the polyarylate resin (R-3). Was the same as the total amount of the material of aryloyl halide in. The viscosity average molecular weights of the polyarylate resins (R-1), (R-2) and (R-4) to (R-8) are 50,500, 51,000, 50,500, 51,500, respectively. , 50,500, 50,500 and 51,000.

Next, the ¹ H-NMR spectrum of the synthesized polyarylate resins (R-1) to (R-8) was measured using a proton nuclear magnetic resonance spectrometer (manufactured by JASCO Corporation, resonance frequency: 300 MHz). .. Deuterated chloroform was used as a solvent. Tetramethylsilane (TMS) was used as an internal standard sample. As a representative example of the polyarylate resins (R-1) to (R-8), FIG. 9 shows the ¹ H-NMR spectrum of the polyarylate resin (R-3). In FIG. 9, the horizontal axis represents the chemical shift (unit: ppm), and the vertical axis represents the signal intensity (unit: arbitrary unit). It was confirmed from the ¹ H-NMR spectrum shown in FIG. 9 that the polyarylate resin (R-3) was obtained. Other polyarylate resin (R-1), (R -2) and (R-4) ~ (R -8) are similarly by ¹ H-NMR spectrum, respectively polyarylate resin (R-1), It was confirmed that (R-2) and (R-4) to (R-8) were obtained.

[Electron acceptor compound]
In addition to the electron acceptor compounds (E1-1) to (E4-1) described in the first embodiment, an electron acceptor compound (E5-1) was prepared. The electron acceptor compound (E5-1) is an electron acceptor compound represented by the following chemical formula (E5-1).

<Manufacture of photoconductor>
[Photoreceptor (A-1)]
Hereinafter, a method for manufacturing the photoconductor (A-1) according to Example 1 will be described.

(Formation of intermediate layer)
First, surface-treated titanium oxide (“Prototype SMT-A” manufactured by Teika Co., Ltd., average primary particle size 10 nm) was prepared. Specifically, a surface-treated titanium oxide was prepared using alumina and silica, and further surface-treated with methylhydrogenpolysiloxane while wet-dispersing the surface-treated titanium oxide. This surface-treated titanium oxide (2 parts by mass) and polyamide resin Amilan (registered trademark) (“CM8000” manufactured by Toray Industries, Inc.) (1 part by mass) were added to the solvent. Amylan is a quaternary copolyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610. A solvent containing methanol (10 parts by mass), butanol (1 part by mass) and toluene (1 part by mass) was used as the solvent. These were mixed for 5 hours using a bead mill to disperse the material in the solvent. This dispersion was filtered using a filter with an opening of 5 μm. This prepared the coating liquid for intermediate|middle layers.

The obtained coating liquid for intermediate layer was applied to the surface of an aluminum drum-shaped support (diameter 30 mm, total length 246 mm) as a conductive substrate by a dip coating method. Subsequently, the applied intermediate layer coating solution was dried at 130° C. for 30 minutes to form an intermediate layer (film thickness 2.0 μm) on the conductive substrate (drum-shaped support).

(Formation of charge generation layer)
Y-type titanyl phthalocyanine (1.5 parts by mass) and a polyvinyl acetal resin (“S-REC BX-5” manufactured by Sekisui Chemical Co., Ltd.) as a base resin (1 part by mass) were added to the solvent. As the solvent, a solvent containing propylene glycol monomethyl ether (40 parts by mass) and THF (40 parts by mass) was used. These were mixed for 2 hours using a bead mill to disperse the material in the solvent. This dispersion was filtered using a filter with an opening of 3 μm. This prepared the charge generation layer coating liquid. The resulting charge generation layer coating liquid was applied onto the intermediate layer formed as described above by the dip coating method and dried at 50° C. for 5 minutes. As a result, a charge generation layer (film thickness 0.3 μm) was formed on the intermediate layer.

(Formation of charge transport layer)
75 parts by mass of a hole transporting agent (HTM-1), 0.5 parts by mass of a hindered phenolic antioxidant (“IRGANOX (registered trademark) 1010” manufactured by BASF Corporation) as an additive, and an electron acceptor compound. 3 parts by mass of (E1-1) and 100 parts by mass of polyarylate resin (R-1) as a binder resin were added to the solvent. As the solvent, a solvent obtained by mixing 560 parts by mass of THF and 140 parts by mass of toluene was used. Using an ultrasonic disperser, these materials were dispersed in a solvent for 2 minutes to prepare a charge transport layer coating solution.

Next, the charge generation layer coating liquid was applied onto the charge generation layer by the same operation as the above-mentioned charge generation layer coating liquid. Then, it was dried at 120° C. for 40 minutes to form a charge transport layer (film thickness: 20 μm) on the charge generation layer to obtain a photoconductor (A-1).

[Photoreceptors (A-2) to (A-13) and Photoreceptors (B-1) to (B-3)]
Photoconductors (A-2) to (A-13) and photoconductors (B-1) to (B-3) were respectively prepared in the same manner as the photoconductor (A-1) except that the following points were changed. Manufactured.

(change point)
The polyarylate resin (R-1) as the binder resin used in the production of the photoconductor (A-1) was changed to the polyarylate resin shown in Table 2. The electron acceptor compound (E1-1) used in the production of the photoconductor (A-1) was changed to the electron acceptor compound shown in Table 2. The mixed solvent of THF and toluene (mass ratio 8:2) used in the charge transport layer coating liquid for forming the charge transport layer of the photoconductor (A-1) was changed to the mixed solvent shown in Table 2. ..

<Evaluation method>
[Martens hardness measurement]
The Martens hardness of the photosensitive layer surface was measured for each of the obtained photoconductors (A-1) to (A-13) and photoconductors (B-1) to (B-3). The Martens hardness was measured by a nanoindentation method based on the ISO14577 standard using a hardness meter (“FISCHERSCOPE (registered trademark) HM2000XYp” manufactured by Fischer Instruments Co., Ltd.). The measurement conditions are as follows: a diamond pyramidal pyramidal indenter (facing angle: 135 degrees) is brought into contact with the surface of the photosensitive layer in an environment of a temperature of 23° C. and a humidity of 50% RH, and then the indenter is subjected to a condition of 10 mN/5 seconds. The load was gradually applied, and after reaching 10 mN, the load was held for 1 second, and the load was unloaded 5 seconds after the holding. The results are shown in Table 3. The higher the Martens hardness of the photosensitive layer surface, the more the occurrence of filming tends to be suppressed.

[Measurement of scratch depth]
The scratch depth of the photosensitive layer was measured for each of the obtained photoconductors (A-1) to (A-13) and photoconductors (B-1) to (B-3). The scratch depth is defined by JIS K5600-5-5 (Japanese Industrial Standard K5600: general test method for paint, Part 5: mechanical properties of coating film, Section 5: scratch hardness (loading needle method)). It measured by the method mentioned later using the apparatus 200 (refer FIG. 5).

Hereinafter, the scratching device 200 defined by JIS K5600-5-5 will be described with reference to FIG. FIG. 5 is a diagram showing an example of the configuration of the scratching device 200. The scratching device 200 includes a fixing base 201, a fixing tool 202, a scratching needle 203, a supporting arm portion 204, two shaft supporting portions 205, a base 206, two rail portions 207, and a weight pan 208. , A constant speed motor (not shown). A weight 209 is placed on the weight pan 208.

In FIG. 5, the X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is the vertical direction. The X-axis direction indicates the longitudinal direction of the fixed base 201. The Y-axis direction indicates a direction orthogonal to the X-axis direction within a plane parallel to the upper surface 201a (mounting surface) of the fixed base 201. The X-axis direction, the Y-axis direction, and the Z-axis direction in FIGS. 6 to 8 described later are also the same as in FIG.

The fixed base 201 corresponds to the test plate fixed base in JIS K5600-5-5. The fixed base 201 includes an upper surface 201a, one end 201b, and the other end 201c. The upper surface 201a of the fixed base 201 is a horizontal surface. The one end 201b faces the two shaft support portions 205.

The fixture 202 is provided on the upper surface 201a of the fixed base 201 on the side of the other end 201c. The fixture 202 fixes the measurement target (photoreceptor 1) on the upper surface 201 a of the fixing base 201.

The scratching needle 203 has a tip 203b (see FIG. 6). The tip 203b has a hemispherical structure with a diameter of 1 mm. The material of the tip 203b is sapphire.

The support arm portion 204 supports the scratching needle 203. The support arm portion 204 rotates about the support shaft 204a in a direction in which the scratching needle 203 approaches the photosensitive body 1 and a direction in which the scratching needle 203 separates from the photosensitive body 1.

The two shaft support portions 205 rotatably support the support arm portion 204.

The base 206 includes an upper surface 206a. Two shaft support portions 205 are provided on one end side of the upper surface 206a.

The two rail portions 207 are provided on the other end side of the upper surface 206a. The two rail portions 207 are provided so as to face each other in parallel. The two rail portions 207 are each provided in parallel with the longitudinal direction (X-axis direction) of the fixed base 201. The fixed base 201 is attached between the two rail portions 207. The fixed base 201 is horizontally movable along the rail portion 207 in the longitudinal direction (X-axis direction) of the fixed base 201.

The weight pan 208 is provided on the scratching needle 203 via the support arm portion 204. A weight 209 is placed on the weight pan 208.

The constant speed motor moves the fixed base 201 in the X-axis direction along the rail portion 207.

The method of measuring the scratch depth will be described below. The scratch depth measuring method includes the following first step, second step, third step, and fourth step. As the scratching device 200, a surface property measuring device (“HEIDON TYPE14” manufactured by Shinto Scientific Co., Ltd.) was used. The scratch depth was measured in an environment of a temperature of 23° C. and a humidity of 50% RH. The shape of the photoconductor 1 was a drum shape (cylindrical shape).

(First step)
In the first step, the photosensitive member 1 was fixed to the upper surface 201a of the fixed base 201 so that the longitudinal direction of the photosensitive member 1 was parallel to the longitudinal direction of the fixed base 201. At this time, the photoconductor 1 was attached such that the direction of the central axis L ₂ (rotational axis) of the photoconductor 1 was parallel to the longitudinal direction of the fixed base 201.

(Second step)
In the second step, the scratching needle 203 was brought into vertical contact with the surface 3c of the photosensitive layer 3. In addition to FIG. 5, a method of vertically contacting the scratching needle 203 with the surface 3c of the photosensitive layer 3 of the drum-shaped photosensitive member 1 will be described with reference to FIGS. 6 and 7.

FIG. 6 is a cross-sectional view taken along the line IV-IV of FIG. 5, and is a cross-sectional view when the scratching needle 203 is brought into contact with the photoconductor 1. FIG. 7 is a side view of the fixed base 201, the scratching needle 203, and the photoconductor 1 shown in FIG.

The scratching needle 203 was brought close to the photoconductor 1 so that the extension line of the central axis A ₁ of the scratching needle 203 was perpendicular to the upper surface 201a of the fixed base 201. Next, on the surface 3c of the photosensitive layer 3 of the photoconductor 1, the tip 203b of the scratching needle 203 is brought into contact with the point farthest from the upper surface 201a of the fixed base 201 in the vertical direction (Z-axis direction) (contact point P ₂ ). Let As a result, the tip 203b of the scratching needle 203 was brought into contact with the photoconductor 1 so that the central axis A ₁ of the scratching needle 203 was perpendicular to the tangent line A ₂ . At this time, the line segment connecting the contact point P _{1 of the} upper surface 201a and the contact point P _{2 of the} tip 203b was orthogonal to the central axis L ₂ of the photoconductor 1. The tangent line A ₂ is the tangent line at the abutting point P ₂ of the outer circumference circle formed by the cross section of the photoconductor 1 perpendicular to the central axis L ₂ .

(Third step)
Next, the third step will be described with reference to FIGS. In the third step, a load W of 10 g was applied from the scratching needle 203 to the photosensitive layer 3 in a state where the scratching needle 203 was vertically contacted with the surface 3c of the photosensitive layer 3. Specifically, 10 g of the weight 209 was placed on the weight pan 208. In this state, the fixed base 201 was moved. Specifically, the constant speed motor was driven to move the fixed base 201 horizontally in the X-axis direction along the rail portion 207. That is, the one end 201b of the fixed base 201 was moved from the first position N ₁ to the second position N ₂ . The second position N ₂ was located downstream of the first position N ₁ . The downstream side is a side in which the fixed base 201 is positioned in a direction away from the two shaft support portions 205 in the longitudinal direction of the fixed base 201. Along with the movement of the fixed base 201 in the longitudinal direction, the photoconductor 1 also moved horizontally in the longitudinal direction of the fixed base 201. The moving speed of the fixed base 201 and the photoconductor 1 was 30 mm/min. The moving distance between the fixed base 201 and the photoconductor 1 was 30 mm. The moving distance of the fixed base 201 and the photoconductor ₁ was equivalent to the distance D _1-2 between the first position N ₁ and the second position N ₂ . As a result of the movement of the fixed base 201 and the photoconductor 1, a scratch S was formed on the surface 3c of the photosensitive layer 3 of the photoconductor 1 by the scratching needle 203.

Next, the scratch S will be described with reference to FIG. 8 in addition to FIGS. 5 to 7. FIG. 8 shows scratches S formed on the surface 3c of the photosensitive layer 3. The scratch S was formed perpendicular to the upper surface 201a of the fixed base 201 and the tangent line A ₂ . Further, the scratch S was formed so as to pass through the line L ₃ shown in FIG. 7. The line L ₃ is a line composed of a plurality of contact points P ₂ . The line L ₃ was parallel to the upper surface 201 a of the fixed base 201 and the central axis L ₂ of the photoconductor 1. The line L ₃ was perpendicular to the central axis A ₁ of the scratching needle 203.

(Fourth step)
In the fourth step, the scratch depth, which is the maximum value of the depth Ds of the scratch S, was measured. Specifically, the photoconductor 1 was removed from the fixed base 201. Using a three-dimensional interference microscope ("WYKO NT-1100" manufactured by Bruker), the scratch S formed on the photosensitive layer 3 of the photoconductor 1 is observed at a magnification of 5 and the depth Ds of the scratch S is measured. did. The depth Ds of the scratch S was the distance from the tangent line A ₂ to the valley of the scratch S. The maximum value of the depth Ds of the scratch S was defined as the scratch depth. The results are shown in Table 3. The smaller the scratch depth of the photosensitive layer 3 is, the more the occurrence of filming tends to be suppressed.

[Evaluation of filming resistance]
The filming resistance of each of the obtained photoconductors (A-1) to (A-13) and photoconductors (B-1) to (B-3) was evaluated. As the evaluation of the filming resistance, the following filming rate was measured and the image was evaluated.

[Measurement of filming rate]
The photoconductor is mounted on a color printer (“C711dn” manufactured by Oki Data Co., Ltd.), the charging potential is set to −600 V, and the image I is printed on 2,000 sheets under the environment of temperature 32° C. and humidity 85% RH. (Cyan color pattern image with a print rate of 1%) was printed. Next, the image I was printed on 2,000 sheets of paper in an environment of a temperature of 10° C. and a humidity of 15% RH. After the printing was completed, the photoconductor was taken out from the color printer. The surface of the taken-out photoconductor (the surface of the photosensitive layer) was observed with an optical microscope (“Sener KK” manufactured by Nikon Corporation) to obtain an observed image. The observation conditions were an optical microscope field of view of 1.7 mm×2.1 mm square, and an observation magnification of 50 times. Next, using the image analysis software (Image J), the obtained observation image was binarized under the condition that the brightness value 180 was the threshold value. The binarized image was analyzed and the ratio of the area of the deposit to the entire image was calculated. Specifically, a pixel having a luminance value less than the threshold value is set as an area where filming occurs. Pixels having a luminance value equal to or higher than the threshold value are set as an area where filming does not occur. Then, the area (Af) of the area where filming has occurred and the area (An) of the area where filming has not occurred are obtained from the analysis image. From the obtained Af and An, the area ratio A (unit: %) of the region where the filming occurred was calculated according to the calculation formula “area ratio A=100×Af/(Af+An)”. The area ratio A was measured at three arbitrary points on the surface of the photoconductor, and the number average value of the area ratio A was determined by dividing the sum of the three area ratios A by 3. The number average value of the obtained area ratio A was defined as the filming rate. The results are shown in Table 3. It should be noted that the lower the filming rate, the less likely filming occurs on the surface of the photoconductor.

[Image evaluation]
The photoconductor is mounted on a color printer (“C711dn” manufactured by Oki Data Co., Ltd.), the charging potential is set to −600 V, and the image I is printed on 2,000 sheets under the environment of temperature 32° C. and humidity 85% RH. (Cyan color pattern image with a print rate of 1%) was printed. Next, the image I was printed on 2,000 sheets of paper in an environment of a temperature of 10° C. and a humidity of 15% RH. After the printing was completed, a halftone image (cyan color image having an image density of 25%) was printed on one sheet of paper in an environment of a temperature of 10° C. and a humidity of 15% RH, and this was used as an evaluation image. The obtained evaluation image was visually checked for white spots, and evaluated according to the following criteria. The results are shown in Table 3. When filming occurs on the surface of the photoconductor, white spots tend to occur in the formed image.

(Evaluation criteria)
A (especially good): No white spots were observed in the evaluation image.
B (Good): White spots were slightly confirmed in the evaluation image, but there was no white spot in actual use.
C (defective): White spots were clearly confirmed in the evaluation image.

As shown in Table 2, the photoconductors (A-1) to (A-13) are the polyarylate resins (R-1) to (R-8) having the repeating units included in the general formula (1). Either was contained in the charge transport layer. The photoconductors (A-1) to (A-13) include the electron acceptor compound (E1-1) included in the general formula (E1), the general formula (E2), the general formula (E3), or the general formula (E4). ) To (E4-1) were contained in the charge transport layer. As shown in Table 3, the photoconductors (A-1) to (A-13) had a filming rate of 0.9% or more and 2.3% or less. The image evaluation of the photoconductors (A-1) to (A-13) was A (particularly good).

As shown in Table 2, the photoconductor (B-1) contained the polyarylate resin (R-9) not included in the general formula (1) in the charge transport layer. The photoconductor (B-2) did not contain an electron acceptor compound in the charge transport layer. The photoconductor (B-3) contains an electron acceptor compound (E5-1) not included in the general formula (E1), the general formula (E2), the general formula (E3), and the general formula (E4) in the charge transport layer. Was. As shown in Table 3, the filming rates of the photoconductors (B-1) to (B-3) were 4.1% or more and 7.4% or less. The image evaluation of the photoconductors (B-1) to (B-3) was C (defective).

As is clear from the above results, the photoconductors (A-1) to (A-13) were more excellent in filming resistance than the photoconductors (B-1) to (B-3).

The electrophotographic photosensitive member according to the present invention can be used in an image forming apparatus such as a multifunction machine.

Claims (4)

An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer,
The photosensitive layer has a charge generation layer and a charge transport layer,
The charge generation layer contains a charge generation agent,
The charge transport layer contains a hole transport material, a binder resin, and an electron acceptor compound,
The binder resin has the following chemical formula (R-1), chemical formula (R-2), chemical formula (R-3), chemical formula (R-4), chemical formula (R-5), chemical formula (R-6), chemical formula (R R-7) or a polyarylate resin represented by the chemical formula (R-8) ,
The electron acceptor compound is an electrophotographic photoreceptor containing a compound represented by the following chemical formula (E1-1), chemical formula (E2-1), chemical formula (E3-1), or chemical formula (E4-1) .
The electrophotographic photosensitive member according to claim 1, wherein the content of the electron acceptor compound is 1 part by mass or more and 10 parts by mass or less based on 100 parts by mass of the binder resin. An image carrier,
A charging unit for charging the surface of the image carrier,
An exposure unit that exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier;
A developing unit for developing the electrostatic latent image as a toner image,
An image forming apparatus comprising: a transfer unit that transfers the toner image from the image carrier to a transfer target,
An image forming apparatus, wherein the image carrier is the electrophotographic photosensitive member according to claim 1. A process cartridge comprising the electrophotographic photosensitive member according to claim 1.