JP6264304B2 - Electrophotographic photosensitive member, method for manufacturing electrophotographic photosensitive member, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member, a method for manufacturing an electrophotographic photosensitive member, an image forming apparatus, and a process cartridge.

  In an electrophotographic image forming apparatus (for example, a printer or a multifunction machine), an electrophotographic photosensitive member is used as an image carrier. In general, an electrophotographic photoreceptor includes a conductive substrate and a photosensitive layer provided directly or indirectly on the conductive substrate. A photoreceptor having a photosensitive layer containing a charge generating agent, a charge transporting agent (for example, a hole transporting agent), and a resin (organic material) for binding them is called an electrophotographic organic photoreceptor.

  Among electrophotographic organic photoreceptors, a hole transport agent and a charge generating agent are contained in the same layer, and the electrophotographic organic photoreceptor that realizes both functions of charge generation and charge transport in the same layer is a single layer type. It is called an electrophotographic photoreceptor.

In recent years, in addition to development of monochrome image forming apparatuses, development of color image forming apparatuses has been progressing. Further, downsizing and speeding up of image forming apparatuses are progressing. Among them, the electrophotographic photosensitive member is required to have high sensitivity in order to cope with a high-speed process. However, when the electrophotographic photosensitive member is used in a state where it is exposed to a gas of an oxidizing substance (for example, ozone) or a nitrogen oxide (for example, NO _x ), and when it is used repeatedly, There is a problem that the sensitivity tends to decrease. Specifically, there is a problem that the charged potential of the photosensitive layer tends to decrease.

  Here, Patent Document 1 discloses an image forming apparatus including an electrophotographic photosensitive member including at least a diarylamine compound as an outermost layer.

  Patent Document 2 discloses an electrophotographic photosensitive member having a photosensitive layer containing a triphenylamine-based charge transfer agent (charge transfer agent) and a charge generator composed of oxytitanium phthalocyanine (titanyl phthalocyanine). A photographic apparatus is disclosed.

JP 2008-152232 A JP 2008-145708 A

However, in the electrophotographic photosensitive member provided in the apparatuses described in Patent Document 1 and Patent Document 2, the state is exposed to an oxidizing substance (for example, ozone) gas or a nitrogen oxide (for example, NO _x ) gas. It is difficult to suppress a decrease in the charged potential of the photosensitive layer when it is used in the above and when it is used repeatedly.

The present invention has been made in view of the above problems, and an object of the present invention is to use a photoreceptor in a state where it is exposed to an oxidizing substance (for example, ozone) or a nitrogen oxide (for example, NO _x ) gas. It is an object to provide an electrophotographic photosensitive member that is excellent in stability of the charged potential on the surface of the photosensitive member, whether it is a case or a case of repeated use. Another object of the present invention is to provide a method for producing an electrophotographic photosensitive member that can easily form a homogeneous photosensitive layer and can improve the stability of the charged potential on the surface of the photosensitive member. Furthermore, an object of the present invention is to provide an image forming apparatus and a process cartridge that can suppress the occurrence of an image defect caused by a decrease in the charged potential on the surface of the photoreceptor by including the above-described electrophotographic photoreceptor. That is.

  The electrophotographic photoreceptor of the present invention includes a photosensitive layer provided directly or indirectly on a conductive substrate. The photosensitive layer contains at least a charge generator, an n-type pigment, an electron transport agent, a hole transport agent, and a binder resin in the same layer. As the charge generator, phthalocyanine or a phthalocyanine derivative is contained. Content of the said n-type pigment is 0.03 mass part or more and 3 mass parts or less with respect to 1 mass part of the said phthalocyanine or the said phthalocyanine derivative. As the hole transport agent, one or more kinds of compounds represented by the following formula (1) are contained.

In the formula (1), R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are each independently an alkyl group that may have a substituent or an alkoxy group that may have a substituent. Represents an aryl group which may have a substituent, an aryloxy group which may have a substituent, an aralkyl group which may have a substituent, a halogen atom, or a hydrogen atom. n1 and n2 each independently represents an integer of 0 or more and 4 or less.

  The method for producing an electrophotographic photoreceptor of the present invention is the above-described method for producing an electrophotographic photoreceptor. The method for producing an electrophotographic photosensitive member of the present invention includes a coating liquid containing at least the charge generator, the n-type pigment, the electron transport agent, the hole transport agent, the binder resin, and a solvent, and the conductive substrate. A photosensitive layer forming step of forming the photosensitive layer by applying at least a part of the solvent contained in the applied coating solution; The solvent includes at least one of tetrahydrofuran and toluene.

  The image forming apparatus of the present invention exposes the surface of the image carrier by exposing the image carrier, a charging unit that charges the surface of the image carrier, and the surface of the image carrier charged by the charging unit. An exposure unit that forms an electrostatic latent image, a developing unit that develops the electrostatic latent image as a toner image, and a transfer unit that transfers the toner image from the image carrier to a transfer target. The charging polarity of the charging unit is positive. The process speed of the image carrier is 120 mm / second or more. The image carrier is the above-described electrophotographic photosensitive member.

  The process cartridge of the present invention includes the above-described electrophotographic photosensitive member.

According to the electrophotographic photoreceptor of the present invention, the photoreceptor is used repeatedly even when it is used in a state where it is exposed to an oxidizing substance (for example, ozone) or a nitrogen oxide (for example, NO _x ) gas. Even in this case, the stability of the charged potential on the surface of the photoreceptor can be improved. In addition, according to the method for producing an electrophotographic photosensitive member of the present invention, a homogeneous photosensitive layer is easily formed, and the stability of the charged potential on the surface of the photosensitive member is easily improved. Furthermore, according to the image forming apparatus or the process cartridge of the present invention, by providing the above-described electrophotographic photosensitive member, it is possible to suppress the occurrence of image defects caused by a decrease in the charged potential on the surface of the photosensitive member.

(A), (b), and (c) are schematic sectional views showing the structure of the electrophotographic photosensitive member according to the first embodiment, respectively. 2 is a CuKα characteristic X-ray diffraction spectrum chart of an example of a titanyl phthalocyanine crystal used in the electrophotographic photosensitive member of the first embodiment. It is a differential scanning calorimetry spectrum chart of an example of the titanyl phthalocyanine crystal used in the electrophotographic photosensitive member of the first embodiment. 6 is a CuKα characteristic X-ray diffraction spectrum chart of another example of a titanyl phthalocyanine crystal used in the electrophotographic photosensitive member of the first embodiment. It is a differential scanning calorimetry spectrum chart of another example of the titanyl phthalocyanine crystal used in the electrophotographic photosensitive member of the first embodiment. It is the schematic which shows the structure of the image forming apparatus provided with the electrophotographic photoreceptor which concerns on 3rd embodiment.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. The present invention can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, about the location where description overlaps, although description may be abbreviate | omitted suitably, the summary of invention is not limited.

<First embodiment: electrophotographic photoreceptor>
The first embodiment relates to an electrophotographic photoreceptor (hereinafter sometimes simply referred to as “photoreceptor”). Hereinafter, the electrophotographic photosensitive member of the present embodiment will be described with reference to FIG.

  The photoreceptor 1 includes a photosensitive layer 3 provided directly or indirectly on a conductive substrate 2. The photosensitive layer 3 contains at least a charge generator, an n-type pigment, an electron transport agent, a hole transport agent, and a binder resin in the same layer.

  The photosensitive layer 3 contains phthalocyanine or a phthalocyanine derivative as a charge generating agent. The photosensitive layer 3 contains one or more of the compounds represented by the above formula (1) as a hole transport agent.

The photosensitive layer 3 provided in the photoreceptor 1 contains phthalocyanine or a phthalocyanine derivative as a charge generating agent. Furthermore, the photosensitive layer 3 contains an n-type pigment. Thereby, the dispersibility of the phthalocyanine or the phthalocyanine derivative in the photosensitive layer 3 tends to be improved. Further, the photosensitive layer 3 contains one or more of the compounds represented by the above formula (1) as a hole transport agent. By using a combination of phthalocyanine or a phthalocyanine derivative, an n-type pigment, and a compound represented by the formula (1), a high-density and homogeneous photosensitive layer 3 can be easily formed. As a result, it is considered that the contact area between the charge generator and the hole transport agent can be increased. By increasing the contact area, the charge injection property (ease of receiving charges) from the charge generating agent to the hole transporting agent is improved. Furthermore, since the compound (hole transport agent) represented by the formula (1) tends to have a high charge retention rate, it becomes easy to suppress charge trapping in combination with improvement in charge injection property. As a result, when the photoreceptor 1 is used in a state where it is exposed to an oxidizing substance (for example, ozone) or a nitrogen oxide (for example, NO _x ) gas, the stability of the charged potential on the surface of the photoreceptor 1 (anti-resistance) Gasity) can be improved. Further, the stability (repetitive characteristics) of the charged potential on the surface of the photoreceptor 1 when the photoreceptor 1 is repeatedly used can be improved.

  The photosensitive layer 3 is provided directly or indirectly on the conductive substrate 2. For example, as shown in FIG. 1A, the photosensitive layer 3 may be directly provided on the conductive substrate 2. Alternatively, as shown in FIG. 1B, an appropriate intermediate layer 4 may be provided between the conductive substrate 2 and the photosensitive layer 3. Further, as shown in FIGS. 1A and 1B, the photosensitive layer 3 may be exposed as the outermost layer. Alternatively, as shown in FIG. 1C, a protective layer 5 may be appropriately provided on the photosensitive layer 3.

  The thickness of the photosensitive layer 3 of the photoreceptor 1 is not particularly limited as long as it can sufficiently function as a photosensitive layer. The thickness of the photosensitive layer 3 is, for example, 5 μm or more and 100 μm or less, and preferably 10 μm or more and 50 μm or less.

  Hereinafter, the conductive substrate 2 and the photosensitive layer 3 will be described. Further, the intermediate layer 4 that may be provided in the photoreceptor 1 will be described.

[1. Conductive substrate]
The conductive substrate 2 is not particularly limited as long as it can be used as the conductive substrate of the photoreceptor 1. As the conductive substrate 2, a conductive substrate formed of a material having at least a surface portion having conductivity can be used. Examples of the conductive substrate 2 include a conductive substrate composed of a conductive material; and a conductive substrate on which a plastic material is coated with a conductive material. Examples of the conductive material include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. These conductive materials may be used alone or in combination of two or more (for example, as an alloy). Among these materials having conductivity, aluminum or an aluminum alloy is preferable because charge transfer from the photosensitive layer 3 to the conductive substrate 2 is good.

  The shape of the conductive substrate 2 can be appropriately selected according to the structure of the image forming apparatus to be used. For example, a sheet-like conductive substrate or a drum-shaped conductive substrate can be used. Further, the thickness of the conductive substrate 2 can be appropriately selected according to the shape of the conductive substrate 2.

[2. Photosensitive layer]
The photosensitive layer 3 included in the photoreceptor 1 contains at least a charge generating agent, an n-type pigment, an electron transport agent, a hole transport agent, and a binder resin in the same layer. Hereinafter, the charge generator, the n-type pigment, the electron transport agent, the hole transport agent, and the binder resin contained in the photosensitive layer 3 will be described. Further, additives that may be included in the photosensitive layer 3 as necessary will be described.

[2-1. Phthalocyanine or its derivative]
The photosensitive layer 3 contains phthalocyanine or a phthalocyanine derivative as a charge generating agent. When the photosensitive layer 3 contains phthalocyanine or a phthalocyanine derivative and an n-type pigment described later, the dispersibility of the phthalocyanine or the phthalocyanine derivative in the photosensitive layer 3 can be easily improved.

Examples of the phthalocyanine include X-type metal-free phthalocyanine represented by the following formula (X—H ₂ Pc). Examples of the phthalocyanine derivative include a titanyl phthalocyanine crystal represented by the following formula (TiOPc) and a phthalocyanine crystal coordinated with a metal other than titanium oxide (for example, V-type hydroxygallium phthalocyanine). Such phthalocyanines or phthalocyanine derivatives may be used singly or in combination of two or more.

  The crystal form of titanyl phthalocyanine contained in the photosensitive layer 3 may be any of Y type, α type, and β type. Further, the photosensitive layer 3 may contain a plurality of types of titanyl phthalocyanine crystals having different crystal types as a charge generating agent. However, in order for the photosensitive layer 3 to have stable and excellent electrical characteristics, the photosensitive layer 3 has a main peak at a Bragg angle (2θ ± 0.2 °) of 27.2 ° in the CuKα characteristic X-ray diffraction spectrum. It is preferable to contain Y-type titanyl phthalocyanine crystal having The main peak in the CuKα characteristic X-ray diffraction spectrum corresponds to a peak having the first or second highest intensity in a range where the Bragg angle (2θ ± 0.2 °) is 3 ° or more and 40 ° or less.

  Hereinafter, crystals of α-type, β-type, and Y-type titanyl phthalocyanine will be described.

(Α-type titanyl phthalocyanine crystal)
The α-type titanyl phthalocyanine crystal has peaks at Bragg angles (2θ ± 0.2 °) of 7.4 ° and 28.6 ° in the CuKα characteristic X-ray diffraction spectrum.

(Β-type titanyl phthalocyanine crystal)
The β-type titanyl phthalocyanine crystal has a peak at 26.2 ° of the Bragg angle (2θ ± 0.2 °) in the CuKα characteristic X-ray diffraction spectrum.

(Y-type titanyl phthalocyanine crystal)
The Y-type titanyl phthalocyanine crystal has a main peak at 27.2 ° of the Bragg angle (2θ ± 0.2 °) in the CuKα characteristic X-ray diffraction spectrum. Such Y-type titanyl phthalocyanine crystals are classified into three types according to differences in thermal characteristics (specifically, thermal characteristics (A) to (C) shown below) in a differential scanning calorimetry (DSC) spectrum.
(A) In the thermal characteristics by DSC, it has a peak (for example, one peak) in the range from 50 ° C. to 270 ° C. in addition to the peak accompanying vaporization of adsorbed water.
(B) In the thermal characteristics by DSC, there is no peak in the range of 50 ° C. or more and 400 ° C. or less other than the peak accompanying vaporization of adsorbed water.
(C) In the thermal characteristics by DSC, there is no peak in the range of 50 ° C. or more and 270 ° C. or less other than the peak due to vaporization of adsorbed water, and a peak in the range of 270 ° C. or more and 400 ° C. or less (for example, one peak) Have

  Hereinafter, among Y-type titanyl phthalocyanine crystals having a main peak at 27.2 ° with a Bragg angle (2θ ± 0.2 °) in a CuKα characteristic X-ray diffraction spectrum, Y-type titanyl phthalocyanine crystals having thermal characteristics (A) “Y-type titanyl phthalocyanine (A)”, Y-type titanyl phthalocyanine crystal having thermal characteristics (B) as “Y-type titanyl phthalocyanine (B)”, and Y-type titanyl phthalocyanine crystals having thermal characteristics (C) as “Y Type titanyl phthalocyanine (C) ".

  Each of the Y-type titanyl phthalocyanines (A) to (C) is considered to have a high quantum yield in the wavelength region of 700 nm or more and excellent charge generation ability.

  Each of the Y-type titanyl phthalocyanines (B) and (C) is excellent in crystal stability, hardly undergoes crystal transition in an organic solvent, and is easily dispersed in the photosensitive layer 3.

<CuKα characteristic X-ray diffraction spectrum>
The crystal structure of titanyl phthalocyanine can be estimated based on the optical characteristics shown by the CuKα characteristic X-ray diffraction spectrum. Hereinafter, an example of a method for measuring the CuKα characteristic X-ray diffraction spectrum will be described.

  A sample (titanyl phthalocyanine crystal) is filled in a sample holder of an X-ray diffractometer (for example, “RINT 1100” manufactured by Rigaku Corporation), an X-ray tube Cu, a tube voltage 40 kV, a tube current 30 mA, and a CuKα characteristic X An X-ray diffraction spectrum is measured under the condition of a line wavelength of 1.542 mm. 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 Y-type titanyl phthalocyanine crystal has a main peak at 27.2 ° of the Bragg angle (2θ ± 0.2 °) in the CuKα characteristic X-ray diffraction spectrum. The α-type titanyl phthalocyanine crystal has a peak at 28.6 ° of the Bragg angle (2θ ± 0.2 °) in the CuKα characteristic X-ray diffraction spectrum. The β-type titanyl phthalocyanine crystal has a peak at a Bragg angle (2θ ± 0.2 °) of 26.2 ° in the CuKα characteristic X-ray diffraction spectrum.

  FIG. 2 is a CuKα characteristic X-ray diffraction spectrum chart of an example of a titanyl phthalocyanine crystal used in the photoreceptor 1 according to this embodiment. FIG. 4 is a CuKα characteristic X-ray diffraction spectrum chart of another example of the titanyl phthalocyanine crystal used in the photoreceptor 1 according to this embodiment. 2 and 4, the horizontal axis indicates the Bragg angle 2θ (°), and the vertical axis indicates the intensity (cps). From the spectrum charts of FIGS. 2 and 4, it can be estimated that the measured crystal form of titanyl phthalocyanine is mainly Y-type.

<Differential scanning calorimetry spectrum>
The crystal structure of titanyl phthalocyanine can be estimated based on the thermal characteristics shown in the differential scanning calorimetry spectrum. Hereinafter, an example of a method for measuring the differential scanning calorimetry spectrum will be described.

  A sample for evaluation of titanyl phthalocyanine crystal powder is placed on a sample pan, and a differential scanning calorimetry spectrum is measured using a differential scanning calorimeter (for example, “TAS-200 type DSC8230D” manufactured by Rigaku Corporation). The measurement range is, for example, 40 ° C. or more and 400 ° C. or less, and the temperature rising rate is, for example, 20 ° C./min.

  Y-type titanyl phthalocyanine (B) has no peak in the range of 50 ° C. or more and 400 ° C. or less in addition to the peak accompanying vaporization of adsorbed water in the differential scanning calorimetry spectrum.

  Y-type titanyl phthalocyanine (C) has no peak in the range of 50 ° C. or higher and 270 ° C. or lower in the differential scanning calorimetry spectrum other than the peak accompanying vaporization of adsorbed water. (For example, one peak).

  Y-type titanyl phthalocyanine (A) has a peak in the range of 50 ° C. or higher and 270 ° C. or lower in addition to the peak accompanying vaporization of adsorbed water in the differential scanning calorimetry spectrum.

  FIG. 3 is a differential scanning calorimetry spectrum chart of an example of a titanyl phthalocyanine crystal used in the photoreceptor 1 according to this embodiment. Specifically, it is a differential scanning calorimetry spectrum chart of a titanyl phthalocyanine crystal shown by the CuKα characteristic X-ray diffraction spectrum chart of FIG. In FIG. 3, the horizontal axis represents temperature (° C.), and the vertical axis represents heat flux (mcal / second). In the spectrum chart of FIG. 3, no peak is observed in the range of 50 ° C. or more and 400 ° C. or less other than the peak accompanying vaporization of adsorbed water. Therefore, it can be estimated that the measured titanyl phthalocyanine crystal is mainly Y-type titanyl phthalocyanine (B).

  FIG. 5 is a differential scanning calorimetry spectrum chart of another example of a titanyl phthalocyanine crystal used in the photoreceptor 1 according to this embodiment. Specifically, it is a differential scanning calorimetry spectrum chart of a titanyl phthalocyanine crystal shown in the CuKα characteristic X-ray diffraction spectrum chart of FIG. In FIG. 5, the horizontal axis represents temperature (° C.), and the vertical axis represents heat flux (mcal / second). In the spectrum chart of FIG. 5, no peak is observed in the range of 50 ° C. or higher and 270 ° C. or lower except for the peak accompanying vaporization of adsorbed water, and one peak is observed at 296 ° C. (range of 270 ° C. or higher and 400 ° C. or lower). The Therefore, it can be estimated that the measured titanyl phthalocyanine crystal is mainly Y-type titanyl phthalocyanine (C).

<Method of synthesizing titanyl phthalocyanine crystal>
Next, a method for synthesizing titanyl phthalocyanine crystal will be described. An example of a method for synthesizing Y-type titanyl phthalocyanine (B) is shown below.

  First, a titanyl phthalocyanine compound is synthesized by the following reaction formula (R-1) or (R-2). In Reaction Formulas (R-1) and (R-2), Y represents a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, e represents an integer of 0 or more and 4 or less, and R represents an alkyl group. And base represents a base.

  In the reaction formula (R-1), a titanyl phthalocyanine compound is synthesized by reacting phthalonitrile or a derivative thereof with a titanium alkoxide. In the reaction formula (R-2), a titanyl phthalocyanine compound is synthesized by reacting 1,3-diiminoindoline or a derivative thereof with a titanium alkoxide.

  Subsequently, a pigmentation pretreatment is performed. Specifically, the titanyl phthalocyanine compound obtained by the reaction formula (R-1) or (R-2) is added to a water-soluble organic solvent, and the mixture is stirred for a certain time while heating. Thereafter, the mixed solution is allowed to stand for a certain period of time under a condition lower than that at the time of stirring to be stabilized.

  In the pre-pigmentation treatment, for example, alcohols (more specifically, methanol, ethanol, isopropanol, etc.), N, N-dimethylformamide, N, N-dimethylacetamide, propionic acid, acetic acid, N-methylpyrrolidone And one or more water-soluble organic solvents selected from the group consisting of ethylene glycol can be used. A small amount of a water-insoluble organic solvent may be added to the water-soluble organic solvent. The stirring in the pre-pigmentation treatment is preferably performed for 1 hour or more and 3 hours or less under a condition of a constant temperature (for example, a predetermined temperature selected from 70 ° C. to 200 ° C.). The stabilization treatment after stirring is preferably performed for 5 hours or more and 10 hours or less under a constant temperature condition. The temperature of the mixed solution during the stabilization treatment is preferably 10 ° C. or more and 50 ° C. or less, and more preferably 22 ° C. or more and 24 ° C. or less.

  Subsequently, the water-soluble organic solvent is dried to obtain a crude crystal of a titanyl phthalocyanine compound. Subsequently, the obtained crude crystal is dissolved in a solvent according to a conventional method, and then dropped into a poor solvent to be recrystallized. Thereafter, the titanyl phthalocyanine compound is pigmented through each step of filtration, washing with water, milling, filtration, and drying. As a result, Y-type titanyl phthalocyanine (B) is obtained.

  Examples of the poor solvent for recrystallization include water, alcohols (more specifically, methanol, ethanol, isopropanol, etc.), and water-soluble organic solvents (more specifically, acetone, dioxane, etc.). One or more selected from the group consisting of can be used.

  The milling treatment is a treatment in which the solid after washing with water is dispersed in a non-aqueous solvent without drying and then the dispersion is stirred. Examples of the solvent for dissolving the crude crystals include halogenated hydrocarbons (more specifically, dichloromethane, chloroform, ethyl bromide, butyl bromide, etc.), trihaloacetic acids (more specifically, trifluoro 1 or more types selected from the group consisting of acetic acid, trichloroacetic acid, or tribromoacetic acid) and sulfuric acid can be used. As the non-aqueous solvent for milling treatment, for example, a halogen-based solvent such as chlorobenzene or dichloromethane can be used.

  Y-type titanyl phthalocyanine (B) can also be synthesized by the following method.

  After the pigmentation pretreatment, a crude crystal of a titanyl phthalocyanine compound obtained by drying a water-soluble organic solvent is treated by an acid paste method. Specifically, the crude crystal is dissolved in an acid, and the obtained solution is dropped into water under ice cooling. Thereafter, the solution is stirred for a certain time under a temperature condition of 22 ° C. or higher and 24 ° C. or lower, and the titanyl phthalocyanine compound is recrystallized in the liquid to obtain a low crystalline titanyl phthalocyanine compound. In addition, as an acid used for the acid paste method, for example, concentrated sulfuric acid or sulfonic acid is preferable.

  Subsequently, the obtained low crystalline titanyl phthalocyanine compound is filtered, and the obtained solid is washed with water. Thereafter, the milling process described above is performed. After the milling treatment, the Y-type titanyl phthalocyanine (B) is obtained by filtering and drying the solid.

[2-2. n-type pigment]
The photosensitive layer 3 contains an n-type pigment.

  Hereinafter, the n-type pigment will be described. Pigments are roughly classified into n-type pigments and p-type pigments. An n-type pigment is a pigment whose main charge carrier is an electron. A p-type pigment is a pigment whose main charge carrier is a hole.

  Examples of n-type pigments include perylene pigments and azo pigments.

  Hereinafter, the perylene pigment used as the n-type pigment will be described. The perylene pigment is, for example, a compound used for an electrophotographic photoreceptor, and is a compound having a perylene skeleton represented by the following formula (PI).

  In formula (PI), X and Y each independently represent a divalent organic group.

  The perylene pigment is preferably a compound represented by the following formula (P-II).

In formula (P-II), R ²¹ and R ²² each independently represent a hydrogen atom or a monovalent organic group, and Z represents an oxygen atom or a nitrogen atom.

In formula (P-II), preferred examples of R ²¹ and R ²² include a hydrogen atom, an aliphatic hydrocarbon group, an aralkyl group which may have a substituent, and an aryl group which may have a substituent. And a heterocyclic group which may have a substituent. As a hetero atom which a heterocyclic group contains, a nitrogen atom, an oxygen atom, and a sulfur atom are mentioned, for example.

When R ²¹ and R ²² are aliphatic hydrocarbon groups, the aliphatic hydrocarbon group may have any of a linear structure, a branched structure, a cyclic structure, or a combination thereof. The aliphatic hydrocarbon group may be saturated or unsaturated, and is preferably saturated.

  When the aliphatic hydrocarbon group is linear or branched, the linear or branched aliphatic hydrocarbon group is preferably an aliphatic hydrocarbon group having 1 to 20 carbon atoms, An aliphatic hydrocarbon group having 1 to 10 carbon atoms is more preferable, an aliphatic hydrocarbon group having 1 to 6 carbon atoms is particularly preferable, and an aliphatic hydrocarbon group having 1 to 4 carbon atoms is most preferable. Preferable specific examples of the linear or branched aliphatic hydrocarbon group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert- A butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, and n-decyl group are mentioned. Of these, a methyl group is preferable.

  When the aliphatic hydrocarbon group is cyclic, the cyclic aliphatic hydrocarbon group is preferably a cyclic aliphatic hydrocarbon group having 3 to 10 carbon atoms, and a cyclic aliphatic hydrocarbon group having 5 to 8 carbon atoms. Is more preferable. Preferable specific examples of the cyclic aliphatic hydrocarbon group include a cyclohexyl group and a cyclopentyl group.

When R ²¹ and R ²² are an aralkyl group, the aralkyl group is preferably an aralkyl group having 7 to 12 carbon atoms. Preferable specific examples of the aralkyl group include a benzyl group, a phenethyl group, an α-naphthylmethyl group, and a β-naphthylmethyl group.

When R ²¹ and R ²² are aryl groups, examples of the aryl group include monocyclic aryl groups and condensed cyclic aryl groups. When the aryl group is a fused cyclic aryl group, the fused cyclic aryl group contains at least one benzene ring. The bond of the fused cyclic aryl group is bonded to the benzene ring. The number of rings constituting the condensed ring in the condensed cyclic aryl group is preferably 3 or less. In the condensed cyclic aryl group, the ring condensed with the benzene ring having a bond may be an aromatic ring or an aliphatic ring. In the condensed cyclic aryl group, the ring condensed with a benzene ring having a bond is preferably a 4- to 8-membered ring, more preferably a 5-membered or 6-membered ring. Examples of the aryl group include aryl groups having 6 to 14 carbon atoms (for example, a single ring or a condensed ring). Examples of the monocyclic aryl group include a phenyl group. Examples of the condensed aryl group include a bicyclic ring (for example, a naphthyl group, an indenyl group, or a 1,2,3,4-tetrahydronaphthyl group), a tricyclic ring (for example, an anthryl group, a phenanthryl group, a fluorenyl group, or Acenaphthylenyl group). Of these, a phenyl group is preferable.

When R ²¹ and R ²² are heterocyclic groups, the heterocyclic ring may be a single ring or a condensed ring. The heterocyclic group may be an aliphatic group or an aromatic group. When the heterocyclic group is a condensed ring, the number of rings constituting the condensed ring is preferably 3 or less. In the heterocyclic group, the ring constituting the condensed ring is preferably a 4- to 8-membered ring, and more preferably a 5-membered or 6-membered ring.

  Preferable specific examples of the heterocyclic ring contained in the heterocyclic group include pyrrolidine, tetrahydrofuran, piperidine, piperazine, morpholine, thiomorpholine, thiophene, furan, pyrrole, imidazole, pyrazole, isothiazole, isoxazole, pyridine, pyrazine, pyrimidine. , Pyridazine, triazole, tetrazole, indole, 1H-indazole, purine, 4H-quinolidine, isoquinoline, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, benzofuran, benzoxazole, benzothiazole, benzimidazole, benzimidazolone, And phthalimide.

When R ²¹ and R ²² are an aralkyl group, an aryl group, or a heterocyclic group, the cyclic group contained in these groups may have a substituent. Examples of the substituent include an alkyl group having 1 to 6 carbon atoms (preferably a methyl group), an alkoxy group having 1 to 6 carbon atoms, a phenyl group, a halogen atom, a hydroxyl group, a cyano group, and a nitro group. It is done.

  Another preferred example of the perylene pigment is a compound represented by the following formula (P-III).

In formula (P-III), R ²³ , R ²⁴ , R ²⁵ , and R ²⁶ are each independently a hydrogen atom or a monovalent organic group. R ²³ and R ²⁴ , or R ²⁵ and R ²⁶ may combine with each other to form a ring.

In the formula (P-III), preferred examples of R ²³ , R ²⁴ , R ²⁵ , and R ²⁶ include a hydrogen atom, an aliphatic hydrocarbon group, an aralkyl group, an aryl group, and a heterocyclic group. Examples of the hetero atom that the heterocyclic group may contain include a nitrogen atom, an oxygen atom, and a sulfur atom.

When R ²³ , R ²⁴ , R ²⁵ , and R ²⁶ are an aliphatic hydrocarbon group, an aralkyl group, an aryl group, or a heterocyclic group, R ²¹ and R ²² in formula (P-II) have been described. A group similar to the group is preferred. When R ²³ , R ²⁴ , R ²⁵ , and R ²⁶ are an aralkyl group, an aryl group, or a heterocyclic group, the cyclic group contained in these groups may have a substituent. Examples of the substituent include an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, a halogen atom, a hydroxyl group, a cyano group, and a nitro group.

R ²³ and R ²⁴ , or R ²⁵ and R ²⁶ may combine with each other to form a ring. The ring formed by combining R ²³ and R ²⁴ or R ²⁵ and R ²⁶ may be an aromatic ring or an aliphatic ring, and may be a hydrocarbon ring or a heterocyclic ring. Preferable examples of the ring formed by combining R ²³ and R ²⁴ or R ²⁵ and R ²⁶ include a benzene ring, a naphthalene ring, a pyridine ring, and a tetrahydronaphthalene ring.

  Preferable specific examples of the perylene pigment include compounds represented by the following formulas (P1) to (P17). The substitution position of the pyridyl group in formula (P5) and the fluoro group in formula (P12) is not particularly limited, and a compound having a substituent at any substitution position can also be used suitably.

  Next, an azo pigment used as an n-type pigment will be described. An azo pigment is a compound used for an electrophotographic photoreceptor, and is not particularly limited as long as it is a compound containing an azo group (—N═N—) in its structure.

  As the azo pigment, any of a monoazo pigment and a polyazo pigment (for example, a bisazo pigment, a trisazo pigment, and a tetrakisazo pigment) can be used. The azo pigment may be a tautomer of a compound having an azo group. The compound having an azo group may be substituted with a chlorine atom.

  As the azo pigment, for example, a known azo pigment can be used. As the azo pigment, preferably pigment yellow (14, 17, 49, 65, 73, 83, 93, 94, 95, 128, 166, and 77), pigment orange (1, 2, 13, 34, and 36), And pigment red (30, 32, 61, and 144).

  Preferable specific examples of the azo pigment include a compound represented by the following formula (A1) (Pigment Yellow 128), a compound represented by the following Formula (A2) (Pigment Yellow 93), and the following Formula (A3). Compound (Pigment Orange 13), and a compound represented by the following formula (A4) (Pigment Yellow 83).

  Content of an n-type pigment is 0.03 mass part or more and 3 mass parts or less with respect to 1 mass part of phthalocyanine or a phthalocyanine derivative. If the content of the n-type pigment is too small relative to the content of phthalocyanine or phthalocyanine derivative, it is difficult to obtain a sufficient effect for improving dispersibility. If the content of the n-type pigment is excessive with respect to the content of phthalocyanine or phthalocyanine derivative, charge generation or charge injection properties are likely to be hindered.

  From the viewpoint of charging stability of the surface of the photoreceptor 1, the photosensitive layer 3 may contain one or more selected from the group consisting of the above-mentioned perylene pigment and the above-mentioned azo pigment as an n-type pigment. preferable.

  The n-type pigment may be an n-type pigment other than a perylene pigment and an azo pigment. Examples of n-type pigments other than perylene pigments and azo pigments include, for example, polycyclic quinone pigments, squarylium pigments, pyranthrone pigments, perinone pigments, isoindoline pigments, quinacdrine pigments, pyrazolone pigments, and benzimidazo. Known organic pigments such as Ron-based pigments can be mentioned. More specifically, a compound represented by the following formula (B1) (Pigment Yellow 110), a compound represented by the following Formula (B2) (Pigment Yellow 139), and a compound represented by the following Formula (B3) ( Pigment red 209).

  More preferably, the photosensitive layer 3 contains two or more n-type pigments. Thereby, it becomes easy to improve the dispersibility of the n-type pigment and the phthalocyanine or the phthalocyanine derivative in the photosensitive layer 3, and it becomes easy to suppress charge trapping.

  It should be noted that other pigments may be contained in the photosensitive layer 3 in addition to the n-type pigment, as long as the effect is not impaired. Other pigments include, for example, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, indigo pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (specifically, Selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon), pyrylium salts, ansanthrone pigments, triphenylmethane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments. It is done.

  In the photoreceptor 1, the total content of the charge generating agent and the n-type pigment is preferably 0.1 parts by mass or more and 50 parts by mass or less, and 0.5 parts by mass or more with respect to 100 parts by mass of the binder resin. More preferably, it is 30 parts by mass or less.

[2-3. Electron transport agent]
The photosensitive layer 3 contains an electron transport agent. As a result, the photosensitive layer 3 can transport electrons and easily impart bipolar (bipolar) characteristics to the photosensitive layer 3.

  Examples of the electron transport agent include quinone compounds (for example, naphthoquinone compounds, diphenoquinone compounds, anthraquinone compounds, azoquinone compounds, nitroanthraquinone compounds, or dinitroanthraquinone compounds), diimide compounds (for example, naphthalenetetra compounds). Carboxylic acid diimide derivatives), hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, dinitroanthracene compounds, dinitroacridine compounds, Tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, succinic anhydride, maleic anhydride, or dibromomaleic anhydride And the like.

  Specific examples of the quinone compound include compounds represented by the following formulas (ETM-1), (ETM-2), and (ETM-4).

  Specific examples of the diimide-based compound include compounds represented by the following formula (ETM-3).

  Specific examples of the hydrazone-based compound include compounds represented by the following formula (ETM-5).

  Such an electron transport agent is used individually by 1 type or in combination of 2 or more types.

  In the photoreceptor 1, the content of the electron transport agent is preferably 5 parts by mass or more and 100 parts by mass or less, and more preferably 10 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the binder resin. .

[2-4. Hole transport agent]
The photosensitive layer 3 contains 1 or more types of the compound represented by following formula (1) as a hole transport agent. The compound represented by the formula (1) has a high charge retention and tends to stabilize the charged potential on the surface of the photoreceptor 1.

In formula (1), R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are each independently an alkyl group that may have a substituent, an alkoxy group that may have a substituent, An aryl group that may have a substituent, an aryloxy group that may have a substituent, an aralkyl group that may have a substituent, a halogen atom, or a hydrogen atom. n1 and n2 each independently represents an integer of 0 or more and 4 or less.

When R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are alkyl groups, the alkyl group is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms. Preferably, an alkyl group having 1 to 6 carbon atoms is particularly preferable, and an alkyl group having 1 to 4 carbon atoms is most preferable. The alkyl group may be linear or branched. Preferable specific examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, and n-hexyl. Group, n-heptyl group, n-octyl group, n-nonyl group, and n-decyl group. Among these, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, or a tert-butyl group is preferable, and a methyl group, an ethyl group, or an n-butyl group is more preferable.

When R ¹ , R ² , R ³ , R ⁴ and R ⁵ are alkoxy groups, the alkoxy group is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms. An alkoxy group having 1 to 6 carbon atoms is particularly preferable, and an alkoxy group having 1 to 4 carbon atoms is most preferable. The alkoxy group may be linear or branched. Preferable specific examples of the alkoxy group include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, n-pentyloxy group, n -Hexyloxy group, n-heptyloxy group, n-octyloxy group, n-nonyloxy group, and n-decyloxy group are mentioned. Of these, a methoxy group is preferable.

When R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are aryl groups, examples of the aryl group include aryl groups having 6 to 14 carbon atoms (for example, monocyclic or condensed rings). be able to. Examples of the monocyclic aryl group include a phenyl group. Examples of the condensed ring aryl group include a bicyclic aryl group (for example, a naphthyl group) and a tricyclic aryl group (for example, an anthryl group or a phenanthryl group). Of these, a naphthyl group is preferable.

When R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are aryloxy groups, examples of the aryloxy group include an aryloxy group having 6 to 14 carbon atoms (for example, a monocyclic ring or a condensed ring) ). Examples of the monocyclic aryloxy group include a phenoxy group. Examples of the condensed aryloxy group include a bicyclic aryloxy group (eg, naphthyloxy group) and a tricyclic aryloxy group (eg, anthryloxy group or phenanthryloxy group). Can do.

When R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are aralkyl groups, examples of the aralkyl group include aralkyl groups having 7 to 20 carbon atoms, preferably 7 to 12 carbon atoms. Of the aralkyl group. Preferable specific examples of the aralkyl group include a benzyl group, a phenethyl group, an α-naphthylmethyl group, and a β-naphthylmethyl group.

When R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are halogen atoms, examples of the halogen atom include a fluoro group, a chloro group, a bromo group, and an iodo group. Of these, a chloro group is preferred.

When R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are each independently an alkyl group or an alkoxy group, the alkyl group and the alkoxy group may each have a substituent. . Examples of the substituent include a halogen atom (for example, a fluoro group, a chloro group, a bromo group, or an iodo group), a nitro group, a cyano group, an amino group, a hydroxyl group, a carboxyl group, a sulfanyl group, a carbamoyl group, and a carbon number of 1. An alkoxy group having 12 or less carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, an alkylsulfanyl group having 1 to 12 carbon atoms, an alkylsulfonyl group having 1 to 12 carbon atoms, an alkanoyl group having 1 to 12 carbon atoms, An alkoxycarbonyl group having 1 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms (for example, a monocyclic, bicyclic condensed ring, or tricyclic condensed ring), and a heterocyclic group having 6 to 14 members. For example, a monocyclic, a bicyclic condensed ring, or a tricyclic condensed ring) can be mentioned. When the alkyl group or the alkoxy group has a plurality of substituents, the plurality of substituents may be the same or different. The substitution position of the substituent is not particularly limited.

When R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are each independently an aryl group, an aryloxy group, or an aralkyl group, the aryl group, aryloxy group, and aralkyl group are each You may have a substituent. Examples of the substituent include a halogen atom (for example, a fluoro group, a chloro group, a bromo group, or an iodo group), a nitro group, a cyano group, an amino group, a hydroxyl group, a carboxyl group, a sulfanyl group, a carbamoyl group, and a carbon number of 1. An alkyl group having 12 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a carbon number An alkylsulfanyl group having 1 to 12 carbon atoms, an alkylsulfonyl group having 1 to 12 carbon atoms, an alkanoyl group having 1 to 12 carbon atoms, an alkoxycarbonyl group having 1 to 12 carbon atoms, and an aryl group having 6 to 14 carbon atoms (For example, a monocyclic ring, a bicyclic condensed ring, or a tricyclic condensed ring) and a heterocyclic group having 6 to 14 members (for example, a single ring , It may be mentioned bicyclic fused ring, or Sanwachijimigowa). When the aryl group, aryloxy group, or aralkyl group has a plurality of substituents, the plurality of substituents may be the same or different. The substitution position of the substituent is not particularly limited.

From the viewpoint of charging stability of the photosensitive layer 3, R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are each independently an alkyl group having 1 to 6 carbon atoms, and 1 to 6 carbon atoms. It preferably represents an alkoxy group or a hydrogen atom.

  n1 and n2 each independently represents an integer of 0 or more and 4 or less. From the viewpoint of charging stability of the photosensitive layer 3, n1 and n2 each independently preferably represents an integer of 0 or more and 2 or less, and more preferably represents an integer of 0 or 1.

  Specific examples of the compound represented by the above formula (1) contained in the photosensitive layer 3 as the hole transport agent include hole transport agents (HTM-1) to (HTM) shown in Table 1 described later in Examples. -17).

  The photosensitive layer 3 can also contain 2 or more types of the compound represented by Formula (1) as a hole transport agent.

  The photosensitive layer 3 may further contain another hole transporting agent in addition to the compound represented by the formula (1) as long as the effect is not impaired. As another hole transport agent, a known hole transport agent can be appropriately selected. When a hole transporting agent having film-forming properties (for example, polyvinyl carbazole) is used as another hole transporting agent, the content of the binder resin may be reduced because it also serves as a binder resin. .

  In the photoreceptor 1, the total content of the hole transport agent is preferably 10 parts by mass or more and 200 parts by mass or less, and preferably 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the binder resin. More preferred.

[2-5. Binder resin]
Examples of the binder resin include a thermoplastic resin, a thermosetting resin, and a photocurable resin. Examples of the thermoplastic resin include polycarbonate resin, styrene resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, 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, alkyd resin, polyamide resin, urethane resin, polyarylate resin, polysulfone resin , Diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, or polyester resin. Examples of the thermosetting resin include silicone resins, epoxy resins, phenol resins, urea resins, melamine resins, and other crosslinkable thermosetting resins. As a photocurable resin, an epoxy acrylate resin or a urethane-acrylate copolymer is mentioned, for example.

  Among these resins, a polycarbonate resin is preferable because the photosensitive layer 3 having an excellent balance of workability, mechanical properties, optical properties, and / or wear resistance can be obtained. Examples of the polycarbonate resin include bisphenol Z type polycarbonate resin, bisphenol B type polycarbonate resin, bisphenol CZ type polycarbonate resin, bisphenol C type polycarbonate resin, and bisphenol A type polycarbonate resin. More specifically, examples of the polycarbonate resin include a resin having a repeating unit represented by the following formula (Resin-1).

In the formula (Resin-1), R ³³ and R ³⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms which may have a substituent. R ³³ and R ³⁴ are preferably a hydrogen atom.

In R ³³ and R ³⁴ , examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an iso-propyl group.

In R ³³ and R ³⁴ , the alkyl group having 1 to 3 carbon atoms may have a substituent. Examples of the substituent include a halogen atom (for example, a fluoro group, a chloro group, a bromo group, an iodo group), a nitro group, a cyano group, an amino group, a hydroxyl group, a carboxyl group, a sulfanyl group, a carbamoyl group, and one or more carbon atoms. An alkoxy group having 12 or less carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, an alkylsulfanyl group having 1 to 12 carbon atoms, an alkylsulfonyl group having 1 to 12 carbon atoms, an alkanoyl group having 1 to 12 carbon atoms, carbon Examples thereof include an alkoxycarbonyl group having 1 to 12 carbon atoms and an aryl group having 6 to 14 carbon atoms.

  These binder resins may be used individually by 1 type, and may be used in combination of 2 or more type.

  The molecular weight of the binder resin is preferably 20000 or more and more preferably 20000 or more and 65000 or less in terms of viscosity average molecular weight. If the molecular weight of the binder resin is too low, it is difficult to form the photosensitive layer 3 densely, and it is difficult to improve gas resistance and repeatability. Furthermore, if the molecular weight of the binder resin is too low, the abrasion resistance of the binder resin cannot be sufficiently increased, and the photosensitive layer 3 is easily worn. On the other hand, if the molecular weight of the binder resin is too high, the binder resin is difficult to dissolve in the solvent when the photosensitive layer 3 is formed, and the viscosity of the coating solution becomes too high, so that the formation of the photosensitive layer 3 tends to be difficult.

[2-6. Additive]
In the photoreceptor 1 of this embodiment, at least one of the photosensitive layer 3, the intermediate layer 4, and the protective layer 5 may contain various additives as long as the electrophotographic characteristics are not adversely affected. . Additives include, for example, deterioration inhibitors (specifically, antioxidants, radical scavengers, singlet quenchers, or ultraviolet absorbers), softeners, surface modifiers, extenders, thickeners. , Dispersion stabilizers, waxes, acceptors, donors, surfactants, plasticizers, sensitizers, and leveling agents. Examples of the antioxidant include BHT (di (tert-butyl) p-cresol), hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidinone, or derivatives thereof, organic sulfur compounds, And organic phosphorus compounds.

[3. Middle layer]
The photoreceptor 1 of the present embodiment may have an intermediate layer 4 (for example, an undercoat layer). The intermediate layer is located between the conductive substrate 2 and the photosensitive layer 3. The intermediate layer 4 contains, for example, inorganic particles and a resin used for the intermediate layer 4 (resin for the intermediate layer 4). The presence of the intermediate layer 4 makes it possible to smooth the flow of current generated when the photosensitive member 1 is exposed while suppressing an increase in resistance while maintaining an insulating state capable of suppressing the occurrence of leakage.

  As the inorganic particles, for example, metal (for example, aluminum, iron, or copper), metal oxide (for example, titanium oxide, alumina, zirconium oxide, tin oxide, or zinc oxide) particles, or non-metal oxide (for example, , Silica) particles. These inorganic particles may be used individually by 1 type, and may use 2 or more types together.

  The resin for the intermediate layer 4 is not particularly limited as long as it is a resin that can be used as a resin for forming the intermediate layer.

  Note that the photoreceptor 1 of the present embodiment can be manufactured by a manufacturing method described later in the second embodiment.

The electrophotographic photosensitive member of this embodiment has been described above with reference to FIG. According to the electrophotographic photoreceptor of this embodiment, the photoreceptor is repeatedly used even when it is used in a state where it is exposed to an oxidizing substance (for example, ozone) or a nitrogen oxide (for example, NO _x ) gas. Even when it is used, the stability of the charged potential on the surface of the photoreceptor can be improved. For this reason, the electrophotographic photosensitive member of this embodiment can be suitably used as an image carrier in various image forming apparatuses.

<Second Embodiment: Method for Producing Electrophotographic Photosensitive Member>
Hereinafter, with reference to FIG. 1 again, a method for manufacturing the electrophotographic photosensitive member of the present embodiment will be described. The manufacturing method of this embodiment is a manufacturing method of the photoreceptor 1 of the first embodiment. The manufacturing method of this embodiment includes a photosensitive layer forming step. The manufacturing method of the present embodiment may further include a coating solution preparation step as necessary in addition to the photosensitive layer forming step. Hereinafter, the coating solution preparing step and the photosensitive layer forming step will be described.

[1. Coating liquid preparation process]
In the coating solution preparation step, a coating solution (a coating solution for the photosensitive layer 3) is prepared by adding at least a charge generator, an n-type pigment, an electron transport agent, a hole transport agent, and a binder resin to the solvent. You may add various additives to a solvent as needed.

  The solvent contained in the coating solution can contain at least one of tetrahydrofuran and toluene. By using such a solvent, the solubility and / or dispersibility of the charge generator, the n-type pigment, the electron transport agent, the hole transport agent, and the binder resin in the coating liquid tends to be improved. As a result, the homogeneous photosensitive layer 3 is easily formed, and the stability of the charged potential on the surface of the photoreceptor 1 is easily improved.

  The coating solution may further contain another solvent in addition to at least one of tetrahydrofuran and toluene. Other solvents include, for example, alcohols (eg, methanol, ethanol, isopropanol, or butanol), aliphatic hydrocarbons (eg, n-hexane, octane, or cyclohexane), aromatic hydrocarbons (eg, benzene, Or xylene), halogenated hydrocarbons (eg, dichloromethane, dichloroethane, carbon tetrachloride, or chlorobenzene), ethers (eg, dimethyl ether, diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, or propylene glycol monomethyl ether), ketones ( For example, acetone, methyl ethyl ketone, or cyclohexanone), esters (for example, ethyl acetate or methyl acetate), dimethylformaldehyde, N, N-dimethylphenol Muamido (DMF), or dimethylsulfoxide. These other solvents are used singly or in combination of two or more.

  In the coating solution preparation process, the charge generator, n-type pigment, electron transport agent, hole transport agent, binder resin, and various additives as necessary are mixed with the solvent and dissolved in the solvent. Alternatively, it may be dispersed. For mixing or dispersing, for example, a bead mill, a roll mill, a ball mill, an attritor, a paint shaker, or an ultrasonic disperser can be used. The coating liquid may contain, for example, a surfactant in order to improve the dispersibility of each component.

[2. Photosensitive layer forming step]
In the photosensitive layer forming step, the coating solution containing at least the charge generating agent, the n-type pigment, the electron transporting agent, the hole transporting agent, the binder resin, and the solvent obtained in the coating solution preparing step is placed on the conductive substrate 2. Apply. The method for applying the coating solution is not particularly limited as long as the coating solution can be uniformly applied onto the conductive substrate 2. Examples of the coating method include a dip coating method, a spray coating method, a spin coating method, and a bar coating method.

  Subsequently, at least a part of the solvent contained in the coating solution applied on the conductive substrate 2 is removed to form the photosensitive layer 3. The method for removing at least part of the solvent contained in the photosensitive layer coating solution is not particularly limited as long as it is a method capable of evaporating the solvent in the photosensitive layer coating solution. Examples of the method for removing at least a part of the solvent include heating, reduced pressure, and combined use of heating and reduced pressure. More specifically, a method of performing heat treatment (hot air drying) using a high-temperature dryer or a vacuum 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. In the photosensitive layer forming step, at least a part of the solvent contained in the photosensitive layer coating solution may be removed. In addition, after the photosensitive layer forming step, the photosensitive layer 3 may contain a solvent (for example, at least one of tetrahydrofuran and toluene) contained in the photosensitive layer coating solution.

  In addition, the manufacturing method of this embodiment may further include the process of forming the intermediate | middle layer 4, and / or the process of forming the protective layer 5, as needed. In the step of forming the intermediate layer 4 and the step of forming the protective layer 5, a known method can be appropriately selected.

  The method for manufacturing the electrophotographic photosensitive member of the present embodiment has been described above with reference to FIG. According to the manufacturing method of this embodiment, a homogeneous photosensitive layer is easily formed, and the stability of the charged potential on the surface of the photoreceptor is easily improved.

<Third embodiment: Image forming apparatus>
The third embodiment relates to an image forming apparatus. Hereinafter, the image forming apparatus of the present embodiment will be described with reference to FIG. FIG. 6 is a schematic diagram illustrating a configuration of an image forming apparatus 6 of the present embodiment including the photoreceptor 1 of the first embodiment.

  The image forming apparatus 6 includes an image carrier (corresponding to the photoreceptor 1), a charging unit (corresponding to the charging device 27), an exposure unit (corresponding to the exposure device 28), and a developing unit (corresponding to the developing device 29). And a transfer part (corresponding to the primary transfer roller 33). The charging unit charges the surface of the image carrier. The exposure unit exposes the surface of the charged 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 a transfer target (corresponding to the intermediate transfer belt 20). The image carrier is the photoreceptor 1 of the first embodiment.

  The image forming apparatus 6 is not particularly limited as long as it is an electrophotographic image forming apparatus. The image forming apparatus 6 may be, for example, a monochrome image forming apparatus or a color image forming apparatus. In order to form toner images of different colors using different color toners, the image forming apparatus 6 of the present embodiment may be a tandem color image forming apparatus.

  Hereinafter, the image forming apparatus 6 will be described by taking a tandem color image forming apparatus as an example. The image forming apparatus 6 includes a plurality of photoreceptors 1 (corresponding to image carriers) arranged in parallel in a predetermined direction and a plurality of developing devices 29. The plurality of developing devices 29 are respectively disposed to face the photoreceptor 1. The plurality of developing devices 29 carry and carry toner on the surface of the developing device 29. Each of the plurality of developing devices 29 includes a developing roller. The developing roller supplies the conveyed toner to the surface of the corresponding photoreceptor 1. As the photoconductor 1, the photoconductor 1 of the first embodiment can be used.

  As shown in FIG. 6, the image forming apparatus 6 has a box-shaped device housing 7. In the device housing 7, a paper feeding unit 8, an image forming unit 9, and a fixing unit 10 are provided. The paper feed unit 8 feeds the paper P. The image forming unit 9 transfers the toner image based on the image data to the paper P while conveying the paper P fed from the paper feeding unit 8. The fixing unit 10 fixes the unfixed toner image transferred on the paper P by the image forming unit 9 to the paper P. Further, a paper discharge unit 11 is provided on the upper surface of the device housing 7. The paper discharge unit 11 discharges the paper P fixed by the fixing unit 10.

  The paper supply unit 8 includes a paper supply cassette 12, a first pickup roller 13, paper supply rollers 14, 15 and 16, and a registration roller pair 17. The paper feed cassette 12 is provided so as to be detachable from the device housing 7. Various sizes of paper P are stored in the paper feed cassette 12. The first pickup roller 13 is provided at the upper left position of the paper feed cassette 12. The first pickup roller 13 takes out the sheets P stored in the sheet feeding cassette 12 one by one. The paper feed rollers 14, 15 and 16 convey the paper P taken out by the first pickup roller 13. The registration roller pair 17 temporarily supplies the paper P conveyed by the paper feed rollers 14, 15, and 16 to the image forming unit 9 at a predetermined timing.

  The paper feed unit 8 further includes a manual feed tray (not shown) and a second pickup roller 18. The manual feed tray is attached to the left side surface of the device housing 7. The second pickup roller 18 takes out the paper P placed on the manual feed tray. The paper P taken out by the second pickup roller 18 is conveyed by the paper feed rollers 14, 15 and 16, and is supplied to the image forming unit 9 by the registration roller pair 17 at a predetermined timing.

  The image forming unit 9 includes an image forming unit 19, an intermediate transfer belt 20, and a secondary transfer roller 21. A toner image is primarily transferred onto the intermediate transfer belt 20 by the image forming unit 19 on the surface of the intermediate transfer belt 20 (contact surface with the primary transfer roller 33). The toner image to be primarily transferred is formed based on image data transmitted from a host device such as a computer. The secondary transfer roller 21 secondarily transfers the toner image on the intermediate transfer belt 20 onto the paper P fed from the paper feed cassette 12.

  The image forming unit 19 includes a yellow toner supply unit 25, a magenta toner supply unit 24, and a cyan toner from the upstream side (right side in FIG. 6) to the downstream side of the driven roller 31 in the rotation direction of the intermediate transfer belt 20. A supply unit 23 and a black toner supply unit 22 are sequentially arranged. In each of the units 22, 23, 24, and 25, a photosensitive member 1 (corresponding to an image carrier) is disposed at the center position of each unit. The photoreceptor 1 is disposed so as to be rotatable in the direction of an arrow (clockwise).

  Around each photosensitive member 1, a charging device 27 (corresponding to a charging unit), an exposure device 28 (corresponding to an exposure unit), a developing device 29 (corresponding to a developing unit), and a primary transfer roller 33 (corresponding to a transfer unit). ) And a cleaning device (not shown) are arranged in order from the upstream side in the rotation direction of each photoconductor 1 with the charging device 27 as a reference. The photoreceptor 1 has been described in detail in the first embodiment.

The photosensitive member 1 is rotationally driven in a direction indicated by an arrow (clockwise) at a predetermined peripheral speed (process speed). The process speed of the photoreceptor 1 can be set to 120 mm / second or more. When the process speed is 120 mm / second or more, image formation can be performed at high speed, and image formation efficiency can be improved. Further, in a high-speed process with a high process speed, the photoconductor tends to be deteriorated due to generation of an oxidizing substance (for example, ozone) gas or a nitrogen oxide (for example, NO _x ) gas. However, as described above, the photoconductor 1 of the first embodiment is not limited to the photoconductor 1 even in the presence of an oxidizing substance (for example, ozone) gas or a nitrogen oxide (for example, NO _x ) gas. The surface has an excellent charge potential stability. Therefore, it is considered that the image forming apparatus 6 according to the present embodiment includes the photoreceptor 1 according to the first embodiment, so that deterioration of the photoreceptor 1 can be suppressed even if the process speed is 120 mm / second or more.

The charging device 27 (corresponding to a charging unit) charges the surface of the photoreceptor 1 (corresponding to an image carrier) to a positive polarity. Specifically, the charging device 27 uniformly charges the peripheral surface of the photoreceptor 1 rotated in the direction of the arrow to positive polarity. The charging device 27 is not particularly limited as long as the peripheral surface of the photoreceptor 1 can be uniformly charged to a positive polarity. The charging device 27 may be a non-contact charging device or a contact charging device. Examples of the charging device 27 include a corona charging device, a charging roller, and a charging brush. As the charging device 27, a contact-type charging device (specifically, a charging roller or a charging brush) is preferable, and a charging roller is more preferable. By using a charging device 27 of contact type, the gas generated from the charging device 27 (e.g., gas of nitrogen oxides, such as gas, or NO _X oxidising substances such as ozone) easily reduce emissions of Become. As a result, it is considered that the deterioration of the photosensitive layer 3 due to the gas is suppressed and the design in consideration of the office environment can be achieved.

  When the charging device 27 includes a contact-type charging roller, the charging roller charges the peripheral surface (surface) of the photoconductor 1 while being in contact with the photoconductor 1. As such a charging roller, for example, a charging roller that rotates depending on the rotation of the photosensitive member 1 while being in contact with the photosensitive member 1 can be used. Moreover, as a charging roller, the charging roller by which the surface part was comprised with resin at least is mentioned, for example. More specifically, as the charging roller, for example, there is a charging roller including a core metal rotatably supported, a resin layer formed on the core metal, and a voltage application unit that applies a voltage to the core metal. Can be mentioned. The charging device 27 equipped with such a charging roller can charge the surface of the photoreceptor 1 that is in contact with the resin through the resin layer when the voltage application unit applies a voltage to the cored bar.

  The voltage applied by the charging device 27 is not particularly limited. However, it is preferable that the charging device 27 applies only the DC voltage, rather than when the charging device 27 applies an AC voltage or when a superimposed voltage obtained by superimposing the AC voltage on the DC voltage is applied. This is because when the charging device 27 applies only a DC voltage, the amount of wear of the photosensitive layer 3 tends to decrease. As a result, a suitable image can be formed. The DC voltage applied to the photoreceptor 1 by the charging device 27 is preferably 1000 V or more and 2000 V or less, more preferably 1200 V or more and 1800 V or less, and particularly preferably 1400 V or more and 1600 V or less.

  The resin constituting the resin layer of the charging roller is not particularly limited as long as the peripheral surface of the photoreceptor 1 can be charged satisfactorily. Specific examples of the resin constituting the resin layer include a silicone resin, a urethane resin, and a silicone-modified resin. The resin layer may contain an inorganic filler.

  A static eliminator (not shown) may be provided on the upstream side of the charging device 27 in the rotation direction of the photoreceptor 1. The static eliminator neutralizes the peripheral surface of the photoreceptor 1 after the primary transfer of the toner image to the intermediate transfer belt 20 is completed. The peripheral surface of the photoreceptor 1 cleaned and discharged by the cleaning device and the charge eliminator is sent to the charging device 27 and newly charged.

  However, the image forming apparatus 6 of the present embodiment can be designed not to include a static eliminator (corresponding to a static eliminator). In other words, the image forming apparatus 6 of the present embodiment can employ a static elimination-less method in which the static eliminator is omitted. When the image forming apparatus 6 adopts the static elimination-less method, the photosensitive member 1 is charged again by the charging device 27 without performing static elimination on the area that has been transferred to the intermediate transfer belt 20. In an image forming apparatus that employs a static elimination-less method, the surface potential of the photoreceptor is usually liable to decrease. However, as described above, the photoreceptor 1 of the first embodiment tends to be excellent in the stability of the charged potential on the surface of the photoreceptor 1 even when charging is repeated. For this reason, the image forming apparatus 6 according to the present embodiment includes the photoreceptor 1 according to the first embodiment, thereby suppressing a decrease in the surface potential of the photoreceptor 1 even when the image forming apparatus 6 does not include a static eliminator. It is considered possible.

  The exposure device 28 (corresponding to an exposure unit) is a so-called laser scanning unit. The exposure device 28 exposes the surface of the charged photoconductor 1 (corresponding to an image carrier) to form an electrostatic latent image on the surface of the photoconductor 1. Specifically, the exposure device 28 irradiates the peripheral surface (surface) of the photoreceptor 1 uniformly charged by the charging device 27 with laser light based on image data input from a host device such as a personal computer. . Thereby, an electrostatic latent image based on the image data is formed on the peripheral surface (front surface) of the photoreceptor 1.

  The developing device 29 (corresponding to a developing unit) develops the electrostatic latent image as a toner image. Specifically, the developing device 29 supplies toner to the peripheral surface of the photoreceptor 1 on which the electrostatic latent image is formed, and forms a toner image based on the image data. Then, the formed toner image is primarily transferred to the intermediate transfer belt 20. The cleaning device cleans the toner remaining on the peripheral surface of the photoreceptor 1 after the primary transfer of the toner image to the intermediate transfer belt 20 is completed.

  The intermediate transfer belt 20 is an endless belt rotating body. The intermediate transfer belt 20 is stretched around a driving roller 30, a driven roller 31, a backup roller 32, and a plurality of primary transfer rollers 33. The intermediate transfer belt 20 is disposed so that the peripheral surfaces of the plurality of photosensitive members 1 are in contact with the surface (contact surface) of the intermediate transfer belt 20.

  Further, the intermediate transfer belt 20 is pressed against the photoconductor 1 by a primary transfer roller 33 disposed to face each photoconductor 1. In the pressed state, the intermediate transfer belt 20 rotates endlessly by a plurality of primary transfer rollers 33. The driving roller 30 is rotationally driven by a driving source such as a stepping motor, and gives a driving force for rotating the intermediate transfer belt 20 endlessly. The driven roller 31, the backup roller 32, and the plurality of primary transfer rollers 33 are rotatably provided. The driven roller 31, the backup roller 32, and the primary transfer roller 33 rotate following the endless rotation of the intermediate transfer belt 20 by the driving roller 30. The driven roller 31, the backup roller 32, and the primary transfer roller 33 are driven to rotate via the intermediate transfer belt 20 according to the main rotation of the driving roller 30 and support the intermediate transfer belt 20.

  The transfer unit transfers the toner image from the image carrier to the transfer target. Specifically, the primary transfer roller 33 applies a primary transfer bias (specifically, a bias having a polarity opposite to the charging polarity of the toner) to the intermediate transfer belt 20 (corresponding to a transfer target). As a result, the toner image formed on each photoconductor 1 is rotated between the photoconductor 1 and the primary transfer roller 33 in the direction of the arrow (counterclockwise) by driving the drive roller 30. 20 is sequentially transferred (primary transfer).

  The secondary transfer roller 21 applies a secondary transfer bias (specifically, a bias having a polarity opposite to that of the toner image) to the paper P. As a result, the toner image primarily transferred onto the intermediate transfer belt 20 is transferred onto the paper P between the secondary transfer roller 21 and the backup roller 32. As a result, an unfixed toner image is transferred onto the paper P.

  The fixing unit 10 fixes the unfixed toner image transferred to the paper P by the image forming unit 9. The fixing unit 10 includes a heating roller 34 and a pressure roller 35. The heating roller 34 is heated by an energized heating element. The pressure roller 35 is disposed to face the heating roller 34, and the circumferential surface of the pressure roller 35 is pressed against the circumferential surface of the heating roller 34.

  The transfer image transferred to the paper P by the secondary transfer roller 21 in the image forming unit 9 is fixed to the paper P by a fixing process by heating when the paper P passes between the heating roller 34 and the pressure roller 35. The Then, the paper P subjected to the fixing process is discharged to the paper discharge unit 11. In addition, a plurality of transport rollers 36 are disposed at appropriate positions between the fixing unit 10 and the paper discharge unit 11.

  The paper discharge unit 11 is formed by recessing the top of the device housing 7. A paper discharge tray 37 that receives the discharged paper P is provided at the bottom of the recessed portion.

  The image forming apparatus of this embodiment has been described above with reference to FIG. The image forming apparatus of the present embodiment includes the photoconductor of the first embodiment as an image carrier. By providing such a photoconductor, the image forming apparatus of the present embodiment can suppress the occurrence of image defects caused by a decrease in the charged potential on the surface of the photoconductor.

<Fourth embodiment: Process cartridge>
The fourth embodiment relates to a process cartridge. The process cartridge of this embodiment includes the electrophotographic photosensitive member of the first embodiment.

  The process cartridge can include, for example, the united photoconductor of the first embodiment. The process cartridge may be designed to be detachable from the image forming apparatus. For example, the process cartridge may employ a configuration in which at least one selected from the group consisting of a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and a charge eliminating unit is unitized in addition to the photosensitive member. it can. When the process cartridge is used in an image forming apparatus adopting a static elimination-less method, the static elimination unit may be omitted. In this case, the process cartridge may employ a configuration in which at least one selected from the group consisting of a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit is unitized in addition to the photosensitive member. Here, the charging unit, the exposure unit, the development unit, the transfer unit, the cleaning unit, and the charge removal unit are respectively the charging unit (corresponding to the charging device 27) and the exposure unit (in the exposure device 28) described in the third embodiment. Equivalent), developing unit (corresponding to developing device 29), transfer unit (corresponding to primary transfer roller 33), cleaning unit (corresponding to cleaning device), and static eliminating unit (corresponding to static eliminator). it can.

  The process cartridge of this embodiment has been described above. The process cartridge of the present embodiment includes the photosensitive member of the first embodiment as an image carrier. By providing such a photoconductor, the process cartridge of the present embodiment can suppress the occurrence of image defects caused by a decrease in the charged potential on the surface of the photoconductor when attached to the image forming apparatus. Further, since such a process cartridge is easy to handle, it can be easily and quickly replaced including the photosensitive member when the sensitivity characteristic of the photosensitive member is deteriorated.

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

[1. Preparation of electrophotographic photoreceptor]
Photoreceptors (A-1) to (A-34) and (B-1) using phthalocyanine or a derivative thereof, an n-type pigment, a hole transporting agent (HTM), an electron transporting agent (ETM), and a binder resin. ) To (B-6) were prepared.

[1-1. Phthalocyanine or its derivative]
In preparing the photoreceptors (A-1) to (A-34) and (B-1) to (B-6), the following phthalocyanines or derivatives thereof were used as charge generating agents. Specifically, the following charge generator (X-H ₂ Pc), charge generator (Y-TiOPc (A)), charge generator (Y-TiOPc (B)), and charge generator (Y-TiOPc) (C)) was used.

Charge generator (X—H ₂ Pc): X-type metal-free phthalocyanine represented by the following formula (X—H ₂ Pc).

  Charge generator (Y-TiOPc (A)): a titanyl phthalocyanine represented by the following formula (TiOPc), which is a Y-type titanyl phthalocyanine crystal having the thermal characteristics (A). This titanyl phthalocyanine crystal had a main peak at 27.2 ° in the Bragg angle (2θ ± 0.2 °) and no peak at 26.2 ° in the CuKα characteristic X-ray diffraction spectrum. The titanyl phthalocyanine crystal had a peak in the range of 50 ° C. or higher and 270 ° C. or lower in addition to the peak accompanying vaporization of adsorbed water in the differential scanning calorimetry spectrum.

  Charge generator (Y-TiOPc (B)): a titanyl phthalocyanine represented by the following formula (TiOPc), which is a Y-type titanyl phthalocyanine crystal having the thermal characteristics (B). This titanyl phthalocyanine crystal had a main peak at 27.2 ° in the Bragg angle (2θ ± 0.2 °) and no peak at 26.2 ° in the CuKα characteristic X-ray diffraction spectrum. This titanyl phthalocyanine crystal had no peak in the range of 50 ° C. or higher and 400 ° C. or lower in the differential scanning calorimetry spectrum other than the peak accompanying vaporization of adsorbed water.

  Charge generator (Y-TiOPc (C)): a titanyl phthalocyanine represented by the following formula (TiOPc), which is a Y-type titanyl phthalocyanine crystal having the thermal characteristics (C). This titanyl phthalocyanine crystal had a main peak at 27.2 ° in the Bragg angle (2θ ± 0.2 °) and no peak at 26.2 ° in the CuKα characteristic X-ray diffraction spectrum. This titanyl phthalocyanine crystal does not have a peak in the range of 50 ° C. or higher and 270 ° C. or lower in the differential scanning calorimetry spectrum, but has one peak in the range of 270 ° C. or higher and 400 ° C. or lower. Had.

[1-2. n-type pigment]
The following n-type pigments were used for the preparation of the photoreceptors (A-1) to (A-34) and (B-3) to (B-6). Specifically, one or more of the compounds represented by the following formulas (A1) to (A4), (B1) and (P1) to (P3) were used. Hereinafter, the compounds represented by formulas (A1) to (A4), (B1), and (P1) to (P3) are converted into pigments (A1) to (A4), (B1), and (P1) to (P1, respectively). P3) may be described.

[1-3. Hole transport agent]
The following hole transport agents were used for the preparation of the photoconductors (A-1) to (A-34) and (B-1). Specifically, one or more of hole transport agents (HTM-1) to (HTM-17) were used. The hole transport agents (HTM-1) to (HTM-17) are each a compound represented by the following formula (1), and R ¹ , R ² , R ³ , R ^{4 in the} formula (1). , R ⁵ , n1 and n2 are compounds represented by the substituents shown in Table 1 below and integers.

In addition, the meaning of the symbol used in Table 1 is shown below.
p-: Para m-: meta CH ₃ -: Methyl C ₂ H ₅ -: ethyl C ₄ H ₉ -: n- butyl CH ₃ O-: methoxy

  The following hole transport agents were used for the preparation of the photoreceptors (B-2) to (B-6). Specifically, any of compounds represented by the following formulas (HTM-A), (HTM-B), (HTM-D), and (HTM-E) was used. Hereinafter, the compounds represented by the formulas (HTM-A), (HTM-B), (HTM-D), and (HTM-E) are respectively represented by a hole transport agent (HTM-A) and (HTM-B). ), (HTM-D), and (HTM-E).

[1-4. Electron transport agent]
For the preparation of the photoreceptors (A-1) to (A-34) and (B-1) to (B-6), any of the following electron transfer agents was used. Specifically, any of compounds represented by the following formulas (ETM-1) to (ETM-5) was used. Hereinafter, the compounds represented by Formulas (ETM-1) to (ETM-5) may be referred to as electron transporting agents (ETM-1) to (ETM-5), respectively.

[1-5. Binder resin]
The following binder resins were used for the preparation of the photoreceptors (A-1) to (A-34) and (B-1) to (B-6). Specifically, a resin having a repeating unit represented by the following formula (Resin-1) (polycarbonate resin, viscosity average molecular weight 30000) was used. Hereinafter, a resin having a repeating unit represented by the formula (Resin-1) may be referred to as a binder resin (Resin-1).

In the formula (Resin-1), R ³³ and R ³⁴ represent a hydrogen atom.

[1-6. Preparation of photoconductor (A-1)]
Charge generator (Y-TiOPc (C)) 2.00 parts by mass, n-type pigment (P1) 1.20 parts by mass (Charge generator (Y-TiOPc (C)) 1 part by mass n-type pigment ( P1) (corresponding to 0.6 parts by mass), 60 parts by mass of hole transport agent (HTM-1), 40 parts by mass of electron transport agent (ETM-1), 100 parts by mass of binder resin (Resin-1), and tetrahydrofuran 800 Part by weight was added to the ball mill container. The contents were mixed and dispersed for 50 hours using a ball mill to prepare a coating solution for the photosensitive layer. The obtained coating solution was applied on a conductive substrate by a dip coating method. As the conductive substrate, an aluminum drum-shaped support (diameter 30 mm, total length 238.5 mm) was used. The applied coating solution (coating film) was heated at 100 ° C. for 60 minutes to remove tetrahydrofuran from the coating film. Thereby, a photoreceptor (A-1) was obtained. The film thickness of the photosensitive layer of the obtained photoreceptor (A-1) was 25 μm.

[1-7. Preparation of photoreceptors (A-2) to (A-34) and (B-1) to (B-6)]
As shown in Tables 2 to 4 below, except for changing the type and addition amount of phthalocyanine or its derivative, the type and addition amount of n-type pigment, the type and addition amount of hole transport agent, and the type of electron transport agent Prepared photoreceptors (A-2) to (A-34) and (B-1) to (B-6) in the same manner as in the preparation of photoreceptor (A-1). Photoconductors (A-1) to (A-34) are examples, and (B-1) to (B-6) are comparative examples.

[2. Evaluation]
Each of the photoreceptors (A-1) to (A-34) and (B-1) to (B-6) obtained as described above was evaluated as follows.

[2-1. Evaluation of ozone resistance]
Photoconductors (A-1) to (A-34) and (B-1) to (B-6) were exposed to ozone, and changes in the charging potential on the surface of each photoconductor before and after the exposure were evaluated. . That is, using a drum sensitivity tester (manufactured by Gentec Co., Ltd.), the photoconductor is rotated four times under a current condition of 8 μA (circumferential speed 31 rpm), and the surface potential of the photoconductor for four rounds is set. It was measured. The measured surface potential was defined as the initial charging potential V _A 0. Next, the photoconductor was allowed to stand for 6 hours at room temperature (23 ° C.) in an atmosphere having an ozone concentration of 10 ppm in a dark place. This exposed the photoreceptor to ozone. The surface potential of the photoconductor immediately after ozone exposure was measured by the same method as the measurement of the initial charging potential V _A 0. The measured surface potential was defined as the charging potential V _A immediately after exposure. The initial charging potential V _A 0 and the charging potential V _A immediately after exposure were measured at a temperature of 23 ° C. and a humidity of 50% RH. Based on the obtained initial charging potential V _A 0 and the charging potential V _A immediately after exposure, ΔV _A 0 was calculated from the following calculation formula 1. Based on the calculated ΔV _A 0, ozone resistance was evaluated according to the following criteria. The smaller ΔV _A 0 is, the better the ozone resistance of the photoreceptor is. A to C were evaluated as acceptable. The obtained results are shown in Tables 2 to 4.
ΔV _A 0 = (initial charging potential V _A 0 [V]) − (charging potential V _A [V] immediately after exposure) (Calculation Formula 1)
Ozone resistance evaluation A: Less than 30V Ozone resistance evaluation B: 30V or more and less than 40V Ozone resistance evaluation C: 40V or more and less than 50V Ozone resistance evaluation D: 50V or more

[2-2. Evaluation of repeatability]
For the photoconductors (A-1) to (A-34) and (B-1) to (B-6), charging and exposure were alternately repeated, and changes in the charging potential before and after the repetition were evaluated. That is, using a drum sensitivity tester (manufactured by Gentec), the photosensitive member is charged to +700 V at a peripheral speed of 100 rpm (process speed of 157 mm / second), and the surface potential of the photosensitive member is measured. did. Next, monochromatic light (wavelength: 780 nm, full width at half maximum: 20 nm) was extracted from the light of the halogen lamp using a bandpass filter, and the extracted monochromatic light was irradiated (exposed) on the surface of one circumference of the photoreceptor. The amount of light was set so that the average value of the surface potential for one round after exposure was 150V. Further, the same charging and exposure were repeated alternately for each round. 1000 sets of endurance tests were alternately repeated one by one. The surface potential of the sample (photoreceptor) during the durability test was measured. Specifically, the average surface potential at the time of charging of the 10th set was set to the initial charging potential V _B 0 [V]. In addition, the average surface potential at the time of charging for the 1000th set was defined as a charging potential V _B [V] after repetition. The initial charging potential V _B 0 and the repeated charging potential V _B were measured at a temperature of 23 ° C. and a humidity of 50% RH. Further, the charge removal of the photoreceptor was not performed after each exposure. Based on the obtained initial charging potential V _B 0 and repeated charging potential V _B , ΔV _B 0 was calculated from the following calculation formula 2. Based on the calculated ΔV _B 0, the repetitive characteristics of the photoconductor were evaluated according to the following criteria. The smaller ΔV _B 0 is, the better the repeatability of the photoreceptor is. A to C were evaluated as acceptable. The obtained results are shown in Tables 2 to 4.
ΔV _B 0 = (initial charging potential V _B 0 [V]) − (repetitive charging potential V _B [V]) (Calculation Formula 2)
Repeatability evaluation A: Less than 30V Repeatability evaluation B: 30V or more and less than 40V Repeatability evaluation C: 40V or more and less than 50V Repeatability evaluation D: 50V or more

[2-3. Comprehensive evaluation]
Moreover, comprehensive evaluation of each evaluation mentioned above was performed according to the following reference | standard. The obtained results are shown in Tables 2 to 4.
Overall evaluation A: The evaluation of ozone resistance and repetitive characteristics was A.
Overall evaluation B: There was one or more evaluations of B, but there was no evaluation of C and D.
Overall evaluation C: There was one or more evaluations of C, but there was no evaluation of D.
Overall evaluation D: There was one or more evaluations of D.

  In Tables 2 to 4, HTM and ETM represent a hole transport agent and an electron transport agent, respectively.

  The photosensitive layers of the photoreceptors (A-1) to (A-34) contained phthalocyanine or a phthalocyanine derivative and an n-type pigment. Moreover, content of the n-type pigment was 0.03 mass part or more and 3 mass parts or less with respect to 1 mass part of phthalocyanine or a phthalocyanine derivative. Furthermore, 1 or more types of the compound represented by Formula (1) were contained as a hole transport agent. Therefore, as is clear from Tables 2 to 4, the photoreceptors (A-1) to (A-34) were excellent in ozone resistance and repeatability.

  On the other hand, the n-type pigment was not contained in the photosensitive layer of the photoreceptor (B-1). The photosensitive layer of the photoreceptor (B-2) did not contain the n-type pigment and the compound represented by the formula (1). The photosensitive layer of the photoreceptors (B-3) to (B-6) did not contain the compound represented by the formula (1). Therefore, the photoreceptors (B-1) to (B-6) were inferior in ozone resistance and repeatability.

  The electrophotographic photosensitive member according to the present invention can be suitably used for an image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 2 Conductive base | substrate 3 Photosensitive layer 4 Intermediate | middle layer 5 Protective layer 6 Image forming apparatus 7 Equipment housing 8 Paper feed part 9 Image forming part 10 Fixing part 11 Paper discharge part 12 Paper feed cassette 13 First pick-up roller 14 Feed roller 15 Feed roller 16 Feed roller 17 Registration roller pair 18 Second pickup roller 19 Image forming unit 20 Intermediate transfer belt 21 Secondary transfer roller 22 Black toner supply unit 23 Cyan toner supply unit 24 Magenta toner supply Unit 25 Yellow toner supply unit 27 Charging device 28 Exposure device 29 Developing device 30 Driving roller 31 Followed roller 32 Backup roller 33 Primary transfer roller 34 Heating roller 35 Pressure roller 36 Conveying roller 37 Discharge tray

Claims (11)

An electrophotographic photoreceptor comprising a photosensitive layer provided directly or indirectly on a conductive substrate,
The photosensitive layer contains at least a charge generator, an n-type pigment, an electron transport agent, a hole transport agent, and a binder resin in the same layer,
As the charge generator, phthalocyanine or a phthalocyanine derivative is contained,
The content of the n-type pigment is 0.03 parts by mass or more and 3 parts by mass or less with respect to 1 part by mass of the phthalocyanine or the phthalocyanine derivative.
An electrophotographic photosensitive member containing one or more compounds represented by the following formula (1) as the hole transport agent.

In the formula (1),
R ¹ , R ² , R ³ , R ⁴ , and R ⁵ each independently have an alkyl group that may have a substituent, an alkoxy group that may have a substituent, or a substituent. An aryloxy group which may have a substituent, an aryloxy group which may have a substituent, an aralkyl group which may have a substituent, a halogen atom or a hydrogen atom;
n1 and n2 each independently represents an integer of 0 or more and 4 or less. In the formula (1), R ¹ , R ² , R ³ , R ⁴ , and R ⁵ are each independently an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or The electrophotographic photosensitive member according to claim 1, which represents a hydrogen atom.   The electrophotographic photosensitive member according to claim 1, wherein the phthalocyanine derivative is a titanyl phthalocyanine crystal. The titanyl phthalocyanine crystal is
In the CuKα characteristic X-ray diffraction spectrum, it has a main peak at 27.2 ° with a Bragg angle (2θ ± 0.2 °),
In the differential scanning calorimetry spectrum, there is no peak in the range of 50 ° C or more and 270 ° C or less other than the peak accompanying vaporization of adsorbed water, or there is a peak in the range of 270 ° C or more and 400 ° C or less, or differential scanning calorimetry The electrophotographic photosensitive member according to claim 3, wherein in the spectrum, there is no peak in a range of 50 ° C. or more and 400 ° C. or less other than the peak accompanying vaporization of adsorbed water.   The electrophotographic photoreceptor according to any one of claims 1 to 4, wherein the n-type pigment is at least one selected from the group consisting of perylene pigments and azo pigments.   The electrophotographic photosensitive member according to claim 1, wherein the n-type pigment is two or more n-type pigments.   The electrophotographic photosensitive member according to any one of claims 1 to 6, wherein the hole transport agent is at least two of the compounds represented by the formula (1). A coating liquid containing at least the charge generating agent, the n-type pigment, the electron transporting agent, the hole transporting agent, the binder resin, and a solvent is coated on the conductive substrate, and is included in the coated coating liquid. A photosensitive layer forming step of forming at least a part of the solvent to form the photosensitive layer,
The method for producing an electrophotographic photosensitive member according to claim 1, wherein the solvent contains at least one of tetrahydrofuran and toluene. An image carrier;
A charging unit that charges the surface of the image carrier;
Exposing the surface of the image carrier charged by the charging unit 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;
The charging polarity of the charging part is positive.
The process speed of the image carrier is 120 mm / second or more,
An image forming apparatus, wherein the image carrier is the electrophotographic photosensitive member according to claim 1.   10. The image forming apparatus according to claim 9, wherein the image carrier is charged again by the charging unit in a region that has been transferred to the transfer target without discharging. 10.   A process cartridge comprising the electrophotographic photosensitive member according to claim 1.

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