JP2017151254A - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor that suppresses the occurrence of a white spot phenomenon.SOLUTION: An electrophotographic photoreceptor comprises a conductive substrate and a photosensitive layer. The photosensitive layer is a single-layer photosensitive layer containing a charge generating agent, an electron transport agent, a hole transport agent, and a binder resin. The electron transport agent contains a quinone derivative represented by the general formula (1). When the photosensitive layer is rubbed with calcium carbonate, the amount of charge of the calcium carbonate is 7 μC/g or more. In the general formula (1), Rand Rrespectively have the same definition as Rand Rdescribed in the specification.SELECTED DRAWING: Figure 1

Description

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

  The electrophotographic photosensitive member is used in an electrophotographic image forming apparatus. As the electrophotographic photosensitive member, for example, a multilayer electrophotographic photosensitive member or a single layer type electrophotographic photosensitive member is used. The electrophotographic photoreceptor includes a photosensitive layer. The multilayer electrophotographic photoreceptor includes, as a photosensitive layer, a charge generation layer having a charge generation function and a charge transport layer having a charge transport function. The single layer type electrophotographic photosensitive member includes a single layer type photosensitive layer having a charge generation function and a charge transport function as a photosensitive layer.

  When an image is formed by an electrophotographic image forming apparatus, an image defect called a white spot phenomenon may occur. The white spot phenomenon is, for example, a minute image defect (more specifically, a diameter of 0.5 mm or more and 2.5 mm or less in an area (image area) formed by transferring a toner image onto a recording medium. This is a phenomenon in which a circular image defect) occurs.

  The photosensitive layer provided in the electrophotographic photosensitive member described in Patent Document 1 contains, for example, a compound represented by the following chemical formula (E-1).

JP 2005-173292 A

  However, the electrophotographic photoreceptor described in Patent Document 1 cannot sufficiently suppress the occurrence of the white spot phenomenon.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic photosensitive member that suppresses the occurrence of a white spot phenomenon. Another object of the present invention is to provide a process cartridge and an image forming apparatus that suppress the occurrence of a white spot phenomenon.

  The electrophotographic photoreceptor of the present invention includes a conductive substrate and a photosensitive layer. The photosensitive layer is a single-layer photosensitive layer containing a charge generating agent, an electron transport agent, a hole transport agent, and a binder resin. The electron transport agent includes a quinone derivative represented by the general formula (1). The charge amount of the calcium carbonate when the photosensitive layer and the calcium carbonate are rubbed is 7 μC / g or more.

In the general formula (1), R ¹ is an alkyl group having 1 to 8 carbon atoms which may have a substituent, and a carbon atom number which may have an alkyl group having 1 to 6 carbon atoms. Represents a group selected from the group consisting of an aryl group having 6 to 14 carbon atoms and a cycloalkyl group having 3 to 10 carbon atoms. The group is substituted with one or more halogen atoms. Two R ^{1 s} may be the same or different. R ² represents a hydrogen atom, an optionally substituted alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 14 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or Represents a heterocyclic group having 3 to 14 carbon atoms which may have a substituent. Two R ^{2 s} may be the same as or different from each other.

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

  The image forming apparatus of the present invention includes an image carrier, a charging unit, an exposure unit, a developing unit, and a transfer unit. The image carrier is the above-described electrophotographic photosensitive member. The charging unit charges the surface of the image carrier positively. The exposure unit exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier. The developing unit develops the electrostatic latent image as a toner image. The transfer unit transfers the toner image from the surface of the image carrier to a recording medium while being in contact with the surface of the image carrier.

  According to the electrophotographic photosensitive member of the present invention, the occurrence of the white spot phenomenon can be suppressed. Further, according to the process cartridge and the image forming apparatus of the present invention, it is possible to suppress the occurrence of the white spot phenomenon.

(A), (b) and (c) are schematic sectional views showing an example of the electrophotographic photosensitive member according to the first embodiment of the present invention. It is a figure which shows an example of the image forming apparatus which concerns on 2nd embodiment of this invention. ^{1 is} a ¹ H-NMR spectrum of a quinone derivative (1-1). It is a figure which shows the outline | summary of the measuring device of a triboelectric charge amount.

  Hereinafter, embodiments of the present invention will be described in detail. 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.

  Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. In addition, when “polymer” is added after the compound name to indicate the polymer name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof.

  Hereinafter, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 4 carbon atoms, carbon An alkyl group having 1 to 3 atoms, an alkyl group having 2 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and 6 to 14 carbon atoms The aryl group, the heterocyclic group having 3 to 14 carbon atoms, the cycloalkyl group having 3 to 10 carbon atoms, and the cycloalkylidene group having 3 to 10 carbon atoms, respectively, It has the following meaning.

  Examples of the halogen atom (halogen group) include a fluorine atom (fluoro group), a chlorine atom (chloro group), a bromine atom (bromo group), or an iodine atom (iodo group).

  The alkyl group having 1 to 8 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, And neopentyl, n-hexyl, n-heptyl, or n-octyl.

  The alkyl group having 1 to 6 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, A neopentyl group or a hexyl group is mentioned.

  The alkyl group having 1 to 5 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 5 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, Or a neopentyl group is mentioned.

  The alkyl group having 1 to 4 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group.

  The alkyl group having 1 to 3 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group.

  An alkyl group having 2 to 4 carbon atoms is unsubstituted. Examples of the alkyl group having 2 to 4 carbon atoms include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group.

  An alkoxy group having 1 to 6 carbon atoms is unsubstituted. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentoxy group, and hexyl. An oxy group is mentioned.

  An alkoxy group having 1 to 4 carbon atoms is unsubstituted. Examples of the alkoxy group having 1 to 4 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, and tert-butoxy group.

  An aryl group having 6 to 14 carbon atoms is unsubstituted. Examples of the aryl group having 6 to 14 carbon atoms include an unsubstituted aromatic monocyclic hydrocarbon group having 6 to 14 carbon atoms and an unsubstituted aromatic condensed bicyclic carbon group having 6 to 14 carbon atoms. A hydrogen group or an unsubstituted aromatic condensed tricyclic hydrocarbon group having 6 to 14 carbon atoms. Examples of the aryl group having 6 to 14 carbon atoms include a phenyl group, a naphthyl group, an anthryl group, and a phenanthryl group.

  A heterocyclic group having 3 to 14 carbon atoms is unsubstituted. The heterocyclic group having 3 to 14 carbon atoms includes, for example, one or more (preferably 1 to 3) heteroatoms selected from the group consisting of a nitrogen atom, a sulfur atom, and an oxygen atom, A 5- or 6-membered monocyclic heterocyclic group having aromaticity; a heterocyclic group in which such monocycles are condensed with each other; or such a monocycle and a 5- or 6-membered hydrocarbon ring A condensed heterocyclic group can be mentioned. Specific examples of the heterocyclic group include thiophenyl group, furanyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, isothiazolyl group, isoxazolyl group, oxazolyl group, isoxazolyl group, thiazolyl group, isothiazolyl group, furazanyl group, pyranyl group, pyridyl group. , Pyridazinyl group, pyrimidinyl group, pyrazinyl group, indolyl group, 1H-indazolyl group, isoindolyl group, chromenyl group, quinolinyl group, isoquinolinyl group, purinyl group, pteridinyl group, triazolyl group, tetrazolyl group, 4H-quinolidinyl group, naphthyridinyl group, A benzofuranyl group, a 1,3-benzodioxolyl group, a benzoxazolyl group, a benzothiazolyl group, or a benzimidazolyl group can be mentioned.

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

  A cycloalkylidene group having 3 to 10 carbon atoms is unsubstituted. Examples of the cycloalkylidene group having 3 to 10 carbon atoms include a cyclopropylidene group, a cyclobutylidene group, a cyclopentylidene group, a cyclohexylidene group, a cycloheptylidene group, a cyclooctylidene group, and a cyclononylidene group. Or a cyclohexylidene group.

<First embodiment: electrophotographic photoreceptor>
The first embodiment of the present invention relates to an electrophotographic photoreceptor. Hereinafter, the structure of an electrophotographic photoreceptor (hereinafter sometimes referred to as a photoreceptor) will be described with reference to FIG. FIG. 1 shows an example of a photoreceptor 1 according to the first embodiment.

  As shown in FIG. 1A, the photoreceptor 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. 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 provided directly on the conductive substrate 2. The photoreceptor 1 may further include an intermediate layer. As shown in FIG. 1B, the 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. The photoreceptor 1 may further include a protective layer. As shown in FIG. 1C, a protective layer 5 may be provided on the photosensitive layer 3. The structure of the photoreceptor 1 has been described above with reference to FIG.

  The photosensitive layer 3 is a single-layer type photosensitive layer 3c containing a charge generating agent, an electron transport agent, a hole transport agent, and a binder resin. The electron transport agent includes a quinone derivative represented by the general formula (1) (hereinafter sometimes referred to as a quinone derivative (1)). The amount of charge of calcium carbonate when the photosensitive layer and calcium carbonate are rubbed is 7 μC / g or more. The photoreceptor according to the first embodiment can suppress the occurrence of the white spot phenomenon. The reason is presumed as follows.

  Here, for the sake of convenience, the white spot phenomenon will be described. An electrophotographic image forming apparatus includes an image carrier (photosensitive member), a charging unit, an exposure unit, a developing unit, and a transfer unit. When the image forming apparatus adopts the direct transfer method, the transfer unit transfers the toner image developed by the developing unit to a recording medium (for example, recording paper). More specifically, the transfer unit transfers the toner image developed on the surface of the photoconductor to a recording medium while being in contact with the surface of the photoconductor. As a result, a toner image is formed on the recording medium.

  In the transfer of the toner image, the recording medium may be rubbed on the surface of the photoreceptor, and the recording medium may be charged (so-called frictional charging). In such a case, the recording medium tends to be charged to the same polarity as the charged polarity (positive polarity) of the photoreceptor and the chargeability tends to decrease, or tends to be charged to the opposite polarity (negative polarity) (so-called reverse charging). When the recording medium is charged in this way, minute components (for example, paper dust) of the recording medium may move and adhere to the surface of the photoreceptor. If minute components adhere to the image area on the surface of the photoreceptor, a defect (white spot) may occur in the image formed on the recording medium. A phenomenon in which such an image defect occurs is called a white spot phenomenon. The method for evaluating the occurrence of the white spot phenomenon will be described in detail in Examples.

  In the photoreceptor according to the first embodiment, the quinone derivative (1) has a halogen atom, and the amount of charge of calcium carbonate when rubbing the photosensitive layer with calcium carbonate is 7 μC / g or more. For this reason, in the photoconductor according to the first embodiment, even if the recording medium rubs against the surface of the photoconductor in the transfer portion, the recording medium has the same polarity as the charged polarity of the photoconductor and the chargeability is not easily lowered. It tends to be less prone to reverse charging. Therefore, it is considered that minute components (for example, paper dust) are less likely to adhere to the surface of the photoreceptor, and the occurrence of the white spot phenomenon is suppressed.

  The measurement of the charge amount of calcium carbonate will be described in detail in Examples. The charge amount of calcium carbonate is preferably 7 μC / g or more and 15 μC / g or less. Calcium carbonate is the main component of paper powder. If the charge amount of calcium carbonate is less than 7.0 μC / g, the repulsive force acting between the photoconductor and the paper dust is not sufficiently large, so that the paper dust tends to adhere to the surface of the photoconductor, and the white spot The phenomenon occurs.

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

  The photosensitive layer may further contain an additive. Hereinafter, a conductive substrate, a charge generator, an electron transport agent, a hole transport agent, a binder resin, an additive, and an intermediate layer will be described as each element of the photoreceptor. In addition, a method for manufacturing the photoreceptor will be described.

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

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

[2. Charge generator]
The charge generator is not particularly limited as long as it is a charge generator for a photoreceptor. Examples of the charge generator include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, indigo pigments, azurenium pigments, cyanine Pigments, inorganic photoconductive materials (more specifically, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, amorphous silicon, etc.) powders, pyrylium pigments, ansanthrone pigments, triphenylmethane pigments, selenium Examples thereof include pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments. A charge generating agent may be used individually by 1 type, and may be used in combination of 2 or more type.

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

  Examples of the crystal of metal-free phthalocyanine include an X-type crystal of metal-free phthalocyanine (hereinafter sometimes referred to as X-type metal-free phthalocyanine). Examples of the crystal of titanyl phthalocyanine include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter sometimes referred to as α-type titanyl phthalocyanine, β-type titanyl phthalocyanine, and Y-type titanyl phthalocyanine, respectively). . Examples of the crystal of hydroxygallium phthalocyanine include a V-type crystal of hydroxygallium phthalocyanine. Examples of chlorogallium phthalocyanine crystals include chlorogallium phthalocyanine type II crystals.

  For example, in a digital optical image forming apparatus (for example, a laser beam printer or a facsimile using a light source such as a semiconductor laser), it is preferable to use a photoreceptor having sensitivity in a wavelength region of 700 nm or more. Since it has a high quantum yield in a wavelength region of 700 nm or more, the charge generator is preferably a phthalocyanine-based pigment, and more preferably a metal-free phthalocyanine. In order to suppress the white spot phenomenon when the photosensitive layer contains the quinone derivative (1), the charge generating agent preferably contains an X-type metal-free phthalocyanine.

  Y-type titanyl phthalocyanine has a main peak at 27.2 ° of the Bragg angle (2θ ± 0.2 °) in the CuKα characteristic X-ray diffraction spectrum, for example. The main peak in the CuKα characteristic X-ray diffraction spectrum is 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.

  For the photoreceptor applied to the image forming apparatus using the short wavelength laser light source, Ansanthrone pigment is preferably used as the charge generating agent. The wavelength of the short wavelength laser light is, for example, not less than 350 nm and not more than 550 nm.

  When the photoreceptor is a multilayer photoreceptor, the content of the charge generating agent is preferably 5 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the base resin contained in the charge generation layer. More preferably, it is at least 500 parts by mass.

  When the photoreceptor is a single layer type photoreceptor, the content of the charge generating agent is 0.1 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the binder resin contained in the single layer type photosensitive layer. It is preferably 0.5 parts by mass or more and 30 parts by mass or less, and more preferably 0.5 parts by mass or more and 4.5 parts by mass or less.

[3. Electron transport agent]
The electron transport agent contains a quinone derivative (1). The quinone derivative (1) is represented by the general formula (1).

In the general formula (1), R ¹ is an alkyl group having 1 to 8 carbon atoms which may have a substituent, and an alkyl group having 1 to 6 carbon atoms which may have a substituent. It represents a group selected from the group consisting of an aryl group having 14 or less and a cycloalkyl group having 3 to 10 carbon atoms. The group is substituted with one or more halogen atoms. Two R ^{1 s} may be the same or different. R ² represents a hydrogen atom, an optionally substituted alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 14 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or Represents a heterocyclic group having 3 to 14 carbon atoms which may have a substituent. Two R ^{2 s} may be the same as or different from each other.

In general formula (1), the alkyl group having 1 to 8 carbon atoms represented by R ¹ is preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 2 to 4 carbon atoms, More preferred are an ethyl group, an isopropyl group, or a tert-butyl group. The alkyl group having 1 to 8 carbon atoms may have a substituent. Examples of such a substituent include a halogen atom or an aryl group having 6 to 14 carbon atoms, and a fluorine atom, a chlorine atom, or a phenyl group is preferable. The aryl group having 6 to 14 carbon atoms may have a halogen atom. When the aryl group having 6 to 14 carbon atoms is a phenyl group, the substitution position of the halogen atom in the phenyl group is, for example, relative to the position at which the phenyl group is bonded to the alkyl group having 1 to 8 carbon atoms. Examples include ortho position (o position), meta position (m position), para position (p position), or at least two of these, and the para position is preferred. The alkyl group having 1 to 8 carbon atoms having a substituent is a carbon having an alkyl group having 1 to 5 carbon atoms having a halogen atom, or an aryl group having 6 to 14 carbon atoms substituted with a halogen atom. An alkyl group having 1 to 5 atoms is preferable, an alkyl group having 2 to 4 carbon atoms having a halogen atom, or an alkyl group having 2 to 4 carbon atoms having a phenyl group substituted with a halogen atom. Preferably, 2-chloro-1,1-dimethylethyl group, 2,2,2-trichloro-1,1-dimethylethyl group, 1,1-dimethyl-1- (4-chlorophenyl) methyl group, 1- (4 -Chlorophenyl) ethyl group, 2-chloro-1-phenylethyl group, 2-chloro-1- (4-chlorophenyl) ethyl group, or 1- (4-fluorophenyl) More preferably an ethyl group.

In general formula (1), the alkyl group having 1 to 6 carbon atoms represented by R ² may have a substituent. Examples of such a substituent include a halogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, or a cyano group. In general formula (1), the heterocyclic group having 3 to 14 carbon atoms represented by R ² may have a substituent. Examples of such a substituent include a halogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and a cyano group.

In general formula (1), R ¹ preferably represents an alkyl group having 1 to 5 carbon atoms which may have an aryl group having 6 to 14 carbon atoms. At least ^one of the aryl group having 6 to 14 carbon atoms and the alkyl group having 1 to 5 carbon atoms represented by R ¹ is preferably substituted with one or more halogen atoms. The two R ¹ are preferably the same as each other. R ² preferably represents a hydrogen atom. Two R ² are preferably the same as each other.

In the general formula (1), the total number of halogen atoms contained in the two groups represented by R ¹ is preferably 4 or more, more preferably 4 or more and 6 or less, from the viewpoint of suppressing the white spot phenomenon.

  Specific examples of the quinone derivative (1) include quinone derivatives represented by chemical formulas (1-1) to (1-7) (hereinafter referred to as quinone derivatives (1-1) to (1-7)). There is).

(Production method of quinone derivative (1))
The quinone derivative (1) includes, for example, a reaction formula represented by the reaction formula (R-1) (hereinafter sometimes referred to as reaction (R-1)) and a reaction formula represented by the reaction formula (R-2) ( Hereinafter, it may be produced according to or according to a reaction (which may be referred to as reaction (R-2)). The production method of the quinone derivative (1) includes, for example, reaction (R-1) and reaction (R-2).

In reaction (R-1), R ¹ and R ² are the same meanings as R ¹ and R ² in the general formula (1).

In the reaction (R-1), 1 equivalent of a compound represented by the chemical formula (A) (naphthol derivative) (hereinafter, referred to as naphthol derivative (A) may be described. In general formula (1), R ¹ When OH represents a hydrogen atom, the naphthol derivative (A) indicates naphthol.) And 1 equivalent of the compound represented by the general formula (B) (alcohol derivative) (hereinafter, referred to as alcohol derivative (B)). ) In the presence of concentrated sulfuric acid in a solvent to obtain a compound represented by the general formula (C), which is an equivalent of an intermediate (hereinafter sometimes referred to as naphthol derivative (C)). . In the reaction (R-1), it is preferable to add 1 mol to 2.5 mol of the alcohol derivative (B) with respect to 1 mol of the naphthol derivative (A). When 1 mol or more of alcohol derivative (B) is added to 1 mol of naphthol derivative (A), the yield of naphthol derivative (C) is easily improved. On the other hand, when 2.5 mol or less of alcohol derivative (B) is added to 1 mol of naphthol derivative (A), unreacted alcohol derivative (B) hardly remains after reaction (R-1). Purification of (1) becomes easy. The reaction temperature for reaction (R-1) is preferably room temperature (eg, 25 ° C.). The reaction time for reaction (R-1) is preferably from 1 hour to 10 hours. Reaction (R-1) can be performed in a solvent. As a solvent, organic acid aqueous solution (for example, acetic acid) is mentioned, for example.

  More specifically, in the reaction (R-1), the naphthol derivative (A) and the alcohol derivative (B) are reacted. After the reaction, ion-exchanged water is added to the reaction solution and extracted into an organic layer. As an organic solvent contained in an organic layer, chloroform or ethyl acetate is mentioned, for example. The organic layer is added with an alkaline aqueous solution, and the organic layer is washed and neutralized. Examples of the alkali include an alkali metal hydroxide (more specifically, sodium hydroxide, potassium hydroxide, etc.), or an alkaline earth metal hydroxide (more specifically, calcium hydroxide, etc.). ).

  In the reaction (R-1), it is considered that a carbocation is generated as a reaction intermediate from the alcohol derivative (B). For this reason, as alcohol derivative (B), the secondary alcohol which has a tertiary alcohol or an aryl group, for example is preferable. In the present specification, the secondary alcohol having an aryl group means a secondary alcohol in which an aryl group is bonded to a carbon atom to which a hydroxyl group is bonded. Such a secondary alcohol is considered to have an electron delocalized by the aryl group and stabilize the carbocation.

In reaction (R-2), R ¹ and R ² are the same meanings as R ¹ and R ² in the general formula (1).

In the reaction (R-2), when two R ¹ are the same as each other and the two R ² are the same as each other, 2 equivalents of the naphthol derivative (C) are reacted in the presence of an oxidizing agent to give 1 equivalent of A quinone derivative (1) is obtained. In reaction (R-2), it is preferable to add 1 mol of an oxidizing agent to 1 mol of naphthol derivative (C). Examples of the oxidizing agent include chloranil, potassium permanganate, and silver oxide. The reaction temperature for reaction (R-2) is preferably room temperature (eg, 25 ° C.). The reaction time for reaction (R-2) is preferably from 1 hour to 10 hours. Examples of the solvent include chloroform and dichloromethane.

The method for producing the quinone derivative (1) is such that, when the quinone derivative (1) has at least one of two R ¹ and two R ² different from each other, 2 equivalents of the naphthol derivative (C) A quinone derivative (R-2) is reacted in the same manner as in the reaction (R-2) in which two R ^{1 s} are the same and two R ^{2 s} are the same except that the naphthol derivative (C) is changed to 1 equivalent. 1) can be obtained.

  The method for producing the quinone derivative (1) may include other steps (for example, a purification step) as necessary. An example of such a process is a purification process. Examples of the purification method include known methods (more specifically, filtration, chromatography, crystal folding, etc.).

  The electron transfer agent may further contain another electron transfer agent other than the quinone derivative (1) in addition to the quinone derivative (1). Another electron transport agent is appropriately selected from known electron transport agents.

  Examples of other electron transfer agents include quinone compounds (quinone compounds other than the quinone derivative (1)), diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3, 4,5,7-tetranitro-9-fluorenone compound, dinitroanthracene compound, dinitroacridine compound, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride Acid, or dibromomaleic anhydride. Examples of quinone compounds other than the quinone derivative (2) include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds. These electron transfer agents may be used alone or in combination of two or more.

  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 in the photosensitive layer.

  The content of the quinone derivative (1) in the electron transfer agent is preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass with respect to the total mass of the electron transfer agent. It is particularly preferred.

[4. Hole transport agent]
As the hole transport agent, for example, a nitrogen-containing cyclic compound or a condensed polycyclic compound can be used. Examples of the nitrogen-containing cyclic compound and the condensed polycyclic compound include diamine derivatives (more specifically, benzidine derivatives, N, N, N ′, N′-tetraphenylphenylenediamine derivatives, N, N, N ′. , N′-tetraphenylnaphthylenediamine derivative, or N, N, N ′, N′-tetraphenylphenanthrylenediamine derivative, etc.), oxadiazole compounds (more specifically, 2,5-di ( 4-methylaminophenyl) -1,3,4-oxadiazole etc.), styryl compounds (more specifically 9- (4-diethylaminostyryl) anthracene etc.), carbazole compounds (more specifically polyvinyl Carbazole, etc.), organic polysilane compounds, pyrazoline compounds (more specifically, 1-phenyl-3- (p-dimethylaminophenyl) pyrazo Emissions, etc.), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compound, or triazole-based compounds. These hole transport agents may be used alone or in combination of two or more. Of these hole transfer agents, the compound represented by the general formula (2) (benzidine derivative) is preferable.

In General Formula (2), R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , and R ²⁶ are each independently an alkyl group having 1 to 6 carbon atoms, or 1 to 6 carbon atoms. Represents an alkoxy group. r, s, v, and w each independently represent an integer of 0 or more and 5 or less. t and u each independently represents an integer of 0 or more and 4 or less.

In general formula (2), each of R ^{21 to} R ²⁶ preferably independently represents an alkyl group having 1 to 6 carbon atoms, and more preferably represents an alkyl group having 1 to 3 carbon atoms. More preferably, it represents a methyl group. r, s, v, w, t, and u preferably represent 1.

  The compound represented by the general formula (2) is preferably a compound represented by the chemical formula (H-1) (hereinafter sometimes referred to as the compound (H-1)).

  The content of the hole transport agent is preferably 10 parts by mass or more and 200 parts by mass or less, and more 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 in the photosensitive layer.

[5. Binder resin]
The binder resin disperses and fixes a charge generating agent or the like in the photosensitive layer. Examples of the binder resin include a thermoplastic resin, a thermosetting resin, and a photocurable resin. Examples of the thermoplastic resin include polycarbonate resin, polyarylate resin, styrene-butadiene resin, styrene-acrylonitrile resin, styrene-maleic acid resin, acrylic acid resin, styrene-acrylic acid resin, polyethylene resin, and ethylene-vinyl acetate resin. , Chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate resin, alkyd resin, polyamide resin, urethane resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyester resin, Or a polyether resin is mentioned. As a thermosetting resin, a silicone resin, an epoxy resin, a phenol resin, a urea resin, or a melamine resin is mentioned, for example. Examples of the photocurable resin include an epoxy-acrylic acid resin (more specifically, an acrylic acid derivative adduct of an epoxy compound) or a urethane-acrylic acid resin (more specifically, urethane compound). Acrylic acid derivative adducts, etc.). These binder resins may be used individually by 1 type, and may be used in combination of 2 or more type.

  Among these resins, a polycarbonate resin is preferable because a single-layer type photosensitive layer and a charge transport layer excellent in balance of workability, mechanical properties, optical properties, and abrasion resistance can be obtained. As the polycarbonate resin, for example, a polycarbonate resin represented by the general formula (3) is preferable (hereinafter sometimes referred to as a polycarbonate resin (3)).

In the general formula (3), R ³¹ , R ³² , R ³³ , and R ³⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R ³² and R ³³ may represent a cycloalkylidene group having 3 to 10 carbon atoms formed by bonding to each other. m and n are integers of 0 or more and satisfy m + n = 100. n represents an integer of 60 or more and 100 or less.

In the general formula (3), R ³¹ and R ³⁴ preferably represent a hydrogen atom. R ³² and R ³³ preferably represent a cycloalkylidene group having 3 to 10 carbon atoms formed by bonding to each other, and more preferably a cyclohexylidene group.

  Examples of the polycarbonate resin (3) include polycarbonate resins represented by the chemical formula (R-1) or (R-2) (hereinafter referred to as polycarbonate resins (R-1) and (R-2), respectively). Sometimes).

  The viscosity average molecular weight of the binder resin is preferably 40,000 or more, and more preferably 40,000 or more and 52,500 or less. When the viscosity average molecular weight of the binder resin is 40,000 or more, it is easy to improve the wear resistance of the photoreceptor. When the viscosity average molecular weight of the binder resin is 52,500 or less, the binder resin is easily dissolved in a solvent during formation of the photosensitive layer, and the viscosity of the charge transport layer coating solution or single layer type photosensitive layer coating solution is increased. Not too much. As a result, it becomes easy to form a charge transport layer or a single-layer type photosensitive layer.

[6. Additive]
The photosensitive layer may contain various additives as long as the electrophotographic characteristics of the photoreceptor are not adversely affected. Examples of the additive include a deterioration inhibitor (more specifically, an antioxidant, a radical scavenger, a quencher, or an ultraviolet absorber), a softener, a surface modifier, a bulking agent, a thickener, A dispersion stabilizer, wax, acceptor, donor, surfactant, plasticizer, sensitizer, or leveling agent may be mentioned. Examples of the antioxidant include hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone, or a derivative thereof, an organic sulfur compound, or an organic phosphorus compound.

[7. Middle layer]
The intermediate layer contains, for example, inorganic particles and a resin (interlayer resin) used for the intermediate layer. The presence of the intermediate layer makes it easy to suppress a rise in resistance by smoothing the flow of current generated when the photosensitive member is exposed while maintaining an insulating state to the extent that leakage can be suppressed.

  Examples of the inorganic particles include metal (more specifically, aluminum, iron, copper, etc.) particles, metal oxide (more specifically, titanium oxide, alumina, zirconium oxide, tin oxide, or zinc oxide). Etc.) or non-metal oxide (more specifically, silica etc.) 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 is not particularly limited as long as it is used as a resin for forming the intermediate layer.

  The intermediate layer may contain various additives as long as the electrophotographic characteristics of the photoreceptor are not adversely affected. The additive is the same as the additive for the photosensitive layer.

[8. Photoconductor manufacturing method]
With reference to FIG. 1, an example of the manufacturing method of the photoreceptor 1 will be described. The method for manufacturing the photoreceptor 1 includes, for example, a photosensitive layer forming step. In the photosensitive layer forming step, the photosensitive layer coating solution is applied onto the conductive substrate 2, and the solvent contained in the applied photosensitive layer coating solution is removed to form the photosensitive layer 3. The photosensitive layer coating solution contains at least a charge generating agent, a hole transporting agent, a quinone derivative (1) as an electron transporting agent, a binder resin, and a solvent. The coating solution for the photosensitive layer is prepared by dissolving or dispersing a charge generator, a hole transport agent, a quinone derivative (1) as an electron transport agent, and a binder resin in a solvent. An additive may be added to the photosensitive layer coating solution as necessary.

  The solvent contained in the photosensitive layer coating solution is not particularly limited as long as each component contained in the photosensitive layer coating solution can be dissolved or dispersed. Examples of the solvent include alcohols (more specifically, methanol, ethanol, isopropanol, butanol, etc.), aliphatic hydrocarbons (more specifically, n-hexane, octane, cyclohexane, etc.), aromatics, and the like. Group hydrocarbons (more specifically, benzene, toluene, xylene, etc.), halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, etc.), ethers (more specifically, Are dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, or diethylene glycol dimethyl ether), ketones (more specifically, acetone, methyl ethyl ketone, or cyclohexanone), esters (more specifically, ethyl acetate, or Acetic acid Chill etc.), dimethyl formaldehyde, N, N-dimethylformamide (DMF), or dimethylsulfoxide. These solvents may be used alone or in combination of two or more. Of these solvents, solvents other than halogenated hydrocarbons are preferred in order to improve the workability during production of the photoreceptor 1.

  The photosensitive layer coating solution is prepared by mixing each component and dispersing in a solvent. For mixing or dispersing, for example, a bead mill, a roll mill, a ball mill, an attritor, a paint shaker, or an ultrasonic disperser is used.

  The photosensitive layer coating solution may contain, for example, a surfactant or a leveling agent in order to improve the dispersibility of each component or the surface smoothness of each formed layer.

  The method for applying the photosensitive layer coating solution is not particularly limited as long as it is a method that can uniformly apply the photosensitive layer coating solution 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.

  The method for removing 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 the solvent include heating, reduced pressure, or 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.

  The method for manufacturing the photoreceptor 1 may further include a step of forming the intermediate layer 4 and / or a step of forming the protective layer 5 as necessary. In the step of forming the intermediate layer 4 and the step of forming the protective layer 5, a known method is appropriately selected.

  For example, the photoreceptor 1 is used as an image carrier in an image forming apparatus.

  The photoconductor according to the first embodiment has been described above. According to the photoconductor according to the first embodiment, the white spot phenomenon of the photoconductor can be suppressed.

<Second Embodiment: Image Forming Apparatus>
The second embodiment relates to an image forming apparatus. The image forming apparatus according to the third embodiment includes an image carrier, a charging unit, an exposure unit, a developing unit, and a transfer unit. The charging unit charges the surface of the image carrier to positive polarity. 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 surface of the image carrier to a recording medium while being in contact with the surface of the image carrier. The image carrier is the photoreceptor according to the first embodiment.

  The image forming apparatus according to the third embodiment can suppress the occurrence of the white spot phenomenon. The reason is presumed as follows. In the image forming apparatus according to the third embodiment that employs the direct transfer method, when the image carrier and the recording medium come into contact with each other in the transfer unit, the recording medium tends to be rubbed and charged positively. In the charging portion, the surface of the image carrier is charged to a positive polarity. For this reason, electrostatic repulsion acts between the surface of the image carrier and the frictionally charged recording medium. As a result, it is considered that minute components (for example, paper dust) derived from the recording medium (for example, paper) are difficult to adhere to the surface of the image carrier, and the occurrence of the white spot phenomenon is suppressed.

  Hereinafter, the image forming apparatus 100 will be described with reference to FIG. FIG. 2 shows an example of the configuration of the image forming apparatus 100.

  The image forming apparatus 100 is not particularly limited as long as it is an electrophotographic image forming apparatus. The image forming apparatus 100 may be, for example, a monochrome image forming apparatus or a color image forming apparatus. When the image forming apparatus 100 is a color image forming apparatus, the image forming apparatus 100 employs, for example, a tandem method. Hereinafter, the tandem image forming apparatus 100 will be described as an example.

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

  The image forming unit 40 includes the image carrier 1, a charging unit 42, an exposure unit 44, a developing unit 46, and a transfer unit 48. The image carrier 1 is provided at the center position of the image forming unit 40. The image carrier 1 is provided to be rotatable in the arrow direction (counterclockwise). Around the image carrier 1, a charging unit 42, an exposure unit 44, a developing unit 46, and a transfer unit 48 are provided in order from the upstream side in the rotation direction of the image carrier 1 with the charging unit 42 as a reference. The image forming unit 40 may further include one or both of a cleaning unit (not shown) and a charge removal unit (not shown).

  The charging unit 42 charges the surface of the image carrier 1 to a positive polarity. The charging unit 42 is a non-contact type or contact type charging unit. Examples of the non-contact charging unit 42 include a corotron charger and a scorotron charger. Examples of the contact-type charging unit 42 include a charging roller or a charging brush.

  The image forming apparatus 100 can include a charging roller as the charging unit 42. When charging the surface of the image carrier 1, the charging roller comes into contact with the surface of the image carrier 1. When a minute component adheres to the surface of the image carrier 1, the minute component is pressed against the surface of the image carrier 1 by the charging roller that has come into contact. Thereby, a minute component is easily fixed on the surface of the image carrier 1. However, the image forming apparatus 100 includes the image carrier 1 that can suppress the occurrence of the white spot phenomenon caused by the adhesion of minute components derived from the recording medium P. For this reason, even when the image forming apparatus 100 includes a charging roller as the charging unit 42, it is difficult for minute components to adhere to the surface of the image carrier 1, and the occurrence of the white spot phenomenon can be suppressed.

  The exposure unit 44 exposes the surface of the charged image carrier 1. As a result, an electrostatic latent image is formed on the surface of the image carrier 1. The electrostatic latent image is formed based on image data input to the image forming apparatus 100.

  The developing unit 46 supplies toner to the surface of the image carrier 1 and develops the electrostatic latent image as a toner image.

  The developing unit 46 can clean the surface of the image carrier 1. In other words, the image forming apparatus 100 can employ a so-called cleaner-less method. The developing unit 46 can remove components remaining on the surface of the image carrier 1 (hereinafter sometimes referred to as residual components). An example of the residual component is a toner component, and more specifically, a toner or a free external additive. Another example of the residual component is a non-toner component (micro component), more specifically, paper dust. In the image forming apparatus 100 that employs the cleaner-less method, residual components on the surface of the image carrier 1 are not scraped off by a cleaning unit (for example, a cleaning blade). For this reason, in the image forming apparatus 100 that employs the cleaner-less method, a residual component usually tends to remain on the surface of the image carrier 1. However, the image carrier 1 can suppress the occurrence of the white spot phenomenon caused by the adhesion of minute components derived from the recording medium P. Therefore, even if the image forming apparatus 100 including such an image carrier 1 adopts a cleaner-less method, minute components, particularly paper dust, hardly remains on the surface of the image carrier 1. As a result, the image forming apparatus 100 can suppress the occurrence of the white spot phenomenon.

In order for the developing unit 46 to efficiently clean the surface of the image carrier 1, it is preferable to satisfy the following conditions (a) and (b).
Condition (a): A contact developing method is adopted, and a peripheral speed (rotational speed) difference is provided between the image carrier 1 and the developing unit 46.
Condition (b): The surface potential of the image carrier 1 and the potential of the developing bias satisfy the following formulas (b-1) and (b-2).
0 (V) <potential of developing bias (V) <surface potential of unexposed area of image carrier 1 (V) (b-1)
Development bias potential (V)> Surface potential (V) of the exposure area of the image carrier 1> 0 (V) (b-2)

  When the contact development method shown in the condition (a) is adopted and a peripheral speed difference is provided between the image carrier 1 and the development unit 46, the surface of the image carrier 1 comes into contact with the development unit 46, and the image Adhering components on the surface of the carrier 1 are removed by friction with the developing unit 46. The peripheral speed of the developing unit 46 is preferably faster than the peripheral speed of the image carrier 1.

  Condition (b) assumes that the charging polarity of the toner, the surface potential of the unexposed area of the image carrier 1, the surface potential of the exposed area of the image carrier 1 and the potential of the developing bias are all positive. ing. That is, it is assumed that the development method is a reversal development method. Note that the surface potential of the unexposed area and the exposed area of the image carrier 1 are determined by the charging unit 42 after the toner image is transferred from the image carrier 1 to the recording medium P and the charging unit 42 performs the next round of image bearing. Measured before charging the surface of the body 1.

  When the mathematical expression (b-1) of the condition (b) is satisfied, it acts between the toner remaining on the image carrier 1 (hereinafter sometimes referred to as residual toner) and the unexposed area of the image carrier 1. The electrostatic repulsive force is larger than the electrostatic repulsive force acting between the residual toner and the developing unit 46. Therefore, residual toner in the unexposed area of the image carrier 1 moves from the surface of the image carrier 1 to the developing unit 46 and is collected.

  When the mathematical expression (b-2) of the condition (b) is satisfied, an electrostatic repulsive force that acts between the residual toner and the exposed area of the image carrier 1 acts between the residual toner and the developing unit 46. Smaller than electric repulsion. Therefore, the residual toner in the exposed area of the image carrier 1 is held on the surface of the image carrier 1. The toner held in the exposure area of the image carrier 1 is used as it is for image formation.

  The transfer belt 50 conveys the recording medium P between the image carrier 1 and the transfer unit 48. The transfer belt 50 is an endless belt. The transfer belt 50 is provided to be rotatable in the arrow direction (clockwise).

  The transfer unit 48 transfers the toner image developed by the developing unit 46 from the surface of the image carrier 1 to the recording medium P. When the toner image is transferred from the image carrier 1 to the recording medium P, the image carrier 1 is in contact with the recording medium P. That is, the image forming apparatus 100 employs a so-called direct transfer method. An example of the transfer unit 48 is a transfer roller.

  Each of the image forming units 40a to 40d sequentially superimposes toner images of a plurality of colors (for example, four colors of black, cyan, magenta, and yellow) on the recording medium P on the transfer belt 50. When the image forming apparatus 100 is a monochrome image forming apparatus, the image forming apparatus 100 includes an image forming unit 40a, and the image forming units 40b to 40d are omitted.

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

  The image forming apparatus according to the second embodiment has been described above. The image forming apparatus according to the second embodiment can suppress the occurrence of the white spot phenomenon by including the photoconductor according to the first embodiment as an image carrier.

<Third embodiment: Process cartridge>
The third embodiment relates to a process cartridge. A process cartridge according to the third embodiment includes the photoconductor according to the first embodiment. Next, the process cartridge according to the third embodiment will be described with reference to FIG. The process cartridge includes a unitized image carrier 1. The process cartridge employs a configuration in which at least one selected from the group consisting of the charging unit 42, the exposure unit 44, the developing unit 46, and the transfer unit 48 is unitized in addition to the image carrier 1. The process cartridge corresponds to each of the image forming units 40a to 40d, for example. The process cartridge may further include one or both of a cleaning device (not shown) and a static eliminator (not shown). The process cartridge is designed to be detachable from the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and when the sensitivity characteristics and the like of the image carrier 1 are deteriorated, the process cartridge can be easily and quickly replaced including the image carrier 1.

  As described above, the process cartridge according to the third embodiment is provided. The process cartridge according to the third embodiment can suppress the occurrence of the white spot phenomenon by including the photoconductor according to the first embodiment as an image carrier.

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

<1. Photosensitive Material>
The following electron transport agent, hole transport agent, charge generator, and binder resin were prepared as materials for forming the photosensitive layer of the photoreceptor.

[1-1. Electron transport agent]
Quinone derivatives (1-1) to (1-7) were prepared as electron transport agents. The quinone derivatives (1-1) to (1-7) were produced by the following methods, respectively.

[1-1-1. Production of quinone derivative (1-1)]
A quinone derivative (1-1) according to the reaction represented by the reaction formula (r-1) and the reaction formula (r-2) (hereinafter sometimes referred to as the reaction (r-1) and (r-2), respectively). ) Was manufactured.

  In reaction (r-2), the naphthol derivative (1C) which is an intermediate product was obtained by reacting the naphthol derivative (1A) (1-naphthol) with the alcohol derivative (1B). Specifically, 1.44 g (0.010 mol) of naphthol derivative (1A), 1.57 g (0.010 mol) of alcohol derivative (1B), and 30 mL of acetic acid were charged into a flask to prepare an acetic acid solution. Concentrated sulfuric acid 0.98g (0.010mol) was dripped at the flask contents, and it stirred at room temperature for 8 hours. Ion exchange water and chloroform were added to the flask contents to obtain an organic layer. The organic layer was washed with an aqueous sodium hydroxide solution and neutralized. Subsequently, anhydrous sodium sulfate was added to the organic layer, and the organic layer was dried. The dried organic layer was distilled off under reduced pressure to obtain a crude product containing a naphthol derivative (1C).

  In the reaction (r-2), the naphthol derivative (1C) was oxidized to obtain a quinone derivative (1-1). Specifically, a crude product containing a naphthol derivative (1C) and 100 mL of chloroform were charged into a flask to prepare a chloroform solution. 2.46 g (0.010 mol) of chloranil was added to the flask contents and stirred at room temperature for 8 hours. Subsequently, the contents of the flask were filtered to obtain a filtrate. The solvent of the obtained filtrate was distilled off to obtain a residue. The residue obtained by silica gel column chromatography was purified using chloroform as a developing solvent. Thereby, a quinone derivative (1-1) was obtained. The yield of the quinone derivative (1-1) was 1.68 g, and the yield of the quinone derivative (1-1) from the naphthol derivative (1A) was 60 mol%.

[1-1-2. Production of quinone derivatives (1-2) to (1-7)]
Except for changing the following points, quinone derivatives (1-2) to (1-7) were produced in the same manner as in the production of the quinone derivative (1-1). In addition, each raw material used in manufacture of a quinone derivative (1-2)-(1-7) was added by the same mole number as the mole number of a corresponding raw material in manufacture of a quinone derivative (1-1).

  Table 1 shows the naphthol derivative (A), alcohol derivative (B), and naphthol derivative (C) in the reaction (r-1). In Table 1, 1A in the naphthol derivative (A) column indicates the naphthol derivative (1A). 1B to 7B in the column of alcohol derivative (B) represent alcohol derivatives (1B) to (7B), respectively. 1C-7C in the naphthol derivative (C) column represents naphthol derivatives (1C)-(7C), respectively.

  The alcohol derivative (1B) used in the reaction (r-1) was changed to any of the alcohol derivatives (2B) to (7B). As a result, in reaction (r-1), crude products containing naphthol derivatives (2C) to (7C), respectively, were obtained instead of naphthol derivative (1C).

  Table 1 shows the naphthol derivative (C) and the quinone derivative (1) in the reaction (r-2). In Table 1, 1-1 to 1-7 in the quinone derivative (1) column represent quinone derivatives (1-1) to (1-7), respectively. The crude product containing the naphthol derivative (1C) used in the reaction (r-2) was changed to a crude product containing any one of the naphthol derivatives (2C) to (7C). As a result, in reaction (r-2), quinone derivatives (1-2) to (1-7) were obtained instead of quinone derivative (1-1), respectively.

  Table 1 shows the yield and yield of the quinone derivative (1). In Table 1, alcohol derivatives (2B) to (7B) are represented by the following chemical formulas (2B) to (7B), respectively. Naphthol derivatives (2C) to (7C) are represented by the following chemical formulas (2C) to (7C), respectively.

Next, ¹ H-NMR spectra of the produced quinone derivatives (1-1) to (1-7) were measured using a proton nuclear magnetic resonance spectrometer (manufactured by JASCO Corporation, 300 MHz). CDCl ₃ was used as the solvent. Tetramethylsilane (TMS) was used as an internal standard sample. Of these, the quinone derivative (1-1) is given as a representative example. FIG. 3 shows the ¹ H-NMR spectrum of the quinone derivative (1-1). In FIG. 3, the vertical axis represents signal intensity (unit: arbitrary unit), and the horizontal axis represents chemical shift (unit: ppm). The chemical shift value of the quinone derivative (1-1) is shown below.
Quinone derivative (1-1): ¹ H-NMR (300 MHz, CDCl ₃ ) δ = 8.30 (d, 2H), 7.18-7.74 (m, 16H), 4.57 (q, 2H) , 1.50 (d, 6H).

^{From the 1} H-NMR spectrum and the chemical shift value, it was confirmed that the quinone derivative (1-1) was obtained. Similarly, other quinone derivatives (1-2) to (1-7) have quinone derivatives (1-2) to (1-7) obtained from ¹ H-NMR spectrum and chemical shift value, respectively. It was confirmed.

[1-1-3. Preparation of compounds (E-1) to (E-2)]
As electron transporting agents, compounds represented by chemical formulas (E-1) to (E-2) (hereinafter sometimes referred to as compounds (E-1) to (E-2), respectively) were prepared.

[1-2. Hole transport agent]
The compound (H-1) described in the first embodiment was prepared as a hole transport agent.

[1-3. Charge generator]
As the charge generating agent, the compound (C-1) described in the first embodiment was prepared. The compound (C-1) was a metal-free phthalocyanine (X-type metal-free phthalocyanine) represented by the chemical formula (C-1). The crystal structure of the compound (C-1) was X type.

[1-4. Binder resin]
The polycarbonate resins (R-1) and (R-2) described in the first embodiment were prepared as binder resins.

<2. Manufacture of single layer type photoreceptor>
Using the material for forming the photosensitive layer, single layer type photoreceptors (A-1) to (A-14) and single layer type photoreceptors (B-1) to (B-4) were produced.

[2-1. Production of Single Layer Type Photoreceptor (A-1)]
In the container, 2 parts by mass of the compound (C-1) as a charge generating agent, 50 parts by mass of the compound (H-1) as a hole transporting agent, and 30 parts by mass of the quinone derivative (1-1) as an electron transporting agent Then, 100 parts by mass of polycarbonate resin (R-1) as a binder resin and 600 parts by mass of tetrahydrofuran as a solvent were added. The contents of the container were mixed for 12 hours using a ball mill to disperse the material in the solvent. This obtained the coating liquid for single layer type photosensitive layers. The single-layer photosensitive layer coating solution was coated on an aluminum drum-shaped support as a conductive substrate using a dip coating method. The applied coating liquid for single-layer type photosensitive layer was dried with hot air at 120 ° C. for 80 minutes. As a result, a single-layer type photosensitive layer (thickness 30 μm) was formed on the conductive substrate. As a result, a single layer type photoreceptor (A-1) was obtained.

[2-2. Production of Single Layer Type Photoconductors (A-2) to (A-14) and Single Layer Type Photoconductors (B-1) to (B-4)]
The single-layer photoconductors (A-2) to (A-14) and the single-layer photoconductor (A-14) and the single-layer photoconductor (A-1) are manufactured in the same manner as in the production of the single-layer photoconductor (A-1) except for the following points. B-1) to (B-4) were produced. The quinone derivative (1-1) as the electron transport agent used for the production of the single-layer type photoreceptor (A-1) was changed to the type of electron transport agent shown in Table 2. The binder resin used for the production of the single layer type photoreceptor (A-1) was changed to the type of binder resin shown in Table 2. Table 2 shows configurations of the photoconductors (A-1) to (A-14) and the photoconductors (B-1) to (B-4). In Table 2, resin, HTM, and ETM indicate a binder resin, a hole transport agent, and an electron transport agent, respectively. In Table 2, R-1 and R-2 in the resin column indicate polycarbonate resins (R-1) and (R-2), respectively. H-1 in the HTM column represents the compound (H-1). 1-1 to 1-7 and E-1 to E-2 in the ETM column represent quinone derivatives (1-1) to (1-7) and compounds (E-1) to (E-2), respectively. .

<3. Evaluation of photoconductor>
[3-1. Evaluation of electrical characteristics (sensitivity characteristics) of single-layer type photoconductor]
The electrical characteristics (sensitivity characteristics) were evaluated for each of the produced single layer type photoreceptors (A-1) to (A-14) and single layer type photoreceptors (B-1) to (B-4). . The electrical characteristics were evaluated in an environment with a temperature of 23 ° C. and a humidity of 50% RH (relative humidity).

Using a drum sensitivity tester (Gentec Co., Ltd.), the surface of the single layer type photoreceptor was charged to positive polarity. The charging condition was set to 31 rpm for the single layer type photoreceptor. The surface potential of the single-layer type photoreceptor immediately after charging was set to + 600V. Next, monochromatic light (wavelength 780 nm, half-value width 20 nm, light energy 1.5 μJ / cm ² ) was extracted from the white light of the halogen lamp using a bandpass filter. The surface of the monolayer type photoreceptor was irradiated with the extracted monochromatic light. The surface potential of the single-layer photoreceptor was measured after 0.5 seconds had elapsed from the end of irradiation. The measured surface potential was defined as a sensitivity potential (V _L , unit V). Table 2 shows the measured sensitivity potential (V _L ) of the single-layer type photoreceptor. Note that the smaller the absolute value of the sensitivity potential (V _L ), the better the sensitivity characteristics of the single layer type photoreceptor.

[3-2. Evaluation of electrical characteristics (friction charging) of single-layer type photoconductor]
The amount of charge of the calcium carbonate (the amount of triboelectric charge) when the photosensitive layer and the calcium carbonate were rubbed was measured. Calcium carbonate is the main component of paper powder. Hereinafter, a method for measuring the triboelectric charge amount of calcium carbonate when the photosensitive layer 3 and calcium carbonate are rubbed will be described with reference to FIG. FIG. 4 shows an outline of a triboelectric charge measuring device. The triboelectric charge amount of calcium carbonate was measured by performing the following first step, second step, third step and fourth step. A jig 10 was used to measure the triboelectric charge amount of calcium carbonate.

  As shown in FIG. 4, the jig 10 includes a first table 12, a rotation shaft 14, a rotation drive unit 16 (for example, a motor), and a second table 18. The rotation drive unit 16 rotates the rotation shaft 14. The rotation shaft 14 rotates around the rotation axis S of the rotation shaft 14. The first table 12 is integrated with the rotation shaft 14 and rotates about the rotation axis S. The second base 18 is fixed without rotating.

(First step)
In the first step, two photosensitive layers 3 were prepared. Hereinafter, one of the photosensitive layers 3 is referred to as a first photosensitive layer 30, and the other of the photosensitive layers 3 is referred to as a second photosensitive layer 32. Photosensitive layer coating solution prepared when producing any one of the above-described single layer type photoreceptors (A-1) to (A-14) and single layer type photoreceptors (B-1) to (B-4). Was applied to an overhead projector sheet (hereinafter sometimes referred to as an OHP sheet) wound around an aluminum pipe (diameter: 78 mm). The applied coating solution was dried at 120 ° C. for 80 minutes. As a result, a sheet for evaluation of triboelectric chargeability on which the photosensitive layer 3 having a film thickness of 30 μm was formed was produced. As a result, a first sheet provided with the first photosensitive layer 30 (film thickness L1: 30 μm) and the first OHP sheet 20, and a second photosensitive layer 32 (film thickness L2: 30 μm) and the second OHP sheet 22 are provided. A second sheet was obtained. The size of the first OHP sheet 20 and the second OHP sheet 22 was 5 cm in length and 5 cm in width, respectively.

(Second step)
In the second step, 0.007 g of calcium carbonate was placed on the first photosensitive layer 30. Then, the second photosensitive layer 32 was placed on the calcium carbonate layer 24. The specific procedure was as follows.

  First, the first OHP sheet 20 and the first table 12 were bonded using a double-sided tape, and the first sheet was fixed to the first table 12. The second OHP sheet 22 and the second table 18 were bonded using a double-sided tape, and the second sheet was fixed to the second table 18. On the first photosensitive layer 30 provided in the first sheet, 0.007 g of calcium carbonate was placed, and the calcium carbonate layer 24 was formed so that the film thickness was uniform. In the third step, the amount of calcium carbonate is such that the calcium carbonate is sufficiently and uniformly rubbed between the first photosensitive layer 30 and the second photosensitive layer 32 in a rotation time of 60 seconds, and the calcium carbonate is sufficiently uniform. The amount that can be charged. The calcium carbonate layer 24 is formed on the first photosensitive layer 30 around the rotation axis S so as not to fall off between the first photosensitive layer 30 and the second photosensitive layer by the rotation of the rotation driving unit 16 in the third step. It is formed inside. Then, the second photosensitive layer 32 and the calcium carbonate layer 24 are brought into contact with each other so that the first photosensitive layer 30 and the second photosensitive layer 32 face each other with the calcium carbonate layer 24 interposed therebetween. A second photosensitive layer 32 was placed thereon. Accordingly, the first table 12, the first OHP sheet 20, the first photosensitive layer 30, the calcium carbonate layer 24, the second photosensitive layer 32, the second OHP sheet 22, and the second table 18 are arranged in this order from the bottom. It was. The centers of the first table 12, the first OHP sheet 20, the first photosensitive layer 30, the calcium carbonate layer 24, the second photosensitive layer 32, the second OHP sheet 22, and the second table 18 pass through the rotation axis S. Arranged.

(Third step)
In the third step, the first photosensitive layer 30 was rotated at a rotational speed of 60 rpm for 60 seconds in an environment of a temperature of 23 ° C. and a humidity of 50% RH while the second photosensitive layer 32 was fixed. Specifically, the rotation drive unit 16 is configured to rotate the rotation shaft 14, the first table 12, the first OHP sheet 20, and the first photosensitive layer 30 around the rotation axis S at a rotation speed of 60 rpm for 60 seconds. Was driven. Thereby, calcium carbonate was rubbed between the first photosensitive layer 30 and the second photosensitive layer 32, and the calcium carbonate was charged.

(Fourth step)
In the fourth step, the calcium carbonate charged in the third step was taken out from the jig 10 and sucked using a charge amount measuring device (a suction type small charge amount measuring device, “MODEL 212HS” manufactured by Trek). The total amount of electricity Q (unit μC) and mass M (unit g) of the sucked calcium carbonate were measured using a charge amount measuring device. The triboelectric charge amount (unit μC / g) of calcium carbonate was calculated from the formula “triboelectric charge amount = Q / M”.

  Table 2 shows the measured triboelectric charge amount of calcium carbonate. In addition, it shows that calcium carbonate is easy to be positively charged with respect to the 1st photosensitive layer 30 and the 2nd photosensitive layer 32, so that the triboelectric charge amount of calcium carbonate is a large positive value. Moreover, it shows that the 1st photosensitive layer 30 and the 2nd photosensitive layer 32 are easy to be negatively charged with respect to calcium carbonate, so that the triboelectric charge amount of calcium carbonate is a large positive value.

[3-3. Evaluation of image characteristics (measurement of the number of white spots)]
For each of the single layer type photoreceptors (A-1) to (A-14) (Examples 1 to 14) and the single layer type photoreceptors (B-1) to (B-4) (Comparative Examples 1 to 4) On the other hand, the image characteristics were evaluated. The evaluation of image characteristics was performed in an environment of a temperature of 32.5 ° C. and a humidity of 80% RH. As an evaluation machine, an image forming apparatus (“monochrome printer FS-1300D” manufactured by Kyocera Document Solutions Co., Ltd.) was used. This image forming apparatus employs a non-contact development method, a direct transfer method, and a blade cleaning method. In this image forming apparatus, a scorotron charger is provided as a charging unit. As a recording medium, “Kyocera Document Solutions Brand Paper VM-A4” (A4 size) sold by Kyocera Document Solutions Inc. was used. A one-component developer (prototype) was used for evaluation by the evaluation machine.

  Using an evaluation machine, images I (images with a printing rate of 1%) were continuously printed on 20,000 sheets of recording media under the condition of a single layer type photoreceptor rotating at 168 mm / sec. Subsequently, an image II (black solid image, length 285 mm × width 197 mm, A4 size) was printed on one recording medium. The recording medium on which the image II was formed was observed with the naked eye, and the presence or absence of image defects in the formed image was observed. As the image defect, the number of white spots appearing in the black solid image was counted. When paper dust adheres to the photoreceptor, white spots tend to appear in the black solid image. Table 2 shows the number of white spots appearing in the black solid image. It is shown that the smaller the number of white spots, the more the occurrence of image defects (occurrence of white spot phenomenon) due to the adhesion of paper dust is suppressed.

  As shown in Table 2, in the photoreceptors (A-1) to (A-14), the single-layer type photosensitive layer has a charge generator, a hole transport agent, and a quinone derivative (1-1) as an electron transport agent. Any one of-(1-7) and binder resin were contained. The quinone derivatives (1-1) to (1-7) were quinone derivatives represented by the general formula (1). In the photoreceptors (A-1) to (A-14), the triboelectric charge amount of calcium carbonate was 8.1 μC / g or more and 9.4 μC / g or less.

  In the photoconductors (A-1) to (A-14), the number of white spots was 27 or more and 39 or less.

  As shown in Table 2, in the photoreceptors (B-1) to (B-4), the single-layer type photosensitive layer includes a compound (E-1) as a charge generator, a hole transport agent, and an electron transport agent. It contained any one of (E-2) and a binder resin. Compounds (E-1) to (E-2) were not quinone derivatives (1). The triboelectric charge amount of calcium carbonate was +5.0 μC / g or more and +6.3 μC / g or less.

  In the photoreceptors (B-1) to (B-4), the number of white spots was 65 or more and 96 or less.

  Photoconductors (A-1) to (A-14) containing a quinone derivative represented by the general formula (1) are photoconductors (B-1) containing compounds (E-1) to (E-2). ) To (B-4), it is clear that the occurrence of the white spot phenomenon can be suppressed. Further, the image forming apparatus including the photoconductors (A-1) to (A-14) suppresses the occurrence of the white spot phenomenon as compared with the image forming apparatus including the photoconductors (B-1) to (B-4). Obviously you can.

  The photoreceptor and the process cartridge according to the present invention can be used in an image forming apparatus. The image forming apparatus according to the present invention can be used in a copying machine and a printer.

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 2 Conductive base | substrate 3 Photosensitive layer 3c Single layer type photosensitive layer

Claims (10)

An electrophotographic photosensitive member comprising a conductive substrate and a photosensitive layer,
The photosensitive layer is a single-layer photosensitive layer containing a charge generating agent, an electron transport agent, a hole transport agent, and a binder resin,
The electron transport agent includes a quinone derivative represented by the general formula (1),
The electrophotographic photosensitive member, wherein a charge amount of the calcium carbonate when the photosensitive layer and the calcium carbonate are rubbed is 7 μC / g or more.

In the general formula (1),
R ¹ is an alkyl group having 1 to 8 carbon atoms which may have a substituent, an aryl group having 6 to 14 carbon atoms which may have an alkyl group having 1 to 6 carbon atoms, And a group selected from the group consisting of cycloalkyl groups having 3 to 10 carbon atoms,
The group is substituted with one or more halogen atoms;
The two R ^{1 s} may be the same or different from each other;
R ² represents a hydrogen atom, an optionally substituted alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 14 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or Represents a heterocyclic group having 3 to 14 carbon atoms which may have a substituent;
Two R ^{2 s} may be the same as or different from each other. In the general formula (1),
R ¹ represents an alkyl group having 1 to 5 carbon atoms which may have an aryl group having 6 to 14 carbon atoms,
At least one of the aryl group and the alkyl group represented by R ¹ is substituted with one or a plurality of the halogen atoms,
Two R ¹ 's are identical to each other;
R ² represents a hydrogen atom,
The electrophotographic photosensitive member according to claim 1, wherein two R ² are the same as each other. In the general formula (1),
The electrophotographic photosensitive member according to claim 1, wherein the total number of the halogen atoms contained in the two groups represented by R ¹ is 4 or more. The electrophotographic photosensitive member according to claim 1, wherein the hole transport agent includes a compound represented by the general formula (2).

In the general formula (2),
R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , and R ²⁶ each independently represents an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms,
r, s, v, and w each independently represent an integer of 0 to 5,
t and u each independently represents an integer of 0 or more and 4 or less. The electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the binder resin contains a polycarbonate resin represented by the general formula (3).

In the general formula (3),
R ³¹ , R ³² , R ³³ , and R ³⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
R ³² and R ³³ may represent a cycloalkylidene group having 3 to 10 carbon atoms formed by bonding to each other;
m and n are integers of 0 or more, satisfying m + n = 100,
n represents an integer of 60 or more and 100 or less.   A process cartridge comprising the electrophotographic photosensitive member according to claim 1. An image carrier;
A charging unit that charges the surface of the image carrier positively;
An exposure unit that exposes the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier;
A developing unit for developing the electrostatic latent image as a toner image;
A transfer unit that transfers the toner image from the surface of the image carrier to a recording medium while being in contact with the surface of the image carrier;
An image forming apparatus, wherein the image carrier is the electrophotographic photosensitive member according to any one of claims 1 to 5.   The image forming apparatus according to claim 7, wherein the charging unit is a charging roller.   The image forming apparatus according to claim 7, wherein the developing unit develops the electrostatic latent image as the toner image while being in contact with the surface of the image carrier.   The image forming apparatus according to claim 7, wherein the developing unit cleans the surface of the image carrier.

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