JP6481650B2 - Electrophotographic photoreceptor - Google Patents

Description

  The present invention relates to a naphthalene tetracarbodiimide derivative and an electrophotographic photosensitive member.

  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 2005-154444 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 a naphthalene tetracarbodiimide derivative that suppresses the occurrence of the white spot phenomenon of an electrophotographic photosensitive member. Another object of the present invention is to provide an electrophotographic photosensitive member that suppresses the occurrence of a white spot phenomenon.

  The naphthalene tetracarbodiimide derivative of the present invention is represented by the general formula (1).

In the general formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 6 carbon atoms and a phenylcarbonyl group, which may have any of 6 to 14 carbon atoms. And a group selected from the group consisting of an aryl group having 7 to 20 carbon atoms, an alkyl group having 1 to 8 carbon atoms, and a cycloalkyl group having 3 to 10 carbon atoms. The group may be substituted with one or more halogen atoms. At least one of R ¹ and R ² has one or more halogen atoms.

  The electrophotographic photosensitive member of the present invention includes a conductive substrate and a photosensitive layer. The photosensitive layer contains a charge generating agent, a hole transporting agent, a binder resin, and the naphthalene tetracarbodiimide derivative described above.

  The naphthalene tetracarbodiimide derivative of the present invention can suppress the generation of white spots on an electrophotographic photoreceptor. In addition, according to the electrophotographic photosensitive member of the present invention, the occurrence of the white spot phenomenon can be suppressed.

(A), (b) and (c) are schematic sectional views showing examples of the electrophotographic photosensitive member according to the second embodiment of the present invention, respectively. (A), (b) and (c) is a schematic sectional drawing which shows another example of the electrophotographic photoreceptor which concerns on 2nd embodiment of this invention, respectively. ^{1 is} a ¹ H-NMR spectrum of a naphthalene tetracarbodiimide derivative (1-1) according to a first embodiment of the present invention. 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 3 carbon atoms, an aryl group having 6 to 14 carbon atoms, carbon An aralkyl group having 7 to 20 atoms, an aralkyl group having 7 to 9 carbon atoms, and a cycloalkyl group having 3 to 10 carbon atoms have the following meanings unless otherwise specified.

  As a halogen atom, a fluorine atom, a chlorine atom, or a bromine atom is mentioned, for example.

  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, s-butyl group, t-butyl group, pentyl group, isopentyl group, A neopentyl group, n-hexyl group, n-heptyl group, or n-octyl group may be mentioned.

  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, s-butyl group, t-butyl group, pentyl group, isopentyl group, A neopentyl group or a hexyl group is mentioned.

  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.

  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.

  An aralkyl group having 7 to 20 carbon atoms is unsubstituted. The aralkyl group having 7 to 20 carbon atoms is a group in which an aryl group having 6 to 14 carbon atoms and an alkyl group having 1 to 6 carbon atoms are bonded. The alkyl group having 1 to 6 carbon atoms in the aralkyl group having 7 to 20 carbon atoms is linear or branched and unsubstituted. Examples of the aralkyl group having 7 to 20 carbon atoms include phenylmethyl group (benzyl group), 2-phenylethyl group (phenethyl group), 1-phenylethyl group, 3-phenylpropyl group, and 4-phenylbutyl. Groups.

  Aralkyl groups having 7 to 9 carbon atoms are unsubstituted. The aralkyl group having 7 to 9 carbon atoms is a group in which a phenyl group and an alkyl group having 1 to 3 carbon atoms are bonded. Examples of the aralkyl group having 7 to 9 carbon atoms include a phenylmethyl group, a 2-phenylethyl group, a 1-phenylethyl group, and a 3-phenylethyl group.

  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.

<First embodiment: Naphthalene tetracarbodiimide derivative>
[1. Naphthalene tetracarbodiimide derivative]
The first embodiment of the present invention relates to a naphthalene tetracarbodiimide derivative. The naphthalene tetracarbodiimide derivative according to the first embodiment is represented by the general formula (1). Hereinafter, the naphthalene tetracarbodiimide derivative represented by the general formula (1) may be referred to as a naphthalene tetracarbodiimide derivative (1).

In general formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 6 carbon atoms and a phenylcarbonyl group which may have any of 6 to 14 carbon atoms. A group selected from the group consisting of an aryl group, an aralkyl group having 7 to 20 carbon atoms, an alkyl group having 1 to 8 carbon atoms, and a cycloalkyl group having 3 to 10 carbon atoms. The group may be substituted with one or more halogen atoms. At least one of R ¹ and R ² has one or more halogen atoms.

  The naphthalene tetracarbodiimide derivative (1) according to the first embodiment can suppress the white spot phenomenon of the photoreceptor. 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 photoreceptor to a recording medium. 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 of the photoconductor and the chargeability tends to decrease, or tends to be charged to the opposite 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 later in detail in the examples.

  The naphthalene tetracarbodiimide derivative (1) according to the first embodiment has a halogen atom. For this reason, when the photosensitive layer of the photoreceptor contains the naphthalene tetracarbodiimide derivative (1), the recording medium has the same polarity as the charged polarity of the photoreceptor even if the recording medium rubs against the surface of the photoreceptor in the transfer portion. Therefore, the chargeability tends not to decrease and the reverse charge tends to hardly occur. Therefore, it is considered that minute components are less likely to adhere to the surface of the photoreceptor, and the occurrence of the white spot phenomenon is suppressed.

Subsequently, the naphthalenetetracarbodiimide derivative (1) according to the first embodiment will be described. In general formula (1), the aryl group having 6 to 14 carbon atoms represented by R ¹ and R ² is preferably a phenyl group. The aryl group having 6 to 14 carbon atoms may have a substituent. Examples of such a substituent include a halogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenylcarbonyl group, and a chlorine atom, a methyl group, an ethyl group, or a phenylcarbonyl group is preferable. The number of substituents is preferably an integer of 1 or more and 3 or less. When the aryl group having 6 to 14 carbon atoms is a phenyl group, the substitution position of the substituent in the phenyl group is, for example, an ortho position (o position), a meta position relative to the position where the phenyl group is bonded to the nitrogen atom. Position (m-position), para-position (p-position), or at least two of these. Examples of the phenyl group having a substituent include 4-chloro-2-phenylcarbonylphenyl group, 2,6-dichlorophenyl group, 2,4,6-trichlorophenyl group, and 2-ethyl-6-methylphenyl group. Can be mentioned.

In general formula (1), the aralkyl group having 7 to 20 carbon atoms represented by R ¹ and R ² is preferably an aralkyl group having 7 to 9 carbon atoms, and more preferably a 1-phenylethyl group. The aralkyl group having 7 to 20 carbon atoms may have a substituent. Examples of such a substituent include an alkyl group having 1 to 6 carbon atoms or a halogen atom. Examples of the aralkyl group having 7 to 20 carbon atoms having a halogen atom include 1- (2,4-dichlorophenyl) ethyl group.

In general formula (1), R ¹ and R ² may be the same or different. When R ¹ and R ² are the same as each other, R ¹ and R ^{2 each} have one or more aralkyl groups having 7 or more and 9 or less halogen atoms, or one phenylcarbonyl group and one halogen atom. It preferably represents an aryl group having 6 to 14 carbon atoms.

In the general formula (1), when R ¹ and R ² are different from each other, ^one of R ¹ and R ² has 6 to 14 carbon atoms having at least one alkyl group having 1 to 3 carbon atoms. The following aryl groups are represented, and the other of R ¹ and R ² may have an aralkyl group having 7 or more and 9 or less carbon atoms having one or more halogen atoms, or may have a phenylcarbonyl group. It is preferable to represent an aryl group having 6 to 14 carbon atoms having an atom.

In general formula (1), the groups represented by R ¹ and R ² may be substituted with one or more halogen atoms, and at least one of R ¹ and R ² has one or more halogen atoms. The number of halogen atoms included in the groups represented by R ^1, the total number of the number of halogen atoms included in the groups represented by R ² is an integer of 1 or more, preferably 3 or 4.

  Specific examples of the naphthalene tetracarbodiimide derivative (1) include naphthalene tetracarbodiimide derivatives represented by chemical formulas (1-1) to (1-6) (hereinafter referred to as naphthalene tetracarbodiimide derivatives (1-1) to (1-6). ) May be described.

[2. Method for producing naphthalene tetracarbodiimide derivative (1)]
[2-1. When R ¹ and R ² are different from each other]
In the general formula (1), when R ¹ and R ² are different from each other, the naphthalene tetracarbodiimide derivative (1) is represented by, for example, the reaction formula represented by the reaction formula (R-1) or the reaction formula (R-2). In accordance with or in accordance with the reaction formula and the reaction formula represented by the reaction formula (R-3) (hereinafter may be referred to as reaction (R-1), reaction (R-2) and reaction (R-3), respectively) Manufactured according to similar methods. The production method of the naphthalenetetracarbodiimide derivative (1) includes, for example, reaction (R-1), reaction (R-2), and reaction (R-3).

In reaction (R-1), R ¹ has the same meaning as R ¹ in the general formula (1). R ³ represents an alkyl group, and preferably represents an alkyl group having 1 to 3 carbon atoms.

  In the reaction (R-1), 1 mole equivalent of the compound represented by the general formula (A) (hereinafter sometimes referred to as the compound (A)) and 1 mole equivalent of the general formula (B). A compound (primary amine compound) (hereinafter sometimes referred to as compound (B)) is reacted in the presence of a base to give 1 mole equivalent of a compound represented by general formula (C) (hereinafter, Compound (C)) may be obtained. Compound (C) is an intermediate product. In reaction (R-1), it is preferable to add 1 mol or more and 2.5 mol or less of compound (B) with respect to 1 mol of compound (A). When 1 mol or more of compound (B) is added to 1 mol of compound (A), the yield of compound (C) can be easily improved. On the other hand, when 2.5 mol or less of compound (B) is added to 1 mol of compound (A), unreacted compound (B) hardly remains after reaction (R-1). Purification becomes easy. The reaction temperature for reaction (R-1) is preferably 80 ° C. or higher and 150 ° C. or lower. The reaction time for reaction (R-1) is preferably 1 hour or more and 8 hours or less. Reaction (R-1) can be performed in a solvent. Examples of the solvent include dioxane. The base preferably has low nucleophilicity from the viewpoint of improving the yield of the compound (C). Examples of such a base include N, N-diisopropylethylamine (Hunig base).

In reaction (R-2), R ¹ has the same meaning as R ¹ in the general formula (1). In reaction (R-2), R ³ has the same meaning as R ³ in the reaction (R-1).

  In the reaction (R-2), 1 molar equivalent of the compound (C) is reacted in the presence of an acid, and 1 molar equivalent of the compound represented by the general formula (D) (hereinafter referred to as the compound (D)). There are things). Compound (D) is an intermediate product. In the reaction (R-2), the ester of the compound (C) is hydrolyzed in the presence of an acid to form a dicarboxylic acid, and then the dicarboxylic acid is closed to form a carboxylic anhydride. As a result, compound (D) is produced. The reaction time for reaction (R-2) is preferably 5 hours or longer and 30 hours or shorter. The reaction temperature for reaction (R-2) is preferably 70 ° C or higher and 150 ° C or lower. As the acid, for example, trifluoroacetic acid is preferable. The acid may function as a solvent.

In reaction (R-3), R ¹ and R ² are the same meanings as R ¹ and R ² in the general formula (1).

  In the reaction (R-3), 1 mole equivalent of the compound (D) and 1 mole equivalent of the compound represented by the general formula (E) (primary amine compound) (hereinafter referred to as the compound (E)) Is obtained in the presence of a base to give 1 molar equivalent of naphthalenetetracarbodiimide derivative (1). In reaction (R-3), it is preferable to add 1 mol or more and 2.5 mol or less of compound (E) with respect to 1 mol of compound (D). When 1 mol or more of compound (E) is added with respect to 1 mol of compound (D), the yield of naphthalene tetracarbodiimide derivative (1) is easily improved. On the other hand, when 2.5 mol or less of compound (E) is added to 1 mol of compound (D), unreacted compound (E) hardly remains after reaction (R-3), and naphthalene tetracarbodiimide derivative ( Purification of 1) becomes easy. The reaction temperature for reaction (R-3) is preferably 80 ° C. or higher and 150 ° C. or lower. The reaction time for reaction (R-3) is preferably 1 hour or more and 8 hours or less. Reaction (R-3) can be performed in a solvent. Examples of the solvent include dioxane. From the viewpoint of improving the yield of the naphthalenetetracarbodiimide derivative (1), the base preferably has a low nucleophilicity. Examples of such a base include N, N-diisopropylethylamine (Hunig base).

The manufacturing method of naphthalene tetracarboxylic carbodiimide derivative (1), the reaction of (R-1) ~ order of imidization by primary amines having a primary amine and R ² having R ¹ in (R-3) It may be changed. The naphthalene tetracarbodiimide derivative (1) includes, for example, a reaction formula represented by a reaction formula (R′-1), a reaction formula represented by a reaction formula (R′-2), and a reaction formula represented by a reaction formula (R′-3). (Hereinafter, it may be described as reaction (R′-1), reaction (R′-2) and reaction (R′-3), respectively)) or by a method analogous thereto.

  Specifically, the reaction (R′-1) is the same as the reaction (R-1) except that the compound (B) is changed to the compound (E). Reaction (R′-2) was carried out except that the compound (C) was changed to a compound represented by the general formula (C ′) (hereinafter sometimes referred to as compound (C ′)). The reaction is the same as in 2). In the reaction (R′-3), the compound (D) is changed to a compound represented by the general formula (D ′) (hereinafter sometimes referred to as the compound (D ′)), and the compound (E) is converted into the compound (E). The reaction is the same as the reaction (R-3) except that the reaction is changed to (B). The manufacturing method of a naphthalene tetracarbodiimide derivative (1) includes reaction (R-4), for example.

[2-2. When R ¹ and R ² are the same]
In the general formula (1), when R ¹ and R ² are the same as each other, the naphthalenetetracarbodiimide derivative (1) is represented by, for example, a reaction formula (hereinafter referred to as a reaction (R-4) ) Or by a method analogous thereto. For convenience, in the reaction formula (R-4), R ² in the general formula (1) is replaced with R ¹ .

  In the reaction (R-4), the compound represented by 1 molar equivalent of the chemical formula (F) (hereinafter sometimes referred to as the compound (F)) and 1 molar equivalent of the general formula (G). A compound (primary amine compound) (hereinafter sometimes referred to as compound (G)) is reacted in the presence of a base to obtain 1 molar equivalent of naphthalene tetracarbodiimide derivative (1). In reaction (R-4), it is preferable to add 2 mol or more and 5 mol or less of compound (G) with respect to 1 mol of compound (F). When 2 mol or more of compound (G) is added with respect to 1 mol of compound (F), the yield of naphthalene tetracarbodiimide derivative (1) is easily improved. On the other hand, when 5 mol or less of compound (G) is added to 1 mol of compound (F), unreacted compound (G) hardly remains after reaction (R-4), and naphthalene tetracarbodiimide derivative (1). Is easily purified. The reaction temperature for reaction (R-4) is preferably 80 ° C. or higher and 150 ° C. or lower. The reaction time for reaction (R-4) is preferably from 1 hour to 8 hours. Reaction (R-4) can be performed in a solvent. Examples of the solvent include picoline (methylpyridine). From the viewpoint of improving the yield of the naphthalenetetracarbodiimide derivative (1), the base preferably has a low nucleophilicity. Examples of such a base include N, N-diisopropylethylamine (Hunig base).

  The production method of the naphthalene tetracarbodiimide derivative (1) may include an appropriate 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.).

<Second Embodiment: Electrophotographic Photosensitive Member>
The second embodiment of the present invention relates to an electrophotographic photoreceptor (hereinafter sometimes referred to as a photoreceptor). The photoreceptor includes a conductive substrate and a photosensitive layer. Examples of the photoreceptor include a multilayer electrophotographic photoreceptor (hereinafter sometimes referred to as a multilayer photoreceptor) or a single layer electrophotographic photoreceptor (hereinafter referred to as a single layer photoreceptor). ).

[1. Multilayer photoreceptor]
In the multilayer photoreceptor, the photosensitive layer includes a charge generation layer and a charge transport layer. Hereinafter, the structure of the multilayer photoreceptor will be described with reference to FIG. FIG. 1 shows the structure of a laminated photoreceptor that is an example of the photoreceptor 1 according to the second embodiment.

  In FIG. 1, the photoconductor 1 is a laminated photoconductor. As shown in FIG. 1A, the multilayer photoreceptor as the photoreceptor 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 includes a charge generation layer 3a and a charge transport layer 3b. In order to improve the abrasion resistance of the multilayer photoconductor, as shown in FIG. 1A, a charge generation layer 3a is provided on the conductive substrate 2, and a charge transport layer 3b is provided on the charge generation layer 3a. It is preferable to be provided. As shown in FIG. 1B, in the laminated type photoreceptor as the photoreceptor 1, the charge transport layer 3b is provided on the conductive substrate 2, and the charge generation layer 3a is provided on the charge transport layer 3b. Good.

  As shown in FIG. 1C, the multilayer photoreceptor may include a conductive substrate 2, a photosensitive layer 3, and an intermediate layer (undercoat layer) 4. The intermediate layer 4 is provided between the conductive substrate 2 and the photosensitive layer 3. Further, a protective layer 5 (see FIG. 2) may be provided on the photosensitive layer 3.

  The thicknesses of the charge generation layer 3a and the charge transport layer 3b are not particularly limited as long as the functions as the respective layers can be sufficiently expressed. The thickness of the charge generation layer 3a is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 3 μm or less. The thickness of the charge transport layer 3b is preferably 2 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less.

[2. Single-layer type photoreceptor]
Hereinafter, the structure of the single-layer type photoreceptor will be described with reference to FIG. FIG. 2 shows the structure of a single-layer type photoreceptor that is another example of the photoreceptor 1 according to the second embodiment.

  In FIG. 2, the photoreceptor 1 is a single-layer photoreceptor. As shown in FIG. 2A, the single layer type photoreceptor as the photoreceptor 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. The single layer type photoreceptor includes a single layer type photosensitive layer 3 c as the photosensitive layer 3. The single-layer type photosensitive layer 3 c is a single photosensitive layer 3.

  As shown in FIG. 2B, the single layer type photoreceptor as the photoreceptor 1 may include a conductive substrate 2, a single layer type photosensitive layer 3 c, and an intermediate layer (undercoat layer) 4. . The intermediate layer 4 is provided between the conductive substrate 2 and the single-layer type photosensitive layer 3c. Further, as shown in FIG. 2C, a protective layer 5 may be provided on the single-layer type photosensitive layer 3c.

  The thickness of the single-layer type photosensitive layer 3c is not particularly limited as long as the function as a single-layer type photosensitive layer can be sufficiently expressed. The thickness of the single-layer photosensitive layer 3c is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

  The structure of the photoreceptor 1 has been described above with reference to FIGS.

  The photoreceptor according to the second embodiment includes a photosensitive layer. The photosensitive layer contains a charge generating agent, a hole transport agent, a binder resin, and a naphthalene tetracarbodiimide derivative (1). In the multilayer photoconductor, the charge generation layer contains, for example, a charge generation agent and a binder resin for charge generation agent (hereinafter sometimes referred to as a base resin). The charge transport layer contains, for example, a naphthalene tetracarbodiimide derivative (1), a hole transport agent, and a binder resin as an electron acceptor compound. In the single layer type photoreceptor, the single layer type photosensitive layer contains, for example, a charge generator, a naphthalene tetracarbodiimide derivative (1) as an electron transport agent, a hole transport agent, and a binder resin. The charge generation layer, charge transport layer, and single-layer type photosensitive layer may further contain an additive. Hereinafter, a conductive substrate, an electron transport agent, an electron acceptor compound, a hole transport agent, a charge generating agent, a binder resin, a base resin, an additive, and an intermediate layer will be described as elements of the photoreceptor. In addition, a method for manufacturing the photoreceptor will be described.

[3. 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.

[4. Electron transfer agent, electron acceptor compound]
As already described above, in the multilayer photoreceptor, the charge transport layer contains the naphthalene tetracarbodiimide derivative (1) as an electron acceptor compound. In the single layer type photoreceptor, the single layer type photosensitive layer contains a naphthalene tetracarbodiimide derivative (1) as an electron transport agent. When the photosensitive layer contains the naphthalene tetracarbodiimide derivative (1), the photoreceptor according to the second embodiment can suppress the occurrence of the white spot phenomenon.

  When the photoreceptor is a multilayer photoreceptor, the content of the naphthalene tetracarbodiimide derivative (1) is 10 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the binder resin contained in the charge transport layer. It is more preferable that it is 20 parts by mass or more and 100 parts by mass or less.

  When the photoreceptor is a single layer type photoreceptor, the content of the naphthalene tetracarbodiimide derivative (1) is 10 parts by mass or more and 200 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 10 parts by mass or more and 100 parts by mass or less, and more preferably 10 parts by mass or more and 75 parts by mass or less.

  The charge transport layer may further contain another electron acceptor compound in addition to the naphthalene tetracarbodiimide derivative (1). The single layer type photosensitive layer may further contain another electron transporting agent in addition to the naphthalene tetracarbodiimide derivative (1). Other electron acceptor compounds and electron transport agents include, for example, quinone compounds, diimide compounds (diimide compounds other than naphthalene tetracarbodiimide derivative (1)), hydrazone compounds, malononitrile compounds, thiopyran compounds, and trinitro. Thioxanthone compound, 3,4,5,7-tetranitro-9-fluorenone compound, dinitroanthracene compound, dinitroacridine compound, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, Mention may be made of succinic anhydride, maleic anhydride or dibromomaleic anhydride. Examples of quinone compounds 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.

[5. Hole transport agent]
When the photoreceptor is a multilayer photoreceptor, the charge transport layer may contain a hole transport agent. When the photoreceptor is a single layer type photoreceptor, the single layer type photosensitive layer may contain a 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, 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-methyl) Aminophenyl) -1,3,4-oxadiazole, etc.), styryl compounds (more specifically, 9- (4-diethylaminostyryl) anthracene, etc.), carbazole compounds (more specifically, polyvinylcarbazole, etc.) Organic polysilane compounds, pyrazoline compounds (more specifically, 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline, etc.), hydrazo System compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, or triazole compound. 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 the 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. It is preferable that r, s, v, and w each independently represent 0 or 1. t and u preferably represent 0 or 1, and more preferably represent 1.

  The benzidine derivative 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)).

  When the photoreceptor is a multilayer photoreceptor, the content of the hole transport agent is preferably 10 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the binder resin contained in the charge transport layer. More preferably, it is 20 parts by mass or more and 100 parts by mass or less.

  When the photoreceptor is a single layer type photoreceptor, the content of the hole transport agent is 10 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the binder resin contained in the single layer type photosensitive layer. Is more preferably 10 parts by mass or more and 100 parts by mass or less, and particularly preferably 10 parts by mass or more and 75 parts by mass or less.

[6. Charge generator]
When the photoreceptor is a multilayer photoreceptor, the charge generation layer may contain a charge generation agent. When the photoreceptor is a single layer type photoreceptor, the single layer type photosensitive layer may contain a charge generating agent.

  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 crystals 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). It is done. 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 pigment, more preferably a metal-free phthalocyanine or titanyl phthalocyanine. In order to particularly improve the electrical characteristics of the photoreceptor when the photosensitive layer contains a naphthalene tetracarbodiimide derivative (1), as the charge generator, X-type metal-free phthalocyanine or Y-type titanyl phthalocyanine is more preferable. Titanyl phthalocyanine is particularly preferred. In order to suppress the white spot phenomenon when the photosensitive layer contains the naphthalene tetracarbodiimide derivative (1), the charge generator preferably contains X-type metal-free phthalocyanine or Y-type titanyl phthalocyanine, and X-type metal-free phthalocyanine. It is more preferable to contain.

  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.

(Measuring method of CuKα characteristic X-ray diffraction spectrum)
An example of a method for measuring the CuKα characteristic X-ray diffraction spectrum will be described. A sample (titanyl phthalocyanine) is filled in a sample holder of an X-ray diffractometer (for example, “RINT (registered trademark) 1100” manufactured by Rigaku Corporation), an X-ray tube Cu, a tube voltage 40 kV, a tube current 30 mA, and CuKα. An X-ray diffraction spectrum is measured under the condition of a characteristic X-ray 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.

  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.

[7. 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, 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 resin (acrylic acid derivative adduct of a urethane compound). Can be mentioned. 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. Examples of the polycarbonate resin include a bisphenol Z-type polycarbonate resin represented by the following chemical formula (Resin-1) (hereinafter sometimes referred to as Z-type polycarbonate resin (Resin-1)), a bisphenol ZC-type polycarbonate resin, and bisphenol. C-type polycarbonate resin or bisphenol A-type polycarbonate resin may be mentioned. Z-type polycarbonate resin (Resin-1) is preferable from the viewpoints of good compatibility with the naphthalene tetracarbodiimide derivative (1) and improvement in dispersibility of the naphthalene tetracarbodiimide derivative (1) in the photosensitive layer.

  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.

[8. Base resin]
When the photoreceptor is a multilayer photoreceptor, the charge generation layer contains a base resin. The base resin is not particularly limited as long as it is a base resin applicable to the photoreceptor. Examples of the base resin include a thermoplastic resin, a thermosetting resin, and a photocurable resin. Examples of the thermoplastic resin include styrene-butadiene resin, styrene-acrylonitrile resin, styrene-maleic acid resin, styrene-acrylic acid resin, acrylic resin, polyethylene resin, ethylene-vinyl acetate resin, chlorinated polyethylene resin, poly Vinyl chloride resin, polypropylene resin, ionomer, vinyl chloride-vinyl acetate resin, alkyd resin, polyamide resin, urethane resin, polycarbonate resin, polyarylate resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin or A polyester resin is mentioned. Examples of the thermosetting resin include silicone resins, epoxy resins, phenol resins, urea resins, melamine resins, and other crosslinkable thermosetting resins. 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, an acrylic acrylic resin). Acid derivative adducts, etc.). A base resin may be used individually by 1 type, and may be used in combination of 2 or more type.

  The base resin contained in the charge generation layer is preferably different from the binder resin contained in the charge transport layer. This is because the charge generation layer is not dissolved in the solvent of the charge transport layer coating solution. In the production of a layered photoreceptor, it is common to form a charge generation layer on a conductive substrate and form a charge transport layer on the charge generation layer. This is because when forming the charge transport layer, a charge transport layer coating solution is applied onto the charge generation layer.

[9. Additive]
The photosensitive layer (charge generation layer, charge transport layer, or single layer type photosensitive layer) of the photoreceptor may contain various additives as necessary. 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, donor, surfactant, plasticizer, sensitizer, or leveling agent may be mentioned.

[10. Middle layer]
The intermediate layer (undercoat layer) contains, for example, inorganic particles and a resin (intermediate layer resin) used for the intermediate layer. The presence of the intermediate layer is considered to suppress the increase in resistance by smoothing the flow of current generated when the photosensitive member is exposed while maintaining an insulating state capable of suppressing the occurrence of leakage.

  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 particles (more specifically, silica etc.). 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 can be used as a resin for forming the intermediate layer. The intermediate layer may contain various additives. The additive is the same as the additive for the photosensitive layer.

[11. Photoconductor manufacturing method]
When the photoreceptor is a multilayer photoreceptor, the multilayer photoreceptor is manufactured, for example, as follows. First, a charge generation layer coating solution and a charge transport layer coating solution are prepared. A charge generation layer is formed by applying a coating solution for charge generation layer onto a conductive substrate and drying. Subsequently, the charge transport layer coating liquid is applied on the charge generation layer and dried to form the charge transport layer. Thereby, a laminated photoreceptor is manufactured.

  The charge generation layer coating solution is prepared by dissolving or dispersing the charge generation agent and components added as necessary (for example, base resin and various additives) in a solvent. The coating solution for the charge transport layer is prepared by dissolving or dispersing the electron acceptor compound and components added as necessary (for example, a binder resin, a hole transport agent, and various additives) in a solvent.

  Next, when the photoconductor is a single layer type photoconductor, the single layer type photoconductor is manufactured, for example, as follows. The single-layer type photoreceptor is manufactured by applying a coating solution for a single-layer type photosensitive layer onto a conductive substrate and drying it. The single-layer photosensitive layer coating solution dissolves or disperses an electron transport agent and components added as necessary (for example, a charge generator, a hole transport agent, a binder resin, and various additives) in a solvent. It is manufactured by.

  The solvent contained in the coating solution for charge generation layer, the coating solution for charge transport layer or the coating solution for single layer type photosensitive layer (hereinafter sometimes referred to as coating solution) dissolves each component contained in the coating solution. Or as long as it can disperse | distribute, it does not specifically limit. 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. Hydrocarbons (more specifically, benzene, toluene, xylene, etc.), halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, etc.), ethers (more specifically, , Dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, or propylene glycol monomethyl ether), ketones (more specifically, acetone, methyl ethyl ketone, cyclohexanone, etc.), esters More specifically, ethyl acetate or methyl acetate, etc.), dimethylformamide, dimethyl formamide, or dimethyl sulfoxide and the like. These solvents are used alone or in combination of two or more. In order to improve the workability during the production of the photoreceptor, it is preferable to use a non-halogen solvent (a solvent other than the halogenated hydrocarbon) as the solvent.

  The 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 can be used.

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

  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. 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 drying the coating solution is not particularly limited as long as the solvent in the coating solution can be evaporated. For example, the method of heat-processing (hot-air drying) is mentioned using a high-temperature dryer or a vacuum dryer. 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 addition, the manufacturing method of a photoreceptor may further include one or both of a step of forming an intermediate layer and a step of forming a protective layer as necessary. A known method is appropriately selected in the step of forming the intermediate layer and the step of forming the protective layer.

  The photoreceptor according to the second embodiment has been described above. According to the photoconductor of the second embodiment, the electrical characteristics of the photoconductor can be improved.

  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 transporting agent, hole transporting agent, charge generating agent, and binder resin were prepared as materials for forming the single-layered photosensitive layer of the single-layered photoreceptor.

[1-1. Electron transport agent]
Naphthalene tetracarbodiimide derivatives (1-1) to (1-6) were prepared as electron transport agents. Naphthalene tetracarbodiimide derivatives (1-1) to (1-6) were produced by the following methods, respectively.

[1-1-1. Production of naphthalenetetracarbodiimide derivative (1-1)]
A naphthalene tetracarbodiimide derivative (1-1) was produced according to the reaction represented by the reaction formula (r-4) (hereinafter sometimes referred to as reaction (r-4)).

  In the reaction (r-4), 2.68 g (10 mmol) of the compound (F) (naphthalene-1,4,5,8-tetracarboxylic dianhydride) and the compound represented by the chemical formula (1G) 4. 64 g (20 mmol) and 50 mL of picoline were put into a flask to prepare a picoline solution. The temperature of the flask contents was raised to 100 ° C. and maintained at 100 ° C., and the flask contents were stirred for 4 hours. After the reaction, ion exchange water was put into the flask and extracted with chloroform. The solvent (picoline) in the organic layer was removed to obtain a residue. The obtained residue was purified by silica gel column chromatography using chloroform as a developing solvent. Thereby, a naphthalene tetracarbodiimide derivative (1-1) was obtained. The yield of naphthalene tetracarbodiimide derivative (1-1) was 4.16 g, and the yield of naphthalene tetracarbodiimide derivative (1-1) from compound (F) in reaction (r-4) was 60 mol%. .

[1-1-2. Production of naphthalenetetracarbodiimide derivative (1-5)]
A naphthalene tetracarbodiimide derivative (1-5) was produced in the same manner as in the production of the naphthalene tetracarbodiimide derivative (1-1) except that the following points were changed. In addition, each raw material used in manufacture of a naphthalene tetracarbodiimide derivative (1-5) was added by the same mole number as the mole number of a corresponding raw material in manufacture of a naphthalene tetracarbodiimide derivative (1-1).

  In the production of the naphthalene tetracarbodiimide derivative (1-5), the compound (1G) used in the reaction (r-4) was changed to the compound (5G). As a result, a naphthalene tetracarbodiimide derivative (1-5) was obtained instead of the naphthalene tetracarbodiimide derivative (1-1). Table 1 shows the compound (F), the compound (G), and the naphthalenetetracarbodiimide derivative (1) in the reaction (r-4). In Table 1, F represents compound (F). 1G represents the compound (1G), and 5G represents the compound (5G).

  Table 1 shows the yield and yield of the naphthalene tetracarbodiimide derivative (1). Compound (5G) is represented by chemical formula (5G).

[1-1-3. Production of naphthalenetetracarbodiimide derivative (1-2)]
Reactions represented by reaction formulas (r′-1), (r′-2), and (r′-3) (hereinafter, reaction (r′-1), reaction (r′-2), and reaction (respectively) naphthalene tetracarbodiimide derivative (1-2) was produced according to (which may be described as r′-3).

  In the reaction (r′-1), 3.42 g (10 mmol) of the compound (1A), 1.35 g (10 mmol) of the compound (2E), 1.3 g (10 mmol) of N, N-diisopropylethylamine, Dioxane 50mL was put into the flask to prepare a dioxane solution. The temperature of the flask contents was raised to 100 ° C. and maintained at 100 ° C., and the flask contents were stirred for 2 hours. After the reaction, dioxane was removed to obtain a residue. The residue obtained by silica gel column chromatography was purified using ethyl acetate / hexane (volume ratio V / V = 1/2) as a developing solvent. As a result, an intermediate product represented by the chemical formula (2C ′) (hereinafter sometimes referred to as compound (2C ′)) was obtained.

  In reaction (r′-2), compound (2C ′) and 15 mL of trifluoroacetic acid were charged into a flask to prepare a trifluoroacetic acid solution. Compound (2C ′) was used in reaction (r′-2) in the total amount obtained in reaction (r′-1). The temperature of the flask contents was raised to 80 ° C. and maintained at 80 ° C., and the flask contents were stirred for 24 hours. After the reaction, trifluoroacetic acid was removed to obtain a residue. The residue obtained by silica gel column chromatography was purified using ethyl acetate / hexane (volume ratio V / V = 1/4) as a developing solvent. As a result, an intermediate product represented by the chemical formula (2D ′) (hereinafter sometimes referred to as compound (2D ′)) was obtained.

  In the reaction (r′-3), a compound (2D ′), 2.32 g (10 mmol) of the compound represented by the chemical formula (2B), 1.3 g (10 mmol) of diisopropylethylamine, and 50 mL of dioxane were added to a flask. To prepare a dioxane solution. The temperature of the flask contents was raised to 100 ° C. and maintained at 100 ° C., and the flask contents were stirred for 2 hours. After the reaction, dioxane was removed to obtain a residue. The residue obtained by silica gel column chromatography was purified using ethyl acetate as a developing solvent. Thereby, a naphthalene tetracarbodiimide derivative (1-2) was obtained. The yield of naphthalene tetracarbodiimide derivative (1-2) is 2.69 g, and the yield of naphthalene tetracarbodiimide derivative (1-2) from compound (1A) in reactions (r′-1) to (r′-3) is as follows. The rate was 45 mol%.

[1-1-4. Production of naphthalenetetracarbodiimide derivatives (1-3) to (1-4) and (1-6)]
Except for the following changes, naphthalene tetracarbodiimide derivatives (1-3) to (1-4) and (1-6) were prepared in the same manner as in the production of naphthalene tetracarbodiimide derivative (1-2). Manufactured. In addition, each raw material used in the synthesis | combination of a naphthalene tetracarbodiimide derivative (1-3)-(1-4) and (1-6) is a raw material corresponding in manufacture of a naphthalene tetracarbodiimide derivative (1-2). It was added in the same number of moles as the number of moles.

  In the production of naphthalenetetracarbodiimide derivatives (1-3) to (1-4) and (1-6), the compound (2B) used in the reaction (r′-3) was converted into the compounds (3B), (4B), And (5B). As a result, naphthalene tetracarbodiimide derivatives (1-3), (1-4), and (1-6) were obtained instead of naphthalene tetracarbodiimide derivative (1-2), respectively. Table 2 shows compound (A), compound (D), compound (B), and naphthalene tetracarbodiimide derivative (1) in reactions (r′-1) to (r′-3).

  Table 2 shows the yield and yield of the naphthalene tetracarbodiimide derivative (1). Compounds (3B), (4B), and (6B) are represented by the following chemical formulas (3B), (4B), and (6B), respectively.

Next, ¹ H-NMR spectra of the produced naphthalene tetracarbodiimide derivatives (1-1) to (1-6) 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. Among these, naphthalene tetracarbodiimide derivative (1-1) is given as a representative example. FIG. 3 shows the ¹ H-NMR spectrum of the naphthalene tetracarbodiimide 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 naphthalene tetracarbodiimide derivative (1-1) is shown below.
Naphthalene tetracarbodiimide derivative (1-1): ¹ H-NMR (300 MHz, CDCl ₃ ) δ = 8.70 (d, 4H), 7.62-7.75 (m, 8H), 7.36-7. 55 (m, 8H).

^{From the 1} H-NMR spectrum and the chemical shift value, it was confirmed that the naphthalene tetracarbodiimide derivative (1-1) was obtained. Similarly, other naphthalene tetracarbodiimide derivatives (1-2) to (1-6) are converted into naphthalene tetracarbodiimide derivatives (1-2) to (1-6) by ¹ H-NMR spectrum and chemical shift value, respectively. It was confirmed that it was obtained.

[1-1-5. Preparation of compounds (E-1) to (E-3)]
As electron transporting agents, compounds represented by chemical formulas (E-1) to (E-3) (hereinafter sometimes referred to as compounds (E-1) to (E-3), respectively) were prepared.

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

[1-3. Charge generator]
As the charge generating agent, the compounds (C-1) and (C-2) described in the second embodiment were 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.

  The compound (C-2) was titanyl phthalocyanine (Y-type titanyl phthalocyanine) represented by the chemical formula (C-2). Moreover, the crystal structure of the compound (C-2) was Y type.

[1-4. Binder resin]
As a binder resin, a Z-type polycarbonate resin (Resin-1) (“Panlite (registered trademark) TS-2050” manufactured by Teijin Ltd., viscosity average molecular weight 50,000) was prepared.

<2. Manufacture of single layer type photoreceptor>
Single layer type photoreceptors (A-1) to (A-12) and single layer type photoreceptors (B-1) to (B-6) were produced using the material for forming the photosensitive layer.

[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 a naphthalene tetracarbodiimide derivative (1-1) 30 as an electron transporting agent 100 parts by mass of Z-type polycarbonate resin (Resin-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-12) and Single Layer Type Photoconductors (B-1) to (B-6)]
A single-layer photoconductor (A-2) to (A-12) and a single-layer photoconductor (A-12) and a single-layer photoconductor B-1) to (B-6) were produced. The compound (C-1) as the charge generating agent used in the production of the single layer type photoreceptor (A-1) was changed to the type of charge generating agent shown in Table 3. The naphthalene tetracarbodiimide 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 3. Table 3 shows the configurations of the photoconductors (A-1) to (A-12) and the photoconductors (B-1) to (B-6). In Table 3, CGM, HTM, and ETM represent a charge generator, a hole transport agent, and an electron transport agent, respectively. In Table 3, xH ₂ Pc and Y-TiOPc in the CGM column indicate X-type metal-free phthalocyanine and Y-type titanyl phthalocyanine, respectively. H-1 in the HTM column represents the compound (H-1). 1-1 to 1-6 and E-1 to E-3 in the ETM column are naphthalene tetracarbodiimide derivatives (1-1) to (1-6) and compounds (E-1) to (E-3), respectively. Indicates.

<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 photoreceptors (A-1) to (A-12) and single-layer photoreceptors (B-1) to (B-6). . 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 3 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-12) and single layer type photoreceptors (B-1) to (B-6). 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 centered on the rotation axis S so that the calcium carbonate layer 24 does not fall from between the first photosensitive layer 30 and the second photosensitive layer 32 by driving of the rotation driving unit 16 in the third step. 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 rotated so that the rotation shaft 14, the first table 12, the first OHP sheet 20, and the first photosensitive layer 30 are rotated around the rotation axis S at a rotation speed of 60 rpm for 60 seconds. 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 3 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)]
The image characteristics were evaluated for each of the single layer type photoreceptors (A-1) to (A-12) and the single layer type photoreceptors (B-1) to (B-6). 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 297 mm × width 210 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 3 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 3, in the photoreceptors (A-1) to (A-12), the photosensitive layer has a charge generator, a hole transport agent, and a naphthalene tetracarbodiimide derivative (1-1) as an electron transport agent. Any one of (1-6) was contained. The naphthalene tetracarbodiimide derivatives (1-1) to (1-6) were naphthalene tetracarbodiimide derivatives represented by the general formula (1). In the photoreceptors (A-1) to (A-12), the number of white spots was 13 or more and 24 or less.

  As shown in Table 3, in the photoreceptors (B-1) to (B-6), the photosensitive layer includes compounds (E-1) to (E) as charge generating agents, hole transporting agents, and electron transporting agents. -3) any one of them. Compounds (E-1) to (E-3) were not naphthalene tetracarbodiimide derivatives (1). In the photoconductors (B-1) to (B-6), the number of white spots was 38 or more and 70 or less.

  It is clear that the naphthalene tetracarbodiimide derivatives (1-1) to (1-6) can suppress the occurrence of the white spot phenomenon of the photoreceptor as compared with the compounds (E-1) to (E-3). It is clear that the photoreceptors (A-1) to (A-12) can suppress the occurrence of the white spot phenomenon as compared with the photoreceptors (B-1) to (B-6).

  The naphthalene tetracarbodiimide derivative according to the present invention can be used for a photoreceptor. The photoreceptor according to the present invention can be used in an image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 3 Photosensitive layer 3a Charge generation layer 3b Charge transport layer 3c Single layer type photosensitive layer

Claims (5)

An electrophotographic photosensitive member comprising a conductive substrate and a photosensitive layer,
The photosensitive layer includes a charge generator, a hole transport agent, a binder resin, and naphthalene represented by the chemical formula (1-2), (1-3), (1-4), or (1-6). An electrophotographic photoreceptor containing a tetracarbodiimide derivative.

  The electrophotographic photoreceptor according to claim 1, wherein the naphthalenetetracarbodiimide derivative is represented by the chemical formula (1-3) or (1-4). The charge generating agent comprises an X-type metal-free phthalocyanine or Y type titanyl phthalocyanine, electrophotographic photosensitive member according to claim 1 or 2. 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 photosensitive layer is a single-layer type photosensitive layer, the electrophotographic photoreceptor according to any one of claims 1-4.

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