JP2022181415A - Electrophotographic photoreceptor - Google Patents

Abstract

To provide an electrophotographic photoreceptor which allows for nicely forming a photosensitive layer and offers superior sensitivity characteristics and wear resistance.SOLUTION: A photosensitive layer of an electrophotographic photoreceptor provided herein comprises a charge generating layer and a charge transport layer. The charge generating layer contains a charge generating agent. The charge transport layer contains a hole transport agent, a binder resin, and a phthalocyanine pigment. The binder resin contains a polyarylate resin. The polyarylate resin has four specific repeating units (1), (2), (3), (4). Content of the repeating unit (3) is more than 0% and less than 20% with respect to the total of the repeating units (1) and (3). Content of the phthalocyanine pigment is 0.15-0.50 pts.mass, inclusive, with respect to 100.00 pts.mass of the binder resin. The phthalocyanine pigment is metal-free phthalocyanine or a compound represented by a specific structural formula.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electrophotographic photoreceptor.

An electrophotographic photoreceptor is used as an image carrier in an electrophotographic image forming apparatus (for example, a printer or a multifunction machine). An electrophotographic photoreceptor has a photosensitive layer. As the electrophotographic photoreceptor, for example, a single-layer electrophotographic photoreceptor and a laminated electrophotographic photoreceptor are used. A single-layer electrophotographic photoreceptor includes a single-layer photosensitive layer having a charge generation function and a charge transport function. A laminated electrophotographic photoreceptor includes a photosensitive layer including a charge generation layer having a charge generation function and a charge transport layer having a charge transport function.

Patent Document 1 describes an electrophotographic photoreceptor whose surface layer contains a polyarylate resin obtained from a dihydric carboxylic acid component and a dihydric phenol component represented by the following formula.

JP-A-10-20514

However, the electrophotographic photoreceptor described in Patent Document 1 is insufficient in abrasion resistance. Further, the present inventors have found that the electrophotographic photoreceptor described in Patent Document 1 is insufficient in terms of the solubility of the binder resin in solvents and the sensitivity characteristics.

The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic photoreceptor in which a photosensitive layer can be satisfactorily formed and which has excellent sensitivity characteristics and abrasion resistance.

The electrophotographic photoreceptor of the present invention comprises a conductive substrate and a photosensitive layer. The photosensitive layer includes a charge generation layer and a charge transport layer. The charge generation layer contains a charge generation agent. The charge transport layer contains a hole transport agent, a binder resin, and a phthalocyanine pigment. The binder resin includes polyarylate resin. The polyarylate resin has repeating units represented by formulas (1), (2), (3) and (4). The content of the repeating unit represented by formula (3) with respect to the total number of repeating units represented by formulas (1) and (3) is more than 0% and less than 20%. The content of the phthalocyanine pigment is 0.15 parts by mass or more and 0.50 parts by mass or less with respect to 100.00 parts by mass of the binder resin. The phthalocyanine pigment is a metal-free phthalocyanine or a compound represented by formula (11).

In formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group, and X represents a divalent group represented by formula (X1) or (X2). In formula (2), W represents a divalent group represented by formula (W1) or (W2).

In formula (X1), t represents an integer of 1 or more and 3 or less, and * represents a bond. In formula (X2), R ³ and R ⁴ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ and R ⁴ represent groups different from each other, and * represents a bond. show.

In the formulas (W1) and (W2), * represents a bond.

In formula (11), M represents a metal atom which may have a ligand.

The electrophotographic photoreceptor of the present invention can satisfactorily form a photosensitive layer and is excellent in sensitivity characteristics and abrasion resistance.

1 is a partial cross-sectional view of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. 1 is a partial cross-sectional view of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. 1 is a partial cross-sectional view of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. ¹ H-NMR spectrum of polyarylate resin H;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is by no means limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. It should be noted that descriptions of overlapping descriptions may be omitted as appropriate, but the gist of the invention is not limited. Hereinafter, compounds and derivatives thereof may be collectively referred to by adding "system" to the name of the compound. In addition, when the name of a polymer is expressed by adding "system" to the name of a compound, it means that the repeating unit of the polymer is derived from the compound or its derivative. In addition, "general formula" and "chemical formula" are collectively described as "formula". "Each independently" in the description of the formula means that they may represent the same group or different groups. The phrase "may have a ligand" means that it may be coordinately bonded to a ligand. "Having a ligand" means being coordinately bonded to a ligand. Unless otherwise specified, each component described in this specification may be used singly or in combination of two or more. In this specification, the "sensitivity characteristics" of the electrophotographic photoreceptor include both the sensitivity characteristics for printing solid images and the sensitivity characteristics for printing halftone images.

First, the substituents used in this specification are described. Halogen atoms (halogen groups) include, for example, fluorine atoms (fluoro groups), chlorine atoms (chloro groups), bromine atoms (bromo groups), and iodine atoms (iodo groups).

an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 1 to 3 carbon atoms, and an alkyl group having 1 to 3 carbon atoms; Each alkyl group is straight or branched and unsubstituted unless otherwise specified. Examples of alkyl groups 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, n-pentyl group, 1 -methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylpropyl group, 2-ethylpropyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethyl butyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1-ethylbutyl 2-ethylbutyl and 3-ethylbutyl groups, linear and branched heptyl groups, and linear and branched octyl groups. Examples of an alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 1 to 3 carbon atoms, and an alkyl group having 3 carbon atoms each have Among the groups described as examples of the alkyl group of 1 to 8, it is a group having a corresponding number of carbon atoms.

A perfluoroalkyl group having 1 to 10 carbon atoms, a perfluoroalkyl group having 3 to 10 carbon atoms, a perfluoroalkyl group having 5 to 7 carbon atoms, and a perfluoroalkyl group having 6 carbon atoms are , each is linear or branched and unsubstituted unless otherwise specified. The perfluoroalkyl group having 1 to 10 carbon atoms, for example, trifluoromethyl group, perfluoroethyl group, perfluoro-n-propyl group, perfluoroisopropyl group, perfluoro-n-butyl group, perfluoro -sec-butyl group, perfluoro-tert-butyl group, perfluoro-n-pentyl group, perfluoro-1-methylbutyl group, perfluoro-2-methylbutyl group, perfluoro-3-methylbutyl group, perfluoro-1 -ethylpropyl group, perfluoro-2-ethylpropyl group, perfluoro-1,1-dimethylpropyl group, perfluoro-1,2-dimethylpropyl group, perfluoro-2,2-dimethylpropyl group, perfluoro- n-hexyl group, perfluoro-1-methylpentyl group, perfluoro-2-methylpentyl group, perfluoro-3-methylpentyl group, perfluoro-4-methylpentyl group, perfluoro-1,1-dimethylbutyl group, perfluoro-1,2-dimethylbutyl group, perfluoro-1,3-dimethylbutyl group, perfluoro-2,2-dimethylbutyl group, perfluoro-2,3-dimethylbutyl group, perfluoro-3 ,3-dimethylbutyl group, perfluoro-1,1,2-trimethylpropyl group, perfluoro-1,2,2-trimethylpropyl group, perfluoro-1-ethylbutyl group, perfluoro-2-ethylbutyl group, and perfluoro-3-ethylbutyl group, linear and branched perfluoroheptyl group, linear and branched perfluorooctyl group, linear and branched perfluorononyl group, and linear and branched perfluorodecyl groups. Examples of perfluoroalkyl groups having 3 to 10 carbon atoms, perfluoroalkyl groups having 5 to 7 carbon atoms, and perfluoroalkyl groups having 6 carbon atoms are perfluoroalkyl groups having 1 to 10 carbon atoms. Among the groups described as examples of the alkyl group, it is a group having the corresponding number of carbon atoms.

Each of the alkanediyl group having 1 to 6 carbon atoms and the alkanediyl group having 1 to 3 carbon atoms is linear or branched and unsubstituted, unless otherwise specified. Examples of the alkanediyl group having 1 to 6 carbon atoms include a methanediyl group (methylene group), ethanediyl group, n-propanediyl group, isopropanediyl group, n-butanediyl group, sec-butanediyl group and tert-butanediyl group. group, n-pentanediyl group, 1-methylbutanediyl group, 2-methylbutanediyl group, 3-methylbutanediyl group, 1-ethylpropanediyl group, 2-ethylpropanediyl group, 1,1-dimethylpropanediyl group , 1,2-dimethylpropanediyl group, 2,2-dimethylpropanediyl group, n-hexanediyl group, 1-methylpentanediyl group, 2-methylpentanediyl group, 3-methylpentanediyl group, 4-methylpentane diyl group, 1,1-dimethylbutanediyl group, 1,2-dimethylbutanediyl group, 1,3-dimethylbutanediyl group, 2,2-dimethylbutanediyl group, 2,3-dimethylbutanediyl group, 3, 3-dimethylbutanediyl group, 1,1,2-trimethylpropanediyl group, 1,2,2-trimethylpropanediyl group, 1-ethylbutanediyl group, 2-ethylbutanediyl group, and 3-ethylbutanediyl group is mentioned. Examples of the alkanediyl group having 1 to 3 carbon atoms are groups having the corresponding number of carbon atoms among the groups described as examples of the alkanediyl group having 1 to 6 carbon atoms.

Unless otherwise specified, an alkoxy group having from 1 to 8 carbon atoms may be straight or branched and unsubstituted. Examples of alkoxy groups having 1 to 8 carbon atoms include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, 1-methylbutoxy group, 2-methylbutoxy group, 3-methylbutoxy group, 1-ethylpropoxy group, 2-ethylpropoxy group, 1,1-dimethylpropoxy group, 1,2-dimethylpropoxy group, 2,2- dimethylpropoxy group, n-hexyloxy group, 1-methylpentyloxy group, 2-methylpentyloxy group, 3-methylpentyloxy group, 4-methylpentyloxy group, 1,1-dimethylbutoxy group, 1,2- dimethylbutoxy group, 1,3-dimethylbutoxy group, 2,2-dimethylbutoxy group, 2,3-dimethylbutoxy group, 3,3-dimethylbutoxy group, 1,1,2-trimethylpropoxy group, 1,2, 2-trimethylpropoxy, 1-ethylbutoxy, 2-ethylbutoxy, 3-ethylbutoxy, linear and branched heptyloxy, and linear and branched octyloxy is mentioned.

Aryloxy groups having 6 to 14 carbon atoms are unsubstituted unless otherwise specified. Examples of aryloxy groups having 6 to 14 carbon atoms include phenoxy, naphthoxy, indacenyloxy, biphenylenyloxy, acenaphthylenyloxy, anthryloxy, and phenanthryl An oxy group can be mentioned. The substituents used in the present specification have been described above.

<Electrophotographic photoreceptor>
An electrophotographic photoreceptor (hereinafter also referred to as a photoreceptor) according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 to 3 each show a partial cross-sectional view of the photoreceptor 1 of this embodiment. The photoreceptor 1 is also called a laminated electrophotographic photoreceptor. As shown in FIG. 1, the photoreceptor 1 of this embodiment includes, for example, a conductive substrate 2 and a photosensitive layer 3. As shown in FIG. The photosensitive layer 3 includes a charge generation layer 3a and a charge transport layer 3b. That is, the photoreceptor 1 includes the charge generation layer 3a and the charge transport layer 3b as the photosensitive layer 3. As shown in FIG.

As shown in FIG. 1, a charge generation layer 3a may be provided on the conductive substrate 2, and a charge transport layer 3b may be provided on the charge generation layer 3a. Alternatively, as shown in FIG. 2, the charge transport layer 3b may be provided on the conductive substrate 2, and the charge generation layer 3a may be provided on the charge transport layer 3b.

As shown in FIG. 3, the photoreceptor 1 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2 and the photosensitive layer 3 . An intermediate layer 4 is provided between the conductive substrate 2 and the photosensitive layer 3 . As shown in FIGS. 1 and 2, in the photoreceptor 1 the photosensitive layer 3 may be provided directly on the conductive substrate 2 . Alternatively, as shown in FIG. 3, in the photoreceptor 1, the photosensitive layer 3 may be provided on the conductive substrate 2 with the intermediate layer 4 interposed therebetween. When the photoreceptor 1 includes the intermediate layer 4, as shown in FIG. 3, the intermediate layer 4 is provided on the conductive substrate 2, the charge generation layer 3a is provided on the intermediate layer 4, and the A charge transport layer 3b may be provided. Alternatively, the intermediate layer 4 may be provided on the conductive substrate 2, the charge transport layer 3b may be provided on the intermediate layer 4, and the charge generation layer 3a may be provided on the charge transport layer 3b.

The photoreceptor 1 may further include a protective layer (not shown) in addition to the conductive substrate 2 and the photosensitive layer 3 . A protective layer is provided on the photosensitive layer 3 . As shown in FIGS. 1 to 3, a photosensitive layer 3 (for example, a charge transport layer 3b or a charge generation layer 3a) may be provided as the outermost layer of the photoreceptor 1. FIG. Alternatively, a protective layer may be provided as the outermost layer of the photoreceptor 1 .

As shown in FIG. 1, a photosensitive layer 3 (preferably, a charge transport layer 3b) is preferably provided as the outermost layer of the photoreceptor 1. As shown in FIG. More preferably, the charge transport layer 3b is a single layer and is provided as the outermost surface layer of the photoreceptor 1 . By providing the charge transport layer 3b containing a polyarylate resin (PA), which will be described later, as the outermost layer, the wear resistance of the photoreceptor 1 is further improved.

The charge generation layer 3a contains a charge generation agent. The charge generation layer 3a may contain a base resin, if necessary. The charge-generating layer 3a may contain additives, if necessary. Although the thickness of the charge generation layer 3a is not particularly limited, it 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 charge generation layer 3a is, for example, a single layer.

The charge transport layer 3b contains a hole transport agent, a binder resin and a phthalocyanine pigment. The charge transport layer 3b may contain additives as required. Although the thickness of the charge transport layer 3b is not particularly limited, it is preferably 2 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less. The charge transport layer 3b is, for example, a single layer. The photoreceptor 1 has been described above with reference to FIGS. 1 to 3. FIG. The photoreceptor will be described in more detail below.

(Charge generating agent)
Examples of the charge generating agent contained in the charge generating layer include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaline pigments, and indigo pigments. Pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g. selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon), pyrylium pigments, anthanthrone-based pigments, triphenylmethane-based pigments, threne pigments, toluidine-based pigments, pyrazoline-based pigments, and quinacridone-based pigments. The photosensitive layer may contain only one charge-generating agent, or may contain two or more charge-generating agents.

A phthalocyanine pigment is a pigment having a phthalocyanine structure. Examples of phthalocyanine pigments include metal-free phthalocyanines and metal phthalocyanines. Metal phthalocyanines include, for example, titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. A metal-free phthalocyanine is represented by the formula (CGM-1). Titanyl phthalocyanine is represented by formula (CGM-2).

The phthalocyanine pigment may be crystalline or amorphous. Examples of metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter sometimes referred to as X-type metal-free phthalocyanine). Examples of titanyl phthalocyanine crystals include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter sometimes referred to as α-type, β-type, and Y-type titanyl phthalocyanine).

For example, it is preferable to use a photoreceptor having sensitivity in a wavelength region of 700 nm or more for a digital optical image forming apparatus (for example, a laser beam printer or facsimile using a light source such as a semiconductor laser). As the charge generating agent, a phthalocyanine-based pigment is preferred, metal-free phthalocyanine or titanyl phthalocyanine is more preferred, titanyl phthalocyanine is still more preferred, and Y-type titanyl phthalocyanine is particularly preferred, since it has a high quantum yield in a wavelength region of 700 nm or more. .

Y-type titanyl phthalocyanine has a main peak at, for example, a Bragg angle (2θ±0.2°) of 27.2° in its CuKα characteristic X-ray diffraction spectrum. The main peak in the CuKα characteristic X-ray diffraction spectrum is the peak having the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is 3° or more and 40° or less. Y-type titanyl phthalocyanine does not have a peak at 26.2° C. in its CuKα characteristic X-ray diffraction spectrum.

The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, a sample (titanyl phthalocyanine) is filled in a sample holder of an X-ray diffraction device (for example, "RINT (registered trademark) 1100" manufactured by Rigaku Corporation), and the X-ray tube Cu, tube voltage 40 kV, tube current 30 mA, Also, the X-ray diffraction spectrum is measured under the condition that the wavelength of the CuKα characteristic X-ray is 1.542 Å. The measurement range (2θ) is, for example, 3° or more and 40° or less (start angle: 3°, stop angle: 40°), and the scanning speed is, for example, 10°/min. A main peak is determined from the obtained X-ray diffraction spectrum, and the Bragg angle of the main peak is read.

The content of the charge generating agent is preferably 10 parts by mass or more and 300 parts by mass or less, more preferably 100 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the base resin.

(base resin)
Examples of the base resin contained in the charge generation layer are the same as examples of the other binder resin contained in the charge transport layer, which will be described later.

(binder resin)
The binder resin contained in the charge transport layer includes polyarylate resin. This polyarylate resin has repeating units represented by formulas (1), (2), (3) and (4). The content of the repeating unit represented by formula (3) with respect to the total number of repeating units represented by formulas (1) and (3) is greater than 0% and less than 20%.

In formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group, and X represents a divalent group represented by formula (X1) or (X2). In formula (2), W represents a divalent group represented by formula (W1) or (W2).

In formula (X1), t represents an integer of 1 or more and 3 or less, and * represents a bond. In formula (X2), R ³ and R ⁴ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ and R ⁴ represent groups different from each other, and * represents a bond. .

In formulas (W1) and (W2), * represents a bond.

Hereinafter, the repeating units represented by formulas (1), (2), (3), and (4) are referred to as "repeating units (1), (2), (3), and (4)," respectively. may be described. Also, the content of repeating unit (3) with respect to the total number of repeating units (1) and (3) may be described as "content (3)". A polyarylate resin having repeating units (1), (2), (3), and (4) and having a content (3) of greater than 0% and less than 20% is referred to as "polyarylate resin (PA )” may be described.

The polyarylate resin (PA) essentially has repeating units (1), (2), (3) and (4). Since the polyarylate resin (PA) has such a repeating unit, it has excellent solubility in solvents, and can improve the wear resistance of the photoreceptor when contained in the photoreceptor layer.

The content (3) is the percentage of the number N 3 of the repeating units (3) with respect to the total number N ₁ of the repeating units (1) and the number N ₃ of the repeating units (3) _of the polyarylate resin (PA) ( That is, 100×N ₃ /(N ₁ +N ₃ )). When the content (3) is less than 20%, the solubility of the polyarylate resin (PA) in solvents is improved. When the content (3) is greater than 0%, that is, the content (3) is not 0%, abrasion resistance of the photoreceptor is improved when the polyarylate resin (PA) is contained in the photosensitive layer. The content (3) is preferably 1% or more, more preferably 5% or more. Also, the content (3) is preferably 19% or less, more preferably 10% or less.

The content of repeating unit (4) with respect to the total number of repeating units (2) and (4) is greater than 0% and less than 100%. The content of repeating unit (4) with respect to the total number of repeating units (2) and (4) is sometimes referred to as "content (4)". The content (4) is the percentage of the number N4 of the repeating units (4) with respect to the total number _N2 of the repeating units (2) and the number _N4 of the repeating units ( ₄ ) of the polyarylate resin (PA) ( That is, 100×N ₄ /(N ₂ +N ₄ )). Since the content (4) is greater than 0%, ie the content (4) is not 0%, the polyarylate resin (PA) has repeating units (4). By having the repeating unit (4), the solubility of the polyarylate resin (PA) in a solvent is improved, and when the polyarylate resin (PA) is contained in the photosensitive layer, the wear resistance of the photoreceptor is improved. do. On the other hand, the content (4) is less than 100%, ie the content (4) is not 100%, so the polyarylate resin (PA) has repeating units (2). Having the repeating unit (2) improves the wear resistance of the photoreceptor when the polyarylate resin (PA) is contained in the photoreceptor layer. The content (4) is preferably 1% or more, more preferably 10% or more, and even more preferably 35% or more. Also, the content (4) is preferably 99% or less, more preferably 80% or less, and even more preferably 65% or less.

Contents (3) and (4) are each obtained by measuring the ¹ H-NMR spectrum of the polyarylate resin (PA) using a proton nuclear magnetic resonance spectrometer, and each repeating unit in the obtained ¹ H-NMR spectrum. can be calculated from the ratio of characteristic peaks.

In formula (1), R ¹ and R ² preferably represent a methyl group.

In formula (X1), t preferably represents 2.

In formula (X2), R ³ represents a hydrogen atom and R ⁴ represents a methyl group, an ethyl group, or an alkyl group having 3 carbon atoms, R ³ represents a methyl group and R ⁴ represents an ethyl group or carbon Preferably, R ³ represents an ethyl group and R ⁴ represents an alkyl group of 3 carbon atoms. More preferably, R ³ represents a methyl group and R ⁴ represents an ethyl group.

The bond represented by * in formulas (X1) and (X2) is bonded to the carbon atom to which X in formula (1) is bonded. The bond represented by * in formulas (W1) and (W2) is bonded to the carbon atom to which W in formula (2) is bonded.

Examples of the repeating unit (1) include, for example, repeating units represented by formulas (1-1), (1-2), and (1-3) (hereinafter referred to as repeating units (1-1), ( 1-2) and (1-3)).

Repeating unit (2) is a repeating unit represented by formula (2-1) or (2-2) (hereinafter each may be described as repeating unit (2-1) and (2-2) ).

In one embodiment, in formula (1), R ¹ and R ² preferably represent a methyl group, and X preferably represents a divalent group represented by formula (X1). More preferably, the repeating unit (1) is the repeating unit (1-1). repeating unit (1) is repeating unit (1-1) and repeating unit (2) is repeating unit (2-1); or repeating unit (1) is repeating unit (1-1) and More preferably, the repeating unit (2) is the repeating unit (2-2).

In another embodiment, in formula (1), R ¹ and R ² preferably represent hydrogen atoms, and X preferably represents a divalent group represented by formula (X2). More preferably, repeating unit (1) is repeating unit (1-2). repeating unit (1) is repeating unit (1-2) and repeating unit (2) is repeating unit (2-1); or repeating unit (1) is repeating unit (1-2) and More preferably, the repeating unit (2) is the repeating unit (2-2). By containing the polyarylate resin (PA) described in another aspect in the photosensitive layer, the wear resistance of the photosensitive member is further improved.

The polyarylate resin (PA) may have terminal groups. Terminal groups possessed by the polyarylate resin (PA) include, for example, terminal groups represented by formulas (T-1) and (T-2). As the terminal group represented by formula (T-1), a terminal group represented by formula (T-DMP) (hereinafter sometimes referred to as terminal group (T-DMP)) is preferable. As the terminal group represented by formula (T-2), a terminal group represented by formula (T-PFH) (hereinafter sometimes referred to as terminal group (T-PFH)) is preferable.

In formula (T-1), R ¹¹ represents an alkyl group having 1 to 6 carbon atoms or a halogen atom, and p represents an integer of 0 to 5. R ¹¹ preferably represents an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and still more preferably a methyl group. p preferably represents an integer of 1 or more and 3 or less, more preferably 2;

In formula (T-2), R ¹² represents an alkanediyl group having 1 to 6 carbon atoms, and Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms. R ¹² preferably represents an alkanediyl group having 1 to 3 carbon atoms, more preferably a methylene group. Rf preferably represents a perfluoroalkyl group having 3 to 10 carbon atoms, more preferably a perfluoroalkyl group having 5 to 7 carbon atoms, and a perfluoroalkyl group having 6 carbon atoms. It is more preferable to express

* in formulas (T-1), (T-2), (T-DMP), and (T-PFH) represents a bond. The bonds indicated by * in the formulas (T-1), (T-2), (T-DMP), and (T-PFH) are repeats derived from dicarboxylic acids located at the ends of the polyarylate resin (PA) It is bound to the unit (more specifically, repeating unit (2) or (4)).

Preferred examples of polyarylate resins (PA) include polyarylate resins (PA-1) to (PA-4) shown in Table 1. Polyarylate resins (PA-1) to (PA-4) each have repeating units shown in Table 1 as repeating units (1) to (4). In Table 1 and Table 2 described later, units (1) to (4) represent repeating units (1) to (4), respectively.

Further preferred examples of the polyarylate resin (PA) include polyarylate resins (PA-a) to (PA-h) shown in Table 2. Polyarylate resins (PA-a) to (PA-h) each have repeating units shown in Table 2 as repeating units (1) to (4) and end groups shown in Table 2.

In the polyarylate resin (PA), a bisphenol-derived repeating unit (more specifically, the repeating unit (1) or (3)) and a dicarboxylic acid-derived repeating unit (more specifically, the repeating unit (2) or (4)) are adjacent to each other. That is, the repeating unit (1) may be combined with the repeating unit (2) or may be combined with the repeating unit (4). Moreover, the repeating unit (3) may be bonded to the repeating unit (2) or may be bonded to the repeating unit (4). The number of repeating units derived from bisphenol is approximately the same as that of repeating units derived from dicarboxylic acid, and satisfies the formula "the number of repeating units derived from dicarboxylic acid = the number of repeating units derived from bisphenol + 1". Polyarylate resins (PA) can be, for example, random copolymers, alternating copolymers, periodic copolymers, or block copolymers.

The polyarylate resin (PA) may have only one repeating unit (1) as the repeating unit (1), or may have two or more (for example, two) repeating units (1). good too. The polyarylate resin (PA) may have only one type of repeating unit (2) as the repeating unit (2), or may have two types of repeating units (2).

The polyarylate resin (PA) may further have repeating units other than repeating units (1) to (4) as repeating units. However, in order to improve the solubility in a solvent and improve the wear resistance of the photoreceptor when contained in the photosensitive layer, the repeating unit (1) in the total number of repeating units possessed by the polyarylate resin (PA) The content of (4) is preferably 90% or more, more preferably 95% or more, still more preferably 99% or more, and particularly preferably 100%. That is, the polyarylate resin (PA) particularly preferably has only repeating units (1) to (4) as repeating units.

In order to improve solubility in solvents, the content of repeating units (3) in the total number of repeating units derived from bisphenol in the polyarylate resin (PA) is preferably 20% or less, and less than 20%. is more preferable.

The viscosity average molecular weight of the polyarylate resin (PA) is preferably 10,000 or more, more preferably 30,000 or more, still more preferably 50,000 or more, and 55,000 or more. is particularly preferred. When the polyarylate resin (PA) has a viscosity average molecular weight of 10,000 or more, the abrasion resistance of the photoreceptor is improved when it is contained in the photosensitive layer of the photoreceptor. On the other hand, the viscosity average molecular weight of the polyarylate resin (PA) is preferably 80,000 or less, more preferably 70,000 or less, and even more preferably 60,000 or less. When the viscosity average molecular weight of the polyarylate resin (PA) is 80,000 or less, the solubility of the polyarylate resin (PA) in solvents is improved. The viscosity average molecular weight of polyarylate resin (PA) is measured according to JIS (Japanese Industrial Standard) K7252-1:2016.

Next, a method for producing the polyarylate resin (PA) will be described. Examples of a method for producing a polyarylate resin (PA) include a method of condensation polymerization of bisphenol for forming repeating units derived from bisphenol and dicarboxylic acid for forming repeating units derived from dicarboxylic acid. A known synthetic method (for example, solution polymerization, melt polymerization, or interfacial polymerization) can be employed for the polycondensation.

Examples of bisphenols for constituting repeating units derived from bisphenol include compounds represented by formulas (BP-1) and (BP-3) (hereinafter referred to as compounds (BP-1) and (BP-3 ) may be described). Examples of dicarboxylic acids for forming repeating units derived from dicarboxylic acids include compounds represented by formulas (DC-2) and (DC-4) (hereinafter referred to as compounds (DC-2) and (DC -4) may be described). R ¹ , R ² and X in formula (BP-1) have the same definitions as R ¹ , R ² and X in formula (1). W in formula (DC-2) has the same meaning as W in formula (2).

Percentage of the amount (unit: mol) of the compound (BP-3) with respect to the total amount (unit: mol) of the compounds (BP-1) and (BP-3) in the production of the polyarylate resin (PA) is the content It corresponds to (3). Further, the percentage of the amount (unit: mol) of compound (DC-4) with respect to the total amount (unit: mol) of compounds (DC-2) and (DC-4) corresponds to the content (4).

Bisphenols may be used after being derivatized to aromatic diacetates. Dicarboxylic acids may be used after being derivatized. Examples of derivatives of dicarboxylic acids include dicarboxylic acid dichlorides, dicarboxylic acid dimethyl esters, dicarboxylic acid diethyl esters, and dicarboxylic acid anhydrides. A dicarboxylic acid dichloride is a compound in which two “—C(=O)—OH” groups of a dicarboxylic acid are each substituted with a “—C(=O)—Cl” group.

A terminal terminator may be added in the polycondensation of bisphenol and dicarboxylic acid. End cappers include, for example, 2,6-dimethylphenol and 1H,1H-perfluoro-1-heptanol. A terminal group (T-DMP) can be formed by using 2,6-dimethylphenol as a terminal terminator. A terminal group (T-PFH) can be formed by using 1H,1H-perfluoro-1-heptanol as a terminal terminator.

One or both of a base and a catalyst may be added in the polycondensation of bisphenol and dicarboxylic acid. Examples of bases include sodium hydroxide. Examples of catalysts include benzyltributylammonium chloride, ammonium chloride, ammonium bromide, quaternary ammonium salts, triethylamine, and trimethylamine.

The photosensitive layer may contain only one type of polyarylate resin (PA) as a binder resin, or may contain two or more types of polyarylate resins (PA). Further, the photosensitive layer may contain only a polyarylate resin (PA) as a binder resin, and may further contain a binder resin other than the polyarylate resin (PA) (hereinafter sometimes referred to as other binder resin). may contain. Other binder resins include, for example, thermoplastic resins (more specifically, polyarylate resins other than polyarylate resins (PA), polycarbonate resins, styrene resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, coalescence, styrene-maleic acid copolymer, styrene-acrylic acid copolymer, acrylic copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, chloride vinyl-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyvinyl acetal resins, and polyether resins), thermosetting resins (more Specifically, silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins), and photocurable resins (more specifically, epoxy-acrylic acid resins , and urethane-acrylic acid copolymers).

(phthalocyanine pigment)
The phthalocyanine pigment contained in the charge transport layer is a metal-free phthalocyanine or a compound represented by formula (11). Hereinafter, the "compound represented by formula (11)" may be referred to as "phthalocyanine pigment (11)". Also, "metal-free phthalocyanine or phthalocyanine pigment (11)" may be described as "predetermined phthalocyanine pigment". By containing the predetermined phthalocyanine pigment in the charge transport layer, the sensitivity characteristics, particularly the sensitivity characteristics when printing a solid image and the sensitivity characteristics when printing a halftone image are improved.

First, the metal-free phthalocyanine will be explained. The metal-free phthalocyanine is a compound represented by formula (K-1) (hereinafter sometimes referred to as phthalocyanine pigment (K-1)). The formula (K-1) is the same as the formula (CGM-1) already described, but in order to distinguish them, the metal-free phthalocyanine contained in the charge transport layer is represented by the formula (K-1), The metal-free phthalocyanine contained in the charge generation layer is represented by formula (CGM-1). The metal-free phthalocyanine may be crystalline or amorphous. Examples of metal-free phthalocyanine crystals include X-type metal-free phthalocyanine.

Next, the phthalocyanine pigment (11) will be described. In the following formula (11), M represents a metal atom which may have a ligand.

In formula (11), the metal atom represented by M preferably represents a titanium atom, a gallium atom, a copper atom, a zinc atom, or a lead atom, more preferably a titanium atom or a gallium atom, and a titanium atom. It is more preferable to express

In formula (11), the metal atom represented by M may have a ligand. Examples of such ligands include alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, aryloxy groups having 6 to 14 carbon atoms, halogen atoms, and hydroxy groups. , and oxo groups (=O). Among these, when a ligand other than an oxo group is coordinated, two ligands may be coordinated to the metal atom. A ligand is preferably a halogen atom (more preferably a chlorine atom), a hydroxy group, or an oxo group.

In formula (11), M is a titanium atom optionally having a ligand, a gallium atom optionally having a ligand, a copper atom optionally having a ligand, a ligand It is preferable to represent a zinc atom which may have a ligand, or a lead atom which may have a ligand, a titanium atom which may have a ligand, or a gallium atom which may have a ligand More preferably, it represents a titanium atom with a ligand or a gallium atom with a ligand. A titanium atom having a ligand preferably represents a titanium atom having an oxygen atom as a ligand (that is, TiO). A gallium atom having a ligand is preferably a gallium atom having a chlorine atom as a ligand (ie GaCl) or a gallium atom having a hydroxy group as a ligand (ie GaOH).

The phthalocyanine pigment (11) may be crystalline or amorphous. As the phthalocyanine pigment (11), for example, titanyl phthalocyanine, hydroxygallium phthalocyanine, or chlorogallium phthalocyanine is preferable, and titanyl phthalocyanine is more preferable. Titanyl phthalocyanine is a compound represented by formula (K-2) (hereinafter sometimes referred to as phthalocyanine pigment (K-2)). The formula (K-2) is the same as the formula (CGM-2) already described, but in order to distinguish between them, the titanyl phthalocyanine contained in the charge transport layer is represented by the formula (K-2). Titanyl phthalocyanine contained in the generating layer is represented by formula (CGM-2). Crystals of titanyl phthalocyanine include α-type, β-type, and Y-type titanyl phthalocyanine.

The content of the predetermined phthalocyanine pigment is 0.15 parts by mass or more and 0.50 parts by mass or less with respect to 100.00 parts by mass of the binder resin.

When the photoreceptor is exposed to light, charge tends to be generated not only from the charge generating agent contained in the charge generating layer, but also from certain phthalocyanine pigments contained in the charge transport layer. Therefore, by containing a predetermined phthalocyanine pigment in the charge-transporting layer, the sensitivity characteristics of the photoreceptor, particularly when printing a solid image, are improved. Such an effect becomes remarkable when the content of the predetermined phthalocyanine pigment is 0.15 parts by mass or more with respect to 100.00 parts by mass of the binder resin.

On the other hand, if the content of the predetermined phthalocyanine pigment exceeds 0.50 parts by mass with respect to 100.00 parts by mass of the binder resin, when the photoreceptor is exposed to light, the charge transport layer blocks the exposure light, It tends to be difficult to reach the generation layer. When the content of the predetermined phthalocyanine pigment is 0.50 parts by mass or less per 100.00 parts by mass of the binder resin, the exposure light is less likely to be blocked by the charge transport layer and the exposure light reaches the charge generation layer satisfactorily. . As a result, the sensitivity characteristics of the photoreceptor, especially when printing a solid image, are improved.

The charge transport layer may contain only one of the metal-free phthalocyanine and the phthalocyanine pigment (11), or may contain two or more. When two or more kinds of metal-free phthalocyanine and phthalocyanine pigment (11) are contained, the content of the predetermined phthalocyanine pigment means the total content of two or more kinds of metal-free phthalocyanine and phthalocyanine pigment (11).

In order to further improve the sensitivity characteristics of the photoreceptor, the predetermined phthalocyanine pigment contained in the charge transport layer is preferably the same as the charge generating agent contained in the charge generating layer.

(Hole transport agent)
Examples of hole transport agents include triphenylamine derivatives, diamine derivatives (e.g., N,N,N',N'-tetraphenylbenzidine derivatives, N,N,N',N'-tetraphenylphenylenediamine derivatives, N,N,N',N'-tetraphenylnaphthylenediamine derivatives, N,N,N',N'-tetraphenylphenanthrylenediamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole), styryl compounds (e.g., 9-(4-diethylaminostyryl)anthracene), carbazole compounds ( polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole thiadiazole-based compounds, imidazole-based compounds, pyrazole-based compounds, and triazole-based compounds. The photosensitive layer may contain only one hole transport agent, or may contain two or more hole transport agents.

Suitable examples of the hole transport agent include compounds represented by formula (20) (hereinafter sometimes referred to as hole transport agent (20)). When the photosensitive layer contains the hole transport agent (20) together with the polyarylate resin (PA) and the predetermined phthalocyanine pigment, the photosensitive layer can be formed more favorably, and the sensitivity characteristics and abrasion resistance of the photoreceptor are further improved. do.

In formula (20), R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁵ and R ³⁶ each independently represent an alkyl group having 1 to 8 carbon atoms or a phenyl group. R ³⁷ and R ³⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group. b1, b2, b3 and b4 each independently represents an integer of 0 or more and 5 or less. b5 and b6 each independently represent an integer of 0 or more and 4 or less. d and e each independently represent 0 or 1;

In formula (20), when b1 represents an integer of 2 or more and 5 or less, a plurality of R ³¹ may represent the same group or different groups. When b2 represents an integer of 2 or more and 5 or less, a plurality of R ³² may represent the same group or different groups. When b3 represents an integer of 2 or more and 5 or less, a plurality of R ³³ may represent the same group or different groups. When b4 represents an integer of 2 or more and 5 or less, a plurality of R ³⁴ may represent the same group or different groups. When b5 represents an integer of 2 or more and 4 or less, a plurality of R ³⁵ may represent the same group or different groups. When b6 represents an integer of 2 or more and 4 or less, a plurality of R ³⁶ may represent the same group or different groups.

In formula (20), R ³¹ to R ³⁶ each independently preferably represent an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, More preferably, it represents a methyl group or an ethyl group. R ³⁷ and R ³⁸ preferably represent a hydrogen atom. b1, b2, b3, and b4 preferably each independently represent an integer of 0 or more and 2 or less. b5 and b6 preferably represent 0; d and e preferably represent 1;

A more preferable example of the hole transport agent is a compound represented by formula (HTM-1) (hereinafter sometimes referred to as hole transport agent (HTM-1)).

The content of the hole transport agent is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 20 parts by mass or more and 100 parts by mass or less, and 40 parts by mass with respect to 100 parts by mass of the binder resin. It is more preferable that the amount is not less than 60 parts by mass and not more than 60 parts by mass.

(Additive)
Additives include, for example, ultraviolet absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, donors, surface active agents, plasticizers, sensitizers, electron acceptor compounds, and leveling agents. As the leveling agent, silicone oil is preferable, and silicone oil having a dimethylpolysiloxane structure is more preferable.

(combination of materials)
In order to form a good photosensitive layer and improve the sensitivity characteristics and wear resistance of the photoreceptor, the binder resin should be polyarylate resins (PA-1) to (PA-4) and polyarylate resin (PA-a). (PA-h) and polyarylate resins A to I, and the phthalocyanine pigment is preferably phthalocyanine pigment (K-1). For the same reason, the binder resin is one of polyarylate resins (PA-1) to (PA-4), polyarylate resins (PA-a) to (PA-h), and polyarylate resins A to I. Preferably, the phthalocyanine pigment is the phthalocyanine pigment (K-1) and the hole transport agent is the hole transport agent (HTM-1). For the same reason, the binder resin is one of polyarylate resins (PA-1) to (PA-4), polyarylate resins (PA-a) to (PA-h), and polyarylate resins A to I. Preferably, the phthalocyanine pigment is the phthalocyanine pigment (K-1) and the charge generating agent is titanyl phthalocyanine. For the same reason, the binder resin is one of polyarylate resins (PA-1) to (PA-4), polyarylate resins (PA-a) to (PA-h), and polyarylate resins A to I. It is preferable that the phthalocyanine pigment is the phthalocyanine pigment (K-1) and the charge generating agent is a metal-free phthalocyanine. The polyarylate resins A to I will be described in detail in Examples.

In order to form a good photosensitive layer and improve the sensitivity characteristics and wear resistance of the photoreceptor, the binder resin should be polyarylate resins (PA-1) to (PA-4) and polyarylate resin (PA-a). (PA-h) and polyarylate resins A to I, and the phthalocyanine pigment is preferably phthalocyanine pigment (K-2). For the same reason, the binder resin is one of polyarylate resins (PA-1) to (PA-4), polyarylate resins (PA-a) to (PA-h), and polyarylate resins A to I. preferably the phthalocyanine pigment is the phthalocyanine pigment (K-2) and the hole transport agent is the hole transport agent (HTM-1). For the same reason, the binder resin is one of polyarylate resins (PA-1) to (PA-4), polyarylate resins (PA-a) to (PA-h), and polyarylate resins A to I. Preferably, the phthalocyanine pigment is the phthalocyanine pigment (K-2) and the charge generating agent is titanyl phthalocyanine. For the same reason, the binder resin is one of polyarylate resins (PA-1) to (PA-4), polyarylate resins (PA-a) to (PA-h), and polyarylate resins A to I. It is preferable that the phthalocyanine pigment is the phthalocyanine pigment (K-2) and the charge generating agent is a metal-free phthalocyanine.

(Conductive substrate)
The conductive substrate is not particularly limited as long as at least the surface portion is made of a conductive material. An example of the conductive substrate is a conductive substrate made of a conductive material. Another example of a conductive substrate is a conductive substrate coated with a material having electrical conductivity. Conductive materials include, for example, aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. Among these electrically conductive materials, aluminum and aluminum alloys are preferred because of good charge transfer from the photosensitive layer to the conductive substrate.

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

(middle layer)
The intermediate layer (undercoat layer) contains, for example, inorganic particles and a resin used for the intermediate layer (intermediate layer resin). The presence of the intermediate layer makes it possible to maintain an insulating state to the extent that leakage can be suppressed, and to smooth the flow of current generated when the photosensitive member is exposed to light, thereby suppressing an increase in resistance.

Examples of inorganic particles include particles of metals (e.g., aluminum, iron, and copper), particles of metal oxides (e.g., titanium oxide, alumina, zirconium oxide, tin oxide, and zinc oxide), and non-metal oxides. (eg, silica) particles.

Examples of the intermediate layer resin are the same as the examples of other binder resins already described. In order to form the intermediate layer and the photosensitive layer satisfactorily, the resin for the intermediate layer is preferably different from the binder resin contained in the photosensitive layer. The intermediate layer may contain additives. Examples of additives contained in the intermediate layer are the same as examples of additives contained in the photosensitive layer.

(Manufacturing method of photoreceptor)
An example of a method for manufacturing a photoreceptor will be described below. A method for manufacturing a photoreceptor includes, for example, a charge generation layer forming step and a charge transport layer forming step. In the charge generation layer forming step, first, a coating liquid for forming the charge generation layer (hereinafter sometimes referred to as a charge generation layer coating liquid) is prepared. A charge generation layer coating liquid is applied onto a conductive substrate. Next, at least part of the solvent contained in the applied charge-generating layer coating liquid is removed to form the charge-generating layer. The charge generating layer coating liquid contains, for example, a charge generating agent, a base resin, and a solvent. Such a charge generation layer coating liquid is prepared by dissolving or dispersing a charge generation agent and a base resin in a solvent. The charge generation layer coating liquid may further contain additives, if necessary.

In the charge transport layer forming step, first, a coating liquid for forming the charge transport layer (hereinafter sometimes referred to as a charge transport layer coating liquid) is prepared. The charge transport layer coating liquid is applied onto the charge generation layer. Next, at least part of the solvent contained in the applied charge transport layer coating liquid is removed to form the charge transport layer. The charge transport layer coating liquid contains a hole transport agent, a binder resin, a phthalocyanine pigment, and a solvent. The charge transport layer coating liquid can be prepared by dissolving or dispersing a hole transporting agent, a binder resin, and a phthalocyanine pigment in a solvent. The charge-transporting layer coating liquid may further contain additives, if necessary.

The solvent contained in the charge-generating layer coating liquid and the charge-transporting layer coating liquid (hereinafter collectively referred to as the coating liquid in some cases) dissolves or disperses each component contained in the coating liquid. It is not particularly limited as long as possible. Examples of solvents include alcohols (more specifically, methanol, ethanol, isopropanol, butanol, etc.), aliphatic hydrocarbons (more specifically, n-hexane, octane, cyclohexane, etc.), aromatic hydrocarbons, etc. Hydrogen (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, and diethylene glycol dimethyl ether), ketones (more specifically, acetone, methyl ethyl ketone, cyclohexanone, etc.), esters (more specifically, ethyl acetate, methyl acetate, etc.), Dimethylformaldehyde, dimethylformamide, and dimethylsulfoxide.

The solvent contained in the charge-transporting layer coating liquid is preferably different from the solvent contained in the charge-generating layer coating liquid. This is because when the charge-transporting layer coating liquid is applied onto the charge-generating layer, it is preferable that the charge-generating layer does not dissolve in the solvent of the charge-transporting layer coating liquid.

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

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

Methods for removing at least part of the solvent contained in the coating liquid include, for example, heating, reduced pressure, or combined use of heating and reduced pressure. More specifically, a method of heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer can be mentioned. The heat treatment temperature is, for example, 40° C. or higher and 150° C. or lower. The heat treatment time is, for example, 3 minutes or more and 120 minutes or less.

The method for manufacturing a photoreceptor may further include one or both of the step of forming an intermediate layer and the step of forming a protective layer, if necessary. Known methods can be appropriately selected for the step of forming the intermediate layer and the step of forming the protective layer.

EXAMPLES Hereinafter, the present invention will be described more specifically using examples. However, the present invention is in no way limited to the scope of the examples.

<Preparation of polyarylate resins A to N>
Polyarylate resins A to I according to examples and polyarylate resins J to N according to comparative examples were synthesized by the following method. The compositions of polyarylate resins A to N are shown in Table 3 below.

In Table 3, "BisCZ", "BisB", "BisZ", "BP", "14NACC", "26NACC", "DPEC", "TPC", and "IPC" are each represented by the following formula (BisCZ), Compounds represented by (BisB), (BisZ), (BP), (14NACC), (26NACC), (DPEC), (TPC), and (IPC) (hereinafter referred to as compounds (BisCZ) and (BisB), respectively) , (BisZ), (BP), (14NACC), (26NACC), (DPEC), (TPC), and (IPC)).

Moreover, the meaning of each term in Table 3 is as follows.
Monomer: Monomer used to synthesize the polyarylate resin Forming unit: Repeating unit formed from the corresponding monomer Resin: Polyarylate resin Bisphenol addition rate: Total amount of bisphenol monomer added in the synthesis of the polyarylate resin (unit: mol) Percentage (unit: %) of the amount (unit: mole) of the corresponding bisphenol monomer to
Dicarboxylic acid addition rate: Percentage (unit: %) of the amount (unit: mol) of the corresponding dicarboxylic acid monomer with respect to the total amount (unit: mol) of the dicarboxylic acid monomer added in the synthesis of the polyarylate resin
Molecular weight: viscosity average molecular weight Unit: repeating unit TPC/IPC: mixture of compound (TPC) and (IPC) having a molar ratio of 1/1 50/50 in TPC/IPC column: dicarboxylic acid addition rate of compound (TPC) 50% and the dicarboxylic acid addition rate of the compound (IPC) is 50% DMP: 2,6-dimethylphenol PFH: 1H,1H-perfluoro-1-heptanol Unmeasurable: In the solvent for viscosity molecular weight measurement The viscosity-average molecular weight could not be measured because the polyarylate resin did not dissolve.

(Synthesis of polyarylate resin A)
A three-necked flask equipped with a thermometer, a three-way cock, and a dropping funnel was used as a reaction vessel. A reaction vessel was charged with a monomer compound (BisCZ) (38.95 mmol), a monomer compound (BP) (2.05 mmol), and a terminal terminator, 2,6-dimethylphenol (0.413 mmol). ), sodium hydroxide (98 mmol), and benzyltributylammonium chloride (0.384 mmol). The air in the reaction vessel was replaced with argon gas. Water (300 mL) was added to the contents of the reaction vessel. The contents of the reaction vessel were stirred at 50° C. for 1 hour. The contents of the reaction vessel were cooled to 10° C. to give an alkaline aqueous solution SA.

Next, the dicarboxylic acid dichloride (16.0 mmol) of the monomer compound (14NACC) and the dicarboxylic acid dichloride (16.0 mmol) of the monomer compound (26NACC) were dissolved in chloroform (150 mL). This gave a chloroform solution SB.

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

(Synthesis of polyarylate resins B to N)
Each of the polyarylate resins B to N was synthesized in the same manner as the synthesis of the polyarylate resin A, except that the monomers shown in Table 3 were used at the addition ratios shown in Table 3. The amount of each bisphenol monomer to be added was set so that the total amount of bisphenol monomer was 41.0 millimoles and the bisphenol addition rate shown in Table 3 was obtained. For example, in the synthesis of polyarylate resin B, the amount of compound (BisB) added is 38.95 millimoles (=41.0×95/100), and the amount of compound (BP) added is 2.05 millimoles (=41 .0×5/100). The amount of each dicarboxylic acid monomer to be added was set so that the total amount of the dicarboxylic acid monomer was 32.0 millimoles and the dicarboxylic acid addition rate shown in Table 3 was obtained. For example, in the synthesis of polyarylate resin B, the amount of compound (14NACC) added is 16.0 mmol (=32.0×50/100), and the amount of compound (26NACC) added is 16.0 mmol (=32 .0×50/100).

Using a proton nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd., 600 MHz), ¹ H-NMR spectra of the obtained polyarylate resins A to N were measured. Deuterated chloroform was used as solvent. Tetramethylsilane (TMS) was used as an internal standard sample. FIG. 4 shows the ¹ H-NMR spectrum of polyarylate resin H, which is a representative example of polyarylate resins AN. From chemical shifts read from the ¹ H-NMR spectrum, it was confirmed that polyarylate resin H was obtained. Polyarylate resins A to G and I to N were also confirmed by the same method to be obtained.

<Preparation of polyarylate resin O>
A polyarylate resin O according to a comparative example was prepared. Polyarylate resin O is represented by the following formula (O). The number attached to the lower right of the bisphenol-derived repeating unit in the formula (O) is the content of the corresponding bisphenol-derived repeating unit with respect to the total number of bisphenol-derived repeating units contained in the polyarylate resin O (unit: %). In addition, the number attached to the lower right of the repeating unit derived from the dicarboxylic acid in the formula (O) indicates the number of repeating units derived from the corresponding dicarboxylic acid with respect to the total number of repeating units derived from the dicarboxylic acid contained in the polyarylate resin O. The content rate (unit: %) is shown. Polyarylate resin O had terminal groups derived from 2,6-dimethylphenol as terminal groups. The viscosity average molecular weight of polyarylate resin O was 54,400.

<Measurement of viscosity average molecular weight>
The viscosity average molecular weight of the polyarylate resin was measured according to JIS (Japanese Industrial Standard) K7252-1:2016. The measured viscosity average molecular weights are shown in Table 3.

<Production of Photoreceptor>
(Production of photoreceptor (A-1))
First, an intermediate layer was formed. A surface-treated titanium oxide (“Prototype SMT-A” manufactured by Tayca Co., Ltd., number average primary particle diameter 10 nm) was prepared. SMT-A was obtained by surface-treating titanium oxide with alumina and silica, and further surface-treating it with methylhydrogenpolysiloxane while dispersing the surface-treated titanium oxide in a wet process. Next, 2 parts by mass of SMT-A, and 1 part by mass of a polyamide resin (“Amilan (registered trademark) CM8000” manufactured by Toray Industries, Inc., a quaternary copolymerized polyamide resin of polyamide 6, polyamide 12, polyamide 66 and polyamide 610) , 10 parts by mass of methanol, 1 part by mass of butanol, and 1 part by mass of toluene were mixed for 5 hours using a bead mill to obtain an intermediate layer coating liquid. The intermediate layer coating liquid was filtered using a filter with an opening of 5 μm. Thereafter, the intermediate layer coating liquid was applied to the surface of the conductive substrate by a dip coating method. A drum-like support made of aluminum was used as the conductive substrate. Subsequently, the applied intermediate layer coating liquid was dried at 130° C. for 30 minutes to form an intermediate layer (thickness: 1.5 μm) on the conductive substrate.

Next, a charge generation layer was formed. Specifically, 1.5 parts by mass of Y-type titanyl phthalocyanine as a charge generating agent, 1.0 parts by mass of polyvinyl acetal resin (“S-Lec BX-5” manufactured by Sekisui Chemical Co., Ltd.) as a base resin, and 1.0 part by mass of propylene glycol monomethyl 40.0 parts by mass of ether and 40.0 parts by mass of tetrahydrofuran were mixed for 12 hours using a bead mill to obtain a charge generation layer coating liquid. The charge generation layer coating liquid was filtered using a filter with an opening of 3 μm. The resulting filtrate was applied onto the intermediate layer by dip coating and dried at 50° C. for 5 minutes. Thus, a charge generation layer (thickness: 0.3 μm) was formed on the intermediate layer.

Next, a charge transport layer was formed. Specifically, 45.00 parts by mass of a hole transport agent (HTM-1), 100.00 parts by mass of a polyarylate resin A as a binder resin, 0.30 parts by mass of a phthalocyanine pigment (K-1), and silicone Oil ("KF96-50cs" manufactured by Shin-Etsu Chemical Co., Ltd., silicone oil having a dimethylpolysiloxane structure) 0.07 parts by mass, 560.00 parts by mass of tetrahydrofuran, and 140.00 parts by mass of toluene are mixed, A coating liquid for a charge transport layer was obtained. The charge transport layer coating liquid was applied onto the charge generation layer by dip coating and dried at 120° C. for 40 minutes. Thus, a charge transport layer (thickness: 30 μm) was formed on the charge generation layer to obtain a photoreceptor (A-1). Photoreceptor (A-1) had an intermediate layer on the conductive substrate, a charge generation layer on the intermediate layer, and a charge transport layer on the charge generation layer.

(Production of photoreceptors (A-2) to (A-12), (B-1) to (B-4) and (B-6) to (B-12))
The polyarylate resin shown in Table 5 was used, and instead of 0.30 parts by mass of the phthalocyanine pigment (K-1), the compound shown in the "pigment, etc." column of Table 5 was used in the amount shown in Table 5. Photoreceptors (A-2) to (A-12), (B-1) to (B-4) and (B-6) to (B-12) were each produced.

"K-1" and "K-2" in the column "pigments, etc." in Table 5 indicate phthalocyanine pigments (K-1) and (K-2), respectively. "K-3", "K-4", and "K-5" shown in the "pigments, etc." column of Table 5 are the following formulas (K-3), (K-4), and (K- The compound represented by 5) is shown.

(Production of photoreceptor (B-5))
A photoreceptor (B-5) was produced in the same manner as the photoreceptor (A-1), except that 0.30 parts by mass of the phthalocyanine pigment (K-1) was not added.

<Evaluation of Solubility in Solvent>
In an environment at a temperature of 22° C., 3 g of polyarylate resin and tetrahydrofuran in such an amount that the concentration of polyarylate resin becomes 15% by mass were stirred for 60 minutes to obtain an evaluation liquid. The evaluation solution was visually observed, and the solubility of the polyarylate resin in the solvent tetrahydrofuran was evaluated according to the following criteria. The polyarylate resin rated A or B was determined to have good solubility in the solvent, and the polyarylate resin rated C was determined to have poor solubility in the solvent. Table 4 shows the evaluation results of each polyarylate resin.

(Evaluation criteria for solubility in solvents)
A: The polyarylate resin was completely dissolved in tetrahydrofuran, and cloudiness and gelation of the evaluation solution were not observed.
B: White turbidity of the evaluation liquid was confirmed, but gelling of the evaluation liquid was not confirmed.
C: Gelation of the evaluation solution was confirmed.

<Evaluation of Sensitivity Characteristics When Printing Solid Images>
The sensitivity characteristics of the photoreceptor when printing a solid image (hereinafter sometimes referred to as sensitivity characteristics A) were evaluated. Specifically, the sensitivity characteristics of the photoreceptor were evaluated using a drum sensitivity tester (manufactured by Gentec Co., Ltd.) under an environment of a temperature of 25° C. and a relative humidity of 50% RH. Specifically, using a drum sensitivity tester, the photoreceptor was charged so that the surface potential of the photoreceptor was -550V. Then, monochromatic light (wavelength: 780 nm, exposure amount: 0.87 μJ/cm ² ) extracted from halogen lamp light using a bandpass filter was irradiated onto the surface of the photoreceptor. The exposure amount of 0.87 μJ/cm ² corresponds to the exposure amount when printing a solid image. The surface potential of the photoreceptor was measured when 50 milliseconds had passed since the irradiation of the monochromatic light, and was defined as the post-exposure potential A (V _LA , unit: -V). Table 5 shows the post-exposure potential A of each photosensitive member. From the post-exposure potential A, the sensitivity characteristic A of the photoreceptor was evaluated according to the following criteria.

(Evaluation criteria for sensitivity characteristic A)
Good: The absolute value of the post-exposure potential A is 120 V or less.
Poor: The absolute value of the post-exposure potential A is over 120V.

<Evaluation of Sensitivity Characteristics When Printing Halftone Images>
The sensitivity characteristics of the photoreceptor when printing halftone images (hereinafter sometimes referred to as sensitivity characteristics B) were evaluated. Sensitivity characteristics B were evaluated in the same manner as sensitivity characteristics A except that the exposure amount was changed from 0.87 μJ/cm ² to 0.15 μJ/cm ² . The exposure amount of 0.15 μJ/cm ² corresponds to the exposure amount when printing a halftone image. The surface potential of the photoreceptor was measured when 50 milliseconds had passed since the irradiation of the monochromatic light, and was defined as the post-exposure potential B (V _LB , unit: -V). Table 5 shows the post-exposure potential B of each photosensitive member. From the post-exposure potential B, the sensitivity characteristic B of the photoreceptor was evaluated according to the following criteria.

(Evaluation criteria for sensitivity characteristic B)
Good: The absolute value of the post-exposure potential B is over 250V.
Poor: The absolute value of the post-exposure potential B is 250 V or less.

<Abrasion resistance evaluation>
A color printer (“C711dn” manufactured by Oki Data Co., Ltd.) was used as an evaluation machine for the abrasion resistance evaluation. Cyan toner was filled in the toner cartridge of the evaluation machine. First, the film thickness T1 of the charge transport layer of the photoreceptor was measured. The photoreceptor was then mounted on the evaluation machine. Next, an image I (pattern image with a print rate of 1%) was printed on 10,000 sheets of paper using an evaluation machine under a normal temperature and normal humidity environment (temperature of 23° C. and relative humidity of 50% RH). Image I was then printed on 10,000 sheets of paper using the evaluation machine under a high-temperature and high-humidity environment (temperature of 32° C. and relative humidity of 85% RH). Next, the image I was printed on 10,000 sheets of paper using the evaluation machine under a low-temperature and low-humidity environment (temperature of 10° C. and relative humidity of 15% RH; hereinafter sometimes referred to as LL environment). After printing under the LL environment, the evaluator was allowed to stand for 2 hours. Next, a solid image (a solid image with an image density of 100%) was printed on one sheet of paper under the LL environment. After that, the film thickness T2 of the charge transport layer of the photoreceptor was measured. Then, the amount of wear (T1-T2, unit: μm), which is the change in thickness of the charge transport layer before and after printing, was determined. Table 5 shows the obtained wear amount. From the amount of abrasion, the abrasion resistance of the photoreceptor was evaluated according to the following criteria.

(Abrasion resistance evaluation criteria)
Good: Wear amount is 2.0 μm or less.
Poor: The amount of wear exceeds 2.0 µm.

In Table 4, "resin" indicates polyarylate resin, and "solubility" indicates evaluation of solubility in solvents. The meanings of the terms in Table 5 are as follows. "Resin" indicates a polyarylate resin. "Pigment, etc." indicates a phthalocyanine pigment or other compounds. “Sensitivity A” indicates the evaluation of the sensitivity characteristic A. "V _LA " indicates the post-exposure potential A of the photoreceptor in the sensitivity characteristic A evaluation. “Sensitivity B” indicates the evaluation of the sensitivity characteristic B. “V _LB ” indicates the post-exposure potential B of the photoreceptor in the sensitivity characteristic B evaluation. "Preparation not possible" indicates that the corresponding evaluation could not be performed because the polyarylate resin was not dissolved in the solvent for forming the charge transport layer coating liquid and the charge transport layer coating liquid could not be prepared. "-" indicates that the corresponding component was not used.

As can be seen from Table 3, polyarylate resins J to N were not included in polyarylate resins (PA). Moreover, as can be understood from the formula (O), the polyarylate resin O was not a resin included in the polyarylate resin (PA). As can be seen from Table 5, in photoreceptors (B-1) to (B-4) and (B-11) to (B-12), the binder resin did not contain polyarylate resin (PA). rice field. Therefore, as shown in Tables 4 and 5, the solubility of the polyarylate resins J and M in solvents was poor, and the charge transport layer coating liquid could not be prepared using the polyarylate resins J and M. The charge transport layers of the photoreceptors (B-1) and (B-4) could not be formed. Further, as shown in Table 5, the abrasion resistance of the photoreceptors (B-2) and (B-3) was poor. Further, as shown in Table 5, the sensitivity characteristic A and abrasion resistance of the photoreceptors (B-11) and (B-12) were poor.

As can be seen from Table 5, the charge transport layer of photoreceptor (B-5) did not contain the specified phthalocyanine pigment. Therefore, the sensitivity characteristics A and B of the photosensitive member (B-5) were unsatisfactory.

As can be seen from Table 5, in the photoreceptor (B-6), the content of the prescribed phthalocyanine pigment was less than 0.15 parts by mass with respect to 100.00 parts by mass of the binder resin. Therefore, the sensitivity characteristic A of the photoreceptor (B-6) was unsatisfactory.

As can be seen from Table 5, in the photoreceptor (B-7), the content of the predetermined phthalocyanine pigment was more than 0.50 parts by mass with respect to 100.00 parts by mass of the binder resin. Therefore, the sensitivity characteristic A of the photoreceptor (B-7) was unsatisfactory.

As can be seen from Table 5, photoreceptors (B-8) to (B-10) contained any of additives (K-3) to (K-5), but additive (K- None of 3) to (K-5) were the specified phthalocyanine pigments. Therefore, the sensitivity characteristics A of the photoreceptors (B-8) to (B-10) were unsatisfactory.

On the other hand, as can be understood from Table 3, polyarylate resins A to I were resins included in polyarylate resin (PA). As can be seen from Table 5, the charge transport layers of photoreceptors (A-1) to (A-12) contain a resin contained in a polyarylate resin (PA) as a binder resin and a prescribed phthalocyanine pigment. rice field. In the photoreceptors (A-1) to (A-12), the content of the phthalocyanine pigment is 0.15 parts by mass or more and 0.50 parts by mass or less with respect to 100.00 parts by mass of the binder resin. rice field. For this reason, the photoreceptors (A-1) to (A-12) were able to form a good photosensitive layer, and were able to improve the sensitivity characteristics (more specifically, the sensitivity characteristics A and B) and the abrasion resistance. .

From the above, it was shown that the photoreceptors of the present invention including the photoreceptors (A-1) to (A-12) can form a good photosensitive layer and can improve the sensitivity characteristics and abrasion resistance.

A photoreceptor according to the present invention can be used in an image forming apparatus.

1: photoreceptor (electrophotographic photoreceptor)
2: Conductive substrate 3: Photosensitive layer 3a: Charge generation layer 3b: Charge transport layer

Claims (11)

comprising a conductive substrate and a photosensitive layer;
The photosensitive layer includes a charge generation layer and a charge transport layer,
The charge generation layer contains a charge generation agent,
The charge transport layer contains a hole transport agent, a binder resin, and a phthalocyanine pigment,
The binder resin includes a polyarylate resin,
The polyarylate resin has repeating units represented by formulas (1), (2), (3), and (4), and the total number of repeating units represented by formulas (1) and (3) , the content of the repeating unit represented by the formula (3) is greater than 0% and less than 20%,
The content of the phthalocyanine pigment is 0.15 parts by mass or more and 0.50 parts by mass or less with respect to 100.00 parts by mass of the binder resin,
The electrophotographic photoreceptor, wherein the phthalocyanine pigment is a metal-free phthalocyanine or a compound represented by formula (11).

(In formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group, X represents a divalent group represented by formula (X1) or (X2),
In formula (2), W represents a divalent group represented by formula (W1) or (W2). )

(In the formula (X1), t represents an integer of 1 or more and 3 or less, * represents a bond,
In formula (X2), R ³ and R ⁴ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ and R ⁴ represent groups different from each other, and * represents a bond. show. )

(In the above formulas (W1) and (W2), * represents a bond.)

(In formula (11) above, M represents a metal atom which may have a ligand.) 2. The electrophotographic photoreceptor according to claim 1, wherein in formula (1), ^R1 and ^R2 represent a methyl group, and X represents a divalent group represented by formula (X1). 3. The electrophotographic photoreceptor according to claim 1, wherein the repeating unit represented by formula (1) is a repeating unit represented by formula (1-1).

The repeating unit represented by the formula (1) is a repeating unit represented by the formula (1-1), and the repeating unit represented by the formula (2) is represented by the formula (2-1). 4. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the repeating unit is

The repeating unit represented by formula (1) is a repeating unit represented by formula (1-1), and the repeating unit represented by formula (2) is represented by formula (2-2). 4. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the repeating unit is

2. The electrophotographic photoreceptor according to claim 1, wherein R1 ^{and R2} in formula (1) represent a hydrogen atom, and X represents a divalent group represented by formula (X2). 7. The electrophotographic photoreceptor according to claim 1, wherein the repeating unit represented by formula (1) is a repeating unit represented by formula (1-2).

The repeating unit represented by formula (1) is a repeating unit represented by formula (1-2), and the repeating unit represented by formula (2) is represented by formula (2-1). 8. The electrophotographic photoreceptor according to claim 1, 6, or 7, which is a repeating unit.

9. The electrophotographic photoreceptor according to claim 1, wherein the phthalocyanine pigment is the metal-free phthalocyanine. The electrophotographic photoreceptor according to any one of claims 1 to 9, wherein the hole transport agent contains a compound represented by formula (20).

(In formula (20), R ³¹ to R ³⁶ each independently represent an alkyl group having 1 to 8 carbon atoms or a phenyl group; R ³⁷ and R ³⁸ each independently represent a hydrogen atom; represents an alkyl group having 1 to 8 carbon atoms or a phenyl group, b1, b2, b3, and b4 each independently represent an integer of 0 to 5; b5 and b6 each independently represent 0 represents an integer of 4 or less, and d and e each independently represent 0 or 1.) The electrophotographic photoreceptor according to any one of claims 1 to 10, wherein the hole transport agent contains a compound represented by formula (HTM-1).

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