JP7259514B2 - Electrophotographic photoreceptor - Google Patents

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 having a photosensitive layer. The binder resin for this photosensitive layer is a polyarylate resin having a structure represented by the following chemical formula.

Japanese Patent Application Laid-Open No. 2003-322982

However, the inventors' studies have revealed that the image forming member described in Patent Document 1 is insufficient in abrasion resistance.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor that is excellent in wear resistance and capable of suppressing the occurrence of fogging in formed images.

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 at least a hole transport agent and a binder resin. The binder resin includes polyarylate resin. The polyarylate resin contains repeating units represented by general formula (1), repeating units represented by chemical formula (2), and repeating units represented by chemical formula (3). The ratio n ₁ /n 2 of the number n ₁ of repeating units represented by the general formula (1) to the number n ₂ of repeating units represented by the chemical formula ( ₂ ) is 1.0 or more. The hole transport agent includes a compound represented by general formula (21), general formula (22), general formula (23), chemical formula (HTM-10), or general formula (24). The content of the hole transport agent is 30 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the binder resin.

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group, R ³ represents a methyl group, and R ⁴ represents a hydrogen atom or an alkyl group having 2 or 3 carbon atoms. show. Alternatively, R ¹ and R ² each represent a methyl group, and R ³ and R ⁴ combined together represent a cycloalkylidene group having 5 or 6 carbon atoms.

In general formula (21), R ¹¹ , R ¹² , and R ¹³ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. . b1, b2 and b3 each independently represent an integer of 0 or more and 5 or less. In general formula (22), R ²¹ , R ²² , and R ²³ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. . d1, d2 and d3 each independently represents an integer of 0 or more and 5 or less. In general formula (23), R ³¹ , R ³² , R ³³ and R ³⁴ each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms. . R ³⁵ and R ³⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and e1, e2, e3, and e4 are Each independently represents an integer of 0 or more and 5 or less. In general formula (24), R ⁴¹ , R ⁴² , R ⁴³ and R ⁴⁴ each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms. . f1, f2, f3, and f4 each independently represent an integer of 0 or more and 5 or less.

The electrophotographic photoreceptor of the present invention is excellent in wear resistance and can suppress the occurrence of fogging in formed images.

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.

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. The present invention 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.

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).

Alkyl group having 1 to 8 carbon atoms, alkyl group having 1 to 5 carbon atoms, alkyl group having 1 to 4 carbon atoms, alkyl group having 1 to 3 carbon atoms, alkyl group having 2 carbon atoms Each group and alkyl group having 3 carbon atoms is linear 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, 1,2-dimethylpropyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethyl butyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2 -trimethylpropyl, 1-ethylbutyl, 2-ethylbutyl and 3-ethylbutyl groups, linear and branched heptyl groups, and linear and branched octyl groups. an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 2 carbon atoms, and an alkyl group having 3 carbon atoms Examples are groups having the corresponding number of carbon atoms among the groups mentioned as examples of alkyl groups each having from 1 to 8 carbon atoms.

Each alkoxy group having 1 to 8 carbon atoms and alkoxy group having 1 to 3 carbon atoms is linear or branched and unsubstituted unless otherwise specified. 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, 1,2-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, 1,2,2-trimethylpropoxy, 1-ethylbutoxy, 2-ethylbutoxy, 3-ethylbutoxy, linear and branched heptyloxy groups, and linear and A branched octyloxy group can be mentioned. Examples of the alkoxy group having 1 to 3 carbon atoms are groups having the corresponding number of carbon atoms among the groups described as examples of the alkoxy group having 1 to 8 carbon atoms.

Aryl groups containing 6 to 14 carbon atoms are unsubstituted unless otherwise specified. Examples of aryl groups having 6 to 14 carbon atoms include phenyl, naphthyl, indacenyl, biphenylenyl, acenaphthylenyl, anthryl and phenanthryl groups. The substituents used in the present specification have been described above.

<Electrophotographic photoreceptor>
The structure of an electrophotographic photoreceptor (hereinafter also referred to as photoreceptor) 1 of this embodiment will be described below with reference to FIGS. 1 to 3. FIG. 1 to 3 each show a partial cross-section of the photoreceptor 1. FIG.

As shown in FIG. 1, the photoreceptor 1 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. In other words, the photoreceptor 1 is a laminated electrophotographic photoreceptor including the charge generation layer 3a and the charge transport layer 3b as the photosensitive layer 3. As shown in FIG. The charge generation layer 3a is, for example, a single layer. The charge transport layer 3b is, for example, a single layer.

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

As shown in FIG. 3, the photoreceptor 1 may include a conductive substrate 2, a photosensitive layer 3, and an intermediate layer 4 (undercoat layer). 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 comprise a conductive substrate 2, a photosensitive layer 3, and a protective layer (not shown). A protective layer is provided on the photosensitive layer 3 . As shown in FIGS. 1 and 2, 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, the charge transport layer 3b is preferably provided as the outermost surface 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) and a predetermined hole transport agent, which will be described later, as the outermost layer, the wear resistance of the photoreceptor 1 is further improved, and fogging in the formed image is reduced. The occurrence can be further suppressed.

The charge generation layer 3a contains a charge generation agent. The charge generation layer 3a may contain a base resin. 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 transport layer 3b contains at least a hole transport agent and a binder resin. The charge transport layer 3b may further contain a third compound described later, if necessary. The charge transport layer 3b may further contain additives, if necessary. 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 structure of the photoreceptor 1 has been described above with reference to FIGS. 1 to 3. FIG. The photoreceptor will be described in more detail below.

(binder resin)
The charge transport layer contains a polyarylate resin as a binder resin. The polyarylate resin contains repeating units represented by general formula (1), repeating units represented by chemical formula (2), and repeating units represented by chemical formula (3). The ratio n ₁ /n 2 of the number n ₁ of repeating units represented by the general formula (1) to the number n ₂ of repeating units represented by the chemical formula (2) is 1.0 or more _.

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a methyl group, R ³ represents a methyl group, and R ⁴ represents a hydrogen atom or an alkyl group having 2 or 3 carbon atoms. show. Alternatively, in general formula (1), R ¹ and R ² each represent a methyl group, and R ³ and R ⁴ are combined to represent a cycloalkylidene group having 5 or 6 carbon atoms.

Hereinafter, the repeating unit represented by the general formula (1), the repeating unit represented by the chemical formula (2), and the repeating unit represented by the chemical formula (3) are respectively referred to as the repeating unit (1) and the repeating unit (2 ), and repeating unit (3). Further, the repeating unit (1), the repeating unit (2) and the repeating unit (3) are included, and the ratio n ₁ /n 2 of the number n ₁ of the repeating unit (1) to the number n ₂ of the repeating unit ( ₂ ) is A polyarylate resin having a polyarylate of 1.0 or more may be referred to as a polyarylate resin (PA).

A polyarylate resin (PA) can improve the abrasion resistance of the photoreceptor when it is contained in the charge transport layer. The reason is presumed as follows.

First, the polyarylate resin (PA) contains repeating units (2) and repeating units (3). Thereby, the abrasion resistance of the photoreceptor can be improved.

Second, the polyarylate resin (PA) contains repeating units (1). This can improve the solubility of the polyarylate resin (PA) in the solvent for forming the charge transport layer. _{Furthermore , the polyarylate} resin ( PA) can be further improved in solubility. By improving the solubility of the polyarylate resin (PA), the charge transport layer can be suitably formed, and the wear resistance of the photoreceptor can be improved.

Next, general formula (1) will be described in detail. Examples of the alkyl group having 2 or 3 carbon atoms represented by R ⁴ in general formula (1) include ethyl group, n-propyl group and isopropyl group. The alkyl group having 2 or 3 carbon atoms is preferably an ethyl group or an isopropyl group.

The cycloalkylidene group having 5 or 6 carbon atoms represented by R ³ and R ⁴ in general formula (1) combined with each other includes a cyclopentylidene group and a cyclohexylidene group. A cyclopentylidene group and a cyclohexylidene group are divalent groups represented by the following chemical formulas (5) and (6), respectively. As the cycloalkylidene group having 5 or 6 carbon atoms, a cyclohexylidene group is preferred.

Preferred examples of the repeating unit (1) are represented by chemical formula (1-1), chemical formula (1-2), chemical formula (1-3), chemical formula (1-4), and chemical formula (1-5). repeating units. Hereinafter, repeating units represented by chemical formulas (1-1), chemical formula (1-2), chemical formula (1-3), chemical formula (1-4), and chemical formula (1-5) are referred to as repeating units ( 1-1), (1-2), (1-3), (1-4), and (1-5).

The polyarylate resin (PA) may contain only one repeating unit (1). Alternatively, the polyarylate resin (PA) may contain two or more repeating units (1).

The ratio n ₁ /n 2 of the number n ₁ of repeating units (1) contained in the polyarylate resin (PA) to the number n ₂ of repeating units ( ₂ ) contained in the polyarylate resin (PA) is 1.0. That's it. That is, the number n ₁ of repeating units (1) is equal to or greater than the number n ₂ of repeating units ( ₂ ). When the ratio n ₁ /n ₂ is 1.0 or more, the solubility of the polyarylate resin (PA) in the solvent for forming the charge transport layer can be improved, and the wear resistance of the photoreceptor can be improved. can. In order to improve the wear resistance of the photoreceptor, the ratio _n1 / _n2 is preferably 10.0 or less, more preferably 5.0 or less. In order to improve the wear resistance of the photoreceptor while improving the solubility of the polyarylate resin (PA) in the solvent for forming the charge transport layer, the ratio n ₁ /n ₂ is 1.0, 2.0. , 3.0, 5.0 and 10.0. The ratio n ₁ /n ₂ may be, for example, 1.0 or more and less than 2.0, or 2.0 or more and 5.0 or less. The ratio _n1 / _n2 may be, for example, 1.0 or 3.0.

The ratio n ₁ /n ₂ can be adjusted by changing the amount of the compound (BP-1) and the amount of the compound (BP-2) added when producing the polyarylate resin (PA). . The compound (BP-1) and compound (BP-2) will be described later.

The ratio n ₁ /n ₂ was obtained by measuring the ¹ H-NMR spectrum of the polyarylate resin (PA) using a proton nuclear magnetic resonance spectrometer, and measuring the peak characteristic of each repeating unit in the obtained ¹ H-NMR spectrum. can be obtained by calculating the ratio of

Specific examples of polyarylate resins (PA) include the following polyarylate resins.
A polyarylate resin containing repeating units (1-1), (2), and (3) and having a ratio n ₁ /n ₂ of 2.0 or more and 5.0 or less (referred to as polyarylate resin (I) there is);
A polyarylate resin containing repeating units (1-5), (2), and (3) and having a ratio n ₁ /n ₂ of 2.0 or more and 5.0 or less (referred to as polyarylate resin (II) there is);
A polyarylate resin containing repeating units (1-2), (2), and (3) and having a ratio n ₁ /n ₂ of 2.0 or more and 5.0 or less (referred to as polyarylate resin (III) there is);
A polyarylate resin containing repeating units (1-3), (2), and (3) and having a ratio n ₁ /n ₂ of 2.0 or more and 5.0 or less (referred to as polyarylate resin (IV) there is);
A polyarylate resin containing repeating units (1-4), (2), and (3) and having a ratio n ₁ /n ₂ of 2.0 or more and 5.0 or less (referred to as polyarylate resin (V) ₎ ; and a polyarylate resin ( _polyarylate resin (VI ).

More specific examples of the polyarylate resin (PA) include polyarylate resins represented by chemical formulas (R-1) to (R-6) (hereinafter referred to as polyarylate resins (R-1) to (R -6)) may be mentioned. In the chemical formulas (R-1) to (R-6), the number attached to the lower right of each repeating unit is the percentage (%) of the number of each repeating unit to the total number of repeating units contained in the polyarylate resin ). The total number of repeating units is the sum of the number of bisphenol-derived repeating units and the number of dicarboxylic acid-derived repeating units. For convenience of description, two repeating units (3) are shown in each of the chemical formulas (R-1) to (R-6). However, the percentage of the number of repeating units (3) to the total number of repeating units contained in each of the polyarylate resins (R-1) to (R-6) was 50.0% (two repeating units (3) is the sum of the numbers attached to the lower right of ).

In the polyarylate resin (PA), the bisphenol-derived repeating unit and the dicarboxylic acid-derived repeating unit are adjacently bonded to each other. Bisphenol-derived repeating units are, for example, repeating units (1) and (2). Further, the dicarboxylic acid-derived repeating unit is, for example, the repeating unit (3). Polyarylate resins (PA) can be, for example, random copolymers, alternating copolymers, periodic copolymers, or block copolymers.

The polyarylate resin (PA) may contain only repeating units (1), (2) and (3) as repeating units. In addition to repeating units (1), (2), and (3), the polyarylate resin (PA) may further contain repeating units other than these repeating units. The charge transport layer may contain only one type of polyarylate resin (PA), or may contain two or more types of polyarylate resins (PA).

The viscosity average molecular weight of the polyarylate resin (PA) is preferably 10,000 or more, more preferably 20,000 or more, still more preferably 30,000 or more, and 40,000 or more. is particularly preferred. When the viscosity average molecular weight of the polyarylate resin (PA) is 10,000 or more, the abrasion resistance of the photoreceptor can be improved. 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. When the viscosity average molecular weight of the polyarylate resin (PA) is 80,000 or less, the polyarylate resin (PA) is easily dissolved in the solvent for forming the charge transport layer.

A method for producing the polyarylate resin (PA) is not particularly limited. Examples of a method for producing a polyarylate resin (PA) include a method of condensation polymerization of bisphenol for forming bisphenol-derived repeating units and dicarboxylic acid for forming dicarboxylic acid-derived repeating units. For polycondensation, known synthesis methods (eg, solution polymerization, melt polymerization, or interfacial polymerization) can be employed.

As bisphenol for constituting the bisphenol repeating unit of polyarylate resin (PA), for example, compounds represented by general formula (BP-1) and chemical formula (BP-2) (hereinafter referred to as compound (BP-1) and (BP-2) may be described). As the dicarboxylic acid for constituting the dicarboxylic acid repeating unit of the polyarylate resin (PA), for example, a compound represented by the chemical formula (DC-3) (hereinafter sometimes referred to as compound (DC-3)) is mentioned. R ¹ , R ² , R ³ and R ⁴ in general formula (BP-1) have the same meanings as R ¹ , R ² , R ³ and R ⁴ in general formula (1).

Preferred examples of the compound (BP-1) include compounds represented by chemical formulas (BP-1-1) to (BP-1-5) (hereinafter referred to as compounds (BP-1-1) to (BP -1-5)).

A bisphenol for forming a bisphenol-derived repeating unit may be used after being derivatized to an aromatic diacetate. A dicarboxylic acid for forming a dicarboxylic acid-derived repeating unit 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.

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 charge transport layer may contain only a polyarylate resin (PA) as a binder resin. The charge transport layer may further contain a binder resin other than the polyarylate resin (PA) (hereinafter sometimes referred to as other binder resin) as a binder resin.

Other binder resins include, for example, thermoplastic resins (more specifically, polycarbonate resins, styrene resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene- Acrylic acid copolymer, acrylic copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, vinyl chloride-vinyl acetate copolymer, polyester resin, alkyd 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). mentioned.

(Hole transport agent)
The charge transport layer contains, as a hole transport agent, a compound represented by general formula (21), general formula (22), general formula (23), chemical formula (HTM-10), or general formula (24) (hereinafter referred to as (21), (22), (23), (HTM-10), and (24)), respectively.

By containing the hole transporting agent (21), (22), (23), (HTM-10), or (24) in the charge transporting layer, the occurrence of fogging in the formed image can be suppressed. The reason is presumed as follows. An image that uses a reversal development method, a charging device negatively charges a photoreceptor, and an electrostatic latent image that is developed with negatively charged toner (more specifically, toner that is a non-magnetic one-component developer). A forming apparatus will be described as an example. During development, negatively charged toner is placed on the developing member of the developing device provided in the image forming apparatus. Contact of the negatively charged toner on the development member with the photoreceptor can cause negative charging of the negatively charged toner and reverse charging of the negatively charged toner to a positive polarity. Of the toner on the developing member, some of the toner that has not been used for image formation returns to the developing device and is used again for development. When the toner is used again for development, the toner whose negative charging property has decreased due to contact with the photoreceptor and the toner which has been reversely charged tend to adhere to the white paper portion of the formed image. As a result, fogging occurs in the formed image. The charge transport layer contains a hole transport agent (21), (22), (23), (HTM-10), or (24) to provide a negatively charged toner even when in contact with a photoreceptor. It is possible to suppress the deterioration of the negative chargeability of the toner and the reverse charging of the negatively charged toner to the positive polarity. Therefore, it is possible to suppress the occurrence of fogging in the formed image. This advantage is pronounced when polyarylate resins (PA) and these hole transport agents are included in the charge transport layer. The hole transport agents (21), (22), (23), (HTM-10) and (24) are described below.

In general formula (21), R ¹¹ , R ¹² and R ¹³ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. b1, b2 and b3 each independently represent an integer of 0 or more and 5 or less.

In general formula (21), when b1 represents an integer of 2 or more and 5 or less, a plurality of R ¹¹ may be the same or different. When b2 represents an integer of 2 or more and 5 or less, a plurality of R ¹² may be the same or different. When b3 represents an integer of 2 or more and 5 or less, a plurality of R ¹³ may be the same or different.

In general formula (21), R ¹¹ , R ¹² and R ¹³ each independently preferably represent an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms, methyl more preferably represents a group or a methoxy group. b1, b2, and b3 preferably each independently represent 0 or 1;

In general formula (22), R ²¹ , R ²² and R ²³ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. d1, d2 and d3 each independently represents an integer of 0 or more and 5 or less.

In general formula (22), when d1 represents an integer of 2 or more and 5 or less, a plurality of R ²¹ may be the same or different. When d2 represents an integer of 2 or more and 5 or less, a plurality of R ²² may be the same or different. When d3 represents an integer of 2 or more and 5 or less, a plurality of R ²³ may be the same or different.

In general formula (22), R ²¹ , R ²² and R ²³ each independently preferably represent an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms, methyl more preferably represents a group or a methoxy group. Each of d1, d2 and d3 preferably independently represents an integer of 0 or more and 2 or less.

In general formula (23), R ³¹ , R ³² , R ³³ and R ³⁴ each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms. R ³⁵ and R ³⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms. e1, e2, e3, and e4 each independently represent an integer of 0 or more and 5 or less.

In general formula (23), when e1 represents an integer of 2 or more and 5 or less, a plurality of R ³¹ may be the same or different. When e2 represents an integer of 2 or more and 5 or less, a plurality of R ³² may be the same or different. When e3 represents an integer of 2 or more and 5 or less, a plurality of R ³³ may be the same or different. When e4 represents an integer of 2 or more and 5 or less, a plurality of R ³⁴ may be the same or different.

In general formula (23), R ³¹ , R ³² , R ³³ and R ³⁴ each independently represent an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. Preferably, it represents a methyl group or a methoxy group. R ³⁵ and R ³⁶ preferably each independently represent an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. It is preferable that each of e1, e2, e3 and e4 independently represents an integer of 0 or more and 2 or less.

In general formula (24), R ⁴¹ , R ⁴² , R ⁴³ and R ⁴⁴ each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms. f1, f2, f3, and f4 each independently represent an integer of 0 or more and 5 or less.

In general formula (24), when f1 represents an integer of 2 or more and 5 or less, a plurality of R ⁴¹ may be the same or different. When f2 represents an integer of 2 or more and 5 or less, a plurality of R ⁴² may be the same or different. When f3 represents an integer of 2 or more and 5 or less, a plurality of R ⁴³ may be the same or different. When f4 represents an integer of 2 or more and 5 or less, a plurality of R ⁴⁴ may be the same or different.

In general formula (24), R ⁴¹ , R ⁴² , R ⁴³ and R ⁴⁴ preferably each independently represent an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. f1, f2, f3, and f4 preferably each independently represent 0 or 1.

Preferred examples of hole transport agents include compounds represented by chemical formulas (HTM-1) to (HTM-11). Hereinafter, the compounds represented by chemical formulas (HTM-1) to (HTM-11) may be referred to as hole transport agents (HTM-1) to (HTM-11), respectively. Since the hole transport agent (HTM-10) has already been described, it will not be described again.

The hole transport agents (HTM-1) to (HTM-2) are each suitable examples of the hole transport agent (21). Hole transport agents (HTM-3) through (HTM-8) are each suitable examples of hole transport agents (22). A hole transport agent (HTM-9) is a suitable example of a hole transport agent (23). A hole transport agent (HTM-10) is a suitable example of a hole transport agent (24).

The charge transport layer contains, as a hole transport agent, for example, a compound of one of the hole transport agents (21), (22), (23), (HTM-10) and (24). The charge transport layer may contain only hole transport agent (21), (22), (23), (HTM-10), or (24) as the hole transport agent. In addition to the hole transport agent (21), (22), (23), (HTM-10), or (24), the charge transport layer contains a hole transport agent other than these as the hole transport agent. (hereinafter sometimes referred to as other hole transport agent) may be further contained.

Other hole transport agents include, for example, 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), oxa Diazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole), styryl compounds (e.g., 9-(4-diethylaminostyryl)anthracene), carbazole compounds compounds (e.g., polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds , thiazole-based compounds, thiadiazole-based compounds, imidazole-based compounds, pyrazole-based compounds, and triazole-based compounds.

The content of the hole transport agent is 30 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the binder resin. If the content of the hole transporting agent is less than 30 parts by mass, the negative chargeability of the negatively charged toner is lowered and the negatively charged toner is reversely charged when the photoreceptor and the negatively charged toner come into contact with each other. As a result, fogging occurs in the formed image. On the other hand, when the content of the hole transport agent exceeds 45 parts by mass, the abrasion resistance of the photoreceptor is lowered. When the charge transport layer contains two or more hole transport agents, the content of the hole transport agents is the total content of the two or more hole transport agents.

(Third compound)
A third compound may be included in the charge transport layer, for example as an electron acceptor compound. The third compound has a ketone structure or a dicyanomethylene structure. By containing the third compound in the charge transport layer, it is possible to improve the electrical properties of the photoreceptor while improving the wear resistance of the photoreceptor and suppressing the occurrence of fogging in formed images. The third compound may have both a ketone structure and a dicyanomethylene structure.

The third compound is preferably at least one compound (for example, one compound) among the compounds represented by general formulas (31) to (39). Hereinafter, the compounds represented by general formulas (31) to (39) may be referred to as third compounds (31) to (39), respectively.

In general formulas (31) to (39), Q ³¹ to Q ⁵⁷ are each independently a hydrogen atom; a halogen atom; an alkyl group having 1 to 5 carbon atoms; and an aryl group having 6 to 14 carbon atoms. represents an optionally substituted alkoxy group having 1 to 3 carbon atoms; or a phenyl group optionally substituted with an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms.

A chlorine atom is preferable as the halogen atom represented by Q ³¹ to Q ⁵⁷ in general formulas (31) to (39).

The alkyl group having 1 to 5 carbon atoms represented by Q ³¹ to Q ⁵⁷ in general formulas (31) to (39) includes methyl group, ethyl group, n-butyl group, tert-butyl group, or 1, A 1-dimethylpropyl group is preferred.

The alkoxy group having 1 to 3 carbon atoms represented by Q ³¹ to Q ⁵⁷ in general formulas (31) to (39) is preferably a methoxy group. An alkoxy group having 1 to 3 carbon atoms may be substituted with an aryl group having 6 to 14 carbon atoms. As the aryl group having 6 to 14 carbon atoms which is a substituent of the alkoxy group having 1 to 3 carbon atoms, a phenyl group is preferable. As the alkoxy group having 1 to 3 carbon atoms substituted with an aryl group having 6 to 14 carbon atoms, a phenylmethoxy group is preferable.

The phenyl group represented by Q ³¹ to Q ⁵⁷ in formulas (31) to (39) may be substituted with an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. As the alkyl group having 1 to 3 carbon atoms, which is a substituent of the phenyl group, a methyl group or an ethyl group is preferable.

Each of Q ³¹ to Q ³⁴ in general formula (31) preferably represents an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, methyl more preferably represents a radical or a tert-butyl radical.

Each of Q ³⁵ to Q ³⁸ in the general formula (32) preferably represents an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, methyl more preferably represents a radical or a tert-butyl radical.

Each of Q ³⁹ to Q ⁴⁰ in general formula (33) preferably represents an alkyl group having 1 to 5 carbon atoms, more preferably a 1,1-dimethylpropyl group.

Each of Q ⁴¹ to Q ⁴² in general formula (34) preferably represents an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and tert -Butyl group is more preferred. Q ⁴³ to Q ⁴⁷ each independently preferably represent a hydrogen atom or a halogen atom, more preferably a hydrogen atom or a chlorine atom. Q ⁴³ , Q ⁴⁴ , Q ⁴⁶ and Q ⁴⁷ each preferably represent a hydrogen atom. Q ⁴⁵ preferably represents a halogen atom, more preferably a chlorine atom.

Each of Q ⁴⁸ to Q ⁵¹ in general formula (35) preferably represents an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and tert -Butyl group is more preferred.

Each of Q ⁵² to Q ⁵³ in the general formula (36) preferably represents a phenyl group substituted with an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. It more preferably represents a phenyl group substituted with one or two alkyl groups having 1 to 3 carbon atoms, and even more preferably represents a 2-ethyl-6-methylphenyl group.

Q ⁵⁴ in the general formula (37) preferably represents an alkyl group having 1 to 5 carbon atoms, more preferably represents an alkyl group having 1 to 4 carbon atoms, and represents an n-butyl group. is more preferred.

Each of Q ⁵⁵ to Q ⁵⁶ in general formula (38) preferably represents a hydrogen atom.

Q ⁵⁷ in the general formula (39) preferably represents an alkoxy group having 1 to 3 carbon atoms substituted with an aryl group having 6 to 14 carbon atoms, and the number of carbon atoms substituted by a phenyl group. It is more preferable to represent 1 or more and 3 or less alkoxy groups, and it is even more preferable to represent a phenylmethoxy group.

The third compound is preferably at least one compound (for example, one compound) among the compounds represented by chemical formulas (E-1) to (E-11). Hereinafter, the compounds represented by chemical formulas (E-1) to (E-11) may be referred to as third compounds (E-1) to (E-11), respectively.

The third compounds (E-1) to (E-2) are each suitable examples of the third compound (31). Each of the third compounds (E-3) to (E-4) is a preferred example of the third compound (32). The third compound (E-5) is a preferred example of the third compound (33). The third compound (E-6) is a preferred example of the third compound (34). The third compound (E-7) is a preferred example of the third compound (35). The third compound (E-8) is a preferred example of the third compound (36). The third compound (E-9) is a preferred example of the third compound (37). The third compound (E-10) is a preferred example of the third compound (38). The third compound (E-11) is a preferred example of the third compound (39).

The charge transport layer may contain only the third compound as an electron acceptor compound, or may further contain an electron acceptor compound other than this. The content of the third compound is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, and 0.5 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the binder resin. is more preferred.

(Charge generating agent)
The charge generation layer contains a charge generation agent. Examples of charge generating agents include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaline pigments, indigo pigments, azulenium pigments, cyanine pigments, 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-based pigments, toluidine-based pigments , pyrazoline-based pigments, and quinacridone-based pigments. The charge-generating layer may contain only one type of charge-generating agent, or may contain two or more types thereof.

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 chemical formula (CGM-1). Titanyl phthalocyanine is represented by the chemical 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)
The charge generation layer may contain a base resin. Examples of the base resin are the same as other binder resins contained in the charge transport layer.

(Additive)
Additives contained in the photosensitive layer (more specifically, the charge generation layer and the charge transport layer) include, for example, ultraviolet absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, They include bulking agents, bulking agents, thickeners, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, electron acceptor compounds, and leveling agents.

(combination of materials)
In order to improve the abrasion resistance of the photoreceptor and suppress the occurrence of fogging in the formed image, the combination of the polyarylate resin and the hole transport agent contained in the charge transport layer should be selected from combination No. 1 shown in Table 1. Each of F1 to F36 is preferred. For the same reason, the combination of the polyarylate resin and the hole transport agent contained in the charge transport layer is the combination No. 1 shown in Table 1. It is more preferable that each of F1 to F36 and the charge generation agent contained in the charge generation layer is Y-type titanyl phthalocyanine.

In order to improve the wear resistance of the photoreceptor and suppress the occurrence of fogging in the formed image, the combination of the polyarylate resin, the hole transport agent, and the third compound contained in the charge transport layer should be selected as shown in Table 2 and Table 2. Combination No. 3 shown in FIG. Each of G1 to G66 is preferred. For the same reason, the combination of the polyarylate resin, the hole transport agent, and the third compound contained in the charge transport layer is the combination No. shown in Tables 2 and 3. Each of G1 to G66 and the charge generating agent contained in the charge generating layer is more preferably Y-type titanyl phthalocyanine.

The meanings of the terms in Tables 1 to 3 are as follows. "No." indicates "combination No.". "Resin" means "polyarylate resin". "HTM" stands for "hole transport agent".

(Conductive substrate)
The conductive substrate is not particularly limited as long as it can be used as the conductive substrate of the photoreceptor. At least the surface portion of the conductive substrate may be 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. These conductive materials may be used alone, or two or more of them may be used in combination (for example, as an alloy). 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. One of these inorganic particles may be used alone, or two or more thereof may be used in combination.

Examples of the intermediate layer resin are the same as the other binder resins contained in the charge transport 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. A photoreceptor manufacturing method includes a charge generating 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, and a solvent. The charge transport layer coating liquid can be prepared by dissolving or dispersing a hole transport agent and a binder resin in a solvent. The charge transport layer coating liquid may further contain at least one of a third compound and an additive, 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. These solvents may be used singly or in combination of two or more.

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.

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

<Hole transport agent>
As hole transport agents, the hole transport agents (HTM-1) to (HTM-11) described in the embodiment were prepared.

<Hole Transport Agent Used in Comparative Example>
As hole transport agents used in comparative examples, hole transport agents (HTM-A) to (HTM-E) were prepared. The hole transport agents (HTM-A) to (HTM-E) are represented by the following chemical formulas (HTM-A) to (HTM-E), respectively.

<Third compound>
As the third compounds, the third compounds (E-1) to (E-11) described in the embodiment were prepared.

<Polyarylate Resins (R-1) to (R-6)>
Each of the polyarylate resins (R-1) to (R-6) described in the embodiments was synthesized by the following method.

(Synthesis of polyarylate resin (R-1))
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 compound (BP-1-1) (30.9 mmol), compound (BP-2) (10.3 mmol), p-tert-butylphenol (0.413 mmol), and sodium hydroxide. (98 mmol) and benzyltributylammonium chloride (0.384 mmol) were charged. 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 until the temperature of the contents of the reaction vessel reached 10° C. to obtain an alkaline aqueous solution A.

Next, the compound (DC-3) dicarboxylic acid dichloride (32.4 mmol) was dissolved in chloroform (150 mL). A chloroform solution B was thus obtained.

Using a dropping funnel, the chloroform solution B was slowly added dropwise to the alkaline aqueous solution A 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. Thus, a polyarylate resin (R-1) was obtained.

(Synthesis of polyarylate resin (R-2))
In the same manner as in the synthesis of polyarylate resin (R-1), except that compound (BP-1-1) (30.9 mmol) was changed to compound (BP-1-5) (30.9 mmol), A polyarylate resin (R-2) was obtained.

(Synthesis of polyarylate resin (R-3))
In the same manner as in the synthesis of the polyarylate resin (R-1), except that the compound (BP-1-1) (30.9 mmol) was changed to the compound (BP-1-2) (30.9 mmol), A polyarylate resin (R-3) was obtained.

(Synthesis of polyarylate resin (R-4))
In the same manner as in the synthesis of the polyarylate resin (R-1), except that the compound (BP-1-1) (30.9 mmol) was changed to the compound (BP-1-3) (30.9 mmol), A polyarylate resin (R-4) was obtained.

(Synthesis of polyarylate resin (R-5))
In the same manner as in the synthesis of the polyarylate resin (R-1), except that the compound (BP-1-1) (30.9 mmol) was changed to the compound (BP-1-4) (30.9 mmol), A polyarylate resin (R-5) was obtained.

(Synthesis of polyarylate resin (R-6))
Compound (BP-1-1) (30.9 mmol) and compound (BP-2) (10.3 mmol), compound (BP-1-1) (20.6 mmol) and compound (BP-2) A polyarylate resin (R-6) was obtained in the same manner as the synthesis of the polyarylate resin (R-1), except that it was changed to (20.6 mmol).

The viscosity average molecular weights of the obtained polyarylate resins (R-1), (R-2), (R-3), (R-4), (R-5), and (R-6) are, respectively, 50,500, 51,000, 45,000, 47,300, 45,500 and 48,700.

Using a proton nuclear magnetic resonance spectrometer (manufactured by JASCO Corporation, 300 MHz), ¹ H-NMR spectra of the obtained polyarylate resins (R-1) to (R-6) were measured. CDCl ₃ was used as solvent. Tetramethylsilane (TMS) was used as an internal standard sample. As a representative example of polyarylate resins (R-1) to (R-6), the chemical shift value of polyarylate resin (R-6) is shown below. It was confirmed from the chemical shift value that a polyarylate resin (R-6) was obtained. Polyarylate resins (R-1) to (R-5) were confirmed by the same method to be obtained respectively.

Polyarylate resin (R-6): ¹ H-NMR (300 MHz, CDCl ₃ ) δ = 8.21-8.26 (m, 8H), 7.25-7.29 (m, 4H), 7.07 -7.23 (m, 20H), 2.16 (q, 2H), 1.65 (s, 3H), 0.78 (t, 3H).

<Preparation of polyarylate resin used in Comparative Example>
Further, polyarylate resins (RA) to (RD) were prepared as polyarylate resins used in comparative examples. Each of the polyarylate resins (RA) to (RC) is represented by the following chemical formulas (RA) to (RC). The number attached to the lower right of each repeating unit indicates the percentage (%) of the number of each repeating unit with respect to the total number of repeating units contained in the polyarylate resin.

The polyarylate resin (RD) contains only the following repeating units (BP-A) and (BP-C) as bisphenol-derived repeating units. The polyarylate resin (RD) contains only the following repeating units (3), (DC-T) and (DC-I) as dicarboxylic acid-derived repeating units. Percentage of the number of repeating units (BP-A), percentage of the number of repeating units (BP-C), percentage of the number of repeating units (3) with respect to the total number of repeating units contained in the polyarylate resin (RD) , the percentage of the number of repeating units (DC-T), and the percentage of the number of repeating units (DC-I) are respectively 25.0%, 25.0%, 25.0%, 15.0%, and 10.0%.

The viscosity average molecular weights of the polyarylate resins (RA), (RB), (RC), and (RD) are 45,300, 51,000, 46,700, and 46,800.

<Structure of each polyarylate resin>
Table 4 shows the composition of each polyarylate resin. Specifically, the types of bisphenol-derived repeating units of polyarylate resins (R-1) to (R-6) and (RA) to (RD), ratios n ₁ /n ₂ , and dicarboxylic acid-derived repeating units The types of are shown in Table 4. "-" in Table 4 indicates that there is no applicable value.

<Production of Photoreceptor>
Next, photoconductors (A-1) to (A-28) and (B-1) to (B-11) were produced by the following method.

(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 generating layer (thickness: 0.3 μm) was formed on the intermediate layer.

Next, a charge transport layer was formed. Specifically, 45 parts by mass of a hole transport agent (HTM-1), 100 parts by mass of a polyarylate resin (R-1) as a binder resin, 2 parts by mass of a third compound (E-1), and 550 parts by mass of tetrahydrofuran parts and 150 parts by mass of toluene were mixed to obtain a charge transport layer coating liquid. 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: 20 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.

(Photoreceptors (A-2) to (A-11), (A-14) to (A-28), (B-1) to (B-4), and (B-7) to (B-11 )Manufacturing of)
Photoreceptors (A-2) to ( A-11), (A-14) to (A-28), (B-1) to (B-4), and (B-7) to (B-11) were each produced.

(Production of photoreceptors (A-12) to (A-13) and (B-5) to (B-6))
Photoreceptor (A-12) was produced in the same manner as photoreceptor (A-1) except that the amount of hole transport agent (HTM-1) added was changed to the amount shown in Tables 5 and 7. ~ (A-13), and (B-5) ~ (B-6) were each produced.

<Evaluation>
Each of the photoreceptors (A-1) to (A-28) and (B-1) to (B-11), which are photoreceptors to be evaluated, were evaluated by the following methods.

<Evaluation of triboelectrification property of toner>
The triboelectrification amount of the toner when rubbed with the photosensitive layer (more specifically, the charge transport layer) of the photoreceptor was measured by the following method. A jig (manufactured by Kyocera Document Solutions Co., Ltd.) was used to measure the triboelectric charge amount of the toner.

First, circular overhead projector (OHP) films with a diameter of 4 cm were prepared as the first film and the second film. The charge transport layer coating solution used in the production of the photoreceptor (A-1) was applied onto each of the first film and the second film. The applied charge transport layer coating liquid was dried with hot air at 120° C. for 40 minutes. Thus, a first film having a charge transport layer (thickness of 20 μm) and a second film having a charge transport layer (thickness of 20 μm) were obtained. 0.1 g of toner for color printer (magenta toner for “C542dnw” manufactured by Oki Data Co., Ltd., average particle size: 10 μm) was placed on the charge transport layer provided on the first film. A charge transport layer provided in a second film was placed on top of the toner. Thus, the first film, the charge transport layer, the toner, the charge transport layer, and the second film were arranged in order from the bottom. In an environment of a temperature of 50° C. and a relative humidity of 50% RH, using a jig, while fixing the charge transport layer provided on the second film, the charge provided on the first film was rotated at a rotation speed of 60 rpm for 1 minute. The transport layer was rotated. This rubbed the toner between the two charge transport layers and triboelectrically charged the toner. The triboelectrically charged toner was taken out from the jig and sucked using a charge amount measuring device (suction type compact charge amount measuring device, "MODEL 212HS" manufactured by Trek). The total amount of electricity Q (unit: +μC) and the mass M (unit: g) of the attracted toner were measured using a charge amount measuring device. The triboelectrification amount (unit: μC/g) of the toner was obtained from the formula "amount of triboelectrification=Q/M". Next, the charge transport layer coating solution used in the production of the photoreceptor (A-1) was applied to each of the photoreceptors (A-2) to (A-28) and (B-1) to (B-11). Photoreceptors (A-2) to (A-28) were measured in the same manner as the measurement of the triboelectric charge amount of the toner for the photoreceptor (A-1), except that the coating liquid for the charge transport layer used in the production was changed. and (B-1) to (B-11) were measured. Tables 5 to 7 show the measured triboelectric charge amounts of the toner. Based on the triboelectrification amount of the toner, the triboelectrification property of the toner was evaluated according to the following criteria.
[Evaluation Criteria for Triboelectrification of Toner]
Good: The triboelectrification amount of the toner is -20.0 μC/g or less.
Poor: The amount of triboelectrification of the toner exceeds -20.0 μC/g.

<Abrasion resistance evaluation>
A color printer (“C542dnw” manufactured by Oki Data Co., Ltd.) was used as an evaluation machine for evaluating abrasion resistance. Cyan toner was filled in the toner cartridge of the evaluation machine. First, the film thickness T1 of the photosensitive layer (more specifically, the charge transport layer) of the photoreceptor was measured. The photoreceptor was then mounted on the evaluation machine. Next, under an environment of a temperature of 23° C. and a relative humidity of 50% RH, an image I (pattern image with a print rate of 1%) was printed on 300,000 sheets of paper using the evaluation machine. After printing 300,000 sheets, the film thickness T2 of the photosensitive layer of the photoreceptor was measured. Then, the amount of wear (T1-T2, unit: μm), which is the change in thickness of the photosensitive layer before and after printing, was determined. The amount of wear is shown in Tables 5-7. The wear resistance of the photoreceptor was evaluated according to the following criteria from the obtained wear amount.
[Abrasion resistance evaluation criteria]
Good: Wear amount is 3.0 μm or less.
Poor: The amount of wear exceeds 3.0 μm.

<Evaluation of Fog Suppression>
After completing the above <evaluation of wear resistance>, the evaluation machine was moved to a high-temperature and high-humidity environment (temperature of 32.5°C and relative humidity of 85%). This evaluation machine was of a reversal development system, in which the charging device negatively charged the photoreceptor, and the electrostatic latent image was developed with the negatively charged toner. Image II (blank paper image) was printed on one sheet of paper using the evaluation machine under a high-temperature and high-humidity environment. Using a reflection densitometer ("RD914" manufactured by X-Rite), the reflection density A of the blank image area of the printed paper and the reflection density B of the unprinted paper were measured. Then, the fog density (FD) was obtained based on the formula "FD=reflection density A-reflection density B". Based on the obtained FD, it was evaluated whether or not the occurrence of fogging in the formed image was suppressed according to the following criteria. Evaluation results are shown in Tables 5 to 7.

[Evaluation Criteria for Suppression of Fog]
Evaluation A (good): FD is 0.0% or more and less than 0.5%.
Evaluation B (slightly poor): FD is 0.5% or more and less than 2.5%.
Evaluation C (poor): FD is 2.5% or more.

<Evaluation of electrical properties>
Evaluation of electrical properties was performed under an environment of a temperature of 10° C. and a relative humidity of 20% RH. The surface of the photoreceptor was charged to −600 V using a drum sensitivity tester (manufactured by Gentec Co., Ltd.). Then, a bandpass filter was used to extract monochromatic light (wavelength 780 nm, light energy 0.8 μJ/cm ² ) from the white light of the halogen lamp. The surface of the photoreceptor was irradiated with the extracted monochromatic light. The surface potential of the photoreceptor was measured 80 milliseconds after the start of irradiation. The measured surface potential was taken as post-exposure potential (V _L , unit: V). The post-exposure potentials are shown in Tables 5-7. From the measured post-exposure potential, the electrical properties of the photoreceptor were evaluated according to the following criteria.

[Evaluation criteria for electrical characteristics]
Good: The absolute value of the initial post-exposure potential (V _L ) of the photosensitive member is 100 V or less.
Poor: The absolute value of the post-exposure potential (V _L ) of the initial photoreceptor is over 100V.

Terms in Tables 5 to 7 are as follows. "Resin" refers to polyarylate resin. "HTM" indicates hole transport agent. "Amount" indicates the content of the hole transport agent with respect to 100 parts by mass of the binder resin. "Parts" indicates parts by mass. The "toner triboelectric charge amount" indicates the triboelectric charge amount of the toner when rubbed against the photosensitive layer of the photoreceptor. "FD" indicates the evaluation result of fog suppression in the formed image. "Not dissolved" indicates that the binder resin was not dissolved in the solvent during the preparation of the charge transport layer coating liquid, and the charge transport layer could not be formed.

The charge generation layers of photoreceptors (A-1) to (A-28) contained a charge generation agent. As shown in Tables 5 and 6, the charge transport layers of photoreceptors (A-1) to (A-28) consisted of a hole transport agent and a binder resin (more specifically, a polyarylate resin (R- 1) to (R-6)) at least. As shown in Table 4, polyarylate resins (R-1) to (R-6) each contain repeating unit (1), repeating unit (2), and repeating unit (3). The ratio n ₁ / _{n 2} of the number n ₁ of repeating units (1) to the number n 2 of ( ₂₎ was 1.0 or more. As shown in Tables 5 and 6, the hole transport agent is included in general formula (21), general formula (22), general formula (23), chemical formula (HTM-10), or general formula (24). was one of the hole transport agents (HTM-1) to (HTM-11). The content of the hole transport agent was 30 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the binder resin.

As shown in Tables 5 and 6, the photoreceptors (A-1) to (A-28) had an abrasion loss of 3.0 μm or less, and these photoreceptors were excellent in abrasion resistance.

As shown in Tables 5 and 6, the triboelectrification amount of the toner when rubbed against the charge transport layer of the photoreceptors (A-1) to (A-28) was -20.0 μC/g or less. . When images were formed using photoreceptors (A-1) to (A-28), the evaluation result of anti-fogging was A. As shown by these facts, when the toner comes into contact with the charge transport layers of the photoreceptors (A-1) to (A-28), the toner is satisfactorily negatively charged to a desired value or less. was able to suppress the occurrence of fogging in the formed image.

As shown in Tables 5 and 6, the absolute value of the post-exposure potential of the photoreceptors (A-1) to (A-28) was 100 V or less, and these photoreceptors maintained their electrical properties and their durability. It was shown that the abrasion resistance is excellent and the occurrence of fogging in the formed image can be suppressed.

From the above, it was shown that the photoreceptor according to the present invention is excellent in wear resistance and can suppress the occurrence of fogging in formed images.

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 (8)

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 at least a hole transport agent and a binder resin,
The binder resin includes a polyarylate resin, and the polyarylate resin includes repeating units represented by general formula (1), repeating units represented by chemical formula (2), and chemical formula (3). The ratio n ₁ /n ₂ of the number n ₁ of repeating units represented by the general formula (1) to the number n ₂ of repeating units represented by the chemical formula (2) is 1. is 0 or more,
The hole transport agent includes a compound represented by general formula (21), general formula (22), general formula (23), chemical formula (HTM-10), or general formula (24),
An electrophotographic photoreceptor, wherein the content of the hole transport agent is 30 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the binder resin.

(In the general formula (1),
R ¹ and R ² each independently represent a hydrogen atom or a methyl group, R ³ represents a methyl group, and R ⁴ represents a hydrogen atom or an alkyl group having 2 or 3 carbon atoms, or
R ¹ and R ² each represent a methyl group, and R ³ and R ⁴ are combined to represent a cycloalkylidene group having 5 or 6 carbon atoms. )

(In general formula (21), R ¹¹ , R ¹² and R ¹³ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. and b1, b2, and b3 each independently represent an integer of 0 or more and 5 or less,
In general formula (22), R ²¹ , R ²² , and R ²³ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. , d1, d2, and d3 each independently represent an integer of 0 to 5,
In general formula (23), R ³¹ , R ³² , R ³³ and R ³⁴ each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms. , R ³⁵ , and R ³⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and e1, e2, e3, and e4 are , each independently represents an integer from 0 to 5,
In general formula (24), R ⁴¹ , R ⁴² , R ⁴³ and R ⁴⁴ each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms. , f1, f2, f3, and f4 each independently represent an integer of 0 or more and 5 or less. ) The repeating unit represented by the general formula (1) is represented by chemical formula (1-1), chemical formula (1-2), chemical formula (1-3), chemical formula (1-4), or chemical formula (1-5). 2. The electrophotographic photoreceptor of claim 1, which is a repeating unit represented by:

In general formula (21), R ¹¹ , R ¹² and R ¹³ each independently represent an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms; b2 and b3 each independently represent 0 or 1,
In general formula (22), R ²¹ , R ²² and R ²³ each independently represent an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms; d2 and d3 each independently represent an integer of 0 or more and 2 or less,
In general formula (23), R ³¹ , R ³² , R ³³ and R ³⁴ each independently represent an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. , R ³⁵ and R ³⁶ each independently represent an alkyl group having 1 to 3 carbon atoms, e1, e2, e3 and e4 each independently represents an integer of 0 to 2,
In general formula (24), R ⁴¹ , R ⁴² , R ⁴³ and R ⁴⁴ each independently represent an alkyl group having 1 to 3 carbon atoms, f1, f2, f3 and f4 each 3. The electrophotographic photoreceptor of claim 1, which independently represents 0 or 1. The hole transport agent has chemical formula (HTM-1), chemical formula (HTM-2), chemical formula (HTM-3), chemical formula (HTM-4), chemical formula (HTM-5), chemical formula (HTM-6), chemical formula (HTM-7), chemical formula (HTM-8), chemical formula (HTM-9), chemical formula (HTM-10), or chemical formula (HTM-11). 1. The electrophotographic photoreceptor according to claim 1.

The charge transport layer further contains a third compound,
5. The electrophotographic photoreceptor according to claim 1, wherein the third compound has a ketone structure or a dicyanomethylene structure. 6. The electrophotographic photoreceptor according to claim 5, wherein the third compound is at least one of the compounds represented by formulas (31) to (39).

(In the general formulas (31) to (39), Q ³¹ to Q ⁵⁷ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 14 carbon atoms, represents an alkoxy group having 1 to 3 carbon atoms which may be substituted with a group, or a phenyl group which may be substituted by an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. .) 7. The electrophotographic photoreceptor according to claim 5, wherein the third compound is at least one of compounds represented by chemical formulas (E-1) to (E-11).

The electrophotographic photoreceptor according to any one of claims 1 to 7, wherein the charge transport layer is a single layer and provided as the outermost layer.

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