JP7135619B2 - electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor.

Electrophotographic photoreceptors are used in electrophotographic image forming apparatuses. As the electrophotographic photoreceptor, for example, a laminated electrophotographic photoreceptor or a single-layer electrophotographic photoreceptor is used. A laminated electrophotographic photoreceptor includes, as photosensitive layers, a charge generation layer having a charge generation function and a charge transport layer having a charge transport function. A single-layer electrophotographic photoreceptor includes a single-layer photosensitive layer having a charge generation function and a charge transport function as a photosensitive layer.

The electrophotographic photoreceptor described in Patent Document 1 includes a photosensitive layer. This photosensitive layer contains, as an electron-transporting substance, for example, a naphthalenetetracarboxylic acid diimide derivative having a structure represented by the chemical formula (E-1).

JP 2005-154444 A

However, the present inventors have found that the electrophotographic photoreceptor described in Patent Document 1 is insufficient in terms of sensitivity characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor having excellent sensitivity characteristics.

The electrophotographic photoreceptor of the present invention comprises a conductive substrate and a single photosensitive layer. The photosensitive layer contains at least a charge generating agent and a compound represented by general formula (1).

In the general formula (1), R ¹ is an aryl group having 6 to 22 carbon atoms which may be substituted with an alkyl group having 1 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, It represents a cycloalkyl group having 3 to 20 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 3 to 30 carbon atoms which may be substituted with a --CO--OR ² group. R ² represents an alkyl group having 1 to 8 carbon atoms.

The electrophotographic photoreceptor of the present invention has excellent sensitivity characteristics.

1 is a partial cross-sectional view showing an example of the structure of an electrophotographic photoreceptor according to an embodiment of the invention; FIG. 1 is a partial cross-sectional view showing an example of the structure of an electrophotographic photoreceptor according to an embodiment of the invention; FIG. 1 is a partial cross-sectional view showing an example of the structure of an electrophotographic photoreceptor according to an embodiment of the 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. "--COOEt" in the general formula and chemical formula each represents an ethoxycarbonyl group.

Next, definitions of substituents used in the present specification will be explained. An alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 6 carbon atoms, and an alkyl group having 1 to 3 carbon atoms are each linear branched or unsubstituted. Examples of alkyl groups having 1 to 10 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 group, 1-ethylbutyl group, 2-ethylbutyl group, 3-ethylbutyl group, linear and branched heptyl group, n-octyl group, 2-ethylhexyl group, branches other than 2-ethylhexyl group Chain octyl groups, linear and branched nonyl groups, and linear and branched decyl groups are included. Examples of the alkyl group having 1 to 8 carbon atoms are groups having 1 to 8 carbon atoms among the groups described as examples of the alkyl group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms are groups having 1 to 6 carbon atoms among the groups described as examples of the alkyl group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms are groups having 1 to 3 carbon atoms among the groups described as examples of the alkyl group having 1 to 10 carbon atoms.

an alkyl group having 3 to 30 carbon atoms, an alkyl group having 3 to 10 carbon atoms, an alkyl group having 5 to 10 carbon atoms, an alkyl group having 5 to 8 carbon atoms, and an alkyl group having 5 to 8 carbon atoms, or Each of the 8 alkyl groups is straight or branched and unsubstituted. The alkyl group having 3 to 30 carbon atoms is preferably an alkyl group having 3 to 10 carbon atoms. Examples of the alkyl group having 3 or more and 10 or less carbon atoms are groups having 3 or more and 10 or less carbon atoms among the groups described as examples of the alkyl group having 1 or more and 10 or less carbon atoms. Examples of the alkyl group having 5 or more and 10 or less carbon atoms are groups having 5 or more and 10 or less carbon atoms among the groups described as examples of the alkyl group having 1 or more and 10 or less carbon atoms. Examples of the alkyl group having 5 to 8 carbon atoms are groups having 5 to 8 carbon atoms among the groups described as examples of the alkyl group having 1 to 10 carbon atoms. Examples of alkyl groups having 5 or 8 carbon atoms are groups having 5 or 8 carbon atoms among the groups described as examples of alkyl groups having 1 to 10 carbon atoms.

An alkoxy group having 1 to 6 carbon atoms and an alkoxy group having 1 to 3 carbon atoms are each straight or branched and unsubstituted. Examples of alkoxy groups having 1 to 6 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- Examples include trimethylpropoxy, 1,2,2-trimethylpropoxy, 1-ethylbutoxy, 2-ethylbutoxy, and 3-ethylbutoxy. Examples of the alkoxy group having 1 to 3 carbon atoms are groups having 1 to 3 carbon atoms among the groups described as examples of the alkoxy group having 1 to 6 carbon atoms.

The aryl group having 6 to 22 carbon atoms, the aryl group having 6 to 14 carbon atoms, and the aryl group having 6 to 10 carbon atoms are each unsubstituted. Examples of aryl groups having 6 to 22 carbon atoms include phenyl, naphthyl, indacenyl, biphenylenyl, acenaphthylenyl, anthryl and phenanthryl, tetracenyl, tetraphenyl, chrysenyl, pyrenyl, and triphenylenyl. benzophenanthrenyl, picenyl, perylenyl, and pentaphenyl groups. Examples of aryl groups having 6 to 14 carbon atoms include phenyl, naphthyl, indacenyl, biphenylenyl, acenaphthylenyl, anthryl and phenanthryl groups. Examples of the aryl group having 6 to 10 carbon atoms include a phenyl group and a naphthyl group.

A cycloalkyl group having 3 to 20 carbon atoms and a cycloalkyl group having 3 to 10 carbon atoms are each unsubstituted. Examples of cycloalkyl groups having 3 to 10 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, and cyclododecyl. cyclotridecyl, cyclotetradecyl, cyclopentadecyl, cyclohexadecyl, cycloheptadecyl, cyclooctadecyl, cyclononadecyl, and cycloicosanyl groups. Examples of the cycloalkyl group having 3 to 10 carbon atoms are groups having 3 to 10 carbon atoms among the groups described as examples of the cycloalkyl group having 3 to 20 carbon atoms.

An aralkyl group having from 7 to 20 carbon atoms is unsubstituted. Examples of the aralkyl group having 7 to 20 carbon atoms include an alkyl group having 1 to 6 carbon atoms substituted with an aryl group having 6 to 14 carbon atoms. The definitions of the substituents used in the present specification have been described above.

<Electrophotographic photoreceptor>
Next, the structure of an electrophotographic photoreceptor (hereinafter sometimes referred to as a photoreceptor) according to an embodiment of the present invention will be described. 1, 2, and 3 are partial cross-sectional views showing the structure of a photoreceptor 1, which is an example of this embodiment. As shown in FIG. 1, the photoreceptor 1 includes a conductive substrate 2 and a photosensitive layer 3. As shown in FIG. The photosensitive layer 3 is a single layer. The photosensitive layer 3 may be provided directly on the conductive substrate 2, as shown in FIG. Further, as shown in FIG. 2, the photoreceptor 1 may comprise, for example, a conductive substrate 2, an intermediate layer 4 (for example, an undercoat layer), and a photosensitive layer 3. FIG. In the example shown in FIG. 2, the photosensitive layer 3 is indirectly provided on the conductive substrate 2 via the intermediate layer 4 . Further, as shown in FIG. 3, the photoreceptor 1 may have a protective layer 5 as the outermost layer. The thickness of the photosensitive layer 3 is not particularly limited. The thickness of the photosensitive layer 3 is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less. The structure of the photoconductor 1 has been described above with reference to FIGS. 1, 2, and 3. FIG. The photoreceptor according to this embodiment will be described in more detail below.

<Photosensitive layer>
The photosensitive layer contains at least a charge generating agent and a compound represented by formula (1). The photosensitive layer may further contain a hole transport agent. The photosensitive layer may further contain a binder resin. The photosensitive layer may further contain additives, if desired.

(Compound represented by general formula (1))
The photosensitive layer contains a compound represented by formula (1) (hereinafter sometimes referred to as compound (1)). The photosensitive layer contains compound (1), for example, as an electron transport agent.

In general formula (1), R ¹ is an aryl group having 6 to 22 carbon atoms which may be substituted with an alkyl group having 1 to 10 carbon atoms; an aralkyl group having 7 to 20 carbon atoms; A cycloalkyl group having 3 to 20 atoms; an alkoxy group having 1 to 6 carbon atoms; or an alkyl group having 3 to 30 carbon atoms which may be substituted with -CO-OR ² group. In the --CO--OR ² group, R ² represents an alkyl group having 1 to 8 carbon atoms.

By containing the compound (1) in the photosensitive layer, the sensitivity characteristics of the photoreceptor can be improved. The reason is presumed as follows. Compound (1) has four carbonyl groups that are electron-accepting groups and has a given chemical structure. Therefore, compound (1) has excellent electron-accepting and electron-transporting properties. Further, when a line perpendicular to the condensed site of two benzene rings in general formula (1) is drawn, compound (1) has an asymmetric structure with respect to this line. Compound (1) having an asymmetric structure and a predetermined chemical structure improves the solubility of compound (1) in a solvent for forming a photosensitive layer. Moreover, the compound (1) has an asymmetric structure and a predetermined chemical structure, so that the compatibility of the compound (1) with the binder resin is improved. By improving the solubility and compatibility of compound (1), there is a tendency that a uniform photosensitive layer can be formed, and the sensitivity characteristics of the photoreceptor are improved. Also, crystallization of the photosensitive layer of the photoreceptor can be suppressed.

The aryl group having 6 to 22 carbon atoms represented by R ¹ in general formula (1) is preferably an aryl group having 6 to 10 carbon atoms, more preferably a phenyl group.

The aryl group having 6 to 22 carbon atoms represented by R ¹ in general formula (1) may be substituted with an alkyl group having 1 to 10 carbon atoms. The alkyl group having 1 to 10 carbon atoms which is a substituent of the aryl group having 6 to 22 carbon atoms is preferably an alkyl group having 1 to 6 carbon atoms, and an alkyl group having 1 to 3 carbon atoms. groups are more preferred, and methyl and ethyl groups are even more preferred. The number of substituents in the aryl group having 6 to 22 carbon atoms (i.e., alkyl group having 1 to 10 carbon atoms) is preferably 1 to 5, and 1 or 2. One is more preferable, and two is even more preferable. When an aryl group having 6 to 22 carbon atoms is substituted with an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 22 carbon atoms substituted with an alkyl group having 1 to 10 carbon atoms The group is preferably an aryl group having 6 to 10 carbon atoms substituted with an alkyl group having 1 to 6 carbon atoms, more preferably a phenyl group substituted by an alkyl group having 1 to 3 carbon atoms. , an ethylmethylphenyl group is more preferred, and a 2-ethyl-6-methylphenyl group is particularly preferred.

The aralkyl group having 7 to 20 carbon atoms represented by R ¹ in general formula (1) is preferably an alkyl group having 1 to 6 carbon atoms substituted with an aryl group having 6 to 14 carbon atoms. , an alkyl group having 1 to 3 carbon atoms substituted with a phenyl group is more preferred, and a benzyl group is even more preferred.

The cycloalkyl group having 3 to 20 carbon atoms represented by R ¹ in general formula (1) is preferably a cycloalkyl group having 3 to 10 carbon atoms.

The alkoxy group having 1 to 6 carbon atoms represented by R ¹ in general formula (1) is preferably an alkoxy group having 1 to 3 carbon atoms.

The alkyl group having 3 to 30 carbon atoms represented by R ¹ in general formula (1) is preferably an alkyl group having 3 to 10 carbon atoms, more preferably an alkyl group having 5 to 10 carbon atoms. , more preferably an alkyl group having 5 to 8 carbon atoms, more preferably an alkyl group having 5 or 8 carbon atoms, and particularly preferably an n-octyl group, a 2-ethylhexyl group, or a 3-methylbutyl group.

The alkyl group having 3 to 30 carbon atoms represented by R ¹ in general formula (1) may be substituted with —CO—OR ² group. In the --CO--OR ² group, R ² represents an alkyl group having 1 to 8 carbon atoms. The alkyl group having 1 to 8 carbon atoms represented by R ² is preferably an alkyl group having 1 to 3 carbon atoms, more preferably an ethyl group. The number of substituents (i.e., —CO—OR ² groups) possessed by the alkyl group having 3 or more and 30 or less carbon atoms represented by R ¹ is preferably 1 or more and 5 or less, and 1 or more and 3 or less. is more preferable, and one is even more preferable.

In order to improve the sensitivity characteristics of the photoreceptor, in general formula (1), R ¹ is an aryl group having 6 to 22 carbon atoms which may be substituted with an alkyl group having 1 to 10 carbon atoms; It preferably represents an aralkyl group having 7 to 20 carbon atoms; or an alkyl group having 3 to 30 carbon atoms which may be substituted with a --CO--OR ² group. R ² preferably represents an alkyl group having 1 to 8 carbon atoms.

In order to further improve the sensitivity characteristics of the photoreceptor, in general formula (1), R ¹ may represent an alkyl group having 5 to 10 carbon atoms which may be substituted with a —CO—OR ² group. preferable. R ² preferably represents an alkyl group having 1 to 3 carbon atoms. When R ¹ is a long-chain alkyl such as an alkyl group having 5 to 10 carbon atoms, the compatibility between the binder resin and the compound (1) is improved, and the compound (1) is uniformly distributed in the photosensitive layer. It tends to disperse. The uniform dispersion of compound (1) further improves the sensitivity characteristics of the photoreceptor.

In order to particularly improve the sensitivity characteristics of the photoreceptor, in general formula (1), R ¹ preferably represents an alkyl group having from 5 to 10 carbon atoms substituted with a --CO--OR ² group. R ² preferably represents an alkyl group having 1 to 3 carbon atoms. For example, when the binder resin is a polycarbonate resin having a carbonyl group, the alkyl group represented by R ¹ and having 5 to 10 carbon atoms is substituted with a —CO—OR ² group to form the binder resin and the compound (1). compatibility is further improved. In addition, the compound (1) is easily dispersed uniformly in the photosensitive layer, and the sensitivity characteristics of the photoreceptor are particularly improved.

Preferred examples of compound (1) include compounds represented by chemical formulas (1-1), (1-2), (1-3), (1-4), and (1-5) (hereinafter, Each of them may be described as compounds (1-1), (1-2), (1-3), (1-4), and (1-5)).

The photosensitive layer may contain only one compound (1), or may contain two or more compounds (1). The photosensitive layer may contain only the compound (1) as an electron transport agent, and in addition to the compound (1), an electron transport agent other than the compound (1) (hereinafter referred to as other electron transport agent) There is) may be further contained. Examples of other electron transport agents include quinone compounds, diimide compounds, hydrazone compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, and dinitroanthracene compounds. compounds, dinitroacridine-based compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Examples of quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds.

The content of compound (1) is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 20 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the binder resin. When the content of the compound (1) is 5 parts by mass or more with respect to 100 parts by mass of the binder resin, it is easy to improve the sensitivity characteristics of the photoreceptor. When the content of the compound (1) is 100 parts by mass or less per 100 parts by mass of the binder resin, the compound (1) is easily dissolved in the solvent for forming the photosensitive layer, and a uniform photosensitive layer is easily formed.

Compound (1) is produced, for example, according to the reaction represented by the following reaction formula (R-1) (hereinafter sometimes referred to as reaction (R-1)) or by a method analogous thereto. The compounds represented by general formulas (A) and (B) shown in Reaction Formula (R-1) are hereinafter referred to as compounds (A) and (B), respectively. R ¹ in general formula (B) has the same definition as R ¹ in general formula (1).

In reaction (R-1), 1 molar equivalent of compound (A) is reacted with 2 molar equivalents of compound (B) to obtain 1 molar equivalent of compound (1). Specifically, compound (A) and compound (B) are stirred in a solvent in the presence of a base. Examples of bases include potassium carbonate, sodium carbonate, and potassium phosphate. Examples of solvents include N,N-dimethylformamide and tetrahydrofuran. Reaction (R-1) is preferably carried out under an inert gas atmosphere. Examples of inert gases include nitrogen gas and argon gas. The reaction temperature of reaction (R-1) is preferably 50° C. or higher and 150° C. or lower. The reaction time of reaction (R-1) is preferably 0.5 hours or more and 5 hours or less. After carrying out the reaction (R-1), the resulting compound (1) may be purified. Purification methods include, for example, known methods (eg, filtration, silica gel chromatography, or crystallization).

(Charge generating agent)
The charge-generating agent is not particularly limited as long as it is a charge-generating agent for photoreceptors. 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 or amorphous silicon), pyrylium pigments, anthanthrone-based pigments, triphenylmethane-based pigments, threne-based pigments, toluidine-based pigments, Examples include 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.

Examples of phthalocyanine pigments include metal-free phthalocyanines and metal phthalocyanines. Metal-free phthalocyanine is represented by the chemical formula (CGM2). Metal phthalocyanines include, for example, titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. Titanyl phthalocyanine is represented by the chemical formula (CGM1). The phthalocyanine pigment may be crystalline or amorphous. The crystal shape of the phthalocyanine-based pigment (for example, α-type, β-type, Y-type, V-type, or II-type) is not particularly limited, and phthalocyanine-based pigments having various crystal shapes can be used.

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 pigment is preferable, a metal-free phthalocyanine or titanyl phthalocyanine is more preferable, and an X-type metal-free phthalocyanine or a Y-type titanyl phthalocyanine is even more preferable, because it has a high quantum yield in a wavelength region of 700 nm or more. , Y-type titanyl phthalocyanines are particularly preferred.

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.

An example of the method for measuring the CuKα characteristic X-ray diffraction spectrum will be described. A sample (titanyl phthalocyanine) is filled in a sample holder of an X-ray diffraction device (for example, "RINT (registered trademark) 1100" manufactured by Rigaku Co., Ltd.), and an X-ray tube Cu, tube voltage 40 kV, tube current 30 mA, and CuKα An X-ray diffraction spectrum is measured under the condition of a characteristic X-ray wavelength of 1.542 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.

Anthanthrone-based pigments are preferably used as charge generating agents in photoreceptors applied to image forming apparatuses using short-wavelength laser light sources (for example, laser light sources having a wavelength of 350 nm or more and 550 nm or less).

The content of the charge generating agent is preferably 0.1 parts by mass or more and 50 parts by mass or less, more preferably 0.5 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the binder resin. It is particularly preferable that the amount is 0.5 parts by mass or more and 4.5 parts by mass or less.

(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.

The photosensitive layer preferably contains a compound represented by formula (10) (hereinafter sometimes referred to as compound (10)). The photosensitive layer preferably contains, for example, compound (10) as a hole transport agent.

In general formula (10), R ¹⁰¹ , R ¹⁰² , R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ and R ¹⁰⁶ each independently represent an alkyl group having 1 to 6 carbon atoms, It represents an alkoxy group or an aryl group having 6 to 14 carbon atoms. a, b, c, and d each independently represents an integer of 0 to 5; e and f each independently represents an integer of 0 or more and 4 or less.

When a represents an integer of 2 or more and 5 or less, a plurality of R ¹⁰¹ may be the same or different. When b represents an integer of 2 or more and 5 or less, a plurality of R ¹⁰² may be the same or different. When c represents an integer of 2 or more and 5 or less, a plurality of R ¹⁰³ may be the same or different. When d represents an integer of 2 or more and 5 or less, a plurality of R ¹⁰⁴ may be the same or different. When e represents an integer of 2 or more and 4 or less, a plurality of R ¹⁰⁵ may be the same or different. When f represents an integer of 2 or more and 4 or less, a plurality of R ¹⁰⁶ may be the same or different.

In general formula (10), R ¹⁰¹ , R ¹⁰² , R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ and R ¹⁰⁶ preferably each independently represent an alkyl group having 1 to 6 carbon atoms. It is more preferable to represent 1 or more and 3 or less alkyl groups, and it is further preferable to represent a methyl group. Each of a, b, c and d independently represents 0 or 1, more preferably 1. Preferably, e and f each independently represent 0 or 1, more preferably 1.

Preferred examples of compound (10) include compounds represented by the following chemical formula (10-1) (hereinafter sometimes referred to as compound (10-1)).

The photosensitive layer may contain only compound (10) as a hole transport agent. The photosensitive layer may further contain a hole transport agent other than compound (10) in addition to compound (10) as a hole transport agent.

The content of the hole transport agent is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the binder resin.

(binder resin)
Examples of binder resins include thermoplastic resins, thermosetting resins, and photocurable resins. Examples of thermoplastic resins include polycarbonate resins, polyarylate resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, acrylic acid polymers, styrene-acrylic acid copolymers, Polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, urethane resin, polysulfone resin, diallyl phthalate Resins, ketone resins, polyvinyl butyral resins, polyester resins, and polyether resins. Thermosetting resins include, for example, silicone resins, epoxy resins, phenolic resins, urea resins, and melamine resins. Examples of photocurable resins include acrylic acid adducts of epoxy compounds and acrylic acid adducts of urethane compounds. The photosensitive layer may contain only one binder resin, or may contain two or more binder resins.

Among these resins, a polycarbonate resin is preferable as the binder resin because it provides a photosensitive layer having an excellent balance of workability, mechanical properties, optical properties, and abrasion resistance. Examples of polycarbonate resins include bisphenol ZC-type polycarbonate resins, bisphenol C-type polycarbonate resins, bisphenol A-type polycarbonate resins, and bisphenol Z-type polycarbonate resins. A bisphenol Z-type polycarbonate resin has a repeating unit represented by the following chemical formula (20). Hereinafter, a polycarbonate resin having a repeating unit represented by chemical formula (20) may be referred to as polycarbonate resin (20).

(Additive)
Additives include, for example, deterioration inhibitors (e.g., antioxidants, radical scavengers, singlet quenchers, or UV absorbers), softeners, surface modifiers, extenders, thickeners, and dispersion stabilizers. , waxes, acceptors, donors, surfactants, plasticizers, sensitizers, and leveling agents.

(combination of materials)
Materials contained in the photosensitive layer are preferably any of the following combinations. In one example of the combination, the electron transport agent comprises compound (1-1), (1-2), (1-3), (1-4), or (1-5), and the hole transport agent comprises compound ( 10-1). In one example of the combination, the electron transport agent comprises compound (1-1), (1-2), (1-3), (1-4), or (1-5), and the binder is polycarbonate resin (20) including. In one example of the combination, the electron transport agent comprises compound (1-1), (1-2), (1-3), (1-4), or (1-5), and the charge generating agent is X-type non- Contains metal phthalocyanines. In one example of the combination, the electron transport agent comprises compound (1-1), (1-2), (1-3), (1-4), or (1-5), and the charge generator is Y-type titanyl Contains phthalocyanines. In one example of the combination, the electron transport agent comprises compound (1-1), (1-2), (1-3), (1-4), or (1-5), and the hole transport agent comprises compound ( 10-1), and the binder contains a polycarbonate resin (20). In one example of the combination, the electron transport agent comprises compound (1-1), (1-2), (1-3), (1-4), or (1-5), and the hole transport agent comprises compound ( 10-1), the binder contains polycarbonate resin (20), and the charge generator contains X-type metal-free phthalocyanine. In one example of the combination, the electron transport agent comprises compound (1-1), (1-2), (1-3), (1-4), or (1-5), and the hole transport agent comprises compound ( 10-1), the binder contains polycarbonate resin (20), and the charge generator contains Y-type titanyl phthalocyanine.

<Conductive substrate>
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 conductive material. Conductive materials include, for example, aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. One of 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 conductive materials, aluminum or an aluminum alloy is preferable because charge transfer from the photosensitive layer to the conductive substrate is favorable.

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 existence of the intermediate layer smoothes the flow of current generated when the photoreceptor is exposed to light while maintaining an insulating state to the extent that leakage can be suppressed, thereby suppressing an increase in resistance.

Examples of inorganic particles include particles of metals (e.g., aluminum, iron, or copper), particles of metal oxides (e.g., titanium oxide, alumina, zirconium oxide, tin oxide, or 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 those of the binder resin contained in the photosensitive layer. The intermediate layer may contain additives as needed. Examples of additives contained in the intermediate layer are the same as examples of additives contained in the photosensitive layer.

<Method for manufacturing photoreceptor>
A photoreceptor is manufactured by, for example, coating a conductive substrate with a coating liquid for forming a photosensitive layer (hereinafter sometimes referred to as coating liquid) and drying the coating. The coating liquid is prepared by dissolving or dispersing the charge generating agent, compound (1), and optionally added components (e.g., hole transport agent, binder resin, and additives) in a solvent. .

The solvent contained in the coating liquid is not particularly limited as long as it can dissolve or disperse each component contained in the coating liquid. Examples of solvents include alcohols (eg methanol, ethanol, isopropanol or butanol), aliphatic hydrocarbons (eg n-hexane, octane or cyclohexane), aromatic hydrocarbons (eg benzene, toluene or xylene), Halogenated hydrocarbons (e.g. dichloromethane, dichloroethane, carbon tetrachloride or chlorobenzene), ethers (e.g. dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether or propylene glycol monomethyl ether), ketones (e.g. acetone, methyl ethyl ketone or cyclohexanone), esters (eg, ethyl acetate or methyl acetate), dimethylformaldehyde, dimethylformamide, and dimethylsulfoxide. One type of these solvents may be used alone, or two or more types may be used in combination. A non-halogen solvent (a solvent other than halogenated hydrocarbons) is preferably used in order to improve the workability during the production of the photoreceptor.

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

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

A method for drying the coating liquid is not particularly limited as long as the solvent in the coating liquid can be evaporated. For example, 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 photoreceptor manufacturing method may further include one or both of the step of forming an intermediate layer and the step of forming a protective layer, if necessary. A known method is 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.

<Material for Forming Photosensitive Layer>
As materials for forming the photosensitive layer of the photoreceptor, the following charge-generating agent, hole-transporting agent, binder resin, and electron-transporting agent were prepared.

(Charge generating agent)
Y-type titanyl phthalocyanine and X-type metal-free phthalocyanine were prepared as charge generating agents. The Y-type titanyl phthalocyanine was a titanyl phthalocyanine represented by the chemical formula (CGM1) described in the embodiment and having a Y-type crystal structure. The X-type metal-free phthalocyanine was represented by the chemical formula (CGM2) described in the embodiment and was a metal-free phthalocyanine having an X-type crystal structure.

(Hole transport agent)
Compound (10-1) described in the embodiment was prepared as a hole transport agent.

(binder resin)
As a binder resin, the polycarbonate resin (20) described in the embodiment was prepared. The viscosity average molecular weight of the polycarbonate resin (20) was 50,000.

(Electron transport agent)
Compounds (1-1) to (1-5) described in the embodiment were prepared as electron transport agents. Each of compounds (1-1) to (1-5) was synthesized by the following method.

(Synthesis of compound (1-1))
A compound (1-1) was synthesized according to the reaction represented by the following reaction formula (r-1) (hereinafter referred to as reaction (r-1)). The compounds (A-1) and (B-1) to (B-5) described below are represented by the chemical formulas (A-1) and (B-1) in the reaction formula (r-1), and represented by chemical formulas (B-2) to (B-5) described later. The yield of each compound was determined by molar ratio conversion.

In reaction (r-1), compound (A-1) and compound (B-1) were reacted to obtain compound (1-1). Specifically, the compound (A-1) (1.00 g, 3.7 mmol) and potassium carbonate (1.50 g, 11.2 mmol) were dissolved in 10 mL of N,N-dimethylformamide (DMF) to obtain a DMF solution. got The DMF solution was stirred at 70° C. for 1 hour under a nitrogen gas atmosphere. After stirring for 1 hour, compound (B-1) (2.69 g, 11.2 mmol) was added to the DMF solution and stirred at 100°C for 2 hours. After stirring for 2 hours, water was added to the DMF solution and extracted with chloroform to obtain an organic layer (chloroform layer). The organic layer was concentrated under reduced pressure to obtain a crude product containing compound (1-1). The crude product was purified by silica gel column chromatography using chloroform as a developing solvent to obtain compound (1-1). The yield of compound (1-1) was 0.55 g. The yield of compound (1-1) from compound (A-1) was 30%.

(Synthesis of compounds (1-2) to (1-5))
Each of compounds (1-2) to (1-5) was synthesized in the same manner as the synthesis of compound (1-1), except for the following changes. Compound (B-1) (2.69 g, 11.2 mmol) was added in the synthesis of compound (1-1). Compounds (B) were added in amounts and types indicated in the column. Table 1 shows yields and yields of compounds (1-2) to (1-5) from the compounds shown in the column of compound (A).

The compounds (B-2) to (B-5) are respectively represented by the following chemical formulas (B-2) to (B-5).

Using ^{a 1} H-NMR (proton nuclear magnetic resonance spectrometer), ¹ H-NMR spectra of synthesized compounds (1-1) to (1-5) were measured. The magnetic field strength was set at 300 MHz. Deuterated chloroform (CDCl ₃ ) was used as solvent. Tetramethylsilane (TMS) was used as an internal standard. As a representative example of compounds (1-1) to (1-5), the chemical shift values of the ¹ H-NMR spectrum of compound (1-1) are shown below. It was confirmed from the chemical shift value of the measured ¹ H-NMR spectrum that compound (1-1) was obtained. It was confirmed from the chemical shift values of the measured ¹ H-NMR spectrum that compounds (1-2) to (1-5) were obtained for compounds (1-2) to (1-5) as well. .

Compound (1-1): ¹ H-NMR (300 MHz, CDCl ₃ ) δ = 7.91 (d, 2H), 7.64 (d, 2H), 4.17-4.22 (m, 4H), 1.78 (m, 4H), 1.23-1.41 (m, 20H), 0.81-0.85 (m, 6H).

A compound represented by the following chemical formula (E-1) (hereinafter referred to as compound (E-1)) was prepared as an electron transport agent used in Comparative Examples.

<Production of Photoreceptor>
Photoreceptors (A-1) to (A-10) and (B-1) to (B-2) were produced using materials for forming a photosensitive layer.

(Production of photoreceptor (A-1))
2 parts by mass of X-type metal-free phthalocyanine as a charge generating agent, 50 parts by mass of compound (10-1) as a hole transporting agent, 30 parts by mass of compound (1-1) as an electron transporting agent, polycarbonate as a binder resin 100 parts by mass of resin (20) and 600 parts by mass of tetrahydrofuran as a solvent were mixed for 12 hours using a ball mill. Thus, a coating liquid was obtained. The coating liquid was applied onto a conductive substrate (drum-shaped support made of aluminum, diameter 30 mm, total length 238.5 mm) using a blade coating method. The applied coating liquid was dried with hot air at 120° C. for 80 minutes. Thus, a single-layered photosensitive layer (30 μm thick) was formed on the conductive substrate to obtain a photoreceptor (A-1).

(Production of photoreceptors (A-2) to (A-10) and (B-1) to (B-2))
Each of the photoreceptors (A-2) to (A-10) and (B-1) to (B-2) was produced in the same manner as the photoreceptor (A-1) except that the following points were changed. manufactured. X-type metal-free phthalocyanine was used as a charge generating agent in the production of photoreceptor (A-1), but photoreceptors (A-2) to (A-10) and (B-1) to (B-2) The type of charge generator shown in Table 2 was used in each of the preparations of . Compound (1-1) was used as an electron transport agent in the production of photoreceptor (A-1). ) were used in the preparation of each of the types of electron transport agents shown in Table 2.

<Evaluation of sensitivity characteristics>
Sensitivity characteristics were evaluated for each of the photoreceptors (A-1) to (A-10) and (B-1) to (B-2). Evaluation of the sensitivity characteristics was performed under an environment of a temperature of 23° C. and a relative humidity of 50% RH. First, the surface of the photosensitive member 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, half width: 20 nm, light energy: 1.5 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 50 milliseconds after the end of irradiation. The measured surface potential was taken as post-exposure potential (V _L , unit: +V). Table 2 shows the post-exposure potential (V _L ) of the photoreceptor. A smaller positive value of the post-exposure potential (V _L ) indicates better sensitivity characteristics (especially, photosensitivity characteristics) of the photoreceptor.

<Evaluation of presence or absence of crystallization>
The entire surfaces (photosensitive layers) of the photoreceptors (A-1) to (A-10) and (B-1) to (B-2) were observed with the naked eye. Then, the presence or absence of a crystallized portion in the photosensitive layer was confirmed. Table 2 shows the confirmation results.

In Table 2, CGM, ETM, V _L , X—H ₂ Pc, and Y-TiOPc represent charge generator, electron transport agent, post-exposure potential, X-type metal-free phthalocyanine, and Y-type titanyl phthalocyanine, respectively. . In Table 2, "none" indicates that no crystallized portion was observed in the photosensitive layer, and "slightly crystallized" indicates that some crystallized portion was observed in the photosensitive layer.

Photoreceptors (A-1) to (A-10) each had a conductive substrate and a single photosensitive layer. The photosensitive layer contained at least a charge generating agent and compound (1). Specifically, the photosensitive layer contained any one of compounds (1-1) to (1-5) included in general formula (1). As is clear from Table 2, the post-exposure potentials of the photosensitive members (A-1) to (A-10) were +110 V or less. In addition, no crystallized portion was observed in the photosensitive layers of photoreceptors (A-1) to (A-10).

On the other hand, the photosensitive layers of photoreceptors (B-1) to (B-2) did not contain compound (1). Specifically, the compound (E-1) was contained in the photosensitive layer of the photoreceptors (B-1) to (B-2), but the compound (E-1) is included in the general formula (1). It was not a compound that was As is clear from Table 2, the post-exposure potentials of the photosensitive members (B-1) to (B-2) were +130 V or higher. Further, the photosensitive layers of the photoreceptors (B-1) to (B-2) were confirmed to have some crystallized portions.

As described above, the photoreceptors (A-1) to (A-10) were superior in sensitivity characteristics to the photoreceptors (B-1) to (B-2). Photoreceptors (A-1) to (A-10) exhibited suppressed crystallization of the photosensitive layer compared to photoreceptors (B-1) to (B-2).

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

Reference Signs List 1 electrophotographic photoreceptor 2 conductive substrate 3 photosensitive layer 4 intermediate layer 5 protective layer

Claims (8)

comprising a conductive substrate and a single photosensitive layer,
An electrophotographic photoreceptor, wherein the photosensitive layer contains at least a charge generating agent and a compound represented by formula (1).

(In the general formula (1), R ¹ is
an aryl group having 6 to 22 carbon atoms which may be substituted with an alkyl group having 1 to 10 carbon atoms;
an aralkyl group having 7 to 20 carbon atoms,
a cycloalkyl group having 3 to 20 carbon atoms,
an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 3 to 30 carbon atoms which may be substituted with a —CO—OR ² group, where R ² is an alkyl group having 1 to 8 carbon atoms; represents a group. ) In the general formula (1), R ¹ is
an aryl group having 6 to 22 carbon atoms which may be substituted with an alkyl group having 1 to 10 carbon atoms;
represents an aralkyl group having 7 to 20 carbon atoms, or an alkyl group having 3 to 30 carbon atoms which may be substituted with a —CO—OR ² group, where R ² is an alkyl group having 1 to 8 carbon atoms; 2. The electrophotographic photoreceptor of claim 1, which represents a group. In the general formula (1), R ¹ represents an alkyl group having 5 to 10 carbon atoms which may be substituted with a —CO—OR ² group, and R ² represents an alkyl group having 1 to 3 carbon atoms. 3. The electrophotographic photoreceptor according to claim 1, which represents a group. In the general formula (1), R ¹ represents an alkyl group having 5 to 10 carbon atoms substituted with a —CO—OR ² group, and R ² represents an alkyl group having 1 to 3 carbon atoms. 4. The electrophotographic photoreceptor according to any one of claims 1 to 3, represented. The compound represented by the general formula (1) is a compound represented by the chemical formula (1-1), (1-2), (1-3), (1-4), or (1-5). 3. The electrophotographic photoreceptor according to claim 1 or 2.

The electrophotographic photoreceptor according to any one of claims 1 to 5, wherein the photosensitive layer further contains a compound represented by general formula (10).

(In general formula (10), R ¹⁰¹ , R ¹⁰² , R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ and R ¹⁰⁶ are each independently an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 14 carbon atoms,
a, b, c, and d each independently represent an integer of 0 to 5,
e and f each independently represents an integer of 0 or more and 4 or less. ) 7. The electrophotographic photoreceptor according to claim 6, wherein the compound represented by general formula (10) is a compound represented by chemical formula (10-1).

The electrophotographic photoreceptor according to any one of claims 1 to 7, wherein the photosensitive layer further contains a polycarbonate resin having a repeating unit represented by chemical formula (20).

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