JP7211098B2 - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Description

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

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.

US Pat. No. 4,500,000 describes an imaging member with at least one charge transport layer containing a terphenyldiamine charge transport component of particular structure. A terphenyldiamine charge transport component is represented, for example, by chemical formula (II).

JP 2007-293342 A

However, the inventors of the present invention have found that the image forming member described in Patent Document 1 is insufficient in improving charging stability and suppressing crystallization of the photosensitive layer.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor capable of improving charging stability and suppressing crystallization of a photosensitive layer. Another object of the present invention is to provide a process cartridge and an image forming apparatus capable of forming good images by including such an electrophotographic photoreceptor.

The electrophotographic photoreceptor of the present invention comprises a conductive substrate and a photosensitive layer. The photosensitive layer contains at least a charge generating agent, a hole transporting agent and a binder resin. The hole transport agent contains a compound represented by general formula (1). The binder resin includes a polycarbonate resin having a repeating unit represented by general formula (20) and a repeating unit represented by general formula (21).

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the number of carbon atoms in the group represented by R ¹ and the carbon atom in the group represented by R ² The sum with the number is 2. R ³ and R ⁴ each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the sum of the number of carbon atoms in the group represented by R ³ and the number of carbon atoms in the group represented by R ⁴ is 2 .

In general formulas (20) and (21), Q ¹ and Q ² represent a hydrogen atom, and Q ³ and Q ⁴ each independently represent an alkyl group having 1 to 6 carbon atoms. Alternatively, Q ¹ and Q ² each independently represent an alkyl group having 1 to 6 carbon atoms, and Q ³ and Q ⁴ represent a hydrogen atom.

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

An image forming apparatus of the present invention includes an image carrier, a charging device, an exposure device, a developing device, and a transfer device. The charging device charges the surface of the image carrier. The exposure device exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier. The developing device develops the electrostatic latent image into a toner image. The transfer device transfers the toner image from the image carrier to a recording medium. The image carrier is the electrophotographic photosensitive member described above.

According to the electrophotographic photoreceptor of the present invention, it is possible to improve charging stability and suppress crystallization of the photosensitive layer. Further, according to the process cartridge and the image forming apparatus of the present invention having such an electrophotographic photoreceptor, excellent images can be formed.

1 is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. 1 is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. 1 is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. 1 is a partial cross-sectional view of a laminated electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. 1 is a partial cross-sectional view of a laminated electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. 1 is a partial cross-sectional view of a laminated electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to an embodiment of the present invention; FIG. 1 is a cross-sectional view showing an example of an image forming apparatus; 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).

The alkyl group having 1 to 6 carbon atoms and the alkyl group having 1 to 3 carbon atoms are each straight or branched and unsubstituted. Examples of alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group and isopentyl. , neopentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-ethyl-1-methylpropyl, and straight and branched hexyl groups. 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 6 carbon atoms. The substituents used in the present specification have been described above.

<Electrophotographic photoreceptor>
The present embodiment relates to an electrophotographic photoreceptor (hereinafter sometimes referred to as a photoreceptor). The photoreceptor of this embodiment includes a conductive substrate and a photosensitive layer. The photosensitive layer contains at least a charge generating agent, a hole transporting agent and a binder resin. The photoreceptor is, for example, a single-layer electrophotographic photoreceptor (hereinafter sometimes referred to as a single-layer photoreceptor) or a laminated electrophotographic photoreceptor (hereinafter sometimes referred to as a laminated photoreceptor). is.

(Single layer photoreceptor)
A single-layer photoreceptor 1, which is an example of a photoreceptor, will be described below with reference to FIGS. 1 to 3. FIG. 1 to 3 each show a partial cross-sectional view of a single-layer photoreceptor 1. FIG.

As shown in FIG. 1, the single-layer photoreceptor 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. As shown in FIG. The photosensitive layer 3 provided in the single-layer photoreceptor 1 is a single layer. Hereinafter, the "single-layer photosensitive layer 3" may be referred to as "single-layer photosensitive layer 3a".

As shown in FIG. 2, the single-layer photoreceptor 1 may include a conductive substrate 2, a single-layer photoreceptor layer 3a, and an intermediate layer 4 (undercoat layer). The intermediate layer 4 is provided between the conductive substrate 2 and the single-layer photosensitive layer 3a. As shown in FIG. 1, the monolayer type photosensitive layer 3a may be provided directly on the conductive substrate 2. FIG. Alternatively, as shown in FIG. 2, the single-layer type photosensitive layer 3a may be provided on the conductive substrate 2 with an intermediate layer 4 interposed therebetween.

As shown in FIG. 3, the single-layer photoreceptor 1 may include a conductive substrate 2, a single-layer photoreceptor layer 3a, and a protective layer 5. As shown in FIG. A protective layer 5 is provided on the single-layer photosensitive layer 3a. As shown in FIGS. 1 and 2, a single-layer photoreceptor layer 3a may be provided as the outermost layer of the single-layer photoreceptor 1. FIG. Alternatively, as shown in FIG. 3, the protective layer 5 may be provided as the outermost surface layer of the single-layer photoreceptor 1 .

The single-layer type photosensitive layer 3a contains a charge generating agent, a hole transporting agent and a binder resin. The single-layer type photosensitive layer 3a may further contain an electron transport agent. The single-layer type photosensitive layer 3a may contain additives as necessary.

Although the thickness of the single-layer type photosensitive layer 3a is not particularly limited, it is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less. The single-layer photoreceptor 1 has been described above with reference to FIGS. 1 to 3. FIG.

(Laminated photoreceptor)
Next, a laminated photoreceptor 10, which is an example of a photoreceptor, will be described with reference to FIGS. 4 to 6. FIG. 4 to 6 each show a partial cross-sectional view of the laminated photoreceptor 10. FIG.

As shown in FIG. 4, the laminated photoreceptor 10 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 3b and a charge transport layer 3c. That is, the laminated photoreceptor 10 includes the charge generation layer 3b and the charge transport layer 3c as the photosensitive layer 3. As shown in FIG. The charge generation layer 3b is, for example, a single layer. The charge transport layer 3c is, for example, a single layer.

As shown in FIG. 4, in the laminated photoreceptor 10, the charge generation layer 3b may be provided on the conductive substrate 2, and the charge transport layer 3c may be provided on the charge generation layer 3b. Alternatively, as shown in FIG. 5, in the laminated photoreceptor 10, the charge transport layer 3c may be provided on the conductive substrate 2, and the charge generation layer 3b may be provided on the charge transport layer 3c.

As shown in FIG. 6, the laminated photoreceptor 10 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. 4 and 5, in the laminated photoreceptor 10, the photosensitive layer 3 may be provided directly on the conductive substrate 2. FIG. Alternatively, as shown in FIG. 6, in the laminated photoreceptor 10, the photosensitive layer 3 may be provided on the conductive substrate 2 with the intermediate layer 4 interposed therebetween. In the case where the laminated photoreceptor 10 includes the intermediate layer 4, as shown in FIG. A charge transport layer 3c may be provided thereon. Alternatively, the intermediate layer 4 may be provided on the conductive substrate 2, the charge transport layer 3c may be provided on the intermediate layer 4, and the charge generation layer 3b may be provided on the charge transport layer 3c.

The laminated photoreceptor 10 may include a conductive substrate 2, a photosensitive layer 3, and a protective layer 5 (see FIG. 3). A protective layer 5 is provided on the photosensitive layer 3 . A photosensitive layer 3 (for example, a charge transport layer 3 c or a charge generation layer 3 b ) may be provided as the outermost layer of the multilayer photoreceptor 10 . Alternatively, the protective layer 5 may be provided as the outermost layer of the laminated photoreceptor 10 .

The charge generation layer 3b contains a charge generation agent. The charge generation layer 3b may contain a charge generation layer binder resin (hereinafter sometimes referred to as a base resin). The charge-generating layer 3b may contain additives, if necessary. The charge transport layer 3c contains a hole transport agent and a binder resin. The charge transport layer 3c may contain additives as required.

Although the thickness of the charge generating layer 3b 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. Although the thickness of the charge transport layer 3c is not particularly limited, it is preferably 2 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less. The laminated photoreceptor 10 has been described above with reference to FIGS. 4 to 6. FIG. The photoreceptor will be further described below.

(Charge generating 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 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 (specifically, the charge-generating layer or single-layer type photosensitive layer) may contain only one type of charge-generating agent, or may contain two or more types thereof.

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 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. 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.

When the photoreceptor is a single layer type photoreceptor, the content of the charge generating agent is preferably 0.1 parts by mass or more and 50 parts by mass or less, and preferably 0.5 parts by mass with respect to 100 parts by mass of the binder resin. It is more preferable that the content is 4.5 parts by mass or less. When the photoreceptor is a multilayer photoreceptor, the content of the charge generating agent is preferably 10 parts by mass or more and 300 parts by mass or less, and 100 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the base resin. is more preferable.

(Hole transport agent)
The hole transport agent includes a compound represented by the following general formula (1) (hereinafter sometimes referred to as compound (1)). The photosensitive layer (single layer type photosensitive layer or charge transport layer) contains compound (1) as a hole transport agent.

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the number of carbon atoms in the group represented by R ¹ and the number of carbon atoms in the group represented by R ² is 2. R ³ and R ⁴ each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the sum of the number of carbon atoms in the group represented by R ³ and the number of carbon atoms in the group represented by R ⁴ is 2 .

Hereinafter, "R ¹ and R ² each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the sum of the number of carbon atoms in the group represented by R ¹ and the number of carbon atoms in the group represented by R ² is 2, R ³ and R ⁴ each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the sum of the number of carbon atoms in the group represented by R ³ and the number of carbon atoms in the group represented by R ⁴ is 2” may be described as “a predetermined substituent”. In addition, ``R <sup>1</sup> is positioned at the para position of the phenyl group, R <sup>2</sup> is positioned at the ortho position of the phenyl group, R <sup>3</sup> is positioned at the para position of the phenyl group, and R <sup>4</sup> is positioned at the ortho position of the phenyl group'' is defined as ``predetermined positions. It is sometimes described as “located in

By containing the compound (1) as a hole transport agent in the photosensitive layer, the charging stability of the photoreceptor can be improved and crystallization of the photosensitive layer can be suppressed. The reason is presumed as follows. The charging stability is a characteristic that allows the photoreceptor to be charged to a charging potential within a predetermined range even when images are repeatedly formed on a recording medium. For convenience of explanation, A and B are shown in the following general formula (1), and the phenyl groups represented by A and B are described as phenyl groups A and B, respectively.

The first reason will be explained. R ¹ to R ⁴ in general formula (1) are predetermined substituents, not bulky substituents. Non-bulky substituents represented by R ¹ to R ⁴ tend to fill minute voids in the photosensitive layer. Further, by positioning R ¹ to R ⁴ at predetermined positions, it becomes easy to fill minute gaps in the photosensitive layer. Therefore, when R ¹ to R ⁴ are predetermined substituents and R ¹ to R ⁴ are positioned at predetermined positions, deterioration of quality of the photoreceptor from the outside of the photoreceptor is prevented when images are repeatedly formed on a recording medium. It is possible to prevent contaminants (eg, gas, etc.) from entering the photosensitive layer. This improves the charging stability of the photoreceptor.

The second reason will be explained. R ¹ to R ⁴ in general formula (1) are predetermined substituents, and R ¹ to R ⁴ are positioned at predetermined positions. When R ¹ to R ⁴ in general formula (1) are not predetermined substituents (for example, methoxy group or butyl group) and when R ¹ to R ⁴ are not positioned at predetermined positions, The hole-transporting ability of the hole-transporting agent is lowered, and the charging stability is lowered. When R ¹ to R ⁴ in general formula (1) are predetermined substituents and R ¹ to R ⁴ are positioned at predetermined positions, the hole transport ability of compound (1) is improved and the charging stability of the photoreceptor is improved. improve sexuality.

A third reason will be explained. In general, compounds having a terphenyl structure tend to cause crystallization of photosensitive layers. The present inventors have made extensive studies and found that R ¹ to R ⁴ in general formula (1) are predetermined substituents, R ¹ to R ⁴ are positioned at predetermined positions, and phenyl groups A and B are methyl at the para position. It has been found that crystallization of the photosensitive layer can be suppressed by having a group. Predetermined substituents positioned at predetermined positions and the methyl groups at the para positions of the phenyl groups A and B increase the intermolecular force between other molecules contained in the photosensitive layer and the compound (1). An appropriate distance is provided, but not too much. Therefore, crystallization of the photosensitive layer can be suppressed.

A fourth reason will be explained. As already mentioned, R ¹ to R ⁴ in general formula (1) are predetermined substituents, not bulky substituents. Compounds with bulky substituents (eg, phenylbutadienyl groups, or butyl groups) tend to cause crystallization of the photosensitive layer. Also, R ¹ to R ⁴ are located at predetermined positions. When R ¹ to R ⁴ are predetermined non-bulky substituents and R ¹ to R ⁴ are positioned at predetermined positions, crystallization of the photosensitive layer can be suppressed. The reason why the charging stability of the photosensitive member can be improved and the crystallization of the photosensitive layer can be suppressed has been described above.

Suitable examples of compound (1) include compounds represented by chemical formulas (1-1), (1-2), and (1-3) (hereinafter referred to as compounds (1-1), (1- 2), and may be described as (1-3)). Compounds (1-1) and (1-2) are more preferred as compound (1) in order to particularly suppress crystallization of the photosensitive layer.

The content of the hole transport agent is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 65 parts by mass or more, relative to 100 parts by mass of the binder resin. The content of the hole transport agent is preferably 300 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 75 parts by mass or less, relative to 100 parts by mass of the binder resin.

The photosensitive layer may contain only one compound (1) as a hole transport agent. Alternatively, the photosensitive layer may contain two or more compounds (1) as hole transport agents. Moreover, the photosensitive layer may contain only compound (1) as a hole transport agent. Alternatively, the photosensitive layer further contains a hole transport agent other than compound (1) (hereinafter sometimes referred to as another hole transport agent) in addition to compound (1) as a hole transport agent. may

Other hole transport agents include, for example, oxadiazole compounds (eg, 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole), styryl compounds (eg, 9- (4-diethylaminostyryl)anthracene), carbazole 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 compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

Compound (1) can be produced, for example, according to the reaction represented by the following reaction formula (r1) (hereinafter sometimes referred to as reaction (r1)). Y in general formula (a) represented by reaction formula (r1) represents a halogen atom. R ¹ , R ² , R ³ and R ⁴ in general formulas (b) and (c) have the same definitions as R ¹ , R ² , R ³ and R ⁴ in general formula (1) . The compounds represented by general formulas (a), (b) and (c) are sometimes referred to as compounds (a), (b) and (c), respectively.

In reaction (r1), 1 molar equivalent of compound (a), 1 molar equivalent of compound (b), and 1 molar equivalent of compound (c) are reacted to obtain 1 molar equivalent of compound (1). . When R ¹ and R ³ in general formula (1) are the same and R ² and R ⁴ are the same, 1 molar equivalent of compound (b) and 1 molar equivalent of compound (c ), two molar equivalents of compound (b) are used.

Reaction (r1) may be carried out in the presence of a palladium catalyst. Palladium catalysts include, for example, palladium(II) acetate, palladium(II) chloride, sodium hexachloropalladium(IV) tetrahydrate, and tris(dibenzylideneacetone)dipalladium(0).

Reaction (r1) may be carried out in the presence of a ligand. Ligands include, for example, (4-dimethylaminophenyl)di-tertbutylphosphine, tricyclohexylphosphine, triphenylphosphine, and methyldiphenylphosphine.

Reaction (r1) may be carried out in the presence of a base. Bases include, for example, sodium tert-butoxide, tripotassium phosphate, and cesium fluoride. The amount of the base to be added is preferably 1 molar equivalent or more and 10 molar equivalents or less with respect to 1 molar equivalent of compound (b).

Reaction (r1) may be carried out in a solvent. Solvents include, for example, xylene, toluene, tetrahydrofuran, and dimethylformamide.

The reaction temperature of reaction (r1) is preferably 80° C. or higher and 140° C. or lower. The reaction time of reaction (r1) is preferably 1 hour or more and 10 hours or less. Reaction (r1) may be carried out under an inert gas (eg, argon gas) atmosphere.

(binder resin)
The binder resin contains a polycarbonate resin having a repeating unit represented by general formula (20) and a repeating unit represented by general formula (21). The photosensitive layer (single layer type photosensitive layer or charge transport layer) contains, as a binder resin, a polycarbonate resin having a repeating unit represented by general formula (20) and a repeating unit represented by general formula (21). .

In general formulas (20) and (21), Q ¹ and Q ² represent a hydrogen atom, and Q ³ and Q ⁴ each independently represent an alkyl group having 1 to 6 carbon atoms. Alternatively, Q ¹ and Q ² each independently represent an alkyl group having 1 to 6 carbon atoms, and Q ³ and Q ⁴ represent a hydrogen atom.

Hereinafter, "polycarbonate resin having a repeating unit represented by general formula (20) and a repeating unit represented by general formula (21)" may be referred to as "polycarbonate resin (PC)". In addition, the “repeating unit represented by the general formula (20)” shall be described as the “repeating unit (20)”, and the “repeating unit represented by the general formula (21)” shall be described as the “repeating unit (21)”. There is

By containing a polycarbonate resin (PC) as a binder resin in the photosensitive layer, the charging stability of the photoreceptor can be improved and crystallization of the photosensitive layer can be suppressed. The reason is presumed as follows.

The alkyl groups having 1 to 6 carbon atoms represented by Q ¹ to Q ⁴ in general formulas (20) and (21) tend to fill minute voids in the photosensitive layer. Therefore, when images are repeatedly formed on a recording medium, it is possible to prevent a component (for example, gas) from the outside of the photoreceptor, which deteriorates the quality of the photoreceptor, from entering the photosensitive layer. This improves the charging stability of the photoreceptor. However, if the number of alkyl groups having 1 to 6 carbon atoms in the polycarbonate resin is too large, crystallization of the photosensitive layer is caused. Therefore, in general formulas (20) and (21), Q ¹ and Q ² represent a hydrogen atom, and Q ³ and Q ⁴ each independently represent an alkyl group having 1 to 6 carbon atoms, or Q ¹ and Q ² each independently represent an alkyl group having 1 to 6 carbon atoms, and Q ³ and Q ⁴ represent a hydrogen atom, thereby forming an alkyl group having 1 to 6 carbon atoms possessed by the polycarbonate resin. Adjust the number of In this way, it is possible to improve the charging stability of the photoreceptor and suppress the crystallization of the photoreceptor layer. In particular, when the photosensitive layer contains both polycarbonate resin (PC) and compound (1) which is a hole transport agent, these advantages become remarkable.

In general formulas (20) and (21), the alkyl group having 1 to 6 carbon atoms represented by Q ¹ , Q ² , Q ³ and Q ⁴ is preferably an alkyl group having 1 to 3 carbon atoms, A methyl group is more preferred.

In order to improve charging stability and suppress crystallization of the photosensitive layer, the ratio of the number of repeating units (20) to the total number of repeating units (20) and (21) is 30% or more and 90% or less. 40% or more and 80% or less is more preferable, 50% or more and 70% or less is still more preferable, and 55% or more and 65% or less is particularly preferable. Hereinafter, the "ratio of the number of repeating units (20) to the total number of repeating units (20) and (21)" may be referred to as "ratio n". The ratio n is not a value obtained from one resin chain, but a number average value obtained from the entire polycarbonate resin (PC) (multiple resin chains).

In order to improve charging stability and suppress crystallization of the photosensitive layer, the polycarbonate resin (PC) contains a repeating unit represented by the chemical formula (20-1) and a repeating unit represented by the chemical formula (21-1). Polycarbonate resins having units are preferred. Hereinafter, the “repeating unit represented by the chemical formula (20-1)” will be referred to as the “repeating unit (20-1)”, and the “repeating unit represented by the chemical formula (21-1)” will be referred to as the “repeating unit (21-1 )” may be described. Also, the "polycarbonate resin having the repeating unit (20-1) and the repeating unit (21-1)" may be referred to as "first polycarbonate resin".

In order to improve charging stability and suppress crystallization of the photosensitive layer, the polycarbonate resin (PC) contains a repeating unit represented by the chemical formula (20-2) and a repeating unit represented by the chemical formula (21-2). Polycarbonate resins having units are also preferred. Hereinafter, the “repeating unit represented by the chemical formula (20-2)” will be referred to as the “repeating unit (20-2)”, and the “repeating unit represented by the chemical formula (21-2)” will be referred to as the “repeating unit (21-2 )” may be described. Also, the "polycarbonate resin having the repeating unit (20-2) and the repeating unit (21-2)" may be referred to as "second polycarbonate resin".

Preferred examples of the first polycarbonate resin include a polycarbonate resin represented by the following chemical formula (R-1) (hereinafter sometimes referred to as polycarbonate resin (R-1)). Preferred examples of the second polycarbonate resin include a polycarbonate resin represented by the following chemical formula (R-2) (hereinafter sometimes referred to as polycarbonate resin (R-2)). In the chemical formulas (R-1) and (R-2), the number attached to the lower right of the repeating unit indicates the ratio (unit: %) of the number of corresponding repeating units to the total number of repeating units possessed by the polycarbonate resin. show.

The arrangement of the repeating units (20) and (21) in the polycarbonate resin (PC) is not particularly limited. That is, the polycarbonate resin (PC) may be any of random copolymers, alternating copolymers, periodic copolymers, and block copolymers.

The polycarbonate resin (PC) may have only repeating units (20) and (21) as repeating units. Alternatively, the polycarbonate resin (PC) may further have repeating units other than repeating units (20) and (21) as repeating units.

Examples of the method for producing a polycarbonate resin include a method of interfacial condensation polymerization of a diol compound and phosgene (so-called phosgene method) and a method of transesterification of a diol compound and diphenyl carbonate. Specific examples of diol compounds used in the phosgene method include compounds represented by the following general formulas (20A) and (21A). Q ¹ , Q ² , Q ³ and Q ⁴ in general formulas (20A) and (21A) are respectively Q ¹ , Q ² , Q ³ and Q ⁴ in general formulas (20) and (21) is synonymous with By changing the added amount of the compound represented by the general formula (20A) with respect to the added amount of the compound represented by the general formula (21A), the ratio n can be changed.

The photosensitive layer may contain only a polycarbonate resin (PC) as a binder resin. Alternatively, the photosensitive layer may further contain a binder resin other than polycarbonate resin (PC) as a binder resin (hereinafter sometimes referred to as other binder resin). Other binder resins include, for example, thermoplastic resins (more specifically, polycarbonate resins other than polycarbonate resins (PC), polyarylate resins, styrene resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, , styrene-maleic acid copolymer, styrene-acrylic acid copolymer, acrylic copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, vinyl chloride - vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral 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).

The viscosity-average molecular weight of the binder resin is preferably 20,000 or more, more preferably 25,000 or more, even more preferably 30,000 or more. Also, the viscosity average molecular weight of the binder resin is preferably 70,000 or less, more preferably 50,000 or less, and even more preferably 40,000 or less. When the viscosity-average molecular weight of the binder resin is 20,000 or more, the photosensitive layer becomes difficult to wear. On the other hand, when the viscosity-average molecular weight of the binder resin is 70,000 or less, the binder resin is easily dissolved in the solvent, and the formation of the photosensitive layer is facilitated.

(base resin)
When the photoreceptor is a laminated photoreceptor, the charge generating layer contains a base resin. Examples of base resins include thermoplastic resins (more specifically, polycarbonate resins, polyarylate 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, 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-based resins and urethane-acrylic acid-based copolymers). . The charge generation layer may contain only one of these base resins, or may contain two or more of them. In order to form the charge generation layer and the charge transport layer satisfactorily, the base resin contained in the charge generation layer is preferably different from the binder resin contained in the charge transport layer.

(Electron transport agent)
When the photoreceptor is a single-layer photoreceptor, the single-layer photoreceptor contains an electron transport agent. Examples of electron transport agents include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, dinitroanthracene compounds, dinitroacridine 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 single-layer type photosensitive layer may contain only one electron transport agent, or may contain two or more electron transport agents.

Preferred examples of the electron transport agent include compounds represented by general formula (10) (hereinafter sometimes referred to as compound (10)). When the electron transport agent is compound (10), it tends to favorably form a complex with compound (1), which is a hole transport agent. Then, the formed complex dissolves satisfactorily in the solvent to form a uniform monolayer type photosensitive layer. Therefore, crystallization of the single-layer type photosensitive layer can be further suppressed.

In general formula (10), Q ¹¹ and Q ¹² each independently represent an alkyl group having 1 to 6 carbon atoms. The alkyl group having 1 to 6 carbon atoms represented by Q ¹¹ and Q ¹² in general formula (10) is preferably a 1,1-dimethylpropyl group.

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

The content of the electron transport agent is preferably 5 parts by mass or more and 150 parts by mass or less, preferably 10 parts by mass or more and 50 parts by mass or less, and 20 parts by mass or more and 40 parts by mass with respect to 100 parts by mass of the binder resin. It is more preferably not more than parts by mass.

(Additive)
Additives include, for example, antioxidants, radical scavengers, singlet quenchers, ultraviolet absorbers, softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, donors, surface active agents, plasticizers, sensitizers, electron acceptor compounds, and leveling agents.

(combination of materials)
In order to suppress the crystallization of the photosensitive layer while improving the charging stability, the combination of the hole transport agent and the binder resin is selected from combination example No. 1 shown in Table 1. Any one of 1 to 12 is preferable. For the same reason, the combination of the hole transport agent and the binder resin is the combination example No. 1 shown in Table 1. 1 to 12, and the electron transport agent is preferably compound (E-1). For the same reason, the combination of the hole transport agent and the binder resin is the combination example No. 1 shown in Table 1. 1 to 12, and the charge generating agent is preferably Y-type titanyl phthalocyanine. For the same reason, the combination of the hole transport agent and the binder resin is the combination example No. 1 shown in Table 1. 1 to 12, the electron transporting agent is compound (E-1), and the charge generating agent is preferably Y-type titanyl phthalocyanine.

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

(Manufacturing method of photoreceptor)
As a method for manufacturing a photoreceptor, an example of a method of manufacturing a single-layer photoreceptor and an example of a method of manufacturing a multi-layer photoreceptor will be described.

A method for manufacturing a single layer photoreceptor includes a step of forming a single layer photoreceptor. In the single-layer type photosensitive layer forming step, a coating liquid for forming a single-layer type photosensitive layer (hereinafter sometimes referred to as a single-layer type photosensitive layer coating liquid) is prepared. A single-layer type photosensitive layer coating solution is applied onto a conductive substrate. Then, at least part of the solvent contained in the coated photosensitive layer coating liquid is removed to form a single layer type photosensitive layer. The single-layer photosensitive layer coating liquid contains, for example, a charge generating agent, a hole transporting agent, a binder resin, and a solvent. The single-layer photosensitive layer coating liquid is prepared by dissolving or dispersing a charge generating agent, a hole transporting agent and a binder resin in a solvent. The single-layer type photosensitive layer coating solution may further contain an electron transport agent. The single-layer type photosensitive layer coating solution may further contain additives, if necessary.

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

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

The solvent contained in the single-layer photosensitive layer coating liquid, the charge generation layer coating liquid, and the charge transport layer coating liquid (hereinafter, these may be collectively referred to as coating liquids) There are no particular limitations as long as each component contained can be dissolved or dispersed. 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.

<Image forming apparatus>
Next, an image forming apparatus including the photoreceptor of this embodiment will be described. A tandem color image forming apparatus will be described below as an example with reference to FIG. FIG. 7 is a cross-sectional view showing an example of an image forming apparatus.

The image forming apparatus 110 shown in FIG. 7 includes image forming units 40a, 40b, 40c, and 40d, a transfer belt 50, and a fixing device 52. Hereinafter, each of the image forming units 40a, 40b, 40c, and 40d will be referred to as the image forming unit 40 when there is no need to distinguish between them.

The image forming unit 40 includes an image carrier 100 , a charging device 42 , an exposure device 44 , a developing device 46 , a transfer device 48 and a cleaning device 54 . The image carrier 100 is the photoreceptor of this embodiment (more specifically, the single-layer photoreceptor 1 or the multi-layer photoreceptor 10).

As already described, according to the photoreceptor of the present embodiment (more specifically, the single-layer photoreceptor 1 or the multilayer photoreceptor 10), the charging stability of the photoreceptor is improved and the photoreceptor layer 3 is improved. Suppression of crystallization becomes possible. Therefore, the image forming apparatus 110 can form a good image on the recording medium P by including such a photoreceptor as the image carrier 100 .

An image carrier 100 is provided at a central position of the image forming unit 40 . The image carrier 100 is rotatable in the arrow direction (counterclockwise). Around the image carrier 100, there are a charging device 42, an exposure device 44, a developing device 46, a transfer device 48, and a cleaning device 54 in the order described from the upstream side in the rotational direction of the image carrier 100. be provided.

Each of the image forming units 40a to 40d sequentially superimposes toner images of a plurality of colors (for example, four colors of black, cyan, magenta, and yellow) on the recording medium P on the transfer belt 50. FIG.

The charging device 42 charges the surface (for example, the peripheral surface) of the image carrier 100 . The charging device 42 is, for example, a scorotron charger.

The exposure device 44 exposes the charged surface of the image carrier 100 . Thereby, an electrostatic latent image is formed on the surface of the image carrier 100 . The electrostatic latent image is formed based on image data input to image forming apparatus 110 .

The developing device 46 supplies toner to the surface of the image carrier 100 and develops the electrostatic latent image into a toner image. The developing device 46 develops the electrostatic latent image into a toner image while being in contact with the surface of the image carrier 100 . That is, the image forming apparatus 110 employs the contact development method. The developing device 46 is, for example, a developing roller. When the developer is a one-component developer, the developing device 46 supplies toner, which is a one-component developer, to the electrostatic latent image formed on the image carrier 100 . When the developer is a two-component developer, the developing device 46 supplies the electrostatic latent image formed on the image carrier 100 with the toner, which is contained in the two-component developer, and the carrier. Thus, the image carrier 100 carries a toner image.

The transfer belt 50 conveys the recording medium P between the image carrier 100 and the transfer device 48 . The transfer belt 50 is an endless belt. The transfer belt 50 is rotatable in the arrow direction (clockwise).

The transfer device 48 transfers the toner image developed by the developing device 46 from the surface of the image carrier 100 to the recording medium P which is a transfer target. Specifically, the transfer device 48 transfers the toner image from the surface of the image carrier 100 to the recording medium P while the surface of the image carrier 100 and the recording medium P are in contact with each other. That is, the image forming apparatus 110 employs a direct transfer method. The transfer device 48 is, for example, a transfer roller.

The cleaning device 54 collects toner adhering to the surface of the image carrier 100 . The cleaning device 54 has a housing 541 and a cleaning roller 542 . Note that the cleaning device 54 does not have a cleaning blade. Cleaning roller 542 is disposed within housing 541 . Cleaning roller 542 is arranged to contact the surface of image carrier 100 . The cleaning roller 542 polishes the surface of the image carrier 100 and collects the toner adhering to the surface of the image carrier 100 into the housing 541 .

The recording medium P onto which the toner image has been transferred by the transfer device 48 is conveyed to the fixing device 52 by the transfer belt 50 . The fixing device 52 is, for example, a heating roller and/or a pressure roller. The unfixed toner image transferred by the transfer device 48 is heated and/or pressed by the fixing device 52 . The toner image is fixed on the recording medium P by heating and/or pressing the toner image. As a result, an image is formed on the recording medium P. FIG.

An example of the image forming apparatus has been described above, but the image forming apparatus is not limited to the image forming apparatus 110 described above. Although the image forming apparatus 110 described above is a color image forming apparatus, the image forming apparatus may be a monochrome image forming apparatus. In this case, the image forming apparatus may have, for example, only one image forming unit. Further, although the image forming apparatus 110 described above employs a tandem system, the image forming apparatus may employ, for example, a rotary system. Although the scorotron charger has been described as an example of the charging device 42, the charging device may be a charging device other than the scorotron charger (for example, a charging roller, a charging brush, or a corotron charger). Although the image forming apparatus 110 described above employs a contact developing method, the image forming apparatus may employ a non-contact developing method. Although the image forming apparatus 110 described above employs a direct transfer method, the image forming apparatus may employ an intermediate transfer method. When the image forming apparatus employs an intermediate transfer method, the transfer target corresponds to an intermediate transfer belt. Although the cleaning device 54 described above has the cleaning roller 542 and no cleaning blade, the cleaning device may have the cleaning roller 542 and the cleaning blade. Although the image forming unit 40 described above does not include a static elimination device, the image forming unit may further include a static elimination device.

<Process cartridge>
Next, with continued reference to FIG. 7, an example of a process cartridge including the photoreceptor of this embodiment (more specifically, the single-layer photoreceptor 1 or the multi-layer photoreceptor 10) will be described. A process cartridge corresponds to each of the image forming units 40a to 40d. A process cartridge includes an image carrier 100 . The image carrier 100 is the photoreceptor of this embodiment (more specifically, the single-layer photoreceptor 1 or the multi-layer photoreceptor 10). The process cartridge further includes at least one of the charging device 42 and the cleaning device 54 in addition to the image carrier 100 .

As already described, according to the photoreceptor of the present embodiment (more specifically, the single-layer photoreceptor 1 or the multilayer photoreceptor 10), the charging stability of the photoreceptor is improved and the photoreceptor layer 3 is improved. Suppression of crystallization becomes possible. Therefore, the process cartridge can form a good image on the recording medium P by including such a photosensitive member as the image carrier 100 .

The process cartridge may further include at least one of the exposure device 44 , the development device 46 and the transfer device 48 in addition to the image carrier 100 , the charging device 42 and the cleaning device 54 . The process cartridge may further include a static eliminator (not shown). The process cartridge is designed to be detachable from the image forming apparatus 110 . Therefore, the process cartridge is easy to handle, and when the sensitivity characteristics of the image carrier 100 deteriorate, the process cartridge including the image carrier 100 can be easily and quickly replaced. The process cartridge provided with the photoreceptor of the present embodiment has been described above with reference to FIG.

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.

First, as materials for forming a single-layer type photosensitive layer of a single-layer type photoreceptor, the following charge-generating agent, electron-transporting agent, hole-transporting agent, and binder resin were prepared.

(Charge generating agent)
Y-type titanyl phthalocyanine described in the embodiment was prepared as a charge generating agent.

(Electron transport agent)
As an electron transport agent, the compound (E-1) described in the embodiment was prepared.

(Hole transport agent)
Compounds (1-1) to (1-3) described in the embodiment were prepared as hole transport agents. Each of compounds (1-1) to (1-3) was synthesized by the following method.

(Synthesis of compound (1-1))
4,4″-dibromo-p-terphenyl (11.98 g, 30.9 mmol), palladium(II) acetate (0.069 g, 0.307 mmol), (4-dimethylaminophenyl ) Di-tertbutylphosphine (0.205 g, 0.772 mmol) and sodium tert-butoxide (7.702 g, 80.15 mmol) were charged. The air in the flask was replaced with nitrogen gas by repeating degassing and nitrogen gas replacement in the flask twice. Into the flask was then charged (2,4-dimethylphenyl)(4′-methylphenyl)amine (13.85 g, 63.3 mmol) and xylene (100 mL). The contents of the flask were stirred at 120° C. for 3 hours under reflux. The temperature of the flask contents was then lowered to 50°C. The contents of the flask were filtered to remove ash to obtain a filtrate. Activated clay (“SA-1” manufactured by Japan Activated clay Co., Ltd., 24 g) was added to the filtrate, and the mixture was stirred at 80° C. for 10 minutes to obtain a mixture. The mixture was then filtered to obtain a filtrate. The filtrate was evaporated under reduced pressure to obtain a residue. 20 g of toluene was added to the residue and heated to 100°C. The residue was dissolved in toluene by heating to obtain a solution. n-Hexane was added to the solution until the solution became slightly cloudy. Then, the solution was cooled to 5° C. and the precipitated crystals were collected by filtration. The resulting crystals were dried to obtain compound (1-1). The yield of compound (1-1) was 18.2 g. The yield of compound (1-1) from 4,4''-dibromo-p-terphenyl was 90.8 mol%.

(Synthesis of compound (1-2))
Compound (1- A compound (1-2) was obtained in the same manner as in the synthesis of 1).

(Synthesis of compound (1-3))
Compound (1- A compound (1-3) was obtained in the same manner as in the synthesis of 1).

¹ H-NMR spectra of synthesized compounds (1-1) to (1-3) were measured using a proton nuclear magnetic resonance spectrometer (manufactured by JASCO Corporation, 300 MHz). CDCl ₃ was used as solvent. Tetramethylsilane (TMS) was used as an internal standard sample. As a representative example of compounds (1-1) to (1-3), the chemical shift value of compound (1-1) is shown below. It was confirmed from the chemical shift value that compound (1-1) was obtained. Compounds (1-2) and (1-3) were confirmed by the same method to obtain compounds (1-2) and (1-3).

Compound (1-1): ¹ H-NMR (300 MHz, CDCl ₃ ) δ = 7.57 (s, 4H), 7.42-7.45 (m, 4H), 7.01-7.07 (m , 18H), 2.34 (s, 6H), 2.29 (s, 6H), 2.03 (s, 6H).

Next, as hole transport agents used in Comparative Examples, compounds represented by the following chemical formulas (H-4) to (H-14) (hereinafter referred to as compounds (H-4) to (H-14), respectively) may be described) were prepared.

(binder resin)
As binder resins, the polycarbonate resins (R-1) and (R-2) described in the embodiment were prepared. The polycarbonate resin (R-1) had a viscosity average molecular weight of 32,500. The polycarbonate resin (R-2) had a viscosity average molecular weight of 33,300.

Further, polycarbonate resins represented by the following chemical formulas (R-3) and (R-4) were prepared as hole transport agents used in comparative examples. The polycarbonate resin (R-3) had a viscosity average molecular weight of 33,000. The polycarbonate resin (R-4) had a viscosity average molecular weight of 32,500. In the chemical formulas (R-3) and (R-4), the number attached to the lower right of the repeating unit indicates the ratio (unit: %) of the number of corresponding repeating units to the total number of repeating units possessed by the polycarbonate resin. show.

<Production of single-layer photoreceptor>
Single-layer photoreceptors (A-1) to (A-4) and (B-1) to (B-13) are prepared using the charge generating agent, hole transport agent, binder resin, and electron transport agent described above. manufactured.

(Production of single-layer photoreceptor (A-1))
3 parts by mass of Y-type titanyl phthalocyanine as a charge generating agent, 70 parts by mass of compound (1-1) as a hole transport agent, 100 parts by mass of polycarbonate resin (R-1) as a binder resin, and a compound as an electron transport agent 30 parts by mass of (E-1) and 800 parts by mass of tetrahydrofuran as a solvent were mixed for 50 hours using a ball mill to obtain a single-layer photosensitive layer coating solution. A single-layer type photosensitive layer coating liquid was applied onto a conductive substrate (an aluminum drum-shaped support) by a dip coating method. The coated single-layer type photosensitive layer coating solution was dried with hot air at 120° C. for 60 minutes. In this manner, a single-layer photosensitive layer (thickness: 28 μm) was formed on the conductive substrate to obtain a single-layer photosensitive member (A-1). In the single-layer photoreceptor (A-1), a single-layer photoreceptor layer was provided on a conductive substrate.

(Production of single-layer photoreceptors (A-2) to (A-4) and (B-1) to (B-13))
Single-layer photoreceptors (A-2) to (A) were prepared in the same manner as in the production of single-layer photoreceptor (A-1), except that the types of hole transport agents and binder resins shown in Table 2 were used. -4) and each of (B-1) to (B-13) were produced.

<Evaluation of Sensitivity Characteristics of Single Layer Type Photoreceptor>
For each of the single-layer photoreceptors (A-1) to (A-4) and (B-1) to (B-13), the sensitivity characteristics were measured under an environment of a temperature of 10°C and a relative humidity of 15% RH. evaluated. Specifically, the surface of the single-layer photoreceptor was charged to +750 V using a drum sensitivity tester (manufactured by Gentec Co., Ltd.). Next, monochromatic light (wavelength: 780 nm, exposure amount: 0.7 μJ/cm ² ) was extracted from the light of the halogen lamp using a band-pass filter and irradiated onto the surface of the single-layer photoreceptor. The surface potential of the single-layer photoreceptor was measured 70 milliseconds after the end of irradiation with monochromatic light. The measured surface potential was defined as post-exposure potential V _L (unit: +V) of the single-layer photoreceptor. Table 2 shows the post-exposure potential V _L of the single-layer photoreceptor. The smaller the absolute value of the post-exposure potential _VL , the better the sensitivity characteristics of the single-layer photoreceptor.

<Evaluation of charging stability of single-layer photoreceptor>
For each of the single-layer type photoreceptors (A-1) to (A-4) and (B-1) to (B-13), charge stability was achieved in an environment of a temperature of 10°C and a relative humidity of 15% RH. evaluated the sex. An evaluation machine (a modified machine of "FS-C5250DN" manufactured by Kyocera Document Solutions Co., Ltd.) was used to evaluate the charging stability. The evaluator was equipped with a scorotron charger and cleaning roller and no cleaning blade. The evaluation machine employed a contact development system equipped with a development roller and a direct transfer system. The exposure-to-develop time was set at 70 ms.

First, using the evaluation machine, image A (full white paper image) was printed on three sheets of recording media (A4 size paper). When printing on each sheet, the surface potential of the single-layer photoreceptor was measured at a position facing the developing roller (developing position). Since exposure is not performed when printing a blank image, the measured surface potential corresponds to the charging potential. The surface potential was measured three times in total, once for printing one sheet of paper. The average value of the surface potentials measured three times was taken as the charging potential V ₀₁ (unit: +V) before the printing test.

A print test was then conducted. The printing test was a test in which image B (printing pattern image with a printing rate of 5%) was printed on 10,000 sheets of recording media (A4 size paper) at intervals of 15 seconds using an evaluator. Immediately after the printing test, image A (all white paper image) was printed on three recording media (A4 size paper). When printing on each sheet, the surface potential of the single-layer photoreceptor was measured at the development position. The surface potential was measured three times in total, once for printing one sheet of paper. The average value of the surface potentials measured three times was taken as the charging potential V ₀₂ (unit: +V) after the printing test.

A value obtained by subtracting the charge potential V ₀₂ after the print test from the charge potential V ₀₁ before the print test (V ₀₁ -V ₀₂ ) was defined as the charge potential drop ΔV ₀ (unit: V). Table 2 shows the charge potential drop amount ΔV ₀ . The smaller the charging potential drop amount ΔV ₀ (unit: V), the better the charging stability of the single-layer photoreceptor.

<Evaluation of Suppression of Crystallization of Single-layer Photoreceptor>
The entire surfaces (photosensitive layers) of the single-layer type photoreceptors (A-1) to (A-4) and (B-1) to (B-13) were observed with the naked eye. Then, the presence or absence of a crystallized portion in the photosensitive layer was confirmed. Based on the confirmation results, whether or not crystallization was suppressed was evaluated according to the following evaluation criteria. Table 2 shows the evaluation results. The single-layer type photoreceptor with an evaluation of C was evaluated as not having suppressed crystallization of the photosensitive layer.

(Evaluation Criteria for Suppression of Crystallization)
Evaluation A: No crystallized portion was observed.
Evaluation B: Some crystallized portions were confirmed.
Evaluation C: A crystallized portion was clearly confirmed.

In Table 2, HTM, resin, ETM, V _L , and ΔV ₀ indicate the hole transport agent, binder resin, electron transport agent, post-exposure potential, and charge potential drop, respectively.

As shown in Table 2, the single-layer photosensitive layers of the single-layer photoreceptors (A-1) to (A-4) contain compound (1) (specifically, compound (1 -1) to (1-3)). The single-layer type photosensitive layers of the single-layer type photoreceptors (A-1) to (A-4) are polycarbonate resin (PC) having repeating units (20) and repeating units (21) (specifically contained a polycarbonate resin (either of (R-1) and (R-2)). The charge potential drop ΔV ₀ of the single-layer photoreceptors (A-1) to (A-4) was 14 V or less. The single-layer type photoreceptors (A-1) to (A-4) were evaluated as A or B for crystallization inhibition. Therefore, the single-layer type photoreceptors (A-1) to (A-4) were able to achieve both improved charging stability and suppressed crystallization of the photosensitive layer. Further, the post-exposure potential V _L of the single-layer photoreceptors (A-1) to (A-4) is +100 V or more and +108 V or less, and the single-layer photoreceptors (A-1) to (A-4) have a sensitivity of Both the improvement of charging stability and the suppression of crystallization of the photosensitive layer could be achieved without impairing the properties.

From the above, it was shown that the photoreceptor according to the present invention can achieve both improved charging stability and suppressed crystallization of the photosensitive layer. Since the photoreceptor according to the present invention can achieve both improved charging stability and suppression of crystallization of the photosensitive layer, a process cartridge and an image forming apparatus equipped with the photoreceptor according to the present invention can form excellent images. can be done.

A photoreceptor and a process cartridge according to the present invention can be used in an image forming apparatus. The image forming apparatus according to the present invention can be used to form an image on a recording medium.

Reference Signs List 1: single-layer electrophotographic photosensitive member 2: conductive substrate 3: photosensitive layer 10: laminated electrophotographic photosensitive member 42: charging device 44: exposure device 46: developing device 48: transfer device 100: image carrier 110: image Forming device 542: cleaning roller P: recording medium

Claims (13)

comprising a conductive substrate and a photosensitive layer;
The photosensitive layer contains at least a charge generating agent, a hole transporting agent and a binder resin,
The hole transport agent contains a compound represented by the general formula (1),
The electrophotographic photoreceptor, wherein the binder resin includes a polycarbonate resin having a repeating unit represented by general formula (20) and a repeating unit represented by general formula (21).

(In the general formula (1),
R ¹ and R ² each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the sum of the number of carbon atoms in the group represented by R ¹ and the number of carbon atoms in the group represented by R ² is 2; ,
R ³ and R ⁴ each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the sum of the number of carbon atoms in the group represented by R ³ and the number of carbon atoms in the group represented by R ⁴ is 2 . )

(In the general formulas (20) and (21),
Q ¹ and Q ² each represent a hydrogen atom, and Q ³ and Q ⁴ each independently represent an alkyl group having 1 to 6 carbon atoms, or
Q ¹ and Q ² each independently represent an alkyl group having 1 to 6 carbon atoms, and Q ³ and Q ⁴ represent a hydrogen atom. ) 2. The electrophotographic photoreceptor according to claim 1, wherein the compound represented by general formula (1) is a compound represented by chemical formula (1-1), (1-2), or (1-3). .

3. The electrophotographic photoreceptor according to claim 2, wherein the compound represented by general formula (1) is a compound represented by chemical formula (1-1) or (1-2). The polycarbonate resin is
A polycarbonate resin having a repeating unit represented by the chemical formula (20-1) and a repeating unit represented by the chemical formula (21-1), or a repeating unit represented by the chemical formula (20-2) and a chemical formula ( 21-2).

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

(In general formula (10), Q ¹¹ and Q ¹² each independently represent an alkyl group having 1 to 6 carbon atoms.) 7. The electrophotographic photoreceptor according to claim 6, wherein the compound represented by general formula (10) is a compound represented by chemical formula (E-1).

A process cartridge comprising the electrophotographic photoreceptor according to any one of claims 1 to 7. an image carrier;
a charging device that charges the surface of the image carrier;
an exposure device that exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier;
a developing device that develops the electrostatic latent image as a toner image;
a transfer device for transferring the toner image from the image carrier to a transfer target;
An image forming apparatus, wherein the image carrier is the electrophotographic photosensitive member according to any one of claims 1 to 7. The transfer-receiving material is a recording medium,
10. The image forming apparatus according to claim 9, wherein said transfer device transfers said toner image from said image carrier to said recording medium while said surface of said image carrier and said recording medium are in contact with each other. 11. The image forming apparatus according to claim 9, wherein said developing device develops said electrostatic latent image as said toner image while being in contact with said surface of said image carrier. The image forming apparatus according to any one of claims 9 to 11, wherein the charging device is a scorotron charger. The image forming apparatus according to any one of claims 9 to 12, further comprising a cleaning roller that polishes the surface of the image carrier and collects toner adhering to the surface of the image carrier. Device.

Images