CN109074010B - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

The photosensitive layer (3) of the electrophotographic photoreceptor (1) is a single-layer photosensitive layer (3c) containing a charge generating agent and an electron transporting agent. The electron transporting agent contains a compound represented by the following general formula (1). The charge amount of calcium carbonate is +7.0 [ mu ] C/g or more after the photosensitive layer (3) is rubbed with calcium carbonate. In the general formula (1), R₁And R₂Independently of each other, represents: a halogen atom, a C1-C8 alkyl group having 1 or more halogen atoms, a C3-C10 cycloalkyl group having 1 or more halogen atoms, a C6-C14 aryl group having 1 or more halogen atoms, a C6-C14 aryl group having 1 or more halogen atoms and a C1-C6 alkyl group, or a C7-C20 aralkyl group having 1 or more halogen atoms. p and q are each independently an integer of 1 to 5. [ CHEM 1 ]

Description

Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Technical Field

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

Background

Electrophotographic photoreceptors are used in electrophotographic image forming apparatuses. The electrophotographic photoreceptor includes a photosensitive layer. Examples of the electrophotographic photoreceptor include a laminated electrophotographic photoreceptor and a single-layer electrophotographic photoreceptor. The laminated electrophotographic photoreceptor comprises: a charge generation layer having a charge generation function and a charge transport layer having a charge transport function are used as the photosensitive layer. The single-layer electrophotographic photoreceptor includes a single-layer photosensitive layer having charge generation and charge transport functions as a photosensitive layer.

In the electrophotographic photoreceptor described in patent document 1, a photosensitive layer is provided on a conductive substrate. The photosensitive layer contains at least a charge generating agent, a charge transporting agent, a surfactant and a binder resin. The hydrophobic portion of the surfactant is a structure derived from a fluorinated propene derivative.

[ patent document ]

Patent document 1: japanese patent application laid-open No. 2010-230912

Disclosure of Invention

The electrophotographic photoreceptor described in patent document 1 can suppress the generation of fog to some extent. However, the electrophotographic photoreceptor described in patent document 1 still has room for improvement in suppressing the occurrence of white spots in the formed image.

In view of the above-described problems, it is an object of the present invention to provide an electrophotographic photoreceptor capable of suppressing the occurrence of white spots in a formed image. Another object of the present invention is to provide a process cartridge and an image forming apparatus, which are capable of suppressing the occurrence of white spots in an image formed by including such an electrophotographic photoreceptor.

The electrophotographic photoreceptor of the present invention includes a conductive substrate and a photosensitive layer. The photosensitive layer is a monolayer type photosensitive layer containing a charge generating agent and an electron transporting agent. The electron transporting agent comprises a compound represented by the following general formula (1). After the photosensitive layer is rubbed with calcium carbonate, the charge amount of the calcium carbonate is more than +7.0 mu C/g.

[ CHEM 1 ]

In the general formula (1), R₁And R₂Independently of each other, represents: a halogen atom, a C1-C8 alkyl group having 1 or more halogen atoms, a C3-C10 cycloalkyl group having 1 or more halogen atoms, a C6-C14 aryl group having 1 or more halogen atoms, a C6-C14 aryl group having 1 or more halogen atoms and a C1-C6 alkyl group, or a C7-C20 aralkyl group having 1 or more halogen atoms. p and q are each independently an integer of 1 to 5.

The process cartridge of the present invention includes the electrophotographic photoreceptor.

An image forming apparatus of the present invention includes: the electrophotographic photoreceptor, the charging section, the exposure section, the developing section, and the transfer section. The charging section charges a surface of the electrophotographic photoreceptor. The exposure section exposes the charged surface of the electrophotographic photoreceptor to form an electrostatic latent image on the surface of the electrophotographic photoreceptor. The developing section develops the electrostatic latent image into a toner image. The transfer section transfers the toner image from the electrophotographic photoreceptor to a recording medium. When the transfer section transfers the toner image from the electrophotographic photoreceptor to the recording medium, the electrophotographic photoreceptor is brought into contact with the recording medium.

[ Effect of the invention ]

The electrophotographic photoreceptor of the present invention can suppress the occurrence of white spots in the formed image. Further, the process cartridge and the image forming apparatus of the present invention are provided with such an electrophotographic photoreceptor, and can suppress the occurrence of white spots in the formed image.

Drawings

Fig. 1A is a cross-sectional view of an exemplary electrophotographic photoreceptor according to an embodiment of the present invention.

Fig. 1B is a cross-sectional view of an exemplary electrophotographic photoreceptor according to an embodiment of the present invention.

Fig. 1C is a cross-sectional view of an exemplary electrophotographic photoreceptor according to an embodiment of the present invention.

Fig. 2 is a diagram for explaining a method of measuring the charge amount of calcium carbonate after the photosensitive layer and calcium carbonate are rubbed.

Fig. 3 is a schematic diagram of an example of an image forming apparatus including an electrophotographic photoreceptor according to an embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. The present invention can be implemented with appropriate modifications within the scope of the object of the present invention. Note that, although the description may be omitted as appropriate, the gist of the present invention is not limited thereto.

Hereinafter, the compound and its derivatives may be collectively referred to by adding "class" to the compound name. When a "class" is added after the compound name to indicate the polymer name, the repeating unit indicating the polymer is derived from the compound or a derivative thereof. The reactions represented by the reaction equations (R-1) and (R-2) may be referred to as reactions (R-1) and (R-2), respectively. The compounds represented by general formulae (1), (2), (4), (5), (6), (a), (B) and (C) may be referred to as compounds (1), (2), (4), (5), (6), (a), (B) and (C), respectively. The compounds represented by the chemical formulas (1-1) to (1-5), (2-1) to (2-3), (A-1), (B-1) to (B-5), (CGM-1), (CGM-2), (E-1) and (E-2) may be described as compounds (1-1) to (1-5), (2-1) to (2-3), (A-1), (B-1) to (B-5), (CGM-1), (CGM-2), (E-1) and (E-2), respectively.

Hereinafter, unless otherwise specified, the halogen atom, C1-C6 alkyl group, C1-C8 alkyl group, C3-C10 cycloalkyl group, C6-C14 aryl group, C7-C20 aralkyl group and C1-C6 alkoxy group each have the following meanings.

Halogen atoms (halogen groups) such as: a fluorine atom (fluoro group), a chlorine atom (chloro group), a bromine atom (bromo group), or an iodine atom (iodo group).

The C1-C6 alkyl group is linear or branched and unsubstituted. C1-C6 alkyl such as: methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl or hexyl.

The C1-C8 alkyl group is linear or branched and unsubstituted. C1-C8 alkyl such as: methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, or octyl.

C3-C10 cycloalkyl is unsubstituted. C3-C10 cycloalkyl for example: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, or cyclodecyl.

C6-C14 aryl is, for example: C6-C14 unsubstituted aromatic monocyclic hydrocarbon group, C6-C14 unsubstituted aromatic condensed bicyclic hydrocarbon group or C6-C14 unsubstituted aromatic condensed tricyclic hydrocarbon group. C6-C14 aryl, for example: phenyl, naphthyl, anthryl or phenanthryl.

C7-C20 aralkyl is unsubstituted. C7-C20 aralkyl is C1-C6 alkyl combined with C6-C14 aryl.

The C1-C6 alkoxy group is linear or branched and unsubstituted. C1-C6 alkoxy, for example: methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, pentoxy, isopentoxy, neopentoxy or hexoxy.

<1 > photoreceptor

The present embodiment relates to an electrophotographic photoreceptor (hereinafter, may be referred to as a photoreceptor). The photoreceptor according to the present embodiment includes a conductive substrate and a photosensitive layer.

The structure of the photoreceptor 1 will be described below with reference to fig. 1A to 1C. Fig. 1A to 1C are cross-sectional views of an example of the photoreceptor 1 according to the present embodiment.

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

As shown in fig. 1B, the photoreceptor 1 may include: a conductive substrate 2, a monolayer type photosensitive layer 3c, and an intermediate layer 4 (undercoat layer). The intermediate layer 4 is provided between the conductive substrate 2 and the monolayer photosensitive layer 3 c. As shown in fig. 1A, the photosensitive layer 3 may be directly provided on the conductive substrate 2, and as shown in fig. 1B, the photosensitive layer 3 may be indirectly provided on the conductive substrate 2 via the intermediate layer 4.

As shown in fig. 1C, the photoreceptor 1 may include: a conductive substrate 2, a monolayer type photosensitive layer 3c and a protective layer 5. The protective layer 5 is disposed on the monolayer photosensitive layer 3 c.

The thickness of the monolayer photosensitive layer 3c is not particularly limited as long as it sufficiently functions as a monolayer photosensitive layer. The thickness of the monolayer photosensitive layer 3c is preferably 5 μm to 100 μm, and more preferably 10 μm to 50 μm.

The monolayer type photosensitive layer 3c as the photosensitive layer 3 contains a charge generating agent and a compound (1) as an electron transporting agent. The monolayer photosensitive layer 3c may contain one or more of a hole transporting agent and a binder resin. The monolayer photosensitive layer 3c may contain additives as required. The charge generating agent, the electron transporting agent, and components (for example, a hole transporting agent, a binder resin, or an additive) added as needed are contained in the photosensitive layer 3 (hereinafter, may be referred to as a single-layer photosensitive layer 3c) of one layer.

In order to suppress the occurrence of white spots in the formed image, the single-layer photosensitive layer 3c containing the compound (1) is preferably disposed as the outermost layer of the photoreceptor 1.

The structure of the photoreceptor 1 is described above with reference to fig. 1A to 1C. Next, elements of the photoreceptor will be explained.

<1-1. photosensitive layer >

The photosensitive layer contains a compound (1) as an electron-transporting agent. The charge amount of calcium carbonate (hereinafter, sometimes referred to as the charge amount of calcium carbonate) after the photosensitive layer and calcium carbonate are rubbed together is + 7.0. mu.C/g or more. From this, the photoreceptor of the present embodiment is presumed to have the following advantages.

For ease of understanding, one reason for the generation of white dots in the formed image is explained. When a recording medium (e.g., paper) comes into contact with a photoreceptor in image formation, minute components (e.g., paper dust) of the recording medium may adhere to the surface of the photoreceptor. When the fine component adheres to the surface of the photoreceptor, light for exposing the photoreceptor in an exposure step for image formation may be blocked by the fine component. The surface potential of the portion of the photoreceptor where the light for exposure is blocked by the fine component is difficult to decrease. The toner is less likely to adhere to a portion where the reduction in surface potential is insufficient, and white spots are generated in the formed image.

Among them, when a recording medium (e.g., paper) is brought into contact with a photoreceptor in image formation, minute components (e.g., paper powder) of the recording medium are rubbed by the photoreceptor, and are sometimes charged to a negative polarity or a positive polarity lower than a desired value. In contrast, the photosensitive layer of the photoreceptor of the present embodiment contains the compound (1). Since the compound (1) contains a halogen atom, it has a large electronegativity. When the fine component is brought into contact with the photoreceptor of the present embodiment and rubbed by the photoreceptor containing the compound (1) having a large electronegativity, the fine component may be charged to a positive polarity equal to or higher than a desired value. When the surface of the photoreceptor is charged to a positive polarity in the charging step of image formation, the surface of the photoreceptor charged to the positive polarity electrically repels the fine component of the positive polarity charged to a desired value or more. The more positive the charge amount of the fine component is, the more the electric repulsion with the surface of the photoreceptor becomes. Thus, the fine component is less likely to adhere to the surface of the photoreceptor. Thereby enabling to suppress the generation of white spots in the formed image.

Further, when the compound (1) is contained as the electron transporting agent, a uniform photosensitive layer can be more easily formed than when a surfactant containing a halogen atom is added. The reason for this is that the surfactant has a property of being easily aligned on the surface of the photosensitive layer. It is considered that by forming a photosensitive layer in which the compound (1) is uniformly dispersed, the occurrence of white spots in the formed image can be suppressed even in long-term image formation in which the photosensitive layer is easily abraded.

As described above, the charge amount of calcium carbonate is + 7.0. mu.C/g or more. Calcium carbonate is an example of a fine component of a recording medium, that is, a main component of paper powder. When the charge amount of calcium carbonate is less than + 7.0. mu.C/g, the electrification property of the fine component is insufficient after the photoreceptor and the fine component of the recording medium are rubbed, and white spots are likely to occur on the formed image. The amount of charge of calcium carbonate is preferably + 7.0. mu.C/g to + 15.0. mu.C/g, more preferably + 8.0. mu.C/g to + 10.0. mu.C/g, and particularly preferably + 8.5. mu.C/g to + 10.0. mu.C/g.

Hereinafter, a method for measuring the charge amount of calcium carbonate after the photosensitive layer 3 and calcium carbonate are rubbed together will be described with reference to fig. 2. The charge amount of calcium carbonate was measured by performing the first step, the second step, the third step, and the fourth step. In the first step, 2 photosensitive layers 3 are prepared, one photosensitive layer 3 being a first photosensitive layer 30 and the other photosensitive layer 3 being a second photosensitive layer 32. The first photosensitive layer 30 and the second photosensitive layer 32 are circular with a diameter of 3 cm. In the second step, 0.007g of calcium carbonate was placed on the first photosensitive layer 30. Thereby, the calcium carbonate layer 24 made of calcium carbonate is formed. Next, a second photosensitive layer 32 is placed on the calcium carbonate layer 24. In the third step, the first photosensitive layer 30 is rotated at a rotation speed of 60rpm for 60 seconds in an environment where the temperature is 23 ℃ and the relative humidity is 50% RH while the second photosensitive layer 32 is fixed. Thus, calcium carbonate contained in the calcium carbonate layer 24 is rubbed between the first photosensitive layer 30 and the second photosensitive layer 32, and the calcium carbonate is charged. In the fourth step, the charged calcium carbonate is sucked by a charge amount measuring device. The total quantity of electricity Q and the mass M of the calcium carbonate sucked were measured by a charged quantity measuring device, and the charged quantity of the calcium carbonate was calculated according to the formula Q/M. The charged amount of calcium carbonate was measured by the method described in examples. Referring to fig. 2, a method for measuring the charge amount of calcium carbonate after the photosensitive layer 3 is rubbed with calcium carbonate is described.

The photosensitive layer contains the compound (1) as an electron transport agent, and can not only suppress the occurrence of white spots in an image to be formed, but also improve the electrical characteristics (hereinafter referred to as sensitivity characteristics) of the photoreceptor. Since the compound (1) has an ether bond, it has high solubility in a solvent used for forming the photosensitive layer, and thus tends to form a uniform photosensitive layer.

(Electron transport agent)

The electron transporting agent comprises the compound (1). The electron transport agent transports electrons in the monolayer photosensitive layer, for example, and imparts bipolar (bipolar) characteristics to the monolayer photosensitive layer. The single-layer photosensitive layer contains the compound (1) as an electron transporting agent, and when a sheet of paper comes into contact with the photoreceptor, a fine component (for example, paper dust) of the recording medium is rubbed by the photoreceptor containing the compound (1) having a large electronegativity, whereby the fine component can be charged to a desired positive value.

The compound (1) is represented by the following general formula (1). The compound (1) is a naphthoquinone derivative.

[ CHEM 2 ]

In the general formula (1), R₁And R₂Independently of each other, represents: a halogen atom; C1-C8 alkyl having 1 or more halogen atoms; C3-C10 cycloalkyl having 1 or more halogen atoms; a C6-C14 aryl group having 1 or more halogen atoms, a CC6-C14 aryl of C1-C6 alkyl; or C7-C20 aralkyl having 1 or more halogen atoms.

R of the general formula (1)₁And R₂The halogen atom represented is preferably a chlorine group or a fluorine group. R₁And R₂Each independently represents a halogen atom₁Halogen atom represented by (A) and (R)₂The halogen atoms represented may be the same or different. For example, it may be R₁And R₂Both represent a chlorine group. For example, R may be₁Represents a chloro group, R₂Represents a fluorine group.

R of the general formula (1)₁And R₂The C1-C8 alkyl group, C3-C10 cycloalkyl group, C6-C14 aryl group and C7-C20 aralkyl group represented by the above formulae are each substituted with 1 or more halogen atoms. Such a halogen atom is preferably a chlorine group or a fluorine group. The number of halogen atoms in each of the C1-C8 alkyl group, C3-C10 cycloalkyl group, C6-C14 aryl group and C7-C20 aralkyl group is preferably 1 to 5, more preferably 1 to 3. Furthermore, R of the formula (1)₁And R₂The C6-C14 aryl groups represented may have C1-C6 alkyl groups.

In the general formula (1), R₁And R₂The substitution position (binding position) of (c) is not particularly limited. R₁And R₂Can be respectively combined with any position of ortho-position, meta-position and para-position of the phenoxy.

In order to preferably suppress the generation of white spots in the formed image, R is preferable₁And R₂Each independently represents a halogen atom.

In the general formula (1), p and q are each independently an integer of 1 to 5. When p represents an integer of 2 to 5, a plurality of R₁May be the same or different. When q represents an integer of 2 to 5 inclusive, a plurality of R₂May be the same or different. In order to particularly suppress the occurrence of white spots in the formed image, it is preferable that p and q each independently represent an integer of 3 to 5. The larger the number of halogen atoms of the 2 phenoxy groups bonded to the naphthalene diimide, the more positive the charge amount of the fine component (for example, paper powder) of the recording medium is, when the fine component is rubbed by the photoreceptor.

In the general formula (1), the group represented by the following general formula (4) is preferably the same as the group represented by the following general formula (5). This is because the compound (1) can be efficiently produced by reducing the raw materials or reaction steps, and the compound (1) can suppress the occurrence of white spots in the formed image.

[ CHEM 3 ]

In the general formula (4), R₁And p and R in the formula (1)₁And p have the same meaning. R in the general formula (4)₁And preferred examples of p and R in the formula (1)₁And p are the same as preferred examples. Y is₁Represents a binding site to a naphthalene ring.

[ CHEM 4 ]

In the general formula (5), R₂And q and R in the general formula (1)₂And q have the same meaning. R in the general formula (5)₂And preferred examples of q and R in the formula (1)₂And q are the same as preferred examples. Y is₂Represents a binding site to a naphthalene ring.

Y of a group represented by the general formula (4)₁Y with a group represented by the following general formula (6)₁And (4) combining. Then, Y in the general formula (4)₁The oxygen atom bound to Y in the formula (6)₁The bonded carbon atoms form single bonds. Y of a group represented by the general formula (5)₂Y with a group represented by the general formula (6)₂And (4) combining. Then, Y in the general formula (5)₂The oxygen atom bound to Y in the formula (6)₂The bonded carbon atoms form single bonds. In the general formula (6), Y₁And Y₂Both represent binding sites.

[ CHEM 5 ]

When the group represented by the general formula (4) is the same as the group represented by the general formula (5), R in the general formula (1)₁、R₂P and q have the following relationships. In the general formula (1), R₁And R₂Represent the same groups. P and q are the same as each other and represent an integer of 1 to 5 inclusive. When p and q represent the same integer of 2 to 5, a plurality of R₁A plurality of R which may be the same or different₂May be the same or different. In this case, R bonded to one bonding position of one phenoxy group₁With the R bound to other phenoxy groups₁R in the corresponding substitution position₂The same is true. For ease of understanding, an example will be described. For example, R bound to the para position of a phenoxy group₁With R bound in the ortho position₁May be the same or different. In this case, R bonded to the para-position of another phenoxy group₂With R bound in the ortho position₂May be the same or different. In this case, R bonded to the para-position of one phenoxy group₁With R bound to para-positions of other phenoxy groups₂The same is true. R bound in ortho position to a phenoxy group₁With R bound to an ortho position to other phenoxy groups₂The same is true.

When the group represented by the general formula (4) is the same as the group represented by the general formula (5), the general formula (1) is represented by, for example, the following general formula (1'). R in the formula (1')₁And p is each independently R in the formula (1)₁And p have the same meaning.

[ CHEM 6 ]

Specific examples of the compound (1) include compounds (1-1) to (1-5). The compounds (1-1) to (1-5) are represented by the following chemical formulae (1-1) to (1-5), respectively.

[ CHEM 7 ]

[ Process for producing Compound (1) ]

The compound (1) can be produced, for example, by the following reaction (R-1) or a method similar thereto. In addition to these reactions, appropriate steps may be included as necessary. R in the reaction equation represented by reaction (R-1)₁、R₂P and q and R in the general formula (1)₁、R₂P and q have the same meaning. X represents a halogen atom.

[ CHEM 8 ]

In the reaction (R-1), 1 molar equivalent of the compound (a), 1 molar equivalent of the compound (B), and 1 molar equivalent of the compound (C) are reacted to obtain 1 molar equivalent of the compound (1). The reaction temperature of the reaction (R-1) is preferably 0 ℃ to 50 ℃ inclusive, more preferably 20 ℃ to 30 ℃ inclusive. The reaction time of the reaction (R-1) is preferably 0.5 to 5 hours, more preferably 1 to 2 hours.

The reaction (R-1) may be carried out in the presence of a base. Bases such as: potassium carbonate, sodium hydroxide or sodium hydride. These bases may be used alone or in combination of two or more. The amount of the base to be added is preferably 2 mol or more and 5 mol or less based on 1 mol of the compound (a).

The reaction (R-1) may be carried out in a solvent. Solvents such as: n, N-Dimethylformamide (DMF) or Tetrahydrofuran (THF).

If necessary, the compound (1) as the target compound can be isolated by purifying the reaction product obtained in the reaction (R-1). The purification method may be suitably a well-known method. For example, purification can be performed by crystallization or silica gel column chromatography. Solvents used for purification such as: chloroform, hexane, and mixed solvents of chloroform and hexane.

When the group represented by the general formula (4) in the compound (1) is the same as the group represented by the general formula (5) in the production of the compound (1), the compound (B) is the same compound as the compound (C). In this case, in the reaction (R-1), 1 molar equivalent of the compound (a) and 2 molar equivalents of the compound (B) may be reacted to obtain 1 molar equivalent of the compound (1). This makes it possible to omit the step of producing the compound (C) or to omit the use of the compound (C).

The monolayer type photosensitive layer may contain only the compound (1) as an electron transporting agent. The monolayer photosensitive layer may contain, in addition to the compound (1), an electron-transporting agent other than the compound (1) (hereinafter, may be referred to as another electron-transporting agent). Other electron transport agents are for example: quinone compounds, imide compounds, hydrazone 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 or dibromomaleic anhydride. Quinone compounds are exemplified by: a diphenoquinone compound, an azoquinone compound, an anthraquinone compound, a naphthoquinone compound, a nitroanthraquinone compound or a dinitroanthraquinone compound. The electron-transporting agent may be used alone or in combination of two or more. The content of the compound (1) is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass, relative to the total mass of the electron transporting agent.

The content of the compound (1) as the electron transport agent is 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 20 parts by mass or more per 100 parts by mass of the binder resin, the sensitivity characteristics of the photoreceptor are easily improved. When the content of the compound (1) is 40 parts by mass or less based on 100 parts by mass of the binder resin, the compound (1) is easily dissolved in a solvent for forming a photosensitive layer, and a uniform photosensitive layer is easily formed.

(Charge generating agent)

The monolayer type photosensitive layer as the photosensitive layer contains a charge generating agent. The charge generating agent is not particularly limited as long as it is a charge generating agent for a photoreceptor. Charge generators such as: phthalocyanine pigments, perylene pigments, disazo pigments, trisazo pigments, dithione-pyrrolopyrrole (dithioketo-pyrrozole) pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaric acid pigments, indigo pigments, azulene pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium-tellurium, selenium-arsenic, cadmium sulfide or amorphous silicon), pyran pigments, anthanthrone pigments, triphenylmethane pigments, threne pigments, toluidine pigments, pyrazoline pigments or quinacridone pigments. One kind of charge generating agent may be used alone, or two or more kinds may be used in combination.

Phthalocyanine pigments such as: metal-free phthalocyanine or metal phthalocyanine represented by the chemical formula (CGM-1). Metal phthalocyanines such as: oxytitanium phthalocyanine, hydroxygallium phthalocyanine or chlorogallium phthalocyanine represented by the chemical formula (CGM-2). The phthalocyanine pigment may be crystalline or amorphous. The crystal shape (for example, α -type, β -type, Y-type, V-type, or II-type) of the phthalocyanine pigment is not particularly limited, and phthalocyanine pigments having various crystal shapes can be used.

[ CHEM 9 ]

[ CHEM 10 ]

Examples of metal phthalocyanine-free crystals are: an X-type crystal of metal-free phthalocyanine (hereinafter, sometimes referred to as X-type metal-free phthalocyanine). Crystals of oxytitanium phthalocyanine such as: an α -type, β -type or Y-type crystal of oxytitanium phthalocyanine (hereinafter, sometimes referred to as "α -type, β -type or Y-type oxytitanium phthalocyanine"). Crystals of hydroxygallium phthalocyanine such as V-type crystals of hydroxygallium phthalocyanine. Crystals of chlorogallium phthalocyanine such as type II crystals of chlorogallium phthalocyanine.

For example, in a digital optical image forming apparatus (for example, a laser printer or a facsimile machine using a light source such as a semiconductor laser), a photoreceptor having sensitivity in a wavelength region of 700nm or more is preferably used. The charge generating agent is preferably a phthalocyanine-based pigment, more preferably a metal-free phthalocyanine or oxytitanium phthalocyanine, and still more preferably an X-type metal-free phthalocyanine or a Y-type oxytitanium phthalocyanine, from the viewpoint of having a high quantum yield in a wavelength region of 700nm or more. When the photosensitive layer contains the compound (1) as a hole transporting agent, the charge generating agent is more preferably Y-type oxytitanium phthalocyanine in order to improve sensitivity characteristics in particular.

For example, Y-type oxytitanium phthalocyanine has a main peak at 27.2 ° of the bragg angle (2 θ ± 0.2 °) in the CuK α characteristic X-ray diffraction spectrum. The main peak in the CuK α characteristic X-ray diffraction spectrum means a peak having a first or second large intensity in a range where the bragg angle (2 θ ± 0.2 °) is 3 ° or more and 40 ° or less.

The measurement method of CuK α characteristic X-ray diffraction spectrum is exemplified. A sample (oxytitanium phthalocyanine) was filled in a sample holder of an X-ray diffraction apparatus (for example, "RINT (Japanese registered trademark) 1100" manufactured by Rigaku Corporation), and X-ray wavelengths characterized by an X-ray tube Cu, a tube voltage of 40kV, a tube current of 30mA and CuK. alpha. were measured

Under the conditions of (1), an X-ray diffraction spectrum was measured. For example, the measurement range (2 θ) is 3 ° to 40 ° (start angle: 3 °; stop angle: 40 °), and the scanning speed is 10 °/min.

In the photoreceptor used in the image forming apparatus using a short-wavelength laser light source (for example, a laser light source having a wavelength of 350nm to 550 nm), an anthraquinone-based pigment is preferably used as the charge generating agent.

The content of the charge generating agent is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass, and particularly preferably 0.5 to 4.5 parts by mass, based on 100 parts by mass of the binder resin contained in the single-layer photosensitive layer.

(hole transport agent)

The monolayer type photosensitive layer contains, for example, a hole transporting agent. Hole-transporting agents such as: triphenylamine derivatives, diamine derivatives (e.g., N ' -tetraphenylbenzidine derivatives, N ' -tetraphenylphenylenediamine derivatives, N ' -tetraphenylnaphthalenediamine derivatives, N ' -tetraphenylphenylenediamine (N, N ' -tetraphenylphenylenediamine) derivatives or bis (aminophenylvinyl) benzene derivatives), oxadiazole compounds (e.g., 2, 5-bis (4-methylaminophenyl) -1, 3, 4-oxadiazole), styrenic compounds (e.g., 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 or triazole compounds. The hole-transporting agent may be used alone or in combination of two or more.

An example of the hole transporting agent is compound (2). The compound (2) is represented by the general formula (2).

[ CHEM 11 ]

In the general formula (2), R₂₁～R₂₆Independently of one another, represents a C1-C6 alkyl group or a C1-C6 alkoxy group. r, s, v and w are each independently an integer of 0 to 5. t and u are each independently an integer of 0 to 4.

In the general formula (2), R₂₁～R₂₆Each independently preferably represents a C1-C6 alkyl group, more preferably a methyl group. r, s, v and w are each independently preferably 0 or 1. t and u are each independently preferably 0 or 1.

Specific examples of the compound represented by the general formula (2) include compounds (2-1), (2-2) and (2-3). The compounds (2-1), (2-2) and (2-3) are represented by the following chemical formulae (2-1), (2-2) and (2-3), respectively.

[ CHEM 12 ]

[ CHEM 13 ]

[ CHEM 14 ]

The ionization potential of the hole-transporting agent is preferably 5.35eV or more and 5.55eV or less. When the ionization potential of the hole transport agent is 5.35eV or more, the hole transport agent hardly releases electrons. If the photosensitive layer contains a hole transporting agent that is difficult to release electrons, the hole transporting agent is difficult to release electrons with respect to paper dust from paper when the photoreceptor is in contact with a recording medium (e.g., paper), and the paper dust tends to have a positive polarity. By containing the compound (1) as an electron transport agent and the hole transport agent having a predetermined ionization potential in the photosensitive layer, the paper powder is more likely to have a positive polarity, and the adhesion of the paper powder to the photoreceptor can be particularly suppressed. On the other hand, when the ionization potential of the hole transporting agent is 5.55eV or less, the efficiency of transferring holes from the charge generating agent to the hole transporting agent can be improved.

The ionization potential of the hole transporting agent can be measured, for example, using an atmospheric ultraviolet photoelectron analyzer ("AC-1" manufactured by riken corporation). The method of measuring the ionization potential of the hole transporting agent is the method described in the examples or an alternative method thereof.

The hole-transporting agent is preferably the compound (2-1) in terms of having a predetermined ionization potential and particularly suppressing adhesion of paper powder to the photoreceptor.

The content of the hole transporting agent contained in the monolayer photosensitive layer is preferably 10 to 200 parts by mass, more preferably 10 to 100 parts by mass, with respect to 100 parts by mass of the binder resin.

(Binder resin)

The monolayer type photosensitive layer contains a binder resin. Examples of binding resins are: a thermoplastic resin, a thermosetting resin, or a photocurable resin. Thermoplastic resins such as: polycarbonate resins, polyarylate resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, acrylic polymers, styrene-acrylic acid copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomer resins, vinyl chloride-vinyl acetate copolymers, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyester resins, or polyether resins. Thermosetting resins such as: silicone resins, epoxy resins, phenolic resins, urea-formaldehyde resins or melamine resins. The photocurable resin is, for example: epoxy acrylates (acrylic acid adducts of epoxy compounds) or polyurethane-acrylates (acrylic acid adducts of polyurethane compounds). These binder resins may be used alone or in combination of two or more.

Among these resins, polycarbonate resins are preferred in view of obtaining a monolayer type photosensitive layer having a relatively excellent balance among processability, mechanical properties, optical properties and abrasion resistance. Polycarbonate resins such as: bisphenol ZC type polycarbonate resin, bisphenol C type polycarbonate resin, or bisphenol a type polycarbonate resin. Another example of the polycarbonate resin is a resin represented by the following general formula (3) (hereinafter, sometimes referred to as resin (3)).

[ CHEM 15 ]

In the general formula (3), R₃₁～R₃₆Each independently represents a hydrogen atom, a C1-C6 alkyl group or a C6-C14 aryl group. Wherein R is₃₅And R₃₆May be combined with each other to represent a C5-C7 cycloalkylene group. m represents a number of 0.00 to 0.90. n represents a number of 0.10 to 1.00. m + n is 1.00.

R in the general formula (3)₃₁～R₃₆The C1-C6 alkyl group represented is preferably a C1-C4 alkyl group, more preferably a methyl group.

R in the general formula (3)₃₁～R₃₆The C6-C14 aryl group represented is preferably a phenyl group.

In the general formula (3), R is preferred₃₁、R₃₂、R₃₃And R₃₄Both represent hydrogen atoms. R₃₅And R₃₆Preferably they are bonded to each other to form a C5-C7 cycloalkylene radical, more preferably they are bonded to each other to form a cyclohexylene radical.

In the general formula (3), R is preferably₃₁、R₃₂、R₃₃And R₃₄All represent a hydrogen atom, R₃₅And R₃₆Bonded to each other to represent cyclohexylene (cyclohexylidene). In the general formula (3), more preferably, R₃₁、R₃₂、R₃₃And R₃₄All represent a hydrogen atom, R₃₅And R₃₆In combination with each other, each represents cyclohexylene (cyclohexylene), m represents a number of 0.30 to 0.70 inclusive, n represents a number of 0.30 to 0.70 inclusive, and m + n is 1.00.

In the general formula (3), it is preferable that m is 0.00, n is 1.00, and R is₃₃And R₃₄All represent a hydrogen atom, R₃₅And R₃₆Bonded to each other to represent cyclohexylene (cyclohexylidene).

The resin (3) contains a repeating structural unit represented by the general formula (3a) (hereinafter, sometimes referred to as a repeating unit (3a)) and a repeating structural unit represented by the general formula (3b) (hereinafter, sometimes referred to as a repeating unit (3 b)). And R in the general formula (3a)₃₁And R₃₂Are respectively connected with R in the general formula (3)₃₁And R₃₂Have the same meaning. R in the general formula (3b)₃₃、R₃₄、R₃₅And R₃₆Are respectively connected with R in the general formula (3)₃₃、R₃₄、R₃₅And R₃₆Have the same meaning.

[ CHEM 16 ]

[ CHEM 17 ]

In the general formula (3), m represents: the ratio (mole fraction) of the amount (mole number) of the substance of the repeating unit (3a) to the amount (mole number) of the total substance of the repeating unit (3a) and the repeating unit (3b) in the resin (3). n represents: the ratio (mole fraction) of the amount (mole number) of the substance of the repeating unit (3b) to the amount (mole number) of the total substance of the repeating unit (3a) and the repeating unit (3b) in the resin (3). Preferably 0.00. ltoreq. m.ltoreq.0.70, more preferably 0.00. ltoreq. m.ltoreq.0.40. Also preferably, m is 0.00 or 0.30. ltoreq. m.ltoreq.0.70.

The resin (3) may be a random copolymer obtained by randomly copolymerizing the repeating unit (3a) and the repeating unit (3 b). Alternatively, the resin (3) may be an alternating copolymer in which the repeating unit (3a) and the repeating unit (3b) are alternately copolymerized. Alternatively, the resin (3) may be a periodic copolymer obtained by periodically copolymerizing 1 or more kinds of the repeating units (3a) and 1 or more kinds of the repeating units (3 b). Alternatively, the resin (3) may be a block copolymer obtained by copolymerizing a block comprising a plurality of repeating units (3a) and a block comprising a plurality of repeating units (3 b).

Specific examples of the resin (3) include polycarbonate resins represented by the following chemical formula (3-1) or (3-2). The polycarbonate resin represented by chemical formula (3-1) is a resin in which m in general formula (3) is 0.00 and n is 1.00. The polycarbonate resin represented by the chemical formula (3-1) is composed of only the repeating unit (3 b). The polycarbonate resin represented by chemical formula (3-2) is a resin in which m in general formula (3) is 0.40 and n is 0.60.

[ CHEM 18 ]

[ CHEM 19 ]

The viscosity average molecular weight of the binder resin is preferably 20,000 or more, more preferably 20,000 or more and 52,500 or less. When the viscosity average molecular weight of the binder resin is 20,000 or more, the abrasion resistance of the photoreceptor is easily improved. When the viscosity average molecular weight of the binder resin is 52,500 or less, the binder resin is easily dissolved in a solvent at the time of forming the photosensitive layer, and the viscosity of the coating liquid for the monolayer type photosensitive layer does not become too high. Thereby easily forming a monolayer type photosensitive layer.

The method for producing the binder resin is not particularly limited as long as the resin (3) can be produced. An example of the method for producing the resin (3) is a method of polycondensing a diol compound constituting a repeating unit of a polycarbonate resin with phosgene (so-called phosgene method). More specifically, for example, a method of polycondensing a diol compound represented by the general formula (3c), a diol compound represented by the general formula (3d), and phosgene. Further, R in the general formula (3c)₃₁And R₃₂Are respectively connected with R in the general formula (3)₃₁And R₃₂Have the same meaning. R in the general formula (3d)₃₃、R₃₄、R₃₅And R₃₆Are respectively connected with R in the general formula (3)₃₃、R₃₄、R₃₅And R₃₆Have the same meaning. Another example of the method for producing the resin (3) is a method of subjecting a diol compound and diphenyl carbonate to an ester exchange reaction.

[ CHEM 20 ]

[ CHEM 21 ]

(additives)

The monolayer type photosensitive layer may contain additives as required. Additives such as: degradation inhibitors (e.g., antioxidants, radical scavengers, singlet quenchers, or ultraviolet absorbers), softening agents, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, acceptors, donors, surfactants, plasticizers, sensitizers, or leveling agents. Antioxidants such as: hindered phenols (e.g., di-t-butyl-p-cresol), hindered amines, p-phenylenediamine, arylalkanes, hydroquinones, spirochromans (spirochromans), spiroindanones (spiroindanones), or derivatives thereof; organic sulfur compounds or organic phosphorus compounds.

<1-2. conductive substrate >

The conductive substrate is not particularly limited as long as it can be used as a conductive substrate of a photoreceptor. The conductive substrate may be formed of a conductive material at least on the surface portion. The conductive substrate may be, for example, a conductive substrate formed of a conductive material. The conductive substrate may be a conductive substrate coated with a conductive material, for example. Conductive materials such as: aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, or 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 conductive materials, aluminum or an aluminum alloy is preferable in terms 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. The conductive substrate may have a sheet-like or drum-like shape, for example. The thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

<1-3. intermediate layer >

The intermediate layer (undercoat layer) contains, for example, inorganic particles and a resin (resin for intermediate layer) for the intermediate layer. It can be considered that: since the intermediate layer is present, the current generated when the photoreceptor is exposed can be smoothly flowed while maintaining an insulating state to such an extent that the occurrence of electric leakage can be suppressed, thereby suppressing an increase in resistance.

Inorganic particles such as: particles of a metal (e.g., aluminum, iron, or copper), a metal oxide (e.g., titanium dioxide, aluminum oxide, zirconium oxide, tin oxide, or zinc oxide); or particles of a non-metal oxide (e.g., silica). These inorganic particles may be used alone or in combination of two or more.

The resin for the intermediate layer is not particularly limited as long as it can be used as a resin for forming the intermediate layer. The intermediate layer may also contain additives. Examples of the additive of the intermediate layer are the same as those of the photosensitive layer.

<1-4 > method for producing photoreceptor

The photoreceptor is manufactured, for example, as follows. The photoreceptor is produced by applying a coating liquid for a single-layer photosensitive layer on a conductive substrate and drying the coating liquid. The coating liquid for a monolayer type photosensitive layer is produced by dissolving or dispersing a charge generating agent, an electron transporting agent, and components added as needed (for example, a hole transporting agent, a binder resin, and an additive) in a solvent.

The solvent contained in the coating liquid for the monolayer photosensitive layer is not particularly limited as long as it can dissolve or disperse each component contained in the coating liquid. Solvents such as: alcohols (e.g., methanol, ethanol, isopropanol, or butanol), aliphatic hydrocarbons (e.g., n-hexane, octane, or cyclohexane), aromatic hydrocarbons (e.g., 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 (e.g., ethyl acetate or methyl acetate), dimethyl formaldehyde, dimethyl formamide, or dimethyl sulfoxide. These solvents may be used alone or in combination of two or more. In order to improve the workability in the production of the photoreceptor, a non-halogenated solvent (a solvent other than halogenated hydrocarbon) is preferably used as the solvent.

The components are mixed and dispersed in a solvent to prepare a coating liquid. For the mixing or dispersing, for example, a bead mill, roll mill, ball mill, attritor, paint shaker or ultrasonic disperser can be used.

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

The method of coating with the coating liquid for the monolayer photosensitive layer is not particularly limited as long as the coating liquid can be uniformly applied to the conductive substrate. Examples of the coating method include: dip coating, spray coating, spin coating or bar coating.

The method for drying the coating liquid for the monolayer photosensitive layer is not particularly limited as long as the solvent in the coating liquid can be evaporated. For example, there is a method of performing heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer. The heat treatment conditions are, for example, a temperature of 40 ℃ to 150 ℃ and a time of 3 minutes to 120 minutes.

The method for manufacturing the photoreceptor may further include one or both of the step of forming the intermediate layer and the step of forming the protective layer, as necessary. The step of forming the intermediate layer and the step of forming the protective layer can be realized by appropriately selecting a known method.

<2. image Forming apparatus >

Next, an image forming apparatus 100 including the photoreceptor 1 according to the present embodiment will be described with reference to fig. 3. Fig. 3 shows an example of the configuration of the image forming apparatus 100.

The image forming apparatus 100 is not particularly limited as long as it is an electrophotographic image forming apparatus. For example, the image forming apparatus 100 may be a monochrome image forming apparatus or a color image forming apparatus. When the image forming apparatus 100 is a color image forming apparatus, the image forming apparatus 100 employs, for example, a tandem system. The tandem image forming apparatus 100 will be described below by way of example.

The image forming apparatus 100 includes: image forming units 40a, 40b, 40c, and 40d, transfer belt 50, and fixing unit 52. Hereinafter, the image forming units 40a, 40b, 40c, and 40d are all described as the image forming unit 40 in the case where distinction is not necessary.

The image forming unit 40 includes: the photoreceptor 1, a charging section 42, an exposure section 44, a developing section 46, and a transfer section 48. The photoreceptor 1 is disposed at the center of the image forming unit 40. The photoreceptor 1 is provided to be rotatable in the arrow direction (counterclockwise). Around the photoreceptor 1, a charging section 42, an exposure section 44, a development section 46, and a transfer section 48 are provided in this order from the upstream side in the rotation direction of the photoreceptor 1 with reference to the charging section 42. The image forming unit 40 may further include a cleaning unit (not shown), a discharging unit (not shown), or both of them.

The charging section 42 charges the surface of the photoreceptor 1. The charging unit 42 is of a non-contact type or a contact type. The non-contact type charging unit 42 is, for example, a corotron charger or a grid corotron charger. The contact type charging unit 42 is, for example, a charging roller or a charging brush.

The image forming apparatus 100 may include a charging roller as the charging unit 42. When the surface of the photoreceptor 1 is charged, the charging roller contacts the photoreceptor 1. In the case where a fine component (e.g., paper dust) of the recording medium P (e.g., paper) adheres to the surface of the photoreceptor 1, the fine component is pressed against the surface of the photoreceptor 1 by contact with the charging roller. Thus, the fine component is easily adhered to the surface of the photoreceptor 1. However, the image forming apparatus 100 includes the photoreceptor 1, and the photoreceptor 1 can suppress the occurrence of white spots due to the adhesion of fine components. Therefore, even when the image forming apparatus 100 includes the charging roller as the charging section 42, the fine component is less likely to adhere to the surface of the photoreceptor 1, and the occurrence of white spots in the formed image can be suppressed.

The charging section 42 preferably charges the surface of the photoreceptor 1 with a positive polarity. When the photoreceptor 1 of the present embodiment is in contact with the recording medium P and rubbed, the recording medium P may be charged to a positive polarity. When the surface of the photoreceptor 1 is charged to a positive polarity by the charging section 42, the surface of the photoreceptor 1 electrically repels the recording medium P charged to a positive polarity by friction. As a result, fine components (e.g., paper dust) of the recording medium P are less likely to adhere to the surface of the photoreceptor 1, and the occurrence of white spots in the formed image can be suppressed.

The exposure section 44 exposes the surface of the charged photoreceptor 1. Thereby, an electrostatic latent image is formed on the surface of the photoreceptor 1. An electrostatic latent image is formed based on image data input to the image forming apparatus 100.

The developing section 46 supplies toner to the electrostatic latent image formed on the photoreceptor 1. Thereby, the electrostatic latent image is developed into a toner image. The photoreceptor 1 corresponds to an image bearing member for bearing a toner image. The toner may be used as a one-component developer. Alternatively, the toner may be mixed with a desired carrier and used in a two-component developer. In the case where the toner is used as the one-component developer, the developing section 46 supplies the toner as the one-component developer to the electrostatic latent image formed on the photoreceptor 1. In the case where the toner is used in a two-component developer, the developing section 46 supplies the toner contained in the two-component developer and the toner in the carrier to the electrostatic latent image formed on the photoreceptor 1.

The developing section 46 develops the electrostatic latent image into a toner image while contacting the photoreceptor 1. That is, the image forming apparatus 100 may employ a so-called contact development system. When a fine component (e.g., paper dust) of the recording medium P adheres to the surface of the photoreceptor 1, the fine component is pressed against the surface of the photoreceptor 1 by contact with the developing unit 46. Thus, the fine component is easily adhered to the surface of the photoreceptor 1. However, the image forming apparatus 100 includes the photoreceptor 1, and the photoreceptor 1 can suppress the occurrence of white spots due to the adhesion of fine components. Therefore, even if the image forming apparatus 100 employs the contact development method, the fine components are less likely to adhere to the surface of the photoreceptor 1, and the occurrence of white spots in the formed image can be suppressed.

The developing unit 46 can clean the surface of the photoreceptor 1. That is, the image forming apparatus 100 may adopt a so-called cleanerless system. The developing unit 46 can remove components remaining on the surface of the photoreceptor 1 (hereinafter, sometimes referred to as "residual components"). An example of a residual component is a toner component, more specifically, a toner or a free external additive. Other examples of the residual component are a non-toner component, more specifically, a minute component (for example, paper dust) of the recording medium P. In the image forming apparatus 100 employing the cleanerless system, residual components on the surface of the photoreceptor 1 cannot be scraped off by a cleaning portion (e.g., a cleaning blade). Therefore, in the image forming apparatus 100 adopting the cleanerless system, residual components are generally likely to remain on the surface of the photoreceptor 1. However, the photoreceptor 1 of the present embodiment can suppress the occurrence of white spots due to the adhesion of fine components. Therefore, even if the cleanerless system is adopted in the image forming apparatus 100 including the photoreceptor 1, residual components, particularly fine components (for example, paper dust) of the recording medium P, are less likely to remain on the surface of the photoreceptor 1. Thus, the image forming apparatus 100 can suppress the occurrence of white spots in the formed image.

The developing unit 46 preferably satisfies the following conditions (a) and (b) in order to efficiently clean the surface of the photoreceptor 1.

Condition (a): in the contact development method, a difference in rotational speed (rotational speed) is provided between the photoreceptor 1 and the developing unit 46.

Condition (b): the surface potential of the photoreceptor 1 and the potential of the developing bias satisfy the following equations (b-1) and (b-2).

0(V) < potential of developing bias (V) < surface potential of unexposed region (V) … … (b-1) of photoreceptor 1

Potential of developing bias (V) > surface potential of exposed region of photoreceptor 1 (V) > 0(V) … … (b-2)

When the contact development method is employed and a difference in rotation speed is provided between the photoreceptor 1 and the developing section 46 as shown in condition (a), the surface of the photoreceptor 1 contacts the developing section 46, and the adhering components on the surface of the photoreceptor 1 are removed by friction with the developing section 46. The rotation speed of the developing unit 46 is preferably higher than the rotation speed of the photoreceptor 1.

In the condition (b), it is assumed that the development method is a reversal development method. In order to improve the sensitivity characteristics of the photoreceptor 1, which is a single-layer type photoreceptor, it is preferable that the charging polarity of the toner, the surface potential of the unexposed area of the photoreceptor 1, the surface potential of the exposed area of the photoreceptor 1, and the potential of the developing bias are all positive. After the transfer section 48 transfers the toner image from the photoreceptor 1 to the recording medium P, and before the charging section 42 charges the surface of the photoreceptor 1 of the next turn, the surface potential of the unexposed area and the surface potential of the exposed area of the photoreceptor 1 are measured.

When the formula (b-1) of the condition (b) is satisfied, the electrostatic repulsive force acting between the toner remaining on the photoreceptor 1 (hereinafter, sometimes referred to as the residual toner) and the unexposed area of the photoreceptor 1 is larger than the electrostatic repulsive force acting between the residual toner and the developing portion 46. Therefore, the residual toner in the unexposed area of the photoreceptor 1 moves from the surface of the photoreceptor 1 to the developing section 46 and is recovered.

When the formula (b-2) of the condition (b) is satisfied, the electrostatic repulsive force acting between the residual toner and the exposure region of the photoreceptor 1 is smaller than the electrostatic repulsive force acting between the residual toner and the developing portion 46. Therefore, the residual toner in the exposed area of the photoreceptor 1 remains on the surface of the photoreceptor 1. The toner held in the exposed area of the photoreceptor 1 is directly used for image formation.

The transfer belt 50 conveys the recording medium P between the photoreceptor 1 and the transfer section 48. The transfer belt 50 is an endless belt. The transfer belt 50 is provided to be rotatable in an arrow direction (clockwise direction).

The transfer section 48 transfers the toner image developed by the developing section 46 from the photoreceptor 1 to the recording medium P. When the toner image is transferred from the photoreceptor 1 to the recording medium P, the photoreceptor 1 contacts the recording medium P. That is, the image forming apparatus 100 employs a so-called direct transfer system. The transfer section 48 is, for example, a transfer roller.

Toner images of several colors (for example, four colors of black, cyan, magenta, and yellow) are sequentially superimposed on the recording medium P on the transfer belt 50 by the image forming units 40a to 40d, respectively. When image forming apparatus 100 is a monochrome image forming apparatus, image forming apparatus 100 includes image forming unit 40a, but does not include image forming units 40b to 40 d.

The fixing section 52 heats and/or pressurizes the unfixed toner image transferred to the recording medium P by the transfer section 48. The fixing unit 52 is, for example, a heating roller and/or a pressure roller. The toner image is heated and/or pressurized, whereby the toner image is fixed to the recording medium P. As a result, an image is formed on the recording medium P.

<3. Process Cartridge >

Next, with continued reference to fig. 3, a process cartridge including the photoreceptor 1 according to the present embodiment will be described. The process cartridges correspond to the respective image forming units 40a to 40 d. The processing box is provided with a photosensitive body 1. The process cartridge may further include at least 1 of a charging section 42, an exposure section 44, a developing section 46, and a transfer section 48 in the photoreceptor 1. The process cartridge may further include a cleaning device (not shown), a power remover (not shown), or both. The process cartridge is designed to be detachable from the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and when the sensitivity characteristics and the like of the photoreceptor 1 deteriorate, the process cartridge including the photoreceptor 1 can be replaced easily and quickly.

[ examples ] A method for producing a compound

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the scope of the examples.

<1. materials for photoreceptors >

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

<1-1. Charge generating agent >

A compound (CGM-1X) is prepared as a charge generating agent. The compound (CGM-1X) is a metal-free phthalocyanine represented by the chemical formula (CGM-1) described in the embodiments. Further, the crystal structure of the compound (CGM-1X) is X type.

<1-2. hole transporting agent >

The compounds (2-1), (2-2) and (2-3) described in the embodiment were prepared as hole transporters. Next, the ionization potentials of the compounds (2-1), (2-2) and (2-3) were measured by the following methods. As a result, the ionization potential of the compound (2-1) was 5.51 eV. The ionization potential of the compound (2-2) was 5.64 eV. The ionization potential of the compound (2-3) was 5.58 eV.

The ionization potential of the hole transporting agent was measured using an atmospheric ultraviolet photoelectron analyzer ("AC-1" manufactured by riken corporation). The measurement conditions are as follows.

(conditions for measuring ionization potential)

Measurement start energy: 4.50eV

End of measurement energy: 6.20eV

Energy interval (gradient): 0.10eV

Counting time: 10

<1-3. Binder resin >

Resins (3-1a) and (3-2a) were prepared as binder resins.

The resin (3-1a) is a polycarbonate resin represented by the chemical formula (3-1) described in the embodiments. The viscosity-average molecular weight of the resin (3-1a) was 30000.

The resin (3-2a) is a polycarbonate resin represented by the chemical formula (3-2) described in the embodiments. The viscosity-average molecular weight of the resin (3-2a) was 30000.

<1-4. Electron transporting agent >

The compounds (1-1) to (1-5) described in the embodiment were prepared as an electron-transporting agent. The compounds (1-1) to (1-5) were produced by the following methods, respectively.

(production of Compound (1-1))

Compound (1-1) is produced according to the following reaction (R-2).

[ CHEM 22 ]

In the reaction (R-2), the compound (A-1) is reacted with the compound (B-1) to obtain the compound (1-1). Hereinafter, the compound (A-1) may be referred to as a first raw material of the reaction (R-2), and the compound (B-1) may be referred to as a second raw material of the reaction (R-2). 2.56g (0.02 mol) of Compound (B-1), 50mL of N, N-Dimethylformamide (DMF), and 2.76g (0.02 mol) of potassium carbonate were placed in a flask. The contents of the flask were stirred at 45 ℃. A solution of 2.27g (0.01 mol) of compound (A-1, 2, 3-dichloro-1, 4-naphthoquinone) in DMF (30mL) was added to the flask. The contents of the flask were stirred at room temperature (25 ℃) for 2 hours. Next, ion-exchanged water was added to the flask. The contents of the flask were then suction filtered to give the crude product. The crude product obtained was purified by silica gel column chromatography using a mixed solvent of chloroform and hexane (volume ratio 1: 1) as a developing solvent. Compound (1-1) is obtained. The yield of the compound (1-1) was 2.87g, and the yield of the compound (1-1) from the compound (A-1) was 70 mol%.

(production of Compounds (1-2) to (1-5))

Compounds (1-2) to (1-5) were produced by the same method as that for the production of the compound (1-1) except for the following modifications. The second raw material for reaction (R-2) was changed from compound (B-1) in the production of compound (1-1) to the second raw material shown in Table 1. The mass of the second raw material added in reaction (R-2) was changed from 2.56g in the production of compound (1-1) to the mass of the second raw material added shown in Table 1. The number of moles of each raw material used for the production of the compounds (1-2) to (1-5) is the same as the number of moles of the corresponding raw material used for the production of the compound (1-1). As a result, instead of the compound (1-1), the compounds (1-2) to (1-5) were obtained as the reaction product of the reaction (R-2). The yields of the compounds (1-2) to (1-5) obtained in the reaction (R-2) are shown in Table 1. The yields of the first starting material from the reaction (R-2) of the compounds (1-2) to (1-5) are shown in Table 1.

[ TABLE 1 ]

The compounds (B-1) to (B-5) in Table 1 are represented by the following chemical formulae (B-1) to (B-5), respectively.

[ CHEM 23 ]

Then, by¹H-NMR (proton Nuclear magnetic resonance Spectroscopy) of the produced Compounds (1-1) to (1-5)¹H-NMR spectrum was measured. The magnetic field strength was set at 300 MHz. Deuterated chloroform (CDCl) was used₃) As a solvent. Tetramethylsilane (TMS) was used as an internal standard.

As representative examples of the compounds (1-1) to (1-5), those of the compound (1-1) to be measured¹H-NMThe chemical shift values of the R spectrum are shown below. According to the measured¹The chemical shift value of the H-NMR spectrum confirmed that the compound (1-1) was obtained. The other compounds (1-2) to (1-5) were similarly measured¹The chemical shift values in the H-NMR spectrum confirmed that the compounds (1-2) to (1-5) were obtained, respectively.

Compound (1-1):¹H-NMR(300MHz，CDCl₃)δ＝8.11(dd，2H)、7.79(dd，2H)、7.18-7.24(m，4H)、6.81-6.86(m，4H)。

compounds (E-1) and (E-2) are also prepared as electron transporters. The compounds (E-1) and (E-2) are represented by the following chemical formulae (E-1) and (E-2), respectively.

[ CHEM 24 ]

[ CHEM 25 ]

<2 > production of photoreceptor

The photoreceptors (P-1) to (P-22) were produced using a material for forming a single-layer photosensitive layer.

<2-1 > production of photoreceptor (P-1)

2 parts by mass of a compound (CGM-1X) as a charge generating agent, 50 parts by mass of a compound (2-1) as a hole transporting agent, 30 parts by mass of a compound (1-1) as an electron transporting agent, 100 parts by mass of a resin (3-1a) as a binder resin, and 600 parts by mass of tetrahydrofuran as a solvent were charged into a container. The contents of the vessel were mixed for 12 hours using a ball mill to disperse the material in the solvent. Thus, a coating liquid for a monolayer photosensitive layer was obtained. The coating liquid for the monolayer photosensitive layer was applied on an aluminum drum support (diameter 30mm, total length 238.5mm) as a conductive substrate by a dip coating method. The applied coating liquid for the monolayer photosensitive layer was dried with hot air at 120 ℃ for 80 minutes. Thus, a monolayer type photosensitive layer (film thickness: 30 μm) was formed on the conductive substrate. Thus, photoreceptor (P-1) was obtained.

<2-2 > production of photoreceptors (P-2) to (P-22) >

The photoreceptors (P-2) to (P-22) were manufactured by the same method as that for the photoreceptor (P-1) except for the following modifications. The compound (1-1) as an electron-transporting agent used in the production of the photoreceptor (P-1) was changed to an electron-transporting agent of the kind shown in Table 2. The content (addition amount) of the electron transport agent relative to 100 parts by mass of the binder resin was changed from 30 parts by mass in the production of the photoreceptor (P-1) to the content (addition amount) shown in Table 2. The compound (2-1) used as the hole-transporting agent in the production of the photoreceptor (P-1) was changed to the type shown in Table 2. The resin (3-1a) used as a binder resin for producing the photoreceptor (P-1) was changed to a binder resin of the type shown in Table 2.

<3. evaluation of sensitivity characteristics >

The manufactured photoreceptors (P-1) to (P-22) were evaluated for sensitivity characteristics. The sensitivity characteristics were evaluated at 23 ℃ and 50% RH relative humidity. First, the surface of the photoreceptor was charged to +600V using a drum sensitivity tester (manufactured by GENTEC corporation). Then, monochromatic light (wavelength of 780nm, half-width of 20nm, light energy of 1.5. mu.J/cm) was extracted from the white light of the halogen lamp using a band-pass filter²). The extracted monochromatic light is irradiated to the surface of the photoreceptor. The surface potential of the photoreceptor after 0.5 second from the end of the irradiation was measured. The measured surface potential was taken as a sensitivity potential (V)_LThe unit: + V, hereinafter referred to as post-exposure potential). Measured post-exposure potential (V) of the photoreceptor_L) As shown in table 2. In addition, post-exposure potential (V)_L) The smaller the absolute value of (a) is, the more excellent the sensitivity characteristics of the photoreceptor are.

<4. measurement of the amount of electrification of calcium carbonate >

The charge amount of calcium carbonate was measured for each of the manufactured photoreceptors (P-1) to (P-22).

Hereinafter, referring again to fig. 2, a method of measuring the charge amount of calcium carbonate after the photosensitive layer 3 (corresponding to the monolayer type photosensitive layer 3c) and calcium carbonate are rubbed together will be described. The charge amount of calcium carbonate was measured by the first step, the second step, the third step, and the fourth step described below. The jig 10 was used to measure the charge amount of calcium carbonate.

The jig 10 includes: a first base 12, a shaft 14, a rotary drive unit 16 (e.g., a motor), and a second base 18. The rotation driving unit 16 rotates the rotation shaft 14. The shaft 14 rotates about a rotation axis S of the shaft 14. The first base 12 is integral with the rotary shaft 14 and rotates about the rotary shaft S. The second base 18 is fixed without rotating.

(first step)

In the first step, 2 photosensitive layers 3 are prepared. Hereinafter, one of the 2 photosensitive layers 3 is referred to as a first photosensitive layer 30, and the other is referred to as a second photosensitive layer 32. First, a first film 20 is prepared, and the first film 20 includes a first photosensitive layer 30 having a film thickness L1 of 30 μm. Then, a second film 22 was prepared, and the second film 22 was provided with the second photosensitive layer 32 having a film thickness L2 of 30 μm. Specifically, an overhead projector (OHP) film is used as the first film 20 and the second film 22. The first film 20 and the second film 22 each had a circular shape with a diameter of 3 cm. The first film 20 and the second film 22 are coated with a coating liquid for a single-layer photosensitive layer used in the production of the photoreceptor (P-1). The applied coating liquid for the monolayer photosensitive layer was dried with hot air at 120 ℃ for 80 minutes. Thereby, the first film 20 having the first photosensitive layer 30 and the second film 22 having the second photosensitive layer 32 are obtained.

(second step)

In the second step, 0.007g of calcium carbonate was placed on the first photosensitive layer 30. Thereby, the calcium carbonate layer 24 made of calcium carbonate is formed on the first photosensitive layer 30. Then, the second photosensitive layer 32 is placed on the calcium carbonate layer 24. The specific process of the second step is as follows.

First, first film 20 is fixed to first base 12 with a double-sided tape. 0.007g of calcium carbonate was supported on the first photosensitive layer 30 of the first film 20. Thereby, the calcium carbonate layer 24 made of calcium carbonate is formed on the first photosensitive layer 30. The second film 22 is secured to the second submount 18 with double sided tape so that the calcium carbonate layer 24 is in contact with the second photosensitive layer 32. Thus, the first base 12, the first film 20, the first photosensitive layer 30, the calcium carbonate layer 24, the second photosensitive layer 32, the second film 22, and the second base 18 are arranged in this order from the bottom up, and the centers of the first base 12, the first film 20, the first photosensitive layer 30, the second photosensitive layer 32, the second film 22, and the second base 18 pass through the rotation axis S.

(third step)

In the third step, the first photosensitive layer 30 is rotated at a rotation speed of 60rpm for 60 seconds in an environment where the temperature is 23 ℃ and the relative humidity is 50% RH while the second photosensitive layer 32 is fixed. Specifically, the rotation driving unit 16 is driven to rotate the shaft 14, the first base 12, the first film 20, and the first photosensitive layer 30 about the rotation axis S at a rotation speed of 60rpm for 60 seconds. Thereby, calcium carbonate contained in the calcium carbonate layer 24 is rubbed between the first photosensitive layer 30 and the second photosensitive layer 32, and the calcium carbonate is charged.

(fourth step)

In the fourth step, the calcium carbonate charged in the third step is taken out of the jig 10 and sucked by a charge measuring device (suction type small-sized charge measuring device, "MODEL 212 HS" manufactured by TREK corporation). The total quantity of electricity Q (unit: + μ C) and the mass M (unit: g) of the calcium carbonate sucked were measured with a charged quantity measuring apparatus. The charge amount of calcium carbonate (triboelectric charge amount, unit: + μ C/g) was calculated according to the formula "charge amount ═ Q/M".

The charge amount of calcium carbonate in each of the photoreceptors (P-2) to (P-22) was evaluated by the same method as that for measuring the charge amount of calcium carbonate in the photoreceptor (P-1), except for changing the following points. In the first step, the coating liquids for the single-layer photosensitive layers used in the production of the photoreceptors (P-2) to (P-22) are used instead of the coating liquids for the single-layer photosensitive layers used in the production of the photoreceptor (P-1).

The charge amounts of calcium carbonate calculated for the photoreceptors (P-1) to (P-22) are shown in Table 2. The larger the positive charge amount of calcium carbonate, the more easily the calcium carbonate is positively charged to the first photosensitive layer 30 and the second photosensitive layer 32.

<5. evaluation of image characteristics >

The manufactured photoreceptors (P-1) to (P-22) were evaluated for image characteristics. The evaluation of the image characteristics was carried out at a temperature of 32.5 ℃ and a relative humidity of 85% RH. An image forming apparatus (a changer of "monochrome printer FS-1300D" manufactured by Kyowa office information systems Co., Ltd.) was used as the evaluation equipment. Specifically, the non-contact development mode is modified to the contact development mode. The scraper cleaning mode is changed into a cleaner-free mode. The grid corotron charger is modified into a charging roller. The charging polarity of the charging roller is set to positive polarity. The image forming apparatus employs a direct transfer system. The recording medium used was "Jing porcelain office information System Brand paper VM-A4" (size A4) sold by Jing porcelain office information System, Inc. Evaluation of evaluation equipment a one-component developer (test production sample) was used.

With the evaluation apparatus, image I (image with print coverage of 1%) was continuously printed on 20000 sheets of recording medium under the condition that the rotation speed of the photoreceptor was 168 mm/sec. Next, image II (black solid image of a4 size) was printed on 1 recording medium. The recording medium on which the image II was formed was observed with the naked eye, and the number of white dots appearing in the image II was counted. The more minute components (e.g., paper dust) of the recording medium adhere to the photoreceptor, the more the number of white dots in the image II tends to increase. The number of white dots appearing in image II is shown in table 2.

In Table 2, HTM, ETM and V_LRespectively represent a hole transporting agent, an electron transporting agent, and a post-exposure potential. The ETM content (addition amount) represents the content (addition amount) of the electron transport agent with respect to 100 parts by mass of the binder resin.

[ TABLE 2 ]

The photosensitive layers of the photoreceptors (P-1) to (P-14) and (P-19) to (P-22) are single-layer photosensitive layers containing a charge generating agent, a binder resin and a compound (1). Specifically, the compound (1) contains any one of the compounds (1-1) to (1-5) contained in the general formula (1). After the photosensitive layer is rubbed with calcium carbonate, the charge amount of the calcium carbonate is more than +7.0 mu C/g. Therefore, as can be seen from table 2, in these photoreceptors, the number of white spots in the formed image is small, and the occurrence of white spots is suppressed. Further, in these photoreceptors, the occurrence of white spots in the formed image can be suppressed without impairing the sensitivity characteristics of the photoreceptor.

In the photoreceptors (P-1) to (P-14) and (P-19) to (P-22), the photosensitive layers of the photoreceptors (P-1) to (P-10) and (P-19) to (P-22) contain the compound (2-1) as a hole transporting agent. Therefore, as can be seen from Table 2, the photoreceptors (P-1) to (P-10) and (P-19) to (P-22) have smaller absolute values of post-exposure potential and particularly excellent sensitivity characteristics as compared with the photoreceptors (P-11) to (P-14). Further, the photoreceptors (P-1) to (P-10) and (P-20) to (P-22) have a smaller number of white dots in the formed image than the photoreceptors (P-11) to (P-14), and particularly suppress the occurrence of white dots.

On the other hand, the photosensitive layers of the photoreceptors (P-15) to (P-18) do not contain the compound (1). The compound (E-1) is not a compound contained in the general formula (1). Specifically, the compound (E-1) has no halogen atom. Further, the compound (E-2) is not a compound contained in the general formula (1). Specifically, the compound (E-2) has a halogen atom without having a skeleton of the compound represented by the general formula (1). In addition, the charge amount of calcium carbonate in the photosensitive layer of the photoreceptors (P-15) to (P-18) is less than + 7.0. mu.C/g. Therefore, as can be seen from table 2, these photoreceptors have a large number of white spots in the formed image, and the occurrence of white spots in the formed image cannot be suppressed.

As described above, the photoreceptor according to the present invention can suppress the occurrence of white spots in the formed image. Further, the process cartridge and the image forming apparatus according to the present invention can suppress the occurrence of white spots in the formed image.

[ industrial applicability ]

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

Claims (11)

1. An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer,

the photosensitive layer is a monolayer type photosensitive layer containing a charge generating agent and an electron transporting agent,

the electron transport agent comprises a compound represented by the following chemical formula (1-4),

after the photosensitive layer is rubbed with calcium carbonate, the charge amount of the calcium carbonate is more than +7.0 mu C/g,

2. the electrophotographic photoreceptor according to claim 1,

the photosensitive layer also contains a hole-transporting agent,

the ionization potential of the hole transport agent is 5.35eV or more and 5.55eV or less.

3. The electrophotographic photoreceptor according to claim 1,

the photosensitive layer also contains a hole-transporting agent,

the hole transporting agent is represented by the following chemical formula (2-1),

4. the electrophotographic photoreceptor according to claim 1,

the photosensitive layer further contains a binder resin,

the content of the compound represented by the chemical formula (1-4) is 20 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the binder resin.

5. The electrophotographic photoreceptor according to claim 1,

the photosensitive layer further contains a binder resin containing a resin represented by the following general formula (3),

in the general formula (3) described above,

R₃₁～R₃₆each independently represents a hydrogen atom, a C1-C6 alkyl group or a C6-C14 aryl group,

R₃₅and R₃₆May be combined with each other to represent C5-C7 cycloalkylene,

m represents a number of 0.00 to 0.90,

n represents a number of 0.10 to 1.00,

m+n＝1.00。

6. a kind of processing box is disclosed, which comprises a box body,

the electrophotographic photoreceptor according to claim 1.

7. An image forming apparatus is provided in which a toner cartridge is accommodated in a housing,

comprising the electrophotographic photoreceptor according to claim 1, a charging section, an exposure section, a developing section and a transfer section,

the charging section charges a surface of the electrophotographic photoreceptor,

the exposure section exposes the surface of the electrophotographic photoreceptor after charging to form an electrostatic latent image on the surface of the electrophotographic photoreceptor,

the developing section develops the electrostatic latent image into a toner image,

the transfer section transfers the toner image from the electrophotographic photoreceptor to a recording medium,

when the transfer section transfers the toner image from the electrophotographic photoreceptor to the recording medium, the electrophotographic photoreceptor is brought into contact with the recording medium.

8. The image forming apparatus according to claim 7,

the developing section develops the electrostatic latent image into the toner image while contacting the electrophotographic photoreceptor.

9. The image forming apparatus according to claim 7,

the developing section cleans the surface of the electrophotographic photoreceptor.

10. The image forming apparatus according to claim 7,

the charging section is a charging roller.

11. The image forming apparatus according to claim 7,

the charging section charges the surface of the electrophotographic photoreceptor to a positive polarity.

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