JP2011158540A - Electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having higher sensitivity than before. <P>SOLUTION: The electrophotographic photoreceptor 10 includes a conductive substrate 12 and a photosensitive layer 14, wherein the photosensitive layer 14 contains a benzo azulene derivative expressed by general formula (1). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer.

  In the image forming apparatus, various photosensitive members having sensitivity in the wavelength region of the light source used in the apparatus are used. One is an inorganic photoreceptor using an inorganic material such as selenium for the photosensitive layer, and the other is an organic photoreceptor using an organic material for the photosensitive layer. Organic photoconductors are easier to manufacture than inorganic photoconductors, and have a variety of material options such as charge generators, charge transport agents (electron transport agents and hole transport agents), binder resins, etc. Due to its high degree of freedom, it has been used frequently in recent years.

  In organic photoreceptors, a photosensitive layer has a laminated structure of a charge generation layer containing a charge generation agent and a charge transport layer containing a charge transport agent, a so-called multilayer photoreceptor, and the photosensitive layer comprises a charge generation agent. And a so-called single-layer type photoreceptor having a single-layer structure containing a charge transfer agent.

  Generally, 3,5-dimethyl-3 ', 5'-di-t-butyldiphenoquinone is used as the electron transporting agent contained as a charge transporting agent in these organic photoreceptors. However, sufficient photosensitivity cannot be obtained with a photoreceptor containing this electron transport agent.

  Patent Document 1 discloses an acetylazulene derivative represented by the general formula (E) (as represented by the general formula (E)) as a compound capable of effectively reducing the residual potential of the electrophotographic photosensitive member and obtaining high photosensitivity. , R is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms. And X represents a halogen atom). However, the electrophotographic photoreceptor using the acetylazulene derivative disclosed in Patent Document 1 still has a problem that the photosensitivity is still insufficient.

JP 2009-2972 A (paragraphs 0007 to 0011)

  An object of the present invention is to provide an electrophotographic photoreceptor having higher photosensitivity.

  As a result of intensive studies to solve the above problems, the present inventors have used a benzoazulene derivative having a specific structure represented by the following general formula (1) as an electron transport agent, thereby improving the sensitivity of the electrophotographic photoreceptor. A new fact that it can be improved has been found, and the present invention has been completed.

  That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor provided with a conductive substrate and a photosensitive layer, and the photosensitive layer contains a benzoazulene derivative represented by the general formula (1). It is characterized by.

  Here, in general formula (1), R1 is a halogen-substituted alkyl group or (—COOR4) (R4 is an unsubstituted or substituted alkyl group having 1 to 8 carbon atoms, or an unsubstituted group having 6 to 18 carbon atoms. Or a substituted aryl group, an unsubstituted or substituted aralkyl group having 7 to 18 carbon atoms, or an unsubstituted or substituted cycloalkyl group having 3 to 12 carbon atoms, and R2 and R3 represent 1 to carbon atoms. An alkyl group having 6 carbon atoms, an aryl group having 6 to 12 carbon atoms that may have an alkyl group having 1 to 6 carbon atoms, an aralkyl group having 6 to 12 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or 1 to 1 carbon atom 6 represents an alkoxy group.

  Compared with the acetylazulene derivative represented by the general formula (E), the benzoazulene derivative represented by the general formula (1) has a π-electron conjugate plane that is rich in electron acceptability. Therefore, the benzoazulene derivative exhibits high charge mobility, the photosensitive layer containing the benzoazulene derivative has improved electron transport properties, and the electrophotographic photoreceptor having such a photosensitive layer has higher photosensitivity. .

  In the electrophotographic photoreceptor, the benzoazulene derivative represented by the general formula (1) is preferably a compound represented by the formula (1-1).

  In the electrophotographic photoreceptor, it is also preferable that the benzoazulene derivative represented by the general formula (1) is a compound represented by the formula (1-2).

  In the electrophotographic photoreceptor, it is also preferable that the benzoazulene derivative represented by the general formula (1) is a compound represented by the formula (1-3).

  The benzoazulene derivatives represented by the formulas (1-1), (1-2), and (1-3) can effectively reduce the residual potential of the electrophotographic photosensitive member and reliably obtain high photosensitivity. It is a compound that can be.

  In the electrophotographic photosensitive member, the photosensitive layer is preferably a single layer type. The single-layer type photosensitive layer has the advantage that the layer structure is simple and the productivity is excellent, the film defects when forming the layer can be suppressed, the interface between the layers is small, and the optical characteristics can be improved.

  In the electrophotographic photoreceptor, it is also preferable that the photosensitive layer is a laminated type. The laminated photosensitive layer has the advantages that the functions such as charge generation and charge transport are separated into each layer, so that the constituent materials are not wasted and the sensitivity is easily improved.

  According to the present invention, since the benzoazulene derivative represented by the general formula (1) contained in the photosensitive layer of the electrophotographic photosensitive member has a wider π-electron conjugate plane, the electron transport property of the photosensitive layer is improved, The residual potential of the electrophotographic photosensitive member is effectively reduced, and high photosensitivity can be obtained. By using the electrophotographic photosensitive member of the present invention in an image forming apparatus, a good image can be obtained.

(A)-(c) is a schematic sectional drawing for demonstrating the structure of the electroconductive base | substrate and single layer type photosensitive layer concerning embodiment of this invention. (A)-(f) is a schematic sectional drawing for demonstrating the structure of the electroconductive base | substrate and laminated type photosensitive layer which concern on embodiment of this invention.

  The electrophotographic photoreceptor according to the exemplary embodiment has a configuration including a conductive substrate and a photosensitive layer, more specifically, a configuration in which a photosensitive layer is provided on the conductive substrate. The photosensitive layer contains at least an electron transport agent, a charge generator, and a binder resin, and further contains a hole transport agent as necessary. The photosensitive layer includes a single-layer type photosensitive layer and a laminated type photosensitive layer. The electrophotographic photosensitive member according to this embodiment can be applied to any photosensitive layer. In this embodiment, the photosensitive layer contains a benzoazulene derivative represented by the general formula (1) as an electron transport agent.

<Electron transport agent>
In the electrophotographic photoreceptor according to the exemplary embodiment, a benzoazulene derivative represented by the general formula (1) is used as an electron transport agent. This benzoazulene derivative will be described.

  In the benzoazulene derivative represented by the general formula (1), a benzene ring is condensed and bonded to azulene, which is a non-benzene aromatic compound in which a 5-membered ring and a 7-membered ring are condensed. The hydrogen at the position is substituted with ON in which oxygen is double-bonded, and the π-electron conjugate plane having a high electron accepting property as a whole has a relatively enlarged structure. Therefore, the benzoazulene derivative exhibits high charge mobility, the photosensitive layer containing the benzoazulene derivative has improved electron transport properties, and the electrophotographic photoreceptor provided with such a photosensitive layer has higher photosensitivity. It is considered a thing.

  In the general formula (1), R1 is selected from a halogen-substituted alkyl group and (—COOR4). Here, R4 is an unsubstituted or substituted alkyl group having 1 to 8 carbon atoms, an unsubstituted or substituted aryl group having 6 to 18 carbon atoms, an unsubstituted or substituted aralkyl group having 7 to 18 carbon atoms, and a carbon number. Selected from 3 to 12 unsubstituted or substituted cycloalkyl groups. R2 and R3 are each an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms which may have an alkyl group having 1 to 6 carbon atoms, an aralkyl group having 6 to 12 carbon atoms, and 3 to 10 carbon atoms. Selected from cycloalkyl groups and alkoxy groups having 1 to 6 carbon atoms.

  Examples of the halogen-substituted alkyl group for R1 include groups such as chloromethyl, trifluoromethyl, dibromoethyl, trichloropropyl, and perfluorobutyl.

  Examples of the alkyl group having 1 to 8 carbon atoms in R4 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, s-pentyl, t -Pentyl, neopentyl, n-hexyl, isohexyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, 1,2-dimethylbutyl, 2,3-dimethylbutyl, n- Examples include heptyl, n-octyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl and the like.

  Examples of the aryl group having 6 to 18 carbon atoms in R4 include groups such as phenyl, naphthyl, biphenyl, tolyl, cumenyl, xylyl, anthryl, phenanthryl.

  Examples of the aralkyl group having 7 to 18 carbon atoms in R4 include groups such as benzyl, α-methylbenzyl, phenethyl, styryl, cinnamyl, 3-phenylpropyl, 4-phenylbutyl, 5-phenylpentyl and 6-phenylhexyl. Is mentioned.

  Examples of the cycloalkyl group having 3 to 12 carbon atoms in R4 include groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and cyclododecyl.

  The alkyl group, aryl group, aralkyl group and cycloalkyl group in R4 may have at least one substituent. The substituent is not particularly limited as long as it does not hinder the solubility of the benzoazulene derivative represented by the general formula (1) in the solvent used for forming the photosensitive layer. Examples thereof include an alkyl group, an alkoxy group, a halogen group, a carboxyl group, a carboxylate group (ester group), an acyl group, an amino group, an alkylamino group, a nitro group, a mercapto group, and an aryl group. From the viewpoint of further expanding the π-electron conjugate plane and improving the sensitivity of the electrophotographic photoreceptor, a carboxylate group and an aryl group are preferable.

  Examples of the alkyl group having 1 to 6 carbon atoms in R2 and R3 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, and s-pentyl. , T-pentyl, neopentyl, n-hexyl, isohexyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, 1,2-dimethylbutyl, 2,3-dimethylbutyl, etc. The group of is mentioned.

  Examples of the aryl group having 6 to 12 carbon atoms in R2 and R3 include groups such as phenyl, naphthyl, tolyl, and xylyl.

  Examples of the aralkyl group having 6 to 12 carbon atoms in R2 and R3 include groups such as benzyl, α-methylbenzyl, 3-phenylpropyl, 4-phenylbutyl, 5-phenylpentyl and 6-phenylhexyl.

  Examples of the cycloalkyl group having 3 to 10 carbon atoms in R2 and R3 include groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl.

  Examples of the alkoxy group having 1 to 6 carbon atoms in R2 and R3 include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, s-butoxy, t-butoxy, pentyloxy, isopentyloxy, and neopentyloxy. And groups such as hexyloxy.

(Synthesis method)
The benzoazulene derivative represented by the general formula (1) is, for example, a chloroform solution of the compound represented by the formula (A) (R1, R2, R3, and R4 are the same as those in the general formula (1)). , M-chloroperoxybenzoic acid was added and reacted while cooling to 0 ° C. under an inert gas, ethyl acetate was added to remove the organic layer, the solvent was distilled off, and the residue was purified by column chromatography. It can be synthesized by purification.

(Specific examples of benzoazulene derivatives)
Specific examples of the benzoazulene derivative represented by the general formula (1) include compounds represented by the formulas (1-1), (1-2), and (1-3).

  The benzoazulene derivative represented by the formula (1-1) is a compound in the case where R1 is a trifluoromethyl group, R2 is a methoxy group, and R3 is a methyl group in the general formula (1) ( Molecular weight: 292.3). The benzoazulene derivative represented by the formula (1-2) is (—COOR4) when R4 is an ethyl group in the general formula (1), R2 is a methoxy group, and R3 is a methyl group. Compound (molecular weight: 296.4). The benzoazulene derivative represented by the formula (1-3) is a compound in the case where R1 is a trifluoromethyl group, R2 is a phenyl group, and R3 is a methyl group in the general formula (1) ( Molecular weight: 338.4). The benzoazulene derivatives represented by the formulas (1-1), (1-2), and (1-3) can effectively reduce the residual potential of the electrophotographic photosensitive member and reliably obtain high photosensitivity. It is a compound that can be.

  In this embodiment, in addition to the benzoazulene derivative represented by the general formula (1), other known electron transport agents can be used in combination. As such other electron transporting agent, an electron transporting agent having a high electron transporting ability is preferable from the viewpoint of minimizing the decrease in photosensitivity of the electrophotographic photosensitive member due to the combined use. Examples of such other electron transporting agents include diphenoquinone derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, thioxanthone derivatives (2,4,8-trinitrothioxanthone, etc.), fluorenone derivatives (3 , 4,5,7-tetranitro-9-fluorenone derivatives, etc.), anthracene derivatives, acridine derivatives, dinitrobenzene, dinitroanthracene, dinitroacridine, succinic anhydride derivatives, maleic anhydride derivatives, dibromomaleic anhydride derivatives, etc. A compound rich in properties may be mentioned. These other electron transport agents may be used alone or in combination of two or more.

<Charge generator>
As the charge generating agent used in the present embodiment, various materials conventionally used as charge generating agents can be used without limitation. Examples of such a charge generator include an X-metal-free phthalocyanine represented by the formula (x-H ₂ Pc), hydroxygallium phthalocyanine, chlorogallium phthalocyanine, α-titanyl phthalocyanine, and a formula (Y-TiOPc). Phthalocyanine pigments such as Y-oxotitanyl phthalocyanine and V-hydroxygallium phthalocyanine, perylene pigments, bisazo pigments, diketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, Organic photoconductors such as indigo pigments, azulenium pigments, cyanine pigments, pyrylium pigments, ansanthrone pigments, triphenylmethane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments, selenium, selenium -Inorganic photoconductive materials such as tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon. Of these, metal-free phthalocyanine, chlorogallium phthalocyanine, α-titanyl phthalocyanine, Y-oxo titanyl phthalocyanine, and V-hydroxygallium phthalocyanine are preferable. These charge generating agents may be used alone or in combination of two or more. Thereby, a charge generating agent having an absorption wavelength in a desired wavelength region can be obtained.

  Among charge generating agents, in particular, a laser beam printer using a light source such as a semiconductor laser or an image forming apparatus of a digital optical system such as a facsimile requires a photoreceptor having sensitivity in a wavelength region of 700 nm or more. Phthalocyanine pigments such as metal-free phthalocyanine and oxotitanyl phthalocyanine are preferably used. In addition, it does not specifically limit about the crystal form of a phthalocyanine pigment, A various thing is used. On the other hand, an analog optical image forming apparatus such as an electrostatic copying machine using a white light source such as a halogen lamp requires a photosensitive member having sensitivity in the visible region. For example, a perylene pigment or a bisazo pigment is used. Etc. are preferably used.

<Binder resin>
As the binder resin for dispersing each component in the photosensitive layer, various resins conventionally used in the photosensitive layer can be used without limitation. Examples of such a binder resin include a styrene polymer, a styrene-butadiene copolymer, a styrene-acrylonitrile copolymer, a styrene-maleic acid copolymer, an acrylic polymer, a styrene-acrylic copolymer, Polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, polyamide, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin , Thermoplastic resins such as polyether resins, silicone resins, epoxy resins, phenol resins, urea resins, melamine resins, unsaturated polyesters, alkyd resins, polyurethanes, other crosslinkable thermosetting resins, and epoxy- Acrylate, urethane - photocurable resin such as acrylate. These binder resins may be used alone or in combination of two or more. Of these, styrene polymers, acrylic polymers, styrene-acrylic copolymers, polyesters, polycarbonates, polyarylate, alkyd resins, and the like are preferable.

<Hole transport agent>
In this embodiment, the photosensitive layer may further contain a hole transport agent. In particular, when the photosensitive layer is a single layer type, an electron transporting agent and a hole transporting agent are preferably used in combination in the photosensitive layer. As a hole transport agent used in the present embodiment, various materials conventionally used as a hole transport agent can be used without limitation. Examples of such hole transporting agents include N, N, N ′, N′-tetraphenylbenzidine derivatives, N, N, N ′, N′-tetraphenylphenylenediamine derivatives having high hole transporting ability. N, N, N ′, N′-tetraphenylnaphthylenediamine derivative, N, N, N ′, N′-tetraphenylphenanthrylenediamine derivative, 2,5-di (4-methylaminophenyl) -1 Oxadiazole compounds such as 1,4-oxadiazole, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, organic polysilane compounds, 1-phenyl-3- ( Pyrazoline compounds such as p-dimethylaminophenyl) pyrazoline, hydrazone compounds, indole compounds, oxazole compounds , Isoxazole compounds, thiazole compounds, Chiajizoru compounds, imidazole compounds, pyrazole compounds, nitrogen-containing cyclic compounds such as triazole compounds and include condensed polycyclic compounds. These hole transport agents may be used singly or in combination of two or more. Of these, the compound represented by the formula (H-1) is preferable.

  In addition, when using the hole transport agent which has film formability, such as polyvinyl carbazole, binder resin is not necessarily required.

<Photosensitive layer>
In the electrophotographic photoreceptor according to the exemplary embodiment, the photosensitive layer containing the benzoazulene derivative represented by the general formula (1) is provided on a conductive substrate. The composition of the photosensitive layer differs between the single-layer type photosensitive layer and the laminated type photosensitive layer, but in any photosensitive layer, each component such as a charge generating agent and a charge transporting agent is dissolved or dispersed in a solvent together with a binder resin or the like. The obtained coating solution is formed by coating the conductive substrate directly or via an undercoat layer and drying.

(Single layer type)
In the present embodiment, the single-layer type photosensitive layer is one in which an electron transport agent, a charge generator, a binder resin, and the like are contained in a single photosensitive layer. For example, in the electrophotographic photoreceptor 10 shown in FIG. 1A, a single monolayer type photosensitive layer 14 is formed on the surface of a conductive substrate 12. Such a single-layer type photosensitive layer 14 has an advantage that it has a simple layer structure, is excellent in productivity, can suppress film defects when forming a layer, has few interfaces between layers, and can improve optical characteristics. There is.

  The charge transfer agent includes an electron transfer agent and a hole transfer agent. In particular, in a single layer type photosensitive layer, it is preferable to use an electron transfer agent and a hole transfer agent in combination. The reason is that the electrophotographic photosensitive member can be used for both a positive charging type and a negative charging type.

  The film thickness of the single layer type photosensitive layer is 5 to 100 μm, preferably 10 to 50 μm. In the single-layer type photosensitive layer, the charge generating agent is contained in an amount of 0.1 to 50 parts by weight, preferably 0.5 to 30 parts by weight with respect to 100 parts by weight of the binder resin, and the electron transport agent is 5 to 5 parts. It is good to make it contain in the ratio of 100 mass parts, Preferably 10-80 mass parts. Moreover, when it contains a hole transport agent, it is good to contain a hole transport agent in the ratio of 5-500 mass parts with respect to 100 mass parts of binder resin, Preferably it is 25-200 mass parts.

(Laminated type)
In this embodiment, the multilayer photosensitive layer is obtained by laminating a charge transport layer containing a charge transport agent and a charge generation layer containing a charge generator on a conductive substrate. For example, in the electrophotographic photoreceptor 20 shown in FIG. 2A, the charge generation layer 24 and the charge transport layer 22 are laminated in this order on the conductive substrate 12, and the electrophotographic photoreceptor shown in FIG. In FIG. 20, the charge transport layer 22 and the charge generation layer 24 are laminated in this order on the conductive substrate 12. Such a laminated photosensitive layer has the advantages that the functions such as charge generation and charge transport are separated into each layer, so that the constituent materials are not wasted and the sensitivity is easily improved.

  Note that a photoconductive layer containing a charge generation agent and a charge transport agent may be combined with the charge transport layer or the charge generation layer. Various combinations of the layered photosensitive layer are conceivable depending on the order of stacking the charge generation layer and the charge transport layer, the type of charge transport agent (electron transport agent, hole transport agent) contained in both layers, and the like. In this embodiment, at least one of the charge transport layer and the photoconductive layer contains a benzoazulene derivative represented by the general formula (1) as an electron transport agent. In order to more smoothly transfer electrons from the charge generation layer to the charge transport layer, the charge generation layer preferably contains a benzoazulene derivative represented by the general formula (1).

  The film thickness of the charge generation layer is 0.01 to 5 μm, preferably 0.1 to 3 μm. The film thickness of the charge transport layer is 2 to 100 μm, preferably 5 to 50 μm. In the charge generation layer of the multilayer photosensitive layer, the charge generation agent may be contained in an amount of 5 to 1000 parts by weight, preferably 30 to 500 parts by weight, with respect to 100 parts by weight of the binder resin. In the charge transport layer of the multilayer photosensitive layer, the electron transport agent may be contained in an amount of 1 to 250 parts by weight, preferably 5 to 150 parts by weight, with respect to 100 parts by weight of the binder resin. Moreover, when using an electron transport agent and a hole transport agent together, the total amount of an electron transport agent and a hole transport agent is 10-500 mass parts with respect to 100 mass parts of binder resin, Preferably it is 30-200 mass. It is good to make it contain in the ratio of a part.

  Both the single-layer type photosensitive layer and the multilayer type photosensitive layer can be applied to the electrophotographic photosensitive member according to the present embodiment. However, the effect of using the benzoazulene derivative represented by the general formula (1) is simple. It appears remarkably in the layer type photosensitive layer.

  In the photosensitive layer, in addition to the components such as the charge generator and the charge transport agent, various additives may be blended in a range that does not adversely affect image formation in both the single layer type and the multilayer type. it can. Such additives include, for example, deterioration inhibitors such as antioxidants, radical scavengers, singlet quenchers, ultraviolet absorbers, softeners, plasticizers, surface modifiers, extenders, thickeners. , Dispersion stabilizers, waxes, acceptors, donors and the like. In order to improve sensitivity, for example, known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator.

<Conductive substrate>
As the conductive substrate used in the present embodiment, various materials having conductivity can be used without limitation. Examples of such conductive materials include simple metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass, and the above metals. And a plastic material in which conductive fine particles such as carbon black are dispersed, and a glass coated with aluminum iodide, tin oxide, indium oxide, or the like.

  A barrier layer may be formed between the conductive substrate and the photosensitive layer or between each layer as long as the characteristics of the electrophotographic photosensitive member are not impaired. A protective layer may be formed on the surface of the photosensitive layer. For example, in the case of a single-layer type photosensitive layer, even if a barrier layer 16 is formed between the coating liquid 12 for the conductive substrate charge generation layer and the photosensitive layer 14 as shown in FIG. Good. Further, as shown in FIG. 1C, a protective layer 18 may be formed on the surface of the photosensitive layer 14. On the other hand, in the laminated photosensitive layer, a barrier layer 16 may be formed between the conductive substrate 12 and the charge generation layer 24 as shown in FIG. Further, as shown in FIG. 2D, a barrier layer 16 may be formed between the charge generation layer 24 and the charge transport layer 22. Further, as shown in FIG. 2E, a barrier layer 16 may be formed between the conductive substrate 12 and the charge transport layer 22. Further, as shown in FIG. 2F, a barrier layer 16 may be formed between the charge transport layer 22 and the charge generation layer 24. Further, in each of the stacked photosensitive layers shown in FIGS. 2A to 2F, a protective layer may be formed on the surface.

  The conductive substrate is used in the form of a drum or a sheet depending on the structure of the image forming apparatus to be used. This conductive substrate preferably has sufficient mechanical strength.

<Method for producing electrophotographic photoreceptor>
The single-layer type electrophotographic photoreceptor is, for example, an electron transport agent containing at least a benzoazulene derivative represented by the general formula (1) dissolved in a solvent together with a charge generator, a hole transport agent, a binder resin, or the like. The coating liquid obtained by dispersing is coated on a conductive substrate using a method such as vapor deposition or dip coating, and dried. On the other hand, in the multilayer electrophotographic photosensitive member, for example, a charge generation layer containing a charge generation agent is first formed on a conductive substrate using a method such as vapor deposition or dip coating, and then the charge generation layer is formed. On top of this, a coating solution obtained by dissolving or dispersing an electron transport agent containing at least the benzoazulene derivative represented by the general formula (1) in a solvent together with a binder resin or the like is deposited or dip coated. It is manufactured by applying and drying using

  In order to form a single-layer type photosensitive layer, for example, an electron transport agent, a charge generator and a binder resin, and optionally a hole transport agent and other additives, together with a solvent, a roll mill, a ball mill, an attritor, What is necessary is just to prepare the coating liquid for single layer type photosensitive layers by mixing using a paint shaker, an ultrasonic disperser, etc., apply | coating this coating liquid on a conductive substrate by a well-known means, and drying. In order to form a laminated photosensitive layer, for example, according to the case of forming the single-layer photosensitive layer, a charge generation layer coating solution and a charge transport layer coating solution are prepared. What is necessary is just to apply | coat a coating liquid in order by a well-known means on an electroconductive base | substrate, and to dry and laminate | stack.

  Examples of the solvent used for the preparation of the coating solution include alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, and aromatic carbonization such as benzene, toluene and xylene. Halogenated hydrocarbons such as hydrogen, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dioxane, dioxolane, ketones such as acetone, methyl ethyl ketone, cyclohexanone, Examples include esters such as ethyl acetate and methyl acetate, dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide. These solvents may be used alone or in combination of two or more.

  If necessary, the coating solution may further contain a surfactant, a leveling agent, etc. for improving the dispersibility of the charge generating agent and the charge transporting agent and the surface smoothness of the electrophotographic photosensitive member. It may be added.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to a following example at all.

<Synthesis of benzoazulene derivative>
(Synthesis Example 1)
The benzoazulene derivative represented by the above formula (1-1) was synthesized as follows. M-Chloroperoxybenzoic acid (molecular weight: 172.5, max: 77%) was added to a chloroform solution of 0.32 g (1 mmol) of the compound represented by the formula (A-1) (molecular weight: 318.3). 52 g (3 mmol) was added, and the mixture was allowed to react for 3 hours while cooling to 0 ° C. with ice water under nitrogen gas. After adding ethyl acetate, the organic layer was taken out and the solvent was distilled off. It melt | dissolved and refine | purified with silica gel column chromatography, 0.22g of benzoazulene derivatives (molecular weight: 292.3) represented by Formula (1-1) were obtained (yield: 75%).

(Synthesis Example 2)
A benzoazulene derivative represented by the above formula (1-2) was synthesized according to Synthesis Example 1. However, instead of the compound represented by the formula (A-1), 0.32 g (1 mmol) of the compound represented by the formula (A-2) (molecular weight: 322.4) was used, and the formula (1-2) 0.15 g of a benzoazulene derivative (molecular weight: 296.4) represented by the formula (yield: 50%) was obtained.

(Synthesis Example 3)
A benzoazulene derivative represented by the above formula (1-3) was synthesized according to Synthesis Example 1. However, instead of the compound represented by the formula (A-1), 0.36 g (1 mmol) of the compound represented by the formula (A-3) (molecular weight: 364.4) is used, and the formula (1-3) 0.20 g of a benzoazulene derivative (molecular weight: 338.4) represented by the formula (yield: 60%) was obtained.

<Manufacture of electrophotographic photoreceptor>
(Charge generator)
As shown in Table 1, in Examples 1, 3, 5 and Comparative Example 1, the X-type metal-free phthalocyanine represented by the above formula (x-H ₂ Pc) was used as a charge generator. In Examples 2, 4, 6 and Comparative Example 2, Y-type oxotitanyl phthalocyanine represented by the above formula (Y-TiOPc) was used as a charge generator.

(Hole transport agent)
As shown in Table 1, in Examples 1 to 6 and Comparative Examples 1 and 2, the compound represented by the above formula (H-1) was used as a hole transport agent.

(Electron transfer agent)
As shown in Table 1, in Examples 1 to 6, the benzoazulene derivatives represented by the above formulas (1-1), (1-2), and (1-3) were used as electron transport agents. In Comparative Examples 1 and 2, an acetylazulene derivative represented by the formula (E-1) was used as an electron transport agent.

(Binder resin)
In Examples 1 to 6 and Comparative Examples 1 and 2, bisphenol Z type polycarbonate resin (viscosity average molecular weight: 50,000) represented by the formula (Resin-1) was used as the binder resin.

(Examples 1 to 6 and Comparative Examples 1 and 2)
The electrophotographic photoreceptors of Examples 1 to 6 and Comparative Examples 1 and 2 having a monolayer type photosensitive layer were produced by combining a charge generating agent, a hole transporting agent and an electron transporting agent as shown in Table 1. That is, tetrahydrofuran was used as a solvent, and 5 parts by weight of a charge generating agent, 60 parts by weight of a hole transporting agent, 25 parts by weight of an electron transporting agent and 100 parts by weight of a binder resin were added to 800 parts by weight of tetrahydrofuran. This mixture was mixed and dispersed for 1 hour using an ultrasonic disperser to prepare a coating solution for a single-layer type photosensitive layer. Next, the prepared coating solution is applied onto the surface of an aluminum base tube as a conductive substrate by a dip coating method and dried with hot air at 100 ° C. for 30 minutes, whereby an electron having a single-layer type photosensitive layer with a film thickness of 25 μm. A photographic photoreceptor was produced.

<Evaluation of sensitivity characteristics>
The sensitivity characteristics (photosensitivity) of the produced electrophotographic photosensitive member were evaluated. That is, the electrophotographic photosensitive member is charged to 700 V using a drum sensitivity tester (manufactured by GENTEC), and then monochromatic light having a wavelength of 780 nm extracted from the light of the halogen lamp using a bandpass filter (half-color) Value width: 20 nm, light quantity: 1.5 μJ / cm ² ) was exposed (irradiation time: 0.08 seconds). Then, the surface potential (residual potential) when 0.33 seconds passed from the start of exposure was measured, and the value was defined as sensitivity (V). The results are shown in Table 1.

  As is apparent from Table 1, the electrophotographic photoreceptors of Examples 1 to 6 using the benzoazulene derivative represented by the general formula (1) as the electron transport agent are the electrophotographic photoreceptors of Comparative Examples 1 and 2. As compared with the above, the residual potential was effectively reduced and the sensitivity was high.

  As described above in detail, according to the present invention, an electrophotographic photosensitive member having higher photosensitivity can be obtained by incorporating the benzoazulene derivative represented by the general formula (1) into the photosensitive layer. became.

  Therefore, the electrophotographic photosensitive member of the present invention is expected to contribute to high image quality and high performance of various image forming apparatuses such as copying machines and printers.

DESCRIPTION OF SYMBOLS 10 Single layer type electrophotographic photosensitive member 12 Conductive base | substrate 14 Photosensitive layer 16 Barrier layer 18 Protective layer 20 Laminated type electrophotographic photosensitive member 22 Charge transport layer 24 Charge generation layer

Claims (6)

An electrophotographic photosensitive member comprising a conductive substrate and a photosensitive layer,
The electrophotographic photosensitive member, wherein the photosensitive layer contains a benzoazulene derivative represented by the general formula (1).

(In the general formula (1), R1 is a halogen-substituted alkyl group or (—COOR4) (R4 is an unsubstituted or substituted alkyl group having 1 to 8 carbon atoms, an unsubstituted or substituted group having 6 to 18 carbon atoms. An aryl group of 7 to 18 carbon atoms, an unsubstituted or substituted aralkyl group having 7 to 18 carbon atoms, or an unsubstituted or substituted cycloalkyl group having 3 to 12 carbon atoms), and R2 and R3 each represent 1 to 6 carbon atoms. An alkyl group, an aryl group having 6 to 12 carbon atoms which may have an alkyl group having 1 to 6 carbon atoms, an aralkyl group having 6 to 12 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, or an alkyl group having 1 to 6 carbon atoms Represents an alkoxy group.) The electrophotographic photoreceptor according to claim 1, wherein the benzoazulene derivative represented by the general formula (1) is a compound represented by the formula (1-1).
The electrophotographic photosensitive member according to claim 1, wherein the benzoazulene derivative represented by the general formula (1) is a compound represented by the formula (1-2).
The electrophotographic photoreceptor according to claim 1, wherein the benzoazulene derivative represented by the general formula (1) is a compound represented by the formula (1-3).
  The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is a single layer type.   The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is a laminated type.