JP2006065114A - Electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively decrease a residual potential and to obtain high sensitivity by using a specified compound having high charge mobility as an electron transporting agent. <P>SOLUTION: An electrophotographic photoreceptor has a photosensitive layer containing at least a charge generating agent, an electron transporting agent and a binder resin on a conductive substrate, wherein the electron transporting agent comprises a compound expressed by formula. In the formula, each of R<SB>1</SB>and R<SB>2</SB>represents an alkyl group, alkoxy group, halogen atom, halogenated alkyl group, hydrogen atom or aryl group; A represents an oxygen atom or a carbon atom having at least either a cyano group or a 1-8C alkoxy carbonyl group; X represents a divalent or trivalent aromatic hydrocarbon group; and n represents an integer 2 or 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 an image forming apparatus, various photosensitive members having sensitivity in a wavelength region of a 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 easy to manufacture and have a wide range of research in recent years because they have a wide variety of material choices such as charge generators, charge transport agents, binder resins, and the like, and have a high degree of freedom in functional design.

  The organic photoconductor includes a so-called laminated photoconductor comprising a charge generating layer containing a charge generating agent and a charge transporting layer containing a charge transporting agent, and a single layer comprising a charge generating agent and a charge transporting agent. And so-called single-layer type photoreceptors.

  The charge transfer agent includes a hole transfer agent and an electron transfer agent, and high charge mobility is required. In general, since many charge transport agents having high charge mobility are hole transport agents, many organic photoreceptors that are put to practical use use hole transport agents.

For example, Patent Document 1 below discloses an electrophotographic photoreceptor using an electron transport agent having an azoquinone structure. According to Patent Document 1, it is said that an electrophotographic photoreceptor excellent in electrical characteristics, particularly sensitivity and residual potential can be obtained. However, since the electrophotographic photoreceptor described in Patent Document 1 does not always have sufficient sensitivity, development of an electrophotographic photoreceptor having higher sensitivity is desired.
JP 2000-147806 A (Claim 1, General Formula (I))

  An object of the present invention is to provide an electrophotographic photoreceptor having high sensitivity.

［式中、Ｒ₁，Ｒ₂は、同一または異なる基であって、水素原子、炭素数１〜８のアルキル基、炭素数１〜８のアルコキシ基、ハロゲン原子、炭素数１〜８のハロゲン化アルキル基、または置換基を有していてもよいアリール基を表す。Ａは、酸素原子、またはシアノ基および炭素数１〜８のアルコキシカルボニル基から選ばれる少なくとも一方を有する炭素原子を表す。Ｘは、置換基を有していてもよい２価または３価の芳香族炭化水素基を表す。ｎは２または３の整数を表す。］ The electrophotographic photosensitive member of the present invention for solving the above problems is an electrophotographic photosensitive member in which a photosensitive layer containing at least a charge generating agent, an electron transporting agent and a binder resin is provided on a conductive substrate, The electron transfer agent is a compound represented by the following general formula (I).

[Wherein R ₁ and R ₂ are the same or different groups, and are a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a halogen atom, or a halogen having 1 to 8 carbon atoms. Represents an alkyl group or an aryl group which may have a substituent. A represents an oxygen atom or a carbon atom having at least one selected from a cyano group and an alkoxycarbonyl group having 1 to 8 carbon atoms. X represents a divalent or trivalent aromatic hydrocarbon group which may have a substituent. n represents an integer of 2 or 3. ]

  Since the electrophotographic photosensitive member of the present invention uses the above compound having a high charge mobility as an electron transport agent, the residual potential can be effectively reduced and high sensitivity can be obtained, whereby a good image can be obtained. can get.

  The electrophotographic photosensitive member of the present invention is obtained by providing, on a conductive substrate, a photosensitive layer containing at least a charge generating agent, an electron transporting agent and a binder resin, and further containing a hole transporting agent as necessary. . The photosensitive layer includes a single-layer type photosensitive layer and a laminated type photosensitive layer, and any photosensitive layer can be applied to the present invention.

  The single-layer type photosensitive layer is composed of a single photoconductive layer containing a charge generating agent, a charge transporting agent and a binder resin in the same layer. This single-layer type photosensitive layer has an advantage that the layer structure is simple and the productivity is excellent, the film defects when forming the layer can be suppressed, and the optical characteristics can be improved with few interfaces between layers.

  On the other hand, the laminated photosensitive layer is constituted by laminating a charge transport layer containing a charge transport agent and a charge generation layer containing a charge generator on a conductive substrate. Further, a photoconductive layer containing a charge transporting agent together with a charge generating agent may be combined with a charge transporting layer and a charge generating layer. There are various combinations of the layered photosensitive layer depending on the order of formation of the charge generation layer, the charge transport layer, etc., and the type of the charge transport agent (hole transport agent or electron transport agent) contained in both layers. In the invention, at least one of the charge transport layer and the photoconductive layer contains the compound represented by the above general formula (I) as an electron transport agent. Since the laminated photoconductor separates functions such as charge generation and charge transport in each layer, it has the advantage that there is little waste of constituent materials and it is easy to improve sensitivity.

  Examples of the charge generator include phthalocyanine pigments such as metal-free phthalocyanine, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, α-titanyl phthalocyanine, Y-titanyl phthalocyanine, and V-hydroxygallium phthalocyanine, perylene pigments, bisazo pigments, diketopyrrolo Pyrrole pigment, metal-free naphthalocyanine pigment, metal naphthalocyanine pigment, squaraine pigment, trisazo pigment, indigo pigment, azulenium pigment, cyanine pigment, pyrylium pigment, ansanthrone pigment, triphenylmethane pigment, selenium pigment, toluidine pigment, Organic photoconductors such as pyrazoline pigments and quinacridone pigments, inorganic photoconductors such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon And the like. These charge generating agents may be used alone or in combination of two or more.

  In particular, phthalocyanine-based pigments, particularly metal-free phthalocyanine, titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine are used as a charge generator. It is preferable in terms of electrical characteristics of the photoreceptor when used as an exposure light source.

  The electron transport agent used in the present invention is a compound represented by the general formula (I). As described above, in the formula (I), X is a divalent or trivalent aromatic hydrocarbon group which may have a substituent, that is, an aromatic hydrocarbon which may have a substituent. It represents a divalent or trivalent group having a structure in which two or three hydrogen atoms bonded to the ring are removed.

  Examples of the aromatic hydrocarbon include benzene, naphthalene, biphenyl, anthracene, phenanthrene and the like. Specific examples in the case where X is a divalent group include phenylene, naphthylene, biphenylene, anthrylene, phenanthrylene and the like.

In the formula (I), R ₁ and R ₂ are the same or different groups, and are a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a halogen atom, or 1 carbon atom. Represents a halogenated alkyl group of 8 to 8 or an aryl group which may have a substituent;

Examples of the alkyl group represented by R ₁ and R ₂ include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl. And straight chain or branched alkyl groups having 1 to 8 carbon atoms.

  Examples of the alkoxy group include methoxy, ethoxy, propoxy, isopropoxy, butoxy, t-butoxy, pentyloxy, hexyloxy and the like.

  Examples of the halogenated alkyl group include monochloromethyl, monobromomethyl, monoiodomethyl, monofluoromethyl, dichloromethyl, dibromomethyl, diiodomethyl, difluoromethyl, trichloromethyl, tribromomethyl, triiodomethyl, trifluoromethyl, and monochloroethyl. Carbon number substituted with 1 to 3 halogen atoms such as monobromoethyl, monoiodoethyl, monofluoroethyl, dibromobutyl, diiodobutyl, difluorobutyl, chlorohexyl, bromohexyl, iodohexyl, fluorohexyl, etc. Examples thereof include 1 to 8 alkyl groups.

  Examples of the aryl group include phenyl, tolyl, xylyl, biphenylyl, o-terphenyl, naphthyl, anthryl, phenanthryl and the like. These aryl groups may have a substituent. Examples of the substituent include a hydroxy group, an alkoxy group, a halogen group, an amino group, and a carboxy group.

  In formula (I), A represents an oxygen atom or a carbon atom having at least one selected from a cyano group and an alkoxycarbonyl group having 1 to 8 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentyloxycarbonyl and the like.

Specific examples of the compound represented by the general formula (I) include compounds represented by the following formulas (I-1) to (I-14).

Next, a method for synthesizing the compound represented by the general formula (I) will be described.
First, two hydrogen atoms bonded to a ring of p-formylphenol which may have a substituent and an aromatic hydrocarbon which may have a substituent are replaced with two hydrazyl groups. A substituted hydrazine compound, a solvent such as toluene, and zinc chloride are added and refluxed, and then poured into water. Subsequently, the obtained product is washed with water, dried with sodium sulfate, hexane is added, and a condensation reaction product of p-formylphenol and a hydrazine compound is obtained by crystallization. Next, the condensation reaction product is stirred with an oxidizing agent such as potassium permanganate in chloroform and purified by silica gel column chromatography, and the compound represented by the general formula (I) (when A is an oxygen atom) )

A synthesis method in which A in general formula (I) is a carbon atom having at least one selected from a cyano group and an alkoxycarbonyl group will be described.
First, in benzene, the compound of general formula (I) obtained by the above synthesis method and malononitrile, dialkyl malonate or general formula NC—CH ₂ —R (R represents an alkoxycarbonyl group having 1 to 8 carbon atoms) ), A piperidine, and a catalytic amount of benzoic acid are stirred and mixed, and heated to reflux while removing the produced water, and then poured into water. Subsequently, the obtained product is washed with water, dried with sodium sulfate, purified by silica gel column chromatography, and a compound represented by the general formula (I) (A is selected from at least one selected from a cyano group and an alkoxycarbonyl group). To have a carbon atom).

  In the present invention, in addition to the above-described electron transport agent, a known electron transport agent may be further contained in the photosensitive layer. Examples of such 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 (3,4,4, etc.). 5,7-tetranitro-9-fluorenone derivatives), anthracene derivatives, acridine derivatives, dinitrobenzene, dinitroanthracene, dinitroacridine, succinic anhydride derivatives, maleic anhydride derivatives, dibromomaleic anhydride derivatives, etc. The compound which has is mentioned.

  Examples of the hole transport agent include N, N, N ′, N′-tetraphenylbenzidine derivatives, N, N, N ′, N′-tetraphenylphenylenediamine derivatives, N, N, N ′, N′-tetra. Oxazines such as phenylnaphthylenediamine derivatives, N, N, N ′, N′-tetraphenylphenanthrylenediamine derivatives, 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole Pyrazoline compounds such as azole compounds, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, organic polysilane compounds, and 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline , Hydrazone compounds, indole compounds, oxazole compounds, isoxazols System compounds, thiazole compounds, Chiajizoru compounds, imidazole compounds, pyrazole compounds, and nitrogen-containing cyclic compounds, such as triazole compounds, and condensed polycyclic Conductor compound.

  As the binder resin, for example, styrene polymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic polymer, 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, polyether resin Thermoplastic resins such as silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, unsaturated polyester, alkyd resin, polyurethane, other crosslinkable thermosetting resin, and epoxy-acre relay , Urethane - like photocurable resin such as acrylate. These can be used alone or in combination of two or more.

  In addition to the components described above, various additives can be blended in the photosensitive layer within a range that does not adversely affect image formation. Examples of such additives include antioxidants, radical scavengers, singlet quenchers, deterioration inhibitors such as UV absorbers, softeners, plasticizers, surface modifiers, extenders, thickeners, dispersions Stabilizers, waxes, acceptors, donors and the like can be mentioned. In order to improve sensitivity, for example, known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator.

  As the conductive substrate, various conductive materials can be used. For example, iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel And a simple metal such as brass, a plastic material on which the above metal is deposited or laminated, and glass coated with aluminum iodide, tin oxide, indium oxide, or the like. The conductive substrate is used in the form of a drum or a sheet according to the structure of the image forming apparatus to be used. The conductive substrate preferably has sufficient mechanical strength.

  Single layer type photosensitive layer consists of charge generator, electron transport agent, binder resin, hole transport agent and other additives as appropriate, with appropriate solvent, roll mill, ball mill, attritor, paint shaker, ultrasonic disperser A dispersion liquid may be prepared by mixing using the above, and the dispersion liquid may be coated on a conductive substrate by a known means and dried. The thickness of the photosensitive layer after drying is 5 to 100 μm, preferably 10 to 50 μm.

  Examples of the solvent for preparing the dispersion include alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, Halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ketones such as acetone, methyl ethyl ketone, cyclohexanone, ethyl acetate , Esters such as methyl acetate, dimethylformaldehyde, dimethylformamide, dimethyl sulfoxide, etc.These solvents may be used alone or in combination of two or more. Further, in order to improve the dispersibility of the charge generating agent and the charge transport agent and the smoothness of the surface of the photoreceptor, a surfactant, a leveling agent or the like may be used.

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

  In addition, the electrophotographic photosensitive member having a single-layer type photosensitive layer as the photosensitive layer has advantages that the structure is simple and easy to manufacture, the generation of film defects can be suppressed, and the optical characteristics can be improved. There is. In addition, a photoreceptor having a single-layer type photosensitive layer can be used for both positively charged and negatively charged types by using both an electron transporting agent and a hole transporting agent as charge transporting agents. The application range of the photoreceptor can be expanded.

  The layered photosensitive layer is prepared by mixing a charge generating agent and a charge transporting agent together with an appropriate binder resin and solvent using a roll mill, ball mill, attritor, paint shaker, ultrasonic disperser, etc. The dispersion may be applied on a conductive substrate by a known means and dried. The thickness of each layer after drying is 0.01 to 5 μm, preferably 0.1 to 3 μm for the charge generation layer, and 2 to 100 μm, preferably 5 to 50 μm for the charge transport layer.

  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 mass, preferably 30 to 500 parts by mass with respect to 100 parts by mass of the binder resin. In the charge transport layer, the electron transport agent may be contained in an amount of 10 to 500 parts by weight, preferably 30 to 200 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 is 10-500 mass parts with respect to 100 mass parts of binder resin, Preferably it is good to make it contain in the ratio of 30-200 mass parts.

  Between the single layer type photosensitive layer or the multilayer type photosensitive layer and the conductive substrate, or between the charge generation layer and the charge transport layer constituting the multilayer type photosensitive layer, as long as the characteristics of the photosensitive member are not hindered. A layer, a barrier layer, or the like may be formed. A protective layer may be formed on the surface of the photosensitive layer.

  Hereinafter, the electrophotographic photosensitive member of the present invention will be described in more detail with reference to Reference Examples, Examples and Comparative Examples, but the present invention is not limited only to the following Examples.

[Reference Example 1]
Synthesis examples of the compound represented by the formula (I-1) will be described based on the following reaction scheme. First, 23.4 g (0.1 mol) of compound (a), 13.8 g (0.1 mol) of compound (b-1), 300 mL of toluene, and 13.6 g of ZnCl ₂ were added to a reactor equipped with a Dean Stark. (0.1 mol) was added, refluxed for 1 hour, and poured into 600 mL of water. Subsequently, the obtained product was washed with water, dried over sodium sulfate, hexane was added, and 22.8 g (yield 78%) of compound (c) was obtained by crystallization. Next, 22 g (0.075 mol) of the compound (c) was stirred overnight with 15.8 g (0.1 mol) of potassium permanganate in 150 mL of chloroform and subjected to silica gel column chromatography (chloroform / hexane = 1/1). Purification gave 19 g (yield 90%) of compound (I-1).

[Reference Example 2]
In the above reaction scheme, the following compound (b-2), (b-8), (b-9), (b-10) or (b-11) is used in place of the compound (b-1). Thus, the compound (I-2), (I-8), (I-9), (I-10) or (I-11) was obtained, respectively.

[Reference Example 3]
Furthermore, a method for synthesizing a compound in which A in Formula (I) is a carbon atom having at least one of a cyano group and an alkoxycarbonyl group will be described based on the following reaction scheme. First, 15 g (0.026 mol) of the compound of the formula (I-1) was charged with 4.2 g (0.064 mol) of malononitrile, 5.4 g (0.064 mol) of piperidine, and a catalytic amount of benzoic acid in 200 mL of benzene. The mixture was stirred and mixed, and the produced water was heated to reflux while being removed by Dean Stark, and then poured into 600 mL of water. Subsequently, the obtained product was washed with water, dried over sodium sulfate, and purified by silica gel column chromatography (chloroform / hexane = 1/1) to obtain 19 g of a compound of formula (I-12) (yield 90%). Obtained. Further, the compounds represented by the above formulas (I-13) and (I-14) were synthesized by using the following compound (d) instead of malononitrile.

[Examples and Comparative Examples]
<Production of electrophotographic photoreceptor>
100 parts by weight of binder resin (bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 50,000 having a repeating unit represented by the following formula Resin-1) and hole transporting agent (bottom) with respect to 800 parts by weight of tetrahydrofuran as a solvent. Formula H-1) 50 parts by mass, charge generator shown in Table 1 (X-type metal-free phthalocyanine: PcH ₂ or Y-type titanyl phthalocyanine: PcTiO) 3 parts by mass, and electron transport agent shown in Table 1 (formula I- 1 to I-3, I-12 to I-14, the following formula E-1) 50 parts by mass were added. This mixture was mixed and dispersed with an ultrasonic disperser for 1 hour to prepare a dispersion for a single-layer type photosensitive layer. Next, the obtained dispersion is applied on a conductive substrate (aluminum tube) by dip coating, dried with hot air at 100 ° C. for 30 minutes, and an electron having a single-layer type photosensitive layer having a thickness of 30 μm. A photographic photoreceptor was obtained.

Next, the sensitivity characteristics of the electrophotographic photosensitive member obtained above were evaluated as follows. 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 (half-color) extracted from the light of the halogen lamp using a hand pulse filter. Value width: 20 nm, light intensity: 1.5 μJ / m ² ) was exposed [irradiation time: 0.08 seconds (80 msec)]. Then, the surface potential Vr (V) at the time when 0.33 seconds (330 msec) elapsed from the start of exposure was measured and used as the sensitivity. The results are shown in Table 1.

  From Table 1, the electrophotographic photosensitive materials of Examples 1 to 6 using the compounds represented by the formulas (I-1) to (I-3) and (I-12) to (I-14) as electron transport agents. It can be seen that the body has higher sensitivity than Comparative Example 1.

Claims (1)

An electrophotographic photosensitive member in which a photosensitive layer containing at least a charge generating agent, an electron transporting agent and a binder resin is provided on a conductive substrate, wherein the electron transporting agent is a compound represented by the following general formula (I) An electrophotographic photoreceptor, characterized in that

[Wherein R ₁ and R ₂ are the same or different groups, and are a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a halogen atom, or a halogen having 1 to 8 carbon atoms. Represents an alkyl group or an aryl group which may have a substituent. A represents an oxygen atom or a carbon atom having at least one selected from a cyano group and an alkoxycarbonyl group having 1 to 8 carbon atoms. X represents a divalent or trivalent aromatic hydrocarbon group which may have a substituent. n represents an integer of 2 or 3. ]