JP4680735B2 - Electrophotographic photoreceptor - Google Patents

Description

  The present invention relates to an electrophotographic photoreceptor containing a charge transport agent excellent in solubility in an organic solvent and compatibility with a binder resin used for forming a photosensitive layer.

  In an image forming apparatus such as a laser printer, a copying machine, or a facsimile, an organic photoreceptor having sensitivity suitable for a wavelength region of a light source used in the apparatus is used. This organic photoconductor is easier to manufacture than conventional inorganic photoconductors, and there are various options for constituent materials of the photoconductor such as a charge transport agent, a charge generator, and a binder resin. Widely used because of its high cost.

  The organic photoreceptor includes a single-layer photoreceptor in which a charge generator is dispersed in a photosensitive layer containing a charge transport agent, a charge generation layer containing a charge generator, and a charge transport layer containing a charge transport agent. There are laminated type photoconductors in which are separated and laminated. In any of the above photoreceptors, in order to improve the sensitivity characteristic, it is required to use a charge transport agent having a high charge transport property. Thus, various charge transport agents have been proposed, and Patent Documents 1 and 2 disclose stilbene derivatives represented by the following general formulas (A) and (B), respectively.

However, although the stilbene derivatives disclosed in the above publications are generally excellent in charge transport properties, they have low solubility in organic solvents and low compatibility with the binder resin used to form the photosensitive layer. It is not uniformly dispersed and charge transfer is unlikely to occur. Therefore, although the stilbene derivative itself has a high charge mobility, when it is used as a charge transfer agent for a photoreceptor, the characteristics cannot be sufficiently exhibited, and the photoreceptor is not suitable for long-term use. There is a problem that the residual potential becomes high and the photosensitivity becomes insufficient.
JP 58-065440 JP 62-010652 A

  An object of the present invention is to provide an electrophotographic photoreceptor excellent in sensitivity characteristics by using a charge transfer agent excellent in solubility in an organic solvent and compatibility with a binder resin used for forming a photosensitive layer.

  As a result of intensive studies to solve the above problems, the present inventors have found that in the charge transfer agent, a group represented by the following general formula (2) in the following general formula (1) is Position, the solubility in organic solvents and the compatibility with the binder resin can be remarkably improved, and precipitation of crystals in the photosensitive layer can be prevented to obtain a highly sensitive electrophotographic photosensitive member. The present inventors have found a new fact that it is possible to complete the present invention.

That is, the electrophotographic photoreceptor using the charge transport agent of the present invention has the following characteristics.
(1) A electrophotographic photoreceptor having a photosensitive layer containing at least a charge generating material and a charge transporting material, the charge transport agent, Ri Do a compound represented by the following general formula (1), the following general in the formula (1), a group represented by the following general formula (2) is an electrophotographic photosensitive member characterized that you substituted in the meta and para positions to the nitrogen atom.

（式（１），（２）中、Ｒ ₁ は、水素原子またはアリール基を示す。Ｒ ₂ 〜Ｒ ₄ およびＲ ₆ は、水素原子を示す。Ｒ ₅ は、水素原子またはアルキル基を示す。Ａｒ₁およびＡｒ₂は、置換基としてメチル基またはエチル基を有していてもよいアリール基を示す。ｎは０または１の整数、ｍは２を示す。）

(Equation (1), in (2), R ₁ is shows a water atom or an aryl group. R ₂ to R ₄ and R ₆ are .R ₅ represents a hydrogen atom, a hydrogen atom or an alkyl group . Ar ₁ and Ar ₂ shows an aryl group which may have a methyl group or an ethyl group as a substituent to .n is an integer of 0 or 1, m represents 2.)

(2) In the general formula (1), in at least one of the aromatic rings Ar ₁ and Ar ₂ , a methyl group or an ethyl group is substituted in the ortho position with respect to the nitrogen atom to which the aromatic ring is bonded. The electrophotographic photosensitive member according to (1), which is characterized.

  According to the charge transfer agent comprising the general formula (1) of the present invention, the solubility in an organic solvent and the compatibility with a binder resin are remarkably improved, so that the precipitation of crystals in the photosensitive layer is prevented, and the high sensitivity. An electrophotographic photoreceptor can be obtained.

Hereinafter, the present invention will be described in detail. The electrophotographic photoreceptor of the present invention is provided with a photosensitive layer containing at least a charge generating agent and a charge transporting agent, and the charge transporting agent comprises a compound represented by the above general formula (1).
As described above, the charge transfer agent according to the present invention is represented by the general formula (1), and the substituents R _{1 to} R _{6 in the} formula (1) are the same or different groups, A hydrogen atom, an alkyl group, an alkoxy group, a phenoxy group, an aryl group, or an aralkyl group is shown. n represents an integer of 0 or 1, and m represents an integer of 2 or 3. Preferably n is 0 and m is 2. When m is 2, the group represented by the general formula (2) is preferably a meta position and a meta position, or a combination of a meta position and a para position with respect to a nitrogen atom. More preferred are the meta and para positions. When m is 3, the group represented by the formula (2) is preferably located at the meta position, the meta position, and the para position. Ar ₁ and Ar ₂ represent an aryl group or a heterocyclic group, and they may have a substituent. In Ar ₁ and Ar ₂ , at least one group other than hydrogen selected from alkyl, halogen, phenyl, alkoxy and phenoxy is substituted at the ortho position with respect to the nitrogen atom to which the aromatic ring is bonded. It is preferable.

Examples of the alkyl group in R _{1 to} R ₆ include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, pentyl group, isopentyl group, C1-C6 alkyl groups, such as a neopentyl group and a hexyl group, are mentioned. Examples of the alkoxy group include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, s-butoxy, t-butoxy, pentyloxy, isopentyloxy, neopentyloxy, hexyloxy and the like.
Examples of the aryl group in R _{1 to} R ₆ , Ar ₁ and Ar ₂ include aryl groups having 6 to 20 carbon atoms such as a phenyl group, a naphthyl group, a tolyl group, a xylyl group, an anthryl group, and a phenanthryl group. . The aryl group may have a substituent, and examples of the substituent include an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms.
Further, among R ₁ to R _6, it is preferable that at least one is an alkyl group having 1 to 6 carbon atoms. By having an alkyl group having 1 to 6 carbon atoms at a specific substitution position, it is possible to effectively have a twisted structure in the molecule of the charge transport agent, and the solubility in the compound binder resin is improved. Mobility can be increased.
Examples of the aralkyl group in R _{1 to} R ₆ include benzyl, α-methylbenzyl, phenethyl, styryl, cinnamyl, 3-phenylpropyl, 4-phenylbutyl, 5-phenylpentyl, and 6-phenylhexyl groups. The bonding position is not particularly limited.
Examples of the heterocyclic group for Ar ₁ and Ar ₂ include furyl, pyranyl, piperazinyl, piperidino, piperidyl, pyrrolidinyl, pyrrolyl, oxazolyl, thiazolylimidazolyl, triazolyl, pyridyl, benzofuranyl, indolyl and the like.

In the compound represented by the formula (1), it is preferable that at least one group represented by the formula (2) is located in the meta position with respect to the nitrogen atom. Since at least one group represented by the formula (2) is located at the meta position with respect to the nitrogen atom, the symmetry is lost, and it is considered that the solubility in an organic solvent and the compatibility with a binder resin are excellent. Similarly, in the above formula (1), in at least one of the aromatic rings Ar ₁ and Ar ₂ , at least a substituent other than hydrogen is located at the ortho position with respect to the nitrogen atom to which the aromatic ring is bonded. It is considered that the symmetry is lost and the solubility in organic solvents and the compatibility with the binder resin are excellent.

  Examples of the compound represented by the above formula (1) according to the present invention include HT-1 to HT-3 shown below. However, the compounds that can be used as the charge transport agent in the present invention are not limited to these.

(Synthesis method)
Any compound included in the formula (1) in the present invention can be synthesized by a known production method. For example, HT-3 can be obtained by the following method using a Wittig reaction and a coupling reaction. That is, first, compound (3) which is a phosphite derivative is subjected to a substitution reaction at a temperature of 0 to 10 ° C., dry THF (tetrahydrofuran) and sodium methoxide are added, and the mixture is stirred for 20 to 50 minutes. To do. Next, the compound (4) which is an aldehyde derivative dissolved in dry THF is added to the obtained reaction solution, and the mixture is stirred at room temperature for 10 to 15 hours. The resulting reaction solution can be extracted with toluene or the like to obtain compound (5).

…（Ｒ−１）

次に、得られた化合物（５）と化合物（６）とを、下記の反応式によりカップリング反応させる。すなわち、Ｐｄ触媒の存在下でアニリン誘導体とクロロベンゼンとのカップリング反応により得られる化合物（６）と前記化合物（５）とをｏ−キシレンに加えて、Ｐｄ触媒の存在下で置換反応を行い、１００〜１３０℃で２〜４時間攪拌する。その後室温まで冷却し、得られた反応液をトルエンなどで抽出し、本発明にかかるＨＴ−３が得られる。

... (R-1)

Next, the obtained compound (5) and compound (6) are subjected to a coupling reaction according to the following reaction formula. That is, the compound (6) obtained by the coupling reaction of an aniline derivative and chlorobenzene in the presence of a Pd catalyst and the compound (5) are added to o-xylene, and a substitution reaction is performed in the presence of a Pd catalyst. Stir at 100-130 ° C. for 2-4 hours. Thereafter, the mixture is cooled to room temperature, and the resulting reaction solution is extracted with toluene or the like to obtain HT-3 according to the present invention.

…（Ｒ−２）

本発明における式（１）に含まれる他の化合物も、前記化合物（４）および化合物（６）を、所望の基を有する化合物に代えることにより、前記と同様にして合成することができる。

... (R-2)

Other compounds included in the formula (1) in the present invention can also be synthesized in the same manner as described above by replacing the compounds (4) and (6) with compounds having a desired group.

  As described above, the electrophotographic photosensitive member of the present invention contains a charge transporting agent comprising a compound included in the formula (1) in the photosensitive layer.

The photosensitive layer is composed of a single layer type photoreceptor in which a charge generator and a charge transport agent are mixed in the same layer, a layer containing a charge generator, and a layer containing a charge transport agent. Each photosensitive layer is obtained by dissolving and dispersing each component such as a charge generating agent and a charge transporting agent in a solvent together with a binder resin and the like. It is formed by applying and drying the resulting coating solution on a conductive substrate.
As described above, the electrophotographic photoreceptor of the present invention contains a compound contained in the formula (1) having good solubility in a solvent and high charge transportability, and therefore, compared with a conventional electrophotographic photoreceptor. And high sensitivity. Moreover, according to the electrophotographic photosensitive member of the present invention, since the compatibility between the compound contained in the formula (1) and the binder resin is good, the long-term stability of the photosensitive layer is improved.

(Charge generator)
Next, examples of the charge generating agent according to the present invention include metal-free phthalocyanine, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, α-titanyl phthalocyanine, Y-titanyl phthalocyanine, V-hydroxygallium phthalocyanine, and phthalocyanine pigments and perylene pigments. Bisazo pigment, diketopyrrolopyrrole pigment, metal-free naphthalocyanine pigment, metal naphthalocyanine pigment, squaraine pigment, trisazo pigment, indigo pigment, azurenium pigment, cyanine pigment, pyrylium pigment, ansanthrone pigment, triphenylmethane pigment, Organic photoconductors such as selenium pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, amorphous silicon Inorganic photoconductive material and the like such emissions. These charge generating agents may be used alone or in combination of two or more.

  In the present invention, a phthalocyanine pigment, particularly a metal-free phthalocyanine (for example, X-type metal-free phthalocyanine), titanyl phthalocyanine, hydroxygallium phthalocyanine and chlorogallium phthalocyanine is used as a charge generator. In view of the electrical characteristics of the photoreceptor when red or infrared light having a wavelength of 650 nm or more is used as an exposure light source, it is preferable.

(Hole transport agent)
The charge transport agent used in the electrophotographic photosensitive member of the present invention is a hole transport agent and is composed of a compound included in the formula (1).
In the electrophotographic photoreceptor of the present invention, various conventionally known hole transport agents may be contained in the photosensitive layer in combination with the compound (1). Examples of such other hole transporting agents include bisstilbenediamine derivatives, bistriphenylamine derivatives, triphenylaminostyryl derivatives, stilbeneamine-hydrazone derivatives, and the like.

(Electron transfer agent)
Examples of the electron transporting agent 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. Can be mentioned.

(Binder resin)
In the electrophotographic photoreceptor of the present invention, conventionally known various resins can be adopted as the binder resin for forming a layer containing each component such as a charge generator and a charge transport agent. Among them, the use of at least one resin selected from the group consisting of polycarbonate, polyester, polyarylate, polystyrene, and polymethacrylic acid ester as the binder resin is the compound represented by the above formula (1) according to the present invention. From the standpoint of further improving the compatibility, and the properties such as the strength and abrasion resistance of the photosensitive layer. Moreover, the binder resin exemplified above is excellent in compatibility with the charge generating agent and the charge transport agent, and does not have a site in the molecule that interferes with the charge transport property of the charge transport agent. Therefore, by using such a binder resin, an electrophotographic photosensitive member with higher sensitivity can be obtained.

(Dispersion medium)
As a dispersion medium used for preparing a coating solution for forming a photosensitive layer by dispersing and dissolving the charge generating agent, hole transporting agent, electron transporting agent, binder resin and the like exemplified above, a coating solution for forming a photosensitive layer is used. Various organic solvents conventionally used can be used. Specifically, 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; dichloromethane, dichloroethane and chloroform , Halogenated hydrocarbons such as carbon tetrachloride and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone and cyclohexanone; ethyl acetate and methyl acetate And esters such as dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide.

  In addition, although not limited thereto, tetrahydrofuran, dioxane, dioxolane, cyclohexanone, among various organic solvents, can be used to stably disperse each component such as a charge generator, a charge transport agent, and a binder resin. It is preferable to use at least one organic solvent selected from the group consisting of toluene, xylene, dichloromethane, dichloroethane and chlorobenzene.

(Additive)
In the coating solution for forming the photosensitive layer, in addition to the above-mentioned components, various conventionally known additives such as an antioxidant, a radical scavenger, a singlet quencher are used as long as they do not adversely affect the electrophotographic characteristics. Deterioration inhibitors such as char and ultraviolet absorbers, softeners, plasticizers, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, acceptors, donors, and the like can be blended. In order to improve the sensitivity of the photosensitive layer, a known sensitizer such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator. Further, a surfactant, a leveling agent or the like may be used in order to improve the dispersibility of the charge transport agent or charge generator and the smoothness of the photosensitive layer surface.

(Conductive substrate)
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.
The conductive substrate used in the present invention is not limited to this, but the surface thereof may be subjected to an oxide film treatment or a resin film treatment.

(Manufacture of single layer type electrophotographic photoreceptor)
The single-layer type electrophotographic photosensitive member includes a charge generator, the compound (1) of the present invention (hole transport agent), a binder resin, and an electron transport agent and the above additives as necessary. The photosensitive layer forming coating solution thus obtained is dispersed or dissolved in an appropriate dispersion medium, coated on a conductive substrate, and dried to form a photosensitive layer.

  In the photosensitive layer forming coating solution, the charge generating agent may be blended 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. What is necessary is just to mix | blend a hole transport agent in the ratio of 5-200 weight part with respect to 100 weight part of binder resin, Preferably it is 50-150 weight part. What is necessary is just to mix | blend an electron transport agent in the ratio of 5-200 weight part with respect to 100 weight part of binder resin, Preferably it is 10-100 weight part. In the case where the electron transport agent and the hole transport agent are used in combination, the total amount of the electron transport agent and the hole transport agent is 20 to 500 parts by weight, preferably 30 to 200 parts by weight with respect to 100 parts by weight of the binder resin. It is appropriate to do.

The thickness of the photosensitive layer obtained by applying the coating solution for forming the photosensitive layer is preferably set to 5 to 100 μm, particularly 10 to 50 μm.
When preparing a coating solution for forming a photosensitive layer, the above-exemplified charge generator, charge transport agent, insoluble azo pigment, binder resin, etc., together with an appropriate solvent, roll mill, ball mill, attritor, paint shaker, ultrasonic dispersion What is necessary is just to disperse and mix using well-known means, such as a machine.

(Manufacture of multilayer electrophotographic photoreceptors)
In the case of a laminated photoreceptor, a charge generator and a hole transport agent are mixed together with a suitable binder resin and solvent using a roll mill, ball mill, attritor, paint shaker, ultrasonic disperser, etc. What is necessary is just to prepare and apply | coat this dispersion liquid on an electroconductive base | substrate by a well-known means, and to make it dry. 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 photoconductor, the charge generation agent is preferably contained in an amount of 5 to 1000 parts by weight, particularly 30 to 500 parts by weight, based on 100 parts by weight of the binder resin. In the charge transport layer, the hole transport agent may be contained in an amount of 10 to 100 parts by weight, particularly 30 to 80 parts by weight with respect to 100 parts by weight of the binder resin. Moreover, when using together a positive hole transport agent and an electron transport agent, it is good to contain the total amount in the ratio of 10-500 weight part with respect to 100 weight part of binder resin, especially 30-200 weight part.

  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 Examples and Comparative Examples, but the present invention is not limited only to the following Examples.

(Synthesis of hole transport agent)
(1) Synthesis of Compound (3) First, the compound represented by Formula (3) was synthesized according to the following reaction formula. That is, 20 g (0.0788 mol) of 1-bromo-3,4-di (chloromethyl) benzene and 39.3 g (0.236 mol) of triethyl phosphite were added to a 200 mL flask and heated at 180 ° C. And stirred for 8 hours. Then, after cooling to room temperature, excess phosphorous acid triethyl ester was distilled off under reduced pressure to obtain 29.6 g of a compound represented by the formula (3) (yield 82.3%).

…（Ｒ−３）

... (R-3)

(2) Synthesis of Compound (5) Next, the compound represented by the above formula (5) was synthesized according to the above reaction formula (R-1). That is, after adding 15 g (0.0328 mol) of the compound represented by formula (3) into a 500 mL two-necked flask, argon gas replacement was performed and 100 mL of dried tetrahydrofuran (THF) and 28% sodium were added. 15.2 g (0.0787 mol) of methoxide was added and stirred at 0 ° C. for 30 minutes. Next, 9.54 g (0.0722 mol) of the compound represented by the formula (4) was dissolved in 300 mL of dry THF and added to this reaction solution, followed by stirring at room temperature for 12 hours. Thereafter, the reaction solution was poured into ion exchanged water and extracted with toluene, and the organic layer was washed 5 times with ion exchanged water. Next, the organic layer was dried over anhydrous sodium sulfate, and the solvent was distilled off. Thereafter, the residue was purified with a toluene / methanol mixed solvent (toluene / methanol = 20 mL / 100 mL) to obtain a compound represented by the formula (5). Yield 10.3 g (76% yield).

(3) Synthesis of Compound (6) Next, the compound represented by the above formula (6) was synthesized according to the following reaction formula. That is, 85 g (0.755 mol) of chlorobenzene, 0.662 g (0.00189 mol) of (2-biphenyl) dicyclohexylphosphine (Pcy), tris (dibenzylideneacetone) dipalladium (Pd2 (dba) ) 3) 0.864 g (0.000944 mol), t-butoxy sodium (t-BuONa) 54.4 g (0.566 mol), 102 g (0.755 mol) of the compound represented by the following formula (7), purified o -After adding xylene 1000mL, argon gas substitution was performed and it stirred at 120 degreeC for 5 hours. Then, after cooling to room temperature, the organic layer was washed 3 times with ion exchange water. Next, the organic layer was dried over anhydrous sodium sulfate, further treated with activated clay, and xylene was distilled off under reduced pressure. Thereafter, the residue was purified by column chromatography (developing solvent: chloroform / hexane) to obtain 128 g of a compound represented by the formula (6) (yield: 80.2%).

…（Ｒ−４）

... (R-4)

(4) Synthesis of HT-3 Finally, HT-3 was synthesized according to the above reaction formula (R-2). That is, in a 300 mL two-necked flask, 7.5 g (0.0181 mol) of compound (5), 0.0159 g (0.0000453 mol) of (2-biphenyl) dicyclohexylphosphine (Pcy), tris (dibenzylideneacetone) di 0.0207 g (0.0000226 mol) of palladium (Pd2 (dba) 3), 1.3 g (0.0136 mol) of t-butoxy sodium (t-BuONa), 3.82 g (0.0181 mol) of compound (6), After adding 150 mL of purified o-xylene, argon gas substitution was performed, and the mixture was stirred at 120 ° C. for 3 hours. Then, after cooling to room temperature, the organic layer was washed 3 times with ion exchange water. Next, the organic layer was dried over anhydrous sodium sulfate, further treated with activated clay, and xylene was distilled off under reduced pressure. Thereafter, the residue was purified by column chromatography (developing solvent: chloroform / hexane) to obtain 7.25 g of the target compound (HT-3) (yield 73.7%).

(Synthesis of HT-1 and 2)
In the synthesis of HT-3, HT-1 in the present invention is obtained by replacing the compound (4) described above with a compound represented by the following formula (8), substituting chlorobenzene with p-chloroethylbenzene, and further replacing the compound (7) with The compound was synthesized in the same manner as HT-3 by replacing with the compound represented by the following formula (9).

また、ＨＴ−２は、前記ＨＴ−３の合成において、前記した化合物（４）を下記式（１０）で表わされる化合物に代え、さらに化合物（７）を下記式（１１）で表わされる化合物に代えることにより、ＨＴ−３と同様にして合成した。

In addition, in the synthesis of HT-3, HT-2 is obtained by replacing the compound (4) with a compound represented by the following formula (10), and further replacing the compound (7) with a compound represented by the following formula (11). By replacing it, it synthesize | combined like HT-3.

[Examples 1 to 9 and Comparative Examples 1 to 6]
[Manufacture of electrophotographic photosensitive member]
(Hole transport agent)
As the hole transport agent, the above-described HT-1 to HT-3 and the following hole transport agents (HT-4, 5) were used.

(Electron transfer agent)
As the electron transport agent, the following three types of electron transport agents (ET-1 to ET-3) were used.

Example 1
5 parts by weight of X-type metal-free phthalocyanine as a charge generating agent, 80 parts by weight of HT-1 as a hole transporting agent, 50 parts by weight of ET-1 as an electron transporting agent, and 100 parts by weight of polycarbonate as a binder resin Were mixed and dispersed in a ball mill for 50 hours together with 800 parts by weight of tetrahydrofuran as a solvent to prepare a coating solution for a single-layer type photosensitive layer. Next, this coating solution was applied on a conductive substrate made of an aluminum base tube by a dip coating method and dried with hot air at 100 ° C. for 30 minutes to produce a photosensitive layer having a thickness of 25 μm as a single layer type photoreceptor.
(Examples 2-9, Comparative Examples 1-6)
In the coating solution for a single-layer type photosensitive layer produced in Example 1, HT-1 to 5 as a hole transport agent and ET-1 to 3 as an electron transport agent were used instead of the combinations shown in Table 1, A single-layer photoconductor was produced in the same manner as in Example 1.

(Evaluation test and evaluation method)
Any of the electrophotographic photoreceptors produced in Examples 1 to 9 and Comparative Examples 1 to 6 was installed in a GENTEC drum sensitivity tester, and an electrical property test and the presence or absence of crystallization on the drum surface were evaluated It was. In the electrical characteristic test, first, charging was performed so that the initial surface potential V ₀ was + 700V. Next, monochromatic light (light intensity 1.5 μJ / cm ² ) having a wavelength of 780 nm (half-width 20 nm) extracted from the white light of the halogen lamp using a bandpass filter is irradiated on the surface of the photosensitive member for 1.5 seconds to be exposed. The surface potential at the time when 0.5 seconds elapsed from the start was measured, and this was defined as the residual potential V _L (V). This was regarded as one step, and this step was repeated for 500 minutes, and the evaluation at the final repetition time was performed. The presence or absence of crystallization on the drum surface was confirmed by visual observation at the final repetition point. These results are shown in Table 1.
Regarding the crystallization of the drum surface, the case where crystallization was not observed was marked with ◯, and the case where it was recognized was marked with x.

The results are shown in Table 1.

As is clear from Table 1, in the electrophotographic photoreceptors of Comparative Examples 1 to 3 using HT-4, the residual potential V _L is high and sufficient sensitivity cannot be obtained, and HT-5 is used. In all of the electrophotographic photoreceptors of Comparative Examples 4 to 6, crystals were precipitated in the photosensitive layer, and thus could not be put to practical use.

In contrast, in the electrophotographic photoreceptors of Examples 1 to 9 using HT-1, HT-2, and HT-3 of the present invention, the residual potential V _L is low, and crystals are precipitated in the photosensitive layer. Thus, a highly sensitive electrophotographic photosensitive member could be obtained.

Claims (2)

An electrophotographic photosensitive member provided with a photosensitive layer containing at least a charge generating agent and a charge transporting agent,
The charge transfer agent comprises a compound represented by the following general formula (1), and in the following general formula (1), groups represented by the following general formula (2) are in the meta position and the para position with respect to the nitrogen atom. An electrophotographic photosensitive member characterized by being substituted.

(In Formulas (1) and (2), R ₁ represents a hydrogen atom or an aryl group. R _{2 to} R ₄ and R ₆ represent a hydrogen atom. R ₅ represents a hydrogen atom or an alkyl group. Ar ₁ and Ar ₂ represent an aryl group optionally having a methyl group or an ethyl group as a substituent, n is an integer of 0 or 1, and m is 2. In the general formula (1), at least one of the aromatic rings Ar ₁ and Ar ₂ is substituted with a methyl group or an ethyl group in the ortho position with respect to the nitrogen atom to which the aromatic ring is bonded. The electrophotographic photosensitive member according to claim 1.