JPH08248656A - Electrophotographic photosensitive material - Google Patents

Abstract

PURPOSE: To provide an electrophotographic photosensitive material with more sensitivity than usual to ensure smooth injection and transport of electrons from charge generating agent. CONSTITUTION: Thioxanten derivatives as electron transport agent, shown by the formula, and electron acceptable compound with the oxidation-reduction potential being -0.8 through -1.1V are contained in a photosensitive layer. In the formula, R<1> is an alkyl group or an aralkyl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used in an image forming apparatus such as an electrostatic copying machine, a laser printer and a plain paper facsimile machine.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, an organic photoconductor (OPC) having sensitivity in a wavelength region of a light source of the image forming apparatus is often used. As an organic photoreceptor, there are many laminated photoreceptors in which a charge generation layer and a charge transport layer are laminated, but a single-layer organic photoreceptor in which a charge generator and a charge transport agent are dispersed in the same layer. Is also known.

Charge transport agents used in these photoconductors are required to have high carrier mobility, but most charge transport agents having high carrier mobility have hole transporting properties, and therefore are practically used. The photoreceptor used in (1) is limited to a negative charging type laminated organic photoreceptor having a charge transport layer as the outermost layer in terms of mechanical strength. However, the negatively charged organic photoconductor uses negative corona discharge, and thus has a large amount of ozone generated, and there is a problem that the generated ozone pollutes the environment or deteriorates the photoconductor. It was

Therefore, in order to eliminate such drawbacks,
The use of an electron transfer agent as a charge transfer agent has been studied, and JP-A-1-206349 proposes to use a compound having a diphenoquinone structure as an electron transfer agent for an electrophotographic photoreceptor. There is. However, electron transfer agents such as diphenoquinones generally have poor compatibility with the binder resin and have a long hopping distance, so that electron transfer does not easily occur in a low electric field. Therefore, the residual potential of the electrophotographic photosensitive member was considerably high and the photosensitivity was not sufficient.

Further, if the organic photoreceptor can be used in a single-layer dispersion type, the production of the photoreceptor is facilitated, there are many advantages in preventing the occurrence of coating defects and improving the optical characteristics. In such a single-layer type organic photoconductor, one photoconductor can be used for both positive charging and negative charging, and the application range of the photoconductor can be expanded. Since it has a problem that the transport of electrons and holes is hindered by the interaction with the hole transport material, it has not yet been put into practical use.

The main object of the present invention is to solve the above-mentioned technical problems and to provide an electrophotographic photosensitive member in which injection and transportation of electrons from a charge generating agent are smoothly carried out and sensitivity is improved as compared with the conventional one. That is.

[0007]

[Means and Actions for Solving the Problems] Japanese Patent Laid-Open No. 5-1
Japanese Patent No. 65232 discloses general formula (2):

[0008]

Embedded image

[Wherein R ^a and R ^b are the same or different and each is an oxycarbonyl group substituted with an alkyl group, an aryl group or an aralkyl group, an alkyl group, an alkoxy group,
It represents a hydroxyl group, a nitro group, a cyano group, a halogen atom or a hydrogen atom. ] The electrophotographic photoreceptor which uses the thioxanthene derivative represented by these as an electron transfer material is disclosed.

Since the thioxanthene derivative itself has excellent compatibility with the binder resin, it has an excellent electron-transporting ability especially in a low electric field. Does not interact with the agent, that is,
It does not form a charge transfer complex that hinders the transport of electrons and holes. However, the electrophotographic photoreceptor disclosed in the above-mentioned prior application is not fully utilized in terms of the excellent properties of the thioxanthene derivative as described above, and it cannot be said that it is sufficient in terms of sensitivity.

When the inventors examined the cause of this, it was difficult to match the thioxanthene derivative with the charge generating agent, so that the electron injection from the charge generating agent to the electron transferring agent was insufficient, and therefore, It was found that the photosensitivity of the photoconductor was reduced. In other words, electrons in the electron-hole pairs generated by irradiation of the charge generating agent with light are not efficiently injected into the thioxanthene derivative that is the electron transporting agent, so that the rate of recombination with holes and disappearance is high. It is large, and as a result, the photosensitivity of the photoreceptor becomes insufficient.

[0012] Therefore, the present inventors have shown that among the above thioxanthene derivatives, the electron transport ability is excellent especially in a low electric field,
And to identify the structure that does not interact with the hole transport agent, to the thioxanthene derivative of such a specific structure,
The composition of the photoconductor, which can more smoothly inject the electrons from the charge generating agent, was further examined. As a result, the thioxanthene derivative has the general formula (1):

[0013]

Embedded image

[In the formula, R ¹ represents an alkyl group or an aralkyl group. ] When the thioxanthene derivative having the above-mentioned specific structure is preferably used in combination with an electron-accepting compound having a redox potential of -0.8 to -1.1 V, the electron-accepting compound is charged. Since it works to extract electrons from the generator and transfer them to the thioxanthene derivative, it is found that the injection of electrons from the charge generator to the thioxanthene derivative is smooth, and the photosensitivity of the photoconductor is improved. It came to completion.

That is, in the electrophotographic photoreceptor of the present invention, the thioxanthene derivative represented by the general formula (1), which is an electron transfer agent, and the oxidation-reduction potential of -0.8 are provided on the conductive substrate.
It is characterized in that a photosensitive layer containing an electron-accepting compound of ˜-1.1 V is provided. The present invention will be described below.
Examples of the alkyl group corresponding to the group R ¹ in the general formula (1) include, for example, methyl, ethyl, normal propyl, isopropyl, normal butyl, secondary butyl, tertiary butyl, pentyl, hexyl, and the like. 6 is an alkyl group.

Examples of the aralkyl group include benzyl group, benzhydryl group, trityl group, phenethyl group and the like. Specific examples of the thioxanthene derivative (1) include, but are not limited to, compounds represented by the formula (1-1).

[0017]

[Chemical 4]

The electron accepting compound having an oxidation-reduction potential of -0.8 to -1.1 V, which is used in combination with the thioxanthene derivative (1), is a LUMO [Lowest Unoccupied Mole].
The energy level of (cular orbital, ground empty molecular orbital) is lower than that of the charge generating agent, so that the electron is extracted from the charge generating agent when the electron-hole pair is generated in the charge generating agent by light irradiation. Work. Therefore, the rate of disappearance due to the recombination of electrons and holes in the charge generation agent is reduced, and the charge generation efficiency is improved. In addition, the electron-accepting compound also has a function of efficiently transmitting the electrons extracted from the charge generating agent to the thioxanthene derivative which is the electron transferring agent. Therefore, in the combined system of the above two, the injection and transport of electrons from the charge generating agent are smoothly performed, and the sensitivity of the photoconductor is improved as compared with the conventional case.

The reason why the redox potential of the electron-accepting compound is limited within the above range is as follows. That is,
An electron-accepting compound having a redox potential of higher than −0.8 V drops electrons that move while repeating trap-detrap to a level that cannot be detrapped, and causes a carrier trap, which hinders electron transport, As a result, the sensitivity of the photoconductor is reduced.

On the contrary, in the case of an electron accepting compound having a redox potential smaller than -1.1 V, the LUMO energy level becomes higher than that of the charge generating agent, and when the electron-hole pair is generated, Since the electron does not transfer to the electron-accepting compound,
The charge generation efficiency is not improved, and the sensitivity of the photoconductor is also reduced. The redox potential of the electron-accepting compound is preferably −0.85 to −1.00 V, even within the above range, in consideration of the sensitivity of the photoconductor.

The oxidation-reduction potential is measured, for example, by using the following materials by a three-electrode type cyclic voltammetry. Electrode: working electrode (glassy carbon electrode), counter electrode (platinum electrode) Reference electrode: silver nitrate electrode (0.1 mol / liter AgNO)
₃ - acetonitrile) Measurement solution electrolyte: perchlorate tetra -n- butylammonium 0.1 mol analyte: electron transporting agent 0.001 mol solvent: formulated with CH ₂ Cl ₂ 1 liter or more materials measurement solution Prepare.

Then, as shown in FIG. 1, the index voltage (V)
And the current (μA) are calculated, E ₁ and E shown in the same figure are obtained.
₂ and are measured, and the redox potential is determined by the following calculation formula. Redox potential = (E ₁ + E ₂ ) / 2 (V) Such an electron-accepting compound has an electron-accepting property,
And its redox potential is not particularly limited as long as it is a compound in the range of -0.8 to -1.1 V, for example, benzoquinone compound, naphthoquinone compound, anthraquinone compound, diphenoquinone compound, malononitrile compound, Thiopyran compounds, 2,4,8-trinitrothioxanthone, 3,4,5,7-tetranitro-
Among fluorenone-based compounds such as 9-fluorenone and electron-accepting compounds such as dinitroanthracene, dinitroacridine, nitroanthraquinone and dinitroanthraquinone, compounds having a redox potential within the above range are
Used by choice.

Among them, the general formula (3):

[0024]

Embedded image

[Wherein R ² , R ³ , R ⁴ and R ⁵ are the same or different and each have a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, a cycloalkyl group or a substituent. Is an amino group. ] A benzoquinone compound represented by the general formula (4):

[0026]

[Chemical 6]

[Wherein R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different and each has a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, a cycloalkyl group or a substituent. Is an amino group. ] A compound belonging to the diphenoquinone compound represented by the above formula and having an oxidation-reduction potential within the above range is preferably used.

The alkyl group and aralkyl group in the above formulas include the same groups as described above. Examples of the alkoxy group include alkoxy groups having 1 to 6 carbon atoms such as methoxy, ethoxy, propoxy, t-butoxy, pentyloxy and hexyloxy groups.
Examples of the aryl group include a phenyl group and a naphthyl group. Further, as the cycloalkyl group,
Examples thereof include cycloalkyl groups having 3 to 6 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. Further, examples of the amino group which may have a substituent include an amino group, and also a monomethylamino, dimethylamino, monoethylamino, diethylamino group and the like.

Specific examples of benzoquinone compounds include:
For example, but not limited to, equation (3-1):

[0030]

[Chemical 7]

Examples thereof include p-benzoquinone (redox potential -0.81 V) represented by: Specific examples of the diphenoquinone-based compound include, but are not limited to, for example, 3,5-dimethyl-3 ′ represented by the formula (4-1),
5'-di-t-butyl-4,4'-diphenoquinone (oxidation-reduction potential -0.86 V) and the compound represented by the formula (4-2) 3,
5,3 ', 5'-tetrakis (t-butyl) -4,4'
-Diphenoquinone (oxidation-reduction potential -0.94 V) and the like.

[0032]

Embedded image

These electron-accepting compounds can be used alone or in combination of two or more kinds.
The photosensitive layer containing the electron-accepting compound and the thioxanthene derivative represented by the general formula (1) includes so-called single-layer type and laminated type, and the present invention is applicable to both of them. Although possible, the interaction between the charge generating agent, the thioxanthene derivative and the electron-accepting compound as described above is particularly remarkable in the single-layer type photosensitive layer. Further, the structure of the present invention can be applied to both the positive charging type and the negative charging type, but in consideration of the suppression of ozone generation described above, it is preferable to use the positive charging type.

In the positive charging type photoreceptor, the electrons released from the charge generating agent in the exposure step are smoothly injected into the thioxanthene derivative as the electron transferring agent by the action of the electron accepting compound, and then the thioxanthene is used. It transfers to and from the derivative to move to the surface of the photosensitive layer and cancels the positive charge (+) charged on the surface of the photosensitive layer in advance. On the other hand, holes (+) are injected into the hole transfer material, move to the conductive substrate without being trapped in the middle, and are canceled by the negative charge (−) applied to the conductive substrate in advance. In this way, the sensitivity of the positive charging type photoconductor is considered to be improved.

As the hole-transporting agent, conventionally known hole-transporting substances are used, and examples thereof include diamine compounds and 2,5-
Oxadiazole compounds such as di (4-methylaminophenyl) -1,3,4-oxadiazole, 9- (4-
Styryl compounds such as diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, organic polysilane compounds, 1-phenyl-3- (p
-Pyrazoline compounds such as dimethylaminophenyl) pyrazolin, hydrazone compounds, triphenylamine compounds, indole compounds, oxazole compounds,
Examples thereof include nitrogen-containing cyclic compounds such as isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds and triazole compounds, condensed polycyclic compounds, and the like.

These hole transfer agents are used alone or in combination of two or more. Further, when using a hole transporting agent having film-forming properties such as polyvinylcarbazole, the binder resin is not always necessary. Among the above hole transfer agents, those having an ionization potential of 5.0 to 5.6 eV are preferably used. Further, those having a mobility of 1 × 10 ⁻⁶ cm ² / V · sec or more at an electric field strength of 3 × 10 ⁵ V / cm are particularly preferable.

The hole transporting agent suitable for the present invention which satisfies the above conditions is not limited to this, but is, for example, N, N, N ', N'-tetrakis (p-methylphenyl) -3,3'. -Dimethylbenzidine, 1,1-bis (4-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene, N-ethyl-3-carbazolylaldehyde diphenylhydrazone, p-N, N-diethylbenzaldehyde diphenyl Hydrazone, 4- [N,
Examples thereof include N-bis (p-toluyl) amino] -β-phenylstilbene.

The value of the ionization potential is measured using a photoelectron analyzer (AC-1 manufactured by Riken Keiki Co., Ltd.) under the atmosphere. In the present invention, by using the hole transfer material having an ionization potential within the above range, it is possible to further reduce the residual potential and improve the sensitivity. The reason is not always clear, but it is considered as follows.

That is, the easiness of injecting the charge from the charge generating agent to the hole transferring material is closely related to the ionization potential of the hole transferring material, and the ionization potential of the hole transferring material is more than the above range. If it is also large, the degree of charge injection from the charge generating agent to the hole transporting agent becomes low, or the degree of transfer of holes between the hole transporting agents becomes low, resulting in a decrease in sensitivity. Recognized as something.

On the other hand, in a system in which a hole transfer material and an electron transfer material coexist, it is necessary to pay attention to the interaction between them, that is, the formation of a charge transfer complex, as described above. When such a complex is formed between the two, recombination occurs between the holes and the electrons, and the mobility of the charge is lowered as a whole. When the ionization potential of the hole transfer material is smaller than the above range, the tendency to form a complex with the electron transfer material increases, and electron-hole recombination occurs, resulting in an apparent quantum yield. Is likely to decrease, resulting in a decrease in sensitivity.

Therefore, the ionization potential of the hole transfer material is preferably within the above range. Examples of the charge generating agent include selenium, selenium-tellurium, amorphous silicon, pyrylium salts, azo pigments, disazo pigments,
Ansanthuron pigment, phthalocyanine pigment, naphthalocyanine pigment, indigo pigment, triphenylmethane pigment, slene pigment, toluidine pigment, pyrazoline pigment, quinacridone pigment, dithioketopyrrolopyrrole pigment, etc. . These charge generating agents may be used alone or in combination of two or more so as to have an absorption wavelength in a desired region.

Regarding the above-mentioned charge generating agent, in connection with the use of a hole transfer material having an ionization potential of 5.0 to 5.6 eV, a material having an ionization potential balanced with the hole transfer material, specifically The ionization potential is 5.0-
It is desirable to use 5.6 eV, particularly 5.32 to 5.38 eV in order to reduce the residual potential and improve the sensitivity.

As the binder resin for dispersing the above components, various resins conventionally used in organic photosensitive layers can be used. For example, a styrene polymer and a styrene-butadiene copolymer. , Styrene-acrylonitrile copolymer, styrene-maleic acid copolymer,
Acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, ionomer, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide , Thermoplastic resins such as polyurethane, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, polyester resin, silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, etc. Examples thereof include crosslinkable thermosetting resins, and photocurable resins such as epoxy acrylate and urethane-acrylate. These binder resins can be used alone or in combination of two or more. Suitable resins are styrene polymers, acrylic polymers, styrene-acrylic copolymers, polyesters, alkyd resins, polycarbonates, polyarylates and the like.

In the photosensitive layer, various additives known per se, such as an antioxidant, a radical scavenger, a singlet quencher, and the like, within a range that does not adversely affect the electrophotographic characteristics,
A deterioration inhibitor such as an ultraviolet absorber, a softening agent, a plasticizer, a surface modifier, a bulking agent, a thickener, a dispersion stabilizer, a wax, an acceptor, a donor and the like can be added. The amounts of these additives to be added may be the same as conventional amounts. For example, the sterically hindered phenolic antioxidant is preferably added in an amount of about 0.1 to 50 parts by weight with respect to 100 parts by weight of the binder resin.

In order to improve the sensitivity of the photosensitive layer,
For example, known sensitizers such as terphenyl, halonaphthoquinones and acenaphthylene may be used in combination with the charge generating agent. In addition to the thioxanthene derivative which is an electron transfer agent, another conventionally known electron transfer agent may be contained in the photosensitive layer. Examples of such electron transfer agents include benzoquinone-based, diphenoquinone-based, malononitrile, thiopyran-based compounds, tetracyanoethylene, 2,4,8-
Fluorenone compounds such as trinitrothioxanthone, 3,4,5,7-tetranitro-9-fluorenone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride Etc.

As the conductive substrate on which the photosensitive layer containing each of the above components is formed, various conductive materials can be used, such as aluminum, copper, tin and platinum.
A simple substance of metal such as silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, or brass, a plastic material in which the above metal is vapor-deposited or laminated, aluminum iodide, tin oxide, indium oxide, etc. The coated glass etc. are illustrated.

The conductive substrate may be in the form of a sheet, a drum or the like, as long as the substrate itself has conductivity or the surface of the substrate has conductivity. Further, it is preferable that the conductive substrate has sufficient mechanical strength when used. The single-layer type photosensitive layer is manufactured by applying a coating solution containing the above-mentioned components onto a conductive substrate and drying the coating.

In the single-layer type photoreceptor, the charge generating agent is preferably added to the photosensitive layer in an amount of 0.5 to 10 parts by weight, particularly 0.5 to 5 parts by weight, based on 100 parts by weight of the binder resin. .
The hole transfer agent is used in an amount of 5 to 10 relative to 100 parts by weight of the binder resin.
It is preferable to add 0 parts by weight, particularly 50 to 80 parts by weight, in the photosensitive layer. The electron transfer agent is preferably added to the photosensitive layer in an amount of 5 to 100 parts by weight, particularly 10 to 80 parts by weight, based on 100 parts by weight of the binder resin. The compounding amount of the electron transfer agent is the compounding amount of the derivative when only the thioxanthene derivative represented by the general formula (1) is used alone as the electron transfer agent, and the thioxanthene derivative and other In the case of using together with the electron transfer agent of, the total amount of each electron transfer agent is compounded.

Further, the electron-accepting compound is a binder resin 100.
0.1 to 40 parts by weight, preferably 0.5
It is preferable to mix it in the photosensitive layer in a proportion of ˜20 parts by weight. The thickness of the single-layer type photosensitive layer is 5 to 50 μm, particularly 10 to 40
It is preferably about μm. Further, in order to obtain a laminated type photosensitive layer, a charge generating agent is vapor-deposited on a conductive substrate to form a charge generating layer, or a charge generating agent and a binder resin are required by means such as coating. A charge generation layer containing a hole transfer material may be formed, and a charge transfer layer containing a thioxanthene derivative as an electron transfer material and a binder resin may be formed on the charge generation layer. Alternatively, conversely to the above, the charge transport layer may be formed on the conductive substrate, and then the charge generation layer may be formed.

The electron-accepting compound may be blended in any of the layers described above, but it is preferably blended in the charge-generating layer in consideration of the effect of withdrawing electrons from the charge-generating agent described above. Further, an electron-accepting compound may be blended in both the charge generation layer and the charge transport layer. In the laminated photoreceptor,
The charge generating agent and the binder resin constituting the charge generating layer can be used in various ratios, but the charge generating agent is 5 to 1000 parts by weight, particularly 3 parts by weight with respect to 100 parts by weight of the binder resin.
It is preferably used in a proportion of 0 to 500 parts by weight.

When the charge-generating layer contains an electron-accepting compound, it is added in an amount of 0.1 with respect to 100 parts by weight of the binder resin.
˜40 parts by weight, preferably 0.5 to 20 parts by weight. The electron-transporting agent and the binder resin that form the charge-transporting layer can be used in various proportions within a range that does not hinder the transport of electrons and a range that does not crystallize. It is preferable to use 10 to 500 parts by weight, especially 25 to 200 parts by weight, of the electron transfer agent based on 100 parts by weight of the binder resin so that electrons can be easily transported. The compounding amount of the electron transport agent is
Similarly to the above, as the electron transfer agent, when only the thioxanthene derivative represented by the general formula (1) is used alone, it is the compounding amount of the derivative, and the thioxanthene derivative and other electron transporting agents. When used in combination with the agent, it is the total compounding amount of each electron transfer agent.

When the charge-transporting layer contains an electron-accepting compound, it is added in an amount of 0.1 with respect to 100 parts by weight of the binder resin.
˜40 parts by weight, preferably 0.5 to 20 parts by weight. Regarding the thickness of the laminated type photosensitive layer, it is preferable that the charge generation layer is formed to have a thickness of about 0.01 to 5 μm, particularly 0.1 to 3 μm, and the charge transport layer has a thickness of 2 to 100 μm.
It is preferable that it is formed to a thickness of m, especially about 5 to 50 μm.

In the single-layer type photoreceptor, between the conductive substrate and the photosensitive layer, in the laminated type photoreceptor, between the conductive substrate and the charge generating layer, or between the conductive substrate and the charge transport layer. A barrier layer may be formed between the above and the above in a range that does not impair the characteristics of the photoreceptor. A protective layer may be formed on the surface of the photosensitive layer. When the photosensitive layer is formed by a coating method, the charge generating agent, the charge transporting agent, the binder resin and the like exemplified above are used together with a suitable solvent by a known method, for example, a roll mill, a ball mill, an attritor,
A dispersion liquid may be prepared by dispersing and mixing with a paint shaker or an ultrasonic disperser, and the dispersion liquid may be applied and dried by a known means.

As the solvent for forming the dispersion liquid, various organic solvents can be used. For example, alcohols such as methanol, ethanol, isopropanol and butanol, and aliphatic hydrocarbons such as n-hexane, octane and cyclohexane. , Aromatic hydrocarbons such as benzene, toluene, xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, acetone, methyl ethyl ketone , Ketones such as cyclohexanone, esters such as ethyl acetate and methyl acetate, dimethylformaldehyde, dimethylformamide, dimethylsulfoxide and the like. That. These solvents are 1 type or 2 types.
A mixture of two or more species can be used.

Further, in order to improve the dispersibility of the charge transport agent or the charge generating agent and the smoothness of the photosensitive layer surface, a surfactant,
A leveling agent or the like may be used.

[0056]

EXAMPLES The present invention will be described below with reference to examples and comparative examples. << Single Layer Type Photoreceptor >> Example 1 5 parts by weight of a charge generating agent, X-type metal-free phthalocyanine (Xφ) having Ip = 5.38 eV, and an electron transfer agent, represented by the formula (1-1) Thioxanthene derivative 3
0 parts by weight and p-benzoquinone represented by the above formula (3-1), which is an electron-accepting compound (oxidation-reduction potential -0.81).
V) 10 parts by weight and a hole transporting agent represented by the formula (5):

[0057]

[Chemical 9]

50 parts by weight of N, N, N ', N'-tetrakis (p-methylphenyl) -3,3'-dimethylbenzidine (Ip = 5.56 eV) represented by: and a polycarbonate as a binder resin 100 parts by weight of the solvent is 8
A single layer type photosensitive layer coating solution was prepared by mixing and dispersing with 00 parts by weight of tetrahydrofuran in a ball mill for 50 hours. Then, this coating solution is applied to the surface of the aluminum base tube, which is a conductive base material, by a dip coating method, and 1
Drying with hot air for 60 minutes at 00 ° C, film thickness 15-20 μm
An electrophotographic photoreceptor having the single-layer photosensitive layer of was prepared. Example 2 An electron-accepting compound represented by the above formula (4-1) 3,
5-Dimethyl-3 ', 5'-di-t-butyl-4,4'-
An electrophotographic photoreceptor having a single-layer type photosensitive layer was produced in the same manner as in Example 1 except that 10 parts by weight of diphenoquinone (oxidation-reduction potential -0.86 V) was used. Example 3 An electron-accepting compound represented by the above formula (4-2)
5,3 ', 5'-tetrakis (t-butyl) -4,4'
An electrophotographic photosensitive member having a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 10 parts by weight of diphenoquinone (oxidation-reduction potential -0.94 V) was used. Example 4 An electrophotographic photosensitive member having a single-layer type photosensitive layer was prepared in the same manner as in Example 3 except that 5 parts by weight of oxotitanyl phthalocyanine (Tiφ) with Ip = 5.32 eV was used as the charge generating agent. did. Example 5 An electron-accepting compound represented by the above formula (4-2) 3,
5,3 ', 5'-tetrakis (t-butyl) -4,4'
An electrophotographic photoreceptor having a single-layer type photosensitive layer was produced in the same manner as in Example 3 except that the compounding amount of diphenoquinone (oxidation-reduction potential -0.94V) was 25 parts by weight. Comparative Example 1 An electron-accepting compound represented by the formula (3-2):

[0059]

[Chemical 10]

An electron having a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that 10 parts by weight of 2,5-dichloro-p-benzoquinone (redox potential -0.51 V) represented by A photographic photoreceptor was produced. Comparative Example 2 An electrophotographic photosensitive member having a single-layer type photosensitive layer was prepared in the same manner as in Example 1 except that the electron-accepting compound was not added. Comparative Example 3 An electrophotographic photosensitive member having a single-layer type photosensitive layer was prepared in the same manner as in Comparative Example 2 except that 5 parts by weight of oxotitanyl phthalocyanine (Tiφ) having Ip = 5.32 eV was used as the charge generating agent. did. << Layered Photoreceptor >> Example 6 2 parts by weight of Xφ which is a charge generating agent and 3,5,3 ′, 5′-tetrakis (t) represented by the above formula (4-2) which is an electron accepting compound. -Butyl) -4,4'-diphenoquinone (oxidation-reduction potential -0.94 V) 0.05 part by weight and polyvinyl butyral 1 part by weight as a binder resin,
A charge generation layer coating liquid was prepared by mixing and dispersing it in a ball mill together with parts by weight of dichloromethane. Then, this coating solution was applied to the surface of an aluminum base tube as a conductive base material by a dip coating method and dried with hot air at 100 ° C. for 60 minutes to form a charge generation layer having a thickness of 0.5 μm. .

Next, the above formula (1-1), which is an electron transfer agent, is used.
80 parts by weight of a thioxanthene derivative represented by and 100 parts by weight of a polycarbonate as a binder resin were mixed and dispersed with 800 parts by weight of benzene in a ball mill to prepare a coating solution for a charge transport layer. Then, this coating solution is applied onto the charge generation layer by a dip coating method,
The film was dried with hot air at 60 ° C. for 60 minutes to form a charge transporting layer having a film thickness of 15 μm, whereby an electrophotographic photosensitive member having a laminated photosensitive layer was produced. Comparative Example 4 An electrophotographic photoreceptor having a laminated photosensitive layer was produced in the same manner as in Example 6 except that the electron-accepting compound was not added to the charge generation layer coating liquid.

With respect to the photoconductors of the above examples and comparative examples,
The following photosensitivity test was conducted to evaluate its characteristics. Photosensitivity test Using a drum sensitivity tester manufactured by GENTEC, an applied voltage was applied to the surface of each of the photoconductors of Examples and Comparative Examples to charge the surface to + 700V. Then, a wavelength of 780 nm (half-value width of 20 nm) and a light intensity of 16 μW / c were extracted from a white light of a halogen lamp which is an exposure light source of the tester using a bandpass filter.
The surface of the photoconductor in the charged state is irradiated with irradiation of m ² monochromatic light (irradiation time 80 msec.), and 330 times from the start of exposure.
msec. The surface potential at the point of time passed is the post-exposure potential V
It was measured as L (V). The smaller the post-exposure potential VL (V), the higher the sensitivity of the photoreceptor.

The results are shown in Table 1.

[0064]

[Table 1]

[0065]

INDUSTRIAL APPLICABILITY The electrophotographic photosensitive member of the present invention has a specific oxidation-reduction potential of a thioxanthene derivative having excellent properties as an electron transfer agent, and is excellent in the effect of withdrawing electrons from the charge generating agent. High sensitivity due to the provision of a photosensitive layer containing an electron-accepting compound. Therefore, the use of the electrophotographic photosensitive member of the present invention has a unique effect that the speed of an image forming apparatus such as an electrostatic copying machine, a laser printer, or a plain paper facsimile machine can be increased.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between traction voltage (V) and current (μA) for obtaining the redox potential of an electron-accepting compound.

Claims (1)

[Claims] 1. A compound represented by the general formula (1), which is an electron transfer agent, on a conductive substrate: [In the formula, R ¹ represents an alkyl group or an aralkyl group. ]
With a thioxanthene derivative represented by
An electrophotographic photoreceptor comprising a photosensitive layer containing an electron-accepting compound of 0.8 to -1.1V.