JPH05134432A - Bipolar electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide a bipolar electrophotographic sensitive body having high sensitivity and high durability. CONSTITUTION:This electrophotographic sensitive body consists essentially of an electric conductive substrate and a photosensitive layer formed on the substrate and the photosensitive layer contains a binaphthyltetracarboxylic acid diimide compd. represented by the formula and a hole transferring material. In the formula, R is <=8C alkyl, aralkyl or aryl, Rc is <=8C cycloalkylene or arylene and each of A1 and A2 is H, <=4C alkyl, nitro, cyano, carboxylic acid ester or halogen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bipolar electrophotographic photoconductor, and more specifically, a highly sensitive and highly durable bipolar electron containing a specific binaphthyltetracarboxylic acid diimide compound and a hole transport material in a photosensitive layer. The present invention relates to a photographic photoreceptor.

[0002]

2. Description of the Related Art In recent years,
The development of electrophotographic copying machines and printers has been remarkable, and various forms, types, and functions of models have been developed according to the application, and a wide variety of photoconductors are being developed correspondingly. .. Conventionally, inorganic compounds such as cadmium sulfide and selenium alloy have been mainly used as electrophotographic photoreceptors from the viewpoint of sensitivity and durability. However, these often use harmful substances and cause pollution. Further, when using a selenium alloy having good sensitivity, it is necessary to form a thin film on a conductive support by a vapor deposition method or the like, resulting in poor productivity and high cost.

On the other hand, the organic photoconductor can be incinerated,
It has the advantage of being pollution-free, and many of them can be formed into thin films by coating and are easy to mass-produce. Therefore, it has an advantage that the cost can be significantly reduced and that it can be processed into various shapes depending on the application. As the organic photoreceptor, an azo compound, a charge generating layer containing a charge generating material such as a phthalocyanine compound is provided on a conductive support, and a hydrazone compound, a triarylamine compound, or the like on the charge generating layer.
The negative charge function separation type, which is provided with a charge transport layer containing a hole transport material typified by a stilbene compound or the like, is in the mainstream.
This negative charging function-separated type organic photoconductor is mainly used in reversal development type printers using negative toner, and there is a strong demand for a high-sensitivity, high-durability product that enables higher speed and smaller size. Has been done.

On the other hand, in a general copying machine, a positive charging / normal developing system using a negative toner is adopted, but in spite of its toxicity, selenium alloy is still the mainstream.
One of the reasons is that a positively charged organic photoconductor which can be used as it is has not been put into practical use because an excellent organic electron transport material has not been developed, and another is that it has a high sensitivity for a high-speed copying machine. Another reason is that a highly durable organic photoreceptor has not been obtained. However, negatively charged type photoconductors have a problem that ozone and nitrogen oxides are generated during the negative charging process by a corona charger and deteriorate the photoconductors, and therefore development of a positively charged high-performance organic photoconductor is strongly desired. ing.

As described above, in the field of electrophotographic photoconductors, both positively charged and negatively charged organic photoconductors are required. Not only is the production efficiency of the body increased, but a wide degree of freedom is also given to the design of copiers and printers, the selection of toner polarity, etc., and its ripple effect is immeasurable. At present, only two cases have been reported as the bipolar photoreceptor.
One is a mixture of electron transporting material, trinitrofluorenone, with hole-transporting polyvinylcarbazole (Journal of Applied Physics, Vol. 43,
5033 (1972)). Since these compounds form a charge transfer complex, their transport ability is hindered, and the hole mobility becomes smaller as the concentration of trinitrofluorenone increases. Trinitrofluorenone is highly toxic and poses a serious problem in practical use. The other is known to be a mixture of a diphenoquinone derivative which is an electron transport material and a triarylamine derivative which is a hole transport material (Proceedings of the 65th Annual Meeting of the Electrophotographic Society, p. 77 ( 1990
Year)). Unlike the former, these compounds do not form a charge transfer complex, so that both compounds are independent of each other, and the charge transporting ability (electrons and holes) increases depending on their concentration. Therefore, it is possible to increase the sensitivity and it is expected to be put into practical use, but there is a problem in the stability of the diphenoquinone derivative, and decomposition during repeated use adversely affects the durability of the photoreceptor.

As described above, the bipolar photoreceptor has many problems, and it is strongly desired in the art to improve and put them into practical use. The object of the present invention is exactly at this point, high sensitivity including a binaphthyltetracarboxylic acid diimide compound which is an excellent electron transporting compound and a hole transporting material in order to solve such a problem in the photosensitive layer, high durability To provide a bipolar electrophotographic photosensitive member.

[0007]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, the present invention has a conductive support and a photosensitive layer formed thereon as an essential constituent element, and a general formula in the photosensitive layer
A bipolar electrophotographic photoreceptor comprising the binaphthyltetracarboxylic acid diimide compound represented by (1) and a hole transport material.

[0008]

[Chemical 2]

(Wherein R is an alkyl group having 8 or less carbon atoms,
An aralkyl group or an aryl group, and Rc represents a cycloalkylene group having 8 or less carbon atoms or an arylene group. A ₁ and A ₂ are the same or different and each represents a hydrogen atom, an alkyl group having 4 or less carbon atoms, a nitro group, a cyano group, a carboxylic acid ester group or a halogen atom. ) In the general formula (1), R is an alkyl group having 8 or less carbon atoms,
An aralkyl group or an aryl group is shown, and examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, n.
Examples thereof include groups such as -heptyl and n-octyl. Examples of the aralkyl group include a phenyl group in which an aryl group portion is unsubstituted or substituted with an alkyl group and the like, and an alkylene group portion has 1 to 3 carbon atoms. Examples thereof include a benzyl group and a phenylethyl group. Examples of the aryl group include a phenyl group and a naphthyl group which are unsubstituted or substituted with an alkyl group or the like. Rc represents a cycloalkylene group having 8 or less carbon atoms or an arylene group, and examples of the cycloalkylene group include:
Examples thereof include groups such as cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene and cyclooctylene, and a cyclohexylene group is preferable.
Further, examples of the arylene group include a phenylene group and a naphthylene group. In the general formula (1), A ₁ ,
A ₂ is the same or different and represents a hydrogen atom, an alkyl group having 4 or less carbon atoms, a nitro group, a cyano group, a carboxylic acid ester group or a halogen atom, and examples of the alkyl group having 4 or less carbon atoms include methyl, ethyl and n. Examples thereof include -propyl, isopropyl, n-butyl, isobutyl, sec-butyl and the like. Examples of the halogen atom include chlorine atom, fluorine atom and bromine atom. Also, A ₁ , A ₂
May be bonded to any position of the naphthalene ring.

The binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) used in the present invention can be synthesized according to a known method used when synthesizing a general carboxylic acid imide. For example, the general formula
(2) Condensing ω-amino acid ester represented by H ₂ N-CH ₂ -Rc-COOR (2) (wherein R and Rc are the same as in formula (1)) and binaphthyltetracarboxylic dianhydride Can be obtained by As another method, first, the ω-amino acid represented by the general formula (3) H ₂ N-CH ₂ -Rc-COOH (3) (wherein Rc is the same as the formula (1)) and the binaphthyltetracarboxylic acid are shown. Condensate with dianhydride,
Then, by esterification, the target compound can be obtained in high yield.

The bulky cycloalkylene or arylenecarboxylic acid ester group is substituted at the terminal of the N-substituted alkyl group of the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) thus produced. By doing so, the stability can be remarkably increased as compared with the conventionally known carboxylic acid diimide compound (German Patent No. 2306399), and the compatibility with the solvent and the binder is significantly increased. It has become possible to improve. Also, it has almost no crystallinity and maintains an amorphous state at room temperature.
No deterioration was observed during use. Moreover,
Due to the steric hindrance of the cycloalkylene or arylene group,
Without forming a charge transfer complex with a donor compound such as a hole-transporting compound, both the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) and the hole-transporting compound are increased in concentration. The charge transport ability is improved, and the sensitivity of the photoconductor can be improved.

Typical examples of the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) used in the present invention include the following compounds (compounds (4) to (28)). The present invention is not limited to these.

[0013]

[Chemical 3]

[0014]

[Chemical 4]

[0015]

[Chemical 5]

[0016]

[Chemical 6]

[0017]

[Chemical 7]

[0018]

[Chemical 8]

[0019]

[Chemical 9]

These compounds are soluble in many solvents, for example, aromatic solvents such as benzene, toluene, xylene, tetralin and chlorobenzene; halogen compounds such as dichloromethane, chloroform, trichloroethylene, tetrachloroethylene and carbon tetrachloride. Solvents; ester solvents such as methyl acetate, ethyl acetate, propyl acetate, methyl formate, ethyl formate; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone; ether solvents such as diethyl ether, dipropyl ether, dioxane, tetrahydrofuran; methanol ,ethanol,
It is soluble in alcohol solvents such as isopropyl alcohol; dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like.

In producing the electrophotographic photosensitive member,
A photosensitive layer is formed into a thin film on a conductive support. As the base material of the conductive support, a metal such as aluminum or nickel, a metal vapor-deposited polymer film, a metal laminated polymer film, or the like can be used, and the conductive support is in a drum shape, a sheet shape, or a belt shape. To form. As the photosensitive layer, it is possible to adopt any of a function separation type including a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material, and a single layer type including both the charge generating material and the charge transporting material in the same layer. Is.

First, the function-separated type photoconductor will be described in detail. The charge generation layer is composed of a charge generation material and, if necessary, a binder and an additive, and can be formed by a method such as a vapor deposition method, a plasma CVD method, a coating method and the like. The charge generating material is not particularly limited, and any organic material or inorganic material can be suitably used as long as it absorbs light having a specific wavelength to be irradiated and efficiently generates charges.
Examples of the organic charge generating material include perylene pigments, polycyclic quinone pigments, metal-free phthalocyanine pigments, metal phthalocyanine pigments, bisazo pigments, trisazo pigments, thiapyrylium salts, squarium salts, and azurenium pigments. Examples of the inorganic charge generating material include zinc oxide,
Cadmium sulfide, selenium, selenium alloy, amorphous silicon, amorphous silicon carbide and the like can be mentioned. The organic charge generating material can be dispersed mainly in the binder, and the charge generating layer can be formed by coating. The thickness of the formed charge generation layer is preferably 0.1 to 2.0 μm, more preferably 0.1 to 1.0 μm.

The binder used if necessary is not particularly limited as long as it is an insulating resin. For example, condensation polymers such as polycarbonate, polyarylate, polyester, polyamide; polyethylene, polystyrene, styrene-acryl copolymer. Polyacrylate, polymethacrylate, polyvinyl butyral, polyvinyl formal, polyacrylonitrile, polyacrylamide, acrylonitrile-butadiene copolymer, polyvinyl chloride,
Addition polymers such as vinyl chloride-vinyl acetate copolymers; polysulfones, polyether sulfones, silicone resins, etc. are appropriately used, and one kind or a mixture of two or more kinds can be used. The amount of the binder used is 0.1 to 3% by weight, preferably 0.1 to 2% by weight, based on the charge generating material.

The additives used as required include antioxidants, quenchers, dispersants, adhesion aids, sensitizers and the like. The coating means for the charge generation layer is not particularly limited, and for example, a dip coater, a bar coater, a calendar coater, a gravure coater, a spin coater or the like can be used as appropriate, and electrodeposition coating or spray coating is also possible. Etc. are also possible.

Next, the general formula (1) is formed on the charge generation layer.
The charge transport layer containing the binaphthyl tetracarboxylic acid diimide compound represented by and the hole transport material is formed into a thin film. The coating method is mainly used as a thin film forming method,
The binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) and the hole transport material are dissolved in a solvent together with a binder and an additive used if necessary, and coated on the charge generation layer. , And then dry it.
The solvent to be used is not particularly limited as long as it is a solvent in which the above-mentioned compound and the binder used as necessary are dissolved, and the charge generation layer is insoluble, for example, benzene, toluene, xylene, tetralin, Aromatic solvents such as chlorobenzene; Halogen solvents such as dichloromethane, chloroform, trichloroethylene, tetrachloroethylene, carbon tetrachloride; methyl acetate, ethyl acetate,
Ester solvents such as propyl acetate, methyl formate and ethyl formate; ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone; ether solvents such as diethyl ether, dipropyl ether, dioxane and tetrahydrofuran; alcohols such as methanol, ethanol and isopropyl alcohol. Examples of system solvents include dimethylformamide, dimethylacetamide, and dimethylsulfoxide.

As the hole transporting material, a generally known hole transporting material can be used. For example, a hydrazone compound, a stilbene compound, a triarylamine compound,
Examples thereof include a pyrazoline compound, an oxadiazole compound, an oxazole compound, a polyvinylcarbazole compound, and a triphenylmethane compound, and typical examples thereof include the following formulas (CT-1) to (CT-5). The ones shown are listed. These can be used alone or in combination of two or more.

[0027]

[Chemical 10]

The amount of the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) is used in the entire charge transport layer.
It is 10% by weight to 50% by weight, and if it is less than this, the electron transporting ability is lowered. The amount of the hole transport material used is 10 to 50% by weight of the entire charge transport layer, and if it is less than this, the hole transport ability is lowered, and if it is more than this, the binaphthyl tetracarboxylic acid represented by the general formula (1) is used. The concentration of the acid diimide compound becomes low and the electron transporting ability becomes low. The binder used as necessary may be the same as that used in the charge generation layer. The amount of the binder used is 0.1 to 3 weight ratio with respect to the charge transport material, preferably 0.1 to 2
It is a weight ratio. When the amount of the binder used is more than 3% by weight, the concentration of the charge transport material (the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) and the hole transport material) in the charge transport layer becomes small, The sensitivity becomes poor. On the other hand, if it is less than 0.1 weight ratio, the effect as a binder will not be exhibited. Further, as additives used as necessary, antioxidants, quenchers, dispersants, adhesion aids,
A sensitizer etc. can be mentioned. The coating means for the charge transport layer may be the same as that for the charge generation layer.

The thickness of the charge transport layer thus formed is 10 to 50 μm, more preferably 10 to 30 μm.
Is. If the film thickness is larger than 50 μm, it takes a long time to transport the charge, which causes a decrease in sensitivity. on the other hand,
If it is less than 10 μm, the mechanical strength is lowered and the life of the photoreceptor is shortened, which is not preferable. As described above, a function-separated electrophotographic photoreceptor containing a binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) and a hole transport material can be prepared, but in the present invention, a conductive support and If necessary, an undercoat layer, an adhesive layer, a barrier layer, etc. may be provided between the charge generation layers.

Next, the single-layer type photosensitive layer will be described. In this case, the photosensitive layer is composed of a charge generating material, a binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) and a hole transporting material, and a binder and an additive which are optionally used, and these are added to a solvent. It can be obtained by dispersing, dissolving and coating. As the charge generating material, the hole transporting material, the solvent, and the binder and the additive which are optionally used, the same ones as those used in the function separation type can be used. Further, the thin film forming method can also adopt the same method. The amount of the charge generation material used is 0.1% by weight to 10% by weight of the entire photosensitive layer. If the amount is less than this, the amount of generated charges is reduced and the sensitivity of the photoreceptor is lowered. On the other hand, if the amount is larger than this, the potential on the surface of the photoreceptor becomes unstable, which is not preferable. The amount of the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) is from 10% by weight to the entire photosensitive layer.
It is 40% by weight, and if it is less than 40% by weight, the electron transporting ability is lowered. The amount of the hole transport material used is 10 to 40% by weight based on the whole photosensitive layer. If the amount is less than this, the hole transport ability is lowered, and if it is more than this, the electron transport ability is lowered.

The thickness of the photosensitive layer obtained as described above is 5 to 40 μm, and if the thickness is smaller than this, the potential on the surface of the photosensitive member becomes unstable, which is not preferable. On the other hand, if it is thicker than this, the sensitivity tends to decrease. As described above, the general formula
(1) It is possible to prepare a single-layer type electrophotographic photoreceptor containing a binaphthyltetracarboxylic acid diimide compound and a hole transport material represented by, but in the present invention, it is further necessary between the conductive support and the photosensitive layer. An undercoat layer, an adhesive layer, a barrier layer and the like can be provided accordingly.

The electrophotographic photosensitive member thus obtained can be used as either a positive charging type or a negative charging type.
In the case of the positive charging type, first, the surface of the photoreceptor is positively charged by a corona charger or the like. After charging, the charge is generated by the charge generating material by exposure, the negative charges are transported to the surface, and the positive charges on the surface are neutralized. On the other hand, positive charges remain in the unexposed areas. In the case of regular development, negative toner is used, and toner adheres to the portion where this positive charge remains, and development is performed. In the case of reversal development, a positive toner is used, and the toner is attached to the portion where the charge is neutralized, and the toner is developed. As for the negative charging type, first, it is charged negatively by a corona charger or the like. After charging, the charge is generated in the charge generating material by exposure, the positive charges are transported to the surface, and the negative charges on the surface are neutralized. On the other hand, negative charges remain in the unexposed areas. For regular development,
Positive toner is used, and the toner adheres to the portion where the negative charge remains to be developed. In the case of reversal development, a negative toner is used, and the toner is attached to the portion where the charge is neutralized, and development is performed. The electrophotographic photoreceptor of the present invention can be used in any polarity and in any developing method, has high sensitivity and high durability, and can provide high image quality.

[0033]

[Examples] The present invention will be specifically illustrated below with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited thereto.

Synthesis Example Synthesis of Binaphthyltetracarboxylic Acid Diimide Compound (Exemplified Compound (8)) 73 g (18.6 mmol) of binaphthyltetracarboxylic dianhydride in a 500 ml three-necked flask equipped with a stirrer and a cooling tube.
4- (aminomethyl) cyclohexanecarboxylic acid 7 g
(44.8mmol), dimethylformamide (DMF) 300ml
Was charged and refluxed for 15 hours. The hot DMF solution was filtered and the filtrate was cooled to room temperature. After standing for 1 day, the precipitated crystals were filtered, washed twice with water and twice with methanol, and dried. As described above, 9.6 g (yield 77%) of a diimide compound having a terminal carboxylic acid was obtained. Next, the crystals were placed in a 500 ml three-necked flask equipped with a stirrer and a cooling tube,
300 ml of n-butanol and 1 ml of concentrated sulfuric acid were put therein and refluxed for 8 hours. Then, the mixture was left at room temperature for 1 day, and the generated pale red crystals were filtered. The crystals were washed once with n-butanol and twice with methanol, and dried to obtain 10.1 g (yield 90%) of a target compound, a binaphthyltetracarboxylic acid diimide compound (Exemplified compound (8)). ..

Example 1 5 g of X-type metal-free phthalocyanine and 5 g of butyral resin (S-REC BM-2, manufactured by Sekisui Chemical Co., Ltd.) were dissolved in 90 ml of cyclohexanone and kneaded in a ball mill for 24 hours.
The obtained dispersion was applied onto an aluminum plate with a bar coater so that the film thickness after drying was 0.15 μm, and dried to form a charge generation layer. Next, 5 g of a binaphthyltetracarboxylic acid diimide compound (compound (8)), 5 g of diethylaminobenzaldehyde diphenylhydrazone (CT-1), and 5 g of a polycarbonate resin (Lexan 131-111, manufactured by Engineering Plastics Co., Ltd.) were added to 90 ml of dichloroethane.
Was dissolved in, and was applied onto the previously formed charge generation layer by a blade coater so that the film thickness after drying was 25 μm, and dried to form a charge transport layer.

The function-separated bipolar electrophotographic photoreceptor thus produced was charged with a corona voltage of 4.5 kV using EPA-8100 manufactured by Kawaguchi Electric Co., Ltd., and the initial potential V ₀ was 640 V. there were. The surface potential V ₂ after standing for 2 seconds in the dark became 630V. Then, a semiconductor laser having an oscillation wavelength of 780 nm was irradiated to determine the half-exposure amount E _1/2, which was 0.40 μJ / cm ² and the residual potential V _R was 5.1V. Next, after repeating the above operation 5000 times, V ₀ , V
₂ , E _1/2 and V _R were measured and found to be 630V and
620V, 0.41μJ / cm ² , and 10.7V, showing high sensitivity and high durability. Next, using the same evaluation machine, the same photoreceptor, -4.
Charged with a corona voltage of 5kV and set the initial V ₀ , V ₂ , E
_1/2, was measured V _R, respectively -630V, -610
V, 0.39 μJ / cm ² , and -3.7V. After 5000 iterations _{V 0, V 2, E 1/2} , was measured V _R, respectively ^{-620V, -610V, 0.40μJ / cm 2} , a -8.7V, high sensitivity, showed high durability It was As described above, both positive charging and negative charging showed high sensitivity and high durability.

Examples 2 to 8 Photosensitive members were prepared in the same manner as in Example 1 except that the binaphthyltetracarboxylic acid diimide compounds having the compound numbers shown in Table 1 were used, and their performances were evaluated. The results are shown in Table 1. As in Example 1, both positive charging and negative charging showed high sensitivity and high durability.

[0038]

[Table 1]

Examples 9 to 12 Photoreceptors were prepared in the same manner as in Example 1 except that the compound having the compound number shown in Table 2 was used as the hole transport material, and the performance was evaluated. The results are shown in Table 2. As in Example 1, both positive charging and negative charging showed high sensitivity and high durability.

[0040]

[Table 2]

Example 13 1 g of X-type metal-free phthalocyanine, 5 g of binaphthyltetracarboxylic acid diimide compound (compound (8)), 5 g of diethylaminobenzaldehyde diphenylhydrazone (CT-1),
5 g of polycarbonate resin (Lexan 131-111, manufactured by Engineering Plastics Co., Ltd.) was added to dichloroethane.
It was dissolved in 90 ml and coated on an aluminum plate with a blade coater so that the film thickness after drying was 30 μm, and dried to form a photosensitive layer. The single-layer bipolar electrophotographic photosensitive member thus produced was charged with a corona voltage of 4.5 kV using EPA-8100 manufactured by Kawaguchi Electric Co., Ltd., and the initial potential V ₀ was 620 V. The surface potential V ₂ after standing for 2 seconds in the dark became 600V. Then, a semiconductor laser with an oscillation wavelength of 780 nm was irradiated to obtain the half-exposure amount E _1/2 .
It was 0.40 μJ / cm ² and the residual potential V _R was 4.3V.
Next, after repeating the above operation 5000 times, V ₀ , V ₂ , E
_1/2, was measured V _R, respectively 630V, 610
V, 0.41 μJ / cm ² , and 10.8 V, showing high sensitivity and high durability. Next, using the same evaluation machine, the same photoconductor, -4.5kV
Is charged with a corona voltage, the initial _{V 0, V 2, E 1/2} ,
Measurement of the V _R, respectively -620V, -600V, 0.
It was 39 μJ / cm ² and −6.0V. V after repeating 5000 times
_{When 0} , V ₂ , E _1/2 , and V _R were measured, each was −6
The values were 00V, -590V, 0.40 µJ / cm ² , and -10.7V, which showed high sensitivity and high durability. As described above, both positive charging and negative charging showed high sensitivity and high durability.

Comparative Example 1 Instead of the binaphthyltetracarboxylic acid diimide compound
A photoreceptor was prepared in the same manner as in Example 1 except that 2,4,7-trinitro-9-fluorenone was used, and the performance was evaluated. Early V ₀ in the positive charge, V _2, E _1/2, was measured V _R, respectively 620V, 610V, 0.66μJ / cm
² , 41.1V. V ₀ , V ₂ , E after 5,000 repetitions
_1/2, was measured V _R, respectively 570V, 520V, 2.
It was 17 μJ / cm ² and 137.3 V, and was inferior in both sensitivity and durability. Next, in negative charging, the initial V ₀ , V ₂ , E
_1/2, was measured V _R, respectively -580V, -570
V, 0.78 μJ / cm ² , and -54.6V. After 5000 iterations _{V 0, V 2, E 1/2} , was measured V _R, respectively ^{-540V, -510V, 3.36μJ / cm 2} , a -149.9V, inferior sensitivity and durability both there were. As described above, both positive charging and negative charging were inferior in sensitivity and durability.

Claims (1)

[Claims] 1. A conductive support and a photosensitive layer formed thereon are essential components, and the photosensitive layer contains a binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) and a hole transport material. A bipolar electrophotographic photosensitive member characterized in that [Chemical 1] (In the formula, R represents an alkyl group having 8 or less carbon atoms, an aralkyl group or an aryl group, and Rc represents a cycloalkylene group or an arylene group having 8 or less carbon atoms. A ₁ and A ₂ are the same or different and each is a hydrogen atom. Represents an alkyl group having 4 or less carbon atoms, a nitro group, a cyano group, a carboxylic acid ester group or a halogen atom.)