JPH05158259A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To provide an electrophotographic sensitive body having high sensitivity and high durability. CONSTITUTION:This electrophotographic sensitive body has an electric conductive substrate, an electric charge generating layer and an electric charge transferring layer as essential constituent elements and the electric charge generating layer contains binaphthyltetracarboxylic acid diimide represented by the formula [where R is <=8C alkyl, aralkyl or aryl, each of R' and R'' is <=8C alkylene, R' and R'' may be different from each other, Rc is 8C cycloalkylene or arylene, each of A1 and A2 is H, <=4C alkyl, nitro, cyano, carboxylic ester or halogen and each of (k), (m) and (n) is 0 or 1 but all of (k), (m) and (n) are not 0].

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrophotographic photoreceptor,
More specifically, it relates to a highly sensitive and highly durable electrophotographic photoreceptor containing a specific binaphthyltetracarboxylic acid diimide compound in the charge generation layer.

[0002]

2. Description of the Related Art In recent years,
The development of copying machines and printers using electrophotography is remarkable, and various forms, types, and functions of models have been developed according to the application, and a wide variety of photoconductors to be used are being developed. .. 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 an organic photoreceptor, a function in which a charge generation layer is provided on a conductive support and a charge transport layer containing a hole transport material typified by hydrazone compounds, triarylamine compounds, stilbene compounds, etc. is further provided thereon. Separation type is the mainstream. However, with respect to the organic photoconductor, problems remain in its sensitivity and durability, and it is strongly desired to develop an organic photoconductor with high sensitivity and high durability.

One of the causes of the low sensitivity of the organic photoreceptor is considered to be the low charge generation efficiency of the charge generating material such as an azo compound, a phthalocyanine compound, a polycyclic quinone compound and a perylene compound. This charge generation efficiency is almost 100% for inorganic compounds, but 30-40% for organic compounds.
Is. Various attempts have been made to increase the charge generation efficiency. One of them is addition of an acceptor compound, for example, addition of dimethyl terephthalate, benzoquinone compound, trinitrofluorenone, etc. has been tried (Electrophotographic Society Journal, Vol. 24, No. 1, p. 2 (1985).
Year)). However, although the charge generation efficiency has been improved in all cases, there are problems in safety, stability, compatibility, etc., and no satisfactory results have been obtained. On the other hand, it is considered that the reason why the durability of the organic photoreceptor is poor is not only deterioration of the materials such as the charge generating material and the charge transporting material used, but also the accumulation of space charge during repeated use. ing. This causes an increase in residual potential, a decrease in initial potential, and the like, resulting in a decrease in image density, blurring of characters, a decrease in contrast, and the like. In particular, accumulation of negative charges in the charge generation layer is considered to be an important factor for photoconductor fatigue, and addition of an acceptor compound has been proposed as a method for removing it (for example, Journal of Electrophotographic Society,
Volume 30, Issue 1, Page 2 (1991)). As the acceptor compound, for example, the same compounds as described above can be used, but the same problems as described above will occur.

As described above, many problems remain in the improvement of the sensitivity and the durability of the organic photoconductor, and there is a strong demand in the technical field for a high-performance photoconductor which is an improvement thereof. It's a reality. This is the purpose of the present invention,
It is an object of the present invention to provide an electrophotographic photosensitive member having high sensitivity and high durability as a solution to this problem.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a binaphthyltetracarboxylic acid diimide compound represented by the following general formula (1) as an acceptor compound in a charge generation layer. Found that the electrophotographic photoconductor containing in 1 has excellent high sensitivity and high durability,
The present invention has been completed. That is, the present invention is characterized in that the conductive support, the charge generation layer, the charge transport layer are essential components, and the charge generation layer contains a binaphthyltetracarboxylic acid diimide compound represented by the general formula (1). An electrophotographic photoreceptor is provided.

[0007]

[Chemical 2]

(Wherein R is an alkyl group having 8 or less carbon atoms,
Aralkyl group or an aryl group, R ', R "is the same or different from each carbon atoms to 8 following alkylene groups, Rc is .A ₁ showing a cycloalkylene group or an arylene group having 8 or less carbon atoms,
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. k, m, and n are the same or different and are integers of 0 or 1, and k, m, and n are not all 0. ) 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 having 8 or less carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, isopentyl, neopentyl, n.
Groups such as -hexyl, n-heptyl, n-octyl, and the like, and the aralkyl group is a phenyl group or the like in which the aryl group portion is unsubstituted or substituted with an alkyl group and the like, and the alkylene group portion has 1 to 1 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 and the like. R'and R "are the same or different and represent a linear or branched alkylene group having a carbon number of 8 or less, and include, for example, methylene, ethylene, propylene, trimethylene, butylene, isobutylene, tetramethylene, n-pentylene, isopentylene, neopentylene, Examples thereof include groups such as n-hexylene and n-octylene, preferably a methylene group and an ethylene group, Rc represents a cycloalkylene group having 8 or less carbon atoms or an arylene group, and examples of the cycloalkylene group include: Cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene,
A group such as cyclooctylene can be mentioned, and a cyclohexylene group is preferable. Further, examples of the arylene group include a phenylene group and a naphthylene group. k, m, and n are the same or different and are integers of 0 or 1, and all are not 0.

In the general formula (1), 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. Examples of the alkyl group having the number of 4 or less include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and the like. Examples of the halogen atom include chlorine atom, fluorine atom and bromine atom. Further, A ₁ and 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) H ₂ N- (R ") _n- (Rc) _m- (R ') _k -COOR (2) (wherein R, R', R", Rc, k, m, n are expressed by the formula ( Same as 1))
It can be obtained by condensing the ω-amino acid ester represented by and binaphthyltetracarboxylic dianhydride. As another method, first, the general formula (3) H ₂ N- (R ") _n- (Rc) _m- (R ') _k -COOH (3) (wherein R, R', R", Rc, k, m and n are the same as in formula (1))
The target compound can be obtained in high yield by condensing the ω-amino acid represented by and the binaphthyltetracarboxylic dianhydride and then esterifying.

The N-substituted alkyl group of the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) thus produced is substituted with a carboxylic acid ester group. By doing so, the acceptor property can be exhibited, and the sensitivity of the photoconductor can be increased. Not only that, the stability thereof can be markedly increased as compared with the fluorenone-based electron transport material, and the compatibility with the solvent and the binder can be greatly improved. In addition, it has almost no crystallinity, and it was not observed that it remains in an amorphous state at room temperature and deteriorates during use. The binaphthyl tetracarboxylic acid diimide compound is described in German Patent No. 2306399, but it has not been described at all in its application to an electrophotographic photoreceptor, and its effectiveness has been clarified in the present invention. .. Further, although the German patent exemplifies a binaphthyltetracarboxylic acid diimide compound having a terminal ester group, the effectiveness of the ester group is not mentioned. The present invention has found that the ester group improves the stability, high acceptor property, and compatibility of the compound, and has found that the application to an electrophotographic photoreceptor is effective.

Representative examples of the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) used in the present invention include the following (compounds (4) to (41)). 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]

[0020]

[Chemical 10]

[0021]

[Chemical 11]

[0022]

[Chemical 12]

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,
For example, the charge generation layer and the charge transport layer are formed in a thin film on the conductive support. As the base material of the conductive support,
A metal such as aluminum or nickel, a metal vapor deposition polymer film, a metal laminated polymer film, or the like can be used, and the conductive support is formed in a drum shape, a sheet shape, or a belt shape.

The charge generation layer comprises a charge generation material and the general formula (1)
The binaphthyl tetracarboxylic acid diimide compound represented by, and optionally a binder and an additive, can be prepared by a method such as a vapor deposition method, a plasma CVD method, or a coating method. The charge generating material is not particularly limited,
Any material that absorbs light having a specific wavelength to be irradiated and efficiently generates an electric charge can be suitably used.
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. The charge generating material is mainly dispersed in a solvent and a binder, and the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) is dissolved in the solvent to prepare a coating solution, and charge generation is performed by coating. Layers can be formed. The thickness of the formed charge generation layer is 0.1 to
2.0 μm is preferable, and 0.1 to 1.0 μm is more preferable. The amount of the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) is 0.0
It is from 01 to 80% by weight, preferably from 0.01 to 60% by weight. If the amount is less than 0.001% by weight, the effect of increasing the sensitivity and durability cannot be expected, and if the amount is more than 80% by weight, the concentration of the charge generating material is low, resulting in insufficient sensitivity.

The binder used if necessary is not particularly limited as long as it is an insulating resin. For example, a condensation polymer such as polycarbonate, polyarylate, polyester, polyamide; polyethylene, polystyrene, styrene-acrylic 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.

Further, as an additive used if necessary, an antioxidant, a quencher, a dispersant, an adhesion aid, a sensitizer and the like can be mentioned. 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, a charge transport layer containing a hole transport compound (charge transport material) is formed in a thin film on the charge generation layer. A coating method is mainly used as a thin film forming method,
The charge transport material may be dissolved in a solvent together with a binder and an additive used if necessary, and applied on the charge generation layer, and then dried. The charge transport material used is not particularly limited, and examples thereof include hydrazone compounds, stilbene compounds, triarylamine compounds, pyrazoline compounds, oxadiazole compounds,
Oxazole compounds, polyvinylcarbazole compounds,
Any triphenylmethane compound or the like can be preferably used. As a typical example of these, the following formula (42) is used.
~ (46) are listed.

[0029]

[Chemical 13]

The solvent used is not particularly limited as long as it is a solvent in which the above compounds and the binder used as the case requires, and the charge generation layer does not dissolve.
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,
It is preferably 0.1 to 2 weight ratio. When the amount of the binder used is more than 3% by weight, the concentration of the charge transport material in the charge transport layer becomes small and 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. In addition, examples of additives that can be used as needed include antioxidants, quenchers, dispersants, adhesion aids, and sensitizers. 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, an electrophotographic photoreceptor containing the binaphthyltetracarboxylic acid diimide compound represented by the general formula (1) in the charge generation layer can be prepared, but in the present invention, a conductive support and a charge generation layer are further added. An undercoat layer, an adhesive layer, a barrier layer and the like can be provided between the layers, if necessary.

When the electrophotographic photosensitive member thus obtained is used, the surface of the photosensitive member is first charged negatively by a corona charger or the like. After charging, by exposing, charge is generated in the charge generation layer, and positive charges are injected into the charge transport layer,
This is transported to the surface through the charge transport layer, and the surface negative charges are neutralized. Further, the negative charges generated in the charge generation layer are transported to the conductive substrate to neutralize the positive charges. On the other hand, negative charges remain in the unexposed areas. In the case of regular development, positive 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 negative toner is used, and the toner is attached to the portion where the charge is neutralized, and development is performed. The electrophotographic photosensitive member of the present invention can be used in any developing method and can provide high image quality.

[0033]

EXAMPLES The present invention will now be specifically illustrated with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 X-type metal-free phthalocyanine (5 g), binaphthyltetracarboxylic acid diimide compound (compound (20)) (1 g) and butyral resin (S-REC BM-2, manufactured by Sekisui Chemical Co., Ltd.) (5 g) were dissolved in 90 ml of cyclohexanone. It was kneaded for 24 hours in a ball mill. The resulting dispersion was applied onto an aluminum plate with a bar coater so that the film thickness after drying would be 0.15 μm, and dried to form a charge generation layer. Next, diethylaminobenzaldehyde diphenylhydrazone (compound (42)) 5
g, 5 g of polycarbonate resin (Lexan 131-111, manufactured by Engineering Plastics Co., Ltd.) are dissolved in 90 ml of dichloroethane, and the film thickness after drying with a blade coater is 25 μm on the charge generation layer previously formed. Thus coated and dried to form a charge transport layer.

The electrophotographic photosensitive member produced in this manner was manufactured by Kawaguchi Electric Co., Ltd., an electrostatic copying paper test apparatus EPA-
When charged with a corona voltage of −5.5 kV using 8100, the initial surface potential V ₀ was −830 V. 2 in the dark
The surface potential V ₂ after standing for ₂ seconds became −820V. Then, a semiconductor laser with an oscillation wavelength of 780 nm is irradiated to halve the exposure amount E.
_{When 1/2} was obtained, it was 0.29 μJ / cm ² , and the residual potential V
_R was -1.6V. Next, after repeating the above operation 5000 times and measuring V ₀ , V ₂ , E _1/2 and V _R ,
It was −820 V, −800 V, 0.29 μJ / cm ² , and −4.8 V, respectively, and the performance of the photoreceptor was not deteriorated, and high sensitivity and high durability were exhibited.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1, except that the binaphthyltetracarboxylic acid diimide compound was omitted.
Performance evaluation was performed. As a result, the initial V ₀ , V ₂ , E
_1/2, V _R respectively -810V, -780V, 0.62μJ / c
m ^2, was -35V. Next, after repeating the above operation 5000 times and measuring V ₀ , V ₂ , E _1/2 and V _R ,
The values were -780 V, -760 V, 0.78 µJ / cm ² , and -78.5 V, respectively, and both were inferior in sensitivity and durability.

Examples 2 to 8 Example 1 was repeated except that the binaphthyltetracarboxylic acid diimide compounds having the numbers shown in Table 1 were used.
A photoconductor was prepared in the same manner as above, and the performance was evaluated. The results are shown in Table 1, and like the results of Example 1, high sensitivity and high durability were exhibited.

[0038]

[Table 1]

Examples 9 to 12 Photoreceptors were prepared in the same manner as in Example 1 except that the charge transporting materials having the numbers shown in Table 2 were used, and their performances were evaluated. The results are shown in Table 2, and Example 1
Similar to the result of 1., it showed high sensitivity and high durability. Comparative Examples 2 to 5 Photosensitive members were prepared and performance evaluations were carried out in the same manner as in Examples 9 to 12 except that the binaphthyltetracarboxylic acid diimide compound was excluded. The results are shown in Table 2, and both were inferior in sensitivity and durability.

[0040]

[Table 2]

Example 13 A photoconductor was prepared in the same manner as in Example 1 except that dibromoanthanthrone represented by the following formula (47) was used in place of the X-type metal-free phthalocyanine, and a semiconductor laser was used as an irradiation light source. The performance was evaluated in the same manner except that a halogen lamp with an illuminance of 5 lux was used instead.
As a result, the initial _{V 0, V 2, E 1/2} , each _{V R -840V, -820V, 1.2 lux} · sec, was -4.3V.
Next, after repeating the operation 5000 times, V ₀ , V ₂ , E _1/2 ,
Measurement of the V _R, respectively -830V, -820V,
It was 1.3 lux · sec and −9.8 V, and was excellent in both sensitivity and durability.

[0042]

[Chemical 14]

Comparative Example 6 A photoconductor was prepared in the same manner as in Example 13 except that the binaphthyltetracarboxylic acid diimide compound was omitted, and the performance was evaluated. As a result, the initial V ₀ , V ₂ ,
E _1/2, V _R, respectively -810V, -800V, 2.4 lux ·
It was sec and -47.0V. Next, after repeated 5000 times _{operation, V 0, V 2, E} 1/2, was measured for V _R, are each -780V, -760V, 4.1 lux · sec , -127.7V, sensitivity, durability Both were inferior.

Comparative Example 7 A photoconductor was prepared in the same manner as in Example 1 except that trinitrofluorenone represented by the following formula (48) was used in place of the binaphthyltetracarboxylic acid diimide compound, and the performance was evaluated. As a result, the initial V ₀ , V ₂ , E _1/2 ,
V _R respectively ^{-800V, -780V, 0.32μJ / cm 2} , -6.2
It was V. Next, after repeating the operation 5000 times, V ₀ , V
₂ , E _1/2 , V _R were measured and found to be -620V,
It was −530 V, 0.71 μJ / cm ² , and −37.7 V, and the durability was poor.

[0045]

[Chemical 15]

Claims (1)

[Claims] 1. A conductive support, a charge generating layer, and a charge transporting layer are essential components, and the charge generating layer contains a binaphthyltetracarboxylic acid diimide compound represented by the general formula (1). Electrophotographic photoreceptor. [Chemical 1] (In the formula, R is an alkyl group having 8 or less carbon atoms, an aralkyl group or an aryl group, R ′ and R ″ are the same or different and are alkylene groups having 8 or less carbon atoms, and Rc is a cycloalkylene group having 8 or less carbon atoms or Represents 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, and k, m and n are They are the same or different and are integers of 0 or 1, and k, m, and n are not all 0.)