JPH0519505A - Bipolar electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain high sensitivity and high durability by using a conductive substrate and a photosensitive layer formed on the substrate as essential structural elements and incorporating a specified naphthalenedicarboximido compound and a positive hole transfer material in the photosensitive layer. CONSTITUTION:The photosensitive layer contains naphthalenedicarboximido compound represented by formula I and the positive hole transfer material and in formula I, R is <=8 C alkyl, aralkyl, or aryl; Rc is <=8 C cyclo alkylene or arylene; and each of A1 and A2 is, independently, H, <=4 C alkyl, nitro, cyano, carboxylate, or halogen. This compound of formula I can be synthesized by the known method used for synthesizing general carboximido compounds.

Description

Detailed Description of the Invention

[0001]

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

[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 charge separation type organic photoconductor is mainly used in reversal development type printers using negative toner, and there is a strong demand for high sensitivity and high durability that enable 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 and high durability including a naphthalene dicarboxylic acid imide compound and a hole transport material which are excellent electron transporting compounds as a solution to such problems in the photosensitive layer. An object is to provide a bipolar electrophotographic photoreceptor.

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems, and as a result, completed the present invention. 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 a naphthalenedicarboxylic acid imide 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), Rc represents a cycloalkylene group or an arylene group having 8 or less carbon atoms, and examples of the cycloalkylene group 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. R represents an alkyl group having 8 or less carbon atoms, an aralkyl group or an aryl group, and as the alkyl group,
For example, 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.
A benzyl group can be mentioned as the aralkyl group. Examples of the aryl group include a phenyl group and a naphthyl group. In the general formula (1), A ₁ , A ₂
Are the same or different and represent 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-propyl. And groups such as isopropyl, n-butyl, isobutyl, sec-butyl and the like. Examples of the halogen atom include chlorine atom, fluorine atom and bromine atom.

The naphthalenedicarboxylic acid imide compound represented by the general formula (1) in the present invention can be synthesized according to a known method used in the synthesis of ordinary carboxylic acid imides. For example, a ω-amino acid ester represented by the general formula (2) H ₂ N-CH ₂ -Rc-COOR (2) (wherein R and Rc are the same as those in the formula (1)) is condensed with naphthalene dicarboxylic acid anhydride. Can be obtained by Alternatively,
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)) is condensed with naphthalene dicarboxylic acid anhydride, and then, The target compound can be obtained in high yield by esterification with.

The thus-prepared naphthalenedicarboxylic acid imide compound represented by the general formula (1) has a bulky cycloalkylene or arylenecarboxylic acid ester group substituted at the terminal of the N-substituted alkyl group. By doing so, a conventionally known naphthalenedicarboxylic acid imide compound (Journal of the American Chemical Society, 89, 23, 5925 (19
67)), the stability can be increased significantly,
It has become possible to greatly improve the compatibility with solvents and binders. Further, it has almost no crystallinity, maintains an amorphous state at room temperature, and is not observed to deteriorate during use. Furthermore, due to the steric hindrance of the cycloalkylene group or the arylene group, it does not form a charge transfer complex with a donor compound such as a hole transporting compound, and the naphthalenedicarboxylic imide compound represented by the general formula (1) As for the hole transporting compound, the charge transporting ability is improved as the concentration thereof is increased, and the sensitivity of the photoreceptor can be improved.

Typical examples of the naphthalenedicarboxylic acid imide compound represented by the general formula (1) used in the present invention include the following compounds (compounds (4) to (38)). The invention is not limited to these.

[0013]

[Chemical 3]

[0014]

[Chemical 4]

[0015]

[Chemical 5]

[0016]

[Chemical 6]

[0017]

[Chemical 7]

[0018]

[Chemical 8]

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 containing both the charge generating material and the charge transporting material in the same layer. Is.

First, the function-separated type photoreceptor 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 as 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.

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 naphthalene dicarboxylic acid imide compound and the hole transport material is formed into a thin film.
The coating method is mainly used as a thin film forming method, and the general formula
(1) a naphthalenedicarboxylic acid imide compound represented by
Further, the hole transport material may be dissolved in a solvent together with a binder and an additive used if necessary, and the solution may be coated on the charge generation layer and then dried. The solvent to be used is not particularly limited as long as it is a solvent in which the above compound and the binder used as necessary are dissolved and the charge generating layer is not dissolved. As the hole transporting material, a generally known hole transporting material can be used, and for example, a hydrazone compound, a stilbene compound, a triarylamine compound, a pyrazoline compound, an oxadiazole compound, an oxazole compound, a polyvinylcarbazole compound, Examples thereof include triphenylmethane compounds, and typical examples thereof include the following formulas (CT-1) to (CT-
Examples include those shown in 5). These can be used alone or in combination of two or more.

[0025]

[Chemical 9]

The naphthalenedicarboxylic acid imide compound represented by the general formula (1) is used in an amount of 10% by weight to 50% by weight based on the entire charge transport layer. The amount of the hole transport material used is 10 of the entire charge transport layer.
If it is less than this, the hole transporting ability is lowered, and if it is more than 50% by weight, the concentration of the naphthalenedicarboxylic acid imide compound represented by the general formula (1) is lowered and the electron transporting ability is lowered. 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% by weight, preferably 0.1 to 2% by weight, based on the charge transport material. If the amount of the binder used is more than 3% by weight, the concentration of the charge transport material (the naphthalene dicarboxylic acid imide compound represented by the general formula (1) and the hole transport material) in the charge transport layer becomes small, and the sensitivity is lowered. Becomes worse. 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, a function-separated electrophotographic photoreceptor containing the naphthalene dicarboxylic acid imide compound represented by the general formula (1) and a hole transport material can be prepared. If necessary, an undercoat layer, an adhesive layer, a barrier layer, etc. may be provided between the generating 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 naphthalene dicarboxylic acid imide 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 dispersed in a solvent. It can be obtained by 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 charge generating material used is 0.1% to 10% by weight of the entire photosensitive layer.
If the amount is less than this, the amount of electric charges generated is reduced, and the sensitivity of the photoconductor is lowered. If more than this,
This is not preferable because the potential on the surface of the photoreceptor becomes unstable. General formula
The amount of the naphthalene dicarboxylic acid imide compound represented by (1) is 10% by weight to 40% by weight of the entire photosensitive layer,
If it is less than this, 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
Although it is possible to produce a single-layer type electrophotographic photoreceptor containing a naphthalene dicarboxylic acid imide compound and a hole transport material represented by (1), in the present invention, if necessary between the conductive support and the photosensitive layer. It is also possible to provide an undercoat layer, an adhesive layer, a barrier layer and the like.

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.

[0031]

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 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 naphthalenedicarboxylic acid imide 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 dissolved in 90 ml of dichloroethane. This was coated on the previously formed charge generation layer with a blade coater so that the film thickness after drying was 25 μm, and dried to form a charge transport layer.

The functionally 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 630 V. there were. The surface potential V ₂ after standing for 2 seconds in the dark became 620V. 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 5.5V.
Next, after repeating the above operation 5000 times, V ₀ , V ₂ , E
_{When 1/2} and V _R were measured, they were 620 V and 610, respectively.
V, 0.40 μJ / cm ² , 9.8 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 -600V, -590V, 0.4
It was 0 μJ / cm ² and −6.3V. After 5000 iterations _{V 0, V 2, E 1/2} , was measured V _R, respectively ^{-590V, -580V, 0.41μJ / cm 2} , a -13.7V, 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 10 Example 1 was repeated except that the naphthalenedicarboxylic acid imide compounds having the compound 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. As in Example 1, both positive charging and negative charging showed high sensitivity and high durability.

[0035]

[Table 1]

Examples 11 to 14 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.

[0037]

[Table 2]

Example 15 X-type metal-free phthalocyanine 1 g, naphthalenedicarboxylic acid imide compound (compound (8)) 5 g, diethylaminobenzaldehyde diphenylhydrazone (CT-1) 5 g, polycarbonate resin (Lexan 131-111, Engineering Plastics (stock) 5 g) was dissolved in 90 ml of dichloroethane, 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. Using the EPA-8100 manufactured by Kawaguchi Electric Mfg. Co., Ltd., the single-layer bipolar electrophotographic photoreceptor thus prepared was used.
When charged with a corona voltage of 5 kV, the initial potential V ₀ was
It was 640V. The surface potential V ₂ after standing for 2 seconds in the dark is 6
It became 20V. Next, irradiation with a semiconductor laser with an oscillation wavelength of 780 nm was carried out, and the half-exposure amount E _1/2 was determined to be 0.39 μJ /
cm ^2, and the residual potential V _R was 4.0V.

Next, after repeating the above operation 5000 times, V
_{When 0} , V ₂ , E _1/2 , and V _R were measured, each was 6
30V, 610V, 0.40μJ / cm ² , 11.3V, high sensitivity,
It showed high durability. Next, the same photoreceptor was charged with a corona voltage of −4.5 kV using the same evaluation machine to obtain the initial V ₀ , V
₂ , E _1/2 , V _R were measured, each was -630
V, -620V, 0.40 μJ / cm ² , and -5.0V. V ₀ after 5000 iterations, V _2, E _1/2, was measured for V _R, respectively ^{-630V, -620V, 0.41μJ / cm 2} , -10.0
V, showing high sensitivity and high durability. As mentioned above,
Both positive charging and negative charging showed high sensitivity and high durability.

Comparative Example 1 2,4,7 instead of the naphthalene dicarboxylic acid imide compound
A photoreceptor was prepared in the same manner as in Example 1 except that -trinitro-9-fluorenone was used, and the performance was evaluated. Initially measured V ₀ , V ₂ , E _1/2 , and V _R in positive charging were 620 V, 610 V, 0.66 μJ / cm ² , 41.
It was 1V. V ₀ , V ₂ , E _1/2 after repeating 5000 times,
V _R was measured and found to be 570V, 520V, and 2.17, respectively.
It was μJ / cm ² and 137.3 V, and both sensitivity and durability were poor. 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 for V _R, respectively ^{-540V, -510V, 3.36μJ / cm 2} , -14
The voltage was 9.9 V, and both sensitivity and durability were poor.
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 naphthalene dicarboxylic acid imide compound represented by the general formula (1) and a positive layer are contained in the photosensitive layer. A bipolar electrophotographic photoreceptor comprising a hole transport material. [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.)