JPH02113258A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain the electrophotographic sensitive body which has high sensitivity and with which the potential at the time of repetitive use is stably maintained by providing a charge generating layer contg. a disazo pigment having a specific structure and a charge transfer layer contg. a styryl compd. having a specific structure to the photosensitive body. CONSTITUTION:This photosensitive body has the charge generating layer and the charge transfer layer on a conductive base. The charge generating layer contains the disazo pigment expressed by the formula I as a charge generating material and the charge transfer layer contains the styryl compd. expressed by the formula II or the formula III as a charge transfer material. In the formulas I to III, R1 to R4 denote an alkyl group, aralkyl group, etc.; R5, R6 denote a hydrogen atom, alkoxy group, etc.; Ar1 to Ar3 denote an arom. cyclic group, heterocyclic group, X1 to X4 denote a hydrogen atom, alkyl group, etc.; Z denotes an oxygen atom, sulfur atom; Y denotes a single bond, -CH2-CH2, etc. The electrophotographic sensitive body having the high sensitivity and the excellent potential stability is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically, a charge generation layer containing a charge generation substance and a carrier on which the charge generation substance has been generated are received and transported. The present invention relates to a laminated electrophotographic photoreceptor having a charge transport layer containing a charge transport material.

[Prior art]

Such organic photoreceptors include photoconductive polymers typified by poly-N-vinylcarbazole and 2.
Electrophotographic photoreceptors having a photosensitive layer mainly composed of a charge transfer complex formed from a Lewis acid such as 4,7-dolinitro-9-fluorenone have already been put to practical use. However, this photoreceptor is not necessarily satisfactory in sensitivity and durability.

On the other hand, functionally separated electrophotographic photoreceptors, in which charge generation and charge transport functions are performed by separate materials, have brought about significant improvements in sensitivity and durability, which were considered to be shortcomings of conventional organic photoreceptors. Such a functionally separated photoreceptor has a wide range of materials to choose from for charge-generating substances and charge-transporting substances.
This method has the advantage that an electrophotographic photoreceptor having arbitrary characteristics can be produced relatively easily. In particular, as electrophotographic photoreceptors have come to be used not only in copiers but also in laser beam printers, LED printers, etc. in recent years,
A functionally separated type is suitable for setting a spectral sensitivity range that matches the emission wavelength of the light source used.

As charge generating substances, various azo pigments, phthalocyanine pigments, polycyclic quinone pigments, cyanine dyes, squaric acid dyes, pyrylium salt dyes, and the like are known. Among them, many structures have been proposed for azo pigments because of their strong light resistance, large charge generation ability, and ease of material synthesis. For example, as a disazo pigment similar to the present invention, JP-A-56-1
No. 16040, JP-A-57-182747,
JP-A-58-49952, JP-A-58-1154
No. 47, JP-A-59-72448, JP-A-Sho 5
Publication No. 9-155848.

JP-A-58-115445, JP-A-58-115
446, Japanese Unexamined Patent Publication No. 59-7365, etc. are already known. The azo pigment used here as a charge-generating substance is required to (i) be stable against heat and light, and (it) be easy to disperse if it exhibits charge-generating ability in a separated state. and (iii) the charge generation ability does not change with temperature, (iv) the characteristics do not change during repeated use, (V) the spectral sensitivity range is effective for the light source used. and (vi) the charge transport substance is not limited. In practical terms, it is important to satisfy these requirements at a high level on average. Although some of the above-mentioned known pigments satisfy some of the above requirements, none satisfy all of them to a high level.

On the other hand, hydrazone compounds, pyrazoline compounds, stilbene compounds, triarylmethane compounds, arylamine compounds, and the like are known as charge transport substances. These compounds are required to (i) be stable against light and heat, (it) be stable against ozone, NO, nitric acid, etc. generated by corona discharge, and (if
) exhibiting high transport ability; and (iv) exhibiting high compatibility with organic solvent binders.

An example of the combination of the above-mentioned known azo pigment and a charge transport substance is disclosed in JP-A-58-18636.

JP-A-57-204551, JP-A-59-440
No. 50, JP-A-59-44051, JP-A-5
9-157644, JP 60-24549, JP 60-24550, JP 60-24
551, JP-A-60-24552, and the like.

Although photoreceptors made with these combinations have little potential fluctuation during repeated use, they often have major drawbacks in image characteristics, such as image deterioration due to changes in the usage environment (this is a problem in actual use). It has become.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a functionally separated photoreceptor having a charge generation layer and a charge transport layer, which has high sensitivity, maintains a stable potential during repeated use, and is compatible with the usage environment (temperature, humidity). An object of the present invention is to provide an electrophotographic photoreceptor that can exhibit stable sensitivity and image characteristics regardless of fluctuation.

Another object of the present invention is to provide an azo pigment which can be easily dispersed and whose dispersion liquid changes little over time.

Another object of the present invention is to provide an electrophotographic photoreceptor that exhibits sufficiently high sensitivity to light sources in the range of 600 to 700 nm.

Another object of the present invention is to provide a photoreceptor that is stable against ozone, NO, nitric acid, etc. generated by corona discharge.

[Means for solving problems]

As a result of studies by the present inventors, a laminated electrophotographic photoreceptor having a charge generation layer containing a disazo pigment with a specific structure and a charge transport layer containing a styryl compound with a specific structure solves the above problems and is superior. It was discovered that the electrophotographic properties of

That is, the present invention provides a laminated electrophotographic photoreceptor having a charge generation layer and a charge transport layer on a conductive support, in which the charge generation layer is a charge generation substance represented by the general formula (1) or the general formula (3). The electrophotographic photoreceptor is characterized in that it contains a disazo pigment, and the charge transport layer contains a styryl compound represented by the general formula (2) as a charge transport substance.

In general formula (1), R1 and R2 are alkyl groups.

It represents an aralkyl group, an aromatic ring group, or a heterocyclic group, specifically an alkyl group such as methyl, ethyl, propyl, butyl, an aralkyl group such as benzyl, phenethyl, or naphthylmethyl, phenyl, or diphenyl.

Aromatic ring groups such as naphthyl and anthryl, and carbazole, dibenzofuran, and benzimidacylon.

Examples include heterocyclic groups such as benzthiazole, thiazole, and pyridine.

In addition, these alkyl groups, aralkyl groups, aryl groups, aromatic ring groups and heterocyclic groups include, for example, alkyl groups such as methyl, ethyl, and propyl, or alkoxy groups such as methoxy, ethoxy, and propoxy, and fluorine, chlorine, and bromine groups. It may have a halogen atom or a substituent such as a nitro group, a cyano group, or a trifluoromethyl group. ArI and Ar2
represents an aromatic ring group or a heterocyclic group, and specific examples of these aromatic ring groups and heterocyclic groups are the same as above. Further, these aromatic ring groups and heterocyclic groups may have a substituent, such as an alkyl group or an alkoxy group as mentioned above.

Examples include a halogen atom and a cyano group.

X,,X2. X3 and X4 are hydrogen atoms, alkyl groups such as methyl, ethyl, propyl, and methoxy.

It represents an alkoxy group such as ethoxy or propoxy, a halogen atom, a nitro group, a cyano group, or a trifluoromethyl group, and not all of them are hydrogen atoms.

Z represents an oxygen atom or a sulfur atom.

In the general formulas (2) and (3), R3 and R4 represent an alkyl group, an aralkyl group, an aromatic ring group, or a heterocyclic group, and specifically, methyl and ethyl.

It represents alkyl groups such as propyl and butyl, aralkyl groups such as benzyl, phenethyl and naphthylmethyl, aromatic ring groups such as phenyl, diphenyl, naphthyl and anthryl, and heterocyclic groups such as pyridyl, quinolyl, thienyl and furyl. Furthermore, these alkyl groups, aralkyl groups, aromatic ring groups and heterocyclic groups may have substituents (for example, alkyl groups such as methyl, ethyl, propyl, methoxy, ethoxy, propoxy, etc.). alkoxy group,
Examples include halogen atoms such as fluorine, chlorine, and bromine, and nitro groups.

R6 and R8 represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. Specific examples of the alkyl group and alkoxy group are the same as above.

Further, the alkyl group and alkoxy group may have the above-mentioned substituents.

Ar3 represents an aromatic ring group or a heterocyclic group, specifically,
Indicates aromatic ring groups such as phenyl and naphthyl, or heterocyclic groups such as pyridyl, quinolyl, thienyl, and furyl. The aromatic ring group and the heterocyclic group may have a substituent. This Ar
Examples of substituents that 3 may have include alkyl groups such as methyl, ethyl, and propyl, alkoxy groups such as methoxy, ethoxy, and propoxy, halogen atoms such as fluorine, chlorine, and bromine, and nitro groups.

In general formula (3), Y represents a single bond, -CH2CH2- or -CH=CH-.

Further, among the charge-generating substances, the disazo pigment having the structure represented by the general formula (4) is particularly excellent in terms of electrophotographic properties.

General formula (4) In general formula (4), R7 and R8 are hydrogen atoms, methyl,
Alkyl groups such as ethyl and propyl, benzyl.

Aralkyl groups such as phenethyl and naphthylmethyl, aromatic ring groups such as phenyl, naphthyl and anthranyl, methoxy,
Indicates an alkoxy group such as ethoxy or propoxy, a halogen atom such as fluorine, chlorine, or bromine, a nitro group, a cyano group, or a trifluoromethyl group.

R8 and R8° are hydrogen atoms, methyl, and ethyl.

Alkyl groups such as propyl, benzyl, phenethyl.

Aralkyl groups such as naphthylmethyl, aromatic ring groups such as phenyl, naphthyl, anthranyl, and methoxy.

Alkoxy groups such as ethoxy and propoxy, fluorine.

A halogen atom such as chlorine or bromine, a cyano group or a trifluoromethyl group, and an alkyl group, aromatic ring group, or aralkyl group for R7, R8, Ro and Rto.

and alkoxy groups may have substituents (for example, alkyl groups such as methyl, ethyl, propyl, alkoxy groups such as methoxy, ethoxy, propoxy, halogen atoms such as fluorine, chlorine, bromine, nitro groups, cyano group or trifluoromethyl group.

z, Xl, X2. X3 and X4 have the same meaning as in general formula (1).

Representative examples of charge generating substances and charge transporting substances used in the present invention are listed below.

Charge-generating substance G-2 G-13 G-14 I r G-Emperor G-A G-37 G-Hato G-49 G-50 G-Toshi E I G-絽α しIC! G-61 G-62 CF3 G-tei α G-73 G-74 Edge 2 Nυ2 G-86 G-91 G-97 G-98 +04 +05 Shi215 Shi2H5 f (I l UILII s G-121 G-122 GI S Former It CI! Charge Transport Material 1-13 T-62 T-63 The electrophotographic photoreceptor of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing the layer structure of the electrophotographic photoreceptor of the present invention.

The charge generation layer 2 containing the disazo pigment represented by the general formula (1) should contain as much (
containing the above-mentioned photoconductive compound and a thin film layer, e.g.
It is preferable to form a thin film layer having a thickness of 1 μm or less, preferably 0.01 μm to 1 μm.

The charge generating layer 2 can be formed by dispersing the above-mentioned disazo pigment in a suitable binder and coating it on a support, or can be obtained by forming a vapor deposited film using a vacuum vapor deposition apparatus. The binder used in forming the charge generating layer by coating can be selected from a wide variety of insulating resins and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. Preferably,
Polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate,
Examples include insulating resins such as polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is 80% by weight or less,
A suitable amount is preferably 40% by weight or less.

The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the underlying charge transport layer or subbing layer.

Specific organic solvents include methanol, ethanol,
Alcohols such as isopropanol, ketones such as acetone, methyl ethyl ketone, cyclohexanone, N
, amides such as N-dimethylformamide 1N1N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol motumethyl ether,
Methyl acetate.

Esters such as ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, or aromatic compounds such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene etc. can be used.

Coating can be performed using a coating method such as a dip coating method, a spray coating method, a Meyer bar coating method, or a blade coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying at a temperature of 30°C to 200°C for 5 minutes to 2
It can be done stationary or under a draft for a range of hours.

The charge transport layer 3 is electrically connected to the charge generation layer 2 described above, and is capable of receiving and receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. It has a function. At this time, the charge transport layer 3 is preferably laminated on the charge generation layer 2, but the charge transport layer 3 may be laminated below the charge generation layer 2.

The charge transport layer 3 can be formed by dissolving and coating the charge transport material described above together with a suitable binder.

Resins that can be used as binders include, for example, acrylic resins, polyarylates, polyesters, polycarbonates, polystyrene, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formal, polysulfones, polyacrylamides, polyamides, chlorinated rubbers, etc. resin, or poly-N-vinylcarbazole,
Mention may be made of organic photoconductive polymers such as polyvinylanthracene and polyvinylpyrene.

Since the charge transport layer 3 has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. - For boat fishing, the range is 5 μm to 35 μm, but the preferred range is 8 μm.
It is μm to 30 μm. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

A photosensitive layer 4 having such a laminated structure of the charge generation layer 2 and the charge transport layer 3 is provided on the conductive support 1 . As the conductive support 1, the support itself is conductive;
For example, aluminum, aluminum alloy, stainless steel, etc. can be used, and in addition, plastics having a layer formed by vacuum evaporation of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc., conductive A support in which particles (e.g., carbon black, silver particles, etc.) are coated on a plastic or metal support with a suitable binder;
A support made of plastic or paper impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used.

A subbing layer having a barrier function and an adhesive function can also be provided between the conductive support 1 and the photosensitive layer 4.

The subbing layer can be formed from casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. .

The thickness of the undercoat layer is 0.1 μm to 5 μm, preferably 0.1 μm to 5 μm.
A suitable thickness is 5 μm to 3 μm.

The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines, but also in electrophotographic application fields such as laser printers, LED printers, liquid crystal printers, and laser plate making. can be fully expressed.

〔Example〕

The present invention will be explained below with reference to Examples.

Example 1 A 0.1 μm undercoat layer made of vinyl chloride-maleic anhydride-vinyl acetate copolymer resin was provided on an aluminum plate.

Next, 5 g of the above-exemplified disazo pigment (G-13) was added to a solution in which 2 g of butyral resin (degree of butyralization 63 mol%, number average molecular weight 20,000) was dissolved in 95 ml of cyclohexanone, and dispersed in a sand mill for 20 hours.

This dispersion was applied onto the previously formed undercoat layer using a Mayer bar so that the film thickness after drying was 0.5 μm, and dried to form a charge generation layer.

Next, 5 g of the above-exemplified styryl compound (T-39) and 5 g of bisphenol 2 type polycarbonate resin (viscosity average molecular weight 30,000) were dissolved in 70 ml of chlorobenzene, and this was applied onto the charge generation layer so that the film thickness after drying was 22 μm.
A charge transport layer was formed by applying a Mayer bar and drying to prepare photoreceptor No. 1.

The electrophotographic photoreceptor thus prepared was statically charged with a corona charge of -5.5 KV using an electrostatic copying paper tester Model 5P-428 manufactured by Kawaguchi Denki, and after being kept in a dark place for 1 hour, the illuminance was It was exposed to light using a 2j'ux halogen lamp and its charging characteristics were examined. As for the charging characteristics, the surface potential (vo) and the exposure amount (6%) required to attenuate the potential (VD) to A when dark decayed for 1 second were measured.

The results are shown below.

Vo: 720V VD: -700V E'4: 0.99 lux e sec Next, the light intensity of lμW/c was applied to the light source of the electrostatic copy paper tester.
Spectral sensitivity was measured using rd monochromatic light.

Sensitivity is when the surface potential (VO) is -700v and the surface potential is -
Exposure amount required to reach 200V EΔ6oov (μJ/
Crrr) was measured, Crrr was calculated, and plotted against wavelength, the results are shown in FIG.

Furthermore, this photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with a -5.6 KV corona charger, an exposure optical system, a developing device, a transfer charger, a static elimination exposure optical system, and a cleaner, and its image characteristics were examined. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Image characteristics using this copying machine were evaluated in three environments: humidity 10% temperature 5°C, humidity 50% temperature 18°C, and humidity 80% temperature 35°C.

Good images faithful to the original were obtained in both environments. Even after the 10,000th print, no blurring or blurring of the image was observed, indicating that the present photoreceptor exhibited good image characteristics.

Example 2 A photoreceptor was prepared in the same manner as in Example 1 except that disazo pigments G-10, G-11, G-19 and G-14 were used in place of the disazo pigment (G-13) in Example 1. We fabricated and measured the charging characteristics and spectral sensitivity. Charging characteristics are shown in Table 1, and spectral sensitivity is shown in Figure 3.

Table 1 Example photoreceptor No. Disazo pigment Vo (V)
Vo (V) E! 4 (j!ux-sec)2
2 G-10-720-6901,3
433G-11-740-7042, 1144G-14
-700-6501, 5555G-19-700-68
00,90 Comparative Examples 1 and 2 A photoreceptor was prepared in exactly the same manner as in Example 1 except that the following comparative disazo pigment (1) described in JP-A-59-157644 was used. Then, the charging characteristics were investigated in the same manner as in Example 1. Furthermore, a similar evaluation was performed on a comparative pigment (2) having the following structure.

Comparative pigment (2) The results are shown in Table 2.

Table 2 represents a decrease in potential, and a positive sign represents an increase in potential.

From Tables 1 and 2, it can be seen that the electrophotographic photoreceptor according to the present invention has high sensitivity.

Examples 6 to 10 The photoreceptors used in Examples 1 to 5 and Comparative Example 1.2 were used in an electrophotographic machine equipped with a corona charger, an exposure optical system, a developer, a transfer charger, a static elimination exposure optical system, and a cleaner. A photoreceptor was attached to the cylinder. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copying machine, the initial bright area potential (VL) and dark area potential (VD) were set to -200V and -700V, respectively, and the bright area potential (VL100'') and dark area potential (y) after being used 10,000 times. +0000) was measured. The results are shown in Table 3. Note that ΔvD + Δv
From the negative sign in Table 3 for L, it can be seen that the photoreceptor using the disazo pigment of the present invention has less potential fluctuation during repeated use.

Comparative Examples 5-11 Examples 1-5, Comparative Example 1. Photoreceptors were prepared in exactly the same manner as in Examples 1 to 5, except that a hydrazone compound having the following structure was used in place of the styryl compound (T-39) used in Example 2, and the charging characteristics were measured. Further, the amount of potential fluctuation was measured in exactly the same manner as in Examples 6 to 10. The results are shown in Table 4.

Table 4 From Table 4, a photoreceptor having excellent properties can be obtained by combining the disazo pigment of the present invention and a styryl compound. Furthermore, it can be seen that in the disazo pigment of the present invention, even if the charge transporting substance is changed, the characteristics deteriorate little and the range of selection of the charge transporting substance is wide.

Example 11 5 g of the above-exemplified disazo pigment (G-45) was mixed with 100 mj of cyclohexanone! and dispersed in a ball mill for 10 minutes. This dispersion was applied onto an aluminum plate to form a carrier generation layer so that the film thickness after drying was 0.5 μm.

Next, 10 g of the exemplary charge transport material T-60 and bisphenol A type polycarbonate resin (viscosity average molecular weight 28
000) Log is dissolved in 70 ml of 1,2-dichloroethane, and this solution is applied onto the carrier generation layer so that the film thickness after drying is 18 μm to form a carrier transport layer. The body was created.

The electrophotographic properties of the photoreceptor obtained as described above were measured in the same manner as in Example 1. 100 more similar measurements
This was repeated 0 times. Furthermore, after the dispersion used in this example was left to stand for one month, a photoreceptor was prepared in the same manner as above, and its electrophotographic properties were measured. The results are shown in Table 5.

Table 5 Table 6 Comparative Example 12 A comparative photoreceptor was prepared in the same manner as in Example 11 using the following bisazo pigment described in JP-A-59-7365 as a carrier generating material.

When this comparative photoreceptor was measured in the same manner as in Example 11, the results shown in Table 6 were obtained.

As is clear from the above results, the carrier-generating substance of the comparative example can exhibit characteristics even if the dispersion time is short, but the dispersion liquid changes over time and becomes a major obstacle in practical use. The electrophotographic photoreceptor of the present invention can exhibit sufficient characteristics even if the dispersion time is short, and there is almost no change in the dispersion liquid over time, making it excellent in practical use.

〔Effect of the invention〕

The combination of a disazo pigment and a styryl compound according to the present invention improves carrier generation efficiency and carrier transport efficiency within the photosensitive layer, resulting in high sensitivity, durability, and particularly excellent potential stability. An electrophotographic photoreceptor can be obtained. Further, the disazo pigment of the present invention has good stability in its dispersed state and exhibits excellent properties in practical use. Further, the photoreceptor of the present invention exhibits high electrophotographic sensitivity in the LED emission wavelength range by selecting substituents of the azo pigment.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the layer structure of an electrophotographic photoreceptor, and FIGS. 2 and 3 are diagrams showing the spectral sensitivity of Examples.

Claims (2)

[Claims] (1) In a laminated electrophotographic photoreceptor that has a charge generation layer and a charge transport layer on a conductive support, the charge generation layer is a charge generation substance and has the general formula (1) ▲Mathematical formula, chemical formula, table, etc.▼ (In the formula, R_1 and R_2 represent an alkyl group, an aralkyl group, an aromatic ring group, or a heterocyclic group, Ar_1 and Ar_2 represent an aromatic ring group or a heterocyclic group, X_1,
_2, X_3 and X_4 represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a nitro group, a cyano group or a trifluoromethyl group, and are not all hydrogen atoms. Z represents an oxygen atom or a sulfur atom. ) The charge transport layer contains a disazo pigment as a charge transport substance, and the general formula (2) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Or the general formula (3) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_3 and R_4 represent an alkyl group, an aralkyl group, an aromatic ring group or a heterocyclic group, and R_5 and R_
6 represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom, and Ar_3 represents an aromatic ring group or a heterocyclic group. Y is a single bond, -CH_2-CH_2- or -CH
=CH-. ) An electrophotographic photoreceptor comprising a styryl compound represented by: (2) The charge generating substance has the general formula (4) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R_7 and R_8 are hydrogen atoms, alkyl groups,
It represents an aralkyl group, an aromatic ring group, an alkoxy group, a halogen atom, a nitro group, a cyano group, or a trifluoromethyl group, and R_9 and R_1_0 are a hydrogen atom, an alkyl group,
It represents an aralkyl group, an aromatic ring group, an alkoxy group, a halogen atom, a cyano group, or a trifluoromethyl group. Z_1
, X_1, X_2, X_3 and X_4 are general formula (1)
has the same meaning as ) The electrophotographic photoreceptor according to claim 1, which is a disazo pigment represented by: