JPH0260171B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more specifically,
The present invention relates to a novel electrophotographic photoreceptor having a photosensitive layer containing an azo compound. More specifically, the present invention relates to a highly durable electrophotographic photoreceptor that has high sensitivity and is suitable for repeated use. Conventionally, electrophotographic photoreceptors having a photosensitive layer mainly composed of an inorganic photoconductor such as selenium, zinc oxide, or cadmium sulfide have been widely known. However, these are not necessarily satisfactory in terms of sensitivity, thermal stability, moisture resistance, durability, etc., and in particular, selenium and cadmium sulfide are toxic, so there are restrictions in production and handling. On the other hand, electrophotographic photoreceptors having a photosensitive layer containing an organic photoconductive compound as a main component are relatively easy to manufacture, inexpensive, and easy to handle, and are generally more expensive than selenium photoreceptors. It has many advantages such as excellent thermal stability, and has attracted a lot of attention in recent years. Poly-N-vinylcarbazole is well known as such an organic photoconductive compound.
Electrophotographic photoreceptors having a photosensitive layer mainly composed of a charge transfer complex formed from this and a Lewis acid such as 2,4,7-trinitro-9-fluorenone are not necessarily satisfactory in terms of sensitivity and durability. . On the other hand, a laminated type or dispersed type functionally separated photoreceptor in which the carrier generation function and the carrier movement function are assigned to separate substances, respectively,
There is a wide selection range of each material, charging characteristics, sensitivity,
In terms of electrophotographic properties such as durability, it has the advantage that electrophotographic photoreceptors having arbitrary properties can be produced relatively easily. Conventionally, various carrier-generating substances or carrier-transferring substances have been proposed. For example, an electrophotographic photoreceptor has been put into practical use that has a photosensitive layer that combines a carrier generation layer made of amorphous selenium and a carrier transfer layer mainly composed of poly-N-vinylcarbazole. However, the carrier generation layer made of amorphous selenium has the disadvantage of poor durability. In addition, various proposals have been made to use organic dyes and pigments as carrier generating substances. 52-4241, JP-A-54-46558, JP-B-Sho 56-11945, etc. are already known. However, these azo compounds are not always satisfactory in terms of characteristics such as sensitivity, residual potential, and stability when used repeatedly, and the selection range of carrier transfer substances is also limited. The reality is that nothing that fully satisfies the wide range of demands has yet to be obtained. The object of the invention is to be stable to heat and light;
Another object of the present invention is to provide an electrophotographic photoreceptor containing an azo compound having excellent carrier generation ability. Another object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity, low residual potential, and excellent durability whose characteristics do not change even after repeated use. Still another object of the present invention is to provide an electrophotographic photoreceptor containing an azo compound that can effectively act as a carrier generating substance even in combination with a wide variety of carrier transfer substances. As a result of intensive research to achieve the above object, the present inventors have discovered that an azo compound represented by the following general formula () can function as an active ingredient of a photoreceptor, thereby completing the present invention. K0474 (In the formula, A is a divalent residue bonded to the N atom forming an azo with the C atom, and R may be the same or different, hydrogen, methyl, ethyl,
Nitro, halogen, R' is hydrogen, halogen, X is -O-, -S-, -NH-, a is 1
or an integer of 2. ) That is, in the present invention, by using the azo compound represented by the general formula () as a photoconductive substance forming the photosensitive layer of an electrophotographic photoreceptor, the azo compound of the present invention can also be used as an excellent carrier. By utilizing only the carrier generation ability and using it as a carrier generation material in a so-called function-separated photoreceptor, in which carrier generation and transport are performed using separate substances, the film has excellent physical properties, and has improved charge retention, sensitivity, and residual potential. To create an electrophotographic photoreceptor that has excellent electrophotographic properties such as, has little fatigue deterioration even when used repeatedly, and can exhibit stable properties without changing the above-mentioned properties even when exposed to heat or light. Can be done. Specific examples of the azo compound useful in the present invention represented by the general formula () include those having the following structural formula, but the azo compound of the present invention is not limited to this. . K0475 K0476 K0477 K0478 K0479 K0480 K0481 K0482 K0483 K0484 K0485 K0486 K0487 K0488 K0489 K0490 K0491 K0492 K0493 K0494 K0495 K0496 K0497 K0498 K049 9 K0500 K0501 K0502 K0503 K0504 K0505 K0506 K0507 K0508 K0509 K0510 K0511 K0512 K0513 K0514 K0515 K0516 K0517 K0518 K0519 K0520 K0521 K0522 K0523 K052 4 K0525 K0526 K0527 K0528 K0529 K0530 K0531 K0532 K0533 K0534 The azo compound represented by the above general formula () usually contains a diamine represented by the general formula H ₂ N-A-NH ₂ (wherein A has the same meaning as above). Either by tetrazotization by a method and then coupling the corresponding coupler in the presence of an alkali, or once the tetrazonium salt of the diamine is isolated in the form of a borofluoride salt or zinc chloride double salt, etc., a suitable solvent, e.g. It can be easily synthesized by coupling with a coupler in a solvent such as N,N-dimethylformamide or dimethylsulfoxide in the presence of an alkali. Next, a method for synthesizing representative examples of the azo compounds used in the present invention will be shown. Synthesis Example 1 (Exemplary Compound No. 13) 3,3'-dichlorobenzidine 2.5g (10mmole)
was added to a mixture of 6 ml of concentrated hydrochloric acid and 20 ml of water to disperse it, and a solution of 1.4 g (21 mmole) of sodium nitrite dissolved in water was added dropwise under ice cooling, and the mixture was allowed to react for about 1 hour under cooling. Then activated carbon was added and filtered to obtain an aqueous tetrazonium solution. 3-(2-benzothiazolyl)-2-naphthol (melting point 183.5-185.0℃) as a coupling component
5.6g (20mmole), 6g (40mmole) of triethanolamine as an organic amine and 20ml of DMF.
It was dissolved in 200 ml of DMSO and cooled to 0-5°C. Next, the above diazonium salt solution was added dropwise to the Kappler solution, and the resulting blue-purple paste liquid was
The mixture was kept at 0.degree. C. and stirred for an additional 3 hours. The formed precipitate was filtered and thoroughly washed with acetone and then water.
Ethyl acetate was extracted using a Soxhlet extractor and used as a washing liquid, and after drying, 4.8 g of blue-purple powder was obtained.
The melting point was 335°C (decomposed). Synthesis Example 2 (Exemplified Compound No. 35) A tetrazonium salt aqueous solution was prepared in substantially the same manner as in Synthesis Example 1, and 3-(2
-benzoxazolyl)-2-naphthol (melting point
(173.5-176°C) Using trietheramine as the organic amine and a mixed solvent of DMF and water as the reaction solvent, a coupling reaction was carried out under ice cooling, and a purple powder was obtained by the same purification method as in the synthesis example. The melting point was 312°C (decomposed). Other azo compounds of the present invention can also be obtained according to the above synthesis examples. The electrophotographic photoreceptor of the present invention has the general formula ()
Various types of photosensitive layers containing one or more types of azo compounds represented by the above are well known, and the photosensitive layer of the electrophotographic photoreceptor of the present invention may be in any of them. Usually, the photosensitive layer is of the type exemplified below. A photosensitive layer made of an azo compound A photosensitive layer containing an azo compound dispersed in a binder A photosensitive layer containing an azo compound dispersed in a well-known charge transfer substance Photosensitive layer laminated with a charge transfer layer containing a charge transfer layer The azo compound represented by the above general formula generates charge carriers with extremely high efficiency when it absorbs light. Although the generated carrier can be transferred using an azo compound as a medium, it is preferable to transfer the generated carrier using a known charge transfer material as a medium. From this point of view, photosensitive layers in the form of and are particularly preferred. Charge transfer substances are generally classified into two types: electron transfer substances and hole transfer substances, and both can be used in the photosensitive layer of the photoreceptor of the present invention, and mixtures or mixtures of substances having the same function can be used. , mixtures of different functionalities can also be used. Examples of substances having electron transfer include electron-withdrawing compounds having electron-withdrawing groups such as nitro groups, cyano groups, and ester groups; examples of these include:
2,4,7-trinylofluorenone, 2,4,
Nitrated fluorenone such as 5,7-tetranitrophylolenon, or tetracyanoquinodimetas, tetracyanoethylene, 2,4,5,7-
Examples include compounds such as tetranitroxanthone and 2,4,8-trinitrothioxanthone, and polymerized versions of these electron-withdrawing compounds. Furthermore, examples of electron-donating organic photoconductive compounds that can be used as hole transport media include the following. K0535 K0536 K0537 K0538 K0539 K0540 K0541 K0542 K0543 K0544 K0545 K0546 K0547 K0548 K0549 K0550 K0551 K0552 K0553 K0554 K0555 K0556 K0557 K0558 K055 9 K0560 K0561 K0562 K0563 K0564 K0565 K0566 K0567 K0568 K0569 K0570 K0571 K0572 K0573 K0574 K0575 K0576 K0577 K0578 K0579 K0580 K0581 K0582 K0583 K058 4 K0585 K0586 K0587 K0588 K0589 K0590 K0591 K0592 K0593 K0594 K0595 K0596 K0597 K0598 K0599 K0600 K0601 K0602 K0603 K0604 K0605 K0606 K0607 K0608 K060 9 K0610 K0611 K0612 K0613 K0614 K0615 K0616 K0617 K0618 K0619 K0620 K0621 K0622 etc. Other polymeric compounds that may be used include poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, polyglycidylcarbazole, polyvinylacenaphthylene, ethylcarbazole-formaldehyde resin, etc. Can be done.
The carrier transfer substances are not limited to those described herein, and when used, one type or a mixture of two or more types of carrier transfer substances can be used. The electrophotographic photoreceptor of the present invention can be manufactured by a conventional method. For example, an electrophotographic photoreceptor having the above-mentioned type of photosensitive layer has the general formula ()
A coating solution obtained by dissolving or dispersing an azo compound represented by in a suitable medium is applied onto a conductive support and dried to form a photosensitive layer with a thickness of usually several μm to several tens of μm. can be manufactured. The medium for preparing the coating solution may be a basic solvent that dissolves an azo compound such as n-butylamine or ethylenediamine, or tetrahydrofuran, 1,
Ethers such as 4-dioxane: Ketones such as methyl ethyl ketone and cyclohexanone: Aromatic hydrocarbons such as toluene and xylene: Aprotic polar solvents such as N,N-dimethylformamide, acetonitrile, N-methylpyrrolidone, and dimethyl sulfoxide: Examples include alcohols such as methanol, ethanol, and isopropanol; esters such as ethyl acetate, methyl acetate, and methyl cellosolve acetate; and media for dispersing azo compounds such as chlorinated hydrocarbons such as dichloroethane and chloroform. When using a medium for dispersing the azo compound, it is necessary to micronize the azo compound to a particle size of 5 μm or less, preferably 3 μm or less, and optimally 1 μm or less. Furthermore, as the conductive support on which the photosensitive layer is formed, any of those employed in well-known electrophotographic photoreceptors can be used. Specifically, examples include metal drums and sheets made of aluminum, copper, etc., and laminates and vapor deposits of these metal foils. Further examples include plastic films, plastic drums, paper, etc. which are coated with a conductive substance such as metal powder, carbon black, copper iodide, or polymer electrolyte together with a suitable binder to conductivity treatment. Also included are plastic sheets and drums that contain conductive substances such as metal powder, carbon black, and carbon fibers and are rendered conductive. An electrophotographic photoreceptor having the above type of photosensitive layer can be produced by dissolving a binder in a coating liquid used for forming the above type of photosensitive layer. In this case, the medium of the coating liquid is preferably one that dissolves the binder. Examples of binders include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic esters, and methacrylic esters, phenoxy resins, polysulfones, arylate resins, polycarbonates, polyesters, cellulose esters, cellulose ethers, urethane resins, and epoxy resins. Examples include various polymers such as resins and acrylic polyol resins. The amount of binder used is usually
It is in the range of 0.1 to 5 times the weight. In forming this type of photosensitive layer, it is preferable that the azo compound be present in the binder in the form of fine particles, for example, with a particle size of 3 μm or less, particularly 1 μm or less. Similarly, an electrophotographic photoreceptor having the above-mentioned type of photosensitive layer can be manufactured by dissolving a charge transfer medium in the coating liquid used to form the above-mentioned type of photosensitive layer. As the charge transfer medium, any of those exemplified above can be used. Apart from charge transport media which can themselves be used as binders, such as polyvinylcarbazole and polyglycidylcarbazole, it is preferred to use other binders. As the binder, any of those exemplified above can be used. In this case, the amount of binder used is usually in the range of 5 to 10 μm times the weight of the azo compound, and the amount of charge transfer medium used is usually 0.2 times the weight of the binder.
~1.5 times by weight, preferably 0.3 to 1.2 times by weight. In the case of a charge transport medium which itself can be used as a binder, it is usually used 5 to 10 times the weight of the azo compound. In this type of photosensitive layer, as in the above-mentioned type of photosensitive layer, it is preferable that the bisazo compound is present in the charge transport medium and the binder in the form of fine particles. If a coating solution obtained by dissolving a charge transfer medium in a suitable medium is applied onto the photosensitive layer of the type of ~ above and dried to form a charge transfer layer, an electrophotographic photosensitive layer having the photosensitive layer of the type described above can be obtained. body can be manufactured. In this case, the photosensitive layer of the type ~ plays the role of a charge generation layer. The charge transfer layer does not necessarily need to be provided above the charge generation layer, but may be provided between the charge generation layer and the conductive support. However, the former is preferable in terms of durability. The charge transfer layer is formed in the same manner as the photosensitive layer described above. That is, the coating liquid for forming the photosensitive layer described above, except that the azo compound is removed, may be used as the coating liquid. Typically the charge generating layer is between 5 and 50 micrometers thick. Of course, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a known sensitizer. Suitable sensitizers include Lewis acids and dyes that form charge transfer complexes with organic photoconductive materials. Examples of Lewis acids include chloranil, 2,3
-dichloro-1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone, 1
- quinones such as chloro-5-nitroanthraquinone, 2-chloroanthraquinone, and phenanthrenequinone, aldehydes such as 4-nitropenzaldehyde, 9-penzoylanthracene, indanedione, 3,5-dinitrobenzophenone,
Ketones such as 3,3',5,5'-tetranitrobenzophenone, acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride, tetracyanoethylone,
Cyano compounds such as terephthalmalonitrile and 4-nitrobenzalmalonitrile; electronic compounds such as 3-benzalphthalide, 3-(a-cyano-P-nitrobenzal) phthalide, and 3-(a-cyano-P-nitrobenzal) phthalides; Includes inhalable compounds. Examples of dyes include triphenylmethane dyes such as methyl violet, brilliant green, and crystal violet, thiazine dyes such as methylene blue, quinone dyes such as quinizarin, cyanine dyes, pyrylium salts, thiapyrylium salts, and benzopyrylium salts. It will be done. In addition to the above, it may contain inorganic photoconductive fine particles such as selenium and selenium-arsenic alloy, and organic photoconductive pigments such as copper, phthalocyanine pigments, and perylene pigments. Furthermore, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a well-known plasticizer in order to improve film formability, flexibility, and mechanical strength. Examples of the plasticizer include phthalate esters, phosphate esters, epoxy compounds, chlorinated paraffins, chlorinated fatty acid esters, aromatic compounds such as methylnaphthalene, and the like. It goes without saying that it may also include an adhesive layer, an intermediate layer, and a transparent insulating layer, if necessary. The photoreceptor using the azo compound of the present invention has high sensitivity and good color sensitivity, and when used repeatedly, there is little variation in sensitivity and chargeability, little optical fatigue, and extremely high durability. It is. Furthermore, the photoreceptor of the present invention can be widely used in electrophotographic applications such as photoreceptors for printers using lasers, cathode ray tubes (CRTs), and light emitting diodes (LEDs) as light sources, and offset printing plates in addition to electrophotographic copying machines. . Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 A vinyl chloride:vinyl acetate:maleic anhydride copolymer (Eslec MF, manufactured by Sekisui Chemical Co., Ltd.) was placed on a conductive support made of a polyester film laminated with aluminum foil (Alpet 85 manufactured by Daido Kako Co., Ltd., aluminum film thickness 10 μm). -10) Thickness consisting of
2g of Exemplified Compound No. 4 to form an intermediate layer of 0.05μ
and polyacrylate resin (Unitika U-100)
An azo compound dispersion obtained by adding 2g of 1,2-dichloroethane to 100ml of 1,2-dichloroethane and dispersing it in a paint conditioner for about 1 hour is applied onto the intermediate layer so that the film thickness after drying is 0.5μ. A carrier generating layer is formed by drying, and 5 g of a carrier transfer substance N,N-dibenzylaminobenzaldehyde-1,1-diphenylhydrazone is added with 7 g of polyarylate resin and 50 g of 1,2-dichloroethane.
The electrophotographic photoreceptor of the present invention was prepared by coating and drying a solution dissolved in 1 ml of the solution to a dry film thickness of 12 μm to form a carrier transfer layer. After storing this photoreceptor in a dark place at a room temperature of 30°C for one week, this electrophotographic photoreceptor was attached to an electrostatic paper tester "SP-428" (manufactured by Kawaguchi Denki Seisakusho), and the following characteristic tests were conducted. . That is, a voltage of -6KV is applied to the charger to charge the photosensitive layer by corona discharge for 5 seconds, and the potential Vo (-V) at that time and the illuminance on the surface of the photosensitive layer are then
The exposure amount E1/2 (lux·sec) required to attenuate the surface potential of the photosensitive layer to 1/2 by irradiating it with light from a halogen lamp under a condition of 30 lux was determined. In addition, the surface potential after exposure with an exposure amount of 30 lux·sec, that is, the residual potential E50 (-V) was determined. Similar measurements were repeated 500 times. Further exposure was performed for 0.3 seconds at 300 lux using a tungsten lamp as a light source to eliminate the residual potential to completely reduce the residual potential to zero. The results are shown in Table 1.

[Table] Examples 2 to 6 A total of five types of electrophotographic photoreceptors were prepared in the same manner as in Example 1, except that Exemplified Compounds 2, 13, 18, 24, and 50 were used as carrier generating substances, respectively. Similar characteristic tests were conducted for each of them. The results were as shown in Table 2.

[Table] Example 7 An example in which an intermediate layer of 0.04μ was formed on the surface of an aluminum drum with a diameter of 80nm, and a film made of a vinyl chloride:vinyl acetate (87:13) copolymer (manufactured by Union Carbide Co., Ltd., VYHH) was formed. Add 4 g of Compound 13 to 400 ml of 1,2-dichloroethane and disperse it for about 3 hours using a paint conditioner. Apply the resulting dispersion onto the intermediate layer so that the film thickness after drying is 0.5 μ. It was dried to form a carrier generation layer. On this carrier generation layer, a carrier transfer substance represented by the structural formula K0623, N,N-diethylaminobenzaldehyde, -1-phenyl-1-
10g of allyl hydrazone with 12g of polycarbonate resin (Teijin Panlite L-1250) 1.2
- A solution dissolved in 100 ml of dichloroethane was applied and dried to a film thickness of 15 μm after drying to form a carrier transfer layer, thereby producing a drum-type electrophotographic photoreceptor according to the present invention. When this electrophotographic photoreceptor was installed in our modified commercially available cartridge-type electrophotographic copying machine and a copied image was formed, a clear visible image with high contrast and faithful to the original was obtained. Copy again
This was repeated 1,000 times, and until the end, a visible image equivalent to the first one was obtained. Example 8 The reflection spectrum of the drum-type electrophotographic photoreceptor obtained in Example 7 was measured using a spectrophotometer equipped with an integrating sphere (Shimadzu UV-365), and it was found that the maximum absorption wavelength was around 640 nm. did. Furthermore
When the spectral sensitivity at 630 nm and 640 nm was measured using a monochrome meter, the energy required to halve the potential was approximately 3.5 erg/cm ² for both wavelengths, which is a very high photoreceptor, and gas laser light was used as the light source. It was found that the photoreceptor was sufficiently durable for practical use. Examples 9 to 13 An intermediate layer with a thickness of 0.05μ made of vinyl chloride:vinyl acetate copolymer (Kanebirakku L-CP manufactured by Kaneka Co., Ltd.) was formed on a conductive support made of a polyester film on which aluminum was vapor-deposited. Compound 23,
A solution of azo compounds 30, 36, 47, and 53 dissolved in n-butylamine is applied onto the intermediate layer to determine the film thickness.
A carrier generation layer of 0.1μ was formed. Next, 5 g of 1-diethylaminophenyl-3-phenyl-5-styrylpyrazoline and a polyester resin (manufactured by Toyobo Co., Ltd., Vylon) were placed on the carrier generating layer.
An electrophotographic photoreceptor of the present invention was prepared by dissolving 5 g of 200) in 40 ml of 1,2-dichloroethane and drying the solution to form a carrier transfer layer such that the film thickness after drying was 14 μm. The reflection and absorption curves of these five types of photoreceptors in total were determined, and the maximum absorption wavelength in the visible to near-infrared region and the energy required to reduce the potential by half at that wavelength were determined according to Example 8. The results are shown in Table 3. The initial potential Vo of all photoreceptors exceeded 700 (-V). Applied voltage −
6KV

[Table] Example 14 Styrene on an Al plate with grained surface oxidation:
Methyl methacrylate: methacrylic acid copolymer (acid value 185), exemplary compound 35 and diethylamino-
Benzaldehyde-N-phenyl-N-4-ethylbenzylhydrazone was blended in a weight ratio of 1.5:0.2:1.0 and dissolved in dioxane (resin component,
A dispersion solution containing a hydrazone compound (azo compound) was applied and dried to prepare a single-layer photoreceptor with a film thickness of 6 μm. The photoreceptor thus prepared was subjected to an electrophotographic property test using the electrostatic paper tester described above. The applied voltage was +6KV Vo = 420 (+V) E1/2 = 6 (lux seconds). In addition, when this photoreceptor is visualized with a developer (toner) and then treated with an alkaline processing solution (for example, 3% triethanolamine, 10% ammonium carbonate, and 20% polyethylene glycol with an average molecular weight of 190 to 210), the toner The non-adherent areas were easily eluted, and by washing with water containing sodium silicate, a printing original plate could be easily prepared. When offset printing is performed using this original plate, approximately
It was found that it could withstand printing of 100,000 sheets. The optimum exposure amount (light source: halogen lamp) for obtaining a visible toner image was 50 lux and 1.5 seconds. In addition, when creating a printing original plate, it was performed by direct plate making without using a base material.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing an azo compound represented by the following general formula () on a conductive support. K0464 (In the formula, A is a divalent residue bonded to the N atom forming an azo with the C atom, and R is hydrogen, methyl, ethyl, nitro, or halogen, which may be the same or different. , R′ is hydrogen, halogen,
X is -O-, -S-, -NH-, and a is an integer of 1 or 2. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains a carrier transfer substance and a carrier generation substance, and the carrier generation substance is an azo compound represented by the general formula (). 3. The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. K0465 (where m, n are 0 or 1, X, R, R',
a has the same meaning as the first term. ) 4. The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. K0466 (wherein Y is hydrogen, halogen, nitro, lower alkoxy, lower alkyl, X, R, R', a
is synonymous with the first term. ) 5. The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. K0467 (In the formula, Z is hydrogen, halogen, cyano,
X, R, R', and a have the same meanings as in the first term. ) 6 The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. K0468 (in the formula, X' is -O-, -S-, -NH-,
X, R, R', and a have the same meanings as in the first term. ) 7. The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. K0469 (In the formula, R ₁ is hydrogen, alkyl, allyl, propenyl, benzyl which may have a substituent, phenyl which may have a substituent, X, R, R',
a has the same meaning as the first term. ) 8. The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. K0470 (In the formula, X, R, R', and a have the same meanings as in paragraph 1.) 9 Claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. The electrophotographic photoreceptor described above. K0471 (In the formula, R ₂ is hydrogen, alkyl, allyl, propargyl, or benzyl which may have a substituent, and X, R, R', and a have the same meanings as in item 1.) 10 The above general formula The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by () is a compound represented by the following structural formula. K0472 (In the formula, R ₃ is hydrogen, alkyl, allyl, propargyl, or benzyl which may have a substituent, and X, R, R', and a have the same meanings as in item 1.) 11 General The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the formula () is a compound represented by the following structural formula. K0473 (In the formula, R ₄ and R ₅ are hydrogen, halogen, alkyl,
They are methoxy and nitro, and X, R, R' and a have the same meanings as in the first term. )