JPS62160453A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body high in sensitivity and small in potential fluctuation after durability test by using an electrostatic charge transfer material having an oxidation potential in the optimum range in combination with a charge generating material. CONSTITUTION:The charge transfer material to be used has an oxidation poten tial of (alpha-0.2)-alphaV within the matching limit, where alpha is the oxidation potential of the charge generating material. When the charge transfer material has the oxidation potential above that alpha of the charge generating material, the sensitiv ity of the photosensitive body abruptly lowers, and an carrier injection efficiency flowing from a charge generating layer to a charge transfer layer deteriorates, especially in the case of using a laminate type photosensitive body. Accordingly, the oxidation potential of the charge transfer material needs to be <=alpha.V. If it is below alpha-0.2V, dark potential decay after the durability test becomes too much.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an organic photoconductor, and particularly to an electrophotographic photoreceptor in which a photoconductive layer contains a charge transporting substance and a charge generating substance.

[Conventional technology]

Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known so far.

On the other hand, since the discovery that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. For example, organic photoconductive I-rimers such as bori-N-vinyl carno-oazole, polyvinylanthracene, carbazole, antho2cene, pyrazolines, oxadiazoles,
Low-molecular organic photoconductors such as hydrazones and teraryl alkanes, phthalcyanine pigments, azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indib dyes, thioindigo dyes, and squaric acid methine dyes. Pigments and dyes are known. In particular, organic pigments and dyes with photoconductivity are easier to synthesize than inorganic materials, and the range of options for selecting compounds that exhibit photoconductivity in an appropriate wavelength range has expanded, so there are many available. Photoconductive organic pigments and dyes have been proposed.

For example, US Pat. No. 4,123,270, US Pat. No. 42,476
No. 14, No. 4251613, No. 4251614, No. 4256821, No. 4260672, No. 4268596, No. 4278747, No. 429
As disclosed in Japanese Patent No. 3628, electrophotographic photoreceptors are known that use a disazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer that is functionally separated into a charge generation layer and a charge transport layer.

Electrophotographic photoreceptors using such organic photoreceptors can be produced by coating by appropriately selecting a binder. It has the advantage that the sensitive wavelength range can be freely controlled by selection.

The laminated photoreceptor, which is obtained by laminating a charge transport layer and a charge generation layer mainly composed of a charge generation material, is different from other single-layer thermal photoreceptors due to its sensitivity and increased residual potential after durability tests. Although it was advantageous, it was still not at a sufficient level.

Furthermore, when the thickness of the charge generation layer is increased to 2 μm or more, a decrease in dark area potential is observed in durability tests. In a glass charging photoreceptor in which a charge transport layer and a charge generation layer are laminated in this order, it is necessary to increase the film thickness to avoid problems such as wear and scratches due to durability. A decrease in dark potential is observed.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and provide a multilayer electrophotographic photoreceptor with high sensitivity, no decrease in dark area potential even after a durability test, and extremely low residual potential.

The present invention achieves the above object by providing a photoconductive layer containing at least a charge generating substance and a charge transporting substance on a conductive support.

The present inventors have discovered that the present invention can be achieved by using a charge transport material having an oxidation potential within a specific range with respect to a charge generation material in an electrophotographic photoreceptor, and have thus completed the present invention.

[Means for solving problems]

That is, the present invention provides at least a conductive substrate.

In an electrophotographic photoreceptor having a photoconductive layer containing a charge generating substance and a charge transporting substance, the oxidation potential of the charge generating material is α(
b) Then, the limit oxidation potential that suits itself is α-0,2
(b) An electrophotographic photoreceptor characterized by using a charge transport material in the range of αM to αM.

The present invention will be explained in detail below.

The relationship between the sensitivity of electrophotographic photoreceptors and the ionization-tension of charge transport substances has been debated for some time, but it is generally believed that there is a certain correspondence between ionization 4-tension and oxidation potential. , the inventors ionize the oxidation potential? Focusing on the possibility of using this material as a substitute for tensile, we investigated the relationship between the oxidation potential of charge-generating substances and charge-transporting substances and electrophotographic properties, and as a result, we found the following relationship.

The oxidation potential of the charge transport substance was measured by cyclic ruthanmetry using acetonitrile as a solvent, tetra-n-butylammonium perchlorate as a supporting electrolyte, and a saturated calomel electrode as an electrode.

As the value of the oxidation potential, the peak value (Box) of the first and second waves was adopted. However, the measurement is not limited to this method, and can be determined by potentiometry or polarography.

When an electrophotographic photoreceptor was prepared by combining a specific charge-generating material with a charge transport material having m oxidation potentials, the sensitivity of the electrophotographic photoreceptor and the oxidation potential Bo of the charge transport material were
A relationship was found between x and x as shown in Figure 1. Here, the sensitivity of the electrophotographic photoreceptor is -5kV.
Exposure 'JI required to attenuate the dark potential (VD) to 1/2 after being charged by corona discharge and left in a dark place for 5 seconds.
It is expressed as E 1/2 (Lux・s@e).

As shown in Figure 1, the sensitivity of the electrophotographic photoreceptor is
While the oxidation potential of the charge transport material is low, ET (tux-s@c) only shows a slight increase with respect to the increase in oxidation potential, and no noticeable decrease is observed.

However, when the oxidation potential of the charge transport substance exceeds a certain voltage, E T (tuxamae) increases rapidly and the sensitivity deteriorates rapidly. Therefore, E 1/ in the low oxidation potential range
2 Find the intersection point of the extension of the graph of (Lux・see) and the extension of the graph of E 1/2 (Lux・-・e) in the high oxidation potential range, and calculate the voltage α (b) of the intersection point for the corresponding “
It is defined as "the upper limit of oxidation potential compatible with charge-generating substances".

In other words, if the oxidation potential of the charge transporting materials combined in a certain charge generating material exceeds a certain voltage α, the sensitivity of the resulting electrophotographic photoreceptor will decrease rapidly. From the viewpoint of sensitivity, it is necessary that the oxidation potential of the substance be below α (b). Furthermore, when the oxidation potential of the charge transport material exceeds α (b), the efficiency of carrier injection from the charge generation layer to the charge transport layer becomes poor, especially in the case of a laminated photoreceptor.

On the other hand, it has been found that the oxidation potential of the charge transport material needs to be below αv) and above a certain voltage from other aspects.

That is, the oxidation potential of the charge transport substance is α-0.2ff)
If it is less than that, the dark potential after the durability test will decrease significantly.

Therefore, the charge transport material used in the present invention is α-0,2
It has an oxidation potential in the range of (b) to α (b).

The photoconductive layer and the charge generation layer in the electrophotographic photoreceptor of the present invention include the above-mentioned charge generation substance and, if necessary, a charge transport substance having an oxidation potential range of the present invention, together with a suitable binder (or without a binder) on a substrate. It can be formed by coating on the surface of the substrate, and it can also be obtained by forming a vapor-deposited film using a vacuum evaporation apparatus.

The pine paste that can be used when forming the charge generating layer by t-a process can be selected from a wide range of insulating resins, and organic photoconductive resins such as poly-N-vinylcarbazole, -ripynylanthracene and polyvinylpyrene can be used. You can choose from Rimmer. Preferably - ribinyl petyral, polyarylate (condensation polymer of bisphenol A and heptalic acid, etc.)
, polycarbonate, ester, phenoxy resin,
Polyvinyl acetate, acrylic resin,? Examples include insulating resins such as lyacrylamide resin, polyamide, 4-rivinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, I-rivinyl alcohol, and polyvinylpyrrolidone.

The resin contained in the photoconductive layer and the charge generation layer is 100 times or less (weight ratio) of the charge generation substance, especially in the case of a laminated type, since the thickness of the charge generation layer is 2μ or more, it is preferably 0.1 to 5μ.
0 times is suitable.

Solvents that dissolve these resins vary depending on the type of resin; specific organic solvents include alcohols such as methanol, ethanol, and isopro/4-nol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; - Dimethylformamide, amides such as N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane,
Ethers such as ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, methylene chloride, dichloroethylene, carbon tetrachloride,
Aliphatic halogenated hydrocarbon M6 such as trichlorethylene
Alternatively, aromatic compounds such as benzene, toluene, xylene, refloin, monochlorobenzene, dichlorobenzene, etc. can be used.

Coating methods include dip coating, spray coating, spinner coating, bead coating,
This can be carried out using a coating method such as a Mayer coating method, a blade coating method, a roller coating method, or a curtain coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying can be carried out at 30° C. to 200° C. for a period of 5 minutes to 2 hours, either stationary or with air blowing.

The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving and taking charge carriers injected from the charge generation layer in the presence of an electric field, and transporting these charge carriers. have.

At this time, this charge transport layer may be laminated on or under the charge generation layer.

The substance that transports charge carriers (charge transport material) in the charge transport layer is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The term "electromagnetic waves" used herein includes the broad definition of "light rays" including r-rays, X-rays, far-infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both layers trap each other, resulting in a decrease in sensitivity.

Examples of charge transport materials used in the present invention include Hagiren,
N-Ethylcarbazole, N-(soglovircarpazole, N-methyl-N-phenylhuman 2sino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole ,N,N-di7-dylhydrazino-3-methylidene-1
O-ethylphenothiazine, N,N-diphenylhydrazino-3-methylidene-10-ethylphenozine, P-diethylaminobenzaldehyde-N, N-diphenylhydrazone, P-diethylaminobenzaldehyde-N-α-su7thiruN- Phenylhydrazono, P-
Pyrrolidinobenzaldehyde-N,N-diphenylhydrazone, 1,3.3-trimethylindolenine-ω
-aldehyde-N,N-diphenylhydrazino, hydrazones such as P-diethylpenzaldehyde-3-methylbenzthiazolinone-2-hydrazone, 2,5-bis(
P-diethylaminophenyl) -1,3,4-oxadiazole, l-phenyl-3-(p-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-C noryl (2)) -3 -CP-diethylaminostyryl)-s-(p-diethylaminophenyl)virasorin, 1-C pyridyl (2), l-3-(
P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[6-medoxypyridyl (2))-3-(P-diethylaminostyryl)-
s-(p-diethylamino7enyl)pyrazoline, l
-(Pyrisol(3))-3-CP-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, l-(Levidyl(2):l-3-CP-diethylaminosteryl)-5-(P-diethylaminosteryl)-5-(P-diethylaminophenyl)pyrazoline, phenyl)pyrazoline, l-[pyridyl(2))-3-(P-diethylaminostyryl)-4-methyl-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)
) -, 3-(α-methyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, l-7enyl-3-(P-diethylaminostyryl)
Pyrazolines such as -4-methyl-5-(P-diethylaminophenyl)pyrazoline, 1-722-3-(α-benzyl-P-diethylaminostyryl)-5-CP-diethylaminophenyl)pyrazoline, spiropyrazoline, 2 -(P-diethylaminostyryl)-6-dinithylaminopenzoxasol, 2-(P-N ethylaminophenyl)-4-(P-dimethylaminophenyl)
-Oxazole compounds such as 5-(2-chlorophenyl)oxazole, 2-(P-diethylaminosteryl)
Thiazole compounds such as -6-dinithylaminopenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-)f-ruphenyl)-phenylmethane, 1.1-bis(4-N,N- Die f Ruamino 2
Examples include polyarylalkanes such as -methylphenyl)hegetane, 1,L2t2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, and triphenylamine.

The charge transport material is not limited to those described here, and when used, one type of charge transport material or a mixture of two or more CJs can be used.

Further, in the present invention, a charge transporting substance of the 181 class or two or more types having an oxidation potential range of the present invention can be added to the charge generation layer, and the sensitizing effect thereof becomes even more remarkable. At that time, the compound may be the same as or different from the compound used in the charge transport layer.

When adding a charge transport substance to the charge generation layer, the compound is
100 times (weight ratio) or less than the charge generating substance, preferably 0
．． A ratio of 1 to 30 times (weight ratio) is suitable from the viewpoint of high sensitivity, low residual potential, and repetition stability.

To form a charge transport layer, a film can be formed by selecting an appropriate binder. Examples of resins that can be used as binders include acrylic resins, polyacrylates, 4-lyesters, and ? Licargenate, polystyrene,
acrylonitrile-styrene corimer, acrylonitrile-tutadiene corimer, -rivinylnotyral,
Insulating resins such as polyvinyl formal, polysulfone, polyacrylamide, I-lyamide, chlorinated fluorocarbons, or stream-N-vinylcarbazole, ? Examples include organic photoconductive 4-rimers such as ribinylanthracene and 4-lipinyl♂rene.

Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Typically it is 5 microns to 50 microns, with a preferred range of 10 microns to 30 microns. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

Such a photosensitive layer is provided on a substrate having a conductive layer, ie, a conductive support. Examples of substrates having conductor r6LHfIt- include those in which the substrate itself has a 4-volt conductor, such as aluminum, aluminum alloy, copper, zinc, stainless steel,
vanadium, molybdenum, chromium, titanium, nickel,
Indium, gold, platinum, etc. can be used, and in addition to aluminum, aluminum alloy, indium oxide,
Glasstic (e.g.,
Use a substrate made by coating f:7 stick with carbon black, silver particles, etc.) together with a suitable binder, a substrate made by impregnating conductive particles with glass stick or paper, a glass stick having conductive 4-rimer, etc. I can do it.

A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. Subbing layer, casein,
Polyvinyl alcohol, nitrocellulose, ethylene-
It can be formed from acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc.

The thickness of the undercoat layer is suitably 0.1 micron to 40 micron, preferably 0.1 micron to 3 micron.

When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, and the charge transport material in the charge transport layer is an electron transport material, it is necessary to positively charge the surface of the charge transport layer. When exposed to light after being charged, electrons generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface and neutralize the positive charge, causing the surface potential to attenuate and creating static between the unexposed area and the exposed area. Electrocontrast occurs. A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. This can be directly fixed, or the toner image can be transferred to paper, f:7 stick film, etc., then developed and fixed.

Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, and then visually imaged and fixed. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones.

On the other hand, when the charge transport material consists of a hole transport material, the surface of the charge transport layer must be negatively charged, and when exposed to light after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. , which then reaches the surface and neutralizes the negative charges, resulting in attenuation of the surface potential and an electrostatic contrast between the surface potential and the unexposed area.

During development, it is necessary to use a positively charged toner, contrary to the case where an electron transport material is used.

Even when using a photoreceptor in which a conductive layer, a charge transport layer, and a charge generation layer are laminated in this order, charging, exposure, development, and fixing processes can be adopted depending on the polarity thereof.

The electrophotographic photoreceptor according to the present invention is susceptible to deterioration due to ultraviolet rays, ozone, etc., dirt due to oil, etc., scratches due to cutting powder of metal, etc., and exposure due to photoreceptor contact members such as developing members, transfer members, cleaning members, etc. A protective layer may be further provided on the charge generation layer or the charge transport layer for the purpose of preventing scratches and abrasion of the body. In order to form an electrostatic latent gQ on this protective layer, it is desirable that the surface resistivity is 10 Ω or more.

The first layer used in the present invention is made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, 4-arylate, -urethane, sterene-butadiene fluoride, etc. The photosensitive layer can be formed by dissolving a resin such as reamer, styrene-acrylic acid: ff/9mer, or styrene-acrylonitrile corimer in a suitable organic solvent and drying it.

Moreover, additives such as ultraviolet absorbers can be added to the resin liquid. At this time, the thickness of the protective layer is generally 0.05~
20 microns, particularly preferably in the range 0.2 to 5 microns.

〔Example〕

The present invention will be described below with reference to examples.Example 1 An ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 mJ of water) was coated on an aluminum cylinder by a dip coating method, and dried. A subbing layer with a work load of 1.01 was formed.

Next, 1 part by weight of the charge generating material shown as charge generating material A (1) in Table 1, butyral resin (S-LEC BM-2:
5 parts by weight of Sekisui Chemical @) and 3 parts of isopropyl alcohol
0 parts by weight? -Dispersed for 4 hours using a Lumil disperser. This dispersion was applied onto the previously formed subbing layer by a dip coating method and dried to form a charge generation layer. At this time! The thickness was 2.0μ.

Next, add 1 part by weight of the compound in Table 1, Table 2, Charge Transport Materials (1).

1 part by weight of polysulfone 411 resin (P[oo: manufactured by Union Carbide Co., Ltd.) and 61 parts by weight of monochlorobenzene were mixed and dissolved by stirring with a stirrer. This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer. What is the film thickness at this time?

It was 12μ.

A corona discharge of 15 kV was applied to the photoconductor prepared in this manner. The surface potential at this time was measured (initial potential v0).

Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 5 seconds (dark decay v5). Sensitivity is determined by the amount of exposure required to attenuate the potential v5 after dark decay (E44 tu
g, sec).

These results were as follows.

Vo -610 Gelt V5 -600 Gelt EH 3,9 tux-sec Initial dark potential (Vo
) and bright area potential (VL), and then make a copy of this photoreceptor 8! (NP150Z manufactured by Canon Co., Ltd.) for 1000
After using it 0 times, I measured the dark potential and bright potential.

The results are shown in Table 3.

Table 3 Initial Comparative Example 1.2 After 10,000 Times Durability Comparative Example 1.2 Same as Example 1 except that the following compounds were used in place of the specific charge transport substance A(1) compound used in Example 1. Prepare the photoreceptor by method.

A friend who measures the characteristics of this photoreceptor. These results are shown in Table 4.

Table 4 Comparative Compound (1) Comparative Compound (2) Table 5 Comparative Compound (2) has a greater sensitivity in oxidation potential (0.80 V) than the limit compatible oxidation potential α = 0.75 V of charge generating substance (1). It's bad, and the increase in vL after endurance is large. or,
The oxidation potential (0.33V) of comparative compound (1) is α-0,
2(V), and the VD decreases often after durability.

Example 2 The undercoat layer was formed in the same manner as in Example 1.

Next, add 1 part by weight of the charge generating substance 41 to 1! 5 parts by weight of cargo transport material 41 and polysulfone resin (P170
0: Union Carbide Co., Ltd.) and 40 parts by weight of monochlorobenzene were dispersed for 4 hours using a 1-dol mill disperser.

This dispersion was first formed and coated onto the t undercoat layer by dip coating, and the t0 film thickness was 15 μm.

As Comparative Example 3.4, Comparative Compounds (1) and (2) were used in place of the charge transport substance (1), and Example 1 was prepared.
A photoreceptor was prepared in exactly the same manner. The characteristics of these photoreceptors were measured and the results are shown in Table 6.

Examples 3-6 The entire undercoat layer was formed in the same manner as in Example 1.

Next, 1 part by weight of the compound shown in Table (2), 1 part of polycarbonate resin (Panlite L-1250), and 6 parts of dioxane were stirred and dissolved, and the coating solution was coated by full dip coating. Processed and dried to form a charge transport layer. At this time, the film thickness was 15μ.

Furthermore, 11 parts of the charge generating material shown in Table (1), 8 parts by weight of Ilicargenate resin (Panlite L-1250) and 10 parts by weight of dioxane were dispersed for 4 hours using a ball mill disperser. This dispersion was coated on the previously formed charge transport layer by the Sdale coating method and dried to a thickness of 5 μm.

Table 7 shows the characteristics of these photoreceptors. The NP-1502 copying machine was modified for positive charging and measurements were taken.

The results are shown in Table 7.

Comparative Examples 5 to 8 Photoreceptors were prepared in exactly the same manner as in Examples 2 to 5, except that the same charge generation materials were used and only the charge transport material was added to the compounds shown in Table 8. Its characteristics are shown in Table 9.

Table 8 CH.

Example 7 An undercoat layer and a charge transport layer were formed in the same manner as in Example 2. Is it true that 1 part by weight of the pigment in Table 1 charge generation substance 46 and 0.5 part by weight of the charge transport substance Muro in Table 2? Licargenate resin () Gunlite L-1250) 8 parts by weight Example 2
It was dispersed in the same manner as above, applied by spray coating, and dried to a thickness of 5μ.

Table 10 shows the characteristics of this photoreceptor.

Table 10 This photoreceptor was then repeatedly copied 20,000 times using a NP-1502 copying machine modified to use a glass battery. As a result, good quality images were obtained even after repeating 20,000 copies. As a result, it can be seen that the photoreceptor of the present invention has excellent durability as well.

The above examples and comparative examples are summarized as shown in Fig. 2. Limit oxidation potential (α) compatible with charge-generating substances and oxidation potential E of charge-transporting substances. The difference in x (CT material) is 0.2v
If it is more than that, the difference in vd after 10,000 cycles is large.

Particularly noticeable is the charged photoreceptor.

Also, the oxidation potential E of the charge transport substance. When x (CT material) is larger than α, the sensitivity is poor and the increase in vL after durability is also significant.

``Effects of the Invention'' As is clear from the above, the present invention uses a charge transporting material with an oxidation potential within the optimum range as a charge generating material, thereby achieving extremely high sensitivity and less potential fluctuation after durability compared to conventional ones. It is possible to provide electrophotographic photoreceptors.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the oxidation potential of the charge transport material and sensitivity, and Figure iiiIg2 is a graph showing the relationship between the oxidation potential of the charge transport material, the difference in αM, and the difference in dark potential after 10,000 cycles. It is. a: Laminated type θ-charging photoreceptor b: Laminated type e-charging photoreceptor. Agent: Patent Attorney Minoru Yamashita, Eox (CT material)

Claims (1)

[Scope of Claims] 1) In an electrophotographic photoreceptor having a photoconductive layer containing at least a charge generating substance and a charge transporting substance on a conductive support, the limit oxidation potential compatible with the charge generating substance is α(V). An electrophotographic photoreceptor characterized by using a charge transport material having an oxidation potential in the range of α-0.2 (V) to α (V). 2) Claim 1, wherein the photoreceptor is a laminated electrophotographic photoreceptor in which at least a charge generation layer and a charge transport layer are provided on a conductive support, and the charge generation layer has a thickness of 2μ or more. The electrophotographic photoreceptor described in . 3) The electrophotographic photoreceptor according to claim 2, wherein the charge generation layer contains a charge transport material having an oxidation potential in the range of α-0.2 (V) to α (V).