JPH0513508B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a new electrophotographic photosensitive material, and more particularly to an electrophotographic photoreceptor containing a metallocene compound having a specific molecular structure in a photoconductive layer. BACKGROUND ART Conventionally, pigments and dyes exhibiting photoconductivity have been published in numerous publications. For example, RCA Review Vol.23. 413～419
(1962.9) published on the photoconductivity of phthalocyanine pigments, and an electrophotographic photoreceptor using this phthalocyanine pigment was patented in the US patent.
This is disclosed in Publication No. 3397086, Publication No. 3816118, etc. In addition, examples of organic semiconductors used in electrophotographic photoreceptors include US Pat. No. 4,315,983;
Publication No. 4327169 and Research Disclosure 20517
(1981.5), methine squaritate dye shown in U.S. Patent No. 3824099, U.S. Patent No. 3898084,
Examples include disazo dyes disclosed in Publication No. 4251613 and the like. Such organic semiconductors are easier to synthesize than inorganic semiconductors, and can be synthesized as compounds that are highly photoconductive to light in the required wavelength range. The electrophotographic photoreceptor formed on a transparent substrate is
Although it has the advantage of improved color sensitivity, there are very few that can be put to practical use in terms of sensitivity and durability. Problems to be Solved by the Invention The present inventors have completed the present invention as a result of intensive research aimed at improving the various drawbacks of organic semiconductor materials and obtaining a photoconductive material with excellent electrophotographic properties. A first object of the present invention is to provide a novel organic semiconductor coating. The second object is to provide an electrophotographic photoreceptor that can be used in all existing electrophotographic processes, improves the conventional drawbacks, and provides higher electrophotographic response gain. Means and Effect for Solving the Problems The present invention provides an electrophotographic photoreceptor having a conductive substrate and a photoconductive layer, wherein the photoconductive layer has the general formula However, in the formula, m is an integer of 0, 1 or 2, n is an integer of 0 or 1, and Y is a 5- to 6-membered heterocycle that may have a substituent or a benzene or Indicates a residue for forming a 5- to 6-membered heterocycle condensed with an aromatic ring such as naphthalene, specifically,

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

[Formula] etc., (where A is 0, S, Se, N-
R ₇ or

[Formula], R ₁ to _{R 4} and R ₇ to _{R 9} are hydrogen or an alkyl group such as methyl or ethyl, or an optionally substituted phenyl group, and R ₅ and R ₆ are hydrogen or methyl, ethyl, an aliphatic group such as methoxy or a halogen atom such as chlorine or bromine), R is methyl,
M represents an aliphatic group such as ethyl, propyl, butyl or an aralkyl group such as phenyl or benzyl.
Represents a transition metal selected from Ti, V, Cr, Fe, Co, Ni and Rn, and X- is iodine, chlorine, bromine,
It is composed of an electrophotographic photoreceptor characterized by containing a metallocene compound having an anionic functional group such as perchloric acid, fluoroboric acid, and para-toluenesulfonic acid. The metallocene compound of general formula () used in the present invention can be synthesized by methods known in the literature. i.e. J. Appl. Chem.Biotechnol, 1976,
It can be generally synthesized by applying the method described in 26, 71. Specific examples of the metallocene compounds used in the present invention are listed below. The above exemplified compounds do not limit the scope of the claims of the present invention. The film containing the metallocene compound described above exhibits photoconductivity and can be used in the photosensitive layer of the electrophotographic photoreceptor described below. That is, in a specific example of the present invention, an electrophotographic photoreceptor is formed by forming a film of the metallocene compound of the general formula () on a conductive substrate by vacuum evaporation, or by forming a film by dispersing it in a suitable binder. can be created. In a preferred embodiment of the present invention, the photoconductive coating described above can be applied as a charge generation layer in an electrophotographic photoreceptor in which the photosensitive layer of the electrophotographic photoreceptor is functionally separated into a charge generation layer and a charge transport layer. The charge generation layer contains as much of the above-mentioned photoconductive compound as possible in order to obtain sufficient absorbance, and is a thin film layer, for example, 5μ or less, preferably in order to shorten the range of the generated charge carriers. 0.01〜
A thin film layer having a thickness of 1 μm is preferable.
This means that most of the incident light is absorbed by the charge generation layer, producing many charge carriers;
Furthermore, this is due to the need to inject the generated charge carriers into the charge transport layer without being deactivated by recombination or trapping. The charge generation layer can be formed by dispersing the above-mentioned compound in a suitable binder and coating it on a conductive substrate, or it can be obtained by forming a vapor deposited film using a vacuum vapor deposition apparatus. I can do it. Binders that can be used to form the charge generating layer by coating can be selected from a wide variety of insulating resins, and can also be selected from 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, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, Examples include insulating resins such as epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is 80% by weight.
Below, preferably 40% by weight or less is suitable. The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the charge transport layer or undercoat layer described below. Specific organic solvents include alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, N,N-dimethylformamide,
Amides such as N,N-dimethylacetamide,
Sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform,
methylene chloride, dichloroethylene, carbon tetrachloride,
Aliphatic halogenated hydrocarbons such as trichloroethylene, aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. Coating can be carried out using coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and carting coating. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying at 30-200℃ for 5 minutes
It can be carried out stationary or under ventilation for a period of 2 hours. The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. ing. At this time, this charge transport layer may be laminated on or under the charge generation layer. The substance that transports charge carriers in the charge transport layer (hereinafter referred to as charge transport substance) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The term "electromagnetic waves" as used herein includes a broad definition of "light rays" including gamma rays, X-rays, ultraviolet rays, visible light, near infrared rays, infrared 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 capture each other, resulting in a decrease in sensitivity. Charge transport substances include electron transport substances and hole transport substances, and electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2, 4,5,7-tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,
4,5,7-tetranitroxanthone, 2,4,
Examples include electron-withdrawing substances such as 8-trinitrooxanthone, and polymerization of these electron-withdrawing substances. As the hole transport substance, pyrene, N-ethylcarbazole, N-isopropylcarbazole, N
-Methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3
-methylidene-10-ethylphenothiazine, N,
N-diphenylhydrazino-3-methylidene-10
-Ethylphenoxazine, P-diethylaminobenzaldehyde-N,N-diphenylhydrazone, P-diethylaminobenzaldehyde-N-
α-Naphthyl-N-phenylhydrazone, P-pyrrolidinobenzaldehyde-N,N-diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone, P-diethylbenzaldehyde -Hydrazones such as 3-methylbenzthiazolinone-2-hydrazone, 2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole, 1-
Phenyl-3-(P-diethylaminostyryl)-
5-(P-diethylaminophenyl)pyrazoline,
1-[quinolyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(P-diethylaminostyryl)-5-( P-diethylaminophenyl)pyrazoline, 1-[6-methoxy-pyridyl(2)]-3-(P-diethylaminostyryl)-
5-(-diethylaminophenyl)pyrazoline,
1-[Pyridyl(3)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[Lepidyl(2)]-3-(-diethylaminostyryl)-5-(P -diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(P
-diethylaminostyryl)-4-methyl-5-
(P-diethylaminophenyl)pyrazoline, 1
-[Pyridyl(2)]-3-(α-methyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-phenyl-3-(P-
diethylaminostyryl)-4-methyl-5-(P
-diethylaminophenyl)pyrazoline, 1-phenyl-3-(α-benzyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, spiropyrazoline and other pyrazolines, 2-(P-diethylaminostyryl)- 6-
Diethylaminobenzoxazole, 2-(P-
oxazole compounds such as diethylaminophenyl)-4-(P-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2-(P-
thiazole compounds such as diethylaminostyryl)-6-diethylaminobenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane,
1,1-bis(4-N,N-diethylamino-2
-methylphenyl)heptane, 1,1,2,2-
Tetrakis (4-N,N-dimethylamino-2-
Polyarylalkanes such as methylphenyl)ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, etc. There is. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can also be used. Further, these charge transport substances can be used alone or in combination of two or more. When the charge transport material does not have film-forming properties,
A film can be formed by selecting an appropriate binder. Resins that can be used as binders are:
For example, insulating resins such as acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, or poly-N-vinyl. Organic photoconductive polymers such as carbazole, polyvinylanthracene, polyvinylpyrene and the like may be mentioned. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally it is 5 to 30μ, but the preferred range is 8 to 20μ. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. Examples of the substrate having a conductive layer include those whose substrate itself is conductive, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel,
Indium, gold, platinum, etc. can be used,
In addition, plastics having a layer formed by vacuum evaporation of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc., such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, (polyfluorinated ethylene, etc.), a substrate made of plastic coated with conductive particles (e.g. carbon black, silver particles, etc.) together with a suitable binder, a substrate made of plastic or paper impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used. A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. The undercoat layer is made of 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. It can be formed by The appropriate thickness of the undercoat layer is 0.1 to 5 microns, preferably 0.5 to 3 microns. 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 is an electron transport material, the surface of the charge transport layer must be positively charged, and exposure after charging is required. Then, in the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface and neutralize the positive charges, causing attenuation of the surface potential and creating an electrostatic contrast with the unexposed area. A visible image is 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, plastic film, etc. and 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, then developed and fixed. The type of developer, developing method, and fixing method may be any known developer or known method, and are not limited to a specific one. On the other hand, when the charge transport material is made of a hole transport material, it is necessary to charge the charge transport surface negatively, 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. Thereafter, it reaches the surface and neutralizes the negative charge, causing a decrease in surface potential and creating an electrostatic contrast with the unexposed area.
During development, it is necessary to use a positively charged toner, contrary to the case where an electron transporting substance is used. When using a photoreceptor in which a conductive layer, a charge transport layer, and a charge generation layer are laminated in this order, and the charge transport material is made of an electron transport material, the charge generation layer must be negatively charged, and when exposed after being charged, it is exposed to light. In this case, electrons generated in the charge generation layer are injected into the charge transport layer and then reach the substrate. On the other hand, holes generated in the charge generation layer reach the surface and the surface potential is attenuated, creating an electrostatic contrast with the unexposed area. A visible image is obtained by developing the electrostatic latent image thus formed with a positively charged toner. This can be directly fixed, or the toner image can be transferred to paper, plastic film, etc. and 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, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or methods, and are not limited to specific ones. On the other hand, when the charge transport material is a hole transport material, it is necessary to positively charge the surface of the charge generation layer, and when exposed to light after charging, the holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. Then it reaches the substrate. On the other hand, electrons generated in the charge generation layer reach the surface, and an electrostatic contrast is generated between the electrons and the unexposed area where the surface potential is attenuated. During development, it is necessary to use a negatively charged toner, contrary to the case where an electron transporting substance is used. In another specific example of the present invention, organic photoconductive materials such as the aforementioned hydrazones, pyrazolines, oxazoles, thiazoles, triarylmethanes, polyarylalkanes, triphenylamines, poly-N-vinylcarbazoles, etc. sexual substances and zinc oxide,
The photosensitive coating may contain the metallocene compound described above as a sensitizer for inorganic photoconductive substances such as cadmium sulfide and selenium. This photosensitive film is formed by coating these photoconductive substances and the above-mentioned metallocene compound together with a binder. Another specific example of the present invention is disclosed in Japanese Unexamined Patent Application Publication No. 1986-
It can also be used as a type of photoreceptor in which a charge generating material is added to a charge transfer complex as disclosed in Japanese Patent No. 916483 (photoconductive member). All of the photoreceptors contain at least one metallocene compound selected from the compounds represented by the general formula () of the present invention, and are used in combination with other photoconductive pigments or dyes having different light absorptions, if necessary. By doing so, it is possible to increase the sensitivity of this photoreceptor or to create a panchromatic photoreceptor. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers and CRTs.
It can also be widely used in electrophotographic applications such as printers. The present invention will be explained below using examples. Examples 1 to 17 Ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 ml of water) on an aluminum plate
was applied with a Mayer bar so that the film thickness after drying was 1.0μ, and dried. Next, 17 types of coating liquids were prepared by adding 5 g of each of the 17 metallocene compounds mentioned as specific examples to a solution of 2 g of butyral resin (butyralization degree: 63 mol %) dissolved in 95 ml of isopropyl alcohol. After each coating solution was dispersed in a sand mill, it was applied onto the casein subbing layer described above using a Mayer bar so that the film thickness after drying was 0.1 μm, and dried to form a charge generation layer. Next, 5 g of P-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone and polymethyl methacrylate (number average molecular weight
100,000) was dissolved in 70 ml of benzene, and this was applied onto the charge generation layer using a Mayer bar so that the film thickness after drying was 12μ, and dried to form a charge transport layer. The 17 types of electrophotographic photoreceptors created in this way were tested using an electrostatic copying paper tester model manufactured by Kawaguchi Electric Co., Ltd.
Dynamically corona-charge at -5KV using SP-428, hold for 1 second in a dark place, and then reduce the illuminance to 5KV.
It was exposed to UV light for 4 seconds and its charging characteristics were examined. As for the charging characteristics, the initial charging potential (V _O ) and the exposure amount (E1/2) required to attenuate the potential to 1/2 after dark decaying for 1 second were measured. In addition, the residual potential after 20 ux, sec exposure is expressed as _VR . The results are shown in Table 1.

【table】

【table】

[Table] Comparative examples 1 to 5 A photoreceptor was prepared in the same manner as in Example 1 except that the metallocene compound of Example 1 was used as the comparative compound, and the characteristics were investigated. The results are shown in Table 2.

[Table] All of the comparative examples have lower sensitivity and larger residual potential than the examples of the present invention. Furthermore, using the charge measuring device used in Example 1,
The same charging and exposing operation as in Example 1 was repeated 5000 times using a dynamic method, and the changes in the initial charging potential V _O and the residual potential _VR after exposure were investigated and are shown in Table 3. The same measurements were also carried out for the photoreceptors of Examples 1, 3, 10, and 17.

[Table] Although the photoreceptors of the comparative examples all have high initial residual potentials, the residual potentials upon repeated use are extremely high, which pushes up the V _O levels, which is a major problem due to their lack of practical stability. On the contrary, it is clear that the examples of the present invention are extremely stable even after repeated use and have excellent properties in practical use. Examples 18-20 A casein subbing layer was coated on an alumina plate in the same manner as in Example 1. Next, a charge transport layer containing the hydrazone compound used in Example 1 as a charge transport substance had a film thickness of 12 μm after drying.
It was coated with a Mayer bar to give the following properties and dried to form a charge transport layer. Next, the three coating solutions of Examples 1, 5, and 10 were applied onto the charge transport layer using a Mayer bar so that the film thickness after drying was 0.1 μm, and dried to form a charge generation layer. The charging characteristics of the three types of electrophotographic photoreceptors thus prepared were examined in the same manner as in Example 1.
This +5KV caused a corona charge. This result is the fourth
Shown in the table.

[Table] Example 21 1 g of poly-N-vinylcarbazole and 5 g of the above-mentioned exemplified metallocene compound No. 9 were added to 10 g of 1,2-dichloroethane, and the mixture was thoroughly stirred. The coating solution thus prepared was applied onto a polyethylene terephthalate film on which aluminum was vapor-deposited using a doctor blade so that the dry film thickness was 15 μm. The charging characteristics of this photoreceptor were measured in the same manner as in Example 1. However, the charging polarity was set to be positive. As a result, V _O is +585, E1/2 is 3.6ux, sec
It was hot. Example 22 A photoreceptor was prepared in exactly the same manner as in Example 21, except that the exemplified metallocene compound No. 16 was used in place of the exemplified metallocene compound No. 9 used in the preparation of the electrophotographic photoreceptor in Example 21. After that, the charging characteristics of this photoreceptor were measured. However, the charging polarity was set as positive. This result shows that V _O is +590V, E1/2 is 3.0ux,
It was hot in sec. Example 23 Fine particle zinc oxide (Sazex2000 manufactured by Sakai Chemical Co., Ltd.) 10
g, 4 g of acrylic resin (Dyanal LR009 manufactured by Mitsubishi Rayon Co., Ltd.), 10 g of toluene, and 10 mg of the above-mentioned exemplified metallocene compound No. 3 were thoroughly mixed in a ball mill, and the resulting coating solution was applied to aluminum-deposited polyethylene. It was applied onto a terephthalate film using a doctor blade to a dry film thickness of 21 μm, and dried to produce an electrophotographic photoreceptor. When the spectral sensitivity of this electrophotographic photoreceptor was measured using spectrophotography using electrophotography, it was found that the photoreceptor of this example was more sensitive on the long wavelength side than the zinc oxide coating that did not contain the metallocene compound mentioned above. It was found that it has. Example 24 An ammonia aqueous solution of casein was coated on an aluminum plate with a thickness of 100 μm and dried to form a subbing layer with a thickness of 1.1 μm. Next, 5 g of 2,4,7-trinitro-9-fluorene and 5 g of poly-N-vinylcarbazole (number average molecular weight: 300,000) were dissolved in 70 ml of tetrahydrofuran to form a charge transfer complex compound. 1 g of this charge transfer complex compound and the above-mentioned exemplified metallocene compound No. 15
5g of polyester (Byron, manufactured by Toyobo Co., Ltd.)
Add to the solution dissolved in 70ml of tetrahydrofuran,
Dispersed. This dispersion was applied onto the undercoat layer so that the film thickness after drying was 12μ, and dried. The charging characteristics of the photoreceptor thus prepared were measured in the same manner as in Example 1. However, the charging polarity was set to be positive.
This result shows that V _O is +570V and E1/2 is 3.4ux, sec
showed that. Example 25 A polyvinyl alcohol film having a thickness of 1.1 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. Next, the above-mentioned dispersion of metallocene compound No. 2 used in Example 2 was placed on the polyvinyl alcohol layer formed earlier so that the film thickness after drying was
It was coated with a Mayer bar to a thickness of 0.5μ and dried to form a charge generation layer. Next, 5 g of 1-[pyridyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline and polyarylate (condensation polymer of bisphenol A and terephthalic acid-isophthalic acid) A solution obtained by dissolving 5 g in 70 ml of tetrahydrofuran was coated on the charge generation layer so that the film thickness after drying was 10 μm, and dried to form a charge transport layer. The charging characteristics of the electrophotographic photoreceptor thus prepared were measured in the same manner as in Example 1. The results were as follows. V _O : -600V, E1/2: 2.5ux, sec Effects of the Invention As is clear from the above, the present invention provides high sensitivity and good repeatability by using the specific metallocene compound. It was possible to obtain an electrophotographic photoreceptor that can be used even in charging mode.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor having a conductive substrate and a photoconductive layer, wherein the photoconductive layer has the general formula However, in the formula, m is 0, 1 or 2, n is an integer of 0 or 1, and Y is a 5- to 6-membered heterocycle that may have a substituent or an aromatic ring that may have a substituent. Represents a residue for forming a 5- to 6-membered heterocycle fused with, R represents an optionally substituted aliphatic group or aryl group, M represents Ti, V, Cr, Fe, Co,
Indicates a transition metal selected from Ni and Rn,
An electrophotographic photoreceptor comprising a metallocene compound, wherein - represents an anionic functional group.