JPH032872A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve sensitivity and potential stability at the time of repeated use by forming a photosensitive layer contg. an azo pigment. CONSTITUTION:A photoconductive layer contg. an azo pigment obtd. by bringing a chain compd. having an active methylene group and an arom. diazonium salt into azo coupling is formed. Since the azo pigment contg. the active methylene compd. as a coupler component has an electron attracting group bonding directly to the alpha-, beta- or gamma-position of the azo group in a conjugate state unlike a naphthol-azo pigment, a shift to the longer wavelength side, an increase of the extinction coefft. and intramolecular electric charge separation due to intramolecular electric charge transfer occur easily. Accordingly, higher sensitivity is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to electrophotographic photoreceptors, and more particularly to electrophotographic photoreceptors containing charge generating materials that provide improved electrophotographic properties.

(Prior Art and its Problems) Conventionally, inorganic photoreceptors having a photosensitive layer containing selenium, cadmium sulfide, zinc oxide, etc. as main components have been widely used as electrophotographic photoreceptors.

These photoreceptors are not necessarily satisfactory in terms of thermal stability, moisture resistance, durability, etc. Particularly, selenium and cadmium sulfide are toxic and therefore have limitations in production and handling.

On the other hand, organic photoreceptors having a photosensitive layer containing an organic photoconductive compound as a main component have many advantages, such as compensating for the above-mentioned drawbacks of inorganic photoreceptors, and have attracted attention in recent years.

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

On the other hand, functionally separated electrophotographic photoreceptors in which the charge generation function and the charge transport function are shared by separate substances 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 the advantage that there is a wide selection range of materials for each of the charge-generating substance and the charge-transporting substance, and that an electrophotographic photoreceptor having arbitrary characteristics can be produced relatively easily. .

As charge-generating substances, various azo pigments, phthalocyanine pigments, polycyclic quinone door materials, cyanine dyes, squaric acid dyes, biryllium chemical dyes, etc. 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.

These azo pigments can generally be obtained by azo coupling of a coupler component having a phenolic hydroxyl group and a diazonium salt. Examples of such coupler components include naphthol couplers described in JP-A-47-37543, JP-A-56-94358, JP-A-57-58154, and JP-A-58-1.2.
benzocarbazole coupler described in Publication No. 2967,
Naphthalimide couplers described in Japanese Patent Publication No. 60-5941, perinone couplers described in Japanese Patent Application Laid-open No. 57-176055, and the like are known.

Many azo pigments produced using such coupler components have been proposed, but very few have been put into practical use because they have problems in terms of sensitivity and potential stability during repeated use.

Therefore, an object of the present invention is to provide a novel electrophotographic photoreceptor.

A second object of the present invention is to provide an electrophotographic photoreceptor that maintains practical high sensitivity and stable potential characteristics during repeated use, and exhibits good image characteristics.

(Means for Solving the Problems) The present inventor has conducted studies to solve the problems of the prior art described above, and as a result has arrived at the present invention.

That is, the present invention is an electrophotographic photoreceptor characterized by comprising a photoconductive layer containing an azo pigment obtained by azo coupling a chain compound having an active methylene group and an aromatic diazonium salt.

(Function) The azo pigment used in the present invention, which has an active methylene compound as a coupler component, has an electron-withdrawing group directly conjugated to the α-, β-, or γ-position of the azo group, compared to known naphthol-based azo pigments. As a result, the wavelength becomes longer and the extinction coefficient increases due to intramolecular charge transfer, and higher sensitivity can be achieved by easily causing intramolecular charge separation.

(Preferred embodiment) In the present invention, the chain compound having an active methylene group is
Benzene activated by an electron-withdrawing group such as a carbamoyl group, thiocarbamoyl group, thiocarbonyl group, sulfone group, dicyanomethylenecarbonyl group, cyano group, nitro group or cyanogen group, nitro group, trifluoromethyl group, halogen atom, etc. It is preferable that the active methylene group has a chain active methylene group activated by at least one group selected from an aryl group such as a ring or a naphthalene ring, and in particular, the active methylene compound is a compound represented by the following general formula (1). The effect is remarkable in the case of

and these may be the same or different. R1
and R2 is a cyano group, a nitro group, an aryl group such as a phenyl group, a naphthyl group, a phenanthryl group, a pyrenyl group, or a perylene group even if it has a substituent, a hetero group such as a carbamoyl group, a thiocarbamoyl group, a pyridyl group, or a quinolyl group. Indicates a ring group, A1. A2, A3 and A4 represent hydrogen atoms or cyan groups, n and m represent integers from 0 to 2, and k
and β represents an integer of 0 or 1.

The substituents that R' and R2 may have include a nitro group, a cyano group, a halogen group such as chlorine, fluorine or bromine,
Alkyl groups such as methyl, ethyl or propyl groups, aryl groups such as phenyl or naphthyl groups, aralkyl groups such as benzyl or phenethyl groups, alkoxy groups such as methoxy or ethoxy groups, trifluoromethyl groups, trichloromethyl or a halogen-substituted alkyl group such as a dichloromethyl group.

Specific examples of the chain compound having an active methylene group used in the present invention are shown below.

H, C (GoμH-Phl 2 1 NH-Ph / H, C \ NH-Ph / Shimph / C0NHCONH-Ph so, ph Azo-coupled with the above coupler component Azonium compounds include diazonium salts, tetrazonium salts,
Hexazonium salt or octazonium salt etc. are used,
They are obtained as monoazo pigments, disazo pigments, trisazo pigments or tetrakisazo pigments, respectively.

The azonium salts include hydrocarbon aromatic rings such as benzene, naphthalene, fluorene, phenanthrene, anthracene, and pyrene, furan, thiophenone, pyridine, indole, benzothiazole, carbazole, acridone,
Heteroaromatic rings such as dibenzothiophenone, benzoxazole, benzotriazole, oxadiazole, thiazole, etc., and those in which the above aromatic rings are bonded directly or with an aromatic group or a non-aromatic group, such as triphenylamine, diphenylamine, N-methyldiphenylamine,
biphenyl, terphenyl, binaphthyl, fluorenone, phenanthrenequinone, anthraquinone, benzanthrone, diphenyloxadiazole, phenylbenzoxazole, diphenylmethane, diphenylsulfone, diphenyl ether, benzophenone, stilbene,
It can be obtained from distyrylbenzene, tetraphenyl-p-phenylenediamine, tetraphenylbenzidine, etc.

Examples of substituents that the aromatic hydrocarbon group or aromatic heterocyclic group may have through the bonding group include alkyl groups such as methyl, ethyl, propyl, butyl, alkoxy groups such as methoxy and ethoxy, and dimethyl Examples include dialkylamino groups such as amino and diethylamino, halogen atoms such as fluorine, chlorine, and bromine, hydroxy groups, nitro groups, cyan groups, and halomethyl groups.

Next, specific examples of azonium salts used in the present invention are listed below. However, the diazonium group is omitted and only the bonding position is shown.

diazonium salt C2H8 Hs CJs C,H.

CH.

Specific examples of the azo pigment of the present invention are shown below.

C211s The azo pigment of the present invention is not limited by the above specific examples.

As for the structure of the azo pigment of the present invention, for example, azollH4 synthesized by the reaction of the active methylene compound 41 and azonium salt Al-1 has the following tautomers of azo type and vidrazodone type. It has been confirmed from the IR spectrum that the hydrazone type is preferential.

Although which structure has priority in other azo pigments varies depending on the synthesis conditions, coupler structure, substituent group of the azonium salt, etc., in the present invention, the azo type is described for convenience.

The above specific examples of couplers, specific examples of azonium salts, and specific examples of azo pigments are not intended to limit the scope of the claims of the present invention.

Further, although only azo type isomers are shown as specific examples of azo pigments, hydrazone type or other possible tautomers may be used.

Next, a synthesis example of the azo pigment used in the present invention will be shown below.

(Synthesis example) Synthesis of disazo pigment (9) 1.5 g of malonic acid-m-nitrophenylamide (4,
9 mmol), N,N-dimethylformamide 100
ml and cooled to 10°C. To this solution was added 1 g (2.3 mmol) of the following tetrazonium salt. 0.47 g (4.6 mmol) of 2 minute diameter triethylamine was added dropwise,
The mixture was stirred at 10° C. for 1 hour. Thereafter, the reaction solution was filtered, and the residue was washed with 100 ml of methanol and then vacuum dried to obtain 0.9 g of a black-blue pigment.

The coating containing the azo pigment described above exhibits photoconductivity and can therefore 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 can be produced by forming a film on a conductive substrate by dispersing the azo pigment in a suitable binder.

In a preferred embodiment of the present invention, a photoconductive coating containing the above-mentioned specific azo pigment is used as a charge generation layer in an electrophotographic photoreceptor in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. can be applied.

The charge generating layer contains the aforementioned specific azo pigments which exhibit as much photoconductivity as possible in order to obtain sufficient absorbance;
In addition, in order to efficiently transport the generated charge carriers to the interface between the charge transport layer and the conductive substrate, a thin film layer, for example, 5 μm or less, preferably 0.01 to 1 μm, is used.
A thin film layer having a thickness of m is desirable.

This means that most of the incident light is absorbed by the charge generation layer, generating many charge carriers, and that the generated charge carriers are not deactivated by recombination or trapping, and the charge transport layer This is due to the need to inject.

The binder that can be used to form 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, polyvinyl benzal, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, Examples include insulating resins such as urethane resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is suitably 80% by weight or less, 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 charge transport layer or undercoat layer described below.

Specific organic solvents include methanol, ethanol,
Alcohols such as Impropatool, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, dichlorohexanone, N.

Amides such as N-dimethylformamide and 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, and methylene chloride. , aliphatic halogenated hydrocarbons such as dichloroethylene, carbon tetrachloride, and trichlorethylene, or aromatics such as benzene, toluene, xylene, monochlorobenzene, and dichlorobenzene.

Coating can be done by dip coating method, spray coating method,
spinner coating method, bead coating method, Meyer bar coating method, blade coating method,
This can be carried out using a coating method such as 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 a temperature of 30 to 200° C. for 5 minutes to 2 hours, either stationary or under ventilation.

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 to the surface. have.

At this time, the charge transport layer may be laminated above or below the charge generation stores.

Charge transporting substances include electron transporting substances and hole transporting substances, and electron transporting substances include chloranil, tetracyanoethylene, tetracyanoquinodimethane, 2,
4,5.7-tetranitro-9-fluorenone, 2,4
, 5,7-titranitroxanthone, 2,4,84linitrothioxanthone, and other electron-withdrawing substances, as well as polymers of these electron-withdrawing substances.

Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, and N,N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine. , p-diethylaminobenzaldehyde-N,N-
Diphenylhydrazone, p-pyrrolidinobenzaldehyde-N,N-diphenylhydrazone, p-diethylaminobenzaldehyde-3-methylbenzthiazolinone-
2-hydrazones such as hydrazone, 2,
5-bis(p-diethylaminophenyl)-1,3,4
-Oxadiazole, 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(p
-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, l-[pyridyl(3)]-3
-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridyl (2)
] -3-, (p-diethylaminostyryl)-4-methyl-5-(p-diethylaminophenyl)pyrazoline, 1-phenyl-3-(p-diethylaminostyryl)
-4-Methyl-5-(p-diethylaminophenyl)pyrazoline, spiropyrazoline and other pyrazolines, α-phenyl-4-N, N-diphenylaminostilbene, N
-ethyl-3(α-phenylstyryl)carbazole,
Styryl compounds such as 9-dibenzylaminobenzylidene-9H-fluorenone, 5-p-ditolylaminobenzylidene-5H-dibenzo[a,d]cycloheptene,
2-(P-diethylaminostyryl)-6-dinithylaminopenzoxazole, 2-(p-diethylaminophenyl)-4-(p-dimethylaminophenyl)-5-
Oxazole compounds such as (2-chlorophenyl)oxazole, 2-(p-diethylaminostyryl)-6-
Thiazole compounds such as dinithylaminobenzothiazole, bis(4-diethylamino-2-methylphenyl)
Triarylmethane compounds such as phenylmethane, 1,
1-bis(4-N,N-diethylamine-2-methylphenyl)hebutane, 1.1,2.2-tetrakis(4-
Polyarylalkanes such as N,N-dimethylamine-2-methylphenyl)ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9
-vinyl anthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin and the like. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can also be used.

Also, these charge transport materials have 1 f! [Or two or more types can be used in combination.

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 include, for example, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, etc. Examples include insulating resins and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. - 5 to 40 μm for boat fishing, but the preferred range is 10 to 30 LLm. 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. As such a substrate, a metal whose substrate itself is conductive can be used.Other examples include aluminum, aluminum alloy, indium oxide, tin oxide, and indium oxide.
Plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyethylene fluoride, etc.) having a layer formed of a tin oxide alloy or the like by vacuum evaporation can be used, and conductive particles ( For example, a substrate in which plastic is coated with carbon black, silver particles, etc.) together with a suitable binder, a substrate in which plastic or paper is impregnated with conductive particles, a plastic having a conductive polymer, etc. can be used.

A subbing layer having barrier and adhesive functions may also be provided between the conductive support and the photosensitive layer.

The subbing layer is casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, and gelatin.

It can be formed from aluminum oxide or the like.

The thickness of the undercoat layer is 0.1 to 5 μm, preferably 0.5 μm.
A suitable thickness is 3 μm to 3 μm.

Furthermore, another specific example of the present invention is an electrophotographic photoreceptor containing the above-mentioned azo pigment and a charge transporting substance in the same layer. At this time, a charge transfer complex compound consisting of poly-N-vinylcarbazole and trinitrofluorenone can be used in addition to the above-mentioned charge transport substance.

The electrophotographic photoreceptor of this example can be prepared by dispersing the above-mentioned azo pigment and charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran, and then forming a film thereon.

In any electrophotographic photoreceptor, the pigment used contains at least one type of pigment, and its crystal form may be amorphous or crystalline.

In addition, if necessary, pigments with different light absorptions may be used in combination to increase the sensitivity of the photoreceptor, or two or more types of azo pigments may be combined for the purpose of obtaining a panchromatic photoreceptor.
Alternatively, it can also be used in combination with a charge generating substance selected from known dyes and pigments.

The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines, but also in a wide range of electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

〔Example) Next, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 8 5 g of methoxymethylated nylon resin (average molecular weight 32,000) and 10 g of alcohol-soluble copolymerized nylon resin (average molecular weight 29,000) were placed on an aluminum substrate.
was dissolved in 95 g of methanol and applied with a Mayer bar to form an undercoat layer having a thickness of 1 LLm after drying.

Next, 3 g of the above-exemplified azo pigment (No. 12) was added to a solution prepared by dissolving 2 g of butyral resin (butyralization degree 63 mol%) in 95 ml of cyclohexanone, and the mixture was heated in a sand mill for 2 g.
Dispersed for 0 hours. This dispersion was applied onto the previously formed undercoat layer using a Mayer bar and dried to form a charge generation layer so that the film thickness after drying was 0.2 LLm.

Polymethyl methacrylate resin (number average molecular weight 100.
000) was dissolved in 40 ml of toluene, and this was applied onto the charge generation layer using a Mayer bar so that the film thickness after drying was 17 μm, and dried to form a charge transport layer.
A photoreceptor of Example 1 was prepared.

Photoreceptors corresponding to Examples 2 to 8 were prepared in exactly the same manner using other exemplary pigments shown in Table 1 below in place of azo pigments No. 12.

The electrophotographic photoreceptor thus prepared was statically charged with corona at 15 Kv using an electrostatic copying paper tester Moddel SP-428 manufactured by Kawaguchi Denki, held in a dark place for 1 second, and then exposed at an illuminance of 101 ux. The charging characteristics were investigated.

The charging characteristics include the surface potential (vo) and the amount of exposure (E) required to attenuate the potential by half after leaving it in the dark for 1 second.
l/□) was measured. The results are shown in Table 1 below.

Table 1 From the results, it can be seen that all the electrophotographic photoreceptors of the present invention have sufficient charging ability and excellent sensitivity.

Examples 9 to 12 Using the electrophotographic photoreceptors prepared in Examples 2, 6, 7, and 8, fluctuations in bright area potential and dark area potential during repeated use were measured.

As a method, the photoreceptor was attached to a cylinder of an electrophotographic photoreceptor equipped with a -6.5 KV corona charger, an exposure optical system, a developing device, a transfer charger, a Zn removal optical system, and a cleaner. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copying machine, the initial dark area potential (V, ) and light area potential (VL) were set to around -700V and -200V, respectively, and the
The amount of variation in dark area potential (ΔVO) and the amount of variation in light area potential (ΔV, , ) when used twice were measured. The results are shown in Table 2 below. Note that a negative sign in the amount of change in potential represents a decrease in potential, and a positive sign represents an increase in potential.

15. In place of 16 and 17, the following comparative azo pigments 1.2.
A photoreceptor was prepared in exactly the same manner as in Example 1, except that samples 3 and 4 were used, and the charging characteristics similar to those in Examples 1 to 8 and potential fluctuations during repeated use were measured in the same manner as in Examples 9 to 12. The results are shown in Table 3 below.

Comparative Pigment Comparative Examples 1 to 4 Azo pigment 8 used in Examples 2.6.7 and 8, HO-C
CH.

An alcohol film was formed. Next, the disazo pigment dispersion used in Example 5 was applied onto the previously formed polyvinyl alcohol layer using a Mayer bar so that the film thickness after drying was 0.2 μm, and dried to form a charge generation layer. did.

From Examples 2.6.7.9.10 to 12 and Comparative Examples 1 to 4, it can be seen that the photoreceptor using the azo pigment of the present invention has less sensitivity and potential fluctuation during repeated use.

Example 13 4 g of a styryl compound represented by polyvinyl with a film thickness of 0.5 tLm and 5 g of polyarylate resin (condensation polymer of bisphenol A and terephthalic acid-isophthalic acid) were placed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film in 40 ml of tetrahydrofuran. A charge transport layer was formed by coating and drying a solution dissolved in the above liquid on the charge generation layer so that the film thickness after drying was 20 μm. The charging characteristics and durability characteristics of the photoreceptor thus prepared were measured by the same method as in Examples 1 and 9. The results are shown below.

V,, 690 (-V) E +/z; 4, O (1ux, sec,)
ΔVo ;-E) (v) Δv, ,; 2 (■) Example 14 A photoreceptor was prepared by applying the charge generation layer and charge transport layer of the photoreceptor prepared in Example 13 in the reverse order, and the experiment was carried out. The charging characteristics were evaluated in the same manner as in Example 1.

However, the charging characteristics were set to 10.

■. ;650(+v).

El/2; 1.3 (1ux, sec,) Example 15 On the charge generation layer prepared in Example 6, 5 g of 2゜4.7-dolinitro-9-fluorenone and poly-4,4゛-dioxy A solution prepared by dissolving 6 g of diphenyl-2,2' propane carbonate (molecular weight 250,000) in 70 ml of monochlorobenzene was coated and dried so that the film thickness after drying was 15 μm.

The electrophotographic photoreceptor thus produced was evaluated in the same manner as in Example 1. However, the charging polarity is only 10V; 650 (+v) El/2: 3. O (lux, sec,) Example 16 2.4.74 linitro-9-fluorenone 6g and poly-
N-vinylcarbazole (number average molecular ffi 350,
000) was dissolved in 70 ml of tetrahydrofuran to form a charge transfer complex compound.

This charge transfer complex compound and the above-mentioned azo pigment (No.
7) 2g of polyester resin (Vylon; manufactured by Toyobo)
5 g was dissolved in 70 ml of tetrahydrofuran and dispersed. This dispersion was applied onto the subbing layer prepared in Example 1 and dried to form a photosensitive layer having a thickness of 18 μm.

The photoreceptor thus produced was evaluated in the same manner as in Example 1. However, the charging polarity was set to 10.

Vo; 650 (+v) E +7i; 4, 5 (lux, sec,) Examples 17 to 20 An undercoat layer was provided on an aluminum substrate in the same manner as in Example 1. Next, a charge generation layer was formed in the same manner as in Example 1 using the above-mentioned azo pigment No. 9.

Next, a charge transport layer was formed in the same manner as in Example 1 using a triarylamine compound having the following structure to prepare a photoreceptor.

All photoreceptors corresponding to Examples 18 to 2o were prepared in the same manner using other exemplary pigments shown in Table 3 in place of azo pigment No. 9. In exactly the same way, surface potential (vo) and exposure amount (E, /2)
was measured. The results are shown in Table 4.

Examples 21 to 24 Using the electrophotographic photoreceptors prepared in Examples 17 to 20,
In the same manner as in Example 21, the amount of variation in bright area potential (ΔVL) and the amount of variation in dark area potential (Δ■.) during repeated use were measured. The results are shown in Table 5 below.

Example 25 The photoreceptor prepared in Example 6 was subjected to a corona discharge of 15 KV. 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 1 second. Sensitivity is the exposure amount (E station, microjoule/c) required to attenuate the potential Vl after dark decay to A.
The evaluation was made by measuring rn'). At this time, a gallium/aluminum/propylene ternary semiconductor laser (output: 5 mw; oscillation wavelength: 780 nm) was used as a light source. These results were as follows.

■. ;-690v Vl ;-685V E,,,; 1.5 microjoules/crn' Next, a laser beam printer (Canon, LBP-CXI) which is a reversal development type electrophotographic printer equipped with the same semiconductor laser as above. The above photoreceptor was replaced with an LBP-CX photoreceptor, and an actual image forming test was conducted under the following conditions.

Surface potential after primary charging: 70OV, surface potential after image exposure: -150V (exposure i: 12.Ou
J/crn') Transfer potential +700V, developer polarity; negative polarity, process speed; 50 mm/sec, image exposure scanning method; image scanning, - exposure before next charging;
Full red exposure was performed at 501 ux-sec. Image formation was performed by line scanning a laser beam in accordance with character and image signals, and good prints were obtained for both characters and images. Furthermore, when 3,000 images were printed continuously, stable and good prints were obtained from the initial stage up to 3,000 sheets.

(Effects of the Invention) As described above, by using the azo pigment of the present invention in the photosensitive layer, the generation efficiency and/or injection efficiency of carriers inside the photoreceptor are improved, and the sensitivity and the efficiency of carrier injection during repeated use are improved. A photoreceptor with excellent potential stability can be obtained.

Patent applicant: Canon Co., Ltd.

Claims (3)

[Claims] (1) An electrophotographic photoreceptor comprising a photoconductive layer containing an azo pigment obtained by azo coupling a chain compound having an active methylene group and an aromatic diazonium salt. (2) The chain compound having an active methylene group is selected from a carbamoyl group, a thiocarbamoyl group, a thiocarbonyl group, a sulfone group, a dicyanomethylenecarbonyl group, a cyano group, a nitro group, or an aryl group having an electron-withdrawing group. The electrophotographic photoreceptor according to claim 1, having a linear active methylene group activated by at least one group. (3) The electrophotographic photoreceptor according to claim 1, wherein the active methylene compound is a compound represented by the following general formula (1). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) (In the formula, X^1 and
There are chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Indicates a group, and these may be the same or different. R^
1 and R^2 represent a cyano group, a nitro group, an aryl group which may have a substituent, a carbamoyl group, a thiocarbamoyl group, or a heterocyclic group, and A^1, A^2, A^3 and A^
4 represents a hydrogen atom or a cyano group, and n and m are 0 to 2
k and l represent integers of 0 or 1. )