JP2641061B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member containing a disazo pigment having a specific molecular structure in a photosensitive layer.

2. Description of the Related Art Electrophotography is a method of coating an insulating material in a dark place whose electric resistance changes according to the dose received during image exposure, as disclosed in US Pat. No. 2,297,691. A photoconductive material made of a support is used.

The basic characteristics required of an electrophotographic photoreceptor using this photoconductive material are (1) that it can be charged to an appropriate potential in a dark place, (2) that there is little dissipation of electric charge in a dark place, 3) Charges can be quickly dissipated by light irradiation.

Conventionally, selenium, zinc oxide,
Inorganic photoreceptors having a photosensitive layer mainly composed of an inorganic photoconductive compound such as cadmium sulfide have been widely used. However, they satisfy the above conditions (1) to (3), but do not always satisfy thermal stability, moisture resistance, durability and the like. For example, when selenium is crystallized, its characteristics as a photoreceptor are deteriorated, so that it is difficult to manufacture, and selenium is crystallized due to heat, fingerprints and the like, and the performance as a photoreceptor is deteriorated. Cadmium sulfide has problems in moisture resistance and durability, and zinc oxide has problems in smoothness, hardness and friction resistance.

Furthermore, the photosensitive wavelength range of many inorganic photosensitive members is limited. For example, in the case of selenium, the photosensitive wavelength range is the blue range, and there is almost no sensitivity in the red range.

Therefore, various methods have been proposed to extend the photosensitivity to a long wavelength region, but there are many restrictions on the selection of the photosensitive wavelength region.
Even when zinc oxide or cadmium sulfide is used as the photoreceptor, the photosensitive wavelength range of the photoreceptor itself is narrow, and it is necessary to add various sensitizers.

In order to overcome the disadvantages of these inorganic photoreceptors, electrophotographic photoreceptors containing various organic photoconductive compounds as main components have been actively developed in recent years.

For example, Japanese Patent Publication No. 50-10496 and U.S. Pat. No. 3,484,237 disclose a photoreceptor having a photosensitive layer containing poly-N-vinylcarbazole and 2,4,7-trinitrofluorenone-9-one. N-vinylcarbazole sensitized with a pyrylium salt dye (Japanese Patent Publication No. 48-25658)
and so on.

These organic electrophotographic photoreceptors improved the disadvantages of the inorganic electrophotographic photoreceptor to some extent, but generally had low photosensitivity and were not suitable for repeated use. In order to overcome these drawbacks, various photoconductors have recently been proposed as organic electrophotographic photoconductors. Among them, a layer containing a substance that generates charge carriers when irradiated with light (hereinafter referred to as a charge generation substance) (hereinafter referred to as a charge generation substance) , A charge generation layer) and a layer mainly composed of a substance that receives and transports the charge carriers generated by the charge generation layer (hereinafter, charge transport substance) (hereinafter, referred to as a charge transport substance).
Some of the laminated photoconductors (which are referred to as a charge transport layer) are practically used because they generally have higher sensitivity than conventional organic electrophotographic photoconductors and can withstand repeated use.

Such an organic photoconductive compound is easier to synthesize than an inorganic photoconductive compound, and furthermore, it is possible to control the color sensitivity because the photosensitive wavelength range of the visible light sensitivity can be changed relatively easily by molecular design. Is a non-polluting, highly productive and economical product that is far superior to inorganic semiconductors. Not a few.

However, at present, there are still many places where the durability, especially the stability of the potential when repeatedly used, is inferior to the inorganic photoconductive compound represented by amorphous silicon in the presence or absence of a potential change due to environmental fluctuations. .

In addition, if the electrophotographic photoreceptor is left in a place where a certain amount of light hits, the potential of the portion to which the light hits is attenuated. Was not.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel electrophotographic photoreceptor, and have a stable potential characteristic when repeatedly using a practical high sensitivity characteristic in a visible light region, and To provide an electrophotographic photoreceptor having improved photomemory characteristics, and to provide a novel photoconductive compound.

[Means for Solving the Problems and Action] The present invention comprises an electrophotographic photoreceptor characterized in that the photosensitive layer contains a disazo pigment represented by the following general formula (1).

General formula In the formula, R ₁ represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, a heterocyclic group or a halogen group, and R ₂ and R ₃ have a hydrogen atom and a substituent Represents an alkyl group, an aryl group, an aralkyl group, a heterocyclic group or a halogen group, and A represents a coupler residue having a phenolic hydroxyl group.

More specifically, groups other than hydrogen atoms represented by R ₁ , R ₂ and R ₃ are groups such as methyl, ethyl, propyl, isopropyl, and butyl as unsubstituted alkyl groups, halogen groups,
As a substituted alkyl group substituted with a cyano group, etc. _{-CH 2 -CCl 3, -CH 2 -CN} , groups such as -CHF-CH ₂ F, benzyl aralkyl group, phenethyl, groups such as naphthylmethyl, phenyl as aryl group, a naphthyl, group, such as anthryl, further, A benzene ring moiety of an aryl group substituted with a halogen group, an alkyl group such as methyl or ethyl, or a substituted alkyl group such as chloromethyl; a heterocyclic group such as pyridine, thienyl, furyl, carbazolyl, or a heterocyclic group; A group in which one or more hydrogen atoms of the group are substituted with a halogen group, a substituted or unsubstituted alkyl group, and examples of the halogen group include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

More preferred specific examples of the coupler residue having a phenolic hydroxyl group represented by A include the following general formulas (2) to (2).
The residue shown by (8) is mentioned.

General formula In the formula, X is condensed with a benzene ring to form a naphthalene ring, an anthracene ring, a carbazole ring, a benzocarbazole ring,
Represents a residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring such as a dibenzcarbazole ring, a dibenzofuran ring, a dibenzonaphthofuran ring, a diphenylene sulfide ring, and a fluorenone ring, and may have a substituent. .

R ₄ and R ₅ are a hydrogen atom, an alkyl group which may have a substituent, an aryl, an aralkyl group, a heterocyclic group or R ₄ ,
And a cyclic amino group containing a nitrogen atom to which R ₅ is bonded in the ring.

Specific examples of the alkyl group include methyl, ethyl, propyl, and butyl; specific examples of the aralkyl group; benzyl, phenethyl, and naphthylmethyl; and specific examples of the aryl group include phenyl, diphenyl, naphthyl, and anthryl. Specific examples include carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, pyridine and the like.

R ₆ represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group which may have a substituent, and specific examples of R ₆ are the same as those described above for R ₄ and R ₅ .

Examples of the substituent in the alkyl group, the aryl group, the aralkyl group, the alkoxy group and the heterocyclic group represented by the substituents R _{4 to} R _{6 in} the general formulas (2) to (4) include a fluorine atom,
Halogen atoms such as chlorine atom, iodine atom and bromine atom,
Alkyl groups such as methyl, ethyl, propyl, isopropyl and butyl, alkoxy groups such as methoxy, ethoxy, propoxy and phenoxy, nitro groups, cyano groups, dimethylamino, dibenzylamino, diphenylamino, morpholino, substituted amino such as piperidino and pyrrolidino And the like.

Y represents an aromatic hydrocarbon divalent group or a heterocyclic divalent group containing a nitrogen atom in the ring, and the aromatic hydrocarbon divalent group is a monocyclic aromatic hydrocarbon such as o-phenylene; Hydrogen divalent group, o-naphthylene, perinaphthylene, 1,2-
Anthrylene, a divalent group of a condensed polycyclic aromatic hydrocarbon such as 9,10-phenanthrylene and the like, and as a divalent group of a heterocyclic ring containing a nitrogen atom in the ring, a 3,4-pyrazoldiyl group, Examples thereof include divalent groups such as a 2,3-pyridinediyl group, a 4,5-pyrimidinediyl group, a 6,7-indazolediyl group, and a 6,7-quinolinediyl group.

In the formula, R ₇ represents an aryl group or a heterocyclic group which may have a substituent.Specifically, the aryl group is phenyl, naphthyl, anthryl, pyrenyl, and the heterocyclic group is pyridyl, thienyl, furyl, It represents a carbazolyl group.

Further, examples of the substituent of the aryl group and the heterocyclic group include a halogen atom such as a fluorine atom, a chlorine atom, an iodine atom, and a bromine atom; an alkyl group such as methyl, ethyl, propyl, isopropyl, and butyl; methoxy, ethoxy, propoxy, and phenoxy. And substituted amino groups such as alkoxy group, nitro group, cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino and pyrrolidino.

R ₈ and R ₉ represent an alkyl group which may have a substituent, an aralkyl group, an aryl group, or a heterocyclic group, and specifically, as the alkyl group, methyl, ethyl, propyl, butyl, and the aralkyl group Benzyl, phenethyl, naphthylmethyl, aryl groups include phenyl, diphenyl, naphthyl, anthryl, and heterocyclic groups include carbazolyl, thienyl, pyridyl, furyl, and the like.Also, alkyl groups, aralkyl groups, aryl groups, and heterocyclic groups Examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, an iodine atom and a bromine atom; an alkyl group such as methyl, ethyl, propyl, isopropyl and butyl; an alkoxy group such as methoxy, ethoxy, propoxy and phenoxy; and a nitro group. , Cyano group, dimethylamino, dibenzylamino, dife Arylamino, morpholino, piperidino, and substituted amino groups such as pyrrolidino.

Specific examples of the disazo pigment represented by the general formula (1) are listed below.

As a description method, A which is a coupler residue having a central skeleton of a disazo pigment and a phenolic hydroxyl group is described.

Illustrative pigment (1) Exemplary pigment (2) Central skeleton: Same as above Exemplary pigment (3) Central skeleton: Same as above Exemplary pigment (4) Central skeleton: Same as above Exemplary pigment (5) Central skeleton: Same as above Exemplary pigment (6) Central skeleton: Same as above Exemplary pigment (7) Central skeleton: Same as above Exemplary pigment (8) Central skeleton: Same as above Exemplary pigment (9) Central skeleton: Same as above Exemplary pigment (10) Central skeleton: Same as above Illustrative pigment (11) Central skeleton: Same as above Exemplary pigment (12) Central skeleton: Same as above Illustrative pigment (13) Central skeleton: Same as above Illustrative pigment (14) Central skeleton: Same as above Illustrative pigment (15) Central skeleton: Same as above Illustrative pigment (16) Central skeleton: Same as above Illustrative pigment (17) Central skeleton: Same as above Illustrative pigment (18) Central skeleton: Same as above Illustrative pigment (19) Central skeleton: Same as above Illustrative pigment (20) Central skeleton: Same as above Illustrative pigment (21) Central skeleton: Same as above Illustrative pigment (22) Central skeleton: Same as above Illustrative pigment (23) Central skeleton: Same as above Exemplary pigment (24) Central skeleton: Same as above Exemplary pigment (25) Central skeleton: Same as above Illustrative pigment (26) Central skeleton: Same as above Illustrative pigment (27) Central skeleton: Same as above Exemplary pigment (28) Central skeleton: Same as above Exemplary pigment (29) Central skeleton: Same as above Exemplary pigment (30) Central skeleton: Same as above Exemplary pigment (31) Central skeleton: Same as above Exemplary pigment (32) Central skeleton: Same as above Illustrative pigment (33) Central skeleton: Same as above Illustrative pigment (34) Central skeleton: Same as above Illustrative pigment (35) Central skeleton: Same as above Exemplary pigment (36) Central skeleton: Same as above Illustrative pigment (37) Central skeleton: Same as above Illustrative pigment (38) Central skeleton: Same as above Illustrative pigment (39) Central skeleton: Same as above Exemplary pigment (40) Central skeleton: Same as above Illustrative pigments (41) Illustrative pigment (42) Central skeleton: Same as above Illustrative pigment (43) Central skeleton: Same as above Illustrative pigment (44) Central skeleton: Same as above Illustrative pigment (45) Central skeleton: Same as above Illustrative pigments (46) Exemplary pigment (47) Central skeleton: Same as above Illustrative pigment (48) Illustrative pigment (49) Illustrative pigments (50) Illustrative pigments (51) Illustrative pigment (52) Central skeleton: Same as above Illustrative pigment (53) Central skeleton: Same as above Illustrative pigment (54) Central skeleton: Same as above Illustrative pigment (55) Central skeleton: Same as above Illustrative pigment (56) Illustrative pigment (57) Central skeleton: Same as above Illustrative pigment (58) Central skeleton: Same as above Illustrative pigments (59) Exemplary pigment (60) Central skeleton: Same as above Illustrative pigments (61) Illustrative pigment (62) Central skeleton: Same as above Illustrative pigments (63) Illustrative pigment (64) Central skeleton: Same as above Illustrative pigment (65) Illustrative pigment (66) Exemplary pigment (67) Central skeleton: Same as above Illustrative pigment (68) Illustrative pigment (69) Central skeleton: Same as above Illustrative pigment (70) Illustrative pigments (71) Exemplary pigment (72) Central skeleton: Same as above Illustrative pigment (73) Exemplary pigment (74) Central skeleton: Same as above Exemplary pigment (75) Central skeleton: Same as above Illustrative pigment (76) Illustrative pigment (77) Central skeleton: Same as above Illustrative pigment (78) Illustrative pigment (79) Central skeleton: Same as above Exemplary pigment (80) Central skeleton: Same as above Illustrative pigment (81) Illustrative pigment (82) Central skeleton: Same as above Illustrative pigment (83) Central skeleton: Same as above Illustrative pigment (84) Central skeleton: Same as above Illustrative pigment (85) Central skeleton: Same as above Illustrative pigment (86) Central skeleton: Same as above Illustrative pigment (87) Central skeleton: Same as above Illustrative pigment (88) Central skeleton: Same as above Illustrative pigment (89) Central skeleton: Same as above Exemplary pigment (90) Central skeleton: Same as above Exemplary pigment (91) Central skeleton: Same as above Exemplary pigment (92) Central skeleton: Same as above Exemplary pigment (93) Central skeleton: Same as above Exemplary pigment (94) Central skeleton: Same as above Illustrative pigment (95) Central skeleton: Same as above Illustrative pigment (96) Central skeleton: Same as above Illustrative pigment (97) Central skeleton: Same as above Illustrative pigment (98) Central skeleton: Same as above Illustrative pigment (99) Central skeleton: Same as above Exemplary pigment (100) Central skeleton: Same as above Illustrative pigment (101) Central skeleton: Same as above Illustrative pigment (102) Central skeleton: Same as above Illustrative pigment (103) Central skeleton: Same as above Illustrative pigment (104) Central skeleton: Same as above Illustrative pigment (105) Central skeleton: Same as above Exemplary pigment (106) Central skeleton: Same as above Illustrative pigment (107) Central skeleton: Same as above Illustrative pigment (108) Central skeleton: Same as above Illustrative pigment (109) Central skeleton: Same as above Illustrative pigment (110) Central skeleton: Same as above Illustrative pigment (111) Central skeleton: Same as above Illustrative pigment (112) Central skeleton: Same as above Illustrative pigment (113) Central skeleton: Same as above Illustrative pigment (114) Central skeleton: Same as above Illustrative pigment (115) Central skeleton: Same as above Illustrative pigment (116) Central skeleton: Same as above Illustrative pigment (117) Central skeleton: Same as above Illustrative pigment (118) Central skeleton: Same as above Illustrative pigment (119) Central skeleton: Same as above Illustrative pigment (120) Central skeleton: Same as above The disazo pigment represented by the general formula (1) used in the present invention is, for example, tetrazotized by treating an amine represented by the following structural formula with nitrous acid by an ordinary method. Then, a coupler having a coupler residue represented by any of formulas (2) to (8) is subjected to aqueous coupling in the presence of an alkali, or the tetrazonium salt of the amine is converted into a form such as a borofluoride salt or a zinc chloride double salt. Once isolated, a suitable solvent such as N, N-dimethylformamide,
It can be produced by coupling with the coupler in a solvent such as dimethyl sulfoxide in the presence of an alkali.

Synthesis Example (Synthesis of Illustrative Pigment (21)) 80 ml of water and 16.6 ml of concentrated hydrochloric acid (0.19 mol) in a 500 ml beaker
Was added thereto, and while cooling in an ice water bath, 6.475 g (0.029 mol) of the amine represented by the above structural formula was added, and the liquid temperature was adjusted to −2 ° C. while stirring.

Next, a solution prepared by dissolving 6.3 g (0.0915 mol) of sodium nitrite in 10 ml of water was added dropwise over 20 minutes while controlling the liquid temperature to 2 ° C. or lower. After the addition was completed, the mixture was further stirred at the same temperature for 15 minutes.

Carbon was added to the reaction solution, followed by filtration to obtain a tetrazotized solution.

Next, 700 ml of dimethylformamide was placed in a 2 beaker, and 19.9 g (0.20 mol) of triethylamine was added thereto.
-Hydroxy-3-naphthoic acid-2'-chloroanilide
27.24 g (0.0915 mol) was added and dissolved.

While cooling the coupler solution to 10 ° C. and controlling the solution temperature to 5 to 10 ° C., the above-mentioned tetrazotized solution was added dropwise with stirring over 30 minutes, and then stirred at room temperature for 2 hours, and the reaction solution was filtered. Thereafter, the mixture was washed with water and filtered to obtain a water paste containing 39.5 g of a crude pigment in terms of solid content.

Next, stirring filtration was repeated four times at room temperature using 400 ml of N, N-dimethylformamide.

Thereafter, the mixture was repeatedly stirred and filtered twice with 400 ml of methyl ethyl ketone, and dried under reduced pressure at room temperature to obtain 18.8 g of a purified pigment.

Yield 80%, decomposition point 250 ° C or higher Elemental analysis Calculated value (%) Experimental value (%) C 74.4 74.1 H3.8 3.6 N 9.0 8.2 Above, the synthesis method of typical pigments was explained, but other disazo pigments were also used. Synthesized in a similar manner.

The electrophotographic photoreceptor of the present invention has a photosensitive layer containing a disazo pigment represented by the general formula (1) on a conductive support.
The form of the photosensitive layer may be any known form, but the photosensitive layer containing the disazo pigment represented by the general formula (1) is used as a charge generation layer, and the charge generation layer containing a charge transport material is used as the charge generation layer. A laminated function-separated type photosensitive layer is particularly preferred.

The charge generation layer can be formed by applying a coating solution obtained by dispersing the above disazo pigment together with a binder resin in an appropriate solvent onto a conductive support by a known method, and having a thickness of, for example, 5 μm. Below, preferably
It is desirable to form a thin film layer having a thickness of 0.1 to 1 μm.

The binder resin used at this time is selected from a wide range of insulating resins or organic photoconductive polymers. And the like, and the amount used is determined by the content in the charge generation layer.
It is at most 80% by weight, preferably at most 40% by weight.

The solvent used is preferably selected from those which dissolve the resin and do not dissolve the charge transport layer and the undercoat layer described below.

Specifically, tetrahydrofuran, ethers such as 1,4-dioxane, cyclohexanone, ketones such as methyl ethyl ketone, amides such as N, N-dimethylformamide, methyl acetate, esters such as ethyl acetate, toluene, xylene, Examples include aromatics such as chlorobenzene, alcohols such as methanol, ethanol, and 2-propanol; and aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene.

The charge transport layer is stacked on or below the charge generation layer, and has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting the carriers.

The charge transporting layer is formed by dissolving a charge transporting material in a solvent together with a suitable binder resin if necessary, and applying the solution. The thickness of the charge transporting layer is generally 5 to 40 μm.
-30 μm is preferred.

The charge transporting substance includes an electron transporting substance and a hole transporting substance. Examples of the electron transporting substance include 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil, and tetralane. Examples thereof include electron-withdrawing substances such as cyanoquinodimethane, and those obtained by polymerizing these electron-withdrawing substances.

Examples of the hole transporting substance include polycyclic aromatic compounds such as pyrene and anthracene, carbazole-based, indole-based, imidazole-based, oxazole-based, thiazole-based, oxadiazole-based, pyrazole-based, pyrazoline-based, thiadiazole-based, and triazole-based compounds. Heterocyclic compounds such as
hydrazone compounds such as p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, α-phenyl-4′-N, N-diphenylaminostilbene, 5 Styryl compounds such as-[4- (di-p-tolylamino) benzylidene] -5H-dibenzo [a, d] cycloheptene, benzidine compounds, triarylmethane compounds, triphenylamine, or a group comprising these compounds; (E.g., poly-N-vinylcarbazole, polyvinylanthracene, etc.) having a polymer in the main chain or side chain.

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can be used.

These charge transport materials can be used alone or in combination of two or more.

When the charge transport material does not have a film-forming property, an appropriate binder can be used. Specifically, insulating resins such as acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, polyacrylamide, polyamide, and chlorinated rubber; or organic photoconductive materials such as poly-N-vinylcarbazole and polyvinylanthracene And the like.

As the conductive support on which the photosensitive layer is formed, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, platinum and the like are used. In addition, a plastic (eg, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, etc.) obtained by forming a film of such a metal or alloy by a vacuum evaporation method, or conductive particles (eg, carbon black, silver particles, etc.) with an appropriate binder A support coated on a plastic or metal substrate together with a resin, a support in which conductive particles are impregnated in plastic or paper, or the like can be used.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer.

The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, aluminum oxide, or the like.

The thickness of the undercoat layer is 5 μm or less, preferably 0.1 to 3 μm.
Is appropriate.

As another specific example of the present invention, an electrophotographic photosensitive member in which the above-mentioned disazo pigment and a charge transporting substance are contained in the same layer can be mentioned. At this time, poly-N is used as a charge transport material.
A charge transfer complex consisting of vinylcarbazole and trinitrofluorenone can also be used.

The electrophotographic photoreceptor of this example can be formed by applying and drying a liquid in which the above-mentioned disazo pigment and the charge transfer complex are dispersed in an appropriate resin solution.

The pigment used in any of the electrophotographic photoreceptors may be a combination of two or more disazo pigments represented by the general formula (1), or a combination with a known charge generating substance.

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

[Examples] Examples 1-27 Aqueous ammonia solution of casein (casein) was placed on an aluminum plate.
11.2%, 1 g of aqueous ammonia, and 222 ml of water) were applied by a Meyer bar so that the film thickness after drying was 1.0 μm, and dried.

Next, 5 g of the exemplified pigment (21) was added to cyclohexanone 95
To a solution of 2 g of butyral resin (butyralization degree: 63 mol%) dissolved in 2 ml was dispersed with a sand mill for 2 hours. The thickness of this dispersion after drying on the casein layer formed earlier is 0.
It was applied to a thickness of 5 μm using a Meyer bar and dried to form a charge generation layer.

Next, 5 g of a hydrazone compound having the following structural formula 5 g of hydrazone compound and 5 g of polycarbonate (number average molecular weight of 40,000) are dissolved in 60 ml of chlorobenzene, and this solution is applied on a charge generating layer with a Meyer bar so that the film thickness after drying becomes 29 μm, and dried to dry. A transport layer was formed, and an electrophotographic photosensitive member of Example 1 was prepared.

The following exemplifying pigments were used in place of the azo pigments in place of the exemplifying pigment (21), and the other conditions were the same as those in Example 1 and Examples 2 to 27 were used.
An electrophotographic photoreceptor corresponding to was prepared.

The electrophotographic photoreceptor thus prepared was corona-charged at −5 KV in a static manner using an electrostatic copying paper tester (Model EPA-8100, manufactured by Kawaguchi Electric Co., Ltd.), and charged in a dark place.
After holding for 2 seconds, exposure was carried out at an illuminance of 2 lux, and charging characteristics were examined.

As the charging characteristics, the surface potential (V ₀ ) and the exposure amount (E1 / 2) required to attenuate the potential after dark decay for one second to half were measured.

The same measurement was performed 150 times in succession, and the 150th
V ₀ was measured, and the _value of the difference from the initial V ₀ [V ₀ (initial) −V ₀ (150th time)] was measured as falling ΔV ₀ .

Further, after measuring the surface potential (V ₀ ) of the same type of electrophotographic photoreceptor, the photoreceptor was left under a daylight type fluorescent lamp for 3 minutes.

 The light amount at this time was 1,000 lux.

Then, 3 minutes and left dark, the front and the same measuring method, measuring the V _0, V ₀ -V ₀ ² is a variation of chargeability of V ₀ which after exposed to light as V ₀ ² Was used as a photo memory.

 The measurement results will be described later.

Comparative Examples 1 to 5 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the azo pigment having the following structural formula was used, and the same properties as in Example 1 were measured.

 The results are shown.

(Comparative Example 1) Comparative pigment (described in JP-A-57-195767) (Comparative Example 2) Comparative pigment (described in JP-A-61-272754) (Comparative Example 3) Comparative pigment (described in JP-A-61-43662) (Comparative Example 4) Comparative pigment (described in JP-A-56-167759) (Comparative Example 5) Comparative pigment (described in JP-A-55-69148) (Comparative Example 6) Comparative pigment (described in JP-A-61-151547) (Comparative Example 7) Comparative pigment (described in JP-A-61-107250) From these results, it can be seen that all of the electrophotographic photoreceptors of the present invention have a sufficient charging ability and a sufficient sensitivity, and furthermore have little potential fluctuation (ΔV ₀ ) and photo memory.

For example, in the case of Comparative Examples 2 and 4, which are examples in which the coupler component is the same, and the central skeleton is changed, and Examples 13, 14, 16, and 21, when Comparative Example 1 is compared with Examples 9 and 19, as is apparent. Compared with the electrophotographic photoreceptor of the comparative example, the electrophotographic photoreceptor of the present invention is more excellent in sensitivity in many cases, and even if the sensitivity is the same, the potential fluctuation is small and the photo memory is small.

Example 28 On the charge generation layer prepared in Example 1, 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-4,4'-dioxydiphenyl-2,2-propane carbonate (molecular weight: 30)
A coating solution prepared by dissolving 5 g of the compound in 70 ml of tetrahydrofuran was applied so that the coating amount after drying was 10 g / m ^2, and dried.

The charging characteristics of the thus prepared electrophotographic photosensitive member were measured in the same manner as in Example 1.

 The charging polarity at this time was +. The results are shown.

V ₀ : +510 V E1 / 2: 4.1 lux, sec ΔV ₀ : −20 V Photo memory: −15 V Example 29 A 0.5 μm-thick polyvinyl alcohol film was formed on the aluminum surface of an aluminum-deposited polyethylene terephthalate film.

Next, the film thickness after drying the dispersion liquid of the disazo pigment used in Example 1 was formed on the polyvinyl alcohol layer formed earlier.
The resultant was coated with a Meyer bar to a thickness of 0.5 μm and dried to form a charge generation layer.

Then the structural formula 5 g of a pyrazoline compound and 5 g of polyarylate (condensed polymer of bisphenol A and terephthalic acid-isophthalic acid) in 70 ml of tetrahydrofuran are coated on the charge generating layer so that the film thickness after drying is 15 μm, and then dried. Thus, a charge transport layer was formed.

The electrophotographic photosensitive member thus produced was evaluated in the same manner as in Example 1. The results are shown.

V ₀ : −650 V E1 / 2: 2.1 lux, sec Δ: +15 V Photo memory: −10 V Example 30 An aqueous ammonia solution of casein (described above) was applied on an aluminum plate having a thickness of 100 μm, and dried to obtain a film thickness of 0.5. An undercoat layer of μm was formed.

Next, a charge transfer complex was prepared by dissolving 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-N-vinylcarbazole (number average molecular weight 300,000) in 70 ml of tetrahydrofuran.

1 g of this charge transfer complex and 1 g of the exemplary pigment (9) were added to a solution of 5 g of polyester (byron, manufactured by Toyobo Co., Ltd.) in 70 ml of tetrahydrofuran and dispersed. This dispersion was applied on the undercoat layer so that the film thickness after drying was 12 μm, and dried to prepare an electrophotographic photosensitive member.

 The charging characteristics were measured in the same manner as in Example 1.

 The charging polarity at this time was +. The results are shown.

V ₀ : + 680V E1 / 2: 3.9lux, sec Example 31 The same charge transport layer and charge generation layer as in Example 1 were sequentially laminated on the casein layer of the aluminum plate provided with the casein layer used in Example 1, An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 1 except for the layer configuration, and the charging characteristics were measured in the same manner. The charging polarity at this time was +. The results are shown.

V ₀ : +595 V E1 / 2: 1.98 lux, sec [Effect of the Invention] In the electrophotographic photoreceptor of the present invention, by using a specific disazo pigment for the photosensitive layer, carriers are generated inside the photosensitive layer containing the disazo pigment. An electrophotographic photoreceptor having improved efficiency and / or carrier transport efficiency, and having excellent sensitivity and potential stability during durable use.

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member comprising a photosensitive layer containing a disazo pigment represented by the following general formula (1). General formula In the formula, R ₁ represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, a heterocyclic group or a halogen group, and R ₂ and R ₃ have a hydrogen atom and a substituent Represents an alkyl group, an aryl group, an aralkyl group, a heterocyclic group or a halogen group, and A represents a coupler residue having a phenolic hydroxyl group.