JPH09258468A - Electrophotographic photoreceptor and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having excellent electric characteristics which can form an image without image defects when the photoreceptor is used for an image forming method by contact electrification, and to provide an image forming device using this photoreceptor. SOLUTION: This electrophotographic photoreceptor 1 has a base layer between a conductive base body and a photosensitive layer. The base layer contains an electron transfer org. pigment, polyvinyl acetal resin and melamine resin. As the polyvinylacetal resin, a poliyvinylbutylal resin is preferable. As for the electron transfer org. pigment, ploycyclic quinone pigment, perylene pigment, naphthalene tetracarboxylic acid diimidazole pigment, etc., can be used. This electrophotographic photoreceptor can be attached to an image forming device having a contact electrifying device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member having an improved undercoat layer and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Electrophotographic devices are used in the fields of copying machines, laser beam printers, and the like because of their high speed and high printing quality. An organic photoconductor (OPC) using an organic photoconductive material has been developed as a photoconductor used in an electrophotographic apparatus, and is now widely used. The photosensitive member is also composed of a single layer type photosensitive member in which a charge transfer complex structure or a charge generating material is dispersed in a binder resin, and a function separation type photosensitive member in which a charge generating layer and a charge transport layer are separated. The structure has changed and the performance of the photoconductor has improved. In this function-separated type photoreceptor structure, at present, a structure in which an undercoat layer is formed on an aluminum substrate, and then a charge generation layer and a charge transport layer are formed, has become the mainstream.

With the progress of electrophotographic apparatus, higher quality image quality has been required for the performance of the photoconductor. In order to improve the repeating stability and environmental stability of the photoconductor, all of the charge generation layer, the charge transporting layer and the undercoat layer are important for the electrophotographic characteristics such as sensitivity, image quality and repeating stability. Have an impact. Furthermore, the substrate is
Various materials such as extruded tubes, ED tubes, and EI tubes have come to be used for the purpose of cost reduction and improvement of image quality defects. Furthermore, in order to reduce the occurrence of interference fringes,
A method for roughening the surface of the substrate has also been studied.

However, the surface of the substrate usually has many defects such as crystallized substances, pickups and dents. For example, ED used as a low-cost pipe
There is a peeling on the surface of the aluminum substrate called a pickup in the tube. With such surface defects,
An uneven portion is formed in the film forming state of the photoconductor, which causes local concentration of an electric field when the photoconductor is charged, which causes a charge leak. Furthermore, when used in a contact charging process using a charging roll, the above-mentioned surface defects or coating film defects of the conductive substrate cause charge leakage between the charging roll and the charging roll, resulting in black spots or white spots at the leak point. Cause spot defects. When this phenomenon is remarkable, the charging ability of the charging roll itself is reduced, and charging failure is caused in the entire axial direction of the photoconductor.

Depending on the photoconductor, an aluminum substrate may be subjected to honing treatment, rough cutting, in order to prevent interference fringes.
The surface may be roughened by performing an etching process or the like, but the roughening may locally cause abnormal projections on the surface of the substrate. Even in such a case, there is a problem that an image quality defect occurs and a current leak occurs at the contact between the charging roll and the photoconductor. To solve these problems, it is effective to form an undercoat layer having a sufficient substrate concealing ability and carrier blocking property on the surface of the substrate or to form a conductive layer to conceal defects in the substrate.

As the undercoat layer formed on the surface of the substrate, various resins such as maleic acid ester copolymers are disclosed in JP-A-52-10138 and JP-A-52-2083.
A polyester resin is disclosed in JP-A-52-256.
Copolymerized nylon is disclosed in JP-A-52-10.
No. 0240 discloses polyvinyl alcohol, and
No. 2,121,325 proposes an epoxy resin, and JP-A No. 54-26379 proposes a styrene-butadiene resin. However, when the undercoating layer is formed by using these resins alone, secondary obstacles such as increase in residual potential and increase in environmental change occur in electric characteristics, and also an effect of improving image defects such as black spots or white spots. Often not at a sufficient level.

Further, by adding metal oxide fine particles or metal fine particles to the resin of the undercoat layer, it has been attempted to reduce the resistance of the undercoat layer and to improve the electrical characteristics and the image quality. . However, when the metal fine particles are added, a conductive path is formed in the undercoat layer, and holes are injected from the substrate side, which causes problems such as fogging and white spots.

When used in a contact charging process using a charging roll, charge leakage easily occurs between the charging roll and a photoconductor which does not cause image quality defects when a normal scorotron is used. Causes black or white spot spot defects, or
This causes a decrease in the charging ability of the charging roll itself, resulting in a charging failure in the entire axial direction of the photoconductor. In order to prevent this leak, it is effective to make the undercoat layer as thick as possible.
Even if good electrical characteristics can be obtained up to a film thickness of about m, if the film is made thicker than that, the residual potential increases remarkably and becomes a level that cannot be used. In order to prevent current leakage due to the contact charging roll, it is desirable that the thickness of the undercoat layer be thicker than about 3 μm. There was a need for a subbing layer that would not cause any obstacles.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to provide a material for the undercoat layer which has higher image quality and does not adversely affect electric characteristics. is there. That is, the object of the present invention is:
An object of the present invention is to provide an electrophotographic photoreceptor having excellent electric characteristics and having few image quality defects. Another object of the present invention is to provide an image forming apparatus using an electrophotographic photosensitive member which can form an image having no image quality defect when used in a contact charging type image forming method.

[0010]

Means for Solving the Problems As a result of intensive investigations by the present inventors on a material for forming an undercoat layer which has a high image quality and does not adversely affect the electrical characteristics, an electron transporting organic pigment and a polyvinyl acetal resin are formed in the undercoat layer. It was found that the above-mentioned object can be achieved by containing the above and a phenol resin, and the present invention has been completed. The present invention provides an electrophotographic photosensitive member provided with an undercoat layer between a conductive substrate and a photosensitive layer,
The undercoat layer contains an electron-transporting organic pigment, a polyvinyl acetal resin, and a phenol resin. In the present invention, the polyvinyl acetal resin is preferably a polyvinyl butyral resin.

An image forming apparatus of the present invention is characterized by having the above-mentioned electrophotographic photosensitive member and a charger, and an image forming method using the same is to charge the above electrophotographic photosensitive member. Then, the method comprises the steps of imagewise exposing, developing, and transferring and fixing, and it is applicable to a system in which a charging device is brought into contact with the surface of the electrophotographic photosensitive member and an electric charge is supplied from the outside to charge it.

[0012]

Embodiments of the present invention will be described below in detail. The electrophotographic photosensitive member of the present invention has a structure in which an undercoat layer is formed on a conductive substrate, and a photosensitive layer is further formed thereon. The photosensitive layer may have any layer structure. However, a laminated type photoreceptor in which a charge generation layer and a charge transport layer are formed in this order has excellent performance such as repeated stability and environmental change. It is preferable because it exists. Hereinafter, the laminated type photoreceptor will be mainly described.

As the conductive substrate, copper, aluminum,
In addition to metals such as nickel and iron, a cylindrical, belt-shaped or sheet-shaped substrate made of plastic or paper that has been made conductive by evaporating a metal on the surface or forming a coating film in which conductive powder is dispersed. Can be used. In order to prevent interference fringes, the surface of the conductive substrate can be roughened by a method such as etching, anodic oxidation, wet blasting method, sand blasting method, rough cutting, and centerless cutting.

In the present invention, an undercoat layer is provided on the above conductive substrate. The undercoat layer of the present invention contains at least an electron-transporting organic pigment, a polyvinyl acetal resin, and a phenol resin. A resin composed of a mixture of a polyvinyl acetal resin and a phenol resin is a resin that reacts and cures. Therefore, after the film formation, even when applying a coating liquid for forming the charge generation layer and the charge transport layer. Never elute. Further, since this resin contains a polyvinyl acetal resin as a constituent, it has excellent pigment dispersibility. Further, since the electron-transporting organic pigment is added to the resin, the electrons formed in the charge generation layer are quickly moved to the substrate side, and the electrons are accumulated in the undercoat layer to increase the residual potential. There is an advantage that it can be prevented and a stable electrical property can be obtained.

Conventionally, it has been attempted to stabilize the electric characteristics by adding low resistance fine particles such as tin oxide, antimony oxide or a mixture thereof to the undercoat layer.
In this case, since there is no resistance to the injection of holes from the side of the conductive substrate, there is a problem that image defects such as white spots and fog occur. Since it functions as a sufficient resistance layer for the injection of holes from the substrate, it is possible to prevent image quality defects due to the injection of holes.

When a resin such as a urethane resin, a melamine resin or an epoxy resin, which has been proposed as a curable resin, is used alone, sufficient dispersibility cannot be obtained as compared with a butyral resin. A cured film formed by mixing butyral resin and isocyanate is disclosed in JP-A-62-276560 to JP-A-62-27656.
As disclosed in Japanese Patent Publication No. 3 and the like, generally, when isocyanate is used, the residual potential of the photoconductor is often increased due to repeated use and changes in environment. Further, Japanese Unexamined Patent Publication (Kokai) No. 61-240247 discloses an undercoat layer using a mixture of a phenol resin and an acetal-modified polyvinyl alcohol, but one having sufficiently stable electric characteristics has not been obtained. On the other hand, in the present invention, by using a cured film of a mixed resin of a polyvinyl acetal resin and a phenol resin for the undercoat layer using an electron transporting pigment, it is effective in achieving both dispersibility and electrical characteristics. .

Examples of the polyvinyl acetal resin used in the present invention include polyvinyl butyral resin and polyvinyl formal resin. The polyvinyl butyral resin is obtained by reacting a polyvinyl alcohol resin with butyraldehyde, and the polyvinyl formal resin is obtained by reacting a polyvinyl alcohol resin with formaldehyde. Of these polyvinyl acetal resins, those containing 50 to 75 mol% of vinyl acetal, 10 to 50 mol% of polyvinyl alcohol and 0 to 15 mol% of polyvinyl acetate in the structure are preferable. Among the polyvinyl acetal resins, the polyvinyl butyral resin is more preferable in terms of dispersibility and electric characteristics.

The phenolic resin used in the present invention includes phenolic hydroxyl groups such as phenol, cresol, xylenol, p-alkylphenol, p-phenylphenol, chlorophenol, bisphenol A, phenolsulfonic acid and resorcin. Examples thereof include aldehydes such as formalin and furfural, or hexamethylenetetramine that generates formalin when heated, those obtained by addition-polymerizing acetals having an aldehyde group by ring opening under acidic conditions, and modified resins thereof.

An electron-transporting organic pigment is used in the undercoat layer of the present invention. Whether the organic pigment has a hole-transporting property or an electron-transporting property is determined by the hole-transporting property. It is determined by whether the electron transportability is high or the electron transportability is high. As a more specific determination method, for example, several μm to 10 μm in which an organic pigment to be determined is dispersed in a binder resin
The degree of coating film is charged by using both positive charging and negative charging, and it is determined by which charging electrode shows higher sensitivity. Negative charging shows higher sensitivity. For example, it is a method of distinguishing from an electron transporting organic pigment.

Further, depending on the type of pigment, there are some pigments that cannot produce a carrier with a single pigment. In this case, the determination method is several μm to 10 in which the organic pigment to be determined is dispersed.
By forming a submicron-order charge generation layer made of different materials on a coating film of μm, and irradiating light having a wavelength at which the charge generation layer has sensitivity to form a carrier,
This is a method of injecting a carrier into an organic pigment for which the transport polarity of the lower layer is desired, and determining at which charging polarity the greater potential attenuation occurs. In addition,
On a coating film of several μm to 10 μm in which an organic pigment is dispersed,
Form a thin charge transport layer of submicron to 1 μm,
By irradiating the organic pigment to be discriminated with light having sensitivity, a carrier is formed at the pigment / thin layer charge transport layer interface,
There is a method of injecting a carrier into the organic pigment layer and discriminating according to which charging polarity causes larger potential attenuation.

Examples of the compound of the electron-transporting organic pigment thus identified include perylene tetracarboxylic acid diimide pigment, perylene tetracarboxylic acid diimidazole pigment, polycyclic quinone pigment, anthraquinone acridone pigment, and naphthalene tetracarboxylic acid. Examples include diimidazole pigments and the like. More specifically, as the perylene tetracarboxylic acid diimide pigment, the following exemplified compound No.
1-1 to No. 1-10, and as the perylene tetracarboxylic acid diimidazole pigment, the following exemplary compound No. 2-1 to No. 2-7, and as the anthraquinone acridone pigment, the following exemplified compound No.
3-1 to No. 3-40, and as the polycyclic quinone pigment, the following exemplified compound No. 4-1 to No. 4-4
1, and examples of the naphthalenetetracarboxylic acid diimidazole pigment include the following exemplary compound No. 5-1 to N
o. 5-6 can be given.

(Specific Examples of Perylene Tetracarboxylic Acid Diimide Pigment)

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[0023]

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(Specific Examples of Perylene Tetracarboxylic Acid Diimidazole Pigment)

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(Specific examples of anthraquinone acridone pigment)

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[0026]

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[0027]

[Chemical 6]

[0028]

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[0029]

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[0030]

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(Specific examples of polycyclic quinone pigment)

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[0032]

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[0033]

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[0034]

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[0035]

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[0036]

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(Specific Examples of Naphthalene Tetracarboxylic Acid Diimidazole Pigment)

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In the undercoat layer of the present invention, the electron transporting organic pigment is contained in an amount of 5 to 90% by weight based on the total weight.
Usually, particles having a particle size of 0.001 to 0.5 μm are used. Further, the phenol resin is contained in the range of 3 to 50% by weight in the total resin components of the polyvinyl acetal resin and the phenol resin. In the undercoat layer, various organic fine powders or inorganic fine powders different from the electron-transporting pigments should be added for the purpose of preventing light fringes from generating interference fringes and improving dispersibility. You can In particular, white pigments such as titanium oxide, zinc oxide, zinc white, zinc sulfide, lead white and lithopone, inorganic pigments as extender pigments such as alumina, calcium carbonate, barium sulfate, Teflon resin particles, benzoguanamine resin particles, styrene resin Particles are effective. The particle size of the added fine powder used is 0.01 to
Those having a thickness of 3 μm are used. If the particle size is too large, the unevenness of the undercoat layer becomes severe, and the electrical nonuniformity becomes large, and image quality defects are likely to occur. Further, if the particle size is too small, a sufficient light scattering effect cannot be obtained. These fine powders are added as needed, and when added, the weight ratio is 1 to 70 relative to the solid content of the undercoat layer.
%, More preferably 5 to 60% by weight.

By increasing the thickness of the undercoat layer,
Since the concealment of irregularities on the base material is enhanced, increasing the film thickness generally tends to reduce spot-like image quality defects, but at the same time, the electrical characteristics such as increase in residual potential also deteriorate, so the film thickness is It was limited to the range of 0.1 to 3 μm. However, since the undercoat layer in the present invention is less deteriorated in terms of electrical characteristics even if it is made thicker, it can be set to a range of 10 μm. Further, the thicker the film, the less likely the leakage defect is to occur even in a charging method such as a contact charging method in which a current leak is likely to occur. Therefore, in the present invention, the thickness of the undercoat layer is 2 to 1
It is possible to set in the range of 0 μm.

To form a coating liquid for forming the undercoat layer,
An electron-transporting organic pigment or the like is added to the solution in which the resin component is dissolved and the dispersion treatment is performed. As a method of dispersing the added fine powder in the resin, a method such as a roll mill, a ball mill, a vibration ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker can be used.

In the present invention, the charge generation layer provided on the above-mentioned undercoat layer is formed by forming a charge generation substance by vacuum vapor deposition, or by dispersing the charge generation substance together with an organic solvent and a binder resin and applying the dispersion. As the charge generating substance, amorphous selenium, crystalline selenium, selenium-tellurium alloy, selenium-
Arsenic alloys, other selenium compounds and selenium alloys, inorganic photoconductive materials such as zinc oxide and titanium oxide, metal-free phthalocyanine, titanyl phthalocyanine, copper phthalocyanine, tin phthalocyanine, gallium phthalocyanine, chloroindium phthalocyanine and other phthalocyanine pigments, square Lithium type, aromatic polycyclic compound type, azo type,
Various organic pigments and dyes such as pyrylium salts and thiapyrylium salts are used. In addition, these organic pigments generally have several crystal forms, and in particular, phthalocyanine pigments are known to have various crystal forms such as α and β, but a sensitivity suitable for the purpose can be obtained. Any crystal type can be used as long as it is a pigment.

Examples of the binder resin used in the charge generation layer include the following. That is, polycarbonate resin such as bisphenol A type, bisphenol Z type or bisphenol C type, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer resin, vinylidene chloride- Examples thereof include acrylonitrile copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, and poly-N-vinylcarbazole.

These binder resins can be used alone or in admixture of two or more. The compounding ratio (weight ratio) of the charge generating material and the binder resin is preferably in the range of 10: 1 to 1:10. The film thickness of the charge generation layer is generally set in the range of 0.01 to 5 μm, preferably 0.05 to 2.0 μm. As a method for dispersing the charge generation material in the resin, a roll mill, a ball mill, a vibrating ball mill, an attritor, a dyno mill, a sand mill, a colloid mill or the like can be used.

Examples of the charge transport material used for the charge transport layer formed on the charge generation layer are as follows. Oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline,
Pyrazoline derivatives such as 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline, triphenylamine, tri (p-methyl) phenylamine, N, N- Screw (3,
4-dimethylphenyl) biphenyl-4-amine, aromatic tertiary amino compounds such as dibenzylaniline, N,
Aromatic tertiary diamino compounds such as N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1-biphenyl] -4,4'-diamine, 3- (4'-dimethylamino) Phenyl) -5,6-di- (4'-methoxyphenyl) -1,2,4-triazine and other 1,2,4-triazine derivatives, 4-diethylaminobenzaldehyde-
Hydrazone derivatives such as 1,1-diphenylhydrazone,
Quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) -benzofuran, p
Α-stilbene derivatives such as-(2,2-diphenylvinyl) -N, N-diphenylaniline, enamine derivatives,
Carbazole derivatives such as N-ethylcarbazole, hole-transporting substances such as poly-N-vinylcarbazole and its derivatives; quinone compounds such as chloranil, bromoanil, anthraquinone, tetracyanoquinodimethane compounds, 2,4,7- Trinitrofluorenone, 2,4
Fluorenone compounds such as 5,7-tetranitro-9-fluorenone, xanthone compounds, thiophene compounds,
Examples thereof include an electron transporting substance such as a diphenoquinone compound; and a polymer having a group composed of the above compound in its main chain or side chain. These charge transport materials can be used alone or in combination of two or more.

Specific examples of the binder resin used in the charge transport layer include acrylic resin, polyarylate, polyester resin, polycarbonate resin such as bisphenol A type, bisphenol Z type or bisphenol C type, polystyrene, acrylonitrile-styrene copolymer, etc. Polymers, acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formal, polysulfones, polyacrylamides, polyamides, insulating resins such as chlorinated rubber, or organic photoconductive polymers such as polyvinyl carbazole, polyvinyl anthracene, polyvinyl pyrene, etc. Copolymer resin of.

For the charge transport layer, a solution prepared by dissolving the above charge transport material and the binder resin in a suitable solvent is applied,
It can be formed by drying. Examples of the solvent used for forming the charge transport layer include aromatic hydrocarbons such as benzene, toluene and chlorobenzene, ketones such as acetone and 2-butanone, halogenated fats such as methylene chloride, chloroform and ethylene chloride. Examples thereof include group hydrocarbons, cyclic or linear ethers such as tetrahydrofuran, dioxane, ethylene glycol and diethyl ether, and mixed solvents thereof. The compounding ratio of the charge transport material and the binder resin is preferably in the range of 10: 1 to 1: 5. The thickness of the charge transport layer is generally 5 to
The thickness is set to 50 μm, preferably 10 to 40 μm.

Additives such as antioxidants, light stabilizers, and heat stabilizers in the photosensitive layer for the purpose of preventing deterioration of the photoreceptor due to ozone or oxidizing gas generated in the electrophotographic apparatus, or light or heat. Can be added. For example, as the antioxidant, hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, organic phosphorus compounds and the like are used. Examples of the light stabilizer include benzophenone, benzotriazole, dithiocarbamate, tetramethylpiperidine, and other derivatives.

The electrophotographic photoreceptor of the present invention may contain at least one electron-accepting substance for the purpose of improving sensitivity, reducing residual potential, and reducing fatigue during repeated use. Examples of the electron accepting substance that can be used in the present invention include succinic anhydride, maleic anhydride, dibromomaleic anhydride, phthalic anhydride, tetrabromophthalic anhydride, tetracyanoethylene, tetracyanoquinodimethane, and o-diene. Examples thereof include nitrobenzene, m-dinitrobenzene, chloranil, dinitroanthraquinone, trinitrofluorenone, picric acid, o-nitrobenzoic acid, p-nitrobenzoic acid and phthalic acid. Among these, fluorenone, quinone and C
Benzene derivatives having an electron-withdrawing substituent such as 1, CN, NO _{2 and the} like are particularly preferred. The coating for forming the photosensitive layer can be performed using a coating method such as a dip coating method, a spray coating method, a bead coating method, a blade coating method, a roller coating method. In the case of not using a humidification treatment method, it is preferable to heat-dry after touch-drying at room temperature. The heat drying is preferably performed at a temperature of 30 to 200 ° C. for 5 minutes to 2 hours.

If necessary, a surface protective layer can be formed on the photosensitive layer. As the surface protective layer, there is an insulating resin protective layer or a low resistance protective layer in which a resistance adjusting agent is added to the insulating resin. As the low resistance protective layer, for example,
An example is a layer in which conductive particles are dispersed in an insulating resin. The conductive particles have an electric resistance of 10 ⁹ Ω.
Fine particles having an average particle size of 0.3 μm or less, preferably 0.1 μm or less and having a color of cm or less and exhibiting white, gray or bluish white are suitable, and examples thereof include molybdenum oxide, tungsten oxide, antimony oxide, tin oxide, and oxide. Examples thereof include titanium, indium oxide, a solid solution or mixture of tin oxide and antimony or antimony oxide, or a mixture of these metal oxides in a single particle or a coated material. Among them, tin oxide, and a solid solution of tin oxide and antimony or antimony oxide are preferable because they can appropriately adjust the electric resistance and can make the protective layer substantially transparent (Japanese Patent Application Laid-Open No. 2004-242242). Showa 57-3084
No. 7, JP-A-57-128344). Examples of the insulating resin include condensation resins such as polyamide, polyurethane, polyester, epoxy resin, polyketone and polycarbonate, and vinyl polymers such as polyvinyl ketone, polystyrene and polyacrylamide.

The electrophotographic photosensitive member of the present invention is a light lens type copying machine, a laser beam printer emitting near infrared light or visible light, a digital copying machine, an LED printer,
It can be used for an electrophotographic apparatus such as a laser facsimile. The electrophotographic photosensitive member of the present invention can be used together with a one-component or two-component regular developer or reversal developer.

The electrophotographic photosensitive member obtained by the present invention is
Excellent in concealing defects of the conductive substrate, defects such as crystallized substances and pickups that the aluminum substrate has, and occurrence of charge leakage due to abnormal projections that occur during blasting processing during interference fringe prevention processing. Suppressed, good characteristics with less current leakage can be obtained not only in corotron charging but also in a contact charging method using a charging roller, a charging brush, film charging, or the like. For example, in a system in which a conductive elastic roller is brought into contact with the surface of an electrophotographic photosensitive member, a DC voltage of about several hundred volts to 2 KV is externally applied to the surface of the photosensitive member to be charged. Further, in order to improve the uniformity of charging, an AC voltage may be superimposed on a DC voltage and applied to the charging member.

Next, the image forming apparatus of the present invention will be described. FIG. 1 shows an example of an image forming apparatus using the electrophotographic photosensitive member of the present invention, in which a charger 3 to which a voltage is supplied from a power source 2 provided outside the apparatus is attached to a photosensitive drum 1. It is arranged so as to contact the surface. An image input device 4, a developing device 5, a pressure transfer device or an electrostatic transfer device 6, a cleaner device 9, and a de-exposure device 10 are provided around the photosensitive drum 1. Reference numeral 7 is a sheet, and 8 is a fixing device. In the image forming apparatus of the present invention, a charging roll is shown as the charging device, but a charging brush or a blade type film charging device may be used. A direct current voltage is applied to the charger from a power source 2 provided outside the apparatus, but an alternating voltage may be applied on the direct current voltage in order to improve the uniformity of charging.

The image forming method according to the present invention includes, for example,
It is carried out as follows. That is, the photosensitive drum 1
A charger 3 to which a direct current voltage in the range of 50 to 2000 V is applied to the surface of the device from a power source 2 provided outside the device.
To charge. For example, in the case of a method in which the conductive elastic roller is brought into contact with the surface of the photoconductor, a DC voltage of about 1 to 2 KV may be applied. Next, an electrostatic latent image is formed by exposure with light from an image input device 4 such as an optical system for irradiating a document image or a laser or LED. The formed electrostatic latent image is visualized as toner by the developing device 5 and converted into a toner image. In this case, a magnetic brush method can be used for development. Then, the toner image is transferred onto the sheet 7 by the pressure transfer device or the electrostatic transfer device 6 and fixed by the fixing device 8. On the other hand, the photosensitive drum 1 after transfer
The toner remaining on the surface is removed by the cleaner device 9 using a blade, and the electric charge slightly remaining on the surface of the photosensitive drum 1 is erased by the deexposure device 10.

[0054]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. Example 1 16 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 600 parts by weight of n-butyl alcohol and stirred. In addition, phenol resin (SK
103, manufactured by Sumitomo Jules) was added and stirred. Further, to this solution, as an electron-transporting pigment, the exemplified compound No. 120 parts by weight of 4-6 was added, and dispersion treatment was performed for 3 hours using a sand mill to obtain a coating liquid for forming an undercoat layer. This coating liquid was subjected to liquid honing treatment to obtain Ra =
Using a ring coating device, it was coated on a 30 mmφ ED tube aluminum substrate roughened to 0.18 μm.
Curing treatment was performed at 0 ° C. for 1 hour to form an undercoat layer having a film thickness of 5 μm. As a charge generating material, 3 parts by weight of gallium phthalocyanine chloride, 2 parts by weight of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar Co., Ltd.), and 180 parts by weight of butyl acetate were mixed with a sand mill.
Time-dispersed. The obtained dispersion was applied onto the undercoat layer by dip coating and dried to form a charge generation layer having a thickness of 0.2 μm. Next, N, N'-diphenyl-N, N'-
Bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine 4 parts by weight and bisphenol Z
6 parts by weight of a polycarbonate resin (molecular weight 40,000) and 80 parts by weight of chlorobenzene were added and dissolved. The obtained solution was applied onto the charge generation layer and dried at 120 ° C. for 30 minutes to form a charge transport layer having a film thickness of 20 μm, and an electrophotographic photosensitive member having three layers was produced. The obtained electrophotographic photosensitive member was mounted on a printer (PC-PR1000 / 4R, manufactured by NEC Corporation) having a contact charging system, and a copying operation was performed. Table 1 shows the results obtained regarding the residual potential and the image quality of the electrophotographic photosensitive member at that time.

[Confirmation of electron transportability] In Example 1,
A drum having an undercoat layer and a charge generation layer according to the present invention formed on a conductive substrate was prepared. This drum was charged to −200 V by using a scorotron and irradiated with light of 780 nm to excite photocarriers by the charge generation layer.
An optical attenuation characteristic of 10 V · m ² / mJ was obtained. On the other hand, even when this same drum was charged to +200 V and the same light irradiation was performed, no light attenuation was observed. Therefore, it was confirmed that the organic pigment (Exemplified Compound No. 4-6) used in the undercoat layer in the invention was an electron-transporting organic pigment.

Comparative Example 1 30 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 600 parts by weight of n-butyl alcohol and stirred. This coating solution was roughened to Ra = 0.18 μm by liquid honing treatment, and was 30 mm.
It was coated on a φ ED tube aluminum substrate by using a ring coating device, and was cured at 150 ° C. for 30 minutes to form an undercoat layer having a film thickness of 4 μm. Further, a charge generation layer and a charge transport layer were sequentially formed by the same method as in Example 1 to produce an electrophotographic photoreceptor. The obtained electrophotographic photosensitive member was evaluated in the same manner as in Example 1, and the results shown in Table 1 were obtained.

Comparative Example 2 16 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 500 parts by weight of n-butyl alcohol and stirred. Furthermore, phenol resin (SK1
03, manufactured by Sumitomo Jules) and stirred to obtain a coating liquid for forming an undercoat layer. This coating solution was roughened to Ra = 0.18 μm by liquid honing treatment.
It was applied on an ED tube aluminum substrate having a diameter of mmφ using a ring coating device, and was subjected to a curing treatment at 150 ° C. for 1 hour to form an undercoat layer having a film thickness of 5 μm. Further, a charge generation layer and a charge transport layer were sequentially formed by the same method as in Example 1 to produce an electrophotographic photoreceptor. The obtained electrophotographic photosensitive member was evaluated in the same manner as in Example 1, and the results shown in Table 1 were obtained.

Comparative Example 3 16 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 600 parts by weight of n-butyl alcohol and stirred. Further, the compound No. 120 parts by weight of 4-6 was added, and dispersion treatment was performed for 3 hours using a sand mill to obtain a coating liquid for forming an undercoat layer. This coating solution was roughened to Ra = 0.18 μm by liquid honing treatment, and was 30 mm.
It is coated on the φ ED tube aluminum substrate using a ring coating device, and cured at 150 ° C. for 30 minutes,
An undercoat layer having a film thickness of 5 μm was formed.

Comparative Example 4 16 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 600 parts by weight of n-butyl alcohol and stirred. To the obtained solution, 8 parts by weight of an isocyanate compound (GR4000K, manufactured by Kansai Paint Co., Ltd.) was added and stirred. Further, the compound No. 120 parts by weight of 4-6 was added,
Dispersion treatment was carried out for 3 hours using a sand mill to obtain a coating liquid for forming an undercoat layer. This coating solution was applied onto a 30 mmφ ED tube aluminum substrate roughened to Ra = 0.18 μm by a liquid honing process using a ring coating device, followed by curing treatment at 150 ° C. for 1 hour. Film thickness 5
An undercoat layer of μm was formed.

Comparative Example 5 16 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 600 parts by weight of n-butyl alcohol and stirred. Instead of the phenol resin in Example 1, 18 parts by weight of acetylacetone zirconium butyrate (ZC540, manufactured by Matsumoto Pharmaceutical Co., Ltd.) as a curing agent was added and stirred to dissolve. Further, the compound No. 4-6 to 12
0 parts by weight was added, and dispersion treatment was performed for 3 hours using a sand mill to obtain an undercoat layer forming coating liquid. This coating solution was applied onto a 30 mmφ ED tube aluminum substrate roughened to Ra = 0.18 μm by a liquid honing process using a ring coating device, followed by curing treatment at 150 ° C. for 1 hour. An undercoat layer having a film thickness of 5 μm was formed. in this case,
Many cracks were generated in the undercoat layer during coating.

[0061]

[Table 1]

In the electrophotographic photosensitive member having the undercoat layer obtained in Example 1, no abnormal image quality due to leak discharge was observed when a print test was carried out by a printer having a contact charging device. Further, the electrophotographic photosensitive member of Example 1 had a low residual potential and stable electric characteristics were obtained. On the other hand, the electrophotographic photosensitive members of Comparative Examples 1 and 2 had low sensitivity and high residual potential, so that an image could not be obtained. Further, the electrophotographic photosensitive member of Comparative Example 3 had a large dark decay and could not obtain a sufficiently high charging potential. The electrophotographic photosensitive member of Comparative Example 4 had a high residual potential, and the electrophotographic photosensitive member of Comparative Example 5 had cracks in the undercoat layer, and the effect thereof also appeared in the image quality.

Example 2 16 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 550 parts by weight of cyclohexanone and stirred. Further, 8 parts by weight of a phenol resin (Priofen J-325, manufactured by Dainippon Ink and Chemicals, Inc.) was added and stirred. Further, in this solution, as an electron-transporting organic pigment, the exemplified compound No. 60 parts by weight of 1-5 was added, and the dispersion treatment was performed for 20 hours using a ball mill to obtain a coating liquid for forming an undercoat layer. This coating solution was roughened to Ra = 0.18 μm by liquid honing treatment.
It was applied onto an ED tube aluminum substrate having a diameter of mmφ using a ring coating device, and cured at 170 ° C. for 1 hour to form an undercoat layer having a thickness of 4 μm. 15 parts by weight of hydroxygallium phthalocyanine as a charge generating material,
A mixed solution of 10 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.) and 300 parts by weight of n-butyl alcohol was dispersed for 4 hours by a sand mill. The obtained dispersion is applied on the undercoat layer,
After drying, a charge generation layer having a thickness of 0.2 μm was formed. Next, 4 parts by weight of N, N-bis (3,4-dimethylphenyl) biphenyl-4-amine and 6 parts by weight of bisphenol Z polycarbonate resin (molecular weight 40,000) were added to 80 parts by weight of chlorobenzene and dissolved. The resulting solution is applied onto the charge generation layer and dried to give a film thickness of 2
A charge transporting layer having a thickness of 0 μm was formed to prepare an electrophotographic photoreceptor having three layers. A printer (PC-PR1000 / 4R,
It was attached to a product made by NEC Corporation) and a copy operation was performed. Table 2 shows the results obtained regarding the residual potential and the image quality of the electrophotographic photosensitive member at that time.

Examples 3 to 9 As the electron transporting organic pigment, the exemplified compound No. 1 used in Example 2 was used. An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the organic pigments (shown by the exemplified compound numbers) shown in Table 2 were used in place of 1-5, and the evaluations were the same. Went to. Table 2 shows the obtained results. Comparative Examples 6 to 8 As the electron transporting organic pigment, the exemplified compound No. 1 used in Example 2 was used. An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the hole-transporting organic pigments shown in Table 2 were used instead of 1-5, and their evaluation was performed in the same manner. Table 2 shows the obtained results.

[0065]

[Table 2]

Example 10 16 parts by weight of polyvinyl butyral resin (S-REC BM-1, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 600 parts by weight of n-butyl alcohol by stirring. Further, 8 parts by weight of a phenol resin (Priofen J-325, manufactured by Dainippon Ink and Chemicals, Inc.) was added and stirred. Further, in this solution, as an electron-transporting organic pigment, the exemplified compound No. 120 parts by weight of 4-6 was added, and dispersion treatment was performed for 3 hours using a sand mill to obtain a coating liquid for forming an undercoat layer. The obtained coating solution is
A 30 mmφ ED tube aluminum substrate roughened to Ra = 0.18 μm by liquid honing was applied using a ring coating device, and cured at 150 ° C. for 1 hour to form an undercoat layer. . In this case, an undercoat layer was obtained in which the film thickness of the undercoat layer was changed within the range of 1 to 8 μm. As a charge generating material, a mixed solution of 15 parts by weight of hydroxygallium phthalocyanine, 10 parts by weight of polyvinyl butyral resin (S-REC BM-S, manufactured by Sekisui Chemical Co., Ltd.), and 300 parts by weight of n-butyl alcohol was subjected to dispersion treatment for 4 hours by a sand mill. The resulting dispersion was applied onto the undercoat layer and dried to form a charge generation layer having a thickness of 0.2 μm. Next, 4 parts by weight of N, N-bis (3,4-dimethylphenyl) biphenyl-4-amine and bisphenol Z polycarbonate resin (molecular weight 40,000) 6
And 80 parts by weight of chlorobenzene were added and dissolved. The obtained solution was applied onto the charge generation layer and dried to form a charge transport layer having a film thickness of 20 μm, and an electrophotographic photosensitive member having three layers was produced. The obtained electrophotographic photosensitive member was mounted on a printer (PC-PR1000 / 4R, manufactured by NEC Corporation) having a contact charging system, and a copying operation was performed. Table 3 shows the results obtained regarding the residual potential and the image quality of the electrophotographic photosensitive member at that time.

Comparative Example 9 16 parts by weight of polyvinyl butyral resin (S-REC BM-1, manufactured by Sekisui Chemical Co., Ltd.) was mixed with 600 parts by weight of n-butyl alcohol and stirred. Further, 8 parts by weight of an epoxy resin (Epiclon P439, manufactured by Dainippon Ink and Chemicals, Inc.) was added and stirred. This solution was used as a coating liquid for forming an undercoat layer without adding an electron transporting pigment. This coating solution was applied onto a 30 mmφ ED tube aluminum substrate roughened to Ra = 0.18 μm by a liquid honing process using a ring coating device, followed by curing treatment at 150 ° C. for 1 hour. A pull layer was formed. In this case, the undercoat layer was obtained by changing the film thickness of the undercoat layer in the range of 1 to 5 μm. Further, a charge generation layer and a charge transport layer were sequentially formed by the same method as in Example 10 to prepare an electrophotographic photoreceptor having three layers. The obtained electrophotographic photosensitive member was used in Example 10.
Was evaluated in the same manner as described above. Table 3 shows the obtained results.

[0068]

[Table 3]

As can be seen from Table 3 above, the electrophotographic photosensitive member of Example 10 using the electron transporting organic pigment in the undercoat layer shows the electrical characteristics even if the film thickness of the undercoat layer is changed to a large value. All showed good characteristics. On the other hand, in the electrophotographic photosensitive member of Comparative Example 9 in which the electron transporting organic pigment is not used in the undercoat layer,
As the film thickness of the undercoat layer increased, the sensitivity was decreased and the residual potential was significantly increased, making it impossible to obtain an image.

[0070]

As described above, the electrophotographic photoreceptor of the present invention can obtain a stable low residual potential by using the electron transporting organic pigment, the polyvinyl acetal resin and the phenol resin for forming the undercoat layer. Even if the contact charging method is used, current leakage does not occur and a copied image with excellent image quality can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus using an electrophotographic photosensitive member of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Power supply, 3 ... Charging device, 4 ... Image input device, 5 ... Developing device, 6 ... Pressure transfer device or electrostatic transfer device, 7 ... Paper, 8 ... Fixing device, 9 ... Cleaner device 1
0 ... Exposing device.

Claims (6)

[Claims] 1. An electrophotographic photoreceptor having an undercoat layer provided between a conductive substrate and a photosensitive layer, wherein the undercoat layer contains an electron transporting organic pigment, a polyvinyl acetal resin and a phenol resin. Characteristic electrophotographic photoreceptor. 2. The electrophotographic photosensitive member according to claim 1, wherein the polyvinyl acetal resin is a polyvinyl butyral resin. 3. The electrophotographic photosensitive member according to claim 1, wherein the electron-transporting organic pigment is a polycyclic quinone pigment. 4. The electrophotographic photosensitive member according to claim 1, wherein the electron transporting organic pigment is a perylene pigment. 5. The electrophotographic photosensitive member according to claim 1, wherein the electron transporting organic pigment is a naphthalenetetracarboxylic acid diimidazole pigment. 6. An image forming apparatus using the electrophotographic photosensitive member according to claim 1 in a contact charging type image forming apparatus.