JPH11223954A - Electrophotographic photoreceptor and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positively electrifiable electrophotographic photoreceptor provided with an electric charge transportation layer having electronic transportation property and constituted so that residual potential is small, image contrast is secured, the production of ozone is reduced, adhesion between a supporting body is excellent and a faulty image is not formed and to provide an image forming method using it. SOLUTION: The electrophotographic photoreceptor is constituted so as to be provided with an electric charge generation layer, the first electric charge transportation layer and the second electric charge transportation layer on the electrical conductive supporting body in this turn. Then, the first electric charge transportation layer is composed of the layer obtained by including an organic electronic transporting material in binder. Besides, the electric charge transportation layer having the electronic transportation property is composed of the layer obtaining the condition of α<=0.6 when relation between the working function ϕCTL of the electric charge transportation layer and the working function ϕM of a sample-side conductive electrode obtained by changing the sample-side conductive electrode when the working function of the electric charge transportation layer is obtained by measuring contact potential difference is made linearly approximate by the expression of ϕCTL=αΝM+β [(α) and (β) in the expression are the constant]. The second electric charge transportation layer is positioned at the outermost surface of the photoreceptor and static friction coefficient between a cleaning blade is <=1.0.

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 for forming an electrostatic latent image, and more particularly, to an electrophotographic photosensitive member having a layer containing an electron transporting compound and an image using the same. It relates to a forming method.

[0002]

2. Description of the Related Art Heretofore, in copiers, printers, faxes, etc. based on electrophotographic technology, excellent features such as high sensitivity, low dependence on temperature and humidity, and high-speed response to semiconductor laser light, etc. As a result, organic photoconductors have been widely used.

In such an electrophotographic photoreceptor, a function separation type configuration in which a charge generation function and a charge transport function are shared by different substances significantly widens the range of materials to be selected. Since the chemical structure group can be designed, excellent materials have been developed for both the charge generation material and the charge transport material.

Various organic dyes and organic pigments have been proposed as charge generating substances. For example, polycyclic quinone compounds typified by dibromoanthranthrone, pyrylium compounds, eutectic complexes of pyrylium compounds with polycarbonate, squarium compounds, phthalocyanine compounds, azo compounds and the like are known.

[0005] As the charge transporting substance, compounds having a nitrogen-containing heterocyclic nucleus represented by oxazole, oxadiazole, thiazole, thiadiazole, imidazole and the like and a condensed ring nucleus thereof, polyarylalkane compounds, pyrazoline compounds, Hydrazone compounds, triarylamine compounds, styryl compounds, styryltriphenylamine compounds, β-phenylstyryltriphenylamine compounds, butadiene compounds, hexatriene compounds, carbazole compounds, etc. are known. All of these charge transport materials were hole transportable.

Conventionally, when a photoreceptor is manufactured by combining a charge generating substance and a charge transporting substance, a charge generating layer containing a charge generating substance is provided on an electrode, and a charge transporting layer containing a charge transporting substance is provided thereon. In the case of a laminated structure, a photosensitive member having the highest durability can be obtained. For this reason, most of the present organic photoconductors have such a configuration.

On the other hand, since the above-mentioned charge transporting substance has a hole transporting property, such an electrophotographic photosensitive member is operated by negatively charging the surface of the photosensitive member. For charging, a corona discharge method that can operate at high speed and obtain stable charging characteristics is generally used. Ozone is generated during corona discharge, but in recent years, with the speeding up of the electrophotographic process, an increase in the amount of ozone generated per unit time has become a concern. There has been a demand for a highly durable photoconductor.

From this viewpoint, an organic photoreceptor having a laminated structure in which an electron transporting charge transporting layer is formed as an upper layer has been developed.
Examples of the electron transporting substance include 2,4,7-trinitrofluorenone and JP-A-1-206349 and JP-A-2-2148.
No. 66, JP-A-5-279852, USP 5,46
No. 8,583 and the like have been proposed.

However, even when these electron transporting materials are used, the conventional charge transporting layer has a serious impairment in the charge injection characteristics from the charge generating material, so that the light response operation as an electrophotographic photoreceptor is problematic. A remarkable residual potential remained, and a potential contrast required for image formation could not be obtained.

In the image forming method using an organic photoreceptor, when cleaning is performed by the blade cleaning method, not only the removal of residual toner on the photoreceptor but also the occurrence of abrasion and scratches on the surface of the photoreceptor. cause. Therefore, a method has been proposed in which a lubricating substance is contained in the outermost surface layer of the photoreceptor to impart lubricity to the outermost layer, thereby improving wear and damage of the photoreceptor. For example, Japanese Patent Application Laid-Open No. Sho 61-219049 discloses a method in which a charge transporting layer which is the outermost surface layer of a photoreceptor contains a silicone resin or a fluorine resin as a binder resin.
No. 2 or JP-A-63-65449 proposes a method of incorporating fine particles of silicone resin or fine particles of fluororesin.

On the other hand, in the electrophotographic industry, higher image quality is increasingly demanded, and for this reason, finer toner particles of a developer are being studied. For example, JP-A-60-131551 describes that a toner having an average particle diameter of 10 μm or less is used.

However, when the photoreceptor containing a lubricating substance in the surface layer of the photoreceptor is cleaned by the cleaning blade method as described above, the abrasion and damage of the photoreceptor surface are certainly improved, Frequently, cleaning failure occurs, resulting in an increase in fog and a decrease in image quality. In particular, when the toner in the developer used for development is fine particles, the deterioration of the image quality due to the above-mentioned cleaning failure becomes remarkable.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a positively chargeable photoreceptor having an electron transporting charge transporting layer, having a small residual potential, ensuring image contrast, and generating less ozone. An object of the present invention is to provide an electrophotographic photosensitive member having good adhesion to a support and free from image defects, and an image forming method using the same.

[0014]

The object of the present invention is achieved by adopting the following constitution.

(1) In an electrophotographic photosensitive member having a charge generating layer, a first charge transporting layer, and a second charge transporting layer on a conductive support in this order, the first charge transporting layer contains an organic electron transporting substance as a binder. When the work function of the charge transport layer is determined by measuring the contact potential difference, the work function φ of the charge transport layer obtained by changing the sample-side conductive pole is obtained. _When the relationship between _CTL and the work function φ _M of the sample-side conductive _pole is linearly approximated by the equation (a), α ≦ 0.
6. The electrophotographic photoreceptor, wherein the electrophotographic photoreceptor has a layer structure of 6, and the second charge transport layer is located on the outermost surface of the photoreceptor, and has a coefficient of static friction with a cleaning blade of 1.0 or less.

Φ _CTL = α · φ _M + β (a) (α and β in the formula are constants) (2) The charge generation layer and the charge transport layer are laminated to constitute (1). The electrophotographic photosensitive member according to the above.

(3) An image forming method using the electrophotographic photosensitive member according to the above (1) or (2), wherein the photosensitive member is cleaned with a cleaning blade after charging, image exposure, development and transfer. Method.

The inventors of the present invention have examined the above problems in detail, and found that an image defect generated when the surface was cleaned with a cleaning blade was replaced with a positively chargeable organic photoreceptor containing a lubricating substance in the outermost surface layer. The present invention was found to be solved by controlling the coefficient of static friction of the photosensitive member with respect to the cleaning blade by using the above formula, and completed the present invention.

If the coefficient of static friction of the photoreceptor with respect to the cleaning blade is larger than 1.0, black streaks and the like are generated by turning up the blade (reversal of the blade tip), resulting in poor cleaning.

The coefficient of static friction μ is usually HEI when the photosensitive member is in the form of a sheet, a plate, or an endless belt.
Surface property tester (model HEIDON-1) manufactured by DON
4).

However, in practice, the photosensitive drum incorporated in the electrophotographic image forming apparatus is mainly a photosensitive drum. In this case, the static friction coefficient μ is measured by measuring the rotational torque T (kg · cm) of the photosensitive drum. It is determined by measurement.

That is, the rotational torque T of the photosensitive drum itself
₁ (kg · cm) and the rotation torque T ₂ of the photosensitive drum with the blade cleaning member pressed against the load F (kg).
(Kg · cm) is measured and calculated by the following equation.

Static friction coefficient μ = (T ₂ −T ₁ ) / (F · γ) where γ is the radius (cm) of the photosensitive drum.

The present inventors have found that the work function of the charge transport layer is important in order to achieve the object of the present invention by enhancing the charge injection characteristics into the electron transport charge transport layer.

The electron transporting charge transporting layer in the present invention may have a hole transporting ability, but means an electron transporting ability that is superior to the hole transporting ability.

The ability to transport holes and electrons can be determined by combining a charge-generating substance with an electrophotographic photoreceptor to form an electrophotographic photoreceptor and controlling the photosensitivity in an operation mode controlled by hole transport and the photosensitivity in an operation mode controlled by electron transport. , Can be determined by comparison.

For example, when a photoreceptor is manufactured by laminating a charge generating layer and a charge transporting layer on a conductive support in this order, the photosensitivity (eg, half-exposure amount) in the positive charging mode depends on the electron transporting ability. And the photosensitivity in the negative charging mode indicates the hole transporting ability. Therefore, the case where the photosensitivity in the positive charging mode is higher is referred to as electron transport dominance.

When contact potential difference measurement is used to determine the work function of the charge transport layer alone, a phenomenon in which the work function of the charge transport layer changes when the sample-side conductive electrode is changed is observed.
The inventors pay attention to the work function of the sample-side conductive electrode at this time, and when the relationship between the work function φ _CTL of the charge transport layer and the work function φ _M of the sample-side conductive electrode is linearly approximated by the equation (a), , Α
It has been found that the object of the present invention is achieved by using a charge transport layer satisfying ≦ 0.6 (α and β in the formula are constants).

Φ _CTL = α · φ _M + β (a) Regarding the cause of the generation of a remarkable residual potential in a photoreceptor using an electron transporting charge transporting layer, the inventors of the present invention have proposed a method in which a photoreceptor has a photo-response in a photogenerating layer. It was confirmed that there was an obstacle in the process of injecting the generated electrons into the charge transport layer.

The injection of electrons from the charge generation layer to the charge transport layer is achieved by the movement of electrons from the electron conduction level of the charge generation substance toward the electron conduction level of the charge transport substance. The energy value of the electron conduction level of these organic compounds can be estimated by measuring the reduction potential. Generally, the reduction potential of the electron transporting substance used for the organic photoreceptor is -0.4 to-with respect to the Ag / AgCl electrode.
1 (V), from which it can be estimated that the electron conduction level of the electron transporting substance is located in the vicinity of -3.9 to -4.3 (eV). On the other hand, the electron conduction level of the charge generating substance is approximately in the range of -3 to -4 (eV), and it can be said that the electron conduction level is higher in energy than the electron conduction level of the charge transporting substance. That is, as long as the electronic levels of both substances alone are compared, no energy hindrance is found for the electron injection from the charge generating substance to the charge transporting substance.

On the other hand, the conductive support (electrode), the charge generation layer, and the charge transport layer constituting the electrophotographic photoreceptor have different Fermi levels when each exists alone.
It is known that, when these are brought into close contact with each other to form a photoreceptor, the potential of each layer changes in the direction in which the Fermi level coincides throughout. That is, it should be considered that the electron conduction levels of the charge generating substance and the charge transporting substance in the photoreceptor are determined through a potential change due to contact, unlike the case of each layer alone.

In an actual photosensitive member, when the electrode, the charge generation layer and the charge transport layer are in contact with each other, the electron capacity of the electrode is much larger than that of the organic semiconductor. Equilibrium is reached in accordance with the Fermi level of Further, even in a photoconductor in which an electrode, a charge generation layer, and a charge transport layer are laminated in this order, for example, "Japan Hardcopy '
94, Proceedings P229-232 ", the charge transport material penetrates deeply into the charge generation layer and exists at a sufficient concentration at the interface with the electrode. It can be said that the electron level of the charge transport layer is also determined by the potential equilibrium with the electrode.

The present inventors have paid attention to the problem of the charge injection process in the photoreceptor using the electron transporting charge transport layer, and particularly focused on the electron level of the charge transport layer which is in contact equilibrium with the electrode. As a means for measuring the contact equilibrium, there is a contact potential difference measurement. In the contact potential difference measurement, a work function of a measurement target layer is determined by measuring a potential difference generated in contact with a specific metal (typically, gold is used).
For the measurement, a technique generally called a Kelvin method is used. For the Kelvin method and the work function determination method,
There is a detailed description in "New Experimental Chemistry Course 18 -Interface and Colloid-" (edited by The Chemical Society of Japan, pages 181 to 192).

When determining the work function of the charge transport layer,
A charge transport layer is provided on the conductive electrode on the sample side to make a sample, and the gold electrode is used as a counter electrode and the surface of the charge transport layer and the gold electrode (counter electrode)
A potential difference measurement with respect to the surface is performed. The charge transport layer is in contact with the gold electrode via the sample-side electrode, but when sufficient electron transfer from the high Fermi level to the low Fermi level through the contact interface occurs and the equilibrium is reached, The contact potential difference between the charge transport layer and the gold electrode should be constant irrespective of the metal interposed therebetween, and the work function of the charge transport layer should also be constant. However, in actual measurement results, the value of the work function of the charge transport layer changes depending on the work function of the sample-side conductive electrode. This means, for example, "Japan
Hardcopy '90 Fall Meeting
Proceedings P80-P83 "and the like. This indicates that the contact equilibrium between the charge transport layer and the sample-side electrode is different from that due to ideal electron transfer, and has attracted attention as a behavior that reflects the electronic properties of the charge transport layer. You.

The relationship between the charge transport layer and the sample side electrode obtained by such a contact potential difference measurement can be said to just suggest the relationship between the charge transport layer and the electrode in the electrophotographic photosensitive member. A correlation with the injection property is expected, and as a result, a correlation with the residual potential characteristic of the photoconductor is expected.

From such a viewpoint, the inventors have measured the contact potential difference of the charge transport layer alone to solve the problem of the residual potential in the photoreceptor using the electron transport charge transport layer. The relationship between the function φ _CTL and the work function φ _M of the sample-side electrode was examined. As a result, if the electron-transporting charge-transporting layer, both it was confirmed that a substantially linear relationship over the entire range of the measured phi _M.

[0037] This is the case of the hole-transporting charge-transporting layer, it can be said to exhibit significantly different behavior with respect to the both regions to be independent in the region and phi _M as a linear relationship appears. Furthermore, in the case of the hole transporting charge transporting layer, the inclination α of the linear region is
It is clear that α is substantially equal to 1 in any sample, whereas in the case of the electron transporting charge transporting layer, the slope of the straight line changes greatly depending on the sample.
This is considered to indicate an important feature of the electron transporting charge transport layer different from the hole transporting charge transport layer.

Φ _CTL and φ _M in the electron transporting charge transport layer
The slope α of the linear relationship with the conventional charge transport layer changes within the range of 0.65 to 1.

However, in this case, when a specific electron transporting substance and a specific binder are combined, it is presumed that some physical change probably occurs inside the charge transport layer, and this inclination can be α ≦ 0.6. That was found. Furthermore, surprisingly, such α ≦ 0.6
It was found that, in the photoreceptor having the charge transport layer, the characteristics of injecting electrons from the charge generation layer were improved and the residual potential was reduced.

The lower limit of the value of α is α = 0, but the value may be α <0 due to a measurement error or the like.
Therefore, it can be said that α ≧ −0.1 as the actually measured value. Further, the work function phi _M of electrodes can be used for the conductive support is in the range of 3.6～6EV.

In the present invention, the electron transporting substance which can be used for forming the electron transporting charge transporting layer is not particularly limited, but is typically represented by the general formula (A):
The compounds represented by (D) are useful, and specific examples thereof are shown below.

[0042]

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In the formula, X represents> SO ₂ ,> C = Q ₂ ,
_1, Q ₂ is = O, = S, = N -R 7, = C (Z 1) (Z 2)
Represents

Here, Z ₁ and Z ₂ represent electron withdrawing groups. R ₁ and R _2, or R ₃ and R ₄ may be bonded to each other to form an aromatic ring or an aliphatic ring, and R ₅ and R ₆ are ＮN—R ₇ or ＣC ( R ₈ ) and (R ₉ ). R _{1 to} R _{9 each} represent a hydrogen atom, a halogen, a cyano, a substituted vinyl group, a substituted or unsubstituted alkyl group, an aryl group, or a heterocyclic group.

Preferred substituents of the substituted vinyl group are phenyl, cyano and alkoxycarbonyl groups. Preferred alkyl groups have 1 to 20 carbon atoms, and preferred aryl groups are benzene, naphthalene and pyrene. Preferred heterocyclic groups are pyridine, thiophene, quinoline, and oxazole.

Preferred substituents for the alkyl, aryl and heterocyclic groups are alkoxy, vinyl, phenyl, alkyl, halogen, trifluoromethyl, cyano, amino, alkylamino, arylamino, nitro, alkoxycarbonyl, asil, styryl , Alkylcarbamide, alkylsulfonamide, and carbamoyl.

Preferred electron-withdrawing groups are cyano,
Nitro, halogen, trifluoromethyl, alkoxycarbonyl, acyl, aryloxycarbonyl, sulfone, and phenyl or naphthyl substituted with these groups.

[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

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[0055]

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[0056]

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[0057]

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[0058]

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[0059]

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[0060]

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[0061]

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Further, in a preferred embodiment of the present invention,
The photoreceptor is formed by laminating a charge generation layer and a plurality of charge transport layers on a conductive support, and among the plurality of charge transport layers, the charge transport layer forming the outermost surface layer of the photoreceptor has the lubricity. A substance is contained, and the coefficient of static friction of the outermost surface layer with respect to the cleaning blade is 1.0 or less.

The reason why the photoreceptor having the above-mentioned structure is used is that when the outermost surface layer of the photoreceptor contains a lubricating substance for the purpose of improving abrasion and damage at the time of cleaning of the photoreceptor, the lubricating material may be lubricated as in the known example. When the active substance is contained in the entire charge transport layer,
The electrophotographic performance of the photoconductor decreases. Therefore, the charge transport layer is composed of a plurality of charge transport layers, and the lower charge transport layer does not contain the lubricating substance, or even if it does, the electrophotographic performance of the photoreceptor is not degraded. In addition to ensuring sufficient performance, the charge transport layer as the outermost surface layer contains the lubricating substance necessary for ensuring sufficient abrasion resistance so that the coefficient of static friction with respect to the cleaning blade is 1.0 or less, and preferably 1 or less. A photoreceptor having a ratio of 0.0 to 0.1 is preferable.

FIG. 1 shows a typical example of a photoreceptor having a plurality of charge transport layers laminated on the charge generation layer. In the figure, 1 is a conductive support, 2 is an intermediate layer, 3 is a charge generation layer, 4 is a first charge transport layer, 5 is a second charge transport layer, and the lubricating substance is the second charge transport layer. It is contained in the transport layer 5. As the lubricating substance, a siloxane structure or a resin containing the structure or fine resin particles thereof, or a fluorine-based resin or fine resin particles thereof are preferably used.

When the resin fine particles are used, the volume average particle diameter is 0.05 to 10 μm, preferably 0.1 to 5 μm, and the binder is contained in the outermost surface layer (second charge transport layer 5) of the photoreceptor. It is contained in an amount of 0.01 to 50 parts by weight based on 100 parts by weight of the resin.

Examples of the lubricating substance include, for example,
JP-A-324453, page 6, column 9, which is a resin or resin fine particle having a siloxane structure, and is commercially available, for example, under the trade name "Tospearl" (manufactured by Toshiba Silicone Co., Ltd.).

The present applicant has previously proposed Japanese Patent Application No. 6-13 / 1994.
A polycarbonate resin or fine resin particles containing a siloxane structure described on pages 22 to 25 of JP-A-8884, and a siloxane structure described on pages 13 to 36 of JP-A-6-258669 are grafted. Examples include polycarbonate resin or resin fine particles.

As another lubricating substance, for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyfluoroethylene described in page 1, column 1 of JP-A-4-284449, etc. , Polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl There is a fluorine atom-containing resin selected from the group consisting of vinyl ether copolymers or resin fine particles thereof.

As the conductive support (electrode), a metal plate,
A metal drum is used, and a thin layer of a conductive compound such as a conductive polymer or indium oxide, or a metal such as aluminum or palladium is provided on a base such as paper or plastic film by means of coating, vapor deposition, lamination, or the like. Can be used.

The photosensitive layer is formed by applying and drying a previously prepared coating solution by dip coating, spray coating, bar coating, roll coating, blade coating, applicator coating, or by vacuum evaporation. Is used. The coating liquid for the charge generation layer is a liquid in which the charge generation substance is dispersed alone or together with a binder or an additive in the form of fine particles dispersed in an appropriate dispersion medium using a dispersion device such as an ultrasonic disperser, a ball mill, a sand mill, and a homomixer. Can be prepared. The coating solution for the charge transport layer is generally prepared by dissolving a charge transport material in a solvent together with a suitable binder and adding an additive or the like as necessary.

As the solvent used for coating, for example,
Acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, ethylene glycol dimethyl ether, toluene, xylene, acetophenone, chloroform, dichloromethane, dichloroethane, trichloroethane, methanol, ethanol,
Examples thereof include propanol and butanol.

Examples of the binder that can be used for forming the charge generation layer or the charge transport layer include the following.

Polycarbonate Polycarbonate Z resin Acrylic resin Methacrylic resin Polyvinyl chloride Polyvinylidene chloride Polystyrene Styrene-butadiene copolymer Polyvinyl acetate Polyvinyl formal Polyvinyl butyral Polyvinyl acetal Polyvinyl carbazole Styrene alkyd resin Silicone resin Silicone alkyd resin Polyester Phenol resin Polyurethane Epoxy Resin Vinylidene chloride-acrylonitrile copolymer Vinyl chloride-vinyl acetate copolymer Vinyl chloride-vinyl acetate-maleic anhydride copolymer Particularly preferred electron transporting substance is the general formula (A). On the other hand, the binder is preferably polystyrene, a polystyrene copolymer, polycarbonate, polyarylate, polyester, or the like. The ratio of the charge generating substance to the binder is 1/9.
The weight ratio is preferably 9 to 9/1, and more preferably 1/2 to 6/1.

The thickness of the charge generation layer is 0.01 to 20 μm
However, it is more preferably 0.05 to 5 μm. The thickness of the charge transport layer is 1 to 100 μm,
0 μm is preferred.

As the binder used for the intermediate layer, the protective layer and the like, those mentioned above for the charge generation layer and the charge transport layer can be used.
Nylon resin, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-maleic anhydride copolymer, ethylene-
Ethylene resins such as vinyl acetate-methacrylic acid copolymer, polyvinyl alcohol, cellulose derivatives and the like are effective. Further, a curable binder utilizing thermal curing or chemical curing of melamine, epoxy, isocyanate or the like can be used.

In the photosensitive layer, potential characteristics, storability,
Various additives can be contained for the purpose of improving durability and environmental dependency.

The thickness of the first charge transport layer 4 is 5 to 50.
μm, preferably 10 to 40 μm, and the thickness of the second charge transport layer 5 is 0.2 to 30 μm, preferably 0.4 to 40 μm.
20 μm.

The volume average particle size of the resin fine particles is measured by a laser diffraction / scattering type particle size distribution analyzer LA-700 (manufactured by Horiba, Ltd.).

Next, an image forming method according to the present invention will be described.

FIG. 2 is a schematic structural view for explaining the image forming method of the present invention.

In FIG. 2, reference numeral 10 denotes an organic photosensitive drum rotating in the direction of an arrow, and 11 denotes a charger for uniformly charging the photosensitive drum, which is a corona discharge charger, a roller charger, or a magnetic charger. A brush charger may be used.
Reference numeral 12 denotes analog image exposure or digital image exposure using LEO, LBO, or the like, and an electrostatic latent image is formed on the photoconductor by the image exposure. This electrostatic latent image is brought into contact or non-contact by a developing device 13 containing a one-component or two-component developer, preferably a two-component developer containing a fine particle toner having a volume average of 2 to 9 μm. The toner image is formed on the photoconductor by being developed by the contact. This toner image is electrostatically transferred by a transfer unit (transfer unit or roller transfer unit by corona discharge) 14 onto the transfer material P conveyed at a proper timing, separated by a separation electrode 15, and fixed by a conveyance unit 16 to a fixing unit 17. And fixed.

After the transfer, the surface of the photoreceptor is neutralized by a static eliminator 18, and is cleaned by being brought into contact with the photoreceptor 10 in a counter direction by a cleaning blade 19 according to the present invention. Ready for next image formation.

The cleaning blade 19 is preferably made of a urethane rubber cover elastic plate having a rebound resilience of 35 to 60% at room temperature as described above, and is preferably brought into contact with the photosensitive drum 10 in the counter direction.

In the present invention, preferable values of the contact load p, contact angle θ and free length L of the cleaning blade on the photosensitive member are p = 15 to 20 g / cm, and θ = 15 to
25 ° and L = 8-12 mm.

[0085]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto. In the text, “parts” means “parts by weight”.

Contact Potential Difference Measurement and Work Function Plot Contact potential difference measurement was carried out using palladium (P
d), indium tin oxide (ITO), nickel-chromium alloy (Ni-Cr), titanium (Ti), aluminum (Al), aluminum-chromium alloy (Al
A sample was prepared by spin-coating an electrode made of -Cr) or the like, followed by drying, and the measurement was performed in the air using the Kelvin method. The work function φ _CTL of the charge transport layer thus obtained is represented as a work function plot with respect to the work function φ _M of the corresponding electrode metal (measured without applying the charge transport layer) (the result is shown in FIG. 3 (a)). To (d)).

Example 1 Surface roughness Rz by cutting with sintered diamond
A solution obtained by dissolving an alcohol-soluble polyamide resin in alcohol was applied on an aluminum drum having a diameter of 80 mm and adjusted to 0.8 to form an undercoat layer having a dry film thickness of 0.3 μm.

Using a sand mill, 1 part of titanyl phthalocyanine having a maximum peak at a black angle of 27.2 ± 0.2 in X-ray diffraction, 0.5 part of silicone butyral resin, and 50 parts of methyl isopropyl ketone as a dispersion medium. Dip-coating the dispersed liquid, and dry film thickness 0.4μm
Was formed.

Next, an electron transporting material (A-
7) 1 part and polystyrene “stylon 6” as binder
79 "(manufactured by Asahi Dow) is dissolved in 7 parts of THF (tetrahydrofuran) to prepare a charge transport layer coating solution 1.
This was applied and dried to form a first charge transport layer having a thickness of 20 μm.

Further, the coating liquid of the second charge transport layer (a) to (e) prepared by adding the organic fine particles shown in the following table to the coating liquid of the first charge transport layer was applied and dried, and the surface of 7 μm was formed. The charge transport layer was formed to produce electrophotographic photosensitive member samples 1 to 5.

Further, polycarbonate "Iupilon Z-200" was used instead of polystyrene as the binder in the charge transport layer.
Sample 6 was prepared in exactly the same manner as Sample 1 except that (Mitsubishi Gas Chemical Company) was used.

[0092]

[Table 1]

A1: Silicone resin organic fine particles “Tospearl 120” (manufactured by Toshiba Silicone Co., Ltd.) A2: Fluororesin organic fine particles “Rubron L-2” (manufactured by Daikin Industries, Ltd.) A3: Silicone resin organic fine particles Tospearl 130 "
(Manufactured by Toshiba Silicone Co., Ltd.) A4: Silicone resin organic fine particles "Tospearl 145"
(Toshiba Silicone Co., Ltd.) Performance Evaluation Regarding the presence or absence of black spots and the cleaning property, the above photoreceptor sample was subjected to Konica Corp. digital electrophotographic copying machine Konica 7050 (laser image exposure, two-component
The image was mounted as a photoreceptor for magnetic brush development, and an original image having a white portion, a solid black portion, a halftone portion, and a character portion was copied and evaluated.

The occurrence of black spots was evaluated by observing the copied image with the naked eye and divided into four stages of ◎ to XX.

◎ 1 or less black spots in B4 size image ○ 2 to 4 black spots in B4 size image × 5 to 20 black spots in B4 size image XX 21 or more black spots in B4 size image Regarding the cleaning property, the surface of the photoreceptor was observed after copying 30,000 sheets or when a failure appeared in the copied image.

With respect to the potential stability, the following values were measured for the first copy and the 100th continuous copy.

VH: Surface potential at the developing position of the portion not exposed to the laser VL: Surface potential at the developing position of the portion exposed to the laser The results are shown in Tables 2 and 3.

[0098]

[Table 2]

[0099]

[Table 3]

Samples 1 to 3, which are the photoreceptors of the present invention, have good performance in each case, but samples 4 to 6 outside the present invention have problems in characteristics.

Example 2 Photoconductor samples 7 and 8 were prepared in the same manner as in Sample 1 of Example 1 except that the electron transporting material was changed to (A-59) and (A-11), and the performance was similarly measured. Table 4 below shows the results of the evaluation.

[0102]

[Table 4]

[0103]

[Table 5]

As is clear from Tables 4 and 5, both Samples 7 and 8 in the present invention showed good performance.

[0105]

According to the present invention, a positively charged photoreceptor having a charge transporting layer having an electron transporting property, having a small residual potential, ensuring image contrast, and generating little ozone, and having an adhesive property to a support. It is possible to provide an electrophotographic photoreceptor having no image defects and an image forming method using the same.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a photoconductor in which a plurality of charge transport layers according to the present invention are stacked.

FIG. 2 is a schematic configuration diagram illustrating an image forming method of the present invention.

FIG. 3 is a graph showing the relationship between the work function φ _CTL of the charge transport layer and the work function φ _M of the sample-side electrode.

DESCRIPTION OF SYMBOLS 1 Conductive support 2 Intermediate layer 3 Charge generation layer 4 First charge transport layer 5 Second charge transport layer 10 Organic photoreceptor drum 11 Charger 12 Image exposure 13 Developer 14 Transfer device 15 Separation electrode 16 Conveying means 18 Static eliminator 19 Cleaning blade 20 Static elimination lamp P Transfer material

Claims (3)

[Claims] 1. An electrophotographic photoreceptor having a charge generation layer, a first charge transport layer, and a second charge transport layer on a conductive support in this order, wherein the first charge transport layer contains an organic electron transport material in a binder. When the work function of the electron transporting charge transporting layer is determined by contact potential difference measurement, the work function of the charge transporting layer obtained by changing the sample-side conductive _pole φ _CTL When the relationship between the work function φ _M of the sample-side conductive electrode and the work function φ _M is linearly approximated by the equation (a), the layer structure is such that α ≦ 0.6, and the second charge transport layer is Wherein the coefficient of static friction with the cleaning blade is 1.0 or less. φ _CTL = α · φ _M + β (a) (where α and β are constants) 2. The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer and the charge transport layer are laminated. 3. An image forming method using the electrophotographic photosensitive member according to claim 1 or 2, wherein the photosensitive member is cleaned with a cleaning blade after charging, image exposure, development and transfer.