JP2019095700A - Electrophotographic image forming apparatus - Google Patents

Abstract

To provide a tandem type electrophotographic image forming apparatus which suppresses slipping of a toner, and achieves long lives of an organic photoreceptor and the apparatus.SOLUTION: A tandem type electrophotographic image forming apparatus using an organic photoreceptor in which a charge generating layer, a charge transport layer and a protective layer containing a cured resin component that is a cured product of a polymerizable compound are laminated in this order on a conductive support includes a plurality of image formation units including electrostatic latent image formation means, development means, lubricant supply means that supplies a lubricant to the surface of the organic photoreceptor, and cleaning means that removes a toner remaining on the surface of the organic photoreceptor with a cleaning blade, and in at least one of combinations of the two adjacent image formation units, a content Ca of the charge transport substance in the protective layer of the organic photoreceptor contained in the image formation unit arranged in the upstream side and a content Cb of the charge transport substance in the protective layer of the organic photoreceptor contained in the image formation unit arranged in the downstream side satisfy a predetermined relationship.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electrophotographic image forming apparatus.

  In an electrophotographic image forming apparatus, an electrophotographic photosensitive member (hereinafter, also simply referred to as "photosensitive member") is used to form an electrostatic latent image corresponding to an image to be formed. The surface of the photosensitive member is charged by the charging member of the image forming apparatus. The electrostatic latent image is formed by irradiating light to the surface of a charged photoreceptor. When toner is supplied to the photosensitive member on which the electrostatic latent image is formed, a toner image is formed. The toner image is transferred to a recording medium. The toner remaining on the surface of the photosensitive member after transfer is removed by the cleaning member of the image forming apparatus. As the photosensitive member, an organic photosensitive member having a conductive support and an organic photosensitive layer disposed on the conductive support is known.

  The cured surface layer functions as a protective layer because of its excellent abrasion resistance and abrasion resistance, and can reduce the amount of wear of the surface of the organic photoreceptor by the cleaning blade when cleaning the organic photoreceptor, so It contributes to prolonging the life of the photoreceptor. However, even a protective layer having excellent abrasion resistance and abrasion resistance may cause scratches, and deformation of the cleaning blade may occur, which may increase the frequency of toner slippage.

  Here, from the viewpoint of further reducing the amount of wear on the surface of the organic photoreceptor, improvement of the above problem has been attempted, and optimization of the physical properties of the protective layer has been studied. For example, in Patent Document 1, the image carrier has a surface layer containing a curable resin, and the universal hardness and the elastic deformation rate of the image carrier are within a predetermined range, and developers each having a different color are contained. And at least one of the plurality of developing means includes abrasive particles in the developer and a rubbing member for rubbing the image carrier as a cleaning means for the image carrier after transfer An image forming apparatus having a cleaning blade is disclosed. Here, the abrasive particles have the effect of enhancing the cleaning property. In the document, in such an image forming apparatus, mechanical degradation of the photosensitive member surface layer is less likely to occur by controlling the universal hardness and elastic deformation ratio to a predetermined range, and such a technique It is disclosed that it can contribute to preventing accumulation of discharge products and the like, and in particular, to prevent image flow under a high humidity environment.

JP 2005-208325 A

  However, even when the physical properties of the protective layer are optimized as in the technique of Patent Document 1, the amount of wear on the surface of the organic photoreceptor disposed downstream is sufficiently reduced in the tandem type electrophotographic image forming apparatus. As a result, the life of the organic photoreceptor may be shortened, and toner slippage may easily occur. Therefore, in the tandem type electrophotographic image forming apparatus, the life extension can not be realized in the plurality of organic photosensitive members, and there is a problem that the toner easily passes through. In particular, in electrophotographic image formation using charging means by a proximity charging method such as a charging roller, since the discharge distance is short, a large amount of discharge occurs from the charging means toward the organic photoreceptor, and the surface of the organic photoreceptor is greatly degraded. From the above, the above-mentioned problems become greater.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide means capable of suppressing toner slippage and achieving long life of an organic photosensitive member, and hence of the apparatus itself, in a tandem type electrophotographic image forming apparatus.

  The above problems of the present invention are solved by the following means.

A tandem-type electrophotographic image using an organic photoreceptor in which at least a charge generation layer, a charge transport layer, and a protective layer containing a cured resin component which is a cured product of a polymerizable compound are sequentially laminated on a conductive support Forming device,
An electrostatic latent image forming unit that forms an electrostatic latent image on the organic photosensitive member; and a developing unit that supplies a toner to the organic photosensitive member to develop the electrostatic latent image to form a toner image A plurality of image forming units provided with lubricant supply means for supplying a lubricant to the surface of the organic photoreceptor, and cleaning means for removing the toner remaining on the surface of the organic photoreceptor with a cleaning blade,
The protective layer of the organophotoreceptor included in the at least one image forming unit further comprises a charge transport material,
100 parts by mass of a polymerizable compound constituting a cured resin component in the protective layer of the organic photoreceptor A contained in the image forming unit disposed on the upstream side, at least one of the combinations of two adjacent image forming units The charge transport material content is Ca (parts by mass), and the charge relative to 100 parts by mass of the polymerizable compound constituting the cured resin component in the protective layer of the organic photoreceptor B contained in the image forming unit disposed on the downstream side An electrophotographic image forming apparatus satisfying the following formula (1) when the content of the transport material is Cb (parts by mass).

  According to the present invention, in the tandem type electrophotographic image forming apparatus, there is provided a means capable of suppressing the toner slipping through and realizing the organic photosensitive member, and hence the life extension of the device itself.

FIG. 1 is a cross-sectional view schematically showing a structure of an organic photosensitive member in a tandem-type electrophotographic image forming apparatus according to an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view showing a structure of a tandem-type electrophotographic image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged schematic view showing an arrangement relationship between an organic photosensitive member and a cleaning blade in a tandem type electrophotographic image forming apparatus according to an embodiment of the present invention. FIG. 6 is an explanatory view illustrating an evaluation method of the electrophotographic image forming apparatus.

  Hereinafter, preferred embodiments of the present invention will be described. In the present specification, “X to Y” indicating a range means “X or more and Y or less”. Moreover, unless otherwise indicated, operation, physical properties, etc. are measured under the conditions of room temperature (20 to 25 ° C.) / Relative humidity 40 to 50% RH.

  In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Also, the dimensional proportions of the drawings are exaggerated for the convenience of the description, and may differ from the actual proportions.

  Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Also, the dimensional proportions of the drawings are exaggerated for the convenience of the description, and may differ from the actual proportions.

  One embodiment of the present invention uses an organic photoreceptor in which at least a charge generation layer, a charge transport layer, and a protective layer containing a cured resin component which is a cured product of a polymerizable compound are sequentially laminated on a conductive support. An electrostatic latent image forming unit for forming an electrostatic latent image on the organic photosensitive member, and supplying the toner to the organic photosensitive member to form the electrostatic latent image. Developing means for developing an image to form a toner image, lubricant supplying means for supplying a lubricant to the surface of the organic photosensitive member, and cleaning means for removing toner remaining on the surface of the organic photosensitive member with a cleaning blade; And the protective layer of the organophotoreceptor further comprising a plurality of image forming units comprising at least one of the image forming units further comprising a charge transport material, and a combination of two adjacent image forming units Content of the charge transport material relative to 100 parts by mass of the polymerizable compound constituting the cured resin component in the protective layer of the organic photoreceptor A contained in the image forming unit disposed on the upstream side, at least one of Part), the content of the charge transport material relative to 100 parts by mass of the polymerizable compound constituting the cured resin component in the protective layer of the organic photoreceptor B contained in the image forming unit disposed downstream is Cb (parts by mass ) Relates to an electrophotographic image forming apparatus which satisfies the following formula (1).

  The present inventors estimate the mechanism by which the problem is solved by the above configuration as follows.

  Since the surface of the organic photoreceptor having a protective layer containing a cured resin component is unlikely to be worn away, foreign substances such as residual toner firmly attached to the surface are scraped off by the cleaning blade together with the very thin region of the surface of the organic photoreceptor. It becomes difficult to be removed. As a result, the slipperiness of the surface of the organic photoreceptor is reduced, the friction between the surface of the organic photoreceptor and the cleaning blade is increased, and the blade torque is increased. In particular, in the tandem type electrophotographic image forming apparatus, the toner transferred to the intermediate transfer belt from the organic photosensitive member disposed on the upstream side is transferred to the non-image portion of the organic photosensitive member disposed on the downstream side. Reverse transcription occurs. As a result, the amount of toner (reverse transfer toner) reversely transferred to the downstream side of the organic photoreceptor is larger, and the amount of toner reaching the cleaning blade for cleaning the organic photoreceptor is also larger. Such a cleaning blade for cleaning the organic photosensitive member disposed on the downstream side is reduced in slipperiness with respect to the surface of the organic photosensitive member, and the friction between the surface of the organic photosensitive member and the cleaning blade is further increased.

  As an example of the means for suppressing the increase in friction between the surface of the organic photosensitive member and the cleaning blade in consideration of the characteristics of such a protective layer, the supply of a lubricant to the surface of the organic photosensitive member can be mentioned. However, in the organic photoreceptor disposed downstream of the tandem type electrophotographic image forming apparatus, as described above, the friction between the surface of the organic photoreceptor and the cleaning blade becomes extremely large. Even if supplied, much of the lubricant present on the surface of the organic photoreceptor will be scraped off by the cleaning blade. For this reason, the amount of lubricant on the organic photoreceptor disposed downstream is relatively smaller than the amount of lubricant on the organic photoreceptor disposed upstream. At this time, in the organic photoreceptor disposed downstream, as in the case where no lubricant is used, the protective layer is scratched to shorten the life of the organic photoreceptor, and toner slippage is likely to occur. .

  In particular, in the case of using a charging unit based on a proximity charging method such as a charging roller, since the discharge distance is short, the surface of the organic photoreceptor is largely deteriorated, and high film strength is required.

  Here, it is conceivable to increase the surface hardness of the organic photosensitive member as an example of means for suppressing the occurrence of scratches on the surface of the organic photosensitive member. However, in the tandem type electrophotographic image forming apparatus, when the surface hardness of the plurality of organic photosensitive members is uniformly increased, in the organic photosensitive member disposed on the upstream side where the amount of lubricant present on the surface of the organic photosensitive member increases, The friction between the surface of the organic photoreceptor and the cleaning blade is excessively reduced. And as a result, the amount of wear of the organic photoreceptor becomes excessively small. For this reason, in the organic photosensitive member disposed on the upstream side, cleaning failure is likely to occur.

  On the other hand, in the tandem type electrophotographic image forming apparatus according to the present invention, the charge transport material is contained in the protective layer of at least one organic photosensitive member, and the charge transport contained in the protective layer of the organic photosensitive member disposed on the upstream side The content of the substance is set to a value higher than the content of the charge transport substance contained in the protective layer of the organic photoreceptor disposed downstream. The charge transport material acts as a plasticizer while adjusting the electrical resistance of the organic photoreceptor, so that the film quality of the protective layer of the downstream organic photoreceptor having a low content of the charge transport material is hardened. As a result, the occurrence of scratches is suppressed even on the downstream side of the organic photosensitive member, which tends to run out of lubricant. In addition, the content of the charge transport material contained in the protective layer of each organic photosensitive member is set as a predetermined relationship according to the position of each organic photosensitive member among the plurality of organic photosensitive members The film quality is adjusted, and the degree to which the reverse transfer toner is scraped off by the cleaning blade along with the very thin area of each organic photoreceptor surface is changed. Then, the amount of reverse transfer toner on each organic photoreceptor surface changes, and the slipperiness of each organic photoreceptor surface, and the friction between each organic photoreceptor surface and the cleaning blade change, so that each organic photoreceptor surface is changed. The amount of lubricant scraped off by the cleaning blade changes. From this, the amount of lubricant on the surface of each organic photosensitive member becomes an optimum value according to the film quality of the protective layer of each organic photosensitive member. As a result, in the organic photoreceptor disposed on the upstream side, the necessary and sufficient amount of wear by the cleaning blade is achieved, and the cleaning performance is improved. Further, in the organic photosensitive member disposed downstream, an increase in friction between the surface of the organic photosensitive member and the cleaning blade is suppressed, and the generation of a scratch in the protective layer is suppressed. As a result, the life of the organic photosensitive member can be extended, and the occurrence of toner slip-through can be suppressed.

  As described above, according to the present invention, different amounts of reverse transfer toner, different amounts of lubricant that can be present on each organic photosensitive member, and respective organic photosensitive members in the arrangement of each organic photosensitive member in a tandem type electrophotographic image forming apparatus To optimize the relationship between the content of the charge transport material in the protective layer of Thus, in the tandem-type electrophotographic image forming apparatus according to the present invention, in the organic photoreceptors included in a plurality of image forming units, the toner is prevented from slipping through, and the life of the organic photoreceptor and thus the life of the apparatus itself is increased. To be realized.

  The above mechanism is based on speculation, and its correctness does not affect the technical scope of the present invention.

<Organic photoreceptor>
The organic photoreceptor refers to an electrophotographic photoreceptor in which an organic compound bears at least one of the charge generation function and the charge transport function which are essential for the construction of the electrophotographic photoreceptor, and known organic charge generation substances or organic charge A known organic photoreceptor such as a photoreceptor composed of a transport material, a photoreceptor in which a polymer complex has a charge generation function and a charge transport function, is included.

[Configuration of Organic Photosensitive Member]
Hereinafter, an electrophotographic image forming apparatus according to an embodiment of the present invention will be described with reference to the attached drawings. However, the present invention is not limited to only one embodiment described below.

  FIG. 1 is a schematic cross-sectional view showing the structure of an organic photoreceptor in a tandem-type electrophotographic image forming apparatus according to an embodiment of the present invention.

  In the electrophotographic image forming apparatus according to one embodiment of the present invention, the organic photoreceptor 100 has a structure in which at least the charge generation layer 103a, the charge transport layer 103b, and the protective layer 104 are sequentially stacked on the conductive support 101. Have. Here, in the case where the organic photosensitive member has a laminated structure in which the charge generation layer 103 a and the charge transport layer 103 b are directly laminated, the laminated structure portion is also referred to as the organic photosensitive layer 103.

  The organic photosensitive member 100 may be configured to have an intermediate layer 102 between the conductive support 101 and the charge generation layer 103a, as shown in FIG.

  Hereinafter, the respective layers constituting the organic photoreceptor will be described in detail.

[Protective layer]
The organic photoreceptor has a protective layer as the outermost surface layer on the side opposite to the conductive support side. The protective layer improves the low abrasion and scratch resistance of the surface of the organic photoreceptor, reduces the occurrence of toner slip-through, and contributes to prolonging the life of the organic photoreceptor and thus the electrophotographic image forming apparatus.

  The thickness of the protective layer is not particularly limited, but is preferably 0.2 to 10 μm, and more preferably 0.5 to 6 μm. When the film thickness of the protective layer is 0.2 μm or more, the effect of prolonging the life of the organic photoreceptor is excellent. Further, if it is 10 μm or less, generation of transfer memory can be further reduced.

  Hereinafter, each component of the protective layer forming material will be described in detail.

(Curable resin component)
The protective layer contains a cured resin component which is a cured product of a polymerizable compound from the viewpoint of low abrasion resistance and scratch resistance. The cured resin component constituting the protective layer is obtained by polymerizing and curing the polymerizable compound by irradiation with actinic radiation such as ultraviolet light and electron beam. As the polymerizable compound, a monomer (polyfunctional polymerizable compound) having two or more polymerizable functional groups can be used in combination with a monomer (monofunctional polymerizable compound) having one polymerizable functional group. Specifically, examples of the polymerizable compound include styrene monomers, acrylic monomers, methacrylic monomers, vinyl toluene monomers, vinyl acetate monomers, N-vinylpyrrolidone monomers, and the like.

An acrylic monomer having two or more acryloyl groups (CH ₂ CHCHCO—) or methacryloyl groups (CH ₂ CCCH ₃ CO—) as a polymerizable compound, which can be cured in a small amount of light or in a short time. Particularly preferred are methacrylic monomers, or oligomers of these.

  In the present invention, the polymerizable compounds may be used alone or in combination. Moreover, although these polymerizable compounds may use a monomer, you may oligomerize and use them.

  Hereinafter, preferable specific examples of the polymerizable compound are shown.

Here, in the chemical formulas showing the above exemplified compounds (M1) to (M14), R represents an acryloyl group (CH ₂ 2CHCO—), and R ′ represents a methacryloyl group (CH ₂ CCCH ₃ CO—).

  As the polymerizable compound, it is preferable to use a monomer having three or more polymerizable functional groups. As the polymerizable compound, two or more compounds may be used in combination, but also in this case, it is preferable to use a monomer having three or more polymerizable functional groups in a proportion of 50% by mass or more.

  These polymerizable compounds and cured resin components may be used alone or in combination of two or more.

(Metal oxide particles)
In the electrophotographic image forming apparatus of the present invention, the protective layer of the organic photoreceptor contained in at least one image forming unit preferably contains metal oxide particles.

  In particular, in at least one of the organic photoreceptors contained in the two image forming units satisfying the above formula (1), the protective layer of the organic photoreceptor more preferably contains metal oxide particles, both images More preferably, the protective layer of the organic photoreceptor contained in the forming unit contains metal oxide particles. Most preferably, in all the image forming units included in the electrophotographic image forming apparatus, the protective layer of the organic photoreceptor preferably contains metal oxide particles. The metal oxide particles contained in the protective layer of the organic photoreceptor of different image forming units may be identical to or different from each other.

  The metal oxide particles contribute to the improvement of the film strength of the protective layer. On the other hand, when metal oxide particles are added to a protective layer containing a cured resin component, transfer memory tends to occur easily. In particular, in the tandem-type image forming apparatus, as described above, the degree of abrasion of the organic photoreceptor and the occurrence of toner slippage due to the reverse transfer toner differ between the upstream image forming unit and the downstream image forming unit. It was found that the degree of generation of the transfer memory also differs depending on whether the image forming unit is a chromatic color unit or a black unit. Specifically, when metal oxide particles are added to the protective layer containing a cured resin component, the occurrence of transfer memory is not large in the black unit, but a large transfer memory occurs in the chromatic color unit. In particular, it has been found that a remarkable transfer memory occurs in a green chart in which two colors are overlapped using a yellow color unit and a cyan color unit. The reason why the transfer memory has a difference between the black unit and the chromatic unit is not clear, but it is considered that the black is a single color and the visual sensitivity is low.

  However, in the electrophotographic image forming apparatus according to the present embodiment, by adding the charge transport material to the protective layer, the resistance of the protective layer is adjusted, the generation of the transfer memory is suppressed, and the image quality stability is improved. Therefore, the film strength and the electrical characteristics can be compatible by adjusting the addition amount of the charge transport material according to the position of the image forming unit and whether it is a unit for a chromatic color or a unit for black. It is possible to obtain an electrophotographic image forming apparatus in which toner slippage is small, generation of transfer memory is suppressed, and the life of the organic photoreceptor is improved.

  The number average primary particle size of the metal oxide particles is preferably 1 to 300 nm, more preferably 3 to 100 nm, and still more preferably 5 to 40 nm.

  The number average primary particle size of metal oxide particles is a photographic image obtained by photographing a 10000 × magnification photograph with a scanning electron microscope (manufactured by Nippon Denshi Co., Ltd.) and randomly capturing 300 particles with a scanner (aggregated particles are This can be calculated by using the automatic image processing and analyzing apparatus “LUZEX AP (software version Ver. 1.32)” (manufactured by Nireco Co., Ltd.).

  Examples of metal oxide particles contained in the protective layer include silica (silicon oxide), magnesium oxide, zinc oxide, lead oxide, alumina (aluminum oxide), zirconium oxide, tin oxide, titania (titanium oxide), niobium oxide, Molybdenum oxide, vanadium oxide or the like can be used. Among these, tin oxide is preferable from the viewpoint of electrical characteristics.

  The metal oxide particles are not particularly limited, and particles produced by a known production method can be used.

  The metal oxide particles may be surface-modified by a surface modifier having a reactive organic group (hereinafter, also referred to as a "reactive organic group-containing surface modifier").

  As the reactive organic group-containing surface modifier, those which react with hydroxy groups and the like present on the surface of the metal oxide particles are preferable, and as such a reactive organic group-containing surface modifier, for example, a silane coupling agent And titanium coupling agents.

  Moreover, as a reactive organic group containing surface modifier, the surface modifier which has a radically polymerizable reactive group is preferable. As a radically polymerizable reactive group, a vinyl group, an acryloyl group, a methacryloyl group etc. are mentioned, for example. Such a radically polymerizable reactive group can also react with the polymerizable compound to form a strong protective layer. As a surface modifier having a radically polymerizable reactive group, a silane coupling agent having a radically polymerizable reactive group such as a vinyl group, an acryloyl group or a methacryloyl group is preferable.

  The reactive organic group-containing surface modifier is preferably a silane coupling agent having the above radical polymerizable group, and examples thereof include the following compounds S-1 to S-31.

_{S-1: CH 2 = CHSi} (CH 3) (OCH 3) 2
_{S-2: CH 2 = CHSi} (OCH 3) 3
S-3: CH ₂ = CHSiCl ₃
S-4: CH ₂ CHCHCOO (CH ₂ ) ₂ Si (CH ₃ ) (OCH ₃ ) _{2
S-5: CH 2 = CHCOO} (CH 2) 2 Si (OCH 3) 3
S-6: CH ₂ = CHCOO (CH ₂ ) ₂ Si (OC ₂ H ₅ ) (OCH ₃ ) ₂
S-7: CH ₂ = CHCOO (CH ₂ ) ₃ Si (OCH ₃ ) ₃
S-8: CH ₂ = CHCOO (CH ₂ ) ₂ Si (CH ₃ ) Cl _{2
S-9: CH 2 = CHCOO} (CH 2) 2 SiCl 3
_{S-10: CH 2 = CHCOO} (CH 2) 3 Si (CH 3) Cl 2
_{S-11: CH 2 = CHCOO} (CH 2) 3 SiCl 3
_{S-12: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-13: CH 2 = C} (CH 3) COO (CH 2) 2 Si (OCH 3) 3
S-14: CH ₂ CC (CH ₃ ) COO (CH ₂ ) ₃ Si (CH ₃ ) (OCH ₃ ) ₂
S-15: CH ₂ CC (CH ₃ ) COO (CH ₂ ) ₃ Si (OCH ₃ ) ₃
S-16: CH ₂ CC (CH ₃ ) COO (CH ₂ ) ₂ Si (CH ₃ ) Cl _{2
S-17: CH 2 = C} (CH 3) COO (CH 2) 2 SiCl 3
_{S-18: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
S-19: CH ₂ CC (CH ₃ ) COO (CH ₂ ) ₃ SiCl _{3
S-20: CH 2 = CHSi} (C 2 H 5) (OCH 3) 2
_{S-21: CH 2 = C} (CH 3) Si (OCH 3) 3
_{S-22: CH 2 = C} (CH 3) Si (OC 2 H 5) 3
_{S-23: CH 2 = CHSi} (OCH 3) 3
S-24: CH ₂ CC (CH ₃ ) Si (CH ₃ ) (OCH ₃ ) _{2
S-25: CH 2 = CHSi} (CH 3) Cl 2
_{S-26: CH 2 = CHCOOSi} (OCH 3) 3
_{S-27: CH 2 = CHCOOSi} (OC 2 H 5) 3
S-28: CH ₂ CC (CH ₃ ) COOSi (OCH ₃ ) ₃
S-29: CH ₂ = C (CH ₃ ) COOSi (OC ₂ H ₅ ) _{3
S-30: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3
_{S-31: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) 2 (OCH 3)
In addition, as the reactive organic group-containing surface modifying agent, a silane compound having a reactive organic group capable of radical polymerization may be used other than the compounds shown in the above exemplified compounds (S-1) to (S-31). . The reactive organic group-containing surface modifiers may be used alone or in combination of two or more. The processing amount (addition amount) of the reactive organic group-containing surface modifying agent is preferably 0.1 to 200 parts by mass, and more preferably 7 to 70 parts by mass with respect to 100 parts by mass of the particles.

  The method of treating the untreated metal oxide particles with the reactive organic group-containing surface modifier is not particularly limited. For example, a slurry containing solid metal oxide particles and a reactive organic group-containing surface modifier (solid particles And the like) and the like. By this method, surface modification of the untreated metal oxide particles proceeds while preventing reaggregation of the untreated metal oxide particles. Thereafter, the solvent is removed and powdered.

  As a surface modification device, a wet media dispersion type device is mentioned, for example. In this wet media dispersion type apparatus, beads are packed as media in a container, and further, a stirring disk mounted vertically to a rotating shaft is rotated at high speed to break and crush aggregate particles of untreated metal oxide particles. It is an apparatus having a dispersing step. The wet media dispersion type device is not limited as long as the untreated metal oxide particles can be sufficiently dispersed and surface modified when surface modification is performed on the untreated metal oxide particles, for example, vertical type Various types such as horizontal type, continuous type and batch type can be adopted. Specifically, sand mills, ultravisco mills, pearl mills, grain mills, dyno mills, agitator mills, dynamic mills, etc. may be mentioned. These dispersion-type devices are pulverized and dispersed by impact crushing, friction, shear, shear stress and the like using grinding media such as balls and beads.

  As the beads used in the wet media dispersion type apparatus, balls made of glass, alumina, zircon, zirconia, steel, flint stone or the like as a raw material can be used, but those made of zirconia or zircon are particularly preferable. The size of the beads is usually about 1 to 2 mm in diameter, preferably about 0.1 to 1.0 mm.

  Although various materials such as stainless steel, nylon, ceramic and the like can be used for the disk and the inner wall of the container used in the wet media dispersion type apparatus, ceramic disks such as zirconia and silicon carbide and the inner wall of the container are particularly preferable.

  These metal oxide particles may be used alone or in combination of two or more.

  The content of the metal oxide particles is not particularly limited, but is preferably 100 to 200 parts by mass, and 110 to 170 parts by mass with respect to 100 parts by mass of the polymerizable compound for constituting the cured resin component. Is more preferred. Within the above range, the life of the organic photoreceptor, and hence the electrophotographic image forming apparatus can be prolonged, and the occurrence frequency of toner leakage can be further improved.

(Charge transport material)
In the electrophotographic image forming apparatus of the present invention, the protective layer of the organic photoreceptor contained in at least one image forming unit contains a charge transport material. The charge transport substance in the protective layer is a substance having charge transportability that transports charge carriers in the protective layer, and is a substance capable of adjusting the electrical resistance of the protective layer. For example, amine compounds such as N, N-dialkylaniline compounds, diarylamines, triarylamines, pyrazoline compounds, carbazole compounds, imidazole compounds, triazole compounds, oxazole compounds, styryl compounds, stilbene compounds, etc. may be used.

  The charge transport material can be appropriately selected from known compounds, but the protective layer is represented, for example, by the following general formula (1) from the viewpoints of scratch resistance, charge injection characteristics, low occurrence probability of transfer memory, etc. It is preferable to contain a charge transport material having a structure.

In the above general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represent an alkyl group having 1 to 7 carbon atoms or an alkoxy group having 1 to 7 carbon atoms. k, l and n each independently represent an integer of 0 to 5, and m represents an integer of 0 to 4. However, when k, l, n or m is 2 or more, plural R _{1 's} , R _{2' s} , R _{3 's} and R _{4' s} may be the same as or different from each other . Among these, R ₁ , R ₂ , R ₃ and R ₄ are preferably each independently an alkyl group having 1 to 3 carbon atoms. In addition, k, l, n and m are preferably each independently an integer of 0 to 1. An example of a preferred compound is CTM-1 used in the examples.

  As a compound represented by the said General formula (1), the thing of Unexamined-Japanese-Patent No. 2015-114454 can be used, for example. Moreover, it can synthesize | combine by the well-known synthetic | combination method, for example, the method currently indicated by Unexamined-Japanese-Patent No. 2006-143720 etc.

  These charge transport materials may be used alone or in combination of two or more. The charge transport materials contained in the protective layer of the organic photoreceptor of different image forming units may be identical to or different from each other, but are preferably identical to each other.

  The amount of the charge transport material added is the content of the charge transport material in the protective layer of organophotoreceptor A contained in the image formation unit disposed upstream in at least one of the combinations of two adjacent image formation units. There is no particular limitation as long as Ca and the content Cb of the charge transport substance of the organic photoreceptor B contained in the image forming unit disposed on the downstream side satisfy Formula (1): Ca> Cb. When two or more types of charge transport substances are used in combination, the total amount of charge transport substances contained in the protective layer of each organic photoreceptor is adjusted to satisfy the above formula (1).

  Preferably, in the image forming unit other than the most downstream, the addition amount of the charge transporting substance is 1 to 25 parts by mass, more preferably 5 with respect to 100 parts by mass of the polymerizable compound for constituting the cured resin component. -20 parts by mass. Within the above range, the electrical characteristics are further improved, and the life of the organic photoreceptor, and hence the electrophotographic image forming apparatus, the transfer memory suppressing effect, and the toner frequency reducing effect are further improved.

  On the other hand, in the most downstream image forming unit, the addition amount of the charge transport material is preferably 0 to 25 parts by mass with respect to 100 parts by mass of the polymerizable compound for constituting the cured resin component, and 0 to 5 It is more preferable that it is a mass part, it is further more preferable that it is 0-2 mass parts, it is still more preferable that it is 0-1 mass part, and it is most preferable that it is 0 mass part. That is, in a preferred embodiment, the protective layer of the organic photoreceptor of the most downstream image forming unit does not contain a charge transport material. The lower the image forming unit, the larger the amount of reverse transfer toner from the upstream image forming unit, and the more the organic photoreceptor is worn away, so high film strength is required, but the charge transport material acts as a plasticizer. Therefore, it is advantageous not to include the charge transport substance in the most downstream unit that requires the highest film strength.

  In a preferred embodiment of the present invention, the combination of two adjacent image forming units is a combination of image forming units provided with toners of different colors, and at least one image forming unit is a unit for chromatic color. The protective layer of the organic photoreceptor contained in the unit for chromatic color contains a charge transport material, and at least one image forming unit is a unit for black, and the protective layer of the organic photoreceptor contained in the unit for black Contains no charge transport material. With the above configuration, the effects of the present invention can be more remarkably obtained. In addition, since the black unit has a low visual sensitivity of the transfer memory as compared with the chromatic unit, a high-quality and highly reliable image can be obtained without the addition of a charge transport material.

(Specific radical scavenger)
The protective layer may contain a radical scavenger having a structure represented by the following general formula (2).

  The polymerizable compound described above can be polymerized in the presence of a specific radical scavenger represented by the following general formula (2). This particular radical scavenger functions as a crosslinker sealant. That is, the specific radical scavenger can adjust the crosslink density by the addition ratio and the like. Therefore, when the cured resin component is obtained by polymerizing the polymerizable compound in the presence of a specific radical scavenger, the protective layer has appropriate film strength (abrasion resistance), and the cleaning blade The surface of the organic photoreceptor is appropriately worn away by cleaning means such as. Therefore, even if a discharge product or the like adheres to the surface of the organic photosensitive member, the surface of the organic photosensitive member is worn away and refreshed, so that the image flow in the formed image can be prevented.

In the above general formula (2), R ₅ and R ₆ each independently represent an alkyl group having 1 to 6 carbon atoms. If R ₅ and R ₆ are an alkyl group having 1 to 6 carbon atoms, the influence of steric hindrance of the radical scavenger can be reduced, and control of the crosslinking reaction becomes easy. In addition, R ₅ and R ₆ are each preferably independently an alkyl group having 4 or 5 carbon atoms, from the viewpoint of stability of the trapped radical, and each independently represents a tert-butyl group or a tert-pentyl group. And more preferably a tert-pentyl group. These specific radical scavengers may be used alone or in combination of two or more.

  As the specific radical scavenger, either a synthetic product or a commercial product may be used. As a commercial product, for example, SUMILIZER (registered trademark) GS manufactured by Sumitomo Chemical Co., Ltd. can be mentioned.

  Although the addition amount of the specific radical scavenger is not particularly limited, it is preferably 1 to 30 parts by mass, and 2 to 125 parts by mass with respect to 100 parts by mass of the polymerizable compound for constituting the cured resin component. It is more preferable that Within the above range, the life of the organic photoreceptor, and hence the electrophotographic image forming apparatus can be prolonged, and the occurrence frequency of toner leakage can be further improved. In addition, the image flow suppression effect in the formed image can be obtained.

(Polymerization initiator)
The polymerizable compound for constituting the above-mentioned cured resin component is preferably polymerized using a polymerization initiator.

  As a polymerization initiator, it is preferable to use a radical polymerization initiator. The radical polymerization initiator is not particularly limited, but is preferably a photopolymerization initiator, more preferably an acyl phosphine oxide compound, an alkyl phenone compound, an oxime ester compound and a thioxanthone compound, and further an acyl phosphine oxide compound and an oxime ester compound preferable. These polymerization initiators may be used alone or in combination of two or more.

  The acyl phosphine oxide compound is not particularly limited, but, for example, the following compounds can be preferably used.

  The oxime ester compound is not particularly limited, but, for example, the following compounds can be preferably used.

  These polymerization initiators may be used alone or in combination of two or more.

  The content of the polymerization initiator is preferably 0.1 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the polymerizable compound. Within the above range, the life of the organic photoreceptor, and hence the life of the electrophotographic image forming apparatus, the effect of suppressing the transfer memory in the formed image, and the effect of decreasing the frequency of toner penetration are further improved.

(Other ingredients)
The protective layer may further contain other components, and may contain, for example, an antioxidant, lubricant particles, and the like.

  The antioxidant is not particularly limited, but, for example, those described in JP-A-2000-305291 can be preferably used.

  The lubricant particles are not particularly limited, and for example, fluorine atom-containing resin particles can be added. The fluorine atom-containing resin particles are not particularly limited, but, for example, tetrafluoroethylene resin, trifluorochlorinated ethylene resin, hexafluorochlorinated ethylene propylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluoride difluoride Ethylene chloride resin, and these copolymers etc. are mentioned. These can be used individually by 1 type or in mixture of 2 or more types. Among these, tetrafluoroethylene resin and vinylidene fluoride resin are particularly preferable.

[Conductive Support]
The conductive support constituting the organic photoreceptor is not particularly limited as long as it has conductivity, and for example, a drum or sheet of a metal such as aluminum, copper, chromium, nickel, zinc, stainless steel or the like is formed A metal foil of aluminum, copper or the like laminated on a plastic film, an aluminum, indium oxide, tin oxide or the like deposited on a plastic film, a metal provided with a conductive layer by coating a conductive substance alone or with a binder resin , Plastic films and paper.

[Intermediate layer]
In the organic photoreceptor, an intermediate layer having a barrier function and an adhesive function can be provided between the conductive support and the organic photosensitive layer. It is preferable to provide an intermediate layer in consideration of various failure prevention and the like.

  Such an intermediate layer contains, for example, a binder resin (hereinafter, also referred to as “intermediate layer binder resin”) and, if necessary, conductive particles and metal oxide particles.

  The binder resin for the intermediate layer is not particularly limited, and examples thereof include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide resin, polyurethane resin, gelatin and the like. Among these, alcohol-soluble polyamide resins are preferred. These intermediate layer binder resins may be used alone or in combination of two or more.

  The intermediate layer can contain various conductive particles and metal oxide particles for the purpose of adjusting resistance. For example, various metal oxide particles such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, and bismuth oxide can be used. In addition, ultrafine particles of indium oxide doped with tin, tin oxide doped with antimony, and zirconium oxide can be used.

  The number average primary particle size of such metal oxide particles is preferably 0.3 μm or less, more preferably 0.1 μm or less.

  These metal oxide particles may be used alone or in combination of two or more. When two or more are mixed, they may be in the form of solid solution or fusion.

  The content ratio of the conductive particles or the metal oxide particles is preferably 20 to 400 parts by mass, and more preferably 50 to 350 parts by mass with respect to 100 parts by mass of the binder resin.

  The thickness of the intermediate layer is preferably 0.1 to 15 μm, more preferably 0.3 to 10 μm.

[Charge generation layer]
The charge generation layer in the organic photosensitive layer constituting the organic photosensitive member contains a charge generation material and a binder resin (hereinafter, also referred to as "charge generation layer binder resin").

  Examples of the charge generating material include azo raw materials such as sudan red and diane blue, quinone pigments such as pyrene quinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, pyranthrone, diphthaloyl pyrene and the like. Although a ring quinone pigment, a phthalocyanine pigment, etc. are mentioned, it is not limited to these. Among these, polycyclic quinone pigments and titanyl phthalocyanine pigments are preferable. These charge generation materials may be used alone or in combination of two or more.

  A known resin can be used as the binder resin for the charge generation layer, and for example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, Polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and copolymer resin containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin, chloride Vinyl-vinyl acetate-maleic anhydride copolymer resin), poly-vinylcarbazole resin, etc. may be mentioned, but it is not limited thereto. Among these, polyvinyl butyral resin is preferable. These charge generation layer binder resins may be used alone or in combination of two or more.

  The content ratio of the charge generation material in the charge generation layer is preferably 1 to 600 parts by mass, more preferably 50 to 500 parts by mass with respect to 100 parts by mass of the binder resin for charge generation layer.

  The layer thickness of the charge generation layer varies depending on the characteristics of the charge generation substance, the characteristics of the binder resin for the charge generation layer, the content ratio, etc., but it is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm. is there.

[Charge transport layer]
The charge transport layer in the organic photosensitive layer constituting the organic photoreceptor contains a charge transport substance and a binder resin (hereinafter, also referred to as a “charge transfer layer binder resin”).

  Examples of the charge transport material of the charge transport layer include triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds and the like as materials that transport charges (holes).

  The charge transport layer formed in the lower layer of the protective layer preferably contains a charge transport substance having high mobility and a large molecular weight, and such charge transport substance is represented by the above general formula (1) Those different from the compounds are preferably used.

  A known resin can be used as the binder resin for the charge transport layer, and polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylic acid ester resin, styrene-methacrylic acid ester Although copolymer resin etc. are mentioned, polycarbonate resin is preferable. Further, polycarbonate resins of BPA (bisphenol A) type, BPZ (bisphenol Z) type, dimethyl BPA type, BPA-dimethyl BPA copolymer type and the like are preferable in view of anti-cracking, abrasion resistance and charging characteristics. These charge transport layer binder resins may be used alone or in combination of two or more.

  The content ratio of the charge transport material in the charge transport layer is preferably 10 to 500 parts by mass, and more preferably 20 to 250 parts by mass with respect to 100 parts by mass of the binder resin for charge transport layer.

  The layer thickness of the charge transport layer varies depending on the properties of the charge transport substance, the properties and the content of the binder resin for the charge transport layer, etc., but it is preferably 5 to 40 μm, more preferably 10 to 30 μm.

  In the charge transport layer, an antioxidant, an electronic conductive agent, a stabilizer, a silicone oil and the like may be added. As the antioxidant, those disclosed in JP-A-2000-305291, and as the electron conductive agent, disclosed in JP-A-50-137543, JP-A-58-76483, etc. are preferable.

[Method of producing organic photoreceptor]
The organic photoreceptor is not particularly limited, but is preferably produced by a production method having the following steps.

Step (1): A step of forming an intermediate layer by applying a coating liquid for forming an intermediate layer on the outer peripheral surface of the conductive support, if necessary, and drying it,
Step (2): A coating solution for charge generation layer formation is applied to the outer peripheral surface of the conductive support or the outer peripheral surface of the intermediate layer formed on the conductive support in the step (1), and dried. Forming a charge generation layer by
Step (3): A coating solution for charge transport layer formation is applied to the outer peripheral surface of the charge generation layer formed on the intermediate layer, and dried to form a charge transport layer,
Step (4): A step of forming a protective layer by applying a coating solution for forming a protective layer on the outer peripheral surface of the charge transport layer formed on the charge generation layer, polymerizing and curing it.

  The concentration of each component in the coating solution for forming each layer is appropriately selected in accordance with the layer thickness and production rate of each layer.

  In the coating solution for forming each layer, an ultrasonic dispersing machine, a ball mill, a sand mill, a homomixer or the like can be used as a dispersing means for particles such as conductive particles and metal oxide particles and charge generating substances. However, it is not limited to these.

  The application method of the coating liquid for forming each layer is not particularly limited, and examples thereof include dip coating, spray coating, spinner coating, bead coating, blade coating, beam coating, slide hopper method, and circular There are known methods such as a slide hopper method.

  Although the drying method of a coating film can be suitably selected according to the kind of solvent, and layer thickness, heat drying is preferable.

  The details of the formation process of each layer will be described below.

(Step (1): Formation of Intermediate Layer)
The intermediate layer is prepared by dissolving the intermediate layer binder resin in a solvent to prepare a coating solution (hereinafter, also referred to as “intermediate layer forming coating solution”), and, if necessary, conductive particles and metal oxide particles. After the dispersion, the coating solution can be applied on the conductive support in a constant layer thickness to form a coating, and the coating can be formed by drying.

  The coating solution for forming an intermediate layer is preferably applied using a dip coating method.

  As a solvent used in the formation process of an intermediate | middle layer, what disperse | distributes electroconductive particle and metal oxide particle | grains favorable, and melt | dissolves the binder resin for intermediate | middle layers, especially a polyamide resin is preferable. Specifically, alcohols having 1 to 4 carbon atoms such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, tert-butanol, sec-butanol (2-butanol), etc. are the solubility of the polyamide resin And excellent in coating performance and preferable. In addition, as co-solvents that can be used in combination with the above-mentioned solvent to improve the storage stability and the dispersibility of particles and obtain a preferable effect, benzyl alcohol, toluene, dichloromethane, cyclohexanone, tetrahydrofuran and the like can be mentioned.

(Step (2): Formation of Charge Generating Layer)
In the charge generation layer, a charge generation substance is dispersed in a solution in which a binder resin for charge generation layer is dissolved in a solvent to prepare a coating liquid (hereinafter, also referred to as “coating liquid for forming charge generation layer”). The coating solution can be applied on the intermediate layer to a constant layer thickness to form a coating, and the coating can be formed by drying.

  It is preferable to apply | coat the coating liquid for charge generation layer formation using the dip coating method.

  Examples of the solvent used to form the charge generation layer include toluene, xylene, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate, tert-butyl acetate, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, tert-butanol, sec-butanol (2-butanol), methyl cellosolve, 4-methoxy-4-methyl-2-pentanone, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, diethylamine And the like, but not limited thereto.

(Step (3): Formation of Charge Transport Layer)
The charge transport layer is prepared by dissolving a binder resin for charge transport layer and a charge transport substance in a solvent (hereinafter, also referred to as “coating liquid for forming charge transport layer”), and the coating solution is used for charge generation. It can apply | coat to a fixed layer thickness on a layer, form a coating film, and it can form by drying the said coating film.

  The coating solution for forming a charge generation layer is preferably coated by a slide hopper method using a circular slide hopper coating apparatus, and can be coated by a method disclosed in, for example, JP-A-2015-114454.

  Examples of the solvent used to form the charge transport layer include toluene, xylene, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n- Examples include, but are not limited to, butanol, tert-butanol, sec-butanol (2-butanol), tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, pyridine, diethylamine and the like.

(Step (4): Formation of Protective Layer)
The protective layer is formed by adding a polymerizable compound and, if necessary, other components such as metal oxide particles, a polymerization initiator, a specific radical scavenger, and a charge transport substance to a known solvent and applying a coating solution (hereinafter referred to as The coating solution is also applied to the outer peripheral surface of the charge transport layer formed in step (3) to form a coating film. The film is dried and irradiated with actinic radiation such as ultraviolet light and electron beam to polymerize the polymerizable compound component in the coating film, and a protective layer can be formed by curing.

  The coating solution for forming a protective layer is preferably coated by a slide hopper method using a circular slide hopper coating apparatus, and can be coated by a method disclosed in, for example, JP-A-2015-114454.

  As the solvent used for forming the protective layer, any solvent can be used as long as it can dissolve or disperse the polymerizable compound, metal oxide particles, etc. For example, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n -Butanol, tert-butanol, sec-butanol (2-butanol), benzyl alcohol, toluene, xylene, dichloromethane, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3 -Dioxolane, pyridine, diethylamine and the like, but it is not limited thereto.

  The method of reacting the polymerizable compound is not particularly limited, and examples thereof include a method of reacting by electron beam cleavage, a method of adding a radical polymerization initiator, and reacting by light and heat.

  The cured resin component is produced by irradiating the coating film with actinic radiation as a curing treatment to generate radicals for polymerization, and to form and cure crosslinks by intermolecular and intramolecular crosslink reaction to cure. As the actinic radiation, ultraviolet light and electron beam are more preferable, and ultraviolet light is particularly preferable because it is easy to use.

  As the ultraviolet light source, any light source that generates ultraviolet light can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, flash (pulsed) xenon and the like can be used.

Although the irradiation conditions differ depending on each lamp, the irradiation dose of actinic radiation is preferably 5 to 500 mJ / cm ² , more preferably 5 to 100 mJ / cm ² .

  The power of the lamp is preferably 0.1 to 5 kW, more preferably 0.5 to 4 kW, and still more preferably 0.5 to 3 kW.

  The irradiation time for obtaining the necessary actinic radiation dose is preferably 0.1 seconds to 10 minutes, and more preferably 0.1 seconds to 5 minutes from the viewpoint of working efficiency.

  In the step of forming the protective layer, drying can be performed before and after irradiation with actinic radiation and during irradiation with actinic radiation, and the timing of drying can be appropriately selected by combining these.

<Electrophotographic image forming apparatus>
An electrophotographic image forming apparatus according to one aspect of the present invention comprises, on a conductive support, at least a charge generation layer, a charge transport layer, and a protective layer containing a cured resin component which is a cured product of a polymerizable compound. A tandem-type electrophotographic image forming apparatus using a stacked organic photosensitive member, comprising: electrostatic latent image forming means for forming an electrostatic latent image on the organic photosensitive member; and supplying toner to the organic photosensitive member. Developing means for developing the electrostatic latent image to form a toner image, lubricant supplying means for supplying a lubricant to the surface of the organic photoreceptor, and cleaning means for removing the toner remaining on the surface of the organic photoreceptor by a cleaning blade And a plurality of image forming units provided with

  Here, the electrophotographic image forming apparatus further comprises charging means for charging the surface of the organic photoreceptor, and the electrostatic latent image forming means described above exposes the organic photoreceptor charged by the charging means to It is preferable that it is an exposure means for forming an electrostatic latent image. Preferably, the electrophotographic image forming apparatus further comprises a transfer unit for transferring the toner image formed on the organic photoreceptor. That is, an electrophotographic image forming apparatus according to an embodiment of the present invention comprises at least the charging unit, the exposure unit (electrostatic latent image forming unit), the developing unit, the transfer unit, the lubricant supplying unit, and the cleaning unit. Particularly preferred.

  In particular, the electrophotographic image forming apparatus according to one aspect of the present invention preferably includes proximity charging type charging means such as a charging roller, a charging brush, a charging belt, and a charging blade. When such a charging unit is used, the deterioration of the surface of the organic photoreceptor tends to be large, so that the effects of the present invention can be more remarkably obtained. Among them, from the viewpoint of the stability of charging, it is preferable to use a charging roller as the charging unit.

[Arrangement of Image Forming Unit and Organic Photosensitive Member]
The electrophotographic image forming apparatus according to an embodiment of the present invention has two or more image forming units including a predetermined organic photoreceptor, preferably three or more, and more preferably four or more. Moreover, it is preferable to have eight or less image forming units. Among these, it is particularly preferable to have four image forming units.

  Preferably, the combination of the two adjacent image forming units is a combination of image forming units provided with toners of different colors. That is, the electrophotographic image forming apparatus according to an embodiment of the present invention has two or more image forming units provided with toners of different colors, preferably three or more, and four or more. More preferable. In addition, it is preferable to have eight or less image forming units provided with toners of different colors. Among these, it is particularly preferable to have four image forming units provided with toners of different colors. Thus, the electrophotographic image forming apparatus according to an embodiment of the present invention has one or more combinations of two adjacent image forming units provided with toners different in color from each other, and the combinations are two or more. It is preferable to have, and it is more preferable to have three or more. In addition, it is preferable to have seven or less combinations of two adjacent image forming units provided with toners of different colors. Among these, it is particularly preferable to have three combinations of two adjacent image forming units provided with toners of different colors. The effect of this invention will be exhibited more as it is the said range.

  In the present specification, toners having different colors means that the colors of the developed colors are different, such as yellow, magenta, cyan, black, etc., and they have the same color but different shades of light. The difference between is not included.

  In the electrophotographic image forming apparatus according to one aspect of the present invention, at least one of a combination of two adjacent image forming units is a charge in the protective layer of the organophotoreceptor A included in the image forming unit disposed upstream. When the content of the transport material is Ca, and the content of the charge transport material in the protective layer of the organic photoreceptor B contained in the image forming unit disposed downstream is Cb, the following formula (1) is satisfied.

  Here, Ca and Cb are each represented by the content (parts by mass) of the charge transport substance with respect to 100 parts by mass of the polymerizable compound constituting the cured resin component in the protective layer of the organic photoreceptor A and the organic photoreceptor. Ru.

  If the formula (1) is not satisfied, the hardness of the organic photoreceptor B, which has a relatively small amount of lubricant on the organic photoreceptor, may be insufficient, and the surface of the protective layer may be damaged. As a result, the life of the organic photosensitive member may be shortened, and toner slippage may occur. In order to suppress the occurrence of such a problem, it is necessary to satisfy the above equation (1) in at least one adjacent image forming unit.

  In the electrophotographic image forming apparatus according to one aspect of the present invention, the three or more image forming units are provided with electrostatic latent image forming means, developing means, lubricant supplying means, and cleaning means. It is preferable that at least two of the combinations of two adjacent image forming units provided with toners having different colors satisfy the above equation (1), and more preferably at least three satisfy the above equation (1). It is further preferable that all the combinations satisfy the above formula (1). Within the above range, the life of the organic photoreceptor, and hence the life of the electrophotographic image forming apparatus, and the reduction in the frequency of toner penetration are further improved. In addition, even when metal oxide particles are added to the protective layer, the effect of suppressing the generation of transfer memory is high.

  In the electrophotographic image forming apparatus according to an aspect of the present invention, it is preferable that all combinations of two adjacent image forming units satisfy the following formula (2). In such a case, as the amount of reverse transfer toner increases from upstream to downstream, the content of the charge transport material in the protective layer of the organic photoreceptor of the image forming unit is from upstream to downstream Since the ratio decreases toward the end, it is excellent in the effect of enhancing both the toner slip-through and the life of the organic photoreceptor as a whole.

  In the electrophotographic image forming apparatus according to one aspect of the present invention, a combination of two adjacent image forming units is preferably a combination of image forming units provided with toners of different colors. By doing this, it is possible to improve the toner slip-through and the life of the organic photosensitive member, and at the same time, control the arrangement of the image forming unit provided with different color toners so as to minimize the influence on the image quality by the reverse transfer toner. can do. Therefore, high quality images can be obtained more easily.

  Furthermore, the combination of two adjacent image forming units is preferably a combination of image forming units provided with toners of different colors, and the image forming unit on the most downstream side is a black unit. Preferably, at least one image forming unit is a chromatic color unit. By arranging the organic photoreceptor for black which is darker on the downstream side, the darker color is arranged on the inner side in the formed image, and the image quality can be improved. In addition, since the reverse transfer toner reversely transferred to the darker organic photoreceptor for black is a lighter color, the influence of the reverse transfer toner on the image quality can be reduced. In addition, although the organic photoreceptor of the image forming unit on the most downstream side is required to have hardness higher than that on the upstream side, even if metal oxide particles are added to the protective layer to increase the hardness, the visual sensitivity of the transfer memory is It is difficult to be a problem because it is low. As a result, it is possible to minimize the addition of the charge transport material for adjusting the electrical resistance of the protective layer, which is preferable because a decrease in the hardness of the protective layer due to the addition of the charge transport material can be suppressed.

  In a preferred embodiment of the present invention, the combination of two adjacent image forming units is a combination of image forming units provided with toners different in color from one another, and the most downstream image forming unit is a unit for black. And have a plurality of chromatic color units upstream. The protective layer of the organic photosensitive member of the black unit, which is the most downstream image forming unit, does not contain the charge transport material, and the protective layers of the organic photosensitive member in the plurality of chromatic color units on the upstream side contain the charge transport material. Do. At this time, in the organic photoreceptors of the plurality of chromatic color units on the upstream side, the content of the charge transport material relative to 100 parts by mass of the polymerizable compound constituting the cured resin component in the protective layer can be made constant. . By doing so, even when the number of image forming units is increased to four or more, for example, the effects of the present invention can be easily obtained, and the productivity is excellent. Alternatively, the content of the charge transport material relative to 100 parts by mass of the polymerizable compound constituting the cured resin component in the protective layer of the organic photoreceptor in the plurality of chromatic color units on the upstream side is set to a constant value. The content of the charge transport material relative to 100 parts by mass of the polymerizable compound constituting the cured resin component in the protective layer of the organic photoreceptor in the unit may be designed to be smaller than that of the chromatic color unit.

  Here, the chromatic color refers to a color (for example, yellow, magenta, cyan, etc.) in which saturation appears in the hue. Black is achromatic.

[Configuration of Electrophotographic Image Forming Apparatus]
Hereinafter, an electrophotographic image forming apparatus according to an embodiment of the present invention will be described with reference to the attached drawings. However, the present invention is not limited to only one embodiment described below.

  FIG. 2 is a schematic cross-sectional view showing the structure of a tandem type electrophotographic image forming apparatus according to an embodiment of the present invention, and FIG. 3 is a tandem type electrophotographic image forming apparatus according to an embodiment of the present invention FIG. 2 is an enlarged schematic view showing an arrangement relationship between an organic photosensitive member and a cleaning blade.

  This electrophotographic image forming apparatus is referred to as a tandem type color image forming apparatus, and includes four sets of image forming units (image forming units) 10Y, 10M, 10C, and 10K, an intermediate transfer unit 70, and a sheet feeding unit. 21 and fixing means 24. A document image reader SC is disposed on the top of the main body A of the electrophotographic image forming apparatus.

  The four image forming units 10Y, 10M, 10C and 10K rotate around the photosensitive members 1Y, 1M, 1C and 1K, charging units 2Y, 2M, 2C and 2K, and exposure units 3Y, 3M, 3C and 3K. Developing means 4Y, 4M, 4C, 4K, primary transfer rollers 5Y, 5M, 5C, 5K as primary transfer means, and cleaning means 6Y, 6M, 6C, 6K for cleaning photoreceptors 1Y, 1M, 1C, 1K. It is configured.

  The electrophotographic image forming apparatus according to an embodiment of the present invention uses the organic photoreceptors described above as the photoreceptors 1Y, 1M, 1C, and 1K.

  The image forming units 10Y, 10M, 10C, and 10K have the same configuration except that the colors of the provided toners are different such as yellow (Y), magenta (M), cyan (C), and black (K). It is. Therefore, in the following, the image forming unit 10Y will be described in detail as an example.

  The image forming unit 10Y includes a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 6Y around the photosensitive member 1Y, which is an image forming member, and a yellow (Y) toner image is formed on the photosensitive member 1Y. It forms.

  The charging means 2Y is a means for uniformly charging the surface of the photoreceptor 1Y to a negative polarity. In the electrophotographic image forming apparatus of the present embodiment, it is preferable to use a charging roller as the charging unit 2Y.

  The charging roller is disposed close to the photosensitive member, and charges the photosensitive member to a desired polarity and potential by applying a voltage of, for example, about -2.5 to -1.5 kV to the charging roller.

  As a voltage applied to the charging roller, a DC charging method in which only a DC electric field is applied to charge the photosensitive member, and an AC in which an AC electric field is superimposed on a DC electric field is applied to the charging member to charge the photosensitive member. Although any of the charging methods can be used, an AC charging method capable of obtaining a leveling effect by an AC electric field is preferable because it is excellent in charge uniformity.

  In the above AC charging method, as a voltage applied to the charging roller, a DC electric field or an AC electric field can be selected from among a DC constant voltage, a DC constant current, an AC constant voltage, and an AC constant current.

  The exposure unit 3Y is a unit that performs exposure based on an image signal (yellow) on the photosensitive member 1Y to which a uniform potential is applied by the charging unit 2Y, and forms an electrostatic latent image corresponding to the yellow image. is there. As this exposure means 3Y, one comprising an LED in which light emitting elements are arranged in an array in the axial direction of the photosensitive member 1Y and an imaging element, or a laser optical system is used.

  The developing means 4Y comprises, for example, a developing sleeve 41Y that contains a magnet and holds a developer and rotates and holds a developer, and a voltage application device that applies a DC and / or AC bias voltage between the developing sleeve and the developing sleeve. is there.

  The developing means 4Y contains a Y component developer (for example, a two-component developer containing toner and magnetic carrier as main components). The developing means 4Y causes the electrostatic latent image to be visualized to form a toner image by depositing a toner of Y component on the surface of the photosensitive member 1Y. Specifically, a developing bias is applied to the developing sleeve 41Y, and a developing electric field is formed between the photosensitive member 1Y and the developing sleeve 41Y. The charged toner (negative polarity) on the developing sleeve 41Y moves to and adheres to the exposed portion on the surface of the photoreceptor 1Y due to the potential difference between the photoreceptor 1Y (negative polarity) and the developing sleeve 41Y. That is, the developing unit 4Y develops the electrostatic latent image by the reversal development method.

  The cleaning means 6Y is a means for removing the toner remaining on the surface of the photoreceptor 1Y. The cleaning means 6Y of the present embodiment includes a cleaning blade. The cleaning blade includes a support member 31 and a blade member 30 supported on the support member 31 via an adhesive layer (not shown). The blade member 30 is disposed in such a manner that its tip end faces in the opposite direction (counter direction) to the rotational direction of the photosensitive member 1Y at the contact portion with the surface of the photosensitive member 1Y.

  The support member 31 is not particularly limited, and conventionally known ones can be used, and examples thereof include those made of rigid metal, elastic metal, plastic, ceramic and the like. Among them, rigid metal is preferable.

  The blade member 30 is not particularly limited, and, for example, polyurethane, silicone rubber, fluororubber, chloropyrene rubber, butadiene rubber and the like can be used. Among them, polyurethane is preferable in that appropriate strength and flexibility capable of being in contact with the rotating photosensitive member 1Y can be obtained. For example, a blade member 30 using polyurethane is obtained by mixing a dehydrated polyol and an isocyanate compound, and reacting the mixture in a temperature range of 100 to 120 ° C. for 30 to 90 minutes by adding a crosslinking agent to the prepolymer obtained. It can be manufactured by pouring into a mold and curing. For example, polyester polyols such as polyethylene adipate and polycaprolactone can be used as the polyol, and diphenylmethane diisocyanate can be used as the isocyanate compound. Moreover, as a crosslinking agent, 1, 4- butanediol, trimethylol propane, ethylene glycol, these mixtures etc. can be used.

  The blade member 30 may be configured to include a hardened layer at a portion in contact with the photosensitive element 1Y. By providing the hardened layer in the contact portion, the hardness of the blade member main body can be easily adjusted so that flexibility to an extent that the blade member 30 bends appropriately when contacting the photosensitive member 1Y can be obtained. The hardened layer may be a layer provided on the surface of the blade member 30, but from the viewpoint of enhancing the durability, it is preferable that a part of the main body of the blade member 30 be processed.

  When polyurethane is used as the substrate of the blade member 30, the contact portion of the blade member 30 with the photosensitive member 1Y is impregnated with an isocyanate compound for a certain period of time, and the polyurethane contained in the blade member 30 is reacted with the isocyanate compound. The reactive part can be formed as a hardened layer. The cured layer thus formed contains a polymer of polyurethane and an isocyanate compound. A urethane bond having active hydrogen is present in the polyurethane constituting the blade member 30, and the polyurethane contained in the blade member 30 and the cured layer are contained by reacting the urethane bond and the impregnated isocyanate compound. Allophanate bonds can be formed between the polymer and the polymer to increase the hardness of the cured layer. In addition, since the multimerization reaction of the impregnated isocyanate compound also proceeds simultaneously, a thick cured layer can be formed, and the cured layer is thick even if the cured layer is worn, so that the blade member 30 has a good hardness. It can be maintained for a period.

  The blade member 30 preferably has an inclination angle θ of 5 to 20 ° with respect to the surface of the photosensitive member 1Y from the viewpoint of enhancing the scraping power of the residual toner and obtaining higher cleaning performance. Moreover, the linear pressure of the blade member 30 can be suitably adjusted within the range of the linear pressure set in a known blade member.

  In the electrophotographic image forming apparatus shown in FIG. 2, among the image forming unit 10Y, the photosensitive member 1Y, the charging unit 2Y, the developing unit 4Y, a lubricant supplying unit (not shown) described later and the cleaning unit 6Y are integrally supported. It may be provided as a process cartridge, and the process cartridge may be configured to be detachable from the apparatus main body A via a guide means such as a rail.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction, and an intermediate transfer unit 70 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1K in the drawing. The intermediate transfer body unit 70 is a semiconductive endless belt-like intermediate transfer body 77 rotatably supported by a plurality of rollers 71, 72, 73, 74 and rotatably supported, and two as secondary transfer means. It consists of the next transfer roller 5b and the cleaning means 6b.

  The image forming units 10Y, 10M, 10C, and 10K and the intermediate transfer member unit 70 are housed in a housing 80, and the housing 80 is configured to be able to be pulled out of the apparatus main body A via the support rails 82L and 82R. It is done.

  The fixing unit 24 includes, for example, a heat roller fixed by a heating roller provided with a heating source inside and a pressure roller provided in a pressure-contacted state so that a fixing nip portion is formed on the heating roller. One of the methods is mentioned.

  In FIG. 2, 20 is a sheet feeding cassette, 22A, 22B, 22C, 22D is an intermediate roller, 23 is a registration roller, 25 is a sheet discharging roller, 26 is a sheet discharging tray, and P is a transfer material. It shows each.

  Although FIG. 2 shows the image forming apparatus of the present invention as a color laser printer, the electrophotographic image forming apparatus according to an embodiment of the present invention may be configured as a copying machine. Further, in the image forming apparatus according to one aspect of the present invention, a light source other than the laser, for example, an LED light source can be used as the exposure light source.

  In FIG. 2, an image forming apparatus having four image forming units corresponding to YMCK has been described as an example of a preferable image forming apparatus of the present invention, but in addition to these, clear, white, gold, silver, etc. An image forming apparatus further having an image forming unit corresponding to a color is also mentioned as another preferable example.

[Lubricant supply means]
An electrophotographic image forming apparatus according to an aspect of the present invention includes a lubricant supply unit that supplies a lubricant to the surface of an organic photoreceptor.

  The lubricant is not particularly limited, and any known lubricant can be appropriately selected, but it is preferable to contain a fatty acid metal salt.

  The fatty acid metal salt is not particularly limited, but is preferably a metal salt of a saturated or unsaturated fatty acid having 10 or more carbon atoms. For example, zinc laurate, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, cadmium stearate, magnesium stearate, zinc stearate, stearate Acid aluminum stearate, potassium stearate, lithium stearate, sodium stearate, zinc oleate, magnesium oleate, iron oleate, cobalt oleate, copper oleate, lead oleate, manganese oleate, aluminum oleate , Zinc palmitate, cobalt palmitate, lead palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, lead caprate Zinc linolenate, cobalt linolenate, calcium linolenate, zinc ricinoleate, and the like ricinoleic acid cadmium. Among these, zinc stearate is preferred from the viewpoints of lubricity, spreadability and hygroscopicity.

  As the fatty acid metal salt, either a synthetic product or a commercially available product may be used. As a commercially available product, for example, Zinc Stearate S manufactured by NOF Corporation can be mentioned.

  These fatty acid metal salts may be used alone or in combination of two or more.

  The lubricant supplying means is not particularly limited, and examples thereof include a method of supplying a lubricant by a method of applying a solid lubricant by a brush roller (hereinafter also referred to as "sliding agent coating means").

  When a lubricant application unit is used, for example, in the image forming unit 10Y of the electrophotographic image forming apparatus shown in FIG. 2, the lubricant application unit is downstream of the cleaning unit 6Y and upstream of the charging unit 2Y in the rotational direction of the photosensitive member 1Y. It is preferred that the However, the arrangement position of the lubricant application unit is not limited to the downstream side of the cleaning unit 6Y and the upstream side of the charging unit 2Y. The lubricant application means is not particularly limited, but preferably comprises, for example, a solid lubricant and a lubricant application member composed of a brush roller. Specifically, the lubricant application means contacts the lubricant stock composed of solid lubricant having a rectangular solid shape and the surface of the photosensitive element 1Y and sensitizes the lubricant scraped off by rubbing the surface of the lubricant stock. It is preferable to comprise a brush roller applied to the surface of the body 1Y, a pressure spring for pressing the lubricant stock against the brush roller, and a drive mechanism for rotationally driving the brush roller. In the brush roller, the tip of the brush abuts on the surface of the photosensitive member 1Y. Further, it is preferable that the brush roller is rotationally driven at the same speed in the same rotation as the photosensitive member 1Y. On the downstream side of the lubricant application means and on the upstream side of the charging means 2Y, a leveling blade may be provided which uniformly applies the lubricant supplied to the surface of the photoreceptor 1Y by the lubricant application means. In addition, it does not restrict | limit in particular about a lubricant application means, A well-known means can be referred suitably, For example, Unexamined-Japanese-Patent No. 2016-188950 etc. can be referred.

  The lubricant supplying means is not particularly limited, but, for example, a finely powdered lubricant externally added to the toner base particles may be developed in the developing means (for example, 4Y in FIGS. 2 and 3). By means of the action of the electric field, means (hereinafter also referred to as "toner containing means") for supplying the organic photoreceptor (for example, 1Y in the above-mentioned FIG. 2 and FIG. 3) can be mentioned. That is, the toner containing means is a means for supplying the fine powdery lubricant contained in the toner to the organic photoreceptor by the action of the developing electric field formed in the developing means. Since the toner containing means does not intervene in the intermediate member such as the brush roller like the above-mentioned lubricant application means, it is particularly preferable because the lubricant supply amount does not vary due to the contamination of the lubricant or the contamination or deterioration of the intermediate member. .

  In the toner containing means, a finely powdered lubricant is externally added as an external additive to toner base particles described later. The volume-based median diameter Dw of the finely powdered lubricant is preferably 0.3 to 25 μm, and more preferably 0.5 to 20 μm. Within the above range, since the size of the lubricant is appropriately small, the adhesion to the toner base particles is appropriately increased, and the occurrence of migration in the developing means becomes more difficult to occur, whereby the lubricant supply is further increased. It will be enough. In addition, since the size of the lubricant is moderately large, the migration of the lubricant onto the organic photoreceptor becomes easier by appropriately reducing the adhesion to the toner base particles. Thus, the lubricant can be uniformly supplied onto the organic photoreceptor. The volume-based median diameter Dw of the lubricant should be measured and calculated using an apparatus in which a computer system for data processing (manufactured by Beckman Coulter) is connected to Coulter Multisizer 3 (manufactured by Beckman Coulter). Obtained by It is also possible to measure the particle diameter of the lubricant externally added to the toner base particles (colored particles) by a known method such as electron microscope photography. For the evaluation method of the volume-based median diameter Dw of the finely powdered lubricant, the description of paragraphs “0031” and “0032” of JP-A-2010-175701 can be referred to. Details are described in the examples.

  The amount of the finely divided lubricant added is preferably 0.01 to 0.5 parts by mass, and more preferably 0.03 to 0.3 parts by mass, with respect to the total mass of the toner. Within the above range, the effects of the present invention are more exhibited while the influence on the chargeability of the toner is suppressed.

  The method of mixing the toner base particles and the lubricant is not particularly limited, and a known method can be appropriately selected. For example, Henschel mixer (registered trademark) manufactured by Mitsui Miike Kako Co., Ltd. can be used.

[Toner and developer]
In the present specification, "toner base particles" constitute the base of "toner particles". The “toner base particles” contain at least a binder resin and a colorant, and may further contain other components such as a releasing agent (wax) and a charge control agent, as required. "Toner base particles" are referred to as "toner particles" by the addition of external additives. And "toner" means an aggregate of "toner particles".

  The electrophotographic image forming apparatus according to an embodiment of the present invention is not particularly limited, and various known toners can be used.

  As the toner, either a pulverized toner or a polymerized toner may be used, but from the viewpoint of obtaining an image of high image quality, it is preferable to use a polymerized toner.

  The average particle size of the toner is not particularly limited, but is preferably 2 to 8 μm in terms of volume based median diameter. By setting this range, the resolution can be further increased.

  In addition, as described above, when toner lubricant particles are supplied to the organic photosensitive member by the action of the developing electric field formed in the developing device, toner lubricant particles are used as toner base particles, as described above. A fine powder lubricant can be externally added as an external additive.

  In addition, as an external additive, inorganic particles such as silica and titania having an average particle diameter of about 10 to 300 nm and an abrasive of about 0.2 to 3 μm are appropriately added to the toner base particles as an external additive. Can.

  When the toner is used as a two-component developer, conventionally known materials such as ferromagnetic metals such as iron, ferromagnetic metals and alloys such as aluminum and lead, compounds of ferromagnetic metals such as ferrite and magnetite, etc. The magnetic particle which consists of can be used. Among these, ferrite is particularly preferable.

  As the carrier, it is preferable to use one further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. There is no particular limitation on the resin composition for coating, but it is preferable to use, for example, a cyclohexyl methacrylate-methyl methacrylate copolymer.

  The volume-based median diameter of the carrier is preferably in the range of 15 to 100 μm, and more preferably in the range of 25 to 60 μm.

  The concentration of the toner contained in the two-component developer is preferably 4.0% by mass or more and 8.0% by mass or less.

  As mentioned above, although embodiment of this invention was described concretely, embodiment of this invention is not limited to said example, A various change can be added.

  The effects of the present invention will be described using the following examples and comparative examples. In the following examples, "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise stated. The present invention is not limited to the following examples.

<Manufacture of organic photoreceptor>
The structural formulas of the compounds used in the examples are shown below.

[Production of Organic Photosensitive Member [1]]
(Preparation of conductive support)
The surface of a cylindrical aluminum support having a diameter of 30 mm was cut to prepare a conductive support [1] in which the surface was finely roughened.

(Formation of middle layer)
The dispersion liquid of the following composition was diluted twice with the same mixed solvent, and allowed to stand overnight, followed by filtration (filter; using Ligi mesh 5 μm filter manufactured by Nippon Pall Co., Ltd.) to prepare a coating liquid [1] for forming an intermediate layer.

Binder resin: Polyamide resin “CM 8000” (manufactured by Toray Industries, Inc.) 1 part Metal oxide particles: titanium oxide “SMT 500 SAS” (manufactured by Tayca Corporation) 3 parts Solvent: methanol 10 parts Using a sand mill as a dispersing machine, batchwise Dispersion was performed for 10 hours. The intermediate layer-forming coating solution [1] was applied onto the conductive support [1] by dip coating to form an intermediate layer [1] having a dry layer thickness of 2 μm.

(Formation of charge generation layer)
Charge generating material: Charge generating material (CG-1) below 20 parts Binder resin: Polyvinyl butyral resin "# 6000-C" (made by Denka Co., Ltd.)
10 parts Solvent: 700 parts of tert-butyl acetate Solvent: 300 parts of 4-methoxy-4-methyl-2-pentanone are mixed and dispersed for 10 hours using a sand mill to prepare a coating solution [1] for charge generation layer formation. did. The coating solution [1] for charge generation layer formation was applied onto the intermediate layer [1] by dip coating to form a charge generation layer [1] having a dry layer thickness of 0.3 μm.

(Synthesis of charge generating material (CG-1))
(1) Synthesis of amorphous titanyl phthalocyanine Disperse 29.2 parts by mass of 1,3-diiminoisoindoline in 200 parts by mass of o-dichlorobenzene, and add 20.4 parts by mass of titanium tetra-n-butoxide. It heated at 150-160 degreeC under nitrogen atmosphere for 5 hours. After leaving to cool, the precipitated crystals are filtered, washed with chloroform, washed with a 2% aqueous hydrochloric acid solution, then with water, then with methanol and dried, and 26.2 parts by mass (yield 91%) of crude titanyl phthalocyanine Obtained.

  Then, the crude titanyl phthalocyanine was dissolved by stirring in 250 parts by mass of concentrated sulfuric acid at 5 ° C. or less for 1 hour, and poured into 5000 parts by mass of water at 20 ° C. The precipitated crystals were filtered and thoroughly washed with water to obtain 225 parts by mass of a wet paste product.

  The wet paste product was frozen in a freezer and thawed again, followed by filtration and drying to obtain 24.8 parts by mass (yield 86%) of amorphous titanyl phthalocyanine.

(2) Synthesis of (2R, 3R) -2,3-butanediol adduct titanyl phthalocyanine 10.0 parts by mass of the above amorphous titanyl phthalocyanine and 0.94 parts by mass of (2R, 3R) -2,3-butanediol ( 0.6 equivalent ratio (equivalent ratio is equivalent ratio to titanyl phthalocyanine, hereinafter the same) was mixed in 200 parts by mass of ortho-dichlorobenzene (ODB), and heated and stirred at 60 to 70 ° C. for 6.0 hours. After standing overnight, methanol is added to the reaction solution, and the crystals formed are filtered, and the crystals after filtration are washed with methanol to obtain ((2R, 3R) -2,3-butanediol adduct titanyl phthalocyanine, charge generation Substance) CG-1: 0.30 mass parts were obtained.

The X-ray diffraction spectrum of the charge generating material (CG-1) has clear peaks at 8.3 °, 24.7 °, 25.1 °, and 26.5 °. There is a peak in the 576 and 648 in the mass spectra, O-Ti-O both absorption appears Ti = O near 970 cm ^-1, around 630 cm ^-1 in the IR spectrum. In addition, thermal analysis (TG) shows a weight loss of about 7% at 390-410 ° C., so 1: 1 adducts and non-adducts of titanyl phthalocyanine and (2R, 3R) -2,3-butanediol It is presumed to be a mixture of titanyl phthalocyanines). It is 31.2 m < ² > / g when BET specific surface area of the obtained charge generating substance (CG-1) is measured with a flow type specific surface area automatic measuring device (micrometrics flow soap type: Shimadzu Corp. make). The

(Formation of charge transport layer)
Charge transport material: 225 parts of the compound A, binder resin: 300 parts of polycarbonate resin “Z300” (manufactured by Mitsubishi Gas Chemical Co., Ltd.), antioxidant: 6 parts of “Irganox (registered trademark) 1010” (manufactured by BASF Japan Ltd.) Solvent: 1600 parts of THF (tetrahydrofuran), solvent: 400 parts of toluene, and 1 part of silicone oil "KF-50" (manufactured by Shin-Etsu Chemical Co., Ltd.) are mixed and dissolved, and coating liquid [1] for charge transport layer formation is dissolved. Prepared.

  The charge transport layer forming coating solution [1] is coated on the charge generation layer [1] using a circular slide hopper coating apparatus (circular amount regulation type coating apparatus) to form a charge transport layer having a dry layer thickness of 20 μm [1] ] Was formed.

(Formation of protective layer)
The following metal oxide particles: 136 parts of tin oxide particles [1], polymerizable compounds: 100 parts of the above exemplified compound (M1) (wherein R ′ represents a methacryloyl group (CH ₂ CCCH ₃ CO—)), Charge transport substance: 15 parts of the above exemplified compound (CTM-1), polymerization initiator: 7 parts of the above exemplified compound (P1), solvent: 280 parts of 2-butanol, solvent: 70 parts of tetrahydrofuran are mixed and stirred, and sufficiently dissolved It disperse | distributed and prepared coating liquid [1] for protective layer formation. The coating solution [1] for forming a protective layer was coated on the charge transport layer [1] using a circular slide hopper coating apparatus to form a coating film. After drying the formed coating film, the distance from the light source to the surface of the coating film is set to 100 mm under a nitrogen stream using a metal halide lamp, and ultraviolet light is irradiated for 1 minute with a lamp output of 4 kW, and the dry layer thickness is 4.0 μm. A protective layer was formed. Thus, an organic photoreceptor [1] was obtained.

(Preparation of tin oxide particles [1])
The following tin oxide particles [1] were prepared by using the following tin oxide [1] as an untreated metal oxide particle and using the above exemplified compound (S-15) as a surface modifying agent as shown below. .

First, tin oxide (number average primary particle diameter: 20 nm, volume resistivity: 1.05 × 10 ⁵ (Ω · cm)) manufactured by CIK Nanotech Co., Ltd. was prepared as tin oxide [1].

Next, 100 parts of tin oxide [1], surface modifier (exemplified compound (S-15): CH ₂ = C (CH ₃ ) COO (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ), 30 parts, toluene / isopropyl A surface modification was performed by adding a mixed solution of 300 parts of a mixed solvent of alcohol = 1/1 (mass ratio) to a sand mill together with zirconia beads at about 40 ° C. and stirring at a rotational speed of 1500 rpm. Further, the above treated mixture is taken out, charged into a Henschel mixer (registered trademark), stirred at a rotational speed of 1500 rpm for 15 minutes, and dried at 120 ° C. for 3 hours to finish surface modification, surface modified tin oxide particles [ 1] was produced.

[Production of Organic Photosensitive Substances [2] to [4]]
In the formation of the protective layer in the production of the organic photoreceptor [1], the addition amounts of the polymerizable compound (M1), the polymerization initiator (P1), the tin oxide particles [1] and the charge transport substance (CTM-1) used are as follows Organic photoreceptors [2] to [4] were produced in the same manner except that they were changed according to Table 1.

<Evaluation of organic photoreceptors>
The protective layer forming materials in the respective organic photoreceptors are shown in Table 1 below and Table 2 below. In addition, the volume ratio of each component of Table 2 was calculated by setting the total of each component except a solvent as 100, the specific gravity of tin oxide 6.95, the ratio of other organic materials as 1.1, and calculating it from the mass ratio .

<Manufacture of developer>
Preparation of Colorant Dispersion
(Preparation of Colorant Dispersion [K])
90 g of sodium dodecyl sulfate was stirred and dissolved in 1600 ml of ion exchange water. While this solution is being stirred, 420 g of carbon black (Regal 330R: made by Cabot Corporation) is gradually added, followed by dispersion treatment using a stirring device “Claremix” (made by M. Technique Co., Ltd.) A dispersion of agent particles was prepared. This is referred to as "colorant dispersion 1". It was 110 nm when the particle size of the coloring agent particle in this coloring agent dispersion liquid [K] was measured using electrophoresis light scattering photometer "ELS-800" (made by Otsuka Electronics Co., Ltd.).

(Preparation of Colorant Dispersion [C])
In the preparation example of the colorant dispersion [K], instead of carbon black as the colorant, C.I. I. A pigment dispersion liquid [Cy] was prepared in the same manner as in Pigment Blue 15: 3, except that colorant particles having a particle diameter of 112 nm in terms of a volume-based median diameter were dispersed.

(Preparation of Colorant Dispersion [M])
In the preparation example of the colorant dispersion [K], instead of carbon black as the colorant, C.I. I. A colorant dispersion [M] in which colorant particles having a particle diameter of 115 nm as a volume-based median diameter were dispersed was similarly prepared except that the pigment red 122 was used.

(Preparation of Colorant Dispersion [Y])
In the preparation example of the colorant dispersion [K], instead of carbon black as the colorant, C.I. I. Pigment Yellow 74 was prepared in the same manner as above, to prepare a colorant dispersion [Y] in which colorant particles having a particle diameter of 118 nm as a volume-based median diameter were dispersed.

[Preparation of Toner Base Particles]
(Preparation of Toner Base Particles [1])
(Production of Resin Particle A)
First-stage polymerization: Charge 8 g of sodium dodecyl sulfate and 3 L of ion-exchanged water into a 5 L reaction vessel equipped with a stirring device, temperature sensor, cooling pipe, and nitrogen introduction device, and stir at 230 rpm under a nitrogen stream. The temperature was raised to 80 ° C. After the temperature rise, 10 g of potassium persulfate dissolved in 200 g of ion-exchanged water is added, the solution temperature is again adjusted to 80 ° C., the following monomer mixture is added dropwise over 1 hour, and heated at 80 ° C. for 2 hours The polymerization was carried out by stirring to produce resin particles. This is referred to as "resin particle (1H)".

Styrene 480g
250 g of n-butyl acrylate
68.0 g of methacrylic acid
16.0 g of n-octanethiol.

Second Stage Polymerization A 5 L reaction vessel equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen introduction device was charged with a solution of 7 g of sodium polyoxyethylene (2) dodecyl ether sulfate in 800 ml of ion-exchanged water. After heating to 98 ° C., add a solution of 260 g of the resin particles (1H) and a solution of the following monomer solution at 90 ° C. And dispersed for 1 hour to prepare a dispersion containing emulsified particles (oil droplets).

223 g styrene
142 g of n-butyl acrylate
n-octanethiol 1.5 g
190 g of polyethylene wax (melting point 70 ° C.).

  Then, an initiator solution in which 6 g of potassium persulfate is dissolved in 200 ml of ion-exchanged water is added to this dispersion, and the system is heated and stirred at 82 ° C. for 1 hour to carry out polymerization to produce resin particles. did. This is referred to as "resin particle (1HM)".

Third-stage polymerization Further, a solution of 11 g of potassium persulfate in 400 ml of ion-exchanged water was added, and the mixture was heated to 82 ° C.
Styrene 405 g
n-butyl acrylate 162 g
33 g of methacrylic acid
n-octanethiol 8g
The monomer mixture consisting of the above was added dropwise over 1 hour. After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C. to prepare a dispersion of resin particles. Let this be a dispersion liquid of "resin particle A." A part of the dispersion liquid of the resin particle A was collected, and after washing and drying, the Tg of the resin particle A was 21 ° C.

(Preparation of resin particles B)
In a 5-liter reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction device, 2.3 g of sodium dodecyl sulfate and 3 liters of ion-exchanged water are charged, and the internal temperature is stirred while stirring at 230 rpm under a nitrogen stream. The temperature was raised to 80 ° C. After the temperature rise, 10 g of potassium persulfate dissolved in 200 g of ion-exchanged water is added, the solution temperature is again adjusted to 80 ° C., the following monomer mixture is added dropwise over 1 hour, and heated at 80 ° C. for 2 hours The polymerization was carried out by stirring to prepare resin particles, and a dispersion liquid of resin particles was prepared. Let this be a dispersion liquid of "resin particle B."

520 g of styrene
210 g of n-butyl acrylate
68.0 g of methacrylic acid
16.0 g of n-octanethiol.

  A part of the dispersion of the resin particles B was collected, and after washing and drying, the Tg of the resin particles B was 48 ° C.

(Aggregation and fusion process)
300 g of resin particles A in terms of solid content, 1400 g of ion exchanged water, and 120 g of “colorant dispersion liquid (K)” in a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introducing device A solution of 3 g of sodium polyoxyethylene (2) dodecyl ether sulfate dissolved in 120 ml of ion-exchanged water was charged, the liquid temperature was adjusted to 30 ° C., and a 5 N aqueous solution of sodium hydroxide was added to adjust pH to 10. Then, an aqueous solution in which 35 g of magnesium chloride was dissolved in 35 ml of ion-exchanged water was added under stirring at 30 ° C. for 10 minutes. After holding for 3 minutes, the temperature rising was started, the system was heated up to 90 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 90 ° C. In this state, the particle diameter of the associated particles is measured with "Coulter Multisizer 3", and 260 g of the dispersion liquid of resin particles B is added when the median diameter on a volume basis becomes 3.1 μm, and further particle growth. The reaction was continued. When the desired particle size is obtained, an aqueous solution in which 150 g of sodium chloride is dissolved in 600 ml of ion-exchanged water is added to stop particle growth, and heating and stirring at a liquid temperature of 98.degree. Inter-particle fusion was allowed to proceed to a circularity of 0.965 as measured by FPIA-2100. Thereafter, the solution temperature was cooled to 30 ° C., and hydrochloric acid was added to adjust the pH to 4.0, and the stirring was stopped.

(Washing and drying process)
The particles produced in the aggregation / fusion process were solid-liquid separated by a basket type centrifuge "MARK III model number 60 × 40" (manufactured by Matsumoto Machine Sales Co., Ltd.) to form a wet cake of toner base particles. The wet cake is washed with ion exchange water at 45 ° C. until the electric conductivity of the filtrate reaches 5 μS / cm in the basket type centrifuge, and then transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) The toner base particle [1] was produced by drying until the water content became 0.5% by mass.

(Preparation of Toner Base Particles [2])
Toner base particles [2] were produced in the same manner as in the preparation step of toner base particles [1] except that the colorant dispersion was changed to the colorant dispersion [C].

(Preparation of Toner Base Particles [3])
Toner base particles [3] were produced in the same manner as in the preparation process of toner base particles [1] except that the colorant dispersion was changed to the colorant dispersion [M].

(Preparation of Toner Base Particles [4])
Toner base particles [4] were produced in the same manner as in the preparation process of toner base particles [1] except that the colorant dispersion was changed to the colorant dispersion [Y].

[Preparation of Toner]
(Preparation of Toner [1])
Toner base particle [1] 100 parts by mass, 0.6 parts by mass of silica particles NAX-50 (manufactured by Nippon Aerosil Co., Ltd.), 0.6 parts by mass of silica particles R805 (manufactured by Nippon Aerosil Co., Ltd.), and titania particles STT30S 0.2 parts by mass of titanium industry Co., Ltd., and 0.05 parts by mass of zinc stearate particles (product name: Zinc Stearate S, manufactured by NOF Corporation, median diameter Dw 15 μm on a volume basis) which is a finely divided lubricant The mixture was added and mixed with a Henschel mixer (registered trademark) “FM10B” (manufactured by Mitsui Miike Kako Co., Ltd.) for 12 minutes at a stirring blade peripheral speed of 40 m / sec and a processing temperature of 30 ° C. Thereafter, coarse particles were removed using a sieve with an opening of 90 μm to produce toner [1].

  Here, the volume-based median diameter Dw of the powdery lubricant is measured using an apparatus in which a computer system for data processing (manufactured by Beckman Coulter) is connected to Coulter Multisizer 3 (manufactured by Beckman Coulter). It evaluated by calculating. As a measurement procedure, 0.02 g of a finely powdered lubricant is acclimated with 20 ml of a surfactant solution (a surfactant solution prepared by diluting a neutral detergent containing a surfactant component 10 times with pure water) and then ultrasonicated. Dispersion was performed for 1 minute to prepare a lubricant dispersion. The lubricant dispersion was pipetted into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand until the concentration indicated by the measuring instrument reached 5% to 10%. In the measuring machine, the number of particles counted was 25,000, the aperture diameter was 50 μm, and the frequency value was calculated by dividing the range of 1 to 30 μm, which is the measurement range, into 256 parts. Then, the particle diameter of 50% from the larger one of the volume integration fraction was taken as the volume-based median diameter.

(Preparation of Toners [2] to [4])
Toners [2] to [4] were prepared in the same manner except that toner base particles [1] in the preparation process of toner [1] were changed to toner base particles [2] to [4].

[Production of developer]
(Production of Two-Component Developer [1])
The toner concentration of the ferrite carrier having a volume-based median particle diameter of 33 μm coated with a copolymer resin of cyclohexyl methacrylate and methyl methacrylate (monomer ratio 1: 1) with respect to toner [1] is 6.0 mass% Two-component developer [1] was produced by mixing as described above.

(Production of Two-Component Developer [2] to [4])
In the preparation of the two-component developer [1], two-component developers [2] to [4] were produced in the same manner except that toner [1] was changed to toners [2] to [4].

<Manufacture of electrophotographic image forming apparatus>
In the electrophotographic image forming apparatus, bizhub C360 (bizuhub is a registered trademark of the company) manufactured by Konica Minolta Co., Ltd. is used after being modified so that charging by a charging roller can be performed. The bizhub C360 is a laser exposure with a wavelength of 780 nm, an intermediate transfer that performs reversal development, and a tandem-type color multifunction peripheral (MFP: Multi-Function Peripheral).

  More specifically, bizhub C360 has four adjacent image forming units provided with toners different in color from one another, and each image forming unit charges the surface of the organic photosensitive member with a charging roller and An exposure unit (electrostatic latent image forming unit) for exposing the organic photosensitive member charged by the charging unit to form an electrostatic latent image; and supplying toner to the organic photosensitive member to develop the electrostatic latent image. Development means for forming a toner image, transfer means for transferring a toner image formed on an organic photoreceptor, lubricant supply means for supplying a lubricant to the surface of the organic photoreceptor, and toner remaining on the surface of the organic photoreceptor And cleaning means for removing with a cleaning blade.

  Here, each of the manufactured developers [1] to [4] was loaded into four adjacent image forming units. In addition, the organic photoreceptors [1] to [4] prepared above are mounted as the organic photoreceptors of the four image forming units in a combination as described in Table 3 below, and each of Examples and Comparative Examples. An electrophotographic imaging apparatus was manufactured.

  Here, the lubricant supply unit is a unit (toner-containing unit) for supplying a finely powdered lubricant externally added to the toner to the organic photosensitive member by the action of the developing electric field formed in the developing unit.

<Evaluation of Electrophotographic Image Forming Apparatus>
After printing out 300,000 sheets of A4 size image of 5% printing area ratio of each color of YMCK on A4 size neutral paper in the atmosphere of 20 ° C., relative humidity 50% RH, image evaluation of each photosensitive member (slip, transfer memory ) Was performed as follows.

(Evaluation of slippery)
In an environment of 10 ° C. and 15% RH, a halftone image (a) having a coverage ratio of 80% so that a black area is located in the front and a white area is located in the rear in the paper transport direction (FIG. 4A) Reference Example 2) was printed on A3 size neutral paper at 20,000 sheets, and the white area of the 20,000th sheet was visually observed, and toner slip-through was evaluated based on the following criteria. The case where the evaluation result is "◎" and "○" was judged as pass.

(Evaluation criteria)
◎: no dirt was found on the white background,
○: A slight streak of dirt was generated on the white background, but there is no practical problem,
X: Clear streak-like stains occur on the white background, and there is a problem in practical use.

(Evaluation of transfer memory)
An image (b) (see FIG. 4B) in which a solid pattern is output at the first rotation of the photosensitive member and a halftone pattern is output at the second rotation of the photosensitive member under an environment of 10 ° C. and 15% RH. Printed on “A3 / POD Gloss Coat (A3 size, 100 g / m ² )” (manufactured by Oji Paper Co., Ltd.), the first rotation of the solid pattern in the second rotation halftone pattern of the test image obtained The occurrence, that is, the occurrence of memory (b ′) (see FIG. 4 (b ′)) was visually observed, and the case where the evaluation result was “◎” and “○” was judged as pass.

  In addition to the evaluation in each unit single color, in the color unit, using the Y unit and the C unit, evaluation was performed on the green chart of the two-color overlapping. The case where the evaluation result is "◎" and "○" was judged as pass.

(Evaluation criteria)
:: Memory is not observed,
○: slight memory is observed,
X: Memory is clearly observed.

  The evaluation results of the electrophotographic image forming apparatus are shown in Tables 3 and 4 below. In Tables 3 and 4 below, Y, M, C, and K indicate that the color of the toner included in each image forming unit is yellow (Y), magenta (M), cyan (C), respectively. , Corresponds to black (K) color.

  According to the results of Tables 3 and 4, according to the tandem-type electrophotographic image forming apparatus according to the present invention, generation of transfer memory is suppressed, toner slippage is suppressed, and the organic photosensitive member, and hence the apparatus itself It was confirmed that a long life could be realized.

1Y, 1M, 1C, 1K Photosensitive members 2Y, 2M, 2C, 2K Charging means (charging roller)
3Y, 3M, 3C, 3K Exposure means 4Y, 4M, 4C, 4K Development means 5Y, 5M, 5C, 5K Primary transfer roller 5b Secondary transfer roller 6Y, 6M, 6C, 6K, 6b Cleaning means 10Y, 10M, 10C, 10B 10K image forming unit 20 sheet feeding cassette 21 sheet feeding means 22A, 22B, 22C, 22D Intermediate roller 23 registration roller 24 fixing means 25 sheet discharging roller 26 sheet discharging tray 30 blade member 31 support member 41Y developing sleeve 70 provided in developing means 4Y Intermediate transfer unit 71, 72, 73, 74 Roller 77 Intermediate transfer unit 80 Case 82L, 82R Support rail A Main body SC Document image reading device P Transfer material 100 Organic photoconductor 101 Conductive support 102 Intermediate layer 103a Charge generation layer 103 b charge transport layer 103 organic photosensitive layer 104 Protective layer.

Claims (13)

A tandem-type electrophotographic image using an organic photoreceptor in which at least a charge generation layer, a charge transport layer, and a protective layer containing a cured resin component which is a cured product of a polymerizable compound are sequentially laminated on a conductive support Forming device,
An electrostatic latent image forming unit that forms an electrostatic latent image on the organic photosensitive member; and a developing unit that supplies a toner to the organic photosensitive member to develop the electrostatic latent image to form a toner image A plurality of image forming units provided with lubricant supply means for supplying a lubricant to the surface of the organic photoreceptor, and cleaning means for removing the toner remaining on the surface of the organic photoreceptor with a cleaning blade,
The protective layer of the organophotoreceptor included in the at least one image forming unit further comprises a charge transport material,
100 parts by mass of a polymerizable compound constituting a cured resin component in the protective layer of the organic photoreceptor A contained in the image forming unit disposed on the upstream side, at least one of the combinations of two adjacent image forming units The charge transport material content is Ca (parts by mass), and the charge relative to 100 parts by mass of the polymerizable compound constituting the cured resin component in the protective layer of the organic photoreceptor B contained in the image forming unit disposed on the downstream side An electrophotographic image forming apparatus satisfying the following formula (1) when the content of the transport material is Cb (parts by mass).
Three or more of the image forming units are provided,
The electrophotographic image forming apparatus according to claim 1, wherein at least two of the combinations of the two adjacent image forming units satisfy the equation (1). The electrophotographic image forming apparatus according to claim 1, wherein all combinations of the two adjacent image forming units satisfy the following formula (2).
  The electrophotographic image forming apparatus according to any one of claims 1 to 3, wherein all combinations of the two adjacent image forming units satisfy the formula (1).   The image forming apparatus according to any one of claims 1 to 4, wherein the combination of the two adjacent image forming units is a combination of image forming units provided with toners having different colors. The electrophotographic image forming apparatus according to any one of claims 1 to 5, wherein the charge transport material has a structure represented by the following general formula (1).
In [Formula _{(1), R 1, R} 2, R 3 and _{R 4} each independently represent an alkyl group or an alkoxy group having 1 to 7 carbon atoms, 1 to 7 carbon atoms. k, l and n each independently represent an integer of 0 to 5, and m represents an integer of 0 to 4. However, when k, l, n or m is 2 or more, a plurality of R ₁ , R ₂ , R ₃ or R ₄ may be the same as or different from each other . ]   The electrophotographic image forming apparatus according to any one of claims 1 to 6, wherein the protective layer of the organic photoreceptor contained in at least one image forming unit contains metal oxide particles.   The electrophotographic image forming apparatus according to any one of claims 1 to 7, wherein the protective layer of the organic photoreceptor contained in the most downstream image forming unit does not contain a charge transport material.   The combination of two adjacent image forming units is a combination of image forming units provided with toners having different colors, and the most downstream image forming unit is a black unit. An electrophotographic image forming apparatus according to any one of the preceding claims.   The combination of the two adjacent image forming units is a combination of image forming units provided with toners of different colors, and at least one image forming unit is a chromatic color unit, and the chromatic color unit is The protective layer of the organic photoreceptor contained in the above contains a charge transport material, at least one image forming unit is a unit for black, and the protective layer of the organic photoreceptor contained in the unit for black contains no charge transport material, An electrophotographic image forming apparatus according to any one of claims 1 to 9.   The electrophotographic image forming apparatus according to any one of claims 1 to 10, wherein the lubricant contains a fatty acid metal salt.   12. The lubricant supplying device according to any one of claims 1 to 11, wherein the lubricant supplying device is a device for supplying the lubricant in the form of fine powder contained in the toner to the organic photoreceptor by the action of the developing electric field formed in the developing device. An electrophotographic image forming apparatus according to any one of the preceding claims.   The electrophotographic image according to any one of claims 1 to 12, further comprising charging means for charging the surface of the organic photoreceptor with a charging roller before forming an electrostatic latent image on the organic photoreceptor. Forming device.