JP2020091360A - Electrophotographic photoreceptor, method for manufacturing electrophotographic photoreceptor, and image forming apparatus - Google Patents

Abstract

To provide an electrophotographic photoreceptor that, when a protective layer is increased in thickness, is excellent in thin line reproducibility and transfer memory, prevents the occurrence of cleaning failure and image deletion in the last period of durable use, and can extend its life, a method for manufacturing an electrophotographic photoreceptor, and an image forming apparatus.SOLUTION: An electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a photosensitive layer and a protective layer formed in this order on a conductive support. The protective layer contains a resin component obtained by curing a polymerizable compound and metal oxide particles; the thickness of the protective layer is 5 μm or more; the volume resistivity of the metal oxide particles increases from a surface of the protective layer toward the photosensitive layer; the volume resistivity of the metal oxide particles is within a range of 1×10to 1×10Ω cm.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electrophotographic photosensitive member, a method for manufacturing an electrophotographic photosensitive member, and an image forming apparatus, and in particular, when a protective layer is thickened, it is excellent in fine line reproducibility and transfer memory, and cleaning failure and image at the end of durability The present invention relates to an electrophotographic photosensitive member or the like that can prevent the occurrence of flow and have a long life.

In recent years, an electrophotographic photosensitive member having high durability (hereinafter, also simply referred to as a “photosensitive member”) has been demanded in response to an image forming apparatus that has achieved high speed and high image quality.
Generally, there is a problem that the surface of the photoconductor is worn due to the contact with the photoconductor. Therefore, it is desired that the protective layer (also referred to as the surface layer) of the photoconductor has excellent abrasion resistance, and that the protective layer be thickened to further prolong the life. However, if the film is made thicker, there is a problem that the thin line reproducibility is deteriorated due to hole diffusion and the transfer memory is deteriorated due to insufficient response. Further, there is a problem that cleaning failure and image deletion occur at the end of durability due to the long life.
For example, in Patent Document 1, in order to improve the wear resistance of the protective layer of the photoreceptor, the protective layer contains conductive metal oxide particles having low resistance. However, in the photoconductor described in Patent Document 1, since the thickness of the protective layer is as thin as about 3 μm, there is no problem such as the decrease in reproducibility of the fine line and the deterioration of the transfer memory due to the thickening of the film.

JP, 2013-61625, A

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is to improve the thin line reproducibility and the transfer memory when the protective layer is thickened, and to prevent cleaning defects and image deletion at the end of durability. An object of the present invention is to provide an electrophotographic photosensitive member, an electrophotographic photosensitive member manufacturing method, and an image forming apparatus that can prevent the occurrence of the above-described problem and can prolong the service life.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this inventor WHEREIN: In the process of investigating the cause of said problem, when the thickness of a protective layer was 5 micrometers or more, the volume resistivity of the metal oxide particle contained in a protective layer was set. Increasing the volume resistivity of the metal oxide particles from the surface side toward the photosensitive layer side and setting the volume resistivity of the metal oxide particles within a specific range provides excellent fine line reproducibility and transfer memory, and prevents defective cleaning and image deletion from occurring. It was found that an electrophotographic photosensitive member or the like that can be provided can be provided, and the present invention has been completed.
That is, the above-mentioned subject concerning the present invention is solved by the following means.

1. An electrophotographic photoreceptor comprising a photosensitive layer and a protective layer formed in this order on a conductive support,
The protective layer contains a resin component obtained by curing a polymerizable compound, and metal oxide particles,
The thickness of the protective layer is 5 μm or more,
The volume resistivity of the metal oxide particles increases from the surface side of the protective layer toward the photosensitive layer side, and the volume resistivity of the metal oxide particles is 1×10 ³ to 1×10 ^9. Ω・c
An electrophotographic photosensitive member characterized by being in the range of m.

2. The protective layer contains a charge transport material,
2. The electrophotographic photosensitive member according to item 1, wherein the content rate of the charge transport substance increases from the surface side of the protective layer toward the photosensitive layer side.

［一般式（１）中、Ｒ_１、Ｒ_２、Ｒ_３及びＲ_４は、それぞれ独立して、炭素数１〜７のアルキル基、又は炭素数１〜７のアルコキシ基を表す。ｋ、ｌ及びｎは、それぞれ独立して、０〜５の整数を表し、ｍは、０〜４の整数を表す。ただし、ｋ、ｌ、ｎ又はｍが２以上である場合においては、複数存在するＲ_１、Ｒ_２、Ｒ_３又はＲ_４は、互いに同一のものであっても、異なるものであってもよい。］ 3. 3. The electrophotographic photosensitive member according to item 2, wherein the charge transport material has a structure represented by the following general formula (1).

[In general formula (1), R< ₁ >, R< ₂ >, R< ₃ > and R< ₄ > respectively independently represent a C1-C7 alkyl group or a C1-C7 alkoxy group. 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 present} may be the same or different from each other. .. ]

4. The electrophotographic photoreceptor according to any one of items 1 to 3, wherein the protective layer has a thickness of 6 μm or more.

5. A method for manufacturing an electrophotographic photosensitive member according to any one of items 1 to 4, wherein the electrophotographic photosensitive member is manufactured by:
A method for manufacturing an electrophotographic photosensitive member, characterized in that the protective layer is formed using a circular slide hopper coating device.

6. An image forming apparatus comprising an electrophotographic photosensitive member, a charging unit, an exposing unit, a developing unit, a transfer unit, and a cleaning unit,
An image forming apparatus, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of items 1 to 4.

7. Furthermore, a means for supplying a lubricant is provided,
The means for supplying the lubricant supplies the finely powdered lubricant externally added to the electrostatic image developing toner to the electrophotographic photosensitive member by the action of the developing electric field formed in the developing means. 7. The image forming apparatus according to item 6, wherein.

8. Item 7. The image forming apparatus according to Item 7, which contains zinc stearate as the lubricant.

By the above-mentioned means of the present invention, when the protective layer is thickened, the fine line reproducibility and the transfer memory are excellent, and it is possible to prevent the cleaning failure and the image deletion at the end of the durability and to prolong the life. It is possible to provide a body, a method for manufacturing an electrophotographic photosensitive member, and an image forming apparatus.
The mechanism of action or mechanism of action of the present invention has not been clarified, but is presumed as follows.
It is desired to increase the thickness of the protective layer of the photoconductor, and in order to increase the film thickness, the inclusion of metal oxide particles having a relatively low volume resistivity in the protective layer improves the electrical characteristics and improves the transfer memory. However, the fine line reproducibility deteriorates and image deletion occurs in the latter half of the durability test.
On the other hand, when the protective layer contains metal oxide particles having a relatively high volume resistivity, fine line reproducibility is good and image deletion is less likely to occur, but the electrical characteristics are poor and transfer memory is likely to occur. Can not be converted.
Even when the metal oxide particles having an appropriate volume resistance are used, one of the qualities is rate-determining, and conventionally, the upper limit of the thickness of the protective layer is about 4 μm.
Further, by using the metal oxide particles and the charge transfer agent in combination, the fine line reproducibility and the transfer memory were improved, and it became possible to increase the thickness of the protective layer.However, addition of the charge transfer agent reduces the film strength, After long-term use, scratches were likely to occur, and cleaning failure (slip through) occurred after endurance.
From the above, in the present invention, by increasing the volume resistivity of the metal oxide particles from the surface side of the protective layer of the photoreceptor toward the photosensitive layer side, diffusion can be suppressed while ensuring the mobility of charges. Therefore, both transfer memory and fine line reproducibility can be achieved, and image deletion in the latter half of durability where surface resistance decreases due to oxidative deterioration and hydrophilicity can be prevented. Therefore, it is possible to increase the thickness of the protective layer to 5 μm or more. It is possible to provide a highly durable photoconductor that does not generate.

Cross-sectional schematic view showing an example of the structure of the electrophotographic photosensitive member of the present invention Cross-sectional schematic view showing an example of the image forming apparatus of the present invention An enlarged schematic diagram showing the positional relationship between the photoconductor and the cleaning blade in the image forming apparatus of the present invention. Explanatory drawing for explaining the evaluation method of the photoconductor of the present invention

The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a photosensitive layer and a protective layer formed in this order on a conductive support, wherein the protective layer is a resin obtained by curing a polymerizable compound. Component and metal oxide particles, the thickness of the protective layer is 5 μm or more, the volume resistivity of the metal oxide particles from the surface side of the protective layer toward the photosensitive layer side. The volume resistivity of the metal oxide particles is increased and is in the range of 1×10 ³ to 1×10 ⁹ Ω·cm.
This feature is a technical feature common to or corresponding to each of the following embodiments.

As an embodiment of the present invention, it is preferable that the protective layer contains a charge-transporting substance, and the content rate of the charge-transporting substance increases from the surface side of the protective layer toward the photosensitive layer side. .. The more the charge transport agent is added, the greater the effect of improving the deterioration of electric characteristics. The increased roughness causes poor cleaning. Therefore, the charge transfer agent increases the concentration on the side of the photosensitive layer where many metal oxide particles having a large volume resistivity that deteriorate electrical characteristics are present, and decreases the concentration toward the surface side to form a protective layer. It is possible to obtain a photoconductor having a long life without increasing the problem of thin line reproducibility, transfer memory, image deletion, and cleaning failure. Further, by increasing the concentration of the charge transport agent on the photosensitive layer (charge transport layer) side, hole injection from the charge transport layer to the protective layer is promoted, and the effect of improving fine line reproducibility and transfer memory is further enhanced.

Further, it is preferable that the charge transport material has a structure represented by the general formula (1) from the viewpoint of scratch resistance of the protective layer, charge injection characteristics, low probability of occurrence of transfer memory, and the like.
Further, the thickness of the protective layer is preferably 6 μm or more from the viewpoint of manifesting the effects of the present invention.

The method for producing an electrophotographic photosensitive member of the present invention is characterized in that the protective layer is formed using a circular slide hopper coating device. Thereby, a thick and uniform protective layer can be formed.

The electrophotographic photoreceptor of the present invention is suitably used for an image forming apparatus including an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit.

The image forming apparatus of the present invention further comprises means for supplying a lubricant, wherein the means for supplying the lubricant is the developing means for supplying the finely powdered lubricant externally added to the electrostatic image developing toner. In the case of supplying the lubricant to the electrophotographic photosensitive member by the action of the developing electric field formed in, the lubricant is not contaminated and the lubricant supply amount is larger than in the case where the lubricant is supplied by a lubricant applying means such as a brush roller. Is preferable in that no variation occurs.
In addition, it is preferable to contain zinc stearate as the lubricant from the viewpoint of lubricity, spreadability and hygroscopicity.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and after that as a lower limit and an upper limit.

[Outline of Electrophotographic Photoreceptor of the Present Invention]
The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a photosensitive layer and a protective layer formed in this order on a conductive support, wherein the protective layer is a resin obtained by curing a polymerizable compound. Component and metal oxide particles, the thickness of the protective layer is 5 μm or more, the volume resistivity of the metal oxide particles from the surface side of the protective layer toward the photosensitive layer side. The volume resistivity of the metal oxide particles is increased and is in the range of 1×10 ³ to 1×10 ⁹ Ω·cm.
Further, in the photoreceptor of the present invention, it is preferable that the protective layer contains a charge transporting substance, and the content rate of the charge transporting substance increases from the surface side of the protective layer toward the photosensitive layer side. ..

<Volume resistivity of metal oxide particles>
The volume resistivity of the metal oxide particles according to the present invention is in the range of 1×10 ³ to 1×10 ⁹ Ω·cm. When it is 1×10 ³ Ω·cm or more, charge diffusion and latent image deletion do not occur, fine line reproducibility is good, and image deletion can be prevented. When it is 1×10 ⁹ Ω·cm or less, electrical characteristics are good, and deterioration of the transfer memory due to insufficient response can be prevented. Even when the charge transfer substance is larger than 1×10 ⁹ Ω·cm, the electrical characteristics are improved by adding the charge transport substance and the transfer memory is improved, but the film strength is lowered because the charge transport substance acts as a plasticizer. However, scratches are likely to occur, and cleaning failure (slip through) may occur, which is not preferable.
Although the upper limit concentration of the charge transport material varies depending on the process, it is preferably 10% or less of the total volume of the protective layer.

(Measurement method of volume resistivity)
The volume resistivity (Ω·cm) of the metal oxide particles can be measured as follows. Electrical resistance is generally used as a measure of the conductivity of a substance. The value showing this resistance per unit volume (1 cm×1 cm×1 cm) is the volume resistivity (Volume Resistivity, unit Ω·cm).
That is, it can be obtained by flowing a constant current I(A) in the cross-sectional area W×t and measuring the potential difference V(V) between the electrodes separated by the distance L.
Definition of volume resistivity (Ω·cm) Cross-sectional area=W×t
Resistance R=V/I
Volume resistivity VR (Ω·cm)=(W×t/L)×(V/I)
The volume resistivity (Ω·cm) of the metal oxide particles according to the present invention is obtained by filling a container having electrodes arranged in parallel with an interval of 2 mm with the metal oxide particles and measuring the direct current resistance at a potential difference of 500 V between both electrodes. Yokogawa Hewlett-Packard Co., Ltd. 4329A High Resistance
Measured by Meter.

In the present invention, the volume resistivity of the metal oxide particles increases from the surface side of the protective layer toward the photosensitive layer side. Here, the volume resistivity may increase intermittently from the surface side of the protective layer toward the photosensitive layer side, or may increase continuously, but may increase continuously. It is more preferable from the viewpoint of manifesting the effect of the present invention.
Specifically, the change in volume resistivity is preferably such that the volume resistivity is in the range of 10 to 10 ⁶ Ω·cm when the layer thickness of the protective layer is in the range of ⁵ to 10 μm, and the layer thickness of the protective layer is Is more preferably in the range of ⁵ to ⁸ μm and the volume resistivity is in the range of 10 ² to 10 ⁵ Ω·cm.

Examples of means for intermittently increasing the volume resistivity include a protective layer having a laminated structure formed by laminating a plurality of layers, and changing the volume resistivity of the metal oxide particles contained in each layer. .. Specifically, for example, as shown in FIG. 1, a laminated structure including a first protective layer (104a), a second protective layer (104b), and a third protective layer (104c) in order from the photosensitive layer side to the protective layer side. The first protective layer (104a) has a structure in which the volume resistivity of the metal oxide particles contained in the first protective layer (104a) is maximized, and the volume resistivity of the metal oxide particles in the second protective layer (104b) is the first protective layer (104a). It is preferable that the volume resistivity of the metal oxide particles of the third protective layer (104c) is minimized. The number of layers is at least two, and more preferably three or more.
Further, as a means for continuously increasing the volume resistivity, it is preferable to contain metal oxide particles having a gradually increasing volume resistivity from the surface side of the protective layer toward the photosensitive layer side. In order to continuously change the volume resistivity, for example, spray coating is preferably used.
In the photoconductor of the present invention, the volume resistivity of the metal oxide particles is detected from the surface side of the protective layer toward the photosensitive layer side by a lapping tape or the like. Can be detected by gradually abrading and measuring the volume resistance and surface resistance.

[Structure of electrophotographic photoreceptor]
FIG. 1 is a schematic sectional view showing an example of the structure of the electrophotographic photosensitive member of the present invention.
The photoconductor 100 has a structure in which at least a charge generation layer 103a, a charge transport layer 103b, and a protective layer 104 are sequentially stacked on a conductive support 101. Here, when the photoconductor has a laminated structure in which the charge generation layer 103a and the charge transport layer 103b are directly laminated, the laminated structure portion is also referred to as a photosensitive layer 103.
As shown in FIG. 1, the photoconductor 100 may have a configuration having an intermediate layer 102 between the conductive support 101 and the charge generation layer 103a.
Hereinafter, each layer constituting the photoconductor will be described in detail.

<Protective layer>
The photoconductor has a protective layer as the outermost layer on the side opposite to the conductive support side. The protective layer protects the surface of the photoconductor, improves low abrasion resistance and scratch resistance, reduces the occurrence of toner slipping through, and contributes to prolonging the life of the photoconductor, and by extension, the electrophotographic image forming apparatus.
The protective layer according to the present invention has a thickness of 5 μm or more. More preferably, it is in the range of 6 to 10 μm, particularly preferably in the range of 6 to 8 μm. When the thickness of the protective layer is 5 μm or more, the effect of extending the life of the photoconductor is excellent. Further, if it is 10 μm or less, generation of transfer memory can be further reduced.

The protective layer according to the present invention contains a resin component obtained by curing a polymerizable compound and metal oxide particles. Further, the protective layer preferably further contains a charge transport substance.

(Cured 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 a polymerizable compound by irradiation with active rays such as ultraviolet rays and electron beams and curing the compound.
As the polymerizable compound, a monomer having two or more polymerizable functional groups (polyfunctional polymerizable compound) may be used, and a monomer having one polymerizable functional group (monofunctional polymerizable compound) may be used in combination. Specific examples of the polymerizable compound include a styrene-based monomer, an acrylic-based monomer, a methacrylic-based monomer, a vinyltoluene-based monomer, a vinyl acetate-based monomer, and an N-vinylpyrrolidone-based monomer.

As the polymerizable compound, less amount or less since the time curing in is possible, acryloyl group _(CH 2 = CHCO-) or methacryloyl group acrylic monomer having _{(CH 2 =} CCH 3 CO-) two or more , Methacrylic monomers, or oligomers thereof are particularly preferable.
In the present invention, the polymerizable compounds may be used alone or in combination. Further, these polymerizable compounds may be used as a monomer, but may be used as an oligomer.

Preferred specific examples of the polymerizable compound are shown below.

Here, in the chemical formulas showing the exemplified compounds (M1) to (M14), R represents an acryloyl group (CH ₂ ═CHCO—), and R′ represents a methacryloyl group (CH ₂ ═CCH ₃ CO—).
As the polymerizable compound, it is preferable to use a monomer having three or more polymerizable functional groups. Further, as the polymerizable compound, two or more kinds of compounds may be used in combination, and in this case also, 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)
The protective layer according to the present invention contains metal oxide particles.
The metal oxide particles contribute to improving the film strength of the protective layer.
The number average primary particle diameter of the metal oxide particles is preferably within the range of 1 to 300 nm, more preferably within the range of 3 to 100 nm, and further preferably within the range of 5 to 40 nm.
The number average primary particle diameter of the metal oxide particles is a photographic image in which a scanning electron microscope (manufactured by JEOL Ltd.) was used to take a 10000 times magnified photograph, and 300 particles were randomly captured by a scanner (aggregated particles are Can be calculated by using an automatic image processing analysis device “LUZEX AP (software version Ver.1.32)” (manufactured by Nireco Corporation).

Examples of the metal oxide particles include silica (silicon oxide), magnesium oxide, zinc oxide, lead oxide, alumina (aluminum oxide), zirconium oxide, tin oxide, titania (titanium oxide), niobium oxide, molybdenum oxide, and oxide. Vanadium or the like can be used. Among these, tin oxide is preferable from the viewpoint of electrical characteristics.
The metal oxide particles according to the present invention are not particularly limited, and particles produced by a known production method can be used.

The metal oxide particles may be surface-modified with a surface modifier having a reactive organic group (hereinafter, also referred to as “reactive organic group-containing surface modifier”).
The reactive organic group-containing surface modifier is preferably one that reacts with a hydroxy group or the like present on the surface of the metal oxide particles, and such a reactive organic group-containing surface modifier is, for example, a silane coupling agent. , Titanium coupling agents and the like.
Further, as the reactive organic group-containing surface modifying agent, a surface modifying agent having a radical polymerizable reactive group is preferable. Examples of the radically polymerizable reactive group include a vinyl group, an acryloyl group, a methacryloyl group and the like. Such a radically polymerizable reactive group can also react with a polymerizable compound to form a strong protective layer. As the surface modifier having a radical polymerizable reactive group, a silane coupling agent having a radical polymerizable reactive group such as vinyl group, acryloyl group and 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 = CHCOO} (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 = C} (CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-15: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-16: CH 2 = C} (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 = C} (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 = C} (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 = C} (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)

As the reactive organic group-containing surface modifier, a silane compound having a radically polymerizable reactive organic group may be used in addition to the compounds shown in the exemplified compounds (S-1) to (S-31). .. The reactive organic group-containing surface modifier may be used alone or in combination of two or more. The treatment amount (addition amount) of the reactive organic group-containing surface modifier is preferably in the range of 0.1 to 200 parts by mass, more preferably in the range of 7 to 70 parts by mass, relative to 100 parts by mass of the particles. Within.

The method for treating the untreated metal oxide particles with the reactive organic group-containing surface modifier is not particularly limited, but for example, a slurry containing the untreated metal oxide particles and the reactive organic group-containing surface modifier (solid particles And the like). By this method, re-aggregation of untreated metal oxide particles is prevented, and at the same time, surface modification of untreated metal oxide particles proceeds. After that, the solvent is removed to make powder.

Examples of the surface modification device include a wet media dispersion type device. This wet media dispersion type device fills beads as media in a container and further rotates a stirring disk mounted perpendicular to the rotation axis at high speed to crush and crush aggregate particles of untreated metal oxide particles. It is an apparatus having a dispersion step. The wet media dispersion type device is not limited as long as it can sufficiently disperse the untreated metal oxide particles when surface-modifying the untreated metal oxide particles, and the surface can be modified. Various types such as horizontal type, continuous type and batch type can be adopted. Specific examples include a sand mill, ultra visco mill, pearl mill, gren mill, dyno mill, agitator mill and dynamic mill. These dispersion type devices use a crushing medium (media) such as balls and beads to perform fine crushing and dispersion by impact crushing, friction, shearing, shear stress and the like.

As the beads used in the wet media dispersion type apparatus, balls made of glass, alumina, zircon, zirconia, steel, flint stone, etc. 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, but preferably about 0.1 to 1.0 mm.
Various materials such as stainless steel, nylon, and ceramics can be used for the disk and the inner wall of the container used in the wet media dispersion type apparatus, but a disk and the inner wall of the container made of ceramic such as zirconia or silicon carbide are particularly preferable.
You may use these metal oxide particles individually by 1 type or in mixture of 2 or more types.

The content of the metal oxide particles is not particularly limited, but is preferably in the range of 100 to 200 parts by mass with respect to 100 parts by mass of the polymerizable compound for constituting the cured resin component,
More preferably, it is within the range of 110 to 170 parts by mass. Within the above range, the effects of extending the life of the photoconductor, by extension, the electrophotographic image forming apparatus, and reducing the frequency of occurrence of toner slip through are further improved.

(Charge transport material)
The protective layer according to the present invention preferably contains a charge transport substance.
The charge-transporting substance is a substance having a charge-transporting property that transports charge carriers in the protective layer, and is a substance capable of adjusting the electric resistance of the protective layer.
For example, N,N-dialkylaniline compounds, amine compounds such as diarylamine compounds and triarylamine compounds, pyrazoline compounds, carbazole compounds, imidazole compounds, triazole compounds, oxazole compounds, styryl compounds, stilbene compounds and the like can be used.

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

In the 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, a plurality of R ₁ , R ₂ , R ₃ and R ₄ may be the same or different from each other. .. Among these, it is preferable that R ₁ , R ₂ , R ₃ and R ₄ are 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. One example of a preferred compound is CTM-1 used in the examples.
As the compound represented by the general formula (1), for example, those described in JP-A-2015-114454 can be used. Further, it can be synthesized by a known synthesis method, for example, a method disclosed in Japanese Patent Laid-Open No. 2006-143720.
These charge transport materials may be used alone or in combination of two or more.

The amount of the charge transport substance added is in the range of 1 to 25 parts by mass, and more preferably in the range of 5 to 20 parts by mass, with respect to 100 parts by mass of the polymerizable compound for constituting the cured resin component. .. Within the above range, the electrical characteristics will be better, and the life of the photoconductor, and by extension, the electrophotographic image forming apparatus, the effect of suppressing transfer memory, and the effect of reducing the occurrence frequency of toner slippage will be further improved.

(Specific radical scavenger)
The protective layer may contain a radical scavenger having a structure represented by the following general formula (2).
The above polymerizable compound 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 cross-linking sealant. That is, the crosslinking density of the specific radical scavenger can be adjusted by the addition ratio and the like. Therefore, since the cured resin component is obtained by polymerizing the polymerizable compound in the presence of the specific radical scavenger, the protective layer has appropriate film strength (wear resistance), and the cleaning blade The surface of the photoconductor is appropriately depleted by cleaning means such as. Therefore, even if a discharge product or the like adheres to the surface of the photoconductor, the surface of the photoconductor is depleted and refreshed, so that image deletion in a formed image can be prevented.

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

The specific radical scavenger may be a synthetic product or a commercially available product, and examples of the commercially available product include Sumilizer (registered trademark) GS manufactured by Sumitomo Chemical Co., Ltd.
The addition amount of the specific radical scavenger is not particularly limited, but 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. More preferably. Within the above range, the effects of extending the life of the photoconductor, by extension, the electrophotographic image forming apparatus, and reducing the frequency of occurrence of toner slip through are further improved. Further, the effect of suppressing the image deletion in the formed image can be obtained.

(Polymerization initiator)
The polymerizable compound for forming the above-mentioned cured resin component is preferably polymerized using a polymerization initiator.
As the polymerization initiator, it is preferable to use a radical polymerization initiator. The radical polymerization initiator is not particularly limited, but photopolymerization initiators are preferable, and among them, acylphosphine oxide compounds, alkylphenone compounds, oxime ester compounds, thioxanthone compounds are more preferable, and acylphosphine oxide compounds, oxime ester compounds are more preferable. preferable. These polymerization initiators may be used alone or in combination of two or more.

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

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 photoconductor, and by extension, the electrophotographic image forming apparatus, the effect of suppressing the transfer memory in the formed image, and the effect of reducing the frequency of toner slippage are further improved.

(Other ingredients)
The protective layer may further contain other components, for example, an antioxidant and lubricant particles may be contained.
The antioxidant is not particularly limited, but for example, those described in JP 2000-305291 A can be preferably used.

The lubricant particles are not particularly limited, but, for example, fluorine atom-containing resin particles can be added.
The fluorine atom-containing resin particles are not particularly limited, but examples thereof include tetrafluoroethylene resin, trifluoroethylene chloride resin, hexafluoroethylene chloride propylene resin, vinyl fluoride resin, vinylidene fluoride resin, and difluoride difluoride. Examples thereof include ethylene chloride resin and copolymers thereof. These can be used alone or in combination of two or more. Among these, tetrafluoroethylene resin and vinylidene fluoride resin are particularly preferable.

<Conductive support>
The conductive support constituting the photoconductor is not particularly limited as long as it has conductivity, for example, aluminum, copper, chromium, nickel, zinc, stainless or other metal formed into a drum or sheet, Laminated metal foil such as aluminum or copper on a plastic film, aluminum, indium oxide, vapor deposited on a plastic film such as tin oxide, a metal provided with a conductive layer by applying a conductive substance alone or with a binder resin, Examples include plastic films and paper.

<Middle layer>
The photoreceptor may be provided with an intermediate layer having a barrier function and an adhesive function between the conductive support and the photosensitive layer. It is preferable to provide the intermediate layer in consideration of various failure prevention.
Such an intermediate layer contains, for example, a binder resin (hereinafter, also referred to as “intermediate layer binder resin”) and, if necessary, conductive particles or 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. Of these, alcohol-soluble polyamide resins are preferable. These intermediate layer binder resins may be used alone or in combination of two or more.

Various conductive particles and metal oxide particles can be contained in the intermediate layer 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, zirconium oxide, or the like can be used.

The number average primary particle diameter of such metal oxide particles is preferably 0.3 μm or less, and 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 kinds are mixed, they may be in the form of solid solution or fusion.

The content ratio of the conductive particles or metal oxide particles is preferably in the range of 20 to 400 parts by mass, and more preferably in the range of 50 to 350 parts by mass with respect to 100 parts by mass of the binder resin.
The layer thickness of the intermediate layer is preferably in the range of 0.1 to 15 μm, more preferably 0.3 to 10 μm.

<Charge generation layer>
The charge generation layer in the photosensitive layer that constitutes the photoreceptor contains a charge generation substance and a binder resin (hereinafter, also referred to as “binder resin for charge generation layer”).
Examples of the charge generating substance include azo raw materials such as Sudan red and Diane blue, quinone pigments such as pyrenequinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, pyranthrone and diphthaloylpyrene. Examples thereof include, but are not limited to, ring quinone pigments and phthalocyanine pigments. Among these, polycyclic quinone pigments and titanyl phthalocyanine pigments are preferable. These charge generating substances may be used alone or in combination of two or more.

As the binder resin for the charge generation layer, known resins can be used, 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 resin). Vinyl-vinyl acetate-maleic anhydride copolymer resin), poly-vinylcarbazole resin, and the like, but are 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-generating substance in the charge-generating layer is preferably in the range of 1 to 600 parts by mass, and more preferably in the range of 50 to 500 parts by mass, relative to 100 parts by mass of the binder resin for the charge-generating layer. Is.
The layer thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics of the binder resin for the charge generation layer, the content ratio, etc., but is preferably in the range of 0.01 to 5 μm, more preferably 0.05. Within the range of ˜3 μm.

<Charge transport layer>
The charge transport layer in the photosensitive layer constituting the photoconductor contains a charge transport substance and a binder resin (hereinafter, also referred to as “binder resin for charge transport layer”).
Examples of the charge-transporting substance of the charge-transporting layer include substances that transport charges (holes), such as triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, and butadiene compounds.
The charge transport layer formed under the protective layer preferably contains a charge transport substance having high mobility and a large molecular weight. Such a charge transport substance is represented by the above general formula (1). Those different from the above compounds are preferably used.

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

The content ratio of the charge transporting material in the charge transporting layer is preferably in the range of 10 to 500 parts by mass, more preferably in the range of 20 to 250 parts by mass with respect to 100 parts by mass of the binder resin for the charge transporting layer. Is.
The layer thickness of the charge transport layer varies depending on the characteristics of the charge transport material, the characteristics of the binder resin for the charge transport layer, the content ratio, etc., but is preferably in the range of 5 to 40 μm, more preferably in the range of 10 to 30 μm. Within.
An antioxidant, an electronic conductive agent, a stabilizer, silicone oil and the like may be added to the charge transport layer. The antioxidant is preferably disclosed in JP-A-2000-305291, and the electronic conductive agent is preferably disclosed in JP-A-50-137543 and JP-A-58-76833.

[Method for manufacturing electrophotographic photoreceptor]
The photoreceptor of the present invention is not particularly limited, but is preferably manufactured by a manufacturing method having the following steps.
Step (1): A step of forming an intermediate layer by applying a coating solution for forming an intermediate layer on the outer peripheral surface of the conductive support and drying it, if necessary.
Step (2): A coating liquid for forming a charge generating layer is applied to the outer peripheral surface of the conductive support or to the outer peripheral surface of the intermediate layer formed on the conductive support in the step (1) and dried. A step of forming a charge generation layer by
Step (3): A step of forming a charge transport layer by applying a coating solution for forming a charge transport layer on the outer peripheral surface of the charge generating layer formed on the intermediate layer and drying the coating solution.
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 generating layer, polymerizing and curing the coating solution.

The concentration of each component in the coating liquid for forming each layer is appropriately selected according to the layer thickness of each layer and the production rate.
In the coating liquid for forming each layer, an ultrasonic disperser, a ball mill, a sand mill, a homomixer or the like can be used as a means for dispersing particles such as conductive particles or metal oxide particles or a charge generating substance. However, it is not limited to these.
The method of applying the coating solution for forming each layer is not particularly limited, and examples thereof include a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, a slide hopper method, and a circular shape. Known methods such as the slide hopper method can be used.
The method for drying the coating film can be appropriately selected depending on the type of solvent and the layer thickness, but thermal drying is preferred.

The details of the process of forming each layer will be described below.
(Step (1): Formation of Intermediate Layer)
The intermediate layer is prepared by dissolving a binder resin for an intermediate layer in a solvent to prepare a coating solution (hereinafter, also referred to as “intermediate layer forming coating solution”), and if necessary, conductive particles or metal oxide particles are added. After the dispersion, the coating liquid can be applied on the conductive support to form a coating film having a certain thickness, and the coating film can be dried.

The coating liquid for forming the intermediate layer is preferably applied by a dip coating method.
The solvent used in the step of forming the intermediate layer is preferably a solvent in which the conductive particles and the metal oxide particles are well dispersed and the binder resin for the intermediate layer, particularly the polyamide resin, is dissolved. Specifically, alcohols having 1 to 4 carbon atoms such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, tert-butanol, and sec-butanol (2-butanol) are soluble in the polyamide resin. And excellent in coating performance, which is preferable. Further, as a cosolvent which can be used in combination with the above solvent in order to improve the storage stability and the dispersibility of particles and can obtain a preferable effect, benzyl alcohol, toluene, dichloromethane, cyclohexanone, tetrahydrofuran and the like can be mentioned.

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

The charge generation layer forming coating liquid is preferably applied by a dip coating method.
Examples of the solvent used for forming 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 However, the present invention is not limited to these.

(Step (3): Formation of Charge Transport Layer)
The charge transport layer is prepared by preparing a coating liquid (hereinafter, also referred to as “charge transport layer forming coating liquid”) in which a binder resin for the charge transport layer and a charge transporting substance are dissolved in a solvent, and generating the charge from the coating liquid. It can be formed by applying a certain layer thickness on a layer to form a coating film, and drying the coating film.
The charge generation layer forming coating liquid is preferably applied by a slide hopper method using a circular slide hopper coating device, and for example, it can be applied by a method disclosed in JP-A-2015-114454.
Examples of the solvent used for forming 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 thereof include, but are not limited to, butanol, tert-butanol, sec-butanol (2-butanol), tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, pyridine and diethylamine.

(Step (4): Formation of protective layer)
The protective layer is a coating solution prepared by adding the polymerizable compound, the metal oxide particles, a polymerization initiator, if necessary, a specific radical scavenger, and other components such as a charge transport substance to a known solvent. , "Also referred to as a "coating solution for forming a protective layer") is prepared, and the coating solution for forming a protective layer is applied to the outer peripheral surface of the charge transport layer formed in step (3) to form a coating film. The protective layer can be formed by drying the coating film and irradiating it with an actinic ray such as an ultraviolet ray or an electron beam to polymerize the polymerizable compound component in the coating film and curing it.
Further, the protective layer according to the present invention is formed such that the volume resistivity of the metal oxide particles increases from the surface side toward the photosensitive layer side. The volume resistivity may be increased intermittently from the surface side of the protective layer toward the photosensitive layer side, or may be increased continuously, but it is more preferable to increase continuously.
As a means for intermittently increasing the volume resistivity of the metal oxide particles from the surface side of the protective layer toward the photosensitive layer side, as described above, the protective layer is formed by laminating a plurality of layers. The structure may be changed to change the volume resistivity of the metal oxide particles contained in each layer. In addition, as a means for continuously increasing the size, as described above, it is preferable to include metal oxide particles having a large volume resistivity gradually from the surface side of the protective layer toward the photosensitive layer side.

The protective layer-forming coating liquid is preferably applied by a slide hopper method using a circular slide hopper coating device, and for example, it can be applied by a method disclosed in 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, the metal oxide particles, and the like, and examples thereof include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, and 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 not limited thereto.

The method of reacting the polymerizable compound is not particularly limited, but examples thereof include a method of reacting by electron beam cleavage, and a method of adding a radical polymerization initiator and reacting with light or heat.
The curable resin component is produced by irradiating the coating film with actinic rays as a curing treatment, generating radicals to polymerize, and forming a cross-linking bond by inter-molecular and intra-molecular crosslinking reaction to cure. As the actinic rays, ultraviolet rays and electron rays are more preferable, and ultraviolet rays are particularly preferable because they are easy to use.

As the ultraviolet light source, any light source that emits ultraviolet light can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a super high pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a flash (pulse) xenon, etc. can be used.
Irradiation conditions vary depending on each lamp, but the irradiation dose of actinic radiation is preferably in the range of 5 to 500 mJ/cm ² , and more preferably in the range of 5 to 100 mJ/cm ² .
The power of the lamp is preferably in the range of 0.1 to 5 kW, more preferably in the range of 0.5 to 4 kW, still more preferably in the range of 0.5 to 3 kW.
The irradiation time for obtaining the necessary irradiation dose of actinic radiation is preferably 0.1 seconds to 10 minutes, and more preferably 0.1 seconds to 5 minutes from the viewpoint of work efficiency.
In the step of forming the protective layer, drying can be performed before and after the irradiation of the actinic rays and during the irradiation of the actinic rays, and the timing of the drying can be appropriately selected by combining these.

[Electrophotographic image forming apparatus]
The electrophotographic photoreceptor of the present invention is preferably used in an electrophotographic image forming apparatus, and the electrophotographic image forming apparatus (hereinafter, also simply referred to as “image forming apparatus”) is the electrophotographic photoreceptor of the present invention. The charging unit, the exposing unit, the developing unit, the transfer unit, and the cleaning unit are provided.
Further, the image forming apparatus further comprises means for supplying a lubricant, wherein the means for supplying the lubricant causes the finely powdered lubricant externally added to the electrostatic charge image developing toner to be added to the developing means. It is preferable to supply the electrophotographic photosensitive member by the action of the developing electric field formed.
Further, it is preferable to contain zinc stearate as the lubricant.

The charging unit is preferably a proximity charging type charging unit such as a charging roller, a charging brush, a charging belt, or a charging blade. Since the deterioration of the surface of the photoconductor tends to increase when such a charging means is used, the effect of the present invention can be more remarkably obtained. Above all, from the viewpoint of charging stability, it is preferable to use a charging roller as the charging means.

An image forming apparatus according to an embodiment of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to only one mode described below.
FIG. 2 is a schematic cross-sectional view showing the structure of a tandem type electrophotographic image forming apparatus according to one embodiment of the present invention, and FIG. 3 is a tandem type electrophotographic image forming apparatus according to one embodiment of the present invention. FIG. 6 is an enlarged schematic diagram showing a positional relationship between a photoconductor and a cleaning blade.
The image forming apparatus is called 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 body unit 70, a sheet feeding unit 21 and The fixing means 24. A document image reading device SC is arranged above the main body A of the electrophotographic image forming apparatus.

The four image forming units 10Y, 10M, 10C and 10K rotate around the photoconductors 1Y, 1M, 1C and 1K, charging means 2Y, 2M, 2C and 2K, exposure means 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 the photoconductors 1Y, 1M, 1C, 1K. It is configured.
The electrophotographic image forming apparatus according to an aspect of the present invention uses the above-described photoconductors of the present invention as the photoconductors 1Y, 1M, 1C, and 1K.

The image forming units 10Y, 10M, 10C, and 10K have the same configuration except that the colors of the toners included are yellow (Y), magenta (M), cyan (C), and black (K), respectively. Is. Therefore, the image forming unit 10Y will be described in detail below as an example.
The image forming unit 10Y includes a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a cleaning unit 6Y around a photoconductor 1Y which is an image forming body, and has a yellow (Y) color on the photoconductor 1Y.
To form a toner image.

The charging unit 2Y is a unit that uniformly charges the surface of the photoconductor 1Y in a negative polarity. In the electrophotographic image forming apparatus of this embodiment, it is preferable to use a charging roller as the charging unit 2Y.
The charging roller is disposed close to the photoconductor, and charges the photoconductor to a desired polarity and potential by applying a voltage of about -2.5 to -1.5 kV to the charge 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 photoconductor, and an AC in which a DC electric field is superposed with an AC electric field is applied to the charging member to charge the photoconductor Although any of the charging methods can be used, the AC charging method, which can provide a leveling effect by an AC electric field, is preferable because of excellent charging uniformity.

In the AC charging method, as the 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 forms an electrostatic latent image corresponding to a yellow image by performing exposure on the photoconductor 1Y to which a uniform potential is applied by the charging unit 2Y, based on the image signal (yellow). is there. As the exposing unit 3Y, a unit including LEDs in which light emitting elements are arranged in an array in the axial direction of the photoconductor 1Y and an image forming element, or a laser optical system is used.

The developing means 4Y is composed of, for example, a developing sleeve 41Y that contains a magnet and rotates while holding a developer, a photosensitive member, and a voltage applying device that applies a DC and/or AC bias voltage between the developing sleeve 41Y and the photosensitive member. is there.
The developing means 4Y contains a Y component developer (for example, a two-component developer containing toner and a magnetic carrier as main components). The developing unit 4Y attaches toner of the Y component to the surface of the photoconductor 1Y to visualize the electrostatic latent image and form a toner image. Specifically, a developing bias is applied to the developing sleeve 41Y, and a developing electric field is formed between the photoconductor 1Y and the developing sleeve 41Y. Due to the potential difference between the photoconductor 1Y (negative polarity) and the developing sleeve 41Y, the charged toner (negative polarity) on the developing sleeve 41Y moves and adheres to the exposed portion on the surface of the photoconductor 1Y. That is, the developing means 4Y develops the electrostatic latent image by the reversal developing method.

The cleaning unit 6Y is a unit that removes the toner remaining on the surface of the photoconductor 1Y. The cleaning means 6Y of this 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 arranged such that its tip end faces the direction (counter direction) opposite to the rotation direction of the photoconductor 1Y at the contact portion with the surface of the photoconductor 1Y.

The support member 31 is not particularly limited, and any conventionally known one can be used, and examples thereof include those manufactured from rigid metal, elastic metal, plastic, ceramic and the like. Of these, a rigid metal is preferable.

The blade member 30 is not particularly limited, but, for example, polyurethane, silicone rubber, fluororubber, chloropyrene rubber, butadiene rubber or the like can be used. Among them, polyurethane is preferable because it can obtain appropriate strength and flexibility that can contact the rotating photoreceptor 1Y. The blade member 30 using polyurethane is obtained by, for example, mixing a dehydrated polyol and an isocyanate compound and reacting them in a temperature range of 100 to 120° C. for 30 to 90 minutes by adding a cross-linking agent to the prepolymer. It can be manufactured by injecting into a mold and curing. Polyester polyols such as polyethylene adipate and polycaprolactone can be used as the polyol, and diphenylmethane diisocyanate can be used as the isocyanate compound. Further, as the cross-linking agent, 1,4-butanediol, trimethylolpropane, ethylene glycol, a mixture thereof, or the like can be used.
The blade member 30 may have a configuration in which a hardened layer is provided in a portion in contact with the photoconductor 1Y. By providing the hardened layer in the contact portion, the hardness of the blade member main body can be easily adjusted so that the blade member 30 can be flexibly flexed to the extent that the blade member 30 contacts the photoconductor 1Y. The hardened layer may be a layer provided on the surface of the blade member 30, but from the viewpoint of enhancing durability, it is preferable that a part of the main body of the blade member 30 is a processed layer.

When polyurethane is used as the base material of the blade member 30, the contact portion of the blade member 30 with the photoreceptor 1Y is impregnated with the isocyanate compound for a certain period of time, and the polyurethane contained in the main body of the blade member 30 is reacted with the isocyanate compound. The reaction portion can be formed as a hardened layer. The cured layer thus formed contains a polymer of polyurethane and an isocyanate compound. Urethane bonds having active hydrogen are 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 with the impregnated isocyanate compound. An allophanate bond that enhances the hardness of the cured layer can be formed with the polymer. Further, since the polymerization reaction of the impregnated isocyanate compound also progresses at the same time, it is possible to form a thick hardened layer, and even if the hardened layer is worn, the hardened layer is thick, so that the blade member 30 has good hardness. Can be maintained for a period of time.
The blade member 30 preferably has an inclination angle θ of 5 to 20° with respect to the surface of the photoconductor 1Y, from the viewpoint of enhancing the scraping force of the residual toner and obtaining higher cleaning performance. Further, the linear pressure of the blade member 30 can be appropriately adjusted within the range of the linear pressure set in a known blade member.

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

The image forming units 10Y, 10M, 10C, and 10K are arranged in a vertical column, and an intermediate transfer body unit 70 is arranged on the left side of the photoconductors 1Y, 1M, 1C, and 1K in the figure. The intermediate transfer body unit 70 is wound around a plurality of rollers 71, 72, 73, 74 and is rotatably supported by a semi-conductive endless belt-shaped intermediate transfer body 77 and a secondary transfer means. It comprises a next transfer roller 5b and a cleaning means 6b.
The image forming units 10Y, 10M, 10C, and 10K and the intermediate transfer body unit 70 are housed in a housing 80, and the housing 80 can be pulled out from the apparatus main body A via support rails 82L and 82R. Has been done.

The fixing unit 24 is, for example, a heat roller fixing device including a heating roller having a heating source inside and a pressure roller provided in pressure contact with the heating roller so as to form a fixing nip portion. One of the methods is mentioned.
In FIG. 2, 20 is a paper feed cassette, 22A, 22B, 22C and 22D are intermediate rollers, 23 is a registration roller, 25 is a paper discharge roller, 26 is a paper discharge tray, and P is a transfer material. Shown respectively.
Although the image forming apparatus of the present invention is shown as a color laser printer in FIG. 2, the electrophotographic image forming apparatus according to one embodiment of the present invention may be configured as a copying machine. Further, in the image forming apparatus according to the aspect of the present invention, a light source other than a 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, other types such as 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.

<Means for supplying lubricant>
The electrophotographic image forming apparatus according to one aspect of the present invention preferably includes a lubricant supply unit that supplies a lubricant to the surface of the photoconductor.

The lubricant is not particularly limited, and known ones 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 a saturated or unsaturated fatty acid metal salt having 10 or more carbon atoms is preferable. For example, zinc laurate, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, zinc stearate, stearate. Aluminum oxide, indium 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, cadmium ricinoleate, etc. Can be mentioned. Among these, zinc stearate is preferable from the viewpoint of lubricity, spreadability and hygroscopicity.

As the fatty acid metal salt, a synthetic product or a commercially available product may be used, and examples of the commercially available product include zinc stearate S manufactured by NOF CORPORATION.
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 means for supplying the lubricant by a method of applying a solid lubricant with a brush roller (hereinafter, also referred to as “lubricant applying means”).

When the lubricant applying unit is used, for example, in the image forming unit 10Y of the image forming apparatus shown in FIG. 2, the lubricant applying unit is arranged on the downstream side of the cleaning unit 6Y and the upstream side of the charging unit 2Y in the rotation direction of the photoconductor 1Y. Preferably. However, the arrangement position of the lubricant applying means is not limited to the downstream side of the cleaning means 6Y and the upstream side of the charging means 2Y.
The lubricant applying means is not particularly limited, but is preferably constituted by, for example, a solid lubricant and a lubricant applying member including a brush roller. Specifically, the lubricant applying means exposes the lubricant stock, which is made of a solid lubricant having a rectangular parallelepiped shape, and the lubricant scraped by rubbing the surface of the photoconductor 1Y and rubbing the surface of the lubricant stock. It is preferably composed of a brush roller for applying 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. The tip of the brush of the brush roller contacts the surface of the photoconductor 1Y. Further, it is preferable that the brush roller is rotationally driven at the same speed as the rotation direction of the photoconductor 1Y. A leveling blade for uniformly applying the lubricant supplied to the surface of the photoreceptor 1Y by the lubricant applying means may be provided on the downstream side of the lubricant applying means and the upstream side of the charging means 2Y.
The lubricant applying means is not particularly limited, and known means can be appropriately referred to. For example, JP-A-2016-188950 can be referred to.

The lubricant supplying means is not particularly limited, but for example, a fine powder lubricant externally added to the toner base particles is developed by the developing means (for example, 4Y in FIGS. 2 and 3 above). Means (hereinafter, also referred to as “toner-containing means”) for supplying to the photoconductor (for example, 1Y in FIGS. 2 and 3 above) by the action of the electric field can be mentioned. That is, the toner containing means is means for supplying the fine powder lubricant contained in the toner to the photoconductor by the action of the developing electric field formed in the developing means.
Unlike the above-mentioned lubricant applying means, the toner-containing means is particularly preferable because it does not involve an intermediate member such as a brush roller, and therefore does not cause contamination of the lubricant or variation in the lubricant supply amount due to contamination or deterioration of the intermediate member. ..

In the toner-containing means, a fine powder lubricant is externally added as an external additive to the toner base particles described later. The volume-based median diameter Dw of the finely powdered lubricant is preferably in the range of 0.3 to 25 μm, and more preferably in the range of 0.5 to 20 μm. When the content is within the above range, the size of the lubricant is appropriately small, so that the adhesive force with the toner base particles is appropriately increased, and the occurrence of migration in the developing unit is less likely to occur, so that the supply of the lubricant is further improved. Will be enough. Further, since the size of the lubricant is appropriately large, the adhesive force to the toner base particles is appropriately reduced, so that the migration of the lubricant onto the photoreceptor becomes easier. As a result, the lubricant can be uniformly supplied onto the photoconductor.
The volume-based median diameter Dw of the lubricant is measured and calculated using a device in which a data processing computer system (manufactured by Beckman Coulter, Inc.) is connected to Coulter Multisizer 3 (manufactured by Beckman Coulter, Inc.). Is obtained by It is also possible to measure the particle size of the lubricant externally added to the toner base particles (colored particles) by a known method such as electron microscopic photography. For the evaluation method of the volume-based median diameter Dw of the finely powdered lubricant, the description in paragraphs “0031” and “0032” of JP 2010-175701 A can be referred to. Details will be described in Examples.

The amount of the fine powdery lubricant added is preferably within the range of 0.01 to 0.5 parts by mass, and within the range of 0.03 to 0.3 parts by mass, based on the total mass of the toner. Is more preferable. Within the above range, the effect of the present invention can be more exerted while suppressing the influence on the chargeability of the toner.
The method for mixing the toner base particles and the lubricant is not particularly limited, and a known method can be appropriately selected, and for example, a Henschel mixer (registered trademark) manufactured by Nippon Coke Industry Co., Ltd. can be used.

[Toner and developer]
In the present invention, the “toner base particles” constitute the base of the “toner particles”. The “toner base particles” include at least a binder resin and a colorant, and may further include other components such as a release agent (wax) and a charge control agent, if necessary. The "toner base particles" are referred to as "toner particles" by adding an external additive. The “toner” means an aggregate of “toner particles”.

The image forming apparatus 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 can be used, but it is preferable to use the polymerized toner from the viewpoint of obtaining an image with high image quality.
The average particle size of the toner is not particularly limited, but it is preferably within a range of 2 to 8 μm in volume-based median size. By setting this range, the resolution can be further increased.

Further, as described above, in the toner base particles, when a lubricant supply means for supplying a fine powdery lubricant contained in the toner to the photoconductor by the action of a developing electric field formed in the developing means is used, -Like lubricant can be added externally as an external additive.
Further, to the toner base particles, 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 having an average particle diameter of about 0.2 to 3 μm are externally added as appropriate as external additives. You can

When the toner is used as a two-component developer, as a carrier, a conventionally known material such as a ferromagnetic metal such as iron, an alloy of a ferromagnetic metal and aluminum or lead, or a compound of a ferromagnetic metal such as ferrite or magnetite is used. Magnetic particles consisting of can be used. Among these, ferrite is particularly preferable.

As the carrier, it is preferable to use a carrier further coated with a resin or a so-called resin dispersion type carrier in which magnetic particles are dispersed in the resin. The resin composition for coating is not particularly limited, but it is preferable to use, for example, a cyclohexyl methacrylate-methyl methacrylate copolymer or the like.
The volume-based median diameter of the carrier is preferably in the range of 15 to 100 μm, more preferably in the range of 25 to 60 μm.
The concentration of the toner contained in the two-component developer is preferably in the range of 4.0 to 8.0% by mass.
Although the embodiment of the present invention has been specifically described above, the embodiment of the present invention is not limited to the above example, and various modifications can be made.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
The structural formulas of the compounds used in the examples are shown below.

[Preparation of metal oxide particles [A]]
Metal oxide particles (SnO ₂ , average particle size 20 μm) were added to methanol, and the mixture was dispersed for 30 minutes using a US homogenizer. Next, 3-methacryloxypropyltrimethoxysilane (KBM503; Shin-Etsu Chemical Co., Ltd.) and toluene were added as a coupling agent, and the mixture was stirred at room temperature for 1 hour. Further, the solvent was removed by an evaporator and then the mixture was heated at 120° C. for 1 hour to obtain metal oxide particles [A] surface-modified with a coupling agent.

[Preparation of Metal Oxide Particles [B] to [H]]
In the production of the metal oxide particles A, the metal oxide particles [B] to [H] having the volume resistivity shown in the following Table I are prepared by appropriately adjusting the compounding amounts of methanol, SnO ₂ , a coupling agent and toluene. Was produced. The metal oxide particles [B] - [H] Both with SnO _2.

[Production of Photoreceptor [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] having a finely roughened surface.

<Formation of intermediate layer>
A dispersion liquid having the following composition was diluted twice with the same mixed solvent, allowed to stand overnight and filtered (filter; Rigimesh 5 μm filter manufactured by Nippon Pall Co., Ltd.) was used to prepare a coating liquid [1] for forming an intermediate layer.
Binder resin: Polyamide resin "CM8000" (manufactured by Toray) 1 part by mass Metal oxide particles: Titanium oxide "SMT500SAS" (manufactured by Teika) 3 parts by mass Solvent: Methanol 10 parts by mass Batch type using a sand mill as a disperser Dispersion was carried out for 10 hours. The coating solution [1] for forming an intermediate layer was applied onto the conductive support [1] by a dip coating method to form an intermediate layer [1] having a dry layer thickness of 2 μm.

<Formation of charge generation layer>
Charge generating substance: 20 parts by mass of the following charge generating substance (CG-1) Binder resin: Polyvinyl butyral resin "#6000-C" (manufactured by Denka)
10 parts by mass Solvent: t-butyl acetate 700 parts by mass Solvent: 4-methoxy-4-methyl-2-pentanone 300 parts by mass are mixed and dispersed for 10 hours using a sand mill, and a charge generation layer forming coating solution [1 ] Was prepared. This charge generation layer forming coating solution [1] was applied onto the intermediate layer [1] by a dip coating method to form a charge generation layer [1] having a dry layer thickness of 0.3 μm.

<Synthesis of charge generating substance (CG-1)>
(1) Synthesis of amorphous titanyl phthalocyanine 1,2-diiminoisoindoline; 29.2 parts by mass are dispersed in 200 parts by mass of o-dichlorobenzene, and titanium tetra-n-butoxide; 20.4 parts by mass are added. It heated at 150-160 degreeC for 5 hours under nitrogen atmosphere. After cooling, the precipitated crystals were filtered, washed with chloroform, washed with 2% hydrochloric acid aqueous solution, washed with water and methanol, and dried to obtain 26.2 parts by mass (yield 91%) of crude titanyl phthalocyanine.
Next, the crude titanyl phthalocyanine was dissolved by stirring in 250 parts by mass of concentrated sulfuric acid at 5° C. or lower for 1 hour, and this was poured into 5000 parts by mass of water at 20° C. The precipitated crystals were filtered and sufficiently washed with water to obtain 225 parts by mass of wet paste product.
This wet paste product was frozen in a freezer, thawed again, filtered and dried to obtain 24.8 parts by mass of amorphous titanyl phthalocyanine (yield 86%).

(2) Synthesis of (2R,3R)-2,3-butanediol adduct titanyl phthalocyanine 10.0 parts by mass of the 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, the same applies hereinafter) 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 was added to the reaction solution, the resulting crystals were filtered, and the filtered crystals were washed with methanol to obtain a charge generating substance containing (2R,3R)-2,3-butanediol adduct titanyl phthalocyanine. ) CG-1: 10.3 parts by mass was obtained.
In the X-ray diffraction spectrum of the charge generating substance (CG-1), there are 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. Further, in thermal analysis (TG), there is a mass loss of about 7% at 390 to 410°C. Therefore, 1:1 adduct and non-adduct (addition of titanyl phthalocyanine and (2R,3R)-2,3-butanediol) (Not) estimated to be a mixture of titanyl phthalocyanines. The BET specific surface area of the obtained charge generating substance (CG-1) was measured by a flow-type specific surface area automatic measuring device (Micrometrics Flowsoap type: Shimadzu Corporation), and it was 31.2 m ² /g.

<Formation of charge transport layer>
Charge transporting substance: 225 parts by mass of the compound A, binder resin: 300 parts by mass of polycarbonate resin "Z300" (manufactured by Mitsubishi Gas Chemical Co., Inc.), antioxidant: 6 parts by mass of "Irganox 1010" (manufactured by BASF Japan), solvent: THF( 1600 parts by mass of tetrahydrofuran), 400 parts by mass of solvent:toluene, and 1 part by mass of silicone oil "KF-50" (manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed and dissolved to prepare a coating liquid [1] for forming a charge transport layer. .
The coating liquid [1] for forming a charge transport layer was applied onto the charge generation layer [1] using a circular slide hopper coating device to form a charge transport layer [1] having a dry layer thickness of 20 μm.

<Formation of first protective layer>
The above metal oxide fine particles [E]: 118 parts by mass of tin oxide fine particles (average particle size 20 nm, volume resistance 3.5×10 ⁶ Ω·cm), polymerizable compound: 100 parts by mass of the above exemplified compound (M1), polymerization Initiator: 6.2 parts by mass of the exemplified compound (P1), 280 parts by mass of solvent: 2-butanol, and 70 parts by mass of tetrahydrofuran: mixed and stirred to sufficiently dissolve and disperse, and a coating solution for forming a protective layer [1 ] Was prepared. The coating liquid [1] for forming the first protective layer is applied onto the charge transport layer using a circular slide hopper coating device to form a coating film, which is irradiated with ultraviolet rays for 1 minute using a metal halide lamp to form a dry layer. A first protective layer having a thickness of 2.0 μm was formed.

<Formation of second protective layer>
118 parts by mass of the above metal oxide fine particles [D]: tin oxide fine particles (average particle diameter 20 nm, volume resistance 8.9×10 ⁵ Ω·cm), polymerizable compound: 100 parts by mass of the above exemplified compound (M1), polymerization Initiator: 6.2 parts by mass of the exemplified compound (P1), solvent: 280 parts by mass of 2-butanol, solvent: 70 parts by mass of tetrahydrofuran, and mixed and stirred to sufficiently dissolve/disperse the coating liquid for forming a protective layer [2. ] Was prepared. The coating solution [2] for forming the second protective layer is applied onto the first protective layer using a circular slide hopper coating device to form a coating film, which is irradiated with ultraviolet rays for 1 minute using a metal halide lamp and dried. A second protective layer having a layer thickness of 2.0 μm was formed.

<Formation of third protective layer>
118 parts by mass of the above metal oxide fine particles [C]: tin oxide fine particles (average particle size 20 nm, volume resistance 5.5×10 ⁴ Ω·cm), polymerizable compound: 100 parts by mass of the above exemplified compound (M1), polymerization Initiator: 6.2 parts by mass of the above exemplified compound (P1), solvent: 280 parts by mass of 2-butanol, solvent: 70 parts by mass of tetrahydrofuran, mixed and stirred to sufficiently dissolve and disperse, and a coating liquid for forming the third protective layer. [3] was prepared. This third protective layer forming coating liquid [3] is applied onto the second protective layer using a circular slide hopper coating device to form a coating film, which is irradiated with ultraviolet rays for 1 minute using a metal halide lamp and dried. A third protective layer having a layer thickness of 2.0 μm was formed.

[Production of Photoreceptor [2]]
A photoconductor [2] was produced in the same manner as in the production of the photoconductor [1] except that the formation of the first to third protective layers was changed as follows.
<Formation of first protective layer>
In the formation of the first protective layer of the photoconductor [1], metal oxide particles [G] were used in place of the metal oxide particles [E], and the CTM-1 was further added. A coating solution for forming the first protective layer was formed in the same manner except that the addition amount was changed, and the coating solution was applied to form the first protective layer.

<Formation of second protective layer>
In the formation of the second protective layer of the photoconductor [1], the metal oxide particles [E] were used in place of the metal oxide particles [D], and the CTM-1 was further added. A second protective layer-forming coating liquid was formed in the same manner except that the addition amount was changed, and the coating liquid was applied to form the second protective layer.

<Formation of third protective layer>
In the formation of the third protective layer of the photoconductor [1], the metal oxide particles [B] were used in place of the metal oxide particles [C], and the CTM-1 was further added. A third protective layer-forming coating liquid was formed in the same manner except that the addition amount was changed, and the coating liquid was applied to form the third protective layer.

[Production of Photoreceptors [3] to [16]]
In the formation of the first to third protective layers of the photoconductor [2], the types and addition amounts of metal oxide particles, charge transport substances, polymerizable compounds, polymerization initiators, etc., the thickness of the protective layer, etc. are shown in the following table. Photoconductors [3] to [16] were manufactured in the same manner except that the changes were made as shown in II to Table VII.

As the image forming apparatus, bizhub C360 manufactured by Konica Minolta Co., Ltd. (bizhub is a registered trademark of the same company) was used. The bizhub C360 is a tandem-type color multi-function peripheral (MFP: Multi-Function Peripheral) that performs laser exposure with a wavelength of 780 nm, intermediate transfer that performs reversal development. Under an atmosphere of 20[° C.] and relative humidity of 50[% RH], an A4 size image with a printing area ratio of 5% for each color of YMCK is printed on 100 A4 size neutral paper.
After printing out 10,000 sheets, the image evaluation of each photoconductor was performed as follows.

[Evaluation]
<Poor cleaning>
After the durability test, in an environment of 10° C. and 15% RH, a halftone image with a coverage rate of 80% is arranged so that a black background portion is located in the front part and a white background part is located in the rear part in the paper transport direction (see FIG. (d)) was printed on 30,000 sheets of A3 neutral paper, the white background of the 20,000th sheet was visually observed, and cleaning failure (toner slippage) was evaluated based on the following criteria. The case where the evaluation results were “⊚” and “◯” was judged to be acceptable.
(Evaluation criteria)
⊚: No stain was found on the white background (pass)
◯: Slight streaky stains were generated on the white background, but there was no practical problem (pass).
X: Clear streaky stains are generated on the white background, which is a practical problem (fail)

<Image stream>
After the endurance test, in an environment of 30° C. and 80% RH, an A4 size character image with an image ratio of 6% was printed laterally on A4 size neutral paper 10,000 sheets, and immediately after that, the The power was turned off, and 12 hours after the main power was turned off, the main power was turned on. Then, immediately after the printable state, a halftone image (Fig. 4(b): relative reflection density of 0.4 with a Macbeth densitometer) and a 6-dot lattice image (Fig. (See (c)) and were printed respectively. The printed halftone image and the above-mentioned lattice image were visually observed, and the presence or absence of image deletion was evaluated for each photoconductor based on the following criteria. The case where the evaluation results were “⊚” and “◯” was judged to be acceptable.
(Evaluation criteria)
⊚: There is no density unevenness in the halftone image, and there are no defects or thin line widths in the lattice image (pass).
◯: In the halftone image, a band-shaped density reduction region along the long axis direction of the photoconductor is observed, but in the lattice image, there is no defect or thin line width (pass).
Δ: Defects or thin line widths are observed in the lattice image (fail)
×: No grid image is formed (fail)

<Transfer memory>
Before the durability test, an image in which a solid pattern is output at the first rotation of the photoconductor and a halftone pattern is output at the second rotation of the photoconductor in an environment of a temperature of 10° C. and a humidity of 15% RH (see FIG. 4A). Was printed on A3 neutral paper, and the history of the solid pattern history of the first rotation in the halftone pattern of the second rotation of the obtained test image, that is, the memory generation was visually observed, and the evaluation result was " The cases of "A" and "○" were judged to be acceptable.
In addition to the evaluation with each unit single color, the Y unit and the C unit were used as the color unit, and the evaluation was performed with a two-color superposed green chart.
(Evaluation criteria)
◎: Memory is not observed (pass)
○: A slight memory is observed (pass)
△: Memory is observed (failed)
×: Memory is clearly observed (failure)

<Thin line reproducibility>
Before the endurance test, the internal mounting pattern No. was set in a 30° C./80% RH environment. 6/dot lattice image (see FIG. 4(c)) was printed on 53/Dot1 (a typical exposure pattern formed in a dot shape having regularity) on A3 neutral paper. The printed halftone image and the above-mentioned lattice image were visually observed, and the presence or absence of image deletion was evaluated for each photoconductor based on the following criteria. The case where the evaluation results were “⊚” and “◯” was judged to be acceptable.
(Evaluation criteria)
⊚: There is no loss or thin line width in the lattice image (pass)
◯: In the lattice image, a part of the line width is slightly thin, but there is no practical problem (pass)
Δ: Defects or thin line widths are observed in the lattice image (fail)
×: No grid image is formed (fail)

As shown in the above results, the photoconductor of the present invention is superior to the photoconductor of the comparative example in fine line reproducibility and transfer memory, and it is clear that defective cleaning and image deletion can be prevented.

1Y, 1M, 1C, 1K Photoconductors 2Y, 2M, 2C, 2K Charging means (charging roller)
3Y, 3M, 3C, 3K Exposure means 4Y, 4M, 4C, 4K Developing means 5Y, 5M, 5C, 5K Primary transfer roller 5b Secondary transfer roller 6Y, 6M, 6C, 6K, 6b Cleaning means 10Y, 10M, 10C, 10K Image forming unit 20 Paper feeding cassette 21 Paper feeding means 22A, 22B, 22C, 22D Intermediate roller 23 Registration roller 24 Fixing means 25 Paper discharging roller 26 Paper discharging tray 30 Blade member 31 Supporting member 41Y Developing sleeve 70 provided in developing means 4Y Intermediate transfer body unit 71, 72, 73, 74 Roller 77 Intermediate transfer body 80 Housing 82L, 82R Support rail A Main body SC Original image reading device P Transfer material 100 Photoconductor 101 Conductive support 102 Intermediate layer 103a Charge generation layer 103b Charge transport layer 103 Photosensitive layer 104 Protective layer 104a First protective layer 104b Second protective layer 104c Third protective layer

Claims (8)

An electrophotographic photoreceptor comprising a photosensitive layer and a protective layer formed in this order on a conductive support,
The protective layer contains a resin component obtained by curing a polymerizable compound, and metal oxide particles,
The thickness of the protective layer is 5 μm or more,
The volume resistivity of the metal oxide particles increases from the surface side of the protective layer toward the photosensitive layer side, and the volume resistivity of the metal oxide particles is 1×10 ³ to 1×10 ^9. An electrophotographic photoreceptor characterized by being in the range of Ω·cm. The protective layer contains a charge transport material,
The electrophotographic photosensitive member according to claim 1, wherein the content rate of the charge transport material increases from the surface side of the protective layer toward the photosensitive layer side. The electrophotographic photoreceptor according to claim 2, wherein the charge transport material has a structure represented by the following general formula (1).

[In general formula (1), R< ₁ >, R< ₂ >, R< ₃ > and R< ₄ > respectively independently represent a C1-C7 alkyl group or a C1-C7 alkoxy group. 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 present} may be the same or different from each other. .. ] The electrophotographic photosensitive member according to any one of claims 1 to 3, wherein the protective layer has a thickness of 6 µm or more. A method of manufacturing an electrophotographic photosensitive member according to claim 1, wherein the electrophotographic photosensitive member is manufactured by:
A method for manufacturing an electrophotographic photosensitive member, characterized in that the protective layer is formed using a circular slide hopper coating device. An image forming apparatus comprising an electrophotographic photosensitive member, a charging unit, an exposing unit, a developing unit, a transfer unit, and a cleaning unit,
An image forming apparatus, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of claims 1 to 4. Furthermore, a means for supplying a lubricant is provided,
The means for supplying the lubricant supplies the finely powdered lubricant externally added to the electrostatic image developing toner to the electrophotographic photosensitive member by the action of the developing electric field formed in the developing means. The image forming apparatus according to claim 6, wherein: The image forming apparatus according to claim 7, wherein the lubricant contains zinc stearate.

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