JP7484451B2 - Organic photoreceptor, electrophotographic image forming apparatus, and method for manufacturing organic photoreceptor - Google Patents

Description

The present invention relates to an organic photoreceptor, an electrophotographic image forming apparatus, and a method for manufacturing an organic photoreceptor, and in particular to an organic photoreceptor that can suppress uneven wear of the photoreceptor caused by an uneven supply of lubricant and achieve a long life.

2. Description of the Related Art In recent years, in order to meet the demands of image forming apparatuses that are intended to achieve higher speeds and higher image quality, there has been a demand for organic photoreceptors (hereinafter, also simply referred to as "photoreceptors") that have high durability.
In particular, in the charging roller method, the lubricant added externally to the toner is supplied onto the photoconductor by the action of the developing electric field, but when the toner is transported to the developing machine, the lubricant is supplied in excess upstream of the transport path and the amount supplied downstream decreases, resulting in a gradient in the amount of lubricant formed in the axial direction of the photoconductor, causing a gradient in the amount of wear (uneven wear) of the photoconductor.
In order to suppress uneven wear of the protective layer, a technology has been disclosed in which a specific compound is contained in the protective layer and the surface hardness at the axial center of the photoreceptor is made lower than the surface hardness at both axial ends (see, for example, Patent Document 1). However, this technology does not take into consideration the prevention of uneven wear of the photoreceptor in the region where the lubricant supply amount is excessive and the region where the lubricant supply amount is small, and therefore it is not possible to prevent uneven wear of the photoreceptor. As a result, there is a problem that the life of the photoreceptor is shortened.

JP 2012-93382 A

The present invention was made in consideration of the above problems and circumstances, and the problem to be solved is to provide an organic photoreceptor, an electrophotographic image forming apparatus, and a method for manufacturing an organic photoreceptor that can suppress uneven wear of the photoreceptor caused by an uneven amount of lubricant supply and achieve a long life.

In the course of investigating the causes of the above problems in order to solve the above problems, the inventors discovered that by varying the surface hardness of the photoreceptor in a gradual manner along the axial direction and adjusting the film strength in accordance with the gradual change (bias) in the amount of lubricant supplied, it is possible to maintain a uniform amount of wear on the photoreceptor and achieve a long service life, thus arriving at the present invention.
That is, the above-mentioned problems of the present invention are solved by the following means.

1. An organic photoreceptor having at least an organic photosensitive layer formed on a cylindrical conductive support,
the universal hardness of the outermost layer in the image forming region of the organic photosensitive layer changes continuously and inclined along an axial direction parallel to a rotation axis from one end to the other end in the axial direction of the organic photoreceptor , and
The organic photoreceptor has a gradient change in the universal hardness along the axial direction in a range of 10 to 50 N/ ^mm2 .

2. The organic photoreceptor according to claim 1, wherein the slope change is in the range of 20 to 40 N/ ^mm2 .

3. The organic photoreceptor described in paragraph 1 or 2, characterized in that the outermost layer is a protective layer containing at least metal oxide particles in a cured resin obtained by curing a polymerizable compound.

〔一般式（１）中、Ｒ_１、Ｒ_２、Ｒ_３及びＲ_４は、各々、水素原子、炭素数１～７のアルキル基、炭素数１～７のアルコキシ基を示す。ｋ、ｌ及びｎは、各々、１～５の整数を示し、ｍは、１～４の整数を示す。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。〕 4. The organic photoreceptor according to item 3, wherein the protective layer contains a charge transport material having a structure represented by the following general formula (1):

[In general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom, an alkyl group having 1 to 7 carbon atoms, or an alkoxy group having 1 to 7 carbon atoms. k, l and n each represent an integer of 1 to 5, and m represents an integer of 1 to 4. However, when k, l, n or m is 2 or more, the multiple R ₁ , R ₂ , R ₃ or R ₄ may be the same or different.]

5. A tandem-type electrophotographic image forming apparatus comprising at least a charging means for charging the surface of an organic photoreceptor, a means for supplying a lubricant to the surface of the organic photoreceptor, and a means for removing toner remaining on the surface of the organic photoreceptor with a cleaning blade,
5. An electrophotographic image forming apparatus comprising the organic photoreceptor according to any one of claims 1 to 4 as the organic photoreceptor.

6. The electrophotographic image forming apparatus described in paragraph 5, characterized in that the lubricant supplying means supplies the lubricant in the form of fine powder, which is externally added to the toner, to the organic photoreceptor by the action of a developing electric field formed in the means for forming a toner image.

7. The electrophotographic image forming apparatus according to claim 5 or 6, wherein the charging means is a charging roller.

8. A method for producing the organic photoreceptor according to claim 3 or 4, comprising the steps of:
The method for producing an organic photoreceptor, wherein the protective layer is formed using a circular slide hopper coating apparatus.

According to the above-mentioned means of the present invention, it is possible to provide an organic photoreceptor, an electrophotographic image forming apparatus, and a method for manufacturing an organic photoreceptor, which are capable of suppressing uneven wear of the photoreceptor due to uneven supply of lubricant and achieving a long service life.
Although the mechanism by which the effects of the present invention are manifested or the mechanism by which the effects of the present invention are acted upon has not been clarified, it is speculated as follows.
In the charging roller process, where the photoconductor is susceptible to wear and lifespan is an issue, the lubricant added externally to the toner is supplied onto the photoconductor by the action of the developing electric field, but when the toner is transported to the developing machine, the lubricant is supplied in excess upstream of the transport path and the amount supplied downstream decreases, resulting in a gradient in the amount of lubricant formed in the axial direction of the photoconductor, causing a gradient in the amount of wear (uneven wear).
As a countermeasure, it is known to form patch images between sheets of paper to partially accelerate wear of the photoconductor or to increase the amount of lubricant supplied, but this poses the problem of increased toner consumption.
Therefore, the present invention can maintain a uniform amount of wear and achieve a long life of the photoconductor by changing the surface hardness of the photoconductor in a gradual manner along the axial direction and adjusting the film strength according to the unevenness of the lubricant supply amount. Specifically, a low hardness area is arranged in an area where the lubricant is excessively supplied and the amount of wear is small (for example, the upstream side of the lubricant transport path) to promote wear, and a high hardness area that can suppress wear is arranged in an area where the amount of lubricant supply is small (for example, the downstream side of the lubricant transport path) to prevent uneven wear.
Since the lubricant supply rate has a continuous gradient, the surface hardness of the photoconductor can also be changed continuously, resulting in more uniform wear. As a result, patch control, which increases toner consumption, and auxiliary mechanisms such as a lubricant application mechanism and cleaning brush are not required, making it possible to provide an inexpensive, long-lasting image forming device.

FIG. 1 is a schematic cross-sectional view showing an example of the structure of an organic photoreceptor of the present invention. FIG. 1 is a schematic cross-sectional view illustrating an example of an electrophotographic image forming apparatus according to the present invention. FIG. 1 is a partial cross-sectional view for illustrating the configuration of an example of a light irradiation device used in the examples. FIG. 1 is a cross-sectional view for explaining an example of the configuration of a circular slide hopper coating device used in the examples.

The organic photoreceptor of the present invention is an organic photoreceptor having at least an organic photosensitive layer formed on a cylindrical conductive support, characterized in that the universal hardness of the outermost layer in an image forming region of the organic photosensitive layer varies in a gradient along an axial direction parallel to a rotation axis, and the gradient change amount of the universal hardness along the axial direction is within a range of 10 to 50 N/ ^mm2 .
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 slope change amount is within a range of 20 to 40 N/ ^mm2 in that uneven wear can be further suppressed.

In addition, it is preferable that the outermost layer is a protective layer containing at least metal oxide particles in a cured resin obtained by curing a polymerizable compound, in terms of improving the strength of the outermost layer and stabilizing image quality by adjusting the resistance.

It is preferable that the protective layer contains a charge transport agent having the structure represented by the general formula (1) from the viewpoints of scratch resistance, charge injection characteristics, and low probability of transfer memory occurrence.

The organic photoreceptor of the present invention is suitable for use in a tandem-type electrophotographic image forming apparatus equipped with at least a charging means for charging the surface of the organic photoreceptor, a means for supplying a lubricant to the surface of the organic photoreceptor, and a means for removing any remaining lubricant on the surface of the organic photoreceptor with a cleaning blade, thereby providing an inexpensive, long-life image forming apparatus.

In addition, it is preferable that the lubricant supplying means is a means for supplying the lubricant in a fine powder form, which has been externally added to the toner, to the organic photoreceptor by the action of a developing electric field formed in a means for forming a toner image, in that the lubricant is not contaminated and there is no variation in the amount of lubricant supplied, compared to when the lubricant is supplied by a lubricant application means such as a brush roller.
Furthermore, it is preferable that the charging means is a charging roller from the viewpoint of charging stability.

In the method for producing an organic photoreceptor of the present invention, it is preferable that the protective layer is formed using a circular slide hopper coating device, in order to minimize dissolution of the protective layer.

The present invention, its components, and the form and mode for implementing the present invention are described below. Note that in this application, "~" is used to mean that the numerical values before and after it are included as the lower and upper limits.

[Summary of the organic photoreceptor of the present invention]
The organic photoreceptor of the present invention (hereinafter, also simply referred to as "photoreceptor") is an organic photoreceptor having at least an organic photosensitive layer formed on a cylindrical conductive support, characterized in that the universal hardness of the outermost surface layer in an image forming region of the organic photosensitive layer varies in a gradient along an axial direction parallel to a rotation axis, and the gradient change amount of the universal hardness along the axial direction is within a range of 10 to 50 N/ ^mm2 .
In the present invention, the term "axial direction" refers to the direction of the rotation axis (longitudinal direction) of a drum-shaped photoconductor.
The "image forming area" is an area for forming a toner image on the surface of the photoconductor, excluding both ends in the axial direction, and the area varies depending on the paper passing width. Specifically, the area is an area excluding a range of 3 to 10% of the total axial length of the photoconductor (the length between both ends in the axial direction) from both ends of the photoconductor toward the center in the axial direction.

[Universal hardness]
In the present invention, the universal hardness (HU) is defined by the following formulas (1) and (2).

In the above formulas (1) and (2), F is the test load (N), A(h) is the surface area ( ^mm2 ) of the indenter in contact with the test object, and h is the indentation depth (mm) when the test load is applied. A(h) is calculated from the shape and indentation depth of the indenter, and when the indenter is a Vickers indenter, it is calculated as 26.43 x ^h2 from the angle a (136°) of the opposing faces of the pyramidal penetrator.
In the present invention, the universal hardness (HU) can be measured using a commercially available hardness measuring device, and is measured under the following measurement conditions using an ultra-microhardness tester "H-100V" (manufactured by Fisher Instruments).
-Measurement condition-
Measuring instrument: Ultra-micro hardness tester "H-100V" (manufactured by Fisher Instruments)
Indenter shape: Vickers indenter (a=136°)
Measurement environment: 20°C, 60% RH
Maximum test load: 3mN
Loading speed: 3 mN/20 sec
Maximum load creep time: 5 seconds Unloading speed: 3 mN/20 seconds

In the present invention, the gradient change in universal hardness was calculated as follows: Four points were measured at 45° intervals in the circumferential direction at positions 20 mm from the top end to the bottom end in the axial direction of the photoconductor, and the average of these four points was defined as the universal hardness of the top end, and three points were measured at equal angles in the circumferential direction at positions 20 mm from the bottom end to the top end of the photoconductor, and the average of these three points was defined as the universal hardness of the bottom end, and the difference between the calculated average universal hardness of the top end and the average universal hardness of the bottom end was defined as the gradient change.
The gradient change in the universal hardness is within the range of 10 to 50 N/ ^mm2 . If it is 10 N/ ^mm2 or more, the effect of suppressing uneven wear is high, and if it is 50 N/ ^mm2 or less, uneven wear due to differences in surface hardness can be reduced. Moreover, the gradient change is more preferably within the range of 20 to 40 N/ ^mm2 .

The universal hardness may be inclined continuously or stepwise along the axial direction, and may be inclined in the axial direction according to the inclination of the lubricant supply amount. Specifically, in the case of a cured protective layer made of a cured resin and metal oxide particles, the universal hardness is preferably within a range of 200 to 280 N/mm2 in the region where the lubricant is excessively supplied (upstream side of the lubricant transport path, for example, one end side in the axial direction of the photoconductor), and is preferably within ^a range of 240 to 300 N/ ^mm2 in the region where the lubricant supply amount is reduced (downstream side of the lubricant transport path, for example, the other end side in the axial direction of the photoconductor).

The universal hardness changes in a gradient along the axial direction of the photoreceptor, and means for keeping the amount of gradient change in the universal hardness within the above range include controlling the light irradiation conditions after applying a coating liquid for forming a protective layer to be provided as the outermost layer of the photoreceptor, and adjusting the amount of metal oxide particles and the amount of charge transport agent added to the protective layer.
The reason why the universal hardness of the outermost surface layer of the photoconductor can be changed by the light irradiation device is that the universal hardness is correlated with the cumulative amount of light irradiated onto the photoconductor, and the cumulative amount of light irradiated is determined by (cumulative amount of light irradiated) = (amount of light irradiated per unit area of the photoconductor drum surface) x (irradiation time per unit area). Therefore, the universal hardness of the outermost surface layer of the photoconductor can be changed by changing (i) the amount of light irradiated or (ii) the irradiation time.

Therefore, for example, when using the light irradiation device described in JP 2013-57787 A, by (i) changing the light irradiation intensity at any position or (ii) changing the lifting speed of the organic photosensitive workpiece (i.e., changing the irradiation time) when lifting the organic photosensitive workpiece from the bottom to the top of the transport path space, it is possible to change the integrated amount of light irradiated on the photosensitive drum surface in the long axis direction of the photosensitive body, and to change the surface hardness of the photosensitive body. In particular, the means of (ii) changing the lifting speed of the organic photosensitive workpiece is preferable from the viewpoint of controllability.

In addition, in devices other than the light irradiation device and the devices in the embodiments described below, for example, by using a line UV-LED chip facing the photosensitive workpiece and changing the intensity of the irradiation light between each LED chip in the axial direction, the integrated amount of irradiation light can be changed, thereby obtaining an effect equivalent to that of the present invention.
The preferred amounts of the metal oxide particles and the charge transport material to be added will be described later.
Here, the "photoreceptor workpiece" in the present invention refers to a photosensitive layer on a conductive support and an uncured film formed on the photosensitive layer.

The organic photoreceptor of the present invention refers to a photoreceptor in which at least one of the charge generating function and charge transporting function, which are essential for the photoreceptor's construction, is exerted by an organic compound, and includes all known organic photoreceptors, such as organic photoreceptors having an organic photosensitive layer composed of a known organic charge generating substance or organic charge transporting substance (charge transport agent) and those having an organic photosensitive layer in which the charge generating function and charge transporting function are composed of a polymer complex.

[Configuration of Organic Photoreceptor]
FIG. 1 is a schematic cross-sectional view showing an example of the structure of an organic photoreceptor of the present invention.
As shown in FIG. 1, a photoreceptor 100 of the present invention has at least an organic photosensitive layer formed on a conductive support 101 .
The organic photosensitive layer is composed of at least a charge generating layer 103a laminated from the conductive support 101 side, and a charge transport layer 103b laminated on the charge generating layer 103a. An intermediate layer 102 may be provided between the conductive support 101 and the charge generating layer 103a. Furthermore, a configuration having a protective layer 104 on the charge transport layer 103b is preferred in terms of improving abrasion resistance.
Each layer constituting the photoreceptor will now be described in detail.

<Protective Layer>
The photoreceptor preferably has a protective layer as the outermost layer on the side opposite to the conductive support, which protects the surface of the photoreceptor, improves low wear and scratch resistance, reduces the occurrence of toner slip-through, and contributes to extending the life of the photoreceptor and, ultimately, the electrophotographic image forming apparatus.
When the outermost surface layer of the photoreceptor is a protective layer, the universal hardness of the protective layer changes in a gradient along an axial direction parallel to the rotation axis in the image forming region, as described above, and the gradient change amount of the universal hardness along the axial direction is within a range of 10 to 50 N/ ^mm2 .

The thickness of the protective layer is preferably within the range of 0.2 to 10 μm, and more preferably within the range of 0.5 to 6 μm. If it is within this range, it is highly effective in extending the life of the photoconductor, and the occurrence of transfer memory can be further reduced.

The protective layer according to the present invention preferably contains at least metal oxide particles in a cured resin obtained by curing a polymerizable compound. In addition, from the viewpoint of making the hardness of the protective layer fall within the above-mentioned universal hardness range, it is preferable to carry out a polymerization reaction for obtaining a cured resin in the presence of a specific radical scavenger. By using a specific radical scavenger, the crosslinking reaction in the polymerization reaction can be controlled, and the crosslink density (universal hardness) of the polymer can be easily controlled as a formula.
The protective layer preferably further contains a charge transport material.

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

As the polymerizable compound, since it is possible to cure with a small amount of light or in a short time, it is particularly preferable to use an acrylic monomer, a methacrylic monomer, or an oligomer thereof having two or more acryloyl groups (CH ₂ ═CHCO—) or methacryloyl groups (CH ₂ ═CCH ₃ CO—).
In the present invention, the polymerizable compounds may be used alone or in combination. These polymerizable compounds may be used as monomers or as oligomers.

Specific examples of preferred polymerizable compounds are shown below.

In the chemical formulas showing the above exemplary 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. In addition, as the polymerizable compound, two or more compounds may be used in combination, but even in this case, it is preferable to use the monomer having three or more polymerizable functional groups in a ratio of 50 mass% or more.
These polymerizable compounds and curable resin components may be used alone or in combination of two or more.

(Metal oxide particles)
The protective layer according to the present invention preferably contains metal oxide particles.
The metal oxide particles contribute to improving the film strength of the protective layer and improving the stability of image quality by adjusting the resistance.
The number average primary particle size of the metal oxide particles is preferably within a range of 1 to 300 nm, more preferably within a range of 3 to 100 nm, and even more preferably within a range of 5 to 40 nm.
The number average primary particle size of the metal oxide particles can be calculated by taking a 10,000x magnified photograph using a scanning electron microscope (manufactured by JEOL Ltd.), randomly capturing 300 particles using a scanner, and analyzing the photographic image (excluding agglomerated particles) using an automatic image processing and analysis device "LUZEX AP (software version Ver. 1.32)" (manufactured by Nireco Corporation).

Examples of the metal oxide particles that can be used include silica (silicon oxide), magnesium oxide, zinc oxide, lead oxide, alumina (aluminum oxide), zirconium oxide, tin oxide, titania (titanium oxide), niobium oxide, molybdenum oxide, vanadium oxide, etc. Among these, tin oxide is preferred from the viewpoint of electrical properties.
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, for example, composite particles having a core-shell structure composed of an insulating particle (core) and a carrier (shell) supported on the surface of the insulating particle and composed of a conductive metal oxide.

The metal oxide particles may be surface-modified with a surface modifier having a reactive organic group (hereinafter also referred to as a "reactive organic group-containing surface modifier").
The reactive organic group-containing surface modifier is preferably one that reacts with hydroxyl groups present on the surface of the metal oxide particles. Examples of such reactive organic group-containing surface modifiers include silane coupling agents and titanium coupling agents.
In addition, as the reactive organic group-containing surface modifier, a surface modifier having a radical polymerizable reactive group is preferable. Examples of the radical polymerizable reactive group include a vinyl group, an acryloyl group, and a methacryloyl group. Such a radical 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 a vinyl group, an acryloyl group, or a methacryloyl group is preferable.

The reactive organic group-containing surface modifier is preferably a silane coupling agent having the above-mentioned radical polymerizable group, and examples thereof include the following compounds S-1 to S-31.
S-1: _CH2 =CHSi( _CH3 )( _OCH3 ) ₂
S-2: _CH2 =CHSi( _OCH3 ) ₃
S-3: _CH2 = _CHSiCl3
S-4: _CH2 =CHCOO( _CH2 ) _2Si ( _CH3 )( _OCH3 ) ₂
S-5: _CH2 =CHCOO( _CH2 ) _2Si ( _OCH3 ) ₃
S-6: _CH2 =CHCOO( _CH2 ) _2Si ( _OC2H5 )( _{OCH3 ) 2}
S-7: _CH2 =CHCOO( _CH2 ) _3Si ( _OCH3 ) ₃
S-8: _CH2 =CHCOO( _CH2 ) _2Si ( _CH3 ) _Cl2
S-9: _CH2 = _CHCOO ( _CH2 ) _2SiCl3
S-10: _CH2 =CHCOO( _CH2 ) _3Si ( _CH3 ) _Cl2
S-11: _CH2 = _CHCOO ( _CH2 ) _3SiCl3
S-12: _CH2 =C( _CH3 )COO( _CH2 ) _2Si ( _CH3 )( _OCH3 ) ₂
S-13: _CH2 =C( _CH3 )COO( _CH2 ) _2Si ( _OCH3 ) ₃
S-14: _CH2 =C( _CH3 )COO( _CH2 ) _3Si ( _CH3 )( _OCH3 ) ₂
S-15: _CH2 =C( _CH3 )COO( _CH2 ) _3Si ( _OCH3 ) ₃
S-16: _CH2 =C( _CH3 )COO( _CH2 ) _2Si ( _CH3 ) _Cl2
S-17: _CH2 =C( _CH3 )COO( _{CH2 ) 2SiCl3}
S-18: _CH2 =C( _CH3 )COO( _CH2 ) _3Si ( _CH3 ) _Cl2
S-19: _CH2 =C( _CH3 )COO( _{CH2 ) 3SiCl3}
S-20: _CH2 =CHSi( _C2H5 )( _{OCH3 ) 2}
S-21: _CH2 =C( _CH3 )Si( _OCH3 ) ₃
S-22: _CH2 =C( _CH3 )Si _{( OC2H5} ) ₃
S-23: _CH2 =CHSi( _OCH3 ) ₃
S-24: _CH2 =C( _CH3 )Si( _CH3 )( _OCH3 ) ₂
S-25: _CH2 =CHSi( _CH3 ) _Cl2
S-26: _CH2 =CHCOOSi( _OCH3 ) ₃
S-27: _CH2 = _CHCOOSi ( _OC2H5 ) ₃
S-28: _CH2 =C( _CH3 )COOSi( _OCH3 ) ₃
S-29: _CH2 =C( _CH3 )COOSi( _{OC2H5 ) 3}
S-30: _CH2 =C( _CH3 )COO( _CH2 ) _3Si ( _{OC2H5 ) 3}
S-31: _CH2 =CHCOO( _CH2 ) _2Si ( _CH3 ) ₂ ( _OCH3 )

In addition, 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 above exemplary compounds (S-1) to (S-31). The reactive organic group-containing surface modifier may be used alone or in a mixture of two or more types. The treatment amount (addition amount) of the reactive organic group-containing surface modifier is preferably within the range of 0.1 to 200 parts by mass, more preferably within the range of 7 to 70 parts by mass, per 100 parts by mass of the particles.

The method for treating untreated metal oxide particles with a reactive organic group-containing surface modifier is not particularly limited, but examples include a method of wet-disintegrating a slurry (a suspension of solid particles) containing untreated metal oxide particles and a reactive organic group-containing surface modifier. This method prevents re-agglomeration of the untreated metal oxide particles while simultaneously promoting surface modification of the untreated metal oxide particles. The solvent is then removed to produce a powder.

An example of a surface modification device is a wet media dispersion device. This wet media dispersion device is a device that has a process of crushing, pulverizing, and dispersing agglomerated particles of untreated metal oxide particles by filling a container with beads as media and rotating a stirring disk attached perpendicular to the rotating shaft at high speed. The wet media dispersion device is not limited as long as it can sufficiently disperse untreated metal oxide particles when performing surface modification on the untreated metal oxide particles and can perform surface modification, and various types can be adopted, such as vertical and horizontal types, continuous and batch types. Specific examples include sand mills, ultravisco mills, pearl mills, grain mills, dyno mills, agitator mills, and dynamic mills. These dispersion devices use grinding media (media) such as balls and beads to perform fine pulverization and dispersion by impact crushing, friction, shear, shear stress, etc.

As beads used in the wet media dispersion device, balls made of raw materials such as glass, alumina, zircon, zirconia, steel, flint, etc. can be used, but those made of zirconia or zircon are particularly preferred. The size of the beads is usually about 1 to 2 mm in diameter, but it is preferable to use beads of about 0.1 to 1.0 mm.
The disks and inner walls of the container used in the wet media dispersion type apparatus can be made of various materials such as stainless steel, nylon, and ceramic, but disks and inner walls of the container made of ceramics such as zirconia or silicon carbide are particularly preferred.
These metal oxide particles may be used alone or in combination of two or more kinds.

The content of the metal oxide particles depends on the particle size and resistance, but is preferably within the range of 5 to 25 volume % of the entire protective layer. If it is 5 volume % or more, a sufficient filler effect is obtained, and if it is 25 volume % or less, the film quality is good and it is possible to prevent the film resistance from becoming too small, which leads to a deterioration in dot reproducibility and image flow.

(Charge Transport Agent)
The protective layer according to the present invention preferably contains a charge transport material.
The charge transport agent is a substance that has a charge transporting property for transporting charge carriers in the protective layer and is a substance that can adjust the electrical resistance of the protective layer.
For example, amine compounds such as N,N-dialkylaniline compounds, diarylamine compounds, and triarylamine compounds, pyrazoline compounds, carbazole compounds, imidazole compounds, triazole compounds, oxazole compounds, styryl compounds, and stilbene compounds can be used.

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

[In general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom, an alkyl group having 1 to 7 carbon atoms, or an alkoxy group having 1 to 7 carbon atoms. k, l and n each represent an integer of 1 to 5, and m represents an integer of 1 to 4. However, when k, l, n or m is 2 or more, the multiple R ₁ , R ₂ , R ₃ or R ₄ may be the same or different.]

The charge transport agent having the structure represented by the general formula (1) may be, for example, one described in JP-A-2015-114454. It may also be synthesized by a known synthesis method, for example, the method disclosed in JP-A-2006-143720.

Examples of charge transport agents having the structure represented by the above general formula (1) include, but are not limited to, the following compounds (CTM-1 to CTM-17).

These charge transport materials may be used alone or in combination of two or more.
The amount of the charge transport agent added is preferably within the range of 5 to 30% by volume of the entire film. If it is 5% by volume or more, sufficient hole transport properties can be ensured and the effect of suppressing transfer memory can be improved. Also, if it is 39% by volume or less, the film quality is not deteriorated due to the plasticizer effect, the amount of scraping is reduced, and the life is extended.

(Specific radical scavengers)
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 specific radical scavenger functions as a blocking agent for crosslinking. That is, the specific radical scavenger can adjust the crosslink density by its addition ratio, etc. Therefore, since the cured resin component is obtained by polymerizing the polymerizable compound in the presence of a specific radical scavenger, the protective layer has an appropriate film strength (abrasion resistance), and the photoconductor surface is appropriately worn down by a cleaning means such as a cleaning blade. Therefore, even if discharge products or the like adhere to the photoconductor surface, the photoconductor surface is worn down and refreshed, so that image flow in the formed image can be prevented.

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

The specific radical scavenger may be a synthetic product or a commercially available product, and an example of a commercially available product is Sumilizer (registered trademark) GS manufactured by Sumitomo Chemical Co., Ltd.
The amount of the specific radical scavenger to be added is not particularly limited, but is preferably within the range of 1 to 30 parts by mass, more preferably within the range of 2 to 125 parts by mass, relative to 100 parts by mass of the polymerizable compound for constituting the curable resin component. When the amount is within the above range, the effect of extending the life of the photoreceptor and thus the electrophotographic image forming apparatus and reducing the frequency of toner slip-through can be further improved. In addition, the effect of suppressing image flow in the formed image can be obtained.

(Polymerization initiator)
The polymerizable compound for constituting the above-mentioned curable resin component is preferably polymerized using a polymerization initiator.
As the polymerization initiator, it is preferable to use a radical polymerization initiator. As the radical polymerization initiator, there is no particular limitation, but a photopolymerization initiator is preferable, among which an acylphosphine oxide compound, an alkylphenone compound, an oxime ester compound, and a thioxanthone compound are more preferable, and an acylphosphine oxide compound and an oxime ester compound are even more preferable. These polymerization initiators may be used alone or in combination of two or more kinds.

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

The oxime ester compound is not particularly limited, but 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 within a range of 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the polymerizable compound. Within the above range, the life of the photoreceptor and therefore the electrophotographic image forming apparatus is extended, the effect of suppressing transfer memory in the formed image, and the effect of reducing the frequency of toner slip-through are further improved.

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

The lubricant particles are not particularly limited, 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, trifluorochloroethylene resin, hexafluorochloroethylene propylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluorodichloroethylene 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 preferred.

<Conductive Support>
The conductive support constituting the photoreceptor is not particularly limited as long as it is conductive, and examples thereof include metals such as aluminum, copper, chromium, nickel, zinc, stainless steel, etc., formed into a drum or sheet shape, metal foils such as aluminum or copper laminated onto plastic films, plastic films onto which aluminum, indium oxide, tin oxide, etc. have been vapor-deposited, and metals, plastic films, and papers onto which a conductive layer has been provided by applying a conductive substance alone or together with a binder resin.

<Middle class>
The photoreceptor may have an intermediate layer between the conductive substrate and the photosensitive layer, the intermediate layer having a barrier function and an adhesive function. In consideration of preventing various types of failures, it is preferable to provide the intermediate layer.
Such an intermediate layer contains, for example, a binder resin (hereinafter, also referred to as "binder resin for intermediate layer") and, if necessary, conductive particles and metal oxide particles.
The binder resin for the intermediate layer is not particularly limited, and examples thereof include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide resin, polyurethane resin, gelatin, etc. Among these, alcohol-soluble polyamide resin is preferable. These binder resins for the intermediate layer may be used alone or in combination of two or more.

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

The number average primary particle size 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 kinds. When two or more kinds are mixed, they may be in the form of a solid solution or fusion.

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

<Charge Generation Layer>
The charge generating layer in the photosensitive layer constituting the photoreceptor contains a charge generating substance and a binder resin (hereinafter also referred to as "binder resin for charge generating layer").
Examples of the charge generating material include, but are not limited to, 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, polycyclic quinone pigments such as pyranthrone and diphthaloylpyrene, and phthalocyanine pigments. Among these, polycyclic quinone pigments and titanyl phthalocyanine pigments are preferred. These charge generating materials 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, such as 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 resins containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin), poly-vinyl carbazole resin, etc., but are not limited to these. Among these, polyvinyl butyral resin is preferred. These binder resins for the charge generation layer may be used alone or in a mixture of two or more.

The content of the charge generating material in the charge generating layer is preferably within a range of 1 to 600 parts by weight, and more preferably within a range of 50 to 500 parts by weight, per 100 parts by weight of the binder resin for the charge generating layer.
The thickness of the charge generating layer varies depending on the characteristics of the charge generating material, the characteristics and content of the binder resin for the charge generating layer, etc., but is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.05 to 3 μm.

<Charge Transport Layer>
The charge transport layer in the photosensitive layer constituting the photoreceptor contains a charge transport material and a binder resin (hereinafter also referred to as "binder resin for charge transport layer").
Examples of the charge transport material of the charge transport 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 material having high mobility and large molecular weight, and such a charge transport material is preferably different from the compound represented by the general formula (1).

The binder resin for the charge transport layer may be a known resin, such as polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylic acid ester resin, or styrene-methacrylic acid ester copolymer resin, with polycarbonate resin being preferred. Furthermore, polycarbonate resins of BPA (bisphenol A) type, BPZ (bisphenol Z) type, dimethyl BPA type, or BPA-dimethyl BPA copolymer type are preferred 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 types.

The content of the charge transport material in the charge transport layer is preferably within a range of 10 to 500 parts by weight, and more preferably within a range of 20 to 250 parts by weight, per 100 parts by weight of the binder resin for the charge transport layer.
The thickness of the charge transport layer varies depending on the characteristics of the charge transport material and the characteristics and content of the binder resin for the charge transport layer, but is preferably in the range of 5 to 40 μm, more preferably in the range of 10 to 30 μm.
The charge transport layer may contain an antioxidant, an electronic conductive agent, a stabilizer, silicone oil, etc. As the antioxidant, those disclosed in JP-A-2000-305291 and as the electronic conductive agent, those disclosed in JP-A-50-137543 and JP-A-58-76483 are preferred.

[Method of manufacturing organic photoreceptor]
The method for producing an organic photoreceptor of the present invention is characterized in that the protective layer is formed by using a circular slide hopper coating device.
Furthermore, the method for producing a photoreceptor of the present invention includes a step of forming an uncured film containing a polymerizable compound on a photosensitive layer on a conductive support, and a step of irradiating the uncured film with light to form a protective layer containing a cured resin. In the step of forming the protective layer, when irradiating the workpiece on which the uncured film has been formed with light, it is preferable to irradiate the workpiece with light by changing the conveying speed at any position on the workpiece. In addition, although not particularly limited, it is preferable to produce the photoreceptor by a production method having the following steps.

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

The concentration of each component in the coating solution for forming each layer is appropriately selected according to the thickness of each layer and the production speed.
In the coating liquid for forming each layer, means for dispersing particles such as conductive particles and metal oxide particles, charge generating substances, etc. may be, but is not limited to, an ultrasonic disperser, a ball mill, a sand mill, a homomixer, etc.
The method for applying the coating solution for forming each layer is not particularly limited, and examples thereof include known methods such as 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 slide hopper method.
The method for drying the coating film can be appropriately selected depending on the type of solvent and the layer thickness, but heat drying is preferred.

The steps of forming each layer will be described in detail below.
(Step (1): Formation of intermediate layer)
The intermediate layer can be formed by dissolving a binder resin for the intermediate layer in a solvent to prepare a coating liquid (hereinafter also referred to as "coating liquid for forming an intermediate layer"), dispersing conductive particles or metal oxide particles as necessary, applying the coating liquid to a certain layer thickness on a conductive support to form a coating film, and drying the coating film.

The intermediate layer forming coating liquid is preferably applied by a dip coating method.
The solvent used in the intermediate layer forming step is preferably one that disperses the conductive particles and metal oxide particles well and dissolves the binder resin for the intermediate layer, particularly the polyamide resin. 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 preferred because they have excellent solubility and coating performance for polyamide resins. In addition, examples of co-solvents that can be used in combination with the above solvent to improve storage stability and particle dispersibility and that provide favorable effects include benzyl alcohol, toluene, dichloromethane, cyclohexanone, and tetrahydrofuran.

(Step (2): Formation of Charge Generation Layer)
The charge generation layer can be formed by dispersing a charge generation material 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 a "coating liquid for forming the charge generation layer"); applying the coating liquid to a certain layer thickness on the intermediate layer to form a coating film; and drying the coating film.

The charge generating layer forming coating liquid is preferably applied by a dip coating method.
Examples of the solvent used in forming the charge generating layer include toluene, xylene, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate,
Examples of the solvent include, but are not limited to, 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, and diethylamine.

(Step (3): Formation of Charge Transport Layer)
The charge transport layer can be formed by preparing a coating liquid (hereinafter also referred to as a "coating liquid for forming a charge transport layer") in which a binder resin for the charge transport layer and a charge transport material are dissolved in a solvent, applying the coating liquid to a certain layer thickness on the charge generation layer to form a coating film, and drying the coating film.
The charge transport layer forming coating liquid is preferably applied by a dip coating method.
Examples of solvents used in forming the charge transport layer include, but are not limited to, toluene, xylene, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-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 can be formed by preparing a coating liquid (hereinafter also referred to as a "protective layer-forming coating liquid") by adding the polymerizable compound, the metal oxide particles, and, if necessary, other components such as a polymerization initiator, a specific radical scavenger, and a charge transport material to a known solvent, applying this protective layer-forming coating liquid to the outer peripheral surface of the charge transport layer formed in step (3) to form a coating film, drying this coating film, and irradiating it with active rays such as ultraviolet rays or electron beams to polymerize and harden the polymerizable compound components in the coating film, thereby forming the protective layer.

The protective layer-forming coating liquid is preferably applied by a slide hopper method using a circular slide hopper coating device, and can be applied by the method disclosed in, for example, JP-A-2015-114454.
As the solvent used in forming the protective layer, any solvent can be used as long as it can dissolve or disperse the polymerizable compound, metal oxide particles, etc., and examples thereof include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, tert-butanol, sec-butanol (2-butanol), benzyl alcohol, toluene, xylene, dichloromethane, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, diethylamine, and the like, but are not limited thereto.

The method for 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 cured resin component is produced by irradiating the coating with actinic radiation as a curing treatment, generating radicals to polymerize, and forming crosslinks through intermolecular and intramolecular crosslinking reactions to harden the coating. As the actinic radiation, ultraviolet rays and electron beams are more preferable, and ultraviolet rays are particularly preferable because they are easy to use.

The ultraviolet light source can be any light source that generates ultraviolet light, including, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, and a flash (pulse) xenon lamp.
Although the irradiation conditions differ depending on the lamp, the amount of actinic radiation is preferably within the range of 5 to 500 mJ/cm ² , and more preferably within the range of 5 to 100 mJ/cm ² .
The lamp power is preferably in the range of 0.1 to 5 kW, more preferably in the range of 0.5 to 4 kW, and even more preferably in the range of 0.5 to 3 kW.
The irradiation time for obtaining a necessary dose of actinic radiation is preferably from 0.1 seconds to 10 minutes, and from the viewpoint of work efficiency, more preferably from 0.1 seconds to 5 minutes.
In the step of forming the protective layer, drying can be carried out before, after, or during irradiation with actinic rays, and the timing of drying can be appropriately selected by combining these.

(Protective Layer Curing Device and Conditions)
In the present invention, the universal hardness is changed in a gradient along the axial direction of the photoreceptor by changing the light irradiation conditions after coating the protective layer, so that the gradient change amount is within the range of 10 to 50 N/ ^mm2 .
As described above, the universal hardness is correlated with the cumulative amount of light irradiated onto the photoconductor, so the universal hardness of the outermost surface layer of the photoconductor can be changed by changing the light irradiating device.
Therefore, for example, when using the light irradiation device described in JP 2013-57787 A or in the examples described later, by (i) changing the light irradiation intensity at any position when the photosensitive workpiece is pulled up from below, or (ii) changing the workpiece pull-up speed (i.e., changing the irradiation time), the integrated amount of light irradiated on the photosensitive drum surface in the long axis direction of the photosensitive body can be changed, and the surface hardness of the photosensitive body can be changed. In particular, the means of (ii) changing the workpiece pull-up speed is preferable.

[Electrophotographic Image Forming Apparatus]
The electrophotographic image forming apparatus of the present invention (hereinafter simply referred to as "image forming apparatus") is a tandem-type electrophotographic image forming apparatus comprising at least a charging means for charging the surface of an organic photoreceptor, a means for supplying a lubricant to the surface of the organic photoreceptor, and a means for removing toner remaining on the surface of the organic photoreceptor with a cleaning blade, and is characterized in that the organic photoreceptor of the present invention described above is used as the organic photoreceptor.
It is also preferable that the image forming apparatus comprises an exposure unit, a development unit, a transfer unit and a cleaning unit.
It is preferable that the lubricant supplying means is a means for supplying the lubricant in a fine powder form, which is externally added to the toner, to the organic photoreceptor by the action of a developing electric field formed in a means for forming a toner image (developing means).
The lubricant preferably contains zinc stearate.

The charging means is preferably a charging means of a proximity charging type such as a charging roller, a charging brush, a charging belt, or a charging blade. The use of such charging means tends to cause greater deterioration of the photoreceptor surface, so the effects of the present invention can be more pronounced. In particular, from the viewpoint of charging stability, it is preferable to use a charging roller as the charging means.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings, however, the present invention is not limited to the embodiment 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.
The image forming apparatus is called a tandem type color image forming apparatus, and is composed of four sets of image forming sections (image forming units) 10Y, 10M, 10C, and 10K, an intermediate transfer unit 70, a paper feed means 21a, and a fixing means 24. An original image reading device SC is disposed on the upper part of the main body A of the electrophotographic image forming apparatus.

The four image forming units 10Y, 10M, 10C, 10K are centered around photoconductors 1Y, 1M, 1C, 1K and are composed of charging means 2Y, 2M, 2C, 2K, exposure means 3Y, 3M, 3C, 3K, rotating 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.
In the electrophotographic image forming apparatus according to one embodiment of the present invention, the above-described photoconductor of the present invention is used as each of the photoconductors 1Y, 1M, 1C, and 1K.

The image forming units 10Y, 10M, 10C, and 10K have the same configuration except that the toners they contain are different colors, i.e., yellow (Y), magenta (M), cyan (C), and black (K), respectively. Therefore, the image forming unit 10Y will be described in detail below as an example.
The image forming unit 10Y has a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 6Y around a photoconductor 1Y which is an image forming body, and forms a yellow (Y) toner image on the photoconductor 1Y.

The charging means 2Y is a means for uniformly charging the surface of the photoreceptor 1Y to a negative polarity. In the electrophotographic image forming apparatus of this embodiment, it is preferable to use a charging roller as the charging means 2Y.
The charging roller is disposed close to the photoconductor, and a voltage of, for example, about −2.5 to −1.5 kV is applied to the charging roller to charge the photoconductor to a desired polarity and potential.
The voltage applied to the charging roller may be a DC charging method in which only a DC electric field is applied to charge the photoconductor, or an AC charging method in which a DC electric field superimposed with an AC electric field is applied to the charging member to charge the photoconductor. However, the AC charging method, which provides a smoothing effect by the AC electric field, is preferred because it provides superior charging uniformity.

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

The exposure means 3Y is a means for exposing the photoconductor 1Y, which has been given a uniform potential by the charging means 2Y, based on an image signal (yellow) to form an electrostatic latent image corresponding to the yellow image. This exposure means 3Y is composed of an LED in which light-emitting elements are arranged in an array in the axial direction of the photoconductor 1Y and an imaging element, or a laser optical system, etc. are used.

The developing means 4Y is composed of, for example, a developing sleeve (not shown) that has a built-in magnet and rotates while holding developer, a photosensitive member, and a voltage application device that applies a DC and/or AC bias voltage between the developing sleeve.
The developing unit 4Y contains a Y component developer (e.g., a two-component developer mainly composed of toner and a magnetic carrier). The developing unit 4Y visualizes the electrostatic latent image and forms a toner image by attaching the Y component toner to the surface of the photoconductor 1Y. Specifically, a developing bias is applied to the developing sleeve, and a developing electric field is formed between the photoconductor 1Y and the developing sleeve. Due to the potential difference between the photoconductor 1Y (negative polarity) and the developing sleeve, the charged toner (negative polarity) on the developing sleeve moves to and attaches to the exposed portion of the surface of the photoconductor 1Y. That is, the developing unit 4Y develops the electrostatic latent image by a reversal development method.

The cleaning means 6Y is a means for removing toner remaining on the surface of the photoreceptor 1Y. In this embodiment, the cleaning means 6Y includes a cleaning blade. This cleaning blade is composed of a support member (not shown) and a blade member supported on this support member via an adhesive layer (not shown). The blade member is arranged with its tip facing in the opposite direction (counter direction) to the rotation direction of the photoreceptor 1Y at the contact portion with the surface of the photoreceptor 1Y.

In the electrophotographic image forming apparatus shown in FIG. 2, the photoconductor 1Y, charging means 2Y, developing means 4Y, lubricant supply means (not shown) and cleaning means 6Y of the image forming unit 10Y are supported integrally and provided as a process cartridge, and this process cartridge may be configured to be detachable from the main body A of the apparatus via guide means such as rails.

The image forming units 10Y, 10M, 10C, and 10K are arranged in a vertical line, and an intermediate transfer unit 70 is arranged on the left side of the photoconductors 1Y, 1M, 1C, and 1K in the figure. The intermediate transfer unit 70 is made up of a semiconductive endless belt-like intermediate transfer body 77 wound around a plurality of rollers 71, 72, 73, and 74 and rotatably supported, a secondary transfer roller 5b as a secondary transfer means, and a cleaning means 6b.
The image forming units 10Y, 10M, 10C, and 10K and the intermediate transfer unit 70 are housed in a housing 80, and the housing 80 is configured so as to be capable of being pulled out from the apparatus main body A via support rails 82L and 82R.

The fixing means 24 may be, for example, a heat roller fixing type that is composed of a heating roller having a heat source inside and a pressure roller that is placed in pressure contact with the heating roller so as to form a fixing nip portion.
In FIG. 2, 20 denotes a paper feed cassette, 22A, 22B, 22C, and 22D denote intermediate rollers, 23a denotes a registration roller, 25a denotes a paper discharge roller, 26 denotes a paper discharge tray, and P denotes a transfer material.
2, the image forming apparatus of the present invention is shown as a color laser printer, but the electrophotographic image forming apparatus according to one embodiment of the present invention may be configured as a copier. In addition, in the image forming apparatus according to one embodiment of the present invention, a light source other than a laser, for example, an LED light source, can also 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 preferred image forming apparatus of the present invention, but other preferred examples include image forming apparatuses having image forming units corresponding to other colors, such as clear, white, gold, and silver.

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

The lubricant is not particularly limited and may be appropriately selected from known lubricants, but it is preferable that the lubricant contains a fatty acid metal salt.
The fatty acid metal salt is not particularly limited, but is preferably a metal salt of a saturated or unsaturated fatty acid having 10 or more carbon atoms. Examples thereof include zinc laurate, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, zinc stearate, aluminum stearate, 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 linoleate, cobalt linoleate, calcium linoleate, zinc ricinoleate, and cadmium ricinoleate. Among these, zinc stearate is preferred from the viewpoints of lubricity, spreadability and moisture absorption.

As the fatty acid metal salt, a synthetic product or a commercially available product may be used. An example of a commercially available product is 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, but examples include a means for supplying lubricant by applying a solid lubricant with a brush roller (hereinafter also referred to as a "lubricant application means").

When a lubricant applicator is used, for example, in the image forming unit 10Y of the image forming apparatus shown in Fig. 2, the lubricant applicator is preferably disposed downstream of the cleaning device 6Y and upstream of the charging device 2Y in the rotation direction of the photoreceptor 1Y. However, the location of the lubricant applicator is not limited to the downstream of the cleaning device 6Y and upstream of the charging device 2Y.
The lubricant application means is not particularly limited, but is preferably composed of, for example, a solid lubricant and a lubricant application member made of a brush roller. Specifically, the lubricant application means is preferably composed of a lubricant stock made of a solid lubricant having a rectangular parallelepiped shape, a brush roller that contacts the surface of the photoreceptor 1Y and applies the lubricant scraped off by rubbing the surface of the lubricant stock to the surface of the photoreceptor 1Y, a pressure spring that presses the lubricant stock against the brush roller, and a drive mechanism that rotates and drives the brush roller. The brush roller has a tip of a brush that contacts the surface of the photoreceptor 1Y. In addition, it is preferable that the brush roller is rotated at a constant speed in the same direction as the rotation direction of the photoreceptor 1Y. A leveling blade that uniformly applies the lubricant supplied to the surface of the photoreceptor 1Y by the lubricant application means may be provided downstream of the lubricant application means and upstream of the charging means 2Y.
In addition, the lubricant application means is not particularly limited and any known means can be appropriately referred to, for example, JP 2016-188950 A and the like.

The lubricant supplying means is not particularly limited, and may be, for example, a means (hereinafter also referred to as "toner containing means") that supplies a fine powder lubricant added externally to the toner base particles to a photoconductor (for example, 1Y in FIG. 2 above) by the action of a developing electric field formed in a developing means (for example, 4Y in FIG. 2 above). That is, the toner containing means is a means that supplies a fine powder lubricant contained in the toner to the photoconductor by the action of a developing electric field formed in the developing means.
The toner containing means is particularly preferred because, unlike the above-mentioned lubricant application means, it does not involve an intermediate member such as a brush roller, and therefore there is no contamination of the lubricant or variation in the amount of lubricant supplied due to contamination or deterioration of the intermediate member.

In the toner containing means, a fine powder lubricant is externally added to the toner base particles described later as an external additive. The volume-based median diameter Dw of the fine powder lubricant is preferably in the range of 0.3 to 25 μm, and more preferably in the range of 0.5 to 20 μm. In the above range, the size of the lubricant is appropriately small, so that the adhesive force with the toner base particles is appropriately large, and migration within the developing means is less likely to occur, resulting in a more sufficient supply of the lubricant. In addition, the size of the lubricant is appropriately large, so that the adhesive force with the toner base particles is appropriately small, and therefore the migration of the lubricant onto the photoconductor is easier. This allows the lubricant to be uniformly supplied onto the photoconductor.
The volumetric median diameter Dw of the lubricant is obtained by measuring and calculating using a device in which a Coulter Multisizer 3 (manufactured by Beckman Coulter) is connected to a computer system for data processing (manufactured by Beckman Coulter). It is also possible to measure the particle size of the lubricant in a state in which it is externally added to the toner base particles (colored particles) by a known method such as electron microscope photography. For the method of evaluating the volumetric median diameter Dw of a fine powder lubricant, the descriptions in paragraphs "0031" and "0032" of JP2010-175701A can be referred to. Details will be described in the Examples.

The amount of the fine powder lubricant added is preferably within a range of 0.01 to 0.5 parts by mass, and more preferably within a range of 0.03 to 0.3 parts by mass, based on the total mass of the toner. Within this range, the effect on the chargeability of the toner is suppressed, and the effects of the present invention are more effectively exhibited.
The method for mixing the toner base particles and the lubricant is not particularly limited, and any known method can be appropriately selected. For example, the mixing can be performed using a Henschel Mixer (registered trademark) manufactured by Nippon Coke and Engineering Co., Ltd.

[Toner and Developer]
In the present invention, the term "toner base particles" refers to a particle that constitutes the base of "toner particles." The "toner base particles" contain at least a binder resin and a colorant, and may contain other components such as a release agent (wax) and a charge control agent as necessary. The "toner base particles" are called "toner particles" when an external additive is added. And, "toner" refers to an aggregate of "toner particles."

In the image forming apparatus of the present invention, various known toners can be used without any particular limitation.
As the toner, either a pulverized toner or a polymerized toner can be used, but from the viewpoint of obtaining high quality images, it is preferable to use a polymerized toner.
The average particle size of the toner is not particularly limited, but is preferably within the range of 2 to 8 μm in volumetric median diameter, which allows for higher resolution.

In addition, as described above, when a lubricant supplying means is used that supplies the fine powder lubricant contained in the toner to the photoconductor by the action of the developing electric field formed in the developing means, the fine powder lubricant can be added externally to the toner base particles as an external additive.
Further, inorganic particles such as silica and titania having an average particle size of about 10 to 300 nm, and abrasives having an average particle size of about 0.2 to 3 μm can be added to the toner base particles in appropriate amounts as external additives.

When the toner is used as a two-component developer, the carrier may be magnetic particles made of conventionally known materials such as ferromagnetic metals such as iron, alloys of ferromagnetic metals with aluminum and lead, and compounds of ferromagnetic metals such as ferrite and magnetite. Of these, ferrite is particularly preferred.

The carrier is preferably coated with a resin or a so-called resin-dispersed carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, but it is preferable to use, for example, a cyclohexyl methacrylate-methyl methacrylate copolymer.
The volume-based median diameter of the carrier is preferably within a range of 15 to 100 μm, and more preferably within a range of 25 to 60 μm.
The concentration of the toner contained in the two-component developer is preferably within a 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.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these. In the following examples, unless otherwise specified, operations were performed at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

The structural formulas of the compounds used in the examples are shown below.

[Manufacture of organic photoreceptor workpiece [1]]
<Preparation of conductive support>
An electrically conductive support [1] was prepared by machining the surface of a cylindrical aluminum support having a diameter of 30 mm and a length of 360 mm to give a finely roughened surface.

<Formation of intermediate layer>
A dispersion having the following composition was diluted two-fold with the same mixed solvent, left to stand overnight, and then filtered (using a filter; Rigimesh 5 μm filter manufactured by Nippon Pall Corporation) to prepare a coating solution [1] for forming an intermediate layer.
Binder resin: Polyamide resin "CM8000" (manufactured by Toray Industries, Inc.)
1 part by mass Metal oxide particles: titanium oxide "SMT500SAS" (manufactured by Teika Corporation)
Dispersion was carried out for 10 hours in a batch manner using a sand mill as a dispersing machine. The intermediate layer forming coating solution [1] was applied onto a 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 material: 20 parts by weight of the following charge generating material (CG-1) Binder resin: Polyvinyl butyral resin "#6000-C"
(manufactured by Denki Kagaku Kogyo Co., Ltd.) 10 parts by weight Solvent: t-butyl acetate 700 parts by weight Solvent: 4-methoxy-4-methyl-2-pentanone
The mixture was mixed in an amount of 300 parts by weight and dispersed for 10 hours using a sand mill to prepare a coating solution [1] for forming a charge generating layer. The coating solution [1] for forming a charge generating layer was applied onto the intermediate layer [1] by a dip coating method to form a charge generating layer [1] having a dry thickness of 0.3 μm.

<Synthesis of Charge Generation Material (CG-1)>
(1) Synthesis of amorphous titanyl phthalocyanine 29.2 parts by mass of 1,3-diiminoisoindoline was dispersed in 200 parts by mass of o-dichlorobenzene, and 20.4 parts by mass of titanium tetra-n-butoxide was added thereto, followed by heating for 5 hours at 150 to 160° C. in a nitrogen atmosphere. After cooling, the precipitated crystals were filtered, washed with chloroform, washed with a 2% aqueous hydrochloric acid 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 in 250 parts by mass of concentrated sulfuric acid at 5° C. or lower by stirring for 1 hour, and the solution was poured into 5,000 parts by mass of water at 20° C. The precipitated crystals were filtered and thoroughly washed with water to obtain 225 parts by mass of a wet paste product.
This wet paste was frozen in a freezer and then 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 above amorphous titanyl phthalocyanine and 0.94 parts by mass of (2R,3R)-2,3-butanediol (0.6 equivalent ratio) (equivalent ratio is the equivalent ratio to titanyl phthalocyanine, the same applies hereinafter) were mixed in 200 parts by mass of orthodichlorobenzene (ODB) and heated and stirred for 6.0 hours at 60 to 70° C. After leaving it overnight, methanol was added to the reaction solution to filter the resulting crystals, and the filtered crystals were washed with methanol to obtain CG-1: 10.3 parts by mass (charge generating material containing (2R,3R)-2,3-butanediol adduct titanyl phthalocyanine).
The X-ray diffraction spectrum of the charge generating material (CG-1) shows clear peaks at 8.3°, 24.7°, 25.1°, and 26.5°. The mass spectrum shows peaks at 576 and 648, and the IR spectrum shows both Ti=O absorption at around 970 cm ^-1 and O-Ti-O absorption at around 630 cm ^-1 . Thermal analysis (TG) shows a mass loss of about 7% at 390 to 410°C, so it is presumed to be a mixture of a 1:1 adduct of titanyl phthalocyanine and (2R,3R)-2,3-butanediol and a non-adduct (non-added) titanyl phthalocyanine. The BET specific surface area of the obtained charge generating material (CG-1) was measured by a flow type automatic specific surface area measuring device (Micrometrics Flow Soap type: Shimadzu Corporation) and was found to be 31.2 m ² /g.

<Formation of Charge Transport Layer>
Charge transport material: 225 parts by weight of the above compound A, binder resin: 300 parts by weight of polycarbonate resin “Z300” (manufactured by Mitsubishi Gas Chemical Company, Inc.), antioxidant: 6 parts by weight of “Irganox 1010” (manufactured by BASF Japan Ltd.), solvent: 1,600 parts by weight of THF (tetrahydrofuran), solvent: 400 parts by weight of toluene, and 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.
This charge transport layer forming coating solution [1] was applied onto the charge generating layer [1] by dip coating to form a charge transport layer [1] having a dry thickness of 20 μm.

<Formation of protective layer>
The following metal oxide fine particles: tin oxide fine particles [1] 136 parts by weight, polymerizable compound: the above-mentioned exemplary compound (M1) 100 parts by weight, charge transport agent: the above-mentioned exemplary compound (CTM-1) 15 parts by weight, polymerization initiator: the above-mentioned exemplary compound (P1) 7 parts by weight, solvent: 2-butanol 280 parts by weight, solvent: tetrahydrofuran 70 parts by weight were mixed and stirred, and thoroughly dissolved and dispersed to prepare a protective layer forming coating liquid [1]. This protective layer forming coating liquid [1] was applied onto the charge transport layer [1] using a circular slide hopper coating device to form a coating film, and an uncured film was formed and dried at room temperature for 20 minutes. This was the organic photoreceptor workpiece [1].

[Manufacture of organic photoreceptor workpiece [2]]
The following metal oxide fine particles: silica fine particles [2] 54 parts by mass, polymerizable compound: the above-mentioned exemplary compound (M1) 100 parts by mass, charge transport agent: the above-mentioned exemplary compound (CTM-2) 36 parts by mass, polymerization initiator: the above-mentioned exemplary compound (P1) 7 parts by mass, radical scavenger: "Sumilizer GS (the above-mentioned general formula (1) in which R ₁ is a tert-pentyl group and R ₂ is a tert-pentyl group)" (manufactured by Sumitomo Chemical Co., Ltd.) 5 parts by mass, solvent: 2-butanol 280 parts by mass, and solvent: tetrahydrofuran 70 parts by mass were mixed, stirred, and thoroughly dissolved and dispersed to prepare a protective layer-forming coating liquid [2].
This protective layer forming coating solution [2] was applied to the charge transport layer [1] in the production of the organic photoreceptor workpiece [1] using a circular slide hopper coating device to form a coating film, and an uncured film was formed and dried at room temperature for 20 minutes. This is the organic photoreceptor workpiece [2].

[Manufacture of organic photoreceptor workpiece [3]]
The following metal oxide fine particles: tin oxide fine particles [1], 127 parts by mass; polymerizable compound: the above-mentioned exemplary compound (M1), 100 parts by mass; polymerization initiator: the above-mentioned exemplary compound (P1), 7 parts by mass of radical scavenger: "Sumilizer GS (in the above general formula (1), R ₁ is a tert-pentyl group and R ₂ is a tert-pentyl group)" (manufactured by Sumitomo Chemical Co., Ltd.), 280 parts by mass of 2-butanol solvent, and 70 parts by mass of tetrahydrofuran solvent were mixed, stirred, and thoroughly dissolved and dispersed to prepare a protective layer-forming coating liquid [2].
This protective layer forming coating solution [2] was applied to the charge transport layer [1] in the production of the organic photoreceptor workpiece [1] using a circular slide hopper coating device to form a coating film, and an uncured film was formed and dried at room temperature for 20 minutes. This is the organic photoreceptor workpiece [3].

[Manufacture of organic photoreceptor workpiece [4]]
The following metal oxide fine particles: tin oxide fine particles [1], 118 parts by mass, polymerizable compound: the above-mentioned exemplary compound (M1), 100 parts by mass, polymerization initiator: the above-mentioned exemplary compound (P1), solvent: 280 parts by mass, and solvent: tetrahydrofuran, were mixed, stirred, and thoroughly dissolved and dispersed to prepare a protective layer-forming coating solution [3].
This protective layer forming coating solution [3] was applied onto the charge transport layer [1] in the production of the organic photoreceptor workpiece [1] using a circular slide hopper coating device to form a coating film, and an uncured film was formed and dried at room temperature for 20 minutes. This is the organic photoreceptor workpiece [4].

<Preparation of tin oxide microparticles [1]>
The following tin oxide [1] was used as untreated metal oxide fine particles, and the above-mentioned exemplary compound (S-15) was used as a surface modifier to carry out surface modification as shown below to prepare tin oxide fine particles [1].
First, tin oxide (number average primary particle size: 20 nm, volume resistivity: 1.05×10 ⁵ (Ω·cm)) manufactured by CIK Nanotech Co., Ltd. was prepared as tin oxide [1].
Next, a mixture of 100 parts by mass of tin oxide [1], 30 parts by mass of a surface modifier (exemplary compound (S-15): CH ₂ ═C(CH ₃ )COO(CH ₂ ) ₃ Si(OCH ₃ ) ₃ ), and 300 parts of a mixed solvent of toluene/isopropyl alcohol = 1/1 (mass ratio) was placed in a sand mill together with zirconia beads and stirred at about 40° C. and a rotation speed of 1500 rpm to perform surface modification. Furthermore, the above treatment mixture was removed and placed in a Henschel mixer and stirred at a rotation speed of 1500 rpm for 15 minutes, and then dried at 120° C. for 3 hours to complete the surface modification, thereby producing surface-modified tin oxide microparticles [1].

<Preparation of Silica Microparticles [2]>
100 parts by mass of "silica fine particles" having a number average primary particle size of 20 nm as metal oxide fine particles, 10 parts by mass of "exemplified compound S-15" as a surface treatment agent, and 1000 parts by mass of methyl ethyl ketone were placed in a wet sand mill (media: alumina beads having a diameter of 0.5 mm) and mixed at 30° C. for 6 hours. Thereafter, the methyl ethyl ketone and alumina beads were separated from the silica fine particles by filtration, and the silica fine particles were dried at 60° C. In this manner, radically polymerizable silica fine particles [2] were prepared.

Table I-1 shows the amount of each material added to the protective layer in parts by mass, and Table I-2 shows the volume ratio of each material when the total volume of the protective layer is taken as 100. The calculations were made assuming a specific gravity of tin oxide of 6.95, a specific gravity of silica of 2.2, and a specific gravity of other organic materials of 1.1.

[Production of organic photoreceptor [1]]
The organic photoreceptor workpiece [1] was irradiated with light while moving it from the bottom to the top of the workpiece transport path space using a light irradiation device shown in Figures 3 and 4 (similar to Figures 1 and 3 described in JP-A-2013-57787), forming a 4.0 μm protective layer [1] and obtaining an organic photoreceptor [1]. The dimensions of the light irradiation device and workpiece, as well as the manufacturing conditions, are shown below.
The speed at which the workpiece passed through the light exit window during lifting was continuously slowed from 20 mm/s to 10 mm/s from the upper end to the lower end of the workpiece.
The conditions for the light irradiation device shown in FIG.

-Inner diameter of lower frame: 40mm
・Outer diameter of lower machine frame: 100 mm
- Inner diameter of partition wall: 46 mm
- Vertical length of lower frame: 870 mm
- Vertical length of upper machine frame: 8 mm
Vertical size of gas outlet: 3 mm
Vertical size of light exit window: 7 mm
Distance between gas discharge port and the bottom end of the machine frame (L ₁ ): 855 mm
Distance between gas discharge port and top end of machine frame ( _L2 ): 12 mm
Cross-sectional area of gas ascending passage: 7.82 ^cm2
- Inner diameter of triangular prism: 40 mm
Number of optical fibers constituting the light guide member: 4000 Optical fiber diameter φ: 0.2 mm
Light source: Xenon lamp, 4kW
Intensity (near the light exit window, wavelength 365 nm): 4000 mW/cm ²
- Light irradiation intensity (work surface): 1800 mW/ ^cm2
Nitrogen gas flow rate (constant): 4 L/min
(Distance between workpiece and light exit window: 5 mm)
(Distance between workpiece and gas outlet: 5 mm)

[Production of organic photoreceptors [2] to [ 6 ]]
As shown in Table II below, organic photoreceptors [2] to [ 6 ] were produced in the same manner as in Example I using each organic photoreceptor workpiece, except that the speed at which the light passed through the light exit window was changed.

[Universal hardness]
The universal hardness (HU) of each of the produced organic photoreceptors was measured by the following method.
The universal hardness (HU) can be measured using a commercially available hardness measuring device, and was measured under the following measurement conditions using an ultra-microhardness tester "H-100V" (manufactured by Fisher Instruments).
-Measurement condition-
Measuring instrument: Ultra-micro hardness tester "H-100V" (manufactured by Fisher Instruments)
Indenter shape: Vickers indenter (a=136°)
Measurement environment: 20°C, 60% RH
Maximum test load: 3mN
Loading speed: 3 mN/20 sec
Maximum load creep time: 5 seconds Unloading speed: 3 mN/20 seconds
For each photoreceptor, measurements were taken at four points 20 mm from the top end toward the bottom end, at 45° intervals in the circumferential direction, and the average of these four points was taken as the universal hardness of the top end. In addition, measurements were taken at three points 20 mm from the bottom end toward the top end, at equal angles in the circumferential direction, and the average of these three points was taken as the universal hardness of the bottom end. Furthermore, the difference between the calculated average universal hardness of the top end and the average universal hardness of the bottom end was calculated as the slope change, and is shown in the table below.

[evaluation]
The image forming apparatus used was a bizhub C658 (bizuhub is a registered trademark of the company) manufactured by Konica Minolta, Inc. The bizhub C658 is a tandem type color multifunction peripheral (MFP: Multi-Function Peripheral) that performs intermediate transfer and reversal development with a laser exposure of 780 nm wavelength. After printing and outputting 200,000 A4 size images with a printing area ratio of 5% for each color of YMCK on A4 size neutral paper under an atmosphere of 20 [°C] and relative humidity of 50 [% RH], a halftone image (b: relative reflection density 0.4 using a Macbeth densitometer) was printed, and the occurrence of density unevenness was evaluated.
The wear evaluation of each photoreceptor was carried out as follows.

(1) Abrasion The thickness of the photosensitive layer was measured before and after the durability test described above, and the amount of film thickness reduction was calculated and evaluated.
The difference between the average wear amount (upper end wear amount) of four points spaced 45° apart in the circumferential direction over a distance of 50 mm from the upper end to the lower end in the axial direction of the photosensitive member and the average wear amount (lower end wear amount) of four points spaced 45° apart in the circumferential direction over a distance of 50 mm from the lower end to the upper end was evaluated as the amount of uneven wear.
The film thickness was measured using an eddy current type film thickness measuring device "EDDY560C" (manufactured by HELMUT FISCHER GMBTE CO.).
The uneven wear was evaluated based on the following criteria. The evaluation results of "good" and "good" were judged to be acceptable.
(Evaluation criteria)
○: Uneven wear amount is less than 0.5 μm and there is no unevenness in density (passed)
△: The amount of uneven wear was 0.5 μm or more and less than 1.0 μm, and slight density unevenness occurred, but there was no problem in practical use (Pass).
×: Uneven wear amount is 1.0 μm or more, and density unevenness occurs (failure)

As shown by the above results, the photoreceptor of the present invention is able to suppress uneven wear and make wear more uniform than the photoreceptor of the comparative example.

100 Photoreceptor 101 Conductive support 102 Intermediate layer 103a Charge generating layer 103b Charge transport layer 103 Photosensitive layer 104 Protective layer 1Y, 1M, 1C, 1K Photoreceptors 2Y, 2M, 2C, 2K Charging means (charging roller)
3Y, 3M, 3C, 3K Exposure means 4Y, 4M, 4C, 4K Development means 5Y, 5M, 5C, 5K Primary transfer roller 5b Secondary transfer roller 6Y, 6M, 6C, 6K, 6b Cleaning means 10Y, 10M, 10C, 10K Image forming unit 20 Paper feed cassette 21a Paper feed means 22A, 22B, 22C, 22D Intermediate roller 23a Registration roller 24 Fixing means 25a Paper discharge roller 26 Paper discharge tray 70 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 11 Light source 12 Light guide member 13 Storage space 13A Light introduction port 13B Insertion hole 115 Light exit window 16 Triangular prism 19 Fixing member 21 Gas ascending flow path 23 Gas introduction flow path member 25 Gas discharge port 28 Gas introduction port 30 Machine frame 31 Lower machine frame 32 Upper machine frame S Work transport path space W Work 251 Substrate 254 Storage tank 255 Pressure pump 260 Coating head 261 Coating liquid outlet 262 Coating liquid distribution slit 263 Coating liquid distribution chamber 264 Supply pipe 265 Slide surface 266 Lip-like portion 267 Discharge port L Coating liquid F Uncured film

Claims (8)

An organic photoreceptor having at least an organic photosensitive layer formed on a cylindrical conductive support,
the universal hardness of the outermost layer in the image forming region of the organic photosensitive layer changes continuously and inclined along an axial direction parallel to a rotation axis from one end to the other end in the axial direction of the organic photoreceptor , and
The organic photoreceptor has a gradient change in the universal hardness along the axial direction in a range of 10 to 50 N/ ^mm2 . 2. An organic photoreceptor according to claim 1, wherein said slope change is in the range of 20 to 40 N/ ^mm2 . The organic photoreceptor according to claim 1 or 2, characterized in that the outermost layer is a protective layer containing at least metal oxide particles in a cured resin obtained by curing a polymerizable compound. 4. The organic photoreceptor according to claim 3, wherein the protective layer contains a charge transport material having a structure represented by the following general formula (1):

[In general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom, an alkyl group having 1 to 7 carbon atoms, or an alkoxy group having 1 to 7 carbon atoms. k, l and n each represent an integer of 1 to 5, and m represents an integer of 1 to 4. However, when k, l, n or m is 2 or more, the multiple R ₁ , R ₂ , R ₃ or R ₄ may be the same or different.] A tandem-type electrophotographic image forming apparatus comprising at least a charging means for charging a surface of an organic photoreceptor, a means for supplying a lubricant to the surface of the organic photoreceptor, and a means for removing toner remaining on the surface of the organic photoreceptor with a cleaning blade,
5. An electrophotographic image forming apparatus comprising the organic photoreceptor according to claim 1 as the organic photoreceptor. The electrophotographic image forming apparatus according to claim 5, characterized in that the lubricant supplying means supplies the lubricant in the form of fine powder, which is externally added to the toner, to the organic photoreceptor by the action of a developing electric field formed in a means for forming a toner image. The electrophotographic image forming apparatus according to claim 5 or 6, characterized in that the charging means is a charging roller. A method for producing the organic photoreceptor according to claim 3 or 4, comprising the steps of:
The method for producing an organic photoreceptor, wherein the protective layer is formed using a circular slide hopper coating apparatus.

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