JP2011022425A - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor in which the generation of an image defect caused by friction is suppressed while improving its durability compared with the case where the average density of a charge transport material in the surface region from the surface on the side far from a conductive support body to the inside of 1 μm in a charge transport layer is not 0.3 times or more nor 0.6 times or less the average density of the charge transport material in the whole charge transport layer. <P>SOLUTION: The electrophotographic photoreceptor includes: a conductive support body; and, in order from the side close to the conductive support body, a charge generation layer and a single charge transport layer containing a charge transport material, the film thickness of the charge transport layer is ≥38 μm, and, in the charge transport layer, the average density of the charge transport material in a region from the surface on the side far from the conductive support body to the inside of 1 μm is 0.3 to 0.6 times the average density of the charge transport material in the whole of the charge transport layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an image forming apparatus.

Electrophotographic image formation is widely used in fields such as copying machines and laser beam printers. As an electrophotographic photosensitive member used in an electrophotographic apparatus (hereinafter sometimes simply referred to as “photosensitive member”), an electrophotographic photosensitive member using an organic photoconductive material which is inexpensive and excellent in terms of manufacturability and disposal is mainly used. Has come to occupy. In particular, the functionally separated organic photoreceptor, in which a charge generation layer that generates charges upon exposure and a charge transport layer that transports charges, is superior in terms of electrophotographic characteristics, and various proposals have been made and put into practical use. It has become.
With respect to the organic photoreceptor, measures for extending the lifetime have been studied. For example, there is a method of further providing a surface protective layer on the charge transport layer.

In addition, as a photoreceptor having little deterioration in image quality and sensitivity even after long-term use, it has two or more charge transport layers, and at least the surface region side of the charge transport layer has a viscosity average molecular weight of 4.0 ×. The layer is a layer having a film thickness of 1 to 10 μm containing 10 ⁴ or more polycarbonate and 10 to 50% by weight of organic fine particles, and the concentration of the charge transport material in the charge transport layer on the substrate side is the charge transport on the surface region side. An electrophotographic photosensitive member having a density higher than that in the layer has been proposed (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 7-128872

  The problem of the present invention is that the average concentration of the charge transport material in the surface region from the surface farther from the conductive support in the charge transport layer to the inner side of 1 μm is less than the average concentration of the charge transport material in the entire charge transport layer. An object of the present invention is to provide an electrophotographic photosensitive member that improves the durability and suppresses the occurrence of image defects due to friction as compared with the case where it is not 3 times or more and 0.6 times or less.

  The above problem is solved by the following means. That is,

The invention according to claim 1
In order from the conductive support, the side closer to the conductive support, a charge generation layer, and a single charge transport layer containing a charge transport material,
The charge transport layer has a thickness of 38 μm or more,
In the charge transport layer, the average concentration of the charge transport material in the region from the surface far from the conductive support to the inner side of 1 μm is not less than 0.3 times the average concentration of the charge transport material in the entire charge transport layer. It is an electrophotographic photosensitive member that is 6 times or less.

The invention according to claim 2
2. The electrophotographic photosensitive member according to claim 1, wherein the concentration of the charge transport material in the charge transport layer continuously increases in the film thickness direction from the surface far from the conductive support toward the other surface. is there.

The invention according to claim 3
The electrophotographic photosensitive member according to claim 1 or 2,
A contact-type charging device for charging the surface of the electrophotographic photosensitive member;
An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
A developing device that develops an electrostatic latent image formed on the surface of the electrophotographic photosensitive member using toner to form a toner image;
A transfer device for transferring the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the transfer target;
An image forming apparatus having

The invention according to claim 4
The electrophotographic photosensitive member according to claim 1 or 2,
Contact type charging device for charging the surface of the electrophotographic photosensitive member, electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member, and forming on the surface of the electrophotographic photosensitive member using toner A developing device for developing the formed electrostatic latent image to form a toner image, a transfer device for transferring the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the transfer target, and the surface of the electrophotographic photosensitive member after transfer And at least one selected from the group consisting of cleaning devices for removing residual toner of
The process cartridge is detachable from the main body of the image forming apparatus.

According to the first aspect of the present invention, the average concentration of the charge transport material in the region from the surface far from the conductive support to the 1 μm inner side in the charge transport layer is the average concentration of the charge transport material in the entire charge transport layer. An electrophotographic photosensitive member is provided that suppresses the occurrence of image defects due to friction while improving durability, as compared with the case of not being 0.3 times or more and 0.6 times or less.
According to the invention of claim 2, the concentration of the charge transport material in the charge transport layer does not continuously increase in the film thickness direction from the surface far from the conductive support toward the other surface. As compared with the above, an electrophotographic photosensitive member that suppresses the occurrence of image defects due to friction is provided.
According to the invention of claim 3, the average concentration of the charge transport material in the region from the surface far from the conductive support to the 1 μm inner side in the charge transport layer is the average concentration of the charge transport material in the entire charge transport layer. An image forming apparatus is provided that suppresses the occurrence of image defects due to friction while improving durability as compared with the case of not having an electrophotographic photosensitive member that is 0.3 times or more and 0.6 times or less.
According to the invention of claim 4, the average concentration of the charge transport material in the region from the surface far from the conductive support to the 1 μm inner side in the charge transport layer is the average concentration of the charge transport material in the entire charge transport layer. A process cartridge is provided that improves the durability and suppresses the occurrence of image defects due to friction as compared with the case of not having an electrophotographic photosensitive member that is 0.3 times or more and 0.6 times or less.

1 is a schematic cross-sectional view showing a preferred embodiment of an electrophotographic photosensitive member of the present embodiment. It is a figure showing an example of the concentration gradient of the charge transport material in the charge transport layer according to this embodiment. 1 is a schematic configuration diagram showing a preferred embodiment of an electrophotographic apparatus of the present embodiment. It is a schematic block diagram which shows other embodiment of the electrophotographic apparatus of this embodiment. 1 is a schematic configuration diagram illustrating a preferred embodiment of a process cartridge according to the present embodiment. 3 is a concentration distribution of a charge transport material in a film thickness direction of the charge transport layer obtained in Example 1. FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  The present inventors examined increasing the thickness of the charge transport layer in order to improve durability. Although the durability against friction and the like is improved by increasing the thickness of the charge transport layer, the electrostatic capacity of the photoreceptor is reduced, and the potential of the photoreceptor surface is disturbed when charged by friction with other members. It has become clear that image defects are likely to occur. This image quality defect is particularly noticeable when the charge transport layer has a thickness of 38 μm or more, and it has been found that it becomes more prominent when combined with a highly sensitive charge generating material.

  Further, the image defect due to the frictional charging described above will be described. The charge transport material contained in the charge transport layer is a substance having a strong donor property or acceptor property in order to express its function. For example, in a negatively charged photoreceptor, a charge transport material having a strong donor property is used. Therefore, such a photoreceptor has a property of being easily positively charged by frictional charging when it comes into contact with another member. The presence of a charge transport material that is easily triboelectrically charged tends to disturb the image by charging.

  In view of the nature of the charge transport material, if the amount of the charge transport material on the surface is reduced, image quality defects due to frictional charging are reduced. However, if the total amount of the charge transport material present in the charge transport layer is reduced, the original charge transport capability is lowered. If the amount of the charge transport material is reduced until it is sufficiently effective to improve image quality defects due to frictional charging, it may cause a decrease in image density due to an increase in residual potential when used repeatedly. .

  In consideration of the above situation, the present inventors examined reducing the amount of the charge transport material in the surface region far from the support in the charge transport layer. As a result, image quality defects due to frictional charging can be suppressed, and in the case of the surface region, even if the amount of the charge transport material is reduced, the original function is not impaired, and a decrease in image density is suppressed even after repeated use. In particular, it has been clarified that the above effect is remarkably exhibited when a concentration gradient of the charge transport material is provided in the single charge transport layer.

In addition, although the reason that the said effect is show | played by reducing the quantity of charge transport material about a surface region is estimated as follows, this invention is not limited by the following estimation.
The frictional charging occurs remarkably when the process cartridge is installed in the main body of the image forming apparatus. After the installation, the frictional charging does not occur much. Further, when wear progresses with use, the thickness of the charge transport layer itself decreases, and the influence of frictional charging is reduced. Further, when the surface is scraped and the surface roughness is increased by use, the contact area is reduced, so that triboelectric charging is less likely to occur.

  From the above, it is presumed that image defects due to friction can be suppressed by reducing the amount of the charge transport material that is easily frictionally charged in the surface region. As a further effect, in the case of the surface region, even if the amount of the charge transport material is reduced, an increase in the residual potential upon repeated use is suppressed, and a decrease in image density is suppressed.

  Furthermore, in the method of providing a plurality of charge transport layers having different concentrations of the charge transport material, an interface exists between the plurality of charge transport layers, and the electrophotographic characteristics are unstable due to the interface, and the image quality is likely to be impaired. Revealed.

  As a result of further intensive studies by the present inventors, in the single charge transport layer, the concentration of the charge transport material on the surface is lowered, and the region from the surface far from the support to the inner side of 1 μm (hereinafter referred to as “surface”). The average concentration of the charge transport material in the region) may be 0.3 to 0.6 times the average concentration of the charge transport material in the entire charge transport layer, It has been found that image defects due to friction can be suppressed, and as a further effect, an increase in residual potential when used repeatedly is suppressed, and a decrease in image density is suppressed. Further, it has been found that the use of such a charge transport layer can achieve the above-described effect even in a highly sensitive photoreceptor using a highly sensitive charge generation layer.

Hereinafter, the electrophotographic photosensitive member of this embodiment will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of the electrophotographic photosensitive member of the present embodiment. An electrophotographic photosensitive member 1 shown in FIG. 1 includes a function-separated photosensitive layer 3 in which a charge generation layer 5 and a charge transport layer 6 are separately provided, and a conductive substrate (conductive support) (simply The subbing layer 4, the charge generation layer 5, and the charge transport layer 6 are stacked in this order on the substrate 2. Here, the charge transport layer 6 is the outermost layer (layer disposed on the side farthest from the base 2) in the photoreceptor 1. Hereinafter, each element of the photoreceptor 1 will be described.

  Any conductive substrate 2 may be used as long as it is conventionally used. For example, metals such as aluminum, nickel, chromium, stainless steel, and plastic films provided with thin films such as aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, ITO, etc. Examples thereof include paper coated with or impregnated with a property-imparting agent, and a plastic film. The shape of the substrate 2 is not limited to a drum shape, and may be a sheet shape or a plate shape.

When a metal pipe is used as the conductive substrate 2, the surface may remain as it is, or a process such as mirror cutting, etching, anodizing, rough cutting, centerless grinding, sand blasting, wet honing, etc. is performed in advance. May be.
In this specification, “conductive” means that the volume resistivity is less than 10 ⁷ Ω · cm, and the same applies hereinafter unless otherwise specified. “Semiconductive” means a volume resistivity of 10 ⁷ Ωcm or more and 10 ¹³ Ωcm or less, and the same applies hereinafter unless otherwise specified.

  The undercoat layer 4 is provided as necessary for the purpose of preventing light reflection on the surface of the substrate 2 and preventing inflow of unnecessary carriers from the substrate 2 to the photosensitive layer 3. Materials for the undercoat layer 4 include metal powders such as aluminum, copper, nickel, and silver, conductive metal oxides such as antimony oxide, indium oxide, tin oxide, and zinc oxide, carbon fiber, carbon black, and graphite. Examples thereof include a conductive material such as powder dispersed in a binder resin and coated on a support. Further, two or more kinds of metal oxide fine particles may be mixed and used. Furthermore, the metal oxide particles may be subjected to a surface treatment with a coupling agent to control the powder resistance.

The binder resin contained in the undercoat layer 4 includes acetal resins such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, and polyvinyl chloride resin. , Polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, and other known polymer resin compounds, and charge transport properties A charge transporting resin having a group or a conductive resin such as polyaniline is used.
Among these, resins that are insoluble in the upper coating solvent are preferably used, and phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, epoxy resins, and the like are particularly preferably used.

The ratio of the metal oxide particles and the binder resin in the undercoat layer 4 is not particularly limited and can be set arbitrarily.
When the undercoat layer 4 is formed, a coating solution in which the above components are added to a solvent is used. Examples of such solvents include aromatic hydrocarbon solvents such as toluene and chlorobenzene, aliphatic alcohol solvents such as methanol, ethanol, n-propanol, iso-propanol, and n-butanol, acetone, cyclohexanone, and 2-butanone. Ketone solvents, halogenated aliphatic hydrocarbon solvents such as methylene chloride, chloroform, ethylene chloride, cyclic or linear ether solvents such as tetrahydrofuran, dioxane, ethylene glycol, diethyl ether, methyl acetate, ethyl acetate, n acetate -Organic solvents, such as ester solvents, such as butyl.
These solvents may be used alone or in combination of two or more. When mixing, any solvent may be used as long as the binder resin dissolves as the mixed solvent.

  In addition, as a method for dispersing metal oxide particles in the coating solution for forming the undercoat layer, media dispersers such as a ball mill, a vibration ball mill, an attritor, a sand mill, a horizontal sand mill, an agitator, an ultrasonic disperser, a roll mill Medialess dispersers such as high-pressure homogenizers are used. Further, examples of the high-pressure homogenizer include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high pressure state, and a penetration method in which the fine liquid is penetrated and dispersed in a high pressure state.

As a method of applying the coating solution for forming the undercoat layer thus obtained on the substrate 2, a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating method, Examples include a curtain coating method.
The thickness of the undercoat layer 4 is preferably 15 μm or more, and more preferably 20 μm or more and 50 μm or less. Resin particles may be added to the undercoat layer 4 to adjust the surface roughness. Examples of the resin particles include silicone resin particles and cross-linked PMMA resin particles.

  Further, the surface of the undercoat layer 4 may be polished for adjusting the surface roughness. Examples of the polishing method include buffing, sandblasting, wet honing, and grinding.

Although not shown, an intermediate layer may be further provided on the undercoat layer 4 in order to improve electrical characteristics, improve image quality, improve image quality maintenance, and improve photosensitive layer adhesion.
The binder resin used for the intermediate layer is acetal resin such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate. In addition to polymer resin compounds such as resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, melamine resin, zirconium, titanium, aluminum, manganese, silicon atoms, etc. Contains organometallic compounds.
These compounds are used alone or as a mixture or polycondensate of a plurality of compounds. Among them, an organometallic compound containing zirconium or silicon is excellent in performance, such as a low residual potential, a small potential change due to the environment, and a small potential change due to repeated use.

As the solvent used for forming the intermediate layer, known organic solvents, for example, aromatic hydrocarbon solvents such as toluene and chlorobenzene, aliphatics such as methanol, ethanol, n-propanol, iso-propanol, and n-butanol Alcohol solvents, ketone solvents such as acetone, cyclohexanone and 2-butanone, halogenated aliphatic hydrocarbon solvents such as methylene chloride, chloroform and ethylene chloride, cyclic or straight chain such as tetrahydrofuran, dioxane, ethylene glycol and diethyl ether Examples include ether solvents, ester solvents such as methyl acetate, ethyl acetate, and n-butyl acetate.
These solvents are used alone or in combination of two or more. When mixing, any solvent can be used as long as it can dissolve the binder resin as a mixed solvent.

  As the coating method for forming the intermediate layer, usual methods such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating are applied.

  In addition to improving the coatability of the upper layer, the intermediate layer also serves as an electrical blocking layer. Therefore, when forming the intermediate layer, the thickness of the intermediate layer is set in the range of 0.1 μm to 3 μm. Further, the intermediate layer in this case may be used as the undercoat layer 4.

The charge generation layer 5 is formed by dispersing a charge generation material in an appropriate binder resin. As such a charge generation material, phthalocyanine pigments such as metal-free phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine are used.
In particular, a chlorogallium phthalocyanine crystal having strong diffraction peaks at Bragg angles (2θ ± 0.2 °) of at least 7.4 °, 16.6 °, 25.5 ° and 28.3 ° with respect to CuKα characteristic X-ray, CuKα Strong diffraction peaks at a Bragg angle (2θ ± 0.2 °) of at least 7.7 °, 9.3 °, 16.9 °, 17.5 °, 22.4 ° and 28.8 ° with respect to characteristic X-rays A metal-free phthalocyanine crystal having a Bragg angle (2θ ± 0.2 °) with respect to CuKα characteristic X-ray of at least 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 °, 25. Hydroxygallium phthalocyanine crystals having strong diffraction peaks at 1 ° and 28.3 °, Bragg angles (2θ ± 0.2 °) with respect to CuKα characteristic X-rays of at least 9.6 °, 24.1 ° and 27.2 ° Strong diffraction pea Titanyl phthalocyanine crystals having is preferred in view of high sensitivity.
In addition, when the charge transport layer according to the present embodiment is applied, even when the above-described highly sensitive charge generation material is used, image defects due to friction and a decrease in image density when used repeatedly are effective. It can be suppressed.

In addition, quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, anthrone pigments, quinacridone pigments and the like are used as charge generation materials. These charge generation materials may be used alone or in combination of two or more.
Examples of the binder resin in the charge generation layer include polycarbonate resin such as bisphenol A type or bisphenol Z type, acrylic resin, methacrylic resin, polyarylate resin, polyester resin, polyvinyl chloride resin, polystyrene resin, acrylonitrile-styrene copolymer Combined resin, acrylonitrile-butadiene copolymer, polyvinyl acetate resin, polyvinyl formal resin, polysulfone resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate, vinyl chloride-vinyl acetate -Maleic anhydride resin, silicone resin, phenol-formaldehyde resin, polyacrylamide resin, polyamide resin, poly-N-vinylcarbazole resin and the like.
These binder resins are used alone or in combination of two or more.

The mixing ratio of the charge generation material and the binder resin is preferably in the range of 10: 1 to 1:10.
When the charge generation layer 5 is formed, a coating solution in which the above components are added to a solvent is used. Examples of such solvents include aromatic hydrocarbon solvents such as toluene and chlorobenzene, aliphatic alcohol solvents such as methanol, ethanol, n-propanol, iso-propanol, and n-butanol, acetone, cyclohexanone, and 2-butanone. Ketone solvents, halogenated aliphatic hydrocarbon solvents such as methylene chloride, chloroform, ethylene chloride, cyclic or linear ether solvents such as tetrahydrofuran, dioxane, ethylene glycol, diethyl ether, methyl acetate, ethyl acetate, n acetate -Organic solvents, such as ester solvents, such as butyl.
These solvents are used alone or in combination of two or more. When mixing, any solvent can be used as long as it dissolves the binder resin as a mixed solvent.

  In order to disperse the charge generation material in the resin, the coating liquid is subjected to a dispersion treatment. As a dispersion method, a media disperser such as a ball mill, a vibrating ball mill, an attritor, a sand mill, or a horizontal sand mill, or a medialess disperser such as an agitator, an ultrasonic disperser, a roll mill, or a high-pressure homogenizer is used. Further, examples of the high-pressure homogenizer include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high pressure state, and a penetration method in which the fine liquid is penetrated and dispersed in a high pressure state.

Examples of methods for applying the coating solution thus obtained onto the undercoat layer 4 include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating, and the like. Is mentioned.
The film thickness of the charge generation layer 5 is desirably 0.01 μm or more and 5 μm or less, and more desirably 0.05 μm or more and 2.0 μm or less.

  The charge transport layer 6 corresponds to a surface layer in the electrophotographic photoreceptor 1 and is a single layer, and includes at least a charge transport material and a binder resin. The thickness of the charge transport layer 6 is 38 μm or more, and the charge transport material in the region (surface region) 6b from the surface far from the support (hereinafter sometimes referred to as “outermost surface”) 6a to the inner side of 1 μm. The average concentration is not less than 0.3 times and not more than 0.6 times the average concentration of the charge transport material in the entire charge transport layer 6.

  The average concentration of the charge transport material in the entire charge transport layer 6 is measured by FT-IR. Specifically, the entire charge transport layer is powdered and mixed with KBr, and then pressed to produce pellets. The infrared absorbance specific to the charge transport material and the binder component are measured by FT-IR, and the binder is measured. The ratio of the infrared absorbance of the charge transport layer to the infrared absorbance of the component is taken as the average concentration. Alternatively, the charge transport layer is cut at an angle, and the infrared absorbance at the position corresponding to the depth direction from the surface is measured by ATR on the shaved slope, and the infrared of the charge transport layer with respect to the infrared absorbance of the binder component is measured. The ratio of absorbance can also be an average value. In this case, it is an average value of 10 values in the film thickness direction.

The average concentration of the charge transport material in the surface region 6b is not less than 0.3 times and not more than 0.6 times, preferably not less than 0.3 times and 0.5 times the average concentration of the charge transport material in the entire charge transport layer 6. Is less than double.
The concentration of the charge transport material in the surface region 6b is measured by FT-IR. Specifically, FT-IR is measured at any five locations in the region from the outermost surface 6a to the inner side of 1 μm. The average value of the ratio of the infrared absorbance of the charge transport layer to the infrared absorbance of the binder component at this time is taken as the average concentration of the surface region 6b, and this average value is 0. 0 of the average concentration of the charge transport material in the entire charge transport layer. It is 3 times or more and 0.6 times or less.

  More preferably, the concentration gradient of the charge transport material continuously increases in the film thickness direction from the outermost surface of the charge transport layer 6 toward the boundary with the charge generation layer 5 as shown in FIG. . In the charge transport layer 6 having such a concentration gradient of the charge transport material, image defects due to friction and an increase in residual potential due to repeated use are effectively suppressed.

  Examples of the charge transport material include oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1- [ Pyrazoline derivatives such as pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline, triphenylamine, N, N′-bis (3,4-dimethylphenyl) biphenyl- Aromatic tertiary amino compounds such as 4-amine, tri (p-methylphenyl) aminyl-4-amine, dibenzylaniline, N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine Aromatic tertiary diamino compounds such as 3- (4'-dimethylaminophenyl) -5,6-di- (4'-methoxyphenyl) -1,2,4 1,2,4-triazine derivatives such as triazine, hydrazone derivatives such as 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, 6-hydroxy-2,3- Benzofuran derivatives such as di (p-methoxyphenyl) benzofuran, α-stilbene derivatives such as p- (2,2-diphenylvinyl) -N, N-diphenylaniline, enamine derivatives, carbazole derivatives such as N-ethylcarbazole, poly -Hole transport materials such as -N-vinylcarbazole and its derivatives, quinone compounds such as chloranil and broanthraquinone, tetraanoquinodimethane compounds, 2,4,7-trinitrofluorenone, 2,4,5,7 Fluoreno such as tetranitro-9-fluorenone And electron transport materials such as thiophene compounds, xanthone compounds, and thiophene compounds, and polymers having groups derived from the above-described compounds in the main chain or side chain. These charge transport materials are used alone or in combination of two or more.

  Examples of the binder resin in the charge transport layer 6 include polycarbonate resin such as bisphenol A type or bisphenol Z type, acrylic resin, methacrylic resin, polyarylate resin, polyester resin, polyvinyl chloride resin, polystyrene resin, acrylonitrile- Styrene copolymer resin, acrylonitrile-butadiene copolymer resin, polyvinyl acetate resin, polyvinyl formal resin, polysulfone resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate-anhydrous Insulating resins such as maleic acid resin, silicone resin, phenol-formaldehyde resin, polyacrylamide resin, polyamide resin, chlorine rubber, and polyvinylcarbazole, polyvinyl Anthracene, organic photoconductive polymers such as polyvinyl pyrene, and the like. These binder resins are used alone or in combination of two or more.

  The charge transport layer 6 is formed using a coating solution in which the above components are added to a solvent. Solvents used for forming the charge transport layer include known organic solvents, for example, aromatic hydrocarbon solvents such as toluene and chlorobenzene, and fats such as methanol, ethanol, n-propanol, iso-propanol, and n-butanol. Aromatic alcohol solvents, ketone solvents such as acetone, cyclohexanone and 2-butanone, halogenated aliphatic hydrocarbon solvents such as methylene chloride, chloroform and ethylene chloride, cyclic or straight chain such as tetrahydrofuran, dioxane, ethylene glycol and diethyl ether And ether solvents such as methyl ether, methyl acetate, ethyl acetate, and n-butyl acetate. These solvents may be used alone or in combination of two or more.

  Among these solvents, the average concentration of the charge transport material in the charge transport layer 6 according to the present embodiment, that is, the surface region 6b is 0.3 times or more and 0.6 times the average concentration of the charge transport material in the entire charge transport layer 6. In order to achieve the following, it is preferable to use a solvent having a solubility of the charge transport material of 500 mg / mL or less, more preferably 300 mg / mL or less.

The electrophotographic photosensitive member is generally produced by a dip coating method, but the surface layer preferably has a smooth surface in order to obtain a good image. An organic solvent is used for the coating solution, but an orange peel (skin skin) or the like is likely to be generated on the surface during drying, and a leveling agent is often used to prevent this. Dimethyl silicone oil is often used as the leveling agent.
In addition, fluorine particles such as PTFE may be dispersed in the charge transport layer 6 for the purpose of reducing the friction coefficient. The amount of the fluorine-based particles to be dispersed is preferably 0.5% by mass or more and 20% by mass or less in the charge transport layer, and more preferably 2% by mass or more and 10% by mass or less.

  As a dispersion method for dispersing the fluorine-based resin particles in the charge transport layer forming coating solution used to form the charge transport layer 6, media dispersion such as a ball mill, a vibration ball mill, an attritor, a sand mill, and a horizontal sand mill can be used. A medialess disperser such as an agitator, an agitator, an ultrasonic disperser, a roll mill, or a high pressure homogenizer is used. Further, examples of the high-pressure homogenizer include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high pressure state, and a penetration method in which the fine liquid is penetrated and dispersed in a high pressure state.

The charge transport layer forming coating solution thus obtained can be applied on the charge generation layer 5 by dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating. Ordinary methods such as curtain coating are used.
The film thickness of the charge transport layer is preferably from 38 μm to 60 μm, and more preferably from 39 μm to 45 μm.

  The charge transport layer 6 according to the present embodiment includes a coating film formed from the solubility of the coating solvent and the charge transport material, the compatibility between the charge transport material and the binder resin, the volatilization rate of the coating solvent, and the coating liquid for forming the charge transport layer. It is produced in consideration of the drying speed of the. Specifically, the charge transport layer according to this embodiment is produced by selecting the type of solvent and / or adjusting the molecular weight of the charge transport material and the binder resin.

The reason why the charge transport layer according to this embodiment is produced by the above adjustment is presumed as follows.
When the coating film is formed by applying the charge transport layer forming coating solution, drying starts from the surface of the coating film. When the binder resin in the coating film is fixed by drying, the charge transport material having a small molecular weight moves to the unsolidified inner side. As this occurs sequentially, it is assumed that the concentration distribution of the charge transport material in the film thickness direction as shown in FIG. 2 is formed.

As a solvent for forming the charge transport layer according to this embodiment, it is desirable to use tetrahydrofuran and toluene together, and the mixing ratio is a mass ratio, and tetrahydrofuran: toluene is 9: 1 or more and 3: 7 or less. It is desirable that it is 9: 1 or more and 5: 5 or less.
In the mixed solvent of tetrahydrofuran and toluene, when the content ratio of toluene is increased, the difference in the concentration gradient of the charge transport material is decreased, and when the content ratio of tetrahydrofuran is increased, the difference in the concentration gradient of the charge transport material is increased.

  The molecular weight of the binder resin is preferably 8000 or more and 100,000 or less, and more preferably 10,000 or more and 40000 or less, as the weight average molecular weight Mw.

The molecular weight of the binder resin was measured using “HLC-8120GPC, SC-8020 (manufactured by Tosoh Corporation)” as GPC (gel permeation chromatography) and “TSKgel, SuperHM-H (Tosoh ( Two (6.0 mm ID × 15 cm) ”manufactured by the company, and THF (tetrahydrofuran) is used as an eluent.
The measurement was performed at a sample concentration of 0.5% by mass and a flow rate of 0.6 ml / min. Sample injection volume 10 μl, measurement temperature 40 ° C., using an IR detector. The calibration curve is "Polystylene standard sample TSK standard" manufactured by Tosoh Corporation: "A-500", "F-1", "F-10", "F-80", "F-380", "A-2500 ”,“ F-4 ”,“ F-40 ”,“ F-128 ”, and“ F-700 ”.

  The molecular weight of the charge transport material is preferably 200 or more and 3000 or less, more preferably 300 or more and 1500 or less, and more preferably 400 or more and 1000 or less.

  For the purpose of preventing deterioration of the photoreceptor due to ozone, nitrogen oxide, light, or heat generated in the image forming apparatus, an antioxidant, a light stabilizer, a heat stabilizer, etc. are included in each layer constituting the photosensitive layer 3. Additives may be added. For example, examples of the antioxidant include hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds. Examples of light stabilizers include derivatives such as benzophenone, benzoazole, dithiocarbamate, and tetramethylpipen.

Next, the electrophotographic apparatus and the process cartridge of this embodiment will be described.
The electrophotographic apparatus of this embodiment includes at least an electrophotographic photosensitive member, a contact-type charging device that charges the surface of the electrophotographic photosensitive member, and a static image that forms an electrostatic latent image on the charged surface of the electrophotographic photosensitive member. An electrostatic latent image forming device, a developing device that develops an electrostatic latent image formed on the surface of the electrophotographic photosensitive member using toner to form a toner image, and a toner image formed on the surface of the electrophotographic photosensitive member And a transfer device for transferring the image to the surface of the transfer object.

  FIG. 3 is a cross-sectional view schematically showing a basic configuration of a preferred embodiment of the electrophotographic apparatus of this embodiment. An electrophotographic apparatus 200 shown in FIG. 3 is connected to the electrophotographic photosensitive member 207 of the present embodiment, a contact charging type charging device (contact charging device) 208 that charges the electrophotographic photosensitive member 207, and the charging device 208. A power source 209, an exposure device 210 that forms an electrostatic latent image by exposing the electrophotographic photosensitive member 207 charged by the charging device 208, and a toner that develops the electrostatic latent image formed by the exposure device 210 with toner. The image forming apparatus includes a developing device 211 that forms an image, a transfer device 212 that transfers a toner image formed by the developing device 211 to a transfer medium 500, a cleaning device 213, a static eliminator 214, and a fixing device 215. In this case, the static eliminator 214 may not be provided.

  The contact charging device 208 has a charging roll, and a voltage is applied to the charging roll when the photosensitive member 207 is charged. As the voltage range, the DC voltage is preferably positive or negative 50 V or more and 2000 V or less, more preferably 100 V or more and 1500 V or less, depending on the required photosensitive member charging potential. When the AC voltage is superimposed, the peak-to-peak voltage is desirably 400 V or more and 1800 V or less, more desirably 800 V or more and 1600 V or less, and further desirably 1200 V or more and 1600 V or less. The frequency of the AC voltage is desirably 50 Hz or more and 20,000 Hz or less, and more desirably 100 Hz or more and 5,000 Hz or less.

  As the charging roll, one provided with an elastic layer, a resistance layer, a protective layer, etc. on the outer peripheral surface of the core material is preferably used. The charging roll rotates at a peripheral speed following the photosensitive member by contacting the photosensitive member 207 without contacting the photosensitive member 207, and functions as a charging device. May be charged by rotating at different peripheral speeds.

When the roller-shaped member is brought into contact with the photosensitive member, the roller member rotates at a peripheral speed following the photosensitive member without any driving means, and functions as a charging device. However, some driving means may be attached to the roller member, and the roller member may be charged by rotating at a peripheral speed different from that of the photosensitive member.
The core material is conductive and generally used is iron, copper, brass, stainless steel, aluminum, nickel, or the like. In addition, a resin molded product in which conductive particles or the like are dispersed may be used.
The material of the elastic layer has conductivity or semiconductivity, and generally is a material in which conductive particles or semiconductive particles are dispersed in a rubber material. As the rubber material, EPDM, polybutadiene, natural rubber, polyisobutylene, SBR, CR, NBR, silicone rubber, urethane rubber, epichlorohydrin rubber, SBS, thermoplastic elastomer, norbornene rubber, fluorosilicone rubber, ethylene oxide rubber and the like are used.

Examples of the conductive particles or semiconductive particles include carbon black, zinc, aluminum, copper, iron, nickel, chromium, titanium, and other metals, ZnO—Al ₂ O ₃ , SnO ₂ —Sb ₂ O ₃ , In ₂ O ₃ — Metal oxides such as SnO ₂ , ZnO—TiO ₂ , MgO—Al ₂ O ₃ , FeO—TiO ₂ , TiO ₂ , SnO ₂ , Sb ₂ O ₃ , In ₂ O ₃ , ZnO, MgO can be used, These materials may be used alone or in combination of two or more.

Resistance layer and dispersed conductive particles or semiconductive particles in the binder resin as the material of the protective layer, obtained by controlling the resistance, desirably 10 ³ [Omega] cm or more 10 ¹⁴ [Omega] cm or less as resistivity, 10 ⁵ More preferably, it is Ωcm or more and 10 ¹² Ωcm or less, and more preferably 10 ⁷ Ωcm or more and 10 ¹² Ωcm or less. The film thickness is preferably from 0.01 μm to 1000 μm, more preferably from 0.1 μm to 500 μm, and even more preferably from 0.5 μm to 100 μm.

  As binder resin, acrylic resin, cellulose resin, polyamide resin, methoxymethylated nylon, ethoxymethylated nylon, polyurethane resin, polycarbonate resin, polyester resin, polyethylene resin, polyvinyl resin, polyarylate resin, polythiophene resin, PFA, FEP, A polyolefin resin such as PET, a styrene butadiene resin, or the like is used.

  As the conductive particles or semiconductive particles, the same carbon black, metal, and metal oxide as the elastic layer are used. If necessary, an antioxidant such as hindered phenol and hindered amine, a filler such as clay and kaolin, and a lubricant such as silicone oil may be added. As a means for forming these layers, a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like is used.

  As the exposure device 210, an optical system device or the like that exposes a light source such as a semiconductor laser, an LED (light emitting diode), a liquid crystal shutter, or the like on the surface of the electrophotographic photosensitive member is used.

  As the developing device 211, a known developing device using a normal or reversal developer such as a one-component system or a two-component system is used. The shape of the toner used in the developing device 211 is not particularly limited, and may be indefinite, spherical or other specific shape.

  Examples of the transfer device 212 include a roller-type contact charging member, a contact-type transfer charger using a belt, a film, a rubber blade, or the like, or a scorotron transfer charger or a corotron transfer charger using corona discharge. It is done.

  The cleaning device 213 is for removing residual toner adhering to the surface of the electrophotographic photosensitive member after the transfer process. The cleaned electrophotographic photosensitive member is repeatedly used for the image forming process described above. . As the cleaning device, a cleaning blade, brush cleaning, roll cleaning, or the like is used. Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

  The electrophotographic apparatus of this embodiment may further include a static eliminator 214 such as an erase light irradiation apparatus as shown in FIG. Thereby, when the electrophotographic photosensitive member is repeatedly used, the phenomenon that the residual potential of the electrophotographic photosensitive member is brought into the next cycle is prevented, so that the image quality is further improved.

  FIG. 4 is a cross-sectional view schematically showing the basic configuration of another embodiment of the electrophotographic apparatus of this embodiment. An electrophotographic apparatus 220 shown in FIG. 4 is an intermediate transfer type electrophotographic apparatus. In the housing 400, four electrophotographic photoreceptors 401a to 401d (for example, the electrophotographic photoreceptor 401a is yellow and the electrophotographic photoreceptor 401b is magenta). The electrophotographic photosensitive member 401c forms an image of cyan and the electrophotographic photosensitive member 401d forms a black image), which are arranged in parallel along the intermediate transfer belt 409.

Here, the electrophotographic photoreceptors 401a, 401b, 401c, and 401d mounted on the electrophotographic apparatus 220 are the electrophotographic photoreceptors of this embodiment, respectively.
Each of the electrophotographic photosensitive members 401a, 401b, 401c, and 401d can be rotated in a predetermined direction (counterclockwise on the paper surface), and the charging rolls 402a, 402b, 402c, and 402d are developed along the rotation direction. 404a, 404b, 404c, 404d, primary transfer rolls 410a, 410b, 410c, 410d, and cleaning blades 415a, 415b, 415c, 415d are arranged. Each of the developing devices 404a, 404b, 404c, and 404d is supplied with toners of four colors of black, yellow, magenta, and cyan accommodated in the toner cartridges 405a, 405b, 405c, and 405d, and the primary transfer roll 410a, 410b, 410c, and 410d are in contact with the electrophotographic photosensitive members 401a, 401b, 401c, and 401d through the intermediate transfer belt 409, respectively.

  Further, a laser light source (exposure device) 403 is arranged in the housing 400, and irradiates the surfaces of the charged electrophotographic photosensitive members 401a, 401b, 401c, and 401d with laser light emitted from the laser light source 403. As a result, charging, exposure, development, primary transfer, and cleaning are sequentially performed in the rotation process of the electrophotographic photosensitive members 401a, 401b, 401c, and 401d, and the toner images of the respective colors are superimposed on the intermediate transfer belt 409. Transcribed.

  The intermediate transfer belt 409 is supported with a predetermined tension by a drive roll 406, a support roll 408, and a tension applying roll 407, and can rotate without causing deflection due to the rotation of these rolls. The secondary transfer roll 413 is disposed so as to be in contact with the support roll 408 through the intermediate transfer belt 409. The intermediate transfer belt 409 that has passed between the support roll 408 and the secondary transfer roll 413 is cleaned by, for example, a cleaning blade 416 disposed in the vicinity of the drive roll 406 and then repeatedly used for the next image forming process. Is done.

  A tray (transfer medium tray) 411 is provided in the housing 400, and the transfer medium 500 such as paper in the tray 411 is transferred between the intermediate transfer belt 409 and the secondary transfer roll 413 by the transfer roll 412. In addition, the paper is sequentially transferred between two fixing rolls 414 that are in contact with each other, and then discharged to the outside of the housing 400.

  In the above description, the case where the intermediate transfer belt 409 is used as the intermediate transfer member has been described. However, the intermediate transfer member may have a belt shape like the intermediate transfer belt 409 or a drum shape. Also good. In the case of a belt shape, conventionally known resins are used as the resin material used as the base material of the intermediate transfer member. For example, polyimide resin, polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene terephthalate (PAT), ethylenetetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, PC / PAT blend material, polyester Resin materials such as polyether ether ketone and polyamide, and resin materials using these as main raw materials. Further, a resin material and an elastic material may be blended and used.

Next, the process cartridge of this embodiment will be described.
The process cartridge of the present embodiment is detachable from the main body of the image forming apparatus, and includes at least an electrophotographic photosensitive member, a charging device that charges the surface of the electrophotographic photosensitive member, and the surface of the charged electrophotographic photosensitive member An electrostatic latent image forming device for forming an electrostatic latent image on the surface, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member using toner to form a toner image, and the surface of the electrophotographic photosensitive member And at least one selected from the group consisting of a transfer device for transferring the toner image formed on the surface of the transfer member and a cleaning device for removing residual toner on the surface of the electrophotographic photosensitive member after transfer. Have.

  FIG. 5 is a cross-sectional view schematically showing a basic configuration of a preferred embodiment of a process cartridge including the electrophotographic photosensitive member of the present embodiment. In the process cartridge 300, a charging device 208, a developing device 211, a cleaning device 213, an opening 218 for exposure, and an opening 217 for static elimination exposure are combined with an electrophotographic photosensitive member 207 using a mounting rail 216. , And integrated.

  The process cartridge 300 is detachable from the main body of the electrophotographic apparatus including the transfer device 212, the fixing device 215, and other components (not shown). It constitutes a photographic apparatus.

  According to the electrophotographic apparatus and the process cartridge, an electrophotographic cartridge and an electrophotographic apparatus are provided in which fluctuations in electrical characteristics and occurrence of image quality defects are suppressed even when the photosensitive member is rubbed due to vibration or long-term storage.

  The transfer medium is not particularly limited as long as it is a medium that transfers a toner image formed on the electrophotographic photosensitive member. For example, when transferring directly from an electrophotographic photosensitive member to a transfer medium such as paper, paper or the like is the transfer medium. When an intermediate transfer member is used, the intermediate transfer member is a transfer medium.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Example 1]
100 parts by mass of zinc oxide (average particle size: 70 nm, manufactured by Teica, specific surface area value: 15 m ² / g) is stirred and mixed with 500 parts by mass of tetrahydrofuran, and KBM603 (manufactured by Shin-Etsu Chemical Co., Ltd.) 1 is used as a silane coupling agent. .25 parts by mass was added and stirred for 2 hours. Thereafter, tetrahydrofuran was distilled off under reduced pressure, baking was performed at 120 ° C. for 3 hours, and zinc oxide particles surface-treated with a silane coupling agent were obtained.

  60 parts by mass of the surface-treated zinc oxide particles, 0.6 parts by mass of alizarin, 13.5 parts by mass of blocked isocyanate (Sumidule 3173, manufactured by Sumitomo Bayern Urethane Co., Ltd.) as a curing agent, and butyral resin (BM-1, manufactured by Sekisui Chemical Co., Ltd.) 15 parts by mass, 38 parts by mass of a solution obtained by dissolving 85 parts by mass of methyl ethyl ketone and 25 parts by mass of methyl ethyl ketone are mixed, and 4 hours in a sand mill using glass beads having a diameter of 1 mm. The dispersion liquid was obtained.

  To the obtained dispersion, 0.005 parts by mass of dioctyltin dilaurate and 4.0 parts by mass of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicone) are added as a catalyst to obtain an undercoat layer coating solution. It was. This coating solution was applied onto an aluminum substrate having a diameter of 30 mm by a dip coating method, followed by drying and curing at 180 ° C. for 40 minutes to obtain an undercoat layer having a thickness of 25 μm.

  Next, as a charge generation material, at least 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 °, Bragg angle (2θ ± 0.2 °) with respect to CuKα characteristic X-ray, 15 parts by mass of hydroxygallium phthalocyanine crystals having strong diffraction peaks at 25.1 ° and 28.3 °, 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Union Carbide) and n-butyl alcohol 300 parts by mass of the mixture was dispersed in a sand mill for 4 hours using glass beads having a diameter of 1 mm to obtain a coating solution for a charge generation layer. This charge generation layer coating solution was dip coated on the undercoat layer and dried to obtain a charge generation layer having a thickness of 0.2 μm.

  Next, 0.5 parts by mass of tetrafluoroethylene resin particles (average particle size: 0.2 μm) and 0.01 part by mass of Aron GF400 (manufactured by Toagosei Co., Ltd.) as a dispersion aid, 4 parts by mass of tetrahydrofuran, toluene The mixture was thoroughly stirred and mixed with 1 part by mass to obtain a tetrafluoroethylene resin particle suspension.

  Next, 4 parts by mass of N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine as a charge transport material, 6 parts by mass of bisphenol Z-type polycarbonate resin (viscosity average molecular weight: 40,000), oxidation As an inhibitor, 0.1 part by mass of 2,6-di-t-butyl-4-methylphenol was mixed, and 24 parts by mass of tetrahydrofuran and 11 parts by mass of toluene were mixed and dissolved.

After adding the tetrafluoroethylene resin particle suspension to this and stirring and mixing, 500 kgf / cm ² using a high pressure homogenizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.) equipped with a through-type chamber having a fine flow path. 200 ppm of a leveling agent (KP340, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the obtained coating material obtained by repeating the dispersion treatment under pressure up to 6 times to obtain a coating material for forming a charge transport layer.
This coating solution was dip-coated on the charge generation layer in an environment of 30 ° C. and dried at 115 ° C. for 40 minutes to form a charge transport layer having a thickness of 40 μm, thereby obtaining the intended electrophotographic photosensitive member.

When the concentration of the charge transport material in the charge transport layer of the photoreceptor was confirmed by FT-IR by the above-described method, the average concentration of the charge transport material in the surface region of the charge transport layer was found to be the charge transport of the entire charge transport layer. It was 0.45 times the average concentration of the material. The concentration distribution of the charge transport material in the film thickness direction of the charge transport layer was measured by FT-IR, and the result is shown in FIG. Note that the concentration distribution in FIG. 6 is the concentration of the charge transport material obtained by using the infrared absorbance of 1590 cm ⁻¹ as the absorption of the charge transport material and 1011 cm ⁻¹ infrared absorbance as the absorption of the binder resin.
Using the photoreceptor thus obtained, the following tests were conducted.

  The initial image quality is evaluated by mounting the photosensitive member on a process cartridge for DocuCenter C3300 manufactured by Fuji Xerox Co., Ltd., and vibrating the process cartridge under the vibration conditions (1) to (3) shown in Table 1 and then the process cartridge. Was mounted on the DocuCentre C3300. A full-tone halftone image with an image area of 30% is printed on A3 paper in a 22 ° C./55% RH environment, and an image of a location that was not in contact with the image density where the charging member was in contact when vibrated. The concentration was measured with a Macbeth densitometer and evaluated according to the following evaluation criteria. The obtained results are shown in Table 2.

(Double-circle): The image density difference of a contact part and a non-contact part is 0.05 or less.
○: The image density difference between the contact portion and the non-contact portion exceeds 0.05 and is 0.1 or less.
(Triangle | delta): The image density difference of a contact part and a non-contact part exceeds 0.1, and is 0.15 or less.
X: The image density difference between the contact part and the non-contact part exceeds 0.15.

  In addition, in order to confirm the suitability for repeated use, 10,000 sheets were printed based on an image with an area coverage of 5% including a 1-dot line image in A4 size and color under an environment of 28 ° C. and 85% RH. A test was conducted. The residual potential (VRp) after neutralization of the photoconductor after the initial printing test (first sheet) and 10,000 sheets was measured, and the difference between the initial residual potential and the residual potential after printing 10,000 sheets ( ΔRp) was calculated and evaluated according to the following evaluation criteria. The obtained results are shown in Table 2.

(Double-circle): (DELTA) Rp is 30V or less (circle): (DELTA) Rp exceeds 30V and is 50V or less.
(Triangle | delta): (DELTA) Rp exceeds 50V and is 80V or less.
X: ΔRp exceeds 80V.

[Example 2]
A photoconductor was prepared and evaluated in the same manner as in Example 1 except that 4 parts by mass of N, N′-bis (3,4-dimethylphenyl) biphenyl-4-amine was used as the charge transport material. The average concentration of the charge transport material in the surface region was 0.32 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 38 μm.

[Example 3]
Except for using a titanyl phthalocyanine crystal having strong diffraction peaks at Bragg angles (2θ ± 0.2 °) of at least 9.6 °, 24.1 ° and 27.2 ° with respect to CuKα characteristic X-rays as a charge generation material, A photoconductor was prepared and evaluated in the same manner as in Example 1. The average concentration of the charge transport material in the surface region was 0.46 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

[Example 4]
A photoconductor was prepared and evaluated in the same manner as in Example 3 except that 4 parts by mass of N, N′-bis (3,4-dimethylphenyl) biphenyl-4-amine was used as the charge transport material. The average concentration of the charge transport material in the surface region was 0.30 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 38 μm.

[Example 5]
A photoconductor was prepared and evaluated in the same manner as in Example 1 except that the coating was performed at a higher lifting speed during the dip coating. The average concentration of the charge transport material in the surface region was 0.32 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 50 μm.

[Example 6]
A photoreceptor was prepared and evaluated in the same manner as in Example 1 except that the environment during dip coating was 25 ° C. The average concentration of the charge transport material in the surface region was 0.43 times the average concentration of the charge transport material in the entire charge transport layer. The thickness of the charge transport layer was 46 μm.

[Example 7]
Evaluation was performed in the same manner as in Example 1 except that the solvent used for preparing the charge transport layer coating material was changed to 18 parts by mass of tetrahydrofuran and 18 parts by mass of toluene. In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.58 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 42 μm.

[Example 8]
Evaluation was performed in the same manner as in Example 1 except that the solvent used for preparing the charge transport layer coating material was changed to 32 parts by mass of tetrahydrofuran and 4 parts by mass of toluene. In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.33 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

[Example 9]
Evaluation was performed in the same manner as in Example 1 except that the binder resin was changed to bisphenol A type polycarbonate (viscosity average molecular weight: 29000).
In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.56 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

[Comparative Example 1]
Evaluation was performed in the same manner as in Example 1 except that the charge transport layer was dried at 150 ° C. for 40 minutes.
In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.62 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

[Comparative Example 2]
Evaluation was performed in the same manner as in Example 1 except that the photoconductor produced in Example 1 was heated in an oven at 150 ° C. for 40 minutes.
In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.75 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

[Comparative Example 3]
A photoconductor was prepared and evaluated in the same manner as in Example 1 except that the solvent used for preparing the charge transport layer coating material was changed to 35 parts by mass of toluene. In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.23 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

[Comparative Example 4]
A photoconductor was prepared and evaluated in the same manner as in Example 1 except that the solvent used for preparing the charge transport layer coating material was changed to 35 parts by mass of toluene and dried at 105 ° C. for 40 minutes. In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.15 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

[Comparative Example 5]
A photoconductor was prepared and evaluated in the same manner as in Example 3 except that the photoconductor prepared in Example 3 was heated in an oven at 150 ° C. for 40 minutes.
In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.74 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

[Comparative Example 6]
The charge transport layer coating material used in Example 1 was slowed at the time of dip coating to form a first charge transport film coated with 20 μm.
Further, on this first charge transport film, 2 parts by mass of N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine, a bisphenol Z-type polycarbonate resin (viscosity average molecular weight: 40,000) 8 parts by mass, except that the coating material prepared in the same manner as the coating material for the charge transport layer used in Example 1 was applied to a thickness of 20 μm to form a second charge transport film to obtain a photoreceptor. It was.
In the charge transport layer of this photoreceptor, the average concentration of the charge transport material in the surface region was 0.33 times the average concentration of the charge transport material in the entire charge transport layer. The film thickness of the charge transport layer was 40 μm.

DESCRIPTION OF SYMBOLS 1 ... Electrophotographic photoreceptor, 2 ... Conductive substrate (conductive support), 3 ... Photosensitive layer, 4 ... Undercoat layer, 5 ... Charge generation layer, 6 ... Charge transport layer, 200 ... Electrophotographic apparatus, 207 ... Electrophotographic photosensitive member, 208 ... charging device, 209 ... power supply, 210 ... exposure device, 211 ... developing device, 212 ... transfer device, 213 ... cleaning device, 214 ... staticizer, 215 ... fixing device, 216 ... mounting rail, 217 ... opening for static elimination exposure, 218 ... opening for exposure, 220 ... electrophotographic apparatus, 300 ... process cartridge, 400 ... housing, 402a to 402d ... charging roll, 403 ... laser light source (exposure apparatus), 404a ... 404d... Development device, 405a to 405d... Toner cartridge, 406... Drive roll, 407. ... intermediate transfer belts, 410a to 410d ... primary transfer roll, 411 ... tray (tray to be transferred), 412 ... transfer roll, 413 ... secondary transfer roll, 414 ... fixing roll, 415a to 415d ... cleaning blade, 416 ... Cleaning blade, 500 ... transfer medium

Claims (4)

In order from the conductive support, the side closer to the conductive support, a charge generation layer, and a single charge transport layer containing a charge transport material,
The charge transport layer has a thickness of 38 μm or more,
In the charge transport layer, the average concentration of the charge transport material in the region from the surface far from the conductive support to the inner side of 1 μm is not less than 0.3 times the average concentration of the charge transport material in the entire charge transport layer. An electrophotographic photosensitive member of 6 times or less.   The electrophotographic photosensitive member according to claim 1, wherein the concentration of the charge transport material in the charge transport layer continuously increases in the film thickness direction from the surface far from the conductive support toward the other surface. The electrophotographic photosensitive member according to claim 1 or 2,
A contact-type charging device for charging the surface of the electrophotographic photosensitive member;
An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
A developing device that develops an electrostatic latent image formed on the surface of the electrophotographic photosensitive member using toner to form a toner image;
A transfer device for transferring the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the transfer target;
An image forming apparatus. The electrophotographic photosensitive member according to claim 1 or 2,
Contact type charging device for charging the surface of the electrophotographic photosensitive member, electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member, and forming on the surface of the electrophotographic photosensitive member using toner A developing device for developing the electrostatic latent image formed to form a toner image, a transfer device for transferring the toner image formed on the surface of the electrophotographic photosensitive member to the surface of the transfer target, and the surface of the electrophotographic photosensitive member after transfer And at least one selected from the group consisting of cleaning devices for removing residual toner,
A process cartridge that is detachable from the image forming apparatus main body.