JP2015114350A - Electrophotographic photoreceptor and image forming apparatus having the same - Google Patents

Abstract

The present invention provides an electrophotographic photoreceptor excellent in wear resistance and having good electrical characteristics. An electrophotographic photoreceptor in which a photosensitive layer is laminated on an undercoat layer provided on a conductive substrate, the undercoat layer containing metal oxide fine particles and a binder resin, The surface layer contains a charge transport material, a binder resin, and tetrafluoroethylene resin fine particles, and the binder resin in the outermost surface layer is 25 to 35 mJ / mm 2 in the charge transport layer excluding the tetrafluoroethylene resin fine particles. A surface free energy value in a range, and tetrafluoroethylene resin fine particles are (1) an aggregate of primary particles having an average particle diameter of 0.1 to 0.5 μm and an aggregate of secondary particles. (2) contained in the range of 1 to 30% by weight of the binder resin component in the outermost surface layer, and (3) primary particles and particles in a content ratio of less than 80% by weight. Secondary particles having a diameter of less than 1 μm, and (4) content of 5% by weight or less In containing 3μm or more secondary particles. [Selection] Figure 1

Description

The present invention relates to an electrophotographic photosensitive member and an image forming apparatus including the same.
More specifically, the present invention relates to an electrophotographic photosensitive member in which a photosensitive layer is laminated on an undercoat layer containing metal oxide fine particles provided on a conductive support. An electrophotographic photoreceptor comprising a surface layer containing at least a charge transport material, a binder resin exhibiting a specific surface free energy after curing, and a tetrafluoroethylene resin fine particle having a specific particle size and a specific ratio, and the electrophotographic photoconductor The present invention relates to an electrophotographic image forming apparatus (also referred to as “image forming apparatus”).

  In an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile machine, an image is formed by the following electrophotographic process.

  First, a photosensitive layer of an electrophotographic photosensitive member (also referred to as “photosensitive member”) provided in the image forming apparatus is uniformly charged to a predetermined potential by a charger. Next, the photosensitive member is exposed to light (for example, laser light) emitted from the exposure unit according to the image information, and an electrostatic latent image is formed on the photosensitive member. A developer is supplied from the developing means to the formed electrostatic latent image, and the electrostatic latent image is developed by attaching colored fine particles called toner, which is a component of the developer, to the surface of the photoreceptor, Visualize as a toner image. Further, the formed toner image is transferred from the surface of the photoreceptor to a transfer material such as recording paper by a transfer unit, and fixed by a fixing unit.

  However, not all the toner on the surface of the photoconductor is transferred to the recording paper and transferred during the transfer operation by the transfer means, but a part of the toner remains on the surface of the photoconductor. Further, the paper dust of the recording paper that comes into contact with the photoconductor during transfer may remain attached to the surface of the photoconductor. Such foreign matters such as residual toner and adhering paper dust on the surface of the photosensitive member adversely affect the quality of the formed image and are removed by the cleaning device.

  In recent years, cleaner-less technology has advanced, and there is also a method of removing the foreign matter by a system (so-called development and cleaning system) that collects residual toner by a cleaning function added to the developing unit without having an independent cleaning unit. . In this method, after the surface of the photosensitive member is cleaned, the surface of the photosensitive layer is neutralized by a static eliminator or the like so that the electrostatic latent image disappears.

  A photoreceptor used in such an electrophotographic process is configured by laminating a photosensitive layer containing a photoconductive material on a conductive substrate made of a conductive material.

  Examples of the photoconductor include an inorganic photoconductor using an inorganic photoconductive material, and an organic photoconductor using an organic photoconductive material (organic photoconductor “Organic Photoconductor; OPC”). However, due to recent research and development, the sensitivity and durability of organic photoreceptors have improved, and organic photoreceptors are now often used.

  Further, in recent years, a laminated type photoreceptor in which a photosensitive layer is functionally separated into a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material has become mainstream. In many cases, a charge transport layer in which a charge transport material having a charge transport capability is dispersed in a molecular form in a binder resin is formed on a charge generation layer in which a charge generation material is deposited or dispersed in a binder resin. This is a negatively charged photosensitive member laminated. In addition, a single-layer type photoreceptor in which a charge generation material and a charge transport material are uniformly dispersed and dissolved in the same binder resin has also been proposed. Further, in order to improve the print image quality, an undercoat layer is provided between the conductive substrate and the photosensitive layer.

In electrophotographic photoreceptors that are currently in practical use, a photosensitive layer is formed on a conductive support, but carrier injection from the conductive support is likely to occur. As a result, image defects occur due to disappearance or reduction of the surface charge.
Undercoat layer between conductive support and photosensitive layer in order to prevent this image loss, cover defects on the surface of conductive support, improve charging property, improve adhesion of photosensitive layer, improve coating property (Intermediate layer) is provided.

Conventionally, as the undercoat layer, various resin materials and inorganic compound particles such as those containing titanium oxide powder have been studied.
As the resin material used when the undercoat layer is formed of a single resin layer, polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, Examples of the resin material include melamine resin, silicon resin, polyvinyl butyral resin, and polyamide resin.
Further, copolymer resins containing two or more of the above resins, and casein, gelatin, polyvinyl alcohol, ethyl cellulose, and the like are known. Of these, polyamide resins are particularly preferred (patents) Reference 1).

  However, in an electrophotographic photosensitive member having a single layer of resin such as polyamide as an undercoat layer, the accumulation of residual potential is large, resulting in a decrease in sensitivity and image fogging. This tendency becomes remarkable especially in a low humidity environment.

  Therefore, in order to prevent the occurrence of image defects due to the influence of the conductive support without being affected by the environment and to improve the residual potential, the undercoat layer contains titanium oxide powder that has not been surface-treated ( Patent Document 2), further containing titanium oxide fine particles coated with alumina or the like to improve the dispersibility of titanium oxide powder (Patent Document 3), and metal oxide surface-treated with a titanate coupling agent The thing containing the particle (patent document 4) or the thing containing the metal oxide particle which surface-treated with the silane compound (patent document 5) etc. is proposed.

However, the provision of the undercoat layer also suppresses the injection of charges from the photosensitive layer, which causes new problems such as sensitivity reduction and response speed reduction.
In recent years, electrophotographic apparatuses such as digital copying machines and printers have been miniaturized and speeded up, and high sensitivity and high responsiveness corresponding to high speed have been demanded as photoreceptor characteristics.

Therefore, as an approach for solving the above problem, development of an electrically stable charge transport layer is being actively promoted.
Further, as a characteristic required for the charge transport layer, due to the nature of the organic material, there is surface wear caused by slid printing of a cleaner or the like around the photoreceptor. In order to overcome this drawback, efforts have been made to improve the mechanical properties of the material on the surface of the photoreceptor.

  As a document showing a technique for improving the mechanical properties of the material on the surface of the photoreceptor, Patent Document 6 discloses that the protective layer contains filler particles. Further, studies have been made to add fluorine-based particles (fluorine resin particles) to the surface as a filler (for example, Patent Document 7).

  Fluorine-based particles are characterized by a high lubrication function derived from the material, as well as improving the mechanical properties of the photoconductor as a filler, as well as frictional force with the member that contacts the photoconductor process by providing lubricity This contributes to the improvement of printing durability on the surface of the photoreceptor by reducing the above.

  An example of the fluorine-based particles is polytetrafluoroethylene: tetrafluoroethylene resin (PTFE) fine particles. While PTFE fine particles have an excellent lubricating function as a material, they have a drawback that since they are not polar, the cohesive force of the particles is very large and the dispersibility is extremely poor. Therefore, when the PTFE fine particles are dispersed in the surface layer of the photoreceptor, it is necessary to use a dispersion aid (for example, Patent Document 8), and as a result, the photoreceptor electrical characteristics are deteriorated. In addition, when a general-purpose resin for a photoconductor, for example, polycarbonate is used and tetrafluoroethylene resin fine particles are dispersed, primarily, aggregates of 1 μm or less become the majority and dispersion proceeds (Patent Document 9). There is a problem with its stability over time. Moreover, the electrical stability also shows a tendency to deteriorate due to the addition of tetrafluoroethylene resin particles.

  As described above, although the surface treatment method for the metal oxide particles contained in the undercoat layer and the development for improving the printing durability of the surface of the photoconductor are underway, the effect is still not sufficient, and the environmental stability Therefore, development of an electrophotographic photosensitive member having both high sensitivity, high response, and high printing durability is desired.

Japanese Patent Laid-Open No. 48-47344 JP-A-56-52757 JP 59-93453 A JP-A-4-172362 JP-A-4-222972 JP-A-1-172970 Japanese Patent No. 3148571 Japanese Patent No. 3186010 Japanese Patent Laid-Open No. 2005-43765

  The problem to be solved by the present invention is to suppress the deterioration of the sensitivity of the photoreceptor due to the influence of temperature and humidity, there is little change in sensitivity during repeated use, high sensitivity, high response, high printing durability, image defects and An object is to provide an electrophotographic photosensitive member free from fog and an image forming apparatus using the electrophotographic photosensitive member.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention are electrophotographic photoreceptors in which a photosensitive layer is laminated on an undercoat layer provided on a conductive support, the undercoat layer. Includes a metal oxide, and the outermost surface layer of the photoreceptor includes at least a charge transport material, a binder resin exhibiting a specific surface free energy after curing, and a tetrafluoroethylene resin fine particle having a specific particle size and a specific ratio. The present inventors have found that the above problems can be solved by an electrophotographic photoreceptor including the electrophotographic photoreceptor and an electrophotographic image forming apparatus including the electrophotographic photoreceptor, and have completed the present invention.

Thus, according to the present invention, a laminated type photosensitive material in which at least a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated in this order on an undercoat layer provided on a conductive substrate. An electrophotographic photosensitive member in which a single layer type photosensitive layer containing a layer or a charge generation material and a charge transport material is laminated,
The undercoat layer includes fine metal oxide particles and a binder resin;
The outermost surface layer of the photoreceptor includes at least a charge transport material, a binder resin, and tetrafluoroethylene resin fine particles;
In the charge transport layer formed by using the coating solution for forming the charge transport layer excluding the tetrafluoroethylene resin fine particles, the binder resin in the outermost surface layer has a surface free energy value in the range of 25 to 35 mJ / mm ^2. Show
The tetrafluoroethylene resin fine particles are
(1) It is composed of primary particles having an average particle diameter of 0.1 to 0.5 μm and secondary particles that are aggregates of secondary particles that are aggregates of primary particles.
(2) included in the range of 1 to 30% by weight of the binder resin component in the outermost surface layer,
(3) including primary particles and secondary particles having a particle diameter of less than 1 μm in a content ratio of less than 80% by weight;
(4) Provided is an electrophotographic photosensitive member comprising secondary particles of 3 μm or more at a content ratio of 5% by weight or less.

  Further, according to the present invention, the metal oxide fine particles have an average primary particle diameter of 20 to 100 nm and a weight ratio of 10/90 to 95/5 with respect to the binder resin in the undercoat layer. The electrophotographic photoreceptor described above is contained.

  Further, according to the present invention, the electrophotographic photoreceptor, wherein the metal oxide fine particles are titanium oxide or zinc oxide surface-treated with anhydrous silicon dioxide, and the binder resin in the undercoat layer is a polyamide resin. Is provided.

  According to the invention, the tetrafluoroethylene resin fine particles contain primary particles having an average particle diameter of 0.2 to 0.4 μm, and 5 to 15% by weight of the binder resin component of the outermost surface layer. The electrophotographic photosensitive member described above is included.

  In addition, according to the present invention, there is provided the electrophotographic photoreceptor, wherein the tetrafluoroethylene resin fine particles are contained in an amount of 8 to 12% by weight of the binder resin component of the outermost surface layer.

In addition, according to the present invention, there is provided the electrophotographic photosensitive member, wherein the surface free energy value is in a range of 27 to 32 mJ / mm ² .

  Further, according to the present invention, the multilayer photosensitive layer is formed of two charge transport layers having different charge transport substance concentrations, and the outermost surface charge transport layer contains tetrafluoroethylene resin fine particles. The electrophotographic photosensitive member is provided.

  Further, according to the present invention, the electrophotographic photosensitive member, a charging unit that charges the electrophotographic photosensitive member, and an exposing unit that exposes the charged electrophotographic photosensitive member to form an electrostatic latent image; Developing means for developing the electrostatic latent image with toner to form a toner image; transfer means for transferring the toner image onto a recording material; and fixing for fixing the transferred toner image on the recording material An image forming apparatus including the means is provided.

  According to the present invention, in an electrophotographic photoreceptor produced using a coating solution having excellent dispersion stability over a long period of time, the photosensitive layer, the charge transport layer, or the protective layer covering the photosensitive layer is the outermost surface layer. The outermost surface layer of the electrophotographic photosensitive member contains a binder resin exhibiting a specific surface free energy after heat drying and tetrafluoroethylene resin fine particles, while maintaining abrasion resistance, and having good environmental stability. An electrophotographic photoreceptor having both repetitive characteristics can be provided.

It is a schematic diagram which shows the cross section of the electrophotographic photoreceptor which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the cross section of the electrophotographic photoreceptor which concerns on Embodiment 2 of this invention. It is a schematic diagram which shows the cross section of the electrophotographic photoreceptor which concerns on Embodiment 3 of this invention. It is a schematic diagram which shows the cross section of the structure of the image forming apparatus which concerns on Embodiment 4 of this invention.

  The electrophotographic photoreceptor according to the present invention includes an undercoat layer containing metal oxide fine particles and a binder resin on a conductive substrate, and a photosensitive layer is laminated on the undercoat layer, and the outermost surface layer is It is characterized by containing a binder resin showing a specific surface free energy value after drying and fluorine-based resin fine particles having a specific particle diameter, preferably tetrafluoroethylene resin fine particles in a specific ratio.

  In addition, the electrophotographic photoreceptor according to the present invention (hereinafter sometimes simply referred to as “photoreceptor”) has a charge on an undercoat layer containing metal oxide fine particles and a binder resin provided on a conductive substrate. A charge generating layer containing a generating substance and a charge transporting layer containing a charge transporting substance are laminated in this order, and a laminated type photosensitive layer or a single layer type photosensitive layer containing a charge generating substance and a charge transporting substance is laminated. And

In the laminated photoreceptor, two charge transport layers having different charge transport substance concentrations may be formed. In this case, the outermost charge transport layer contains tetrafluoroethylene resin fine particles. It is preferable.
The laminated photoreceptor may further be provided with a protective layer as an outermost surface layer. In this case, it is preferable that the protective layer contains the tetrafluoroethylene resin fine particles.

  The image forming apparatus (electrophotographic image forming apparatus) of the present invention is configured to expose the electrophotographic photosensitive member, charging means for charging the electrophotographic photosensitive member, and electrostatically expose the charged electrophotographic photosensitive member. An exposure unit that forms a latent image; a developing unit that develops the electrostatic latent image with toner to form a toner image; a transfer unit that transfers the toner image onto a recording material; and the transferred toner image The image forming apparatus includes a fixing unit that fixes the recording material, and further includes a cleaning unit that removes and collects toner remaining on the electrophotographic photosensitive member, and a surface charge remaining on the electrophotographic photosensitive member. Neutralizing means. The image forming apparatus of the present invention may be configured to include the electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a transfer unit.

  Hereinafter, embodiments and examples of the present invention will be described in detail with reference to FIGS. Note that the embodiments and examples described below are merely specific examples of the present invention, and the present invention is not limited thereto.

Embodiment 1
FIG. 1 is a schematic view showing a cross section of the electrophotographic photosensitive member according to the present exemplary embodiment. The electrophotographic photosensitive member 1 according to this exemplary embodiment includes a cylindrical conductive base 11 made of a conductive material, an undercoat layer (intermediate layer) 15 formed on the outer peripheral surface of the conductive base 11, and an undercoat. And a photosensitive layer 14 formed on the outer peripheral surface of the layer 15.
As shown in FIG. 1, the photosensitive layer 14 includes a charge generation layer 12 and a charge transport layer 13. The charge generation layer 12 is laminated on the outer peripheral surface of the undercoat layer 15 and contains a charge generation material. The charge transport layer 13 is laminated on the outer peripheral surface of the charge generation layer 12 and contains a charge transport material.
In the example of FIG. 1, the charge transport layer 13 among the layers constituting the photosensitive layer 14 corresponds to the surface layer of the photoreceptor 1.

Conductive substrate 11
The conductive substrate 11 serves as an electrode of the photoreceptor 1 and also functions as a support member for the layers (ie, the undercoat layer 15 and the photosensitive layer 14) disposed on the outside.
The shape of the conductive substrate 11 is cylindrical in the present embodiment, but is not limited to a cylindrical shape, and may be a columnar shape, a sheet shape, an endless belt shape, or the like.

  Examples of the conductive material constituting the conductive substrate 11 include a conductive metal such as aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum, or the conductive material. An alloy material of a conductive metal. Alternatively, as the conductive material, a conductive metal such as aluminum, tin oxide, gold, or indium oxide, or an alloy material or metal oxide of the conductive metal may be used.

In addition, the conductive material is obtained by laminating or vapor-depositing a metal foil made of the conductive metal on the surface of a polymer material (polyethylene terephthalate, nylon, polyester, polyoxymethylene, polystyrene, etc.), hard paper or glass. It is good.
Alternatively, a material obtained by depositing or applying a layer of a conductive compound such as a conductive polymer, tin oxide, or indium oxide on the surface of the polymer material, hard paper, or glass may be used as the conductive material. The conductive substrate 11 is formed by processing the above conductive material into a predetermined shape.

If necessary, the surface of the conductive substrate 11 is irregularly reflected within a range that does not affect the image quality, such as anodic oxide film treatment, surface treatment with chemicals or hot water, coloring treatment, or roughening the surface. It is preferable to perform the treatment.
In an electrophotographic process using a laser as an exposure light source, the wavelengths of the laser light are uniform, so the laser light reflected on the surface of the photoconductor and the laser light reflected inside the photoconductor cause interference, and the interference due to this interference occurs. Stripes may appear on the image and cause image defects. However, by performing the above-described treatment on the surface of the conductive substrate 11, it is possible to prevent image defects due to interference of laser light having the same wavelength.

Undercoat layer (intermediate layer) 15
The undercoat layer 15 has a function of preventing charge injection from the conductive support 11 to the single-layer type photosensitive layer or the multilayer type photosensitive layer (which serves as a barrier against hole injection).
In other words, the undercoat layer suppresses a decrease in chargeability of the single layer type photosensitive layer or the multilayer type photosensitive layer, suppresses a decrease in surface charge other than a portion to be erased by exposure, and causes image defects such as fogging. Is prevented.

However, when only the resin layer is formed as the undercoat layer as conventionally studied, the volume resistance value of the undercoat layer is high, so that the movement of the charge generated in the charge generation layer is hindered, and the sensitivity as a photoconductor. There was a detrimental effect of significantly lowering.
Further, when an ion conductive type conductive material such as a polymer electrolyte or an inorganic salt is added to the resin, the conductivity of the undercoat layer is affected by a change in humidity. That is, the conductivity is increased in a high humidity environment and the conductivity is decreased in a low humidity environment, which has a detrimental effect on the environmental stability of sensitivity as a photoreceptor.

In view of this, an inorganic pigment having a volume resistance value that is less affected by humidity and that is easy to transfer charges and does not impair the sensitivity of the photoreceptor is preferably used as the conductive material in the undercoat layer.
Examples of such inorganic pigments include titanium oxide, zinc oxide, zinc sulfate, alumina, silica, calcium carbonate, barium sulfate and the like.

  In addition, when considering that the sensitivity of the photosensitive member does not decrease, white light that absorbs little to visible light or near infrared, or a color tone close to that, coherent interference such as laser light used in the light source of image forming apparatuses in recent years. When writing an image with light, the refractive index is large so as to suppress the occurrence of moiré, and the ratio of the resin and the conductive material in the undercoat layer is appropriately selected to maintain the strength of the undercoat layer. A metal oxide is more preferable as the conductive material because it suppresses generation of image defects due to aggregation and the volume resistance value is easily optimized, and examples thereof include titanium oxide and zinc oxide.

However, when surface-untreated titanium oxide or zinc oxide fine particles are used, since the titanium oxide or zinc oxide particles to be used are fine particles, the coating liquid for the undercoat layer is sufficiently dispersed for a long period of time. During use or storage of the coating solution, the titanium oxide and zinc oxide fine particles tend to aggregate, and the occurrence of this aggregate may not be avoided.
Therefore, when an undercoat layer is formed using the above-mentioned coating solution for an undercoat layer containing untreated titanium oxide or zinc oxide fine particles that has been stored for a long period of time, defects in the coating film and uneven coating occur, resulting in image defects. Can occur.

In addition, charge injection from the conductive support is likely to occur due to defects in the coating film and coating unevenness, so that the chargeability of the micro area is reduced and black spots are generated.
Furthermore, attempts have been made to improve the dispersibility in the undercoat layer by applying a surface treatment of titanium oxide or zinc oxide with alumina. However, the subbing is performed on the drum which is a conductive support in the dip coating process. When forming a layer, it is necessary to produce a large amount of coating liquid. When dispersion treatment is performed for a long time, black spots are generated due to re-aggregation of titanium oxide or zinc oxide, resulting in deterioration of image quality. There was a problem to do.

This is because the effect of surface treatment of titanium oxide or zinc oxide is reduced by peeling off the surface-treated alumina or zinc oxide by long-time dispersion treatment, and re-aggregation of titanium oxide or zinc oxide occurs, resulting in image defects. In addition, it is considered that the injection of electric charges from the conductive support is likely to occur, and the charging property of the micro area of the undercoat layer is lowered to generate black spots.
Further, such black spots become prominent when used for a long time in a high-temperature and high-humidity environment, and the image quality is significantly lowered.

On the other hand, silicon dioxide may be used in combination with alumina so that the surface treatment of titanium oxide or zinc oxide is sufficiently performed. However, when surface treatment is performed with silicon dioxide in combination with alumina, crystal water is contained.
It is considered that the undercoat layer is easily influenced by humidity in each environment by being attracted by the crystal water, and not only the image quality is deteriorated but also the sensitivity of the photoreceptor is affected.

In addition, when the surface of titanium oxide or zinc oxide is coated with a magnetic metal oxide such as Fe ₂ O _3, it chemically interacts with the phthalocyanine pigment contained in the photosensitive layer, and the photosensitive layer It is not preferable because the body characteristics, particularly the sensitivity and chargeability, are reduced.

  Therefore, the inventors of the present invention include a titanium oxide or zinc oxide particles surface-treated with anhydrous silicon dioxide so that the surface-treated titanium oxide or zinc oxide in the undercoat layer can be used. It was found that the dispersibility of the metal oxide was improved and an undercoat layer in which the metal oxide was uniformly dispersed was formed, and the present invention was completed.

  The undercoat layer covering the surface of the conductive support reduces the degree of unevenness, which is a defect on the surface of the conductive support, and makes the surface uniform, thereby forming a single layer type photosensitive layer or a multilayer type photosensitive layer. And the adhesion (adhesiveness) between the conductive support and the single layer type photosensitive layer or the multilayer type photosensitive layer can be improved.

Although the environmental characteristics are improved when the film thickness is reduced in the conventional undercoat layer, the adhesiveness between the conductive support and the photosensitive layer is lowered, and an image defect caused by the defect of the conductive support is generated. was there.
On the other hand, if the thickness of the undercoat layer is increased, there is a problem that the sensitivity is lowered and the environmental characteristics are deteriorated, and there is a limitation on the practical film thickness to achieve both reduction of image defects and improvement of stability of electrical characteristics. Was supposed to be.

  The crystal form of the above titanium oxide or zinc oxide may be any of rutile, anatase, and amorphous, and may be a mixture of two or more of these, and the shape thereof is generally granular. Although a thing is used, a needle-like or dendritic thing can also be used.

  In the present invention, the term “needle shape” used for the crystal form of the inorganic compound may be an elongated shape including a rod shape, a column shape, a spindle shape, and the like. Therefore, like a so-called medical or sewing needle, It does not necessarily have to be extremely long and narrow, and the tip does not need to be sharp.

Therefore, the average primary particle diameter of titanium oxide or zinc oxide contained in the undercoat layer is more preferably in the range of 20 nm to 100 nm.
If the average primary particle size is 20 nm or less, the dispersibility is poor, aggregation may occur, the viscosity increases, and the stability as a liquid tends to be unfavorable.
Moreover, it is very difficult to apply the coating solution for the undercoat layer further thickened to the conductive support, resulting in poor productivity.
On the other hand, if the average primary particle size is 100 nm or more, the chargeability of the microregions is lowered when the undercoat layer is formed, and black spots are easily generated, which is not preferable.

With such a titanium oxide or zinc oxide having an average primary particle size, good dispersibility can be obtained, and it can be uniformly dispersed in the binder resin.
The average primary particle diameter of titanium oxide or zinc oxide or the average primary particle diameter of titanium oxide surface-treated with anhydrous silicon dioxide is based on the measurement of SEM (S-4100; manufactured by Hitachi High-Technologies Corporation) photograph. This is a value obtained by measuring and averaging the particle diameters of 50 or more particles.

  The content in the undercoat layer of titanium oxide or zinc oxide fine particles subjected to surface treatment with anhydrous silicon dioxide is 10 to 99% by weight, preferably 30 to 99% by weight, more preferably 35 to 95% by weight. It is a range.

If the content of titanium oxide or zinc oxide is lower than 10% by weight, the sensitivity is lowered, charges are accumulated in the undercoat layer, and the residual potential tends to increase. Such a phenomenon becomes prominent particularly in the repetitive characteristics under low temperature and low humidity.
Further, if the content of titanium oxide or zinc oxide is higher than 95% by weight, it is not preferable because aggregates are easily generated in the undercoat layer and image defects are likely to occur.

The volume resistance value of the titanium oxide or zinc oxide fine particles is preferably 10 ⁵ to 10 ¹⁰ Ωcm.
When the volume resistance value of the powder is less than 10 ⁵ Ωcm, the resistance value as the undercoat layer decreases, and the undercoat layer does not function as a charge blocking layer.

For example, in the case of inorganic compound particles subjected to a conductive treatment such as a tin oxide conductive layer doped with antimony, the volume resistivity of the powder is very low, 10 ⁰ Ωcm to 10 ¹ Ωcm, and this was used. The undercoat layer does not function as a charge blocking layer, deteriorates the chargeability as the characteristics of the photoreceptor, and cannot be used because fog and black spots (black spots) occur in the image.

In addition, when the volume resistance value of the powder of titanium oxide or zinc oxide fine particles is higher than 10 ¹⁰ Ωcm and equal to or more than the volume resistance value of the binder resin itself, the resistance value as the undercoat layer is too high, It is not preferable because the transport of carriers generated during light irradiation is suppressed and prevented, the residual potential is increased, and the photosensitivity is lowered.

The amount used for the surface treatment of anhydrous silicon dioxide covering the surface of titanium oxide or zinc oxide fine particles is preferably 0.1 to 50% by weight with respect to parts by weight of titanium oxide or zinc oxide to be used.
If the amount of anhydrous silicon dioxide used is less than 0.1% by weight, the surface of titanium oxide or zinc oxide cannot be sufficiently covered with anhydrous silicon dioxide, so that the effect of the surface treatment is hardly exhibited.

  Further, if the amount of anhydrous silicon dioxide used exceeds 50% by weight, excess anhydrous silicon dioxide that is not used for coating the titanium oxide fine particles remains, and the effect of containing titanium oxide and zinc oxide fine particles is reduced, and substantially Since there is no substitute for containing silicon dioxide fine particles, the sensitivity of the photoreceptor is lowered and image fogging occurs, which is not preferable.

  In addition, when an organic compound such as a common coupling agent is used on the surface of titanium oxide or zinc oxide fine particles, the resistance value of the undercoat layer increases and the sensitivity change due to the influence of humidity decreases, but the sensitivity itself deteriorates. Image fog may occur.

Binder resin for undercoat layer As the binder resin contained in the undercoat layer, the same material as that used for forming the undercoat layer with a single resin layer is used. For example, among resin materials such as polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, silicon resin, butyral resin, polyamide resin, and their repeating units Copolymer resins containing two or more, and casein, gelatin, polyvinyl alcohol, ethyl cellulose and the like are known. Among these, alcohol-soluble polyamide resins, butyral resins, and vinyl acetate resins are preferable, and polyamide resins are more preferable.

  The reason for this is that the polyamide resin contained in the undercoat layer does not dissolve or swell with respect to the solvent used when forming the photoreceptor layer on the undercoat layer as a property of the binder resin. In addition, it has excellent adhesion to the conductive support, has flexibility, and has good affinity with the metal oxide contained in the undercoat layer. It is considered that the storage stability is excellent.

Among polyamide resins, an alcohol-soluble nylon resin can be preferably used.
Examples of the alcohol-soluble nylon resin include so-called nylons such as 6-nylon, 6,6-nylon, 6,10-nylon, 11-nylon, 12-nylon, and the like, as well as N-alkoxymethyl-modified nylon, N- A type in which nylon is chemically modified, such as alkoxyethyl-modified nylon, is preferable.

Therefore, the electrophotographic photoreceptor according to the present invention is characterized in that the binder resin contained in the undercoat layer is an organic solvent-soluble polyamide resin.
The polyamide resin as the binder resin contained in the undercoat layer is easy to be familiar with the metal oxide particles and has excellent adhesion to the conductive support. Can maintain the flexibility of the membrane.

Furthermore, since the polyamide resin contained in the formed undercoat layer does not swell or dissolve in the solvent for the photoreceptor coating solution, it prevents occurrence of coating defects and unevenness in the undercoat layer, and has excellent image characteristics. An electrophotographic photoreceptor having the above can be provided.
In the present invention, the metal oxide particles are preferably used in a weight ratio of 10/90 to 95/5 with respect to the binder resin.

  As a method for dispersing the coating solution for the undercoat layer, an ultrasonic disperser that does not use a dispersion medium or a disperser such as a ball mill, a bead mill, or a paint conditioner that uses a dispersion medium can be used. A binder dissolved in an organic solvent can be used. A disperser using a dispersion medium in which an inorganic compound is charged into the resin solution and the inorganic compound can be dispersed with a strong force applied from the disperser through the dispersion medium is preferable.

As a material of the dispersion medium, it is preferable to use glass, zircon, or alumina, preferably zirconia or titania having high wear resistance.
The shape of the dispersion medium may be any shape and size such as a bead shape of about 0.3 mm to several mm and a ball shape of about several cm.

When glass is used as the material of the dispersion medium, it is not preferable because the viscosity of the dispersion increases and storage stability deteriorates.
This is because when the metal oxide fine particles used in the present invention are dispersed, the powerful force given from the disperser is used not only as energy to disperse the metal oxide fine particles but also as energy to wear the dispersion medium itself. As a result, the dispersion medium material generated by the abrasion of the dispersion medium is mixed into the dispersion coating liquid, so that the dispersibility and storage stability of the dispersion coating liquid deteriorate, and the undercoat layer of the electrophotographic photosensitive member is formed. This is considered to be based on having some influence on the coating property and the film quality of the undercoat layer.

  As the organic solvent used in the dispersion for forming the undercoat layer of the electrophotographic photosensitive member according to the present invention, a general organic solvent can be used, but a more preferable alcohol-soluble nylon resin is used as the binder resin. For this, an organic solvent such as a lower alcohol having 1 to 4 carbon atoms is used.

  More specifically, the lower alcohol selected from the group consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol is used as the solvent for the coating solution for the undercoat layer. Is preferred.

An undercoat layer is formed by applying an undercoat layer coating solution prepared by dispersing the polyamide resin and titanium oxide fine particles in the lower alcohol to the conductive support and drying.
The undercoat layer is obtained, for example, by applying the undercoat layer coating solution of the present invention on a conductive support and drying the obtained coating film.

In the case of a sheet, the coating solution for the undercoat layer is a baker applicator method, a bar coater method (for example, a wire bar coater method), a casting method, a spin coating method, a roll method, a blade method, a bead method, or a curtain method. In the case of a drum, a spray method, a vertical ring method, a dip coating method, etc. are mentioned.
As the coating method, an optimum method may be selected in consideration of the physical properties and productivity of the coating solution, and the dip coating method, the blade coater method, and the spray method are particularly preferable.

The thickness of the undercoat layer is preferably in the range of 0.01 to 10 μm, more preferably 0.05 to 5 μm.
If the thickness of the undercoat layer is less than 0.01 μm, the undercoat layer substantially does not function as an undercoat layer, and a uniform surface property cannot be obtained by covering defects of the conductive support. Carrier injection cannot be prevented, and chargeability is lowered, which is not preferable.
Also, it is not preferable to make the undercoat layer thicker than 10 μm because it becomes difficult to produce a photoreceptor when the undercoat layer is applied by dip coating, and the sensitivity of the photoreceptor is lowered.

Charge generation layer 12
The charge generation layer 12 contains, as a main component, a charge generation material that generates charges by absorbing light.
Substances effective as the charge generation substance include organic photoconductive materials containing organic pigments and inorganic photoconductive materials containing inorganic pigments.

  Examples of the organic photoconductive materials include azo pigments such as monoazo pigments, bisazo pigments and trisazo pigments, indigo pigments such as indigo and thioindigo, perylene pigments such as peryleneimide and perylene anhydride, anthraquinone and Organic photoconductive materials such as polycyclic quinone pigments such as pyrenequinone, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, squarylium dyes, pyrylium salts, thiopyrylium salts, and triphenylmethane dyes.

Examples of the inorganic photoconductive material include selenium, selenium alloy, arsenic-selenium, cadmium sulfide, zinc oxide, amorphous silicon, and other inorganic photoconductors.
However, titanyl phthalocyanine is preferable as the charge generating material in the present invention, but the X-ray diffraction spectrum shows a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 °, and 7.3 °, 9 Crystalline titanyl phthalocyanine having diffraction peaks at .4 °, 9.7 °, and 27.3 ° is particularly preferable from the viewpoint of the effect exhibited by the combination with other components of the present invention.

  Charge generation materials include triphenylmethane dyes represented by methyl violet, crystal violet, knight blue and Victoria blue, erythrosine, rhodamine B, rhodamine 3R, acridine dyes represented by acridine orange and frapeosin, methylene blue and methylene They may be used in combination with sensitizing dyes such as thiazine dyes typified by green, oxazine dyes typified by capri blue and meldra blue, cyanine dyes, styryl dyes, pyrylium salt dyes or thiopyrylium salt dyes.

As a method of forming the charge generation layer 12, the charge generation material is vacuum-deposited on the surface of the conductive substrate 11, or the charge generation layer is obtained by dispersing the charge generation material in a suitable solvent. A method of applying the liquid to the surface of the conductive substrate 11 is used.
In particular, it is obtained by dispersing a charge generating substance in a binder resin solution obtained by mixing a binder resin as a binder in a solvent by a conventionally known method to prepare a coating solution for a charge generating layer. A method of applying the applied coating solution (coating solution) to the surface of the conductive substrate 11 is preferably used. Hereinafter, this method will be described.

  Examples of the binder resin used for the charge generation layer 12 include polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, and polyarylate resin. And resins such as phenoxy resin, polyvinyl butyral resin, polyvinyl chloride resin and polyvinyl formal resin, and copolymer resins containing two or more repeating units constituting these resins.

Specific examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. be able to.
The binder resin is not limited to these, and a commonly used resin can be used as the binder resin. These resins may be used alone or in combination of two or more.

  Examples of the solvent for the charge generation layer coating solution include halogenated hydrocarbons such as dichloromethane or dichloroethane; alcohols such as methanol and ethanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; Ethers such as tetrahydrofuran or dioxane; alkyl ethers of ethylene glycol such as 1,2-dimethoxyethane; aromatic hydrocarbons such as benzene, toluene or xylene; or N, N-dimethylformamide or N, N-dimethylacetamide An aprotic polar solvent such as is used.

  Among the above solvents, non-halogen organic solvents are preferably used in consideration of the global environment. One of the above solvents may be used alone, or a mixed solvent of two or more may be used.

In the charge generation layer 12 including the charge generation material and the binder resin, the ratio W1 / W2 between the weight W1 of the charge generation material and the weight W2 of the binder resin is 10/100 (10/100). It is preferable that it is 400/100 (400/100).
When the ratio W1 / W2 is less than 10/100, the sensitivity of the photoreceptor 1 may be lowered.
On the other hand, when the ratio W1 / W2 exceeds 400/100, not only the film strength of the charge generation layer 12 decreases, but also the dispersibility of the charge generation material decreases and coarse particles increase. The surface charge other than the portion to be reduced is reduced, and image defects, particularly the fogging of images called black spots where toner adheres to a white background and minute black spots are formed may increase.
Therefore, it was determined that the preferable range of the ratio W1 / W2 is 10/100 to 400/100.

The charge generation material may be pulverized in advance by a pulverizer before being dispersed in the binder resin solution.
Examples of the pulverizer used for the pulverization treatment include a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic disperser.
Examples of the disperser used when dispersing the charge generating substance in the binder resin solution include a paint shaker, a ball mill, and a sand mill. As a dispersion condition at this time, it is preferable to select an appropriate condition so that impurities are not mixed due to wear of a container used and a member constituting the disperser.

Examples of the coating method for the charge generation layer coating liquid include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method. Among these application methods, an optimum method can be selected in consideration of the physical properties and productivity of the application.
Among these coating methods, in particular, the dip coating method is a method of forming a layer on the surface of the substrate by immersing the substrate in a coating tank filled with a coating solution and then pulling it up at a constant speed or a speed that changes sequentially. Since it is relatively simple and excellent in terms of productivity and cost, it is often used in the production of photoreceptors.
In addition, in order to stabilize the dispersibility of a coating liquid, the apparatus used for the dip coating method may be provided with a coating liquid dispersing apparatus represented by an ultrasonic generator.

The film thickness of the charge generation layer 12 is preferably 0.05 to 5 μm, more preferably 0.1 to 1 μm.
If the thickness of the charge generation layer 12 is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity of the photoreceptor 1 may be lowered.
On the contrary, when the film thickness of the charge generation layer 12 exceeds 5 μm, the charge transfer inside the charge generation layer 12 becomes a rate-determining step in the process of erasing the surface charge of the photosensitive layer 12, and the sensitivity of the photoreceptor 1 is lowered. Sometimes.
Therefore, the thickness of the charge generation layer 12 was determined to be 0.05 to 5 μm.

Charge transport layer 13
A charge transport layer 13 is provided on the outer peripheral surface of the charge generation layer 12. The charge transport layer 13 includes a charge transport material having an ability to accept and transport the charge generated by the charge generation material contained in the charge generation layer 12, and a binder resin that binds the charge transport material.
In addition, filler particles can be added to the charge transport layer 13 for the purpose of improving wear resistance and the like.
Furthermore, an antioxidant, a sensitizer, and various additives such as a plasticizer or a leveling agent can be added to the charge transport layer 13 as necessary.

  Various additives may be added to the charge transport layer 13 as necessary. That is, a plasticizer or a leveling agent may be added to the charge transport layer 13 in order to improve the film formability, flexibility, or surface smoothness. Examples of the plasticizer include dibasic acid esters such as phthalate esters, fatty acid esters, phosphate esters, chlorinated paraffins, and epoxy type plasticizers. Moreover, as said leveling agent, a silicone type leveling agent etc. can be mentioned, for example.

  Examples of the charge transport material include enamine derivatives, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds. , Polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, Examples thereof include stilbene derivatives and benzidine derivatives.

As the binder resin constituting the charge transport layer 13, a polycarbonate resin mainly composed of polycarbonate known in the art is suitably selected for reasons such as excellent transparency and printing durability.
In addition to the above polycarbonate resin, as the binder resin as the second component, for example, a vinyl polymer resin such as a polymethyl methacrylate resin, a polystyrene resin, a polyvinyl chloride resin, or two of repeating units constituting them. Copolymer resin containing two or more, or polyester resin, polyester carbonate resin, polysulfone resin, phenoxy resin, epoxy resin, silicone resin, polyarylate resin, polyamide resin, polyether resin, polyurethane resin, polyacrylamide resin and phenol resin Alternatively, a copolymer resin having a polycarbonate skeleton and a polydimethylsiloxane skeleton can be used.

Further, a thermosetting resin obtained by partially cross-linking these resins may be used.
These resins may be used alone, or a mixture of two or more kinds may be used.
The above-mentioned polycarbonate resin is the main component means that the weight percent of the polycarbonate resin in the total binder resin constituting the charge transport layer occupies the highest proportion, preferably 50 to 90 wt%. It means that it is in the range.

The binder resin as the second component is lower than the content of the polycarbonate resin with respect to the total weight of the binder resin constituting the charge transport layer 13, and is in the range of 10 to 50% by weight. It means a binder resin that can be used.
The ratio of the charge transport material and the binder resin in the charge transport layer is preferably in the range of 10/10 to 10/18 by weight ratio.

The filler particles are roughly classified into organic filler particles and inorganic filler particles mainly composed of metal oxides, but have the following restrictions as basic requirements. That is, when the relative dielectric constant of the charge transport layer 13 becomes significantly large as εr> 10 as compared with the average relative dielectric constant (εr≈3) of the organic photoreceptor, the charge transport layer 13 is not uniform. Therefore, it is considered that the electrical characteristics are adversely affected, so that the relative dielectric constant of the charge transport layer 13 should be relatively small.
Considering this point, organic filler particles are more advantageous than metal oxides.
Furthermore, among organic filler particles, fluorine fine particles (fluorine resin fine particles) are excellent in lubricity.

Therefore, the present invention is characterized in that tetrafluoroethylene resin (PTFE: polytetrafluoroethylene) fine particles are used as the fluorine-based particles that are filler particles added to the charge transport layer 13.
The tetrafluoroethylene resin fine particles are
(1) It is composed of primary particles having an average particle diameter of 0.1 to 0.5 μm and secondary particles that are aggregates of secondary particles that are aggregates of primary particles.
(2) included in the range of 1 to 30% by weight of the binder resin component of the charge transport layer,
(3) including primary particles and secondary particles having a particle diameter of less than 1 μm in a content ratio of less than 80% by weight;
(4) It contains secondary particles of 3 μm or more in a content ratio of 5% by weight or less.

  When the tetrafluoroethylene resin fine particles are added to the charge transport layer, the tetrafluoroethylene resin having a small particle diameter is used in order to minimize the adverse effects on light scattering and electrical carriers in the charge transport layer 13. It is preferable to use fine particles. Therefore, in the present invention, PTFE fine particles having an average primary particle diameter of 0.1 to 0.5 μm, more preferably 0.2 to 0.4 μm are preferably used.

When the average primary particle diameter of the PTFE fine particles is smaller than 0.1 μm, aggregation of the primary particles becomes remarkable and light scattering increases.
Further, when the average primary particle of the PTFE fine particles is larger than 0.5 μm, the light scattering by the primary particles increases accordingly.
Therefore, the average primary particle size of the PTFE fine particles was determined to be within a proper range of 0.1 to 0.5 μm.

  The tetrafluoroethylene resin fine particles are preferably contained in the range of 1 to 30% by weight of the binder resin component in the charge transport layer.

By containing the tetrafluoroethylene resin particles in an amount of 1 to 30% by weight, more preferably 5 to 15% by weight, based on the binder resin in the charge transport layer, the printing durability is excellent, and Provided is a photoreceptor that can achieve both stabilization of electric characteristics.
When the content concentration of the tetrafluoroethylene resin fine particles relative to the binder resin in the charge transport layer is less than 1% by weight, the effect of improving the abrasion resistance of the photoreceptor by adding the tetrafluoroethylene resin fine particles is not observed.
In addition, when the content concentration of the tetrafluoroethylene resin fine particles with respect to the binder resin in the charge transport layer is 30% by weight or more, the electrical characteristics of the photosensitive member are remarkably deteriorated and cannot be actually used in the image forming apparatus.

  Further, as a method of dispersing the tetrafluoroethylene resin particles as filler particles, a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, a paint shaker, or the like is used in the same manner as the oxide fine particles added to the undercoat layer. The general method used can be used. In addition, it is possible to produce a more stable dispersion coating liquid by using a media-less type dispersion device that uses a very strong shearing force that is generated by passing the dispersion liquid through a micro gap at an ultrahigh pressure. It becomes.

  As in the case where the charge generation layer 12 is formed by coating, the charge transport layer 13 is formed by, for example, dissolving a charge transport material, a binder resin, the filler particles, and / or the additive in an appropriate solvent. It is formed by dispersing and preparing a coating liquid for forming a charge transport layer and coating the obtained coating liquid (coating liquid) on the outer peripheral surface of the charge generation layer 12.

  Examples of the solvent for the coating solution for forming the charge transport layer include aromatic hydrocarbons such as benzene, toluene, xylene and monochlorobenzene, halogenated hydrocarbons such as dichloromethane and dichloroethane, ethers such as tetrahydrofuran, dioxane and dimethoxymethyl ether, And aprotic polar solvents such as N, N-dimethylformamide. One of these solvents may be used alone, or two or more thereof may be mixed and used.

In addition, a solvent such as alcohols, acetonitrile, or methyl ethyl ketone can be further added to the above solvent as necessary. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.
Examples of the coating method for the charge transport layer forming coating solution include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method. Among these coating methods, the dip coating method is particularly excellent in various respects as described above, and is often used when the charge transport layer 13 is formed.

The film thickness of the charge transport layer 13 is 5 to 40 μm, more preferably 10 to 30 μm.
If the thickness of the charge transport layer 13 is less than 5 μm, the charge retention ability is lowered, which is not preferable.
On the other hand, if the thickness of the charge transport layer 13 exceeds 40 μm, the resolution of the photoreceptor 1 is lowered, which is not preferable.
Therefore, the suitable range of the film thickness of the charge transport layer 13 was determined to be 5 to 40 μm.

Additives to photosensitive layer 14 Each layer of the photosensitive layer 14 (charge generation layer 12 and charge transport layer 13) has an electron accepting material in order to improve sensitivity and to suppress a rise in residual potential and fatigue due to repeated use. In addition, one or more sensitizers such as dyes may be added.

  Examples of the electron acceptor include acid anhydrides such as succinic anhydride, maleic anhydride, phthalic anhydride, 4-chloronaphthalic anhydride, cyano compounds such as tetracyanoethylene and terephthalmalondinitrile, 4-nitrobenzaldehyde, and the like. Aldehydes, anthraquinones such as anthraquinone and 1-nitroanthraquinone, polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, and diphenoquinone compounds The electron-withdrawing material can be used. Moreover, what polymerized these electron-withdrawing materials can also be used.

As the dye, for example, an organic photoconductive compound such as xanthene dye, thiazine dye, triphenylmethane dye, quinoline pigment or copper phthalocyanine can be used. These organic photoconductive compounds function as optical sensitizers.
Further, an antioxidant or an ultraviolet absorber may be added to each layer of the photosensitive layer 14. In particular, it is preferable to add an antioxidant or an ultraviolet absorber to the charge transport layer 14b, and the stability of the coating solution when forming each layer by coating can be improved.

  Furthermore, the addition of an antioxidant to the charge transport layer 13 can reduce deterioration of the photosensitive layer with respect to an oxidizing gas such as ozone or nitrogen oxide. Examples of the antioxidant include phenol compounds, hydroquinone compounds, tocopherol compounds, and amine compounds. Among these, a hindered phenol derivative or a hindered amine derivative, or a mixture thereof is preferably used.

Embodiment 2
In the first embodiment, the laminated photosensitive layer is described in which the photosensitive layer 14 includes the charge generation layer 12 and the charge transport layer 13. However, like the photosensitive member 1 shown in FIG. May be formed of a single layer. That is, a single-layer type that is a layer laminated on the outer peripheral surface of a cylindrical conductive substrate 11 made of a conductive material and an undercoat layer 15 formed thereon, and contains a charge generation material and a charge transport material. It may be formed with the photosensitive layer 14. In this case, the charge generating material can be added and dispersed in the charge transport layer forming coating solution according to the present invention to obtain a single layer type photosensitive layer coating solution.
In the configuration of FIG. 2, the entire photosensitive layer 14 is a surface layer of the photoreceptor 1, and the PTFE fine particles are added to the photosensitive layer 14.

Embodiment 3
As shown in FIG. 3, a plurality of charge transport layers may be formed. 3 includes a conductive substrate 11 and a photosensitive layer 14 formed on the outer peripheral surface of an undercoat layer 15 formed thereon. The photosensitive layer 14 includes a charge generation layer 12 formed on the outer peripheral surface of the undercoat layer 15, a first charge transport layer 13A formed on the outer peripheral surface of the charge generation layer 12, and an outer peripheral surface of the first charge transport layer 13A. The second charge transport layer 13B is formed.

  3 is formed so that the content of the charge transport material in the first charge transport layer 13A is different from the content of the second charge transport layer 13B. Further, in the configuration of FIG. 3, the second charge transport layer 13B corresponds to the outermost surface layer among the layers constituting the photosensitive layer 14, and the tetrafluoroethylene resin fine particles are compared with the second charge transport layer 13B. Is added.

  In addition, a protective layer is formed on the outer peripheral surface of the photosensitive layer, and one embodiment of the present invention can be applied to a photoreceptor having the protective layer as a surface layer. In this embodiment, it is preferable to add tetrafluoroethylene resin fine particles to the binder resin of the protective layer.

Surface Free Energy of Photoreceptor Surface free energy (γ) is often used as an index representing the surface wettability of the photoreceptor. In order to deteriorate wettability, that is, to improve surface repellency, a material having a low surface free energy is used. PTFE fine particles are typical and widely used. In addition, the γ value on the surface of the photosensitive layer can be lowered by mixing a component having a low surface free energy with the binder resin used on the surface of the photoreceptor (most of which is a charge transport layer).
For example, a repeating structure having a siloxane skeleton may be used as a copolymer. A copolymer binder resin containing a fluorinated ethylene skeleton may be used.
By changing the component ratio of these copolymers, the surface free energy on the surface of the formed photosensitive layer can be controlled.

Embodiment 4
Image Forming Apparatus Next, an electrophotographic image forming apparatus provided with the photoreceptor according to the present invention will be described.
FIG. 4 is a schematic cross-sectional view showing the inside of the image forming apparatus 30 of the present embodiment.
The image forming apparatus 30 is a laser printer. The image forming apparatus 30 includes a photosensitive member 1, a semiconductor laser 31, a rotary polygon mirror 32, an imaging lens 34, a mirror 35, a corona charger 36, a developing device 37, a transfer paper cassette 38, a paper feed roller 39, a registration roller 40, A transfer charger 41, a separation charger 42, a transport belt 43, a fixing device 44, a paper discharge tray 45, and a cleaner 46 are provided.

  The photoreceptor 1 is mounted on the image forming apparatus 30 so as to be rotatable in the direction of an arrow 47 by a driving unit (not shown). The laser beam 33 emitted from the semiconductor laser 31 is scanned by the rotary polygon mirror 32. The imaging lens 34 has f-θ characteristics, and reflects the laser beam 33 by the mirror 35 to form an image on the surface of the photoreceptor 1. As the photosensitive member 1 is rotated, the laser beam 33 is scanned and imaged as described above, and an electrostatic latent image corresponding to image information is formed on the surface of the photosensitive member 1.

  The corona charger 36, the developing device 37, the transfer charger 41, the separation charger 42, and the cleaner 46 are provided in this order from the upstream side to the downstream side in the rotation direction of the photosensitive member 1 indicated by an arrow 47. The corona charger 36 is provided upstream of the image forming point of the laser beam 33 in the rotation direction of the photoconductor 1 and uniformly charges the surface of the photoconductor 1. By irradiating (exposing) the laser beam 33 to the uniformly charged surface of the photosensitive member 1, a difference in charge amount occurs between the irradiated portion and other portions, and the above-described electrostatic latent image is formed. .

  The developing device 37 is provided on the downstream side in the rotation direction of the photosensitive member 1 with respect to the image forming point of the laser beam 33, and supplies toner to the electrostatic latent image formed on the surface of the photosensitive member 1. Develop as a toner image. The transfer paper 48 accommodated in the transfer paper cassette 38 is taken out one by one by a paper feed roller 39 and given to a transfer charger 41 by a registration roller 40. The toner image is transferred to the transfer paper 48 by the transfer charger 41. The separation charger 42 neutralizes the transfer paper on which the toner image is transferred and separates it from the photoreceptor 1.

  The transfer paper 48 separated from the photoreceptor 1 is conveyed to the fixing device 44 by the conveying belt 43, and an image is formed by fixing the toner image by the fixing device 44 and is discharged to the paper discharge tray 45. In addition, after the transfer paper 48 is separated by the separation charger 42, the photosensitive member 1 that continues to rotate is cleaned by a cleaner 46 of toner and paper dust remaining on the surface thereof. The cleaned portion of the photoreceptor 1 is neutralized by a static eliminator (static elimination lamp) 50. Such a series of image forming processes is repeated by the rotation of the photoreceptor 1.

  The image forming apparatus 30 is not limited to the configuration shown in FIG. 4 and may be either a monochrome printer or a color printer as long as it uses a photoconductor. In addition, the image forming apparatus 30 can be various printers, copiers, facsimiles, multi-function machines, and the like that use an electrophotographic process.

  Hereinafter, the present embodiment will be described in more detail using examples, but the present embodiment is not limited to the following description.

Example 1
Preparation of undercoat layer The following components:
Maxlite (registered trademark) TS-043 (manufactured by Showa Denko KK: anhydrous silicon dioxide treated titanium oxide: titanium oxide 90 wt%, anhydrous silicon dioxide 10 wt%, titanium oxide particle diameter 30 nm, anhydrous silicon dioxide treated titanium oxide particle diameter 32 nm ) 1 part by weight Polyamide resin (manufactured by Toray: CM8000) 9 parts by weight Ethanol 50 parts by weight Tetrahydrofuran 50 parts by weight as a dispersion medium in a 16,500 ml horizontal bead mill 80% volume of silicon nitride beads having a diameter of 0.5 mm Then, the above components were accumulated in a stirring tank and sent to a disperser via a diaphragm pump to circulate and disperse for 15 hours to produce 3,000 g of an undercoat layer coating solution.

  Fill this coating liquid into a coating tank, and use an aluminum cylindrical support with a diameter of 30 mm and a total length of 345 mm as a conductive support, and form an undercoat layer of 0.15 μm on the conductive support by dip coating. did.

Preparation of charge generation layer As a charge generation material, the maximum diffraction peak is shown at a Bragg angle (2θ ± 0.2 °) of 27.3 ° with respect to X-ray of CuKα1.541５４, and 7.3 °, 9.4 °, 9 Oxotitanyl phthalocyanine having diffraction peaks at .7 ° and 27.3 ° is used as a charge generation material, and butyral resin (trade name: ESREC BM-2, manufactured by Sekisui Chemical Co., Ltd.) is used as a binder resin.

Then, 1 part by weight of the charge generation material and 1 part by weight of the binder resin are mixed with 98 parts by weight of methyl ethyl ketone, and the mixture is dispersed for 8 hours with a paint shaker to prepare 3 liters of coating solution for forming the charge generation layer. The mixture after the dispersion treatment was used as a coating solution. Next, as in the case of forming the undercoat layer, a coating solution for forming a charge generation layer was applied to the surface of the undercoat layer by a dip coating method.
That is, the obtained coating solution for forming the charge generation layer is filled in a coating tank, and the drum-like support with the undercoat layer formed is dipped in the coating solution, then pulled up, and naturally dried to obtain a charge having a thickness of 0.3 μm. A generation layer was formed.

Preparation of charge transport layer 6 parts by weight of tetrafluoropolyethylene resin fine particles (Lublon L2, Daikin Industries) having an average primary particle size of about 0.2 μm and 0.12 parts by weight of GF-400 (Toagosei) as a particle dispersant In addition, as a charge transport layer binder resin, TS2050 (Teijin Chemicals) 52.25 parts by weight, low surface free energy (γ) polycarbonate: (copolymer having polycarbonate skeleton and polydimethylsiloxane skeleton, viscosity average molecular weight (Mv ): About 50,000) 2.75 parts by weight, and the following formula:
35 parts by weight of the compound 1 (T2269: manufactured by Tokyo Chemical Industry Co., Ltd., N, N, N ′, N ′,-tetrakis (4-methylphenyl) benzidine) was used as a charge transport material.

  Then, a suspension having a solid content of 21% by weight was prepared by mixing tetrahydrofuran as a solvent. Thereafter, using a wet emulsifying dispersion device (NVL-AS160: manufactured by Yoshida Kikai Kogyo Co., Ltd.), a dispersion treatment was performed by performing a 5 pass operation under the condition of a set pressure of 100 MPa. Thus, 3 kg of charge transport layer forming coating solution was prepared and dispersed, and the coating solution was used as the coating solution.

  And the coating liquid for charge transport layer formation was apply | coated to the charge generating layer surface by the dip coating method. That is, the obtained coating liquid for forming a charge transport layer is filled in a coating tank, the drum-like support on which the charge generation layer is formed is dipped in the coating liquid, pulled up, dried at 120 ° C. for 1 hour, and a film thickness of 28 μm. The charge transport layer was formed. In this manner, a photoreceptor having the structure shown in FIG. 1 was produced.

At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 34.8 mJ / mm ² .
The photoconductor surface free energy was determined by a contact angle measuring device CA-X (manufactured by Kyowa Interface Co., Ltd.) and analysis software EG-11 (manufactured by Kyowa Interface Co., Ltd.).

Example 2
The coating solution for undercoat layer used in Example 1 has the following components:
Titanium oxide (Al ₂ O ₃ , SiO ₂ · nH ₂ O treatment: manufactured by Teica: MT-500SA: titanium oxide 90% by weight, Al (OH) 3 5% by weight, SiO ₂ · nH ₂ O 0 5% by weight)
4 parts by weight Maxlite (registered trademark) TS-043 (manufactured by Showa Denko) 5.5 parts by weight Polyamide resin (Toray: CM8000) 0.5 parts by weight Methanol 120 parts by weight 1,3-dioxolane 120 parts by weight Except for the above, after preparing an undercoat layer in the same manner as in Example 1, a function-separated electrophotographic photoreceptor was prepared in the same manner as in Example 1.

Example 3
Instead of Maxlite (registered trademark) TS-043 (manufactured by Showa Denko KK), the coating solution component for the undercoat layer used in Example 1, Maxlite (registered trademark) ZS-032 (manufactured by Showa Denko KK: anhydrous dioxide dioxide) Silicon-treated zinc oxide: undercoating layer in the same manner as in Example 1 except that 80% by weight of zinc oxide, 20% by weight of anhydrous silicon dioxide, zinc oxide particle diameter of 25 nm, and anhydrous silicon dioxide-treated zinc oxide particle diameter of 31 nm) were used. After that, a function-separated type electrophotographic photosensitive member was produced in the same manner as in Example 1.

Example 4
Except that Maxlite (registered trademark) TS-043 (manufactured by Showa Denko KK), a coating solution component for the undercoat layer used in Example 1, was changed to anhydrous silicon dioxide-coated titanium oxide fine particles 1 obtained in Production Example 1. Produced a function-separated electrophotographic photosensitive member in the same manner as in Example 1.

Example 5
Except that Maxlite (registered trademark) TS-043 (manufactured by Showa Denko KK), a coating solution component for the undercoat layer used in Example 1, was changed to anhydrous silicon dioxide-coated titanium oxide fine particles 1 obtained in Production Example 2. Produced a function-separated electrophotographic photosensitive member in the same manner as in Example 1.

Example 6
A function-separated electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the undercoat layer coating component used in Example 1 was changed to the following.
Maxlite (registered trademark) TS-043 (manufactured by Showa Denko KK) 2 parts by weight Polyamide resin (manufactured by Toray Industries, Inc .: CM8000) 0.05 part by weight Methanol 50 parts by weight 1,3-dioxolane 50 parts by weight

Example 7
A function-separated electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the dry thickness of the undercoat layer produced in Example 1 was changed to 0.04 μm.

Example 8
A function-separated electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the dry film thickness of the undercoat layer produced in Example 1 was changed to 6.00 μm.

Example 9
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a coating solution for forming a charge transport layer was prepared in the same manner as in Example 3 except that 49.5 parts by weight of TS2050 (Teijin Chemicals) and 5.5 parts by weight of the above low γ polycarbonate were added as the charge transport layer binder resin. Then, a photoreceptor was prepared using the coating solution.
At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 25.9 mJ / mm ² .

Example 10
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a coating solution for forming a charge transport layer was prepared in the same manner as in Example 3 except that 16.5 parts by weight of TS2050 (Teijin Chemicals) and 38.5 parts by weight of the above low γ polycarbonate were added as the charge transport layer binder resin. Then, a photoreceptor was prepared using the coating solution.
At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 31.5 mJ / mm ² .

Comparative Example 1
The coating solution for undercoat layer used in Example 1 has the following components:
Zinc oxide (alumina, organopolysiloxane treatment: Sakai Chemical Co., Ltd .: FINEX-30WL
2) 0.1 part by weight Polyamide resin (manufactured by Toray Industries, Inc .: CM8000) 0.9 part by weight Methanol 50 parts by weight 1,3-dioxolane The same as in Example 1, except that the amount was changed to 50 parts by weight. A photographic photoreceptor was prepared.

Comparative Example 2
1 part by weight of Maxlite (registered trademark) TS-043 (manufactured by Showa Denko KK) as a coating solution component for the undercoat layer used in Example 1 was used for titanium oxide (surface untreated: Ishihara Sangyo Co., Ltd .: TTO-55N). A function-separated electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the amount was changed to 1 part by weight.

Comparative Example 3
1 part by weight of Maxlite (registered trademark) TS-043 (manufactured by Showa Denko KK), the coating solution component for the undercoat layer used in Example 1, was silicon dioxide (surface untreated: manufactured by Electrochemical Co., Ltd .: UFP-80). A function-separated electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the amount was changed to 1 part by weight.

Comparative Example 4
1 part by weight of Maxlite (registered trademark) TS-043 (manufactured by Showa Denko KK), a coating solution component for the undercoat layer used in Example 1, was treated with alumina-treated titanium oxide (TTO-55A: manufactured by Ishihara Sangyo Co., Ltd .: titanium oxide). A function-separated electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the content was changed to 2 parts by weight (95% by weight, Al (OH) ₃ 5% by weight).

Comparative Example 5
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a charge transport layer forming coating solution was prepared in the same manner as in Example 1 except that 11 parts by weight of TS2050 (Teijin Kasei) and 44 parts by weight of the low γ polycarbonate were added as the charge transport layer binder resin. A photoreceptor was prepared using the coating solution.
At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 24.2 mJ / mm ² .

Comparative Example 6
In the same manner as in Example 1, an undercoat layer and a charge generation layer were prepared. Thereafter, a charge transport layer forming coating solution was prepared in the same manner as in Example 1 except that 55 parts by weight of TS2050 (Teijin Chemicals) was added as the charge transport layer binder resin, and then the photoreceptor was used with the coating solution. It was created.
At this time, a photosensitive layer from which the tetrafluoroethylene resin fine particles and the dispersant were removed was prepared in the same manner as described above from the formulation of the charge transport layer, and the surface free energy: γ value of the outermost surface layer of the photoreceptor was measured. However, it was 41.6 mJ / mm ² .

Evaluation of surface free energy in Examples and Comparative Examples Measurement of surface free energy on the surface of the photoconductor in a state not including the fluorine fine particles used in Examples 1 to 9 and Comparative Examples 1 to 3, and contact angle manufactured by Kyowa Interface Science Co., Ltd. It calculated using the meter.

(A) Evaluation of environmental stability of electrical characteristics A digital copying machine in which the electrophotographic photoreceptors of Examples 1 to 10 and Comparative Examples 1 to 6 are modified so that the exposure amount and the exposure development time can be arbitrarily changed for the photoreceptor test ( Sharp Corporation: MX-M503N) and evaluated the environmental stability of the initial electrical characteristics.
As an evaluation method, under an environment of low temperature / low humidity (L / L, 5 ° C./10%) and high temperature / high humidity (H / H, 35 ° C./85%), an exposure amount of 0.2 μJ / cm ² , The surface potential on the photoconductor upon irradiation with 0.6 μJ / cm ² was measured (initial charging voltage −600 V, exposure development time 60 msec), and the surface potential difference ΔV _LL− between the surface potential at low temperature / low humidity and the high temperature / high humidity. _HH was used as an evaluation standard. That is, the smaller the value of ΔV _LL-HH , the better the environmental stability with respect to electrical characteristics.
Environmental stability was evaluated according to the following criteria of surface potential difference ΔV _LL-HH .
VG: Very good (0 ≦ ΔV _LL-HH <40).
G: Good (40 ≦ ΔV _LL-HH <80).
B: Bad (80 ≦ ΔV _LL-HH <120).
VB: Very bad (120 ≦ ΔV _LL-HH ).

(B) VL repetitive stability evaluation The electrophotographic photosensitive members of Examples 1 to 10 and Comparative Examples 1 to 6 were mounted on the above-described digital copying machine (manufactured by Sharp Corporation: MX-M503N), and high temperature / high humidity ( The surface potential VL (V) on the photosensitive member at the time of irradiation with an exposure amount of 0.6 μJ / cm ² is measured under an environment of H / H, 35 ° C./85% (initial charging voltage −900 V, exposure development time). 60 msec), the difference between the VL (V) at the time of exposure after repeating charge-exposure-static elimination 10,000 times and the VL (V) at the time of the first (initial) exposure, using ΔVL (V) as an evaluation criterion, Evaluation was made according to the following criteria.
VG: Very good (0 ≦ ΔVL <30).
G: Good (30 ≦ ΔVL <60).
B: Bad (60 ≦ ΔVL <90).
VB: Very bad (90 ≦ ΔVL).

(C) Durability Evaluation The electrophotographic photosensitive members of Examples 1 to 10 and Comparative Examples 1 to 6 are mounted on a digital copying machine (manufactured by Sharp: MX-M503N), and 100K sheets are used to evaluate the durability of each characteristic. The image characteristics and printing durability (film slippage (μm)) at the end of actual photoaging were evaluated.
The evaluation criteria for image characteristics are as follows.
Evaluation criteria:
VG: Very good: no black spotted defects.
G (good): There is a black spot defect, but there is no problem in use.
B (Poor): There are many black spotted defects and there is a problem in use.
VB (very bad): Image fogging occurred.

The standards for evaluating printing durability are as follows.
Evaluation criteria:
VG: Very good (0 ≦ film slippage (μm) <0.5).
G: Good (0.5 ≦ slip amount (μm) <1.0).
B: Poor (1.0 ≦ slip amount (μm) <1.5).
VB: Very bad (1.50 ≦ slip amount (μm)).
As mentioned above, the result evaluated by the method as described in said (a)-(c) is shown in the following tables.

  By comparing the results of Examples 1 to 10 and Comparative Examples 1 to 4, the surface treatment method using anhydrous silicon dioxide for the metal fine particles contained in the undercoat layer in the present invention is effective for environmental stability and sensitivity evaluation. It turns out that there is.

Further, from the comparison between Examples 1 to 10 and Comparative Examples 5 and 6, in order to realize environmental stability, high sensitivity, and high responsiveness, the charge transport layer is a photosensitive layer excluding tetrafluoroethylene resin fine particles. It has been found effective that the surface free energy value after formation is in the range of 25 to 35 mJ / mm ² .

  Further, the photoreceptor according to the present invention has good initial and post-aging sensitivity, image and film reduction results in durability evaluation, and is not affected by humidity even after long-term use, and has excellent environmental stability. It has been found that a photographic photoreceptor can be provided and an image forming apparatus for an excellent output image can be provided over a long period of time.

From comparison between Examples 1 to 3 and Comparative Examples 1 to 3, it was found that the performance was further improved with respect to environmental stability and repetitive characteristics by using titanium oxide or zinc oxide fine particles among the metal fine particles.
From comparison between Example 1 and Examples 4 and 5, it was found that the average primary particle diameter of the titanium oxide fine particles was more preferably 20 nm to 100 nm from the viewpoint of environmental stability.

  From comparison between Example 1 and Examples 7 and 8, it was found that the thickness of the undercoat layer is more preferably 0.05 μm to 5 μm from the viewpoint of environmental stability, sensitivity, and responsiveness.

  According to the present invention, a coating liquid for forming a charge transport layer capable of producing an electrophotographic photosensitive member that does not cause deterioration of electrical characteristics even when used for a long period of time, an electrophotographic printer, a copy produced using the coating liquid It is possible to provide an electrophotographic photosensitive member and an image forming apparatus which are mounted on an image forming apparatus such as a copier, a multi-function machine, and a facsimile machine.

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 11 Conductive substrate 12 Charge generation layer 13, 13A, 13B Charge transport layer 14 Photosensitive layer 15 Undercoat layer (intermediate layer)
30 Laser printer (image forming device)
DESCRIPTION OF SYMBOLS 31 Semiconductor laser 32 Rotating polygon mirror 33 Laser beam 34 Imaging lens 35 Mirror 36 Corona charger 37 Developer 38 Transfer paper cassette 39 Paper feed roller 40 Registration roller 41 Transfer charger 42 Separation charger 43 Conveyor belt 44 Fixer 45 Exhaust Paper tray 46 Cleaner 47 Arrow 48 Transfer paper 49 Exposure means 50 Static eliminator

Claims (8)

A laminated photosensitive layer in which a charge generation layer containing at least a charge generation material and a charge transport layer containing a charge transport material are laminated in this order on an undercoat layer provided on a conductive substrate, or a charge generation material and a charge An electrophotographic photosensitive member in which a single-layer type photosensitive layer containing a transport material is laminated,
The undercoat layer includes fine metal oxide particles and a binder resin;
The outermost surface layer of the photoreceptor includes at least a charge transport material, a binder resin, and tetrafluoroethylene resin fine particles;
In the charge transport layer formed by using the coating solution for forming the charge transport layer excluding the tetrafluoroethylene resin fine particles, the binder resin in the outermost surface layer has a surface free energy value in the range of 25 to 35 mJ / mm ^2. Show
The tetrafluoroethylene resin fine particles are
(1) It is composed of primary particles having an average particle diameter of 0.1 to 0.5 μm and secondary particles that are aggregates of secondary particles that are aggregates of primary particles.
(2) included in the range of 1 to 30% by weight of the binder resin component in the outermost surface layer,
(3) including primary particles and secondary particles having a particle diameter of less than 1 μm in a content ratio of less than 80% by weight;
(4) An electrophotographic photoreceptor comprising secondary particles of 3 μm or more at a content ratio of 5% by weight or less.   The metal oxide fine particles have an average primary particle diameter of 20 to 100 nm and are contained in a weight ratio of 10/90 to 95/5 with respect to the binder resin in the undercoat layer. 2. The electrophotographic photosensitive member according to 1.   The electrophotographic photoreceptor according to claim 1, wherein the metal oxide fine particles are titanium oxide or zinc oxide surface-treated with anhydrous silicon dioxide, and the binder resin in the undercoat layer is a polyamide resin.   The tetrafluoroethylene resin fine particles include primary particles having an average particle diameter of 0.2 to 0.4 μm and are included in a range of 5 to 15% by weight of the binder resin component of the outermost surface layer. The electrophotographic photosensitive member according to any one of to 3.   The electrophotographic photosensitive member according to claim 1, wherein the tetrafluoroethylene resin fine particles are contained in an amount of 8 to 12% by weight of the binder resin component of the outermost surface layer. The electrophotographic photosensitive member according to claim 1, wherein the surface free energy value is in a range of 27 to 32 mJ / mm ² .   The multilayer photosensitive layer is formed of two charge transport layers having different charge transport substance concentrations, and the charge transport layer of the outermost layer contains tetrafluoroethylene resin fine particles. The electrophotographic photosensitive member according to any one of the above.   An electrophotographic photosensitive member according to claim 1, a charging means for charging the electrophotographic photosensitive member, and the charged electrophotographic photosensitive member is exposed to form an electrostatic latent image. An exposure unit; a developing unit that develops the electrostatic latent image with toner to form a toner image; a transfer unit that transfers the toner image onto a recording material; and the transferred toner image on the recording material. An image forming apparatus including fixing means for fixing.