JP2018025707A - Electrophotographic photoreceptor, electrophotographic image forming apparatus, and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor that can provide memory resistance for a long period and prevent the occurrence of image defects including black dots and fogging.SOLUTION: An electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor that includes at least an intermediate layer, charge generating layer, and a charge transport layer in this order on a conductive substrate, and used in an electrophotographic image forming apparatus of an eraseless system. The intermediate layer includes rutile-type titanium dioxide particles and anatase type titanium oxide particles as titanium oxide particles; the titanium oxide particles have an average particle diameter within a range of 10 to 50 nm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrophotographic photosensitive member, an electrophotographic image forming apparatus, and a process cartridge. More specifically, the present invention relates to an electrophotographic photosensitive member that can provide memory resistance over a long period of time under so-called “eraseless” conditions and can prevent image defects such as black spots and fog. .

  Space saving and cost reduction of an electrophotographic image forming apparatus (hereinafter also simply referred to as “image forming apparatus”) and reduction of light damage to an electrophotographic photosensitive body (hereinafter also simply referred to as “photosensitive body”). In view of the above, there is a demand for a photoreceptor corresponding to a process (so-called “eraseless”) that does not perform photostatic removal after transfer. However, when a conventional photoreceptor is used for an eraseless image forming apparatus, image defects such as memory resistance, black spots, and fog are generated, which is a problem. In response to these problems, for example, a photoconductor corresponding to eraseless in which an intermediate layer contains a conductive metal oxide and an acceptor compound has been proposed (see, for example, Patent Document 1).

  In order to make it possible to use the photoconductor corresponding to these eraseless for a longer period of time, the photoconductor layer configuration is changed such as introduction of a protective layer on the surface of the photoconductor. For this reason, a further improvement in memory resistance is required for the photoreceptor corresponding to the eraseless.

By introducing metal oxide particles having high electron conductivity into the intermediate layer, the memory resistance can be further improved. However, in this configuration, since the hole injection blocking property from the conductive support to the photosensitive layer is weakened, it cannot be compatible with the suppression of image defects such as black spots and fog.
In addition, in the case of using titanium oxide particles as metal oxide particles, the combined use of anatase-type titanium oxide particles and rutile-type titanium oxide particles having high blocking properties as particles having high electron conductivity has been studied (for example, , See Patent Document 2).
However, in this case, it has been difficult to find a condition that achieves both further improvement in memory resistance and suppression of image defects such as black spots and fog.

JP 2006-221094 A JP 2009-066941 A

  The present invention has been made in view of the above-mentioned problems and circumstances, and its solution is to provide memory resistance over a long period of time under eraseless conditions and to generate image defects such as black spots and fog. An object of the present invention is to provide an electrophotographic photosensitive member that can be prevented.

In order to solve the above problems, the present inventor, in the process of studying the cause of the above problems, the electrophotographic photosensitive member has an intermediate layer containing specific titanium oxide particles under specific conditions. Under the conditions, the present inventors have found that memory resistance can be obtained over a long period of time and that image defects such as black spots and fog can be prevented from occurring.
That is, the said subject which concerns on this invention is solved by the following means.

1. An electrophotographic photosensitive member having at least an intermediate layer, a charge generation layer, and a charge transport layer in this order on a conductive support, and used in an eraseless type electrophotographic image forming apparatus,
The intermediate layer contains, as titanium oxide particles, rutile titanium oxide particles and anatase titanium oxide particles,
An electrophotographic photoreceptor, wherein the titanium oxide particles have an average particle diameter in the range of 10 to 50 nm.

  2. The electrophotographic photosensitive member according to item 1, wherein the rutile type titanium oxide particles and the anatase type titanium oxide particles each have an average particle size in the range of 10 to 50 nm.

  3. 3. The mass ratio of the anatase-type titanium oxide particles with respect to the total amount of the titanium oxide particles contained in the intermediate layer is in the range of 0.60 to 0.95. Electrophotographic photoreceptor.

  4). From the first aspect, the cured resin obtained by polymerization reaction of the crosslinkable polymerizable compound has a protective layer containing metal oxide fine particles and a charge transport material on the charge transport layer. The electrophotographic photosensitive member according to any one of Items 3 to 3.

5. The surfaces of the anatase-type titanium oxide particles and the rutile-type titanium oxide particles are modified with an organic compound,
The electrophotographic photosensitive material according to any one of items 1 to 4, wherein the organic compound is different in type between the anatase-type titanium oxide particles and the rutile-type titanium oxide particles. body.

  6). 6. The electrophotographic photosensitive member according to any one of items 1 to 5, wherein surfaces of the anatase-type titanium oxide particles and the rutile-type titanium oxide particles are modified with an inorganic compound. .

  7). The mass ratio of the anatase-type titanium oxide particles to the total amount of the titanium oxide particles contained in the intermediate layer is in the range of 0.60 to 0.80. The electrophotographic photoreceptor according to any one of the above.

  8). The electrophotographic photosensitive member according to any one of Items 1 to 7, wherein the charge transport layer has a thickness in the range of 10 to 20 μm.

9. An electrophotographic image forming apparatus comprising an electrophotographic photosensitive member and having a charging process, an exposure process, a development process, and a transfer process,
The electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of items 1 to 8,
An electrophotographic image forming apparatus characterized by having no charge eliminating means by light.

  10. A process cartridge for use in the electrophotographic image forming apparatus according to item 9, wherein the process cartridge includes at least the electrophotographic photosensitive member according to any one of items 1 to 8 and a charging unit. A process cartridge comprising at least one of an exposure unit, a developing unit, and a cleaning unit, and is configured to be able to be inserted into and removed from the electrophotographic image forming apparatus.

By the above means of the present invention, it is possible to provide an electrophotographic photoreceptor and the like that can obtain memory resistance over a long period of time under eraseless conditions and can prevent image defects such as black spots and fog.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is considered as follows.

[Cause of pattern memory]
2. Description of the Related Art Conventionally, in an image forming apparatus having a photostatic process, negative charges accumulate at the interface between a charge generation layer and an intermediate layer due to a continuous exposure history. In addition, when the photoreceptor has a protective layer, positive charges remain and accumulate at the interface between the protective layer and the charge transport layer, resulting in further reduction in sensitivity of the photoreceptor. Along with this, after exposure, the potential of the latent image forming portion decreases with respect to the potential of the background portion, and a pattern memory is generated.
The present inventor considered that since there is no residual charge removal step by photostatic discharge under the eraseless condition, it is necessary to further reduce the accumulation of residual charges in order to prevent the generation of pattern memory.

[Reduction of residual negative charge between charge generation layer / interlayer and suppression of image defects]
When the present inventors introduce anatase-type titanium oxide particles having a high electron transporting property into the intermediate layer in a certain amount (preferably 60% or more) with respect to the total titanium oxide amount, the residual negative charge between the charge generation layer / interlayer is reduced. It was found that it can be reduced to a sufficient level. Also, under eraseless conditions, if a certain amount (preferably 5% or more) of rutile titanium oxide having a high electron blocking property is introduced with respect to the total amount of titanium oxide, image defects such as black spots and fog are suppressed. be able to.
It should be noted that, under the eraseless condition, it is considered that a sufficient amount of electron blocking is exhibited even with a relatively small amount of rutile-type titanium oxide particles because excess energy injection due to light static elimination is eliminated. In addition, by making the average particle diameter of the titanium oxide particles in the range of 10 to 50 nm, it becomes possible to form a uniform intermediate layer film with good dispersibility, leading to suppression of image defects such as black spots and fog. .

[Dispersion of residual positive charge between protective layer / charge transport layer]
It is considered that the sensitivity reduction due to the accumulation of positive charges could be improved by the following mechanism. The positive charge remaining due to the continuous exposure history is normally accumulated in a concentrated manner at the interface between the protective layer and the charge transport layer, so that a steep local electric field is generated due to a high charge density, which becomes a barrier against charge transfer. Only by improving the design of the protective layer, the barrier for charge transfer could not be eliminated.
Here, the present inventor introduces a certain amount (preferably 5% or more) of rutile-type titanium oxide having high electron retention in the intermediate layer, based on the total amount of titanium oxide. I found that I could attract a certain amount. As a result, positive charges accumulated at the interface between the protective layer and the charge transport layer are appropriately dispersed in the charge transport layer, the steep local electric field is relaxed, and as a result, sensitivity reduction is suppressed.
With this effect, it is considered that the generation of pattern memory can be suppressed and the memory resistance can be improved.

Partial sectional view showing an example of the layer structure of the electrophotographic photosensitive member of the present invention Schematic sectional view showing an example of an image forming apparatus using the electrophotographic photosensitive member according to the present invention.

  The electrophotographic photosensitive member of the present invention has at least an intermediate layer, a charge generation layer, and a charge transport layer in this order on a conductive support, and is used in an eraseless type electrophotographic image forming apparatus. The intermediate layer contains rutile titanium oxide particles and anatase titanium oxide particles as titanium oxide particles, and the average particle size of the titanium oxide particles is in the range of 10 to 50 nm. Features. This feature is a technical feature common to or corresponding to the claimed invention. As a result, the present invention provides an effect that memory resistance can be obtained over a long period of time under eraseless conditions, and image defects such as black spots and fog can be prevented from occurring.

  Each of the rutile titanium oxide particles and the anatase titanium oxide particles preferably has an average particle size in the range of 10 to 50 nm. Thereby, generation | occurrence | production of image defects, such as a pattern memory, black spots, and fog, can be suppressed more.

  The mass ratio of the anatase-type titanium oxide particles to the total amount of the titanium oxide particles contained in the intermediate layer is preferably in the range of 0.60 to 0.95. Thereby, generation | occurrence | production of image defects, such as a pattern memory, black spots, and fog, can be suppressed more.

  It is preferable to have a protective layer containing metal oxide fine particles and a charge transport material on the charge transport layer in a cured resin obtained by a polymerization reaction of a crosslinkable polymerizable compound. Thereby, it is possible to improve both the durability and the memory resistance of the photoreceptor.

  The surfaces of the anatase-type titanium oxide particles and the rutile-type titanium oxide particles are modified with an organic compound, and the type of the organic compound is the anatase-type titanium oxide particles and the rutile-type titanium oxide particles. Each is preferably different. Thereby, the electronic block property of an intermediate | middle layer improves moderately.

  The surfaces of the anatase-type titanium oxide particles and the rutile-type titanium oxide particles are preferably modified with an inorganic compound. Thereby, the electronic block property of an intermediate | middle layer and the electron retention of a titanium oxide particle improve moderately.

  The mass ratio of the anatase-type titanium oxide particles to the total amount of the titanium oxide particles contained in the intermediate layer is preferably in the range of 0.60 to 0.80. Thereby, generation | occurrence | production of image defects, such as a pattern memory, black spots, and fog, can be suppressed more.

  The thickness of the charge transport layer is preferably in the range of 10 to 20 μm. As a result, the internal electric field of the photoconductor is strengthened, and the accumulated charge due to the continuous exposure history is reduced.

  The electrophotographic photosensitive member of the present invention is an electrophotographic image forming apparatus having a charging process, an exposure process, a developing process, and a transfer process, and can be suitably used for an electrophotographic image forming apparatus that does not have a charge eliminating means by light. As a result, even under an eraseless condition, memory resistance can be obtained over a long period of time, and image defects such as black spots and fog can be prevented.

  The electrophotographic photosensitive member of the present invention is a process cartridge used in an electrophotographic image forming apparatus, and the process cartridge is integrated with at least one of a charging unit, an exposure unit, a developing unit, or a cleaning unit. It can be suitably used for a process cartridge that is configured to be able to be taken in and out of the electrophotographic image forming apparatus. As a result, even under an eraseless condition, memory resistance can be obtained over a long period of time, and image defects such as black spots and fog can be prevented.

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

  In the present invention, the eraseless type electrophotographic image forming apparatus refers to an electrophotographic image forming apparatus that does not perform photostatic removal after transfer.

≪Overview of electrophotographic photoreceptor≫
The electrophotographic photoreceptor of the present invention (hereinafter also simply referred to as “photoreceptor”) has at least an intermediate layer, a charge generation layer, and a charge transport layer in this order on a conductive support, and is an eraseless system. The electrophotographic photoreceptor used in the electrophotographic image forming apparatus according to claim 1, wherein the intermediate layer contains, as titanium oxide particles, rutile titanium oxide particles and anatase titanium oxide particles, and the average particle diameter of the titanium oxide particles Is in the range of 10 to 50 nm.
FIG. 1 shows a specific example of a preferred schematic configuration of the photoreceptor of the present invention. As shown in FIG. 1, the photoreceptor according to the present invention comprises an electrophotographic photoreceptor in which an intermediate layer 1b, a charge generation layer 1c, a charge transport layer 1d, and a protective layer 1e are laminated in this order on a conductive support 1a. 1 is formed, and the organic photosensitive layer 1f is preferably composed of the charge generation layer 1c and the charge transport layer 1d. The intermediate layer 1b contains titanium oxide particles 1bA whose surface is modified with a surface modifier described later (hereinafter also referred to as “surface modified”), and the protective layer 1e contains metal oxide. It is preferable that the fine particle 1eA and the charge transport material are contained.

[Middle layer]
The intermediate layer contains, as titanium oxide particles, rutile-type titanium oxide particles and anatase-type titanium oxide particles (hereinafter, collectively referred to as “titanium oxide particles” when there is no need to distinguish between them).
Specifically, the intermediate layer constituting the photoreceptor of the present invention is, for example, specific rutile type titanium oxide particles and anatase type titanium oxide particles in a binder resin (hereinafter also referred to as “binder resin for intermediate layer”). Is contained.
The intermediate layer provides a barrier function and an adhesive function between the conductive support and the organic photosensitive layer.

  Examples of the intermediate layer binder resin include polyamide resin, casein, polyvinyl alcohol resin, nitrocellulose, ethylene-acrylic acid copolymer, vinyl chloride resin, vinyl acetate resin, polyurethane resin, and gelatin. Among these, it is preferable to use a polyamide resin from the viewpoint of suppressing dissolution of the binder resin for the intermediate layer when a charge generation layer forming coating liquid described later is applied on the intermediate layer. Further, since the organically treated rutile type titanium oxide particles are preferably dispersed in alcohols, it is more preferable to use an alcohol-soluble polyamide resin such as a methoxymethylolated polyamide resin.

<Titanium oxide particles>
The average particle diameter of the titanium oxide particles according to the present invention is in the range of 10 to 50 nm. In particular, the average particle size of each of the rutile-type titanium oxide particles and the anatase-type titanium oxide particles, which will be described later, is in the range of 10 to 50 nm, so that image defects such as pattern memory and black spots and fog are more likely to occur. Since it can suppress, it is preferable.
Moreover, the peak top of the particle size distribution in the titanium oxide particles exists in the range of 10 to 50 nm. There may be a plurality of peak tops or a single peak top. However, when there are a plurality of peak tops, it is preferable that any of the peak tops is within a range of 10 to 50 nm from the viewpoint of the effect of the present invention.

Titanium oxide has three types of crystal forms, anatase type, rutile type, and brookite type, but there are few industrial applications for brookite. In the three crystal forms, the most stable crystal is the rutile type, and when there is no transition control agent or accelerator, the anatase type changes to the rutile type at 915 ± 15 ° C., and the brookite changes to the rutile type at 650 ° C. or higher. These crystal types can be identified by X-ray diffraction images unique to each crystal by powder X-ray diffraction.
The two crystal forms, anatase type and rutile type, have different physical properties such as electron conductivity and dielectric constant. By appropriately controlling the particle size and addition amount of these titanium oxides, the electron transport property and the electron block property of the intermediate layer can be set to appropriate values.

  The titanium oxide particles used in the present invention can be produced by a known technique such as a gas phase method, a chlorine method, a sulfuric acid method, or a plasma method. The mixing ratio is the ratio of the mass to the total titanium oxide amount by measuring the total titanium oxide amount, each of the anatase type titanium oxide and the rutile type titanium oxide. The titanium oxide particles contained in the intermediate layer preferably have a mass ratio of anatase-type titanium oxide particles to all titanium oxide particles in the range of 0.60 to 0.95, more preferably 0.60 to 0.80. Is within the range. If the mass ratio of the anatase-type titanium oxide particles is 0.6 or more, the generation of pattern memory due to negative charge accumulation at the interface between the charge generation layer and the intermediate layer can be further suppressed, and conversely, the rutile type titanium oxide. If the mass ratio is 0.05 or more, the electron blocking property of the intermediate layer is sufficient, and the occurrence of image defects such as black spots and fog can be further suppressed.

  The surface of the titanium oxide particles used in the present invention is preferably modified with a surface modifier. Examples of the surface modifier include inorganic compounds and organic compounds, and examples of the organic compounds include reactive organic silicon compounds and organic titanium compounds. The surface modifiers may be used alone or in combination of two or more. Above all, when the surface of anatase-type titanium oxide particles and rutile-type titanium oxide particles is modified with an organic compound, the type of organic compound is different between anatase-type titanium oxide particles and rutile-type titanium oxide particles. Is preferred. Thereby, rutile type titanium oxide particles are unevenly distributed, and as a result, the electron blocking property of the intermediate layer is appropriately improved. Moreover, when the surface of anatase type titanium oxide particles and rutile type titanium oxide particles is modified with an inorganic compound, the electron blocking property of the intermediate layer and the electron retention property of the titanium oxide particles are preferably improved.

  Examples of the surface modifier for inorganic compounds include alumina, silica, zirconia, and hydrates thereof. Among these, the combination of alumina, silica, alumina and silica is particularly preferable because the degree of hydrophobicity of the titanium oxide particles can be easily controlled. These may be used alone or in combination of two or more. In addition, as titanium oxide particles subjected to surface modification with an inorganic compound, commercially available titanium oxide particles treated with silica or alumina may be used. Examples of such commercially available products include F-1S02 (manufactured by Showa Denko KK) T-805 (manufactured by Nippon Aerosil Co., Ltd.), STT-30A, STT-65S-S (manufactured by Titanium Industry Co., Ltd.), TAF-500T, and TAF. -1500T (manufactured by Fuji Titanium Industry Co., Ltd.), MT-100S, MT-100T, MT-500SA, MT-100SA (manufactured by Teika), IT-S (manufactured by Ishihara Sangyo Co., Ltd.) and the like.

  Examples of reactive organosilicon compounds include methyltrimethoxysilane, n-butyltrimethoxysilane, n-hexyltrimethoxysilane, dimethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltrimethoxy. Alkoxy such as silane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 2-methacryloxyethyltrimethoxysilane, 3-methacryloxybutylmethyldimethoxysilane, etc. Silane; hexamethyldisilazane, and polysiloxane compounds such as methylhydrogenpolysiloxane. Among these, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, and methylhydrogenpolysiloxane are particularly preferable because the degree of hydrophobicity of the titanium oxide particles can be easily controlled.

  Organic titanium compounds include alkoxy titanium (ie, titanium alkoxide), titanium polymer, titanium acylate, titanium chelate, tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecyl benzene sulfonyl titanate and bis (dioctyl pyro). Phosphate) oxyacetate titanate and the like can be used. Of these, titanium acylate and titanium chelate are particularly preferable.

  The surface modification of the titanium oxide particles with the surface modifier can be performed by a known method, and is not particularly limited, and wet treatment or dry treatment can be employed. As the dry treatment, the dispersion of titanium oxide particles in a cloud shape by stirring or the like may be sprayed with a hydrophobizing agent solution dissolved with alcohol or the like, or a vaporized hydrophobizing agent may be contacted and adhered. it can. In addition, as a surface modification method by wet treatment, for example, a solution in which a surface modifier is dispersed in water or an organic solvent, titanium oxide particles are added and mixed or stirred, or titanium oxide particles are dispersed in a solution. The hydrophobizing agent can be dropped and adhered therein. Moreover, you may perform a wet crushing process by a bead mill etc. in the case of a wet process. Thereafter, the obtained solution can be filtered and dried, and the obtained titanium oxide particles can be annealed (baked).

  The temperature at the time of mixing and stirring during the wet treatment is preferably about 25 to 150 ° C, more preferably 30 to 60 ° C. The mixing / stirring time is preferably 0.1 to 10 hours, and more preferably 0.2 to 5 hours. The annealing temperature can be, for example, 100 to 220 ° C., preferably 110 to 150 ° C. The annealing treatment time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours. 20-50 degreeC is preferable and the process temperature in the case of performing a wet crushing process, More preferably, it is 30-40 degreeC. The time for the wet crushing treatment is preferably 10 to 120 minutes, more preferably 20 to 70 minutes.

  In the wet surface modification method, the amount of the surface modifier used varies depending on the purpose and the type of the surface modifier, and thus cannot be defined unconditionally. It is preferable to appropriately select and modify the surface. For example, in the case of a reactive organosilicon compound, 0.1 to 20 parts by mass, more preferably 1 to 15 parts by mass can be used with respect to 100 parts by mass of untreated titanium oxide particles. In the case of an organic titanium compound, 0.1 to 20 parts by mass, more preferably 2 to 15 parts by mass can be used with respect to 100 parts by mass of untreated titanium oxide particles. The addition amount of the solvent is preferably 100 to 600 parts by mass, more preferably 200 to 500 parts by mass with respect to 100 parts by mass of the untreated titanium oxide particles.

  If the usage-amount of a surface modifier is more than said lower limit, respectively, sufficient surface modification can be performed with respect to an untreated titanium oxide particle. On the other hand, if the amount of the surface modifier used is less than or equal to the above upper limit value, the surface modifiers react with each other, so that a uniform film is not attached to the surface of the titanium oxide particles, and leakage is likely to occur. Can be prevented.

  Whether the titanium oxide particles contained in the intermediate layer are surface-modified is determined by confirming the production process or performing an inorganic analysis of the surface of the titanium oxide particles contained in the intermediate layer by transmission type, energy dispersive X-ray analysis ( This can be confirmed by TEM-EDX) or wavelength dispersive X-ray fluorescence analysis (WDX).

(Measuring method of average particle size)
The average particle diameter of the particles according to the present invention is measured as follows. That is, a sample particle (for example, titanium oxide particle) is photographed with a scanning electron microscope at a magnification of 100000 times, and the sample particle is binarized using an automatic image processing analyzer, and is randomly selected. The horizontal ferret diameter for 100 particles is calculated, and the average value (number average primary particle diameter) is obtained as “average particle diameter”. Here, the horizontal ferret diameter means the length of a side parallel to the x-axis of the circumscribed rectangle when the image of the particle as a sample is binarized.

(Peak top of particle size distribution)
First, the average particle diameter of the primary particles of 100 randomly selected particles measured as described above is measured to obtain a particle size distribution. In this particle size distribution, the particle size at the peak maximum point is defined as “peak top of particle size distribution”.

(Mass ratio)
The mass ratio of the anatase-type titanium oxide particles to the total amount of titanium oxide particles contained in the intermediate layer can be obtained from the following formula.
Mass ratio of anatase-type titanium oxide = anatase-type titanium oxide mass / total titanium oxide mass In addition, when mixing titanium oxide powder whose crystal type is known, the ratio of the addition amount is adopted as it is.

Here, as a method for detecting the amount of titanium oxide from the photoreceptor, there is a method in which the mass is extracted from the intermediate layer and the mass is measured, and the ratio of the anatase type and the rutile type is calculated by X-ray diffraction. The ratio of the anatase type and the rutile type is obtained by the following formula. In the powder X-ray diffraction of titanium oxide, the intensity IA of the strongest interference line of the anatase type (plane index 101) and the strongest interference line of the rutile type (plane index 110) ) Is measured and calculated by the following formula.
Ratio of anatase type (%) = 100 / (1 + 1.265 × IR / IA)

  The above intermediate layer may contain other metal oxide fine particles other than the titanium oxide particles. Other metal oxide fine particles are not particularly limited. For example, zinc oxide, alumina (aluminum oxide), silica (silicon oxide), tin oxide, antimony oxide, indium oxide, bismuth oxide, magnesium oxide, lead oxide, tantalum oxide Metal oxide fine particles such as yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, niobium oxide, molybdenum oxide, vanadium oxide, indium oxide doped with tin, antimony doped Fine particles such as tin oxide and zirconium oxide can be used. These can be used individually by 1 type or in combination of 2 or more types. When two or more kinds are used in combination, they may be solid solutions or fused bodies. The average particle size of such particles is preferably, for example, 300 nm or less, and more preferably 100 nm or less.

[Method for forming intermediate layer]
The intermediate layer as described above is obtained by, for example, dissolving or dispersing the binder resin for the intermediate layer in a solvent, and then uniformly dispersing the titanium oxide particles to obtain a dispersion. It can be formed by preparing a coating solution for forming an intermediate layer, coating the coating solution for forming an intermediate layer on the surface of the conductive support to form a coating film, and drying the coating film.

The solvent used for forming the intermediate layer is not particularly limited as long as it can dissolve the binder resin for the intermediate layer and can obtain good dispersibility of the titanium oxide particles. When the resin is used, good solubility and coating performance can be expressed for the polyamide resin, so that methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol, etc. Alcohols are preferably used. These solvents can be used alone or as a mixed solvent of two or more.
Moreover, in order to improve the preservability and the dispersibility of the titanium oxide particles, a cosolvent may be used in combination. Examples of the cosolvent include benzyl alcohol, toluene, cyclohexanone, and tetrahydrofuran.

  As a means for dispersing the titanium oxide particles, an ultrasonic disperser, a bead mill, a ball mill, a sand mill, a homomixer, or the like can be used.

  Although the density | concentration of the binder resin for intermediate | middle layers in the coating liquid for intermediate | middle layer formation changes also with the layer thickness and coating method of an intermediate | middle layer, the usage-amount of the solvent with respect to 100 mass parts of binder resin for intermediate | middle layers is 100-3000 mass parts, for example. It is preferable that it is 500 to 2000 parts by mass.

  The method for applying the intermediate layer forming coating solution is not particularly limited, and examples thereof include a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, and a slide hopper method. .

  As a method for drying the coating film, a known drying method can be appropriately selected according to the type of the solvent and the thickness of the intermediate layer to be formed, and it is particularly preferable to perform heat drying. Drying conditions can be 10 to 60 minutes at 100 to 150 ° C., for example.

The thickness of the intermediate layer is preferably 0.5 to 15 μm, and more preferably 1 to 7 μm.
If the thickness of the intermediate layer is 0.5 μm or more, the entire surface of the conductive support can be sufficiently covered, so that the injection of holes from the conductive support can be sufficiently blocked, As a result, the occurrence of image defects such as black spots and fog can be further suppressed. On the other hand, if the thickness of the intermediate layer is 15 μm or less, the electrical resistance can be made appropriate and sufficient electron transport properties can be obtained, and as a result, the occurrence of density unevenness can be further suppressed.

[Conductive support]
The conductive support only needs to have conductivity, for example, a metal such as aluminum, copper, chromium, nickel, zinc and stainless steel formed into a drum or a sheet, or a metal foil such as aluminum or copper. Examples include those laminated on plastic films, aluminum, indium oxide, tin oxide, etc. deposited on plastic films, metals with conductive layers applied alone or with a binder resin, plastic films, and paper. .

[Charge generation layer]
The charge generation layer contains a charge generation material (CGM), and optionally contains a binder resin (hereinafter also referred to as “binder resin for charge generation layer”), and further contains other additives. May be.

  Examples of charge generation materials include azo raw materials such as Sudan Red and Diane Blue, quinone compounds such as pyrenequinone and anthanthrone, quinocyanine compounds, perylene compounds, indigo compounds such as indigo and thioindigo, and many such as pyranthrone and diphthaloylpyrene. Examples thereof include, but are not limited to, ring quinone compounds and phthalocyanine compounds. Of these, phthalocyanine compounds are preferred. These charge generation materials may be used alone or in combination of two or more.

  As the phthalocyanine compound, for example, a phthalocyanine compound having a central metal can be used, and it is preferable to use a compound in which the central metal has at least one of Ti, Fe, V, Ga, Si, Pb, Al, Zn, and Mg. . Among these, it is more preferable to use a titanyl phthalocyanine compound having Ti as a central metal, and has a maximum peak at a Bragg angle (2θ ± 0.2) of 27.3 ° in X-ray diffraction by CuKα rays, and 7.4 Y-type titanyl phthalocyanine showing clear diffraction peaks at °, 9.7 °, 24.2 °, Bragg angles (2θ ± 0.2) 8.3 °, 24.7 °, 25.1 °, 26. 2,3-butanediol adduct titanyl phthalocyanine showing a clear diffraction peak at 5 ° is particularly preferred because of its high sensitivity.

  As the binder resin for the charge generation layer, a known resin can be used, and examples thereof include a formal resin, a butyral resin, a silicone resin, a silicone-modified butyral resin, and a phenoxy resin.

The content ratio of the charge generation material in the charge generation layer is preferably 20 to 600 parts by mass, more preferably 50 to 500 parts by mass with respect to 100 parts by mass of the binder resin for charge generation layer.
When the mixing ratio of the charge generating layer binder resin and the charge generating material is in the above range, high dispersion stability is obtained in the coating solution for forming the charge generating layer, which will be described later. The resistance is suppressed to be low, and an increase in residual potential due to repeated use can be extremely suppressed.

  The charge generation layer as described above is prepared by, for example, preparing a charge generation layer forming coating solution by adding and dispersing a charge generation material in a charge generation layer binder resin dissolved in a known solvent. It can be formed by applying a coating liquid for layer formation onto the surface of the intermediate layer to form a coating film and drying the coating film.

  As the solvent used for forming the charge generation layer, a solvent capable of dissolving the binder resin for the charge generation layer may be used. For example, ketone solvents such as methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, cyclohexanone, acetophenone, etc. , Ether solvents such as tetrahydrofuran, dioxolane and diglyme, alcohols such as methyl cellosolve, ethyl cellosolve and butanol, ester solvents such as ethyl acetate and t-butyl acetate, aromatic solvents such as toluene and chlorobenzene, dichloroethane In addition, a large number of halogen solvents such as trichloroethane can be mentioned, but the invention is not limited thereto. These can be used individually by 1 type or in mixture of 2 or more types.

Examples of the means for dispersing the charge generating substance include the same method as the means for dispersing the titanium oxide particles in the intermediate layer forming coating solution.
Examples of the coating method for the charge generation layer forming coating solution include the same methods as those mentioned as the coating method for the intermediate layer forming coating solution.

  The layer thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics and the content ratio of the binder resin for the charge generation layer, but is preferably 0.01 to 2 μm, more preferably 0.15 to 1.5 μm. is there.

[Charge transport layer]
The charge transport layer contains a hole transport charge transport material (CTM) and a binder resin (hereinafter also referred to as “binder resin for charge transport layer”), and contains an antioxidant or the like as required. It may be. The charge transport layer may be composed of two or more layers.

  Examples of the charge transport material for the charge transport layer include a charge transport material such as a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, and a butadiene compound.

  As the binder resin for the charge transport layer, known resins can be used. For example, polystyrene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester Insulating resins such as resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of the repeating structural units of these resins, and poly-N-vinylcarbazole And high molecular organic semiconductors. Among these, it is preferable to use a polycarbonate resin from the viewpoint of obtaining the dispersibility of the charge transport material (CTM) and good electrophotographic characteristics.

  The content ratio of the charge transport material in the charge transport layer is preferably 10 to 200 parts by weight with respect to 100 parts by weight of the charge transport layer binder resin.

  In the charge transport layer, an antioxidant, an electronic conductive agent, a stabilizer, silicone oil, or the like may be added. An antioxidant is a substance having a property of preventing or suppressing the action of oxygen under conditions such as light, heat, and discharge, for example, against an auto-oxidizing substance present in or on the surface of the photoreceptor.

  The thickness of the charge transport layer varies depending on the characteristics of the charge transport material, the characteristics and the content ratio of the binder resin for the charge transport layer, and is preferably 10 to 40 μm. More preferably, the thickness of the charge transport layer is in the range of 10 to 20 μm in that the internal electric field of the photoreceptor is increased and the accumulated charge due to the continuous exposure history is reduced.

The charge transport layer as described above can be prepared by adding and dispersing a charge transport material (CTM) and, if necessary, an antioxidant in a binder resin for a charge transport layer dissolved in a known solvent. It can be formed by preparing a coating liquid for forming a layer, coating the coating liquid for forming a charge transport layer on the surface of the charge generation layer to form a coating film, and drying the coating film.
Examples of the solvent used for forming the charge transport layer include the same solvents as those used for forming the charge generation layer.
In addition, as the method for applying the charge transport layer forming coating solution, the same method as the method for applying the charge generating layer forming coating solution can be used.

[Protective layer]
The electrophotographic photoreceptor of the present invention may further have a protective layer on the charge transport layer. The protective layer plays a role of protecting the photoreceptor from the external environment and impact. The photoreceptor of the present invention contains metal oxide fine particles and a charge transport material in a cured resin obtained by polymerizing a crosslinkable polymerizable compound (hereinafter also referred to as a “protective layer binder resin”). It is preferable to have a protective layer on the charge transport layer from the viewpoint that both the durability improvement and the memory resistance can be achieved.
Such a protective layer preferably contains metal oxide fine particles and a charge transport material in the protective layer binder resin.

<Metal oxide fine particles>
The metal oxide fine particles (metal oxide fine particles 1eA in FIG. 1) contribute to the improvement of the strength of the protective layer and the stability of the image quality by adjusting the resistance.
Examples of the metal oxide fine particles include titanium oxide, zinc oxide, alumina (aluminum oxide), silica (silicon oxide), tin oxide, antimony oxide, indium oxide, bismuth oxide, magnesium oxide, lead oxide, tantalum oxide, yttrium oxide. , Cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, niobium oxide, molybdenum oxide, vanadium oxide and other fine particles, tin-doped indium oxide, antimony-doped tin oxide and zirconium oxide Fine particles such as can be used. These can be used individually by 1 type or in combination of 2 or more types. When two or more kinds are used in combination, they may be solid solutions or fused bodies.

  The average particle diameter of the metal oxide fine particles is preferably 1 to 300 nm, more preferably 3 to 100 nm.

  The average particle diameter of the metal oxide fine particles can be determined by the same method as the above average particle diameter measuring method.

It is preferable that metal oxide microparticles | fine-particles are contained in the ratio of 1-200 mass parts with respect to 100 mass parts of binder resin for protective layers, More preferably, it is 50-150 mass parts.
When the content ratio of the metal oxide fine particles is 1 part by mass or more with respect to 100 parts by mass of the protective layer binder resin, sufficient strength can be obtained in the protective layer and sufficient image quality stability can be obtained. On the other hand, the content ratio of the metal oxide fine particles is 200 parts by mass or less with respect to 100 parts by mass of the binder resin for the protective layer, thereby preventing the formation of the coating film from being inhibited when the protective layer is formed. Can do.

[Surface-modified metal oxide fine particles]
The metal oxide fine particles contained in the protective layer are preferably those whose surface is modified with a surface modifier from the viewpoint of obtaining dispersibility and improving wear resistance. For the purpose of further enhancement, the surface is preferably modified with a surface modifier having a reactive organic group, and the reactive organic group is surface-modified with a surface modifier that is a radically polymerizable reactive group. More preferably it is. By using a surface modifier having a radical polymerizable reactive group, when the protective layer binder resin is a cured resin of the following polymerizable compound, it forms a strong protective layer to react with the polymerizable compound. Can do.

As the surface modifier, a surface modifier that reacts with a hydroxy group or the like present on the surface of the metal oxide fine particle before surface modification can be used, and as these surface modifiers, various silane coupling agents, Examples include titanium coupling agents, inorganic oxides, fluorine-modified silicone oils, fluorine-based surfactants, and fluorine-based graft polymers.
As the surface modifier having a radically polymerizable reactive group, it is preferable to use a silane coupling agent having an acryloyl group or a methacryloyl group. Examples of the surface modifier having such a radically polymerizable reactive group include the following: Known compounds are exemplified.

_{S-1: CH 2 = CHSi} (CH 3) (OCH 3) 2
_{S-2: CH 2 = CHSi} (OCH 3) 3
S-3: CH ₂ = CHSiCl _{3
S-4: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-5: CH 2 = CHCOO} (CH 2) 2 Si (OCH 3) 3
_{S-6: CH 2 = CHCOO} (CH 2) 2 Si (OC 2 H 5) (OCH 3) 2
_{S-7: CH 2 = CHCOO} (CH 2) 3 Si (OCH 3) 3
_{S-8: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) Cl 2
_{S-9: CH 2 = CHCOO} (CH 2) 2 SiCl 3
_{S-10: CH 2 = CHCOO} (CH 2) 3 Si (CH 3) Cl 2
S-11: CH ₂ = CHCOO (CH ₂ ) ₃ SiCl _{3
S-12: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-13: CH 2 = C} (CH 3) COO (CH 2) 2 Si (OCH 3) 3
_{S-14: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-15: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-16: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) Cl 2
_{S-17: CH 2 = C} (CH 3) COO (CH 2) 2 SiCl 3
_{S-18: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
_{S-19: CH 2 = C} (CH 3) COO (CH 2) 3 SiCl 3
_{S-20: CH 2 = CHSi} (C 2 H 5) (OCH 3) 2
_{S-21: CH 2 = C} (CH 3) Si (OCH 3) 3
_{S-22: CH 2 = C} (CH 3) Si (OC 2 H 5) 3
_{S-23: CH 2 = CHSi} (OCH 3) 3
_{S-24: CH 2 = C} (CH 3) Si (CH 3) (OCH 3) 2
_{S-25: CH 2 = CHSi} (CH 3) Cl 2
_{S-26: CH 2 = CHCOOSi} (OCH 3) 3
_{S-27: CH 2 = CHCOOSi} (OC 2 H 5) 3
_{S-28: CH 2 = C} (CH 3) COOSi (OCH 3) 3
_{S-29: CH 2 = C} (CH 3) COOSi (OC 2 H 5) 3
_{S-30: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3

  As the surface modifier, in addition to the compounds represented by S-1 to S-34, a silane compound having a reactive organic group capable of performing a radical polymerization reaction can be used. These surface modifiers can be used alone or in combination of two or more.

  Moreover, the usage-amount of a surface modifier is although it does not restrict | limit in particular, It is preferable that it is 0.1-100 mass parts with respect to 100 mass parts of metal oxide fine particles before a process.

[Surface modification method of metal oxide fine particles]
Specifically, the surface modification of the metal oxide fine particles is performed by wet-grinding a slurry (suspension of solid particles) containing the metal oxide fine particles before the treatment and the surface modifier, thereby finely dividing the metal oxide fine particles. At the same time, the modification to the surface of the particles proceeds, and then the solvent is removed to form powder.

  The slurry is preferably mixed at a ratio of 0.1 to 100 parts by mass of the surface modifier and 50 to 5000 parts by mass of the solvent with respect to 100 parts by mass of the metal oxide fine particles before treatment.

An apparatus used for wet pulverization of the slurry includes a wet media dispersion type apparatus.
The wet media dispersion type device is filled with beads as media in a container, and further agitation discs mounted perpendicular to the rotation axis are rotated at high speed to crush and disperse the aggregated particles of metal oxide fine particles. There is no problem as long as the metal oxide fine particles are sufficiently dispersed and the surface can be modified when the surface modification is performed on the metal oxide fine particles, for example, vertical and horizontal types. Various types such as a continuous type and a batch type can be used. Specifically, a sand mill, an ultra visco mill, a pearl mill, a glen mill, a dyno mill, an agitator mill, a dynamic mill, or the like can be used. These dispersion-type devices are pulverized and dispersed by impact crushing, friction, shearing, shear stress, etc. using a grinding medium (media) such as balls and beads.

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

  Various materials such as stainless steel, nylon, and ceramic can be used for the disk and container inner wall used in the wet media dispersion type apparatus. In the present invention, a ceramic disk such as zirconia or silicon carbide is particularly used. Or the inner wall of the container.

<Charge transport material>
As the charge transporting material contained in the protective layer, various known charge transporting materials can be used. However, when ultraviolet rays are used for the curing treatment when forming the protective layer, the wavelength is 450 nm or less. It is preferred to use a charge transport material that does not absorb light or is small.
A compound represented by the following general formula (1) can be used as a charge transport material that does not absorb or has a small light absorption in a short wavelength region of 450 nm or less.

In the general formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 7 carbon atoms or an alkoxy group having 1 to 7 carbon atoms, k , L and n are integers of 1 to 5, and m is an integer of 1 to 4. When k, l, m, and n are 2 or more, the plurality of groups may be the same as or different from each other.
Examples of the charge transport material represented by the general formula (1) include, but are not limited to, the following compounds (CTM-1 to CTM-22).

[Curing resin (binder resin for protective layer)]
The binder resin for protective layer is a cured resin obtained by a polymerization reaction of a crosslinkable polymerizable compound.
The cured resin is a crosslinkable polymerizable compound, specifically a compound having two or more radical polymerizable functional groups (hereinafter also referred to as “polyfunctional radical polymerizable compound”) such as ultraviolet rays or electron beams. It is preferably obtained by a polymerization reaction by irradiation with actinic rays.

[Polyfunctional radical polymerizable compound]
Since the polyfunctional radical polymerizable compound can be cured in a small amount of light or in a short time, an acryloyl group (CH ₂ ═CHCO—) or a methacryloyl group (CH ₂ ═CCH ₃ CO—) is used as the radical polymerizable functional group. ) Is particularly preferably an acrylic monomer having 2 or more) or oligomers thereof. Accordingly, the curable resin is preferably an acrylic resin formed from an acrylic monomer or an oligomer thereof.

  Examples of these polyfunctional radically polymerizable compounds include the following compounds.

However, in the chemical formulas showing the above exemplary compounds M1 to M15, R represents an acryloyl group (CH ₂ ═CHCO—), and R ′ represents a methacryloyl group (CH ₂ ═CCH ₃ CO—).

  For the protective layer, in addition to the above cured resin that is a binder resin for the protective layer, for example, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, acrylic resin, A melamine resin, vinyl chloride-vinyl acetate copolymer and the like can be used in combination. These can be used individually by 1 type or in combination of 2 or more types.

  Furthermore, the protective layer may contain lubricant particles, various antioxidants, and the like, if necessary, in addition to the protective layer binder resin, the metal oxide fine particles, and the charge transport material as described above.

<Lubricant particles>
Examples of the lubricant particles include fluorine atom-containing resin particles. Fluorine atom-containing resin particles include tetrafluoroethylene resin, trifluorinated ethylene chloride resin, hexafluoroethylene chloride propylene resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene difluoride dichloride resin, and their co-polymers. A polymer etc. are mentioned, These can be used individually by 1 type or in combination of 2 or more types. Among these, it is particularly preferable to use a tetrafluoroethylene resin and a vinylidene fluoride resin.
The average particle size of the lubricant particles is preferably 0.01 to 1 μm, more preferably 0.05 to 0.5 μm.
It is preferable that a lubricant particle is contained in the ratio of 5-70 mass parts with respect to 100 mass parts of binder resin for protective layers, More preferably, it is 10-60 mass parts.

  The thickness of the protective layer is preferably 0.2 to 10 μm, more preferably 0.5 to 6 μm.

<Method for forming protective layer>
The protective layer is formed by adding a polyfunctional radical polymerizable compound, metal oxide fine particles, a charge transporting material, and a known resin, a polymerization initiator, a lubricant particle, an antioxidant, etc. to a solvent as necessary. The coating liquid can be prepared by applying the coating liquid on the surface of the charge transport layer by a known method to form a coating film, followed by curing treatment.

(Polymerization initiator)
As a method for polymerizing the polyfunctional radically polymerizable compound, a method using an electron beam cleavage reaction or a method using light or heat in the presence of a radical polymerization initiator can be employed.
The polymerization initiator that can be contained in the protective layer is a radical polymerization initiator that initiates the polymerization reaction of the polyfunctional radical polymerizable compound, and examples thereof include a thermal polymerization initiator and a photopolymerization initiator. It is preferable to use an agent.

  Examples of the photopolymerization initiator include diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl-ketone, 4- (2-hydroxyethoxy) phenyl- (2 -Hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1 ("Irgacure 369" (manufactured by BASF Japan)), 2-hydroxy-2-methyl -1-phenylpropan-1-one, 2-methyl-2-morpholino (4-methylthiophenyl) propan-1-one, 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime, etc. Acetophenone-based or ketal-based photopolymerization initiators; benzoin, benzoin methyl ether, benzene Benzoin ether photopolymerization initiators such as inethyl ether, benzoin isobutyl ether, benzoin isopropyl ether; benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl ether Benzophenone photopolymerization initiators such as acrylated benzophenone and 1,4-benzoylbenzene; 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone And thioxanthone photopolymerization initiators.

  Other photopolymerization initiators include ethyl anthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine Oxide (“Irgacure 819” (manufactured by BASF Japan)), bis (2,4-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10-phenanthrene, acridine compound , Triazine compounds and imidazole compounds. Moreover, what has a photopolymerization promotion effect can also be used individually or together with the said photoinitiator. Examples of the photopolymerization-promoting effect include triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino) ethyl benzoate, 4,4′- Examples include dimethylaminobenzophenone.

These polymerization initiators may be used alone or in combination of two or more.
The usage-amount of a polymerization initiator is 0.1-20 mass parts with respect to 100 mass parts of polyfunctional radically polymerizable compounds, Preferably it is 0.5-10 mass parts.

(solvent)
Solvents used for forming the protective layer include methanol, ethanol, propyl alcohol, i-propyl alcohol, butanol, t-butanol, sec-butanol, benzyl alcohol, toluene, xylene, dichloromethane, methyl ethyl ketone, cyclohexane, ethyl acetate, Examples include, but are not limited to, butyl acetate, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine.
These can be used individually by 1 type or in mixture of 2 or more types.

  Examples of the means for dispersing the metal oxide fine particles and the lubricant particles include the same method as the means for dispersing the titanium oxide particles in the intermediate layer forming coating solution.

  Examples of the coating method for the protective layer forming coating solution include the same methods as those for the intermediate layer forming coating solution. However, in order not to dissolve the binder resin such as the photosensitive layer as much as possible, spray coating is used. The slide hopper method is preferably used, and the slide hopper method using a circular slide hopper applicator is more preferably used.

  In the curing process, the coating film is irradiated with actinic radiation to generate radicals, polymerize, and form a cross-linking bond by cross-linking reaction between molecules and within the molecule to harden to produce a protective layer binder resin. Is preferred. As the actinic ray, it is preferable to use light such as ultraviolet light and visible light and an electron beam, and it is particularly preferable to use ultraviolet light from the viewpoint of ease of use.

As the ultraviolet light source, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is usually 5 to 500 mJ / cm ² , preferably 5 to 100 mJ / cm ² . The output voltage of the light source is preferably 0.1 to 5 kW, and particularly preferably 0.5 to 3 kW.

  As the electron beam source, for example, a curtain beam type electron beam irradiation apparatus can be preferably used. The acceleration voltage at the time of irradiation with an electron beam is preferably 100 to 300 kV. The absorbed dose is preferably 0.5 to 10 Mrad.

  The irradiation time of the actinic radiation may be a time for obtaining the necessary irradiation amount of the actinic radiation, specifically, 0.1 second to 10 minutes is preferable, and from the viewpoint of curing efficiency or work efficiency, 0.1 second to 5 seconds. Minutes are more preferred.

  The coating film may be dried before and after irradiation with active rays and during irradiation with active rays. The timing for performing the drying process can be appropriately selected in combination with the irradiation condition of the active rays. The drying conditions for the protective layer can be appropriately selected depending on the type of solvent used in the coating solution, the thickness of the protective layer, and the like. The drying temperature is preferably room temperature (20 ° C.) to 180 ° C., particularly preferably 80 to 140 ° C. The drying time is preferably 1 to 200 minutes, particularly preferably 5 to 100 minutes.

≪Electrophotographic image forming device≫
An electrophotographic image forming apparatus according to the present invention is an electrophotographic image forming apparatus that includes an electrophotographic photosensitive member and includes a charging process, an exposure process, a developing process, and a transfer process. A photographic photoreceptor is preferred.

  The electrophotographic image forming apparatus using the electrophotographic photosensitive member of the present invention will be described below. FIG. 2 is a cross-sectional configuration diagram of a full-color electrophotographic image forming apparatus showing an example of an embodiment of the present invention. In the following description, it is assumed that the electrophotographic photoreceptor of the present invention is used for the photoreceptors 1Y, 1M, 1C, and 1Bk.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes four sets of image forming units 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 7a, a sheet feeding unit 21, and a fixing unit. Means 24. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  An image forming unit 10Y for forming a yellow image includes a charging unit (charging process) 2Y, an exposure unit (exposure process) 3Y, and a developing unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. It has a means (development process) 4Y, a primary transfer roller 5Y as a primary transfer means (transfer process), and a cleaning means 6Y. An image forming unit 10M for forming a magenta image includes a drum-shaped photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, and It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C as a primary transfer unit, and It has cleaning means 6C. The image forming unit 10Bk that forms a black image includes a drum-shaped photoreceptor 1Bk as a first image carrier, a charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk as a primary transfer unit, and a cleaning unit. 6Bk.

  The four sets of image forming units 10Y, 10M, 10C, and 10Bk are centered around the photoreceptors 1Y, 1M, 1C, or 1Bk, charging means 2Y, 2M, 2C, or 2Bk, and exposure means 3Y, 3M, 3C, or 3Bk. The developing means 4Y, 4M, 4C or 4Bk and the cleaning means 6Y, 6M, 6C or 6Bk for cleaning the photoreceptors 1Y, 1M, 1C or 1Bk.

  The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of the toner images to be formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are different, and the image forming unit 10Y is taken as an example in detail. Explained.

  The image forming unit 10Y includes a charging unit 2Y (hereinafter also referred to as “charger 2Y”), an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 6Y around a photoconductor 1Y that is an image forming body. A yellow (Y) toner image is formed on the body 1Y. In the present embodiment, in the image forming unit 10Y, at least the photoreceptor 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 6Y are provided so as to be integrated.

  The charging unit 2Y is a unit that applies a uniform potential to the photoreceptor 1Y. In this embodiment, a corona discharge type charger 2Y is used as the photoreceptor 1Y.

  The exposure unit 3Y is a unit that performs exposure based on an image signal (yellow) on the photoreceptor 1Y to which a uniform potential is applied by the charger 2Y, and forms an electrostatic latent image corresponding to a yellow image. As the exposure means 3Y, an exposure element 3Y composed of an LED having light emitting elements arranged in an array in the axial direction of the photoreceptor 1Y and an imaging element (trade name: SELFOC (registered trademark) lens) or laser optical A system or the like is used.

  The developing means 4Y includes, for example, a developing sleeve and a photosensitive member that have a built-in magnet and rotate while holding the developer, and a voltage applying device that applies a DC and AC bias voltage or a DC or AC bias voltage between the developing sleeve and the developing sleeve. It is made up of.

  The endless belt-shaped intermediate transfer body unit 7a has an endless belt-shaped intermediate transfer body 70 as a semiconductive endless belt-shaped second image carrier wound around a plurality of rollers and rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10Bk is sequentially transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means. Thus, a synthesized color image is formed. A transfer material P as a transfer material (a support for carrying a fixed final image: for example, plain paper, a transparent sheet, etc.) housed in the paper feed cassette 20 is fed by a paper feed means 21 and a plurality of intermediates. After passing through the rollers 22A, 22B, 22C, 22D and the registration roller 23, they are conveyed to a secondary transfer roller 5b as a secondary transfer means, and are secondarily transferred onto the transfer material P, and the color images are collectively transferred. The transfer material P onto which the color image has been transferred is fixed by the fixing means 24, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus. Here, a toner image transfer support formed on a photosensitive member such as an intermediate transfer member or a transfer material is collectively referred to as a transfer medium.

  On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 5b as the secondary transfer means, the residual toner is removed by the cleaning means 6b from the endless belt-shaped intermediate transfer body 70 in which the transfer material P is separated by curvature. The

  During the image forming process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5b contacts the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through the secondary transfer roller 5b.

  Further, the housing 8 can be pulled out from the main body A of the image forming apparatus via the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10Bk, and an endless belt-shaped intermediate transfer body unit 7a.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. An endless belt-like intermediate transfer body unit 7a is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1Bk in the drawing. The endless belt-shaped intermediate transfer body unit 7a includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 76, 73, and 74, primary transfer rollers 5Y, 5M, 5C, and 5Bk, and a cleaning unit 6b. It consists of.

[Static elimination process]
Conventionally, some electrophotographic image forming apparatuses have a configuration capable of performing a static elimination process by light irradiation after transfer, and examples of the static elimination means (photo static elimination apparatus) that perform this process include fluorescent lamps, LEDs, and the like. used. In addition, the light used in the static elimination process is often light having an exposure energy that is at least three times that of the exposure light.
However, in the electrophotographic image forming apparatus employing the photoconductor of the present invention, it is possible to achieve both long-term memory resistance and prevention of image defects such as black spots and fog without using the above-mentioned static eliminating means. Therefore, it can be set as the structure which does not have a static elimination means. Thus, it is preferable to use a configuration that does not include an optical charge eliminating device, because it is possible to realize space saving and cost reduction of the image forming apparatus, and to reduce light damage to the photoconductor.

≪Process cartridge≫
The electrophotographic image forming apparatus of the present invention includes the electrophotographic photosensitive member of the present invention and the above-described charging unit (charging unit), exposure unit (exposure unit), developing unit (developing unit), or cleaning unit (cleaning unit). It is preferable to configure as a process cartridge (image forming unit) integrally including at least one, and to configure this image forming unit so that it can be taken in and out (detachable) with respect to the main body of the electrophotographic image forming apparatus. In addition to a charging unit, an exposure unit, a developing unit, a process cartridge (image forming unit) having at least one of a transfer unit (transfer unit) and a separation unit (separator) together with a photosensitive member is formed. A single image forming unit that is detachable from the main body may be used, and a structure that is detachable by using a guide means such as a rail of the apparatus main body may be used.

  The electrophotographic image forming apparatus of the present invention is generally applicable to electrophotographic image forming apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers, but also displays, recordings, and light printing using electrophotographic technology. It can also be widely applied to apparatuses such as plate making and facsimile.

  The embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

In the following, the average particle diameter of the titanium oxide particles was determined as follows.
First, titanium oxide particles were photographed with a scanning electron microscope “JSM-7500F” (manufactured by JEOL Ltd.) at a magnification of 100,000. Next, an automatic image processing analyzer “LUZEX AP (software version Ver. 1.32)” (manufactured by Nireco) is used for photographic images (excluding aggregated particles) obtained by scanning the obtained photographs. The titanium oxide particles were binarized. Then, the horizontal direction ferret diameter about 100 randomly selected titanium oxide particles was calculated, and the average value (number average primary particle diameter) was determined as “average particle diameter”.

[Production of surface-modified titanium oxide particles]
<Preparation of surface-modified titanium oxide particles A-1>
500 parts by mass of inorganic-treated titanium oxide (SKT-002; manufactured by Teika Co., Ltd.) obtained by subjecting anatase-type titanium oxide having an average particle size of 30 nm to silica (SiO ₂ ) treatment, and 15 parts by mass of methyl hydrogen polysiloxane (MHPS) And 1300 parts by mass of toluene were stirred and mixed, followed by wet crushing treatment at 35 ° C. with a mill residence time of 35 minutes using a bead mill. Toluene was separated and removed by distillation under reduced pressure from the slurry obtained by wet crushing treatment. The obtained dried product was baked with MHPS at 120 ° C. for 1.5 hours. Then, it grind | pulverized with the pin mill and obtained the surface-modified titanium oxide particle A-1.

<Preparation of surface-modified titanium oxide particles A-2>
500 parts by mass of inorganically treated titanium oxide (SKT-002; manufactured by Teika Co., Ltd.) obtained by subjecting anatase type titanium oxide having an average particle size of 30 nm to silica treatment is stirred and mixed with 2000 parts of toluene, and 3-methacryloxypropyltrimethoxysilane is mixed. 65 parts by mass (KBM-503; manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred at 50 ° C. for 3 hours. Thereafter, toluene was distilled off under reduced pressure and baked at 130 ° C. for 3 hours. Thereby, surface-modified titanium oxide particles A-2 were obtained.

<Preparation of surface-modified titanium oxide particles A-3>
In the surface-modified titanium oxide particles A-1, an inorganic treated titanium oxide (SKT-012) manufactured by subjecting the titanium oxide particles to silica and alumina (Al ₂ O ₃ ) treatment on anatase-type titanium oxide having an average particle diameter of 10 nm; The surface-modified titanium oxide particles A-3 were obtained in the same manner as the surface-modified titanium oxide particles A-1, except that the product was changed to (1).

<Preparation of surface-modified titanium oxide particles A-4>
In the surface-modified titanium oxide particles A-1, the titanium oxide particles are changed to anatase-type titanium oxide (SKT-011; manufactured by Teika Co., Ltd.) having an average particle diameter of 15 nm, and silica treatment (surface modification with an inorganic compound) is performed. Surface-modified titanium oxide particles A-4 were obtained in the same manner as the surface-modified titanium oxide particles A-1, except that they were not applied.

<Preparation of surface-modified titanium oxide particles A-5>
Surface modified titanium oxide particles A-2 except that the titanium oxide particles were changed to inorganic-treated titanium oxide (F-1S02; manufactured by Showa Denko KK) obtained by subjecting anatase-type titanium oxide having an average particle size of 90 nm to silica treatment. Surface-modified titanium oxide particles A-5 were obtained in the same manner as the modified titanium oxide particles A-2.

<Preparation of surface-modified titanium oxide particles R-1>
In the surface-modified titanium oxide particles A-2, the titanium oxide particles were changed to rutile-type titanium oxide having an average particle size of 35 nm and inorganic-treated titanium oxide (SMT-500SAS; manufactured by Teika Co., Ltd.). Except for the above, surface-modified titanium oxide particles R-1 were obtained in the same manner as surface-modified titanium oxide particles A-2.

<Production of surface-modified titanium oxide particles R-2>
Surface modification of the surface-modified titanium oxide particles A-1 except that they were changed to inorganic treated titanium oxide (SMT-500SAS; manufactured by Teika Co., Ltd.) obtained by subjecting rutile titanium oxide having an average particle size of 35 nm to silica and alumina treatment. Surface-modified titanium oxide particles R-2 were obtained in the same manner as the finished titanium oxide particles A-1.

<Preparation of surface-modified titanium oxide particles R-3>
In the surface-modified titanium oxide particles A-2, except that the titanium oxide particles were changed to inorganic-treated titanium oxide (SKM-003; manufactured by Teika Co., Ltd.) obtained by subjecting rutile titanium oxide having an average particle size of 15 nm to silica treatment. Surface-modified titanium oxide particles R-3 were obtained in the same manner as the surface-modified titanium oxide particles A-2.

<Preparation of surface-modified titanium oxide particles R-4>
Surface-modified titanium oxide particles A-1, except that the surface-modified titanium oxide particles A-1 were changed to rutile-type titanium oxide (SMT-150MK; manufactured by Teika Co., Ltd.) with an average particle diameter of 15 nm and were not subjected to silica treatment. In the same manner as A-1, surface-modified titanium oxide particles R-4 were obtained.

<Preparation of surface-modified titanium oxide particles R-5>
The surface-modified titanium oxide particles A-1 were changed to rutile-type titanium oxide (manufactured by NanoAmor) having an average particle diameter of 60 nm, and were the same as the surface-modified titanium oxide particles A-1 except that the silica treatment was not performed. Then, surface-modified titanium oxide particles R-5 were obtained.

<Preparation of surface-modified titanium oxide particles AR-1>
Surface modified titanium oxide particle A-1 except that it was changed to anatase / rutile mixed crystal titanium oxide (P-25; manufactured by Nippon Aerosil Co., Ltd.) with an average particle diameter of 20 nm and no silica treatment was applied. Surface-modified titanium oxide particles AR-1 were obtained in the same manner as the modified titanium oxide particles A-1. It is known from the X-ray diffraction intensity that AR-1 is composed of a mixed crystal of anatase type: rutile type = 0.75: 0.25.

  Table 1 summarizes the crystal types, average particle diameters, and surface treatment agents of the titanium oxide particles A-1 to A-5, R-1 to R-5, and AR-1.

[Preparation of Photoreceptor 1]
(1) Production of conductive support A conductive support [1] having a rough surface was obtained by cutting the surface of a cylindrical aluminum support having a diameter of 30 mm.

(2) Formation of intermediate layer 100 parts by mass of a polyamide resin represented by the following chemical formula (N-1) is added to 1850 parts by mass of a mixed solvent of ethanol / n-propyl alcohol / tetrahydrofuran (volume ratio 50/20/30). The mixture was stirred and mixed at 20 ° C., and 200 parts by mass of the surface-modified titanium oxide particles (A-1) and 100 parts by mass of the surface-modified titanium oxide particles (R-1) were added to this solution. Dispersed as 2 hours. The solution was allowed to stand for a whole day and night, and then filtered under a pressure of 50 kPa using a rigid mesh 5 μm filter manufactured by Nippon Pole Co., thereby preparing an intermediate layer forming coating solution [1].

  The intermediate layer-forming coating solution [1] thus obtained is applied to the outer peripheral surface of the washed conductive support [1] by a dip coating method and dried at 120 ° C. for 30 minutes to obtain a dry film. An intermediate layer [1] having a thickness of 2 μm was formed.

(3) Formation of charge generation layer (3-1) Preparation of charge generation material [CG-1] 29.2 parts by mass of 1,3-diiminoisoindoline was dispersed in 200 parts by mass of o-dichlorobenzene, and titanium tetra 20.4 parts by mass of n-butoxide was added and heated at 150 to 160 ° C. for 5 hours in a nitrogen atmosphere. After cooling, the precipitated crystals were filtered, washed successively with chloroform, 2% aqueous hydrochloric acid, water and methanol, and dried to obtain 26.2 parts by mass (yield 91%) of crude titanyl phthalocyanine.

Next, this crude titanyl phthalocyanine was dissolved by stirring in 250 parts by mass of concentrated sulfuric acid at 5 ° C. or less for 1 hour, poured into 5000 parts by mass of water at 20 ° C., the precipitated crystals were filtered, washed with water, and wet paste 225 parts by mass of product were obtained.
This wet paste product was frozen in a freezer, thawed again, filtered and dried to obtain 24.8 parts by mass of amorphous titanyl phthalocyanine (yield 86%).
10.0 parts by mass of this amorphous titanyl phthalocyanine and 0.94 parts by mass of (2R, 3R) -2,3-butanediol (0.6 equivalent ratio) (equivalent ratio is equivalent ratio to titanyl phthalocyanine, hereinafter the same) It mixed in 200 mass parts of ortho dichlorobenzene (ODB), and it heat-stirred at 60-70 degreeC for 6.0 hours. After standing overnight, methanol was added to the reaction solution, and the resulting crystals were filtered, and the filtered crystals were washed with methanol to contain (2R, 3R) -2,3-butanediol adduct titanyl phthalocyanine. 10.3 parts by mass of a charge generating material [CG-1] made of a pigment was obtained. In the X-ray diffraction spectrum of the charge generation material [CG-1], clear peaks occur at 8.3 °, 24.7 °, 25.1 °, and 26.5 °, and in the mass spectrum at 576 and 648. peak occurs in IR spectra Ti = O in the vicinity of 970 cm ^-1, is both absorbed O-Ti-O in the vicinity of 630 cm ^-1 appeared. In thermal analysis (TG), a mass loss of about 7% occurred at 390 to 410 ° C. From the above, the charge generating substance [CG-1] is a mixture of a titanyl phthalocyanine and a (2R, 3R) -2,3-butanediol 1: 1 adduct and a non-adduct (not added) titanyl phthalocyanine. It is estimated to be.

(3-2) Preparation of Coating Solution for Forming Charge Generation Layer [1-1] The following raw materials were mixed, and a circulating ultrasonic homogenizer “RUS-600TCVP” (manufactured by Nippon Seiki Seisakusho, 19.5 kHz, 600 W) was used. The dispersion was used at a circulating flow rate of 40 L / H to prepare a coating solution [1-1] for forming a charge generation layer.
-Charge generation material [CG-1] 24 parts by mass-Polyvinyl butyral resin "ESREC BL-1" (manufactured by Sekisui Chemical Co., Ltd.) 12 parts by mass-Solvent: methyl ethyl ketone / cyclohexanone = 4/1 (V / V) 600 parts by mass

(3-3) Formation of Charge Generation Layer The charge generation layer forming coating solution [1-1] is applied onto the intermediate layer [1] by a dip coating method to form a coating film, and this coating film is dried. Then, a charge generation layer [1] having a layer thickness of 0.5 μm was formed.

(4) Formation of charge transport layer The following raw materials were mixed and dissolved to prepare a charge transport layer forming coating solution [1].
Charge transport material: 225 parts by mass of a compound represented by the following chemical formula (A) Binder resin for charge transport layer: polycarbonate resin "Z300" (manufactured by Mitsubishi Gas Chemical Company) 300 parts by massAntioxidant "Irganox 1010" (BASF 6 parts by mass / solvent: 1600 parts by mass of THF / solvent: 400 parts by mass of toluene / silicone oil “KF-50” (manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by mass

  On the charge generation layer [1], the charge transport layer forming coating solution [1] is applied using a circular slide hopper coating apparatus to form a coating film, and the coating film is dried, and the layer thickness is 15 μm. A charge transport layer [1] was formed.

(5) Formation of protective layer (5-1) Production of metal oxide fine particles Untreated tin oxide (manufactured by CIK Nanotech, average particle size: 20 nm, volume resistivity: 1.05 × 10 ⁵ (Ω · cm) ) 100 parts by mass, 30 parts by mass of the above exemplified compound (S-15: CH ₂ ═C (CH ₃ ) COO (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) as a surface modifier, toluene / isopropyl alcohol = 1/1 300 parts by mass of a mixed solvent (mass ratio) was mixed, and this was put into a sand mill together with zirconia beads, and surface modification was performed by stirring at about 40 ° C. and a rotation speed of 1500 rpm. Further, the surface-modified mixture was taken out, put into a Henschel mixer, stirred at a rotational speed of 1500 rpm for 15 minutes, and then dried at 120 ° C. for 3 hours to produce tin oxide fine particles [1].

(5-2) Formation of protective layer Metal oxide fine particles: Tin oxide fine particles [1] 105 parts by mass Polymerizable compound: Methacrylate monomer “SR350” (manufactured by Nippon Kayaku Co., Ltd.)
100 parts by mass / charge transporting material: Exemplified Compound CTM-13 12 parts by mass / polymerization initiator: “Irgacure 184” (manufactured by BASF Japan) 5 parts by mass / radical scavenger: “Sumilyzer GS” (manufactured by Sumitomo Chemical Co., Ltd.) 5 parts by mass Part / solvent: 320 parts by mass of 2-butanol / solvent: 80 parts by mass of tetrahydrofuran A coating liquid composition consisting of 80 parts by mass was mixed and stirred to sufficiently dissolve and disperse to prepare a coating liquid [1] for forming a protective layer.

  This coating liquid for forming a protective layer [1] is applied onto the charge transport layer [1] using a circular slide hopper applicator, and then irradiated with ultraviolet rays for 1 minute using a metal halide lamp, resulting in a dry film thickness of 3 A protective layer [1] having a thickness of 0.0 μm was formed, whereby the photoreceptor 1 was produced.

[Production of photoconductors 2 to 10, 14 to 19 and 21]
In the production of the photoreceptor 1, the photoreceptors 2 to 10, 14 to 19, and 21 are similarly prepared except that the type and addition amount of the titanium oxide particles added to the intermediate layer forming coating solution are changed according to Table 2 below. Obtained.

[Preparation of Photoreceptor 11]
In the production of the photoreceptor 1, the type and amount of titanium oxide particles added to the coating solution for forming the intermediate layer were changed according to Table 2 below, and the thickness of the charge transport layer was changed to 28 μm. A photoreceptor 11 was obtained.

[Production of Photoreceptor 12]
In the production of the photoreceptor 1, the type and amount of titanium oxide particles added to the intermediate layer forming coating solution are changed according to Table 2 below, the thickness of the charge transport layer is changed to 28 μm, and the protective layer is not formed. A photoconductor 12 was obtained in the same manner as above.

[Preparation of photoconductors 13 and 22]
In the production of the photoconductor 1, the type and amount of titanium oxide particles added to the coating solution for forming the intermediate layer were changed according to Table 2 below, and the photoconductor 13 was similarly formed except that the protective layer was not formed. 22 was obtained.

[Preparation of Photoreceptor 20]
In addition to the change in the type and amount of titanium oxide particles added to the coating solution for forming the intermediate layer to 300 parts by mass of the anatase type / rutile type mixed crystal (AR-1) in the production of the photoreceptor 1 Obtained the photoreceptor 20 in the same manner.

[Evaluation of photoconductors 1 to 22]
Photoconductors 1 to 22 were mounted on a commercially available full-color composite machine “bizhub C287” (manufactured by Konica Minolta), and evaluation was performed using electrophotographic image forming apparatuses 1 to 22.
First, an endurance test (hereinafter also referred to as “long-term printing”) in which 50,000 double-sided continuous printing of each character image with an image ratio of 5% is performed at A4 horizontal feed, is performed before long-term printing (initial stage) and long-term printing test. Later, pattern memory and black spots and fog were evaluated.
The photosensitive members 21 and 22 were evaluated in the state of irradiating erase light with the photostatic discharge device of the electrophotographic image forming apparatus attached (in Table 2, the photostatic charge is “present”). With respect to the photoreceptors 1 to 20, the evaluation was performed in a state where the light neutralization device of the electrophotographic image forming apparatus was removed (in Table 2, the light neutralization is described as “none”).

(1) Evaluation of pattern memory Before and after long-term printing, in the environment of a temperature of 10 ° C. and a humidity of 15% RH, a vertical solid band image was transferred onto a transfer material: “A3 / POD gloss coat (A3 size, 100 g / m ² ) "(manufactured by Oji Paper Co., Ltd.), 5 sheets are continuously printed, followed by printing one sheet of a solid image. Occurrence of the history of the solid band portion of the obtained solid image, that is, generation of the pattern memory was visually observed and evaluated according to the following evaluation criteria. The results are shown in Table 3.
-Evaluation criteria-
A: Memory is not observed (pass)
B: A slight memory is observed in a part of the belt solid part (pass)
C: A slight memory is observed in the whole band (pass)
D: Memory is observed (failed)
E: Memory is clearly observed (failed)

(2) Evaluation of black spots and fog Before and after long-term printing, transfer material: “A3 / POD gloss coat (A3 size, 100 g / m ² )” in an environment of temperature 30 ° C. and humidity 80% RH (Oji Paper Co., Ltd.) A solid image (white solid image) was formed under the conditions of a grid voltage of −800 V and a developing bias of −650 V, and the presence or absence of black spots and fog on the obtained transfer material was visually observed. And it evaluated according to the following evaluation criteria. The results are shown in Table 3.
-Evaluation criteria-
A: Black spots and fog are not observed (pass)
B: Slight black spots and fog are observed when enlarged, but at a level that does not cause any practical problems (pass)
C: Slight black spots and fog are observed visually (failure)
D: Black spots and fog are conspicuously observed (failed)

From Table 3, it was shown that according to the present invention, the memory resistance can be obtained over a long period of time and the occurrence of image defects such as black spots and fog can be prevented under the eraseless condition.
As for the photoreceptors 1 to 13, there is one or two peak tops of the particle size distribution in the titanium oxide particles, both within the range of 10 to 50 nm, and the total titanium oxide of the anatase type titanium oxide particles. The mass ratio with respect to the particles was in the range of 0.60 to 0.95. For the photoreceptor 19, there were two peak tops in the particle size distribution in the titanium oxide particles, one of which was outside the range of 10 to 50 nm. Further, with respect to the photoreceptors 14 and 15, the mass ratio of the anatase-type titanium oxide particles to the total titanium oxide particles was outside the range of 0.60 to 0.95. Therefore, it is considered that the photoconductors 1 to 13 are more excellent in pattern memory after the durability test than the photoconductors 14, 15, and 19.

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 1a Conductive support 1b Intermediate layer 1bA Titanium oxide particles 1c Charge generation layer 1d Charge transport layer 1e Protective layer 1eA Metal oxide fine particles 1f Organic photosensitive layers 1Y, 1M, 1C, 1Bk photoreceptors 2Y, 2M, 2C, 2Bk Charging unit 3Y, 3M, 3C, 3Bk Exposure unit 4Y, 4M, 4C, 4Bk Developing unit 6Y, 6M, 6C, 6Bk Cleaning unit 10Y, 10M, 10C, 10Bk Image forming unit

Claims (10)

An electrophotographic photosensitive member having at least an intermediate layer, a charge generation layer, and a charge transport layer in this order on a conductive support, and used in an eraseless type electrophotographic image forming apparatus,
The intermediate layer contains, as titanium oxide particles, rutile titanium oxide particles and anatase titanium oxide particles,
An electrophotographic photoreceptor, wherein the titanium oxide particles have an average particle diameter in the range of 10 to 50 nm.   2. The electrophotographic photosensitive member according to claim 1, wherein an average particle diameter of each of the rutile titanium oxide particles and the anatase titanium oxide particles is in a range of 10 to 50 nm.   3. The mass ratio of the anatase-type titanium oxide particles with respect to the total amount of the titanium oxide particles contained in the intermediate layer is in the range of 0.60 to 0.95. 3. Electrophotographic photoreceptor.   The cured resin formed by a polymerization reaction of a crosslinkable polymerizable compound has a protective layer containing metal oxide fine particles and a charge transport material on the charge transport layer. The electrophotographic photosensitive member according to claim 3. The surfaces of the anatase-type titanium oxide particles and the rutile-type titanium oxide particles are modified with an organic compound,
5. The electrophotographic photosensitive member according to claim 1, wherein the type of the organic compound is different between the anatase-type titanium oxide particles and the rutile-type titanium oxide particles. body.   6. The electrophotographic photoreceptor according to claim 1, wherein surfaces of the anatase-type titanium oxide particles and the rutile-type titanium oxide particles are modified with an inorganic compound. .   The mass ratio of the anatase-type titanium oxide particles to the total amount of the titanium oxide particles contained in the intermediate layer is in the range of 0.60 to 0.80. The electrophotographic photoreceptor according to any one of the above.   The electrophotographic photosensitive member according to any one of claims 1 to 7, wherein the charge transport layer has a thickness in the range of 10 to 20 µm. An electrophotographic image forming apparatus comprising an electrophotographic photosensitive member and having a charging process, an exposure process, a development process, and a transfer process,
The electrophotographic photoreceptor is the electrophotographic photoreceptor according to any one of claims 1 to 8,
An electrophotographic image forming apparatus characterized by having no charge eliminating means by light.   A process cartridge for use in the electrophotographic image forming apparatus according to claim 9, wherein the process cartridge includes at least the electrophotographic photosensitive member according to any one of claims 1 to 8, and a charging unit. A process cartridge comprising at least one of an exposure unit, a developing unit, and a cleaning unit, and is configured to be able to be inserted into and removed from the electrophotographic image forming apparatus.

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