JP2020030384A - Manufacturing method for electrophotographic photoreceptor - Google Patents

Abstract

To provide a manufacturing method for an electrophotographic photoreceptor with which it is possible to achieve both potential stability and leak resistance.SOLUTION: Provided is a manufacturing method for an electrophotographic photoreceptor comprising a support, an intermediate layer, and a photosensitive layer in the order stated. The manufacturing method is characterized by including: a first calcination step for calcining metal oxide particles at a temperature T1 higher than or equal to 200°C under a reduction atmosphere; a second calcination step for calcinating the metal oxide particles calcined in the first calcination step at a temperature T2 higher than or equal to 200°C under an oxidative atmosphere; a step for preparing a coating solution for the intermediate layer that contains the metal oxide particles calcined in the second calcination step; and a step for forming the intermediate layer using the coating solution for the intermediate layer, and that the temperature T1 in the first calcination step is higher than the temperature T2 in the second calcination step.SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing an electrophotographic photosensitive member.

  For electrophotographic photoreceptors used in electrophotographic devices, etc., such as concealing defects on the surface of the support, protecting the photosensitive layer from electrical destruction, improving chargeability, improving the ability to prevent charge injection from the support to the photosensitive layer, etc. For the purpose, various layers are often provided between the support and the photosensitive layer.

  Among the layers provided between the support and the photosensitive layer, there is known a technique of providing an intermediate layer for the purpose of stabilizing the charging potential and solving the problem of image defects such as black spots. Also, a technique in which metal oxide particles having an oxygen deficiency provided by performing a reduction treatment on an intermediate layer are dispersed in a resin is known. Photosensitive members have been proposed. In general, the reduced metal oxide particles have higher conductivity than the untreated metal oxide, so that the residual potential during image formation hardly increases, and the dark portion potential and the bright portion potential fluctuate. Hateful. Further, by providing such an intermediate layer between the support and the photosensitive layer to hide the defects on the surface of the support, the allowable range of the defects on the surface of the support is increased. As a result, there is also an advantage that productivity of the electrophotographic photosensitive member can be improved because the allowable use range of the support is greatly expanded.

JP-A-2011-53406

  Although the electrophotographic photoreceptor is designed with a sufficient withstand voltage against the electric field intensity expected in the image forming process, there are conductive foreign substances in the photosensitive layer and scratches on the photosensitive layer surface. In some cases, a local high electric field is applied unintentionally. Further, in recent years, image quality of electrophotography has been improved, and in order to set high contrast (the potential difference between the light portion potential of the photoreceptor and the development potential), the applied voltage of charging is set high, and the film thickness of the photosensitive layer is increased. It is in a severe situation against photoconductor leakage, for example, by reducing the film thickness. Therefore, the leak resistance of the electrophotographic photosensitive member is required more than ever. According to the study of the present inventors, in the electrophotographic photoreceptor described in Patent Document 1, while the potential stability with long-term use is good, when the contrast is set high or the thickness of the photosensitive layer is reduced. In some cases, a drum leak occurred.

  Accordingly, it is an object of the present invention to provide a method of manufacturing an electrophotographic photoreceptor capable of achieving both potential stability and leak resistance even when the contrast is high or the thickness of the photosensitive layer is small.

  The above object is achieved by the present invention described below. That is, the method for producing an electrophotographic photosensitive member according to the present invention is a method for producing an electrophotographic photosensitive member having a support, an intermediate layer, and a photosensitive layer in this order. A first firing step in which the particles are fired at a temperature T1 of 200 ° C. or higher in a reducing atmosphere, and a metal oxide particle fired in the first firing step is heated to a temperature of 200 ° C. or higher in an oxidizing atmosphere. A second firing step of firing at a temperature T2, a step of preparing a coating liquid for an intermediate layer containing metal oxide particles fired in the second firing step, and a step of using the coating liquid for an intermediate layer. Forming an intermediate layer, wherein the temperature T1 in the first firing step is higher than the temperature T2 in the second firing step.

  According to the method for manufacturing an electrophotographic photoreceptor of the present invention, it is possible to provide a method for manufacturing an electrophotographic photoreceptor capable of achieving both potential stability and leak resistance.

FIG. 4 is a top view for explaining a method of measuring a volume resistivity of an intermediate layer in the present invention. FIG. 4 is a cross-sectional view for explaining a method for measuring a volume resistivity of an intermediate layer in the present invention. It is a figure for explaining a stationary leak test device in an example of the present invention.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments.

  Although the detailed mechanism has not been clarified, the present inventors speculate as follows why the electrophotographic photoreceptor manufactured by the above manufacturing method has high leak resistance while suppressing potential fluctuation. are doing.

  In a general electrophotographic process, the bright portion potential is formed as follows. First, after the surface of the electrophotographic photosensitive member is negatively charged to a certain potential, the photosensitive layer is irradiated with light to generate holes and photoelectrons. The generated holes cancel out the charges on the surface of the photoreceptor, and the photoelectrons quickly flow toward the grounded support, thereby forming a light portion potential.

  When there is an intermediate layer between the photosensitive layer and the support, the intermediate layer allows the photoelectrons to flow quickly to the support, whereby the potential can be stabilized. In general, when a metal oxide is reduced and calcined, oxygen vacancies can be introduced into the metal oxide, electrons can move between the vacancy levels, and charges can move smoothly. Therefore, it is considered that the potential stability is improved by reducing the metal oxide particles used in the intermediate layer.

  In the intermediate layer, the metal oxide particles are dispersed in an electrically insulating resin, and it is considered that charges flow through the metal oxide particles by so-called percolation. In the case of metal oxide particles in which a defect level has been introduced by a reduction treatment, charges flow smoothly, while a large electric current flows when the above-mentioned high electric field is applied, so that a drum leak is likely to occur. Can be On the other hand, as in the production method of the present invention, the metal oxide particles in which the defect level has been introduced by the reduction treatment are again oxidized at a temperature lower than the temperature at the time of the reduction treatment, so that the introduced defect level is obtained. It is considered that oxygen is introduced into a defect level near the outermost surface of the metal oxide particles. Therefore, it is speculated that leak resistance is improved because there is no defect level on the surface of the metal oxide particles and an unnecessarily large current does not flow even when a high electric field is applied.

[Electrophotographic photoreceptor]
The method for producing an electrophotographic photosensitive member according to the present invention relates to a method for producing an electrophotographic photosensitive member having at least a support, an intermediate layer, and a photosensitive layer.

Examples of a method for forming each layer described later in the method for producing an electrophotographic photoreceptor of the present invention include a method in which a coating solution for each layer is prepared, applied in a desired layer order, and dried. At this time, the application method of the application liquid includes dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, ring coating and the like. Among these, dip coating is preferred from the viewpoints of efficiency and productivity.
Hereinafter, each layer will be described.

<Support>
The electrophotographic photoreceptor used in the present invention has a support. The support is preferably a conductive support having conductivity. Further, examples of the shape of the support include a cylindrical shape, a belt shape, and a sheet shape. Among them, a cylindrical support is preferable. Further, the surface of the support may be subjected to electrochemical treatment such as anodic oxidation, blast treatment, centerless polishing treatment, cutting treatment, or the like.

  As the material of the support, metal, resin, glass, and the like are preferable. Examples of the metal include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among them, an aluminum support using aluminum is preferable. In addition, conductivity may be imparted to the resin or glass by a process such as mixing or coating a conductive material.

<Intermediate layer>
In the present invention, an intermediate layer is formed on a support. By providing the intermediate layer, it is possible to conceal scratches and irregularities on the surface of the support and to control the reflection of light on the surface of the support.The intermediate layer contains metal oxide particles and a binder resin. I do.

  Metal oxide particles having various shapes such as a sphere, a polyhedron, an ellipsoid, a flake, and a needle can be used. Among them, spherical, polyhedral, and elliptical shapes are preferred from the viewpoint of reducing image defects such as black spots. Further, it is more preferable that the shape is a spherical shape or a polyhedral shape close to a spherical shape.

  Examples of the material of the metal oxide particles include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. The metal oxide particles are preferably composed of anatase-type or rutile-type titanium oxide, and more preferably composed of anatase-type titanium oxide. The use of anatase-type titanium oxide makes it more difficult for the dark portion potential and the light portion potential to fluctuate.

  When titanium oxide particles are used as the metal oxide particles, it is preferably particles obtained by coating titanium oxide as a core material with titanium oxide (hereinafter, also referred to as “titanium oxide-coated titanium oxide particles”). With the structure in which the titanium oxide as the core material is covered with the titanium oxide, the effect of suppressing the potential fluctuation due to the reduction treatment becomes more remarkable. Titanium oxide coating The titanium oxide of the coating layer of titanium oxide is titanium oxide doped with niobium or tantalum, that is, titanium oxide as a core material is coated with titanium oxide doped with niobium or tantalum. Preferably, particles are used. By doping with niobium or tantalum, trivalent titanium ions can be stably present. For this reason, at the time of reduction firing, oxygen vacancies are easily introduced, high conductivity is obtained, and an intermediate layer having a large effect of suppressing fluctuations in the light portion potential can be obtained. The doping amount of niobium or tantalum is preferably 0.5% by mass or more and 10% by mass or less of the total mass of the titanium oxide particles. If the doping amount is 0.5% by mass or less, it is difficult to obtain the effect of suppressing the fluctuation in the dark portion potential and the bright portion potential. When the doping amount is 10% by mass or more, the electrophotographic photoreceptor easily leaks. The doping amount is more preferably 1% by mass or more and 7% by mass or less of the total mass of the titanium oxide.

  After undergoing a first firing step (reduction firing) in which the metal oxide particles are fired at a temperature T1 of 200 ° C. or higher in a reducing atmosphere, the metal oxide particles are heated to 200 ° C. or higher in an oxidizing atmosphere and reduced. It is necessary to go through a second firing step (oxidizing firing) of firing at a temperature T2 higher than the temperature T1 at the time of firing. Here, the reduction firing means firing at least in an atmosphere gas and at a temperature at which oxygen vacancies can be introduced into the metal oxide. Examples of the atmosphere gas at the time of reduction firing include hydrogen gas, organic substance decomposition gas, and ammonia gas. Further, the organic substance decomposition gas refers to a substance obtained by decomposing an organic substance, for example, carbon black, by heating at a temperature of 600 ° C. or more in a low oxygen concentration state such as in an inert gas atmosphere, for example, in a nitrogen atmosphere. . The determination as to whether or not oxygen deficiency has been introduced into the metal oxide particles is made based on, for example, the presence or absence of an increase in weight with respect to a temperature rise in an oxygen atmosphere by a thermal analysis using a thermogravimetric differential thermal analyzer (TG-DTA). it can. Here, the term “oxidative firing” means firing in an atmosphere containing oxygen.

  The average primary particle size of the metal oxide particles is preferably 50 nm or more and 500 nm or less. When the average primary particle size of the metal oxide particles is 50 nm or more, reaggregation of the metal oxide particles is less likely to occur after preparing the coating solution for the intermediate layer. If the metal oxide particles are re-agglomerated, the stability of the coating solution for the intermediate layer is likely to be reduced, and cracks are likely to be generated on the surface of the formed intermediate layer. When the average primary particle size of the metal oxide particles is 500 nm or less, the surface of the intermediate layer is hardly roughened. If the surface of the intermediate layer is roughened, local charge injection into the photosensitive layer is likely to occur, and the leak resistance decreases. The average primary particle size of the metal oxide particles is more preferably 100 nm or more and 400 nm or less.

  The surface of the titanium oxide particles of the present invention may be treated with a silane coupling agent or the like.

  The intermediate layer preferably contains metal oxide particles in an amount of 20% by volume or more and 50% by volume or less based on the total volume of the intermediate layer. When the content of the titanium oxide particles of the present invention in the intermediate layer is less than 20% by volume based on the total volume of the intermediate layer, the distance between the metal oxide particles of the present invention tends to be long. As the distance between the metal oxide particles increases, the volume resistivity of the conductive layer tends to increase. Then, the flow of charges tends to be stagnant during image formation, the residual potential tends to rise, and the dark portion potential and the bright portion potential tend to fluctuate. When the content of the metal oxide particles in the intermediate layer is more than 50% by volume based on the total volume of the conductive layer, the titanium oxide particles of the present invention are likely to be in contact with each other. The portion where the titanium oxide particles of the present invention are in contact is a portion where the volume resistivity of the intermediate layer is locally low, and the electrophotographic photosensitive member is likely to leak. More preferably, the intermediate layer contains metal oxide particles in an amount of 30% by volume or more and 45% by volume or less based on the total volume of the intermediate layer.

  The intermediate layer may further have another conductive particle to the extent that the effect of the present invention is not impaired. Examples of the material of another conductive particle include a metal oxide, a metal, and carbon black. Examples of the metal oxide include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of the metal include aluminum, nickel, iron, nichrome, copper, zinc, and silver.

  When a metal oxide is used as another conductive particle, the surface of the metal oxide may be treated with a silane coupling agent or the like, or the metal oxide may be doped with an element such as phosphorus or aluminum or its oxide. .

  Further, another conductive particle may have a laminated structure including a core material particle and a coating layer covering the particle. Examples of the core material particles include titanium oxide, barium sulfate, and zinc oxide. Examples of the coating layer include metal oxides such as tin oxide.

  When a metal oxide is used as the conductive particles other than the titanium oxide of the present invention, the volume average particle diameter is preferably from 1 nm to 500 nm, more preferably from 3 nm to 400 nm.

Examples of the binder resin include a polyester resin, a polycarbonate resin, a polyvinyl acetal resin, an acrylic resin, a silicone resin, an epoxy resin, a melamine resin, a polyurethane resin, a phenol resin, and an alkyd resin.
As the binder material of the present invention, a thermosetting phenol resin or a thermosetting polyurethane resin is preferable. When a curable resin is used as a binder for the conductive layer, the binder contained in the conductive layer coating liquid is a monomer and / or oligomer of the curable resin.

  Further, the intermediate layer may further contain a concealing agent such as silicone oil, resin particles, and titanium oxide.

  The average thickness of the intermediate layer is preferably 0.5 μm or more and 50 μm or less, more preferably 1 μm or more and 40 μm or less, and particularly preferably 5 μm or more and 35 μm or less.

In the present invention, the volume resistivity of the intermediate layer is preferably from 1.0 × 10 ⁸ Ω · cm to 1.0 × 10 ¹³ Ω · cm. When the volume resistivity of the intermediate layer is 1.0 × 10 ¹³ Ω · cm or less, the flow of charges is less likely to be interrupted at the time of image formation, the residual potential is less likely to rise, and the fluctuations in the dark part potential and the light part potential are more pronounced. Less likely to occur. On the other hand, when the volume resistivity of the intermediate layer is 1.0 × 10 ⁸ Ω · cm or more, the amount of electric charge flowing through the intermediate layer during charging of the electrophotographic photosensitive member is not likely to be too large, and leakage is unlikely to occur. . Further, the volume resistivity of the intermediate layer is more preferably from 1.0 × 10 ⁸ Ω · cm to 1.0 × 10 ¹² Ω · cm.

  A method for measuring the volume resistivity of the intermediate layer of the electrophotographic photosensitive member will be described with reference to FIGS. FIG. 1 is a top view for explaining a method for measuring the volume resistivity of the intermediate layer, and FIG. 2 is a cross-sectional view for explaining a method for measuring the volume resistivity of the intermediate layer.

  The volume resistivity of the intermediate layer is measured in a normal temperature and normal humidity (temperature of 23 ° C./relative humidity of 50%) environment. A copper tape 203 (manufactured by Sumitomo 3M, model No. 1181) is attached to the surface of the intermediate layer 202, and this is used as an electrode on the surface side of the intermediate layer 202. The support 201 is an electrode on the back surface side of the intermediate layer 202. A power supply 206 for applying a voltage between the copper tape 203 and the support 201 and a current measuring device 207 for measuring a current flowing between the copper tape 203 and the support 201 are provided. Further, in order to apply a voltage to the copper tape 203, a copper wire 204 is placed on the copper tape 203, and a copper tape similar to the copper tape 203 is placed on the copper wire 204 so that the copper wire 204 does not come off from the copper tape 203. The copper wire 204 is fixed to the copper tape 203 by attaching the copper wire 205. A voltage is applied to the copper tape 203 using a copper wire 204.

The background current value when no voltage is applied between the copper tape 203 and the support 201 is I ₀ (A), and the current value when only a DC voltage (DC component) is applied at −1 V is I ( A), the film thickness d (cm) of the intermediate layer 202 and the area of the electrode (copper tape 203) on the surface side of the intermediate layer 202 are S (cm ² ), and the equation [ρ = 1 / (II) ₀ ) × S / d] is defined as the volume resistivity ρ (Ω · cm) of the intermediate layer 202.
In this measurement, in order to measure a minute current amount of 1 × 10 ⁻⁶ A or less in absolute value, it is preferable to use a device capable of measuring a small current as the current measuring device 207. Examples of such a device include a pA meter 4140B manufactured by Yokogawa Hewlett-Packard. Incidentally, the volume resistivity of the intermediate layer can be measured by peeling off each layer (photosensitive layer, etc.) on the intermediate layer from the electrophotographic photoreceptor, even when the measurement is performed with only the intermediate layer formed on the support. The same value is obtained even when measurement is performed with only the intermediate layer left.

In the present invention, the volume resistivity (powder resistivity) of the particles as a powder is preferably 1.0 × 10 ¹ Ω · cm or more and 1.0 × 10 ⁶ Ω · cm or less. When the powder resistivity is within this range, it is easy to obtain an intermediate layer having the above-described preferable volume resistivity range. Further, the powder resistivity of the particles is more preferably from 1.0 × 10 ² Ω · cm to 1.0 × 10 ⁵ Ω · cm. In the present invention, the powder resistivity of the particles is measured in an environment at normal temperature and normal humidity (temperature 23 ° C./relative humidity 50%). In the present invention, a resistivity meter Loresta GP manufactured by Mitsubishi Chemical was used as a measuring device. The particles of the present invention to be measured were solidified at a pressure of 500 kg / cm ² to form a pellet-shaped measurement sample, and the applied voltage was 100 V.

  The intermediate layer can be formed by preparing a coating liquid for an intermediate layer containing the above-described materials and a solvent, forming this coating film, and drying the coating film. Examples of the solvent used for the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Examples of a dispersion method for dispersing the conductive particles in the conductive layer coating liquid include a method using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

<Undercoat layer>
In the present invention, an undercoat may be provided on the intermediate layer. By providing the undercoat layer, the adhesive function between the layers is enhanced, and a charge injection blocking function can be provided.

  The undercoat layer preferably contains a resin. Further, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.

  As the resin, polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl phenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin , Polyamic acid resin, polyimide resin, polyamideimide resin, cellulose resin and the like.

  Examples of the polymerizable functional group of the monomer having a polymerizable functional group include isocyanate group, blocked isocyanate group, methylol group, alkylated methylol group, epoxy group, metal alkoxide group, hydroxyl group, amino group, carboxyl group, thiol group, Examples include a carboxylic anhydride group and a carbon-carbon double bond group.

  In addition, the undercoat layer may further contain an electron transporting substance, metal oxide particles, metal particles, a conductive polymer, or the like for the purpose of improving electric characteristics. Among these, it is preferable to use an electron transporting substance and metal oxide particles.

  Examples of the electron transporting material include a quinone compound, an imide compound, a benzimidazole compound, a cyclopentadienylidene compound, a fluorenone compound, a xanthone compound, a benzophenone compound, a cyanovinyl compound, an aryl halide compound, a silole compound, and a boron-containing compound. . An undercoat layer may be formed as a cured film by using an electron transporting substance having a polymerizable functional group as the electron transporting substance and copolymerizing the electron transporting substance with the monomer having a polymerizable functional group.

  Examples of the metal oxide particles include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide. Examples of the metal particles include gold, silver, and aluminum. When metal oxides or metal particles are used for the undercoating intermediate layer, the surface may be treated with a silane coupling agent or the like.

  The undercoat layer may further contain an additive.

  The average thickness of the undercoat layer is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 40 μm or less, and particularly preferably 0.3 μm or more and 30 μm or less.

  The undercoat layer can be formed by preparing a second intermediate layer coating solution containing the above-described materials and a solvent, forming the coating film, and drying and / or curing the coating film. Examples of the solvent used for the coating liquid include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

<Photosensitive layer>
The photosensitive layers of the electrophotographic photosensitive member are mainly classified into (1) a laminated photosensitive layer and (2) a single-layer photosensitive layer. (1) The laminated photosensitive layer has a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance. (2) The single-layer type photosensitive layer has a photosensitive layer containing both a charge generating substance and a charge transporting substance.

(1) Laminated photosensitive layer The laminated photosensitive layer has a charge generation layer and a charge transport layer.

(1-1) Charge Generation Layer The charge generation layer preferably contains a charge generation substance and a resin.

  Examples of the charge generating substance include an azo pigment, a perylene pigment, a polycyclic quinone pigment, an indigo pigment, and a phthalocyanine pigment. Among these, azo pigments and phthalocyanine pigments are preferred. Among the phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred.

  The content of the charge generating substance in the charge generation layer is preferably from 40% by mass to 85% by mass, more preferably from 60% by mass to 80% by mass, based on the total mass of the charge generation layer. preferable.

  As the resin, polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin And polyvinyl chloride resin. Among these, polyvinyl butyral resin is more preferable.

  Further, the charge generation layer may further contain additives such as an antioxidant and an ultraviolet absorber. Specific examples include a hindered phenol compound, a hindered amine compound, a sulfur compound, a phosphorus compound, a benzophenone compound, and the like.

  The average thickness of the charge generation layer is preferably from 0.1 μm to 1 μm, and more preferably from 0.15 μm to 0.4 μm.

  The charge generation layer can be formed by preparing a charge generation layer coating solution containing the above-described materials and a solvent, forming the coating film, and drying the coating film. Examples of the solvent used for the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

(1-2) Charge transport layer The charge transport layer preferably contains a charge transport material and a resin.

  Examples of the charge transport substance include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having a group derived from these substances. Can be Among these, a triarylamine compound and a benzidine compound are preferable.

  The content of the charge transporting substance in the charge transporting layer is preferably from 25% by weight to 70% by weight, more preferably from 30% by weight to 55% by weight, based on the total weight of the charge transporting layer. preferable.

  Examples of the resin include a polyester resin, a polycarbonate resin, an acrylic resin, and a polystyrene resin. Among these, polycarbonate resins and polyester resins are preferred. As the polyester resin, a polyarylate resin is particularly preferable.

  The content ratio (mass ratio) between the charge transport material and the resin is preferably from 4:10 to 20:10, and more preferably from 5:10 to 12:10.

  Further, the charge transport layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipperiness imparting agent, and a wear resistance improver. Specifically, hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane modified resins, silicone oil, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles And the like.

  The average thickness of the charge transport layer is preferably from 5 μm to 50 μm, more preferably from 8 μm to 40 μm, and particularly preferably from 9 μm to 30 μm.

  The charge transport layer can be formed by preparing a charge transport layer coating solution containing the above-described materials and a solvent, forming the coating film, and drying the coating film. Examples of the solvent used for the coating liquid include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Among these solvents, ether solvents and aromatic hydrocarbon solvents are preferred.

(2) Single-layer type photosensitive layer The single-layer type photosensitive layer is formed by preparing a coating solution for a photosensitive layer containing a charge-generating substance, a charge-transporting substance, a resin, and a solvent, forming this coating film, and then drying it. can do. The charge generating substance, the charge transporting substance, and the resin are the same as those exemplified in the above “(1) Laminated photosensitive layer”.

<Protective layer>
In the present invention, a protective layer may be provided on the photosensitive layer. By providing the protective layer, the durability can be improved.

  The protective layer preferably contains conductive particles and / or a charge transport material and a resin.

  Examples of the conductive particles include metal oxide particles such as titanium oxide, zinc oxide, tin oxide, and indium oxide.

  Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having a group derived from these materials. Among these, a triarylamine compound and a benzidine compound are preferable.

  Examples of the resin include a polyester resin, an acrylic resin, a phenoxy resin, a polycarbonate resin, a polystyrene resin, a phenol resin, a melamine resin, and an epoxy resin. Among them, polycarbonate resin, polyester resin and acrylic resin are preferable.

  Further, the protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the reaction at that time include a thermal polymerization reaction, a photopolymerization reaction, and a radiation polymerization reaction. Examples of the polymerizable functional group of the monomer having a polymerizable functional group include an acryl group and a methacryl group. As the monomer having a polymerizable functional group, a material having charge transport ability may be used.

  The protective layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipperiness imparting agent, and an abrasion resistance improver. Specifically, hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane modified resins, silicone oil, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles And the like.

  The average thickness of the protective layer is preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 7 μm or less.

  The protective layer can be formed by preparing a protective layer coating solution containing the above-described materials and a solvent, forming the coating film, and drying and / or curing the coating film. Examples of the solvent used for the coating liquid include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, and aromatic hydrocarbon solvents.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples unless it exceeds the gist. In the following description of the examples, “parts” are based on mass unless otherwise specified.

<Production example of metal oxide particles>
(Titanium oxide particles 1)
The titanium oxide particles of the present invention can be produced by a known sulfuric acid method. The details will be described below. A fine nucleus composed of titanium hydroxide was added to the aqueous solution of titanyl sulfate, and the mixture was hydrolyzed by heating and boiling to obtain a hydrous titanium dioxide slurry.

  The aqueous titanium dioxide slurry containing niobium ions was filtered, washed, and dried at 110 ° C. for 8 hours to obtain an intermediate. This intermediate was heated in a hydrogen atmosphere at 500 ° C. for 1 hour to perform reduction firing, thereby obtaining a powder of titanium oxide particles 1 having an average primary particle diameter of 220 nm.

(Titanium oxide particles 2)
The powder of the titanium oxide particles 1 was heated in the air at 300 ° C. for 1 hour to perform oxidative firing, thereby obtaining a powder of the titanium oxide particles 2 having an average primary particle size of 220 nm.

(Titanium oxide particles 3)
The powder of the titanium oxide particles 1 was heated in the air at 500 ° C. for 1 hour to perform oxidation and firing, thereby obtaining a powder of the titanium oxide particles 2 having an average primary particle size of 220 nm.

(Titanium oxide particles 4)
In the production method of the titanium oxide particles 2, 0.1 wt% of carbon black (trade name: Toka Black # 7360SB, manufactured by Tokai Carbon) is added to the weight of the intermediate at the time of reduction firing, and firing is performed at 800 ° C. in a nitrogen atmosphere. Then, titanium oxide particles 4 were obtained in the same manner as the titanium oxide particles 2 except that the temperature during the oxidizing and firing was set to 500 ° C.

(Titanium oxide particles 5-7)
In the production of the titanium oxide particles 4, the oxidization was performed in the same manner as the titanium oxide particles 4 except that the atmosphere gas during the reduction firing was a mixed gas of nitrogen and air at the partial pressure ratio shown in Table 1 and the oxidation firing was not performed. Titanium particles 5 to 7 were obtained.
(Titanium oxide particles 8)
The intermediate in the method for producing the titanium oxide particles 1 was prepared by adding 0.1 wt% of carbon black (trade name: Toka Black # 7360SB, manufactured by Tokai Carbon) based on the weight of the intermediate, and then at 800 ° C. in an air atmosphere. By oxidizing and firing, titanium oxide particles 8 were obtained.

(Tin oxide particles 1)
30.0 kg of metal tin was dissolved in 39.7 kg of 35% by mass hydrochloric acid to obtain a tin chloride (divalent) aqueous solution (A). Next, 352.5 g of a tin chloride (divalent) aqueous solution (A) and 209.5 g of hydrochloric acid having a concentration of 35% by mass were mixed to obtain a tin chloride (divalent) aqueous solution (B). Next, the tin chloride (divalent) aqueous solution (B) was kept at 80 ° C. 188.5 g of nitric acid having a concentration of 60% by mass was dropped into this solution maintained at 80 ° C. over 68 minutes to obtain a tin chloride (tetravalent) aqueous solution (C). Next, 1 liter of pure water was placed in a 2 liter separable flask and maintained at 60 ° C. While stirring 1 liter of the pure water at 60 ° C. at a stirring rotation speed of 298 rpm, 733.3 g of tin chloride (tetravalent) aqueous solution (C) and 28 mass% ammonia water were maintained at a pH of 2.0 during the reaction. The reaction was carried out by simultaneously supplying over 122 minutes to produce a tin-containing precipitate. After the formation of the tin-containing precipitate, the mixture was stirred at 60 ° C. for 30 minutes, and left still at room temperature overnight to mature the precipitate. The tin-containing precipitate was adjusted to pH 8 and stirred at room temperature for 30 minutes. Next, suction filtration was performed, washing was performed, and a precipitate was collected. This precipitate was dried at 130 ° C. Next, the dried precipitate was filled in an alumina boat and fired in a tubular furnace. The firing temperature was 1100 ° C. for 30 minutes, and the rate of temperature rise was 10 ° C./min up to 900 ° C. and 5 ° C./min from 900 ° C. As the atmosphere gas, only air was flowed from room temperature to 1000 ° C, and 2.5% by volume hydrogen chloride gas-97.5% by volume air was flowed from 1000 ° C to 1100 ° C. After firing, the air was cooled by flowing only air, and the powder taken out of the furnace was washed with water and dried to obtain tin oxide powder. The obtained tin oxide powder was wet-pulverized and fired in hydrogen gas at 300 ° C. for 1 hour to obtain tin oxide particles 1 having an average primary particle diameter of 300 nm which was reduced and fired.

(Tin oxide particles 2)
The tin oxide particles 1 were fired in air at 250 ° C. for 1 hour to obtain tin oxide particles 2 which were oxidized and fired.

(Titanium oxide coated titanium oxide particles 1)
As the base powder, anatase type titanium oxide having an average primary particle size of 200 nm was used. A titanium sulfate solution containing 35.0 g of titanium in terms of TiO ₂ was prepared. 100 g of the substrate was purely dispersed to form a 1 L suspension, which was heated to 60 ° C. The solution for titanium sulfuric acid and 10 mol / L sodium hydroxide were added dropwise over 3 hours so that the pH of the suspension became 2-3. After dropping the whole amount, the suspension was filtered and washed to obtain an intermediate.

  The intermediate is heated in a hydrogen gas at 500 ° C. for 1 hour to perform reduction firing, and then heated in the air at 300 ° C. for 1 hour to perform oxidation firing to obtain titanium oxide-coated titanium oxide particles 1. Obtained.

(Niobium doped titanium oxide coated titanium oxide particles 1)
In the production of the titanium oxide-coated titanium oxide particles 1, except that a titanium niobium sulfate solution containing 33.7 g of titanium in terms of TiO ₂ and 2.9 g of niobium in terms of Nb ₂ O ₅ was used instead of the titanium sulfate solution. Similarly to the titanium oxide-coated titanium oxide particles 1, niobium-doped titanium oxide-coated titanium oxide particles 1 were obtained.

(Niobium doped titanium oxide coated titanium oxide particles 2)
In the production of niobium-doped titanium oxide-coated titanium oxide particles 1, niobium-doped titanium oxide-coated titanium oxide particles were produced in the same manner as niobium-doped titanium oxide-coated titanium oxide particles 1, except that ammonia was used instead of hydrogen as an atmosphere gas for reduction firing. 2 was obtained.

(Niobium doped titanium oxide coated titanium oxide particles 3)
In the production of the niobium-doped titanium oxide-coated titanium oxide particles 1, during the reduction firing, 0.1 wt% of carbon black (trade name: Toka Black # 7360SB, manufactured by Tokai Carbon) is added to the weight of the intermediate, and the reduction firing is performed. Niobium-doped titanium oxide in the same manner as niobium-doped titanium oxide-coated titanium oxide particles 1 except that the firing temperature was 800 ° C. and the temperature at the time of oxidizing and firing was 400 ° C. using nitrogen instead of hydrogen as the atmosphere gas Coated titanium oxide particles 3 were obtained.

(Niobium-doped titanium oxide coated titanium oxide particles 4 to 6)
Niobium-doped titanium oxide-coated titanium oxide particles 4 to 6 were obtained in the same manner as niobium-doped titanium oxide-coated titanium oxide particles 3 except that the temperature during the oxidizing and firing was set to the temperature shown in Table 2.

(Niobium-doped titanium oxide-coated titanium oxide particles 7)
Niobium-doped titanium oxide-coated titanium oxide particles 7 were obtained in the same manner as niobium-doped titanium oxide-coated titanium oxide particles 3 except that the atmosphere during the oxidizing and firing was a mixed gas in which the partial pressure of oxygen and air was 50:50.

(Niobium doped titanium oxide coated titanium oxide particles 8)
Niobium-doped titanium oxide-coated titanium oxide particles 8 were obtained in the same manner as for niobium-doped titanium oxide-coated titanium oxide particles 3, except that the heating time during the oxidizing and firing was 3 hours.

[Example of preparation of coating solution for intermediate layer]
(Example of preparation of coating solution 1 for intermediate layer)
50 parts of a phenol resin (monomer / oligomer of phenol resin) (trade name: Plyofen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g / cm ² ) as a binder material Was dissolved in 35 parts of 1-methoxy-2-propanol as a solvent to obtain a solution.

To this solution, 63 parts of titanium oxide particles 2 were added, and this was placed in a vertical sand mill using 120 parts of glass beads having an average particle size of 1.0 mm as a dispersion medium. The dispersion liquid temperature was 23 ± 3 ° C., and the number of revolutions was 1500 rpm (periphery). The dispersion treatment was performed for 4 hours under the condition of a speed of 5.5 m / s) to obtain a dispersion. Glass beads were removed from the dispersion with a mesh. After removing the glass beads, 0.01 parts of silicone oil (trade name: SH28 PAINT ADDITIVE, manufactured by Dow Corning Toray) as a leveling agent and silicone resin particles (trade name: Dow Corning) as a surface roughness imparting material 10 parts of Tospearl 120, manufactured by Momentive Performance Materials, average particle size: 2 μm, density: 1.3 g / cm ² ) were added and stirred, and then PTFE filter paper (trade name: PF060, manufactured by Advantech Toyo) was used. The coating solution for intermediate layer 1 was prepared by filtration under pressure.

(Examples of Preparation of Coating Solutions 2 to 19 for Intermediate Layer)
Except that the metal oxide particles used in the preparation of the coating solution for the intermediate layer were as shown in Table 3, respectively, the coating solutions for the intermediate layer 2 were prepared in the same manner as in the preparation example of the coating solution 1 for the intermediate layer. 19 was prepared.

(Example of Preparation of Coating Solution 20 for Intermediate Layer)
15 parts of butyral resin (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) as a binder material and 18.75 parts of blocked isocyanate resin (trade name: TPA-B80E, 80% solution, manufactured by Asahi Kasei) Was dissolved in a mixed solvent of 45 parts of methyl ethyl ketone / 1 and 85 parts of 1-butanol to obtain a solution. 63 parts of niobium-doped titanium oxide-coated titanium oxide particles 3 are added to this solution, and this is placed in a vertical sand mill using 120 parts of glass beads having an average particle size of 1.0 mm as a dispersion medium, and the dispersion liquid is rotated at a temperature of 23 ± 3 ° C. Dispersion treatment was performed for 4 hours under conditions of several 1500 rpm (5.5 m / s in peripheral speed) to obtain a dispersion. Glass beads were removed from the dispersion with a mesh. After removing the glass beads, 0.01 part of silicone oil (trade name: SH28 PAINT ADDITIVE, manufactured by Dow Corning Toray) as a leveling agent, and a cross-linked polymethyl methacrylate ( 5 parts of PMMA) particles (trade name: Techpolymer SSX-102, manufactured by Sekisui Chemical Co., Ltd., average primary particle size: 2.5 μm) were added and stirred, and PTFE filter paper (trade name: PF060, manufactured by Advantech Toyo) was added. The resultant was subjected to pressure filtration to prepare a coating liquid 20 for an intermediate layer.

<Production example of electrophotographic photoreceptor>
(Electrophotographic photoreceptor 1)
An aluminum cylinder (JIS-A3003, aluminum alloy) having a length of 257 mm and a diameter of 24 mm manufactured by a manufacturing method including an extrusion step and a drawing step was used as a support.

  The coating solution 1 for an intermediate layer is applied onto a support by dip coating in a normal temperature and normal humidity (23 ° C./50% RH) environment, and the obtained coating film is dried and thermally cured at 170 ° C. for 30 minutes to obtain a film. An intermediate layer having a thickness of 30 μm was formed.

100 parts of rutile-type titanium oxide particles (average primary particle size: 50 nm, manufactured by Teica) are stirred and mixed with 500 parts of toluene, and in formula (1), m = 0, n = 3, and vinyltriene in which R ¹ is a methyl group. 3.0 parts of methoxysilane (trade name: KBM-1003, manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and the mixture was stirred for 8 hours. Thereafter, the toluene was distilled off under reduced pressure and dried at 120 ° C. for 3 hours to obtain rutile-type titanium oxide particles surface-treated with vinyltrimethoxysilane.

  18 parts of rutile-type titanium oxide particles surface-treated with vinyltrimethoxysilane, 4.5 parts of N-methoxymethylated nylon (trade name: Toresin EF-30T, manufactured by Nagase ChemteX), copolymer nylon resin (trade name) : Amilan CM8000, manufactured by Toray) was added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion.

  This dispersion was subjected to dispersion treatment using glass beads having a diameter of 1.0 mm by a vertical sand mill for 5 hours to prepare a coating liquid for an undercoat layer. This undercoat layer coating solution was applied onto the intermediate layer by dip coating, and the obtained coating film was dried at 100 ° C. for 10 minutes to form a 2.0 μm-thick undercoat layer.

  Next, the Bragg angles (2θ ± 0.2 °) in the CuKα characteristic X-ray diffraction were changed to 7.5 °, 9.9 °, 16.3 °, 18.6 °, 25.1 ° and 28.3 °. A glass bead having a diameter of 0.8 mm was prepared by mixing 10 parts of a crystal form of hydroxygallium phthalocyanine (charge generating substance) having a strong peak, 5 parts of polyvinyl butyral (trade name: Esrec BX-1, manufactured by Sekisui Chemical Co., Ltd.), and 250 parts of cyclohexanone And a dispersion treatment was performed under the conditions of a dispersion treatment time of 3 hours, and then 250 parts of ethyl acetate was added to prepare a coating solution for a charge generation layer. This coating solution for a charge generation layer was applied onto the undercoat layer by dip coating, and the obtained coating film was dried at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.15 μm.

  Next, 6.0 parts of an amine compound (charge-transporting substance) represented by the following formula (CT1), 2.0 parts of an amine compound (charge-transporting substance) represented by the following formula (CT2), and bisphenol Z-type polycarbonate (Trade name: Z400, manufactured by Mitsubishi Engineering-Plastics Corporation) having 10 parts, a repeating structural unit represented by the following formula (B-1) and a repeating structural unit represented by the following formula (B-2), and 0.36 parts of a siloxane-modified polycarbonate having a terminal structure represented by (B-3) ((B-1) :( B-2) = 95: 5 (molar ratio)) and 60 parts of o-xylene / dimethoxy A coating solution for a charge transport layer was prepared by dissolving in a mixed solvent of 40 parts of methane / 2.7 parts of methyl benzoate. The charge transport layer coating solution was applied onto the charge generation layer by dip coating, and the obtained coating film was dried at 125 ° C. for 30 minutes to form a charge transport layer having a thickness of 12.0 μm.

As described above, the electrophotographic photoreceptor 1 in which the charge transport layer was the surface layer was manufactured.

(Electrophotographic photoreceptors 2 to 13)
Except that the coating solution for the intermediate layer used in the production of the electrophotographic photoreceptor was changed from the coating solution for the intermediate layer 1 as shown in Table 4, in the same manner as in the production example of the electrophotographic photoreceptor 1, Electrophotographic photosensitive members 2 to 13 were manufactured.

(Electrophotographic photoreceptor 14)
An electrophotographic photoreceptor 14 was produced in the same manner as in the production example of the electrophotographic photoreceptor 8, except that the undercoat layer described below was not formed on the intermediate layer.

(Electrophotographic photoreceptors 15 to 21)
Except that the coating solution for the intermediate layer used in the production of the electrophotographic photoreceptor was changed from the coating solution for the intermediate layer 1 as shown in Table 4, in the same manner as in the production example of the electrophotographic photoreceptor 1, Electrophotographic photoreceptors 15 to 21 were manufactured.

[Evaluation]
(Evaluation of the effect of suppressing fluctuations in dark area potential and bright area potential during repeated use)
Each of the electrophotographic photoreceptors manufactured above was mounted on a Hewlett-Packard laser beam printer, Color LaserJet Enterprise M552, and subjected to a paper passing durability test under an environment of a temperature of 23 ° C. and a relative humidity of 50%. In the paper passing durability test, a printing operation was performed in an intermittent mode in which a character image having a printing rate of 2% was output one by one on letter paper, and 25,000 sheets of images were output. Then, at the start of the paper passing durability test and at the end of the output of 25,000 sheets of images, the potential at the time of exposure (bright portion potential) was measured. The potential measurement was performed using a solid black image. The bright portion potential at the beginning (at the start of the paper passing durability test) was Vl, and the bright portion potential after the completion of the image output of 25,000 sheets was Vl '. Then, a bright portion potential variation amount ΔVl (= | Vl ′ | − | Vl |), which is a difference between the bright portion potential Vl ′ after the completion of the image output of 25,000 sheets and the initial bright portion potential Vl, was obtained. Table 5 shows the results.

(Static leak test of electrophotographic photoreceptor)
A static leak test of the electrophotographic photosensitive member manufactured as described above was performed as follows. FIG. 3 shows a static leak test apparatus. The static leak test is performed in a normal temperature and normal humidity (23 ° C./50% RH) environment. Both ends of the electrophotographic photoreceptor 1 are mounted on a fixed base 13 and fixed so as not to move. The portion 14 of the electrophotographic photosensitive member 1 that contacts the support is connected to the ground via a 100 kΩ reference resistor 15. A φ6 stepped metal core 16 having a φ20 stepped portion 16a having a width of 50 mm is brought into contact with one end 5N such that the stepped portion 16a comes into contact with the central portion of the photosensitive layer 17 of the electrophotographic photosensitive member 1. A power supply 18 for applying a voltage is connected to the stepped core 16. A voltage of −3 kV is applied to the stepped metal core 16, and the time from the application of the voltage to the leakage of the photosensitive layer (leakage resistance time) is measured. Leakage was determined by monitoring the voltage applied to the 100 kΩ reference resistor 15 connected to the ground. Table 5 shows the results. The test was performed with an upper limit of 30 minutes (1800 seconds), and those that did not leak for 30 minutes were indicated as "no leak" in Table 5.

REFERENCE SIGNS LIST 1 electrophotographic photosensitive member 2 axis 3 charging means 4 exposure light 5 developing means 6 transfer means 7 transfer material 8 fixing means 9 cleaning means 10 pre-exposure light 11 process cartridge 12 guide means

Claims (4)

A method for producing an electrophotographic photosensitive member having a support, an intermediate layer, and a photosensitive layer, in this order,
The production method
A first firing step of firing the metal oxide particles under a reducing atmosphere at a temperature T1 of 200 ° C. or higher;
A second firing step of firing the metal oxide particles fired in the first firing step at a temperature T2 of 200 ° C. or higher in an oxidizing atmosphere;
Preparing a coating liquid for an intermediate layer containing the metal oxide particles fired in the second firing step;
Forming an intermediate layer using the coating liquid for the intermediate layer,
Has,
The method for producing an electrophotographic photosensitive member, wherein the temperature T1 in the first baking step is higher than the temperature T2 in the second baking step.   2. The method according to claim 1, wherein the metal oxide particles are titanium oxide particles.   The method according to claim 2, wherein the titanium oxide particles are particles obtained by coating titanium oxide as a core material with titanium oxide. 3. The method for producing an electrophotographic photoreceptor according to claim 2, wherein the titanium oxide particles are particles obtained by coating titanium oxide as a core material with titanium oxide doped with niobium or tantalum.