JP2007147746A - Electrophotographic photoreceptor, process cartridge, image forming device, and method for manufacturing electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor that can sufficiently suppress decrease in image density due to repeated use and production of a negative memory and has excellent repeated potential characteristics and environmental stability, to provide a method for manufacturing the electrophotographic photoreceptor, and to provide an electrophotographic device and a process cartridge. <P>SOLUTION: The electrophotographic photoreceptor 1 has a functional layer containing zinc oxide particles, the functional layer 3 containing zinc oxide particles satisfying formula (1):A≤50 or the zinc oxide particles subjected to a surface treatment, wherein A represents an electric conductivity (μS/cm) of a mixture liquid at 25°C prepared by mixing the zinc oxide particles with pure water having the electric conductivity of 1.0 μS/cm to obtain the concentration of 2.5 mass%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  An electrophotographic apparatus is an apparatus capable of obtaining high-quality printing at high speed, and is used as a copying machine, a laser beam printer, or the like. As an electrophotographic photoreceptor (hereinafter sometimes simply referred to as “photoreceptor”) mounted in an electrophotographic apparatus, an organic photoreceptor using an organic photoconductive material has become the mainstream, and the configuration thereof is also a photosensitive layer. Has changed to a function separation type comprising a charge generation layer and a charge transport layer, and the performance has been improved. In addition to these functional layers, those having an undercoat layer (also referred to as “intermediate layer”) between the conductive support and the photosensitive layer, and those having a protective layer as the outermost layer are also known. Yes.

  Of the functional layers described above, the undercoat layer and the protective layer often contain metal oxide particles from the viewpoint of improving the electrical characteristics of the photoreceptor. Among metal oxide particles, zinc oxide particles have advantages such as electrical characteristics and work function as a semiconductor suitable as a photoreceptor material, and easy control of the particle size that affects the electrical characteristics of the photoreceptor. For example, the provision of an undercoat layer containing zinc oxide particles (see, for example, Patent Documents 1 and 2) can be expected to improve the repetitive potential characteristics and environmental stability of the electrophotographic photosensitive member. In addition, zinc oxide particles are a highly useful material in terms of safety and cost superior to other metal oxides.

Japanese Patent Laid-Open No. 4-191861 JP 2002-91045 A

  However, the photoreceptor having the undercoat layer described in Patent Documents 1 and 2 has room for improvement in the following points.

  That is, according to the study by the present inventors, the photoreceptor containing zinc oxide particles may cause image quality defects such as negative memory in which the density of the image is reduced or the image of the exposed portion is whitened during repeated use due to the difference in production lots. It turns out that there is.

  The lot where image quality defects may occur may be identified by performing an environmental acceleration test or the like (for example, potential measurement using a charge-exposure repeated test machine) on the manufactured photoreceptor. Therefore, it is difficult to sufficiently maintain the product yield only by such a quality control method. Therefore, in actual production, it is important to manufacture a photoconductor that can sufficiently suppress the image quality defects.

  The present invention has been made in view of the above circumstances, and can sufficiently reduce image density reduction and negative memory generation, and is excellent in repetitive potential characteristics and environmental stability. It is an object of the present invention to provide a method for manufacturing a photoreceptor, an electrophotographic apparatus, and a process cartridge.

  As a result of intensive studies to achieve the above object, the present inventor has first obtained the knowledge that the electrophotographic characteristics of a photoreceptor containing zinc oxide particles differ depending on the production lot of zinc oxide particles. Furthermore, even when the general properties (volume average particle size, etc.) of zinc oxide particles are the same, it has been found that the above-mentioned image quality defects occur, and the knowledge that the cause is ionic impurities eluted from the zinc oxide particles Got. As a result of further research based on such knowledge, the use of zinc oxide particles whose ionic impurity elution amount is not more than a specific value as a constituent material of the undercoat layer causes the occurrence of the image quality defect over a long period of time. As a result, the present invention has been completed.

That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor provided with a functional layer containing zinc oxide particles, and the functional layer has zinc oxide particles satisfying the following formula (1) or the zinc oxide particles on the surface. It is characterized by containing what was processed.
A ≦ 50 (1)
Here, in the formula (1), A is a mixture solution at 25 ° C. when zinc oxide particles are mixed with pure water having an electric conductivity of 1.0 μS / cm or less so that the concentration becomes 2.5 mass%. Electric conductivity (μS / cm) is shown.

  According to the electrophotographic photosensitive member of the present invention, it is possible to sufficiently suppress the reduction in image density and the occurrence of negative memory due to repeated use, and to effectively exhibit the excellent electrical property improvement effect due to the zinc oxide particles. Is possible. Further, by applying the photoreceptor of the present invention excellent in repetitive potential characteristics and environmental stability to an image forming apparatus, high image quality can be achieved at a high level.

  The reason why the above-described effects are achieved by the present invention is presumed as follows. That is, the zinc oxide particles contained as the constituent material of the electrophotographic photosensitive member have a primary particle size of 300 nm or less from the viewpoint of ensuring the film formability of the functional layer and appropriate conductivity when dispersed in the binder resin. Such zinc oxide particles are generally produced by a wet process via basic zinc carbonate. It is considered that ionic impurities such as sodium chloride, calcium chloride, sulfate and carbonate mixed in the process of producing basic zinc carbonate influence the stability of the electrophotographic characteristics of the photoreceptor. More specifically, in the conventional photoreceptor, the ionic impurities or ions generated from the impurities form localized levels in the functional layer to trap carriers, or the functional layer is conductive. When it is provided adjacent to the support, impurities corrode the support and a semiconductive or insulating film is formed at the interface between the support and the functional layer. It is thought that the rise and the decrease of the charged potential are caused. On the other hand, in the photoconductor of the present invention, the amount of ionic impurities eluted from the zinc oxide particles is limited to a specific value, so that the zinc oxide particles are sufficiently mixed in the functional layer. Can also prevent the above-described carrier capture and film formation, and as a result, it is presumed that the above-described effects were obtained. Further, the present inventors consider that ions that adversely affect the electrophotographic characteristics of the photoconductor are not only chlorine ions but also sodium ions and the like are factors that cause the potential characteristics to fluctuate by capturing electrons. In particular, in a high temperature and high humidity environment, it is considered that most of the ionic impurities contained in the zinc oxide particles change the conductivity of the functional layer due to moisture absorption. According to the present invention, since the above fluctuation can be effectively prevented by defining the total amount of ionic impurities contained in the zinc oxide particles, an electrophotographic photoreceptor excellent in repetitive potential characteristics and environmental stability can be realized. The present inventors infer that it has become.

  In the electrophotographic photosensitive member of the present invention, the functional layer is brought into contact with pure water, a preparation step of preparing basic zinc carbonate particles, a pure water contact step of bringing basic zinc carbonate particles into contact with pure water, and pure water. It is preferable to include zinc oxide particles that satisfy the above formula (1) obtained by culturing basic zinc carbonate particles and obtaining zinc oxide particles, or those obtained by surface treatment of the zinc oxide particles. As a result, the effect of suppressing the increase in the residual potential of the electrophotographic photosensitive member and the occurrence of negative memory can be further enhanced, and a photosensitive member excellent in repetitive potential characteristics and environmental stability can be more reliably realized.

  The above effect is due to the ionic impurities eluted from the zinc oxide particles that cause image quality defects in the conventional electrophotographic photosensitive member. By reducing the impurity concentration, electrophotographic characteristics due to ionic impurities can be obtained. The ionic impurity content of the zinc oxide particles finally obtained by bringing the basic zinc carbonate particles into contact with pure water is extremely low. It is thought that it was played by being able to reduce.

  In addition, since the ionic impurities affecting the image quality defect are efficiently removed in the manufacturing process of the zinc oxide particles, the photoconductor including the zinc oxide particles can exhibit excellent cost performance.

  From the viewpoint of obtaining the above effect more reliably, the pure water preferably has an electrical conductivity at 25 ° C. of 1.0 μS / cm or less.

  In the electrophotographic photoreceptor of the present invention, the functional layer has zinc oxide satisfying the above formula (1) obtained through a preparation step of preparing zinc oxide particles and a water contact step of bringing the zinc oxide particles into contact with water. It is preferable to include particles or those obtained by surface-treating the zinc oxide particles.

  Here, the “water” refers to any of tap water, RO-treated water, distilled water, or pure water.

  According to the photoreceptor provided with the functional layer, since the occurrence of the image quality defect can be sufficiently suppressed by using zinc oxide particles obtained by a cheaper means, it is possible to satisfactorily balance the productivity and the electrical property improvement effect. It becomes possible. The reason why such an effect is obtained is that the ionic impurities are considered to be concentrated on the surface of the zinc oxide particles, and the ionic impurities are removed from the zinc oxide particles by performing a water contact step after the zinc oxide particle preparation step. It is inferred that it can be effectively removed.

  From the viewpoint of more reliably suppressing the occurrence of image quality defects, the water preferably has an electric conductivity at 25 ° C. of 250 μS / cm or less.

  The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor comprising a conductive support and a photosensitive layer provided on the conductive support, wherein the functional layer is a conductive support and a photosensitive layer. It is preferable to arrange | position between.

  As described above, when the functional layer according to the present invention is provided as the undercoat layer, it is possible to further improve the electric characteristics as compared with the conventional photoreceptor. As described above, according to the present invention, even when zinc oxide particles are sufficiently blended in the undercoat layer, ionic impurities derived from zinc oxide particles form localized levels and trap carriers. It is thought that it is possible to sufficiently prevent the ionic impurities from corroding the support surface and forming a semiconductive or insulating film at the interface between the support and the undercoat layer. It is presumed that the increase in the residual potential and the decrease in the charging potential due to repeated use can be sufficiently suppressed.

  In the electrophotographic photoreceptor of the present invention, it is preferable that the functional layer includes a surface treatment of the zinc oxide particles with a silane coupling agent having an amino group. As a result, it is possible to drastically enhance the effect of preventing a decrease in charging potential while sufficiently maintaining the effect of suppressing image density reduction and negative memory generation due to repeated use. As the reason why such an effect is obtained, the present inventors infer as follows.

  That is, when the zinc oxide particles satisfy the above formula (1), when the surface treatment is performed with the silane coupling agent, the reaction rate of the silane coupling agent to the zinc oxide surface is improved, and between the zinc oxide particles Alternatively, it is considered that an effective rectifying action can be expressed at the interface between the zinc oxide particles and the functional layer. As a result, it is presumed that the effect of preventing the decrease in the charging potential is highly enhanced.

  The present invention also includes a liquid mixture adjusting step of adjusting the liquid mixture by mixing zinc oxide particles with pure water having an electric conductivity of 1.0 μS / cm or less so that the concentration is 2.5% by mass; In a quality inspection method for zinc oxide particles, comprising: a measurement step of measuring electrical conductivity at 25 ° C .; and a step of determining whether or not the measured value of electrical conductivity obtained in the measurement step is 50 μS / cm or less. A preparatory step of preparing zinc oxide particles whose surface conductivity is determined to satisfy a predetermined condition, or a surface treatment of the zinc oxide particles; A processing target preparation step for preparing a processing body and a coating liquid containing the zinc oxide particles or the surface-treated zinc oxide particles are prepared, and the coating liquid is applied onto the processing target and dried. Ability to form layers And a layer forming step. A method for producing an electrophotographic photosensitive member is provided.

  Here, the object to be processed is an electrophotographic photosensitive member in which a functional layer is formed, and has a configuration in which a functional layer and a layer formed after formation of the functional layer are excluded from the target electrophotographic photosensitive member. Is. When the functional layer is formed last, the functional layer is removed from the target electrophotographic photosensitive member.

  According to the method for producing an electrophotographic photosensitive member of the present invention, it is possible to effectively obtain the electrophotographic photosensitive member of the present invention that can sufficiently suppress image density reduction and negative memory generation by repeated use.

  In the method for producing an electrophotographic photosensitive member of the present invention, the zinc oxide particles are prepared by preparing a basic zinc carbonate particles, a pure water contact step of bringing the basic zinc carbonate particles into contact with pure water, and pure water. It is preferable to be obtained by a method for producing zinc oxide particles, which comprises culturing the contacted basic zinc carbonate particles to obtain zinc oxide particles. As a result, it is possible to further enhance the effect of suppressing the increase in the residual potential of the electrophotographic photoreceptor to be manufactured and the generation of negative memory.

  Further, from the viewpoint of satisfactorily balancing the productivity and the electrical property improving effect, in the method for producing the electrophotographic photosensitive member of the present invention, the zinc oxide particles are provided with a preparation step in which zinc oxide particles are prepared, and the zinc oxide It is preferable to be obtained through a treatment method of zinc oxide particles including a water contact step of bringing the particles into contact with water.

  The present invention also forms the toner image by developing the electrophotographic photosensitive member of the present invention, a charging means for charging the electrophotographic photosensitive member, and the electrostatic latent image formed on the electrophotographic photosensitive member with toner. There is provided a process cartridge characterized by comprising at least one selected from the group consisting of developing means for cleaning and cleaning means for removing toner remaining on the surface of the electrophotographic photosensitive member.

  The present invention also provides the electrophotographic photoreceptor of the present invention, a charging means for charging the electrophotographic photoreceptor, an exposure means for forming an electrostatic latent image on the charged electrophotographic photoreceptor, An image forming apparatus comprising: developing means for developing a latent image with toner to form a toner image; and transfer means for transferring the toner image from an electrophotographic photosensitive member to a transfer target. To do.

  These process cartridges and image forming apparatuses are provided with the electrophotographic photosensitive member of the present invention excellent in repetitive potential characteristics and environmental stability, so that occurrence of image quality defects due to repetitive use is sufficiently suppressed, and high performance over a long period of time. A quality image can be formed.

  According to the present invention, it is possible to sufficiently suppress image density reduction and negative memory generation due to repeated use, an electrophotographic photoreceptor excellent in repeated potential characteristics and environmental stability, a method for producing such an electrophotographic photoreceptor, and An electrophotographic apparatus and a process cartridge can be provided.

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

  First, the manufacturing method of the zinc oxide particle which concerns on this invention which is a constituent material of the electrophotographic photoreceptor of this invention is demonstrated. In the present embodiment, a method for producing zinc oxide particles used as a constituent material of the undercoat layer 3 included in the electrophotographic photosensitive member 1 (hereinafter referred to as “photosensitive member 1”) shown in FIG.

The zinc oxide particles according to the present invention must satisfy the following formula (1).
A ≦ 50 (1)
Here, in the formula (1), A is a mixture solution at 25 ° C. when zinc oxide particles are mixed with pure water having an electric conductivity of 1.0 μS / cm or less so that the concentration becomes 2.5 mass%. Electric conductivity (μS / cm) is shown.

  Whether or not the finally obtained zinc oxide particles satisfy the above-mentioned predetermined condition, for example, with pure water having an electric conductivity of 1.0 μS / cm or less so that the concentration of zinc oxide particles is 2.5% by mass. A mixed solution adjusting step for mixing and adjusting the mixed solution, a measuring step for measuring the electric conductivity of the mixed solution at 25 ° C., and whether the measured value of the electric conductivity obtained in the measuring step is 50 μS / cm or less It can confirm by the quality inspection method of a zinc oxide particle provided with the process of discriminating.

  More specifically, the following procedure is performed. (1) Zinc oxide particles are added to pure water having an electric conductivity of 1.0 μS / cm or less so that the concentration is 2.5 mass%. Next, (2) zinc oxide particles in pure water are sufficiently dispersed by means such as an ultrasonic disperser, a ball mill, or a homogenizer. Next, (3) using an electric conductivity meter, the electric conductivity (temperature of 25 ° C.) of pure water in which zinc oxide particles are dispersed is measured. Next, when the electrical conductivity measured in (4) and (3) is 50 μS / cm or less, it is determined that the predetermined condition is satisfied.

  In the present embodiment, it is preferable that A in the above formula (1) is 10 or more and 50 or less from the viewpoint of more reliably suppressing the potential increase of the exposed portion. Further, A is more preferably 10 or more and 40 or less from the viewpoint of further enhancing the effect of suppressing the increase in the residual potential of the electrophotographic photosensitive member 1 and the generation of negative memory. Moreover, when A is 10 or more, the dispersibility of the zinc oxide particles in the coating liquid for forming the functional layer can be improved, and the dispersion time can be shortened. Furthermore, since the functional layer can be formed more uniformly, the above effect can be obtained more reliably.

  As the zinc oxide particles used as the constituent material of the photoconductor of the present embodiment, those determined to satisfy the predetermined condition in the quality inspection method may be used, or the oxidation of the present embodiment described below. In the method for producing zinc particles, the conditions under which the finally obtained zinc oxide particles satisfy the above formula (1) are confirmed in advance, and the zinc oxide particles produced under those conditions may be used.

  As 1st Embodiment of the manufacturing method of the zinc oxide particle which concerns on this invention, the preparation process which prepares basic zinc carbonate particle, the pure water contact process which makes a basic zinc carbonate particle contact pure water, and pure water And a culturing step of culturing the contacted basic zinc carbonate particles to obtain zinc oxide particles.

  Basic zinc carbonate particles can be prepared, for example, by precipitating a hydrochloric acid solution of zinc with an alkaline solution. Examples of the alkaline solution include an aqueous sodium carbonate solution and an aqueous potassium carbonate solution.

  The pure water used in the pure water contact step preferably has an electric conductivity at 25 ° C. of 1.0 μS / cm or less, and more preferably 0.8 μS / cm or less.

  Examples of the method of bringing basic zinc carbonate particles into contact with pure water include, for example, a method of flowing pure water through basic zinc carbonate particles arranged on a filter, and basic zinc carbonate particles in pure water filled in a container. The method of immersing is included. In particular, the former method is preferable in that it does not require a step of separating basic zinc carbonate after contact with pure water and is excellent in removal efficiency of ionic impurities. In the former method, the flow rate of pure water with respect to 1 part by mass of basic zinc carbonate particles is preferably set to 1 part by mass / min or more, and more preferably set to 2 parts by mass / min or more. The temperature of pure water at this time is preferably in the range of 5 to 30 ° C. The time for flowing the pure water is not particularly limited as long as the zinc oxide particles finally obtained through the subsequent steps satisfy the above formula (1), but the production efficiency of the zinc oxide particles is suppressed while suppressing the amount of pure water used. From the viewpoint of ensuring, it is preferably 2 to 30 minutes. In the latter method, the mass ratio of pure water to basic zinc carbonate particles (basic zinc carbonate particles / pure water) is preferably set to 1/1 to 1/100. Moreover, it is preferable that the temperature of a pure water is the range of 5-30 degreeC. Furthermore, from the viewpoint of ensuring the production efficiency of zinc oxide particles while suppressing the amount of pure water used, the mass ratio of pure water to basic zinc carbonate particles (basic zinc carbonate particles / pure water) is set to 1/5 to 1. / 50, and it is preferable to stir the immersion water.

  The culturing step is performed by heating the basic zinc carbonate particles that have undergone the pure water contact step, for example, in air or in a reduced pressure environment at 500 to 600 ° C. for 1 to 5 hours.

  Zinc oxide particles satisfying the above formula (1) obtained through the above-described culturing process are used for the production of a photoreceptor as a constituent material of the undercoat layer.

  Moreover, as 2nd Embodiment of the manufacturing method of the zinc oxide particle which concerns on this invention, a manufacturing method provided with the preparatory process which prepares a zinc oxide particle, and the water contact process which makes a zinc oxide particle contact water is mentioned. Such a production method is also a method for treating zinc oxide particles to obtain the zinc oxide particles according to the present invention.

  As the zinc oxide particles prepared in the preparation step, those manufactured by various chemical or physical processes known in the art can be used. For example, you may use what was manufactured by the indirect method (French method) described in JISK1410, or the direct method (American method). Further, zinc oxide particles obtained by roasting zinc carbonate obtained by reacting zinc chloride with sodium carbonate may be used. Moreover, you may use the zinc oxide particle obtained by the wet manufacturing method which culture | cultivates the basic zinc carbonate formed by precipitating the hydrochloric acid solution of zinc with an alkaline solution. Also, it is obtained by a vapor phase method in which a heating means such as plasma is applied to metal zinc in a reduced-pressure atmosphere to evaporate the metal zinc, and the generated ultrafine particles are oxidized by applying a cooling gas containing oxygen and crystal growth is stopped. Zinc oxide particles may also be used.

  In the present embodiment, it is preferable to prepare zinc oxide particles obtained by a wet manufacturing method from the viewpoint of preparing zinc oxide particles having a particle size suitable for the electrical characteristics of the electrophotographic photosensitive member at a lower cost.

  Examples of the method of bringing the zinc oxide particles into contact with water include a method of flowing water through the zinc oxide particles arranged on the filter and a method of immersing the zinc oxide particles in water filled in the container. In particular, the former method is preferable in that it does not require a step of separating zinc oxide after contact with water and is excellent in removal efficiency of ionic impurities. In the former method, the flow rate of water relative to 1 part by mass of the zinc oxide particles is preferably set to 1 part by mass / min or more, and more preferably set to 2 parts by mass / min or more. The temperature of water at this time is preferably in the range of 10 to 40 ° C. The time for flowing water is not particularly limited as long as the zinc oxide particles finally obtained through the subsequent steps satisfy the above formula (1), but ensures the production efficiency of the zinc oxide particles while suppressing the amount of water used. From the viewpoint, it is preferably 1 to 30 minutes. In the latter method, the mass ratio of water to zinc oxide particles (zinc oxide particles / water) is preferably 1/1 to 1/100. Moreover, it is preferable that the temperature of water is the range of 10-40 degreeC. Furthermore, from the viewpoint of ensuring the production efficiency of zinc oxide particles while suppressing the amount of water used, the mass ratio of water to zinc oxide particles (zinc oxide particles / water) is preferably 1/5 to 1/50. It is preferable to stir the immersion water.

  Moreover, any of tap water, RO treated water, distilled water, or pure water can be used as the water. From the viewpoint of more reliably suppressing the occurrence of image quality defects while suppressing an increase in manufacturing cost, the water preferably has an electric conductivity of 250 μS / cm or less at 25 ° C.

  The zinc oxide particles satisfying the above formula (1) obtained through the water contact step are dried under conditions of, for example, a pressure of 100 mmHg (133332.2 Pa) or less and a temperature of 50 to 200 ° C. for 1 to 10 hours. It is used for the production of a photoreceptor as a constituent material of the pulling layer.

  The zinc oxide particles according to the present invention used as the constituent material of the undercoat layer preferably have a volume average particle diameter of 500 to 3000 nm, and more preferably 1000 to 2500 nm. In the present embodiment, “average particle diameter of zinc oxide particles” indicates a value obtained based on the specific surface area of zinc oxide particles measured by the BET method. The BET method is a method for obtaining the specific surface area (BET specific surface area) of zinc oxide particles from the amount of gas adsorbed by adsorbing a gas such as nitrogen to zinc oxide particles.

When the BET specific surface area of the zinc oxide particles measured by the BET method is Sm ² / g and the specific gravity of the zinc oxide particles is ρ (= 5.6), the average particle diameter (BET diameter) [μm] of the zinc oxide particles is , Average particle diameter = 6 / (S · ρ)
Can be obtained as

In addition, the zinc oxide particles according to the present invention used as a constituent material of the undercoat layer preferably have a specific surface area of 10 m ² / g or more, more preferably 10 to 20 m ² / g, and 12 to 18 m ^2. More preferably, it is / g.

(Electrophotographic photoreceptor)
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of the electrophotographic photosensitive member of the present invention. An electrophotographic photoreceptor 1 shown in FIG. 1 includes a conductive support 2, an undercoat layer 3 provided on the conductive support 2, and a photosensitive layer 4 provided on the undercoat layer 3. ing. The photosensitive layer 4 has a stacked structure of a charge generation layer 5 formed on the undercoat layer 3 and a charge transport layer 6 formed on the charge generation layer 5. And the undercoat layer 3 in this embodiment contains zinc oxide particles whose measured values of electrical conductivity satisfy a predetermined condition in the quality inspection method described above.

  Hereinafter, each component of the electrophotographic photoreceptor 1 will be described.

  First, the conductive support 2 will be described. As the conductive support 2, for example, a metal drum such as aluminum, copper, iron, stainless steel, zinc, and nickel; on a sheet, paper, plastic, or glass, aluminum, copper, gold, silver, platinum, palladium, titanium, Deposit metal such as nickel-chromium, stainless steel, copper-indium, deposit conductive metal compounds such as indium oxide and tin oxide, laminate metal foil, carbon black, indium oxide, oxide By applying a dispersion of tin-antimony oxide powder, metal powder, copper iodide or the like in a binder resin, a known material such as a drum-like, sheet-like, or plate-like material subjected to conductive treatment can be used.

  When a metal pipe substrate is used as the conductive support, the surface is still subjected to processing such as mirror cutting, etching, anodizing, rough cutting, centerless grinding, sand blasting, and wet honing, even if the surface is still a bare pipe. It doesn't matter.

  Next, the undercoat layer 3 will be described. The undercoat layer 3 includes zinc oxide particles whose measured values of electrical conductivity satisfy a predetermined condition in the quality inspection method described above, and a binder resin. The undercoat layer 3 prevents the injection of charges from the conductive support 2 to the photosensitive layer 4 when the photosensitive layer 4 having a laminated structure is charged, and the photosensitive layer 4 with respect to the conductive support 2. Thus, it has an action as an adhesive layer that can be integrally bonded and held.

  Binder resins include acetal resins such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride. -High molecular resin compounds such as vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol resin, phenol-formaldehyde resin, melamine resin.

The zinc oxide particles according to the present invention contained in the undercoat layer 3 may be obtained by surface-treating zinc oxide particles satisfying the above formula (1). Further, two or more kinds of zinc oxide particles having different surface treatments or particles having different particle diameters can be mixed and used. As the zinc oxide particles, the ratio is preferably not less than ^{10 m} 2 / g surface area, more preferably those which are 10 to 20 m ² / g, it shall even more preferably 12~18m ² / g. Those having a specific surface area value of 10 m ² / g or less tend to cause a decrease in chargeability and tend to make it difficult to obtain good electrophotographic characteristics.

  The surface treatment agent for zinc oxide particles is not particularly limited as long as desired characteristics can be obtained, and can be selected from known materials. Examples thereof include silane coupling agents, titanate coupling agents, aluminum coupling agents, and surfactants. In particular, a silane coupling agent is preferably used because good electrophotographic characteristics can be obtained. Furthermore, a silane coupling agent having an amino group is preferably used because it gives a good blocking property to the undercoat layer.

  Any silane coupling agent having an amino group can be used as long as it can obtain desired photoreceptor characteristics. Specifically, γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (amino Examples include, but are not limited to, ethyl) -γ-aminopropylmethylmethoxysilane, N, N-bis (β-hydroxyethyl) -γ-aminopropyltriethoxysilane, and the like.

  Two or more silane coupling agents can be used in combination. Examples of the silane coupling agent that can be used in combination with the silane coupling agent having an amino group include vinyltrimethoxysilane, γ-methacryloxypropyl-tris (β-methoxyethoxy) silane, β- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl)- γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethylmethoxysilane, N, N-bis (β-hydroxyethyl) -γ-aminopropyltriethoxysilane, γ-chloropropyltri Examples include methoxysilane. The present invention is not limited to, et al.

  As the surface treatment method, any known method can be used, but a dry method or a wet method can be used.

  When surface treatment is performed by a dry method, a silane coupling agent dissolved in an organic solvent is dropped and sprayed with dry air or nitrogen gas while stirring zinc oxide particles with a mixer having a large shearing force. Thus, the zinc oxide particles can be uniformly treated. The addition or spraying is preferably performed at a temperature below the boiling point of the solvent. Spraying at a temperature equal to or higher than the boiling point of the solvent is not preferred because the solvent evaporates before the zinc oxide particles are uniformly treated, and the silane coupling agent is locally concentrated, making uniform treatment difficult. After addition or spraying, baking is preferably performed at 100 ° C. or higher. Baking can be carried out in an arbitrary range as long as the temperature and time allow the desired electrophotographic characteristics to be obtained.

  In the wet method, zinc oxide particles are dispersed in a solvent by stirring or ultrasonic waves, or using a sand mill, attritor, ball mill, etc., and after adding or stirring or dispersing a silane coupling agent solution, the solvent is removed. Uniformly processed. The solvent is distilled off by filtration or distillation. After removing the solvent, baking is preferably performed at 100 ° C. or higher. Baking can be carried out in an arbitrary range as long as the temperature and time allow the desired electrophotographic characteristics to be obtained. In the wet method, moisture contained in the zinc oxide particles can be removed before adding the surface treatment agent. Specific examples thereof include a method of removing zinc oxide particles while stirring and heating in a solvent used for the surface treatment, and a method of removing azeotropically with the solvent.

  The undercoat layer 3 may further contain a conductive material in addition to the zinc oxide particles according to the present invention.

  Examples of the conductive material include metal oxides such as tin oxide, titanium oxide, and aluminum oxide, and organometallic compounds. As organometallic compounds, zirconium chelate compounds, zirconium alkoxide compounds, organic zirconium compounds such as zirconium coupling agents, titanium chelate compounds, titanium alkoxide compounds, organotitanium compounds such as titanate coupling agents, aluminum chelate compounds, aluminum coupling agents In addition to organoaluminum compounds such as antimony alkoxide compounds, germanium alkoxide compounds, indium alkoxide compounds, indium chelate compounds, manganese alkoxide compounds, manganese chelate compounds, tin alkoxide compounds, tin chelate compounds, aluminum silicon alkoxide compounds, aluminum titanium alkoxide compounds, And aluminum zirconium alkoxide compounds. .

  The above-mentioned metal oxide may be surface-treated, and as the surface treatment agent and the surface treatment method, the above-described surface treatment agent and surface treatment method for zinc oxide particles can be used.

  The undercoat layer 3 is configured using a coating solution for forming an undercoat layer containing the above constituent materials.

  As a method for mixing / dispersing the coating solution for forming the undercoat layer, a conventional method using a ball mill, a roll mill, a sand mill, an attritor, an ultrasonic wave, or the like is applied. Mixing / dispersing is performed in an organic solvent, and any organic solvent that dissolves the binder resin and does not cause gelation or aggregation when the zinc oxide particles are mixed / dispersed may be used.

  Examples of the organic solvent include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, and methylene chloride. Ordinary organic solvents such as chloroform, chlorobenzene and toluene. These can be used individually by 1 type or in mixture of 2 or more types.

  The coating method used when providing the undercoat layer 3 is a normal method such as a blade coating method, a Mayer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method. Can be used.

  The thickness of the undercoat layer 3 is preferably 1 to 30 μm, more preferably 15 to 25 μm. The undercoat layer 3 preferably has a Vickers hardness of 30 or more.

Moreover, it is preferable that the undercoat layer 3 has an appropriate resistance for obtaining leak resistance. Therefore, the volume resistivity of the undercoat layer 3 is preferably 10 ⁸ to 10 ¹³ Ω · cm. More preferably, it is 10 ⁹ to 10 ¹² Ω · cm. If the volume resistivity is less than 10 ⁸ Ω · cm, it tends to be difficult to obtain sufficient leakage resistance. On the other hand, if it exceeds 10 ¹³ Ω · cm, the residual potential tends to increase. The volume resistivity of the undercoat layer 3 is controlled by changing the electrical resistance value of the zinc oxide particles themselves according to the present invention and the amount of addition thereof, and changing the dispersion state of the zinc oxide particles in the binder resin. Can do. For example, in this embodiment, the electrical resistance value tends to increase due to the zinc oxide particles undergoing the water contact step. In addition, zinc oxide particles having an electric conductivity at 25 ° C. of 10 μS / cm or more when mixed with pure water having an electric conductivity of 1.0 μS / cm or less so as to have a concentration of 2.5 mass%. By using it, the dispersion state can be improved.

  The content of the zinc oxide particles according to the present invention contained in the undercoat layer 3 is preferably 35 to 40% by mass based on the total solid content of the undercoat layer 3. Moreover, in this embodiment, it is more preferable to contain zinc oxide particles so that the volume resistivity of the undercoat layer 3 satisfies the above preferable range.

  The charge generation layer 5 is formed by forming a charge generation material on the undercoat layer 3 by vacuum deposition, or by dispersing the charge generation material together with an organic solvent and a binder resin to prepare a coating solution. Is applied on the undercoat layer 3.

  Examples of charge generation materials include amorphous selenium, crystalline selenium, selenium-tellurium alloy, selenium-arsenic alloy, other selenium compounds and selenium alloys, inorganic photoconductors such as zinc oxide and titanium oxide, metal-free phthalocyanine, titanyl phthalocyanine, Various phthalocyanine pigments such as copper phthalocyanine, tin phthalocyanine and gallium phthalocyanine, various organic pigments and dyes such as squalium, anthanthrone, perylene, azo, anthraquinone, pyrene, pyrylium salt, thiapyrylium salt, etc. it can. In addition, organic pigments generally have several types of crystals. In particular, phthalocyanine pigments are known for various crystal types including α-type and β-type. Any of these crystal forms can be used as long as the pigment is obtained.

  In the present embodiment, the following compounds are particularly suitable as charge generation materials that can provide excellent performance. That is, at the Bragg angles (2θ ± 0.2 °) of the X-ray diffraction spectrum using Cukα rays, diffraction peaks are present at positions of at least 7.6 °, 10.0 °, 25.2 °, 28.0 °. At least 7.3 °, 16.5 °, 25.4 °, and 28 at a Bragg angle (2θ ± 0.2 °) of an X-ray diffraction spectrum using hydroxygallium phthalocyanine typified by a crystal type having Cukα rays At least 9.5 °, 24. at a Bragg angle (2θ ± 0.2 °) of an X-ray diffraction spectrum using chlorogallium phthalocyanine represented by a crystal type having a diffraction peak at a position of 1 ° and Cukα rays. Titanyl phthalocyanine typified by a crystal form having diffraction peaks at 2 ° and 27.3 ° is preferably used as the charge generation material. These materials may be slightly different from the above values depending on the crystal shape and measurement method, but the same as long as the X-ray diffraction patterns substantially match. It can be judged that it is a crystal form.

  Examples of the binder resin in the charge generation layer 5 include the following. That is, polycarbonate resin such as bisphenol A type or bisphenol Z type and copolymers thereof, polyarylate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer Resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, etc. It is done.

  These binder resins can be used alone or in combination of two or more. The blending ratio (mass ratio) between the charge generating material and the binder resin is preferably in the range of 10: 1 to 1:10. The organic solvent is not particularly limited as long as it can dissolve or disperse the above binder resin. For example, methanol, ethanol, n-butanol, benzyl alcohol, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, acetic acid Examples include n-butyl, dioxane, tetrahydrofuran, methylene chloride, chloroform, toluene, xylene, chlorobenzene, dimethylformamide, dimethylacetamide, water, and the like. One of these may be used alone, or a mixture of two or more. It may be used as.

  Dispersion of charge generation material, binder resin and organic solvent can be performed by sand mill, colloid mill, attritor, dyno mill, jet mill, coball mill, roll mill, ultrasonic disperser, gorin homogenizer, microfluidizer, optimizer, milder. Etc. can be used.

  Examples of the application method of the coating liquid include dip coating method, ring coating method, spray coating method, bead coating method, blade coating method, roller coating method, knife coating method, and curtain coating method depending on the shape and application of the photoreceptor. It can be performed using a coating method. Drying is preferably performed by heating after touch drying at room temperature. The heat drying is desirably performed at a temperature in the range of 30 ° C. to 200 ° C. for a time in the range of 5 minutes to 2 hours.

  The thickness of the charge generation layer 5 is generally set in the range of 0.01 to 5 μm, preferably 0.05 to 2.0 μm.

  The charge transport layer 6 is formed by dispersing a charge transport material together with an organic solvent and a binder resin to prepare a coating solution, and coating the coating solution on the charge generation layer 5.

  Examples of the charge transport material used for the charge transport layer 6 include the following. That is, oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1- [pyridyl- (2)] Pyrazoline derivatives such as -3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline, triphenylamine, tri (P-methyl) phenylamine, N, N-bis (3,4-dimethylphenyl) Aromatic tertiary amino compounds such as biphenyl-4-amine, dibenzylaniline, 9,9-dimethyl-N, N-di (p-tolyl) fluoren-2-amine, N, N′-diphenyl-N, Aromatic tertiary diamino compounds such as N′-bis (3-methylphenyl)-[1,1-biphenyl] -4,4′-diamine, 3- (4′dimethyl) 1,2,4-triazine derivatives such as (laminophenyl) -5,6-di- (4′-methoxyphenyl) -1,2,4-triazine, 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, 4 -Diphenylaminobenzaldehyde-1,1-diphenylhydrazone, [p- (diethylamino) phenyl] (1-naphthyl) phenylhydrazone, 1-pyrenediphenylhydrazone, 9-ethyl-3-[(2methyl-1-indolinylimino ) Methyl] carbazole, 4- (2-methyl-1-indolinyliminomethyl) triphenylamine, 9-methyl-3-carbazole diphenylhydrazone, 1,1-di- (4,4′-methoxyphenyl) acrylaldehyde Diphenylhydrazone, β, β-bis (methoxyphenyl) vinyl Hydrazone derivatives such as diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) -benzofuran, p- (2,2- Hole transport materials such as α-stilbene derivatives such as diphenylvinyl) -N, N-diphenylaniline, enamine derivatives, carbazole derivatives such as N-ethylcarbazole, poly-N-vinylcarbazole and derivatives thereof; chloranil, bromoanil, anthraquinone Quinone compounds such as tetracyanoquinodimethane compounds, 2,4,7-trinitrofluorenone, fluorenone compounds such as 2,4,5,7-tetranitro-9-fluorenone, 2- (4-biphenyl)- 5- (4-t-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (4-naphthyl) -1,3,4-oxadiazole, 2,5-bis (4-diethylaminophenyl) 1,3,4-oxa Oxadiazole compounds such as diazole, xanthone compounds, thiophene compounds, 3,3 ′, 5,5′-tetra-t-butyldiphenoquinone, 3,5-dimethyl-3 ′, 5′-di- Examples thereof include an electron transport material such as a diphenoquinone compound such as t-butyl-4,4′-diphenoquinone; or a polymer having a group consisting of the compounds shown above in the main chain or side chain. These charge transport materials can be used alone or in combination of two or more.

  In the laminated type photoconductor, the charge polarity of the photoconductor varies depending on the charge transport polarity of the charge transport material. When a hole transport material is used, the photoreceptor is used with negative charge, and when an electron transport material is used, it is used with positive charge. When both are mixed, a photoconductor having both charged polarities is possible.

  As the binder resin used for the charge transport layer 6, any resin can be used, but it is particularly desirable to use a resin that is compatible with the charge transport material and has an appropriate strength. Examples of such binder resins include various polycarbonate resins and copolymers thereof, such as bisphenol A, bisphenol Z, bisphenol C, and bisphenol TP, polyarylate resins and copolymers thereof, polyester resins, methacrylic resins, Acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer Resin, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-acrylic copolymer resin, ethylene-alkyd resin, poly-N-vinylcarbazole resin, polyvinyl butyral resin, polyphenylene ether Etc. Le resins. These resins can be used alone or as a mixture of two or more.

  The molecular weight of the polymer used as the binder resin is appropriately selected depending on the film formation conditions such as the film thickness of the photosensitive layer and the solvent, but is usually 3000 to 300,000, more preferably 20,000 to 20 in terms of viscosity average molecular weight. A range of 10,000.

  The charge transport layer 6 can be formed by applying a coating solution in which the charge transport material and the binder resin are dissolved in a suitable solvent on the charge generation layer 5 and drying. Examples of the solvent used for forming the charge transport layer 6 include aromatic hydrocarbons such as benzene, toluene and chlorobenzene, ketones such as acetone and 2-butanone, and halogens such as methylene chloride, chloroform and ethylene chloride. Cycloaliphatic hydrocarbons, cyclic or linear ethers such as tetrahydrofuran, dioxane, ethylene glycol and diethyl ether, or a mixed solvent thereof can be used. A small amount of silicone oil can be added to the coating solution as a leveling agent for improving the smoothness of the coating film. The blending ratio (mass ratio) of the charge transport material and the binder resin is preferably 10: 1 to 1: 5.

  Dispersion of charge transport material, binder resin and organic solvent can be done with sand mill, colloid mill, attritor, dyno mill, jet mill, coball mill, roll mill, ultrasonic disperser, gorin homogenizer, microfluidizer, optimizer, milder, etc. Can be used.

  Examples of the application method of the coating liquid include dip coating method, ring coating method, spray coating method, bead coating method, blade coating method, roller coating method, knife coating method, and curtain coating method depending on the shape and application of the photoreceptor. It can be performed using a coating method. Drying is preferably performed by heating after touch drying at room temperature. The heat drying is desirably performed at a temperature in the range of 30 ° C. to 200 ° C. for a time in the range of 5 minutes to 2 hours.

  The thickness of the charge transport layer 6 is generally set in the range of 5 to 50 μm, preferably 10 to 40 μm.

  Further, for the purpose of preventing deterioration of the photoreceptor due to ozone, oxidizing gas, or light or heat generated in the image forming apparatus, the photosensitive layer 4 composed of the charge generation layer 5 and the charge transport layer 6 is included in the photosensitive layer 4. Additives such as antioxidants, light stabilizers and heat stabilizers can be added.

  Specific examples of the antioxidant include 2,6-di-tert-butyl-4-methylphenol, styrenated phenol, n-octadecyl-3- (3 ′, 5′-) for phenolic antioxidants. Di-t-butyl-4'-hydroxyphenyl) -propionate, 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2-t-butyl-6- (3'-t- Butyl-5'-methyl-2'-hydroxybenzyl) -4-methylphenyl acrylate, 4,4'-butylidene-bis- (3-methyl-6-tert-butyl-phenol), 4,4'-thio- Bis- (3-methyl-6-tert-butylphenol), 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, tetrakis- [methylene- -(3 ', 5'-di-t-butyl-4'-hydroxy-phenyl) propionate] -methane, 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5- Methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane, 3-3 ′, 5′-di-t-butyl-4′- And hydroxyphenyl) stearyl propionate. Among hindered amine compounds, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1- [2- [3 -(3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2, 2,6,6-tetramethylpiperidine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione, 4, -Benzoyloxy-2,2,6,6-tetramethylpiperidine, dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine heavy succinate Compound, poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diimyl} {(2,2,6,6-tetramethyl- 4-piperidyl) imino} hexamethylene {(2,3,6,6-tetramethyl-4-piperidyl) imino}], 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2- n-Butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), N, N′-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N— (1,2,2,6,6, -pentamethyl-4piperidyl) amino] -6-chloro-1,3,5-triazine condensate and the like. Dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythritol-tetrakis- ( β-lauryl-thiopropionate), ditridecyl-3,3′-thiodipropionate, 2-mercaptobenzimidazole and the like. Examples of the organophosphorus antioxidant include trisnonylphenyl phosfte, triphenyl phosfte, tris (2,4-di-t-butylphenyl) -phosfte, and the like. Among the above antioxidants, organic sulfur-based antioxidants and organic phosphorus-based antioxidants are called secondary antioxidants, and primary antioxidants such as the above-mentioned phenolic antioxidants or amine-based antioxidants. A synergistic effect can be acquired by using together with antioxidant.

  Examples of the light stabilizer include derivatives such as benzophenone, benzotriazole, dithiocarbamate, and tetramethylpiperidine.

  Examples of the benzophenone light stabilizer include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 2,2'-di-hydroxy-4-methoxybenzophenone. 2-(-2′-hydroxy-5′-methylphenyl-)-benzotriazole, 2- [2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″) as benzotriazole light stabilizers , 6 ″ -tetra-hydrophthalimido-methyl) -5′-methylphenyl] -benzotriazole, 2-(-2′-hydroxy-3′-tert-butyl-5′-methylphenyl-)-5-chloro Benzotriazole, 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl-)-5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′, 5′-t-butylphenyl) -)-Benzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) -benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-amylphenyl-)- Examples include benzotriazole. In addition, 2,4, di-t-butylphenyl-3 ', 5'-di-t-butyl-4'-hydroxybenzoate, nickel dibutyl-dithiocarbamate, and the like can be used.

Further, at least one kind of electron accepting substance can be contained in the photosensitive layer 4 for the purpose of improving the sensitivity, reducing the residual potential, and reducing fatigue during repeated use. Examples of such an electron accepting substance include succinic anhydride, maleic anhydride, dibromomaleic anhydride, phthalic anhydride, tetrabromophthalic anhydride, tetracyanoethylene, tetracyanoquinodimethane, o-dinitrobenzene, m-dinitrobenzene, Examples include chloranil, dinitroanthraquinone, trinitrofluorenone, picric acid, o-nitrobenzoic acid, p-nitrobenzoic acid, and phthalic acid. Of these, fluorenone-based or quinone-based compounds and benzene derivatives having an electron-withdrawing substituent such as —Cl, —CN, and —NO ₂ are particularly preferable.

  Furthermore, a protective layer can be formed on the photosensitive layer as necessary.

Examples of the protective layer include a layer in which semiconductive fine particles and a charge transporting substance are dispersed in an insulating resin. As the semiconductive fine particles, fine particles having an electric resistance of 10 ⁹ Ω · cm or less and a white, gray or bluish average particle size of 0.3 μm or less, preferably 0.1 μm or less are suitable. Examples of the insulating resin include condensation resins such as polyamide, polyurethane, polyester, epoxy resin, polyketone, and polycarbonate, and vinyl polymers such as polyvinyl ketone, polystyrene, polyacrylamide, and polyvinyl butyral.

  Further, a protective layer can be formed by reacting a charge transporting substance having a reactive functional group with a thermoplastic resin or a thermosetting resin.

  Next, a preferred example of the image forming apparatus of the present invention will be described with reference to FIG.

(Image forming device)
FIG. 2 is a schematic diagram showing a preferred embodiment of the image forming apparatus of the present invention. An image forming apparatus 100 shown in FIG. 2 includes, in an image forming apparatus main body (not shown), a process cartridge 120 including the electrophotographic photosensitive member 1 of the present invention, an exposure device 130, a transfer device 140, and an intermediate transfer member. 150. In the image forming apparatus 100, the exposure device 130 is disposed at a position where the exposure can be performed on the electrophotographic photosensitive member 1 from the opening of the process cartridge 120, and the transfer device 140 is interposed through the intermediate transfer member 150. 1 and a part of the intermediate transfer member 150 is disposed so as to be in contact with the electrophotographic photosensitive member 1.

  The process cartridge 120 is obtained by integrating a charging device 121, a developing device 125, and a cleaning device 127 together with an electrophotographic photosensitive member 1 with a mounting rail in a case. The case is provided with an opening for exposure.

  The charging device 121 is for charging the electrophotographic photosensitive member 1 by a contact method. For example, a brush charger, a roll-shaped contact charging device, or the like can be used. In this embodiment, a non-contact charging device such as a corotron, a scorotron, or an ion discharger can be used instead of the contact charging device.

  As the exposure device 130, various devices such as a laser beam light source, an LED, a polysilicon TFT drive fluorescent display element array, and a liquid crystal shutter exposure device can be used. The wavelength of the light source can be selected according to the sensitivity range of the photoreceptor. In the case of using a laser beam light source, an infrared laser having a wavelength of 600 to 850 nm, which falls from red to the near-infrared region, is generally used, but the purpose is to reduce the beam light or to increase the matching with the sensitivity of the photoreceptor. Thus, a light source on the low wavelength side such as blue light (350 to 500 nm) can be used.

  Further, it is also possible to use a method in which a multi-beam type light source is used as a laser light source and light is guided to each color portion with a single laser light source for exposure. When an LED array is used, compared with a laser scanner printer, there is no rotating part such as a polygon mirror, which is advantageous for speeding up and downsizing.

  The developing device 125 develops the electrostatic latent image on the electrophotographic photosensitive member 1 to form a toner image. As the developer, a known one-component, two-component, or a developer having a configuration in the middle thereof can be used. As the toner, either a mixed / pulverized toner or a polymerized toner can be used. The particle size of the toner is appropriately set according to the system setting. In the case of solid toner, the particle size of the toner is preferably set in the range of 3 to 20 μm. It is also possible to use a spherical toner so as to obtain a more suitable image quality.

  A known developing sleeve of the developing device 125 can be used. Aluminum, stainless steel, etc. can be used as the material. In order to stably convey the developer to the development region for a long period of time, it is effective to subject the surface of the developing sleeve to a surface roughening treatment such as a thermal spraying treatment, a sand blasting treatment, and a grooving treatment. In the case of forming a color image in which a plurality of color toners are superimposed, it is effective to use a non-contact development method in which toner mixing is small.

  The transfer device 140 may be any device that transfers the toner image on the electrophotographic photosensitive member 1 to a transfer medium (intermediate transfer member 150). For example, a roll-shaped one that is normally used is used.

  As the intermediate transfer member 150, a belt-like member (intermediate transfer belt) made of polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber or the like having semiconductivity is used. Further, as the form of the intermediate transfer member 150, a drum-like member can be used in addition to the belt-like member.

  As the cleaning device 127, a known device such as blade cleaning, brush cleaning, magnetic brush cleaning, air cleaning or the like is used. Further, in order to improve the cleaning efficiency and stabilize the potential of the photoreceptor, a static elimination exposure apparatus may be provided.

  As described above, the image forming apparatus 100 includes the electrophotographic photoreceptor 1 of the present invention. As a result, it is possible to form an image having no image quality defect over a long period of time.

  FIG. 3 is a schematic view showing another embodiment of the image forming apparatus of the present invention. The image forming apparatus 200 is a tandem full-color image forming apparatus equipped with four process cartridges 120. In the image forming apparatus 200, four process cartridges 120 are arranged in parallel on the intermediate transfer member 150, and one electrophotographic photosensitive member can be used for one color. The image forming apparatus 200 has the same configuration as that of the image forming apparatus 100 except that the image forming apparatus 200 is a tandem system.

  FIG. 4 is a schematic view showing another embodiment of the image forming apparatus of the present invention. The image forming apparatus 300 shown in FIG. 4 is a so-called four-cycle type image forming apparatus that forms toner images of a plurality of colors with one electrophotographic photosensitive member. The image forming apparatus 300 includes a photosensitive drum 301 that is rotated in a direction indicated by an arrow C in the drawing at a predetermined rotational speed by a driving device (not shown). The electrophotographic photosensitive member 1 of the form is configured. A charging device 322 for charging the outer peripheral surface of the photosensitive drum 301 is provided above the photosensitive drum 301.

  An exposure device 330 including a surface emitting laser array as an exposure light source is disposed above the charging device 322. The exposure device 330 modulates a plurality of laser beams emitted from a light source in accordance with an image to be formed and deflects the laser beams in the main scanning direction so that the axis of the photosensitive drum 301 is on the outer peripheral surface of the photosensitive drum 301. Scan in parallel. As a result, an electrostatic latent image is formed on the outer peripheral surface of the charged photosensitive drum 301.

  A developing device 325 is disposed on the side of the photosensitive drum 301. The developing device 325 includes a roller-shaped container that is rotatably arranged. Four accommodating portions are formed inside the accommodating body, and developing devices 325Y, 325M, 325C, and 325K are provided in the accommodating portions. Each of the developing devices 325Y, 325M, 325C, and 325K includes a developing roller 326, and stores toner of Y, M, C, and K colors therein.

  The full-color image is formed by the image forming apparatus 300 while the photosensitive drum 301 rotates four times. That is, while the photosensitive drum 301 rotates four times, the charging device 322 charges the outer peripheral surface of the photosensitive drum 301, and the exposure device 330 includes Y, M, C, and K image data representing a color image to be formed. Scanning the outer peripheral surface of the photosensitive drum 301 with the laser beam modulated according to any one of the above is repeated while switching the image data used for modulation of the laser beam every time the photosensitive drum 301 rotates. Further, the developing device 325 operates the developing device corresponding to the outer peripheral surface in a state where any of the developing rollers 326 of the developing devices 325Y, 325M, 325C, and 325K corresponds to the outer peripheral surface of the photosensitive drum 301. The photosensitive drum 301 1 develops the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 301 into a specific color and forms a toner image of the specific color on the outer peripheral surface of the photosensitive drum 301. Each time it rotates, the process is repeated while rotating the container so that the developing unit used for developing the electrostatic latent image is switched. Thus, every time the photosensitive drum 301 rotates once, Y, M, C, and K toner images are sequentially formed on the outer peripheral surface of the photosensitive drum 301 so as to overlap each other. When the drum 301 rotates four times, a full color toner image is formed on the outer peripheral surface of the photosensitive drum 301.

  Further, an endless intermediate transfer belt 350 is disposed substantially below the photosensitive drum 301. The intermediate transfer belt 350 is wound around rollers 351, 353, and 355, and is arranged so that the outer peripheral surface is in contact with the outer peripheral surface of the photosensitive drum 301. The rollers 351, 353, and 355 are rotated by a driving force of a motor (not shown) and rotate the intermediate transfer belt 350 in the direction of arrow D in FIG.

  A transfer device (transfer device) 340 is disposed on the opposite side of the photosensitive drum 301 with the intermediate transfer belt 350 interposed therebetween, and the toner image formed on the outer peripheral surface of the photosensitive drum 301 is intermediate transferred by the transfer device 340. The image is transferred to the image forming surface of the belt 350.

  A lubricant supply device 329 and a cleaning device 327 are disposed on the outer peripheral surface of the photosensitive drum 301 on the opposite side of the developing device 325 across the photosensitive drum 301. When the toner image formed on the outer peripheral surface of the photosensitive drum 301 is transferred to the intermediate transfer belt 350, the lubricant is supplied to the outer peripheral surface of the photosensitive drum 301 by the lubricant supply device 329, and the The area carrying the transferred toner image is cleaned by the cleaning device 327.

  A tray 360 is disposed below the intermediate transfer belt 350, and a large number of sheets P as recording materials are accommodated in the tray 360 in a stacked state. A take-out roller 361 is disposed obliquely above and to the left of the tray 360, and a roller pair 363 and a roller 365 are arranged in this order on the downstream side in the take-out direction of the paper P by the take-out roller 361. The uppermost recording sheet in the stacked state is taken out from the tray 360 by the take-out roller 361 rotating, and is conveyed by the roller pair 363 and the roller 365.

  Further, a transfer device 342 is disposed on the opposite side of the roller 355 with the intermediate transfer belt 350 interposed therebetween. The paper P conveyed by the roller pair 363 and the roller 365 is sent between the intermediate transfer belt 350 and the transfer device 342, and the toner image formed on the image forming surface of the intermediate transfer belt 350 is transferred by the transfer device 342. . A fixing device 344 having a pair of fixing rollers is disposed downstream of the transfer device 342 in the conveyance direction of the paper P. The paper P on which the toner image is transferred is transferred by the fixing device 344. After being fused and fixed, it is discharged out of the image forming apparatus 300 and placed on a paper discharge tray (not shown).

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

<Manufacture of zinc oxide particles>
(Production Example 1)
To a solution in which 10 parts by mass of zinc chloride was dissolved in 50 parts by mass of tap water, a solution in which 8 parts by mass of sodium carbonate was dissolved in 40 parts by mass of tap water was gradually added to precipitate basic zinc carbonate. Next, the liquid in which basic zinc carbonate is precipitated is filtered through a membrane filter, and then the basic zinc carbonate on the filter is purified with pure water (electric conductivity (25 ° C.): 0.8 μm S / cm, temperature: 20 ° C.). Washing was performed at 1000 parts by mass for 20 minutes. The basic zinc carbonate after washing was cultured at 550 ° C. for 4 hours to obtain zinc oxide particles (volume average particle size: 2.3 μm, specific surface area: 15 m ² / g). This zinc oxide particle was designated as “zinc oxide particle-1A”. The tap water used above had an electric conductivity of 202 μS / cm at 25 ° C.

  Next, 100 parts by mass of the “zinc oxide particles-1A” obtained above and a mixed solvent of 450 parts by mass of toluene and 50 parts by mass of methanol are mixed with stirring, and γ- (2 -Aminoethyl) 1.5 parts by mass of aminopropyltrimethoxysilane (trade name “KBM603”, manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and the mixture was further stirred for 2 hours. Subsequently, after removing the solvent by distillation under reduced pressure, it was heated at 120 ° C. for 2 hours to obtain surface-treated zinc oxide particles. This zinc oxide particle was designated as “zinc oxide particle-1B”.

(Production Example 2)
To a solution in which 10 parts by mass of zinc chloride was dissolved in 50 parts by mass of tap water, a solution in which 8 parts by mass of sodium carbonate was dissolved in 40 parts by mass of tap water was gradually added to precipitate basic zinc carbonate. Next, the liquid in which basic zinc carbonate was precipitated was filtered with a membrane filter, and then the basic zinc carbonate on the filter was washed with 500 parts by mass of tap water for 10 minutes. The basic zinc carbonate after washing was cultured at 550 ° C. for 4 hours to obtain zinc oxide particles (volume average particle size: 2.1 μm, specific surface area: 16 m ² / g). The tap water used above had an electric conductivity of 202 μS / cm at 25 ° C.

  Next, 1 part by mass of the zinc oxide particles obtained above was placed on a membrane filter, and washed by filtration with 50 parts by mass of tap water for 10 minutes. Subsequently, the washed zinc oxide particles were dried under reduced pressure at 100 ° C. for 2 hours (pressure: 10 mmHg (1333.22 Pa)). The dried zinc oxide particles were designated as “zinc oxide particles-2A”. The tap water used for washing had an electric conductivity of 202 μS / cm at 25 ° C.

  Next, 100 parts by mass of the “zinc oxide particles-2A” obtained above and a mixed solvent of 450 parts by mass of toluene and 50 parts by mass of methanol are mixed with stirring, and γ- (2 -Aminoethyl) 1.5 parts by mass of aminopropyltrimethoxysilane (trade name “KBM603”, manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and the mixture was further stirred for 2 hours. Subsequently, after removing the solvent by distillation under reduced pressure, it was heated at 120 ° C. for 2 hours to obtain surface-treated zinc oxide particles. This zinc oxide particle was designated as “zinc oxide particle-2B”.

(Production Example 3)
First, in Production Example 1, instead of washing the basic zinc carbonate with pure water, the zinc oxide particles before surface treatment were treated in the same manner as in Production Example 1 except that the washing was performed with 500 parts by mass of tap water for 10 minutes. Obtained. This zinc oxide particle was designated as “zinc oxide particle-3A”. The tap water used above had an electric conductivity of 202 μS / cm at 25 ° C.

  Next, surface-treated zinc oxide particles were prepared in the same manner as in Production Example 1 except that “Zinc oxide particles-3A” obtained above was used instead of “Zinc oxide particles-1A” in Production Example 1. Got. This zinc oxide particle was designated as “zinc oxide particle-3B”.

(Production Example 4)
First, in Production Example 1, instead of washing the basic zinc carbonate with pure water, the zinc oxide particles before surface treatment were treated in the same manner as in Production Example 1 except that the washing was performed with 500 parts by mass of tap water for 20 minutes. Obtained. This zinc oxide particle was designated as “zinc oxide particle-4A”. The tap water used above had an electric conductivity of 202 μS / cm at 25 ° C.

  Next, surface-treated zinc oxide particles were prepared in the same manner as in Production Example 1 except that “Zinc oxide particles-4A” obtained above was used instead of “Zinc oxide particles-1A” in Production Example 1. Got. This zinc oxide particle was designated as “zinc oxide particle-4B”.

<Measurement of electrical conductivity>
The electric conductivity of pure water in which the zinc oxide particles-1A, zinc oxide particles-2A, zinc oxide particles-3A and zinc oxide particles-4A obtained above were dispersed was determined according to the following procedure. The obtained results are shown in Table 1.
(1) Zinc oxide particles are added to pure water having an electric conductivity of 1.0 μS / cm or less so that the concentration is 2.5 mass%.
(2) Using an ultrasonic generator (“UA150”, manufactured by Kokusai Electric Ltec Co., Ltd.), zinc oxide particles in pure water are ultrasonically dispersed for 10 minutes.
(3) Using an electric conductivity meter (“CEH-12”, manufactured by HORIBA, Ltd.), the electric conductivity (temperature: 25 ° C.) of the mixed liquid (dispersed liquid) in which the zinc oxide particles are dispersed is measured.

<Production of electrophotographic photoreceptor>
Example 1
First, a cylindrical aluminum substrate (diameter 30 mm, length 349 mm, wall thickness 1 mm) was prepared.

  Next, 60 parts by mass of the surface-treated “zinc oxide particles-1B” obtained in Production Example 1 and 15 parts by mass of blocked isocyanate (“Sumijoule BL3175”, manufactured by Sumitomo Bayern Urethane Co., Ltd.) as a curing agent, As a catalyst, 0.015 parts by mass of dioctyltin dilaurate (manufactured by Kishida Chemical Co., Ltd.), 5 parts by mass of butyral resin (“BM-1”, manufactured by Sekisui Chemical Co., Ltd.) dissolved in 45 parts by mass of methyl ethyl ketone, and 10 methyl ethyl ketone Mass parts were mixed, and dispersion was obtained by dispersing for 2 hours with a dynomill using 1 mmφ glass beads. Next, 4 parts by mass of dispersion obtained by dispersing 6 parts by mass of silicone resin particles (“Tospearl 145”, manufactured by Toshiba GE Silicone) as interference prevention powder in 4 parts by mass of methyl ethyl ketone in 100 parts by mass of the obtained dispersion. This was added to obtain a coating solution for forming the undercoat layer. This coating solution was applied onto an aluminum substrate by a dip coating method, followed by drying and curing at 160 ° C. for 40 minutes to form an undercoat layer having a thickness of 23.5 μm.

  Next, gallium chloride phthalocyanine 15 having diffraction peaks at positions where the Bragg angle (2θ ± 0.2 °) in the X-ray diffraction spectrum is at least 7.4 °, 16.6 °, 25.5 °, and 28.3 °. Part by mass is mixed with 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (“VMCH”, manufactured by Nippon Unicar Co., Ltd.) and 300 parts by mass of n-butyl acetate, and this is mixed with glass beads having an outer diameter of 1 mm in a sand mill for 4 hours. A coating solution for forming a charge generation layer was prepared by a dispersion treatment. The obtained coating solution was dip-coated on a conductive support provided with an undercoat layer, and dried at room temperature to form a charge generation layer having a thickness of 0.2 μm.

  Next, 6 parts by mass of N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1 ′] biphenyl-4,4′-diamine and bisphenol Z polycarbonate resin (viscosity average molecular weight 40 , 000) 10 parts by mass was sufficiently dissolved in 48 parts by mass of tetrahydrofuran to prepare a coating solution for charge transport layer. The obtained coating solution was dip-coated on the charge generation layer, heated at 115 ° C. for 40 minutes to form a charge transport layer having a thickness of 20 μm, and an electrophotographic photosensitive member was obtained. This electrophotographic photosensitive member was designated as “PR-1”.

(Example 2)
An electrophotographic photosensitive member was obtained in the same manner as in Example 1, except that “zinc oxide particles-2B” were used instead of “zinc oxide particles-1B” in Example 1. This electrophotographic photosensitive member was designated as “PR-2”.

(Comparative Example 1)
An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that “zinc oxide particles-3B” was used instead of “zinc oxide particles-1B” in Example 1. This electrophotographic photosensitive member was designated as “RPR-1.”

(Comparative Example 2)
An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that “zinc oxide particle-4B” was used instead of “zinc oxide particle-1B” in Example 1. This electrophotographic photosensitive member was designated as “RPR-2”.

<Evaluation of electrical characteristics of electrophotographic photoreceptor>
For the electrophotographic photoreceptors prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the amount of increase in the exposed portion potential after repeated use was measured according to the following method. The obtained results are shown in Table 2.
(Amount of increase in exposure area potential)
The electrophotographic photoreceptor to be evaluated was mounted on a photoreceptor potential inspection machine, and the charging / exposure process was repeated 275,000 cycles in a high temperature and high humidity environment at a temperature of 28 ° C. and a humidity of 80% RH. From the difference between the initial exposure potential VL ₀ and the exposure potential VL _27.5k after ₂₇₅₀₀₀ cycles (| VL ₀ −VL _27.5k |), the amount of increase (ΔVL) in the exposed area potential was calculated.

<Electrophotographic characteristic evaluation of electrophotographic photosensitive member>
The electrophotographic photoreceptors prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were each mounted on a modification tester of a printer PR-2000FW manufactured by NEC Corporation, and the following image formation test was performed.

(Image formation test)
Using the image forming apparatus prepared above, 3000 images having a black belt pattern were continuously formed on a white solid in a high temperature and high humidity environment of 28 ° C. and 80% RH. Thereafter, an image (A4 size) was formed under the same environment, and the image quality at that time was visually evaluated based on the following evaluation criteria. The results are shown in Table 2.
[Image density]
A: In the continuous black belt pattern printing portion, the image forming portion has a sufficiently high density and appears black.
B: In the continuous black belt pattern printing portion, the image forming portion has a lighter density and appears gray.
C: In the black belt pattern continuous printing portion, the density of the image forming portion is light and looks white.
[Negative memory: Indicates the degree of decrease in the image density formed in the black belt pattern continuous printing portion from the image density formed in the non-continuous printing portion]
0: The density difference cannot be discriminated at all.
1: The density difference is small and difficult to distinguish.
2: Can be determined by carefully observing the density difference.
3: The density difference can be easily distinguished.
4: The density difference is large and the image appears to be gray.
5: The density difference is large, and the image appears to be grayish white.
6: The density difference is extremely large, and the image appears white.

  As shown in Table 2, the photoreceptors of Examples 1 and 2 using the surface-treated zinc oxide particles satisfying the above formula (1) as the constituent material of the undercoat layer have the potential of the exposed area by repeated use. It was confirmed that the increase was suppressed. In addition, it was confirmed that the photoreceptors of Examples 1 and 2 can sufficiently suppress the reduction in image density and the occurrence of negative memory due to repeated use even in a high temperature and high humidity environment.

It is a schematic cross-sectional view showing a preferred example of the electrophotographic photosensitive member of the present invention. 1 is a schematic configuration diagram illustrating a preferred embodiment of an image forming apparatus of the present invention. It is a schematic block diagram which shows other suitable embodiment of the image forming apparatus of this invention. It is a schematic block diagram which shows other suitable embodiment of the image forming apparatus of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrophotographic photosensitive member, 2 ... Conductive support body, 3 ... Undercoat layer, 4 ... Photosensitive layer, 5 ... Charge generation layer, 6 ... Charge transport layer, 100, 200, 300 ... Image forming apparatus, 120 ... Process Cartridge, 121 ... charging device, 125 ... developing device, 127 ... cleaning device, 130 ... exposure device, 140 ... transfer device, 150 ... intermediate transfer member, 301 ... photosensitive drum, 322 ... charging device, 325 ... developing device, 327 ... Cleaning device, 330 ... Exposure device, 340 ... Transfer device, 350 ... Intermediate transfer belt.

Claims (4)

An electrophotographic photoreceptor comprising a functional layer containing zinc oxide particles,
The electrophotographic photosensitive member, wherein the functional layer contains zinc oxide particles satisfying the following formula (1) or a surface-treated zinc oxide particle.
A ≦ 50 (1)
[In Formula (1), A is the electrical conductivity at 25 ° C. of the mixed solution when zinc oxide particles are mixed with pure water having an electrical conductivity of 1.0 μS / cm or less so that the concentration becomes 2.5 mass%. Degree (μS / cm). ] An electrophotographic photoreceptor according to claim 1;
A charging means for charging the electrophotographic photosensitive member; a developing means for developing a latent electrostatic image formed on the electrophotographic photosensitive member with toner to form a toner image; and At least one selected from the group consisting of cleaning means for removing toner remaining on the surface;
A process cartridge comprising: An electrophotographic photoreceptor according to claim 1;
Charging means for charging the electrophotographic photosensitive member;
Exposure means for forming an electrostatic latent image on the charged electrophotographic photosensitive member;
Developing means for developing the electrostatic latent image with toner to form a toner image;
Transfer means for transferring the toner image from the electrophotographic photosensitive member to a transfer target;
An image forming apparatus comprising: A mixed solution adjusting step of adjusting the mixed solution by mixing zinc oxide particles with pure water having an electric conductivity of 1.0 μS / cm or less so that the concentration becomes 2.5% by mass, and the electric conduction of the mixed solution at 25 ° C. In the quality inspection method for zinc oxide particles, comprising: a measuring step for measuring the degree; and a step of determining whether or not the measured value of electrical conductivity obtained in the measuring step is 50 μS / cm or less. A preparatory step of preparing zinc oxide particles that have been determined that the measured value of the condition satisfies a predetermined condition or a surface treatment of the zinc oxide particles;
To-be-processed object preparation step for preparing a to-be-processed object to be an electrophotographic photoreceptor with a functional layer formed;
Adjusting the coating liquid containing the zinc oxide particles or the surface-treated zinc oxide particles, applying the coating liquid on the object to be treated, and drying to form the functional layer; and
A method for producing an electrophotographic photoreceptor, comprising:

Images