Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus

Abstract

The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an electrophotographic apparatus. Provided is an electrophotographic photosensitive member comprising a conductive support, a photosensitive layer, and a protective layer, wherein the protective layer contains conductive particles, the content of the conductive particles in the protective layer is 40% to 70% by volume, and the volume resistivity of the protective layer is 1.0×10 9 Ω·cm to 1.0×10 14 Ω·cm.

Description

Technical Field

[0001] The present invention relates to an electrophotographic photosensitive member, a process cartridge including the electrophotographic photosensitive member, and an electrophotographic apparatus including the electrophotographic photosensitive member. Background Art

[0002] As an electrophotographic photosensitive member installed in an electrophotographic apparatus, an electrophotographic photosensitive member containing an organic photoconductive substance (charge generating substance) has been widely used.

[0003] Recently, in order to achieve a long life of electrophotographic photosensitive members and high image quality during repeated use, it is required to improve the mechanical durability (wear resistance) of electrophotographic photosensitive members. Meanwhile, when the mechanical durability of the electrophotographic photosensitive member is improved, discharge products generated during the charging process remain on the surface of the electrophotographic photosensitive member, which may cause image smearing.

[0004] The material used for the surface layer of an electrophotographic photosensitive member degrades due to oxidizing gases such as ozone and nitrogen oxides generated by discharge on the surface of the electrophotographic photosensitive member. Furthermore, the surface of the electrophotographic photosensitive member has a low electrical resistance due to moisture adsorption. These phenomena are believed to cause image smear.

[0005] Furthermore, as the wear resistance of the surface of the electrophotographic photosensitive member becomes higher, the surface of the electrophotographic photosensitive member is less likely to be restored (removal of substances causing image offset such as deteriorated materials or adsorbed moisture), and image offset is more likely to occur.

[0006] As a technique for suppressing image smear, a method of adding an additive to the surface layer of an electrophotographic photosensitive member is used. Japanese Patent Application Laid-Open No. 2014-199391 discloses a technique for suppressing image smear by adding an additive having a specific alkylamine structure to the surface layer of an electrophotographic photosensitive member containing a curable resin. Furthermore, Japanese Patent Application Laid-Open No. 2013-008014 discloses a technique for suppressing image smear caused by an electrophotographic photosensitive member by adding a polymer obtained by polymerizing a specific urea compound to the surface layer of the electrophotographic photosensitive member.

[0007] In the techniques disclosed in Japanese Patent Application Laid-Open No. 2014-199391 and Japanese Patent Application Laid-Open No. 2013-008014, image smear cannot be sufficiently suppressed during electrophotographic processing. Summary of the Invention

[0008] An object of the present invention is to provide an electrophotographic photosensitive member excellent in suppressing image offset.

[0009] Furthermore, another object of the present invention is to provide a process cartridge including the electrophotographic photosensitive member and an electrophotographic apparatus including the electrophotographic photosensitive member.

[0010] The above objects are achieved by the following present invention.

[0011] According to one aspect of the present invention, an electrophotographic photosensitive member includes a conductive support, a photosensitive layer, and a protective layer, wherein the protective layer contains conductive particles, the content of the conductive particles in the protective layer is 40 volume % to 70 volume %, and the volume resistivity of the protective layer is 1.0×10 9 Ω·cm to 1.0×10 14 Ω·cm.

[0012] According to another aspect of the present invention, a process cartridge integrally supports an electrophotographic photosensitive member and at least one unit selected from the group consisting of a charging unit, a developing unit, and a cleaning unit, and is detachably mountable to a main body of an electrophotographic apparatus.

[0013] According to still another aspect of the present invention, an electrophotographic apparatus includes an electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a transfer unit.

[0014] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a diagram schematically showing an example of the constitution of the electrophotographic photosensitive member according to the present invention.

[0016] Figure 2 It is a diagram showing an example of a schematic configuration of a process cartridge in which the electrophotographic photosensitive member according to the present invention is mounted and an electrophotographic apparatus including the process cartridge. DETAILED DESCRIPTION

[0017] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0018] The electrophotographic photosensitive member according to the present invention comprises a conductive support, a photosensitive layer, and a protective layer, wherein the protective layer contains conductive particles, the content of the conductive particles in the protective layer is 40 volume % to 70 volume %, and the volume resistivity of the protective layer is 1.0×10 9 Ω·cm to 1.0×10 14 Ω·cm.

[0019] Here, the volume resistivity may be determined using a picoammeter (pA) as follows.

[0020] First, comb-shaped gold electrodes were fabricated by vapor deposition on polyethylene terephthalate (PET) film. The inter-electrode distance (D) was 180 μm, the electrode length (L) perpendicular to the direction in which the comb teeth extend was 5.9 cm, and there were six pairs of comb teeth (12 in total).

[0021] Next, a protective layer with a thickness (T) of 2 μm was applied to the manufactured comb-shaped gold electrodes. The protective layer was large enough to cover the electrode length perpendicular to the direction in which the comb teeth extend, as well as the gaps between the electrodes. Subsequently, under an environment of 23°C and 50% RH, the direct current (DC) (I) was measured when a 100V DC voltage (V) was applied to the comb-shaped gold electrodes. The volume resistivity was calculated using the following formula.

[0022] Volume resistivity (Ω·cm) = V(V) × T(cm) × L(cm) / {I(A) × D(cm)}

[0023] The present inventors presume that the reason why the electrophotographic photosensitive member according to the present invention excels in suppressing image offset is as follows.

[0024] As described above, low resistance on the surface of the electrophotographic photosensitive member is considered to be one of the causes of image offset. In the present invention, the electrophotographic photosensitive member includes a protective layer as a surface layer of the electrophotographic photosensitive member, the protective layer contains conductive particles in a ratio of 40 volume % to 70 volume %, and the volume resistivity of the protective layer is 1.0×10 9 Ω·cm to 1.0×10 14 Ω·cm, which is relatively high. Therefore, it is believed that the electrophotographic photosensitive member according to the present invention has charge retention, and during the electrophotographic process, charge is directly injected from the charging member into the conductive particles in the protective layer. Therefore, it is believed that discharge between the charging member and the electrophotographic photosensitive member is suppressed, thereby reducing the amount of discharge products generated. As a result, it is believed that the surface of the electrophotographic photosensitive member is less likely to have low resistance due to discharge products, thereby effectively suppressing image smear.

[0025] The injectability of the electrophotographic photosensitive member according to the present invention is preferably 0.70 or more, more preferably 0.75 or more, and still more preferably 0.80 or more.

[0026] Here, the injectability can be evaluated as follows.

[0027] Under an environment of a temperature of 23° C. and a humidity of 50% RH, the electrophotographic photosensitive member was installed in an electrophotographic apparatus, 1,000 V was applied to the charging roller using a direct current, and the electrophotographic photosensitive member was charged while being rotated at 60 rpm. In this case, the value given by A / 1,000 was defined as the injectability, where A is a value obtained by measuring the potential on the surface of the electrophotographic photosensitive member.

[0028] In the following, reference will be made to Figure 1 The constitution of the electrophotographic photosensitive member of the present invention will be described.

[0029] <Support>

[0030] In the present invention, the support 21 is a conductive support having conductivity. Examples of the shape of the support may include cylindrical, strip, and sheet. Among them, a cylindrical support is preferred. In addition, the surface of the support may be subjected to electrochemical treatment such as anodizing, sandblasting, or cutting.

[0031] As a material for the support, metal, resin, or glass is preferable.

[0032] Examples of the metal may include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among them, an aluminum support obtained by using aluminum is preferable.

[0033] In the case where the material for the support is resin or glass, conductivity is imparted by a treatment such as mixing or coating with a conductive material.

[0034] <Conductive Layer>

[0035] In the electrophotographic photosensitive member according to the present invention, a conductive layer may be provided on the support. Providing the conductive layer can shield scratches or irregularities on the surface of the support, or control light reflection on the surface of the support.

[0036] The conductive layer preferably contains conductive particles and a resin.

[0037] Examples of materials for the conductive particles may include metal oxides, metals, and carbon black.

[0038] Examples of metal oxides may include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of metals may include aluminum, nickel, iron, nickel-chromium alloy, copper, zinc, and silver.

[0039] Among them, metal oxides are preferably used for the conductive particles, and particularly titanium oxide, tin oxide, or zinc oxide is more preferably used for the conductive particles.

[0040] In the case where a metal oxide is used for the conductive particles, 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 an oxide thereof.

[0041] In addition, the conductive particles may have a laminated structure including core particles and a coating layer covering the core particles. Examples of materials for the core particles may include titanium oxide, barium sulfate, and zinc oxide. Examples of materials for the coating layer may include metal oxides such as tin oxide.

[0042] Furthermore, in the case where a metal oxide is used for the conductive particles, the volume average particle diameter of the conductive particles is preferably 1 nm to 500 nm, and more preferably 3 nm to 400 nm.

[0043] Examples of the resin may include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, and alkyd resin.

[0044] In addition, the conductive layer may further contain a masking agent such as silicone oil, resin particles, or titanium oxide.

[0045] The conductive layer can be formed by preparing a conductive layer coating liquid containing the above-mentioned materials and a solvent, forming a coating film thereof on a support, and drying the coating film. Examples of solvents used in the coating liquid may include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Examples of methods for dispersing conductive particles in the conductive layer coating liquid may include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

[0046] The thickness of the conductive layer is preferably 1 μm to 40 μm, and particularly preferably 3 μm to 30 μm.

[0047] <Base Coating>

[0048] In the present invention, an undercoat layer 22 may be provided on the support or the conductive layer. By providing the undercoat layer, the interlayer adhesion function can be improved and a charge injection blocking function can be imparted.

[0049] The primer layer preferably contains a resin. Alternatively, the primer layer can be formed into a cured film by polymerization of a composition containing a monomer having a polymerizable functional group.

[0050] Examples of the resin may include polyester resins, polycarbonate resins, polyvinyl acetal resins, acrylic resins, epoxy resins, melamine resins, polyurethane resins, phenolic resins, polyvinylphenolic resins, alkyd resins, polyvinyl alcohol resins, polyethylene oxide resins, polypropylene oxide resins, polyamide resins, polyamic acid resins, polyimide resins, polyamideimide resins, and cellulose resins.

[0051] Examples of the polymerizable functional group contained in the monomer having a polymerizable functional group may include an isocyanate group, a blocked isocyanate group, a methylol group, an alkylated methylol group, an epoxy group, a metal alkoxide group, a hydroxyl group, an amino group, a carboxyl group, a thiol group, a carboxylic anhydride group, and a carbon-carbon double bond group.

[0052] Furthermore, in order to improve electrical properties, the undercoat layer may further contain an electron transporting substance, a metal oxide, a metal, a conductive polymer, etc. Among them, an electron transporting substance or a metal oxide is preferably used.

[0053] Examples of the electron transporting substance may include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, halogenated aryl compounds, silole compounds, and boron-containing compounds. An electron transporting substance having a polymerizable functional group may be used as the electron transporting substance and copolymerized with the above-mentioned monomer having a polymerizable functional group to form an undercoat layer as a cured film.

[0054] Examples of metal oxides may include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide.Examples of metals may include gold, silver, and aluminum.

[0055] The metal oxide particles contained in the undercoat layer may be surface-treated using a surface treatment agent such as a silane coupling agent.

[0056] As a method for surface-treating the metal oxide particles, a general method can be used, and examples thereof include a dry method and a wet method.

[0057] In the dry method, while the metal oxide particles are stirred in a mixer capable of high-speed stirring, such as a Henschel mixer, an alcohol aqueous solution, an organic solvent solution, or an aqueous solution containing a surface treatment agent is added to the metal oxide particles and uniformly dispersed in the metal oxide particles, followed by drying.

[0058] In the wet method, the metal oxide particles and the surface treatment agent are stirred in a solvent or dispersed using glass beads in a sand mill. After dispersion, the solvent is removed by filtration or vacuum distillation. Preferably, after the solvent is removed, the particles are calcined at 100°C or above.

[0059] The undercoat layer may further contain additives, and may contain known materials, for example, metal powder such as aluminum, a conductive substance such as carbon black, a charge transporting substance, a metal chelate compound, and an organic metal compound.

[0060] Examples of the charge transporting material may include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, halogenated aryl compounds, silole compounds, and boron-containing compounds. A charge transporting material having a polymerizable functional group may be used as the charge transporting material and copolymerized with a monomer having a polymerizable functional group to form an undercoat layer as a cured film.

[0061] The undercoat layer can be formed by preparing an undercoat layer coating solution containing various materials and a solvent, forming a coating film thereof on the support or the conductive layer, and drying and / or curing the coating film.

[0062] The solvent used in the undercoat layer coating solution may include organic solvents such as alcohols, sulfoxides, ketones, ethers, esters, aliphatic halogenated hydrocarbons, and aromatic compounds. In the present invention, an alcohol solvent or a ketone solvent is preferably used.

[0063] Examples of the dispersion method for preparing the coating liquid for the undercoat layer may include methods using a homogenizer, an ultrasonic disperser, a ball mill, a sand mill, a roll mill, a vibration mill, an attritor, and a liquid collision type high-speed disperser.

[0064] The average thickness of the undercoat layer is preferably 0.1 μm to 10 μm, and more preferably 0.1 μm to 5 μm.

[0065] <Photosensitive Layer>

[0066] The photosensitive layer of an electrophotographic photosensitive member is mainly classified into (1) a laminated photosensitive layer and (2) a single-layer photosensitive layer. (1) A laminated photosensitive layer is a photosensitive layer having a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance. (2) A single-layer photosensitive layer is a photosensitive layer containing both a charge generating substance and a charge transporting substance.

[0067] (1) Laminated photosensitive layer

[0068] The laminated photosensitive layer has a charge generating layer 23 and a charge transporting layer 24 .

[0069] (1-1) Charge Generation Layer

[0070] The charge generating layer 23 preferably contains a charge generating substance and a resin.

[0071] Examples of the charge generating material may include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among them, azo pigments or phthalocyanine pigments are preferred. Among phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, or hydroxygallium phthalocyanine pigments are preferred.

[0072] The content of the charge generating substance in the charge generating layer is preferably 40% by mass to 85% by mass, and more preferably 60% by mass to 80% by mass, relative to the total mass of the charge generating layer.

[0073] Examples of the resin may include polyester resins, polycarbonate resins, polyvinyl acetal resins, polyvinyl butyral resins, acrylic resins, silicone resins, epoxy resins, melamine resins, polyurethane resins, phenolic resins, polyvinyl alcohol resins, cellulose resins, polystyrene resins, polyvinyl acetate resins, and polyvinyl chloride resins. Among them, polyvinyl butyral resin is more preferred.

[0074] In addition, the charge generation layer may further contain additives such as an antioxidant or an ultraviolet absorber, etc. Specific examples thereof may include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0075] The charge generating layer can be formed by preparing a charge generating layer coating solution containing the above-mentioned materials and a solvent, forming a coating film thereof on a support, a conductive layer, or an undercoat layer, and drying the coating film. Examples of the solvent used in the coating solution include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

[0076] The average thickness of the charge generating layer is preferably 0.1 μm to 1 μm, and more preferably 0.15 μm to 0.4 μm.

[0077] (1-2) Charge transport layer

[0078] The charge transport layer 24 preferably contains a charge transport substance and a resin.

[0079] Examples of the charge transporting substance may include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among them, triarylamine compounds or benzidine compounds are preferred.

[0080] The content of the charge transporting substance in the charge transporting layer is preferably 25% by mass to 70% by mass, and more preferably 30% by mass to 55% by mass, relative to the total mass of the charge transporting layer.

[0081] Examples of the resin may include polyester resins, polycarbonate resins, acrylic resins, and polystyrene resins. Among them, polycarbonate resins or polyester resins are preferred. As the polyester resin, polyarylate resins are particularly preferred.

[0082] The content ratio (mass ratio) of the charge transporting substance to the resin is preferably 4:10 to 20:10, and more preferably 5:10 to 12:10.

[0083] In addition, the charge transport layer may further contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, lubricity-imparting agents, or wear resistance improvers. Specific examples thereof may include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, silicone-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0084] The charge transport layer can be formed by preparing a charge transport layer coating solution containing the above-mentioned materials and a solvent, forming a coating film thereof on the charge generating layer, and drying the coating film. Examples of solvents used in the coating solution may include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Among these solvents, ether solvents or aromatic hydrocarbon solvents are preferred.

[0085] The average thickness of the charge transport layer is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, and particularly preferably 10 μm to 30 μm.

[0086] (2) Single-layer photosensitive layer

[0087] A single-layer photosensitive layer can be formed by preparing a photosensitive layer coating solution containing a charge generating substance, a charge transporting substance, a resin, and a solvent, forming a coating film thereof on a support, a conductive layer, or an undercoat layer, and drying the coating film. Examples of the materials for the charge generating substance, the charge transporting substance, and the resin are the same as those in "(1) Laminated Photosensitive Layer."

[0088] <Protection layer>

[0089] The protective layer 25 may include a polymer of a compound having a polymerizable functional group and a binder resin.

[0090] Examples of polymerizable functional groups may include isocyanate groups, blocked isocyanate groups, methylol groups, alkylated methylol groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxyl groups, thiol groups, carboxylic acid anhydride groups, carbon-carbon double bond groups, alkoxysilyl groups, and silanol groups. Monomers having charge transporting ability may also be used as compounds having polymerizable functional groups. In particular, the protective layer preferably comprises a polymer of a composition containing a free radical polymerizable monomer.

[0091] Examples of the binder resin may include polyester resin, acrylic resin, phenoxy resin, polycarbonate resin, polystyrene resin, phenol resin, melamine resin and epoxy resin. Among them, acrylic resin is preferred.

[0092] Examples of the conductive particles contained in the protective layer may include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide.

[0093] In the case where a metal oxide is used for the conductive particles, the metal oxide may contain elements such as niobium, phosphorus, and aluminum, and oxides thereof.

[0094] In addition, the conductive particles may have a laminated structure including a core particle and a coating layer covering the core particle. Examples of materials for the core particles may include titanium oxide, barium sulfate, and zinc oxide. Examples of materials for the coating layer may include metal oxides such as titanium oxide or tin oxide.

[0095] The conductive particles are particularly preferably titanium oxide particles containing niobium.

[0096] Examples of the shape of the niobium-containing titanium oxide particles include various shapes such as spherical, polyhedral, ellipsoidal, flake, and needle-like. Of these, spherical, polyhedral, and ellipsoidal shapes are preferred from the perspective of reducing image defects such as black spots. In the present invention, it is more preferred that the niobium-containing titanium oxide particles have a spherical shape or a polyhedral shape close to a spherical shape.

[0097] The titanium oxide particles containing niobium are preferably anatase titanium oxide particles or rutile titanium oxide particles, and more preferably anatase titanium oxide particles. By using anatase titanium oxide particles, injectability is improved.

[0098] In the present invention, the conductive particles are particularly preferably particles containing anatase-type titanium oxide particles as a core material and titanium oxide covering the surface of the core material and containing niobium.

[0099] When the conductive particles include titanium oxide particles containing niobium, the content of niobium in the conductive particles is preferably 0.5% by mass to 15.0% by mass, and more preferably 2.6% by mass to 10.0% by mass. When the content of niobium in the conductive particles is 0.5% by mass or more, the effect of suppressing image offset can be enhanced, and when the content of niobium in the conductive particles is 15.0% by mass or less, the volume resistivity of the protective layer does not become too high.

[0100] In the case where a metal oxide is used for the conductive particles, the surface of the metal oxide particles is preferably treated with a silane coupling agent or the like from the viewpoint of dispersibility and liquid stability.

[0101] Furthermore, in the case where a metal oxide is used for the conductive particles, the volume average particle diameter of the conductive particles is preferably 1 nm to 500 nm, more preferably 3 nm to 300 nm, and still more preferably 5 nm to 100 nm.

[0102] From the perspective of suppressing image smear and the strength of the protective layer, the content of the conductive particles in the protective layer is 40% to 70% by volume, and preferably 45% to 65% by volume. When the content of the conductive particles in the protective layer is 40% by volume or more, the effect of suppressing image smear can be fully achieved, and when the content of the conductive particles in the protective layer is 70% by volume or less, the protective layer itself can be prevented from becoming brittle.

[0103] The protective layer may further contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, lubricity-imparting agents, or wear resistance improvers. Specific examples of the additives may include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, silicone-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0104] The protective layer can be formed by preparing a protective layer coating solution containing the above-mentioned materials and a solvent, forming a coating film thereof on the photosensitive layer, and drying and / or curing the coating film. Examples of the solvent used in the coating solution can include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, and aromatic hydrocarbon solvents.

[0105] From the viewpoint of charge retention, the volume resistivity of the protective layer is 1.0×10 9 Ω·cm to 1.0×10 14 Ω·cm, and preferably 1.0×10 10 Ω·cm to 1.0×10 13 Ω·cm.

[0106] Here, the charge retention is an index for simply evaluating stable retention of charge on the surface of an electrophotographic photosensitive member to which a rectangular wave voltage is applied (ie, stability of a latent image) from changes in the shape of the rectangular wave with time.

[0107] Use steps 1 through 4 below to determine charge retention:

[0108] Step 1: Under an environment of a temperature of 23° C. and a humidity of 50% RH, while rotating the electrophotographic photosensitive member at a rotation speed of 30 rpm, a voltage was applied to the surface of the electrophotographic photosensitive member from one direction, and the voltage was a rectangular wave voltage having a frequency of 1 Hz, a Voffset of −450 V, and a Vpp of 500 V;

[0109] Step 2: measuring the potential on the surface of the electrophotographic photosensitive member at a position where the portion of the surface of the electrophotographic photosensitive member to which the voltage is applied rotates for 0.30 seconds at a measurement interval of 100 μs for a predetermined time within a range of 10 seconds to 20 seconds;

[0110] Step 3: Plotting the values ​​obtained by measurement using μs as the unit of the horizontal axis and V as the unit of the vertical axis, and determining the slope of each of a regression line derived from the first 25 measurement points and a regression line derived from the last 25 measurement points at each measurement point; and

[0111] Step 4: A value calculated by averaging the absolute values ​​of the maximum and minimum values ​​of the obtained slopes is defined as charge retention.

[0112] In step 3, since the number of measurement points for deriving the regression line is less than 25, the first 24 points obtained from the start of measurement and the 24 points obtained before the end of measurement are not used as data for determining the slope.

[0113] The charge retention is preferably 9.5 or more and more preferably 10.0 or more.

[0114] The thickness of the protective layer is preferably 0.2 μm to 5 μm and more preferably 0.5 μm to 3 μm.

[0115] [Process cartridge and electrophotographic apparatus]

[0116] The process cartridge according to the present invention integrally supports the above-mentioned electrophotographic photosensitive member and at least one unit selected from the group consisting of a charging unit, a developing unit, and a cleaning unit, and is detachably mountable to a main body of an electrophotographic apparatus.

[0117] Furthermore, an electrophotographic apparatus according to the present invention includes the above-mentioned electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a transfer unit.

[0118] Figure 2 An example of a schematic configuration of an electrophotographic apparatus having a process cartridge including an electrophotographic photosensitive member is shown.

[0119] A cylindrical (drum-shaped) electrophotographic photosensitive member 1 is rotationally driven around an axis 2 in the direction of an arrow at a predetermined peripheral speed (process speed). During the rotation, the surface of the electrophotographic photosensitive member 1 is charged to a predetermined positive or negative potential by a charging unit 3. Figure 2 , a roller charging system using a roller-type charging member is shown, but a charging system such as a corona charging system, a proximity charging system, or an injection charging system may also be employed.

[0120] The surface of the charged electrophotographic photosensitive member 1 is irradiated with exposure light 4 emitted from an exposure unit (not shown), and an electrostatic latent image corresponding to target image information is formed on the surface of the electrophotographic photosensitive member 1. The exposure light 4 is light whose intensity is adjusted corresponding to a time-series electric digital image signal of the target image information, and is output from an image exposure unit for, for example, slit exposure or laser beam scanning exposure.

[0121] The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1 is developed (normal development or reversal development) using the toner stored in the developing unit 5, and a toner image is formed on the surface of the electrophotographic photosensitive member 1. The toner image formed on the surface of the electrophotographic photosensitive member 1 is transferred onto a transfer material 7 by a transfer unit 6. In this case, a bias voltage having a polarity opposite to the charge remaining on the toner is applied to the transfer unit 6 from a bias power supply (not shown).

[0122] Furthermore, in the case where the transfer material 7 is paper, the transfer material 7 is taken out from a paper feeding unit (not shown) and fed between the electrophotographic photosensitive member 1 and the transfer unit 6 in synchronization with the rotation of the electrophotographic photosensitive member 1. The transfer material 7 on which the toner image is transferred from the electrophotographic photosensitive member 1 is separated from the surface of the electrophotographic photosensitive member 1 to be conveyed to the fixing unit 8, and the toner image is subjected to a fixing process by the fixing unit 8. Thus, the transfer material 7 is printed as an image formed product (printed product or copied product) to the outside of the electrophotographic apparatus.

[0123] The electrophotographic apparatus may further include a cleaning unit 9 for removing attached matter such as toner remaining on the surface of the electrophotographic photosensitive member 1 after transfer. In addition, a so-called cleanerless system configured to remove attached matter by means of the developing unit 5 or the like may be used without separately providing the cleaning unit 9.

[0124] In the present invention, the electrophotographic photosensitive member 1 and a plurality of components selected from the charging unit 3, the developing unit 5 and the cleaning unit 9 can be accommodated in a container and integrally supported to form a process cartridge 11. Furthermore, the process cartridge formed as described above can be detachably mounted to the main body of the electrophotographic apparatus.

[0125] For example, the process cartridge is constructed as follows. At least one selected from the charging unit 3, the developing unit 5, and the cleaning unit 9 is integrally supported together with the electrophotographic photosensitive member 1 to form a cartridge. The cartridge can be used as a process cartridge 11 that is detachably mounted to the main body of the electrophotographic apparatus using a guide unit 12 such as a rail of the main body of the electrophotographic apparatus.

[0126] The electrophotographic apparatus may further include a static-eliminating mechanism for performing a static-eliminating treatment on the surface of the electrophotographic photosensitive member 1 by means of pre-exposure light 10 from a pre-exposure unit (not shown). In addition, in order to detachably attach the process cartridge 11 of the present invention to the main body of the electrophotographic apparatus, a guide unit 12 such as a rail may be provided.

[0127] The electrophotographic photosensitive member according to the present invention can be used for, for example, a laser beam printer, an LED printer, a copying machine, a facsimile machine, and a composite machine thereof.

[0128] According to the present invention, there can be provided an electrophotographic photosensitive member excellent in suppressing image offset, a process cartridge including the electrophotographic photosensitive member, and an electrophotographic apparatus including the electrophotographic photosensitive member.

[0129] [Example]

[0130] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Without departing from the gist of the present invention, the present invention is not limited to the following Examples. In addition, in the description of the following Examples, unless otherwise stated, term "part" is based on mass.

[0131] Hereinafter, the present invention will be described in more detail with reference to Examples. In the Examples, "parts" means "parts by mass".

[0132] <Production of Conductive Particles>

[0133] (Production of Niobium-Containing Titanium Oxide Particles (T1-1))

[0134] As the core material, approximately spherical anatase-type titanium dioxide particles having a volume average particle size of 150 nm and a niobium content of 0.20 mass % were used. 100 g of the core material was dispersed in water to obtain 1 L of an aqueous suspension, and the aqueous suspension was heated to 60°C.

[0135] A niobium solution obtained by dissolving 3 g of niobium pentachloride (NbCl₅) in 100 mL of 11.4 mol / L hydrochloric acid was mixed with 600 mL of a titanium sulfate solution containing 33.7 g of Ti to prepare a titanium niobate solution. The obtained titanium niobate solution and a 10.7 mol / L aqueous sodium hydroxide solution were simultaneously added dropwise over 3 hours to adjust the pH of the aqueous suspension to 2 to 3.

[0136] After the dropwise addition was completed, the suspension was filtered, washed, and dried at 110° C. for 8 hours. The dried product was heat-treated at 800° C. for 1 hour in an air atmosphere to obtain a powder of niobium-containing titanium oxide particles (T1-1) having a core material containing titanium oxide and a coating layer containing titanium oxide containing niobium.

[0137] (Production of Niobium-Containing Titanium Oxide Particles (T1-2) to (T1-10))

[0138] In the production of niobium-containing titanium oxide particles (T1-1), the volume average particle size of the core material used was changed as shown in Table 1, and the coating conditions were appropriately changed. Powders of each of niobium-containing titanium oxide particles (T1-2) to (T1-10) were obtained in the same manner as in the production of niobium-containing titanium oxide particles (T1-1), except for the above conditions. The contents shown in Table 1 refer to the niobium content in the niobium-containing titanium oxide particles and are values ​​obtained by measurement using elemental analysis using X-ray fluorescence (XRF).

[0139] (Production of Niobium-Containing Titanium Oxide Particles (T2-1))

[0140] Niobium sulfate (a water-soluble niobium compound) was added to the titanyl sulfate aqueous solution so that the amount of niobium ions was 1.0% by mass relative to the amount of titanium (calculated as titanium dioxide). Fine particle cores formed of titanium hydroxide were added to the titanyl sulfate aqueous solution, and the mixture was hydrolyzed by heating and boiling to obtain a hydrous titanium dioxide slurry.

[0141] The aqueous titanium dioxide slurry containing niobium ions was filtered and washed with water, and then dried at 110° C. for 8 hours. The dried product was heat-treated at 800° C. for 1 hour in an air atmosphere to obtain a powder of titanium oxide particles (T2-1) containing niobium.

[0142] (Production of Niobium-Containing Titanium Oxide Particles (T2-2) to (T2-5))

[0143] In the production of niobium-containing titanium oxide particles (T2-1), the amount of niobium sulfate added to the aqueous titanyl sulfate solution, the size of the fine particle cores added during hydrolysis, and the temperature and hydrolysis rate during hydrolysis were appropriately adjusted. Thus, powders of each of niobium-containing titanium oxide particles (T2-2) to (T2-5) having a volume average particle diameter as shown in Table 1 were obtained.

[0144] [Table 1]

[0145]

[0146] <Production of Electrophotographic Photosensitive Member>

[0147] (Example 1)

[0148] As a support (conductive support), an aluminum cylinder (JIS-A3003, aluminum alloy) having a diameter of 24 mm and a length of 257.5 mm was used.

[0149] Next, prepare the following materials.

[0150] 214 parts of titanium oxide (TiO2) particles coated with oxygen-deficient tin oxide (SnO2) as metal oxide particles (volume average particle size: 230 nm)

[0151] 132 parts of phenolic resin (monomer / oligomer of phenolic resin) as a binder material (trade name: Plyophen J-325, resin solid content: 60% by mass, manufactured by Dainippon Ink And Chemicals, Inc.)

[0152] 98 parts of 1-methoxy-2-propanol as solvent

[0153] These materials were added to a sand mill using 450 parts of glass beads having a diameter of 0.8 mm, and dispersed under the conditions of a rotation speed of 2,000 rpm, a dispersion treatment time of 4.5 hours, and a cooling water setting temperature of 18° C., thereby obtaining a dispersion liquid. The glass beads were removed from the dispersion liquid using a mesh (opening: 150 μm).

[0154] Silicone resin particles (trade name: TOSPEARL 120, average particle size of 2 μm, manufactured by Momentive Performance Materials, Inc.) as a surface roughness imparting agent are added to the obtained dispersion. The amount of silicone resin particles added is set to 10% by mass relative to the total mass of the metal oxide particles and the binder material in the dispersion after removing the glass beads. In addition, silicone oil (trade name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.) as a leveling agent is added to the dispersion so that the content of silicone oil is 0.01% by mass relative to the total mass of the metal oxide particles and the binder material in the dispersion.

[0155] Next, a solvent in which methanol and 1-methoxy-2-propanol (mass ratio: 1:1) are mixed with each other is added to the dispersion so that the total mass of the metal oxide particles, the binder material, and the surface roughness imparting agent in the dispersion (i.e., the mass of the solid content) is 67% by mass relative to the mass of the dispersion. Thereafter, the mixture is stirred to prepare a conductive layer coating liquid.

[0156] The conductive layer coating liquid was applied onto the support by dip coating, and heating was performed at 140° C. for 1 hour, thereby forming a conductive layer having a thickness of 30 μm.

[0157] Next, prepare the following materials.

[0158] 3.11 parts of an electron transporting substance represented by the following formula (E-1)

[0159] 6.49 parts of blocked isocyanate (trade name: Duranate SBB-70P, manufactured by Asahi Kasei Corporation)

[0160] 0.4 parts of styrene-acrylic resin (trade name: UC-3920, manufactured by Toagosei Co., Ltd.)

[0161] 1.8 parts of silica slurry (trade name: IPA-ST-UP, solid content concentration: 15% by mass, viscosity: 9 mPa·s, manufactured by Nissan Chemical Industries, Ltd.)

[0162] These materials were dissolved in a solvent in which 48 parts of 1-butanol and 24 parts of acetone were mixed to prepare an undercoat layer coating solution. The undercoat layer coating solution was applied to the conductive layer by dip coating and heated at 170° C. for 30 minutes to form an undercoat layer having a thickness of 0.7 μm.

[0163]

[0164] Next, 10 parts of crystalline hydroxygallium phthalocyanine having peaks at 7.5° and 28.4° in a diagram obtained by CuKα characteristic X-ray diffraction and 5 parts of polyvinyl butyral resin (trade name: S-LEC BX-1, manufactured by SEKISUI CHEMICAL CO., LTD.) were prepared.

[0165] These materials were added to 200 parts of cyclohexanone and dispersed for 6 hours using a sand mill apparatus using glass beads having a diameter of 0.9 mm. 150 parts of cyclohexanone and 350 parts of ethyl acetate were further added thereto and diluted, thereby obtaining a charge generating layer coating liquid.

[0166] The obtained coating liquid was applied onto the undercoat layer by dip coating, and drying was performed at 95° C. for 10 minutes, thereby forming a charge generating layer having a thickness of 0.20 μm.

[0167] X-ray diffraction measurement was performed under the following conditions.

[0168] [Powder X-ray diffraction measurement]

[0169] Measuring machine used: X-ray diffractometer RINT-TTRII, manufactured by Rigaku Corporation

[0170] X-ray tube: Cu

[0171] Tube voltage: 50KV

[0172] Tube current: 300mA

[0173] Scanning method: 2θ / θ scanning

[0174] Scanning speed: 4.0° / min

[0175] Sampling interval: 0.02°

[0176] Starting angle (2θ): 5.0°

[0177] End angle (2θ): 40.0°

[0178] Accessories: Standard sample rack

[0179] Filter: Not used

[0180] Incident Monochromator: Use

[0181] Counter monochromator: Not used

[0182] Diverging slits: open

[0183] Divergence longitudinal limiting slit: 10.00mm

[0184] Scattering slit: Open

[0185] Light receiving slit: open

[0186] Flat Monochromator: Use

[0187] Counter: Scintillation counter

[0188] Next, prepare the following materials.

[0189] 6 parts of a charge transporting substance (hole transporting substance) represented by the following formula (C-1)

[0190] 3 parts of a charge transporting substance (hole transporting substance) represented by the following formula (C-2)

[0191] 1 part of a charge transporting substance (hole transporting substance) represented by the following formula (C-3)

[0192] 10 parts of polycarbonate (trade name: Iupilon Z400, manufactured by Mitsubishi Engineering-Plastics Corporation)

[0193] 0.02 parts of a polycarbonate resin having copolymerized units of the following formulae (C-4) and (C-5) (x / y = 0.95 / 0.05: viscosity average molecular weight = 20,000)

[0194] These materials were dissolved in a solvent in which 25 parts of o-xylene, 25 parts of methyl benzoate, and 25 parts of dimethoxymethane were mixed to prepare a charge transport layer coating liquid. The charge transport layer coating liquid was applied to the charge generating layer by dip coating to form a coating film, and the coating film was dried at 120° C. for 30 minutes to form a charge transport layer having a thickness of 12 μm.

[0195]

[0196]

[0197] Next, prepare the following materials.

[0198] 100 parts of titanium oxide particles containing niobium (T1-1, specific gravity: 4 g / cm 3 )

[0199] 3 parts of a compound represented by the following formula (S-1) as a silane coupling agent (trade name: KBM-3033, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0200]

[0201] These materials were mixed with 200 parts of toluene, the mixture was stirred with a stirrer for 4 hours, and the stirred mixture was filtered, washed, and then heat-treated at 130° C. for 3 hours. Surface treatment was performed as described above.

[0202] Next, prepare the following materials.

[0203] 1 part of a compound represented by the following structural formula (O-1) as a binder resin

[0204] 4 parts of surface-treated niobium-containing titanium oxide particles as conductive particles

[0205] These materials were mixed with a solvent in which 5 parts of 1-propanol and 5 parts of cyclohexane were mixed with each other, and the mixture was stirred with a stirrer for 6 hours.As described above, a protective layer coating liquid was prepared.

[0206] The protective layer coating liquid was applied to the charge transport layer by dip coating to form a coating film, and the resulting coating film was dried at 50°C for 6 minutes. Thereafter, under a nitrogen atmosphere, at an accelerating voltage of 70 kV and a beam current of 5.0 mA, the coating film was irradiated with an electron beam for 1.6 seconds while the support (irradiated object) was rotated at a speed of 300 rpm. The dose at the protective layer position was 15 kGy.

[0207] Thereafter, in a nitrogen atmosphere, the temperature of the coating film was raised to 117° C. The oxygen concentration from the electron beam irradiation to the subsequent heat treatment was 10 ppm.

[0208] Next, the coating film was naturally cooled in air until the coating film temperature was 25° C. and then heat-treated for 1 hour at a coating film temperature of 120° C., thereby forming a protective layer having a thickness of 2 μm. As described above, the electrophotographic photosensitive member according to Example 1 was produced.

[0209]

[0210] (Examples 2 to 23)

[0211] Each electrophotographic photosensitive member according to Examples 2 to 23 was produced in the same manner as in Example 1, except that the kind of the niobium-containing titanium oxide particles and the content (volume %) in the protective layer were changed as shown in Table 2.

[0212] (Example 24)

[0213] The type and amount of the silane coupling agent used for the surface treatment of the niobium-containing titanium oxide particles were changed to 4 parts of a compound represented by the following formula (S-2) (trade name: KBM-3103C, manufactured by Shin-Etsu Chemical Co., Ltd.) An electrophotographic photosensitive member according to Example 24 was produced in the same manner as in Example 1 except for this.

[0214]

[0215] (Example 25)

[0216] Prepare the following materials.

[0217] 100 parts of tin oxide particles (trade name: S-2000, manufactured by Mitsubishi Materials Corporation)

[0218] 20 parts of the compound represented by formula (S-2)

[0219] These materials were mixed with 200 parts of toluene, the mixture was stirred with a stirrer for 4 hours, and the stirred mixture was filtered, washed, and then heat-treated at 130° C. for 3 hours. As described above, the surface treatment of the tin oxide particles was performed.

[0220] An electrophotographic photosensitive member according to Example 25 was produced in the same manner as in Example 1, except that the kind and amount of the conductive particles for forming the protective layer in Example 1 were changed to 7 parts of surface-treated tin oxide particles.

[0221] (Example 26)

[0222] In Example 25, the type and amount of the silane coupling agent used for the surface treatment of the tin oxide particles were changed to a compound represented by the following formula (S-3) (trade name: KBM-3066, manufactured by Shin-Etsu Chemical Co., Ltd.) An electrophotographic photosensitive member according to Example 26 was produced in the same manner as in Example 25 except for this.

[0223]

[0224] (Example 27)

[0225] In Example 1, the kind of the binder resin for forming the protective layer was changed to a compound represented by the following structural formula (O-2).

[0226]

[0227] (Example 28)

[0228] In Example 1, the type and amount of the binder resin used to form the protective layer were changed to 1.7 parts of a phenolic resin (monomer / oligomer of a phenolic resin) (trade name: Plyophen J-325, resin solids content: 60% by mass, manufactured by Dainippon Ink And Chemicals, Inc.). Furthermore, the type and amount of the mixed solvent used to form the protective layer were changed to 5 parts of 1-methoxy-2-propanol and 4 parts of methanol to prepare a protective layer coating liquid. This protective layer coating liquid was applied to the charge transport layer by dip coating to form a coating film. The coating film was then dried at 160°C for 30 minutes to form a protective layer having a thickness of 2 μm. Aside from this, an electrophotographic photosensitive member according to Example 28 was produced in the same manner as in Example 1.

[0229] (Example 29)

[0230] Prepare the following materials.

[0231] 1 part blocked isocyanate (trade name: Duranate SBN-70D, manufactured by Asahi Kasei Corporation)

[0232] 1 part of polyvinyl acetal resin (trade name: KS-5Z, manufactured by SEKISUI CHEMICAL CO., LTD.)

[0233] In Example 1, the type and amount of the binder resin used to form the protective layer were changed to the above materials. Furthermore, the type and amount of the mixed solvent used to form the protective layer were changed to 9 parts 1-butanol and 6 parts acetone to prepare a protective layer coating liquid. This protective layer coating liquid was applied to the charge transport layer by dip coating to form a coating film. The coating film was then dried at 170°C for 30 minutes to form a protective layer with a thickness of 2 μm. Aside from this, an electrophotographic photosensitive member according to Example 29 was produced in the same manner as in Example 1.

[0234] (Example 30)

[0235] In Example 1, the type and amount of the binder resin used to form the protective layer were changed to a polyester resin having a weight-average molecular weight (Mw) of 100,000, with a ratio of 1 part of the structural unit of the following formula (O-3) to the structural unit of the following formula (O-4) being 5 / 5. Furthermore, the type and amount of the mixed solvent used to form the protective layer were changed to 12 parts of chlorobenzene and 8 parts of dimethoxymethane to prepare a protective layer coating liquid. This protective layer coating liquid was applied to the charge transport layer by dip coating to form a coating film. Thereafter, the coating film was dried at 120°C for 30 minutes to form a protective layer having a thickness of 2 μm. Aside from this, an electrophotographic photosensitive member according to Example 30 was produced in the same manner as in Example 1.

[0236]

[0237] (Comparative Examples 1 to 4)

[0238] In Example 1, the kind of niobium-containing titanium oxide particles used to form the protective layer and the content (volume %) in the protective layer were changed as shown in Table 3. Electrophotographic photosensitive members according to Comparative Examples 1 to 4 were produced in the same manner as in Example 1 except for this.

[0239] (Comparative Example 5)

[0240] A protective layer coating liquid was prepared as follows.

[0241] First, prepare the following materials.

[0242] 10 parts of a radical polymerizable monomer (trade name: TMPTA, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0243] 5 parts of the compound represented by the following formula (H-1)

[0244] 0.15 parts of the compound represented by the following formula (H-2)

[0245] 0.15 parts of the compound represented by the following formula (H-3)

[0246] 1.5 parts of fluororesin particles (trade name: MPE-056, manufactured by Chemours-Mitsui Fluoroproducts Co., Ltd.)

[0247] 0.75 parts of photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF Japan Ltd.)

[0248]

[0249] These materials were mixed with 100 parts of tetrahydrofuran, and the mixture was stirred with a stirrer for 6 hours, whereby a protective layer coating liquid was prepared.

[0250] The protective layer coating liquid was applied to the charge transport layer by spraying in a nitrogen stream to form a coating film, and the coating film was placed in a nitrogen stream for 10 minutes until it was dry to the touch. Thereafter, ultraviolet irradiation was performed under the following conditions in an ultraviolet ray irradiation booth in which the interior was replaced with nitrogen so that the oxygen concentration was 2% or less.

[0251] Metal halide lamp: 160W / cm

[0252] Irradiation distance: 120mm

[0253] Irradiation intensity: 700mW / cm 2

[0254] Irradiation time: 60 seconds

[0255] Furthermore, the coating film was dried at 130° C. for 20 minutes, thereby forming a protective layer having a thickness of 5 μm. An electrophotographic photosensitive member according to Comparative Example 5 was produced in the same manner as in Example 1 except for this.

[0256] (Comparative Example 6)

[0257] Prepare the following materials.

[0258] 97 parts of the compound represented by the following formula (H-4)

[0259] 3 parts of the compound represented by the following formula (H-5)

[0260] These materials are dissolved in 100 parts of n-propanol, and 100 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name: ZEORORA H, manufactured by Zeon Corporation) is further added, whereby a protective layer coating liquid is prepared.

[0261] An electrophotographic photosensitive member according to Comparative Example 6 was produced in the same manner as in Example 1 except that this protective layer coating liquid was used.

[0262]

[0263]

[0264] (Comparative Example 7)

[0265] Prepare the following materials.

[0266] 100 parts by mass of antimony-doped tin oxide particles (trade name: T-1, manufactured by Mitsubishi Materials Corporation)

[0267] 3 parts of a compound represented by the following formula (H-6)

[0268] 10 parts by mass of a fluorine atom-containing compound (trade name: LS-1090, manufactured by Shin-Etsu Silicone Co., Ltd.)

[0269] These materials were mixed with 250 parts of ethanol, the mixture was stirred with a stirrer for 48 hours, and the stirred mixture was filtered, washed with water and then heat-treated at 150° C. for 3 hours. Surface treatment of antimony-doped tin oxide particles was performed as described above.

[0270] Further prepare the following materials.

[0271] 18 parts of the compound represented by formula (O-1)

[0272] 6.8 parts of 2-methylthioxanthone as a photopolymerization initiator

[0273] 45 parts surface-treated tin oxide particles

[0274] 14 parts of tetrafluoroethylene resin particles (average particle size: 0.18 μm)

[0275] These materials were mixed with 150 parts of ethanol and the mixture was dispersed with a sand mill for 90 hours.As described above, a protective layer coating liquid was prepared.

[0276] The protective layer coating liquid was applied to the charge transport layer prepared in the same manner as in Example 1 by dip coating to form a coating film, and the obtained coating film was dried at 50° C. for 6 minutes. In addition, curing of the coating film using ultraviolet rays was performed in the same manner as in Comparative Example 5. Except for this, an electrophotographic photosensitive member according to Comparative Example 7 was produced in the same manner as in Example 1.

[0277]

[0278] (Comparative Example 8)

[0279] Prepare the following materials.

[0280] 10 parts of niobium-containing titanium oxide particles (volume average particle size 6 nm, niobium content 0.5 mass %)

[0281] 10 parts of the compound represented by the following formula (H-7)

[0282] 1 part polymerization initiator (1-hydroxycyclohexyl (phenyl) ketone)

[0283] These materials were mixed with 40 parts of n-propanol, and the mixture was dispersed with a sand mill for 2 hours, thereby preparing a protective layer coating liquid.

[0284] An electrophotographic photosensitive member according to Comparative Example 8 was produced in the same manner as in Comparative Example 7, except that the protective layer coating liquid was used.

[0285]

[0286] <Evaluation of injectability>

[0287] The injection property was evaluated using a modified electrophotographic apparatus (laser beam printer) (trade name: HP LaserJet Enterprise Color M553dn, manufactured by Hewlett-Packard Company). The electrophotographic apparatus used for the evaluation was modified so that the image exposure amount, the amount of current flowing from the charging roller to the support of the electrophotographic photosensitive member (hereinafter referred to as "total current"), and the voltage applied to the charging roller were adjusted and measured.

[0288] In addition, the cyan process cartridge of the electrophotographic apparatus was modified, and a potential probe (Model 6000B-8, manufactured by Trek Japan) was installed at the development position. Next, the surface potential was measured at the center of the electrophotographic photosensitive member using a surface potentiometer (Model 344, manufactured by Trek Japan).

[0289] The electrophotographic photosensitive member according to each of Examples and Comparative Examples was installed under an environment of a temperature of 23°C and a humidity of 50% RH, 1,000 V was applied to the charging roller using a direct current, and the electrophotographic photosensitive member was charged while being rotated at 60 rpm. The injectability was determined by measuring the potential A on the surface of the electrophotographic photosensitive member at this time, that is, A / 1,000.

[0290] The results are shown in Tables 2 and 3.

[0291] <Evaluation of Charge Retention>

[0292] The charge retention was measured using a photosensitive member testing device (trade name: CYNTHIA59, manufactured by GEN-TECH, Inc.). The electrophotographic photosensitive members according to the Examples and Comparative Examples were installed in the photosensitive member testing device under an environment of 23°C temperature and 50% RH. Furthermore, a conductive rubber roller having a diameter of 8 mm was used as a charging member, and the charging device was set to apply a rectangular wave voltage having a frequency of 1 Hz, a Voffset of −450 V, and a Vpp of 500 V to the surface of the electrophotographic photosensitive member.

[0293] In the measurement of the potential, a surface potential probe (Model 6000B-8, manufactured by Trek Japan) was installed at a position 1 mm away from the electrophotographic photosensitive member, and a surface potentiometer (Model 344, manufactured by Trek Japan) was used.

[0294] The charge retention was determined according to the above steps 1 to 4 under the above conditions.

[0295] When an electrophotographic photosensitive member prepared as follows was measured as an index for when the charge retention was high, the charge retention was 11.2.

[0296] A polycarbonate layer having a thickness of 20 μm (trade name: Iupilon Z400, manufactured by Mitsubishi Engineering-Plastics Corporation) was formed on an aluminum cylinder having a diameter of 24 mm and a length of 257.5 mm (JIS-A3003, aluminum alloy).

[0297] The results are shown in Tables 2 and 3.

[0298] <Image Defacement Evaluation>

[0299] As the electrophotographic apparatus, a modified version of a laser beam printer (trade name: HP LaserJet Enterprise Color M553dn, manufactured by Hewlett-Packard Company) was used. The electrophotographic apparatus used for evaluation was modified so that the image exposure amount, the amount of current flowing from the charging roller to the support of the electrophotographic photosensitive member (hereinafter referred to as "total current"), and the voltage applied to the charging roller were adjusted and measured.

[0300] First, the electrophotographic apparatus and the electrophotographic photosensitive members according to each of Examples and Comparative Examples were left to stand under a temperature 30° C. / humidity 80% RH environment for 24 hours or more, and then the electrophotographic photosensitive member was installed in a cyan cartridge of the electrophotographic apparatus.

[0301] Next, the applied voltage was applied while gradually increasing from -400 V to -2,000 V at intervals of 100 V, and the total current at each applied voltage was measured. A graph was then drawn using the applied voltage and the total current as the horizontal and vertical axes, respectively, and the applied voltage was set by determining the applied voltage at which the current value deviated by 100 μA from the linear approximation curve at applied voltages of -400 V to -800 V.

[0302] Next, solid image output was performed using only cyan on A4-size plain paper, and the image exposure was set so that the density on the paper obtained using a spectrodensitometer (trade name: X-Rite 504, manufactured by X-Rite Incorporated) was 1.45.

[0303] Next, 10,000 sheets of an A4-sized square grid image with a line width of 0.1 mm and a line spacing of 10 mm were continuously output using only cyan. After outputting these images, the main power of the electrophotographic apparatus was turned off, and the apparatus was left standing for three days in an environment of 30°C and 80% RH. After this standing, the main power of the electrophotographic apparatus was turned on, and a single sheet of the square grid image was similarly output. The output image was visually observed for image smear, and image smear was evaluated based on the following criteria. The same evaluation was performed by setting the number of output sheets to 20,000.

[0304] The evaluation levels are as follows.

[0305] Level 5: No anomalies observed on the grid image.

[0306] Level 4: The horizontal lines on the grid pattern are broken, but no abnormalities are observed in the vertical lines.

[0307] Level 3: The horizontal lines on the grid image disappear, but no abnormalities are observed in the vertical lines.

[0308] Level 2: The horizontal lines on the grid image disappear, and the vertical lines are broken.

[0309] Level 1: The horizontal lines on the grid image disappear, and the vertical lines also disappear.

[0310] In this case, the horizontal lines on the grid image refer to lines parallel to the cylinder axis direction of the electrophotographic photosensitive member, and the vertical lines refer to lines perpendicular to the cylinder axis direction of the electrophotographic photosensitive member.

[0311] The results are shown in Tables 2 and 3.

[0312] [Table 2]

[0313]

[0314] [Table 3]

[0315]

[0316] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An electrophotographic photosensitive member comprising: conductive support, photosensitive layer and protective layer, Characterized in that the protective layer contains conductive particles, The content of the conductive particles in the protective layer is 40 volume % to 70 volume %, The volume resistivity of the protective layer is 1.0×10 9 Ω·cm to 1.0×10 14 Ω·cm, The conductive particles are titanium oxide particles containing niobium, and The content of niobium in the conductive particles is 2.6% to 10.0% by mass. The conductive particles are particles comprising the following substances: Anatase titanium oxide as a core material, and Titanium oxide covers the surface of the core material and contains niobium.

2. The electrophotographic photosensitive member according to claim 1, wherein the charge retention is 9.5 or more, the charge retention being determined by the following steps 1 to 4: Step 1: Under an environment of a temperature of 23° C. and a humidity of 50% RH, while rotating the electrophotographic photosensitive member at a rotation speed of 30 rpm, a voltage is applied to the surface of the electrophotographic photosensitive member from one direction, and the voltage is a rectangular wave voltage having a frequency of 1 Hz, a Voffset of −450 V, and a Vpp of 500 V; Step 2: measuring the potential on the surface of the electrophotographic photosensitive member at a position where the portion of the surface of the electrophotographic photosensitive member to which the voltage is applied rotates for 0.30 seconds at a measurement interval of 100 μs for a predetermined time within a range of 10 seconds to 20 seconds; Step 3: Plotting the values ​​obtained by measurement using μs as the unit of the horizontal axis and V as the unit of the vertical axis, and determining the slope of each of a regression line derived from the first 25 measurement points and a regression line derived from the last 25 measurement points at each measurement point; and Step 4: A value calculated by averaging the absolute values ​​of the maximum and minimum values ​​of the obtained slopes is defined as the charge retention property. 3 . The electrophotographic photosensitive member according to claim 1 , wherein the protective layer comprises a polymerization product of a composition containing a radical polymerizable monomer.

4. A processing cartridge, characterized in that: The process cartridge integrally supports the electrophotographic photosensitive member according to any one of claims 1 to 3 and at least one unit selected from the group consisting of a charging unit, a developing unit, and a cleaning unit, and is detachably mountable to a main body of an electrophotographic apparatus.

5. An electronic photographic device, characterized in that It includes the electrophotographic photosensitive member according to any one of claims 1 to 3, a charging unit, an exposure unit, a developing unit, and a transfer unit.

Images