Patent Application
20230350315
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.
In recent years, the diversification of the users of an electrophotographic apparatus has been advancing, and hence there has been a growing need for an electrophotographic photosensitive member that achieves high image quality for a longer term than a related-art one.
In International Publication No. WO2019/077705, as a technology concerning an improvement in image quality, there is a description of a technology including setting the internal stress value of an electroconductive support within the range of from −30 to 5 MPa.
In Japanese Patent Application Laid-Open No. 2009-150958, as a technology of improving image quality from the viewpoint of accuracy, there is a description of a technology including heating an element tube made of an Al alloy at from 190 to 550° C. before its cutting.
In addition, in Japanese Patent Application Laid-Open No. 2017-111409, there is a description of a technology including setting the average area of the crystal grains of an Al alloy having specific composition to from 3 to 100 μm2.
According to an investigation made by the inventors of the present invention, when an electrophotographic photosensitive member described in International Publication No. WO2019/077705, Japanese Patent Application Laid-Open No. 2009-150958, or Japanese Patent Application Laid-Open No. 2017-111409 was subjected to long-term storage under high temperature and high humidity, potential fluctuation at the time of continuous output was exacerbated, or reductions in electrophotographic characteristics, such as a reduction in sensitivity to exposure as compared to that before storage and the occurrence of an image defect, occurred in some cases.
Accordingly, an object of the present invention is to provide an electrophotographic photosensitive member that achieves both of the suppression of potential fluctuation at the time of continuous output and the suppression of reductions in electrophotographic characteristics, such as a reduction in sensitivity as compared to that before storage and the occurrence of an image defect, when subjected to long-term storage under high temperature and high humidity.
The object is achieved by the present invention described below. That is, an electrophotographic photosensitive member according to one aspect of the present invention includes: a support having a cylindrical shape; and a photosensitive layer, wherein a surface of the support is formed of Al and/or an Al alloy, wherein the surface of the support comprises Al crystal grains having: (α) a plane at −15° or more and less than +15° with respect to a {001} orientation; (β) a plane at −15° or more and less than +15° with respect to a {101} orientation; and (γ) a plane at −15° or more and less than +15° with respect to a {111} orientation, and wherein a ratio of an area occupied by the Al crystal grain having the (γ) to a total area of the surface of the support is more than 10% and 50% or less, and a ratio of an area occupied by the Al crystal grain having the (α) or the (β) to the remaining area is 80% or more.
A process cartridge according to another aspect of the present invention includes: 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, the process cartridge integrally supporting the electrophotographic photosensitive member and the at least one unit, and being removably mounted onto a main body of an electrophotographic apparatus.
An electrophotographic apparatus according to still another aspect of the present invention includes: the above-mentioned electrophotographic photosensitive member; a charging unit; an exposing unit; a developing unit; and a transferring unit.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The present invention is described in detail below by way of an exemplary embodiment.
With a view to solving the above-mentioned technical problems occurring in the related art, the inventors of the present invention have conceived that the characteristics of the surface of an aluminum-made support of an electrophotographic photosensitive member are important, and have investigated the orientations of polycrystalline crystal grains of the surface of the aluminum-made support.
Aluminum has the following three crystal orientations according to a broad classification: a {101} orientation, a {001} orientation, and a {111} orientation. As described in “Kobelnics” ([No. 28], Vol. 14, 2005. OCT), in general, for example, as illustrated in
In the present invention, the crystal grains having the above-mentioned three crystal orientations are expressed as follows:
An expression of an Al crystal orientation of the surface of the support in the present invention, such as a plane of the {001} orientation, is a representation of an Al crystal plane with Miller indices. That is, the plane of the {001} orientation is a comprehensive expression of Miller indices representing any one of the crystal lattice planes (001), (010), (100), (00-1), (0-10), and (−100).
It is known that crystal grains have crystal orientation dependence resulting from the arrangement and density of atoms. In an aluminum-made support in the related art, crystal grains having the three kinds of crystal orientations are randomly present at nearly equal ratios, and hence it is conceived that potential fluctuation tended to be relatively large owing to the contribution of the crystal grains each having (γ). Accordingly, it is preferred for an electron to flow easily from the viewpoint of suppressing potential fluctuation, and hence it is presumed that, for example, as illustrated in
In addition, it is conceived that, in an electrophotographic photosensitive member using the aluminum-made support in the related art, the oxidation of the surface of the support progresses to make it difficult for an electron to flow, resulting in a reduction in sensitivity. It is considered that, of the three kinds of crystal orientations, (γ) is most densely packed with atoms, and hence also has small surface energy and is stable. Accordingly, surface energy is preferably small from the viewpoint of stability against oxidation, and hence it is presumed that, for example, as illustrated in
For those reasons, it is presumed that, in order to achieve the object of the present invention, the ratio between the area of (α) and/or (β) and the area of (γ) needs to be appropriately balanced.
The inventors of the present invention have made extensive investigations, and as a result, the effect of the present invention has been obtained by setting the ratio of the area occupied by (γ) to the total area of the surface of the support to more than 10% and 50% or less. The ratio of the area occupied by (γ) to the total area of the surface of the support is preferably set to from 11 to 50%, and particularly when the ratio was set to from 20 to 40%, the effect of the present invention was able to be achieved more satisfactorily.
In addition, in general, a support for an electrophotographic photosensitive member, whose surface is formed of Al and/or an Al alloy, typically has an oxide film on the surface, and hence has satisfactory corrosion resistance. However, when the oxide film is not sufficient for some reason, corrosion occurs locally on the surface of the support to reduce electrophotographic characteristics in some cases. In particular, under a severe environment such as high temperature and high humidity, there arises a problem in that, among different kinds of local corrosion, galvanic corrosion, which occurs owing to the formation of a local battery between aluminum and a dissimilar metal, progresses.
Al and the Al alloy contain, to some extent, dissimilar metals, such as inevitable impurities and additives, which are also precipitated on the surface of the support. The dissimilar metals are abundantly found at a crystal grain boundary of Al, and corrosion caused thereby is called intergranular corrosion. As described above, (γ) is mostly densely packed with atoms among the three kinds of crystal orientations, and hence is stable. In contrast, however, it may be said that (α) and (β) are sparsely packed with atoms as compared to (γ). In addition, an orientation difference (angle) between (α) and (β) is larger than that between (α) and (γ) or between (β) and (γ). For those reasons, it is presumed that, at the time of the formation of crystal grains, the dissimilar metals are most liable to precipitate on the surfaces of the crystal grains between (α) and (β), and intergranular corrosion is liable to occur between the crystal grains having (α) and (β).
Accordingly, in order to suppress intergranular corrosion, the crystal grain boundary between (α) and (β) needs to be reduced, and it is presumed that the ratio of any one of (α) or (β) is desirably increased.
The inventors of the present invention have made extensive investigations, and as a result, the effect of the present invention has been obtained by setting the remaining area excluding (γ), that is, the ratio of the area occupied by any one of (α) or (β) to the total of the areas of (α) and (β) to 80% or more. The effect is conceived to be higher when the ratio of the area occupied by any one of (α) or (β) to the total of the areas of (α) and (β) is closer to 100%, but the upper limit is preferably about 95% from the standpoint of production cost and a technical standpoint.
General examples of the dissimilar metals, such as inevitable impurities and additives, contained in Al and/or the Al alloy include Si, Fe, Cu, Mg, Zn, Cr, Ti, and Mn. Of those, Mn solidly dissolves in Al, and hence hardly precipitates as a simple substance, thereby being less liable to cause intergranular corrosion, and hence is not included in the dissimilar metals in the present invention.
In addition, as the content of the dissimilar metals in the Al alloy becomes smaller, intergranular corrosion becomes less liable to occur. Specifically, the Al alloy preferably contains 1.0 mass % or less in total of the dissimilar metals Si, Fe, Cu, Mg, Zn, Cr, and Ti. However, the lower limit is preferably about 0.1 mass % from the standpoints of processability, strength, and production cost.
(Method of measuring Crystal Orientations of Al Crystal Grains of Surface of Support)
In the present invention, the crystal orientations of the Al crystal grains of the surface of the support may be measured, for example, as described below.
First, the surface of the support is treated, for example, by buffing and with an aqueous solution of sodium hydroxide, and the measurement of the crystal orientations of the Al crystal grains is performed for points within 20 μm from the surface of the support before the treatment. The measurement of the crystal orientations is preferably performed by an SEM-EBSP method.
A Field Emission-Scanning Electron Microscope (FE-SEM) including an Electron Back Scatter diffraction Pattern (EBSP) detector is used for the measurement by the SEM-EBSP method. Herein, the “EBSP” refers to a Kikuchi pattern (Kikuchi lines) obtained from backscattered electrons occurring when an electron beam is allowed to enter the surface of a test piece, and the crystal orientations at the electron beam incidence position can be determined by analyzing the pattern. In addition, the “Kikuchi pattern” refers to a pattern that appears behind an electron diffraction image in a pair of white and black parallel lines, in a band shape, or in an array shape at the time of scattering and diffraction of electron beams hit on a crystal.
For example, a field emission scanning electron microscope (product name: JSM-6500F, manufactured by JEOL Ltd.) may be used as the FE-SEM including the EBSP detector.
The ratio of the area occupied by the Al crystal grains having each of the above-mentioned crystal orientations may be determined as described below.
As illustrated in
The area occupied by the Al crystal grains having each crystal orientation may be calculated using software included with the microscope, or may be calculated by, for example, subjecting the orientations obtained through the measurement to hue mapping of the regions of the Al crystal grains having the respective crystal orientations in which the hue “h” of an HSV color space is used to determine the range of (α) to be 0≤h<60 and 300≤h<360, the range of (β) to be 60≤h<180, and the range of (γ) to be 180≤h<300.
In the present invention, the average area of the Al crystal grains in the surface of the support is preferably 5 μm2 or more. The average area of the Al crystal grains in the surface of the support may be determined as described below.
First, regions similar to those described above are observed, and the area of the region of each Al crystal grain identified through the observation is determined. Next, all Al crystal grains, each of which is in a 100 μm square region observed, and does not cross the region in the frame of the 100 μm square region, are used as a population, and an average is calculated for the areas of the regions occupied by the Al crystal grains.
[Electrophotographic Photosensitive Member]
An electrophotographic photosensitive member according to the present invention includes a support having a cylindrical shape and a photosensitive layer.
An example of a method of producing the electrophotographic photosensitive member according to the present invention is a method including: preparing coating liquids for respective layers to be described later; applying the liquids in a desired layer order; and drying the liquids. In this case, examples of a method of applying each of the coating liquids include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Of those, dip coating is preferred from the viewpoints of efficiency and productivity.
The support and the respective layers are described below.
<Support>
The electrophotographic photosensitive member according to the present invention includes a support having a cylindrical shape, and the surface of the support is formed of at least any one selected from Al and an Al alloy. In addition, the surface of the support may be subjected to, for example, hot water treatment, blast treatment, or cutting treatment.
<Al Alloy to be Used as Support>
From the viewpoint of controlling the crystal orientations, the support is preferably a 3000 series Al alloy such as a JIS A3003 alloy or a 6000 series Al alloy such as a JIS A6063 alloy. The JIS A3003 alloy is specifically an Al alloy containing 0.6 mass % or less of Si, 0.7 mass % or less of Fe, 0.05 to 0.2 mass % of Cu, 1.0 to 1.5 mass % of Mn, and 0.1 mass % or less of Zn. In addition, the JIS A6063 alloy is specifically an Al alloy containing 0.2 to 0.6 mass % of Si, 0.35 mass % or less of Fe, 0.1 mass % or less of Cu, 0.1 mass % or less of Mn, 0.45 to 0.9 mass % of Mg, 0.1 mass % or less of Cr, 0.1 mass % or less of Zn, and 0.1 mass % or less of Ti.
<Method of Producing Support>
A method of producing the support is not particularly limited as long as the method enables the production of a support that satisfies the requirement of the present invention.
An example of the method of producing the support is a method including the following four steps.
When the crystal orientations are controlled through annealing, the crystal orientations can be controlled by adjusting a temperature increase time, an annealing temperature, a maintenance time, and a cooling time.
In particular, when the annealing temperature is set to from 405 to 450° C., there occurs such recrystallization that planes of crystal grains having the (α) orientation and the (β) orientation appear on the surface. Accordingly, the ratio of the area occupied by the crystal grains having the (α) orientation and the (β) orientation in the surface of the support is increased.
In addition, for example, when a cooling rate is set to 8° C./min or more until the temperature of the support becomes 150° C., the appearance of the Al crystal grains each having the (β) crystal orientation on the surface is suppressed, and the Al crystal grains each having the (γ) crystal orientation easily appear on the surface. Accordingly, the ratio of the area occupied by the Al crystal grains each having the (β) crystal orientation in the surface of the support is reduced, and the ratio of the area occupied by the Al crystal grains each having the (γ) crystal orientation therein is increased.
Further, the crystal orientations are also changed by a temperature increase rate and the maintenance time, and hence it is preferred that the temperature increase rate be set to 40° C./min or less, and the maintenance time be set to 2.5 hours or less.
In addition, a thermal history is important at the time of the control of the crystal orientations, and hence a product that has undergone the above-mentioned steps of performing hot extrusion processing and cold drawing is preferably annealed before use.
<Electroconductive Layer>
In the present invention, an electroconductive layer may be arranged on the support. The arrangement of the electroconductive layer can conceal flaws and irregularities in the surface of the support, and control the reflection of light on the surface of the support.
The electroconductive layer preferably contains electroconductive particles and a resin.
A material for the electroconductive particles is, for example, a metal oxide, a metal, or carbon black.
Examples of the metal oxide include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of the metal include aluminum, nickel, iron, nichrome, copper, zinc, and silver.
Of those, a metal oxide is preferably used as the electroconductive particles, and in particular, titanium oxide, tin oxide, and zinc oxide are more preferably used.
When the metal oxide is used as the electroconductive 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.
In addition, each of the electroconductive particles may be of a laminated construction having a core particle and a coating layer coating the particle. Examples of the core particle include titanium oxide, barium sulfate, and zinc oxide. The coating layer is, for example, a metal oxide such as tin oxide.
In addition, when the metal oxide is used as the electroconductive particles, their volume-average particle diameter is preferably from 1 to 500 nm, more preferably from 3 to 400 nm.
Examples of the resin include a polyester resin, a polycarbonate resin, a polyvinyl acetal resin, an acrylic resin, a silicone resin, an epoxy resin, a melamine resin, a polyurethane resin, a phenol resin, and an alkyd resin.
In addition, the electroconductive layer may further contain a concealing agent, such as a silicone oil, resin particles, or titanium oxide.
The electroconductive layer has a thickness of preferably from 1 to 50 μm, particularly preferably from 3 to 40 μm.
The electroconductive layer may be formed by preparing a coating liquid for an electroconductive layer containing the above-mentioned materials and a solvent, forming a coat thereof, and drying the coat. Examples of the solvent to be used for the coating liquid include an alcohol-based solvent, a sulfoxide-based solvent, a ketone-based solvent, an ether-based solvent, an ester-based solvent, and an aromatic hydrocarbon-based solvent. As a dispersion method for dispersing the electroconductive particles in the coating liquid for an electroconductive layer, there are given methods including using a paint shaker, a sand mill, a ball mill, and a liquid collision-type high-speed disperser.
<Undercoat Layer>
In the present invention, an undercoat layer may be arranged on the support or the electroconductive layer. The arrangement of the undercoat layer can improve an adhesive function between layers to impart a charge injection-inhibiting function.
The undercoat layer preferably contains a resin. In addition, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.
Examples of the resin include a polyester resin, a polycarbonate resin, a polyvinyl acetal resin, an acrylic resin, an epoxy resin, a melamine resin, a polyurethane resin, a phenol resin, a polyvinyl phenol resin, an alkyd resin, a polyvinyl alcohol resin, a polyethylene oxide resin, a polypropylene oxide resin, a polyamide resin, a polyamic acid resin, a polyimide resin, a polyamide imide resin, and a cellulose resin.
Examples of the polymerizable functional group of the monomer having a polymerizable functional group 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 acid anhydride group, and a carbon-carbon double bond group.
In addition, the undercoat layer may further contain an electron-transporting substance, a metal oxide, a metal, an electroconductive polymer, and the like for the purpose of improving electric characteristics. Of those, an electron-transporting substance and a metal oxide are preferably used.
Examples of the electron-transporting substance include a quinone compound, an imide compound, a benzimidazole compound, a cyclopentadienylidene compound, a fluorenone compound, a xanthone compound, a benzophenone compound, a cyanovinyl compound, a halogenated aryl compound, a silole compound, and a boron-containing compound. 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 the undercoat layer as a cured film.
Examples of the metal oxide include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide. Examples of the metal include gold, silver, and aluminum.
In addition, the undercoat layer may further contain an additive.
The undercoat layer has a thickness of preferably from 0.1 to 50 μm, more preferably from 0.2 to 40 μm, particularly preferably from 0.3 to 30 μm.
The undercoat layer may be formed by preparing a coating liquid for an undercoat layer containing the above-mentioned materials and a solvent, forming a coat thereof, and drying and/or curing the coat. Examples of the solvent to be used for the coating liquid include an alcohol-based solvent, a ketone-based solvent, an ether-based solvent, an ester-based solvent, and an aromatic hydrocarbon-based solvent.
<Photosensitive Layer>
The photosensitive layer of the electrophotographic photosensitive member is mainly classified into (1) a laminate-type photosensitive layer and (2) a monolayer-type photosensitive layer. (1) The laminate-type photosensitive layer has a charge-generating layer containing a charge-generating substance and a charge-transporting layer containing a charge-transporting substance. (2) The monolayer-type photosensitive layer has a photosensitive layer containing both a charge-generating substance and a charge-transporting substance.
(1) Laminate-Type Photosensitive Layer
The laminate-type photosensitive layer includes the charge-generating layer and the charge-transporting layer.
(1-1) Charge-Generating Layer
The charge-generating layer preferably contains the charge-generating substance and a resin.
Examples of the charge-generating substance include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Of those, azo pigments and phthalocyanine pigments are preferred. Of the phthalocyanine pigments, an oxytitanium phthalocyanine pigment, a chlorogallium phthalocyanine pigment, and a hydroxygallium phthalocyanine pigment are preferred.
The content of the charge-generating substance in the charge-generating layer is preferably from 40 to 85 mass %, more preferably from 60 to 80 mass % with respect to the total mass of the charge-generating layer.
Examples of the resin include a polyester resin, a polycarbonate resin, a polyvinyl acetal resin, a polyvinyl butyral resin, an acrylic resin, a silicone resin, an epoxy resin, a melamine resin, a polyurethane resin, a phenol resin, a polyvinyl alcohol resin, a cellulose resin, a polystyrene resin, a polyvinyl acetate resin, and a polyvinyl chloride resin. Of those, a polyvinyl butyral resin is more preferred.
In addition, the charge-generating layer may further contain an additive, such as an antioxidant or a UV absorber. Specific examples thereof include a hindered phenol compound, a hindered amine compound, a sulfur compound, a phosphorus compound, and a benzophenone compound.
The charge-generating layer has a thickness of preferably from 0.1 to 1 μm, more preferably from 0.15 to 0.4 μm.
The charge-generating layer may be formed by preparing a coating liquid for a charge-generating layer containing the above-mentioned materials and a solvent, forming a coat thereof, and drying the coat. Examples of the solvent to be used for the coating liquid include an alcohol-based solvent, a sulfoxide-based solvent, a ketone-based solvent, an ether-based solvent, an ester-based solvent, and an aromatic hydrocarbon-based solvent.
(1-2) Charge-Transporting Layer
The charge-transporting layer preferably contains the charge-transporting substance and a resin.
Examples of the charge-transporting substance include a polycyclic aromatic compound, a heterocyclic compound, a hydrazone compound, a styryl compound, an enamine compound, a benzidine compound, a triarylamine compound, and a resin having a group derived from each of these substances. Of those, a triarylamine compound and a benzidine compound are preferred.
The content of the charge-transporting substance in the charge-transporting layer is preferably from 25 to 70 mass %, more preferably from 30 to 55 mass % with respect to the total mass of the charge-transporting layer.
Examples of the resin include a polyester resin, a polycarbonate resin, an acrylic resin, and a polystyrene resin. Of those, a polycarbonate resin and a polyester resin are preferred. A polyarylate resin is particularly preferred as the polyester resin.
A content ratio (mass ratio) between the charge-transporting substance and the resin is preferably from 4:10 to 20:10, more preferably from 5:10 to 12:10.
In addition, the charge-transporting layer may contain an additive, such as an antioxidant, a UV absorber, a plasticizer, a leveling agent, a slipperiness-imparting agent, or a wear resistance-improving agent. Specific examples thereof include a hindered phenol compound, a hindered amine compound, a sulfur compound, a phosphorus compound, a benzophenone compound, a siloxane-modified resin, a silicone oil, fluorine resin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.
The charge-transporting layer has a thickness of from 5 to 50 μm, more preferably from 8 to 40 μm, particularly preferably from 10 to 30 μm.
The charge-transporting layer may be formed by preparing a coating liquid for a charge-transporting layer containing the above-mentioned materials and a solvent, forming a coat thereof, and drying the coat. Examples of the solvent to be used for the coating liquid include an alcohol-based solvent, a ketone-based solvent, an ether-based solvent, an ester-based solvent, and an aromatic hydrocarbon-based solvent. Of those solvents, an ether-based solvent or an aromatic hydrocarbon-based solvent is preferred.
(2) Monolayer-Type Photosensitive Layer
The monolayer-type photosensitive layer may be formed by preparing a coating liquid for a photosensitive layer containing the charge-generating substance, the charge-transporting substance, a resin, and a solvent, forming a coat thereof, and drying the coat. Examples of the charge-generating substance, the charge-transporting substance, and the resin are the same as those listed as the materials in the section “(1) Laminate-type Photosensitive Layer.”
<Protective Layer>
In the present invention, a protective layer may be arranged on the photosensitive layer. The arrangement of the protective layer can improve durability.
The protective layer preferably contains electroconductive particles and/or a charge-transporting substance, and a resin.
Examples of the electroconductive particles include particles of metal oxides, such as titanium oxide, zinc oxide, tin oxide, and indium oxide.
Examples of the charge-transporting substance include a polycyclic aromatic compound, a heterocyclic compound, a hydrazone compound, a styryl compound, an enamine compound, a benzidine compound, a triarylamine compound, and a resin having a group derived from each of these substances. Of those, a triarylamine compound and a benzidine compound are preferred.
Examples of the resin include a polyester resin, an acrylic resin, a phenoxy resin, a polycarbonate resin, a polystyrene resin, a phenol resin, a melamine resin, and an epoxy resin. Of those, a polycarbonate resin, a polyester resin, and an acrylic resin are preferred.
In addition, the protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. As a reaction in this case, there are given, for example, a thermal polymerization reaction, a photopolymerization reaction, and a radiation polymerization reaction. Examples of the polymerizable functional group of the monomer having a polymerizable functional group include an acryloyl group and a methacryloyl group. A material having a charge-transporting ability may be used as the monomer having a polymerizable functional group.
The protective layer may contain an additive, such as an antioxidant, a UV absorber, a plasticizer, a leveling agent, a slipperiness-imparting agent, or a wear resistance-improving agent. Specific examples thereof include a hindered phenol compound, a hindered amine compound, a sulfur compound, a phosphorus compound, a benzophenone compound, a siloxane-modified resin, a silicone oil, fluorine resin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.
The protective layer has a thickness of preferably from 0.5 to 10 μm, more preferably from 1 to 7 μm.
The protective layer may be formed by preparing a coating liquid for a protective layer containing the above-mentioned materials and a solvent, forming a coat thereof, and drying and/or curing the coat. Examples of the solvent to be used for the coating liquid include an alcohol-based solvent, a ketone-based solvent, an ether-based solvent, a sulfoxide-based solvent, an ester-based solvent, and an aromatic hydrocarbon-based solvent.
[Process Cartridge and Electrophotographic Apparatus]
A process cartridge according to the present invention is characterized in that the process cartridge integrally supports the electrophotographic photosensitive member described above and at least one unit selected from the group consisting of: a charging unit; a developing unit; and a cleaning unit, and is removably mounted onto the main body of an electrophotographic apparatus.
In addition, an electrophotographic apparatus according to the present invention is characterized by including the electrophotographic photosensitive member described above and at least one unit selected from the group consisting of: a charging unit; an exposing unit; a developing unit; and a transferring unit.
An example of the schematic configuration of an electrophotographic apparatus including a process cartridge including an electrophotographic photosensitive member is illustrated in
An electrophotographic photosensitive member 1 having a cylindrical shape is rotationally driven about a shaft 2 in a direction indicated by the arrow at a predetermined peripheral speed. The surface of the electrophotographic photosensitive member 1 is charged to a predetermined positive or negative potential by a charging unit 3.
Although a roller charging system based on a roller-type charging member is illustrated in the figure, a charging system, such as a corona charging system, a contact charging system, or an injection charging system, may be adopted.
The charged surface of the electrophotographic photosensitive member 1 is irradiated with exposure light 4 from an exposing unit (not shown), and hence an electrostatic latent image corresponding to target image information is formed thereon. The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1 is developed with a toner stored in a 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 transferring unit 6. The transfer material 7 onto which the toner image has been transferred is conveyed to a fixing unit 8, is subjected to treatment for fixing the toner image, and is printed out to the outside of the electrophotographic apparatus.
The electrophotographic apparatus may include a cleaning unit 9 for removing a deposit such as the toner remaining on the surface of the electrophotographic photosensitive member 1 after the transfer. In addition, a so-called cleaner-less system in which the deposit is removed with the developing unit 5 or the like without separate arrangement of the cleaning unit 9 may be used.
The electrophotographic apparatus may include an electricity-removing mechanism for subjecting the surface of the electrophotographic photosensitive member 1 to electricity-removing treatment with pre-exposure light 10 from a pre-exposing unit (not shown). In addition, a guiding unit 12 such as a rail may be arranged for removably mounting a process cartridge 11 according to the present invention onto the main body of the electrophotographic apparatus.
The electrophotographic photosensitive member according to the present invention can be used in, for example, a laser beam printer, an LED printer, a copying machine, a facsimile, and a multifunctional peripheral thereof.
According to the present invention, the electrophotographic photosensitive member that achieves both of the suppression of potential fluctuation at the time of continuous output and the suppression of reductions in electrophotographic characteristics, such as a reduction in sensitivity through storage and the occurrence of an image defect, when subjected to long-term storage under high temperature and high humidity can be provided. In addition, according to the present invention, the process cartridge and the electrophotographic apparatus each capable of exhibiting a similar effect can be provided.
The present invention is described in more detail below by way of Examples and Comparative Examples. The present invention is by no means limited to the following Examples, and various modifications may be made without departing from the gist of the present invention. In the description in the following Examples, “part(s)” is by mass unless otherwise specified.
[Production of Support]
A support was produced by the following method.
An extruded tube formed of a JIS A6063 alloy and subjected to hot extrusion molding was subjected to cold drawing processing to provide a drawn tube having an outer diameter of 30.8 mm, an inner diameter of 28.5 mm, and a length of 370 mm.
Next, annealing is performed. The drawn tube was loaded into an electric furnace, increased in temperature at a temperature increase rate of 5° C./min, and then maintained at 420° C. for 2 hours. Subsequently, the drawn tube was cooled at 6° C./min until its temperature became 150° C., and was removed from the electric furnace after 24 hours.
The surface of the tube was subjected to mirror cutting after the annealing. Thus, “SupportA-1” having an outer diameter of 30.5 mm, an inner diameter of 28.5 mm, and a length of 370 mm was obtained. The production conditions of Support A-1 are shown in Table 1.
The elemental analysis of the drawn tube used showed that the tube was formed of an Al alloy containing 0.4 mass % of Si, 0.3 mass % of Fe, 0.06 mass % of Cu, 0.08 mass % or less of Mn, 0.65 mass % of Mg, 0.05 mass % of Cr, 0.07 mass % of Zn, and 0.06 mass % of Ti. The total of dissimilar metals (Si, Fe, Cu, Mg, Zn, Cr, and Ti) was 1.59 mass %.
Supports were each produced in the same manner as in the production example of Support A-1 except that in the production example of Support A-1, the same drawn tube was used, and the annealing conditions were changed as shown in Table 1. The resultant supports are referred to as “Support A-2 to Support A-10 and Support C-1 to Support C-11.” The production conditions of Supports A-2 to A-10 and C-1 to C-11 are shown in Table 1.
An extruded tube formed of an Al—Mg alloy (JIS A5005 alloy) and subjected to hot extrusion molding was subjected to cold drawing processing to provide a drawn tube having an outer diameter of 30.8 mm, an inner diameter of 28.5 mm, and a length of 370 mm.
Next, annealing is performed. The drawn tube was loaded into an electric furnace, increased in temperature at a temperature increase rate of 5° C./min, and then maintained at 420° C. for 2 hours. Subsequently, the drawn tube was cooled at 6° C./min until its temperature became 150° C., and was removed from the electric furnace after 24 hours.
The surface of the tube was subjected to mirror cutting after the annealing. Thus, “Support A-11” having an outer diameter of 30.5 mm, an inner diameter of 28.5 mm, and a length of 370 mm was obtained. The production conditions of Support A-11 are shown in Table 1.
The elemental analysis of the drawn tube used showed that the tube was formed of an Al alloy containing 0.07 mass % of Si, 0.06 mass % of Fe, 0.03 mass % of Cu, 0.67 mass % of Mg, 0.05 mass % of Cr, and 0.02 mass % of Zn. The total of dissimilar metals (Si, Fe, Cu, Mg, Zn, Cr, and Ti) was 0.9 mass %.
Supports were each produced in the same manner as in the production example of Support A-11 except that in the production example of Support A-11, the same drawn tube was used, and the annealing conditions were changed as shown in Table 1. The resultant supports are referred to as “Support C-12 and Support C-13.” The production conditions of Supports C-12 and C-13 are shown in Table 1.
An extruded tube formed of a JIS A3003 alloy and subjected to hot extrusion molding was subjected to cold drawing processing to provide a drawn tube having an outer diameter of 30.8 mm, an inner diameter of 28.5 mm, and a length of 370 mm.
Next, annealing is performed. The drawn tube was loaded into an electric furnace, increased in temperature at a temperature increase rate of 30° C./min, and then maintained at 435° C. for 1 hour. Subsequently, the drawn tube was cooled at 15° C./min until its temperature became 150° C., and was removed from the electric furnace after 24 hours.
The surface of the resultant was subjected to mirror cutting after the annealing. Thus, “Support B-1” having an outer diameter of 30.5 mm, an inner diameter of 28.5 mm, and a length of 370 mm was obtained. The production conditions of Support B-1 are shown in Table 1.
The elemental analysis of the drawn tube used showed that the tube was formed of an Al alloy containing 0.2 mass % of Si, 0.3 mass % of Fe, 0.09 mass % of Cu, 1.3 mass % of Mn, and 0.02 mass % of Zn. The total of dissimilar metals (Si, Fe, Cu, Mg, Zn, Cr, and Ti) was 0.61 mass %.
Supports were each produced in the same manner as in the production example of Support B-1 except that in the production example of Support B-1, the same drawn tube was used, and the annealing conditions were changed as shown in Table 1. The resultant supports are referred to as “Support B-2 to Support B-10 and Support D-1 to Support D-11.” The production conditions of Supports B-2 to B-10 and D-1 to D-11 are shown in Table 1.
[Production of Electrophotographic Photosensitive Member]
An electrophotographic photosensitive member was produced by forming a photosensitive layer on the surface of a support by the following method.
The support A-1 was used as a support.
Next, 100 parts of zinc oxide particles (specific surface area: 19 m2/g, powder resistivity: 3.6×106Ω·cm) serving as a metal oxide were stirred and mixed with 500 parts of toluene, and 0.8 part of a silane coupling agent was added to the mixture, followed by stirring for 6 hours. The silane coupling agent used is N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (product name: KBM-602, manufactured by Shin-Etsu Chemical Co., Ltd.). After that, toluene was evaporated under reduced pressure, and the residue was dried under heating at 130° C. for 6 hours to provide surface-treated zinc oxide particles.
Next, the following materials were prepared.
Those materials were dissolved in a mixed solution of 73.5 parts of methyl ethyl ketone and 73.5 parts of 1-butanol. 80.8 Parts of the surface-treated zinc oxide particles and 0.8 part of 2,3,4-trihydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to the solution, and the mixture was subjected to dispersion with a sand mill apparatus using glass beads each having a diameter of 0.8 mm under an atmosphere at 23±3° C. for 3 hours.
Next, the following materials were prepared.
Those materials were added to the solution after dispersion, and the mixture was stirred to prepare a coating liquid for an undercoat layer.
The coating liquid for an undercoat layer was applied onto the support by dip coating, and the resultant coat was dried for 40 minutes at 160° C. to form an undercoat layer having a thickness of 18 μm.
Next, the following materials were prepared.
Those materials were loaded into a sand mill using glass beads each having a diameter of 1 mm, and the mixture was subjected to dispersion treatment for 4 hours. After that, 700 parts of ethyl acetate was added to the dispersed product to prepare a coating liquid for a charge-generating layer. The coating liquid for a charge-generating layer was applied onto the undercoat layer by dip coating, and the resultant coat was dried for 15 minutes at 80° C. to form a charge-generating layer having a thickness of 0.17 μm.
Next, the following materials were prepared.
Those materials were dissolved in a mixed solvent of 600 parts of mixed xylene and 200 parts of dimethoxymethane to prepare a coating liquid for a charge-transporting layer. The coating liquid for a charge-transporting layer was applied onto the charge-generating layer by dip coating to form a coat, and the resultant coat was dried for 30 minutes at 100° C. to form a charge-transporting layer having a thickness of 18 μm.
Next, a mixed solvent of 20 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane (product name: ZEORORA H, manufactured by Zeon Corporation) and 20 parts of 1-propanol was filtered with a polyflon filter (product name: PF-040, manufactured by Advantec Toyo Kaisha, Ltd.).
In addition, the following materials were prepared.
Those materials were added to the mixed solvent. The mixture was filtered with a polyflon filter (product name: PF-020, manufactured by Advantec Toyo Kaisha, Ltd.) to prepare a coating liquid for a second charge-transporting layer (protective layer). The coating liquid for a second charge-transporting layer was applied onto the charge-transporting layer by dip coating, and the resultant coat was dried in the atmosphere for 6 minutes at 50° C. After that, in nitrogen, the coat was irradiated with electron beams for 1.6 seconds under the conditions of an acceleration voltage of 70 kV and an absorbed dose of 8,000 Gy while the support (irradiation target body) was rotated at 200 rpm. Subsequently, the coat was heated by increasing its temperature from 25° C. to 125° C. in nitrogen over 30 seconds. The oxygen concentrations of the atmosphere at the time of the electron beam irradiation and at the time of the heating after the irradiation were each 15 ppm. Next, the coat was subjected to heating treatment in the atmosphere for 30 minutes at 100° C. to form a 5-micrometer thick second charge-transporting layer (protective layer) cured by the electron beams.
Next, a linear groove was formed on the surface of the protective layer with a polishing sheet (product name: GC3000, manufactured by Riken Corundum Co., Ltd.). The feeding speed of the polishing sheet was set to 40 mm/min, the number of revolutions of the product to be processed was set to 240 rpm, and the pressing pressure of the polishing sheet against the product to be processed was set to 7.5 N/m2. The feeding direction of the polishing sheet and the rotation direction of the product to be processed were set to be the same direction. In addition, a backup roller having an outer diameter of 40 cm and an Asker C hardness of 40 was used. The linear groove was formed in the peripheral surface of the product to be processed under the foregoing conditions over 10 seconds.
Thus, Photosensitive Member A-1 was produced.
Electrophotographic photosensitive members were each produced in exactly the same manner as in Photosensitive Member A-1 except that a support shown in Table 2 was used. The resultant electrophotographic photosensitive members are referred to as “Photosensitive Member A-2 to Photosensitive Member A-11, Photosensitive Member B-1 to Photosensitive Member B-10, Photosensitive Member C-1 to Photosensitive Member C-13, and Photosensitive Member D-1 to Photosensitive Member D-11.”
[Evaluation]
The above-mentioned crystal orientation measurement method was performed for each of the produced supports.
Positions corresponding to ⅛, 2/8, ⅜, 4/8, ⅝, 6/8, and ⅞ of the full length of the support from one of the ends thereof in the axial direction thereof are determined. Further, at each of the positions, the support is divided into four parts of 90° each in the circumferential direction thereof. At each of the 28 points where the dividing lines in the axial direction and the dividing lines in the circumferential direction intersect, a 10 mm square fragment is cut out so that the point of intersection between the dividing line in the axial direction and the dividing line in the circumferential direction is at its center. The protective layer of each of the fragments was removed with a polishing sheet, and then the photosensitive layer thereof was removed with methyl ethyl ketone. After that, the surface of the support was exposed and subjected to mirror finishing by buffing. Next, the resultant was treated by being immersed in an aqueous solution of sodium hydroxide for 1 minute to provide a sample for crystal orientation observation.
Observation by the SEM-EBSP method was performed for a 100 μm square region set so that the center on the surface of the resultant sample, that is, the above-mentioned point of intersection between the dividing line in the axial direction of the support and the dividing line in the circumferential direction thereof was at its center, and the ratio of the area occupied by Al crystal grains having each crystal orientation and the average area of the Al crystal grains were calculated. The results are shown in Table 2.
[Storage under High Temperature and High Humidity]
One each of the produced supports and photosensitive members was stored under 50° C./95% RH for 28 days. Each photosensitive member was used for “evaluation of potential fluctuation,” “evaluation of sensitivity reduction,” and “evaluation of image defect” to be described later, and each support was used for “evaluation of intergranular corrosion” to be described later.
[Evaluation of Potential Fluctuation]
Each photosensitive member after the storage under high temperature and high humidity was stored under a 23° C./50% RH environment for 1 day, and was then subjected to the evaluation of potential fluctuation under the 23° C./50% RH environment by the following method.
The surface potential of the electrophotographic photosensitive member was measured as follows: a cartridge for development was removed from an evaluation apparatus (product name: imagePRESS C910, manufactured by Canon Inc.); a potential probe (product name: model 6000B-8, manufactured by Trek, Inc.) was set in the position of the cartridge; and the measurement was performed with a surface potentiometer (model 344: manufactured by Trek, Inc.). The position of the probe was set to the center position in the axial direction of the electrophotographic photosensitive member.
First, the dark potential (Vd) of the photosensitive member was adjusted to −600 V. Next, the exposure light quantity of an exposing apparatus was adjusted to 0.25 μJ/cm2. The measurement of a light potential was performed for 12 points arranged every 30° in the circumferential direction of the electrophotographic photosensitive member at the center position in the axial direction thereof, and an average in one circumference of the photosensitive member was calculated. The average was adopted as an initial potential.
After that, the cartridge for development was returned to the original position, and an A3 full-surface halftone image was continuously output on 2,000 sheets. After that, the potential probe was set in the position of the cartridge again, and an average in one circumference of the electrophotographic photosensitive member was calculated in the same manner as that described above. The average was adopted as a potential after endurance. Then, the absolute value of a difference between the potential after endurance and the initial potential was calculated, and was adopted as a measured value for potential fluctuation. In addition, the following ranking was performed for the measured value. The results are shown in Table 3.
[Evaluation of Sensitivity Reduction]
Each photosensitive member was evaluated for its sensitivity before and after the storage under high temperature and high humidity. The photosensitive member to be evaluated was stored under a 23° C./50% RH environment for 1 day, and was then evaluated under the 23° C./50% RH environment by the following method.
The same electrophotographic apparatus as the image evaluation apparatus was used for the evaluation, and the photosensitive member was mounted on its cyan station. The cartridge for development was removed, a potential probe (product name: model 6000B-8, manufactured by Trek, Inc.) was set in the position of the cartridge, and measurement was performed with a surface potentiometer (model 344: manufactured by Trek, Inc.). The position of the probe was set to the center position in the axial direction of the electrophotographic photosensitive member.
The dark potential (Vd) of the photosensitive member was adjusted to −600 V Next, the exposure light quantity of the exposing apparatus was adjusted to 0.25 μJ/cm2. The measurement of a light potential was performed for 12 points arranged every 30° in the circumferential direction of the electrophotographic photosensitive member at the center position in the axial direction thereof, and an average in one circumference of the photosensitive member was calculated. The average was adopted as the light potential of the photosensitive member. Then, the absolute value of a difference between light potentials after the storage under high temperature and high humidity and before the storage was calculated, and was adopted as a measured value for sensitivity reduction. In addition, the following ranking was performed for the measured value. The results are shown in Table 3.
[Evaluation of Image Defect]
Each photosensitive member was subjected to the evaluation of an image defect before and after the storage under high temperature and high humidity. The photosensitive member to be evaluated was stored under a 23° C./50% RH environment for 1 day, and was then subjected to the evaluation under the 23° C./50% RH environment by the following method.
The same electrophotographic apparatus as the image evaluation apparatus was used for the evaluation, and the photosensitive member was mounted on its cyan station. After automatic gradation correction had been performed, image evaluation was performed as described below.
Solid white and solid black images were output using A4 size paper GFC-081 (81.0 g/m2, Canon Marketing Japan Inc.), and the numbers of image defects, that is, black spots and white spots, in an area corresponding to one circumference of the electrophotographic photosensitive member in the output images were visually evaluated. The numbers of black spots and white spots each having a diameter of 0.1 mm or more were evaluated. The “area corresponding to one circumference of the electrophotographic photosensitive member” is a rectangular region having a length of 297 mm, which is the long-side length of A4 paper, and a width of 96.1 mm, which corresponds to one circumference of the electrophotographic photosensitive member.
No image defect was detected for the photosensitive member before the storage under the high-temperature and high-humidity environment. In addition, there was no image defect having a diameter of 0.2 mm or more even after storage. Accordingly, a result was obtained through evaluation for an image defect having a diameter of from 0.1 to 0.2 mm in the images for the photosensitive member after the storage under high temperature and high humidity. The following ranking was performed. The results are shown in Table 3.
[Evaluation of Intergranular Corrosion]
Each support after the storage under high temperature and high humidity was subjected to the evaluation of intergranular corrosion by the following method. Positions corresponding to ⅛, 2/8, ⅜, 4/8, ⅝, 6/8, and ⅞ of the full length of the support from one of the ends thereof in the axial direction thereof are determined. Further, at each of the positions, positions on the support divided into four parts of 900 each in the circumferential direction are determined. At each of the 28 points where the dividing lines in the axial direction and the dividing lines in the circumferential direction intersect, a 10 mm square region is set so that the point of intersection between the dividing line in the axial direction and the dividing line in the circumferential direction is at its center. Then, microscopic observation of the 100 mm2 region is performed, and when local corrosion of a size of 0.03 mm or more is present at a crystal grain boundary, it is determined that intergranular corrosion is present at that observation site. This was performed for 28 sites. In addition, the following ranking was performed. The results are shown in Table 3.
[Overall Evaluation]
Overall evaluation was performed for the results obtained by performing ranking for the above-mentioned three items (“evaluation of potential fluctuation,” “evaluation of sensitivity reduction,” and “evaluation of intergranular corrosion”) by the following criteria. The results are shown in Table 3.
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.
This application claims the benefit of Japanese Patent Application No. 2022-075304, filed Apr. 28, 2022, and Japanese Patent Application No. 2023-052149, filed Mar. 28, 2023, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-075304 | Apr 2022 | JP | national |
| 2023-052149 | Mar 2023 | JP | national |
