Electrophotographic photoreceptor, image forming apparatus, image forming system, and image forming method

Abstract

To provide an electrophotographic photoreceptor that has an extended length in an axial direction, and that can prevent dirt on an image when two-component developer including toner and carrier is used and can prevent uneven wear of the surface of the photoreceptor, an image forming apparatus, an image forming system, and an image forming method.SOLUTION: An electrophotographic photoreceptor includes a conductor support and a photosensitive layer laminated in this order. The length in an axial direction of the electrophotographic photoreceptor is 400 mm or more. The Martens hardness of the surface of the electrophotographic photoreceptor changes from one end to the other end in the axial direction. The difference between the maximum value and the minimum value of the Martens hardness in the axial direction is 10 N / mm2 or more and 100 N / mm2 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrophotographic photoreceptor, an image forming apparatus, an image forming system, and an image forming method. [Background technology]

[0002] In electrophotographic image forming apparatuses, an electrophotographic photoconductor (hereinafter also simply referred to as "photoconductor") is used to form an electrostatic latent image corresponding to the image to be formed. In electrophotographic image forming apparatuses, first, a photoconductor with a charged surface is irradiated with light to form an electrostatic latent image. Next, toner is supplied from a developing device (developing roller) to the photoconductor to form a toner image corresponding to the electrostatic latent image. Finally, the toner image is transferred and fixed onto a recording medium such as paper.

[0003] As an example of such a photoreceptor, Patent Document 1 discloses an electrophotographic photoreceptor in which a conductive substrate, an undercoat layer, a charge generating layer, a charge transport layer, and an inorganic protective layer are laminated in this order, and the undercoat layer, the charge transport layer, and the inorganic protective layer each have a film elastic modulus of 5 GPa or more. Patent Document 1 states that the electrophotographic photoreceptor can suppress the occurrence of dents on the outermost surface (inorganic protective layer) caused by hard objects such as carriers.

[0004] For example, Patent Document 2 discloses an image forming apparatus having an electrophotographic photoreceptor in which a conductive substrate, an organic photosensitive layer, and an inorganic protective layer are laminated in this order, and using a toner having an external additive liberation rate of 2% by mass or less. According to Patent Document 2, the image forming apparatus can suppress the formation of recesses on the photoreceptor surface due to carrier scattering.

[0005] For example, Patent Document 3 discloses an electrophotographic photoreceptor in which a conductive substrate, a photosensitive layer, and a surface protective layer containing a specific compound and a specific charge transport material are laminated in this order, and the hardness of the axial center of the photoreceptor surface is lower than that of both axial ends. Patent Document 3 states that the electrophotographic photoreceptor can suppress uneven wear of the surface protective layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-008688 A [Patent Document 2] JP 2017-062369 A [Patent Document 3] JP 2012-093382 A Summary of the Invention [Problem to be solved by the invention]

[0007] As disclosed in Patent Documents 1 to 3, various photoreceptors are known.

[0008] Photoreceptors are required to suppress uneven wear on their surfaces, because uneven wear causes a large gap between the cleaning blade and the photoreceptor in areas where wear is greatest, allowing toner to slip through the gap and making images more susceptible to staining.

[0009] Incidentally, electrophotographic image forming apparatuses are required to form images on recording media of various sizes, and in particular, there is an increasing demand for forming high-quality images on recording media of larger sizes (e.g., A3 size and B2 size).

[0010] Therefore, the present inventors have considered increasing the size of the photoconductor (specifically, the axial length of the photoconductor) in order to form an image on a recording medium of a larger size. The present inventors have also attempted to use a two-component developer containing toner and carrier from the viewpoint of facilitating the imparting of charge to the toner. However, when an image is formed on a photoconductor with a longer axial length using a two-component developer containing toner and carrier, uneven wear of the photoconductor surface is suppressed, but a problem occurs in which image stains occur at specific positions.

[0011] The present invention has been made in consideration of the above circumstances, and aims to provide an electrophotographic photoreceptor, an image forming apparatus, an image forming system, and an image forming method that are photoreceptors with an increased axial length, that can suppress image contamination when a two-component developer containing toner and carrier is used, and that can suppress uneven wear of the photoreceptor surface. [Means for solving the problem]

[0012] In order to achieve the above object, one aspect of the present invention relates to the following electrophotographic photoreceptors [1] to [9]. [1] A conductive support; A photosensitive layer; an electrophotographic photoreceptor including the above in the order of lamination, The length of the electrophotographic photoreceptor in the axial direction is 400 mm or more, the Martens hardness of the surface of the electrophotographic photosensitive member varies between one end and the other end in the axial direction, The difference between the maximum and minimum values ​​of the Martens hardness in the axial direction is 10 N / mm 2 More than 100N / mm 2 Below is the Electrophotographic photoreceptor. [2] The difference between the maximum and minimum Martens hardness values ​​is 15N / mm 2 More than 50N / mm 2 The electrophotographic photoreceptor according to [1], [3] The Martens hardness of the surface of the electrophotographic photoreceptor varies in a gradient from the one end to the other end along the axial direction. The electrophotographic photoreceptor according to [1] or [2]. [4] The average Martens hardness of the surface of the electrophotographic photoreceptor in the axial direction is 150 N / mm 2 More than 350N / mm 2 The electrophotographic photoreceptor according to any one of [1] to [3] below. [5] The average Martens hardness of the surface of the electrophotographic photoreceptor in the axial direction is 170 N / mm 2 More than 300N / mm 2 The electrophotographic photoreceptor according to any one of [1] to [4] below. [6] The electrophotographic photoreceptor according to any one of [1] to [5], further comprising a protective layer for protecting the photosensitive layer, the protective layer being disposed on a surface side of the photosensitive layer. [7] The electrophotographic photoreceptor according to [6], wherein the protective layer contains metal oxide particles. [8] The electrophotographic photoreceptor according to [7], wherein the protective layer is a cured product of a polymerizable composition containing a polymerizable compound. [9] The electrophotographic photoreceptor according to [8], wherein the polymerizable compound is a polymerizable compound that is polymerized by actinic rays.

[0013] In order to achieve the above object, one aspect of the present invention relates to an image forming apparatus according to the following items

[10] to

[13] .

[10] An electrophotographic photoreceptor according to any one of [1] to [9], a developing device for forming a toner image on the electrophotographic photoreceptor; Image forming device.

[11] The image forming apparatus according to

[10] , wherein the electrophotographic photosensitive member rotates at a peripheral speed of 280 mm / sec or more and 700 mm / sec or less.

[12] The developing device includes a container for containing a developer containing a toner and a carrier, and a developing roller for transporting the contained developer and supplying the toner to the electrophotographic photosensitive member, The image forming apparatus according to

[10] or

[11] , wherein the number of the developing rollers included in the developing device is two or more.

[13] An image forming apparatus as described in claim

[12] , wherein the developing roller rotates in a direction opposite to the rotation of the electrophotographic photosensitive member.

[0014] In order to achieve the above object, one aspect of the present invention relates to the image forming systems described below in

[14] and

[15] .

[14] An electrophotographic photoreceptor according to any one of [1] to [9], a developing device for forming a toner image on the electrophotographic photoreceptor; A developer containing a toner and a carrier, the developer being supplied to the developing device; having Image forming system.

[15] The image forming system according to

[14] , wherein the volume average particle diameter of the carrier is 20 μm or more and 70 μm or less.

[0015] In order to achieve the above object, one embodiment of the present invention relates to an image forming method according to the following items

[16] to

[18] .

[16] An image forming method using a two-component developer containing a toner and a carrier, A step of charging the surface of the electrophotographic photoreceptor according to any one of claims 1 to 9; applying the toner of the two-component developer to the surface of the charged electrophotographic photoreceptor; transferring the applied toner onto a recording medium; having Image forming method.

[17] The image forming method according to

[16] , wherein the volume average particle diameter of the carrier is 20 μm or more and 70 μm or less.

[18] The image forming method according to

[17] , wherein the volume average particle diameter of the carrier is 25 μm or more and 45 μm or less. Effect of the Invention

[0016] According to the present invention, there is provided an electrophotographic photoreceptor, an image forming apparatus, an image forming system, and an image forming method, which are photoreceptors with an increased axial length, and which can suppress image contamination when a two-component developer containing toner and carrier is used, and which can suppress uneven wear of the photoreceptor surface. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a partial cross-sectional view showing an exemplary layer structure of an electrophotographic photoreceptor according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a graph showing the change in Martens hardness in the axial direction of photoreceptors 1 to 4 in the examples of the present invention. [Figure 4] FIG. 4 is a graph showing the change in Martens hardness in the axial direction of photoreceptors 5 to 8 in an embodiment of the present invention. [Diagram 5] FIG. 5 is a graph showing the change in Martens hardness in the axial direction of photoreceptors 9 to 12 in an embodiment of the present invention. [Figure 6] FIG. 6 is a graph showing the change in Martens hardness in the axial direction of the photoreceptors 13 to 15 in an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1. Electrophotographic Photoreceptor 1 is a partial cross-sectional view showing an exemplary layer structure of an electrophotographic photoreceptor (hereinafter simply referred to as "photoreceptor") 100 in one embodiment of the present invention. The photoreceptor 100 in this embodiment has a conductive support 110, an intermediate layer 120, a charge generation layer 130, a charge transport layer 140, and a protective layer 150, which are laminated in this order. Note that the intermediate layer 120 and the protective layer 150 are optional components. In this specification, the charge generation layer 130 and the charge transport layer 140 are collectively referred to as the photosensitive layer.

[0019] The photoreceptor 100 in this embodiment has an axial length of 400 mm or more, and the Martens hardness of the surface of the photoreceptor 100 varies from one end to the other end in the axial direction. The difference between the maximum and minimum values ​​of the Martens hardness in the axial direction is 10 N / mm 2 More than 100N / mm 2 The following is the result.

[0020] As described above, by increasing the axial length of the photoconductor, it is possible to accommodate large-format printing, but when a two-component developer containing toner and carrier is used, image contamination occurs. The causes of this are considered to be as follows.

[0021] The developing device in the image forming apparatus includes a container for containing a developer, and a developing roller for conveying the contained developer and supplying the toner to the photoconductor. When a two-component developer containing a toner and a carrier is used, the container is replenished with toner from time to time, and the carrier and toner in the container are charged by being stirred.

[0022] In this case, as the axial length of the photoconductor was increased, the developing device (the storage section and the developing roller) also had to be increased in axial length to the same extent as the photoconductor. As a result, it is believed that the toner did not spread sufficiently in the area of ​​the storage section away from the toner supply position, and the amount of toner was significantly less than in the area close to the toner supply position. In contrast, the amount of carrier in the storage section in the axial direction tends to be constant because the toner is returned from the photoconductor to the storage section after being applied to the photoconductor. Therefore, it is believed that the amount of carrier relative to the amount of toner is excessive in the area away from the toner supply position compared to the area close to the toner supply position.

[0023] In this state, when the developer is transported by the developing roller, the amount of carrier becomes excessive relative to the amount of toner even in the area on the developing roller corresponding to the area where the amount of carrier is excessive. When the amount of carrier becomes excessive relative to the amount of toner, it is considered that the carrier is likely to come into contact with the surface of the photoconductor when the toner is supplied from the developing roller to the photoconductor, and when it comes into contact, the contact time with the surface of the photoconductor becomes longer. And, among the carriers transported by the developing roller, carriers with smaller particle diameters and carriers with lower magnetic properties are considered to be less likely to be held by the developing roller and more likely to fall off. From these facts, it is considered that in the area on the developing roller, when the toner is supplied from the developing roller to the photoconductor, the carriers that are likely to fall off the developing roller fall off (scatter) from the developing roller and become more likely to adhere to the surface of the photoconductor corresponding to the area.

[0024] If the carrier adheres to the photoreceptor, the carrier may rub against the photoreceptor during toner transfer, or may get into the gap between the cleaning blade and the photoreceptor, causing scratches (dents) on the surface of the photoreceptor. It is believed that when new toner is applied to a photoreceptor with such scratches, the toner will get into the scratches. If an image is formed in this state, it is believed that the toner that has gotten into the scratches is likely to cause image contamination, particularly in non-image forming areas.

[0025] In response to this, the inventors have discovered that the above-mentioned problem can be solved by changing the Martens hardness of the photoreceptor surface between one end and the other end in the axial direction of a photoreceptor 100 having an axial length of 400 mm or more.

[0026] By varying the Martens hardness of the photoreceptor surface in the axial direction, a region with higher hardness can be formed on the photoreceptor surface. Since this region has higher scratch resistance than other regions, by making the region of the photoreceptor 100 to which the carrier is likely to adhere a region with higher hardness than the above, it is possible to make the photoreceptor surface less susceptible to scratches caused by carrier adhesion. As a result, it is made difficult for toner to get into the scratches, and image contamination can be suppressed.

[0027] On the other hand, if the change in the Martens hardness in the axial direction (the difference between the maximum value and the minimum value) becomes too large, uneven wear of the photoconductor surface is likely to occur.

[0028] As a result of the study by the present inventors, it was decided that the difference between the maximum and minimum values ​​of the Martens hardness in the axial direction should be 10 N / mm 2 More than 100N / mm 2 It has been found that the uneven wear can be suppressed while suppressing the image staining by setting the following.

[0029] In addition, although Patent Document 1 and Patent Document 2 suppress the occurrence of scratches on the photoreceptor surface caused by the carrier, according to the inventors, when the axial length of these photoreceptors was increased, image staining could not be sufficiently suppressed.

[0030] Based on the above findings, the electrophotographic photoreceptor 100 according to this embodiment will be described below.

[0031] 1-1.Conductive support The conductive support 110 is a member that supports the intermediate layer 120, the charge generating layer 130, the charge transport layer 140, and the protective layer 150, and has a conductive surface that is in contact with at least the intermediate layer 120 (or the charge generating layer 130 when the photoreceptor 100 does not include the intermediate layer 120).

[0032] Examples of the conductive support 110 include a metal drum or sheet, a plastic film having a laminated metal foil, a plastic film having a layer of a vapor-deposited conductive material, a metal member having a conductive layer formed by applying a paint made of a conductive material or a conductive material and a binder resin, a plastic film, and paper. Examples of the metal include aluminum, copper, chromium, nickel, zinc, and stainless steel. Examples of the conductive material include the above metals, indium oxide, and tin oxide. The metal is preferably aluminum from the viewpoint of improving the workability and robustness of the conductive support 110 and making the conductive support 110 lighter. The thickness of the peripheral wall of the conductive support 110 can be, for example, 0.05 mm or more and 0.15 mm or less.

[0033] 1-2. Middle class The intermediate layer 120 is disposed between the conductive support 110 and the charge generation layer 130, and has a function of removing charges (typically electrons) from the charge generation layer 130 to the conductive support 110 side, a function of suppressing leakage of charges (typically holes) from the conductive support 110 to the charge generation layer 130, an adhesive function, etc. The intermediate layer 120 contains a binder resin for intermediate layers and conductive particles.

[0034] Examples of the binder resin for the intermediate layer include polyamide resin, casein, polyvinyl alcohol resin, nitrocellulose, ethylene-acrylic acid copolymer, vinyl chloride resin, vinyl acetate resin, polyurethane resin and gelatin. The binder resin for the intermediate layer may be one kind or more kinds.

[0035] Examples of the particle body of the conductive particles include metal oxide particles including aluminum oxide (alumina), aluminum hydroxide, zinc oxide, titanium oxide, tin oxide, antimony oxide, zirconium oxide, indium oxide, and bismuth oxide, as well as particles of conductive materials such as tin-doped indium oxide, antimony-doped tin oxide, and zirconium oxide.

[0036] From the viewpoint of further enhancing the ability to remove charges toward the conductive support in the intermediate layer 120, the conductive material is preferably an n-type semiconductor. Examples of the conductive material as the n-type semiconductor include titanium oxide, zinc oxide, aluminum oxide, aluminum hydroxide, and tin oxide. From the viewpoint of enhancing the conductivity of the intermediate layer 120 and enhancing the dispersibility of the conductive particles in the intermediate layer 120, the conductive material is preferably titanium oxide, tin oxide, and zinc oxide, and more preferably titanium oxide. The crystal type of the titanium oxide may be anatase type, rutile type, or amorphous type. The crystal type of the titanium oxide may be one type or more types.

[0037] The content of the conductive particles is, for example, preferably 50 parts by volume or more and 200 parts by volume or less, and more preferably 80 parts by volume or more and 120 parts by volume or less, relative to 100 parts by volume of the binder resin in the intermediate layer.

[0038] The thickness of the intermediate layer 120 is preferably 0.1 μm or more and 15.0 μm or less, and more preferably 0.3 μm or more and 10.0 μm or less.

[0039] 1-3. Charge generation layer The charge generating layer 130 includes, for example, a binder resin for the charge generating layer and a charge generating material dispersed in the binder resin for the charge generating layer.

[0040] Examples of the binder resin for the charge generating layer include formal resin, butyral resin, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, silicone modified butyral resin, phenoxy resin, melamine resin, copolymer resin containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin and vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, etc.), and poly-vinylcarbazole resin, etc. The binder resin for the charge generating layer may be one type or more than one type.

[0041] Examples of the charge generating material for the charge generating layer include azo raw materials including Sudan Red and Diane Blue, quinone pigments including pyrenequinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments including indigo and thioindigo, pyranthrone, diphthaloylpyrene polycyclic quinone compounds, and phthalocyanine pigments. The charge generating material for the charge generating layer may be one or more kinds.

[0042] The phthalocyanine pigment may have a central metal. Examples of the central metal include Ti, Fe, V, Si, Pb, Al, Zn, and Mg. The central metal may be one type or more. From the viewpoint of increasing the sensitivity of the charge generating layer, the phthalocyanine pigment is preferably a titanyl phthalocyanine compound having Ti as the central metal. From the same viewpoint, the titanyl phthalocyanine compound is preferably a Y-type titanyl phthalocyanine compound having a maximum peak at a Bragg angle (2θ±0.2) of 27.3° and clear diffraction peaks at 7.4°, 9.7°, and 24.2° in X-ray diffraction using CuKα rays, and a 2,3-butanediol adduct titanyl phthalocyanine having clear diffraction peaks at Bragg angles of 8.3°, 24.7°, 25.1°, and 26.5°.

[0043] The content of the charge generating material is preferably 20 parts by weight to 600 parts by weight, more preferably 50 parts by weight to 500 parts by weight, per 100 parts by weight of the binder resin for the charge generating layer. In a charge generating layer having a content of the charge generating material within the above range, the dispersibility of the charge generating material is increased, so that the electrical resistance of the charge generating layer is easily reduced, and an increase in residual charge accompanying use of the photoreceptor is more unlikely to occur.

[0044] The thickness of the charge generating layer 130 may be, for example, from 0.01 μm to 5 μm, preferably from 0.05 μm to 3 μm, more preferably from 0.05 μm to 2 μm, and even more preferably from 0.15 μm to 1.5 μm.

[0045] 1-4.Charge transport layer The charge transport layer 140 has, for example, a binder resin for the charge transport layer and a charge transporting compound dispersed in the binder resin for the charge transport layer. When the photoreceptor 150 does not have a protective layer 150 described later, the charge transport layer 140 constitutes the surface of the photoreceptor 100.

[0046] The binder resin for the charge transport layer is a thermoplastic resin or a thermosetting resin. Examples of the binder resin for the charge transport layer include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, and melamine resin. The binder resin for the charge transport layer may be a copolymer containing two or more kinds of repeating unit structures of the binder resin for the charge transport layer. Among these, the binder resin for the charge transport layer is preferably a polycarbonate resin having low water absorption and high mechanical strength.

[0047] Examples of the charge transporting compound include triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds and butadiene compounds. The charge transporting compound is preferably the following compound A and N-(4-methylphenyl)-N-{4-(β-phenylstyryl)phenyl}-p-toluidine, and is preferably compound A. The charge transporting compound may be one or more kinds.

[0048] [ka]

[0049] The content of the charge transporting compound is preferably 10 parts by mass or more and 200 parts by mass or less based on 100 parts by mass of the binder resin for the charge transport layer.

[0050] The charge transport layer 140 may be a single layer or may be composed of multiple layers. When composed of multiple layers, the charge transport layer 140 can be prepared by applying a solution of the binder resin for the charge transport layer, in which the charge transport compound is dispersed, onto an already prepared charge transport layer. When the charge transport layer 140 is composed of multiple layers, the number of layers of the charge transport layer 140 is preferably 2 to 4, more preferably 2 to 3.

[0051] The charge transport layer 140 may contain metal oxide particles for the charge transport layer. This can increase the strength of the charge transport layer 140. In particular, when the charge transport layer 140 constitutes the surface of the photoconductor 100, the metal oxide particles can further suppress the occurrence of scratches on the surface of the photoconductor 100 caused by the carrier, and can further suppress image staining due to toner slip-through. Examples of metal oxides that are materials for the metal oxide particles include titanium oxide, zinc oxide, alumina (aluminum oxide), silica (silicon dioxide), tin oxide, antimony oxide, indium oxide, bismuth oxide, magnesium oxide, lead oxide, tantalum oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, niobium oxide, molybdenum oxide, vanadium oxide, indium oxide doped with tin, tin oxide doped with antimony, and zirconium oxide. Of these, silica (silicon dioxide) and tin oxide are preferred. and the like are included.

[0052] The content of the metal oxide particles for the charge transport layer is preferably 5 to 100 parts by volume, more preferably 15 to 30 parts by volume, per 100 parts by volume of the binder resin of the charge transport layer 140.

[0053] The thickness of each layer of the charge transport layer 140 can be, for example, 5 μm or more and 40 μm or less. From the viewpoint of strengthening the internal electric field of the photoreceptor 100 and suppressing an increase in residual charge accompanying use of the photoreceptor 100, the thickness of the charge transport layer 140 is preferably 10 μm or more and 40 μm or less, and more preferably 10 μm or more and 30 μm or less. The thickness of the charge transport layer 140 can be appropriately adjusted depending on the type of binder resin for the charge transport layer 140 and the type and content of the charge transport compound.

[0054] The charge transport layer 140 may optionally contain other components, such as antioxidants.

[0055] The charge generating layer 130 and the charge transport layer 140 may be configured as a single-layer photosensitive layer. In this case, the photosensitive layer may be configured, for example, of a single layer containing a binder resin for the photosensitive layer, the charge transport compound, and the charge generating material. The thickness of the single-layer photosensitive layer may be, for example, 10 μm or more and 50 μm or less, and is preferably 20 μm or more and 40 μm or less.

[0056] Examples of the binder resin for the photosensitive layer constituting the single-layer photosensitive layer include polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, copolymer resin containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin), polyvinylcarbazole resin, polyacrylate resin, styrene-acrylonitrile copolymer resin, polymethacrylic acid ester resin, and styrene-methacrylic acid ester copolymer resin.

[0057] 1-5.Protective layer The protective layer 150 is a layer for protecting the charge generating layer 130 and the charge transport layer 140 (photosensitive layer). The protective layer 150 is disposed on the surface side of the charge transport layer 140 (photosensitive layer). In this case, the protective layer 150 constitutes the surface of the photoreceptor 100.

[0058] The protective layer 150 protects the surface of the photoreceptor 100, and improves scratch resistance by making the photoreceptor less susceptible to scratches caused by carriers. This reduces the occurrence of toner slippage, and further suppresses image staining. In addition, the protective layer 150 further suppresses uneven wear of the photoreceptor 100 surface.

[0059] The protective layer 150 includes, for example, a binder resin for the protective layer and a charge transporting compound for the protective layer.

[0060] Examples of the binder resin for the protective layer include polyvinyl butyral resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, alkyd resin, silicone resin, acrylic resin, melamine resin, and vinyl chloride-vinyl acetate copolymer. The binder resin for the protective layer may be one kind or more kinds.

[0061] The protective layer 150 (specifically, the binder resin for the protective layer) is preferably a cured product of a polymerizable composition containing a polymerizable compound. This enhances the durability of the surface of the photoreceptor 100, and further suppresses the occurrence of scratches on the surface of the photoreceptor 100 caused by the carrier. As a result, image staining can be further suppressed. In addition, at this time, the protective layer 150 can suppress uneven wear of the photoreceptor surface. In this case, the radical polymerizable composition may further contain metal oxide particles for the surface layer and a charge transport material for the surface layer, which will be described later.

[0062] Examples of the polymerizable compound include a polymerizable compound that is polymerized by heat (thermally polymerizable compound) and a polymerizable compound that is polymerized by actinic rays (actinic ray polymerizable compound), etc. Among these, the actinic ray polymerizable compound is preferred.

[0063] Examples of the thermally polymerizable compound include an epoxy compound, an isocyanate compound, a melamine compound, a urea compound, a urethane compound, and an ester compound.

[0064] Examples of the actinic radiation polymerizable compound include cationic polymerizable compounds and radical polymerizable compounds. Of these, radical polymerizable compounds are preferred. The radical polymerizable compound is a compound having a radical polymerizable functional group. The radical polymerizable functional group is preferably a (meth)acryloyl group. In this specification, the term "(meth)acryloyl group" refers to an acryloyl group or a methacryloyl group.

[0065] Examples of the radically polymerizable compound include compounds represented by the following formulae M1 to M15: In the following formulae M1 to M15, R represents an acryloyl group, and R' represents a methacryloyl group.

[0066] [ka] [ka]

[0067] Examples of actinic rays include electron beams, ultraviolet rays, α rays, γ rays, and X-rays, etc. Among these, ultraviolet rays and electron beams are preferred, and ultraviolet rays are more preferred.

[0068] From the viewpoint of making the surface of the photoreceptor 100 less susceptible to scratches caused by the carrier, the protective layer 150 preferably contains metal oxide particles for the protective layer. When the protective layer 150 contains metal oxide particles, unevenness can be formed on the surface of the protective layer 150, and the surface roughness can be increased. This reduces the contact area between the cleaning blade and the surface of the photoreceptor 100 (protective layer 150), and the wear and chatter of the cleaning blade can be suppressed. As a result, the toner can be more effectively prevented from slipping through between the cleaning blade and the photoreceptor 100. Furthermore, when the protective layer 150 contains metal oxide particles, the elastic deformation rate of the protective layer 150 can be improved. This prevents the carrier from sinking into the photoreceptor surface, and more effectively prevents scratches from being formed on the photoreceptor surface. For these reasons, image staining can be more effectively suppressed. Furthermore, the metal oxide particles for the protective layer can suppress uneven wear of the photoreceptor surface.

[0069] Examples of metal oxides constituting the metal oxide particles for the protective layer include titanium oxide, zinc oxide, alumina (aluminum oxide), silica (silicon dioxide), tin oxide, antimony oxide, indium oxide, bismuth oxide, magnesium oxide, lead oxide, tantalum oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, niobium oxide, molybdenum oxide, vanadium oxide, indium oxide doped with tin, tin oxide doped with antimony, and zirconium oxide. Among these, silica (silicon dioxide) and tin oxide are preferred. The metal oxide particles for the protective layer may be one type or more types.

[0070] The number average primary particle size of the metal oxide particles for the protective layer can be, for example, 1 nm or more and 300 nm or less, and is preferably 3 nm or more and 100 nm or less.

[0071] The particle size of the conductive particles can be determined by loading a 10,000x magnified photograph taken by a scanning electron microscope (manufactured by JEOL Ltd.) into a scanner, randomly selecting 300 particle images from the resulting photographic image, excluding aggregated particles, and binarizing the images using an automatic image processing and analysis system "LUZEX AP" (manufactured by Nireco Corporation, "LUZEX" is a registered trademark of the company, software Ver. 1.32) to calculate the horizontal Feret's diameter of each of the particle images, and then calculating the average value to obtain the number average primary particle size. Here, the horizontal Feret's diameter refers to the length of the side parallel to the x-axis of the circumscribing rectangle when the particle image is binarized.

[0072] The content of the metal oxide particles for the protective layer is preferably 5 to 100 parts by volume, more preferably 15 to 30 parts by volume, relative to 100 parts by volume of the binder resin in the protective layer. By having the content of the metal oxide particles for the protective layer within the above range, the strength of the protective layer 150 can be further increased, and the occurrence of scratches on the surface of the photoreceptor 100 due to the carrier can be further suppressed. In addition, the image quality stability and film formability of the protective layer 150 can be improved.

[0073] In order to improve the dispersibility of the metal oxide particles for the protective layer, the metal oxide particles for the protective layer are preferably surface-treated with a surface treatment agent.Examples of the surface treatment agent include silane coupling agents, titanium coupling agents, inorganic oxides, fluorine-modified silicone oils, fluorine-based surfactants and fluorine-based graft polymers.The surface treatment agent may be one type or more than one type.

[0074] When the surfaces of the metal oxide particles for the protective layer are surface-treated with the surface treatment agent, the components of the surface treatment agent after reaction are supported on the surfaces of the metal oxide particles in the protective layer. The surface treatment of the metal oxide particles for the protective layer can be performed by a known method.

[0075] From the viewpoint of further suppressing the occurrence of image memory, the protective layer preferably contains a charge transporting compound for the protective layer. The charge transporting compound for the protective layer is a compound that imparts charge transporting ability to the protective layer. The charge transporting compound for the protective layer may be appropriately selected from known compounds as long as it can exhibit the function. For example, when the protective layer is composed of a film polymerized and cured by ultraviolet light of the radical polymerizable composition, the charge transporting compound for the protective layer is preferably a compound that has low absorption of ultraviolet light or does not absorb ultraviolet light. The charge transporting compound for the protective layer includes triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, and butadiene compounds. The charge transporting compound is preferably the following compound A, and N-(4-methylphenyl)-N-{4-(β-phenylstyryl)phenyl}-p-toluidine.

[0076] The content of the charge transport compound for the protective layer is, for example, preferably 20 parts by mass or more and 100 parts by mass or less, more preferably 40 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the binder resin for the protective layer. When the content of the charge transport compound for the protective layer is 20 parts by mass or more, the occurrence of image memory is more easily suppressed. When the content of the charge transport compound for the protective layer is 100 parts by mass or less, the strength of the protective layer 150 is more increased.

[0077] The protective layer 150 may contain other components as necessary. Examples of the other components include a polymerization initiator and an antioxidant.

[0078] The polymerization initiator may be any one that can initiate polymerization of the polymerizable compound by heating or irradiation with active rays. For example, when the polymerizable compound is a radical polymerizable compound as an active ray polymerizable compound, the polymerization initiator can be a radical polymerization initiator. Note that, when the polymerizable compound can be polymerized by irradiation with electron beams, the polymerization initiator is not required. Examples of the polymerization initiator include Ominirad 819 (manufactured by IGM.Resin.BV).

[0079] The thickness of the protective layer 150 is, for example, preferably 0.2 μm or more and 10 μm or less, more preferably 0.5 μm or more and 6 μm or less, and even more preferably 1.5 μm or more and 5.0 μm or less.

[0080] 1-6. Physical properties of photoreceptors As described above, the Martens hardness of the surface of the photoreceptor 100 varies from one end to the other end in the axial direction of the photoreceptor 100. The difference between the maximum and minimum values ​​of the Martens hardness in the axial direction is 10 N / mm 2 More than 100N / mm 2 Less than 15N / mm 2 More than 75N / mm 2 More preferably, it is 15N / mm 2 More than 50N / mm 2More preferably, it is 15 N / mm or less. 2 By setting the carrier pressure to 75 N / mm or more, the occurrence of scratches on the surface of the photoconductor due to the carrier can be further suppressed, and image staining can be further suppressed. 2 By keeping the load below 50N / mm, uneven wear on the photoconductor surface can be suppressed. 2 By keeping the above-mentioned uneven wear at or below the above-mentioned range, it is possible to further suppress the uneven wear.

[0081] The Martens hardness can be measured under the following measurement conditions using an ultra-microhardness tester (H-100V, manufactured by Fisher Instruments Co., Ltd.). Indenter shape: Vickers indenter (a=136°) Measurement environment: 20℃, 60% RH Maximum test load: 3mN Loading speed: 3mN / 20sec Maximum load creep time: 5 seconds Unloading speed: 3mN / 20sec

[0082] Specifically, the Martens hardness is measured using the above device at three points that divide the circumferential direction of the photoconductor into equal angles, at 50 mm intervals from a position 30 mm from one end of the photoconductor to a position 30 mm from the other end in the axial direction of the photoconductor. At this time, by confirming that there is a maximum value and a minimum value among the measured hardness at each of the three points, it can be determined that the Martens hardness changes in the axial direction.

[0083] In addition, in this embodiment, the difference between the maximum and minimum values ​​of the Martens hardness can be obtained by calculating the difference between the maximum and minimum values ​​of the Martens hardness in the axial direction at each of the three points and averaging these.

[0084] The Martens hardness may vary linearly or exponentially from one end to the other end in the axial direction, or may vary so as to have a maximum value between the one end and the other end. The Martens hardness may vary linearly or exponentially from the one end to an arbitrary position, and may be a constant value from the position to the other end. Furthermore, the Martens hardness may be a first value (constant value) from the one end to an arbitrary position, and the difference from the first value from the arbitrary position to the other end may be 10 N / mm 2 More than 100N / mm 2 It may be a second value (a constant value) that is less than or equal to the first value.

[0085] It is preferable that the Martens hardness has a gradient change from one end to the other end in the axial direction. In this specification, "the Martens hardness has a gradient change" means that the Martens hardness of the surface of the photoreceptor 100 increases or decreases continuously from one end to the other end in the axial direction of the photoreceptor 100. The gradient change in the Martens hardness can be determined by confirming that the hardness at each measurement point in the axial direction of the three points is different from the hardness at the adjacent measurement points in the above measurement method.

[0086] In this embodiment, when the photoreceptor 100 includes the protective layer 150, and the protective layer 150 is a cured product of a polymerizable composition containing a polymerizable compound, the Martens hardness in the axial direction can be changed by changing the degree of polymerization of the polymerizable compound in the axial direction. For example, when the polymerizable compound is an actinic ray polymerizable compound, the Martens hardness in the axial direction can be changed by irradiating the protective layer coating liquid with actinic rays (e.g., ultraviolet rays) while changing the intensity of the actinic rays in the axial direction. In this case, for example, when the actinic rays are ultraviolet rays, the intensity (light amount) of the ultraviolet rays can be changed to 5 mW / cm. 2 More than 100mW / cm 2 It is preferable to vary the power within the range of 15 mW / cm 2 More than 80mW / cm 2 It is more preferable to change the power within the range of 25 mW / cm 2 More than 50mW / cm 2It is more preferable to vary it within the following ranges:

[0087] When the protective layer 150 does not contain a polymerizable compound, and when the photoreceptor 100 does not contain a protective layer 150, the Martens hardness in the axial direction can be changed by changing the dryness of the coating liquid for forming the outermost layer of the photoreceptor 100 (protective layer 150 not containing a polymerizable compound or charge transport layer 140) in the axial direction. For example, the Martens hardness can be changed by drying the coating liquid while changing the infrared output of an infrared dryer in the axial direction. In this case, the Martens hardness can be changed by setting the infrared output to 0.1 mW / cm. 2 More than 10mW / cm 2 It is preferable to change the power within the range of 1.0 mW / cm 2 More than 9.0mW / cm 2 It is more preferable to change the power within the range of 2.0 mW / cm 2 More than 7.5mW / cm 2 It is more preferable to vary it within the following ranges:

[0088] The average Martens hardness of the surface of the photoreceptor 100 in the axial direction is 150 N / mm 2 More than 350N / mm 2 It is preferable that the resistance is less than 170N / mm 2 More than 300N / mm 2 More preferably, it is 200N / N / mm or less. 2 More than 250N / mm 2 More preferably, it is equal to or less than 150N / mm 2 By satisfying the above conditions, the scratch resistance of the surface of the photoreceptor 100 can be improved, the occurrence of scratches caused by the carrier can be further suppressed, and image staining can be further suppressed. In addition, the wear resistance of the entire photoreceptor surface can be improved at this time, so uneven wear of the photoreceptor surface can be further suppressed. In addition, 2 By setting the thickness of the cleaning blade to be equal to or less than 1 mm, the surface of the photoconductor 100 can be appropriately worn down and refreshed by the cleaning blade. This makes it easier to remove moisture and discharge products adsorbed on the surface of the photoconductor 100, thereby suppressing image deletion.

[0089] The average value of the Martens hardness can be obtained by averaging the hardness at all the measurement points in the above-mentioned measurement method. In addition, when the protective layer 150 contains an actinic radiation polymerizable compound, the average value of the Martens hardness can be adjusted by adjusting the intensity of the actinic radiation (e.g., ultraviolet rays) irradiated to the protective layer coating liquid or the irradiation time of the actinic radiation. In addition, when the coating liquid for forming the outermost layer of the photoreceptor 100 is dried using an infrared drier, the average value of the Martens hardness can be adjusted by adjusting the infrared output or irradiation time.

[0090] In this embodiment, the length of the photoreceptor 100 in the axial direction is 400 mm or more.

[0091] 1-7. Photoconductor manufacturing method The method for producing the photoreceptor 100 includes, for example, a step of forming an intermediate layer 120 on the surface of the conductive support 110, a step of forming a photosensitive layer (charge generating layer 130 and charge transport layer 140) on the conductive support 110 (intermediate layer 120), and a step of forming a protective layer 150 on the photosensitive layer. Note that the step of forming the intermediate layer 120 and the step of forming the protective layer 150 are optional components.

[0092] (Formation of intermediate layer 120) In the step of forming the intermediate layer 120, an intermediate layer coating liquid containing the above-mentioned conductive fine particles, a binder resin for the intermediate layer, and a solvent is applied, and then dried and solidified to form the intermediate layer 120. The intermediate layer coating liquid is preferably prepared by dispersing the above-mentioned components using a sand mill or the like.

[0093] Examples of the solvent used in the intermediate layer coating solution include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, and sec-butanol.

[0094] The method for applying the intermediate layer coating solution is not particularly limited, and may be a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, a circular amount control type coating method, or the like.

[0095] (Formation of Charge Generation Layer 130) In the step of forming the charge generation layer 130, a charge generation layer coating liquid containing a charge generation material, a binder resin for the charge generation layer, and a solvent is applied onto the conductive support 110 (or onto the intermediate layer 120 if a step of forming an intermediate layer is performed), and then dried and solidified to form the charge generation layer 130. The charge generation layer coating liquid is preferably prepared by dispersing the above components using a sand mill or the like.

[0096] Examples of the solvent used in the charge generating layer coating liquid include toluene, xylene, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine.

[0097] The method for applying the charge generating layer coating solution is not particularly limited, and may be a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, a circular amount control type coating method, or the like.

[0098] (Formation of Charge Transport Layer 140) In the step of forming the charge transport layer 140, a charge transport layer coating liquid containing a charge transport compound, a binder resin for the charge transport layer, and a solvent is applied onto the charge generation layer 130, and then dried and solidified to form the charge transport layer 140. The charge transport layer coating liquid can be prepared by stirring the above components by a known stirring method.

[0099] Examples of the solvent used in the charge transport layer coating solution include toluene, xylene, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane.

[0100] The method for applying the charge transport layer coating solution is not particularly limited, and may be a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, a circular amount control type coating method, or the like.

[0101] The charge transport layer coating solution may be dried by natural drying, heat drying, or drying using an infrared dryer. When the charge transport layer 140 constitutes the surface of the photoreceptor 100, it is preferable to dry it using an infrared dryer. At this time, as described above, by drying while changing the infrared output in the axial direction of the photoreceptor 100, the Martens hardness in the axial direction of the photoreceptor 100 can be changed.

[0102] (Formation of protective layer 150) In the step of forming the protective layer 150, a protective layer coating liquid containing a binder resin for the protective layer, a charge transport compound for the protective layer, and other components as necessary is applied onto the photosensitive layer and solidified to form the protective layer 150. The protective layer coating liquid is preferably prepared by stirring the components in a light-shielding environment by a known stirring method.

[0103] Examples of solvents used in the protective layer coating solution include toluene, xylene, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, 2-butanol, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone.

[0104] The method for applying the protective layer coating solution is not particularly limited, and may be a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, a circular amount control type coating method, or the like.

[0105] The method for solidifying the protective layer coating liquid is, for example, a drying and solidifying method, but when the protective layer coating liquid contains a polymerizable compound, it is preferable to use a method in which the protective layer coating liquid is heated or irradiated with active rays to polymerize the polymerizable compound and harden the protective layer coating liquid. At this time, as described above, the Martens hardness can be changed by changing the polymerization degree of the polymerizable compound in the axial direction of the photoreceptor 100.

[0106] 2. Image forming apparatus and image forming system 2 is a schematic diagram showing the configuration of an image forming apparatus according to one embodiment of the present invention. Image forming apparatus 10 has an image reading section 20, an image forming section 30 (including a photoconductor 32 (the above-mentioned photoconductor 100) and a developing device 35), an intermediate transfer section 40, a fixing device 60, and a recording medium conveying section 80. The configuration of image forming apparatus 10 other than the photoconductor 32 can be the same as that of a known image forming apparatus.

[0107] The image reading unit 20 reads an image from the document D and obtains image data for forming an electrostatic latent image. The image reading unit 20 includes a paper feeder 21, a scanner 22, a CCD sensor 23, and an image processing unit 24.

[0108] The image forming section 30 includes, for example, four image forming units 31 corresponding to the respective colors of yellow, magenta, cyan, and black. The image forming unit 31 has a photoconductor (electrophotographic photoconductor) 32, a charging device 33, an exposure device 34, a developing device 35, and a cleaning device 36.

[0109] The photoconductor 32 is a negatively charged organic photoconductor having photoconductivity. The photoconductor 32 is charged by the charging device 33. The charging device 33 is a contact-type charging device that charges the photoconductor 32 by contacting a contact charging member such as a charging roller or a charging brush with the photoconductor 32, for example, a contact-type charging device that charges the photoconductor 32 by contact with the photoconductor 32 using a charging roller. The peripheral speed of the photoconductor 32 is preferably 280 mm / sec or more and 700 mm / sec or less, and more preferably 300 mm / sec or more and 650 mm / sec or less. By making the peripheral speed 280 mm / sec or more, it is possible to suppress the charge amount on the photoconductor surface from decreasing from when the photoconductor surface is charged until the toner is supplied, and to make it difficult for the electrostatic latent image to disappear. This makes it easier to form a toner image. In addition, by making the peripheral speed 700 mm / sec or less, the photoconductor 32 is made less susceptible to wear, and image smearing due to toner slipping through and uneven wear of the photoconductor 32 can be further suppressed. In addition, by setting the peripheral speed to 700 mm / sec or less, the surface of the photoconductor can be more easily refreshed by the cleaning blade, and moisture and discharge products on the surface of the photoconductor can be more effectively removed, thereby making it possible to more effectively suppress image deletion.

[0110] In this embodiment, the above-described photoreceptor 100 is used as the photoreceptor 32 in FIG.

[0111] The exposure device 34 forms an electrostatic latent image by irradiating light onto the charged photoconductor 32. The exposure device 34 is, for example, a semiconductor laser.

[0112] The developing device 35 supplies toner to the photoconductor 32 on which the electrostatic latent image is formed, to form a toner image corresponding to the electrostatic latent image. Here, the term "toner image" refers to a state in which the toner is aggregated in the form of an image. Any known toner can be used as the toner. The toner may be a one-component developer or a two-component developer. The one-component developer is composed of toner particles. The two-component developer is composed of toner particles and carrier particles. The toner particles are composed of toner base particles and an external additive such as silica attached to the surface of the toner base particles. The toner base particles are composed of, for example, a binder resin, a colorant, and a wax.

[0113] Examples of the carrier material include conventionally known materials such as ferromagnetic metals such as iron, alloys of ferromagnetic metals with metals such as aluminum and lead, and oxides of ferromagnetic metals such as ferrite and magnetite. Among these, ferrite is particularly preferred.

[0114] The carrier is preferably a carrier whose surface is coated with a resin, or a resin-dispersed carrier in which magnetic particles are dispersed in a resin. The type of the resin is not particularly limited, but a cyclohexyl methacrylate-methyl methacrylate copolymer or the like is preferable.

[0115] When the two-component developer is used, the developing device 35 may have, for example, a storage section 35a for storing the two-component developer and a developing roller 35b for transporting the stored developer and supplying toner to the photoconductor 32. In this case, the number of developing rollers 35b included in the developing device 35 is preferably two or more. In an image forming apparatus using a photoconductor with an increased axial length, when there are two or more developing rollers, the contact time between the carrier included in the transported developer and the photoconductor becomes longer. Therefore, the carrier is more likely to adhere to the photoconductor, and scratches are generated on the photoconductor surface corresponding to the above-mentioned area where the carrier is excessive, which makes it easy for image stains to occur. In contrast, the photoconductor 32 (the above-mentioned photoconductor 100) in this embodiment can suppress the generation of scratches on the photoconductor surface corresponding to the above-mentioned area where the carrier is excessive, so that the effect of the present invention becomes more pronounced when there are two or more developing rollers.

[0116] It is preferable that the developing roller 35b rotates in the opposite direction to the rotation of the photoconductor 32. In an image forming apparatus using a photoconductor with an increased axial length, when the developing roller 35b rotates in the opposite direction to the photoconductor 32, the contact time between the carrier contained in the transported developer and the photoconductor becomes longer. Therefore, scratches are likely to occur on the photoconductor surface corresponding to the above-mentioned area where the carrier is excessive, and image stains are likely to occur. In contrast, the photoconductor 32 (the above-mentioned photoconductor 100) in this embodiment can suppress the generation of scratches on the photoconductor surface corresponding to the above-mentioned area where the carrier is excessive, so that the effect of the present invention becomes more pronounced when the developing roller 35b rotates in the opposite direction to the photoconductor 32.

[0117] The cleaning device 36 removes residual toner from the photoreceptor 32. The cleaning device 36 includes, for example, a cleaning blade.

[0118] The intermediate transfer section 40 includes a primary transfer unit 41 and a secondary transfer unit 42 .

[0119] The primary transfer unit 41 has an intermediate transfer belt 43, a primary transfer roller 44, a backup roller 45, a plurality of first support rollers 46, and a cleaning device 47. The intermediate transfer belt 43 is an endless belt. The intermediate transfer belt 43 is stretched by the backup roller 45 and the first support roller 46. The intermediate transfer belt 43 runs in one direction at a constant speed on an endless track by at least one of the backup roller 45 and the first support roller 46 being rotationally driven.

[0120] The secondary transfer unit 42 includes a secondary transfer belt 48, a secondary transfer roller 49, and a plurality of second support rollers 50. The secondary transfer belt 48 is an endless belt. The secondary transfer belt 48 is stretched by the secondary transfer roller 49 and the second support rollers 50.

[0121] The fixing device 60 includes a fixing belt 61, a heating roller 62, a first pressure roller 63, a second pressure roller 64, a heater, a temperature sensor, an airflow separating device, a guide plate, and a guide roller.

[0122] The fixing belt 61 is made up of a base layer, an elastic layer, and a release layer laminated in this order. The fixing belt 61 is supported by a heating roller 62 and a first pressure roller 63 with the base layer on the inside and the release layer on the outside.

[0123] The heating roller 62 has a rotatable aluminum sleeve and a heater disposed therein. The first pressure roller 63 has, for example, a rotatable core metal and an elastic layer disposed on the outer circumferential surface thereof.

[0124] The second pressure roller 64 is disposed opposite the first pressure roller 63 via the fixing belt 61. The second pressure roller 64 is disposed so as to be able to approach and move away from the first pressure roller 63, and when the second pressure roller 64 approaches the first pressure roller 63, it presses the elastic layer of the first pressure roller 63 via the fixing belt 61, forming a fixing nip portion which is a contact portion with the fixing belt 61.

[0125] The airflow separating device is a device for promoting separation of the recording medium S from the fixing belt 61 by generating an airflow from the downstream side in the moving direction of the fixing belt 61 toward the fixing nip portion.

[0126] The guide plate is a member for guiding the recording medium S having an unfixed toner image thereon to the fixing nip portion. The guide roller is a member for guiding the recording medium S having the fixed toner image thereon from the fixing nip portion to the outside of the image forming apparatus 10.

[0127] The recording medium transport section 80 has three paper feed tray units 81 and a plurality of registration roller pairs 82. The paper feed tray unit 81 accommodates recording media S (standard paper, special paper, etc. in this embodiment) identified based on basis weight, size, etc., by preset type. The registration roller pairs 82 are arranged to form a desired transport path.

[0128] In such an image forming apparatus 10, first, the photoconductor 32, which has been charged by contact with a charging roller, is irradiated with light to form an electrostatic latent image, and then toner is supplied to the surface of the photoconductor 32 to form a toner image corresponding to the electrostatic latent image. The toner image is transferred to the recording medium S by the intermediate transfer unit 40, which is fed by the recording medium conveying unit 80. The recording medium S to which the toner image has been transferred by the intermediate transfer unit 40 is fixed to the recording medium S by the fixing device 60. The recording medium to which the toner image has been fixed is guided by a guide roller toward the outside of the image forming apparatus 10. In this manner, an image can be formed.

[0129] The image forming apparatus 10 may have a lubricant supplying section (not shown) for supplying a lubricant to the surface of the photoconductor. By supplying a lubricant to the photoconductor, the surface of the photoconductor becomes less susceptible to wear.

[0130] In this specification, in image forming apparatus 10 having the above-mentioned photoconductor 32 (photoconductor 100) and developing device 35, a state in which developer containing toner and carrier is supplied to developing device 35 is defined as an image forming system.

[0131] In the image forming system, the volume average particle diameter of the carrier is preferably 20 μm or more and 70 μm or less, and more preferably 25 μm or more and 45 μm or less. When the particle diameter is 20 μm or more, the carrier is less likely to separate (scatter) from the developing roller, and the generation of scratches on the photoreceptor surface by the carrier can be further suppressed, thereby further suppressing image staining. When the particle diameter is 70 μm or less, the time until the charge amount of the toner becomes stable can be shortened. The volume average particle diameter can be measured by HELOS, a laser diffraction type particle size distribution measuring device equipped with a wet disperser, manufactured by SYMPATEC.

[0132] 3.Image forming method The image forming method in this embodiment is an image forming method using a two-component developer containing toner and a carrier, and includes the steps of charging the surface of the photoreceptor 32 (photoreceptor 100), applying the toner of the developer to the charged surface of the photoreceptor 32 (photoreceptor 100), and transferring the applied toner to a recording medium. The image forming method can be performed using the image forming apparatus 10.

[0133] The two-component developer is composed of a toner and a carrier. The toner is composed of toner base particles and an external additive such as silica attached to the surface of the toner base particles. The toner base particles are composed of, for example, a binder resin, a colorant, and a wax. The volume average particle diameter of the carrier is preferably 20 μm or more and 70 μm or less, and more preferably 25 μm or more and 45 μm or less. When the particle diameter is 20 μm or more, the carrier is less likely to separate (scatter) from the developing roller, and the generation of scratches on the photoreceptor surface by the carrier can be further suppressed, thereby further suppressing image staining. When the particle diameter is 70 μm or less, the time until the charge amount of the toner is stabilized can be shortened.

[0134] 3-1. Charging process In this process, the surface of the photoconductor 32 is charged. Specifically, the charging roller in the charging device 33 is brought into contact with the photoconductor 32, so that the surface of the photoconductor 32 can be charged.

[0135] 3-2. Process of forming electrostatic latent image In this embodiment, the image forming method may include a step of forming an electrostatic latent image by irradiating light onto the surface of the charged photoconductor 32. Specifically, this step includes irradiating light onto the charged photoconductor 32 by the exposure device 34 to form an electrostatic latent image.

[0136] 3-3. Toner application process In this process, toner is applied to the charged surface of the photoreceptor 32 (on which an electrostatic latent image is formed). Specifically, the developer contained in the container 35a of the developing device 35 is transported by the developing roller 35b, and the toner of the developer that is charged with a polarity opposite to that of the photoreceptor 32 is applied to the surface of the photoreceptor 32. If the image forming method includes a process of forming the electrostatic latent image, a toner image corresponding to the electrostatic latent image can be formed by this process.

[0137] 3-4. Transfer process In this step, the toner applied to the surface of the photoreceptor 32 is transferred to the recording medium. Specifically, in the image forming apparatus 10, the toner is transferred from the photoreceptor 32 to the intermediate transfer unit 40, and the toner image is transferred from the intermediate transfer unit 40 to the recording medium S sent by the recording medium conveying unit 80. Note that in this embodiment, the toner image may be transferred directly from the photoreceptor 32 to the recording medium S. In this embodiment, a step of fixing the transferred toner image may be included after this step. EXAMPLES

[0138] The present invention will now be described with reference to examples, which should not be construed as limiting the scope of the present invention.

[0139] 1. Preparation of electrophotographic photoreceptor 1-1. Preparation of photoreceptor 1 Photoreceptor 1 was prepared by the following procedure, in which an intermediate layer, a charge generating layer, a charge transport layer and a protective layer were laminated in this order on a conductive support.

[0140] <Conductive support> The surface of a drum-shaped aluminum support having a diameter of 60 mm and a length in the direction of the rotation axis of 600 mm was machined to prepare a conductive support.

[0141] <Middle Class> Using a sand mill as a dispersing machine, a mixture of the following components was subjected to a batch-type dispersion treatment for 10 hours. The mixture was then diluted twice with methanol, allowed to stand overnight, and filtered using a Rigimesh 5 μm filter manufactured by Nippon Pall Corporation to obtain an intermediate layer coating solution. Binder resin: 1 part by weight of polyamide resin (Amilan CM8000, manufactured by Toray Industries, Inc.) (Amilan is a registered trademark of the company.) Titanium oxide (Teika Corporation, SMT500SAS) 3 parts by weight Methanol 10 parts by weight

[0142] The intermediate layer coating solution was applied to the surface of the conductive support by dip coating so as to give a dry film thickness of 2 μm, and then dried to obtain an intermediate layer.

[0143] <Charge generation layer> Using a sand mill as a dispersing machine, a mixture of the following components was subjected to a dispersion treatment for 10 hours to obtain a charge generating layer coating liquid. Charge generating material: pigment (a mixed crystal of a 1:1 adduct of titanyl phthalocyanine and (2R,3R)-2,3-butanediol, which has clear peaks at 8.3°, 24.7°, 25.1°, and 26.5° in Cu-Kα characteristic X-ray diffraction spectrum measurement, and unadducted titanyl phthalocyanine) 20 parts by mass Polyvinyl butyral resin (#6000-C, manufactured by Denki Kagaku Kogyo Co., Ltd.) 10 parts by mass t-Butyl acetate 700 parts by mass 4-Methoxy-4-methyl-2-pentanone 300 parts by mass

[0144] The charge generating layer coating liquid was applied to the surface of the intermediate layer by dip coating so as to give a dry film thickness of 0.3 μm, and then dried to obtain a charge generating layer.

[0145] The above pigment was synthesized as follows.

[0146] (Synthesis of titanyl phthalocyanine) 29.2 parts by mass of 1,3-diiminoisoindoline was added to 200 parts by mass of o-dichlorobenzene and stirred, and 20.4 parts by mass of titanium tetra-n-butoxide was added thereto, and the mixture was heated and stirred at a temperature of 150 to 160°C for 5 hours under a nitrogen atmosphere. After that, the mixture was allowed to cool to precipitate crystals, which were then filtered and taken out. The crystals thus taken out were then washed with chloroform, washed with a 2% aqueous hydrochloric acid solution, washed with water and methanol, and dried. As a result, 26.2 parts by mass (yield 91%) of crude titanyl phthalocyanine was obtained.

[0147] The crude titanyl phthalocyanine was dissolved in 250 parts by mass of concentrated sulfuric acid (temperature 5°C or less) by stirring for 1 hour, and the solution was poured into 5000 parts by mass of water (temperature 20°C). The precipitated crystals were filtered and thoroughly washed with water to obtain 225 parts by mass of a wet paste product. The obtained wet paste product was frozen in a freezer, thawed again, filtered, and dried to obtain 24.8 parts by mass of amorphous titanyl phthalocyanine.

[0148] (Pigment Preparation) 10.0 parts by mass of the amorphous titanyl phthalocyanine and 0.94 parts by mass (0.6 equivalent ratio) (equivalent ratio is the equivalent ratio to titanyl phthalocyanine, the same applies hereinafter) of (2R,3R)-2,3-butanediol were mixed in 200 parts by mass of orthochlorobenzene (ODB) and heated and stirred for 6 hours at a liquid temperature of 60 to 70° C. After leaving it overnight, methanol was added and the resulting crystals were filtered, and the filtered crystals were washed with methanol to obtain 10.3 parts by mass of a pigment.

[0149] The pigment was analyzed, and the X-ray diffraction spectrum showed clear peaks at 8.3°, 24.7°, 25.1°, and 26.5°, and the mass spectrum showed peaks at 576 and 648. The IR spectrum also showed a peak at 970 cm -1 Near Ti=O, 630 cm -1Both O-Ti-O absorptions appeared around 390°C. Thermal analysis (TG) showed a mass loss of about 7% at 390-410°C. From these analysis results, the pigment was estimated to be a mixture of a 1:1 adduct of titanyl phthalocyanine and (2R,3R)-2,3-butanediol, and unadducted titanyl phthalocyanine. The BET specific surface area of ​​the pigment was measured using an automatic flow type specific surface area measuring device (Micrometrics Flow Soap type, Shimadzu Corporation) and found to be 31.2 m 2 / g.

[0150] <Charge transport layer> The following components were mixed by stirring to obtain a charge transport layer coating solution 1. Charge transport compound: 225 parts by mass of the following compound A Polycarbonate resin (Z300, manufactured by Mitsubishi Gas Chemical Co., Ltd.) 300 parts by mass Antioxidant (Irganox 1010, manufactured by BASF) 6 parts by mass Tetrahydrofuran 1600 parts by mass Toluene 400 parts by mass Silicone oil (KF-50, Shin-Etsu Chemical Co., Ltd.) 1 part by mass

[0151] [ka]

[0152] The charge transport layer coating solution 1 was applied to the surface of the intermediate charge generating layer by dip coating so that the dry thickness was 20 μm, and then naturally dried to obtain a charge transport layer 1.

[0153] <Protective layer> The following components were mixed by stirring in a dark environment. Trimethylolpropane trimethacrylate (SR350, manufactured by Sartomer Corporation) 100 parts by mass Charge transport material: 20 parts by weight of the above compound A Tetrahydrofuran 40 parts by mass 2-butanol 400 parts by mass

[0154] Thereafter, 10 parts by mass of a polymerization initiator (Omnirad819, manufactured by IGM.Resins.BV) was added and stirred in a light-shielded environment to obtain protective layer coating solution 1.

[0155] The protective layer coating solution 1 was applied onto the charge transport layer using a dip coating device. The applied protective layer coating solution 1 was irradiated with ultraviolet light (wavelength 365 nm) using a metal halide lamp for 42 seconds to obtain a protective layer having a dry thickness of 3.0 μm. At this time, the amount of ultraviolet light at the center in the axial direction of the conductive support was 100% (light amount 34 mW / cm2). 2 ) and ultraviolet light was irradiated while gradually increasing the amount of ultraviolet light in the range of 97% to 103% from one end to the other end in the axial direction.

[0156] 1-2. Preparation of photoreceptors 2 to 8 and 16 Photoreceptor 2 to photoreceptor 8 and photoreceptor 16 were prepared in the same manner as photoreceptor 1, except that the irradiation time of ultraviolet light to protective layer coating liquid 1 and the range of change in the amount of ultraviolet light from one end to the other end in the axial direction were changed as shown in Table 1.

[0157] 1-3. Preparation of photoreceptor 9 Charge transport layer coating solution 2 was prepared as described below, and photoreceptor 9 was prepared in the same manner as photoreceptor 1, except that charge transport layer 2 was formed by applying this to charge transport layer 1 instead of protective layer coating solution 1.

[0158] The following components were mixed and dispersed for 5 hours using a sand mill to obtain a charge transport layer coating solution 2. Charge transport compound: N-(4-methylphenyl)-N-{4-(β-phenylstyryl)phenyl}-p-toluidine 180 parts by mass Polycarbonate resin (Z300, manufactured by Mitsubishi Gas Chemical Co., Ltd.) 300 parts by mass Antioxidant (Irganox 1010, manufactured by BASF) 6 parts by mass Tetrahydrofuran 1600 parts by mass Toluene 400 parts by mass

[0159] The charge transport layer coating solution 2 was applied onto the charge transport layer 1 using a circular slide hopper type coating device, and dried for 10 minutes using an infrared dryer to obtain a charge transport layer 2 having a dry thickness of 10 μm. At this time, the infrared output of the central part in the axial direction of the conductive support was set to 100% (output 5 mW / cm 2 ) and infrared rays were irradiated while gradually increasing the amount of ultraviolet light in the range of 85% to 115% from one end to the other end in the axial direction.

[0160] 1-4. Preparation of photoreceptor 10 Charge transport layer coating solution 3 was prepared as described below, and photoreceptor 10 was prepared in the same manner as photoreceptor 9, except that charge transport layer coating solution 3 was prepared and applied to charge transport layer 1 instead of charge transport layer coating solution 2 to form charge transport layer 3.

[0161] The following components were mixed and dispersed for 5 hours using a sand mill to obtain a charge transport layer coating solution 3. Charge transport compound: N-(4-methylphenyl)-N-{4-(β-phenylstyryl)phenyl}-p-toluidine 180 parts by mass Polycarbonate resin (Z300, manufactured by Mitsubishi Gas Chemical Co., Ltd.) 300 parts by mass Silicon dioxide particles (Primary treatment: dimethyldichlorosilane, secondary treatment: particles with an average primary particle size of 50 nm that have been surface-treated with hexamethyldisilazane, manufactured by Nippon Aerosil Co., Ltd.) 30 parts by mass Antioxidant (Irganox 1010, manufactured by BASF) 6 parts by mass Tetrahydrofuran 1600 parts by mass Toluene 400 parts by mass

[0162] 1-5. Preparation of photoreceptor 11 An intermediate layer, a charge generating layer, and a charge transport layer were formed on the conductive support in the same manner as in the case of the photoreceptor 1. Then, a protective layer coating solution 2 was prepared as follows.

[0163] The following components were mixed by stirring in a dark environment. Trimethylolpropane trimethacrylate (SR350, manufactured by Sartomer Corporation) 100 parts by mass Tin oxide particles (NanoTek Powder SnO2, manufactured by CI Kasei Co., Ltd.) 100 parts by mass Charge transport material: 20 parts by weight of the above compound A Tetrahydrofuran 40 parts by mass 2-butanol 400 parts by mass

[0164] Thereafter, 10 parts by mass of a polymerization initiator (Ominirad819, manufactured by IGM.Resis.BV) was added and stirred in a light-shielded environment to obtain protective layer coating solution 2.

[0165] The protective layer coating solution 2 was applied onto the charge transport layer using a dip coating device. The applied protective layer coating solution 1 was irradiated with ultraviolet light (wavelength 365 nm) using a metal halide lamp for 60 seconds to obtain a protective layer having a dry thickness of 3.0 μm. At this time, the amount of ultraviolet light at the center in the axial direction on the conductive support was 100% (light amount 34 mW / cm2). 2 ) and ultraviolet light was irradiated while gradually increasing the amount of ultraviolet light in the range of 90% to 110% from one end to the other end in the axial direction.

[0166] 1-6. Preparation of photoreceptor 12 Protective layer coating liquid 3 was prepared as follows, and photoreceptor 12 was prepared in the same manner as photoreceptor 11, except that protective layer coating liquid 3 was used instead of protective layer coating liquid 2.

[0167] The following components were mixed by stirring in a dark environment. Trimethylolpropane trimethacrylate (SR350, manufactured by Sartomer Corporation) 100 parts by mass Silicon dioxide particles (Primary treatment: dimethyldichlorosilane, secondary treatment: particles with an average primary particle size of 50 nm that have been surface-treated with hexamethyldisilazane, manufactured by Nippon Aerosil Co., Ltd.) 30 parts by mass Charge transport material (CTM) 20 parts by mass Tetrahydrofuran 40 parts by mass 2-butanol 400 parts by mass

[0168] Thereafter, 10 parts by mass of a polymerization initiator (Ominirad819, manufactured by IGM.Resins.BV) was added and stirred in a light-shielded environment to obtain protective layer coating solution 3.

[0169] 1-7. Preparation of photoreceptor 13 Photoreceptor 13 was prepared in the same manner as photoreceptor 1, except that the method for forming the charge transport layer was changed as follows, and no protective layer was formed on the charge transport layer.

[0170] The charge transport coating solution was applied onto the charge generating layer using a circular slide hopper type coating device, and then dried for 10 minutes using an infrared dryer to obtain a charge transport layer having a dry thickness of 20 μm. At this time, the infrared output at the center in the axial direction of the conductive support was set to 100% (output 34 mW / cm 2 ) and infrared rays were irradiated while gradually increasing the amount of ultraviolet light in the range of 85% to 115% from one end to the other end in the axial direction.

[0171] 1-8. Preparation of photoreceptors 14 and 15 Photoreceptor 14 was prepared in the same manner as photoreceptor 4, except that the axial length of the conductive support was changed to 400 mm. Photoreceptor 15 was prepared in the same manner as photoreceptor 4, except that the axial length was changed to 800 mm.

[0172] 1-9. Preparation of photoreceptor C1 The axial length of the conductive support was changed to 360 mm, and when UV rays were irradiated onto the protective layer coating solution 1, the amount of UV light was not changed from one end of the conductive support to the other end in the axial direction, and the amount of UV light was 100% (light amount 34 mW / cm) over 42 seconds. 2 Photoreceptor C1 was prepared in the same manner as photoreceptor 1, except that ultraviolet light was irradiated at 1000 nm.

[0173] 1-10. Preparation of photoreceptor C2 When irradiating the protective layer coating solution 1 with ultraviolet light, the amount of ultraviolet light was not changed from one end to the other end of the axial direction of the conductive support, and the ultraviolet light amount was 100% (light amount 34 mW / cm) for 42 seconds. 2 Photoreceptor C2 was prepared in the same manner as photoreceptor 1, except that ultraviolet light was irradiated at 100 nm.

[0174] 1-11. Preparation of photoreceptors C3 and C4 Photoreceptors C3 and C4 were prepared in the same manner as photoreceptor 1, except that when irradiating protective layer coating solution 1 with ultraviolet light, the ultraviolet light irradiation time and the ultraviolet light amount from one end to the other end in the axial direction were as shown in Table 1.

[0175] <Martens hardness> The Martens hardness (HU) of the photoreceptor surface was measured using an ultra-microhardness tester (H-100V, manufactured by Fisher Instruments) under the following measurement conditions. Indenter shape: Vickers indenter (a=136°) Measurement environment: 20℃, 60% RH Maximum test load: 3mN Loading speed: 3mN / 20sec Maximum load creep time: 5 seconds Unloading speed: 3mN / 20sec

[0176] The Martens hardness was measured at three points equally spaced apart in the circumferential direction of the photoreceptor, at 50 mm intervals from a position 30 mm from one end of the photoreceptor to a position 30 mm from the other end in the axial direction of the photoreceptor. Then, the difference between the maximum and minimum Martens hardness in the axial direction at each of the three circumferential points was calculated, and the average of the differences between the maximum and minimum values ​​at the three circumferential points was calculated.

[0177] In addition, the average value of all the Martens hardness data obtained by the above measurements was calculated and defined as the average value in the axial direction.

[0178] 3 to 6 are graphs showing the hardness at each measurement point in the axial direction for photoreceptors 1 to 15. From these results, it was found that the Martens hardness of the surfaces of photoreceptors 1 to 15 changes in a gradient in the axial direction.

[0179] [Table 1]

[0180] 2. Image forming equipment <Experiment 1> A developing device was prepared with two developing rollers, the rotation direction of which was opposite to that of the photoconductor 1. An image forming apparatus was prepared by incorporating the photoconductor 1 and the above developing device into an evaluation machine (bizhub PRESS C1070, manufactured by Konica Minolta, Inc., equipped with a lubricant supply unit) that had been modified so that the peripheral speed of the photoconductor was 550 mm / sec.

[0181] <Experiment 2~Experiment 16, Experiment 23, Experiment 24, Experiment 27, Experiment 28> An image forming apparatus was prepared in the same manner as in Experiment 1, except that the photoreceptors used were changed as shown in Tables 2 and 3.

[0182] <Experiment 17> An image forming apparatus was produced in the same manner as in Experiment 16, except that the number of developing rollers was changed to one.

[0183] <Experiment 18> An image forming apparatus was fabricated in the same manner as in Experiment 16, except that the developing roller was rotated in the same direction as the photoreceptor 16 was rotated.

[0184] <Test 19> An image forming apparatus was fabricated in the same manner as in Experiment 4, except that the number of developing rollers was changed to one.

[0185] <Test 20> An image forming apparatus was fabricated in the same manner as in Experiment 4, except that the developing roller was rotated in the same direction as the photoreceptor 4 was rotated.

[0186] <Experiment 21, Experiment 22> An image forming apparatus was prepared in the same manner as in Experiment 4, except that the peripheral speed of the photoreceptor 4 was changed as shown in Table 3.

[0187] <Experiment 25> An image forming apparatus was produced in the same manner as in Experiment 24, except that the number of developing rollers was changed to one.

[0188] <Experiment 26> An image forming apparatus was fabricated in the same manner as in Experiment 24, except that the rotation direction of the developing roller was the same as the rotation direction of the photoreceptor C2.

[0189] 3. Evaluation <Slip-through (image dirt)> The image forming apparatuses prepared above were used as evaluation machines modified so that the lubricant supply speed from the lubricant supply unit was 1 / 3 of the initial setting. Using this evaluation machine and a two-component developer containing cyan toner and a carrier (a carrier in which ferrite is coated with a cyclohexyl methacrylate-methyl methacrylate copolymer, volume average particle size 40 μm), a halftone image with a coverage rate of 80% was formed on A3 neutral paper in an environment of 10°C and 20% RH, with the printed part on the front side in the paper transport direction and the white part on the rear side, and 20,000 copies were printed. At this time, the 420 mm side of the paper was set to the front and rear in the paper transport direction. The white part of the 20,000th sheet of paper was visually observed to evaluate the toner slip-through. The evaluation criteria for the slip-through evaluation are as follows. The evaluation result was considered to be pass when it was between "5" and "3". In this evaluation, the less the toner slip-through, the less damage to the photoconductor. 5: No stains were found on the white background. 4: Slight short streaks were observed on the white background, but this does not pose any practical problems. 3: Slight streaks were observed on the white background, but this does not pose a problem for practical use. 2: There are obvious streaks on the white background, which is problematic for practical use. 1: There are clear streaky stains in multiple places on the white background, making it unusable.

[0190] The volume average particle size of the carrier was measured using a laser diffraction particle size distribution measuring device equipped with a wet disperser, HELOS manufactured by SYMPATEC.

[0191] <Image blur> Using each of the image forming devices prepared above and a two-component developer containing a cyan toner and a carrier (a carrier in which ferrite is coated with a cyclohexyl methacrylate-methyl methacrylate copolymer, volume average particle size 40 μm), 2000 sheets of A3-size neutral paper were printed with a horizontal band image of 10% coverage in a high-temperature and high-humidity environment of 30°C and 80% RH, and then the actual machine was stopped. At this time, the 420 mm sides of the paper were set to the front and rear in the paper transport direction. After that, after 12 hours or more had passed, 100 sheets of halftone images with a coverage rate of 100% were output. Then, five points were randomly selected from the 100th halftone image, and the dot shapes were ranked by magnification observation. The evaluation criteria for image flow evaluation are as follows. An evaluation result of "5" to "3" was considered to be acceptable. 5: Dots are formed without any problems in all five locations. 4: Dots are formed without any problems in 4 out of 5 locations, but the dot shape in one location is blurred. 3: Dots are formed without any problems in three out of five locations, but the dot shapes are blurred in two locations. 2: Dots are formed without any problems in two of the five locations, but the dot shapes are blurred in three locations. 1: Of the 5 locations, 0 to 1 location had no dots formed without problems.

[0192] <Uneven wear of photoconductor> Using each of the image forming devices prepared above and a two-component developer containing black toner and carrier (type, particle size), 300,000 horizontal band images with a coverage rate of 10% were printed on A3 neutral paper in an environment of 20°C and 50% RH. After printing, the amount of film thickness reduction of the photoreceptor (outermost layer) from the initial state was measured. The difference between the maximum and minimum amount of wear in the axial direction of the photoreceptor was defined as the amount of uneven wear and was ranked. The evaluation criteria for uneven wear evaluation of the photoreceptor are as follows. An evaluation result of "5" to "3" was considered to be a pass. 5: Uneven wear was less than 0.05 μm 4: The amount of uneven wear was more than 0.05 μm and less than 0.1 μm. 3: The amount of uneven wear was more than 0.1 μm and less than 0.3 μm. 2: The amount of uneven wear was more than 0.3 μm and less than 0.5 μm. 1: Uneven wear was greater than 0.5 μm

[0193] The evaluation results are summarized in Tables 2 and 3.

[0194] [Table 2]

[0195] [Table 3]

[0196] From Tables 2 and 3, for photoconductors with an axial length of 400 mm or more, the Martens hardness of the photoconductor surface changes between one end and the other end in the axial direction, and the difference between the maximum and minimum values ​​of the Martens hardness is 10 N / mm 2 More than 100N / mm 2 It was found that by keeping the above-mentioned thickness within the range, uneven wear can be suppressed while suppressing image staining. [Industrial Applicability]

[0197] According to the present invention, the photoconductor has an increased axial length, and when a two-component developer containing a toner and a carrier is used, image contamination can be suppressed and uneven wear of the photoconductor surface can be suppressed. Therefore, the present invention is particularly useful in the field of large-format printing. [Explanation of symbols]

[0198] 10 Image forming device 20 Image reading unit 21 Paper feeder 22 Scanner 23 CCD sensor 24 Image Processing Section 30 Image forming section 31 Image forming unit 32 Photoreceptor 33 Charging device 34 Exposure equipment 35 Developing device 36 Cleaning equipment 40 Intermediate transfer unit 41 Primary transcription unit 42 Secondary transfer unit 43 Intermediate transfer belt 44 Primary transfer roller 45 Backup roller 46 First support roller 47 Cleaning Equipment 48 Secondary transfer belt 49 Secondary transfer roller 50 Second support roller 60 Fixing device 61 Fixing belt 64 Second pressure roller 80 Recording medium transport unit 81 Paper feed tray unit 82 Registration roller pair D Manuscript S Paper (recording medium) 100 Photoreceptor 110 Conductive support 120 Middle Class 130 Charge generating layer 140 Charge transport layer 150 protective layer

Claims

1. A conductive support; A photosensitive layer; an electrophotographic photoreceptor including the above-mentioned layers laminated in this order, The length of the electrophotographic photoreceptor in the axial direction is 400 mm or more, the Martens hardness of the surface of the electrophotographic photosensitive member varies between one end and the other end in the axial direction, The difference between the maximum and minimum values ​​of the Martens hardness in the axial direction is 10 N / mm ２ More than 100N / mm ２ Below is the Electrophotographic photoreceptor.

2. The difference between the maximum and minimum values ​​of the Martens hardness is 15 N / mm ２ 50N / mm or more ２ 2. The electrophotographic photoreceptor according to claim 1, wherein:

3. the Martens hardness of the surface of the electrophotographic photosensitive member changes in a gradient from the one end to the other end along the axial direction; The electrophotographic photoreceptor according to claim 1 .

4. The average Martens hardness of the surface of the electrophotographic photosensitive member in the axial direction is 150 N / mm ２ 350N / mm or more ２ 2. The electrophotographic photoreceptor according to claim 1, wherein:

5. The average Martens hardness of the surface of the electrophotographic photosensitive member in the axial direction is 170 N / mm ２ 300N / mm or more ２ 2. The electrophotographic photoreceptor according to claim 1, wherein:

6. The electrophotographic photoreceptor according to claim 1 , further comprising a protective layer disposed on a surface side of the photosensitive layer for protecting the photosensitive layer.

7. The electrophotographic photoreceptor according to claim 6 , wherein the protective layer contains metal oxide particles.

8. The electrophotographic photoreceptor according to claim 6 , wherein the protective layer is a cured product of a polymerizable composition containing a polymerizable compound.

9. The electrophotographic photoreceptor according to claim 8 , wherein the polymerizable compound is a polymerizable compound that is polymerized by actinic rays.

10. The electrophotographic photoreceptor according to any one of claims 1 to 9, a developing device for forming a toner image on the electrophotographic photoreceptor; Image forming device.

11. 11. The image forming apparatus according to claim 10, wherein the electrophotographic photosensitive member rotates at a peripheral speed of 280 mm / sec or more and 700 mm / sec or less.

12. the developing device includes a container for containing a developer including a toner and a carrier, and a developing roller for transporting the contained developer and supplying the toner to the electrophotographic photosensitive member, the number of the developing rollers included in the developing device is two or more; The image forming apparatus according to claim 10.

13. The image forming apparatus according to claim 12 , wherein the developing roller rotates in a direction opposite to the direction in which the electrophotographic photosensitive member rotates.

14. The electrophotographic photoreceptor according to any one of claims 1 to 9, a developing device for forming a toner image on the electrophotographic photoreceptor; a developer containing a toner and a carrier, the developer being supplied to the developing device; having Image forming system.

15. 15. The image forming system according to claim 14, wherein the volume average particle diameter of the carrier is 20 [mu]m or more and 70 [mu]m or less.

16. An image forming method using a two-component developer containing a toner and a carrier, A step of charging the surface of the electrophotographic photoreceptor according to any one of claims 1 to 9; applying the toner of the two-component developer to the surface of the charged electrophotographic photoreceptor; transferring the applied toner onto a recording medium; having Image forming method.

17. 17. The image forming method according to claim 16, wherein the volume average particle diameter of the carrier is 20 μm or more and 70 μm or less.

18. The volume average particle size of the carrier is 25 μm or more and 45 μm or less. The image forming method according to claim 17.

Images