Electrophotographic photoreceptor, image forming apparatus, and image forming method

Abstract

To provide an electrophotographic photoreceptor which may reduce rotational torque of the photoreceptor as well as an increase in rotational torque during prolonged use when a cured layer obtained by curing a charge transporting compound having a radical polymerizable group is used as a protective layer.SOLUTION: The present invention relates to an electrophotographic photoreceptor comprising a conductive support body, photosensitive layer, and protective layer laminated in the described order. The protective layer is formed of a cured product of a composition containing a charge transporting compound having a radical polymerizable functional group, and metal oxide particles surface-treated with a surface treatment agent having a silicone chain in a side chain.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In electrophotographic image forming apparatuses, an electrophotographic photoreceptor (hereinafter also simply referred to as "photoreceptor") is used to form an electrostatic latent image corresponding to the image to be formed. In an electrophotographic image forming apparatus, first, light is shone onto a photoreceptor whose surface has been charged to form an electrostatic latent image. Next, toner is supplied to the photoreceptor to form a toner image corresponding to the electrostatic latent image. Finally, the toner image is transferred to a recording medium such as paper and fixed.

[0003] The photoconductor is cleaned by removing any remaining toner on its surface that has not been transferred using a cleaning blade or similar tool. This cleaning process wears down the surface of the photoconductor, so it needs to be replaced periodically. However, there is a demand to improve the wear resistance of the photoconductor to extend its lifespan and reduce the frequency of replacement.

[0004] It is known that the abrasion resistance of a photoreceptor can be improved by using a cured layer, which is formed by curing a charge-transporting compound having radical polymerizable groups, as a protective layer located on the outermost surface (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-105223 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] According to the inventors' findings, when a cured layer, obtained by curing a charge-transporting compound having a radical polymerizable group, is used as a protective layer to improve the wear resistance of a photoreceptor, as described in Patent Document 1, friction with the cleaning blade increases, and the rotational torque of the photoreceptor tends to increase. Furthermore, during long-term use, an increase in the rotational torque of the photoreceptor also occurs.

[0007] The present invention has been made in view of the above problems, and aims to provide an electrophotographic photoreceptor that reduces the rotational torque of the photoreceptor and also reduces the increase in rotational torque during long-term use when a cured layer obtained by curing a charge transport compound having a radical polymerizable group is used as a protective layer, an image forming apparatus equipped with the electrophotographic photoreceptor, and an image forming method using the electrophotographic photoreceptor. [Means for solving the problem]

[0008] One aspect of the present invention for achieving the above objectives relates to the following electrophotographic photoreceptors [1] to [8]. [1] A conductive support and Photosensitive layer, A protective layer, An electrophotographic photoreceptor containing these elements stacked in this order, The protective layer is formed from a cured product of a composition comprising a charge-transporting compound having a radical polymerizable functional group and metal oxide particles surface-treated with a surface treatment agent having a silicone chain as a side chain. Electrophotographic photoreceptor. [2] The electrophotographic photoreceptor according to [1], wherein the metal oxide particles are further surface-treated with a surface treatment agent having a radical polymerizable functional group. [3] The electrophotographic photoreceptor according to [1] or [2], wherein the charge transport compound having the radical polymerizable functional group is a compound represented by the following general formula (1). [ka] (In general formula (1), Ar 1 and Ar 2independently represents a structure represented by the general formula (2), Ar 3 represents a structure represented by the general formula (2) or the general formula (3), D independently represents a structure represented by -(-(CH2) d -(O-(CH2) f -) e -O-CO-C(CH3)=CH2) or -(-(CH2) d -(O-(CH2) f -) e -O-CO-CH=CH2), d and f independently represent an integer of 0 or more and 5 or less, e represents an integer of 0 or 1, c1 to c3 independently represent an integer of 0, 1 or 2, Ar 3 when represents a structure represented by the general formula (2), the total number of D in the compound is 1 or 2, Ar 3 when represents a structure represented by the general formula (3), the total number of D in the compound is 1.)

Chemical formula

Chemical formula

[0009] Another aspect of the present invention for achieving the above objectives relates to the image forming apparatus described in [7] below. An image forming apparatus having an electrophotographic photoreceptor as described in any of [7][1] to [6].

[0010] Furthermore, another aspect of the present invention for achieving the above objectives relates to the image forming method described in [8] below. A step of charging the surface of an electrophotographic photoreceptor by bringing a charging roller into contact with an electrophotographic photoreceptor as described in any of [8][1] to [6], The steps include: applying toner to the surface of the charged electrophotographic photoreceptor; A step of transferring the applied toner to a recording medium, An image forming method having the following characteristics. [Effects of the Invention]

[0011] According to the present invention, an electrophotographic photoreceptor is provided that, when a cured layer obtained by curing a charge-transporting compound having a radical polymerizable group is used as a protective layer, reduces the rotational torque of the photoreceptor and also reduces the increase in rotational torque during long-term use; an image forming apparatus equipped with the electrophotographic photoreceptor is provided; and an image forming method using the electrophotographic photoreceptor is provided. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a partial cross-sectional view showing an exemplary layer configuration of an electrophotographic photoreceptor according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram showing the configuration of an image forming apparatus according to one embodiment of the present invention. [Modes for carrying out the invention]

[0013] 1. Electrophotographic photoreceptor Figure 1 is a partial cross-sectional view showing an exemplary layer configuration of an electrophotographic photoreceptor 100 according to 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, stacked in this order.

[0014] 1-1. Conductive support 110 The conductive support 110 supports the intermediate layer 120, the charge generation layer 130, the charge transport layer 140, and the protective layer 150, and is a member whose surface, at least, is in contact with the intermediate layer 120 and is conductive. Examples of the conductive support 110 include a metal drum or sheet, a plastic film having laminated metal foil, a plastic film having a layer of vapor-deposited conductive material, a metal member having a conductive layer coated with a conductive material or a paint consisting of 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 metal, indium oxide, and tin oxide. From the viewpoint of improving the processability and robustness of the conductive support 110 and making the conductive support 110 lighter, the metal is preferably aluminum. The thickness of the peripheral wall of the conductive support 110 can be, for example, about 0.1 mm.

[0015] 1-2. Middle layer 120 The intermediate layer 120 is positioned between the conductive support 110 and the charge generation layer 130 and has functions such as removing charge (typically electrons) from the charge generation layer 130 to the conductive support 110, suppressing charge (typically holes) leakage from the conductive support 110 to the charge generation layer 130, and providing adhesion. The intermediate layer 120 includes a binder resin and conductive particles for the intermediate layer.

[0016] Examples of binder resins 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 type or more.

[0017] Examples of the conductive particles mentioned above include metal oxide particles such as 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. From the viewpoint of further improving the charge removal ability to the conductive support side in the intermediate layer 120, the conductive material is preferably an n-type semiconductor. Examples of the conductive material as an n-type semiconductor include titanium oxide, zinc oxide, aluminum oxide, aluminum hydroxide, and tin oxide. Furthermore, from the viewpoint of improving the conductivity of the intermediate layer 120 and improving the dispersibility of 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 form of titanium oxide may be anatase, rutile, or amorphous. The crystal form of titanium oxide may be one type or more.

[0018] The content of the conductive particles is preferably 50 to 200 parts by volume, and more preferably 80 to 120 parts by volume, relative to 100 parts by volume of binder resin in the intermediate layer.

[0019] 1-3. Charge generation layer 130 The charge generation layer 130 comprises, for example, a binder resin for the charge generation layer and a charge generation material dispersed in the binder resin for the charge generation layer.

[0020] Examples of binder resins for the charge generation 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, phenolic resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, silicone-modified butyral resin, phenoxy resin, melamine resin, copolymer resins containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin and vinyl chloride-vinyl acetate-maleic anhydride copolymer resin), and polyvinylcarbazole resin. The binder resin for the charge generation layer may be one type or more.

[0021] Examples of charge-generating materials for the charge-generating layer include azo raw materials such as Sudan Red and Diane Blue, quinone pigments such as pyrenequinone and anthantrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, pyranthrone, diphthaloylpyrene polycyclic quinone compounds, and phthalocyanine pigments. The above charge-generating materials for the charge-generating layer may be one type or more.

[0022] The phthalocyanine pigment described above 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 or more. From the viewpoint of increasing the sensitivity of the charge generation layer, the phthalocyanine pigment is preferably a titanylphthalocyanine compound having Ti as the central metal. Also, from a similar viewpoint, the titanylphthalocyanine compound is preferably a Y-type titanylphthalocyanine compound having a maximum peak at Bragg angle (2θ±0.2) 27.3° and clear diffraction peaks at 7.4°, 9.7° and 24.2° in X-ray diffraction by CuKα rays, and a 2,3-butanediol adduct titanylphthalocyanine having clear diffraction peaks at Bragg angles 8.3°, 24.7°, 25.1° and 26.5°.

[0023] The content of the charge generating substance is preferably 20 parts by mass or more and 600 parts by mass or less per 100 parts by mass of the binder resin for the charge generating layer, and more preferably 50 parts by mass or more and 500 parts by mass or less. A charge generating layer in which the content of the charge generating substance is within the above range has higher dispersibility of the charge generating substance, which makes it easier to reduce the electrical resistance of the charge generating layer and can further suppress the increase in residual charge associated with the use of the photoreceptor.

[0024] The charge generation layer 130 is produced, for example, by an immersion coating method in which a conductive support having an intermediate layer 120 formed on it is immersed in a solution of a binder resin for charge generation layers, in which a charge generation material is dispersed.

[0025] The thickness of the charge generation layer 130 may be, for example, 0.01 μm or more and 5 μm or less, preferably 0.05 μm or more and 3 μm or less, more preferably 0.05 μm or more and 2 μm or less, and even more preferably 0.15 μm or more and 1.5 μm or less.

[0026] 1-4.Charge transport layer 140 The charge transport layer 140 comprises, for example, a binder resin for the charge transport layer and a charge transport material dispersed in the binder resin for the charge transport layer.

[0027] The binder resin for the charge transport layer is a thermoplastic resin or a thermosetting resin. Examples of binder resins for the charge transport layer include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butylal resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, and melamine resin. The binder resin for the charge transport layer may also be a copolymer containing two or more repeating unit structures of the above-mentioned binder resins for the charge transport layer. Of these, the binder resin for the charge transport layer is preferably a polycarbonate resin, which has low water absorption and high mechanical strength.

[0028] Examples of the charge transport materials mentioned above include triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, and butadiene compounds. These charge transport materials may be one or more types.

[0029] The content of the above-mentioned charge transport material is preferably 10 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the binder resin for the charge transport layer.

[0030] The charge transport layer 140 is produced, for example, by an immersion coating method in which the conductive support on which the charge generating layer is formed is immersed in a solution of the binder resin for the charge transport layer in which the charge transport material is dispersed, and by applying the solution of the binder resin for the charge transport layer in which the charge transport material is dispersed to the surface of the charge generating layer 130 and drying it.

[0031] The thickness of the charge transport layer 140 can be, for example, 5 μm to 40 μm. From the viewpoint of strengthening the internal electric field of the photoreceptor 100 and suppressing the increase in residual charge associated with the use of the photoreceptor 100, the thickness of the charge transport layer 140 is preferably 10 μm to 40 μm, and more preferably 10 μm to 30 μm. 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, as well as the type and content of the charge transport substance.

[0032] The charge generation 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 composed of, for example, a single layer containing a binder resin for the photosensitive layer, the charge transport material, and the charge generation material. The thickness of the single-layer photosensitive layer can be, for example, 10 μm or more and 50 μm or less, and is preferably 20 μm or more and 40 μm or less.

[0033] Examples of binder resins for the photosensitive layer that constitute 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, phenolic resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, copolymer resins 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.

[0034] 1-5.Protective layer 150 The protective layer described above is a layer for protecting the charge generation layer 130 and the charge transport layer 140 (photosensitive layer). The protective layer 150 is positioned on the surface side of the charge transport layer 140 (photosensitive layer) and constitutes the surface of the photoreceptor 100. The protective layer 150 includes a binder resin for the protective layer and metal oxide particles for the protective layer.

[0035] In this embodiment, the protective layer 150 is formed from a cured product of a composition comprising a charge-transporting compound having a radical polymerizable functional group and metal oxide particles surface-treated with a surface treatment agent having a silicone chain as a side chain.

[0036] The above cured product is surface-treated with a surface treatment agent having silicone chains as side chains on the metal oxide particles. This surface treatment agent having silicone chains as side chains easily orients the silicone chains outward from the metal oxide fine particles. Furthermore, the above surface treatment agent easily exposes the silicone chains, which are oriented outward from the metal oxide fine particles present in the outermost layer of the cured product, to the outside from the surface of the cured product. The surface treatment agent having silicone chains as side chains can reduce friction with the cleaning blade and decrease the rotational torque of the photoreceptor 100 by using the silicone chains exposed to the outside from the surface of the cured product (protective layer 150).

[0037] Furthermore, the silicone chains oriented outward from the metal oxide fine particles can enhance the compatibility between the charge-transporting compound having radical polymerizable functional groups and the metal oxide fine particles in the composition before curing. As a result, the metal oxide fine particles are more easily dispersed uniformly in the composition and more easily exist uniformly in the cured product, and the silicone chains are also more easily exposed uniformly outward from the surface of the cured product. Therefore, a surface treatment agent having silicone chains as side chains can effectively reduce the rotational torque of the protective layer 150.

[0038] Furthermore, because the charge transport compound having a radical polymerizable functional group has high compatibility with metal oxide fine particles, the charge transport compound having a radical polymerizable functional group is easily dispersed uniformly in the composition. The uniformly dispersed charge transport compound having a radical polymerizable functional group then readily encounters other polymerizable compounds during curing, effectively generating intermolecular reactions. As a result, the surface treatment agent having a silicone chain as a side chain is less likely to produce unreacted polymerizable compounds, thereby suppressing the increase in rotational torque caused by these unreacted polymerizable compounds.

[0039] On the other hand, because silicone chains have high bonding energy, they are less susceptible to degradation caused by discharges that charge the photoreceptor 100, or by oxides (discharge products) generated by such discharges. Therefore, surface treatment agents that have silicone chains as side chains can further reduce the degradation of metal oxides, which are inherently resistant to degradation, thereby reducing the increase in rotational torque during long-term use.

[0040] Furthermore, as described above, the cured product constituting the protective layer 150 is less likely to produce unreacted polymerizable compounds. Therefore, the cured product is less prone to deterioration due to unexpected reactions of the functional groups of the unreacted polymerizable compounds during use, and the rotational torque is less likely to increase during long-term use. Moreover, the cured product is less prone to image blurring when used in high-temperature and high-humidity environments, which occurs due to the reaction of the functional groups of the unreacted polymerizable compounds with discharge products.

[0041] Furthermore, the fact that the protective layer 150 is formed from a cured product of a composition containing a charge-transporting compound having a radical polymerizable functional group can be confirmed by measuring and analyzing the alkali hydrolysate of the protective layer 150 using known methods such as NMR, IR, and mass spectrometry.

[0042] Furthermore, the fact that the protective layer 150 is formed from a cured product of a composition containing metal oxide particles surface-treated with a surface treatment agent having ricone chains as side chains can be confirmed by observing a cross-section of the protective layer 150 with a scanning electron microscope (SEM) and mapping the captured cross-sectional image by molecular mapping.

[0043] 1-5-1. Charge transport compounds having radical polymerizable functional groups Charge-transporting compounds having radical polymerizable functional groups can suppress the generation of image memory due to their charge-transporting structure. On the other hand, by having radical polymerizable functional groups, they can incorporate charge-transporting substances into the polymerization chain during curing, suppressing the detachment of the charge-transporting structure due to friction, and improving the abrasion resistance of the protective layer 150. A charge-transporting compound having radical polymerizable functional groups is any compound that has both a charge-transporting functional group and a radical polymerizable functional group.

[0044] The charge-transporting functional group described above may be any known charge-transporting functional group having a π-conjugated moiety. From the viewpoint of improving compatibility with metal oxide particles surface-treated with a surface treatment agent having a silicone chain as a side chain, it is preferable that the charge-transporting functional group has a small molecular size of the π-conjugated moiety.

[0045] The above-mentioned radical polymerizable functional group may be any known radical polymerizable functional group such as a vinyl group or a (meth)acryloyl group, but a (meth)acryloyl group is preferred. In this specification, (meth)acryloyl means either acryloyl or methacryloyl, or both. A charge transport compound having a radical polymerizable functional group preferably has one or two of the above-mentioned radical polymerizable functional groups in its molecule, and more preferably has one of the above-mentioned radical polymerizable functional groups in its molecule.

[0046] Examples of charge transport compounds having radical polymerizable functional groups with these characteristics include compounds represented by the following general formula (1).

[0047] [ka]

[0048] In general formula (1), Ar 1 and Ar 2 The structure is independently represented by general formula (2), and Ar 3 This represents a structure that can be expressed by general formula (2) or general formula (3).

[0049] D is independent, -(-(CH2) d -(O-(CH2) f -) e -O-CO-C(CH3)=CH2) or -(-(CH2) d -(O-(CH2) f -) e The structure is represented as -O-CO-CH=CH2).

[0050] d and f independently represent integers between 0 and 5 (inclusive). Preferably, d and f are integers between 1 and 4 (inclusive).

[0051] e represents an integer of 0 or 1. Preferably, e is 1. In particular, compounds in which the sum of c1 to c3 is 1, e is 1, and at least one of d and f is an integer between 1 and 4 have a structure containing relatively long chains such as alkyl chains and alkylene oxide chains, resulting in higher compatibility with other materials during manufacturing and better dispersion. Furthermore, during curing, the polymerizable group (D) moves easily due to the relatively long chains, thereby facilitating the curing reaction. Due to these effects, the above compounds enhance the stability of the cured product and are less likely to remain unreacted, thus reducing the increase in rotational torque during long-term use and making image blurring less likely when used in high-temperature and high-humidity environments.

[0052] c1 to c3 independently represent integers 0, 1, or 2. However, Ar 3 When the structure is represented by general formula (2), the total number of D in the compound is 1 or 2, and Ar 3 When the structure is represented by general formula (3), the total number of D atoms in the compound is 1. [ka] [ka]

[0053] In general formulas (2) and (3), R 1 and R 2 R independently represents a functional group or atom selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group substituted with an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom. However, in general formula (3), the two R 2 These groups may bond to form a cyclic structure. Of these, alkyl groups having 1 to 4 carbon atoms are preferred, and methyl groups are more preferred.

[0054] t is an independent integer between 1 and 3, preferably 1 or 2, and more preferably 1.

[0055] Examples of compounds represented by general formula (1) in which the total number of D molecules is 1 include the following compounds.

[0056] [ka]

[0057] [ka]

[0058] [ka]

[0059] [ka]

[0060] Examples of compounds represented by general formula (1) in which the total number of D molecules is 2 include the following compounds.

[0061] [ka]

[0062] [ka]

[0063] 1-5-2. Metal oxide particles surface-treated with a surface treatment agent having silicone chains as side chains. Metal oxide particles surface-treated with a surface treatment agent having silicone chains as side chains can appropriately adjust the electrical resistance of the protective layer 150 to improve image quality stability and enhance the wear resistance of the protective layer 150.

[0064] The metal oxides constituting the metal oxide particles are oxides of metals or metalloids (in this specification, metal and metalloid oxides are collectively referred to as "metal oxides"). Examples of metal oxides include silica (silicon dioxide), magnesium oxide, zinc oxide, lead oxide, aluminum oxide, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, tin oxide, titanium oxide, niobium oxide, molybdenum oxide, vanadium oxide, tin-doped indium oxide, antimony-doped tin oxide, and zirconium oxide. There may be one or more metal oxide particles. If there are two or more metal oxide particles, they may be a solid solution or a fused body. Of these, silica and tin oxide are preferred from the viewpoint of increasing the hardness of the protective layer 150 to enhance wear resistance, ensuring light transmittance of the protective layer, and suppressing deterioration of electrical properties during long-term use in low-humidity, low-temperature environments.

[0065] The number-average primary particle size of the metal oxide particles can be, for example, between 1 nm and 300 nm, and preferably between 3 nm and 100 nm. The number-average primary particle size of the metal oxide particles can be measured by the same method as the number-average primary particle size of the metal oxide particles for the intermediate layer described above. The number-mean primary particle size of metal oxide particles can be obtained, for example, by scanning a 10,000x magnified photograph taken with a scanning electron microscope (such as one manufactured by JEOL Ltd.), scanning it, randomly binarizing 300 particle images (excluding aggregated particles) from the resulting photographic image using an automated image processing and analysis system such as "LUZEX AP" (manufactured by Nireco Corporation, "LUZEX" is a registered trademark of the company, software Ver. 1.32), calculating the horizontal Ferret diameter of each particle image, and then calculating the average value. Here, the horizontal Ferret diameter refers to the length of the side parallel to the x-axis of the circumscribing rectangle obtained when the above particle image is binarized.

[0066] The content of metal oxide particles is preferably 1 to 100 parts by mass, and more preferably 5 to 80 parts by mass, per 100 parts by mass of binder resin. The higher the content of metal oxide particles, the higher the hardness of the protective layer 150 and the higher its wear resistance. By not having an excessive amount of metal oxide particles, it is possible to ensure light transmittance, facilitate the formation of high-resolution latent images, and reduce the occurrence of image defects due to aggregation of metal oxide particles.

[0067] The metal oxide particles are surface-treated with a surface treatment agent having silicone chains in its side chains. The surface treatment agent is a surface treatment agent having a polymer main chain, a surface treatment functional group, and side chains containing silicone chains.

[0068] The main chain of the above polymer can be a main chain made of (meth)acrylic copolymer or a silicone chain.

[0069] The above surface treatment functional group can be a carboxyl group, a hydroxyl group, or an alkoxysilyl group.

[0070] The side chains containing the silicone chains preferably have dimethylsiloxane structures as repeating units. The number of dimethylsiloxane structures as repeating units is preferably 3 to 100 per side chain, more preferably 3 to 50, and even more preferably 3 to 30.

[0071] Furthermore, when the main chain of the polymer is a silicone chain, it is preferable that the silicone chain serving as the main chain of the polymer also has a similar structure.

[0072] The surface treatment agent having a silicone chain in its side chain preferably has a number-average molecular weight of 1,000 to 300,000.

[0073] Examples of commercially available surface treatment agents having a main chain made of (meth)acrylic copolymer and side chains containing silicone chains include Cymac US-350 (manufactured by Toagosei Co., Ltd., "Cymac" is a registered trademark of the company), as well as KP-541, KP-574, and KP-578 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0074] Examples of commercially available surface treatment agents having a main chain made of silicone chains and side chains containing silicone chains include KF-9908 and KF-9909 (both manufactured by Shin-Etsu Chemical Co., Ltd.).

[0075] These surface treatment agents, which have silicone chains in their side chains, may be used individually or in combination of two or more types.

[0076] The amount of surface treatment agent having a silicone chain as a side chain applied to metal oxide particles is preferably, for example, 1 to 10 parts by mass, and more preferably 3 to 7 parts by mass, per 100 parts by mass of metal oxide particles. The above amount can be appropriately adjusted depending on the number-average primary particle size of the metal oxide particles and the type of surface treatment agent.

[0077] The metal oxide particles preferably have radical polymerizable functional groups. These radical polymerizable functional groups enhance the compatibility between the metal oxide fine particles and the polymerizable compound, making it easier to disperse the metal oxide fine particles more uniformly in the composition. This more effectively improves the wear resistance of the protective layer 150, as well as more effectively reduces torque, suppresses the increase in rotational torque, and suppresses image blur in high-temperature and high-humidity environments. For example, the metal oxide particles are preferably surface-modified with a surface modifier having radical polymerizable functional groups.

[0078] The above-mentioned surface modifier can be a surface modifier that can react with functional groups (hydroxyl groups, etc.) present on the surface of metal oxide particles, such as a silane coupling agent or a titanium coupling agent, and which has a radical polymerizable functional group.

[0079] Examples of such surface modifiers include silane coupling agents having a (meth)acryloyl group.

[0080] Examples of silane coupling agents containing a (meth)acryloyl group include the following compounds: S-1: CH2=CHSi(CH3)(OCH3)2 S-2: CH2=CHSi(OCH3)3 S-3: CH2=CHSi(OC2H5)3 S-4: CH2=CHCH2Si(OCH3)3 S-5: CH2=CHCH2Si(OC2H5)3 S-6:CH2=CHCOO(CH2)2Si(CH3)(OCH3)2 S-7: CH2=CHCOO(CH2)2Si(OCH3)3 S-8: CH2=CHCOO(CH2)3Si(OCH3)3 S-9: CH2=CHCOO(CH2)3Si(OC2H5)3 S-10:CH2=CHCOO(CH2)3Si(CH3)(OCH3)2 S-11: CH2=CHCOO(CH2)3SiCl3 S-12:CH2=CHCOO(CH2)3Si(CH3)Cl2 S-13:CH2=C(CH3)COO(CH2)2Si(CH3)(OCH3)2 S-14:CH2=C(CH3)COO(CH2)2Si(OCH3)3 S-15:CH2=C(CH3)COO(CH2)3Si(CH3)(OCH3)2 S-16:CH2=C(CH3)COO(CH2)3Si(OCH3)3 S-17:CH2=C(CH3)COO(CH2)3Si(OC2H5)3 S-18:CH2=C(CH3)COO(CH2)3Si(CH3)Cl2 S-19: CH2=C(CH3)COO(CH2)3SiCl3 S-20:CH2=C(CH3)COO(CH2)8Si(OCH3)3

[0081] The surface modifier is not limited to the above-mentioned compounds; it may also be a silane compound having a radically polymerizable functional group, etc.

[0082] These surface modifiers having radical polymerizable functional groups may be used individually or in combination of two or more.

[0083] The amount of surface treatment agent applied to the metal oxide particles for the protective layer is preferably, for example, 0.1 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the metal oxide particles for the protective layer. The amount of treatment can be appropriately adjusted depending on the number-average primary particle size of the metal oxide particles and the type of surface treatment agent.

[0084] Treatment of metal oxides with surface treatment agents having silicone chains in their side chains (and surface modifiers having radically polymerizable functional groups) can be carried out by wet grinding a slurry (suspension of solid particles) containing metal oxide particles and these surface treatment agents (and surface modifiers) to refine the metal oxide particles while simultaneously advancing the surface treatment (and surface modification) of the particles, and then removing the solvent to produce a powder.

[0085] The slurry is preferably a mixture of 100 parts by mass of metal oxide particles, 0.1 to 100 parts by mass of a surface treatment agent (and surface modifier), and 50 to 5000 parts by mass of a solvent.

[0086] Wet grinding of slurries can be performed using known wet media dispersion apparatuses. A wet media dispersion apparatus is an apparatus that has a process of crushing, grinding, and dispersing aggregated metal oxide particles by filling a container with beads as media and further rotating a stirring disc mounted perpendicular to the rotating shaft at high speed. Wet media dispersion apparatuses can be used in any form, such as vertical or horizontal, continuous or batch. Examples of wet media dispersion apparatuses include sand mills, ultravisco mills, pearl mills, gren mills, dyno mills, agitator mills, and dynamic mills.

[0087] The beads used in these wet media dispersion devices can be balls made from materials such as glass, alumina, zircon, zirconia, steel, and flint. Of these, zirconia and zircon are preferred. The size of the beads is usually about 1 to 2 mm in diameter, but in this embodiment, it is preferable to use beads about 0.1 to 1.0 mm in diameter from the viewpoint of effectively performing surface treatment (and surface modification).

[0088] The disks and inner walls of the containers of a wet media dispersion apparatus can be made of stainless steel, nylon, ceramic, etc., but in this embodiment, from the viewpoint of effectively performing surface treatment (and surface modification), the disks and inner walls of the containers are preferably made of ceramics such as zirconia and silicon carbide.

[0089] 1-5-3. Other ingredients The protective layer 150 may contain other components as needed. Examples of such other components include polymerizable compounds (excluding charge transport compounds having radical polymerizable functional groups, and metal oxide nanoparticles surface-modified with surface treatment agents having silicone chains in their side chains and surface modifiers having radical polymerizable functional groups), polymerization initiators (or their residues), lubricant particles, and antioxidants.

[0090] The polymerizable compound mentioned above may be any known radical polymerizable compound.

[0091] The above radical polymerizable compounds preferably have two or more radical polymerizable functional groups. Furthermore, the radical polymerizable functional groups are preferably (meth)acryloyl groups. Examples of the above radical polymerizable compounds having (meth)acryloyl groups include compounds represented by the following formulas M1 to M15.

[0092] [ka]

[0093] [ka]

[0094] In the above formulas M1 to M15, R represents an acryloyl group and R' represents a methacryloyl group.

[0095] Examples of the lubricant particles mentioned above include fluororesin particles. Examples of fluororesins constituting these fluororesin particles include tetrafluoroethylene resin, trifluoroethylene chloride resin, hexafluoroethylene chloride propylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluoroethylene chloride resin, and copolymers thereof. The fluororesin is preferably tetrafluoroethylene resin or vinylidene fluoride resin. The lubricant particles may consist of one type or more.

[0096] The number-average primary mean particle size of the above lubricant particles is preferably 0.01 μm or more and 1 μm or less, and more preferably 0.05 μm or more and 0.5 μm or less.

[0097] The content of the above-mentioned lubricant particles is preferably 5 parts by mass or more and 70 parts by mass or less per 100 parts by mass of binder resin for the protective layer, and more preferably 10 parts by mass or more and 60 parts by mass or less.

[0098] The thickness of the protective layer 150 is preferably, for example, 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.

[0099] The protective layer 150 can be prepared by applying a composition containing the above-described charge-transporting compound having a radical polymerizable functional group and metal oxide particles surface-treated with a surface treatment agent having the above-described silicone chain as a side chain to a photosensitive layer and curing it by irradiation with ultraviolet light or an electron beam. The above composition may optionally contain a polymerization initiator and the above-described other components. When curing the composition by irradiation with an electron beam, the composition does not need to contain a polymerization initiator.

[0100] The polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator, but a photopolymerization initiator is preferred. The polymerization initiator is preferably a radical polymerization initiator.

[0101] Examples of radical polymerization initiators include alkylphenone compounds and phosphine oxide compounds, among others.

[0102] The polymerization initiator is preferably a compound having an α-aminoalkylphenone structure or an acylphosphine oxide structure, and more preferably a compound having an acylphosphine oxide structure. An example of a compound having an acylphosphine oxide structure is IRGACURE 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) (manufactured by IGM Resins BV, "IRGACURE" is a registered trademark of BASF).

[0103] These polymerization initiators may be used individually or in combination of two or more.

[0104] The content of the polymerization initiator in the composition is preferably in the range of 0.1 parts by mass to 20 parts by mass, and more preferably 0.5 parts by mass to 10 parts by mass, per 100 parts by mass of the polymerizable compound.

[0105] 2. Image forming apparatus and image forming method Figure 2 is a schematic diagram showing the configuration of an image forming apparatus according to one embodiment of the present invention. The image forming apparatus 0 includes an image reading unit 20, an image forming unit 30, an intermediate transfer unit 40, a fixing unit 60, and a recording medium transport unit 80. The components of the image forming apparatus 10, other than the photoreceptor 32, can be the same as those of a known image forming apparatus.

[0106] The image reading unit 20 reads an image from the original 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.

[0107] The image forming unit 30 includes, for example, four image forming units 31 corresponding to yellow, magenta, cyan, and black. Each image forming unit 31 includes a photoreceptor (electrophotographic photoreceptor) 32, a charging device 33, an exposure device 34, a developing device 35, and a cleaning device 36.

[0108] The photoreceptor 32 is a negatively charged organic photoreceptor that is photoconductive. The photoreceptor 32 is charged by a charging device 33. The charging device 33 is a contact-type charging device that charges the photoreceptor 32 by bringing a contact charging member, such as a charging roller or a charging brush, into contact with it. For example, it is a contact-type charging device that charges by contact with a charging roller. In such a contact-type charging device, it is difficult to increase the amount of charge transport material that can be contained in the protective layer in order to maintain the strength of the protective layer. As a result, the movement of charge from the photoreceptor layer to the protective layer is suppressed, and in particular, the charge (typically electrons) after transfer is not easily discharged from the protective layer side and tends to remain inside the photoreceptor, easily generating transfer memory. Therefore, in this embodiment, the charge after transfer is made easier to discharge to the conductive support side via an intermediate layer, thereby suppressing the generation of transfer memory.

[0109] In this embodiment, the photoreceptor 100 described above is used as the photoreceptor 32 in Figure 2.

[0110] The exposure device 34 irradiates the charged photoreceptor 32 with light to form an electrostatic latent image. The exposure device 34 is, for example, a semiconductor laser. The developing device 35 supplies toner to the photoreceptor 32 on which the electrostatic latent image has been formed to form a toner image corresponding to the electrostatic latent image. The developing device 35 is, for example, a known developing device in an electrophotographic image forming apparatus. The cleaning device 36 removes residual toner from the photoreceptor 32. Here, "toner image" refers to a state in which toner has accumulated in an image-like manner.

[0111] The toner can be any known toner. The toner may be a one-component developer or a two-component developer. The one-component developer consists of toner particles. The two-component developer consists of toner particles and carrier particles. The toner particles consist of toner matrix particles and external additives such as silica attached to their surface. The toner matrix particles consist of, for example, a binder resin, a colorant, and a wax.

[0112] The intermediate transfer unit 40 includes a primary transfer unit 41 and a secondary transfer unit 42.

[0113] The primary transfer unit 41 includes 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 rollers 46. The intermediate transfer belt 43 travels on the endless track at a constant speed in one direction by the rotational drive of at least one of the backup rollers 45 and the first support rollers 46.

[0114] 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.

[0115] 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 separation device, a guide plate, and guide rollers.

[0116] The fixing belt 61 has a base layer, an elastic layer, and a release layer laminated in that order. The fixing belt 61 is supported by a heating roller 62 and a first pressure roller 63 with the base layer facing inward and the release layer facing outward.

[0117] The heating roller 62 has a rotatable aluminum sleeve and a heater disposed inside it. The first pressure roller 63 has, for example, a rotatable core and an elastic layer disposed on its outer surface.

[0118] The second pressure roller 64 is positioned opposite the first pressure roller 63 via a fixing belt 61. The second pressure roller 64 is positioned to move closer to and further away from the first pressure roller 63, and when it approaches the first pressure roller 63, it presses against the elastic layer of the first pressure roller 63 via the fixing belt 61, forming a fixing nip portion which is the contact point with the fixing belt 61.

[0119] The airflow separation device is a device that generates an airflow from the downstream side in the direction of movement of the fixing belt 61 toward the fixing nip, thereby promoting the separation of the recording medium S from the fixing belt 61.

[0120] The guide plate is a component for guiding the recording medium S having an unfixed toner image to the fixing nip section. The guide roller is a component for guiding the recording medium with the fixed toner image from the fixing nip section to outside the image forming apparatus 10.

[0121] The recording medium transport unit 80 has three paper feed tray units 81 and a plurality of registration roller pairs 82. The paper feed tray units 81 contain recording media (in this embodiment, standard paper, specialty paper, etc.) S identified based on basis weight, size, etc., according to a preset type. The registration roller pairs 82 are arranged to form a predetermined transport path.

[0122] In this image forming apparatus 10, first, a photoreceptor 32 that has been charged by contact with a charging roller is irradiated with light to form an electrostatic latent image. Then, toner is supplied to the surface of the photoreceptor 32 to form a toner image corresponding to the electrostatic latent image. The toner image is transferred to the recording medium S, which has been transported by the recording medium transport unit 80, in the intermediate transfer unit 40. The recording medium S, on which the toner image has been transferred in the intermediate transfer unit 40, is fixed to the recording medium S in the fixing unit 60. The recording medium with the fixed toner image is guided out of the image forming apparatus 10 by guide rollers. In this way, an image can be formed. [Examples]

[0123] The present invention will be described in more detail below, but this description is not intended to limit the present invention.

[0124] 1. Fabrication of an electrophotographic photoreceptor 1-1. Preparation of Photoreceptor 1 A photoreceptor 1 was fabricated by following the procedure below, in which an intermediate layer, a charge generation layer, a charge transport layer, and a protective layer were laminated in that order on a conductive support.

[0125] <Conductive support> A cylindrical aluminum support with a diameter of 30 mm was machined to create a conductive support with a surface roughness of Rz = 1.5 (μm).

[0126] <Middle class> A sand mill was used as a disperser to perform a batch dispersion treatment on the mixture of the following components for 10 hours. After that, the mixture was diluted twice with methanol, allowed to stand overnight, and then filtered using a 5 μm RigiMesh filter manufactured by Nippon Pall Co., Ltd. to obtain the intermediate layer coating solution. Polyamide resin (Toray Industries, Inc., Amiran CM8000) 1 part by mass (Amiran is a registered trademark of the company.) Titanium oxide (manufactured by Teika Co., Ltd., SMT500SAS) 3 parts by mass 10 parts by mass of methanol

[0127] The above-mentioned intermediate layer coating solution was applied to the surface of the conductive support by immersion coating to a dry film thickness of 2 μm, and then dried to obtain the intermediate layer.

[0128] <Charge generation layer> A sand mill was used as a disperser to disperse a mixture of the following components for 10 hours to obtain a charge generation layer coating solution. Charge-generating material: Titanyl phthalocyanine pigment (a titanyl phthalocyanine pigment having the maximum diffraction peak at at least 27.3° in Cu-Kα characteristic X-ray diffraction spectrum measurement) 20 parts by mass Polyvinyl butyral resin (manufactured by Denki Kagaku Kogyo Co., Ltd., #6000-C) 10 parts by mass 700 parts by mass of t-butyl acetate 4-Methoxy-4-methyl-2-pentanone 300 parts by mass

[0129] The above charge generation layer coating solution was applied to the surface of the intermediate layer by immersion coating to a dry film thickness of 0.3 μm, and then dried to obtain the charge generation layer.

[0130] <Charge transport layer> The following components were stirred and mixed to obtain a charge transport layer coating solution. Charge transport material (CTM-A) 225 parts by mass Polycarbonate resin (manufactured by Mitsubishi Gas Chemical Company, Z300) 300 parts by mass Antioxidant (BASF, Irganox 1010) 6 parts by mass 1600 parts by mass of tetrahydrofuran Toluene 400 parts by mass Silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF-54) 1 part by mass

[0131] The above-mentioned transport generation layer coating solution was applied to the surface of the above-mentioned medium charge generation layer by immersion coating method to a dry film thickness of 20 μm, and then dried to obtain a charge transport layer.

[0132] <Protective layer> The following components were stirred and mixed to obtain protective layer coating solution 1. Radical polymerizable charge transport compound A3: 85 parts by mass 10 parts by mass of silica particles surface-treated with a surface treatment agent (Shin-Etsu Chemical Co., Ltd., KF9908) having silicone chains as side chains. Polymerization initiator (Ominirad819, manufactured by IGM.Resis.BV) 5 parts by mass 350 parts by mass of tetrahydrofuran 2-Butanol 150 parts by mass

[0133] The protective layer coating solution 1 was applied to the surface of the charge transport layer using a circular slide hopper coating machine. Subsequently, the applied protective layer coating solution 1 was irradiated with ultraviolet light (wavelength 385 nm) from a xenon lamp for 1 minute to obtain a protective layer with a dry film thickness of 3.0 μm.

[0134] 1-2. Preparation of Photoreceptor 2 A protective layer coating solution 2 was prepared in the same manner as protective layer coating solution 1, except that a polymerization initiator was not added instead of protective layer coating solution 1. A protective layer with a dry film thickness of 30 μm was obtained by irradiating with an electron beam instead of ultraviolet light, in the same manner as photoreceptor 1.

[0135] 1-3. Preparation of photoreceptors 3 to 13 Photoreceptors 3 to 12 were obtained in the same manner as photoreceptor 1, except that protective layer coating solutions 3 to 13, whose compositions are shown in Table 1, were used instead of protective layer coating solution 1. As shown in Table 1, when preparing photoreceptor 8, light from a mercury xenon lamp was used instead of ultraviolet light to obtain the protective layer.

[0136] The abbreviations listed in Table 1 represent the following compounds or products, respectively.

[0137] (monomer) SR350: Trimethylolpropane trimethacrylate (manufactured by Sartmar, SR350)

[0138] (charge transport compound) A1: Compound represented by the following general formula (4)

[0139] [ka]

[0140] A2: Compound represented by the following general formula (5)

[0141] [ka]

[0142] A3: Compound represented by the following general formula (6)

[0143] [ka]

[0144] A4: Compound represented by the following general formula (7)

[0145] [ka]

[0146] (Surface treatment agent 1) Surface treatment agent 1 is a surface treatment agent having a silicone chain as a side chain. KF9908: Manufactured by Shin-Etsu Chemical Co., Ltd., KF9908 (main chain is a silicone chain) KF9909: Manufactured by Shin-Etsu Chemical Co., Ltd., KF9909 (main chain is a silicone chain) KP-574: Manufactured by Shin-Etsu Chemical Co., Ltd., KP-574 (main chain is (meth)acrylic copolymer) KP-578: Manufactured by Shin-Etsu Chemical Co., Ltd., KP-578 (main chain is (meth)acrylic copolymer)

[0147] (Surface treatment agent 2) Surface treatment agent 2 is a surface treatment agent having a radical polymerizable functional group. KBM503: Manufactured by Shin-Etsu Chemical Co., Ltd., KBM503 (containing a methacryloyl group)

[0148] (Surface treatment agent 3) Surface treatment agent 3 is a surface treatment agent having a silicone chain as its main chain, but no silicone chains as its side chains. X-22-4105: Manufactured by Shin-Etsu Chemical Co., Ltd., X-22-4105

[0149] (Polymerization initiator) 819: Ominirad819, manufactured by IGM.Resis.BV.

[0150] (Curing conditions) UV: Irradiation with ultraviolet light (wavelength 385nm) from a xenon lamp. EB: Electron beam irradiation Mercury Xe: Irradiated with light from a mercury xenon lamp.

[0151] [Table 1]

[0152] 2. Evaluation A commercially available color multifunction printer, the "bizhub C650i" (manufactured by Konica Minolta, Inc.), equipped with a electrostatic roller process, was used to install photoconductors 1 through 13. Each photoconductor was then independently subjected to durability tests under different environmental conditions, printing 500,000 sheets of A4 paper with a 6% image area ratio, double-sided, continuously. The following evaluations were performed before or after the durability tests.

[0153] 2-1. Starting torque of the cleaning blade (initial and after durability testing) Before the durability test (initial stage) and after the durability test in a 23°C, 50%RH environment, the static torque on the surface of the photoreceptor was measured by rotating a torque gauge (manufactured by Tohnichi Manufacturing Co., Ltd., MODEL 6BTG) connected to the drum shaft of the photoreceptor. Five measurements were taken, and the average value was used as the torque value. ◎: The measured torque value was 1.0 kgf·cm or less. ○: The measured torque value was greater than 1.0 kgf·cm and less than or equal to 2.0 kgf·cm. ×: The measured torque value was 2.0 kgf·cm or higher.

[0154] 2-2. Image distortion (after durability test) After durability testing in a 30°C / 85%RH environment (high temperature and high humidity environment), the main power to the color multifunction printer was immediately shut off. Twelve hours after shutting off, the power was turned back on, and after the printer was ready to print, a halftone image (relative reflectance of 0.4 as measured by a Macbeth densitometer) was immediately printed across the entire surface of A3 pH paper, and a 6-dot grid image was also printed across the entire surface of A3 pH paper. The condition of each printed image was visually observed, and the following evaluations were performed. ◎: No reduction in density occurred in any part of either the halftone image or the grid image. ○: A thin, band-like decrease in density along the long axis of the photoreceptor was observed in the halftone image, but no decrease in density was observed in any part of the grid image. ×: Significant loss of the grid image due to reduced density in certain areas, as well as noticeable thinning of line widths, was observed.

[0155] 2-3. Electrical characteristics (after durability test) After durability testing in a 10°C / 15%RH environment (low humidity / low temperature environment), the photoreceptor was exposed to light with its charging potential set to -800V, and the surface potential of the photoreceptor was measured after exposure. ◎: The surface potential after exposure was 0V to -150V. ○: The surface potential after exposure was -150V to -250V. ×: The surface potential after exposure was -250V~

[0156] The evaluation results for photoreceptors 1 to 13 are shown in Table 2.

[0157] [Table 2]

[0158] As shown in Tables 1 and 2, forming a protective layer with a cured product of a composition containing a charge-transporting compound having a radical polymerizable functional group and metal oxide particles surface-treated with a surface treatment agent having a silicone chain as a side chain reduced the rotational torque of the photoreceptor and also reduced the increase in rotational torque during long-term use. [Industrial applicability]

[0159] According to the present invention, the torque of the photoreceptor can be reduced and the durability of the photoreceptor can be increased. The present invention is expected to contribute to the further popularization of image forming methods using photoreceptors. [Explanation of Symbols]

[0160] 10 Image forming apparatus 20 Image reading unit 21 Paper feeder 22 Scanners 23 CCD sensor 24 Image Processing Unit 30 Image forming unit 31 Image forming unit 32 Photoreceptor 33 Charging device 34 Exposure equipment 35 Developing equipment 36 Cleaning device 40 Intermediate transfer section 41 Primary Transfer Unit 42 Secondary Transfer Unit 43 Intermediate transfer belt 44 Primary transfer roller 45 Backup Rollers 46. ​​First support roller 47 Cleaning device 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 Resist Roller vs D Manuscript S Paper (recording medium) 100 photoreceptor 110 Conductive support 120 Middle Class 130 Charge generation layer 140 Charge transport layer 150 protective layer

Claims

1. A conductive support, Photosensitive layer, A protective layer, An electrophotographic photoreceptor containing these elements stacked in this order, The protective layer is formed from a cured product of a composition comprising a charge-transporting compound having a radical polymerizable functional group and metal oxide particles surface-treated with a surface treatment agent having a silicone chain as a side chain. Electrophotographic photoreceptor.

2. The electrophotographic photoreceptor according to claim 1, wherein the metal oxide particles are further surface-treated with a surface treatment agent having a radical polymerizable functional group.

3. The electrophotographic photoreceptor according to claim 1 or 2, wherein the charge transporting compound having the radical polymerizable functional group is a compound represented by the following general formula (1). 【Chemistry 1】 (In general formula (1), Ar １ and Ar ２ This independently shows a structure represented by general formula (2), Ar ３ This represents a structure that can be expressed by general formula (2) or general formula (3), D is independently, -(-(CH ２ )) ｄ -(O-(CH ２ )) ｆ -) ｅ -O-CO-C(CH ３ )=CH ２ ) or -(-(CH ２ )) ｄ -(O-(CH ２ )) ｆ -) ｅ -O-CO-CH=CH ２ ) represents the structure shown, d and f independently represent an integer of 0 or more and 5 or less, e represents an integer of 0 or 1, c1 to c3 independently represent integers 0, 1, or 2. Ar ３ When the structure is represented by general formula (2), the total number of D in the compound is 1 or 2. Ar ３ When the structure is represented by general formula (3), the total number of D atoms in the compound is 1. 【Chemistry 2】 【Transformation 3】 (In general formulas (2) and (3), R １ and R ２ R independently represents a functional group or atom selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group substituted with an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom, provided that in general formula (3), two R ２ They may combine to form a ring structure. (t independently represents an integer between 1 and 3, inclusive.)

4. The compound represented by the general formula (1) is Ar ３ The electrophotographic photoreceptor according to claim 3, wherein the compound exhibits a structure represented by general formula (3).

5. The electrophotographic photoreceptor according to claim 3, wherein the compound represented by the general formula (1) is a compound in which the sum of c1 to c3 is 1, e in the structure represented by D is 1, and at least one of d and f is an integer between 1 and 4.

6. The electrophotographic photoreceptor according to claim 1 or 2, wherein the metal oxide particles are silica particles.

7. An image forming apparatus having an electrophotographic photoreceptor according to claim 1 or 2.

8. A step of bringing a charging roller into contact with the electrophotographic photoreceptor according to claim 1 or 2 to charge the surface of the electrophotographic photoreceptor, The steps include: applying toner to the surface of the charged electrophotographic photoreceptor; A step of transferring the applied toner to a recording medium, An image forming method having the following characteristics.

Images