Image forming device

Abstract

To provide an image forming apparatus in which density unevenness hardly occurs in an image and filming hardly occurs on the surface of a photosensitive member. [Solution] The image forming device comprises a photosensitive member, a charging device, an electrostatic latent image forming device, a developing device, a transfer device, and a photosensitive member cleaning device, wherein the toner constituting the developer contained in the developing device contains toner particles, titanic acid compound particles, and silica particles, the surface layer of the photosensitive member contains a polyarylate resin having dicarboxylic acid units (A) represented by formula A and diol units (B) represented by formula B, and the cleaning blade of the photosensitive member cleaning device has a first polyurethane layer that contacts the photosensitive member and has a hardness of 85 degrees or more and 95 degrees or less, and a second polyurethane layer that supports the first polyurethane layer and has a hardness of 55 degrees or more and 70 degrees or less. JPEG2026035030000043.jpg44109

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses an image forming apparatus in which a photoreceptor has a laminated photosensitive layer in which a charge generation layer and a charge transport layer are laminated in this order on a conductive support, the charge transport layer contains a charge transport material, a binder resin, and fluorine-based resin fine particles, the contact angle of the charge transport layer surface with pure water is 85° or more, and a toner is used in which a core made of strontium titanate to which silica has been added is externally added, and strontium titanate fine powder and silica fine particles are surface-treated with a silane compound to make it hydrophobic.

[0003] Patent Document 2 discloses a toner for developing electrostatic images, which is a toner to which inorganic particles A and silica particles B are externally added, wherein the inorganic particles A contain calcium titanate or barium titanate, the number average particle size of the primary particles of the inorganic particles A is 40 nm to 80 nm, the number average particle size of the primary particles of the silica particles B is 60 nm to 120 nm, and the circularity of the silica particles B is 0.95 to 1.00.

[0004] Patent Document 3 discloses an image forming apparatus that includes an image carrier in which, when viewed in cross section of the image carrier, a virtual line connecting the contact point between the image carrier and the cleaning member and the center O of the image carrier is defined as a line segment X, the angle θ that the line segment X forms with a horizontal plane Y is 0 degrees or more and 30 degrees or less, and a cleaning member having a Type A durometer hardness of 65 degrees or more and 80 degrees or less, and that uses toner to which titanate compound particles doped with lanthanum and an element of Group 5 of the periodic table are externally added. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-143015 [Patent Document 2] Japanese Patent Publication No. 2021-071614 [Patent Document 3] Japanese Patent Publication No. 2020-187183 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide an image forming apparatus in which density unevenness is unlikely to occur in an image and filming is unlikely to occur on the surface of a photosensitive member. [Means for solving the problem]

[0007] Specific means for solving the above problems include the following aspects: Each formula is the same as the formula with the same number described below.

[0008] <1> A photoreceptor; a charging device that charges the surface of the photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the photoreceptor; a developing device that contains a developer containing toner and develops the electrostatic latent image formed on the surface of the photoreceptor to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a cleaning device having a cleaning blade that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor; the toner comprises toner particles, titanate compound particles, and silica particles; the surface layer of the photoreceptor contains a polyarylate resin having a dicarboxylic acid unit (A) represented by formula A and a diol unit (B) represented by formula B, the cleaning blade has a first polyurethane layer that is in contact with the photoreceptor and has a hardness of 85 degrees or more and 95 degrees or less, and a second polyurethane layer that is a layer that supports the first polyurethane layer and has a hardness of 55 degrees or more and 70 degrees or less, Image forming device. <2> In the dynamic viscoelasticity measurement of the cleaning blade, when the maximum value of the loss tangent in the temperature range of 0°C or higher and 30°C or lower is defined as tanδ(Max) and the minimum value thereof is defined as tanδ(Min), the relationship between tanδ(Max) and tanδ(Min) is satisfied. <1> 2. The image forming apparatus according to claim 1 . <3> the photoreceptor has a charge generating layer and a charge transport layer, and the charge transport layer is the surface layer; <1> or <2> 2. The image forming apparatus according to claim 1 . <4> the weight average molecular weight of the polyarylate resin contained in the surface layer of the photoreceptor is 80,000 or more and 150,000 or less; <1> ~ <3> 10. The image forming apparatus according to claim 9, wherein: <5> the titanic acid compound particles contained in the toner have an average primary particle size of 20 nm or more and 100 nm or less; <1> ~ <4> 10. The image forming apparatus according to claim 9, wherein: <6> the average primary particle size of the silica particles contained in the toner is 50 nm or more and 150 nm or less; <1> ~ <5> 10. The image forming apparatus according to claim 9, wherein: <7> The titanate compound particles include alkaline earth metal titanate particles. <1> ~ <6> 10. The image forming apparatus according to claim 9, wherein: <8> the titanate compound particles include strontium titanate particles containing a dopant; <1> ~ <7> 10. The image forming apparatus according to claim 9, wherein: <9> the dopant comprises lanthanum; <8> 2. The image forming apparatus according to claim 1 . <10> The cleaning blade contacts the surface of the photoreceptor with a pressing pressure of 1 gf / mm or more and 4 gf / mm or less. <1> ~ <9> 10. The image forming apparatus according to claim 9, wherein: <11> The dicarboxylic acid unit (A) contains at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1), a dicarboxylic acid unit (A2) represented by formula (A2), and a dicarboxylic acid unit (A3) represented by formula (A3). <1> ~ <10> 10. The image forming apparatus according to claim 9, wherein: <12> The diol unit (B) comprises at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8). <1> ~ <11> 10. The image forming apparatus according to claim 9, wherein: [Effects of the Invention]

[0009] <1> , <3> , <7> , <8> , <9> , <11> and <12> According to this, an image forming device is provided in which density unevenness in images is less likely to occur compared to a configuration in which the surface layer of the photoreceptor does not contain polyarylate resin but contains polycarbonate resin, a configuration in which the hardness of the first polyurethane layer is greater than 95 degrees, and a configuration in which the hardness of the second polyurethane layer is greater than 70 degrees, and in which filming is less likely to occur on the surface of the photoreceptor compared to a configuration in which the hardness of the first polyurethane layer is less than 85 degrees and a configuration in which the hardness of the second polyurethane layer is less than 55 degrees. <2> According to this, an image forming device is provided in which density unevenness is less likely to occur in the image and filming is less likely to occur on the surface of the photosensitive member compared to a configuration in which tanδ(Max)>0.5 or tanδ(Max)-tanδ(Min)>0.1. <4> According to the present invention, an image forming apparatus is provided in which density unevenness is less likely to occur in an image than in an embodiment in which the weight average molecular weight of the polyarylate resin contained in the surface layer of the photoreceptor is less than 80,000, and in which filming is less likely to occur on the surface of the photoreceptor than in an embodiment in which the weight average molecular weight of the polyarylate resin is more than 150,000. <5> According to the present invention, an image forming apparatus is provided in which fogging is less likely to occur in images than in an embodiment in which the average primary particle size of the titanate compound particles contained in the toner is less than 20 nm, and which is less likely to cause blurring in images than in an embodiment in which the average primary particle size of the titanate compound particles is more than 100 nm. <6> According to the present invention, an image forming apparatus is provided in which fogging is less likely to occur in images than in an embodiment in which the average primary particle size of silica particles contained in the toner is less than 50 nm, and in which blurring and fogging are less likely to occur in images than in an embodiment in which the average primary particle size of silica particles is more than 150 nm. <10> According to this, an image forming apparatus is provided in which density unevenness is less likely to occur in the image and filming is less likely to occur on the surface of the photosensitive member, compared to a configuration in which the cleaning blade contacts the surface of the photosensitive member with a pressing pressure of less than 1 gf / mm and a configuration in which the cleaning blade contacts the surface of the photosensitive member with a pressing pressure of more than 4 gf / mm. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 10 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. [Figure 3] FIG. 2 is a partial cross-sectional view showing an example of a layer structure of a photoreceptor according to the present embodiment. [Figure 4] FIG. 4 is a partial cross-sectional view showing another example of the layer structure of the photoreceptor according to the present embodiment. [Figure 5] FIG. 2 is a schematic diagram illustrating an example of a cleaning blade according to the present embodiment. [Figure 6] FIG. 2 is a schematic diagram illustrating an example of a cleaning blade according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0023] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0012] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0013] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0014] When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0015] In the present disclosure, each component may contain multiple corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified. In the present disclosure, the composition may contain multiple types of particles corresponding to each component. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0016] In the present disclosure, alkyl groups and alkylene groups include any of linear, branched and cyclic groups, unless otherwise specified. In the present disclosure, a hydrogen atom in an organic group, aromatic ring, linking group, alkyl group, alkylene group, aryl group, aralkyl group, alkoxy group, aryloxy group, or the like may be substituted with a halogen atom. In the present disclosure, when a compound is represented by a structural formula, the symbols (C and H) representing carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain may be omitted. In the present disclosure, "(meth)acrylic" is an expression that includes both acrylic and methacrylic, and "(meth)acrylate" is an expression that includes both acrylate and methacrylate. In the present disclosure, the term "structural unit" of a copolymer or resin has the same meaning as a monomer unit.

[0017] In this disclosure, the term "photoreceptor" refers to an "electrophotographic photoreceptor." In this disclosure, the "axial direction" of a photoreceptor means the direction in which the rotation axis of the photoreceptor extends, and the "circumferential direction" of a photoreceptor means the rotation direction of the photoreceptor.

[0018] <Image forming device> The image forming apparatus according to this embodiment includes: A photoreceptor; a charging device for charging the surface of the photoreceptor; an electrostatic latent image forming device that forms an electrostatic latent image on the surface of a charged photoreceptor; a developing device that contains a developer containing toner and develops the electrostatic latent image formed on the surface of the photosensitive member to form a toner image; a transfer device that transfers the toner image onto the surface of a recording medium; and a cleaning device having a cleaning blade that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor.

[0019] The image forming apparatus according to this embodiment includes: The toner constituting the developer contained in the developing device contains toner particles, titanic acid compound particles, and silica particles, The surface layer of the photoreceptor contains a polyarylate resin having a dicarboxylic acid unit (A) represented by formula A and a diol unit (B) represented by formula B, The cleaning blade has a first polyurethane layer that comes into contact with the photoreceptor and has a hardness of 85 degrees or more and 95 degrees or less, and a second polyurethane layer that supports the first polyurethane layer and has a hardness of 55 degrees or more and 70 degrees or less.

[0020] [ka]

[0021] In formula (A), Ar A1 and Ar A2 each independently represents an aromatic ring which may have a substituent, and L A is a single bond or a divalent linking group, and n A1 is 0, 1 or 2. In formula (B), Ar B1 and Ar B2 each independently represents an aromatic ring which may have a substituent, and L B is a single bond, an oxygen atom, a sulfur atom, or -C(Rb 1 )(Rb 2 )- and n B1 is 0, 1 or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group.

[0022] In the present disclosure, a polyarylate resin having dicarboxylic acid units (A) represented by formula A and diol units (B) represented by formula B may be referred to as a "polyarylate resin (S)."

[0023] According to the image forming apparatus of this embodiment, density unevenness is unlikely to occur in the image, and filming (the formation of a film) is unlikely to occur on the surface of the photosensitive member.

[0024] Toners containing externally added titanate compound particles and silica particles have been known. These toners are less likely to produce blurred or foggy images (a phenomenon in which toner adheres to areas of a photoreceptor where there is no electrostatic latent image, resulting in the appearance of an unintended image on a recording medium). However, because the amount of external additives transferred to the photoreceptor is relatively small, the frictional force between the photoreceptor and the cleaning blade tends to be large. As a result, the difference in wear between the image and non-image areas on the photoreceptor surface increases, resulting in uneven density. Furthermore, the behavior of the cleaning blade tip becomes unstable, resulting in poor cleaning performance. Increasing the hardness of the cleaning blade to stabilize the behavior of the cleaning blade tip also increases the difference in wear between the image and non-image areas on the photoreceptor surface. In contrast, the image forming apparatus according to this embodiment has excellent abrasion resistance because the surface layer of the photoreceptor contains polyarylate resin (S). The polyarylate resin (S) has aromatic ring stacking that bonds resin molecules together through intermolecular forces, improving the abrasion resistance of the surface layer. In addition, the image forming device according to this embodiment has a relatively hard layer (first polyurethane layer) on the side of the cleaning blade that comes into contact with the photosensitive member, and is supported by a relatively soft layer (second polyurethane layer), thereby stabilizing the behavior of the tip of the cleaning blade and improving cleaning performance.

[0025] The first polyurethane layer of the cleaning blade is a polyurethane layer having a hardness of 85 degrees or more and 95 degrees or less. If the hardness of the first polyurethane layer is less than 85 degrees, the cleaning ability may be poor and filming may occur on the surface of the photoreceptor. From the viewpoint of suppressing the occurrence of filming on the surface of the photoreceptor, the hardness of the first polyurethane layer is 85 degrees or more, preferably 86 degrees or more, more preferably 87 degrees or more, and even more preferably 88 degrees or more. If the hardness of the first polyurethane layer exceeds 95 degrees, the difference in the amount of wear between the image area and the non-image area on the surface of the photoreceptor increases, which may cause density unevenness in the image. From the viewpoint of suppressing the occurrence of density unevenness in the image, the hardness of the first polyurethane layer is 95 degrees or less, preferably 94 degrees or less, more preferably 93 degrees or less, and even more preferably 92 degrees or less.

[0026] The second polyurethane layer of the cleaning blade is a polyurethane layer having a hardness of 55 degrees or more and 70 degrees or less. If the hardness of the second polyurethane layer is less than 55 degrees, the cleaning blade may turn over, reducing cleaning power and causing filming on the surface of the photoreceptor. From the viewpoint of suppressing filming on the surface of the photoreceptor, the hardness of the second polyurethane layer is 55 degrees or more, preferably 58 degrees or more, more preferably 60 degrees or more, and even more preferably 62 degrees or more. If the hardness of the second polyurethane layer exceeds 70 degrees, the difference in the amount of wear between the image area and the non-image area on the surface of the photoreceptor increases, which may cause density unevenness in the image. From the viewpoint of suppressing the occurrence of density unevenness in the image, the hardness of the second polyurethane layer is 70 degrees or less, preferably 69 degrees or less, more preferably 68 degrees or less, and even more preferably 67 degrees or less.

[0027] The configuration of the image forming apparatus according to this embodiment will be described in detail below.

[0028] The image forming apparatus according to this embodiment includes a photosensitive member, a charging device, an electrostatic latent image forming device, a developing device, a transfer device, and a photosensitive member cleaning device. The image forming apparatus according to this embodiment may further include a fixing device that fixes the toner image transferred onto the surface of the recording medium, and a de-electrification device that irradiates the surface of the photosensitive member with de-electrification light to de-electrify the toner image after it has been transferred and before it is charged. The image forming apparatus according to this embodiment may have a cartridge structure (process cartridge) in which the portion including the photosensitive member is detachably attached to the image forming apparatus.

[0029] The image forming apparatus according to the present embodiment may be a direct transfer type image forming apparatus in which a toner image formed on the surface of a photoreceptor is directly transferred to a recording medium, or an intermediate transfer type image forming apparatus in which a toner image formed on the surface of a photoreceptor is primarily transferred to the surface of an intermediate transfer body, and the toner image transferred to the surface of the intermediate transfer body is then secondarily transferred to the surface of a recording medium. The intermediate transfer type transfer apparatus, for example, has an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer device that primarily transfers the toner image formed on the surface of the photoreceptor onto the surface of the intermediate transfer body, and a secondary transfer device that secondarily transfers the toner image transferred to the surface of the intermediate transfer body onto the surface of a recording medium.

[0030] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. The main parts shown in the drawings will be described, and the description of the rest will be omitted.

[0031] FIG. 1 is a schematic diagram showing an example of the configuration of an image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 100 according to this embodiment includes a process cartridge 300 having a photosensitive member 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is disposed in a position where it can expose the photosensitive member 7 through the opening of the process cartridge 300, and the transfer device 40 is disposed in a position facing the photosensitive member 7 with the intermediate transfer member 50 interposed therebetween, with a portion of the intermediate transfer member 50 being in contact with the photosensitive member 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer member 50 onto a recording medium (e.g., paper). The intermediate transfer member 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to examples of transfer devices.

[0032] 1 integrally supports within a housing a photosensitive member 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a photosensitive member cleaning device). The cleaning device 13 has a cleaning blade 131 (an example of a cleaning member), and the cleaning blade 131 is disposed so as to come into contact with the surface of the photosensitive member 7.

[0033] FIG. 1 shows an example of an image forming apparatus equipped with a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of photoreceptor 7, and a fibrous member 133 (flat brush-shaped) that assists cleaning, which may be arranged as needed.

[0034] FIG. 2 is a schematic diagram showing another example of the image forming apparatus according to the present embodiment. 2 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one photosensitive body is used per color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem-type apparatus.

[0035] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0036] [Photoreceptor] The photoreceptor 7 has a structure in which a photosensitive layer is disposed on a conductive substrate. The photosensitive layer may be a laminated type photosensitive layer consisting of a charge generating layer and a charge transport layer, or may be a single-layer type photosensitive layer. Details of the photoreceptor will be described later.

[0037] [Charging device] The charging device 8 may be a contact type charger using, for example, a conductive or semi-conductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, etc. The charging device 8 may also be a known charger such as a non-contact type roller charger, or a scorotron charger or corotron charger that uses corona discharge.

[0038] [Exposure equipment] Examples of the exposure device 9 include optical equipment that exposes the surface of the photoconductor 7 with light such as semiconductor laser light, LED light, or liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity range of the photoconductor. The wavelength of semiconductor lasers is mainly near-infrared, with an oscillation wavelength around 780 nm. However, this wavelength is not limited to this, and lasers with an oscillation wavelength in the 600 nm range or blue lasers with an oscillation wavelength of 400 nm to 450 nm may also be used. Furthermore, for color image formation, a surface-emitting laser light source capable of outputting multiple beams is also effective.

[0039] [Developing device] The developing device 11 may be, for example, a general developing device that develops by contact or non-contact application of a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected according to the purpose. For example, it may be a known developing device that has a function of applying a one-component developer or a two-component developer to the photoreceptor 7 using a brush, roller, or the like. Among these, a developing roller that holds the developer on its surface is preferred.

[0040] The developer used in the developing device 11 may be a one-component developer containing only toner, or a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Details of the toner and developer will be described later.

[0041] [Cleaning device] The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131. Details of the cleaning blade will be described later.

[0042] [Transfer device] Examples of the transfer device 40 include a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a known transfer charger such as a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0043] [Intermediate transfer body] A belt-like material (intermediate transfer belt) containing semiconductively-conductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. is used as the intermediate transfer body 50. The intermediate transfer body may be in the form of a drum other than a belt.

[0044] The operation of forming an image by image forming apparatus 100 shown in FIG. 1 will be described. The photoreceptor 7 rotates at a predetermined speed. A charging device 8 charges the surface of the photoreceptor 7 . The charged surface of the photoreceptor 7 is irradiated with, for example, a laser beam from the exposure device 9, and an electrostatic latent image is formed on the surface of the photoreceptor 7. The electrostatic latent image formed on the photoreceptor 7 moves to a development position as the photoreceptor 7 rotates. At the development position, the electrostatic latent image on the photoreceptor 7 is developed into a toner image by a developing device 11 and made visible. The toner image formed on the photoreceptor 7 moves to the primary transfer position as the photoreceptor 7 rotates. At the primary transfer position, a transfer bias is applied to the transfer device 40, and an electrostatic force from the photoreceptor 7 toward the transfer device 40 acts on the toner image on the photoreceptor 7, transferring the toner image to the intermediate transfer body 50. The intermediate transfer member 50 travels at a predetermined speed, and the toner image is transferred to a recording medium at the secondary transfer position by a secondary transfer device. The toner remaining on the surface of the photoreceptor 7 is removed and collected by the cleaning device 13.

[0045] The photoconductor included in the image forming apparatus according to this embodiment will be described in detail below. The cleaning blade of the photoconductor cleaning device included in the image forming apparatus according to this embodiment will also be described in detail. The toner and developer used in the developing device included in the image forming apparatus according to this embodiment will also be described in detail.

[0046] [Photoreceptor] An embodiment of the photoreceptor will be described with reference to FIGS.

[0047] FIG. 3 is a partial cross-sectional view schematically illustrating an example of the layer structure of a photoreceptor. Photoreceptor 10A shown in FIG. 3 has a laminated photosensitive layer. Photoreceptor 10A has a structure in which an undercoat layer 2, a charge generation layer 3, and a charge transport layer 4 are laminated in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute a photosensitive layer 5 (a so-called function-separated photosensitive layer). Photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The undercoat layer 2 may or may not be present. In the photoreceptor 10A, the charge transport layer 4 is the surface layer.

[0048] Fig. 4 is a partial cross-sectional view schematically showing another example of the layer structure of a photoreceptor. The photoreceptor 10B shown in Fig. 4 has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are laminated in this order on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 2 and the photosensitive layer 5. The undercoat layer 2 may or may not be present. In the photoreceptor 10B, the photosensitive layer 5 is the surface layer.

[0049] In the image forming apparatus according to this embodiment, the surface layer of the photoreceptor contains a polyarylate resin (S). The polyarylate resin (S) has aromatic rings that stack together to bond resin molecules with intermolecular forces, improving the abrasion resistance of the surface layer.

[0050] [Polyarylate resin (S)] The surface layer of the photoreceptor contains, as a binder resin, a polyarylate resin (S) having at least a dicarboxylic acid unit (A) and a diol unit (B). The polyarylate resin (S) may contain a dicarboxylic acid unit other than the dicarboxylic acid unit (A). The polyarylate resin (S) may contain a diol unit other than the diol unit (B).

[0051] The dicarboxylic acid unit (A) is a structural unit represented by the following formula (A).

[0052] [ka]

[0053] In formula (A), Ar A1 and Ar A2 each independently represents an aromatic ring which may have a substituent, and L A is a single bond or a divalent linking group, and n A1 is 0, 1 or 2.

[0054] Ar A1 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0055] Ar A1 The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. A1 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0056] Ar A2 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0057] Ar A2 The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. A2 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0058] L A When is a divalent linking group, examples of the divalent linking group include an oxygen atom, a sulfur atom, -C(Ra 1 )(Ra 2 )-, where Ra 1 and Ra 2 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms; 1 and Ra 2 may be bonded to form a cyclic alkyl group.

[0059] Ra 1 and Ra 2 The alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0060] Ra 1 and Ra 2 The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0061] Ra 1 and Ra 2 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Ra1 and Ra 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, more preferably 6.

[0062] The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by the following formula (A2), and a dicarboxylic acid unit (A3) represented by the following formula (A3): The dicarboxylic acid unit (A) more preferably contains at least one selected from the group consisting of the dicarboxylic acid unit (A1) and the dicarboxylic acid unit (A2), and further preferably contains the dicarboxylic acid unit (A1).

[0063] [ka]

[0064] In formula (A1), n 101 and n 102 are each independently an integer of 0 to 4, 101 Ra 101 and n 102 Ra 102 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 101 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 102 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0065] [ka]

[0066] In formula (A2), n 201 is an integer between 0 and 6, and n201 Ra 201 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 201 is preferably an integer of 0 or more and 4 or less, more preferably 0, 1 or 2, and even more preferably 0.

[0067] [ka]

[0068] In formula (A3), n 301 , n 302 and n 303 are each independently an integer of 0 to 4, 301 Ra 301 , n 302 Ra 302 and n 303 Ra 303 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 301 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 302 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 303 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0069] Ra in formula (A1) 101 and Ra 102 , Ra in formula (A2) 201 and Ra in formula (A3) 301 , Ra 302 and Ra 303 Since the specific and preferred embodiments of Ra are the same as those of 101 , Ra 102 , Ra 201 , Ra301 , Ra 302 and Ra 303 These will be collectively referred to as "Ra".

[0070] The alkyl group having 1 to 10 carbon atoms represented by Ra may be linear, branched, or cyclic. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms. Examples of the linear alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. Examples of branched alkyl groups having 3 to 10 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group. Examples of the cyclic alkyl group having 3 to 10 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups formed by linking these monocyclic alkyl groups.

[0071] The aryl group having 6 to 12 carbon atoms for Ra may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0072] The alkyl group in the alkoxy group having 1 to 6 carbon atoms, represented by Ra, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0073] Specific examples of the dicarboxylic acid unit (A1) include dicarboxylic acid units (A1-1) to (A1-3), but the dicarboxylic acid unit (A1) is not limited thereto.

[0074] [ka]

[0075] Specific examples of the dicarboxylic acid unit (A2) include dicarboxylic acid units (A2-1) to (A2-3), but the dicarboxylic acid unit (A2) is not limited thereto.

[0076] [ka]

[0077] Specific examples of the dicarboxylic acid unit (A3) include dicarboxylic acid units (A3-1) to (A3-4), but the dicarboxylic acid unit (A3) is not limited thereto.

[0078] [ka]

[0079] The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of the above specific examples (A1-3), (A2-3) and (A3-3), more preferably contains at least one selected from the group consisting of (A1-3) and (A2-3), and even more preferably contains at least (A1-3).

[0080] The dicarboxylic acid units (A1) to (A3) contained in the polyarylate resin (S) may be of one type or two or more types.

[0081] The total mass proportion of the dicarboxylic acid units (A1) to (A3) in the polyarylate resin (S) is preferably 15 mass % or more and 60 mass % or less. When the total mass proportion of the dicarboxylic acid units (A1) to (A3) is 15% by mass or more, the surface layer has good abrasion resistance. From this viewpoint, the total mass proportion of the dicarboxylic acid units (A1) to (A3) is more preferably 20% by mass or more, and even more preferably 25% by mass or more. When the total mass proportion of the dicarboxylic acid units (A1) to (A3) is 60 mass% or less, peeling of the surface layer can be suppressed. From this viewpoint, the total mass proportion of the dicarboxylic acid units (A1) to (A3) is more preferably 55 mass% or less, and even more preferably 50 mass% or less.

[0082] The dicarboxylic acid unit (A) contained in the polyarylate resin (S) may be of one type or two or more types.

[0083] The polyarylate resin (S) may contain dicarboxylic acid units other than the dicarboxylic acid units (A). Examples of the other dicarboxylic acid units include aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acid units (e.g., cyclohexanedicarboxylic acid), and lower alkyl ester units thereof (e.g., having 1 to 5 carbon atoms). The polyarylate resin (S) may contain one or more types of these dicarboxylic acid units.

[0084] The diol unit (B) is a structural unit represented by the following formula (B).

[0085] [ka]

[0086] In formula (B), Ar B1 and Ar B2 each independently represents an aromatic ring which may have a substituent, and L B is a single bond, an oxygen atom, a sulfur atom, or -C(Rb 1 )(Rb 2 )- and n B1 is 0, 1 or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group.

[0087] Ar B1 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0088] Ar B1The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. B1 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0089] Ar B2 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0090] Ar B2 The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. B2 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0091] Rb 1 and Rb 2 The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 18 carbon atoms, more preferably 1 to 14 carbon atoms, and even more preferably 1 to 10 carbon atoms.

[0092] Rb 1 and Rb 2 The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0093] Rb 1 and Rb 2The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Rb 1 and Rb 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, more preferably 6.

[0094] The diol unit (B) preferably contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the formula (B2), a diol unit (B3) represented by the formula (B3), a diol unit (B4) represented by the formula (B4), a diol unit (B5) represented by the formula (B5), a diol unit (B6) represented by the formula (B6), a diol unit (B7) represented by the formula (B7), and a diol unit (B8) represented by the formula (B8).

[0095] It is more preferable that the diol unit (B) contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the formula (B2), a diol unit (B4) represented by the formula (B4), a diol unit (B5) represented by the formula (B5), and a diol unit (B6) represented by the formula (B6): It is more preferable that the diol unit (B1) contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), a diol unit (B5) represented by the following formula (B5), and a diol unit (B6) represented by the following formula (B6): It is even more preferable that the diol unit (B1) contains at least one selected from the group consisting of a diol unit (B2) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), and a diol unit (B6) represented by the following formula (B6): It is most preferable that the diol unit (B1) contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1) and a diol unit (B2) represented by the following formula (B2).

[0096] [ka]

[0097] In formula (B1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, and Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 401 , Rb 501 , Rb 801 and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0098] Rb 101 The number of carbon atoms in the branched alkyl group having 4 to 20 carbon atoms in the formula Rb is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 101 Specific examples of the aryl group include an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, an isododecyl group, a sec-dodecyl group, a tert-dodecyl group, a tert-tetradecyl group, and a tert-pentadecyl group.

[0099] [ka]

[0100] In formula (B2), Rb 102is a linear alkyl group having 4 to 20 carbon atoms, and Rb 202 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 402 , Rb 502 , Rb 802 and Rb 902 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0101] Rb 102 The carbon number of the linear alkyl group having 4 to 20 carbon atoms in the formula (Rb) is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 102 Specific examples of the alkyl group include an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, a tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-icosyl group.

[0102] [ka]

[0103] In formula (B3), Rb 113 and Rb 213 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; d is an integer of 7 to 15; Rb 403 , Rb 503 , Rb 803 and Rb 903 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0104] Rb 113 and Rb 213 The number of carbon atoms in the linear alkyl group having 1 to 3 carbon atoms is preferably 1 or 2, and more preferably 1. Specific examples of such groups include a methyl group, an ethyl group, and an n-propyl group. Rb 113 and Rb 213 The alkyl group in the alkoxy group having from 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 4 carbon atoms is preferably from 1 to 3, more preferably 1 or 2, and even more preferably 1. Specific examples of such groups include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group. Rb 113 and Rb 213 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0105] [ka]

[0106] In formula (B4), Rb 104 and Rb 204 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 404 , Rb 504 , Rb 804 and Rb 904 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0107] Rb 104 The alkyl group having 1 to 3 carbon atoms in the formula (1) may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or 2, and more preferably 1. 104 Specific examples of the group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0108] [ka]

[0109] In formula (B5), Ar 105 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 205 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 405 , Rb 505 , Rb 805 and Rb 905 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0110] Ar 105 The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Ar 105 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Ar 105 The aryl group in the aralkyl group having 7 to 20 carbon atoms according to the above formula may be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of the aralkyl group having 7 to 20 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a 4-phenylbutyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, a phenylnonyl group, a naphthylmethyl group, a naphthylethyl group, an anthracenylmethyl group, and a phenyl-cyclopentylmethyl group.

[0111] [ka]

[0112] In formula (B6), Rb 116 and Rb 216 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; e is an integer of 4 to 6; Rb406 , Rb 506 , Rb 806 and Rb 906 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0113] Rb 116 and Rb 216 The number of carbon atoms in the linear alkyl group having 1 to 3 carbon atoms is preferably 1 or 2, and more preferably 1. Specific examples of such groups include a methyl group, an ethyl group, and an n-propyl group. Rb 116 and Rb 216 The alkyl group in the alkoxy group having from 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 4 carbon atoms is preferably from 1 to 3, more preferably 1 or 2, and even more preferably 1. Specific examples of such groups include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group. Rb 116 and Rb 216 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0114] [ka]

[0115] In formula (B7), Rb 407 , Rb 507 , Rb 807 and Rb 907 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0116] [ka]

[0117] In formula (B8), Rb 408 , Rb 508 , Rb 808 and Rb 908 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0118] Rb in formula (B1) 201 , Rb in formula (B2) 202 , Rb in formula (B4) 204 and Rb of formula (B5) 205 Since the specific and preferred embodiments of Rb are the same as those of Rb, 201 , Rb 202 , Rb 204 and Rb 205 "Rb 200 " is collectively referred to as ".

[0119] Rb 200 The alkyl group having 1 to 3 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, and more preferably 1 carbon atom. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0120] Rb in formula (B1) 401 , Rb in formula (B2) 402 , Rb in formula (B3) 403 , Rb in formula (B4) 404 , Rb in formula (B5) 405 , Rb in formula (B6) 406 , Rb in formula (B7) 407 and Rb of formula (B8) 408 Since the specific and preferred embodiments of Rb are the same as those of Rb, 401 , Rb 402 , Rb 403 , Rb 404 , Rb 405 , Rb 406 , Rb 407 and Rb 408 "Rb 400 " is collectively referred to as ".

[0121] Rb 400 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0122] Rb 400 The alkyl group in the alkoxy group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0123] Rb 400 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0124] Rb in formula (B1) 501 , Rb in formula (B2) 502, Rb in formula (B3) 503 , Rb in formula (B4) 504 , Rb in formula (B5) 505 , Rb in formula (B6) 506 , Rb in formula (B7) 507 and Rb of formula (B8) 508 Since the specific and preferred embodiments of Rb are the same as those of Rb, 501 , Rb 502 , Rb 503 , Rb 504 , Rb 505 , Rb 506 , Rb 507 and Rb 508 "Rb 500 " is collectively referred to as ".

[0125] Rb 500 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0126] Rb 500 The alkyl group in the alkoxy group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0127] Rb 500 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0128] Rb in formula (B1) 801 , Rb in formula (B2) 802 , Rb in formula (B3) 803 , Rb in formula (B4) 804 , Rb in formula (B5) 805 , Rb in formula (B6) 806 , Rb in formula (B7) 807 and Rb of formula (B8) 808 Since the specific and preferred embodiments of Rb are the same as those of Rb, 801 , Rb 802 , Rb 803 , Rb 804 , Rb 805 , Rb 806 , Rb 807 and Rb 808 "Rb 800 " is collectively referred to as ".

[0129] Rb 800 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0130] Rb 800 The alkyl group in the alkoxy group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0131] Rb 800 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0132] Rb in formula (B1) 901 , Rb in formula (B2) 902 , Rb in formula (B3) 903 , Rb in formula (B4) 904 , Rb in formula (B5) 905 , Rb in formula (B6) 906 , Rb in formula (B7) 907 and Rb of formula (B8) 908 Since the specific and preferred embodiments of Rb are the same as those of Rb, 901 , Rb 902 , Rb 903 , Rb 904 , Rb 905 , Rb 906 , Rb907 and Rb 908 "Rb 900 " is collectively referred to as ".

[0133] Rb 900 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0134] Rb 900 The alkyl group in the alkoxy group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0135] Rb 900 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0136] Specific examples of the diol unit (B1) include diol units (B1-1) to (B1-6), but the diol unit (B1) is not limited thereto.

[0137] [ka]

[0138] Specific examples of the diol unit (B2) include diol units (B2-1) to (B2-11), but the diol unit (B2) is not limited thereto.

[0139] [ka]

[0140] Specific examples of the diol unit (B3) include diol units (B3-1) to (B3-4), but the diol unit (B3) is not limited thereto.

[0141] [ka]

[0142] Specific examples of the diol unit (B4) include diol units (B4-1) to (B4-7), but the diol unit (B4) is not limited thereto.

[0143] [ka]

[0144] Specific examples of the diol unit (B5) include diol units (B5-1) to (B5-6), but the diol unit (B5) is not limited thereto.

[0145] [ka]

[0146] Specific examples of the diol unit (B6) include diol units (B6-1) to (B6-4), but the diol unit (B6) is not limited thereto.

[0147] [ka]

[0148] Specific examples of the diol unit (B7) include diol units (B7-1) to (B7-3), but the diol unit (B7) is not limited thereto.

[0149] [ka]

[0150] Specific examples of the diol unit (B8) include diol units (B8-1) to (B8-3), but the diol unit (B8) is not limited thereto.

[0151] [ka]

[0152] The diol unit (B) contained in the polyarylate resin (S) may be one type or two or more types.

[0153] The mass proportion of the diol units (B) in the polyarylate resin (S) is preferably 25 mass % or more and 80 mass % or less. When the mass proportion of the diol units (B) is 25 mass% or more, peeling of the surface layer can be suppressed. From this viewpoint, the mass proportion of the diol units (B) is more preferably 30 mass% or more, and even more preferably 35 mass% or more. When the mass proportion of the diol unit (B) is 80 mass% or less, solubility in a coating liquid for forming a surface layer can be maintained and abrasion resistance can be improved. From this viewpoint, the mass proportion of the diol unit (B) is more preferably 75 mass% or less, and even more preferably 70 mass% or less.

[0154] Examples of diol units other than the diol units (B) include aliphatic diol units (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol) and alicyclic diol units (e.g., cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A). The polyarylate resin (S) may contain one or more types of these diol units.

[0155] The terminals of the polyarylate resin (S) may be blocked or modified with a terminal blocking agent or a molecular weight modifier used during production. Examples of the terminal blocking agent or molecular weight modifier include a monohydric phenol, a monovalent acid chloride, a monohydric alcohol, and a monovalent carboxylic acid. Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m Examples include o-phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, and 2-phenyl-2-(3-hydroxyphenyl)propane. Examples of monovalent acid chlorides include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetic acid chloride, butyric acid chloride, octylic acid chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and substituted versions thereof. Examples of monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenethyl alcohol. Examples of the monocarboxylic acid include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0156] The weight average molecular weight of the polyarylate resin (S) is preferably 80,000 or more, more preferably 90,000 or more, and even more preferably 100,000 or more, from the viewpoint of the abrasion resistance of the surface of the photoreceptor. The weight average molecular weight of the polyarylate resin (S) is preferably 150,000 or less, more preferably 140,000 or less, and even more preferably 130,000 or less, from the viewpoint of suppressing the occurrence of filming on the surface of the photoreceptor by allowing the surface of the photoreceptor to be appropriately scraped off and refreshed by the cleaning blade.

[0157] The molecular weight of the polyarylate resin (S) is a molecular weight measured by GPC (gel permeation chromatography) in terms of polystyrene. GPC uses tetrahydrofuran as an eluent. The polyarylate resin (S) to be subjected to GPC is obtained by the following method. The photoreceptor is immersed in various solvents (which may be mixed solvents) to determine the solvent in which the surface layer (charge transport layer or single-layer photosensitive layer) dissolves. The photoreceptor is immersed in a solvent in which the surface layer dissolves, and the surface layer is extracted. The solution from which the surface layer has been extracted is added dropwise to a poor solvent for the polyarylate resin (S) (for example, a non-polar solvent such as hexane or toluene, or a lower alcohol such as methanol or isopropanol. The poor solvent may be a mixed solvent), to reprecipitate the polyarylate resin (S). If necessary, the reprecipitation process is repeated twice. The reprecipitate is vacuum dried to obtain the polyarylate resin (S).

[0158] The polyarylate resin (S) can be obtained by conventional polycondensation of a monomer that provides the dicarboxylic acid unit (A) and a monomer that provides the diol unit (B), optionally with other monomers. Examples of methods for polycondensation of monomers include interfacial polymerization, solution polymerization, and melt polymerization. Interfacial polymerization is a polymerization method for obtaining a polyester by mixing a dicarboxylic acid halide dissolved in a water-immiscible organic solvent with a dihydric alcohol dissolved in an alkaline aqueous solution. Literature related to interfacial polymerization includes WMA Reckson, J. Poly. Sci., XL399, 1959, and Japanese Patent Publication No. 1965-1959. Because interfacial polymerization has a faster reaction rate than solution polymerization, it can suppress hydrolysis of the dicarboxylic acid halide, resulting in the production of a high-molecular-weight polyester resin.

[0159] [Conductive substrate] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, belts, etc. coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.), or alloys. Here, "conductive" refers to a material having a volume resistivity of 1×10 13 This means that the resistance is less than Ω·cm.

[0160] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm to 0.5 μm inclusive in order to suppress interference fringes that occur when irradiated with laser light. When incoherent light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for extending the life of the conductive substrate by suppressing defects caused by surface irregularities.

[0161] Examples of methods for roughening the surface include wet honing, which involves spraying an abrasive suspended in water onto the conductive substrate; centerless grinding, which involves pressing the conductive substrate against a rotating grinding wheel and continuously grinding the substrate; and anodizing.

[0162] As a method for roughening the surface, there may be mentioned a method in which, without roughening the surface of the conductive substrate, conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the surface is roughened by the particles dispersed in the layer.

[0163] Anodizing is a surface roughening treatment that uses a metallic (e.g., aluminum) conductive substrate as the anode and anodizes it in an electrolyte solution to form an oxide film on the surface of the conductive substrate. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active in its original state, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, in which the micropores of the oxide film are sealed by volume expansion caused by hydration in pressurized steam or boiling water (with the addition of a metal salt such as nickel), converting the film into a more stable hydrated oxide.

[0164] The thickness of the anodic oxide film is preferably, for example, from 0.3 μm to 15 μm, inclusive, and within this range, the film tends to exhibit barrier properties against injection and also tends to suppress an increase in residual potential due to repeated use.

[0165] The conductive substrate may be subjected to a treatment with an acidic treatment solution or a boehmite treatment. Treatment with an acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution are, for example, in the range of 10% by mass to 11% by mass for phosphoric acid, 3% by mass to 5% by mass for chromic acid, and 0.5% by mass to 2% by mass for hydrofluoric acid, with the total concentration of these acids preferably in the range of 13.5% by mass to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness of the coating is preferably 0.3 μm to 15 μm.

[0166] The boehmite treatment is carried out, for example, by immersing the steel sheet in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the steel sheet with heated steam at 90°C to 120°C for 5 to 60 minutes. The coating film preferably has a thickness of 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution with low coating solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0167] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0168] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ω cm or more 1×10 11 Examples include inorganic particles with a particle size of Ω·cm or less. Among these, inorganic particles having the above resistance value are preferably metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0169] The specific surface area of ​​inorganic particles measured by the BET method is, for example, 10 m 2 / g or more is preferable. The volume average particle size of the inorganic particles is, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

[0170] The content of the inorganic particles is, for example, preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, relative to the binder resin.

[0171] The inorganic particles may be surface-treated, and two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0172] Examples of the surface treatment agent include a silane coupling agent, a titanate-based coupling agent, an aluminum-based coupling agent, a surfactant, etc. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0173] Examples of silane coupling agents having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0174] Two or more silane coupling agents may be used in combination. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0175] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

[0176] The amount of the surface treatment agent to be used is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0177] Here, it is preferable that the undercoat layer contains an electron-accepting compound (acceptor compound) together with the inorganic particles, from the viewpoint of improving the long-term stability of the electrical properties and the carrier blocking property.

[0178] Examples of the electron-accepting compound include electron-transporting substances such as quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; and benzophenone compounds. In particular, the electron-accepting compound is preferably a compound having an anthraquinone structure, such as a hydroxyanthraquinone compound, an aminoanthraquinone compound, or an aminohydroxyanthraquinone compound, and more specifically, anthraquinone, alizarin, quinizarin, anthrarphine, purpurin, or a derivative thereof.

[0179] The electron-accepting compound may be contained in the undercoat layer in a dispersed state together with the inorganic particles, or may be contained in a state of being attached to the surfaces of the inorganic particles.

[0180] The electron-accepting compound can be attached to the surface of the inorganic particles by, for example, a dry method or a wet method.

[0181] The dry method is a method in which, while stirring inorganic particles using a mixer or the like with high shear force, an electron-accepting compound is added dropwise, either directly or dissolved in an organic solvent, or sprayed together with dry air or nitrogen gas to adhere the electron-accepting compound to the surface of the inorganic particles. The electron-accepting compound is preferably added dropwise or sprayed at a temperature below the boiling point of the solvent. After the electron-accepting compound has been added dropwise or sprayed, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as they achieve electrophotographic properties.

[0182] The wet method involves dispersing inorganic particles in a solvent using, for example, stirring, ultrasonic waves, a sand mill, an attritor, or a ball mill, while adding an electron-accepting compound. The mixture is stirred or dispersed, and then the solvent is removed to adhere the electron-accepting compound to the surfaces of the inorganic particles. The solvent can be removed, for example, by filtration or distillation. After solvent removal, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as electrophotographic properties are obtained. In the wet method, moisture contained in the inorganic particles may be removed before adding the electron-accepting compound. Examples of such methods include a method of removing the moisture by stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

[0183] The attachment of the electron-accepting compound may be carried out before or after the inorganic particles are surface-treated with a surface-treating agent, or the attachment of the electron-accepting compound and the surface treatment with a surface-treating agent may be carried out simultaneously.

[0184] The content of the electron-accepting compound is, for example, 0.01% by mass or more and 20% by mass or less, and preferably 0.01% by mass or more and 10% by mass or less, based on the inorganic particles.

[0185] Examples of binder resins used in the undercoat layer include known polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents. Examples of binder resins used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline), and the like.

[0186] Among these, the binder resin used in the undercoat layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and in particular, a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resins, phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins, and polyamide resins, polyester resins, polyether resins, methacrylic resins, acrylic resins, polyvinyl alcohol resins, and polyvinyl acetal resins with a curing agent is preferred. When two or more of these binder resins are used in combination, the mixing ratio is set as necessary.

[0187] The undercoat layer may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of additives include known materials such as polycyclic condensation and azo electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Silane coupling agents are used for the surface treatment of inorganic particles as described above, and may also be added to the undercoat layer as an additive.

[0188] Examples of silane coupling agents as additives include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0189] Examples of zirconium chelate compounds include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0190] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-normal-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0191] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0192] These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0193] The undercoat layer preferably has a Vickers hardness of 35 or more. The surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to between 1 / (4n) (n is the refractive index of the upper layer) and 1 / 2 of the wavelength λ of the exposure laser used to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. The surface of the undercoat layer may be polished to adjust the surface roughness. Examples of polishing methods include buffing, sandblasting, wet honing, and grinding.

[0194] The formation of the undercoat layer is not particularly limited, and a known formation method can be used. For example, the undercoat layer can be formed by forming a coating film of a coating liquid for forming an undercoat layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0195] Examples of solvents for preparing the coating liquid for forming the undercoat layer include known organic solvents, such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include ordinary organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0196] Examples of a method for dispersing inorganic particles when preparing a coating liquid for forming an undercoat layer include known methods such as using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0197] Examples of methods for applying the coating liquid for forming the undercoat layer onto the conductive substrate include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0198] The thickness of the undercoat layer is set, for example, preferably at least 15 μm, more preferably in the range of from 20 μm to 50 μm.

[0199] [Middle layer] An intermediate layer may be further provided between the undercoat layer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (such as polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, and melamine resins. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in the intermediate layer may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0200] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0201] The formation of the intermediate layer is not particularly limited, and a known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of a coating liquid for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it if necessary. The intermediate layer can be formed by any of the usual coating methods, such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating.

[0202] The thickness of the intermediate layer is preferably set in the range of, for example, 0.1 μm to 3 μm, and the intermediate layer may also be used as an undercoat layer.

[0203] [Charge generation layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Alternatively, the charge generation layer may be a vapor-deposited layer of the charge generation material. A vapor-deposited layer of the charge generation material is suitable for use with an incoherent light source such as an LED (Light Emitting Diode) or an organic EL (Electroluminescence) image array.

[0204] Examples of the charge generating material include azo pigments such as bisazo and trisazo; fused-ring aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0205] Among these, in order to be compatible with laser exposure in the near-infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material, specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, titanyl phthalocyanine, etc.

[0206] On the other hand, in order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include fused ring aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments.

[0207] The above charge generating material may also be used when an incoherent light source such as an LED or organic EL image array having a central emission wavelength of 450 nm or more and 780 nm or less is used.

[0208] When n-type semiconductors such as fused-ring aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark current is less likely to occur, and even in thin films, image defects known as black spots can be suppressed. The n-type is determined by the polarity of the photocurrent that flows using the commonly used time-of-flight method, and materials that more easily pass electrons as carriers than holes are considered n-type.

[0209] The binder resin used in the charge generating layer may be selected from a wide range of insulating resins, and may also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (e.g., polycondensation product of bisphenols and aromatic dicarboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin, etc. Here, "insulating" means a material having a volume resistivity of 1×10 13 This means that the resistance is Ω·cm or more. These binder resins may be used alone or in combination of two or more.

[0210] The compounding ratio of the charge generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass.

[0211] The charge generating layer may contain other known additives.

[0212] The formation of the charge generation layer is not particularly limited, and a known formation method can be used. For example, the charge generation layer can be formed by forming a coating film of a coating liquid for forming the charge generation layer by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer can also be formed by vapor deposition of the charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when a fused ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0213] Examples of solvents for preparing the coating liquid for forming the charge generating layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene, etc. These solvents may be used alone or in combination of two or more.

[0214] Methods for dispersing particles (e.g., charge generating material) in the coating liquid for forming the charge generating layer include, for example, media dispersers such as ball mills, vibration ball mills, attritors, sand mills, and horizontal sand mills, and medialess dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion liquid is dispersed by passing through a fine flow path under high pressure. During this dispersion, it is effective to adjust the average particle size of the charge generating material in the coating liquid for forming the charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0215] Examples of methods for applying the coating liquid for forming the charge generating layer onto the undercoat layer (or onto the intermediate layer) include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0216] The thickness of the charge generating layer is set, for example, preferably in the range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0217] [Charge transport layer] The charge transport layer is a layer containing a charge transport material and a binder resin.

[0218] Examples of charge transport materials include electron transport compounds such as quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. Examples of charge transport materials also include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination, but are not limited to these.

[0219] The charge transport material may be a polymer charge transport material, such as poly-N-vinylcarbazole, polysilane, or other known compounds having charge transport properties, and among these, polyester polymer charge transport materials are preferred.

[0220] Examples of the charge transport material or polymeric charge transport material include polycyclic aromatic compounds, aromatic nitro compounds, aromatic amine compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds (particularly triphenylamine compounds), diamine compounds, oxadiazole compounds, carbazole compounds, organic polysilane compounds, pyrazoline compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, cyano compounds, benzofuran compounds, aniline compounds, butadiene compounds, and resins having groups derived from these substances. Specifically, paragraphs 0078 to 0080 of Japanese Patent Application Laid-Open No. 2021-117377, paragraphs 0046 to 0048 of Japanese Patent Application Laid-Open No. 2019-035900, paragraphs 0052 to 0053 of Japanese Patent Application Laid-Open No. 2019-012141, paragraphs 0122 to 0134 of Japanese Patent Application Laid-Open No. 2021-071565, and paragraphs 0122 to 0134 of Japanese Patent Application Laid-Open No. 2021-015223 Examples of the compounds include those described in paragraphs 0101 to 0110 of JP 2013-097300 A, paragraph 0116, paragraphs 0309 to 0316 of WO 2019 / 070003 A, paragraphs 0103 to 0107 of JP 2018-159087 A, and paragraphs 0102 to 0113 of JP 2021-148818 A.

[0221] From the viewpoint of charge mobility, the charge transport material preferably contains at least one selected from the group consisting of a compound (C1) represented by the following formula (C1), a compound (C2) represented by the following formula (C2), a compound (C3) represented by the following formula (C3), and a compound (C4) represented by the following formula (C4).

[0222] [ka]

[0223] In formula (C1), Ar T1 , Ar T2 and Ar T3 are each independently an aryl group, -C6H4-C(R T4 )=C(R T5)(R T6 ) or -CH-CH=CH-CH=C(R T7 )(R T8 ) is R T4 , R T5 , R T6 , R T7 and R T8 R is independently a hydrogen atom, an alkyl group, or an aryl group. T5 and R T6 When is an aryl group, the aryl groups are connected to each other by -C(R 51 )(R 52 )- and / or -C(R 61 )=C(R 62 R 51 , R 52 , R 61 and R 62 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0224] The group in formula (C1) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0225] From the viewpoint of charge mobility, the compound (C1) is preferably an aryl group or —CH—CH═CH—CH═C(R T7 )(R T8 ) is preferred, and a compound (C'1) represented by the following formula (C'1) is more preferred.

[0226] [ka]

[0227] In formula (C'1), R T111 , R T112 , R T121 , R T122 , R T131 and R T132are each independently a hydrogen atom, a halogen atom, an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 3 carbon atoms), a phenyl group, or a phenoxy group. Tj1, Tj2, Tj3, Tk1, Tk2, and Tk3 are each independently 0, 1, or 2.

[0228] [ka]

[0229] In formula (C2), R T201 , R T202 , R T211 and R T212 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, -C(R T21 )=C(R T22 )(R T23 ) or -CH=CH-CH=C(R T24 )(R T25 ) is R T21 , R T22 , R T23 , R T24 and R T25 R is independently a hydrogen atom, an alkyl group, or an aryl group. T221 and R T222 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2.

[0230] The group in formula (C2) may be substituted with a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0231] From the viewpoint of charge mobility, the compound (C2) is preferably an alkyl group, an aryl group, or -CH=CH-CH=C(R T24 )(R T25) is preferred, and the compound having at least one alkyl group, aryl group, or -CH=CH-CH=C(R T24 )(R T25 ) is more preferred.

[0232] [ka]

[0233] In formula (C3), R T301 , R T302 , R T311 and R T312 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, -C(R T31 )=C(R T32 )(R T33 ) or -CH=CH-CH=C(R T34 )(R T35 ) is R T31 , R T32 , R T33 , R T34 and R T35 R is independently a hydrogen atom, an alkyl group, or an aryl group. T321 , R T322 and R T331 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are each independently 0, 1, or 2.

[0234] The group in formula (C3) may be substituted with a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0235] [ka]

[0236] In formula (C4), R T401 , R T402 , R T411 and R T412 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, -C(R T41 )=C(R T42 )(R T43 ) or -CH=CH-CH=C(R T44 )(R T45 ) is R T41 , R T42 , R T43 , R T44 and R T45 R is independently a hydrogen atom, an alkyl group, or an aryl group. T421 , R T422 and R T431 are each independently a hydrogen atom, a halogen atom, an alkyl group having from 1 to 5 carbon atoms, or an alkoxy group having from 1 to 5 carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are each independently 0, 1, or 2.

[0237] The group in formula (C4) may be substituted with a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0238] The content of the charge transport material in the charge transport layer is preferably 20% by mass or more and 70% by mass or less, more preferably 25% by mass or more and 65% by mass or less, and even more preferably 30% by mass or more and 60% by mass or less, based on the total mass of the charge transport layer.

[0239] The charge transport layer contains at least a polyarylate resin (S) as a binder resin. The proportion of the polyarylate resin (S) in the total amount of binder resins contained in the charge transport layer is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 55% by mass or more. When the polyarylate resin (S) is used in combination with another resin, the other resin to be used in combination is preferably a polycarbonate resin.

[0240] The charge transport layer may contain a binder resin other than the polyarylate resin (S). Examples of the other binder resin include polyester resins other than the polyarylate resin (S), polycarbonate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, and polysilanes. These binder resins may be used alone or in combination of two or more.

[0241] The charge transport layer may contain other known additives, such as antioxidants, leveling agents, antifoaming agents, fillers, and viscosity modifiers.

[0242] The formation of the charge transport layer is not particularly limited, and a known formation method can be used. For example, the charge transport layer can be formed by forming a coating film of a coating liquid for forming the charge transport layer in which the above components are added to a solvent, drying the coating film, and heating it if necessary.

[0243] Examples of solvents for preparing the coating solution for forming the charge transport layer include ordinary organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents may be used alone or in combination.

[0244] Examples of a coating method for applying the coating liquid for forming the charge transport layer onto the charge generating layer include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0245] The thickness of the charge transport layer is, for example, 5 μm or more and 50 μm or less. From the viewpoints of the photosensitivity and wear life of the photoreceptor, it is preferably 20 μm or more, more preferably 22 μm or more, and even more preferably 25 μm or more. From the viewpoint of the residual potential, it is preferably 50 μm or less, more preferably 47 μm or less, and even more preferably 45 μm or less.

[0246] [Single-layer photosensitive layer] The single-layer photosensitive layer (charge generation / charge transport layer) is a layer containing a charge generation material, a charge transport material, a binder resin, and, if necessary, other additives. These materials are the same as those described for the charge generation layer and the charge transport layer.

[0247] The single-layer photosensitive layer contains at least a polyarylate resin (S) as a binder resin. The proportion of the polyarylate resin (S) in the total amount of binder resins contained in the single-layer photosensitive layer is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 55% by mass or more. When the polyarylate resin (S) is used in combination with another resin, the other resin to be used in combination is preferably a polycarbonate resin.

[0248] The content of the charge generating material in the single-layer photosensitive layer is preferably 0.1% by mass to 10% by mass, more preferably 0.8% by mass to 5% by mass, based on the total mass of the single-layer photosensitive layer.

[0249] The content of the charge transport material contained in the single-layer photosensitive layer is preferably 25% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 65% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less, based on the total mass of the single-layer photosensitive layer.

[0250] The method for forming the single-layer photosensitive layer is the same as the method for forming the charge generating layer and the charge transport layer.

[0251] The film thickness of the single-layer photosensitive layer is, for example, 5 μm or more and 50 μm or less. From the viewpoints of the photosensitivity and wear life of the photoreceptor, it is preferably 10 μm or more, more preferably 12 μm or more, and even more preferably 15 μm or more. From the viewpoint of the residual potential, it is preferably 50 μm or less, more preferably 47 μm or less, even more preferably 45 μm or less, and even more preferably 40 μm or less.

[0252] [Cleaning blade] An embodiment of the cleaning blade will be described with reference to FIG. Fig. 5 is a schematic diagram showing an example of a cleaning blade provided in a photoreceptor cleaning device of an image forming apparatus according to this embodiment. Fig. 5 is a cross section taken in a direction perpendicular to the axial direction of the photoreceptor, showing the cleaning blade in contact with the photoreceptor. The cleaning blade 30 shown in FIG. 5 is used, for example, as the cleaning blade 131 in the cleaning device 13 shown in FIG.

[0253] The cleaning blade 30 has a first polyurethane layer 31 and a second polyurethane layer 32. The cleaning blade 30 is joined to the support member 70 at the second polyurethane layer 32.

[0254] The first polyurethane layer 31 forms the surface of the cleaning blade 30 that faces the photoreceptor 7 . The corners 31E of the first polyurethane layer 31 and their vicinity are the portions that come into contact with the rotating photoreceptor 7 and clean the surface of the photoreceptor 7.

[0255] The second polyurethane layer 32 is present on the back side of the first polyurethane layer 31 (the surface opposite to the surface facing the photoreceptor 7). The corner 32E of the second polyurethane layer 32 is a corner that faces the corner 31E of the first polyurethane layer 31 on the tip surface of the cleaning blade 30.

[0256] The support member 70 has, for example, an L-shape. The support member 70 is made of, for example, a metal such as aluminum or stainless steel. The support member 70 is joined to the cleaning blade 30 by, for example, an adhesive. A pressure member (not shown) is joined to the support member 70. The pressure member applies pressure to the support member 70, thereby pressing the cleaning blade 30 against the photoreceptor 7.

[0257] The hardness of the first polyurethane layer 31 is measured in the vicinity of the corner 31E. The hardness of the second polyurethane layer 32 is measured in the vicinity of the corner 32E. Hardness is measured in accordance with JIS K6253:1997 "Testing Method for Hardness of Vulcanized and Thermoplastic Rubber" using a Type A durometer as specified in JIS K7215:1986 "Testing Method for Durometer Hardness of Plastics." Specifically, the indenter of the Type A durometer is pressed in the thickness direction at a position 5 mm from the apex of the corner toward the support member, and the maximum value on the pointer is read within one second. This measurement is performed 10 times approximately evenly in the direction parallel to the axial direction of the photoreceptor, and the average value is taken as the hardness of the polyurethane layer.

[0258] The hardness of the first polyurethane layer of the cleaning blade is 85 degrees or more and 95 degrees or less, preferably 86 degrees or more and 94 degrees or less, more preferably 87 degrees or more and 93 degrees or less, and even more preferably 88 degrees or more and 92 degrees or less. The hardness of the second polyurethane layer of the cleaning blade is 55 degrees or more and 70 degrees or less, preferably 58 degrees or more and 69 degrees or less, more preferably 60 degrees or more and 68 degrees or less, and even more preferably 62 degrees or more and 67 degrees or less.

[0259] In dynamic viscoelasticity measurement, the cleaning blade 30 preferably satisfies tanδ(Max)≦0.5 and tanδ(Max)−tanδ(Min)≦0.1, where tanδ(Max) is the maximum value of the loss tangent and tanδ(Min) is the minimum value in the temperature range of 0°C to 30°C. When the loss tangent satisfies the above relationship, stable cleaning performance can be achieved without being affected by temperature fluctuations. Tan δ(Max) is preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less. The value of tan δ(Max)−tan δ(Min) is preferably 0.1 or less, more preferably 0.05 or less, and even more preferably 0.03 or less.

[0260] The dynamic viscoelasticity of the cleaning blade 30 was measured as follows. The cleaning blade 30 is cut into a rectangle having a length of 20 mm in a direction parallel to the axial direction of the photosensitive member and a length of 5 mm in a direction perpendicular to the axial direction of the photosensitive member, and this is used as a sample. The sample is placed on a measuring device and subjected to dynamic viscoelasticity measurement under the following measurement conditions to measure the storage modulus and loss modulus. The loss tangent tanδ is calculated from the storage modulus and loss modulus, and a graph showing the relationship between the measurement temperature and the loss tangent tanδ is drawn. Measurement device: Exstar-DMS-6100 (Hitachi High-Tech Science Corporation (formerly Seiko Instruments Inc.)) ·Distance: 20mm Frequency: 1Hz Temperature range: starting temperature -40℃, ending temperature 60℃ Heating rate: 2℃ / min

[0261] The hardness of the first polyurethane layer 31, the hardness of the second polyurethane layer 32, and the loss tangent tanδ of the cleaning blade 30 can be controlled, for example, by using a urethane rubber having a hard segment and a soft segment as the material and adjusting the content ratio of the hard segment and the soft segment contained in the urethane rubber.

[0262] Fig. 6 is a schematic diagram illustrating the pressing pressure of the cleaning blade against the photosensitive member, and shows the first polyurethane layer and the second polyurethane layer together without distinction. Fig. 6 shows a cross section cut in a direction perpendicular to the axial direction of the photosensitive member.

[0263] The cleaning blade 60 shown in FIG. 6 is joined to and supported by a support member 70. A pressure member (not shown) is joined to the support member 70. The pressure member presses the support member 70, thereby pressing the cleaning blade 60 against the photoreceptor 7. A corner 60E of the cleaning blade 60 and its vicinity come into contact with the rotating photoreceptor 7 to clean the surface of the photoreceptor 7. The photoreceptor 7 rotates in the direction of arrow A.

[0264] The pressing pressure NF (gf / mm) of the cleaning blade 60 against the photosensitive member 7 is a force calculated by the following formula.

[0265] NF=d·E·t 3 / 4L 3 E: Young's modulus of the blade (gf / mm 2 ) L: Free length of the blade (mm): L in FIG. 6 (length of the part not joined to the support member 70) t: Blade thickness (mm): t in Figure 6 d: Depth of blade penetration into the photoconductor (mm): d in Figure 6

[0266] Blade Young's modulus (gf / mm 2 ) is measured in accordance with JIS K6251:1997 "Vulcanized rubber and thermoplastic rubber - Determination of tensile properties." The sample is fixed to the measuring device and the Young's modulus at 25% elongation is measured under the following measurement conditions. Measuring device: Strograph VE1D (Toyo Seiki Seisakusho Co., Ltd.) Test piece size: Dumbbell-shaped No. 3 Test speed: 500mm / min Number of measurements: 3 The force ΔS (MPa) applied to a unit cross-sectional area and the elongation Δa per unit length were measured, and the Young's modulus E (gf / mm 2 ) is calculated. E=10 2 ×ΔS / Δa Here, ΔS is calculated from the load F (N), sample thickness t (mm), and sample width w (mm) using the following formula: Δa is calculated from the sample reference length L (mm) and sample elongation ΔL (mm) when a load is applied using the following formula: ΔS=F / (w×t) Δa=ΔL / L

[0267] The pressure of the cleaning blade 60 against the photoreceptor 7 is preferably 1 gf / mm or more, more preferably 1.5 gf / mm or more, and even more preferably 2 gf / mm or more, from the viewpoint of suppressing filming on the surface of the photoreceptor. The pressure of the cleaning blade 60 against the photoreceptor 7 is preferably 4 gf / mm or less, more preferably 3.5 gf / mm or less, and even more preferably 3 gf / mm or less, from the viewpoint of stabilizing the behavior of the tip of the cleaning blade and ensuring cleaning performance.

[0268] The cleaning blade can be manufactured by the following method. The first and second polyurethane layers are manufactured separately and then bonded together with an adhesive. The materials for the first polyurethane layer and the second polyurethane layer are poured into a mold at different times to bond the interfaces of the two materials.

[0269] Polyurethanes are generally polymers of polyisocyanates and polyols. The polyurethane is preferably a urethane rubber, and the hardness of the urethane rubber can be controlled by adjusting the content ratio of the hard segment to the soft segment contained in the urethane rubber.

[0270] Examples of polyisocyanates include 4,4'-diphenylmethane diisocyanate (MDI), 2,6-toluene diisocyanate (TDI), 1,6-hexane diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI), and 3,3-dimethylbiphenyl-4,4-diisocyanate (TODI). As the polyisocyanate, MDI, NDI and HDI are preferred.

[0271] The polyols include high molecular weight polyols and low molecular weight polyols. The polymer polyol is a polyol having a number average molecular weight of 500 or more (preferably 500 or more and 5000 or less). Examples of the polymer polyol include well-known polyols such as polyester polyols obtained by dehydration condensation of low-molecular-weight polyols and dibasic acids, polycarbonate polyols obtained by reaction of low-molecular-weight polyols and alkyl carbonates, polycaprolactone polyols, and polyether polyols. Examples of low molecular weight polyols include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,20-eicosanediol.

[0272] The soft segment material may be a polymer polyol component among polyols. One type of soft segment material may be used alone, or two or more types may be used in combination.

[0273] A chain extender is preferably used as the hard segment material, and examples of the chain extender include polyols having a molecular weight of 300 or less, such as 1,4-butanediol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylene glycol, triethylene glycol, trimethylolpropane, glycerin, pentaerythritol, sorbitol, and 1,2,6-hexanetriol. The hard segment material may be used alone or in combination of two or more.

[0274] The hard segment material may be a resin having a functional group capable of reacting with an isocyanate group. The resin is preferably a flexible resin, and from the viewpoint of flexibility, a linear aliphatic resin is preferable. Examples of the resin include an acrylic resin containing two or more hydroxyl groups, a polybutadiene resin containing two or more hydroxyl groups, and an epoxy resin containing two or more epoxy groups.

[0275] Urethane rubber can be produced by molding a composition obtained by mixing polyisocyanate, polyol (e.g., hard segment material and soft segment material), crosslinking agent, and catalyst. Examples of crosslinking agents include diols, triols, tetraols, etc. Examples of catalysts include tertiary amines, quaternary ammonium salts, and organotin compounds.

[0276] [toner] The toner contains toner particles, and titanate compound particles and silica particles externally added to the toner particles. The toner is obtained by externally adding an external additive to the toner particles.

[0277] [Toner particles] The toner particles are composed of, for example, a binder resin, a colorant, a release agent, and other additives.

[0278] -Binder resin- Examples of binder resins include homopolymers of monomers such as styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), and vinyl resins made of copolymers of two or more of these monomers. Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures of these with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these. These binder resins may be used alone or in combination of two or more.

[0279] As the binder resin, a polyester resin is preferable. Examples of polyester resins include known polyester resins.

[0280] The polyester resin may be, for example, a condensation polymer of a polycarboxylic acid and a polyhydric alcohol. As the polyester resin, a commercially available product or a synthesized product may be used.

[0281] Examples of polycarboxylic acids include aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acids (such as cyclohexanedicarboxylic acid), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as polycarboxylic acids. As the polycarboxylic acid, a trivalent or higher carboxylic acid having a crosslinked or branched structure may be used in combination with a dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polycarboxylic acids may be used alone or in combination of two or more.

[0282] Examples of polyhydric alcohols include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, preferred polyhydric alcohols are aromatic diols and alicyclic diols, and more preferred are aromatic diols. As the polyhydric alcohol, a trihydric or higher polyhydric alcohol having a crosslinked or branched structure may be used in combination with the diol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more.

[0283] The glass transition temperature (Tg) of the polyester resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower. The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, is determined from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K7121-1987 "Method for measuring transition temperature of plastics."

[0284] The weight average molecular weight (Mw) of the polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the polyester resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less. The weight average molecular weight and number average molecular weight are measured by gel permeation chromatography (GPC). Molecular weight measurements by GPC are performed using a Tosoh GPC HLC-8120GPC measuring device, a Tosoh TSKgel SuperHM-M (15 cm) column, and THF solvent. The weight average molecular weight and number average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0285] The polyester resin can be obtained by a known production method, for example, by carrying out the reaction at a polymerization temperature of 180°C or higher and 230°C or lower, reducing the pressure in the reaction system as necessary, and removing water and alcohol generated during the condensation. If the raw material monomer is not soluble or compatible at the reaction temperature, a high-boiling solvent may be added as a solubilizer to dissolve it. In this case, the polycondensation reaction is carried out while distilling off the solubilizer. If a monomer with poor compatibility is present, it is advisable to first condense the poorly compatible monomer with the acid or alcohol to be polycondensed, and then polycondense it with the main component.

[0286] The content of the binder resin is preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, based on the total mass of the toner particles.

[0287] -Coloring agent- Examples of colorants include carbon black, chrome yellow, Hansa Yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, and ultramarine blue. pigments such as phthalocyanine blue, chalco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate; dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based; and inorganic pigments such as titanium compounds and silica.

[0288] The colorant is not limited to a substance that absorbs light in the visible light region, but may be, for example, a substance that absorbs light in the near-infrared region, or may be a fluorescent colorant. Examples of colorants that have absorption in the near-infrared region include aminium salt compounds, naphthalocyanine compounds, squarylium compounds, and croconium compounds. Examples of fluorescent colorants include the fluorescent colorants described in paragraph 0027 of JP 2021-127431 A.

[0289] The colorant may be a colorant having luster. Examples of the luster colorant include metal powders such as aluminum, brass, bronze, nickel, stainless steel, and zinc; mica coated with titanium oxide or yellow iron oxide; coated flaky inorganic crystal substrates such as barium sulfate, layered silicates, and layered aluminum silicates; single-crystal plate-like titanium oxide, basic carbonates, bismuth oxychloride, natural guanine, flaky glass powder, and metal-deposited flaky glass powder.

[0290] The colorant may be used alone or in combination of two or more kinds. The colorant may be surface-treated as needed, and may be used in combination with a dispersant.

[0291] The toner particles may contain a colorant or may not contain a colorant. The toner may be a toner that does not contain a colorant in the toner particles, that is, a so-called transparent toner.

[0292] When the toner particles contain a colorant, the content of the colorant is preferably from 1% by mass to 30% by mass, and more preferably from 3% by mass to 15% by mass, based on the total mass of the toner particles.

[0293] -Mold release agent- Examples of release agents include hydrocarbon waxes, natural waxes such as carnauba wax, rice wax, and candelilla wax, synthetic or mineral / petroleum waxes such as montan wax, and ester waxes such as fatty acid esters and montanic acid esters, but are not limited thereto.

[0294] The melting temperature of the release agent is preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121-1987 "Method for measuring transition temperatures of plastics."

[0295] The content of the release agent is preferably from 1% by mass to 20% by mass, and more preferably from 5% by mass to 15% by mass, based on the total mass of the toner particles.

[0296] -Other additives- Examples of other additives include known additives such as magnetic materials, charge control agents, inorganic powders, etc. These additives are contained in the toner particles as internal additives.

[0297] -Characteristics of toner particles, etc.- The toner particles may be toner particles having a single layer structure, or may be toner particles having a so-called core-shell structure composed of a core (core particle) and a coating layer (shell layer) that coats the core. The toner particles having a core-shell structure may be composed of, for example, a core composed of a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer composed of a binder resin.

[0298] The volume average particle size (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less. The average particle size of toner particles is measured using a Coulter Multisizer II (Beckman Coulter) and an ISOTON-II (Beckman Coulter) electrolyte. 0.5 mg to 50 mg of the sample to be measured is added to 2 ml of a 5% by weight aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate), and this is added to 100 ml to 150 ml of electrolyte. The electrolyte containing the sample is dispersed in an ultrasonic disperser for 1 minute, and the particle size is measured using a Coulter Multisizer II with a 100 μm aperture in the range of 2 μm to 60 μm. A total of 50,000 particles are sampled. Based on the measured particle size distribution, a volume or number distribution is plotted from the smallest diameter side, and the particle size at 50% of the cumulative size is taken as the volume average particle size D50v or number average particle size D50p.

[0299] The toner particles may be produced by any of a dry production method (for example, a kneading and pulverization method) and a wet production method (for example, an aggregation and coalescence method, a suspension polymerization method, and a dissolution and suspension method). There are no limitations on these production methods, and any known production method may be used.

[0300] [Titanium oxide compound particles] The titanate compound particles may be particles containing a titanate compound as a main component. The titanate compound is called a metatitanate, which is a salt formed from, for example, titanium oxide and another metal oxide or another metal carbonate.

[0301] The titanate compound particles are preferably alkaline earth metal titanate particles. Alkaline earth metal titanate is a salt represented by the composition formula RTiO3 (wherein R is one or more alkaline earth metals).

[0302] Examples of titanate compound particles include particles of strontium titanate (SrTiO3), calcium titanate (CaTiO3), magnesium titanate (MgTiO3), barium titanate (BaTiO3), lead titanate (PbTiO3), zinc titanate (ZnTiO3), etc. One type of titanate compound particle may be used alone, or two or more types may be used in combination.

[0303] The titanate compound particles may contain a dopant, such as lanthanoids (e.g., lanthanum and cerium), silica, aluminum, magnesium, calcium, barium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, niobium, molybdenum, ruthenium, palladium, indium, antimony, tantalum, tungsten, rhenium, iridium, platinum, bismuth, yttrium, zirconium, niobium, silver, or tin.

[0304] The strontium titanate particles may contain a dopant, such as lanthanoids (e.g., lanthanum, cerium), silica, aluminum, magnesium, calcium, barium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, niobium, molybdenum, ruthenium, palladium, indium, antimony, tantalum, tungsten, rhenium, iridium, platinum, bismuth, yttrium, zirconium, niobium, silver, or tin.

[0305] When the titanate compound particles contain a dopant, the amount of the dopant is preferably 0.1 mol % or more and 20 mol % or less, more preferably 0.1 mol % or more and 15 mol % or less, and even more preferably 0.1 mol % or more and 10 mol % or less, relative to the metal atoms other than titanium. When the alkaline earth metal titanate particles contain a dopant, the amount of the dopant is preferably 0.1 mol % or more and 20 mol % or less, more preferably 0.1 mol % or more and 15 mol % or less, and even more preferably 0.1 mol % or more and 10 mol % or less, relative to the alkaline earth metal atoms. When the strontium titanate particles contain a dopant, the amount of the dopant relative to strontium is preferably 0.1 mol % to 20 mol %, more preferably 0.1 mol % to 15 mol %, and even more preferably 0.1 mol % to 10 mol %.

[0306] The surfaces of the titanic acid compound particles may be subjected to a hydrophobic treatment. Examples of hydrophobic treatment agents include silane coupling agents and silicone oils. Examples of silane coupling agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and vinyltriacetoxysilane. Examples of silicone oils include dimethylpolysiloxane, methylhydrogenpolysiloxane, and methylphenylpolysiloxane.

[0307] The average primary particle size of the titanate compound particles is preferably 20 nm or more, more preferably 25 nm or more, and even more preferably 30 nm or more, from the viewpoint of suppressing the occurrence of fogging in an image. The average primary particle size of the titanate compound particles is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 60 nm or less, from the viewpoint of preventing blurring of images.

[0308] The average primary particle size of the titanate compound particles is determined as follows. Energy dispersive X-ray analyzer (EDX device) (manufactured by Horiba, EMAX Evolution X-Max80mm 2The toner is photographed at 40,000x magnification using a scanning electron microscope (SEM) (Hitachi High-Technologies, S-4800) equipped with a ion beam splitter. 200 titanate compound particles are identified within one field of view based on the presence of titanium and oxygen elements using EDX analysis. The images of the 200 titanate compound particles are analyzed using image processing and analysis software WinRoof (Mitani Shoji Co., Ltd.). The circular equivalent diameter of the primary particles is determined, and the circular equivalent diameter that is 50% cumulative from the smallest diameter side in the distribution of circular equivalent diameters is taken as the average primary particle size.

[0309] The amount of titanic acid compound particles added externally is preferably 0.1 to 3.0 parts by mass, more preferably 0.3 to 2.0 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of toner particles. The amount of alkaline earth metal titanate particles added externally is preferably 0.1 to 3.0 parts by mass, more preferably 0.3 to 2.0 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of toner particles. The amount of strontium titanate particles added externally is preferably 0.1 to 3.0 parts by mass, more preferably 0.3 to 2.0 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of toner particles. The amount of the lanthanum-doped strontium titanate particles added externally is preferably 0.1 parts by mass or more and 3.0 parts by mass or less, more preferably 0.3 parts by mass or more and 2.0 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1.5 parts by mass or less, relative to 100 parts by mass of the toner particles.

[0310] [Silica particles] The silica particles may be either dry silica or wet silica. Examples of dry silica include combustion silica (fumed silica) obtained by burning a silane compound; and deflagration silica obtained by explosively burning metal silicon powder. Examples of wet silica include wet silica obtained by the neutralization reaction of sodium silicate with mineral acid (precipitation silica synthesized and agglomerated under alkaline conditions, and gel silica particles synthesized and agglomerated under acidic conditions); colloidal silica obtained by polymerizing acidic silicic acid in an alkaline state; and sol-gel silica obtained by hydrolysis of an organosilane compound (e.g., alkoxysilane).

[0311] In order to improve the function of the silica particles as an external additive, the silica particles are preferably silica particles having a hydrophobic surface, more preferably silica particles having a hydrophobic surface with a silicon-containing organic compound. Examples of the silicon-containing organic compound include the silicon-containing organic compounds mentioned above for the titanic acid compound particles.

[0312] From the viewpoint of suppressing the occurrence of fogging in an image, the average primary particle size of the silica particles is preferably 50 nm or more, more preferably 60 nm or more, and even more preferably 70 nm or more. The average primary particle size of the silica particles is preferably 150 nm or less, more preferably 120 nm or less, and even more preferably 100 nm or less, from the viewpoint of suppressing the occurrence of blurring and fogging in an image. The silica particles may be a mixture of silica particles having a relatively large particle size and silica particles having a relatively small particle size.

[0313] The method for measuring the average primary particle size of the silica particles is as follows. Energy dispersive X-ray analyzer (EDX device) (manufactured by Horiba, EMAX Evolution X-Max80mm 2The toner is photographed at 40,000x magnification using a scanning electron microscope (SEM) (Hitachi High-Technologies, S-4800) equipped with a ion beam splitter. 200 silica particles are identified within one field of view based on the presence of Si elements using EDX analysis. The images of the 200 silica particles are analyzed using image processing and analysis software WinRoof (Mitani Corporation). The circle-equivalent diameter of each primary particle image is determined. The circle-equivalent diameter that is 50% cumulative from the smallest diameter side in the circle-equivalent diameter distribution is taken as the average primary particle size.

[0314] The amount of silica particles added externally is preferably 0.1 to 3.0 parts by mass, more preferably 0.3 to 2.0 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of toner particles.

[0315] The total external addition amount of silica particles and titanic acid compound particles is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 4.0 parts by mass or less, and even more preferably 1.0 parts by mass or more and 3.0 parts by mass or less, relative to 100 parts by mass of toner particles. The total external addition amount of silica particles and alkaline earth metal titanate particles is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 4.0 parts by mass or less, and even more preferably 1.0 parts by mass or more and 3.0 parts by mass or less, relative to 100 parts by mass of toner particles. The total external addition amount of silica particles and strontium titanate particles is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 4.0 parts by mass or less, and even more preferably 1.0 parts by mass or more and 3.0 parts by mass or less, relative to 100 parts by mass of toner particles. The total external addition amount of the lanthanum-doped strontium titanate particles is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 4.0 parts by mass or less, and even more preferably 1.0 parts by mass or more and 3.0 parts by mass or less, relative to 100 parts by mass of the toner particles.

[0316] [Other external additives] The toner may be a toner to which an external additive other than titanic acid compound particles and silica particles is added. Examples of the external additive other than titanic acid compound particles and silica particles include TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n , inorganic particles such as Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, and MgSO4; and resin particles such as polystyrene, polymethyl methacrylate, and melamine resin. These may be used alone or in combination of two or more.

[0317] The surfaces of the inorganic particles used as external additives are preferably subjected to a hydrophobic treatment. Examples of hydrophobic treatment agents include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents.

[0318] [Developer] The developer may be a one-component developer containing only toner, or a two-component developer containing a mixture of toner and carrier.

[0319] The carrier is not particularly limited, and known carriers can be used. Examples of the carrier include a coated carrier in which the surface of a core material made of magnetic powder is coated with a resin; a magnetic powder dispersion type carrier in which magnetic powder is dispersed and mixed in a matrix resin; and a resin impregnated type carrier in which porous magnetic powder is impregnated with a resin. A carrier in which a magnetic powder dispersion type carrier or a resin impregnated type carrier is used as a core material and the surface of this is coated with a resin may also be used.

[0320] Examples of magnetic powder include magnetic metals such as iron, nickel, and cobalt; and magnetic oxides such as ferrite and magnetite.

[0321] Examples of coating resins and matrix resins include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid ester copolymer, straight silicone resins containing organosiloxane bonds or modified products thereof, fluororesin, polyester, polycarbonate, phenolic resin, and epoxy resin. The coating resin and matrix resin may contain other additives such as conductive particles. Examples of conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0322] Examples of methods for coating the surface of the core material with a resin include a method using a coating layer-forming solution in which the coating resin and various additives (used as needed) are dissolved in an appropriate solvent. The solvent is not particularly limited and may be selected taking into consideration the type of resin used, its suitability for application, etc. Specific resin coating methods include an immersion method in which the core material is immersed in a solution for forming a coating layer; a spray method in which the solution for forming a coating layer is sprayed onto the surface of the core material; a fluidized bed method in which the solution for forming a coating layer is sprayed onto the core material while it is suspended in flowing air; and a kneader coater method in which the core material of the carrier and the solution for forming a coating layer are mixed in a kneader coater and then the solvent is removed.

[0323] The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably toner:carrier=1:100 to 30:100, and more preferably 3:100 to 20:100. [Example]

[0324] The present embodiment will be described in detail below with reference to examples, but the present embodiment is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are by mass. In the following description, synthesis, processing, manufacturing, testing, etc. were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0325] <Production of strontium titanate particles> La-doped strontium titanate particles with a hydrophobic surface treatment using isobutyltrimethoxysilane (i-BTMS) were produced using a known wet process and surface treatment method, as well as dopant-free and surface-untreated strontium titanate particles. The particle size of the strontium titanate particles was controlled by varying the length of time the materials were dropped during granulation using the wet process. Table 1 shows the physical properties of the strontium titanate particles.

[0326] [Table 1]

[0327] <Production of Silica Particles> Silica particles with hydrophobic surfaces treated with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) were produced using a known sol-gel method and surface treatment method. The particle size of the silica particles was controlled by varying the length of time the materials were added during granulation using the sol-gel method. Table 2 shows the physical properties of the silica particles.

[0328] [Table 2]

[0329] <Synthesis of polyarylate resin (S)> Polyarylate resins (1) to (8) were synthesized as polyarylate resin (S). In synthesizing all of these resins, polymerization was carried out in the presence of an end-capping agent, 4-tert-butylphenol, to cap the ends of the polyarylate resin. Table 3 shows the units and compositions that make up the polyarylate resin. A1-3 and the like shown in Table 3 are specific examples of the dicarboxylic acid unit (A) already described. B1-4 and the like shown in Table 3 are specific examples of the diol unit (B) already described.

[0330] [Table 3]

[0331] <Synthesis of polycarbonate resin> According to a conventional method, a polycarbonate resin (1) having a viscosity average molecular weight of 80,000 and consisting of the following structural units was synthesized.

[0332] [ka]

[0333] <Photoreceptor manufacturing> - Formation of undercoat layer - As a conductive substrate, an aluminum cylindrical tube having an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 1.6 mm was prepared.

[0334] Zinc oxide (average particle size 70 nm, specific surface area 15 m 2 100 parts of a silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 500 parts of toluene by stirring, and 1.3 parts of a silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred for 2 hours. The toluene was then distilled off under reduced pressure, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0335] 110 parts of the surface-treated zinc oxide was mixed with 500 parts of tetrahydrofuran and stirred, and a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added, followed by stirring for 5 hours at 50° C. The solid content was then filtered off under reduced pressure and dried under reduced pressure at 60° C. to obtain zinc oxide with alizarin added thereto.

[0336] A solution of 60 parts alizarin-modified zinc oxide, 13.5 parts blocked isocyanate (product name: Sumidur 3175, Sumitomo Bayer Urethane Co., Ltd.), and 15 parts butyral resin (product name: S-LEC BM-1, Sekisui Chemical Co., Ltd.) dissolved in 68 parts methyl ethyl ketone was mixed with 5 parts methyl ethyl ketone and dispersed in a sand mill using 1 mm diameter glass beads for 2 hours to obtain a dispersion. To the dispersion, 0.005 parts dioctyltin dilaurate as a catalyst and 4 parts silicone resin particles (product name: Tospearl 145, Momentive Performance Materials Japan, LLC) were added to obtain a coating solution for forming an undercoat layer. The coating solution for forming the undercoat layer was applied to the outer surface of a conductive substrate by dip coating and dried and cured at 185°C for 35 minutes to form an undercoat layer with an average thickness of 25 μm.

[0337] - Formation of charge generation layer - A mixture consisting of 15 parts of hydroxygallium phthalocyanine (CGL) as a charge-generating material (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in the X-ray diffraction spectrum using CuKα characteristic X-rays), 10 parts of vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using 1 mm diameter glass beads for 4 hours. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion and stirred to obtain a coating solution for forming a charge-generating layer. The coating solution for forming the charge-generating layer was dip-coated onto the undercoat layer and dried at room temperature (25°C±3°C) to form a charge-generating layer with an average thickness of 0.25 μm.

[0338] - Formation of charge transport layer - Binder resin: 60 parts polyarylate resin or polycarbonate resin ·Charge transport material: CTM-1 40 parts 270 parts tetrahydrofuran 30 parts toluene The above materials were mixed by stirring to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was dip-coated onto the charge generation layer and dried at 145°C for 30 minutes to form a charge transport layer with an average thickness of 40 μm. The types of binder resins used in the production of the photoreceptors (1) to (9) are as shown in Table 4. The chemical structure of the charge transport material CTM-1 is shown below.

[0339] [ka]

[0340] [Table 4]

[0341] <Cleaning blade manufacturing> A polyol was obtained by polymerizing a polyol material in a 1:1 molar ratio and then treating it to form OH groups at the terminals. The polyol, chain extender, polyisocyanate, and crosslinker were mixed in the molar ratios listed in Table 5 to form the material for the second polyurethane layer, which was poured into a mold. The material for the first polyurethane layer, prepared in the same manner, was then poured into the mold to form a two-layer urethane rubber sheet. The hardness of the first and second polyurethane layers was controlled by the type and composition of the materials. Table 5 shows the hardness of each layer, the type and composition of the materials, and the loss tangent (tanδ) of the cleaning blade.

[0342] [Table 5]

[0343] Example 1 [Toner and developer manufacturing] Black toner particles (volume average particle size 5 μm) having a core-shell structure were prepared. The binder resin of the core was an amorphous polyester resin and a crystalline polyester resin, and the binder resin of the shell was an amorphous polyester resin.

[0344] 100 parts of the black toner particles were mixed with 1 part of strontium titanate particles (1) and 2.5 parts of silica particles (1), and the mixture was mixed at 10,000 rpm for 30 seconds using a sample mill. The mixture was then sieved using a vibrating sieve with 45 μm openings to obtain an externally-added toner.

[0345] A carrier was prepared by coating ferrite particles (average particle size 35 μm) with a resin. The coating resin layer was a resin layer in which carbon black was dispersed in a cyclohexyl methacrylate-monoethylaminoethyl methacrylate copolymer.

[0346] The toner with the external additives and the carrier were placed in a V-blender and stirred for 20 minutes, after which the mixture was sieved through a sieve with 212 μm openings to obtain a developer.

[0347] [Manufacturing of image forming devices] A photoreceptor (1) and a cleaning blade (1) were installed in a modified image forming apparatus DocuCentre-V C7775 (Fujifilm Business Innovation Co., Ltd.), and the above developer was stored in the developing device.

[0348] <Examples 2 to 24 and Comparative Examples 1 to 6> The image forming apparatus was equipped with a photoreceptor and a cleaning blade in the combination shown in Table 6. In addition, the toner external additives were changed as shown in Table 6, and toner and developer were manufactured and placed in the developing device.

[0349] <Performance evaluation> The following performance evaluations were carried out using each of the image forming apparatuses of the examples and comparative examples. The evaluation results are shown in Table 6.

[0350] [Fuzzy] In an environment of 28°C and 85% relative humidity, 6,000 black solid images with 100% image density were printed on A4 plain paper. The image on the 6,000th sheet was observed with the naked eye, and the presence or absence of white fading was classified as follows: A: No fading is observed. B: Blurring is observed in an area of ​​less than 3%, but this does not pose a problem in practical use. C: Blurring is observed in an area of ​​less than 5%, but is within the practical allowable range. D: Blurring is clearly observed, and it is problematic for practical use.

[0351] [Cover] In an environment with a temperature of 15°C and a relative humidity of 10%, 10,000 black images with an image density of 5% were printed on A4 plain paper. Next, 10 black images with an image density of 40% were printed on A4 plain paper. The 10 images were observed with the naked eye and with a 5x magnifying glass, and the presence or absence of fog was classified as follows: G1: No overlapping is permitted on all 10 sheets. G2: A slight fog can be seen on one sheet with a magnifying glass, but this does not affect practical use. G3: Slight fogging can be seen on several sheets with a magnifying glass, but is within practical tolerances. G4: Fog is visible to the naked eye on multiple sheets, and is problematic for practical use. G5: Fog was visible to the naked eye on all 10 sheets, which was problematic for practical use.

[0352] [Uneven density] In an environment with a temperature of 28°C and a relative humidity of 85%, 100,000 black images with an image density of 5% were printed on A4 plain paper. Next, one black halftone image with an image density of 50% was printed on another sheet of A4 plain paper. The image was observed with the naked eye, and the presence or absence of density unevenness was classified as follows: A: No uneven density is observed. B: Slight density unevenness is observed in less than 20% of the entire image area, but this does not pose a problem in practical use. C: Density unevenness is observed in 20% or more and less than 60% of the entire image area, but is within the practical tolerance range. D: Obvious density unevenness was observed in 60% or more of the entire image area, which is problematic for practical use.

[0353] [Filming] In an environment with a temperature of 28°C and a relative humidity of 85%, 10,000 black images with an image density of 1% were printed on A4 plain paper. Next, one black halftone image with an image density of 50% was printed on another sheet of A4 plain paper. The image on this sheet was observed with the naked eye, and the surface of the photoreceptor was observed under a microscope, and the presence or absence of filming was classified as follows: G1: No filming on the photosensitive drum, no white streaks in the image. G2: There is slight filming on the photosensitive drum, and no white streaks in the image. G3: Streaky filming is observed on the photosensitive drum, and no white streaks are observed on the image. G4: There is streaky filming on the photosensitive drum and white streaks on the image.

[0354] [Table 6]

[0355] The meanings of the abbreviations in Table 6 are as follows: 1st PU layer: 1st polyurethane layer 2nd PU layer: 2nd polyurethane layer PAR: Polyarylate resin PC: Polycarbonate resin

[0356] The image forming apparatus of the present disclosure includes the following aspects: Each equation is the same as the previously described equation with the same number.

[0357] (Addendum) (((1))) A photoreceptor; a charging device that charges the surface of the photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the photoreceptor; a developing device that contains a developer containing toner and develops the electrostatic latent image formed on the surface of the photoreceptor to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a cleaning device having a cleaning blade that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor; the toner comprises toner particles, titanate compound particles, and silica particles; the surface layer of the photoreceptor contains a polyarylate resin having a dicarboxylic acid unit (A) represented by formula A and a diol unit (B) represented by formula B, the cleaning blade has a first polyurethane layer that is in contact with the photoreceptor and has a hardness of 85 degrees or more and 95 degrees or less, and a second polyurethane layer that is a layer that supports the first polyurethane layer and has a hardness of 55 degrees or more and 70 degrees or less, Image forming device. (((2))) The image forming apparatus according to (((1))), wherein, in dynamic viscoelasticity measurement of the cleaning blade, when the maximum value of the loss tangent in the range of 0°C or higher and 30°C or lower is tanδ(Max) and the minimum value is tanδ(Min), the values ​​satisfy tanδ(Max)≦0.5 and tanδ(Max)−tanδ(Min)≦0.1. (((3))) The image forming apparatus according to (((1))) or (((2))), wherein the photoreceptor has a charge generating layer and a charge transport layer, and the charge transport layer is the surface layer. (((4))) The image forming apparatus according to any one of (((1))) to (((3))), wherein the polyarylate resin contained in the surface layer of the photoreceptor has a weight average molecular weight of 80,000 or more and 150,000 or less. (((5))) The image forming apparatus according to any one of (((1))) to (((4))), wherein the titanic acid compound particles contained in the toner have an average primary particle size of 20 nm or more and 100 nm or less. (((6))) The image forming apparatus according to any one of (((1))) to (((5))), wherein the average primary particle size of the silica particles contained in the toner is 50 nm or more and 150 nm or less. (((7))) The image forming apparatus according to any one of (((1))) to (((6))), wherein the titanate compound particles include alkaline earth metal titanate particles. (((8))) The image forming apparatus according to any one of (((1))) to (((7))), wherein the titanate compound particles include strontium titanate particles containing a dopant. (((9))) The image forming apparatus according to (((8))), wherein the dopant includes lanthanum. (((10))) The image forming apparatus according to any one of (((1))) to (((9))), wherein the cleaning blade contacts the surface of the photosensitive member with a pressing pressure of 1 gf / mm or more and 4 gf / mm or less. (((11))) The image forming apparatus according to any one of (((1))) to (((10))), wherein the dicarboxylic acid unit (A) comprises at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1), a dicarboxylic acid unit (A2) represented by formula (A2), and a dicarboxylic acid unit (A3) represented by formula (A3). (((12))) The image forming apparatus according to any one of (((1))) to (((11))), wherein the diol unit (B) comprises at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8).

[0358] According to (((1))), (((3))), (((7))), (((8))), (((9))), (((11))) and (((12))), an image forming apparatus is provided in which density unevenness in an image is less likely to occur compared to an embodiment in which the surface layer of a photoreceptor does not contain a polyarylate resin but contains a polycarbonate resin, an embodiment in which the hardness of the first polyurethane layer exceeds 95 degrees, and an embodiment in which the hardness of the second polyurethane layer exceeds 70 degrees, and in which filming is less likely to occur on the surface of the photoreceptor compared to an embodiment in which the hardness of the first polyurethane layer is less than 85 degrees and an embodiment in which the hardness of the second polyurethane layer is less than 55 degrees. According to (((2))), an image forming apparatus is provided in which density unevenness is less likely to occur in the image and filming is less likely to occur on the surface of the photosensitive member, compared to an embodiment in which tan δ(Max)>0.5 or tan δ(Max)-tan δ(Min)>0.1. According to (((4))), an image forming apparatus is provided in which density unevenness is less likely to occur in an image than in an embodiment in which the weight average molecular weight of the polyarylate resin contained in the surface layer of the photoreceptor is less than 80,000, and in which filming is less likely to occur on the surface of the photoreceptor than in an embodiment in which the weight average molecular weight of the polyarylate resin is more than 150,000. According to (((5))), an image forming apparatus is provided in which fogging is less likely to occur in images than in an embodiment in which the average primary particle size of the titanate compound particles contained in the toner is less than 20 nm, and which is less likely to cause blurring in images than in an embodiment in which the average primary particle size of the titanate compound particles is more than 100 nm. According to (((6))), an image forming apparatus is provided in which fogging is less likely to occur in an image than in an embodiment in which the average primary particle size of the silica particles contained in the toner is less than 50 nm, and in which blurring and fogging are less likely to occur in an image than in an embodiment in which the average primary particle size of the silica particles is more than 150 nm. According to (((10))), an image forming apparatus is provided in which density unevenness in an image is less likely to occur and filming is less likely to occur on the surface of the photosensitive member, compared to an embodiment in which the cleaning blade contacts the surface of the photosensitive member with a pressing pressure of less than 1 gf / mm and an embodiment in which the cleaning blade contacts the surface of the photosensitive member with a pressing pressure of more than 4 gf / mm. [Explanation of symbols]

[0359] 7 photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll-shaped), 133 fibrous member (flat brush-shaped), 300 process cartridge

[0360] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 10A photoreceptor, 10B photoreceptor

[0361] 30, 60 cleaning blade, 31 first polyurethane layer, 32 second polyurethane layer, 31E, 32E, 60E corner portion, 70 support member

Claims

1. A photoreceptor; a charging device that charges the surface of the photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the photoreceptor; a developing device that contains a developer containing toner and develops the electrostatic latent image formed on the surface of the photoreceptor to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a cleaning device having a cleaning blade that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor; the toner comprises toner particles, titanate compound particles, and silica particles; The surface layer of the photoreceptor contains a polyarylate resin having a dicarboxylic acid unit (A) represented by the following formula A and a diol unit (B) represented by the following formula B: the cleaning blade has a first polyurethane layer that is in contact with the photoreceptor and has a hardness of 85 degrees or more and 95 degrees or less, and a second polyurethane layer that is a layer that supports the first polyurethane layer and has a hardness of 55 degrees or more and 70 degrees or less, Image forming device. 【Chemistry 1】 In formula (A), Ar Ａ１ and Ar Ａ２ each independently represents an aromatic ring which may have a substituent, and L Ａ is a single bond or a divalent linking group, n Ａ１ is 0, 1 or 2. In formula (B), Ar Ｂ１ and Ar Ｂ２ each independently represents an aromatic ring which may have a substituent, and L Ｂ is a single bond, an oxygen atom, a sulfur atom, or -C(Rb １ )(Rb ２ )- and n Ｂ１ is 0, 1 or 2. １ and Rb ２ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb １ and Rb ２ may be bonded to form a cyclic alkyl group.

2. 2. The image forming apparatus according to claim 1, wherein, in a dynamic viscoelasticity measurement of the cleaning blade, when the maximum value of the loss tangent in the temperature range of 0° C. or higher and 30° C. or lower is defined as tanδ(Max) and the minimum value is defined as tanδ(Min), the relationship between tanδ(Max) and tanδ(Min) is satisfied.

3. 2. The image forming apparatus according to claim 1, wherein the photoreceptor has a charge generating layer and a charge transport layer, and the charge transport layer is the surface layer.

4. 2. The image forming apparatus according to claim 1, wherein the polyarylate resin contained in the surface layer of the photoreceptor has a weight average molecular weight of 80,000 or more and 150,000 or less.

5. 2. The image forming apparatus according to claim 1, wherein the titanic acid compound particles contained in the toner have an average primary particle size of 20 nm or more and 100 nm or less.

6. 2. The image forming apparatus according to claim 1, wherein the average primary particle size of the silica particles contained in the toner is 50 nm or more and 150 nm or less.

7. The image forming apparatus according to claim 1 , wherein the titanate compound particles include alkaline earth metal titanate particles.

8. 2. The image forming apparatus according to claim 1, wherein the titanate compound particles include strontium titanate particles containing a dopant.

9. 9. The imaging apparatus of claim 8, wherein the dopant comprises lanthanum.

10. 2. The image forming apparatus according to claim 1, wherein the cleaning blade contacts the surface of the photosensitive member with a pressing pressure of 1 gf / mm or more and 4 gf / mm or less.

11. 2. The image forming apparatus according to claim 1, wherein the dicarboxylic acid unit (A) comprises at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by the following formula (A2), and a dicarboxylic acid unit (A3) represented by the following formula (A3). 【Chemistry 2】 In formula (A1), n １０１ and n １０２ are each independently an integer of 0 to 4, １０１ Ra １０１ and n １０２ Ra １０２ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A2), n ２０１ is an integer of 0 to 6, ２０１ Ra ２０１ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A3), n ３０１ , n ３０２ and n ３０３ are each independently an integer of 0 to 4, ３０１ Ra ３０１ , n ３０２ Ra ３０２ and n ３０３ Ra ３０３ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

12. 2. The image forming apparatus according to claim 1, wherein the diol unit (B) comprises at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the formula (B2), a diol unit (B3) represented by the formula (B3), a diol unit (B4) represented by the formula (B4), a diol unit (B5) represented by the formula (B5), a diol unit (B6) represented by the formula (B6), a diol unit (B7) represented by the formula (B7), and a diol unit (B8) represented by the formula (B8). 【Transformation 3】 【Chemistry 4】 In formula (B1), Rb １０１ is a branched alkyl group having 4 to 20 carbon atoms, and Rb ２０１ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０１ , Rb ５０１ , Rb ８０１ and Rb ９０１ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B2), Rb １０２ is a linear alkyl group having 4 to 20 carbon atoms, and Rb ２０２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０２ , Rb ５０２ , Rb ８０２ and Rb ９０２ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B3), Rb １１３ and Rb ２１３ are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; d is an integer of 7 to 15; Rb ４０３ , Rb ５０３ , Rb ８０３ and Rb ９０３ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B4), Rb １０４ and Rb ２０４ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０４ , Rb ５０４ , Rb ８０４ and Rb ９０４ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B5), Ar １０５ is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb ２０５ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０５ , Rb ５０５ , Rb ８０５ and Rb ９０５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B6), Rb １１６ and Rb ２１６ are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; e is an integer of 4 to 6; Rb ４０６ , Rb ５０６ , Rb ８０６ and Rb ９０６ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B7), Rb ４０７ , Rb ５０７ , Rb ８０７ and Rb ９０７ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B8), Rb ４０８ , Rb ５０８ , Rb ８０８ and Rb ９０８ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

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