JP2018180318A - Image forming device and image formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that prevents the occurrence of fogging and maintains cleaning performance by a cleaning member as well.SOLUTION: The image forming device comprises an image carrier 13, a developing device 11, and a cleaning member 27. The image carrier 13 includes a conductive base 311 having a rough surface 313 and a photosensitive layer 315 provided on the rough surface 313. On the surface 13s of the image carrier 13 are formed a projection P1 that corresponds to a projection formed on the rough surface 313 and a recess P2 that corresponds to a recess formed on the rough surface 313. The arithmetic average roughness Ra of surface 13s of the image carrier 13 is 40 nm to 65 nm inclusive. The image forming device further includes a developer. The toner included in the developer includes a plurality of toner particles. Each of the toner particles includes a plurality of resin particles as external additives. The blocking rate of the resin particles is 15 mass% to 40 mass% inclusive. The number average primary particle size of the resin particles is 50 nm to 70 nm inclusive.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus and an image forming method.

  Image forming apparatuses often include an image carrier, a developing device, and a cleaning member. The image carrier holds an electrostatic latent image on the surface. The developing device develops the electrostatic latent image using toner. The cleaning member is brought into pressure contact with the surface of the image carrier to remove transfer residual toner (toner remaining on the surface of the image carrier without being transferred to the recording medium) from the surface of the image carrier.

  The toner includes a plurality of toner particles (see, for example, Patent Document 1). Patent Document 1 describes the following. The toner particles each have toner base particles and an external additive attached to the surface of the toner base particles. The external additive contains a plurality of resin particles. The resin particles each have a predetermined hardness.

Japanese Patent Application Laid-Open No. 10-268554

  When the external additive contains a plurality of resin particles, the chargeability of the toner can be stabilized. However, if the resin particles are detached from the surface of the toner base particles during image formation, the chargeability of the toner may fluctuate. Therefore, fog may occur in the formed image. Hereinafter, the resin particles detached from the surface of the toner base particles will be referred to as "desorbed particles". Also, "the occurrence of fogging in the formed image" is simply described as "the occurrence of fogging".

  As a method of preventing the occurrence of fogging, for example, it is conceivable to use resin particles having a small particle diameter. However, as the particle size of the resin particles becomes smaller, the resin particles tend to slip through between the image carrier and the cleaning member. When the resin particles rub off between the image carrier and the cleaning member, it becomes difficult for the resin particles to be collected by the cleaning member. Therefore, the cleaning performance of the surface of the image carrier by the cleaning member (hereinafter referred to as "cleaning performance by the cleaning member") may be lowered. When the cleaning performance by the cleaning member is lowered, image defects in the form of vertical stripes may be formed in the formed image.

  As described above, the prevention of the occurrence of fogging and the maintenance of the cleaning performance by the cleaning member are in a trade-off relationship. Therefore, it is difficult to simultaneously prevent the occurrence of fogging and maintain the cleaning performance by the cleaning member. However, it is required to achieve both the prevention of the occurrence of fogging and the maintenance of the cleaning performance by the cleaning member.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an image forming apparatus and an image forming method capable of achieving both prevention of occurrence of fog and maintenance of cleaning performance by a cleaning member. .

The image forming apparatus according to the present invention forms an image on a recording medium using a developer. The image forming apparatus includes the developer. The developer includes a toner and a carrier that positively charges the toner by friction. The toner comprises a plurality of toner particles. The toner particles each include toner base particles and an external additive attached to the surface of the toner base particles. The external additive contains a plurality of resin particles. The toner base particles and the resin particles each have positive chargeability stronger than the carrier. The blocking ratio of the resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 15% by mass or more and 40% by mass or less as measured by a mesh of 75 μm. The number average primary particle diameter of the resin particles is 50 nm or more and 70 nm or less. The image forming apparatus further includes an image carrier holding an electrostatic latent image on the surface, a developing device developing the electrostatic latent image using the toner, and a pressure contact with the surface of the image carrier. And a cleaning member for removing the developer remaining on the surface of the image carrier from the surface of the image carrier. The image carrier has a conductive substrate having a rough surface, and a photosensitive layer provided on the rough surface. Irregularities corresponding to the irregularities formed on the rough surface are formed on the surface of the image carrier. Arithmetic mean roughness Ra of the surface of the image carrier is 40 nm or more and 65 nm or less.

In the image forming method according to the present invention, an image is formed on a recording medium using a developer. The developer includes a toner and a carrier that positively charges the toner by friction. The toner comprises a plurality of toner particles. The toner particles each include toner base particles and an external additive attached to the surface of the toner base particles. The external additive contains a plurality of resin particles. The toner base particles and the resin particles each have positive chargeability stronger than the carrier. The blocking ratio of the resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 15% by mass or more and 40% by mass or less as measured by a mesh of 75 μm. The number average primary particle diameter of the resin particles is 50 nm or more and 70 nm or less. The image forming method includes forming an electrostatic latent image on the surface of an image carrier, supplying the toner to the electrostatic latent image, and developing the electrostatic latent image as a toner image. And transferring the toner image to the recording medium, and removing the developer remaining on the surface of the image carrier from the surface of the image carrier after the toner image is transferred to the recording medium. . The image carrier has a conductive substrate having a rough surface, and a photosensitive layer provided on the rough surface. Irregularities corresponding to the irregularities formed on the rough surface are formed on the surface of the image carrier. Arithmetic mean roughness Ra of the surface of the image carrier is 40 nm or more and 65 nm or less.

  According to the present invention, it is possible to simultaneously prevent the occurrence of fogging and maintain the cleaning performance by the cleaning member.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a view showing the configuration of a developing device provided in the image forming apparatus according to the embodiment of the present invention. It is the figure which expanded the area | region III shown in FIG. FIG. 2 is a view showing the configuration of a developer included in the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, an image forming apparatus and an image forming method according to an embodiment of the present invention will be sequentially described by taking an image forming apparatus adopting a touch-down developing method as an example, with reference to the drawings. In the drawings, the same reference numerals represent the same or corresponding parts. The dimensional relationships such as length, width, thickness, depth and the like have been changed as appropriate for the sake of clarity and simplification of the drawings, and do not represent actual dimensional relationships. The image forming apparatus according to the present embodiment may be an image forming apparatus adopting a two-component developing method.

[Image forming apparatus]
The configuration of the image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a view showing the configuration of an image forming apparatus according to the present embodiment. The image forming apparatus 10 is a tandem type electrophotographic apparatus. Specifically, the image forming apparatus 10 includes image forming units 10A to 10D corresponding to the respective colors, an exposure device 17, a transfer belt 21, a secondary transfer roller 23, a fixing device 25, and a control unit 29. Each of the image forming units 10A to 10D includes a developing device 11, an image carrier 13, a charging device 15, a primary transfer roller 19, and a cleaning member 27.

  The developing device 11 contains a developer. The developing device 11 performs development using electrostatic latent image developing toner (hereinafter, simply referred to as “toner”) contained in the developer.

  The image carrier 13 is supported by the housing of the image forming apparatus 10 in a rotatable manner. More specifically, the image carrier 13 is driven by, for example, a motor (not shown) to rotate along the rotational direction R3.

  The image carrier 13 holds an electrostatic latent image on the surface (circumferential surface). The toner is electrically attracted to the electrostatic latent image. Thereby, a toner image is formed on the surface of the image carrier 13. The image carrier 13 corresponds to a photosensitive drum.

  The charging device 15 is provided around the image carrier 13 and uniformly charges the surface of the image carrier 13. The charging device 15 is not particularly limited as long as it is a device capable of uniformly charging the surface of the image carrier 13, and may be a contact-type charger or a non-contact-type charger. . The contact type charger is preferably, for example, a charging roller or a charging brush. The non-contact type charger is preferably, for example, a corotron charger or a scorotron charger.

  The exposure device 17 exposes the uniformly charged surface of the image carrier 13 to form an electrostatic latent image on the surface of the image carrier 13. The exposure device 17 is preferably, for example, a laser scanning unit.

  The primary transfer roller 19 faces the image carrier 13 across the transfer belt 21. The primary transfer roller 19 transfers the toner image (toner image formed on the surface of the image carrier 13) onto the transfer belt 21 or the recording medium M. The transfer belt 21 is preferably an endless belt.

  The secondary transfer roller 23 transfers the toner image transferred to the transfer belt 21 to the recording medium M. Therefore, when the primary transfer roller 19 transfers the toner image to the recording medium M, the secondary transfer roller 23 can be omitted.

  The fixing device 25 fixes the toner image transferred to the recording medium M to the recording medium M. The fixing device 25 is preferably, for example, a nip fixing type fixing device. The fixing device of the nip fixing type usually has a heating roller and a pressure roller.

  The cleaning member 27 is provided around the image carrier 13. More specifically, when the portion of the image carrier 13 to which the primary transfer roller 19 is opposed is a base point in the rotational direction R3 of the image carrier 13, the cleaning member 27 is closer to the image carrier than the primary transfer roller 19. It is located downstream of the 13 rotation directions R3.

  The cleaning member 27 is disposed along the longitudinal direction of the image carrier 13 and is pressed against the surface of the image carrier 13. In the cleaning member 27, a portion pressed against the surface of the image carrier 13 is referred to as a "tip", and a portion opposite to the tip is referred to as a "proximal". At the contact point between the front end of the cleaning member 27 and the surface of the image carrier 13, the rotational direction R3 of the image carrier 13 and the direction from the base end to the front end of the cleaning member 27 are opposite to each other. is there. Thus, the cleaning member 27 can remove the transfer residual toner from the surface of the image carrier 13. The cleaning member 27 corresponds to a cleaning blade, and is preferably a rubber cleaning blade.

  The control unit 29 controls the image forming apparatus 10 to execute image formation. The image forming apparatus 10 forms an image on the recording medium M by causing the CPU to execute a predetermined control program stored in the ROM by the control unit 29. The control unit 29 may be embodied in cooperation with an electronic circuit and / or a program provided outside the image forming apparatus 10. More specifically, the control unit 29 may be embodied as a user executes or downloads a program held in a predetermined server on the communication network.

  The configuration of the developing device 11 will be described in detail with reference to FIG. FIG. 2 is a view showing the configuration of the developing device 11. The developing device 11 includes a housing 111, a developer conveyance path 113, a developer stirring and conveying member 115, a developer carrier 121, a developer regulating member 131, and a toner carrier 141. The developer transport path 113, the developer stirring and transporting member 115, the developer carrier 121, the developer regulating member 131, and the toner carrier 141 are disposed in the housing 111.

  The developer transport path 113 contains a developer. Developer transport path 113 includes a first transport path 113A and a second transport path 113B. The first transport path 113A and the second transport path 113B are partitioned by the partition wall 117 and extend in parallel with each other. In the present embodiment, the first transport path 113A and the second transport path 113B correspond to a storage portion for storing the developer.

  The developer stirring and conveying member 115 includes a first stirring screw 115A and a second stirring screw 115B. The first stirring screw 115A is disposed in the first conveyance path 113A, and the axial direction of the first stirring screw 115A is parallel to the longitudinal direction of the first conveyance path 113A. The second stirring screw 115B is disposed in the second conveyance path 113B, and the axial direction of the second stirring screw 115B is parallel to the longitudinal direction of the second conveyance path 113B. As described above, the first transport path 113A and the second transport path 113B extend in parallel with each other. Therefore, the first stirring screw 115A and the second stirring screw 115B extend in parallel with each other.

  The first stirring screw 115A has a spiral stirring blade and conveys the developer in the first conveyance path 113A while stirring. The second stirring screw 115B has a spiral stirring blade and conveys the developer in the second conveyance path 113B while stirring. The first stirring screw 115A and the second stirring screw 115B convey the developer in opposite directions.

  The developer carrier 121 faces the developer stirring and conveying member 115, and is supported by the casing 111 in a rotatable manner. The developer carrier 121 is driven by, for example, a motor (not shown) to rotate along the rotational direction R1.

  The developer carrier 121 has a non-rotatable magnet roll. The magnet roll has a plurality of magnetic poles at least at its surface. As a magnetic pole which a magnet roll has, the N pole and S pole based on a permanent magnet are mentioned, for example. Hereinafter, among the plurality of magnetic poles of the magnet roll, the magnetic pole facing the second stirring screw 115B is referred to as "the upper pole 123", and the magnetic pole facing the developer regulating member 131 is referred to as the "regulating pole 125". The magnetic pole facing the toner carrier 141 is referred to as “main pole 127”. When the scooping pole 123 is a base point in the rotational direction R1 of the developer carrier 121, the regulating pole 125 is located downstream of the scooping pole 123 in the rotational direction R1 of the developer carrier 121, and the main pole 127 is The developer carrier 121 is located downstream of the regulating electrode 125 in the rotational direction R 1 of the developer carrier 121.

  The developer carrier 121 magnetically pumps the developer from the second transport path 113B to the surface 121s of the developer carrier 121 by the magnetic force of the suction pole 123. As a result, a layer made of a developer (hereinafter, referred to as a “magnetic brush layer”) is formed on the surface 121s of the developer carrier 121. The developer carrier 121 corresponds to a magnetic roller.

  The developer regulating member 131 extends along the longitudinal direction of the developer carrier 121 (more specifically, the axial direction of the magnet roll). The developer regulating member 131 faces the regulating electrode 125 of the developer carrier 121 and is magnetized by the regulating electrode 125. Therefore, the developer regulating member 131 is preferably made of a magnetic material.

  The developer restricting member 131 has a support member 133 and a restricting surface 135. The support member 133 is fixed to the housing 111 and supports the developer regulating member 131. The regulating surface 135 corresponds to the front end surface of the developer regulating member 131, and more specifically, faces the surface 121s of the developer carrier 121. A first gap (so-called regulation gap) G1 is provided between the regulation surface 135 and the surface 121s of the developer carrier 121.

  When the developer carrier 121 rotates along the rotational direction R1, the magnetic brush layer is conveyed into the first gap G1. Thus, the thickness of the magnetic brush layer is regulated by the developer regulating member 131. The developer regulating member 131 corresponds to a developer regulating blade.

  The toner carrier 141 faces the main electrode 127 of the developer carrier 121 and is supported by the casing 111 in a rotatable manner. The toner carrier 141 is driven by, for example, a motor (not shown) to rotate along the rotational direction R2. A second gap G2 is provided between the surface 141s of the toner carrier 141 and the surface 121s of the developer carrier 121.

  When the toner carrier 141 rotates along the rotational direction R2 and a predetermined potential difference is generated between the surface 141s of the toner carrier 141 and the surface 121s of the developer carrier 121, the toner contained in the magnetic brush layer is generated. The toner moves from the surface 121 s of the developer carrier 121 to the surface 141 s of the toner carrier 141. Thus, a layer (toner layer) made of toner is formed on the surface 141s of the toner carrier 141.

  Further, the toner carrier 141 faces the image carrier 13 through the opening formed in the housing 111. A third gap G3 is provided between the surface 141s of the toner carrier 141 and the surface 13s of the image carrier 13.

  When the image carrier 13 rotates along the rotational direction R3 and a predetermined potential difference is generated between the surface 141s of the toner carrier 141 and the surface 13s of the image carrier 13, the toner constituting the toner layer becomes the toner It flies from the surface 141s of the carrier 141 to the surface 13s of the image carrier 13 (more specifically, the portion of the surface 13s of the image carrier 13 exposed by the exposure device 17). Thereby, the electrostatic latent image is developed as a toner image. The toner carrier 141 corresponds to a developing roller.

  The configuration of the image carrier 13 will be described in detail with reference to FIG. FIG. 3 is an enlarged view of a region III shown in FIG. The image carrier 13 has a conductive substrate 311 and a photosensitive layer 315. The conductive substrate 311 has a rough surface 313. The photosensitive layer 315 is provided on the rough surface 313.

  The image carrier 13 has a convex portion P1 and a concave portion P2. The convex portion P1 is formed corresponding to the convex portion formed on the rough surface 313 of the conductive substrate 311. The recess P2 is formed corresponding to the recess formed on the rough surface 313 of the conductive substrate 311. The arithmetic average roughness Ra of the surface 13s of the image carrier 13 is 40 nm or more and 65 nm or less. Here, the arithmetic mean roughness Ra of the surface 13s of the image carrier 13 is measured according to the method defined in JIS (Japanese Industrial Standard) B 0601: 1994.

  The rough surface 313 of the conductive substrate 311 is preferably a blast surface. Here, a blast surface means the surface formed by blasting. If the rough surface 313 is a blast surface, the unevenness is likely to be irregularly formed in the axial direction of the conductive substrate 311 and irregular in the circumferential direction of the conductive substrate 311 in the rough surface 313. Therefore, the convex portion P1 and the concave portion P2 are easily irregularly formed in the axial direction of the image carrier 13 and irregularly formed in the circumferential direction of the image carrier 13 on the surface 13s of the image carrier 13 respectively. . Here, the axial direction of the conductive substrate 311 corresponds to the axial direction of the image carrier 13. The circumferential direction of the conductive substrate 311 corresponds to the circumferential direction of the image carrier 13.

  When the rough surface 313 of the conductive substrate 311 is a blast surface, the formation of the rough surface 313 is facilitated, so the convex portion P1 and the concave portion P2 are easily formed on the surface 13s of the image carrier 13. As a result, the arithmetic average roughness Ra of the surface 13s of the image carrier 13 is likely to be 40 nm or more and 65 nm or less.

  Blasting includes, for example, sand blasting, shot blasting, grit blasting, and bead blasting. The surface roughness of the rough surface 313 tends to increase as the amount of the abrasive to be sprayed on the conductive substrate 311 (hereinafter referred to as the “spray amount of the abrasive”) increases, the surface of the image carrier 13 The arithmetic mean roughness Ra of 13 s tends to be large. It is considered that the same tendency is exhibited when the abrasive spray speed is increased. In addition, since the surface roughness of the rough surface 313 tends to decrease as the abrasive spray amount decreases, the arithmetic average roughness Ra of the surface 13s of the image carrier 13 tends to decrease. It is considered that the same tendency is exhibited when the abrasive spray speed is reduced. Preferably, the rough surface 313 is formed by setting processing conditions in the blast processing such that the arithmetic average roughness Ra of the surface 13s of the image carrier 13 is 40 nm or more and 65 nm or less.

  The conductive substrate 311 is preferably a cylindrical element tube made of metal. As a metal which comprises an element pipe | tube, aluminum, iron, titanium, or magnesium is mentioned, for example.

  The photosensitive layer 315 may be an organic photosensitive layer using an organic photoconductor or an inorganic photosensitive layer using an inorganic photoelectric material, but is preferably an amorphous silicon photosensitive layer formed by vapor deposition of a silane gas, for example. . If the photosensitive layer 315 is an amorphous silicon photosensitive layer, the durability of the photosensitive layer 315 is improved. Thus, even when the image forming apparatus 10 is used for a long time, it is possible to prevent the surface shape of the image carrier 13 from being changed. Therefore, even when the image forming apparatus 10 is used for a long time, the arithmetic average roughness Ra of the surface 13s of the image carrier 13 can be easily maintained at 40 nm or more and 65 nm or less.

  The photosensitive layer 315 may be a single layer or may be formed by laminating two or more layers. When the photosensitive layer 315 is a single layer, the photosensitive layer 315 preferably contains a charge generating agent and a charge transporting agent. When two or more layers are laminated to constitute the photosensitive layer 315, the photosensitive layer 315 preferably includes an undercoat layer, a charge generation layer, and a charge transport layer. A protective layer for protecting the photosensitive layer 315 may be provided on the peripheral surface of the photosensitive layer 315.

  The developer contained in the image forming apparatus 10 will be described with reference to FIG. FIG. 4 is a view showing the structure of the developer. The developer 41 includes a toner including a plurality of toner particles 51 and a carrier for developing an electrostatic latent image including a plurality of carrier particles 61 (hereinafter, simply referred to as a “carrier”). The toner particles 51 each include toner base particles 53 and an external additive attached to the surface of the toner base particles 53. The external additive includes a plurality of resin particles 55. The carrier particles 61 each include a carrier core 63 and a coat layer 65 that covers the surface of the carrier core 63. Each of the toner base particles 53 and the resin particles 55 has positive chargeability stronger than that of the carrier. As described above, in the present embodiment, the toner base particles 53 and the resin particles 55 have the same polarity.

  Here, if the strength of the chargeability is not specified at all, it corresponds to the ease of triboelectric charging. For example, the toner can be triboelectrically charged by mixing with a standard carrier (anionic: N-01, cationic: P-01) provided by the Japan Imaging Society and stirring. Before and after the triboelectric charging, for example, the surface potential of the toner particles is measured by KFM (Kelvin probe force microscope), and the charging property is stronger as the potential change is large before and after the triboelectric charging. When the developer is a two-component developer, the toner contained in the developer is charged positively or negatively by friction with the carrier in the developing device.

  The number average primary particle diameter of the resin particles 55 is 50 nm or more and 70 nm or less. The number average primary particle diameter of the resin particles 55 is the number average value of the circle equivalent diameter of the primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope if nothing is specified. is there.

The blocking ratio of the resin particles 55 is 15% by mass or more and 40% by mass or less. Here, “the blocking ratio of the resin particles 55 is 15% by mass to 40% by mass” means blocking of the resin particles 55 after pressure for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ^2. It means that the rate is 15% by mass or more and 40% by mass or less as measured by a mesh of 75 μm. The blocking ratio of the resin particles 55 is measured by the method described in the examples to be described later, or a method analogous thereto.

  The low blocking ratio of the resin particles means that the resin particles are difficult to be thermally compressed, which means that the resin particles have high hardness. Therefore, as the blocking ratio of the resin particles 55 becomes lower, the resin particles 55 tend to be easily detached from the surface of the toner base particles 53.

  The high blocking ratio of the resin particles means that the resin particles are easily thermally compressed, and therefore, the hardness of the resin particles is low. Therefore, as the blocking ratio of the resin particles 55 becomes higher, the resin particles 55 tend to adhere to the surfaces of other members. Other members include, for example, the image carrier 13 or the carrier particles 61.

  In order to make the blocking ratio of the resin particles 55 40% by mass or less, it is necessary to extremely increase the hardness of the resin particles 55. For example, when the resin particles 55 are produced using a high purity crosslinking agent, the blocking ratio of the resin particles 55 tends to be 40% by mass or less. More specifically, when resin particles 55 are produced using divinylbenzene (crosslinking agent) having a purity of 80%, the blocking ratio of the resin particles 55 tends to be 40% by mass or less. If the resin particle 55 is manufactured by changing the compounding amount of the crosslinking agent, the blocking ratio of the resin particle 55 can be changed. For example, as the compounding amount of the crosslinking agent is increased, the blocking ratio of the resin particles 55 tends to decrease. In addition, the blocking ratio of the resin particles 55 tends to increase as the blending amount of the crosslinking agent is reduced.

  In the developer 41, the external additive may further include external additive particles different from the resin particles 55. Examples of external additive particles different from the resin particles 55 include silica particles or titanium oxide particles. Also, the carrier particle 61 may not include the coat layer 65. That is, the carrier particles 61 may be composed of a carrier core.

  The configuration of the image forming apparatus 10 has been described above with reference to FIGS. 1 to 4. In the image forming apparatus 10, the prevention of the occurrence of fogging and the maintenance of the cleaning performance by the cleaning member 27 can be compatible. Hereinafter, the effects of the image forming apparatus 10 will be described in detail.

  In the image forming apparatus 10, the number average primary particle diameter of the resin particles 55 is 70 nm or less. Thereby, even when image formation is performed in a situation where detachment of the resin particles 55 easily occurs, detachment of the resin particles 55 from the surface of the toner base particles 53 can be prevented.

  In the image forming apparatus 10, the blocking ratio of the resin particles 55 is 15% by mass or more. Thereby, the hardness of the resin particles 55 can be prevented from becoming too high. Therefore, even in the case where image formation is performed in a situation where detachment of the resin particles 55 is likely to occur, detachment of the resin particles 55 from the surface of the toner base particles 53 can be prevented.

  For example, in the present embodiment, the toner base particles 53 and the resin particles 55 have the same polarity. Therefore, since the toner base particles 53 and the resin particles 55 easily electrostatically repel, the resin particles 55 are easily detached from the surface of the toner base particles 53. However, in the present embodiment, the number average primary particle diameter of the resin particles 55 is 70 nm or less, and the blocking ratio of the resin particles 55 is 15% by mass or more. Therefore, even if the toner base particles 53 and the resin particles 55 have the same polarity, the resin particles 55 may be detached from the surface of the toner base particles 53 during image formation (hereinafter, “during image formation” Of the resin particles 55) can be prevented.

  Further, the image forming apparatus is required to operate in a temperature range of 10 ° C. or more and 40 ° C. or less. Generally, when image formation is performed in a low temperature environment, the temperature of the developer tends to be low. Since the hardness of the resin particles tends to increase as the temperature of the developer decreases, the resin particles tend not to be fixed to the surface of the toner base particles. However, in the present embodiment, the blocking ratio of the resin particles 55 is 15% by mass or more. Therefore, even if the temperature of the developer 41 is lowered, the hardness of the resin particles 55 can be prevented from becoming excessively high. Furthermore, in the present embodiment, the number average primary particle diameter of the resin particles 55 is 70 nm or less. From these facts, even in the case of performing image formation in a low temperature environment, detachment of the resin particles 55 during image formation can be prevented.

  Further, in the present embodiment, the touch down development method is adopted. Generally, when an image is formed using an image forming apparatus adopting a touch-down developing method, an alternating electric field is formed between a developer carrier and a toner carrier. The AC electric field acting on the toner particles makes it easy for the resin particles to detach from the surface of the toner base particles. However, in the present embodiment, the number average primary particle diameter of the resin particles 55 is 70 nm or less, and the blocking ratio of the resin particles 55 is 15% by mass or more. Therefore, even when image formation is performed in an image forming apparatus (more specifically, the image forming apparatus 10) in which the touch-down development method is adopted, detachment of the resin particles 55 during image formation can be prevented.

  As described above, in the present embodiment, even when image formation is performed in a situation in which detachment of the resin particles 55 is likely to occur, detachment of the resin particles 55 during image formation can be prevented. More specifically, even when image formation is performed in a low temperature environment using the image forming apparatus 10, detachment of the resin particles 55 during image formation can be prevented. As a result, the chargeability of the toner can be effectively prevented from fluctuating during image formation. Therefore, the toner can be effectively prevented from causing the charging failure. Therefore, the occurrence of fogging can be effectively prevented.

  In the image forming apparatus 10, the number average primary particle diameter of the resin particles 55 is 50 nm or more. Thus, even if the resin particles 55 are detached from the surface of the toner base particles 53 during image formation, the detached particles can be prevented from slipping between the image carrier 13 and the cleaning member 27. Thus, the separated particles can be collected by the cleaning member 27. Therefore, the cleaning performance by the cleaning member 27 can be maintained.

  In the image forming apparatus 10, the blocking ratio of the resin particles 55 is 40% by mass or less. Thereby, it can prevent that the hardness of the resin particle 55 becomes low too much. Therefore, even when the resin particles 55 are detached from the surface of the toner base particles 53 during image formation, adhesion of the detached particles to the surface 13 s of the image carrier 13 can be prevented. Therefore, since the detached particles are easily collected by the cleaning member 27, the cleaning performance by the cleaning member 27 can be maintained.

  In the image forming apparatus 10, the arithmetic average roughness Ra of the surface 13s of the image carrier 13 is 40 nm or more and 65 nm or less. Thereby, even when the detached particles adhere to the surface 13s of the image carrier 13, the contact area between the surface 13s of the image carrier 13 and the surface of the detached particles can be suppressed to a small value. Therefore, the adhesion of the detached particles to the surface 13s of the image carrier 13 can be suppressed low. This also prevents the detached particles from adhering to the surface 13s of the image carrier 13. Therefore, since the detached particles are easily collected by the cleaning member 27, the cleaning performance by the cleaning member 27 can be maintained.

  When the separated particles are collected by the cleaning member 27, the separated particles can be prevented from adhering to the surface 13 s of the image carrier 13. Thus, if an image is formed using the image forming apparatus 10, an image excellent in image quality can be formed. For example, it is possible to prevent the formation of vertical streak-like image defects in the formed image.

The present inventors have confirmed that even if the image forming apparatus has the following configurations P and Q, if the image forming apparatus does not have the following configuration R, the cleaning performance by the cleaning member is degraded. (See Comparative Examples 5 and 6 described later).
Configuration P: The number average primary particle diameter of the resin particles 55 is 50 nm or more and 70 nm or less.
Configuration Q: The blocking ratio of the resin particles 55 is 15% by mass or more and 40% by mass or less.
Configuration R: The arithmetic mean roughness Ra of the surface 13s of the image carrier 13 is 40 nm or more and 65 nm or less.

The following can be considered as the reason why the cleaning performance by the cleaning member is lowered when the arithmetic mean roughness Ra of the surface of the image carrier is too small.
As the arithmetic mean roughness Ra of the surface of the image carrier decreases, the contact area between the surface of the image carrier and the surface of the cleaning member tends to increase. Therefore, when the arithmetic mean roughness Ra of the surface of the image carrier is too small, it is difficult to suppress the frictional force generated between the surface of the image carrier and the surface of the cleaning member at the time of cleaning. As a result, the cleaning member may be broken. When the cleaning member is broken, detached particles may slip through the broken portion of the cleaning member between the image carrier and the cleaning member. Therefore, the cleaning performance by the cleaning member is easily reduced.

The following can be considered as the reason why the cleaning performance by the cleaning member is lowered when the arithmetic mean roughness Ra of the surface of the image carrier is too large.
As the arithmetic mean roughness Ra of the surface of the image carrier increases, the depressions formed on the surface of the image carrier tend to be larger. When the concave portion formed on the surface of the image carrier becomes large, the detached particles easily pass through the concave portion formed on the surface of the image carrier and rub off between the image carrier and the cleaning member. Therefore, the cleaning performance by the cleaning member is easily reduced.

[Image formation method]
In the image forming method using the image forming apparatus 10, the control unit 29 executes image formation. The CPU can execute a predetermined control program to perform the charging process, the exposure process, the development process, the transfer process, the fixing process, and the cleaning process. Hereinafter, the charging process, the exposure process, the developing process, the transfer process, the fixing process, and the cleaning process will be described in order.

  First, in the charging step, the control unit 29 controls the charging device 15 to uniformly charge the surface 13s of the image carrier 13. Next, in the exposure process, the control unit 29 controls the exposure device 17 to expose the uniformly charged surface 13s of the image carrier 13. Thereby, an electrostatic latent image is formed on the surface 13s of the image carrier 13.

  Subsequently, in the developing process, the control unit 29 controls the developing device 11 and the image carrier 13 to develop the electrostatic latent image as a toner image. Specifically, first, the control unit 29 causes the first stirring screw 115A to stir the developer 41 in the first conveyance path 113A, and causes the second stirring screw 115B to stir the developer 41 in the second conveyance path 113B. Thus, the developer 41 is conveyed in the first conveyance path 113A while being stirred, and is then conveyed in the second conveyance path 113B while being stirred.

  At the same time, the control unit 29 magnetically pumps up the developer 41 from the second conveyance path 113B to the surface 121s of the developer carrier 121. Thus, a magnetic brush layer is formed on the surface 121s of the developer carrier 121.

  At the same time, the control unit 29 rotates the developer carrier 121 along the rotational direction R1. Thus, the thickness of the magnetic brush layer is regulated by the developer regulation member 131 to a predetermined thickness.

  At the same time, the control unit 29 rotates the toner carrier 141 along the rotational direction R2 while contacting the magnetic brush layer. The control unit 29 biases each of the developer carrier 121 and the toner carrier 141 so that a predetermined potential difference is generated between the surface 121s of the developer carrier 121 and the surface 141s of the toner carrier 141. Apply. Thereby, the toner contained in the magnetic brush layer moves from the surface 121s of the developer carrier 121 to the surface 141s of the toner carrier 141. Thus, a layer (toner layer) made of toner is formed on the surface 141s of the toner carrier 141.

  At the same time, the control unit 29 rotates the image carrier 13 along the rotational direction R3. As a result, the toner constituting the toner layer flies from the surface 141 s of the toner carrier 141 to the exposed portion of the surface 13 s of the image carrier 13. Thus, the electrostatic latent image is developed as a toner image.

  Subsequently, in the transfer step, the control unit 29 controls the transfer device to transfer the toner image to the recording medium M. The control unit 29 may control the primary transfer roller 19, the transfer belt 21 and the secondary transfer roller 23 to transfer the toner image to the recording medium M (intermediate transfer system), or the primary transfer roller 19 and the transfer belt 21 may be controlled to transfer the toner image to the recording medium M (direct transfer method).

  Subsequently, in the fixing process, the control unit 29 controls the fixing device 25 to fix the unfixed toner image on the recording medium M by heating and / or pressing. Thus, the image is fixed on the recording medium M.

  Subsequently, in the cleaning process, the control unit 29 controls the cleaning member 27 to remove the transfer residual toner from the surface 13s of the image carrier 13.

[Preferred Method for Producing Developer]
Hereinafter, the preferable manufacturing method of the developer in the present embodiment will be described without referring to the drawings. The method of producing a developer according to the present embodiment preferably includes a step of producing a toner, and more preferably further includes a mixing step.

<Production process of toner>
The toner production process preferably includes a production process of toner base particles, a production process of resin particles, and an external addition process. The plurality of toner particles produced simultaneously are considered to have substantially the same configuration.

(Production process of toner base particles)
The process of producing toner mother particles preferably includes a process of producing a toner core, and more preferably further includes a process of forming a shell layer. A capsule toner can be manufactured by sequentially performing the manufacturing process of the toner core and the forming process of the shell layer. A non-capsulated toner can be manufactured if the process of forming the shell layer is not performed after the process of manufacturing the toner core. Here, the capsule toner includes a toner core and a shell layer formed on the surface of the toner core. Non-capsulated toner comprises a toner core but no shell layer. In non-capsulated toner, the toner core corresponds to toner mother particles.

  In the toner core production process, it is preferable to produce the toner core by a known aggregation method or a known grinding method. In the shell layer forming step, it is preferable to form the shell layer by, for example, in-situ polymerization method, in-liquid curing coating method, or coacervation method.

(Production process of resin particles)
It is preferable that the manufacturing process of resin particles includes the preparation process of the dispersion liquid of resin particles, and the drying process of the dispersion liquid of resin particles.

  In the step of preparing a dispersion of resin particles, it is preferable to polymerize (for example, emulsion polymerization) a monomer having an unsaturated bond in the molecule in an aqueous medium. Here, the aqueous medium is preferably water or a dispersion medium containing water as a main component. When the aqueous medium comprises water, the water is preferably ion exchanged water or pure water. The dispersion medium containing water as a main component is preferably a mixture of a surfactant and water, or a mixture of an emulsifier and water. The surfactant is preferably, for example, a cationic surfactant.

  The monomer having an unsaturated bond in the molecule includes a monomer that functions as a crosslinking agent. As a monomer which functions as a crosslinking agent, divinylbenzene of 80% or more of purity is mentioned, for example. In addition, by adjusting the polymerization time of the monomer having an unsaturated bond in the molecule (hereinafter referred to as "polymerization time of monomer"), resin particles having a desired number average primary particle diameter can be obtained. Specifically, the number average primary particle diameter of the resin particles tends to increase as the polymerization time of the monomer increases. In addition, the number average primary particle diameter of the resin particles tends to decrease as the polymerization time of the monomer decreases.

  In the step of drying the dispersion of resin particles, the dispersion of resin particles is dried. The method for drying the dispersion of resin particles is not particularly limited as long as the material and physical properties of the resin particles do not change before and after drying of the dispersion of resin particles. When the dispersion of resin particles is dried, a powder composed of a plurality of resin particles is obtained.

(External addition process)
In the external addition step, it is preferable to mix the obtained powder (a plurality of resin particles) and the toner base particles using a mixer (for example, an FM mixer manufactured by Nippon Coke Industry Co., Ltd.). Thereby, resin particles adhere to the surface of the toner base particles. Thus, a toner containing a large number of toner particles is obtained.

  It is preferable that 80% by number or more of resin particles adhere to the surface of the toner base particles. More preferably, 90% by number or more of resin particles are attached to the surface of the toner base particles. 100% by number of resin particles may be attached to the surface of the toner base particle, or even if a small number of resin particles (for example, less than 5% by number of resin particles) are present away from the surface of the toner base particle Good.

<Mixing process>
In the mixing step, the obtained toner and the carrier are preferably mixed and stirred. At this time, the toner particles are preferably added in an amount of 1 to 20 parts by mass, and more preferably 3 to 15 parts by mass with respect to 100 parts by mass of carrier particles. Also, mixing and stirring of the toner particles and the carrier particles can be performed using a mixer (for example, a ball mill, a Nauta mixer, a rocking mixer, etc.). Thus, a developer is obtained.

[Example of preferred material of developer]
As a material which comprises the developer in this embodiment, the material shown below is mentioned, for example. In the following, “system” may be added after the compound name to generically generically refer to the compound and the derivative thereof. When a “system” is added after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Moreover, acryl and methacryl may be generically called "(meth) acryl" generically. In addition, acrylonitrile and methacrylonitrile may be generically generically referred to as "(meth) acrylonitrile".

<Toner core>
(Binder resin)
In the toner core, usually, the binder resin occupies most (for example, 85% by mass or more) of the components. Therefore, it is considered that the properties of the binder resin greatly affect the properties of the entire toner core.

  Further, by combining and using a plurality of resins as the binder resin, the properties of the binder resin (specifically, the hydroxyl value, the acid value, the glass transition point, or the softening point) can be adjusted. For example, when the binder resin has an amino group or an amido group, the toner core tends to be cationic.

  The binder resin preferably contains a thermoplastic resin. As a thermoplastic resin, polyester resin, a styrene resin, acrylic acid resin, an olefin resin, a vinyl resin, a polyamide resin, or a urethane resin can be used, for example. As acrylic resin, acrylic acid ester polymer or methacrylic acid ester polymer can be used, for example. As an olefin resin, a polyethylene resin or a polypropylene resin can be used, for example. As a vinyl resin, a vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, or N-vinyl resin can be used, for example. Further, a copolymer of each of these resins, that is, a copolymer in which any repeating unit is introduced into the above-mentioned resin can also be used as a thermoplastic resin constituting toner particles. For example, a styrene-acrylic acid based resin or a styrene-butadiene based resin can also be used as the thermoplastic resin constituting the binder resin. Hereinafter, a polyester resin which is an example of the binder resin will be described in detail.

(Binder resin: polyester resin)
Polyester resins are copolymers of one or more alcohols with one or more carboxylic acids. As an alcohol for synthesizing a polyester resin, for example, a dihydric alcohol or a trivalent or higher alcohol shown below can be used. As the dihydric alcohol, for example, diols or bisphenols can be used. As a carboxylic acid for synthesizing a polyester resin, for example, a divalent carboxylic acid or a trivalent or higher carboxylic acid shown below can be used.

  Preferred examples of diols include aliphatic diols. Preferred examples of aliphatic diols include diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α, ω-alkanediol, 2-butene-1,4-diol, and 1,4-cyclohexanedihydrate. Methanol, dipropylene glycol, polyethylene glycol, polypropylene glycol or polytetramethylene glycol may be mentioned. The α, ω-alkanediols are, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,7 It is preferable that it is 8-octanediol, 1,9-nonanediol, or 1,12-dodecanediol.

  Preferable examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

  Preferred examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, and 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane or 1,3,5- Trihydroxymethylbenzene is mentioned.

  Preferred examples of divalent carboxylic acids include aromatic dicarboxylic acids, α, ω-alkanedicarboxylic acids, unsaturated dicarboxylic acids, or cycloalkanedicarboxylic acids. The aromatic dicarboxylic acid is preferably, for example, phthalic acid, terephthalic acid or isophthalic acid. The α, ω-alkanedicarboxylic acid is preferably, for example, malonic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid or 1,10-decanedicarboxylic acid. The unsaturated dicarboxylic acid is preferably, for example, maleic acid, fumaric acid, citraconic acid, itaconic acid or glutaconic acid. The cycloalkane dicarboxylic acid is preferably, for example, cyclohexane dicarboxylic acid.

  Preferred examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylene carboxyl) Methane, 1,2,7,8-octane tetracarboxylic acid, pyromellitic acid, or Empol trimer acid can be mentioned.

(Release agent)
The release agent is used, for example, for the purpose of improving the fixability or high-temperature offset resistance of the positively chargeable toner. In order to enhance the cationic property of the toner core, it is preferable to prepare the toner core using a wax having cationic property.

  The release agent is, for example, an aliphatic hydrocarbon wax, a vegetable wax, an animal wax, a mineral wax, a wax containing fatty acid ester as a main component, or a wax in which part or all of a fatty acid ester is deoxidized. Is preferred. The aliphatic hydrocarbon wax is preferably, for example, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or Fischer-Tropsch wax. Aliphatic hydrocarbon waxes also include these oxides. The vegetable wax is preferably, for example, candelilla wax, carnauba wax, wax wax, jojoba wax, or rice wax. The animal wax is preferably, for example, beeswax, lanolin, or spermaceti. The mineral wax is preferably, for example, ozokerite, ceresin or petrolatum. The waxes mainly composed of fatty acid esters are preferably, for example, montanic acid ester waxes or castor waxes. One type of wax may be used alone, or two or more types of waxes may be used in combination.

  A compatibilizer may be added to the toner core in order to improve the compatibility between the binder resin and the release agent.

(Charge control agent)
The charge control agent is used, for example, for the purpose of improving the charge stability or charge rise characteristics of the positively chargeable toner. The charge rising characteristic of the positively chargeable toner is an indicator of whether or not the positively chargeable toner can be charged to a predetermined charge level in a short time. By including a positively chargeable charge control agent in the toner core, the cationic property of the toner core can be enhanced. By including a negatively chargeable charge control agent in the toner core, the anionic property of the toner core can be enhanced.

(Colorant)
As the colorant, known pigments or dyes may be used in accordance with the color of the positively chargeable toner. In order to form a high quality image using positively chargeable toner, the amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner core may contain a black colorant. Examples of black colorants include carbon black. The black colorant may be a colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner core may contain color colorants such as yellow colorants, magenta colorants, or cyan colorants.

  As the yellow colorant, for example, one or more compounds selected from the group consisting of condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds can be used. Examples of yellow colorants include C.I. I. Pigment yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191 or 194), Naphthol Yellow S, Hansa Yellow G or C.I. I. You can use bat yellow.

  The magenta colorant is selected, for example, from the group consisting of condensation azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. One or more compounds can be used. Examples of magenta colorants include C.I. I. Pigment red (2, 3, 5, 6, 7, 19, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254) can be used.

  As the cyan colorant, for example, one or more compounds selected from the group consisting of a copper phthalocyanine compound, an anthraquinone compound, and a basic dye lake compound can be used. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62 or 66), phthalocyanine blue, C.I. I. Bat blue or C.I. I. Acid Blue can be used.

<Shell layer>
The shell layer preferably contains a thermoplastic resin. As a thermoplastic resin which a shell layer contains, the thermoplastic resin as described in the above-mentioned (binding resin) can be used, for example.

<Resin particles>
The resin constituting the resin particles is preferably at least one of a crosslinked acrylic resin and a crosslinked styrene-acrylic resin. The cross-linked acrylic acid resin and the cross-linked styrene-acrylic acid resin each have excellent chargeability. In addition, the cross-linked acrylic acid resin and the cross-linked styrene-acrylic acid resin are each easier to produce fine particles than a melamine resin. More preferably, the resin constituting the resin particles is a crosslinked styrene-acrylic acid resin.

  The crosslinked acrylic resin is a copolymer of one or more acrylic monomers and one or more crosslinking agents. If the one or more crosslinking agents contain divinylbenzene having a purity of 80% or more, the blocking ratio of the resin particles is likely to be 15% by mass or more and 40% by mass or less. As an acrylic acid-based monomer used to synthesize a crosslinked acrylic acid-based resin, acrylic acid-based monomers shown below can be suitably used.

  The crosslinked styrene-acrylic acid resin is a copolymer of one or more styrene monomers, one or more acrylic monomers, and one or more crosslinking agents. If the one or more crosslinking agents contain divinylbenzene having a purity of 80% or more, the blocking ratio of the resin particles is likely to be 15% by mass or more and 40% by mass or less. As a styrene-type monomer used in order to synthesize | combine crosslinked styrene-acrylic acid type resin, the styrene-type monomer shown below can be used conveniently. As an acrylic acid type monomer used in order to synthesize a crosslinked styrene-acrylic acid type resin, acrylic acid type monomers shown below can be suitably used.

  Preferred examples of styrenic monomers include styrene, alkylstyrenes, hydroxystyrenes or halogenated styrenes. The alkylstyrene is preferably, for example, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene or 4-tert-butylstyrene. Hydroxystyrene is preferably, for example, p-hydroxystyrene or m-hydroxystyrene. The halogenated styrene is preferably, for example, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene or p-chlorostyrene.

  Preferred examples of the acrylic acid-based monomer include (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Preferred examples of (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, (meth) acrylic Examples include n-butyl acid, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Preferred examples of (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylic acid, 3-hydroxypropyl (meth) acrylic acid, 2-hydroxypropyl (meth) acrylic acid, or (meth) acrylic The acid 4-hydroxybutyl is mentioned.

<Carrier>
The carrier particles may be composed of a carrier core, or may have a carrier core and a coat layer.

  The carrier core preferably contains a magnetic material, and is more preferably composed of a magnetic material. The magnetic material contained in the carrier core is preferably ferrite or magnetite, more preferably ferrite. Ferrites include, for example, magnetite (spinel ferrite), barium ferrite, Mn ferrite, Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg ferrite, Ca-Mg ferrite, Li ferrite, Cu-Zn ferrite, or Mn-Mg- It is preferable that it is Sr ferrite.

  The coat layer covers the surface of the carrier core. The coat layer preferably contains a resin, and is more preferably composed of a resin. The resin contained in the coat layer is preferably, for example, one selected from the group consisting of silicone resins, acrylic resins, styrene-acrylic acid resins, polyester resins and fluorine resins.

  An embodiment of the present invention will be described. In the examples, unless otherwise specified, the evaluation results (values indicating the shape, physical properties, etc.) of the powder are selected from a considerable number of average particles from the powder, and each of the average particles is selected. The number average of the values measured for The powder includes, for example, a toner core, toner base particles, an external additive, and a toner.

Further, the number average particle diameter of the powder is the number average value of the circle equivalent diameter of the primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope if nothing is specified. is there. If the measured value of the volume median diameter (D ₅₀ ) of the powder is not specified at all, the Coulter principle (pore electrical resistance method) is made using “Coulter Counter Multisizer 3” manufactured by Beckman Coulter, Inc. It is the value measured based on it. The measured value of the acid value is a value measured according to "JIS (Japanese Industrial Standard) K 0070-1992" unless otherwise specified. The melting point (Mp) is a value measured using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified.

[Evaluation 1]
In Evaluation 1, using resin particles (more specifically, each of resin particles B-11 to B-15) having mutually different number average primary particle diameters, an image forming apparatus (more specifically, device A-) is used. 11 to A-15) were produced. Using the obtained image forming apparatus, the cleaning performance of the cleaning member was evaluated, and the fog density was evaluated. Table 1 shows the configuration of the image forming apparatus manufactured in Evaluation 1. In Table 1, "particle diameter" indicates the number average primary particle diameter of resin particles. In the “blending amount of DVB”, the blending amount of divinylbenzene at the time of production of resin particles is described. The arithmetic mean roughness Ra of the surface of the image carrier is described in "Roughness Ra".

  Below, the manufacturing method of resin particle B-11-B-15, and the measuring method of physical-property value are demonstrated first. Next, the manufacturing method of apparatus A-11-A-15, an evaluation method, and an evaluation result are demonstrated in order. In addition, in the evaluation which an error produces, the measurement value of a considerable number which an error becomes small enough was obtained, and the arithmetic mean of the obtained measurement value was made into the evaluation value.

[Method of Manufacturing Resin Particles B-11 to B-15]
In a four-necked flask (volume: 1000 mL) equipped with a stirrer, condenser, thermometer, and nitrogen introduction pipe, 600 g of deionized water, 100 g of butyl methacrylate (BMA), 20 g of styrene, and 60 g of Divinylbenzene (DVB, crosslinking agent), 15 g of benzoyl peroxide (BPO, polymerization initiator), and 6 g of a cationic surfactant (Kohamine (registered trademark) 24 P, manufactured by Kao Corporation, component: lauryl trimethyl ammonium chloride 25 mass% aqueous solution) was added with stirring. The temperature in the flask was raised to 90 ° C. while supplying nitrogen gas to the flask and stirring the contents of the flask at a stirring speed of 90 rpm. The temperature in the flask was maintained at 90.degree. C. for a predetermined period of time while continuing the nitrogen gas supply and agitation of the contents of the flask. While the temperature in the flask was maintained at 90 ° C., the contents of the flask were reacted (polymerization reaction). Thus, an emulsion of resin particles was obtained. The obtained emulsion was dried to obtain resin particles (powder).

  By adjusting the time (holding time) to keep the temperature in the flask at 90 ° C., resin particles having a desired number average primary particle diameter could be obtained. More specifically, the number average primary particle diameter of the resin particles tended to increase as the retention time was extended. In addition, as the holding time is shortened, the number average primary particle diameter of the resin particles tends to be smaller. Thus, resin particles B-11 to B-15 were obtained.

[Method of Measuring Physical Property Values of Resin Particles B-11 to B-15]
<Method of measuring number average primary particle diameter>
The number average primary particle diameter of the obtained resin particles (more specifically, each of resin particles B-11 to B-15) was measured using a scanning electron microscope (SEM). The results are shown in Table 1.

  The obtained resin particles had a sharp particle size distribution. More specifically, resin particles B-11 substantially contain only resin particles having a particle size of about 40 nm. The resin particles B-12 substantially contained only resin particles having a particle size of about 50 nm. The resin particles B-13 substantially contained only resin particles having a particle size of about 60 nm. The resin particles B-14 substantially contained only resin particles having a particle size of about 70 nm. The resin particles B-15 substantially contained only resin particles having a particle size of about 80 nm.

<Method of measuring blocking rate>
The blocking ratio of the resin particles (more specifically, each of the resin particles B-11 to B-15) was measured by the following method. Specifically, first, a measurement jig (manufactured by KYOCERA Document Solutions Inc.) was prepared. The jig for measurement is a table (material: austenitic stainless steel) on which a cylindrical hole (diameter: 10 mm, depth: 10 mm) is formed, and a cylindrical indenter (diameter: 10 mm, material: austenitic stainless steel) , Equipped with a heater.

Next, in an environment of a temperature of 23 ° C. and a humidity of 50% RH, 10 mg of resin particles (target of measurement) were placed in the holes (measurement site) formed in the table. The measurement site was heated to 160 ° C. by a heater, and a pressure of 0.1 kgf / mm ² was applied to the measurement site with an indenter (load: about 100 N) for 5 minutes. Thereafter, the entire amount of resin particles present at the measurement site was recovered, and set on a sieve (200 mesh specified by JIS Z8801-1) having a known weight of 75 μm. And the mass of the sieve containing resin particles was measured. Thus, the mass of the resin particles on the sieve (the mass of the resin particles before suction) was determined.

Subsequently, the resin particles on the sieve were sucked from below the sieve using a suction machine ("V-3 SDR" manufactured by Amano Co., Ltd.). By this suction, only the resin particles not blocking among the resin particles on the sieve passed through the sieve. After suction, the mass of resin particles (resin particles remaining on the sieve) which did not pass through the sieve was measured. Then, based on the mass of resin particles before suction and the mass of resin particles after suction (mass of resin particles that did not pass through the sieve), the blocking ratio of resin particles according to the following formula [unit: mass%] I asked for. The blocking ratio of the resin particles was calculated to be 25% by mass.
Blocking ratio = 100 × mass of resin particles after suction / mass of resin particles before suction

[Method of Manufacturing Device A-11]
<Method of producing developer>
First, toner base particles were manufactured. Specifically, 100 parts by mass of a polyester resin (acid number: 5.6 mg KOH / g, melting point: 105 ° C.) and 4 parts by mass of a colorant (C.I.) using an FM mixer (manufactured by Japan Coke Industry Co., Ltd.) Pigment blue 15: 3, component: copper phthalocyanine pigment, and 5 parts by mass of a mold release agent (Nippon Oil Co., Ltd. "Nissan Electol (registered trademark) WEP-3", component: ester wax, melting temperature: 73 And 1 part by mass of a charge control agent ("BONTRON (registered trademark) P-51" manufactured by Orient Chemical Industries Co., Ltd., component: quaternary ammonium salt) were mixed. The obtained mixture was melt-kneaded using a twin-screw extruder (Ikegai "PCM-30 type") to obtain a melt-kneaded product. The obtained melt-kneaded product was pulverized using a mechanical pulverizer (Freund Turbo Co., Ltd. “turbo mill”) to obtain a pulverized product. The obtained pulverized material was classified using a classifier (Nippon Mining & Mining Co., Ltd. "Elbow Jet"). Thus, toner base particles having a volume median diameter (D ₅₀ ) of 6.8 μm were obtained.

  Next, an external additive was externally added to the surface of the toner base particles. Specifically, first, 100 parts by mass of toner base particles and 1 part by mass of hydrophobic silica particles (manufactured by Nippon Aerosil Co., Ltd. "AEROSIL (registered trademark) over 5 minutes using an FM mixer (manufactured by Japan Coke Industry Co., Ltd.) (Trademark) RA-200H ") was mixed. Next, 1 part by mass of resin particles B-11 was further added to the FM mixer and then mixed for 5 minutes. Thus, Toner T-11 including a plurality of toner particles was obtained.

  Subsequently, the obtained toner T-11 and a carrier were mixed. Specifically, using a powder mixer (“rocking mixer (registered trademark)” manufactured by Aichi Electric Co., Ltd.), 9 parts by mass of the toner T-11 and 100 parts by mass of the carrier were mixed for 30 minutes. Here, the carrier was provided with a carrier core and a coat layer. The carrier core was composed of Mn-Mg-Sr ferrite. The coat layer was composed of a mixed resin of a polyamideimide resin and PFA, and covered the surface of the carrier core. Thus, a developer TC-11 was obtained.

<Method of supplying developer>
First, a multi-function device (having “image carrier C-12 attached as an image carrier in“ Taskalfa 6052 ci ”manufactured by Kyocera Document Solutions Inc.) was prepared. In more detail, the prepared multifunction machine was provided with the image carrier C-12, the developing device and the cleaning member. Also, the prepared multi-function device is configured to be developable by the touch-down development method. More specifically, the developing device has a developer carrier and a toner carrier. The developer carrier and the toner carrier are each configured to rotate in a state where the developer carried on the surface of the developer carrier is in contact with the toner carrier. Each of the toner carrier and the image carrier C-12 is such that the toner carried on the surface of the toner carrier flies toward the electrostatic latent image to develop the electrostatic latent image as a toner image, It was configured. The image carrier C-12 had an aluminum base and an amorphous silicon photosensitive layer. Sandblasting was applied to the circumferential surface of the aluminum base pipe. The amorphous silicon layer was provided on the circumferential surface of the aluminum pipe. The arithmetic average roughness Ra of the surface of the amorphous silicon layer (corresponding to the arithmetic average roughness of the surface of the image carrier) was measured according to the method defined in JIS (Japanese Industrial Standard) B 0601: 1994. Arithmetic mean roughness Ra of the surface of the amorphous silicon layer was 40 nm.

  Next, the toner T-11 was supplied to the toner container of the multifunction machine. In addition, developer TC-11 was supplied to the developing device of the multifunction machine. After that, installation operation was done. Thus, the developer TC-11 was filled in the developer conveyance path of the developing device. Thus, an apparatus A-11 was obtained.

[Method of Manufacturing Apparatuses A-12 to A-15]
Devices A-12 to A-15 were produced in accordance with the method for producing device A-11, respectively, except that resin particles B-12 to B-15 were used instead of resin particles B-11.

[Method of Evaluating Each of Devices A-11 to A-15]
<Method of evaluating the cleaning performance by the cleaning member: abrasion test>
Under an environment of a temperature of 10 ° C. and a humidity of 10% RH, using an image forming apparatus (more specifically, each of the apparatuses A-11 to A-15), a printing ratio of 20% to A4 size plain paper The 100,000 pattern images were continuously printed. Thereafter, a halftone image (resolution: 300 dpi) was printed on the entire surface of A3 size printing paper. In the obtained halftone image, it was visually confirmed that there were no image defects in vertical stripes.

The evaluation criteria of the cleaning performance by the cleaning member are shown below. Also, the evaluation results are shown in Table 2.
(Evaluation criteria)
○ (Good): In the halftone image, no vertical streak-like image defect was found.
X (Poor): Vertical streak-like image defects were observed in halftone images.

<Method of evaluating fog density>
Under an environment of a temperature of 10 ° C. and a humidity of 10% RH, using an image forming apparatus (more specifically, each of the apparatuses A-11 to A-15), a printing rate of 5% on A4 size plain paper The 100,000 pattern images were continuously printed. Thereafter, an evaluation image with a printing rate of 100% was formed on A4 size plain paper. Then, the reflection density of the blank part of the image for evaluation was measured using a color reflection densitometer ("R710" manufactured by Ihara Electronics Co., Ltd.). And fog density (FD) was computed based on a following formula.
FD = (reflection density of blank area) − (reflection density of unprinted paper)

  The calculation results are shown in Table 2. Here, when the fogging density (FD) was 0.100 or less, it was evaluated that the occurrence of fogging was suppressed. On the other hand, when the fogging density (FD) was over 0.100, it was evaluated that fogging occurred.

[Evaluation results of each of devices A-11 to A-15]
Table 2 shows the evaluation results of each of the devices A-11 to A-15. In Table 2, "Particle diameter" describes the number average primary particle diameter of the resin particles. In "Cleaning", the evaluation result of the cleaning performance by the cleaning member is described. The calculation result of fog density (FD) is described in "fog density (FD)".

  The image forming apparatuses according to the first to third embodiments (more specifically, the apparatuses A-12 to A-14) each have a basic configuration described later. The basic configuration provided in the image forming apparatus according to Examples 1 to 3 is as follows. Specifically, the devices A-12 to A-14 each include an image carrier, a developing device, and a cleaning member. Asperities corresponding to the asperities formed on the circumferential surface of the aluminum pipe (surface of the conductive base) were formed on the surface of the image carrier. Arithmetic mean roughness Ra of the surface of the image carrier was 40 nm or more and 65 nm or less. Devices A-12 to A-14 contained developers TC-12 to TC-14, respectively. The developers TC-12 to TC-14 each contained a toner and a carrier. The toner contained a plurality of toner particles, and the toner particles contained toner base particles and an external additive, respectively. The toner base particles and the external additive each have a stronger positive charge than the carrier. The external additive contained a plurality of resin particles. The blocking ratio of the resin particles was 15% by mass or more and 40% by mass or less. The number average primary particle diameter of the resin particles was 50 nm or more and 70 nm or less.

  As shown in Table 2, the devices A-12 to A-14 were each excellent in the cleaning performance by the cleaning member. In addition, when image formation was performed using each of the devices A-12 to A-14, occurrence of fogging could be prevented in the formed image.

  The image forming apparatuses according to Comparative Examples 1 and 2 (more specifically, the apparatuses A-11 and A-15) did not have the above-described basic configuration. Specifically, in the device A-11, the number average primary particle diameter of the resin particles was less than 50 nm. And apparatus A-11 was inferior to the cleaning performance by a cleaning member. Moreover, in the apparatus A-15, the number average primary particle diameter of the resin particle was over 70 nm. Then, when image formation was performed using the device A-15, fogging occurred in the formed image.

[Evaluation 2]
In Evaluation 2, an image forming apparatus (more specifically, an apparatus A) is formed using resin particles (more specifically, each of resin particles B-13 and B-21 to B-25) having different blocking ratios. -13 and A-21 to A-25, respectively) were produced. Using the obtained image forming apparatus, the cleaning performance of the cleaning member was evaluated, and the fog density was evaluated. Table 3 shows the configuration of the image forming apparatus evaluated in Evaluation 2. In Table 3, "Particle diameter" indicates the number average primary particle diameter of resin particles. In the “blending amount of DVB”, the blending amount of divinylbenzene at the time of production of resin particles is described. The arithmetic mean roughness Ra of the surface of the image carrier is described in "Roughness Ra".

  Below, the manufacturing method of apparatus A-21-A-25, and the evaluation method are demonstrated in order first. Next, evaluation results of the devices A-13 and A-21 to A-25 will be described.

[Method of Manufacturing Each of Devices A-21 to A-25]
First, each of resin particles B-21 to B-25 was manufactured. At this time, each of resin particles B-21 to B-25 was produced according to the method described in Evaluation 1 above, except that the blending amount of divinylbenzene was changed to the value shown in Table 3. Next, developers TC-21 to TC-25 were manufactured using resin particles B-21 to B-25, respectively, according to the method described in Evaluation 1 described above. Thereafter, each of devices A-21 to A-25 was produced according to the method described in Evaluation 1 above.

[Method of Evaluating Each of Devices A-21 to A-25]
Each of the devices A-21 to A-25 was evaluated according to the method described in Evaluation 1 above. The results are shown in Table 4.

[Evaluation results of each of devices A-13 and A-21 to A-25]
Table 4 shows the evaluation results of each of the devices A-13 and A-21 to A-25. In Table 4, the "blocking rate" describes the blocking rate of the resin particles. In "Cleaning", the evaluation result of the cleaning performance by the cleaning member is described. The calculation result of fog density (FD) is described in "fog density (FD)".

  The image forming apparatuses (more specifically, the apparatuses A-13 and A-22 to A-24) according to Examples 2 and 4 each have the above-described basic configuration. And as shown in Table 4, apparatus A-13 and A-22-A-24 each were excellent in the cleaning performance by a cleaning member. In addition, when image formation was performed using each of the devices A-13 and A-22 to A-24, occurrence of fogging could be prevented in the formed image.

  The image forming apparatuses according to Comparative Examples 3 and 4 (more specifically, the apparatuses A-21 and A-25) did not have the above-described basic configuration. Specifically, in the device A-21, the blocking ratio of the resin particles was less than 15% by mass. Then, when image formation was performed using the device A-21, fogging occurred in the formed image. Moreover, in the apparatus A-25, the blocking rate of the resin particle was over 40 mass%. And apparatus A-25 was inferior to the cleaning performance by a cleaning member.

[Evaluation 3]
In Evaluation 3, an image forming apparatus (more specifically, using image carriers (more specifically, each of image carriers C-11 to C-15) different in surface arithmetic average roughness Ra from each other is used. , Devices A-31 to A-35). Using the obtained image forming apparatus, the cleaning performance of the cleaning member was evaluated, and the fog density was evaluated. Table 5 shows the configuration of the image forming apparatus manufactured in Evaluation 3. In Table 5, “particle diameter” indicates the number average primary particle diameter of resin particles. In the “blending amount of DVB”, the blending amount of divinylbenzene at the time of production of resin particles is described. The arithmetic mean roughness Ra of the surface of the image carrier is described in "Roughness Ra".

  Below, the manufacturing method of apparatus A-31-A-35, an evaluation method, and an evaluation result are demonstrated in order.

[Method of Manufacturing Devices A-31 to A-35]
First, according to the method described in Evaluation 1 described above, developer TC-13 was produced using resin particles B-13.

  Next, image carriers C-11 to C-15 were prepared. Specifically, after sandblasting the circumferential surface of the aluminum base tube, an amorphous silicon photosensitive layer was formed on the circumferential surface of the aluminum base tube. Thus, each of the image carriers C-11 to C-15 was obtained. Arithmetic mean roughness Ra of each surface of the image carriers C-11 to C-15 was measured according to the method defined in JIS (Japanese Industrial Standard) B 0601: 1994. The results are shown in Table 5.

  In the sand blasting process, the arithmetic mean roughness Ra of the surface of the image carrier can be determined by adjusting at least one of the amount of abrasive to be sprayed on the aluminum pipe (the amount of abrasive sprayed) and the spray speed of the abrasive. It could be made the desired value. More specifically, the arithmetic mean roughness Ra of the surface of the image carrier tends to increase as the abrasive spray amount increases. The same tendency was shown when the blasting speed of the abrasive increased. In addition, the arithmetic mean roughness Ra of the surface of the image carrier tends to decrease as the amount of the abrasives sprayed decreases. The same tendency was shown when the abrasive spray speed was reduced.

  Each of the obtained image carriers C-11 to C-15 was attached to a multifunction peripheral. Thereafter, each of devices A-31 to A-35 was obtained according to the method described in Evaluation 1 above.

[Method of Evaluating Each of Devices A-31 to A-35]
Each of the devices A-31 to A-35 was evaluated according to the method described in Evaluation 1 above. The results are shown in Table 6.

[Evaluation results of each of devices A-31 to A-35]
Table 6 shows the evaluation results of each of the devices A-31 to A-35. In Table 6, in "Roughness Ra", arithmetic mean roughness Ra of the surface of the image carrier is described. In "Cleaning", the evaluation result of the cleaning performance by the cleaning member is described. The calculation result of fog density (FD) is described in "fog density (FD)".

  The image forming apparatuses (more specifically, the apparatuses A-32 to A-34) according to Examples 7 to 9 each have the above-described basic configuration. And as shown in Table 6, apparatus A-32-A-34 were each excellent in the cleaning performance by a cleaning member. In addition, when image formation was performed using each of the devices A-32 to A-34, occurrence of fogging could be prevented in the formed image.

  The image forming apparatuses according to Comparative Examples 5 and 6 (more specifically, the apparatuses A-31 and A-35) did not have the above-described basic configuration. Specifically, in the device A-31, the arithmetic mean roughness Ra of the surface of the image carrier was less than 40 nm. And apparatus A-31 was inferior to the cleaning performance by a cleaning member. Further, in the device A-35, the arithmetic average roughness Ra of the surface of the image carrier was more than 65 nm. And apparatus A-35 was inferior to the cleaning performance by a cleaning member.

The present inventors have confirmed that the image forming apparatus having the following configurations p to s is excellent in the cleaning performance by the cleaning member. The present inventors have also confirmed that when an image is formed using an image forming apparatus having the following configurations p to s, occurrence of fogging can be prevented in the formed image.
Configuration p: The number average primary particle diameter of the resin particles is 50 nm or more and 70 nm or less.
Configuration q: The blocking ratio of the resin particles is 15% by mass or more and 40% by mass or less.
Configuration r: The arithmetic mean roughness Ra of the surface of the image carrier is 40 nm or more and 65 nm or less.
Configuration s: The developing method is a two-component developing method.

  The image forming apparatus according to the present invention can be used as, for example, a copying machine, a printer, or a multifunction machine.

10 image forming apparatus 11 developing device 13 image carrier 13s image carrier surface 27 cleaning member 41 developer 51 toner particles 53 toner base particles 55 resin particles 121 developer carrier 121s developer carrier surface 141 toner carrier 141s Toner carrier surface 311 conductive substrate 313 rough surface 315 photosensitive layer M recording medium

Claims (5)

An image forming apparatus for forming an image on a recording medium using a developer,
The image forming apparatus includes the developer.
The developer includes toner and a carrier that positively charges the toner by friction;
The toner comprises a plurality of toner particles,
Each of the toner particles includes toner base particles and an external additive attached to the surface of the toner base particles,
The external additive includes a plurality of resin particles,
Each of the toner base particles and the resin particles has a positive chargeability stronger than that of the carrier,
The blocking ratio of the resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 15% by mass or more and 40% by mass or less as measured by a mesh of 75 μm.
The number average primary particle diameter of the resin particles is 50 nm or more and 70 nm or less,
The image forming apparatus is
An image carrier for holding an electrostatic latent image on the surface;
A developing device that develops the electrostatic latent image using the toner;
A cleaning member that is in pressure contact with the surface of the image carrier and removes the developer remaining on the surface of the image carrier from the surface of the image carrier;
, And,
The image carrier is
A conductive substrate having a rough surface,
A photosensitive layer provided on the rough surface;
Have
Irregularities corresponding to the irregularities formed on the rough surface are formed on the surface of the image carrier,
An image forming apparatus, wherein the arithmetic mean roughness Ra of the surface of the image carrier is 40 nm or more and 65 nm or less. The developing device is
An accommodating portion for accommodating the developer;
A developer carrier for carrying the developer supplied from the storage section on the surface thereof;
A toner carrier that receives the toner from the developer carrier and carries the toner on the surface;
Have
The developer carrier and the toner carrier are each configured to rotate in a state where the developer carried on the surface of the developer carrier is in contact with the toner carrier.
The toner carrier and the image carrier each develop the electrostatic latent image as a toner image by causing the toner carried on the surface of the toner carrier to fly toward the electrostatic latent image. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured as follows.   The image forming apparatus according to claim 1, wherein the rough surface is a blast surface. An image forming method for forming an image on a recording medium using a developer, comprising:
The developer includes toner and a carrier that positively charges the toner by friction;
The toner comprises a plurality of toner particles,
Each of the toner particles includes toner base particles and an external additive attached to the surface of the toner base particles,
The external additive includes a plurality of resin particles,
Each of the toner base particles and the resin particles has a positive chargeability stronger than that of the carrier,
The blocking ratio of the resin particles after pressing for 5 minutes at a temperature of 160 ° C. and a pressure of 0.1 kgf / mm ² is 15% by mass or more and 40% by mass or less as measured by a mesh of 75 μm.
The number average primary particle diameter of the resin particles is 50 nm or more and 70 nm or less,
The image forming method is
Forming an electrostatic latent image on the surface of the image carrier;
Supplying the toner to the electrostatic latent image to develop the electrostatic latent image as a toner image;
Transferring the toner image to the recording medium;
Removing the developer remaining on the surface of the image carrier from the surface of the image carrier after transferring the toner image to the recording medium;
Including
The image carrier is
A conductive substrate having a rough surface,
A photosensitive layer provided on the rough surface;
Have
Irregularities corresponding to the irregularities formed on the rough surface are formed on the surface of the image carrier,
The image forming method, wherein the arithmetic mean roughness Ra of the surface of the image carrier is 40 nm or more and 65 nm or less. Developing the electrostatic latent image as the toner image
Supporting the developer on the surface of a developer carrier;
Forming a toner layer containing the toner on the surface of the toner carrier opposite to the developer carrier;
Flying the toner contained in the toner layer toward the electrostatic latent image;
Including
When the toner layer is formed on the surface of the toner carrier, the toner is formed of the developer carrier while rubbing the surface of the toner carrier with the developer carried on the surface of the developer carrier. The image forming method according to claim 4, wherein the toner is moved from the surface to the surface of the toner carrier.

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