Developing apparatus, two-component developer, electrophotographic image forming method, and electrophotographic image forming apparatus

Abstract

To provide a developing device that can prevent scattering of toner, minimize maintenance, and obtain stable image quality for a long period.SOLUTION: A developing device causes two-component developer to be adsorbed on a surface of a rotating developing sleeve by using a magnetic force to form a magnetic brush, causes the magnetic brush to rub an electrostatic latent image carrier, and develops an electrostatic latent image formed on a surface of the electrostatic latent image carrier to form a toner image. The developing device comprises a case that accommodates the two-component developer and the developing sleeve, and an air filter. The air filter has a thickness of 2-20 mm and a density gradient in which the pressure drop at a wind speed of 10 cm / s is 2-40 Pa, forms an air current sucked into the case from the gap between the developing sleeve and the case, and forms an air current exhausted from inside the case through the air filter. The two-component developer accommodated in the case includes two-component developer composed of magnetic particles each having a surface coated by a resin layer. The resin layer includes at least one or more types of electrified particles.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a developing device, 2 components a developer, an electrophotographic image forming method, and an electrophotographic image forming apparatus.

Background Art

[0002] In an electrophotographic image forming method using a two-component developer, a stable image can be obtained even under environmental variations by controlling the toner concentration of the two-component developer. In the two-component development type image forming method, a magnetic brush obtained by adsorbing a two-component developer in which toner and magnetic particles are mixed to a rotating developing sleeve using a magnetic force is rubbed against an electrostatic latent image carrier, and an electrostatic latent image formed on the surface of the electrostatic latent image carrier is developed to form a toner image.

[0003] In the two-component developer, the toner and the magnetic particles are attached by an electrostatic force, and the toner may come off from the magnetic particles. When the toner comes off from the magnetic brush, the toner scatters in the image forming apparatus, which is a problem that the image forming apparatus does not operate normally.

[0004] In Patent Documents 1 and 2, it has been proposed that by containing and exposing charged fine particles in a coating film, the charging of the carrier and the toner is maintained, the electrostatic adhesion force is maintained, and toner scattering is improved.

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a developing device that can suppress toner scattering over a long period of time, minimize maintenance, and obtain stable image quality. [[ID=�3]]

Means for Solving the Problems

[0006] To solve the above-mentioned problems, one aspect of the present invention is a developing apparatus that forms a toner image by magnetically adsorbing a two-component developer containing toner and a magnetic carrier onto the surface of a rotating developing sleeve to form a magnetic brush, rubbing the magnetic brush against an electrostatic latent image carrier, and developing the electrostatic latent image formed on the surface of the electrostatic latent image carrier, comprising a case for housing the two-component developer and the developing sleeve, and an air filter mounted on the case. The toner contains matrix particles, and the average particle size of the matrix particles is 5 to 20 μm. The air filter has a thickness of 2 to 20 mm and a density gradient with a pressure loss of 2 to 40 Pa at a wind speed of 10 cm / s, and forms an airflow that draws air into the case from the gap between the developing sleeve and the case, and forms an airflow that discharges the air inside the case to the outside of the case through the air filter. The case has a supply port on which the air filter is installed. The airflow discharged to the outside of the case is formed by a path through which air inside the case is discharged to the outside of the case via the air filter at the supply port by a fan or pump provided in the electrophotographic image forming apparatus. The developing apparatus comprises a two-component developer housed in the case, which is composed of magnetic particles whose surfaces are coated with a resin layer, and the resin layer contains at least one type of electrostatically charged particle. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a developing apparatus that can suppress toner scattering over a long period of time, minimize maintenance, and obtain stable image quality. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing an example of an image forming apparatus. [Figure 2] This is a cross-sectional view showing the developing unit in Figure 1. [Figure 3] This is a longitudinal cross-sectional view showing the image-forming area in Figure 1. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described below.

[0010] <Developing equipment> Figure 1 shows an example of an image forming apparatus that realizes the developing apparatus according to this embodiment. Figure 2 is a cross-sectional view showing the developing unit, which is part of the image forming apparatus of Figure 1. Figure 3 is a cross-sectional view showing the image forming unit (including the developing unit), which is part of the image forming apparatus of Figure 1. In this embodiment, a printer is given as an example of an image forming apparatus, but the invention is not limited to this, and other image forming apparatuses such as copiers, facsimile machines, and multifunction printers may be used.

[0011] The image forming apparatus 1 of this embodiment includes a paper feeding unit 210, a transport unit 220, an image forming unit 230, a transfer unit 240, and a fuser unit 250.

[0012] The paper feeding unit 210 includes a paper feed cassette 211 on which the paper to be fed P is stacked, and a paper feed roller 212 that feeds the paper P from the paper feed cassette 211 one sheet at a time.

[0013] The transport unit 220 includes a roller 221, a pair of timing rollers 222, and a paper discharge roller 223. The roller 221 transports the paper P fed by the paper feed roller 212 toward the transfer unit 240. The pair of timing rollers 222 hold the leading edge of the paper P transported by the roller 221 and wait, then send the paper P to the transfer unit 240 at a predetermined timing. The paper discharge roller 223 discharges the paper P, on which the color toner image has been fixed, into the paper discharge tray 224.

[0014] As shown in Figure 1, the image forming unit 230 includes, in order from left to right at predetermined intervals, an image forming unit Y, an image forming unit C, an image forming unit M, an image forming unit K, and an exposure unit 233.

[0015] Image forming unit Y forms an image using a developer containing yellow toner. Image forming unit C uses a developer containing cyan toner. Image forming unit M uses a developer containing magenta toner. Image forming unit K uses a developer containing black toner.

[0016] In addition, when indicating any one of the image forming units (Y, C, M, K), it is referred to as an image forming unit.

[0017] Also, the developer has toner and a carrier. The four image forming units (Y, C, M, K) only use different developers, and their mechanical configurations are substantially the same.

[0018] The image forming units (Y, C, M, K) are provided rotatable clockwise in FIG. 1. The image forming units (Y, C, M, K) include a photosensitive drum (231Y, 231C, 231M, 231K), a charger (232Y, 232C, 232M, 232K), a developing device (180Y, 180C, 180M, 180K), and a cleaner (236Y, 236C, 236M, 236K).

[0019] In the photosensitive drum (231Y, 231C, 231M, 231K), an electrostatic latent image and a toner image are formed. When indicating any one of the photosensitive drums (231Y, 231C, 231M, 231K), it is referred to as the photosensitive drum 231.

[0020] The charger (232Y, 232C, 232M, 232K) uniformly charges the surface of the photosensitive drum (231Y, 231C, 231M, 231K). When indicating any one of the chargers (232Y, 232C, 232M, 232K), it is referred to as the charger 232.

[0021] The developing device (180Y, 180C, 180M, 180K) develops the electrostatic latent image formed on the surface of the photosensitive drum (231Y, 231C, 231M, 231K) into a toner image using toner of each color. When indicating any one of the developing devices (180Y, 180C, 180M, 180K), it is referred to as the developing device 180.

[0022] The cleaning units (236Y, 236C, 236M, 236K) are equipped with a doctor blade 236A, which removes toner remaining on the surface of the photoconductor drum (231Y, 231C, 231M, 231K) using the doctor blade 236A. Note that when referring to any of the cleaning units (236Y, 236C, 236M, 236K), it is referred to as cleaning unit 236.

[0023] Furthermore, the image forming unit (Y, C, M, K) is equipped with toner cartridges (234Y, 234C, 234M, 234K) and sub-hoppers (160Y, 160C, 160M, 160K).

[0024] Toner cartridges (234Y, 234C, 234M, 234K) contain toner of each color. Note that when referring to any of the toner cartridges (234Y, 234C, 234M, 234K), it is simply referred to as "toner cartridge 234".

[0025] The sub-hoppers (160Y, 160C, 160M, 160K) are used to replenish the toner supplied from the toner cartridges (234Y, 234C, 234M, 234K). Note that when referring to any of the sub-hoppers (160Y, 160C, 160M, 160K), it will be referred to as sub-hopper 160.

[0026] The toner contained in the toner cartridge 234 is discharged by a suction pump (not shown) and supplied to the sub-hopper 160 via a supply pipe (not shown). The sub-hopper 160 transports the toner supplied from the toner cartridge 234 and replenishes it to the developer unit 180. The developer unit 180 uses the toner replenished by the sub-hopper 160 to develop the electrostatic latent image formed on the photoreceptor drum 231.

[0027] The photoreceptor drum 231 is not particularly limited, but examples include inorganic photoreceptor drums such as amorphous silicon photoreceptor drums and selenium photoreceptor drums, and organic photoreceptor drums such as polysilane photoreceptor drums and phthalopolymethine photoreceptor drums.

[0028] The charger 232 is not particularly limited, but examples include known contact chargers equipped with conductive or semiconductive rolls, brushes, films, rubber blades, etc., and non-contact chargers that utilize corona discharge, such as Corotron and Scorotron.

[0029] The charger 232 is preferably positioned in contact with or without contact with the photoreceptor drum 231, and the surface of the photoreceptor drum 231 is charged by superimposing DC and AC voltages.

[0030] Furthermore, the charger 232 is a charging roller positioned in close, non-contacting proximity to the photoreceptor drum 231 via a gap tape, and it is preferable to charge the surface of the photoreceptor drum 231 by superimposing a DC voltage and an AC voltage onto the charging roller.

[0031] The exposure unit 233 reflects the laser light L emitted from the light source 233a based on image information using polygon mirrors 233b (233bY, 233bC, 233bM, 233bK) which are rotated by a motor, and irradiates the photoreceptor drum 231 (231Y, 231C, 231M, 231K).

[0032] The exposure unit 233 is not particularly limited as long as it is capable of exposing the surface of the photoreceptor drum 231, which has been charged by the charger 232, to the image to be formed. Examples of exposure units 233 include copying optical systems, rod lens array systems, laser optical systems, and liquid crystal shutter optical systems.

[0033] Alternatively, a back-facing method may be employed in which the back side of the photoreceptor drum 231 is exposed in an image-like manner.

[0034] The developing unit 180 is not particularly limited as long as it is capable of developing using a developer. Preferably, the developing unit 180 is one that contains a developer and applies the developer to the electrostatic latent image by contact or non-contact, and more preferably a developing unit equipped with a container for the developer.

[0035] The developing unit 180 may be a single-color developing unit or a multi-color developing unit.

[0036] The cleaning device 236 is not particularly limited as long as it is capable of removing toner remaining on the surface of the photoreceptor drum 231. Preferably, the cleaning device 236 is equipped with cleaning members such as a magnetic brush cleaner, electrostatic brush cleaner, magnetic roller cleaner, blade cleaner, brush cleaner, or web cleaner.

[0037] After the toner has been removed from the photoreceptor drum 231 by the cleaning device 236, the photoreceptor drum 231 is de-staticized, and any remaining potential is removed, thus completing the series of imaging processes performed on the photoreceptor drum 231.

[0038] The transfer section 240 includes a drive roller 241, a driven roller 242, an intermediate transfer belt 243, primary transfer rollers (244Y, 244C, 244M, 244K), a secondary opposing roller 245, and a secondary transfer roller 246.

[0039] The drive roller 241 is located on the toner cartridge 234Y side of the image forming unit Y. The driven roller 242 is located on the toner cartridge 234K side of the image forming unit K. The intermediate transfer belt 243 is configured to rotate counterclockwise in Figure 1 in conjunction with the drive of the drive roller 241.

[0040] The primary transfer rollers (244Y, 244C, 244M, 244K) are positioned opposite the photoreceptor drum 231, with the intermediate transfer belt 243 in between. The secondary opposing rollers 245 and 246 are positioned opposite each other, with the intermediate transfer belt 243 in between, at the transfer position of the toner image to the paper P. When referring to any of the primary transfer rollers (244Y, 244C, 244M, 244K), it is referred to as primary transfer roller 244.

[0041] A primary transfer bias with polarity opposite to that of the toner is applied to the primary transfer roller 244. Meanwhile, the intermediate transfer belt 243 is sandwiched between the primary transfer roller 244 and the photoreceptor drum 231 to form a primary transfer nip.

[0042] As a result, the toner images of each color formed on the surface of the photoreceptor drum 231 are transferred (primary transfer) onto the intermediate transfer belt 243. In this case, as the intermediate transfer belt 243 rotates in the direction of the arrow in Figure 1, the toner images of each color formed on the photoreceptor drum (231Y, 231C, 231M, 231K) are sequentially transferred onto the intermediate transfer belt 243 to form a color toner image.

[0043] A secondary transfer bias is applied to the secondary transfer roller 246 of the transfer section 240. Meanwhile, the intermediate transfer belt 243 is sandwiched between the secondary opposing roller 245 and the secondary transfer roller 246, forming a secondary transfer nip. As a result, the color toner image formed on the intermediate transfer belt 243 is transferred (secondary transfer) to the paper P sandwiched between the secondary transfer roller 246 and the secondary opposing roller 245.

[0044] The fuser unit 250 includes a fuser belt 251 with an internal heater that heats the paper P, and a pressure roller 252 that rotatably applies pressure to the fuser belt 251 to form a nip. This applies heat and pressure to the color toner image on the paper P, fixing the color toner image. The paper P with the fixed color toner image is then ejected to the paper output tray 224 by the paper output roller 223, completing the image forming process.

[0045] Next, the configuration of the developing unit and the imaging unit equipped with the developing unit will be described in more detail using Figures 2 and 3.

[0046] The developing unit 180 includes a first storage section 181, a first transport screw 182 provided in the first storage section 181, a second storage section 183, a second transport screw 184 provided in the second storage section 183, a developing roller 185, a doctor blade 186, and a density detection sensor 187. The first storage section 181 and the second storage section 183 are pre-storing carriers.

[0047] The first storage section 181 has a supply port B1 connected to the sub-hopper 160. Based on the detection results from the density detection sensor 187, the supply of toner by the sub-hopper 160 is controlled so that the proportion of toner in the developer (toner concentration) is within a predetermined range.

[0048] The toner supplied to the first storage section 181 is mixed and agitated with the carrier by the first transport screw 182 and the second transport screw 184, and circulates through the communication holes B2 and B3 in the direction of the arrows in Figure 2 between the first storage section 181 and the second storage section 183. At this time, the circulating toner is attracted to the carrier by triboelectric charging.

[0049] The developing roller 185 is housed in the second housing section 183, except for the portion facing the photosensitive drum 231.

[0050] The developing roller 185 contains a magnetic roller (not shown), and the toner being transported within the second storage section 183 is attracted to the developing roller 185 along with the carrier by the magnetic force emitted by the magnetic roller. In Figure 3, the developing roller 185 rotates in the direction of the arrow, and the developer attracted to the developing roller 185 is transported as the developing roller 185 rotates, and its thickness is regulated by the doctor blade 186.

[0051] The developer, whose thickness is restricted, is transported by the developing roller 185 to a position opposite the photoreceptor drum 231, and toner is attracted to the electrostatic latent image formed on the photoreceptor drum 231. As a result, a toner image is formed on the photoreceptor drum 231. The developer that has consumed the toner on the developing roller 185 is returned to the second storage section 183 as the developing roller 185 rotates. The developing roller 185 is an example of a developing sleeve in the developing apparatus of this embodiment.

[0052] Furthermore, the developer that has consumed the toner is transported through the second storage section 183 by the second transport screw 184 and returned to the first storage section 181 via the communication hole B3.

[0053] The developing unit 180 uses a two-component developer, which will be described later. Hereafter, the developing unit may be referred to as the developing section. The two-component developer contains toner and magnetic particles called carriers (hereinafter sometimes referred to as magnetic carriers).

[0054] In the image forming apparatus 1 of this embodiment, in the developing unit 180 (developing section), a two-component developer (hereinafter sometimes referred to as "developer"), which is a mixture of toner and a magnetic carrier, is attracted to a rotating developing roller 185 (developing sleeve) by magnetic force to form a magnetic brush. The developing roller 185 is an example of a developing sleeve in a developing apparatus.

[0055] Then, this magnetic brush is rubbed against the electrostatically latent image-bearing photoreceptor drum 231, developing the electrostatic latent image on the photoreceptor drum 231 and forming a toner image. The photoreceptor drum 231 is an example of an electrostatic latent image carrier in a developing device.

[0056] In a developer unit 180 that holds a two-component developer, the developing roller 185 is housed in the second housing section 183. Since the developer is placed on the developing roller 185 and moved toward the photoreceptor drum 231, a gap is required within the second housing section 183. Furthermore, after developing the toner on the photoreceptor drum 231, a gap is required in the second housing section 183 to return the developer. Note that the second housing section 183 is an example of a case in a developing device.

[0057] Some of the developer in the developing roller 185 is outside the second storage section 183, and a large amount of toner that has separated from the carrier is scattered from here. Therefore, by creating an airflow (hereinafter referred to as the suction airflow) that is drawn inward into the developing roller 185 in the gap between the second storage section 183 and the developing roller 185, the scattered toner can be returned to the second storage section 183.

[0058] This significantly reduces toner scattering within the image forming apparatus 1. However, creating a suction airflow in the gap between the second storage section 183 and the developing roller 185 requires air to be discharged from other developing section locations. In this case, toner scattering from this area becomes a problem.

[0059] Therefore, the filter shown below is installed in the part of the developer unit 180 where toner is likely to scatter, thereby suppressing toner scattering from inside the developer unit 180. In this embodiment, the filter is attached to the toner supply port B1 of the developer unit 180.

[0060] (filter) The filter disclosed herein is a filter with a density gradient, having a thickness of 2 to 20 mm and a pressure loss of 2 to 40 Pa at an air velocity of 10 cm / s. The 2 to 20 mm thickness and density gradient in the thickness direction, with the mesh becoming coarser towards the inside of the developer unit 180, reduces toner clogging and allows the filter to maintain its effectiveness for a long period. This filter is an example of an air filter in a developing apparatus.

[0061] The pressure loss of the filter at an airflow velocity of 10 cm / s is preferably 5 to 30 Pa. If the pressure loss is 2 Pa or less, the filter mesh becomes too coarse, leading to toner leakage. If the pressure loss is 40 Pa or more, the filter mesh becomes too fine, causing toner to clog easily, prematurely preventing air from being expelled from the filter, and making it impossible to maintain the suction airflow through the gap in the developing sleeve.

[0062] Regarding the airflow in the developing apparatus, it is preferable to install a fan in the image forming apparatus to create a path for air to be discharged.

[0063] In the example shown in Figure 3, there is a gap between the developer unit 180 and the developing roller 185, allowing toner to scatter from the developer and from the magnetic brush located outside the developer unit 180. On the other hand, a filter is installed at the supply port B1, and an airflow (hereinafter referred to as exhaust airflow) is created that is discharged from the space 190 through the filter to the outside of the developer unit 180.

[0064] As a result, in this embodiment, a suction airflow is generated inside the developer unit 180 from the gap between the developing roller 185 and the developer unit 180, allowing the scattered toner to be returned to the inside of the developer unit 180.

[0065] (Developer) The developer of this disclosure is a two-component developer having a carrier and a toner.

[0066] (Career) The carrier of this disclosure consists of magnetic particles whose surfaces are coated with a resin layer, and the resin layer contains at least one type of charged particle. That is, the carrier contains charged particles in its coating layer.

[0067] In this embodiment, by including electrostatically charged particles in the carrier coating layer, the charging function of these particles can suppress the decrease in the carrier's charging capacity when toner is distributed over a high image area, thereby suppressing toner scattering associated with the decrease in charge.

[0068] In particular, by combining it with the aforementioned developing unit (developer 80), the amount of toner adhering to the filter is reduced, minimizing the reduction in airflow due to filter clogging, and making it possible to suppress toner scattering for a long period of time. As a result, in this embodiment, toner scattering can be efficiently suppressed, and a developing apparatus can be provided that suppresses toner scattering for a long period of time, minimizes maintenance, and provides stable image quality.

[0069] Here, charged particles refer to particles with a relatively low ionization potential, specifically particles with a lower ionization potential than alumina particles (Sumitomo Chemical Co., Ltd., AA-03). For measuring the ionization potential, for example, an ionization potential measuring device (Sumitomo Heavy Industries, Ltd., PYS-202) is used.

[0070] Preferred charged particles include barium sulfate, zinc oxide, magnesium oxide, magnesium hydroxide, and hydrotalcite, with barium sulfate being the most preferred among these.

[0071] By using barium sulfate, zinc oxide, magnesium oxide, magnesium hydroxide, and hydrotalcite as charged particles, the charge of the carrier can be stably maintained. As a result, the developer and toner are electrostatically attracted to each other, which can more efficiently suppress toner scattering.

[0072] When barium sulfate is used as the charged particle, the amount of barium element exposed on the surface of the coating layer is preferably 0.2 atomic percent or more, and more preferably 0.3 atomic percent or more. Since the charge exchange for charging the toner takes place on the surface of the coating layer, in carriers where the exposure of barium sulfate to the surface of the coating layer is extremely small, the charge-imparting ability of barium sulfate is only exhibited when the coating layer is significantly worn away due to long-term carrier use.

[0073] The amount of barium exposed on the surface of carriers can be detected by calculating the atomic percentage of barium element using peak analysis with an X-ray photoelectron spectroscopy (XPS) analyzer (Shimadzu / KRATOS, AXIS / ULTRA). In the XPS analyzer, the beam irradiation area is approximately 900 μm × 600 μm, and detection is performed within a range of 25 carriers × 17. The penetration depth is 0 to 10 nm, and information near the surface of the carriers is detected.

[0074] The specific measurement method is as follows: Measurement mode: Al: 1486.6 eV, Excitation source: Monochrome (Al), Detection method: Spectral mode, Magnetic lens: OFF. First, the elements to be detected are identified by a wide-area scan, and then, peaks are detected for each element using a narrow scan. After that, the atomic percentage of barium for all detected elements is calculated using the included peak analysis software.

[0075] The amount of barium exposed is an example of the barium concentration determined by XPS analysis. It is preferable that the amount of barium exposed on the surface of the coating layer is 0.2 atomic percent or more, because this allows the charge imparting ability to be maintained not only when the coating layer is worn away, but also when toner components adhere to the carrier surface (so-called spent) due to long-term use.

[0076] There are no particular restrictions on the particle size of the charged particles, but when the average thickness of the total resin layer is T, it is preferable that the particle size h satisfies the following equation. h / 2 ≤ T ≤ h

[0077] By making the particle size of the charged particles larger than the thickness of the resin layer, the probability of the charged particles protruding from the surface of the resin coating layer increases. When the tops of the charged particles protrude from the resin coating layer, they function as spacers between the object being rubbed and the resin of the coating layer when carriers rub against each other, the wall of the containment container, or the carrier and the transport jig, thereby extending the life of the coating layer.

[0078] Furthermore, this is preferable from the viewpoint of charge imparting function because it increases the probability of contact between the charged particles and the toner. Also, if the thickness T of the resin layer is greater than half the particle size of the charged particles, the charged particles can be firmly captured in the resin layer, making it less likely for the charged particles to detach from the resin coating layer.

[0079] The particle size of charged particles can be confirmed by conventionally known methods. For example, before carrier formation, it can be measured using a particle size distribution analyzer (Nanotic Track UPA series, manufactured by Nikkiso Co., Ltd.). After carrier formation, it can be confirmed by, for example, cutting the coating layer on the carrier surface with a focused ion beam (FIB) and observing the cross-section with a scanning electron microscope (SEM) or energy-dispersive X-ray analysis (EDX). Examples are given below.

[0080] The carrier is mixed with embedding resin (Devcon, two-component, 30-minute curing epoxy resin), left overnight or longer to cure, and a rough cross-sectional sample is prepared by mechanical polishing. The cross-section is then finished using a cross-section polisher (JEOL, SM-09010) under conditions of an acceleration voltage of 5.0kV and a beam current of 120μA.

[0081] This is captured using a scanning electron microscope (Carl Zeiss, Merlin®) under conditions of an acceleration voltage of 0.8kV and a magnification of 30,000x. The captured images are imported into TIFF format, and the equivalent circle diameter of 100 barium sulfate particles is measured using image analysis software (Media Cybernetics, Image-Pro Plus), and the average value is used.

[0082] It should be noted that this is not the only method of verification. Similarly, the thickness of the coating layer can also be measured from the captured images. However, since there are individual differences in particles and variations in the thickness of the coating layer depending on the location, measurements should not be limited to just one particle / one location, but rather a statistically sound number of measurements (n) should be taken.

[0083] The core material particles used in the image-forming carriers of this disclosure can be appropriately selected from among those known for use as two-component carriers in electrophotography, depending on the purpose. In particular, Mn ferrite is preferred because it is a material with relatively high magnetization, making it easy to set the magnetic moment per carrier particle within an appropriate range from the viewpoint of carrier adhesion resistance.

[0084] The magnetization of a carrier in a 1000 [Oe] magnetic field is 56 [Am]. 2 / kg] or more than 73[Am 2 It is preferable that it be less than [ / kg].

[0085] Even if the internal porosity is reduced and the mass of a single particle is increased, the magnetization remains 56 [Am]. 2 If the magnetization is less than 56[Am / kg], the magnetic moment per particle becomes low, making it easier for carrier adhesion to occur. Also, if the magnetization is less than 56[Am] 2 When the value is above [ / kg], not only is carrier adhesion less likely to occur, but the carriers rub against each other with strong force on the developer carrier, which promotes the scraping off of the aforementioned spent material and is also preferable from the viewpoint of maintaining the charging capacity of the carriers.

[0086] The carrier magnetization is 72[Am] 2 If the magnetization is above [ / kg], the magnetization is too high, causing the developer with reduced toner density after development to remain on the developing roller and re-enter the developing area. This reduces the image density of solid images after the second pass of the developing roller, making it easier to produce abnormal images with vertical bands.

[0087] To bring the carrier magnetization within the above range, the magnetization of the core material in a magnetic field of 1000 [Oe] should be 66 [Am]. 2 / kg] or more than 75[Am 2 It is preferable that it be less than [ / kg].

[0088] The magnetization of the carrier core material was measured using a room-temperature vibrating sample magnetometer (VSM) (VSM-P7, manufactured by Toei Kogyo Co., Ltd.). An external magnetic field was applied continuously for one cycle in the range of 0 to 1000 [Oe], and the magnetization σ1000 at an external magnetic field of 1000 [Oe] was measured.

[0089] It is preferable that the coating layer contains a conductive material for the purpose of adjusting resistance.

[0090] Traditionally, carbon black has been widely used as a conductive material. When used as a developer for extended periods, friction and collisions between carriers or with toner can cause carbon black, or resin fragments containing carbon black, to detach from the carrier coating layer, adhering to toner particles or being developed as is. This problem is particularly noticeable in developers combined with yellow, white, or transparent toners, resulting in color clouding (staining).

[0091] Therefore, it is preferable that the conductive material be as white as possible, or nearly colorless. In particular, materials with good color and conductive properties include compounds obtained by doping tin oxide with tungsten, indium, phosphorus, or any of their oxides, and these can be used as the element itself or as particles on the surface of a substrate particle.

[0092] As substrate particles, conventional or novel materials can be used, such as aluminum oxide and titanium oxide.

[0093] Silicone resin, acrylic resin, or a combination of these can be used as the carrier coating resin. While acrylic resin has excellent abrasion resistance due to its strong adhesion and low brittleness, its high surface energy can lead to problems such as a decrease in charge due to the accumulation of toner components when combined with toners that are prone to splattering.

[0094] In that case, this problem can be solved by using a silicone resin in combination, which has a low surface energy, making it difficult for toner components to be spent and thus reducing the accumulation of spent components that cause film peeling.

[0095] However, silicone resins have weaknesses such as poor adhesion and high brittleness, resulting in poor abrasion resistance. Therefore, it is important to achieve a good balance between the properties of these two types of resins, which makes it possible to obtain a coating film that is resistant to spending and also has abrasion resistance. This is because silicone resins have low surface energy, making it difficult for toner components to spend, and thus reducing the accumulation of spent components that cause film peeling.

[0096] As used herein, "silicone resin" refers to all commonly known silicone resins. Examples of silicone resins include, but are not limited to, straight silicone consisting only of organosilosane bonds, and silicone resins modified with alkyds, polyesters, epoxys, acrylics, urethanes, etc.

[0097] For example, commercially available straight silicone resins include KR271, KR255, and KR152 from Shin-Etsu Chemical, and SR2400, SR2406, and SR2410 from Toray Dow Corning Silicone. In this case, it is possible to use the silicone resin alone, but it is also possible to use other components that undergo cross-linking reactions, charge adjustment components, etc., simultaneously.

[0098] Furthermore, examples of modified silicone resins include Shin-Etsu Chemical's KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), and KR305 (urethane modified), and Toray Dow Corning Silicone's SR2115 (epoxy modified) and SR2110 (alkyd modified).

[0099] Examples of condensation catalysts include titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, and aluminum-based catalysts. Among these, titanium-based catalysts are preferred, and among titanium-based catalysts, titanium diisopropoxybis(ethyl acetate) is more preferred. This is thought to be because it has a strong effect in promoting the condensation reaction of silanol groups and is less prone to catalyst deactivation.

[0100] As used herein, "acrylic resin" refers to all resins containing an acrylic component and is not particularly limited. While acrylic resin can be used alone, it is also possible to use at least one other component that undergoes a crosslinking reaction simultaneously. Examples of other components that undergo a crosslinking reaction include, but are not limited to, amino resins and acidic catalysts.

[0101] Examples of amino resins include, but are not limited to, guanamine and melamine resins. Furthermore, an acidic catalyst refers to a substance that exhibits catalytic activity. Examples of acidic catalysts include, but are not limited to, those having reactive groups such as fully alkylated, methylol group, imino group, and methylol / imino group.

[0102] Furthermore, it is even more preferable that the coating layer contains a crosslinked product of acrylic resin and amino resin. This makes it possible to suppress fusion between the coating layers while maintaining appropriate elasticity.

[0103] While the amino resin is not particularly limited, melamine resin and benzoguanamine resin are preferred because they can improve the carrier's ability to impart charge. Furthermore, if it is necessary to moderately control the carrier's ability to impart charge, melamine resin and / or benzoguanamine resin may be used in combination with other amino resins.

[0104] The acrylic resin that can be crosslinked with the amino resin is preferably one having hydroxyl groups and / or carboxyl groups, and more preferably one having hydroxyl groups. This further improves adhesion with core material particles and conductive fine particles, and also improves the dispersion stability of the conductive fine particles. In this case, the acrylic resin is preferably one with a hydroxyl value of 10 mg KOH / g or more, and more preferably one with a hydroxyl value of 20 mg KOH / g or more.

[0105] In this disclosure, the composition for the coating layer preferably contains a silane coupling agent. This allows for the stable dispersion of conductive fine particles.

[0106] Silane coupling agents are not particularly limited, but examples include r-(2-aminoethyl)aminopropyltrimethoxysilane, r-(2-aminoethyl)aminopropylmethyldimethoxysilane, r-methacryloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-r-aminopropyltrimethoxysilane hydrochloride, r-glycidoxypropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, r-chloropropyltrimethoxysilane, hexamethyldisilazane, and r-anilino Examples include propyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, r-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1,3-divinyltetramethyldisilazane, methacrylateoxyethyldimethyl(3-trimethoxysilylpropyl)ammonium chloride, and two or more of these may be used in combination.

[0107] Commercially available silane coupling agents include AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, sh6062, Z-6911, sz6300, sz6075, sz6079, sz6083, sz6070, sz6072, Z-6721, AY43-004, and Z-6 Examples include 187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048, Z-6403, AY43-206M, AY43-206E, Z6341, AY43-210MC, AY43-083, AY43-101, AY43-013, AY43-158E, Z-6920, Z-6940 (manufactured by Toray Silicone Co., Ltd.), etc.

[0108] The amount of silane coupling agent added is preferably 0.1 to 10% by mass relative to the silicone resin. If the amount of silane coupling agent added is less than 0.1% by mass, the adhesion between the core material particles or conductive fine particles and the silicone resin will decrease, and the coating layer may peel off during long-term use. If it exceeds 10% by mass, toner filming may occur during long-term use.

[0109] The volume-average particle size of the carrier core material used in this disclosure is not particularly limited, but from the viewpoint of preventing carrier adhesion and carrier scattering, a volume-average particle size of 20 μm or more is preferred. Furthermore, from the viewpoint of preventing the occurrence of abnormal images such as carrier streaks and preventing a decrease in image quality, a particle size of 100 μm or less is preferred. In particular, using a particle size of 20 to 60 μm can more effectively meet the demands for high image quality in recent years.

[0110] The volume-average particle size (hereinafter referred to as average particle size) can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer (Nikkiso Co., Ltd., Microtrac particle size distribution analyzer model HRA9320-X100).

[0111] (toner) The toner is contained in a two-component developer together with the carrier. The toner of this disclosure contains a binder resin and may be any of the following: monochrome toner, color toner, white toner, transparent toner, or toner having a metallic luster. Its manufacturing method may be a conventionally known method such as pulverization or polymerization, or another method.

[0112] For example, when manufacturing toner using a grinding method, first, the molten mixture obtained by kneading the toner materials is cooled, then ground and classified to produce matrix particles. Next, to further improve transferability and durability, an external additive is added to the matrix particles to produce toner.

[0113] In this case, the equipment used to knead the toner material is not particularly limited, but examples include batch-type two-roll extruders; Banbury mixers; continuous twin-screw extruders such as the KTK type twin-screw extruder (manufactured by Kobe Steel, Ltd.), TEM type twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), twin-screw extruder (manufactured by KCK Co., Ltd.), PCM type twin-screw extruder (manufactured by Ikegai Iron Works Co., Ltd.), and KEX type twin-screw extruder (manufactured by Kurimoto Iron Works Co., Ltd.); and continuous single-screw kneaders such as the Co-Kneader (manufactured by Buss Co., Ltd.).

[0114] Furthermore, when grinding the cooled molten mixture, it can be coarsely ground using a hammer mill, Rotoplex, etc., and then finely ground using a jet-stream pulverizer, a mechanical pulverizer, etc. It is preferable to grind it so that the average particle size is 3 to 15 μm.

[0115] Furthermore, when classifying the crushed molten mixture, a wind-powered classifier or the like can be used. It is preferable to classify the material so that the average particle size of the parent particles is 5 to 20 μm.

[0116] Furthermore, when adding external additives to the parent particles, mixing and stirring with mixers causes the external additives to break down and adhere to the surface of the parent particles.

[0117] The binder resin is not particularly limited, but examples include styrene and its substituted homopolymers such as polystyrene, poly-p-styrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin, etc., and two or more of these may be used in combination.

[0118] The binder resin for pressure fixing is not particularly limited, but examples include polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene; olefin copolymers such as ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, and ionomer resin; epoxy resin, polyester, styrene-butadiene copolymer, polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, and phenol-modified terpene resin, and two or more of these may be used in combination.

[0119] The colorants (pigments or dyes) are not particularly limited, but examples include yellow pigments such as cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake; orange pigments such as molybdenum orange, permanent orange GTR, pyrazolone orange, balkan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK; red iron oxide, cadmium red, permanent red 4R, lysol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, and rhodamine red. Examples of pigments include red pigments such as Ki B, Alizarin Lake, and Brilliant Carmine 3B; purple pigments such as Fast Violet B and Methyl Violet Lake; blue pigments such as Cobalt Blue, Alkali Blue, Victoria Blue Lake, Phthalocyanine Blue, Metalless Phthalocyanine Blue, Partially Chlorinated Phthalocyanine Blue, Fast Sky Blue, and Indanthrene Blue BC; green pigments such as Chrome Green, Chromium Oxide, Pigment Green B, and Malachite Green Lake; black pigments such as azine dyes such as Carbon Black, Oil Furnace Black, Channel Black, Lamp Black, Acetylene Black, and Aniline Black, metal salt azo dyes, metal oxides, and composite metal oxides; and white pigments such as Titanium Dioxide. Two or more of these may be used in combination, and they may not be used in the case of transparent toner.

[0120] While not particularly limited, examples of release agents include polyethylene, polypropylene and other polyolefins, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, ester wax, and more than one of these may be used in combination.

[0121] Furthermore, the toner may further contain a charge control agent. The antistatic agent is not particularly limited, but may include nigrosine; azine dyes having alkyl groups with 2 to 16 carbon atoms; CIBasic Yello 2 (CI41000), CIBasic Yello 3, CIBasic Red 1 (CI45160), CIBasic Red 9 (CI42500), CIBasic Violet 1 (CI42535), CIBasic Violet 3 (CI42555), CIBasic Violet 10 (CI45170), CIBasic Violet 14 (CI42510), CIBasic Blue 1 (CI42025), CIBasic Blue 3 (CI51005), CIBasic Blue 5 (CI42140), CIBasic Blue 7 (CI42595), CIBasic Blue 9 (CI52015), CIBasic Blue 24 (CI52030), CIBasic Blue 25 (CI52025), CIBasic Blue Examples include basic dyes such as 26 (CI44045), CIBasic Green 1 (CI42040), and CIBasic Green 4 (CI42000); lake pigments of these basic dyes; quaternary ammonium salts such as CISolvent Black 8 (CI26150), benzoylmethylhexadecylammonium chloride, and decyltrimethyl chloride; dialkyltin compounds such as dibutyl and dioctyl; dialkyltin borate compounds; guanidine derivatives; polyamine resins such as vinyl polymers and condensation polymers having amino groups; metal complex salts of monoazo dyes; salicylic acid; metal complexes of dialkylsalicylic acid, naphthoic acid, and dicarboxylic acids such as Zn, Al, Co, Cr, and Fe; sulfonated copper phthalocyanine pigments; organoboro salts; fluorine-containing quaternary ammonium salts; and calixalene compounds, although two or more may be used in combination. For color toners other than black, metal salts of white salicylic acid derivatives are preferred.

[0122] Examples of external additives are not particularly limited, but include inorganic particles such as silica, titanium dioxide, alumina, silicon carbide, silicon nitride, and boron nitride; and resin particles such as polymethyl methacrylate particles and polystyrene particles with an average particle size of 0.05 to 1 μm obtained by soap-free emulsion polymerization. Two or more types may be used in combination. Among these, metal oxide particles such as silica and titanium dioxide, whose surfaces have been hydrophobized, are preferred.

[0123] Furthermore, by using hydrophobically treated silica and hydrophobically treated titanium dioxide in combination, and by adding a larger amount of hydrophobically treated titanium dioxide than hydrophobically treated silica, a toner with excellent charge stability against humidity can be obtained.

[0124] <Developer for electrophotographic image formation> The electrophotographic image-forming developer according to this embodiment is used in the image forming apparatus (developing apparatus) described above. Specifically, the two-component developer described above is used as the electrophotographic image-forming developer. Therefore, the effects of the developing apparatus according to this embodiment can be obtained with the electrophotographic image-forming developer of this embodiment.

[0125] In other words, the electrophotographic image-forming developer of this embodiment, when used in the above-described developing apparatus, can suppress toner scattering over a long period of time, minimize maintenance, and obtain stable image quality. Note that the above-described two-component developer is just one example of an electrophotographic image-forming developer.

[0126] <Electrophotographic Image Formation Method> In the electrophotographic image forming method according to this embodiment, an image is formed using the above-described electrophotographic image forming developer. Therefore, the effects of the image forming apparatus (developing apparatus) according to this embodiment can be obtained in the electrophotographic image forming method of this embodiment.

[0127] In other words, the electrophotographic image forming method of this embodiment, by using the above-mentioned electrophotographic image forming developer, suppresses toner scattering over a long period of time, minimizes maintenance, and allows for stable image quality.

[0128] <Electrophotographic image forming apparatus> The electrophotographic image forming apparatus according to this embodiment includes the above-described electrophotographic image forming developer. Therefore, the electrophotographic image forming apparatus of this embodiment can obtain the effects of the developer according to this embodiment.

[0129] In other words, the electrophotographic image forming apparatus of this embodiment, by being equipped with the above-mentioned electrophotographic image forming developer, can suppress toner scattering over a long period of time, minimize maintenance, and obtain stable image quality. The image forming apparatus 1 described above is also an example of an electrophotographic image forming apparatus. [Examples]

[0130] The present invention will be described below with reference to examples and comparative examples. However, the present invention is not limited to these examples. In the following, "parts" refers to parts by mass, and "%" refers to mass percent. Furthermore, various tests and evaluations will be carried out according to the methods described below.

[0131] [Career Development] (Career 1) <Core material> · Mn ferrite (σ1000:68[Am 2 / kg], average particle size: 35μm)

[0132] <Resin liquid 1> • Acrylic resin solution (solids content concentration: 50%) 10 parts • Silicone resin solution (solid content concentration: 50%) 190 parts • Toluene 500 copies • Aminosilane Part 2 Barium sulfate (average particle size: 0.35 μm) 100 units • Conductive filler (phosphorus-doped tin oxide) (powder resistivity: 30 [Ω·cm]) 50 units • Phosphate ester dispersant (4 parts) • Silicone-based defoaming agent (silicone content: 1%) 5 parts • Silicone crosslinking catalyst (dibutyltin acetate) 10 parts

[0133] The materials for resin liquid 1 were dispersed in a homomixer for 10 minutes to prepare a resin layer forming solution. The resin layer forming solution of resin liquid 1 was applied to the core material surface at a rate of 30 g / min using a spiral coater (manufactured by Okada Seikou Co., Ltd.) at a 60°C atmosphere to a thickness of 0.5 μm, and then dried. The layer thickness was adjusted by changing the amount of liquid. The obtained carrier was fired in an electric furnace at 200°C for 1 hour, and after cooling, it was crushed using a sieve with a mesh size of 100 μm to obtain carrier 1.

[0134] (Career 2) Carrier 2 was obtained in the same manner as Carrier 1, except that the amount of barium sulfate in Carrier 1 was changed from 100 parts to 50 parts.

[0135] (Career 3) Carrier 3 was obtained in the same manner as carrier 1, except that 100 parts of barium sulfate in carrier 1 were replaced with 100 parts of magnesium oxide (average particle size: 0.35 μm).

[0136] (Career 4) Carrier 4 was obtained in the same manner as carrier 1, except that 100 parts of barium sulfate in carrier 1 were replaced with 100 parts of magnesium hydroxide (average particle size: 0.3 μm).

[0137] (Career 5) Carrier 5 was obtained in the same manner as Carrier 1, except that 100 parts of barium sulfate in Carrier 1 were replaced with 100 parts of hydrotalcite (average particle size: 0.4 μm).

[0138] (Career 6) Carrier 6 was obtained in the same manner as carrier 1, except that 100 parts of barium sulfate in carrier 1 were replaced with 100 parts of zinc oxide (average particle size: 0.4 μm).

[0139] (Career 7) Carrier 7 was obtained in the same manner as carrier 1, except that 100 parts of barium sulfate in carrier 1 were replaced with 100 parts of alumina (average particle size: 0.35 μm).

[0140] (Career 8) Carrier 8 was obtained in the same manner as Carrier 1, except that 100 parts of barium sulfate in Carrier 1 were changed to 0 parts.

[0141] Table 1 shows the prescriptions for carriers 1-8.

[0142] [Table 1]

[0143] For carriers 1-8, the concentration of barium element (Ba detection amount) was measured by XPS analysis of the carrier surface. The results for the Ba detection amount are shown in Table 2.

[0144] [Table 2]

[0145] Examples 1-10 and Comparative Examples 1-5 using carriers 1-8 were evaluated using a modified commercially available digital full-color multifunction printer (IMAGIO® MP C5002, manufactured by Ricoh Co., Ltd.).

[0146] The configuration of the IMAGIO MP C5002 is almost identical to that shown in Figures 1-3. A 1cm x 20cm hole was drilled directly above the screw that recirculates the developer in the developer unit shown in Figure 2, and various filters were attached and evaluated.

[0147] Furthermore, to create an airflow that draws air in through the gaps in the developing sleeve, the top of the filter in the developing section is sealed, and the air is discharged using a tube and pump so that air can escape from inside the developing unit.

[0148] (Toner scattering) Carrier 1-8 and the four toners of the IMAGIO MP C5002 were mixed to achieve a toner density of 7% each, creating a developer, which was then loaded into the device (digital full-color multifunction printer).

[0149] Furthermore, toner scattering was evaluated by printing 100,000 images in which black, yellow, magenta, and cyan toners each accounted for 5% of the image area.

[0150] The toner accumulated at the bottom of the developing unit was sucked up and collected, and its mass was measured. Furthermore, the toner contamination inside the machine, the modified pump unit, and the wall areas exposed to the exhaust airflow from the pump were evaluated. The evaluation criteria are shown below. A and B are considered good, and C is considered poor.

[0151] A: Visually, there was no toner splatter, and no toner came off on the cloth when wiped. B: Visually, there was no toner splatter, but when wiped with a cloth, a small amount of toner came off on the cloth. C: Toner splatter is visible to the naked eye.

[0152] Table 3 shows the filter and carrier combinations (Examples 1-8, Comparative Examples 1-5) and the evaluation results of toner scattering.

[0153] [Table 3]

[0154] Table 3 shows that the developing apparatus (image forming apparatus) of this disclosure suppresses toner scattering, requires no maintenance for a long period of time, and is less prone to malfunctions of the image forming apparatus.

[0155] Although embodiments of the present invention have been described above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the invention as described in the claims. [Explanation of symbols]

[0156] 1. Image forming apparatus (developing apparatus) 180 Developer 181 First Detention Unit 182 First conveying screw 183 Second Detention Unit 184 Second conveyor screw 185 Developing Roller 186 Doctor Blade 187 Concentration detection sensor 190 Space B1 supply port B2, B3 communication hole 210 Paper feed section 211 Paper feed cassette 212 Paper feed roller 220 Conveying section 221 Laura 222 Timing Roller 223 Paper output roller 224 Paper Output Tray 230 Image creation section Y, C, M, K Image Forming Unit 231, 231Y, 231C, 231M, 231K Photoconductor Drum 232, 232Y, 232C, 232M, 232K chargers 233 Exposure Unit 233a light source 233b, 233bY, 233bC, 233bM, 233bK Polygon Mirror 234, 234Y, 234C, 234M, 234K Toner Cartridges 236, 236Y, 236C, 236M, 236K cleaner 240 Transfer section 241 Drive roller 242 Driven roller 243 Intermediate transfer belt 244 Primary Transfer Roller 245 Secondary opposing roller 246 Secondary Transfer Roller 250 Fuser 251 Fixing belt 252 Pressure roller P paper [Prior art documents] [Patent Documents]

[0157] [Patent Document 1] Japanese Patent Publication No. 2016-212254 [Patent Document 2] International Publication No. 2017 / 159333

Claims

1. A developing apparatus that forms a toner image by magnetically adsorbing a two-component developer containing toner and a magnetic carrier onto the surface of a rotating developing sleeve to form a magnetic brush, rubbing the magnetic brush against an electrostatic latent image carrier, and developing the electrostatic latent image formed on the surface of the electrostatic latent image carrier, A case for housing the two-component developer and the developing sleeve, The case is fitted with an air filter, The toner contains matrix particles, and the average particle size of the matrix particles is 5 to 20 μm. The air filter has a thickness of 2 to 20 mm and a density gradient with a pressure loss of 2 to 40 Pa at a wind speed of 10 cm / s. An airflow is formed that draws air into the case from the gap between the developing sleeve and the case. An airflow is formed that discharges the air inside the case to the outside of the case through the air filter. The case has a supply port on which the air filter is installed. The airflow discharged to the outside of the case is formed by a path through which air inside the case is discharged to the outside of the case via the air filter at the supply port by a fan or pump provided in the electrophotographic image forming apparatus. The two-component developer housed in the case comprises the two-component developer composed of magnetic particles whose surfaces are coated with a resin layer, The resin layer contains at least one type of electrostatically charged particle, Developing device.

2. The charged particles are at least one inorganic fine particle selected from barium sulfate, zinc oxide, magnesium oxide, magnesium hydroxide, and hydrotalcite. The developing apparatus according to claim 1.

3. The charged particles are barium sulfate. The developing apparatus according to claim 1 or 2.

4. The concentration of barium element on the surface of the magnetic carrier contained in the two-component developer, as determined by XPS analysis, is 0.2 atomic percent or more. The developing apparatus according to claim 3.

5. Used in a developing apparatus according to any one of claims 1 to 4, The magnetic particles include the surface of which is coated with the resin layer, Two-component developer.

6. An image is formed using the two-component developer described in claim 5. A method for forming electrophotographic images.

7. The two-component developer according to claim 5, Electrophotographic image forming apparatus.

Images