JP2012150156A - Developing device, process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device, a process cartridge and an image forming device capable of reducing the amount of scattered toner.SOLUTION: In a developing device which comprises a toner carrier which is disposed opposite to a photoreceptor and carries toner for developing an electrostatic latent image formed on the photoreceptor, a plurality of first plate-shaped electrodes 24 arranged in a row at equal intervals and a plate-like second electrode 25 arranged in parallel with the row of the first electrodes 24, and develops the electrostatic latent image by applying a voltage to the electrodes 24 and 25 to hop the toner, the photoreceptor and the toner carrier are used as a belt and arranged so as to form a nip in parallel to the surface where a developing belt 21 and a photoreceptor belt 6 face each other, and the first electrode 24 and the second electrode 25 are provided oppositely to the photoreceptor belt 6 across the developing belt 21 in the intermediate region in the belt travelling direction in the nip on the parallel surface.

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus that develop an electrostatic latent image using toner.

  There are many development systems in practical use in image forming apparatuses such as copiers, printers, facsimiles, or their combined machines. Typical examples include a two-component development system and a one-component development system. .

  The two-component development method is suitable for high-speed development, and is the mainstream method for current medium speed and high-speed output machines. In order to aim for high image quality, it is necessary to make the state of the developer in contact with the electrostatic latent image very dense. For this reason, the carrier particles are now being reduced in diameter, and carriers of about 30 μm are beginning to be used on a commercial level. However, the demand for higher image quality is increasing, and the required dot size of the pixel itself needs to be equal to or smaller than the current carrier particle size. Carrier particles need to be small. However, as the carrier diameter is reduced, the permeability of the carrier particles decreases, so that the carrier is easily detached from the developing roller. If the detached carrier particles adhere to the latent image carrier, the carrier adheres. Not only does this cause image defects, but it also causes various side effects such as scratching the latent image carrier from that point. In order to prevent this carrier detachment, attempts have been made to increase the magnetic permeability of carrier particles from the material surface and to increase the magnetic force of the magnet included in the developing roller. Development is extremely difficult due to this balance. In addition, due to the downsizing of the developing roller, the developing roller is becoming smaller in diameter, and it becomes difficult to design a developing roller having a strong magnetic field configuration that can completely prevent carrier detachment. Yes.

  In the first place, the two-component development method is a process that forms a toner image by rubbing the ears of a two-component developer called a magnetic brush against the electrostatic latent image. Unevenness is likely to occur. Although the image quality can be improved by forming an alternating electric field between the developing roller and the latent image carrier, it is difficult to completely eliminate the fundamental image unevenness such as the unevenness of the ears of the developer.

  In order to improve transfer efficiency and cleaning efficiency in the process of transferring the developed toner image to the latent image carrier and the process of cleaning the toner remaining on the latent image carrier after the transfer, the latent image carrier It is necessary to reduce the non-electrostatic adhesion force between the body and the toner as much as possible. As a method for reducing the non-electrostatic adhesion between the latent image carrier and the toner, it is known that reducing the friction coefficient on the surface of the latent image carrier is effective. Since the spikes of the agent smoothly pass through the developing portion, the development efficiency and the dot reproducibility become very poor.

The one-component development method is the mainstream method of current low-speed output machines because the mechanism is small and light.
In the one-component development method, in order to form a toner thin layer on the developing roller, a toner regulating member such as a blade or a roller is brought into contact, and at that time, the toner is charged by friction with the developing roller or the toner regulating member. . The charged toner layer formed as a thin layer on the developing roller is transported to the developing unit and developed. The developing system here is largely divided into a contact type and a non-contact type, the former is a non-contact between the developing roller and the latent image carrier, and the latter is in contact. In any method, the toner layer thinned on the developing roller is sufficiently pressed, so that the toner responsiveness to the electric field in the developing unit is very poor. Therefore, in general, in order to obtain high image quality, it is mainstream to form a strong alternating electric field between the developing roller and the latent image carrier. However, even if this alternating electric field is formed, an electrostatic latent image is formed. On the other hand, it is difficult to stably develop a certain amount of toner, and it is difficult to uniformly develop high resolution minute dots.

  In addition, in this one-component developing system, a very large stress is applied to the toner when the toner thin layer is formed on the developing roller, so that the toner circulating in the developing device is deteriorated very quickly. As the toner deteriorates, unevenness and the like are likely to occur even in the process of forming a toner thin layer on the developing roller, which is generally not suitable as a high-speed or highly durable image forming apparatus.

Patent Documents 1 and 2 describe a flare development system capable of realizing high image quality (high resolution dot reproducibility) compared to these conventional development systems.
In the flare development method, a toner carrier having a plurality of electrodes therein is disposed to face the latent image carrier, and a voltage that changes with time is applied to the plurality of electrodes. The toner on the toner carrier is hopped by the electric field generated between the electrodes, and is supplied onto the latent image carrier.

  However, it has been found that the flare development method causes toner scattering. Then, when the scattered toner was examined, it was found that most of the scattered toner was a toner with insufficient charge amount as shown in FIG.

  Further, as a result of observing the toner development process from the side surface of the toner carrier and the latent image carrier to the latent image, as shown in FIG. 5, the toner floats in the vicinity of the hopping toner layer and moves in the rotation direction of the toner carrier. I was able to confirm. Thereafter, it was confirmed that the moving floating toner does not pass through the developing nip and proceeds in the direction opposite to the rotation direction of the photosensitive member without being developed.

  From these results, when the charged toner is hopped by the electric field formed between the electrodes, the weakly charged toner is pushed out from the hopping area, floats in the vicinity of the hopping area, and the air flow in the rotation direction created by the toner carrier Carried in. It can be estimated that the weakly charged toner carried in this way is scattered in the vicinity of the developing nip entrance on the turbulent air generated by the collision between the airflow generated by the toner carrier and the airflow generated by the latent image carrier.

  In order to reduce such toner scattering, it is conceivable to reduce the amount of weakly charged toner that is easily scattered. Weakly charged toner, for example, can be reduced to some extent by sufficiently stirring the toner, but it is stirred to the maximum extent in the apparatus being implemented, and without further increase in the size of the apparatus, the further stirring area is increased, The current situation is that it is difficult to reduce weakly charged toner.

  It is an object of the present invention to provide a developing device, a process cartridge, and an image forming apparatus that can reduce the amount of scattered toner.

  In order to achieve the above object, the present invention is arranged in a row with a toner carrier that is disposed opposite to a latent image carrier and holds toner for developing an electrostatic latent image formed on the latent image carrier. A plurality of plate-like first electrodes arranged at intervals, and a plate-like second electrode arranged in parallel to the row of the first electrodes, and applying a voltage to these electrodes In the developing device for developing the electrostatic latent image by hopping the toner, a belt is used as the latent image carrier and the toner carrier, and the toner carrier belt and the latent image carrier belt are parallel to each other. The first electrode and the second electrode are arranged so as to form a nip of a surface, and are opposed to the latent image carrier belt across the toner carrier belt in an intermediate region of the parallel surface nip in the belt running direction. Development characterized by comprising two electrodes To propose a location.

  The present invention further includes a third electrode facing the latent image carrier belt with the toner carrier belt interposed therebetween, and the third electrode is in the nip of the parallel surface and in the belt running direction. It is advantageous to apply a voltage that is arranged downstream of the electrode and always attracts the toner.

  Further, according to the present invention, a two-component developing unit for supplying toner to the toner carrier belt is provided, and the two-component developer unit develops at a position facing the toner carrier belt in front of the nip of the parallel surface. It is advantageous if a roller is provided, and a fourth electrode is disposed opposite the developing roller with the toner carrier belt interposed therebetween to supply toner to the toner carrier belt.

  In order to achieve the above object, the present invention removes the latent image carrier, a charging device for uniformly charging the latent image carrier, and toner remaining on the latent image carrier after toner image transfer. A process cartridge is proposed in which at least one of the cleaning devices to be integrated with the developing device according to claims 1 to 3 is formed detachably with respect to the main body of the image forming apparatus.

  In order to achieve the above object, the present invention proposes an image forming apparatus comprising a plurality of developing devices according to claims 1 to 3 or a plurality of process cartridges according to claim 4.

  According to the present invention, since the toner carrier belt and the latent image carrier belt face each other, a parallel nip is formed, and the toner is hopped in the nip. Even if a flare development method capable of realizing high image quality is used, contamination due to toner scattering can be reduced.

1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to the present invention. It is side surface explanatory drawing which shows the developing device of the apparatus. It is explanatory drawing which shows other embodiment of this invention. It is a figure which shows the charge amount of the normal toner and the scattering toner in the conventional flare development. It is explanatory drawing explaining the problem of the conventional flare development.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view of an image forming apparatus equipped with a developing device according to the present invention, and FIG. 2 is an enlarged cross-sectional view of the developing device used in the image forming apparatus of FIG.

  1 and 2, reference numeral 1 denotes an apparatus main body of a tandem type color copier as an image forming apparatus, 2 denotes a document conveying unit that conveys a document to a document reading unit, and a document reading unit that reads image information of a document (not shown). ) 3 is a paper discharge tray on which output images are stacked, 4 is a paper feed unit for storing a recording medium P such as transfer paper, and 5 is a registration roller for adjusting the conveyance timing of the recording medium P, 6Y, 6M, and 6C. , 6BK is a photoreceptor belt as a latent image carrier on which toner images of yellow, magenta, cyan, and black are formed, and 9 is an electrostatic latent image formed on each photoreceptor belt 6Y, 6M, 6C, 6BK. A developing device 11 for developing an image indicates a transfer bias roller for transferring a toner image formed on each of the photoreceptor belts 6Y, 6M, 6C, and 6BK in an overlapping manner on the recording medium P. Each of the photoreceptor belts 6Y, 6M, 6C, and 6BK is wound around rollers 7 and 8, respectively, and one of the rollers 7 and 8 is rotated in the counterclockwise direction by a driving unit (not shown) so as to travel in the direction of the arrow. Is done.

  Also, 10 is a paper conveying belt for conveying the recording medium P, 12 is a fixing device for fixing an unfixed image on the recording medium P, 13 is a toner for each color of yellow, cyan, magenta, and black to each developing device 5. The toner container to supply is shown.

Next, an operation during normal color image formation in the image forming apparatus will be described.
First, a document is transported from a document table by a transport roller (not shown) of the document transport unit 2 and placed on a contact glass of a document reading unit (not shown). Then, the document reading unit optically reads the image information of the document placed on the contact glass.

  Specifically, the original reading unit scans the original image on the contact glass while irradiating light emitted from the illumination lamp. Then, the light reflected from the original is imaged on the color sensor via the mirror group and the lens. The color image information of the original is read for each color separation light of RGB (red, green, blue) by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to a writing unit (not shown). Then, laser light (not shown) based on the image information of each color is emitted from the writing unit toward the corresponding photosensitive belts 6Y, 6M, 6C, and 6BK.

  On the other hand, when the four photosensitive belts 6Y, 6M, 6C, and 6BK are each rotated counterclockwise by a driving unit (not shown), the surfaces thereof are uniform at a portion facing the charging device (not shown). Is charged (charging process). Thus, a charging potential is formed on the photoreceptor belts 6Y, 6M, 6C, and 6BK. Thereafter, the surfaces of the charged photoreceptor belts 6Y, 6M, 6C, and 6BK reach the irradiation positions of the respective laser beams.

  In the writing unit, laser beams corresponding to the image signals are emitted from the four light sources corresponding to the respective colors. Each laser beam passes through a different optical path for each color component of yellow, magenta, cyan, and black (exposure process).

  The laser beam corresponding to the yellow component is applied to the surface of the first photosensitive belt 6Y from the left side of the paper. At this time, the yellow component laser light is scanned in the rotational axis direction (main scanning direction) of the photoreceptor belt 6Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photoreceptor belt 6Y charged by the charging unit. Similarly, magenta component, cyan component, and black component laser beams are applied to the surface of each photoreceptor belt 5, and electrostatic latent images of each color component are formed on each photoreceptor belt 6.

  Thereafter, the surfaces of the photoreceptor belts 6Y, 6M, 6C, and 6BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing device 9, respectively. Then, each color toner is supplied from each developing device 9 onto the photoreceptor belts 6Y, 6M, 6C, and 6BK, and the latent images on the photoreceptor belts 6Y, 6M, 6C, and 6BK are developed (development process).

  Thereafter, the surfaces of the photosensitive belts 6Y, 6M, 6C, and 6BK after the development process reach the facing portions of the paper conveying belt 10, respectively. Here, a transfer bias roller 11 is installed at each facing portion so as to abut on the inner peripheral surface of the paper transport belt 10. Each color formed on the photoreceptor belts 6Y, 6M, 6C, and 6BK on the recording medium P that has been transported by the paper transport belt 10 traveling in the clockwise direction in the drawing at the position of the transfer bias roller 11 is shown. The toner images are transferred one after another (transfer process).

  Untransferred toner is unavoidably left on the surfaces of the photoreceptor belts 6Y, 6M, 6C, and 6BK after the transfer process, and the remaining toner is collected by a cleaning device (not shown). Thereafter, the surfaces of the photoreceptor belts 6Y, 6M, 6C, and 6BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoreceptor drums 6Y, 6M, 6C, and 6BK is completed.

  Here, the recording medium P transported between the photosensitive belt 6 and the paper transport belt 10 (transfer nip) is transported from the paper feed unit 4 via the registration roller 5 and the like. Specifically, the recording medium P fed by the paper feed roller 4a from the paper feeding unit 4 that stores the recording medium P is conveyed toward the transfer nip in a timely manner after passing through the conveyance guide. Then, the recording medium P on which the full color image has been transferred in the transfer step is then guided to the fixing device 12. In the fixing device 12, the color image is fixed on the recording medium P at the nip between the fixing roller and the pressure roller. The recording medium P after the fixing step is discharged as an output image outside the apparatus main body by a discharge roller and stacked on the discharge tray 3, thus completing a series of image forming processes.

Next, the developing device 9 of the present embodiment will be described with reference to FIG.
In FIG. 2, the developing device 9 includes a developing belt device 20 disposed below the photosensitive belt 6 and a two-component developing unit unit 30, and the developer in the two-component developing unit unit 30 passes through a developing roller 31. It is configured to be supplied to the developing belt device 20.

  The developing belt device 20 includes a developing belt 21 and a first electrode 24, a second electrode 25, a third electrode 26, and a fourth electrode 27 as a toner carrier that is wound around rollers 22 and 23 and travels in the direction of the arrow. is doing. The developing belt 21 has a base layer, an elastic layer, and a surface layer (not shown) from the inside of the belt loop. The base layer is, for example, a layer containing or laminating a material that hardly stretches, such as a fluorine-based resin with little elongation or a rubber material with a large elongation, such as canvas. The surface layer is a layer made of a material having a low surface energy and exhibiting good releasability from the toner, such as a fluorine resin. The elastic layer is a layer made of an elastic material such as fluorine-based rubber or acrylonitrile-butadiene copolymer rubber, and is provided in order to exert a certain degree of elasticity on the entire belt. The photosensitive belt 6 is made of an organic photosensitive material exhibiting photosensitivity, and is further a belt-like one coated with a filler-reinforced charge transport layer having a thickness of 3.5 to 5.0 [μm]. is there.

  The photosensitive belt 6 and the developing belt 21 are both wider than the maximum image forming width, and the developing belt 21 is formed with a slightly longer running side than the photosensitive belt 6. The opposite sides of the photosensitive belt 6 and the developing belt 21 are substantially parallel, and most of the photosensitive belt 6 overlaps the developing belt 21 as shown in the figure. Although the depth direction is not shown, it overlaps in this direction, and a mechanical nip is formed between the photosensitive belt 6 and the developing belt 21. In the mechanical nip N, the photosensitive belt 6 and the developing belt 21 travel in the directions of arrows. Reference numerals 6a and 21a are tension rollers.

  In the running side of the developing belt 21, the first electrode 24 and the third electrode 26 are juxtaposed substantially in the center in the lateral direction at the overlapping portion with the photosensitive belt 6, and close to the upper running side of the developing belt 21. Has been placed. The first electrode 24 is divided into a plurality of electrodes having an electrode width of 80 to 100 μm. When the width of the first electrode 24 is smaller than 80 μm, the electrode width is too thin, and thus one electrode may be cut off. On the contrary, when the width is larger than 100 μm, the electric field at the center of the electrode is weak. Therefore, the toner adhering to the central portion of the electrode is difficult to hop, and the electrode width of the first electrode 24 is set to 80 to 100 μm. Further, when the distance between the electrodes in the first electrode 24 is set to 100 to 300 μm and the distance between the electrodes is smaller than the electrode width, the contribution of the second electrode 25 is blocked by the first electrode 24, and it is difficult to reach the surface layer. (The electric lines of force from the second electrode 25 converge directly on the first electrode 24, and the electric lines of force appearing on the surface layer are reduced). Moreover, when the distance between electrodes is too large, the electric field at the center between the electrodes is weakened. Accordingly, the distance between the electrodes is preferably equal to or more than 3 times the electrode width. In this embodiment, the electrode width is set to 100 μm and the distance between the electrodes is set to 150 μm.

  The second electrode 25 is disposed directly below the first electrode 24, and the electrode width is the sum of the total first electrode 24 width and the distance between all electrodes. The electrode width in the direction is 1000 μm.

  The third electrode 26 arranged on the right side of the first electrode 24 has an electrode width of 100 to 300 μm. Further, the electrode width of the fourth electrode 27 disposed between the developing roller 31 and the developing belt 21 described later is 80 to 100 μm.

  The 1st electrode 24, the 3rd electrode 25, and the 4th electrode 27 are set as the structure which laminated | stacked the metal and the surface layer on it on the insulating layer. Specific examples of the electrodes include, for example, an insulating layer: polyimide (thickness 20 μm), first, third, and fourth electrodes: copper (thickness 5 μm), surface layer: polycarbonate (thickness 10 μm), In particular, a flexible printed circuit board that is thin and elastic is fused. Here, the insulating layer is preferably an insulating material, and in this embodiment, polycarbonate, alkyd melamine, or the like is used. The thickness of the insulating layer is 3 μm to 50 μm. If it is smaller than 3 μm, the insulation between the first electrode 24 and the second electrode 25 cannot be maintained, and there is a possibility that leakage occurs between the first electrode 24 and the second electrode 25. On the other hand, if it is larger than 50 μm, the voltage applied to the second electrode 25 is weakened by the insulating layer and hardly comes out on the surface layer, and the electric field created by the first electrode 24 and the second electrode 25 on the surface layer becomes weak. When the electric field becomes weak, it becomes difficult for the toner to hop on the surface layer.

  The second electrode 25 is a metal plate such as SUS or aluminum. In addition, it is also possible to form a metal layer such as aluminum or copper on the surface layer of a resin plate such as polyacetal (POM) or polycarbonate (PC). There are various methods for forming this metal layer, such as metal plating, vapor deposition, and adhesion of a metal film together with an adhesive layer.

  The two-component developing unit 30 contains a developer (not shown) including a magnetic carrier and a negatively chargeable toner. This developer is agitated and conveyed by two agitating screws 35 and 36 and is frictionally charged. The charged developer is delivered to the supply screw 32 and contacts the surface of the developing roller 31 in the axial direction during supply and conveyance. Then, it is carried on the surface of the developing roller 31 due to the influence of the magnetic field extending from the roller surface toward the supply screw 32 and is pumped up from the supply screw 32 as the roller surface rotates. And it is conveyed to the position facing the magnetic doctor blade 34 with the rotation of the roller surface. In this facing position, the developer is regulated in layer thickness when it passes through the doctor gap, which is the gap between the developing roller 31 and the magnetic doctor blade 34, and the frictional charging of the toner is promoted. In this embodiment, the doctor gap is set to about 500 [μm].

The developer that has passed through the doctor gap reaches the developing region facing the developing belt 21 as the roller surface rotates. In this developing region, the developing belt 21 and the developing roller 31 are opposed to each other with a developing gap of about 300 [μm]. On the roller surface in the developing region, the magnetic carrier in the developer is raised by the magnetic force from the developing magnetic pole (not shown) of the mag roller in the developing roller 31 to form a magnetic brush. The formed magnetic brush moves while the tip of the magnetic brush is rubbed against the developing belt 21, and causes the toner to adhere to the developing belt 21 by the developing electric field formed by the fourth electrode 27 and the developing roller 31 to which a voltage is applied. . By this adhesion, a thin layer of toner is formed on the developing belt 21. The charge amount of the toner in the developer conveyed to the development region is −10 to −50 [μC / g], preferably −15 to −45 [μC / g]. The magnetic force, stirring performance, doctor gap, etc. of the magnetic pole of the mag roller (not shown) are set so as to be in this range. In this embodiment, the developer transport amount per unit area is 30 mg / cm ² , the linear speed ratio between the developing roller 31 and the developing belt 21 is 1.5, and the voltage applied to the fourth electrode 27 is −50V. .

  The toner that has not moved to the developing belt 21 is collected in the container of the two-component developing unit as the developing roller 31 rotates, and is collected by a collecting screw (not shown). It has become. The downstream of the supply screw 32 and the recovery screw (not shown) and the upstream of the stirring screw 36 are in communication with each other, and an appropriate amount of the developer whose toner density has decreased after the development has been completed is supplied from the toner supply port 37 on the stirring screw 36. The toner density is kept appropriate by the toner to be applied. The amount of toner to be replenished is determined based on a value detected by a toner density sensor (not shown) that measures the toner density of the developer. The developer whose toner concentration has been returned to the proper state after being replenished with toner is conveyed and uniformized while being agitated in the agitated screws 35 and 36 with the replenished toner. The downstream of the agitation screw 35 and the upstream of the supply screw 32 are in communication with each other, and the developer whose toner density is optimized and uniformed is conveyed again through the supply screw 32 to the development region by the developing roller.

  In the normal direction magnetic pattern (not shown) of the mag of the developing roller 31, the P1 pole (N) is the developing pole, the peak magnetic force is 100 mT, the P2 pole (S) is the peak magnetic force 86MT, and the P3 pole (N) is the peak magnetic force. 52 mT, P4 pole (S) has a peak magnetic force of 70 mT, and P5 pole (S) has a peak magnetic force of 78 mT. In the present invention, the magnetic flux density can be arbitrarily set within a certain range. However, if the magnetic flux density is too high, torque increase and agent deterioration are promoted on the developing roller 31.

  The P4 and P5 poles of the included mag roller (not shown) are arranged in the same polarity to exert a repulsive force, and the centrifugal force generated by the rotation of the developing roller 31 is applied to complete separation from the developing roller 31.

In this embodiment, when the peripheral speed of the developing roller 31 is Vs and the peripheral speed Vp of the photosensitive member, it is desirable to adjust Vs / Vp so that it is in the range of 1.5 to 2.5.
The thin toner is conveyed to a position on the first electrode 24 as the developing belt 21 rotates. A voltage is applied to the first electrode 24 by a first voltage applying unit, and a voltage is applied to the second electrode 25 by a second voltage applying unit. The voltage applied by the first voltage applying means is most preferably a rectangular wave, but may be a sine wave or a triangular wave. In this embodiment, a rectangular wave voltage having a phase difference π is applied to the first electrode 24 and the second electrode 25, and an electric field is generated between the electrodes due to a potential difference caused by this phase difference. The toner that has reached the first electrode 24 by the developing belt 21 reciprocates while being hopped by this electric field. As a potential difference, 1500 V to 3000 V is generated. When the difference is smaller than 1500 V, the electric field between the electrodes becomes small, and the toner does not hop. If the difference is greater than 3000 V, leakage may occur between the electrodes over time. When the leak occurs, an electric field is not generated between the electrodes thereafter, and the toner does not hop. Usually, the frequency of the bias to be applied is 0.1 kHz to 10 kHz. If the frequency is lower than 0.1 kHz, toner hopping will not be achieved at the developing speed. When the frequency is higher than 10 kHz, the toner cannot follow the voltage switching. The central value of the voltage is varied between the image portion potential and the non-image portion potential depending on the development conditions.

  The hopped toner is developed on the photosensitive belt 6 by a developing electric field between the first electrode 24 and the second electrode 25 and the image portion on the photosensitive belt 6. The toner that has not contributed to the development is pulled back onto the development belt 21 by an electric field formed by the third electrode 26 to which a voltage is applied and the photosensitive belt 6. The pulled toner is conveyed by the rotation of the developing belt 21 and is collected from the developing belt 21 by a collecting roller (not shown). The collected toner is returned to the developer container and circulated in the developing device. The voltage applied to the third electrode 26 of this embodiment is -50V.

The coverage of the carrier with the toner is 10 to 80%, preferably 20 to 60%. The coverage is calculated by the following formula.
Coverage (%) = (Wt / Wc) × (ρc / ρt) × (Dc / Dw) × (1/4) × 100

  In the above formula, Dc is the carrier weight average particle diameter (μm), Dw is the toner weight average particle diameter (μm), Wt is the toner weight (g), Wc is the carrier weight (g), and ρt is the toner true The density (g / cm3) and ρc represent the true carrier density (g / cm3).

The weight average particle size is calculated based on the particle size distribution (relationship between the number frequency and the particle size) of the particles measured on the basis of the number. The weight average particle diameter Dw in this case is represented by the following formula.
Dw = {1 / Σ (nD3)} × {Σ (nD4)}

  In the above formula, D represents the representative particle size (μm) of particles present in each channel, and n represents the total number of particles present in each channel. The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram, and in the present embodiment, a length of 2 μm is adopted. Further, as the representative particle size of the particles existing in each channel, the lower limit value of the particle size stored in each channel was adopted.

  The developer applied to this embodiment has a toner weight average particle diameter of 4.0 to 8.0 μm, and a ratio (Dw) of the toner weight average particle diameter (Dw) to the number average particle diameter (Dn). / Dn) is desirably 1.20 or less. The reduction in toner particle size is indispensable for increasing the resolution, but as a side effect, fluidity and storage stability tend to deteriorate. When the toner particle diameter is less than 4.0 μm, the fluidity of the developer is extremely deteriorated, and it becomes difficult to ensure a uniform toner concentration in the developer. Further, the reduction in the toner particle diameter is a direction in which the coverage with respect to the carrier increases. When the coverage is excessively high, there is a concern that the carrier contamination is accelerated and the toner is scattered.

  As a means for improving the fluidity of the toner and the developer, there is a method of adding a large amount of additives to the toner. However, since a side effect occurs, an essential improvement cannot be expected. However, by making the particle size distribution of the toner uniform, the side effects associated with reducing the toner particle size are overcome. In other words, it is desirable that the weight average and number average particle diameter ratio Dw / Dn of the toner is close to 1. By making it 1.20 or less, the effect of suppressing the deterioration of fluidity can be obtained, and a small particle diameter toner is used. Even in this case, the toner density can be made uniform. As described above, the toner has a weight average particle diameter of 4.0 to 8.0 μm and a toner weight average / number average particle diameter ratio Dw / Dn of 1.20 or less, in addition to image density stability. Thus, the resolution is improved and a higher quality image can be obtained. Further, by making the ratio of the number of particles of 3 μm or less in the toner particle size distribution 5% or less, the quality improvement effect in fluidity and storage stability is remarkable, and in the toner replenishment property to the developing device and the toner charge rising property. A good level is obtained.

  The particle size distribution of the toner can be measured by various methods. In this embodiment, the toner particle size distribution is measured using a small hole passage method (Coulter counter method). As a measuring device, C0ULTERC0UNTERM0DELTA2 (manufactured by Coulter) was used, an interface for outputting the number distribution and volume distribution was connected, and an aperture (pore) of 100 μm was used. As a measuring method, first, a toner measurement sample is dispersed in a surfactant added to an electrolytic aqueous solution. The dispersed sample is injected into another 1% NaCl electrolysis solution, and a current is passed between the electrodes through the electrolyte in which the electrodes are placed on both sides of the aperture tube. The particle size distribution of 2 to 40 μm particles is measured from the resistance change at this time, and the number average particle diameter and the weight average particle diameter are obtained from the average distribution.

  It is preferable to add a fluidity imparting agent to the toner. Various fluidity-imparting agents that can be used are listed, and it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when both fine particles have an average particle size of 50 nm or less and are stirred and mixed, the electrostatic force and van der Waals force with the toner can be reduced, and the fluidity of the toner is improved. Can be planned. As a result, a desired charge level of the developer can be obtained, good image quality can be obtained, and transfer residual toner can be reduced. Further, the titanium oxide fine particles are excellent in environmental stability and image density stability, but tend to deteriorate the charge rising characteristics. Therefore, if the amount of titanium oxide fine particles added is larger than the amount of silica fine particles added, it is considered that the influence of deterioration of charging rise characteristics becomes large. However, when the addition amount of the hydrophobic silica fine particles is in the range of 0.3 to 1.5 (wt%) and the hydrophobic titanium oxide fine particles is in the range of 0.2 to 1.2 (wt%), the charge rising characteristics are large. Even if copying is repeated, stable image quality can be obtained and toner scattering can be suppressed.

  Further, by adding hydrophobic silica having a large particle diameter of 80 to 140 (nm) in average particle diameter, performance is further improved with respect to transferability and developability. In particular, the effect of improving the quality is remarkable in a developer using a toner having a small particle diameter such that the average particle diameter of the toner is 7 (μm) or less. That is, the additive having a large particle size acts as a spacer between the toner particles, and it is possible to suppress the toner aggregation at the time of toner transfer compression and the embedding of the additive on the toner surface at the time of empty stirring of the developing machine. As a result, solid image density unevenness due to transfer failure and toner fluidity decrease due to additive embedding do not occur, and a high-quality image can be obtained over a long period of time.

  The weight average particle diameter Dw of the carrier in the developer is 20 to 60 (μm), more preferably 20 to 40 (μm). When the weight average particle diameter Dw of the carrier is larger than 60 (μm), the magnetic carrier holding power on the photoconductor is strong and the carrier adhesion hardly occurs, but the carrier surface area per unit weight is small. When the toner concentration is increased to obtain a high image density, the scumming increases rapidly. In addition, when the dot diameter of the latent image is small, the variation in the dot diameter increases. On the other hand, when the weight average particle diameter Dw of the carrier is smaller than 20 μm, the magnetic moment per carrier particle is lowered, the magnetic carrier holding force on the developing sleeve is weakened, and carrier adhesion is likely to occur.

The magnetic moment per carrier particle when a magnetic field of 1000 · (103 / 4π) [A / m] is applied is 70 (A · m 2 / kg) or less. If the height is higher than this, the magnetic brush becomes hard and tends to have a trace or a blurred image. The lower limit is not particularly limited, but is usually about 50 (A · m 2 / kg). When the magnetic moment is less than 50 (A · m 2 / kg), the magnetic carrier holding force on the developing sleeve is reduced, and carrier adhesion is likely to occur.
The magnetic moment of the carrier can be measured as follows. Using a BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.), 1.0 g of carrier particles are packed in a cylindrical cell and set in an apparatus. The magnetic field is gradually increased to 3000 oersteds, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 oersteds. Further, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is illustrated, and the magnetic moment of 1000 oersted is calculated from the figure.

Examples of carrier core particles include ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li ferrite, Mn—Zn ferrite, Cu—Zn ferrite, Ni—Zn ferrite, Ba ferrite, and Mn. -Mg-Sr ferrite, Mn ferrite and the like. Ferrite is a sintered body generally represented by the following formula.
(M0) x (N0) y (Fe203) z
However, x + y + z = 100 mOl%, and M and N are Ni, Cu, Zn, Li, Mg, Mn, Sr, Ca, etc., respectively, and the divalent metal oxide and the trivalent iron oxide Consists of a complete mixture.

但し、式中、Ｒ１は水素原子、ハロゲン原子、ヒドロキシ基、炭素数１〜４の低級アルキル基、またはアリール基（フェニル基、トリル基など）を示す。Ｒ２は、炭素数１〜４のアルキレン基、またはアリーレン基（フェニレン基など）を示す。 Hereinafter, the carrier and toner materials used in the present embodiment will be described. First, the carrier used in the present embodiment is composed of magnetic core particles and a resin layer covering the surface. As the resin for forming this resin layer, a known resin conventionally used in the production of carriers can be used. For example, a silicone resin containing a repeating unit represented by the following chemical formula 1 can be preferably used for the resin layer of the carrier.

In the formula, R1 represents a hydrogen atom, a halogen atom, a hydroxy group, a lower alkyl group having 1 to 4 carbon atoms, or an aryl group (such as a phenyl group or a tolyl group). R2 represents an alkylene group having 1 to 4 carbon atoms or an arylene group (such as a phenylene group).

Examples of the straight silicone resin used for the resin layer of the carrier include KR271, KR272, KR282, KR252, KR255, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406 (manufactured by Toray Dow Corning Silicone). A modified silicone resin can be used for the resin layer of the carrier. Examples of such materials include epoxy-modified silicone, acrylic-modified silicone, phenol-modified silicone, urethane-modified silicone, polyester-modified silicone, and alkyd-modified silicone. Specific examples of the modified silicone resin include epoxy modified product: ES-1001N, acrylic modified silicone: KR-5208, polyester modified product: KR-5203, alkyd modified product: KR-206, urethane modified product: KR-305 ( As mentioned above, Shin-Etsu Chemical Co., Ltd.), epoxy modified product: SR2115, alkyd modified product: SR2110 (manufactured by Toray Dow Corning Silicone Co., Ltd.) and the like.
The silicone resin can contain an appropriate amount (0.001 to 30% by weight) of an aminosilane coupling agent. Examples of such a silicone resin include the following.
_{H 2 N (CH 2) 3Si} (0CH3) 3: MW179.3
_{H 2 N (CH 2) 3Si} (0C2H5) 3: MW221.4
_{H 2 NCH 2 CH 2 CH 2} Si (CH 3) 2 (0C 2 H 5): MW161.3
_{H 2 NCH 2 CH 2 CH 2} Si (CH 3) (0C 2 H 5) 2: MW191.3
_{H 2 NCH 2 CH 2 NHCH 2} Si (0CH 3) 3: MW194.3
_{H 2 NCH 2 CH 2 NHCH 2} CH 2 CH 2 Si (CH 3) (0CH 3) 2: MW206.4
_{H 2 NCH 2 CH 2 NHCH 2} CH 2 CH 2 Si (0CH 3) 3: MW224.4
_{(CH 3) 2 NHCH 2 CH} 2 CH 2 Si (CH 3) (0C 2 H 5) 2: MW219.4
_{(C 4 H 9) 2 NC} 3 H 6 Si (0CH 3) 3: MW291.6

  Furthermore, it is also possible to use for the resin layer of a carrier the thing shown below individually or in mixture with the said silicone resin. Polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, Styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer) Polymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, Styrene-phenyl methacrylate copolymer, etc.) Styrene resins such as styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylate ester copolymer, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, ketone resin, ethylene -Ethyl acrylate copolymer, xylene resin, polyamide resin, phenol resin, polycarbonate resin, melamine resin and the like.

  As a method for forming the resin layer on the surface of the core particles of the carrier, a known method such as a spray drying method, a dipping method, or a powder coating method can be applied. In particular, the method using a fluidized bed type coating apparatus is effective for forming a uniform coated film.

  The thickness of the resin layer formed on the surface of the carrier core particles is usually 0.02 to 1 μm, preferably 0.03 to 0.8 μm. Since the thickness of the resin layer is extremely small, the particle size distribution of the carrier made of core material particles covering the resin layer and the carrier core material particles is substantially the same.

Further, the resistivity of the carrier can be adjusted as necessary, and the resistivity of the carrier can be adjusted by adjusting the resistance of the coating resin on the core particle and controlling the film thickness. In order to adjust the carrier resistance, it is also possible to add conductive fine powder to the coating resin layer. As the conductive fine particles, conductive Zn0, metal or metal oxide powder such as Al, _Sn0 doped Sn0 ₂ or various elements were prepared in a variety of ways _{2, TiB 2, ZnB 2,} M0B 2 , etc. Borides, silicon carbide, polyacetylene, polyparaphenylene, poly (para-phenylene sulfide) polypyrrole, conductive polymers such as polyethylene, carbon black such as furnace black, acetylene black, and channel black. These conductive fine powders are uniformly dispersed by using a dispersing machine using a medium such as a ball mill or a bead mill or a stirrer equipped with high-speed rotating blades after being put into a solvent used for coating or a resin solution for coating. can do.

  The toner applied to the exemplary embodiment includes at least a binder resin, a colorant, a release agent, and a charge control agent. This toner is an amorphous or spherical toner prepared by various toner manufacturing methods such as a polymerization method and a granulation method. Either magnetic toner or non-magnetic toner can be used.

  As the toner binder resin used here, all those conventionally used as toner binder resins are applicable. Specifically, homopolymers of styrene such as polystyrene, polychlorostyrene, and polyvinyltoluene, and substituted products thereof; styrene / p-chlorostyrene copolymer, styrene / propylene copolymer, styrene / vinyltoluene copolymer, styrene / Vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / octyl acrylate copolymer, styrene / methyl methacrylate copolymer Styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / vinyl ethyl ether copolymer, styrene / Vinyl methyl ketone copolymer, styrene / Styrene copolymer such as styrene / butadiene copolymer, styrene / isoprene copolymer, styrene / acrylonitrile / indene copolymer, styrene / maleic acid copolymer, styrene / maleic acid ester copolymer; polymethyl methacrylate, Polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyvinyl butyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic Base petroleum resin, chlorinated paraffin, paraffin wax and the like, and these may be used alone or in admixture of two or more.

Here, as the colorant of the toner, dyes and pigments capable of obtaining toners of each color of yellow, magenta, cyan, and black can be used, and all pigments and dyes that have been conventionally used as toner colorants can be applied. It is. Specifically, nigrosine dye, aniline blue, calco oil blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, phthalocyanine green, Hansa Yellow G rhodamine 6C lake, chrome yellow, quinacridone, benzidine yellow, malachite green, malachite Examples thereof include green hexalate, rose bengal, monoazo dye / pigment, disazo dye / pigment, and trisazo dye / pigment. The amount of these colorants to be used is generally 1-30 wt%, preferably 3-20 wt%, relative to the binder resin.
As the toner charge control agent, either a positive charge control agent or a negative charge control agent can be used. In the case of a color toner, a transparent to white one that does not impair the color tone is used. Is preferred. For example, quaternary ammonium salts, imidazole metal complexes, salts, and the like are used as positive polarity, and salicylic acid complexes, salts, organic boron salts, calixarene compounds, and the like as negative polarity.

Further, in order to give the toner releasability, plant waxes such as candelilla wax, carnauba wax, rice wax, wax, jojoba oil, as well as synthetic waxes such as low molecular weight polyethylene and polypropylene; Animal waxes such as beeswax, lanolin and whale wax; mineral waxes such as montan wax and ozokerite; fat waxes such as hardened castor oil, hydroxystearic acid, fatty acid amide, phenol fatty acid ester, etc. These can be used alone or in admixture of two or more.
In addition to the above release agents, the toner contains various plasticizers (dibutyl phthalate, dioctyl phthalate, etc.), resistance, and the like for the purpose of adjusting the thermal, electrical and physical properties of the toner as required. It is also possible to add auxiliaries such as adjusting agents (tin oxide, lead oxide, antimony oxide, etc.). Furthermore, fluidity-imparting agents other than the above releasing agents and auxiliaries can be mixed with the toner as necessary. Examples of the fluidity-imparting agent include silica fine particles, titanium oxide fine particles, aluminum oxide fine particles, magnesium fluoride fine particles, silicon carbide fine particles, boron carbide fine particles, titanium carbide fine particles, zirconium carbide fine particles, boron nitride fine particles, titanium nitride fine particles, nitriding. Zirconium fine particles, magnetite fine particles, molybdenum disulfide fine particles, aluminum stearate fine particles, magnesium stearate fine particles, zinc stearate fine particles, fluorine resin fine particles, acrylic resin fine particles, and the like can be mentioned alone or in combination of two or more. Is possible. The fluidity-imparting agent preferably has a primary particle size of less than 0.1 μm and a hydrophobization degree of 40 or more whose surface is hydrophobized with a silane coupling agent or silicon oil.

  A known method is used as a method for producing the toner. For example, a binder resin, a colorant and a pigment, a charge control agent, and if necessary, a release agent and the like are sufficiently mixed using a mixing machine such as a Henschel mixer and a ball mill at an appropriate ratio. Then, melt-kneading is performed using a screw-type extrusion continuous kneader, a two-roll mill, a three-roll mill, or a pressure heating kneader. In the case of a color toner, for the purpose of improving the dispersibility of the pigment, it is common to use, as a colorant, a master batch pigment obtained by previously melt-kneading a part of the binder resin and the pigment. The kneaded product obtained by the above method is cooled and solidified, and then coarsely pulverized using a pulverizer such as a hammer mill. Further, the coarsely pulverized product is pulverized with a jet mill pulverizer and then subjected to surface treatment using a rotor pulverizer connected to an airflow classifier or the like. For example, examples of the collision pulverizer include a hammer mill, a ball mill, a tube mill, and a vibration mill. I-type and IDS type collision type crushers (manufactured by Nippon Pneumatic Industrial Co., Ltd.) are preferably used as jet type crushers equipped with compressed air and a collision plate as main components. Examples of the rotor pulverizer include a roll mill, a pin mill, and a fluidized bed jet mill. In particular, as a rotor type pulverizer having a fixed container as an outer wall and a rotating piece having the same central axis as that of the fixed container, turbo mills (manufactured by Turbo Kogyo Co., Ltd.), kryptron (manufactured by Kawasaki Heavy Industries, Ltd.) Fine mill (manufactured by Nippon Pneumatic Industry Co., Ltd.) can be used. As the connected classifier, a dispersion separator (DS) classifier (manufactured by Nippon Pneumatic Kogyo Co., Ltd.), a multi-division classifier (Elbow Jet; manufactured by Nittetsu Mining Co., Ltd.) or the like can be used. Furthermore, fine powder classification can be performed using an airflow classifier or a mechanical classifier to obtain fine particles.

  Furthermore, when adding and mixing a fluidity-imparting agent to the fine particles obtained by the above method, known equipment such as a Henschel mixer, a super mixer, and a ball mill can be used. Alternatively, a toner may be directly produced from a monomer, a colorant and a fluidity imparting agent by a suspension polymerization method or a non-aqueous dispersion polymerization method.

Next, another embodiment of the present invention will be described with reference to FIG.
A process cartridge PC shown in FIG. 3 is obtained by integrating a charging device 41, a developing device 9, and a cleaning device. The process cartridge PC is detachable from the image forming apparatus main body, and the developing device 9 having the same configuration as that of the above embodiment is employed.

  In the image forming apparatus having the process cartridge PC, the photosensitive belt 6 is rotationally driven at a predetermined peripheral speed. In the rotating process, the photosensitive belt 6 is uniformly charged with a predetermined positive or negative potential on its peripheral surface by the charging device 41, and then receives image exposure light from image exposure means such as slit exposure or laser beam scanning exposure. Then, an electrostatic latent image is sequentially formed on the peripheral surface of the photosensitive belt 6, and the formed electrostatic latent image is developed with toner by the developing device 9, and the developed toner image is supplied to a paper feeding unit (not shown). To the recording belt P fed in synchronization with the rotation of the photosensitive belt 6 between the developing belt 21 and a paper conveying belt (not shown).

  The recording medium P that has received the image transfer is separated from a paper conveying belt (not shown), introduced into an image fixing means (not shown), and fixed on the image, and printed out as a copy (copy). . The surface of the photoreceptor belt 6 after the image transfer is cleaned by removing the transfer residual toner by the cleaning device 42, and after being further neutralized, it is repeatedly used for image formation.

According to this embodiment, the process cartridge PC can be detached independently and can be easily replaced separately.
Examples of the present invention will be described below, but the present invention is not limited to these examples.

The machine conditions for a full-color printer are as follows.
Photoconductor belt linear velocity 246 (mm / sec)
Development belt / photosensitive belt linear speed ratio 1.6
Developing roller / developing belt linear speed ratio 1.6
Gp (gap between developing roller and developing belt 21) 0.3 (mm)
Gp (gap between developing belt and photosensitive belt 6) 0.3 (mm)
Gd (Developing roller-Doctor Gap) 0.3 (mm)
Developer pumping amount 30 (mg / cm ² )
Roller diameter φ16 (mm)
Main pole angle 3 °
Main pole magnetic flux density 100 (mT)
Non-image part potential V0-600 (V)
Post-exposure potential VL-100 (V)
Development bias VB (DC component) -850 (V)
VPP (AC component) 1500 (V)
Frequency 700 (Hz)

  ΔID is used as an evaluation standard representing the degree of toner scattering. Here, a method for measuring ΔID will be described. First, non-image formation is performed on the photosensitive belt under the above conditions, and toner attached to the non-image is collected using a printer. Next, the ID of the collected printer pack and the new printer pack with no toner attached are measured, and the difference is calculated. The numerical value obtained in this way is called ΔD. Here, the quality of toner scattering was determined by setting the granularity to 0.01 or less as ◯, 0.02 to 0.04 as Δ, and 0.05 or more as x. In addition, X-Lite (made by AMTEC) was used for the density | concentration measurement.

（比較例１） The results are shown in Table 1.

(Comparative Example 1)

In the first embodiment, the latent image carrier and the toner carrier are formed into a cylindrical shape, thereby developing the generation position of the turbulence generated by the collision between the airflow created by the toner carrier and the airflow created by the latent image carrier. The same operation as in Example 1 was performed except that the nip was not performed.
(Comparative Example 2)

Example 1 was carried out in the same manner as Example 1 except that the toner was hopped over the entire area of the toner carrier.
(Comparative Example 3)

In Example 1, it carried out like Example 1 except not using a 3rd electrode.
(Comparative Example 4)
In Example 1, the same procedure as in Example 1 was performed except that the weakly charged toner was increased without using the two-component developing unit.
(Comparative Example 5)

  Example 1 was carried out in the same manner as Example 1 except that the turbulent airflow generation position was before the development nip, the toner was hopped over the entire toner carrier, and the third electrode was not used, but weakly charged toner was increased.

6 Photosensitive Belt 20 Developing Belt Device 21 Developing Belt 24 First Electrode 25 Second Electrode 26 Third Electrode 27 Fourth Electrode 30 Two-component Developing Unit 31 Developing Roller

JP 2007-133388 A JP 2002-341656 A

Claims (5)

Formed into a plurality of plates arranged at equal intervals in a row, with a toner carrier that holds toner for developing the electrostatic latent image formed on the latent image carrier and is disposed opposite the latent image carrier And a plate-like second electrode arranged in parallel with the first electrode row, and applying an electric voltage to these electrodes causes the toner to hop to form an electrostatic latent image. In the developing device for developing,
A belt is used as the latent image carrier and the toner carrier, and the toner carrier belt and the latent image carrier belt are arranged so as to form a parallel nip between the mutually facing surfaces.
A developing device comprising the first electrode and the second electrode in an intermediate region in the belt running direction at the nip of the parallel surfaces, facing the latent image carrier belt with the toner carrier belt interposed therebetween. .   2. The developing device according to claim 1, further comprising a third electrode facing the latent image carrier belt with the toner carrier belt interposed therebetween, wherein the third electrode is in the nip of the parallel surface and in the belt running direction. A developing device, which is disposed downstream of the first electrode and applies a voltage that always attracts toner.   3. The developing device according to claim 1, further comprising a two-component developing unit that supplies toner to the toner carrier belt, and the two-component developer unit faces the toner carrier belt in front of a nip of the parallel surface. A developing device comprising: a developing roller disposed at the position; and a fourth electrode disposed opposite the developing roller with the toner carrier belt interposed therebetween to supply toner to the toner carrier belt.   4. At least one of the latent image carrier, a charging device that uniformly charges the latent image carrier, and a cleaning device that removes toner remaining on the latent image carrier after the transfer of a toner image; and A process cartridge, wherein the developing cartridge is integrated with the developing device according to the above, and is detachable from the main body of the image forming apparatus.   An image forming apparatus comprising a plurality of developing devices according to claim 1 or a plurality of process cartridges according to claim 4.

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