JP6981171B2 - A developing device and an image forming device equipped with the developing device. - Google Patents

Description

The present invention relates to a developing apparatus and an image forming apparatus including the developing apparatus, and more particularly to a two-component developing type developing apparatus using a two-component developing agent containing a magnetic carrier and a toner, and an image forming apparatus provided thereof. ..

In the image forming apparatus, a latent image formed on an image carrier made of a photoconductor or the like is developed by a developing apparatus and visualized as a toner image. As such a developing device, a two-component developing type developing device using a two-component developing agent containing a magnetic carrier and toner is used.

The two-component developing type developing apparatus includes a developing container for accommodating a developing agent, a first stirring and transporting member and a second stirring and transporting member for stirring and transporting the developer, and a developer supplied from the second stirring and transporting member. A developing apparatus including a developing roller (developer carrier) for carrying the developing roller is known. The first stirring and transporting member transports the developer to one side in the axial direction of the developing roller, and the second stirring and transporting member supplies the developer to the developing roller while transporting the developer to the other side (opposite to one side). do. The developer is mixed and conveyed by a stirring unit in the developer and pumped onto a developing roller to form a magnetic brush. The layer thickness of the magnetic brush is regulated by a regulating member, and the toner in the magnetic brush reveals an electrostatic latent image on the photoconductor by the developing electric field. The toner that has not been used for development is collected from the developing roller, sent to the stirring unit, mixed and conveyed with the newly supplied toner, and used again for development.

In a conventional developing apparatus as described above, a portion for separating a developing agent used for developing a high image area from a developing sleeve and collecting it on a developing agent transport member (screw) and a new developing agent on the developing sleeve. Since the part to be pumped up and supplied is relatively close, the developer that has been separated and recovered will be pumped up and supplied to the developing sleeve again, and will be used for development without being replenished with new toner, resulting in uneven image density. There was a problem that it would end up. Further, when new toner is replenished to a portion where the amount of the developer is small, a portion where the replenishment toner concentration is locally high is generated. Since the replenishing toner is not sufficiently mixed with the carrier and the amount of charge is low, a fog image or uneven image density occurs when a portion having a high replenishing toner concentration is used for development.

Therefore, various methods have been proposed in which the developer in the developing apparatus and the replenishing toner are sufficiently mixed. For example, in Patent Document 1, a detour transport for stirring is performed separately from the developing agent supply section and the recovery section. Disclosed is a developing apparatus in which a section is provided to improve the mixing and dispersion of the recovered developer whose density has been reduced by a stirring means and the replenished toner, and to make the image density uniform. Further, the toner used in the developing apparatus has a volume average particle size of 3 to 8 μm, and the ratio (Dv / Dn) of the volume average particle size (Dv) to the number average particle size (Dn) is 1.00 to 1. It is also stated that it is in the range of 40.

According to the method of Patent Document 1, the toner concentration (weight ratio of the toner to the carrier) is detected accurately even in the toner having slightly inferior mixing and dispersibility, so that the density unevenness of the toner in the developing agent and the resulting image are obtained. It is possible to suppress density unevenness.

Japanese Unexamined Patent Publication No. 2008-203705

The toner carried on the carrier is restrained from moving in the magnetic brush on the developing roller and receives a large force, while the toner is freely moved in the stirring portion, so that the force received is small. As the toner circulates between the developing roller and the stirring part, the change in the contact distance between the toner and the carrier causes a change in the capacitance of the contact surface, and the amount of charge increases on the developing roller where the capacitance increases. In the stirring section where the capacitance decreases, it is relaxed and the amount of charge decreases. As a result, when new toner is replenished in the stirring part where the charge of the stagnant toner in the developer is being relaxed, it becomes easier to receive electrons from the replenished toner, and electrostatic action between the toner particles occurs. There was a risk of poor charging of the toner.

In view of the above problems, the present invention is a developing apparatus capable of sufficiently stirring the toner in the developing agent recovered from the developing agent carrier so that the charge relaxation of the toner occurs efficiently, and an image forming apparatus provided with the same. The purpose is to provide the device.

In order to achieve the above object, the first configuration of the present invention is a developing apparatus including a developing container, a developer carrier, a toner supply port, a first transport path, and a second transport path. .. The developing container contains a two-component developer containing a carrier and toner. The developer carrier is rotatably supported by the developing container and supports the developer in the developing container on the surface. The toner supply port is provided in the developing container and supplies toner into the developing container. The first transport path transports the developer from the toner supply port to the developer carrier. The second transport path transports the developer from the developer carrier to the toner supply port. When the transport path length of the first transport path is the first transport path length L1, the transport path length of the second transport path is the second transport path length L2, and the axial length of the developer carrier is X, the following formula is used. (1), (2)
L2 ≧ 2X ・ ・ ・ (1)
L1 ≧ X ... (2)
Meet.

According to the first configuration of the present invention, the developer peeled off from the developer carrier by satisfying the second transport path length L2 and the axial length X of the developer carrier L2 ≧ 2X. It is conveyed while being agitated for a sufficient distance to the position of the toner supply port. Therefore, it is possible to secure the charge relaxation time of the retained toner, and it is possible to suppress the toner scattering due to the insufficiently charged toner and the occurrence of the background fog due to the back-charged (negatively charged) toner. Further, when the first transport path length L1 and the axial length X of the developer carrier satisfy L1 ≧ X, the replenished toner replenished from the toner replenishment port is stirred at a sufficient distance to the developer carrier. Be transported. Therefore, it is possible to suppress the occurrence of charging defects due to insufficient dispersion of toner.

Schematic cross-sectional view showing the overall configuration of the color printer 100 provided with the developing devices 3a to 3d of the present invention. Side sectional view showing the structure of the developing apparatus 3a according to the embodiment of the present invention. A plan sectional view showing the structure of the third transport chamber 22c and the fourth transport chamber 22d of the developing apparatus 3a of the present embodiment. A graph showing the Q / S relationship when plotting with the cumulative value of the surface area S per toner particle on the horizontal axis and the cumulative value of the charge amount Q per toner particle on the vertical axis.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a color printer 100 provided with the developing devices 3a to 3d of the present invention, and here shows a tandem color printer. In the main body of the color printer 100, four image forming portions Pa, Pb, Pc and Pd are arranged in the order of Pd to Pa from the upstream side in the transport direction (right side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (black, yellow, magenta, and cyan), and are cyan, magenta, and yellow, respectively, depending on each step of charging, exposure, development, and transfer. And black images are formed sequentially.

Photoreceptor drums 1a, 1b, 1c and 1d carrying visible images (toner images) of each color are disposed of these image forming portions Pa to Pd, respectively, and are further rotated clockwise in FIG. An intermediate transfer belt 8 is provided adjacent to each image forming portion Pa to Pd.

When image data is input from a host device such as a personal computer, first, the surfaces of the photoconductor drums 1a to 1d are uniformly charged by the chargers 2a to 2d. Next, the exposure apparatus 5 irradiates light according to the image data to form an electrostatic latent image corresponding to the image data on the photoconductor drums 1a to 1d. The developing devices 3a to 3d are filled with a predetermined amount of a two-component developer (hereinafter, also simply referred to as a developing agent) containing toners of black, yellow, magenta, and cyan by toner containers 4a to 4d. The toner in the developer is supplied onto the photoconductor drums 1a to 1d by 3a to 3d and adheres electrostatically. As a result, a toner image corresponding to the electrostatic latent image formed by the exposure from the exposure apparatus 5 is formed.

Then, an electric field is applied between the primary transfer rollers 6a to 6d and the photoconductor drums 1a to 1d at a predetermined transfer voltage by the primary transfer rollers 6a to 6d, and black, yellow, magenta and magenta on the photoconductor drums 1a to 1d are applied. The cyan toner image is primarily transferred onto the intermediate transfer belt 8. Toner and the like remaining on the surfaces of the photoconductor drums 1a to 1d after the primary transfer are removed by the cleaning devices 7a to 7d.

The transfer paper P on which the toner image is transferred is housed in a paper cassette 16 arranged at the lower part of the color printer 100, and the transfer paper P is moved at a predetermined timing via the paper feed roller 12a and the resist roller pair 12b. It is conveyed to the secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8 and the nip portion (secondary transfer nip portion) of the intermediate transfer belt 8. The transfer paper P on which the toner image is secondarily transferred is conveyed to the fixing portion 13.

The transfer paper P conveyed to the fixing portion 13 is heated and pressurized by the fixing roller pair 13a to fix the toner image on the surface of the transfer paper P, and a predetermined full-color image is formed. The transfer paper P on which the full-color image is formed is discharged to the discharge tray 17 as it is (or after being distributed to the reverse transfer path 18 by the branch portion 14 and the images are formed on both sides) by the discharge roller pair 15.

FIG. 2 is a side sectional view showing a configuration of a developing device 3a according to an embodiment of the present invention mounted on the color printer 100. FIG. 3 is a plan sectional view (YY'arrow cross-sectional view of FIG. 2) showing the structures of the third transport chamber 22c and the fourth transport chamber 22d of the developing apparatus 3a. Although the developing device 3a arranged in the image forming unit Pa of FIG. 1 will be described here, the configuration of the developing devices 3b to 3d arranged in the image forming units Pb to Pd is basically the same. Is omitted. Further, FIG. 2 shows a state in which the developing device 3a is viewed from the back surface side of FIG. 1, and the arrangement of each member in the developing device 3a is reversed from that of FIG.

As shown in FIG. 2, the developing apparatus 3a includes a developing roller (developer carrier) 20, a developing container 21, a regulating blade 25, and five stirring transfer screws 42a to 42e. The developing container 21 constitutes the outer shell of the developing device 3a, and the inside is partitioned into the first transport chamber 22a to the fifth transport chamber 22e by the partition portion 23. A two-component developer composed of a carrier and toner is housed in the developing container 21. Further, the developing container 21 rotatably holds the developing roller 20, the regulating blade 25, and the stirring and transporting screws 42a to 42e.

The developing roller 20 includes a fixed shaft (not shown) and a developing sleeve 20a. A magnet (not shown) having a plurality of magnetic poles is fixed to the fixed shaft, and the developing sleeve 20a is rotatably held. In the vicinity of the developing sleeve 20a, a regulating blade 25 is provided which is arranged at a predetermined distance from the developing sleeve 20a and regulates the layer thickness of the magnetic brush on the surface of the developing sleeve 20a. The developing sleeve 20a is rotated in the arrow direction (counterclockwise direction) in FIG. 2 by a drive mechanism including a motor and gears (not shown). Further, a developing voltage obtained by superimposing an AC voltage on a DC voltage is applied to the developing sleeve 20a.

When the developing sleeve 20a to which the developing voltage is applied rotates in the counterclockwise direction of FIG. 2, the toner carried on the surface of the developing sleeve 20a is caused by the potential difference between the potential of the developing sleeve 20a and the potential of the exposed portion of the photoconductor drum 1a. Is supplied to the photoconductor drum 1a. The toner sequentially adheres to the exposed portion on the photoconductor drum 1a that rotates in the clockwise direction, and the electrostatic latent image on the photoconductor drum 1a is developed.

The stirring transfer screws 42a to 42e are provided in the first transfer chamber 22a to the fifth transfer chamber 22e, respectively. The stirring and transporting screws 42a to 42e stir the developer to charge the toner in the developer to a predetermined level. This holds the toner in the carrier.

As shown in FIG. 3, a communication portion 23a is provided at one end in the longitudinal direction (left end in FIG. 3) of the partition portion 23 that partitions the third transport chamber 22c and the fourth transport chamber 22d. Further, one end of the partition portion 23 that partitions the first transport chamber 22a and the second transport chamber 22b (the front side of the paper in FIG. 2), and one end of the partition portion 23 that partitions the first transport chamber 22a and the fifth transport chamber 22e. A communication portion 23a is also formed in the portion (the back side of the paper surface in FIG. 2). As a result, the developer circulates in the first transport chamber 22a to the fifth transport chamber 22e. Then, the developer is supplied to the developing roller 20 from the stirring transfer screw 42b arranged in the second transfer chamber 22b, and a magnetic brush is formed on the developing roller 20.

Further, at one end (left end in FIG. 3) of the first transport chamber 22a, a toner replenishment port 30 for replenishing toner is provided in the developing container 21. A toner supply path (not shown) connected to the toner container 4a (see FIG. 1) is connected to the toner supply port 30. The toner replenished from the toner replenishment port 30 is mixed with the developer in the first transport chamber 22a and the second transport chamber 22b and supplied to the developing roller 20 while being stirred. The transport path from the toner supply port 30 to the developing roller 20 is referred to as a first transport path A (indicated by a white arrow in FIG. 3), and the transport path length of the first transport path A is referred to as a first transport path length L1. .. Since the second transport chamber 22b faces the developing roller 20, the first transport path L1 is specifically the length of the first transport chamber 22a.

On the other hand, the developer on the developing roller 20 that was not used for development is peeled off from the developing roller 20 and collected in the third transport chamber 22c. Then, when the stirring and transporting screws 42c and 42d rotate, the developer in the third transporting chamber 22c is transported in one direction (from right to left in FIG. 3) and passes through the communication portion 23a provided in the partition portion 23. Is transported to the fourth transport chamber 22d. Then, the developer in the fourth transport chamber 22d is transported in the opposite direction (from left to right in FIG. 3), and from the opening 24 formed at the end opposite to the communication portion 23a into the fifth transport chamber 22e. Fall into.

The developer in the fifth transfer chamber 22e is conveyed in one direction (from the front to the back in FIG. 2) by the stirring transfer screw 42e, and joins one end of the first transfer chamber 22a in which the toner supply port 30 is formed. The transport path from the developing roller 20 to the toner supply port 30 is referred to as a second transport path B (indicated by the black arrow in FIGS. 2 and 3), and the transport path length of the second transport path B is the second transport path length. It is called L2. Specifically, the second transport path L2 is the total length of the third transport chamber 22c to the fifth transport chamber 22e.

As described above, the toner carried on the carrier is restricted in movement (subjects magnetic binding force) in the magnetic brush on the developing roller 20, so that the toner passes through the regulating blade 25 (regulating portion). The physical stress you receive increases. On the other hand, since the toner can move freely in the first transport chamber 22a to the fifth transport chamber 22e (stirring unit), the physical stress received by the toner is reduced. Therefore, the contact distance between the toner particles and the carrier particles differs between the regulating portion and the stirring portion, and the capacitance of the toner and the carrier increases in the regulating portion. Further, in the regulation section, deterioration and deterioration of the toner external additive existing on the toner surface also occur. As a result, the ionization potential of the toner itself is lower in the regulation section than in the stirring section.

That is, when the toner existing in the developing container 22 (hereinafter referred to as stagnant toner) circulates between the regulating portion and the stirring portion, the change in the contact distance between the toner particles and the carrier particles causes static electricity on the contact surface between the carrier and the toner. In the regulation part where the electrostatic capacity increases due to the change in the electric capacity, the charge progresses and the charge amount increases, and in the stirring part where the electrostatic capacity decreases, the charge is relaxed and the charge amount decreases.

Therefore, the toner newly replenished from the toner container 4a (hereinafter referred to as replenishment toner) exchanges electrons with the carrier, and at the same time, the ionization potential is lowered to easily receive the electrons. Electronic transfer is also performed between.

Specifically, when the toner is replenished from the toner replenishment port 30 in the first transport chamber 22a where the relaxation of the charge of the retained toner in the developer is progressing, the replenishment toner imparts electrons to the carrier and is charged. Although it is (positively charged), electrons are also applied from the replenishing toner to the stagnant toner. As a result, the amount of positive charge of the retained toner is reduced, and toner scattering due to insufficiently charged toner and background fog due to back-charged (negatively charged) toner occur.

Therefore, in the developing apparatus 3a of the present embodiment, the charge relaxation time of the retained toner is secured by setting the second transport path length L2 to a certain length or more. Specifically, when the length of the developing roller 20 in the axial direction (longitudinal direction) is X, the following equation (1)
L2 ≧ 2X ・ ・ ・ (1)
The second transport path length L2 is determined so as to satisfy the above conditions.

According to this configuration, the developer on the developing roller 20 peeled off from the developing roller 20 is conveyed to the position of the toner supply port 30 while being stirred at a sufficient distance. Therefore, it is possible to secure the charge relaxation time of the retained toner, and it is possible to suppress the toner scattering due to the insufficiently charged toner and the occurrence of the background fog due to the back-charged (negatively charged) toner.

Further, when the replenishing toner replenished in the developing container 22 from the toner replenishing port 30 is supplied to the developing roller 20 without being sufficiently agitated with the stagnant toner, the charged amount of the replenishing toner does not sufficiently increase and the toner scatters. And the skin fog occurs. Therefore, it is necessary that the first transport path length L1 and the axial length X of the developing roller 20 satisfy the following equation (2).
L1 ≧ X ... (2)

In the present invention, as described above, the toner whose charge amount has increased due to a large physical stress (increased capacitance due to a decrease in the distance between the toner particles and the carrier particles) applied to the developer in the regulated blade 25 (regulated portion) can be obtained. This is intended to promote charge relaxation when the second transport path B from the developing roller 20 to the toner supply port 30 is transported. The electrical characteristics of the developer affect this charge relaxation. It is known that the charge relaxation phenomenon of toner and carriers in the developer occurs exponentially, and the time constant, which is the rate constant of the exponential function, is proportional to 1 / tan δ. That is, if the tan δ of the toner and the carrier is too small, charge relaxation does not occur, and if it is too large, it is not necessary to extend the relaxation path (second transport path B). When the time constant is τ, the process of decaying the charge amount Q is shown by the following equation (3) as a function of time t.
Q = Qmax ^* exp (-t / τ) ・ ・ ・ (3)

In the developing devices 3a to 3d of the present invention, 1V of the dielectric loss tan θt of the toner is set so that the developing agent does not easily change the charge amount due to the change in physical stress depending on the location (position) in the developing container 22. It is preferable to use a developing agent having a measured value of 0.005 to 0.01 at 100 kHz and a carrier dielectric loss tan θc of 0.05 to 0.2 at 1 V and 100 kHz. By using such a toner and a carrier, the toner and the carrier can hold a necessary and sufficient charge amount at any place in the developing container 22.

Others The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, an example of supplying a developer to the developing roller 20 from the stirring transfer screw 42b has been shown, but the present invention is not limited to this. A developer carrier such as a magnetic roller is further provided between the stirring and transporting screw 42b and the developing roller 20, and after supplying the developing agent from the stirring and transporting screw 42b to the magnetic roller and the like, toner is applied to the developing roller 20 from the magnetic roller and the like. May be supplied. In this case, the transport path from the toner supply port to the magnetic roller is the first transport path, and the transport path from the magnetic roller to the toner supply port is the second transport path.

Further, the present invention is not limited to the tandem color printer 100 shown in FIG. 1, and the developer is transferred from the toner supply port 30 to the developing roller 20 of a digital or analog monochrome copier, a color copier, a facsimile, etc. It can be applied to various image forming devices including a developing device including a first transport path A for transporting the developer and a second transport path B for transporting the developer from the developing roller 20 to the toner supply port 30. Hereinafter, the effects of the present invention will be described in more detail with reference to Examples.

The relationship between the ratio of the second transport path length L2 from the developing roller 20 to the toner supply port 30 and the axial length X of the developing roller 20 and the toner charge amount was investigated. As a testing machine, a color multifunction device (TASKalfa2552ci, manufactured by Kyocera Document Solutions Co., Ltd.) equipped with the developing devices 3a to 3d shown in FIG. 2 was used. When the ratio of the second transport path length L2 to the axial length X of the developing roller 20 is 3: 1 (L2 = 3X) and 2: 1 (L2 = 2X) (the present inventions 1 and 2). The ratio of the second transport path length L2 to the axial length X of the developing roller 20 is 1.5: 1 (L2 = 1.5X), 1: 1 (L2 = 1X), 0.2: X. In the case of (L2 = 0.2X) (Comparative Examples 1 to 3), the charge amount distribution of the toner was compared. In the present inventions 1 and 2 and Comparative Examples 1 to 3, the relationship between the first transport path length L1 from the toner supply port to the developing roller and the axial length X of the developing roller 20 is L1 = X.

The developer is a two-component developer consisting of a positively charged toner having an average particle size of 6.5 μm and a ferrite carrier having an average particle size of 35 μm, and the carrier ratio (weight ratio, T / C) to the toner is 8. %. The toner and carrier tan δ (measured values at 1 V and 100 kHz) were 0.01 and 0.15, respectively. The amount of the developer charged into the developing apparatus 3a is 720 g for the present invention 1 (L2 = 3X), 590 g for the present invention 2 (L2 = 2X), and Comparative Example 1 (L2) in consideration of the second transport path length L2. = 1.5X) was 520 g, Comparative Example 2 (L2 = 1X) was 450 g, and Comparative Example 3 (L2 = 0.2X) was 300 g.

As a test method, a pattern of three character images having a printing rate of 1% was continuously printed 500 times in an environment of 20 ° C. and 65% RH. In this state, the change in the charge amount in the second transport path B from the developing roller 20 to the toner supply port 30 was actually measured, and the relationship between the second transport path length L2 and the average charge amount of the toner was simulated. After that, 100 sheets of a document having a printing rate of 30% were continuously printed, and the spread of the charge amount distribution (Q / S deviation; relative average deviation) when the toner was replenished at a printing rate equivalent to 50% was simulated.

The toner charge amount was measured by fixing 5 mg of the developer on a neodymium magnet and measuring under the following conditions. The Q / S for each particle is calculated using the obtained charge amount Q per particle and the particle diameter D, sorted in order from the smallest value of Q / S, and 1 on the horizontal axis as shown in FIG. The cumulative value of the surface area S per particle was taken, and the cumulative value of the charge amount Q per particle was taken on the vertical axis and plotted (curve R1 in FIG. 4). Then, let R2 be a straight line representing an ideal state in which the Q / S of each particle is constant, let A be the area of the region surrounded by R1 and R2, and let B be the area of the region surrounded by R1 and the X axis. , The deviation from R2 (Q / S deviation) is shown by the ratio of A to A + B. This Q / S deviation was calculated as an index showing the degree of background fog and toner scattering.

The evaluation criteria were ◯ when the Q / S deviation was less than 25%, Δ when the Q / S deviation was 25% or more and less than 30%, and × when the Q / S deviation was 30% or more. The evaluation results are shown in Table 1 together with the average charge amount and the Q / S deviation.

As is clear from Table 1, in the developing apparatus 3a of the present inventions 1 and 2 in which the second transport path length L2 is at least twice the axial length X of the developing roller 20 (L2 ≧ 2X), the average charging amount is respectively. Was 26.7 μC / g and 28.3 μC / g, and the charging of the toner in the second transport path B was suppressed. Further, the Q / S deviations were 20.3% and 21.2, respectively, and it was confirmed that the background fog and toner scattering were suppressed.

On the other hand, in the developing devices 3a of Comparative Examples 1 to 3 in which the second transport path length L2 is less than twice the axial length X of the developing roller 20 (L2 <2X), the average charge amount is 31.6 μC, respectively. It was / g, 32.7 μC / g, and 34.2 μC / g, and the amount of charge of the toner increased in the second transport path B. In addition, the Q / S deviations were 28.7%, 33.7%, and 35.7%, respectively, and it was confirmed that background fog and toner scattering occurred.

INDUSTRIAL APPLICABILITY The present invention can be used in a two-component developing type developing apparatus using a two-component developing agent containing a magnetic carrier and a toner. By utilizing the present invention, a developer capable of sufficiently stirring the toner in the developer recovered from the developer carrier and an image forming apparatus provided with the same can be provided so that the charge of the toner can be alleviated efficiently. can do.

3a-3d developing device 20 developing roller (developer carrier)
21 Development container 22a 1st transport room 22b 2nd transport room 22c 3rd transport room 22d 4th transport room 22e 5th transport room 23 Partition 25 Restriction blade 30 Toner supply port 42a to 42e Stirring transport screw 100 Color printer (image formation) Device)
A 1st transport route B 2nd transport route

Claims (3)

A developing container containing a two-component developer containing a carrier and toner,
A developer carrier that is rotatably supported by the developing container and supports the developer in the developing container on the surface, and a developer carrier.
A toner supply port provided in the developing container and supplying toner into the developing container,
A first transport path for transporting the developer from the toner supply port to the developer carrier,
In a developing apparatus provided with a second transport path for transporting the developer from the developer carrier to the toner supply port.
When the transport path length of the first transport path is the first transport path length L1, the transport path length of the second transport path is the second transport path length L2, and the axial length of the developer carrier is X. The following equations (1) and (2)
L2 ≧ 2X ・ ・ ・ (1)
L1 ≧ X ... (2)
A developing device characterized by satisfying. The two components are such that the measured value of the dielectric loss tang tan θt of the toner at 1 V and 100 kHz is 0.005 to 0.01, and the measured value of the dielectric loss tang tan θc of the carrier at 1 V and 100 kHz is 0.05 to 0.2. The developing apparatus according to claim 1, wherein a developing agent is used. An image forming apparatus including the developing apparatus according to claim 1 or 2.

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