JPH09127771A - Developing device, processing cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device where the thin toner layer of a developing sleeve is stably and excellently formed. SOLUTION: An elastic blade 7 and an elastic roller 6 abut on the developing sleeve 5. The elastic blade 7 is provided with an elastic rubber layer 16 abutting on the nip part of the developing sleeve 5 and the conductive layer 17 of a metallic thin sheet supporting the elastic rubber layer 16 from a rear surface. A power source 18 is connected to the conductive layer 17, and alternating electric field is formed between the conductive layer 17 and the developing sleeve 5. Thus, the reciprocating motion of toner 8 is made between the elastic blade 7 and the developing sleeve 5, so that the toner 8 flocculated at the time of being sent to the regulation part of the elastic blade 7 by the elastic roller 6 is disentangled. Consequently, the thin toner layer is formed in the state of being always stablized and also dripping is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, a developing device applied to the image forming apparatus, and at least a developing device which is detachably attached to an image forming apparatus main body. The present invention relates to a process cartridge that is said to be.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, an electrostatic latent image formed on an image carrier is visualized as a toner image by a developing device.

As one of such developing devices, various dry one-component developing devices have been proposed and put into practical use. However, it is difficult for any developing device to form a thin layer of toner, which is a one-component developer, on a developer carrier.

However, at the present time when improvement in image resolution, sharpness, etc. is required, development of a toner thin layer forming method and its apparatus is indispensable, and some measures have been proposed for this. There is.

For example, as shown in Japanese Patent Laid-Open No. 54-43038, an elastic blade, which is a rubber or metal regulating member, is brought into contact with a developing sleeve, which is a developer carrying member, and the elastic blade and the developing sleeve. The toner is allowed to pass between the abutting portions of the developing roller and regulated so that a thin layer of the toner is formed on the developing sleeve, and sufficient tribo is imparted to the toner by friction at the abutting portions.

In this case, when the non-magnetic toner is regulated by the elastic blade, a toner supply member for supplying the toner onto the developing sleeve is required separately. this is,
This is because in the case of magnetic toner, the toner can be supplied onto the developing sleeve by the magnetic force of the magnet in the developing sleeve, but in the case of non-magnetic toner, the toner cannot be supplied by the magnetic force.

Accordingly, the present applicant has disclosed in Japanese Patent Application Laid-Open No. 58-116.
A developing device was proposed in Japanese Patent No. 559. In the developing device of this proposal, as shown in FIG. 4, the developing sleeve 30 is placed at a position upstream of the elastic blade 29 in the rotational direction of the developing sleeve 30 in the developing container 28 containing the non-magnetic toner 27 as a one-component developer. An elastic roller 31 having a fur brush structure that abuts on the developing sleeve 30 is installed to peel off the toner 27 remaining on the developing sleeve 30 without being consumed for the development and a new toner 2 on the developing sleeve 30.
I am trying to supply 7.

With the above-described structure, the thin layer of the non-magnetic toner 27 can be formed well on the developing sleeve 30, and the electrostatic latent image on the image carrier can be well developed. Becomes

[0009]

However, when the developing operation is repeated a number of times using the above-mentioned developing device, the toner stays in the toner intrusion portion sandwiched between the elastic blade 29 and the developing sleeve 30 which are the layer thickness regulating means. Due to the partial agglomeration of the toner in the longitudinal direction, the layer thickness of the thin toner layer formed on the developing sleeve 30 becomes uneven in the longitudinal direction of the developing sleeve 30, or the agglomerated toner is generated by the elastic blade 29 of the developing sleeve 30. Since the toner 27 is sandwiched in the contact nip with respect to 30, the toner 27 is not coated locally, and a white stripe appears.

Further, this phenomenon is excellent in transferability when transferring from an image carrier to a transfer material by a transfer means (not shown), and transfer residual toner remaining on the image carrier without being transferred is transferred to a blade, a fur brush or the like. The toner having advantages such as less wear of the image carrier due to high lubricity when cleaning by the cleaning means, that is, toner having a spherical shape and a smooth surface (spherical coefficient S
F-1 is 100 to 180, and the shape factor SF-2 is 1.
A toner having a particle size of 00 to 140, which will be described in detail later, is more prominently seen. Particularly, since the adhesion between the toners is weak, the coating becomes non-uniform and the toner layer thickness becomes excessive, and On both sides of the white line,
Toner spills from the surface of the developing sleeve 30 to the outside (referred to as toner spill), which is not preferable.

Therefore, a first object of the present invention is to provide a developing device capable of stably and satisfactorily forming a thin toner layer on a developer carrying member, an image forming apparatus equipped with this developing device,
Another object of the present invention is to provide a process cartridge that includes at least the developing device and is detachable from the main body of the image forming apparatus.

A second object of the present invention is to develop a developing device which does not cause toner spillage, particularly when a spherical toner having a highly smooth surface is used, an image forming apparatus equipped with this developing device, and at least the above-mentioned developing device. An object of the present invention is to provide a process cartridge that includes the apparatus and is detachably attached to the main body of the image forming apparatus.

[0013]

The above object can be achieved by a developing device, a process cartridge, and an image forming apparatus according to the present invention. In summary, the present invention is directed to a developer container containing a non-magnetic one-component developer, a rotatable developer carrier extending into the opening of the developer container, and a developer for the developer carrier. A rotatable developer supply provided so as to abut on an upstream side in the rotation direction of the developer carrying member with respect to an abutting portion of the elastic restricting member abutting via the elastic restricting member and the developer carrying body. In a developing device having a member, the elastic restriction member has a conductive layer at least in the abutting portion across an elastic layer in the longitudinal direction of the developer carrier, and between the conductive layer and the developer carrier. The developing device is characterized by forming an alternating electric field.

Shape factor SF-of the non-magnetic one-component developer
1 is 100 to 180, and the shape factor SF-2 is 100.
It is preferably ˜140.

When the frequency of the alternating electric field is f (Hz), the electric field strength between peaks and peaks is E (V / m), and the peripheral speed of the developer carrying member is v (m / s), the frequency is f
Is preferably 2.5 × 10 ³ × v ≦ f, f ≦ 3000, and the electric field strength E is 2 × 10 ⁵ ≦ E ≦ 9 × 10 ⁵ .

According to another aspect of the present invention, there is provided a process cartridge including at least the above-mentioned developing device and being detachable from the image forming apparatus.

According to another aspect of the present invention, there is provided an image forming apparatus including the above-mentioned developing device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device, process cartridge and image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIGS. 1 and 2 are block diagrams of an image forming apparatus and a developing apparatus of Embodiment 1. In FIG. 1, a photosensitive drum 1 as a latent image carrier rotates in the direction of arrow A and is uniformly charged by a charging device 2 for charging the photosensitive drum 1 to form an electrostatic latent image on the photosensitive drum 1. An electrostatic latent image is formed on the surface by the laser light 3 which is the exposure means for writing.

This electrostatic latent image is disposed in the vicinity of the photosensitive drum 1 and is developed as a process cartridge by the developing device 4 which is detachable from the image forming apparatus and visualized as a toner image. In this embodiment, so-called reversal development for forming a toner image on the exposed portion is performed.

The visualized toner image on the photosensitive drum 1 is transferred onto the paper 13 which is a recording medium by the transfer roller 9, and the transfer residual toner remaining on the photosensitive drum 1 without being transferred is scraped off by the cleaning blade 10. The photosensitive drum 1, which is stored in the waste toner container 11 and cleaned, repeats the above operation to form an image.

On the other hand, the paper 13 onto which the toner image has been transferred is fixed by the fixing device 12 and discharged outside the device to complete the printing operation.

The developing device 4 according to the present invention will be further described with reference to FIG.

In FIG. 2, a developing container 14 containing a non-magnetic toner 8 as a one-component developer is located at an opening extending in the longitudinal direction of the developing container 14 and faces the photosensitive drum 1 as a developer carrier. A developing sleeve 5 is provided so that the electrostatic latent image on the photosensitive drum 1 can be developed and visualized.

In the developing device 4, the developing sleeve 5 is
At the opening, the right substantially half peripheral surface shown in the figure is projected into the developing container 14, and the left substantially half peripheral surface is exposed outside the developing container 14 and is horizontally provided. The surface exposed to the outside of the developing container 14 is the developing device 4
Is opposed to the photosensitive drum 1 located on the left side of, with a small micro area. The developing sleeve 5 is rotationally driven in the direction of arrow B, and the surface thereof has appropriate irregularities for increasing the probability of rubbing against the toner 8 and favorably carrying the toner 8.

At the upper position thereof, the elastic blade 7 as an elastic regulating member is supported by the pressing plate 15 so that the vicinity of the free end side of the elastic blade 7 is brought into surface contact with the outer peripheral surface of the developing sleeve 5. It is provided and the contact direction is
The front end side of the contact portion is located on the upstream side in the rotation direction of the developing sleeve 5 in a so-called counter direction.

Further, the elastic blade 7 has an elastic layer 16 provided in the longitudinal direction of the developing sleeve 5 at least at a contact portion with the developing sleeve 5, and a conductive layer 17 supporting the elastic layer 16 from the back surface. ing. In this embodiment, urethane rubber, silicon rubber or the like is used as the elastic layer 16, and a metal thin plate of SUS or phosphor bronze having spring elasticity is provided as the conductive layer 17. That is, this thin plate maintains the pressure contact force of the elastic blade 7 with respect to the developing sleeve 5, and at the same time, the developing sleeve 5 in the present invention.
And also functions as an electrode when an alternating electric field is formed between and.

A power source 18 capable of applying AC and DC is connected to the conductive layer 17 which is a thin metal plate as the electrode and is controlled so as to form a predetermined alternating electric field with the developing sleeve 5. .

The method and effect of applying the alternating electric field formed between the developing sleeve 5 and the elastic blade 7 will be described in detail later.

The elastic roller 6, which is a developer supplying member, is in contact with the contact portion of the elastic blade 7 with the surface of the developing sleeve 5 on the upstream side in the rotating direction of the developing sleeve 5, and is rotatably supported. There is.

In the developing device 4 as described above, during the developing operation, the toner 8 in the developing container 14 is sent in the direction of the elastic roller 6 as the stirring member 19 rotates in the direction of arrow C.

Further, the toner 8 is carried to the vicinity of the developing sleeve 5 by the elastic roller 6 rotating in the direction of the arrow D, and is carried on the elastic roller 6 at the contact portion between the developing sleeve 5 and the elastic roller 6. The toner 8 is frictionally charged by being rubbed against the developing sleeve 5, and adheres to the developing sleeve 5.

After that, as the developing sleeve 5 rotates in the direction of arrow B, the toner 8 is sent under pressure contact with the elastic blade 7 to which an alternating voltage (blade AC bias) superposed with a direct current by the power source 18 is applied. Then, after a proper tribo (triboelectric charge amount) is received, a thin layer is formed on the developing sleeve 5, and then the developing sleeve 5 is conveyed to a developing portion which is a portion facing the photosensitive drum 1.

Undeveloped toner that has not been consumed in the developing section is transferred to the developing sleeve 5 as the developing sleeve 5 rotates.
Collected from the bottom of A seal member 2 is provided in this recovery portion.
0 is provided to allow passage of undeveloped toner into the developing container 14 and prevent the toner in the developing container 14 from leaking from the lower portion of the developing sleeve 5.

The collected undeveloped toner on the developing sleeve 5 is peeled off from the surface of the developing sleeve 5 at the contact portion between the elastic roller 6 and the developing sleeve 5. Most of the peeled toner is transported as the elastic roller 6 is rotated and mixed with the toner 8 in the developing container 14, and the charged electric charge of the toner is dispersed. At the same time, new toner is supplied onto the developing sleeve 5 by the rotation of the elastic roller 6, and the above-described operation is repeated.

In the developing section, the latent image on the photosensitive drum 1 has a power source 21 between the developing sleeve 5 and the photosensitive drum 1.
By applying an AC voltage (development AC bias) on which DC is superimposed, a toner image is developed.

Next, specific examples of the respective constituent elements of the developing device 4 in this embodiment will be described below.

As the developing sleeve 5, a sleeve surface made of aluminum having a diameter of 16 mm is subjected to a regular blasting treatment with glass beads (# 600) to have a surface roughness Rz of about 3 μm, and the gap between the developing drum 5 and the photosensitive drum 1 is 300 μm. And the peripheral speed of the photosensitive drum 1 is 50 mm /
It was rotated at a peripheral speed of 80 mm / s which was slightly faster than s.

The toner 8 is a non-magnetic one-component developer,
As described above, the transfer residual toner, which has excellent transferability and remains on the photosensitive drum 1 without being transferred, is highly lubricated when it is cleaned by a cleaning unit such as a blade or a fur brush. A toner having advantages such as a small amount, that is, a toner having a spherical shape and a smooth surface is used. Specifically, the shape factors used are SF-1 of 100 to 180 and SF-2 of 100 to 140.

These SF-1 and SF-2 are Hitachi F
Randomly toner image 1 using E-SEM (S-800)
00 values are sampled, the image information is introduced into an image analysis device (Luzex3) manufactured by Nikole Co., Ltd. through an interface, analysis is performed, and a value obtained by calculation by the following formula is defined.

SF-1 = {(MXLNG) ² / AREA} × (π / 4) × 100 SF-2 = {(PERI) ² / AREA} × (π / 4) × 100 (MXLNG: absolute maximum length, AREA: toner projected area, PERI: perimeter) The shape factor SF-1 of this toner indicates the degree of sphericity, and 10
As it increases from 0, it gradually changes from a spherical shape to an amorphous shape. SF-2 indicates the degree of unevenness, and the unevenness on the surface of the toner becomes more remarkable as the value increases from 100.

As a method for producing the toner, if the toner is within the range of the above-mentioned shape factor, in addition to the production method by a so-called crushing method, there are disclosed in JP-A-36-10231 and JP-A-59-53856. A method for directly producing a toner by using the suspension polymerization method described, or a dispersion polymerization method for directly producing a toner by using an aqueous solvent in which a soluble and obtained polymer is insoluble as a monomer, or It is possible to produce a toner by using an emulsion polymerization method typified by a soap-free polymerization method which directly polymerizes in the presence of a water-soluble polar initiator to produce a toner.

In this embodiment, the toner shape factor S
F-1 to 100-180, SF-2 to 100-140
The suspension polymerization method under normal pressure or under pressure can be used to obtain a fine particle toner having a sharp particle size distribution and a particle size distribution of 4 to 8 μm. Acrylate, salicylic acid metal compound as a charge control agent, saturated polyester as a polar resin, and a colorant are added, and a weight average particle diameter of 7 μm
m colored suspended particles were produced.

Then, 1.5 wt% of hydrophobic silica is added to this.
% By external addition, a negative-polarity toner 8 having excellent transferability as described above and less wear during cleaning of the photosensitive drum 1 was manufactured.

The elastic roller 6 has a foam skeletal sponge structure or a fur brush structure in which fibers such as rayon and nylon are planted on a core metal, and the toner 8 is supplied to the developing sleeve 5 and the undeveloped toner is peeled off. This is preferable, and in the present embodiment, a 12 mm elastic roller 6 having polyurethane foam on a cored bar was used. The width of contact between the elastic roller 6 and the developing sleeve 5 is 1 to 8 m.
It is preferable that m is effective, and it is preferable that the abutting portion has a relative speed with respect to the developing sleeve 5. In this embodiment, the abutting width is set to 3 mm, and the peripheral speed of the elastic roller 6 is set as the developing operation. It was rotationally driven at a predetermined timing by a driving means (not shown) so that it was 50 mm / s (the relative speed to the developing sleeve 5 was 130 mm / s).

The elastic blade 7 has a structure in which urethane rubber having a thickness of 1.0 mm is bonded as an elastic layer 16 to a conductive layer 17 which is a thin metal plate made of phosphor bronze having a spring elasticity and a thickness of 0.1 mm. There is. The contact pressure with respect to the developing sleeve 5 was 30 g / cm (the linear pressure was measured by inserting three metal thin plates with known friction coefficients into the contact part and extracting the center one with a spring only). ).

Next, the method and effect of applying the alternating electric field formed between the developing sleeve 5 and the elastic blade 7 according to the present invention will be described in detail.

As described above, the developing sleeve 5 and the elastic blade 7 are connected to the power sources 21 and 18 capable of applying an AC voltage and a DC voltage, respectively, and are used as a developing bias from the power source 21 during the developing operation. 5 has a square wave as an AC component and a peak-to-peak voltage of 2000
V, frequency 2000 Hz, and -400 V is applied as a DC component. As a result, the latent image potential V1 of the exposed portion of the photosensitive drum 1 is -150 V (the potential of the non-exposed portion is -600 V).
The so-called reversal development in which the toner 8 having a negative polarity is developed with respect to V) is performed.

The blade bias applied to the conductive layer 17 of the elastic blade 7 has a DC component of -400 V, which is the same as the developing bias, and an AC component of a rectangular wave having the same phase as the developing bias, with a peak-peak voltage of 1400 V and a frequency of 2.
000 Hz is applied.

Here, the rubber elastic layer 16 is the developing sleeve 5
In terms of preventing leakage between the conductive layer 17 and the conductive layer 17, it is of course possible to have a resistance of a predetermined value or more, and the volume resistance is 10 ¹⁰ Ω · c.
m or more.

By setting the developing bias and the blade bias in this manner, a peak-to-peak voltage of 600 V and a frequency of 20 V are generated between the developing sleeve 5 and the elastic blade 7.
A potential difference of 00 Hz will occur.

With the above-described structure, the toner 8 entering the contact nip portion of the elastic blade 7 with the developing sleeve 5 is in the vicinity of the inlet due to the force of the alternating electric field and the elastic blade 7 side and the developing sleeve 5. The toner reciprocates between itself and the side, so-called reciprocating motion, and the toner that has agglomerated is loosened in this portion, and is regulated by the elastic blade 7 in a stable state at all times.

As a result, the toner which has passed through the regulating portion of the elastic blade 7 which is caused when the developing operation is repeated, which is a conventional problem, is prevented from spilling the toner 8 from the surface of the developing sleeve 5 to the outside. A thin developer layer having a uniform thickness can be stably formed on the photosensitive drum 5, and the electrostatic latent image on the photosensitive drum 1 can be favorably developed with a uniform density in the longitudinal direction.

The present inventors conducted an experiment to find out the optimum range of the alternating electric field between the elastic blade 7 and the developing sleeve 5 in this embodiment. That is, the developing device 4 of this embodiment
With the elastic blade 7 grounded, the toner coating state on the developing sleeve 5 was confirmed without applying the AC voltage only to the developing sleeve 5 (DC voltage is 0 V) and performing the developing operation.

Specifically, after the developing sleeve 5 is rotated for 5 hours while changing the peak-to-peak voltage of the voltage applied to the developing sleeve 5 and the frequency, the toner coating state on the developing sleeve 5 is changed. It was observed and evaluated. The evaluation results are shown in Table 1 below.

[0056]

[Table 1]

In this experiment, the optimum range of the alternating electric field is a region surrounded by a thick line in Table 1. First, regarding the frequency, 100Hz has the effect of preventing fluttering, but
Light and shade unevenness was generated at a cycle of 1 / 100S in the circumferential direction on the developing sleeve 5, and the fluttering occurred at 4000 Hz. The reason for this is that if the applied frequency is too low, the cycle of the toner 8 coming and going between the elastic blade 7 side and the developing sleeve 5 side appears in the coating as it is, and if it is too high, the positive and negative switching of the applied electric field is too fast. Therefore, it is considered that the toner 8 cannot follow up, and a good toner loosening effect does not occur.

Therefore, considering that the peripheral speed of the developing sleeve 5 in this experiment is 80 mm / s, the frequency f (H
The appropriate range of z) is that the peripheral speed of the developing sleeve 5 is v (m /
s), 200 / (80 × 10 ⁻³ ) ≦ f / v,
f ≦ 3000, that is, 2.5 × 10 ³ × v ≦ f, f ≦ 30
00.

Regarding the peak-to-peak voltage, 100
Below V, there is no vibration effect of the elastic blade 7 and drops occur, and above 1000 V, the toner violently reciprocates on the downstream side of the developing sleeve 5 contact portion of the elastic blade 7 in the direction of rotation of the developing sleeve 5, and from this portion to the outside. As a result, the toner is scattered.

Therefore, considering that the thickness of the elastic layer 16 of the elastic blade 7 of this experiment is 1 mm, the proper electric field strength E between peaks is 2 × 10 ⁵ ≦ E ≦ 9 ×.
It becomes 10 ⁵ .

Within the proper range described above, the elastic blade 7,
By providing an alternating electric field between the developing sleeves 5, a good coating was stably obtained.

Second Embodiment Next, a second embodiment of the developing device according to the present invention will be described with reference to FIG.

In the developing device 22 of this embodiment, a plate blade 24 made of urethane rubber having a thickness of 1 mm and having a plate rubber shape, which is different from that of the first embodiment, is used as the elastic blade 23.
An electrode 26 is provided on the back surface side of the contact portion with the developing sleeve 25, and an alternating electric field under the conditions described in the first embodiment is formed between the electrode 26 and the developing sleeve 25.

As a result, the same effect as that of the first embodiment can be obtained. Of course, although the elastic layer having a thickness of 1 mm was used in Examples 1 and 2, it can be changed and the strength of the alternating electric field may be within the range of the present invention. The development sleeve used was blasted,
For example, a sleeve in which a coating material in which a conductive material such as carbon or graphite is dispersed in a resin material such as phenol is coated may be used, and other respective members can be appropriately selected within the scope of the present invention.

Further, in Embodiments 1 and 2, the process cartridge is composed of a developing device which can be attached to and detached from the main body of the image forming apparatus, but is fixed in the main body of the image forming apparatus.
It may be used as a developing device configured to replenish only toner, or may be formed integrally with the developing device, the photosensitive drum, the cleaning blade, the waste toner container, the charging device, or any one of them. It may be used as a process cartridge that can be attached to and detached from the image forming apparatus main body.

[0066]

As is clear from the above description, according to the present invention, the elastic regulating member has the conductive layer at least in the contact portion with the developer carrying member through the elastic layer in the longitudinal direction. By forming an alternating electric field between the conductive layer and the developer carrying member, it is possible to stably and favorably form a thin toner layer on the developer carrying member, and in particular a spherical toner having a high surface smoothness. When a toner is used, the developing device is capable of obtaining a high-quality image without the occurrence of toner spillage, an image forming device equipped with this developing device, and at least the developing device described above, which is detachable from the main body of the image forming device. A process cartridge can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an image forming apparatus using a developing device according to a first exemplary embodiment of the present invention.

FIG. 2 is a configuration diagram showing the developing device of FIG.

FIG. 3 is a configuration diagram illustrating a developing device according to a second exemplary embodiment of the present invention.

FIG. 4 is a configuration diagram showing an example of a conventional non-magnetic one-component developing device.

[Explanation of symbols]

 4, 22 developing device 5, 25 developing sleeve (developer carrier) 6 elastic roller (developer supply member) 7, 23 elastic blade (elasticity regulating member) 14 developing container 16 elastic layer 17 conductive layer 24 plate blade (high resistance Layer) 26 electrode (conductive layer)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Sakakibara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A developing container for accommodating a non-magnetic one-component developer, a rotating developer carrier extending to an opening of the developing container, and a developer carrier for the developer carrier. An elastic regulation member in contact with the elastic regulation member, and a rotatable developer supply member provided in contact with the contact portion of the elastic regulation member with the developer carrying body on the upstream side in the rotation direction of the developer carrying body. In the developing device, the elastic regulation member has a conductive layer at least in the abutting portion across an elastic layer across a longitudinal direction of the developer carrier, and an alternating electric field is provided between the conductive layer and the developer carrier. A developing device characterized by forming. 2. The shape factor SF of the non-magnetic one-component developer
-1 is 100 to 180, and the shape factor SF-2 is 10.
The developing device according to claim 1, wherein the developing device is 0 to 140. 3. The frequency of the alternating electric field is f (Hz), the peak-to-peak electric field strength is E (V / m), and the peripheral speed of the developer carrying member is v (m / s). The developing device according to claim 1, wherein the frequency f is 2.5 × 10 ³ × v ≦ f, f ≦ 3000, and the electric field intensity E is 2 × 10 ⁵ ≦ E ≦ 9 × 10 ⁵ . 4. A process cartridge comprising at least the developing device according to claim 1 and detachably attached to an image forming apparatus. 5. An image forming apparatus comprising the developing device according to claim 1.