JPH03100687A - Developing device - Google Patents

Abstract

PURPOSE:To form a thin layer of toner on a developer holding body satisfactorily by providing a means to form a parallel magnetic field traversing the confronting part of a toner holding body with the developer holding body. CONSTITUTION:A developer 9 applied to a developer holding roller 1 is carried to the confronting part Q with a toner holding roller 6. At the confronting part Q with the toner holding roller 6, the parallel magnetic field in which the magnetic poles S1 and N3 of magnet rollers 2, 12 are set almost in parallel is formed so as to traverse the confronting part. The circulating flow of the developer 9 is generated at the confronting part Q by the almost parallel magnetic field, and the toner 4 in the developer 9 is sufficiently rubbed and charged, and also, the developer 9 is strongly brought into contact with the toner holding roller 6. In such a way, the thin layer of toner can be formed on the developer holding body satisfactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device using a two-component developer having toner and a carrier, and particularly to a developing device that satisfactorily forms a thin layer of toner on a developer carrier. This invention relates to a developing device that makes it possible to do this.

As a developing device using a two-component developer containing toner and carrier (magnetic particles), there is known a developing device disclosed in Japanese Patent Application Laid-Open No. 116240/1983.

In such a developing device, a two-component developer including toner and carrier is stirred by a stirring means to triboelectrically charge the toner.
The charged toner from the developer is attached to a conductive roller, carried on it, and conveyed to a development position between the image carrier and the conductive roller is biased with a polarity opposite to the charged polarity of the toner. An electric field is applied by a bias power source to adhere toner to the electrostatic latent image formed on the image carrier, and the electrostatic latent image is visualized as a toner image.

However, in this type of developing device, if the toner concentration of the developer becomes higher than permissible, the amount of toner adhering to the conductive roller will be excessively large, causing image fogging and toner scattering. This causes the inconvenience of being stored away.

Another example of a developing device using a two-component developer includes a developing sleeve as a developer carrier with a built-in magnetic field generating means, and an image carrier that is in contact with the circumferential surface of the developing sleeve to regulate the carrier. A device is known in which an elastic blade is provided to apply toner to a predetermined thickness to be conveyed to a developing position, as disclosed in, for example, Japanese Patent Laid-Open No. 62-96956.

In this developing device, an elastic blade is brought into elastic contact with the developing sleeve, and the toner is agitated by circulating carrier near the blade, so that the toner is coated with a sufficient amount of so-called tribo. .

However, in order to circulate the carrier sufficiently, sufficient space is required, and the amount of carrier must also be kept small to obtain the tribo. The existence rate of carriers must be 10% or less. As a result, with such a small amount of carrier, the amount of toner conveyed is insufficient, and the toner cannot be sufficiently conveyed to the development position, resulting in a so-called ghost phenomenon.

In addition, in devices where the elastic blade itself is made of a magnetic material and uses magnetic force to regulate the carrier, an immobile layer of carrier is created near the blade, making it difficult to circulate the carrier and supply toner to the developing sleeve. becomes insufficient,
As expected, there was a problem of a ghost phenomenon occurring.

Based on the above, it is possible to stabilize the thin layer of applied toner over a wide range of toner concentrations relative to the carrier of a two-component developer with a simple configuration that does not require a toner concentration control mechanism. A developing method that can easily obtain high-density, high-quality images without fogging or toner scattering, and without leaving any history of previous development, and which also enables inexpensive and compact equipment. Development of a device is desired.

Therefore, an object of the present invention is to provide a developing device having the above characteristics.

・The above-mentioned purpose of increasing the number of days is achieved by the developing device according to the present invention. In summary, the present invention provides a developer carrier that supports a two-component developer including toner and a carrier and transports the developer, and a developer carrier disposed opposite to the developer carrier. a toner carrier that comes into contact with the developer carried on the body to receive, carry, and convey the toner in the developer;
a toner regulating member that is brought into contact with a downstream position in the rotational direction of the toner carrier at a portion of the toner carrier that faces the developer carrier, and that regulates the amount of toner carried on the toner carrier that passes through the toner carrier; The developing device is characterized in that the developing device is provided with means for forming a parallel magnetic field across the opposing portion.

According to one aspect of the present invention, the parallel magnetic field is generated by magnetic fields of mutually polarized magnets located at the opposing portions of the magnet provided in the developer carrier and the magnet provided in the toner carrier. formed by different magnetic poles.

Further, the toner regulating member is made of an elastic blade, and the elastic blade is disposed facing in a direction opposite to the toner conveying direction. Furthermore, a DC electric field or an AC electric field superimposed thereon is formed between the developer carrier and the toner carrier.

Oketsu 1 Examples of the present invention will be described in detail below.

FIG. 1 is a schematic diagram showing an embodiment of the developing device of the present invention.

As shown in FIG. 1, the developing device of the present invention faces a developer carrying roller 1 as a developer carrying member which rotates in a direction A and is disposed in a developing container 7 containing a two-component developer 9. A toner carrying roller 6 as a toner carrying member that rotates in the direction B is provided, and an elastic blade 8 that comes into contact with the toner carrying roller 6 is provided.

The developer 9 is a mixture containing the toner 4 and the carrier 3 made of magnetic particles having a larger particle size. A magnetic or non-magnetic doctor blade 5 that regulates the amount of developer 9 applied onto the roller 1 is arranged on the top of the developer carrying roller 1 at a distance from the roller 1 . A magnet roller 2 serving as a magnetic field generating means is installed inside the developer carrying roller 1 so as to be immovable with respect to the rotation of the roller 1. The magnet roller 2 has Nl in the direction of rotation of the roller 1.
, St%Ng, and Sx, and the magnetic pole S1 is connected to the elastic blade 8 of the portion Q facing the toner carrying roller 6.
It is located at a location on the downstream side in the rotational direction of the developer carrying roller 1.

The toner carrying roller 6 is connected to the photosensitive drum 1 as an image carrying member.
The developer container 7 is disposed at the opening of the developer container 7 facing the roller 1, and is disposed close to the roller 1 so as to be in contact with the developer 9 carried by the roller 1 at a portion Q facing the developer carrying roller 1. . A magnet roller 12 is immovably disposed inside the toner carrying roller 6, and the magnetic pole N of the magnet roller 12 is the same as that of the magnet roller 2 in the developer carrying roller 1.
The magnetic pole SL is located at a position opposite to the magnetic pole SL. In this embodiment, the magnetic force of these magnetic poles S+ and Ns is 500 Gauss.

The elastic blade 8 is located downstream of the portion Q facing the developer carrying roller 1 in the rotational direction of the toner carrying roller 6.
The magnetic poles S, , N of the magnet roller 2.12 are provided so as to be in contact with the magnetic brush of the developer 9 formed on the developer carrying roller 1, and the direction of conveyance of the toner by the roller 6 (rotational direction of the roller 6) is ), it is inclined from above and abuts against the roller 6 in a counter direction. The elastic blade 8 is deformed as shown in the figure by being pressed against the toner carrier roller 6, and is urged so that the tip of the blade 8 comes into contact with the roller 6.

Next, the operation of the present developing device will be explained.

The two-component developer 9 accommodated in the developing container 7 forms a circulating flow C by the action of the rotational force of the developer carrying roller 1, the magnetic force of the magnet roller 2, and gravity, and the action of this circulating flow C and the action of the developing container Stirring member 13 provided at the lower part of 7
By this action, the carrier 3 and the toner 4 in the developer 9 are mixed and stirred, and furthermore, the toner 4 is charged by frictional charging.

The mixed and agitated developer 9 is transferred to the developer carrying roller l.
A regulated amount is applied and supported by the doctor blade 5. The remaining developer 9 regulated by the doctor blade 5 is returned into the developer container 7 and incorporated into the circulating flow C of the developer 1 again to be stirred and mixed.

In this embodiment, a doctor blade 5 and a developer carrying roller 1 are used.
The gap between the two is set to 800 μm. Further, in order to stabilize the amount of developer 9 applied onto the developer carrying roller 1, the magnetic pole N of the magnet roller 2 is positioned at the location of the doctor blade 5. It is better to position the magnetic pole Nl slightly inclined at an angle θ on the upstream side in the rotational direction of the roller 1 than the position T facing the blade 5, since the developer 9
The circulating flow C can be formed more smoothly.

The above angle θ is preferably 5° to 15′.

The developer 9 coated on the developer carrying roller 1 is conveyed by the roller 1 to a portion Q facing the toner carrying roller 6 . At a portion Q facing the toner carrying roller 6, magnetic poles S, , N of a magnet roller 2.12 are placed across the portion Q facing the toner carrying roller 6.
, form substantially parallel parallel magnetic fields.

Next, the state of the facing portion Q between the developer carrying roller 1 and the toner carrying roller 6 will be explained based on FIG.

The developer 9 applied and carried on the developer carrying roller 1 as described above is conveyed to a portion Q facing the toner carrying roller 6 by rotation of the roller 1 in the direction of arrow A. In this opposing portion Q, the magnet roller 2 in the developer carrying roller l is
A substantially parallel parallel magnetic field (the lines of magnetic force are indicated by broken lines f in FIG. 2) formed by the magnetic pole S1 of the toner carrying roller 6 and the magnetic pole N of the magnetic roller 12 in the toner carrying roller 6 is applied to the surface of the respective rollers l and 6. A vertical force acting on the developer 9 carried on the developer carrying roller 1 acts on the developer 9 and the rollers l,
A laminar flow of the developer 9 is generated by the conveyance force caused by the rotation of the developer 9 . In the vicinity of the developer carrying roller 1, there is a laminar flow in the direction of rotation, and in the vicinity of the toner carrying roller 6, a laminar flow in the direction of rotation similarly occurs.

One laminar flow C of this developer 9 is conveyed as the toner carrying roller 6 rotates, but since the elastic blade 8 is urged to contact the roller 6 as described above, the laminar flow C of the developer 9 is The developer 9 constituting the stream C, except for the toner transferred and applied to the roller 6, is bounced off the blade 8 as shown by arrow e. The repelled developer 9 becomes a circulating flow, merges with the other laminar flow, is conveyed by the developer carrying roller 1, and is returned into the developer container 7.

In this way, in the facing portion Q, the magnetic pole S of the magnet roller 2.12 in the developer carrying roller 1 is located.

The circulating flow of the developer 9 (C
-46-11) ) occurs.

According to such a circulating flow of the developer 9, the toner 4 in the developer 9 is sufficiently triboelectrically charged, and since the developer 9 and the toner carrying roller 6 are in strong contact, a sufficient amount of toner 4 is generated. It is applied to the roller 6. Furthermore, there is also an action of loosening the residual toner that has not been subjected to development and has been collected while remaining on the toner carrying roller 6, and replacing it with new toner, so that the history of the previous development is not left behind.

Note that it is necessary to ensure that the developer 9 is not supplied relatively excessively at the opposing portion Q between the developer carrying roller 1 and the toner carrying roller 6. For this reason, in this embodiment, at the opposing portion Q, The gap was set to 700 μm.

Next, the function of the elastic blade 8 as a developer regulating member will be explained.

As described above, the elastic blade 8 is arranged so that its tip comes into contact with the toner carrying roller 6. By bringing the tip of the elastic blade 8 into contact with the toner carrying roller 6 in this manner, it becomes possible to scrape off excess toner 4 applied on the roller 6 and allow an appropriate amount of toner 4 to pass through.

At this time, the toner concentration of the developer 9 carried on the developer carrying roller 1 is made relatively high, so that the amount of toner 4 supplied from the roller 1 to the toner carrying roller 6 is always slightly excessive. At the same time, by removing the applied excess toner 4 and the accompanying carrier 3 with the elastic blade 8, a constant amount of toner 4 can be applied onto the toner carrying roller 6 at all times.

Generally, the amount of toner 4 transferred from developer carrying roller 1 to toner carrying roller 6 depends largely on the concentration of toner 4 in developer 9 carried on roller 1, and when the toner concentration is high, the amount of toner 4 transferred is However, when the toner concentration is low, the amount of transfer is small. Transferred to this toner carrying roller 6,
If the amount of toner applied is excessively large, it may cause image fogging or toner scattering. Therefore, it is necessary to always control the amount of toner 4 applied to the toner carrying roller 6 to an appropriate amount.

In the present invention, even if the toner concentration of the developer 9 changes greatly, an appropriate amount of toner 4 is applied to the toner carrying roller 6 by the action of the elastic blade 8, so that the above-mentioned disadvantages do not occur.

According to experiments conducted by the present inventors, the toner concentration of the developer (toner weight/carrier weight x 100 (%)) is 10 to 40.
Even within a wide range of %, a certain amount of toner 4 could be applied onto the toner carrying roller 6.

Next, stabilization of toner application by the elastic blade 8 will be described in more detail.

FIG. 3 is a schematic diagram showing a contact portion of the elastic blade 8 that contacts the toner carrying roller 6. As shown in FIG.

The developer 9 carried on the developer carrying roller 1 and conveyed to the opposing part Q with the toner carrying roller 6 is transferred to the toner carrying roller 6 from the laminar flow C in the opposing part Q as described above. Transferred, applied. The applied toner 4 and accompanying carrier 3 are carried to the contact portion with the elastic blade 8 as the toner carrying roller 6 rotates.

At this contact portion, the relatively strong (charged toner 4) of the applied toner 4 has a strong adhesion force to the toner carrying roller 6, so it contacts against the sliding force of the elastic blade 8. Although it passes through the gap between the contact parts, the toner 4 with a weak charge is scraped off, and the carrier 3 with a large particle size cannot pass through the gap and is similarly scraped off.

In this way, an appropriate amount of toner 4 is deposited on the surface of the toner carrying roller 6 after passing through the contact portion of the elastic blade 8.
A thin layer of toner 4 can be formed.

Here, the term "appropriate amount" refers to the amount of toner applied within a range that provides a developed image with sufficient density, no image fogging, and no scattering of toner 4 to the surroundings.According to experiments conducted by the present inventors, styrene / When using a toner whose main component is acrylic resin, the appropriate amount of toner to be applied is 0.5 to 1.2 mg/cm.
, preferably 0.7 to 1.0 mg7cm''.

For details on how to set the elastic blade 8, refer to the elastic blade 8
There are two types: a type in which the ridge at the corner of the tip end is brought into pressure contact with the toner carrying roller 6, and a type in which the abdomen at the end part is brought into pressure contact with the toner carrying roller 6. In the case of the former type, as shown in FIG. 4, if the elastic blade 8 is set too high relative to the toner carrying roller 6, all of the applied toner 4 will be stripped off. In the case of the latter type, as shown in FIG. 5, if the tip of the elastic blade 8 lifts up too much from the toner carrying roller 6, the lifted area 11 is likely to be clogged with the carrier 3, resulting in uneven coating. Therefore, it is necessary to urge the tip of the elastic blade 8, that is, the tip and the vicinity thereof, so as to come into contact with the toner carrying roller 6.

FIG. 6 is an explanatory diagram illustrating the amount of penetration of the elastic blade 8.

In FIG. 6, the dotted line indicates the position of the tip of the elastic blade 8 assuming that the toner carrying roller 6 is not present, and the solid line indicates the actual position of the elastic blade 8 when the toner carrying roller 6 is present. It shows.

Intrusion amount g of elastic roller 8 into toner carrying roller 6 The length between the corner R on the roller 6 side) is 0.5 to 2 mm in order to urge the tip of the elastic blade 8 (the tip and its vicinity) to contact the toner carrying roller 6. is preferred.

As for the material of the elastic blade 8, it is preferable to use a material that can regulate the carrier 3 and also impart a charge of a desired polarity to the toner 4 through friction when it comes into contact with the toner 4.

Although it depends on the material of the toner, for example, in order to positively charge a toner whose main component is polystyrene, Eglenebrobylene, fluororubber, natural rubber, polychlorobutadiene, N, B, R, etc. are effective. be. On the other hand, silicone rubber, polyurethane, styrene-butadiene rubber, etc. are effective for negatively charging.

The hardness of the rubber described above is preferably 50 to 70@ in terms of JISA hardness. If the angle is 70 degrees or more according to JISA, the elasticity of the rubber becomes too strong (the pressure at the contact part becomes too high, and the thin layer of toner 4 formed on the toner carrying roller 6 becomes excessively thin, resulting in insufficient The density of the image will not be obtained.On the other hand, if the angle is less than 50 degrees, the rubber itself will be weak and it will be difficult to obtain sufficient pressure to place the contact portion.

As the carrier 3 used in this example, conventionally known ferromagnetic or paramagnetic particles can be used, such as metal particles of iron, chromium, nickel, cobalt, etc., triiron tetroxide, gamma ferric oxide, etc. Metal oxides such as iron, chromium dioxide, manganese oxide, and ferrite, alloys such as manganese and copper alloys, resin carriers in which the above magnetic particles are dispersed in resin materials, coated carriers in which the upper two magnetic particles are coated with resin materials, etc. can be used. Further, since the carrier 3 is not applied to the surface of the toner carrying roller 6, it is possible to use either a conductive carrier or an insulating carrier.

Regarding the particle sizes of the carrier 3 and toner 4, in order to reliably regulate the carrier 3 by the above-mentioned elastic blade 8, the particle size of the toner 4 is 1 to 20 μm, and the particle size of the carrier 3 is in the range of 40 to 200 μm. If the particle size of the carrier 3 is preferably less than 40 μm, it will be difficult to regulate the carrier 3 by the elastic blade 8, and if it exceeds 200 μm, the ability to hold the toner 4 on the toner carrying roller 6 will decrease. It becomes noticeable.

In addition, it is preferable to add minute irregularities to the surfaces of the developer carrying roller 1 and the toner carrying roller 6 rather than making them mirror-finished in order to uniformly apply the toner 4. Furthermore, in order to control the charge imparting ability, it is preferable to add minute irregularities to the surfaces. Alternatively, a resin or a resin in which conductive particles such as carbon are dispersed may be applied.

In the above embodiment, the magnetic forces of the magnetic pole S of the magnet roller 2 in the developer carrying roller 1 and the magnetic pole Ns of the magnet roller 12 in the toner carrying roller 6 are each equal to 500 Gauss, but the present invention is not limited to this. , magnetic pole S1 is 60
The magnetic force of the magnetic pole Sl of the magnetic roller 2 on the developer carrying roller 1 side is set to a value stronger than the magnetic pole N of the magnetic roller 12 on the toner carrying roller 6 side, such as 0 Gauss and magnetic pole N of 300 Gauss. I can do it.

In this way, the magnetic pole S1 of the magnet 2 on the side of the developer carrying roller 1 is strengthened. Developer carrying roller 1 than laminar flow C
The laminar flow of the developer 9 caused by the rotation of the developer 9 results in a larger flow. For this reason, on the toner carrying roller 6 side, disturbances tend to occur in the laminar flow C in the vicinity thereof (as a result, the amount of frictional charge applied to the toner 4 increases, and the transfer of the toner 4 to the toner carrying roller 6 becomes more efficient). Furthermore, since the flow of the developer 9 in the facing part Q can be made smoother, when designing the gap between the rollers 1 and 6 in the facing part Q, the tolerance can be widened. There is also the advantage of being predictable.

FIG. 7 is a schematic diagram showing another embodiment of the developing device of the present invention.

In the developing device of this embodiment, two magnetic poles sea and Sll of the same polarity are used as magnetic poles at a portion Q of the magnet roller 2 in the developer carrying roller 1, where the developer carrying roller l and the toner carrying roller 6 face each other. It is characterized by the provision of . The other structure of the developing device of this embodiment is basically the same as that shown in FIG. 1, and the same reference numerals in FIG. 7 as in FIG. 1 indicate the same members.

In this embodiment, the magnetic poles S1m, 5ltl of the magnet roller 2 in the developer carrying roller 1 and the magnetic pole N3 of the magnet roller 12 in the toner carrying roller 6 are both 400 Gauss.

In this way, the magnet roller 2 inside the developer carrying roller 1
, two magnetic poles s1. , S +t+, the substantially parallel parallel magnetic field formed by these magnetic poles S1, S lt+ and the magnetic pole N of the magnet roller 12 inside the toner carrying roller 6 creates a repulsive magnetic field at the center thereof. , the developer 9 bounces around in that part, and the circulation flow of the developer 9 is disturbed. Therefore, the toner 4 in the developer 9 is sufficiently triboelectrically charged by the generated turbulence, and the remaining toner in the developer on the toner carrying roller 6 is efficiently replaced with the remaining toner of the previous development. This has the advantage that history is even less likely to occur.

FIG. 8 is a schematic diagram showing still another embodiment of the developing device of the present invention.

In the developing device of this embodiment, in order to form a DC electric field or an AC electric field superimposed thereon at the facing portion Q between the developer carrying roller 1 and the toner carrying roller 6, an AC power source 14 and an AC electric field are connected between these rollers 1 and 6. The feature is that a DC power supply 15 is inserted in series.

The other structure of the developing device of this embodiment is basically the same as that shown in FIG. 1, and the same reference numerals in FIG. 8 as in FIG. 1 indicate the same members.

To give an example in this embodiment, when a negatively charged toner is used as the toner 4 of the developer 9, a voltage obtained by superimposing an AC voltage of 1600 Hz and 100 OVp-p on a DC voltage of 500V (7) is applied to the toner carrying voltage. is applied to the roller 6 to form an alternating current electric field at the opposing portion Q of the roller 1.6.

According to this, since an alternating current electric field is formed in the opposing portion Q of the developer carrying roller 1 and the toner carrying roller 6, the toner 4 is transferred from the developer 9 on the developer carrying roller 1 to the toner carrying roller 6. can be carried out satisfactorily. Further, by adjusting the magnitude of the applied voltage, the amount of transferred toner can be controlled, and furthermore, by forming a reverse electric field, it is also possible to peel off the toner 4 on the toner carrying roll 6.

In the above description, an alternating current electric field with superimposed direct current electrolysis was formed at the facing portion Q of the developer carrying roller 1 and the toner carrying roller 6. However, by applying only a direct current voltage to the toner carrying roller 6, Alternatively, a direct current electric field may be formed in the opposing portion Q. This also provides the same effect as described above.

1 As explained above, in the developing device of the present invention, the toner carrier is disposed opposite to the developer carrier carrying and conveying the two-component developer, and the developer carrier of the toner carrier is A toner regulating member is disposed in contact with the downstream position of the toner carrier in the rotational direction, and a toner regulating member is disposed in a position facing the toner carrier at the opposing portion of the developer carrier magnet and the toner carrier magnet.
Since magnetic poles of different polarity are arranged to form a parallel magnetic field across the opposing parts, the toner concentration with respect to the carrier of the two-component developer can be applied over a wide range with a simple configuration that does not require a toner concentration control mechanism. By stably obtaining a thin layer of applied toner, you can easily obtain high-density, high-quality images without fogging or toner scattering (and without leaving any traces of previous development). It can also be made cheaper and smaller.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the developing device of the present invention. FIG. 2 is an explanatory diagram showing the state of the opposed portion between the developer carrying roller and the toner carrying roller in the developing device shown in FIG. FIG. 3 is a schematic diagram showing a contact portion of an elastic blade that contacts a toner carrying roller in the developing device shown in FIG. 1. FIG. FIG. 4 and FIG. 5 are explanatory diagrams each showing a contact mode of the elastic blade of FIG. 3. FIG. 6 is an explanatory diagram showing the amount of penetration of the elastic blade of FIG. 3 into the toner carrying roller. FIG. 7 is a schematic diagram showing another embodiment of the developing device of the present invention. FIG. 8 is a schematic diagram showing still another embodiment of the developing device of the present invention. 2.12: Magnet roller 3: Carrier 4: Toner 5: Doctor blade 6: Toner carrying roller 8: Elastic blade 9: Two-component developer 14.15: Power supply l: Developer carrying roller 1 Figure 4 Figure 5 Figure 6 Factor 2 Figure 7

Claims (1)

[Scope of Claims] 1) A developer carrier carrying a two-component developer having toner and a carrier and transporting the developer, and the developer disposed opposite to the developer carrier. a toner carrier that receives, carries, and conveys the toner in the developer by contacting the developer carried on the carrier; and the toner in a portion of the toner carrier that faces the developer carrier. In a developing device provided with a toner regulating member that is brought into contact with a downstream position in the rotational direction of the carrier and regulates the amount of toner carried on the toner carrier passing through, means for forming a parallel magnetic field that crosses the opposing portion. Features a developing device. 2) The parallel magnetic field is formed by magnetic poles of a magnet provided in the developer carrier and a magnet provided in the toner carrier, which are located at the opposing portions and have mutually different polarities. 1. The developing device according to 1. 3) The developing device according to claim 1 or 2, wherein the toner regulating member is made of an elastic blade, and the elastic blade is disposed facing in a direction opposite to a direction in which the toner is conveyed. 4) Claim 1, wherein a direct current electric field or an alternating current electric field superimposed thereon is formed between the developer carrier and the toner carrier.
, 2 or 3.