JPH0830093A - Image forming device and process cartridge - Google Patents

Abstract

PURPOSE:To form a high quality image by preventing a strongly charged toner layer from being formed on a developing sleeve and simultaneously, toner from being scattered. CONSTITUTION:A conductive rubber layer 21 is provided in a position where an elastic blade 20 faces the developing sleeve 9, to form an alternating field therebetween and a toner layer. Moreover, the magnetic pole N1 of a magnet roll 18 is provided in the downstream position in the rotational direction of the developing sleeve 9 of its abutting part on the elastic blade 20. Thus, the formation of the strongly charged toner layer on the developing sleeve is prevented and the scattered toner is attracted to the sleeve 9 to prevent the scattering of the toner.

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 a laser printer or a copying machine, and is characterized by a developing device.

[0002]

2. Description of the Related Art A conventional image forming apparatus such as a copying machine or a printer using an electrophotographic system will be described with reference to a schematic configuration diagram shown in FIG.

In FIG. 7, a photosensitive drum 2, which is a latent image carrier, is rotatably installed at a substantially central portion of an image forming apparatus main body 1, and is rotated in one direction about its rotation axis.
The surface of the photosensitive drum 2 is uniformly charged by the charging device 3, and then the exposure device 4 performs image exposure to form a latent image. The latent image on the photosensitive drum 2 is developed by the developing device 5.

The developing device 5 is provided with a developing container 7 for containing the developer 6, and a developing sleeve 9 as a developer carrying member is rotatably installed in an opening of the developing container 7 facing the photosensitive drum 2. . A blade 8 which is a developer regulating member is installed above the developing sleeve 9, and the blade 8 regulates the layer thickness of the developer 6 carried on the developing sleeve 9,
A developer layer is formed.

The developer 6 formed as a developer layer is conveyed to the developing section facing the photosensitive drum 2 as the developing sleeve 9 rotates, and is used for developing the latent image formed on the photosensitive drum 2. . During development, a development bias power source 19 connected to the development sleeve 9 applies a development bias between the development sleeve 9 and the photosensitive drum 2 to accelerate development. The latent image on the photosensitive drum 2 is visualized as a toner image by development.

On the other hand, the transfer material 11 is fed from the cassette 11a by the paper feed roller 12 between the contact portion between the photosensitive drum 2 and the transfer roller 10. The toner image on the photosensitive drum 1 is
It is transferred onto the transfer material 11 by the transfer roller 10. The transfer material 11 on which the toner image has been transferred by the transfer roller 10 is conveyed to the fixing device 14, where the toner image is fixed on the transfer material 11 by heat and pressure to form a permanent image, and then the transfer material 11 is placed outside the image forming apparatus. Is discharged.

The photosensitive drum 2 is cleaned by a cleaning device 15 to remove the toner remaining on the surface of the photosensitive drum 2 and then charged again, and the above image forming process is repeated.

In order to facilitate the maintenance of the image forming apparatus, the developing device 5 is used as a developing process unit, and the photosensitive drum 2, the charging roller 3 and the cleaning device 15 are integrated into a process cartridge 17, which is widely used. .

A one-component developer is often used as the developer of such a developing process unit. When a magnetic toner is used as the developer 6, a magnet roll 18 which is a magnetic field generating means for holding the developer on the developing sleeve 9 with a magnetic force is fixed in the developing sleeve 9.

By the way, in recent years, for the purpose of improving the resolution of electrophotographic images, there is a tendency to reduce the particle diameter of toner to about 6 μm. Toner with a smaller particle size has a larger number of particles per unit volume than toner with a large particle size, so it is difficult to give each toner particle an opportunity to contact the surface of the developing sleeve or blade evenly, and the toner is uniformly charged. Difficult to make In particular, in a developing device in which the blade is arranged in non-contact with the developing sleeve, the toner charging efficiency is low and toner uneven charging is likely to occur, image density and resolution are lowered, and fog in the non-image area and toner scattering are worsened. To do.

For this reason, as the installation method of the blade, a contact method in which the side surface of the blade is brought into contact with the developing sleeve so as to rub it is often used. In the contact method, the toner is pressed against both the developing sleeve and the blade to rub against each other, so that the toner has a higher capability of charging the toner than the non-contact method, and is suitable for a toner having a small particle size. As the material of the contact type blade, a metal spring material such as phosphor bronze or an elastic rubber material such as urethane or silicon is used, and is set so that a predetermined contact pressure is applied to the developing sleeve.

However, when the charge amount of the toner is increased more than necessary, a strongly charged toner layer (strongly charged toner layer) is formed on the surface of the developing sleeve or the blade to cover it.
Various harmful effects will occur.

That is, a large electrostatic reflection force acts on the strongly charged toner layer between the strongly charged toner layer and the developing sleeve or the blade. Further, the toner adhering to the surface of the developing sleeve or the blade also has a physical adsorption force. Therefore, they cannot be easily peeled off from their surface.

Further, the strongly charged toner layer impedes the contact between the toner supplied later and the developing sleeve or blade. For this reason, frictional electrification between toner particles increases, the amount of toner (reversal toner) charged to opposite polarities relatively increases, and there are cases in which image density decreases and fog in non-image areas increases.

Furthermore, when a part of the toner in the strongly charged toner layer is used for development, a difference occurs in the charge amount between the developed image portion and the non-developed non-image portion toner, and the next development will result in a difference. There was a case where a ghost phenomenon that the influence of the image of [1] appears. Particularly in a low temperature and low humidity environment, the toner in the strongly charged toner layer on the developing sleeve is more strongly charged to cause uneven charging, or uneven application of the toner layer, which may cause unevenness in the image.

As described above, when the strongly charged toner layer is formed on the developing sleeve, the adverse effect thereof is caused. Further, in the case of a toner having a small particle size, since the toner adheres densely to the surface of the developing sleeve or the blade, the adverse effect thereof tends to be remarkable.

[0017]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that when a toner having a small particle size is used and the charging efficiency of the toner is improved by the blade of the above contact system, the strongly charged toner layer generated in a low humidity environment is According to the method disclosed in Japanese Patent Publication No. 63-41068, for the purpose of removing the toner layer to alleviate unevenness in toner application and charging, a developing sleeve and a non-contact member facing the developing sleeve are provided. Attempts were made to remove the strongly charged toner layer by applying an alternating electric field. However, in order to sufficiently remove the strongly charged toner layer, it is necessary to apply a strong and uniform electric field, and uneven discharge such as leak is likely to occur, which is not suitable for practical use.

As a method of preventing the uneven discharge such as the above-mentioned leakage, the blade is constituted by an electrode portion and a high resistance layer which covers the electrode portion and contacts the developing sleeve, and the electrode portion of the blade is formed. By applying a voltage and applying a slight vibration due to the electric field to the blade and the toner at and near the rubbing portion between the blade and the developing sleeve, the strongly charged toner layer and the foreign matter on the developing sleeve are removed. There is a method that can alleviate uneven coating.

By applying an appropriate electric field between the blade and the developing sleeve by using this method, the toner on the developing sleeve can be sufficiently loosened, and the strongly charged developer layer and the foreign matter formed on the developing sleeve. It has become possible to obtain a high-quality image by good development by eliminating the above-mentioned problems and alleviating unevenness in coating of the developer and uneven charging due to these.

However, this method has a problem of toner scattering. Conventionally, in a developing device in which a magnetic one-component toner is carried and conveyed on the developing sleeve by a magnet roll in the developing sleeve and a layer is formed by an elastic blade, the toner is strongly attracted to the sleeve, so toner scattering does not pose a problem. However, in this method, the toner reciprocates between the developing sleeve and the blade, so that the toner is scattered. Problems such as stains on the image and stains on the inside of the main body occurred.

Therefore, an object of the present invention is to provide an image forming apparatus which prevents the formation of a strongly charged toner layer on a developer carrying member and prevents the toner from scattering, thereby forming a high quality image. .

[0022]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A developer carrying body carrying and transporting a magnetic developer, a magnetic field generating means fixedly arranged in the developer carrying body, and a developer contacting the developer carrying body to apply and regulate the developer in a predetermined layer thickness. In an image forming apparatus provided with a developing device having a developer layer thickness regulating member, the developer layer thickness regulating member has an electrode at least at a position facing the developer carrier, and the developer of the electrode. A high resistance layer is provided on the carrier side, an alternating electric field is formed between the developer carrier and the developer layer thickness regulating member to form the developer layer, and one of the magnetic poles of the magnetic field generating means is The image forming apparatus is arranged at a position downstream of a contact portion between the developer carrier and the developer layer thickness regulating member in a rotation direction of the developer carrier.

At a position facing one of the magnetic poles of the magnetic field generating means disposed at the downstream position of the contact portion between the developer carrying member and the developer layer thickness regulating member in the rotating direction of the developer carrying member, It is preferable to dispose the magnetic member at a constant distance from the developer carrying member.

According to another aspect of the present invention, a developer carrying member carrying and carrying a developer, and a developer layer for contacting the developer carrying member to apply and regulate the developer to a predetermined layer thickness. In an image forming apparatus including a developing device having a thickness regulating member, the developer layer thickness regulating member has an electrode at least at a position facing the developer carrier, and a high resistance layer on the developer carrier side of the electrode. And a developer layer is formed by forming an alternating electric field between the developer carrier and the developer layer thickness regulating member, and an electrode plate is provided between the developer carrier and the developer layer thickness regulating member. At a position downstream of the contact portion in the rotation direction of the developer carrier,
An image forming apparatus is provided, which is arranged in parallel with the developer carrying member while keeping a constant distance, and has a potential in the same direction as the charging polarity of the developer with reference to the developer carrying member. .

One of the magnetic poles of the magnetic field generating means is disposed at a position downstream of the contact portion between the developer carrying body and the developer layer thickness regulating member in the rotating direction of the developer carrying body, and A conductive magnetic member is disposed at a position facing one of the magnetic poles with a constant distance from the developer carrier, and the conductive magnetic member is used as a reference for the developer with respect to the developer carrier. It is preferable to set the potential in the same direction as the charging polarity.

According to still another aspect of the present invention, a developing device, a latent image carrier, charging means for the latent image carrier and / or
Alternatively, there is provided a process cartridge characterized by being integrally formed with the cleaning means and being detachable from the main body of the image forming apparatus.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. In the following embodiments, the present invention will be described as being embodied in the image forming apparatus described above with reference to FIG. Therefore, the same members as those described above are designated by the same reference numerals.

Embodiment 1 FIG. 1 is a schematic configuration diagram showing a first embodiment of a developing device of an image forming apparatus according to the present invention. The developing container 7 contains a negatively-charged one-component magnetic toner 6. The toner 6 is attracted to the non-magnetic conductive developing sleeve 9 by the magnetic force of the magnet roll 18 which is a magnetic field generating means, and is conveyed in accordance with the rotation in the arrow direction.

Then, the developing sleeve 9 serving as a developer carrying member.
The elastic blade 20 as a developer layer thickness regulating member is in contact with the rotation direction of the developing sleeve 9 in the counter direction, and the toner is formed into a predetermined uniform layer and an electric charge is applied to the latent image carrier. It is conveyed to a position (developing region) facing the barrel photoconductor 2.

The elastic blade 20 is provided with an electrode 21, a conductive rubber in this embodiment, on at least the surface facing the developing sleeve 9, and a high resistance layer 22 is interposed to prevent leakage with the developing sleeve 9. It abuts the developing sleeve 9 and is supported by the conductive support member 23. The electrode 21 of the elastic blade 20 is configured so that a predetermined bias can be applied by the power supply 27. A predetermined bias is applied to the developing sleeve 9 by the developing bias power source 19 to develop the electrostatic latent image formed on the photoconductor 2.

A magnet roll 18 is fixedly arranged inside the developing sleeve 9. As the magnetic poles of the magnet roll, a pole S2 for attracting and carrying the toner, a pole S1 for forming a spike of the toner in the developing region and reducing fog, and a toner not used for development in the developing container 7 And a scattering prevention pole N1 disposed downstream of the contact portion between the developing sleeve and the elastic blade in the sleeve rotation direction.

In this embodiment, the photoconductor 2 and the developing sleeve 9 are
Are opposed to each other with a space of SD = 100 μm (hereinafter referred to as SD gap) at the closest portion. During image formation (image area),
Development is performed by applying Vdc = -500V to the developing sleeve. The electrode 21 of the elastic blade has Vpp =
A rectangular wave AC bias of 1600 V and f = 800 Hz was applied.

In order to increase the triboelectric charging efficiency of the toner and form a sufficiently charged toner layer, an electric field in both directions which changes with time is applied as an electric field between the developing sleeve and the elastic blade. It is desirable that a high electric field be applied in the direction toward the elastic blade. This is because the effect of peeling off the strongly charged toner on the sleeve is increased.

Now, with reference to FIG. 5, the temporal changes in the potentials of the developing sleeve and the elastic blade and the movement of the toner at the blade contact portion will be described.

The time change of the potential of the developing sleeve is maintained at -500V as shown by the dotted line. An alternating current is applied to the elastic blade as shown by the solid line, and the potential difference between the elastic blade and the developing sleeve repeats (+) and (−), and the toner particles are respectively elastic blade → developing sleeve (B → S), A force is applied in the direction of the elastic blade → developing sleeve (S → B). The potential difference is larger when S → B, and the potential difference is formed so that the regular toner largely moves from the developing sleeve toward the elastic blade. As described above, the reciprocating motion is actively performed between the developing sleeve and the elastic blade, so that the scattering of toner increases.

In particular, at the developing sleeve contact portion of the elastic blade, the magnetic poles are not arranged so as to shorten the ears of the toner and improve the charging efficiency, so the magnetic force is small and the toner easily scatters.

In this embodiment, the scattering prevention pole N is located at the downstream position of the contacting portion of the developing sleeve and the elastic blade in the sleeve rotation direction.
By providing 1, the scattered toner can be returned to the developing sleeve again.

The scattering prevention pole N1 has an angle θ ₀ of 30 ° from the contact position between the developing sleeve and the elastic blade, a distance of 4.0 mm on the circumference of the developing sleeve, and a normal line on the developing sleeve surface of the N1 pole. The magnetic flux density in the direction was set to 650 gauss.

As the scattering prevention pole N1, the magnetic flux density in the normal direction is 600 gauss or more, the angle between the contact portion of the developing sleeve and the elastic blade and the pole is within 90 °, and the distance on the circumference of the developing sleeve is 12 If it is set within 0.6 mm, the same effect as that of the setting of this embodiment can be obtained.

As described above, the anti-scattering pole N is located at the downstream position of the contacting portion between the developing sleeve and the elastic blade in the sleeve rotation direction.
By providing No. 1, the scattered toner can be drawn back onto the developing sleeve again, and high-quality image formation without toner scattering can be achieved through long-term use.

In this embodiment, the case where the DC bias is applied to the developing sleeve and the AC bias is applied to the blade pole has been described. However, the AC bias may be applied to both the developing sleeve and the blade pole, or the AC bias may be applied to the developing sleeve. Even when a DC bias is applied to the blade pole, the same effect can be obtained.

Second Embodiment Next, a second embodiment of the developing device according to the present invention will be described with reference to FIGS. The present embodiment is characterized in that a magnetic member is provided at a position facing the anti-scattering pole of the magnet roll with a constant distance from the developing sleeve.

In this embodiment, the photosensitive member 2 and the developing sleeve 9 are
Face each other while keeping the SD gap = 300 μm. During image formation (image area), Vdc = -4 on the developing sleeve.
Square wave f = 1800 Hz with V superposed on 00V, Vpp =
Development is performed by applying 1.6 kV. Then, the electrode of the elastic blade is grounded.

Now, with reference to FIG. 6, temporal changes in the potentials of the developing sleeve and the elastic blade and the movement of the toner at the blade contact portion will be described.

An AC bias as shown by a dotted line is applied to the developing sleeve. The elastic blade has zero potential as shown by the solid line, the potential difference between the elastic blade and the developing sleeve repeats (+) and (-), and the toner particles are respectively elastic blade → developing sleeve (B → S), A force is applied in the direction of the elastic blade → developing sleeve (S → B). The potential difference is larger when S → B, and the potential difference is formed so that the regular toner largely moves from the developing sleeve toward the elastic blade. In this way, the reciprocating motion is performed between the developing sleeve and the elastic blade, so that the scattering of toner increases.

In this embodiment, the anti-scattering pole N is provided at the downstream position of the contacting portion between the developing sleeve and the elastic blade in the sleeve rotation direction.
No. 1 was provided, and the magnetic member 30 was arranged facing the N1 in parallel with the sleeve with a distance of 0.4 mm. An iron plate having a width of 1.0 mm was used as the magnetic member 30 and was set to the same potential as the developing sleeve. The material of the magnetic member is not limited to magnetite-dispersed resin, rubber magnet, or the like, and may be used.

The scattering prevention pole N1 has an angle θ ₀ of 30 ° from the contact position of the sleeve and the blade, a distance of 4.0 mm on the circumference of the developing sleeve, and a magnetic flux density in the normal direction on the sleeve surface of the pole. It was set to 650 gauss.

As described above, the anti-scattering pole N1 is provided at the downstream position of the abutting portion of the developing sleeve and the blade in the sleeve rotation direction, and the magnetic member is arranged opposite to the anti-scattering pole N1 with the sleeve at a constant interval. The scattered toner can be returned to the developing sleeve again more effectively than in Example 1, and a high-quality image can be formed without scattering during long-term use.

Third Embodiment Next, a third embodiment of the developing device according to the present invention will be described with reference to FIG. In this embodiment, a toner-scattering prevention electrode plate is provided at a position downstream of the contact portion between the developing sleeve and the elastic blade in the sleeve rotation direction at a constant distance from the developing sleeve, and the toner charging polarity is the same as that of the toner with reference to the developing sleeve. It is characterized in that the potential is set in the direction. In this embodiment, the developing sleeve, the elastic blade, and the bias are set in the same manner as in the first embodiment. As the toner, a non-magnetic one-component toner is used, and no magnet roller is provided inside the developing sleeve.

A scattering prevention electrode plate 31 is provided at a position downstream of the contact portion between the developing sleeve 9 and the elastic blade 20 in the sleeve rotation direction. The anti-scattering electrode plate 31 is a metal plate having a width of 2.0 mm, and is arranged in parallel with the developing sleeve with a distance of 0.5 mm, and the power source 32 supplies -1.0 kV (developing sleeve-5.
00V) was applied.

The anti-scattering electrode plate 31 may have a high resistance surface to prevent leakage, and it is more preferable if the shape is curved along the developing sleeve.

As described above, the anti-scattering electrode plate is provided at the downstream position in the sleeve rotation direction of the contact portion between the developing sleeve and the blade, and the potential is set in the same direction as the toner charging polarity with respect to the developing sleeve (this embodiment). In the case of the example, the toner is −
The polarity, sleeve-500 V, blade-1.0 kV) allowed the scattered toner to be returned to the direction of the developing sleeve, and high-quality image formation without toner scattering was possible during long-term use.

Fourth Embodiment Next, a fourth embodiment of the developing device according to the present invention will be described with reference to FIG. This embodiment is a combination of the second embodiment and the third embodiment, and a higher scattering prevention effect can be obtained. That is, it has the same configuration as that of the second embodiment, and is characterized in that the conductive magnetic member 30 is set to a potential in the same direction as the charging polarity of the toner with reference to the developing sleeve.

In this embodiment, the photoconductor 2 and the developing sleeve 9 are
Face each other while keeping the SD gap = 300 μm. During image formation (image area), Vdc = -4 on the developing sleeve.
Square wave f = 1800 Hz with V superposed on 00V, Vpp =
Development is performed by applying 1.6 kV. Then, the electrode of the elastic blade is grounded.

In this embodiment, a scattering prevention pole N1 is provided at a position downstream of the abutting portion of the developing sleeve 9 and the elastic blade 20 in the sleeve rotation direction. Further, a distance of 0.4 mm is provided in parallel with the sleeve so as to face the scattering prevention pole N1. The magnetic member 30 was arranged while maintaining the above. An iron plate with a width of 1.0 mm is used as the magnetic member 30, and Vdc = Synchronized with the developing sleeve by the power source 32.
Square wave with -700V superimposed f = 1800Hz, Vpp
= 1.6 kV (sleeve-300 V bias) was applied. The material of the magnetic member is not limited to this as long as it is a conductive magnetic material, and can be used. The scattering prevention pole has an angle θ ₀ of 30 from the contact position between the developing sleeve and the elastic blade.
The distance on the sleeve circumference was 4.0 mm, and the magnetic flux density in the normal direction on the sleeve surface of the scattering prevention pole was 650 gauss.

As described above, the anti-scattering pole N is provided at the downstream position in the sleeve rotation direction of the contact portion between the developing sleeve and the elastic blade.
No. 1 is provided, and the magnetic member is disposed facing the sleeve with a constant distance from the sleeve, and the potential in the same direction as the charging polarity of the toner is set on the basis of the developing sleeve. Therefore, it was possible to form a high-quality image without toner scattering during long-term use.

The present invention is not limited by the shape, constitution and material of the elastic blade and the developing sleeve. For example, a resin such as phenol or epoxy, or rubber can be used as the developing sleeve. The developing method may be contact or non-contact, and the developing bias is DC.
Any of application, AC application, DC, AC superposition method, etc. may be used.

Further, the developing device may be integrated with at least the photosensitive member, and may be detachably provided as a process cartridge in the main body of the image forming apparatus.

[0059]

As is apparent from the above description, in the image forming apparatus according to the present invention, the developer layer thickness regulating member has an electrode at least at a position facing the developer carrying member, and the development of the electrode is performed. A high resistance layer is provided on the agent carrier side, an alternating electric field is formed between the developer carrier and the developer layer thickness regulating member to form the developer layer, and one of the magnetic poles of the magnetic field generating means is formed as described above. By arranging the contact portion between the developer carrier and the developer layer thickness regulating member at a downstream position in the developer carrier rotation direction,
It is possible to prevent the formation of a strongly charged toner layer on the developer carrying member and prevent the toner from scattering, and to form a high quality image.

Further, the developer layer thickness regulating member has an electrode at least at a position facing the developer carrier, and a high resistance layer is provided on the developer carrier side of the electrode, and the developer carrier and the developer layer are provided. An alternating electric field is formed between the developer control member and the thickness control member to form a developer layer, and the electrode plate is located downstream of the contact portion between the developer support member and the developer layer thickness control member in the rotation direction of the developer support member. In addition, the same effect as above can be obtained by arranging the developer carrier in parallel with the developer carrier at a constant distance and setting the potential in the same direction as the charge polarity of the developer on the basis of the developer carrier. You can

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing a second embodiment of the developing device of the image forming apparatus according to the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the developing device of the image forming apparatus according to the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of the developing device of the image forming apparatus according to the present invention.

FIG. 5 is a graph showing voltage changes of the developing sleeve and the elastic blade in the first embodiment.

FIG. 6 is a graph showing voltage changes of a developing sleeve and an elastic blade in the second embodiment.

FIG. 7 is a schematic configuration diagram showing a conventional image forming apparatus.

[Explanation of symbols]

 2 Photoreceptor (Image Carrier) 5 Developing Device 8 Elastic Blade (Developer Layer Thickness Controlling Member) 9 Developing Sleeve (Developer Carrier) 18 Magnet Roll (Magnetic Field Generating Means) 20 Elastic Blade (Developer Layer Thickness Controlling Member) 21 conductive rubber layer (electrode) 22 high resistance layer 30 conductive magnetic member 31 shatterproof electrode plate

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Claims (5)

[Claims] 1. A developer carrying member carrying and carrying a magnetic developer, a magnetic field generating means fixedly arranged in the developer carrying member, and a developer having a predetermined layer thickness in contact with the developer carrying member. In an image forming apparatus including a developing device having a developer layer thickness regulating member that applies and regulates the developer layer thickness regulating member, the developer layer thickness regulating member has an electrode at least at a position facing the developer carrier, A high resistance layer is provided on the side of the developer carrying member of the electrode, and an alternating electric field is formed between the developer carrying member and the developer layer thickness regulating member to form the developer layer, and the magnetic pole of the magnetic field generating means. An image forming apparatus, wherein one of the above is disposed at a position downstream of a contact portion between the developer bearing member and the developer layer thickness regulating member in the rotation direction of the developer bearing member. 2. A position opposed to one of the magnetic poles of the magnetic field generating means, which is disposed at a position downstream of the contact portion between the developer carrier and the developer layer thickness regulating member in the developer carrier rotation direction. ,
2. The image forming apparatus according to claim 1, wherein a magnetic material member is arranged at a constant distance from the developer carrying member. 3. A developing device having a developer carrying member for carrying and carrying the developer, and a developer layer thickness regulating member for contacting the developer carrying member to apply and regulate the developer to a predetermined layer thickness. In the image forming apparatus, the developer layer thickness regulating member has an electrode at least at a position facing the developer carrier, and a high resistance layer is provided on the developer carrier side of the electrode. An alternating electric field is formed between the developer carrier and the developer layer thickness regulating member to form the developer layer, and the electrode plate carries the developer at the contact portion between the developer carrier and the developer layer thickness regulating member. It is characterized in that it is arranged in parallel with the developer carrier at a downstream position in the body rotation direction while keeping a constant interval, and has a potential in the same direction as the charge polarity of the developer with respect to the developer carrier. Image forming apparatus. 4. A magnetic field is generated by arranging one of the magnetic poles of the magnetic field generating means at a position downstream of a contact portion between the developer carrier and the developer layer thickness regulating member in the rotation direction of the developer carrier. A conductive magnetic material member is arranged at a position facing one of the magnetic poles of the means at a constant distance from the developer carrying body, and the conductive magnetic body member is based on the developer carrying body. 4. The image forming apparatus according to claim 1, wherein the potential is set in the same direction as the charge polarity of the developer. 5. A developing device according to any one of claims 1 to 4, a latent image carrier, and a charging unit and / or a cleaning unit for the latent image carrier are integrally formed to form an image. A process cartridge characterized by being detachable from the main body of the forming apparatus.