JP3029137B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method and an apparatus used in an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile, and more particularly to a developing method in which a developer is carried on a developer carrier. The present invention relates to a developing method and an apparatus for performing development by transporting the developer to a developing unit facing an electrostatic latent image carrier.

[0002]

2. Description of the Related Art In a developing device of this type, a developer carrier having a thin layer of developer formed on a surface thereof and an electrostatic latent image carrier are opposed to each other in a developing section. 2. Description of the Related Art There is known an image forming apparatus which forms an electric field capable of transferring a developer on a body to an electrostatic latent image carrier and develops the electrostatic latent image on the electrostatic latent image carrier. In this developing device, there is a threshold value for transferring the developer from the developer carrier to the electrostatic latent image carrier, and the developer adheres to an image portion having a surface potential exceeding the threshold value. On the other hand, since the developer hardly adheres to an image portion having a surface potential equal to or lower than the threshold value, there is a problem that an image having a so-called γ and poor gradation is formed. However, it is known that this problem can be solved by forming an alternating electric field having a relatively low frequency in the developing section (for example, see Japanese Patent Publication No. 64-1013).

However, simply applying a low-frequency alternating electric field to the developing section lowers the image density if the condition of the alternating electric field is such that the gradation property can be improved. However, there is a problem that the line portion of the image becomes thicker when the value is increased. Further, in this type of developing device, particularly when a non-magnetic toner is used as a developer, when a reciprocating motion of the non-magnetic toner is caused, the toner is turned into a powder cloud and the image density is significantly reduced. (See, for example, Japanese Patent Publication No. 2-14706). In recent years, along with diversification of output information of an image created by an image forming apparatus, higher image quality than ever has been desired. Accordingly, the present applicant has previously described, in a developing device that carries a developer on a developer carrier and performs development in a developing unit where the developer carrier and the electrostatic latent image carrier are opposed to each other, A developer carrier having a large number of electric field arrangements formed on its surface as an agent carrier, and a voltage applying means for forming an electric field in the developing section, and a potential on the electrostatic latent image carrier, A developing device characterized in that the movement of the developer is controlled by an electric field determined by the correlation between the electric potential on the developer carrier and the electric field formed by the voltage applying means. Such a developing device forms a large number of electric field arrangements on a surface as a developer carrying member, and a potential on the electrostatic latent image carrying member, a potential on the developer carrying member, and an electric field formed by the voltage applying means. The movement of the developer is controlled by the electric field determined by the correlation between the toner and the developer, whereby an appropriate amount of the developer is attached to the electrostatic latent image on the electrostatic latent image carrier. There is an advantage that a developed image having excellent reproducibility and gradation can be obtained.

[0004]

However, in the above-mentioned developing device, the image quality is improved by the characteristics such as good fluidity, good triboelectric charging on the developer carrier, and uniform charge. When a developer having a substantially spherical and uniform small particle diameter is used, depending on a specific structure for forming a large number of electric field arrangements on the surface of the developer carrying member, a frictionally charged developing agent may be used. It has been confirmed that there is a possibility that an undesired charge is injected into the developer from the surface of the developer carrier, or that a leakage of a developing bias occurs. Therefore, an object of the present invention is to obtain a developed image having a high image density and excellent in the reproducibility and gradation of a diagram, and a substantially spherical and uniform small particle. An object of the present invention is to provide a developing device that can achieve higher image quality by using a developer having a diameter.

[0005]

In order to achieve the above object, the present invention is directed to an electrostatic latent image carrier for carrying an electrostatic latent image and a developer carrier for carrying a developer. is opposed in the developing unit, the developing device for developing and applying a bias at the developing portion, as the developer carrying member,
On the conductive substrate, two substances having different resistances of 10 ³ Ωcm or more are provided regularly or irregularly so that the substances are mixedly exposed on the surface, and at least one of the surfaces of the two substances is exposed. A developer carrier whose exposed portion is triboelectrically charged to a polarity opposite to or the same as the polarity of the developer to form a large number of minute electric fields on the surface, and the developer is substantially spherical.
Shaped and uniform small particle size developer
Therefore, it is charged, and in the charged state, the current
Use the one carried on the image agent carrier, and
A frictional charging means for frictionally charging the developer with a polarity ; and an electric field determined by a correlation between an electric potential on the electrostatic latent image carrier , an electric field due to the bias, and an electric field on the developer carrier. Characterized by controlling the movement of the object.
A second aspect of the present invention, in the developing apparatus of claim 1, is characterized in that the upper Symbol developer is a spherical microcapsule toner triboelectricity to the resin shells agent configured to coat the resin core material. The invention according to claim 3 is the developing device according to claim 1.
Wherein the small electric field is a closed electric field.
Is what you do. The invention according to claim 4 is the developing device according to claim 1.
The developing unit supported by the developer carrier
Is provided to regulate the layer thickness of the developer conveyed to the
In addition, the frictional charging means is more developer than the layer thickness regulating means.
On the upstream side in the transport direction, the developer is transported more than the developing unit.
It is characterized by being located on the downstream side in the direction.

[0006]

According to the present invention, a large number of electric fields are formed on the surface of the developer carrier, and the potential is formed by the potential on the electrostatic latent image carrier, the potential on the developer carrier, and the voltage applying means. The movement of the developer is controlled by the electric field determined by the correlation with the electric field, whereby an appropriate amount of the developer is attached to the electrostatic latent image on the electrostatic latent image carrier. Here, a developer having a substantially spherical and uniform small particle size is used as the developer, and the developer is sufficiently charged, while a high charge amount developer having a small particle size is transferred to the surface of the developer carrier. The bias is set to a relatively high voltage so that the developer can be transferred to the image portion on the electrostatic latent image carrier by overcoming this adhesive force. Then, as the developer carrying member, two kinds of substances having different resistances which are mixedly exposed on the surface,
0 ³ using a developer carrying member which is formed with the material of the Ωcm or more resistors, by this, even when the voltage is applied for a relatively high voltage of the injection of unwanted charge the developer on the surface occurs Or a bias leak is prevented from occurring.

[0007]

FIG. 1 is a schematic view showing an example of a developing device according to the present invention. First, the overall structure and operation will be clarified.
In FIG. 1, a belt-shaped photoconductor 1, which is an example of a latent image carrier, is driven in the direction of arrow A, and a developing device 2 is provided to face the photoconductor. In the toner container 3 of the developing device 2, a non-magnetic toner 4 from which an auxiliary agent is removed as necessary, that is, a non-magnetic one-component developer is stored. The specific volume resistivity of the toner is, for example, about 10 ⁷ to 10 ¹² Ωcm. In the present invention, a substantially spherical toner having a uniform small particle diameter is used as the toner 4 as described later. On the front and rear side plates of the toner container 3, a developing roller 5 is supported in a state where a part thereof is exposed from the opening of the container. It is rotationally driven at the number of rotations. The developing roller 5 is an example of a toner carrier, but a belt-shaped toner carrier may be used instead of the roller 5. A toner supply roller 6 as an example of a toner supply member is supported on the front and rear side plates of the toner container 3. The roller 6 contacts the developing roller 5 at a rotation speed of, for example, 300 rpm in a counterclockwise direction (or in a clockwise direction). Good). The toner 4 in the toner container 3 is conveyed to the toner supply roller 6 while being stirred by the agitator 7 rotating clockwise, and then supplied to the developing roller 5 by the roller 6. At the time of this supply, the toner is frictionally charged to a predetermined polarity, in this example, a positive polarity having a polarity opposite to that of the electrostatic latent image on the photosensitive member 1, electrostatically adheres to the peripheral surface of the developing roller 5, and is carried on the developing roller 5. Is done. The configuration and operation related to this will be described later in detail. The toner supplied and carried on the peripheral surface of the developing roller 5 as described above is
It is conveyed by the rotation of the roller 5 and is leveled by a doctor blade 8 which is an example of a layer thickness regulating member, and is regulated to a uniform thickness. Next, the toner is conveyed to a developing area 9 where the photoconductor 1 and the developing roller 5 are opposed to each other, where the toner is electrostatically transferred to an electrostatic latent image formed on the photoconductor 1 and the latent image is converted into a visible image. Become The doctor blade 8 is the elastic support member 3
0 supported. The toner that has not passed through the development area 9 without being used for development is returned to the toner supply roller 6 while being carried on the development roller 5. Further, the visible image formed on the photoreceptor 1 is transferred to a transfer sheet (not shown) and fixed on the transfer sheet by a fixing device.

The above-described structure itself is the same as that of a conventional developing device. In such a conventional developing device, it is difficult to transport a large amount of non-magnetic toner that is sufficiently charged to a developing area. In some cases, the density of the visible image formed by this may decrease. Therefore, in the illustrated developing device, as schematically shown in FIG.
For example, a conductive roller 10 made of metal such as Al, Fe, Cu, etc.
And a medium resistor 1 fixed to the peripheral surface thereof
2 and a high-resistance body 11 are used. The resistivity of the medium resistor 12 is higher than the resistivity of the conductive substrate surface (the conductive roller 10 in this example), for example, 1
0 ³ to 10 ⁸ Ωcm, and the resistivity of the high-resistance body 11 is higher than that of the medium-resistance body 12.
It is set to 0 ^{9-10 15} about Ωcm. Both resistors 1
Reference numerals 1 and 12 are made of a dielectric material having such a resistivity. FIG. 3 showing an enlarged view of the developing roller surface.
As can be seen from FIG. 3 (b) and FIG. 3 (c) showing a partial cross-sectional view near the same surface, the high resistance elements 11 and the medium resistance elements 12 are arranged regularly (or in an irregular state). These are exposed on the surface of the developing roller 5. Each medium resistor 12
And the shape of the high-resistance body 11 can be set as appropriate, but when the surface shape is rectangular as illustrated in FIG. 3, the lengths D1 and D2 of the sides are set to appropriate values of, for example, about 10 to 500 μm. be able to. Such a resistor 11,
12 and the resistivity thereof are set so that the strength of a closed electric field described later can be increased so that an optimal amount of toner can be carried on the developing roller 5, and that the toner on the surface has a medium resistance. The selection is appropriately made so as not to inject undesired charges into the toner on the body 12 or to leak the developing bias. In this example, the high resistance element 11 and the medium resistance element 12
A material having a polarity opposite to the charging polarity of the toner, that is, a material that is frictionally charged to a negative polarity is selected. Further, if necessary, a bias voltage such as direct current, alternating current, direct current superimposed alternating current, or pulse can be applied to the conductive roller 10 of the developing roller 5 to improve the image quality of a visible image, and the roller 10 is grounded. Such a configuration is also possible. The same applies to the toner supply roller 6. When the toner carrier comprises a belt, a medium resistor and a high resistor are laminated and fixed on the surface of the conductive base of the belt in the above-described state. On the other hand, the toner supply roller 6 that is in contact with the developing roller 5 contacts the high resistance element 11 and the medium resistance element 12 of the development roller 5 and frictionally charges them to a polarity (negative polarity) opposite to the charging polarity of the toner. It is composed of In the example shown in FIGS. 1 and 3, the toner supply roller 6 is made of a conductor core member 14 and a cylindrical foam (for example, polyurethane foam) 15 laminated therearound, and the foam 15 is elastic. When the toner supply roller 6 is used while being pressed against the developing roller 5 while being deformed, the foam 15 may be made of a material that frictionally charges the resistors 11 and 12 to the negative polarity as described above. Good. Foam 15
Instead, a known brush, such as a fur brush, may be used.

In the illustrated developing device, as described above, the image quality is improved by such characteristics that the fluidity is good, the triboelectric charging on the developer carrying member is performed well, and a uniform charge can be obtained. And a substantially spherical toner having a uniform small particle diameter. Such toners are known per se. For example, there are a regular pulverized toner (amorphous), which is mechanically rolled into a spherical shape while heating, and a product produced by suspension polymerization. As an example of the latter, styrene 170 parts by weight 2-ethylhexyl acrylate 30 parts by weight Chromium chain of di-tert-butylsalicylic acid 3 parts by weight Polymerization initiator 2,2-Azobis (2,4-dimethylvaleronitlite) (60 ° C.) 240 minutes: 10 parts by weight of paraffin wax (melting point 70 ° C (manufactured by Nippon Seiro)) 30 parts by weight Colorant (carbon black) 4 parts by weight 4 parts by weight of the above material at 60 ° C The monomer composition was prepared by dissolving or dispersing while maintaining the composition. Separately, the above monomer composition was added to an aqueous dispersion medium in which 20 g of a polyacrylic acid aqueous solution (manufactured by Wako Pure Chemical Industries) and 10 g of sodium sulfate were dissolved in 1200 parts by weight of ion-exchanged water. K. The mixture was stirred at 8000 rpm for 60 minutes using a homomixer to granulate the monomer composition. Thereafter, the mixture was reacted at a temperature of 60 ° C. for 7 hours and then at a temperature of 80 ° C. for 4 hours while stirring with a paddle stirrer. After completion of the polymerization, the reaction product was cooled, sodium hydroxide was added, the dispersant was dissolved, and the mixture was filtered, washed with water, and dried to obtain a black toner. In the present embodiment, a spherical microcapsule toner having a structure in which a resin core material coated with a frictionally charged resin shell material, which is known per se, may be used.

The more detailed operation of the above configuration will be described below. As described above with reference to FIG.
The developing roller portion that has passed the developing area 9 moves to the toner supply roller 6 and contacts the roller 6. Here, the toner carried on the developing roller 5 and not supplied to the development is mechanically and electrically scraped off by the toner supply roller 6. At the same time, the high resistance body 11 of the developing roller 5
And the medium resistor 12 comes into contact with the toner supply roller 6 and is charged to the negative polarity opposite to the charging polarity of the toner by the friction. At this time, even if an electrostatic residual image due to the influence of the electrostatic latent image of the photoconductor 1 remains on the resistors 11 and 12 on the peripheral surface of the developing roller passing through the developing area 9, the friction with the toner supply roller 6 is maintained. As a result, the resistors 11 and 12 are charged to a substantially saturated state, the residual image is eliminated, and the developing roller 5 is initialized. On the other hand, the toner 4 carried to the developing roller 5 while being in contact with the peripheral surface of the toner supplying roller 6 is frictionally charged to a positive polarity by friction with the toner supplying roller 6 as schematically shown in FIG. At this time, the friction with the developing roller 5 causes the toner to be more positively frictionally charged and adheres to the peripheral surface of the developing roller 5 electrostatically. At this time, the high-resistance element 11 and the medium-resistance element 12 of the developing roller 5 are triboelectrically charged to the negative polarity. However, since their resistances are different from each other, as shown schematically in FIG. Resistor 1
The charge amount of 1 is larger than the charge amount of the middle resistor 11, and a difference occurs between the two surface potentials. Therefore, a closed electric field is formed between the two resistors 11 and 12. Since a large number of high resistance elements 11 and medium resistance elements 12 are arranged alternately on the surface of the conductive roller 10 so as to be countless, the developing roller 5
A number of minute closed electric fields (microfields) are formed on the surface of the developing roller in a state of being uniformly distributed on the surface of the developing roller. That is, when considering the lines of electric force representing the state of the electric field, the lines of electric force E are formed in the space near the surface of the developing roller 5 as represented by a large number of arc-shaped lines in FIG. The lines of electric force exit from the developing roller 5 and return to the same developing roller 5, and a number of closed electric fields are formed near the surface of the roller 5. Thus, an electric field having a large electric field gradient is formed near the surface of the developing roller. Since the surface sizes of the high resistance body 11 and the medium resistance body 12 are very small as described above,
Each closed electric field is also very small, whereby the intensity of each closed electric field is greatly increased by a so-called edge effect or fringing effect (peripheral electric field effect). Due to such a high intensity closed electric field, the positively charged toner is strongly attracted to the surface of the high resistance body 11 as shown schematically in FIG. Is held. That is, the charged toner is given a strong binding force inside the closed electric field, and is held on the developing roller 5 along the line of electric force. At this time, the toner is strongly frictionally charged due to the friction between the toner supply roller 6 and the developing roller 5 and is held on the surface of the developing roller 5 by the action of a strong micro electric field. When the layer thickness of the toner is regulated by a doctor blade 8 made of, for example, urethane, a sufficiently charged toner is strongly held on the surface of the developing roller 5 by a minute closed electric field, but a toner having a small charge amount is mixed with the toner. However, the toner is removed by the contact pressure with the doctor blade 8, so that only the toner having a large charge amount is conveyed to the developing area 9 in a larger amount than before, and the electrostatic latent image is formed as described above. Visualize. The electric field between the developing roller 5 and the photosensitive member 1 in the developing region 9 has a large electrode effect, and the toner on the developing roller 5 is likely to adhere to the photosensitive member 1. In this manner, the image density of the visible image can be increased and the background can be prevented from being stained. In the vicinity of the surface of the developing roller 5, only a small closed electric field is formed over the entire surface as schematically shown in FIG. In any case, since a closed electric field is present, the intensity is increased and a large amount of toner can be carried.

As described above, according to the present embodiment, it is possible to carry a large amount of sufficiently charged toner on the developing roller 5 and transport it to the developing area, where it can be used for development. A medium resistance element 12 and a high resistance element 11 having a resistance of 10 ³ Ωcm or more are arranged on the surface of the roller 5, and the conductive surface of the conductive roller is not exposed on the surface of the developing roller 5. For this reason,
In the developing area 9, the leakage of electric charge between the photoconductor 1 and the developing roller 5 can be reliably suppressed, and the problem that the electrostatic latent image formed on the photoconductor 1 is disturbed can be effectively suppressed. Thus, a high quality visible image can be formed.

Although the non-contact development is performed in the development area 9 in the example of FIG. 1, the latent image may be visualized by a contact development method. In the above example, the high-resistance element 1
1 and the medium resistor 12 are charged to the opposite polarity to the toner, but both resistors 11 and 12 are charged to the same polarity as the charge polarity of the toner, and a large amount of toner is attached to the surface of the medium resistor 12 in particular. You can also. Further, the middle resistor 12 is not substantially charged, and only the high resistor 11 is charged to a predetermined polarity.
A toner can be carried by forming a closed electric field between these elements. In short, at least the high-resistance element of the high-resistance element and the medium-resistance element is charged, and a difference in the surface electric potential between the high-resistance element and the medium-resistance element causes the closed electric field. Is formed to carry the toner. Further, as a substrate for laminating and fixing the high-resistance element and the medium-resistance element, only a surface on which these resistance elements are laminated is made conductive, and this conductive layer is grounded or a predetermined bias voltage is applied thereto. You may make it. Further, at least the high-resistance element of the high-resistance element and the medium-resistance element is charged to a predetermined polarity, and a small electric field is formed near the surface of the toner carrier due to a difference in the surface potential to visualize the latent image. Supply roller 6 as charging means for adhering non-magnetic toner used for
However, other independent charging means may be used as appropriate.

Next, a developing device according to another embodiment of the present invention will be described. This developing device is different from the above-described embodiment in the configuration of the developing roller 6, and the other configuration is basically the same as that in the above-described embodiment. For example, as shown in FIG. 2, the developing roller 6 of the present embodiment
At least 10 on the layer consisting of
Surface protective layer 4 made of a dielectric material having a resistance of ³ Ωcm or more
0 is provided. As the substance constituting each of the resistors 11 and 12, a substance having the same resistivity as that of the above embodiment can be used. However, in the case of this embodiment, the surface protective layer 40 is not preferable for the toner. Since charge injection and the like can be prevented, a substance having a resistivity of less than 10 ³ Ωcm can be used particularly as the medium resistor 12. In this example, both resistors 11 and 12 have a layer thickness of 500 μm on the substrate 10 and have a checkerboard pattern of 100 to 500 μm.
m, and the thickness of the surface protective layer 40 is 100
μm, and a developing bias of 1000 to 1500 V peak-to-peak, and a frequency of 25
When a development was performed by applying a pulse voltage of 0 to 500 Hz superimposed with DC minus 250 V, the image density was high without bias leakage and the like, and the reproducibility and gradation of the diagram were improved. Excellent developed images could be obtained.

Next, a developing apparatus according to still another embodiment of the present invention will be described. This developing device also has a developing roller 6
Is different from the above embodiments, and the rest is basically the same as the above embodiments. For example, as shown in FIG. 4 (IV), the developing roller 6 of this embodiment is
A substance 50 having a resistivity higher than that of the substrate is fixed on the surface of the substrate, and a surface protective layer 40 is provided thereon similarly to the above embodiment. Substance 50 having a resistivity higher than that of the substrate
For example, an epoxy resin in which carbon is dispersed can be used, and the surface protective layer 40 can be made of, for example, a fluorine resin. 4 (I) to 4 (IV)
FIG. 3 also shows an example of a method of manufacturing such a roller 6. In this example, a masking member 60 for forming irregularities on a checkered pattern at 300 μm intervals is provided on a roller 10 of a conductive substrate. To form irregularities with a step of 500 μm (I, II), bury the epoxy resin in which carbon is dispersed and fix them (III), and then protect the surface with a 100 μm-thick fluororesin. Layer 40 was formed.

[0015]

According to the present invention, the electric field is determined by the electric field determined by the correlation between the electric potential on the electrostatic latent image carrier, the electric potential on the developer carrier, and the electric field formed by the voltage applying means. The transfer of the developer is controlled, and this allows an appropriate amount of developer to adhere to the electrostatic latent image on the electrostatic latent image carrier, resulting in a high image density and excellent line diagram reproducibility and gradation. A developed image can be obtained. In addition, a developer having a substantially spherical and uniform small particle diameter is used as the developer, whereby the developer can be charged uniformly and sufficiently, so that the image quality can be improved. Further, as the developer carrying member, the two substances to each other in different resistance to coexist exposed on the surface, with at least 10 ³ [Omega] cm or more developer bearing member which is formed with the material of the resistance, by this, a comparison of the Even when a very high voltage is applied, it is possible to prevent undesirable injection of charge into the developer on the surface and occurrence of bias leak. In particular, when performing development by forming an alternating electric field in the developing section using a pulse voltage or an AC voltage as a developing bias, an electric field for transferring the developer toward the electrostatic latent image carrier is formed. During the period, from the surface of the developer carrier to the developer, the injection of the charge of the opposite polarity to the developer charge polarity is likely to occur,
According to the present invention, this can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a developing device.

FIG. 2 is a partially enlarged view of the vicinity of a surface of a developing roller that can be used in the developing device of the present invention.

3A and 3B show another developing roller that can be used in the developing device of the present invention, wherein FIG. 3A is a partial cross section at a contact portion with the toner supply roller, FIG. 3B is an enlarged view of the surface thereof, (C) is a partially enlarged view near the surface, and (d) is an explanatory diagram showing lines of electric force of a minute closed electric field formed near the surface.

FIG. 4 is a process diagram of a manufacturing process of still another developing roller that can be used in the developing device of the present invention.

[Explanation of symbols]

Reference Signs List 2 developing device, 4 non-magnetic toner 9 developing region, 11 high-resistance 12 medium-resistance

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuichi Ueno 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Junko Tomita 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-55-62469 (JP, A) JP-A-1-142557 (JP, A) JP-A-2-25868 (JP, A) JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/08-15/09 G03G 9/00

Claims (4)

(57) [Claims] An image forming apparatus includes an electrostatic latent image carrier that carries an electrostatic latent image and a developer carrier that carries a developer in a developing section, and a bias is applied to the developing section to perform development. as the developer carrying member, on a conductive substrate, 10 ³ [Omega] cm or more different two materials resistors provided regularly or irregularly the substance with mixed exposed on the surface, at least the two using a developer carrying member for forming a plurality of micro-electric field on the species of one exposed part on the surface is frictionally charged to a polarity opposite or same polarity of the developer surface of the material, as developer Substantially spherical and uniform small particle size
An image agent that is charged by frictional charging
What is carried on the developer carrier by the minute electric field
And a frictional charging means for frictionally charging the exposed portion to a predetermined polarity.
Wherein the movement of the developer is controlled by an electric field determined by a correlation between an electric potential on the electrostatic latent image carrier , an electric field due to the bias, and an electric field on the developer carrier. Developing device. 2. The developing device according to claim 1, wherein said developer is a spherical microcapsule toner having a resin core material coated with a resin shell material frictionally charged. 3. The method according to claim 2, wherein the small electric field is a closed electric field.
The developing device according to claim 1, wherein 4. The developing unit supported by the developer carrier
Is provided to regulate the layer thickness of the developer conveyed to the
Ke The frictional charging means is transported more developer than the layer thickness regulating means.
Direction upstream side and the developer transport direction relative to the developing section.
2. The developing device according to claim 1, wherein the developing device is located downstream.