JPH10142937A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner from being leaked outside a developer tank even when it is scatted on the inside of the developer tank and to obtain a high- quality image without surface fogging by arranging a seal member on a more downstream side than a developing area in the moving direction of magnetic developer. SOLUTION: The seal member 8 is formed of polyethylene terephthalate so as to be like a plate, for example. Then, one end thereof is fixed to the upper side surface of the developer tank 1 and the free end thereof is elastically brought into contact with the surface of the magnetic developer 2 attracted to the surface of a developing roll 3 on the more downstream side than the developing area in the moving direction of the developer 2. A scraping member 7 is formed to be like a round bar and proximately arranged to the roll 3 on the downstream side of the seal member 8. By forming a magnetic brush by directly attracting the developer 2 in the tank 1 to the surface of the roll 3 and rubbing an electrostatic charge image formed on the surface of a photoreceptor drum 4 by the magnetic brush, the high-quality image without density irregularity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical permanent magnet member in which magnetic poles of different polarities are arranged at equal intervals in the circumferential direction on the surface of an image carrier which carries an electrostatic charge image and moves. A developing device comprising a developing roller, which supplies a magnetic developer to the surface of the developing roller to develop the electrostatic image, particularly to prevent toner scattering of the magnetic developer,
The present invention relates to a developing device capable of obtaining a high quality image without fogging.

[0002]

2. Description of the Related Art In an image forming method using electrophotography or electrostatic recording, an electrostatic charge image formed on the surface of an image carrier such as a photoconductor or a dielectric is suction-held on a developing roll. A final image is obtained by developing by a magnetic brush method via a magnetic developer and directly fixing the obtained toner image, or by fixing the toner image after transferring it onto a transfer member such as plain paper.

The developing roll has a developer supporting member or sleeve made of a non-magnetic material, and a permanent magnet member disposed inside the sleeve and having a plurality of magnetic poles on its surface. The image carrier is opposed to the surface of the image carrier at a predetermined interval so as to form a development area between the carrier and the surface of the carrier. The magnetic developer held on the sleeve is conveyed to the developing area by the relative rotation of the sleeve and the permanent magnet member, so that the toner contained in the magnetic developer adheres to the electrostatic charge image to form a toner image. can get.

On the other hand, in an electrophotographic apparatus represented by a copying machine or a printer, it is strongly desired to reduce the cost and size of the apparatus, and the structure of a developing roll is also changing to meet this demand. That is, it has been proposed to omit the sleeve constituting the developing roll, directly adsorb the magnetic developer on the surface of the permanent magnet member, and convey the magnetic developer to the developing area by rotation of the permanent magnet member (for example, Japanese Patent Application Laid-Open (JP-A) no. 1962-20
No. 1463).

[0005]

In the case of performing the magnetic brush development using the developing roll in which the sleeve is omitted as described above, the thickness of the developer layer formed on the surface of the permanent magnet member depends on the thickness of the magnetic pole. Since there is a difference between the top and the magnetic pole and a difference in developability, the rotation of the permanent magnet member causes the peaks and valleys of the developer layer to come into contact with the image carrier surface alternately, thereby moving the image carrier. There is a problem in that the image density varies along the direction, and in particular, the reproducibility of the halftone is reduced. In order to eliminate the density unevenness as described above, it is conceivable to rotate the permanent magnet member at a high speed. However, this causes an increase in driving torque, scattering of the developer, and noise, which poses a practical problem. is there.

In order to solve the above-mentioned problems, the present applicant has already determined that the moving directions of the developing roll and the image carrier in the developing area where the developing roller and the image carrier face each other are opposite to each other. An application has been filed for the invention to be improved (Japanese Patent Application No. 8-49733).

According to the above-mentioned improved invention, it is possible to eliminate development unevenness corresponding to the magnetic pole pitch, which is a problem in a developing device using a developing roll in which a sleeve is omitted, and to obtain a high quality image. Is played. However, subsequent studies have revealed that there are some problems.

That is, in a developing apparatus using a developing roll without a sleeve as described above, when a so-called two-component system composed of a mixed material of a toner and a magnetic carrier is used as a magnetic developer, The upper magnetic developer is removed from the surface of the developing roll once through a scraping member such as a scraper after passing through the developing area, replenished with toner, mixed well, and adsorbed and transported to the developing roll again. It is necessary to maintain a proper developing action.

FIG. 2 is a cross-sectional view of an essential part showing an example of an embodiment of the improved invention. In FIG. 2, reference numeral 1 denotes a developer tank which accommodates a two-component magnetic developer and a rotatable developing roll 3 formed of a permanent magnet member below the developer tank. Note that magnetic poles of different polarities are arranged at equal intervals in the circumferential direction on the surface of the developing roll 3.

Reference numeral 4 denotes a photosensitive drum, which is rotatably formed in the direction of the arrow, and is provided so as to face the developing roll 3 with an appropriate gap therebetween. The developing roll 3 and the photosensitive drum 4
Is formed so that the moving directions are opposite to each other in a developing region where the two are opposed to each other. Reference numeral 5 denotes a doctor blade, which is provided in the developer tank 1 and faces the developing roll 3 via an appropriate gap to regulate the layer thickness of the magnetic developer 2 adsorbed on the developing roll 3.

Reference numeral 6 denotes a mixing member, which is provided in the developer tank 1 and uniformly mixes the toner constituting the magnetic developer 2 with the magnetic carrier. Numeral 7 denotes a scraping member for scraping off the magnetic developer 2 after the development is completed. The scraping member 7 is formed, for example, in a plate shape and provided so as to be in sliding contact with the surface of the developing roll 3.

With the above configuration, the magnetic developer 2 in the developer tank 1 is directly attracted to the surface of the developing roll 3 to form a magnetic brush, and the electrostatic image formed on the surface of the photosensitive drum 4 is magnetically transferred. By rubbing with a brush, a high-quality image without density unevenness can be obtained. After the development is completed, the magnetic developer 2 is removed from the surface of the developing roll 3 by the scraping member 7, the toner is replenished in the developer tank 1, uniformly mixed by the mixing member 6, and again mixed with the developing roll 3. It is conveyed by suction.

However, simply placing the scraping member 7 in contact with or close to the developing roll 3 after the completion of development as shown in FIG. 2 causes the following inconvenience. That is, the accumulation of the magnetic developer 2 removed and riding on the scraping member 7 makes a motion that is reversed in the direction opposite to the moving direction of the surface of the developing roll 3 due to the influence of the moving magnetic field by the developing roll 3.

In particular, since the change of the moving magnetic field by the multi-polar magnetized developing roll 3 is abrupt and frequent, the deposition motion of the magnetic developer 2 is also abrupt and frequent. As a result, the scraping member 7 Cloud-like toner scattering occurs from the tip. Although the main cause of toner scattering in the developer tank 1 is the scraping member 7, it is also generated by the rotation of the mixing member 6 and the developing roll 3. Such cloud-like toner scattering causes not only contamination in the developing device but also fogging or the like in which toner adheres to the photoconductor drum 4, which causes a problem of deteriorating image quality.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a developing apparatus capable of obtaining a high-quality image without fogging even when toner scatters in a developer tank.

[0016]

In order to solve the above-mentioned problems, according to the present invention, a magnetic pole having a different polarity is provided on the surface in the circumferential direction so as to face an image carrier which carries an electrostatic image and moves. A developing roller composed of a cylindrical permanent magnet member arranged at equal intervals is provided in a developer tank, and a moving direction of the developing roller and the image carrier in a developing region where the developing roller and the image carrier are opposed to each other. Are formed in opposite directions to each other, a magnetic developer is adsorbed on the surface of the developing roll, and the electrostatic image is visualized by bringing the magnetic developer into contact with the image carrier. In the developing device,
A plate-shaped seal member is provided in a developer tank on the downstream side in the moving direction of the magnetic developer from the developing area so that its free end is in contact with the magnetic developer adsorbed on the surface of the developing roll. Technical measures were adopted.

In the present invention, the material forming the seal member is preferably a plastic material such as Mylar or a non-magnetic material such as stainless steel, but may be a ferromagnetic material. That is, the seal member may be formed of, for example, an iron plate, and the free end side of the seal member may be magnetically attracted to the developing roll. According to the experiment, a sufficient effect was obtained by using both the 0.5 mm thick Mylar sheet and the 0.06 mm thick SUS304 (non-magnetic) and SUS416 (ferromagnetic) sheets.

When a scraping member is used, the scraping member may be formed in a plate shape or a round bar shape from a nonmagnetic material, and may be provided in contact with or close to the surface of the developing roll. In the present invention, the pitch P between magnetic poles of different polarity in the developing roll is
It can be formed to 0.5 to 10 mm. If the pitch P between the magnetic poles of different polarities is less than 0.5 mm, it is difficult to form magnetic poles,
In addition, the value of the surface magnetic flux density becomes small, the amount of magnetic developer adsorbed and held on the surface of the developing roll decreases, and fogging occurs and developability decreases, which is not preferable. On the other hand, if the pitch P exceeds 10 mm, the thickness of the magnetic developer differs between the magnetic poles of the permanent magnet member constituting the developing roll and between the magnetic poles, and the difference increases, resulting in uneven image density. This is inconvenient. The preferred range of the magnetic pole pitch P is 1 to 5 mm.

Next, the ratio Vm / Vp of the peripheral speed Vm (mm / sec) of the developing roll to the moving speed Vp (mm / sec) of the image carrier is 5
If it exceeds, the driving torque of the developing roll becomes large, noise is generated, and the toner constituting the magnetic developer is scattered or the magnetic carrier is worn, which is not preferable. On the other hand, if Vm / Vp is less than 1, the electrostatic image on the image carrier in the developing region does not evenly encounter the magnetic poles constituting the developing roll and the toner on the image carrier. The supply capacity is insufficient, and density unevenness occurs in the image, which is likely to be inconvenient. That is, since the toner in the magnetic developer is consumed in each of the developing steps, in order to maintain a predetermined image density, the developing roll is rotated so that the speed ratio is about three times or more of the lower limit. Although it is preferable that the toner concentration in the magnetic developer is as high as 40 to 50% by weight even when Vm / Vp is around 1, a good image can be obtained. It is.

In the present invention, at least the support / transport portion of the magnetic developer of the cylindrical permanent magnet member can be formed of an isotropic hard ferrite magnet. That is, according to the isotropic hard ferrite magnet, the ferrite powder (M
OnnFe ₂ O ₃ (M: at least one of Ba, Sr, and Pb;
Using a raw material containing n = 5 to 6)), for example, by a method such as a rubber press method or an extrusion molding method, a cylindrical molded body molded in a magnetic field-free state is processed into a predetermined size after sintering,
By magnetizing the outer peripheral surface, a cylindrical permanent magnet member having a desired magnetic pole pitch and surface magnetic flux density can be obtained. On the other hand, in the case of a plastic magnet or a rubber magnet, it is necessary to produce an anisotropic molded body by molding in a magnetic field from the viewpoint of surface magnetic flux density, and thus there is a problem that the number of magnetic poles cannot be increased.

In the above case, the diameter of the developing roll at each position in the axial direction can be made substantially the same, and the magnetic pole can be provided only in the axial middle portion corresponding to the developing width. That is, the non-magnetized portions at both ends of the developing roll formed to have substantially the same diameter over the entire length can be used as a support portion, a drive portion, a seal portion, a gap spacer portion and the like.

In the present invention, a doctor blade made of, for example, a conductive metal material and regulating the layer thickness of the magnetic developer is provided so as to come into contact with the magnetic developer adsorbed on the surface of the developing roll. A bias voltage for the purpose of, for example, reversal development, fog prevention, or the like can be applied to the magnetic developer via the electrode member. This means is effective when the developing roll is formed of a high electric resistance material or an electrically insulating material such as a hard ferrite magnet.

Further, in the present invention, at least the surface of the developing roll is formed to be conductive, and a bais voltage for the above purpose can be applied to the magnetic developer via the developing roll. As means for forming the surface of the developing roll to be conductive, for example, there is a means for plating a conductive metal material such as Ni, Al, Cu, Ag, and Au with a thickness of 1 to 5 μm.
Also, the CVD method of nitride such as TiN and CrN or P
Coating by the VD method is also possible.

Next, the surface magnetic flux density of the developing roll is 100 to
Preferably, it is formed at 800G. Surface magnetic flux density is 10
If it is less than 0 G, it is not preferable because the magnetic developer has insufficient adsorbing and holding power on the developing roll and scatters. On the other hand, if the surface magnetic flux density exceeds 800 G, in the case of a magnetic toner, it becomes difficult for the toner to adhere to the electrostatic charge image formed on the surface of the image carrier, and the image quality deteriorates, which is inconvenient. Further, the thickness of the attracted magnetic developer layer becomes excessive, the driving torque of the developing roll increases, and a wide developing gap is required, so that it is difficult to obtain a strong developing electric field.

Next, as the magnetic developer used in the present invention, a mixed powder of a magnetic toner and a magnetic carrier (toner concentration of 10 to 90% by weight) and a mixed powder of a non-magnetic toner and a magnetic carrier (toner concentration 5 to 70% by weight). The reason that the toner can be used in such a wide toner concentration range is that the magnetic developer adsorbed and supported by the developing roll is supplied to the image carrier in a state as it is, and the substantial magnetic developer is relatively moved with respect to the developing roll. Without exercise
It is considered that the toner scattering power is extremely small.
For this reason, toner density control is generally unnecessary.

When a two-component magnetic developer is used, a toner whose concentration has been adjusted to a predetermined value in advance is charged into a developer tank, or a magnetic carrier is adsorbed on the surface of a developing roll. Then, only the toner may be supplied into the developer tank.

The toner may be either magnetic or non-magnetic, but is preferably an insulating toner having a volume resistivity of 10 ¹⁴ Ω · cm or more from the viewpoint of improving transferability. Those which are easily charged by friction with a doctor blade or the like (the frictional charge amount is 10 μc / g or more in absolute value) are preferred. The average particle diameter of the toner is 5 to 10 μm in order to obtain a high-definition image.
It is preferable to form it.

The composition of the toner is the same as that of a commonly used toner, such as a binder resin (styrene-acrylic copolymer, polyester resin, etc.), a colorant (carbon black, etc., but magnetite is used as a magnetic powder described later). In some cases, it may not be added) as essential components, and as optional components, magnetic powder (magnetite, soft ferrite, etc.), charge control agent (nigrosin, metal-containing azo dye, etc.), release agent (polyolefin, etc.), Those containing (internally and / or externally) a fluidizing agent (hydrophobic silica) can be used.
In the case of using a magnetic toner, the amount of the magnetic powder is preferably 70% by weight or less, since the fixability is deteriorated if the magnetic powder is large. By appropriately selecting a coloring agent, a color toner can be obtained.

Further, the average particle size of the carrier is 10 to 50 μm.
Are particularly preferred. This is because, when the average particle diameter is 50 μm or less, the allowable toner concentration range is widened and a sufficient amount of toner charge can be obtained. However, when the average particle diameter is smaller than 10 μm, carrier adhesion tends to occur.

The carrier may be a mixture of two or more of the above magnetic particles. For example, the average particle size is 60 to 120.
magnetic particles having a large particle diameter of μm and an average particle diameter of 10 to 50 μm
And magnetic particles having an average particle diameter of 10 to 5
It may be mixed with binder type magnetic particles having a small particle size of 0 μm. The mixing ratio may be determined in consideration of the size and magnetic characteristics of the magnetic particles.

Next, the volume resistivity of the magnetic carrier is 10 ³
Those having a value of from 10 to ^{13 13} Ω · cm are preferable. Volume resistivity is 10
^If it is less than ³ Ω · cm, adhesion to the image carrier is liable to occur and the image quality is deteriorated. On the other hand, when the volume resistivity exceeds 10 ¹³ Ω · cm, the developing property is lowered and the image density is lowered, which is disadvantageous.

The saturation magnetization σs of the magnetic carrier is 20 e
Those exceeding mu / g are preferable, and examples thereof include iron powder, ferrite, magnetite, and binder-type particles in which magnetic powder is dispersed in a resin. If the saturation magnetization s is less than 20 emu / g, carrier adhesion is likely to occur, which is not preferable.

The magnetization value was measured using a vibrating sample magnetometer (VSM-3 manufactured by Toei Kogyo Co., Ltd.), and the average particle size (volume) of the toner was measured by a particle size analyzer (Coulter Electronics Co., Ltd.). It was measured using a counter model TA-II). The average particle size (weight average) of the carrier is
It was calculated from the particle size distribution measured by a multi-sieve shaking machine.

The value of the volume resistivity is determined by measuring an appropriate amount (10 or more mg) of the sample and improving the dial gauge.
Fill into a 3.05mm Teflon (trade name) cylinder,
Under a load of 0.1 kg, D.D. C. 100
V / cm electric field, and D.C. C. 400
The resistance was calculated by applying an electric field of 0 V / cm and measuring.
4329 made by Yokogawa Hewlett-Packard for resistance measurement
A type insulation resistance meter was used. Further, the triboelectric charge amount is determined by first mixing a magnetic developer adjusted to a toner concentration of 5% by weight, blowing the toner at a blow pressure of 1.0 kgf / cm ² , and using a blow-off powder charge amount measuring device (TB, manufactured by Toshiba Chemical Co., Ltd.). -2
00 type).

Next, in the present invention, when the gaps between the developing roll and the magnetic developer layer thickness regulating means and the image carrier are t and g, respectively, t = 0.1 to 0.3 mm and g−t = 0.05 to
It can be 0.20 mm. Further, it is needless to say that the value of t can be further reduced and the magnetic developer is not in contact with the image carrier through the gap g.

With the above configuration, the magnetic brush is formed directly on the outer surface of the developing roll composed of a permanent magnet member, which is a suction and support means for the magnetic developer having a configuration lacking the sleeve, and is formed on the surface of the image carrier. The development can be performed by rubbing the electrostatic charge image or by flying the toner, and a high-quality image free from density unevenness and fog can be obtained.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cross-sectional view of a main portion showing an embodiment of the present invention, and the same portions are denoted by the same reference numerals as in FIG. In FIG. 1, reference numeral 8 denotes a sealing member which is formed, for example, in a 0.5 mm-thick plate from polyethylene terephthalate, and has one end fixed to the upper side surface of the developer tank 1 and the free end of the magnetic developer 2 from the developing area. Magnetic developer 2 adsorbed on the surface of developing roll 3 on the downstream side in the moving direction
Is provided so as to elastically contact the surface of the substrate. Next, the scraping member 7 is formed in a round bar shape having a diameter of 3 to 6 mm by, for example, SUS303, and provided downstream of the seal member 8 in close proximity to the developing roll 3 (a gap of about 0.2 mm).

With the above configuration, the magnetic developer 2 in the developer tank 1 is directly attracted to the surface of the developing roll 3 to form a magnetic brush, and the electrostatic image formed on the surface of the photosensitive drum 4 is transferred to the magnetic brush. As a result, a high-quality image without density unevenness can be obtained. The magnetic developer 2 after passing through the developing area is returned into the developer tank 1 with the rotation of the developing roll 3. However, since the inside and outside of the developer tank 1 are blocked by the seal member 8, the magnetic developer 2 is removed from the surface of the developing roll 3. When the magnetic developer 2 is removed via the scraping member 7, even if the toner of the magnetic developer 2 is scattered, the magnetic developer 2 is prevented from leaking out of the developer tank 1.

Since the seal member 8 is provided so as to elastically contact the surface of the developing roll 3, the magnetic developer 2 having passed through the developing area is sealed while adsorbed on the surface of the developing roll 3. The developer can easily pass through the member 8 and enter the developer tank 1. In addition, if the seal member 8 has a structure inclined with respect to the flow of the magnetic developer 2 so that all the flow of the magnetic developer 2 can pass through the contact portion with the magnetic developer 2 without obstruction, It is also possible to form a rigid body having no flexibility.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a photosensitive drum 4 is made to have a diameter of 3 by OPC.
0 mm, the peripheral speed Vp = 120 mm / sec, and the surface potential was -650 V. Next, the developing roll 3 was formed in a cylindrical shape with an outer diameter of 20 mm using, for example, an isotropic ferrite magnet (YBM-3 manufactured by Hitachi Metals), magnetized with 32 poles, and had a surface magnetic flux density of 500 G. The peripheral speed Vm of the developing roll 3 and the photosensitive drum Vp were set to Vm / Vp = 1.3, the developing gap was set to 0.45 mm and the doctor gap was set to 0.35 mm, and a DC bias voltage of -500 V was applied from the doctor blade 5.

The toner was made non-magnetic and prepared as follows. That is, bisphenol A type polyester (binder resin; Mw = 19,600, Mn = 2,000) by weight ratio
87 parts, carbon black (colorant; Mitsubishi Chemical # 5)
0) 10 parts, polypropylene (release agent; Sanyo Chemical T
P32) 2 parts and a charge control agent (Nippon Kayaku Kaya Charge T-2N) 1 part are dry mixed. The mixture is melted and kneaded in a twin-screw ruder heated to 150 degrees, cooled, and the cooled material is coarsely pulverized by a mechanical pulverizer until it passes through a wire mesh having an opening diameter of 1 mm. Then, a wind pulverizer / jet mill And pulverized. This is a wind classifier (Alpine 100
(MZR) so as to obtain a volume average particle size of about 10 μm, and a negatively chargeable powder was prepared. Hydrophobic silica (superplasticizer; Aerosil R9 manufactured by Nippon Aerosil Co., Ltd.) is added to this powder.
72) 0.5 part was added to obtain a toner. The volume resistivity of this toner is 9 × 10 ¹⁴ Ω · cm, and the triboelectric charge is −28 μm.
c / g.

Next, an iron powder carrier (average particle diameter 50 μm, volume specific resistance 10 ⁷ Ω · cm, saturation magnetization 180 emu / g) coated with a silicone resin was used as a magnetic carrier, and mixed with the toner described above to obtain a toner concentration of 45%. % By weight of the magnetic developer. Transfer the visualized toner image to plain paper,
Heat roll fixing (linear pressure 1 kg / cm, temperature 160 ° C.). Table 1 shows a comparative example together with a case where the same image was formed by the developing device shown in FIG.

In Table 1, background fog is a result of evaluating toner fog on a white background image. ○ indicates no toner fogging, Δ indicates slight occurrence but practically usable, and × indicates unusable toner due to excessive fog.

[0044]

[Table 1]

As is clear from Table 1, in the comparative example using the developing device shown in FIG. 2, when removing the magnetic developer 2 after passing through the developing area, the cloud-like toner scatters as described above. As a result, it is recognized that the toner leaks out of the developing device and adheres to the surface of the photosensitive drum 4 to cause fog. And this land fog is 5 consecutive
It is recognized that it becomes remarkable after the formation of the image of 100,000 sheets. On the other hand, in the embodiment of the present invention, it is recognized that a high-quality image free from background fog can be formed not only in the initial stage of development but also after 500,000 continuous sheets.

[0046]

Since the present invention has the configuration and operation as described above, the following effects can be obtained. (1) By providing a seal member on the downstream side of the developing area in the moving direction of the magnetic developer, even if toner scatters inside the developer tank, it does not leak out of the tank and is free from ground fog. A quality image is obtained. (2) Since only the permanent magnet member is used as the component of the developing roll, the sleeve can be omitted, and the developing device and the image forming apparatus can be reduced in size. (3) Since the moving direction of the developing roll in the developing area is opposite to the moving direction of the image carrying means, a high quality image without pitch unevenness can be obtained even when the developing roll is rotated at a low speed. (4) Since the magnetic developer is directly adsorbed and held on the surface of the developing roll, the transportability and the shape stability of the magnetic brush are improved, the developability is good, and a high-quality image is obtained. . (5) When a two-component magnetic developer is used, the toner concentration can be set in a wide range, the toner concentration control means can be omitted, and the whole apparatus can be made compact.

[Brief description of the drawings]

FIG. 1 is a main part cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part showing an example of an embodiment of the improved invention.

[Explanation of symbols]

 3 developing roll 7 scraping member 8 sealing member

Claims (1)

[Claims] 1. A developing roller comprising a cylindrical permanent magnet member having magnetic poles of different polarities arranged on a surface thereof at equal intervals in a circumferential direction, facing a moving image bearing member carrying an electrostatic charge image. In addition to providing the developer in the developer tank, the developing roller and the image carrier in the developing area where the developing roller and the image carrier face each other are formed so that the moving directions of the developing roller and the image carrier are opposite to each other. A developing device configured to visualize the electrostatic charge image by bringing the magnetic developer into contact with the image carrier while adsorbing the magnetic developer; A developing device, wherein a plate-shaped seal member is provided in a tank such that a free end thereof is in contact with a magnetic developer adsorbed on a surface of the developing roll.