JPH1138762A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which forms a magnetic brush of a two-component developer containing toner and magnetic carrier and turns visible the latent image due to the difference in the electrostatic potential by contacting the brush with an image carrier, wherein the image disturbance caused by the brush rubbing of the toner image is precluded to produce a high quality image with a stable density. SOLUTION: The developing bias voltage impressed between a developer carrier 3 and an image carrier 2 is set in a region where the increasing developing toner amount with the developing bias voltage saturates substantially. The developer should contain two or more sorts of toners having different electrostatic charge amounts. The first toner among the two or more sorts is transferred to the image carrier to form a toner image, while the second toner remains attached to a magnetic carrier and makes no transfer to the image carrier. The produced toner image is precluded from directly touching the carrier owing to attachment of the second toner to the carrier to ensure reduction in the image disturbance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a developing device used for an image forming apparatus such as a printer, and more particularly to a developing device using a two-component developer in which a toner and a carrier are mixed.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic method, an electrostatic latent image formed on an image carrier is visualized by adhering toner, and this visible image is transferred onto a recording sheet to form an image. It is configured to perform copying or the like. As a developing device for visualizing a latent image formed on an image carrier in such a device, there are a developing device using a one-component developer and a developing device using a two-component developer containing a toner and a carrier. As a developing device using a two-component developer, a developing device in which a developer carrier whose peripheral surface is rotationally driven is disposed in close proximity to an image carrier and has a magnetic field generating means having a plurality of magnetic poles therein is generally used. Have been. In such a developing device, the developer supplied to the surface of the developer carrier is held by the magnetic force generated by the magnetic field generating means, thereby forming a magnetic brush in which carriers are connected in a spike shape. Then, the magnetic brush is rubbed or brought close to the image carrier by rotation of the peripheral surface of the developer carrier. Since a bias voltage is applied to the developer carrier, an electric field is generated between the developer carrier and the electrostatic latent image, and by this action, the charged toner in the developer is transferred to the image area, The latent image on the image carrier is developed.

A developing device using such a two-component developer has features such as easy charging of toner and hardly causing aggregation of toner particles. As the two-component developing device, there are a two-component developing device using a so-called insulative carrier having almost no conductivity, and a two-component developing device using a so-called conductive carrier having a little electric resistance and showing some conductivity.

In magnetic brush development using a two-component developer containing a conductive carrier, the amount of developed toner does not change even when the developing bias voltage fluctuates somewhat or the amount of charge of the toner fluctuates. Development can be performed in a saturated state. This performs development as follows.

In general, when the developing contrast Vs increases, as shown in FIG. 9, the developing toner amount increases, but reaches a saturation region where the developing toner amount hardly increases above a certain developing contrast Vsa. That is, the setting of the developing contrast Vs utilizes this saturation region, and the DC component Vbias and the electrostatic latent potential of the developing bias potential are set so that the developing contrast enters the region where the developing toner amount is saturated. The potential V1 of the exposed portion of the image is set.

In order to set the developing bias in the saturation region, it is necessary that the magnetic carrier has a low resistivity. As shown in FIG. 10, a so-called magnetic brush in which magnetic carriers to which toner is attached is spike-shaped is formed on the developer carrier, but if the resistivity of the magnetic carrier is low, the magnetic brush becomes conductive. And the potential of the so-called virtual developing electrode becomes closer to the image carrier. Therefore, an electric field for transferring the toner is formed between the vicinity of the tip of the magnetic brush and the surface of the image carrier. As a result, the amount of toner in the region to which the electric field is applied is limited to that existing near the tip of the magnetic brush, that is, near the image carrier, and the amount of toner contributing to development is limited.
When the developing bias voltage is equal to or higher than a certain value, the developing toner amount becomes saturated. If the amount of toner adhering to the carrier, that is, the concentration of the toner with respect to the carrier, is always kept constant, even if the charge amount of the toner changes due to environmental fluctuation or the like, the developing toner amount is kept almost constant, Development at an appropriate density is always performed.

[0007]

However, in the two-component development using a so-called conductive carrier as described above, the following problems may occur. In the developing region where the image carrier and the developer carrier are opposed to each other, the developer carrier is often driven at a higher peripheral speed than the image carrier. Then, the transfer of the toner from the entrance of the developing area to the latent image is started, and all the toner adhering near the tip of the magnetic brush is transferred before reaching the exit of the developing area. The magnetic brush rubs the developed toner image on the image carrier from behind.

At this time, the carrier at the tip end of the carrier forming the magnetic brush has no toner attached thereto, and the toner is re-transferred from the toner image on the image carrier and adheres to the carrier. If such toner re-adhesion occurs, the toner image on the image carrier is disturbed, and the development in the saturated state does not occur, and the amount of the developed toner fluctuates. Also,
An abnormal discharge occurs between the carrier and the image carrier, which may disturb the already developed toner image.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing apparatus capable of obtaining a high-quality image with stable density and no image disturbance. .

[0010]

According to a first aspect of the present invention, there is provided a developing device, comprising: a developing device which is close to an image carrier having a surface on which a latent image is formed due to a difference in electrostatic potential; A developer carrier having an endless peripheral surface that is disposed so as to face and is driven to rotate, and magnetically adsorbs a two-component developer including a magnetic carrier and a toner to the endless peripheral surface. Conveyed to a development area in proximity to the image carrier,
In a developing device for selectively transferring toner to the image carrier to visualize the latent image, a developing bias voltage applied between the developer carrier and the image carrier is equal to the developing bias voltage. It is set in a region where the increase in the amount of developing toner with the increase is substantially saturated, and the two-component developer, when charged by stirring, contains two or more types of toners having different charged amounts, The first toner is charged in the developing area to an amount of charge that transfers from the developer carrier to a latent image on the image carrier, and the second toner adheres to the magnetic carrier. It is assumed that it is charged to the amount of charge passing through the development area as it is.

Although the first toner and the second toner are charged to have the same polarity as shown in FIG.
As shown in (b), it may be charged to the opposite polarity. When both toners are charged to the same polarity, the first toner is charged within a range of a charge amount capable of transferring to the image carrier in the developing bias electric field, and the second toner is charged more. Use something. This utilizes the following phenomena.

The Coulomb force attracted to the image carrier in the developing bias electric field increases almost in proportion to the charge amount of the toner, but the adhesive force acting between the toner and the magnetic carrier is the secondary of the charge amount of the toner. Function. Then, the toner charged in the area where the Coulomb force is dominant (the area indicated by the symbol A in FIG. 7) is transferred to the image carrier. Therefore, the second toner having a larger charge amount than the area A does not transfer to the image carrier.

In the above-described developing device, the two-component developer magnetically adsorbed on the developer carrier becomes a magnetic brush in which magnetic carriers are connected in a spike shape, and the developer is developed by moving the peripheral surface of the developer carrier. Conveyed to the area. In the development area,
The developing bias voltage is set so that the amount of the developing toner becomes saturated. Of the first toner attached to the magnetic brush, the toner in the transferable range is almost completely transferred to the image carrier and the latent toner is transferred. Visualize the image. At this time, the second toner contained in the developer on the developer carrier has a different charge charge distribution region from the first toner, and does not transfer to the image carrier and adheres to the surface of the magnetic carrier. Has been left.

The magnetic brush after transferring substantially the entire amount of the transferable first toner to the image carrier may rub against the toner image already formed on the downstream side of the developing area. As shown in FIG. 8, the second toner adheres to the surface of the magnetic carrier, and the second toner is directly interposed between the first toner transferred to the image carrier and the magnetic carrier. The chance of contact between the two is reduced. Therefore, it is possible to reduce the possibility that the first toner once transferred to the image carrier is re-adhered to the magnetic carrier.

The magnetic carrier has a position where the toner easily adheres and a position where the toner hardly adheres due to minute irregularities on the surface. However, after the first toner is transferred to the image carrier, the second toner is transferred. Occupies a position where the toner easily adheres, and even if it comes into contact with the first toner on the image carrier, it is difficult to cause re-adhesion. Therefore, the development can be performed with the developing toner amount being saturated. Further, by interposing the second toner between the first toner and the magnetic carrier, the distance between the magnetic carrier and the image carrier can be maintained, and the occurrence of abnormal discharge can be prevented, and the toner image can be prevented. Can be prevented from being disturbed.

According to a second aspect of the present invention, in the developing device according to the first aspect, the two-component developer is configured such that a concentration (% by weight) of the first toner contained in the two-component developer is TC1, and Assuming that the toner concentration (% by weight) is TC2, about 5 (% by weight) ≦ TC1 + TC2 ≦ about 12 (% by weight) about 4 (% by weight) ≦ TC1 ≦ about 11 (% by weight) about 1 (% by weight) ) ≤ TC2 ≤ about 8 (% by weight).

In the developing device according to the present invention, in order to form a toner image having a sufficient density, the concentration TC1 of the toner capable of transferring to the image carrier, that is, the first toner, is about 4% by weight or more. Is required. On the other hand, the first
In order to obtain the effect of preventing the toner from re-adhering to the magnetic carrier, the concentration TC2 of the second toner needs to be about 1% by weight or more. Therefore, the total amount of these toners needs to be about 5% by weight or more.

Further, in order to stir and mix the toner and the magnetic carrier to sufficiently charge the first toner, the concentration of all toners must be about 12% by weight or less.
Therefore, if the second toner contains about 1% by weight or more, the concentration TC1 of the first toner is about 11% by weight.
Assuming that about 4% by weight or more is secured as the first toner, the concentration TC2 of the second toner is about 8% by weight or less. Therefore, by satisfying the above three conditions, it is possible to perform development with a sufficient density, and to perform development with a stable density or development without image disturbance due to abnormal discharge by developing in a state where the amount of developing toner is saturated. it can.

According to a third aspect of the present invention, in the developing device of the first aspect, the charging polarity of the first toner and the second toner is reversed as shown in FIG. Things.

By using such a first toner and a second toner, it is easy to sufficiently charge the first toner to be transferred to the image carrier, and it is possible to develop a high-density image with a sufficient density. Becomes

According to a fourth aspect of the present invention, in the developing device according to the first aspect, the first toner and the second toner are made of the same binder resin and the same pigment, and the charge control agent The charging characteristics are set so as to be different from each other by the addition of.

According to a fifth aspect of the present invention, in the developing device according to the first aspect, the second toner comprises the first toner.
And transparent particles formed of the same resin as the binder resin used in the toner of (1).

As in the above-described developing device, the two-component developer is firstly used.
When the first toner and the second toner are included, the second toner may be slightly transferred to the image bearing member. In particular, when the charging polarity of the second toner is the same as that of the first toner, it is conceivable that the toner is transferred to the image portion on the image carrier together with the first toner. However, in this developing device, the second toner contains the same binder resin and the same pigment as the first toner, so that even if the second toner transfers to the image portion, no image defect occurs, High image quality is maintained.

When the charge amount of the second toner is smaller than that of the first toner or when the charge polarity is opposite, the transfer to the background portion of the image carrier can be considered. In the case of transparent particles containing no, no defects such as fogging occur.

According to a sixth aspect of the present invention, there is provided the developing device according to the first aspect, wherein the developing device is disposed adjacent to the developer carrying member on the downstream side of the developing area, and is provided in the second component developer.
And a toner collecting roll for electrically adsorbing the toner and peeling the toner from the magnetic carrier.

In this developing device, the first toner is consumed for development after passing through the developing area, and the second toner is electrically attracted to the second toner from the developer in which the concentration of the second toner is increased.
Lower the toner density. Then, the newly supplied first toner is mixed, agitated, and supplied to the developer carrier again with the concentrations of the first toner and the second toner set to predetermined values. Therefore, the density of the first toner and the density of the second toner of the developer supplied to the developing area can be maintained at approximately predetermined values.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a developing device according to an embodiment of the invention described in claim 1, claim 2, claim 3 or claim 4. The developing device 1 is disposed so as to face the image carrier 2,
Has a gap of 0.5 mm from the developing sleeve 4 and rotates at a peripheral speed of 150 mm / sec in the direction indicated by the arrow in the figure. On the image carrier 2, the exposed portion potential -200 V and the non-exposed portion potential-
A 650 V latent image is formed.

The developing device 1 has a housing for accommodating a two-component developer, and an opening is provided at a position of the housing facing the image carrier 2, and the opening faces the image carrier. Developer carrier 3 is arranged as described above. Above the developer carrier 3, a layer thickness regulating member 6 for regulating the developer layer on the surface of the developer carrier to a constant thickness is provided. In this housing, two screw augers 7 and 8 are arranged substantially horizontally and parallel to each other.

The developer carrier 3 has a developing sleeve 4 rotatably supported and a magnet roll 5 fixed and supported inside the developing sleeve 4, and the surface of the developing sleeve 4 is caused by the magnetic force of the magnet roll 5. The two-component developer is adsorbed on the image bearing member and transported to a position facing the image carrier 2 by orbiting the developing sleeve.

The developing sleeve 4 is provided with a layer thickness regulating member 6 and a .0.
With a gap of 7 mm and a peripheral speed of 300 mm / sec
It rotates in the direction of the arrow shown inside. The developing sleeve 4 is made of a conductive non-magnetic material, for example, aluminum, and its surface is formed by blasting to have minute irregularities of several microns with a ten-point average roughness Rz. Further, a power supply (not shown) supplies Vp-p = 1.
AC component of 5KV, frequency f = 6KHz and Vdc = -50
A voltage on which a DC component of 0 V is superimposed is applied.

The magnet roll 5 has passed through a developing magnetic pole S1 forming a spike of developer at a position facing the image carrier 2, and a developing section where the image carrier 2 and the developer carrier 3 are facing. The later developer is peeled off from the surface of the developing sleeve 4, and two separated magnetic poles N3 and N4 of the same polarity which are arranged adjacently to eliminate the image history, and the developer mixed and agitated in the agitating section is developed by the developing sleeve. And a layer-forming magnetic pole S2 that forms a spike of the developer near the layer thickness regulating member 6 to adjust the developer to a predetermined thickness. The transport magnetic poles N1 and N2 for maintaining the developer on the surface of the developing sleeve 4 are magnetized.

The screw augers 7 and 8 have a diameter of 20 mm.
mm and a pitch of 6 mm, and is driven to rotate in the same direction to stir and transport the developer. Since these screws have spiral wings in opposite directions, the directions of the developer transported by the respective screw augers are opposite to each other.

FIG. 2 is a schematic structural view of the two-component developer contained in the developing device 1 and includes two types of toner charged to different amounts of charge. The two-component developer includes a magnetic carrier 10, a first toner 11 charged to a charge amount (negative in this embodiment) capable of transferring to an electrostatic latent image on the image carrier 2, and an image carrier The second toner 12 is charged to a charge amount (in this embodiment, a polarity opposite to that of the first toner) that is not transferred to the second toner 12. Carrier 1
0, the first toner 11 and the second toner 12 are as follows.

[Carrier] Core material: magnetite (MX030A, average particle size 50 μm)
m, manufactured by Fuji Electric Chemical Co.) 100 parts by weight Coating material: styrene-methyl methacrylate copolymer (copolymerization ratio 20:80) 1.8 parts by weight Antimony-doped tin oxide / potassium titanate (Denthol BK-100, resistance 10 ⁴⁾ Ω · cm, fiber length 15μm,
0.3 μm fiber diameter, manufactured by Otsuka Chemical Co., Ltd.) 0.9 parts by weight toluene
13.5 parts by weight

Production method: The above-mentioned components except magnetite are dispersed in a sand mill for 1 hour to prepare a coating resin layer forming solution. Next, the solution for forming a coating resin layer and magnetite are put into a vacuum degassing type kneader, and stirred at a temperature of 60 ° C. for 20 minutes while reducing the pressure to form a coating resin layer, and the carrier 10 is obtained.

The thickness of the coating resin layer of the carrier 10 is 0.9 μm, and the content of the conductive powder in the coating resin layer is 1 μm.
It was 2% by volume. When the carrier 10 was observed with a scanning electron microscope, it was confirmed that there was no exposed surface and the carrier 10 was almost uniformly coated. Further, the resistance of the magnetite and the carrier 10 was measured in the form of a magnetic brush, and 10 ⁴ V
/ Cm electric field extrapolated to 4
× 10 ⁻⁵ Ω · cm and 4 × 10 ⁷ Ω · cm.

Further, a coating resin layer forming solution was applied to a thickness of 0.9 μm on an ITO conductive glass substrate using an applicator to form a coating resin layer. The resistance value of this coating resin layer is 4 × 10 ⁵ at an electric field of 100 V / cm.
Ω · cm. Note that all the resistance measurements in the present embodiment were performed at a temperature of 20 ° C. and a humidity of 55%.

[First toner] Polyester (number average molecular weight: 4,300, weight average molecular weight: 9,800, T
g = 58 ° C.) 94 wt% and 6 wt% of a coloring material are kneaded and pulverized to have an average particle diameter of 7 μm.

[Second Toner] The first toner 11 was prepared by internally adding cecilpictyl chloride at 3% by weight, and the charging sequence was as follows: second toner>carrier> first toner.

Further, when the concentration (% by weight) of the first toner 11 contained in the two-component developer is TC1 and the concentration (% by weight) of the second toner 12 is TC2,
C1 is set to about 7 to 8 (% by weight), and TC2 is set to about 3 to 4 (% by weight). At this time, TC1 and T
The value of C2 is about 5 (% by weight) ≦ TC1 + TC2 ≦ about 12 (% by weight) about 4 (% by weight) ≦ TC1 ≦ about 11 (% by weight) about 1 (% by weight) ≦ TC2 ≦ about 8 (% by weight) Satisfies both conditions.

Next, the operation of the developing device will be described. The two-component developer contained in the housing and including the first toner and the second toner is supplied to the screw auger 7,
By the rotation of 8, a circular transfer is performed. At this time, a part of the developer is attracted from the front screw auger 7 to the developer carrier 3 by magnetic attraction. Unlike the conventional developing device, there is no partition wall between these screw augers, which separates the transfer region of the adjacent screw auger. For this reason, the developer is pushed by the wings of the screw augers 7 and 8 and is conveyed in the axial direction of the screw auger. The surrounding developer is pushed so as to spread outside the screw auger. Due to this force, the flow of the developer conveyed by both screw augers interferes with each other in almost the entire area in the axial direction of the screw auger, and agitation and
Mixing is performed. For this reason, a sufficient amount of charge is imparted to the toner, and the entire developer is agitated in a short time, so that the toner concentration becomes uniform throughout the axial direction of the screw auger.

The developer thus stirred and conveyed is attracted to the surface of the developing sleeve 4 in a region where the magnetic field of the attracting magnetic pole S3 of the developer carrier 3 reaches, and the magnetic brush in which the magnetic carriers 10 are connected in a spike shape. Becomes Then, as the developing sleeve 4 rotates, the layer forming magnetic pole S2 passes through the transport magnetic pole N2.
Transported to

The developer conveyed to the layer forming magnetic pole S2 is regulated to a constant layer thickness by the layer thickness regulating member 6, and at this time, the excess developing material cut off from the developing sleeve 4 by the layer thickness regulating member 6. The agent falls into the stirring / conveying area, and is again subjected to stirring / conveying by the screw augers 7, 8.
On the other hand, the developer layer regulated to a certain layer thickness is the carrier magnetic pole N
1, the developing magnetic pole S1 is reached, and is affected by a developing electric field formed between the image carrier 2 and the developer carrier 3 in the developing area. In this area, the developing bias voltage is set so that the amount of developing toner becomes saturated, and the first toner 11 attached to the magnetic brush near the transferable tip is the image carrier 2. And the latent image is visualized. At this time, the second toner 12 contained in the two-component developer on the developer carrier 3 has the charging series of the magnetic carrier 1.
Since it is larger than 0, it is not transferred to the image carrier 2 and remains attached to the surface of the magnetic carrier.

In addition to the second toner 12, the first toner 11 and the magnetic carrier 10 not used for development
Are transported to the areas of the separated magnetic poles N4 and N3 in which the same polarity magnetic poles are arranged adjacently by the rotation of the developing sleeve 4,
It is peeled off from the developing sleeve 4. Then, they are again stirred and conveyed by the screw augers 7 and 8.

In the developing device described above, the first toner 11 near the tip of the magnetic brush in the developing area is applied to the image carrier 2.
After the transfer, the magnetic brush may rub against the toner image already formed on the downstream side of the developing area. However, the second toner 12 adheres to the surface of the magnetic carrier 10 and the first toner 11 transferred to the image carrier 2
The chance that the two directly contact each other with the second toner 12 interposed between the magnetic carrier 10 and the second toner 12 is reduced. Therefore, the first toner 11 once transferred to the image carrier 2 can be prevented from re-adhering to the magnetic carrier.

The magnetic carrier 10 has a position where the toner easily adheres and a position where the toner hardly adheres due to minute irregularities on the surface. However, after the first toner 11 is transferred to the image carrier 2, Even if the second toner 12 occupies a position where the toner easily adheres to the first toner 11 on the image carrier 2, re-adhesion hardly occurs. Therefore, it is possible to perform the development with the developing toner amount in a saturated state. Further, by interposing the second toner 12 between the first toner 11 and the magnetic carrier 10, the distance between the magnetic carrier 10 and the image carrier 2 can be maintained, and the occurrence of abnormal discharge can be prevented. Thus, the disturbance of the toner image can be eliminated.

Further, as described above, the first component is added to the two-component developer.
When the toner 11 and the second toner 12 are included,
Although slightly, the second toner 12 may be transferred to the image carrier 2. However, in the present embodiment, the second
The first toner 11 contains the same binder resin and the same pigment as the first toner 11, and the image is not defective even if the second toner 12 is transferred to the image portion, and high image quality is maintained. Can be.

Next, the concentration TC1 (% by weight) of the first toner contained in the two-component developer and the concentration T
The result of an experiment for obtaining a preferable range of C2 (% by weight) will be described. FIG. 3 shows the density TC of the second toner.
7 is a diagram showing a change in the amount of toner re-adhered to the carrier when the toner developed on the image carrier 2 is changed when the number 2 is changed. As is clear from this figure, it can be seen that the higher the concentration TC2 of the second toner, the smaller the amount of re-adhesion to the carrier 10. Therefore, it is understood that the concentration TC2 of the second toner is desirably about 1 (% by weight) or more.

FIG. 4 is a diagram showing a change in the charge amount of the first toner when the total toner concentration (TC1 + TC2) of the first toner and the second toner is changed. According to this figure, it is apparent that the smaller the total toner density is, the higher the charge amount of the first toner density is. Therefore, it is understood that the total toner concentration is desirably about 12 (% by weight) or less.

Further, the first toner is transferred to the image carrier 2 by a printing test when the density TC1 of the first toner is changed.
In order to transfer to the first toner concentration TC1 of about 4
(% By weight) was confirmed to be necessary. According to the result of the above experiment, the first toner concentration TC1 and the second toner concentration TC2 are about 5 (% by weight) ≦ TC1 + TC2 ≦ about 12 (% by weight) about 4 (% by weight) ≦ TC1 ≦ about 11 ( It is understood that when any of the conditions of about 1 (% by weight) ≦ TC2 ≦ about 8 (% by weight) is satisfied, the developed toner image shows almost saturation characteristics without disturbing the developed toner image.

In the developing device, both the first toner and the second toner are made of the same binder resin and the same coloring material, and the charging characteristics are set to be different from each other by adding a charge control agent. But second
May be used as a transparent toner without mixing a coloring material. That is, when the charging polarity of the second toner is opposite to that of the first toner,
Although it is conceivable that the second toner is transferred to the background portion of the image carrier, it is possible to prevent generation of defects such as fogging by using transparent particles containing no coloring material as the second toner. it can.

FIG. 5 is a schematic structural view showing a developing device according to an embodiment of the present invention. This developing device has a configuration similar to that of the developing device shown in FIG. 1, and further includes a toner collection roller 29 disposed downstream of the developing region in the rotation direction of the developer carrier 23 and in close proximity to the developer carrier 23.
And a scrape blade 30 which is in contact with the toner collecting roll 29.

The toner collecting roll 29 is made of aluminum, and is supplied with a voltage from a power supply (not shown). The second toner inside can be peeled off and adsorbed from the magnetic carrier. The scrape blade 30 is made of a non-magnetic material,
For example, it is made of SUS304, and is capable of peeling off the second toner attached to the surface by being in contact with the developer carrier 23. The other structure of this developing device is the same as that of the developing device shown in FIG.

In such a developing device, the first
After the toner is consumed for the development, the developer in which the concentration of the second toner has been increased is conveyed to a position facing the toner collecting roll 29 by the rotation of the developing sleeve 24. In the facing area, the developer carrier 23 and the toner collection roll 29
The second toner is separated from the magnetic carrier by the action of the electric field formed between the magnetic carrier and the second toner, and is electrically attracted to the surface of the toner collecting roll 29. As a result, the concentration of the second toner in the two-component developer is reduced, and the two-component developer is caused to act by the separation magnetic poles N4 and N3, so that the developer carrier 23
And is returned to the developer stirring section. In the developer stirring section, the peeled developer is supplied to the screw augers 27, 2 and
By the rotation of 8, the toner and the two-component developer containing the first toner are mixed and stirred, the concentrations of the first toner and the second toner are adjusted to predetermined values, and supplied to the developer carrier 23 again. . Therefore, it is possible to maintain the density of the first toner and the density of the second toner in the two-component developer supplied to the development area at approximately predetermined values.

[0055]

As described above, the developing device according to the present invention has good developer stirring performance,
It is possible to make the concentrations of the first toner and the second toner uniform and to provide a sufficient toner charge amount. Further, in the developing area, only the first toner attached to the carrier is transferred to the electrostatic latent image on the image carrier, and the second toner is transported on the developer carrier while attached to the carrier.
It is possible to reduce the reattachment of the first toner once transferred on the image carrier to the magnetic carrier. For this reason, it is possible to obtain a good image without toner disturbance and density fluctuation. After the development, the second toner adhered to the magnetic brush is peeled off, and then mixed with the developer in the developer agitating section, so that the concentrations of the first toner and the second toner in the developer become substantially predetermined. Value can be maintained. For this reason, it is possible to prevent fluctuations in the toner concentration of the developer supplied to the developing area, and to obtain a stable image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a developing device according to an embodiment of the present invention described in claim 1, 2, 3, or 4;

FIG. 2 is a configuration diagram showing a two-component developer used in the developing device.

FIG. 3 shows a second toner concentration TC2 in the developing device.
FIG. 5 is a diagram showing a relationship between the amount of re-adhesion to a carrier.

FIG. 4 illustrates a first toner and a second toner in the developing device.
FIG. 6 is a diagram showing a relationship between the total toner concentration and the first toner charge amount.

FIG. 5 is a schematic configuration diagram showing a developing device according to an embodiment of the invention described in claim 6;

FIG. 6 is a diagram illustrating an example of a charge amount distribution of a first toner and a second toner.

FIG. 7 is a diagram illustrating a relationship between an adhesive force between a toner and a carrier and a Coulomb force.

FIG. 8 is an enlarged view showing the state of the toner and the magnetic brush on the image carrier near the exit of the developing area.

FIG. 9 is a diagram illustrating a saturation region of a developing toner amount with respect to a contrast voltage.

FIG. 10 is a schematic diagram showing a state of a magnetic brush at a position where an image carrier and a developer carrier are opposed to each other.

[Explanation of symbols]

 1,21 Developing device 2,22 Image carrier 3,23 Developer carrier 4,24 Developing sleeve 5,25 Magnet roll 6,26 Layer thickness regulating member 7,8,27,28 Screw auger 29 Toner recovery roll 30 Scrape blade

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Taku Fukuhara 430 Sakai Nakai-cho, Ashigara-gun, Kanagawa Green Tech Nakai Inside Fuji Xerox Co., Ltd.

Claims (6)

[Claims] 1. A developer carrier having an endless peripheral surface which is disposed so as to be closely opposed to an image carrier on a surface of which a latent image is formed due to a difference in electrostatic potential and is driven to rotate. A two-component developer containing a magnetic carrier and a toner is magnetically adsorbed on the endless peripheral surface, and is conveyed to a development area close to and opposed to the image carrier, and the toner is selectively transferred to the image carrier. In the developing device for visualizing the latent image, the developing bias voltage applied between the developer carrier and the image carrier is substantially saturated with an increase in the amount of the developing toner caused by the increase in the developing bias voltage. The two-component developer, when charged by stirring,
The charge amount includes two or more types of toners having different charge amounts, and the first toner is charged to the charge amount that transfers from the developer carrier to the latent image on the image carrier in the developing area. Wherein the second toner is charged to an amount of electric charge passing through the developing region while adhering to the magnetic carrier. 2. The developing device according to claim 1, wherein a concentration (% by weight) of the first toner included in the two-component developer is TC1, and a concentration (% by weight) of the second toner is included. ) As TC2, about 5 (% by weight) ≦ TC1 + TC2 ≦ about 12 (% by weight) about 4 (% by weight) ≦ TC1 ≦ about 11 (% by weight) about 1 (% by weight) ≦ TC2 ≦ about 8 ( (% By weight). 3. The developing device according to claim 1, wherein, when the two-component developer is stirred, the first toner and the second toner are charged with opposite polarities. Developing device. 4. The developing device according to claim 1, wherein the first toner and the second toner are made of the same binder resin and the same pigment, and the charge characteristics of the first toner and the second toner are mutually changed by adding a charge control agent. A developing device, which is set differently. 5. The developing device according to claim 1, wherein the second toner is a transparent particle formed of the same resin as a binder resin used in the first toner. . 6. The developing device according to claim 1, wherein the developing device is disposed downstream of the developing area and close to the developer carrier, and electrically adsorbs the second toner in the two-component developer. And a toner recovery roll for separating the toner carrier from the magnetic carrier.