JPH10133480A - Developing device and color electrophotographic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent carrier from adhering to a developing roll by using a specified carrier. SOLUTION: In this developing device 8, where the outer peripheral surface of the developing roll 2 is rubbed by the mixed agent layer of magnetic carrier and toner attracted to a carrying magnetic roll 3 so as to form a toner layer on the outer peripheral surface, and the toner layer is brought into contact with a photoreceptor 1 so as to develop an electrostatic latent image on the surface of the photoreceptor 1; the magnetic carrier having resistance value being 10<8> to 10<12> Ωcm is used. By using the carrier having such resistance value, charge is injected in the magnetic carrier by bias voltage applied on the roll 3 and the magnetic carrier is electrostatically charged to have the same polarity as that of the bias voltage. As a result, electrostatic repulsive force acts on the magnetic carrier in a direction where the carrier is separated from the roll 3 and a part of the magnetic carrier is shifted to the roll 2. Thus, the magnetic carrier is prevented from adhering to the roll 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing apparatus used for an electrophotographic apparatus such as a copying machine, a printer, a facsimile, and the like, and a color electrophotographic apparatus using the developing apparatus.

[0002]

2. Description of the Related Art A developing device includes a two-component developing device using a two-component developer containing a carrier and a toner, and a one-component developing device using only a toner.
There is a one-component developing device using a component developer. The one-component developing device is advantageous in that it does not use a carrier and does not require a mechanism for controlling the mixing ratio of a developer, and is advantageous in miniaturization and cost reduction. It is often used in equipment. As shown in FIG. 2, a conventional one-component developing device 21 using a non-magnetic toner includes a developing roll 2 facing a photoreceptor 1 and a blade 18.
And a transport roll 20, a stirring blade 7 provided in the toner hopper 6, and a toner leakage preventing member 19. The toner in the toner hopper 6 is opened 1 by the stirring blade 7.
3 is supplied to the vicinity of the transport roll 20, and further transported by the transport roll 20 to the vicinity of the developing roll 2.
At 8, the toner is applied to the outer peripheral surface of the developing roll 2 to form a toner layer. The rotation of the developing roll 2 causes the toner layer 12 conveyed to the portion facing the photoreceptor 1 to come into contact with the electrostatic latent image on the photoreceptor 1 and to apply a developing electric field to the developing unit to form the electrostatic latent image. Develop to form a toner image.

[0003] Such a non-magnetic one-component developing apparatus is disclosed in Japanese Patent Publication No. 7-43546 and Japanese Utility Model Publication No. 7-20683. In addition, the magnetic one-component developing device includes:
It is disclosed in Japanese Patent Publication No. 2-48901.

Further, in a developing apparatus using a developing roll having only a toner layer formed on a surface thereof, examples of using a carrier magnetic roll and a carrier are disclosed in JP-A-55-77764 and JP-A-62-192772. As described, a method of performing contact development by using an elastic roll as a developing roll is disclosed in JP-A-3-59576 and JP-A-61-61576.
As described in JP-A-239266 and JP-A-61-100775, there has been proposed a method of performing a non-contact development by providing a gap between a toner layer on a developing roll and a photoreceptor. .

[0005]

However, a conventional non-magnetic one-component developing apparatus in which only a toner layer is formed on the outer peripheral surface of a developing roll by using a transporting magnetic roll and a carrier has a problem in that environmental conditions are required because a carrier is used. Depending on the developing conditions and the carrier, the carrier tends to adhere to the developing roll to cause image defects such as white spots on the printed image.

Further, when such a non-magnetic one-component developing device is used to obtain a high-speed and high-definition color image or to apply low-temperature fixing required for power saving,
Toner filming occurs on the outer peripheral surface of the developing roll, which tends to degrade image quality and shorten the life of replacement of the developing device.

When a method of forming only a toner layer on the outer peripheral surface of a developing roll using a carrier magnetic roll and a carrier is applied to high-speed printing, when an elastic developing roll is brought into contact with a photosensitive member to perform development, a rubber is used. And the surface of the sponge roll tends to be deformed, and the replacement cycle tends to be short. Also, when non-contact development is performed, the reproducibility of fine halftone images and gradation tends to be insufficient.

A first object of the present invention is to provide a developing device capable of preventing carrier adhesion to a developing roll.

A second object of the present invention is to prevent the occurrence of toner filming on the outer peripheral surface of a developing roll in a developing device in which only the toner is applied to the outer peripheral surface of a developing roll to perform development. Further, it is an object of the present invention to provide a developing device capable of ensuring high image quality at high speed.

A third object of the present invention is to provide a color electrophotographic apparatus using such a developing device.

[0011]

According to the present invention, a toner layer is formed on the outer peripheral surface of a developing roll by rubbing the outer peripheral surface of the developing roll with a mixture layer of carrier and toner adsorbed on a magnetic roll. And a developing device for developing an electrostatic latent image on the surface of the photoconductor by contacting the photoconductor with the photoconductor, or by rubbing the outer peripheral surface of the photoconductor with a mixture layer of carrier and toner adsorbed on a magnetic roll. In a developing device for developing an electrostatic latent image on a surface, a resistance value of the carrier is set to 10 ⁸ to 10 ¹² Ωcm. The carrier adjusted to such a resistance value is prevented from adhering (moving) to the developing roller or the photoconductor due to the electrostatic force.

Further, the developing roll is constructed by fitting an elastic roll into a metal or resin sleeve.

Further, the mixture is used at a toner concentration lower than the saturated toner concentration to a saturated toner concentration.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a vertical sectional side view of a developing device according to a first embodiment of the present invention. In FIG. 1, a developing device 8 includes a developing roll 2 facing the photoreceptor 1, a conveying magnetic roll 3, a regulating plate 4, a stirring blade 7 provided in a toner hopper 6, and bias power supplies 14 and 1.
5 and a developer guide plate 5. Toner hopper 6
The toner inside is supplied from the opening 13 to the vicinity of the upper part or the rear part of the transport magnetic roll 3 from the opening 13 by the stirring blade 7 to form the toner reservoir 9.

The transporting magnetic roll 3 adsorbs a mixture 11 obtained by mixing a magnetic carrier and a toner on its outer peripheral surface and rotates counterclockwise. The admixture 11 that is attracted to the transport magnetic roll 3 and rotates (moves) in the counterclockwise direction together with the transport magnetic roll 3 is mixed with a predetermined thickness by a regulating plate 4 provided on the outer periphery of the transport magnetic roll 3. The excess surplus mixture 11 on the outside, which is regulated by the mixture layer 10 and scraped off by the regulation plate 4, makes a U-turn along the mixture guide plate 5 and circulates in the mixture chamber 36, thereby forming the toner reservoir 9 Mix with toner.

The mixture layer 10 formed on the outer circumferential surface of the transport magnetic roll 3 regulated by the regulating plate 4 is brought into contact with the developing roll 2 while rotating in the counter direction with the developing roll 2, and the transport magnetic roll 3 and the developing roll are brought into contact with each other. The toner layer 12 is formed on the outer peripheral surface of the developing roll 2 by applying an electric field between the developing roller 2 and the toner layer 12.
Is transported to a portion facing the photoreceptor 1 by the rotation of the developing roll 2 and is brought into contact with the photoreceptor 1, and a developing electric field is applied to the developing section to develop the electrostatic latent image to form a toner image. That is, since the magnetic carrier and the toner constituting the mixture 11 held by the transport magnetic roll 3 are charged with opposite polarities by frictional charging, an electric field acts between the transport magnetic roll 3 and the developing roll 2. By doing so, only the toner can be transferred to the outer peripheral surface of the developing roll 2.

The developing roll 2 has a low hardness (for example, a rubber hardness of about 1 to about 20 to 60 μm) formed on a metal or resin sleeve.
5 to 35 degrees (JIS-A))
It is formed into an elastic roll. The metal or resin sleeve prevents the developing roller 2 from being scratched or worn, and reduces the thickness so that the elasticity of the rubber roll can be maintained so that soft contact with the photosensitive member 1 can be obtained even when the sleeve is brought into contact with the photosensitive member 1. It was done. For the metal sleeve, Ni, SUS, or the like can be used, and it is preferable that the metal sleeve be a non-magnetic material. However, if the metal sleeve is magnetic, the carrier adhesion to the developing roll 2 tends to increase. It is desirable to form a nonmagnetic layer (5 to 20 μm) on the surface by metal plating, metal coating, or resin coating. Also, the resin used for coating the resin sleeve or the metal sleeve is desirably durable and imparts conductivity to prevent electrostatic charge-up, and is conductive to polyimide, polyamide, fluorine, and silicon-based resins. Those to which an agent has been added can be used. Therefore, even when the printing speed is high or the peripheral speed ratio k between the developing roller 2 and the photosensitive member 1 is slightly large (k = 1.5 to 2.0), the developing roller 2 and the photosensitive member 1 This has the effect of lengthening the replacement cycle.
The developing roll 2 used had a diameter of 15 to 40 mm.

The rubber roll can be used either insulative or conductive. In the case of an insulative rubber roll (for example, a resistance value of about 10 ¹³ to 10 ¹⁶ Ωcm), power supply for applying a developing bias is as follows. A conductive rubber roll (for example, having a resistance value of about 10
^In the case of ⁷ to 10 ⁸ Ωcm), there is an advantage that power can be supplied by using the axis of the developing roll 2.

When the printing speed is relatively low, or when the peripheral speed between the developing roll 2 and the photosensitive member 1 is almost equal, a low hardness (for example, rubber hardness) is used without using a metal sleeve for the developing roll 2. May be formed as a single (or surface-coated) rubber roll of about 15 to 55 degrees (JIS-A).

The transporting magnetic roll 3 is an equidistant multipolar magnetized naked magnet body (so-called sleeveless mag roll) rotatably arranged to face the developing roll 2 with a gap (first gap) therebetween. It is. This sleeveless mag roll (magnet body) has 8 to 64 magnetic poles and a magnetic force of 400 to
It was composed of a single magnet roll magnetized in the range of 800 gauss, and its peripheral speed Ut was set so that the ratio to the peripheral speed Us of the developing roll 2 was in the range of 1.5 to 5.0. The magnet body may be covered with a non-magnetic material for protection and for introducing a bias voltage to the surface. Further, in the magnetic roll using such a sleeveless mag roll, since the mixture layer 10 adsorbed on the outer peripheral surface does not roll on the outer peripheral surface, the mixture layer 10 having a saturated toner concentration is formed. However, toner scattering does not occur.

Further, the transport magnetic roll 3 may be configured by arranging a sleeve concentrically with the magnet body. In this case, the number of magnetic poles is 8 to 24, and the magnetic force of the magnetic pole portion is 400 to 80.
A magnet body magnetized in a range of 0 Gauss is used. Then, in order to bring the mixed agent layer 10 into contact with the developing roll 2 while rotating in the counter direction, the magnet roll is rotated clockwise, the sleeve is rotated counterclockwise, and the peripheral speed of the sleeve and the peripheral speed of the developing roll 2 are changed. The ratio with the speed Us is 1.0 to 1.5.
And the rotational speed of the magnet body is set in the range of 1.5 to 4.0 of the sleeve rotational speed.

Further, a second gap for regulating the mixed agent layer 10 to a predetermined thickness is set between the transport magnetic roll 3 and the regulating plate 4. This second gap is 0.5-0.8 mm
Is desirable. The difference between the first gap formed between the developing roll 2 and the transport magnetic roll 3 and the second gap formed between the regulating plate 4 and the transport magnetic roll 3 is 0 to 0.
Set within a range of 2 mm.

Bias power supplies 14 and 15 are connected to the developing roll 2 and the transport magnetic roll 3 (the same bias is also applied to the regulating plate 4 as the transport magnetic roll 3), and a DC voltage or a DC voltage and an AC voltage are connected. Is applied.

Mixture 11 to be held on the transporting magnetic roll 3
When the carrier particle size exceeds 100 μm, brush-like unevenness becomes noticeable in the toner layer on the developing roll 2,
Since the carrier adhesion tends to increase at 40 μm or less, the carrier having a particle size of 50 to 100 μm and the particle size of 5 to 100 μm are used.
A mixture of 11 μm toner was used.

In this embodiment, the toner concentration (Wt%: toner weight × 1) of the mixture layer 10 that has passed through the regulating plate 4
00 / carrier weight) may be set between 7 and 25 Wt% in consideration of the charge amount of the toner and the transport amount of the mixture.
More preferably, the toner concentration of the mixture 11 in the mixing chamber 36 is passed through the regulating plate 4 so that the saturation toner concentration (range of 13 to 25 Wt%) determined according to the toner particle size and the carrier particle size is obtained. It is configured to be able to maintain higher than the toner concentration of the subsequent mixture layer 10. Here, the saturated toner concentration is measured as the toner concentration after passing through the regulating plate 4 when the mixture 11 adjusted to a sufficiently high toner concentration (about 25 Wt%) is supplied and only the transport magnetic roll 3 is rotated. be able to. The reason that the toner concentration of the mixture layer 10 after passing through the regulating plate 4 takes a saturation value is that the maximum amount of toner that can be transported when the mixture layer (magnetic brush) 10 passes through the regulating plate 4 is as follows. The amount of toner that can be attracted to the carrier surface by electrostatic force, that is, about 1 to 3 layers, and even if more than that is held in the gap between the carrier and the toner,
It is considered that the magnetic brush is separated due to the rotational movement of the magnetic brush, the swing of the magnetic brush when passing through the restricting plate 4, and the effect of electrostatic force acting on the restricting plate 4. Therefore, there is a limit to the amount of toner that can be conveyed, and this value is considered to correspond to the saturated toner density. Therefore, if the toner concentration of the mixture layer 10 after passing through the regulating plate 4 is set to this saturation value, the toner concentration in the mixture layer 10 can be reduced without installing a toner concentration detection sensor (without complicating the device configuration). The advantage that the mixing ratio can be maintained stably is obtained.

The material of the carrier desirably has a function of scraping off the toner remaining on the developing roll 2 after developing the electrostatic latent image on the photosensitive member 1 in addition to the function of charging and conveying the toner. It has been found that iron powder carriers are more desirable. Further, it has been found that a resin carrier and a ferrite carrier can be used by increasing the magnetic force and peripheral speed of the transporting magnetic roll 3 or by using other toner scraping means together. The resin carrier has a bulk specific gravity of 1.0
~1.6g / cm ^3, that of spherical and amorphous saturation magnetization 60~80emu / g, also ferrite carrier has a bulk density 2.2~2.7g / cm ^3, with the saturation magnetization 30 95emu / g A substantially spherical shape can be used.

Further, in order to form a sufficient toner layer on the developing roll 2, the gap (first gap) between the transport magnetic roll 3 and the developing roll 2 is set to 0.5 to 1.0 mm, When the bias voltage was higher (400 V or more in terms of the potential difference), the carrier adhered to the developing roll 2 and tended to increase depending on the material of the carrier.

Therefore, an experiment on carrier adhesion and carrier resistance was conducted. The resistance value of the carrier was measured with the configuration shown in FIG. That is, the test carrier 37 is held at a thickness of 5 mm in the measurement container 40, and a load of 8 g / cm ² is applied to the sample by the weight 38 also serving as an electrode, and the lead wires 43 and ⁴ are applied.
4 are connected to a disc-shaped electrode (40φ) divided by an insulating material 41 at the bottom of a weight 38 and a measuring container 40, respectively.
0 V / cm) was applied to measure the resistance R (Ω). Further, based on the measured resistance value R (Ω), a specific resistance ρ (Ωcm) was obtained from the equation (1).

Ρ (Ωcm) = R (Ω) × A (cm ² ) / t (cm) (1) A: electrode area (cm ² ) t: thickness of carrier under test (c)
m) Further, under a constant applied voltage (100 V), if the load is too small, the resistance value tends to vary, and in some cases, the resistance value changes greatly depending on the load. If too much, it becomes difficult to correlate with carrier adhesion. Therefore, in the present invention, the carrier resistance (specific resistance) is defined with an allowable range of about 5% for a load of 8 g / cm ² .

In the case of a non-coated carrier, the resistance value of the carrier depends on the material, surface condition, and particle size of the core material. Agent (eg, carbon or titanium oxide)
And that the resistance value can be changed by changing the content of the conductive agent.

Further, as a developing condition, a sleeveless mag roll having a diameter of 21 mm, 16 poles and 550 to 650 gauss is used as the transporting magnetic roll 3, and the developing roll 2 has a rubber hardness of about 20 degrees (JIS-A). A conductive rubber roll is formed by fitting a metal sleeve having a non-magnetic Ni plating (thickness: 10 to 15 μm) to a Ni electroformed sleeve having a thickness of about 30 μm, and the peripheral speed ratio of the transport magnetic roll to the developing roll is 2 ３3, and the carrier adhesion state was investigated. Regarding the toner concentration of the mixture layer 10 that has passed through the regulating plate 4, when the saturation concentration is set to 18 to 25 (Wt%), the carrier adhesion is higher than when the toner concentration is set to 10 to 15 (Wt%). It became less.

[0033]

[Table 1]

Table 1 shows the results of investigations on the carrier resistance (specific resistance), the carrier adhesion state, and the formation of the toner layer on the developing roll using seven types of ferrite carriers having an average particle size of about 80 μm. The toner is
The average particle size is 11 μm, and the toner concentration is 10 to 1
5 (Wt%) was set.

From Table 1, it can be seen that (1) the carrier adhesion tends to increase when the carrier resistance is lower than 10 ⁸ (see carrier G), and (2) to prevent carrier adhesion, the carrier resistance must be 10 ⁸ It turned out that it is effective to set it to Ωcm or more, more desirably 10 ⁹ Ωcm or more. The reason is that when the carrier resistance decreases, charge injection occurs in the carrier due to the bias voltage applied to the transporting magnetic roll 3, and the carrier is charged to the same polarity as the polarity of the bias voltage. It is presumed that an electrostatic repulsion acts in a direction away from the magnetic roll 3 and a part of the carrier moves to the developing roll 2.

(3) The carrier resistance is set to 10 ¹² Ωcm.
In the case of the above setting (carrier A), the amount of toner adhered on the developing roll 2 was small, and the formation of the toner layer was insufficient. This is presumed to be due to the fact that, in addition to the increase in the charge amount of the toner, the developing electric field acting on the gap (first gap) between the transport magnetic roll 3 and the developing roll 2 is reduced.

Therefore, from the above, the carrier resistance is 10 ⁸
Omegacm～10 ¹² range Ωcm is desirable, furthermore, 10 ⁸
It is determined that the range of Ωcm to 5 × 10 ¹¹ Ωcm is more desirable. In addition, carriers having such a resistance value include:
As described above, a resin coating containing a conductive agent is applied to iron powder or ferrite, and the resistance after coating can be adjusted to be in the range of 10 ⁸ Ωcm to 10 ¹² Ωcm. Furthermore, not only the resistance value after coating but also the resistance value of the core material before coating is 10 ⁸ Ωcm to 10 ¹² Ωcm.
It is more desirable to adjust so as to fall within the range of stability. If the coating agent wears out over a long period of use,
This is because the resistance value of the core material comes closer to with a decrease in the coating amount. The resistance value of the core material can be adjusted by selecting the material of the core material in the case of a ferrite carrier, or by adjusting the surface oxidation of the core material in the case of an iron powder carrier.

Further, a mixture guide plate 5 is provided on the upper portion of the transporting magnetic roll 3, and the mixture 11 is U-turned by the regulating plate 4 and the mixture guide plate 5 so as to circulate downward so that the mixture 11 When the toner was mixed with the toner in the toner reservoir 9 formed in the vicinity of the rear portion from above the transporting magnetic roll 3, the temporal stability of image quality such as image density and fogging was improved.

The developing device 8 having such a configuration is applied to an electrophotographic printer, using an organic photoreceptor (OPC) as the photoreceptor 1 and applying a contrast potential on the photoreceptor 1 at a peripheral speed of 100 to 400 mm / sec. Forms an electrostatic latent image of about 450 V, and sets the peripheral speed of the developing sleeve 2 to about 1 to about the peripheral speed of the photosensitive member.
When reversal development was performed by applying a developing bias of 250 to 350 V to the developing sleeve 2, carrier adhesion did not occur on the developing roll 2 and the outer peripheral surface of the photoconductor 1, and the image density was 1. 3-1.4 (OD) could be secured. Further, even when long-term printing was performed, filming of the toner on the developing roll 2 did not occur.

The reason why the occurrence of filming of the toner in high-speed printing was prevented was that, as described above, the blade that contacts the developing roll 2 and applies the toner to the outer peripheral surface of the developing roll 2 was used. Without providing the toner layer on the outer peripheral surface of the developing roll 2 using a magnetic brush,
At the same time, it is considered that the stress applied to the toner on the developing roll 2 was reduced by scraping off the toner remaining on the developing roll 2 with the magnetic brush.

(Second Embodiment) A second embodiment shown in FIG. 3 is a color electrophotographic apparatus in which the above-described developing device is applied to four image forming units installed corresponding to respective colors.

This color electrophotographic apparatus comprises four developing devices 8-1 and 8- using toners of colors corresponding to respective colors.
2, 8-3 and 8-4 are converted to four photoconductors 1-1, 1-2, and 1
-3, 1-4, and by setting the timing of writing the latent image by the exposure light beam 24 in consideration of the transfer timing to the printing paper 22, the position at which the electrostatic latent image is formed is controlled. Forming an electrostatic latent image corresponding to each color on the outer peripheral surface of the photoconductors 1-1 to 1-4, and developing the electrostatic latent images by developing units 8-1 to 8-4 to form toner images of each color; Transfer devices 25-1, 25-2, 25-3, 25-4
There is an electrophotographic apparatus that forms a color image by sequentially transferring toner images of each color onto a printing paper 22 and superimposing the toner images of the respective colors.

The developing devices according to the present invention described above are applied to the developing devices 8-1 to 8-4.
The image of each color is detected to control the image density of each color. In FIG. 3, four developing devices 8-1 to 8-4 are provided.
Only the control system of one of the developing devices 8-1 is specifically illustrated, but the same applies to the other developing devices 8-2 to 8-4. The following description is made only for the control system of the developing device 8-1.

In the developing device 8-1, the color image sensor 27 detects the density of the toner image. Based on the detection value of the color image sensor 27, the developing roll 2-
A rotation control unit 29, a bias control unit 30, and an image control unit 28 are provided to control the bias power supplies 14 and 15 and the rotation driving units 16 and 17 of the magnetic roller 1 and the transport magnetic roll 3-1. Around the photoreceptor 1, a transfer unit 25-1,
Photoconductor 1 after transfer by 25-2, 25-3, 25-4
Cleaners 26-1, 26-2, 26-3, 26-4 for cleaning toner remaining in -1, 1-2, 1-3, 1-4
Further, a fixing unit 31 for fixing the unfixed toner image to the printing paper 22 by heat fusion is provided behind the final-stage transfer unit 25-4.

In the color electrophotographic apparatus having such a configuration, when a toner image of each color is formed on the photoreceptors 1-1 to 1-4 and color printing is performed, the density of the developed toner image is determined by the toner image. By controlling at least one of the electric field or the peripheral speed ratio between the developing rolls 2-1 to 2-4 and the transport magnetic rolls 3-1 to 3-4 based on the result detected by the sensor 27, the photosensitive A desired amount of toner can be attached (developed) to the outer peripheral surface of the body 1-1 to 1-4;
Even in long-term printing, a color image does not deteriorate due to a decrease or fluctuation in image density.

(Third Embodiment) A third embodiment shown in FIG. 4 is different from the first embodiment in that a mixture guide plate is provided between the transport magnetic roll 3 and the toner reservoir 9. A second transport roll (such as a sponge roll or a rotating brush) 32 that contacts or approaches the second transport roll 5 is added, and a toner layer is formed on the outer peripheral surface of the second transport roll 32 and the mixture 11 that moves (see FIG. This is a developing device forcibly brought into contact with the mixture moving in the mixing chamber 36 along the guide plate 5 or the mixture 11) adsorbed and moved on the transport magnetic roll 3 as shown by an arrow.

According to the third embodiment, an effect of reducing fog is obtained as compared with the first embodiment.

(Fourth Embodiment) As shown in FIG. 5, the developing device of the third embodiment is different from the developing device of the third embodiment in place of the second transport roll 32 of the third embodiment.
A second stirring member 33 (such as a stirring blade or a screw auger) is provided to forcibly mix the toner in the toner reservoir 9 and the mixture 11.

This developing device also had the effect of preventing image density unevenness from occurring even during long-term printing and reducing fog.

As the second stirring member 33, a member having an action of loosening the toner in the toner reservoir 8 and the mixture in the mixing chamber 36, for example, a rotating thin wire or a thin flat plate can be used.

(Fifth Embodiment) As shown in FIG. 5, the developing device in the fifth embodiment
In the developing device according to the embodiment, further, two screw augers 3 having different conveying directions (in the axial direction) are further provided.
4, 35 are installed. In this embodiment, during long-term printing, there was obtained an effect that the density of the image in the axial direction did not become uneven and the fog was further reduced.

(Sixth Embodiment) The first to fifth embodiments described above
In the embodiment, an example in which a layer of only toner is formed on a developing roll by a transport magnetic roll and an electrostatic latent image on a photoreceptor is developed by the developing roll has been described. Photoconductor 1 by layer (magnetic brush)
To develop the electrostatic latent image. The peripheral speed of the OPC photoreceptor is about 150 to 200 mm / sec.
c. The peripheral speed of the transporting magnetic roll is set to 1.
The configuration is such that the gap between the magnetic transport roll and the photoconductor is 0.5 to 1.0 mm, and a bias voltage of -300 to -900 V is applied to the transport magnetic roll and the regulating plate. The toner average particle diameter is set to 8 to 10 μm, the carrier average particle diameter is set to about 80 to 100 μm, and the toner concentration is set to 12 to 18%. The magnetic roll has a diameter of 20 to 4
A multi-pole magnetized body of 0 mm, 16 to 64 poles, and 500 to 800 G was used.

Also in such an embodiment, by setting the carrier resistance in the range of 10 ⁸ Ωcm to 10 ¹² Ωcm, a sufficient image density of 1.3 (OD) can be obtained and the mixture layer (magnetic brush) can be obtained. ), The effect of preventing the carrier from migrating to the photoreceptor and adhering to the outer peripheral surface of the photoreceptor was obtained.

[0054]

According to the present invention, a mixture of a carrier and a toner is used to attract a magnetic roll to a carrier and rub the outer circumferential surface of the developing roll to form only a toner layer on the outer circumferential surface of the developing roll. In a developing device for developing an electrostatic latent image,
By setting the electric resistance value of the carrier to 10 ⁸ to 10 ¹¹ Ωcm, it is possible to prevent the carrier from adhering to the developing roll, and to fill the outer peripheral surface of the developing roll with the toner even after long-term high-speed printing. It is possible to prevent occurrence of ming.

Further, a carrier as described above is also used as a developing device for developing an electrostatic latent image on the photoconductor by rubbing the photoconductor with a mixture layer (magnetic brush) held on a conveying magnetic roll. This has the effect of preventing the carrier from adhering to the photoreceptor.

Further, in a high-speed color electrophotographic apparatus to which such a developing device is applied, it is possible to prevent a carrier from adhering to a photoreceptor or a developing roll and to prevent a change in image density. There is an effect that can be secured stably.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view of a developing device according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a conventional developing device.

FIG. 3 is a schematic configuration diagram of a color electrophotographic apparatus according to a second embodiment of the present invention.

FIG. 4 is a vertical sectional side view of a part of a developing device according to a third embodiment of the present invention.

FIG. 5 is a vertical sectional side view of a part of a developing device according to fourth and fifth embodiments of the present invention.

FIG. 6 is an explanatory diagram relating to a measurement state of a resistance value of a carrier.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Development roll, 3 ... Conveying magnetic roll, 4 ... Regulator plate, 5 ... Mixture guide plate, 6 ... Toner hopper, 7 ... Stirring blade, 8 ... Developing device, 9 ... Toner pool, 10 ... Mixture layer, 11 ... mixture.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FIG03G 9/10 361 (72) Inventor Joru Shimazaki 7-1-1, Omikamachi, Hitachi City, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Kunio Fukuchi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (17)

[Claims] An outer peripheral surface of a developing roll is rubbed with a mixture layer of carrier and toner adsorbed on a magnetic roll to form a toner layer on the outer peripheral surface, and the toner layer is brought into contact with a photoreceptor. A developing device for developing an electrostatic latent image on the surface of the photoreceptor, wherein the resistance value of the carrier is set to 10 ⁸ to 10 ¹² Ωcm. 2. The developing device according to claim 1, wherein said mixture has a saturated toner concentration. 3. The developing device according to claim 1, wherein the carrier is formed by applying a resin coating containing a conductive agent to a ferrite powder core material having a resistance value of 10 ⁸ to 10 ¹² Ωcm. 4. The carrier according to claim 1, wherein the carrier further comprises a conductive agent after forming an oxide film on the surface of the iron powder core material and adjusting the resistance value of the core material to 10 ⁸ to 10 ¹² Ωcm. A developing device characterized in that the developing device is formed by applying a resin coat. 5. The magnetic roll according to claim 1, wherein a restricting plate is provided above the magnetic roll so as to face the magnetic roll, and a mixture regulated by the restricting plate is guided to the rear of the magnetic roll. A mixture guide plate circulating toward the magnetic roller, and mixing the circulating mixture with the toner supplied behind the magnetic roll. 6. The magnetic roll according to claim 1, wherein the magnetic roll has 8 to 64 magnetic poles and the magnetic force of the magnetic pole portion is 400 to 500.
A developing device comprising a multi-pole magnetized magnet set in a range of 800 Gauss. 7. A developing device according to claim 1, wherein said developing roll is formed by fitting an elastic roll into a metal sleeve. 8. The method according to claim 7, wherein the absolute value of the difference between the first gap formed between the developing roll and the magnetic roll and the second gap formed between the regulating plate and the magnetic roll is 0 to 10.
A developing device characterized in that it is set in a range of 0.2 mm. 9. The method according to claim 1, wherein the ratio of the peripheral speed of the magnetic roll to the peripheral speed of the developing roll is 1.50 to 5.
A developing device characterized by being set to a range of 0. 10. The developing device according to claim 1, wherein the bias voltage applied to the developing roll is obtained by superimposing a DC voltage and an AC voltage. 11. A developing device for forming a magnetic brush by adsorbing a mixture obtained by mixing a carrier and a toner on a magnetic roll, and rubbing a photosensitive member with the magnetic brush for development. Is a multi-pole magnetized magnet body having 16 to 64 poles and the magnetic force of the magnetic pole part set to a range of 500 to 800 Gauss, wherein the resistance value of the carrier is 10 ⁸ to 10 ¹² Ωcm. Developing device. 12. The developing device according to claim 11, wherein said mixture has a saturated toner concentration. 13. The developing device according to claim 11, wherein the carrier is formed by applying a resin coat containing a conductive agent to a ferrite powder core material having a resistance value of 10 ⁸ to 10 ¹² Ωcm. 14. The carrier according to claim 11, wherein the carrier further contains a conductive agent after forming an oxide film on the surface of the iron powder core material and adjusting the resistance value of the core material to 10 ⁸ to 10 ¹² Ωcm. A developing device characterized in that the developing device is formed by applying a resin coat. 15. The magnetic roll according to claim 11, wherein a regulating plate is provided above the magnetic roll so as to face the magnetic roll, and a mixture regulated by the regulating plate is guided to the rear of the magnetic roll. A mixture guide plate circulating toward the magnetic roller, and mixing the circulating mixture with the toner supplied behind the magnetic roll. 16. A plurality of developing devices each containing a mixture corresponding to each color are arranged around a plurality of photoconductors, and a plurality of latent images corresponding to each color are formed by one or more rotations of the photoconductor. 14. A color electrophotographic apparatus for executing a step of forming a plurality of color toner images on the photosensitive member by developing with a plurality of developing devices, wherein the plurality of developing devices are provided. A color electrophotographic apparatus wherein at least one of an electric field or a peripheral speed ratio between a developing roll and a magnetic roll is controlled based on a toner image of each color. 17. A plurality of developing devices each containing a mixture corresponding to each color are arranged around a plurality of photoconductors, and a plurality of latent images corresponding to each color are formed by one or more rotations of the photoconductor. 16. A color electrophotographic apparatus for performing a step of forming a plurality of color toner images on the photosensitive member by developing with a plurality of developing devices, wherein the plurality of developing devices are provided. A color electrophotographic apparatus characterized by applying the above.