JPH0862971A - Image forming device - Google Patents

Abstract

PURPOSE: To enhance developing efficiency and to obtain a high quality image by forming an oscillating electric field with a developing sleeve at a first electrode and an electric field for moving toner to the nonimage part of an image carrier at a second electrode. CONSTITUTION: A first vibrating electric field is generated between the first electrode 85a provided on an insulating member 85b abutted on a developer layer on the developing sleeve 81 and it, to form a strong AC electric field and generate a toner cloud. The second electrode 85c is provided on the first electrode 85a, so that an electric field P1 for moving the toner toward a photoreceptor belt 1 and an electric field P2 for moving the toner toward the first electrode 85a are formed to work for preventing infiltration toward the second electrode 85c and moving the toner toward the nonimage part of the belt 1. Thus, the sticking of the toner to an electrode plate 85, especially the electrode upper part of the second electrode 85c can be prevented. Moreover, the toner image which has already been formed on the image carrier is prevented from reversely flying up to the developing sleeve 81 and the electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image in an image recording apparatus such as an electrophotographic copying machine or a printer using a one-component developer or a two-component developer in which magnetic carrier particles and toner particles are mixed. Alternatively, it relates to a developing device for developing a magnetic latent image. In particular, the present invention relates to a developing device that is preferably used in a recording device that forms a multicolor image composed of a composite of a plurality of toner images on an image carrier, and more specifically, a developer carrier vibrates in a developing area facing the image carrier. The present invention relates to an image forming apparatus having a developing device that causes toner particles to fly from a developer layer formed in a layer thickness that does not rub the surface of an image carrier to a surface of a developer carrier to adhere to an electrostatic image on the surface of the image carrier.

[0002]

2. Description of the Related Art Conventionally, in electrophotographic copying machines and the like,
As a developing device as described above, as described in JP-A-59-223467, the applicant of the present application, a control electrode for controlling the flight of toner particles is provided in the developing area, and a bias voltage having an AC voltage component is applied. A method of developing under an oscillating electric field generated by application has been proposed. Further, the conventional developing method using a toner cloud has a low developing speed and developing efficiency, and only an image having a low sharpness can be obtained, and it is possible to eliminate the drawback that stains in the machine easily occur due to scattering of toner particles. As a developing device as described in JP-A-5-346736, JP-A-6-19289, etc., the developer layer on the surface of the developer carrier (developing sleeve) is contacted with the developer layer at the upstream side of the developing area. By providing a plate-like elastic electrode plate having a control electrode located upstream of the region and downstream of the contact portion,
Many proposals have been made to form an oscillating electric field between the developer transport body and the electrode plate.

[0003]

However, in the above proposal, the toner wraps around the upper part of the electrode plate during use and the toner adheres to the electrode plate to stain the electrode, or adheres to the image carrier. Toner is attracted to the electrodes,
Since the toner deposited on the electrodes has a drawback of re-adhering to the image carrier, color mixture or image destruction may occur when applied to a color image forming apparatus.

The present invention solves this problem and improves it.
Image formation having a developing device capable of preventing / removing toner from adhering to or depositing on an electrode plate, particularly an electrode portion, by electric means or mechanical means, improving development efficiency and obtaining a high quality image. The purpose is to provide a device.

[0005]

The above-mentioned objects are as follows. First, as an electric means, a developer is carried onto a developing sleeve (developer carrying body), and toner is made to fly to an image carrier in an oscillating electric field. In an image forming apparatus having a developing device for developing,
An electrode plate made of a plate-shaped member having an electrode is provided between the developing sleeve and the image carrier, and the electrode plate includes a first electrode close to the developing sleeve, the first electrode and the image carrier. A second electrode disposed between the bodies, the first electrode forming an oscillating electric field with the developing sleeve, and the second electrode forming an electric field for moving toner to a non-image portion of the image carrier. And an image forming apparatus having a developing device.

An image forming apparatus having a developing device characterized in that an electric field for moving toner to the first electrode is formed between the first electrode and the second electrode. In the non-image formation, a voltage for forming an electric field for moving the toner to the image carrier is applied to the first electrode or the second electrode, or the first electrode or the second electrode is in a floating state. An image forming apparatus having a developing device is also a preferred embodiment. Further, an image forming apparatus having a developing device characterized by superposing a toner image on the image carrier is also a preferred embodiment.

Secondly, as a mechanical means, an image forming device is provided which has a developing device for carrying the developer onto a developing sleeve (developer carrier) and causing the toner to fly to the image carrier in an oscillating electric field for development. In the apparatus, an electrode plate composed of a plate-shaped member having an electrode is provided between the developing sleeve and the image carrier, and means for moving the electrode plate to the image carrier is attached to the electrode plate. This is achieved by an image forming apparatus having a developing device, characterized in that the toner is rubbed against the rotating image carrier to clean it.

An image forming apparatus having a developing device characterized in that an electric field for transferring toner to the image carrier is formed between the electrode and the image carrier is a preferred embodiment.

[0009]

EXAMPLE A first example of the first invention of the present invention will be described. FIG. 1 is a sectional configuration diagram showing an example of a color image forming apparatus provided with the developing device of the present invention as a suitable developing means.

In FIG. 1, reference numeral 1 denotes an image carrier, for example, a photoconductor which is a belt-shaped image carrier made of a flexible belt coated or vapor-deposited with a photoconductor, and the photoconductor belt 1 is rotated. It is installed between the rollers 2 and 3 and is conveyed in the clockwise direction by the driving of the rotating roller 2.

Reference numeral 4 denotes a guide member fixed to the main body of the apparatus so as to be inscribed in the photoconductor belt 1. The photoconductor belt 1 is tensioned by the action of the tension roller 5 so that the inner peripheral surface thereof slides on the guide member 4. Rub.

Reference numeral 6 denotes a scorotron charger, which is a charging means, and 7
Is an optical writing device using a laser beam as image exposure means,
Denoted at 8A to 8D are developing devices of the present invention which are a plurality of developing means for accommodating a developer of a specific color, respectively, and these image forming means are arranged at a portion of the photosensitive belt 1 which is in contact with the guide member 4. .

The developing units 8A, 8B, 8C and 8D will be described in detail later, but they contain, for example, yellow, magenta, cyan and black developers, respectively, and maintain a predetermined gap with the photosensitive belt 1. A developing sleeve (developer carrier) 81 is provided and has a function of visualizing a latent image on the photosensitive belt 1 by a non-contact reversal developing method. Unlike the contact development, the non-contact development has an advantage that it does not hinder the movement of the photosensitive belt 1.

A transfer device 12 and a cleaning device 13 are a blade 13a of the cleaning device 13 and a toner carrying roller 13
b is kept at a position separated from the surface of the photoconductor belt 1 during image formation and is pressed against the surface of the photoconductor belt 1 only as shown in the figure during cleaning after image transfer.

A color image forming process by the color image forming apparatus is performed as follows.

First, when image data, which is a color signal, output from the color image forming apparatus is input to the optical writing device 7, a laser generated by a semiconductor laser which is a writing light source (not shown) in the optical writing device 7 is generated. The beam (writing light) passes through a collimator lens and a cylindrical lens (not shown), is rotationally scanned by a rotary polygon mirror 74 rotated by a drive motor 71, passes through an fθ lens 75 and a cylindrical lens 76, and two mirrors 77, 78 therebetween. Thus, the optical path is bent by the charger, and the main scanning is performed on the peripheral surface of the photoconductor belt 1 to which uniform charges are applied by the charger 6 of the scorotron, which is a charging means, and main scanning is performed to form a bright line.

On the other hand, when the scanning is started, the laser beam is detected by an index sensor (not shown), and the first
The laser beam modulated by the color signal of (1) scans the peripheral surface of the photosensitive belt 1. Therefore, a latent image corresponding to the first color is formed on the peripheral surface of the photosensitive belt 1 by the main scanning by the laser beam and the sub-scanning by the conveyance of the photosensitive belt 1. This latent image is subjected to reversal development by the developing device 8A loaded with yellow (Y) toner (visual medium) in the developing means, and a toner image is formed on the belt surface. The obtained toner image is held on the belt surface and is separated from the peripheral surface of the photoconductor belt 1 as a cleaning device.
It passes under the blade 13a of 13 and enters the next image forming cycle.

That is, the photoconductor belt 1 is recharged by the scorotron charger 6, and then the second color signal is input to the optical writing device 7 to the belt surface in the same manner as in the case of the first color signal described above. Is written to form a latent image. The latent image is reverse-developed by the developing device 8B loaded with magenta (M) toner as the second color.

The magenta (M) toner image is formed in the presence of the previously formed yellow (Y) toner image.

8C is a developing device having cyan (C) toner, and cyan (C) is formed on the belt surface in the same manner as the first and second colors.
To form a toner image.

Further, 8D is a developing device having a black toner, which forms a black toner image on the surface of the belt by superposing it by the same processing as the above-mentioned color. A direct current or an alternating current bias is applied to the sleeves of the developing devices 8A, 8B, 8C and 8D, non-contact reversal development is performed by a two-component developer which is a developing means, and the substrate is grounded. The photoconductor belt 1 is designed to be developed in a non-contact manner.

Thus, the color toner image formed on the peripheral surface of the photosensitive belt 1 is sent from the paper feeding cassette 14 through the paper feeding guide 15 by applying a high voltage having a polarity opposite to that of the toner at the transfer portion. It is transferred to the transfer material.

That is, the transfer material contained in the paper feeding cassette 14 is carried out by the rotation of the paper feeding roller 16 and one of the uppermost layers is carried out, and the timing is adjusted with the image formation on the photosensitive belt 1 via the timing roller 17. And is supplied to the transfer device 12.

The transfer material which has received the transfer of the image is surely separated from the photosensitive belt 1 which suddenly changes its direction along the rotating roller 2 and goes upward, and after the image is fused by the fixing roller 18, it is ejected. It is discharged onto the tray 20 via the paper roller 19.

On the other hand, the photosensitive belt 1 which has been transferred to the transfer material is further conveyed and the residual toner is removed by the cleaning device 13 in which the blade 13a and the toner conveying roller 13b are brought into pressure contact with each other, and the end is completed. Then, the blade 13a is separated again, and a little later, the toner carrying roller 13b is separated, and a new image forming process is started.

As the color image forming apparatus using the developing device of the present invention, the belt-shaped image carrier has been described, but the image forming apparatus having the drum-shaped image carrier can be similarly used.

The developing devices 8A to 8D have the same structure, and will be denoted by reference numeral 8 below. 2, FIG. 3, and FIG. 4 are schematic sectional views showing one embodiment of a developing device using a two-component developer as the first embodiment of the first invention used in the present invention. 2 is a sectional view of the first embodiment of the apparatus of the present invention, FIG. 3 is an enlarged sectional view showing the developing action in the vicinity of the developing area A of the first embodiment, and FIG. 4 is a developing area A and electrodes. FIG. 9 is a dimensional relationship diagram near the plate 85. 81 is 10 ~
A non-magnetic material such as 20 mmφ aluminum or stainless steel, the surface of which is sandblasted and is rotatably supported with a rough surface of 0.5 to 5 μm according to JIS 10 point average roughness (JIS-B0610). A developing sleeve, which is a carrier, is a magnet body provided inside the developing sleeve 81 and having a plurality of N and S magnetic poles on its surface in the circumferential direction. The developing sleeve 81 and the magnet body 82 constitute a developer carrying carrier. ing. The developing sleeve 81 is rotatable with respect to the magnet body 82, and the drawing shows that the developing sleeve 81 rotates in the left direction of the arrow. In addition, the magnetic body of the developing unit
The N and S magnetic poles 82 are normally magnetized to a magnetic flux density of 500 to 1500 gauss, and the magnetic force forms a layer of the developer D composed of toner particles and carrier particles, that is, a magnetic brush on the surface of the developing sleeve 81. . This magnetic brush moves in the same direction as the rotation of the developing sleeve 81 by the rotation of the developing sleeve 81, and is conveyed to the developing area A. This developing sleeve 81
The magnetic brush formed on the top is the electrode plate 85 or the photoconductor belt 1.
N and S placed near the development area with the closest position to
Due to the magnetic poles, the ears lie down, and the gap between the developing sleeve 81 and the regulating blade 86 and the developing sleeve 81 and the photoreceptor belt 1 are maintained so as not to come into contact with the surface of the photoreceptor belt 1.
The gap is adjusted. The magnetic pole position may be arranged such that the magnetic pole faces the vicinity of the closest position to the photoconductor. Further, it is also possible to adopt a configuration in which the included magnet body is rotated.

Reference numerals 83 and 84 denote agitators for circulating the developer D back and forth in the figure to agitate the developer to homogenize the components, and 85 is provided on the upstream side of the developing area A to form an oscillating electric field. The electrode plate 85 is a plate-shaped member, and the electrode plate 85 has a thickness of 50 to 300 μm and is made of an insulating material such as resin or rubber provided to press the developer. Become 50
~ 500μm width (S1), 1 ~ 100μm thick linear first electrode
85a and a linear second electrode 85c made of a conductive material such as metal and having a width of 50 to 1000 μm (S2) and a thickness of 1 to 100 μm are integrally provided at the tip of the insulating member 85b, and the tip is also provided with an insulating material 85d. It is used as an insulation coat. The second electrode 85
The width of c is not limited to the tip portion and may be the entire area. 86 is a regulation blade which is a developer regulation means made of a non-magnetic material or a magnetic material provided to regulate the height and amount of the magnetic brush, 87
Is a scraper for removing the magnetic brush passing through the developing area A from the developing sleeve 81, 88 is a developer reservoir, and 89 is a casing.

The developing sleeve 81 has a DC bias power source E1.
A bias voltage in which alternating current is superimposed on direct current is applied through the protection resistor R1 by the alternating current bias power supply AC. Also,
The first electrode 85a of the electrode plate 85 receives a DC bias voltage from the DC bias power source E2 via the protection resistor R2, and the second electrode 85c receives a DC bias voltage from the DC bias power source E3 via the protection resistor R3. Applied respectively.

The tip position of the electrode plate 85 is located on the upstream side θ ₁ of the developing area A from the center line connecting the closest position between the image carrier 1 and the developing sleeve 81 and the center of the developing sleeve. Further, θ ₂ is also on the upstream side of the developing area A and is an electrode plate 85 which is a pressing member.
It is the closest position. The first and second electrodes are located between θ ₁ and θ ₂ , and preferably θ ₁ ≦ first and second electrode width positions ≦ θ ₂ . The front end of the first electrode 85a and the front end of the second electrode 85c may be located at substantially the same position, and the rear end of the second electrode 85c may be located upstream of the rear end position of the first electrode 85a. preferable. Here, θ ₁ is usually set to 0 to 10 °, and θ ₂ is usually set to 0 to 30 °. The dimensional relationship between the electrode width and the development gap and the electrode position is preferably S2 ≧ S1. Further, the relationship between the developing gap d and the electrode position is formed between the developing sleeve 81 and the first electrode 85a sufficiently stronger than the second oscillating electric field formed between the developing sleeve 81 and the image carrier 1. In order to generate a sufficient toner cloud by the first oscillating electric field, d4 ≧ d1 + d2 is preferable, more preferably d4 ≧ d1 + d2 + d3, and the relationship between the electrodes 85a and 85c and the developing sleeve is 0.5 ≦ (d1 + d2) / d3 ≦ 2 is preferable. However, S1: the width of the first electrode 85a S2: the width of the second electrode 85c d1: the closest distance between the lowermost end of the electrode plate 85 and the developing sleeve 81 d2: the center of the thickness of the first electrode 85a and the electrode Distance between bottom edge of plate 85 d3: Distance between center of thickness of first electrode 85a and center of thickness of second electrode 85c d4: Distance between center of thickness of second electrode 85c and photoreceptor belt 1 Interval d: Closest distance between the developing sleeve 81 and the photosensitive belt 1 (developing gap) The dimension of the distance is preferably d1 of 50 to 200 μm.
m, d2 + d3 is 50 ~ 400μm, d1 + d2 + d3 is 100 ~
The value of 600 μm, d4 is 200 to 1000 μm, and the value of d is 300 to 1500 μm.

In the present invention, a first oscillating electric field (first electric field) is applied between the developing sleeve 81 and the first electrode 85a provided on the insulating member 85b which abuts the developer layer on the developing sleeve 81. To generate a toner cloud. From this, the first electrode 85a is composed of the developing sleeve 81 and the electrode plate.
It is preferable to set it on the upstream side of the closest position (θ ₂ ) to 85. The second electrode 85c is provided on the first electrode 85a, and an electric field P1 for moving the toner toward the photoconductor belt 1 is provided.
And forming an electric field P2 for moving the toner toward the first electrode 85a, preventing the toner from wrapping around toward the second electrode 85c, and moving the toner toward the non-image portion of the photosensitive belt 1. This works to prevent toner from adhering to the electrode plate 85, especially the upper part of the second electrode 85c. Further, it prevents the toner image already formed on the image carrier from flying back to the developing sleeve 81 or the electrode.

A strong AC electric field is formed between the first electrode 85a and the developing sleeve 81 to generate a toner cloud.
Since the distance between the second electrode 85c and the developing sleeve 81 is large, the AC electric field is weak, and further, the application of the DC voltage forms an electric field for moving the toner to the developing sleeve 81 side.
And from this, the second electrode 85c becomes the first electrode 85a.
Or a wider width (S2 ≧ S1). Then, the toe cloud is prevented from adhering to the surface of the electrode plate 85.

An electric field for moving toner to the first electrode 85a is formed between the second electrode 85c and the first electrode 85a, and a photosensitive field is formed between the second electrode 85c and the photosensitive belt 1. An electric field for moving the toner to the body belt 1 is formed to prevent the toner from entering the upper surface of the electrode plate 85. The electric field formed by the second electrode 85c is called the third electric field. More specifically, the third electric field includes an electric field P2 formed with the first electrode 85a, an oscillating electric field formed with the developing sleeve 81, and an electric field P1 formed with the photosensitive belt 1. In this apparatus, the first oscillating electric field (developing sleeve 81 and the first electrode 85a) is compared with the oscillating electric field (which is referred to as a second electric field) formed between the photosensitive belt 1 and the developing sleeve 81. The strength of the electric field formed between them is larger than the strength of the second oscillating electric field, and the third electric field maintains the generation of the toner cloud to maintain the space between the photosensitive belt 1 and the electrode plate 85. Is also characterized in that an electric field for moving toner to the photosensitive belt 1 is formed.

In the color image forming apparatus described above, reversal development is performed using an OPC photosensitive member that is negatively charged as the photosensitive member of the photosensitive belt 1. If the photosensitive member is charged to -800 V, for example, the electrode plate 85 E of the first electrode 85a of
2 is 0 to -800V whose absolute value is smaller than the photoconductor potential, and E3 of the second electrode 85c is set to -800V or more to be a voltage for moving the negatively charged toner to the photoconductor belt 1. To the E1 of the developing sleeve 81, a bias voltage AC1 of a −700V DC voltage component and an AC voltage component is applied. AC voltage component is frequency 100Hz~20KH _Z, preferably the peak-to-peak voltage at 2～10KH _Z is 200～4000V. E2 can be set to E2 = E1, but it is preferable that E2 is made lower to be a bias for drawing the negatively charged toner from the developer layer. That is, it is more preferable that the DC electric field formed between the developing sleeve 81 and the first electrode 85a moves the toner toward the first electrode 85a.

On the other hand, a voltage higher than the non-image portion potential of the photosensitive belt 1 is applied to the second electrode 85c. As a result, the developing sleeve 8 is attached to the second electrode 85c of the electrode plate 85.
1. Since a voltage whose absolute value is higher than that of the first electrode 85a is applied, an electric field for moving the toner toward the photosensitive belt 1 or the developing sleeve 85 and the first electrode 85a is formed, and the electrode plate
No toner adheres to the upper portion of 85, and the toner image on the photosensitive belt 1 does not adhere to the second electrode 85c even in the superposition process.

By the first oscillating electric field, the toner particles are vibrated in the direction of the lines of electric force, so that the toner can fly and a toner cloud can be sufficiently generated.
This toner cloud is assisted in the flight toward the latent image on the photoconductor by the second oscillating electric field, and good development is performed. Further, the electric field P1 toward the photosensitive belt 1 is generated by the third electric field.
Also, an electric field P2 is formed in the direction of the first electrode 85a, so that the electrode plate 85 is prevented from being contaminated and the toner from flowing upward.

Here, it is important that the first, second and third oscillating electric fields have the same phase. Since they are in the same phase, development is carried out without causing undulations of toner vibration. Moreover, even if a strong oscillating electric field is formed, dielectric breakdown does not occur.

The waveform of the AC voltage component is not limited to a sine wave, and may be a rectangular wave or a triangular wave. Although the frequency is also related, the higher the voltage value, the more the toner vibrates, but on the other hand, dielectric breakdown such as fogging and lightning strike phenomenon easily occurs. The occurrence of fogging is prevented by the DC voltage component,
Dielectric breakdown can be prevented by coating the surfaces of the electrodes 85a and 85c and the developing sleeve 81 with resin or an oxide film in an insulating or semi-insulating manner.

As described above, the developing device of the present invention can
The magnetic brush of the component developer is kept in non-contact with the photoconductor belt 1 which is an image carrier, and a toner cloud is generated by the first and second oscillating electric fields to improve separation and flight to the photoconductor belt 1. , Improves the selective adsorption property to the electrostatic image and prevents the carrier particles from adhering to the photosensitive belt 1,
Therefore, it is possible to use fine particles as toner particles and carrier particles so that high-quality images can be developed. The developer is composed of the following carrier particles and toner particles. It is preferable to use.

Generally, when the average particle size of the magnetic carrier particles is large, the state of the ears of the magnetic brush formed on the developing sleeve 81 becomes rough. Therefore, even if the electrostatic latent image is developed while being vibrated by the electric field. However, there is a problem that unevenness is likely to appear in the toner image and the toner density at the ears becomes low, so that high-density development is not performed. To solve this problem, the average particle size of the magnetic carrier particles should be reduced, and as a result of experiments, it was found that the above problems do not occur when the weight average particle size is 50 μm or less. However, if the particle size of the magnetic carrier is too small, the magnetic carrier tends to adhere to the surface of the photoconductor belt 1 together with the toner particles and scatter easily. These phenomena are also related to the strength of the magnetic field acting on the carrier and the strength of the magnetization of the carrier due to it, but in general, the above tendency gradually begins to appear when the weight average particle diameter of the magnetic carrier is 15 μm or less. It becomes noticeable at 5 μm or less.
Therefore, in this developing device, the weight average particle diameter of the magnetic carrier of the developer D is preferably 50 μm or less and 5 μm or less.
As described above, those having a thickness of 15 μm or more are preferably used. In order to make the magnetic brush low and uniform, the magnetization is
10 to 50 emu / g is preferable. When the magnetic carrier is spherical, the stirring property of the toner particles and the carrier particles and the transport property of the developer D are improved, and the charge controllability of the toner is further improved. It is preferable because it prevents aggregation of particles.

Such a magnetic carrier is a metal such as iron, chromium, nickel, cobalt or the like or a compound or alloy thereof such as iron, chromium, nickel or cobalt, which is the same as a conventional magnetic carrier as a magnetic substance, for example, iron trioxide, γ-oxidation. Spherical particles of ferromagnet such as ferric iron, chromium dioxide, manganese oxide, ferrite, manganese-copper alloy, or the surface of those magnetic particles are styrenic resin, vinyl resin,
Spherical coating of resin such as ethylene resin, rosin-modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, silicon resin, fluororesin, or resin containing dispersed magnetic fine particles The particles obtained by making particles can be obtained by selecting the particle size by a conventionally known average particle size selecting means.

Forming the carrier particles into a spherical shape with a resin or the like as described above, in addition to the above-mentioned effects, makes the developer layer formed on the developer carrying carrier uniform, and There is also an effect that a high bias voltage can be applied to the carrier. That is, the carrier particles are made spherical by a resin or the like, in general, the carrier particles are easily magnetized and adsorbed in the long axis direction, but their directionality disappears due to the spherical shape, so that the developer layer is uniformly formed, The occurrence of locally low resistance regions and uneven layer thickness is prevented. Further, with the increase in the resistance of the carrier particles, there is no edge portion as seen in the conventional carrier particles, concentration of the electric field on the edge portion does not occur,
As a result, even if a high bias voltage is applied to the developer transport carrier, the electrostatic latent image is not disturbed by the discharge to the electrode member or the surface of the photosensitive belt 1 and the bias voltage is not broken down. Gives the effect of. The fact that this high bias voltage can be applied means that the effects as described above in the development under the oscillating electric field of the present invention can be sufficiently exerted. And, the wax as described above is also used for spheroidizing the carrier particles having the above effects, but from the viewpoint of the durability of the carrier, it is preferable to use the resin as described above. Resistivity of 10 ⁸ Ωcm or more, especially 10 ¹³
Those in which magnetic particles having an insulating property of Ωcm or more are formed are preferable. The resistivity, after tapping putting particles into a container having a cross section of 0.50 cm ^2, a load of 1Kg / cm ² on packed particles, between the load and a bottom electrode 1000
It is a value obtained by reading the current value when a voltage that generates an electric field of V / cm is applied. If this resistivity is low,
When a bias voltage is applied to the developer carrying carrier, charges are injected into the carrier particles, and the carrier particles are likely to adhere to the surface of the photosensitive belt 1 or the breakdown of the bias voltage is likely to occur.

In summary of the above, the magnetic carrier particles are spherical so that the ratio of the major axis to the minor axis is at most 3 times, preferably at most 2 times, and protrusions such as needle-shaped parts and edge parts. And has a resistivity of 10 ⁸ Ωcm or more, preferably 10 ¹³ Ωcm
The above is the proper condition. Further, such magnetic carrier particles are obtained by increasing the resistance of spherical magnetic particles by forming an oxide film or the like. It is produced by subjecting to spheroidizing treatment or obtaining dispersed resin particles by a spray drying method.

Next, the toner particles will be described. Generally, when the average particle size of toner particles is small, the amount of charge qualitatively decreases in proportion to the square of the particle size, and the adhesive force such as the Van der Waals force is relatively large, and the toner particles are easily scattered. While fogging easily occurs, it becomes difficult to separate from the carrier particles of the magnetic brush. In the conventional magnetic brush developing method, such a problem becomes remarkable when the average particle diameter is 10 μm or less. In the developing device of the present invention, this problem is solved by developing with a magnetic brush under a double oscillating electric field. That is, the toner particles adhering to the ears of the magnetic brush are
Is strongly vibrated in the oscillating electric field to easily separate from the ears to form a toner cloud, and the toner cloud is carried to the developing area A in the immediate vicinity of the cloud and toner particles are formed on the electrostatic latent image under the second oscillating electric field. It will be faithfully absorbed. Further, the toner particles having a low charge amount hardly move to the image portion or the non-image portion, and the toner does not rub against the photosensitive belt 1, so that the toner particles may adhere to the photosensitive belt 1 by frictional charging. It will be used up to a toner particle size of about 1 μm. The weakening of the bond between the toner particles and the carrier particles by the oscillating electric field reduces the adhesion of the carrier particles accompanying the toner particles to the photosensitive belt 1, and
The ears of the magnetic brush are kept in non-contact with the surface of the photosensitive belt 1, and the toner particles having a large charge amount with respect to the carrier particles are selectively transferred to the electrostatic latent image under the oscillating electric field as described above. This significantly reduces the adhesion of carrier particles to the photosensitive belt 1.

As the average particle diameter of the toner becomes large, the roughness of the image becomes conspicuous as already mentioned. Usually, for development with a resolution of fine lines arranged at a pitch of about 10 lines / mm, even a toner having an average particle size of about 20 μm does not pose any problem, but when a finely divided toner having an average particle size of 1 to 5 μm is used, The resolution is remarkably improved, and a clear high-quality image in which the difference in grayscale is faithfully reproduced is provided. For the above reasons, the average particle diameter of the toner is 10 μm or less, preferably 1 to 7 μm. Further, since the toner particles follow the electric field, the charge amount of the toner particles is 3 μc /
It is desirable that it is larger than g (preferably 3 to 50 μc / g). Especially when the particle size is small, a high charge amount is required.

Such a toner can be obtained by the same method as the conventional toner. That is, it is possible to use a toner obtained by selecting non-magnetic or magnetic non-magnetic or magnetic toner particles of the conventional toner by the average particle size selection means. Above all, it is preferable that the toner particles are magnetic particles containing magnetic fine particles, and it is particularly preferable that the amount of the magnetic fine particles is 60 wt% or less, particularly preferably 30 wt% or less. When the toner particles contain magnetic particles, the toner particles are affected by the magnetic force contained in the developer carrying carrier, so that the uniform forming property of the magnetic brush is further improved and the fogging Generation is prevented, and toner particles are less likely to be scattered. However, if the amount of the magnetic material contained is too large, the magnetic force between the particles and the carrier particles becomes too large, and it becomes impossible to obtain a sufficient development density. Then, it becomes difficult to control triboelectric charging, and the toner particles are easily damaged.

In summary, in the developing device of the present invention, as the preferable toner particles, the resin as described for the carrier particles and further the fine particles of the magnetic substance are used, and the coloring component such as carbon and the electrification if necessary. It is composed of particles having an average particle size of 20 μm or less, preferably 10 μm or less, particularly preferably 1 to 7 μm, which can be produced by the same method as a conventionally known toner particle producing method by adding a control agent and the like.

For the developing device of the present invention, a developer in which the spherical carrier particles and the toner particles as described above are mixed in the same proportion as in the conventional two-component developer is preferably used. Further, if necessary, a fluidizing agent for improving fluidity of particles and a cleaning agent useful for cleaning the surface of the image bearing member are mixed. As the fluidizing agent, colloidal silica, silicon varnish, metal soap, nonionic surface active agent or the like can be used, and as the cleaning agent, fatty acid metal salt, organic group-substituted silicon or fluorine surface active agent or the like can be used. You can

As the developer and the developing device as described above, spherical ferrite is coated with a resin and the weight average particle diameter is 30 μm.
m, magnetic strength of 30 emu / g, resistivity of 10 ¹⁴ Ωcm or more, spherical magnetic carrier, 100 parts by weight of styrene-acrylic resin (SANYO Kasei Hymer up110), toner, color pigment
Toner particles of each developer D in each developer pool 88 are used by the apparatus shown in FIG. 2 using non-magnetic particles obtained by a pulverization granulation method having a weight average particle diameter of 10 parts by weight of 5 μm. Development was carried out under the condition that the ratio was 10 wt% with respect to the carrier particles. The average charge of each toner is -15
It was μc / g.

In the color image forming apparatus shown in FIG. 1 equipped with such a developing device, the photosensitive belt 1 is an OPC photosensitive member, the peripheral speed thereof is 180 mm / sec, and the electrostatic latent image formed on the photosensitive belt 1 is the highest. Potential -800V, minimum potential -50V (since reversal development, non-image portion potential -800V, image portion potential -50V), developing sleeve 81 outer diameter 15mm, its rotation speed 200rp
m, the magnetic flux density on the N and S magnetic poles facing the developing area A of the magnet body 82 is 1200 gauss, the upstream N pole is 10 °, and the downstream S pole is
The pole is 30 °, the thickness of the developer D layer in the developing portion when the developing bias is not applied is 0.25 mm, the gap between the developing sleeve 81 and the photosensitive belt 1 is 0.95 mm, and the bias voltage applied to the developing sleeve 81 is DC voltage component -700 V, an AC voltage component 10KH _Z, a peak-to-peak voltage 1200 V, the first electrode 85a is developing sleeve
Apply DC voltage of -500V at 0.3mm from 81,
5c was installed 0.075 mm from the first electrode 85a and a DC voltage of -1000 V was applied. In this embodiment, the developer D on the developing sleeve 81 does not contact the surface of the photosensitive belt 1.

After developing under the above-mentioned conditions, it was transferred onto plain transfer paper by corona discharge, and passed through a heat roller fixing device having a surface temperature of 140 ° C. to fix the transfer paper. The image has no edge effect and no fog, and is extremely clear with high density, and after recording 50,000 sheets continuously, it is possible to obtain a stable recorded image from the beginning to the end, and Almost no toner adhered to the electrode plate 85.

In the above-described embodiments, since a specific developing device is selectively used, the other developing devices which are not used stop the rotation state of the developing sleeve and stop the AC bias applied to the developing sleeve. That is, to the developing sleeve 81, a bias of −1000 V, which is in a floating state or the same polarity as the toner and which is higher than the non-image portion potential of the photoconductor, is applied. A bias of -1000 V, which has the same polarity as the toner and is higher than the non-image area potential of the photoconductor, was applied to the electrodes 85a and 85c.
One or both of the electrodes 85a and 85c may be floating. This prevents the toner from moving from the toner image on the photoconductor to the electrode plate. A potential pattern of approximately 0 V is formed before and after the image area, and conditions for removing the toner on the developing sleeve and the electrodes that have stopped are set to prevent color mixture of toner in the image area. Further, as the electrode plate, the one having the structure shown in FIG. 7C described later is used. A 75 μm-thick epoxy plate containing glass fibers is attached, and the first electrode 85a is 10 μm thick on the 150 μm-thick epoxy plate.
m, width 500 μm, second electrode 85c thickness 10 μm, width 1000 μm
The structure with the linear electrode attached was used.

A second embodiment of the first invention will be described with reference to FIGS. 4, 5 and 6 by taking as an example a one-component developer comprising the following non-magnetic toner. The same parts as those in the first embodiment are designated by the same reference numerals.

The developing devices 8A to 8D have the same structure, and will be denoted by reference numeral 8 below. 5 and 6
FIG. 1 is a schematic sectional view showing an embodiment of a developing device of the first invention used in the present invention. FIG. 5 is a sectional view of a second embodiment of the device of the present invention, and FIG. 6 is an enlarged sectional view showing the developing action near the developing area A. Development area A and electrode plate 85 in FIG.
The dimensional relationship diagram in the vicinity is the same as in the first embodiment. 81 for 10
~ 20mmφ Aluminum, stainless steel, etc. non-magnetic material, the surface is sandblasted, and the surface is subjected to roughening of 0.5 to 5μm according to JIS 10 point average roughness (JIS-B0610) and rotatably supported developer carrier. Is a developing sleeve, 83 is a stirrer for stirring the developer D to make the components uniform, 184 is a fur brush for supplying the developer D to the developing sleeve 81, and 186 is the thickness of the developer layer on the sleeve 81. A regulating blade made of a rubber plate regulating 85, an electrode plate 85 which is a plate-like member provided on the upstream side of the developing area A for forming an oscillating electric field, the electrode plate 85 having a thickness of 50 to 300 μm, and on the developing sleeve 81. The first linear member having a width of 50 to 500 μm and a thickness of 1 to 100 μm made of a conductive material such as metal is attached to the tip of an insulating member 85b made of an insulator such as resin or rubber provided so as to press the developer D. Of the electrode 85a and the insulating member 85b A linear second electrode 85c made of a conductive material such as metal and having a width of 50 to 1000 μm and a thickness of 1 to 100 μm is integrally provided at the tip, and the tip is also made of an insulating material 85d.
Insulation coated with. The width of the second electrode 85c is not limited to the tip portion and may be the entire area. The layer of the developer D, the layer thickness of which is regulated by the electrode plate 85, is moved by the rotation of the developing sleeve 81 and is conveyed to the developing area A. Note that the reference numeral 85 can also serve as a control blade 86 that controls the thickness of the developer layer on the developing sleeve 81. This developing sleeve
The pressure contact between the developing sleeve 81 and the electrode plate 85 and the gap between the developing sleeve 81 and the photosensitive belt 1 are adjusted so that the developer layer formed on the 81 does not contact the surface of the photosensitive belt 1 and maintains the gap. . Reference numeral 88 is a developer reservoir, and 89 is a casing.

The developing sleeve 81 has a DC bias power source E1.
A bias voltage in which alternating current is superimposed on direct current is applied through the protection resistor R1 by the alternating current bias power supply AC. Also,
The first electrode 85a of the electrode plate 85 receives a DC bias voltage from the DC bias power source E2 via the protection resistor R2, and the second electrode 85c receives a DC bias voltage from the DC bias power source E3 via the protection resistor R3. Applied respectively.

The tip position of the electrode plate 85 is located on the upstream side θ ₁ of the developing area A from the center line connecting the closest position between the image carrier 1 and the developing sleeve 81 and the center of the developing sleeve. Further, θ ₂ is also on the upstream side of the developing area A and is an electrode plate 85 which is a pressing member.
It is the closest position. The first and second electrodes are located between θ ₁ and θ ₂ , and preferably θ ₁ ≦ first and second electrode width positions ≦ θ ₂ . The front end of the first electrode 85a and the front end of the second electrode 85c may be located at substantially the same position, and the rear end of the second electrode 85c may be located upstream of the rear end position of the first electrode 85a. preferable. Here, θ ₁ is usually set to 0 to 10 °, and θ ₂ is usually set to 0 to 30 °. The dimensional relationship between the electrode width and the development gap and the electrode position is preferably S2 ≧ S1. Further, the relationship between the developing gap d and the electrode position is formed between the developing sleeve 81 and the first electrode 85a sufficiently stronger than the second oscillating electric field formed between the developing sleeve 81 and the image carrier 1. In order to generate a sufficient toner cloud by the first oscillating electric field, d4 ≧ d1 + d2 is preferable, more preferably d4 ≧ d1 + d2 + d3, and the relationship between the electrodes 85a and 85c and the developing sleeve is 0.5 ≦ (d1 + d2) / d3 ≦ 2 is preferable. However, S1: the width of the first electrode 85a S2: the width of the second electrode 85c d1: the closest distance between the lowermost end of the electrode plate 85 and the developing sleeve 81 d2: the center of the thickness of the first electrode 85a and the electrode Distance between bottom edge of plate 85 d3: Distance between center of thickness of first electrode 85a and center of thickness of second electrode 85c d4: Distance between center of thickness of second electrode 85c and photoreceptor belt 1 Interval d: Closest distance between the developing sleeve 81 and the photosensitive belt 1 (developing gap) The dimension of the distance is preferably d1 of 50 to 200 μm.
m, d2 + d3 is 50 ~ 400μm, d1 + d2 + d3 is 100 ~
The value of 600 μm, d4 is 200 to 1000 μm, and the value of d is 300 to 1500 μm.

In the present invention, a first oscillating electric field (first electric field) is applied between the developing sleeve 81 and the first electrode 85a provided on the insulating member 85b that abuts the developer layer on the developing sleeve 81. To generate a toner cloud. From this, the first electrode 85a is composed of the developing sleeve 81 and the electrode plate.
It is preferable to set it on the upstream side of the closest position (θ ₂ ) to 85. The second electrode 85c is provided on the first electrode 85a, and an electric field P1 for moving the toner toward the photoconductor belt 1 is provided.
And forming an electric field P2 for moving the toner toward the first electrode 85a, preventing the toner from wrapping around toward the second electrode 85c, and moving the toner toward the non-image portion of the photosensitive belt 1. This works to prevent toner from adhering to the electrode plate 85, especially the upper part of the second electrode 85c. Further, it prevents the toner image already formed on the image carrier from flying back to the developing sleeve 81 or the electrode.

A strong AC electric field is formed between the first electrode 85a and the developing sleeve 81 to generate a toner cloud.
Since the distance between the second electrode 85c and the developing sleeve 81 is large, the AC electric field is weak, and further, the application of the DC voltage forms an electric field for moving the toner to the developing sleeve 81 side.
And from this, the second electrode 85c becomes the first electrode 85a.
Or a wider width (S2 ≧ S1). Then, the toner cloud is prevented from adhering to the surface of the electrode plate 85.

An electric field for moving toner to the first electrode 85a is formed between the second electrode 85c and the first electrode 85a, and a photosensitivity is provided between the second electrode 85c and the photosensitive belt 1. An electric field for moving the toner to the body belt 1 is formed to prevent the toner from entering the upper surface of the electrode plate 85. The electric field formed by the second electrode 85c is called the third electric field. More specifically, the third electric field includes an electric field P2 formed with the first electrode 85a, an oscillating electric field formed with the developing sleeve 81, and an electric field P1 formed with the photosensitive belt 1. In this apparatus, the first oscillating electric field (developing sleeve 81 and the first electrode 85a) is compared with the oscillating electric field (which is referred to as a second electric field) formed between the photosensitive belt 1 and the developing sleeve 81. The strength of the electric field formed between them is larger than the strength of the second oscillating electric field, and the third electric field maintains the generation of the toner cloud to maintain the space between the photosensitive belt 1 and the electrode plate 85. Is also characterized in that an electric field for moving toner to the photosensitive belt 1 is formed.

In the color image forming apparatus, reversal development is carried out by using a negatively charged OPC photoconductor as the photoconductor of the photoconductor belt 1. Assuming that the photoconductor is charged to, for example, -800V, the E of the first electrode 85a of the electrode plate 85 is
2 is 0 to -800V whose absolute value is smaller than the photoconductor potential, and E3 of the second electrode 85c is set to -800V or more to be a voltage for moving the negatively charged toner to the photoconductor belt 1. To the E1 of the developing sleeve 81, a bias voltage AC1 of a −700V DC voltage component and an AC voltage component is applied. AC voltage component is frequency 100Hz~20KH _Z, preferably the peak-to-peak voltage at 2～10KH _Z is 200～4000V. E2 can be set to E2 = E1, but it is preferable that E2 is made lower to be a bias for drawing the negatively charged toner from the developer layer. That is, it is more preferable that the DC electric field formed between the developing sleeve 81 and the first electrode 85a moves the toner toward the first electrode 85a.

On the other hand, a voltage higher than the non-image portion potential of the photosensitive belt 1 is applied to the second electrode 85c. As a result, the developing sleeve 8 is attached to the second electrode 85c of the electrode plate 85.
1. Since a voltage whose absolute value is higher than that of the first electrode 85a is applied, an electric field for moving the toner toward the photosensitive belt 1 or the developing sleeve 85 and the first electrode 85a is formed, and the electrode plate
No toner adheres to the upper portion of 85, and the toner image on the photosensitive belt 1 does not adhere to the second electrode 85c even in the superposition process.

By the first oscillating electric field, the toner particles are vibrated in the direction of the lines of electric force, so that the toner can fly and a toner cloud can be sufficiently generated.
This toner cloud is assisted in the flight toward the latent image on the photoconductor by the second oscillating electric field, and good development is performed. Further, the electric field P1 toward the photosensitive belt 1 is generated by the third electric field.
Also, an electric field P2 is formed in the direction of the first electrode 85a, so that the electrode plate 85 is prevented from being contaminated and the toner from flowing upward.

Here, it is important that the first, second and third oscillating electric fields have the same phase. Since they are in the same phase, development is carried out without causing undulations of toner vibration. Moreover, even if a strong oscillating electric field is formed, dielectric breakdown does not occur.

The waveform of the above AC voltage component is not limited to a sine wave, and may be a rectangular wave or a triangular wave. Although the frequency is also related, the higher the voltage value, the more the toner vibrates, but on the other hand, dielectric breakdown such as fogging and lightning strike phenomenon easily occurs. The occurrence of fogging is prevented by the DC voltage component,
Dielectric breakdown can be prevented by coating the surfaces of the electrodes 85a and 85c and the developing sleeve 81 with resin or an oxide film in an insulating or semi-insulating manner.

In general, when the average particle diameter of the toner becomes small, the charge amount qualitatively decreases in proportion to the square of the particle diameter, and the adhesive force such as the Van der Waals force becomes relatively large, and the developing sleeve It strongly adheres to 81 and is easily scattered on the non-image portion, and fogging is likely to occur. In the conventional developer layer developing method, when the average particle diameter is 10 μm or less, such a problem becomes remarkable.

In the developing device of the present invention, this point is solved by performing the development with the developer layer under a double oscillating electric field. That is, the toner particles are strongly vibrated in the first oscillating electric field to form a toner cloud apart from the developing sleeve 81, and are carried to the developing area A in the immediate vicinity of the cloud, and are weaker than the first oscillating electric field. Under the second oscillating electric field, the toner particles are adhered to the electrostatic latent image faithfully. Further, the toner having a low charge amount is hardly transferred to the image portion or the non-image portion, and the toner does not rub against the photosensitive belt 1, so that the toner is not attached to the photosensitive belt 1 by frictional charging. Therefore, even toner particles having a particle diameter of about 1 μm can be used.

When the average particle diameter of the toner becomes large, the roughness of the image becomes noticeable. Usually, for development with the resolution of fine lines arranged at a pitch of about 10 lines / mm, the average particle size is 20 μm.
There is no problem even if the toner is a small amount, but the average particle size is 1 to 7
The use of micronized toner of μm greatly improves the resolving power and gives a clear high-quality image in which the difference in density is faithfully reproduced. For the above reasons, the average particle diameter of the toner is 10 μm or less, preferably 1 to 7 μm. Further, since the toner particles follow the electric field, it is desirable that the charge amount of the toner particles is larger than 1 to 3 μc / g (preferably 3 to 30 μc / g). Especially when the particle size is small, a high charge amount is required.

Such a toner can be obtained by the same method as the conventional toner. That is, it is possible to use a toner in which spherical or amorphous non-magnetic toner particles of the conventional toner are selected by the average particle size selection means.

In the developing device of the present invention, preferable toners are resins such as styrene resin, vinyl resin, ethylene resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, palmitic acid, stearin. An average particle size that can be produced by the same method as a conventionally known toner particle manufacturing method, using a resin such as a fatty acid wax such as an acid, and adding a coloring component such as a color pigment and a charge control agent as necessary. Is 20 μm or less, preferably 10 μm or less, and particularly preferably 1 to 7 μm.

In the developing device of the present invention, a developer comprising spherical non-magnetic toner particles as described above is preferably used, and in order to improve the flow slippage of the particles, if necessary. A fluidizing agent and a cleaning agent useful for cleaning the surface of the image bearing member are mixed. As a fluidizing agent,
Colloidal silica, silicon varnish, metal soap, nonionic surface active agents, etc. can be used, and fatty acid metal salts, organic group-substituted silicon, surface active agents such as fluorine, etc. can be used as cleaning agents.

As the developer and the developing device as described above, styrene-acrylic resin (SANYO Kasei Hymer u
p110) 100 parts by weight, and 10 parts by weight of the color pigment, the non-magnetic particles obtained by the pulverization and granulation method and having a weight average particle diameter of 5 μm were used to perform development with the apparatus shown in FIG. The average charge amount of each toner was −5 μc / g.

In the color image forming apparatus shown in FIG. 1 equipped with such a developing device, the photosensitive belt 1 is an OPC photosensitive member, its peripheral speed is 180 mm / sec, and the electrostatic latent image formed on the photosensitive belt 1 is the highest. Potential -800V, minimum potential -50V (since reversal development, non-image part potential -800V, exposure part potential -50V), developing sleeve 81 outer diameter 15mm, its rotation speed 150rpm,
The thickness of the developer D layer is 0.02 mm, the gap between the developing sleeve 81 and the photosensitive belt 1 is 0.50 mm, the bias voltage applied to the developing sleeve 81 is a DC voltage component −700 V, an AC voltage component 4 KH _Z ,
A peak-to-peak voltage of 1000 V is applied, and a DC voltage of 0 V is applied to the first electrode 85a by 0.2 mm from the developing sleeve 81, and a second electrode 8a is applied.
5c was installed 0.075 mm from the first electrode 85a and a DC voltage of -1000 V was applied. In this embodiment, the developer D on the developing sleeve 81 does not contact the surface of the photosensitive belt 1.

After developing under the above-mentioned conditions, it was transferred onto plain transfer paper by corona discharge, and passed through a heat roller fixing device having a surface temperature of 140 ° C. to fix the transfer paper. The image has no edge effect and no fog, and is extremely clear with high density, and after recording 50,000 sheets continuously, it is possible to obtain a stable recorded image from the beginning to the end, and Almost no toner adhered to the electrode plate 85.

In the above embodiment, while the specific developing device is being used, the other developing devices which are not used stop the rotation state of the developing sleeve and stop the AC bias applied to the developing sleeve. That is, a bias of -1000 V, which is higher than the potential of the non-image portion of the photoconductor in the floating state or the same polarity as the toner, was applied. A bias of -1000 V, which is higher than that of the non-image area of the photoconductor having the same polarity as the toner, was applied to the electrodes 85a and 85c. This prevents the toner from moving from the toner image on the photoconductor to the electrode plate. The electrodes 85a, 85
One or both of c may be floating. or,
As the electrode plate 85, a structure having a thickness of 150 μm was used in which the linear electrodes 85a and 85c were attached to an epoxy plate containing the same glass fibers as in the previous embodiment and having a thickness of 75 μm.

As described above, in the developing device of the image forming apparatus of the present invention, the developer layer of the one-component or two-component developer is kept in non-contact with the photosensitive belt 1 which is the image carrier. And a toner cloud is generated by the second oscillating electric field to improve separation and flight to the photoconductor belt 1 and improve selective adsorption to an electrostatic image, thus making it possible to use fine particles of toner. Thus, the high quality image is developed and the toner is prevented from adhering to the electrode plate or the electrode.

FIG. 7 shows another configuration example of the electrode plate. In FIG. 7A, electrodes 185a and 185c are formed on both sides of one insulating member 185b. FIG. 7 (B)
Is a structure in which electrodes 185a and 185c are formed on two insulating members 185b, respectively, and they are adhered to each other.
5a is arranged close to the developing sleeve 181 side. Figure 7
FIG. 7C shows an electrode plate 185 formed by bonding the opposite surfaces of FIG. 7B to each other, and in this case, the electrode 185a is the developing sleeve via the insulating member 185b.
It faces the 181 side. FIG. 7D shows the developing sleeve 181.
The side end has a step, and a space for forming a toner cloud is provided. In this case,
The electrode plate of (A) and an insulating member having no electrode are attached at different positions. FIG. 7E is the same as FIG.
Electrode 185c which is a modification of (C) and is close to the image carrier side
Is formed over the entire area. In this manner, the electrode 185c can be formed over the entire area as shown in FIG. 7E in FIGS. 7A, 7B, 7C, and 7D.

As a method of manufacturing the electrode plate 85 in the first and second embodiments of the first invention (FIG. 7C), the electrode plate 85, which is a plate-shaped member, is thick on the side of the photosensitive belt 1. A glass epoxy film having two electrodes each having a thickness of 75 μm and a developing sleeve 81 side having a thickness of 75 μm is laminated and adhered. That is, a first electrode 85a and a second electrode 85c made of copper foil having a thickness of 2 μm and corresponding to the electrode width and having a length of 0.5 mm and 3 mm in the rotation direction of the developing sleeve 81 are formed on the film in advance, Next, they were attached to each other to form a laminated structure in which an insulating film coat made of an insulating member 85d having a thickness of 0.02 mm was formed. The electrode plate thus formed has the structure shown in FIG. The electrode pattern on each film is formed by photoetching. The connection of the first electrode 85a and the second electrode 85c to the power source is made through a protective resistor at the portions where the respective electrodes extend outside the width of the developing area as shown in FIG. 2 and FIG. ing.

Subsequently, as an embodiment of the second invention, FIG.
An example will be described in which the toner mechanically deposited on the electrode plate 285 is forcibly transferred to and removed from the photoconductor belt 200 by using. The image forming process by the color image forming apparatus and the developing device are the same as those in the embodiment described in the first invention. This removing operation is performed during non-image formation.

At the time of image formation, it is fixed to the holder 291 by the pressing member 290 and the set screw 290a, and bridged between the spring hooking shaft 291c on the holder 291 and the shaft 294 provided on the developing device 8 (shown in FIG. 1). Stopper by spring 293
The electrode plate 285, which is pressed against the developing sleeve 281 to the position regulated by 292, is provided on the holder 291 while rotating the photoconductor belt 200 each time when the apparatus is started and when non-image formation is performed during image formation. The solenoid SD laid over the hole 291b is turned on, and the holder 291 is pulled upward. The electrode plate 285 is rotated about the holder rotation shaft 291a in the arrow direction (clockwise rotation) in the figure and is in a state of being rubbed against the photosensitive belt 200 (dotted line state in the figure). At this time, an electric field for moving the toner to the image carrier is formed on the first electrode 285a and the second electrode 285c of the electrode plate 285 as in the first and second embodiments of the first invention. A voltage is applied to transfer the adhered toner on the insulating agent 285d on the electrode plate 285 to the photoconductor belt 200 to remove the toner on the electrode plate 285. The rubbing state between the photoconductor belt 200 and the electrode plate 285 can be either a light contact state or a pressure contact state depending on the setting of the solenoid SD.

In the description of the present invention, the reversal development is used, but the regular development can be similarly applied.
At that time, the voltage applied to the developing sleeve and the electrodes may be set to a voltage which also acts on the electric field acting on the toner in the reversal development.

[0081]

As described above, in the developing device of the image forming apparatus of the present invention, a sufficient amount of development is performed by the oscillating electric field between the first electrode of the electrode plate, which is a plate member, and the developer carrier. Because the agent efficiently forms a cloud, the electrostatic image on the image carrier can be developed into a toner image of sufficient density without fogging by the oscillating electric field in the developing area, and the developer can be mixed on the surface of the electrode plate on the image carrier side of the color mixture. The remarkable effect is that the deposition is prevented by the electric field of the second electrode. Also, a method has been provided in which the toner deposited on the electrode plate can be easily removed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a color image forming apparatus including a developing device of the present invention.

FIG. 2 is a partial sectional view showing the first embodiment of the first invention of the developing device of the present invention.

FIG. 3 is an enlarged sectional view showing the developing action in the vicinity of the developing area A of the developing device of the first embodiment of the first invention.

FIG. 4 is a development area A and an electrode plate of the development device of the first invention.
It is a dimensional relationship diagram of the vicinity of 85.

FIG. 5 is a partial sectional view showing a second embodiment of the first invention of the developing device of the present invention.

FIG. 6 is an enlarged cross-sectional view showing the developing action in the vicinity of the developing area A of the developing device of the second embodiment of the first invention.

FIG. 7 is a cross-sectional view showing a configuration example of an electrode plate of the present invention.

FIG. 8 is a partial cross-sectional view showing a second invention embodiment of the developing device of the present invention.

[Explanation of symbols]

 1,200 Photoconductor belt 4 Guide member 6 Scorotron charger 7 Optical writing device 8, 8A, 8B, 8C, 8D Developing device 12 Transfer device 13 Cleaning device 81,181 Developing sleeve 83,84 Stirrer 85,185,285 Electrode Plates 85a, 185a, 285a First electrodes 85b, 185b Insulating members 85c, 185c, 285c Second electrodes 85d, 185d, 285d Insulating material 86, 186 Control blade 87 Scraper 88 Developer pool 89 Casing 184 Fur brush 285e Adhesive toner 290 Pressing member 291 Holder 292 Stopper AC AC bias power supply E1, E2, E3 DC bias power supply R1, R2, R3 Protective resistance A Development area D Developer P One-way electric field to photoconductor belt SD solenoid

Claims (6)

[Claims] 1. An image forming apparatus having a developing device for carrying a developer onto a developing sleeve (developer carrying body) and causing the toner to fly to an image carrying body in an oscillating electric field for development.
An electrode plate made of a plate-shaped member having an electrode is provided between the developing sleeve and the image carrier, and the electrode plate includes a first electrode close to the developing sleeve, the first electrode and the image carrier. A second electrode disposed between the bodies, the first electrode forming an oscillating electric field with the developing sleeve, and the second electrode forming an electric field for moving toner to a non-image portion of the image carrier. An image forming apparatus having a developing device. 2. An image forming apparatus having a developing device according to claim 1, wherein an electric field for moving toner to the first electrode is formed between the first electrode and the second electrode. apparatus. 3. At the time of non-image formation, a voltage for forming an electric field for moving the toner to the image carrier is applied to the first electrode or the second electrode, or the first electrode or the second electrode is in a floating state. An image forming apparatus having the developing device according to claim 1. 4. An image forming apparatus having a developing device according to claim 1, wherein a toner image is superposed on the image carrier. 5. An image forming apparatus having a developing device for carrying a developer onto a developing sleeve (developer carrier) and causing toner to fly to the image carrier in an oscillating electric field for development.
An electrode plate composed of a plate-shaped member having an electrode is provided between the developing sleeve and the image carrier, and means for moving the electrode plate to the image forming body is provided to rotate the toner adhered to the electrode plate. An image forming apparatus having a developing device, characterized in that it is rubbed against the moving image carrier to clean it. 6. An image forming apparatus having a developing device according to claim 5, wherein an electric field for transferring toner to the image carrier is formed between the electrode and the image carrier.