JPH09127786A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact developing device capable of stably obtaining an image provided with excellent resolution and the developing property, without longitudinal stripes and unevenness of development, by preventing waviness and warpage of a control electrode. SOLUTION: The developing device 8a is provided with the control electrode 83 consisting of the electrode part 83a placed thereon capable of applying voltage, fixed to an insulating member 83b held in contact with or arranged close to the developing layer, in a developing area A or on the upstream part of the developing area A of a developing sleeve 81 for transporting developer, while opposing a photoreceptor belt 1. In this case, the control electrode 83 is composed as a multilayered structure consisting of the insulating member 83b composed of ceramics for supporting the electrode part 83a, and the reinforcing member 83c for reinforcing the insulating member 83b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for non-contact development of an electrostatic latent image by using a one-component or two-component developer in an image forming apparatus such as an electrophotographic copying machine.

[0002]

2. Description of the Related Art Conventionally, as one of developing methods used in an electrophotographic copying machine or the like, there is a one-component developing method using a non-magnetic toner. This developing method has a cylindrical sleeve rotatably supported with its surface roughened, the charged toner is supported on the surface of the developing sleeve, and the toner is conveyed to a developing area for developing.

In contrast to the one-component developing method, a two-component developing method is generally used in which a two-component developer comprising a magnetic carrier having a particle size of several tens to several hundreds of μm and a non-magnetic toner having an average particle size of about 10 μm is used. Is also often used.

In any of the developing methods, since toner particles having an average particle size of about 10 μm are used, there is a problem in that it is difficult to obtain a high-quality image in which delicate lines, dots, shade differences, and the like are reproduced. In order to obtain such high-quality images, it is considered essential to make the toner particles and carrier particles finer. However, if the toner particles are particularly fine particles of 10 μm or less, the following problems occur. Since the influence of the Van der Waals force is relatively large with respect to the Coulomb force at the time of development, so-called fog occurs in which toner particles adhere to other parts of the image background, and a DC bias to the developer transport body occurs. It is difficult to prevent even by applying. Since the carrier coverage of the toner is increased, the charge control becomes difficult. In addition, toner aggregation easily occurs. In the two-component developing method, since the carrier coverage of the toner is high, it becomes more difficult to control the charge. As the carrier particles are made smaller in order to reduce the carrier coverage, the carrier particles also adhere to the electrostatic latent image portion of the image forming body. It is considered that this is because the magnetic bias force was reduced and the carrier particles adhered to the image forming body together with the toner particles. Further, when the bias voltage increases, carrier particles also adhere to other parts of the image background.

The above-mentioned side effects are more conspicuous when the toner or carrier is made into fine particles, and there is a problem that a clear image cannot be obtained. Therefore, it is difficult to actually make the particles fine. As a method for solving this problem, a plate-shaped member having an electrode in the upstream portion of the developing area is brought into contact with the developing sleeve so that the former becomes stronger between the electrode and the developing sleeve and between the developing sleeve and the photoconductor. Creates an oscillating electric field,
The method of developing the toner in the developer by clouding is
JP-A-5-346736, JP-A-6-17548
No. 5 publication.

[0006]

However, in the above-mentioned control electrode method, the distance between the developer transport body and the control electrode changes due to the waviness and warpage in the longitudinal direction of the control electrode.
The developability becomes non-uniform, causing deterioration in image quality such as vertical stripes and uneven development.

If the thickness of the control electrode is increased in order to improve the linearity of the control electrode, it becomes difficult to install the control electrode in a narrow developing space.

The present invention solves the problems of the control electrode method, suppresses the undulation and warpage of the control electrode plate, has no vertical stripes, development unevenness, etc., and stably provides high-quality images with high resolution and developability. It is an object to provide a non-contact developing device to be obtained.

[0009]

The above object is to provide an insulating member which is in contact with or close to a developer layer at a development area or an upstream portion of the development area of a developer carrying body which carries a developer, facing the image forming body. In a non-contact developing device having a control electrode, which is fixed to an electrode and is provided with an electrode portion to which a voltage can be applied, the control electrode reinforces the insulating member made of ceramic that supports the electrode portion. This is achieved by a developing device having a multilayer structure including a reinforcing member.

Further, the developing device is characterized in that the whole or at least a part of the insulating member is reinforced by a reinforcing member with or without an adhesive layer.

Alternatively, the developing device is a preferable embodiment in which the reinforcing member is made of an insulating resin.

[0012]

FIG. 6 is a schematic diagram showing an example of a color image forming apparatus equipped with the developing device of the present invention as a suitable developing means.

In FIG. 6, reference numeral 1 denotes a photoconductor belt which is a belt-shaped image forming body made of a flexible belt coated or vapor-deposited with a photoconductor, and the photoconductor belt 1 includes rotating rollers 2 and 3. It is installed between and is conveyed in the clockwise direction by driving 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 a tension roller 5, so that the inner peripheral surface of the guide member 1 becomes the guide member. Rub 4

6 is a scorotron charger which is a charging means,
Reference numeral 7 is a laser writing device using a laser beam which is an image exposing means, and 8A to 8D are developing devices of the present invention which are a plurality of developing means each containing a developer of a specific color. Is disposed in a portion of the photoconductor belt 1 in contact with the guide member 4.

Each of the developing devices 8A, 8B, 8C and 8D will be described in detail later. For example, each of the developing devices 8A, 8B, 8C and 8D accommodates yellow, magenta, cyan and black developers, respectively, and has a predetermined gap from the photosensitive belt 1. Each developing sleeve 81 to be kept is provided, and has a function of making the latent image on the photosensitive belt 1 visible 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.

Reference numeral 12 is a transfer device, and 13 is a cleaning device. The blade 13a and the toner discharge roller 13b of the cleaning device 13 are kept at a position apart from the surface of the photosensitive belt 1 during image formation, and at the time of cleaning after image transfer. Only as shown in the figure, it is pressed against the surface of the photosensitive belt 1.

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

First, the formation of a multicolor image according to this embodiment is performed according to the following image forming system.

(B) Color image data is obtained by an image data input section in which an image sensor scans an original image. (B)
The image data processing unit performs arithmetic processing on this data to create image data. (C) The image data is temporarily stored in the image memory. (D) Next, this image data is taken out at the time of recording and is inputted to the color image forming apparatus of FIG. 6 which is a recording section.

That is, when image data, which is a color signal output from an image reading device separate from the color image forming device, is input to the laser writing device 7, the writing light source (not shown) in the laser writing device 7 is input. The laser beam (writing light) generated by the semiconductor laser is a rotary polygon mirror 74 rotated by a drive motor 71 through a collimator lens and a cylindrical lens (not shown).
Is rotated and scanned by the fθ lens 75 and the cylindrical lens 76, and the optical path is bent by the two mirrors 77 and 78 between the fθ lens 75 and the cylindrical lens 76, and the circumference of the photoconductor belt 1 to which a uniform charge is previously given by the charger 6 of the scorotron. Raster scanning is performed by the main scanning performed by being projected on the surface and the sub-scanning caused by the movement of the photosensitive belt 1 to form a latent image.

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 developed by the developing device 8A in which yellow (Y) toner (visual medium) is loaded in the developing means, and a toner image is formed on the belt surface. The obtained toner image passes under the blade 13a and the toner discharge roller 13b of the cleaning device 13, which is a cleaning unit, which is separated from the peripheral surface of the photosensitive belt 1 while being held on the belt surface, and the next image forming cycle is performed. to go into.

That is, the photoconductor belt 1 is recharged by the charger 6, and then the second color signal is input to the laser writing device 7, and the belt is processed in the same manner as in the case of the first color signal described above. Writing is performed on the surface to form a latent image. The latent image is 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.

A developing device 8C has a cyan (C) toner, and forms a cyan (C) toner image on the surface of the belt in the same manner as the first and second colors.

Further, 8D is a developing device having a black toner, which forms a black toner image on the surface of the belt by superimposing it by the same processing as the above-mentioned color. A DC or even AC bias voltage is applied to the developing sleeve 81 of each of the developing devices 8A, 8B, 8C and 8D.
Non-contact development is performed by a two-component developer which is a developing means, and development is performed in non-contact with the photosensitive belt 1 whose base is grounded.

The color toner image thus 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 accommodated in the paper feed cassette 14 is carried out by the rotation of the paper feed roller 16 so that one sheet of the uppermost layer 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 having received the transfer of the toner image is surely separated from the photosensitive belt 1 which suddenly changes its direction along the rotating roller 2 and goes upward, and the toner image is fused by the fixing roller 18. After being fixed, the paper is ejected onto the tray 20 via the paper ejection roller 19.

On the other hand, the photosensitive belt 1 which has finished the transfer to the transfer material is further conveyed and the blade 13a and the toner discharge roller 13b are brought into pressure contact with each other, and the residual toner is removed by the cleaning device 13 to finish the operation. After closing, the blade 13a is separated again, and a little later, the toner discharge 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, a belt-shaped image forming body is described, but an image forming apparatus having a drum-shaped image forming body can be similarly used.

The developing devices 8A to 8D have the same structure, and the developing device contains (a) a one-component developer and (b) a two-component developer, and has a magnetic pole in the developing area. One in which one of the two magnetic poles is arranged, (c) a two-component developer is accommodated, and adjacent magnetic poles in the developing sleeve are arranged so as to sandwich the developing region. The developing device (a) accommodating the one-component developer of the present invention has a reference numeral 8a.
The developing device of (b) containing the two-component developer is indicated by reference numeral 8b, and the developing device of (c) containing the two-component developer is indicated by reference numeral 8c.

In the developing device of the present invention, the control electrode commonly has an insulating member made of ceramics for supporting the electrode portion,
It is characterized by having a multi-layered structure including a reinforcing member that reinforces the insulating member.

The developing device of the present invention will be described below.

(Embodiment 1) FIGS. 1A and 1B are a schematic sectional view and a sectional view of an essential part of a developing device 8a containing a non-magnetic one-component developer.

In the figure, reference numeral 81 is a developing sleeve of a developer carrying carrier made of a non-magnetic material such as aluminum.
85A is a stirring screw that stirs the developer D to make the components uniform, and 85C is a fur brush that supplies the developer D to the developing sleeve 81 while stirring the developer D. 86A is a regulation blade that regulates the thickness of the developer layer. Since the toner is charged by rubbing the toner against the developing sleeve 81, an elastic blade type made of elastic rubber such as urethane rubber or silicon rubber is preferable.

Reference numeral 83 denotes an electrode portion 83a capable of applying a voltage on an insulating member 83b made of ceramic, which is an electrically insulating material, provided on the upstream side of the developing area A so as to abut the layer of the developer D, and further the electrode portion 83a. The control electrode is composed of a reinforcing member 83c provided to reinforce the insulating member 83b on the downstream side, and the details thereof will be described later. The electrode portion 83a is made of a conductive material such as metal and is linearly provided integrally on the tip of the insulating member 83b.

A cleaning blade 87 removes the toner passing through the developing area A from the developing sleeve 81.
Is a developer reservoir, 89 is a casing, 89a is a support portion provided in the casing 89 for supporting the fixed portion of the insulating member 83b, 90 is a holding plate for fixing the control electrode 83 to the support portion 89a, and 90s is a stop. It is a screw.

As shown in FIG. 1B, the control electrode 83 is installed inside the developing area A or upstream of the developing area A with respect to the rotation of the developing sleeve 81, and at the center of the rotation axis of the developing sleeve 81. O was in the center, closest position 81a and angle When theta ₄ (C in FIG. 1 is closest position 81a and the developing sleeve between the tip portion of the control electrode 83 of the photosensitive belt 1 of the developing sleeve 81 It is a center line connecting the rotation axis center O of 81, and the value of the angle is preferably -5 ° ≦ θ ₄ ≦ 15 °, where the upstream side from the closest position 81a is positive and the downstream side is negative. .

When θ ₄ is smaller than −5 °, the control electrode 83
Covers the development area A too much, and the developability is lowered, and θ ₄ is 15 °.
When it is larger, the control electrode 83 is too far from the developing area A, the generated toner cloud does not sufficiently move to the developing area A, and the developability is deteriorated.

This developing device 8a using the one-component developer D
Then, it is preferable that the surface of the developing sleeve 81 is coated with a material similar to the carrier coating material described later, depending on the chargeability of the toner.

Example 1 above and Examples 2 and 3 described later
The control electrode 83 is placed on the developing sleeve 81 by the developer D.
11 is conveyed, the developer D enters between the insulating member 83b and the developing sleeve 81, so that the developer D bends slightly and the insulating member 83b faces the developing sleeve 81 with a slight gap as shown in FIG. Or, the developing sleeve 81 faces the developing sleeve 81 in a state where there is almost no gap, that is, a state where the developing sleeve 81 is in contact with / close to the developing sleeve 81. Insulating member 8 of control electrode 83
The portion of the developing sleeve 81 where 3b is in contact with / proximity to the developing sleeve 81 is referred to as the closest contact point and is represented by 81b.

The developing sleeve 81 has a DC power source E ₁
AC bias voltage obtained by superposing an AC component on a DC component through the protective resistor R ₁ by the AC power source E ₂ is applied with. Further, the electrode portions 83a bias voltage only a DC component through the protective resistance R ₂ from the DC power source E ₃ is applied. It is preferable to apply a DC voltage having the same polarity as the toner in the developer to the electrode portion 83a from the viewpoint of preventing toner adhesion.

By applying the AC bias voltage as described above, an alternating electric field (which will be referred to as a second oscillating electric field) formed between the photosensitive belt 1 and the developing sleeve 81 and the electrode portion 83a of the control electrode 83 are formed. A first oscillating electric field is generated between the developing sleeve 81 and the developing sleeve 81.

In this case, the electrode portion 83a is the photosensitive belt 1
Since it is provided closer to the developing sleeve 81, the strength is higher than the strength of the first oscillating electric field.

By the first oscillating electric field, the toner particles of the developer D reaching the vicinity of the electrode portion 83a are vibrated in a direction perpendicular to the lines of electric force, so that the toner particles are separated and fly from the carrier to form a cloud haze shape. The toner cloud of can be sufficiently generated. This toner cloud is assisted in the flight toward the latent image on the photosensitive belt 1 by the second oscillating electric field, and uniform development is performed.

At this time, since the AC bias voltage is applied only to the developing sleeve 81, the first oscillating electric field and the second oscillating electric field have the same phase, and the toner particles are transferred from the first oscillating electric field to the second oscillating electric field. Smooth transition to the oscillating electric field.

The waveform of the above AC component is not limited to a sine wave,
A rectangular wave or a triangular wave may be used. Although the frequency is also related, the higher the voltage value is, the more the magnetic brush of the developer D is vibrated, and the separation and flight of the toner particles from the carrier particles are facilitated. Dielectric breakdown easily occurs. The generation of fog is prevented by a DC component, and the insulation breakdown is caused by coating the surface of the developing sleeve 81 with a resin, an oxide film, or the like so as to be insulating or semi-insulating, or the carrier particles of the developer D having an insulating property as described later. It can be prevented by using carrier particles.

Here, when the non-magnetic one-component developer is used, the zero peak voltage (V _OP ) of the AC component of the bias voltage applied to the developing sleeve 81 is the same as that of the photosensitive belt 1 and the developing sleeve 81. The closest distance is Dsd (mm), and the height of the electrode portion 83a from the developing sleeve 81 is h.
₁ (mm), the toner volume average particle diameter in the developer is D ₅₀ (μ
m), when the average charge amount of the toner is Q ₁ (μC / g), 300 · Q ₁ · D ₅₀ · Dsd> V _OP > 5 · Q ₁ · D ₅₀ ·
h ₁ Especially, 200 ・ Q ₁・ D ₅₀・ Dsd> V _OP > 10 ・
It is preferably in the range of Q ₁ · D ₅₀ · h ₁ .

Here, the average charge amount Q ₁ of the non-magnetic one-component toner is a conductive plate of 2 cm × 5 cm, the regulating blade 86A described above, and a developing sleeve 81 having a diameter of 20 mm.
To the developing device 8a having the closest distance of 0.7 mm, the charged one-component developer is supplied to the developing sleeve 81 and the developing sleeve 81 is rotated at 200 rpm, and the superimposed voltage of DC and AC is applied to the developing sleeve 81 ( For example, DC; 100
0 V, AC; 750 V _OP , AC frequency 8 kHz) is applied to develop the toner in the developer on the conductive plate,
This is a value obtained by connecting a conductive plate on which this toner has been developed to a Faraday gauge, blowing the toner off with nitrogen gas, and measuring the charge amount and the weight of the toner blown off at this time.

Further, h ₁ is preferably h ₁ = (0.2 to 0.6) × Dsd from the viewpoints of preventing discharge to the developing sleeve 81 and the photosensitive belt 1 and ensuring developability.

The frequency of the AC component of the bias voltage applied to the developing sleeve 81 is preferably 100 Hz to 20 kHz, and particularly preferably 1 kHz to 10 kHz.

In order to prevent the generation of unnecessary toner cloud in the upstream portion of the transport and to obtain a stable transport amount, the entire electrode portion 83a is provided with an insulating member 83b and a developing sleeve 81 as shown in FIG. 1B. Is formed so as to be arranged only on the side of the closest position 81a of the developing sleeve 81 to the photosensitive belt 1 with respect to the closest contact 81a. Although the circumferential length of the electrode portion 83a depends on the diameter of the developing sleeve 81 and the conveying speed,
05-5 mm, especially 0.1-1 mm is preferable. 0.0
If it is 5 mm or less, a sufficient toner cloud cannot be generated, and if it is 5 mm or more, the toner is charged by vibration and becomes excessively charged, so that the developing property is deteriorated.

As the developer used in the developing device 8a, styrene resin, vinyl resin, ethyl resin,
Rosin-modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin and styrene-
A binder resin such as a copolymer resin such as an acrylic resin or a mixed resin is mixed with a coloring component such as a color pigment, and if necessary, a charge control agent, a release agent such as a wax, etc. It can be obtained by a toner manufacturing method such as a particle method, a suspension polymerization method, or an emulsion polymerization method.

When the average particle size of the developer particles becomes small, the charge amount qualitatively decreases in proportion to the square of the particle size, and the adhesive force such as the Van der Waals force becomes relatively large. It becomes difficult to separate from the developing sleeve 81.

The volume average particle diameter D ₅₀ is used to represent the average particle diameter of the toner. When D ₅₀ is 8 μm or less,
The above-mentioned problems will be noticeable. This point is solved in this developing device by developing under a double oscillating electric field.

When D ₅₀ is 8 μm or more, the resolution is insufficient, and the image roughness becomes noticeable. When a finely divided toner having D ₅₀ = 8 μm or less is used, the resolving power is remarkably improved, and a clear high-quality image in which the tone difference is faithfully reproduced is provided. When the volume average particle diameter D _{50 of the} toner is 4 μm or less, the cohesive force is large and frictional electrification is likely to occur.

For the above reasons, the volume average particle diameter D _{50 of the} toner is
Is preferably 4 to 8 μm.

Here, the volume average particle diameter D used for the average particle diameter
₅₀ is Coulter Counter TA-II type (Aperture 1
00 μm, manufactured by Coulter Corporation).

In the case of the one-component developer D, a fluidizing agent such as colloidal silica can be added to the toner and used as it is as the developer D.

The average charge amount Q ₁ of the one-component developer is ₁ to 30 μC / g, particularly ₁ to 20 μC / g in absolute value.
It is preferable from the viewpoint of securing developability and preventing fogging and scattering.

Here, the average charge amount Q ₁ of the non-magnetic one-component toner is a conductive plate of 2 cm × 5 cm, equipped with the regulating blade 86A described above, and the developing sleeve 8 having a diameter of 20 mm.
The closest distance to the developing device (8a) having 1 is 0.7 mm.
And charging the one-component developer to the developing sleeve 81 and rotating the developing sleeve 81 at 200 rpm, the developing sleeve 81 has a superimposed voltage of DC and AC (for example, DC; 1000).
V, AC; 750V _OP , AC frequency 8kHz) is applied to develop the toner in the developer on the conductive plate, and the conductive plate on which the toner is developed is connected to a Faraday gauge to make the toner nitrogen. It is a value obtained by blowing off with a gas and measuring the charge amount and weight of the toner blown off at this time.

(Embodiment 2) FIG. 2 is a schematic cross-sectional view showing another example of the developing device of the present invention (one in which a two-component developer D containing a non-magnetic toner and a magnetic carrier is contained and magnetic pole development is carried out). It is a figure.

2 (a) and 2 (b) are a schematic sectional view and an enlarged sectional view of an essential part of an example of the device of the present invention.
The same parts as those in FIG.

In the figure, reference numeral 82 is a magnet roll having a plurality of N and S magnetic poles fixed in the developing sleeve 81 in the circumferential direction, and one magnetic pole 82a of the magnet roll 82 is the developing sleeve 81 and the photosensitive belt 1. Development area A closest to
The main magnetic pole is arranged in the inside. The developing sleeve 81 and the magnet roll 82 exert a developer carrying function. Each magnetic pole including the main magnetic pole 82a of the magnet roll 82 is magnetized to have a magnetic flux density of 500 to 1,500 gauss, and the magnetic force thereof causes the developer D on the developing sleeve 81.
Forming a layer of magnetic brushes. The magnetic brush moves in the same direction by the rotation of the developing sleeve 81 and is conveyed to the developing area A. The magnetic brush formed on the developing sleeve 81 does not come into contact with the surface of the photoconductor belt 1 and maintains a gap, so that the gap between the developing sleeve 81 and the regulating blade 86 and the gap Dsd between the developing sleeve 81 and the photoconductor belt 1 are maintained.
Is adjusted.

Reference numerals 85A and 85B are stirring screws for stirring the developer D to make the components uniform, and 86 is a developer regulating means made of a non-magnetic material or a magnetic material provided to regulate the height and amount of the magnetic brush. It is a regulation blade.

As shown in FIG. 2B, the control electrode 83 is installed in the developing area A or upstream of the developing area A with respect to the rotation of the developing sleeve 81, and the rotary shaft O of the developing sleeve 81 is rotated. The angle between the closest position 81a of the developing sleeve 81 to the photoreceptor belt 1 and the main magnetic pole 82a is θ ₁ , and the angle between the closest position 81a and the tip of the control electrode 83 is the same. Is θ ₄ (C in FIG. 2 is a center line connecting the closest position 81a and the center O of the rotation axis of the developing sleeve 81, and the value of the angle is positive on the upstream side of the closest position 81a and negative on the downstream side. ), -10 ° ≤ θ ₁ ≤ 10 ° (θ ₁ -5 °) ≤ θ ₄ ≤ (θ ₁ + 5 °) so that the spike of the developer D in the developing area A is It is preferable in order to improve the development efficiency and maintain high development efficiency and prevent toner scattering.

If θ ₁ is less than −10 ° or exceeds 10 °, the spikes of the developer D in the developing area A are poor and the developability is deteriorated.

When θ ₄ is smaller than (θ ₁ -5 °), the developer D
The control electrode 83 covers too much the spiked portion of the developer, and the developing property is lowered. If θ ₄ is larger than (θ ₁ + 5 °), the spike of the developer D becomes too large and the photosensitive belt 1 is exposed to light. The developer D comes into contact with the body, and blemishes and carrier adhesion occur, causing image distortion.

As described above, by disposing the main magnetic pole 82a in the developing area A and disposing the control electrode 83 in the vicinity thereof so as to press the developer D layer, the spikes of the developer D are moderately formed. It is possible to improve the developability by applying a low developing bias voltage, which was not possible with the conventional technique, without causing carrier adhesion.

In the above embodiment, the developing sleeve 81
An AC bias voltage obtained by superimposing an AC component on a DC component is applied to a DC power source E ₁ and an AC power source E ₂ via a protection resistor R ₁ . Further, the electrode portions 83a bias voltage only a DC component through the protective resistance R ₂ from the DC power source E ₃ is applied. It is preferable to apply a DC voltage having the same polarity as the toner in the developer to the electrode portion 83a from the viewpoint of preventing toner adhesion.

As described above, also in the developing device 8b, an alternating electric field (which will be referred to as a second oscillating electric field) formed between the photosensitive belt 1 and the developing sleeve 81 by the application of the AC bias voltage is generated. A first oscillating electric field is generated between the electrode portion 83a of the control electrode 83 and the developing sleeve 81.

In this case, the electrode portion 83a is the photosensitive belt 1
Since it is provided closer to the developing sleeve 81, the strength of the first oscillating electric field becomes larger than the strength of the second oscillating electric field.

By the first oscillating electric field, the toner particles of the developer D reaching the vicinity of the electrode portion 83a are vibrated in the direction perpendicular to the lines of electric force, so that the toner particles are separated and fly from the carrier to form a cloud haze shape. The toner cloud of can be sufficiently generated. This toner cloud is assisted by the flight toward the latent image on the photosensitive belt 1 by the second oscillating electric field, and uniform development is performed.

At this time, since the AC bias voltage is applied only to the developing sleeve 81, the first oscillating electric field and the second oscillating electric field have the same phase, and the toner particles are transferred from the first oscillating electric field to the second oscillating electric field. Smooth transition to the oscillating electric field.

The waveform of the above AC component is not limited to a sine wave,
A rectangular wave or a triangular wave may be used. Although the frequency is also related, the higher the voltage value is, the more the magnetic brush of the developer D is vibrated, and the separation and flight of the toner particles from the carrier particles are facilitated. Dielectric breakdown easily occurs. The generation of fog is prevented by a DC component, and the insulation breakdown is caused by coating the surface of the developing sleeve 81 with a resin, an oxide film, or the like so as to be insulating or semi-insulating, or the carrier particles of the developer D having an insulating property as described later. It can be prevented by using carrier particles.

In the color image forming apparatus using the second embodiment, reversal development is performed using an OPC photosensitive member that is negatively charged as the photosensitive member of the photosensitive belt 1, and the photosensitive member is charged to -850V, for example. Assuming that the potential of the image area maximum density portion is −50 V, an AC bias voltage obtained by superimposing an AC voltage on a DC voltage of −750 V is applied to the electrode portion 83 a and to the developing sleeve 81 is preferably applied to the developing sleeve 81. Here, the zero peak voltage (V _{0 -P} ) of the AC component applied to the developing sleeve 81 is the closest distance Dsd (mm) between the photosensitive belt 1 and the developing sleeve 81 shown in FIG. The height h ₁ (mm) from the developing sleeve 81 of
When the volume average particle diameter D ₅₀ (μm) of the toner in the developer and the average charge amount of the toner are Q ₂ (μC / g), 20 · Q ₂ · D ₅₀ · Dsd> V _0-P > 3 · Q ₂ · D ₅₀ · h ₁ Especially 10 · Q ₂ · D ₅₀ · Dsd> V _0-P > 5 · Q ₂
It is preferably in the range of D ₅₀ · h ₁ .

Here, the average charge amount Q ₂ of the toner of the two-component developer is a value measured by the same method as the average charge amount Q ₁ of the one-component developer.

(Embodiment 3) FIG. 3 shows still another example of the developing device of the present invention (one in which a two-component developer is accommodated to perform development between magnetic poles), and FIG. 3 (a) is a schematic sectional view. FIG. 3B is an enlarged sectional view of a main part.

In this developing device 8c, two adjacent magnetic poles 82b of a magnet roll 82 fixed in the developing sleeve 81 are provided.
1 and 82c are located on both sides of the developing area A, which is the closest position between the developing sleeve 81 and the photosensitive belt 1.
The same parts as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The angle between the closest position 81a and the downstream magnetic pole 82b about the rotation axis O of the developing sleeve 81 is θ ₂ , and the angle between the closest position 81a and the upstream magnetic pole 82c is the same. Is θ ₃ and the angle with the downstream end of the control electrode 83 is θ ₄ (however, the value of the angle is positive on the upstream side of the closest position 81a and negative on the downstream side). It is preferable that the following formula is satisfied: θ ≦ θ ₂ ≦ −5 ° 5 ° ≦ θ ₃ ≦ 45 ° θ ₂ + 5 ° ≦ θ ₄ ≦ θ ₃ −5 °

With respect to θ ₂ and θ ₃ , within the angle range of the above conditions, the spike of the developer is relatively low and the developer is densely conveyed to the developing area A, so that the carrier is excellent in graininess without sticking or sweeping. You can get the image.

Outside the above range of conditions, these effects are not sufficiently exhibited.

When θ ₄ is smaller than θ ₃ + 5 °, the developing area A is covered with the control electrode 83 so much that the developing property is deteriorated.
When θ ₄ is larger than θ ₂ −5 °, the spikes become too large, and the photoconductor comes into contact with the surface of the photoconductor, causing image distortion such as sweeping and carrier adhesion.

In this developing device 8c, the description of the developing device 8b is applied except for the above description, and therefore the description thereof is omitted.

Next, the control electrode 83 used in the developing devices 8a, 8b and 8c of the present invention will be described.

As shown in FIG. 4A, the control electrode 83 includes an insulating member 83b made of ceramic that supports the electrode portion 83a and a reinforcing member 83c that reinforces the insulating member 83b.
Of at least two layers.

The insulating member 83b is thin so that it can be installed in a narrow space of the developing area A, and in order to maintain the linearity of the entire control electrode 83, the insulating member 83b is preferably made of the following ceramics.

(Ceramic) alumina (Al ₂ O ₃ ) system,
Single crystal sapphire (Al ₂ O ₃ ), forsterite (2
MgO / SiO ₂ system, steatite (MgO / Si)
O ₂ ) -based, zircon (ZrO ₂ · SiO ₂ ) -based, cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ) -based, titania-based, silicon carbide (SiC) -based, silicon nitride (Si ₃ N ₄ ).
Type, zirconia (ZrO ₂ ) type, cermet type.

The ceramic may contain 5 to 20 wt% of resin for imparting elasticity. Further, in order to reduce the surface roughness of the surface on the developing sleeve 81 side, the surface of the insulating member 83b is preferably polished.

Since only ceramic is liable to crack due to shock, vibration, concentrated stress at the mounting portion, etc., a reinforcing member 83c for reinforcing it is attached to the insulating member 83b. The reinforcing member 83c may reinforce part or all of the insulating member 83b as shown in FIGS. 4 (a) and 4 (b).
Insulating member 83b as shown in (a), (c) or (d)
It may be attached to one side or both sides. Further reinforcing member 83
The mounting method of c may be such that it is adhered via an adhesive layer 83e made of an adhesive as shown in FIG. 4 (e), or may be performed by means such as pressure welding or heat fusion as shown in FIG. 4 (f).

(Material of Reinforcing Member) Examples of the reinforcing member 83c include polyester, polyimide, glass epoxy, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-6-fluoropropylene copolymer, polytetrafluoride. Insulating resins such as ethylene, polyamide-imide, polysulfone, triazine resin, polyethylene terephthalate, polyurethane, etc., or composite materials reinforced with glass fiber etc., as well as paper, paper phenol, varnish, silicone rubber, etc. may be used. it can.

It is preferable that the reinforcing member 83c is made of an insulating resin in terms of strength, weight, thickness, impact resistance, and easy adhesion.

When a resin is used as the reinforcing member 83c, as shown in FIG. 4 (g), the resin is dissolved in a solvent such as alcohol or acetone, or a halogen-based or hydrocarbon-based solvent, and the resin is dissolved on the insulating member 83b. A method may be used in which the resin layer is formed by drying the solvent after applying it to the.

(Method for forming electrode portion 83a) Electrolytic copper foil, annealed electrolytic copper foil, beryllium copper foil, etc. are attached to the above insulating member 83b with an adhesive, and a photoetching method using a conventionally known photopolymer, a screen A necessary electrode portion 83a is formed on the insulating member 83b by an etching resist forming method by printing. In addition, a method of printing a conductive ink corresponding to the electrode portion 83a using a relief printing plate, a stencil printing plate, an intaglio printing plate, or a metal deposition method can be used. Further, in order to prevent unnecessary discharge from the electrode portion 83a, it is preferable to cover the electrode portion 83a with a reinforcing member 83c that also serves as an insulating layer (FIGS. 4B and 4D). A method of applying an insulating ink can also be used.

FIG. 5 is a sectional view showing various forms of the control electrode 83. The electrode portion 83a and the reinforcing member 83c are shown in FIG.
As shown in (b), (c), (f), and (m), the insulating member 83
It may be provided not only on the upper surface of b but on the lower surface. In addition, FIG. 5 (d), (e), (f), (h), (k), (l),
As shown in (m), the electrode portion 83a may be provided so that its tip and the tip of the insulating member 83b are aligned with each other.
Furthermore, as shown in FIGS.
The c may be provided on both surfaces of the insulating member 83b.

FIG. 10 is a diagram showing the relationship between the width of the electrode portion 83a and the width of the developing area A. In FIG. 10, W ₃ is the width of the electrode portion 83a (the axial length of the developing sleeve 81), W 3
Assuming that ₄ is the width of the developing area A on the developing sleeve 81a (width of the developer D layer), W ₃ > W ₄ , and the developing area A is also applied to the terminal portion 83a for applying a DC voltage to the electrode portion 83a. It is provided outside the width W _{4 of the} above to prevent generation of unnecessary toner cloud.

Further, the surface roughness Rz of the developing sleeve 81
_When the roughness Rz ₂ (μm) of ₁ (μm) and the surface of the insulating member 83b facing the developing sleeve 81 is Rz ₂ ≧ Rz ₁ , the developer carried on the developing sleeve 81 is carried to the insulating member 83b. And the amount of toner conveyed to the developing area A is reduced, and the image density is reduced. Rz ₁ is 0.2 μm
The range of 20 μm and Rz ₂ in the range of 0.02 μm to 5.0 μm are preferable for obtaining good transportability and high density images without image distortion. The surface roughness Rz
Conforms to JIS B 0601 and is made by Mitutoyo Surft
The measurement was performed using est-402 with a reference length of 25 mm.

In order to prevent an unnecessary toner cloud from being generated in the upstream portion of the transport and to obtain a stable transport amount, the entire electrode portion 83a has an insulating member 83b as shown in FIG. 1 to FIG. And the developing sleeve 81 is formed so as to be disposed only between the closest position 81a of the developing sleeve 81 to the photosensitive belt 1 rather than the closest contact 81b of the developing sleeve 81.

The circumferential length of the electrode portion 83a depends on the diameter of the developing sleeve 81 and the conveying speed, but is 0.05 to 5 mm.
In particular, 0.1 to 1 mm is preferable. If it is less than 0.05 mm, a sufficient toner cloud cannot be generated,
If it is more than m, the toner is charged by vibration and becomes excessively charged, so that the developing property is deteriorated.

The thickness t of the control electrode 83 (see FIG. 4)
When the developing distance, which is the closest distance between the photosensitive belt 1 and the developing sleeve 81, is Dsd (mm), is preferably (1/10) Dsd <t <(2/3) Dsd.

At t> (2/3) Dsd, the electrode portion 83a
Since the dielectric, which is a photoconductor, approaches the top of the
When a high bias voltage is applied to the electrode portion 83a due to an increase in the electric field strength on a, the latent image may be disturbed or another color toner on the photoconductor belt 1 which is an image forming body may be peeled off at the time of forming a multicolor image. There is.

When t <(1/10) Dsd, the electrode portion 83
Since a is separated from the developing sleeve 81, the electric field is weakened and a sufficient toner cloud is not formed. In addition, the control electrode 8
The rigidity of 3 becomes low and it becomes easy to crack.

The thickness of the control electrode 83 is measured by a micrometer (M320-25A, manufactured by Mitutoyo Corporation) at 20 points in the direction of the rotation axis of the developing sleeve 81 of the control electrode 83, and the average of the measured values is taken as the thickness t of the control electrode 83. And

FIG. 9 is a perspective view showing another example of a method of fixing the control electrode 83.

In the figure, 89a is a support portion of the casing 89, 90a is a holding spring plate made of a phosphor bronze plate spring,
90b is a holding plate made of stainless steel, and 90s is a set screw. The set screw 90s uses the screw holes and the set holes provided at, for example, six positions in the longitudinal direction of the support portion 89a, the presser spring plate 90a, and the presser plate 90b at equal intervals, and the support portion 89a has a presser spring. Plate 90a, presser plate 90b
Is pressed, so that the control electrode 83 is fixed to the support portion 89a.

The developing devices 8b and 8c using the two-component developer of the developing device of the present invention having the control electrode 83 configured as described above are in non-contact with the photosensitive belt 1 which is an image forming body. The toner particles are generated by the first and second oscillating electric fields to improve the separation and flight to the photoconductor belt 1 and the selective adsorption to the electrostatic image to improve the photoconductor belt 1 of carrier particles. It is possible to prevent the adherence of the toner particles, and thus it is possible to use fine particles as toner particles or carrier particles, so that high quality images can be developed.
In the two-component developing method, it is preferable to use the developer D composed of the following carrier particles and toner particles.

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,
It suffices to reduce the average particle size of the magnetic carrier particles. As a result of experiments, it has been found that the above problems do not occur when the volume average particle size dc is 10 to 60 μm, preferably 20 to 50 μm.

When the dc is 10 μm or less, it is difficult to magnetize the carrier sufficiently, and the carrier tends to adhere to the surface of the photosensitive belt 1 together with the toner particles, or easily scatter.

If dc is 60 μm or more, the specific surface area of the carrier becomes small, and the toner cannot be sufficiently charged. Further, since the covering ratio is high, toner scattering is also likely to occur.

The volume average particle diameter dc is measured by a laser diffraction type particle size distribution measuring apparatus "HEROS" (S
YMPATEC). First, 10 mg of magnetic particles were added together with a surfactant to 50 m of water using a wet disperser.
g and then an ultrasonic homogenizer (output 15
0W), and the value was measured after performing a pretreatment of dispersing for 1 to 10 minutes while taking care not to cause re-aggregation due to heat generation.

The strength of carrier magnetization (σ1000) is
5 to 60 emu / g, preferably 10 to 40 emu / g
It is. Although this strength depends on the magnetic flux density on the developing sleeve 81, the general magnetic flux density of the developing sleeve 81 is 500.
In the range of up to 1,200 Gauss, the magnetic binding force does not work at less than 5 emu / g, which causes carrier scattering. If it exceeds 60 emu / g, the spikes of the carrier become too high, and it becomes difficult to maintain the non-contact state with the photosensitive belt 1.

The carrier magnetization intensity was measured by filling carrier particles while tapping them into a 0.25 cm × 3 cm ² sample cell, attaching the sample to a pickup coil and setting it in a magnetizer, and automatically measuring the DC magnetization characteristics. Recording device "TY
This is performed by causing the XY recorder to draw a hysteresis curve using "PE3257" (manufactured by Yokogawa Hokushin Electric Co., Ltd.).

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 tetroxide, γ-oxidation, which is the same as in a conventional magnetic carrier as a magnetic body. Spherical particles of ferromagnetic material such as ferric iron, chromium dioxide, manganese oxide, ferrite, manganese-copper alloy, or the surface of these spherical magnetic particles are styrene resin, vinyl resin, ethyl resin , Rosin modified resin, acrylic resin,
It can be obtained by covering spherically with a homopolymer or a copolymer of polyamide resin, epoxy resin, polyester resin, silicon resin, fluorine resin and the like.

Further, a so-called resin dispersion type carrier in which magnetic fine particles are dispersed and contained in these resins can also be used. In this case, since the shape of the carrier becomes irregular, the specific surface area increases, and a sufficient amount of toner required for development can be obtained at a lower surface coverage.
Toner scattering does not occur easily.

Next, the toner particles will be described. Generally, when the average particle size of the toner particles is small, the charge amount qualitatively decreases in proportion to the square of the particle size, and the adhesive force such as the Van der Waals force becomes relatively large. It becomes difficult to separate from the particles. In the conventional magnetic brush developing method, the average particle size is 10 μm.
When it is less than m, such a problem becomes remarkable. In the developing device of the present invention, this problem is solved by performing the development with the magnetic brush under a double oscillating electric field.

When the volume average particle diameter D ₅₀ (μm) of the toner becomes large, the roughness of the image becomes noticeable as already mentioned. If D ₅₀ is used the toner following micronized 10 [mu] m, the resolution is remarkably improved, so give a clear high-quality images shading difference also faithfully reproduced. D ₅₀ is 20μm or more, results in deterioration in image quality, for attachment to the carrier by friction becomes 1μm or less (toner spent) and carrier coating ratio increases, poor charging, scattering and the like easily occurs.

From the above reason, the volume average particle diameter D _{50 of the} toner is
Is 1 to 20 μm, preferably 4 μm ≦ D ₅₀ ≦ 8 μm.

When D ₅₀ > 8 μm, the particle size is large and the resolving power is insufficient, and when D ₅₀ <4 μm, the cohesive force is large, and triboelectrification failure tends to occur.

Here, the volume average particle diameter D used for the average particle diameter
₅₀ is Coulter Counter TA-II type (Aperture 1
00 μm, manufactured by Coulter Corporation).

Since the toner particles follow the electric field, the absolute value of the charge amount of the toner particles in the two-component developer is preferably larger than 1 to 3 μC / g, preferably 3 to 50.
From the viewpoint of securing developability and preventing fogging and scattering, it is preferable that the content is μC / g. In particular, when the particle size is small, a high charge amount is required.

The average charge amount Q ₂ of the toner in the two-component developer is measured in the same manner as the average charge amount Q ₁ of the toner in the one-component developer.

Examples of the binder resin for such toner include styrene resin, vinyl resin, ethyl resin, rosin-modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, and these styrene-acrylic resins. Copolymer resins such as and the like or mixed resins and the like are preferable. Coloring components such as color pigments, a charge control agent, a release agent such as wax, etc. are added to these resins, if necessary, and toners such as conventionally known pulverization granulation method, suspension polymerization method and emulsion polymerization method are used. Obtained by the manufacturing method. That is, it is possible to use a toner in which spherical or amorphous non-magnetic or magnetic toner particles in the conventional toner are selected by the average particle size selection means.

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 material are used, and the coloring component such as carbon and the electrification as required. A volume average particle diameter of 20 μm or less which can be produced by the same method as a conventionally known toner particle manufacturing method by adding a control agent or the like,
Particularly preferably, it is composed of particles of 3 to 10 μm.

Developing device 8 using the two-component developer of the present invention
For b and c, 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, but as a carrier, a general coating carrier ( Density 5-8g / c
m ³ ) is used, the toner concentration in the developer is 2 to 3
0% by weight, preferably 5 to 20% by weight.

When the amount is less than 2% by weight, the number of toners required for development cannot be secured, and the coverage is lowered, resulting in excessive charging and deterioration of developability.

When it is more than 30% by weight, the coverage becomes large and charging failure and toner scattering easily occur.

However, the toner concentration in the developer when the resin dispersion type carrier having a relatively low density (2 to 4 g / cm ³ ) as described above is used as the carrier in the developer,
Slightly higher than when using a general resin-coated carrier,
The content is preferably 5 to 40% by weight, more preferably 10 to 30% by weight.

[Tests of Examples of the Present Invention and Comparative Examples] Example 1 and Comparative Example 1 use a one-component developer.
The developing device 8a shown in FIG.
The photoconductor has a peripheral speed of 180 mm / sec. , The maximum potential of the electrostatic latent image formed on the photoconductor belt 1 is -850V.
(Non-image part potential), the minimum potential is -50 V (image part potential), the outer diameter of the developing sleeve 81 is 20 mm, the rotation speed of the developing sleeve 81 is 172 rpm, and the surface roughness R _z1 of the developing sleeve 81 is 2.5 μm. The process conditions are as described in Table 1 below.

In Examples 2 and 3 and Comparative Examples 2 and 3, the two-component developer is used, and the developing device 8b shown in FIGS.
8c, the photoreceptor belt 1 is an OPC photoreceptor, and the peripheral speed is 180 mm / sec. The maximum potential of the electrostatic latent image formed on the photosensitive belt 1 is −850 V (non-image portion potential), the minimum potential is −50 V (image portion potential), the outer diameter of the developing sleeve 81 is 20 mm, and the developing sleeve 81 is Number of revolutions 39
0 rpm, surface roughness of developing sleeve 81 R _z1 = 1.8 μ
m, the magnetic pole strength of the magnet roller 82 is 700 gauss, and other process conditions are as described in Table 1 below.

The control electrode 83 of Examples 1 to 3 has the structure and dimensions shown in FIG. 7, uses an alumina-based ceramic plate as the insulating member 83b, and as shown in FIG.
3a was formed by a laminate etching method using a copper foil having a circumferential width of 0.5 mm and a thickness of 0.02 mm.
Surface roughness of the insulating member 83b on the developer transporter side R _Z2 = 0.
It is 8 μm and the height h ₁ of the electrode portion 83a is 0.25 mm.

The control electrode 83 of Comparative Examples 1 to 3 has the structure and dimensions shown in FIG. 8, a glass epoxy plate is used as the insulating member 83b, and the electrode portion 83a has a circumferential width of 0.
It was formed by a laminate etching method using a copper foil having a thickness of 5 mm and a thickness of 0.02 mm. The surface roughness R _{Z2 of the} insulating member 83b on the developer carrier side is 0.9 μm, and the height h ₁ of the electrode portion 83a is h ₁ = 0.25 mm.

Elastic blades made of urethane rubber were used as the developer regulating blades 86 and 86A in each of the examples and comparative examples. And the following toner is used.

(One-Component Developer) (Example 1, Comparative Example 1)
For) styrene-acrylic resin 100 parts by weight, color pigment 10
1 part by weight and 2 parts by weight of nigrosine were melted and kneaded, and then pulverized and classified to obtain yellow, magenta, cyan, and black toners having a volume average particle diameter of 5.5 μm. Each of the toners, to which 2 parts by weight of colloidal silica was added as a fluidizing agent, was used as a developer.

The charge amount Q ₁ is Y; -3.2 μC / g,
M; -2.7 [mu] C / g, C; -3.2 [mu] C / g, K;-
It is 3.4 μC / g.

(Two-component developer) (for Examples 3 and 4 and Comparative Examples 3 and 4) Carrier: spherical ferrite particles having a magnetization intensity of 25 emu / g and a surface of a methyl methacrylate / styrene copolymer resin. Spherical carrier obtained by coating. The volume average particle size is 45 μm.

Toner: 100 parts by weight of styrene-acrylic resin, 10 parts by weight of color pigment, and 1 part by weight of nigrosine are melted and kneaded, and then pulverized and classified to have a volume average particle diameter of 5.5.
μm yellow, magenta, cyan, and black toners were obtained. Each toner was actually used by adding 2 parts by weight of colloidal silica as a fluidizing agent.

Preparation of Developer These toners and carriers are used at a toner concentration of 7% by weight.
To prepare a developer.

The charge amount is Y; -20.5 μC / g, M;
-21.3 μC / g, C; -20.7 μC / g, K;-
It is 22.0 μC / g.

[0140]

[Table 1]

Using these development processes, carriers and toners, full color image recording of 50,000 sheets was performed under the conditions shown in Table 1. In Examples 1 to 3 of the present invention, from the beginning to the end, No vertical stripes, no image unevenness, image density,
An image with high resolution could be stably obtained.

On the other hand, in Comparative Examples 1 to 3, as shown in Table 1, when several thousand copies were made, vertical stripes and image unevenness due to undulations and warpage of the control electrode 83 were generated, and stable image formation was achieved. Could not be done.

[0143]

According to the present invention, since the control electrode has a multi-layer structure in which a reinforcing member is mounted, the control electrode is completely prevented from being cracked, undulated, or warped due to impact, vibration, concentrated stress generated in the mounting portion, or the like. Therefore, the electrode portion of the control electrode can be set in the developing gap with high dimensional accuracy. Therefore, it is possible to provide a non-contact developing device capable of stably obtaining a high-quality image having high resolution and developability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a developing device of the present invention and an enlarged sectional view of a main part.

FIG. 2 is a schematic sectional view showing another example of the developing device of the present invention and an enlarged sectional view of a main part.

FIG. 3 is a schematic sectional view showing still another example of the developing device of the present invention and an enlarged sectional view of an essential part.

FIG. 4 is a cross-sectional view showing a plurality of examples of control electrodes of the developing device of the present invention.

FIG. 5 is a cross-sectional view showing various forms of control electrodes of the developing device of the present invention.

FIG. 6 is a schematic configuration diagram showing an example of a color image forming apparatus including a developing device of the present invention.

FIG. 7 is a cross-sectional view showing a configuration and dimensions of a control electrode of an example used in a comparative test.

FIG. 8 is a cross-sectional view showing a configuration and dimensions of a control electrode of a comparative example used in a comparative test.

FIG. 9 is a perspective view showing another example of the method of attaching the control electrode of the present invention.

FIG. 10 is a plan view showing the relationship between the control electrode and the developing sleeve width of the present invention.

FIG. 11 is a cross-sectional view showing an installed state of the control electrode of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor belt (image forming body) 8A to 8D, 8a, 8b, 8c Developing device 81 Developing sleeve (developer carrier) 82 Magnet roll 82a Main magnetic pole 83 Control electrode 83a Electrode portion 83b Insulating member 83c Reinforcing member 86, 86A Control blade A Development area D Developer E ₁ , E ₃ DC power supply E ₂ AC power supply

Claims (5)

[Claims] 1. A voltage-applying device fixed to an insulating member in contact with or close to a developer layer is provided at a developing area or an upstream area of the developing area of a developer carrying body, which is opposed to an image forming body and carries a developer. In a non-contact developing device having a control electrode provided with various electrode portions, the control electrode has a multilayer structure including an insulating member made of ceramic that supports the electrode portion and a reinforcing member that reinforces the insulating member. Is a developing device. 2. The whole of the insulating member, or at least one
The developing device according to claim 1, wherein the portion is reinforced by the reinforcing member. 3. The insulating member is reinforced by the reinforcing member via an adhesive layer.
Or the developing device according to 2. 4. The developing device according to claim 1, wherein the insulating member is directly reinforced by the reinforcing member without an adhesive layer. 5. The developing device according to claim 1, wherein the reinforcing member is made of an insulating resin.