JPH0968863A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device for a multicolor image forming device without prevents fog and color mixture, and having high resolution and development performance, and stably obtains a high quality image. SOLUTION: In a noncontact developing device provided with a linear electrode capable of applying a bias voltage which is stretched opposite a photoreceptor belt 1 (image forming body), near the developing area A of a developing sleeve 81a (developer carrying body) for carrying nonmagnetic one- component developer, and orthogonal to the direction in which the developing sleeve 81a carries the developer, the linear electrode is composed of at least a first linear electrode 841 stretched near the developing sleeve 81a and a second linear electrode 842 stretched nearer to the photoreceptor belt 1 than the first linear electrode 841.

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.

For the one-component developing method, a magnetic carrier having a particle size of several tens to several hundreds of μm and an average particle size of 10 μm are generally used.
A two-component developing method using a two-component developer composed of front and rear non-magnetic toner is also frequently 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, when the toner particles are particularly fine particles of 10 μm or less, the influence of the van der Waals force relative to the Coulomb force at the time of development becomes large, so that so-called fog in which the toner particles adhere to other portions of the image background. And it is difficult to prevent the problem by applying a DC bias to the developer conveying member.
Since the carrier coverage of the toner is increased, the charge control becomes difficult. Further, aggregation of the toner is likely to occur. Two
In the component developing method, since the carrier coverage of the toner becomes 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 is reduced as the particle size of the carrier particles is reduced, and the carrier particles adhere to the image forming body side together with the toner particles. In addition, when the bias voltage is increased, carrier particles also adhere to other portions of the image background.

In the case of making the toner and carrier fine particles, there is a problem that the above-mentioned side effects are more noticeable and a clear image cannot be obtained. Therefore, it is difficult to actually make these fine particles. . To solve this problem,
"Powder cloud development method" (US Pat. No. 2,725,304)
However, recently, as shown below, a control wire, which is a linear electrode to which a bias voltage can be applied, is stretched in the developing area to electrically form a toner cloud, thereby forming a cloud. An example of developing is proposed.

(1) Japanese Unexamined Patent Publication No. 56-271588 A corona wire, which is a plurality of control wires parallel to each other, is provided between the non-contact photosensitive member / developing sleeve, and the corona wires are adjacent to each other. A developing method characterized in that an alternating voltage is applied so that the polarities of the wires are reversed to cause the developer to fly.

(2) Japanese Patent Application Laid-Open No. 57-198470 A grid having a control wire is provided between the latent image holding surface and the toner holding surface, and a direct current and / or an alternating current is provided between the grid and the toner holding surface. And a bias voltage is applied.

[0008]

FIG. 8 is a diagram for explaining the operation of a conventional linear electrode. In the toner cloud developing method using the control wire described above, since only one control wire 84 exists between the developer transport body and the control wire in the developing area, the toner T flying from the developer transport body 81 is Since the toner cloud formed by the control wire 84 cannot be sufficiently controlled and all the toner cloud reaches the image forming body 1, so-called “fogging” occurs in which the toner T adheres to the non-image portion of the image forming body 1. . In addition, the image forming body 1
In a multi-development batch transfer type multi-color image forming apparatus in which multi-color toners are overlaid on each other, there arises a problem that so-called "color mixing" occurs in which toners of other colors adhere to the toner image on the image forming body 1. .

An object of the present invention is to solve the problems of the toner cloud method and to provide a multicolor image forming apparatus which can stably obtain a high quality image free from fog and color mixture, high in resolution and developability. An object is to provide a developing device.

[0010]

SUMMARY OF THE INVENTION The above-described object is to extend in the direction perpendicular to the developer transport direction in the vicinity of the developing area of the developer transport body that transports the non-magnetic one-component developer, facing the image forming body. In a developing device for performing non-contact development having a linear electrode to which a bias voltage can be applied, the linear electrode includes at least a first linear electrode stretched in the vicinity of the developer transport body and the first linear electrode. A developing device (first invention) comprising a second linear electrode stretched on the image forming body side with respect to one electrode.

Alternatively, a magnetic body having a plurality of magnetic poles is fixed inside, facing the image forming body, and the developing is carried out in the vicinity of the developing area of a developer carrying body carrying a two-component developer which is a magnetic developer. In a developing device for non-contact development having a linear electrode to which a bias voltage can be applied, which is stretched in a direction perpendicular to the developer transport direction so as not to contact the surface of the agent transport body, at least the linear electrode is used for the development. A first electrode stretched near the agent carrier and a second electrode stretched closer to the image forming body than the first linear electrode.
The present invention is achieved by a developing device (second invention) characterized by comprising linear electrodes.

[0012]

In the developing device of the present invention (first and second inventions), the developing device of the present invention (first and second inventions) faces the image forming body in common and is formed in the vicinity of the developing area of the developer conveying body for conveying the developer, at a right angle to the developer conveying direction. A non-contact developing device having a linear electrode capable of applying a bias voltage, which is stretched in a direction, wherein the linear electrode is at least a first linear electrode stretched near the developer transport body, It is composed of a second linear electrode stretched closer to the image forming body than the first linear electrode, and a strong oscillating electric field is formed between the first linear electrode and the developer transport body. The toner is clouded by this oscillating electric field to develop the latent image. The toner cloud is, as shown in FIG. 7, the second linear electrode 842 disposed further on the image forming body 1 side than the first linear electrode 841. Controlled by the flight. That is, the second linear electrode applied with a voltage that prevents the toner from flying (for example, in the case of reversal development, a bias voltage having the same polarity as the toner and a slightly higher absolute value than the first linear electrode 841). By 842, first
The speed of the cloud of the toner T having a large acceleration formed by the linear electrode 841 is controlled to limit the generation of unnecessary toner cloud reaching the image forming body 1.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a schematic diagram showing an example of a multicolor image forming apparatus equipped with the developing device of the present invention as a suitable developing means.

In FIG. 3, 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 thereof is the guide member. Rub 4

6 is a scorotron charger which is a charging means, and 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. These image forming means are photosensitive. The guide member 4 of the body belt 1
Is disposed in a portion in contact with.

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 developer of yellow, magenta, cyan and black, 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 photoconductor belt 1 during image formation, and during cleaning after image transfer. Only as shown in the figure, it is pressed against the surface of the photosensitive belt 1.

The process of forming a color image by the multicolor 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 inputted to the recording section, for example, the multicolor image forming apparatus shown in FIG.

That is, when image data, which is a color signal output from an image reading apparatus separate from the multicolor image forming apparatus, is input to the laser writing apparatus 7, the laser writing apparatus 7 performs writing (not shown). A laser beam (writing light) generated by a semiconductor laser which is a light source 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, and has an fθ lens 75 and a cylindrical lens 76. After that, the optical path is bent by the two mirrors 77 and 78 during that time, and the main scanning is performed by being projected on the peripheral surface 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 sub-scanning due to movement of the photosensitive belt 1, and a latent image is formed.

On the other hand, when 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.

This 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, and a black toner image is formed 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 of the uppermost layers is carried out and the photosensitive belt 1 passes through the timing roller 17.
The image is supplied to the transfer device 12 at the same timing as the above image formation.

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 multicolor image forming apparatus using the developing device of the present invention, the 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 both the one containing a one-component developer and the one containing a two-component developer can be used. it can. A developing device accommodating a one-component developer of the present invention (first invention) is indicated by reference numeral 8a, and a developing device accommodating a two-component developer and having a main magnetic pole in a developing sleeve corresponding to a developing region (second invention). ) Is indicated by reference numeral 8b. If they are common, a and b are omitted. Each developing device will be described below.

[Embodiment 1 (First Invention)] FIG. 1 is a schematic sectional view and an essential portion sectional view showing an example of a developing device 8a for accommodating a non-magnetic one-component developer of the present invention.

In the figure, A is a developing area, and 81a is a developing sleeve which is a developer carrying carrier made of a non-magnetic material such as aluminum and is rotatable in the direction of the arrow in the figure. 84
Reference numeral 1 is a first linear electrode which is one of wire-shaped linear electrodes made of a conductive material such as metal, and 842 is a second linear electrode which is another wire-shaped linear electrode made of a conductive material such as metal. It is a striped electrode and is stretched closer to the image forming body 1 side than the first linear pole 841. Reference numeral 851a is a stirring screw for stirring the developer D to uniformly charge the developer D, and 852a is a fur brush for supplying the developer D to the developing sleeve 81a while stirring the developer D. 86a
Is a regulating blade, and since the toner is charged by rubbing the toner against the developing sleeve 81a, an elastic blade type made of elastic rubber such as urethane rubber or silicon rubber is preferable. A cleaning blade 87a removes the magnetic brush passing through the developing area A from the developing sleeve 81a.
88a is a developer reservoir, and 89a is a casing.

A DC voltage (DCs) is applied to the developing sleeve 81a by a DC power supply E ₁ and an AC power supply E _2.
Cs) is superposed on the AC bias voltage via the protection resistor R _1, and the DC bias voltage (DC ₁ ) is applied to the first linear electrode from the DC power source E ₃ via the protection resistor R ₂ . A DC bias voltage (DC ₂ ) is applied to the two linear electrodes by a DC power source E ₄ via a protection resistor R ₃ .

In this embodiment using the one-component developer D, it is preferable to coat the surface of the developing sleeve 81a with a material similar to the carrier coating material described later, depending on the chargeability of the toner.

[Embodiment 2 (Second Invention)] FIG. 2 is a schematic sectional view and a main portion sectional view showing an example of a developing device 8b for containing a magnetic two-component developer of the present invention.

FIGS. 2A and 2B are a schematic sectional view and an enlarged sectional view of an essential part of an example of the device of the present invention.
Reference numeral b denotes a developing sleeve which is a developer carrier made of a non-magnetic material such as aluminum and is rotatable in the direction of the arrow in the figure. Reference numeral 82b is a magnet body having a plurality of N and S magnetic poles fixed in the developing sleeve 81b in the circumferential direction.
One magnetic pole 821b of b is disposed in the developing area A at the closest position 811a between the developing sleeve 81b and the photosensitive belt 1, and this is referred to as the main magnetic pole. The developing sleeve 81b and the magnet body 82b exhibit a developer transport function. Each magnetic pole including the main magnetic pole 821b of the magnet body 82b is 50
It is magnetized to have a magnetic flux density of 0 to 1,500 gauss, and its magnetic force forms a layer of the magnetic developer D, that is, a magnetic brush on the developing sleeve 81b. This magnetic brush moves in the same direction as the developing sleeve 81b rotates and is conveyed to the developing area A. The magnetic brush formed on the developing sleeve 81b does not come into contact with the surface of the photosensitive belt 1 so that a gap is maintained between the developing sleeve 81b and the regulating blade 8.
The gap 6b and the gap between the developing sleeve 81b and the photosensitive belt 1 are adjusted.

Reference numeral 841 denotes a first linear electrode which is one of wire-shaped linear electrodes made of a conductive material such as metal, and 842 denotes another linear electrode stretched closer to the image forming body than the first linear electrode 841. Second linear electrodes, 851b and 852b, which are linear electrodes, are agitation screws for agitating the developer D to homogenize the components, 86
Reference numeral b is a regulating blade which is a developer regulating means made of a non-magnetic material or a magnetic material provided for regulating the height and amount of the magnetic brush, and 87b is the magnetic brush passing through the developing area A and is removed from the developing sleeve 81b. A cleaning blade, 88b is a developer reservoir, and 89b is a casing.

To the developing sleeve 81b, a DC voltage (DCs) is converted into an AC voltage (A) by a DC power supply E ₁ and an AC power supply E _2.
AC bias voltage superposed with Cs) is applied via the protection resistor R _1, and a DC bias voltage (DC ₁ ) is applied to the first linear electrode 841 by the DC power supply E ₃ via the protection resistor R ₂ . A DC bias voltage (DC ₂ ) is applied to the second linear electrode 842 by a DC power supply E ₄ via a protection resistor R ₃ .

The developing sleeve 8 centered on the rotation axis O of the developing sleeve 81b of the main magnetic pole 821b of the magnet body 82b.
The angle between the closest position 811b on the developing sleeve 81b of the photosensitive drum belt 1b and the main magnetic pole 821b is θ.
₃ (°), and the angle between the closest position 811b and the center of the first linear electrode 841 is θ ₁ (°), θ ₁ −10 ≦ θ ₃ ≦ θ ₁ +10 (°) Is negative on the downstream side in the rotation direction of the developing sleeve 81b).

When θ ₃ is out of the above range, the spikes of the developer D in the vicinity of the first linear electrode 841 (developing area A) are insufficient and the developability deteriorates.

The shapes and installation positions of the first linear electrode 841 and the second linear electrode 842 of the first and second embodiments will be described.

First linear electrode 841 and second linear electrode 84
2 has diameters r ₁ and r ₂ , and the developing sleeves 81a and 81b
From the height h ₁ , h ₂ , the closest positions 811a, 811b
(The closest position between the developing sleeve 81 and the photosensitive belt 1)
And an installation angle about the rotation center O between the first linear electrode 841 and the first linear electrode 841 is θ ₁ , and the closest positions 811a and 811 are also the same.
When the installation angle between b and the second linear electrode 842 is θ ₂ , the diameters and installation angles of the first linear electrode 841 and the second linear electrode 842 are preferably set to the values shown in Table 1.

[0046]

[Table 1]

(Diameter of linear electrode) When the diameter of the first linear electrode 841 is smaller than the conditions shown in Table 1, sufficient toner cloud is not generated and the developability is deteriorated. If the thickness is thicker than the condition shown in Table 1, the first linear electrode 8 is formed due to mechanical vibration and formation of an oscillating electric field.
41 easily comes into contact with the developing sleeve 81 and the photoconductor belt 1, and image disturbance occurs.

If the diameter of the second linear electrode 842 is smaller than the conditions shown in Table 1, the toner cloud cannot be smoothly guided from the first linear electrode 841 and the developability and the image disorder occur. Further, since the counter electrode effect by the second linear electrode 842 is reduced, the reproducibility of the line image is deteriorated.

(Height of linear electrode) First linear electrode position 84
When 1 is lower than the condition of Table 1, the first linear electrode 841 is likely to come into contact with the developing sleeve 81 or the photoconductor belt 1 due to the formation of the mechanical vibration or the oscillating electric field, and the image is disturbed. Also,
When it is higher than the conditions shown in Table 1, sufficient toner cloud is not generated and the developability is deteriorated.

Particularly, in the developing device 8a for a one-component developer, compared with the developing device 8b for a two-component developer,
Since the developer layer is low and the adhesive force with the developing sleeve 81a is large, it is necessary to install the first linear electrode 841 closer to the developing sleeve 81a than in the case of a two-component developer.

If the second linear electrode 842 is lower than the conditions shown in Table 1, the counter electrode effect by the second linear electrode 842 is reduced, and thus the reproducibility of the line image is deteriorated.

(Installation Angle of Linear Electrode) First linear electrode 84
If the installation angle θ ₁ of 1 is set outside the range of Table 1, the formed toner cloud cannot be efficiently guided to the second linear electrode 842. If the installation angle θ ₂ of the second linear electrode 842 is set outside the range shown in Table 1, the first linear electrode 8
The toner cloud formed by 41 cannot be efficiently guided to the second linear electrode 842.

The bias voltage (DC ₁ ) applied to the first linear electrode 841 and the bias voltage (DC ₂ ) applied to the second linear electrode 842 are DC of the bias voltage applied to the developing sleeve 81. It is preferable that the components (DCs) have the same polarity and the absolute values are the conditions shown in Table 2.

[0054]

[Table 2]

Bias voltage DC _{1 of} the first linear electrode 841
Is smaller than the range shown in Table 2, the toner cloud is deposited on the first linear electrode 841 and image stain occurs. If it is larger than the range shown in Table 2, a sufficient amount of toner cloud cannot be formed, resulting in defective development.

Bias voltage DC _{2 of} the second linear electrode 842
Is smaller than the range of Table 2, the toner cloud formed by the first linear electrode 841 is likely to be deposited on the second linear electrode 842, and thus image stains are likely to occur. If the range is larger than that in Table 2, the toner cloud formed by the first linear electrode 841 cannot be smoothly guided to the developing area A.

(Material of linear electrode) The material of the first linear electrode 841 and the second linear electrode 842 is metal such as gold, silver, platinum, palladium, copper, nickel, tungsten, or metal oxide such as copper oxide. It is possible to use an object, a composite material obtained by coating glass with copper powder, graphite, nickel, silver or the like, or a conductive material such as graphite or carbon fiber. These materials are desirably insulated for preventing discharge, preventing rust, and imparting strength.

(Linear Electrode Stretching Method) Since the linear electrode stretching method is common to the developing devices 8a and 8b, reference numerals a and b are omitted.

FIG. 4 is a perspective view showing an example of stretched linear electrodes. Reference numeral 812 in FIG.
13, the center portion of the rotary shaft 8 is located on both sides of the developing sleeve 81.
Stretching member made of an insulating material fixedly fitted to 12 so as to be rotatable, first linear electrode 841 and second linear electrode 8
42 is a small hole 813a, 81 formed in the tension member 813.
It can be passed through 3b and stretched at the predetermined setting position.

FIG. 5 is a plan view showing another example of tensioning the linear electrodes. Reference numeral 89 in the drawing denotes a casing made of an insulating material, and the first linear electrode 841 and the second linear electrode 842 can be fixedly installed in the casing 89.

FIG. 6 is a cross-sectional view and a plan view showing still another example of tensioning the linear electrodes. Reference numeral 893 is a rectangular tension frame which is made of an insulating material and is provided in the opening of the developing device 8 facing the photoconductor belt 1. Tensioning frame 89
The first linear electrode 8 in the small holes 893a and 893b formed in
41 and the second linear electrode 842 can be inserted and fixed at the predetermined setting position.

In the developing devices 8a and 8b of the present invention, an alternating electric field formed between the photosensitive belt 1 and the developing sleeves 81a and 81b by applying the above bias voltage (this is referred to as a second oscillating electric field). ), A first oscillating electric field is generated between the first linear electrode 841 and the developing sleeves 81a and 81b.

In this case, since the first linear electrode 841 is provided closer to the developing sleeves 81a and 81b than the photosensitive belt 1, the strength of the first oscillating electric field is larger than the strength of the second oscillating electric field. Become.

By the first oscillating electric field, the toner T reaching the vicinity of the first linear electrode 841 is vibrated in a direction perpendicular to the line of electric force, and in the case of a two-component developer, the toner particles are vibrated. The toner particles can be separated from the carrier and fly, and a cloud-like toner cloud can be sufficiently generated. The toner cloud is suppressed by the second linear electrode 842, and the second oscillating electric field assists the flight toward the latent image on the photoconductor belt 1 to perform proper and uniform development.

At this time, since the AC bias voltage is applied only to the developing sleeves 81a and 81b, 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 first oscillating electric field. Smoothly shift to the oscillating electric field of 2.

The waveform of the AC component of the AC bias voltage applied to the developing sleeves 81a and 81b is not limited to the 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 fogging is prevented by the DC component, and the dielectric breakdown is prevented from occurring in the developing sleeves 81a and 81b.
Can be prevented by insulating or semi-insulating the surface thereof with a resin, an oxide film, or the like, or by using insulating carrier particles as described below as the carrier particles of the developer D.

Next, the toner or carrier which is the developer D used in the present invention will be described.

(Toner of one-component developer) The particle size of the toner is preferably 4 <D ₅₀ <8 (μm), where D ₅₀ (μm) is the volume average particle size.

When D ₅₀ is 8 μm or more, the grain size is large and the resolution is insufficient.

When D ₅₀ is 4 μm or less, the cohesive force becomes large, and frictional electrification tends to occur.

Toner T is styrene resin, vinyl resin, ethyl resin, rosin-modified resin, acrylic resin,
Polyamide resin, epoxy resin, polyester resin,
Copolymer resins such as these styrene-acrylic resins or mixed resins are preferable. To these binder resins, coloring components such as color pigments and, if necessary, a charge control agent, a release agent such as wax, etc. are added, and the conventionally known pulverization and granulation method, suspension polymerization method, emulsion polymerization method, etc. It is obtained by the same method as the toner manufacturing method.

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 of the present invention, a fluidizing agent such as colloidal silica can be added to the above toner and used as it is as the developer D.

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

Here, the average charge amount Q ₁ of the toner of the non-magnetic one-component developer is a conductive plate having a size of 2 cm × 5 cm, the regulating blade 86 described above, and a developing device having a developing sleeve 81 having a diameter of 20 mm ( 8a), the closest distance 0.
AC bias voltage in which DC and AC are superposed on the developing sleeve 81 (for example, DC; 1000V, AC; 750V _OP , A while supplying charged toner to the developing sleeve 81 and rotating at 200 rpm).
C frequency of 8 kHz) is applied to develop the conductive plate with toner, and the conductive plate developed with this toner is connected to a Faraday gauge to blow the toner off with nitrogen gas. It is a value obtained by measuring the amount and the weight.

(Two-Component Developer) In the two-component developing method, it is preferable to use a developer D composed of the toner particles of the one-component developer and the following carrier particles.

Generally, if 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, and as a result of the experiment, the volume average particle size is 10 to 60 μm, preferably 20.
It was found that the above problems did not occur when the thickness was ˜50 μm.

When the thickness is 10 μm or less, it is difficult to magnetize the carrier sufficiently, and the carrier adheres to the surface of the photosensitive belt 1 together with the toner particles.

On the other hand, if it is 60 μm or more, the specific surface area of the carrier becomes small, so that the toner cannot be sufficiently charged. Further, since the covering ratio is high, toner scattering is also likely to occur.

The volume average particle size is measured by a laser diffraction type particle size distribution measuring apparatus "HEROS" (SYM) equipped with a wet dispersion machine.
(Made by PATEC). First, a wet disperser was used to disperse 10 mg of magnetic particles together with a surfactant in 50 mg of water, and then an ultrasonic homogenizer (output 150
In W), be careful not to cause reaggregation due to heat generation,
It is a value measured after performing a pretreatment of dispersing for 1 to 10 minutes.

The strength of carrier magnetization (σ ₁₀₀₀ ) is 5 to
It is 60 emu / g, preferably 10 to 40 emu / g. Although this strength depends on the magnetic flux density on the developing sleeve 81b, the general magnetic flux density of the developing sleeve 81b 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 strength of magnetization of the carrier was determined by filling carrier particles while tapping them into a sample cell of 0.25 cm × 3 cm ² and attaching the sample to a pickup coil and setting it in a magnetizer. "TYPE3
227 ”(manufactured by Yokogawa Hokushin Electric Co., Ltd.) to draw a hysteresis curve on an XY recorder.

Such a magnetic carrier is made of iron, chromium, nickel, which is equivalent to a conventional magnetic carrier as a magnetic material.
Spherical particles of a ferromagnetic material such as a metal such as cobalt, or a compound or alloy thereof, for example, ferric tetroxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite, or a manganese-copper alloy. Or the surface of the spherical magnetic particles is styrene resin, vinyl resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, silicon resin, fluorine resin Etc. or a spherical coating with a copolymer.

Further, a so-called resin dispersion type carrier in which magnetic fine particles are dispersed and contained in these resins can also be used.

The carrier density depends on the magnetic substance content,
Generally 1.8~7g / cm ^3, preferably 2 to 6 g / cm ³
Is good. If it is smaller than 1.8 g / cm ^{3, the} carrier is easily scattered by the rotation of the developing sleeve 81b. If it exceeds 7 g / cm ³ , the stress on the toner increases and the durability of the developer D decreases.

The density was measured by a dry densitometer Accupic 1
330 (manufactured by Micromeritics) was used.

Since the toner particles follow the electric field, the absolute value of the charge amount of the toner particles is preferably larger than 1 to 3 μC / g in the two-component developer, 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.

For the developing device 8b 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. When a general coating carrier (density 5 to 8 g / cm ³ ) is used, the toner concentration in the developer is 2 to 30% by weight, preferably 5 to
It is 20% by weight.

If 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 the content 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 light 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 amount is preferably 5 to 40% by weight, preferably 10 to 30% by weight.

The charge amount of the toner particles is an absolute value of 1 to 3 (μ
C / g) and 3 to 50 (μC / g) are preferable from the viewpoint of securing developability and preventing fog and toner scattering.

(Experimental Example) In a comparative experiment (Example 1, Comparative Example 1, Comparative Example 2) using the one-component developer of the first invention, the developing device shown in FIG. 1 was provided in FIG. Images were formed using the multicolor image forming apparatus shown. The photoconductor belt 1 is an OPC photoconductor, and its peripheral speed is 180 mm / se.
c, maximum potential −850 V (non-image portion potential), minimum potential −50 V (image portion potential) of the electrostatic latent image formed on the photoreceptor belt 1, outer diameter of the developing sleeve 81a 20 mm, rotation of the developing sleeve 81a Number 260 rpm, developing sleeve 81
The surface roughness Rz _{1 of a} is 2.7 μm. As the developer regulating blade 87a, an elastic blade made of urethane rubber was used. And the following toner is used.

100 parts by weight of styrene-acrylic resin, 10 parts by weight of color pigment, and 2 parts by weight of nigrosine were melted and kneaded, and then pulverized and classified to obtain yellow, magenta, cyan, and black particles having a volume average particle diameter of 5.5 μm. Each toner was obtained. 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 of the toner 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.

In a comparative experiment using the two-component developer of the second invention (Example 2, Comparative Example 3 and Comparative Example 4), the multicolor developing device shown in FIG. 2 was used as a developing device. An image was formed using the image forming apparatus. Photoconductor belt 1 is OP
The peripheral speed of the C photoconductor is 180 mm / sec, and the maximum potential of the electrostatic latent image formed on the photoconductor belt 1 is -850V.
(Non-image part potential), minimum potential -50V (image part potential),
The outer diameter of the developing sleeve 81b is 20 mm, and the developing sleeve 81 is
The rotation speed of b is 390 rpm, the surface roughness Rz _{1 of} the developing sleeve 81 b is 1.2 μm, and the magnetic pole strength of the magnet body 82 b in the developing sleeve 81 b is 700 gauss. And the following developers are used.

Carrier: The magnetization intensity is 25 emu / g
The spherical carrier obtained by surface-coating spherical ferrite particles with a methyl methacrylate / styrene copolymer resin.
Volume average particle diameter 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 were mixed so that the concentration of the toner would be 7% by weight to prepare a developer. Toner charge amount is Y; −20.5 μC
/ G, M; -21.3 [mu] C / g, C; -20.7 [mu] C /
g, K; −22.0 μC / g.

Using these developing processes, carriers and toners, under the conditions shown in Table 3,

[0100]

[Table 3]

When 50,000 full-color image recordings were carried out, in Examples 1 and 2 of the present invention, it was possible to stably obtain an image with high image density without fog or color mixture from the beginning to the end.

On the other hand, in Comparative Examples 1 and 3 (only the second linear electrode 842 was installed), the developability was insufficient from the beginning,
It was not possible to obtain a sufficient image density.

Comparative Examples 2 and 4 (first linear electrode 841)
However, it was not possible to obtain an image of good quality due to a large amount of fog and color mixture from the beginning.

[0104]

According to the present invention, since the second linear electrode is installed further on the image forming body side than the first linear electrode, the reproducibility of the line image is good and the generation of unnecessary toner cloud is suppressed. However, it is possible to provide a developing device capable of non-contact development that can stably obtain an image with high image density and high developability without fog or color mixture.

By combining the bias voltage of the first linear electrode and the bias voltage of the second linear electrode, it is possible to change the counter electrode effect and obtain the required gradation. That is, if the bias voltage applied to the first linear electrode is low and the bias voltage applied to the second linear electrode is high, a binary image with high developability can be obtained. On the other hand, when the bias voltage of the first linear electrode is high and the bias voltage of the second linear electrode is low, it is possible to obtain more excellent effects such as obtaining an image with excellent gradation reproducibility. it can.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a developing device of a first invention.

FIG. 2 is a schematic configuration diagram showing an example of a developing device of a second invention.

FIG. 3 is a schematic configuration diagram showing an example of a multicolor image forming apparatus including a developing device of the present invention.

FIG. 4 is a perspective view showing an example of tensioning a first linear electrode and a second linear electrode.

FIG. 5 is a plan view showing another example of tensioning the first linear electrode and the second linear electrode.

6A and 6B are a cross-sectional view and a plan view showing still another example of tensioning the first linear electrode and the second linear electrode.

FIG. 7 is a diagram for explaining the action of the first electrode and the effect of the second electrode of the present invention.

FIG. 8 is a diagram illustrating the operation of a conventional limiting wire.

[Explanation of symbols]

1 Photoconductor Belt (Image Forming Body) 8, 8A, 8B, 8C, 8D Developing Device 81 Developing Sleeve (Developer Transporting Body) 82 Magnet Body 841 First Linear Electrode (Linear Electrode) 842 Second Linear Electrode ( Linear electrode) 86 Control blade A Development area D Developer E ₁ , E ₃ , E ₄ DC bias power supply E ₂ AC bias power supply T Toner

Claims (2)

[Claims] 1. A bias voltage, which is stretched in the direction perpendicular to the developer transport direction, is provided in the vicinity of the developing area of a developer transport body that transports a non-magnetic one-component developer, facing the image forming body. In a developing device for performing non-contact development having a linear electrode, the linear electrode extends at least on the first linear electrode stretched near the developer transport body and on the image forming body side with respect to the first electrode. A developing device comprising a second linear electrode provided. 2. A developing device is provided in the vicinity of a developing area of a developer transporting body for transporting a two-component developer which is a magnetic developer, in which a magnet body having a plurality of magnetic poles is fixed inside, facing the image forming body. In a developing device for performing non-contact development, which has a linear electrode to which a bias voltage can be applied and which is stretched in a direction perpendicular to the developer transport direction in a non-contact manner with the surface of the agent transport body, at least the linear electrode is A developing device comprising a first linear electrode stretched in the vicinity of the agent carrier and a second linear electrode stretched closer to the image forming body than the first electrode.