JPH09269654A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of obtaining a clear recording image without density unevenness, by solving problem such as the developing property deterioration, especially the occurrence of density unevenness depending on an electrode position, in developing devices executing reversal developing by an oscillation electric field, by setting an electrode in a developing space where an image carrier and a developer carrier are opposed to each other for dealing with a small grain size toner. SOLUTION: This developing device, develops the latent image on the image carrier 1, by providing a conductive plate member 45 in the space where the developer carrier 41 and the image carrier 1 is opposing each other, applying at least, DC voltage on the plate member 45, and applying superimposed voltage of the DC component and the AC component on the developer carrier 41 while making the toner flying. In this case, the plate member 45, is composed of the conductive electrode member 45a, and an insulated member 45b supported by the electrode member 45 while held in contact with the developer layer of the developer carrier 41.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device such as an electrophotographic copying / recording device, and more particularly to a plate on the upstream side in the moving direction of the developer carrier in the space where the image carrier and the developer carrier face each other. The present invention relates to a developing device in which a cylindrical member is installed, a two-component developer is supplied to the developer transport body, and the toner is caused to fly under an oscillating electric field for reversal development.

[0002]

2. Description of the Related Art Various methods have been disclosed for forming a color image in a conventional electrophotographic copying / recording apparatus or the like.

Japanese Unexamined Patent Publication (Kokai) No. 60-76766 discloses a color image recording method in which toner images are superposed on an image carrier by using a two-component developer in which toner and an insulating carrier are mixed. This method is very useful because it has features such that the recording apparatus is compact and low-cost, and that the toner charge control is easy because a two-component developer is used. However, the toner particle size conventionally used in this method is relatively coarse, that is, 10 μm or more, and it is not possible to reproduce the density that is faithful to a fine line or a document, and it is incomplete for obtaining a high-quality image. there were. In order to solve this problem, atomization of the toner is indispensable, but it is known that various problems occur when using a fine particle toner of 10 μm or less. As the cause,
The atomization makes the van der Waals force relatively larger than the Coulomb force, making it difficult to prevent fogging by applying a DC bias voltage to the developer carrier. It is difficult to uniformly charge the toner by the atomization. That is, fogging is caused by toner that is not properly charged. Various methods have been proposed to overcome such problems.

In Japanese Unexamined Patent Publication No. 1-94368, a leveling member is set between the center of the developing area and a member for controlling the layer thickness of the developer, and the level of the charging polarity of the toner particles on the leveling member is described. It is disclosed that a DC voltage of opposite polarity is applied as a bias voltage. In this method, since a bias having a polarity opposite to the charging polarity of the toner particles is applied to the leveling member, the toner adheres to the leveling member, which adheres to the image carrier to cause image stains or leveling. When the toner is fused to the member, vertical streaks occur in the image.

Japanese Patent Laid-Open No. 4-115264 discloses an image forming method in which developers of different colors are sequentially applied to an image carrier by a plurality of developing devices to form a visible image composed of the developers of plural colors, and then transferred. In the apparatus, an oscillating electric field is formed between an electrode body, which is arranged in close proximity to and in contact with the developer of the developer carrier, and whose tip is located in the developing area, to form an oscillating electric field for development. A method is disclosed in which the agent is dispersed and ejected from the tip of the electrode body and supplied to the image carrier. In this method, since the electrode body for dispersing and flying the developer is also present in the upstream portion of the contact portion with the developer transport body, a fluctuating electric field similar to that in the developing area is formed during transport of the developer, and Will be returned to the upstream side. As a result, the amount of the developer that passes through the electrode body and is conveyed to the developing area is reduced, and the developability is poor, and the developer returned to the upstream side easily causes toner adhesion to the back surface of the electrode body. Is more likely to occur.

In Japanese Unexamined Patent Publication No. 6-236106, a plate-shaped member having an electrode in the upstream portion of the developing area is brought into contact with a developer carrying body so that the space between the developer carrying body and the image carrier and between the developer carrying body and the plate. The toner is attached to the electrostatic latent image on the image carrier by forming an oscillating electric field in phase with the tip electrode of the plate-shaped member, and the second electrode has a portion upstream of the tip electrode. Is held, and an electric field is formed which acts an electric force from the second electrode to the tip electrode side. In this method, since the absolute value of the DC bias voltage applied to the second electrode is larger than that of the tip electrode, it is good for the developer stain on the electrode.

[0007]

However, in such a control electrode developing method, undulations and distortions that occur when the electrode plate is installed cause differences in the developer transport amount and the electrode position in the developing space, which results in As a result, there is a problem that streaks occur in the output image and uneven density occurs.

It is an object of the present invention to solve the above problems and to provide a developing device capable of obtaining a clear recorded image without density unevenness. That is, in the present application, the electrode member itself is provided with linearity so that the developer can be uniformly transported in the axial direction of the developer transport body, and at the same time, toner scattering to the upstream side of the developer transport body can be prevented. .

[0009]

SUMMARY OF THE INVENTION In a developing device of the present invention for solving the above-mentioned object, a plate-like member which can be energized is installed in a space where a developer carrier and an image carrier face each other, and the plate-like member is provided in the plate-like member. In the developing device, which applies at least a DC voltage and applies a superimposed voltage of a DC component and an AC component to the developer transport body to fly toner to develop the latent image on the image carrier, the plate-shaped member is It is characterized in that it is composed of an electrically conductive electrode member and an insulating member which is supported by the electrode member and is in contact with the developer layer of the developer transport body.

[0010]

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

FIG. 1 is a partial sectional view of an image forming apparatus showing an example of a developing device having a plate-shaped member of the present application. In the figure, 41 is a developer transporter rotatably supported, which is subjected to a surface roughening treatment of 1 to 2 μm according to JIS 10 point average roughness (JIS-B0610) by sandblasting of aluminum alloy, stainless steel, etc.
43 is a stirrer for stirring the developer 42 to make the components uniform,
44 is a supply roller that supplies the developer 42 to the developer transport body 41, 46 is a developer transport control rod that regulates the thickness of the developer layer on the developer transport body 41, and 47 is the developer transport body. A scraper for scraping off the consumed developer 42 on 41. Reference numeral 45 is a plate-shaped member, which is an electrode member 45a.
And the insulating member 45b, and the developing device housing 40
Attached via an insulating member 50.

The electrode member 45a is composed of a conductive member having a thickness of about 25 to 400 μm and capable of conducting electricity. For example, a thin metal plate having elasticity such as a stainless steel plate, a steel plate, a copper alloy plate, a phosphor bronze plate, a beryllium copper plate, an aluminum alloy plate, a nickel plate is preferable, and particularly, a non-magnetic steel such as a phosphor bronze plate or a stainless steel plate (SUS304). And the like are more preferably used.

Further, it is preferable to form a mesh on the electrode member 45a because the pressure applied to the developer layer can be reduced. The shape of the mesh electrode member is shown in the perspective view of FIG. FIG. 2A shows a mesh electrode member 45a having fine meshes in the moving direction of the developer transport body 41. FIG. 2B shows a mesh electrode member 45a having fine meshes in the axial direction of the developer transport body 41. In these mesh-shaped electrode members 45a, it is preferable that the edges of the developer transport body 41 in the moving direction and the edges of the developer transport body 41 in the axial direction are parallel to the lines forming the mesh. Further, as shown in FIG. 2C, it is particularly effective to form the mesh of the mesh of the electrode member 45a so as to intersect with each other, because strength can be obtained in the electrode member 45a.

The insulating member 45b has a length of 10 to 300 m.
It is composed of an insulator having a thickness of about m. For example,
Polyethylene terephthalate, polystyrene, polypropylene, polycarbonate, polybutylene terephthalate, phenol resin, polyimide resin, polyamide imide resin, epoxy resin, polyether resin and the like are preferable, and those reinforced with such an insulator as glass fiber or carbon fiber are used. Is more preferable. Further, it is not possible to use ceramics such as alumina, aluminum nitride, single crystal sapphire, silicon carbide, silicon nitride, zirconia, mullite, cordierite, steatite, and wolsterite, or a mixture of these ceramics with a resin having a dielectric constant. It is preferable because the development gap becomes narrower because of a high value.

In order to bond the electrode member 45a and the insulating member 45b, it is preferable to bond them with a thermosetting resin, an ultraviolet curing resin or the like in addition to an epoxy adhesive, or to bond them with a double-sided tape.

The developer carrier 41 has a DC bias power source E.
A bias voltage capable of superimposing an alternating current on a direct current is applied through the protection resistor R1 by the AC bias power source 1 and the AC bias power source E2. A DC bias power source E3 is connected to the electrode member 45a.
A bias voltage capable of superimposing an alternating current on a direct current is applied through a protective resistor R2 by an alternating current bias power source E4.

FIG. 3 shows the electrode member 4 usable in the present invention.
FIG. 5 is a schematic diagram showing the configuration and arrangement of a plate-shaped member 45 composed of 5a and an insulating member 45b.

As shown in FIG. 3A, the insulating member 45b
Are stacked and supported near the tip of the electrode member 45a. At this time, the width of the electrode member 45a, that is, the insulating member 45
b, the width of the region where the electrode member 45a is laminated is L2, and the width L from the tip of the insulating member 45b to the tip of the electrode member 45a is L.
Let it be 1. In addition, the developer transport body 41 and the insulating member 45
The contact position with a is P, the thickness of the electrode member 45a is h1, and the height of the insulating member 45b at the contact position P is h2. The insulating member 45b is laminated on the electrode member 45a, and the tip end edge of the insulating member 45b is pressed against the surface of the developer transport body 41. With this configuration, the contact position P
Toner scattering does not occur on the upstream side, and the toner concentration of the developer on the downstream side can be kept uniform. In particular, in a color image forming apparatus in which multi-color toners are laminated and formed on the image carrier 1, it is effective to suppress fogging during development.
The exposed portion of the electrode member 45a is preferably coated with an insulating layer of about 10 to 100 μm in order to prevent current leakage. The insulating member 45b is usually supported by the electrode member 45a via an adhesive agent or the like, but the insulating member 45b is positioned and locked at the tip of the electrode member 45a. By directly pressing the carrier 41, the insulating member 45
It is also possible to support b without inclusions.

FIG. 3 (b) shows another embodiment of the insulating member 45b. In this embodiment, the insulating member 45b is
It has a substantially semi-circular cross section, and one point of its arc surface comes into pressure contact with the surface of the developer transport body 41 at a contact position P.

FIG. 3C shows the electrode member 45a and the insulating member 4.
5b shows another embodiment of 5b. In this embodiment, the tip of the insulating member 45b is pressed against the surface of the developer transport body 41 at the contact position P, and at the same time, the tip of the electrode member 45a is contacted on the downstream side of the surface of the developer transport body 41. The pressure contact is made at the position Q. With this configuration, the toner cloud does not occur on the upstream side of the contact position P, and the toner concentration of the developer on the downstream side can be kept uniform.

The configuration and arrangement of the plate member 45 composed of the electrode member 45a and the insulating member 45b used in the developing device 4 of the image forming apparatus has been described above with reference to FIG. It is needless to say that the developing device of the present invention can be similarly applied to those having such a configuration.

FIG. 4 is a schematic block diagram of an image forming apparatus (DC9028 modified machine manufactured by Konica Corp.) using the developing device of the present invention. Reference numeral 1 denotes a photosensitive drum, which is an image carrier having an aluminum tube coated with a photoconductor, and is configured to rotate clockwise.

2 is a scorotron charger which is a charging means, and 3
Is an image writing device using a laser beam as an image exposing means, 4A, 4B, 4C and 4D are developing devices each containing a developer of a specific color, 5 is a transfer device, 6 is a cleaning device, and 8 is an image reading device. is there.

Each of the developing devices 4A, 4B, 4C, 4D
Is yellow (Y), magenta (M), cyan (C),
A developer containing black (K) developer is provided, and each developer transport body 41 having a predetermined gap from the photoconductor drum 1 is provided, and a latent image on the photoconductor drum 1 is visualized by non-contact reversal development. It has a mechanism to change. The developer transport body 41 is configured to rotate counterclockwise.

The transfer belt 5b of the transfer device 5 includes a transfer pole 5a and is kept at a position apart from the surface of the photosensitive drum 1 during image formation, and is transferred after the image formation on the photosensitive drum 1 is completed. Only when transferring to a material, the surface of the photosensitive drum 1 is contacted as shown in the figure.

The cleaning blade 6a and the toner carrying roller 6b of the cleaning device 6 are kept at a position separated from the surface of the photosensitive drum 1 during image formation, and are only shown at the time of cleaning after image transfer as shown in FIG. 1
Is pressed against the surface of A color image is formed by the image forming apparatus as follows.

First, the formation of a multicolor toner image according to this embodiment starts by reading an image. That is, the halogen lamp 80 of the image reading device 8 irradiates the original document placed on the document table 7, and the reflected light is reflected by the first mirror 81,
The lens 8 is reflected by the second mirror 82 and the third mirror 83.
4. The color is separated into blue, red and green through the dichroic prism 85. Blue is a CCD 86 for blue and red is a CCD 8 for red.
7. Green is read by the CCD 88 for green. An analog signal from the CCD is converted into a digital signal by an A / D conversion board (not shown) and image processed.

When the image-processed digital signal is input to the image writing device 3, the semiconductor laser which is a writing light source (not shown) passes through a collimator lens and a cylindrical lens (not shown), and the drive motor 31 is driven.
It is rotated and scanned by the rotating polygon mirror 34 rotated by, the optical path is bent by the mirror 35 through the fθ lens 32 and the cylindrical lens 33, and a uniform charge is given in advance by the scorotron charger 2 as a charging means. The image is projected onto the peripheral surface of the photoconductor drum 1 and main scanning is performed to form a bright line. Therefore, an electrostatic latent image corresponding to the first color is formed on the peripheral surface of the photosensitive drum 1 by the main scanning by the laser beam and the sub-scanning by the rotation of the photosensitive drum 1.

The electrostatic latent image is reversely developed by the developing device 4A loaded with a two-component developer consisting of yellow (Y) toner and a magnetic carrier, and a toner image is formed on the photosensitive drum 1. The obtained toner image is the photosensitive drum 1.
After passing through the transfer device 5 and the cleaning device 6 which are separated from the photoconductor drum 1 while being held on the surface thereof, the next image forming cycle is started.

The photosensitive drum 1 is recharged by the scorotron charger 2, and then a digital signal corresponding to the second color is input to the image writing device 3.
Writing on the surface of the photosensitive drum 1 is performed in the same manner as in the case of the first color signal described above, and an electrostatic latent image is formed. The electrostatic latent image is a developing device 4B loaded with a two-component developer including a magenta (M) toner and a magnetic carrier as a second color.
Reverse development is performed by. This magenta (M) toner image is also formed on the previously formed yellow (Y) toner image.

4C is a developing device having a two-component developer composed of cyan (C) toner and a magnetic carrier, and a cyan (C) toner image is formed on the surface of the photosensitive drum 1 in the same manner as the first and second colors. Form. Further, 4D is a developing device having a two-component developer composed of black toner and a magnetic carrier, and forms a black toner image on the surface of the photosensitive drum 1 by the same processing as the above-mentioned color.

The multicolor toner image thus formed on the peripheral surface of the photosensitive drum 1 is sent from the paper feeding device 9 by applying a high voltage having a polarity opposite to that of the toner to the transfer pole 5a of the transfer device 5. It is configured to be transferred to a transfer material.

That is, the transfer material stored in the paper feeding device 9 is fed to the transfer device 5 at the same timing as the image formation on the photosensitive drum 1 by carrying out the uppermost one sheet by the rotation of the paper feeding roller 10. To be done.

The transfer material having undergone the image transfer in this way is separated from the photosensitive drum 1 along the transfer belt 5b of the transfer device 5. The transfer material separated from the transfer belt 5b by a paper removing electrode (not shown) is conveyed to the fixing device 12 by the conveying belt 11, the image is fused by the fixing roller 12a of the fixing device 12, and then the paper discharge roller 12b.
And is discharged onto the discharge tray 13.

On the other hand, the photosensitive drum 1 which has been transferred to the transfer material is further rotated to bring the blade 6a of the cleaning device 6 and the toner carrying roller 6b into a pressure contact state to remove the residual toner, After finishing the blade 6
a is separated, and shortly thereafter, the toner carrying roller 6b is separated and a new image forming process is started.

FIG. 5 shows an enlarged sectional view of the developing area. An AC bias voltage with a DC bias superimposed is applied to the developer transport body 41 during development, and at least a DC bias voltage is applied when the electrode member 45a is formed. As a result, a first oscillating electric field 48 for flying the toner is formed between the electrode member 45a and the developer carrying body 41, and a first oscillating electric field is created between the image carrier 1 and the developer carrying body 41. A weaker second oscillating electric field 49 is formed. The toner cloud generated by the first oscillating electric field 48 is guided to the second oscillating electric field side and is further guided to the image carrier 1 to promote toner adhesion on the image carrier 1.

When the plate member 45 is set in the developing space A, the angle θ formed by the tip of the electrode portion and the position where the developer carrier 41 and the image carrier 1 face each other is larger in view of developability. Although it is preferable, if it is too large, the effect of installing the electrode member 45a in the developing space A is lost, so θ is 0 to 2
An angle of 0 ° is desirable. If the gap between the photoconductor drum 1 and the developer transport body 41 is small, the bias voltage to be applied can be reduced, but if it is too small, it becomes difficult to install the plate electrode 45 having the electrode portion. 2 to 1.0 mm is preferable. Also, the developer carrier
It is preferable that the distance between 1 and the developer carrying member downstream side electrode portion 45c is 0.2 to 0.6 times the gap between the developer carrying member 41 and the image carrier 1. Moving speed V of the developer transport body 41
_S (mm / sec) and moving speed V _P (mm /
If the ratio of (sec) is large, the developability is improved, but if it is too large, the edge effect at the trailing edge of the image becomes remarkable, so that the range of V _S / V _P = 0.5 to 4.0 is preferable. If the amount of the developer transported by the developer transport body 41 is large, the developability is improved, but if it is too large, the carrier adheres to the photosensitive drum 1 due to the spikes, so that the amount is 5 mg / cm ² to 40 mg / cm ^2. It is preferably included in the range of ² .

The waveform of the AC voltage component applied to the developer carrier 41 is not limited to a rectangular wave, but may be a sine wave or a triangular wave. The higher the voltage value, the more the toner vibrates and the developability improves. However, if the voltage value is too high, the lightning strike phenomenon on the photosensitive drum 1 due to the dielectric breakdown and the fogging on the non-image area become remarkable. Therefore the applied AC bias voltage (V _AC p-p)
Is preferably in the range of 200V to 2kV. If the frequency is low, it is advantageous for the developability and gradation, but if it is too low, the toner previously developed on the image carrier 1 is returned to the developing device to cause color mixing. Therefore, the frequency is 500Hz
To 20 kHz is preferred. The fogging is prevented by controlling the DC voltage component applied to the developer transport body 41, and the dielectric breakdown is provided with an insulating or semi-insulating coating on the surface of the developer transport body 41. The carrier can be prevented by providing an insulating coating.

As the developer used in the developing device of the present invention, preferable toner is styrene resin, vinyl resin,
Acrylic resin, polyamide resin, silicone resin, polyester resin, fluororesin, epoxy resin, and other resins are mixed with a coloring component such as a color pigment or color dye and a charge control agent, etc. It can be made by any method. This is obtained by selecting particles having an average particle size of 20 μm or less, preferably 5 to 10 μm, by a conventionally known particle size selecting method. The charge amount of the toner depends on the particle size, but is preferably 3 to 300 μC / g, and more preferably 10 to 50 μC / g.

The carrier may be a metal such as iron, chromium, nickel, cobalt, zinc or copper, or a compound or alloy thereof such as γ-ferric oxide, chromium dioxide, manganese oxide, or a ferromagnetic material such as ferrite. Spherical particles of the body or paramagnetic material, or those magnetic particles surface spherical coating with a resin such as styrene resin, vinyl resin, ethylene resin, acrylic resin, polyamide resin, polyester resin, or Particles obtained by forming spherical particles of resin or fatty acid wax containing dispersed magnetic fine particles are used. An average particle size of 70 μm or less, preferably about 30 to 50 μm is suitably used. If the average particle diameter is larger than this, unevenness appears in the toner image and the toner density becomes low, so that problems such as high-density development occur. If it is smaller than this, the photosensitive drum 1 together with the toner occurs. It causes a problem of flying above. Further, it is more preferable that the carrier is spherical because the stirring property and the transport property of the toner and the carrier are improved and the charge controllability of the toner is also improved. Coating the carrier particles with a resin or the like has the effect of increasing the bias voltage applied to the developer transport body 41. Therefore, even if a high bias voltage is applied to the developer transport body, the photosensitive drum 1 is not discharged and the image is not disturbed. Further, the carrier having a resistivity of 10 ⁸ Ωcm or more, preferably 10 ¹³ Ωcm or more, is preferable. This resistivity was measured by placing the particles in a container having a cross section of 0.5 cm ² and tapping them, and then putting 1 on the packed particles.
A load of Kg / cm ² is applied, and 1 is applied between the load and the bottom electrode.
It is a value obtained by reading the current value when a voltage that generates an electric field of 000 V / cm is applied. When this resistance value is low, when a bias voltage is applied to the developer transport body 41, electric charges are injected into the carrier, carrier particles adhere to the photosensitive drum, and a bias voltage breakdown easily occurs.

In the developing device of the present invention, the two-component developer in which the spherical carrier and the toner are mixed as described above is preferably used, and a fluidizing agent for increasing the fluidity of the particles, if necessary. Also, a cleaning agent for cleaning the surface of the image forming body can be mixed with the toner. As the fluidizing agent, colloidal silica, silicon varnish, metal soap, nonionic surface active agent and the like can be used, and as the cleaning agent, fatty acid metal salt, organic group-substituted silicon, fluorine and other surface active agents can be used. You can

(Comparative Example) Experimental machine: 9028 (manufactured by Konica Corporation) Modified machine Developer: Carrier is an ferrite having apparent density of 2.45 g / cm ³ , volume average particle diameter of 45 μm, and saturation magnetization of 60 emu / g. Spherical magnetic carrier coated with resin is used. Toner is styrene / acrylic resin 100
A non-magnetic toner having a weight average particle size of 7 μm, which is produced by kneading a charge control agent in an amount of 10 parts by weight of a pigment and a necessary amount of a charge control agent and has a toner ratio of 10 wt% with respect to a carrier, 600 g of a black developer was prepared so that the average toner charge amount measured by the development separation method was −20 μC / g.

Image carrier: OPC photosensitive drum, diameter φ1
80 mm, peripheral speed is 140 mm / sec Developer carrier: Roughened stainless steel by sand blasting, diameter φ20 mm, rotation speed is 300 rpm Plate-shaped member having electrode part: Epoxy resin reinforced by glass fiber (thickness: 0. 16mm) copper foil was formed on the electrode by etching to form an electrode part with a width of 0.5mm, and the dielectric constant at 1MHz was 4.5 at 25 ° C. Gap between developer carrier and image carrier: 0.5mm Closest distance between the agent carrier and the electrode part: 0.25 mm V _S / V _P = 2.24 Developer carrier amount: 10 mg / cm ² Maximum potential of the electrostatic latent image of the image carrier 1 at the black developing position: − 800V Bias voltage applied to electrode part: DC bias voltage:-
700V Bias voltage applied to the developer carrier: DC bias voltage component: -700V AC bias voltage component: 8kHz, 800V When gray paper was copied in monochrome mode under the above conditions, the initial output image showed uneven density. It was an unclear thing. The original width is 100μm, 200μm, 3
When a black line of 00 μm was drawn, the line width was different depending on the place and the original was not reproduced. When 10,000 copies were made under these conditions, the density unevenness became severe and the image became extremely unclear.

Example 1 Experimental machine: 9028 (manufactured by Konica Corporation) Remodeling machine Developer (42): Carrier has an apparent density of 2.45 g / c
m ³ , volume average particle diameter 45 μm, saturation magnetization 60 emu / g
A spherical magnetic carrier obtained by resin-coating ferrite particles consisting of is used. The toner is produced by kneading 100 parts by weight of styrene-acrylic resin and 10 parts by weight of a pigment with a necessary amount of a charge control agent, and by a pulverization and granulation method. 600 g of a black developer was prepared so that the toner ratio of the obtained non-magnetic toner having a weight average particle diameter of 7 μm was 10 wt% with respect to the carrier and the average toner charge amount measured by the development separation method was −20 μC / g.

Photoconductor (1): OPC photoconductor drum (φ1
80) Peripheral speed is 140 mm / sec Developer carrier (41): Stainless steel is roughened by sandblasting, diameter φ20 mm, rotation speed is 300
rpm plate member (45): The insulating member 45b is stacked and supported near the tip of the electrode member 45a. A 0.1 mm thick stainless steel plate was used as the material of the electrode member 45a, a 0.1 mm thick glass epoxy resin plate was used as the insulating member 45b, and an ultraviolet curable resin was used as the adhesive. Further, the width L1 of the electrode member 45a = 0.5 mm, the electrode member 4
Width L2 of the tip eaves portion of 5a = 1 mm, electrode member 45a
Thickness of h1 = 0.1 mm, height of insulating member 45b h2 =
It was formed to 0.1 mm.

Gap between the developer carrier 41 and the image carrier 1:
0.5 mm The closest distance between the developer transport body 41 and the electrode member 45a: 0.
25 mm V _S / V _P = 2.24 Developer transport amount: 10 mg / cm ² Maximum potential of electrostatic latent image on image carrier 1 at black developing position: −800 V Bias voltage applied to electrode member 45 a: DC bias voltage : -700V Bias voltage applied to the developer carrier 41: DC bias voltage component: -700V AC bias voltage component: 8kHz, 800V When gray paper was copied in black and white mode under the above conditions, the output image was a dark image. It was even and clear. Also, when black lines with original widths of 100 μm, 200 μm, and 300 μm were drawn, the original width was reproduced almost faithfully over the entire area. Using this 1
After copying 10,000 copies, the image was clear with no density unevenness as in the initial image. In addition, the original line width was reproduced almost exactly over the entire line width. Also, the toner density is kept almost constant.

(Example 2) Experimental machine: 9028 (manufactured by Konica Corporation) Remodeling machine Developer (42): Carrier apparent density 2.45 g / c
m ³ , volume average particle diameter 45 μm, saturation magnetization 60 emu / g
A spherical magnetic carrier obtained by resin-coating ferrite particles consisting of is used. The toner is produced by kneading 100 parts by weight of styrene-acrylic resin and 10 parts by weight of a pigment with a necessary amount of a charge control agent, and by a pulverization and granulation method. 600 g of a black developer was prepared so that the toner ratio of the obtained non-magnetic toner having a weight average particle diameter of 7 μm was 10 wt% with respect to the carrier and the average toner charge amount measured by the development separation method was −20 μC / g.

Photoconductor (1): OPC photoconductor drum (φ1
80) Peripheral speed is 140 mm / sec Developer carrier (41): Stainless steel is roughened by sandblasting, diameter φ20 mm, rotation speed is 300
rpm plate member (45): The insulating member 45b is stacked and supported near the tip of the electrode member 45a. A mesh-formed stainless steel plate having a thickness of 0.1 mm was used as the material of the electrode member 45a, a glass epoxy resin plate having a thickness of 0.1 mm was used as the insulating member 45b, and an ultraviolet curable resin was used as an adhesive. The shape of the mesh used was an electrode member 45a as shown in FIG. 50 mesh intervals
0 μm, and the line forming the mesh was 100 μm. Further, the width L1 of the electrode member 45a = 0.5 mm, the electrode member 4
Width L2 of the tip eaves portion of 5a = 1 mm, electrode member 45a
Thickness of h1 = 0.1 mm, height of insulating member 45b h2 =
It was formed to have a thickness of 0.1 mm.

Gap between developer carrier 41 and image carrier 1:
0.5 mm The closest distance between the developer transport body 41 and the electrode member 45a: 0.
25 mm V _S / V _P = 2.24 Developer transport amount: 10 mg / cm ² Maximum potential of electrostatic latent image on image carrier 1 at black developing position: −800 V Bias voltage applied to electrode member 45 a: DC bias voltage : -700V Bias voltage applied to the developer carrier 41: DC bias voltage component: -700V AC bias voltage component: 8kHz, 800V When gray paper was copied in black and white mode under the above conditions, the output image was a dark image. It was even and clear. Also, when black lines with original widths of 100 μm, 200 μm, and 300 μm were drawn, the original width was reproduced almost faithfully over the entire area. Using this 1
After copying 10,000 copies, the image was clear with no density unevenness as in the initial image. In addition, the original line width was reproduced almost exactly over the entire line width. Also, the toner density is kept almost constant.

Although the 9028 modified machine is used as the image forming apparatus in the embodiment of the present invention, the present invention can be similarly used for an image forming apparatus having a similar configuration. That is, it is needless to say that an apparatus for writing an image on a photosensitive drum or a photosensitive belt, which is an image carrier, to form an image, such as a copying machine, a printer, a facsimile or a composite machine of these, can be used in the same manner. .

The image forming apparatus of the present invention is suitable for a two-component developer composed of carrier and toner.
A single-component developer can be used with the same constitution.

[0052]

As described above, according to the present invention, it is possible to provide a developing device capable of obtaining a clear recorded image without density unevenness.

That is, an energizable plate-like member is installed in the developing space where the developer carrier and the image carrier are opposed to each other, and the plate-like member is provided with an energizable electrode member and the developing member supported by the electrode member. It is composed of an insulating member that is in contact with the developer layer of the developer carrier, at least a DC voltage is applied to the electrode member, and a superimposed voltage of a DC component and an AC component is applied to the developer carrier to remove the toner. By the developing device that flies and develops the latent image on the image carrier, the effective developing gap is reduced, the developing bias voltage can be set low, and the plate member can be set accurately, The toner density is also kept almost constant, and there is no streak or density unevenness in the output image, and a clear recorded image can be obtained. Further, the toner is prevented from scattering toward the upstream side of the developer transport body, and a clear recorded image can be obtained.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an image forming apparatus having a developing device of the present invention.

FIG. 2 is a perspective view of various mesh-shaped electrode members 45a.

FIG. 3 is a schematic diagram showing the configuration and arrangement of a plate-like member composed of an electrode member and an insulating member used in the developing device of the present invention.

FIG. 4 is an overall configuration diagram showing an embodiment of an image forming apparatus using the developing device of the present invention.

FIG. 5 is an enlarged cross-sectional view showing a developing area of an image forming apparatus using the developing device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum (image bearing member) 4, 4A, 4B, 4C, 4D Developing device 41 Developer carrier 42 Developer 45 Plate member 45a Electrode member 45b Insulating member 46 Developer transport restricting rod 47 Scraper 48 First Oscillating electric field 49 Second oscillating electric field 50 Insulating member A Development space E1 DC bias power source (developer carrier side) E2 AC bias power source (developer carrier side) E3 DC bias power source (electrode side) E4 AC bias power source (electrode) Part side) L2 electrode width P contact position of developer carrier and insulating member

Claims (4)

[Claims] 1. A plate member capable of being energized is installed in a space where a developer carrier and an image carrier face each other, at least a DC voltage is applied to the plate member, and a DC component is applied to the developer carrier. And a developing device for developing a latent image on the image carrier by applying a superimposed voltage of an alternating current component to fly the toner, wherein the plate-shaped member is an electrode member that can be energized, and the developing member is supported by the electrode member. A developing device comprising an insulating member that is in contact with the developer layer of the agent carrier. 2. The developing device according to claim 1, wherein the electrode member of the plate-shaped member is made of non-magnetic steel. 3. The developing device according to claim 1, wherein a mesh is formed on the electrode member of the plate-shaped member. 4. The surface of the plate-shaped member at least on the developer transporting body side is coated with a compound containing fluorine.
Item 6. The developing device according to item 1.