JPH09197808A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device suitable for a non-contact developing method capable of preventing developer from being welded on a control electrode plate and lengthwise stripes or irregularity from occurring by eliminating trouble in the conventional control electrode method. SOLUTION: A developer carrier 41 provided in opposite to an image holding body 1 and a control electrode having an electrode part 48 capable of impressing voltage, which is supported to be cantilevered by an elastic supporting member 50, in a gap between the image holding body 1 and the developer carrier 41 are arranged in this device. At least the surface of the control electrode on a side opposite to the developer carrier 41 is coated with resin containing at least conductive particles and fluorine, and at least the surface on the side opposite to the carrier 41 is coated with at least fluororesin.

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 developing space upstream of a developing space where an image forming body and a developer carrying body face each other. The present invention relates to a developing device in which a control electrode having an electrode portion is installed, a developer is supplied to the developer transport body, and toner is caused to fly under an oscillating electric field to perform development.

[0002]

2. Description of the Related Art Conventionally, as one of the developing methods used in electrophotographic copying machines, there is a one-component developing method using a non-magnetic toner. This developing method has a cylindrical developer carrier (developing sleeve) rotatably supported with a roughened surface, and supports charged toner on the surface of the developing sleeve to develop a developing space (developing area). It is carried to and developed.

For the one-component developing method, a magnetic carrier having a particle size of several tens to several hundreds 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, if the toner particles have a size of 10 μm or less, the influence of the van der Waals force is relatively large with respect to the Coulomb force at the time of development. It becomes difficult to prevent even by applying a DC bias to the developer transport body. Since the carrier coverage of the toner becomes high, the charge control becomes difficult. In the two-component development method, in which toner aggregation easily occurs, the carrier coverage of the toner becomes high, which makes charging control more difficult. To decrease the carrier coverage, the carrier particles are Particles also become attached to the electrostatic latent image portion of the imager. 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 the ground portion 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, an insulating member having an electrode portion in the upstream portion of the developing area is brought into contact with the developer transport body, and the electrode portion and the developer transport body, and the developer transport body and the image formation. A method of forming an oscillating electric field in which the former becomes stronger between the bodies and developing the toner in the developer by clouding is described in JP-A-5-346736 and JP-A-6-17.
No. 5485.

[0007]

However, in the above-mentioned control electrode method, the developer is fused to the control electrode due to frictional heat generated between the control electrode and the developer layer, and development of that portion is performed. The transfer of the agent is hindered, and white lines and unevenness occur on the image.

The object of the present invention is to solve the above problems of the control electrode method, to prevent the developer from being fused to the control electrode plate, to prevent vertical stripes, unevenness, etc., which is suitable for the toner cloud developing method. It is to provide a device.

[0009]

SUMMARY OF THE INVENTION The above-mentioned objects are cantilevered by a supporting member having elasticity in a gap between the image forming body and the developer carrying body, the developer carrying body being opposed to the image forming body. In a developing device in which a supported control electrode having a voltage-applicable electrode part is arranged, at least a surface of the control electrode facing the developer transport body is covered with a resin containing at least conductive fine particles and fluorine. It is achieved by the developing device.

Further, the above object is to apply a voltage, which is cantilevered and supported by a supporting member having elasticity, to a developer carrying body provided facing the image forming body and a gap between the image forming body and the developer carrying body. In a developing device in which a control electrode having a possible electrode portion is arranged, at least the surface of the control electrode facing the developer transport body is covered with a fluorine-based resin. To be done.

[0011]

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

Prior to the description of the embodiments of the present invention, the configuration of a color printer, which is an example of an image forming apparatus having the developing device of the present invention, will be described with reference to the sectional configuration diagram of FIG.

In this color printer, after each color toner image sequentially formed on the image forming body is superimposed, the color image is formed by transferring once on a recording paper in a transfer section, and then the image is formed by a separating means. This is a color image forming apparatus of a method of peeling off from a surface of a formed body.

In FIG. 1, reference numeral 1 denotes a photosensitive drum, which is an image forming member, and is formed by coating an OPC photosensitive member (organic optical semiconductor) on a drum substrate, which is grounded and driven and rotated clockwise in the drawing. Reference numeral 2 denotes a corona charger, which applies uniform charge of high potential VH to the peripheral surface of the photosensitive drum 1 by corona discharge by a grid held at a grid potential VG and a corona discharge wire. Prior to the charging by the corona charger 2, exposure is performed by a PCL (pre-charging static eliminator) 9 using a light emitting diode or the like to eliminate the history of the photoconductor until the previous printing, and the peripheral surface of the photoconductor is neutralized. deep.

After the photosensitive drum 1 is uniformly charged, the image exposure means 3 performs image exposure based on an image signal.
The image exposure unit 3 is a main scanning unit that is driven by an optical system including a polygon mirror that rotates using a laser diode (not shown) as a light emitting source, an fθ lens, and a cylindrical lens reflection mirror. An image is formed. In this printer, the character portion is exposed to form a reverse latent image in which the character portion has a lower potential VL.

Around the peripheral edge of the photosensitive drum 1, developing devices 4Y and 4M each containing a developer composed of toner such as yellow (Y), magenta (M), cyan (C), and black (K) and a carrier are incorporated. , 4C, 4K are provided. These developing devices 4Y, 4M, 4C, 4K
Since they have almost the same configuration, these developing devices will be hereinafter referred to as the developing device 4 as a representative.

FIG. 2 is a sectional view of the developing device 4. In the figure, 40 is a developing device casing, 41 is a developing sleeve which is a developer carrying body having a fixed magnet body 42, and 4
3 is a developer supply roller, 44 is a regulating rod which is a developer transport amount regulating member, 45 and 46 are developer agitating rollers, 47 is a toner replenishing port opening at the upper part of the developing device casing,
D is a two-component developer composed of toner and carrier.

The developer carrier 41 is a hollow cylinder made of aluminum alloy, stainless steel or the like which is roughened by sandblasting or the like, and the surface thereof is indicated by JIS standard 10-point average roughness (JIS-B0610). ~ 2μ
m.

In the space where the developer transport body 41 and the image forming body 1 face each other, the electrode portion 4 supported by the insulating member 49 is provided.
8 has been inserted. The vicinity of the tip of the insulating member 49 is configured to be in pressure contact with the developer transport body 41, and the base of the insulating member 49 is laminated and fixed on the free end side of a cantilevered supporting member.

A bias voltage capable of superimposing an alternating current on a direct current is applied to the developer carrier 41 via a protective resistance R1 by a direct current bias power source E1 and an alternating current power source E2. Further, a bias voltage capable of superimposing an alternating current on a direct current is applied to the electrode portion 48 by a direct current bias power source E3 and an alternating current power source E4 via a protection resistor R2.

At least a DC voltage is applied to the electrode portion 48, and a superimposed voltage of a DC voltage component and an AC voltage component is applied to the developer transport body 41 to remove the toner on the developer transport body 41. The latent image on the image forming body 1 is developed by flying.

First, the development of the first color yellow is carried out by the developing sleeve 41 which contains a magnet and holds the developer and rotates. The developer is, for example, a two-component carrier composed of a carrier having a core of ferrite coated with an insulating resin, and a toner having a pigment as a main material and a charge control agent, silica, titanium oxide, etc., according to the color. A developer can be used. The developer is 100 to 60 on the developing sleeve 41 by the layer forming means.
It is regulated to a layer thickness (developer) of 0 μm and transported to the development area.

The gap between the developing sleeve 41 and the photosensitive drum 1 in the developing area is larger than the layer thickness (developer) of 0.2.
As ~1.0mm, AC bias and V of V _AC during this time
_DC bias of DC is superimposed and applied. V _DC and V _H ,
Since charging of the toner is the same polarity, the toner given the opportunity to leave from the carrier by V _AC is not adhere to a portion of the high V _H of potential than V _DC, the lower V _L portion of potential than V _DC Adhesion and visualization (reversal development) are performed.

After the visualization of the first color is completed, the process proceeds to the image forming process of magenta for the second color, and the scorotron charger 2 again.
Is uniformly charged by the image exposure means 13 to form a latent image based on the image data of the second color. At this time, the charge removal by the PCL 11 performed in the image forming process for the first color is
This is not performed because the toner attached to the image portion of the first color scatters due to a sharp drop in the surrounding electric potential.

A latent image similar to that of the first color is formed on the portion of the photosensitive member having the potential of V _H all over the peripheral surface of the photosensitive drum 10 without the image of the first color, and development is performed. However, in the portion where the first-color image is developed again, the latent image of V _M ′ is formed by the light-shielding toner of the first color and the electric charge of the toner itself.
Developing in response to the potential difference between the _DC and V _M 'is performed. In the overlapping portion of the first color image and the second color image, development of the first color is performed by V
_When the latent image of _L is formed, the balance between the first color and the second color is lost, so that the exposure amount of the first color is reduced and V _H > V _M >
In some cases, the intermediate potential may be V _L.

An image forming process similar to that of the magenta of the second color is performed for the cyan of the third color and the black of the fourth color, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 1.

The toner supply device for controlling and supplying new color toners to the developing devices 4Y, 4M, 4C and 4K is as follows.
A plurality of removable toner cartridges 4A, a plurality of toner containing portions 4B connected to the toner cartridges 4A, and the toner in the toner containing portions 4B are transferred to the developing device 4 (Y, M,
It is composed of a plurality of toner transport units 4D that transport the toner to C, K).

On the other hand, one transfer material (transfer paper or the like) discharged from the paper feeding cassette 5A of the paper feeding section 5 via the half-moon roller 5B is temporarily stopped by the registration roller pair 5C, and the transfer timing is adjusted. At this point, the registration roller pair 5C is rotated to feed the sheet to the transfer area. In the transfer area, the transfer means (transfer roller) 6 is pressed against the peripheral surface of the photosensitive drum 1 in synchronization with the transfer timing, and the supplied transfer material is nipped and a multicolor image is transferred at once. It Then, the transfer material is destaticized by the separating means 7, separated from the peripheral surface of the photosensitive drum 1 and conveyed to the fixing device 8, where a heat roller (upper roller) is used.
The toner is melted by heating and pressurizing the pressure roller 8A and the pressure roller (lower roller) 8B, and then the toner is discharged onto a discharge tray outside the apparatus through discharge rollers 8C and 8D. The transfer means 6 is retracted from the peripheral surface of the photosensitive drum 1 after the transfer material P has passed, and is ready for the formation of the next toner image.

The photosensitive drum 1 from which the transfer material has been separated has residual toner removed and cleaned by pressure contact with the blade 10A of the cleaning device 10, and is again charged by the PCL 9 and charged by the corona charger 2 to form the next image. Enter the process of. The blade 10A moves immediately after cleaning the surface of the photoconductor and retracts from the peripheral surface of the photoconductor drum 1. The waste toner scraped into the cleaning device 10 by the blade 10A is the screw 1
After being discharged by 0B, it is stored in a waste toner collecting container (not shown).

FIG. 3 is a schematic view showing the structure and arrangement of the control electrodes that can be used in the present invention. The control electrode includes an electrode portion 48, an insulating member 49 that holds the electrode portion 48,
The insulating member 49 is supported with high linearity and is fixed to the developing device casing 40 of the developing device 4 by a supporting member 50 having elasticity.

FIG. 3A shows a supporting member 50 having elasticity.
An electrode portion 48 is provided on the side of the tip end facing the image forming body 1 and is pressed against the image forming body 1 at the closest point P by the elasticity of the supporting member 50. Here, the electrode portion 48
Is L, and the closest distance between the tip of the electrode portion 48 and the developer transport body 41 is h. Further, the electrode portion 48 is arranged so as to be located on the downstream side in the rotation direction of the developer transport body 41 with respect to the support member 50 and the closest contact point P of the developer transport body 41. With this configuration, the toner cloud does not occur on the upstream side of the closest contact point P, and the toner concentration of the developer on the downstream side can be kept uniform.

The insulating member 49 is a supporting member 5 having elasticity.
It can also be supported by stacking with 0. At this time, the region where the insulating member 49 and the supporting member 50 are laminated is d1, and the distance from the tip of the supporting member 50 to the tip of the insulating member 49 is d2. Further, the insulating member 49 is normally used by being supported by the supporting member 50 via an adhesive agent or the like, but the insulating member 49 is directly pressed by the supporting member 50 to support the insulating member 49 without inclusions. It is also possible.

FIG. 3B shows a plurality of electrode portions 48a and 48b.
Are formed on both surfaces of the insulating member 49. At this time, it is preferable to reduce the distance between the upstream electrode portion 48a and the downstream electrode portion 48b because the toner can be pushed out to the developing area.

In FIG. 3C, an eaves portion 49a is provided in the vicinity of the tip of the insulating member 49 and in front of the electrode portion 48. This is preferable because fogging at the time of developing the other color toner can be suppressed.

FIG. 3D shows that the position of the laminated surface of the support member 50 with respect to the insulating member 49 having the electrode portion 48 shown in FIG. 3A is changed and supported.

FIG. 3E shows a structure in which the position of the laminated surface of the supporting member 50 with respect to the insulating member 49 having the electrode portion 48 shown in FIG.

FIG. 3F shows that the position of the stacking surface of the support member 50 with respect to the insulating member 49 having the plurality of electrode portions 48a and 48b shown in FIG. 3B is changed and supported.

In the above description, the insulating member 49 having the electrode portion 48 used in the developing device 4 of the image forming apparatus of the present application.
As the configuration and arrangement of the supporting member 50 and the supporting member 50, the one described in FIG. 3 has been described, but it is needless to say that the one having a configuration derived from this can be similarly used in the developing device of the present invention. is there. In addition, the exposed portion of the electrode portions 48, 48a, 48b has a coating layer 5 having a thickness of about 10 to 100 μm in order to prevent current leakage.
It is also desirable to coat 2,55.

FIG. 4A is a sectional view of a control electrode in which a cover layer 55 is formed on the structure of the insulating member 49 having the electrode portion 48 and the supporting member 50 shown in FIG. 3B and the like.
Further, FIG. 4B shows the electrode portion 4 shown in FIG.
8 is a cross-sectional view in which a coating layer 55 is formed on the structure of an insulating member 49 having 8 and a supporting member 50. FIG.

The details of each part of the developing device according to the present invention will be described below.

Control Electrode The control electrode fixes the electrode portion 48, the insulating member 49 holding the electrode portion 48, and the insulating member 49 with high linearity to the developing device casing 40 of the developing device 4. And a supporting member 50 (see FIGS. 2 and 3).

-Electrode portion 48-The electrode portion 48 is formed by using a conventionally known printed circuit board manufacturing method, by attaching an electrolytic copper foil, beryllium copper foil or the like to an insulating member 49 described later with an adhesive, and using a conventionally known photopolymer. The necessary electrode portion 48 is formed on the insulating member 49 by a photo-etching method using the above and an etching resist forming method by screen printing. In addition, a method of printing a conductive ink by letterpress, stencil, intaglio, planographic printing, or a method of depositing a metal can be used.

The preferable range of the width L of the electrode portion 48 is determined by the conditions that give an oscillating electric field to fly from the developer transport body 41 to the image forming body 1. That is, it depends on the moving speed V _S (mm / sec) of the developer transport body 41 and the frequency f _AC (Hz) of the AC bias voltage applied to the developer transport body 41. Moving speed V _S (mm / sec) of the developer transport body 41
Is faster, the amount of developer conveyed is increased, which is effective in improving the developability. However, if too fast, the image density is biased, so 100 to 500 (mm / sec) is preferable. Frequency f
_{If the AC} is low, it is advantageous for the developability and gradation, but if it is too low, the toner previously developed on the photosensitive drum 1 is pulled back to the developing device, resulting in color mixture. Therefore, the frequency f _AC is preferably in the range of 500 Hz to 20 kHz.
However, considering the number of vibrations due to the balance between both electrode plates, 5 ≦ L · f _AC / V _S ≦ 20 is preferable, and the width L (mm) is preferably 0.05 ≦ L ≦ 1.0.

The electrode portion 48 is 100 in the developer transport direction.
Copper foil or Ag / Pd with a width of about μm to 2000 μm
A paste, gold foil, or the like is used and is supported by the insulating member 49.

FIG. 5 is a schematic view showing various configurations of the electrode section. In the figure, (a) is the configuration shown in FIGS. 3 (a) and 3 (d), (b) is a configuration in which an insulating eave member 51 is provided on the electrode portion 48, and (c) and (d) are electrodes. A configuration in which an insulating coating 52 is provided on the portion 48, (e) is a configuration in which the electrode portion 48 is provided below the insulating eaves member 51, and (f) is an insulating member 49 as in FIG. 3 (c). In this structure, an eaves portion 49a is provided in the vicinity of the tip of the electrode and before the electrode portion 48.

5 (g) to 5 (j) show a structure in which a conductive circular wire 53 is used as an electrode portion and is bonded to the insulating member 49 or the insulating eave member 51. FIG. 5 (k)-
(M) is a configuration in which a conductive rectangular wire 54 is used as an electrode portion and is bonded to the insulating member 49 or the insulating eaves member 51.

-Insulating member 49- The insulating member 49 is made of, for example, polyester, polyimide, glass epoxy, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-6-fluoropropylene copolymer, poly-4 fluoride. Insulating resins such as ethylene oxide, polyamideimide, polysulfol, triazine resin, polyethylene terephthalate, polyurethane, etc., or composite materials reinforced with glass fiber etc., paper, paper phenol, varnish, silicone rubber, etc., or ceramics Alumina (Al ₂ O ₃ ) based, single crystal sapphire (A
l ₂ O ₃ ), forsterite (2MgO / SiO ₂ ).
Series, steatite (MgO / SiO ₂ ) series, zircon (ZrO ₂ · SiO ₂ ) series, cordierite (2MgO · 2)
Al ₂ O ₃ .5SiO ₂ ), titania, silicon carbide (S
iC) -based, silicon nitride (Si ₃ N ₄ ) -based, zirconia (Zr
O ₂ ) type ceramics and cermet type ceramics can be used.

In order to impart appropriate elasticity to the insulating member 49, the ceramic has a weight percentage of 5 to 20 wt.
% Resin may be used. Among the above materials, as the insulating member, polyimide, glass epoxy, ethylene-tetrafluoroethylene copolymer, poly-4 fluoride, which has relatively good heat resistance, can withstand the firing temperature during the fluororesin coating. It is preferable to use ethylene oxide, polyamide imide, polysulfol, triazine resin, ceramic type.

-Supporting Member 50-The supporting member 50 is preferably a thin metal plate having high linearity and elasticity. For example, as the conductive member constituting the discharge electrode, copper, copper-zinc, copper-cadmium, phosphor bronze,
A metal, an alloy, or a mixture of copper-beryllium, Corson alloy, aluminum, aluminum alloy, tantalum, tungsten, nickel, molybdenum, stainless steel, gold, titanium, chromium, palladium, silver, or the like can be used. Among these, it is preferable to use a stainless steel thin plate from the viewpoints of cost, flexibility, and the like. Although the thickness of the support member 50 depends on the material, it is preferably 0.03 mm to 1 mm in consideration of the ease of attachment to the insulating member 49. If the thickness is less than 0.03 mm, wrinkles and distortion are likely to occur when mounted on the insulating member 49.
When the thickness is larger than mm, elasticity is lost and the degree of freedom in setting the control electrode is narrowed. When these metal thin plates are used for the supporting member 50, it is preferable that the metal thin plates are insulatingly coated in order to prevent leakage of the voltage applied to the developer transport body 41 and the photoconductor potential.

The thickness t1 of the electrode portion of the control electrode is preferably (1/10) g0 <t1 <(2/3) g0, where the development gap g0 (mm). When the thickness t1 of the electrode portion is ⅔g0 or more, a dielectric is formed on the electrode portion 48, so that an electric field is strengthened above the electrode portion 48 and a latent image is formed when a high voltage is applied to the electrode. Distortion or image forming body 1 at the time of multicolor image formation
There is a risk of peeling off the other color toners above. If the thickness t1 of the electrode portion is 1/10 g0 or less, the electrode portion 4
Since 8 is separated from the developer transport body 41, the electric field is weakened and a sufficient toner cloud is not formed. Moreover, the rigidity of the control electrode plate is lowered, and the control electrode plate is easily cracked. The electrode thickness of the control electrode plate is a micrometer (M320-25, manufactured by Mitutoyo Corporation).
According to A), the average value of the values measured at 20 points in the axial direction of the developer transport body 41 of the electrode portion 48 was defined as the thickness of the electrode portion 48.

Coating Material-1 —Fluorine Resin Coating— The fluorine resin coating is classified into dispersion paint and powder paint. Dispersion paint
A sub-micron order fluororesin dispersed in water or an organic solvent, and a fluorocarbon resin coating prepared by dispersing a fluororesin in a plastic solvent such as epoxy, phenol, amide imide, polyurethane or silicone as a dispersion medium. Say. The fluororesin used as a paint includes tetrafluoroethylene resin (PTFE), vinyl fluoride resin (PVF), tetrafluoroethylene hexafluoropropylene copolymer resin (FEP), vinylidene fluoride resin (PVdF), Examples thereof include fluorinated ethylene / perfluoroalkyl / vinyl ether copolymer resin (PFA) and tetrafluoroethylene / ethylene copolymer resin (ETFE). When performing fluorine coating, pretreatment may be performed in order to increase the affinity between the paint and the object to be coated. Generally, dipping and degreasing with trichlorethylene, perchlorethylene or the like is used. Further, the surface of the article to be coated may be conditioned by blasting or the like.

As a coating method, in the case of dispersion coating, an air spray method, a dip coating method, a spin coating method, a roller coating method, a curtain flow coating method, an electrodeposition coating method and the like can be used. For powder coating, the air spray method, fluidized dipping method, etc. are used. After coating, a coating film is obtained by drying, firing and cooling.

In addition to this, as a method of fluorine coating, coating utilizing a plasma polymerization reaction can be used. For example, by introducing a fluorine-based monomer such as ethylene tetrafluoride (TFE) and performing plasma polymerization in a reactor, a tetrafluoroethylene resin (PTFE) -like coating can be obtained. The coating obtained by this method has the advantage of having few pinholes.

Coating Material-2 At least the surface of the control electrode on the side of the developer transport body 41 is coated with the following coating material composed of conductive fine particles and a resin.

-Conductive Particles-Metal powder of silver, gold, platinum, palladium, copper, nickel, tungsten or the like or a mixture thereof, graphite, composite powder of silver coated on glass, amorphous carbon powder, carbon fiber, etc. .

-Fluorine resin-tetrafluoroethylene resin, tetrafluoroethylene / perfluoropropyl vinyl ether copolymer, ethylene tetrafluoride /
Propylene hexafluoride copolymer, ethylene trifluoride monochloride resin, ethylene / tetrafluoroethylene copolymer, vinylidene difluoride resin, vinyl monofluoride resin, propylene hexafluoride / vinylidene difluoride copolymer , Vinylidene fluoride, vinylidene fluoride / propylene hexafluoride copolymer (fluorine rubber), etc.

The above conductive fine particles and fluororesin are made into an aqueous suspension or a solvent suspension and applied on the coated surface (developer carrier side) on the control electrode and dried (at room temperature to room temperature).
(200 ° C.) or placed as a powder on the coated surface on the control electrode and heated for immobilization. From the viewpoint of preventing distortion of the control electrode due to heat, the former coating method using suspension is preferable.

The surface resistivity after coating and drying is 10 ⁸ Ωc
It is preferably m to 10 ¹¹ Ωcm. When it is less than 10 ⁸ Ωcm, an electric field is formed between the developer transport body 41 and the electrode body 48 on the control electrode, and the developability is deteriorated. If it is larger than 10 ¹¹ Ωcm, the toner is excessively charged or reduced due to frictional charging with the fluororesin, which causes development failure, fog, toner scattering and the like.

The coating thickness is preferably about 5 μm to 100 μm, though it depends on the thickness of the control electrode itself.

By applying the coating as described above to the control electrode, the fusion of the toner in the developer can be prevented by the low surface energy of the fluororesin, and the added conductive fine particles can improve the triboelectric chargeability of the fluororesin. To be reduced,
It is possible to solve the problems of poor development, fogging, and toner scattering due to excessive charging or poor charging.

Toner: As a developer used in the developing device 4 of the present invention, a preferable toner is a styrene resin, a vinyl resin, an ethylene resin, a rosin-modified resin, as a toner binder resin.
A resin such as an acrylic resin, a polyamide resin, an epoxy resin, or a polyester resin, a copolymer resin of these styrene-acrylic resins, or a mixed resin thereof is preferable. To this, a coloring component such as a color pigment, and if necessary, a charge control agent, a release agent such as wax, and the like are added, and the toner production method is the same as conventionally known pulverization method, suspension polymerization method, emulsion polymerization method, or the like. Can be made by. The volume average particle diameter D of the toner is determined by a conventionally known particle size selecting method.
₅₀ (μm) is obtained by selecting particles with 4 μm <D ₅₀ <8 μm. When the average particle diameter D ₅₀ is 8 μm or more, the particle diameter is large and the resolution is insufficient. When it is 4 μm or less, the cohesive force is large and frictional electrification tends to occur. The toner charge is
Although depending on the particle size and the developing method, it is preferably 3 to 50 μC / g, more preferably 10 to 50 μC for a two-component developer.
C / g. For a one-component developer, it is 3 to 30 μC / g.

Carrier A carrier is a metal such as iron, chromium, nickel, cobalt, zinc or copper, or a compound or alloy thereof,
For example, spherical particles of ferromagnetic material or paramagnetic material such as γ-ferric oxide, chromium dioxide, manganese oxide, and ferrite, or surfaces of these magnetic material particles are styrene resin, vinyl resin, ethylene resin, acrylic resin. Resin,
Particles obtained by spherically coating with a resin such as polyamide resin or polyester, or by forming spherical particles of resin or fatty acid wax in which magnetic particles are dispersed and contained are used. The average particle size is 70 μm or less, preferably 30 to 5
Those having a size of about 0 μm are preferably used. If the average particle size is larger than this, unevenness appears in the toner image and the toner concentration becomes low, so that problems such as high-density development occur. If it is smaller than this, the image forming member 1 together with the toner is formed. It causes a problem of flying above. In addition, if the carrier is spherical, the agitation property between the toner and the carrier,
It is more preferable because the transportability is improved and the charge controllability of the toner is also increased. 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 41, the image carrier 1 is not discharged and the image is not disturbed. The resistivity of the carrier is 10 ⁸ Ωcm or more, preferably 10 ¹³ Ωcm
Those exhibiting the above insulating properties are preferable. This resistivity was measured by placing particles in a container having a cross section of 0.5 cm ² and tapping them, and then applying a load of 1 Kg / cm ² on the packed particles, and applying an electric field of 1000 V / cm between the load and the bottom electrode. Is a value obtained by reading the current value when a voltage is generated. When this resistance value is low, when a bias voltage is applied to the developer transport body 41, charges are injected into the carrier and carrier particles adhere to the photosensitive drum,
Bias voltage breakdown is likely to occur.

The volume average particle diameter of the carrier is 10 to 60 μm.
m, preferably 20 to 50 μm. If it is less than 10 μm, it becomes difficult to give sufficient magnetization to the carrier, and carrier adhesion tends to occur. If it is larger than 60 μm, the carrier has a small specific surface area, so that the toner cannot be given sufficient chargeability. Further, since the coverage is high, toner scattering easily occurs.

-Measuring Method-Laser diffraction type particle size distribution measuring device "HE" equipped with a wet disperser
ROS ”(manufactured by SYMPATEC),
The volume-based average particle size is such that 10 mg of magnetic particles are dispersed in 50 ml of water together with a surfactant by a wet disperser,
Next, it is a value measured after performing a pretreatment of dispersing for 1 to 10 minutes while paying attention to re-aggregation due to heat generation with an ultrasonic homogenizer (output 150 W).

The magnetization (σ1000) is 5 to 60 emu /
g, preferably 10 to 40 emu / g. Although it depends on the magnetic flux density on the developer transport body 41, at a magnetic flux density of 500 to 1200 gauss generally used for the developer transport body 41, if the carrier magnetization is smaller than 5 emu / g, the magnetic binding force is reduced. It does not work and causes carrier scattering. Again 6
When it is higher than 0 emu / g, the carrier spike becomes too high, and it is difficult to maintain the non-contact state with the image forming body.

After the carrier particles were filled in a sample cell of 0.25 cm × 3 cm while tapping, the sample was attached to a pickup coil and set in a magnetizer. ) Is used to draw a hysteresis curve on an XY recorder.

Such a magnetic carrier is a metal such as iron, chromium, nickel, cobalt or the like, or a compound or alloy thereof, which is equivalent to a conventional magnetic carrier as a magnetic material, such as ferric tetroxide or γ-ferric oxide. Chromium dioxide, manganese oxide, ferrite, spherical particles of ferromagnetic material such as manganese-copper alloy, or the surface of these spherical magnetic particles, styrene resin, vinyl resin, ethyl resin, rosin modified resin, The acrylic resin, polyamide resin, epoxy resin, polyester resin, silicon resin, fluorine resin or the like can be obtained by spherical coating with a homopolymer or a copolymer.

Developer: Two-component developer When a general coating carrier (density 5 to 8 g / cm ³ ) is used as the carrier in the developer, the toner concentration (% by weight) in the developer is 2 to 30% by weight. %, Preferably 5 to 20% by weight. If it is less than 2% by weight, the number of toners required for development cannot be secured. Further, since the coverage is lowered, excessive charging and deterioration of developability occur. If it is more than 30% by weight, the coverage is increased, so that charging failure and toner scattering are likely to occur. However, when a 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, the toner concentration (% by weight) in the developer is Slightly higher than the coated carrier, 5-40% by weight, more preferably 10-30% by weight is a good range. The charge amount of the toner particles is preferably 10 μC / g to 50 μC / g from the viewpoints of securing developability and preventing fogging and scattering.

The developing device 4 of the present invention preferably uses a two-component developer in which a spherical carrier and a toner are mixed as described above, but fluidization for increasing the fluidity of particles is carried out if necessary. An agent or 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. it can.

One-Component Developer A fluidizing agent such as colloidal silica can be added to the toner obtained above and used as it is as a developer. The charge amount of the one-component developer is 3 to 30 μC / absolute value.
g, particularly 3 to 20 μC / g is preferable from the viewpoint of securing developability, preventing fog, and preventing toner scattering.

Developing Process Two-Component Developing Process FIG. 6 is a partially enlarged sectional view of the developing device showing a developing area A where the image forming body 1 and the developer carrying body 41 in FIG. 3 (d) are close to each other.

An AC bias voltage with a DC bias superimposed is applied to the developer carrier 41 during development, and at least a DC bias voltage is applied when the electrode portion 48 is formed. As a result, a first oscillating electric field F1 for flying the toner is formed between the electrode portion 48 and the developer conveying body 41, and a first oscillating electric field F1 is formed between the image forming body 1 and the developer conveying body 41. A weaker second oscillating electric field F2 is formed. The toner cloud generated by the first oscillating electric field F1 is guided to the second oscillating electric field F2 side and further guided to the image carrier 1 to promote the toner adhesion on the image forming body 1.

At least the surface of the insulating member 49 facing the developer carrier 41 is coated with a resin containing at least conductive fine particles and fluorine.
(First invention). Alternatively, at least the surface of the insulating member 49 on the side facing the developer transport body 41 is coated with a fluororesin (second invention).

When the insulating member 49 having the electrode portion 48 is set in the developing space A, the angle θ formed between the facing position of the developer carrier 41 and the image forming body 1 and the tip of the electrode portion 48 is Considering the property, it is preferable that θ is large, but if it is too large, the effect of installing the electrode portion 48 in the developing space A is lost, so θ is preferably an angle of 0 to 20 °. If the space between the image forming body 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 insulating member 49 having the electrode portion 48. 0.2 to 1.0 mm is preferable. The distance between the developer transport body 41 and the electrode portion 48b on the downstream side of the developer transport body is preferably 0.2 to 0.6 times the gap between the developer transport body 41 and the image forming body 1. The ratio of the moving speed V _S (mm / sec) and the moving velocity V _P of the image forming body 1 of the developer conveying member 41 (mm / sec) is as large as it developability is increased, the image trailing edge is too large Since the edge effect becomes remarkable, 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 is attached to the image forming body 1 by 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, and 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 image forming body 1 due to the dielectric breakdown and the fog on the non-image area become remarkable. Therefore the applied AC bias voltage (V _AC p-p) 2
The range of 00V to 2kV is preferable. If the frequency is low, it is advantageous for the developability and gradation, but if it is too low, the image forming member 1
The toner previously developed above is returned to the developing device 4 to cause color mixing. Therefore, the frequency is preferably in the range of 500 Hz to 20 kHz. Fogging is prevented by controlling the DC voltage component applied to the developer transport body 41, and dielectric breakdown is caused by providing 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.

Single Component Developing Process FIG. 7 is a sectional view and a partially enlarged sectional view of the developing device showing a developing region A in which the image forming body 1 and the developer transport body 41 are close to each other in the single component developing process.

In the figure, parts having the same functions as those in the above embodiment are designated by the same reference numerals. Further, points different from the above embodiment will be described. Here, 43A is a fur brush for supplying developer, and 44A is a regulating blade made of elastic rubber for regulating the thickness of the developer layer. The image forming body 1 is an OPC photosensitive member, the peripheral speed thereof is 180 mm / sec, the maximum potential of the electrostatic latent image formed on the image forming body 1 is −850 V (non-image portion potential), and the minimum potential is −50 V ( (Image portion potential), the outer diameter of the developer transport body 41 is 20 mm, the rotation speed of the developer transport body 41 is 260 rpm, the surface of the developer transport body 41 is coated with styrene-acrylic resin, and the surface roughness Rz thereof is Rz. ₁ is 2.7 μm. Also, a1 = 0.5m
m, a2 = 0.2 mm, θ = + 2 °, the control electrode is shown in FIG.
The one shown in (d) was used. On the side of the insulating member 49 of the control electrode facing the developer transport body 41, a coating layer 55 is formed of the coating material.

As a toner for the one-component developer, styrene-
100 parts by weight of acrylic resin, 10 parts by weight of each color pigment,
1 part by weight of nigrosine was melted and kneaded, and then pulverized and classified to obtain yellow, magenta, cyan, and black color toners having a volume average particle diameter of 8.5 μm. Toners of each color were added with 2 parts by weight of colloidal silica as a fluidizing agent. The density was 1.1 g / cm ³ . The average charge amount of the toner in the developer was -5.7 μc / g.

[0079]

【Example】

(Examples 1, 2, 3, 4 and Comparative Examples 1, 2) The control electrode of the present invention having the coating layer 55 shown in FIGS. 6 and 7 described above, and the conventional control electrode having no coating layer 55. And were mounted on the developing device 4, respectively, and reversal development was performed using the image forming body 1 which is an OPC photosensitive member which is negatively charged. The control electrode and the developer provided in the apparatus used for this experiment were prepared as follows.

Control electrode A (for Comparative Examples 1 and 2) As the insulating member 49 of this control electrode A, the thickness is 0.1 mm.
3D, an electrode portion 48 having a circumferential width (L) of 0.5 mm is formed by a laminate etching method using a copper foil having a thickness of 0.02 mm, as shown in FIG. 3D. did. Further, as shown in FIG. 3D, a supporting member 50 made of a stainless steel plate having a thickness of 0.1 mm was attached with an adhesive. Surface roughness R on the developer carrier side
z = 0.8 μm. This control electrode A is connected to the developing device casing 4
It was fixed at 0.

Control Electrode B (for Examples 1 and 2) The surface of the control electrode B on the side of the developer transporter is coated with an aqueous suspension of a mixture of tetrafluoroethylene resin and amorphous carbon at about 120 ° C. And dried to form a coating layer 55. The film thickness of the coating layer was 18 μm as measured by a micrometer. Surface roughness of carrier side Rz = 1.2
μm. The control electrode B was fixed to the developing device casing 40.

Control Electrode C (Embodiments 3 and 4) An aqueous suspension of tetrafluoroethylene resin is applied to the surface of the control electrode C on the side of the developer transport body 41, and about 12
The coating layer 55 was formed by drying at 0 ° C. When the film thickness of the coating layer 55 was measured with a micrometer, it was 15 μm. The surface roughness of the developer transport body was Rz = 1 μm. The control electrode C was fixed to the developing device casing 40.

Developer-One-component developer (Examples 1, 3 and Comparative Example 1) -Toner: 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. The particles were 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.

Charge amount: Y; 3.3 μC / g, M;-
2.6 μC / g, C; -3.1 μC / g, K; -3.2
μC / g-Two-component developer (Example 2, Comparative Example 2) -Carrier: Obtained by spherically coating spherical ferrite particles having a magnetization intensity of 25 emu / g with a methyl methacrylate / styrene copolymer resin. Spherical carrier. Volume average particle diameter 45 μm.

Toner: Styrene-acrylic resin 100
4 parts by weight, 10 parts by weight of color pigment, and 1 part by weight of nigrosine were melted and kneaded, and then pulverized and classified to obtain a volume average particle size of 5.
5 μm yellow, magenta, cyan, and black toners were obtained. A toner obtained by adding 2.5 parts by weight of colloidal silica as a fluidizing agent to each of the toners was actually used.

Preparation of Developer: These toners and carriers were mixed so as to have a toner concentration of 7 wt% to prepare a developer.

Charge amount: Y; -20.5 μC / g, M;
-20.0 μC / g, C; -19.7 μC / g, K;-
21.5 μC / g

[0088]

[Table 1]

Using these developing processes, carriers and toners, full color image recording of 50,000 sheets was carried out under the conditions shown in Table 1. In Examples 1 to 4, there was no fog from the beginning to the end. A good image could be stably obtained. On the other hand, in Comparative Examples 1 and 2, the toner in the developer was fused from the initial stage, and white streaks were generated in the image due to conveyance failure.

[0090]

As described above, in the developing device having the control electrode, at least the surface of the control electrode facing the image forming body is coated with a fluorine-based resin, or a resin containing conductive fine particles and fluorine. By being configured to be covered by,
It is possible to provide a developing device that performs excellent non-contact development capable of stably obtaining a clear and even image and an image having high resolution and developability.

[Brief description of drawings]

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

FIG. 2 is a partial cross-sectional view of an image forming apparatus showing another example of the developing device of the present invention.

FIG. 3 is a schematic view showing the configuration and arrangement of a plate-shaped member and an elastic member used in the developing device of the present invention.

FIG. 4 is a sectional view of a control electrode in which a coating layer is formed on an insulating member having an electrode portion.

FIG. 5 is a schematic diagram showing various configurations of an electrode section.

FIG. 6 is a partially enlarged cross-sectional view of a developing device showing a developing region A where an image forming body and a developer transport body are close to each other in a two-component developing process.

7A and 7B are a cross-sectional view and a partially enlarged cross-sectional view of a developing device showing a developing region A where an image forming body and a developer transport body are close to each other in a one-component developing process.

[Explanation of symbols]

 1 image forming body (photosensitive drum) 4,4A, 4B, 4C, 4D developing device (developing device) 40 developing device casing 41 developer carrier 48 electrode part 49 insulating member 50 supporting member 51 insulating eaves member 52 insulating Coating layer 53 conductive circular wire 54 conductive square wire 55 coating layer 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 part side) F1 First oscillating electric field F2 Second oscillating electric field L Electrode width P Nearest contact point between developer carrier and plate-like member

Claims (6)

[Claims] 1. A voltage-applyable electrode which is cantilevered by a supporting member having elasticity in a gap between the developer carrying body and the developer carrying body provided so as to face the image forming body. In a developing device in which a control electrode having a portion is arranged, at least a surface of the control electrode facing the developer transport body is covered with a resin containing at least conductive fine particles and fluorine. Development device. 2. A developer carrying body provided to face the image forming body, and a voltage-applyable electrode portion cantilevered by a supporting member having elasticity in a gap between the image forming body and the developer carrying body. In a developing device in which a control electrode having the above is arranged, at least the surface of the control electrode facing the developer transport body is covered with a fluororesin. 3. The developing device according to claim 1, wherein the control electrode having the electrode portion is supported by being laminated on a free end of a supporting member having elasticity. 4. The developing device according to claim 3, wherein the control electrode having the electrode portion is laminated on a surface of the support member facing the developer transport body. 5. The developing device according to claim 3, wherein the control electrode having the electrode portion is laminated on a surface of the supporting member facing the image forming body. 6. The region where the control electrode and the supporting member are laminated is larger than 1 mm, and the distance from the free end of the supporting member to the tip of the control electrode is smaller than 15 mm. The developing device according to any one of 1.