JPH09311555A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device by which irregularity, roughness and fogging are not caused on an image and a high-quality image is stably obtained. SOLUTION: This device 13 is constituted by fixing a magnet roll 131 having plural magnetic poles inside opposedly to a photoreceptor drum 10, and providing a control electrode 80 formed by disposing an electrode part 82 on which voltage can be impressed in the developing area G or at the upstream part of the developing area G of a developing sleeve 130 carrying magnetic developer D to the developing area G. In such a case, oscillating electric field is formed between the sleeve 130 and the electrode 82 by a voltage impressing means impressing at least AC voltage on the sleeve 130 and at least DC voltage on the electrode part 82 of the electrode 80, and the layer of the developer D comes in contact with the drum 10 in the developing area G, and the developer packing rate in the developing area G is set to 0.06 to 0.60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying apparatus, which develops an electrostatic latent image by contact using a two-component developer composed of a magnetic carrier and a non-magnetic toner. Regarding

[0002]

2. Description of the Related Art Conventionally, a magnetic brush developing method using a two-component developer consisting of a magnetic carrier and a non-magnetic toner has been widely used in electrophotographic copying machines and the like.

This developing method is a developing method in which a magnetic brush is formed by a magnet body in a developer carrying body, and the magnetic brush is brought into contact with an image forming body in the developing area to develop a latent image. However, this developing method has a drawback that the developing efficiency is low because only a small part of the developer in the magnetic brush can participate in the development, and the image is liable to be streaked due to rubbing by the magnetic brush. Was.

In view of this, in Japanese Patent Laid-Open No. 62-113160, the filling rate of the developer in the developing area is kept low to prevent sweeping, and an oscillating electric field is formed in the developing area to prevent a decrease in developing efficiency. The technology is disclosed. Further, in order to eliminate the effect of these developer spikes, the developer is conveyed to the developing area in a non-contact manner, and an AC voltage is applied to the electrode portion of the control electrode, which is a plate-like electrode installed upstream of the developing area. To form an oscillating electric field between the electrode portion and the developer transport body,
A toner cloud developing method in which toner in a developer is dispersed and flies to perform development is disclosed in JP-A-63-226675.
JP 63-226678 A, JP 1-9436 A
No. 8 discloses this.

[0005]

However, Japanese Patent Application Laid-Open No.
In the method described in Japanese Patent Application Laid-Open No. 2-113160, the developer in the developing area is in a “rough” state, so that the image is “sharp”.
And "roughness" will be noticeable. Further, in the toner cloud developing method using the two-component developer to which the control electrode method is applied, the control electrodes existing in the developing area indiscriminately cloud the toner, so that the non-image area is not covered. There is a problem that so-called "fogging" occurs, in which various toners adhere.

The present invention solves the problems of the toner cloud developing method using the two-component developer using the control electrode. Firstly, the developing efficiency is high, and the image is "rough" or "rough".
An object of the present invention is to provide a developing device capable of stably obtaining a high-quality image free from defects.

Secondly, it eliminates the problems of the two-component magnetic brush developing method such as "sweeping" and "roughness" of the image and "fogging" which is a problem of the toner cloud developing method. It is an object of the present invention to provide a developing device capable of stably obtaining a high density and high quality image by eliminating the above.

[0008]

A first object of the present invention is to convey a magnetic developer to a developing area by fixing a magnet body facing the image forming body and having a plurality of magnetic poles inside. In a developing device having a plate-shaped control electrode provided with an electrode part capable of applying a voltage in contact with or in the vicinity of the developing region or the upstream part of the developing region, at least an AC voltage is applied to the developer transport body,
An oscillating electric field is formed between the developer carrier and the electrode portion by a voltage applying unit that applies at least a DC voltage to the electrode portion of the control electrode, and the layer of the developer forms the image in the developing area. A developing device which is in contact with the image forming body and has a developer filling rate of 0.06 to 0.60 in the developing area (first invention of claim 1), and an image forming body. , A magnetic body having a plurality of magnetic poles is fixed inside, and an electrode portion capable of applying a voltage is brought into contact with or close to the developing area or the upstream area of the developing area of the developer carrying body for carrying the magnetic developer to the developing area. In a developing device having a plate-shaped control electrode provided, the developer transfer body is provided by a voltage applying means for applying at least a DC voltage to the developer transfer body and at least an AC voltage to the electrode portion of the control electrode. An oscillating electric field between the electrode and In the area, the layer of the developer is in contact with the image forming body, and the developer filling rate in the developing area is 0.06 to 0.60. Invention).

The second object is to provide a developing area or a developing area of a developer carrying body for carrying a magnetic developer to a developing area, in which a magnet body facing the image forming body and having a plurality of magnetic poles is fixed. In a developing device having a plate-shaped control electrode provided with an electrode portion capable of applying a voltage in contact with or in the vicinity of the upstream portion of the area, the developer contacts the image forming body in the developing area, Assuming that the developer filling rate in the developing area is A ₁ and the developer filling rate at the tip of the control electrode is A ₂ , A ₂ <A ₁ <
Developing device characterized by 2.5 A ₂ (claim 4
3rd invention).

[0010]

FIG. 3 is a schematic configuration diagram showing an example of an image forming apparatus provided with the developing device of the present invention as a suitable developing means.

This image forming apparatus comprises an image signal processing section S, a laser writing section K and an image forming section 100. In an image reading apparatus separate from this apparatus, image data of an original image read by an image sensor or The image data of the image edited by the computer is processed in the image signal processing unit S and temporarily stored in the memory M as an image signal.

The image forming unit 10 is started by the start of image recording.
The photosensitive drum drive motor 0 (not shown) rotates to rotate the photosensitive drum 10 in the clockwise direction, and at the same time, the charging action by the DC corona discharge of the charger 11 for charging simultaneously causes a uniform potential on the photosensitive drum 10. Granting is started.

Next, the image signal is input from the memory M to the laser writing section K.

In the image forming unit 100, the image signal from the memory M is controlled by the control unit so that the drive motor 21,
An image recording operation is started by being input to a laser writing section K which is an image exposure means including a polygon mirror 22, an fθ lens 23, a mirror 24, a semiconductor laser (not shown), a correction lens and the like.

That is, the photosensitive drum 1 which is an image forming body.
Reference numeral 0 denotes a photosensitive layer formed by coating an organic photoconductor, OPC, on a drum-shaped base made of a conductor such as aluminum. The base is driven and rotated clockwise in a grounded state. Along with this rotation, the photoconductor drum 10 is charged to a predetermined potential by being charged by the charger 11. On the uniformly charged photosensitive drum 10, an electrostatic latent image corresponding to image data is formed by the laser beam L from the laser writing section K. This electrostatic latent image is subjected to reversal development in a contact state by a magnetic brush of a two-component developer carried by a developing sleeve 130 which is a developer carrying body to which a developing bias voltage of a developing device 13 which is developing means is applied. A visible toner image is formed.

On the other hand, the paper feed cassette 4 loaded in the paper feed section
The transfer paper P is carried out one by one by the carry-out roller 42, and is fed toward the image transfer portion via the carrying path 43. The fed transfer paper P is sent onto the photoconductor drum 10 by the registration roller 44 which operates in synchronization with the toner image on the photoconductor drum 10. This transfer paper P has
The toner image on the photoconductor drum 10 is transferred by the action of the transfer device 14, and the transfer paper P on which the toner image is transferred is separated from the photoconductor drum 10 by the charge removal action of the separator 15, and then the conveyor belt 45. Sent to the fixing device 50 via
After being fused and fixed by the heating roller 51 and the pressure roller 52, the sheet is discharged by a sheet discharge roller 58 to a tray outside the apparatus.

The photoconductor drum 10 continues to rotate, and the toner remaining on the surface of the photoconductor drum 10 without being transferred is removed and cleaned by a cleaning blade 19A which is in pressure contact with a cleaning device 19 which is a cleaning means, and then the charger 11 is charged again. Then, the electric charge is applied, and the next image forming process starts.

FIG. 1 is a schematic sectional view showing an example of a developing device 13 for accommodating the two-component developer of FIG. 3 which is the developing device of the present invention.

In FIGS. 1 (a) and 1 (b), reference numeral 130 denotes a developing sleeve which is a developer carrier, and the surface of which is made of a non-magnetic material such as aluminum is roughly processed by surface treatment such as sandblasting. Can be rotated in the direction of the arrow in the figure. Reference numeral 131 denotes a magnet roll, which is a magnet body having a plurality of N and S magnetic poles fixed in the developing sleeve 130 in the circumferential direction, and one magnetic pole 131 a of the magnet roll 131.
Is disposed in the developing area G where the development is performed in the vicinity of the closest position between the developing sleeve 130 and the photosensitive drum 10, and this is referred to as a main magnetic pole. The magnetic pole adjacent to the upstream side of the main magnetic pole 131a is 131b. The rotating developing sleeve 130 and the magnet roll 131 fixedly positioned exhibit a developer transport function. Main pole 1 of magnet roll 131
Each magnetic pole including 31a is 50 on the surface of the developing sleeve 130.
It is magnetized to a magnetic flux density of 0 to 1,500 gauss, and its magnetic force forms a layer of the developer D, that is, a magnetic brush on the developing sleeve 130. This magnetic brush moves in the same direction by the rotation of the developing sleeve 130, and the developing area G
Transported to Reference numeral 80 denotes a control electrode, which is provided in the developing area G or on the upstream side thereof in contact with or in proximity to the developing sleeve 130. A regulating member 132 is provided on the upstream side of the developing area of the rotating developing sleeve 130, and regulates the amount of the developer conveyed to the developing area G.
A scraping member for scraping off the developer D adhering to 30;
Reference numeral 4 denotes a supply member composed of a fur brush, a sponge, or the like for supplying the developer D to the developing sleeve 130 while stirring.
5 is a stirring screw for stirring the developer D to uniformly charge the toner as the developer, 138 is a developing casing, 13
Reference numeral 9 is a support portion provided in the developing casing 138 for fixing the base portion of the support member 81 of the control electrode 80 to the developing casing 138, and 88 and 89 are support members 81 of the control electrode 80.
Is a pressing plate and a set screw for fixing the to the support portion 139.

In the developing device 13 shown in FIG. 1, g ₀ is the closest distance between the developing sleeve 130 and the photosensitive drum 10, and the magnetic brush of the developer D formed on the developing sleeve 130 is the surface of the photosensitive drum 10. Developing sleeve 130 and the regulating member 13 so that proper development is carried out by contacting with the developing sleeve 130.
The contact force / gap of 2 and g ₀ are adjusted.

The control electrode 80 has an electrode portion 82 to which a voltage can be applied, and an insulating member 83 made of an electrically insulating material provided on the upstream side of the developing area G so as to contact the layer of the developer D.
Further, it comprises a support member 81 coupled to support the insulating member 83 on the upstream side of the electrode portion 82. The electrode portion 82 is made of a conductive material such as metal and is linearly integrated on the tip of the insulating member 83. It is provided.

A developing bias voltage in which a direct current or a direct current and an alternating current are superposed is applied to the developing sleeve 130, and in the developing area G closest to the photoconductor drum 10, the magnetic brush is reversed while being in contact with the photoconductor drum 10. Development is performed.

Next, the structure of the control electrode 80 used in the developing device 13 of the present invention will be described.

As shown in FIG. 7, the control electrode 80 includes an insulating member 83 made of an insulating material such as ceramic for supporting the electrode portion 82, and a supporting member 81 for supporting the insulating member 83.
Consists of The insulating member 83 is joined and integrated with the support member 81 by an adhesive or the like. The base portion of the support member 81 is supported by the pressing plate 88 on the support portion 13 of the developing casing 138.
9 is fixed.

With this structure, the electrode portion 82 of the control electrode 80 is supported by the insulating member 83 having high elasticity, and the supporting member 81 having high linearity near the electrode portion 82.
The insulating member 83 is supported by the developing sleeve 1
The surface of the developer D on the surface of 30 is extremely uniformly contacted with
The layers are uniform.

The support member 81 is shown in FIGS. 7 (a) and 7 (b).
As shown in FIG. 3, it may be coupled to either the upper surface or the lower surface of the insulating member 83.

(Material of Support Member 81) The material of the support member 81 is preferably a thin metal plate having high linearity and elasticity. For example, although metals and alloys used for the linear electrodes described later can be used, it is particularly preferable to use a stainless (SUS) thin plate from the viewpoints of cost and flexibility.

The thickness of the support member 81 depends on the material,
Considering the ease of connection with the insulating member 83, 0.05 m
m to 1 mm is preferred. If it is thinner than 0.05 mm, wrinkles and distortions are likely to occur when it is combined with the insulating member 83,
When the thickness is more than 1 mm, elasticity is lost and the degree of freedom in setting the control electrode 80 is narrowed.

As another material suitable for the support member 81, the following ceramic materials can be used.

Alumina (Al ₂ O ₃ ) system, single crystal sapphire (Al ₂ O ₃ ), forsterite (2MgO / SiO ₂ ).
₂ ) system, steatite (MgO / SiO ₂ ) system, zircon (ZrO ₂ · SiO ₂ ) system, 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 ) and cermet ceramics.

The ceramic may contain 5 to 20% by weight of a resin in order to provide appropriate elasticity.

When the above-mentioned thin metal plate is used for the supporting member 81, it is preferable that the thin metal plate is insulatingly coated with a fluorine resin or the like in order to prevent leakage of the bias voltage applied to the developing sleeve 130 and the photoconductor potential. In particular, as shown by the chain double-dashed line in FIG. 7, at least the surface of the control electrode 80 on the side of the developing sleeve 130 (the insulating member 83 and the supporting member 81) has the following coating material 80b made of a fluororesin.
Is preferably coated.

(Coating material) tetrafluoroethylene resin, tetrafluoroethylene / perfluoropropyl vinyl ether copolymer, tetrafluoroethylene / hexafluoropropylene copolymer, trifluoride / monochloroethylene resin, ethylene /
Tetrafluoroethylene copolymer, vinylidene difluoride resin,
Vinyl monofluoride resin, propylene hexafluoride / vinylidene difluoride copolymer, vinylidene fluoride, vinylidene fluoride / propylene hexafluoride copolymer (fluororubber) and the like.

The above-mentioned fluorine-based resin is dissolved in a suspension or a solvent and applied on the application surface (development sleeve 130 side) on the control electrode 80 and dried (at room temperature to 200 ° C.), or as a powder, control is performed. It is sprayed on the coated surface on the electrode 80 and heated to fix it. From the viewpoint of preventing distortion of the control electrode 80 due to heat, the former application method using suspension is preferable.

The suspension may contain a surfactant, an emulsifier, and a binder resin for fixing the fluororesin, in addition to the fluororesin.

As the binder resin, acrylic resin, epoxy resin, phenol resin, ethylene resin, amide imide resin, urethane resin, silicone, polyphenylene sulfide, polyether sulfone resin and the like are preferably used.

(Thickness of coating) Coating material 8
The thickness of 0a depends on the thickness of the control electrode 80 itself, but is preferably about 5 μm to 100 μm.

The control electrode 80 is coated with the above coating.
, The fusion of the toner in the developer D can be prevented by the low surface energy of the fluororesin.

The insulating member 83 is thin so that it can be installed in a narrow developing zone G, and in order to maintain the linearity of the entire control electrode 80 (in particular, the electrode portion 82), the insulating member 83 is made of the following materials. It is preferable that

(Material of Insulating Member 83) Examples of the insulating member 83 include polyester, polyimide, glass epoxy, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-6-fluoropropylene copolymer, poly-4 fluoride. Ethylene, polyamide imide, polysulfone, triazine resin, polyethylene terephthalate, insulating resin such as polyurethane, or other composite materials reinforced with glass fiber or the like, paper, paper phenol, varnish, silicon rubber, etc. materials, Alumina (Al ₂ O ₃ ) based, single crystal sapphire (Al ₂ O ₃ ) based, forsterite (2MgO / SiO ₂ ) based, steatite
(MgO / SiO ₂ ) system, zircon (ZrO ₂ · SiO ₂ )
System, cordierite (2MgO ・ 2Al ₂ O ₃・ 5Si
O ₂₎ system, titania, silicon carbide (SiC) based, silicon nitride (Si ₃ N ₄₎ type, zirconia (ZrO ₂₎ system can be used each ceramic Cermet.

In order to impart appropriate elasticity to the insulating member 83, the ceramic may contain 5 to 20% by weight of resin. Further, in order to reduce the surface roughness of the surface on the developing sleeve 130 side, the surface of the insulating member 83 is preferably polished.

(Method of forming electrode portion 82) The insulating member 8 described above.
3 is attached with electrolytic copper foil, annealed electrolytic copper foil, beryllium copper foil, etc. by an adhesive, and is required on the insulating member 83 by a photoetching method using a conventionally known photopolymer and an etching resist forming method by screen printing. The electrode portion 82 is formed. In addition, a method of printing the conductive ink by letterpress, stencil, intaglio, or planographic printing corresponding to the electrode portion 82 or a method of evaporating metal can be used.

FIG. 8A shows an example in which the downstream tip of the electrode portion 82 and the downstream tip of the insulating member 83 are aligned with each other, and FIGS. 8B and 8C.
Shows an example in which an eaves member 84 made of an insulating material such as a glass epoxy plate is adhered to the tip of the insulating member 83 with an adhesive or the like, and an electrode portion 82 is formed between the insulating member 83 and the eaves member 84. Further, FIG. 8D shows the eaves member 84.
2 shows an example in which the electrode portion 82 is formed on the lower surface of the tip of the.

The electrode portion 82 of the control electrode 80 is also shown in FIG.
As shown in (a), (b), (c), and (d), a linear electrode having a circular or quadrangular cross section is adhered to the tip of the insulating member 83 with an adhesive or the like to form an electrode. The portion 82 can be formed. Further, as shown in FIG. 9E, a notch 83a may be provided at the tip of the insulating member 83, and a linear electrode may be embedded therein to form the electrode portion 82. Further, as shown in FIGS. 9F and 9G, the insulating member 83
The eaves member 84 is provided at the tip of the eaves member 84.
The electrode portion 82 may be provided by adhering a linear electrode to the lower surface of the tip of the.

(Material of linear electrode) The material of the linear electrode is copper, copper-zinc, copper-cadmium, phosphor bronze, copper-beryllium, Corson alloy, aluminum, aluminum alloy, tantalum, tungsten, nickel, molybdenum. , Stainless steel, gold, titanium, chrome, palladium,
A metal such as silver, a metal oxide such as copper oxide, a composite of glass coated with copper powder, graphite, nickel, silver, or the like, or a conductive material such as graphite or carbon fiber can be used. These materials are desirably insulated for preventing discharge, preventing rust, and imparting strength.

The length of the electrode portion 82 in the circumferential direction of the photosensitive drum 10 depends on the diameter of the developing sleeve 130 and the conveying speed, but is preferably 0.05 to 5 mm, particularly preferably 0.1 to 1 mm. If it is less than 0.05 mm, a sufficient toner cloud cannot be generated, and if it is more than 5 mm, the toner is charged by vibration and becomes excessively charged, so that the developability is reduced.

The electrode portion 82 of the control electrode 80 and the insulating member 83
And the thickness t (see FIG. 7) of the developing gap, which is the closest distance between the photosensitive drum 10 and the developing sleeve 130, is g _0.
If it is (mm), it is preferable that (1/10) g ₀ <t <(2/3) g ₀ .

When t is (2/3) g ₀ or more, the electrode portion 82
Since the dielectric, which is a photoreceptor, comes close to the
The electric field strength becomes strong in the upper part, and there is a risk of disturbing the latent image when a high bias voltage is applied to the electrode part 82.

When t is (1/10) g ₀ or less, the electrode portion 8
2 approaches the developing sleeve 130, an electric discharge occurs between the electrode portion 82 and the developing sleeve 130, and the control electrode 8
It is easy to cause the destruction of 0. Further, the insulating member 83 becomes thinner, its rigidity becomes lower, and it becomes easier to crack.

The thickness of the control electrode 80 is measured by a micrometer (M320-25A manufactured by Mitutoyo Co., Ltd.) at 20 points in the direction of the rotation axis of the developing sleeve 130 of the control electrode 80, and the average value of the measured values is the thickness t of the control electrode 80. And

FIG. 10 is a view showing the relationship between the width of the electrode portion 82 and the width of the developing area G. In FIG. 10, W ₃ is the width of the electrode portion 82 (the axial length of the developing sleeve 130), W ₄
Is the width of the developing area G on the developing sleeve 130 in the axial direction (width of the developer layer), W ₃ > W ₄ , and the terminal portion 82 for applying a DC voltage or an AC voltage to the electrode portion 82.
Also, a is provided in a portion outside the width W ₄ of the developing area G to prevent generation of an unnecessary toner cloud.

Further, the surface roughness R of the developing sleeve 130
z ₁ (μm) and the roughness Rz ₂ (μm) of the surface of the insulating member 83 that faces the developing sleeve 130, when Rz ₂ ≧ Rz ₁ , the developer D conveyed onto the developing sleeve 130 has the insulating member 83. As a result, the amount of toner conveyed to the developing area G is reduced and the image density is reduced. Rz ₁ is 0.2 μm
-20 μm, Rz ₂ is 0.02 μm-5.0 μm
Within the range, good transportability and no image disturbance,
It is preferable to obtain a high density image. The surface roughness R
z conforms to JIS B 0601 and is manufactured by Mitutoyo Surf
Using test-402, the measurement was performed at a reference length of 25 mm.

Next, the setting positions of the magnetic poles in the present invention (first and second inventions) will be described.

The setting positions of the main magnetic pole 131a and the magnetic pole 131b of the magnet roll 131 are set in the following areas.
(See FIG. 1B.) The center line connecting the rotation center of the photosensitive drum 10 and the rotation axis O of the developing sleeve 130 is p, and the center line p and the magnetic pole 131a are centered on the rotation axis O of the developing sleeve 130. If the angle theta ₃ between angle theta _1, a main magnetic pole 131a and angle theta ₂ and the main magnetic pole 131a and the magnetic pole 131b between the control electrode 82 tip _{between, θ 1, θ 2, θ} 3 Is (the downstream side from the center line p in the rotation direction of the developing sleeve 130 is −). −10 ° ≦ θ ₁ ≦ + 10 ° + 20 ° ≦ θ ₃ ≦ + 60 ° θ ₂ = 0.2θ _{3 to} 0.9θ ₃ Preferably.

When θ ₁ is out of the above range, the spikes of the developer D in the developing area near the electrode portion 82 are insufficient and the developing property is deteriorated.

When θ ₃ is smaller than 20 °, the developing area G
The developer filling rate in the vicinity becomes too high, which makes control difficult. When the angle is larger than 60 °, the magnetic poles are too far apart from each other, so that the developer D is not sufficiently conveyed and the developability is deteriorated.

If θ ₁ and θ ₃ are within the above range, the developer D
It is possible to obtain a proper spike and filling rate of the layer.

Further, when θ ₂ is smaller than 0.2θ ₃ , the control electrode 80 suppresses the spike of the developer D due to the main magnetic pole 131a, and the developability is rather deteriorated. When θ ₂ is larger than 0.9θ _{3, the} control electrode 80 is too far away from the developing area G and the effect of the control electrode 80 is reduced.

Next, a method of applying the bias voltage will be described.

The developing sleeve 1 is formed so that an oscillating electric field is formed at least between the developing sleeve 130 and the control electrode 80.
A bias voltage is applied to each of the electrodes 30 of the control electrode 80 and the electrode 30.

As a method of forming the oscillating electric field, at least an AC voltage is applied to the developing sleeve 130 and at least a DC voltage is applied to the control electrode 80 and the electrode portion 82. It is preferable to apply at least a DC voltage to the developing sleeve 130 and at least an AC voltage to the control electrode 80 and the electrode portion 82.

When AC voltage is applied to the developing sleeve 130 (first invention of claim 1) The developing bias voltage applied to the developing sleeve 130 is
An AC bias voltage obtained by superimposing an AC component on a DC component by the DC power source E ₁ and the AC power source E ₂ , and is applied via the protection resistor R ₁ .

E ₁ : In the case of reversal development, the voltage of the DC power source E ₁ for supplying a DC component has the same charging polarity as the potential of the non-image portion of the image forming body (potential of the unexposed portion) and has an absolute value of 30 V
A value lower by ˜200 V, more preferably 50 V to 150 V is preferable.

E ₂ : The zero-peak voltage (V _OP ) of the AC power supply E ₂ for supplying the AC component is 100 to 1,400 V, preferably 300 to 1,000 V, and its frequency is 100 H.
z to 12 kHz, preferably 1 to 10 kHz. The waveform may be a sine wave, a sawtooth wave, or the like other than the rectangular wave.
If the voltage is within this range, the discharge to the electrode portion 82 and the poor developability will not occur.

E ₃ : Furthermore, a DC power source E ₃ is applied to the electrode portion 82.
Bias voltage of only DC component is applied from the protection resistor R ₂ . The voltage of this DC component has the same polarity as E ₁ ,
0.5E ₁ ~1.5E ₁ is preferred. Within this range, toner adhesion to the electrode portion 82 is small and a sufficient toner cloud can be formed.

In the developing device 13 described above, by applying the AC bias voltage to the developing sleeve 130,
A first oscillating electric field is generated between the electrode portion 82 of the control electrode 80 and the developing sleeve 130, and a second oscillating electric field is generated between the photosensitive drum 10 and the developing sleeve 130. Since this AC bias voltage is applied only to the developing sleeve 130, the first oscillating electric field and the second oscillating electric field have the same phase, and the toner particles are smoothly moved from the first oscillating electric field to the second oscillating electric field. Migrate.

Further, since the electrode portion 82 is provided closer to the developing sleeve 130 than the photosensitive drum 10, the strength of the first oscillating electric field is larger than the strength of the second oscillating electric field.

The first oscillating electric field vibrates the toner particles of the developer D reaching the vicinity of the electrode portion 82 in a direction perpendicular to the electric force lines to separate and fly them from the carrier to make the toner cloud-shaped and so-called toner. The cloud can be generated sufficiently. The toner cloud is smoothly guided to the developing area G by the second oscillating electric field, and the developing efficiency is improved because the developing is performed by the toner cloud in addition to the developing by the magnetic brush. In particular, the developing sleeve 130
Since a weak oscillating electric field is formed between the photosensitive drum 10 and the photosensitive drum 10, the toner on the magnetic brush is also easily separated from the carrier. Due to these synergistic effects, high developing efficiency can be obtained even with a low developer filling rate.

At the same time, since development is carried out with a low developer filling rate, an extremely uniform image can be obtained without scratches due to scraping of the magnetic brush. Further, since the fog caused by the cloud is removed by an appropriate rubbing with a magnetic brush, a good image without fog can be obtained.

When an AC voltage is applied to the control electrode 80 (the second invention of claim 2) Further, the bias voltage applied to the control electrode 80 and the developing sleeve 130 is applied to the developing sleeve 130 as shown in FIG. Is a bias voltage of only the DC component applied from the DC power source E ₁ through the protection resistor R ₁ , and the AC bias voltage in which the AC component is superimposed on the DC component of the DC power source E ₃ and the AC power source E ₄ is applied to the electrode portion 82. Can be applied via the protection resistor R ₂ , the same effect as described above can be obtained.

[0071] E _1: E _1, which is applied to the developing sleeve 130
In the case of reversal development, the developing bias voltage of No. 1 has the same charge polarity as the potential of the non-image portion of the image forming body (potential of unexposed portion), and has an absolute value of 30 V to 200 V, more preferably 50 V to
A value lower than 150V is preferred.

In the case of regular development, the absolute value is preferably 20 V to 200 V, and more preferably 50 V to 150 V higher than the maximum image density potential ( _VL ) on the image forming body with the same charge polarity as the image forming body. When the voltage is within this range, fogging is small and sufficient developability can be obtained.

E ₃ : DC voltage E ₃ applied to the electrode portion 82
Has the same polarity as E _1, and is preferably 0.5E _{1 to} 1.5E ₁ . Within this range, toner adhesion to the electrode portion 82 is small and a sufficient toner cloud can be formed.

E ₄ : The zero peak voltage (V _OP ) of the AC power supply E ₄ for supplying the AC component is 100 to 1,200 V, preferably 300 to 800 V, and the frequency is 100 Hz to.
It is 12 kHz, preferably 1 to 10 kHz. The waveform is preferably a rectangular wave, but may be a sine wave, a sawtooth wave, or the like. If the voltage is within this range, neither discharge to the photosensitive drum 10 (image forming body) nor the developing sleeve 130 (developer carrying body) nor defective developability will occur.

A strong oscillating electric field between the developing sleeve 130 and the electrode portion 82 forms a toner cloud, which is guided to the developing area G. In addition to the development using the magnetic brush, the development using the toner cloud improves the development efficiency. In particular, since a unidirectional electric field due to a DC electric field is formed between the developing sleeve 130 and the photoconductor drum 10, there is no unstable toner that tries to return to the developing sleeve 130 side, and there is little fog or missing. , Reproducibility faithful to the latent image can be obtained.

At the same time, since development is carried out at a low developer filling rate, an extremely uniform image can be obtained without scratches due to scraping of the magnetic brush. Further, since the fog caused by the cloud is removed by an appropriate rubbing with a magnetic brush, a good image without fog can be obtained.

Next, the developer filling rate will be described.

In the developing area G, the developer layer is in contact with the photosensitive drum 10, and the developer filling rate A ₁ in the developing area G is preferably 0.06 to 0.60.

The developer filling rate A ₁ is measured as follows.

The apparent density ρ _s (g) of the developer in the developing area G is compared with the static dry density ρ _p (g / cm ³ ) of the developer D.
/ Cm ³ ). That is, A ₁ = ρ _s / ρ _p (1) Here, the apparent density ρ _s (g / cm ³ ) is the weight per unit volume of the developer D existing in the developing space, Volume V (cm ³ ) of the area space (the space surrounded by the developing sleeve 130 and the photosensitive drum 10 where the latent image is developed with toner) and the weight M (g) of the developer D existing in the space You can ask more.

Ρ _s = M / V (2) Further, the volume V (cm ³ ) of the developing zone and the weight M (g) of the developer D present in the space are V = Dsd × W × L (3) M = Dws × W × L (4) where Dsd is the distance (cm) between the developing sleeve 130 and the photoconductor drum 10 in the developing area G as shown in FIG. ,
Dws is the developer transport amount per unit area near the developing area G (g / cm ² ), W is the width of the developer D on the developing sleeve 130 in the longitudinal direction (cm), and L is the developing sleeve in the developing area G. The length (cm) of 130 in the circumferential direction.

By substituting the equations (2) to (4) into the equation (1), the developer filling rate A ₁ can be obtained from A ₁ = Dws / (Dsd × ρ _p ) ... (5).

Ρ _p is obtained by dropping a certain amount of the developer D into a container whose weight (g) and volume (cm ² ) have been measured in advance.
Add developer D until it overflows from the container. After a certain period of time, the developer D overflowing was scraped off, the weight was measured, and the weight difference (g) before and after the developer was dropped was divided by the volume (cm ³ ) to obtain a static bulk density (g / cm ³ ).

Dws is the weight (g) and the adhesive area (c
The developer D is peeled off and adhered from the developing sleeve 130 by the adhesive tape whose m ² ) is measured, and the weight difference (g) of the tape before and after the adhesion is divided by the adhesive area (cm ² ) to obtain D
ws (g / cm ² ) was determined.

Strictly speaking, the curvature of the developing sleeve 130 and the photosensitive drum 10 causes the Dsd to be slightly different depending on the position in the developing area G, but generally, the circumferential length of the developing area G is equal to that of the developing sleeve 130. Since it is extremely small compared to the entire circumference, the curvature is ignored and the re-adjacent distance value of the two is g _0.
There is no problem with using.

In the third aspect of the present invention, in addition to the developer filling rate A _{1 in} the developing area G, the tip portion 80a of the control electrode 80 is provided.
The relationship with the developer filling rate A ₂ is regulated, and A ₂ <A ₁ <2.5A ₂ is characterized.

As a result, since the developer filling rate A ₂ of the tip portion 80a is made smaller than the developer filling rate A ₁ of the developing area G, the toner vibration is likely to occur and the efficiency of toner cloud generation is increased. Further, the developer filling rate A ₁ in the developing area G can be further reduced to 0.05 to 0.50 with the improvement of the cloud generation efficiency, and the developer amount required for the development can be obtained while the development is performed. Since the agent filling rate is low, scraping in the image area is less likely to occur. or,
When developing with a magnetic brush, at the same time, toner that adheres to the non-image area with the toner cloud and fog toner that adheres to the non-image area without generating sweep lines or vertical stripes in the image area can be removed by a coarse magnetic brush. It can be removed by rubbing. Further, unlike the case of a developer having a high density because the filling rate is low in the vicinity of the electrode 80 and the developer is made relatively rough, the control electrode 80 is drawn to the downstream side of the rotation of the developing sleeve 130 and is separated from the surface of the developing sleeve 130. Further, it is possible to prevent the developer D, especially the carrier, from riding on the control electrode 80, and it is possible to prevent the control electrode 80 from being damaged and the image from becoming rough or rough. Here, the developer filling amount A _{2 in the} vicinity of the electrode can be obtained by using the distance Dgd (cm) between the developing sleeve 130 and the photosensitive drum 10 at the electrode tip portion instead of Dsd in the above formula (5). Yes (see Figure 6).

Next, the developer D used in this embodiment will be described.

In the developing device 13 using a two-component developer, a magnetic brush made of a developer is brought into contact with the photosensitive drum 10 which is an image forming body, and a toner cloud is generated by the first and second oscillating electric fields, so that the photosensitive drum is exposed. The separation and flight to the body drum 10 are improved, the selective adsorption to the electrostatic image is improved, and the carrier particles are prevented from adhering to the photosensitive drum 10. Therefore, fine particles are used as toner particles and carrier particles. This makes it possible to develop a high-quality image, but it is preferable to use the developer D composed of the following toner and carrier.

(Toner) Generally, when the average particle diameter of the toner particles becomes small, the charge amount qualitatively decreases in proportion to the square of the particle diameter, and the adhesive force such as the Van der Waals force relatively increases. As a result, the particles easily scatter and fog easily occurs. Then, when the average particle size is 10 μm or less, this problem becomes remarkable. In the developing apparatus of the present invention, this point is solved by performing the development under a double oscillating electric field.

Volume average particle diameter of toner D ₅₀ (μm) When D ₅₀ is larger than 10 μm, the particle diameter is large and the resolving power is insufficient, and when D ₅₀ is smaller than 4 μm, cohesive force is large and frictional electrification is apt to occur.

For the above reasons, the volume average particle diameter D _{50 of the} toner is _50.
Is 1 to 20 μm, preferably 4 μm <D ₅₀ <10 μm
It is.

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

Since the toner particles follow the electric field, the absolute value of the charge amount of the toner particles should be 3 to 50 μC / g, especially in the case of the two-component developer, to secure the developability, fog and scatter. It is desirable from the viewpoint of prevention. In particular, when the particle size is small, a high charge amount is required.

Here, the average charge amount Q ₂ of the toner in the two-component developer is 20 mm in diameter when a conductive plate of 2 cm × 5 cm is used.
Of the developing device 130 having a closest distance of 0.7 mm, and a superimposed voltage of a direct current (DC) and an alternating current (AC) (for example, DC;
1000 V, AC; zero peak voltage 750 V, frequency 8 kHz) is applied to develop on the conductive plate with the toner of the developer D, and the conductive plate developed with this toner is connected to a Faraday gauge. Is blown off with nitrogen gas, and the value obtained by measuring the charge amount and weight of the toner blown off at this time.

Examples of the binder resin for such toner include styrene resin, vinyl resin, ethyl resin, rosin-modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, and these styrene-acrylic resins. Copolymer resins such as and the like or mixed resins and the like are preferable. Coloring components such as color pigments, and if necessary, a charge control agent, a release agent such as wax, and the like are added to these resins, and toners such as conventionally known pulverization granulation method, suspension polymerization method, emulsion polymerization method, etc. It can be manufactured by a method equivalent to the manufacturing method.

(Carrier) In general, when the magnetic carrier particles have a large average particle diameter, the state of the magnetic brush formed on the developing sleeve 130 becomes rough, so that the electrostatic latent image is developed while being vibrated by the electric field. However, there is a problem that unevenness is likely to appear in the toner image and the toner density at the ears becomes low, so that high-density development is not performed. In order to solve this problem, the average particle diameter dc of the magnetic carrier particles may be reduced, and as a result of the experiment, the volume average particle diameter dc is 10 to 1
It was found that the above problems do not occur when the thickness is 00 μm, preferably 20 to 80 μm.

When dc is 10 μm or less, it is difficult to sufficiently magnetize the carrier, and the particles are easily attached to the surface of the photoconductor drum 10 together with the toner particles, or easily scattered.

If dc is 100 μm or more, the specific surface area of the carrier becomes small, and the toner cannot be sufficiently charged. Further, since the carrier coverage of the toner becomes high, toner scattering easily occurs.

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

The strength of magnetization of carriers (maximum magnetization) is 1
0-100 emu / g, preferably 20-80 emu / g
g. This strength depends on the magnetic flux density on the developing sleeve 130, but is 10 emu / g when the general magnetic flux density of the developing sleeve 130 is 500 to 1,200 gauss.
If it is less than the range, the magnetic binding force does not work, which causes carrier scattering. On the other hand, if it exceeds 100 emu / g, the magnetic brush becomes too hard, which not only easily damages the photosensitive layer of the photosensitive drum 10, but also causes an image sweep.

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

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

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

(Developer) As the two-component magnetic developer D used in the developing device 13 of the present invention, the spherical carrier particles and the toner as described above are used in the same ratio as in the conventional two-component developer. A mixed developer is preferably used, but when a general coating carrier (density 5 to 8 g / cm ³ ) is used as a carrier, the toner concentration in the developer is 2 to 20% by weight, preferably 3 to 15% by weight. %.

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

If it is more than 20% by weight, the coverage becomes large, and charging failure and toner scattering easily occur.

However, the toner concentration (% by weight) in the developer when the resin dispersion type carrier having a relatively light density (2 to 4 g / cm ³ ) as described above is used as the carrier in the developer is generally Slightly higher than the case of using the resin-coated carrier of 5 to 40% by weight, more preferably 10 to 30% by weight.
It is good to be in the range of weight%.

The charge amount of the toner particles is 1 to 3 μC in absolute value.
It is preferable that it is more than 3 g / g and 3 μC / g to 50 μC / g from the viewpoint of securing developability and preventing fog / scattering.

The developing device described above is not limited to a monochromatic image forming device, but includes a plurality of image forming portions for yellow (Y), magenta (M), cyan (C), black (K), etc. shown in FIG. The toner image on the photoconductor drum 10 is temporarily transferred by the primary transfer device 14A using the tandem type color image forming apparatus provided side by side or the intermediate transfer member 16 shown in FIG.
It is also applicable to a color image forming apparatus of the intermediate transfer body type in which the toner image on the intermediate transfer body 16 is transferred to the transfer paper P by the secondary transfer device 14B.

[Tests of Examples of the Present Invention and Comparative Examples] (Comparative Experiments for the First Invention) Examples 1 to 7 and Comparative Examples 1 to 9 are provided with the developing device 13 shown in FIG. Three
In the image forming apparatus shown in FIG. 1, the photoconductor drum 10 is made by coating OPC on a substrate made of aluminum and has an outer diameter of 8
0 mm, the number of revolutions is 50 rpm, the maximum potential of the electrostatic latent image formed on the photosensitive drum 10 is -850 V (non-image portion potential), the minimum potential is -50 V (image portion potential), and the outer diameter of the developing sleeve 130 is 20 mm. , The rotation speed of the developing sleeve 130 is 400 rpm, and therefore the linear velocity is 210 mm / se.
c, the peripheral speed ratio of the developing sleeve to the photosensitive drum in the developing area is about 1: 2. Surface roughness of developing sleeve 130 R _z1 =
The thickness was 1.2 μm, g ₀ = 0.5 mm, and h = 0.18 mm.

(Control Electrode) Control Electrodes of Examples 1 to 7 and Comparative Examples 1 to 9 With the configuration and dimensions shown in FIG. 11, a glass epoxy plate having a thickness of 0.1 mm is used as the insulating member 83, and the control electrode shown in FIG. As shown in FIG. 2, the electrode portion 82 has a circumferential width of 0.5 mm,
It was formed by a laminate etching method using a copper foil having a thickness of 0.02 mm. The support member 8 made of a SUS plate having a thickness of 0.1 mm is provided on the opposite side of the insulating member 83 from the electrode portion 82.
1 through an adhesive, and the control electrode 80
The surface of the developing sleeve 130 side was coated with a suspension of a tetrafluoroethylene resin using polyethylene as a binder and dried at about 120 ° C. The coating thickness was 15 μm. The surface roughness on the front side of the developing sleeve 130 is R _z = 1.1 μm. The control electrode 80 having such a configuration is fixed to the supporting portion 139 of the developing casing 138 with the pressing plate 88 and the set screw 89.

Other developer filling rates A ₁ , bias voltages E ₁ , E ₂ , E ₃ and angles θ ₁ , θ ₂ , θ ₃ are as shown in Table 1.

[0114]

[Table 1]

Developer (two-component developer) (common to Examples 1 to 7 and Comparative Examples 1 to 9) Carrier: Spherical ferrite particles having a saturation magnetization of 60 emu / g and methyl methacrylate / styrene copolymerization. A spherical carrier obtained by surface-coating a resin. The volume average particle size is 60 μm.

Toner: 100 parts by weight of styrene-acrylic resin, 10 parts by weight of pigment (carbon black), and 1 part by weight of nigrosine are melted and kneaded, pulverized and classified, and a black toner having a volume average particle diameter of 5.5 μm. Got 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 A developer was prepared by mixing the toner and the carrier so that the toner concentration was 5 wt%.

The static dry density ρ _p of the developer D is 1.90 g /
It was cm ³ .

Here, in Example 1, the carry amount Dws in the developing area G was 10 mg / cm ² = 1.0 × 10 ^-2 g.
/ Cm ² , and the height Dsd of the developing area G is Dsd = g ₀ = 500.
μm = 5.0 × 10 ⁻² cm, therefore the filling factor = (1.0 × 10 ⁻² ) / (5.0 × 10 ⁻² × 1.
90) = 0.11.

In the other Examples and Comparative Examples, the transport amount (Dw) of the developer D is adjusted by adjusting the regulating member 132.
s) was changed to adjust the filling amount.

The charge amount Q _{2 of the} toner is −21.8 μC /
g.

The developing process and carrier described above,
Using toner and the control electrode 80 having the shape shown in FIG. 11, comparative experiments were carried out on image density and image roughness (density unevenness).

With the above-mentioned settings, a black image recording of 100,000 copies (100 k copies) was performed using the above-mentioned developing process, carrier and toner.

Image Density Measuring Method During the black image recording of each of the Examples and Comparative Examples, the copy output density of the solid black portion of the chart density of 1.3 was measured with an image densitometer (Macbeth RD-918, Mac) every 1000 copies.
Beth). Copy output density 1.3
If it was above, the developability was judged to be good.

The results are shown in Table 2 for the image density, and all Examples 1 to 7 were good.
In each of Comparative Examples 1 to 9, some trouble occurred.

[0126]

[Table 2]

Image Roughness During recording of black images in each of the examples and comparative examples, the density unevenness in the halftone portion with a copy output density of 0.7 is measured with an image analyzer RT-2000C (manufactured by Yerman Co.) every 1000 copies. did. The measurement is a window size of 30 μm × 30 μm, and the measurement length is 5 m in the direction perpendicular to the developing direction.
As m, the density was measured at a pitch of 30 μm, and if the standard deviation (σ) of the density unevenness was 0.15 or less, the image was judged to be a good image with no bleeding or roughness.

In each of Examples 1 to 7, good recorded images could be stably obtained from the beginning to the end. On the other hand, in Comparative Examples 1 to 9, as shown in Table 3, the density unevenness was large from the initial stage, and good recorded images could not be obtained.

[0129]

[Table 3]

(Experiment on Second Invention) Developing device shown in FIG. 2 (system in which AC bias voltage is applied to the electrode portion 82 and DC bias voltage is applied to the phenomenon sleeve 130)
And the photosensitive drum 1 in the image forming apparatus shown in FIG.
The reference numeral 0 indicates that the substrate made of aluminum is coated with OPC, the outer diameter is 80 mm, the rotation speed is 50 rpm, and the maximum potential of the electrostatic latent image formed on the photosensitive drum 10 is -850 V.
(Non-image portion potential), the minimum potential is -50 V (image portion potential), the outer diameter of the developing sleeve 130 is 20 mm, the rotation speed of the developing sleeve 130 is 400 rpm, and therefore the linear velocity is 21.
The peripheral speed ratio of the developing sleeve to the photosensitive drum in the developing area is about 1: 2 at 0 mm / sec. Surface roughness of developing sleeve 130 R _z1 = 1.2 μm, g ₀ = 0.5 mm, h = 0.
It was set to 18 mm.

(Control Electrode) Control Electrodes of Examples 8 to 14 and Comparative Examples 10 to 17 With the configuration and dimensions shown in FIG. 11, a glass epoxy plate having a thickness of 0.1 mm was used as the insulating member 83, and the control electrode shown in FIG. As shown in FIG. 2, the electrode portion 82 has a circumferential width of 0.5 mm,
It was formed by a laminate etching method using a copper foil having a thickness of 0.02 mm. The support member 8 made of a SUS plate having a thickness of 0.1 mm is provided on the opposite side of the insulating member 83 from the electrode portion 82.
1 through an adhesive, and the control electrode 80
The surface of the developing sleeve 130 side was coated with a suspension of a tetrafluoroethylene resin using polyethylene as a binder and dried at about 120 ° C. The coating thickness was 15 μm. The surface roughness on the front side of the developing sleeve 130 is R _z = 1.1 μm. The control electrode 80 having such a configuration is fixed to the supporting portion 139 of the developing casing 138 with the pressing plate 88 and the set screw 89.

Other developer filling rates A ₁ , bias voltages E ₁ , E ₃ , E ₄ , angles θ ₁ , θ ₂ , θ ₃ are as shown in Table 4.

[0133]

[Table 4]

Developer Used in Comparative Experiment (Two-Component Developer) (Examples 8-14, Comparative Examples 10-17)
Carrier: A spherical carrier obtained by surface-coating spherical ferrite particles having a saturation magnetization strength of 60 emu / g with a methyl methacrylate / styrene copolymer resin. The volume average particle size is 60 μm.

Toner: 100 parts by weight of styrene-acrylic resin, 10 parts by weight of pigment (carbon black), and 1 part by weight of nigrosine are melted and kneaded, then pulverized and classified to obtain a black toner having a volume average particle diameter of 5.5 μm. Obtained. Colloidal silica is added to the toner as a fluidizing agent at 2.5 times each.
What was added by weight was actually used.

Preparation of Developer The developer was prepared by mixing this toner and carrier so that the toner concentration would be 5 wt%.

The static dry density ρ _p of the developer D is 1.90 g /
cm ³ , here, in Example 8, the carry amount Dws in the developing area G was 10 mg / cm ² = 1.0 × 10 ⁻² g / c.
m ² , height of development area G Dsd = g ₀ = 500 μm = 5.0
× 10 ^-2 cm, therefore the filling factor = (1.0 x 10 ^-2 ) / (5.0 x 10 ^-2 x 1.
90) = 0.11.

In the other Examples and Comparative Examples, the transport amount (Dws) of the developer D is adjusted by adjusting the regulating member 132.
Was changed to adjust the filling rate.

The charge amount Q _{2 of the} toner is −21.8 μC / g
Met.

The developing process and carrier described above,
Using toner and the control electrode 80 having the shape shown in FIG. 11, comparative experiments were carried out on image density and image roughness (density unevenness).

With the above-mentioned settings, a black image recording of 100,000 copies (100 k copies) was performed by using the above-mentioned developing process, carrier and toner.

Image Density Measuring Method During the black image recording of each of the examples and comparative examples, the copy output density of the solid black portion of the chart density of 1.3 was measured with an image densitometer (Macbeth RD-918, Mac) every 1000 copies.
Beth). Copy output density 1.3
If it was above, the developability was judged to be good.

Image Roughness (Density Unevenness) During the black image recording in each of the examples and comparative examples, the density unevenness in the halftone portion with a copy output density of 0.7 is recorded for every 1000 copies, using an image analyzer RT-2000C (Yaman Corporation). Manufactured). The measurement is a window size of 30 μm × 30 μm, and the measurement length is 5 m in the direction perpendicular to the developing direction.
As m, the density was measured at a pitch of 30 μm, and if the standard deviation (σ) of the density unevenness was 0.15 or less, the image was judged to be a good image without any bleeding or roughness.

As shown in Table 6, the results of the comparative experiment on the image roughness show that the good results were obtained in Examples 8 to 14, but some problems occurred in Comparative Examples 10 to 17.

[0145]

[Table 5]

[0146]

[Table 6]

(Comparative Experiment for Third Invention) Using the image forming apparatus of FIG. 3 equipped with the same phenomenon apparatus of FIG. 1 as the comparative experiment for the first invention, a DC voltage was applied to the electrode portion 82 to develop the image. As a comparative experiment example (3-A) in which an AC voltage is applied to the sleeve 130, the image forming apparatus of FIG. 3 including the developing device of FIG. Comparative experimental example of applying voltage (3
-B).

In (3-A), Example 21 was conducted under the conditions shown in Table 7.
.About.25 and comparative examples 21 to 27.

In (3-B), the experimental example 2 was performed under the conditions shown in Table 8.
Comparative experiments of 6 to 30 and Comparative Examples 28 to 34 were conducted.

[0150]

[Table 7]

[0151]

[Table 8]

In the image forming apparatus shown in FIG. 3, the photosensitive drum 10 is formed by coating OPC on a substrate made of aluminum, and has an outer diameter of 80 mm and a rotation speed of 67 rpm. The maximum potential of the electrostatic latent image formed on the photoconductor drum 10 is -85.
0 V (non-image part potential), the minimum potential is -50 V (image part potential), the outer diameter of the developing sleeve 130 is 20 mm, the rotation speed of the developing sleeve 130 is 550 rpm, and therefore the linear velocity is 280.
mm / sec, the peripheral speed ratio of the developing sleeve to the photosensitive drum in the developing area is about 1: 2. Surface roughness of developing sleeve 130 R _z1 = 1.2 μm, Dsd = g ₀ = 0.5 mm, h
= 0.18 mm. The distance Dgd between the developing sleeve and the photosensitive drum near the tip of the control electrode is 1.0 mm.

(Control Electrode) Control Electrodes of Examples 21 to 30 and Comparative Examples 21 to 34 With the structure and dimensions shown in FIG. 11, a glass epoxy plate having a thickness of 0.1 mm is used as the insulating member 83, and the control electrode shown in FIG. As shown in FIG. 2, the electrode portion 82 has a circumferential width of 0.5 mm,
It was formed by a laminate etching method using a copper foil having a thickness of 0.02 mm. The support member 8 made of a SUS plate having a thickness of 0.1 mm is provided on the opposite side of the insulating member 83 from the electrode portion 82.
1 through an adhesive, and the control electrode 80
The surface of the developing sleeve 130 side was coated with a suspension of a tetrafluoroethylene resin using polyethylene as a binder and dried at about 120 ° C. The coating thickness was 15 μm. The surface roughness on the front side of the developing sleeve 130 is R _z = 1.1 μm. The control electrode 80 having such a configuration is fixed to the supporting portion 139 of the developing casing 138 with the pressing plate 88 and the set screw 89.

Developers Used in Comparative Experiments (Two-Component Developers) (Examples 21 to 30 and Comparative Examples 21 to 3)
4) Carrier: A spherical carrier obtained by surface-coating spherical ferrite particles having a saturation magnetization strength of 60 emu / g with a methyl methacrylate / styrene copolymer resin. The volume average particle size is 60 μm.

Toner: 100 parts by weight of styrene-acrylic resin, 10 parts by weight of pigment (carbon black), and 1 part by weight of nigrosine are melted and kneaded, then pulverized and classified, and a black toner having a volume average particle diameter of 5.5 μm. Got Colloidal silica is added to the toner as a fluidizing agent.
What was added 5 parts by weight was actually used.

Adjustment of Developer These toner and carrier are mixed at a toner concentration of 5 wt%.
To prepare a developer.

Static dry density of developer ρ _p = 1.95 g / cm ³ Here, in Example 21, the developer conveyance amount Dws in the developing area G is Dws = 10 mg / cm ³ = 1.0 × 1
0 ^-2 g / cm ² , developer transport amount D near the control electrode 80
ws _{2 is} also 10 mg / cm ² = 1.0 × 10 ^-2 g / cm ² ,
The height Dsd of the developing area G is Dsd = g ₀ = 500 μm =
5.0 × 10 ^-2 cm, the distance Dgd between the developing sleeve and the photosensitive drum near the tip 80a of the control electrode 80 is 1.00
Since 0 μm = 1.0 × 10 ⁻¹ cm, the filling rate ratio A ₁ is the ratio of the developer filling rate A ₁ to the developer filling rate A ₂ .
/ A ₂ becomes 0.11 / 0.05. Other conditions E ₁ ,
E ₂ , E ₃ , E ₄ and θ ₁ are as shown in Tables 7 and 8. In the third invention, there are no particular restrictions on θ ₂ and θ ₃ .

In the other Examples and Comparative Examples, the transport amount (Dw) of the developer D was adjusted by adjusting the regulating member 132.
s) was changed to adjust the filling rate.

The charge amount Q _{2 of the} toner is −22.3 μC / g
Met.

The developing process and carrier described above,
Using toner and the control electrode 80 having the shape shown in FIG. 11, comparative experiments were carried out on image density and image roughness (density unevenness).

With the above-mentioned settings, full-color image recording of 100,000 copies (100 k copies) was performed using the above-mentioned development process, carrier and toner.

Image Density Measuring Method During full-color image recording in each of the examples and comparative examples, the copy output density of a solid black portion having a chart density of 1.3 was measured with an image densitometer (Macbeth RD-918, M) every 1000 copies.
(made by acbeth). When the copy output density was 1.3 or more, the developability was judged to be good.

The results are shown in Table 9 (3
-A), as shown in Table 10 (3-B), and Example 2
1 to 30 were all good, but Comparative Examples 21 to 34
Each of them had some trouble.

[0164]

[Table 9]

[0165]

[Table 10]

Image Roughness During the recording of full-color images in each of the examples and comparative examples, the density unevenness in the halftone portion with a copy output density of 0.7 was measured with an image analyzer RT-2000C (manufactured by Yerman Co.) every 1000 copies. did. Measurement is 30μm × 30μm
When the standard size (σ) of the density unevenness is 0.15 or less, the density is measured at a pitch of 30 μm with a measurement size of 5 mm in the direction perpendicular to the developing direction.
The image was judged to be good, with no blemishes or roughness.

Regarding the image roughness, the experimental result of the example belonging to (3-A) is shown in Table 11, and the experimental result of the example belonging to (3-B) is shown in Table 12.

[0168]

[Table 11]

[0169]

[Table 12]

Good results were obtained in Examples 21 to 25 and Examples 26 to 30, but Comparative Examples 21 to 27 and Comparative Examples 28 to 28 except Comparative Examples 25 and 26 and Comparative Examples 32 and 33. Nos. 34 and 3 were all rough and caused problems.

Fog Measurement Method During image recording in each of the Examples and Comparative Examples, the image density of the non-image portion of the output image was measured with an image densitometer (Ma
cbethRD-918, manufactured by Macbeth).

Fog was judged to be good when the image density was 0.05 or less.

A comparative experiment for fog is shown in Table 13 (3
-A), as shown in Table 14 (3-B), Example 2
Good results were obtained in all of Examples 1 to 25 and Examples 26 to 30, but in Examples 21 to 27 and Comparative Examples 28 to 34, fog was large and problems occurred.

[0174]

[Table 13]

[0175]

[Table 14]

[0176]

According to the present invention, a two-component developer is used,
In a developing device which has a control electrode having an electrode portion to which a voltage can be applied is provided in a developing area or an upstream portion of the developing area and which performs a contact phenomenon, in the first and second inventions, the developer filling in the developing area is performed. The rate is regulated, the developer is moderately rough, the development efficiency is high, the position of the control electrode is stable, the carrier is prevented from climbing up, and the recorded image is stable and a high quality image with no roughness is stabilized. And in the third invention,
The developer filling rate A ₂ at the tip portion of the control electrode is made smaller than the developer filling rate A ₁ in the developing area so that A ₂ <A ₁ <2.5A ₂
As a result, the toner adhered to the non-image area by the toner cloud is developed by the magnetic brush at the same time.
Fogging toner adhering to the non-image area can be removed by rubbing the magnetic brush without generating sweep lines or vertical stripes in the image area, increasing the efficiency of toner cloud generation and developing. In the area G, the developer filling rate A ₁ is 0.0
By setting the ratio to 5 to 0.50, the amount of the developer required for the development can be obtained, but the developer filling rate is low, so that the scraping in the image area does not easily occur. Is not drawn to the downstream side of the rotation of the developer carrier, the position of the control electrode is stable, and the carrier is prevented from climbing up, so the recorded image is rough, rough, and fog-free. It has become possible to provide a developing device that can be stably obtained.

[Brief description of drawings]

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

FIG. 2 is a schematic sectional view showing another example of the developing device of the invention.

FIG. 3 is a schematic cross-sectional view showing an example of a single-color image forming apparatus provided with the developing device of the present invention.

FIG. 4 is a schematic sectional view showing an example of a color image forming apparatus provided with the developing device of the present invention.

FIG. 5 is a schematic cross-sectional view showing another example of a color image forming apparatus including the developing device of the present invention.

FIG. 6 is a cross-sectional view showing a gap between the developing area and the tip of the control electrode.

FIG. 7 is a sectional view showing the structure of a control electrode.

FIG. 8 is a cross-sectional view showing a configuration in the vicinity of an electrode portion of a control electrode.

FIG. 9 is a cross-sectional view showing another configuration near the electrode portion of the control electrode.

FIG. 10 is a plan view showing a width relationship between a control electrode and a developer transport body.

FIG. 11 is a cross-sectional view showing the dimensions and configuration of a control electrode used in a comparative experiment.

[Explanation of symbols]

10 Photoreceptor Drum (Image Forming Body) 11 Scotron Charger 12 Exposure Optical System 13 Developing Device 80 Control Electrode 81 Supporting Member 82 Electrode Part 83 Insulating Member 80a Tip Part 130 Developing Sleeve (Developer Conveying Body) 131 Magnet Roll (Magnetic Body) ) A ₁ , A ₂ developer filling rate E ₁ , E ₃ DC power supply E ₂ , E ₄ AC power supply G Development area p Center line P Transfer paper

Claims (8)

[Claims] 1. A magnetic body having a plurality of magnetic poles is fixed inside the image forming body, and the magnetic body is conveyed to a developing area or an upstream area of the developing area of a developer carrying body for carrying the magnetic developer to the developing area. In a developing device having a plate-shaped control electrode provided with an electrode part which is in contact with or in the vicinity of which a voltage can be applied, at least an AC voltage is applied to the developer carrier and at least a DC voltage is applied to the electrode part of the control electrode. The oscillating electric field is formed between the developer transport body and the electrode portion by the voltage applying means, and the layer of the developer is in contact with the image forming body in the developing area and the developing in the developing area is performed. The agent filling rate is 0.
The developing device is 06 to 0.60. 2. A magnet body having a plurality of magnetic poles is fixed inside the image carrier, and the magnetic body is conveyed to a developing area or an upstream area of the developing area of a developer carrying body. In a developing device having a plate-shaped control electrode provided with an electrode portion capable of applying a voltage that is in contact with or close to, a DC voltage is applied to the developer carrier at least, and an AC voltage is applied to the electrode part of the control electrode. The oscillating electric field is formed between the developer transport body and the electrode portion by the voltage applying means, and the layer of the developer is in contact with the image forming body in the developing area, and the developing in the developing area is performed. The agent filling rate is 0.
The developing device is 06 to 0.60. 3. The developer transport between the image forming body and the developer transport body, which has a main magnetic pole in a developing area of the developer transport body and has a rotation axis of the developer transport body as a center. The angle between the closest position on the body and the main magnetic pole is θ ₁ (°), the angle between the main magnetic pole and the control electrode tip is θ ₂ (°),
When the angle between the main magnetic pole and the magnetic pole adjacent to the upstream side of the main magnetic pole is θ ₃ (°) and the downstream side in the rotation direction of the developer transport body from the closest position is −, −10 _{° ≦ θ 1 ≦ + 10 °} + 20 ° ≦ θ 3 ≦ + 60 ° developing device according to claim 1 or 2, characterized in that the θ ₂ = 0.2θ ₃ ~0.9θ _3. 4. A magnetic body having a plurality of magnetic poles is fixed inside the image forming body, and the magnetic body is conveyed to a developing area or an upstream area of the developing area of the developer carrying body. In a developing device having a plate-shaped control electrode in which a voltage-applying electrode part is arranged in contact with or in proximity to the image forming body, the developing device develops in the developing region. when the replenishing rate a _1, the developer packing ratio at the tip portion of the control electrode and the a _2, a developing device which is a _{a 2 <a 1 <2.5A 2} . 5. The developer filling rate A ₁ in the developing area is 0.
The developing device according to claim 4, wherein the developing device has a thickness of 05 to 0.50. 6. A voltage applying means for applying at least an alternating voltage to the developer carrier and at least a direct voltage to the electrode portion of the control electrode.
Or the developing device described in 5. 7. A voltage applying means for applying at least a direct current voltage to the developer carrier and at least an alternating voltage to the electrode portion of the control electrode.
Or the developing device described in 5. 8. The developer transport between the image forming body and the developer transport body, which has a main magnetic pole in a developing area of the developer transport body and is centered on a rotation axis of the developer transport body. The angle between the closest position on the body and the main magnetic pole is θ ₁ (°),
8. When the downstream side in the rotation direction of the developer transport body from the closest position is defined as −, −10 ° ≦ θ ₁ ≦ + 10 ° is satisfied, and any one of claims 4 to 7 is characterized. Development device.