JPH08220889A - Developing device - Google Patents

Abstract

PURPOSE: To provide a developing device having high developability with stable high resolution at a low developing bias voltage. CONSTITUTION: In the developing device provided with a control electrode 84 constituted in such a manner that an electrode part 84a which is supported by an insulating member 83 abutted on a developer layer and capable of applying a voltage is disposed, in the developing area A of a developer carrier 81 facing an image forming body 1 or a part nearer to the upstream side than the developing area A, the developer D consists of at least toner having dt (μm) volume averaged grain size, carriers having dc (μm) volume averaged grin size and fine grains having da (μm) volume averaged grain size, expressed by equation [(dt +dc )/1000]<da <[(-dt +dc )/50].

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in electrophotographic copying machines and the like,
A magnetic brush developing type developing device using a two-component developer is used. This developing device has a developing sleeve, which is a cylindrical developer carrier, which is rotatably supported and has a magnet roll made of a magnet body having a plurality of magnetic poles inside. Toner particles are attached to the surface of the developing sleeve. The thus-obtained magnetic carrier is held and conveyed to the developing area for development.

Conventionally, as a two-component developing method, generally, magnetic carrier particles having a particle size of several tens μm to several hundreds μm and an average particle size of 10 are used.
A developer consisting of non-magnetic toner particles of around μm is used, and because toner particles and even carrier particles are coarse, it is difficult to obtain a high-quality image that reproduces delicate lines, dots, or density differences. There is. In order to obtain such a high quality image, it is considered necessary to make the toner particles and carrier particles finer. However, if the toner particles are made smaller than 10 μm, the influence of the van der Waals force is relatively large with respect to the Coulomb force during development, and so-called fog occurs in which the toner particles adhere to the background of the image background. As a result, it becomes difficult to prevent fogging even by applying a DC bias voltage to the developer transport body, it becomes difficult to control the triboelectric charging of the toner, and toner aggregation easily occurs. Carrier coverage becomes higher, which makes it more difficult to control charging. In order to reduce carrier coverage, the carrier particles become smaller, so that the carrier particles also adhere to the electrostatic image portion of the image forming body. The problem occurs. This can be caused by
It is considered that the magnetic bias force decreased and the carrier particles adhered to the image forming body side together with the toner particles. Further, when the bias voltage increases, carrier particles also adhere to the ground portion of the image background.

The fine particles of the toner and the carrier have a problem that the above-mentioned side effects are more noticeable and a clear image cannot be obtained. Therefore, the fine particles of the toner and the carrier are actually used. Was difficult.

As a method for solving the above problems, a plate-shaped member having an electrode in the upstream portion of the developing area is brought into contact with a developer carrying body (developing sleeve), and the electrode, the developer carrying body, and the developer carrying body are connected to each other. A method of forming an oscillating electric field in which the former is stronger than that of the image forming body and clouding the toner in the developer to perform development is disclosed in JP-A-5-346736 and JP-A-5-346736.
6-175485.

[0006]

However, in the above-described conventional method, since the plate-shaped member is in contact with the developer layer, the developer layer and the plate-shaped member rub against each other, and the friction heat causes the plate-shaped member to slide. There arises a problem that the toner in the developer (and also the carrier in the case of a coating carrier) is fused to the member. This fusing interferes with good conveyance of the developer layer and causes defects such as white stripes and blanks in the image.

The present invention solves the above-mentioned problems of the control electrode method, and the resolution and
It is an object of the present invention to provide a two-component non-contact developing device which has a high developability and is capable of stably obtaining a high-quality image free from defects such as white lines and image blanks for a long period of time.

[0008]

The above-mentioned object is to apply a voltage, which is supported by an insulating member in contact with a developer layer, to a developing area of a developer carrying body facing an image forming body or an upstream portion of the developing area. In a developing device having a control electrode provided with possible electrode portions, the developer is at least a toner having a volume average particle diameter d _t (μm), a carrier having a volume average particle diameter d _c (μm), and the following formula: It is achieved by a developing device characterized by comprising fine particles having _a volume average particle diameter d _a (μm) satisfying the condition of.

[(D _t + d _c ) / 1000] <d _a <[(d _t + d _c ) / 50]

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing an example of a color image forming apparatus equipped with the developing device of the present invention as a suitable developing means.

In FIG. 1, reference numeral 1 denotes a photoconductor belt which is a belt-shaped image forming body made of a flexible belt coated or vapor-deposited with a photoconductor, and the photoconductor belt 1 includes rotary rollers 2 and 3. It is installed between and is conveyed in the clockwise direction by driving the rotating roller 2.

Reference numeral 4 denotes a guide member fixed to the main body of the apparatus so as to be inscribed in the photoconductor belt 1. The photoconductor belt 1 is tensioned by the action of a tension roller 5, so that the inner peripheral surface of the guide member 1 becomes the guide member. Rub 4

6 is a scorotron charger as a charging means, and 7
Is a laser writing device using a laser beam as an image exposing means, and 8A to 8D are developing devices of the present invention which are a plurality of developing means each containing a developer of a specific color, and these image forming means are photosensitive members. It is arranged at a portion of the belt 1 in contact with the guide member 4.

Each of the developing devices 8A, 8B, 8C and 8D will be described in detail later. For example, each of the developing devices 8A, 8B, 8C and 8D accommodates yellow, magenta, cyan and black developers, respectively. Each developing sleeve (developer carrier) 81 to be kept is provided, and has a function of making the latent image on the photosensitive belt 1 visible by a non-contact reversal developing method. Unlike the contact development, the non-contact development has an advantage that it does not hinder the movement of the photosensitive belt 1.

A transfer device 12 and a cleaning device 13 are a blade 13a of the cleaning device 13 and a toner discharge roller.
13b is kept at a position apart from the surface of the photoconductor belt 1 during image formation and is pressed against the surface of the photoconductor belt 1 as shown in the figure only during cleaning after image transfer.

The process of forming a color image by such a color image forming apparatus is performed as follows.

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

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

That is, when image data, which is a color signal output from an image reading device separate from the color image forming device, is input to the laser writing device 7, the writing light source (not shown) in the laser writing device 7 is input. The laser beam (writing light) generated by the semiconductor laser as described above passes through a collimator lens and a cylindrical lens (not shown), is rotationally scanned by a rotary polygon mirror 74 rotated by a drive motor 71, and has an fθ lens 75 and a cylindrical lens 76.
After that, the optical path is bent by the two mirrors 77 and 78 in the meantime, and the main scanning is performed on the peripheral surface of the photoconductor belt 1 to which uniform charges have been applied in advance by the charger 6 of the scorotron, and the main scanning is performed to form a bright line. Form.

On the other hand, when the scanning is started, the laser beam is detected by an index sensor (not shown), and the first
The laser beam modulated by the color signal of (1) scans the peripheral surface of the photosensitive belt 1. Therefore, a latent image corresponding to the first color is formed on the peripheral surface of the photosensitive belt 1 by the main scanning by the laser beam and the sub-scanning by the conveyance of the photosensitive belt 1. This latent image is developed by the developing device 8A in which yellow (Y) toner (visual medium) is loaded in the developing means, and a toner image is formed on the belt surface. The obtained toner image passes under the blade 13a of the cleaning device 13 and the toner discharge roller 13b as the cleaning means, which is separated from the peripheral surface of the photosensitive belt 1 while being held on the belt surface, and the next image forming cycle is performed. to go into.

That is, the photoconductor belt 1 has the charger 6
Is charged again, and then the second color signal is input to the laser writing device 7, and writing is performed on the belt surface in the same manner as in the case of the first color signal described above to form a latent image. The latent image is developed by the developing device 8B loaded with magenta (M) toner as the second color.

The magenta (M) toner image is formed in the presence of the previously formed yellow (Y) toner image.

Reference numeral 8C denotes a developing device having cyan (C) toner, which forms a cyan (C) toner image on the belt surface in the same manner as the first and second colors.

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

The color toner image thus formed on the peripheral surface of the photosensitive belt 1 is sent from the paper feeding cassette 14 through the paper feeding guide 15 by applying a high voltage having a polarity opposite to that of the toner at the transfer portion. It is transferred to the transfer material.

That is, the transfer material contained in the paper feed cassette 14 is carried out by the rotation of the paper feed roller 16 so that one of the uppermost layers is carried out and the timing is adjusted with the image formation on the photosensitive belt 1 via the timing roller 17. And is supplied to the transfer device 12.

The transfer material having received the transfer of the toner image is surely separated from the photosensitive belt 1 which suddenly changes its direction along the rotating roller 2 and goes upward, and the toner image is fused by the fixing roller 18. After being fixed, the paper is discharged onto the tray 20 via the paper discharge roller 19.

On the other hand, the photosensitive belt 1 which has finished the transfer onto the transfer material is further conveyed and the blade 13a and the toner discharge roller 13b are brought into pressure contact with each other to remove the residual toner in the cleaning device 13 to finish the operation. Then, the blade 13a is separated again, and a little later, the toner discharge roller 13b is separated, and a new image forming process is started.

As the color image forming apparatus using the developing device of the present invention, the belt-shaped image forming body is described, but the image forming apparatus having the drum-shaped image forming body can be similarly used. .

The developing devices 8A to 8D have the same structure, and will be denoted by reference numeral 8 below.

FIG. 2 is a schematic sectional view showing an embodiment of the developing device of the present invention.

2 (a) and 2 (b) are a schematic sectional view and an enlarged sectional view of an essential part of an embodiment of the device of the present invention.
Reference numeral 81 denotes a developing sleeve which is a developer carrier made of a non-magnetic material such as aluminum, and is rotatable in the direction of the arrow in the figure. Reference numeral 82 denotes a plurality of Ns fixed inside the developing sleeve 81.
A magnet body having an S magnetic pole in the circumferential direction, and one magnetic pole 82a of the magnet body 82 is arranged in the developing area A which is the closest position between the developing sleeve 81 and the photosensitive belt 1, and is referred to as a main magnetic pole. . The developing sleeve 81 and the magnet body 82 exhibit a developer transport function. Each magnetic pole including the main magnetic pole 82a of the magnet body 82 is 50
It is magnetized to a magnetic flux density of 0 to 1,500 gauss, and the magnetic force thereof causes a layer of the magnetic developer D on the developer sleeve 81, that is,
This magnetic brush forming a magnetic brush is a developer sleeve
By the rotation of 81, it moves in the same direction and is conveyed to the developing area A. The magnetic brush formed on the developing sleeve 81 does not come into contact with the surface of the photoconductor belt 1 so that a gap is maintained between the developing sleeve 81 and the regulating blade 86 and the developing sleeve 81.
And the gap between the photoconductor belt 1 is adjusted.

Reference numeral 84 designates an electrode portion capable of applying a voltage on an insulating member 83 provided on the upstream side of the developing area A so as to contact the layer of the developer D.
84a and a control electrode in which an eave member 84c is further provided on the electrode portion 84a, and the insulating member 83 is made of an electrically insulating material such as polyester, polyimide, glass epoxy, polyethylene terephthalate or polyamide imide. The electrode portion 84a, which also functions as a shutter member, is made of a conductive material such as metal and is integrally provided linearly on the tip of the insulating member 83. The eaves member 84c is made of a glass epoxy plate or the like. Reference numerals 85A and 85B are stirring screws for stirring the developer D to make the components uniform, and 86 is a developer regulating means made of a non-magnetic material or a magnetic material provided to regulate the height and amount of the magnetic brush. A blade, 87 is a cleaning blade for removing the magnetic brush passing through the developing zone A from the developing sleeve 81, 88 is a developer reservoir, 89 is a casing, and 89a is provided in the casing 89 for supporting the fixed portion of the insulating member 83. The supporting portions 90, 90s are a holding plate and a set screw for fixing the control electrode 84 to the supporting portion 89a.

The control electrode and the developer which compose the developing device of the present invention will be described below.

B. Control Electrode 84-Structure-FIG. 3 is a perspective view and a sectional view showing an example of the control electrode 84. The control electrode 84 shown in FIG. 3 is formed by using a conventionally known printed circuit board manufacturing method, using glass epoxy, polyimide, paper phenol, or the like as the insulating member 83, laminating a conductive member such as copper foil, and then performing an etching treatment. ,
The electrode portion 84a is formed at the tip of the insulating member 83, and the electrode portion 84a is further formed by the eave member 84c made of a glass epoxy plate.
It is formed by coating a and adhering integrally so as to project.

FIG. 4A is a cross-sectional view showing another example of the control electrode 84, which is between the insulating member 83 and an eave member 84d having the same size as the insulating member 83, and the tip of which is the eave member 84d. The electrode portion 84a is formed at a position approximately 0.3 mm from the tip of the.

In FIG. 4B, an electrode portion 84a having a length of 0.5 mm is joined to the upper surface of an insulating member 83 made of a glass epoxy plate, and the tip of the electrode portion 84a is about 0.3 m from the tip of the insulating member 83.
It is formed at the retracted position.

Although the control electrode excluding the eaves members 84c and 84d can be used, the eaves member 84 shown in FIG.
Those having c are preferable because they can prevent the electrode portion 84a from being soiled.

The electrode portion 84a is made by forming a conductive material such as metal into a linear shape with a circular or quadrangular cross section, and affixing it to the tip of the insulating insulating member 83 with an adhesive or the like (FIG. 5).
(A), (b), (g), (h)), a notch 83a is provided at the tip of the insulating member 83, and is sandwiched by this (FIG. 5 (c),
(D)), a concave portion 83c may be provided at the tip of the insulating member 83 and embedded therein (FIGS. 5E and 5F), and the like. The electrode portion 84a may be covered with an insulating resin for preventing unnecessary discharge and for rust prevention.

-Manufacturing Method-As the substrate material, for example, polyester, polyimide,
Glass epoxy, ethylene-4 fluoroethylene copolymer,
Polytetrafluoroethylene-6 fluoropropylene copolymer, poly 4
As the resin material such as ethylene fluoride, polyamide imide, polysulfol, triazine resin and polyethylene terephthalate, an inorganic material such as glass fiber reinforced resin, ceramics, glass and alumina can be used. Electrolytic copper foil, annealed electrolytic copper foil, beryllium copper foil and the like are adhered to these substrates with an adhesive, and photoetching using a conventionally known photopolymer, etching resist composition by screen printing, etc. The necessary electrode parts are formed on the top. In addition, it is possible to use a method of printing a conductive ink corresponding to the electrode portion using a relief printing plate, a stencil printing plate, an intaglio printing plate, a planographic printing plate, a method of depositing a metal, and the like. Further, in order to prevent unnecessary discharge from the electrode, it is preferable to form an insulating coating layer on the electrode portion. In this case, a method of applying a member of the same kind as the substrate material described above or applying an insulating ink. Any method can be used.

Further, it is also possible to use a wire in which the electrode portion is a linear wire (FIGS. 5C, 5E, 5H).
reference).

In order to prevent unnecessary cloud formation in the upstream portion of the transport and to obtain a stable transport amount, the entire electrode portion 84a includes an insulating member 83 and a developing sleeve 81 as shown in FIG. 2B. The developing sleeve 81 is formed so as to be arranged only on the side of the closest position 81a of the developing sleeve 81 to the photosensitive belt 1 with respect to the closest contact 81b. The circumferential length of the electrode portion 84a depends on the diameter of the developing sleeve 81 and the conveying speed, but is preferably 0.05 to 5 mm, and particularly preferably 0.1 to 1 mm. If it is less than 0.05 mm, a sufficient 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 developing property is deteriorated.

[0043] The thickness t of the control electrode 84 (FIG. 3) is the closest distance between the photoreceptor belt 1 and the developing sleeve 81 of the developing zone A is taken as d _1, (1 / 10,000) d ₁ ~ (2/3) d ₁ , particularly (1 / 1,000) d ₁ to (2/3) d ₁ are preferable. (2/3) d ₁
If it is larger, the photoconductor belt 1 and the eaves members 84c, 84d.
Alternatively, since the gap with the electrode portion 84a becomes narrow, the eaves member 84
The c and 84d or the electrode portion 84a are likely to come into contact with the surface of the image forming body 1, and image disturbance is likely to occur. On the contrary (1/1
If it is less than 0,000) d ₁ , the current from the developing sleeve 81 is apt to flow in, a voltage drop is caused and the developability is apt to be lowered.

Assuming that the width of the electrode portion 84a (the length of the developing sleeve 81 in the axial direction) is W ₃ and the width of the developing area on the developing sleeve 81 (the width of the developer D layer) is W ₄ , it is shown in FIG. Like W ₃
As> W ₄ , the terminal portion 84b for applying the DC voltage E ₃ to the electrode portion 84a is also provided in the portion outside the width W _{4 of the} developing area to prevent generation of unnecessary toner cloud.

Further, the surface roughness Rz of the developing sleeve 81
_When the roughness Rz ₂ (μm) of ₁ (μm) and the surface of the insulating member 83 facing the developing sleeve 81 is Rz ₂ ≧ Rz ₁ , the developer carried on the developing sleeve 81 is carried to the insulating member 83. And the amount of toner conveyed to the developing area A is reduced, and the image density is reduced. Rz ₁ is in the range of 0.2 to ₂₀ μm, Rz ₂ is 0.02 to 5.0
The range of μm is preferable for obtaining a high-concentration image with good transportability and no image distortion. The surface roughness Rz was measured according to JIS B 0601 using Surftest-402 manufactured by Mitutoyo at a standard length of 25 mm.

B: Electrode setting conditions As shown in FIG. 2B, the installation position of the control electrode 84 is such that it is located in the developing area A or upstream of the developing area A with respect to the rotation of the developing sleeve 81. The developing pole 81 has a main magnetic pole in the developing area A of the developing sleeve 81, and the closest position 81a on the developing sleeve 81 between the developing sleeve 81 and the photosensitive belt 1 about the rotation axis O of the developing sleeve 81 and the main magnetic pole 82a. Is θ ₁ , and the closest position 81a and the control electrode 84 are also the same.
When the angle between the eaves member 84c and the tip of the eaves member 84c is θ ₄ , (C in FIG. 2 is a center line connecting the closest position 81a and the rotation axis O of the developing sleeve 81, and the value of the angle θ is Contact position 81
a), the upstream side is positive and the downstream side is negative), and -10 ° ≤ θ ₁ ≤ 10 ° (θ ₁ -5 °) ≤ θ ₄ ≤ (θ ₁ + 5 °) It was found that the ears of the developer D in the area A were improved, the development efficiency was kept high, and the toner was prevented from scattering.

When θ ₁ is less than 10 ° or exceeds 10 °, the developing agent D in the developing region A has a poor brushing property and the developing property is deteriorated.

When θ ₄ is smaller than (θ ₁ −5 °), the control electrode 84 covers the ears of the developer D too much, and the developability is deteriorated.
_{When 4} is larger than (θ ₁ + 5 °), the spikes of the developer D become too large, and the developer D comes into contact with the photoconductor of the photoconductor belt 1, causing bleeding and carrier adhesion to cause image distortion. Occurs.

As described above, by disposing the main magnetic pole 82a in the developing area A and disposing the control electrode 84 in the vicinity thereof so as to press the developer D layer, the spike of the developer D is moderated. Further, it was possible to realize the improvement of the developing property, which was not possible with the prior art, by applying a low developing bias voltage without causing the carrier adhesion. In this embodiment, d ₁ = 0.5 mm,
Good developability was obtained with d ₂ = 0.25 mm, θ ₁ = 1 °, and θ ₄ = 2 °. Here, d ₂ is the height (mm) of the electrode portion 84 a from the developing sleeve 81, and (0.2 to 0.6) d ₁ is preferable from the viewpoint of preventing discharge to the developing sleeve and the image forming body and securing developability.

C: Development Process / Emission Electric Field In the above embodiment, the bias voltage in which the AC component is superimposed on the DC component via the protection resistor R _{1 is applied} to the developing sleeve 81 by the DC bias power source E ₁ and the AC bias power source E _2. Is applied. A DC bias power source E ₃ is applied to the electrode portion 84a.
A bias voltage of only the DC component is applied from the protective resistor R ₂ via the protective resistor R ₂ . It is preferable to apply a DC voltage having the same polarity as the toner to the electrode portion 84a from the viewpoint of preventing toner adhesion.

When the DC voltage applied to the developing sleeve 81 is equal to the DC voltage applied to the electrode portion 84a, the DC bias power source E ₁ can be shared, as shown in FIG. 2C. It is possible to avoid complication of the device.

In the developing device 8 of the present invention, by applying the bias voltage as described above, it is possible to control the alternating electric field formed between the photosensitive belt 1 and the developing sleeve 81 (hereinafter referred to as the second oscillating electric field). A first oscillating electric field is generated between the electrode portion 84a of the electrode 84 and the developing sleeve 81.

In the above-mentioned color image forming apparatus, it is assumed that the OPC photosensitive member which is negatively charged is used as the photosensitive member of the photosensitive belt 1 and the reversal development is performed, and the photosensitive member is charged to, for example, -850V. Bias voltage of −750 V is applied to the developing sleeve 81, and bias voltage of −750 V is applied to the developing sleeve 81. AC component has a frequency of 100 Hz to 2
Zero peak voltage (V) at 0kHz, preferably 1kHz to 10kHz
_OP ) {1/2 of peak-peak voltage (V _PP )} will be described in detail later, but the closest distance d ₁ (mm) between the image forming body 1 and the developer carrying body 81, the development of the electrode portion 84a. Height from sleeve d ₂ (mm), toner volume average particle diameter d in developer
_{When t} (μm) and the average charge amount of the toner are Q (μC / g), 20 · Q · d _t · d ₁ > V _OP > 3 · Q · d _t · d
₂ , especially 10 · Q · d _t · d ₁ > V _OP > 5 · Q · d _t · d ₂ . In this case, since the electrode portion 84a is provided closer to the developing sleeve 81 than the photosensitive belt 1, the strength of the first oscillating electric field is higher than the strength of the second oscillating electric field.

The first oscillating electric field vibrates the toner particles of the developer D which have reached the vicinity of the electrode portion 84a in the direction perpendicular to the electric force line, so that the toner particles are separated and fly from the carrier to form a cloud haze shape. The toner cloud of can be sufficiently generated. This toner cloud is assisted by the flight toward the latent image on the photosensitive belt 1 by the second oscillating electric field, and uniform development is performed.

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

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

Next, the carrying amount of the developer D will be described.

In the embodiment described above, the amount of the developer D carried on the developing sleeve 81 preferably satisfies the following conditions.

Now, Dws is the developer carrying amount on the developer carrying member in the developing area (mg / cm ² ), Tc is the toner concentration (%) in the developer, and dt is the toner volume average particle size in the developer. (Μ
m), ρt is the toner density in the developer (g / cm ³ ), vs is the moving speed of the developer carrier in the developing area (mm / s), and vp is the moving speed of the image forming member in the developing area (mm / s), the following formula 1

[0060]

[Equation 1]

The value of D _T represented by is in the range of 1.5 to 9.

When D _T <1.5, the developability is poor because the amount of toner conveyed is small.

When D _T > 9, a toner excess phenomenon occurs and gradation reproducibility deteriorates. In this case, a large amount of toner is conveyed with respect to the required amount of developing toner, so that fog is likely to occur. Further, in order to obtain an appropriate image density, it is necessary to reduce the developing efficiency. Then, the toner having a large particle diameter that is easily developed in the developer D is developed, and the toner having a small particle diameter that is difficult to be developed is accumulated in the developer,
In the long term, so-called "selective development" occurs in which the developability decreases. Further, since toner is lost during transfer and fixing, it is particularly preferable to maintain the value of D _T at 2.5 to 7.5 in order to obtain better gradation reproducibility.

FIG. 7 shows Example 1a of Table 1 and Table 2 described later.
D _T and maximum image density D by changing D _T using the developing device (FIG. 2), developer, and color image forming device (FIG. 2)
The relationship between _m and the density D _{f of the} white background portion of the image is shown. D
As described above, _T is changed by adjusting the gap between the developer amount regulating member 86 and the developer transport body 81. Further, this result is obtained by using only the black developing device 8D in the image forming apparatus of FIG. 2 and by using the black toner having the highest potential (−850V, non-exposed portion) and the lowest potential (−50V, exposed portion) on the image forming body. An image is developed, transferred by corona discharge to a transfer paper, and fixed by a heat roller.
8, manufactured by Macbeth). As shown in FIG, be in the range of D _T is from 1.5 to 9, fog without it can be seen that a high image density good images are acquired. Here, the zero peak voltage (V _OP ) of the AC component applied to the developing sleeve 81 is the closest distance d ₁ (mm) between the image forming body 1 and the developer carrying body 81, and the developing sleeve of the electrode portion 84a. Height d ₂ (mm), toner volume average particle diameter d _t (μm) in the developer, and average charge amount of the toner is Q (μC
/ G), 20 · Q · d _t · d ₁ > V _OP > 3 ·
Q ・ d _t・ d ₂ , especially 10 ・ Q ・ d _t・ d ₁ > V _OP > 5 ・ Q
It is preferable that it is in the range of d _t d ₂ . In Figure 7, zero peak voltage is 130V _OP , is 800V _OP , is 16
This is the case of 00V _OP . The frequency component is 100Hz-20kHz,
Particularly, it is preferably 1 kHz to 10 kHz. The DC component applied to the developer transport body 81 and the electrode portion 84a is set to -750V as in Example 1a. Also, this result is
It goes without saying that the same applies to developing devices other than black.

In order to adjust the carrying amount of the developer D,
A known developer amount regulating member is provided upstream of the contact point of the control electrode 84 with the developing sleeve 81. As the restricting member, an elastic blade type in which an elastic body such as rubber is pressed against the layer of the developer D, or a type in which a magnetic member such as magnetic stainless steel is pressed against the developer D layer by the magnet body 82 in the developing sleeve 81, The developer D faces the magnet body 82 in the developing sleeve 81.
Although there is a spike control type including a non-magnetic blade (regulating blade 86 of FIG. 2) arranged with a certain gap between the sleeve 81 and the like, in the present invention, the gap with the developing sleeve 81 is changed to be relatively easy. In addition, it is preferable to use a spike control type capable of controlling the developer transport amount.

A moving speed ratio v between the developing sleeve 81 and the image forming body
s / vp was adjusted by changing the rotation speed of the developing sleeve 81.

D _WS which is the developer transport amount per unit area
(G / cm ² ) is measured by attaching the developer D on the developing sleeve 81 to an adhesive tape that has been weighed in advance,
It was calculated by dividing the value of the weight difference of the adhesive tape before and after the adhesion of the developer D by the area of the adhesive tape.

As described above, the developing device of the present invention keeps the two-component developer in non-contact with the photoreceptor belt 1 which is an image forming body, and generates a toner cloud by the first and second oscillating electric fields. Therefore, the separation and flight to the photosensitive belt 1 are improved, the selective adsorption property to the electrostatic image is improved, and the carrier particles are prevented from adhering to the photosensitive belt 1. Although it is made possible to use a developer, a high-quality image can be developed, and it is preferable to use a developer D composed of the following carrier particles and toner particles.

D: Toner The volume average particle size (d _t ) is 1 to 20 μm, preferably 3 to 10
μm. When the volume average particle diameter d _t is smaller than 1 μm, the toner adheres to the carrier (toner spent) due to friction and the carrier coverage increases, so that charging failure and scattering easily occur. When the volume average particle diameter d _t is larger than 20 μm, the image quality is deteriorated.

-Measuring method- Coulter counter TA-II type (Aperture 100
μm, manufactured by Beckman Coulter, Inc.).

As the toner binder resin, a resin such as a styrene resin, a vinyl resin, an ethylene resin, a rosin-modified resin, an acrylic resin, a polyamide resin, an epoxy resin, a polyester resin, or a styrene resin thereof.
-A copolymer resin such as an acrylic resin or a mixed resin 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, etc. are added,
It can be produced by a method equivalent to a toner production method such as a conventionally known pulverization method, suspension polymerization method, emulsion polymerization method and the like.

Charging property Since the toner particles follow the electric field, the average charge amount of the toner particles is 1 to 50 μC / g in absolute value, preferably 5
From the viewpoint of securing developability and preventing fog and scattering, it is desirable that the content be -40 μC / g. Especially when the particle size is small, a high charge amount is required.

The average charge amount Q of the toner is as described above while the conductive plate of 2 cm × 5 cm is opposed to the developing roller having a diameter of 20 mm at the closest distance of 0.7 mm, the developer is supplied to the developing roller, and the developing roller is rotated at 200 rpm. Superimposing voltage of DC and AC on the developing roller (for example, DC; 1000V, AC; 750V _OP , AC frequency 8
(KHz) is applied to develop the toner in the developer on the conductive plate, the conductive plate on which the toner is developed is connected to a Faraday gauge, and the toner is blown off with nitrogen gas. It is obtained by measuring the charge amount and the weight of the toner.

Examples of such toner include styrene resin, vinyl resin, ethyl resin, rosin-modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, and styrene-acrylic resin. By adding a coloring component such as a color pigment, a charge control agent, a release agent such as wax, etc. to a polymer resin or a mixed resin, if necessary, a conventionally known pulverization granulation method, suspension polymerization method, emulsification method or the like. It can be obtained by a toner manufacturing method such as a polymerization method. That is, it is possible to use a toner obtained by selecting non-magnetic or magnetic non-magnetic or magnetic toner particles of the conventional toner by the average particle size selection means.

E: Carrier When the two-component developer is used in the developing device of the present invention, the following carrier particles are preferable.

Volume average particle diameter (d _c ) is 10 to 60 μm, preferably 20 to 50 μm. When the volume average particle diameter d _c is smaller than 10 μm, it becomes difficult to give sufficient magnetization to the carrier, and carrier adhesion is likely to occur. Volume average particle diameter d _c
Is more than 60 μm, the carrier has a small specific surface area, so that the toner cannot be sufficiently charged. Further, since the coverage is high, toner scattering easily occurs.

-Measurement Method- Laser diffraction type particle size distribution measuring device "HERO equipped with a wet dispersion machine"
S ”(manufactured by SYMPATEC), which is a volume-based average particle size, and a wet disperser was used to disperse 10 mg of magnetic particles in 50 ml of water together with a surfactant, and then an ultrasonic homogenizer (output 150 W). It is a value measured after performing a pretreatment for dispersing for 1 to 10 minutes while paying attention to re-aggregation due to heat generation.

The strength of magnetization (σ1000) is 5 to 60 emu /
g, preferably 10-40 emu / g.

Although depending on the magnetic flux density on the developer transport body, if the carrier magnetization is smaller than 5 emu / g at the magnetic flux density of 500 to 1200 gauss generally used for the developer transport body,
The magnetic binding force does not work, causing carrier scattering.
On the other hand, if it exceeds 60 emu / g, the carrier spike becomes too high and it is difficult to maintain the non-contact state with the image forming body.

-Measurement method-After charging carrier particles into a sample cell of 0.25 cm x 3 cm ² while tapping them, the sample was attached to a pickup coil and set in a magnetizer, and a DC magnetization characteristic automatic recording device "TYPE
3257 "(manufactured by Yokogawa Hokushin Electric Co., Ltd.) to draw a hysteresis curve on an XY recorder.

Such a magnetic carrier is iron, chromium, nickel, which is equivalent to a conventional magnetic carrier as a magnetic body,
Spherical particles of a metal such as cobalt, or a compound or alloy thereof, such as ferric tetroxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite, manganese-copper alloy, or Styrene resin, vinyl resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, silicone resin, fluorine resin, etc. It can be obtained by spherical coating with a homopolymer or a copolymer.

Also, a so-called resin dispersion type carrier in which magnetic fine particles are dispersed and contained in these resins can be used. In this case, since the carrier has an irregular shape, the specific surface area increases, and a sufficient amount of toner necessary for development can be obtained with a lower surface coverage, toner scattering does not easily occur, and development stability is improved. From the viewpoint of.

F: Added fine particles-A proper gap is formed between the toner / carrier and the control electrode in order to prevent the toner / carrier from rubbing against the control electrode and being fused by the frictional heat. Add fine particles.

From the viewpoint of the effect of preventing toner fusion and the dispersibility of fine particles, the fine particles to be added are preferably inorganic fine particles.
These inorganic fine particles include silicon oxide, aluminum oxide, titanium oxide, zinc oxide, zirconia oxide, chromium oxide, cerium oxide, tungsten oxide, antimony oxide, copper oxide, tin oxide, tellurium oxide, manganese oxide,
Boron oxide, barium titanate, aluminum titanate, magnesium titanate, calcium titanate, oxides such as strontium titanate, carbides such as silicon carbide, tungsten carbide, boron carbide, titanium carbide, silicon nitride, titanium nitride, boron nitride And the like are preferable. These may be used alone or in combination of two or more.

Further, it may be composite fine particles in which the above-mentioned inorganic fine particles are mechanically fixed or melted and adhered to the surface of the organic fine particles. As the organic fine particles, for example, acrylic resin, styrene resin, styrene / acrylic copolymer resin, fluorine resin, silicone resin, olefin polymer, olefin copolymer resin and the like can be used.

Volume average particle diameter d _a (μ
m) is the mean of the toner volume particle size d _t ([mu] m), when the cold blood volume diameter d _c of the carrier ([mu] m), is preferably in the range of the following equation.

[(D _t + d _c ) / 1000] <d _a <[(d _t + d _c ) / 50] d _a ≦ [(d _t + d _c ) / 1000]: Fine particles are present in the concave portions of the toner or carrier surface. The effect of preventing entrapment and fusion does not appear sufficiently. Further, when the added fine particles are small, the added fine particles are likely to be buried in the toner / carrier during long-term use, which causes a problem of stability.

[(D _t + d _c ) / 50] ≦ d _a : The dispersibility of the added fine particles becomes poor and the fluidity of the developer is lowered, so that the image quality is lowered.

The addition amount of these is 0.1 with respect to the toner.
It is preferably 10 to 10 parts by weight, more preferably 0.5 to 5 parts by weight. When the amount is less than 0.1 parts by weight, the number of the fine particles is small, so that the sufficient effect is not exhibited, and when the amount is more than 10 parts by weight, the dispersion of the fine particles becomes poor and the developability is deteriorated.

In the control electrode developing method, unlike the case of a general leveling member, the toner in the developer is vibrated by the control electrode, so that the added fine particles are easily embedded in the toner / carrier surface, and It also becomes easy to detach from the surface. Therefore, it is particularly important that the particle size of fine particles and the number of added parts are within the ranges described above.

By adding the above-mentioned fine particles, in the control electrode method, a proper gap can be formed between the toner / carrier and the control electrode, and fusion can be prevented for a long time. Further, the added fine particles act as an abrasive and can remove the toner / carrier fused to the control electrode surface.

For the volume average particle diameter of these fine particles, an enlarged image (magnification: 50,000 times) of the added fine particles obtained by using a scanning electron microscope is used, and an image analyzer "SPICCA" (Japan Avionics Co., Ltd.) is used. Manufactured), and by image analysis, particles
This is the average value of the equivalent circle diameter (μm) for 500 pieces.

In addition to these fine particles, a conventionally known fluidity-imparting agent such as silicon oxide may be used together in order to impart fluidity to the toner.

In summary, in the developing device of the present invention, the preferable toner particles are the resin as described for the carrier particles and further the fine particles of the magnetic material, and the coloring component such as carbon and the electrification as necessary. A volume average particle diameter of 20 μm or less, particularly preferably 3 to 10 μm, which can be produced by a method similar to a conventionally known method for producing toner particles by adding a control agent or the like, is used.

In the developing device of the present invention, a developer in which the spherical carrier particles and the toner particles as described above are mixed in the same proportion as in the conventional two-component developer is preferably used. When a general coating carrier (density of 5 to 8 g / cm ³ ) is used, the toner concentration in the developer is 2 to 30% by weight, preferably 5 to 20% by weight.
Is.

If the toner concentration 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 the toner concentration is higher than 30% by weight, the coverage will be high,
Poor charging and toner scattering are likely to occur.

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

Note that v _S / v _P in the equation 1 is 1 to
4, preferably 1 to 2.5.

When it is less than 1, the amount of toner conveyed to the developing area A is small and the developing property is deteriorated. When it is more than 4, the toner is excessive in the end portion, especially the rear end portion of the solid image. "Bias" that develops occurs.

It is necessary for v _S / v _P to be as close to 1 as possible in a region larger than 1 so as not to cause the above-mentioned "bias". For the same reason, it is desirable that the developer transport body and the image forming body move in the same direction.

Needless to say, in the above example, if the toner of the two-component developer has magnetism, the magnetic latent image can be visualized under the same developing conditions.

Example An image was formed by using the developing device shown in FIG. 2 and the color image forming device shown in FIG. The photoconductor belt 1 is an OPC photoconductor, the peripheral speed is 180 mm / sec, the maximum potential of the electrostatic latent image formed on the photoconductor belt 1 is -850 V (non-image part potential), and the minimum potential is -50 V (image part). Potential), outer diameter of developing sleeve 81, surface roughness Rz ₁ = 1.2 μm, strength of magnetic force on developing sleeve surface 700 gauss, d ₁ = 0.5 mm, θ ₁ = + 1 °, θ ₄ = + 2
The control electrode 84 uses a glass epoxy plate having a thickness of 0.1 mm as the insulating member 83, and the electrode portion having a width of 0.5 mm in the circumferential direction is formed on the insulating member as shown in FIG. 4 (b). 0.02 mm
Formed by laminating etching method using copper foil of
The tip of the electrode portion 84a is 0.3 mm from the tip of the insulating member 83.
The one set in the receding part was used. The surface roughness Rz _{2 of the} insulating member 83 on the developer carrier side is 0.08 μm. As the developer amount regulating member, a spike-shaped regulating plate type regulating blade 86 as shown in FIG. 2 was used. The voltages applied to the developing sleeve and the electrode part are shown in Table 1.

[0103]

[Table 1]

[0104]

[Table 2]

Carrier: Carrier No. 1 (Examples 1 and 2 and Comparative Examples 1 and 2) Spherical ferrite particles having a magnetization intensity of 25 emu / g were obtained by surface-coating a methyl methacrylate / styrene copolymer resin. The volume average particle diameter d _c is 45 μm and the density is 5.2 g / cm ³ .

Toner (common): 100 parts by weight of styrene-acrylic resin (Haimer up110 manufactured by Sanyo Kasei), color pigment
After melting and kneading 10 parts by weight and 1 part by weight of nigrosine,
Pulverized and classified, yellow with a volume average particle diameter d _t 8.5 μm,
Magenta, cyan, and black toners were obtained. The toner was added with fine particles as shown in Table 3 and used.
The density was 1.1 g / cm ³ .

[0107]

[Table 3]

Developer: A combination of the additive fine particles shown in Table 3 was used to treat the toner as an external additive, and the carrier was mixed with the toner at a toner concentration of 4%. The carrying amount of each is shown in Table 2.

Developing device: Using these developing process, carrier and toner, 50,000 full-color images were recorded under the conditions shown in Table 1. In Examples 1 and 2, toner / carrier fusion to the control electrode did not occur, and stable images having high density and resolution with no conveyance failure were obtained, but in Comparative Examples 1 and 2, from about 1000 copies Toner / carrier fusion to the control electrode started and increased, and as a result, conveyance failure occurred from 2000 copies and white streaks occurred in the image.

[0110]

According to the developing device of the present invention having the above-described structure, a) a carrier having an average particle size of 30 μm or less or an average particle size of 10 μm is used.
There is no problem even if the following toners are used, and it is stable and high when used in an image forming apparatus in which a multicolor image formed by superposing toner images on an image forming body is collectively transferred onto a transfer material to obtain a color image. Developability and gradation can be obtained.

B) A control electrode in which a linear electrode portion and an eaves member are arranged on an insulating member is provided in the developing area or in the upstream area of the developing area, and each volume average particle diameter of toner, carrier and added fine particles is within a predetermined range. By setting to 2, the high resolution and developability of the toner does not adhere to the control electrode plate, and a high quality image free of defects such as white lines and image blemishes can be obtained stably for a long period of time. A contact developing device could be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a color image forming apparatus including a developing device of the present invention.

FIG. 2 is a schematic sectional view showing an embodiment of the developing device of the present invention.

FIG. 3 is a perspective view and a cross-sectional view showing an example of a control electrode.

FIG. 4 is a cross-sectional view showing another example of the control electrode.

FIG. 5 is a cross-sectional view showing another form of the insulating member and the electrode portion of the control electrode.

FIG. 6 is a plan view showing a relationship between each part of the control electrode and the width of the developing sleeve.

FIG. 7 is a graph showing a preferred region of D _T.

[Explanation of symbols]

1 photoconductor belt (image forming body) 6 scorotron charger 7 laser writing device 8, 8A, 8B, 8C, 8D developing device 81 developing sleeve (developer carrier) 82 magnet body 82a main pole 83 insulating member 84 control electrode 84a Electrode parts 84c, 84d Eaves member 86 Control blade A Development area D Developer E ₁ , E ₃ DC bias power supply E ₂ AC bias power supply

Continuation of front page (51) Int.Cl. ⁶ Identification number In-house reference number FI Technical indication location G03G 15/09 G03G 9/10 (72) Inventor Hiroyuki Nomori 2970 Ishikawacho, Hachioji, Tokyo Konica Stock Company

Claims (1)

[Claims] 1. A voltage-applying electrode portion supported by an insulating member in contact with a developer layer is provided in a developing area of a developer transporting body facing the image forming body or in an upstream portion of the developing area. In the developing device having the control electrode, the developer is at least a toner having a volume average particle diameter d _t (μm), a carrier having a volume average particle diameter d _c (μm), and a volume average particle diameter satisfying the following expression. A developing device comprising fine particles of d _a (μm). [(d _t + d _c ) / 1000] <d _a <[(d _t + d _c ) / 50]