JPH0256670B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in a method for developing an electrostatic latent image or a magnetic latent image in an electrophotographic copying apparatus, etc.
Specifically, a developer containing a mixture of magnetic carrier particles and toner particles is supplied to the surface of a developer transport carrier to form a developer layer on the developer transport carrier, and the developer layer forms a developer layer on the surface of the image carrier. The present invention relates to an improvement in a method for developing an electrostatic latent image or a magnetic latent image.

[Prior art]

As an example, an outline of a developing method in an electrophotographic copying apparatus will be described. Regarding this, the magnetic brush development method using a general two-component developer is as follows.
Frictional charging control of toner particles is relatively easy, toner particle aggregation is difficult to occur, the magnetic brush stands up well, has excellent abrasion properties on the image bearing surface, and has sufficient cleaning effect even when used for cleaning. Because of these characteristics, it is widely used even though it is not necessary to control the amount of toner particles relative to carrier particles. However, in the development method in which a magnetic brush is rubbed against the surface of the image carrier, magnetic carrier particles with an average particle size of several tens to hundreds of μm and non-magnetic toner particles with an average particle size of several tens of μm are conventionally used. However, because the toner particles and even the carrier particles are coarse, it is difficult to obtain high-quality images that reproduce delicate lines, dots, and differences in shading. Therefore, in order to obtain high-quality images using this developing method, many efforts have been made in the past, such as coating the carrier particles with resin, improving the magnets in the developer transport carrier, and examining the bias voltage for the developer transport carrier. However, the reality is that stable and fully satisfactory images still cannot be obtained.
Therefore, in order to obtain high quality images, it is considered necessary to make the toner particles and carrier particles even finer. However, when toner particles are made into fine particles with an average particle size of 20 μm or less, especially 10 μm or less, the influence of Van der Waals force appears relative to the Coulomb force during development, and the toner particles also appear in the ground area of the image background. It becomes difficult to prevent fogging even by applying a DC bias voltage to the developer transport carrier, and it becomes difficult to control triboelectric charging of toner particles, making it easier for agglomeration to occur. . On the other hand, as the carrier particles are made finer, the carrier particles also come to adhere to the electrostatic image portion of the image carrier. The reason for this is thought to be that the magnetic bias force was reduced and the carrier particles adhered to the image carrier side together with the toner particles. Note that as the bias voltage increases, carrier particles will also adhere to other parts of the image background.

The problem with micronization is that the side effects mentioned above are more noticeable and clear images cannot be obtained, so it is difficult to actually use micronization of toner particles and carrier particles. It was hot.

[Purpose of the invention]

According to the present invention, fine particles can be used for the toner and carrier of the two-component developer, and fogging and adhesion of carrier particles to the image bearing surface are prevented, and a clear high-quality image can be developed. An electrostatic image developing method is provided.

[Structure of the invention]

The present invention provides a method for developing a latent image on an image carrier with a two-component developer layer formed on a developer transport carrier using a two-component developer consisting of toner particles and magnetic carrier particles. The two-component developer layer on the component developer layer transport carrier and the image carrier are maintained in non-contact, and a control electrode is provided in the gap therebetween to control the flight of toner particles from the developer layer to the image carrier, A developing method characterized in that development is carried out under an oscillating electric field by an alternating current voltage component applied to at least one of the control electrode or the developer transport carrier, and by this feature, the above-mentioned The purpose has been achieved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings, particularly in the case of developing an electrostatic latent image by electrophotography or the like.

1 to 3 are schematic cross-sectional views showing examples of developing devices used in the present invention.

In the figure, 1 rotates in the direction of the arrow, and on the surface,
A drum-shaped image having an electrophotographic photoreceptor layer or dielectric layer on which an electrostatic image is formed by a known charging and exposure device (not shown) or an electrostatic image forming device using a multi-stylus electrode or an ion control electrode. The carrier body 2 is a sleeve made of a non-magnetic material such as aluminum, and 3 is a magnet body that is provided inside the sleeve 2 and has a plurality of N and S magnetic poles on its surface in the circumferential direction. This constitutes a developer transport carrier. The sleeve 2 and the magnet 3 can rotate relative to each other, and the figure shows that the sleeve 2 rotates to the left and the magnet 3 rotates to the right. Further, the N and S magnetic poles of the magnet body 3 are normally magnetized to a magnetic flux density of 500 to 1500 Gauss, and the layer of developer D consisting of toner particles and carrier particles is attached to the surface of the sleeve 2 by the magnetic force. This forms a so-called magnetic brush. This magnetic brush is moved in the same direction as the rotation of the sleeve 2 by the rotation of the sleeve 2 and the magnet body 3, and is conveyed to the development area A. 4 is a layer thickness regulating blade made of magnetic or non-magnetic material that regulates the height and amount of the magnetic brush on the surface of the sleeve 2; 5 is a cleaning blade that removes the magnetic brush that has passed through the development area A from above the sleeve 2; is a developer reservoir; 7 is a stirring screw that stirs the developer D in the developer reservoir 6 to uniformly mix toner particles and carrier particles; 8 is a toner hopper for replenishing toner particles T; 9 is a developer reservoir 6 is a toner supply roller having a concave portion on its surface for dropping toner particles T thereon. That is, the developer reservoir 6 contains a two-component developer consisting of toner particles and carrier particles. The configuration of the developing device up to this point is the same as that of a developing device used in a conventional developing method using a two-component developer. In the device shown in FIG. 1, the magnetic flux densities of the N and S magnetic poles of the magnet body 3 are approximately equal,
The device shown in FIG. 2 differs from the device shown in FIG. 1 in that the magnet 3 rotates in the opposite direction to the sleeve 2, whereas the device shown in FIG. 3 does not rotate. The magnetic flux density of the N and S magnetic poles of the magnet body 3 are not the same, and the magnetic flux density of the magnetic pole facing the image carrier 1 is larger than the magnetic flux density of the other N and S magnetic poles. different from. Note that increasing the magnetic flux density facing the image carrier 1 is not limited to the case where the same N or S magnetic poles are lined up and facing each other as shown in the third figure, but also when the N and S magnetic poles are lined up and facing each other. Of course it's a good thing. By arranging a plurality of magnetic poles to face each other in this manner, it is possible to obtain the effect that development is more stable than when a single pole is posed to face each other.

In contrast to the above-described structure of the developing device, in the developing device used in the present invention, the magnetic brush formed on the sleeve 2 is layered with the sleeve 2 so that a gap is maintained without contacting the surface of the image carrier 1. The gap between the thickness regulating blade 5 and the gap between the sleeve 2 and the image carrier 1 is adjusted, and the gap between the magnetic brush and the image carrier 1 is provided with a wire, such as a wire stretched parallel to the axial direction of the sleeve 2. A control electrode 10 which itself does not prevent toner particles from flying from the magnetic brush to the image carrier 1 is provided, and a voltage having an alternating current voltage component is applied to the control electrode 10 or the sleeve 2, whereby the development area A is An oscillating electric field is formed under the oscillating electric field, and development is performed using a magnetic brush under this oscillating electric field. 11 and 12 are power sources for applying voltage to the control electrode 10 and the sleeve 2, respectively, and 13 and 14 are protection resistors.

A control electrode 10 is placed between the magnetic brush and the image carrier 1.
This is because the gap between the sleeve 2 and the control electrode 10 is several tens of μm or more, and the gap between the control electrode 10 and the image carrier 1 is
It is preferable that the gap between the sleeve 2 and the image carrier 1 is several tens of μm or more, and the gap between the sleeve 2 and the image carrier 1 is 2000 μm or less. When the gap between the sleeve 2 and the control electrode 10 becomes narrower than several tens of micrometers, it becomes difficult to form uniform magnetic brush ears, and it becomes impossible to supply sufficient toner particles to the developing section, resulting in a stable condition. Development is not performed, and if the gap between the control electrode 10 and the image carrier 1 becomes narrower than several tens of micrometers, discharge is likely to occur. Furthermore, if the gap between the sleeve 2 and the image carrier 1 exceeds 2000 μm, the sleeve 2
The electrode effect decreases, making it impossible to obtain a sufficient developed density, and edge effects also become noticeable. Note that the control electrode 10 is preferably one in which wires having a thickness of 100 to 1000 μm are stretched in parallel at intervals of 0.5 to 5 mm. Also, similarly,
Meshes with grid holes of 0.5 to 5 mm are also used.
Such a control electrode 10 provides a sufficient control effect to the toner particles flying from the magnetic brush to the electrostatic image on the image carrier 1, hardly hindering the flight of the toner particles, and even if the toner particles adhere, they can be removed. It has the excellent feature that it can be easily carried out.

Development under an oscillating electric field is performed by applying the following to the control electrode 10 and sleeve 2 set as described above.
This is done by applying a voltage having an alternating current component using power supplies 11 and 12.

(i) A voltage having an AC component is applied only to the control electrode 10. In this case, the control electrode 10 has a frequency of 100Hz.
200 at a frequency of ~10kHz, preferably 1-5kHz
~4000V AC voltage, preferably 600V to it
It is preferable to apply a superimposed voltage of a DC voltage in the range up to 600V, and to apply a DC voltage in the range up to 600V to the sleeve 2. Note that the DC voltage applied to the sleeve 2 is preferably set higher than the potential of the non-image area of the image carrier 1 in order to prevent toner fogging.

(ii) Applying a voltage having an alternating current component to both the control electrode 10 and the sleeve 2. In this case, when the same frequency is used for both AC components, it is usually preferable to apply a larger AC voltage to the sleeve 2 than to the control electrode 10, and when different frequencies are used, to avoid waviness in the electric field. In addition, it is preferable that the frequencies are separated from each other by an integral multiple. Furthermore, it is better to apply a high frequency AC component voltage to the sleeve 2 than to the control electrode 10.
This is preferable because a uniform cloud of toner particles is likely to be formed between the two. Further, it is preferable that the magnitude of the AC voltage component is larger in the sleeve 2 than in the control electrode 10, and it is preferable that DC voltages of up to 600V are applied to the sleeve 2 and the control electrode 10 in a superimposed manner. This sleeve 2
It is also preferable that the DC voltage applied to the image carrier 1 is set higher than the potential of the non-image area of the image carrier 1 in order to prevent toner fogging. In this case as well, the frequency and voltage value of the AC component are preferably in the same range as in case (i).

(iii) A voltage having an AC component is applied only to the sleeve 2. In this case, sleeve 2 has 100Hz~
200 to 10kHz, preferably 1 to 5kHz frequency
It is preferable to apply an AC voltage of 4000V, preferably a DC voltage of up to 600V superimposed thereon, and also apply a suitable DC voltage of up to 600V to the control electrode 10. In this case as well, the DC voltage of the sleeve 2 is preferably set higher than the potential of the non-image area of the image carrier 1 in order to prevent toner fogging.

The waveforms of the above AC component voltages are not limited to sine waves;
It may be a rectangular wave, a triangular wave, or the like. Although the frequency is also related, the higher the voltage value, the more the magnetic brush of the developer is vibrated, and the more easily the toner particles are separated from the carrier particles.
On the other hand, dielectric breakdowns such as fogging and lightning development are more likely to occur. Regarding this, the occurrence of fogging is prevented by the DC voltage component, and the dielectric breakdown is prevented by the control electrode 10.
This can be prevented by coating the surface of the sleeve 2 with an insulating or semi-insulating layer such as a resin or oxide film, or by using insulating carrier particles as described below for the carrier particles of the developer. Can be done.

As described above, in the developing method of the present invention, the magnetic brush of the two-component developer is maintained in a non-contact manner with respect to the image bearing member 1, and the control electrode 10 is provided between the non-contact points, and development by the magnetic brush is carried out. By performing the toner particles under an oscillating electric field, the ability to separate the toner particles from the magnetic brush is improved, the selective adsorption to the electrostatic image is improved, and the carrier particles adhere to the image carrier 1. Therefore, it is possible to use fine toner particles and carrier particles to develop high-quality images. It is preferable to use a two-component developer consisting of toner particles and toner particles.

First, regarding the carrier particles, generally speaking, when magnetic carrier particles have a large average particle size, the ears of the magnetic brush formed on the developer transport carrier become rough, and the electrostatic image is developed while being vibrated by the electric field. However, unevenness tends to appear in the toner image, and the toner concentration in the magnetic brush ear also decreases, causing problems such as high-density development is no longer possible. In order to solve this problem, the average particle size of the carrier particles can be reduced, and as a result of experiments, the average particle size
It was found that the effect begins to appear when the thickness is 50 μm or less, and when the thickness is 30 μm or less, the problems of ◯ and B virtually no longer occur. In addition, the problems of ◯ and ② are also solved by making the magnetic carrier finer particles, which increases the toner concentration in the spikes and enables high-density development. However, if the carrier particles are too fine, they tend to adhere to the surface of the image carrier together with the toner particles, or they tend to scatter. These developments are also related to the strength of the magnetic field acting on the carrier particles and the resulting magnetization of the carrier particles, but in general, a tendency gradually begins to appear when the average particle size of the carrier particles becomes 15 μm or less. ,5μm
This becomes noticeable below. A portion of the carrier particles adhering to the image bearing surface is transferred onto the recording paper along with the toner, and the remaining part is removed from the image bearing surface along with the residual toner by a cleaning device such as a blade or fur brush. With the carrier particles made only of magnetic material, there is a problem that the carrier particles transferred onto the recording paper (○) are not fixed to the recording paper by themselves and easily fall off, and the carrier particles (○) remain on the image carrier surface. There is a problem in that when the carrier particles are removed by a cleaning device, they tend to damage the surface of the image bearing member, which is a photoreceptor. The problems of ◯◯ and ◯ can be solved by forming magnetic carrier particles together with a substance that can be fixed to recording paper, such as resin. That is, since the magnetic carrier particles are formed together with a substance that can be fixed to the recording paper, the carrier particles attached to the recording paper are also fixed by heat and pressure.
Even when it is removed from the surface of the image carrier by the cleaning device, the surface of the image carrier will not be damaged. Therefore, on average the carrier particles are
Even if the particle size is 15 μm or less, the above-mentioned problem (○) does not actually cause any trouble. Furthermore, when the carrier particles are spherical, it improves the agitation performance of the toner and the carrier and the transportability of the developer, and also improves the charge controllability of the toner. Make it difficult.
From the above, the carrier particles are those formed with resin etc., and the average particle diameter of spherical magnetic carrier particles is preferably 50 μm or less, particularly preferably
Those having a diameter of 30 μm or less and 5 μm or more are preferably used.

Such magnetic carrier particles may contain metals such as iron, chromium, nickel, cobalt, etc. as in conventional magnetic carrier particles, or compounds or alloys thereof, such as triiron tetroxide, γ-
Spheroidal particles of ferromagnetic or paramagnetic substances such as ferric oxide, chromium dioxide, manganese oxide, ferrite, manganese-copper alloy, or the surfaces of these particles are coated with styrene resin, vinyl, etc. coated in a spherical shape with a resin such as resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, or fatty acid wax such as palmitic acid or stearic acid, or disperse magnetic fine particles. The average particle size can be obtained by selecting the particle size using a conventionally known average particle size selection means, if necessary.

In addition to the above-mentioned effects, forming the carrier particles into a spherical shape using a resin or the like as described above makes the developer layer formed on the developer transport carrier uniform, and also makes the developer layer formed on the developer transport carrier uniform. It also has the effect of making it possible to apply a high bias voltage to the. That is, the fact that the carrier particles are made spherical by resin or the like is because: (1) Generally, carrier particles tend to be magnetized and attracted in the long axis direction, but by sphericalization, this directionality is lost; The developer layer is formed uniformly, preventing the occurrence of locally low resistance areas and uneven layer thickness. As a result, even if a high bias voltage is applied to the developer transport carrier, the electric field will not be concentrated on the edge portion, and as a result, even if a high bias voltage is applied to the developer transport carrier, it will discharge to the image bearing surface and disturb the electrostatic latent image. This provides the effect that voltage breakdown does not occur. The fact that this high bias voltage can be applied means that the above-mentioned effects of the present invention in development under an oscillating electric field can be fully exhibited. Wax as described above can also be used to make the carrier particles spherical, which produces the above-mentioned effects, but from the viewpoint of the durability of the carrier, it is preferable to use resin as described above. The resistivity of 10 ⁸
It is preferable to form insulating magnetic particles so that the resistance is Ωcm or more, particularly 10 ¹³ Ωcm or more. This resistivity is calculated by placing the particles in a container with a cross-sectional area of 0.50 cm ² and tapping, and then applying 1 kg/kg on the packed particles.
Apply a load of ^cm2 , and connect the load to the bottom electrode.
This value is obtained by reading the current value when applying a voltage that generates an electric field of 1000 V/cm. If this resistivity is low, when a bias voltage is applied to the developer transport carrier, the carrier particles will be charged. Injected carrier particles tend to adhere to the surface of the image carrier, or breakdown of the bias voltage tends to occur.

In summary, the magnetic carrier particles are spherical so that the ratio of the major axis to the minor axis is at least 3 times or less, and there are no protrusions such as needles or edges.
A suitable condition is that the resistivity is 10 ⁸ Ωcm or more, preferably 10 ¹³ Ωcm or more. For such magnetic carrier particles, spherical magnetic particles are made to have high resistance by forming an oxide film, etc., and resin-coated carrier particles are made by selecting spherical magnetic particles as much as possible and coating them with resin. For carriers of magnetic fine particle dispersion systems, use magnetic fine particles as much as possible, perform a spheroidization treatment after forming the dispersed resin particles, or obtain the dispersed resin particles by spray drying. It is manufactured by

Next, regarding toner particles, in general, when the average particle size of toner particles becomes smaller, the amount of charge qualitatively decreases in proportion to the square of the particle size, and the adhesion force such as Van der Waals force becomes relatively large. However, while it becomes easier to scatter and cause fogging,
It becomes difficult to separate from the carrier particles of the magnetic brush. In the conventional magnetic brush development method, such problems become noticeable when the average particle size becomes 10 μm or less. The developing method of the present invention solves this problem by performing development using a magnetic brush under an oscillating electric field, as described above. In other words, the toner particles attached to the ears of the magnetic brush are strongly vibrated by the oscillating electric field, especially in the area where the control electrode is provided.
The toner particles easily separate from the ears to form a cloud, and therefore, the toner particles are faithfully attracted to the electrostatic image on the image carrier at the portion where the control electrode is provided. In addition, due to the low charge amount, toner particles almost never migrate to the image area or non-image area, and since the toner particles are not rubbed against the image carrier surface, they are less likely to adhere to the image carrier surface due to frictional charging. After that, toner particles with a particle size of about 1 μm were used. As a result, a clear toner image with good reproducibility can be obtained by faithfully developing an electrostatic image. In addition, the oscillating electric field weakens the bond between toner particles and carrier particles, which also reduces the adhesion of carrier particles to the image bearing surface along with toner particles.
The fact that the ears of the magnetic brush are kept out of contact with the surface of the image carrier, and the toner particles having a larger charge amount than the carrier particles are selectively transferred to an electrostatic image under an oscillating electric field as described above. Adhesion of carrier particles to the image carrier surface is significantly reduced.

As the average particle size of the toner increases, as already mentioned, the roughness of the image becomes noticeable. Normally, toner with an average particle size of about 20 μm is not a practical problem for developing fine lines arranged at a pitch of about 10 lines/mm with high resolution, but when using fine toner particles with an average particle size of 10 μm or less, The resolution has been significantly improved, and it is now possible to produce clear, high-quality images that faithfully reproduce the differences in shading. For the above reasons, the appropriate particle size of the toner is an average particle size of 20 μm or less, preferably 10 μm or less. In addition, in order for the toner particles to follow the electric field, the amount of charge of the toner particles should be greater than 1 to 3 μc/g (preferably 3 to 3 μc/g).
300μc/g) is desirable. Particularly when the particle size is small, a high amount of charge is required.

Such toners can be obtained in the same manner as conventional toners. That is, it is possible to use a toner in which spherical or amorphous nonmagnetic or magnetic toner particles in conventional toners are sorted by an average particle size sorting means. Among these, it is preferable that the toner particles are magnetic particles containing magnetic fine particles, and in particular, the amount of magnetic fine particles is 60 wt% or less, especially
Preferably it does not exceed 30wt%. When the toner particles contain magnetic particles, the toner particles are influenced by the magnetic force of the magnet included in the developer transport carrier, so that the uniform formation of the magnetic brush is further improved. The occurrence of fogging is prevented, and furthermore, scattering of toner particles becomes less likely to occur. Therefore, in the case of magnetic toner, the DC voltage applied to the control electrode and sleeve to prevent fogging can be lower than the potential of the non-image area of the image carrier. However, if the amount of magnetic material contained is too large, the magnetic force between the carrier particles and the carrier particles becomes too large, making it impossible to obtain a sufficient developing density. As a result, frictional charging control becomes difficult, toner particles are more likely to be damaged, and toner particles are more likely to aggregate with carrier particles.

To summarize the above, the preferred toner in the developing method of the present invention uses the resin described above for the carrier and furthermore fine particles of magnetic material, and contains a coloring component such as carbon and a charge control agent, etc. as necessary. In addition, the average particle size that can be produced by the same method as the conventionally known toner particle production method is
It consists of particles of 20 μm or less, particularly preferably 10 μm or less.

In the developing method of the present invention, a developer in which the above-mentioned spherical carrier particles and toner particles are mixed in the same ratio as in a conventional two-component developer is preferably used; Depending on the conditions, a fluidizing agent for improving the fluidity and sliding of particles, a cleaning agent for cleaning the surface of the image bearing member, etc. are mixed. As the fluidizing agent, colloidal silica, silicone varnish, metal soap, or nonionic surfactant can be used, and as the cleaning agent, fatty acid metal salt, organic group-substituted silicone, fluorine, etc. can be used as a surfactant. Can be done.

As detailed above, in the developing method of the present invention, the ears of the magnetic brush are kept in non-contact with the image carrier, a control electrode is provided between them, and development is performed under an oscillating electric field. Accordingly, the advantages of the two-component developer consisting of fine particle toner and carrier can be fully utilized, and the excellent effect of developing clear, high-quality images can be obtained. In addition, in the present invention, the waveform of the AC voltage component for forming the oscillating electric field is not limited to a sine wave, but may be a rectangular wave or a triangular wave. Furthermore, if the toner in the two-component developer has magnetism, the same developing conditions can be applied to the magnetic latent image.
Of course, it can be visualized.

Next, the present invention will be explained using specific examples.

〔Example〕

Example 1 The carrier has an average particle size of 30 μm and a magnetization of 50 emu/
g, resin-coated spherical ferrite particles with a resistivity of 10 ¹⁴ Ωcm or more were used, and the toner contained styrene, 100 parts by weight of acrylic resin (Himer UP110 manufactured by Sanyo Chemical Co., Ltd.), and carbon black (MA-100 manufactured by Mitsubishi Chemical Co., Ltd.). Using non-magnetic particles obtained by a pulverization granulation method with an average particle size of 10 μm consisting of 10 parts by weight of nigrosine and 5 parts by weight of nigrosine,
Development was carried out using the apparatus shown in FIG. 1 under conditions such that the toner particle ratio of the developer D in the developer reservoir 6 was 10% by weight relative to the carrier particles. The average charge amount of the toner was 15 μc/g.

In this case, the image carrier 1 is a CDS photoreceptor, its peripheral speed is 180 mm/sec, the highest potential of the electrostatic image formed on the image carrier 1 is -500 V, the non-image area potential is -100 V, and the outer diameter of the sleeve 2 is 30 mm. , its rotation speed 100 rpm, magnet body 3
The magnetic flux density of the N and S magnetic poles is 900 Gauss, the rotation speed is 100 rpm, the thickness of the developer layer is 0.4 mm, and the sleeve 2
The gap between the image carrier 1 and the image carrier 1 is 1.5 mm, that is, 1500 μm, and the extending position of the control electrode 10 from the surface of the image carrier 1 is 0.5 mm.
mm, control electrode 10 has -200V DC voltage and 1.5k
A superimposed voltage of AC voltage of 1000 V at Hz was applied, and a DC voltage of -250 V was applied to the sleeve 2. In addition,
The control electrode 10 uses a 1mm wire with a diameter of 0.2mm.
A material stretched parallel to sleeve 2 at a pitch of 2 was used.

The image was developed under the above conditions, transferred to plain paper using a corona discharge transfer device, and then fixed by a heat roller fixing device with a surface temperature of 140°C. The image was very clear, with no dark spots, high density, and even though 50,000 sheets of recording paper were subsequently obtained, it was possible to obtain an image that remained stable and unchanged from beginning to end.

Example 2 Fine ferrite is added to the carrier particles in the resin.
The average particle size of 50wt% dispersed particles is 20μm, and the magnetization is
Using thermally spheroidized magnetic particles with a resistivity of 30 emu/g and a resistivity of 10 ¹⁴ Ωcm or more, and non-magnetic particles with an average particle size of 5 μm as toner particles, development was carried out using the apparatus shown in Figure 2. Developer D in developer reservoir 6
The toner particle ratio is 5wt% to the carrier particles.
The image was developed under the following conditions. The average charge amount of the toner was 30 μc/g.

The conditions for the image carrier 1 in this case are the same as in Example 1, the outer diameter of the sleeve 2 is also 30 mm, however, its rotation speed is 150 rpm, and the magnetic flux density of the magnetic pole facing the development area A of the magnet body 3 is 1200 Gauss. Developer layer thickness 0.5mm,
The gap between the sleeve 2 and the image carrier 1 is 1.0 mm, that is,
The control electrode 10 has a mesh structure in which wires with a diameter of 50 μm are diagonally in the axial direction of the sleeve 2 and cross each other to form 1 mm grid holes, and are stretched at a position 0.3 mm from the surface of the image carrier 1. This control electrode 10 has an AC component of 300
Apply bias voltage of Hz, 700V, sleeve 2
A bias voltage with a DC component of -200V was applied to.

As a result of developing under the above conditions and transferring and fixing onto plain paper under the same conditions as in Example 1, the resulting image on the recording paper was extremely clear with no edge effects or fog, and with high density. Ta. Subsequently, we obtained 50,000 sheets of recording paper, and were able to obtain stable and unchanged images from beginning to end.

Example 3 In contrast to Example 1, the wire tensioning pitch of the control electrode 10 was 2 mm, the AC voltage component of the superimposed voltage applied thereto was 300 Hz, 500 V, and the sleeve 2 was supplied with an AC voltage of 2 kHz, 1000 V in addition to the DC voltage. Development, transfer, and fixing were performed under the same conditions as in Example 1, except that the voltage was applied differently. The recorded images obtained were clear as in Example 1, and remained stable even after 50,000 sheets of recording paper were run.

Example 4 Example 2 was different from Example 2 except that the grid holes in the mesh where the wires of the control electrode 10 crossed were 2 mm, and an AC component of 2 kHz and 400 V was applied to the sleeve 2 in addition to the DC component. Development, transfer, and fixing were performed under the same conditions. The recorded image obtained is
As in the case of Example 2, the image was clear and remained stable even after 50,000 sheets of recording paper were used.

Example 5 The difference from Example 3 was that -150V DC voltage was applied to the control electrode 10, and a superimposed voltage of -250V DC voltage and 1.5kHz, 2000V AC voltage was applied to the sleeve 2. Development, transfer, and fixing were performed under the same conditions as in Example 3. Results similar to those in Examples 1 and 3 were obtained.

Example 6 The same procedure was carried out as in Example 4 except that -200V DC voltage was applied to the control electrode 10, and a superimposed voltage of -200V DC voltage and 1kHz, 800V AC voltage was applied to the sleeve 2. Development, transfer, and fixing were performed under the same conditions as in Example 4. Results similar to those in Examples 2 and 4 were obtained.

[Effects of the Invention] In the conventional magnetic brush development method, when a two-component developer was used, it was not possible to atomize toner particles and carrier particles, making it impossible to record high-quality images. .

However, according to the developing method of the present invention, a control electrode that forms and controls an oscillating electric field is provided in the developing area, so that toner particles form a cloud under the oscillating electric field, so that the average particle size can be reduced. It is possible to use toner with a particle size of 1 to 20 μm or carrier with an average particle size of 5 to 50 μm, and it is possible to obtain records with sufficient image density, gradation, and excellent resolution.

Since the developer is a two-component (or preferably more than one) type developer, the toner is more stable in charging and less likely to aggregate than a one-component type developer.

[Brief explanation of the drawing]

1 to 3 are schematic cross-sectional views showing examples of developing devices used in the present invention. DESCRIPTION OF SYMBOLS 1... Image carrier, 2... Sleeve, 3... Magnet, 4... Layer thickness regulating blade, 5... Cleaning blade, 6... Developer reservoir, 7... Stirring screw, 8... Toner hopper, 9... Toner supply roller, 10... Control electrode, 11, 12... Power supply, 13, 14... Protection resistor.

Claims (1)

[Scope of Claims] 1. A method for developing a latent image on an image carrier with a two-component developer layer formed on a developer transport carrier using a two-component developer consisting of toner particles and magnetic carrier particles. , maintaining the two-component developer layer on the developer transport carrier and the image carrier in non-contact, and
A control electrode for controlling the flight of toner particles from the two-component developer layer to the image carrier is provided in the gap, and is vibrated by an AC voltage component applied to at least either the control electrode or the developer transport carrier. A developing method characterized by performing development under an electric field. 2. The developing method according to claim 1, wherein the carrier particles are insulating particles. 3. The developing method according to claim 1 or 2, wherein the toner particles have an average particle size of 20 μm or less, and the carrier particles have an average particle size of 5 to 50 μm. 4 Determine the number of gaps between the developer transport carrier and the image carrier.
The developing method according to any one of claims 1 to 3, wherein the developing method is set to 10 to 2000 μm.