JPS62192758A - Developing method - Google Patents

Abstract

PURPOSE:To make high developing efficiency with high developing density possible and to eliminate negative characteristic by shifting magnetic particles between a developer carrier and a latent image carrier under the specific condition of an electric field of AC component. CONSTITUTION:A toner particle layer and a magnetic brush layer consisting of toner particles 28 and magnetic particles 27 are provided on a developer carrier 22 and development is made by applying bias electric field consisting of AC component and DC component between the developer carrier 22 and electrostatic latent image carrier 1. The electric field of AC component is made to frequency 200-3,000Hz, and peak to peak voltage is made to voltage that does not destroy the electrostatic latent image and shifts the magnetic particles 27 between the developer carrier 22 and electrostatic latent image 1 in the developing area. Peak-peak voltage is made to 500-2,200Vpp by superposing DC voltage voltage -300V, and a photosensitive drum 1 is held at grounding potential. Thus, developing efficiency is heightened, and a developed image having high image density is made possible, and the negative characteristic is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application) The present invention relates to a developing method for developing an electrostatic latent image formed by electrophotography or electrostatic recording.

(Background Art) The applicant has proposed a development method in which a thin layer of developer is formed on a developer carrier, the developer in the thin layer is brought close to a latent image, and an alternating electric field is applied to this approaching portion to perform development. proposed a device (Japanese Patent Publication Nos. 58-32375 and 58-32377).

This device has a high development efficiency (the ratio of toner that can be consumed for development out of the toner present in the development section) and is very useful in terms of miniaturization. However, the developer used in this device is one component. Since the toner is a magnetic toner, it is essential that the toner contains a magnetic material, which has drawbacks such as poor fixability of developed images and poor reproduction of color images.

As a device to compensate for this drawback, the applicant has developed a method and device that uses non-magnetic toner to form a thin layer of only non-magnetic toner on a developer carrying member, and forms a latent image of the thin layer of only non-magnetic toner. proposed a developing method and apparatus in which development is carried out by applying an alternating electric field to the two faces (Japanese Patent Laid-Open No. 58-1433).
No. 60, specification No. 59-101880).

This is useful because it eliminates the disadvantages caused by the toner containing magnetic materials while maintaining the advantages of the developing device using magnetic toner, but it also has the disadvantages of relatively low density of the developed image and the negative effects described below. It has been found that there are some drawbacks in the development characteristics, such as the fact that the image density may decrease as the latent image potential increases.

Also, what is known as the so-called two-component magnetic brush development method (for example, Japanese Patent Application Laid-open No. 53-93841)
A non-magnetic developer can be used, but the development efficiency is low because the proportion of consumable toner in the magnetic brush in the developing section is low, and scratches caused by the brush may appear on the developed image, like sweeping marks. There are drawbacks.

(Objective of the Invention) Therefore, an object of the present invention is to provide a developing method that has high developing efficiency, can form a developed image with high image density, and has no negative characteristics.

(Summary of the Invention) The present invention has a toner particle layer and a magnetic brush layer made of toner particles and magnetic particles on a developer carrier, and an alternating current between the developer carrier and the electrostatic latent image carrier. In a developing method in which development is performed by applying a bias electric field consisting of a DC component and a DC component, the electric field of the AC component has a frequency of 200 to 3000 Hz, and the peak-to-peak voltage is set such that the electrostatic latent image is not destroyed and the magnetic particles are not damaged in the development area. The developing method is characterized in that the voltage is set to move between the developer carrier and the static '21Hu image.

(Embodiment) FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention.

In this figure, reference numeral 1 denotes an electrostatic latent image carrier that carries an electrostatic latent image to be imaged, and specifically, it is an endlessly movable photosensitive drum, a belt, a dielectric drum, a belt, or the like. The method of forming an electrostatic latent image thereon is not the gist of the present invention, and any known method may be used. In this embodiment, the electrostatic latent image carrier is a photosensitive drum on which an electrostatic latent image is formed by electrophotography, and is rotatable in the direction of arrow a.

The apparatus of this embodiment includes a developer container 21, a developing sleeve 22 (hereinafter simply referred to as a sleeve) that is a developer holding member, a magnet 23 that is a magnetic field generating means, and an amount of developer that is conveyed to the developing section on the sleeve 22. A regulation blade 24 (hereinafter simply referred to as a blade) that controls the
4 etc. Each configuration will be explained below.

Container 21 contains a developer having a mixture of magnetic particles 27 and toner particles 28 . In this embodiment, the toner particles are non-magnetic toner particles having a particle size of 7 to 20 μm and are mainly formed of, for example, 10 parts of carbon and 90 parts of polystyrene. In this embodiment, the toner particles and magnetic particles are stored in the container 21 as a uniform mixture, with the concentration of the magnetic particles being high near the sleeve 22 and low in areas away from the sleeve 22. Good too. Container 21
has an opening at the lower left in FIG.

The sleeve 22 is made of a non-magnetic material such as aluminum, and is provided at the opening of the container 21, with a part of its surface exposed and the other surface protruding into the container 21. The sleeve 22 is rotatably supported about an axis perpendicular to the drawing and is rotationally driven in the direction indicated by the arrow. Although the sleeve 22 is a cylindrical sleeve in this embodiment, it may be an endless belt.

The sleeve 22 opposes the photosensitive drum 1 with a small gap therebetween and constitutes a developing section. Toner and magnetic particles are conveyed to this developing section by a sleeve 22.

The 6T1 stone 23 is fixed statically inside the sleeve 22,
It remains stationary even when the sleeve 22 rotates. The magnet 23 has an N pole 23a that controls the amount of developer applied onto the sleeve 22 in cooperation with a blade 24 to be described later, and an S pole 23a that is a developing magnetic pole.
It has a magnetic pole 23b, an N magnetic pole 23c and an S magnetic pole 23d that transport the developer into the container 21 after passing through the developing section. The south pole and north pole may be reversed. Although this magnet is a permanent magnet in this embodiment, an electromagnet may be used instead.

In this embodiment, the blade 24 has at least its tip made of a non-magnetic material such as aluminum, and the blade 24 is made of a non-magnetic material such as aluminum.
extending in the longitudinal direction of the sleeve 22 near the top of the opening;
Its base is fixed to a container 21, and its distal end is fixed to a sleeve 22.
facing the surface with a gap. The gap between the tip of the blade 24 and the surface of the sleeve 22 is 50 to 500 Atm.
, preferably 100 to 350 μm, and in this example, 300 μm. If this gap is smaller than 50 μm,
Magnetic particles tend to clog this gap, and if the diameter exceeds 500 μm, a large amount of magnetic particles and toner will pass through the gap, making it impossible to form a developer layer with an appropriate thickness on the sleeve 22.

The thickness of the developer layer is smaller than the gap between the photosensitive drum 1 and the sleeve 22 in the developing section, which will be described later.
2). In order to create a developer layer with such a thickness, it is preferable that the gap between the blade tip and the sleeve surface be equal to or smaller than the gap between the sleeve surface and the photosensitive drum surface, but it is also possible to make it larger. .

A magnetic particle circulation limiting member 26 is provided inside the container 21 of the blade 24, and this member 26 is connected to the magnetic particle container 21, which will be described later.
Limit the circulation area within.

The power supply 34 applies a voltage between the photosensitive drum 1 and the sleeve 22 to form an alternating electric field in the gap therebetween, thereby transferring toner from the developer and agent on the sleeve 22 to the photosensitive drum 1. The voltage from the power supply 34 may be a symmetrical alternating voltage in which the peak voltages on the positive side and the negative side are the same, or an asymmetrical alternating voltage in which a DC voltage is superimposed on such an alternating voltage.

As a specific voltage value, for example, dark potential -a o o
For example, a direct current voltage of -300v is superimposed on an electrostatic latent image with a bright area potential of -200v, so that the peak-to-peak voltage is 500 to 2200VPP, and the frequency is 200 to 3000V.
A Hz alternating voltage is applied to the sleeve 22 side, and the photosensitive drum 1
is held at ground potential.

Next, the operation of the developing device of this embodiment will be explained. First, magnetic particles 27 are put into the container 21 . The charged magnetic particles are held on the sleeve 22 by the l1i1 poles 23a and 23d, and the sleeve 22 facing inside the container 21
The magnetic particles adhere to the entire surface of the magnetic particles and form a layer of magnetic particles. In the portion of this magnetic particle layer near the magnetic pole 23a and IQ8i23d, the magnetic particles 27 constitute a magnetic brush. Thereafter, toner 28 is put into the container 21 to form a single layer of toner on the outside of the magnetic particle layer. The magnetic particles 27 initially introduced have a ratio of 2 to 70% (based on the magnetic particles).
Weight) It is preferable that the toner is included, but it is also possible to include only magnetic particles. If the magnetic particles 27 are adsorbed and held as a magnetic particle layer on the surface of the -H sleeve 22, no substantial flow or inclination will occur even if the device is vibrated or tilted considerably, and the state in which the magnetic particles 27 cover the surface of the sleeve 22 will not occur. maintained.

Next, when the sleeve 22 is rotated in the direction of the arrow, the magnetic particles rise from the bottom of the container 21 in a direction along the surface of the sleeve 22 and reach the vicinity of the blade 24. Therefore, a part of the magnetic particles passes through the gap between the tip of the blade 24 and the surface of the sleeve 22 together with the toner, and the other part collides with the member 26, then reverses and descends by gravity on the outside of the ascending path of the magnetic particles. and reaches the bottom of the container 21, and then the sleeve 2
2 and repeat the above operation. In addition, the container 21
magnetic particles 27 rising toward the blade 24 from the bottom of the
Some of them turn around and fall before reaching the vicinity of the blade 24. This is particularly noticeable in magnetic particles far from the surface of the sleeve 22.

In this way, the magnetic particles that turn around and fall near or in front of the blade 24 take in toner particles from the outer toner layer.

By circulating in this manner with the rotation of the sleeve 22, the toner 28 is mixed with the magnetic particles 27 and the sleeve 22.
It becomes electrically charged due to friction with the surface.

Near the front of the blade 24, the magnetic particles 27 near the surface of the sleeve 22 are attracted to the surface of the sleeve 22 by the magnetic pole 23a, and as the sleeve 22 rotates, the blade 2
4 and exits the container 21. At this time, the magnetic particles 27 carry away the toner attached to their surfaces. Further, some of the charged toner particles 28 leave the container on the sleeve 22 while remaining attached to the surface of the sleeve 22 due to the reflection force. Blade 24 regulates the amount of developer applied onto sleeve 22.

The developer layer (mixture of magnetic particles 27 and toner 28) thus formed on the surface of the sleeve 22 reaches a developing section facing the photosensitive drum 1 as the sleeve 22 rotates. Here, toner is transferred from the surface of the sleeve 22 and the surface of the 6n particles onto the latent image by an alternating electric field applied between the photosensitive drum 1 and the sleeve 22, and the latent image is developed.

Next, the behavior of toner and magnetic particles in the developing section will be explained with reference to FIG. In this embodiment, since the electrostatic latent image is composed of negative charges (dark parts of the image), the electric field due to the electrostatic latent image is in the direction indicated by arrow a. Due to mutual friction between the toner particles and the magnetic particles within the developer lid, the toner particles are positively charged and the magnetic particles are negatively charged. Charge is injected into the magnetic particles according to the charge/discharge time constant determined by the material, shape, etc. of the particles, and the polarity of the charge can change depending on the electric field.

The electrostatic latent image is -600V at the mouth part, for example, and the sleeve 2
In the phase in which the positive component of the alternating electric field is applied to the second side, the direction of the electric field due to this matches the direction of the electric field due to the latent image. At this time, the electric field causes the magnetic particles to fi! ! The amount of charge injected into the photosensitive drum 1 reaches its maximum, the magnetic particles become positively charged, and the ears 51 reach their maximum standing state as shown in the figure (Fig. 2 a), with the long ears extending over the surface of the photosensitive drum 1 and the short ears The ears fly to the surface of the photosensitive drum 1 due to the action of the electric field.

On the other hand, since the toner is insulating, the charge injection effect is small and it is always positively charged, so the toner on the sleeve 22 and the surface of the magnetic particles is transferred to the photosensitive drum 1 by the electric field formed in this space. At this time, since the ears 51 stand up in a rough state, the surface of the sleeve 22 is exposed, and the toner 28 separates from both the sleeve 22 surface and the surface of the ears 51. In addition, toner 2 is applied to the ears 51.
Since there is a charge having the same polarity as that of toner 8, the toner 28 on the surface of the ears 51 is more likely to move due to electrical repulsion.

In the phase in which the negative component of the alternating voltage component is applied to the sleeve 22, the electric field due to the alternating voltage (arrow b) is in the opposite direction to the electric field due to the electrostatic latent image (arrow a). Therefore, the electric field in this space becomes stronger in the opposite direction, and the positively charged magnetic particles are drawn toward the sleeve 22, the long ears shrink, and the short ears fly toward the sleeve 22 surface.

On the other hand, since the toner 28 on the photosensitive drum 1 is positively charged as described above, it is reversely transferred to the sleeve 22 or the magnetic particles 27 by the electric field formed in this space. In this way, the toner 28 moves back and forth between the photosensitive drum 1 and the surface of the sleeve 22 or the surface of the magnetic particles 27, and as the photosensitive drum 1 and sleeve 22 rotate,
As the space between them increases, the electric field weakens and the development action is completed.

Conversely, when the electrostatic latent image is bright, for example at -100V, there is almost no charge injected into the ears of the magnetic particles by the electric field even in the phase where the positive component of the alternating electric field is applied to the sleeve 22 side. As will be described later, the magnetic particles are injected and remain negatively charged during the phase in which a negative component is applied to the sleeve, and the long ears shrink due to the electric field, and the short ears fly toward the surface of the sleeve 22.

The toner is transferred to the photosensitive drum 1 by the electric field formed in this space, but at this time, the ears 51 are shrunk.
The surface of the sleeve 22 is covered to suppress the separation of the toner from the sleeve 22, and in addition, since the ears 51 have charges of opposite polarity to the toner, the toner 28 on the surface of the ears 51 is covered.
suppresses toner separation by electric attraction force.

In the phase in which the negative component of the alternating voltage component is applied to the sleeve 22, the electric field in the direction indicated by the opposite arrow is at its maximum, and the amount of charge injected into the ears of the magnetic particles also increases, causing the magnetic particles to become more negatively charged. The ears 51 are in the maximum standing state, and the long ears extend to the surface of the photosensitive drum, and the short ears fly to the surface of the photosensitive drum due to the action of the electric field.

On the other hand, the toner on the photosensitive drum is transferred to the sleeve 22 or the magnetic particles by the electric field formed in this space.

At this time, since the ears 51 are standing up in a rough state, the surface of the sleeve 22 is exposed, making it easier for the toner to return. The toner is further easily separated from the surface of the photoreceptor due to the attraction force.

The ears 51 have triboelectric charges or mirror charges with the toner 28, electrostatic latent image charges on the photosensitive drum 1, and photosensitive drum 1.
There is a charge injected by the alternating electric field between the magnetic particles 27 and the sleeve 22, but its state changes depending on the charging/discharging time constant of the charge determined by the material of the magnetic particles 27 and other factors.

Generally, the lower the resistance value of the magnetic particles, the more charges are injected, and the magnetic particles are developed in dark and bright areas of the image due to charge injection. On the other hand, when the resistance is extremely high, the toner always retains a charge of the opposite polarity, which tends to cause the magnetic particles to fog on the background area. Adhesion can be prevented.

In order to ensure the behavior of the magnetic particles described above, the potential of the bias electric field (a combination of alternating current and direct current components) applied between the developing sleeve and the photoreceptor moves the toner from the photoreceptor toward the developing sleeve. The value of the peak value of the waveform component 2 and the gB part potential V of the photoreceptor is IVp I>Ivo
Preferably, the electric field due to the alternating voltage exceeds the electric field due to the electrostatic latent image.

As described above, the ears of magnetic particles are brought into a flying state of slight but intense vibration due to the above-mentioned alternating electric field.

By applying an alternating electric field to the developing section in this manner and causing the toner and magnetic particles to vibrate and fly, the following effects are produced.

The development efficiency is extremely high because the toner is ejected from the surface of the magnetic brush and sleeve.

Therefore, the amount of developer applied is relatively small, and the resolution of the developed image is increased. In addition, because the developing efficiency is high, it is possible to make the relative speed between the developing sleeve and the photoreceptor almost the same.
Sweeping of the solid development area, which occurs when the relative speed is increased, does not occur. Furthermore, adding relative speed also has the effect of reducing sweeping.

Also, since the magnetic particles are vibrated by an alternating electric field, 1
There are no traces of the magnetic brush, and extremely high-quality developed images can be obtained.

Furthermore, by applying an alternating electric field sufficient to cause the magnetic particles to move through the space formed by the sleeve and the photoreceptor, the dark area behaves together with the toner when the magnetic particles fly as described above, promoting development and brightening. It behaves in the opposite way to that of toner, and has the effect of separating toner adhering to the surface of the photoreceptor, thereby preventing fogging.

Furthermore, the magnetic particles adhering to the surface of the photoreceptor are eventually pulled back toward the developing sleeve by the magnetic force and the moving force caused by the electric field, thereby reducing the amount of magnetic particles adhering to the photoreceptor.

Furthermore, even when the ears of magnetic particles are unevenly distributed, when the magnetic particles fly, some of the ears collapse and have the effect of smoothing out the magnetic particles.

When using magnetic particles 27 with a relatively low resistance value, the alternating voltage applied between the photosensitive drum 1 and the sleeve 22 is as follows:
Settings must be made so that no gap discharge occurs in either the dark or bright areas of the latent image when the peak value is reached. On the other hand, when using ears 51 with a relatively high resistance value, it is possible to prevent the gap voltage from reaching the discharge starting voltage by appropriately selecting the frequency of the alternating voltage and the charging/discharging time constant of the ears 51. preferable.

Taking these into consideration, the resistance of the entire spike 51 in the height direction of the spike 51 with the developing brush in contact with the photosensitive drum 1 is preferably in the range of 10'' to 106 Ωcm;
If you expect a developing electrode effect, set it to 10'. ~106Ωcf
Approximately fI is preferable.

The magnetic particles 27 have an average particle size of 30 to iooμ, preferably 40 to 80μ. In general, the smaller the average particle size, the better the triboelectric charging characteristics of the toner on the sleeve 22, and the sleeve ghost (a phenomenon in which the density decreases due to the rotation of the sleeve immediately after developing a solid black original, or every rotation of the sleeve). (which appears as a phenomenon in which the developing density decreases) will no longer occur. However, if the particle size is small, there is a tendency for the magnetic particles to adhere to the electrostatic holder. The position of this adhesion differs depending on the resistance value of the magnetic particles; for example, those with relatively low resistance will adhere to the image area, and those with high resistance will adhere to the non-image area. This is a general tendency, and in reality, the magnetic properties of magnetic particles, surface shape, and surface treatment materials (including resin coating) also have some influence.

Next, a specific example using the developing device shown in FIG. 1 will be described. In FIG. 1, the sleeve 22 has a diameter of 20 mm.
The surface of the aluminum sleeve was subjected to amorphous sandblasting treatment using alundum abrasive grains, and the magnet 23 was magnetized with four poles, with N and S poles alternating as shown in FIG.

The maximum value of the surface magnetic flux density due to the magnet 23 was about 900 Gauss.

The blade 24 was made of nonmagnetic stainless steel with a thickness of 1.2 mm, and the angle θ was 15°.

As magnetic particles, ferrite with an average particle diameter of 55 μm (maximum 1ifi 60 e
mu/g) was used.

The non-magnetic toner is a toner powder with an average particle size of 10μ consisting of 100 parts of styrene/butadiene copolymer resin and 5 parts of copper phthalocyanine pigment, and 0.6 parts of colloidal silica.
When using blue toner with external addition of %, sleeve 2
A toner coating layer with a coating thickness of about 20 to 30 .mu.m was obtained on the surface of No. 2, and a magnetic particle layer with a thickness of 100 to 200 .mu.m was further formed as an upper layer thereon. The toner is attached to the surface of each magnetic particle.

At this time, the total weight of the magnetic particles and all the toner on the sleeve 22 was about 2.43xlO-2g/cm2.

The magnetic particles are made to stand up by the magnetic field generated by the magnetic pole 23b in the sleeve 22 in the developing area and its vicinity, and the maximum density is 0.
It formed a 9mm standing brush.

When the amount of charge was measured by a blow-off method, the amount of triboelectric charge of the toner on the sleeve and on the magnetic particles was +10 μC/g.

This developing device was installed in a PC-10 copying machine manufactured by Canon Inc., and the distance between the photosensitive drum 3 (made of an organic photosensitive material) and the surface of the sleeve 22 was set to 350 μm. When the electrostatic latent image was developed with the dark potential at -620V, the light potential at -180V, the DC voltage of the bias power supply at -260V, and the frequency and peak-to-peak voltage of the AC component changed, the third A correlation diagram as shown in the figure was obtained.

If the frequency is less than 200 Hz, the vibration flight of the magnetic particles will not be sufficient, and magnetic brush marks will appear on the developed image, which is undesirable.

If the frequency exceeds 3000 Hz, neither the toner nor the magnetic particles can follow the electric field, resulting in an image that is thin and prone to fogging, which is undesirable. The area shaded by vertical lines is the area where discharge is likely to occur between the sleeve and the photoconductor, and this value is even lower in areas with low isobaric pressure at high altitudes. The area shaded with horizontal lines is an area where ground force blur is likely to occur in the background, and the area shaded with diagonal lines is an area where magnetic particles do not fly sufficiently through the gap. Therefore, it is preferable to perform development in the area surrounded by these lines. Further, in view of image density gradation (fogging, latitude, etc.), the frequency is preferably 1 to 2 KHz, and the VPp is preferably in the range of 800 to 1500V.

More preferably 1.4 to 1.8 KHz, 1000 to 1
A region of 350 Vpp is good. Similarly, set the S-D interval to 2.
When I changed it to 50-500μm and developed it with the same settings,
The best image was obtained when the alternating electric field listed in Table 1 was applied.

Based on similar experiments, in practical use the frequency is 1 to 2.2 KHz, V
pp800-2200, S-D gap250-70
Very good images were obtained in the 0 μm range. S
-D gap of 800 μm or more is not preferable because the reproduction of fine lines deteriorates even if the alternating field voltage is increased.

Table I S-D spacing and optimum alternating field The particle size of the magnetic particles can be further refined to, for example, an average particle size of 40 μm.
The appropriate range of the alternating electric field changes when the voltage reaches 500V, and although the frequency is almost the same, the applied voltage is preferably 500 to 1600V. This is because as the particle size of the magnetic particles becomes finer, the surface area increases, the amount of charge on the magnetic particles increases, and the magnetic capacity decreases, which reduces the restraining force of the fixed magnetic pole inside the sleeve, making the force of the electric field more pronounced. It is thought that this occurs due to the exposure to However, small-sized magnetic particles tend to adhere to the photoreceptor, and those with a particle size of 30 μm or less
In a developing device having a developing magnetic pole of ~900 Gauss, the magnetic particles on the photoreceptor cannot be completely recovered even if an alternating voltage is applied.

As explained above, according to this embodiment, high image density,
It is possible to perform development with high development efficiency without fogging, ghost images, uneven sweeping, or negative characteristics.

As the material of the sleeve 22, in addition to aluminum, conductive materials such as brass and stainless steel, paper tubes, and synthetic resin cylinders can be used. Furthermore, if the surfaces of these cylinders are subjected to conductive treatment or made of a conductive material, they can function as developing electrodes. Furthermore, a core roll may be used and a conductive elastic body, for example, a conductive sponge, may be wound around the circumferential surface of the core roll.

Regarding the magnetic pole 23b of the developing section, although the magnetic pole is arranged at the center of the developing section in the embodiment, it may be placed at a position shifted from the center, or the developing section may be arranged between the magnetic poles.

Silica particles may be externally added to the toner to improve fluidity, and abrasive particles may be added to the toner to polish the surface of the photosensitive drum 3, which is a latent image holding member in a transfer image forming method, for example. A toner containing a small amount of magnetic particles may also be used. That is, it has significantly weaker magnetism than magnetic particles, and if possible, magnetic toner can also be used.

In order to prevent the ghost image phenomenon, the sleeve 2 is not subjected to development from the surface of the sleeve 22 that has returned to the container 21 and has been rotated.
The developer layer remaining on the magnetic particle layer 2 may be scraped off once by a soflavor means (not shown), and the scraped sleeve surface may be brought into contact with the magnetic particle layer to re-coat the developer.

A mechanism may be provided that detects the concentration of magnetic particles and toner and automatically replenishes toner according to this output.

The developing device of the present invention can be used as a disposable type developing device that integrates a container 21, a sleeve 22, a blade 24, etc., or as a normal developing device fixed to an image forming apparatus.

(Effects of the Invention) As described above, according to the present invention, a developing device with high image density and high development efficiency is provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device according to an embodiment using the developing method of the present invention. 2(a) and 2(b) are enlarged sectional views of the developing section of the developing device shown in FIG. 1. FIG. FIG. 3 shows a developing device according to an embodiment of the present invention.
Latent image carrier (photosensitive drum) 21... Developer container (container) 22... Developer holding member (sleeve) 23... Magnetic field generating means (magnet) 27... Magnetic particles 28... Toner particles (toner) Uradate Kfh

Claims (3)

[Claims] (1) A toner particle layer and a magnetic brush layer consisting of toner particles and magnetic particles are provided on the developer carrier, and an alternating current component and a direct current component are provided between the developer carrier and the electrostatic latent image carrier. In a developing method in which development is performed by applying a bias electric field, the electric field of the alternating current component has a frequency of 200 to 3000 Hz,
A developing method characterized in that the peak-to-peak voltage is set to a voltage that does not destroy the electrostatic latent image and moves magnetic particles between the developer carrier and the electrostatic latent image in a developing region. (2) The voltage of the AC component of the bias electric field is set to 500 to 2
The developing method according to claim 1, characterized in that the voltage is 200V_P_D. (3) The voltage of the bias power supply is determined by the peak value V_P of the waveform component in the direction of moving the toner from the electrostatic latent image holding member to the developer holding member and the dark area latent image potential V_D on the latent image holding member.
Claim 1 or 2, characterized in that the relationship is |V_P|>|V_D|
Development method described in section.