JPS62112169A - Developing method - Google Patents

Abstract

PURPOSE:To permit the formation of a developed image with a high image density by forming an alternating electric field generating means for forming the alternating electric field to transfer the toner particles deposited on the surface of a developer carrying member conveyed to a developing part to an electrostatic latent image carrying body in the developing part and specifying the rotating speed of the developer carrying body then making development. CONSTITUTION:This device has the 2nd magnetic field generating means 23 positioned on the upper stream of a developer controlling member 24 with respect to the rotating direction of the developer carrying body 22 and the alternating electric field forming means to form the alternating electric field to transfer the toner particles deposited on the surface of the developer carrying member conveyed to the developing part to the electrostatic latent image carrying body in the developing part. The development is executed by impressing the alternating electric field to the toner particles 28 sticking to the surface of the magnetic particles 27 and the toner particles sticking to the surface of the developer carrying body 22 while the rotating speed of the body 22 is controlled to the speed substantially equal to the speed 1.5-0.8 times the rotating speed of the image carrying body 1. Then, just the slight magnetic particles exist in addition to the toner particles in the developing part and maintain a coarse state, i.e., form naps of the coarse state under the influence of magnetic power. The developing characteristic is improved by the effect thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a developing method for developing a latent image formed by electrophotography, electrostatic recording, or the like.

1. The applicant of the present invention forms a thin layer of developer on a developer carrier, and 1.
Bring the developer of the thin layer close to the latent image, and intersect this approaching area!
proposed a developing device that performs development by applying an f electric field (Japanese Patent Publication Nos. 58-32375 and 58-32377,
vinegar).

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 for miniaturization, but 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 for forming a thin layer of only non-magnetic toner on the developer regulating member 7 using non-magnetic toner.

We have proposed a developing method and apparatus in which a thin layer of non-magnetic toner is placed facing the latent image and developed by applying an alternating 1f electric field (Japanese Patent Laid-Open Nos. 58-143360 and 59-101680).
No. Specification).

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; q
) can use all non-magnetic developer, but the ratio of consumable toner in the magnetic brush in the developing section is low, so the development efficiency is low, and scratches from the brush will appear on the developed image, like sweeping marks. There are drawbacks such as.

OBJECTS OF THE INVENTION Accordingly, 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. In addition, it is an object of the present invention to effectively utilize the presence of a small amount of magnetic particles in the development area to prevent image deterioration due to the magnetic particles.

Summary of the Invention According to the present invention, there is provided a developing method for developing an electrostatic latent image on an electrostatic latent image bearing member, the developer container containing a developer having toner particles and magnetic particles; A developing section is formed to face the electrostatic latent image carrier and supplies toner particles to the electrostatic latent image carrier, and also supplies developer from the container to the electrostatic latent image carrier.
a developer carrying member that carries and conveys the magnetic particles to the nuclear development section;
a developer regulating member having a regulating part distal end located in the L direction of the developing section in the rotational direction of the developer carrying member and spaced apart from the surface of the developer carrying member; a second magnetic field generating means provided on the opposite side of the developer regulating member to the developer regulating member, and located in a flow direction relative to the rotational direction of the developer carrier; an alternating electric field formation-L stage that forms an alternating electric field in the developing section that transfers the toner particles carried on the surface of the carrying member to the electrostatic latent image carrier; An alternating electric field is applied to the toner particles attached to the surface of the magnetic particles and the toner particles attached to the surface of the developer carrier while controlling the rotational speed to a substantially constant speed F, which is 1.5 to 0.8 times the rotational speed of the magnetic particle. Since development is performed, there are a small amount of magnetic particles in addition to toner particles in the developing area.
occupies 30% of the volume), this is the magnetic force shadow ff T,
It forms ears in a coarse (rather than dense) state, that is, in a sparse state, and this action improves the development characteristics.

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

In this figure, l denotes the static area to be imaged '11!' which carries the latent image. A latent image carrier, specifically an endless transfer lBJ
It is a photosensitive drum or belt or a dielectric drum or belt that is capable of 'liT. The method of forming a static 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.

2, the apparatus of the embodiment includes a developer container 21, a developing sleeve 22 (hereinafter simply referred to as a sleeve) which is a developer holding member, a magnet 23 which is a magnetic field generating stage F, and a developing image conveyed to the developing section on the sleever 2. It includes a regulating blade 24 (hereinafter simply referred to as a blade) for controlling the amount of the agent, a power source 34 that is an alternating electric field generating means, and the like. 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 pm 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 homogeneous mixture, although the concentration of the magnetic particles is high near the sleeve 22 and low in areas further away from the sleeve 22. Good, 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 L 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 around an axis perpendicular to the drawing, and is rotationally driven in the direction indicated by the arrow at approximately the same speed as the circumferential speed of the photosensitive drum. A: In the embodiment, the sleeve 22 is a cylindrical sleeve, but 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, in which a volume ratio of (1.5 to 30%) magnetic particles is present. This point will be discussed later.

The magnet 23 is fixed statically inside the sleeve 22 and remains stationary even when the sleeve 22 rotates. The 8i stone 23 has an N magnetic pole 23a that works with a blade 24 (described later) to control the amount of developer applied to the sleeve 22 balls, and an S magnetic pole 23b that is a developing magnetic pole.
, has an N magnetic pole 23c and an S magnetic pole 23d for transporting 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.
It extends in the longitudinal direction of the sleeve 22 near the -F portion of the opening, its base is fixed to the container 21, and its distal end faces the surface of the sleeve 22 with a gap therebetween. blade 24
The gap between the tip of the sleeve 22 and the surface of the sleeve 22 is 50 to 500p.
m, preferably from 100 to 350 pm, and in one embodiment 250 pm. If this gap is smaller than 50 gm, magnetic particles tend to clog the gap, and if it exceeds 500 pm, 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. In order to create a developer layer of such 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 should not be larger. It is also possible.

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 zl, 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 a mating electric field in the gap between them, thereby transferring the toner from the developer 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 a mating voltage.

Specific voltage values are 2, for example, dark potential -600V,
For an electrostatic latent image with a bright area potential of -200V, for example,
DC voltage -300V is superimposed to generate peak/beak 'commercial use of 300-2000Vpp, frequency 200-3000Hz.
Alternate voltages are applied to the sleeve 22 side to maintain the photosensitive drum 1 at ground potential.

The dome portion of the container 21 extends in the direction of the photosensitive drum 1 to constitute an extension portion, and prevents the developer (particularly toner particles) from leaking to the outside by 1hL. Further, in order to further ensure the prevention of such leakage, a member 29 is provided on the side surface of the extension portion to receive and restrain the leaked developer.

Furthermore, a scattering prevention part 30 is fixed to the distal end of the extension part along the length f direction of the sleeve 22, as shown in the figure. A voltage of the same polarity as the toner particles is applied to this member 30.1. But that's fine. As a result, the toner scattered from the developing area can be pushed toward the photosensitive drum 3 by the market, thereby preventing the toner from scattering.

Developer blocking IL members 25 are provided at both longitudinal ends of the sleeve 22 to prevent application of developer at both ends of the sleeve 22 .

Next, the operation of the developing device of this embodiment will be explained. First, magnetic particles 27 are put into the container 21. The injected magnetic particles are transferred to the sleeve 2 by the magnetic poles 23a and 23d.
2 and is deposited over the entire surface of the sleeve 22 facing into the container 21, forming a layer of magnetic particles. The magnetic particles 27 constitute a magnetic brush in a portion of the magnetic particle layer near the magnetic poles 23a and 23d. Thereafter, the toner 28 is put into the container 21, and a layer of toner is placed on the outside of the magnetic particle layer. Form. Magnetic particles introduced first - 2
7 preferably contains magnetic particles and 2 to 70% (tonpu) toner, but it is also possible to include only magnetic particles. The magnetic particles 27 are -・μ sleeve 22 surface -1-i
, "'- If the particles are absorbed and retained as a layer of magnetic particles, no substantial flow or inclination will occur even if the device is vibrated or tilted considerably, and the state of covering the surface of the sleeve 22 will be maintained.

Next, when the sleeve 22 is rotated in the direction of the arrow, the magnetic particles rise from the corner of the container 21 in the 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 and then reverses to move outside the 1- ascending path of the magnetic particles due to gravity. It descends to reach the lower part of the container 21, moves up near the sleeve 22 again, and repeats the above operation. In addition.

Some of the magnetic particles 7-27 rising from a portion of the container 21 toward the blade 24 turn around and fall off before reaching the vicinity of the blade 24. This is especially true for Snob 1 and Snob 2.
It is noticeable in the magnetic particles far from the surface of No. 2.

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 2.
2. Charges up due to friction with the surface.

In the vicinity of F-iγ1 of the plate 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, they pass below the blade 24 and exit the container 21. At this time, the magnetic particles 27 carry out the toner attached to the surface thereof, and some of the charged toner particles 28 remain attached to the surface of the sleeve 22 due to the reflection force.
- goes outside the base. The blade 24 regulates the developer layer applied to the sleeve 221:.

The developer layer (mixture of magnetic particles E 27 and toner 28) formed on the surface of the sleeve 22 in this manner reaches a developing section facing the photosensitive drum 1 as the sleeve 22 rotates. Here, toner is transferred to the sleeve 22 by an alternating electric field applied between the photosensitive drum l and the sleeve 22.
and the surface of the magnetic particles into a latent image, and the latent image is developed.

By the rotation of the sleeve 22, the toner particles and magnetic particles that have not been consumed in development are collected into the container zl, and are coated on the sleeve 22 again by the above-mentioned circulation within the container 21, repeating step 1. During this recirculation, the magnetic particles take in toner from the conical layer on the top of the container 21, and are supplied with the amount of toner consumed in development.

FIG. 2 is an enlarged cross-sectional view for explaining the behavior in the developing section. The photosensitive drum l carries charges that make up the latent image, and in this embodiment, the charges that make up the electrostatic image Wj are of negative polarity. , and the toner is positively charged. Further, in this embodiment, the photosensitive drum 1 and the sleeve 22 rotate as indicated by the arrows so that they move in the same circumferential direction. The above-mentioned alternating voltage is applied to the space between these by the power supply 34, and an alternating LL electric field is formed. On the other hand, photosensitive drum 1
There is a magnetic pole 23b of the magnet 23 inside the sleeve 22 corresponding to the closest portion of the sleeve 22.

In this space, there is a developer which is a mixture of magnetic particles +27 and toner 28, which have been conveyed by the rotation of the sleeve 22 as described above. The presence of the magnetic particles 27 here is essentially different from the development method using the so-called one-component non-magnetic developer thin layer (JP-A-58-143360 and JP-A-59-101680 specification i!). In addition, due to the volume ratio of magnetic particles in this area (described later), the amount of magnetic rL7- present is much smaller than in the normal so-called magnetic brush development method, and in this respect, magnetic brush development This method is essentially different from the above method.This small number of magnetic particles 27 forms chain-like ears 51 in a coarse state, that is, in a sparse state, due to the action of the magnetic pole 23a.

The behavior of the magnetic particles 27 in the developing section is special because the degree of freedom is increased.

In other words, these sparse spikes of magnetic particles form a uniform distribution in the direction of the magnetic field lines, and can open both the sleeve surface and the magnetic particle surface, so that the toner adhering to the magnetic particle surface is blocked by the spikes. By forming a uniform open surface on the sleeve surface,
Toner adhering to the sleeve surface can fly from the sleeve surface to the photosensitive drum surface by an alternating electric field.

Here, the behavior of magnetic particles and the flight of toner particles will be explained.

As shown in FIG. 2, in this embodiment, the electrostatic latent image is composed of negative charges (dark portions of the image), so the electric field due to the electrostatic latent image is in the direction indicated by arrow a. The direction of the electric field due to the alternating electric field changes to cross 1f, but when the sleeve 2
In the phase in which the positive component 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 amount of charge injected into the ears 51 by the electric field reaches its maximum, and therefore the ears 51 reach their maximum standing state as shown in the figure, and the long ears extend over the surface of the photosensitive drum 1.

- On the other hand, since the toner 28 on the surface of the sleeve 22 and the magnetic particles 27 is positively charged as described above,
The electric field formed in this space causes the light to be transferred to the photosensitive drum l. At this time, since the ears 51 are raised in a rough state, the surface of the sleeve 22 is exposed, and the toner 28 is exposed.
is separated from both the sleeve 22 surface and the ear 51 surface. In addition, since the spikes 51 are charged with the same polarity as the toner 28, the toner 28 on the surface F of the spikes 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 strong in the opposite direction, the amount of charge injection becomes relatively small, and the ears 51 are brought into a contracted contact state in accordance with the amount of charge injection.

On the other hand, since the toner 28 on the photosensitive drum 1 is positively polarized 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 space between them expands due to the rotation of the photosensitive drum 1 and the sleeve 22, the electric field weakens. At the same time, the developing action is completed.

The spikes 51 are charged with charges injected by frictional charges or mirror charges with the toner 28, static latent image charges on the photosensitive drum 11-, and the intersection 11-' field between the photosensitive drum 1 and the sleeve 22. However, 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.

As described above, the ears 51 of the magnetic particles 27 are brought into a state of slight but intense vibration due to the alternating electric field described in L.

Here, the mass ratio of magnetic particles in the developing section will be explained. The "developing section" is a section to which toner is transferred or supplied from the sleeve 22 to the photosensitive drum 1.

The "volume ratio 1d" is the percentage of the volume occupied by the magnetic particles present in the developing area relative to the volume of the developing area. As a result of various experiments and considerations, the present inventor has found that this volume ratio has an important influence on the L developing device, and that this should be set at 1.5 to 30%, particularly 2.6 to 26%. was found to be extremely preferable.

If it is less than 1.5%, a decrease in the density of the developed image will be observed, a sleeve ghost will occur, a noticeable difference in density will occur between the area where the ears 51 are present and the area where the ears 51 are not present, and the concentration on the surface of the sleeve 22 will be reduced. This is undesirable in that the thickness of the developer layer formed is non-uniform throughout.

If it exceeds 30%, the degree of closure of the sleeve surface increases, which is undesirable because fogging may occur.

In particular, the present invention shows that the image quality does not monotonically deteriorate or increase as the volume ratio increases or decreases, but
A good image density can be obtained in the range of ~30%, and if it is less than 1.5% or more than 30%, poor image quality will occur, and in the above range where the image quality is sufficient, sleeve ghosts will also appear. This is based on the fact that the inventor has discovered that the phenomenon does not occur. The former image quality deterioration is thought to be due to negative characteristics, and the latter is thought to occur because the presence of magnetic particles becomes large and the sleeve 22 surface cannot be opened, and the toner supply from the sleeve 22 surface is significantly reduced. Conceivable.

On the other hand, if it is less than 1.5%, the reproducibility of line images is poor and the image quality and density are significantly lowered. On the other hand, if it exceeds 30%, there will be problems with the magnetic particles damaging the photosensitive drum surface and problems with transfer and fixing caused by the magnetic particles adhering as part of the image.

When the presence of magnetic particles is close to 1.5%, when reproducing a large-area uniform high-density image (solid black),
Since there are cases where partial development unevenness called ``kJ'' occurs (under special circumstances), it is preferable to set a volume ratio that makes it difficult for these to occur.

This value indicates that the volume ratio of magnetic particles to the developing area is 2°6.
% or more, this range becomes a more preferable range. Also, if the presence of magnetic particles is close to 30%, there may be a delay in toner replenishment from the sleeve surface around the area where the ears of magnetic particles come into contact (at high development speeds, etc.), and scales may appear when solid black is reproduced. There is a f3 possibility of causing density unevenness. As a reliable range for preventing this, the L volume ratio of the magnetic particles is preferably 26% or more.

If the volume ratio is in the range of 1.5 to 30%, sleeve 2
The spikes 51 are formed on the second surface F in a preferable sparse state, and the toner in both the sleeve 22 and the spikes 51 and L are released to the photosensitive drum 1 in one minute, and the toner in the sleeve L is also exposed to an alternating electric field. Because of the flying transfer, almost all of the toner is available for development, resulting in high development efficiency (ratio of toner that can be consumed for development out of the toner present in the development area) and high image density. can get.

Preferably, slight but intense vibration of the ears is caused,
This loosens the magnetic particles and the toner adhering to the sleeve 22. In any case, it is possible to prevent uneven sweeping and ghost images that occur in the case of magnetic brushes. Furthermore, the vibration of the ears activates the frictional contact between the magnetic particles '27 and the toner 28, so that the frictional electrification of the toner 28 is reversed and fogging can be prevented. Note that high developing efficiency is suitable for downsizing of the developing device.

The volume ratio of the magnetic particles 27 existing in the developing section is (M/h)X (1/ρ)X [(C/ (T+
C)]. Here, M is the developer per medium area of the sleeve (moderate product...when not standing up), coating weight (g/cm2), and h is the height of the space in the developing area (cm).
), ρ is the true density of magnetic particles g/cm3, C/ (T+C
) is the weight percentage of magnetic particles in the developer on the sleeve.

In addition, the ratio of toner to magnetic particles in the developing section defined in L is preferably 4 to 40 weight:it%.

When the alternating electric field is strong (the rate of change is large or VPP is large) as in the above embodiment, the ears 51 separate from the sleeve 22 or from its base, and the separated magnetic particles 27 are placed between the sleeve 22 and the photosensitive drum 1. It moves back and forth in the space of . Since the energy of this reciprocating motion is large, the effect of the double series of vibrations is further promoted.

The following behavior was detected using a high-speed camera (manufactured by Seisakusho).
This was confirmed by shooting at 0 frames per second.

Even if the gap between the surface of the photosensitive drum 1 and the surface of the sleeve 22 is reduced to increase the contact pressure between the photosensitive drum 1 and the brush 51 and to reduce vibration, the gap is large at the entrance and exit sides of the developing section. - minute vibrations occur, and the above-mentioned effect is produced.

Conversely, it is preferable to increase the gap between the photosensitive drum 1 and the sleeve 22 so that the spikes 51 do not come into contact with the photosensitive drum 1 when no magnetic field is applied, but do come into contact when a magnetic field is applied.

In addition, when using the magnetic particles 27 of relatively low resistance (If), the alternating voltage applied between the photosensitive drum 1 and the sleeve 22 will be applied to the dark and bright areas of the latent image at its peak value. In either case, settings must be made so that gap discharge does not occur.On the other hand, when using the ears 51 with a relatively high resistance value, the frequency of the alternating voltage and the charging/discharging time constant of the ears 51 must be appropriately selected. 1. It is preferable to prevent the gap voltage from reaching the discharge starting voltage.

Considering these 1. In this case, the resistance of the panicle 51 body is:
When the developing brush is in contact with the photosensitive drum, the resistance in the height direction of the ears 51 is preferably 101!1 to 106 ΩCm, and if a developing electrode effect is expected, the resistance is 10
It is preferably about 10 to 10 6 Ωcm.

The magnetic particles 27 have an average particle diameter of 30 to 10-1, preferably 40 to 80. Generally, the smaller the average particle diameter, the better the toner friction zone in the sleeve 22F.
Sleeve ghost (appears as a phenomenon in which the density decreases due to rotation of the sleeve immediately after developing a solid black original, or a phenomenon in which the developed density decreases with each rotation of the sleeve)
will no longer occur. However, if the particle size is small,
This tends to cause adhesion of magnetic particles to the carrier. This landing position differs depending on the resistance value of the magnetic particles; for example, a relatively low-resistance magnetic particle will land at the image area, and a high-resistance one will land at the non-image area by +1. This is a general trend;
In reality, the magnetic properties of magnetic particles and the surface shape 1 surface treatment material (including resin coating) are also affected to some extent.

In a commercial photographic developing apparatus in which the magnetic field of the sleeve 1 in the developing section is 600 to 900 G, adhesion of magnetic particles increases when the particle size is less than 30 microns. Furthermore, sleeve ghosts are noticeable north of 100 Jj, so the J- range is preferable.

In this development method, the conventionally used two-component system 5
A carrier having a relatively high resistance on the order of 0 to 100 islands can be used.

Each magnetic particle may be made of only a magnetic material, or may be a combination of a magnetic material and a non-magnetic material, or the magnetic particles as a whole may be a mixture of one or more types of magnetic particles.

Next, the relationship between the developed image density and the latent image surface potential in the developing method according to the present invention, that is, the so-called V-D curve characteristic will be explained.

In FIG. 3, the V-D curve in this example is indicated by X. The vertical axis is the optical reflection e degree value determined by the Macbeth reflectance meter, and the horizontal axis is the relative potential difference with respect to the photosensitive drum when the sleeve surface is regarded as o', 11th position. This characteristic has no fog in the low potential area and an appropriate slope (so-called "
γ''), and is understood to have excellent characteristics in that sufficient image density can be obtained in the high potential area. As an example of a developing device not according to the present invention, sleeve 1-
When using the so-called one-component non-magnetic developer thin layer development method (Japanese Patent Application Laid-Open No. 58-L A3360) in which development is carried out in the presence F of the magnetic field using non-magnetic toner supplied to the The V-D curve is indicated by Y. This developing method exhibits a negative characteristic in that the image density decreases as the potential increases at a certain potential level, and the image density tends to be insufficient at high potential areas. In comparison, the device of the present invention has no fogging in the low potential area and the slope of γ is gentle in the intermediate potential area, so there is no excessive edge effect, and from the intermediate potential area to the high potential area. Also, it does not exhibit negative characteristics, and sufficient image density can be obtained even at high potential areas.

Next, conditions for forming ears in a preferable state in the developing section will be discussed.

FIG. 4 shows a preferable condition of the ears in the developing section, where each ear is formed independently and uniformly on the sleeve 22 one by one.

On the contrary, FIG. 5 shows an unfavorable condition of the ears, in which the magnetic particles 27 are present in clusters.

If development is performed in this state, scale-like unevenness will occur in the image, which is not preferable.

The inventor believes that the generation of agglomerates of magnetic particles 27 is caused by the blade 24
material and blade 24 viewed from the center of sleeve 22
It has been found that this is influenced by the angle θ between the tip and the magnetic pole 23a.

First, regarding the material of the blade 24, it is preferable to use a non-magnetic material.If a magnetic material is used, the lines of magnetic force will be
, and a strong magnetic binding force on the magnetic particles 27 becomes stronger. In order to overcome this restraining force and exit the container 21, a certain amount of leet mass is required. Until it reaches this mass, it stays near the blade 24 due to strong magnetic binding force. It is not until the square of -L reaches a certain level that the user comes out of the container 21. Therefore, when the sleeve 22 reaches the developing section, it is thought that the state as shown in FIG. 5 will occur.

When the blade 24 is made of non-magnetic material, the blade 24
Since magnetic concentration does not occur near the tip, the above-mentioned lumps are not formed, and the developer is uniformly applied, resulting in the formation of rough and uniform ears in the developing area. Therefore, it is preferable to use a non-magnetic material for the blade 24, provided that it is weakly magnetic (for example, 5US304 (J
It may be made by bending IS) to make it magnetic.

Next, when the angle θ is in the range of 0 to 2 degrees, agglomerates of the magnetic particles 27 are generated, or the developer is not formed as a uniform layer on the sleeve L. This is thought to be due to the fact that the magnetic particles are arranged in a coarse manner along the lines of magnetic force in the vicinity of the blade 24, and only after a certain amount of magnetic particles have accumulated there, are they released. On the other hand, when 0>40''', the effect of regulating the amount of magnetic particles 27 is significantly inferior.
°≦θ≦40" is preferable, and 5°≦θ≦20" is especially &
Something interesting was discovered.

Regarding the relationship between the angle 0 and the developer passing amount, as θ is decreased, the passing amount decreases, and therefore the volume ratio in the developing section decreases, and when 0 is increased, the opposite tendency occurs. jj] of the toner applied onto the surface of the sleeve 22 is substantially constant without being affected by θ.

As mentioned above, in the present invention, the toner is composed of magnetic particles 27.
and the surface of the sleeve 22. As a result of various experiments and considerations, the inventor of the present invention determined that the ratio of these toner amounts, that is, the ratio of the toner held by the magnetic particles to the toner held by the sleeve, was 1 = 2 to 10:1 CII.
Ratio) values within the range are preferred, particularly preferably 1:1 to 5:
It was found that it was within the range of 1. If this ratio is less than 1:2, the V-D curve approaches Y in FIG. 4, which is not preferable. On the other hand, if it is 10.1 or more, the magnetic particles 27 will come into excessive contact with the photosensitive drum l, and the magnetic particles 27 will tend to adhere excessively to the photosensitive drum l, which is not preferable. As a result of various experiments conducted by the inventor, it has been confirmed that when the above ratio is set to 1:2 to 10:1, a good image is produced74).

This ratio can be controlled by changing the surface properties of the sleeve, the triboelectric properties of the toner, and the properties and supply amount of the magnetic particles. Among these factors, factors that have a large influence include the particle size of the magnetic particles and the size of the magnetic particles supplied to the developing area.

In other words, when the particle size is increased, the surface area of the magnetic af to which toner can be attached decreases (assuming that the total volume of magnetic particles is constant for comparison), so the amount of toner adhering to the magnetic particles that is carried to the developing section decreases. .

On the other hand, as if to compensate for this decrease lA, the sleeve + 1st toner waste increases as f increases.If the particle size is made smaller, the opposite tendency occurs.

Regarding the supply amount of magnetic particles to the developing section, if the supply amount is increased by 4, the magnetic particle adhering toner;! l- increases. On the other hand, with this increase, the amount of toner adhering to the sleeve decreases. When the amount of magnetic particles supplied is decreased, the opposite tendency occurs.

By appropriately selecting these, a desired range of the L ratio can be obtained. However, if the amount of magnetic particles supplied is excessively increased, the amount of magnetic particles 27 that directly contact the photosensitive drum 1 will increase, causing the magnetic particles 27 to adhere to the photosensitive drum 1. Furthermore, when the magnetic particles are made finer, the magnetic binding force is reduced, and the magnetic particles also adhere to the latent image carrier. Increasing the amount of magnetic particles supplied and reducing the particle size of the magnetic particles to supply excess toner that is not used for development will reduce the development efficiency.

According to the inventor's various experiments, if the particle size and supply amount of the magnetic particles %27 are appropriately selected, the ratio -1- can be adjusted to l:1 to l:1.
A ratio of 5:1 can be achieved and good development is achieved.

The above ratio can be measured as follows. First, all magnetic particles on the sleeve 22 are attracted from the outside by a magnet. What is attracted by this are magnetic particles and toner particles attached to them. This can be washed and the weight of the magnetic particles P+f-attached toner can be measured. Next, all the toner particles remaining on the sleeve 22 are suctioned with air and collected in a filter, which is then washed to remove the toner beads adhering to the sleeve. Alternatively, if the developing device is stable, the magnetic particles in the sleeve 22 -
After all of the toner is attracted and washed from the outside by a magnet, a separate developer layer is formed, and all of this (magnetic particles, magnetic particles to adhered toner, sleeve-adhered toner) is sucked and washed, and the total toner value is measured. It may be determined by subtracting the value of the magnetic particle-adhered toner.

Next, the circumferential speeds of the photosensitive drum 1 and the sleeve 22 will be described. As mentioned above, the way the toner particles and magnetic particles are interposed between the photosensitive drum l and the sleeve 22 in the developing section has a great effect on image quality. Therefore, an appropriate range exists for the circumferential speed difference between the photosensitive drum 1 and the sleeve 22, and it is preferable that the photosensitive drum 1 and the sleeve 22 have substantially the same speed.
The rotational speed (peripheral speed) is preferably about 1.5 to 0.8 times the rotational speed (peripheral speed) of the photosensitive drum 1.

When the rotational speed (peripheral speed) of the sleeve 22 becomes less than 0.8 times the rotational speed (peripheral speed) of the photosensitive drum 1.

The amount of developer applied to the electrostatic latent image on the surface of the photosensitive drum 1 while passing through the developing section (that is, the total amount of toner particles attached to the toner particles and magnetic particles on the surface of the sleeve 22) ) is reduced, resulting in a decrease in the density of the developed image, and the distribution between areas where the ears 51 are present and areas where they are not becomes unstable, resulting in local density differences. This may occur depending on the particle size and toner particle size. In other words, this becomes a factor that makes it necessary to limit the type of developer used.

Further, the rotational speed (peripheral speed) of the sleeve 22 is
If it exceeds 1.5 times the rotational speed (peripheral speed) of There were cases where there was a delay in toner replenishment from the sleeve surface around the sleeve. In this remarkable case, scale-like density unevenness (roughness of solid black) was observed in areas where the image density was very high when solid black was reproduced. In addition, because the vibration of the ears per development time in the developing section is insufficient, the frictional contact between the magnetic particles and the toner particles may not be very active, and as a result, the toner particles are not sufficiently charged by yl friction. It was also observed that the amount of water was sufficient to cause fogging.

From the above, by keeping the circumferential speed of the sleeve 22' at a substantially constant speed of about 1.5 to 3 degrees of the circumferential speed of the drum, it is possible to reduce the amount of magnetic particles present in the developing section. It is possible to make the most effective use of actions and behaviors.

This speed relationship is not seen at all in conventional two-component development systems (conventionally, the sleeve is more than twice as long as the drum, and Practical-L is 4 to 8 times more), which differentiates it from conventional development. In addition to effectively utilizing the jumping development from the sleeve surface of the single layer of toner formed on the surface of the four sleeves, it is also possible to rationally combine the toe supply of magnetic particles and the action of the magnetic particles themselves. This is a favorable condition for maintaining balance.

Next, an example of a case in which the developing device shown in FIG. 1 is used will be described. In FIG. 1, the sleeve 22 is 520 m in diameter.
The surface of an aluminum sleeve of size m was subjected to amorphous sandblasting treatment using alundum abrasive grains, and the magnet 23 was one shown in Fig. 1 with 4-pole magnetization, with N and S poles alternately arranged. . 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 the magnetic grains-f, ferrite (maximum magnetization 60 emu/g) with a grain size of 70 to 50 g (250/300 mesh) whose surface was coated with silicone resin 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 JLm is obtained on the surface of 2, and a further layer of 100 to 200 JLm is formed on the surface.
A magnetic particle layer was obtained. 8. Toner is deposited on the surface of the magnetic particle hG.

At this time, the total ff1M of the magnetic particles and all the toner in the sleeve 22'' was approximately 2.43 x 10-2 g/am2. The magnetic particles were agitated by the magnetic field generated by the magnetic pole 23b in the sleeve 22 in the developing section and its vicinity. When standing, the maximum length is approximately 0.
It formed a standing brush about 9mm in diameter.

When the amount of charge was measured by a blow-off method, the amount of tripo charge of the toner on the sleeve and on the magnetic particles was +10 C/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 organic photosensitive material) and the surface of the sleeve 22 was set to 350 Ji, m. At this time, the speeds of the photosensitive drum 3 and sleeve 22 are constant, and 66
It was set as m-zen/see. When calculating the volume ratio under these conditions,
It was about 10% (h=350pm, M=2.43
XiO-2g/em2, p=5.5g/cm3. T/
(T+C)=20.4%). When development was carried out using a bias power supply 34 having a frequency of 1800 Hz and a peak-to-peak value of +300 V AC voltage superimposed with -300 V DC voltage, a good blue image was obtained.

Furthermore, when a solid black image was developed and the sleeve surface after development was observed, it was found that most of the toner adhering to the magnetic particles and the toner on the sleeve L were consumed, and development was performed with nearly 100% development efficiency.

As for the development characteristics, it was determined that there was no fog and that the development characteristics shown by the curve X in FIG. 3 were obtained.

As explained below in 1-, according to this embodiment, development can be performed with high image density, high development efficiency, and no fogging, ghost images, uneven sweeping, or negative characteristics.

As the material 1 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 glue material 1, for example, a conductive sponge, may be wrapped 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.

The toner may be externally added with silica particles to improve fluidity, or abrasive particles 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, magnetic toner can also be used as long as it has significantly weaker magnetism than magnetic particles and can be tripo-charged.

In order to prevent the ghost image phenomenon, the developer layer remaining on the sleeve 22 without being subjected to development from the surface of the sleeve 22 that has returned to the container 21 and rotated is once transferred to the scraper 7 in one stage (not shown). Alternatively, the developer may be recoated by scraping off the sleeve surface by bringing the scraped sleeve surface into contact with the magnetic particle layer.

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

The developing method of the present invention can be used either as a disposable type developing device in which the container 21, sleeve 22, blade 24, etc. are integrated, or as a regular developing device fixed to an image forming apparatus.

As described in the detailed description of the invention, according to the undeveloped 1j, a developing method with high image density and high development efficiency is provided, and the presence of a small amount of magnetic particles in the development area is utilized to the maximum, and image deterioration due to the magnetic particles is prevented. can be prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention. 2 is an enlarged sectional view of the developing section of the developing device shown in FIG. 1. FIG. FIG. 3 is a diagram showing a developing characteristic curve of a developing device according to an embodiment of the present invention. FIG. 4 is a sectional view showing a preferred state of formation of ears of magnetic particles in the developing device δ according to the present invention. FIG. 5 is a cross-sectional view showing the formation of ears of magnetic particles, which is also preferable. 1---Latent image carrier (photosensitive drum) 21-m=Developer container (container) 22-m-Developer holding member (sleeve) 23-m-Magnetic field generation f stage (magnet) 27-- magnetic particles

Claims (1)

[Scope of Claims] 1) A developing method for developing an electrostatic latent image on an electrostatic latent image carrier, comprising: a developer container containing a developer having toner particles and magnetic particles; a developer carrying member that faces the latent image carrier and forms a developing section that supplies toner particles to the electrostatic latent image carrier, and carries and conveys developer from the container to the developing section; a first magnetic field generating means provided opposite to the latent image carrier via a developer carrier and bringing the magnetic particles into contact with the developer carrier in the developing section; a developer regulating member having a regulating portion distal end located upstream of the developing section and spaced apart from the surface of the developer carrying member; and a developer regulating member provided opposite to the regulating member via the developer carrying member, the developer regulating member a second magnetic field generating means located upstream of the regulating member in the rotational direction of the developer carrier; and a second magnetic field generating means for transferring toner particles conveyed to the developing section and supported on the surface of the developer carrier to the electrostatic latent image carrier. and an alternating electric field forming means for forming an alternating electric field in the developing section, the rotating speed of the developer carrier being set to 1.5 times the rotational speed of the image carrier.
A developing method in which development is carried out under control at a substantially constant speed of 5 to 0.8 times.