JPS6275684A - Developing device - Google Patents

Abstract

PURPOSE:To obtain high development efficiency with high image density by controlling the supply quantity of magnetic particles and toner particles to a developer carrier member to make the toner content in a developing part smaller than that in a vessel. CONSTITUTION:Magnetic particles 27 and toner particles 28 are stored in a developer vessel 21, and particles 27 and 28 are carried to the developing part, where a photosensitive drum 1 and a sleeve 22 face each other, by the sleeve 22 to develop images. A magnet 23 is fixed stationarily in the sleeve 22, and a magnetic pole 23a of the magnet 23 and a blade 24 are cooperated with each other to control the supply quantity of particles 27 and 28 to the sleeve 22. The toner content in the developing part is made smaller than that in the vessel 21 thereby, and the former is 0.67-0.007 times as large as the latter. The capacity occupied by particles 27 in the developing part is set to 1.5-30% of the capacity of the space demarcated with the drum 1 and the sleeve 22. Thus, a high development efficiency is obtained with high image density.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device for developing a latent image formed by electrophotography or electrostatic recording.

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 a mating electric field is applied to this approaching portion to perform development. proposed a device (Japanese Patent Publication No. 58-32375 S'j, Specification No. 58-32377).

This device has a high development efficiency ('+', 1 go of the toner consumed in development out of the toner present in the development section) and is very useful in terms of miniaturization. Since the developer is a one-component magnetic toner, it is essential that the toner contains a magnetic material, which has drawbacks such as poor fixation of developed images and poor reproduction of color images. has.

In order to compensate for this drawback, the applicant has developed a method and apparatus for forming a thin layer of only non-magnetic toner on a developer carrying member using non-magnetic toner. He proposed a developing method and device in which development is carried out by applying alternating magnetic fields to the latent image (Japanese Patent Laid-Open No. 58-1
No. 43360, Specification No. 59-101680).

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. Defects in development characteristics were found, such as a property of +11 (image density decreases 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.

Furthermore, in a type of developing device that uses a mixture of magnetic particles and toner as a developer, it has not been possible to obtain a well-established preferred distribution of toner content in each part of the developing area.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a developing device that has high developing efficiency, can form a developed image with high image density, and has no negative characteristics.

Another object of the invention is to establish a preferred relationship for toner content in different parts of the development apparatus.

According to the present invention, there is provided a developing device that has magnetic particles and toner particles in a developer container and has a developer carrying member that carries and conveys the magnetic particles and toner particles to a developing section. The container includes a member for regulating the supply of magnetic particles and toner particles to the developer carrying member, and for a toner-containing container in a container.
Since a developing device is provided which is characterized in that the toner content in the developing section is small, good development is possible.

Back J1 Example FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention.

In this figure, ■ is the static image to be imaged 'i14. It is an electrostatic latent image carrier that carries a latent image, specifically an endless moving 0 (
A capable photosensitive drum or belt or 'A', ll
These are f-body drums or healds. This method of forming a static latent image on something is not the gist of Unreleased 1!11,
Any known method may be used. On the main stream side, the electrostatic latent image carrier is a photosensitive drum on which an electrostatic latent image is formed by a photosensitive drum, and is capable of rotating fq 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 blade) that controls the
4 etc. Each configuration will be explained below.

Container 21 contains a developer comprising 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 gm and are mainly composed of 1 part of carboxylic acid and 90 parts of polystyrene. )・What are magnetic particles and magnetic particles? In this embodiment, the concentration of magnetic particles is high near the sleeve 22;
Although they are housed separately and at a low level, they may be housed in the container 21 as a homogeneous mixture. container 2
1 has an opening in the left corner of 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 around an axis perpendicular to the drawing and is rotationally driven in the direction indicated by the arrow. In this embodiment, the sleeve 22 is a cylindrical sleeve, but it may also 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, and magnetic particles exist here in a volume ratio (1.5 to 30%).

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 magnet 23 has an N magnetic pole 23a that works with a blade 24 to be described later to control the amount of developer applied to the sleeve 22'2, 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. 5J4i and N pole may be reversed. Although this magnet is a permanent magnet in this embodiment, an electromagnet may be used instead.

In this embodiment, the plate 24 is made of a non-magnetic material such as aluminum at least at its tip, and is connected to the container 21.
L (extends in the hand direction) of the sleeve 22 near the opening of the sleeve 22, its base is fixed to the container 21 at 1-61, and its distal end faces the surface of the sleeve 22 with a gap.The distal end of the blade 24 The gap between the surface of the sleeve 22 and the surface of the sleeve 22 is 50 to 50
0 gm, i+f is preferably 100 to 350 gm, and in this example is 250 gm. If this gap is smaller than 50gm, magnetic particles will easily clog this gap,
If it exceeds 8 Lm, 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-L. and the sleeve 22 (however, the thickness of the developer at this time is the thickness on the sleeve 22 when no magnetic force is applied). In order to create a developer layer with such a thickness, it is preferable that the gap between the plate tip and the sleeve surface be equal to or smaller than the gap between the sleeve surface and the photosensitive drum surface, but even if it is larger than the gap between the sleeve surface and the photosensitive drum surface, one It is.

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 the toner from the developer in the sleeve 22-1 to the photosensitive drum 1. Even if the voltage from the power supply 34 is a symmetric AC voltage with the same peak voltage on the positive and negative sides,
Asymmetric alternating current in which DC voltage is superimposed on voltage 11. 'It can be voltage. As for the local voltage value, for example, for an electrostatic latent image with a dark area (upper level -600 V) and a bright area (lower level -200 V), for example, a DC voltage of -300 V (lower 1') is calculated as the peak value. A peak voltage of 300 to 2000 Vpp and a frequency of 200 to 3000 Hz AC LI: A voltage is applied to the sleeve 22 side, and the photosensitive drum 1 is held at the ground potential.

The lower part of the container 21 extends in the direction of the photosensitive drum 1 to form an extension, and prevents the developer (particularly toner particles) from leaking to the outside. Further, in order to further ensure the prevention of such leakage 1F, a member 29 is provided on the -L surface of the extension portion to receive and restrain the leaked developer. Furthermore, a scattering prevention +b member 30 is fixed to the tip of the extension along the longitudinal direction f of the sleeve 22 as shown. A submerged pressure having the same polarity as the toner particles may be applied to this member 30, whereby the toner ejected from the development area is pressed toward the photosensitive drum 3 by an electric field.
Toner scattering can be prevented.

At both ends of the length of the sleeve 22, there is a
f7'M material 25 is provided to prevent developer application/Ii at the ends of the sleeves 22i and Q.

Next, the operation of the developing device of this embodiment will be explained. First, magnetic particles 27 are put into the container 21. The treated magnetic particles are held on the sleeve 22 by the Bi poles 23a and 23d and adhere to the entire surface of the sleeve 22 facing into the container 21, forming a magnetic particle layer. The magnetic particles 27 constitute a magnetic brush in a portion of the magnetic particle layer near the magnetic poles 23a and 23d. Thereafter, toner 28 is put into the container 21 to form a single layer of toner on the outside of the magnetic particle layer. Magnetic particles 2 to be introduced first
7 preferably contains 2 to 70% (by weight) of toner based on the magnetic particles, but it is also possible to include only magnetic particles.The magnetic particles 27 are adsorbed and held as a magnetic particle layer on the surface of the -H sleeve 22. For example, vibrations or fairly large tilts of the equipment do not cause substantial flow or tilt;
The surface of the sleeve 22 remains covered.

Next, when the sleeve 22 is rotated in the direction of the arrow, the magnetic particles move into the container. It rises in the direction along the surface of the sleeve 22 from the lower part of (2) and reaches the vicinity of the blade 24. Therefore, a part of the magnetic particles passes through the gap between the tip of the plate 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.
Charges up 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. The blade z4 regulates the amount of developer applied onto the sleeve 22.

As the sleeve 22 rotates, the developer layer (mixture of magnetic particles 27 and toner 28) formed on the surface of the sleeve 22 reaches a developing section on four sides of the photosensitive drum 1. Here, toner is transferred from the surface of the sleeve 22 and the surface of the magnetic 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. The volume ratio of magnetic particles in the developing section is 1.
It is 5-30%. This point will be explained in detail.

Continuously, by the rotation of the sleeve 22, the toner particles and magnetic particles that have not been consumed for development are collected into the container 21, and the process of being coated on the sleeve 22-A again by the above-mentioned circulation action within the container 21 is repeated. During this 11-degree circulation, the magnetic particles take in toner from the toner layer at the top of the container 21, and are supplied with the amount of toner consumed in development.

FIG. 2 is an enlarged sectional view for explaining behavior in the developing section. The photosensitive drum 1 carries charges constituting a latent image, and in this embodiment, it is a static drum. The charge ′ constituting the ff latent image has a negative polarity, and the toner is charged to a positive polarity. Also,
In this embodiment, the photosensitive drum 1 and the sleeve 22 rotate as shown by the arrows so as to 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 electric field is formed. On the other hand, the sleeve 22 corresponds to the closest portion between the photosensitive drum l and the sleeve 22.
There is a magnetic pole 23b of magnet z3 inside.

In this space, there is a developer which is a mixture of magnetic particles 27 and toner 28 that have been conveyed by the rotation of the sleeve 22 as described above. The presence of the magnetic particles 27 here differs from the above-mentioned development method using a thin layer of one-component non-magnetic developer (JP-A-58-143360 and JP-A-59-101680). ing. In addition, due to the volume ratio of magnetic particles in this area (described later), the amount of magnetic particles present is much smaller than in the normal so-called magnetic brush development method, and in this respect, it is similar to the magnetic brush development method. different.

Due to the action of the magnetic pole 23a, this small number of magnetic particles 27 forms the ears 51 connected in a chain in a coarse state, that is, in a sparse state.

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 surface of the magnetic particles is not 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 parts of the image), so the electric field due to the static latent image is in the direction indicated by arrow a. alternating′
Although the direction of the electric field due to the electric field changes alternately, 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 point, the amount of charge injected into the ear 51 by the 1 [field becomes maximum, and therefore the ear 51 reaches its maximum standing state as shown in the figure, and the long ear extends over the surface of the photosensitive drum 1.

On the other hand, since the toner 28 on the surfaces of the sleeve 22 and the magnetic particles 27 is positively charged as described above, it 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, since the spikes 51 are charged with the same polarity as the toner 28, the toner 28 on the surface 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 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 reciprocates between the photosensitive drum 1 and the surface of the sleeve 22 or the surface of the toner 28, and as the space between them expands due to the rotation of the photosensitive drum 1 and sleeve 22, The developing action is completed as it becomes weaker.

In the spike 51, there is a charge injected by J9 friction with the toner 28 (heavy charge or mirror charge, electrostatic latent image charge on the photosensitive drum 1f and an alternating electric field between the photosensitive drum 1 and the sleeve 22). However, the 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 above-mentioned alternating electric field.

Here, the volume ratio of magnetic particles in the developing section will be explained. The "developing section" refers to the sleeve 22 and the photosensitive drum l.
This is the part where Hetochi is transferred or supplied. The "volume ratio" is the percentage of the volume occupied by the magnetic particles present in the developing area relative to the volume of the developing area. In the above developing device, this volume ratio is 1.5 to 30%, especially 2.6 to 2.
It has been found that 6% is 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 surface of the sleeve 22 - This is not preferable in that the thickness of the developer layer formed on L becomes non-uniform as a whole.

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

In particular, according to the present invention, the image quality does not deteriorate or increase as the volume ratio increases or decreases;
．． Sufficient image density can be obtained in the range of 5 to 30%, and 1.5
If it is less than 30% or more than 30%, poor image quality will occur, and the title of the invention is that no sleeve ghost or fog will occur in the RF+ range where this image quality is sufficient.
It is based on the actuality of 1°. ; The deterioration in image quality in 111 is thought to be due to negative characteristics, and the latter is because the amount of magnetic particles present becomes thicker, making it impossible to open the sleeve 22 surface, and the toner supply value from the sleeve 22 surface decreases significantly. It is thought that this will occur.

On the other hand, if it is less than 15%, 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 ``developing unevenness'' occurs (under special circumstances, etc.), it is preferable to set a volume ratio that makes it difficult for this 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. This may result in uneven density. As a reliable range for preventing this, it is more preferable that the volume ratio of the magnetic particles is 26% or less.

If the volume ratio is in the range of 1.5 to 30%, sleeve 2
The spikes 51 are formed on the surface of the sleeve 22 in a sparse manner to a preferable extent, and the toner on both the sleeve 22 and the spikes 51 is sufficiently opened to the photosensitive drum l, and the toner on the sleeve 2 is also transferred by flight due to the alternating electric field. As a result, almost all of the toner is available for development, resulting in high development efficiency (11 parts of the toner present in the development area that can be consumed for development) and high image density. is obtained. Preferably, slight but strong vibrations of the ears are generated, thereby loosening 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, causing friction to the toner 28! The A charge is directed by -1 U, and fogging can be prevented by 11 U. 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/), )x (1/ρ)X [(C/ (T10)
] can be found. Here, M is the application of developer (mixture...non-sugar iI'j) per medium area of the sleeve (g/cm2), h is the current tLJj,
The height of the subspace is cm), ρ is the degree g for the page of magnetic particles, /
am3, C/ (T+C) is a sleeve! - The amount of magnetic particles in the developer of 1. i, ;l□1.

In the developing section defined above, the ratio of toner to magnetic particles is preferably 4 to 40% by weight and 1λ%.

L: When the alternating electric field is strong (the rate of change is large or VPP is large) as on the recorded flow side, the ears 51 separate from the sleeve 22 or from its base, and the separated magnetic particles 27
reciprocates in the space between the sleeve 22 and the photosensitive drum l. Since the energy of this reciprocating motion is large, the effect of the vibration described above is further promoted.

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

Gap between the surface of the photosensitive drum 1 and the surface of the sleeve 22? Even if the contact pressure between the photosensitive drum 1 and the ears 51 is increased and the vibration is reduced by reducing the size, the gaps on the entrance and exit sides of the developing section are large, so sufficient vibration will occur, and the effects described above will be is played.

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

Note 1: When using the magnetic particles 27 having a relatively low resistance value, the alternating voltage applied between the photosensitive drum 1 and the sleeve 22 has a peak value that can be applied to both dark and bright areas of the Wi image. It is necessary to set it so that gap radiation does not occur. On the other hand, when using ears 51 with a relatively high resistance value, the frequency of the alternating 1F pressure and the charging/discharging time constant of the ears 51 should be appropriately selected to prevent the gap voltage from reaching the discharge starting voltage. is preferred.

Taking these into consideration, it is preferable that the overall resistance of the ears 51 is 1015 to 106 Ωcm in the resistance in the height direction of the ears 51 when the ears of magnetic particles are in contact with the photosensitive drum l, and a developing electrode effect is expected. In case 1012~10”Ω
About cm is preferable.

The magnetic particles 27 have an average particle size of 30 to 100, preferably 40 to 80. In general, the smaller the average particle diameter, the better the friction lid and f 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 (which appears as a phenomenon in which the developer density decreases with each rotation) no longer occurs. However, if the particle size is small,
Static 1 [(There is a tendency for magnetic particles to adhere to the holding body. The position of this adhesion varies depending on the resistance value of the magnetic particles.
For example, a relatively low resistance material will adhere to the image area, and a high resistance material will adhere to the non-image area. This is a general tendency, and in reality, the magnetic properties of the magnetic particles, the surface shape, and the surface treatment material (including resin coating) also have some influence.

In a commercial electrophotographic developing apparatus in which the magnetic field of the developing section sleeve is 600 to 900 G, adhesion of magnetic particles increases when the particle size is less than 30 microns. Further, if the particle diameter exceeds 100, sleeve ghosts become noticeable, so the above range is preferable.

In this developing neck, the two-component system 5
A carrier having a relatively high resistance of about 0 to 100 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 two or more types of magnetic particles.

Next, the relationship between the developed image density and the H1 image surface potential of the apparatus 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 the apparatus of this embodiment is indicated by X. The vertical axis is the optical reflection density value measured by Macbeth reflection densitometer;
The horizontal axis represents the relative potential difference with respect to the photosensitive drum when the sleeve surface is assumed to be at the orh level.

This characteristic is said to be excellent in that there is no fog in the low potential area, there is an appropriate slope (so-called "γ") in the intermediate potential area, and sufficient image density can be obtained in the high potential area. As an example of a developing device not according to the present invention, there is a so-called one-component non-magnetic paste thin layer development method in which development is carried out in the presence of an alternating electric field using non-magnetic toner supplied to a sleeve as in the present application. (Unexamined Japanese Patent Publication No. 5 A-143360X=
The V-D curve in the case of using the above specification) is indicated by Y. This developing method exhibits a negative characteristic in that the image density decreases as the potential increases in areas above a certain potential, and the image density tends to be insufficient in the 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. Here, each ridge is formed independently and uniformly on the sleeve 22 one by one.

On the contrary, FIG. 5 shows an unfavorable condition of the ears. Here, the magnetic particles 27 exist in the form of a mass.

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

The generation of agglomerates of magnetic particles 27 is influenced by the angle 0 between the optical end of the blade 24 and the magnetic pole 23a when viewed from the blade I, the material I of the sleeve 22, and the center of the sleeve 22.

First, regarding the material of the plate 24, it is preferable to use a non-magnetic material. If a magnetic material is used, the lines of magnetic force will be concentrated on the blade 24, and a strong magnetic binding force will be exerted on the magnetic particles 27. In order to overcome this restraining force and exit the container 21, a certain amount of mass is required. Until it reaches this mass, it stays near the blade 24 due to strong magnetic binding force. When the mass reaches a certain size, it will go out of the container 21 for the first time. Therefore, sleeve 2
2 and 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, the developer is uniformly applied, and rough and uniform ears are formed 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 (JIS
) or a magnetic material made by bending it to make it magnetic.

Next, regarding the angle 0, as shown in the figure, the blade 2
4 is on the downstream side of the magnetic pole 23a, but in the range of θ and 2'', clusters of magnetic particles 27 occur, or the developer is not formed as a uniform layer on the sleeve 2. This is thought to be because 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 the magnetic particles larger than the -chamber have accumulated here do they leave. On the other hand θ〉4
At 0°, the effect of regulating the amount of magnetic particles 27 is significantly inferior.

Therefore, 2°≦θ≦40′ is preferable, and 5°≦0≦2
It has been found that 0'' is particularly preferred.

Note that regarding the relationship between the angle 0 and the amount of developer passing through, as θ is decreased, the amount of developer passing through decreases, and therefore the volume ratio in the developing section decreases, and as θ is increased, the opposite tendency occurs. The amount of toner applied onto the surface of the sleeve 22 is not affected by θ and remains approximately constant.

As mentioned above, in the present invention, the toner is composed of magnetic particles 27.
and the surface of the sleeve 22. The ratio of these toner amounts, that is, the ratio of toner held by the magnetic particles and toner held by the sleeve, is 1:2 to 1.
A value within the range of 0:1 (weight ratio) is preferable, and particularly preferably,
The ratio is in the range of 1:1 to 5:1. If this ratio is less than 1:2, the V-curve approaches Y in FIG. 4, which is not preferable. On the other hand, if the ratio is north of 10:1, the magnetic particles 27 will come into excessive contact with the photosensitive drum 1 and the magnetic particles 27 will tend to adhere to the photosensitive drum 1 excessively, which is not preferable. As a result of various experiments conducted by the inventor, it has been confirmed that good images can be obtained when the above ratio is 1:2 to 10:l.

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 ratio of the magnetic particles supplied to the development area.

That is, as the particle size increases, the surface area of the magnetic particles to which toner can be attached decreases (for comparison, the total volume of the magnetic particles is constant), so the amount of toner attached to the magnetic particles that is carried to the developing section decreases.

On the other hand, as if to compensate for this decrease, the toner size adhering to the sleeve increases slightly, and when the zero particle size is made smaller, the opposite tendency occurs.

Regarding the amount of magnetic particles supplied to the developing section, when the amount of supplied magnetic particles is increased, the amount of toner adhering to the magnetic particles increases. On the other hand, with this increase, the amount of toner adhering to the sleeve decreases slightly. When the amount of magnetic particles supplied is decreased, the opposite tendency occurs.

By appropriately selecting these, a range of 9 can be obtained for the above ratio. However, if the magnetic particle supply I4 is increased excessively, the amount of the magnetic particles 27 that come into direct contact with 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 above ratio can be increased from 1:1 to 5:
1, and good development is carried out.

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 toner with magnetic particles attached can be measured. Any toner particles remaining on the sleeve 22 can then be drawn by air and collected in a filter, which can be washed to obtain the weight of toner adhered to the sleeve. Alternatively, if the developing device is stable, all the magnetic particles on the sleeve 22 are attracted by a magnet from the outside.

After cleaning, a separate developer layer is formed, and all of this (magnetic particles, magnetic particle-attached toner, and sleeve-attached toner) is sucked, and the total amount of toner is measured after washing, and the amount of toner attached to the magnetic particles is compared with the above amount of toner attached to the magnetic particles. It may also be determined by subtraction.

Next, the toner content (toner amount/(toner amount)+(magnetic particle amount)) in each part of the developing device, which is an important feature of the present invention, will be explained. As a result of various experiments and studies, the inventor of the present invention has found that in a developing method using a mixture of magnetic particles and toner particles, it is preferable that the toner content in the developer container is higher than the toner content in the developing area. I found it.

This is due to the following reason.

When the toner content in the container is low, the developer circulation within the container increases, which increases the number of contacts of the magnetic particles with the toner, and increases the triboelectric charge imparted to the toner than is desired. The toner tends to adhere firmly to the magnetic particles. Therefore, it becomes difficult to adhere to the electrostatic latent image in the developing section, making it impossible to obtain a sufficient developed density. Furthermore, since the toner firmly adheres to the magnetic particles even in the container, it becomes difficult for the toner to separate from the magnetic particles, resulting in a smudge on the newly replenished toner. There is a tendency for ft charge provision to be insufficient. In this case, insufficiently charged toner reaches the developing section, which tends to cause fogging in the developed image.
Furthermore, if the toner content is low, the number of times the magnetic particles come into contact with the toner increases excessively, and the resin material of the toner tends to fuse to the surface of the magnetic particles. Such magnetic particles impart a triboelectric charge to the toner that is different from a predetermined one, causing fogging. This point is particularly noticeable in a developing system in which alternating electric fields are applied in the developing section.

Therefore, it is preferred that the toner content in the container is high.

However, if the developer in the container with a high toner content is supplied as is to the developing section, the toner concentration may be too high, resulting in too high a concentration in the developing section or the lines may be collapsed. On the other hand, if the toner band Mi is insufficient in heavy charge as a whole, fogging occurs.

From the foregoing, it is highly preferable that the toner content in the developing section is desired for the developing action, while the toner content in the container is higher.

In the developing device of this embodiment, the toner content D1 in the container 21 is approximately 30%, and the toner content D1 in the developing section is approximately 30%.
2 is approximately 15%. The toner in the magnetic particles in the container 21 is distributed onto the magnetic particles and the sleeve after passing through the blade section. Due to the circulation of magnetic particles, when toner is taken in from a single layer of toner that is in contact with this circulation layer, the toner concentration in the circulation layer is high and the triboelectric charge is not sufficiently applied to the toner. Due to the circulation and regulation by the blade, the toner rubs against the magnetic particles and is further rubbed on the sleeve. Therefore, sufficient frictional electrification is achieved. After passing through the blade, toner having sufficient charge is distributed and deposited on the magnetic particles and sleeve. Also, during the circular movement of magnetic particles,
The weakly charged toner in the magnetic brush may be swept away from the magnetic particles.

The toner-containing 11I of the magnetic particles in the container is as follows.
, D2 is maintained at a desired value after passing through the blade section even if Di is increased.

This point is significantly different from general two-component developing devices, which require more strict control of toner content. Of course, a simple toner-containing H,1 control device may be provided without the invention.

In particular, in the developing device of this embodiment, toner content j, jD
2 to 20%, 0.67Xdl≧D2≧0.07XD
It is preferable that relationship 1 is satisfied. Furthermore, the amount of developer applied at this time is 0.5 to 5, OX 10-2g/
It is preferable that it is cm'.

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 arantum abrasive grains, and the magnet 23 was one shown in FIG. 1 with four-pole magnetization with north and south poles alternately arranged. The maximum value of the surface magnetic flux density due to the magnet 23 was about 900 Cous.

The blade 24 was made of nonmagnetic stainless steel with a thickness of 1.2 mm, and the angle 0 was set to 15°.

As magnetic particles, for particle size 70 to 50 (250/300 mesh) whose surface is coated with silicone resin (7) 7
x light (M large magnetization 60 emu/g) was used.

The non-magnetic toner is a toner powder with an average particle size of 10 consisting of 100 parts of a styrene/butadiene copolymer resin and 15 parts of copper phthalocyanine threads, and 0.00 parts of colloidal silica.
When blue toner with 6% added externally was used, a toner coating layer with a thickness of 20 to 30 gm was obtained on the surface of the sleeve 22, and a magnetic particle layer of 100 to 200 # was obtained as an upper layer. 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 2.43×10 −2 g/Cm 2 .

At this time, the weight ratio of the toner adhered to the magnetic particles to the toner adhered to the sleeve was approximately 2=1.

The magnetic particles are raised into spikes by the magnetic field generated by the magnetic pole 23b in the sleeve 22 in the developing area and its vicinity, and have a maximum length of about 0.5 mm.
It formed a standing brush about 9mm in diameter.

I1? When the amount was determined using Jilt using the blow-off method, the amount of toner charge on the sleeve and on the magnetic particles was +1.
This developing device was installed in a PC-10 copying machine manufactured by Canon Co., Ltd., and the distance between the photosensitive drum 3 (organic photosensitive material!!J) and the surface of the sleeve 22 was set to 3507 pm. . When the volume ratio was determined under these conditions, it was approximately 10% (h = 35
0ALm, M=2.43X10' g/cm
2, ρ = 5-5 g / Cm 3, T / (
T + C) = 20.4%), and the bias power supply 34 was developed using an AC voltage with a frequency of 1600H2 and a peak-to-peak value of 1300V and a DC voltage of -300V4), and a good blue color was obtained. I got a color image.

In addition, when a black image was developed and the sleeve surface was observed after development, it was found that toner and particles attached to the magnetic particles were removed.
Most of the toner on the knob was consumed and development was performed at a development efficiency of nearly 100%.

Regarding the development characteristics, there was no fog, and the development characteristics shown by the curve X in FIG. 3 could be obtained.

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, in the embodiment, the magnetic pole is arranged at the center of the developing section, but it may be shifted from the center by 1゛η, 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 Shoshu 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 used as a tripod.

In order to prevent the ghost image phenomenon, the developer layer remaining on the sleeve 22 without being subjected to development is once scraped off from the surface of the sleeve 22 which has been rotated back into the container 21 using a scraper means (not shown). The scraped sleeve surface may be brought into contact with the magnetic particle layer to recoat 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.

As explained above, according to the present invention, a developing device with a good J image removable is provided.

[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 shows 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 according to the present invention. FIG. 5 is a cross-sectional view showing the formation of ears of magnetic particles, which is also undesirable. Explanation of symbols lφ...Latent image carrier (photosensitive drum) 21-.Developer container (container) 22..Developer holding member (sleeve) 23..Magnetic field generating means (magnet) 27..Magnetic particle 28.φ Toner particles (toner) Representative drawing Figure 1 Applicant's agent Yama 1) Takashi", 2 Figure 2 Hisashi b Drawing 11- (no change in content) Figure 3 - ζ surface Electricity ° (■ ) Purification of the drawings:'' (Change in content 7゛;ji) ゝ23b ;-Toitourine City IE (Method) % Formula % 3. Relationship with 19 amendments Patent Applicant (ioo) Canon Co., Ltd. 4, Agent address: 2-7-7 Higashishintachibana, Minato-ku, Tokyo 105 (Delivery date: I JJZ s day, 1986) 6. Drawings subject to amendment 7, Contents of amendment - Heartbeat to I As shown in the appendix of Figures 3 to 5 attached to 8 Attachment A/1. [1st record page]
□ ゛ 2 copies-9゜-dark sea-

Claims (1)

[Scope of Claims] 1) In a developing device having a developer carrying member that has magnetic particles and toner particles in a developer container and transports the magnetic particles and toner particles to a developing section while carrying them, the developer A developing device comprising magnetic particles and a member regulating the supply amount of toner particles to a supporting member, and characterized in that the toner content in the developing section is smaller than the toner content in the container. 2) The developing device according to claim 1, wherein the toner content in the developing section is 0.67 to 0.007 times the toner content in the container. 3) In the developing section, the volume occupied by the magnetic particles in the developing section is 1.5 to 30% of the volume of the space defined by the latent image carrier and the developer carrier. A developing device according to claim 1 or 2, characterized in that: 4) Claims 1, 2 and 3, wherein the toner particles are non-magnetic toner particles, and the amount in the developing section is 4 to 40% by weight relative to the magnetic particles.
The developing device according to any one of paragraphs. 5) The developing device according to any one of claims 1, 2, 3, and 4, wherein the volume occupied by the magnetic particles in the developing section is 2.6% to 26%.