JPS6275686A - Developing device - Google Patents

Abstract

PURPOSE:To obtain high development efficiency with high image density by specifying a ratio of the capacity occupied by magnetic particles in a developing part to the capacity of the space demarcated with an electrostatic latent image carrier and a developer carrier member and specifying the average particle size and the resistivity of magnetic particles. CONSTITUTION:The developer consisting of magnetic particles 27 and toner particles 28 is stored in a vessel 21. A sleeve 22 faces a photosensitive drum 1 to form the developing part. An S magnetic pole 23b of a magnet 23 is pro vided in the sleeve 22 in the developing part, and a blade 24 is provided above the developing part. An N magnetic pole 23a is provided in the side opposite to the blade and above the blade 24. A power source 34 applies an alternating voltage between the drum 1 and the sleeve 2. A ratio of the capacity occupied by particles 27 in the developing part to the capacity of the space demarcated with the drum 1 and the sleeve 22 is set to 1.5-30%, and the average particle size of particles 27 is set to 30-100mu. The resistivity in the vertical direction of bristles formed with particles 27 in the state which is in contact with the drum 1 is set to 10<15>-10<6>OMEGAcm. Thus, the high development efficiency is obtained with high image density.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to a developing device for developing a latent image formed by electrophotography, electrostatic recording, or the like.

The applicant forms a thin layer of developer on a developer carrier, brings the developer in the thin layer close to the latent image, and performs development by applying an alternating electric field to this approaching portion. He proposed a developing device (Japanese Patent Publication Nos. 58-32375 and 58-32377).

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

As a device to compensate for this drawback, the applicant has developed a method and device that uses non-magnetic toner to form a thin layer of only non-magnetic toner on a developer carrying member, and forms a latent image of the thin layer of only non-magnetic toner. proposed a developing method and apparatus in which development is carried out by applying an alternating IL electric field to the
360, 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. It has been found that there are some drawbacks in the development characteristics, such as the fact that the image density may decrease as the latent image potential increases.

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

Accordingly, 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.

According to the present invention, there is provided a developing device for developing an electrostatic latent image on an electrostatic latent image carrier, which comprises: a developer container containing a developer having toner particles and magnetic particles; , a developer carrying member that faces the electrostatic 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, which is provided on a side of the developer carrying member opposite to the latent image carrier and causes spikes of magnetic particles to form in the developing section and contact the latent image carrier; and the developer. a developer regulating member having a regulating part distal end located upstream of the developing section in the rotational direction of the carrier and spaced apart from the surface of the developer carrying member; and a developer regulating member provided on the opposite side of the regulating member of the developer carrying member. , a second magnetic field generating means located upstream of the developer regulating member with respect to the rotational direction of the developer carrier; an alternating electric field forming means for forming an alternating electric field in the developing section to transfer an alternating electric field to the image carrier; in the developing section, a space defined by the electrostatic latent image carrier and the developer carrying member; The volume occupied by the magnetic particles in the developing area is 1.5% to 30% of the volume, the average particle size of the magnetic particles is 30 to 100%, and the ears formed by the magnetic particles are latent. According to the present invention, there is provided a developing device characterized in that the resistivity in the height direction of the ears of the IE in contact with the image carrier is 10 15 to 10 6 Ωcm.

In addition to the toner particles, there are a small amount of magnetic particles (occupying 1.5-30% of the volume) in the development area, so that under the influence of the magnetic force, these particles form a coarse (not rich) state 5 (i.e. It forms sparse ears, and this action improves development characteristics.

r51 FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention.

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

The radicals in this embodiment include 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 means, and a developer conveyed on the sleeve 22 to the developing section. A regulating blade 24 (hereinafter simply referred to as a blade) that controls the amount, and a power source 3 that is an alternating electric field forming means.
4 etc. Each configuration will be explained below.

Container 21 contains a developer having a mixture of magnetic particles 27 and toner particles 28 . In this embodiment, the toner particles are non-magnetic toner particles having a particle size of 7 to 20 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 uniform mixture, with the concentration of the magnetic particles being high near the sleeve 22 and low in areas away from the sleeve 22. Good, container 21
has an opening at the lower left in FIG.

The sleeve 22 is made of a non-magnetic material such as aluminum, and is provided at the opening of the container 21, with a part of its surface exposed and the other surface protruding into the container 21. The sleeve 22 is rotatably supported around an axis perpendicular to the drawing, and is rotationally driven in the direction indicated by the arrow.9 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 LA stone 23 cooperates with a blade 24 to be described later to control the amount of developer applied to the sleeve 22'2, and has an N magnetic pole 23a and an S magnetic pole 23, which is a developing magnetic pole.
b. It has an N magnetic pole 23c and an S magnetic pole 23d that transport the developer into the container 21 after passing through the developing section. The south pole and north pole may be reversed. This magnet is a permanent magnet in this example, but
An electromagnet may be used instead.

In this embodiment, the blade 24 has at least its tip made of a non-magnetic material such as aluminum, and the blade 24 is made of a non-magnetic material such as aluminum.
extending in the longitudinal direction of the sleeve 22 near the top of the opening;
Its base is fixed to a container 21, and its distal end is fixed to a sleeve 22.
facing the surface with a gap. The gap between the tip of the blade 24 and the surface of the sleeve 22 is 50 to 500 g, m.
, preferably 100 to 350 Bm, and in this example, 250 ILm. If this gap is smaller than 507 hm, magnetic particles will easily get stuck in this gap, and 500 pm
If the thickness exceeds the above, 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. (However, in this case, the thickness of the developer is the thickness on the sleeve 22 when the magnetic force is not moving.) In order to create a developer layer of such a thickness, The gap between the blade tip and the sleeve surface is preferably equal to or smaller than the gap between the sleeve surface and the photosensitive drum surface, but it is also possible to make it larger.

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

The power supply 34 applies a voltage between the photosensitive drum 1 and the sleeve 22 to form an alternating electric field in the gap therebetween, thereby transferring 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 with the same peak voltage on the positive side and negative side, or an asymmetrical alternating voltage in which a DC voltage is superimposed on such an alternating voltage.Specific voltage values include: For example, for an electrostatic latent image with a dark area potential of -600V and a bright area potential of -200V, a DC voltage of -300V is superimposed to increase the peak/peak voltage by 30V.
An alternating voltage of 0 to 2,000 Vpp and a frequency of 200 to 3,000 Hz is applied to the sleeve 22 side, and the photosensitive drum l 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. Furthermore, in order to further ensure the prevention of such leakage, a member z9 is provided on the upper surface of the extension portion to receive and restrain the leaked toner. Furthermore, a scattering prevention member 30 is fixed to the tip of the extension along the longitudinal direction of the sleeve 22 as shown. A voltage having the same polarity as that of the toner particles may be applied to this member 30, whereby the toner scattered from the development area can be pushed toward the photosensitive drum 3 by an electric field, thereby preventing the toner from scattering.

A developing valve j5 and a stopper member 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, the magnetic particles are held over the entire surface of the sleeve 22 facing into the container 21, and form 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, 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
Preferably, 7 contains 2 to 70% (by weight) of toner based on the magnetic particles, and may be composed of only magnetic particles. If the sleeve 22 is held by suction, no substantial flow or tilt will occur even if the device is vibrated or tilted considerably, and the surface of the sleeve 22 will be maintained in a covered state.

Next, when the sleeve z2 is rotated in the direction of the arrow, the magnetic particles rise from the bottom of the container 21 in a direction along the surface of the sleeve 22 and reach the vicinity of the blade 24. Therefore, a part of the magnetic particles passes through the gap between the tip of the blade 24 and the surface of the sleeve 22 together with the toner, and the other part collides with the member 26, then reverses and descends by gravity on the outside of the ascending path of the magnetic particles. and reaches the bottom of the container 21, and then the sleeve 2
2 and repeat the above operation. Note that 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.
Due to friction with the surface, an electric current is generated.

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 out the toner attached to the surface thereof, and some of the charged toner particles 28 leave the container on the sleeve 22 while remaining attached to the surface of the sleeve 22 by reflection force. Blade 24 regulates the amount of developer applied onto sleeve 22.

The developer layer (mixture of magnetic particles 27 and toner 28) thus formed on the surface of the sleeve 22 reaches a developing section facing the photosensitive drum 1 as the sleeve 22 rotates. Here, toner is transferred from the surface of the sleeve 22 and the surface of the 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 implantation ratio of magnetic particles in the developing area is 1.5.
~30%. This point will be explained in detail.

As the sleeve 22 continues to rotate, the toner particles and magnetic particles that have not been consumed in development are collected into the container 21, and the process is repeated where they are coated on the sleeve 22 again by the above-mentioned circulation action. During the 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. In this embodiment, the charges constituting the electrostatic latent image have a negative polarity, and the toner is charged to a positive polarity. Further, 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, inside the sleeve 22, there is a magnetic pole 23b of the magnet 23 corresponding to the closest portion between the photosensitive drum 1 and the sleeve 22.

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 magnetic particles 27 here differs from the above-mentioned development method using a so-called one-component non-magnetic developer thin layer (JP-A-58-143360 and JP-A-59-101680). There is. 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 that of the normal so-called Ia magnetic brush development method, and in this respect, it is essentially different from 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 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 alternately, but in the phase where the positive component is applied to the sleeve 22 side, the direction of the electric field due to this matches the direction of the electric field due to the latent image. At this time, the electric charge hY injected into the ears 51 by the electric field becomes maximum, and therefore the ears 51 are in the maximum standing state as shown in the figure, and the long ears extend on 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. 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 surface of the sleeve 22 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 l is positively charged as described above, it is reversely transferred to the sleeve 22 or the magnetic particles 27 by the electric field formed in this space. In this way, the toner 28 moves back and forth between the photosensitive drum 1 and the surface of the sleeve 22 or the surface of the toner 28, and as the space between them expands due to the rotation of the photosensitive drum 1 and sleeve 22, the electric field weakens. The developing action is complete.

The ears 51 have frictional charges or mirror charges with the toner 28, electrostatic latent image charges on the photosensitive drum 1, and photosensitive drum l.
There is a charge injected by the alternating electric field between the magnetic particles 27 and the sleeve 22, and its state changes depending on the charge/discharge market time constant 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 area from the sleeve 22 to the photosensitive drum 1.
This is the part where hetoner is transferred or supplied. "Volume ratio" is the percentage of the volume occupied by the magnetic particles present in the developing section with respect to the volume of the developing section.As a result of various experiments and considerations, the inventor of the present invention has found that this volume ratio is important in the above-mentioned developing device. have an effect, and this
．． It has been found that a content of 5 to 30%, particularly 2.6 to 26%, is extremely preferable.

If it is less than 1.5%, the low F of the developed image density will be reduced by 1, sleeve ghost will occur, and a noticeable difference in C degree will occur between the part where the ears 51 are present and the part where they are not. This is undesirable in that the thickness of the developer layer formed on the surface of the sleeve 22 becomes 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
Sufficient image density is obtained in the range of ~30%, image quality deteriorates even if it is less than 1.5% or exceeds 30%, and sleeve ghost and fogging occur in the range of the above values where image quality is sufficient. This is based on the fact that the inventor discovered that there is no such thing. The former image quality deterioration is thought to be due to negative characteristics, and the latter is thought to occur because the amount of magnetic particles present becomes large and the sleeve 22 surface cannot be opened, resulting in a significant decrease in the amount of toner supplied from the sleeve 22 surface. It will be done.

If it is less than 1.5%, the reproducibility of line images is poor and the image quality and density are significantly reduced. 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 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. In addition, 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 (such as when the development speed is high), and scales may appear when solid black is produced. 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 two surfaces in a sparse state to a preferable degree, and the toner on both the sleeve 22 and the spikes 51 is sufficiently exposed to the photosensitive drum 1, and the toner on the sleeve is also transferred by flight due to the alternating electric field. Therefore, almost all the toner is in a state where it can be consumed for development, resulting in high development efficiency (11□1 of the toner that can be consumed for development out of the toner present in the development section) and high image density. It will be done. Preferably, slight but strong vibrations are generated in the ears, 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 from occurring in the case of a magnetic brush.

Furthermore, due to the vibration of the ears, the magnetic particles 27 and toner 28
Friction 91 to the toner 28 becomes active as frictional contact with the toner 28 becomes active.
It is possible to direct the two electric currents and prevent the occurrence of fogging. 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 can be determined as (M/h) Application amount (g
/am2), h is the height of the space in the developing section (cm), and ρ is the true density of the magnetic particles g/cm3. C/(T+c) is the stack-A combination of magnetic particles in the sleeve-hi developer.

The ratio of toner to magnetic particles in the two-layer development area is preferably 4 to 40% by weight.

When the alternating electric field is strong (the rate of change is large or the VPP is large), such as on the sole flow side, the ears 51 separate from the sleeve 22 or from its base, and the separated magnetic particles 27 interact with the sleeve 22 and the photosensitive drum 1. It moves back and forth in the space between. Since the energy of this reciprocating motion is large, the effect of the vibration described above is further promoted.

The following behavior was observed using a high-speed camera (Hitachi model).
This was confirmed by shooting at 00 frames per second.

Even when 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. Therefore, sufficient vibration occurs and the above-mentioned effects are produced.

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.

In addition, 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 is equal to or greater than the voltage applied to both the dark and bright areas of the latent image. It is necessary to set it so that gap discharge does not occur. On the other hand, when using ears 51 with a relatively high resistance value, it is possible to prevent the gap voltage from reaching the discharge starting voltage by appropriately selecting the frequency of the alternating voltage and the charging/discharging time constant of the ears 51. preferable.

Taking these into consideration, the resistance of the entire ear 51 in the height direction of the ear 51 with the ear of magnetic particles in contact with the photosensitive drum 1 is preferably in the range of 1015 to 106-Ωcm, particularly 1012 to 106 Ωcm. is preferred. By setting it in the latter range, a developing electrode effect can be obtained, and the excess amount of carrier can be reduced by 1? Since it is possible to prevent electricity from being generated, deterioration of the carrier can be suppressed.

This resistance is measured as follows. With the ears formed, a conductive material such as an aluminum drum is used in place of the photosensitive drum, and a DC voltage of 200 V, for example, is applied between the conductive sleeve 22 and the aluminum drum.
By determining the voltage drop and current during this period 'A111, the total resistance during this period can be determined. Next, the aluminum tram was removed and the number of ears was counted by microscopic observation (according to actual observation, the heights of the ears were approximately equal). By multiplying the above-mentioned total value of resistance by the number of ears, the resistance in the height direction of the ear 1 at the position m in contact with the photosensitive drum 1 can be calculated.

The average particle size of the magnetic particles 27 is preferably 30 to 100,
Particularly preferably 40 to 80. It is.

In general, the smaller the average particle size, the better the frictional charging properties of the toner in 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 the rotation of the sleeve). (which appears as a phenomenon in which the developed density decreases with each step) no longer occurs. However, if the particle size is small, there is a tendency for the magnetic particles to adhere to the electrostatic holder. The position of this adhesion differs depending on the resistance value of the magnetic particles. For example, if the magnetic particles are relatively low in resistance, they will adhere to the image area, and if they are high in resistance, they will be adhered to the non-image area.

This is a general trend; in fact, the magnetic properties of magnetic particles,
The surface shape and surface treatment material (including resin coating) also have some influence.

The magnetic field on the sleeve of the developing section is 600 to 900 G, and in a secondary photographic developing device, the particle size is 30
If the temperature is below 100 ml, the adhesion of magnetic particles will increase. Also, at 100 or higher, sleeve ghosts become noticeable. Therefore, the range -I- is preferred.

In order to ensure the dispersion of the toner particles among the magnetic particles, the magnetic particle diameter is preferably 80 or less, and conversely, in order to ensure the force to convey the toner particles, it is preferably 40 or more.

In this developing device, the conventionally used two-component type 5
A relatively high resistance carrier 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 latent image surface potential of the apparatus according to the present invention, that is, the so-called V-D curve characteristic will be explained.

FIG. 3 shows the V-D curve in this example device as X, and the vertical axis is the optical reflection density value measured by the 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 O potential.

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, a so-called one-component non-magnetic developer thin-layer development method (specifically, a one-component non-magnetic developer thin layer development method, in which development is carried out in the presence of an alternating electric field with non-magnetic toner supplied onto a sleeve as in the present invention) is used. Kaisho 58-143360 specification M
) is shown 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 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, a non-magnetic material is preferable. When a magnetic material is used, lines of magnetic force are concentrated on the blade 24, and a strong magnetic binding force is 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 plate 24 due to strong magnetic binding force. When the mass reaches a certain level, it will go out of the container 21 for the first time. Therefore, when it reaches the developing section on the sleeve 22, it is thought that the state as shown in FIG. 5 will occur.

If the blade 24 is made of a 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.

Next, when the angle θ is in the range of 0<2'', clusters of magnetic particles 27 occur, or the developer is not formed as a uniform layer on the sleeve. This is thought to be due to the fact that the magnetic particles are arranged in a coarse manner, and only after a certain amount of magnetic particles have accumulated there, will they come out.On the other hand, at 0>40°, the effect of regulating the amount of magnetic particles 27 is significantly inferior. .Therefore, 2°
It has been found that ≦0≦40'' is preferred, and 5''≦0≦20° is particularly preferred.

Regarding the relationship between the angle 0 and the developer passing amount, as 0 is decreased, the amount of developer passing through the developer decreases, and therefore the volume ratio in the developing section decreases, and as θ increases, the opposite tendency occurs. Coated on the surface of the sleeve 22!・The amount of ner is not affected by 0 and is almost 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,
l:1 to 5:1. If this ratio is less than 1:2, the V-D curve approaches Y in FIG. 27 tends to adhere excessively to the photosensitive drum 1, which is undesirable. 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 set to 1:2 to 10:1.

This ratio can be controlled by changing the surface properties of the sleeve, the triboelectric properties of the toner, the properties of the magnetic particles, and the feeder. Among these factors, factors that have a large influence include the particle size of the magnetic particles and the amount of 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 amount of toner adhering to the sleeve increases slightly.If 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 desired range of the above ratio can be obtained. However, if the supply amount of magnetic particles is excessively increased, the μ of the magnetic particles 27 that directly contact the photosensitive drum 1 increases, and the magnetic particles 27 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 various experiments conducted by the inventor, if the particle size and supply amount of the magnetic particles 27 are appropriately selected, the above ratio can be adjusted to 1:1 to 5:1.
Good development can be achieved by setting the value within the range of S.

All of the above ratios can be determined as follows. First, all magnetic particles on the sleeve 22 are attracted from the outside by a magnet. What is attracted by this are the magnetic particles and the toner particles attached to them. By washing this, m:+:: of the toner with magnetic particles attached can be determined as a11. Next, all the toner particles remaining on the sleeve 22.1 are suctioned with air and collected in a filter, which can be washed to remove the toner particles adhering to the sleeve. or.

If the developing device is stable, all the magnetic particles on the sleeve 22 are attracted and cleaned from the outside by a magnet, and then
A separate developer layer is formed, all of it (magnetic particles, toner attached to magnetic particles, toner attached to the sleeve) is sucked up, and the total amount of toner is measured after cleaning.

It may be determined by subtracting the amount from the amount of toner adhered to the magnetic particles described above.

Next, we will discuss a specific example using the developing device shown in FIG. 1. In FIG. 1, the sleeve 22 has a diameter of 20 m.
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 surface magnetic flux density due to the magnet 23 (i) was approximately 900 Gauss.

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

The magnetic particles have a particle size of 70 to 50tt (250/300m) with a silicone resin coating on the surface.

ferrite (maximum magnetization 60 emu/'g) was used.

The non-magnetic toner is a toner powder consisting of 100 parts of a styrene/butadiene copolymer resin and 5 parts of a copper phthalocyanine pigment, with an average particle size of 10 mm, and a colloidal silicate force of 0.6.
When using blue toner with external addition of %, sleeve 2
2. A toner coating layer with a coating thickness of about 20 to 30 gm is obtained on the surface, and an upper layer of 100 to 200 gm is further applied on the surface. A magnetic particle layer was obtained. The toner is attached to the surface of each magnetic particle.

At this time, the total weight of the magnetic particles on the sleeve 22 and all the toner was about 2.43XIO-2g/Cm2.

At this time, the weight ratio of the toner attached to the magnetic particles and the toner attached to the sleeve was about 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. The resistance in the height direction of this ear when it is in contact with the photosensitive drum l is 10
It was 8 to 109 ΩCm.

? When the 3I11 charge was determined using the blow-off method, the amount of tripocharge of the toner on the sleeve and on the magnetic particles was +lO
It was LeC/g.

This developing device was installed in a PC-10 copying machine manufactured by Canon Inc., and the distance between the photosensitive drum 3 (made of an organic photosensitive material) and the surface of the sleeve 22 was set to 350 μm. When the volume ratio was determined under these conditions, it was approximately 10% (h = 350gm
, M=2.43X10' g/cm2,
ρ=5.5g/cm3゜7/(T+C)=20.
4%), /< Frequency 1600 as I7S 7rA34
Hz, -30 to an AC voltage of 1300V peak-to-peak
When development was carried out using a superimposed DC voltage of 0 V, a good blue image was obtained.

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

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 example, high image density,
It is possible to perform development with high development efficiency without fogging, ghost images, uneven sweeping, or negative characteristics.

In addition to aluminum, conductive materials such as brass and stainless steel, paper cylinders, and synthetic resin cylinders can be used as the material for the IJ-F 22. 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 adhesive material, 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, in the embodiment, the magnetic pole is arranged η at the center of the developing section, but 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 supplemented with silica particles in order to increase the L mobility, or abrasive particles, for example, in order to polish the surface of the photosensitive drum 3, which is a latent image holding member in a transfer image forming method. Good, a small amount of magnetism in the toner, ira'ej, *
i-f-<:. ＜'! i L <'￥a. 1. .

,. If possible, magnetic toner may also be used. In order to prevent the ghost image phenomenon, the toner is returned to the container 21 and subjected to development from the rotated surface of the sleeve 22.

The developer layer remaining on the sleeve 22 is once scraped off by a scraper means (not shown), and the scraped sleeve surface is brought into contact with the magnetic particle layer to recoat the image side. Even if you do this: 1. A mechanism is 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 either as a disposable type developing device in which the container 21, sleeve 22, plate 24, etc. are integrated, or as a normal developing device fixed to an image forming apparatus.

As explained below, according to the present invention, a developing device with high image density and high development efficiency is provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device according to an embodiment 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. Description of symbols lφ...Latent image carrier (photosensitive drum) 21...Developer container (container) 22...Developer holding member (sleeve) 23...Magnetic field generation - L stage (magnet) 27...r magnetic particles 28... Toner particles (toner) Representative drawing Figure 1 t, ---" No change in the contents of the drawing) Figure 1 Figure 2 Figure 2 b No change) Figure 3 if? (V) Cleaning of the drawings (no change in content) Teito complete edition (method) % formula % 2. Name of the invention Developing device 3. Person making the amendment/Relationship with 1. Patent applicant (100) Canon Co., Ltd. 4, Agent address: 6th floor, Shinbashi Kokusai Building, 2-7-7 Higashi-Shinbashi, Minato-ku, Tokyo 105 (Shipping date: January 28, 1986) 6. Subject of amendment 14 Surface 7, correction details

Claims (1)

[Scope of Claims] 1) A developing device 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 on a side of the developer carrying member opposite to the latent image carrier and causing spikes of magnetic particles to form in the developing section and contacting the latent image carrier; and rotation of the developer carrier. a developer regulating member having a regulating part distal end located upstream of the developing section in the direction and spaced apart from the surface of the developer carrying member; a second magnetic field generating means located upstream of the regulating member in the rotational direction of the developer carrying member; an alternating electric field forming means for forming an alternating electric field for transfer in the developing section; , the volume occupied by the magnetic particles in the developing area is 1.5% to 30%,
The average particle diameter of the magnetic particles is 30 to 100 μ, and the resistivity in the height direction of the ears is 10^1^5 to 10 when the ears formed by the magnetic particles are in contact with the latent image carrier. ^
A developing device characterized by having a resistance of 6 Ωcm. 2) The developing device according to claim 1, wherein the average particle size is 40 to 80 μm. 3) The developing device according to claim 1 or 2, wherein the resistance is 10^1^2 to 10^6 Ωcm.