JPH0519147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for forming a thin layer of dry developer.
The present invention further relates to a thin layer forming device for non-magnetic developer.

Prior Art Conventionally, various devices have been proposed and put into practical use as dry developing systems. However, in any of the developing methods, it is extremely difficult to form a thin layer of dry developer, and for this reason, the developing device has been constructed by forming a relatively thick layer. However, now that improvements in the clarity, resolution, etc. of developed images are required, it is essential to develop a method for forming a thin layer of dry developer and an apparatus therefor.

Japanese Patent Application Laid-Open No. 43037/1984 has proposed a method for forming a thin layer of a conventionally known dry developer.
And it has been put into practical use. However, this concerned the formation of a thin layer of magnetic developer. In order to make magnetic developers magnetic, it is necessary to add a magnetic substance to the developer. (Magnetic material is usually black)
There are problems such as poor color reproduction.

For this reason, methods for forming a thin layer of non-magnetic developer include a method in which soft bristles such as beaver hair are used as a cylindrical brush and the developer is adhered to the brush, and a method in which the surface is made of fibers such as velvet is used. A method has been proposed in which the developer is coated on the developing roller using a doctor blade or the like.

However, when an elastic blade is used as a doctor blade for the above-mentioned fiber brush, it is possible to regulate the amount of developer, but uniform application is not achieved, and the fibers of the brush are simply rubbed by the fiber brush on the developing roller. Since no triboelectric charge is imparted to the developer present in between, there is a problem in that ghosts and the like are likely to occur.

Purpose of the Invention As a novel method for forming a thin layer that is completely different from the conventional method described above, the applicant et al. formed a magnetic brush made of magnetic particles on the upstream side of the magnetic particle restraining member with respect to the moving direction of the surface of the developer holding member. have already proposed a method of forming a thin layer of non-magnetic developer on a developer holding member using this magnetic brush. However, in this developing device, if the magnetic particles are not sufficiently circulated within the container, the triboelectric effect on the developer will be insufficient, and therefore the developer will not adhere to the sleeve sufficiently. It was found that the final developed image had a lot of fog. Therefore,
The present invention provides an apparatus for forming a thin layer of non-magnetic developer on a developer holding member using magnetic particles confined within a container, in which the magnetic particles are sufficiently circulated within the container. An object of the present invention is to provide a layer forming device.

Structure of the Invention The apparatus of the present invention includes a developer supply container having an opening and containing magnetic particles and a non-magnetic developer therein, and a developing section for developing an electrostatic latent image, which faces the electrostatic latent image carrier. a developer holding non-magnetic member provided in the opening and movable endlessly inside and outside the container; a fixed magnetic field generating means provided inside the holding member; and a fixed magnetic field generating means provided in the vicinity of the top of the opening. , a magnetic particle restraining member that restrains the magnetic particles in the developer supply container together with a magnetic particle restraining magnetic pole of the fixed magnetic field generating means, and forms a non-magnetic developer layer on the holding member to be transported to a developing section. A base layer of magnetic particles is formed on the developer holding member in the container by the magnetic force of the fixed magnetic field generating means, and the magnetic particles of the base layer are transferred to the developer holding member by upward movement of the developer holding member. The developer is caused to move upward along the magnetic particle restraining member, is reversed and moved downward by the magnetic particle restraining member, and is caused to move in a circular motion, and the non-magnetic developer is taken into the base layer from the non-magnetic developer layer on the base layer by the circular motion. This is a thin layer forming device, and since the magnetic particle restraining member is inclined toward the developer supply container side with respect to a vertical line passing through its tip, gravity can be actively used for circulation. , good circulation can be achieved and the possibility of leakage of magnetic particles from between the magnetic particle restraining member and the developer holding member is minimized.

Embodiments Examples of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram of a method and apparatus for forming a thin layer of nonmagnetic developer according to the present invention.

In FIG. 1, 11 is a cylindrical electrophotographic photoreceptor that moves in the direction of the arrow a. A non-magnetic holding member 12 that holds the developer is provided with a gap between the photoconductor 11 and, in this embodiment, the holding member 12 has a cylindrical shape, but it may also have a web shape that moves endlessly. . The same applies to the electrophotographic photoreceptor 11. Along with this movement of the photoreceptor 11, the developer holding member 12 is rotated in the direction of arrow b. A developer supply container 13 is provided to supply developer to the developer holding member 12 . The developer supply container 13 has an opening near its lower part,
A developer holding member 12 is provided in the opening. Since a portion of the developer holding member is exposed to the outside through the opening, its surface moves from the inside of the developer supply container to the outside, and then returns to the inside. An enclosure is formed at the lower part of the developer holding container 13 so as to wrap around the lower part of the developer holding member 12 to prevent the developer from leaking to the outside. A fixed magnetic field generating means for generating a fixed magnetic field, that is, a magnet 14 is fixedly provided inside the developer holding member 12 . Since the magnet 14 is fixed, only the developer holding member 12 rotates. This magnet 14 has a magnetic particle restraining magnetic pole 20, a transporting magnetic pole 21, and a sealing magnetic pole 22, which will be described later.

A magnetic blade 15 (magnetic particle restraining member) made of a magnetic material is arranged near the top of the opening of the developer supply container 12 . There is a magnetic particle restraining magnetic pole 20 of the magnet 14 on the opposite side of the magnetic blade 15 with the developer holding member 12 interposed therebetween. It is arranged at an upstream position in the rotational direction of No. 12, shifted by an angle θ (5 to 50 degrees).

A rear wall plate 13 is located near the bottom of the developer supply container 13.
-1, which ensures the presence of magnetic particles near the bottom of the developer supply container 13 and improves the circulation of the magnetic particles, as will be described later.

Developer supply container 13 facing the seal magnetic pole 21
An iron piece 18 made of magnetic material is provided on the inner wall of the container 13, and a magnetic brush formed between these pieces seals the lower part of the container 13 and also improves the circulation of magnetic particles. The iron piece 18 may be made of a magnet other than metal such as iron, which faces the sealing magnetic pole 21 in a reverse polarity relationship. These magnetic members may be attached to the wall of the container 13 facing the sealing magnetic pole 21, or a part of the container itself may be made of a magnetic material such as iron, and the wall of the container facing the sealing magnetic pole 21 may be used to hold the developer. It may be configured close to the member 12.

The base layer 16 is formed by supplying magnetic particles or a mixture containing magnetic particles and a non-magnetic developer to the developer supply container of the apparatus having such a structure.
The mixture forming the base layer preferably contains about 5 to 70% (by weight) of non-magnetic developer based on the magnetic particles, but may contain only magnetic particles. The particle size of the magnetic particles is between 30 and 200 microns, preferably between 70 and 150 microns. Each magnetic particle may be made of only magnetic material or may be a combination of magnetic material and non-magnetic material.
The magnetic particles in the base layer 16 form a magnetic brush due to the magnetic field generated by the magnet 14, and this magnetic brush performs the circulating action described below. A magnetic brush is also formed between the magnetic particle restraining pole 20 and the magnetic blade 15, which restrains the magnetic particles of the base layer 16 within the developer supply container 13.

By supplying the nonmagnetic developer onto the base layer 16, two layers are formed substantially in the vertical direction, that is, on the outer periphery of the developer holding member 12 and on the outside thereof. The developer layer may be formed using a small amount of magnetic particles added to this non-magnetic developer, but even in this case, the magnetic particle content of the developer layer is smaller than that of the base layer 16. Silica particles may be externally added to this non-magnetic developer in order to improve fluidity, and abrasive particles may be externally added in order to polish the photoreceptor 11. The method for forming the two layers is not limited to supplying the base layer in two stages, for example,
A nearly uniform mixture of magnetic particles and non-magnetic developer for the entire amount of developer layer 17 is supplied, and then vibration is applied to the developer supply container 13 to mix the magnetic particles and non-magnetic developer. Two layers may be formed due to the difference in specific gravity and the magnetic field of the magnet 14.

Even if a nearly uniform mixture of magnetic particles and non-magnetic developer is supplied without forming two layers, as long as it contains enough magnetic particles to form a magnetic brush, it can be carried out. It is possible, but
In order to maintain long-term stability of the magnetic brush, it is preferable to use two layers.

When the developer holding member 12 is rotated with the magnetic particles and developer applied in this manner, the magnetic particles are moved by the magnetic field and gravity of each magnetic pole.
A circular motion is performed as indicated by the dashed arrows in FIG. 2 (magnetic particles have been omitted for clarity). That is, near the outer surface of the developer holding member 12, the magnetic particles in the lower part of the developer supply container 13 rise along the outer periphery of the developer holding member 12 due to the interaction between the magnetic field from the magnet 14 and the rotation of the developer holding member 12. At this time, the nonmagnetic developer and the surface of the developer holding member 12 come into contact, and the nonmagnetic developer in the base layer is electrostatically applied onto the developer holding member 12.

In this embodiment, the non-magnetic developer is charged by friction with the magnetic particles or the developer holding member 12, but preferably there is an oxide film on the surface of the magnetic particles or an oxide film at the same electrostatic level as the non-magnetic developer. By insulating the magnetic particles with resin or the like, reducing the triboelectric charge from the magnetic particles, and allowing the developer holding member 12 to receive the necessary charge, it is possible to prevent the effects of deterioration of the magnetic particles and to prevent the developer holding member 12 from being affected by deterioration. Stable developer application.

The magnetic particles rise as the developer holding member 12 rotates, but due to the magnetic field formed between the magnetic blade 15 and the magnetic particle restraining magnetic pole 20, the gap between the surface of the developer holding member 12 and the tip of the magnetic blade 15 is reduced. be prevented from passing through. Therefore, the magnetic particles in this area are pushed by the magnetic particles sent one after another, rotate and turn around as shown by the dashed arrow in Figure 2, and then fall slowly due to gravity. . During this falling, the non-magnetic developer at the lower part of the developer layer 17 is taken in and returned to the lower part of the developer supply container 13, and this process is repeated.

On the other hand, since the triboelectrically charged developer is non-magnetic, it can pass through without being restrained by the magnetic field existing in the gap between the tip of the magnetic blade 15 and the surface of the developer holding member 12.
The magnetic brush portion formed on the magnetic blade portion coats the surface of the developer holding member 12 uniformly and thinly with the action of mirror force, and the developer is placed on the surface of the developer holding member 12 and then comes out of the developer supply container 13. Development is performed facing the surface of the photoreceptor 11.

Next, the rotation and reversal of the magnetic particles in the magnetic blade 15 will be described in detail.

FIG. 3 shows a case where the magnetic blade 15 is inclined toward the side opposite to the developer supply container 13, that is, toward the photoreceptor 11 with respect to the vertical line passing through the tip of the magnetic blade 15, contrary to the case of the present invention. ing. In this figure, for convenience of explanation, the base layer 16, that is, the magnetic particles constituting the magnetic brush is omitted, but
The outline of the magnetic brush is shown in phantom lines. As shown by arrow c, the magnetic particles rise near the magnetic blade 15 and rotate and reverse, but the direction of the movement is
As shown in the figure, it follows the outer shape of the magnetic blade 15 surface and the magnetic brush. If we pay attention to the external shape of the magnetic brush in the vicinity of the magnetic blade 15, it extends obliquely upward as it goes to the right from the magnetic blade 15 in FIG. Therefore, the tangent e at any point on this imaginary line has an upward component. As mentioned above,
Since magnetic particles exhibit movement along this imaginary line, they must move against gravity. In other words, gravity acts in a direction that weakens the flow of magnetic particles.

FIG. 4 shows the magnetic blade 1 according to the invention.
5 is tilted toward the developer supply container 13 side.
As is clear from this figure, the tangent e of the outline of the magnetic brush at any point near the magnetic blade 15 points diagonally downward, so the magnetic particles near the magnetic blade 15 move according to gravity. Therefore, the magnetic particles fall smoothly here. Furthermore, by tilting the magnetic brush in this way, the pressure exerted by the non-magnetic developer particles on the upper part of the magnetic brush on the magnetic brush near the magnetic blade 15 is alleviated, and since the height of the magnetic brush is small, the magnetic particles The pressure caused by this is also small, and has the effect of preventing magnetic particles from passing through the gap between the magnetic blade 15 and the developer holding member 12. If the magnetic blade 15 is inclined in this direction rather than in the vertical direction, these effects can be obtained, but the greater the inclination, the better the circulation and the better the effect of preventing leakage of magnetic particles.

FIG. 5 explains the influence on circulation due to the shape of the rear wall plate 13-1 of the developer supply container 13 of the present invention.
-1 is excluded. Since other components are the same as those in FIG. 1, detailed explanations will be omitted by assigning the same reference numerals. In the initial state, the magnetic particles in the developer supply container 13 are
Even in the configuration shown in the figure (when there is no rear wall plate 13-1), a good circulation path as shown by the arrow f is taken, and the lower seal part, that is, the lower part of the developer supply container 13 and the developer holding member 12 are connected. Since there are enough magnetic particles in between, the magnetic particles will connect the sealing magnetic pole 21 and the iron piece 1.
A magnetic brush is formed between 8 and 8 to seal the developer particles at this portion, and the developer particles are transferred to the developer supply container 13.
It will not leak or scatter from the bottom of the opening.
However, with long-term operation, the developer holding member 1
As the cumulative number of rotations of 2 increases, most of the magnetic particles gather near the magnetic blade 15, and the amount of magnetic particles in the seal portion decreases. Due to this decrease, the magnetic permeability within the developer supply container 13 decreases, and the magnetic field generated by the magnetic poles within the developer holding member 12 no longer reaches a sufficient level. As a result, the circulation path of the magnetic particles changes as shown by arrow g in FIG. 6, and the developer separated from the magnetic particles during transportation is deposited at the bottom of the developer supply container 13, as shown in FIG. However, the developer layer is in direct contact with the surface of the developer holding member 12, and a large amount is supplied onto the developer holding member 12 from near the seal portion. Therefore, the developer content in the base layer 16 increases, and each magnetic particle cannot sufficiently contact the developer holding member 12, resulting in insufficient triboelectric charging and fogging of the developer.

The rear wall plate 13-1 is provided as shown in FIG. 1, and the horizontal distance L between the surface of the developer holding member 12 and the inner surface of the rear wall plate 13-1 is set from the upstream side to the downstream side in the rotational direction of the developer holding member 12. By increasing the size in the direction (from bottom to top in the drawing), that is, by tilting the rear wall plate 13-1 in the same direction as the magnetic blade 15 of the present invention in this embodiment, the circulation of magnetic particles is improved. In addition, since the presence of magnetic particles in the seal portion can be ensured, the developer layer will not come into direct contact with the developer holding member 12 even during long-term operation, so the above-mentioned problem will not occur. The sealing at the seal portion is also ensured.

The developing method used here is JP-A-55-
18656 is preferred. A voltage is applied between the electrophotographic photoreceptor 11 and the developer holding member 12 by a bias power supply 19 . Bias power supply 1
Although 9 may be an alternating current or a direct current, it is preferable that a direct current is superimposed on an alternating current. The developer provided by the development is supplied from the base layer 16 to the developer holding member 12,
The deficit in the base layer 16 is supplied from the developer layer 17 by the circulation movement described above.

In the case of a two-layer structure, the base layer 16 is formed near the outer surface of the developer holding member 12 from the beginning, and the developer layer 17 either does not contain any magnetic particles or contains magnetic particles unavoidably as the device is used. Since the amount is small enough to compensate for the loss of magnetic particles that occurs during operation, the state of the magnetic brush in the base layer 16 remains approximately constant and does not change even if the operation continues for a long period of time. In this sense, the magnetic particles in base layer 16 are part of the development apparatus rather than the developer material or part thereof.

As a result of actually performing image formation in the above example, a good image with a constant image density was obtained without depending on the weight ratio of the magnetic particles in the developer and the developer. It was also confirmed through environmental testing that the developing device was low-cost.

In the above explanation, a magnetic blade made of a magnetic material such as iron is used as the regulating member, but a non-magnetic blade made of a non-magnetic material such as aluminum, copper, or resin or a non-magnetic material such as resin or aluminum constituting the container is used. The wall of the body can also be used as this regulating member. However, in this case, in order to prevent the magnetic particles from flowing out, it is necessary to make the gap between the sleeve and the regulating member even smaller than when using a magnetic blade. Further, when a magnetic blade is used, it is preferable because a magnetic brush can be stably formed at the developer outlet by the magnetic field between the blade and the magnetic pole.

Effects of the Invention As explained above, according to the present invention, the circulation movement of magnetic particles is improved especially in the vicinity of the magnetic particle restraining member. The developer is easily incorporated into the base layer, and the non-magnetic developer is easily tribo-electrified within this base layer, so a developed image of good quality without fogging can be obtained. This also has the effect of preventing magnetic particles from passing through and leaking through the gap with the surface of the holding member 12.

[Brief explanation of drawings]

1 is a sectional view of a developer thin layer forming device according to the present invention, FIG. 2 is a sectional view showing the circulation of magnetic particles in the device of FIG. 1, and FIG. 3 is a sectional view of the magnetic blade 15 in the device of FIG. FIG. 2 is a cross-sectional view showing a case where the image is tilted to the opposite side to the present invention. FIG. 4 is a cross-sectional view showing the state of circulation of magnetic particles when the device shown in FIG. FIG. 6 is a cross-sectional view showing the state of circulation in the apparatus of FIG. 5 after continued operation. Explanation of symbols, 11: Electrophotographic photoreceptor, 12: Developer holding member, 13: Developer supply container, 14: Fixed magnetic field generating means, 15: Magnetic particle restraining member, 1
6: base layer, 17: non-magnetic developer layer, 18: rear wall plate, 19: bias power supply, 20: magnetic particle restraining magnetic pole, 21: transport magnetic pole, 22: sealing magnetic pole.

Claims (1)

[Scope of Claims] 1. A developer supply container having an opening and containing magnetic particles and a non-magnetic developer therein, and a developer supplying container that faces the electrostatic latent image carrier in a developing section that develops the electrostatic latent image. a non-magnetic member for holding developer provided in the opening and movable endlessly inside and outside the container; a fixed magnetic field generating means provided inside the holding member; a magnetic particle restraining member that, together with a magnetic particle restraining magnetic pole of the magnetic field generation means, restrains the magnetic particles inside the developer supply container and forms a non-magnetic developer layer on the holding member to be transported to a developing section. , forming a base layer of magnetic particles on the developer holding member in the container by the magnetic force of the fixed magnetic field generating means, and moving the magnetic particles of the base layer along the developer holding member by upward movement of the developer holding member. move up and move up,
A developer thin layer forming device in which a magnetic particle restraining member causes a circular motion to be reversed and moved downward, and the nonmagnetic developer is taken into the base layer from a nonmagnetic developer layer on a base layer by the circular motion, A developer thin layer forming device, wherein the magnetic particle restraining member is inclined toward the developer supply container with respect to a vertical line passing through its tip.