JPH0462385B2 - - 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 using a cylindrical brush made of soft bristles like beaver hair and applying the developer to the brush, or using a brush with a surface made of fibers such as velvet. 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 fogging is 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 developer 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 device of the present invention includes a developer supply container having an opening, a developer holding non-magnetic member provided in the opening and movable endlessly between the inside and outside of the container, and a developer holding non-magnetic member provided inside the holding member. a fixed magnetic field generating means formed on the developer holding member inside the developer supply container, a base layer containing magnetic particles capable of holding the developer on the upper part thereof, and a base layer provided on the outside of the developer holding member. and a fixed magnetic field generating means as well as a magnetic particle member that restrains the base layer of the magnetic particles inside the developer supply container, and further includes a member that stirs the interface between the base layer and the developer above the base layer. This has the effect of smoothing the circulation of magnetic particles and ensuring the supply of developer to the base layer.

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 cover the lower part of the developer holding member 12, so that the developer does not leak 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.

24 is a stirring means having a rotational drive shaft 26, a support rod 28, and a stirring member 30, and rotates in the direction of arrow d. The operation of this means will be described later.

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 configuration.
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 described above. 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 arrows in Figure 1, and then fall slowly due to gravity. During this falling, the non-magnetic developer at the bottom of the developer layer 17 is taken in and the developer supply container 1
Return to the bottom of step 3 and repeat.

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. It faces the surface of the photoreceptor 11 and is subjected to development.

Since the magnetic blade 15 is tilted upward toward the developer supply container 13, the magnetic particles in the vicinity of the magnetic blade 15 move according to gravity, and therefore the magnetic particles fall smoothly there. It happens in 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 the developer holding member 12 is also small, and magnetic particles are prevented from passing through the gap between the magnetic blade 15 and the developer holding member 12. The larger the slope, the better the circulation, and the better the effect of preventing leakage of magnetic particles.

A rear wall plate 13-1 is provided as shown in FIG. 1, and the horizontal gap between the surface of the developer holding member 12 and the inner surface of the rear wall plate 13-1 is moved from the upstream side to the downstream side in the rotational direction of the developer holding member 12. In other words, in this embodiment, since the rear wall plate 13-1 is inclined in the same direction as the magnetic blade 15 of the present invention, the seal portion The presence of magnetic particles in the developer holding member 12 can be ensured, the developer layer will not come into direct contact with the developer holding member 12 even during long-term operation, and the sealing at the sealing portion can be ensured.

As shown in FIG. 2, a stirring means 24 is provided near the interface between the base layer and the non-magnetic developer layer, near the point where the non-magnetic developer falls, and this stirring means 24 is attached to the developer supply container 13. A stirring member 30 is attached to the rotary drive shaft 26 by a plurality of support rods 28 and extends in a direction perpendicular to the plane of FIG. The member 30 is rotated in the direction of arrow d by a drive means (not shown). Since the stirring member 30 extends to the vicinity of both ends of the developer supply container 13, sufficient stirring is performed even at these ends. The rotation of the stirring means 24 promotes the circulation of the magnetic particles in the base layer and also takes in the non-magnetic developer on the upper part and supplies it to the base layer, so that the non-magnetic developer is reliably supplied. Stirring means 24 and developer holding member 12
and should be separated by at least 4 mm, preferably about 10 mm.
When the two are closer than this, the developer holding member 12
If an excessive amount of non-magnetic developer is supplied, the triboelectric effect on the non-magnetic developer will be insufficient and fog will occur in the developed image.

FIG. 3 shows a case where the stirring means 24 is arranged so that it does not come into contact with the magnetic particles of the base layer at all. That is, the stirring member 30 does not come into contact with magnetic particles over the entire rotation range of the stirring member 30, and is completely surrounded by the non-magnetic developer. In this case, the effect of promoting the circulation of the magnetic particles and the effect of taking in the non-magnetic developer are small, resulting in a decrease in density particularly at the edges.

On the other hand, as shown in FIG. 4, if the stirring means 24 is placed completely within the base layer, for example, when magnetic particles coated with a soft resin are used as the magnetic particles, the circulation of the magnetic particles becomes rapid.
Insufficient supply of non-magnetic developer. Therefore, problems such as a decrease in image density and white spots occur. Therefore, as shown in FIG. 2, it is desirable to place the stirring means 24 at the interface between the non-magnetic developer and the base layer of magnetic particles.

The rotational speed of the stirring means 24 is preferably 2:1 to 1:00, preferably 1:1 to 1:50, relative to the rotational speed of the developer holding member. In this example, when the rotational speed of the developer holding member was set to 1/2 rotation/second instead of 1 rotation/second, a stable image without fogging or white spots was obtained.

In the embodiment described above, the stirring means 24 is arranged at the bottom of the developer supply container, but it may be arranged near the magnetic blade 15. FIG. 5 shows such an example. Since the constituent elements other than the stirring means 24 are the same as those in the previous embodiment, detailed description will be omitted by assigning the same reference numerals to corresponding elements.

The agitating member 30 is arranged so as to be at least 8 mm apart from the developer holding member, and is attached to be swingable around the rotary drive shaft 26. This swinging movement agitates the magnetic particles rising along the inner surface of the developer supply container of the magnetic blade 15 and causes them to fall to the lower part of the developer supply container. At this time, since the magnetic particles on the top surface of the base layer are removed, the gravity applied from above to the magnetic particles below is reduced, and as a result, the magnetic particles near the magnetic blade 15 are actively pushed up, and the entire magnetic particles circulate. Moreover, since the stirred magnetic particles take in the non-magnetic developer in the vicinity well, the non-magnetic developer is sufficiently replenished.

As the stirring means 24, a rotating means is used in FIG. 2, and an oscillating means is used in FIG. 5, but the reverse may also be used.
Both the upper part and the lower part of the developer supply container may be provided.

The developing direction 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.

When images were actually formed in the above examples, good images with constant image density were obtained, regardless of the weight ratio of the magnetic particles in the developer to the developer.
At the same time, it was confirmed through environmental experiments that the developing device has low environmental dependence.

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 stirring means 24 sufficiently stirs the magnetic particles and takes in the non-magnetic developer, and also ensures tribocharging of the non-magnetic developer. Developer fogging and white spots do not occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developer thin layer forming apparatus to which the present invention can be applied, FIG. 2 is a sectional view of a developer thin layer forming apparatus according to the present invention, and FIG. 3 is an installation of the stirring means 24. FIG. 4 is a cross-sectional view of the structure in which the position of the stirring means 24 is changed. FIG. 5 is a cross-sectional view of the device for forming a thin developer layer according to another embodiment of the present invention. It is a diagram. Explanation of symbols, 11...Electrophotographic photoreceptor, 12...
...Developer holding member, 13...Developer supply container, 1
4...Fixed magnetic field generating means, 15...Magnetic particle restraining member, 16...Base layer, 17...Nonmagnetic developer layer,
20... Magnetic particle restraining magnetic pole, 24... Stirring means.

Claims (1)

[Scope of Claims] 1. A developer supply container having an opening; a non-magnetic member for holding developer that is provided in the opening and is movable endlessly between the inside and outside of the container; and a non-magnetic member provided inside the holding member. a fixed magnetic field generating means; a base layer containing magnetic particles formed on the developer holding member inside the developer supply container and capable of holding the developer thereon; and provided outside the developer holding member; A developing device comprising: a magnetic particle restraining member that restrains the base layer of magnetic particles within a developer supply container together with a fixed magnetic field generating means; and a member that stirs an interface between the base layer and the developer above the base layer. Agent thin layer forming device.