JPH0229212B2 - GENZOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device for developing an electrostatic latent image using a dry developer.

Conventionally, various apparatuses 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 during 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.

An object of the present invention is to provide a developing device that develops an electrostatic latent image by stably forming a thin layer of dry developer on the surface of a developer holding member over a long period of time.

The developing device of the present invention includes a developer supply container, and a developer supply container provided at the opening of the container so as to face the inside and outside of the container and to face the image carrier in the developing section. A non-magnetic rotating member for holding developer, a fixed magnetic field generating means provided inside the rotating member, and a blade member disposed opposite to the rotating member, and in the container, a base layer containing magnetic particles is The magnetic particles move upwardly along the periphery of the rotating member due to the rotation of the rotating member, and are prevented from passing by the magnetic force of the blade member and the fixed magnetic field generating means, and the magnetic particles move outside of the upwardly moving part due to gravity. The base layer moving downwards is placed on the rotating member,
Then, an outer layer is formed on this base layer, which contains a developer and does not contain magnetic particles, or contains only a smaller proportion than the base layer, and the downward movement of the magnetic particles in the base layer causes the outer layer to be formed. This is a developing device that takes in developer from a rotor and conveys the taken in developer to a developing section by a rotating member to develop an electrostatic latent image.

Embodiments 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 for holding the developer is provided with a gap between the photoreceptor 11 and, in the 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 12 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, 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 . Therefore, developer holding member 1
Only 2 rotates. This magnet 14 has N1, S1,
It has magnetic poles of N2, S2, N3, and S3. A magnetic blade 15 made of a magnetic material is arranged near the top of the developer supply container 12 . There is a magnetic pole N1 of the magnet 14 on the opposite side of the magnetic blade across the developer holding member, and the magnetic pole N1 is located at a position upstream in the rotational direction of the developer holding member 12 from the opposing position of the magnetic blade 15. The angle θ (5~
50 degrees).

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. Magnetic pole N1 and magnetic blade 1
A magnetic brush is also formed between the developer supply containers 13 and 5, which restrain the magnetic particles of the base layer 16 within the developer supply container 13.

By supplying a non-magnetic developer onto this base layer 16, two layers are formed substantially in the upper and lower directions. The developer layer may be formed by adding a small amount of magnetic particles to this non-magnetic developer, but even in this case, the magnetic particle content of the developer layer is limited to the base layer 16.
smaller than Silica particles may be externally added to this non-magnetic developer to improve fluidity, and abrasive particles may be externally added to the non-magnetic developer for polishing the photoreceptor 11. The method for forming the two layers is not limited to the one in which the two layers are supplied in two stages, for example, the base layer 16 and the developer layer 17 are supplied in two stages.
A nearly uniform mixture of magnetic particles and non-magnetic developer is supplied, and then vibration is applied to the developer supply container 13 to eliminate the difference in specific gravity between the magnetic particles and the non-magnetic developer and the magnet 14. Two layers may be formed by the magnetic field.

When the developer holding member 12 is rotated with two layers formed in this way, the magnetic particles perform a circular motion as shown in FIG. 2 due to the magnetic field and gravity of each magnetic pole. 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 non-magnetic developer and the surface of the developer holding member 12 contact each other, and the non-magnetic developer in the base layer is electrostatically transferred to the developer holding member 1.
2 is coated on top.

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 pole N1, the developer holding member 12
It is prevented from passing through the gap between the surface and the tip of the magnetic blade 15. Therefore, the magnetic particles in this area are pushed by the magnetic particles that are sent one after another, rotate as shown 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. It faces the surface of the photoreceptor 11 and is subjected to development.

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. The base layer 16 is initially formed near the outer surface of the developer holding member 12, and the developer layer 17 either does not contain any magnetic particles or is free from the loss of magnetic particles that inevitably occur with use of the device. Since the amount is small enough to compensate, the state of the magnetic brush in the base layer 16 remains almost constant even if the operation continues for a long period of time.
It does not change. In this sense, the magnetic particles in base layer 16 are part of the development apparatus rather than the developer material or part thereof.

Further, it is preferable that the developer holding member 12 contacts only the base layer 16 and does not directly contact the developer layer 17. In this case, since the developer holding member 12 does not generate a conveying force on the developer layer 17,
Regardless of the amount of the developer layer 17, the developer content of the base layer 16 does not vary.

It is desirable to consider the thickness of the base layer 16 in relation to the circular motion of the magnetic particles and the uptake of non-magnetic developer. That is, since the upper part of the base layer 16 functions to take in the non-magnetic developer,
Preferably, the upper portion moves as indicated by the arrow in FIG. This is because if the thickness of the base layer 16 is too large, the upper part of the base layer 16, that is, the contact portion with the lower part of the developer layer 17 will not move, making it impossible to take in sufficient non-magnetic developer from the developer layer 17.

Based on the method described above, good results were obtained using a developer having the following configuration.

Base layer: Spherical magnetic particles of 80 to 105 microns, containing 35% (by weight) of non-magnetic developer with an average particle size of about 10 microns based on the magnetic particles.

Non-magnetic developer layer: Only the same developer as the non-magnetic developer in the base layer.

In addition, with the same configuration, a small amount (2
Good results were also obtained with the addition of ~5%) magnetic particles.

In order to subject the thus obtained non-magnetic developer coating layer to a developing action, the electrophotographic photoreceptor 11 having a dark area of -500 V and a bright area of -150 V as an electrostatic latent image is placed on the surface of the electrophotographic photoreceptor 11 and on a cylindrical developer holding member. A voltage with a frequency of 1.6 KHz, a peak-to-peak value of 1.3 KV, and a center value of -250 V was applied between the cylindrical developer holding member 12 and the electrophotographic photoreceptor using a power source E, with a distance of 300 μm between the 12 surfaces. The copying machine produced good clear images without ghosts or fog.

After about 2,000 copies were made, there was no change in image density until the non-magnetic developer layer was almost consumed, and no magnetic particles were used for development.

FIG. 3 is an explanatory diagram showing another embodiment of the method of the present invention. This embodiment is similar to the first embodiment except that a non-magnetic blade is used in place of the magnetic blade 15 of the previous embodiment, so corresponding elements are given the same reference numerals for details. replace it with a more detailed explanation.

As explained above, according to the present invention, the magnetic brush that performs the function of taking in developer and forming a thin layer on the developer holding member 12 is kept constant over a long period of time, so that a stable thin layer can be produced. The layer can be maintained for a long time and therefore good development is achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a developing device using the method of the present invention, FIG. 2 is a schematic sectional view showing the flow in the base layer, and FIG. 3 is a schematic sectional view of a developer device of another embodiment using the method of the present invention. It is a schematic sectional view. Explanation of symbols of main parts 11: Electrophotographic photoreceptor, 12: Developer holding member, 13: Developer supply container, 14: Magnet, 15: Magnetic blade, 16: Base layer, 17: Developer layer, 19: Bias power supply .

Claims (1)

[Scope of Claims] 1. A developer supply container, and a developer holder provided at the opening of the container so as to face the inside and outside of the container and to face the image carrier in the developing section. A base layer containing magnetic particles in the container, comprising: a non-magnetic rotating member, a fixed magnetic field generating means provided inside the rotating member, and a blade member disposed opposite to the rotating member; Due to the rotation of the rotating member, the magnetic particles move upward along the circumference of the rotating member, and are prevented from passing by the magnetic force of the blade member and the fixed magnetic field generating means, and then move downward by gravity on the outside of the upwardly moving part. a base layer is formed on the rotating member, and an outer layer is formed on the base layer that contains a developer and does not contain magnetic particles or contains magnetic particles in a smaller proportion than the base layer; A developing device that takes in developer from the outer layer through the downward movement and conveys the taken in developer to a developing section by a rotating member to develop an electrostatic latent image. 2. The developing device according to claim 1, wherein an alternating current or direct current bias voltage is applied to the rotating member.