JPS59204869A - Developer thin layer forming device - Google Patents

Abstract

PURPOSE:To make a magnetic particle circulate appropriately in a vessel by setting as prescribed a magnetic flux density of a magnetic particle detaining magnetic pole and its half-amplitude level. CONSTITUTION:A fixed magnetic field generating means 14 is provided with a magnetic particle detaining magnetic pole 14-1 and a magnetic particle drawing- up magnetic pole 14-2. This magnetic particle detaining magnetic pole 14-1 detains a magnetic particle in a developer supply vessel 13 together with a magnetic particle detaining member 15. In this state, a magnetic flux density of the magnetic particle detaining magnetic pole 14-1 is set to 300-800 gauss, and its half-amplitude level is set to 50-120 degrees centering around a revolving shaft of a developer holding member 12. By setting in this way, an appropriate circulation can be given to the magnetic particle. In this way, the magnetic particle can be made to circulate appropriately in the vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) The present invention relates to a thin layer forming apparatus for dry type developer. Furthermore,
The present invention relates to an apparatus for forming a thin layer of non-magnetic developer.

Hitherto, various devices have been proposed and put into practical use as a dry developing method. 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, as improvements in the sharpness, resolution, etc. of developed images are currently being sought, it is essential to develop a method for forming a thin layer of dry developer and an apparatus therefor.

As a conventionally known method for forming a thin layer of dry type developer, Japanese Patent Laid-Open No. 54-43037 has been proposed and 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 materials are usually black), which causes problems such as poor color reproduction.

For this reason, as a method for forming a thin layer of non-magnetic developer, there are methods 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.

1. A method and apparatus for forming a thin layer of non-magnetic developer on a developer holding member using bound magnetic particles has been proposed, but in carrying out this method and apparatus, Preferably, the magnetic particles are appropriately circulated within the developer supply container.

The object of the present invention is to improve the circulation of magnetic particles in this type of method and device.

The device of the present invention comprises a developer supply container having an opening near the bottom, a non-magnetic member for holding developer provided in the opening and movable endlessly inside and outside the container, and the holding member. a fixed magnetic field generating means provided inside; and a magnetic particle restraining member provided near the top of the opening to restrain the magnetic particles within the developer supply container together with the magnetic poles of the fixed magnetic field generating means; The magnetic pole that restrains the magnetic particles together with the magnetic particle restraining member has a magnetic flux density of 30 on the surface of the developer holding member.
Since it generates a magnetic field of 0 to 800 Gauss and a half width of 50 degrees to 120 degrees centered on the rotation axis of the developer holding member, circulation occurs reliably, and moreover, this is too strong. This ensures proper circulation and minimizes the possibility of leakage of magnetic particles.

1 Cliff l 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 susceptor 11. Along with this movement of the photoreceptor 11, the developer holding member 12 is rotated in the direction indicated by the arrow. 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, and the 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 supply 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 14-1 (N) and a magnetic particle pumping magnetic pole 14-2 (S). An iron piece 18 made of a magnetic material is provided on the inner wall of the container 13 facing the magnetic particle pumping magnetic pole 14-2. The iron piece 18 may be made of metal other than iron or the like, and may also be a magnet that faces the magnetic particle pumping magnetic pole in a reverse polarity relationship. These magnetic members may be attached to the wall of the container facing the magnetic particle pumping magnetic pole 14-2, or the container itself may be made of a magnetic material such as iron, and the wall of the container facing the magnetic particle pumping magnetic pole 14-2 may be attached. may be arranged close to the developer holding member 12.

A magnetic blade 15 made of a magnetic material and serving as a magnetic particle restraining member is arranged near the top of the opening of the developer supply container 13 . On the opposite side of the magnetic blade 15 with the developer holding member 12 in between, there is a magnetic particle restraining magnetic pole 14-1 of the magnet 14.
The developer holding member 12 is disposed at an upstream position in the rotational direction of the developer holding member 12 at an angle θ (5 to 50 degrees) shifted from the position facing the developer holding member 5 . As the magnetic particle restraining member 15, a blade plate or a wall made of a magnetic material such as iron or a non-magnetic material such as aluminum, copper, or resin may be used.

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 13 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 it may also contain only magnetic particles.

As the magnetic particles, iron powder, ferrite, or those bound with resin can be used. The particle size of the magnetic particles is 30-200 microns, preferably 70-150 microns.

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. 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 magnetic pole 14 - 1 and the magnetic blade 15 , which restrains the magnetic particles of the base layer 16 inside the developer supply container 13 .

By supplying the non-magnetic developer onto the base layer 16, two layers are formed substantially in the vertical direction, that is, on and outside the outer periphery of the developer holding member 12. 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. As the non-magnetic developer, it is possible to use a mixture obtained by kneading a pigment or dye into a resin and pulverizing or encapsulating the mixture. 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 two layers in two stages as described above. For example, it is also possible to supply a substantially uniform mixture of magnetic particles and non-magnetic developer for the entire amount of the base layer 16 and developer layer 17. Thereafter, the developer supply container 13 may be vibrated to form two layers due to the difference in specific gravity between the magnetic particles and the non-magnetic developer and the magnetic field of the magnet 14.

Even when a nearly uniform mixture of magnetic particles and non-magnetic developer is supplied without particularly forming two layers,
This is possible as long as it contains a sufficient amount of magnetic particles to form a magnetic brush, 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 magnetic particles and non-magnetic developer applied in this manner, the magnetic particles circulate as shown by arrow C in FIG. 1 due to the magnetic field and gravity of each magnetic pole. Do some exercise. 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 developer holding member 12
The surfaces of the base layer are in contact with each other, and the non-magnetic 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 it is preferable that the magnetic particles have an oxide film on the surface or be electrostatically at the same level as the non-magnetic developer. By applying insulation treatment using a certain resin, etc. to reduce the amount of tripo imparted by the magnetic particles and allowing the developer holding member 12 to receive the necessary charge, it is possible to prevent the influence of deterioration of the magnetic particles and also to prevent the developer holding member 12 from being affected by deterioration of the magnetic particles. The application of developer to 12 is stabilized.

The magnetic particles rise as the developer holding member 12 rotates, but the magnetic blade 15 and the magnetic particle/child restraining magnetic pole 14-1
The magnetic field formed between the developer holding member 12 and the magnetic blade 15 prevents the developer from passing through the gap between the surface of the member 12 and the tip of the magnetic blade 15 . Therefore, the magnetic particles in this part are pushed by the magnetic particles that are sent one after another and rotate as shown by arrow C in FIG. 1, and then slowly fall 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 the magnetic particles are lifted up again by the action of the magnetic pole 14-2 and the rotation of the developer holding member 12. and repeat this.

On the other hand, since the triboelectrically charged developer is non-magnetic, it can pass through without being restrained by the magnetic field that exists in the gap between the tip of the magnetic blade 15 and the surface of the developer holding member 12, and is developed by the magnetic brush section formed on the magnetic blade section. The surface of the developer holding member 12 is coated uniformly and thinly with the action of mirror force, and the developer supply container 13 that rests on the surface of the developer holding member 12 comes out and faces the surface of the photoreceptor 11 for development. be done.

Here, the movement of the magnetic particles on the developer holding member 12 depending on the width of the magnetic particle restraining magnetic pole 14-1 will be explained.

FIG. 2 shows the angle seen from the rotation center axis of the developer holding member 12 when the half width of the magnetic particle restraining magnetic pole 14-1 is set to 30 degrees, and FIG. 3 shows the same half width set to 30 degrees. A case is shown in which a magnetic pole is added between the magnetic particle restraining magnetic pole 14-1 and the magnetic particle pumping magnetic pole 14-2. In the half-value width and arrangement shown in FIG. 2, the magnetic brush formed by the magnetic particle restraining magnetic pole 14-1 and the magnetic brush formed by the magnetic particle pumping magnetic pole 14-2 are separated, and the magnetic particles are restrained by each magnetic pole, so that circulation is prevented. The magnetic brush becomes extremely weak, and the developer consumed by the developing action cannot be sufficiently taken into the magnetic brush from the developer layer 17, and if development is continued, the developed density will decrease.

Next, as shown in Fig. 3, even when adding magnetic poles to form a three-pole configuration, the half width of the magnetic particle restraining magnetic pole 14-1 is 30
If the magnetic field is about 100°C, the magnetic flux density of the magnetic field changes rapidly on the surface of the developer holding member 12, so the conveying force is strong, and the magnetic particles restrained by the developer holding member 12 by the magnetic particle pumping magnetic pole 14-2 are strongly Since the magnetic brush is conveyed, the movement of the magnetic brush is fast and takes in an excessive amount of developer, making the application of the developer onto the developer holding member 12 unstable and causing the developer particles and the developer holding member to Since the degree of contact with the No. 12 surface is reduced, tripod application to the developer becomes insufficient, and when a development operation is performed, density unevenness and fogging occur. Furthermore, since the magnetic particles move rapidly, the force of restraining the magnetic particles by the magnetic particle restraining magnetic pole 14 - 1 becomes relatively weak, and there is a possibility that the magnetic particles leak into the developer holding member 12 .

FIG. 4 shows a case where the half width of the magnetic particle restraining magnetic pole 14-1 is set to a large value of 50 degrees to 120 degrees, and the distribution of magnetic flux density is widened. In this way, when the width is widened, the movement of the magnetic particles is moderately suppressed, the circulation of the magnetic particles by the magnetic brush is moderate, and the amount of developer taken in by the magnetic brush does not become excessive. A uniform and sufficiently tripo-charged non-magnetic developer thin layer is obtained on 12. Further, since the motion of the magnetic particles is relatively slow, the magnetic particles are reliably restrained by the magnetic particle restraining magnetic pole 14-1, and the magnetic particles are less likely to leak into the developer holding member 12. In particular, when the half-width is set to about 90 degrees, a good image without density unevenness, fogging, or reduction in density can be obtained.

When the half-width of the magnetic particle restraining magnetic pole 14-1 exceeds 120 degrees, the circulation of the magnetic particles is significantly reduced, resulting in an insufficient supply of developer to the magnetic brush, resulting in a decrease in density.

Next, to explain the strength of the magnetic field, if the strength of the magnetic particle restraining magnetic pole 14-1 is less than 300 Gauss, the restraining force of the magnetic particles is weakened, and the magnetic particles leak onto the developer holding member 12 and reach the developing section. It will be reached. On the other hand, if the pressure is 800 Gauss or more, the magnetic particles are strongly pressed and restrained on the developer holding member 12, and the formed non-magnetic developer layer becomes streaky, making it impossible to obtain a good image. . The magnetic particle restraining magnetic pole 14-1 is preferably 300 Gauss to 800 Gauss, preferably 500 Gauss to 600 Gauss.

As explained above, according to the present invention, since the magnetic particle restraining magnetic pole 14-1 forms a magnetic field with a wide half width, appropriate circulation of magnetic particles and reliable uptake of an appropriate amount of non-magnetic developer are ensured. Moreover, the possibility of leakage of magnetic particles is reduced and good development can be achieved.

The developing method used here is JP-A-55-1865.
The method described in 6 is preferred. A voltage is applied between the electrophotographic photoreceptor 11 and the developer holding member 12 by a bias power supply 19. The bias power supply 19 may be an alternating current or a direct current, but preferably one in which alternating current and direct current are superimposed. The developer provided by the development is supplied from the base layer 16 to the developer holding member 12, and the insufficient amount in the base layer 16 is supplied from the developer layer 17 by the above-mentioned circulation movement.

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 is unavoidably formed as the device is used. Therefore, the state of the magnetic brush in the base layer 16 remains substantially 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.

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 no conveying force is generated by the developer holding member 12 to 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, it is desirable that the upper part moves as shown by the arrow in FIG. the thickness of the base layer 16;
This is because if 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.

Next, a specific example of the present invention will be described. In the specific example device, the photoreceptor 11 rotates in the direction of arrow a at a circumferential speed of 60 milliseconds. The developer holding member 12 is moved in the direction of the arrow 6.
It rotates at a circumferential speed of 6 mm/sec, has an outer diameter of 32 mm, and a thickness of 0.
Made of 8mm stainless steel (SUS304). The surface was subjected to amorphous sandblasting using #600 Alundum abrasive grains, and the roughness of the surface in the circumferential direction was reduced to 0.8 microns (
RZ=0.83).

On the other hand, a sintered ferrite type magnet 14 is fixedly disposed inside the rotating developer holding member 12, and its N pole, which is a magnetic particle restraining magnetic pole 14-1, is connected to the magnetic blade 15 to hold the developer. It is set at an angle of 30 degrees (θ in the drawing) from a line connecting the center O of the member 12 and the tip of the magnetic blade 15. The half-width was set at 90 degrees with the rotation axis of the developer holding member 12 as the center angle, as shown in FIG.
The developer holding member 12 of No. 3 is located opposite to an iron piece 18 which is a magnetic member provided on the artificial side.

Developer holding member 1 of this magnetic particle pumping magnetic pole 14-2
The magnetic flux density on the two surfaces had a peak value of 650 Gauss in the presence of the iron piece 18, and 400 Gauss when the iron piece 18 was removed. At this time, the positional relationship between the magnetic particle pumping magnetic pole 14-2 and the iron piece 18 is such that the width of the iron piece 18 in the rotation direction of the developer holding member 12 is 0.5 mm, and the distance between the developer holding member 12 and the iron piece 18 is 0.5 mm. It was set to 1.0 mm.

The magnetic blade 15 is made of iron, and its surface is plated with nickel to prevent rust. The distance between the magnetic blade 15 and the surface of the developer holding member 12 was set at 100 microns.

The magnetic particles have a particle size of 70 to 100 microns, maximum 60 microns.
Spherical ferrite of e mu / g (manufactured by TDK)
100g of was used. On the other hand, as a non-magnetic developer, 3 parts of copper phthalocyanine pigment, 5 parts of negative charge control agent (alkyl salicylate metal chain)'fU were added to 100 parts of polyester resin, and 0.5% of silica was added. Attached average particle size 1
200 g of cyan powder charged with a negative (-) polarity of 2 microns was prepared. After the non-magnetic developer and magnetic particles were thoroughly mixed, they were placed in the developer supply container 13. The mixture of non-magnetic developer and magnetic particles in the developer supply container 13, especially the magnetic particles, is conveyed by the developer holding member 12 under a magnetic field and moves in circulation. It was observed that there were fewer

In the developing device having this configuration, as the developer holding member 12 rotates, approximately 60
A thin layer of micron-thick non-magnetic developer could be formed. When the charging potential of this developer thin layer was measured by a blow-off method, it was confirmed that the developer was uniformly charged at a potential of 7 microcoulombs/g.

On the surface of the photoreceptor l1 facing the developer holding member 12, a charge pattern of +600 V in the dark part and +150 V in the bright part was formed as an electrostatic latent image, and the charge pattern was formed on the developer holding part. Then, the frequency of 800 Hz is applied to the developer holding member 12 by the power source 19.
Peak-to-peak value is 1.4kV, center value is +300V
When a voltage of 100 mL was applied, a high-quality developed image without uneven development, ghosts, images, or fog could be obtained.

Further, regarding the mixture in the developer supply container 13, only the non-magnetic developer was consumed for development, with almost no magnetic particles being consumed. Further, the developing function remained unchanged until almost all of the developer was consumed.

By the way, although the case where the north pole is used as the magnetic particle restraining magnetic pole 14-1 has been illustrated, of course, the south pole may also be used.

In the above specific example, 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 or resin, or a non-magnetic blade made of resin or aluminum that constitutes the container is used. A magnetic wall 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.

As described above, according to the present invention, in an apparatus for forming a thin layer of non-magnetic developer on the developer holding member 12 using magnetic particles restrained by a magnetic field, Good development is achieved because the magnetic particles can be properly circulated within the container.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a developing device using the method of the present invention; FIGS. The figure is an explanatory diagram in which the magnetic flux density distribution in the apparatus according to the present invention is expressed in polar coordinates. Figure 5 is an explanatory diagram in which the magnetic flux density distribution in a specific example of the present invention is expressed in polar coordinates. Explanation of symbols 11: Electrophotographic photoreceptor 12; Developer holding member 13; Developer supply container 14: Fixed magnetic field generating means 14-1: Magnetic particle restraining magnetic pole 14-2: Magnetic particle pumping magnetic pole 15: Magnetic particle restraining member 16 : Base layer 17: Developer layer 19: Bias power supply

Claims (1)

[Scope of Claims] A developer supply container having an opening near the bottom; a developer holding non-magnetic member provided in the opening and movable endlessly within the container and four parts; a fixed magnetic field generating means provided therein; and a magnetic particle restraining member provided near the top of the opening and restraining the magnetic particles in the developer supply container together with a magnetic pole included in the fixed magnetic field generating means; The magnetic pole that restrains the magnetic particles together with the particle restraining member has a magnetic flux density of 3'°00 to 80° on the surface of the developer holding member.
A developer thin layer forming device characterized in that it generates a magnetic field of 0 Gauss and a half width of 50 degrees to 120 degrees around the rotation axis of the developer holding member.