JPH0220110B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device that develops an electrostatic latent image using a non-magnetic developer.

Conventionally, various devices have been proposed and put into practical use as dry one-component developing devices. However, in any of the development methods, it is extremely difficult to form a thin layer of dry one-component developer, and for this reason, a developing device has been constructed by forming a relatively thick layer.

However, as improvements in the clarity, resolution, etc. of developed images are currently being sought, it is essential to develop a method for forming a thin layer of a dry one-component developer and an apparatus therefor.

As a method for forming a thin layer of a conventionally known dry type one-component developer, Japanese Patent Application 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. Magnetic developers must have a magnetic material added to them in order to have magnetism, which causes poor fixing properties when heat fixing the developed image transferred to transfer paper, and adding magnetic material to the developer itself. There are problems such as poor color reproduction during color reproduction.

For this reason, as a method for forming a thin layer of non-magnetic developer,
Proposed methods include using a cylindrical brush made of soft beaver hair to apply the developer, and applying the developer to a developing roller with a surface made of fibers such as velvet using a doctor blade. has been done. However, if an elastic blade is used as a doctor blade for the above fiber brush,
Although it is possible to regulate the amount of developer, it is not applied uniformly, and the fiber brush on the developing roller is simply rubbed, and no triboelectric charge is imparted to the developer present between the fibers of the brush. Therefore, there was a problem that ghosts and the like were likely to occur.

The present invention eliminates the problems of the conventional method described above, and provides a new developing device that forms a uniform thin layer of developer on the surface of a developer holding member and applies sufficient triboelectric charging. The purpose is

The present invention proposes an innovative device for forming a thin layer of non-magnetic one-component developer.

A developing device of the present invention that achieves the above object includes a container for storing a non-magnetic developer and magnetic particles;
A rotating developer holding member that conveys nonmagnetic developer to the latent image carrier, and a nonmagnetic material disposed on the nonmagnetic developer supply outlet side of the container with a gap formed on the surface of the holding member. A coating amount regulating member,
a magnetic pole that is fixedly disposed on the upstream side of the regulating member and on the opposite side via the developer holding member, and forms a brush of magnetic particles on the holding member in the container, the magnetic pole and the regulating member The developing device is characterized in that the brush of the magnetic particles is restrained so as not to flow out of the container, a non-magnetic developer layer is formed on the holding member, and a latent image is developed.

The latent image carrier is a drum-shaped or belt-shaped member having a photoreceptor or an insulating layer, and the magnetic pole is a magnetized axial magnetic pole of a magnetic roller, or a rod-shaped magnet is arranged and supported. It can be fixed on a member. Furthermore, as the developer holding member, it is possible to use a sleeve or an endless belt made of non-magnetic metals such as aluminum, copper, stainless steel, brass, etc. or synthetic resin materials, and the peripheral surface of the sleeve is made of a material that improves toner transportability and charging characteristics. If necessary, a cut surface or an uneven pattern may be provided. Further, as the regulating member made of a non-magnetic material, a blade plate or a wall made of a non-magnetic material such as stainless steel, aluminum, copper, synthetic resin, or synthetic resin whose surface is plated with metal to prevent wear due to magnetic particles may be used.

In the present invention having the above configuration, the magnetic particles and the non-magnetic developer are stirred and mixed by the rotation of the developer holding member,
Furthermore, the magnetic particles circulate within the container due to the frictional force between the holding member and the magnetic particles. For this reason, the non-magnetic developer is mixed with magnetic particles and triboelectrically charged on the sleeve or by the magnetic particles. The triboelectrically charged non-magnetic developer is uniformly and thinly applied to the surface of the developer holding member by mirror force due to the presence of a magnetic brush made of magnetic particles formed near the regulating member.

In the present invention, by arranging the magnetic poles forming the magnetic brush near the regulating member in the above configuration, it is possible to form a wide magnetic brush made of magnetic particles that follow the magnetic field of the magnetic pole near the regulating member of the developer container. becomes. Due to the presence of this magnetic brush, a sufficient amount of non-magnetic developer is incorporated into the magnetic particles circulating and rotating within the container, and the developer remains stable even if a large amount of developer on the developer holding member is consumed during development. This makes it possible to form a thin layer of non-magnetic developer on the holding member.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows a sectional view of a developing device for explaining the developing principle of the present invention.

In the figure, reference numeral 1 denotes an electrophotographic photosensitive drum, which holds a latent image formed by a latent image forming means (not shown), and rotates in the direction of arrow a to pass through a developing position shown in the drawing. A non-magnetic sleeve 2, which is a developer holding member that holds developer, faces the photosensitive drum 1 with a predetermined gap maintained therebetween, and this sleeve 2 rotates in the direction of arrow b. A container 3 made of a non-magnetic material for storing a mixture of a non-magnetic developer 4 and magnetic particles 5 is located above the sleeve 2, and downstream of this container 3 in the rotational direction of the sleeve,
A magnetic blade 6 is screwed.

On the other hand, the sleeve 2 for this magnetic blade 6
A magnet 7 is provided on the opposite side. The installation position of this magnet is determined by the position of the magnetic pole and the magnetic blade 6.
In fact, the effect of the magnetic field created by providing a magnetic pole slightly upstream of the position of the magnetic blade 2 is even better in terms of preventing magnetic particles from flowing out and uniformly applying the developer. get good results.

In the above configuration, the magnetic particles 5 in the container 3 are
A magnetic brush 8 is formed by the magnetic field generated between the S pole of the magnet 7 and the magnetic blade 6. As the sleeve 2 rotates, the magnetic brush 8
The magnetic particles and the non-magnetic developer are stirred and mixed while maintaining the magnetic particles and the non-magnetic developer. In this state, on the magnetic blade side of the container 3, due to the presence of the blade 6, the mixture of developer and magnetic particles is prevented from moving by the blade, rises, and circulates in the direction of arrow c.

As a result, the non-magnetic developer is triboelectrically charged by mixing with the magnetic particles. The charged developer is uniformly and thinly applied to the surface of the sleeve 2 by mirror force by a magnetic brush 8 formed near the magnetic blade 6, and reaches a position facing the photoreceptor drum.

By the way, the magnetic particles 5 constituting the magnetic brush 8
By setting the restraining force due to the magnetic field of the magnet 7 to be larger than the conveying force caused by the frictional force,
It does not flow onto the sleeve 2. If there is non-magnetic developer within the area of the magnetic brush 8, the ratio of the magnetic particles of the magnetic brush 8 to this developer remains approximately constant as the sleeve 2 rotates. Thereby, even if the developer on the sleeve is consumed during development, the developer is automatically supplied to the area of the magnetic brush 8.
Therefore, it is possible to always supply and apply a constant amount of developer onto the sleeve 2.

By the way, when a magnetic material such as iron is used as the regulating member, a strong magnetic field concentration occurs between the regulating member 6 and the magnet 7. Therefore, the magnetic particles existing between the regulating member and the magnet are subjected to a strong restraining force at this portion, and their circular rotational movement is reduced. Under such conditions, the uptake of the above-mentioned non-magnetic developer is reduced, and the non-magnetic developer cannot be sufficiently triboelectrically charged, which may result in uneven development due to uneven coating or the like.

In particular, if a high potential latent image is continuously developed and a large amount of the developer on the sleeve is consumed, the amount of developer in the magnetic brush 8 becomes insufficient, resulting in uneven development. Also, when using a magnetic blade,
In particular, the magnetic particles that should be circulating in the magnetic field concentrated at the tip of the regulating member tend to be tightly packed into the gap formed between the regulating member and the sleeve surface instead of going upwards, causing uneven application of developer onto the sleeve. This also causes partial wear on the surface of the sleeve in its circumferential direction,
This will cause deterioration.

The present invention solves this problem by disposing the magnetic pole S shown in FIG. A magnetic regulating member is provided.

Hereinafter, more detailed embodiments will be described with reference to the drawings.

FIG. 2 shows a sectional view of a developing device showing an embodiment of the present invention. In the drawings, the same members as those in FIG. 1 are designated by the same reference numerals.

In the figure, 7a is a fixed magnet forming a magnetic pole, and the action of the magnet 7 in FIG.
A magnetic brush is formed near the upstream side of a. With the above configuration, no concentrated magnetic field is generated between the non-magnetic blade and the magnet because the blade is a magnetic material, and it is possible to sufficiently generate circular rotational motion of the magnetic particles up to approximately the width of the opening of the container. In addition, since no concentrated magnetic field is generated between the non-magnetic blade and the magnet, the width of the magnetic brush can be set wide due to the magnetic particles generated corresponding to the magnetic poles, and the non-magnetic developer can be spread inside the magnetic brush. This makes it possible to further improve the ability to incorporate Therefore, even if a large amount of developer is consumed during development, sufficient developer can be supplied into the magnetic brush, which prevents uneven development caused by insufficient developer in the brush. can be prevented.

By the way, the magnetic particles 5 constituting the magnetic brush 8
is set so that the restraining force due to the magnetic field of the magnet 7 is larger than the conveying force caused by the frictional force, and the length of the gap formed between the surface of the sleeve 2 and the non-magnetic blade 6 is approximately equal to the average particle diameter of the magnetic particles. By setting the value to several times or less than the developer particle diameter, preferably to the average particle diameter of the magnetic particles, it will not flow out from the container 3 onto the sleeve 2.

Of course, the above gap length setting is determined not only by the particle size of the magnetic particles, but also by the magnetic flux density of the magnetic poles, the magnetic properties of the magnetic particles, the difference in fluidity due to the mixing ratio and material difference between the magnetic particles and the developer, and the sleeve. peripheral speed,
It is determined by considering conditions such as sleeve surface roughness, and is not limited to a specific distance. Similarly, the angle between the sleeve and the blade is set to an appropriate value depending on the conditions.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. In the figure, the same members as in FIG. 1 are given the same reference numerals. In the embodiment device, the photoreceptor drum 1 is indicated by arrow a.
Rotate in the direction. 2 is the outer diameter that rotates in the direction of arrow b
The sleeve is made of stainless steel (SUS304) with a diameter of 32 mm and a thickness of 0.8 mm. Its surface is sandblasted using #600 alundum abrasive grains to achieve a roughness of 0.8 μm (RZ=) on the circumferential surface. did.

On the other hand, a sintered ferrite type magnet 7a is disposed within the sleeve 2, and its S pole is set to be inclined at 25 degrees (θ1 in the figure) with respect to the non-magnetic blade 6a. The magnetic flux density on the sleeve surface of the S pole was 600 Gauss. Non-magnetic blade 6
a is stainless steel (SUS304). This blade 6a has a spacing of 100 μm from the surface of the sleeve 2.
It was set to

The magnetic particles 5 have a particle size of 80 to 106μ, maximum
80g of 62emu/g spherical ferrite (manufactured by TDK)
Using. On the other hand, as non-magnetic developer 4, 3 parts of copper phthalocyanine pigment, 5 parts of negative charge control agent (alkyl salicylic acid metal chain) were internally added to 100 parts of polyester resin, and 0.6% of silica was added externally. 200 g of negatively charged cyan powder with an average particle size of 12 μm was prepared. After thoroughly mixing the non-magnetic developer and the magnetic particles, the container 3
Put it inside. As a result, it was confirmed that these magnetic particles and non-magnetic developer circulated in the direction of the arrow due to the rotation of the sleeve while forming a wide magnetic brush due to the magnetic field corresponding to the lines of magnetic force generated by the magnetic poles.

On the other hand, as the sleeve rotates, a developer layer with a thickness of about 80 μm can be formed on the surface of the sleeve 2.
When the charging potential was measured using the blow-off method,
It was confirmed that it was uniformly charged at a potential of -7 μc/g.

On the surface of the photoreceptor drum 1 facing the sleeve 2, an electrostatic latent image is formed with a dark area of +500V and a bright area of +50V.
to form a charge pattern and increase the distance from the sleeve surface.
It was set to 300μm. Then, the frequency of 800Hz and the peak-to-peak value was set to the above sleeve by power source E.
When we applied a voltage of 1.4 kV with a center value of +200 V, we were able to obtain high-quality developed images without uneven development, ghost images, or fog. Furthermore, regarding the mixture in container 3, the magnetic particles were hardly consumed and only the non-magnetic developer was consumed for development. Further, the developing function remained unchanged until almost all of the developer was consumed.

Incidentally, in the present invention, the number of magnetic poles is not limited to one; a plurality of N poles and S poles may be provided alternately on the upstream side of the S pole as transport poles. The shape of the tip of the regulating blade is not limited to an acute-angled tip as in the embodiment, but may also have a flat surface parallel to or along the sleeve surface.

With the above configuration, the magnetic field is not concentrated on the regulating member, and the density of the brush made of magnetic particles is appropriately coarsened by the magnetic field, so that the developer can be taken into the magnetic brush well. Furthermore, the present invention suppresses the high-speed circulation movement of magnetic particles that occurs when magnetic poles of different polarities are arranged, thereby making it possible to stabilize the shape of the magnetic brush and prevent excessive stirring of the developer.

In addition, in the above-mentioned specific example of the present invention, the case where the S pole was used as the magnetic pole on the container side was exemplified, but of course, the N pole is used as the magnetic pole on the container side.
Even extreme is fine. Furthermore, instead of attaching the regulating member separately from the container, a part of the container made of a non-magnetic material such as aluminum or hard synthetic resin may be used as the regulating plate. In addition, if you are concerned about the developer flowing out on the sleeve entrance side, as shown in Figure 2,
A film material may be attached to the container as the outflow prevention member 9. The magnetic particles applicable to the present invention include:
Iron powder, ferrite, and those bound with resin, which are conventionally used in developers, can be used. Also,
As the non-magnetic developer, a mixture of a resin and a pigment or dye, which is pulverized or encapsulated, can be used.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device for explaining the principle of the present invention, and FIG. 2 is a sectional view of a developing device to which the present invention is applied. In the figure, 2 is a sleeve which is a developer holding member, 3 is a container, 4 is a non-magnetic developer, 5 is a magnetic particle, 6 is a magnetic blade which is a regulating member, and 7 is a magnet.

Claims (1)

[Scope of Claims] 1. A container for storing non-magnetic developer and magnetic particles, a rotating developer holding member for conveying the non-magnetic developer to a latent image carrier, and a supply of the non-magnetic developer to the container. Located on the exit side,
a coating amount regulating member made of a non-magnetic material disposed with a gap formed on the surface of the holding member; and a magnetic pole forming a brush of magnetic particles on the holding member, and the brush of the magnetic particles is restrained by the magnetic pole and the regulating member so that it does not flow out of the container, and the non-magnetic developer is placed on the holding member. A developing device characterized by forming a layer and developing a latent image. 2. The developing device according to claim 1, wherein a voltage having an alternating current component is applied to the developer holding member.