JPS597979A - Magnetic brush developing method of electrostatic image - Google Patents

Abstract

PURPOSE:To adjust the tuft of a magnetic brush to stable short length without causing the blocking of a single-component magnetic developer by cutting the tuft of the magnetic brush right after the magnetic brush passes through a converged magnetic field area between an upstanding tuft accelerating mechanism and a sleeve. CONSTITUTION:A tuft cutting mechanism 6 cut the tuft of the magnetic brush 9a right after the brush 9a passes through the converged magnetic field area 11 between the upstanding tuft accelerating mechanism 10 and sleeve 7. A converged magnetic field, i.e. parallel magnetic field is established between the mechanism 10 and the magnetic pole N or S in the sleeve, and consequently the upstanding tuft of the developer is accelerated to obtain uniform and relatively rough density of the developer there. Then, the tuft cutting is carried out by the tuft cutting mechanism 6 to supply the magnetic brush of the developer stably and quantitatively over the entire circumference of the sleeve 7. Therefore, a picture which is free of light and shade and has uniform and stable density is formed over the entire surface of a photosensitive layer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for developing an electrostatic image with a magnetic brush, and more specifically, an image with stable density is formed by stable spikes, and mutual blocking of developer particles is prevented. The present invention relates to a magnetic brush developing method that prevents the occurrence of white streaks due to foreign matter contamination.

Magnetic brush development is widely used to develop electrostatic images in commercial electrophotography. This magnetic brush development method uses a developing mechanism consisting of a circumferential sleeve made of a non-magnetic material, at least one of which is rotatable, and a magnet within the sleeve. The thickness of the magnetic brush is controlled to a constant value by a cutting mechanism, etc., and the magnetic brush is moved to the position of the photosensitive layer to form a magnetic brush and the photosensitive layer having an electrostatic image. The electrostatic image is developed by rubbing.

The magnetic developer includes a two-component developer consisting of a mixture of a magnetic carrier and a fixable electrostatic powder (toner);
Two types of developers are known: one-component (or carrierless) developers, which are made by dispersing fine powder of magnetic material in a fixing medium and shaping it into particles; each of these developers has its own advantages and disadvantages. It is known to have the following.

First, in a two-component developer, the toner is charged by friction between the magnetic carrier and the toner, and the toner is electrostatically held on the surface of the carrier to form a magnetic brush. Thus, the two-component developer has good magnetic brush formation and good fluidity, and the darkness value of the primary development is determined by the Coulomb force between the toner and the carrier and the Coulomb force between the toner and the electrostatic image. It is determined by the magnitude of the force, and the image formed has the advantage of having less capri.

However, two-component developers have the disadvantage that good images cannot be obtained unless the mixing ratio of magnetic carrier and toner is maintained within a certain range.
During long-term use, toner or resin components in the toner adhere to and accumulate on the surface of the magnetic carrier (generally referred to as spent toner), making it difficult to charge the toner.

On the other hand, -component magnetic developers do not have the above-mentioned problems, but they do not have the trouble of using a magnetic carrier.
- In component-based magnetic developers, it is the developer itself that forms the ears of the magnetic brush, and the darkness value of the development is determined by the magnetic attraction force of the developer against the sleeve and the Coulomb force against the electrostatic image. Since this is determined, various problems arise. In other words, since the -component magnetic developer is composed of a single powder, it is likely to cause blocking due to environmental changes such as temperature and humidity, resulting in decreased fluidity or mobility on the sleeve, which may cause the magnetic brush to stand up. It tends to be defective. Further, since the magnetic material is embedded in the resin, the magnetic attraction force to the developing sleeve is weaker than that of the magnetic carrier, and there is a problem that capri is likely to occur during development.

Therefore, in the development method of -component magnetic developer,
The ears are cut so that the length of the ears of the magnetic brush is extremely short, such as 0.2 to 0.6 baskets. This prevents capri from occurring during development.

Therefore, it is an object of the present invention to always obtain stable spikes when developing an electrostatic image using a magnetic brush of a magnetic developer, particularly a -component magnetic developer, and to cut the spikes to a constant thickness. It is an object of the present invention to provide a magnetic brush development method which can obtain a stable image of fC and density without capri.

Another object of the present invention is to provide a magnetic brush development method that can stably cut the ears to a short length without causing blocking of the -component magnetic developer.

Still another object of the present invention is to provide a magnetic brush developing method that eliminates the occurrence of so-called milling streaks even when foreign matter or coarse particles are mixed into the developer.

According to the present invention, Iij! consists of rubbing the surface of a substrate having an electrostatic image with a magnetic brush of developer formed on a developer conveying sleeve equipped with a magnet inside. In the method for developing an electromagnetic image, a panicle standing promoting mechanism made of a magnetic material is disposed close to the developer introduction side of a panicle cutting mechanism made of a non-magnetic material, and a concentration promoting mechanism between the panicle standing promoting mechanism and the sleeve is arranged. There is provided a developing method characterized in that immediately after the magnetic brush passes through a magnetic field region, the ears of the magnetic brush are cut by the ear cutting mechanism.

The present invention will be explained in detail below with reference to the accompanying drawings.

In FIG. 1 showing an example of a developing device used in the present invention,
A left drum-shaped support 2 having an electrophotographic photosensitive layer 1 on its surface is rotatably provided, and along the moving surface of the photosensitive layer 1, a developing device, generally indicated by a line, is provided.

This developing device 6 is made up of a developer storage chamber 4, a developing roll 5, and a panicle cutting mechanism 6. It consists of a magnet 8 having a large number of poles, and at least one of them is provided so as to be able to rotate around an axis.

The developer in the developer storage chamber 5 is attracted and held on the sleeve 7 to form a magnetic brush 9. This magnetic brush 9 moves over the sleeve 7 at a constant rate as the sleeve 7 or magnet 8 rotates. A zero-grain cutting mechanism 6 that is conveyed in the direction and rubs against the photosensitive layer 1 to develop the electrostatic image on the photosensitive layer 1 is located between the sleeve 7 and the magnetic brush delivery side of the developer storage chamber 5. The magnetic brush 9 is arranged so that a constant clearance (d,) is maintained between the magnetic brushes 9 and 9, and the thickness of the magnetic brush 9 is controlled to a constant value.

As shown in FIG. 1 and the principle diagram (FIG. 2), the important features of the present invention are that the ear cutting mechanism 6 is made of a non-magnetic material, and that the ear cutting mechanism 6 is made of a non-magnetic material, and that Immediately after the magnetic brush 9α passes through the concentrated magnetic field area 11 between the panicle establishment promoting mechanism 10 and the sleeve 7, the magnetic brush 9α is removed by the panicle cutting mechanism 6.
The purpose is to cut the ears of α.

That is, according to the present invention, by arranging the ear standing promoting mechanism 10 made of a magnetic material in close proximity to the developer introduction side of the ear cutting mechanism 6, the ear standing promoting mechanism 10 and the sleeve inner magnetic pole N-4 are
A concentrated magnetic field, that is, a parallel magnetic field is formed between the magnetic field and the S, and as a result, the spikes of the developer are promoted, and the concentration or density of the developer in this area is uniformly relatively coarse. ing. When the spikes are uniform and the density of the developer is uniformly rough, the magnetic brush of the developer is immediately cut off by the non-magnetic spike cutting mechanism 6, thereby cutting the magnetic brush of the developer over the entire circumference of the sleeve 7. It becomes possible to supply it stably and quantitatively. For example, in the present invention, the panicle establishment promotion mechanism 10
By enlarging the magnetic brush 9α with a magnetic magnifying glass and cutting the enlarged magnetic brush 9α with a non-magnetic ear cutting plate 6, it is possible to cut the magnetic brush 9α with extremely high precision, that is, to cut the ears. I'm going back. Therefore, according to the present invention, it is possible to form an image with uniform and stable density without shading over the entire surface of the photosensitive layer 1.

Furthermore, according to the present invention, the cutting of the magnetic brush is carried out under conditions where the density of the developer is coarse and there is no mutual compression of the developer particles. Even when short dimensions are used, mutual blocking of developer particles can be effectively prevented.

Furthermore, if coarse particles generated by aggregation of toner particles and foreign matter such as paper powder or dust that have entered the developing mechanism from the outside, or hard aggregates of toner particles, etc. are blocked at the tip of the ear cutting mechanism 6. Also, due to the effect of the above-mentioned panicle establishment promotion mechanism 10, a magnetic brush is formed to surround this, and the thickness of the magnetic brush passing through this dammed part becomes thinner in a striped manner than other parts. Therefore, the occurrence of white streaks can be effectively eliminated.

The above-mentioned effects are achieved by the panicle establishment promotion mechanism 1 made of magnetic material.
This becomes possible only by arranging the ear cutter 0 and the ear cutting mechanism 6 made of a non-magnetic material in a specific positional relationship as shown in FIG.

Conventionally, the use of a panicle cutting mechanism made of a magnetic material is known as disclosed in Japanese Patent Laid-Open No. 54-43037. However, if the ear cutting mechanism itself is made of a magnetic material, a concentrated magnetic field region is formed directly between the ear cutting mechanism and the sleeve, so that the developer magnetic brush can be magnetically expanded to the desired size. It is extremely difficult to cut it. Moreover, the tip of the ear cutting mechanism made of a magnetic material also has a pole opposite to the opposing magnetic pole t'1. Because it acts as a magnet, the magnetic brush vi tends to be randomly cut between the tip of the cutting mechanism and the sleeve, and as a result, the magnetic brush l on the sleeve becomes quite asymmetrical, making it difficult to create images with varying densities. There is a tendency to form. In addition, since the magnetic brush formed between the tip of the magnetic ear cutting mechanism and the tip of the magnetic ear cutting mechanism tries to get into the space between the tip and the tip of the magnetic ear cutting mechanism, compressive force is generated between the developer particles. This may cause mutual blocking of developer particles. Such drawbacks are, for example,
As shown in Japanese Patent No. 5-128047, the same problem occurs when a coating of a non-magnetic material is provided on the back surface of the magnetic ear cutting mechanism, that is, on the developer magnetic brush delivery side. Moreover, providing the magnetic ear cutting mechanism in close proximity to the sleeve with the narrow clearance necessary for ear cutting increases the torque necessary to drive the rotation of the sleeve or magnet that transports the developer.
Furthermore, these are heated by the generation of eddy currents, and the developer is also heated, making blocking more likely to occur. According to the present invention, these drawbacks can also be effectively eliminated.

Further, Japanese Patent Publication No. 55-36992 discloses that a magnetic material is provided on the magnetic brush delivery side of a spike cutting mechanism made of a non-magnetic material, and the cut magnetic brush is made to stand up, thereby giving disturbance to the developer. is disclosed. In contrast, in the present invention, a magnetic material is provided on the magnetic brush feeding side of the ear cutting mechanism, and ears are cut with the magnetic brush enlarged, and the arrangement and principles of the two are completely different. .

In the present invention, as is clear from the above description,
Clearance d between the magnetic ear standing promotion mechanism 10 and the sleeve 7
2 is the clearance d between the ear cutting mechanism 6 and the sleeve 7,
It is desirable for the purposes of the present invention that the ratio d2/d is generally greater than d2/d, in the range 1.05 to 10, in particular 1.5 to 6.5. That is, if this ratio is smaller than the above range, it will be more difficult to supply a stable and uniform amount of developer than when it is within the above range, resulting in the same drawbacks as when using a magnetic ear cutting mechanism. begins to occur. Moreover, if this ratio is larger than the above range, it is recognized that it tends to be difficult to prevent the occurrence of white streaks due to contamination of foreign matter. still,
The clearance d may be in the range commonly used for one-component magnetic developers, for example, from 0.1 to 1 mm.

Generally, it is preferable to provide the magnetic panicle establishment promotion mechanism 10 in close contact with the feeding side of the panicle cutting mechanism 6, but if the interval is small,
There is no problem even if the two are provided separately.

The panicle establishment promotion mechanism 10 may be made of any magnetic material, such as a soft iron plate,
It can be made of a steel plate, a sintered ferrite plate, a nickel plate, a cobalt plate, etc., and its thickness is sufficient to prevent the phenomenon of corrugation and to make the panicle stand good and uniform, e.g. It is desirable that it be in the range of 0.5 to 5 cranes.

The ear cutting mechanism 6 can be made of any non-magnetic material, such as brass, phosphor bronze, aluminum, duralumin, non-magnetic stainless steel, various ceramics, glass, plastics, etc.

In the present invention, it is preferable that the magnetic brush is conveyed and the ears are cut by fixing the magnet 8 while rotating the spindle 7. In this case, the ear standing promotion mechanism 10 and the magnetic poles of the magnet 8 face each other. By doing so, it becomes possible to cut with high precision. The movement of the magnetic brush 9 is performed in the same direction as the rotational direction of the sleeve.The present invention can of course be applied to a magnet/rotation-sleeve fixation method or a magnet and sleeve simultaneous rotation method, and in this case as well, highly accurate magnetic It becomes possible to cut the brush.

The magnetic brush development method of the present invention is particularly advantageous when using a one-component magnetic toner in which the magnetic brush is cut to a particularly small thickness. As such a component-based magnetic toner, a heat-fixing type or a pressure-fixing type toner can be used, and both a conductive magnetic toner and an electrodetectable magnetic toner can be used. Representative examples of toner compositions are shown below.

Ferromagnetic powder 20-80% Dyed pigment 0.5-5% Release agent 2-15% Conductive agent
0 to 10 Flowability improver 0 to 10
1ch

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an example of a developing device used in the method of the present invention, and FIG. 2 is an enlarged sectional view showing the principle of panicle cutting, in which reference numeral 1 is a photosensitive layer and 3 is a developing device. , 4 is a developer storage chamber, 5 is a developing roll, 6 is a cutting mechanism, 7 is a sleeve, 8 is a magnet,
9 indicates a magnetic brush layer, and 10 indicates a panicle establishment promotion mechanism. Patent applicant: Sanda Kogyo Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] (1) In a method for developing an electrostatic single image, which consists of rubbing the surface of a substrate having an electrostatic image with a magnetic brush of developer formed on a developer conveying sleeve equipped with a magnet inside, Immediately after the magnetic brush passes through a concentrated magnetic field region between the spike-setting promoting mechanism and the sleeve, a spike-setting promoting mechanism made of a magnetic material is disposed close to the developer introduction side of a spike-cutting mechanism made of a magnetic material. A developing method characterized in that the magnetic brush is used to cut the ears using the ear cutting mechanism.