JPS5872972A - Developing device using magnetic brush - Google Patents

Abstract

PURPOSE:To lower the fog density and improve the reproducibility of a low density and the reproducibility of a narrow line, by providing a fixed magnet, which has a developing main pole and repulsive magnetic poles just before this pole, and a counter magnetic pole which is separated from the surface of a sleeve facing these repulsive magnetic poles. CONSTITUTION:A fixed magnet where a developing main pole 4-1 and repulsive magnetic poles 402 just before this pole 4-1 are arranged is provided, and a counter magnet 5 is fixed on a supporting member 6 which is placed apart from a sleeve 2 facing to repulsive magnetic poles 4-2, and these magnets are so arranged that repulsive magnetic poles 4-2 face to the same electrode. A toner is flied magnetically to overdevelop image and non-image parts uniformly, and the toner stuck to the non-image part is picked up to the side of a developing roll in a developing region by the control of a developing roll bias, thereby obtaining a high-quality developed image which is superior in reproducibility of a low density and reproducibility of a narrow line and has the fog density controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush development device that uses one-component magnetic toner.

There are various known developing devices that use one-component magnetic toner, and they can be classified from the viewpoint of charge application to those that use low-resistance magnetic toner, devices that attach toner to an electrostatic latent image by electrostatic induction or polarization, and A device is generally used in which high-resistance magnetic toner is charged and adhered to the electrostatic latent image by means such as injection friction.

A developing method using a one-component abrasive toner is superior in terms of reliability, maintainability, cost, etc., compared to a developing method using a so-called two-component toner, which uses a mixture of toner and carrier. However, on the other hand, low density reproducibility, fine line reproducibility,
Alternatively, sufficient performance cannot be obtained in terms of capri, etc., and capri occurs when trying to improve the above-mentioned reproducibility including image density, and conversely, when capri is controlled, density and reproducibility decrease. have.

In order to solve this problem, Japanese Patent Application Laid-Open No. 55-73058,
Developing using two developing rolls as disclosed in No. 55-138766, No. 56-14268, etc.
A so-called functionally separated developing method has been proposed, in which the two functions of capri removal are performed separately. It is not satisfactory in terms of performance, cost, etc.

In view of the above-mentioned drawbacks, the present invention aims to improve the low density reproducibility and fine line reproducibility and control capri, which are unique to the development method using a one-component developer, while maintaining reliability and the simplicity of the mechanism. The object of the present invention is to provide a novel developing device that obtains the desired results.

An object of the present invention is to provide a magnetic brush developing device which develops an electrostatic latent image formed on an electrostatic latent image carrier by one-component magnetic toner on a sleeve having a fixed magnet therein. A fixed magnet having a repelling magnetic pole immediately before the pole, and an opposing magnetic pole that is spaced apart on the sleeve surface facing the repulsive magnetic pole and whose surface facing the same polarity as the repulsive magnetic pole is provided. This can be achieved by a brush developing device.

FIG. 1 is a schematic diagram of a conventional developing device.

In the figure, reference numeral 1 denotes a photoreceptor r ram which rotates in the direction of arrow a. 2
is a non-magnetic cylindrical sleeve that rotates in the direction of the arrow.
It has Ic1a stone roll 4. The magnet roll has a structure in which block magnets are attached to a cylindrical holder with their magnetic poles alternately arranged. Reference numeral 6 denotes a member that serves both for injecting charges into the toner layer and for trimming, and is an injection electrode that also serves as a trimmer. Reference numeral 7 denotes a nozzle for the developing roll. The relationship between the input density (Dxm) and the surface potential and the relationship (development curve) between the input density (DIM) and the output density (Dout) of this developing device are determined as follows.
Figures (at and (b) K are shown.

5. The dash-dotted line in FIG. 2(a) indicates the bias voltage that suppresses the background density (BKGD) to 0.01 or less. The two-dot chain line is the input concentration (Drsy),
To reproduce 0.2 to Q, 6 or more [6 indicates the required bias voltage.

The Z insumi pressures (which satisfy this background control and low density reproduction) are separated from each other, and when capri density control is performed, the low density side is flat as shown in Fig. 1(b) K, and 0.
Only a very high γ characteristic that rises from around 4 can be obtained.

FIG. 3 is a schematic diagram of an apparatus illustrating the invention.

The structure of this developing device is basically the same as the device shown in Fig. 1, except that a main developing pole indicated by 4-1 and a repelling pole indicated by 4-2 are arranged immediately before the main developing pole. It becomes. 5 and 6
is a counter magnet (5+) fixed on a support member (61) located away from the sleeve 2 facing the repulsive magnetic pole 4-2, and has the same magnetic pole as the repulsive magnetic pole (in the figure, the repulsive pole of N-N pole On the other hand, the opposing N-pole magnets are arranged facing each other.

Next, the state in which the toner on the developing roll adheres to the electrostatic latent image and is developed by this device will be explained.

In FIG. 6, an electrostatic latent image (positive polarity) is formed on the photosensitive drum 1 (Se-based sensitive material). .

On the other hand, the toner on the developing roll passes through the injection electrode 30, and its surface layer is negatively charged by the electric field formed between the sleeve surface and the electrode. Then, it passes between the repelling magnetic pole 4-2 in the front stage of the developing area and the opposing magnet 5. The magnetic flux density distribution on the sleeve surface at this time is shown in FIG. A solid line C in FIG. 4 shows the magnetic flux density distribution in the case where there is no opposing magnet. The movement of toner when there is no opposing magnet is as shown in Figure 5.
At the center of the repellent pole, a toner non-adhesive part and a dripping part are formed in front, and the toner moves in parallel from the pool part to the non-adherent part in a chain-like manner, and the chain is attracted by the main pole. Fall down. On the other hand, the dashed dotted line d in FIG. 4 shows the magnetic flux density distribution when the opposing magnets are arranged at a distance from the repelling magnetic pole.

In this case, the peak of the magnetic flux density distribution is tilted toward the toner transport area due to the arrangement of the opposing magnets, and the toner movement is such that the toner in the top layer flies in a loop as shown in Figure 6. was observed.

The state of flight is determined by the angle and spacing between the repulsive magnetic poles, the angle with the main developing pole, the distance between the opposing magnet and the sleeve (or the repulsive magnetic pole),
Furthermore, it is affected by the angle of the opposing magnets, the moving speed of the sleeve, etc., and the toner is individually knangled from the chain state by the anti-a field from both directions, and the magnetic flux density distribution curve (the magnetic field shown) is It flies and attaches to the body drum.

At this time, since the flying toner is given a negative charge by the injection electrode, it electrostatically adheres to the latent image of the positive electrode with a uniform thickness over the entire area of the dotted image and non-image area, and development is performed.

FIGS. 7(a) and 7(b) K show a state in which the image is uniformly overdeveloped by magnetic flying at the front stage of the developing area. Figure 7(a)
The dashed line in the figure indicates the surface potential of the toner layer. The toner layer potential is negatively charged by the injection electrode, and the contrast with the latent potential is strengthened, resulting in a development curve as shown in FIG. 7(b).

Next, the toner adhering to the photoreceptor drum passes through the main developing pole position in the developing area, as shown in FIGS. 8(a) and (b).
) Receive a similar treatment. That is, the bias applied to the developing roll [broken line in FIG. 8(a)] is
The toner that adheres to the image area strongly adheres to the latent image due to Coulomb force, etc., so it is difficult to receive treatment, and on the other hand, the toner (capri) that adheres to the non-image area does not form the latent image. Because the adhesion force is weak, it is pulled back to the sleeve side due to mechanical and magnetic sliding force and attraction force.As a result, as shown in Figure 8 (b), capri is suppressed and low density reproduction is achieved. A development curve with good properties can be obtained.

As shown here, the above-mentioned low density reproduction and capri control are carried out in stages by uniform overdevelopment (air flying) in the front stage of the development area and treatment (scavenging) in the development area. . Therefore, settings such as the repelling magnetic pole, the magnetic force of the opposing magnet, the arrangement, the injection voltage, the developing roll bias voltage, and the density of the toner brush in the developing area are very important.

These settings are related to each other, but the repulsion magnetic pole (on the IJ-sphere) is 60
0 to 100 Gauss, main developing pole (on sleeve) 700 to 1
200 Gauss, and 900 to 1800 Gauss for both opposing poles, and it is preferable to set the strength IJ of these magnetic poles to be large in the above order.

As explained above, according to the present invention, a repelling magnetic pole and a magnet with the same polarity as the repelling magnetic pole are arranged facing each other in the front stage of the developing area, and the toner injected with charge is passed between the magnets, thereby magnetically distributing the toner. By flying the toner and uniformly overdeveloping the non-image areas of the image, and then picking up the toner adhering to the non-image areas in the developing area onto the developing roll with a developer roll of 1 liter, low density reproducibility and fine line reproduction are achieved. It is possible to obtain a homogeneous and high-quality modern rice cake with excellent properties and a controlled capri concentration.

The present invention will be specifically explained below with reference to Examples.

EXAMPLE Developing was carried out using the developing apparatus according to the present invention shown in FIG. 6 under the following conditions.

Photoreceptor = Se-based photoreceptor Image area potential 5oov, non-image area potential 100V.

Magnetic toner: having a scratch resistance of 1015Ω at 40 Kv/l:x.

Developing device = 67φ5US304 sleeve (120rp
m).

Magnet roll (block magnet).

Main developing pole: 1000 Gauss (on sleeve).

Repulsion magnetic pole 800 Gauss (on sleeve).

Opposing magnet 1200 gauss.

Injection electrode 2 station member (electric field 2 x 104 V/c,).

Current roll/Ziasu: +5oov.

Process speed: 130''/sec - As a comparative example, development was carried out under the same conditions as above except that no opposing magnet was provided. The results obtained are shown in the following table.

Table* As is clear from the results of the input density table, according to the present invention, a repelling magnetic pole and an opposing magnet are placed in the front stage of the developing area, and by first uniformly overdeveloping by magnetic flying, and then performing scavenging in the developing area, capri High quality images with low density and excellent low density reproducibility and fine line reproducibility can be obtained.

The same effect was obtained even when the magnet roll was a magnetized type magnet roll.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional developing device, and Figure 2 (a)
and (bl is the input F concentration (DI
The relationship between M) and surface potential and the relationship between input lightness (DIM) and output astringency (Dout) (Development song 1) Figure 3 is a configuration diagram of the developing device of the present invention, and Figure 4 represents the magnetic flux density distribution, FIG. 5 represents the toner brush shape 11 due to the anti-pole, FIG. 6 represents the movement of toner due to the opposing magnets of the device of the present invention, and FIGS. 7(a) and (b). ) represents the relationship between the input concentration, surface potential, and input concentration in the front stage of the development zone of the apparatus of the present invention, as well as the development curve; and the relationship between surface potential and development bias potential,
and the development curve. Symbols in the figure: 1... Photosensitive drum: 2... Cylindrical non-magnetic sleeve; 6... Injection electrode that also serves as a trimmer: 4... Magnet roll: 4-1... Main developing pole; 4- 2... Repulsion magnetic pole; 5.
... Opposing magnet; 6... Holding member near... Development bias; a, b... Rotation direction; C... Magnetic flux density distribution due to repelling pole; d... Magnetic flux due to repelling pole and opposing magnet Density distribution. #2 Figure II ¥2 Figure 418! 31!21 sS Fig. 6 Fig. 7 FR (a) Fig. 8 Fig. 7 (b) ℃ Machi/TochitΔ艷 DrH No. 81! ! 1

Claims (1)

[Claims] In a magnetic brush developing device that develops an electrostatic latent image formed on an electrostatic image carrier using one-component magnetic toner on a sleeve equipped with a fixed magnet, a main developing pole and a repelling magnetic pole immediately before the main developing pole are used. 1. A magnetic brush developing device characterized by comprising: a fixed magnet having a fixed magnet; and an opposing magnetic pole spaced apart from the sleeve surface facing the repulsive magnetic pole and having a surface with the same polarity as the repulsive magnetic pole facing the magnetic brush developing device.