JPS62129868A - Magnetic brush developing method - Google Patents

Abstract

PURPOSE:To minimize the number of times of supplying a toner and to execute the miniaturization by making the strength of the magnetization of a magnetic carrier stronger than the strength of the magnetization of a toner, making the particle diameter of the magnetic carrier larger than a toner particle diameter and specifying the rotation speed of a sleeve and a magnet roll. CONSTITUTION:The strength of the magnetization of a magnetic carrier 7 is made stronger than the strength of the magnetization of a toner 8 and also, for the particle diameter, the magnetic carrier 7 is made larger than the toner 8. Further, since the rotating speed of a sleeve 2 and a magnet roll 3 is set to the speed in which the magnetic carrier 7 can be individually conveyed and the toner 8 cannot be individually conveyed, only the toner 8 sticking to the surface of the magnetic carrier 7 is conveyed together with the magnetic carrier 7 and held as a magnetic brush on a sleeve 2. Consequently, the number of the toner 8 sticking to the surface of the magnetic carrier 7 to form the magnetic brush comes to be constant, the mixing ratio of both comes to be also constant and the developing with a satisfactory concentration can be executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to development, which is a step in an electrophotographic process, and specifically relates to a magnetic brush formed from a two-component developer consisting of a magnetic carrier and a toner. The present invention relates to a magnetic brush development method that uses a magnetic brush to visualize an electrostatic latent image.

[Conventional technology]

In the electrophotographic process, a sleeve made of a non-magnetic material containing a magnet roll in which N and S poles are separately magnetized in the circumferential direction is opposed to an electrostatic latent image carrier such as a photosensitive drum with a small gap. The two-component developer is held on this sleeve by the magnetic force of a magnet roll to form a magnetic brush, and by rubbing the surface of an electrostatic latent image carrier such as a photosensitive drum with this magnetic brush, the magnetic brush is formed. A magnetic brush development method has conventionally been practiced in which toner therein is attached to an electrostatic latent image carried on an electrostatic latent image carrier to form a visible image.

Generally, the two-component developer used in the magnetic brush development method is made by mixing a magnetic carrier made of iron powder or the like with a particle size of about 100 μm to 200 μm and a non-magnetic toner, but it has good development properties. In order to obtain the desired density, it is necessary to maintain the toner mixing ratio within a very narrow range of 4 to 3 wt%.

Therefore, in the past, the toner content in the two-component developer stored in the container of the developing device was measured and the toner was replenished sequentially, but the proportion of toner in the container was magnetic. The disadvantage is that there are very few carriers.

Therefore, as a technique to improve this drawback, for example,
There is a magnetic brush development method disclosed in Japanese Patent No. 9-24416.

This method uses a magnetic carrier with a particle size of about 5 μm to 30 μm, which is manufactured by finely pulverizing a molten mixture of an insulating resin and a magnetic fine powder. It becomes possible to increase the amount to 6 to 35 wt%.

[Problem that the invention seeks to solve]

However, even if the allowable toner mixing ratio is 6 to 35wt, the proportion of toner in the container of the developing device is smaller than that of magnetic carrier, so it is necessary to replenish the toner many times, and the specified amount of toner must be ensured. However, since the container cannot be made smaller in size, the entire device becomes larger. The object of the present invention is to develop a magnetic brush developing method that can be used easily and miniaturized.

[Friendly means of solving problems]

In order to achieve the above object, the present invention makes the strength of magnetization of the magnetic carrier larger than that of the toner, and also makes the particle size of the magnetic carrier larger than the particle size of the toner. The rotational speed of the sleeve and magnet roll for conveying the magnetic brush of the two-component developer consisting of the two-component developer to the development area is set at a speed that can convey the magnetic carrier alone but cannot convey the toner alone.

[Effect]

By using the above-mentioned means, the mixing ratio of the magnetic carrier and toner of the two-component developer conveyed as a magnetic brush between the sleeve and the electrostatic latent image carrier can always be kept constant, resulting in good developed density. can be easily maintained, and magnetic carrier,
The atomizer and toner can be mixed at a constant mixing ratio on the sleeve.

Therefore, it is possible to have a larger proportion of the toner than the magnetic carrier in the container, and if the amount of the toner to the magnetic carrier is at least a certain amount, the above-mentioned certain mixing ratio can be obtained.

Therefore, it is possible to reduce the frequency of toner replenishment, and also to downsize the container, which in turn allows the device to be downsized.

【Example〕

An embodiment will be described below with reference to the drawings.

FIG. 1 is a side sectional view of a developing device implementing the magnetic brush developing method according to the present invention.

In the figure, reference numeral 1 denotes an electrostatic latent image carrier such as a photosensitive drum, which carries an electrostatic layer image by an optical writing means (not shown) and is rotated at a constant speed in a predetermined direction by a motor (not shown) or the like. It looks like this.

Reference numeral 2 denotes a sleeve made of a non-magnetic material, and the sleeve 2 is arranged to face the electrostatic latent image carrier 1 with a minute gap serving as a development area. A magnet roll 3 having a structure in which a plurality of N poles and S poles are alternately divided and magnetized in the circumferential direction is arranged in a non-contact manner,
The magnet roll 3 and sleeve 2 are rotated independently of each other at different speeds in the direction of arrow A by a motor (not shown) or the like.

Reference numeral 4 denotes a container for containing a two-component developer, and the tip 5 of the bottom plate of this container 4 is located below the sleeve 2 and is connected to the sleeve 2.
An opening 6 is formed between the container 4 and the sleeve 2 at a position opposite to this contact.

1 is a fixed amount of f'Lfc magnetic carrier contained in the bottom side of the container 4, and 8 is a magnetic or non-magnetic toner replenished at the top side of the container 4, both of which contain a two-component developer. In the present invention, the particle size and magnetization strength of the magnetic carrier T are made larger than those of the toner 8.

Specifically, as the magnetic carrier 7, a pulverized mixture of magnetic fine powder and resin, ferrite magnetic powder, iron powder, etc. are used, and the particle size is in the range of 30 μm to 100 μm, and the magnetization strength is 3KOe. (Kloersted) in a magnetic field of 50 emu/f. The toner 8 has a particle size in the range of 5 μm to 20 μm, and a magnetization strength of 30 emu/S′ or less in a magnetic field of 3 KOe.

Reference numeral 9 denotes an impeller for stirring, which is provided in the container 4 so as to be located near the sleeve 2 and near the boundary between the magnetic carrier T and the toner 8, and is rotated by a power source such as a motor (not shown). ing.

In this configuration, development is performed as follows.

First, the sleeve 2 and the magnet roll 3 are rotated at different speeds in the directions indicated by the arrows N, and the impeller 9 is also rotated in a predetermined direction.

Due to the rotation of the impeller 9, the magnetic carrier T and a part of the toner 8 are stirred and mixed in the container 4 to form a two-component developer, and the two-component developer is transferred onto the sleeve 2 by the magnetic force of the magnet roll 3. A magnetic brush is formed by holding the magnetic brush. The structure of this magnetic brush is shown in FIG.

As seen in this figure, the magnetic carriers 1 are connected along the lines of magnetic force of the magnet roll 3, and the toner 8 is attached to the connected magnetic carriers 7 by electrostatic force or magnetic attraction so as to cover the connected magnetic carriers 7.

The magnetic brush thus formed on the sleeve 2 is transported in the direction of the arrow B, which is opposite to the arrow A, as the magnet roll 3 rotates in the direction indicated by the arrow. A layer of component developer is formed,
At the same time as this, the sleeve 2 is moved at a lower speed than the magnet roll 3.
When the developer is rotated in the direction indicated by the arrow, a phenomenon occurs in which the lower side of the two-component developer layer is conveyed in the direction indicated by the arrow. The developer layer is conveyed on the upper side in the direction of arrow B n1
At the bottom, it will be transported in the direction indicated by the arrow.

That is, the upper side of the two-component developer layer formed on the sleeve 2 is transported in the direction of arrow B by the rotation of the sleeve 2 and the magnetic roll 3, passes through the opening 6 of the container 4, and forms an electrostatic latent image. The developing area is a minute gap between the carrier 1 and the sleeve 2.

In this development area, the surface of the electrostatic latent image carrier 1 is rubbed by the magnetic brush to remove the layer of two-component developer, and the toner 8 in the magnetic brush, that is, the surface of the magnetic carrier 7 is adhered to by this. The toner 8 selectively adheres to the portion of the electrostatic latent image carried on the electrostatic latent image carrier 1, and the electrostatic latent image is visualized.

The magnetic brush, which has consumed the two-component developer and toner 8 after rubbing against the electrostatic latent image carrier 1, is further conveyed in the direction of arrow B, and the bottom plate of the container 4 is in contact with the sleeve 2. After colliding with the tip of the layer and changing its direction, it is conveyed in the direction of arrow A, passing through the development area without contacting the electrostatic latent image carrier 1. It is collected into the container 4 through the opening 6.

The recovered two-component developer is mixed with the toner 8 in the container 4 by the impeller 9, and after the consumed toner 8 is replenished onto the surface of the magnetic carrier 7, the developer is transferred to the sleeve 2 again.
It is held as a magnetic plan on top and transported to the development area.

By repeating the above operations, the electrostatic latent image carried on the electrostatic latent image carrier 1 is developed into a visible image.

By the way, in this embodiment, as mentioned above, the magnetization strength of the magnetic carrier 7 is greater than that of the toner 8, so the conveyance speed of the magnetic carrier 7 alone due to the rotation of the magnet roll 3 is equal to that of the toner 8 alone. This is large compared to the transport speed of Therefore, if the conveying speed of the sleeve 20 is set between the conveying speed of both magnetic carriers 7 and the toner 8 due to the rotation of the magnet roll 3, then this conveying speed will be the same as that of the magnetic carrier 7 and the toner 8.
It acts equally on The compacted magnetic carrier 7 is conveyed to the developing area as the magnet roll 3 rotates, but the toner 8 is not conveyed alone, and as shown in FIG. Only the magnetic carrier 7 is transported together with the magnetic carrier 7.

On the other hand, although the particle size of the magnetic carrier 7 is made larger than the particle size of the toner 8, these particle sizes do not become a major factor in the conveying speed due to the rotation of the magnet roll 3. However, when forming the magnetic brush on the sleeve 2,
When the particle size of the magnetic carrier 7 is larger than the particle size of the toner 8, it becomes stable. The reason for this is presumed to be that even though the toner 8 is present between the magnetic carriers 7, the binding force between the magnetic carriers 7 is strong, so that the magnetic carriers 7 directly attract and connect with each other. Then, the toner 8 adheres to the surface of the connected magnetic carriers T, forming a magnetic brush having the structure shown in FIG. It's fleeting.

Therefore, the number of toners 8 adhering to the surface of the magnetic carrier 7 forming the magnetic brush is constant, and the mixing ratio of both toners is also constant.

Therefore, the mixing ratio of the magnetic carrier 7 and the toner 8 of the two-component developer transported to the development area is such that if the ratio of the magnetic carrier 7 and the toner 8 in the container 4 is above a certain ratio, the toner 8 is Regardless of the amount remaining, the mixing ratio of the magnetic carrier 7 and toner 8 of the two-component developer transported to the development area is always constant, making it possible to develop with good density.

It has been confirmed through experiments that good development density can be obtained if the ratio of magnetic carrier 7 and toner 8 in the container 4 is about 10% or more of toner 8 to magnetic carrier Tvc. .

〔Effect of the invention〕

As explained above, in the present invention, the magnetization strength of the magnetic carrier is made larger than the magnetization strength of all toner, the particle size of the magnetic carrier is also made larger than the particle size of the toner, and the rotational speed of the sleeve and magnetic roll is By setting , so that the magnetic carrier alone can be conveyed but the toner alone cannot, the mixing ratio of the magnetic carrier and toner of the two-component developer conveyed to the development area by the rotation of this sleeve and magnet roll can be adjusted. Since it is possible to always maintain a constant value, it is possible to easily maintain a good developed density.

In addition, since the magnetic carrier and toner are mixed at a constant ratio on the sleeve, it is possible to have a larger proportion of the toner in the container than the magnetic carrier, and the toner is kept at a constant mixing ratio with respect to the magnetic carrier. Since the above steps are sufficient, it is possible to reduce the frequency of toner replenishment, and at the same time, it is possible to downsize the container, which in turn has the effect of downsizing the developing device.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an example of a developing device for carrying out the entire magnetic brush developing method according to the present invention, and FIG. 2 is an enlarged view showing the structure of the magnetic brush according to the present invention. Reference Signs List 1: Electrostatic latent image carrier 2 Sleeve 3: Magnetic roll 4: Container 5: Tip 6: Opening 1: Magnetic carrier 8: Toner 9: Impeller Side sectional view of a developing device implementing the present invention, blank 1 - Enlarged diagram showing the toner i-ki brush 2. Written amendment (spontaneous) October 22, 1985 Commissioner of the Japan Patent Office Kuro 1) Mr. Akio 1, Indication of the case 1985 Patent application No. 269418 2, Invention Name: Magnetic brush development method 3, relationship with the amended case Patent applicant address: 1-7-12 Toranomon, Minato-ku, Tokyo Name: (029) Oki Electric Industry Co., Ltd. Representative: Nankai Hashimoto 4, Agent Person's name (6961) Patent attorney Takashi Kanakura 5, Date of amendment order Proprietary claim 1. A two-component developer consisting of: a sleeve; a magnet roll having a structure in which a plurality of north poles and south poles are alternately magnetized in the circumferential direction and disposed within the sleeve; and a magnetic carrier and toner. and a container containing the two-component developer, the container having a bottom plate in contact with the sleeve, the two-component developer in the container being held on the sleeve by the magnetic force of the magnet roll. By rotating the sleeve and the magnet roll in the same direction at different speeds, the magnetic brush is conveyed to a developing area between the sleeve and the electrostatic latent image carrier, and the electrostatic latent image is In the magnetic brush development method in which development is carried out by rubbing the surface of the image carrier with the magnetic brush, the magnetization strength of the magnetic carrier is made stronger than the magnetization strength of the toner, and the particle size of the magnetic carrier is made smaller than that of the toner particles. By setting the rotational speed of the sleeve and magnet roll to a speed that can transport the magnetic carrier alone but cannot transport the toner alone, the magnetic carrier of the magnetic brush and the toner that are transported to the development area are A magnetic brush developing method characterized in that the mixing ratio of the two is always constant. 2. A patent claim characterized in that the magnetic carrier and toner are separately housed in one container, an impeller is provided near the boundary thereof, and the magnetic carrier and toner are mixed with this impeller during development. The magnetic brush development method according to scope 1. 3. Having a particle size of 30 μm to 100 μm3
A magnetic carrier exhibiting a magnetization strength of 50 emu/S' or more in KOe, and a particle size of 5 to 20 μm and 3KOe.
2. The magnetic brush developing method according to claim 1, wherein a toner exhibiting a magnetization strength of 30 emu/g or less is used.

Claims (1)

[Claims] 1. A sleeve made of a non-magnetic material arranged to face the electrostatic latent image carrier with a small gap therebetween, and a plurality of north and south poles alternately arranged in the circumferential direction. A magnet roll having a magnetized structure and disposed within the sleeve, a two-component developer made of a magnetic carrier and a toner, and a container containing the two-component developer, The two-component developer in the container is held on the sleeve by magnetic force to form a magnetic brush, and by rotating the sleeve and the magnet roll in the same direction at different speeds, the magnetic brush is connected to the sleeve and the electrostatic latent image carrier. In the magnetic brush development method, in which development is carried out by rubbing the surface of the electrostatic latent image carrier with the magnetic brush, the magnetic brush is conveyed to a developing area between the carriers and the toner. By making the magnetic carrier stronger and the particle size of the magnetic carrier larger than the toner particle size, and setting the rotational speed of the sleeve and magnetic roll to a speed that allows the magnetic carrier to be transported alone but not the toner alone, the developing A magnetic brush developing method characterized in that the mixing ratio of magnetic carrier and toner in a magnetic brush conveyed to a region is always constant. 2. A patent claim characterized in that the magnetic carrier and toner are separately housed in one container, an impeller is provided near the boundary thereof, and the magnetic carrier and toner are mixed with this impeller during development. The magnetic brush development method according to scope 1. 3. A magnetic carrier having a particle size of 30 μm to 100 μm and exhibiting a magnetization strength of 50 emu/g or more at 3KOe, and a magnetic carrier having a particle size of 5 to 20 μm and 30 emu/g at 3KOe.
2. The magnetic brush developing method according to claim 1, wherein a toner exhibiting a magnetization strength of /g or less is used.