JPH0683205A - Liquid developing device - Google Patents

Abstract

PURPOSE:To efficiently remove a fine magnetic substance layer incorporated at the time of producing a toner grain by removing a magnetic substance fine grain incorporated in a developing liquid by means of a magnetic field provided in a developing part. CONSTITUTION:Until a low concentration developing liquid in which fine coloring toner grain is dispersed about 1-2% acts on an electrostatic latent image on an electrostatic latent image carrier from a developing liquid tank to develop the electrostatic latent image, the fine magnetic substance grain is removed from the developing liquid by a means attracting/removing the fine magnetic substance grain stuck to the surface of toner or incorporated in the developing liquid by using a magnet. In other words, a plate-like magnet 8 in a developing tank is disposed, a fine magnetic grain existing in the developing liquid or on the surface of the toner is attracted/stuck to the magnet by the fluidity in a tank of the developing liquid and removed before the fine magnetic grain reaches a development storage. As the shape of the magnet, the shape of a plate is not adopted, but the shape that a large number of thin plate-like magnets having magnetic poles in the width direction are arrayed like a duckboard or that a large number of magnet balls can be piled up on the bottom part in the tank can be adopted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic wet developing method, and more particularly to an apparatus for removing magnetic fine particles in a developing solution in the wet developing method.

[0002]

2. Description of the Related Art As a developing method for visualizing an electrostatic latent image on an insulative electrostatic latent image bearing member by electrophotography, two methods, a dry method and a wet method, are used. ,
Although it is superior and inferior in handling, the wet developing method comprising fine toner particles is superior when a fine image is required. Various methods are known to prepare such a wet developer,
Although generally used, the insulating resin containing a coloring agent such as a pigment is crushed and dispersed in an insulating liquid together with other additives as necessary to obtain a particle size of 0.1 to 3 μm. The fine particle toner is produced. A ball mill, an attritor, or the like is used as the crushing and dispersing means, and hard particles such as ceramics, glass, and iron are used as the crushing aid. However, in general, steel balls containing carbon steel or the like as a main component are selectively used from the viewpoint of wear resistance. And, this crushing / dispersion is achieved by continuous operation for a long time of several tens of hours. For example, in the case of the patent WO-92 / 01974, it takes 25 to 61 hours with an attritor manufactured by Union Process Co. using carbon steel balls. In such a long work, the steel balls repeatedly collide with each other, resulting in considerable wear, and the finished product has fine magnetic particles of shavings generated at this time. Some of them adhere to the surface of the toner particles and some of them are present in the form of being mixed in the dispersion liquid. According to the experience of the present inventors, this magnetic waste is in a wide range from a maximum diameter of about 80 μm to a minimum diameter of 0.5 μm.

The developer thus produced is treated as a high-concentration developer, and is used in an insulating liquid such as the isoparaffin liquid "Isopar" manufactured by Exxon Co. in an amount of 1.5 to 2.0.
It is added in about a weight percent and used as a wet developer for developing an electrostatic latent image. As described above, since fine iron powder scraps of magnetic material are present in the developer, the fine iron powder scraps also adhere to the latent image together with the toner during development. This iron powder is oxidized over time and changes to blackish brown. When the color of the toner is black, it is good, but when it is bright, the hue is changed, which is a big problem. Also, in the cleaning process following the development and transfer in the printing process, when removing the toner remaining on the latent image carrier, not only the cleaning blade and cleaning roller that come in contact with the toner are damaged but also the latent image It will also damage the surface of the carrier. Furthermore, when the latent image carrier is a photosensitive layer made of an insulating photoconductor, the scratches appear on the image to be subsequently created depending on the scratches created, which is fatal as a photoconductor and unusable. Is likely to become. Therefore, it is necessary to remove such fine magnetic scraps from the developer.

The first conceivable method is to place the prepared high-concentration developer in a strong magnetic field and remove it by attracting and adhering it onto a magnet. In this method, the developer has a high concentration, that is, a high viscosity. Therefore, the fluidity is poor, and in order to increase the removal rate, it is necessary to make the magnetic field stronger, increase the contact area, and take time, and obtain a developer with a high removal rate. Things are actually difficult. Therefore, a method is conceivable in which the developer is made to have a low concentration to remove fine magnetic substance debris. Although this method can remove fine magnetic substance waste efficiently and provides a good developing solution, other problems occur. That is, it is not preferable in various respects to supply the low-concentration developing solution to the user, and it is desirable to increase the concentration. Therefore, it became clear that this method requires a high-concentration step and is not practical.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a mechanism for removing fine magnetic particles contained therein in a developing method using a wet developer prepared by the above-described manufacturing method, to remove magnetic scraps. The amount of high-concentration toner added is small, and therefore the degree of freedom of movement of magnetic material debris is large, and it is provided in a diluted wet developer to remove fine magnetic material debris present in the developer.
The object of the invention is to almost completely prevent the above-mentioned problems caused by the fine dust.

[0006]

That is, according to the present invention, in an electrophotographic liquid developing method for visualizing an electrostatic latent image on an electrostatic latent image bearing member, magnetic fine particles mixed in a developing solution are used as a developing unit. There is provided a liquid developing device characterized by being removed according to a magnetic field provided in the liquid developing device. More specifically, during the period from the developing tank to the electrostatic latent image on the electrostatic latent image carrier, a low-concentration developing solution in which finely colored toner particles are dispersed in an amount of 1 to 2% is applied to develop the latent image. The magnet is used to remove the fine magnetic particles from the developing solution by suctioning and removing the fine magnetic particles adhering to the toner surface or mixed in the developing solution. Since the actual means is suitable for the shape of the wet developing device to be used, in principle, a magnet is used to remove the fine magnetic particles, but the device does not have a certain mechanism. What is missing is easily understood by those skilled in the electrophotographic technology who understand the principle. Therefore, since several examples of the specific technique of the present invention described below are not all countermeasures,
It goes without saying that the present invention is not limited to the scope of the present embodiment.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a conventional copying machine using a wet development method.
This is a schematic representation mainly of the developing section. There, a developer 1 in which fine toner particles are dispersed is pumped up from a developer tank 2 by a pump 3 to form a developer reservoir 5 in a developer reservoir 4. A part of the drum-shaped photoconductor 7 having the electrostatic latent image 6 through the charger 15 and the optical image exposure unit 16 rotates while being immersed in the electrostatic latent image 6, and at the time of immersion, toner adheres to the latent image charge to develop Done. Next, with rotation, the developed image 8 is electrostatically transferred to the intermediate transfer member 11 in the transfer unit 10 after the excess dispersion medium is removed from the surface of the photosensitive member in the squeeze unit 9, and subsequently, , And is melted by the heat roller 13 and transferred to the transfer paper 12. The toner remaining on the photoconductor is scraped off by the cleaning blade 14 in the cleaning section, the photoconductor surface is cleaned, and the initial state of copying is returned. Here, if the fine magnetic material wastes 17 mixed in at the time of preparing the developer exist on the surface of the toner particles and the developer, the cleaning blade 14 and the surface of the photoconductor 7 are damaged during cleaning.

In FIG. 2, a plate-shaped magnet 18 is arranged in the developing tank 2 in the same developing device, and the fine magnetic particles existing in the developing solution or on the toner surface depend on the flow of the developing solution in the tank. The magnets are attracted and adhered to the magnet and are removed before reaching the development reservoir, so that the obstacle as described in FIG. 1 is eliminated. In reality, after removal, 10 μm that existed before removal
The above magnetic debris was almost completely removed, and there was no failure due to this cause in continuous printing. Figure 5
Indicates the particle size and abundance of the magnetic debris present in the diluted developer prepared by dispersing the high-concentration developer prepared as described above in a concentration of 5% by weight in the "ISOPAR L" dispersion medium. It is a thing. FIG. 6 shows the result of measuring the particle size distribution of the magnetic waste after being removed by the magnet as described above by using the particle size distribution analyzer SA-CP3L manufactured by Shimadzu Corporation, as in FIG. is there. It is clear that the magnetic debris having a particle size of 5 μm or more is completely removed.

The shape of the magnet is not limited to the plate-like shape as described above, but a plurality of thin plate-like magnets having magnetic poles in the width direction may be arranged in a cage shape as shown in FIG. Good and
A large number of magnet balls may be deposited on the bottom of the tank.
However, if the magnet is too fine, the magnetic particles will not be attracted to each other and the magnetic force will not reach the outside, reducing the adhesion and removal effect of the fine magnetic material scraps to be removed. It is not preferable because toner adheres electrostatically.

FIG. 4 shows an embodiment of a wet developing apparatus different from that of FIG. 1, in which the developing solution in the developing tank is rotated in the direction opposite to the surface of the photoreceptor by a pump. The electrostatic latent image on the surface of the photoconductor is developed by being supplied to the approaching gap between the surface of the photoconductor of the developing roller 19 and the surface of the developing roller. Here, the reference numerals are the same as those in FIG. The developing solution being pumped up passes through a developing solution transport path 20 arranged so that the magnetic fields face each other by means of a plate-shaped magnet, so that magnetic substance waste existing in the solution is sucked and removed. Has become. In this way, the fine magnetic substance scraps attached to the surface of the magnetic substance are regularly cleaned and removed.

[0011]

According to the means of the present invention, it is possible to easily, efficiently, and simply by means of a simple means / apparatus, to remove fine magnetic material dust mixed in when toner particles are prepared by the conventional wet developer preparation method. It can be removed almost completely, and it is possible to eliminate failures caused by fine magnetic material scraps. INDUSTRIAL APPLICABILITY The present invention is an effective technique for improving the reliability in terms of service life, stability, and service of electrophotographic copying machines and printers by the wet development method. Further, the present invention is a simple means and can be constructed at a low cost.

[0012]

[Brief description of drawings]

FIG. 1 is a schematic view of an electrophotographic copying process using a conventional wet developing device.

FIG. 2 is a schematic diagram of a means for removing fine magnetic substance debris mixed in a developing solution using the wet developing apparatus of the present invention.

FIG. 3 is a schematic view of another means for removing fine magnetic material debris in a developer tank.

FIG. 4 is a schematic diagram of a means for removing fine magnetic substance dust contained in a developing solution in an electrophotographic copying process using another wet developing device.

FIG. 5 is a differential particle size distribution of fine magnetic scraps in a developer before removal.

FIG. 6 is a differential particle size distribution in a developing solution after removing fine magnetic scraps.

[0013]

[Explanation of symbols]

 1: Developer 2: Developer tank 3: Pumping up pump 4: Developer reservoir 5: Developer reservoir 6: Electrostatic latent image 7: Photoconductor 8: Developed image 9: Squeeze portion 10: Transfer portion 11: Intermediate transfer body 12: Transfer paper 13: Heat roller 14: Cleaning blade 15: Charger 16: Photo image exposure part 17: Fine magnetic material waste 18: Plate magnet 19: Development roller 20: Developer transport path consisting of magnet

Claims (1)

[Claims] 1. In an electrophotographic liquid developing method for visualizing an electrostatic latent image on an electrostatic latent image carrier, magnetic fine particles mixed in a developing solution are removed by a magnetic field provided in a developing section. A liquid developing device characterized by the above.