JPS5849972A - Magnetic transfer device - Google Patents

Abstract

PURPOSE:To transfer a magnetic toner image onto a transfer material, by giving a magnetic field to the toner image on a toner image carrier placed in a prescribed relative positional relation. CONSTITUTION:When a transfer material 6 passes through a transfer position defined by the point where a photoreceptor and a belt 9 are close to each other, the magnetic field from the belt 9 acts upon the magnetic toner on the photoreceptor to transfer the toner onto the belt 9 with the magnetic force. In this case, the attraction based on the intensity of the magnetic field acting between the toner and the belt 9 is set to a value larger than that based on the electrostatic force between the toner and an electrostatic latent image. The relative positional relation between the belt 9 and the photoreceptor is set properly in accordance with the intensity of the magnetic field of the belt 9. Thus, the toner image formed on the toner image carrier is transferred with the magnetic force.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic transfer device that forms magnetic toner on a toner image carrier and transfers the toner image onto a transfer material, and is particularly suitable for application to electrophotographic copying machines. This invention relates to a magnetic transfer device. Conventionally, in a transfer-type electrophotographic copying machine, the surface of a photoreceptor is uniformly charged with a charge of a selected polarity, and then the uniformly charged charge is selectively removed by image exposure to generate a static latent gI. !
The electrostatic latent image is developed to form a toner image, and the thus formed toner image is transferred onto a transfer material by a transfer device. In this case, conventional transfer devices include those that use a bias roller and those that use a corona discharger, but generally those that electrostatically transfer the toner gII on the surface of the photoreceptor onto the transfer material. It is. By the way, when copy paper is used as a transfer material, it is affected by the environment such as humidity, and a conductive distribution is formed on the surface of the transfer material, causing uneven transfer. In particular, in a transfer device using a corona discharger, the corona discharge characteristics themselves are easily affected by the external environment (especially humidity), so the degree of uneven transfer F
There is a tendency for the situation to worsen over time.

Conventional transfer devices are based on electrostatic attraction because the toner is comprised of an insulating material that has charge retention properties. That is, when using a magnetic brush as a developing device, it is common to mix toner charged to a predetermined polarity with a carrier such as iron powder that is both conductive and magnetic. (Place 1, two-component developer) In this case, the toner is attracted to the electrostatic latent image composed of charges of opposite polarity and is developed to form a toner image, while the carrier is used again to form a magnetic brush. . By the way, in such a two-component developer, if the mixing ratio of toner and carrier changes too much, it will cause uneven development, so it is necessary to keep the mixing ratio as constant as possible. The equipment had to become more complex. Therefore, in recent years, magnetic toner containing a magnetic material (so-called
-component developer) was proposed, and it has come to be expected that it will equalize the developing performance and simplify the developing device.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a magnetic transfer device that uses magnetic toner to form an image on a toner image carrier and then transfers the toner image onto a transfer material using magnetic force. This is the purpose. That is, the magnetic transfer device of the present invention includes a positioning means for positioning the transfer material at least partially in a predetermined relative positional relationship with the toner image carrier, and a toner image carrier positioned in the predetermined relative positional relationship. The apparatus is characterized in that it has a magnetic field applying means for applying a magnetic field to the upper toner image, and the toner is transferred onto the transfer material by the magnetic field. Therefore, unlike the prior art in which transfer is performed using electrostatic attraction, the present invention performs transfer using magnetic attraction. Therefore, the toner needs to be a magnetic toner. 6 When the present invention is applied to an electrophotographic copying machine, it is possible to use a photoreceptor as a toner image carrier, and a electrostatic latent image is formed on the photoreceptor by performing a conventionally known electrophotographic process, and a magnetic It is also possible to apply toner to form a toner image and then transfer it to a transfer material using the magnetic transfer device of the present invention.

Various embodiments can be considered as the positioning means and the magnetic field applying means. For example, the positioning means may be an endless belt stretched between at least one pair of rollers, and the magnetic field applying means may be a plurality of belts distributed within the belt. It is possible to use embedded magnetic pieces. In this case, in order to improve the reproducibility of the transferred image, it is preferable that the average dispersion distance of the large number of magnet pieces is smaller than the toner diameter.
It is preferable that the belt has conductivity and is connected to a predetermined potential, for example, ground. On the other hand, it is also possible to use a magnetic sleeve as the positioning means and to arrange at least one magnet within the sleeve as the magnetic field applying means. In history,
When the magnetic toner that has been electrostatically attracted to the toner carrier is transferred onto the transfer material using magnetic force, it is desirable to eliminate the electrostatic latent image before transfer. It is preferable to provide a static eliminating means for neutralizing the latent image.

When the toner image bearing member is a photoreceptor having a photoconductive material layer, it is preferable to use a static eliminating device that makes the photoconductive material layer conductive as such a static eliminating means.

Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing one embodiment of the present invention applied to an electrophotographic copying machine, FIG. 2 is an explanatory diagram showing another embodiment of the present invention, and FIG. 3 is a silent latent image. FIG. 4 is an explanatory diagram showing a static elimination lamp for removal, and FIG. 4 is an explanatory diagram illustrating the structure of a magnetic belt in which a large number of magnet pieces are dispersed and embedded, and the same elements are denoted by the same numbers.

Referring to FIG. 1, the photosensitive drum l has a photoconductive layer on a conductive substrate, and is rotated at a constant speed in the direction of the arrow. As the photoreceptor drum l rotates, the surface of the photoreceptor is uniformly charged to a predetermined polarity by the charger 2, and then the document image is imagewise exposed by the exposure device 3, and the uniformly charged charges are selectively removed. and forms an electrostatic latent image. A developing device 4 applies toner to the electrostatic latent image thus formed to perform development and form a visible toner image. Similarly, in this embodiment, development is carried out using a one-component developer (magnetic toner) containing a magnetic material.In the developing device 4, a rotating sleeve containing a built-in magnet is arranged close to the photoreceptor drum l. The toner drawn up by this sleeve is charged in a polarity opposite to that of the photoreceptor drum 1, and then brought into contact with the electrostatic latent image formed on the photoreceptor drum 1 to form the toner image.

The toner image formed on the photoreceptor is then sent to a transfer device 5 and transferred onto a transfer material 6. On the other hand, toner remaining on the photoreceptor without being transferred by the transfer device 5 is cleaned by the cleaning device 7. The photoreceptor is then ready for the subsequent copying process.

Transfer device SFi is a magnetic transfer device implementing the present invention, and in the transfer device 5 shown in FIG. 1, a pair of rows 2
An endless magnetic belt 9 is provided stretched between 8a and 8gb, and is driven and rotated in the direction of the arrow in synchronization with the photosensitive drum 1.

An example of the structure of the magnetic belt 9 is shown in FIG. 4, and it is composed of a belt body 9a made of a conductive elastic material and magnet pieces 9b of the number of sub-lengths embedded in the belt body. In this case, the belt body 9a is made of an elastic material such as rubber, and the magnet pieces 9b are magnetized by embedding conductive magnetic powder such as iron powder or powdered ferrite inside the belt body 9. The average dispersion distance p of the magnet pieces 9b, which constitutes the conductive magnetic belt as a whole, is set to be smaller than the average particle diameter of the magnetic toner used.

Further, in order to encourage the transfer material 6 to be separated from the photosensitive drum l side and attached to the belt 9, it is preferable to connect the belt 9 to ground. Further, a row 28ali disposed close to the photoreceptor drum l side maintains a predetermined distance between the photoreceptor and the belt 9. In this case, it would be better if the belt (belt) 9F1; is pressed against the surface of the photoreceptor, but it is necessary to form a predetermined gap between the photoreceptor and the belt 9, and it remains on the photoreceptor drum 1 during non-transfer. It is possible to prevent the adhered toner from being transferred to the belt 9 and contaminating the belt 9.

A temporary attachment device 1O is disposed above the conveyance path of the belt 9, and temporarily attaches the toner image transferred from the photoreceptor onto the transfer material 6 to the transfer material 6. It is desirable to dispose it as close to the transfer position as possible, taking into account the effects of heat (such as thermal effects on the photoreceptor). As the temporary fixing device 10, it is preferable to use a flash fixing device or the like that instantaneously melts and fixes the toner using radiant heat.On the other hand, the belt 9 may be a plurality of thin belts stretched with gaps between each other or a large number of holes. It is composed of one or more perforated belts, and a suction device 11 is disposed below the conveyance path of the belt 9. Air is sucked from a suction port provided at the top of the suction device 11, and the belt The transfer material 6 placed on the belt 9 is firmly held by the belt 9. A fur brush 12 is disposed below the return path of the belt 9 and close to the roller 8a side, and is driven and rotated while rubbing the surface of the belt 90 to scrape off toner remaining on the belt 9. . The brush 12 also rubs against the blade 13 to clean off the scraped toner, and the toner removed from the brush 12 by the blade 13 is collected into the collection chamber 14. The transfer device 5, in particular the magnetic bell) 9t, is surrounded by a housing 15a, tsb. These housings 15a and 15b are made of magnetic material such as iron plates,
It is preferable to adopt a configuration that also provides magnetic shielding.

To explain the operation of the transfer device 5, the photosensitive drum 10
The registration gula 16 is driven in synchronization with the rotation, and the transfer material 6 is fed. When the transfer material 6 passes through a transfer position defined by the proximity point between the photoreceptor and the belt 9, the magnetic field from the belt 9 acts on the magnetic toner on the photoreceptor, causing the toner to be separated by magnetic force. It is transferred onto the belt 9. In this case, the attractive force based on the magnetic field strength acting between the toner and the belt 9 is:
It must be greater than the attraction force based on electrostatic forces between the toner and the electrostatic atom.

Note that the relative positional relationship between the belt 9 and the photoreceptor can be set as appropriate depending on the magnetic field strength of the belt 9.

Further, in embodiment C, since the toner holds a charge of opposite polarity to the electrostatic latent image, if the belt 9 is made of a conductive material and is connected to ground, the belt at the transfer position is 9
A charge having a polarity opposite to that of the toner forming the toner image is induced in the portion.

Therefore, the electrostatic attractive force between the toner and the electrostatic latent image is reduced, so that the toner is easily transferred onto the transfer material 6, and the charge of the toner existing via the transfer material 6 and the charge in the belt 9 are reduced. Since the induced charges are of opposite polarity, the transfer material 6 tends to be separated from the photoreceptor and attracted onto the cutout 9.

By the way, when a toner image is formed by a so-called reversal development method in which the charge polarity of the donor is the same as that of the electrostatic latent image and the toner is attached to the non-charged portion of the latent image, the toner is transferred to the toner at the time of transfer. Although the electrostatic force that attracts the image carrier does not work, it is still a good idea to connect the conductive belt to ground in order to improve transfer efficiency. 4. In order to reliably separate the transfer material 6 from the photoreceptor even if it adheres to the photoreceptor for some reason, it is preferable to provide a separation claw 17.

The transfer material 6Fi transferred and separated as described above is temporarily attached by the temporary fixing device 10, then sent to the fixing device 18, completely fixed, and discharged onto the tray 19. Further, in order to increase the magnetic field strength at the transfer position, it is also possible to arrange an external magnet within the roller 8a or the like. When an external magnet is provided in this manner, the belt 9 may be made of a non-magnetic material without providing the magnet piece 9b'.

FIG. 2 shows another embodiment of the invention, in which the row 28
There are nine ways to install the sleeve 2o and the magnet 21. That is, the sleeve 20i, which is preferably made of a magnetic material, and the photoreceptor drum l.
It is rotatably arranged at a predetermined distance from the photoreceptor provided on the j1 surface, and a magnet 21 is arranged inside it.

Therefore, the magnetic toner 22 on the surface of the photoreceptor is transferred onto the transfer material 6 under the influence of the magnetic field generated from the magnet 21 at the transfer position. Although FIG. 2 shows a case in which one magnet 21 is provided, a plurality of magnets may be provided.

Next, referring back to FIG. 1, another embodiment of the present invention will be explained. That is, in this other solution, a charge eliminating means 23 is provided upstream of the transfer position for removing the electrostatic latent image on the photoreceptor as a toner carrier. The toner particles that form the toner image on the photoreceptor hold charges of opposite polarity to the electrostatic latent image within the photoreceptor, and are therefore attracted and adhered to the photoreceptor by electrostatic force. In this case, the electrostatic latent image and toner are transferred onto the transfer material by the strength of the magnetic field against the electrostatic attractive force between the electrostatic latent image and the toner, so the electrostatic latent image and toner are transferred before transfer. It is possible to increase the transfer efficiency by reducing the electrostatic attractive force between the two. As such a static eliminating means 23, it is possible to use a known static eliminating device, a specific example of which is shown in FIG. 3. In other words, as shown in FIG. irradiation with a wavelength that makes the photoconductive material layer conductive, thereby removing the electrostatic latent image from the photoreceptor and weakening the electrostatic attraction between the toner image and the photoreceptor. It is possible to improve the transfer efficiency of transfer. Although this embodiment has been described using the static elimination lamp 24, it is also possible to use, for example, a corona discharger when the present invention is applied.

As explained in detail above, according to the present invention, a magnetic field is generated.
Since the transfer is performed by force, it is possible to always ensure the desired transfer performance, especially the uniformity of the transfer efficiency, without being affected by the external environment.

In addition, even when the transfer material is copy paper, uneven transfer is prevented, the transfer efficiency is not affected by the material of the transfer material, and the structure is simplified compared to conventional technology. Transfer can be performed without the need for a high voltage source.

In the above description, different embodiments of the present invention have been described in detail, but the present invention is not limited to these specific examples, and various modifications of #IC can be made without departing from the technical scope. is possible. That is, the present invention relates to a transfer device for toner images formed with magnetic toner, and is applicable not only to electrophotographic copying machines, but also to electrostatic printing machines, electrophotographic engraving machines, facsimile machines, and rape/reproduction machines. 'l
Of course, it is also widely applicable to Japan, Japan, etc. Therefore, the method of forming an electrostatic latent image is not limited to the above-mentioned specific method, but various methods can be applied.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing one embodiment in which the present invention is applied to an electrophotographic copying machine, Fig. 82 is an explanatory diagram showing another embodiment of the present invention, and Fig. 3 is an electrostatic latent image charge removal FIG. 4 is an explanatory diagram showing an example of the structure of a magnetic belt in which a large number of magnet pieces are completely dispersed and embedded. (Explanation of symbols) 5: Magnetic transfer device 6: Transfer materials 8a, 8b: Rollers 9: Magnetic belt 20: ,1. IJ-7'21: al
Stone patent applicant Rico Co., Ltd. −

Claims (1)

[Scope of Claims] 1. In a magnetic transfer device that transfers a toner image formed with magnetic toner on a toner image carrier onto a transfer material, the transfer material is at least partially in contact with the toner image carrier in a predetermined manner. and a magnetic field applying means that applies a magnetic field to the toner image on the toner image bearing member positioned in the predetermined relative positional relationship, and the toner at transfer material is moved by the magnetic field. A magnetic transfer device characterized by transferring onto the surface. 2. In the magnetic transfer device according to item 1 above, the toner image carrier is a photoconductor having a photoconductive material layer, and the toner image is transferred to a nine-electronic latent image formed on the photoconductor. A magnetic transfer device characterized in that it is formed by electrostatic attraction. 3. In the magnetic transfer device according to item 1 or 2 above, the toner image carrier is an endless rotating body that can be driven and rotated, and the positioning means is stretched between at least one pair of rollers and Endless bell driven in synchronization with the body) 1
- A magnetic transfer device, wherein the magnetic field applying means includes a large number of magnet pieces dispersed and buried within the belt. 4. The magnetic transfer device according to item IEa above, wherein an average dispersion distance of the magnet pieces dispersed and embedded in the belt is smaller than an average particle diameter of the toner. 5. Above a! 4. The magnetic transfer device according to item 3, wherein the endless belt is electrically conductive and connected to a predetermined potential. 6.J: The magnetic transfer device according to item 5, wherein the predetermined potential is a ground potential. 7. In the magnetic transfer device according to item 1 or 2 above, the toner image carrier is an endless rotating body that can be driven and rotated, and the positioning means is a magnetic transfer device that is driven and rotated in synchronization with the rotating body. A magnetic transfer device comprising a sleeve, wherein the magnetic field applying means is disposed within the magnetic sleeve and has at least one magnet. 8. In a magnetic transfer device that transfers a toner image formed of good magnetic toner attracted by electrostatic force onto a toner image carrier onto a transfer material by magnetic force, the electrostatic latent on the toner image carrier is eliminated. static eliminating means; positioning means for positioning the transfer material at least partially in a predetermined relative positional relationship with the toner image bearing member; and a toner image on the toner image bearing member positioned in the predetermined relative positional relationship. 1. A magnetic transfer device, comprising: a magnetic field applying means for applying a magnetic field, and a toner image is transferred onto a transfer material by the magnetic field. 9. In the magnetic transfer device according to item 8 above, the toner image carrier is a photoreceptor having a photoconductive material layer;
A magnetic transfer device, wherein the toner image is formed by electrostatically attracting the magnetic toner to an electrostatic latent image formed on the photoreceptor. 10. The magnetic transfer device according to item 9, wherein the static eliminating means is a static eliminating lamp that makes the photoconductive material layer conductive.