JPH0136110B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of obtaining an image on a sheet such as plain paper or plastic film by using a magnetic latent image created by magnetizing a magnetic material and magnetic particles.

2. Description of the Related Art So-called latent image development techniques for obtaining copies of input image information have been put into practical use in various forms and are becoming widely used.

Among these techniques, one called electrophotography is a method in which when a material called a photoconductive semiconductor is irradiated with light or other electromagnetic waves, compared to the unirradiated area,
It takes advantage of the increased electrical conductivity of the irradiated part, and allows image input to be performed instantly using light.
A duplicate image can be obtained relatively quickly. This duplicate image is often formed on paper or the like. However, in electrophotography, in order to obtain a single duplicate image, a photoconductor is charged, image exposed, an electrostatic latent image is formed, and developed with toner, which is an electroscopically colored particle. It requires a process of transferring the toner image onto paper or the like and fixing it using heat or the like to create a semi-permanent image on the paper. Furthermore, in order to reuse the photoconductor, a step of cleaning the toner remaining without being transferred is also required.

Therefore, it is a suitable method for obtaining a relatively small number of duplicate images from an original image, but it is difficult to obtain a large number of duplicate images due to the processing time and time required for each step. It is said that this technology is subject to considerable restrictions in terms of maintaining reliability.

Other methods for obtaining a duplicate image of the original image on plain paper are essentially the same as those required in electrophotography: charging (imparting sensitivity), exposing (forming a latent image), developing, transferring, and fixing. , requiring six cleaning steps for reuse.

Among these, the technology called magnetography in particular forms a magnetic latent image in the form of image-like magnetization of a magnetic material, and uses so-called magnetoscopic particles, which contain a magnetic material and are subjected to a force by a magnetic field. The image is developed with magnetic toner, electrostatically or magnetically transferred to plain paper, etc., and fixed using heat, pressure, etc. to create a semi-permanent image. For reuse, it is necessary to clean the magnetic latent image carrier, which requires approximately the same six steps as electrophotography. The advantage of this method is that either electrical dots or optical image exposure can be used as image information input, and the temporal stability of the magnetic latent image is utilized to eliminate the step of forming the latent image. In principle, it is possible to obtain multiple duplicate images at high speed by repeatedly using a partially formed magnetic latent image many times.

In particular, a recording member having a magnetic latent image is brought close to or in contact with a developing member having magnetic toner electrostatically adhered to its surface, and the magnetic force between the magnetic latent image and the magnetic toner is transferred between the developing member and the magnetic toner. According to the method for developing a magnetic latent image, which develops the magnetic latent image by overcoming the electrostatic force of the magnetic latent image, the developing means is not magnetic, so the magnetic latent image is not destroyed even if the development is repeated many times, and Since the magnetic toner can be brought close to the magnetic latent image, good development can be performed.

However, in this method, since the developing member does not have magnetic force and the toner is attached only by electrostatic force, it is not possible to uniformly supply magnetic toner onto the developing member for development. It was difficult. This invention is intended to improve the above-mentioned drawbacks, and an object of the invention is to uniformly and stably supply toner to a developing member.

Further, the present invention aims to realize good development in the above-mentioned latent image development technique.
Furthermore, the present invention provides a developing method that can achieve the purpose of obtaining a large number of duplicate images by forming a magnetic latent image once.

In the present invention, a magnetic toner supplying member holding magnetic toner on its surface by magnetic force is brought close to or in contact with a developing member which is grounded via a bias power source, and magnetic attraction force between the supplying member and the magnetic toner is provided. is smaller than the electrostatic force between the developing member and the magnetic toner, so that the magnetic toner is uniformly and electrostatically attached to the surface of the developing member, and a magnetic latent image is formed on the developing member to which the toner is attached. The above object is achieved by a method of developing a magnetic latent image in which the magnetic latent image is developed by bringing the recording member close to or in contact with each other so that the magnetic force between the magnetic latent image and the magnetic toner outweighs the electrostatic force between the developing member and the magnetic toner. be.

The donor roll is a conductive roll made of a non-magnetic material to which a bias is applied, and is more preferably provided with an insulating layer {1 μm to 10 mm, plastic film (Mylar, etc.)} on the surface.

In addition, in order to supply toner uniformly and stably to the donor roll, a magnetic roll (which has a non-magnetic sleeve and a magnet inside it and holds the magnetic toner by magnetic force) is used as the toner supply member, and the donor roll and This is done through the exchange with the magnetic roll and the competition between electrostatic attraction and magnetic attraction.

FIG. 1 shows a schematic configuration of the latent image developing system used in the present invention. The explanation will be given below according to the numbers in the figure.
The surface of the magnetic drum 1 is made of a recording layer made of a magnetic material such as iron oxide or chromium dioxide. This shape may be any shape other than the cylindrical shape shown in the figure, such as a belt shape. Cylindrical drum 1 is indicated by arrow 1
Assume that it rotates in one direction. The write magnetic head 2 magnetizes a magnetic body in accordance with an image signal decomposed into dots or lines. A recording member 10 such as paper is passed along a guide 9 from a direction 7 and wound around a magnetic drum 1 on which a magnetic latent image is formed.

The wound recording member 10 is attached to the magnetic drum 1
It is also sent to the developing station 4. At the developing station 4, colored magnetic particles (magnetic toner)
The toner is selectively attracted to the magnetic latent image on the magnetic drum, so when the magnetic drum and recording member are sent to the developing station, the magnetic toner is applied to the recording member according to the magnetic latent image. Attach to.
After passing through the developing station 4, the magnetic toner remains attached to the recording member due to the magnetic force of the magnetic latent image and is sent to a peeling station 5, where the recording member and the magnetic drum are separated. The recording member is then sent to a fixing station 6, where the magnetic toner is fixed onto the recording member as a final semi-permanent image.

The magnetic drum is then demagnetized at the erase magnetic head 3 and is ready for reuse.

A magnetic latent image has good persistence over time, and if this latent image development process is non-destructive to the magnetic latent image, it is possible to create multiple sheets using a single magnetic latent image. It is possible to obtain a duplicate image. At this time, when forming a magnetic latent image, the writing magnetic head 2 is brought into a substantially operational state. During a cycle for producing a large number of copies, both the writing head 2 and the erasing head 3 are kept in a substantially non-operating state, such as by being separated from the magnetic drum 1, and only the developing and peeling operations are performed.
When the cycle for a large number of sheets is completed, the erasing head 3 is operated.

The magnetic latent image forming method described here is just one example, and uses the heat generated by image exposure.
Any method can be used, such as the so-called Curie point demagnetization method or a method that utilizes the optical magnetism effect in which magnetic permeability decreases due to light exposure.

As the developing station in this latent image developing method, any developing method used in a technique called magnetography can be used. Typical methods include a method in which the magnetic toner is caused to fall according to gravity (cascade) and a method in which the magnetic toner is conveyed to the vicinity of the development position using a magnet. However, in this latent image developing technology, in which magnetic toner is attached to a magnetic latent image using a recording member such as paper, the preferred form to be used is to electrostatically transport the magnetic toner to the development position. There is a method in which development is performed by antagonism between an electrostatic force between a member serving as a means and magnetic toner, and a magnetic force between a magnetic latent image and magnetic toner.

According to this method, since the developing means is not magnetic, the magnetic latent image is not destroyed even if development is repeated many times. Since the magnetic latent image can be brought substantially close to the magnetic latent image, good development can be performed.

FIG. 2 is an example of a preferred development method used in the present invention. A recording member 10 is superimposed on a magnetic latent image formed on a magnetic drum 1 and is rotating in a direction 11. The magnetic toner accumulated at the position shown at 15 moves around the permanent magnet roll 13 in accordance with the rotation of the permanent magnet roll 13, which is magnetized alternately to the south pole and the north pole. The bias roll 12 is rotated in a direction 19 while being biased by a bias power supply 18 . On the surface of the bias roll, an electrostatic potential corresponding to the bias power supply voltage is generated, so a charge with the opposite polarity to this electrostatic potential is induced in the magnetic toner, and this induced charge and electrostatic potential (electric field) Due to the Coulomb force, the magnetic toner adheres to the bias roll 12 and is transported to the development nip 22.

In this developing nip, in the area where the magnetic force is present due to the magnetic latent image appearing through the recording member 10, the magnetic force overcomes the Coulomb force, and the magnetic toner leaves the developing nip while being attached to the recording member (see 17). . On the other hand, magnetic toner does not adhere to areas where there is no magnetic latent image.

In this developing method, the electrostatic potential generated by the bias roll 12 greatly contributes to the developing characteristics. At this time, it is necessary to substantially maintain the electrostatic potential acting on the magnetic toner. For this reason, when a magnetic toner with good conductivity is used, it is necessary to form the bias roll from a material with low surface conductivity.

FIG. 3 is an example in which the shape of the bias roll shown in FIG. 2 is changed. In FIG. 3, an insulating layer 21 is provided on the surface of the conductive core 20 so that only an electric field is applied to the magnetic toner while electrical continuity between the bias roll and the magnetic toner is cut off. This is a more preferred embodiment as a latent image developing method.

Another important point in the developing method of the present invention is that it prevents the magnetic toner from adhering to the non-image area of the recording member by a short-range force such as the Van der Waals force. be.

To this end, various forms of countermeasures can be considered. FIG. 4 shows that a bias 23 having the same polarity as the electrostatic potential of the second conveying means is applied to the magnetic latent image carrier to provide electrostatic repulsion to the magnetic toner, thereby transferring the magnetic toner to the non-image area. This is a method to prevent toner from adhering. Further, FIG. 5 shows a method of removing the magnetic toner adhering to the non-image area where there is no magnetic latent image using air pressure from the blower 24 after the development is completed.

In this manner, a developing station suitable for the latent image developing method of the present invention is constructed. Another advantage of the developing method of the present invention, which basically uses electrostatic force to convey magnetic toner to the development position, is that the amount of magnetic toner conveyed can be adjusted by controlling the electrostatic force. This allows the density of the duplicated image to be adjusted.

In the examples of FIGS. 2 to 5, the density of the duplicated image is adjusted by changing the bias voltage applied to the bias roll.

[Brief explanation of drawings]

1 to 5 schematically represent an embodiment of the apparatus used in the method of the invention. Codes in the figure: 1...Magnetic drum, 2...Magnetic head for writing, 3...Magnetic head for erasing, 4...
...Development station, 5...Recording member peeling station, 6...Fixing station, 7...Recording member entrance, 8...Recording member exit, 9...Recording member conveyance guide, 10...Recording member, 11...Rotation Direction, 12... Bias roll, 13... Permanent magnet roll, 14... Magnetic toner reservoir, 15, 16.
17... Magnetic toner, 18... (variable) bias, 19... Rotation direction, 20... Conductive core roll, 21... Surface insulating layer, 22... Development nip,
23...Bias power supply, 24...Blower.

Claims (1)

[Claims] 1. A magnetic toner supply member holding magnetic toner on its surface by magnetic force is brought close to or in contact with a developing member that is grounded via a bias power source, and the magnetic attraction force between the supply member and the magnetic toner is applied to the developing member. Magnetic toner is uniformly electrostatically attached to the surface of the developing member in a manner that is smaller than the electrostatic force between the member and the magnetic toner, and a recording member having a magnetic latent image is formed on the developing member to which the toner is attached. A method for developing a magnetic latent image, in which the magnetic latent image and the magnetic toner are brought into close proximity or in contact with each other, and the magnetic force between the latent image and the magnetic toner is greater than the electrostatic force between the developing member and the magnetic toner.