JPS623420B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for developing and fixing an electrostatic latent image in an electrophotographic system.

In electrophotography, development is performed by adhering toner to an electrostatic latent image formed by some means, but conventional methods have used a two-component developer containing toner and magnetic metal powder. This toner is finally fixed on the recording medium by heating. In addition, when an electrostatic latent image is formed on an intermediate medium, developed, and transferred to transfer paper, the toner adsorbed on the intermediate medium is electrostatically transferred to the transfer paper by applying an electric field. However, the disadvantage is that the transfer paper is electrostatically attracted to the intermediate medium and is difficult to peel off. Further, the developer is applied to the entire surface of the electrostatic latent image carrier using a coating roller, a brush, etc., and the toner is electrostatically attracted only to the charged portion, thereby performing development. However, the solvent of the developer wets not only the charged portion, but also the entire surface of the electrostatic latent image carrier, and is also absorbed by the transfer paper.
During the fixing, it is necessary not only to heat the toner but also to evaporate and dry the solvent, and depending on the type of transfer paper, this liquid absorption and drying may cause shrinkage.

The present invention is characterized in that an electrostatic latent image is developed using a magnetic fluid, and eliminates the need for heat fixing and the need for transfer by applying an electric field, which are required in the conventional method. The aim is to eliminate these drawbacks. By the way, first, what kind of magnetic fluid is used in the present invention will be explained. The original name for this fluid is ``Ferrofluid,'' and it was developed over ten years ago as a result of research in a field of NASA's space program, based on the need to control liquid fuel for rockets. It is a colloidal solution suspended in water or an organic solvent. Fe ₃ O ₄ is suitable as the magnetic fine particles, and its suspension, or magnetic fluid, has a deep black color, has very strong adsorption to paper, and does not come off with an eraser, etc., so it has excellent properties as an ink. have. Moreover, this magnetic fluid has the property of causing attraction and deformation due to magnetic induction when subjected to the action of a magnetic field. Also, the specific resistance of the magnetic fluid is 10 ⁹
It has a low resistance of Ωcm and can be treated as something close to a conductor in the field of electrophotography.

The present invention utilizes the above three characteristics of magnetic fluid, and FIG. 1 shows the principle thereof.

Reference numeral 1 denotes a recording medium capable of carrying an electrostatic latent image, and an electrostatic latent image marked with a + is formed on its surface. A permanent magnet 2 has a magnetic fluid 3 attracted to its upper magnetic pole. The magnetic fluid 3 is raised on the magnetic pole as shown in the figure, but the recording medium 1
has not been in contact with. When the recording medium 1 is moved from the state shown in figure a in the direction indicated by the arrow, the electrostatic latent image portion faces the permanent magnet 2 as shown in figure b. At this time, electrostatic induction of the electrostatic latent image generates a single-pole charge on the upper part of the magnetic fluid 3, producing an electrical attractive force. Then, as shown in figure c, a part of the magnetic fluid 3 near the surface is attracted to the electrostatic latent image + pole of the recording medium 1, and finally d
It is separated as shown in the figure. In this manner, the magnetic fluid 3' is attracted only to the electrostatic latent image portion of the recording medium 1, and does not adhere to other portions, so that the electrostatic latent image becomes a visible image. After that, it may be transferred to transfer paper or may be left adsorbed to the recording medium 1. In the former case, due to the water absorbency of the transfer paper, the transfer paper remains permanently due to its molecular attraction force even without any particular heat-fixing operation. In the latter case, if the recording medium 1 has water absorbency, it will be fixed as is, and even if it does not have water absorbency, it will be in a fixed state when the magnetic fluid 3' dries.

The above is the principle of the present invention, and FIG. 2 shows an example in which the principle is applied to electrostatic recording. Reference numeral 4 denotes a photoreceptor drum which rotates as shown by the arrow, and an image of the document is formed as an electrostatic latent image 6 on the photoreceptor drum 4 by an optical system 5 . A developing section 7 is composed of a container 9 filled with a magnetic fluid 8 and a rotating permanent magnet 10. The rotating permanent magnet 10 is held in a magnetic fluid 8, and a certain amount of the magnetic fluid 8 is constantly attracted to its surface by magnetic attraction. Incidentally, instead of the above-mentioned permanent magnet, a rotating non-magnetic sleeve having a solid permanent magnet arranged therein may be used in the same manner. In any case, the magnetic fluid 8 is not brought into contact with the photosensitive drum 4. Photosensitive drum 4
When the electrostatic latent image 6 passes through this developing section 7, the magnetic fluid 8 on the permanent magnet 10 receives the electric attraction force from the electrostatic latent image from the above-mentioned permanent magnet according to the above-mentioned principle. Since the electrostatic latent image 6 is strong, the magnetic fluid 8 is attracted to the electrostatic latent image 6 and becomes a developed image 11. The magnetic fluid does not adhere to the non-image area, which does not have a latent image, because no electrical attractive force is generated. The photosensitive drum 4 carrying the developed image 11 in this manner transfers the developed image 11 onto the transfer paper 13 in the transfer section 12 . The transfer section 12 is composed of a roller 14 that rolls into contact with the photosensitive drum 4, and there is no need to apply an electric field or the like for transfer, and only pressing by the roller 14 is sufficient. The transfer paper 13 pressed against the developed image 11 attracts the developed image 11 formed of the magnetic fluid 8 from above the photosensitive drum 4 by its own molecular adsorption force, and remains in a fixed state. Since the transfer paper 13 is not attracted to the photoreceptor drum 4, it naturally separates from the photoreceptor drum 4 without any special peeling operation. After that, the photoreceptor drum 4 passes through the cleaning section 16, is neutralized by the static eliminating charger 17, and then is charged again by the static eliminating charger 17.
8 to be charged and reused.

As described above, in the present invention, a magnetic fluid is attracted to an electrostatic latent image by electrostatic induction to form a developed image, and it is also fixed to a transfer paper or a recording medium by its own molecular adsorption force, so that it can be used for fixing. There is no need for a heater, and in the case of a transfer type, there is no need to apply an electric field during transfer, so the transfer paper can be easily peeled off from the intermediate medium, and the latent image is not disturbed during transfer. Since no electric field is applied, the latent image can be repeatedly developed, and multiple copies can be made by forming the latent image once. Magnetic fluid has particularly good performance as ink, so the developed characters and images are extremely sharp. It is characterized by extremely high image quality.

In addition, there is not only developer toner in the background area, but also
Since there is no contact with the solvent, the area will not get dirty and there will be no need to dry the solvent.

[Brief explanation of the drawing]

1A to 1D are explanatory diagrams showing the principle of the present invention, and FIG. 2 is a sectional view of a main part of an electronic copying machine embodying the present invention. 1... Recording body, 2... Permanent magnet, 3, 3'...
Magnetic fluid, 4...Photosensitive drum, 6...Electrostatic latent image, 8...Magnetic fluid, 11...Developer, 13...Transfer paper.

Claims (1)

[Scope of Claims] 1. Magnetic poles to which a magnetic fluid as ink is magnetically attracted are arranged to face each other on the surface of a recording body capable of carrying an electrostatic latent image, and this opposing interval is set such that the magnetic fluid is attached to the recording body. The distance between the charged part is such that it does not come in contact with the uncharged part, but the charged part generates electrostatic induction and is attracted to the recording medium, and development is performed by this attraction, and the molecules of the magnetic fluid caused by the recording medium are A method for developing and fixing an electrostatic latent image, which is characterized by fixing by suction force. 2. On the surface of a recording medium capable of carrying an electrostatic latent image, magnetic poles to which a magnetic fluid as an ink is magnetically attracted are disposed to face each other, and the spacing between the opposing magnetic poles is such that the magnetic fluid is attached to an uncharged area of the recording medium. does not come into contact with the charged portion, but the interval is such that electrostatic induction is generated in the charged portion and the recording medium is attracted, and development is performed by the attraction, and then a transfer paper is brought into contact with the recording medium, A method for developing and fixing an electrostatic latent image, characterized in that transfer is performed by the molecular attraction force of the transfer paper, and further, fixation is performed by the molecular attraction force.