JP4836116B2 - Micro magnetic head array and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly develop a digital latent image which is formed by each magnetic pole as a high resolution image, with the help of a developer. <P>SOLUTION: This micromagnetic head array 11 supported by a base 11d is equipped with an image creating device which forms a magnetic latent image by selectively energizing each magnetic pole (core) 11n and 11s of the micromagnetic head array 11, and a development device 2 which develops the magnetic latent image formed by each magnetic pole of the array 11. The digital magnetic latent image is formed by selectively energizing each magnetic pole of the array 11, and then is developed by the development device 2, and the developed image is transferred to a transfer medium 6 and fixed. In addition, the micromagnetic head array 11 is an assembly of magnetic pole (core) units 11a, each comprising a plurality of north poles 11n and one south pole 11s or a plurality of south poles 11s and one north pole 11n. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a magnetic image forming printer in which a magnetic latent image is directly formed on a magnetic pole (core) of a magnetic head array, then developed using a developer, transferred to a transfer medium such as paper or a substrate, and fixed. More particularly, the present invention relates to a micro magnetic head array having high resolution and a magnetic printer using the same. This technology can be applied to high-speed and high-resolution printing presses.

Conventionally, as a representative example of this type of technology, there is a magnetic printer using magnetography of NIPSON SA (http://www.nipson.com). This magnetic printer uses a magnetic head as in the present invention, but transfers a magnetic latent image to a magnetic thin film provided on the cylinder, and then uses a developer to transfer the magnetic latent image on the magnetic thin film on the cylinder. Then, the image is developed and further transferred to paper (see, for example, JP-A-2000-326547).
As described above, the mainstream of the magnetic printer is to form a magnetic latent image on a magnetic material using a magnetic head, and develop and transfer the magnetic latent image with a developer. For example, Japanese Patent Publication No. Sho 63-45598 (Latent image forming method) and Japanese Patent Publication No. 63-16065 (magnetic printing apparatus).
However, the above-described method requires not only secondary transfer but also cannot form a full-color image.

  In contrast, in the invention described in Japanese Patent No. 3642464 (magnetic printer: Japanese Patent Laid-Open No. 2000-263835), a micro magnetic head array is provided on a flexible substrate, and each element of the micro magnetic head array is provided. It is disclosed that a digital latent image is formed by energization, the image is developed with a developer, and then transferred to paper or the like.

However, according to the present invention, each element (core) of the micro magnetic head array is single, and there is no description of the magnetic field distribution by the arrangement of the N pole and the S pole, and the latent image is created by each element alone. However, in the case of a magnetic field (field), there is no single pole. According to the present invention, when energized, in the case of all N poles, the lines of magnetic force always return to somewhere in the micro magnetic head array and try to close the lines of magnetic force. In such a structure, the magnetic fields cancel each other in the vector direction. In addition, since a magnetic head is a device that uses a leakage magnetic field in the first place, the magnetic circuit is unstable in such a structure, the magnetic flux distribution is very complicated, and each element (core of the micro magnetic head array) ) Large magnetic flux density cannot be obtained. Furthermore, according to the present invention, since the aspect ratio (element height / cross-sectional diameter) of the dimensions of each element is very small, the demagnetizing field due to shape anisotropy is very large even when energized. There is.
Therefore, in such a structure, it is very difficult to develop the developer by adsorbing the developer to each element.

Japanese Patent No. 3642464 JP 2000-326547 A Japanese Examined Patent Publication No. 63-45598 Japanese Examined Patent Publication No. 63-16065

Accordingly, an object of the present invention is to provide a micro magnetic head array capable of realizing a full color image with high resolution by solving the above-described problems in the conventional technology, and an image forming apparatus using the same. .
Specifically, by optimizing the arrangement relationship and dimensions of the N pole and S pole in the micro magnetic head array, the magnetic circuit (magnetic flux distribution) is further stabilized, and the arrangement of the magnetic pole (core) is further improved. By increasing the density and further increasing the leakage flux at each magnetic pole, the technical challenge is to reliably develop the digital latent image formed at each magnetic pole with a developer while maintaining high resolution. is there.

The means for solving the above problems is to form a micro magnetic head array by an assembly of magnetic pole (core) units composed of a plurality of N poles and one S pole, or a plurality of S poles and one N pole. It is based on that.
(1) A solution for solving the above-described problem (corresponding to claim 1) is to selectively energize a micro magnetic head array supported by a substrate and each magnetic pole (core) of the micro magnetic head array. An image creating device for forming a magnetic latent image; and a developing device for developing a magnetic latent image formed on each magnetic pole of the micro magnetic head array, and selectively energizing each magnetic pole of the micro magnetic head array. A micromagnetic for a magnetic printer that forms a digital magnetic latent image, develops the digital magnetic latent image with the developing device, and then forms the image by transferring and fixing the developed image onto a transfer medium. A head array,
The micro magnetic head array is an assembly of magnetic pole (core) units composed of a plurality of N poles and one S pole, or a plurality of S poles and one N pole .
The distance between one S pole and a plurality of N poles in the magnetic pole unit, or the distance between one N pole and a plurality of S poles is at least three times the maximum diagonal (diameter) of the magnetic pole cross-sectional shape. is there.

In this way, by forming a magnetic pole (core) unit composed of a plurality of N poles and one S pole, or a plurality of S poles and one N pole, for example, four N poles and one S pole. The magnetic circuit can be further stabilized, and the leakage magnetic field at the end face of the magnetic pole can be increased.
Therefore, the digital magnetic latent image formed by energizing the magnetic pole can be more reliably developed with the developer.
Further, by making the distance between the S pole and the N pole not more than three times the maximum diagonal (diameter) of the magnetic pole cross-sectional shape, the magnetic field leaking from the end face of each magnetic pole can be further increased. This is because the magnetic field is a field of attenuation and divergence, and the magnetic field attenuation becomes more remarkable as the distance between the magnetic poles increases. If it is 3 times or less, the magnetic field leaking from the end face of the magnetic pole can be increased more reliably .
In order to make the following description easy to understand, all the descriptions of “a magnetic pole (core) unit composed of a plurality of N poles and one S pole or a plurality of S poles and one N pole” are “ The description will be made using a “magnetic pole (core) unit composed of a plurality of N poles and one S pole”.

(2) In the magnetic pole (core) unit, one S pole is surrounded by a plurality of N poles and can be provided at the same distance from the plurality of N poles. (Corresponding to claim 2)
With such a configuration, a high-density magnetic pole arrangement with an SN pole one-to-one structure, which was impossible with a conventional magnetic head, has become possible. When viewed from a plurality of N poles, the magnetic circuit is formed more stably because there is one S pole corresponding to each.

( Delete )

(3) The aspect ratio (major axis / minor axis) of the N pole (S pole) that is the magnetic pole of the magnetic pole (core) unit can be at least 1 or more. (Corresponding to claim 3 )
With such a configuration, it is possible to reduce the influence of the demagnetizing field and realize a smaller current when energizing the N pole (S pole). Therefore, the wiring of the coil becomes thinner and can be designed with high density, and the magnetic field (core) can be excited more reliably by suppressing the influence of the demagnetizing field, and a larger leakage magnetic flux can be applied to the end face of the magnetic pole. Can bring.

(4) Further , the height of the long axis of the one S pole can be made lower than the heights of the long axes of a plurality of N poles in the magnetic pole (core) unit. (Corresponding to claim 4 )
With such a configuration, the end faces of the plurality of N poles have a short distance from the developer, and the end face of one S pole has a long distance so that when viewed from the developer, the end faces of the plurality of N poles Since the leakage magnetic field is larger, the developer can be reliably developed on the end faces of a plurality of N poles. Therefore, the digital image dots can be made smaller.

(5) Each magnetic pole (core) of the micro magnetic head array can be composed of a ferromagnetic material having soft magnetism. (Corresponding to claim 5 )
With such a configuration, a larger magnetic field can be generated with a small excitation current more reliably. Further, since it is soft magnetic, it can be more easily demagnetized with an alternating current, so that the developer remaining on the micro magnetic head array after development and transfer can be more easily cleaned.

(6) Further , each magnetic pole (core) of the micro magnetic head array is selectively energized to form a digital magnetic latent image, the digital magnetic latent image is developed, and then the developed image is After transfer onto the transfer medium, demagnetization can be performed by passing an alternating current through each of the magnetic poles (cores), and the developer remaining on the magnetic poles (cores) can be easily peeled off. (Corresponding to claim 6 )
With such a configuration, after developing and transferring the image, each magnetic pole (core) is demagnetized, so that it is possible to more easily clean the developer remaining in the micro magnetic head array.

(7) A magnetic printer capable of forming a color image by repeatedly superimposing images using the micro magnetic head array described above, or a magnetic printer capable of forming a color image using a plurality of micro magnetic head arrays described above. can do. (Corresponding to claim 7 )
According to such a magnetic printer, a black (BK), cyan (C), magenta (M), and yellow (Y) developer is repeated four times to form a color image. A clear color image can be obtained.

(8) Each magnetic pole (core) of the above-described micro magnetic head array is selectively energized to form a digital magnetic latent image, and an average particle diameter of a developer for developing the digital magnetic latent image is 5 μm to 50 μm. A magnetic printer can be configured. (Corresponding to claim 8 )
According to such a magnetic printer, a clearer color image can be formed.

The effects of the present invention are summarized according to the claims as follows.
(1) The invention according to claim 1 The magnetic circuit is further stabilized by using the micro magnetic head array as an assembly of magnetic pole (core) units composed of a plurality of N poles and one S pole. Since the leakage magnetic field at the end face of the magnetic field can be further increased, the digital magnetic latent image formed by energizing the magnetic pole can be more reliably developed with the developer.
In addition, the magnetic field leaking from the end face of each magnetic pole can be increased more reliably by setting the distance between one S pole and a plurality of N poles to be not more than three times the maximum diagonal (diameter) of the magnetic pole cross section. I can .
(2) Invention of Claim 2 One S pole is surrounded by a plurality of N poles and provided at the same distance from the plurality of N poles, thereby enabling a high-density magnetic pole arrangement with a SN pole one-to-one structure. In addition, when viewed from a plurality of N poles, there is one S pole corresponding to each, and the magnetic circuit can be formed more stably.

(3) Invention of Claim 3 By making the aspect ratio (major axis / minor axis) of the magnetic pole of the magnetic pole (core) unit to be 1 or more, the influence of the demagnetizing field is further reduced, and the N pole (S pole) It is possible to carry out with a smaller current when energizing. Thereby, the wiring of the coil becomes thinner and can be designed with high density. Further, the influence of the demagnetizing field can be suppressed, and the magnetic pole (core) can be excited more reliably, resulting in a larger leakage magnetic flux at the end face of the magnetic pole.

(4) Invention according to claim 4 By making the height of the major axis of one S pole lower than the height of the major axes of the plurality of N poles in the magnetic pole (core) unit, the end faces of the plurality of N poles Since the distance to the developer is shorter than the end face of one S pole and the leakage magnetic field from the end faces of the plurality of N poles is larger, the developer can be reliably developed on the end faces of the plurality of N poles. Thereby, a digital image dot can be made smaller.
(5) Invention of Claim 5 Since each magnetic pole (core) of the micro magnetic head array is composed of a ferromagnetic material having soft magnetism, it is possible to reliably generate a larger magnetic field with a smaller excitation current. . In addition, since each magnetic pole is soft magnetic, it can be easily demagnetized with an alternating current, so that the developer remaining on the micro magnetic head array can be more easily cleaned after development and transfer. .

(6) Invention of Claim 6 After the developed image is transferred onto a transfer medium, demagnetization is performed by passing an alternating current through each magnetic pole (core), and the developer remaining on each magnetic pole (core) is removed. By facilitating peeling, the developer remaining on the micro magnetic head array can be more easily cleaned.
(7) Invention of Claim 7 According to such a magnetic printer, a black (BK), cyan (C), magenta (M), and yellow (Y) developer is repeatedly layered four times to form a color image. Therefore, a clear color image with higher resolution can be obtained.
(8) Invention of Claim 8 According to such a magnetic printer, a clearer color image can be formed.

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram of a magnetic printer, FIG. 2 is an explanatory diagram of a micro magnetic head array, and FIG. 3 is a diagram illustrating a magnetic circuit of the micro magnetic head array and an image of development.
(Basic configuration of magnetic printer)
First, the basic configuration of the magnetic printer according to the present invention will be described with reference to FIG.
A magnetic printer consists of five basic parts. The first part is an image creating unit that forms a magnetic latent image on the rotating drum 1 having the micro magnetic head array 11 disposed on the surface thereof. The rotary drum 1 may be a rigid cylindrical shape or a belt shape having a micro magnetic head array 11 arranged on the surface.
The second part is a developing unit that includes the developing device 2 having the developer 21 and develops the image of the magnetic latent image. The third portion is a transfer portion that transfers an image developed by the developer onto a transfer medium 6 such as paper via a roller 31. The fourth portion is a fixing unit including a fixing device (fixing roller) 4 that fixes an image of the developer transferred to the transfer medium 6 onto the transfer medium. The fifth portion is a cleaning unit including a cleaning device 5 that cleans the developer remaining on the rotary drum 1. Reference numeral 32 denotes a conveyance roller.

(Printing process of magnetic printer)
Next, a series of processes such as image formation, transfer, and fixing of the magnetic printer will be described.
First, each of the N (S) poles of the micro magnetic head array 11 is digitally applied to the micro magnetic head array 11 by an image creation device (not shown) that is turned on or off by switching based on the original image data. A magnetic latent image is formed. Here, the digital magnetic latent image is to excite each magnetic pole of the micro magnetic head array 11 based on the original image data. Although not shown, the excitation power source and the electric circuit constituting the image creating apparatus can be arranged inside or outside the rotating drum 1.

  The digital latent image portion formed on the rotating drum 1 is moved to the developing device 2 by the rotation of the rotating drum, and development is performed by attaching the developer 21 to the excited magnetic pole. The developer 21 may be a magnetic toner or a two-component (carrier and toner) developer. Here, a two-component developer will be used for explanation. The carrier of this developer is made of a ferromagnetic material such as ferrite and is positively charged, and the toner is negatively charged. Accordingly, both the carrier and the toner adhere to the micro magnetic head array 11.

The rotating drum 1 is further rotated and moved to a transfer portion to which a bias voltage is applied. At this time, since the transfer medium 6 such as paper is positively charged by the bias voltage, only the negatively charged toner is transferred to the transfer medium 6, and the positively charged carrier is left as it is in the magnetic pole of the micro magnetic head array 11.
Finally, an alternating current is applied to the magnetic pole of the micro magnetic head array 11 after the transfer to demagnetize, and the remaining carrier is scraped off by a cleaning device (brush or the like) 5 and the transfer medium 6 onto which the toner has been transferred is removed. The paper is conveyed to the fixing device 4 and finally printing is completed by a fixing process.

(Micro magnetic head array)
The micro magnetic head array 11 according to the present invention will be described with reference to FIG.
For the substrate 11d, for example, a flexible material such as a plastic (polyimide) sheet or a thin metal plate is used. After the micro magnetic head array 11 is formed on the substrate 11d, it is brought into close contact with the surface of a hard metal drum or glass drum and integrated. Alternatively, the micro magnetic head array 11 may be directly formed on a hard Si or glass substrate. As the head material, a soft magnetic material used for a high permeability core is desirable. For example, a low coercive force, high saturation magnetic flux density, and high magnetic permeability material such as Fe-Si-B-C amorphous alloy, FeP, permalloy (NiFe alloy), FeCoP, CoP, FeB, FeBSi, and silicon steel are preferable. For the pattern formation of the magnetic poles 11n and 11s, a plating method, etching, or the like is used. The shape of the magnetic poles 11n and 11s is preferably a cylinder or a truncated cone. The excitation coil (wiring) 11b is basically made of Au, Cu, Al or the like having a small resistance. Although the wiring width is limited by the size and pitch of the magnetic poles, a planar coil is basically adopted. The exciting coil 11b was formed mainly by plating. Further, an insulator 11c is provided between the magnetic poles 11n and 11s and the wiring 11b. Furthermore, a protective film 11e of DLC (diamond-like carbon), Si, or SiO ₂ having a thickness of about 20 nm is provided on the uppermost surface.

A high-resolution image forming process by the magnetic pole (core) unit 11a composed of a plurality of N poles 11n, 11n... And one S pole 11s, which is a feature of the present invention, will be described with reference to FIG. It can be seen that the magnetic field circuit (magnetic flux flow) is most stable due to the structure as described above. Leakage magnetic flux can be reliably concentrated on the magnetic pole. Since the magnetic field is a decay field, the middle S pole 11s is lower than the surrounding N poles 11n, 11n, etc., so that it is possible to collect the developer 21 on the N pole 11n during development. In this way, a high resolution image can be obtained.
Although not shown, the number of the plurality of N poles 11n, 11n,... In the magnetic pole (core) unit 11a composed of the plurality of N poles 11n, 11n,. For example, it may be 2 poles, 3 poles, 5 poles or 6 poles.

Next, Embodiment 1 of the present invention will be described with reference to FIGS.
First, the micro magnetic head array 11 was produced as follows.
(1) A 0.2 mm thick stainless steel (SUS304) substrate 11d is exposed using an exposure dry film (negative) (DuPont: Liston 4840) and a mask, and then plated with permalloy (NiFe alloy). Thus, a base portion A was produced as shown in FIG. The thickness of the base portion A was 100 μm.
(2) Further, an exposure dry film was further adhered thereon, and exposure was performed with an exposure mask. Then, as shown in FIG. 2B, a 5-pole post having a diameter of 100 μm made of permalloy was produced by plating. The pitch interval between the four poles 11n, 11n... At the outer peripheral portion was 200 μm. The fifth pole 11s was arranged at the center of the four pole post. The height of the 5-pole post was 180 μm.

(3) Further, the height of only the outer peripheral four poles 11n, 11n,... Finally, the outer peripheral 4 poles 11n, 11n... Were 200 μm high, and the central 1 pole 11s was 180 μm high.
In this way, a cylindrical post B was produced as shown in FIG.
(4) Subsequently, after removing the exposure dry film, a polyimide resin is applied as an insulator 11c between NiFe posts (electrodes) produced by plating, and the thickness thereof is 300 μm. , 11n...
(5) The polyimide resin layer was patterned, and a Cu wiring 11b was formed around the NiFe magnetic pole by plating. The wiring 11b was a planar coil 11b having a width of 10 μm, a depth of 20 μm, a width-to-width pitch of 5 μm, and two turns.
(6) Finally, after planarizing the surface, a SiO ₂ protective film 11e having a thickness of about 20 nm was provided thereon by sputtering.

  Next, based on the original image data, each N (S) pole of the micro magnetic head array 11 manufactured as described above is turned ON or OFF by a switch using an FET (field effect transistor), and digital magnetic A latent image is formed. Here, the digital magnetic latent image is to excite the magnetic poles 11n and 11s of the micro magnetic head array 11 based on the original image data. Although an excitation power source and an electric circuit are not shown, they may be arranged inside or outside the rotary drum 1. Next, the rotation of the rotating drum 1 moves the digital latent image portion formed thereon to the developing device 2, and the developer 21 is attached to the excited magnetic pole for development. As the developer 21, a two-component developer (comprising a carrier and a toner) was used. The carrier of this developer is made of ferrite and is positively charged, and classification is performed so that the average particle diameter is 15 μm. The average particle size of the toner is 5 μm.

  When the rotating drum 1 is further rotated, it is moved to a transfer portion to which a bias voltage is applied. At this time, since the paper 6 is positively charged by the bias voltage, only the negatively charged toner is transferred to the paper 6, and the positively charged carrier is left as it is in the magnetic pole of the micro magnetic head array 11. Finally, demagnetization was performed by passing an alternating current through the magnetic poles of the micro magnetic head array 11 after transfer, and the remaining carrier was scraped off by a cleaning device (brush or the like) 5. Then, black (BK), cyan (C), magenta (M), and yellow (Y) are respectively developed and transferred four times by one rotating drum 1 in the same cycle, and then the paper 6 is transferred to the fixing device 4. The color image formation was finally completed by conveying and fixing process.

The transfer by the above four cycles is not only directly transferred onto paper, but an intermediate transfer belt or the like may be used. Further, instead of performing four cycles with one rotating drum, a four-tandem tandem system as shown in FIG. This quadruple tandem magnetic printer includes four of the same print units as shown in FIG. That is, it is composed of a BK print unit 101 that forms a black image, a C print unit 102 that forms a cyan image, a Y print unit 103 that forms a yellow image, and an M print unit 104 that forms a magenta image. 4 is a photograph showing a state in which the micro magnetic head array on the surface of the rotating drum is actually developed with the developer, which shows four dots in one magnetic pole (core) unit 11a.

Next, a second embodiment of the present invention will be described.
The second embodiment has the same configuration as the first embodiment, but the developer uses silver particles instead of toner. The silver particles are aggregates of primary particles of several tens of nm, and the average particle diameter of the aggregates is about several tens of μm. A silver wiring pattern having a width of 100 μm and a pitch of 200 μm could be printed on a PET film having a thickness of 100 μm by the same process as in Example 1 by mixing the silver particles with 30 μm ferrite particles.
Note that the embodiments and examples of the present invention are examples for explaining the present invention in an easy-to-understand manner, and the present invention is not limited to these descriptions.

FIG. 2 is a schematic diagram for explaining a magnetic printer according to an embodiment of the present invention, where (a) is a schematic diagram of a basic configuration thereof, and (b) is a schematic diagram of a four-tandem color image forming system. These are explanatory drawings of the micro magnetic head array by embodiment of this invention, (a) is the bird's-eye view, (b) is the sectional view, (c) is the perspective view. These are the figures explaining the image of the magnetic circuit of the micro magnetic head array by embodiment of this invention, and image development. These are photographs of a state in which a micro magnetic head array (one magnetic pole unit) is developed with a developer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rotating drum 2 ... Developing device 3 ... Roller 4 ... Fixing device (fixing roller)
5 ... Cleaning device 6 ... Transfer medium (paper)
DESCRIPTION OF SYMBOLS 11 ... Micro magnetic head array 11a ... Magnetic pole (core) unit 11b ... Excitation coil (plane coil, wiring) 11c ... Insulator 11d ... Substrate 11e ... Protective film 11n, 11s ... Magnetic pole (core) 21 ... Developer 101 ... BK print unit 102 ... C print unit 103 ... Y print unit 104 ... M print unit A ... Base part B ... Cylinder post

Claims (9)

A micro magnetic head array supported by a substrate, an image creation device that forms a magnetic latent image by selectively energizing each magnetic pole (core) of the micro magnetic head array, and formed on each magnetic pole of the micro magnetic head array A developing device for developing the magnetic latent image to be developed,
By selectively energizing each magnetic pole of the micro magnetic head array to form a digital magnetic latent image, the digital magnetic latent image is developed by the developing device, and then the developed image is transferred onto a transfer medium. A micro magnetic head array for a magnetic printer that forms an image by fixing the
The micro magnetic head array is an assembly of magnetic pole (core) units composed of a plurality of N poles and one S pole, or a plurality of S poles and one N pole .
The distance between one S pole and a plurality of N poles in the magnetic pole unit, or the distance between one N pole and a plurality of S poles is at least three times or less the maximum diagonal (diameter) of the magnetic pole cross-sectional shape. A featured micro magnetic head array.   In the magnetic pole (core) unit, the one S pole is surrounded by a plurality of N poles and provided at the same distance from the plurality of N poles, or the one N pole is surrounded by a plurality of S poles. 2. The micro magnetic head array according to claim 1, wherein the micro magnetic head array is provided at the same distance from the plurality of S poles. 3. The micro magnetic head according to claim 1, wherein an aspect ratio (major axis / minor axis) of an N pole or an S pole which is a magnetic pole of the magnetic pole (core) unit is at least 1 or more. array. The height of the major axis of the one S pole is lower than the height of the major axes of the plurality of N poles in the magnetic pole (core) unit, or the height of the major axis of the one N pole is The micro magnetic head array according to any one of claims 1 to 3, wherein the height is lower than the height of the major axis of the plurality of S poles therein . 5. The micro magnetic head array according to claim 1 , wherein each magnetic pole (core) of the micro magnetic head array is made of a ferromagnetic material having soft magnetism. Each magnetic pole (core) of the micro magnetic head array is selectively energized to form a digital magnetic latent image, the digital magnetic latent image is developed, and then the developed image is transferred onto a transfer medium. 6. The micromagnetism according to claim 1 , wherein demagnetization is performed by applying an alternating current to each of the magnetic poles, and the developer remaining on each of the magnetic poles is easily peeled off. Head array. A color image is formed by repeatedly superimposing images using the micro magnetic head array according to any one of claims 1 to 6, or a color image is formed using a plurality of the micro magnetic head arrays. A magnetic printer characterized by forming . 7. Development for developing a digital magnetic latent image by selectively energizing each magnetic pole (core) of the micro magnetic head array according to claim 1 to form a digital magnetic latent image. A magnetic printer, wherein the agent has an average particle size of 5 μm to 50 μm . A magnetic printer using the micro magnetic head array according to any one of claims 1 to 6 .