JP2020139211A - Particle coating method and particle coating device - Google Patents

Abstract

To provide a particle coating method and a particle coating device capable of forming a coat with restrained dispersion of thickness on a surface of a magnetic particle.SOLUTION: A particle coating method includes the steps of: putting first magnetic particles and second magnetic particles with a larger average grain diameter than that of the first magnetic particle into a container; fixing the first magnetic particles with a first magnetic force, and fixing the second magnetic particles with a second magnetic force stronger than the first magnetic force at a perpendicular lower part than the first magnetic force; and forming a coat on the surface of the first magnetic particles and the surface of the second magnetic particles by an atomic layer deposition method, while the first and second magnetic particles are fixed. Also, it is preferable that the first and second magnetic particles are heated while the first magnetic particles are fixed with the first magnetic force and the second magnetic particles are fixed with the second magnetic force.SELECTED DRAWING: Figure 1

Description

The present invention relates to a particle coating method and a particle coating device.

In magnetic powder used for inductors and the like, it is necessary to insulate the surface of the particles to suppress eddy currents flowing between the particles. Therefore, a method of forming an insulating film on the particle surface of the magnetic powder by using various film forming methods has been studied.

For example, in Patent Document 1, as a method of coating a thin film on a particle surface by sputtering a coating material on the particles, the particles are housed in a bottomed cylindrical particle container, and the particle container is rotated around the axis of the cylinder. A method is disclosed in which the coating material is sputtered while rotating the rotating shaft while inclining it at a predetermined angle with respect to the horizontal direction.

JP-A-2007-204784

On the other hand, when there is a distribution in the particle size of the particles to be coated with the coating material, that is, when the particle size of the contained particles varies, the film thickness of the thin film may differ greatly for each particle. For example, when the coating material is sputtered, small particles may be hidden behind particles having a large particle size when viewed from the flight direction of the coating material. In such a case, it is possible that no thin film is formed on the surface of the small particles. Then, the insulating property of the small particles is not ensured, and the characteristics of the entire magnetic powder may deteriorate. Therefore, it is required to reduce the variation in the film thickness of the thin film even when the particle size of the particles is distributed, that is, even when the particles having a large particle size and the particles having a small particle size are mixed.

The particle coating method according to the application example of the present invention includes a step of putting a first magnetic particle and a second magnetic particle having a larger average particle size than the first magnetic particle in a container, and the first magnetic particle with the first magnetic force. In the step of fixing and fixing the second magnetic particle with a second magnetic force stronger than the first magnetic force vertically below the first magnetic force, and in a state where the first magnetic particle and the second magnetic particle are fixed. It is characterized by having a step of forming a film on the surface of the first magnetic particles and the surface of the second magnetic particles by an atomic layer deposition method.

It is sectional drawing which shows the particle coating apparatus 1 which concerns on embodiment. FIG. 1 is a cross-sectional view taken along the line AA of FIG. It is a partially enlarged view which shows the vicinity of the magnetic particle shown in FIG. 1 before forming a film. It is a partially enlarged view which shows the vicinity of the magnetic particle shown in FIG. 1 after forming a film. It is the B part enlarged view of FIG. It is a process drawing which shows the particle coating method which concerns on embodiment. It is a figure for demonstrating the particle coating method shown in FIG.

Hereinafter, a preferred embodiment of the particle coating method and the particle coating apparatus of the present invention will be described in detail with reference to the accompanying drawings.

[Particle coating device]
First, the particle coating device according to the embodiment will be described.

FIG. 1 is a cross-sectional view showing a particle coating device 1 according to an embodiment. FIG. 2 is a cross-sectional view taken along the line AA of FIG. FIG. 3 is a partially enlarged view showing the vicinity of the magnetic particles 91 shown in FIG. 1 before forming the coating film 92. FIG. 4 is a partially enlarged view showing the vicinity of the magnetic particles 91 shown in FIG. 1 after the coating film 92 is formed. FIG. 5 is an enlarged view of part B of FIG. In FIGS. 1 and 2 and the drawings described later, the X-axis, the Y-axis, and the Z-axis are set as three axes orthogonal to each other for convenience of explanation. Then, the + Z side will be described as upward, and the −Z side will be described as downward.

The particle coating device 1 shown in FIG. 1 includes a chamber 22 (container) for accommodating the magnetic particles 91, and forms a film 92 on the surface of the magnetic particles 91 by an atomic layer deposition method (ALD). It has a device 2 and a magnetic force generating unit 3 that generates a magnetic force in the chamber 22 and fixes the magnetic particles 91. Further, in addition to the chamber 22 described above, the film forming apparatus 2 introduces a particle supply unit 23 that supplies magnetic particles 91 into the chamber 22, an exhaust unit 24 that exhausts the inside of the chamber 22, and a gas into the chamber 22. A gas introduction unit 26 and a heating unit 28 are provided.

In such a particle coating device 1, as shown in FIG. 3, a coating film 92 is formed on the surface of the magnetic particles 91 in a state where the magnetic particles 91 are fixed by the magnetic force generated by the magnetic force generating unit 3. As a result, the coating film 92 can be formed with the magnetic particles 91 fixed in the chamber 22 without the magnetic particles 91 falling due to their own weight. As a result, the magnetic particles 93 with a coating shown in FIG. 4 can be stably produced.

In addition, the magnetic force generating unit 3 is configured to generate magnetic fields of different strengths at different positions in the vertical direction in the chamber 22. As a result, magnetic forces of different strengths act on the magnetic particles 91 at different positions in the vertical direction. As a result, the magnetic particles 91 are fixed at different positions in the vertical direction for each particle size. Specifically, as will be described later, the magnetic particles 91 have a first magnetic particle 911, a second magnetic particle 912 having a larger particle size than the first magnetic particle 911, and a second magnetic particle 91 having a larger particle size than the second magnetic particle 912. 3 Magnetic particles 913 and. Then, as shown in FIG. 3, the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913 are fixed at different positions in the chamber 22 from vertically above in this order. Then, since the magnetic particles 91 can be fixed with the particle sizes aligned to some extent, the probability that the small particles are hidden behind the conventional particles having a large particle size is low. As a result, variations in the film thickness of the coating film 92 formed on the magnetic particles 91 can be suppressed to a small extent.

Hereinafter, each part of the particle coating device 1 will be described in detail.
As described above, the film forming apparatus 2 shown in FIG. 1 includes a chamber 22, a particle supply unit 23, an exhaust unit 24, a gas introduction unit 26, and a heating unit 28. In such a film forming apparatus 2, the magnetic particles 91 are supplied into the chamber 22 by the particle supply unit 23, the inside of the chamber 22 is exhausted by the exhaust unit 24, and then the gas is introduced by the gas introduction unit 26. Then, the chamber 22 and the magnetic particles 91 are heated by the heating unit 28. By this heating, the raw material gas introduced into the chamber 22 is thermally decomposed, the decomposed product is adsorbed on the surface of the magnetic particles 91, and finally the film 92 is formed.

As shown in FIGS. 1 and 2, the chamber 22 has a cylindrical shape having axes parallel to the Z-axis direction, that is, the vertical direction. The chamber 22 is divided into upper and lower parts via a valve 82. Of these, the processing chamber 222 located above is a chamber that forms a space for performing a film forming process for forming a film 92 on the surface of the magnetic particles 91. On the other hand, the recovery chamber 224 located below is a chamber that forms a space for collecting the magnetic particles 93 with a coating film.

Examples of the constituent material of the processing chamber 222 include a glass material such as quartz glass, a ceramic material such as alumina, and a non-magnetic metal material such as aluminum, titanium, and permalloy.

On the other hand, examples of the constituent material of the recovery chamber 224 include a metal material such as stainless steel in addition to the constituent material of the processing chamber 222 described above.

The valve 82 that separates the lower end of the processing chamber 222 and the upper end of the recovery chamber 224 is composed of a vacuum gate valve or the like, and can open and close between the processing chamber 222 and the recovery chamber 224.

The lower end of the recovery chamber 224 is hermetically sealed with a flange 84. A through hole 842 is provided in the flange 84, and the exhaust portion 24 is connected to the through hole 842.

The particle supply unit 23 includes a particle storage unit 232 that stores magnetic particles 91, a flange 234 that connects the lower end of the particle storage unit 232 and the upper end of the processing chamber 222, and a valve that opens and closes a through hole provided in the flange 234. 236 and. When the valve 236 is opened, the magnetic particles 91 stored in the particle storage unit 232 fall into the processing chamber 222 by its own weight.

The exhaust unit 24 includes a valve 242 attached to the through hole 842, an exhaust pump 244, and a pipe 246 connecting the valve 242 and the exhaust pump 244. By exhausting the inside of the chamber 22 by the exhaust unit 24, the inside of the chamber 22 can be depressurized to a so-called vacuum state.

By closing the valve 242, the through hole 842 can be closed and the exhaust can be temporarily stopped.

The gas introduction unit 26 includes a support member 262 airtightly connected to the upper part of the processing chamber 222, nozzles 263 and 264 provided inside the support member 262, a raw material gas storage unit 265 for storing the raw material gas, and oxidation. It is provided with an oxidant storage unit 266 for storing the agent, a pipe 267 for connecting the raw material gas storage unit 265 and the nozzle 263, and a pipe 268 for connecting the oxidant storage unit 266 and the nozzle 264. The gas introduction unit 26 supplies the raw material gas, the oxidizing agent, and the like necessary for forming the coating film 92 into the chamber 22.

The support member 262 has a bottomed tubular shape having an axis parallel to the X-axis direction, and the opening thereof and the chamber 22 are connected to each other. As a result, a closed space is formed between the inside of the support member 262 and the chamber 22. When the film 92 is formed, this closed space is in a reduced pressure state.

The nozzle 263 is provided inside the support member 262 and sprays the raw material gas sent through the pipe 267 into the chamber 22. Further, the nozzle 264 is also provided inside the support member 262, and sprays the oxidant sent through the pipe 268 into the chamber 22. As a result, the raw material gas and the oxidizing agent can be uniformly supplied into the chamber 22, and a film 92 having a predetermined film thickness can be formed on the surface of the magnetic particles 91 housed in the chamber 22. ..

In the middle of the pipes 267 and 268, valves for adjusting the flow rates of the raw material gas and the oxidizing agent are provided, and the partial pressures of the raw material gas and the oxidizing agent in the chamber 22 can be controlled.

Further, the raw material gas and the oxidizing agent are supplied together with a carrier gas containing an inert gas such as nitrogen gas or argon gas as a main component, if necessary.

The heating unit 28 is provided outside the chamber 22. In this embodiment, as shown in FIG. 1, the magnetic force generating unit 3 is provided on the opposite side of the chamber 22. Such a heating unit 28 heats the magnetic particles 91 fixed to the inner surface of the chamber 22 from the outside of the chamber 22 to raise the temperature.

As long as the heating unit 28 is a member capable of heating the magnetic particles 91 housed inside the chamber 22, the heating principle and arrangement are not particularly limited, but the heater block incorporating the heater wiring is not particularly limited. , Film heaters, seat heaters, sheathed heaters, infrared radiation heaters that emit infrared rays, etc. are used.

In the film forming apparatus 2 as described above, the film 92 is formed by the atomic layer deposition method as described above. The atomic layer deposition method is a method in which two or more types of gases, a raw material gas and an oxidant, are alternately introduced and exhausted repeatedly to react the raw material molecules adsorbed on the surface to be filmed to form a film. Is. In this method, the film thickness of the film 92 to be formed can be controlled with high accuracy. Therefore, a particularly thin film 92 can be formed. Therefore, when the magnetic particles 91 have soft magnetism, if the film thickness of the coating film 92 covering the surface thereof can be reduced, the magnetism per unit volume while maintaining good insulation between the magnetic particles 91. It is possible to produce a dust core having a high density of particles 91. As a result, it is possible to realize the magnetic particles 93 with a coating film capable of producing a dust core or the like having particularly high magnetic characteristics such as magnetic flux density and magnetic permeability.

Further, since the raw material gas and the oxidizing agent wrap around the small gaps to form a film, a portion that is not formed, that is, pinholes are less likely to occur, and a film 92 having a uniform film thickness can be formed. Therefore, it is possible to obtain a coated magnetic particle 93 in which the surface of the magnetic particle 91 is coated with a uniform and thin film 92. Such coated magnetic particles 93 contribute to the realization of a dust core having good insulation between particles.

The magnetic force generating unit 3 is composed of a pair of electromagnets 321 and 222, and is composed of a first electromagnet 32 provided corresponding to the upper part of the processing chamber 222 and a pair of electromagnets 341 and 342 in the vertical direction of the processing chamber 222. A second electromagnet 34 provided corresponding to the central portion of the above, a third electromagnet 36 composed of a pair of electromagnets 361 and 362 and provided corresponding to the lower part of the processing chamber 222, and a first electromagnet 32 thereof. , A control unit 38 that is electrically connected to the second electromagnet 34 and the third electromagnet 36.

The first electromagnet 32 is provided in the upper part of the processing chamber 222 so as to be in close contact with the outer surface of the processing chamber 222. The first electromagnet 32 has a curved surface along the outer surface of the processing chamber 222, and the curved surface thereof and the outer surface of the processing chamber 222 are arranged so as to overlap each other.

Further, the current directions of the pair of electromagnets 321 and 222 are set so that the polarities on the processing chamber 222 side are different from each other. When the polarity of the electromagnet 321 on the processing chamber 222 side is N pole, the polarity of the electromagnet 322 on the processing chamber 222 side is S pole. Therefore, a magnetic field based on the magnetic field line connecting the electromagnet 321 and the electromagnet 322 is generated in the processing chamber 222. Then, when the magnetic particles 91 enter the magnetic field, a first magnetic force is generated in the magnetic particles 91, and the magnetic particles 91 are fixed in a region overlapping the first electromagnet 32 on the inner surface of the processing chamber 222 by the first magnetic force.

The second electromagnet 34 is provided in the central portion of the processing chamber 222 so as to be in close contact with the outer surface of the processing chamber 222. The second electromagnet 34 has a curved surface along the outer surface of the processing chamber 222, and the curved surface thereof and the outer surface of the processing chamber 222 are arranged so as to overlap each other.

Further, the current directions of the pair of electromagnets 341 and 342 are set so that the polarities on the processing chamber 222 side are different from each other. When the polarity of the electromagnet 341 on the processing chamber 222 side is N pole, the polarity of the electromagnet 342 on the processing chamber 222 side is S pole. Therefore, a magnetic field based on the magnetic field line connecting the electromagnet 341 and the electromagnet 342 is generated in the processing chamber 222. Then, when the magnetic particles 91 enter the magnetic field, a second magnetic force is generated in the magnetic particles 91, and the magnetic particles 91 are fixed in a region overlapping the second electromagnet 34 on the inner surface of the processing chamber 222 by the second magnetic force. The second magnetic force is set to be stronger than the first magnetic force.

The third electromagnet 36 is provided in the lower part of the processing chamber 222 so as to be in close contact with the outer surface of the processing chamber 222. The third electromagnet 36 has a curved surface along the outer surface of the processing chamber 222, and the curved surface thereof and the outer surface of the processing chamber 222 are arranged so as to overlap each other.

Further, the current directions of the pair of electromagnets 361 and 362 are set so that the polarities on the processing chamber 222 side are different from each other. When the polarity of the electromagnet 361 on the processing chamber 222 side is N pole, the polarity of the electromagnet 362 on the processing chamber 222 side is S pole. Therefore, a magnetic field based on the magnetic field line connecting the electromagnet 361 and the electromagnet 362 is generated in the processing chamber 222. Then, when the magnetic particles 91 enter the magnetic field, a third magnetic force is generated in the magnetic particles 91, and the magnetic particles 91 are fixed in a region overlapping the third electromagnet 36 on the inner surface of the processing chamber 222 by the third magnetic force. The third magnetic force is set to be stronger than the second magnetic force.

The control unit 38 is composed of a circuit including a microcomputer, an IC, and the like, and controls the direction and magnitude of the current flowing through the first electromagnet 32, the second electromagnet 34, and the third electromagnet 36. As a result, the directions and strengths of the first magnetic force, the second magnetic force, and the third magnetic force acting on the magnetic particles 91 in the processing chamber 222 are controlled.

When a magnetic field is generated in the processing chamber 222 by the magnetic force generating unit 3 as described above, the magnetic particles 91 thrown into the processing chamber 222 along the lines of magnetic force can be captured. Specifically, when the magnetic particles 91 are supplied from the particle supply unit 23 into the processing chamber 222, the magnetic particles 91 fall into the processing chamber 222 by their own weight. At this time, the first electromagnet 32 forms a magnetic field that generates a first magnetic field with respect to the magnetic particles 91, and the second electromagnet 34 forms a magnetic field that generates a second magnetic field with respect to the magnetic particles 91. , The third electromagnet 36 forms a magnetic field that generates a third magnetic force with respect to the magnetic particles 91.

On the other hand, the magnetic particles 91 supplied from the particle supply unit 23 include particles having various particle sizes. Such variations in particle size are present, to varying degrees, in all powders produced by common manufacturing methods. Here, as an example, the relatively small magnetic particles 91 are particularly referred to as "first magnetic particles 911". Further, the magnetic particles 91 larger than the first magnetic particles 911 are particularly referred to as "third magnetic particles 913". Further, the magnetic particles 91 which are larger than the first magnetic particles 911 and smaller than the third magnetic particles 913 are particularly referred to as "second magnetic particles 912". Therefore, the particle size gradually increases in the order of the first magnetic particle 911, the second magnetic particle 912, and the third magnetic particle 913. When the magnetic particles 91 in which the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913 are mixed are supplied from the particle supply unit 23, they become the magnetic particles 91 falling in the processing chamber 222. On the other hand, the first magnetic force, the second magnetic force, and the third magnetic force act in this order.

The above-mentioned "particle size" is the average particle size of the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913 when there are a plurality of them. Therefore, the average particle size of the plurality of second magnetic particles 912 may be larger than the average particle size of the plurality of first magnetic particles 911. Similarly, the average particle size of the plurality of third magnetic particles 913 may be larger than the average particle size of the plurality of second magnetic particles 912.

The difference in particle size between the first magnetic particles 911 and the second magnetic particles 912 and the difference in particle size between the second magnetic particles 912 and the third magnetic particles 913 depend on the average particle size of the magnetic particles 91. However, as an example, it is preferably 1 μm or more and 30 μm or less, and more preferably 3 μm or more and 20 μm or less. If such a difference is secured, the effect of suppressing the variation in the film thickness of the coating film 92 formed on the magnetic particles 91 to be small can be obtained more remarkably.

Further, as described above, the first magnetic force is weaker than the second magnetic force and the third magnetic force. Therefore, among the magnetic particles 91 supplied from the particle supply unit 23 and starting to fall, the relatively small first magnetic particles 911 are captured by the first magnetic force and fixed to the inner surface of the processing chamber 222. On the other hand, the second magnetic particles 912 and the third magnetic particles 913 continue to fall without being captured by the first magnetic force. This is because the second magnetic particles 912 and the third magnetic particles 913 have relatively large masses, so that their gravitational forces exceed the first magnetic force. In other words, the strength of the first magnetic force is set so that such selective capture occurs.

After that, the second magnetic particles 912, which are larger than the first magnetic particles 911 and smaller than the third magnetic particles 913, are captured by the second magnetic force and fixed to the inner surface of the processing chamber 222. On the other hand, the third magnetic particles 913 continue to fall without being captured by the second magnetic force. This is because the third magnetic particle 913 has a relatively large mass and its gravity exceeds the second magnetic force. In other words, the strength of the second magnetic force is set so that such selective capture occurs.

After that, the third magnetic particles 913 are captured by the third magnetic force and fixed to the inner surface of the processing chamber 222.

According to the magnetic force generating unit 3 as described above, particles having various particle diameters contained in the magnetic particles 91 can be fixed in different regions while being classified for each particle size. That is, the first magnetic particles 911 are fixed to the upper part in the processing chamber 222, the second magnetic particles 912 are fixed to the central part in the processing chamber 222, and the third magnetic particles 913 are fixed to the lower part in the processing chamber 222. be able to.

Then, when the film forming process is performed by the atomic layer deposition method in the film forming apparatus 2, the film 92 is formed on the surface of the magnetic particles 91. At this time, since the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913, which have different particle sizes, are divided into different regions for each particle size, the particle size is large as in the conventional case. The problem that small particles are hidden behind the particles is unlikely to occur. Therefore, according to the particle coating device 1 according to the present embodiment, it is possible to keep the variation in the film thickness of the coating film 92 small even when the particle size of the magnetic particles 91 is distributed.

Further, when a magnetic field is generated in the processing chamber 222 by the magnetic force generating unit 3, the magnetic particles 91 housed in the processing chamber 222 are connected to each other along the lines of magnetic force. As a result, a large number of magnetic particles 91 can be fixed and held. As a result, when the film 92 is formed by the atomic layer deposition method, the magnetic particles 91 are suppressed from flying up even if the inside of the processing chamber 222 is exhausted. Therefore, it is possible to suppress the magnetic particles 91 from being caught in the exhaust unit 24, and to suppress the failure of the exhaust unit 24 and the loss of the magnetic particles 91.

Further, when the magnetic particles 91 are connected to each other along the lines of magnetic force, a large number of needle-shaped aggregates of the magnetic particles 91 are formed as shown in FIG. At that time, since such aggregates are formed so as to be parallel to each other in the processing chamber 222, a gap is generated between the aggregates. Therefore, most of the surfaces of the magnetic particles 91 are exposed, and when the raw materials supplied in the atomic layer deposition method are deposited on the surface of the magnetic particles 91 to form a film 92, the magnetic particles 91 come into contact with each other. A coating 92 can be formed on many surfaces, except for some of them. As a result, the coverage of the coating film 92 can be increased. Further, by forming the coating film 92 in a plurality of times by changing the way in which the magnetic particles 91 are connected to each other, as shown in FIG. 4, the coating film 92 that covers almost the entire surface of the magnetic particles 91 is formed. It becomes possible to do.

The arrangement of the electromagnets 321, 322, 341, 342, 361, and 362 may be different from the arrangement shown in the drawing. Further, if necessary, any inclusions may be arranged between the electromagnets 321, 322, 341, 342, 361, 362 and the processing chamber 222.

Further, at least one of the electromagnets 321, 322, 341, 342, 361 and 362 may be replaced with permanent magnets.

Further, the magnetic force generating unit 3 according to the present embodiment includes three electromagnets 32, a second electromagnet 34, and a third electromagnet 36, but the number of these electromagnets is not particularly limited, that is, two, that is, There may be only the first electromagnet 32 and the second electromagnet 34, or four or more.

As described above, the particle coating device 1 according to the embodiment generates a magnetic field in the film forming device 2 for forming the coating film 92 on the surface of the magnetic particles 91 and the chamber 22 (container) by the atomic layer deposition method. It has a magnetic force generating unit 3 for fixing the magnetic particles 91 by a magnetic force generated by a magnetic field. Further, the film forming apparatus 2 includes a chamber 22 which is a container for accommodating magnetic particles 91, an exhaust unit 24 which exhausts the inside of the chamber 22 to reduce the pressure, and a gas introduction unit 26 which introduces a raw material gas or the like into the chamber 22. , Is equipped. Further, the magnetic force generating unit 3 generates a first magnetic force, a second magnetic force stronger than the first magnetic force, and a third magnetic force stronger than the second magnetic force in the chamber 22, and the first magnetic force generates the first magnetic particles 911. It is fixed, the second magnetic particle 912 is fixed by the second magnetic force, and the third magnetic particle 913 is fixed by the third magnetic force.

According to such a particle coating device 1, even when the particle size of the magnetic particles 91 is distributed, it is possible to suppress the variation in the film thickness of the coating film 92 to be small.

Further, the first electromagnet 32, the second electromagnet 34, and the third electromagnet 36, which are the magnetic force generating units 3, are provided outside the chamber 22, respectively, as described above. Therefore, the magnetic particles 91 do not directly adhere to the first electromagnet 32, the second electromagnet 34, and the third electromagnet 36, and the coated magnetic particles 93 after forming the coating 92 can be easily peeled off from the magnetic force. it can. As a result, the magnetic particles 93 with a coating can be easily recovered.

Further, in the present embodiment, as the magnetic force generating unit 3, a first electromagnet 32 that generates a first magnetic force, a second electromagnet 34 that generates a second magnetic force, and a third electromagnet 36 that generates a third magnetic force are used. .. An electromagnet is a member that generates a magnetic field by passing an electric current. As a result, the magnetic force can be generated at the desired timing. Therefore, for example, the magnetic force is not generated when the magnetic particles 91 are transferred, while the magnetic force is generated when the inside of the chamber 22 is exhausted by the exhaust unit 24. , Etc. can be controlled. As a result, it is possible to achieve both suppression of the soaring of the magnetic particles 91 and easy transfer of the magnetic particles 91.

Further, it is preferable that the inner surface of the chamber 22, which is a container, is water-repellent. As a result, it is possible to prevent the magnetic particles 91 from adhering to the inner surface of the chamber 22. In particular, even if the surface of the magnetic particles 91 is removed by performing a pretreatment as described later, a small amount of water may remain, but the water adheres to the inner surface of the chamber 22. It can be one of the causes. Therefore, by applying a water repellent treatment to the inner surface of the chamber 22, it is possible to suppress adhesion caused by moisture.

Examples of the water-repellent treatment include formation of a film containing a fluorine-based material or a silicone-based material, fluorine plasma treatment, and the like.

Further, it is preferable that the chamber 22, which is a container, is mainly made of quartz glass. Since such a chamber 22 has almost no magnetism, the magnetic field generated by the magnetic force generating unit 3 easily penetrates the chamber 22. Therefore, a large amount of magnetic particles 91 can be fixed through the chamber 22.

Further, since quartz glass transmits infrared rays, the chamber 22 made of quartz glass as a main material has translucency, that is, infrared transmissivity. Therefore, the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913 can be heated by irradiating infrared rays from the outside of the chamber 22 (container). When an infrared radiation heater is used as the heating unit 28, the heating unit 28 irradiates infrared rays from the outside of the chamber 22 (container) to heat the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913. .. As a result, the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913 can be efficiently heated regardless of the pressure in the processing chamber 222.

A particle trap 248 as shown in FIG. 5 may be provided in the middle of the pipe 246 of the exhaust unit 24. The particle trap 248 is a mechanism for capturing the magnetic particles 93 with a coating film that are unintentionally caught in the pipe 246 when the inside of the chamber 22 is exhausted.

The particle trap 248 shown in FIG. 5 is composed of a bent portion 2461 formed by bending the extending direction of the pipe 246 by 90 ° and a permanent magnet 2481 provided on the bent portion 2461. In such a particle trap 248, the magnetic particles 93 with a coating that have been unintentionally caught in the pipe 246 are captured by using the magnetic force of the permanent magnet 2481. As a result, it is possible to prevent the coated magnetic particles 93 from reaching the exhaust pump 244, and it is possible to prevent the exhaust pump 244 from failing. It should be noted that the magnetic particles 91 may be captured.

Further, in FIG. 5, particle traps 248 are provided at two places in the middle of the pipe 246. As a result, the magnetic particles 93 with a coating can be captured with a higher probability. The number of particle traps 248 is not particularly limited.

Further, in FIG. 5, the permanent magnet 2481 is arranged outside the arc drawn by the curve at the bent portion 2461 in the pipe 246. As a result, when the coated magnetic particles 93 that have reached the bent portion 2461 along the exhaust flow bend around the bent portion 2461, they gather outside the arc due to centrifugal force, and the coated magnetic particles 93 have a higher probability. Can be captured by the permanent magnet 2484.

Next, the magnetic particles 91 will be described.
The magnetic particles 91 may be particles having hard magnetism, but particles having soft magnetism are preferably used. Since the magnetization of the soft magnetic particles can be controlled by the presence or absence of a magnetic field, it is possible to switch between fixing and releasing depending on the presence or absence of a magnetic field generated by the magnetic force generating unit 3. Therefore, the magnetic particles 91 and the magnetic particles 93 with a coating can be easily transported.

The constituent materials of the magnetic particles 91 include pure iron, Fe-Si alloys such as silicon steel, Fe—Ni alloys such as Permalloy, Fe—Co alloys such as Permenzur, and Fe such as Sendust. In addition to various Fe-based alloys such as −Si—Al-based alloys and Fe—Cr—Si-based alloys, various Ni-based alloys, various Co-based alloys, various amorphous alloys and the like can be mentioned. Of these, the amorphous alloys include Fe-Si-B series, Fe-Si-BC series, Fe-Si-B-Cr-C series, Fe-Si-Cr series, Fe-B series, and Fe-P. -C series, Fe-Co-Si-B series, Fe-Si-B-Nb series, Fe-based alloys such as Fe-Zr-B series, Ni-Si-B series, Ni-P-B series, etc. Ni-based alloys, Co-based alloys such as Co—Si—B based, and the like can be mentioned.

The average particle size of the magnetic particles 91 is not particularly limited, but is preferably 50 μm or less, more preferably 1 μm or more and 30 μm or less, and further preferably 2 μm or more and 20 μm or less. Such relatively fine magnetic particles 91 are useful as magnetic particles for a dust core because the eddy current loss can be suppressed to be small when the magnetic particles 91 are soft magnetic.

[Particle coating method]
Next, as a particle coating method according to the embodiment, a method of forming a film 92 on the surface of the magnetic particles 91 by using the particle coating device 1 shown in FIG. 1 will be described.

FIG. 6 is a process diagram showing a particle coating method according to the embodiment. FIG. 7 is a diagram for explaining the particle coating method shown in FIG.

(S01) Insertion of Magnetic Particles First, the magnetic particles 91 are charged into the particle storage portion 232. The magnetic particles 91 include a first magnetic particle 911 having a relatively small diameter, a second magnetic particle 912 having a relatively medium diameter, and a third magnetic particle 913 having a relatively large diameter. At this time, the valve 236 that opens and closes the lower end of the particle storage portion 232 is closed.

(S02) Fixation of Magnetic Particles Next, after closing the valve 82, the first electromagnet 32, the second electromagnet 34, and the third electromagnet 36 are energized to generate a magnetic field in the processing chamber 222. After that, the valve 236 is opened to gradually drop the magnetic particles 91 into the processing chamber 222. Then, the falling magnetic particles 91 first pass through the magnetic field generated by the first electromagnet 32. At this time, the first magnetic force acts on the magnetic particles 91. On the other hand, gravity also continuously acts on the magnetic particles 91. As a result, when the first magnetic force exceeds the gravity, the magnetic particles 91 can be fixed to the region corresponding to the first electromagnet 32 on the inner surface of the processing chamber 222. Since gravity is proportional to the mass of the magnetic particles 91, whether or not the magnetic particles 91 are fixed is determined according to the mass of the magnetic particles 91, that is, the particle size of the magnetic particles 91.

In the present embodiment, the first magnetic particles 911 are fixed in the region corresponding to the first electromagnet 32, and the second magnetic particles 912 and the third magnetic particles 913 pass through this region. Therefore, the first magnetic particles 911 are mainly selectively fixed in this region.

Subsequently, the second magnetic particles 912 and the third magnetic particles 913 pass through the magnetic field generated by the second electromagnet 34. At this time, a second magnetic force and gravity act on the second magnetic particles 912 and the third magnetic particles 913. In the present embodiment, the second magnetic particles 912 are fixed in the region corresponding to the second electromagnet 34, and the third magnetic particles 913 pass through this region. Therefore, the second magnetic particles 912 are mainly selectively fixed in this region.

Subsequently, the third magnetic particle 913 passes through the magnetic field generated by the third electromagnet 36. At this time, a third magnetic force and gravity act on the third magnetic particles 913. In the present embodiment, the third magnetic particles 913 are fixed in the region corresponding to the third electromagnet 36. Therefore, the third magnetic particles 913 are mainly selectively fixed in this region.

As described above, the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913 are fixed in different regions from each other. At this time, the magnetic particles 91 that are not fixed in any region may be removed from the processing chamber 222. As a result, the extremely coarse magnetic particles 91 can be eliminated, and the particle sizes can be made uniform.

The strengths of the first magnetic force, the second magnetic force, and the third magnetic force can be adjusted by appropriately changing the strength of the magnetic field. Therefore, in this step, if the magnetic field generated by the second electromagnet 34 is stronger than the magnetic field generated by the first electromagnet 32, and the magnetic field generated by the third electromagnet 36 is stronger than the magnetic field generated by the second electromagnet 34. Good.

The difference in magnetic field strength is appropriately set so as to enable the classification as described above, but as an example, the magnetic field generated by the second electromagnet 34 is 10% of the magnetic field generated by the first electromagnet 32. It is preferable that the magnetic field generated by the third electromagnet 36 is 10% or more stronger than the magnetic field generated by the second electromagnet 34. In this way, the magnetic particles 91 can be classified more reliably.

Further, the magnetic flux density on the surface of the first electromagnet 32 is preferably 1000 mT or more. As a result, the strength of the magnetic field generated by the first electromagnet 32 can be made sufficiently strong, and the above-mentioned action can be achieved.

(S03) Decompression in the chamber Next, after closing the valve 236, the valve 82 is opened, and the inside of the chamber 22 is exhausted by the exhaust pump 244. As a result, the pressure inside the chamber 22 is reduced to a vacuum state. At this time, especially when the exhaust pump 244 is in operation, the air in the chamber 22 is agitated rapidly, so that there is a concern that the magnetic particles 91 may fly up. However, in the present embodiment, since the magnetic particles 91 are fixed by magnetic force, this soaring can be suppressed. Therefore, it is possible to suppress the failure of the exhaust pump 244 and the loss of the magnetic particles 91 due to the soaring of the magnetic particles 91.
When the pressure inside the chamber 22 is reached by exhaust gas, the valve 82 is closed.

(S04) Pretreatment Next, the magnetic particles 91 fixed on the inner surface of the treatment chamber 222 are pretreated. Examples of the pretreatment include ozone treatment, radical treatment, ultraviolet treatment, plasma treatment, corona treatment, heat treatment, drying treatment, solvent treatment and the like.

Of these, the pretreatment preferably includes a treatment of oxidizing the surface of the magnetic particles 91 or a treatment of drying the magnetic particles 91. In the treatment of oxidizing the surface of the magnetic particles 91, the oxide film on the surface of the magnetic particles 91 can be strengthened. As a result, in the formation of the coating film 92 described later, the adsorption of the raw material gas is promoted, so that the coating film 92 can be formed more uniformly.

Examples of the treatment for oxidizing the surface of the magnetic particles 91 include ozone treatment and radical treatment. In the ozone treatment, ozone gas is introduced into the chamber 22. In the magnetic particles 91 that have come into contact with ozone gas, the oxide film on the surface is strengthened. Further, in the radical treatment, by introducing hydrogen peroxide into the chamber 22, hydroxyl radicals are generated, and the oxide film on the surface of the magnetic particles 91 is strengthened.

In the process of drying the magnetic particles 91, the water adsorbed on the surface of the magnetic particles 91 is removed. Such moisture causes the formation of the coating film 92, which will be described later, to be inhibited. Therefore, the adhesion of the coating film 92 can be improved by removing the water content in the pretreatment. Examples of the treatment for drying the magnetic particles 91 include a heat treatment for heating the magnetic particles 91, a drying treatment for exposing the magnetic particles 91 to a dehydrated gas, and a solvent treatment for exposing the magnetic particles 91 to a water-soluble solvent such as alcohol.

As described above, the magnetic particles 91 fixed by magnetic force are distributed so as to be continuous, and are arranged in a so-called needle shape. Therefore, there are many gaps around each magnetic particle 91. As a result, the pretreatment can be performed uniformly and efficiently through the gap.

At that time, the pair of electromagnets 321 and 322, the pair of electromagnets 341 and 342, and the pair of electromagnets 361 and 362 may be subjected to pretreatment while switching the direction of the flowing current. That is, the electromagnet 321 and the electromagnet 322 may exchange the polarities of the surfaces on the processing chamber 222 side with each other. As a result, the direction of the magnetic field lines changes, so that the posture of each magnetized magnetic particle 91 can be changed. Then, by performing the pretreatment again in that state, the pretreatment can be applied evenly to the entire surface of each magnetic particle 91, so that the adhesion of the coating film 92, which will be described later, can be further improved.

Then, if necessary, the inside of the chamber 22 is replaced with an inert gas such as nitrogen gas or argon gas, and then the inside of the chamber 22 is exhausted again by the exhaust pump 244.
The preprocessing may be performed as needed or may be omitted.

(S05) Formation of Film Next, the raw material gas, that is, the precursor is introduced into the processing chamber 222 with the valve 82 closed and the inside of the processing chamber 222 sealed. The raw material gas is adsorbed on the surface of the magnetic particles 91. At this time, if the raw material gas is adsorbed on the surface of the magnetic particles 91, it is more difficult to be adsorbed in multiple layers. Therefore, it is possible to control the film thickness of the finally obtained film 92 with high accuracy. Further, since the raw material gas wraps around and adsorbs to the shaded or gapped portion, the coating film 92 can be finally formed uniformly even at a high aspect ratio.

The temperature inside the treatment chamber 222 is appropriately set according to the composition of the raw material gas and the oxidizing agent, but as an example, it is preferably 50 ° C. or higher and 500 ° C. or lower, and 100 ° C. or higher and 400 ° C. or lower. More preferred.
The pressure in the processing chamber 222 is set to 100 Pa or less.

Examples of the raw material gas include a gas containing a precursor of the coating film 92. Specifically, when forming a silicon-based coating 92, as a raw material gas, secondary amines such as dimethylamine, methylethylamine, and diethylamine, trisdimethylaminosilane, bisdiethylaminosilane, and vistershaributylaminosilane. Examples thereof include a reaction product of a secondary amine and trihalosilane.

Next, the valve 82 is opened to discharge the raw material gas, and then the inert gas is introduced as needed. This replaces the raw material gas.

Next, after closing the valve 82, an oxidizing agent is introduced into the processing chamber 222. Examples of the oxidizing agent include ozone, plasma oxygen, water vapor and the like.

The oxidizing agent reacts with the raw material gas adsorbed on the surface of the magnetic particles 91 to form a film 92. Since the oxidant also wraps around the shades and gaps like the raw material gas, the film thickness of the coating film 92 can be controlled with high accuracy and uniformly.

Next, after the valve 82 is opened to discharge the oxidant, an inert gas is introduced as needed to replace the oxidant.

As described above, the magnetic particles 93 with a coating as shown in FIG. 4 can be obtained. That is, the first magnetic particle 931 with a coating formed by forming a coating 92 on the surface of the first magnetic particle 911, the second magnetic particle 932 with a coating formed by forming a coating 92 on the surface of the second magnetic particle 912, and the second magnetic particle 932 with a coating. A coated third magnetic particle 933 having a coating 92 formed on the surface of the three magnetic particles 913 can be obtained.

Examples of the film 92 to be formed include oxides such as silicon oxide, hafnium oxide, tantalum oxide and titanium oxide, and nitrides such as aluminum nitride, titanium nitride and tantalum nitride.

The film thickness of the coating film 92 is not particularly limited, but as an example, it is preferably 1 nm or more and 500 nm or less, and more preferably 2 nm or more and 100 nm or less. With such a film thickness, it can be uniformly formed in a relatively short time.

Further, each process such as introduction and discharge of raw material gas, introduction and discharge of oxidant, introduction and discharge of inert gas is performed by a pair of electromagnets 321 and 322, a pair of electromagnets 341 and 342, and a pair of electromagnets 361 and 362. In the above, the direction of the flowing current may be switched. As a result, each treatment can be applied evenly to the entire surface of each magnetic particle 91.

(S06) Post-treatment Next, the post-treatment is applied to the magnetic particles 93 with a coating in the treatment chamber 222. Examples of the post-treatment include static elimination treatment, radical treatment and the like.

Of these, the static elimination treatment is a treatment for reducing the amount of electric charge due to charging of the magnetic particles 93 with a coating film. By performing such a static elimination treatment, it is possible to suppress aggregation and adhesion of the magnetic particles 93 with a film due to charging. Therefore, when the film 92 is formed again on the magnetic particles 93 with a film as described later, it is possible to suppress the occurrence of film formation defects due to unintended aggregation. An ionizer is used for the static elimination process.

Further, the post-treatment as described above is a treatment performed after forming the coating film 92 on the surface of the magnetic particles 91, and is performed in a state where the magnetic particles 93 with the coating film are fixed by the magnetic force generated by the magnetic field generated from the magnetic force generating portion 3. Is preferable. As a result, there are many gaps around each of the coated magnetic particles 93, and the post-treatment can be performed uniformly and efficiently through the gaps.

At that time, the pair of electromagnets 321 and 322, the pair of electromagnets 341 and 342, and the pair of electromagnets 361 and 362 may be subjected to post-processing while switching the direction of the flowing current. That is, the electromagnet 321 and the electromagnet 322 may exchange the polarities of the surfaces on the processing chamber 222 side with each other. As a result, the direction of the magnetic field lines changes, so that the posture of each magnetized magnetic particle 93 with a coating film can be changed. Then, by performing the post-treatment again in that state, the post-treatment can be uniformly applied to the entire surface of the magnetic particles 93 with the coating film.
The post-processing may be performed as needed or may be omitted.

If the film thickness of the film 92 is insufficient, the film 92 is formed again on the magnetic particles 93 with the film. Then, by stacking a plurality of layers of the coating film 92, a coating film 92 satisfying a target film thickness can be formed.

That is, as described above, the first magnetic particle 911 is fixed by the first magnetic force, the second magnetic particle 912 is fixed by the second magnetic force, and the third magnetic particle 913 is fixed by the third magnetic force. A coating 92 is formed on the surface of the 1 magnetic particle 911, the surface of the second magnetic particle 912, and the surface of the third magnetic particle 913, and the first magnetic particle 931 with a coating, the second magnetic particle 932 with a coating, and the third magnetic with a coating are formed. After changing at least one or all of the steps of obtaining the particles 933 and then the direction of the first magnetic force, the direction of the second magnetic force, and the direction of the third magnetic force, the first magnetic particle 931 with a coating and the second magnetic with a coating are changed. A step of further forming a coating 92 on the surfaces of the particles 932 and the coated third magnetic particle 933 may be performed.

In order to change the direction of the first magnetic force, the polarities of the surfaces on the processing chamber 222 side may be exchanged with each other in the pair of electromagnets 321 and 222, and in order to change the direction of the second magnetic force, the pair of electromagnets 341, In 342, the polarities of the surfaces on the processing chamber 222 side may be exchanged with each other, and in order to change the direction of the third magnetic force, the polarities of the surfaces on the processing chamber 222 side should be exchanged with each other in the pair of electromagnets 361 and 362. It should be. As a result, the directions of the magnetic field lines change, so that the postures of the magnetized first magnetic particles with a coating 931, the second magnetic particles with a coating 932, and the third magnetic particles with a coating 933 can be changed. Then, by forming the coating film 92 again in that state, the coating film 92 can be formed more uniformly.

(S07) Release of Fixing Then, if the film thickness of the coating film 92 is sufficient, the valve 82 is closed, and then the energization of the first electromagnet 32, the second electromagnet 34, and the third electromagnet 36 is stopped. As a result, the magnetic force disappears, so that the magnetic particles 93 with a coating are released from being fixed. As a result, the coated magnetic particles 93 fall into the recovery chamber 224.

(S08) Recovery of Coated Magnetic Particles Next, the coated magnetic particles 93 are taken out from the chamber 22 and recovered. An access door may be provided in the recovery chamber 224, and the coated magnetic particles 93 may be recovered through the access door.

As described above, in the particle coating method according to the present embodiment, the first magnetic particles 911, the second magnetic particles 912 having a larger particle size than the first magnetic particles 911, and the second magnetic particles 912 are contained in the chamber 22 which is a container. In the step S01 in which the third magnetic particles 913 having a larger particle size are inserted, the first magnetic particles 911 are fixed by the first magnetic force, and the second magnetic force is stronger than the first magnetic force vertically below the first magnetic force. Step S02 of fixing the particles 912 and fixing the third magnetic particles 913 with a third magnetic force stronger than the second magnetic force vertically below the second magnetic force, and the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles. It has a step S05 of forming a film 92 on the surface of the first magnetic particle 911, the surface of the second magnetic particle 912, and the surface of the third magnetic particle 913 by the atomic layer deposition method with the magnetic particles 913 fixed. The method.

According to such a method, the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913 having different particle sizes can be fixed to different regions while being aligned for each particle size. That is, the first magnetic particles 911 are fixed to the upper part of the processing chamber 222 by the first magnetic force, the second magnetic particles 912 are fixed to the central portion of the processing chamber 222 by the second magnetic force, and the third magnetic particles 913 are fixed to the processing chamber 222 by the second magnetic force. It is fixed to the lower part of the by the third magnetic force.

Then, when the film forming process is performed by the atomic layer deposition method in the film forming apparatus 2, the film 92 is formed on the surface of the magnetic particles 91. At this time, since the first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913, which have different particle sizes, are divided into different regions for each particle size, the particle size is large as in the conventional case. The problem that small particles are hidden behind the particles is unlikely to occur. Therefore, according to the particle coating method according to the present embodiment, it is possible to suppress the variation in the film thickness of the coating film 92 to be small even when the particle size of the magnetic particles 91 is distributed.

Further, since a large number of magnetic particles 91 are fixed and held by magnetic force, the magnetic particles 91 are suppressed from flying up even if the inside of the processing chamber 222 is exhausted when the coating film 92 is formed by the atomic layer deposition method. .. Therefore, it is possible to suppress the magnetic particles 91 from being caught in the exhaust unit 24, and to suppress the failure of the exhaust unit 24 and the loss of the magnetic particles 91.

Further, when a large number of aggregates of needle-shaped magnetic particles 91 are formed as shown in FIG. 3, such aggregates are formed so as to be parallel to each other in the processing chamber 222, so that the aggregates are between the aggregates. There is a gap in. Therefore, most of the surfaces of the magnetic particles 91 are exposed, and when the raw materials supplied in the atomic layer deposition method are deposited on the surface of the magnetic particles 91 to form a film 92, the magnetic particles 91 come into contact with each other. A coating 92 can be formed on many surfaces, except for some of them. Therefore, as shown in FIG. 4, the film 92 that covers almost the entire surface of the magnetic particles 91 is formed by forming the film 92 in a plurality of times by changing the way in which the magnetic particles 91 are connected to each other. It becomes possible to do.

Further, when forming the coating film 92, the first magnetic particles 911 are fixed by the first magnetic force, the second magnetic particles 912 are fixed by the second magnetic force, and the third magnetic particles 913 are fixed by the third magnetic force. The first magnetic particles 911, the second magnetic particles 912, and the third magnetic particles 913 are heated. As a result, the raw material gas introduced into the chamber 22 is thermally decomposed and the decomposed product is adsorbed on the surface, so that the coating film 92 can be finally uniformly formed.

The heating temperature at this time is appropriately set according to the composition of the raw material gas and the like, but as an example, it is preferably 50 ° C. or higher and 500 ° C. or lower, and more preferably 100 ° C. or higher and 400 ° C. or lower.

Although the particle coating method and the particle coating apparatus of the present invention have been described above based on the illustrated embodiment, the present invention is not limited thereto, and the particle coating method of the present invention is arbitrary in the above embodiment. It may be a method in which the desired step is added. Further, the order of the steps of the above-described embodiment may be changed, or a plurality of steps may be performed simultaneously or in a timely manner. Further, in the particle coating apparatus of the present invention, the configuration of each part of the embodiment may be replaced with an arbitrary configuration having the same function. Further, in the particle coating device of the present invention, any other constituent may be added to the embodiment.

1 ... particle coating device, 2 ... film forming device, 3 ... magnetic force generating part, 22 ... chamber, 23 ... particle supply part, 24 ... exhaust part, 26 ... gas introduction part, 28 ... heating part, 32 ... first electromagnet, 34 ... 2nd electromagnet, 36 ... 3rd electromagnet, 38 ... control unit, 82 ... valve, 84 ... flange, 91 ... magnetic particles, 92 ... coating, 93 ... coated magnetic particles 222 ... processing chamber, 224 ... recovery chamber , 232 ... Particle storage, 234 ... Flange, 236 ... Valve, 242 ... Valve, 244 ... Exhaust pump, 246 ... Piping, 248 ... Particle trap, 262 ... Support member, 263 ... Nozzle, 264 ... Nozzle, 265 ... Raw material gas Storage part, 266 ... Oxidizing agent storage part, 267 ... Piping, 268 ... Piping, 321 ... Electromagnet, 322 ... Electromagnet, 341 ... Electromagnet, 342 ... Electromagnet, 361 ... Electromagnet, 362 ... Electromagnet, 842 ... Through hole, 911 ... No. 1 magnetic particle, 912 ... second magnetic particle, 913 ... third magnetic particle, 931 ... first magnetic particle with coating, 932 ... second magnetic particle with coating, 933 ... third magnetic particle with coating, 2461 ... bent portion, 2484 ... Permanent magnet

Claims (10)

A step of putting the first magnetic particles and the second magnetic particles having a larger average particle size than the first magnetic particles in the container, and
A step of fixing the first magnetic particles with a first magnetic force and fixing the second magnetic particles with a second magnetic force stronger than the first magnetic force vertically below the first magnetic force.
A step of forming a film on the surface of the first magnetic particles and the surface of the second magnetic particles by an atomic layer deposition method with the first magnetic particles and the second magnetic particles fixed.
A particle coating method characterized by having. The claim comprises a step of fixing the first magnetic particles with the first magnetic force and heating the first magnetic particles and the second magnetic particles with the second magnetic particles fixed with the second magnetic force. The particle coating method according to 1. The container is translucent and
The particle coating method according to claim 2, wherein the first magnetic particles and the second magnetic particles are heated by irradiating infrared rays from the outside of the container. In a state where the first magnetic particles are fixed by the first magnetic force and the second magnetic particles are fixed by the second magnetic force, a film is formed on the surface of the first magnetic particles and the surface of the second magnetic particles. , The process of obtaining the first magnetic particles with a coating and the second magnetic particles with a coating,
After changing at least one of the direction of the first magnetic force and the direction of the second magnetic force, a step of further forming a film on the surface of the coated first magnetic particles and the surface of the coated second magnetic particles.
The particle coating method according to any one of claims 1 to 3. A container that houses the first magnetic particles and a second magnetic particle having a particle size larger than that of the first magnetic particles, an exhaust unit that exhausts the inside of the container to reduce the pressure, and a gas introduction unit that introduces gas into the container. A film forming apparatus for forming a film on the surface of the first magnetic particles and the surface of the second magnetic particles by an atomic layer deposition method.
A first magnetic force and a second magnetic force stronger than the first magnetic force are generated in the container, the first magnetic force fixes the first magnetic particles, and the second magnetic force fixes the second magnetic particles. The generator and
A particle coating device characterized by having. The particle coating device according to claim 5, wherein the magnetic force generating portion is provided outside the container. The particle coating device according to claim 5 or 6, wherein the magnetic force generating unit includes a first electromagnet that generates the first magnetic force and a second electromagnet that generates the second magnetic force. The particle coating device according to any one of claims 5 to 7, wherein the container has a water-repellent treatment on its inner surface. The particle coating device according to any one of claims 5 to 8, wherein the container is made of quartz glass as a main material. The particle coating device according to claim 9, further comprising a heating portion provided outside the container and irradiating infrared rays to heat the first magnetic particles and the second magnetic particles.

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