JP6458819B2 - Ferrite sintered magnet - Google Patents

Description

  The present invention relates to a ferrite magnet and a manufacturing method thereof. More specifically, the present invention relates to a ferrite magnet that can suppress the release of particles and the like from the ferrite magnet and a method for manufacturing the same.

  Ferrite magnets are made of ceramics containing iron oxide as a main component, have relatively excellent magnetic properties, and are inexpensive, and thus are used for various applications.

  In addition, by forming a coating layer on the surface of such a ferrite magnet, the properties of the ferrite magnet are improved or other properties are imparted.

  For example, Patent Document 1 describes a magnet in which the surface of a ferrite magnet is covered with a far-infrared radiation material. Patent Document 2 describes an attracting magnet in which the surface of a ferrite magnet is coated with a nonmagnetic substance.

  In the above Patent Documents 1 and 2, the surface of the ferrite magnet is coated by application of a paint containing a pigment, thermal spraying, powder coating, or the like.

  By the way, in a magnet incorporated in a voice coil motor (VCM) for driving a magnetic head of a hard disk drive (HDD), dust generated due to particles falling off from the magnet so that the lubricant on the disk surface is not contaminated. And the release of ions is required. When a ferrite magnet is incorporated as such a magnet for VCM use, there are the following problems.

  Ferrite magnets are ceramics, and are composed of a plurality of ferrite particles, and these particles are bonded via grain boundaries and voids. Therefore, when vibration or impact is applied to the ferrite magnet, the ferrite particles constituting the ferrite magnet may drop off or the gas may be released due to heat or the like relatively easily. For this reason, there is a problem that it is difficult to use the ferrite magnet as a VCM for driving a magnetic head of an HDD.

  As shown in Patent Documents 1 and 2, it is conceivable to coat the surface of the ferrite magnet. However, such a coating layer only covers the surface of the ferrite magnet and does not bind the ferrite particles together. Therefore, when vibration or impact is applied to the ferrite magnet having the coating layer on the surface, there is a problem that the coating layer is dropped and the ferrite particles are dropped and the gas is released.

  Further, in Patent Document 3, in order to simultaneously improve the brittleness of the magnet and protect the surface, the rare earth magnet is impregnated with a resin agent and cured, and then a surface treatment such as plating or painting is performed to form a coating layer. Proposed. However, even if the technique shown in Patent Document 3 is applied to, for example, a ferrite magnet used in a VCM of a small device such as a magnetic head, the adhesion between the protective layer and the impregnating resin agent becomes a problem. When vibration or impact is applied to the ferrite magnet, there is a problem in that the ferrite particles fall off and the gas is released as the coating layer falls off.

Japanese Utility Model Publication No. 62-109407 JP-A-1-295406 JP-A-1-243507

  The present invention has been made in view of such a situation, and an object thereof is to provide a ferrite magnet that can suppress the release of particles and the like from the ferrite magnet and a method for manufacturing the same.

In order to achieve the above object, the ferrite magnet according to the present invention comprises:
A ferrite body composed of a plurality of ferrite particles;
An impregnated phase introduced between the ferrite particles on the surface of the ferrite body;
A ferrite magnet having a final coating layer formed on the outermost surface of the ferrite body,
In the boundary between the impregnated phase and the final coating layer, the final coating layer is in contact with both the ferrite particles and the impregnated phase.

  In the present invention, the impregnated phase formed on the ferrite element body enters the gaps between the ferrite particles so as to be exposed on the surface of the ferrite element body together with the ferrite particles. That is, the impregnated phase exists between the ferrite particles. As a result, since the plurality of ferrite particles are connected and fixed through the impregnation phase, it is possible to effectively prevent the ferrite particles from falling off.

  Furthermore, in the present invention, at the boundary between the impregnated phase and the final coating layer, the final coating layer covers the outer surface of the ferrite element body so as to contact both the ferrite particles and the impregnated phase. For this reason, it is easy to reduce the thickness of the layer from the outer surface of the ferrite body to the outermost surface of the final coating layer, and while maximizing the magnetic properties of the ferrite body, the ferrite particles themselves It is possible to satisfactorily prevent the falling off and the released gas from inside the ferrite element body.

  Further, at the boundary between the impregnated phase and the final coating layer, the final coating layer covers the outer surface of the ferrite body so as to contact both the ferrite particles and the impregnated phase. At the boundary, the ferrite particles function like a wedge for firmly joining them, and the adhesion between these three is improved. Also from this point, it is possible to satisfactorily prevent the dropping of the ferrite particles themselves and the released gas from the inside of the ferrite body.

  Preferably, the impregnation phase is a phase containing one or more inorganic components of Si, Al, Mg, Ca, Fe, Cl, F, or an acrylic resin, an epoxy resin, a polyurethane resin, a polyimide resin, a polyamideimide resin. And a phase containing at least one selected from silicone resins. Among these, as the impregnation phase, an acrylic resin, an epoxy resin, and a silicone resin are preferable, and a silicone resin is particularly preferable. By using a phase containing such a component as an impregnated phase, it is possible to prevent the ferrite particles themselves from falling off, and to prevent gas released from the ferrite element body and eluted ions, as well as cracking and chipping. The effect of preventing chipping can also be achieved.

  Preferably, the final coating layer is composed of any of parylene, epoxy resin, polyimide resin, polyamideimide resin, polyurethane resin, acrylic resin, and silicone resin. More preferably, the said last coating layer is comprised with parylene, an epoxy resin, and a polyimide resin, Most preferably, it is comprised with parylene. By configuring in this way, it is possible to satisfactorily prevent the dropping of the ferrite particles itself, the gas released from the inside of the ferrite body, and the eluted ions, and also the effect of preventing chipping such as cracking and chipping can be achieved. Inconveniences such as edge film peeling do not occur.

In addition, the method of manufacturing a ferrite magnet according to the present invention is as follows.
Preparing a ferrite body composed of a plurality of ferrite particles;
Forming an impregnated phase so as to penetrate into the gaps between the ferrite particles on the surface of the ferrite body;
Polishing the surface of the ferrite body until both the ferrite particles and the impregnated phase are exposed;
Forming a final coating layer on the surface of the ferrite element body where both the ferrite particles and the impregnated phase are exposed.

  According to the method for manufacturing a ferrite magnet according to the present invention, the ferrite magnet of the present invention can be easily manufactured. In addition, since the method of the present invention employs a polishing process after the impregnation phase is formed, chipping such as cracks and chips is performed as compared with the prior art in which the polishing process is performed before the formation of the impregnation phase. Excellent prevention effect.

  The final coating layer may be formed after a primer treatment is performed on the surface of the ferrite body from which both the ferrite particles and the impregnated phase are exposed. In this case, the adhesion of the final coating layer to the ferrite particles and the impregnated phase is further improved.

FIG. 1 is a schematic diagram of a ferrite magnet according to an embodiment of the present invention. FIG. 2 is an enlarged schematic cross-sectional view of a portion II in FIG. 3 (A) to 3 (C) are schematic cross-sectional views showing the main part of the manufacturing process of the ferrite magnet shown in FIG. FIG. 4 is an enlarged schematic cross-sectional view of a main part of a ferrite magnet according to another embodiment of the present invention.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

(Ferrite magnet)
As shown in FIG. 1, the ferrite magnet 1 according to the present embodiment has a ferrite body 10. As shown in FIG. 2, the outermost surface of the ferrite body 10 is covered with a final coating layer 30. In the present embodiment, the final coating layer 30 is preferably formed on the entire surface of the ferrite body 10.

(Ferrite body 10)
The ferrite element body 10 constituting the ferrite magnet 1 is not particularly limited in composition as long as it is hard ferrite or soft ferrite, but the present invention is particularly effective in the case of hard ferrite.

  The ferrite body 10 preferably has a ferrite component as a main component and an additive component.

The ferrite body 10 has a plurality of ferrite particles 11. The additive component may be dissolved in the ferrite particles, or the additive component may be included as a component (grain boundary component) present at the grain boundary between the ferrite particles. In the present embodiment, as grain boundary _components, SiO 2, CaO, alumina and the like.

  The shape of the ferrite particles 11 constituting the ferrite body 10 is not particularly limited, and may be circular or flat, but in this embodiment, it is flat. Although the average particle diameter of the flat direction (longitudinal direction) of each particle | grain 11 is not specifically limited, In this embodiment, it is 0.1-2 micrometers.

  In this embodiment, the ferrite body 10 is dense and preferably has few voids such as pores between the particles 11, but as described below, the impregnated phase 20 is formed in the gaps between the particles 11. It is formed.

(Impregnated phase 20)
The impregnated phase 20 is a phase containing one or more inorganic components of Si, Al, Mg, Ca, Fe, Cl, F, or an acrylic resin, epoxy resin, polyurethane resin, polyimide resin, polyamideimide resin, silicone resin It is comprised with the phase containing at least 1 or more chosen from these, Preferably it is a phase which has an inorganic component as a main component. As long as the inorganic component is the main component, it may be composed of a metal, an oxide, or a composite of these.

Further, when the impregnated phase is composed of an oxide, it preferably contains SiO ₂ , AlO _x , MgO, CaO, FeO _{x and the} like.

  In this embodiment, it is preferable that the impregnation phase 20 contains Si oxide. By doing so, the ion permeability of the impregnated phase 20 can be lowered, the release of ions generated from the element body 10 to the outside can be effectively suppressed, and the ferrite particles 11 and the final coating layer 30 It is also possible to improve the adhesion.

  As shown in FIG. 2, the impregnated phase 20 is impregnated inside the ferrite body 10 and exists so as to connect the ferrite particles 11.

(Final coating layer 30)
In this embodiment, the final coating layer 30 is formed of a material different from that of the impregnated phase 20 in a separate process. The final coating layer 30 is composed of any one of parylene, epoxy resin, polyimide resin, acrylic resin, polyurethane resin, polyamideimide resin, and silicone resin, but preferably composed of parylene, epoxy resin, and polyimide resin. More preferably, it is composed of parylene. Parylene is a general term for para-xylene polymers, and has a structure in which benzene rings are connected via CH ₂ or CF ₂ , and is a stable crystalline polymer that can be formed by vapor deposition polymerization. Also has a feature that film formation is possible.

  As shown in FIG. 2, the thickness t1 of the final coating layer 30 is preferably larger than the average particle diameter of the ferrite particles 11 along the direction of the thickness t1. In the present embodiment, the thickness t1 of the final coating layer 30 substantially matches the thickness of the layer from the outermost surface of the particles 11 constituting the ferrite body 10 to the outermost surface of the final coating layer 30, and the thickness is When the final coating layer 30 is parylene, the minimum coating thickness is 1 to 10 μm, preferably 3 to 8 μm, and more preferably 5 to 8 μm. Moreover, if the last coating layer 30 is resin formed by the apply | coating method like an epoxy resin or a polyimide resin, 10-30 micrometers is preferable.

  In FIG. 2, the short direction of the ferrite particles 11 oriented in a predetermined direction coincides with the direction of the thickness t1 of the final coating layer 30, but depending on the position where the final coating layer 30 covers the element body 10, The longitudinal direction of the ferrite particles 11 may coincide with the direction of the thickness t1 of the final coating layer 30, or the other.

(Boundary between final coating layer 30 and impregnated phase 20)
In the present embodiment, at the boundary 40 between the final coating layer 30 and the impregnated phase 20, the final coating layer 30 is in contact with both the ferrite particles 11 and the impregnated phase 20. The impregnation depth t2 of the impregnation phase 20 is preferably at least three times the average particle diameter in a predetermined direction (the same direction as the thickness t1 of the coating layer 30) in the ferrite particles 11, and the entire thickness of the element body 10 is thin May be the same as the entire thickness of the element body 10.

  At the boundary 40 between the final coating layer 30 and the impregnated phase 20, most of the ferrite particles 11 (80% or more, preferably 90% or more) located on the outermost surface of the element body 10 are in contact with the final coating layer 30. . The situation can be explained as follows from another point of view. At the boundary 40 between the final coating layer 30 and the impregnated phase 20, the ferrite particles 11 are contacted at an area ratio of 80% or more, preferably 90% or more, of the inner surface of the final coating layer 30, and the upper limit of the area ratio is , Determined based on the minimum area ratio of the contact area with the impregnated phase 20, preferably 10% or less, more preferably 1% or less. Note that some of the ferrite particles 11 located on the outermost surface of the element body 10 are arranged so as to bite into the final coating layer 30.

  Whether or not the region existing between the ferrite particles is an impregnated portion can be determined as follows, for example.

  First, the ferrite body is cut along a plane perpendicular to the interface between the ferrite body and the impregnated phase. Using the energy dispersive X-ray spectrometer (EDS) attached to an electron microscope such as a scanning electron microscope (SEM), the content ratio of the metal element constituting the inorganic component contained in the impregnated phase is applied to the cut surface. It can be judged from the distribution.

  Specifically, by performing surface analysis, line analysis, point analysis, etc. on the region between the ferrite particles appearing on the cut surface, a region where the metal element is present in a specific amount from the obtained distribution of the metal element Is defined as the impregnated phase.

  In the present embodiment, as described above, the impregnated phase preferably contains Si oxide. On the other hand, Si oxide may be included as an additive component of the ferrite body. The Si oxide as an additive component is usually present as a grain boundary component at the grain boundary between ferrite particles.

  In such a case, even if Si distribution is obtained by the above method, it is difficult to distinguish between Si derived from the impregnated phase and Si derived from the grain boundary component. Therefore, it is preferable to use the following method.

  First, in a region (grain boundary, etc.) existing between ferrite particles located near the center of the ferrite body, the metal element MA included in the impregnated phase and the metal included in the additive component that is not included in the impregnated phase. The content ratio of the element MB is calculated by the above method. The content ratio (MA / MB) of these elements in terms of mole is set to 1.

  Assuming that the metal element MA derived from the impregnated phase is not impregnated or hardly impregnated between the ferrite particles located near the center of the ferrite element body, the metal element MA in a region existing between the ferrite particles is assumed. And MB are considered to be derived only from grain boundary components.

  Then, in the region where the metal element derived from the impregnated phase exists, the content ratio of MA increases and the content ratio of MB does not change, so the content ratio (MA / MB) in the region becomes larger than 1.

  By using this method, the impregnated phase can be defined even when the metal element contained in the impregnated phase overlaps with the metal element contained in the additive component. Even when the metal element contained in the impregnated phase and the metal element contained in the additive component do not overlap, this method may be used to define the impregnated phase.

(Manufacturing method of ferrite magnet)
Next, an example of a method for manufacturing a ferrite magnet according to the present embodiment will be described.

  First, a raw material for the ferrite body is prepared. As a raw material, oxides such as iron oxide and zinc oxide may be used, and various compounds that become oxides after firing may be used. Moreover, the raw material of an additional component is prepared as needed. The prepared raw material may be calcined.

  Next, the prepared raw material, a binder resin, and the like are mixed, and the mixture is molded into a predetermined shape by a known molding method. In this embodiment, it is molded into a plate shape to obtain a ferrite body molded body. In addition, you may grind | pulverize and granulate etc. in order to set it as the form suitable for shaping | molding as needed. Moreover, you may perform a binder removal process etc. with respect to this molded object as needed.

  Next, the obtained molded body is fired to obtain a sintered body (ferrite body 10 shown in FIG. 3A). The firing conditions are not particularly limited, and may be performed under known conditions. An impregnation phase is formed on the obtained ferrite body.

  First, the outer surface of the ferrite body 10 is washed and dried. This is to remove the oil and moisture present on the surfaces of the particles 11 existing on the outer surface of the element body 10 and the gaps therebetween. The method for cleaning is not particularly limited, but for example, cleaning with a sponge or the like, and ultrasonic cleaning or the like may be performed. After washing, the solvent used for washing is removed from the ferrite body.

  Next, a raw material (sealing agent) for forming the impregnated phase is prepared. In the present embodiment, since the impregnated phase contains Si oxide, a sealing agent containing at least a precursor of Si oxide is prepared. Although it does not restrict | limit especially as a precursor of Si oxide, Si compound is preferable. Specific examples of the sealing agent include silicone resin, silicon alkoxide, cyclic siloxane, silane, and polysilazane. Further, the sealing agent is preferably prepared as a liquid or gaseous raw material in order to reliably impregnate the gaps between the ferrite particles 11.

  In this embodiment, a silicone resin is used as the sealing agent. In the sealing treatment, the cleaned and dried element body 10 is put into the vacuum tank, and then the pressure is reduced, and the air remaining in the pores (gap between the particles 11 and the particles 11) of the element body 10 is removed. remove. After that, the pressure reducing valve is closed, the sealing agent is injected from another line, the entire ferrite element body is immersed, the tank interior is returned to atmospheric pressure, and then the pressure is increased, whereby the sealing treatment is performed. Promotes agent penetration.

  Thereafter, the ferrite element body 10 may be taken out from the inside of the tank, and an excessive sealing agent on the surface may be blown off by a spin dry or rinsed. Further, after that, the sealing agent is cured in the gaps between the particles 11 at least near the surface of the element body 10 as shown in FIG. Is formed. Further, the coating impregnated phase 20 a is also formed on the outer surface of the element body 10.

  Next, in the present embodiment, the base body 10 on which the coating impregnated phase 20a is also formed on the outer surface is subjected to a polishing process by a surface process such as barrel polishing, lapping polishing, sand blasting, or grindstone polishing. As shown in FIGS. 3B and 3C, the polishing conditions are such that the coated impregnated phase 20a formed on the outer surface of the element body 10 is removed and both the ferrite particles 11 and the impregnated phase 20 are removed. This is the condition until exposure occurs. At the time of polishing, the ferrite particles 11a protruding from the coating impregnated phase 20a are also removed by polishing.

  Thereafter, as shown in FIG. 2, the final coating layer 30 is formed on the surface of the ferrite body 10 where both the ferrite particles 11 and the impregnated phase 20 are exposed. In the state shown in FIG. 2, the final coating layer 30 is in contact with both the ferrite particles 11 and the impregnation phase 20 at the boundary 40 between the impregnation phase 20 and the final coating layer 30.

  The obtained ferrite magnet is suitable for a clean environment where a high degree of cleaning is required because dropping of ferrite particles, outgassing, and ion elution are suppressed. Specifically, it is suitable for a magnetic head drive VCM application of an HDD.

(Effect of embodiment)
In the present embodiment, the impregnated phase 20 formed on the ferrite element body 10 enters the gaps between the ferrite particles 11 so as to be exposed on the surface of the ferrite element body 10 together with the ferrite particles 11. That is, the impregnated phase 20 exists between the ferrite particles 11. As a result, since the plurality of ferrite particles 11 are connected and fixed through the impregnation phase, it is possible to effectively suppress the dropping of the ferrite particles 11.

  Furthermore, in the present embodiment, at the boundary between the impregnated phase 20 and the final coating layer 30, the final coating layer 30 covers the outer surface of the ferrite element body 10 so as to contact both the ferrite particles 11 and the impregnated phase 20. Yes. For this reason, it becomes easy to form thinly the thickness t1 of the layer from the outer surface of the ferrite element body 11 to the outermost surface of the final coating layer 30, and while maximizing the magnetic characteristics of the ferrite element body 10, It is possible to satisfactorily prevent the ferrite particles 11 from dropping off, the released gas from the ferrite body 10 and the elution of ions.

  Further, at the boundary between the impregnation phase 20 and the final coating layer 30, the final coating layer 30 covers the outer surface of the ferrite element body 10 so as to contact both the ferrite particles 11 and the impregnation phase 20. At the boundary between the phase 20 and the final coating layer 30, the ferrite particles 11 function as a wedge for firmly joining them, and the adhesion between these three components is improved. Also from this point, it is possible to satisfactorily prevent the ferrite particles 11 from dropping off, the released gas from the ferrite element body, and the ion elution. In addition, by forming the final coating layer 30 from parylene, inconveniences such as edge film peeling can be effectively reduced.

  Furthermore, according to the method of manufacturing a ferrite magnet according to the present embodiment, since the polishing step is employed after the impregnation phase is formed, compared to the conventional technique in which the polishing step is performed before the impregnation phase is formed. Excellent in preventing chipping such as cracking and chipping.

(Another embodiment)
The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, as shown in FIG. 4, a parylene film is formed on the surface of a ferrite body 10 made of ferrite particles 11 without performing surface treatment such as barrel polishing, and the impregnated phase 200 and the final coating layer 300 are made of parylene. You may form simultaneously. In the case of this embodiment, the impregnation phase 200 and the final coating layer 300 can be formed at the same time without the need for barrel polishing, which simplifies the manufacturing process. Further, compared to the above-described embodiment, the particle dropout is somewhat inferior in terms of cracking and chipping during assembly handling, but also in the embodiment shown in FIG. The release of substances (ions and gases) can be satisfactorily prevented, and the effect of preventing chipping such as cracking and chipping can be achieved.

  As yet another embodiment of the present invention, the final coating layer 30 may be formed after applying a primer treatment to the surface of the ferrite body 10 where both the ferrite particles 11 and the impregnated phase 20 are exposed. In this case, the adhesion of the final coating layer 30 to the ferrite particles 11 and the impregnated phase 20 is further improved. The primer treatment is determined according to the material of the final coating layer 30. When the final coating layer is parylene, it is preferable to use ozone cleaning, itro processing, silane processing, or degreasing cleaning as the primer processing.

  When the final coating layer is an epoxy resin or a polyimide resin, it is preferable to use a commercially available primer, ozone cleaning, itro processing, silane processing, or degreasing cleaning as the primer processing.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
Sample 1
First, a hard ferrite magnet (anisotropic ferrite magnet, disk type, diameter 24 mm, thickness 1.3 mm, surface area 1000 mm ² , mass 2.98 g) manufactured by a known method was prepared as a ferrite element.

  In order to remove oil and moisture present on the surface and gaps (pores) of the ferrite body, the ferrite body was washed with acetone and then dried.

  The ferrite body after washing and drying was put into a vacuum tank and the pressure was reduced to 1 torr to remove the air remaining in the pores. Thereafter, the pressure reducing valve was closed, a sealing agent was injected from another line, and the entire ferrite body was immersed. At this time, a silicone resin (HS-100, manufactured by D & D Co., Ltd.) was used as the sealing agent.

With the ferrite element body sufficiently immersed in the sealing agent, the pressure in the tank was returned to atmospheric pressure, and the sealing agent was permeated into the pores. Furthermore, the penetration of the sealing agent was promoted by increasing the pressure in the tank to 5 kg / cm ² .

  The ferrite element body in which the sealing agent sufficiently penetrated was taken out of the tank, and the surface of the ferrite element body was washed using IPA (isopropyl alcohol, manufactured by Junsei Chemical Co., Ltd.) in order to remove the excess sealing agent. The ferrite body after washing was heat-treated at 150 ° C. for 15 minutes to cure the sealing agent remaining on the surface and inside (in the pores) of the ferrite body to form an impregnated phase.

  After passing through the sealing treatment, the ferrite magnet having the impregnated phase formed therein is put into a barrel apparatus (RH-50, manufactured by Chipton Co., Ltd.), and both the ferrite particles and the impregnated phase are formed as shown in FIG. Surface treatment was performed by barrel polishing so as to be exposed. As conditions for barrel polishing, polishing stone: HS-5 used (30 kg / RH-50 input), abrasive: none, compound: none, water: 15 L, number of workpieces: 500 sheets, rotation speed: 30 rpm, processing time : 300 minutes, R application amount: R = 0.2. Furthermore, the surface of the ferrite magnet after barrel polishing was observed with an electron microscope, and it was confirmed that both surfaces of the ferrite particles and the impregnated phase appeared on the surface of the ferrite magnet.

  After the surface treatment, the ferrite magnet on which the surfaces of both the ferrite particles and the impregnated phase are exposed is coated with an epoxy resin (XNR3640LC, manufactured by Nagase ChemteX Corporation) by a coating method to obtain a film thickness. A final coating layer of 10 μm was formed.

<Dust generation (LPC test)>
The finally obtained sample was placed in water (beaker containing 500 ml of ultrapure water), irradiated with ultrasonic waves under the condition of 28 kHz-5 min, and suspended dust (> 0.5 μm) desorbed from the sample into water. Size) was measured with a liquid particle counter (LPC, PMS, lower limit 50 pcs / cc, upper limit 30000 pcs / cc). In the present embodiment, the amount of dust generation is preferably 1640 or less, more preferably 600 or less, and even more preferably 320 or less. The results are shown in Table 1.

<Occurrence rate of cracks and burrs>
Visual inspection was performed on the surface-treated samples (20 samples prepared under the same conditions), and the occurrence rate of cracks and chips was measured. Here, crack refers to a defect having a broken part of 1 mm or more, and chipping refers to a defect having a broken part of less than 1 mm. In this example, the occurrence rate of cracks and burrs was 45% or less, more preferably 15% or less, and even more preferably 5% or less. The results are shown in Table 1.

<Occurrence rate of film peeling>
The surface of the corner (edge portion) of the ferrite magnet was observed with an optical microscope for the sample after forming the final coating layer (20 samples prepared under the same conditions), and the rate of film peeling was measured. Here, the film peeling refers to a case where the final coating layer is swollen or the final coating layer is not formed. In this example, the rate of occurrence of film peeling was 55% or less, more preferably 15% or less, and more preferably 5% or less. The results are shown in Table 1.

  As shown in Table 1, in Sample 1, the impregnated phase formed of the silicone resin can alleviate the impact on the ferrite base body due to barrel polishing, and can effectively prevent the occurrence of cracks and cracks.

  Further, in the sample 1 according to the present invention, surface treatment (barrel polishing) is performed on the ferrite element body after the sealing treatment so that both the ferrite particles and the impregnated phase are exposed as shown in FIG. It has been subjected. As a result, even at the edge portion of the ferrite magnet, where uniform coating treatment is usually difficult, the coating treatment can be easily performed due to the presence of a moderately exposed impregnation phase. In addition, the final coating layer formed in this manner is in contact with both the ferrite particles and the impregnated phase as shown in FIG. 2, and is excellent in adhesion between the final coating layer and the ferrite body. Therefore, the amount of dust generation and the rate of film peeling can be effectively reduced in the finally obtained ferrite magnet.

Sample 2-6
Samples 2 to 6 were prepared in the same manner as Sample 1 except that any one or more of sealing treatment, surface treatment and coating treatment were not performed as shown in Table 1. Evaluation was performed. The results are shown in Table 1.

  As shown in Table 1, Samples 2 to 6 were not subjected to any one or more of sealing treatment, surface treatment, and coating treatment, so the amount of dust generation, the occurrence rate of cracks and chips, and film peeling Any one or more measurement results of the occurrence rate are worsening.

Sample 7
Sample 7 was prepared in the same manner as Sample 1 except that the surface treatment before the sealing treatment was performed instead of the surface treatment after the sealing treatment of Sample 1, and the same evaluation was performed. Similar evaluations were made. The results are shown in Table 1.

  As shown in Table 1, sample 7 has many cracks and burrs after the surface treatment. This is because the impregnated phase is not formed in the ferrite body subjected to the surface treatment, so that the effect of the impregnated phase is obtained, which reduces the impact on the ferrite body accompanying the surface treatment and suppresses cracks and cracks. This is thought to be due to the fact that it was not.

Further, as shown in Table 1, in the sample 7, in the finally obtained sample, the amount of dust generation is worse than that of the sample 1, and film peeling is also frequent. This is because, prior to the coating treatment, the ferrite body after the impregnation treatment was not subjected to a surface treatment that exposes both the ferrite particles and the impregnation phase. It is considered that this is due to the fact that the adhesiveness between the final coating layer and the ferrite body has deteriorated, rather than being in contact with both phases.
(Example 2)

Samples 21-24
Next, the ferrite magnets of Samples 21 to 24 shown below were produced. Table 2 shows the evaluation results of each sample.

  Sample 21 was the same as Sample 1 of Example 1 except that silicon alkoxide (tetraethoxysilane, manufactured by ADEKA Corporation) was used instead of the sealing agent used in Sample 1 of Example 1. Samples were prepared and evaluated in the same manner.

  Sample 22 uses an anaerobic acrylic monomer (PMS-10E, manufactured by Henkel) instead of the sealing agent used in Sample 1 of Example 1, and centrifugal dehydration (50 rpm) as a removal of the excess sealing agent. Thereafter, a sample was prepared in the same manner as the sample 1 of Example 1 except that it was washed with water and not further cured, and the same evaluation was performed.

  Sample 23 was the same as Sample 1 of Example 1 except that a thermosetting acrylic monomer (Resinol 90C, manufactured by Henkel) was used instead of the sealing agent used in Sample 1 of Example 1. Samples were prepared and evaluated in the same manner.

  Sample 24 was prepared in the same manner as Sample 1 of Example 1, except that polysilazane (V110, manufactured by Clariant Japan) was used instead of the sealing agent used in Sample 1 of Example 1. The same evaluation was performed.

  As shown in Table 2, even when the type of the sealing agent was changed, when the sealing process was performed in the same manner as in Sample 1, the sealing process was not performed (Sample 2). In comparison, it was confirmed that all of the dust generation amount, cracking and chipping rate, and film peeling rate were reduced (Samples 21 to 24).

  As shown in Table 2, sample 21 has the effect of reducing the amount of dust generation, the occurrence rate of cracks and chips, and the rate of occurrence of film peeling compared to the other samples (samples 1 and 22 to 24). Inferiority was confirmed. This is because the film quality of the ferrite body after the impregnation treatment becomes too hard due to the formation of the impregnation phase using silicon alkoxide as the sealing agent, and the impregnation phase has an impact on the ferrite body due to the surface treatment. This is considered to be due to insufficient relaxation.

(Example 3)
Samples 31-38
Next, the ferrite magnets of Samples 31 to 38 shown below were produced. The evaluation results of each sample are shown in Table 3.

  Samples 31 and 32 were prepared in the same manner as Sample 1 of Example 1, except that the film thickness shown in Table 3 was used instead of the final coating layer formed in Sample 1 of Example 1. The same evaluation was performed.

  In Samples 33 to 35, polyimide resin (Semicofine, manufactured by Toray Industries, Inc.) was used instead of the coating treatment used in Sample 1 of Example 1, and the film thickness of the final coating layer was set to the film thickness shown in Table 3. Except for the above, a sample was prepared in the same manner as Sample 1 of Example 1, and the same evaluation was performed.

  In Samples 36 to 38, parylene (Parylene-C, manufactured by Japan Parylene Co., Ltd.) was used in place of the coating treatment used in Sample 1 of Example 1, and the film thickness of the final coating layer was as shown in Table 3. A sample was prepared in the same manner as the sample 1 of Example 1 except that the final coating layer was formed by vapor deposition using a gas layer instead of the coating method of Example 1, and the same evaluation was performed.

  As shown in Table 3, when the surface treatment is performed after the sealing treatment and the coating treatment is performed, the same effect as that of the sample 1 is obtained even when the thickness of the coating treatment agent or the final coating layer is changed. It was confirmed that In particular, it was confirmed that the dust generation rate and film peeling can be effectively reduced by increasing the thickness of the final coating layer (Samples 31 to 38).

DESCRIPTION OF SYMBOLS 1,100 ... Ferrite magnet 10 ... Ferrite body 11 ... Ferrite particle 20,200 ... Impregnation phase 30,300 ... Final coating layer 40 ... Boundary

Claims (3)

A ferrite body composed of a plurality of ferrite particles;
On the surface of the ferrite element body, an impregnated phase filling a gap between the ferrite particles;
A ferrite magnet formed on the outermost surface of the ferrite body and having a final coating layer that is a material different from the impregnated phase;
At the boundary between the impregnated phase and the final coating layer, the final coating layer is in contact with both the ferrite particles and the impregnated phase ,
The said last coating layer is comprised with either a parylene, an epoxy resin, a polyimide resin, an acrylic resin, a polyurethane resin, a polyamide-imide resin, and a silicone resin, The ferrite sintered magnet characterized by the above-mentioned.   The impregnation phase is a phase containing one or more inorganic components of Si, Al, Mg, Ca, Fe, Cl, F, or an acrylic resin, epoxy resin, polyurethane resin, polyimide resin, polyamideimide resin, silicone resin The ferrite sintered magnet according to claim 1, wherein the ferrite sintered magnet is a phase including at least one selected from the group consisting of: The ferrite sintered magnet according to claim 1 or 2, wherein the final coating layer has a thickness of 10 to 30 µm .

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