阅读说明：本技术 磁性体粒子、压粉磁芯和线圈部件 (Magnetic particle, dust core, and coil component ) 是由 久保田博信 石田祐也 于 2018-01-05 设计创作，主要内容包括：本发明提供一种磁性体粒子,是具有磁性材料的核和被覆所述磁性材料的核的绝缘被膜而成的磁性体粒子,所述绝缘被膜由含有金属醇盐和有机磷酸或其盐的混合物的溶胶－凝胶反应生成物构成。(The present invention provides a magnetic particle comprising a core of a magnetic material and an insulating coating covering the core of the magnetic material, wherein the insulating coating is composed of a sol-gel reaction product containing a mixture of a metal alkoxide and an organic phosphoric acid or a salt thereof.)

1. A magnetic particle comprising a core of a magnetic material and a 1 st insulating film and a 2 nd insulating film covering the core of the magnetic material,

the 1 st insulating film and the 2 nd insulating film are formed of a sol-gel reaction product.

2. The magnetic particles according to claim 1, wherein one or both of the 1 st insulating film and the 2 nd insulating film is formed of a sol-gel reaction product of a mixture of a metal alkoxide and a surfactant.

3. The magnetic particles according to claim 1 or 2, wherein the 1 st insulating film is formed of a sol-gel reaction product of a mixture of a metal alkoxide, a surfactant, and a silane coupling agent.

4. The magnetic particles according to any one of claims 1 to 3, wherein the 2 nd insulating film is made of a material different from that of the 1 st insulating film.

5. A method for producing magnetic particles, comprising the steps of:

a step of forming a 2 nd insulating film on the core of the magnetic material by a sol-gel reaction, and

and forming a 1 st insulating film on the core of the magnetic material on which the 2 nd insulating film is formed by a sol-gel reaction.

6. The method for producing magnetic particles according to claim 5, wherein,

one or both of the steps of forming the 1 st insulating film and the 2 nd insulating film include a step of mixing a core of the magnetic material, a metal alkoxide, and a surfactant.

7. The method of producing magnetic particles according to claim 5 or 6, wherein the step of forming the 1 st insulating film includes a step of mixing a core of the magnetic material, a metal alkoxide, a surfactant, and a silane coupling agent.

8. The method for producing magnetic particles according to any one of claims 5 to 7, wherein the 2 nd insulating film is made of a material different from the 1 st insulating film.

9. A magnetic particle comprising a core of a magnetic material and an insulating coating film covering the core of the magnetic material,

the insulating film is formed of a reaction product of a metal alkoxide and a surfactant.

10. The magnetic particles according to claim 9, wherein the insulating coating is formed of a reaction product of a metal alkoxide, a surfactant, and a silane coupling agent.

Technical Field

The present invention relates to magnetic particles, and more particularly, to magnetic particles coated with an insulating film. The present invention also relates to a dust core using the magnetic particles and a coil component using the magnetic particles.

Background

Coil components such as inductors and choke coils are used in various electrical and electronic devices. The coil component is generally composed of a coil and a magnetic core. In recent years, electric and electronic devices have been miniaturized, and coil components used for them have been also required to be miniaturized. In addition, the coil component is required to have excellent magnetic, electrical and mechanical properties in addition to being small in size, and therefore, a magnetic core is required to have high magnetic permeability, high magnetic flux density, low loss and high strength. In particular, in order to suppress an increase in eddy current loss during use in a high frequency range, a magnetic core is required to have a high specific resistance. In order to satisfy such a demand, there is known a powder magnetic core in which a soft magnetic material is formed into fine particles (powder), and the surface of each particle is covered with an insulating film and compression-molded. For example, patent document 1 discloses a powder magnetic core obtained by compression molding a powder of a soft magnetic material whose surface is coated with an insulating coating and further coated with a coupling layer made of a silane coupling agent. Patent document 2 discloses a powder magnetic core obtained by compression molding a powder of a magnetic metal material whose surface is coated with carbon and further coated with a metal oxide mainly composed of silicon oxide.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-259939

Patent document 2: japanese patent laid-open publication No. 2013-209693

Disclosure of Invention

The powder magnetic cores described in patent documents 1 and 2 can certainly secure a certain level of specific resistance, but are not sufficient for suppressing eddy current loss in use in a high frequency region.

Accordingly, an object of the present invention is to provide magnetic particles used for producing a powder magnetic core having a high relative permeability and a high specific resistance, a powder magnetic core using the magnetic particles, and a coil component using the magnetic particles.

As a result of intensive studies to solve the above problems, the present inventors have found that magnetic particles capable of producing a member having high specific resistance and high relative permeability can be obtained by forming an insulating coating on the surface of a core of a magnetic material used for producing a powder magnetic core by a sol-gel reaction using a metal alkoxide and an organic phosphoric acid or a salt thereof, and have completed the present invention.

According to the invention of claim 1, there is provided a magnetic particle comprising a core of a magnetic material and an insulating film covering the core of the magnetic material,

the insulating film is formed of a sol-gel reaction product containing a mixture of a metal alkoxide and an organic phosphoric acid or a salt thereof.

Here, "the insulating coating is formed of a sol-gel reaction product" means that the insulating coating contains a sol ー gel reaction product.

According to the invention of claim 2, there is provided a powder magnetic core obtained by compression molding the magnetic particles.

According to the invention of claim 3, there is provided a coil component comprising the above-mentioned powder magnetic core and a coil wound around the powder magnetic core.

According to the 4 th aspect of the present invention, there is provided a coil component comprising a green body containing the above magnetic particles and resin, and a coil embedded in the green body.

According to the 5 th aspect of the present invention, there is provided magnetic particles comprising a core of a magnetic material and an insulating coating covering the core of the magnetic material, wherein the insulating coating is formed from a mixture containing a metal alkoxide and a surfactant. The magnetic particles are mixed with a resin to form a blank of the coil component.

According to the present invention, a magnetic material particle having high surface insulation can be provided by forming an insulating coating on the surface of a core of a magnetic material by a sol-gel reaction using a sol-gel reactant containing an organic phosphoric acid or a salt thereof. Since the specific resistance of the powder magnetic core and the green body obtained by compression molding the magnetic particles of the present invention is large, a coil component in which eddy current loss in a high frequency region is suppressed can be provided by using the powder magnetic core or the green body.

Drawings

Fig. 1 is a schematic cross-sectional view showing a core of a magnetic material of the present invention and 1 st and 2 nd insulating films covering the core.

FIG. 2 is a sectional view showing a coil component using the powder magnetic core of the present invention.

FIG. 3 is a sectional view showing another coil component using the magnetic particles of the present invention.

Description of the symbols

1 magnetic particles

2 nucleus

3 st insulating film

4 nd 2 nd insulating film

10 coil component

11 dust core

12 coil

20 coil component

21 blank

22 coil

Detailed Description

< embodiment 1 >

The magnetic particles of the present invention comprise a core of a magnetic material and a 1 st insulating film comprising a sol-gel reaction product containing a mixture of a metal alkoxide and an organic phosphoric acid or a salt thereof on the surface thereof. That is, the magnetic particles of the present invention have a core and a 1 st insulating film.

The magnetic particles of the present invention are produced as follows.

First, a core of a magnetic material is prepared. The core is a particle of a magnetic material, and the magnetic particle of the present invention includes a particle of a magnetic material as a core and an insulating coating as a shell covering the core (particle).

The magnetic material is not particularly limited, and a soft magnetic material, particularly a soft magnetic material containing iron, is preferable. By using a soft magnetic material, a dust core having a high magnetic flux density and a high magnetic permeability can be obtained.

The soft magnetic material containing iron is not particularly limited, and examples thereof include iron, Fe-Si alloys, Fe-Al alloys, Fe-Ni alloys, Fe-Co alloys, Fe-Si-Al alloys, and Fe-Si-Cr alloys.

The average particle diameter of the cores of the magnetic material (D50: the particle diameter at which the point at which the cumulative value becomes 50% in a cumulative curve in which the total volume is 100%) is not particularly limited, and may be, for example, 0.01 to 300 μm, preferably 1 to 200 μm, and more preferably 10 to 100 μm. By setting the average particle diameter in the above range, the eddy current loss suppressing effect can be increased, and the magnetic permeability can be further increased.

Next, a 1 st insulating film is formed on the core of the magnetic material. The core may be covered with the 2 nd insulating film in advance. That is, the 2 nd insulating film may be present between the 1 st insulating film and the surface of the core.

In the present invention, the 1 st insulating film is formed by a sol-gel reaction. Specifically, the 1 st insulating film is formed of a sol-gel reaction product containing a mixture of a metal alkoxide and an organic phosphoric acid or a salt thereof. The surface of the magnetic particles is preferably formed of the 1 st insulating film. The 1 st insulating film is formed from the above-described sol-gel reaction product, and therefore cracks are less likely to occur and sliding properties are good. Therefore, a powder magnetic core and a coil component having high specific resistance and high relative permeability can be provided.

First, a sol-like mixture containing a metal alkoxide and an organic phosphoric acid or a salt thereof is prepared.

The mixture is obtained by dissolving or dispersing the metal alkoxide and the organic phosphoric acid or a salt thereof in a solvent.

The metal alkoxide is not particularly limited, and examples thereof include M¹(OR¹)_nThe compounds shown. In the formula, M¹Is Si, Ti, Zr or Al. n is an arbitrary number, and can be determined according to M¹The valence of (A) is determined appropriately. R¹Is a hydrocarbyl group, preferably an alkyl or aryl group, more preferably an alkyl group. The alkyl group is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and may be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group or a tert-butyl group. The aryl group is preferably an aryl group having 6 to 12 carbon atoms, more preferably an aryl group having 6 to 8 carbon atoms, and may be, for example, a phenyl group.

In a preferred embodiment, the metal alkoxide is tetraethoxysilane, titanium tetraisopropoxide, zirconium n-butoxide, or aluminum isopropoxide.

The metal alkoxide may be used alone in 1 kind, or in 2 or more kinds.

The above-mentioned organic phosphoric acid is composed of (R)²O)P(＝O)(OH)₂Or (R)²O)₂P (═ O) OH. In the formula, R²Each independently is a hydrocarbyl group. R²The chain length is preferably 5 atoms or more, more preferably 10 atoms or more, and still more preferably 20 atoms or more. Preferably R²The chain length of (b) is preferably 200 atoms or less, more preferably 100 atoms or less, and still more preferably 50 atoms or less. That is, at least 1 hydroxyl group in the phosphoric acid of the organic phosphoric acid is substituted with a hydrocarbon group. The carbon chain length of the hydrocarbon group is preferably 5 atoms or more, more preferably 10 atoms or more, and still more preferably 20 atoms or more. The longer the hydrocarbon group is, the more the slidability of the surface of the magnetic particle can be improved, and the density of the magnetic material in the coil component can be improved, which is preferable. The carbon chain length of the hydrocarbon group may be 100 atoms or less. The hydrocarbyl group of the organophosphate functions as an oleophilic group and the hydroxyl group of the organophosphate functions as a hydrophilic group. The hydroxyl group of the organic phosphoric acid is condensed with a metal alkoxide and/or a silane coupling agent described later to form a sol-gel reaction product. Further, it is considered that the oleophilic group of the organophosphoric acid introduced into the product improves the affinity with the resin of the base constituting the coil component on the surface of the magnetic particles, or reduces the friction between the magnetic particles to contribute to the improvement of the filling rate of the magnetic particles in the coil component.

The hydrocarbon group is preferably a substituted or unsubstituted alkyl ether group or phenyl ether group. Examples of the substituent include an alkyl group, a phenyl group, a polyoxyalkylene styryl group, a polyoxyalkylene alkyl group, and an unsaturated polyoxyethylene alkyl group.

The salt of an organic phosphoric acid is a salt of an organic phosphoric acid anion and a counter cation, wherein H of at least 1 OH group in the organic phosphoric acid is eliminated.

The organic phosphate anion in the organic phosphate may be (R)²O)P(＝O)(O^-)₂、(R²O)P(＝O)(OH)(O^-) Or (R)²O)₂P(＝O)O^-。

The counter cation in the phosphate is not particularly limited, and examples thereof include an ion of an alkali metal such as Li, Na, K, Rb or Cs, an ion of an alkaline earth metal such as Be, Mg, Ca, Sr or Ba, an ion of another metal such as Cu, Zn, Al, Mn, Ag, Fe, Co or Ni, NH₄ ⁺Amine ions, and the like. Preferably, the counter cation may be Li⁺、Na⁺、K⁺、NH₄ ⁺Or an amine ion.

In a preferred embodiment, the organic phosphate is a polyoxyalkylene styryl phenyl ether phosphate, a polyoxyalkylene alkyl ether phosphate, a polyoxyalkylene alkylaryl ether phosphate, an alkyl ether phosphate or an unsaturated polyoxyethylene alkylphenyl ether phosphate, and the counter cation constituting the salt is Li⁺、Na⁺、K⁺、NH₄ ⁺Or an amine ion.

The phosphoric acid or a salt thereof may be used alone in 1 kind or may be used in 2 or more kinds.

In the mixture, the content of the metal alkoxide is preferably 0.06 parts by weight or more and 15.0 parts by weight or less, more preferably 0.1 parts by weight or more and 4.0 parts by weight or less, and still more preferably 0.2 parts by weight or more and 2.0 parts by weight or less, based on 100 parts by weight of the magnetic material. By setting the content of the metal alkoxide within the above range, the specific resistance of the powder magnetic core obtained from the magnetic particles can be further improved.

In the mixture, the content of the organic phosphoric acid or a salt thereof is preferably 0.05 parts by weight or more, more preferably 0.3 parts by weight or more, preferably 0.3 parts by weight or more and 10 parts by weight or less, and more preferably 0.5 parts by weight or more and 5.0 parts by weight or less, based on 100 parts by weight of the magnetic material. When the content of the organic phosphoric acid or a salt thereof is in the above range, the specific resistance of the powder magnetic core obtained from the magnetic particles can be further improved.

In the above mixture, the weight ratio of the metal alkoxide to the organophosphoric acid or salt thereof (metal alkoxide/organophosphoric acid or salt thereof) is preferably 0.06 or more and 40.0 or less, more preferably 0.06 or more and 15.0 or less, and further preferably 0.2 or more and 15.0 or less. When the weight ratio of the metal alkoxide to the organic phosphoric acid or a salt thereof is in the above range, the specific resistance of the powder magnetic core obtained from the magnetic particles can be further improved.

In a preferred embodiment, a part of the metal alkoxide may be replaced with a silane coupling agent. That is, the mixture may further contain a silane coupling agent in addition to the metal alkoxide and the organic phosphoric acid or its salt.

The substitution amount of the silane coupling agent is preferably 2% by weight or more and 50% by weight or less of the metal alkoxide. That is, the content of the silane coupling agent in the mixture is 2% by weight or more and 50% by weight or less, for example, 10% by weight or more and 40% by weight or less, based on the total of the metal alkoxide and the silane coupling agent. By adding the silane coupling agent in an amount within the above range, the specific resistance of the powder magnetic core obtained from the magnetic particles can be further improved.

In the mixture, the total amount of the metal alkoxide and the silane coupling agent may be preferably 0.05% by weight or more and 20.0% by weight or less, more preferably 0.2% by weight or more and 15.0% by weight or less, and still more preferably 0.3% by weight or more and 10% by weight or less, based on the whole mixture.

The silane coupling agent is not particularly limited, and examples thereof include R^aSiR^b _mR^c _3-mThe compounds shown.

In the formula, R^aIs a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms. R^aThe alkyl group is preferably a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, more preferably a substituted or unsubstituted alkyl group having 3 to 20 carbon atoms, and still more preferably a substituted or unsubstituted alkyl group having 8 to 20 carbon atoms.

The substituent of the substituted or unsubstituted alkyl group having 1 to 20 carbon atoms or aryl group having 6 to 20 carbon atoms is not particularly limited, and examples thereof include an acryloyloxy group, a methacryloyloxy group, an epoxy group, a glycidyloxy group, an amino group, a substituted amino group and the like. The substituent of the substituted amino group is not particularly limited, and examples thereof include an alkyl group having 1 to 6 carbon atoms, an aminoalkyl group having 1 to 6 carbon atoms, and the like.

R^bis-OH, -OR^d、－OCOR^d、－NR^d ₂or-NHR^d(in the formulae, R^dIs a substituted OR unsubstituted alkyl group having 1 to 4 carbon atoms, preferably a methyl group), preferably-OR^dMore preferred is a methoxy group or an ethoxy group, and particularly preferred is a methoxy group.

R^cRepresents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and preferably represents a methyl group, an ethyl group or a phenyl group.

m is 1, 2 or 3, preferably 3.

In a preferred embodiment, the silane coupling agent is R^aSi(OR^d)₃。

Examples of the silane coupling agent include octadecyltrimethoxysilane, hexadecyltrimethoxysilane, aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 8-methacryloyloxy-octyltrimethoxysilane, 8- (2-aminoethylamino) octyltrimethoxysilane, 8-glycidyloxy-octyltrimethoxysilane, 3- (methacryloyloxy) propyltrimethoxysilane and decyltrimethoxysilane.

The silane coupling agent may be used alone in 1 kind, or may be used in 2 or more kinds.

The solvent is not particularly limited, but is preferably an alcohol, an ether, a glycol or a glycol ether. In a preferred mode, the solvent may be methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, 1-pentanol, 2-methyl-2-pentanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether or diethylene glycol monohexyl ether. Further, water may be contained as necessary.

The solvent may be used alone in 1 kind, or may be used in 2 or more kinds.

In one embodiment, the mixture may contain various additives, for example, a catalyst, a pH adjuster, a stabilizer, a thickener, and the like. Examples of the additive include an acid compound such as a boric acid compound and a basic compound such as an ammonia compound.

Next, the mixture is applied so as to cover the cores of the magnetic material and dried, whereby the mixture is cured to form an insulating film (1 st insulating film) and magnetic particles are obtained. Drying may be carried out by volatilizing the solvent in the mixture, and the particles coated with the mixture may be heated or blown. It should be noted that if the mixture is heated and dried, the curing of the metal alkoxide and/or the silane coupling agent in the mixture is promoted, and a more dense film is easily formed, which is preferable.

The method of applying the mixture to the particles of the magnetic material is not particularly limited, and examples thereof include a method of adding the particles of the magnetic material to the mixture, stirring the mixture, and filtering the mixture. The stirring time is preferably 10 minutes to 5 hours, more preferably 30 minutes to 3 hours, and still more preferably 1 hour to 2 hours.

In the above embodiment, the mixture is prepared, and the particles of the magnetic material are added to the mixture to apply the mixture to the particles, but the method is not limited thereto. For example, the particles of the magnetic material, the metal alkoxide and/or silane coupling agent, and the organic phosphoric acid or its salt may be added separately and mixed. Alternatively, the insulating coating may be formed by charging particles of the magnetic material with a metal alkoxide and an organic phosphoric acid or a salt thereof, performing a sol-gel reaction, and then charging a silane coupling agent, and further performing a sol-gel reaction.

When heating is performed in the drying step, the heating temperature may be preferably 40 ℃ to 500 ℃, more preferably 50 ℃ to 400 ℃, and still more preferably 60 ℃ to 350 ℃.

When heating is performed in the drying step, the heating time may be preferably 10 minutes to 5 hours, more preferably 30 minutes to 3 hours, and still more preferably 1 hour to 2 hours.

The obtained magnetic particles have high insulation between the particles because the cores are covered with the insulating film (i.e., the 1 st insulating film).

The thickness of the 1 st insulating film is preferably 1nm or more and 100nm or less. By setting the thickness of the 1 st insulating film to 1nm or more, the specific resistance of the magnetic particles can be improved. Further, by setting the thickness of the 1 st insulating film to 100nm or less, the proportion of the magnetic material in the magnetic particles can be increased, and the magnetic characteristics of the coil component can be improved.

As shown in fig. 1, the magnetic particles 1 may further include a 2 nd insulating film 4 between the 1 st insulating film 3 and the core 2 in addition to the 1 st insulating film 3. In this case, even if a crack is generated in the 1 st insulating film on the surface of the particle constituting the magnetic material, the crack is less likely to propagate to the 2 nd insulating film, and a decrease in the insulation of the magnetic particle can be suppressed.

The 2 nd insulating film is composed of a sol-gel reaction product containing a mixture of a metal alkoxide and an organic phosphoric acid or a salt thereof. Alternatively, the 2 nd insulating film is formed of a sol-gel reaction product containing a mixture of a metal alkoxide, an organic phosphoric acid or a salt thereof, and a silane coupling agent. Alternatively, the 2 nd insulating film is formed of a sol-gel reaction product containing a mixture of a metal alkoxide and a silane coupling agent. Alternatively, the 2 nd insulating film is a film of a metal salt such as iron phosphate formed by a chemical conversion treatment with phosphoric acid. Alternatively, the 2 nd insulating film is formed of an oxide of a magnetic material. The 2 nd insulating film may be formed of the same material as the 1 st insulating film or a different material.

The thickness of the 2 nd insulating film and the thickness of the 1 st insulating film are preferably 1nm to 100nm in total. By setting the total thickness of the 1 st and 2 nd insulating films to 1nm or more, the specific resistance of the magnetic particles can be increased. Further, by setting the total thickness to 100nm or less, the proportion of the magnetic material in the magnetic particles can be increased, and the magnetic properties of the coil component can be improved.

The powder magnetic core using the magnetic particles obtained as described above has high relative permeability and high specific resistance. Therefore, when used as a magnetic core of a coil component, the core exhibits high electrical characteristics and can suppress eddy current loss.

Accordingly, the present invention also provides a powder magnetic core obtained by compression molding the magnetic particles of the present invention. As shown in fig. 2, the present invention also provides a coil component 10 including the powder magnetic core 11 of the present invention and a coil 12 wound around the powder magnetic core.

The above-described dust core can be manufactured by a method known in the art. For example, the powder magnetic core of the present invention can be obtained by compression molding a mixed powder in which a binder (for example, silicone resin) is added to the magnetic particles of the present invention, and heat-treating the obtained powder compact.

As shown in fig. 3, the present invention also provides a coil component 20 including a green body 21 containing the magnetic particles and resin obtained as described above, and a coil 22 embedded in the green body.

In this coil component, since the surfaces of the magnetic particles are covered with the 1 st insulating film containing an organic phosphoric acid having a hydrocarbon group or a salt thereof, the magnetic particles can be dispersed in the resin well, and the magnetic permeability of the green body can be improved by improving the filling property of the magnetic particles in the green body. In addition, the concentration of the magnetic flux can be reduced, and the saturation density of the magnetic flux can be improved. In addition, when the magnetic particles are made of a mixture containing a silane coupling agent, the sliding property of the 1 st insulating film can be improved, and the magnetic permeability of the green body can be improved.

< embodiment 2 >

In the present embodiment, the magnetic particles include a core of a magnetic material and an insulating film covering the core, and the insulating film is formed of a mixture of a metal alkoxide and a surfactant. The magnetic material and the metal alkoxide are the same as those in embodiment 1, and therefore, description thereof is omitted.

The surfactant is a compound having a lipophilic group and a hydrophilic group. In the present embodiment, by forming the magnetic particles to contain a surfactant having an oleophilic group and a hydrophilic group, the affinity with the metal alkoxide can be improved by the hydrophilic group, and the surface can be configured to have good sliding properties by disposing the oleophilic group on the surface of the magnetic particles. This improves the affinity with the resin of the base material constituting the coil component, suppresses friction between the magnetic particles, and improves the filling factor of the magnetic particles in the coil component. The organic phosphoric acid or a salt thereof of embodiment 1 is also a surfactant.

The lipophilic group of the surfactant is the hydrocarbon group described in embodiment 1. The hydrocarbon group preferably contains an oxyethylene group. The hydrophilic group of the surfactant is, for example, a hydroxyl group, a sulfonyl group, a phosphate group, an ammonium cation. The surfactant preferably has a hydroxyl group. The hydroxyl group of the surfactant having a hydroxyl group can react with a metal alkoxide or a silane coupling agent, and the surfactant can be introduced into the sol-gel reaction product. Further, the lipophilic group of the surfactant is disposed on the surface of the magnetic particles, and friction between the magnetic particles can be suppressed. The hydrophilic group of the surfactant is particularly preferably a hydroxyl group of phosphoric acid. The hydroxyl group of phosphoric acid has high reactivity and can effectively react with a metal alkoxide or a silane coupling agent.

The surfactant may be any of anionic, nonionic and cationic. Examples of the anionic surfactant include the organic phosphoric acid or a salt thereof described in embodiment 1, sodium polyoxyethylene tridecyl ether sulfate, sodium dodecylbenzenesulfonate, and ammonium polyoxyethylene alkyl ether styrenated phenyl ether sulfate. Examples of the nonionic surfactant include polyoxyethylene tridecyl ether and polyoxyethylene sorbitan monostearate. Examples of the cationic surfactant include lauryl trimethyl ammonium chloride and lauryl dimethyl ethyl ammonium sulfate (lauryl dimethyl ammonium ethyl sulfate).

The content of the surfactant is preferably 0.05 parts by weight or more, more preferably 0.3 parts by weight or more, preferably 0.3 parts by weight or more and 10 parts by weight or less, and more preferably 0.5 parts by weight or more and 5.0 parts by weight or less, with respect to 100 parts by weight of the magnetic material. By setting the content of the surfactant to the above range, the specific resistance of the powder magnetic core obtained from the magnetic particles can be further improved.

The weight ratio of the metal alkoxide to the surfactant (metal alkoxide/surfactant) is preferably 0.06 or more and 40 or less, and more preferably 0.06 or more and 15 or less. By setting the weight ratio of the metal alkoxide to the surfactant to the above range, the specific resistance of the powder magnetic core and the green body obtained from the magnetic particles can be further improved.

The mixture of the present embodiment may further contain a silane coupling agent. Since the silane coupling agent is the same as in embodiment 1, the description thereof is omitted.

The amount of the silane coupling agent is preferably 2% by weight or more and 50% by weight or less of the metal alkoxide. That is, the content of the silane coupling agent in the mixture is 2% by weight or more and 50% by weight or less, for example, 10% by weight or more and 40% by weight or less, based on the total of the metal alkoxide and the silane coupling agent. By adding the silane coupling agent in an amount within the above range, the specific resistance of the powder magnetic core or green body obtained from the magnetic particles can be further improved.

The magnetic particles of the present embodiment can be used as a material for a coil component. The coil component includes, for example, a blank containing magnetic particles and a resin, and a coil embedded in the blank. The coil component using the magnetic particles of the present embodiment is formed of a mixture containing a surfactant, and therefore friction with a resin is suppressed, the filling ratio of the magnetic particles is high, and the magnetic permeability is excellent.

Examples

Example 1

Magnetic particles having a 1 st insulating film formed of a mixture of a metal alkoxide and an organic phosphoric acid or a salt thereof, and a dust core of the magnetic particles were produced as follows.

As a magnetic material, Fe-Si-Cr alloy particles (average particle diameter 30 μm) were prepared. In sample No. 24, Fe-Si-Cr alloy particles (average particle size 30 μm) were prepared by chemical conversion with phosphoric acid. That is, the magnetic particles of sample No. 24 had a coating of a metal phosphate as the 2 nd insulating coating.

As the metal alkoxide, the following compounds were prepared.

Alkoxide 1: tetraethoxysilane

Alkoxide 2: titanium tetraisopropoxide

Alkoxide 3: zirconium n-butoxide

Alkoxide 4: aluminium isopropoxide

The following compounds were prepared as the organic phosphoric acid or a salt thereof.

Phosphate 1: polyoxyalkylene styryl phenyl ether sodium phosphate

Phosphate 2: sodium polyoxyalkylene alkyl ether phosphate

Phosphate 3: polyoxyalkylene alkylaryl ether phosphoric acid monoethanolamine salt

Phosphate 4: sodium alkyl ether phosphate

Phosphate 5: ammonium phosphate of unsaturated polyoxyethylene alkyl phenyl ether

6, phosphoric acid: polyoxyalkylene styryl phenyl ether phosphoric acid

And (3) phosphoric acid 7: polyoxyalkylene alkyl ether phosphoric acid

Phosphoric acid 8: polyoxyalkylene alkylaryl ether phosphoric acid

70g of ethanol in which 10.0g of 16 wt% ammonia water was dissolved was prepared. To this solution, a metal alkoxide and an organic phosphoric acid or a salt thereof were added in such a manner that the use amount thereof was in a ratio shown in table 1 with respect to 100 parts by weight of a magnetic material to be added later.

Then, 30g of the above-mentioned magnetic material (Fe-Si-Cr alloy) was added thereto, and the mixture was stirred for 120 minutes. The reaction solution was filtered, and the treated powder was dried at 80 ℃ for 120 minutes to form an insulating film on the surface of the magnetic material particles. Thereby obtaining magnetic particles having surfaces covered with an insulating film.

Then, the obtained magnetic particles and a silicone resin (4.2 parts by weight per 100 parts by weight of the magnetic material) as a binder were mixed, compression-molded under a pressure of 400MPa, and heated at 200 ℃ for 1 hour to prepare a toroidal core having an inner diameter of 4mm, an outer diameter of 9mm, and a thickness of 1mm and a square plate sample having an inner diameter of 3mm × 3mm × 1 mm.

(evaluation)

Relative magnetic permeability

The relative permeability at 1MHz and 1Vrms was measured for the prepared toroidal core using an RF impedance analyzer (E4991A) manufactured by Agilent Technologies corporation (the average value of n being 3 is shown in table 1).

Specific resistance

A direct current voltage of 900V was applied to the plate sample using a high resistance measuring instrument (R8340A ULTRA HIGH RESISTANCE METER) manufactured by Adventest corporation, and the resistance after 5 seconds was measured, and the specific resistance was calculated from the sample size (the average value of n being 3 is shown in table 1).

[ Table 1]

The metal alkoxide and the organic phosphoric acid or the salt thereof are used in amounts relative to Fe-Si

Amount of 100 parts by weight of Cr alloy particles (parts by weight).

Samples 22 and 23 marked with x are comparative examples.

Inorganic phosphoric acid was used in sample No. 23.

From the above results, it was confirmed that high permeability and high specific resistance can be obtained by using an organic phosphoric acid or a salt thereof. In particular, it was confirmed that samples 3 to 17 using 0.3 parts by weight or more of phosphate per 100 parts by weight of Fe-Si-Cr alloy particles had high magnetic permeability and high specific resistance.

Comparative example 1 (dipping method)

(sample No. 22)

Magnetic particles having an insulating film formed on the surface thereof were obtained in the same manner as in sample No. 11 of the above example except that 70g of ethanol containing no ammonia as a sol-gel reaction catalyst was prepared instead of 70g of ethanol in which 10.0g of 16 wt% aqueous ammonia was dissolved, and the magnetic particles were immersed for 1 minute instead of stirring for 120 minutes after the addition of the magnetic material.

The obtained magnetic particles were measured for relative permeability and specific resistance in the same manner as described above. As a result, the relative magnetic permeability was 27 and the specific resistance was 9.8X 10⁴(Ω·cm)。

(sample No. 23)

Magnetic particles were obtained in the same manner as in example 1, except that inorganic phosphoric acid was used instead of organic phosphoric acid and a salt thereof.

From the above results, it was confirmed that even when a mixture of a metal alkoxide and an organic phosphoric acid having the same composition as that of the present invention is used, a sufficient specific resistance cannot be obtained without using a sol-gel reaction.

When an inorganic phosphoric acid is used instead of an organic phosphoric acid or a salt thereof, the relative permeability and specific resistance are small as compared with the case of using an organic phosphoric acid or a salt thereof. From these results, it is found that the hydrocarbon group of the organic phosphoric acid exerts a specific effect on the improvement of the relative permeability and the specific resistance. Further, table 1 shows that if the weight ratio of the organic phosphoric acid or a salt thereof to the magnetic material is 0.3 parts by weight or more and the weight ratio of the organic phosphoric acid or a salt thereof to the metal alkoxide is 5 or less, a high specific resistance can be obtained.

Example 2

Magnetic particles having an insulating coating formed of a mixture of a metal alkoxide, a silane coupling agent, and an organic phosphoric acid or a salt thereof, and a dust core of the magnetic particles are produced as follows.

The following compounds were prepared as the silane coupling agent acid salt.

Silane coupling agent 1: octadecyl trimethoxy silane

Silane coupling agent 2: hexadecyl trimethoxy silane

Silane coupling agent 3: 3-glycidoxypropyltrimethoxysilane

Silane coupling agent 4: 8-methacryloxy-octyltrimethoxysilane

Silane coupling agent 5: 8- (2-Aminoethylamino) octyltrimethoxysilane

Silane coupling agent 6: 8-glycidyloxy-octyltrimethoxysilane

Silane coupling agent 7: aminopropyltriethoxysilane

Silane coupling agent 8: 3- (methacryloyloxy) propyltrimethoxysilane

Silane coupling agent 9: decyl trimethoxy silane

Magnetic particles and a powder magnetic core were produced in the same manner as in example 1, except that a part of the metal alkoxide was replaced with a silane coupling agent and mixed so as to obtain a coating agent in a ratio shown in table 2. For comparison, sample 11 is shown together.

From the above results, it was confirmed that samples 31 to 44 to which the silane coupling agent was added exhibited higher relative permeability. In particular, in the sample in which the chain length of the silane coupling agent is long, a tendency to have a higher relative permeability is observed.

(example 3)

Magnetic particles were produced in the same manner as in example 1 of embodiment 1 except that other surfactants were used instead of the organic phosphoric acid or its salt in sample nos. 50 to 56, and the specific resistance and the relative permeability were evaluated in the same manner as in example 1. The amounts of the metal alkoxide and the surfactant and the evaluation results are shown in table 3. Table 3 further includes sample numbers 3 to 5, 15 to 18, and 23 of examples 3 and 1. Sample No. 23 is a comparative example.

[ Table 3]

From table 3, it was confirmed that high permeability and high specific resistance can be obtained by using a surfactant having an oleophilic group and a hydrophilic group. In particular, samples 3 to 5, 15 to 18, and 50 to 56 using 0.3 parts by weight or more of a surfactant per 100 parts by weight of the Fe-Si-Cr alloy particles were confirmed to have high magnetic permeability and high specific resistance. Furthermore, among the surfactants, the surfactant used in sample Nos. 3 to 5 and 15 to 18, which use an organic phosphoric acid or a salt thereof, has a molecular weight of 5.6X 10¹¹High specific resistance of not less than Ω · cm.

(example 4)

Magnetic particles and dust cores were produced in the same manner as in sample nos. 50 to 56 of example 3, except that a part of the metal alkoxide in example 3 was replaced with a silane coupling agent and mixed so as to have a ratio shown in table 4 to prepare a coating agent.

As is clear from comparison of sample numbers 60 and 51, 61 and 53, and 62 and 56, the magnetic particles having the insulating film formed of the mixture of the metal alkoxide, the silane coupling agent and the surfactant can provide the coil component having high relative permeability and specific resistance.

Industrial applicability

The magnetic particles of the present invention are suitable for use as a material for coil components. The coil component is particularly suitable for use in electric or electronic equipment used in a high-frequency region.