JPWO2010035874A1 - Magnetic composite for antenna and antenna element using the same - Google Patents

Abstract

The graft copolymer (P) is obtained by graft polymerization of 18 to 67 parts by mass of the monomer (B) with respect to 100 parts by mass of the polymer (A). The polymer (A) is obtained by polymerizing an α-olefin, a conjugated diene, an unsaturated cyclic hydrocarbon, or an ethylenically unsaturated bond-containing aromatic monomer. The monomer (B) comprises an aromatic monofunctional ethylenically unsaturated monomer (b1) and a bifunctional ethylenically unsaturated monomer (b2), and has a mass ratio of (b1) / (b2) Is 70/30 to 95/5. The magnetic composite for antenna comprises a graft copolymer (P) and a spinel ferrite powder (F) having an average particle diameter of 0.05 to 20 μm, and a mass ratio of (P) / (F) of 10/90 to It is obtained by kneading a composition containing 60/40.

Description

  The present invention relates to a magnetic composite for an antenna that can realize an antenna having a size that can be built in a portable terminal device or the like and a high gain, and an antenna element using the same.

  In recent mobile terminal devices, in addition to the normal call communication function, for example, functions such as FM radio broadcast and reception of TV broadcasts extending from the VHF band to the UHF band, or further mobile radio communication in the UHF band high frequency band are installed. It is demanded. In particular, a multifunctional mobile terminal has a large number of built-in antennas due to the mounting of a plurality of the above-described functions, which causes a problem in miniaturization of the terminal itself and provision of design. In order to avoid this problem, there is a demand for a multifunctional antenna that can receive radio waves of a wide range of frequencies by itself. In particular, the superposition of functions is required in both frequency bands of the VHF band to which FM radio broadcasting is allocated and the UHF band to which terrestrial digital broadcasting is allocated. In order to receive radio waves of a wide range of frequencies, naturally, an antenna having a wide bandwidth that can handle each signal frequency is required. However, for example, the wavelength of the radio wave in the UHF band is several tens of centimeters, whereas the wavelength of the radio wave in the VHF band can be several meters. Therefore, an antenna capable of supporting two frequency bands, UHF and VHF, alone is provided. When it is manufactured and built in a portable terminal with a limited volume, miniaturization and widening of the antenna become problems.

It is generally known that the volume of an antenna is almost inversely proportional to the 1/2 power [= (ε · μ) ^1/2 ] of the product of the dielectric constant (ε) and the magnetic permeability (μ) of the material used for the antenna core. Yes. From this relationship, it can be seen that the antenna can be miniaturized by using a high dielectric constant and high permeability material for the antenna core. Further, the antenna core needs to have sufficiently small dielectric loss and magnetic loss in the frequency band to be used. This is because when these losses are large, the signal is smoothed and the signal deteriorates.

  If the external shape of the antenna is simply reduced in size, the gain (or transmission / reception efficiency or sensitivity) may decrease. Therefore, by using a dielectric core having a certain dielectric constant or a soft magnetic core, a conductor is wound around the core, or a conductor pattern is formed around the core in a helical shape. Many techniques that can reduce the size of the antenna while maintaining the gain have been proposed. However, in such a technique, a sintered body of a soft magnetic material that becomes a core of a small antenna has a drawback that it has poor workability because it has high hardness and brittleness. As a technique for avoiding this drawback, Patent Document 1 discloses a technique for obtaining an antenna core having a high dielectric constant and a high magnetic permeability by mixing a soft magnetic powder into a resin to form a magnetic composite. -3.

  In order to make the antenna compatible with a wide range of frequency bands, it is essential that the dielectric characteristics (dielectric constant, dielectric loss) and magnetic characteristics (permeability, magnetic loss) are stabilized in the target frequency band. Therefore, the antenna core material has high dielectric constant, high magnetic permeability, low dielectric loss, and low magnetic loss, and the resin material that is the base of the core material has high dielectric constant and low dielectric loss, and these values have a wide range of frequencies. When stable in a band, an antenna that is smaller and supports a wide frequency band can be obtained.

  Patent Document 1 discloses a ferrite slurry composed of soft magnetic ferrite and a thermoplastic resin, and this thermoplastic resin is polyamide or polyphenylene sulfide selected mainly for heat resistance, strength and rigidity. Such a resin has a large dielectric loss and varies greatly depending on the frequency band. Therefore, since a constant dielectric constant can be maintained in a wide frequency band, the ferrite slurry disclosed in Patent Document 1 cannot provide a broadband-compatible antenna.

  Patent Document 2 discloses a magnetic composition containing a magnetic material and a thermoplastic resin having a cyclic structure such as a thermoplastic norbornene resin or polyarylene sulfide. Patent Document 3 discloses a resin composition containing soft magnetic ferrite powder and a thermoplastic resin such as polyarylene sulfide, polyamide, and polyolefin. In the case where the thermoplastic resin is polyamide, the compositions of Patent Documents 2 and 3 cannot obtain a wideband-compatible antenna as in the case of Patent Document 1. When the thermoplastic resin is a norbornene resin or a polyolefin resin, these resins have low dielectric constant and low dielectric loss, and the dielectric loss is stable. It is expected that it is possible to cope with the bandwidth.

  As a thermoplastic resin having a low dielectric constant and low dielectric loss, such as a norbornene-based resin material, polytetrafluoroethylene, various liquid crystal polymers, modified polyphenylene ether, and the like are also known. However, these resin materials have excellent dielectric properties over a wide frequency band, but have a very rigid structure and thus have a very high melting point or glass transition temperature. Therefore, when mixing the resin material and the magnetic powder, it is necessary to melt at a temperature of +50 to + 150 ° C. from the melting point or glass transition temperature of the resin. It is necessary to carry out mixing at a high temperature, and as a result, oxidative degradation of the resin and soft magnetic material is caused. Therefore, there is a possibility that the low magnetic loss property of the antenna manufactured using the obtained magnetic material is impaired.

  On the other hand, since the polyolefin resin has a low melting point unlike the norbornene-based resin material and the like resin materials, the polyolefin resin can be mixed with the magnetic powder at a relatively low temperature. However, in the case where an antenna core is obtained by actually mixing soft magnetic powder with polypropylene to obtain an antenna element, the permeability becomes smaller than assumed and sufficient miniaturization cannot be realized. This phenomenon is considered to have occurred as a result of excessive thermal load applied to the resin due to the shear required for kneading the soft magnetic powder into the resin, causing the resin to deteriorate and have a low molecular weight. In order to compensate for this, when the amount of soft magnetic powder mixed is increased, the gain is significantly reduced due to a gain reduction phenomenon caused by relaxation loss of the magnetic material. As described above, there is a demand for a magnetic composite for an antenna that can realize an antenna having a high gain with respect to radio waves in a wide frequency band from the VHF band to the UHF band and having a small outer shape.

JP-A-7-142228 JP-A-10-77381 JP 2000-91115 A

  An object of the present invention is to provide a magnetic composite for antenna capable of realizing a small antenna element having high gain with respect to radio waves in a wide frequency band from VHF band to UHF band, and an antenna element using the same. It is to provide.

  As a result of intensive studies to solve the above problems, the inventors of the present invention blend a graft polymer (P) having a specific structure and a specific spinel ferrite powder (F) at a specific ratio in a magnetic composite. As a result, the inventors have obtained knowledge that the above-mentioned problems can be solved, and completed the present invention.

  That is, the magnetic composite for antenna of one embodiment of the present invention is a polymer (A) obtained by polymerizing an α-olefin, a conjugated diene, an unsaturated cyclic hydrocarbon, or an ethylenically unsaturated bond-containing aromatic monomer. It consists of an aromatic monofunctional ethylenically unsaturated monomer (b1) and a bifunctional ethylenically unsaturated monomer (b2) with respect to 100 parts by mass, and the mass ratio of both monomers is (b1) Graft copolymer (P) formed by graft polymerization of 18 to 67 parts by mass of monomer (B) where / (b2) = 70/30 to 95/5, and an average particle size of 0.05 to 20 μm A composition containing spinel ferrite powder (F) is kneaded, and the mass ratio of both components is (P) / (F) = 10/90 to 60/40.

In one example, the spinel-type ferrite powder (F) is represented by the characteristic formula MO · Fe ₂ O ₃ (M represents a metal element), and the electronegativity of the metal element M is 1.55 to 2.33. is there.
In one example, the spinel ferrite powder (F) is represented by the characteristic formula MO.Fe ₂ O ₃ (M represents a metal element), and the metal element M is at least one selected from manganese, nickel, copper, or zinc. It is a seed metal element.

In one example, the surface of the spinel ferrite powder (F) is coated with a silane coupling agent.
Another aspect of the present invention provides an antenna element formed by arranging a conductor on the surface or inside of a molded body obtained by molding the magnetic composite for antenna.

  Yet another embodiment of the present invention provides a method for producing the above-described magnetic composite for antenna. The production method comprises preparing a polymer (A) obtained by polymerizing an α-olefin, a conjugated diene, an unsaturated cyclic hydrocarbon, or an ethylenically unsaturated bond-containing aromatic monomer, and producing an aromatic monofunctional group. A monomer comprising an ethylenically unsaturated monomer (b1) and a bifunctional ethylenically unsaturated monomer (b2) and having a mass ratio of (b1) / (b2) of 70/30 to 95/5 ( B) is prepared, and 18 to 67 parts by mass of the monomer (B) is graft-polymerized with respect to 100 parts by mass of the polymer (A) to prepare a graft copolymer (P). Polymer (P) and spinel ferrite powder (F) having an average particle diameter of 0.05 to 20 μm are kneaded at a mass ratio of (P) / (F) of 10/90 to 60/40, and the antenna A magnetic composite is produced.

According to the present invention, the following effects can be exhibited.
The present invention has high processability and at the same time, (ε ′ · μ ′) ^{1/2, which} is an index of antenna element miniaturization ability, is 3.0 or more, so that sufficient miniaturization can be achieved and a wide range can be achieved. a variation rate mu _v of the frequency band mu 'is within 13% ±, it is possible to obtain an antenna device using the same magnetic composite and antenna can be realized the antenna element corresponding to the wide frequency band .

(A) and (b) are the top views and bottom views of an antenna element according to an embodiment, respectively.

Hereinafter, a magnetic composite for antenna and an antenna element according to an embodiment of the present invention will be described in detail.
The magnetic composite for antennas of the present embodiment (hereinafter also simply referred to as a magnetic composite) is a composition containing a specific graft copolymer (P) shown below and a specific spinel ferrite powder (F). It knead | mixes and the mass ratio of both components is set to (P) / (F) = 10 / 90-60 / 40. The graft copolymer (P) is obtained by graft polymerization of 18 to 67 parts by mass of the monomer (B) with respect to 100 parts by mass of the polymer (A) shown below.

Polymer (A): A polymer obtained by polymerizing an α-olefin, a conjugated diene, an unsaturated cyclic hydrocarbon, or an ethylenically unsaturated bond-containing aromatic monomer.
Monomer (B): consisting of an aromatic monofunctional ethylenically unsaturated monomer (b1) and a bifunctional ethylenically unsaturated monomer (b2), wherein the mass ratio of both monomers is (b1) / (B2) = 70/30 to 95/5.

Spinel ferrite powder (F): Spinel ferrite powder having an average particle size of 0.05 to 20 μm.
[Graft Copolymer (P)]
The graft copolymer (P) can be obtained by graft polymerization of the monomer (B) as the graft component to the polymer (A) as the grafted component.

<Polymer (A)>
The polymer (A) constituting the graft copolymer (P) is a main component having improved thermoplastic properties and dielectric properties and magnetic properties of the graft copolymer (P). The graft copolymer (P) It is a stem component. Specifically, the polymer (A) is a polymer obtained by polymerizing an α-olefin, a conjugated diene, an unsaturated cyclic hydrocarbon, or an ethylenically unsaturated bond-containing aromatic monomer. Such a polymer has a characteristic that the dielectric loss tangent has a low value and its change is small in a wide frequency band, and is essential as a segment constituting the graft copolymer (P).

  Examples of such polymers include polyolefins such as polyethylene, polypropylene, poly-1-butene, and polymethylpentene; ethylene-α-olefin copolymers such as ethylene-propylene copolymer and ethylene-1-butene copolymer. Polymer; Ethylene-cyclic olefin copolymer such as ethylene-norbornene copolymer, hydrogenated product of ring-opening metathesis polymer of cyclic olefin represented by dicyclopentadiene; polystyrene, poly-p-methylstyrene, poly-p -Polystyrene copolymers such as ethyl styrene and poly-p-tert-butyl styrene; hydrogenated styrene-isoprene-styrene di (tri) block copolymer, hydrogenated styrene-butadiene-styrene di (tri) block copolymer, etc. Styrenic block copolymers And the like. Of these polymers, polypropylene and polymethylpentene are preferred from the viewpoint of the heat resistance of the finally obtained magnetic composite. These polymers may be used alone or in combination of two or more. Moreover, what knead | mixed and blended the 2 or more types of polymer by the well-known method previously can also be used.

<Monomer (B)>
The monomer (B) is a component that improves the flow characteristics of the graft copolymer (P) and the dispersibility of the kneaded dissimilar materials, and after the graft copolymerization, the branch component of the graft copolymer (P). It becomes. Usually, when a different material is kneaded and dispersed in the polymer (A), the dispersibility is achieved only by shearing during kneading. On the other hand, since the graft copolymer (P) obtained by graft-bonding the monomer (B) to the graft copolymer (A) has a rigid cross-linked structure in its structure, the monomer ( The structural unit formed by B) plays a role of assisting dispersion when different materials are kneaded, and a magnetic composite having high dispersibility can be obtained. Specifically, as the monomer (B), the dielectric loss of the graft copolymer (P) is 0.002 or less in the frequency band from the VHF band to the UHF band, and the graft copolymer (P) A monomer that forms any crosslinked structure having an effect of enhancing the dispersibility of the spinel ferrite powder (F) when melted can be used. Such a monomer (B) may be any component that can form a three-dimensional cross-linked structure, and in particular, an aromatic monofunctional ethylenically unsaturated monomer (b1) and a bifunctional ethylene. The unsaturated monomer (b2) is used.

  Examples of the aromatic monofunctional ethylenically unsaturated monomer (b1) include styrene; nuclear alkyl-substituted styrene such as p-methylstyrene and p-ethylstyrene; α- such as α-methylstyrene and α-ethylstyrene. Alkyl-substituted styrene; and vinyl vinyl-substituted polycyclic aromatic monomers such as vinyl naphthalene and vinyl anthracene. Of these, styrene is most preferable from the viewpoint of availability.

  Further, as the bifunctional ethylenically unsaturated monomer (b2), divinylbenzene, divinylbiphenyl, divinylnaphthalene, divinylanthracene and the like are preferable. Of these, divinylbenzene is particularly preferred from the standpoint of availability.

  The graft copolymer (P) has a structure in which the monomer (B) is grafted to the polymer (A). Usually, the composite in which the crosslinked structure formed from the monofunctional ethylenically unsaturated monomer (b1) and the bifunctional ethylenically unsaturated monomer (b2) is dispersed in the polymer (A) is In the molding process and the heating process using solder, the polymer (A) exhibits a strong thermoplasticity, causing a resin flow, resulting in a shape change, a resin thinning, and the like. When such a molded product is used as an antenna element or the like, it may be deformed when connected to a substrate, wiring, or the like, and the expected function may not be expressed.

  The flow and deformation at the time of heating are carried out by adding a monomer (B) comprising a monofunctional ethylenically unsaturated monomer (b1) and a bifunctional ethylenically unsaturated monomer (b2) to the polymer (A). This can be solved by graft bonding. The graft bond of the monomer (B) to the polymer (A) is the third monomer in the monofunctional ethylenically unsaturated monomer (b1) and the bifunctional ethylenically unsaturated monomer (b2). As a radical copolymerizable organic peroxide, a peroxide is added to the crosslinked structure formed from the monofunctional ethylenically unsaturated monomer (b1) and the bifunctional ethylenically unsaturated monomer (b2). Achieved by granting performance. The monomer (B) to which the peroxide ability is imparted is kneaded with the polymer (A) and simultaneously undergoes an addition reaction, and the graft copolymer is obtained by grafting the monomer (B) to the polymer (A). (P) can be obtained. The addition amount of the radical copolymerizable organic peroxide may be such that the graft copolymer (P) can maintain its shape at the melting point or higher, and is usually monofunctional ethylenically unsaturated monomer (b1) and bifunctional ethylene. An appropriate amount is about 0.5 to 3.0% by mass with respect to the total amount of the unsaturated unsaturated monomer (b2).

  The mass ratio of the aromatic monofunctional ethylenically unsaturated monomer (b1) to the bifunctional ethylenically unsaturated monomer (b2) in the monomer (B) is (b1) / (b2) = 70. / 30 to 95/5. When the amount of the bifunctional ethylenically unsaturated monomer (b2) is less than 5% by mass, the effect of dispersing the spinel-type ferrite powder (F) by the crosslinked structure based on the monomer (B) is lowered, and as a result Magnetic permeability of the magnetic composite becomes unstable. On the other hand, when the amount of the bifunctional ethylenically unsaturated monomer (b2) is more than 30% by mass, the fluidity at the time of kneading the graft copolymer (P) and the spinel ferrite powder (F) deteriorates, and the spinel Interferes with mixing and dispersion of type ferrite powder (F).

  The mass ratio of the polymer (A) and the monomer (B) is 18 to 67 parts by mass of the monomer (B) with respect to 100 parts by mass of the polymer (A). When the monomer (B) is less than 18 parts by mass, the effect of dispersing the spinel ferrite powder (F) by the crosslinked structure based on the monomer (B) is reduced, and the magnetic permeability of the resulting magnetic composite is reduced. Becomes unstable. On the other hand, when the amount of the monomer (B) is more than 67 parts by mass, the fluidity at the time of kneading the graft copolymer (P) and the spinel ferrite powder (F) deteriorates, and the spinel ferrite powder (F) It interferes with mixing and dispersion.

<Production of Graft Copolymer (P) -Graft Copolymerization Reaction>
The grafting method for producing the graft copolymer (P) may be any generally known method such as a chain transfer method or ionizing radiation irradiation method. Among these methods, the grafting method shown below is preferable from the viewpoint that the grafting efficiency is high and secondary aggregation due to heat does not occur, so that the development of performance is more effective and the production method is simple. .

  When the impregnation graft polymerization method is employed, the graft copolymer (P) is usually produced as follows. First, 100 parts by mass of a polymer (A) formed from an α-olefin, a conjugated diene, an unsaturated cyclic hydrocarbon, or an ethylenically unsaturated bond-containing aromatic monomer is suspended in water, and an aqueous suspension To prepare. Separately, 5 to 400 parts by mass of a monomer (B) representing the total of the monofunctional ethylenically unsaturated monomer (b1) and the bifunctional ethylenically unsaturated monomer (b2) is prepared. A solution in which at least one radical copolymerizable organic peroxide and a radical polymerization initiator having a decomposition temperature of 40 to 90 ° C. for obtaining a half-life of 10 hours is dissolved is prepared. In this solution, the at least one radical copolymerizable organic peroxide is 0.1 to 10 parts by mass with respect to 100 parts by mass of the monomer (B), and the radical polymerization initiator is a monomer ( It is 0.01-5 mass parts with respect to a total of 100 mass parts of B) and a radical copolymerizable organic peroxide. This solution is added to 5 to 400 parts by mass of the monomer (B).

  Next, the solution to which the monomer (B) is added is added to the aqueous suspension of the polymer (A), and the at least one radical copolymerizable organic peroxide is added to the polymer (A). Impregnate. Thereafter, the temperature of the aqueous suspension is increased under the condition that the decomposition of the radical polymerization initiator does not substantially occur, and the monomer (B) and the radical copolymerizable organic peroxide are added in the polymer (A). Copolymerize to obtain the grafted precursor. Finally, the grafted precursor (K) can be obtained by kneading the grafted precursor under melting at 100 to 300 ° C.

  Grafting precursor obtained by impregnating polymer (A) with monomer (B) and radical copolymerizable organic peroxide and copolymerizing monomer (B) in polymer (A) As a method for obtaining the graft copolymer (P) from the above, a known heat mixing method can be used. Specific examples include a Banbury mixer having a heating function and a kneading function, a pressure kneader, a roll, a single screw or twin screw extruder, and the like. Among these methods, using a twin screw extruder, a graft copolymer is supplied from a main hopper, melted and kneaded, and then a rod-shaped product discharged from a die is passed through a pelletizer to form a granulated product (pellet). Is preferable because it is simple and inexpensive. The temperature at that time may be a temperature at which the graft copolymer (P) is sufficiently softened, and is usually in the range of 150 to 300 ° C.

  In this case, the grafting precursor obtained by the above procedure and the polymer (A) in the grafting precursor contain a different kind of α-olefin, conjugated diene, unsaturated cyclic hydrocarbon or ethylenically unsaturated bond. A graft copolymer (P) is obtained by mixing with a grafting precursor composed of a polymer obtained by using an aromatic monomer, and kneading and grafting under melting at 150 to 300 ° C. be able to.

  The radical copolymerizable organic peroxide is a compound that has both the characteristics as a monomer capable of radical copolymerization in the molecule and the characteristics as an organic peroxide, preferably t-butylperoxyacryloyl. Examples thereof include oxyethyl carbonate, t-butyl peroxymethacryloyloxyethyl carbonate, t-butyl peroxyallyl carbonate, t-butyl peroxymethallyl carbonate and the like. Of these, t-butylperoxymethacryloyloxyethyl carbonate is particularly preferred.

  The graft copolymer (P) thus obtained has a form in which domains based on a monomer (B) having a size of about 0.1 to 1.0 μm are dispersed in a matrix made of the polymer (A). Indicates. Since this domain is crosslinked by the bifunctional ethylenically unsaturated monomer (b2), it maintains a solid state without melting during kneading. Therefore, it acts to crush the secondary particles in which the spinel type ferrite powder (F) is agglomerated under kneading, so that the spinel type ferrite powder (F) is dispersed in the graft copolymer (P). work. Such a high dispersion state of the spinel-type ferrite powder (F) can be realized by using a high-torque, high-rotation type special kneader without using the graft copolymer (P). In that case, an extremely high shear stress is applied to the molten resin, so that the molecular chain is broken and the fluidity of the resin is increased. Therefore, although a magnetic composite with good dispersibility of the spinel ferrite powder (F) can be obtained, there are problems such as a decrease in mechanical strength, a decrease in dielectric properties due to a low molecular weight of the resin, and a decrease in moldability due to flow. This makes it impossible to obtain a small antenna element.

  Therefore, by using the graft copolymer (P) having the specific cross-linked structure, such a problem can be avoided, and a high dispersion state can be realized using an inexpensive kneading apparatus. Since resin degradation caused by cutting can be suppressed, a magnetic composite having not only high performance but also excellent reliability can be obtained.

[Spinel type ferrite powder (F)]
In general, soft magnetic ferrite is used for a magnetic composite for an antenna. Soft magnetic ferrite is a ferrite having soft magnetism in which a crystal form is a cubic crystal among sintered metal oxides mainly composed of iron oxide. The spinel-type ferrite powder (F) used in the magnetic composite of the present embodiment is a spinel ferrite having a spinel-type crystal structure, and is represented by the characteristic formula MO · Fe ₂ O ₃ (M represents a metal element). The Here, M is preferably a metal element having an electronegativity of 1.55 to 2.33.

  Examples of metal oxides that can replace MO in spinel ferrite include oxides of many divalent metals in groups 2 to 15 of the periodic table. In this embodiment, the metal oxide MO is used as the metal oxide MO. The constituent metal M is at least one metal selected from the group consisting of Cr, Mn, Fe, Mo, Cd, Pb, Ni, Cu, Sn, Zn and Co. The metal M is a metal having a Pauling electronegativity of 1.55 to 2.33. Specifically, Cr 1.66, Mn 1.55, Fe 1.83, Mo 2.16, Cd 1.69, Pb 2 .33, Ni 1.91, Cu 1.90, Sn 1.96, Zn 1.65 and Co 1.88 [For Pauling's electronegativity, Linus Pauling, Translated by Masao Koizumi, "Introduction to Chemical Bond Theory" (Kyoritsu Shuppan , 1971)].

  When the electronegativity of the metal M takes a relatively low value within this range, the metal oxide MO in the spinel ferrite powder (F) takes a constant value with a relatively low ionicity of the metal-oxygen bond, The surface free energy of the spinel ferrite powder (F) is maintained at an appropriate value. Therefore, the interfacial strength between the spinel ferrite powder (F) and the graft copolymer (P) is relatively low, the affinity with the graft copolymer (P) can be increased, and high dispersibility can be obtained during kneading. Obtainable. Further, among the above M, manganese (Mn), nickel (Ni), copper (Cu), and zinc (Zn) are preferable from the viewpoint of high electrical resistance as ferrite and stability of magnetic permeability in a wide frequency band. The metal M may be a single type or a plurality of types may be contained in the spinel ferrite powder (F). The trace amount metal oxide unintentionally included in the metal M may be included as long as the physical and chemical characteristics of the spinel ferrite powder (F) are not impaired.

  The proportion of the metal oxide MO in the spinel ferrite powder (F) is preferably 17 to 55% by mass, more preferably 20 to 50% by mass. When the MO ratio is out of this range, the magnetic properties of the spinel ferrite powder (F) decrease, such as decrease in magnetic permeability, increase in change with frequency, increase in magnetic loss, and spinel ferrite powder (F). The Curie temperature is lowered, which may cause a problem in the stability of the magnetic properties in the vicinity of room temperature where the magnetic composite is used.

  As a manufacturing method of spinel type ferrite powder (F), well-known manufacturing methods, such as a dry method, a coprecipitation method, and a spray pyrolysis method, can be taken. For example, in the case of the dry method, compounds such as oxides, hydroxides, carbonates, oxalates, nitrates, etc. of each element are weighed in a predetermined mixing ratio, mixed well with a mixer such as a ball mill, and calcined for a predetermined time. After that, the lump obtained can be crushed and classified to obtain a powder. In the case of the coprecipitation method, a solution of a water-soluble salt such as oxalate or nitrate of each element as a raw material is mixed so as to have a predetermined mixing ratio, and is precipitated by adjusting the pH as necessary. Next, the precipitate is filtered off, and the mass obtained after calcining under predetermined conditions is crushed and classified to obtain a powder. In the case of spray pyrolysis, a solution containing each element prepared in the same manner as in the coprecipitation method is introduced and sprayed into a heating furnace at a predetermined temperature to remove the solvent and cause pyrolysis of the solute to recover the product. Thus, powder can be obtained.

  The particle diameter of the spinel ferrite powder (F) is 0.05 to 20 μm, preferably 0.1 to 10 μm, as an average particle diameter measured by a dynamic light scattering method. When the average particle size of the spinel ferrite powder (F) is less than 0.05 μm, the surface area on which the surface of the graft copolymer (P) should be wet becomes too large, and sufficient dispersibility cannot be obtained. On the other hand, when the average particle diameter exceeds 20 μm, the permeability cannot be achieved even if a dispersion effect is obtained, so that the object cannot be achieved.

The shape of the spinel type ferrite powder (F) is preferably substantially spherical or spherical from the viewpoint of easy mixing and dispersion into the graft copolymer (P).
Further, the spinel ferrite powder (F) can reach a better dispersion by being surface-coated with a silane coupling agent. This is because the area covered with the silane coupling agent interposed between the particle surface and the graft copolymer (P) has a value that is intermediate between the surface free energies of the two. As the silane coupling agent used for the surface coating, an organic silane compound having an alkyl group having 6 to 22 carbon atoms or an aryl group having 8 to 14 carbon atoms is preferable in order to increase the affinity with the graft copolymer (P). Used for. Specific examples include p-styryltriethoxysilane, p-styryltrimethoxysilane, and decyltrimethoxysilane. As a method of coating the spinel ferrite powder (F) with these silane coupling agents, a known method such as a wet method, a dry method, an integral method or the like can be suitably used.

  When the surface of the spinel ferrite powder (F) is coated with a silane coupling agent as described above, an area 0.5 to 3.0 times the specific surface area of the spinel ferrite powder (F) is coated. It is preferable to add a silane coupling agent. When the coating area is less than 0.5 times the specific surface area of the spinel ferrite powder (F), the contribution to the surface free energy difference between the graft copolymer (P) and the spinel ferrite powder (F) is small, and the spinel type A magnetic composite with good dispersibility of the ferrite powder (F) cannot be obtained. On the other hand, when the coating area is larger than 3.0 times the specific surface area of the spinel ferrite powder (F), the amount of the silane coupling agent used is more than the specific surface area of the spinel ferrite powder (F). When the spinel ferrite powder (F) is kneaded into the polymer (P), the silane coupling agent falls off from the surface of the spinel ferrite powder (F) and the graft copolymer (P) and the spinel ferrite powder (F) are separated. It cannot play the role of reducing the surface free energy difference. Also, the dropped silane coupling agent diffuses into the graft copolymer (P) and exhibits a plasticizer effect, reducing the heat resistance and magnetic properties (magnetic loss) of the molded product obtained from the magnetic composite. cause.

  The spinel type ferrite powder (F) excellent in affinity with the graft copolymer (P) as described above has high affinity with the graft copolymer (P), and thus the graft copolymer (P) and spinel. The kneading torque required for kneading the type ferrite powder (F) is further reduced. That is, it is possible to obtain a magnetic composite that exhibits the desired antenna characteristics by using the specific graft copolymer (P) and the spinel ferrite powder (F) under milder conditions, both thermally and mechanically. It can be said that there is. As a result, a magnetic composite in a better state can be obtained, and a small antenna element having excellent characteristics, and thus a small antenna can be obtained.

  As for the blending ratio of the graft copolymer (P) and the spinel ferrite powder (F), the mass ratio of both components is (P) / (F) = 10/90 to 60/40. When the spinel type ferrite powder (F) is less than 40% by mass, the resulting magnetic composite has a low dielectric constant and magnetic permeability, making it difficult to sufficiently reduce the size of the antenna element. On the other hand, when the spinel type ferrite powder (F) is more than 90% by mass, the fluidity of the magnetic composite is insufficient, the moldability and the manufacturability may be deteriorated, and the dielectric loss and the magnetic loss are increased. As a result, sufficient gain for radio waves in a wide frequency band cannot be obtained.

[Magnetic composite for antenna]
A magnetic composite for an antenna is a composition containing the graft copolymer (P) and the spinel ferrite powder (F), and the graft copolymer (P) and the spinel ferrite powder (F) are the same as described above. It is obtained by kneading so as to obtain a mass ratio. In this case, examples of the kneading method include a kneading method using a Banbury mixer, a pressure kneader, a roll, a uniaxial or biaxial screw extruder having a heating function and a kneading function. A particularly preferable kneading method is a method using a twin screw extruder, which can be carried out under the same conditions as in the case of obtaining the graft copolymer (P).

  In addition, the magnetic composite for antennas has a nucleating agent, a lubricant, a plasticizer, an antioxidant, a metal deactivator, an ultraviolet absorber, a flame retardant, a colorant, a catalyst deactivator, etc., as long as the purpose is not impaired. Additives can be added. These additives may be kneaded and blended in advance with the graft copolymer (P), or may be added at the same time when the graft copolymer (P) and the spinel ferrite powder (F) are kneaded. .

  In the magnetic composite for antenna of the present invention, when the magnetic content is the same, the magnetic powder has a high magnetic permeability because the dispersed state of the magnetic powder is better than the composite using other low dielectric loss resins. Can be expressed. At this time, the magnetic loss hardly changes. Therefore, the antenna element can be further reduced in size.

In general, the electrical characteristics and magnetic characteristics of a material are represented by a complex dielectric constant and a complex magnetic permeability represented by the following general formula for the material.
Complex permittivity ε = ε ′ + iε ″
Complex permeability μ = μ ′ + iμ ”
Here, the real part ε ′ in ε represents the dielectric constant, and ε ″ / ε ′ represents the degree of dielectric loss of the material by the imaginary part ε ″. This ε ″ / ε ′ is generally known as a dielectric loss tangent tan δ. As for μ, μ ′ represents the magnetic permeability and μ ″ / μ ′ represents the degree of magnetic loss.

  Therefore, in the magnetic composite for antenna, ε ′ is about 5 to 7, and μ ′ is about 1.5 to 2.5. The antenna element can be downsized to a size of 10 × 30 to 10 × 42 (unit: mm) by the effect of the dielectric constant and the magnetic permeability. In addition, since ε ″ / ε ′ is about 0.03 to 0.05 and μ ″ / μ ′ is about 0.10 to 0.30, dielectric loss and magnetic loss are small, and the amount of change thereof is wide frequency. Since the band is stable, high gain can be maintained. Further, ε ′ is substantially constant from the VHF band to the UHF band, and the change of μ ′ is about ± 10% and does not change greatly. Therefore, according to the magnetic composite for antenna, it is possible to realize a small antenna that maintains a high gain for radio waves in a wide frequency band. Furthermore, since the magnetic composite for antenna has thermoplasticity, the antenna core can be manufactured by a low-cost and high-productivity manufacturing method such as an injection molding method, an extrusion molding method, or a pressure pressing method. There is.

[Antenna element]
The antenna element of the present invention is formed by arranging a conductor on the surface or inside of a molded body obtained by molding the magnetic composite. As a method of forming the magnetic composite, a known method such as a T-die method, an inflation molding method, a roll molding method, a press molding method, or an injection molding method can be adopted, but a roll in which internal stress hardly remains in the molded body. It is preferable to use a molding method or an injection molding method. As a conductor disposed on the surface or inside of the molded body, a wire-like or punched-metal conductor can be used. Furthermore, like a (multi-layer) printed wiring board, a patterned conductor formed by directly depositing or embedding a conductive metal on the surface or inside of a molded body and a through-hole connecting each conductor are combined. Things can also be used. When a helical antenna is provided by being spirally wound on the surface, a coated conductor such as a heat-sealed wire can be used. Or it is good also as shapes, such as a patch antenna. Further, a thin film of a nonmagnetic material may be formed between the molded body and the conductor. An example of application of the magnetic composite for antenna of this embodiment to an antenna element is shown in FIG.

  The antenna element shown in FIG. 1 has conductor patterns 3a to 3d and 4a to 4c, a start pattern 6 and a termination pattern 7 on the front surface [FIG. 1 (a)] and back surface [FIG. A coil conductor 2 is formed, which is electrically connected between patterns by a metal conductor 5 and circulates in a helical shape. In a non-limiting example, the core 1 has a flat plate shape. A first control terminal 8, a second control terminal 9, a ground terminal 11 and an input / output terminal 12 are formed on the back surface of the core 1. The first control terminal 8 is directly electrically connected to the start end pattern 6, and the second control terminal 9 is connected to the start end pattern 6 via a variable capacitance diode 10 of a chip-like independent electronic component. The ground terminal 11 is connected to the termination pattern 7, and the input / output terminal 12 is connected to the conductor pattern 4c.

Hereinafter, the embodiment will be described more specifically with reference examples, examples, and comparative examples.
First, evaluation items and test methods for the magnetic composites used in Examples and Comparative Examples are shown.
<Evaluation of electrical and magnetic properties>
In order to reduce the size of the antenna while maintaining the antenna gain, an antenna core material having excellent electrical characteristics and magnetic characteristics is essential. As an evaluation of electric characteristics and magnetic characteristics, a complex dielectric constant and a complex magnetic permeability were measured by a reflection method. From the complex permittivity and the complex permeability, ε ′, ε ″, μ ′, and μ ″ are obtained. From these, the relative permittivity is ε ′, the dielectric loss is ε ″ / ε ′, the relative permeability is μ ′, and the magnetic loss is μ ″ / μ ′, and these values are the average values in the measurement frequency band 77 to 990 MHz. did. Further, (ε ′ · μ ′) ^1/2 was calculated as an index for enabling miniaturization of the antenna element. Moreover, in a normal core material, the magnetic permeability decreases in the VHF band, and the antenna characteristics deteriorate. As ability to respond to this phenomenon, the fluctuation rate to the average value of mu 'in the preceding frequency band is mu _v.

≪Criteria for ε ′ and μ′≫
○: (ε ′ · μ ′) ^1/2 is 3.0 or more.
X: (ε ′ · μ ′) ^1/2 is less than 3.0.

≪Criteria for ε ”and μ” ≫
○: ε ″ / ε ′ is 0.05 or less and μ ″ / μ ′ 0.20 or less.
X: ε ″ / ε ′ is larger than 0.05, or μ ″ / μ ′ is larger than 0.20.

≪μ _v Judgment Criteria≫
○: -13% or more and + 13% or less.
X: Less than -13% and greater than + 13%.

It can be said that the antenna element can be reduced in size when (ε ′ · μ ′) ^1/2 is 3.0 or more. Furthermore, it can be said that an antenna element having a high gain can be obtained when ε ″ / ε ′ is 0.05 or less and μ ″ / μ ′ is 0.20 or less. Furthermore, she can be said that mu _v can be obtained an antenna element having an antenna gain stable in frequency band by the range -13% ~ + 13%. By satisfying all the above conditions, a magnetic composite capable of obtaining a small antenna element having a stable and high gain in the used frequency band can be obtained.

<Method for evaluating dispersibility of spinel ferrite powder (F) as magnetic powder>
In order for the magnetic composite to exhibit excellent dielectric and magnetic properties, the dispersibility of the spinel ferrite powder (F) in the graft copolymer (P) in the magnetic composite is an important factor. The dispersibility of the spinel ferrite powder (F) in the graft copolymer (P) in the magnetic composite is determined by the wettability of the graft copolymer (P) and the spinel ferrite powder (F).

  Evaluation of wettability of graft copolymer (P) and spinel-type ferrite powder (F) is generated by alternately repeating the state of holding at −55 ° C. for 30 minutes and the state of holding at + 105 ° C. for 30 minutes. The heat cycle resistance test was conducted to observe cracks that occurred. The wettability of the graft copolymer (P) and the spinel ferrite powder (F) can be evaluated as their interfacial strength. The interface strength can be indirectly evaluated by heat cycle resistance. When the number of cycles at the time when cracks are observed is less than 500, the interfacial strength between the graft copolymer (P) and the spinel ferrite powder (F) is low, and therefore the wettability and dispersibility are low. . On the other hand, when no cracks are observed 500 times or more, the interfacial strength, wettability and dispersibility of the graft copolymer (P) and the spinel ferrite powder (F) are good, and high dielectric properties and magnetic properties are exhibited. A magnetic complex is obtained.

≪Dispersibility criteria≫
○: Heat cycle resistance is 500 times or more.
X: Heat cycle resistance is less than 500 times.

Next, the manufacturing method of the graft copolymer (P) used for each example is shown as a reference example.
(Reference Example 1)
In a stainless steel autoclave having an internal volume of 5 liters, 2500 g of pure water was added, and 2.5 g of polyvinyl alcohol was dissolved as a suspending agent. Into this, 700 g of polypropylene ["Sun Aroma PM671A" manufactured by Sun Aroma Co., Ltd., MFR: 7 g / (10 min)] was added, stirred and dispersed. Separately, 2.0 g of benzoyl peroxide (trade name “NIPPER BW”, manufactured by NOF Corporation, 75% water-containing product) as a radical polymerization initiator, t-butylperoxy as a radical copolymerizable organic peroxide 7.5 g of methacryloyloxyethyl carbonate (manufactured by NOF Corporation, 40% toluene solution) is dissolved in 60 g of divinylbenzene, which is an aromatic vinyl monomer, and 240 g of styrene, and this solution is placed in the autoclave. Charged and stirred.

  Subsequently, the temperature of the autoclave is raised to 85 to 95 ° C. and stirred for 2 hours to impregnate polypropylene with an aromatic vinyl monomer containing a radical copolymerization initiator and a radical polymerizable organic peroxide. I let you. Thereafter, the temperature was lowered to 75 to 85 ° C., and maintained at that temperature for 5 hours to complete the polymerization. After filtration, washed with water and dried, a grafted precursor was obtained. Subsequently, this grafting precursor was extruded at 210 ° C. with a Laboplast Mill single screw extruder (manufactured by Toyo Seiki Seisakusho) and grafted to obtain a graft copolymer (P).

(Reference Examples 2 to 10)
A graft copolymer belonging to the graft copolymer (P) composed of various polymers (A) and monomers (B) was obtained by the same method as shown in Reference Example 1. Table 1 shows the constitution of each polymer (A). At this time, when the polymer (A) is synthesized and marketed in advance as a copolymer composed of a plurality of segments, the monomer constituting each segment is changed to component (1) and component (2). It was written. Table 2 shows the graft copolymer (P) composed of various combinations and ratios of the polymer (A) and the monomer (B).

表中に用いた略号の意味は次の通りである。
ＰＰ： ポリプロピレン樹脂「サンアロマーＰＭ６７１Ａ」〔商品名、サンアロマー（株）製〕
ＴＰＸ： ポリ４−メチルペンテン−１樹脂「ＴＰＸ ＲＴ１８」〔商品名、三井化学（株）製〕
ＺＥＯＮＥＸ： ノルボルネン系熱可塑性樹脂「ＺＥＯＮＥＸ ＲＳ４２０」〔商品名、日本ゼオン（株）製〕
ＳＥＰＳ２００７： スチレン−エチレンープロピレン−スチレン共重合体樹脂「セプトン」〔商品名、（株）クラレ製〕
ＳＥＰＳ２０６３： スチレン−エチレンープロピレン−スチレン共重合体樹脂「セプトン」〔商品名、（株）クラレ製〕
ＴＴＭ１９４３： 水添ブタジエン−スチレンブロック共重合体樹脂：「タフテック」〔商品名、旭化成（株）製〕
ＥＰＲ： エチレン−プロピレンゴム
ＢＲ： ブタジエンゴム
Ｓｔ： スチレン

The meanings of the abbreviations used in the table are as follows.
PP: Polypropylene resin “Sun Allomer PM671A” [trade name, manufactured by Sun Allomer Co., Ltd.]
TPX: Poly-4-methylpentene-1 resin “TPX RT18” [trade name, manufactured by Mitsui Chemicals, Inc.]
ZEONEX: Norbornene-based thermoplastic resin “ZEONEX RS420” [trade name, manufactured by Nippon Zeon Co., Ltd.]
SEPS 2007: Styrene-ethylene-propylene-styrene copolymer resin “Septon” [trade name, manufactured by Kuraray Co., Ltd.]
SEPS2063: Styrene-ethylene-propylene-styrene copolymer resin “Septon” [trade name, manufactured by Kuraray Co., Ltd.]
TTM1943: Hydrogenated butadiene-styrene block copolymer resin: “Tuftec” [trade name, manufactured by Asahi Kasei Corporation]
EPR: Ethylene-propylene rubber BR: Butadiene rubber St: Styrene

表中に用いた略号の意味は次の通りである。
ＭｅＳｔ： ｐ−メチルスチレン
ＤＶＢ： ジビニルベンゼン
（参考例１１及び１２）
さらに、本発明におけるグラフト共重合体（Ｐ）は２種以上のグラフト前駆体を混合したものでも良く、この混合はグラフト前でもグラフト後でも良いが、より混合しやすいグラフト前に混合することが好ましい。この場合、グラフト共重合体（Ｐ）を得る前段階の２種類の熱可塑性樹脂をそれぞれ（Ａ１）、（Ａ２）と記載し、表３にその構成を示した。

The meanings of the abbreviations used in the table are as follows.
MeSt: p-methylstyrene DVB: divinylbenzene (Reference Examples 11 and 12)
Furthermore, the graft copolymer (P) in the present invention may be a mixture of two or more graft precursors, and this mixing may be performed before or after grafting, but may be mixed before grafting, which is easier to mix. preferable. In this case, the two types of thermoplastic resins in the previous stage for obtaining the graft copolymer (P) are described as (A1) and (A2), respectively, and Table 3 shows the constitution.

Next, the manufacturing method of the spinel type ferrite powder (F) used for each example is shown as a reference example.
(Reference Examples 13 to 19)
Metal oxide powders as raw materials for the magnetic powder were mixed at a ratio as shown in Table 3, and after dehydration and drying, provisional firing was performed in air at 800 ° C. for 4 hours. Then, it was pulverized and further subjected to main firing at the firing temperatures shown in Table 3 to obtain spinel type ferrite powders (F) of Reference Examples 13-17. In Table 3, they are shown as soft magnetic powder (M).

(Reference Example 20)
Further, as the spinel type ferrite powder (F), a commercially available spinel type ferrite powder previously mixed and fired at a predetermined ratio may be used. Table 3 shows a commercially available spinel type ferrite powder corresponding to the spinel type ferrite powder (F) as Reference Example 20.

表中に用いた略号の意味は次の通りである。
ＦＬＲ−２Ｃ： Ｎｉ−Ｚｎ−Ｃｕ系フェライト粉末〔東光（株）製〕
＜実施例１＞
まず、ｐ-スチリルトリメトキシシラン〔商品名「ＫＢＭ１４０３」、信越化学工業（株）製」〕３６ｇを４５ｍＬのメタノールに溶解させ得た溶液とスピネル型フェライト粉末（Ｆ）として参考例１５のＦ５０５０ｂ、６ｋｇを混合させ１５０℃、１ｈの条件で熱処理することによりシランカップリング剤によって表面被覆されたＦ５０５０ｂを得た。次いで、参考例１で得られたグラフト共重合体（Ｐ）４ｋｇに酸化防止剤として１，３，５−トリメチル−２、４、６−トリス（３、５−ジ−ｔ−ブチル−４−ヒドロキシベンジル）ベンゼン〔商品名「Ｉｒｇａｎｏｘ１３３０」、チバ・スペシャルティケミカルズ（株）製〕、ネオペンタンテトライルビス（２、６−ジ−ｔ−ブチル−４−メチルフェニル）ホスファイト〔商品名「アデカスタブＰＥＰ−３６」、（株）ＡＤＥＫＡ製〕をそれぞれ１０ｇずつ、さらに前出の表面被覆されたＦ５０５０ｂをドライブレンドした。得られたドライブレンドをシリンダー温度２１０℃に設定されたスクリュー径３０ｍｍの同軸方向二軸スクリュー押出機〔ＴＥＸ−３０α、（株）日本製鋼所製〕に供給し、磁性複合体を得た。

The meanings of the abbreviations used in the table are as follows.
FLR-2C: Ni—Zn—Cu ferrite powder [manufactured by Toko Co., Ltd.]
<Example 1>
First, F5050b of Reference Example 15 as a solution obtained by dissolving 36 g of p-styryltrimethoxysilane [trade name “KBM1403”, manufactured by Shin-Etsu Chemical Co., Ltd.] in 45 mL of methanol and spinel-type ferrite powder (F), 6 kg was mixed and heat-treated at 150 ° C. for 1 hour to obtain F5050b whose surface was coated with a silane coupling agent. Next, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-l) as an antioxidant was added to 4 kg of the graft copolymer (P) obtained in Reference Example 1. Hydroxybenzyl) benzene (trade name “Irganox 1330”, manufactured by Ciba Specialty Chemicals Co., Ltd.), neopentanetetraylbis (2,6-di-t-butyl-4-methylphenyl) phosphite [trade name “ADK STAB PEP -36 "(manufactured by ADEKA Corporation) each was 10 g, and the above surface-coated F5050b was dry blended. The obtained dry blend was supplied to a coaxial twin screw extruder (TEX-30α, manufactured by Nippon Steel Works Co., Ltd.) having a screw diameter of 30 mm set at a cylinder temperature of 210 ° C. to obtain a magnetic composite.

<Examples 2 to 15>
A magnetic composite was obtained by mixing the graft copolymer (P) shown in Table 2 with the spinel ferrite powder (F) shown in Table 3 at a predetermined ratio. Further, the spinel type ferrite powder (F) may be surface-coated with a silane coupling agent, and a plurality of graft copolymers (P) may be mixed at the same time when the spinel type ferrite powder (F) is mixed. Table 4 shows the evaluation results of these magnetic composites.

表中に記した材料の詳細は次の通りである。
デシルトリメトキシシラン： 〔商品名「ＫＢＭ３１０３」、信越化学工業（株）製〕
３−グリシドキシプロピルトリメトキシシラン： 〔商品名「ＫＢＭ４０３」、信越化学工業（株）製〕
表４において、実施例１〜１５における本発明のアンテナ用磁性複合体によるアンテナ素子の性能評価結果は、全て、（ε’・μ’）^１／２が３．０以上であるとともに、ε”／ε’が０．０５以下、μ”／μ’が０．２０以下である。この結果から、本発明のアンテナ用磁性複合体によって、アンテナ素子を著しく小型化することができるととともに、高い利得を有するアンテナ素子を得ることができることが明らかになった。さらに、μ_ｖが−１３％〜＋１３％の範囲であることから、広範な周波数帯にわたって安定した利得を示す小型アンテナ素子に適する材料であることが明らかになった。

The details of the materials described in the table are as follows.
Decyltrimethoxysilane: [trade name "KBM3103", manufactured by Shin-Etsu Chemical Co., Ltd.]
3-Glycidoxypropyltrimethoxysilane: [trade name “KBM403”, manufactured by Shin-Etsu Chemical Co., Ltd.]
In Table 4, the performance evaluation results of the antenna elements by the magnetic composite for antenna of the present invention in Examples 1 to 15 are all (ε ′ · μ ′) ^1/2 is 3.0 or more and ε ″ / Ε ′ is 0.05 or less, and μ ″ / μ ′ is 0.20 or less. From this result, it became clear that the antenna element of the present invention can significantly reduce the size of the antenna element and obtain an antenna element having a high gain. Further, mu _v from in the range -13% ~ + 13%, it was found to be a material suitable for a small antenna device showing a stable gain over a wide frequency band.

<Comparative Examples 1-8>
In Comparative Examples 1 to 8, magnetic composites were obtained by mixing the graft copolymer (P) shown in Table 2 with the spinel ferrite powder (F) shown in Table 3 at various ratios. The composition of the magnetic composite and the evaluation results are shown in Table 5.

表５に示したように、比較例１では磁性複合体を構成するグラフト共重合体（Ｐ）において単量体（Ｂ）の割合が少なく、スピネル型フェライト粉末（Ｆ）を分散させる効果が小さくなるため磁性複合体の透磁率が小さくなり、アンテナ素子の小型化に適さない結果であった。また、比較例２ではグラフト共重合体（Ｐ）における単量体（Ｂ）の割合が過剰となり、グラフト共重合体（Ｐ）の流動性を著しく損なうため磁性複合体を得ることが困難であった。

As shown in Table 5, in Comparative Example 1, the proportion of the monomer (B) is small in the graft copolymer (P) constituting the magnetic composite, and the effect of dispersing the spinel ferrite powder (F) is small. Therefore, the magnetic composite has a low magnetic permeability, which is not suitable for downsizing of the antenna element. In Comparative Example 2, the proportion of the monomer (B) in the graft copolymer (P) becomes excessive, and the fluidity of the graft copolymer (P) is remarkably impaired, so that it is difficult to obtain a magnetic composite. It was.

  In Comparative Example 3, the proportion of the bifunctional ethylenically unsaturated monomer (b2) constituting the monomer (B) is decreased, and the degree of crosslinking of the monomer (B) is decreased. As a result, the effect of dispersing F) is reduced, the magnetic permeability of the magnetic composite is reduced, and the antenna is not suitable for downsizing. In Comparative Example 4, the proportion of (b2) in the monomer (B) becomes excessive, and the fluidity of the graft copolymer (P) is remarkably impaired, making it difficult to obtain a magnetic composite.

  In Comparative Example 5, the proportion of the spinel ferrite powder (F) in the magnetic composite was reduced, the magnetic composite was reduced in permeability, and was not suitable for miniaturization of the antenna element. In Comparative Example 6, the proportion of the spinel ferrite powder (F) in the magnetic composite became excessive, and it was difficult to obtain a magnetic composite by kneading.

  In Comparative Example 7, since the average particle diameter of the spinel ferrite powder (F) is too smaller than the range specified in the present invention, the total interfacial area to be wetted between the graft copolymer (P) and the spinel ferrite powder (F). As a result, the spinel type ferrite powder (F) formed secondary particles, and the dispersibility of the spinel type ferrite powder (F) was significantly lowered. On the other hand, in Comparative Example 8, since the particle size was too large, the responsiveness to the magnetic field was reduced, and as a result, the magnetic permeability was significantly reduced.

<Comparative Examples 9 and 10>
In Table 5, the composition of the magnetic composite obtained by mixing the norbornene-based thermoplastic resin ZEONEX or the polyolefin-based thermoplastic resin PP (Sun Allomer PM671A) and the spinel-type ferrite powder (F) shown in Table 3 The evaluation results are shown.

  As a result, in Comparative Examples 9 and 10, by mixing the thermoplastic resin that is not the graft copolymer and the spinel ferrite powder (F), the effect of dispersing the spinel ferrite powder (F) by the monomer is obtained. I can't get it. For this reason, the magnetic permeability is reduced in spite of mixing at the same ratio as in Example 1, and a high shearing force is required to disperse the spinel ferrite powder (F). Magnetic loss increased, and a magnetic composite capable of designing a small antenna element could not be obtained.

Claims (6)

For 100 parts by mass of polymer (A) obtained by polymerizing α-olefin, conjugated diene, unsaturated cyclic hydrocarbon or ethylenically unsaturated bond-containing aromatic monomer, aromatic monofunctional ethylenic It consists of an unsaturated monomer (b1) and a bifunctional ethylenically unsaturated monomer (b2), and the mass ratio of both monomers is (b1) / (b2) = 70/30 to 95/5 A composition containing a graft copolymer (P) obtained by graft polymerization of 18 to 67 parts by mass of the monomer (B) and a spinel ferrite powder (F) having an average particle diameter of 0.05 to 20 μm is kneaded. An antenna magnetic composite in which the mass ratio of both components is (P) / (F) = 10/90 to 60/40. The spinel-type ferrite powder (F) is represented by the characteristic formula MO · Fe ₂ O ₃ (M represents a metal element), and the electronegativity of the metal element M is 1.55 to 2.33. 2. The magnetic composite for antenna according to 1. The spinel-type ferrite powder (F) is represented by the characteristic formula MO · Fe ₂ O ₃ (M represents a metal element), and the metal element M is at least one metal selected from manganese, nickel, copper, or zinc. The magnetic composite for antenna according to claim 1, which is an element. The magnetic composite for antenna according to any one of claims 1 to 3, wherein the surface of the spinel ferrite powder (F) is coated with a silane coupling agent. An antenna element formed by arranging a conductor on the surface or inside of a molded body obtained by molding the magnetic composite for antenna according to any one of claims 1 to 4. A method for producing a magnetic composite for antenna according to claim 1,
a polymer (A) prepared by polymerizing an α-olefin, a conjugated diene, an unsaturated cyclic hydrocarbon or an ethylenically unsaturated bond-containing aromatic monomer,
It consists of an aromatic monofunctional ethylenically unsaturated monomer (b1) and a bifunctional ethylenically unsaturated monomer (b2), and the mass ratio of (b1) / (b2) is 70/30 to 95/5. A monomer (B) that is:
Graft polymerization of 18 to 67 parts by mass of the monomer (B) with respect to 100 parts by mass of the polymer (A) to prepare a graft copolymer (P),
The graft copolymer (P) and spinel ferrite powder (F) having an average particle size of 0.05 to 20 μm are kneaded at a mass ratio of (P) / (F) of 10/90 to 60/40. The method for producing a magnetic composite for an antenna.

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