JP2015117172A - Ferrite plate, member for antenna element and antenna element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrite plate suitable for non-contact near distance of wireless communication and for an antenna element having long communication distance, a member for an antenna element containing the ferrite plate and an antenna element containing any of them.SOLUTION: There is provided a ferrite plate formed from a Ni-Cu-Zn-based ferrite sintered body containing oxide of Co and Ti and tungsten oxide as an accessory component of 0.02 to 0.5 mass% in terms of WObased on 100 mass% of a Ni-Cu-Zn-based ferrite mainly containing Fe, Ni, Cu and Zn.

Description

The present invention relates to a ferrite plate suitable for non-contact short-range wireless communication and suitable for an antenna element having a long communication distance, an antenna element member made of the ferrite plate, and an antenna element including any of these.

13.56 MHz band RFID (Radio Frequency IDentification) system or NFC (Near Field Communication) system is a technology that performs near-field wireless communication without contact between an IC card or IC tag and a reader / writer. . Such an IC card or IC tag includes an IC chip and an antenna coil, and the reader / writer also includes an antenna coil.

By bringing the IC card or the like closer to the reader / writer, magnetic flux is generated by electromagnetic induction generated between these antenna coils. By exchanging this magnetic flux between the IC card or the like and the reader / writer, it becomes possible to supply power and exchange information written on the IC chip.

At this time, if the metal of the communication terminal housing cell is integrally arranged on the back surface of the antenna coil, an eddy current is generated in the metal by the generated magnetic flux, and this eddy current is a magnetic field in the opposite direction to the generated magnetic flux. Will be generated. As a result, the generated magnetic flux is weakened and the communication distance is shortened or communication is impossible. Moreover, thermal loss also occurs due to eddy currents.

In order to solve such a problem, it has been proposed to arrange a magnetic body made of a material having high magnetic permeability between the antenna coil and the metal. In general, the permeability μ is expressed as complex permeability μ = μ′−jμ ″ (j is an imaginary unit). The real part μ ′ of the complex permeability is a normal permeability component, and the imaginary part μ ″ is It is a material constant representing loss. These material constants are factors that govern the communication distance in short-range wireless communication. In order to improve the communication distance, it is important to focus the magnetic flux at high μ ′ while suppressing thermal loss at low μ ″.

NiZn-based ferrite materials have a high resistivity, so that loss in a high frequency band can be suppressed, and are often used as magnetic materials for high frequencies. In particular, various ideas have been made to improve high-frequency characteristics by including CoO. For example, in patent document 1, the characteristic improvement as a magnetic core member for antenna modules is made by containing CoO. Patent Document 2 discloses the addition of cobalt ferrite (CoFe ₂ O ₄ ) that has been spineled in advance to improve the dispersibility of Co. In Patent Document 3, the selective reaction of CoO is controlled by adding it as Co ₂ O ₃ .Fe ₂ O ₃ .

Conventionally, in order to block electromagnetic waves of electronic components, a very thin magnetic sheet has been attached to the outer surface thereof. The thin magnetic sheet described in Patent Document 4 has flexibility by dividing the ferrite sheet into a plurality of small pieces having a specific size.

In Patent Document 5, the magnetic material is oxidized to Ni—Cu—Zn ferrite as a sub-component in order to improve impact resistance and improve product yield while having excellent magnetic properties such as low core loss and high magnetic permeability. Inclusion of tungsten, molybdenum oxide and bismuth oxide has been performed.

In Patent Document 6, the magnetic material is provided with a low core loss, high magnetic permeability, and high Curie temperature, the main component composition is adjusted, and the diffraction angle 2θ by X-ray diffraction using Cu—Kα rays is 34. The half-value width of the diffraction peak of the crystal phase at 6 to 36.4 ° is set to 0.4 ° or less to improve mechanical strength (fracture toughness value, three-point bending strength, etc.).

JP 2005-340759 A Japanese Patent No. 5224495 JP 2013-133263 A Japanese Patent No. 4369519 JP 2005-235972 A JP-A-2005-64468

However, the high-frequency magnetic materials disclosed in Patent Documents 1 to 3 have a problem that a sufficient communication distance cannot be obtained when mounted as an antenna element with a decrease in the real part μ ′ of the complex permeability.

Dividing the magnetic material sheet into small pieces in order to impart flexibility as in Patent Document 4 has a problem in that the magnetic properties of the magnetic sheet are deteriorated and a sufficient communication distance cannot be obtained.

The magnetic materials described in Patent Documents 5 and 6 have a problem in that the magnetic permeability is lowered in a high frequency band and is not suitable for a material used for a ferrite plate used for an antenna element or a member for an antenna element.

Even when Patent Documents 1 to 6 are combined, it is difficult to provide a ferrite plate that is divided into small pieces and has flexibility and has a long communication distance in non-contact communication.

The present invention has been made in view of such a situation, and even if it is divided into small pieces to give flexibility, a ferrite plate having a long communication distance in non-contact communication, an antenna element member comprising the ferrite plate, or the An object is to provide an antenna element composed of a ferrite plate or antenna element member and an antenna coil.

In order to solve the above-described problems and achieve the object, the ferrite plate according to the present invention contains Co and Ti oxides, and Ni—Cu—Zn based ferrite containing Fe, Ni, Cu and Zn as main components. It is formed from a Ni—Cu—Zn-based ferrite sintered body containing tungsten oxide as an accessory component in an amount of 0.02 to 0.5 mass% in terms of WO ₃ with respect to 100 mass%. By doing so, even if it is divided into small pieces to give flexibility, a ferrite plate having a long communication distance in non-contact communication can be obtained.

In the ferrite plate according to the present invention, the main component composition of Ni—Cu—Zn ferrite is 45.0 to 49.5 mol% of iron oxide in terms of Fe ₂ O ₃ and 4 to 16 in terms of copper oxide in terms of CuO. 0.0 mol%, zinc oxide 19.0 to 25.0 mol% in terms of ZnO, and the balance is composed of nickel oxide. With respect to the main component, excluding inevitable impurities, Ferrite sintered containing 0.5 to 2% by mass of titanium oxide in terms of TiO ₂ , 0.35 to 2% by mass of cobalt oxide in terms of CoO, and 0.02 to 0.5% by mass of tungsten oxide in terms of WO ₃ Formed from ligatures. By doing so, even if it is divided into small pieces to give flexibility, a thin ferrite plate having a longer communication distance in non-contact communication can be obtained.

In addition, the antenna element member according to the present invention is provided with an adhesive layer on one surface of the ferrite plate and a protective layer on the other surface. It is divided. By doing so, it can be used as a thin antenna element member having a long communication distance in non-contact communication.

The antenna element according to the present invention includes a ferrite plate having the above-described composition or a member for antenna element. By doing so, it can be used as a thin antenna element having a long communication distance in non-contact communication.

According to the present invention, tungsten oxide is contained in the above range as a secondary component for Ni—Cu—Zn based ferrite containing oxides of Co and Ti and mainly composed of Fe, Ni, Cu and Zn. Thereby, even if it is divided into small pieces to give flexibility, a ferrite plate suitable for a thin antenna element having a long communication distance in non-contact communication can be obtained.

FIG. 1 is a schematic exploded perspective view of an antenna element according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional view of an antenna element member according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

As shown in FIG. 1, the antenna element 1 according to an embodiment of the present invention includes an adhesive material layer 18, a loop-shaped antenna coil 14, a protective layer 16, and a ferrite plate 12. In FIG. 1, illustration of a connection terminal to the outside, a communication processing circuit, and the like is omitted. FIG. 2 is a member for an antenna element according to another embodiment of the present invention, and shows a partial cross section taken along line AA of FIG. As shown in FIG. 2, the antenna element member 20 is held by the adhesive layer 18 and the protective layer 16, and the ferrite plate 12 is divided into a large number of small pieces.

The ferrite plate 12 according to the present embodiment is formed from a Ni—Cu—Zn ferrite sintered body containing iron oxide, copper oxide, zinc oxide and nickel oxide as main components.

The main component of 100 mole% of the Ni-Cu-Zn based ferrite sintered body, the content of iron oxide, calculated as _Fe 2 _{O 3,} 45.0 to 49.5 mol%, preferably 45.5 to 48. It is 5 mol%, More preferably, it is 46.0-48.0 mol%. When the content of iron oxide is less than 45.5 mol% in terms of Fe ₂ O ₃ , the real part μ ′ of the complex permeability tends to be low not only in the high frequency band but also in the low frequency band. On the other hand, when the iron oxide content is more than 49.5 mol% in terms of Fe ₂ O ₃ , the resonance frequency of the complex permeability is shifted to the low frequency side, and the imaginary part μ ”of the complex permeability in the high frequency band is In any case, when used as an antenna element, it causes a decrease in communication distance.

In 100 mol% of the main component of the Ni—Cu—Zn ferrite sintered body, the content of copper oxide is 4.0 to 16.0 mol%, preferably 5.6 to 14.8 mol% in terms of CuO. More preferably, it is 6.8-12.0 mol%.
When the content of copper oxide is less than 4.0 mol% in terms of CuO, the real part μ ′ of the complex permeability tends to be lowered not only in the high frequency band but also in the low frequency band. On the other hand, when the content of copper oxide is more than 16.0 mol% in terms of CuO, abnormal grain growth is caused and the real part μ ′ of the complex permeability is improved, but the imaginary part μ ″ tends to deteriorate rapidly. In either case, when used as an antenna element, it causes a decrease in communication distance.

In 100 mol% of the main component of the Ni—Cu—Zn ferrite sintered body, the content of zinc oxide is 19.0 to 25.0 mol%, preferably 20.0 to 24.5 mol% in terms of ZnO. More preferably, it is 21.0 to 24.0 mol%. When the content of zinc oxide is less than 19.0 mol% in terms of ZnO, the real part μ ′ of the complex permeability tends to be low not only in the high frequency band but also in the low frequency band. On the other hand, when the content of zinc oxide is more than 25.0 mol% in terms of ZnO, the resonance frequency of the complex permeability shifts to the low frequency side, and the imaginary part μ ″ of the complex permeability in the high frequency band tends to increase. In either case, when used as an antenna element, it causes a decrease in communication distance.

The remainder of the main component of the Ni—Cu—Zn-based ferrite sintered body may be composed only of nickel oxide, or may contain manganese oxide, which is an unavoidable impurity. When nickel oxide is contained in the balance of the main component, the content of nickel oxide is 9.5 to 32.0 in terms of NiO in 100 mol% of the main component of the Ni—Cu—Zn-based ferrite sintered body. The mol%, preferably 15.0 to 30.0 mol%, more preferably 17.0 to 28.0 mol%. When the content of nickel oxide is less than 9.5 mol% in terms of NiO, the resonance frequency of the complex permeability tends to shift to the low frequency side, and the imaginary part μ ″ of the complex permeability in the high frequency band tends to increase. On the other hand, when the content of nickel oxide is more than 32.0 mol% in terms of NiO, the real part μ ′ of the complex permeability tends to be low not only in the high frequency band but also in the low frequency band. When used as an antenna element, it causes a decrease in communication distance.

The Ni—Cu—Zn-based ferrite sintered body forming the antenna element ferrite plate according to the present embodiment contains titanium oxide, cobalt oxide, and tungsten oxide as subcomponents in addition to the above main components. .

The content of titanium oxide is 0.5 to 2% by mass, preferably 0.6 to 1.9% by mass, more preferably 0.7 to 1.8% by mass in terms of TiO _{2 with} respect to the main component. It is. When the content of titanium oxide is less than 0.5% by mass in terms of TiO _{2 with} respect to the main component, the real part μ ′ of the complex permeability in the high frequency band tends to be low. On the other hand, when the content of titanium oxide is more than 2% by mass in terms of TiO _{2 with} respect to the main component, the resonance frequency of the complex permeability shifts to the low frequency side, and the imaginary part μ of the complex permeability in the high frequency band "" Tends to increase. When used as an antenna element, both cause a reduction in communication distance.

The content of cobalt oxide is 0.35 to 2% by mass, preferably 0.4 to 1.5% by mass, and more preferably 0.5 to 1% by mass in terms of CoO with respect to the main component. When the content of cobalt oxide is less than 0.35 mass% in terms of CoO with respect to the main component, the resonance frequency of the complex permeability exists on the low frequency side, and the imaginary part μ of the complex permeability in the high frequency band On the other hand, when the content of cobalt oxide is more than 2% by mass in terms of CoO with respect to the main component, the real part μ of the complex permeability not only in the high frequency band but also in the low frequency band 'Tends to be low, both of which cause a decrease in communication distance when used as an antenna element.

In addition, said effect is not fully acquired when a titanium oxide and a cobalt oxide are contained independently. That is, the above effect is a composite effect obtained only when the two types of titanium oxide and cobalt oxide are contained and the contents of titanium oxide and cobalt oxide are controlled within the scope of the present invention.

In the Ni—Cu—Zn-based ferrite sintered body forming the ferrite plate according to the present embodiment, the composition range of the main component is controlled to the above range, and in addition, titanium oxide and oxidation are added as subcomponents. A specific amount of cobalt is contained. In particular, by adding titanium oxide, the frequency dependence of the imaginary part μ ″ of the complex permeability shows a steep behavior, and in the vicinity of the RFID or NFC communication frequency of 13.56 MHz, the low μ "It becomes possible. When a ferrite plate formed of a Ni—Cu—Zn ferrite sintered body having such a composition is used as an antenna element, the communication distance can be improved.

The content of tungsten oxide, with respect to the main component, in terms _of WO _3, 0.02 to 0.5 wt%, preferably from 0.04 to 0.3 wt%, more preferably 0.05 to 0.2 % By mass. When the content of tungsten oxide is less than 0.05% by mass in terms of WO _{3 with} respect to the main component, the fracture toughness value of the Ni—Cu—Zn-based ferrite sintered body becomes low, and the high frequency band after small piece division There is a tendency for the real part μ ′ of the complex permeability of the to decrease. On the other hand, when the content of tungsten oxide is more than 0.5% by mass in terms of WO _{3 with} respect to the main component, the resonance frequency of the complex permeability exists on the low frequency side, and the imaginary part μ ”of the high frequency band is When it uses as an antenna element, it becomes a factor which causes the fall of communication distance.

Note that the fracture toughness value of the Ni-Cu-Zn based ferrite sintered body forming the ferrite plate is preferably 1.3 MPa ^{· m 1/2} or more 2.5 MPa ^{· m 1/2} or less. More preferably, it is 1.4 MPa · m ^1/2 or more and 2.5 MPa · m ^1/2 or less, and further preferably 1.5 MPa · m ^1/2 or more and 2.5 MPa · m ^1/2 or less. When the fracture toughness value of the Ni-Cu-Zn-based ferrite sintered body is less than 1.3 MPa · m ^1/2 , when a crack occurs, the crack is likely to progress greatly, making it difficult to handle a thin ferrite plate Thus, the mechanical reliability is likely to be lowered, and when used as an antenna element, it causes a reduction in communication distance. On the other hand, when the fracture toughness value of the Ni—Cu—Zn-based ferrite sintered body is higher than 2.5 MPa · m ^1/2 , the step of dividing the ferrite plate into small pieces in order to give flexibility to the antenna element member It becomes difficult to carry out, and problems occur in manufacturing the antenna element member.

Next, an example of a method for manufacturing a ferrite plate according to the present embodiment will be described.

First, starting materials (raw materials of main components and raw materials of subcomponents) are weighed and mixed so as to have a predetermined composition ratio to obtain a raw material mixture. Examples of the mixing method include wet mixing using a ball mill and dry mixing using a dry mixer. It is preferable to use a starting material having an average particle size of 0.1 to 3 μm.

As a raw material of the main component, iron oxide (α-Fe ₂ O ₃ ), copper oxide (CuO), zinc oxide (ZnO), nickel oxide (NiO), or a composite oxide containing these can be used. In addition, various compounds that become oxides or composite oxides by firing can be used. Examples of the oxide that becomes the above-mentioned oxide upon firing include simple metals, carbonates, oxalates, nitrates, hydroxides, halides, organometallic compounds, and the like.

Titanium oxide (TiO ₂ ), cobalt oxide (Co ₃ O ₄ ), and tungsten oxide (WO ₃ ) can be used as raw materials for the subcomponents. Cobalt oxide may be CoO or cobalt ferrite (CoFe ₂ O ₄ ), but Co ₃ O ₄ is easy to store and handle, has a stable valence even in air, and has excellent mass productivity. Therefore, it is preferable as a raw material for cobalt oxide.

Next, the raw material mixture is calcined to obtain a calcined material. Calcining promotes thermal decomposition of raw materials, homogenization of ingredients, formation of ferrite, disappearance of ultrafine powder due to sintering and grain growth to an appropriate particle size, and converts the raw material mixture into a form suitable for subsequent processes. To be done. Such calcination is preferably performed at a temperature of 800 to 1100 ° C. for about 1 to 3 hours. The calcination may be performed in the air (air), or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. The mixing of the main component raw material and the subcomponent raw material may be performed before calcining or after calcining.

Next, the calcined material is pulverized to obtain a pulverized material. The pulverization is performed in order to dissolve the calcined material and form a powder having appropriate sinterability. When the calcined material forms a large lump, wet pulverization is performed using a ball mill or an attritor after coarse pulverization. The wet pulverization is performed until the average particle diameter of the pulverized material is preferably about 0.5 to 2 μm.

Using the obtained pulverized material, the ferrite plate according to the present embodiment is manufactured. The method for producing the ferrite plate is not limited, but in the following, the sheet method is used.

First, the obtained pulverized material is slurried together with additives such as a solvent, a binder, a dispersant, and a plasticizer to prepare a paste. And the green sheet which has a thickness of 50-350 micrometers is formed using this paste. A plurality of obtained green sheets may be laminated. Next, the formed green sheet is processed into a predetermined shape, and a ferrite plate having a thickness of 30 to 300 μm according to the present embodiment is obtained through a binder removal step and a firing step. Firing is preferably performed at a temperature of 900 to 1300 ° C., usually for about 2 to 5 hours. The firing may be performed in the atmosphere (air) or in an atmosphere having a higher oxygen partial pressure than in the atmosphere. In this way, the ferrite plate according to the present embodiment is obtained.

In the embodiment described above, the ferrite plate is manufactured by the sheet method. For example, after the ferrite powder and the binder resin are mixed, the ferrite plate is manufactured by a known method such as a powder compression molding method, an injection molding method, a calendar method, an extrusion method, or the like. May be.

Next, an adhesive layer 18, for example, a double-sided adhesive tape is provided on one side (one surface) of the obtained ferrite plate. A protective layer 16 is provided on the surface opposite to the surface on which the adhesive material layer is formed (the other surface) to prevent the ferrite plate divided into small pieces from being lost and dropped off. The protective layer is formed by adhering a resin film or sheet constituting the protective layer to the surface of the ferrite plate, if necessary, with an adhesive, or by applying a paint containing the resin constituting the protective layer to the ferrite plate. It is performed by applying to the surface. The ferrite plate is made by holding both sides of the ferrite plate with these two layers (adhesive layer 18 and protective layer 16) and passing them once in the 0 degree direction and 90 degree direction with respect to the roller of the rolling device. Are divided into a large number of planar small pieces in a lattice shape to form voids 19 (see FIG. 2). In this way, the antenna element member having flexibility and flexibility according to the present embodiment is obtained.

Next, the antenna coil 14 for non-contact communication is attached to the surface of the adhesive material layer 18 of the obtained antenna element member 20. The antenna coil 14 has a loop-shaped loop antenna structure with an opening at the center, and the loop shape may be circular, substantially rectangular, or polygonal. Furthermore, the material of the antenna coil 14 can be appropriately selected from conductive metal wire, metal plate, metal foil, metal cylinder, etc., for example, metal wire, metal foil, conductor paste The antenna coil 14 can be formed by plating transfer, sputtering, vapor deposition, or screen printing. Thus, the antenna element 1 according to the present embodiment is obtained.

As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in various aspects. .

Hereinafter, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.

First, Fe ₂ O ₃ , NiO, CuO, and ZnO are prepared as main component materials, and TiO ₂ , Co ₃ O _4, and WO _{3 are} prepared as subcomponent materials, and the predetermined composition ratios shown in Table 1 are obtained. Then, 500 mL of ion-exchanged water was added as a solvent, and wet mixing was performed for 16 hours in a steel ball mill to obtain a raw material mixture.

The obtained powder of the raw material mixture was calcined at a maximum temperature of 800 ° C. for 2 hours using a heating furnace, then cooled in a furnace and crushed with a 30-mesh sieve. Thereafter, 500 mL of ion exchange water was again added as a solvent, and wet pulverization was performed for 16 hours in a steel ball mill to obtain a pulverized material.

100% by mass of ferrite powder of the obtained pulverized material, 3.5% by mass of dioctyl adipate, 8% by mass of butyral resin, and a mixed solution of xylene and isobutyl alcohol as a solvent (xylene: isobutyl alcohol = 6: 4 (mass ratio) )) 72% by mass was mixed, dissolved and dispersed by a ball mill to prepare a slurry containing ferrite powder. The obtained slurry was degassed under reduced pressure with an oil rotary vacuum pump, and then applied to a certain thickness on a polyethylene terephthalate (PET) film with a doctor blade, dried with hot air at 100 ° C. for 30 minutes, and a thickness of about 120 μm. A green sheet was obtained.

Next, the obtained green sheet was heated from room temperature to 500 ° C. at a heating rate of 1 ° C./min, degreased by holding at 500 ° C. for 3 hours, then heated to 1000 ° C. and sintered for 2 hours, A ferrite plate having a thickness of about 100 μm was obtained.

A commercially available acrylic double-sided tape (30 μm) as an adhesive layer is applied to one surface of the obtained ferrite plate, and a single-sided adhesive sheet (30 μm) coated with a commercially available acrylic adhesive is applied as a protective layer to the other surface. Then, the ferrite plate held by the adhesive layer and the protective layer is passed through the roller of the rolling machine whose GAP amount is adjusted to 150 μm once each in the 0 degree direction and the 90 degree direction, so that the ferrite plate is latticed. An antenna element member divided into a large number of planar small pieces was obtained.

When the single-sided adhesive sheet of the antenna element member was peeled and the shape and size of the divided ferrite plate were confirmed, it was divided into a 2 to 3 mm lattice.

<Evaluation of magnetic properties>
The complex permeability is punched into a toroidal shape using a pinnacle mold having an outer diameter of 18 mm and an inner diameter of 10 mm from a member for antenna element having a thickness of 160 μm divided into a number of planar small pieces (the thickness of the ferrite plate is 100 μm). An antenna analyzer (made by Agilent Technologies, product name: RF impedance / material analyzer, model: E4991A) and magnetic material measurement electrode (manufactured by Agilent Technologies, product) Name: magnetic material test fixture, type: 16454A), and magnetic properties were evaluated at a measurement temperature of 25 ° C.

<Antenna communication distance>
From a member for antenna element having a thickness of 160 μm divided into a large number of planar pieces (the thickness of the ferrite plate is 100 μm), a pinnacle mold is used to punch out a rectangle having a size of 50 mm × 40 mm and a sample for measuring a communication distance did. An antenna coil for an NFC system having a size of 50 mm × 40 mm on a surface having an adhesive material layer, on which a copper plate imitating a metal such as a housing cell or a battery pack is disposed on the surface having a protective layer of the antenna element member. A loop antenna structure, pattern: substantially rectangular) was affixed to obtain a measurement tag. An antenna module was configured between the tag and an NFC reader / writer (product name: contactless reader, model: ViVOpay5000, manufactured by ID Tech), and a communication distance of 25 ° C. at a resonance frequency of 13.56 MHz was measured.

<Fracture toughness value>
The fracture toughness value of the Ni—Cu—Zn ferrite sintered body was measured as follows. 10% by weight of an aqueous binder solution containing 6% by weight of polyvinyl alcohol is added to 100% by weight of the ferrite powder of the obtained pulverized material, and the mixture is kneaded and granulated for about 10 minutes. Molded into a cylindrical sample using a compression molding machine and a mold, heated to 1000 ° C. and sintered for 2 hours to obtain a sample for fracture toughness measurement (outer diameter: 10 mm, thickness: 3 mm) . After the sample was mirror-polished, it was subjected to JIS using a Vickers hardness tester (manufactured by FUTURE-TECH, model: FV-800).
The fracture toughness value K _Ic of the Ni—Cu—Zn-based ferrite sintered body was measured by an IF (Indentation Fracture) method based on R1607-2010.

The obtained measurement evaluation results are shown in Table 1. As a reference example, IBF10 (series name manufactured by TDK) was described. In this embodiment, it is desirable that the communication distance is better than IBF10 (50.0 mm or more), or the fracture toughness value is better than IBF10 (1.18 MPa · m ^1/2 or more), and μ ′ is More preferably, it is 165 or more and μ ″ is 7 or less.

From Table 1, it contains oxides of Co and Ti, and contains 100% by mass of Ni—Cu—Zn ferrite containing Fe, Ni, Cu and Zn as main components, and tungsten oxide as an accessory component in the above range. Thus, when the content is within the range of the present invention (Examples 1 to 18), it was confirmed that a good communication distance can be obtained and at the same time a high fracture toughness value can be obtained. On the other hand, when no main component or subcomponent, particularly tungsten oxide, is contained in the above range (Comparative Examples 1 to 8), a decrease in communication distance or a decrease in fracture toughness value is confirmed, and an antenna element for non-contact communication Confirmed not suitable for application

From these results, the ferrite plate of the example according to the present invention has higher mechanical reliability than the comparative example and the reference example, and is easy to handle even if it is thin. Even in such a case, it was confirmed that a long communication distance can be obtained.

As described above, by applying the ferrite plate according to the present invention to the antenna element member, the antenna can be thinned while maintaining a long communication distance. It is also useful in terms of space saving.

DESCRIPTION OF SYMBOLS 1 ... Antenna element 12 ... Ferrite plate 14 ... Antenna coil 16 ... Protective layer 18 ... Adhesive material layer 19 ... Air gap 20 ... Antenna element member

Claims (5)

With respect to 100% by mass of Ni—Cu—Zn based ferrite containing Fe, Ni, Cu and Zn as main components and containing oxides of Co and Ti, tungsten oxide as an accessory component is 0.02 to 0 in terms of WO _3. A ferrite plate formed of a Ni—Cu—Zn ferrite sintered body containing 5 mass%.
2. The ferrite plate according to claim 1, wherein the main component composition of Ni—Cu—Zn-based ferrite is 45.0 to 49.5 mol% of iron oxide in terms of Fe ₂ O ₃ and copper oxide in terms of CuO. 4 to 16.0 mol%, zinc oxide 19.0 to 25.0 mol% in terms of ZnO, and the balance is composed of nickel oxide, excluding inevitable impurities with respect to the main component, as a secondary component, 0.5 to 2 wt% of titanium oxide in terms of TiO _2, 0.35 to 2 wt% of cobalt oxide in terms of CoO, a 0.02-0.5 wt% tungsten oxide in terms _of WO ₃ A ferrite plate formed from a ferrite sintered body characterized by containing.
An adhesive layer is provided on one surface of the ferrite plate, and a protective layer is provided on the other surface, and the ferrite plate is divided into a number of planar small pieces while being held by the two layers. The member for antenna elements using the ferrite plate of description.
An antenna element including the ferrite plate according to claim 1.
An antenna element comprising the antenna element member according to claim 3.

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