JP2023082553A - Magnetic resin composition and processed product - Google Patents

Abstract

To provide a magnetic resin composition which has low viscosity and exhibits low thixotropy property while maintaining suitable magnetic permeability and loss coefficient, and has such a sufficiently high glass transition temperature that a cured product exhibits excellent heat resistance.SOLUTION: A magnetic resin composition contains ferrite particles (A) having a particle diameter (D50) at an integrated value in particle size distribution of 50% of 0.05 μm or more and 0.50 μm or less, magnetic particles (B) having D50 of 3.0 μm or more and a particle diameter (D90) at an integrated value in particle size distribution of 90% of 5.0 μm or more, a liquid epoxy compound (C) that is liquid at 25°C, and a curing agent (D). The liquid epoxy compound (C) contains a liquid epoxy compound (C-1) having two or less epoxy groups in the molecule, and a polyfunctional liquid epoxy compound (C-2) having three or more epoxy groups in the molecule.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present disclosure relates generally to magnetic resin compositions and processed products, and more particularly to magnetic resin compositions containing ferrite particles and processed products made using the same.

Magnetic materials are used in applications such as inductors, motors, and antenna modules. As a magnetic material, a paste-like magnetic resin composition having magnetism is known so that it can be easily processed into a predetermined shape and properties according to the purpose and application.

For example, Patent Document 1 proposes an invention relating to a magnetic paste containing magnetic powder having a predetermined particle size distribution and a binder resin. It is described that uneven distribution of magnetic powder due to operation is suppressed.

WO2020/075745

By the way, magnetic resin compositions used for applications such as inductors are required to have a high magnetic permeability and a low loss factor. In addition, along with the recent miniaturization of electronic parts and the finer patterning of wiring substrates, there is a demand for improvement in filling properties of the composition during processing. For example, when filling a small through-hole having a diameter of about 500 μm or less with a magnetic resin composition, it is desirable to have low viscosity and low thixotropy. In addition, since it is expected that processed products made using the magnetic resin composition can be used in high-temperature environments without problems, it is also desired to have a high glass transition temperature that exhibits excellent heat resistance.

The present disclosure has been made to solve the above problems, and has a low viscosity and low thixotropy while maintaining a suitable magnetic permeability and loss factor, and the cured product has excellent heat resistance. An object of the present invention is to provide a magnetic resin composition and a processed article having a sufficiently high glass transition temperature.

A magnetic resin composition according to an aspect of the present disclosure includes ferrite particles (A) having a particle size (D50) of 0.05 μm or more and 0.50 μm or less at an integrated value of 50% in the particle size distribution, and D50 of 3.0 μm or more. and a magnetic particle (B) having a particle size (D90) of 5.0 μm or more at an integrated value of 90% in the particle size distribution, a liquid epoxy compound (C) that is liquid at 25° C., and a curing agent (D). and The liquid epoxy compound (C) includes a liquid epoxy compound (C-1) having two or less epoxy groups in the molecule and a polyfunctional liquid epoxy compound (C-2) having three or more epoxy groups in the molecule. ) and including.

A processed product according to an aspect of the present disclosure includes a cured product of the magnetic resin composition.

According to the present disclosure, the magnetic resin composition exhibits low viscosity and low thixotropy while maintaining suitable magnetic permeability and loss factor, and its cured product has a sufficiently high glass transition to exhibit excellent heat resistance. have a temperature. The processed product exhibits excellent heat resistance while maintaining suitable magnetic permeability and loss factor.

(1) Magnetic Resin Composition The magnetic resin composition according to this embodiment contains a magnetic filler and a resin material. The magnetic filler contains ferrite particles (A) and magnetic particles (B). The resin material contains a liquid epoxy compound (C) and a curing agent (D).

Here, the liquid epoxy compound (C) is liquid at 25°C. The liquid epoxy compound (C) includes a liquid epoxy compound (C-1) having two or less epoxy groups in the molecule and a polyfunctional liquid epoxy compound (C-2) having three or more epoxy groups in the molecule. and including.

The magnetic resin composition preferably has an E-type viscosity of 20 Pa·s or more and 50 Pa·s or less, and a thixotropic index of preferably 1.5 or more and 5.0 or less when measured at 25° C. and 5 rpm. is. Within this range, for example, even when a through-hole having an inner diameter of 500 μm or less is filled with the magnetic resin composition, voids and poor filling are less likely to occur, and filling can be performed without problems.

The glass transition temperature (Tg) of the cured product of the magnetic resin composition is preferably 100° C. or higher. A cured product of a magnetic resin composition that satisfies this requirement has excellent heat resistance.

(1.1) Magnetic Filler As described above, the magnetic filler includes ferrite particles (A) and magnetic particles (B). Magnetic fillers are particulate matter that can be magnetized. In this way, the magnetic resin composition contains the ferrite particles (A) and the magnetic particles (B), so that a processed product having magnetic properties can be obtained. The processed product includes a cured product of the magnetic resin composition. Magnetic properties are the magnetic properties exhibited when magnetized. Specific examples of magnetic properties include magnetic permeability and magnetic flux density.

As mentioned above, the work piece has magnetic properties, and in particular the work piece according to the present embodiment may have a high magnetic permeability at high frequencies. The high frequency band is, for example, several MHz or more and several GHz or less, including 70 MHz. The real part (μr′) of the complex relative permeability (μr) of the processed product at 70 MHz is preferably 6.0 or more. Thereby, the magnetic permeability at high frequencies can be further increased. The loss factor (tan δ) of the processed product at 70 MHz is preferably 0.10 or less, more preferably 0.08 or less. This makes it possible to further reduce the loss.

The complex relative magnetic permeability (μr) is represented by the formula μr=μ/μ0 (μ: complex magnetic permeability, μ0: vacuum magnetic permeability). The complex permeability (μ) is represented by the formula μ=μ′−iμ″ (μ′: real part, μ″: imaginary part, i: imaginary unit). In the present embodiment, "permeability" mainly means the real part (μr') of the complex relative permeability (μr). The real part (μr′) of the complex relative permeability (μr) is represented by the formula μr′=μ′/μ0. The imaginary part (μr″) of the complex relative permeability (μr) is expressed by the formula μr″=μ″/μ0. The relational expression of the complex relative permeability (μr) is summarized as the following expression (1).

"50% volume average particle size" means the particle size (D50) at 50% integrated value in the particle size distribution measured based on a particle size distribution analyzer based on laser scattering/diffraction method. The "D50 of the ferrite particles (A)" is the D50 of the entire particulate matter contained in the ferrite particles (A), and the "D50 of the magnetic particles (B)" is the particles contained in the magnetic particles (B). means the D50 of the whole material.

"90% volume average particle size" means a particle size (D90) at 90% integrated value in a particle size distribution measured based on a particle size distribution analyzer based on a laser scattering/diffraction method. The "D90 of the ferrite particles (A)" is the D90 of the entire particulate matter contained in the ferrite particles (A), and the "D90 of the magnetic particles (B)" is the particles contained in the magnetic particles (B). means the D90 of the whole material.

<Ferrite particles (A)>
D50 of the ferrite particles (A) is 0.05 μm or more and 0.50 μm or less. Thus, by including the fine ferrite particles (A) in the magnetic resin composition, the viscosity of the magnetic resin composition can be reduced.

The ferrite particles (A) contain at least one kind of ferrite. Ferrite is a ceramic filler whose main component is iron oxide. Ferrite includes soft ferrite exhibiting soft magnetism and hard ferrite exhibiting hard magnetism. Ferrite is classified into spinel ferrite, hexagonal ferrite, garnet ferrite, and the like according to its crystal structure.

Spinel ferrite has a spinel crystal structure. The compositional formula of spinel ferrite is AFe ₂ O ₄ (where A is Mn, Co, Ni, Cu, Zn, etc.). Most spinel ferrites are soft ferrites. Spinel ferrites include, for example, manganese-zinc ferrite (Mn--Zn ferrite), nickel-zinc ferrite (Ni--Zn ferrite), copper-zinc ferrite (Cu--Zn ferrite), and the like. Spinel ferrite has high magnetic permeability and high electrical resistance, and thus has a small eddy current loss in a high frequency band. Magnetite is also a type of spinel ferrite. The composition formula of magnetite is represented by Fe ₃ O ₄ .

Hexagonal ferrite has a magnetoplumbite-type hexagonal crystal structure. The composition formula of hexagonal ferrite is represented by AFe ₁₂ O ₁₉ (A is Ba, Sr, Pb, etc.). Hexagonal ferrite is also called magnetoplumbite ferrite and M-type ferrite. Hexagonal ferrite exhibits a large coercive force due to its large magnetic anisotropy compared to spinel ferrite. Hexagonal ferrite is a typical hard ferrite.

Garnet ferrite has a garnet-type crystal structure. The composition formula of garnet ferrite is represented by RFe ₅ O ₁₂ (R is a rare earth element). Garnet ferrite is also called rare-earth iron garnet (RIG). A typical example of garnet ferrite is yttrium iron garnet (YIG). Garnet ferrite has low magnetic loss at high frequencies.

By including at least one kind of ferrite in the ferrite particles (A), the magnetic permeability of the processed product at high frequencies can be increased.

The ferrite particles (A) preferably contain at least one selected from the group consisting of Mn ferrite (manganese ferrite), Mn—Zn ferrite (manganese zinc ferrite), and magnetite, and the group consisting of Mn ferrite and magnetite. It is more preferable to include at least one more selected one.

Manganese ferrite is ferrite containing manganese. Examples of manganese ferrite include, but are not limited to, manganese ferrite (Mn ferrite), manganese zinc ferrite (Mn—Zn ferrite), iron manganese ferrite (Fe—Mn ferrite), manganese magnesium ferrite (Mn—Mg ferrite), and magnesium manganese strontium ferrite (Mg--Mn--Sr ferrite). By containing at least one selected from the group consisting of manganese ferrite and magnetite in the ferrite particles (A), the magnetic permeability and loss factor (tan δ) of the processed product are well balanced. That is, it becomes easy to increase the magnetic permeability of the processed product and reduce the loss factor (tan δ). In addition, by including magnetite in the magnetic resin composition, the viscosity of the magnetic resin composition can be reduced.

The ferrite particles (A) preferably contain spherical particles, and more preferably at least one of Mn ferrite, Mn—Zn ferrite, and magnetite contains spherical particles. Thereby, the fluidity of the magnetic resin composition can be improved. In other words, it becomes easier to mold the processed product. In addition, high filling of the ferrite particles (A) can be achieved. In particular, when the ferrite particles (A) are highly packed, the magnetic permeability of the processed product can be increased. Moreover, the drillability of the processed product can be improved. Drillability is a measure of how easily a work piece can be processed when the work piece is drilled. Drillability is evaluated by wear rate and the like. In addition, the ferrite particles (A) may include particles having a shape other than a spherical shape. Shapes other than a spherical shape are not particularly limited, but examples thereof include an ellipsoidal shape, a flattened shape, a crushed shape, an amorphous shape, and the like.

The content of the ferrite particles (A) is preferably 0.1% by mass or more and 20.0% by mass or less, more preferably 1% by mass or more and 10% by mass or less, relative to the total mass of the magnetic resin composition. Within this range, the viscosity and thixotropy of the magnetic resin composition can be reduced.

The magnetic resin composition preferably does not substantially contain sendust and amorphous alloys. Here, sendust is a ternary alloy (Fe--Si--Al alloy) consisting of iron, silicon and aluminum. The basic composition of Sendust is Fe-10Si-5Al. On the other hand, an amorphous alloy is a disordered alloy with no regularity in the arrangement of elements. As described above, if the magnetic resin composition does not substantially contain sendust and amorphous alloy, it is possible to suppress deterioration in machinability. However, at least one of sendust and amorphous alloy may be contained in the magnetic resin composition as an unavoidable impurity.

<Magnetic particles (B)>
The D50 of the magnetic particles (B) is 3.0 μm or more, and the D90 of the magnetic particles (B) is 5.0 μm or more. D50 of the magnetic particles (B) is preferably 3.0 μm or more and 6.0 μm or less, and D90 of the magnetic particles (B) is preferably 10.0 μm or more and 20.0 μm or less. By setting it within this range, the drillability of the cured product can be further improved.

Magnetic particles (B) contain at least one ferrite. The crystal structure, properties and preferred shape of the ferrite in the magnetic particles (B) are the same as those of the ferrite particles (A) described above.

The magnetic particles (B) preferably contain Mn ferrite and/or Mn—Zn ferrite, more preferably Mn ferrite. In addition, in this specification, "X and/or Y" means "X", "Y", or "X and Y."

The magnetic particles (B) preferably contain spherical particles, more preferably Mn ferrite and/or Mn—Zn ferrite contain spherical particles. Thereby, the fluidity of the magnetic resin composition can be improved. In other words, it becomes easier to mold the processed product. In addition, high filling of the magnetic particles (B) can be achieved. In particular, when the magnetic particles (B) are highly packed, the magnetic permeability of the processed product can be increased. Moreover, the drillability of the processed product can be improved. The magnetic particles (B) may include particles having a shape other than spherical.

The content of the magnetic particles (B) is preferably 75% by mass or more and 95% by mass or less, more preferably 80% by mass or more and 90% by mass or less, relative to the total mass of the magnetic resin composition. By setting it within this range, the viscosity can be reduced while increasing the magnetic permeability.

(1.2) Resin material The resin material can function as a binder. As described above, the resin material contains a liquid epoxy compound (C) and a curing agent (D). The resin material may contain additives and/or solvents. By including the liquid epoxy compound (C) in the resin material, it becomes easier to mold a processed product from the magnetic resin composition. In addition, since the resin material contains a self-polymerizing material, the pot life (usable time) of the magnetic resin composition can be lengthened. In addition, a processed product having excellent heat resistance and a high glass transition temperature can be obtained by thermal curing in a short period of time.

<Liquid epoxy compound (C)>
The liquid epoxy compound (C) is liquid at 25° C. and includes a liquid epoxy compound (C-1) having two or less epoxy groups in the molecule and a polyfunctional liquid having three or more epoxy groups in the molecule. and an epoxy compound (C-2).

The liquid epoxy compound (C) is at least one selected from the group consisting of bisphenol F-type epoxy resins, bisphenol A-type epoxy resins, alkyldiglycidyl ethers, alkylmonoglycidyl ethers, and alkylphenol monoglycidyl ethers. preferably included.

Although the epoxy equivalent of the liquid epoxy compound (C) is not particularly limited, it is preferably 90 g/eq or more and 200 g/eq or less.

The liquid epoxy compound (C-1) is a liquid epoxy compound that is liquid at 25° C. and has two or less (one or two) epoxy groups in the molecule. In particular, the liquid epoxy compound (C-1) preferably has two epoxy groups in its molecule. The liquid epoxy compound (C-1) may be used alone or in combination of two or more.

The viscosity of the liquid epoxy compound (C-1) at 25°C is not particularly limited. For example, the viscosity of the liquid epoxy compound (C-1) at 25° C. may be 500 mPa·s or less, or may exceed 500 mPa·s.

The liquid epoxy compound (C-1) preferably contains an epoxy-based reactive diluent (C-3). This makes it possible to reduce the viscosity of the magnetic resin composition.

Here, the epoxy-based reactive diluent (C-3) is a liquid epoxy compound that is liquid at 25° C. and has a viscosity of 500 mPa·s or less. Although the viscosity of the epoxy-based reactive diluent (C-3) is not particularly limited as long as it is 500 mPa·s or less, it is preferably 10 mPa·s or more and 500 mPa·s or less. That is, the epoxy-based reactive diluent (C-3) is a liquid epoxy compound (C-1) having a viscosity of 500 mPa·s or less at 25° C. in particular. Thus, since the epoxy-based reactive diluent (C-3) has a viscosity of 500 mPa·s or less at 25° C., it reduces the viscosity and thixotropy of the magnetic resin composition.

The epoxy-based reactive diluent (C-3) has two or less epoxy groups in the molecule. In particular, the epoxy-based reactive diluent (C-3) preferably has two epoxy groups in its molecule.

The polyfunctional liquid epoxy compound (C-2) is a polyfunctional liquid epoxy compound that is liquid at 25° C. and has 3 or more epoxy groups in the molecule. The upper limit of the number of epoxy groups in the molecule of the polyfunctional liquid epoxy compound (C-2) is preferably 4, more preferably 3. The multifunctional liquid epoxy compound (C-2) may be used singly or in combination of two or more. By including the polyfunctional liquid epoxy compound (C-2) in the liquid epoxy compound (C), the glass transition temperature of the cured product of the magnetic resin composition can be raised and the heat resistance can be enhanced.

The viscosity of the polyfunctional liquid epoxy compound (C-2) at 25° C. is not particularly limited, but is, for example, 10 mPa·s or more and 1300 mPa·s or less.

The content of the polyfunctional liquid epoxy compound (C-2) is preferably 10% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 70% by mass or less, relative to the total mass of the liquid epoxy compound (C). Within this range, it is possible to achieve both low viscosity of the magnetic resin composition and good thixotropic properties. In addition, the cured product of the magnetic resin composition can raise the glass transition temperature and improve the heat resistance.

In particular, the liquid epoxy compound (C) contains a liquid epoxy compound (C-1) having a viscosity of more than 500 mPa·s, a polyfunctional epoxy resin compound (C-2), and an epoxy-based reactive diluent (C-3). In this case, the content of the polyfunctional liquid epoxy compound (C-2) is preferably 25% by mass or more and 70% by mass or less with respect to the total mass of the liquid epoxy compound (C). Within this range, it is possible to achieve both low viscosity of the magnetic resin composition and good thixotropic properties. In addition, the cured product of the magnetic resin composition can raise the glass transition temperature and improve the heat resistance.

<Curing agent (D)>
Examples of the curing agent (D) include, but are not particularly limited to, phenol compounds, acid anhydride compounds, amine compounds, imidazole compounds, and the like. Among these, imidazole compounds are preferred. The imidazole compound is a type of curing accelerator and is effective in improving the storage stability and reducing the viscosity of the magnetic resin composition. Thus, the curing agent (D) may contain curing accelerators.

The curing agent (D) is preferably liquid. If the curing agent (D) is liquid, the magnetic resin composition can easily be made into a paste.

The curing accelerator is not particularly limited, but includes, for example, the imidazole compounds described above. The hardening accelerator is preferably encapsulated. If the hardening accelerator is encapsulated, the storage stability of the magnetic resin composition can be improved. Furthermore, by changing the film thickness of the capsule, the curing initiation temperature of the magnetic resin composition can be controlled, and the curing behavior can be adjusted according to the usage pattern. For example, if the film thickness of the capsule is thin, the reaction can be started at a low temperature. On the other hand, if the film thickness of the capsule is increased, the reaction can be initiated at high temperatures and the storage stability at low and normal temperatures can be improved.

<Additive>
The magnetic resin composition may contain additives as long as the effects of the present embodiment are not impaired.

Examples of additives include, but are not limited to, silane coupling agents, dispersants, leveling agents, adhesion imparting agents, and antistatic agents. In particular, when the silane coupling agent and the dispersant are contained in the magnetic resin composition, the dispersibility of the ferrite particles (A) and the magnetic powder (B) in the magnetic resin composition can be improved.

Examples of the silane coupling agent include, but are not limited to, epoxy group-containing alkoxysilane compounds such as γ-glycidoxypropyltrimethoxysilane, mercapto group-containing alkoxysilane compounds such as γ-mercaptopropyltriethoxysilane, and γ Examples include amino group-containing alkoxysilane compounds such as -(2-aminoethyl)aminopropylmethyldimethoxysilane.

As the dispersing agent, various dispersing agents generally used as dispersing agents can be used. Specifically, the dispersant includes, for example, hyperbranched polyesters, hydroxyl group-containing carboxylic acid esters, and alkylammonium salts and phosphate ester salts of polymer copolymers. Commercially available dispersants include, for example, DISPERBYK series manufactured by BYK-Chemie.

<Solvent>
Examples of solvents include, but are not limited to, methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), acetone, and methyl isobutyl ketone (MIBK).

(1.3) Production method The magnetic resin composition is produced by uniformly mixing the raw materials, ferrite particles (A), magnetic particles (B), liquid epoxy compound (C), and curing agent (D). be able to. A known mixer can be used for mixing the raw materials.

(1.4) Forms of Materials Made Using Magnetic Resin Composition Examples of forms of materials made using the magnetic resin composition according to the present embodiment include paste, slurry, sheet, powder, and prepreg. These material forms may contain a magnetic resin composition or a semi-cured product of the magnetic resin composition. “Semi-cured product” refers to a state in which the magnetic resin composition is partially cured to the extent that it can be further cured. That is, the semi-cured product is a state in which the magnetic resin composition is semi-cured (B-staged). These material forms are obtained by coating, heat drying, heat curing, pressurization, kneading, and impregnation.

(1.5) Use The processed product according to the present embodiment includes a cured product of the magnetic resin composition described above. The workpiece may be used to manufacture inductor components and substrate embedded components.

The inductor component includes a coiled wire and an insulating layer covering the coiled wire. The insulating layer has electrical insulating properties and includes the workpiece according to the present embodiment. This makes it easier for the inductor component to control noise in the high frequency band. Inductor components include coils, inductors, filters, reactors, and transformers. Applications of inductor components are not particularly limited, but include, for example, noise filter components and impedance matching circuit components. Noise filters include, for example, low-pass filters and common choke coils.

A substrate-embedded component includes a substrate and an insulating layer covering the substrate. The insulating layer includes a work piece according to the present embodiments. This makes it easier to impart magnetic properties to the board-embedded component. Applications of the substrate-embedded component are not particularly limited, but examples thereof include inductors.

EXAMPLES The present disclosure will be specifically described below with reference to Examples. However, the present disclosure is not limited to the examples.

(1) Preparation of Magnetic Resin Composition A paste-like magnetic resin composition (hereinafter also referred to as “magnetic paste”) was prepared. Raw materials for the magnetic paste are shown below.

(1.1) Magnetic filler ferrite particles (A)
・Mn ferrite (D50: 0.3 μm)
・Mn-Zn ferrite (D50: 0.3 μm)
・Magnetite (D50: 0.3 μm)
Magnetic particles (B)
・Mn ferrite (D50: 5.0 μm, D90: 15 μm)
・Mn-Zn ferrite (D50: 5.0 μm, D90: 15 μm)
・Mn ferrite (D50: 3.5 μm, D90: 9.0 μm)
・Mn-Zn ferrite (D50: 3.5 μm, D90: 9.0 μm)
Others • Mn ferrite (D50: 0.6 µm, D90: 2.0 µm).

(1.2) Resin material liquid epoxy compound (C)
Liquid epoxy compound (C-1)
・ Bisphenol F type epoxy resin (manufactured by Nippon Steel Chemical & Materials Co., Ltd., product name “YDF-8170C”, liquid, number of epoxy groups in the molecule: 2, viscosity at 25 ° C.: 1300 mPa s, epoxy Equivalent: 155-165g/eq)
Polyfunctional liquid epoxy compound (C-2)
- Polyfunctional epoxy resin (manufactured by ADEKA Corporation, trade name "EP-3950S", glycidylamine type, number of epoxy groups in the molecule: 3, viscosity at 25 ° C.: 650 mPa s, epoxy equivalent: 95 g / eq )
Epoxy reactive diluent (C-3)
- Reactive diluent (manufactured by Mitsubishi Chemical Corporation, trade name "YED216D", liquid, number of epoxy groups in the molecule: 2, viscosity at 25 ° C.: 10 mPa s, epoxy equivalent: 110 to 130 g / eq) .

Curing agent (D)
- Imidazole compound (manufactured by Shikoku Kasei Co., Ltd., trade name "2MAOK-PW", imidazole-based epoxy resin curing agent, fine powder).

<Additive>
・ Silane coupling agent (manufactured by Momentive Performance Materials Japan LLC, trade name “Silquest A-187”)
- Dispersant (manufactured by BYK-Chemie Japan Co., Ltd., trade name "DISPERBYK-2152").

(2) Evaluation Items (2.1) Viscosity The viscosity of the magnetic paste was measured using an E-type viscometer (manufactured by TA Instruments, rheometer, model "AR2000ex"). Specifically, the gap between the upper and lower parallel plates with a diameter of 25 mm was set to 300 μm, and after filling this gap with the magnetic paste, a temperature equilibration time of 2 minutes was allowed at normal temperature, and the rotation speed was 5.5. Viscosity measurements were taken at 0 rpm. Tables 1 to 3 show the E-type viscosities of the magnetic pastes.

(2.2) Thixotropic Index Using the E-type viscometer, the viscosity was measured at 0.5 rpm and 5.0 rpm rotations. Settings other than the number of revolutions are the same as in (2.1). Then, the thixotropy index was calculated by the following formula (2). Tables 1 to 3 show the thixotropic indices of the magnetic pastes. In equation (2), the denominator on the right side is the E-type viscosity at a rotation speed of 5.0 rpm, and the numerator is the E-type viscosity at a rotation speed of 0.5 rpm.

(2.3) Magnetic Properties The magnetic paste was cured by heating in the atmosphere to obtain a ring-shaped product for evaluation (outer diameter 7.0 mm, inner diameter 3.5 mm, thickness 1.0 mm). The heating conditions are 130° C. for 2 hours.

Next, using Hewlett-Packard's model "4291ARF Impedance/Material Analyzer", the complex magnetic permeability (μ) at 70 MHz of the above processed product for evaluation was measured. The measurement was performed at room temperature with a current frequency of 1 MHz or more and 500 MHz or less. From the initial magnetization curve obtained by measurement, the magnetic permeability (the real part (μr′) of the complex relative permeability (μr)) and the imaginary part (μr″) were obtained, and the loss factor (tan δ) was calculated from these. Tables 1 to 3 show the magnetic permeability and loss factor of the above processed products for evaluation.

(2.4) Glass transition temperature (Tg)
Using a viscoelastic spectrometer, model "DMS100" manufactured by Seiko Instruments Inc., the glass transition temperature of the cured magnetic paste was measured. At this time, dynamic viscoelasticity measurement (DMA) was performed with a bending module at a frequency of 10 Hz, and the loss tangent (tan δ) when the temperature was raised from room temperature to 280 ° C. at a heating rate of 5 ° C./min shows a maximum. The temperature was taken as the glass transition temperature. Tables 1 to 3 show the glass transition temperatures of the cured magnetic pastes.

Claims (14)

Ferrite particles (A) having a particle size (D50) of 0.05 μm or more and 0.50 μm or less at an integrated value of 50% in the particle size distribution;
Magnetic particles (B) having a D50 of 3.0 μm or more and a particle size (D90) of 5.0 μm or more at an integrated value of 90% in the particle size distribution;
a liquid epoxy compound (C) that is liquid at 25°C;
containing a curing agent (D),
The liquid epoxy compound (C) includes a liquid epoxy compound (C-1) having two or less epoxy groups in the molecule and a polyfunctional liquid epoxy compound (C-2) having three or more epoxy groups in the molecule. ) and including
Magnetic resin composition. The ferrite particles (A) contain at least one selected from the group consisting of Mn ferrite, Mn—Zn ferrite, and magnetite,
The magnetic resin composition according to claim 1. The magnetic particles (B) contain Mn ferrite and/or Mn—Zn ferrite,
The magnetic resin composition according to claim 1 or 2. The ferrite particles (A) and/or the magnetic particles (B) comprise spherical particles,
A magnetic resin composition according to any one of claims 1 to 3. The liquid epoxy compound (C-1) contains an epoxy-based reactive diluent (C-3),
A magnetic resin composition according to any one of claims 1 to 4. The liquid epoxy compound (C) contains at least one selected from the group consisting of bisphenol F-type epoxy resins, bisphenol A-type epoxy resins, alkyldiglycidyl ethers, alkylmonoglycidyl ethers, and alkylphenol monoglycidyl ethers.
A magnetic resin composition according to any one of claims 1 to 5. The content of the ferrite particles (A) is 0.1% by mass or more and 20.0% by mass or less with respect to the total mass of the magnetic resin composition.
A magnetic resin composition according to any one of claims 1 to 6. The content of the magnetic particles (B) is 75% by mass or more and 95% by mass or less with respect to the total mass of the magnetic resin composition.
A magnetic resin composition according to any one of claims 1 to 7. The content of the polyfunctional liquid epoxy compound (C-2) is 10% by mass or more and 80% by mass or less with respect to the total mass of the liquid epoxy compound (C).
A magnetic resin composition according to any one of claims 1 to 8. The content of the polyfunctional liquid epoxy compound (C-2) is 25% by mass or more and 70% by mass or less with respect to the total mass of the liquid epoxy compound (C).
The magnetic resin composition according to any one of claims 5-9. The magnetic particles (B) have a D50 of 3.0 μm or more and 6.0 μm or less and a D90 of 10.0 μm or more and 20.0 μm or less.
A magnetic resin composition according to any one of claims 1 to 10. The E-type viscosity of the magnetic resin composition is 50 Pa s or less,
A magnetic resin composition according to any one of claims 1 to 11. The magnetic resin composition has a thixotropy index of 5.0 or less.
A magnetic resin composition according to any one of claims 1 to 12. A cured product of the magnetic resin composition according to any one of claims 1 to 13,
Processed goods.