Magnetic resin composition and processed products

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]

[0001] The present disclosure relates generally to magnetic resin compositions and processed articles, and more particularly to magnetic resin compositions containing ferrite particles and processed articles made therefrom. [Background technology]

[0002] Magnetic materials are used in applications such as inductors, motors, antenna modules, etc. Known magnetic materials include magnetic resin compositions that are in a paste form and can be easily processed into predetermined shapes and properties depending on the purpose and application.

[0003] 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, and describes that this magnetic paste suppresses uneven distribution of the magnetic powder that occurs over time or with degassing operations such as centrifugation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 075745 Summary of the Invention [Problem to be solved by the invention]

[0005] Magnetic resin compositions used in applications such as inductors are required to have high magnetic permeability and a low loss factor. Furthermore, with the recent trend toward miniaturization of electronic components and finer patterning of wiring boards, improvements in the filling properties of compositions during processing are also required. For example, when filling small through-holes with a diameter of approximately 500 μm or less with a magnetic resin composition, low viscosity and low thixotropy are desirable. Furthermore, since processed products made using magnetic resin compositions are expected to be usable without problems in high-temperature environments, they are also desired to have a high glass transition temperature, which indicates excellent heat resistance.

[0006] The present disclosure has been made to solve the above problems, and aims to provide a magnetic resin composition and processed product that has low viscosity and low thixotropy while maintaining suitable magnetic permeability and loss factor, and that has a glass transition temperature of a cured product that is high enough to exhibit excellent heat resistance. [Means for solving the problem]

[0007] A magnetic resin composition according to one embodiment of the present disclosure contains ferrite particles (A) having a particle size (D50) at 50% cumulative total in the particle size distribution of 0.05 μm or more and 0.50 μm or less, magnetic particles (B) having a D50 of 3.0 μm or more and a particle size (D90) at 90% cumulative total in the particle size distribution 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 per molecule, and a multifunctional liquid epoxy compound (C-2) having three or more epoxy groups per molecule.

[0008] A processed product according to one embodiment of the present disclosure includes a cured product of the magnetic resin composition. [Effects of the Invention]

[0009] According to the present disclosure, the magnetic resin composition exhibits low viscosity and low thixotropy while maintaining suitable magnetic permeability and loss factor, and the cured product thereof has a glass transition temperature high enough to exhibit excellent heat resistance. The processed product exhibits excellent heat resistance while maintaining suitable magnetic permeability and loss factor. DETAILED DESCRIPTION OF THE INVENTION

[0010] (1) Magnetic resin composition The magnetic resin composition according to this embodiment contains a magnetic filler and a resin material. The magnetic filler includes ferrite particles (A) and magnetic particles (B). The resin material includes a liquid epoxy compound (C) and a curing agent (D).

[0011] 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.

[0012] When measured at 25°C and 5 rpm, the magnetic resin composition preferably has an E-type viscosity of 20 Pa·s or more and 50 Pa·s or less, and a thixotropy index of 1.5 or more and 5.0 or less. By keeping the values ​​within these ranges, even when the magnetic resin composition is filled into a through-hole with an inner diameter of 500 μm or less, voids and filling defects are less likely to occur, and the filling can be carried out without any problems.

[0013] The glass transition temperature (Tg) of the cured product of the magnetic resin composition is preferably at least 100° C. A cured product of the magnetic resin composition that satisfies this requirement has excellent heat resistance.

[0014] (1.1) Magnetic filler As described above, the magnetic filler includes ferrite particles (A) and magnetic particles (B). The magnetic filler is a particulate material that can be magnetized. In this way, when the magnetic resin composition includes ferrite particles (A) and magnetic particles (B), a processed product having magnetic properties can be obtained. The processed product includes a cured product of the magnetic resin composition. The magnetic properties are magnetic properties exhibited when magnetized. Specific examples of magnetic properties include magnetic permeability and magnetic flux density.

[0015] As described above, the processed product has magnetic properties, and the processed product according to this embodiment in particular can have high magnetic permeability at high frequencies. The high-frequency frequency band is, for example, from several MHz to several GHz, including 70 MHz. The real part (μr') of the complex relative magnetic permeability (μr) of the processed product at 70 MHz is preferably 6.0 or more. This can further increase the magnetic permeability at high frequencies. Furthermore, the loss factor (tanδ) of the processed product at 70 MHz is preferably 0.10 or less, and more preferably 0.08 or less. This can further reduce loss.

[0016] The complex relative magnetic permeability (μr) is expressed by the formula μr=μ / μ0 (μ: complex magnetic permeability, μ0: magnetic permeability of a vacuum). The complex relative magnetic permeability (μ) is expressed by the formula μ=μ'-iμ" (μ': real part, μ": imaginary part, i: imaginary unit). In this embodiment, "permeability" mainly means the real part (μr') of the complex relative magnetic permeability (μr). The real part (μr') of the complex relative magnetic permeability (μr) is expressed by the formula μr'=μ' / μ0. The imaginary part (μr") of the complex relative magnetic permeability (μr) is expressed by the formula μr"=μ" / μ0. The loss factor (tanδ) is expressed by the formula tanδ=μr" / μr'=μ" / μ'. The relational formulas for the complex relative magnetic permeability (μr) can be summarized as the following formula (1).

[0017]

number

[0018] "50% volume average particle size" refers to the particle size (D50) at 50% of the cumulative value in the particle size distribution measured using a particle size distribution measuring device based on the laser scattering / diffraction method. Note that "D50 of ferrite particles (A)" refers to the D50 of all particulate matter contained in ferrite particles (A), and "D50 of magnetic particles (B)" refers to the D50 of all particulate matter contained in magnetic particles (B).

[0019] "90% volume average particle size" refers to the particle size (D90) at 90% of the cumulative value in the particle size distribution measured using a particle size distribution measuring device based on the laser scattering and diffraction method. "D90 of ferrite particles (A)" refers to the D90 of all particulate matter contained in ferrite particles (A), and "D90 of magnetic particles (B)" refers to the D90 of all particulate matter contained in magnetic particles (B).

[0020] <Ferrite particles (A)> The ferrite particles (A) have a D50 of 0.05 μm or more and 0.50 μm or less. By including fine ferrite particles (A) in the magnetic resin composition in this way, the viscosity of the magnetic resin composition can be reduced.

[0021] The ferrite particles (A) contain at least one type of ferrite. Ferrite is a ceramic filler whose main component is iron oxide. Ferrite includes soft ferrite, which exhibits soft magnetic properties, and hard ferrite, which exhibits hard magnetic properties. Ferrite is classified into spinel ferrite, hexagonal ferrite, garnet ferrite, etc., depending on the crystal structure.

[0022] Spinel ferrite has a spinel-type crystal structure. The formula of spinel ferrite is AFe2O4 (A is Mn, Co, Ni, Cu, Zn, etc.). Most spinel ferrites are soft ferrites. Examples of spinel ferrites include manganese zinc ferrite (Mn-Zn ferrite), nickel zinc ferrite (Ni-Zn ferrite), and copper zinc ferrite (Cu-Zn ferrite). Spinel ferrites have high magnetic permeability and electrical resistance, resulting in low eddy current loss in the high frequency band. Magnetite is also a type of spinel ferrite. The formula of magnetite is Fe3O4.

[0023] Hexagonal ferrite has a magnetoplumbite-type hexagonal crystal structure. The chemical formula of hexagonal ferrite is AFe 12 O 19 (A is Ba, Sr, Pb, etc.) Hexagonal ferrite is also called magnetoplumbite ferrite or M-type ferrite. Hexagonal ferrite has a larger magnetic anisotropy than spinel ferrite, and therefore exhibits a larger coercive force. Hexagonal ferrite is a typical hard ferrite.

[0024] Garnet ferrite has a garnet-type crystal structure. The formula of garnet ferrite is RFeO 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.

[0025] When the ferrite particles (A) contain at least one type of ferrite, the magnetic permeability of the processed product at high frequencies can be increased.

[0026] 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 more preferably contain at least one selected from the group consisting of Mn ferrite and magnetite.

[0027] Manganese-based ferrite is a ferrite containing manganese. Examples of manganese-based 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). Thus, when the ferrite particles (A) contain at least one selected from the group consisting of manganese-based ferrite and magnetite, the balance between the magnetic permeability and loss factor (tan δ) of the processed product is improved. In other words, the magnetic permeability of the processed product is easily increased and the loss factor (tan δ) is easily reduced. Furthermore, by incorporating magnetite into the magnetic resin composition, the viscosity of the magnetic resin composition can be reduced.

[0028] 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. This improves the fluidity of the magnetic resin composition. This means that processed products can be more easily molded. Furthermore, the ferrite particles (A) can be highly packed. In particular, highly packed ferrite particles (A) can increase the magnetic permeability of processed products. Furthermore, the drillability of processed products can be improved. Drillability is a measure of the ease with which a processed product can be machined when drilling holes in the processed product. Drillability is evaluated by wear rate, etc. The ferrite particles (A) may contain particles having a shape other than spherical. Shapes other than spherical are not particularly limited, but examples include ellipsoidal, flat, fractured, and amorphous shapes.

[0029] The content of the ferrite particles (A) is preferably 0.1% by mass or more and 20.0% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, relative to the total mass of the magnetic resin composition. By setting the content within this range, the viscosity and thixotropy of the magnetic resin composition can be reduced.

[0030] It is preferable that the magnetic resin composition is substantially free of sendust and amorphous alloys (non-crystalline 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, amorphous alloys are disordered alloys with no regularity in the arrangement of elements. As described above, if the magnetic resin composition is substantially free of sendust and amorphous alloys, it is possible to suppress a decrease in machinability. However, at least one of sendust and amorphous alloys may be contained in the magnetic resin composition as an unavoidable impurity.

[0031] <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. Preferably, the D50 of the magnetic particles (B) is 3.0 μm or more and 6.0 μm or less, and the D90 of the magnetic particles (B) is 10.0 μm or more and 20.0 μm or less. By keeping the D50 within these ranges, the drilling processability of the cured product can be further improved.

[0032] The magnetic particles (B) contain at least one type of 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.

[0033] The magnetic particles (B) preferably contain Mn ferrite and / or Mn-Zn ferrite, and more preferably Mn ferrite. In this specification, "X and / or Y" means "X," "Y," or "X and Y."

[0034] The magnetic particles (B) preferably contain spherical particles, and more preferably Mn ferrite and / or Mn-Zn ferrite contain spherical particles. This improves the fluidity of the magnetic resin composition. In other words, it makes it easier to mold a processed product. It also allows for a high packing density of the magnetic particles (B). In particular, a high packing density of the magnetic particles (B) allows for a high magnetic permeability of the processed product. It also allows for improved drilling processability of the processed product. The magnetic particles (B) may contain particles having a shape other than spherical.

[0035] The content of the magnetic particles (B) is preferably 75% by mass or more and 95% by mass or less, and more preferably 80% by mass or more and 90% by mass or less, based on the total mass of the magnetic resin composition. By keeping the content within this range, it is possible to increase the magnetic permeability while reducing the viscosity.

[0036] (1.2) Resin materials 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. When the resin material contains the liquid epoxy compound (C), it becomes easier to mold a processed product from the magnetic resin composition. Furthermore, when the resin material contains a self-polymerizing material, the pot life (usable time) of the magnetic resin composition can be extended. Furthermore, a processed product exhibiting a high glass transition temperature with excellent heat resistance can be obtained by thermal curing in a short time.

[0037] <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 epoxy compound (C-2) having three or more epoxy groups in the molecule.

[0038] The liquid epoxy compound (C) preferably contains at least one selected from the group consisting of bisphenol F type epoxy resins, bisphenol A type epoxy resins, alkyl diglycidyl ethers, alkyl monoglycidyl ethers, and alkylphenol monoglycidyl ethers.

[0039] The epoxy equivalent of the liquid epoxy compound (C) is not particularly limited, but is preferably 90 g / eq or more and 200 g / eq or less.

[0040] 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 the molecule. The liquid epoxy compound (C-1) may be used alone or in combination of two or more.

[0041] There are no particular limitations on the viscosity of the liquid epoxy compound (C-1) at 25° C. 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.

[0042] The liquid epoxy compound (C-1) preferably contains an epoxy-based reactive diluent (C-3), which can reduce the viscosity of the magnetic resin composition.

[0043] 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. The viscosity of the epoxy-based reactive diluent (C-3) is not particularly limited as long as it is 500 mPa·s or less, but is preferably 10 mPa·s or more and 500 mPa·s or less. In other words, the epoxy-based reactive diluent (C-3) refers to a liquid epoxy compound (C-1) that has a viscosity of 500 mPa·s or less at 25°C. Thus, because 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.

[0044] The epoxy-based reactive diluent (C-3) has two or less epoxy groups in the molecule, and it is particularly preferred that the epoxy-based reactive diluent (C-3) has two epoxy groups in the molecule.

[0045] The polyfunctional liquid epoxy compound (C-2) is a polyfunctional liquid epoxy compound that is liquid at 25°C and has three or more epoxy groups in the molecule. The upper limit of the number of epoxy groups that the polyfunctional liquid epoxy compound (C-2) has in the molecule is preferably four, more preferably three. The polyfunctional liquid epoxy compound (C-2) may be used alone 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 increased, thereby improving heat resistance.

[0046] 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.

[0047] 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, based on the total mass of the liquid epoxy compound (C). By setting the content within this range, it is possible to achieve both low viscosity and good thixotropy of the magnetic resin composition. Furthermore, the cured product of the magnetic resin composition can have an increased glass transition temperature and improved heat resistance.

[0048] In particular, when the liquid epoxy compound (C) contains a liquid epoxy compound (C-1) with a viscosity of more than 500 mPa·s, a polyfunctional epoxy resin compound (C-2), and an epoxy-based reactive diluent (C-3), the content of the polyfunctional liquid epoxy compound (C-2) is preferably 25% by mass or more and 70% by mass or less, based on the total mass of the liquid epoxy compound (C). By keeping the content within this range, the magnetic resin composition can achieve both low viscosity and good thixotropy. Furthermore, the cured product of the magnetic resin composition can have an increased glass transition temperature and improved heat resistance.

[0049] <Curing agent (D)> The curing agent (D) is not particularly limited, but examples thereof include phenol compounds, acid anhydride compounds, amine compounds, and imidazole compounds. Among these, imidazole compounds are preferred. Imidazole compounds are a type of curing accelerator and are effective in improving the storage stability and reducing the viscosity of the magnetic resin composition. Thus, the curing agent (D) may contain a curing accelerator.

[0050] The curing agent (D) is preferably in a liquid state, since if the curing agent (D) is in a liquid state, the magnetic resin composition can be easily made into a paste state.

[0051] The curing accelerator is not particularly limited, but examples thereof include the above-mentioned imidazole compounds. The curing accelerator is preferably encapsulated in a capsule. If the curing accelerator is encapsulated in a capsule, the storage stability of the magnetic resin composition can be improved. Furthermore, by changing the capsule film thickness, the curing initiation temperature of the magnetic resin composition can be controlled, and the curing behavior can be adjusted to suit the usage form. For example, by making the capsule film thickness thin, the reaction can be initiated at a low temperature. On the other hand, by making the capsule film thickness thick, the reaction can be initiated at a high temperature and the storage stability at low temperatures and room temperature can be improved.

[0052] <Additives> The magnetic resin composition may contain additives within the range that does not impair the effects of this embodiment.

[0053] The additives are not particularly limited, but examples thereof include a silane coupling agent, a dispersant, a leveling agent, an adhesion imparting agent, an antistatic agent, etc. 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.

[0054] The silane coupling agent is not particularly limited, but examples thereof include epoxy group-containing alkoxysilane compounds such as γ-glycidoxypropyltrimethoxysilane, mercapto group-containing alkoxysilane compounds such as γ-mercaptopropyltriethoxysilane, and amino group-containing alkoxysilane compounds such as γ-(2-aminoethyl)aminopropylmethyldimethoxysilane.

[0055] As the dispersant, various dispersants commonly used as dispersants can be used. Specific examples of dispersants include hyperbranched polyesters, hydroxyl group-containing carboxylic acid esters, alkyl ammonium salts of polymer copolymers, and phosphate ester salts. Commercially available dispersants include, for example, the DISPERBYK series manufactured by BYK Chemical Co., Ltd.

[0056] <Solvent> The solvent is not particularly limited, but examples thereof include methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), acetone, and methyl isobutyl ketone (MIBK).

[0057] (1.3) Manufacturing method The magnetic resin composition can be produced by uniformly mixing the raw materials, ferrite particles (A), magnetic particles (B), liquid epoxy compound (C), and curing agent (D). A known mixer can be used to mix the raw materials.

[0058] (1.4) Material forms obtained using magnetic resin compositions Examples of material forms that can be produced using the magnetic resin composition according to this embodiment include paste, slurry, sheet, powder, and prepreg. These material forms may include the magnetic resin composition or a semi-cured product of the magnetic resin composition. The term "semi-cured product" refers to a magnetic resin composition that has been partially cured to the extent that it can be further cured. In other words, a semi-cured product is a magnetic resin composition that has been semi-cured (B-staged). These material forms can be obtained by coating, heat drying, heat curing, pressing, kneading, and impregnation.

[0059] (1.5) Application The processed product according to this embodiment includes a cured product of the magnetic resin composition described above. The processed product may be used to manufacture inductor components and embedded substrate components.

[0060] The inductor component includes a coiled wiring and an insulating layer covering the coiled wiring. The insulating layer has electrical insulation properties and includes the processed product according to this 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 the inductor component are not particularly limited, but examples include components for noise filters and components for impedance matching circuits. Examples of noise filters include low-pass filters and common choke coils.

[0061] The embedded-substrate component includes a substrate and an insulating layer covering the substrate. The insulating layer includes the processed product according to this embodiment. This makes it easier to impart magnetic properties to the embedded-substrate component. Applications of the embedded-substrate component are not particularly limited, but include, for example, inductors. [Example]

[0062] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to the examples.

[0063] (1) Preparation of magnetic resin composition A magnetic resin composition in paste form (hereinafter also referred to as "magnetic paste") was prepared. The raw materials of the magnetic paste are shown below.

[0064] (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).

[0065] (1.2) Resin materials Liquid epoxy compound (C) Liquid epoxy compound (C-1) Bisphenol F type epoxy resin (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name "YDF-8170C", liquid, number of epoxy groups per molecule: 2, viscosity at 25°C: 1300 mPa·s, epoxy equivalent: 155-165 g / eq) Multifunctional liquid epoxy compound (C-2) Multifunctional epoxy resin (ADEKA Corporation, product name "EP-3950S", glycidylamine type, number of epoxy groups per molecule: 3, viscosity at 25°C: 650 mPa·s, epoxy equivalent: 95 g / eq) Epoxy-based reactive diluent (C-3) Reactive diluent (manufactured by Mitsubishi Chemical Corporation, product name "YED216D", liquid, number of epoxy groups per molecule: 2, viscosity at 25°C: 10 mPa·s, epoxy equivalent: 110-130 g / eq).

[0066] Hardener (D) Imidazole compound (manufactured by Shikoku Chemicals Corporation, product name "2MAOK-PW", imidazole-based epoxy resin hardener, fine powder).

[0067] <Additives> Silane coupling agent (manufactured by Momentive Performance Materials Japan, LLC, product name "Silquest A-187") Dispersant (manufactured by BYK Japan Co., Ltd., product name "DISPERBYK-2152").

[0068] (2) Evaluation items (2.1) Viscosity The viscosity of the magnetic paste was measured using an E-type viscometer (TA Instruments, Rheometer, model "AR2000ex"). Specifically, the gap between upper and lower parallel plates with a diameter of 25 mm was set to 300 μm, and the magnetic paste was filled into this gap. After a temperature equilibration period of 2 minutes was allowed to pass at room temperature, the viscosity was measured at a rotation speed of 5.0 rpm. The E-type viscosities of the magnetic pastes are shown in Tables 1 to 3.

[0069] (2.2) Thixotropy index Using the above-mentioned E-type viscometer, viscosity measurements were carried out at rotation speeds of 0.5 rpm and 5.0 rpm. Settings other than the rotation speed were the same as in (2.1). The thixotropy index was then calculated using the following formula (2). The thixotropy indexes of the magnetic pastes are shown in Tables 1 to 3. In formula (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.

[0070]

number

[0071] (2.3) Magnetic properties The magnetic paste was heated and hardened in the atmosphere to obtain a ring-shaped evaluation product (outer diameter 7.0 mm, inner diameter 3.5 mm, thickness 1.0 mm) heated at 130°C for 2 hours.

[0072] Next, the complex permeability (μ) of the above-mentioned evaluation processed product at 70 MHz was measured using a Hewlett-Packard Model 4291ARF Impedance / Material Analyzer. The measurement was carried out at room temperature with a current frequency of 1 MHz to 500 MHz. From the initial magnetization curve obtained by measurement, the permeability (real part (μr') of the complex relative permeability (μr)) and imaginary part (μr") were obtained, and the loss factor (tanδ) was calculated from these. The permeability and loss factor of the above-mentioned evaluation processed product are shown in Tables 1 to 3.

[0073] (2.4) Glass transition temperature (Tg) The glass transition temperature of the cured magnetic paste was measured using a viscoelasticity spectrometer, model "DMS100," manufactured by Seiko Instruments Inc. Dynamic viscoelasticity measurement (DMA) was performed using a bending module at a frequency of 10 Hz, and the temperature at which the loss tangent (tan δ) reached a maximum when the temperature was raised from room temperature to 280°C at a heating rate of 5°C / min was taken as the glass transition temperature. The glass transition temperatures of the cured magnetic paste are shown in Tables 1 to 3.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Table 3]

Claims

1. A magnetic resin composition, The magnetic resin composition is Ferrite particles (A) having a particle size (D50) at 50% cumulative particle size distribution of 0.05 μm or more and 0.50 μm or less; magnetic particles (B) having a D50 of 3.0 μm or more and 6.0 μm or less, and a particle size at 90% cumulative value in the particle size distribution (D90) of 10.0 μm or more and 20.0 μm or less; a liquid epoxy compound (C) that is liquid at 25°C; and a curing agent (D), The content of the ferrite particles (A) is 0.1% by mass or more and 20.0% by mass or less relative to the total mass of the magnetic resin composition, 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, the magnetic particles (B) are made of Mn ferrite and / or Mn—Zn ferrite, The liquid epoxy compound (C) comprises 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, The liquid epoxy compound (C-1) contains an epoxy-based reactive diluent (C-3). Magnetic resin composition.

2. 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 .

3. The ferrite particles (A) and / or the magnetic particles (B) comprise spherical particles. The magnetic resin composition according to claim 1 or 2.

4. The liquid epoxy compound (C) contains at least one selected from the group consisting of bisphenol F type epoxy resin, bisphenol A type epoxy resin, alkyl diglycidyl ether, alkyl monoglycidyl ether, and alkylphenol monoglycidyl ether. The magnetic resin composition according to any one of claims 1 to 3.

5. The content of the polyfunctional liquid epoxy compound (C-2) is 10 mass% or more and 80 mass% or less based on the total mass of the liquid epoxy compound (C). The magnetic resin composition according to any one of claims 1 to 4.

6. The content of the polyfunctional liquid epoxy compound (C-2) is 25 mass% or more and 70 mass% or less based on the total mass of the liquid epoxy compound (C). The magnetic resin composition according to any one of claims 1 to 5.

7. The magnetic resin composition has an E-type viscosity of 50 Pa s or less at a rotation speed of 5.0 rpm. The magnetic resin composition according to any one of claims 1 to 6.

8. The thixotropy index of the magnetic resin composition (E-type viscosity at a rotation speed of 0.5 rpm / E-type viscosity at a rotation speed of 5.0 rpm) is 5.0 or less. The magnetic resin composition according to any one of claims 1 to 7.

9. A magnetic resin composition comprising a cured product of the magnetic resin composition according to any one of claims 1 to 8. Processed products.

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