Soft magnetic resin composition, soft magnetic film, inductor, and method for producing soft magnetic film

Abstract

A soft magnetic resin composition includes a solid content containing flat soft magnetic particles and a resin component, and a dispersion medium. Furthermore, a viscosity (A) at a shear rate of 38.1 s-1 is 300 mPa·s or more. Furthermore, a ratio (A / C) of the viscosity (A) at a shear rate of 38.1 s-1 with respect to a viscosity (C) at a shear rate of 191.5 s-1 is 1.7 or more.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a soft magnetic resin composition, a soft magnetic film and an inductor that use the soft magnetic resin composition, and a method of producing a soft magnetic film using the soft magnetic resin composition.BACKGROUND ART

[0002] In recent years, the installation of wireless communication or wireless power transmission into electronic devices such as personal computers and smartphones has been rapidly spreading. Then, for the extension of the wireless communication distance, the increase in efficiency, and the miniaturization, in the electronic device, a soft magnetic film that converges the magnetic flux is disposed on the periphery, for example, of an antenna and a coil provided in the electronic device.

[0003] Such a soft magnetic film is formed from a soft magnetic resin composition containing flat soft magnetic particles, a resin component, and a dispersion medium (see, for example, Patent Document 1). Specifically, a soft magnetic film is produced by applying a soft magnetic resin composition onto a release liner using an applicator, drying the coating film, and then heat-pressing the coating film.Citation ListPatent Document

[0004] Patent Document 1: Japanese Unexamined Patent Publication No. 2015-092543SUMMARY OF THE INVENTIONPROBLEM TO BE SOLVED BY THE INVENTION

[0005] On the other hand, soft magnetic films are required to have excellent magnetic properties, and be continuously produced in a stable and efficient manner.

[0006] However, when the soft magnetic film of Patent Document 1 is formed, there is a problem that the soft magnetic resin composition does not have a sufficient viscosity, and thus the soft magnetic particles in the soft magnetic resin tend to sediment and be unevenly distributed, and a homogeneous soft magnetic film cannot be stably formed. Such a problem tends to occur particularly when a soft magnetic resin composition is continuously applied at a high speed to form a soft magnetic film.

[0007] The present disclosure provides a soft magnetic resin composition that allows for a stably and efficiently continuous production of a soft magnetic film having excellent magnetic properties, a soft magnetic film and an inductor that use the soft magnetic resin composition, and a method for producing a soft magnetic film using the soft magnetic resin composition.MEANS FOR SOLVING THE PROBLEM

[0008] The present disclosure [1] includes a soft magnetic resin composition including: a solid content containing flat soft magnetic particles and a resin component; and a dispersion medium, wherein a viscosity (A) at a shear rate of 38.1 s -1< is 300 mPa·s or more, and wherein with respect to a viscosity (C) at a shear rate of 191.5 s -1< , a ratio (A / C) of the viscosity (A) at the shear rate of 38.1 s -1< is 1.70 or more.

[0009] The present disclosure [2] includes the soft magnetic resin composition described in the above-described [1], wherein a particle diameter (D90) where a volume-based accumulated value from the smallest particle size of the flat soft magnetic particles is 90% is 80 µm or more and 130 µm or less.

[0010] The present disclosure [3] includes the soft magnetic resin composition described in the above-described [1] or [2], wherein a particle diameter (D50) where a volume-based accumulated value from the smallest particle size of the flat soft magnetic particles is 50% is 30 µm or more and 50 µm or less.

[0011] The present disclosure [4] includes the soft magnetic resin composition described in any one of the above-described [1] to [3], wherein a particle diameter (D10) where a volume-based accumulated value from the smallest particle size of the flat soft magnetic particles is 10% is 5 µm or more.

[0012] The present disclosure [5] includes the soft magnetic resin composition described in any one of the above-described [1] to [4], wherein a solid content concentration of the soft magnetic resin composition is 11% by volume or more and 14% by volume or less.

[0013] The present disclosure [6] includes the soft magnetic resin composition described in any one of the above-described [1] to [5], wherein the resin component contains a thermosetting resin component and a thermoplastic resin component.

[0014] The present disclosure [7] includes the soft magnetic resin composition described in the above-described [6] wherein the thermosetting resin component contains an epoxy resin, and wherein the thermoplastic resin component contains an acrylic resin.

[0015] The present disclosure [8] includes the soft magnetic resin composition described in the above-described [7], wherein the thermosetting resin component further contains a curing agent and a curing accelerator.

[0016] The present disclosure [9] includes the soft magnetic resin composition described in any one of the above-described [1] to [8], wherein a content ratio of the flat soft magnetic particles in the solid content of the soft magnetic resin composition is 45% by volume or more and 70% by volume or less.

[0017] The present disclosure

[10] includes the soft magnetic resin composition described in any one of the above-described [1] to [9], wherein in a cured product of the soft magnetic resin composition, a magnetic permeability at a frequency of 10 MHz is 40 or more.

[0018] The present disclosure

[11] includes a soft magnetic film being a cured product of the soft magnetic resin composition described in any one of the above-described [1] to

[10] .

[0019] The present disclosure

[12] includes an inductor including: the soft magnetic film described in the above-described

[11] ; and a wire.

[0020] The present disclosure

[13] includes a method of producing a soft magnetic film, the method including: an application step of continuously applying the soft magnetic resin composition described in any one of the above-described [1] to

[10] to a substrate at an application rate of 5m / min or more; a drying step of drying a dispersion medium contained in the soft magnetic resin composition applied to the substrate to obtain a semi-cured soft magnetic film; and a curing step of thermally curing the semi-cured soft magnetic film.

[0021] The present disclosure

[14] includes the method described in the above-described

[13] , wherein in the application step, the application rate is continuously or stepwise increased until the application rate reaches 5m / min or more.EFFECTS OF THE INVENTION

[0022] The present disclosure is a soft magnetic resin composition including flat soft magnetic particles, a resin component, and a dispersion medium, and having a viscosity (A) of 300mPa·s or more at the shear rate 38. 1 s -1< , wherein a ratio (A / B) of the viscosity (A) at the shear rate 38.1 s -1< to a viscosity (B) at the shear rate 191. 5 s -1< is 1.7 or more. Therefore, the soft magnetic resin composition has excellent viscosity properties at the time of continuous application, and allows for a stably and efficiently continuous production of a soft magnetic film having excellent magnetic properties.

[0023] The soft magnetic film of the present disclosure is formed from the soft magnetic resin composition of the present disclosure, and thus has excellent magnetic properties and be continuously produced in a stable and efficient manner.

[0024] The inductor of this disclosure includes the soft magnetic film of this disclosure. Therefore, the inductor has excellent magnetic properties.

[0025] The method for producing the soft magnetic film of the present disclosure includes a step of applying the soft magnetic resin composition of the present disclosure to a substrate at an application rate of 5m / min or more. Therefore, it is possible to continuously produce the soft magnetic film in a stable and efficient manner.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a cross-sectional view of an inductor of one embodiment of the present disclosure. FIGS. 2A to 2C are production process diagrams of one embodiment of the inductor shown in FIG. 1. FIG. 2A shows a preparation step, FIG. 2B shows a disposition step, and FIG. 2C shows a curing step. FIG. 3 shows a cross-sectional view of a magnetic wiring circuit board using the soft magnetic film of the present disclosure. FIG. 4 is a graph showing the relationship between the shear rate (s -1< ) and viscosity (mPa·s) of each Example and each Comparative Example. DESCRIPTION OF THE EMBODIMENT1. Soft Magnetic Resin Composition

[0027] The soft magnetic resin composition of the present disclosure includes a solid content containing flat soft magnetic particles and a resin component, and a dispersion medium. The soft magnetic resin composition may contain another additive described below, if necessary.<Flat Soft Magnetic Particles>

[0028] A flat soft magnetic particle is a soft magnetic particle having a flat (plate-like) shape. That is, the flat soft magnetic particle is a soft magnetic particle formed in a shape with a wide surface and a small thickness. The soft magnetic particle, for example, has a low coercive force, a high magnetic permeability, and is easily magnetized when a magnetic field is applied, and easily returned to the original state when the magnetic field is removed.

[0029] Such flat soft magnetic particles are produced, for example, by powdering a soft magnetic material to obtain soft magnetic particles, and flattening the obtained soft magnetic particles (a flattening process).

[0030] The soft magnetic material is not particularly limited, and examples thereof include magnetic stainless (Fe-Cr-Al-Si alloy), sendust (Fe-Si-A1 alloy), permalloy (Fe-Ni alloy), silicon copper (Fe-Cu-Si alloy), Fe-Si alloy, Fe-Si-B(-Cu-Nb) alloy, Fe-Si-Cr-Ni alloy, Fe-Si-Cr alloy, Fe-Si-Al-Ni-Cr alloy, and ferrite. As the soft magnetic material, from the viewpoint of the magnetic properties, preferably, an Fe-Si alloy is used.

[0031] The soft magnetic materials can be used alone or in combination of two or more.

[0032] The soft magnetic material can be pulverized, for example, by a gas atomization method, a water atomization method, a disc atomization method, and a grind method. As a pulverization method, preferably, a gas atomization method is used.

[0033] Specifically, as the gas atomization method, first, the soft magnetic material is heated and dissolved, to obtain a melt metal. Then, the obtained melt metal is allowed to flow from the nozzle, and sprayed with a gas (e.g., an argon gas, a nitrogen gas). The molten metal becomes droplets due to the energy of the gas. The droplets are cooled while falling down, and solidify and form into powders, i.e., particles. In this manner, it is possible to pulverize the soft magnetic material and obtain a soft magnetic powder.

[0034] In the gas atomization method, the melt metal is instantaneously formed into droplets and cooled at the same time, and thus the obtained soft magnetic particles have uniform microstructures. Further, the droplets are continuously formed, and thus the composition difference between the soft magnetic particles is very small.

[0035] The obtained soft magnetic particles may be classified before the flattening process.

[0036] For the flattening process of the soft magnetic particles, for example, an attritor can be used.

[0037] The conditions for the process using an attritor are not particularly limited as long as the soft magnetic particles are processed into flat soft magnetic particles having specific particle diameters i.e. a particle diameter distribution described below.

[0038] The flattening process of the soft magnetic particles may be a wet process, or may be a dry process. As the flattening process of the soft magnetic particles, preferably, a wet process is used.

[0039] In the wet process, it is preferable to use an organic solvent capable of suppressing the oxidation during the process.

[0040] The organic solvent is not particularly limited as long as it can suppress the oxidation during the process, and examples thereof include an alcohol.

[0041] The amount of the organic solvent to be added can be appropriately adjusted, for example, depending on the type of the soft magnetic particles.

[0042] The obtained flat soft magnetic particles, if necessary, may be subjected to a heat treatment, or may be classified.

[0043] The flatness rate or flatness of the flat soft magnetic particle is, for example, 8 or more and 80 or less, and preferably 15 or more and 65 or less.

[0044] The flatness rate of the flat soft magnetic particle is calculated, for example, as an aspect ratio obtained by dividing D50 (described below) that is a particle diameter where a mass-based accumulated value from the smallest particle size of the flat soft magnetic particles is 50% by the average thickness of the flat soft magnetic particles.

[0045] D90 that is a particle diameter where a mass-based accumulated value from the smallest particle size of the flat soft magnetic particles is 90% is, for example, 60µm or more and 150µm or less, preferably 70µm or more and 140µm or less, more preferably 80µm or more and 130µm or less, still more preferably 80µm or more and 110µm or less, and particularly preferably 80µm or more and 100µm or less.

[0046] When the particle diameter D90 of the flat soft magnetic particles is the above-described lower limit or more, the magnetic properties of the soft magnetic film are improved. Further, when the particle diameter D90 of the flat soft magnetic particles is the above-described upper limit or less, the sedimentation of the flat soft magnetic particles in the soft magnetic resin composition is suppressed, and further, the unevenness during the application of the soft magnetic resin composition is suppressed.

[0047] D50 that is a particle diameter where a mass-based accumulated value from the smallest particle size of the flat soft magnetic particles is 50% is, for example, 20 µm or more and 100 µm or less, preferably 25 µm or more and 75 µm or less, more preferably 30 µm or more and 50 µm or less, even more preferably 35 µm or more and 50 µm or less, and particularly preferably 38 µm or more and 47 µm or less.

[0048] When the particle diameter D50 of the flat soft magnetic particles falls within the above-described range, the magnetic properties of the soft magnetic film are improved.

[0049] D10 that is a particle diameter where a mass-based accumulated value from the smallest particle size of the flat soft magnetic particles is 10% is, for example, 5µm or more and 50µm or less, preferably 10µm or more and 30µm or less, more preferably 12 µm or more and 20µm or less, and still more preferably 13µm or more and 17µm or less.

[0050] D10 that is a particle diameter where a mass-based accumulated value from the smallest particle size of the flat soft magnetic particles is 10% is, for example, 5µm or more, preferably 10µm or more, more preferably 12µm or more, still more preferably 13µm or more, and particularly preferably more than 13µm, and, for example, 50µm or less, preferably 30µm or less, more preferably 20µm or less, still more preferably 17µm or less.

[0051] When the particle diameter D10 of the flat soft magnetic particles is the above-described lower limit or more, the soft magnetic film has excellent properties such as appearance, and further, the magnetic properties of the soft magnetic film are improved.

[0052] The flat soft magnetic particles having the above-described particle diameters, i.e., particles distribution can be obtained, for example, by adjusting the conditions for the flattening process of spherical soft magnetic particles, for example, using an attritor, or by classifying the flat soft magnetic particles after the flattening process using a classifier such as a dry classifier. As described above, as necessary, the final particle diameter distribution (diameter distribution of the flat soft magnetic particles after the flattening process) can adjusted also by classifying the soft magnetic particles before the flattening process.

[0053] Further, in order to obtain the flat soft magnetic particles having the above-described particle diameters, two or more types of flat soft magnetic particles having different particle diameters (particle diameter distributions) may be mixed. In other words, the flat soft magnetic particles having specific particle diameters may be used alone, or two or more types of flat soft magnetic particles having different particle diameters (particle diameter distributions) may be used in combination. When two or more types of flat soft magnetic particles having different particle diameters (particle diameter distributions) are used in combination, it is not necessary that the particle diameters of each type of flat soft magnetic particles before mixing fall within the above-described range, and the particle diameters of the flat soft magnetic particles after mixing may be adjusted to the above-described range.

[0054] Each particle diameter of the flat soft magnetic particles, i.e., D10, D50, and, D90 can be measured, for example, using a laser diffractometer for measuring particle diameter distribution (Beckman Coulter, Inc., LS 13 320). Specifically, using a laser diffractometer for measuring particle diameter distribution, the particle diameter distribution of the magnetic powder is adjusted based on volume, thereby measuring D10, D50, and D90. As a measurement sample, a sample obtained by dispersing flat soft magnetic particles in pure water by ultrasonic waves can be used.

[0055] The flat soft magnetic particles have a coercive force of, for example, 10A / m or more and 1000A / m or less, preferably 50A / m or more and 200A / m or less.

[0056] The coercive force can be measured, for example, by using a vibrating sample magnetometer.

[0057] The flat soft magnetic particles have a specific gravity of, for example, 5.0 or more and 8.5 or less, preferably 6.0 or more and 8.0 or less.

[0058] The content ratio (mass ratio) of the flat soft magnetic particles in the solid content of the soft magnetic resin composition is, for example, 70% by mass or more and 95% by mass or less, preferably 80% by mass or more and 92% by mass or less, more preferably 85% by mass or more and 90% by mass or less, and still more preferably 87% by mass or more and 90% by mass or less.

[0059] The content ratio (volume ratio) of the flat soft magnetic particles in the solid content of the soft magnetic resin composition is, for example, 40% by volume or more and 80% by volume or less, preferably 45% by volume or more and 70% by volume or less, more preferably 50% by volume or more and 70% by volume or less, still more preferably 53% by volume or more and 60% by volume or less, and particularly preferably 55% by volume or more and 57% by volume or less.

[0060] When the content ratio of the flat soft magnetic particles in the solid content of the soft magnetic resin composition is the above-described lower limit or more, the soft magnetic film has excellent magnetic properties. Further, when the content ratio of the flat soft magnetic particles in the solid content of the soft magnetic resin composition is the above-described upper limit or less, it is possible to sufficiently ensure the content of the resin component described below, and the soft magnetic film has excellent film formability.

[0061] The volume ratio of each component such as the flat soft magnetic particles is calculated based on the theoretical volume obtained by dividing the mass of each component by the specific gravity of the component (the same applies hereafter). The specific gravity of each component is obtained using a catalog value or a known measurement method (e.g., a specific gravity measurement method).

[0062] Further, the solid content of the soft magnetic resin composition indicates a solid content containing the flat soft magnetic particles and the resin component described below. If necessary, another additive described below may be included therein. When the soft magnetic resin composition does not contain another additive, the solid content of the soft magnetic resin composition is the total amount of the flat soft magnetic particles and the resin component.

[0063] The content ratio (mass ratio) of the flat soft magnetic particles in the soft magnetic resin composition is, for example, 20% by mass or more and 50% by mass or less, preferably 30% by mass or more and 45% by mass or less, more preferably 35% by mass or more and 40% by mass or less, and still more preferably 36% by mass or more and 40% by mass or less.

[0064] The content ratio (volume ratio) of the flat soft magnetic particles in the soft magnetic resin composition is, for example, 3.0% by volume or more and 15.0% by volume or less, preferably 5.0% by volume or more and 10.0% by volume or less, more preferably 5.5% by volume or more and 8.0% by volume or less, and still more preferably 6.0% by volume or more and 8.0% by volume or less.

[0065] When the content ratio of the flat soft magnetic particles in the soft magnetic resin composition is the above-described lower limit or more, it is possible to sufficiently ensure the viscosity when the soft magnetic resin composition is left to stand (viscosity when the shear rate is low), and thus it is possible to suppress the sedimentation and uneven distribution of the flat soft magnetic particles, and further it is possible to highly fill the flat soft magnetic particles, and it is possible to improve the magnetic properties. Further, when the content ratio of the flat soft magnetic particles in the soft magnetic resin composition is the above-described upper limit or less, it is possible to increase the fluidity of the soft magnetic resin composition while the soft magnetic resin composition is applied (to lower the viscosity when the shear rate is high), and therefore, it is possible to continuously apply the soft magnetic resin composition in a stable and efficient manner.<Resin Component>

[0066] The resin component includes, for example, at least one of a thermosetting resin component and a thermoplastic resin component. The resin component preferably includes both a thermosetting resin component and a thermoplastic resin component. If necessary, the resin component may also include an additive. Examples of the additive include the same as another additive described below.

[0067] When the resin component contains both a thermosetting resin component and a thermoplastic resin component, it is possible, as detailed below, to obtain a soft magnetic film having an evenly uniform laminate interface with excellent magnetic permeability when one soft magnetic film is produced by laminating a plurality of soft magnetic films before they are completely cured.[Thermosetting Resin Component]

[0068] Examples of the thermosetting resin component include a thermosetting resin, a curing agent, and a curing accelerator.

[0069] Examples of the thermosetting resin include an epoxy resin. Examples of the thermosetting resin further include an amino resin, an unsaturated polyester resin, a polyurethane resin, a silicone resin, a urea resin, a melamine resin, a thermosetting polyimide resin, and a diallyl phthalate resin. As the thermosetting resin, preferably an epoxy resin is used.

[0070] The thermosetting resins may be used alone or in combination of two or more.

[0071] Examples of the epoxy resin include a bisphenol type epoxy resin (such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, brominated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol AF type epoxy resin), a phenol type epoxy resin (such as phenol novolac type epoxy resin, ortho cresol novolac type epoxy resin), a biphenyl type epoxy resin, a naphthalene type epoxy resin, a fluorene type epoxy resin, a tris hydroxyphenyl methane type epoxy resin, a tetraphenylolethane type epoxy resin, a hydantoin type epoxy resin, a tris glycidyl isocyanurate type epoxy resin, and a glycidyl amine type epoxy resin. As the epoxy resin, preferably a phenol type epoxy resin is used, and more preferably an orthocresol novolac type epoxy resin is used.

[0072] The epoxy resins may be used alone or in combination of two or more.

[0073] When the thermosetting resin is an epoxy resin, the resin has excellent reactivity with a curing agent (such as a phenol resin) described below. As a result, the soft magnetic film has excellent heat resistance and magnetic permeability.

[0074] The epoxy resin has an epoxy equivalent of, for example, 50 g / eq. or more and 300 g / eq. or less, preferably 100g / eq. or more and 250g / eq. or less.

[0075] The epoxy resin has a density of, for example, 0.8g / cm 3< or more and 1.5g / cm 3< or less, preferably, 1.0g / cm 3< or more and 1.3g / cm 3< or less.

[0076] The content ratio of the thermosetting resin in the resin component is, for example, 10% by mass or more and 50% by mass or less, preferably 15% by mass or more and 40% by mass or less, more preferably 20% by mass or more and 35% by mass or less, and still more preferably 25% by mass or more and 30% by mass or less.

[0077] Examples of the curing agent include a phenol resin. In other words, the phenol resin is used, for example, as the curing agent for the epoxy resin.

[0078] Examples of the phenol resin include novolac type phenol resins (such as a phenol novolac resin, a phenol aralkyl resin, a cresol novolac resin, a tert-butyl phenol novolac resin, a nonyl phenol novolac resin), and resol type phenol resins (such as a polyoxystyrene such as polyparaoxystyrene). As the phenol resin, preferably a novolac type phenol resin is used, and more preferably a phenol aralkyl resin is used. Specifically, as the phenol resin, a biphenylene aralkyl type phenol resin is further preferable.

[0079] The phenol resin may be used alone or in combination of two or more.

[0080] When the curing agent is a phenol resin, it is possible to improve the heat resistance while the soft magnetic film is used in an inductor or a circuit board.

[0081] The phenol resin has a hydroxyl group equivalent of, for example, 50g / eq. or more and 300g / eq. or less, preferably 100g / eq. or more and 250g / eq. or less.

[0082] The phenol resin has a density of, for example, 0.8g / cm 3< or more and 1.5g / cm 3< or less, preferably 1.0g / cm 3< or more and 1.3g / cm 3< or less.

[0083] In the resin component, the content ratio of the curing agent is, for example, 10% by mass or more and 50% by mass or less, preferably 15% by mass or more and 40% by mass or less, more preferably 20% by mass or more and 35% by mass or less, and still more preferably 25% by mass or more and 30% by mass or less.

[0084] Examples of the curing accelerator include a catalyst which accelerates the curing of the thermosetting resin by heating.

[0085] Examples of the curing accelerator include an imidazole compound, a triphenylphosphine compound, a triphenylborane compound, and an amino group-containing compound, and preferably, an imidazole compound is used.

[0086] Examples of the imidazole compound include 2-phenylimidazole (trade name "2PZ"), 2-ethyl-4-methylimidazole (trade name "2E4MZ"), 2-methylimidazole (trade name "2MZ"), 2-undecylimidazole (trade name "C11Z"), 2-phenyl-4,5-dihydroxymethylimidazole (trade name "2-PHZ"), 2-phenyl-1H-imidazole 4,5-dimethanol (trade name "2PHZ-PW"), and 2,4-diamino-6-(2'-methylimidazolyl(1)')ethyl-s-triazine-isocyanuric acid adduct (trade name "2MAOK-PW"), and preferably 2-phenyl-1H-imidazole 4,5-dimethanol is used (all of the above-described trade names are manufactured by SHIKOKU KASEI HOLDINGS CORPORATION).

[0087] The curing accelerators may be used alone or in combination of two or more.

[0088] The curing accelerator has a density of, for example, 1.0g / cm 3< or more and 1.8g / cm 3< or less, preferably, 1.2g / cm 3< or more and 1.5g / cm 3< or less.

[0089] The content ratio of the curing accelerator in the resin component is, for example, 0.1% by mass or more and 5.0% by mass or less, preferably 0.3% by mass or more and 3.0% by mass or less, more preferably 0.5% by mass or more and 2.0% by mass or less, and still more preferably 0.7% by mass or more and 1.5% by mass or less.

[0090] When the content ratio of the curing accelerator in the resin component is the above-described upper limit or less, the soft magnetic resin composition obtains an excellent long-term storability at room temperature. On the other hand, when the content ratio of the curing accelerator is the above-described lower limit or more, the soft magnetic film, which is pre-completely-cured, is cured by heating at a low temperature in a short time, and a soft magnetic film can be efficiently produced.

[0091] In the resin component, the content ratio (mass ratio) of the thermosetting resin component is, for example, 25% by mass or more and 90% by mass or less, preferably 35% by mass or more and 80% by mass or less, more preferably 45% by mass or more and 70% by mass or less, and still more preferably 50% by mass or more and 60% by mass or less.

[0092] In the resin component, the content ratio (volume ratio) of the thermosetting resin component is, for example, 25% by volume or more and 85% by volume or less, preferably 35% by volume or more and 75% by volume or less, more preferably 45% by volume or more and 65% by volume or less, and still more preferably 50% by volume or more and 55% by volume or less.[Thermoplastic Resin Component]

[0093] Examples of the thermoplastic resin component include a thermoplastic resin. The thermoplastic resin component preferably consists of a thermoplastic resin.

[0094] Examples of the thermoplastic resin include an acrylic resin, a natural rubber, a butyl rubber, an isoprene rubber, a chloroprene rubber, an ethylene-vinyl acetate copolymer, a polybutadiene resin, a polycarbonate resin, a thermoplastic polyimide resin, a polyamide resin (such as 6-nylon, 6,6-nylon), a phenoxy resin, a saturated polyester resin (e.g., PET, PBT), a polyamideimide resin, and a fluororesin, and preferably an acrylic resin is used.

[0095] The thermoplastic resins may be used alone or in combination of two or more.

[0096] Examples of the acrylic resin include an acrylic ester-based polymer obtained by preparing one type or two or more types of (meth) acrylic acid alkyl ester having a straight-chain or branched alkyl group as a monomer component, and polymerizing the monomer component thereof. The term "(meth)acrylic" represents "acrylic and / or methacrylic."

[0097] The acrylic resin has a weight-average molecular weight of, for example, 1×10 5< or more, preferably 3×10 5< or more, and, for example, 1×10 6< or less.

[0098] When the weight-average molecular weight of the acrylic resin falls within the above-described range, the soft magnetic film has excellent adhesion and heat resistance.

[0099] The weight-average molecular weight is measured by gel permeation chromatography (GPC) as a value in terms of standard polystyrene.

[0100] A glass transition point is obtained by using the maximum value of the loss tangent (tanδ) measured using a dynamic viscoelastic measurement device (DMA, frequency 1Hz, rate of temperature increase 10°C / min).

[0101] The thermoplastic resin has a density of, for example, 0.5g / cm 3< or more and 1.5g / cm 3< or less, preferably 0.8g / cm 3< or more and 1.2g / cm 3< or less.

[0102] In the resin component, the content ratio (mass ratio) of the thermoplastic resin component is, for example, 20% by mass or more and 75% by mass or less, preferably 30% by mass or more and 65% by mass or less, more preferably 35% by mass or more and 55% by mass or less, and still more preferably 40% by mass or more and 50% by mass or less.

[0103] In the resin component, the content ratio (volume ratio) of the thermoplastic resin component is, for example, 25% by volume or more and 80% by volume or less, preferably 35% by volume or more and 70% by volume or less, more preferably 40% by volume or more and 60% by volume or less, and still more preferably 45% by volume or more and 50% by volume or less.

[0104] When the content ratio of the thermoplastic resin component in the resin component falls within the above-described range, the soft magnetic resin composition has excellent film formability, and the pre-completely-cured soft magnetic film has excellent adhesion.

[0105] In addition, the content ratio (mass ratio) of the resin component in the solid content of the soft magnetic resin composition is, for example, 3% by mass or more and 30% by mass or less, preferably 5% by mass or more and 20% by mass or less, more preferably 8% by mass or more and 15% by mass or less.

[0106] The content ratio (volume ratio) of the resin component in the solid content of the soft magnetic resin composition is, for example, 20% by volume or more and 70% by volume or less, preferably 30% by volume or more and 60% by volume or less, more preferably 35% by volume or more and 50% by volume or less, and still more preferably 40% by volume or more and 50% by volume or less.

[0107] When the content ratio of the resin component in the solid content of the soft magnetic resin composition is the above-described lower limit or more, the soft magnetic film has excellent film formability. In addition, when the content ratio of the resin component in the solid content of the soft magnetic resin composition is the above-described upper limit or less, it is possible to ensure the content ratio of the flat soft magnetic particles, the soft magnetic film has excellent magnetic properties.

[0108] The concentration (mass ratio) of the resin component in the soft magnetic resin composition is, for example, 2.0% by mass or more and 10.0% by mass or less, preferably 3.0% by mass or more and 8.0% by mass or less, more preferably 4.0% by mass or more and 5.0% by mass or less, and still more preferably 4.3% by mass or more and 5.0% by mass or less.

[0109] The concentration (volume ratio) of the resin component in the soft magnetic resin composition is, for example, 2.0% by volume or more and 10.0% by volume or less, preferably 3.5% by volume or more and 8.0% by volume or less, more preferably 4.5% by volume or more and 6.0% by volume or less, and still more preferably 4.8% by volume or more and 6.0% by volume or less.

[0110] When the concentration of the resin component in the soft magnetic resin composition is the above-described lower limit or more, it is possible to sufficiently ensure the viscosity when the soft magnetic resin composition is left to stand (viscosity when the shear rate is low), and therefore it is possible to suppress sedimentation and uneven distribution of the flat soft magnetic particles. In addition, when the concentration of the resin component in the soft magnetic resin composition is the above-described upper limit or less, it is possible to increase the fluidity of the soft magnetic resin composition while the soft magnetic resin composition is applied (to lower the viscosity when the shear rate is high), and therefore, it is possible to continuously apply the soft magnetic resin composition in a stable and efficient manner.<Dispersion Medium>

[0111] In the soft magnetic resin composition, the flat soft magnetic particles and the resin component are dispersed in a dispersion medium.

[0112] Examples of the dispersion medium include organic solvents including ketones such as acetone and methyl ethyl ketone (MEK), esters such as ethyl acetate, amides such as N,N-dimethylformamide, ethers such as propylene glycol monomethyl ether, and alcohols such as methanol, ethanol, propanol, and isopropanol. Further, examples of the dispersion medium include an aqueous solvent (e.g., water). As the dispersion medium, preferably ketones are used, and more preferably methyl ethyl ketone is used.

[0113] The solid content concentration (mass ratio) of the soft magnetic resin composition is, for example, 20% by mass or more and 70% by mass or less, preferably 30% by mass or more and 60% by mass or less, more preferably 35% by mass or more and 50% by mass or less, and still more preferably 40% by mass or more and 45% by mass or less.

[0114] The solid content concentration (volume ratio) of the soft magnetic resin composition is, for example, 5% by volume or more and 50% by volume or less, preferably 5% by volume or more and 30% by volume or less, more preferably 8% by volume or more and 20% by volume or less, still more preferably 10% by volume or more and 15% by volume or less, and particularly preferably 11% by volume or more and 14% by volume or less.

[0115] When the solid content concentration of the soft magnetic resin composition is the above-described lower limit or more, it is possible to sufficiently ensure the viscosity when the soft magnetic resin composition is left to stand (viscosity when the shear rate is low), and therefore it is possible to suppress sedimentation and uneven distribution of the flat soft magnetic particles. In addition, when the solid content concentration of the soft magnetic resin composition is the above-described upper limit or less, it is possible to increase the fluidity of the flat soft magnetic particles while the soft magnetic resin composition is applied (to lower the viscosity when the shear rate is high), and therefore, it is possible to continuously apply the soft magnetic resin composition in a stable and efficient manner.

[0116] The soft magnetic resin composition may also contain another additive.

[0117] Examples of the other additive include commercially available or known additives such as a crosslinking agent, an inorganic filler.

[0118] The soft magnetic resin composition is prepared by mixing the above-described flat soft magnetic particles, resin component, and, if necessary, another additive at the above-described ratio, and further dispersing the mixture in the above-described dispersion medium.

[0119] A viscosity (A) of the soft magnetic resin composition at a shear rate of 38.1 s -1< is 300 mPa·s or more, preferably 350 mPa·s or more, more preferably 400 mPa·s or more, still more preferably 420 mPa·s or more, particularly preferably 450 mPa·s or more, and also, for example, 1000 mPa·s or less, preferably 900 mPa·s or less, more preferably 800 mPa·s or less, and still more preferably 750 mPa·s or less, particularly preferably 700 mPa·s or less. In addition, the viscosity (A) of the soft magnetic resin composition at a shear rate of 38.1 s -1< is, for example, 300 mPa·s or more and 1000 mPa·s or less, preferably 350 mPa·s or more and 900 mPa·s or less, more preferably 400 mPa·s or more and 800 mPa·s or less, and still more preferably 420 mPa·s or more and 750 mPa·s or less.

[0120] When the viscosity (A) of the soft magnetic resin composition at a shear rate of 38.1 s -1< is the lower limit or more, it is possible to suppress sedimentation and uneven distribution of the flat soft magnetic particles. Further, when the viscosity (A) of the soft magnetic resin composition at a shear rate of 38.1 s -1< is the upper limit or less, the soft magnetic resin composition has excellent handleability (handling ability).

[0121] A viscosity (B) of the soft magnetic resin composition at a shear rate of 76.6 s -1< is 200 mPa·s or more and 800 mPa·s or less, preferably 250 mPa·s or more and 700 mPa·s or less, more preferably 280 mPa·s or more and 600 mPa·s or less, and still more preferably 300 mPa·s or more and 550 mPa·s or less.

[0122] A viscosity (C) of the soft magnetic resin composition at a shear rate of 191.5 s -1< is 150 mPa·s or more and 500 mPa·s or less, preferably 180 mPa·s or more and 400 mPa·s or less, and more preferably 200 mPa·s or more and 350 mPa·s or less.

[0123] A viscosity (D) of the soft magnetic resin composition at a shear rate of 383 s -1< is 100 mPa·s or more and 400 mPa·s or less, preferably 120 mPa·s or more and 300 mPa·s or less, and more preferably 140 mPa·s or more and 250 mPa·s or less.

[0124] When the viscosity (D) of the soft magnetic resin composition at a shear rate of 383 s -1< is the above-described lower limit or more, it is possible to suppress the sedimentation of the flat soft magnetic particles in the soft magnetic resin composition when the soft magnetic resin composition is applied, and therefore, it is possible to stably apply the soft magnetic resin composition. Further, when the viscosity (D) of the soft magnetic resin composition at a shear rate of 383 s -1< is the upper limit or less, it is possible to increase the fluidity of the flat soft magnetic particles when the soft magnetic resin composition is applied, and therefore, it is possible to continuously apply the soft magnetic resin composition in a stable and efficient manner.

[0125] Hereinafter, with respect to the viscosities (B-D) of the soft magnetic resin composition at shear rates of 76. 6s -1< , 191.5 s -1< , and 383 s -1< , the ratios of the viscosity (A) of the soft magnetic resin composition at a shear rate of 38.1 s -1< are represented as A / B, A / C, and A / D, respectively.

[0126] A / B is, for example, 1.20 or more and 2.00 or less, preferably 1.25 or more and 1.80 or less, more preferably 1.25 or more and 1.40 or less.

[0127] A / C is 1.70 or more, preferably 1.75 or more, more preferably 1.80 or more, still more preferably 1.85 or more, particularly preferably 2.00 or more, and, for example, 3.00 or less, preferably 2.50 or less, more preferably 2.30 or less, and still more preferably 2.10 or less. Further, A / C is, for example, 1.70 or more and 3.00 or less, preferably 1.75 or more and 2.50 or less, more preferably 1.80 or more and 2.30 or less, and still more preferably 1.85 or more and 2.10 or less.

[0128] When A / C is the above-described lower limit or more, it is possible to suppress sedimentation and uneven distribution of the flat soft magnetic particles, and further it is possible to increase the fluidity of the flat soft magnetic particles when the soft magnetic resin composition is applied, and therefore it is possible to continuously apply the soft magnetic resin composition in a stable and efficient manner.

[0129] A / D is, for example, 2.00 or more and 5.00 or less, preferably 2.30 or more and 4.00 or less, more preferably 2.50 or more and 3.50 or less, even more preferably 2.55 or more and 3.30 or less, particularly preferably 2.55 or more and 3.10 or less.

[0130] The above-described viscosities can be determined by the methods described in JIS Z 8803 and ISO 3219 (JIS K 7117-2). Specifically, the viscosities can be measured by using a cone-plate rotational viscometer. The cone-plate rotational viscometer is described in JIS Z 8803 and ISO 3219 (JIS K 7117-2), and the wetted part consists of a cone rotor (conical rotor) and a plate. The sample is filled between the cone and the plate.

[0131] Specifically, the above-described viscosities can be determined by the method described in Examples below.

[0132] The shear rate is also referred to as rate of shear (shear rate), and determined by the following relation expression between the rate of shear, i.e., the shear rate (D), and the rotation rate (N) in the above-described cone-plate rotational viscometer. However, the cone angle (φ) differs depending on the viscometer used for the measurement. D = 2 πN / 60 φ D: Shear rate (s -1< ) N: Rotation rate of conical rotor (rpm) φ: Cone angle 2. Soft Magnetic Film

[0133] The soft magnetic film of the present disclosure is formed, for example, by thermally curing the soft magnetic resin composition. In other words, the soft magnetic film is a cured product of the soft magnetic resin composition.

[0134] The soft magnetic film is, for example, in a completely-cured state.

[0135] The completely-cured state is, for example, a state in which there is no heat generation associated with the curing reaction in the differential scanning calorimetry.

[0136] The soft magnetic film has, for example, a film shape (including a sheet shape).

[0137] The soft magnetic film has a thickness of, for example, 5 µm or more and 500 µm or less, preferably 50 µm or more and 250 µm or less.

[0138] In the soft magnetic film, the volume ratio (excluding voids) of the flat soft magnetic particles is, for example, 40% by volume or more and 80% by volume or less, preferably 45% by volume or more and 70% by volume or less, more preferably 50% by volume or more and 60% by volume or less, and still more preferably 53% by volume or more and 57% by volume or less.

[0139] When the volume ratio of the flat soft magnetic particles in the soft magnetic film falls within the above-described range, the soft magnetic film has excellent magnetic permeability.

[0140] The volume ratio of the flat soft magnetic particles can be measured, for example, by the Archimedes principle.

[0141] In the soft magnetic film, for example, the flat soft magnetic particles contained in the soft magnetic film are distributed in a two-dimensional in-plane direction of the soft magnetic film. That is, a longitudinal direction (direction perpendicular to the thickness direction) of the flat soft magnetic particles is oriented along a plane direction of the soft magnetic film. Therefore, the soft magnetic film has more excellent magnetic properties.

[0142] In the soft magnetic film (a cured product of the soft magnetic resin composition), the magnetic permeability at a frequency of 10MHz is, for example, 40 or more, preferably 45 or more, more preferably 47 or more, even more preferably 49 or more.

[0143] The magnetic permeability at a frequency of 10MHz can be determined, for example, by measuring the impedance at a frequency of 10MHz using an impedance analyzer (E4991B Impedance Analyzer, manufactured by KEYSIGHT).

[0144] The soft magnetic film can be used, for example, as a single layer structure only consisting of a single layer of the soft magnetic film, a multilayer structure where the soft magnetic film is laminated on one surface or both surfaces of a core material, or a multilayer structure where a release liner is laminated on one surface or both surfaces of the soft magnetic film.<Method of Producing Soft Magnetic Film (Method of Using Soft Magnetic Resin Composition)>

[0145] A method of producing the soft magnetic film of the present disclosure includes, for example, an application step of continuously applying the above-described soft magnetic resin composition onto a substrate at an application rate of 5m / min or more, a drying step of drying the dispersion medium contained in the soft magnetic resin composition applied on the substrate to obtain a pre-completely-cured soft magnetic film, and a curing step of thermally curing the pre-completely-cured soft magnetic film.(Application Step)

[0146] In the application step, the soft magnetic resin composition is continuously applied onto the surface of the substrate at an application rate of 5m / min or more.

[0147] Examples of the substrate include a release liner and a core material.

[0148] Examples of the release liner include a polyethylene terephthalate (PET) film, a polyethylene film, a polypropylene film, and paper, and preferably a PET film is used. It is preferable that the surface of the release liner is subjected to a release treatment, for example, by using a fluorine-based release agent, a long-chain alkyl acrylate-based release agent, a silicone-based release agent.

[0149] Examples of the core material include plastic films (e.g., a polyimide film, a polyester film, a polyethylene terephthalate film, a polyethylene naphthalate film, and a polycarbonate film), metal films (e.g., aluminum foil), a glass substrate, a silicon substrate, and a resin substrate reinforced, for example, by a glass fiber or a plastic nonwoven fiber.

[0150] The substrate has an average thickness of, for example, 1 µm or more and 500µm or less.

[0151] The application method is not particularly limited, and can be any method in which continuous application is carried out, and is preferably an application method with excellent mass productivity as a long application. Specifically, examples of the application method include an application using a roll coater and, in particular, an application using a comma head coater.

[0152] The application gap is, for example, 100µm or more and 1000µm or less, preferably 150µm or more and 800µm or less, more preferably 200µm or more and 700µm or less, still more preferably 250µm or more and 600µm or less, and particularly preferably 300µm or more and 500µm or less.

[0153] The application gap is a distance between the application surface of the substrate and the knife roll when a comma head coater is used. The shear rate can be indicated as a ratio of the application gap to the application rate. Therefore, when the application is carried out at the same application rate, and the application gap is reduced, a high shear rate is imparted to the soft magnetic resin composition.

[0154] When the application gap is excessively reduced, depending on the particle diameter of the flat soft magnetic particles contained in the soft magnetic resin composition, the particles are caught in the application gap, and may cause an application streak. In other words, when the application gap is the above-described lower limit or more, it is possible to ensure the shear rate and suppress the application streak due to the catch of the particles.

[0155] The application rate is, for example, 5m / min or more and 50m / min or less, preferably 6m / min or more and 50m / min or less, more preferably 7m / min or more and 30m / min or less, and still more preferably 8m / min or more and 20m / min or less.

[0156] As described above, to impart high shear rate when the application gap is constant, it is necessary to increase the application rate. However, when the application rate is excessively increased, depending on the drying time in the subsequent drying step, a large length of the drying furnace is required, and this makes the apparatus large. That is, when the application rate is the upper limit or less, it is possible to ensure the shear rate and save the apparatus space.

[0157] The above-described application rate indicates an application rate when the soft magnetic resin composition is stably applied. In other words, the application rate does not apply to the start of the application step and the end of the application step.

[0158] Specifically, at the start of the application step, it is preferable to continuously or stepwise increase the application rate until the application rate reaches 5m / min or more.

[0159] At the start of the application step, when the application rate is continuously or stepwise increased, it is possible to suppress the application unevenness occurred in the end portion. More specifically, at the start of the application, by continuously or stepwise increasing the application rate, it is possible to suppress a sudden change in the viscosity of the soft magnetic resin composition and to suppress the application unevenness due to liquid depletion.

[0160] Further, also at the end of the application step, it is preferable to continuously or stepwise reduce the application rate.(Drying Step)

[0161] In the drying step, the dispersion medium contained in the soft magnetic resin composition applied to the substrate is dried to obtain a pre-completely-cured soft magnetic film.

[0162] Example of the drying temperature include 70°C or more and 160°C or less.

[0163] Example of the drying time include 1 minute or more and 5 minutes or less.

[0164] Thus, the dispersion medium contained in the applied soft magnetic resin composition can be dried to obtain a pre-completely-cured film.

[0165] This pre-completely-cured soft magnetic film is a soft magnetic film in a state before being completely cured at room temperature (e.g., 25°C), and is a soft magnetic adhesive film having good adhesion. The pre-completely-cured soft magnetic film is, for example, a state between a soft magnetic resin composition in an uncured state and a soft magnetic film in a completely-cured state at room temperature (e.g., 25°C), and a state in which the curing is slightly progressed.

[0166] The pre-completely-cured soft magnetic film has an average film thickness of, for example, 5µm or more and 500µm or less, preferably 5µm or more and 300µm or less, more preferably 5µm or more and 200µm or less, still more preferably 50µm or more and 150µm or less, and particularly preferably 50µm or more and 100µm or less.(Curing Step)

[0167] In the curing step, the pre-completely-cured soft magnetic film is thermally cured to obtain a soft magnetic film (soft magnetic film in a completely-cured state).

[0168] Specifically, a plurality of pre-completely-cured soft magnetic films obtained in the drying step are prepared, the plurality of pre-completely-cured soft magnetic films are heat-pressed in the thickness direction. Thus, the plurality of pre-completely-cured soft magnetic films are cured to obtain a soft magnetic film. In other words, the soft magnetic film is a soft magnetic film in a completely-cured state.

[0169] Further, the above-described heat press is not limited to a manner of heat pressing only the pre-completely-cured soft magnetic films. Specifically, as detailed below, it is also possible to heat press the pre-completely-cured soft magnetic films together with a wire. Thus, it is possible to cure the pre-completely-cured soft magnetic films and obtain an inductor with a soft magnetic film and a wire.

[0170] The heat press may be carried out using a known press machine, and examples thereof include a parallel-plate press machine.

[0171] The lamination number of semi-cured soft magnetic films can be adjusted according to the desired film thickness of the soft magnetic film and is, for example, 2 or more and 20 or less, preferably 2 or more and 5 or less.

[0172] Examples of the temperature of the heat press include 80°C or more and 200°C or less, preferably 100°C or more and 175°C or less.

[0173] Examples of the time of the heat press include, for example, 0.1 hours or more and 24 hours or less, preferably 0.2 hours or more and 3 hours or less, more preferably 0.2 hours or more and 2 hours or less.

[0174] Examples of the pressure of the heat press include, for example, 10MPa or more and 500MPa or less, preferably 20MPa or more and 200MPa or less.

[0175] Thus, in the soft magnetic film, it is possible to further improve the magnetic permeability of the flat soft magnetic particles and further thin the soft magnetic film.

[0176] Thus, a soft magnetic film in a completely-cured state is produced.

[0177] In the method of producing the above-described soft magnetic film, a plurality of pre-completely-cured soft magnetic films are laminated and heat pressed. However, for example, one (a single layer of) pre-completely-cured soft magnetic film may be heat pressed.

[0178] Such a soft magnetic film can be used, for example, for an inductor or a magnetic wiring circuit board.3. Inductor

[0179] With reference to FIGS. 1 and 2, one embodiment of an inductor of the present disclosure is described.

[0180] An inductor 10 includes, for example, a soft magnetic film 1 and a wire 2. Specifically, as shown in FIG. 1, the inductor 10 includes, for example, a wire 2 and a soft magnetic film 1 covering the entire outer peripheral surface of the wire 2.

[0181] The soft magnetic film 1 includes a resin component 3 and flat soft magnetic particles 4. The flat soft magnetic particles 4 are, for example, dispersed in a two-dimensional in-plane direction of the soft magnetic film 1. The soft magnetic resin composition may contain another additive other than the resin component 3 and the flat soft magnetic particles 4 although the other additive is not shown.

[0182] The wire 2 may be a single wire or a plurality of wires. When the inductor includes a plurality of wires 2, one of the wires 2 and the other of the wires 2 adjacent to the one of the wires 2 in a width direction (first direction) perpendicular to the thickness direction are spaced from each other in the width direction (first direction).

[0183] The wire 2 extends long in a second direction perpendicular to both the thickness direction and the width direction, and the plan view shape is not particularly limited. Examples of the plan view shape of the wire 2 include, for example, a substantially straight shape in a plan view and a substantially U- shape in a plan view.

[0184] The cross-sectional view shape of the wire 2 is not particularly limited, and examples thereof include a substantially circle shape in a cross-sectional view and a substantially rectangular shape in a cross-sectional view. The cross-sectional view shape of the wire 2 is, as shown in FIG. 1, preferably a substantially circle shape in a cross-sectional view.

[0185] The wire 2 includes, for example, a conductive wire 5, and an insulating layer 6 covering the conductive wire 5.

[0186] The conductive wire 5 extends long in the second direction, and has a plan-view shape the same as the above-described shape of the wire 2. Specifically, examples of the plan-view shape of the conductive wire 5 include, for example, a substantially straight shape in a plan view and a substantially U- shape in a plan view.

[0187] Further, the cross-sectional view shape of the conductive wire 5 is the same as the above-described shape of the wire 2. The conductive wire 5 preferably has a substantially circle shape in a cross-sectional view that shares a central axis with the wire 2.

[0188] Examples of a material for the conductive wire 5 include metal conductors such as copper, silver, gold, aluminum, nickel, and an alloy thereof, and preferably copper is used. The conductive wire 5 may have a single-layer structure, or a multi-layer structure in which the surface of a core conductor (for example, copper) is plated (for example, with nickel).

[0189] The conductive wire 5 has a radius of, for example, 25µm or more and 2000µm or less, preferably 50µm or more and 200µm or less.

[0190] The insulating layer 6 is a layer for protecting the conductive wire 5 from chemicals and water, and also preventing a short circuit of the conductive wire 5. The insulating layer 6 is disposed so as to cover the entire outer peripheral surface of the conductive wire 5.

[0191] The insulating layer 6 has, for example, a substantially ring shape in a cross-sectional view that shares a central axis with the wire 2.

[0192] Examples of a material for the insulating layer 6 include insulating resin such as polyvinyl formal, polyester, polyesterimide, polyamide (including nylon), polyimide, polyamideimide, and polyurethane. These may be used alone or in combination of two or more.

[0193] The insulating layer 6 may be composed of a single layer, or a plurality of layers.

[0194] The insulating layer 6 has a thickness which is substantially uniform in a radial direction of the wire 2 at any position in a circumferential direction, and, for example, 1µm or more and 100µm or less, preferably 3µm or more and 50µm or less.< Method of Producing Inductor>

[0195] Such an inductor 10 is produced by a production method, as shown in FIGS. 2A through 2C, including, for example, a preparation step of preparing a pre-completely-cured soft magnetic film 1' and a wire 2, a disposition step of disposing the pre-completely-cured soft magnetic film 1' and the wire 2, and a curing step of curing the pre-completely-cured soft magnetic film 1'.

[0196] First, in the preparation step, for example, a pre-completely-cured soft magnetic film 1' and a wire 2 are prepared. Specifically, in the preparation step, as shown in FIG. 2A, the wire 2 is prepared at one side in the thickness direction of one pre-completely-cured soft magnetic film 1', and another pre-completely-cured soft magnetic film 1' is prepared at one side in the thickness direction of the wire 2.

[0197] The pre-completely-cured soft magnetic film 1' may be used alone, or a plurality of them may be used as shown in FIG. 2A.

[0198] The pre-completely-cured soft magnetic film 1' includes a resin component 3 and flat soft magnetic particles 4. For example, the flat soft magnetic particles 4 are dispersed in the two-dimensional in-plane direction of the pre-completely-cured soft magnetic film 1'. The soft magnetic resin composition may contain another additive other than the resin component 3 and the flat soft magnetic particles 4 although the other additive is not shown.

[0199] Next, as shown in FIG. 2B, in the disposition step, for example, the pre-completely-cured soft magnetic films 1' and the wire 2 are disposed. Specifically, in the disposition step, the wire 2 and the pre-completely-cured soft magnetic films 1' are disposed so that the pre-completely-cured soft magnetic films 1' cover the entire outer peripheral surface of the wire 2.

[0200] As a method of disposing the pre-completely-cured soft magnetic films 1' so as to cover the entire outer peripheral surface of the wire 2, for example, one pre-completely-cured soft magnetic film 1' and another pre-completely-cured soft magnetic film 1' are pressed so as to sandwich the wire 2, and thus the one pre-completely-cured soft magnetic film 1' and the other pre-completely-cured soft magnetic film 1' are deformed, thereby embedding the wire 2.

[0201] Thus, it is possible to dispose the two pre-completely-cured soft magnetic films 1' so as to cover the entire outer peripheral surface of the wire 2.

[0202] Next, in the curing step, as shown in FIG. 2C, the two pre-completely-cured soft magnetic films 1' are cured by heating, thereby producing a soft magnetic film 1. By the curing, the contact interface of the two pre-completely-cured soft magnetic films 1' disappears, and the two pre-completely-cured soft magnetic films 1' form one soft magnetic film 1.

[0203] In the disposition step, the press may be carried out together with the heating at the same time to carry out the curing, thereby forming a soft magnetic film 1. In such a case, the curing step can be omitted.

[0204] Thus, an inductor 10 is obtained.(Modified Example of Inductor)

[0205] The above-described inductor 10 includes only the wire 2 and the soft magnetic film 1, but is not limited thereto.

[0206] Specifically, although not shown, an adhesive layer may be included between the wire 2 and the soft magnetic film 1.

[0207] The adhesive used in the adhesive layer is not particularly limited as long as it is a known adhesive commonly used as an adhesive of the inductor 10, and examples thereof include an epoxy-based adhesive, a polyimide-based adhesive, and an acrylic adhesive.

[0208] The adhesive has an application thickness of, for example, 10µm or more and 100µm or less.

[0209] The above-described Modified Example of the inductor 10 can be, although not shown, produced by using the soft magnetic film 1, the wire 2, and an adhesive.

[0210] Specifically, in the preparation step, the adhesive is applied to one side in the thickness direction of one soft magnetic film 1, and a wire 2 is prepared at one side (to which the adhesive is applied) in the thickness direction of one soft magnetic film 1. Then, the adhesive is applied to the other side in the thickness direction of the other soft magnetic film 1, and the other soft magnetic film is prepared at one side in the thickness direction of the wire 2.

[0211] Next, in the disposition step, the one soft magnetic film 1 and the other soft magnetic film 1 are pressed so as to sandwich the wire 2. Thus, the wire 2 is embedded while being sandwiched by the one soft magnetic film 1 and the other soft magnetic film 1 through the adhesive.

[0212] As a result, the soft magnetic films 1 are disposed so as to cover the entire outer peripheral surface of the wire 2 through the adhesive.

[0213] When the soft magnetic films 1 are used, the curing step is omitted.

[0214] Thus, an inductor 10 is obtained.4. Magnetic Wiring Circuit Board

[0215] With reference to FIG. 3, an embodiment of a magnetic wiring circuit board using the soft magnetic film of the present disclosure is described.

[0216] A magnetic wiring circuit board 11 includes, for example, a soft magnetic film 1 and a circuit board 7.

[0217] Specifically, as shown in FIG. 3, the magnetic wiring circuit board 11 includes, for example, the circuit board 7 and the soft magnetic film 1 in order in the thickness direction (lamination direction). That is, the magnetic wiring circuit board 11 includes the soft magnetic film 1, for example, on one surface in the thickness direction of the circuit board 7.<Method of Producing Magnetic Wiring Circuit Board>

[0218] The magnetic wiring circuit board 11 described above is produced by a production method including, for example, a preparation step of preparing a pre-completely-cured soft magnetic film 1' and a circuit board 7, a lamination step of laminating the pre-completely-cured soft magnetic film 1' on the circuit board 7, and a curing step of curing the pre-completely-cured soft magnetic film 1'.

[0219] First, a pre-completely-cured soft magnetic film 1' and a circuit board 7 are prepared. Specifically, a pre-completely-cured soft magnetic film 1' and a circuit board 7 in which a wiring pattern 8 is formed on a surface of a substrate 9 are prepared.

[0220] Further, the pre-completely-cured soft magnetic film 1' may be used alone, or a plurality of them may be used.

[0221] The pre-completely-cured soft magnetic film 1' includes a resin component 3 and flat soft magnetic particles 4. The flat soft magnetic particles 4 are, for example, arranged in a two-dimensional in-plane direction of the pre-completely-cured soft magnetic film 1'. The soft magnetic resin composition may contain another additive other than the resin component 3 and the flat soft magnetic particles 4.

[0222] The circuit board 7 is, for example, a circuit board used in an electromagnetic induction method, and a wiring pattern 8 such as a loop coil is formed on one surface in the thickness direction of the substrate 9.

[0223] The wiring pattern 8 is, for example, made of a metal material such as copper, and formed by a semi-additive method or a subtractive method.

[0224] The substrate 9 is formed, for example, from an insulating material. Examples of the substrate 9 formed from the insulating material include a glass epoxy substrate, a glass substrate, a polyethylene terephthalate (PET) substrate, a ceramic substrate, and a polyimide substrate.

[0225] Next, in the lamination step, for example, the pre-completely-cured soft magnetic film 1' is laminated on one surface in the thickness direction of the circuit board 7. Specifically, the pre-completely-cured soft magnetic film 1' is brought into contact with the one surface in the thickness direction of the circuit board 7.

[0226] The pre-completely-cured soft magnetic film 1' may be pressed from one side in the thickness direction of the circuit board 7 toward the other side in the thickness direction.

[0227] Next, in the curing step, the pre-completely-cured soft magnetic film 1' is cured by heating to obtain a soft magnetic film 1.

[0228] In the lamination step, the press may be carried out together with the heating at the same time to carry out the curing, thereby forming a soft magnetic film 1. In such a case, the curing step can be omitted.

[0229] Thus, a magnetic wiring circuit board 11 is obtained.(Modified Example of Magnetic Wiring Circuit Board)

[0230] The above-described magnetic wiring circuit board 11 includes the circuit board 7 and the soft magnetic film 1 in order in the thickness direction (lamination direction), but is not limited thereto.

[0231] Specifically, although not shown, the magnetic wiring circuit board may include a circuit board 7, an adhesive layer, and a soft magnetic film 1 in order in the thickness direction (lamination direction).(Uses)

[0232] The soft magnetic film 1 described above can be used for an antenna or a coil included in an electronic device. Further, as described above, the soft magnetic film 1 can be used for the inductor 10, and is mounted, for example, on an electronic device and used as a passive element such as a voltage converting member.Examples

[0233] In reference to Examples and Comparative Examples below, the present disclosure is more specifically described. The present disclosure is however not limited by Examples and Comparative Examples in any manner. The specific numerical values in mixing ratios (content ratios), property values, and parameters used in the following description can be replaced with upper limit values (numerical values defined with "or less" or "less than") or lower limit values (numerical values defined with "or more" or "more than") of corresponding numerical values in mixing ratios (content ratios), property values, and parameters described in the above-described "DESCRIPTION OF THE EMBODIMENT ".<Details of Components>

[0234] The trade names and abbreviations of the components used in each of Examples and Comparative Examples are detailed. Fe-Si alloy: coercive force 500A / m, density 7.17g / cm 3< Orthocresol novolac type epoxy resin: trade name "Epicron N665-EXPS", manufactured by DIC, epoxy equivalent 200g / eq, density 1.19g / cm 3< Acrylic acid ester-based polymer: trade name "Teisan Resin SG-70LN", manufactured by Nagase ChemteX Corporation, solid content concentration 12.5% by mass (methyl ethyl ketone solution), density 1.0g / cm 3< Biphenylene aralkyl-based phenol resin: trade name "MEHC-7851SS", manufactured by Meiwa Plastic Industries, Ltd., hydroxyl group equivalent 203g / eq, density 1.19g / cm 3< Imidazole compound: trade name "2PHZ-PW"; manufactured by SHIKOKU KASEI HOLDINGS CORPORATION, Ltd.; solid content concentration 10.0% by mass (methyl ethyl ketone solution); density 1.33g / cm 3< Example 1<Preparation of Soft Magnetic Particles>

[0235] Fe-Si alloy, which is a soft magnetic material, was processed into spherical soft magnetic particles by a gas atomization method, and the soft magnetic particles were classified. Next, a predetermined process amount of the soft magnetic particles after classification was charged to the attritor. Alcohol and a powdered medium were also charged into this attritor. By using the attritor, the spherical soft magnetic particles were processed into flat shape, the obtained coarsely-refined flat soft magnetic particles were classified with a mesh to obtain the flat soft magnetic particles of Example 1 with desired values of the particle diameters (particle diameter distribution).

[0236] The particle diameters D10, D50, and D90 of the flat soft magnetic particles of Example 1 were measured with a laser diffractometer for measuring particle diameter distribution (Beckman Coulter, LS 13 320). The results are shown in Table 3.<Preparation of Soft Magnetic Resin Composition>

[0237] Next, a soft magnetic resin composition was prepared based on the formulation shown in Preparation Example (I) in Table 1. Specifically, 380 parts by mass of the flat soft magnetic particles of Example 1, 12.7 parts by mass of an ortho cresol novolac type epoxy resin as an epoxy resin, 163.5 parts by mass of an acrylic acid ester-based polymer solution (20.4 parts by mass of solid content) as an acrylic resin, 12.7 parts by mass of a biphenylene aralkyl type phenol resin as a curing agent, and 4.6 parts by mass of an imidazole compound solution (0.5 parts by mass of solid content) as a curing accelerator were mixed.

[0238] Next, a soft magnetic resin composition having a solid content concentration of 11.3% by volume was prepared by adding 452.9 parts by mass of methyl ethyl ketone as a dispersion medium to the above-described mixture.

[0239] The mass (g), volume (cm 3< ), solid content mass (g), and solid content volume (cm 3< ) of each component of the soft magnetic resin composition in Preparation Example (I) are shown in Table 1. In addition, the content ratio (% by mass and % by volume) of the resin component (components other than the flat soft magnetic particles) in the solid content of the soft magnetic resin composition, the content ratio (% by mass and % by volume) of the flat soft magnetic particles in the solid content of the soft magnetic resin composition, the solid content concentration (% by mass and % by volume) of the soft magnetic resin composition, and the content ratio (% by mass and % by volume) of the flat soft magnetic particles in the soft magnetic resin composition in Preparation Example (I) are shown in Table 2.Examples 2 and 3

[0240] Except that the processing time by using the attritor was changed, in the same manner as in Example 1, flat soft magnetic particles of Examples 2 and 3 were prepared. The particle diameters D10, D50, and D90 of the soft magnetic particles of Examples 2 and 3 were measured in the same manner as in Example 1. The results are shown in Table 3.

[0241] In addition, except that the flat soft magnetic particles of Examples 2 and 3 were used, in the same manner as in Example 1, the soft magnetic resin compositions of Examples 2 and 3 were prepared.Example 4

[0242] Except that the processing time by using the attritor was changed, and the size of openings of the mesh for the subsequent classification was changed, in the same manner as in Example 1, flat soft magnetic particles of Example 4 were obtained. The particle diameters D10, D50, and D90 of the soft magnetic particles of Example 4 were measured in the same manner as in Example 1. The results are shown in Table 3.

[0243] In addition, except that except that the flat soft magnetic particles of Example 4 were used, in the same manner as in Example 1, the soft magnetic resin composition of Example 4 was prepared.Comparative Example 1

[0244] Except that in the process by using the attritor, the processing amount of the raw material powder and the processing time thereof were changed, and the size of openings of the mesh for the subsequent classification was changed, in the same manner as in Example 1, flat soft magnetic particles of Comparative Example 1 were obtained. The particle diameters D10, D50, and D90 of the soft magnetic particles of Comparative Example 1 were measured in the same manner as in Example 1. The results are shown in Table 3.

[0245] In addition, except that the flat soft magnetic particles of Comparative Example 1 were used, in the same manner as in Example 1, the soft magnetic resin composition of Comparative Example 1 was prepared.Comparative Example 2

[0246] Except that the flat soft magnetic particles of Example 4 were used, and the amount of the dispersion medium was changed based on the formulation described in Preparation Example (II) in Table 1 to prepare a soft magnetic resin composition, in the same manner as in Example 1, flat soft magnetic particles of Comparative Example 2 were prepared. The solid content concentration of the soft magnetic resin composition of Comparative Example 2 was 10.3% by volume.

[0247] The mass (g), volume (cm 3< ), solid content mass (g), and solid content volume (cm 3< ) of each component of the soft magnetic resin composition in Preparation Example (II) are shown in Table 1. In addition, the content ratio (% by mass and % by volume) of the resin component (components other than the flat soft magnetic particles) in the solid content of the soft magnetic resin composition, the content ratio (% by mass and % by volume) of the flat soft magnetic particles in the solid content of the soft magnetic resin composition, the solid content concentration (% by mass and % by volume) of the soft magnetic resin composition, and the content ratio (% by mass and % by volume) of the flat soft magnetic particles in the soft magnetic resin composition in Preparation Example (II) are shown in Table 2.<Evaluations>[Viscosity]

[0248] The viscosity of the soft magnetic resin composition at 25°C of each of Examples and Comparative Examples was measured. For the viscosity measurement, a viscometer (trade name "RE-85", manufactured by Toki Sangyo Co., Ltd.), and a cone rotor (trade name "1°34'×R24", 1.1ml, rate of shear: 3.83N(1 / s), manufactured by Toki Sangyo Co., Ltd.) were used, and the viscosity at each shear rate was measured. The measurement was carried out at four points where the numbers of revolutions of the cone rotor were 10rpm, 20rpm, 50rpm and 100rpm, respectively. The relationship between the number of revolutions N (rpm) and the shear rate, i.e., the rate of shear in the cone rotor used was 3.83N (s -1< ). Thus, the shear rate at each measurement point was 38.3 (s -1< ) at 10rpm, 76.6 (s -1< ) at 20rpm, 191.5 (s -1< ) at 50rpm, and 383 (s -1< ) at 100rpm. The viscosity at each shear rate was determined as A to D. The results are shown in Table 3. Also, the relationship between the shear rate and the viscosity is shown in the graph in FIG. 4.

[0249] In addition, the ratios (A / B, A / C, and A / D) of the viscosity A to the viscosities B to D were calculated. The results are shown in Table 3.[Continuous Application Properties]

[0250] The soft magnetic resin composition of each of Examples and Comparative Examples was continuously applied onto a release liner (average thickness: 50µm) made of a silicone-release-treated polyethylene terephthalate film by using a comma head coater. The application rate was 10m / min, and the application gap was 350µm. With respect to the continuous application properties, the appearance of the soft magnetic resin composition on the film was evaluated according to the following criteria. The results are shown in Table 3. The appearance of each soft magnetic resin composition on the film was almost unchanged between the state immediately after the application and the state after the drying.

[0251] {Criteria}Good: Uniform application was carried out on the film

[0252] Bad: Application could not be carried out on the film or uniform application could not be carried out on the film (a streak or an uncoated part was observed).[Magnetic Permeability]

[0253] The soft magnetic resin composition of each of Examples and Comparative Examples was continuously applied onto a release liner (average thickness: 50µm) made of a silicone-release-treated polyethylene terephthalate film by using a comma head coater, and then dried at 110°C for 2 minutes. As a result, a pre-completely-cured soft magnetic film which was laminated on the release liner (average thickness of only the pre-completely-cured soft magnetic film: 140 µm) was produced. Four sheets of the pre-completely-cured soft magnetic films were produced, and these soft magnetic films (excluding the release liners) were laminated. The pre-completely-cured soft magnetic film obtained by laminating the four sheets was heat pressed under the conditions of 9MPa, 170 °C, 15 minutes, thereby producing a soft magnetic film with a thickness of 150µm.

[0254] Next, the magnetic permeability of the soft magnetic film formed from the soft magnetic resin composition of each of Examples and Comparative Examples was determined by measuring the impedance at 10MHz using an impedance analyzer (E4991B Impedance Analyzer, manufactured by KEYSIGHT. The results are shown in Table 3.[Table 1]

[0255] Table 1Prep. Ex. (I)Prep. Ex. (II)Mass (g)Volume (cm 3< )Solid content Mass (g)Solid content Volume (cm 3< )Mass (g)Volume (cm 3< )Solid content Mass (g)Solid content Volume (cm 3< )Epoxy resin12.710.612.710.612.710.612.710.6Acrylic resin163.5198.220.420.4163.5198.220.420.4Phenol resin12.710.612.710.612.710.612.710.6Curing accelerator4.65.50.50.34.65.50.50.3Flat soft magnetic particles380.053.0380.053.0380.053.0380.053.0Dispersion medium452.9562.60.00.0519.0644.70.00.0Total1026.3840.5426.295.11092.4922.6426.295.1 [Table 2]

[0256] Table 2Prep. Ex. (I)Prep. Ex. (II)Content ratio of resin component in solid content of magnetic resin composition(% by mass)10.810.8(% by volume)44.244.2Content ratio of flat soft magnetic particles in solid content of magnetic resin composition(% by mass)89.289.2(% by volume)55.855.8Solid content concentration of magnetic resin composition(% by mass)41.539.0(% by volume)11.310.3Content ratio of flat soft magnetic particles in magnetic resin composition(% by mass)37.034.8(% by volume)6.35.7 [Table 3]

[0257] Table 3Ex. 1Ex. 2Ex. 3Ex. 4Comp. Ex. 1Comp. Ex. 2Magnetic resin composition (Prep. Ex. )IIIIIIIParticle size(µm)D1013.813.116.413.913.013.9D5038.442.445.941.643.041.6D9080.987.395.897.9137.097.9Viscosity(mPa·s) at each shear rate(s -1< )38.3(s -1< )A47770542557022524976.6(s -1< )B376516314436192205192(s -1< )C258336205282151148383(s -1< )D187231146198120113Ratios of viscosityA / B1.271.371.351.311.171.21A / C1.852.102.072.021.491.68A / D2.553.052.912.881.882.20EvaluationContinuous application propertiesGoodGoodGoodGoodBadBadMagnetic permeability495152504651

[0258] While the illustrative embodiments of the present invention are provided in the above-described description, such is for illustrative purpose only and it is not to be construed as limiting the scope of the present invention. Modification and variation of the present invention that will be obvious to those skilled in the art is to be covered by the following claims.Industrial Applicability

[0259] The soft magnetic film formed from the soft magnetic resin composition of the present disclosure can be suitably used, for example, for an antenna or a coil provided in an electronic device. Further, such a soft magnetic film can be used in an inductor, is mounted, for example, on an electronic device, and can be used as a passive element such as a voltage converting member. Further, such a soft magnetic film can also be used for a magnetic wiring circuit board.Description of Reference Numerals

[0260] 1Soft magnetic film 2Wire 3Resin component 4Flat soft magnetic particles 10Inductor

Claims

1. A soft magnetic resin composition comprising: a solid content containing flat soft magnetic particles and a resin component; and a dispersion medium, wherein a viscosity (A) at a shear rate of 38.1 s-1 is 300 mPa·s or more, and wherein with respect to a viscosity (C) at a shear rate of 191.5 s-1, a ratio (A / C) of the viscosity (A) at the shear rate of 38.1 s-1 is 1.70 or more.

2. The soft magnetic resin composition according to claim 1, wherein a particle diameter (D90) where a volume-based accumulated value from the smallest particle size of the flat soft magnetic particles is 90% is 80 µm or more and 130 µm or less.

3. The soft magnetic resin composition according to claim 1, wherein a particle diameter (D50) where a volume-based accumulated value from the smallest particle size of the flat soft magnetic particles is 50% is 30 µm or more and 50 µm or less.

4. The soft magnetic resin composition according to claim 1, wherein a particle diameter (D10) where a volume-based accumulated value from the smallest particle size of the flat soft magnetic particles is 10% is 5 µm or more.

5. The soft magnetic resin composition according to claim 1, wherein a solid content concentration of the soft magnetic resin composition is 11% by volume or more and 14% by volume or less.

6. The soft magnetic resin composition according to claim 1, wherein the resin component contains a thermosetting resin component and a thermoplastic resin component.

7. The soft magnetic resin composition according to claim 6, wherein the thermosetting resin component contains an epoxy resin, and wherein the thermoplastic resin component contains an acrylic resin.

8. The soft magnetic resin composition according to claim 7, wherein the thermosetting resin component further contains a curing agent and a curing accelerator.

9. The soft magnetic resin composition according to claim 1, wherein a content ratio of the flat soft magnetic particles in the solid content of the soft magnetic resin composition is 45% by volume or more and 70% by volume or less.

10. The soft magnetic resin composition according to claim 1, wherein in a cured product of the soft magnetic resin composition, a magnetic permeability at a frequency of 10 MHz is 40 or more.

11. A soft magnetic film being a cured product of the soft magnetic resin composition according to any one of claims 1 to 10.

12. An inductor comprising: the soft magnetic film according to claim 11; and a wire.

13. A method of producing a soft magnetic film, the method comprising: an application step of continuously applying the soft magnetic resin composition according to any one of claims 1 to 10 to a substrate at an application rate of 5m / min or more; a drying step of drying a dispersion medium contained in the soft magnetic resin composition applied to the substrate to obtain a pre-completely-cured soft magnetic film; and a curing step of thermally curing the pre-completely-cured soft magnetic film.

14. The method according to claim 13, wherein in the application step, the application rate is continuously or stepwise increased until the application rate reaches 5m / min or more.

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