Method for producing liquid magnetic composition, and method for producing dry film

Abstract

To provide a method for producing a liquid magnetic composition that enables a liquid magnetic composition having reduced coarse particles and aggregates of magnetic powder to be produced through a simple process.SOLUTION: The present invention provides a method for producing a liquid magnetic composition containing a magnetic powder and a liquid component, wherein this method involves filtering a mixture including the magnetic powder dispersed in the liquid component.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a liquid magnetic composition and a method for producing a dry film. [Background technology]

[0002] In recent years, high magnetic permeability is required for magnetic materials such as magnetic powder. However, there is a problem that the magnetic loss increases when trying to achieve high magnetic permeability. Therefore, in some applications, it is important to reduce magnetic loss while maintaining high magnetic permeability. For example, Patent Document 1 discloses that magnetic loss can be reduced by using a conductive paste obtained by dispersing pre-classified magnetic powder in a resin component. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-158316 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, even in a conductive paste obtained by using a magnetic powder that has been classified in advance, the occurrence of agglomerates of the magnetic powder cannot be completely prevented.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an objective of providing a method for producing a liquid magnetic composition that can provide a liquid magnetic composition in which coarse particles and agglomerates of magnetic powder are reduced by a simple method. Another object of the present invention is to provide a method for producing a dry film that can provide a resin layer made of a liquid magnetic composition in which coarse particles and agglomerates of magnetic powder are reduced. [Means for solving the problem]

[0006] The inventors have conducted research into the above-mentioned problems, and have found that although it is possible to remove coarse particles by classifying the magnetic powder before mixing with the liquid component, agglomerates of the magnetic powder may occur when dispersing the magnetic powder in the liquid component. In addition, they have found that even if the magnetic powder is dispersed in the liquid component without classifying it in advance, it is possible to reduce the coarse particles and agglomerates of the magnetic powder by filtering after the dispersion treatment. The present invention is based on such findings. That is, the gist of the present invention is as follows.

[0007] [1] A method for producing a liquid magnetic composition containing a magnetic powder and a liquid component, comprising: A method for producing a liquid magnetic composition, comprising filtering a mixture in which the magnetic powder is dispersed in the liquid component. [2] A first step of blending the magnetic powder and the liquid component to obtain a mixture of the magnetic powder and the liquid component; a second step of agitating the mixture to disperse the magnetic powder in the liquid component; and a third step of filtering the mixture in which the magnetic powder is dispersed in the liquid component to obtain a liquid magnetic composition. [3] The method for producing a liquid magnetic composition according to [1] or [2], wherein the liquid component is at least one selected from the group consisting of a solvent and a liquid resin component. [4] The method for producing a liquid magnetic composition according to [3], wherein the liquid resin component contains an epoxy resin. [5] A step of obtaining a liquid magnetic composition by the method for producing a liquid magnetic composition according to any one of [1] to [4]; applying the liquid magnetic composition to one side of a first film; and drying the liquid magnetic composition to form a resin layer on one side of the first film. Effect of the Invention

[0008] The method for producing a liquid magnetic composition of the present invention is capable of providing a liquid magnetic composition in which the amount of coarse particles and agglomerates of magnetic powder is reduced, by a simple method. Furthermore, the liquid magnetic composition obtained by the present invention can be used as a curable resin composition capable of reducing magnetic loss by containing a curable resin as a liquid component. Furthermore, the method for producing a dry film of the present invention can provide a dry film having a resin layer made of a liquid magnetic composition in which the coarse particles and agglomerates of the magnetic powder are reduced. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In this specification, any numerical range expressed using "~" is intended to include both ends of the range.

[0010] [Method of manufacturing liquid magnetic composition] The method for producing a liquid magnetic composition of the present invention (hereinafter sometimes simply referred to as "the present invention") is a method for producing a liquid magnetic composition containing a magnetic powder and a liquid component, in which the liquid magnetic composition is obtained by filtering a mixture in which the magnetic powder is dispersed in the liquid component.

[0011] In one embodiment of the present invention, a method for producing a liquid magnetic composition includes the following first to third steps.

[0012] (First Step) First, in the first step, the magnetic powder and the liquid component are mixed to obtain a mixture of the magnetic powder and the liquid component. Specifically, materials are appropriately selected from the magnetic powder and the liquid component described below, mixed to obtain a required ratio, and premixed with a stirrer. This results in a mixture of the magnetic powder and the liquid component.

[0013] In the first step, the magnetic powder may be classified in advance or may not be classified. According to the present invention, the magnetic powder can be used without being classified in advance, which increases the freedom of material selection and also shortens the process.

[0014] (Second step) Next, in the second step, the mixture is stirred to disperse the magnetic powder in the liquid component. Specifically, the mixture obtained in the first step is mixed and stirred using a commercially available dispersing machine such as a bead mill or a three-roller mill. This results in a mixture in which the magnetic powder is uniformly dispersed in the liquid component.

[0015] In the second step, the dispersion state of the magnetic powder in the liquid component can be adjusted by the operating conditions of the dispersing machine. When a bead mill is used as the dispersing machine, for example, the operating conditions can be selected as follows: rotation speed 200 to 2000 rpm, stirring time: 30 minutes to 3 hours.

[0016] (Third Step) Next, in the third step, the mixture in which the magnetic powder is dispersed in the liquid component is filtered. Specifically, the mixture in which the magnetic fluid is uniformly dispersed in the liquid component in the second step is filtered using a filtering device. This results in a liquid magnetic composition from which coarse particles and aggregates of the magnetic powder have been removed.

[0017] In the third step, the filtering device used for filtration is not particularly limited. The filter used in the filtering device can be appropriately selected depending on the type and particle size of the magnetic powder used. Examples of the filter include those with a mesh size of 100 to 635 (opening: 150 to 20 μm). In addition, it is preferable to use a non-metallic material such as resin as the material of the filter in order to prevent metal contamination of the liquid magnetic composition.

[0018] In the third step, if the mixture has a high viscosity (low fluidity) and filtration by its own weight is difficult, filtration may be performed while applying pressure to the primary side of the filter of the filtration device (pressure filtration). The pressure during pressure filtration, i.e., the differential pressure between the primary side and the secondary side of the filter of the filtration device, is preferably 0.15 MPa or less, more preferably 0.10 MPa or less. If the pressure difference is 0.15 MPa or less, the filter mesh will not be damaged, and the desired filtration effect can be obtained.

[0019] In the third step, if the viscosity of the mixture varies depending on the temperature, the mixture may be heated and kept at a required temperature during filtration. The temperature of the mixture is preferably in the range of 15 to 70°C.

[0020] (Fourth step) In one embodiment of the present invention, the method for producing the liquid magnetic composition may further include the following fourth step in addition to the first to third steps.

[0021] In the fourth step, a liquid component is mixed with the liquid magnetic composition obtained in the third step. Specifically, any liquid component, i.e., a solvent or liquid resin component, may be added to the liquid magnetic composition from which the coarse particles and aggregates of the magnetic powder have been removed in the third step. This makes it possible to add any component that is undesirable to coexist in the dispersion treatment in the second step or under the pressure and temperature during filtration in the third step after filtration, making it easy to adjust a liquid magnetic composition of a desired composition.

[0022] (Other steps) In one embodiment of the present invention, the method for producing a liquid magnetic composition may include other steps in addition to the first to fourth steps described above. Specifically, for example, between the second step and the third step, a step of blending an optional liquid component (e.g., a solvent) or a step of heating the mixture may be provided in order to adjust the viscosity of the mixture. Furthermore, a step of performing a second filtration may be provided after the fourth step.

[0023] According to the manufacturing method of a liquid magnetic composition of the present invention, even if the magnetic powder is dispersed in a liquid component without prior classification, it is possible to reduce coarse particles and agglomerates of the magnetic powder by filtering after the dispersion treatment, thereby making it possible to provide a liquid magnetic composition that does not contain coarse particles or agglomerates of the magnetic powder.

[0024] In the manufacturing method of the liquid magnetic composition of the embodiment described above, the first to third steps may be clearly identified in some cases, and the steps may not be clearly identified because some of the steps are performed continuously, etc. However, the present invention is characterized in that, since there is a risk of agglomeration of the magnetic powder occurring when dispersing the magnetic powder in the liquid component, the mixture containing the magnetic powder and the liquid component is filtered after the dispersion treatment.

[0025] [Liquid magnetic composition] The liquid magnetic composition obtained by the present invention contains at least a magnetic powder and a liquid component.

[0026] <Magnetic powder> The liquid magnetic composition obtained by the present invention contains magnetic powder. By containing magnetic powder, noise electromagnetic waves in the near electromagnetic field can be suppressed or absorbed, so that a printed wiring board with excellent characteristics such as noise suppression can be obtained even when multiple circuit elements are mounted. In addition, it can be suitably used as an insulating material for high-frequency inductor elements that require high relative permeability at 1 MHz to 200 MHz.

[0027] The magnetic powder can be used without any particular limitation, and examples thereof include non-conductive magnetic materials such as spinel type ferrites such as Mg-Zn ferrite, Mn-Zn ferrite, Mn-Mg ferrite, Cu-Zn ferrite, Mg-Mn-Sr ferrite, and Ni-Zn ferrite, hexagonal type ferrites such as Ba-Zn ferrite, Ba-Mg ferrite, Ba-Ni ferrite, Ba-Co ferrite, and Ba-Ni-Co ferrite, and garnet type ferrites such as Y ferrite, etc. Examples of conductive magnetic materials include Fe alloys such as pure iron powder, Fe-Si alloy powder, Fe-Si-Al alloy powder, Ni powder, Fe-Ni alloy powder, Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, Fe-Ni-Co alloy powder, Fe-Cr alloy powder, Fe-Cr-Si alloy powder, Fe-Ni-Cr alloy powder, or Fe-Cr-Al alloy powder, Ni alloys, and amorphous alloys such as Fe-based amorphous and Co-based amorphous.

[0028] When the liquid magnetic composition obtained by the present invention is a curable resin composition and the cured product is required to be insulating, it is necessary to use a non-conductive magnetic powder as the magnetic powder. However, even if the magnetic powder is conductive, it is possible to use a non-conductive magnetic powder by adjusting the amount of the conductive magnetic powder or by coating the surface with an insulating inorganic or organic material.

[0029] The magnetic powder has a magnetic permeability exceeding 1.0. The magnetic permeability can be measured at a temperature of 25°C and a frequency range of 10 MHz to 1 GHz using, for example, a Keysight E5071C ENA network analyzer as described below, and the measured real part (μ') is the magnetic permeability.

[0030] In addition, as the magnetic powder, commercially available magnetic powders can be used. Specific examples of commercially available magnetic powders include "PST-S" manufactured by Sanyo Special Steel Co., Ltd., "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", and "Fe-80Ni-4MoPF20F" manufactured by Epson Atmix Corporation, "M03S" and "M10S" manufactured by Powdertech Corporation, and "M03S" and "M10S" manufactured by JFE Chemical Corporation. Examples of the magnetic material include "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", "KNI-109", "KNI-109GSM", and "KNI-109GS" manufactured by Toda Kogyo Co., Ltd., "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-714", and "BSN-828" manufactured by Toda Kogyo Co., Ltd., and "JR09P2" manufactured by Japan Metals and Chemical Industries Co., Ltd. One type of magnetic material may be used alone, or two or more types may be used in combination.

[0031] The shape of the magnetic powder is not particularly limited, and examples thereof include spherical, needle-like, plate-like, scaly, hollow, irregular, hexagonal, cubic, and flaky shapes.

[0032] The average particle size of these magnetic powders can be appropriately selected in consideration of dispersibility in liquid components, filling properties in holes, smoothness when a wiring layer is formed on the filled portions, etc. The average particle size of the magnetic powder is preferably in the range of 0.1 μm to 25 μm, more preferably 0.1 μm to 15 μm. The average particle size means the average primary particle size, and the average particle size (D50) can be measured by a laser diffraction / scattering method.

[0033] The content ratio of the magnetic powder in the entire liquid magnetic composition can be appropriately selected depending on the application of the liquid magnetic composition. For example, when the liquid magnetic composition is used as a curable resin composition, the magnetic powder is preferably contained in an amount of 60 to 94 mass % of the entire liquid magnetic composition, more preferably 75 to 94 mass %, and even more preferably 85 to 94 mass %. By setting the content of the magnetic powder within the above range, it is possible to achieve a higher level of compatibility between the characteristics such as noise suppression and the filling property of the curable resin composition.

[0034] From the viewpoint of uniform dispersion in the liquid magnetic composition, a dispersant may be used in combination. As the dispersant, a phosphoric acid ester having an acidic group or a basic group or both, an acrylic copolymer, a polyamine, a polyurethane, a polyester, a polyacrylate, and their phosphates, alkyl ammonium salts, etc., can be suitably used. The above-mentioned dispersants may be used alone or in combination.

[0035] <Liquid components> In the present invention, it is preferable to use at least one of the group consisting of a solvent and a liquid resin component as the liquid component. In this specification, "liquid" refers to a liquid state having fluidity at 25°C, and includes not only liquid but also semi-liquid (paste) forms. Each component constituting the liquid component will be described in detail below.

[0036] (solvent) The liquid magnetic composition obtained by the present invention may contain a solvent. In the liquid magnetic composition, the solvent can function as a dispersion medium for the magnetic powder. In addition, in the liquid magnetic composition, the solvent can function as a dilution solvent for adjusting the viscosity of the composition by using it together with the liquid resin component.

[0037] Examples of the solvent include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as methyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, and acetate esters of the above glycol ethers; alcohols such as ethanol, propanol, ethylene glycol, and propylene glycol; aliphatic hydrocarbons such as octane and decane; and organic solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. These can be used alone or in combination of two or more.

[0038] (liquid resin component) The liquid magnetic composition obtained by the present invention may contain a curable resin as a liquid resin component. As the curable resin, any resin that can be cured by heat or light can be used without particular limitation, and both a thermosetting resin and a photocurable resin may be included. Among them, a thermosetting resin is preferable.

[0039] "Thermosetting resin" As the thermosetting resin, an epoxy resin can be suitably used. Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, hydrogenated bisphenol A type epoxy resins, brominated bisphenol A type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene type epoxy resins, triphenylmethane type epoxy resins, and the like. These may be used alone or in combination of two or more.

[0040] Examples of commercially available epoxy resins include jER 828, 806, 807, YX8000, YX8034, and 834 manufactured by Mitsubishi Chemical Corporation; YD-128, YDF-170, ZX-1059, and ST-3000 manufactured by Nippon Steel Chemical & Material Co., Ltd.; EPICLON 830, 835, 840, 850, N-730A, and N-695 manufactured by DIC Corporation; and RE-306 manufactured by Nippon Kayaku Co., Ltd.

[0041] The blending amount of the thermosetting resin is preferably 3% by mass or more and 25% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the entire liquid magnetic composition.

[0042] "Hardening agent" The liquid magnetic composition obtained by the present invention may contain a curing agent for curing the above-mentioned thermosetting resin. As the curing agent, known curing agents generally used for curing thermosetting resins can be used, such as amines, imidazoles, polyfunctional phenols, acid anhydrides, isocyanates, and polymers containing these functional groups, and a plurality of these may be used as necessary. As the amines, there are dicyandiamide, diaminodiphenylmethane, and the like. As the imidazoles, there are alkyl-substituted imidazoles, benzimidazoles, and the like. In addition, the imidazole compound may be an imidazole latent curing agent such as an imidazole adduct. As the polyfunctional phenols, there are hydroquinone, resorcinol, bisphenol A and its halogen compounds, and further, novolacs and resol resins which are condensates of bisphenol A and aldehydes. As the acid anhydrides, there are phthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, benzophenonetetracarboxylic acid, and the like. The isocyanates include tolylene diisocyanate, isophorone diisocyanate, etc., and these isocyanates may be used after being masked with phenols, etc. These curing agents may be used alone or in combination of two or more kinds.

[0043] Among the above-mentioned curing agents, amines and imidazoles can be preferably used from the viewpoints of adhesion to the conductive part and the insulating part, storage stability, and heat resistance. Preferred are those mainly composed of adduct compounds of aliphatic polyamines such as alkylenediamines having 2 to 6 carbon atoms, polyalkylenepolyamines having 2 to 6 carbon atoms, and aromatic ring-containing aliphatic polyamines having 8 to 15 carbon atoms, or adduct compounds of alicyclic polyamines such as isophoronediamine and 1,3-bis(aminomethyl)cyclohexane, or mixtures of the adduct compounds of the above-mentioned aliphatic polyamines and the adduct compounds of the above-mentioned alicyclic polyamines.

[0044] The adduct compound of the aliphatic polyamine is preferably one obtained by addition reaction of the aliphatic polyamine with aryl glycidyl ether (particularly phenyl glycidyl ether or tolyl glycidyl ether) or alkyl glycidyl ether. The adduct compound of the alicyclic polyamine is preferably one obtained by addition reaction of the alicyclic polyamine with n-butyl glycidyl ether, bisphenol A diglycidyl ether, or the like.

[0045] Examples of the aliphatic polyamines include alkylenediamines having 2 to 6 carbon atoms, such as ethylenediamine and propylenediamine, polyalkylenepolyamines having 2 to 6 carbon atoms, such as diethylenetriamine and triethylenetriamine, and aromatic ring-containing aliphatic polyamines having 8 to 15 carbon atoms, such as xylylenediamine. Commercially available examples of modified aliphatic polyamines include Fujicure FXE-1000, Fujicure FXR-1020, Fujicure FXR-1030, Fujicure FXR-1080, Fujicure FXR-1090M2 (manufactured by Fuji Chemical Industry Co., Ltd.), Ancamine 2089K, Sanmaid P-117, Sanmaid X-4150, Ancamine 2422, Surwet R, Sanmaid TX-3000, and Sanmaid A-100 (manufactured by Air Products Japan Co., Ltd.).

[0046] Examples of alicyclic polyamines include isophorone diamine, 1,3-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, norbornene diamine, 1,2-diaminocyclohexane, and laromine. Commercially available modified alicyclic polyamines include, for example, Ancamine 1618, Ancamine 2074, Ancamine 2596, Ancamine 2199, Sanmaido IM-544, Sanmaido I-544, Ancamine 2075, Ancamine 2280, Ancamine 1934, Ancamine 2228 (manufactured by Air Products Japan Co., Ltd.), Daitoclar F-5197, Daitoclar B-1616 (manufactured by Daito Sangyo Co., Ltd.), Fujicure FXD-821, Fujicure 4233 (manufactured by Fuji Chemical Industry Co., Ltd.), jER Cure 113 (manufactured by Mitsubishi Chemical Corporation), and Laromine C-260 (manufactured by BASF Japan Co., Ltd.).Other examples of polyamine-type curing agents include EH-5015S (manufactured by ADEKA Corporation).

[0047] The imidazoles include, for example, reaction products of epoxy resins and imidazole, etc. Examples of the imidazoles include 2-methylimidazole, 4-methyl-2-ethylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, etc. Examples of commercially available imidazole compounds include imidazoles such as 2E4MZ, C11Z, C17Z, and 2PZ, imidazole AZINE compounds such as 2MZ-A and 2E4MZ-A, imidazole isocyanurates such as 2MZ-OK and 2PZ-OK, and imidazole hydroxymethyl compounds such as 2PHZ and 2P4MHZ (all manufactured by Shikoku Chemical Industry Co., Ltd.). Examples of commercially available imidazole-type latent curing agents include Curesol P-0505 (manufactured by Shikoku Chemical Industry Co., Ltd.).

[0048] The blending amount of the curing agent is preferably 0.4% by mass or more and 2.5% by mass or less in terms of solid content with respect to the entire composition.

[0049] "Other ingredients" The liquid magnetic composition obtained by the present invention may contain a photocurable resin in combination with a thermosetting resin. Photocurable resins include curable resins that can be cured by radical addition polymerization reaction with active energy rays. Specific examples of radical addition polymerization reactive components having one or more ethylenically unsaturated groups in the molecule include commonly known polyester (meth)acrylates, polyether (meth)acrylates, urethane (meth)acrylates, carbonate (meth)acrylates, epoxy (meth)acrylates, etc. Specifically, diacrylates of glycols such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, and propylene glycol; acrylamides such as N,N-dimethylacrylamide, N-methylolacrylamide, and N,N-dimethylaminopropylacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; polyhydric alcohols such as hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, and tris-hydroxyethyl isocyanurate, or polyhydric acrylates such as ethylene oxide adducts, propylene oxide adducts, and ε-caprolactone adducts thereof; phenoxyacrylamide, Polyhydric acrylates such as bisphenol A diacrylate, and ethylene oxide adducts or propylene oxide adducts of these phenols; polyhydric acrylates of glycidyl ethers such as glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; and, without being limited to the above, acrylates and melamine acrylates obtained by directly acridating polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadienes, and polyester polyols, or by urethane acridating them via diisocyanates, and at least one of the methacrylates corresponding to the above acrylates. In this specification, (meth)acrylate is a general term for acrylates, methacrylates, and mixtures thereof, and the same applies to other similar expressions.The above-mentioned photocurable resin is preferably in a liquid state.

[0050] To the liquid magnetic composition obtained by the present invention, a filler treated with a fatty acid to impart thixotropy, or an amorphous filler such as organic bentonite or talc can be added.

[0051] The liquid magnetic composition obtained by the present invention may contain a silane coupling agent, which improves the adhesion between the magnetic powder or filler and the thermosetting resin, and makes it possible to suppress the occurrence of cracks in the cured product.

[0052] The liquid magnetic composition obtained by the present invention may further contain an oxazine compound having an oxazine ring obtained by reacting a phenolic compound, formalin, and a primary amine, if necessary. By containing the oxazine compound, when the liquid magnetic composition obtained by the present invention is used as a curable resin composition, when the curable resin composition filled in the hole of a printed wiring board is cured and then electroless plating is performed on the formed cured product, the liquid magnetic composition can easily roughen the cured product with an aqueous potassium permanganate solution or the like, and can improve the peel strength with the plating.

[0053] Furthermore, known colorants such as phthalocyanine blue, phthalocyanine green, disazo yellow, titanium oxide, carbon black, and naphthalene black may be added to the liquid magnetic composition obtained by the present invention.

[0054] In addition, known thermal polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, tert-butylcatechol, pyrogallol, and phenothiazine can be added to impart storage stability during storage, and known thickeners and thixotropic agents such as clay, kaolin, organic bentonite, and montmorillonite can be added to adjust viscosity. In addition, known additives such as silicone-based, fluorine-based, and polymer-based defoamers, leveling agents, and adhesion-imparting agents such as imidazole-based, thiazole-based, triazole-based, and silane coupling agents can be added. In particular, when organic bentonite is used, the part protruding from the hole surface is easily formed into a protruding state that is easy to polish and remove, and it is preferable because it has excellent polishability.

[0055] In consideration of coatability (printability), the liquid magnetic composition obtained by the present invention preferably has a viscosity of 0.01 to 10 Pa s, and more preferably 0.1 to 5 Pa s. The viscosity of the liquid magnetic composition can be adjusted by the blending amounts of the above-mentioned liquid components, the type and blending amount of the magnetic powder, etc.

[0056] <Applications of liquid magnetic composition> The liquid magnetic composition obtained by the present invention can be used for a wide range of general purposes. In particular, when the liquid magnetic composition obtained by the present invention is used as a curable resin composition, it is preferably used for forming a cured film for a printed wiring board, more preferably for forming a permanent protective film, and even more preferably for use as a solder resist, an interlayer insulating layer, a coverlay, and an intercircuit filler. The liquid magnetic composition obtained by the present invention may be used in a liquid form, or may be made into a dry film as described below.

[0057] [Dry film] The liquid magnetic composition of the present invention can also be used in the form of a dry film comprising a first film and a resin layer obtained from the liquid magnetic composition formed on the first film. The first film in the dry film of the present invention refers to a film that is at least adhered to the resin layer when the film is integrally molded by laminating the dry film by heating or the like onto a substrate or other base material so that the resin layer obtained from the liquid magnetic composition formed on the dry film is in contact with the dry film. The first film may be peeled off from the resin layer in a process after lamination.

[0058] [Dry film manufacturing method] The method for manufacturing a dry film of the present invention involves applying the liquid magnetic composition obtained by the above-mentioned method for manufacturing a liquid magnetic composition of the present invention onto a first film, drying it, and obtaining a dry film using the obtained magnetic composition as a resin layer.

[0059] In one embodiment of the present invention, a method for manufacturing a dry film includes the following steps. A step of obtaining a liquid magnetic composition by the method for producing a liquid magnetic composition of the present invention. Applying the liquid magnetic composition to one side of a first film. A step of drying the applied liquid magnetic composition to form a resin layer on one surface of the first film.

[0060] Specifically, the method for producing a dry film involves diluting the liquid magnetic composition obtained by the method for producing a liquid magnetic composition of the present invention with an organic solvent to adjust the viscosity to an appropriate level, applying the mixture to a uniform thickness on the first film using a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, or the like, and drying the mixture at a temperature of 50 to 130° C. for 1 to 30 minutes to obtain a film. There are no particular limitations on the thickness of the applied film, but the thickness after drying is generally selected appropriately within the range of 1 to 150 μm, preferably 5 to 80 μm.

[0061] As the first film, any known film can be used without any particular limitation, and for example, a film made of a thermoplastic resin such as a polyester film such as polyethylene terephthalate or polyethylene naphthalate, a polyimide film, a polyamideimide film, a polypropylene film, or a polystyrene film can be suitably used. Among these, a polyester film is preferred from the viewpoints of heat resistance, mechanical strength, handling, etc. A laminate of these films can also be used as the first film.

[0062] From the viewpoint of improving mechanical strength, the above-mentioned thermoplastic resin film is preferably a film stretched in a uniaxial or biaxial direction.

[0063] The thickness of the first film is not particularly limited, but can be, for example, 10 μm to 150 μm.

[0064] After forming a resin layer of the liquid magnetic composition obtained by the method for producing a liquid magnetic composition of the present invention on the first film, it is preferable to further laminate a peelable second film on the surface of the resin layer for the purpose of preventing dust from adhering to the surface of the resin layer, etc. The second film in the method for producing a dry film of the present invention refers to a film that is peeled off from the resin layer before lamination when the dry film is laminated by heating or the like so that the resin layer side of the dry film is in contact with a base material such as a substrate to be integrally molded.

[0065] The second film that can be peeled off from the resin layer may be, for example, a polyethylene film, a polytetrafluoroethylene film, a polypropylene film, surface-treated paper, etc., as long as the adhesive strength between the resin layer and the second film is smaller than the adhesive strength between the resin layer and the first film when the second film is peeled off.

[0066] The thickness of the second film is not particularly limited, but can be, for example, 10 μm to 150 μm. EXAMPLES

[0067] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following, "parts" and "%" are all based on mass unless otherwise specified.

[0068] <Preparation of liquid magnetic composition> As the liquid magnetic composition, the following thermosetting resin composition was prepared.

[0069] (Example 1) Powdertech Co., Ltd. M03S (Mn-based ferrite, magnetic powder) 60 parts, DIC Corporation N740 (phenol novolac type epoxy resin) 15 parts, Mitsubishi Chemical Corporation YX-6954BH30 (phenoxy resin) 5 parts, HF-4M (curing agent) 9 parts, Shikoku Chemical Industry Co., Ltd. 2E4MZ (imidazole curing accelerator) 1 part, and cyclohexanone 10 parts were mixed and premixed, and dispersed using a bead mill (Mitsui Mining Co., Ltd.). Next, the mixture obtained after the dispersion treatment was filtered using a nonmetallic 500 mesh (opening: 25 μm). As a result, a thermosetting resin composition of Example 1 was obtained.

[0070] (Example 2) Powdertech Co., Ltd. M03S (Mn-based ferrite, magnetic powder) 60 parts, DIC Corporation N740 (phenol novolac type epoxy resin) 15 parts, Mitsubishi Chemical Corporation YX-6954BH30 (phenoxy resin) 5 parts, HF-4M (curing agent) 9 parts, Shikoku Chemical Industry Co., Ltd. 2E4MZ (imidazole curing accelerator) 1 part, and cyclohexanone 10 parts were mixed and premixed, and dispersed using a bead mill (Mitsui Mining Co., Ltd.). As a result, a thermosetting resin composition of Example 2 was obtained.

[0071] (Example 3) The classified M10S (Mn-based ferrite, magnetic powder) manufactured by Powdertech Co., Ltd. (60 parts), N740 (phenol novolac type epoxy resin) manufactured by DIC Corporation (15 parts), YX-6954BH30 (phenoxy resin) manufactured by Mitsubishi Chemical Corporation (5 parts), HF-4M (curing agent) (9 parts), 2E4MZ (imidazole curing accelerator) manufactured by Shikoku Chemical Industry Co., Ltd. (1 part), and cyclohexanone (10 parts) were mixed and premixed, and dispersed using a bead mill (manufactured by Mitsui Mining Co., Ltd.). As a result, a thermosetting resin composition of Example 3 was obtained.

[0072] (Example 4) Unclassified M10S (Mn-based ferrite, magnetic powder) 60 parts, DIC Corporation N740 (phenol novolac type epoxy resin) 15 parts, Mitsubishi Chemical Corporation YX-6954BH30 (phenoxy resin) 5 parts, HF-4M (curing agent) 9 parts, Shikoku Chemical Industry Co., Ltd. 2E4MZ (imidazole curing accelerator) 1 part, and cyclohexanone 10 parts were mixed and premixed, and dispersed using a bead mill (Mitsui Mining Co., Ltd.). As a result, a thermosetting resin composition of Example 4 was obtained.

[0073] <Method of measuring particle size distribution> The particle size distribution of each of the magnetic powders in Examples 1 to 4 was measured using a particle size distribution measuring device (Microtrac MT3300EXII, Microtrac BEL Co., Ltd., solvent: DPM). The results are shown in Table 1 below.

[0074] <Method of measuring grain value> The thermosetting resin compositions of Examples 1 to 4 were each applied to a grind gauge (SU2050MHJ, manufactured by Daiichi Sokhan Seisakusho Co., Ltd.) using a scraper (SK9225, manufactured by Daiichi Sokhan Seisakusho Co., Ltd.), the scale was read at 10.0 μm intervals, and the upper limit of the range in which 5 or more particles were observed was taken as the particle value. The results are shown in Table 1 below.

[0075] <How to make an evaluation board> Each of the thermosetting resin compositions of Examples 1 to 4 was applied to a carrier film (PET film; Toyobo Co., Ltd. TN-200, thickness 38 μm) using a bar coater so that the resin layer had a thickness of 70 μm after drying. Using an IR drying oven, the resin layer was dried at 70 to 120° C. (average 110° C.) for 5 to 10 minutes so that the residual solvent in the resin layer was 0.5 to 2.5% by mass. Using a vacuum laminator (MVLP-500 manufactured by Meiki Seisakusho) set at 60°C, one black resin layer was laminated onto an 18 μm copper foil, and the carrier film was peeled off. Another black resin layer was laminated onto the peeled surface to form a double black resin layer. A cured coating was formed by heat treatment at 100°C for 30 minutes and 170°C for 30 minutes using a hot air circulation drying oven (DF610, manufactured by Yamato Scientific Co., Ltd.). The copper foil was peeled off from the cured coating and the cured coating was cut into a size of 1 cm x 3 cm.

[0076] <Evaluation method of relative permeability and magnetic loss> The thermosetting resin compositions of Examples 1 to 4 were each measured for relative permeability (μ') and magnetic loss at a temperature of 25°C and a frequency of 10 MHz to 1 GHz using an evaluation device (E5071C ENA Vector Network Analyzer, manufactured by Keysight Technologies), and the average values ​​were calculated for five points around 100 MHz. The results are shown in Table 1 below.

[0077] [Table 1]

[0078] As shown in Table 1, when comparing Example 1 and Example 2, since magnetic powders with similar particle size distributions were used, the relative permeability was similar, but it was confirmed that the particle value and magnetic loss value of Example 1 were smaller than those of Example 2. Both Examples 1 and 2 used magnetic powders that had not been classified in advance, but in Example 1, the mixture obtained after the dispersion treatment was filtered, so it is presumed that the coarse particles and agglomerates of the magnetic powder in the thermosetting resin composition were removed, resulting in a smaller particle value and magnetic loss value.

[0079] In addition, when comparing Example 3 and Example 4, it was confirmed that the relative magnetic permeability was similar, and the particle value and magnetic loss values ​​were also similar, because magnetic powders with similar particle size distributions were used. In Example 3, it is presumed that the particle value and magnetic loss values ​​were similar to those of Example 4, because coarse particles and aggregates of the magnetic powder generated during the premixing and dispersion processes were contained in the thermosetting resin composition, despite the use of magnetic powders that had been classified in advance.

Claims

1. A method for producing a liquid magnetic composition comprising a magnetic powder and a liquid component, comprising: A method for producing a liquid magnetic composition, comprising filtering a mixture in which the magnetic powder is dispersed in the liquid component.

2. A first step of blending the magnetic powder and the liquid component to obtain a mixture of the magnetic powder and the liquid component; a second step of agitating the mixture to disperse the magnetic powder in the liquid component; and a third step of filtering the mixture in which the magnetic powder is dispersed in the liquid component to obtain a liquid magnetic composition.

3. 3. The method for producing a liquid magnetic composition according to claim 1, wherein at least one selected from the group consisting of a solvent and a liquid resin component is used as the liquid component.

4. The method for producing a liquid magnetic composition according to claim 3 , wherein the liquid resin component includes an epoxy resin.

5. Obtaining a liquid magnetic composition by the method for producing a liquid magnetic composition according to claim 1 or 2; applying the liquid magnetic composition to one side of a first film; and drying the liquid magnetic composition to form a resin layer on one side of the first film.

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