Magnetic flexible member and method for manufacturing the same

Abstract

To provide a magnetic flexible member that can be bent and mounted so as to follow the three-dimensional shape of a member to be mounted, such as an inductor, without destroying the structure.SOLUTION: A magnetic flexible member 1 includes a base film 2, an undercoat 3, and a main coat 4 laminated in this order. The base film 2 is made of a flexible resin material. The undercoat 3 is for attaching the main coat 4 to the base film 2, the main coat 4 is formed of a magnetic composite material including a fine powder soft magnetic material 11 and a resin material 12, and a microcrack 7 is provided in the main coat 4 in a direction perpendicular to the surface of the base film 2.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a magnetic flexible member formed by forming a magnetic composite material containing a fine powder soft magnetic material and a resin material, which is attached to an inductor or the like, into a flexible thin plate shape such as a tape shape or a sheet shape, and a method for manufacturing the same.

[0002] [Sustainable Development Goals and Environmental Measures - Electrification and Energy Saving] Air pollution caused by the use of fossil fuels and the deterioration of the global environment due to carbon dioxide emissions have led to global climate change. Along with the search for new energy utilization to solve this problem, there is a demand for innovative technological improvements for further expansion of the use of electrical energy and energy saving for the realization of a decarbonized society. In particular, the replacement of internal combustion engines that burn fossil fuels with electric motors that use the power of storage batteries is remarkable in the field of automobiles, and technological innovation and competition for this purpose are becoming active worldwide. As an energy-saving issue, along with improvements in basic performance such as high-performance storage batteries with large storage capacities and electric motors that can be driven efficiently, in inductors such as coils and transformers used in electrical devices for using electricity, improvement in environmental performance such as reduction of power loss generated during energization is raised.

[0003] [Reduction of Power Loss in Electrical Equipment] As methods for reducing power loss in an inductor, there are reduction of the electrical resistance of the inductor, expansion of the current density of the inductor, reduction of the eddy current of the inductor, etc., and optimization of the material, shape, structure, etc. of the inductor has been carried out. By applying a fine powder soft magnetic material to the surface of the inductor, the magnetic field diffusing from the inductor to the outside is confined as an eddy current in the fine powder soft magnetic material, and the power loss due to the leakage magnetic flux generated in the inductor and adjacent inductors can be reduced. In this case, the fine powder soft magnetic material is preferably spherical,块状, or flat powder. The selection of these fine powder soft magnetic material powders depends on the material, shape, structure, etc. of the inductor to be used, as well as the magnitude and frequency of the alternating current to be energized. Generally, in the case of an alternating current with a high frequency, a fine powder soft magnetic material with a small particle size is good.

[0004] [Reducing magnetic loss by applying finely powdered soft magnetic material to inductors] It has been demonstrated through computer simulations and experiments described in Patent Document 1 that power loss can be reduced by applying a fine soft magnetic material to the surface of an inductor. To apply this to actual inductors, there are two methods: one is to mix the fine soft magnetic material with a resin material to make a paste, which is then applied to the surface of the inductor using an adhesive or glue; the other is to mix the fine soft magnetic material with a resin material to make a flexible thin sheet or tape, which is then attached or wrapped around the surface of the inductor using an adhesive or glue. The specifications of the paste or tape form are an important issue for application to inductors. In particular, when considering the manufacturing method and work for application to inductors, the flexible thin sheet form such as a tape allows for more uniform control of the amount of fine soft magnetic material applied, is easier to handle in terms of supply and transportation, and can be applied to various inductors without the use of special equipment, thus offering a greater practical advantage over the paste form.

[0005] [Required functions for magnetic flexible members to achieve power loss reduction] To date, there have been many types of magnetic tapes and magnetic sheets using fine soft magnetic material, and they have been applied to various inductors. For example, as described in Patent Document 2, there are tape-like or sheet-like materials that suppress GHz-band harmonic noise generated from communication equipment, but none are directly applicable to inductors. The reason for this is that the power applied to the inductor is relatively large, and the heat generated is also large, so the magnetic tape is required to have electrical insulation and heat resistance. Furthermore, the current is large, so the magnetic energy loss is also large, and in order to secure a large amount of fine soft magnetic material to suppress the loss, the thickness of the magnetic tape must be increased, which presents structural and manufacturing difficulties for magnetic tapes.

[0006] [Constraints on magnetic flexible materials for application to inductors] To ensure electrical insulation, it is necessary to apply insulating material to the magnetic tape (magnetic flexible material), even partially. Furthermore, to ensure heat resistance, all materials constituting the magnetic tape must be heat-resistant. In particular, when heat resistance is required for the resin material into which the fine soft magnetic material is mixed, such as silicone resin, the hardness after drying or firing is high, and when applied to magnetic tape, the flexibility (bendability) is poor, making it difficult to wrap around the inductor at corners with small radii or chamfers. In addition, if wrapping is forced, the internal stress of the resin holding the fine soft magnetic material exceeds the allowable value, destroying the structure of the magnetic tape. Therefore, in order to realize a magnetic tape that satisfies the required power loss reduction, electrical insulation, and heat resistance, providing the necessary flexibility for wrapping is a critical challenge. Although this has been explained in the context of inductors, similar challenges exist for magnetic flexible materials attached to magnetic circuit components and electronic components that reach high temperatures. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-018585 [Patent Document 2] Japanese Patent Publication No. 2014-192327 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention was made to solve the aforementioned problems, and aims to provide a magnetic flexible member that can be bent to conform to the three-dimensional shape of a member to be attached, such as an inductor, without damaging its structure, and a method for manufacturing the same. [Means for solving the problem]

[0009] The magnetic flexible member described in claim 1 is laminated in the order of base film, undercoat, and main coat. The main coat side is a magnetic flexible member that is attached to the member to be attached,The base film is made of a flexible resin material, the undercoat is for applying the main coat to the base film, the main coat is made of a magnetic composite material containing fine soft magnetic material and resin material, and the main coat has microcracks provided in a direction perpendicular to the surface of the base film. The microcracks are formed such that the crack width on the side closer to the base film is narrower than the crack width on the side opposite to the base film, and when attached to the member to be attached, the microcracks narrow, and the cracks are formed with a width that allows the magnetic composite materials sandwiching the microcracks to come into contact with each other, and the resin material of the main coat and the undercoat mix near the boundary, and the end of the microcrack on the undercoat side is inside the undercoat. It is characterized by the following.

[0012] Claim 2 The magnetic flexible member described herein is the one described in claim 1, characterized in that the microcracks are provided at intervals of 1 mm or less.

[0013] Claim 3 The magnetic flexible member described herein is the one described in claim 1, and the main coat is characterized in that it partially has voids where the fine soft magnetic material and the resin material are not present.

[0014] Claim 4 The magnetic flexible member described herein is the same as that described in claim 1, and is characterized in that, when the base film is formed in a long length, it has at least the minute cracks in which grooves extend at an angle of approximately -60° to +60° in the plane direction of the base film, with reference to the short direction of the long base film.

[0015] Claim 5 The magnetic flexible member described herein is the one described in claim 1, characterized in that the main coat has a top coat laminated on the side opposite to the base film.

[0016] Claim 6 The method for manufacturing a magnetic flexible member described herein involves laminating a base film, an undercoat, and a main coat in that order. The main coat side is attached to the member to be attached. A method for manufacturing a magnetic flexible member, wherein the base film is made of a flexible resin material, the undercoat is for applying the main coat to the base film, and the main coat is made of a magnetic composite material containing a fine soft magnetic material and a resin material. Then, the undercoat is laminated onto the base film, and the raw materials for the main coat, which are a slurry obtained by mixing the solvent that dissolves the undercoat and the resin material, the fine soft magnetic material, and the resin material, are applied to the undercoat and cured to laminate the main coat. The laminated product of the base film, undercoat, and main coat Magnetic material , While bending the main coat toward the base film, By applying an external tensile force to the main coat, minute cracks are formed in the main coat in a direction perpendicular to the surface of the base film. Furthermore, the microcracks are shaped such that the crack width on the side closer to the base film is narrower than the crack width on the side opposite the base film. When attached to the member to be mounted, the microcracks narrow, resulting in a crack width that allows the magnetic composite materials sandwiching the microcracks to come into contact. The angle at which the main coat is bent toward the base film and the external tensile force are set to form the microcracks so that the end of the microcrack on the undercoat side is inside the undercoat. This is the gist of the invention.

[0017] Claim 7 The method for manufacturing a magnetic flexible member according to claim 6 is as described in claim In the process of applying a tensile force to the main coat of the magnetic member while bending the main coat toward the base film, the magnetic member is brought into contact with a flat plate in a direction in which the main coat is in contact with it, and a block having a chamfered corner where the right-angle corner is beveled at a 45° angle is pressed against the base film, and the magnetic member is pulled by the tensile force while bending the main coat toward the base film at the position of the corner of the block. and is characterized by forming the minute cracks. The method for manufacturing the magnetic flexible member described in claim 8 is the same as that described in claim 7, characterized in that the chamfer amount of the corner of the block is C0.1 to 0.5 mm.

[0018] Claim 9 The method for manufacturing a magnetic flexible member according to claim 6 is as described in claim

[0019] and, when the base film is long, the minute cracks are formed by applying the external tensile force one or more times at an angle of -60° or more and +60° or less with respect to the surface direction of the base film, based on the longitudinal direction of the long base film. 10 Claim 6 The method for manufacturing a magnetic flexible member according to claim

[0020] is as described in claim 11 and is characterized by forming a product that partially has voids where the fine soft magnetic material and the resin material are absent when forming the main coat. 6 Claim The method for manufacturing a magnetic flexible member according to claim

[0021] The magnetic flexible member to which the present invention is applied is laminated in the order of base film, undercoat, and main coat. The main coat is formed of a magnetic composite material containing fine soft magnetic material and resin material, and microcracks are provided in the main coat perpendicular to the surface of the base film. This allows the main coat to be bent to conform to the three-dimensional shape of a member to be attached, such as an inductor, without damaging the structure.

[0022] When microcracks are formed such that the crack width on the side closer to the base film is narrower than the crack width on the side opposite the base film, the main coat can be bent significantly and easily with the base film facing outwards, making it easier to attach to the three-dimensional shape of the part to be fitted.

[0023] When the resin material of the main coat and the undercoat mix near the boundary, and the end of a microcrack on the undercoat side is within the undercoat, the main coat and undercoat are strongly bonded. Therefore, even if a microcrack is introduced into the brittle magnetic composite material, the propagation of the crack can be stopped at the boundary between the undercoat and the magnetic composite material, preventing the main coat from being destroyed.

[0024] When microcracks are spaced at intervals of 1 mm or less, the closer the spacing between the microcracks, the easier the magnetic flexible material is to bend, making it easier to conform to the three-dimensional shape of the part to be attached.

[0025] When the main coat partially contains voids where fine soft magnetic material and resin material are absent, microcracks can easily form, making the magnetic flexible member more flexible.

[0026] If the long base film has at least a few minute cracks that extend in the planar direction of the base film at an angle of approximately -60° to +60°, with the short side of the base film as the reference direction (0°), the magnetic flexible member will bend along the groove, making it easier to wrap the magnetic flexible member around the member to be attached in accordance with the angle of the groove.

[0027] If the top coat is laminated on the side of the main coat opposite to the base film, the main coat is protected. If the top coat also functions as an adhesive, tack, or double-sided tape, the magnetic flexible member can be attached to the member to be attached easily and quickly.

[0028] The method for manufacturing a magnetic flexible member to which the present invention applies involves laminating a base film, an undercoat, and a main coat, and then applying a tensile external force to the main coat, which is made of a magnetic composite material. This allows for the easy formation of microcracks in a direction perpendicular to the surface of the base film.

[0029] When the main coat is bent toward the base film while a tensile external force is applied to the main coat to form microcracks, microcracks can be formed efficiently and easily.

[0030] When forming microcracks by applying a tensile external force at an angle of -60° to +60° in the planar direction of a long base film, with the longitudinal direction of the base film as the reference (0°), the grooves of the microcracks can be formed at approximately any angle.

[0031] When forming the main coat, if a material is formed that partially contains voids where fine soft magnetic material and resin material are absent, microcracks are easily formed starting from these voids, thus allowing for easy formation of microcracks.

[0032] When a top coat is applied to the main coat side opposite the base film after forming microcracks, the fragile main coat can be protected. [Brief explanation of the drawing]

[0033] [Figure 1] This is a schematic perspective view showing the laminated structure of a magnetic flexible member (magnetic tape) to which the present invention is applied. [Figure 2] This is a schematic, partially enlarged cross-sectional view showing the structure of a magnetic flexible member (magnetic tape) to which the present invention is applied. [Figure 3] This is a schematic plan view of the main coat as seen from above, illustrating the direction of the grooves of the microcracks in the magnetic flexible member (magnetic tape) to which the present invention is applied. [Figure 4] This is a schematic diagram illustrating a method for manufacturing a magnetic flexible member (magnetic tape) to which the present invention is applied. [Figure 5] This is a schematic longitudinal cross-sectional view showing a method for manufacturing a magnetic flexible member (magnetic tape) to which the present invention is applied. [Figure 6] This is a schematic plan view illustrating a method for manufacturing a magnetic flexible member (magnetic tape) to which the present invention is applied. [Figure 7] These are diagrams and photographs showing the shape and appearance of the prepared measurement sample (example). [Figure 8] This is a graph showing the measurement results of the relative permeability in the example. [Figure 9] This is a photograph of a cross-section of the example taken with a scanning electron microscope (SEM). [Figure 10] These are magnified photographs of the surface of the example and photographs showing the measurement results of the surface unevenness depth. [Figure 11] This is a magnified photograph of the longitudinal section of the embodiment. [Modes for carrying out the invention]

[0034] The following describes embodiments for carrying out the invention, but the scope of the present invention is not limited to these embodiments.

[0035] Figure 1 shows a schematic perspective view of a magnetic flexible member 1 to which the present invention is applied. Figure 2 shows a schematic partially enlarged cross-sectional view of a magnetic flexible member 1 to which the present invention is applied. The magnetic flexible member 1 is formed in the form of a flexible thin plate (flexible thin plate). The magnetic flexible member 1 is configured as a laminated structure in which a base film 2, an undercoat 3, and a main coat 4 are laminated in that order. The base film 2 is made of a flexible resin material. The undercoat 3 is for attaching the main coat 4 to the base film 2. The main coat 4 is made of a magnetic composite material containing a fine soft magnetic material 11 and a resin material 12 (both see Figure 2). The main coat 4 has microcracks 7 (see Figure 2) provided perpendicular to the surface of the base film 2. If necessary, as shown in the same figure, a topcoat 5 may be laminated on the side of the main coat 4 opposite to the base film 2.

[0036] The figure shows an example of a magnetic flexible member 1, specifically a magnetic tape formed in the shape of a tape. This magnetic flexible member 1 is, for example, a magnetic tape that is wrapped around the outer surface of an inductor (a member to be attached). Hereinafter, the magnetic flexible member 1 to which the present invention is applied will also be referred to as magnetic tape 1. The magnetic flexible member 1 may also be a magnetic sheet formed in the shape of a sheet. The shape of the magnetic flexible member 1 is arbitrary. Since the magnetic flexible member 1 is used by being attached to a member to be attached, such as an inductor, it may be formed in a three-dimensional shape such as a bag or cover that corresponds to the three-dimensional shape of the member to be attached.

[0037] Before specifically describing the present invention, we will first explain the performance requirements for the magnetic tape 1 attached to the inductor, the background leading to the present invention, and an overview of the present invention.

[0038] [Reduction of power loss due to skin effect and proximity effect in inductors using magnetic composite materials] It is generally known that when an alternating current is applied to an inductor, eddy currents are generated inside the inductor due to the skin effect and proximity effect caused by the magnetic flux generated by the current, resulting in power loss as AC copper loss. Since AC copper loss raises the temperature of the inductor, generating heat and neutralizing the applied power, reducing AC copper loss is one of the challenges of energy saving. To minimize the skin effect and proximity effect, the structure and dimensions of the inductor are optimized according to the current value and frequency, but computer simulations and test evaluations have shown that applying fine soft magnetic material to the outer surface of the inductor is even more effective in reducing power loss.

[0039] [Reduction of power loss due to skin effect and proximity effect in inductors using magnetic composite materials] Applying fine soft magnetic material to the outer surface of an inductor is effective in reducing power loss, but the specifications of the fine soft magnetic material to be applied must be changed depending on the operating conditions and environment, such as the AC current value and frequency, and the structure of the inductor. For example, if the current value is high, the magnetic flux will be large, so a fine soft magnetic material of a material and mass that can handle a large saturation magnetic flux density is required, and if the frequency is high, a fine soft magnetic material with a small particle size is required. In addition, in order to increase the efficiency of the inductor, it is necessary to increase the packing factor when winding the copper or aluminum magnet wire used in the inductor, or to change the circular cross-section to a square cross-section, and this cannot be achieved simply by making the magnetic tape used thicker. Therefore, the resin material 12 used in the base film 2, undercoat 3, and main coat 4 must be selected according to the required material, particle size, and mass of the fine soft magnetic material 11 and the packing rate of the fine soft magnetic material 11 to the magnetic tape 1. Furthermore, there is a demand for weight reduction related to energy saving in inductors, and generally a magnetic tape 1 with a high packing rate of fine soft magnetic material is required. It should be noted that magnetic tapes for recording media, which have ferromagnetic materials coated onto the tape, are different in terms of the material and size of the fine magnetic particles used.

[0040] [Brittleness of a mixture of highly filled fine soft magnetic material and a resin material with high heat resistance and electrical insulation properties] Generally, inductors operate at high temperatures, and to prevent short circuits with other electrical components, the resin material 12 used in magnetic composite materials, which are manufactured by mixing fine soft magnetic material 11, requires heat resistance and electrical insulation. In particular, for inductors used in high-frequency, high-current, and high-temperature environments, heat resistance of 130°C or 200°C is required according to the UL510FR temperature rating, which sets the test standards for flame retardancy for electrical insulating adhesive tapes in the UL standard. Therefore, the resin material 12 constituting the magnetic tape 1 is selected from super engineering plastics such as silicone resin, Teflon (registered trademark) resin, and polyimide resin. These resin materials 12 come in many forms, such as hybrid materials mixed with one or more resin materials, and varnishes, powders, and flakes. In general, resin materials 12 are characterized by high strength, high hardness, and high elasticity. Since magnetic composite materials are mixed with the fine soft magnetic material 11 at a high filling rate, even if the resin material 12 is ductile, the composite material becomes brittle. Therefore, if the thickness of the magnetic tape 1 is increased, or if the magnetic tape 1 is attached to the inductor with a small radius of curvature, the inside of the magnetic composite material will break, resulting in partial detachment of the magnetic composite material or breakage of the magnetic tape 1.

[0041] [Improving the flexibility of magnetic tape by introducing microcracks into magnetic composite material] The magnetic composite material constituting the magnetic tape 1 is inherently brittle, making it difficult to wrap around and attach to an inductor as is. Therefore, the inventor considered that a tape structure that is microscopically discontinuous but macroscopically flexible would be ideal, by finely separating or decomposing the tape-like, elongated magnetic composite material into regular or random shapes, and then adhering or bonding these to the base film 2, a supporting material. After considering the materials, structure, manufacturing method, and process for producing the magnetic tape 1, the inventor arrived at the present invention's magnetic tape 1, which satisfies bending resistance despite its brittleness, by adhering or bonding the magnetic composite material to the base film 2 and then introducing microcracks 7 into the magnetic composite material.

[0042] [Suppression of fracture of magnetic composite materials caused by microcracks due to undercoating] Since the magnetic composite material is a composite material in which fine soft magnetic material 11 is embedded inside a resin material 12, the fine soft magnetic material 11 and the resin material 12 are not firmly bonded. Furthermore, tensile stress remains inside the resin material 12 due to volume shrinkage during drying, and because the resin material 12 is thin and narrow as a structural element within the composite material, internal stresses that are acceptable in a single resin material become excessive internal stresses in the resin material 12 of the composite material, making it prone to fracture. Therefore, when introducing microcracks into the magnetic composite material, if the magnetic composite material exists alone, the microcracks propagate rapidly and the magnetic composite material breaks. For this reason, in order to create a magnetic tape 1 into which microcracks 7 are introduced, a resin base film 2 is applied as a support material to maintain the structure and shape of the magnetic tape 1. In particular, since magnetic composite materials made of resin material 12 that require heat resistance and electrical insulation are brittle, the base film 2 is indispensable. Furthermore, since the adhesion between the resin material 12 of the magnetic composite material and the resin material of the base film 2 is generally low, an undercoat 3 consisting of an adhesive or tack agent is applied between the magnetic composite material and the base film 2 to improve adhesion.

[0043] [A magnetic tape with a four-layer structure consisting of a base film, undercoat, main coat, and topcoat.] By constructing a magnetic tape 1 consisting of three layers—a base film 2, an undercoat 3, and a main coat 4 of magnetic composite material—even if microcracks 7 are introduced into the magnetic composite material, the propagation of the cracks can be stopped at the boundary between the adhesive or tack of the undercoat 3 and the magnetic composite material. Therefore, even with a brittle magnetic composite material, a magnetic tape 1 with high bending resistance and excellent attachment to inductors can be obtained. Finally, to maintain the attachment state after attaching the magnetic tape 1 by wrapping it around the inductor, a topcoat 5 based on a heat-resistant and electrically insulating resin material suitable for the surface properties of the inductor to be wrapped is applied to the uppermost surface of the main coat 4 of the magnetic composite material, resulting in a final four-layer magnetic tape 1. The topcoat 5 is formed, for example, by applying an adhesive or tack. Note that the application of the adhesive or tack that forms the topcoat 5 does not affect the microcracks in the magnetic composite material, and the bending resistance of the magnetic tape 1 does not change. Furthermore, even if calendering is added perpendicular to the tape surface before application to improve the accuracy of the adhesive or bonding agent coating thickness, the stress will be in the same direction as the microcracks in the magnetic composite material, so the bending resistance of the magnetic tape will not change.

[0044] [Realizing magnetic tapes that meet requirements through manufacturing methods such as mixing, coating, drying, and processing.] As described above, by selecting the necessary fine soft magnetic material 11 and resin material 12, mixing them, applying and drying them onto the base film 2 (resin material film) to form the main coat 4, creating micro-cracks 7, adding calendering as needed, and applying a top coat 5 (adhesive or adhesive), a magnetic tape 1 is realized that achieves the required reduction in power loss and has excellent heat resistance, electrical insulation, and flexibility.

[0045] [Power loss reduction effect due to magnetic tape with excellent heat resistance, electrical insulation, flexibility, and ease of attachment] [An example of a method for forming microcracks] The magnetic tape 1 of the present invention utilizes the property that when a magnetic composite material, which is a mixture of a heat-resistant and electrically insulating resin material 12 and a finely powdered soft magnetic material 11 at a high filling rate to enhance the power reduction effect, dries and shrinks, high tensile stress is generated internally, causing it to undergo brittle fracture even with the application of small tensile stress. By applying an appropriate external force, microcracks are inflicted perpendicular to the tape surface, giving it high bending resistance despite being a brittle material, making it suitable for mounting inductors with small radii and chamfers.

[0046] [Required characteristics for magnetic tape] The required characteristics of magnetic tape 1 include electromagnetic, chemical, and physical aspects. Electromagnetic properties include power loss reduction, saturation magnetic flux density, and electrical insulation; chemical properties include heat resistance, adhesion / tackiness, and thermal conductivity; and physical properties include bending resistance, tensile strength, elongation, Young's modulus, bending stiffness, and dimensions. The electromagnetic properties, which perform the primary function, depend on the main material selected as the magnetic composite material, which is the main structure of magnetic tape 1. On the other hand, in order to meet the required characteristics of the tape, the required characteristics of the magnetic composite material, which makes up the majority of magnetic tape 1, are important, so the properties of the fine soft magnetic material 11 and resin material 12, which are the raw materials that make up the magnetic composite material, are important. For the other base film 2 and undercoat 3, the raw materials are selected according to the properties of the magnetic composite material, but for the topcoat 5, the raw materials are selected according to the surface properties of the inductor to which magnetic tape 1 is applied.

[0047] [Required properties for magnetic tape raw materials] As described above, the properties required for magnetic tape 1 are clear, but the main and auxiliary materials are selected as follows, taking into consideration the properties necessary to satisfy the manufacturing conditions for producing the magnetic tape. When selecting the fine soft magnetic material 11 from the main materials of the magnetic composite material, the electromagnetic properties of permeability, saturation magnetic flux density, coercivity, and resistivity are considered, the chemical properties of dispersibility, hydrophobicity / hydrophilicity, and hazard are considered, and the physical properties of spherical / flattened shape, particle size / diameter, and true density / bulk density are considered. When selecting the resin material 12, the chemical properties of molecular weight, dispersibility, hydrophobicity / hydrophilicity, heat resistance, hazard / toxicity, drying temperature, drying time, electrical insulation, thermal conductivity, and applicable solvent are considered, and the physical properties of density, viscosity, residual rate, shrinkage rate, and residual stress are considered. Furthermore, when selecting the base film 2 from the auxiliary materials of magnetic tape 1, the chemical properties of heat resistance and the physical properties of tensile strength, Young's modulus, and elongation are considered. When selecting the undercoat 3, the chemical properties of heat resistance and the physical properties of adhesion / tackiness are considered. When selecting topcoat 5, heat resistance as a chemical property and adhesion / tackiness as a physical property should be considered. When magnetic tape 1 is applied to an inductor, it is better to have as little of the material excluding the magnetic composite as possible, considering the efficiency and weight of the inductor, so the base film 2, undercoat 3, and topcoat 5 should be thin.

[0048] The above explains the performance requirements for magnetic tape, the background leading to the present invention, and an overview of the present invention.

[0049] Next, the magnetic flexible member 1 (magnetic tape 1) to which the present invention is applied will be described in detail with reference to Figures 1 to 3.

[0050] The base film 2 is formed in film form from a flexible resin material. The magnetic tape 1 is a magnetic flexible member 1 in which the base film 2 is formed in a long length (tape shape). As mentioned above, when attached to an inductor such as a coil or transformer, the base film 2 is required to have insulating properties as well as heat resistance. For this reason, as the base film 2, it is preferable to use a film (resin film) made of, for example, engineering plastics such as PET (polyethylene terephthalate), super engineering plastics such as PI (polyimide), PPS (polyphenylene sulfide), PEEK (polyether ether ketone), fluororesins such as PTFE (polytetrafluoroethylene), or silicone resin.

[0051] The thickness of the base film 2 is arbitrary, but as an example, a thickness of 10 μm to 100 μm is preferred.

[0052] The undercoat 3 is used to attach the main coat 4 to the base film 2, and is an adhesive, glue, or double-sided tape. The undercoat 3 needs to be flexible and heat resistant at the operating temperature. For this reason, for example, silicone resin adhesives, acrylic resin adhesives, urethane resin adhesives, and rubber adhesives can be preferably used as the undercoat 3.

[0053] The thickness of the undercoat 3 is arbitrary, but as an example, it is preferably an adhesive or tack material with a thickness of at least 5 μm. The undercoat 3 is preferably, for example, 5 μm to 100 μm thick.

[0054] It is preferable that the resin material 12 of the main coat 4 and the resin material of the undercoat 3 mix near the boundary, and that the end of the microcrack 7 on the undercoat 3 side is inside the undercoat 3. This mixing (coexistence) of the resin materials of the undercoat 3 and the main coat 4 near the boundary is preferable because it firmly bonds the undercoat 3 and the main coat 4. Even if a microcrack 7 is introduced into the magnetic composite material, the propagation of the crack can be stopped at the boundary between the undercoat 3 and the main coat 4. Therefore, even if the magnetic composite material is brittle, it will bend smoothly together with the base film 2 without falling off. As a result, the magnetic tape 1 has high bending resistance and excellent attachment to the inductor.

[0055] The main coat 4 is formed from a magnetic composite material containing fine soft magnetic material (soft magnetic powder) 11 and resin material 12, as shown within the circle in Figure 2. The main coat 4 is formed by mixing the fine soft magnetic material 11 and the resin material 12. It is preferable that the fine soft magnetic material 11 is uniformly dispersed in the resin material 12 in the main coat 4.

[0056] The shape of the fine soft magnetic material 11 is arbitrary. For example, one or more types of powders selected from spherical, lumpy, and flattened powders can be used as the fine soft magnetic material 11. Alternatively, powders of different shapes and sizes can be mixed and used as the fine soft magnetic material 11. For example, the fine soft magnetic material 11 is preferably spherical, lumpy, or flattened with a particle size or diameter of 1 μm to 100 μm.

[0057] The material of the fine soft magnetic material 11 is not limited as long as it is a soft magnetic material. For example, one or more types selected from iron powder, Si-Fe powder, amorphous powder, ferrite powder (Mn-Zn, Ni-Zn), Finemet® powder, Sendust powder, and Fe-Si-Al powder can be used as the fine soft magnetic material 11. Soft magnetic powder with its surface covered with an insulating material may also be used as the fine soft magnetic material 11.

[0058] The higher the amount of fine soft magnetic material 11, the better the magnetic properties. The fine soft magnetic material 11 is present in the main coat 4 in a nearly close-packed state at approximately 65-70% by weight (approximately 80% by weight under certain conditions). As an example, it is preferable that the fine soft magnetic material 11 is present in the main coat 4 at an amount of 80% to 20% by weight.

[0059] The resin material 12 must have heat resistance and insulating properties. When the mounted component is an inductor, UL standards require heat resistance of 130°C or 200°C. For this reason, it is preferable to use engineering plastics such as PET (polyethylene terephthalate) which have high heat resistance, super engineering plastics such as PI (polyimide), PPS (polyphenylene sulfide), and PEEK (polyether ether ketone), fluororesins such as PTFE (polytetrafluoroethylene), and silicone resins as the resin material 12.

[0060] For example, the resin material 12 is preferably contained in the main coat 4 in an amount of 30% to 60% by volume.

[0061] As shown in Figure 2, the main coat 4 has microcracks 7, which is a characteristic feature of the present invention. Because the main coat 4 has many microcracks 7 in a direction perpendicular to the base film 2, even if the magnetic composite material of the main coat 4 (fine powder soft magnetic material 11 and resin material 12) itself is difficult to deform, the main coat 4 (magnetic tape 1) can be bent at the grooves of the microcracks 7 to conform to the shape of the member to be attached.

[0062] The magnetic tape 1 is designed to be attached to the member to be mounted with the main coat 4 side (top coat 5 side), which is opposite to the base film 2. In other words, when the magnetic tape 1 is wrapped around the member to be mounted, it is bent towards the top coat 5 side. For this reason, as shown in the figure, it is preferable that the microcracks 7 are formed such that the crack width on the side closer to the base film 2 (the groove side) is narrower than the crack width on the side opposite to the base film 2 (the groove entrance side). When the crack width of the microcracks 7 is wider on the top coat 5 side and narrower on the base film 2 side, the magnetic tape 1 (main coat 4) can bend significantly towards the top coat 5 side without difficulty, making it easier to attach to the member to be mounted along its shape.

[0063] When the magnetic tape 1 is attached to the member to be attached, it is preferable that the fine soft magnetic material 11 is arranged in close proximity to each other. Therefore, when the magnetic tape 1 is attached to the member to be attached, it is preferable that the microcracks 7 are formed with a groove width such that the microcracks 7 narrow and the magnetic composite material on either side of the microcracks 7 comes into contact with each other.

[0064] The spacing P (pitch P) between the microcracks 7 is preferable to be narrower, as this makes it easier to bend the magnetic tape 1 (main coat 4). For example, the spacing P is preferably 1 mm or less. The magnetic flexible member 1 (main coat 4) bends in accordance with the groove direction of the microcracks 7. Therefore, it is preferable to form the groove direction of the microcracks 7 in accordance with the direction in which you want to bend the magnetic flexible member 1 (main coat 4). The more microcracks 7 there are, and the more the groove direction of the microcracks 7 is formed vertically and horizontally, the easier the magnetic tape 1 (main coat 4) becomes to bend. On the other hand, if the number of microcracks 7 increases, there will be more space in the main coat 4, making it difficult for the fine soft magnetic material 11 to be densely arranged. Therefore, the number of microcracks 7 should be set according to the need.

[0065] Furthermore, it is preferable that the main coat 4 partially has voids 21 where the fine soft magnetic material 11 and resin material 12 are not present. As will be described later, having voids 21 makes it easier for microcracks 7 to form.

[0066] Figure 3 shows a schematic plan view of the main coat 4 of the magnetic tape 1, viewed from above, to illustrate the groove direction of the microcracks 7.

[0067] In the figure, arrow L represents the longitudinal direction (length direction) of the magnetic tape 1, and arrow M represents the short direction (width direction) of the magnetic tape 1. The figure shows an example in which the groove direction of the microcrack 7 extends in the short direction M of the magnetic tape 1 (long base film 2). When the base film 2 is formed in a long length, as in the magnetic tape 1, it is preferable that the magnetic tape 1 has at least microcracks 7 whose grooves extend at an angle α of approximately -60° to +60° in the planar direction of the base film 2, with the short direction of the long base film 2 as the reference (0°). When the grooves of the microcracks 7 are formed at such an angle α, the magnetic tape 1 is easier to wrap around the member to be attached.

[0068] Figure (a) shows an example where at least a microcrack 7 is formed in the main coat 4, with the groove extending at an angle α of 0° with respect to the short direction M, as indicated by the dashed line Ka. Area 52a in Figure (a) shows an example where the groove of the microcrack 7 is formed continuously from end to end in the short direction M of the main coat 4. Area 51a in Figure (a) shows an example where the groove of the microcrack 7 is formed discontinuously from end to end in the short direction M of the main coat 4. Area 53a in Figure (a) shows an example where the groove of the microcrack 7 is formed continuously (or discontinuously) from end to end in the short direction M of the main coat 4, and also continuously (or discontinuously) in the longitudinal direction L. In this way, when at least a microcrack 7 is formed in the main coat 4 with the groove extending at an angle α of approximately 0° with respect to the short direction M, the magnetic tape 1 is easy to wrap around the member to be attached at an angle of 0° with respect to the longitudinal direction L. The more grooves there are in the microcracks 7, and the longer the grooves are continuous, the easier it is to wrap the magnetic tape 1 around the member to be attached.

[0069] Note that grooves are not formed in a straight line, but may actually be formed in a curved or zigzag shape. However, the angle of the groove can generally be determined by the approximate (average) angle in the straight-line direction over which the groove extends.

[0070] Figure (b) shows an example where at least a microcrack 7 is formed in the main coat 4, with the groove extending at an angle α (for example, 30°) with respect to the short direction M, as indicated by the dashed line Kb. Range 52b in Figure (b) shows an example where the groove of the microcrack 7 is formed continuously from end to end in the short direction M of the main coat 4. Range 51b in Figure (b) shows an example where the groove of the microcrack 7 is formed discontinuously from end to end in the short direction M of the main coat 4. Range 53b in Figure (b) shows an example where the groove of the microcrack 7 is formed continuously (or discontinuously) from end to end in the short direction M of the main coat 4, and also continuously (or discontinuously) in the longitudinal direction L. Thus, when at least a microcrack 7 is formed in the main coat 4 with the groove extending at approximately an angle α with respect to the short direction M, the magnetic tape 1 is easier to wrap around the member to be attached at an angle α with respect to the longitudinal direction L.

[0071] In this way, by forming the groove direction of the microcracks 7 in accordance with the angle at which the magnetic tape 1 is wrapped around the member to be attached, it becomes easier to wrap the magnetic tape 1, and the number of microcracks 7 can be minimized. As a result, the space in the main coat 4 can be reduced, making it easier to arrange the fine soft magnetic material 11 pieces closely together.

[0072] As shown in Figure 2, the top coat 5 is applied to the surface of the main coat 4. The top coat 5 protects the main coat 4. Since the magnetic tape 1 is intended to be attached to a mounting member such as an inductor with the top coat 5 side facing outwards, it is preferable if the top coat 5 is an adhesive, tack, or double-sided tape, as this eliminates the need to apply an adhesive or tack separately to the surface of the top coat 5, and allows for a thinner thickness. To protect the surface of the top coat 5, a release film or release paper may be applied to the surface of the top coat 5 until use.

[0073] The thickness of topcoat 5 is arbitrary, but as an example, a thickness of 5 μm to 50 μm is preferable.

[0074] Topcoat 5 includes, for example, silicone-based adhesives and acrylic adhesives.

[0075] The magnetic tape 1 may not have a top coat 5. In this case, the user can apply a top coat 5 of any material and attach it to the member to be attached.

[0076] Next, a method for manufacturing the magnetic flexible member 1 (magnetic tape 1) to which the present invention is applied will be described.

[0077] The manufacturing method for the magnetic flexible member 1 involves laminating a base film 2, an undercoat 3, and a main coat 4 in that order, and then applying a tensile external force to the main coat 4 to form microcracks 7 in the main coat 4 perpendicular to the surface of the base film 2.

[0078] Figure 4 shows an example of the manufacturing process for the magnetic flexible member 1. The explanation of the materials and other details of each component, which have already been described, is omitted here.

[0079] First, as shown in Figure (a), an undercoat 3 is laminated onto the base film 2. The undercoat 3 is formed, for example, by applying a liquid adhesive or adhesive (resin material) to the base film 2 and drying it as needed. Alternatively, base films 2 with the undercoat 3 already applied are commercially available and can be purchased and used.

[0080] Next, as shown in Figure (b), the raw materials 15 for the magnetic composite material, which is the raw material for the main coat 4, are prepared. The raw materials 15 for the magnetic composite material are made by mixing fine soft magnetic material 11, liquid resin material 12, and liquid solvent 13 to form a slurry.

[0081] When mixing fine soft magnetic material 11 and resin material 12, which have completely different properties, it is important to select raw materials according to their respective properties and to consider whether a small amount of solvent and additives such as binders and lubricants are necessary to resolve conflicting properties, and to note that these may be added during the mixing process as needed. Furthermore, if the conflicting properties cannot be resolved by additives alone, it is possible to improve the dispersibility during mixing by pre-treating the fine soft magnetic material 11, in particular, with plasma treatment, chemical reaction treatment, or dispersant application treatment. In order to sufficiently disperse the fine soft magnetic material 11 and resin material 12, a mixer such as stirring mixer, rotary mixer, or rotary orbital mixer is used, and the rotation speed, mixing time, and mixing temperature are set according to the properties of the fine soft magnetic material 11 and resin material 12, as well as the viscosity due to the packing rate of the fine soft magnetic material 11 and the amount of solvent added, in order to produce a slurry-like raw material 15 for the magnetic composite material.

[0082] Next, as shown in Figure (c), the raw materials 15 for the magnetic composite material are applied onto the undercoat 3 laminated on the base film 2. For application, a coating machine such as a die coater, roll coater, or doctor blade coater can be used. The slit width, roll width, blade gap, and application speed are set to achieve the required coating thickness.

[0083] Here, the solvent 13 in the raw material 15 of the magnetic composite material dissolves the resin material 12 of the magnetic composite material, but it is preferable that it also dissolves the undercoat 3, which is made of resin. In other words, it is preferable that the solvent 13 is both a solvent for the resin material 12 of the magnetic composite material and a solvent for the undercoat 3. In this case, when the raw material 15 of the magnetic composite material is applied to the undercoat 3, the solvent 13 dissolves the resin material of the undercoat 3, causing the resin material 12 of the magnetic composite material and the undercoat 3 to dissolve and mix together. As a result, the main coat 4 (magnetic composite material) and the undercoat 3 can be firmly bonded together.

[0084] Next, as shown in Figure (d), the raw material 15 of the magnetic composite material is cured to form the main coat 4a. The main coat 4a is in a state before the formation of microcracks 7. When curing the raw material 15 of the magnetic composite material, the solvent 13 in the raw material 15 evaporates and dries by drying by natural drying or heat drying. This drying of the solvent 13 reduces the volume of the raw material 15 (resin material 12). Since the fine soft magnetic material 11 in the raw material 15 is a solid, its volume does not decrease, but the volume of the resin material 12 decreases. As a result, voids 21 are partially formed in the vicinity of the reduced volume of the resin material 12 where the fine soft magnetic material 11 and resin material 12 are not present. The higher the packing density of the fine soft magnetic material 11, the more likely voids 21 are to form. For example, if the fine soft magnetic material 11 is packed to an almost close-packed state (65-70%), many voids 21 will be formed. Furthermore, due to the decrease in volume of the resin material 12, a large shrinkage stress (tensile stress) remains in the resin material 12.

[0085] The magnetic member 91, which has a three-layer structure consisting of a base film 2, an undercoat 3, and a main coat 4a (the main coat before the formation of microcracks 7), has almost no flexibility (bendability) because the main coat 4a is hard and thick.

[0086] Next, as shown in Figure (e), by applying a tensile external force F to the main coat 4a, microcracks 7 perpendicular to the surface of the base film 2 are formed in the main coat 4. Because there are many voids 21 in the main coat 4a and shrinkage stress remains in the resin material 12, many microcracks 7 can be easily formed in the resin material 12 by applying a tensile external force F to the main coat 4a. The microcracks 7 are formed when the resin material 12 tears.

[0087] Since the resin material 12 retains significant shrinkage stress and is fixed to the base film 2, the crack width of the microcracks 7 narrows as it approaches the base film 2. In other words, as shown in Figure 2, the microcracks 7 are formed in a shape where the crack width on the side closer to the base film 2 is narrower than the crack width on the side opposite the base film.

[0088] The magnetic flexible member 101, which has a three-layer structure consisting of a base film 2, an undercoat 3, and a main coat 4, becomes flexible because it has microcracks 7.

[0089] The process of applying a tensile external force F to the main coat 4a shown in Figure (e) may be performed multiple times. By performing this multiple times, a larger number of microcracks 7 can be formed.

[0090] Finally, as shown in Figure (f), a resin material such as an adhesive or tack, which will be the raw material for the top coat 5, is applied to the main coat 4, and dried as needed to form the top coat 5. This completes the magnetic flexible member 1.

[0091] Figure 5 shows a preferred example of a manufacturing process (the process in Figure 4(e)) in which a tensile external force F is applied to the main coat 4a to form microcracks 7. This example is a manufacturing method in which microcracks 7 are formed by bending the main coat 4 toward the base film 2 while applying a tensile external force F to the main coat 4 (base film 2).

[0092] As an example, a magnetic member 91 with a three-layer structure consisting of a base film 2, an undercoat 3, and a main coat 4a (the main coat before the formation of microcracks 7), created in the process shown in Figure 4(d), is brought into contact with a flat plate 31 as shown in Figure 5. The magnetic member 91 is positioned so that the main coat 4a is in contact with the plate 31. Next, a block 32 is pressed against the base film 2 of the magnetic member 91, bending the main coat 4a (magnetic member 91) toward the base film 2 at a predetermined bending angle θ while pulling at a predetermined arbitrary speed (pulling external force F). This bending and pulling external force F forms microcracks 7 in the main coat 4, and a three-layer magnetic flexible member 101 is manufactured. The density (number of generated) and groove width of the microcracks 7 can be adjusted by changing the bending angle θ and the pulling speed (external force F).

[0093] As shown by arrow S in Figure 5, the block 32 may be moved parallel to the plate 31 in the opposite direction to the direction in which the magnetic member 91 is pulled. Alternatively, the magnetic member 91 may be pulled out in the direction of arrow F while the position of the block 32 remains fixed.

[0094] The shape of block 32 is arbitrary. Preferably, the shape of block 32 is such that the cross-sectional shape of the corner portion 35, which is the part that bends the main coat 4 toward the base film 2, is chamfered (a shape having a chamfered corner portion 35), as shown in the figure. One example of chamfering is a C-chamfer, in which a right-angle corner is shaved off at a 45° angle. Depending on the thickness of the magnetic member 91, for example, the amount of chamfering C of the corner portion 35 of block 32 is preferably C0.1 to 0.5 mm. This is because if the corner portion 35 is not a sharp edge, it becomes difficult to create microcracks 7, and if it is too sharp, there is a risk of cutting the base film 2. The shape of block 32 may be a square or polygonal cross-section, or a circular cross-section, as shown in the figure.

[0095] Figure 6 shows an example of a manufacturing process in which a tensile external force F is applied to the main coat 4a to form microcracks 7. This figure is a schematic explanatory diagram of the process in Figure 5 viewed from the planar direction (the direction of the top of Figure 5). In this example, when the base film 2 is long, such as in the magnetic tape 1, an external tensile force F is applied once or multiple times at an angle β of -60° or more and +60° or less with respect to the planar direction of the base film 2, with the longitudinal direction L of the long base film 2 as the reference (0°), thereby producing a magnetic tape 1 having at least microcracks 7 in which grooves extend at an angle α of approximately -60° or more and +60° or less with respect to the short direction M of the long base film, as shown in Figure 3. The angle β may be -45° or more and +45° or less.

[0096] Figure 6(a) shows an example of applying a tensile external force F at an angle β of 0° with respect to the longitudinal direction L of a long base film 2. As shown in Figure 6(a), by applying an external force F in the longitudinal direction L of the base film 2, indicated by the dashed line, and pulling (pulling up) it, a magnetic flexible member 101 having microcracks 7 is manufactured from the magnetic member 91.

[0097] In this way, by applying a tensile external force F at an angle β of 0° with respect to the longitudinal direction L of the long base film 2, a magnetic tape 1 (magnetic flexible member 101) having at least microcracks 7 with grooves extending at an angle α of approximately 0° with respect to the short direction M of the long base film 2 can be manufactured, as shown in Figure 3(a).

[0098] Figure 6(b) shows an example where a tensile external force F is applied at an angle β of 30° to the longitudinal direction L of a long base film 2. As shown in Figure 6(a), by applying an external force F in the longitudinal direction L of the base film 2, indicated by the dashed line, and pulling (pulling) it, a magnetic flexible member 101 having microcracks 7 is manufactured from the magnetic member 91.

[0099] In this way, by applying a tensile external force F at an angle β of 30° with respect to the longitudinal direction L of the long base film 2, a magnetic flexible member 101 (magnetic tape 1) can be manufactured having at least microcracks 7 with grooves extending at an angle α of approximately 30° with respect to the short direction M of the long base film 2, as shown in Figure 3(b).

[0100] As shown in Figure 6(b), when moving block 32 in the S direction, block 32 may be moved in the S1 direction along the longitudinal direction L of the long base film 2, or block 32 may be moved in the S2 direction at an angle β (30° in this example) with respect to the longitudinal direction L of the long base film 2. This is because the angle β of the external force F with respect to the longitudinal direction L of the long base film 2 remains the same whether block 32 is moved in the S1 direction or the S2 direction.

[0101] By performing the process shown in Figure 6 multiple times without changing the angle β, a large number of microcracks 7 that extend at an angle α can be formed. Furthermore, by performing the process shown in Figure 6 multiple times at any different angle β, microcracks 7 that extend at any different angle α can be formed. Depending on the need, the process shown in Figure 6 may be performed multiple times at random angles β. When the number of microcracks 7 increases, the flexibility of the magnetic flexible member 101 (magnetic tape 1) improves, making it easier to attach to the object to be attached.

[0102] The process shown in Figure 6 may be performed, for example, three times, once in each direction: first at an angle β=0°, second at an angle β=-45°, and third at an angle β=+45°, to generate microcracks 7. In this case, a magnetic tape 1 (magnetic flexible member 101) having at least microcracks 7 with grooves extending at angles α=0°, α=-45°, and α=+45° can be manufactured. Since the microcracks 7 are formed by the tearing of the resin material 12, when an external tensile force F is applied at an angle β, microcracks 7 with grooves extending at approximately angle α=angle β are formed, but the angle α varies depending on the location due to the way the tearing occurs. Experiments have shown that the angle α of the grooves of the microcracks 7 is in the range of approximately β ± 15°. Therefore, if the process shown in Figure 6 is performed three times, for example, once in each direction with an angle β=0° in the first pass, an angle β=-45° in the second pass, and an angle β=+45° in the third pass, grooves with angles α=0±15° in the first pass, α=-45±15° in the second pass, and α=+45±15° in the third pass will be formed. As a result, the magnetic tape 1 will have minute cracks 7 in which the grooves extend at an angle α between -60° and +60°.

[0103] If the magnetic flexible member 101 curls due to the introduction of microcracks 7, the curl may be suppressed by heating it in accordance with the temperature characteristics of the magnetic composite material and performing calendering.

[0104] Furthermore, the microcracks 7 in the main coat 4 may be formed by laser processing, water jet processing, or cutting. [Examples]

[0105] [Example 1] [Example of magnetic tape specifications] Magnetic tape 1 has a total thickness of 0.16 mm (0.1 mm of magnetic composite material), a width of 10 mm (after slitting), and a microcrack depth of 0.1 mm (from the surface of the magnetic composite material to the boundary of the undercoat).

[0106] [Examples of raw materials for magnetic tape] For the magnetic tape 1, the base film 2 was a polyimide film (heat resistant to 300°C, thickness 0.0125 mm), and the undercoat 3 was a silicone-based adhesive (toluene solvent, heat resistant to 200°C, coating thickness 0.025 mm). The magnetic composite material for the main coat 4 consisted of fine soft magnetic material 11 / resin material 12 (volume filling rate 70%) with a small amount of binder and lubricant added. The fine soft magnetic material 11 was an iron amorphous powder (manufactured by Epson Atomics; hereinafter referred to as "AMO"), spherical in shape, with an average particle size of 3 μm and a true density of 7 g / cm³. 3 A material with a saturation magnetic flux density of 1,320 Bs (mT), a coercivity of 150 A / m, and hydrophilic properties was used. As the resin material 12, a silicone resin-modified alkyd resin (manufactured by Shin-Etsu Chemical Co., Ltd., xylene solvent, heat resistance 200°C) was used. For the top coat 5, a silicone-based adhesive (toluene solvent, heat resistance 200°C, coating thickness 0.025 mm) was used.

[0107] [Example of a method for manufacturing magnetic tape] The magnetic composite material is prepared by adding a solvent (isopropyl alcohol), a binder (silane coupling agent), a resin material 12, and a lubricant (silicone oil) to a fine soft magnetic material 11, stirring and mixing (high speed 1000 r / min × 60 min), followed by rotational mixing (low speed 30 r / min × 30 min), applying with a slit die coat (thickness 0.1 mm, width 80 mm, speed 30 mm / sec), air drying (30 min), and then heat drying (200°C × 30 min). The undercoat 3 and topcoat 5 are applied with a slit die coat (thickness 0.03 mm, width 80 mm, speed 20 mm / sec).

[0108] The purpose of adding silicone oil as a lubricant is to easily eliminate air bubbles that occur when mixing the fine soft magnetic material 11 and the resin material 12.

[0109] The adhesive of undercoat 3 dissolves when the raw materials of the magnetic composite material are applied, due to solvents such as toluene and xylene contained in the raw materials of the dissolved resin material 12, or isopropyl alcohol added during mixing. The dissolution of undercoat 3 causes the main coat resin material and the undercoat to mix near the boundary. Typically, adhesive products contain toluene.

[0110] [Example of inducing microcracks in magnetic tape] As shown in Figure 5, the microcracks 7 in the magnetic tape 1 are created by applying bending stress (block 32 has a right-angle shape, the chamfer amount of the corner 35 that creates the microcracks in block 32 is C0.1~C0.5 mm, θ=60° upward pulling, and the angles β=0°, -45°, and 45° in Figure 6, pulled up once in each direction for a total of three times), and the flatness after the creation of the microcracks 7 is corrected by heating with upper and lower flat plates (60°C × 10 min). The chamfer amount of the corner 35 of block 32 used in Example 1 and Example 5 is C0.2~0.3 mm.

[0111] [Examples of properties of the fabricated magnetic tape, such as power loss reduction, heat resistance, electrical insulation, and bending resistance] Magnetic tape 1 exhibits the following characteristics for power loss reduction: a real part μ' of the complex relative permeability of 15 (measured with an impedance analyzer at 1 MHz), heat resistance of 200°C, breakdown voltage of 5 kV, tensile strength of 80 N / width 25 mm, and elongation of 10%, making it applicable to high-temperature inductors. The winding mandrel diameter was 50 mm or more when no microcracks were introduced, but it was reduced to 0.9 mm with the introduction of microcracks, dramatically improving bending resistance. The pitch width of the introduced microcracks was 0.2 to 0.5 mm.

[0112] Figure 7 shows the shape, dimensions, and external appearance of a measurement sample (example) made by cutting and laminating the fabricated magnetic tape. The measurement sample was formed by laminating 40 layers of magnetic tape cut into a circular ring with an inner diameter of 10 mm and an outer diameter of 19 mm. The measurement sample has a thickness of 7.5 mm (thickness of the magnetic layer minus the thickness of the resin tape: 5.14 mm).

[0113] Figure 8 shows graphs of the relative permeability measurements for three different cases: Example 2, when AMO with an average particle size of 3 μm and 10 μm was used as the fine soft magnetic material 11 sample; Example 3, when AMO with an average particle size of 2.6 μm was used as the fine soft magnetic material 11 sample; and Example 4, when Fe-Si-Al (flat powder) (diameter 30-50 μm, thickness 0.5 μm) was used as the fine soft magnetic material 11 sample. The other material and other conditions for Examples 2, 3, and 4 are the same as in Example 1.

[0114] Figure 9(a) shows an SEM image of the case where AMO, a mixture of fine soft magnetic material 11 with average particle sizes of 3 μm and 10 μm, was used as the measurement sample (Example 2), and Figure 9(b) shows an SEM image of the case where Fe-Si-Al (flat powder) was used as the fine soft magnetic material 11 of the measurement sample (Example 4). The properties of the magnetic tape can be adjusted by changing the material of the fine soft magnetic material 11.

[0115] Figure 10 shows a magnified photograph of the surface of the main coat of magnetic tape 1 (Example 1) before the top coat was applied. Below the photograph, the measurement results of the surface unevenness depth are shown. The measurement was performed using a digital microscope (OLYMPUS DSX1000). The measurement results show that in the area with microcrack 7, the depth of the groove is narrow and the groove entrance is wide.

[0116] [Example 5] Figure 11 shows a magnified photograph of the longitudinal cross-section of the magnetic tape (Example 5) before the top coat was applied. In Example 5, AMO, a mixture of fine soft magnetic material 11 with average particle sizes of 3 μm and 10 μm, was used. The base film thickness was 0.025 mm, the undercoat thickness was 0.025 mm, the main coat thickness was 0.1 mm, and the thickness of the magnetic tape before the top coat was applied was 0.15 mm. Other material and other conditions for Example 5 were the same as in Example 1.

[0117] [Application to multi-purpose components that require heat resistance and flexibility, and are manufactured by mixing and coating fine powder materials with resin.] Furthermore, since the magnetic flexible member 1 of the present invention has heat resistance, bending resistance, and flexibility due to the imparting of microcracks 7 to the magnetic composite material, it is also suitable for use as a magnetic flexible member attached to magnetic circuit components other than inductors, electronic components, etc. [Explanation of Symbols]

[0118] 1 is a magnetic flexible member (magnetic tape), 2 is a base film, 3 is an undercoat, 4 is a main coat, 4a is the main coat before the formation of microcracks, 5 is a topcoat, 7 is a microcrack, 11 is a fine powder soft magnetic material, 12 is a resin material, 13 is a solvent, 15 is a raw material for magnetic composite material, 21 is a void, 31 is a plate, 32 is a block, 35 is a corner, 51a, 52a, 53a, 51b, 52b, 53b are ranges, 91 is a magnetic member, 101 is a magnetic flexible member, F is the tensile external force, Ka is the direction of extension of the microcrack groove, Kb is the direction of extension of the microcrack groove, L is the longitudinal direction of the magnetic tape, M is the short direction of the magnetic tape, P is the spacing between microcracks, S, S1, S2 are the directions of movement of the block, α is the angle of the microcrack groove relative to the short direction of the base film, β is the angle of the tensile external force on the base film, and θ is the bending angle that pulls up the base film.

Claims

1. A magnetic flexible member is laminated in the order of base film, undercoat, and main coat, with the main coat side being attached to the member to be attached. The base film is made of a flexible resin material. The undercoat is for applying the main coat to the base film. The main coat is formed of a magnetic composite material containing fine soft magnetic material and resin material, The main coat has microcracks provided in a direction perpendicular to the surface of the base film. The aforementioned microcracks are formed such that the crack width on the side closer to the base film is narrower than the crack width on the side opposite to the base film, and when attached to the member to be attached, the microcracks narrow, and the cracks are formed with a width that allows the magnetic composite materials sandwiching the microcracks to come into contact with each other. A magnetic flexible member characterized in that the resin material of the main coat and the undercoat mix near the boundary, and the end of the microcrack on the undercoat side is located within the undercoat.

2. The magnetic flexible member according to claim 1, characterized in that the aforementioned microcracks are provided at intervals of 1 mm or less.

3. The magnetic flexible member according to claim 1, characterized in that the main coat partially has voids where the fine soft magnetic material and the resin material are not present.

4. The magnetic flexible member according to claim 1, characterized in that, when the base film is formed in a long length, it has at least the minute cracks in which grooves extend at an angle of approximately -60° to +60° in the planar direction of the base film, with reference to the short direction of the long base film.

5. The magnetic flexible member according to claim 1, characterized in that a top coat is laminated on the side of the main coat opposite to the base film.

6. A method for manufacturing a magnetic flexible member, wherein a base film, an undercoat, and a main coat are laminated in that order, and the main coat side is attached to a member to be attached, The base film is made of a flexible resin material. The undercoat is for applying the main coat to the base film. The main coat is formed of a magnetic composite material containing fine soft magnetic material and resin material, The undercoat is laminated onto the base film. The raw materials for the main coat, which are a slurry obtained by mixing the solvent that dissolves the undercoat and the resin material, the fine soft magnetic material, and the resin material, are applied to the undercoat and cured to laminate the main coat. By applying a tensile force to the main coat while bending the main coat toward the base film, a magnetic member comprising the base film, undercoat, and main coat is formed in the main coat in a direction perpendicular to the surface of the base film. A method for manufacturing a magnetic flexible member, characterized in that the microcrack has a shape in which the crack width on the side closer to the base film is narrower than the crack width on the side opposite to the base film, the microcrack narrows when attached to the member to be attached, the crack width becomes such that the magnetic composite materials sandwiching the microcrack can come into contact with each other, and the end of the microcrack on the undercoat side is inside the undercoat, by setting the angle at which the main coat is bent toward the base film and the external tensile force to form the microcrack.

7. In the process of applying a tensile external force to the main coat of the magnetic member while bending the main coat toward the base film, The magnetic member is brought into contact with a flat plate in a direction that contacts the main coat. A method for manufacturing a magnetic flexible member according to claim 6, characterized in that a block having a chamfered corner, where the right-angle corner is beveled at a 45° angle, is pressed against the base film, the main coat is bent toward the base film at the position of the corner of the block, and the magnetic member is pulled by the tensile external force to form the microcracks.

8. The method for manufacturing a magnetic flexible member according to claim 7, characterized in that the chamfering amount of the corners of the block is C0.1 to 0.5 mm.

9. The method for manufacturing a magnetic flexible member according to claim 6, characterized in that, when the base film is long, the microcracks are formed by applying the tensile external force once or multiple times at an angle of -60° or more and +60° or less in the planar direction of the base film, with reference to the longitudinal direction of the long base film.

10. The method for manufacturing a magnetic flexible member according to claim 6, characterized in that when forming the main coat, a material is formed that partially has voids where the fine soft magnetic material and the resin material are not present.

11. The method for manufacturing a magnetic flexible member according to claim 6, characterized in that, after forming the aforementioned microcracks, a top coat is laminated onto the surface of the main coat opposite to the base film.

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