Magnetic sheet, magnetic roll, and method for manufacturing a magnetic sheet

Abstract

To provide a magnetic sheet, a magnetic roll, and a method for manufacturing a magnetic sheet that can suppress noise in the high-frequency band. [Solution] The magnetic sheet according to the present invention is a magnetic sheet comprising a magnetic layer, wherein the magnetic layer comprises a soft magnetic powder in the shape of flakes and a binder, wherein the Fe content in the soft magnetic powder is 85% by mass or more, and the thickness of the soft magnetic powder is such that the cumulative distribution value of the thickness of the soft magnetic powder is n% (where n is a variable). n When expressed as, t 90 -t 10 The relationship ≤0.80 μm is satisfied.

Description

[Technical Field]

[0001] This invention relates to a magnetic sheet, a magnetic roll, and a method for manufacturing a magnetic sheet. [Background technology]

[0002] As a countermeasure against electromagnetic wave interference, a method using a magnetic shielding material, such as the one described in Patent Document 1, is known. Patent Document 1 discloses a magnetic shielding material using FeSiCr alloy powder. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-27693 [Overview of the project] [Problems that the invention aims to solve]

[0004] Communication standards such as Wi-Fi (registered trademark) utilize radio waves in frequency bands such as 2.4GHz and 5GHz, and in recent years, wireless communication using even higher frequency bands has been attracting attention. For this reason, there is a need for magnetic sheets that can shield electromagnetic waves in high-frequency bands above 2.4GHz.

[0005] In view of the above issues, the purpose of this disclosure is to provide a magnetic sheet, a magnetic roll, and a method for manufacturing a magnetic sheet that can suppress noise in the high-frequency band. [Means for solving the problem]

[0006] A magnetic sheet according to one aspect of the present disclosure is a magnetic sheet comprising a magnetic layer, wherein the magnetic layer comprises flake-shaped soft magnetic powder and a binder, the Fe content in the soft magnetic powder is 85% by mass or more, and the thickness of the soft magnetic powder is such that the cumulative distribution of the thickness of the soft magnetic powder is n% (where n is a variable). n When expressed as, t 90 -t10 Satisfies the relationship of ≤ 0.80 μm.

[0007] The above-mentioned magnetic sheet may further satisfy the relationship of 0.10 μm ≤ t 10 ≤ 0.30 μm.

[0008] The above-mentioned magnetic sheet may further satisfy the relationship of 0.30 μm ≤ t 50 ≤ 0.50 μm and 0.60 μm ≤ t 90 ≤ 1.00 μm.

[0009] The above-mentioned magnetic sheet may be a Fe-Si-Cr-based alloy.

[0010] The saturation magnetic flux density Bs of the above-mentioned magnetic sheet may be 1.0 T or more.

[0011] In the SEM image of the cross-section in the thickness direction of the magnetic layer of the above-mentioned magnetic sheet, in the randomly selected range of 75 μm × 100 μm, the number of the soft magnetic powder satisfying the major axis of the cross-section being 5 μm or less may be 150 or less.

[0012] In the SEM image of the cross-section in the thickness direction of the magnetic layer of the above-mentioned magnetic sheet, in the randomly selected range of 75 μm × 100 μm, the number of the soft magnetic powder satisfying the major axis of the cross-section being 5 μm or less may be 15% or less of the total number of the soft magnetic powder.

[0013] When the length at which the integrated distribution value of the particle size of the soft magnetic powder of the above-mentioned magnetic sheet is 10% is represented as D 10 the relationship of 3 μm ≤ D 10 may be further satisfied.

[0014] When the length at which the integrated distribution value of the particle size of the soft magnetic powder of the above-mentioned magnetic sheet is n% (n is a variable) is represented as D n the relationship of 3 μm ≤ D 10 ≤ 12 μm and 12 μm ≤ D 50 ≤ 15 μm and 25 μm ≤ D 90The condition ≤29μm may also be satisfied.

[0015] The magnetic sheet described above has a length D such that the cumulative distribution of the particle size of the soft magnetic powder is n% (where n is a variable). n When expressed as, D 90 / D 10 The condition ≤ 10 may also be satisfied.

[0016] The magnetic sheet described above has a length D such that the cumulative distribution of the particle size of the soft magnetic powder is 10%. 10 When expressed as, D 10 / t 10 The condition ≥10 may also be satisfied.

[0017] The magnetic sheet described above may have a real component ε' of the relative permittivity of the magnetic layer of 1 to 7 GHz that is 1300 or less.

[0018] The magnetic sheet described above may have a real component μ' of the relative permeability of the magnetic layer of 1 or more and an imaginary component μ'' of the relative permeability of the magnetic layer of 4 or more over a frequency band of 1 to 7 GHz.

[0019] The magnetic sheet described above may further include a protective layer that reinforces the magnetic layer and an adhesive layer that adheres the magnetic layer and the protective layer to each other.

[0020] A magnetic roll according to one aspect of this disclosure is obtained by winding the above-mentioned magnetic sheet into a roll shape.

[0021] A method for manufacturing a magnetic sheet according to one aspect of the present disclosure comprises the steps of: mixing a flake-shaped soft magnetic powder and a binder to produce a slurry; and forming the slurry into a sheet, wherein the Fe content in the soft magnetic powder is 85% by mass or more, and the thickness of the soft magnetic powder is such that the cumulative distribution of the thickness of the soft magnetic powder is n% (where n is a variable). n When expressed as, t 90 -t 10 The relationship ≤0.80 μm is satisfied. [Effects of the Invention]

[0022] The present invention provides a magnetic sheet, a magnetic roll, and a method for manufacturing a magnetic sheet that can suppress noise in the high-frequency band. [Brief explanation of the drawing]

[0023] [Figure 1] This is a cross-sectional view showing an example of a magnetic sheet according to this embodiment. [Figure 2A] This is an SEM image of a cross-section of the magnetic sheet from Example 1. [Figure 2B] This is an SEM image of the cross-section of the magnetic sheet from Example 2. [Figure 3] This is a perspective view showing a schematic of a measurement and evaluation system for measuring the attenuation of electromagnetic waves by a magnetic sheet. [Figure 4] This is a cross-sectional view of the measurement and evaluation system shown in Figure 3, cut along the cutting line IV-IV. [Figure 5] This graph shows the electromagnetic wave attenuation of the magnetic sheets in the examples and comparative examples. [Figure 6] This graph shows the relative permeability of the magnetic sheets in the examples and comparative examples. [Figure 7] This graph shows the relative permittivity of the magnetic sheets in the examples and comparative examples. [Modes for carrying out the invention]

[0024] Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings have been simplified as appropriate. Furthermore, the multiple configuration examples described below can be implemented independently or in combination as appropriate. These multiple configuration examples have novel features that differ from each other. Therefore, these multiple configuration examples contribute to solving different purposes or problems and contribute to producing different effects. Naturally, the right-handed xyz coordinates shown in Figure 1 and other figures are for convenience in explaining the positional relationships of the components.

[0025] <Magnetic Sheet> First, the magnetic sheet according to the present invention (hereinafter also referred to as "this magnetic sheet") will be described with reference to the drawings. This magnetic sheet is used to suppress noise in the high-frequency band, and is particularly suitable for shielding electromagnetic waves of 2.4 GHz or higher.

[0026] Figure 1 is a cross-sectional view showing an example of a magnetic sheet 10 according to this embodiment. The magnetic sheet 10 shown in Figure 1 is constructed by laminating a magnetic layer 100, an adhesive layer 200, a protective layer 300, an adhesive layer 400, and a metal layer 500 in this order.

[0027] (magnetic layer) The magnetic layer 100 is a layer that absorbs electromagnetic waves, which are noise. The magnetic layer 100 comprises a flake-shaped soft magnetic powder 110 and a binder 120. The soft magnetic powder 110 is oriented to lie flat in the plane direction of the magnetic layer 100 (the xy plane direction in Figure 1) and dispersed while being bound together by the binder 120. As will be described later, the Fe content and thickness distribution of the soft magnetic powder 110 are controlled, so that the real component ε' of the relative permittivity and the imaginary component μ'' of the relative permeability take particularly favorable values. Therefore, noise in the high-frequency band can be effectively suppressed.

[0028] The relative permittivity of the magnetic layer 100 is preferably such that the real component ε' is 1800 or less, and more preferably 1300 or less, across a frequency band of 1 to 7 GHz. If the real component ε' is larger than the above value, the noise suppression effect in the high-frequency band decreases.

[0029] The relative permittivity of the magnetic layer 100 is preferably such that the imaginary component ε'' is 100 or less, and more preferably 50 or less, across a frequency band of 1 to 7 GHz. When the imaginary component ε'' is less than or equal to the above value, the reflection of high-frequency electromagnetic waves at the surface of the magnetic layer 100 is suppressed. This increases the electromagnetic energy absorption efficiency of the magnetic layer 100 and improves the noise suppression effect.

[0030] Furthermore, the relative permeability of the magnetic layer 100 preferably has an imaginary component μ'' of 4 or more, and more preferably 5 or more, across the frequency band of 1 to 7 GHz. When the imaginary component μ'' is greater than or equal to the above value, the noise suppression effect in the high-frequency band is improved. In addition, it is preferable that the imaginary component μ'' is 5 or more, and more preferably 10 or more, in some frequency bands within the 1 to 7 GHz range. In this case, electromagnetic waves in those specific frequency bands can be efficiently shielded. The upper limit of the imaginary component μ'' of the relative permeability is not particularly limited, but for example, it can be 50 or less across the frequency band of 1 to 7 GHz.

[0031] Furthermore, it is preferable that the relative permeability of the magnetic layer 100 has a real component μ' of 1 or more over a frequency band of 1 to 7 GHz. When the real component μ' is greater than or equal to the above value, the magnetic layer 100 becomes more adept at absorbing noise in the high-frequency band, improving the noise suppression effect.

[0032] The thickness T1 of the magnetic layer 100 can be determined as appropriate, but it is preferable to set it to 20 μm or more and 1 mm or less, and preferably 100 μm or less, for ease of handling of the magnetic sheet. By setting the thickness T1 to 100 μm or less, a magnetic sheet can be realized that is easy to wrap around cables, etc., while sufficiently suppressing noise.

[0033] (Soft magnetic powder) The Fe content of the soft magnetic powder 110 is 85% by mass or more, preferably 90% by mass or more. By setting the Fe content to the above value or higher, the imaginary component μ'' of the relative permeability of the magnetic layer 100 can be increased, thereby further enhancing the noise suppression effect in the high-frequency band.

[0034] The soft magnetic powder 110 is not particularly limited as long as it is a metal containing 85% by mass or more of Fe, but it is preferably an Fe-Si-Cr alloy. By selecting an Fe-Si-Cr alloy as the soft magnetic powder 110, the relative permeability μ and magnetic resonance frequency f can be improved. r This makes it easier to control the properties. When the soft magnetic powder 110 is an Fe-Si-Cr alloy, the Si content is preferably 3.0% by mass or more. The Cr content is preferably 1.0% by mass or more. The remainder may also contain Co or Ni.

[0035] The saturation magnetic flux density Bs of the soft magnetic powder 110 is preferably 1.0T or higher, more preferably 1.1T or higher, and particularly preferably 1.5T or higher. When the saturation magnetic flux density Bs of the soft magnetic powder 110 is 1.0T or higher, the imaginary component μ'' of the relative permeability increases, improving noise absorption in the high-frequency band.

[0036] The thickness of the soft magnetic powder 110 such that the cumulative distribution of its thickness is n% (where n is a variable) is t. n When expressed as, t 90 and t 10 is t 90 -t 10 The relationship ≤0.80 μm is satisfied, preferably t 90 -t 10 The relationship ≤0.70μm is satisfied. In this magnetic sheet, t 90 and t 10 Because the difference is small, less than 0.80 μm, there is little variation in the thickness of the soft magnetic powder 110. As a result, the real component ε' of the relative permittivity of the magnetic layer 100 is kept small. Therefore, this magnetic sheet has excellent noise suppression effect in the high-frequency band.

[0037] Also, t 10 is 0.10 μm ≤ t 10 Preferably, the size is ≤0.30 μm, and particularly ≤0.10 μm. 10 It is more preferable that the particle size is ≤0.20 μm. 10 If the particle size is less than 0.10 μm, the proportion of fine powder particles is large, which causes the real component ε' of the relative permittivity of the magnetic layer 100 in the high-frequency band to become large. 10 If the thickness exceeds 0.30 μm, the proportion of relatively thick powder increases, which lowers the packing density of the magnetic layer 100 and reduces the imaginary component μ'' of the relative permeability.

[0038] Also, t 50 is 0.30 μm ≤ t 50 Preferably, the size is ≤0.50 μm, and 0.30 μm ≤ t 50 It is more preferable that the thickness is ≤0.40 μm. Furthermore, t 90 is 0.60μm≦t 90 Preferably, the size is ≤1.00 μm, and 0.80 μm ≤ t 90 It is more preferable that the thickness be ≤0.90 μm. 10 In addition to the range, t 50 t 90 By satisfying the above range, the thickness of the soft magnetic powder 110 takes on a suitable distribution. In this way, by suppressing variations in the thickness of the soft magnetic powder 110 and mixing thin and thick powders in a balanced manner, the real component ε' and imaginary component ε'' of the relative permittivity of the magnetic layer 100 can be brought into a suitable range.

[0039] Furthermore, each of the above t n The value can be measured by determining the thickness of each soft magnetic powder 110 from an SEM image obtained by observing a randomly selected 75 μm × 100 μm area in the cross-section in the thickness direction of the magnetic layer 100.

[0040] Furthermore, the length at which the cumulative distribution of particle size of the soft magnetic powder 110 reaches n% (where n is a variable) is defined as D. n When expressed as, D 10 2μm ≤ D 10 Preferably, 3μm ≤ D10 It is more preferable that 5μm≦D 10 It is especially preferable that this be the case. D 10 If the particle size is less than 2 μm, the proportion of fine powder increases, and the real component ε' of the relative permittivity of the magnetic layer 100 becomes larger.

[0041] Also, 3μm≦D 10 Preferably ≤10μm, and 5μm ≤D 10 It is more preferable that the size is ≤8 μm. Also, 10 μm ≤ D 50 Preferably ≤20μm and ≤D 50 It is more preferable that the size is ≤15μm or less. Also, 20μm ≤D 90 Preferably ≤30μm, and 25μm ≤D 90 It is more preferable that the size is ≤29 μm. 10 , D 50 , and D 90 By setting the above range, the particle size of the soft magnetic powder 110 takes on a suitable distribution. In this way, by suppressing the variation in particle size of the soft magnetic powder 110 and mixing large and small powders in a balanced manner, the real component ε' and imaginary component ε'' of the relative permittivity of the magnetic layer 100 can be set to a suitable range.

[0042] Also, D 90 and D 10 The ratio is D 90 / D 10 It is preferable that the value is ≤10. 90 / D 10 When ≤ 10, the proportion of powders with relatively small or large particle sizes is small, so the real component ε' and imaginary component ε'' of the relative permittivity and the imaginary component μ'' of the relative permeability of the magnetic layer 100 take suitable values.

[0043] Also, D 10 and t 10 The ratio is D 10 / t 10 Preferably, D 10 / t 10 It is more preferable that ≥20, D 10 / t 10It is particularly preferable that the value be ≥40. D 10 / t 10 If it is less than 10, the thickness of the soft magnetic powder 110 is not sufficiently thin relative to the particle size, so the real component ε' of the relative permittivity of the magnetic layer 100 becomes large.

[0044] In this specification, the particle size of the soft magnetic powder 110 refers to the length of the major axis in the cross-section of the soft magnetic powder 110 in the thickness direction. n The value can be measured, for example, by determining the major axis of the cross-section of each soft magnetic powder 110 from an SEM image obtained by observing a randomly selected 75 μm × 100 μm area in the cross-section in the thickness direction of the magnetic layer 100.

[0045] Furthermore, in an SEM image of a randomly selected 75 μm × 100 μm area of ​​the cross-section in the thickness direction of the magnetic layer 100, it is preferable that there are 150 or fewer soft magnetic powders 110 satisfying the condition that the major axis of the cross-section is 5 μm or less. By keeping the number of soft magnetic powders 110 with a major axis of the cross-section of 5 μm or less low, the real component ε' of the relative permittivity of the magnetic layer 100 can be reduced, thereby improving the noise suppression effect in the high-frequency band.

[0046] Furthermore, in an SEM image of a randomly selected 75 μm × 100 μm area of ​​the cross-section in the thickness direction of the magnetic layer 100, it is preferable that the number of soft magnetic powders 110 satisfying a major axis of the cross-section of 5 μm or less is 15% or less of the total number of soft magnetic powders 110, and more preferably 10% or less. By keeping the proportion of soft magnetic powders 110 with a major axis of the cross-section of 5 μm or less low, the real component ε' of the relative permittivity of the magnetic layer 100 can be reduced, thereby improving the noise suppression effect in the high-frequency band.

[0047] (Binder) The binder 120 is not particularly limited as long as it is an organic material, and various binders can be used. For example, an adhesive elastic material can be used, specifically acrylic rubber or a mixture of acrylic rubber and nitrile rubber. The ratio of the binder 120 to the magnetic layer 100 can be, for example, 35% to 65% by volume.

[0048] (Flame retardant) The magnetic layer 100 may further contain a flame retardant (not shown). The flame retardant is not particularly limited as long as it is flame retardant, but from the viewpoint of stability at high temperatures, it is preferable to use a nitrogen-based compound having a decomposition temperature of 300°C or higher, for example, tetrazole compounds, melamine compounds, and mixtures thereof can be used. Particularly preferred examples of flame retardants include tetrazole compounds such as bistetrazolediammonium (C2H8N 10 ), melamine cyanurate can be cited as an example of a melamine-based compound. From the viewpoint of handling, the blending ratio of the flame retardant is preferably 20% by volume or less per 100 units of the magnetic layer.

[0049] (protective layer) The protective layer 300 is a layer that reinforces the magnetic layer 100 and can be made of a flexible sheet-like material. For example, the protective layer 300 can be made of resins such as PET (polyethylene terephthalate), polyvinyl chloride (PVC), polyurethane (PU), or polyimide (PI). The thickness T3 of the protective layer 300 can be, for example, 12 μm to 100 μm from the viewpoint of ease of wrapping around cables, etc.

[0050] (metal layer) The metal layer 500 reflects and shields electromagnetic waves that the magnetic layer 100 could not absorb. The material of the metal layer 500 is not particularly limited as long as it is a metal, but for example, aluminum or copper can be used. The thickness T5 of the metal layer 500 is preferably 7 μm or more from the viewpoint of shielding performance, and preferably 30 μm or less from the viewpoint of handling.

[0051] (Adhesive layer) The adhesive layers 200 and 400 are layers that bond the magnetic layer 100 to the protective layer 300, and the protective layer 300 to the metal layer 500, respectively. The adhesive layers 200 and 400 can each be made of an adhesive sheet material, and can be appropriately selected from polyether-based adhesives, polyester-based adhesives, etc. For example, if the binder 120 contains acrylic rubber, it is preferable that the adhesive layer 200 contains a polyether-based adhesive from the viewpoint of adhesion. The thickness of the adhesive layers 200 and 400 is preferably 0.5 μm or more from the viewpoint of adhesion, but is preferably 5 μm or less, and more preferably 1 μm or less from the viewpoint of handling. By making the adhesive layers 200 and 400 thinner, the magnetic sheet 10 can be made thinner, improving the ease of wrapping around cables and the ease of manufacturing magnetic rolls.

[0052] The configuration of this magnetic sheet is not limited to the examples described above. Specifically, the magnetic sheet only needs to have a magnetic layer and does not need to have a protective layer, adhesive layer, or metal layer. Even with such a configuration, the magnetic layer can absorb electromagnetic waves, thus suppressing noise in the high-frequency band.

[0053] <Magnetic Roll> The magnetic sheet according to the present invention (hereinafter also referred to as "this magnetic sheet") is a magnetic sheet wound into a roll. For example, the width of this magnetic roll can be 100 to 500 mm and the length can be 10 to 50 m. This magnetic roll offers excellent handling, such as portability, and can also be cut into strips of about 5 to 15 mm in width to be used as an intermediate material for manufacturing this magnetic sheet in reel form. By making this magnetic sheet into a reel form, the ease of winding it onto a cable can be further improved.

[0054] <Method for manufacturing magnetic sheets> Next, the method for manufacturing the magnetic sheet (hereinafter also referred to as the manufacturing method) will be described. The manufacturing method is a suitable method for manufacturing the magnetic sheet described above, and comprises a step of mixing flake-shaped soft magnetic powder and a binder to produce a slurry (mixing step), and a step of forming the slurry into a sheet (forming step), wherein the Fe content in the soft magnetic powder is 85% by mass or more, and the thickness t is such that the cumulative distribution value of the thickness of the soft magnetic powder 110 is n% (where n is a variable). n When expressed as, t 90 -t 10 The relationship ≤0.80 μm is satisfied.

[0055] In the mixing process, a slurry is prepared by mixing soft magnetic powder and a binder. The mixing method is not particularly limited, and known methods can be used. Preferably, the proportion of the binder is 35% to 65% by volume relative to the slurry.

[0056] In the molding process, the slurry can be formed into a sheet by, for example, applying it to a smooth substrate. Examples of substrates include resin films such as PET, PVC, PU, ​​and PI. Known methods can be used for application, and can be appropriately selected from methods such as the doctor blade method, dip coating method, roll coating method, spin coating method, curtain coating method, and screen printing method.

[0057] In the drying process, the sheet-like slurry is dried to form a magnetic thin film. If a resin film is used as the substrate in the molding process described above, this process allows for the direct molding of a magnetic sheet in which a magnetic layer (magnetic thin film) is bonded to a protective layer (resin film).

[0058] In addition to the above steps, this manufacturing method may further include a step of peeling the dried magnetic thin film from the substrate (peeling step) and a step of bonding the magnetic thin film to a resin film via an adhesive (bonding step). When these steps are included, a magnetic sheet can be produced in which a magnetic layer (magnetic thin film) is bonded to a protective layer (resin film) via an adhesive layer (adhesive).

[0059] In the demolition process, the molded sheet may be rolled with a roller or the like before the magnetic thin film is demolished. This makes it easier to release the magnetic thin film from the substrate.

[0060] Furthermore, this manufacturing method may also include a step of bonding a metal thin film and a resin film via an adhesive (metal bonding step). If this step is included, a magnetic sheet can be produced in which a metal layer (metal thin film) is bonded to a protective layer (resin film) via an adhesive layer (adhesive). [Examples]

[0061] The present invention will be specifically described below with reference to examples and comparative examples. However, this description is not intended to limit the present invention.

[0062] (Example 1) First, a soft magnetic powder having a composition of Fe-3.5Si-4.5Cr by mass ratio was prepared using the atomization method. This soft magnetic powder was flattened using an attritor to obtain a flaky soft magnetic powder A (saturation magnetic flux density Bs: 1.7T). Next, soft magnetic powder A and a binder were mixed to prepare a slurry. Then, the slurry was applied to a PET resin carrier film at a speed of 2.0 m / min using the doctor blade method, and dried by pressing at 195°C and 11.2 MPa for 330 seconds. After drying, the coating was rolled with a roller and peeled off from the carrier film to obtain a magnetic sheet with a thickness of 100 μm. This was designated as Example 1.

[0063] (Example 2) Furthermore, a soft magnetic powder having a composition of Fe-12.0Si-1.8Cr by mass ratio was prepared using the atomization method. This soft magnetic powder was flattened using an attritor to obtain a flaky soft magnetic powder B (saturation magnetic flux density Bs: 1.2T). Next, the magnetic sheet of Example 2 was obtained using the same procedure as above, except that soft magnetic powder A was replaced with soft magnetic powder B.

[0064] (Comparative Example 1) Also, spherical soft magnetic powder C (saturation magnetic flux density Bs: 1.7 T) having a composition of Fe-3.5Si-4.5Cr by mass ratio was produced using a vapor phase method (thermal plasma method). Subsequently, a magnetic sheet of Comparative Example 1 was obtained by the same procedure except that soft magnetic powder A was changed to soft magnetic powder C in the above method.

[0065] (SEM Observation) Cross-sections of the magnetic sheets of Example 1, Example 2, and Comparative Example 1 were prepared with a cross-section sample preparation device, and a randomly selected range of 75 μm × 100 μm was observed with a scanning electron microscope (SEM). Figures 2A and 2B are SEM images of Example 1 and Example 2, respectively. From the obtained SEM images, the thicknesses (t 10 , t 50 , t 90 , t 100 , average thickness), particle diameters (D 10 , D 50 , D 90 , D 100 , average particle diameter), and the number of powders with a particle diameter (major axis of the cross-section) of 5 μm or less were measured. Also, the difference between t 90 and t 10 (t 90 -t 10 ), and the difference between D 10 and t 10 (D 10 / t 10 ) were calculated. Also, the ratio of the number of fine powders with a particle diameter of 5 μm or less to the number of soft magnetic powders in the SEM image was calculated. The results are shown in Table 1.

[0066]

Table 1

[0067] As shown in Table 1, both Example 1 and Example 2 satisfied the relationship of t 90 -t 10 ≦0.80 μm. On the other hand, in Comparative Example 1, t 90 -t 10 = 9.9 μm, and t 90 and t 10The difference was greater than 0.80 μm.

[0068] (evaluation) The electromagnetic wave attenuation, relative permeability, and relative permittivity were measured for the magnetic sheets of Examples 1 and 2 and Comparative Example 1 at each frequency. The measurement methods and results are as follows.

[0069] [Attenuation Amount] First, the method for measuring attenuation will be explained using Figures 3 and 4. Figure 3 is a perspective view showing a schematic of the measurement and evaluation system 90 for measuring the attenuation of electromagnetic waves by the magnetic sheet 11. Figure 4 is a cross-sectional view of the measurement and evaluation system 90 shown in Figure 3, cut along the cutting line IV-IV. As shown in Figures 3 and 4, the measurement and evaluation system 90 comprises a support base 91, a transmitting antenna 92, a receiving antenna 93, and a copper plate 94.

[0070] The transmitting antenna 92 ​​simulates a noise source, the receiving antenna 93 simulates a victim, and the copper plate 94 simulates a metal casing. The transmitting antenna 92 ​​and the receiving antenna 93 are placed parallel to each other on a support base 91 with a predetermined distance between them. The copper plate 94 is placed 0.5 mm above the transmitting antenna 92 ​​and the receiving antenna 93. The amount of electromagnetic wave attenuation in the magnetic sheet 11 was evaluated by measuring how much the transmission rate (dB) when the signal transmitted from the transmitting antenna 92 ​​is received by the receiving antenna 93 is attenuated before and after the magnetic sheet 11 is attached to the underside of the copper plate 94. The results are shown in Figure 5. Figure 5 is a graph showing the amount of electromagnetic wave attenuation at each frequency in Examples 1 and 2 and Comparative Example 1.

[0071] As shown in Figure 5, the magnetic sheets of Examples 1 and 2 exhibited greater attenuation and superior noise suppression compared to Comparative Example 1 in the 1-5 GHz range. The attenuation of electromagnetic waves at 5 GHz was less than 1.5 dB for the magnetic sheet of Comparative Example 1, while it was 1.5 dB or higher for both the magnetic sheets of Examples 1 and 2. In particular, the magnetic sheet of Example 1 exhibited an attenuation of electromagnetic waves at 5 GHz between 2.5 dB and 4 dB. Furthermore, the magnetic sheet of Example 1 also showed greater attenuation and superior noise suppression compared to Comparative Example 1 in the 5-7 GHz range.

[0072] [Relative permeability] The relative permeability was measured using a network analyzer (manufactured by Keysight) with the coaxial tube method. The results are shown in Figure 6. Figure 6 is a graph showing the relative permeability of electromagnetic waves at each frequency in Examples 1 and 2 and Comparative Example 1.

[0073] As shown in Figure 6, the relative permeability in Examples 1 and 2 showed good values, with the imaginary component μ'' being 4 or higher across the frequency band of 1 to 7 GHz. In particular, in Example 1, the real component μ' of the relative permeability also showed a good value, being 1 or higher across the frequency band of 1 to 7 GHz.

[0074] [relative permittivity] The relative permittivity was measured using a network analyzer (manufactured by Keysight) with the coaxial tube method. The results are shown in Figure 7. Figure 7 is a graph showing the relative permittivity of electromagnetic waves at each frequency in Examples 1 and 2 and Comparative Example 1.

[0075] As shown in Figure 7, the relative permittivity in Examples 1 and 2 showed good values, with the real component ε' being 1800 or less across the 1-7 GHz frequency band. In particular, in Example 1, the real component ε' was 1300 or less across the 1-7 GHz frequency band. Furthermore, in Example 1, the imaginary component ε'' of the relative permittivity was also a good value, being 50 or less across the 1-7 GHz frequency band.

[0076] From the above results, it was found that the magnetic sheet manufactured by this manufacturing method can suppress noise in the high-frequency band. Although the present invention has been described in accordance with the above embodiments, the present invention is not limited to the configuration of the above embodiments, and of course includes various modifications, alterations, and combinations that can be made by a person skilled in the art within the scope of the claims of the present patent application. [Explanation of symbols]

[0077] 10, 11 Magnetic Sheet 100 magnetic layer 110 Soft magnetic powder 120 Binder 200, 400 adhesive layer 300 protective layer 500 metal layers 91 Support stand 92 Transmitting Antenna 93 Receiving antenna 94 Copper plate

Claims

1. A magnetic sheet having a magnetic layer, The magnetic layer comprises a soft magnetic powder in the shape of flakes and a binder. The Fe content in the aforementioned soft magnetic powder is 85% by mass or more. The thickness at which the cumulative distribution of the thickness of the soft magnetic powder reaches n% (where n is a variable) is set to t. ｎ When expressed as, t ９０ -t １０ The relationship ≤ 0.80 μm is satisfied. Magnetic sheet.

2. 0.10 μm ≤ t １０ The relationship ≤ 0.30 μm is further satisfied, The magnetic sheet according to claim 1.

3. 0.30 μm ≤ t ５０ ≤0.50 μm and ≤0.60 μm ≤ t ９０ The relationship ≤ 1.00 μm is further satisfied, The magnetic sheet according to claim 1.

4. The soft magnetic powder is an Fe-Si-Cr alloy. The magnetic sheet according to claim 1.

5. The saturation magnetic flux density Bs of the soft magnetic powder is 1.0 T or higher. The magnetic sheet according to claim 1.

6. In an SEM image of a randomly selected 75 μm × 100 μm area within the cross-section in the thickness direction of the magnetic layer, there are 150 or fewer soft magnetic powder particles whose major axis of the cross-section is 5 μm or less. The magnetic sheet according to claim 1.

7. In an SEM image of a randomly selected 75 μm × 100 μm area within the cross-section in the thickness direction of the magnetic layer, the number of soft magnetic powder particles satisfying a major axis of 5 μm or less in the cross-section is 15% or less of the total number of soft magnetic powder particles. The magnetic sheet according to claim 1.

8. The length at which the cumulative particle size distribution of the soft magnetic powder reaches 10% is defined as D. １０ When expressed as such, 3 μm ≤ D １０ To further satisfy the relationship, The magnetic sheet according to claim 1.

9. Let D represent the length at which the integrated distribution value of the particle size of the soft magnetic powder becomes n% (n is a variable). ｎ When expressed in this way, 3 μm ≤ D １０ ≤12 μm and 12 μm ≤ D ５０ ≤15 μm and ≤25 μm ９０ The condition ≤29 μm is further satisfied. The magnetic sheet according to claim 1.

10. The length at which the cumulative distribution of particle size of the soft magnetic powder reaches n% (where n is a variable) is D. ｎ When expressed as, D ９０ / D １０ To further satisfy the relationship ≤ 10, The magnetic sheet according to claim 1.

11. The length at which the cumulative particle size distribution of the soft magnetic powder reaches 10% is defined as D. １０ When expressed as, D １０ / t １０ To further satisfy the relationship ≥ 10, The magnetic sheet according to claim 1.

12. Over a frequency band of 1 to 7 GHz, the real component ε' of the relative permittivity of the magnetic layer is 1300 or less. The magnetic sheet according to claim 1.

13. Over a frequency band of 1 to 7 GHz, the real component μ' of the relative permeability of the magnetic layer is 1 or more, and the imaginary component μ'' of the relative permeability of the magnetic layer is 4 or more. The magnetic sheet according to claim 1.

14. A protective layer that reinforces the magnetic layer, The system further comprises an adhesive layer that bonds the magnetic layer and the protective layer to each other. A magnetic sheet according to any one of claims 1 to 13.

15. A magnetic roll obtained by winding the magnetic sheet described in claim 14 into a roll shape.

16. A process of preparing a slurry by mixing a flake-shaped soft magnetic powder with a binder, The process includes a step of forming the slurry into a sheet, The Fe content in the aforementioned soft magnetic powder is 85% by mass or more. The thickness at which the cumulative distribution of the thickness of the soft magnetic powder reaches n% (where n is a variable) is set to t. ｎ When expressed as, t ９０ -t １０ The relationship ≤ 0.80 μm is satisfied. A method for manufacturing magnetic sheets.

Images