JP2008135713A - Method of producing laminate-type soft magnetic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a laminate-type magnetic sheet, capable of suppressing a change in sheet thickness and having small variation in a permeability. <P>SOLUTION: The method of producing a laminate-type soft magnetic sheet comprises a step (A) of applying a soft magnetic composition formed by mixing at least a flat soft magnetic powder, an acrylic rubber having glycidyl groups, an epoxy resin, a latent curing agent for the epoxy resin, and a solvent onto a peeling substrate, drying the composition at a temperature T1 at which substantially no curing reaction of the soft magnetic composition occurs, and removing the peeling substrate to obtain a curable soft magnetic sheet; a step (B) of preparing two or more curable soft magnetic sheets to form a laminate; a step (C) of successively compressing the laminate at a temperature T2 at which substantially no curing reaction occurs with a linear-load laminator under linear loads P1, P2 and P3 (P1<P2<P3); and a step (D) of compressing the resulting compressed laminate at a temperature T3 at which curing reaction occurs with a planar-load press to cure the laminate properly, thereby obtaining a laminate-type soft magnetic sheet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a soft magnetic sheet having excellent magnetic characteristics and small thickness change.

  The manufacture of soft magnetic sheets used in various electronic devices is generally performed by a kneading and rolling method. In this method, flat soft magnetic powder, rubber, and a binder such as chlorinated polyethylene are kneaded at a predetermined ratio with a kneader, and the obtained kneaded product is rolled to a predetermined thickness with an apparatus such as a calender roll, and further required. Accordingly, the binder is heated and crosslinked to obtain a single-layer soft magnetic sheet. This method has the advantage that the soft magnetic powder can be filled at a high density, the soft magnetic powder can be oriented in the in-plane direction by rolling, and the sheet thickness can be easily adjusted.

  However, in the case of the kneading and rolling method, since the soft magnetic powder is distorted during kneading, there is a problem that the magnetic properties of the soft magnetic powder itself are lowered and the magnetic permeability of the soft magnetic sheet cannot be increased. Further, there has been a problem that the magnetic permeability is lowered by changing the sheet thickness in a high temperature or high temperature and high humidity environment.

  Therefore, instead of the kneading and rolling method, a soft magnetic sheet is manufactured by a coating method in which the soft magnetic powder is less likely to be distorted (Patent Document 1). In this method, a sheet composition under high temperature, high temperature and high humidity is obtained by applying a liquid composition for forming a soft magnetic sheet composed of flat soft magnetic powder, rubber, resin and solvent onto a release substrate and drying. A soft magnetic sheet with little change is obtained.

JP 2000-243615 A

  However, the coating method is suitable for producing a soft magnetic sheet having a relatively thin sheet thickness, but is not suitable for producing a relatively thick soft magnetic sheet. This is because when the coating is thick, uneven coating thickness tends to occur and drying becomes difficult. For this reason, the present inventors blended a curable resin and a curing agent thereof with a liquid composition for forming a soft magnetic sheet, created a soft magnetic sheet with low curability by a coating method, Attempts were made to make the soft magnetic sheet into a laminated type by temporarily press-bonding at a low temperature and then press-bonding at a relatively high temperature. However, the laminated soft magnetic sheet produced by laminating thin soft magnetic sheets produced by the coating method is relatively thick manufactured by the kneading rolling method, although the change in the thickness of each thin soft magnetic sheet is small. Similar to the single-layer soft magnetic sheet, there is a problem in that the sheet thickness increases in a high temperature or high temperature and high humidity environment, and the magnetic permeability decreases.

  The present invention is intended to solve the above-described problems of the prior art, in which a plurality of thin soft magnetic sheets prepared by a coating method are stacked, and a change in sheet thickness is suppressed and a change in permeability is small. It aims at providing the method which can manufacture a type | mold soft magnetic sheet.

  The present inventor relates to a laminated soft magnetic sheet prepared by laminating thin soft magnetic sheets prepared by a coating method, and the magnetic permeability changes in a direction in which the sheet thickness increases in a high temperature or high temperature and high humidity environment. Two possibilities were considered as reasons for the decline. One is the possibility that air is taken in between the thin soft magnetic sheets constituting the laminated soft magnetic sheet and the sheet expands due to the expansion of the air due to the high temperature. There is a possibility that the distortion generated in the soft magnetic powder is relieved by the high temperature, and the resin thickness constituting the sheet contracts to increase the sheet thickness.

  Assuming that the former is the main factor, the present inventors have obtained the knowledge that when a relatively high pressure is applied during pre-thermal compression bonding of a plurality of soft magnetic sheets, the sheet thickness changes at a level that cannot be ignored. It was. Further, it was assumed that the latter was the main factor, and when a relatively low pressure was applied during temporary thermocompression bonding of a plurality of soft magnetic sheets, it was found that the sheet thickness would also change at a level that cannot be ignored.

  In view of the fact that in order to achieve the object of the present invention, the present inventors cannot simply apply a relatively high pressure or a low pressure at the time of temporary thermocompression bonding. A specific composition was used, and a heating pattern and a pressure application pattern for a laminate of thin soft magnetic sheets formed therefrom were studied in detail. It has been found that the above-mentioned object can be achieved by pre-bonding with a linear pressure at a stage and then finally pressing with a surface pressure at a temperature at which thermosetting proceeds, and the present invention has been completed.

That is, this invention is a manufacturing method of a lamination type soft magnetic sheet, Comprising: The following processes (A)-(D):
(A) A soft magnetic composition obtained by mixing at least a flat soft magnetic powder, an acrylic rubber having a glycidyl group, an epoxy resin, a latent curing agent for epoxy resin, and a solvent is formed on a release substrate. Applying, drying at a temperature T1 at which the curing reaction of the soft magnetic composition does not substantially occur, removing the release substrate, and obtaining a curable soft magnetic sheet;
(B) preparing two or more of the curable soft magnetic sheets and laminating them to obtain a laminate;
(C) At a temperature T2 at which the curing reaction does not substantially occur, the obtained laminate is subjected to linear pressure P1, linear pressure P2, and linear pressure P3 (note that P1 <P2 <P3) at a laminator that applies linear pressure. And (D) a step of compressing the compressed laminate with a press machine that applies a surface pressure to obtain a laminated soft magnetic sheet at a temperature T3 at which a curing reaction subsequently occurs. A featured manufacturing method is provided.

  The present invention uses a specific soft magnetic composition for forming a soft magnetic sheet, and relates to a heating pattern and a pressure application pattern for a laminate of thin soft magnetic sheets formed therefrom, and a temperature at which thermosetting does not proceed. Then, temporary pressure bonding is performed at three, linear, low, medium and high linear pressures, followed by surface pressure bonding at a surface pressure at a temperature at which thermosetting proceeds. For this reason, a change in sheet thickness can be suppressed even in a high temperature or high temperature and high humidity environment, and as a result, the magnetic permeability can be prevented from decreasing.

  The method for producing a laminated soft magnetic sheet of the present invention includes at least the following steps (A) to (D). It demonstrates for every process.

Process (A)
A soft magnetic composition formed by mixing at least a flat soft magnetic powder, an acrylic rubber having a glycidyl group, an epoxy resin, a latent curing agent for epoxy resin, and a solvent is applied onto a release substrate, The soft magnetic composition is dried at a temperature T1 at which the curing reaction does not substantially occur, and the release substrate is removed to obtain a curable soft magnetic sheet.

  As a method for applying the soft magnetic composition onto the release substrate, a known method such as a doctor blade coating method or a comma coater coating method can be used. The coating thickness can be appropriately determined according to the use of the curable soft magnetic sheet and the number of laminated layers, but the coating thickness is usually applied so that the dry thickness is 50 to 200 μm.

  The soft magnetic composition is applied to the release substrate and then dried, and the release substrate is removed to obtain a curable soft magnetic sheet. The drying is performed at a temperature T1 at which the curing reaction of the soft magnetic composition does not substantially occur. dry. Also, the reason for drying at a temperature T1 at which the curing reaction of the soft magnetic composition does not substantially occur is that when the curing reaction proceeds, the compressibility deteriorates, and when μ ′ does not rise and the curing reaction proceeds, This is because the thickness change in a high temperature and high humidity environment becomes large. Here, “the curing reaction does not substantially occur” means that not only the curing reaction does not occur at all but also a slight curing reaction may occur as long as the effect of the invention is not impaired. Means that the crosslinking reaction is uniformly carried out in the final step. An example of a specific means for substantially preventing the curing reaction is to set the temperature T1 to a temperature lower by 5 ° C. or more than the curing reaction start temperature. Although specific temperature T1 changes with compositions of a soft-magnetic composition, it is 130 degrees C or less normally. As a specific method of drying, a known method using a hot air drying furnace, an electric heating furnace, an infrared heating furnace, or the like can be employed.

  In the soft magnetic composition, a soft magnetic powder having a flat shape (flat soft magnetic powder) is used. By arranging the flat soft magnetic powder in a two-dimensional in-plane direction, a high magnetic permeability and a large specific gravity can be realized.

  As a raw material of the flat soft magnetic powder, any soft magnetic alloy can be used, for example, magnetic stainless steel (Fe—Cr—Al—Si alloy), sendust (Fe—Si—Al alloy), permalloy (Fe—Ni). Alloy), silicon copper (Fe—Cu—Si alloy), Fe—Si alloy, Fe—Si—B (—Cu—Nb) alloy, Fe—Si—Cr—Ni alloy, Fe—Si—Cr alloy, Fe— Si-Al-Ni-Cr alloy, ferrite, etc. are mentioned. Among these, Fe-Si-Al alloys or Fe-Si-Cr-Ni alloys can be preferably used from the viewpoint of magnetic properties.

  When these soft magnetic alloys are used for RFID communication, the real part (permeability) μ ′ of the complex relative permeability is relatively large, and the imaginary part (magnetic loss) μ ″ of the complex relative permeability is It is preferable to use one having a relatively small numerical value, whereby the magnetic field emitted from the antenna coil for RFID communication is prevented from being converted into an eddy current by the metal body, thereby improving the communication performance.

  In addition, it is preferable to use a flat soft magnetic alloy having a relatively large resistance in order to reduce the value of μ ″ for the purpose of reducing eddy current loss. In this case, the composition of the soft magnetic alloy is changed. For example, in the case of an Fe—Si—Cr alloy, the Si ratio is preferably 9 to 15% by weight.

  As the flat soft magnetic powder, a soft magnetic powder having a flat shape is used. Preferably, the average particle diameter is 3.5 to 90 μm, the average thickness is 0.3 to 3.0 μm, and more preferably the average particle diameter is 10. ˜50 μm, average thickness is 0.5 to 2.5 μm. Therefore, the flatness is preferably set to 8 to 80, more preferably 15 to 65. In addition, what is necessary is just to classify using a sieve etc. as needed in order to arrange the magnitude | size of a flat soft magnetic powder. In order to increase the magnetic permeability of the soft magnetic material, the particle size of the flat soft magnetic powder is increased to reduce the interval between the particles, and the aspect ratio of the flat soft magnetic powder is increased to increase the aspect ratio of the soft magnetic sheet. It is effective to reduce the influence of the demagnetizing field.

The tap density and the specific surface area (BET method) of the flat soft magnetic powder are inversely proportional to each other. However, when the non-surface area is increased, not only the value of μ ′ but also the value of μ ″ that is not desired to be increased tends to increase. Therefore, the numerical range is set to a preferable range, specifically, the tap density is preferably set to 0.55 to 1.45 g / ml, more preferably 0.65 to 1.40 g / ml, The specific surface area is preferably set to 0.40 to 1.20 m ² / g, more preferably 0.65 to 1.00 m ² / g.

  Further, as the flat soft magnetic powder, for example, a soft magnetic powder that has been coupled with a coupling agent such as a silane coupling agent may be used. By using the soft magnetic powder subjected to the coupling treatment, the reinforcing effect of the interface between the flat soft magnetic powder and the binder resin can be enhanced, and the specific gravity and corrosion resistance can be improved. As the coupling agent, for example, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane and the like can be used. The above-described coupling treatment may be performed on the soft magnetic powder in advance, or at the same time when the flat soft magnetic powder and the binder resin are mixed, the coupling treatment is performed as a result. You may do it.

  If the amount of the flat soft magnetic powder used in the soft magnetic composition is too small, the intended magnetic properties cannot be obtained. If the amount is too large, the amount of the binder resin is relatively small and the moldability is decreased. Is 70 to 90% by weight, more preferably 80 to 85% by weight in the soft magnetic composition excluding.

  The soft magnetic composition uses acrylic rubber as a rubber component in order to impart good flexibility and heat resistance to the laminated soft magnetic sheet. This acrylic rubber always has one or more glycidyl groups in order to improve compatibility with the epoxy resin. Specific examples include EA-AN, BA-EA-AN, BA-AN, BA-MMA and the like.

  If the amount of acrylic rubber used in the soft magnetic composition is too small, sufficient heat processability cannot be obtained, and if it is too large, the rubber elasticity becomes too large and the heat processability deteriorates. It is 9 to 16% by weight in the soft magnetic composition, more preferably 12 to 14% by weight.

  The soft magnetic composition uses an epoxy resin in order to impart good heat processability and dimensional stability to the laminated soft magnetic sheet. Specific examples include phenol novolak, tetraglycidylphenol, o-cresol novolak, tetraglycidylamine, bisphenol A, bisphenol F, bisphenol A glycidyl ether, and the like.

  If the amount of the epoxy resin used in the soft magnetic composition is too small, sufficient heat processability cannot be obtained, and if it is too large, the flexibility is impaired. It is 0 to 6.0% by weight, more preferably 1.5 to 4.0% by weight.

  In addition, specific examples of using a latent curing agent for epoxy resin for curing the epoxy resin in the soft magnetic composition include amine imidazoles and polyamidephenolic acid anhydrides.

  If the amount of the latent curing agent for epoxy resin in the soft magnetic composition is too small, the reliability of the product is lowered (decrease in storage characteristics), and if it is too much, the life of the paint and the life of the sheet are lowered. Since the cost is increased, the amount is preferably 3 to 100 parts by weight, more preferably 10 to 40 parts by weight with respect to 100 parts by weight of the epoxy resin.

  As the solvent, a general general-purpose solvent can be used. For example, alcohols such as ethanol, n-propanol, isopropyl alcohol (IPA) and n-butyl alcohol, esters such as ethyl acetate and n-butyl acetate, Acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), ketones such as cyclohexanone, ethers such as tetrahydrofuran (THF), ethyl cellosolve, n-butyl cellosolve, cellosolves such as cellosolve acetate, toluene, xylene, benzene, etc. General-purpose solvents such as aromatic hydrocarbons can be used. The amount used can be appropriately selected according to the type of composition of the soft magnetic composition, the coating method, and the like.

  As the release substrate, a normal release substrate can be used. For example, a polyester sheet whose surface has been subjected to a silicone release treatment can be used.

  The soft magnetic composition can be prepared by uniformly mixing the above-described components by a conventional method.

Process (B)
Two or more curable soft magnetic sheets obtained in the step (A) are prepared and laminated to obtain a laminate. The number of layers is determined by the use of the laminated soft magnetic sheet. Moreover, when laminating, it is preferable to arrange release sheets on both sides of the laminate of soft magnetic sheets. As the release sheet in this case, a polyester sheet or the like whose surface has been subjected to silicone release treatment can be used.

Process (C)
Next, the laminate obtained in the step (B) is subjected to linear pressure P1, linear pressure P2 and linear pressure P3 (provided that P1 < It compresses sequentially by P2 <P3) and carries out temporary pressure bonding. By performing the temporary pressure bonding in this way, it is possible to prevent the occurrence of defective products due to sheet displacement, to improve the reliability by air bleeding, and to prevent stretching.

  In this step, the reason why the soft magnetic sheet is pressurized at a temperature T2 at which a curing reaction does not substantially occur is to cause a uniform crosslinking reaction in a state where a surface pressure is applied. Here, “substantially no curing reaction” means not only when the curing reaction does not occur at all as in the case of the step (A), but also a slight curing as long as the effect of the invention is not impaired. This means that the reaction may occur, and means that the crosslinking reaction is uniformly performed in the final step. An example of a specific means for substantially preventing the curing reaction is to set the temperature T2 to a temperature lower by 5 ° C. or more than the curing reaction start temperature. Although specific temperature T2 changes with compositions of the soft-magnetic composition which comprises a soft-magnetic sheet, it is 70-130 degreeC normally, Preferably it is 70-100 degreeC. As a specific heating method, a known method using a hot air drying furnace, an electric heating furnace, an infrared heating furnace, or the like can be employed.

  The reason why the line pressure is applied by the laminator that applies the line pressure is to prevent air entrainment. The reason for applying gradually from low to high linear pressure in three stages is to effectively vent the sheet according to the softness and density of the sheet and to prevent sheet misalignment. . Specific examples of the laminator include a metal roll, a rubber roll, and a combination of a metal roll and a rubber roll.

  Specific numerical values of P1, P2, and P3 vary depending on the material of the soft magnetic sheet, the number of laminated layers, etc., but P1 is preferably 2 to 10 kgf / cm, more preferably 3 to 8 kgf / cm, and P2 is preferably 10 20 kgf / cm, more preferably 12-18 kgf / cm, and P3 is preferably 20-50 kgf / cm, more preferably 25-45 kgf / cm.

  In addition, if the line speed of the laminator in this step is too fast, heat is not transmitted and compression does not proceed, causing problems such as poor bonding, and if it is too slow, production efficiency deteriorates and costs increase. It is -5.0 m / min, More preferably, it is 0.5-3.0 m / min.

Process (D)
Subsequently, the laminated soft magnetic sheet of the present invention is subjected to main compression bonding while being compressed and cured by a press machine applying a surface pressure at a temperature T3 at which a curing reaction occurs at the compressed laminate obtained in the step (C). Get. In the obtained laminated soft magnetic sheet, a change in sheet thickness is suppressed even under a high temperature or high temperature and high humidity environment, and as a result, the magnetic permeability does not decrease.

In this step, the reason why the compressed laminate is pressurized at the temperature T3 at which the curing reaction occurs is to advance the crosslinking reaction in a state where the magnetic powders are arranged in the plane. Although specific temperature T3 changes with compositions of a soft-magnetic composition, it is 140-200 degreeC normally, Preferably it is 150-180 degreeC. Further, the reason for applying the pressure by the surface pressure is to perform crosslinking in a state in which the surface is uniformly pressurized. The surface pressure value varies depending on the material of the soft magnetic sheet, the number of laminated layers, and the like, but is preferably 10 to 60 kgf / cm ² , more preferably 15 to 40 kgf / cm ² .

  The laminated soft magnetic sheet obtained by the above manufacturing method is one in which a change in sheet thickness is suppressed and a change in magnetic permeability is small.

  Hereinafter, the present invention will be specifically described by way of examples.

Example 1
(Creation of soft magnetic sheet)
550 parts by weight of flat soft magnetic powder Fe · Si · Cr · Ni (manufactured by Mate Co., Ltd.), 83 parts by weight of acrylic rubber having a glycidyl group (SG80H · 3, manufactured by Nagase ChemteX Corp.), and epoxy resin (Epicoat) 1031S, manufactured by Japan Epoxy Resin Co., Ltd.) 23.1 parts by weight, latent curing agent for epoxy resin (HX3748, manufactured by Asahi Kasei Chemicals Co., Ltd.) 6.9 parts by weight, toluene 270 parts by weight, and ethyl acetate 120 parts by weight To prepare a soft magnetic composition. Regarding the cumulative particle diameter D (μm) of the used flat soft magnetic powder, D10 was 9.4 μm, D50 was 23.9 μm, and D90 was 49.1 μm. The bulk density was 0.6 g / cc, and the tap density was 1.30 g / cc.

  The composition is coated on a release polyester (PET) substrate with a coater, dried at a temperature of less than 80 ° C., then further dried at 100 ° C., and a soft magnetic sheet having a thickness of 100 μm on the release PET substrate. Got.

(Create a laminate of soft magnetic sheets)
The peeled PET substrate was peeled from the soft magnetic sheet described above to obtain a single-layer soft magnetic sheet. Four single-layer soft magnetic sheets were prepared and laminated to obtain a laminate.

(Temporary pressure bonding of laminates of soft magnetic sheets)
The obtained laminate was passed once through a laminator (manufactured by Sony Chemical & Information Device Co., Ltd.) whose roll temperature was set to 70 ° C. at a line speed of 0.5 m / min and a linear pressure of 3.3 kgf / cm. Preliminary pressure bonding was performed by passing twice at a linear pressure of 14.8 kgf / cm and further passing twice at a linear pressure of 29.54 kg / cm.

(Creation of laminated soft magnetic sheet)
Next, the temporarily bonded laminate was compressed with a vacuum press apparatus (manufactured by Kitagawa Seiki) at 165 ° C. for 10 minutes at a pressure of 24.9 kgf / cm ² to obtain a laminated soft magnetic sheet of Example 1. . A cross-sectional view of this laminated soft magnetic sheet is shown in FIG. From FIG. 1, it can be seen that the magnetic powder is densely packed and aligned in the plane direction.

Comparative Example 1
(Creation of soft magnetic sheet)
As in Example 1, a soft magnetic sheet having a thickness of 100 μm was obtained on a peeled PET substrate.

(Create a laminate of soft magnetic sheets)
The peeled PET substrate was peeled from the soft magnetic sheet described above to obtain a single-layer soft magnetic sheet. Four single-layer soft magnetic sheets were prepared and laminated to obtain a laminate.

(Temporary pressure bonding of laminates of soft magnetic sheets)
The obtained laminate was temporarily pressed through a laminator (manufactured by Sony Chemical & Information Device Co., Ltd.) set at a roll temperature of 70 ° C. at a line speed of 0.5 m / min and a linear pressure of 3.3 kgf / cm. Went.

(Creation of laminated soft magnetic sheet)
Next, the temporarily press-bonded laminate was compressed with a vacuum press apparatus (manufactured by Kitagawa Seiki) at a pressure of 24.9 kgf / cm ² to obtain a laminated soft magnetic sheet. A cross-sectional view of the laminated soft magnetic sheet is shown in FIG. FIG. 2 shows that there are slightly more voids at the lamination interface.

Comparative Example 2
(Creation of soft magnetic sheet)
As in Example 1, a soft magnetic sheet having a thickness of 100 μm was obtained on a peeled PET substrate.

(Create a laminate of soft magnetic sheets)
The peeled PET substrate was peeled from the soft magnetic sheet described above to obtain a single-layer soft magnetic sheet. Four single-layer soft magnetic sheets were prepared and laminated to obtain a laminate.

(Temporary pressure bonding of laminates of soft magnetic sheets)
The obtained laminate is temporarily pressed through a laminator (manufactured by Sony Chemical & Information Device Co., Ltd.) whose roll temperature is set to 70 ° C. at a line speed of 0.5 m / min and a linear pressure of 29.5 kgf / cm. Went.

(Creation of laminated soft magnetic sheet)
Next, the temporarily press-bonded laminate was compressed with a vacuum press apparatus (manufactured by Kitagawa Seiki) at a pressure of 24.9 kgf / cm ² to obtain a laminated soft magnetic sheet of Comparative Example 2. A cross-sectional view of this laminated soft magnetic sheet is shown in FIG. From FIG. 3, it can be seen that there are places with high orientation at high density and places with low density at low orientation.

Comparative Example 3
(Creation of soft magnetic sheet)
As in Example 1, a soft magnetic sheet having a thickness of 100 μm was obtained on a peeled PET substrate.

(Create a laminate of soft magnetic sheets)
The peeled PET substrate was peeled from the soft magnetic sheet described above to obtain a single-layer soft magnetic sheet. Four single-layer soft magnetic sheets were prepared and laminated to obtain a laminate. A cross-sectional view of the laminated soft magnetic sheet is shown in FIG. From FIG. 4, it can be seen that a large amount of air gap (air) remains.

(Creation of laminated soft magnetic sheet)
Next, the laminate was compressed at a pressure of 24.9 kgf / cm ² with a vacuum press device (manufactured by Kitagawa Seiki) without being temporarily crimped to obtain a laminated soft magnetic sheet of Comparative Example 3.

Comparative Example 4
(Creation of soft magnetic sheet)
As in Example 1, a soft magnetic sheet having a thickness of 100 μm was obtained on a peeled PET substrate.

(Create a laminate of soft magnetic sheets)
The peeled PET substrate was peeled from the soft magnetic sheet described above to obtain a single-layer soft magnetic sheet. Four single-layer soft magnetic sheets were prepared and laminated to obtain a laminate.

(Creation of laminated soft magnetic sheet)
Next, the laminate was compressed at a pressure of 37.4 kgf / cm ² with a vacuum press device (manufactured by Kitagawa Seiki) without provisional pressure bonding, and a laminated soft magnetic sheet of Comparative Example 4 was obtained. A cross-sectional view of this laminated soft magnetic sheet is shown in FIG. From FIG. 5, it can be seen that the high density area and the air gap area are clearly separated.

(Evaluation)
For the obtained laminated soft magnetic sheet, first, the thickness (t1) and the magnetic permeability μ ′ were measured. The magnetic permeability is preferably 38 or more practically. Further, the thickness (t2) of the soft magnetic sheet after being held for 240 hours (hr) in a high-temperature and high-humidity environment of 85 ° C. and 60% Rh was measured, and the rate of change in thickness [(t1-t2) × 100 / t2 ] (%) Was calculated. The thickness change rate is preferably closer to 0 (in Table 1, G is the case where the thickness change rate is less than 2.0, and NG is the other case). Further, the sheet misalignment occurrence rate (%) was calculated from the number of sheets prepared and the number of sheets stacked. The obtained results are shown in Table 1.

  As can be seen from Table 1, in the case of the laminated soft magnetic sheet of Example 1, the magnetic permeability μ ′ can be increased by passing the laminate of the soft magnetic sheet through a laminator under three-stage pressure conditions before the vacuum press, Moreover, the change in thickness at 85 ° C., 60 Rh%, and 240 hr was also suppressed to 2% or less. Even when the cross section of the soft magnetic sheet was observed, it was found that air was not contained, and the lamination interface was not confirmed. In addition, when 50 laminated soft magnetic sheets were produced, the defective product occurrence rate due to sheet misalignment was 0%.

  In the case of the laminated soft magnetic sheet of Comparative Example 1, the magnetic permeability μ ′ could be increased by passing the soft magnetic sheet through a laminator before vacuum pressing, but the change in sheet thickness at 85 ° C., 60 Rh%, 240 hr. Was 3% or more, and the change in thickness was larger than that in Example 1. When 50 sheets were produced, the sheet deviation was 0 sheets, and the occurrence rate of defective products was 0%.

  In the case of the laminated soft magnetic sheet of Comparative Example 2, the magnetic permeability μ ′ could be increased by passing the soft magnetic sheet through a laminator before the vacuum press, but the thickness change at 85 ° C., 60 Rh%, 240 hr It was 2% or more, and the change in thickness was larger than that in Example 1. When 50 sheets were produced, the sheet shift was 12 sheets, and the incidence of defective products was high.

  In the case of the laminated soft magnetic sheet of Comparative Example 3, since it was not passed through a laminator before being compressed by a vacuum press, as shown in FIG. 4, each of the single-layer soft magnetic sheets constituting the laminated soft magnetic sheet was It can be seen that there is a gap at the interface. Further, the change in thickness at 85 ° C., 60 Rh%, and 240 hr was 2% or more, and the change in thickness was larger than that in Example 1. In addition, the defective product generation rate due to the misalignment of the sheets when 50 sheets were produced was 0%.

  In the case of the laminated soft magnetic sheet of Comparative Example 4, the permeability μ ′ equivalent to that of Example 1 can be obtained by increasing the pressure of the vacuum press, and the gap at the laminated interface is reduced. It is considered that this is a factor that changes the thickness in a high-temperature and high-humidity environment because the compression is performed under a certain pressure. The change in thickness at 85 ° C., 60 Rh%, and 240 hr was 2% or more, which was larger than that in Example 1. In addition, the defective product generation rate due to the misalignment of the sheets when 50 sheets were produced was 0%.

  In the manufacturing method of the present invention, a specific soft magnetic composition for forming a soft magnetic sheet is used, and the heat curing does not proceed with respect to the heating pattern and the pressure application pattern for the laminate of thin soft magnetic sheets formed therefrom. Temporary pressure bonding is performed at three levels of linear pressure, ie, low, medium, and high, followed by main pressure bonding at a surface pressure at a temperature at which thermosetting proceeds. For this reason, a change in the thickness of the laminated soft magnetic sheet can be suppressed even in a high temperature or high temperature and high humidity environment, and as a result, the magnetic permeability can be prevented from decreasing. Further, this soft magnetic sheet is useful as a magnetic flux converging body in an RFID system such as a non-contact type IC card or IC tag, or as a general electromagnetic wave absorber. That is, it is useful as a noise electromagnetic wave absorber for electronic devices such as RFID flexible shield materials and portable digital cameras.

2 is an electron micrograph of a cross section of the laminated soft magnetic sheet of Example 1. FIG. 4 is an electron micrograph of a cross section of a laminated soft magnetic sheet of Comparative Example 1. 4 is an electron micrograph of a cross section of a laminated soft magnetic sheet of Comparative Example 2. 4 is an electron micrograph of a cross section of a laminated soft magnetic sheet of Comparative Example 3. 6 is an electron micrograph of a cross section of a laminated soft magnetic sheet of Comparative Example 4.

Claims (5)

A method for producing a laminated soft magnetic sheet, comprising the following steps (A) to (D):
(A) A soft magnetic composition obtained by mixing at least a flat soft magnetic powder, an acrylic rubber having a glycidyl group, an epoxy resin, a latent curing agent for epoxy resin, and a solvent is formed on a release substrate. Applying, drying at a temperature T1 at which the curing reaction of the soft magnetic composition does not substantially occur, removing the release substrate, and obtaining a curable soft magnetic sheet;
(B) preparing two or more of the curable soft magnetic sheets and laminating them to obtain a laminate;
(C) At a temperature T2 at which the curing reaction does not substantially occur, the obtained laminate is subjected to linear pressure P1, linear pressure P2, and linear pressure P3 (note that P1 <P2 <P3) at a laminator that applies linear pressure. And (D) a step of compressing the compressed laminate with a press machine that applies a surface pressure to obtain a laminated soft magnetic sheet at a temperature T3 at which a curing reaction subsequently occurs. A featured manufacturing method. P1 is 2~10kgf / cm, P2 is 10~20kgf / cm, P3 is 20~50kgf / cm, the manufacturing method according to claim 1, wherein the surface pressure is 10~60kgf / cm ^2.   The manufacturing method according to claim 1 or 2, wherein T1 is 50 to 90 ° C, T2 is 70 to 130 ° C, and T3 is 140 to 200 ° C.   The production method according to any one of claims 1 to 3, wherein a line speed of the laminator in the step (C) is 0.1 to 5 m / min.   The manufacturing method according to any one of claims 1 to 4, wherein in steps (C) and (D), a release sheet is disposed on each of both surfaces of the laminate, and the release sheet is released and compressed.