HK1133949B - Process for the production of laminate-type soft magnetic sheets - Google Patents
Process for the production of laminate-type soft magnetic sheets Download PDFInfo
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- HK1133949B HK1133949B HK09111536.9A HK09111536A HK1133949B HK 1133949 B HK1133949 B HK 1133949B HK 09111536 A HK09111536 A HK 09111536A HK 1133949 B HK1133949 B HK 1133949B
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Description
Technical Field
The present invention relates to a method for producing a soft magnetic sheet having excellent magnetic properties and small thickness variations.
Background
The production of soft magnetic sheets used in various electronic devices is generally carried out by a kneading and rolling method. In this method, flat soft magnetic powder and a binder such as rubber and chlorinated polyethylene are kneaded in a kneader in a predetermined ratio, the resulting kneaded product is rolled into a predetermined thickness in a device such as a roll, and the binder is heated and crosslinked as necessary, thereby obtaining a single-layer soft magnetic sheet. This method has advantages that the soft magnetic powder can be filled at 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 kneading and rolling method, since the soft magnetic powder is strained during kneading, the magnetic properties of the soft magnetic powder itself are lowered, and the magnetic permeability of the soft magnetic sheet cannot be increased. Further, the thickness of the sheet changes in a direction of increasing the thickness under a high-temperature or high-temperature and high-humidity environment, and the permeability is lowered.
Therefore, a soft magnetic sheet is produced by replacing the kneading and rolling method with an application method that is less likely to cause strain in the soft magnetic powder (patent document 1). In this method, a soft magnetic sheet having a small thickness change under high temperature, high temperature and high humidity conditions is obtained by applying a liquid composition for forming a soft magnetic sheet containing flat soft magnetic powder, rubber, resin, and solvent onto a release substrate and drying the composition.
Patent document 1: japanese patent laid-open No. 2000-243615
Disclosure of Invention
However, the coating method is suitable for the case of manufacturing a soft magnetic sheet having a small sheet thickness, and is not suitable for manufacturing a relatively thick soft magnetic sheet. This is because if the coating is thick, unevenness in coating thickness is likely to occur, and drying is also difficult. Therefore, the present inventors tried to prepare a curable thin soft magnetic sheet by a coating method by mixing a curable resin and a curing agent thereof in a liquid composition for forming a soft magnetic sheet, and preliminarily pressing a plurality of the sheets at a relatively low temperature, followed by final pressing at a relatively high temperature, thereby preparing a soft magnetic sheet into a laminate type. However, a laminated soft magnetic sheet obtained by laminating thin soft magnetic sheets produced by a coating method has a problem that the sheet thickness changes in a direction of increasing the thickness in a high-temperature or high-temperature and high-humidity environment, and the magnetic permeability decreases, similarly to a single-layer thick soft magnetic sheet produced by a kneading and rolling method, although the sheet thickness change per thin soft magnetic sheet is small.
The present invention has been made to solve the above-described problems of the conventional art, and an object of the present invention is to: provided is a method for producing a laminated soft magnetic sheet, which can laminate a plurality of thin soft magnetic sheets produced by a coating method, can suppress the variation in sheet thickness, and has a small variation in magnetic permeability.
The present inventors considered that the reason why the sheet thickness of a laminated soft magnetic sheet obtained by laminating thin soft magnetic sheets produced by a coating method changes in the direction of increasing the thickness thereof and the magnetic permeability decreases in a high-temperature or high-temperature and high-humidity environment is as follows: one is that air is introduced into the middle of thin soft magnetic sheets constituting the laminate type soft magnetic sheet, and the sheet thickness is increased by the expansion of the air due to high temperature; in the other, during thermal compression, the strain generated by the flat soft magnetic powder is relaxed by high temperature, and the resin portion constituting the sheet shrinks, whereby the sheet thickness increases.
The present inventors have assumed the former as a main cause and found that if a high pressure is applied when a plurality of soft magnetic sheets are temporarily thermally compressed, the sheet thickness varies at a level that cannot be ignored. Further, assuming the latter as a main factor, it was found that the sheet thickness still varies at a level that cannot be ignored if a lower pressure is applied when temporarily thermally pressing a plurality of soft magnetic sheets.
In view of the fact that the object of the present invention cannot be achieved by simply applying a relatively high pressure or a low pressure at the time of temporary hot pressing, the present inventors have conducted detailed studies on the heating method and the pressure application method of a laminate of thin soft magnetic sheets formed therefrom using a specific material as a soft magnetic composition for forming a soft magnetic sheet, and have found that the above object can be achieved by performing pre-pressing at a temperature at which thermal curing does not proceed and at a low, medium, and high three-stage line pressure, and then performing final pressing at a temperature at which thermal curing proceeds and at a surface pressure, and have completed the present invention.
That is, the present invention provides a method for producing a laminated soft magnetic sheet, characterized by comprising the following steps (a) to (D):
(A) a step of coating a soft magnetic composition on a release substrate, drying the coated soft magnetic composition at a temperature T1 at which a curing reaction of the soft magnetic composition does not substantially occur, and removing the release substrate to obtain a curable soft magnetic sheet, wherein the soft magnetic composition is obtained by mixing at least flat soft magnetic powder, an acrylic rubber having glycidyl groups, an epoxy resin, a latent curing agent for an epoxy resin, and a solvent;
(B) preparing 2 or more sheets of the curable soft magnetic sheet, and laminating the sheets to obtain a laminate;
(C) a step of compressing the resulting laminate sequentially at a line pressure of P1, a line pressure of P2 and a line pressure of P3(P1 < P2 < P3) by a laminator applying the line pressure at a temperature of T2 at which a curing reaction does not substantially occur; and
(D) and then compressing the compressed laminate with a compressor applying a surface pressure at a temperature T3 at which the curing reaction occurs to obtain a laminated soft magnetic sheet.
According to the present invention, a specific composition is used as a soft magnetic composition for forming a soft magnetic sheet, and as for the heating means and the pressure application means for the laminate of the thin soft magnetic sheet thus formed, pre-press bonding is performed at a temperature at which thermal curing does not proceed and at a line pressure of three stages of low, medium and high, followed by final press bonding at a temperature at which thermal curing proceeds and at a surface pressure. This can suppress the change in sheet thickness even under a high-temperature or high-temperature and high-humidity environment, and as a result, the magnetic permeability can be prevented from decreasing.
Brief Description of Drawings
Fig. 1 is a sectional electron microscope photograph of the laminate-type soft magnetic sheet of example 1.
Fig. 2 is a sectional electron micrograph of the laminate-type soft magnetic sheet of comparative example 1.
Fig. 3 is a sectional electron micrograph of the laminate-type soft magnetic sheet of comparative example 2.
Fig. 4 is a sectional electron micrograph of the laminate-type soft magnetic sheet of comparative example 3.
Fig. 5 is a sectional electron micrograph of the laminate-type soft magnetic sheet of comparative example 4.
Best Mode for Carrying Out The Invention
The method for producing a laminated soft magnetic sheet of the present invention has at least the following steps (a) to (D). Each step is explained.
Step (A)
A curable magnetic sheet is obtained by applying a soft magnetic composition, which is obtained by mixing at least flat soft magnetic powder, an acrylic rubber having glycidyl groups, an epoxy resin, a latent curing agent for epoxy resin, and a solvent, to a release substrate, drying the composition at a temperature T1 at which the soft magnetic composition does not substantially undergo a curing reaction, and removing the release substrate.
The method for coating the soft magnetic composition on the release substrate can be a known method such as a blade coating method or a Comma Coater coating method. The coating thickness may be suitably determined depending on the use of the curable soft magnetic sheet or the number of layers, and is usually applied to a dry thickness of 50 to 200 μm.
After the soft magnetic composition was applied to the release substrate, the release substrate was removed by drying at a temperature T1 at which the curing reaction of the soft magnetic composition did not substantially occur, and a curable soft magnetic sheet was obtained. The reason why the drying is performed at the temperature T1 at which the curing reaction of the soft magnetic composition does not substantially occur is that: if the curing reaction proceeds, the compressibility deteriorates and μ' cannot be increased, and if the material on which the curing reaction has proceeded is compressed, the thickness change under a high-temperature and high-humidity environment increases. Here, the meaning of "the curing reaction does not substantially occur" is: not only the case where the curing reaction does not occur at all, but also a slight curing reaction may occur within a range where the effect of the present invention is not impaired, which means that the crosslinking reaction proceeds uniformly in the final step. Specific methods for substantially preventing the curing reaction are: the temperature T1 was set to be 5 ℃ or more lower than the curing reaction initiation temperature. The specific temperature T1 varies depending on the composition of the soft magnetic composition, and is usually 130 ℃ or lower. As a specific drying method, a known method such as a warm air drying furnace, an electric heating furnace, an infrared heating furnace, etc. can be used.
In the soft magnetic composition, a flat powder (flat soft magnetic powder) is used as the soft magnetic powder. The flat soft magnetic powder is aligned in the in-plane direction of the plane, and high magnetic permeability and large specific gravity can be achieved.
As the material of the flat soft magnetic powder, any soft magnetic alloy can be used, for example, magnetic stainless steel (Fe-Cr-Al-Si alloy), iron-silicon-aluminum alloy (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. Among them, from the viewpoint of magnetic properties, an Fe-Si-Al alloy or an Fe-Si-Cr-Ni alloy can be preferably used.
When these soft magnetic alloys are applied to RFID communication, it is preferable to use a soft magnetic alloy having a large value of the real part (permeability) μ' of the complex relative permeability and a small value of the imaginary part (magnetic loss) μ ″ of the complex relative permeability. This prevents the magnetic field emitted from the antenna coil for RFID communication from being converted into eddy current by the metal body, thereby improving communication performance.
In order to reduce the value of μ "and thus the eddy current loss, the flat soft magnetic alloy is preferably an alloy having a large electric resistance. In this case, the resistance can be increased by changing the composition of the soft magnetic alloy. For example, in the case of Fe-Si-Cr alloy, the Si content is preferably 9 to 15 wt%.
As the flat soft magnetic powder, a flat soft magnetic powder can be used, and it is preferable that the average particle diameter is 3.5 to 90 μm and the average thickness is 0.3 to 3.0. mu.m, and it is more preferable that the average particle diameter is 10 to 50 μm and the average thickness is 0.5 to 2.5. mu.m. Therefore, the flattening ratio is preferably set to 8 to 80, more preferably 15 to 65. In order to make the size of the flat soft magnetic powder uniform, the flat soft magnetic powder may be classified by using a sieve or the like as necessary. In order to increase the magnetic permeability of the soft magnetic material, it is effective to increase the particle size of the flat soft magnetic powder to reduce the interval between particles and to increase the aspect ratio of the flat soft magnetic powder to reduce the influence of the diamagnetic field in the soft magnetic sheet.
The tap density and the specific surface area (BET method) of the flat soft magnetic powder are inversely proportional to each other, but if the specific surface area is increased, not only the μ' value but also the μ ″ value which is not desired to be increased tend to be increased, and therefore these numerical value ranges can be set to preferable ranges. Specifically, the tap density is preferably set to 0.55 to 1.45g/mL, more preferably 0.65 to 1.40g/mL, and the specific surface area is preferably set to 0.40 to 1.20m2In g, more preferably from 0.65 to 1.00m2/g。
As the flat soft magnetic powder, for example, a soft magnetic powder subjected to coupling treatment with a coupling agent such as a silane coupling agent can be used. By using the soft magnetic powder subjected to the coupling treatment, the reinforcing effect at the interface between the flat soft magnetic powder and the binder resin can be improved, and the specific gravity and the corrosion resistance can be improved. Examples of the coupling agent include gamma-methacryloxypropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane and the like. The coupling treatment may be performed on the soft magnetic powder in advance, or may be performed by mixing the flat soft magnetic powder with the binder resin, and as a result, the coupling treatment may be performed.
If the amount of flat soft magnetic powder used in the soft magnetic composition is too small, the desired magnetic properties cannot be obtained, and if too large, the amount of binder resin is relatively reduced, and moldability is lowered, so that the amount is preferably 70 to 90% by weight, more preferably 80 to 85% by weight, based on the soft magnetic composition from which the solvent is removed.
In order to impart good flexibility and heat resistance to the laminated soft magnetic sheet, the soft magnetic composition uses an acrylic rubber as a rubber component. In order to improve compatibility with the epoxy resin, the acrylic rubber must have 1 or more glycidyl groups. Specific examples are: EA-AN, BA-MMA, etc.
When the amount of the acrylic rubber used in the soft magnetic composition is too small, sufficient hot workability cannot be obtained, and when it is too large, the rubber elasticity is too large and the hot workability deteriorates, so that the amount of the acrylic rubber is preferably 9 to 16% by weight, more preferably 12 to 14% by weight, based on the soft magnetic composition from which the solvent has been removed.
In order to impart good thermal processability and dimensional stability to the laminated soft magnetic sheet, an epoxy resin is used for the soft magnetic composition. Specific examples are: phenol novolac resins, tetraglycidyl phenol, o-cresol novolac resins, tetraglycidyl amine, bisphenol a, bisphenol F, bisphenol a glycidyl ether, and the like.
When the amount of the epoxy resin used in the soft magnetic composition is too small, sufficient hot workability cannot be obtained, and when it is too large, flexibility is impaired, so that the amount of the epoxy resin is preferably 1.0 to 6.0% by weight, more preferably 1.5 to 4.0% by weight, based on the soft magnetic composition from which the solvent has been removed.
Specific examples of the latent curing agent for epoxy resin used for curing epoxy resin in the soft magnetic composition include: amine imidazoles, polyamide phenolic anhydrides, and the like.
Since the use amount of the latent curing agent for epoxy resin in the soft magnetic composition is too small, the reliability of the product is lowered (storage property is lowered), and when it is too large, the life of the coating material is lowered or the life of the sheet is lowered, and the cost is increased, it is preferably 3 to 100 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the epoxy resin.
As the solvent, a commonly used solvent can be used, and examples thereof include alcohols such as ethanol, n-propanol, Isopropanol (IPA) and n-butanol, esters such as ethyl acetate and n-butyl acetate, ketones such as acetone, Methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone, ethers such as Tetrahydrofuran (THF), cellosolves such as ethyl cellosolve, n-butyl cellosolve and cellosolve acetate, and commonly used solvents such as aromatic hydrocarbons such as toluene, xylene and benzene. The amount of the soft magnetic composition used may be appropriately selected depending on the type of composition of the soft magnetic composition, the coating method, and the like.
The release substrate may be a general release substrate. For example, there are polyester sheets whose surfaces are subjected to silicone release treatment.
The soft magnetic composition can be prepared by uniformly mixing the above components according to a conventional method.
Step (B)
2 pieces of the curable soft magnetic sheet obtained in the above step (A) were prepared, and laminated to obtain a laminate. The lamination number is determined according to the use of the laminated soft magnetic sheet and the like. In the lamination, it is preferable to dispose release sheets on both sides of the laminate of the soft magnetic sheet. The release sheet used in this case may be a polyester sheet whose surface has been subjected to a silicone release treatment.
Step (C)
Subsequently, the laminate obtained in the step (B) was successively compressed at a line pressure P1, a line pressure P2 and a line pressure P3(P1 < P2 < P3) by a laminator for applying a line pressure at a temperature T2 at which a curing reaction did not substantially occur, and subjected to pre-press bonding. Thus, by performing the pre-press, defective products due to the displacement of the sheet can be prevented, reliability can be improved by removing gas, and extension can be prevented.
In this step, the soft magnetic sheet is pressed at a temperature T2 at which the curing reaction does not substantially occur in order to cause a uniform crosslinking reaction in a state where a surface pressure is applied. Here, the phrase "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 within a range not impairing the effect of the invention, as in the case of the step (a), and means that the crosslinking reaction proceeds uniformly in the final step. Specific methods for substantially preventing the curing reaction are: the temperature T2 was set to be 5 ℃ or more lower than the curing reaction initiation temperature. The specific temperature T2 varies depending on the composition of the soft magnetic composition constituting the soft magnetic sheet, and is usually 70 to 130 ℃ and preferably 70 to 100 ℃. As a specific heating method, a known method using a warm air drying furnace, an electric heating furnace, an infrared heating furnace, or the like can be used.
The line pressure is applied by the laminator applying the line pressure in order to prevent the entanglement of air. The pressure is slowly applied from low line pressure to high line pressure in three stages in order to effectively remove gas for bonding softness and density of the sheet, and no lamination shift of the sheet occurs. Specific examples of laminators are: the upper part and the lower part are a metal roller, a rubber roller, a combination of the metal roller and the rubber roller and the like.
Specific values of P1, P2, P3 differ depending on the material, number of layers, etc. of the soft magnetic sheet, P1 is preferably 2 to 10kgf/cm, more preferably 3 to 8 kgf/cm; p2 is preferably 10 to 20kgf/cm, more preferably 12 to 18kgf/cm, and P3 is preferably 20 to 50kgf/cm, more preferably 25 to 45 kgf/cm.
If the linear speed of the laminating machine in the step is too fast, heat cannot be conducted, compression cannot be progressed, and the problems of poor lamination and the like are caused; if the rate is too slow, the production efficiency is deteriorated and the cost is increased, so that the rate is preferably 0.1 to 5.0 m/min, more preferably 0.5 to 3.0 m/min.
Step (D)
Next, the compressed laminate obtained in the step (C) was compressed with a compressor applying a surface pressure at a temperature T3 at which the curing reaction occurred, and cured while performing final press-fitting, to obtain a laminated soft magnetic sheet of the present invention. The obtained laminate-type soft magnetic sheet is suppressed in the variation in sheet thickness even under a high-temperature or high-temperature and high-humidity environment, and as a result, the magnetic permeability is not lowered.
In this step, the reason why the compressed laminate is pressurized at a temperature T3 at which the curing reaction occurs is to cause the crosslinking reaction to proceed in a state in which the magnetic powder is aligned in the plane. The specific temperature T3 varies depending on the composition of the soft magnetic composition and is typically 140-200 deg.C, preferably 150-180 deg.C. The surface pressure is applied to crosslink the film in a uniformly in-plane pressurized state. The value of the surface pressure differs depending on the material, the number of layers, etc. of the soft magnetic sheet, and is preferably 10 to 60kgf/cm2More preferably 15 to 40kgf/cm2。
The laminated soft magnetic sheet obtained by the above production method is suppressed in the variation in sheet thickness and is small in the variation in magnetic permeability.
Examples
The present invention is specifically illustrated by the following examples.
Example 1
(preparation of Soft magnetic sheet)
A soft magnetic composition was prepared by mixing 550 parts by weight of flat soft magnetic powder Fe.Si.Cr.Ni (manufactured by MATE Co., Ltd.), 83 parts by weight of an acrylic rubber having a glycidyl group (SG 80H.3, manufactured by Nagase ChemteX Co., Ltd.), 23.1 parts by weight of an epoxy resin (EPICOAT 1031S, manufactured by Japan epoxy resins Co., Ltd.), 6.9 parts by weight of a latent curing agent for epoxy resin (HX3748, manufactured by Asahi Chemicals Co., Ltd.), 270 parts by weight of toluene and 120 parts by weight of ethyl acetate. Regarding the cumulative particle diameter D (μm) of the flat soft magnetic powder used, D10 was 9.4 μm, D50 was 23.9 μm, and D90 was 49.1 μm. The bulk density was 0.6g/cc, and the tap density was 1.30 g/cc.
The composition was coated on a release Polyester (PET) substrate with a coater, dried at a temperature of less than 80 c, and then dried at 100 c to obtain a soft magnetic sheet having a thickness of 100 μm on the release PET substrate.
(production of laminate of Soft magnetic sheet)
And stripping the PET substrate from the soft magnetic sheet to obtain a single-layer soft magnetic sheet. 4 pieces of the single-layer soft magnetic sheet were prepared and laminated to obtain a laminate.
(Pre-lamination of laminate of Soft magnetic sheets)
The resulting laminate was subjected to pre-press in a laminator (manufactured by Sony Chemical & information device Co., Ltd.) with a roll temperature set to 70 ℃ by passing the laminate 1 time at a linear velocity of 0.5 m/min and a linear pressure of 3.3kgf/cm, 2 times at a linear pressure of 14.8kgf/cm, and 2 times at a linear pressure of 29.54 kg/cm.
(production of laminated Soft magnetic sheet)
Next, the pre-laminated laminate was subjected to vacuum compression at 165 ℃ in a vacuum compression apparatus (Beichuan precision press) at 24.9kgf/cm2Was compressed for 10 minutes under pressure to obtain a laminated type soft magnetic sheet of example 1. A cross-sectional view of the laminated soft magnetic sheet is shown in fig. 1. As can be seen from fig. 1, the magnetic powder is filled with high density and aligned in the in-plane direction.
Comparative example 1
(preparation of Soft magnetic sheet)
A soft magnetic sheet having a thickness of 100 μm was obtained on a peeled PET substrate in the same manner as in example 1.
(production of laminate of Soft magnetic sheet)
And stripping the PET substrate from the soft magnetic sheet to obtain a single-layer soft magnetic sheet. 4 pieces of the single-layer soft magnetic sheet were prepared and laminated to obtain a laminate.
(Pre-lamination of laminate of Soft magnetic sheets)
The resulting laminate was passed 5 times at a linear speed of 0.5 m/min and a linear pressure of 3.3kgf/cm in a laminator (manufactured by Sony Chemical & information device Co., Ltd.) with a roll temperature set to 70 ℃ to perform pre-press-fitting.
(production of laminated Soft magnetic sheet)
Next, the pre-laminated laminate was subjected to vacuum compression at 24.9kgf/cm using a vacuum compression apparatus (Beichuan precision press)2Is compressed to obtain a laminated soft magnetic sheet. A cross-sectional view of the laminated soft magnetic sheet is shown in fig. 2. As can be seen from fig. 2, the lamination interface had a slightly large number of voids.
Comparative example 2
(preparation of Soft magnetic sheet)
A soft magnetic sheet having a thickness of 100 μm was obtained on a peeled PET substrate in the same manner as in example 1.
(production of laminate of Soft magnetic sheet)
And stripping the PET substrate from the soft magnetic sheet to obtain a single-layer soft magnetic sheet. 4 pieces of the single-layer soft magnetic sheet were prepared and laminated to obtain a laminate.
(Pre-lamination of laminate of Soft magnetic sheets)
The resulting laminate was passed 5 times at a linear speed of 0.5 m/min and a linear pressure of 29.5kgf/cm in a laminator (manufactured by Sony Chemical & information device Co., Ltd.) with a roll temperature set to 70 ℃ to perform pre-press-fitting.
(production of laminated Soft magnetic sheet)
Next, the pre-laminated laminate was subjected to vacuum compression at 24.9kgf/cm using a vacuum compression apparatus (Beichuan precision press)2Was compressed by the pressure of (2), and the laminated soft magnetic sheet of comparative example 2 was obtained. A cross-sectional view of the laminated soft magnetic sheet is shown in fig. 3. As can be seen from fig. 3, there are positions where the orientation is high in density and positions where the orientation is insufficient in low density.
Comparative example 3
(preparation of Soft magnetic sheet)
A soft magnetic sheet having a thickness of 100 μm was obtained on a peeled PET substrate in the same manner as in example 1.
(production of laminate of Soft magnetic sheet)
And stripping the PET substrate from the soft magnetic sheet to obtain a single-layer soft magnetic sheet. 4 pieces of the single-layer soft magnetic sheet were prepared and laminated to obtain a laminate. A cross-sectional view of the laminated soft magnetic sheet is shown in fig. 4. As can be seen from fig. 4, many voids (air) remain.
(production of laminated Soft magnetic sheet)
Next, the laminate was subjected to vacuum compression at 24.9kgf/cm using a vacuum press (Beichuan precision press) without pre-press2Was compressed under a pressure of (2) to obtain a laminate type soft material of comparative example 3A magnetic sheet.
Comparative example 4
(preparation of Soft magnetic sheet)
A soft magnetic sheet having a thickness of 100 μm was obtained on a peeled PET substrate in the same manner as in example 1.
(production of laminate of Soft magnetic sheet)
And stripping the PET substrate from the soft magnetic sheet to obtain a single-layer soft magnetic sheet. 4 pieces of the single-layer soft magnetic sheet were prepared and laminated to obtain a laminate.
(production of laminated Soft magnetic sheet)
Next, the laminate was subjected to vacuum compression at 34.7kgf/cm using a vacuum press (Beichuan precision press) without pre-press2Was compressed under the pressure of (2) to obtain a laminated soft magnetic sheet of comparative example 4. A cross-sectional view of the laminated soft magnetic sheet is shown in fig. 5. As can be seen from fig. 5, the high density region and the void (air) region are clearly divided.
(evaluation)
For the obtained laminate type soft magnetic sheet, the thickness (t1) and magnetic permeability (. mu.) were first measured. For practical use, the magnetic permeability is preferably 38 or more. The thickness of the soft magnetic sheet was measured after keeping the sheet at 85 ℃ under a high temperature and humidity environment of 60 Rh% for 240 hours (t2), and the thickness change rate [ (t1-t 2). times.100/t 2] (%) was calculated. The thickness change rate is preferably close to 0 (in table 1, G is evaluated when the thickness change rate is less than 2.0, and NG is evaluated in addition). And the offset incidence (%) of the sheet is the number of sheets in which the sheet lamination offset occurred calculated from the number of prepared sheets. The results obtained are shown in table 1.
[ Table 1]
| Example 1 | Comparative example 1 | Comparative example 2 | Comparative example 3 | Comparative example 4 | |
| Laminator pressure | Staging | Fixing | Fixing | Is free of | Is free of |
| 1 st pass at 70 ℃ kgf/cm] | 3.3 | 3.3 | 29.5 | - | - |
| 2 nd and 3 rd passes at 70 ℃ of kgf/cm] | 14.8 | 3.3 | 29.5 | - | - |
| 4 th and 5 th passes at 70 ℃ of kgf/cm] | 29.5 | 3.3 | 25.9 | - | - |
| Vacuum compression pressure [ kgf/cm ]2] | 24.9 | 24.9 | 24.9 | 24.9 | 37.4 |
| Magnetic permeability mu' (13.56MHz) | 41.6 | 39.7 | 24.3 | 39.6 | 41.4 |
| Thickness Change Rate (%) | 1.70 | 3.20 | 2.80 | 3.80 | 3.60 |
| Evaluation of | G | NG | NG | NG | NG |
| Incidence of plate shift (%) | 0 | 0 | 24 | 0 | 0 |
As is clear from table 1, in the case of the laminated soft magnetic sheet of example 1, the magnetic permeability μ' was increased by passing the laminate of the soft magnetic sheets through the laminator under three-stage pressure conditions before vacuum compression, and the thickness change at 85 ℃, 60 Rh%, and 240 hours was suppressed to a small extent of 2% or less. When the cross section of the soft magnetic sheet was observed, it was found that no air entered and no lamination interface was seen. When a soft magnetic sheet of a 50-sheet laminated type was produced, the occurrence rate of defective products due to the lamination shift of the sheet was 0%.
In the case of the laminate type soft magnetic sheet of comparative example 1, the magnetic permeability μ' can be increased by passing the soft magnetic sheet through a laminator before vacuum compression, but the sheet thickness change at 85 ℃, 60 Rh%, 240 hours is 3% or more, and the thickness change is larger as compared with example 1. When 50 sheets were produced, the shift of the sheet was 0 sheet, and the defective rate was 0%.
In the case of the laminate type soft magnetic sheet of comparative example 2, the magnetic permeability μ' can be increased by passing the soft magnetic sheet through a laminator before vacuum compression, but the sheet thickness change at 85 ℃, 60 Rh%, 240 hours is 2% or more, and the change in thickness is larger as compared with example 1. When 50 sheets were produced, the shift of the sheets was 12, and the occurrence rate of defective products was high.
In the case of the laminated soft magnetic sheet of comparative example 3, since the sheet did not pass through the laminator before being compressed by the vacuum compressor, a gap was generated at the interface of each soft magnetic sheet constituting a single layer of the laminated soft magnetic sheet as shown in fig. 4. Further, the thickness change at 85 ℃, 60 Rh% and 240 hours was 2% or more, and the thickness change was larger than that in example 1. The occurrence rate of defective products due to the lamination shift of the sheets when 50 sheets were produced was 0%.
In the case of the laminated soft magnetic sheet of comparative example 4, the magnetic permeability μ' equivalent to that of example 1 was obtained by increasing the pressure of the vacuum compressor, and the gap at the lamination interface was decreased, but the internal residual strain was compressed at an excessive pressure, which became a factor of the thickness change in the high-temperature and high-humidity environment. Further, the thickness change at 85 ℃, 60 Rh% and 240 hours was 2% or more, and the thickness change was larger than that in example 1. The occurrence rate of defective products due to the lamination shift of the sheets when 50 sheets were produced was 0%.
Industrial applicability
In the production method of the present invention, a specific composition is used as the soft magnetic composition for forming the soft magnetic sheet, and in the heating method and the pressure application method of the laminate of the thin soft magnetic sheet formed therefrom, the pre-press is performed at a temperature at which the thermal curing does not proceed, with a low, medium, and high three-stage line pressure, and then the final press is performed at a temperature at which the thermal curing proceeds, with a surface pressure, and therefore, the variation in thickness of the laminate type soft magnetic sheet can be suppressed even under a high temperature or high temperature and high humidity environment, and as a result, the magnetic permeability is not lowered. The soft magnetic sheet can be used as a magnetic flux concentrator in an RFID system such as a contactless IC card or an IC tag, or a general radio wave absorber. That is, the electromagnetic wave absorber can be used as a flexible shielding material for RFID, and as a noise electromagnetic wave absorber for electronic devices such as portable digital cameras.
Claims (4)
1. A method for producing a laminated soft magnetic sheet, characterized by comprising the following steps (A) to (D):
(A) a step of coating a soft magnetic composition on a release substrate, drying the coated soft magnetic composition at a temperature T1 at which a curing reaction of the soft magnetic composition does not substantially occur, and removing the release substrate to obtain a curable soft magnetic sheet, wherein the soft magnetic composition is obtained by mixing at least flat soft magnetic powder, an acrylic rubber having glycidyl groups, an epoxy resin, a latent curing agent for an epoxy resin, and a solvent;
(B) preparing 2 or more sheets of the curable soft magnetic sheet, and laminating the sheets to obtain a laminate;
(C) a step of sequentially compressing the resulting laminate at a line pressure of P1, P2 and P3 by means of a laminator applying a line pressure at a temperature of T2 at which a curing reaction does not substantially occur, wherein P1 < P2 < P3; and
(D) and then compressing the compressed laminate with a compressor applying a surface pressure at a temperature T3 at which the curing reaction occurs to obtain a laminated soft magnetic sheet.
2. The method according to claim 1, wherein P1 is 2 to 10kgf/cm, P2 is 10 to 20kgf/cm, P3 is 20 to 50kgf/cm, and the surface pressure is 10 to 60kgf/cm2。
3. The process according to claim 1, wherein T1 is 50 to 90 ℃, T2 is 70 to 130 ℃, and T3 is 140 to 200 ℃.
4. The method according to any one of claims 1 to 3, wherein the linear velocity of the laminator in the step (C) is 0.1 to 5 m/min.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP295289/2006 | 2006-10-31 | ||
| JP2006295289 | 2006-10-31 | ||
| PCT/JP2007/069435 WO2008053662A1 (en) | 2006-10-31 | 2007-10-04 | Process for the production of laminate-type soft magnetic sheets |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| HK1133949A1 HK1133949A1 (en) | 2010-04-09 |
| HK1133949B true HK1133949B (en) | 2012-10-05 |
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