JP2008183779A - Manufacturing method of magnetic sheet and magnetic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an extremely high-quality magnetic sheet by reducing a change in thickness due to aging. <P>SOLUTION: When the magnetic sheet 10 formed by using a magnetic painting which is made by mixing at least the magnetic material with a polymeric binder dissolved in a solvent is pressed and compressed with using predetermined press plates 20, 21 in manufacturing the magnetic sheet, ventilation materials 30, 31 having Bekk smoothness of 150 sec/ml or less are interposed between at least the press plates 20, 21 and the one side surface of the magnetic sheet 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a magnetic sheet suitable for use in an IC card, an IC tag, or the like that suppresses electromagnetic wave noise, and to a magnetic sheet manufactured by this manufacturing method.

  In recent years, systems that perform individual management called RFID (Radio Frequency IDentification) are being introduced in various industries. This RFID system stores various data called a transponder in a readable and / or writable manner and has a communication function and a small non-contact integrated circuit (hereinafter referred to as IC) device and a predetermined reader / This is a technique for reading and / or writing data without contact with a transponder by performing wireless communication with a writer. Specifically, in the RFID system, based on the principle of electromagnetic induction, when the magnetic flux is emitted from the reader / writer side loop antenna, the emitted magnetic flux is inductively coupled with the transponder side loop antenna. Magnetically coupled and communication is performed between the transponder and the reader / writer. This RFID system is configured, for example, by configuring a transponder as an IC tag and attaching the IC tag to a product to perform production / distribution management, as well as configuring a transponder as an IC card to collect charges for transportation or to a building It is expected to be applied to various uses such as identification cards used for entering and exiting, and electronic money.

  Such an RFID system eliminates the trouble of loading an IC card into a reader / writer or bringing a metal contact into contact with a conventional contact IC card system. Reading can be performed. In addition, since the RFID system supplies the necessary power from the reader / writer to the transponder by electromagnetic induction, there is no need to incorporate a power source such as a battery in the transponder, and it has a simple configuration and is inexpensive and reliable. It is also possible to provide a high transponder.

  However, in the RFID system, when there is another metal body around the transponder, there is a case where communication is hindered due to the influence. In the electromagnetic induction method, if a metal body is present in the surroundings, a resonance frequency shift or a magnetic flux change due to the change in inductance due to the influence of the metal body occurs, and it becomes impossible to secure electric power. Therefore, in the RFID system, in order to secure a sufficient communication range between the transponder and the reader / writer, it is necessary to provide a loop antenna on the transponder side that can radiate an electromagnetic field having a certain magnetic field strength.

  In this case, in order to reduce the influence of the metal body on the loop antenna by a method other than the spatial arrangement, it is effective to use, for example, a magnetic material, thereby reducing the influence of the metal body and increasing the communication distance. be able to. In recent communication equipment and electronic equipment, as the clock frequency increases, the frequency of noise electromagnetic waves increases, causing malfunction of the equipment itself due to external or internal interference, adverse effects on peripheral equipment, etc. However, magnetic materials are also effective in preventing the occurrence of such electromagnetic interference. Under such circumstances, for example, various composite magnetic sheets (soft magnetic sheets) obtained by dispersing and mixing an appropriate amount of soft magnetic powder in a binder such as rubber or plastics have been proposed.

  In producing such a magnetic sheet, usually, a magnetic coating material is prepared by mixing soft magnetic powder, a polymer binder (binder), and a solvent, and this is coated with a coater to remove PET (polyethylene terephthalate). After the magnetic sheet for one layer is formed by coating, the magnetic sheet formed on the peeling PET is peeled and laminated. And in manufacturing a magnetic sheet, the magnetic sheet as a final product was manufactured by compressing a plurality of laminated magnetic sheets using a laminator or a heat press. Here, the magnetic sheet is compressed in order to increase the filling ratio of the soft magnetic powder and improve the magnetic properties (permeability). However, in manufacturing the magnetic sheet, the magnetic sheet whose thickness is reduced by the compression. It is effective to use a thermosetting binder in order to reduce the swelling of the resin over time.

  As a technique for compressing such a plurality of sheet-like members, there is, for example, Patent Document 1. Further, when performing such compression, in order to apply a uniform pressure to the entire surface of the sheet-like member as a pressing object or to realize easy release, the sheet-like member and the press plate are usually used. A predetermined cushion material or a release film is interposed between them, and as a technique related to the cushion material and the release film, for example, Patent Documents 2 to 4 are proposed.

JP-A-2-248222 JP 2000-52369 A JP 2003-103552 A JP 2006-120839 A

  However, in the conventional method for manufacturing a magnetic sheet, as the magnetic sheets are laminated, a situation in which air is frequently involved between the overlapping magnetic sheets and the magnetic sheets frequently occurs. Here, in order to complete the crosslinking of the binder highly filled with the soft magnetic powder, it is necessary to apply heat and pressure to the magnetic sheet for a predetermined time. For this reason, the magnetic sheet produced by such a production method has a high temperature environment if air entrained between the magnetic sheet and outgas generated in response to the reaction remain in the magnetic sheet even after the compression process. Due to aging under a low temperature or high temperature and high humidity environment, the thickness changes in the direction of increasing thickness, and there is a problem in that a size defect and a change with time of magnetic properties (magnetic permeability) are caused.

  The present invention has been made in view of such circumstances, and the air and outgas present in the magnetic sheet are surely discharged during the compression process to reduce the change in thickness due to aging, and extremely high quality. It is an object of the present invention to provide a magnetic sheet manufacturing method capable of manufacturing a magnetic sheet, and a magnetic sheet manufactured by the manufacturing method.

  As a result of intensive research on the compression process when manufacturing the magnetic sheet, the inventor of the present application has found a technique that can reliably discharge air and outgas present in the magnetic sheet, and has completed the present invention. It was.

  That is, the method for producing a magnetic sheet according to the present invention that achieves the above-described object is a sheet that forms a magnetic sheet using a magnetic paint prepared by mixing at least a magnetic material and a polymer binder dissolved in a solvent. And a compression step of compressing the magnetic sheet formed in the sheet formation step by pressing with a predetermined press plate, and in the compression step, at least one side of the press plate and the magnetic sheet And a ventilation material having a Beck smoothness of 150 seconds / ml or less.

  In addition, the magnetic sheet according to the present invention that achieves the above-described object is a predetermined press plate obtained by using a magnetic coating prepared by mixing at least a magnetic material and a polymer binder dissolved in a solvent. A magnetic sheet produced by pressing and compressing using a material, wherein a ventilation material having a Beck smoothness of 150 seconds / ml or less is interposed between at least the press plate and one side of the sheet The sheet is manufactured by compressing the sheet.

  In the present invention, by performing compression with the ventilation material interposed, it is possible to create a situation in which air and outgas existing in the magnetic sheet can be quickly discharged when pressed by the press plate. Air and outgas can be reliably discharged. Therefore, in the present invention, the change in the thickness of the magnetic sheet due to aging can be reduced, and the amount of air and outgas present in the magnetic sheet is reduced. However, it is possible to manufacture a magnetic sheet having a high magnetic permeability while maintaining a good appearance with no trace of air or outgas being ejected.

  According to the present invention, it is possible to produce a very high-quality magnetic sheet that reduces the change in thickness due to aging and has good appearance and magnetic properties.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  This embodiment is a method of manufacturing a magnetic sheet suitable for use in an IC (Integrated Circuit) card, an IC tag, or the like used in a so-called RFID (Radio Frequency IDentification) system. In particular, this method of manufacturing a magnetic sheet ensures that air and outgas existing in the magnetic sheet are interposed by interposing a ventilation material satisfying a predetermined condition between the magnetic sheet and the press plate when the magnetic sheet is compressed. It is possible to reduce the thickness change due to aging.

  First, when manufacturing a magnetic sheet, a magnetic coating material is prepared by mixing at least a magnetic material and a polymer binder (binder) dissolved in a solvent, and the magnetic coating material is applied onto a predetermined substrate and then dried. To form a magnetic sheet.

  Here, a flat soft magnetic powder is desirable as the magnetic material. As the magnetic material constituting the flat soft magnetic powder, any soft magnetic material can be used. For example, magnetic stainless steel (Fe—Cr—Al—Si based alloy), sendust (Fe—Si—Al based) Alloy), permalloy (Fe-Ni alloy), silicon copper (Fe-Cu-Si alloy), Fe-Si alloy, Fe-Si-B (-Cu-Nb) alloy, Fe-Ni-Cr- Si-based alloys, Fe-Si-Cr-based alloys, Fe-Si-Al-Ni-Cr-based alloys, and the like are suitable. A magnetic sheet produced using a soft magnetic powder made of these soft magnetic materials can be suitably used as an RFID system application or a radio wave absorber because the soft magnetic powder is excellent in soft magnetic properties.

  As the soft magnetic powder, a soft magnetic powder having a flat shape is used, but it is desirable to use a soft magnetic powder having a major axis of 1 to 200 μm and a flatness of 10 to 50. In order to equalize the size of the flat soft magnetic powder, classification may be performed using a sieve or the like as necessary.

  Furthermore, as the soft magnetic powder, for example, a soft magnetic powder that has been subjected to a coupling treatment using 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 between the flat soft magnetic powder and the polymer binder interface 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 coupling treatment may be performed on the soft magnetic powder in advance, or may be performed at the same time when the soft magnetic powder and the binder are mixed, so that the coupling treatment is performed. Good.

  On the other hand, binders (polymer binders) include polyester resins, polyurethane resins, olefin resins such as polyethylene and polypropylene, vinyl resins such as vinyl chloride, vinyl acetate, and ethylene vinyl acetate copolymers, and acrylic resins. Synthetic rubber resins, natural rubber resins, polyamide resins, styrene resins, epoxy resins and the like, and copolymers thereof can be used. In particular, as the binder, it is possible to use a polyester-based resin which is a resin having good processability and capable of orienting a flat soft magnetic powder with high density. As the polyester resin used as the binder, a phosphorus-containing polyester resin having a phosphoric acid residue may be used. The magnetic sheet can be provided with flame retardancy by using this phosphorus-added polyester resin.

  As described above, the phosphorus-added polyester resin has a phosphoric acid residue in the molecule. Specific examples thereof include a phosphorus-modified saturated polyester copolymer. The phosphorus-modified saturated polyester copolymer is obtained by introducing a phosphorus component into the main skeleton of the saturated copolymer polyester, and is obtained by copolymerizing a polyester component and a phosphorus component. Here, as the polyester component, a polymer compound formed from ethylene glycol and terephthalic acid, naphthalenecarboxylic acid, adipic acid, sebacic acid or isophthalic acid, 1,4-butanediol and terephthalic acid, adipic acid or sebacic acid And a polymer compound formed from 1,6-hexanediol and adipic acid, sebacic acid, or isophthalic acid can be used. Moreover, as a phosphorus component, a phosphonate type polyol, a phosphate type polyol, a vinyl phosphonate, an allyl phosphonate, etc. can be used. Thus, the polyester copolymer in which the phosphorus component is introduced into the main skeleton exhibits flame retardancy higher than that obtained by simply mixing and dispersing the phosphorus component in the polyester.

  The phosphorus content of the polyester resin containing phosphorus depends on the type of the main skeleton of the polyester resin, the type of phosphorus component (phosphoric acid residue), and the type of other components constituting the magnetic sheet. However, the phosphorus content is 0.5 wt% to 4.0 wt%. When the phosphorus content is less than 0.5% by weight, flame retardancy is low, and sufficient flame retardancy cannot be obtained unless a large amount of flame retardant is added. On the other hand, if it exceeds 4.0% by weight, the molecular weight of the polyester resin cannot be increased, so that the mechanical strength is lowered.

  Further, the number average molecular weight of the phosphorus-containing polyester-based resin is desirably 8000 to 50000. If the number average molecular weight is less than 8000, the resulting magnetic sheet may have insufficient mechanical strength. On the other hand, when the number average molecular weight is larger than 50000, the obtained magnetic sheet becomes hard, and thus desired flexibility cannot be obtained. The glass transition temperature of the phosphorus-added polyester resin is desirably -20 ° C to 40 ° C. When the glass transition temperature is −20 ° C. or lower, the elastic modulus is lowered at a high temperature, and the adhesive force between soft magnetic powders is lowered in a high temperature environment or a high temperature and high humidity environment. On the other hand, when the glass transition temperature exceeds 40 ° C., the magnetic sheet becomes hard at room temperature.

  In producing a magnetic sheet, such a soft magnetic powder and a binder dissolved in a solvent are mixed to produce a magnetic paint. Here, you may make it add the dispersion | distribution particle | grains disperse | distributed to a polyester resin, without being compatible with the polyester resin which is a binder to a magnetic coating material. Due to the dispersed particles, the magnetic sheet has a smooth surface and can have a good appearance such that no traces of air or outgas jets remain in the polyester resin when compressed in a later step. Here, the dispersed particles are preferably insulative. Furthermore, if the dispersed particles are a flame retardant, flame retardancy can be imparted to the magnetic sheet.

  Any flame retardant can be used, and examples thereof include a zinc-based flame retardant, a nitrogen-based flame retardant, and a hydroxide-based flame retardant. Furthermore, magnesium hydroxide, aluminum hydroxide, etc. can be mentioned. Examples of the zinc-based flame retardant include zinc carbonate, zinc oxide, and zinc borate. Among these, zinc carbonate is preferable. As the nitrogen-based flame retardant, for example, melamine derivatives such as melamine (cyanuric acid triamide), ammelin (cyanuric acid diamide), ammelide (cyanuric acid monoamide), melam, melamine cyanurate, benzoguanamine and the like can be used. In addition, it is desirable to use melamine cyanurate from the viewpoints of dispersibility in polyester resins and mixing properties. Further, carbon black, titanium oxide, boron nitride aluminum nitride, alumina or the like may be added instead of the flame retardant.

  The weight of the dispersed particles is preferably 7/13 or less with respect to the weight of the polyester resin. If the weight of the dispersed particles that are dispersed incompatible with the polyester-based resin is 7/13 or less with respect to the weight of the polyester-based resin, the high-temperature environment or high-humidity remains with good magnetic properties. The dimensional change that the thickness of the magnetic sheet changes under the environment can be suppressed, and good workability can be obtained. On the other hand, when the weight of dispersed particles is added to the polyester resin more than 7/13, the dimensional change of the thickness of the magnetic sheet in a high temperature environment or a high temperature and high humidity environment can be suppressed. It will fall.

  Moreover, it is preferable that the particle size of the dispersed particles dispersed without being compatible with the polyester resin is 0.01 μm to 15 μm. If the particle diameter of the dispersed particles is less than 0.01 μm, the effect of suppressing the change in the thickness of the magnetic sheet cannot be obtained. Moreover, if the particle diameter of the dispersed particles is 15 μm or more, the magnetic properties will be deteriorated.

  When a magnetic sheet is compressed in a later step, air or outgas in the resin is discharged to increase its specific gravity, but normally the passage of air or outgas is limited by the compression. Moreover, the soft magnetic powder blended in a large amount overlaps, so that the binder does not reach a very thin gap, and inevitably voids remain. On the other hand, since the magnetic sheet to which dispersed particles are added is formed smoothly, the amount of air and outgas contained in the magnetic sheet can be reduced, and the specific gravity can be increased. That is, the magnetic sheet can obtain good magnetic properties. In the magnetic sheet, when the specific gravity is increased by compression, the amount of air and the amount of outgas contained therein are reduced, so that the flame retardancy can be further improved.

  Moreover, the magnetic sheet may contain a crosslinking agent in addition to the soft magnetic powder and the polyester resin as the binder. Examples of the crosslinking agent include blocked isocyanate. The blocked isocyanate is an isocyanate compound protected with a protecting group that can be dissociated (deprotected) by heating so that the isocyanate group (—NCO) does not react at room temperature. This blocked isocyanate does not crosslink the polyester resin at room temperature, but when heated above the dissociation temperature of the protecting group, the protecting group is dissociated, the isocyanate group is activated, and the polyester resin is crosslinked.

  In addition, as block isocyanate, it is desirable to use the thing whose dissociation temperature of a protective group is 120 to 160 degreeC. By making this dissociation temperature higher than 120 degreeC, the methyl ethyl ketone and toluene used in order to adjust the viscosity of the magnetic coating material apply | coated on a base material can be evaporated, and the magnetic sheet formed can be dried. On the other hand, when the dissociation temperature is lower than 120 ° C, the protective group of the blocked isocyanate is dissociated when the magnetic paint is applied onto the substrate and dried at a temperature higher than the boiling point of methyl ethyl ketone or toluene. Therefore, there is a possibility that the crosslinking of the polyester resin proceeds. Moreover, since the heat-resistant temperature of the film used for the substrate is 160 ° C. or lower, the dissociation temperature is desirably 160 ° C. or lower. The reaction for crosslinking the polyester resin proceeds slowly even at room temperature, so after the heating is completed, the whole is cooled to room temperature and left for a long time, so that the polyester resin is completely crosslinked and the binder is completely cured. Become.

  Moreover, it is desirable that the blocked isocyanate is blended in an amount of 0.5% by weight or more based on the polyester resin as a binder. Thereby, a sufficient effect can be obtained. When the blended amount of the blocked isocyanate is less than 0.5% by weight, the crosslinking becomes insufficient, and the change in thickness may be increased in a high temperature environment or a high humidity environment.

  Furthermore, when an unprotected isocyanate is used, when the magnetic paint is applied onto the substrate and the solvent is dried to form a sheet, crosslinking of the polyester resin proceeds. However, good magnetic properties cannot be obtained. Moreover, since the hardened thing is compressed, the change that thickness becomes thick becomes large.

  Here, it is not easy to mix flat soft magnetic powder with a polyester-based resin as a binder and fill it with high density. When the flat soft magnetic powder is mixed with the binder, the flat soft magnetic powder is crushed and reduced by the load during mixing, or the magnetic permeability μ ′ is decreased due to a large strain. It is. Therefore, for the mixing of the flat soft magnetic powder and the binder, a polymer binder dissolved in a solvent is used, and the flat soft magnetic powder is mixed as much as possible without applying a load to form a magnetic paint. It is desirable to produce a magnetic sheet by applying to a material.

  In the method for producing a magnetic sheet shown as an embodiment of the present invention, such a magnetic paint is prepared, and this is applied with a desired thickness on a predetermined substrate by applying a coater or doctor blade method or the like. Dry to form a magnetic sheet.

  As the substrate, a film can be used, and examples thereof include polyethylene terephthalate film, polyethylene naphthalate film, polyimide film, polyphenylene sulfide film, polypropylene oxide film, polyethylene film, polypropylene film, polyamide film and the like. it can. Moreover, the thickness can be selected suitably, for example, can be several micrometers-several hundred micrometers. Furthermore, it is desirable that a release agent is applied to the magnetic sheet forming surface.

  Here, at the time of applying the magnetic paint, by applying a magnetic field, an effect of aligning and arranging the flat soft magnetic powder in the in-plane direction can be obtained, and the soft magnetic powder can be filled with high density. Desirably, the drying is performed to such an extent that the solvent content is 1% or less. When the content of the solvent is 1% or more, when the dried magnetic sheet is peeled off from the substrate, it may stretch or tear, and the volatilized solvent swells on the surface of the magnetic sheet. Because it appears. Moreover, the drying temperature after application | coating shall be lower than the crosslinking start temperature of the crosslinking agent, when the crosslinking agent is contained.

  Further, in order to facilitate orientation, it is desirable that the resin as the binder has a high fluidity, and it is desirable to dissolve the binder in a solvent to obtain a magnetic paint having a predetermined viscosity. Various solvents can be used to adjust the viscosity of the magnetic coating material. For example, aromatic hydrocarbon compounds such as benzene, toluene, and xylene, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, and the like can be used.

  The viscosity of the magnetic paint may be adjusted so that it can be applied using a coater, doctor blade method, etc. However, if the viscosity is too low, the binder component will increase, so the specific gravity will decrease when it is made into a sheet. There is a problem of end. The solid content is desirably in the range of 50% to 70%. If the solid content is 70% or more and the viscosity is large, there is a possibility that inconveniences such as inability to apply or streaking in the sheet during application may occur. When the solid content is 50% or less, problems such as repelling with the release agent on the base material occur when the magnetic paint is applied on the base material.

  And in the manufacturing method of a magnetic sheet, when a magnetic sheet is formed in this way, in order to improve the specific gravity, the dried magnetic sheet is compressed. At this time, in this production method, when a crosslinking agent is contained, the magnetic sheet formed by drying is compressed at a temperature equal to or higher than the glass transition temperature of the binder and less than the start of the reaction between the binder and the crosslinking agent. It is desirable to compress at or above the reaction initiation temperature between the binder and the crosslinking agent.

  Now, for example, as shown in FIG. 1, the compression process is performed between a magnetic sheet 10 and two press plates 20 and 21 made of, for example, stainless steel, which sandwich and press the magnetic sheet 10 from both sides. It is carried out with the ventilation materials 30 and 31 satisfying the conditions interposed. The figure shows a state in which the ventilation members 30 and 31 are interposed between both surfaces of the magnetic sheet 10 and the press plates 20 and 21, respectively. What is necessary is just to interpose between at least one press plate among the plates 20 and 21 and one side of the magnetic sheet 10. That is, in the compression process, any one of the ventilation materials 30 and 31 may be used.

  Here, as the ventilation members 30 and 31, sheet-like members such as paper and cloth having a so-called Beck smoothness of 150 seconds / ml or less are used. The Beck smoothness is a parameter defined as the time required for a certain amount of air to pass through the uneven surface of a sheet-like member such as paper or cloth. That is, the predetermined condition of the ventilation members 30 and 31 is that the time required for 1 ml of air to pass through the surfaces of the ventilation members 30 and 31 is 150 seconds or less. In the compression process, air and outgas existing in the magnetic sheet 10 are quickly discharged when the press plates 20 and 21 are pressed by using the air-permeable materials 30 and 31 that allow air to pass through the surface quickly. Since it is possible to create an easy-to-use situation, it is possible to reliably discharge these air and outgas. In addition, there is no restriction | limiting in particular about the thickness of the ventilation materials 30 and 31, Although it can take arbitrary values with the raw material to be used, about 50 micrometers-300 micrometers are desirable actually.

  In addition, it is desirable that at least one surface of the ventilation members 30 and 31 is subjected to a release treatment. In the compression step, the magnetic sheet 10 is easily released after compression by setting the release surfaces of the ventilation members 30 and 31 subjected to the release treatment to be on the magnetic sheet 10 side. Is possible. Further, in the compression process, when the ventilation members 30 and 31 that have not been subjected to the mold release treatment are used, for example, as shown in FIG. 2, between the magnetic sheet 10 and the ventilation members 30 and 31, PET (polyethylene) is used. By interposing the peeling films 40 and 41 made of terephthalate) or the like, the magnetic sheet 10 can be easily released after compression. In this case, it is desirable that the peeling films 40 and 41 have a thickness of 50 μm or less so as not to impair the air permeability of the air-permeable materials 30 and 31.

  As described above, in the method for manufacturing a magnetic sheet shown as an embodiment of the present invention, compression is performed by interposing a ventilation material satisfying a predetermined condition between at least one press plate and one surface of the magnetic sheet. By doing so, it becomes possible to reliably discharge air and outgas existing in the magnetic sheet. Therefore, in this manufacturing method, the change in the thickness of the magnetic sheet due to aging can be reduced, and the amount of air and outgas present in the magnetic sheet is reduced. However, it is possible to manufacture a magnetic sheet having a high magnetic permeability while maintaining a good appearance without leaving a trace of air or outgas.

[Example]
The inventor of the present application actually manufactured a magnetic sheet, and measured the change in thickness of the magnetic sheet before and after aging.

The composition of the magnetic sheet is as follows.
P / B ratio = 5.0
Magnetic material: Flat soft magnetic powder made of Fe-Si-Cr alloy powder having a particle size (D50) of 20 μm Binder: Polyester resin (Byron 300; manufactured by Toyobo Co., Ltd.) and blocked isocyanate as a crosslinking agent ( Polyester resin mixed with Coronate 2507 (manufactured by Nippon Polyurethane Industry Co., Ltd.) at a weight ratio of 97: 3

  Four layers of sheets prepared by applying a magnetic paint using such a composition material to a thickness of 120 μm are laminated, and these are laminated using a laminator set at 80 ° C., and a magnetic sheet having a thickness of about 300 μm. Formed. Then, the magnetic sheet was compressed in the state set in the arrangement as shown in FIG. The combinations of the ventilation material and the release film used at this time are as shown in Table 1 below.

  Specifically, in Example 1, high-quality paper (OK Prince fine quality 70) manufactured by Oji Paper Co., Ltd. was used as a ventilation material, and a PET film (PET38GS, thickness 38 μm) manufactured by Lintec Corporation was used as a peeling film. It was. The Beck smoothness of the ventilation material at this time is 6.2 seconds / ml.

  In Example 2, cushion paper (TF190) manufactured by Toyo Fiber Co., Ltd. was used as the ventilation material, and PET film (PET38GS, thickness 38 μm) manufactured by Lintec Corporation was used as the peeling film. At this time, the Beck smoothness of the ventilation member is 1.7 seconds / ml.

  Further, in Example 3, a nylon mesh (N-NO.110S) manufactured by Tokyo Screen Co., Ltd. was used as a ventilation material, and a PET film (PET38GS, thickness 38 μm) manufactured by Lintec Co., Ltd. was used as a peeling film. The Beck smoothness of the ventilation material at this time is less than 0.1 second / ml.

  Furthermore, in Example 4, a cotton cloth (Kanakin No. 3) defined by the Japanese Standards Association was used as a ventilation material, and a PET film (PET38GS, thickness 38 μm) manufactured by Lintec Corporation was used as a peeling film. . The Beck smoothness of the ventilation material at this time is less than 0.1 second / ml.

  Moreover, in Example 5, while using the base material for adhesive materials (SO base paper 18G) by Daifuku Paper Co., Ltd. as a ventilation material, the PET film (PET38GS, thickness 38 micrometers) by Lintec Co., Ltd. was used as a peeling film. The Beck smoothness of the ventilation material at this time is less than 0.1 second / ml.

  Furthermore, in Example 6, a double-sided release paper (100 GVW, high smooth surface) manufactured by Oji Paper Co., Ltd. was used as a ventilation material, and a PET film (PET38GS, thickness 38 μm) manufactured by Lintec Corporation was used as a peeling film. . At this time, the Beck smoothness of the ventilation member is 146 seconds / ml.

  Furthermore, in Example 7, a double-sided release paper (100 GVW, low smooth surface) manufactured by Oji Paper Co., Ltd. was used as the ventilation material, and a PET film (PET38GS, thickness 38 μm) manufactured by Lintec Corporation was used as the release film. It was. The Beck smoothness of the ventilation material at this time is 66 seconds / ml.

  In Example 8, the same double-sided release paper (100 GVW, low smooth surface) as in Example 7 was used as the air-permeable material, but no release film was interposed.

  In contrast, in Comparative Example 1, release paper (SL-80KCZA) manufactured by Kite Chemical Industry Co., Ltd. was used as the ventilation material, and PET film (PET38GS, thickness 38 μm) manufactured by Lintec Corporation was used as the release film. It was. The Beck smoothness of the ventilation material at this time is 220 seconds / ml.

  In Comparative Example 2, a release paper (EN78P) manufactured by Lintec Corporation was used as the ventilation material, and a PET film (PET38GS, thickness 38 μm) manufactured by Lintec Corporation was used as the peeling film. The Beck smoothness of the ventilation material at this time is 195 seconds / ml.

  Further, in Comparative Example 3, only a PET film (PET38GS, thickness 38 μm) manufactured by Lintec Corporation was interposed as a peeling film without interposing a ventilation material.

  Under such a combination of air-permeable material and release film, the magnetic sheet was compressed at 2.0 MPa for 10 minutes using two press plates made of stainless steel and set at 150 ° C., and about 250 μm A magnetic sheet as a final product was obtained. Then, the compressed magnetic sheet was placed in an oven set at 85 ° C. for 24 hours, and the change in thickness of the magnetic sheet before and after aging was measured. In the judgment evaluation, the case where the thickness return rate of the magnetic sheet is 1.0% or less is set as “◎”, the case where the thickness is larger than 1.0% and 3.0% or less is set as “◯”, and 3.0. A value greater than% and not greater than 5.0% was designated as “Δ”, and a value greater than 5.0% was designated as “X”. In addition, the thickness return rate of the magnetic sheet before and after aging is a standard required for a product of 5.0% or less. The results are shown in Table 2 below.

  As apparent from Table 2 above, the magnetic sheets in Examples 1 to 8 all had a thickness return rate of 5.0% or less, and the results satisfying the criteria required for products were obtained. On the other hand, the magnetic sheets in Comparative Examples 1 to 3 all had a thickness return rate of more than 5.0%, and the desired quality could not be obtained.

  From these results, it can be seen that the manufacturing method proposed in the present invention is extremely effective. In Examples 1 to 8 and Comparative Examples 1 to 3, Fe-Si-Cr alloy powder was used as the flat soft magnetic powder and polyester resin was used as the binder. It is easily guessed that the same result can be obtained by combining the magnetic powder and the resin.

It is a side view explaining the mode of the compression process in the manufacturing method of the magnetic sheet shown as embodiment of this invention. It is a side view explaining the mode of the other compression process in the manufacturing method of the magnetic sheet shown as embodiment of this invention.

Explanation of symbols

10 Magnetic sheet 20, 21 Press plate 30, 31 Ventilation material 40, 41 Peeling film

Claims (9)

A sheet forming step of forming a magnetic sheet using a magnetic coating prepared by mixing at least a magnetic material and a polymer binder dissolved in a solvent;
A compression step of pressing and compressing the magnetic sheet formed in the sheet formation step using a predetermined press plate,
In the compression step, a ventilation material having a Beck smoothness of 150 seconds / ml or less is interposed between at least the press plate and one surface of the magnetic sheet. The ventilation material has been subjected to a release treatment on at least one surface thereof,
In the compression step, the air-permeable material is disposed at least between the press plate and one surface of the magnetic sheet so that the release surface of the air-permeable material subjected to the release treatment is on the magnetic sheet side. The method for producing a magnetic sheet according to claim 1, wherein the magnetic sheet is interposed. The method for producing a magnetic sheet according to claim 1, wherein, in the compression step, a predetermined peeling film is interposed between the magnetic sheet and the air-permeable material. The method for producing a magnetic sheet according to claim 3, wherein the peeling film has a thickness of 50 μm or less. 2. The magnetic sheet according to claim 1, wherein in the compression step, the air-permeable material is interposed between the magnetic sheet and each of the two press plates that sandwich and press the magnetic sheet from both sides. Manufacturing method. The method for producing a magnetic sheet according to any one of claims 1 to 5, wherein the magnetic material is a flat soft magnetic powder. The magnetic sheet according to any one of claims 1 to 6, wherein the magnetic paint contains dispersed particles added so as to be dispersed in the polymer binder. Method. The method for producing a magnetic sheet according to claim 7, wherein the dispersed particles are a flame retardant. A magnetic sheet produced by pressing and compressing a sheet formed using a magnetic paint prepared by mixing at least a magnetic material and a polymer binder dissolved in a solvent using a predetermined press plate. And
A magnetic sheet produced by compressing a sheet with a ventilation material having a Beck smoothness of 150 seconds / ml or less interposed between at least the press plate and one side of the sheet.