JPWO2007007834A1 - Flame retardant soft magnetic sheet - Google Patents

Abstract

The flame-retardant soft magnetic sheet of the present invention contains at least a flat soft magnetic powder and a polyester resin. The polyester resin is a phosphorus-added polyester resin. The phosphorus-added polyester resin has a phosphate residue in the molecule. The phosphorus content of the phosphorus-added polyester resin is preferably 3.0% by weight or more. Thereby, the flame-retardant soft magnetic sheet has sufficient flame retardancy without using a halogen-based flame retardant as a flame retardant, and can reduce a decrease in magnetic properties after an environmental test.

Description

  The present invention relates to a flame retardant soft magnetic sheet that suppresses electromagnetic wave noise, and more particularly to a novel flame retardant soft magnetic sheet using a polyester resin having flame resistance.

  In recent years, in the fields of railway automatic ticket gates, security systems for entering and exiting buildings, electronic money systems, etc., so-called RFID (Radio Frequency IDentification) systems using contactless IC cards, IC tags, etc. Has begun to be introduced. This RFID system includes a non-contact type IC card and a reader / writer that writes and reads data to and from the IC card. In the RFID system, based on the principle of electromagnetic induction, when magnetic flux is released from the loop antenna on the reader / writer side, the radiated magnetic flux is magnetically coupled to the loop antenna on the IC card side by inductive coupling. Communication is performed with the reader / writer.

  In the RFID system as described above, there is no need to load an IC card or contact a metal contact with a reader / writer like a conventional contact IC card system, and data can be written and read easily and at high speed. It can be carried out. Further, in the RFID system, since necessary power is supplied from the reader / writer to the IC card by electromagnetic induction, there is no need to incorporate a power source such as a battery in the IC card, and the configuration can be simplified and the price is low. Thus, a highly reliable IC card can be provided.

  However, for example, if an IC tag with a communication frequency of 13.56 MHz mounted on an IC card is in the vicinity of a metal, communication may not be successful due to the influence. This is because at 13.56 MHz that communicates using the electromagnetic induction method, it is impossible to secure electric power due to a shift in resonance frequency due to an inductance change and a change in magnetic flux due to the influence of a metal nearby. Therefore, in the above-described RFID system, in order to ensure a sufficient communication range between the IC card and the reader / writer, it is necessary to provide a loop antenna on the IC card side that can radiate an electromagnetic field having a certain magnetic field strength. There is.

  In this case, in order to reduce the influence of the metal housing 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 on the metal body and reducing the communication distance. Can be bigger. In recent communication equipment and electronic equipment, the frequency of noise electromagnetic waves increases with the increase in clock frequency, causing malfunction of the equipment itself due to external or internal interference and adverse effects on peripheral equipment. 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.

The soft magnetic sheet exhibits a high magnetic permeability with respect to electromagnetic waves in the quasi-microwave band, absorbs the noise electromagnetic waves, converts the energy into heat, and suppresses electromagnetic noise emission. In that case, the greater the product of the magnetic permeability and thickness of the composite magnetic sheet, the greater the effect of suppressing electromagnetic wave noise. For example, if the thickness is the same, the higher the magnetic sheet permeability, the higher the electromagnetic noise. The inhibitory effect on is increased. For this reason, studies have been made to increase the magnetic permeability of the soft magnetic sheet. For example, a soft magnetic powder having a flat shape is used, and the magnetic permeability is increased by orienting the flat surface in the in-plane direction of the sheet. A composite magnetic sheet has been proposed (see, for example, Patent Document 1).
JP 2002-158488 A

  By the way, in recent years, since the mounting circuit of an electronic device has been densified, the amount of generated heat has increased, and the device temperature has been increasing. Therefore, the circuit may be short-circuited and ignited, but even in such a case, the soft magnetic sheet is required not to ignite. That is, the soft magnetic sheet is required to have not only high magnetic permeability but also excellent heat resistance and practical flame retardancy.

  In general, for example, in order to impart flame retardancy to a plastic material, a so-called flame retardant is added, and halogen-based flame retardants are widely known as flame retardants. However, in recent years, there is a tendency to avoid the use of halogen-based flame retardants in consideration of protection of the global environment, and non-halogen-based flame retardants are used instead of halogen-based flame retardants. For example, Patent Document 1 also discloses that a phosphorus-based flame retardant is added to impart flame retardancy. Examples of the phosphorus-based flame retardant include organic phosphorus compounds such as triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, and isopropyl phenyl phosphate.

  However, when the phosphorus-based flame retardant is used, if the amount added is increased, there are problems such as heat resistance of the resin composition, deterioration of physical properties, volatilization of the organic phosphorus compound under high temperature conditions, and as a result, There is a problem that only a small amount can be added and sufficient flame retardancy cannot be secured. In addition, when a phosphorus-based flame retardant is added, hydrolysis under high temperature and high humidity proceeds, and there is a problem that the magnetic permeability μ ′ decreases after an environmental test at high temperature and high humidity of the magnetic sheet. There is also a problem that even if flammability can be imparted, deterioration in magnetic properties cannot be suppressed.

  The present invention has been proposed in order to solve the above problems, and provides a soft magnetic sheet having sufficient flame retardancy and capable of improving deterioration of magnetic properties after an environmental test. With the goal.

  In order to achieve the above object, the flame-retardant soft magnetic sheet of the present invention contains at least a flat soft magnetic powder and a polyester resin, and the polyester resin is a phosphorus-added polyester resin. .

  In the flame-retardant soft magnetic sheet of the present invention, since a flat soft magnetic powder is used as the soft magnetic powder, the magnetic permeability μ ′ is high by orienting the flat surface in the in-plane direction of the sheet. A soft magnetic sheet is realized.

  On the other hand, in the flame-retardant soft magnetic sheet of the present invention, a phosphorus-added polyester resin is used as a binder. However, this phosphorus-added polyester resin has a phosphoric acid residue in the molecule, and thus has flame resistance. Therefore, the flame retardancy is sufficiently secured. Further, unlike the case where a large amount of flame retardant is added for flame retardancy, there is little hydrolysis, so the decrease in permeability μ ′ is small after the environmental test.

  In the flame-retardant soft magnetic sheet of the present invention, for example, although flame retardant is not used as a flame retardant, for example, at least the flame retardant equivalent to the standard HB of the horizontal combustion test of UL94 is used for the protection of the global environment. It is possible to realize sufficient flame retardancy. In addition, according to the present invention, since it is possible to suppress a decrease in magnetic properties after an environmental test, it is useful as an RFID application or a radio wave absorber, for example, a noise electromagnetic wave absorber for electronic equipment such as a mobile phone or a digital camera. Can be used as

  Hereinafter, the flame-retardant soft magnetic sheet to which the present invention is applied will be described in detail.

  The flame-retardant soft magnetic sheet of the present invention is a sheet obtained by mixing soft magnetic powder and a binder (polymer binder). Here, as the magnetic material constituting the soft magnetic powder, any soft magnetic material can be used. For example, an Fe—Si—Cr alloy, an Fe—Si—Cr—Ni alloy, Sendust (Fe— Si-Al), permalloy (Fe-Ni), and the like are preferable. Soft magnetic sheets prepared using soft magnetic powders made of these soft magnetic materials can be suitably used for RFID applications and radio wave absorbers because the soft magnetic powders are excellent in soft magnetic properties.

  As the soft magnetic powder, a soft magnetic powder having a flat shape is used, and the average particle diameter is preferably 3.5 to 90 μm and the thickness is preferably 2.1 μm or less. In order to equalize the size of the flat soft magnetic powder, classification may be performed using a sieve or the like as necessary. In order to increase the magnetic permeability of the flame-retardant soft magnetic sheet, the particle size of the flat soft magnetic powder is increased to reduce the spacing between the particles, and the aspect ratio of the flat soft magnetic powder is increased to increase the magnetic permeability. It is effective to reduce the influence of the demagnetizing field on the sheet.

The soft magnetic powder may be provided with an insulating layer covering the surface thereof. By using the flat soft magnetic powder on which the insulating layer is formed, μ ″ of the flame-retardant soft magnetic sheet is lowered and Q is improved, so that the communication distance is improved. As a method for forming the insulating layer, there are a method of coating with a resin, a method of forming an oxide film by heating, and a method of forming an oxide film on a soft magnetic powder by a thin film forming technique such as sputtering. As the oxide film, Al ₂ O ₃ , SiO ₂ or the like can be used. As the resin to be coated, acrylate, ester, urethane, epoxy and the like can be used.

  The soft magnetic powder used for the preparation of the flame-retardant soft magnetic sheet may be all soft magnetic powder coated with the insulating layer, or soft magnetic powder that is not covered with insulating coating and soft magnetic powder that is covered with insulating coating. It may be a mixture. In the latter case, the insulating effect can be obtained by setting the proportion of the soft magnetic powder coated with insulation to 5% or more of the entire soft magnetic powder.

  Alternatively, as the 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 polymer binder 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 at the same time when the soft magnetic powder and the binder are mixed, so that the coupling treatment is performed. Also good.

  On the other hand, a phosphorus-added polyester resin is used as the binder (polymer binder). By using a phosphorus-added polyester resin having a phosphoric acid residue in the molecule, flame retardancy can be imparted.

  The phosphorus-added polyester resin has a phosphoric acid residue in the molecule as described above, and 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. As the phosphorus component, phosphonate type polyols, phosphate type polyols, vinyl phosphonates, allyl phosphonates and the like 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 with internal phosphorus is predetermined according to the type of the main skeleton of the polyester resin, the type of phosphorus component (phosphoric acid residue), the type of other components constituting the flame-retardant soft magnetic sheet, and the like. However, it is preferably 3.0% by weight or more. If the phosphorus content is 3.0% by weight or more, it is possible to ensure sufficient flame retardancy.

  The number average molecular weight of the phosphorus-added polyester resin is preferably 3000 to 100,000. More preferably, it is 10,000 to 50,000. The glass transition point of the phosphorus-containing polyester resin is preferably -20 to 100 ° C. More preferably, it is -20-70 degreeC.

  The phosphorus-added polyester resin can be used alone as a binder (polymer binder) to be mixed with the soft magnetic powder. However, if there is no problem with compatibility, one or more other resins are used in combination. It doesn't matter. In this case, other resins include epoxy resin, polyester resin, acrylic resin, aliphatic hydrocarbon resin, rosin resin, nylon resin, phenol resin, polyurethane resin, melamine resin, polyamine resin, urea formaldehyde resin, polyisocyanate. And a mixture of an epoxy compound and an isocyanate compound or an imidazole compound.

  Furthermore, in order to ensure sufficient flame retardancy such as UL94 vertical test method V-1 in a flame retardant soft magnetic sheet, heat resistance, physical property degradation, high temperature conditions, hydrolyzability It is also effective to add a flame retardant so as not to affect the surface properties.

  Any flame retardant can be used as the flame retardant, and examples thereof include a zinc flame retardant, a nitrogen flame retardant, and a hydroxide flame retardant. Furthermore, magnesium hydroxide, aluminum hydroxide, etc. are raised. 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, and benzoguanamine can be used. Melamine cyanurate is preferably used from the viewpoint of dispersibility and mixing properties in the polyester resin. Further, carbon black, titanium oxide, boron nitride aluminum nitride, alumina or the like may be added instead of the flame retardant.

  In the flame-retardant soft magnetic sheet configured as described above, the magnetic permeability μ ′ is preferably 35 or more. If the magnetic permeability μ ′ is 35 or more, the communication distance when mounted on a portable mobile electronic device is 110 mm or more, and convenience is improved.

  The specific gravity of the flame retardant soft magnetic sheet is desirably 3.0 or more. More preferably, it is 3.20 or more. By increasing the specific gravity of the flame retardant soft magnetic sheet, the air contained in the flame retardant soft magnetic sheet is reduced, and the flame retardancy can be further improved.

  The above-mentioned flame-retardant soft magnetic sheet is formed by mixing the soft magnetic powder and a binder (polymer binder containing a phosphorus-added polyester resin) into a sheet. It is not easy to mix with the binder and fill with high density. This is because when flat soft magnetic powder is mixed with a binder, the flat soft magnetic powder is pulverized by a load during mixing and becomes smaller or receives a large strain, which causes a decrease in magnetic permeability μ ′. .

  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 so as not to apply a load. Thus, it is preferable to produce a soft magnetic sheet.

  Furthermore, in order to facilitate orientation, it is preferable that the resin as the binder has high fluidity, and it is preferable 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, and for example, aromatic hydrocarbon compounds such as methyl ethyl ketone, benzene, toluene, and xylene, 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 by the application method described later. However, if the viscosity is too small, the binder component increases, so that there is a problem that the specific gravity is reduced when the sheet is formed. . In addition, when the viscosity is too large, in addition to the above problems, there is a possibility that inconvenience that the coating cannot be performed or a streak enters the sheet at the time of coating may occur.

  In order to use a liquid resin dissolved in the solvent as a binder and form a magnetic coating mixed with soft magnetic powder into a sheet, there is a method of applying the sheet onto a substrate such as a film to form a sheet. As a coating method, a coater, a doctor blade method or the like can be employed. At this time, the thickness of the soft magnetic sheet to be formed can be adjusted to a desired thickness by the coating method.

  At the time of application, 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. Moreover, you may put a press process in order to improve specific gravity. By increasing the specific gravity, air contained in the soft magnetic sheet is reduced, so that the flame retardancy can be further improved.

  Next, specific implementation of the flame-retardant soft magnetic sheet to which the present invention is applied will be described based on experimental results.

  In Examples 1 to 9, a phosphorus-added polyester resin was used as a binder. The phosphorus-added polyester resins in Examples 1 to 4 have a number average molecular weight of 24,000, a glass transition point of 4 ° C., and a phosphorus content of 3.9% by weight. Further, the phosphorus-added polyester resins in Examples 5 to 9 have a number average molecular weight of 24,000, a glass transition point of 4 ° C., and a phosphorus content of 3.8% by weight. On the other hand, in Comparative Examples 1 to 5, a normal polyester resin was used without using the phosphorus-added polyester resin. Among these, in Comparative Examples 2-3, a phosphoric acid ester (trade name CR-741, manufactured by Daihachi Chemical Co., Ltd.), which is a flame retardant, was added instead of using the phosphorus-added polyester resin. In Comparative Examples 4 to 5, melamine cyanurate, a nitrogen-containing organic flame retardant, was added instead of using the phosphorus-added polyester resin.

Using these binders, the soft magnetic powder shown in Table 1 and Table 2 (Fe-Si-Cr, Fe-Si-Cr-Ni, Fe-Si-Al, SiO 2 coated Fe-Si-Cr, SiO ₂ coated Fe- A magnetic paint was prepared by adding Si-Cr-Ni, acrylic resin-coated Fe-Si-Cr), and a silane coupling agent, and a sheet was formed into a flame-retardant soft magnetic sheet. This flame-retardant soft magnetic sheet was passed 10 times through a laminator set at a temperature of 80 ° C. and a pressure of 13.4 kgf / cm, then passed through a laminator set at a temperature of 150 ° C. and a pressure of 13.4 kgf / cm 10 times, The sheet was held at 85 ° C. for 10 minutes to remove the distortion of the sheet. The mixing ratio of each component is as shown in Table 1 and Table 2.

  About the obtained flame-retardant soft magnetic sheet (Examples 1-9 and Comparative Examples 1-5), flame retardance was evaluated according to the vertical test method which UL94 respectively determined. Among these, when each standard of the vertical test method defined by UL94 was not satisfied, the flame retardancy was evaluated according to the horizontal combustion test defined by UL94. In the flame retardant items of Table 1 and Table 2 below, when the standards (V-0, V-1, V-2) of the vertical test method defined by UL94 are reached, V-0 , V-1 and V-2 are written, and when the standard of the horizontal combustion test defined by UL94 is reached without satisfying the standards of the vertical test method defined by UL94, HB is marked and the horizontal defined by UL94 Items that did not meet the criteria of the combustion test were left blank. Further, the magnetic properties (permeability μ ′, magnetic loss μ ″), specific gravity and communication distance of the obtained flame-retardant soft magnetic sheets (Examples 1 to 9 and Comparative Examples 1 to 5) were measured. Further, as an environmental test, the effective magnetic permeability μ ′ and magnetic loss μ ″ and specific gravity after being held in a high-temperature and high-humidity environment at a temperature of 85 ° C. and a humidity of 85% were measured. The communication distance was measured by placing the produced flame-retardant soft magnetic sheet between the antenna device and the shield plate and mounting it on a mobile phone. Permeability μ ′ is obtained by preparing a ring-shaped sample having a diameter of 7 mm, winding a conducting coil around it for 5 turns, and measuring and quantifying the AC permeability at a carrier frequency (13.56 MHz) using an impedance analyzer. Obtained. The results are shown in Tables 3 and 4.

When Examples 1-4 are seen, it turns out that the flame retardance equivalent to the case (comparative example 2) when the phosphate ester was used as a flame retardant was provided. In addition, it is understood that when the phosphorus-added polyester resin is used (Examples 1 to 4), the permeability μ ′ after the environmental test is less decreased than when the flame retardant is used (Comparative Example 2). . Moreover, in Example 5, as a result of using the phosphorus-added polyester resin, the change rate of the magnetic permeability μ ′ after the environmental test was equivalent to that of Comparative Example 1 using a normal polyester resin. Furthermore, in Example 5, compared with the comparative example 2 which added phosphate ester to the normal polyester resin, the magnetic characteristic was good and the fall of the characteristic was also suppressed. In Example 6, the magnetic loss μ ″ could be slightly reduced by replacing part of the Fe—Si—Cr—Ni magnetic powder with SiO ₂ -coated Fe—Si—Cr—Ni. . In Example 7, the magnetic loss μ ″ was slightly reduced by replacing part of the Fe—Si—Cr—Ni magnetic powder with acrylic resin-coated Fe—Si—Cr. . Furthermore, Example 8 and Example 9 satisfy the standard V-0 of the vertical test method defined by UL94 by adding melamine cyanurate, a nitrogen-containing organic flame retardant, as a flame retardant to the phosphorus-added polyester resin, Higher flame retardancy could be imparted.

  On the other hand, although the normal polyester was used for the comparative example 1, it did not satisfy | fill each reference | standard of the vertical test method or the standard of a horizontal combustion test which UL94 defined, and there was no flame retardance. In Comparative Example 2, a phosphoric acid ester was added as a flame retardant to ordinary polyester, but as in Comparative Example 1, there was no flame retardancy. Further, Comparative Example 2 also had poor magnetic characteristics (permeability μ ′, magnetic loss μ ″), and peeling at the lamination interface occurred after the environmental test, so the magnetic characteristics after the environmental test could not be measured. In Comparative Example 3, the amount of phosphate ester used in normal polyester was smaller than that in Comparative Example 2, and peeling at the laminated interface after the environmental test was not confirmed, but magnetic properties (permeability μ ′, The magnetic loss μ ″) was greatly reduced. Further, as shown in Comparative Example 4 and Comparative Example 5, even when melamine cyanurate is added to a normal polyester resin, it does not meet the standards of the vertical test method or horizontal combustion test defined by UL94, and is sufficiently difficult. Flammability was not obtained.

  As is apparent from Tables 3 and 4, it can be seen that by using a phosphorus-containing polyester resin as a binder, higher flame retardancy was imparted compared to a normal polyester not containing phosphorus internally. It can also be seen that higher flame retardancy can be obtained by adding melamine cyanurate to the polyester resin with internal phosphorus.

Claims (12)

  A flame-retardant soft magnetic sheet comprising at least a flat soft magnetic powder and a polyester resin, wherein the polyester resin is a phosphorus-added polyester resin.   The flame-retardant soft magnetic sheet according to claim 1, wherein the phosphorus-added polyester resin has a phosphoric acid residue in the molecule.   The flame-retardant soft magnetic sheet according to claim 1 or 2, wherein the phosphorus-containing polyester resin has a phosphorus content of 3.0% by weight or more.   The flame retardant soft magnetic sheet according to any one of claims 1 to 3, further comprising a flame retardant.   The flame retardant soft magnetic sheet according to claim 4, wherein the flame retardant is a nitrogen-containing organic flame retardant.   The flame retardant soft magnetic sheet according to claim 4, wherein the flame retardant is melamine cyanurate.   The soft magnetic powder is at least one selected from Fe-Si-Cr powder, Fe-Si-Cr-Ni powder, Fe-Si-Al powder, and Fe-Ni powder. The flame-retardant soft magnetic sheet according to any one of claims 1 to 6, wherein:   The flame-retardant soft magnetic sheet according to any one of claims 1 to 7, wherein the permeability μ 'is 35 or more.   The flame-retardant soft magnetic sheet according to any one of claims 1 to 8, wherein the soft magnetic powder is covered with an insulating layer.   The flame-retardant soft magnetic sheet according to claim 9, wherein the insulating layer is an oxide film or a resin film.   The soft magnetic sheet according to any one of claims 1 to 10, wherein the soft magnetic powder is subjected to a coupling treatment.   The flame retardant soft magnetic sheet according to any one of claims 1 to 11, wherein the specific gravity is 3.0 or more.