Europiiisches
`Patentamt
`European
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`Office europien
`des brevets
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`(19)
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`EP 2 117 017 A1
`
`(11)
`
`EUROPEAN PATENT APPLICATION
`
`(43) Date of publication:
`11 .11 .2009 Bulletin 2009/46
`
`(21 ) Application number: 09005258.0
`
`(22) Date of filing: 09.04.2009
`
`(84) Designated Contracting States:
`AT BE BG CH CY CZ DE DK EE ES Fl FR GB GR
`HR HU IE IS IT LILT LU LV MC MK MT NL NO PL
`PT RO SE SI SK TR
`Designated Extension States:
`AL BA RS
`
`(30) Priority: 23.04.2008 JP 200811 2863
`
`(71 ) Applicant: TDK Corpo ration
`To kyo 103-8272 (JP)
`
`(72) Inventors:
`• Matsukawa, Atsuhito
`To kyo 103-8272 (JP)
`
`(51) Int Cl.:
`H01F 1/ 147<200601>
`
`H01F 1120 <2006011
`
`• Wakayama, Katsuhiko
`To kyo 103-8272 (JP)
`• Moro, Hideharu
`Tokyo 103-8272 (JP)
`• Sato, Naoyoshi
`To kyo 103-8272 (JP)
`• Hirai, Yoshihito
`Tokyo 103-8272 (JP)
`• Murayoshi, Toshihisa
`To kyo 103-8272 (JP)
`
`(7 4) Representative: Grunecker, Kinkeldey,
`Stockmair & Sc hwanhausser
`Anwaltssozietat
`Leopoldstrasse 4
`80802 Munchen (DE)
`
`(54)
`
`Flat soft magnetic material and process for its production
`
`(57)
`A flat soft magnetic material to be used for a
`noise-suppressing magnetic sheet, w herein the 50% par(cid:173)
`ticle size D50 (µm), coercive force He (Alm) and bulk
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`10-1
`
`Petitioner Samsung and Google
`Ex-1017, 0001
`
`

`

`EP 2117 017 A1
`
`Description
`
`BACKGROUND OF THE INVENTION
`
`5
`
`Field of the Invention
`
`(0001) The present invention relates to a flat soft magnetic material to be used in a noise-suppressing magnetic sheet,
`and to a process for its production.
`
`10
`
`Related Background Art
`
`15
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`20
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`25
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`(0002) As the operating speeds of digital circuits have increased in recent years, the electromagnetic noise emitted
`from circuits has shifted more toward the high-frequency band. Such noise arises from malfunctioning of the devices
`themselves resulting from internal interference, or malfunctioning of other devices resulting from external interference.
`Further increased packaging density is also becoming necessary in recent years in order to achieve lighter-weight,
`thinner and smaller digital circuit-mounted devices. Electromagnetic shielding materials capable of shielding noise con(cid:173)
`tinue to be developed, and methods have been proposed wherein noise-suppressing parts comprising sheets of oriented
`and dispersed soft magnetic materials are placed near electronic circuits that are the sources of noise.
`(0003) Soft magnetic materials are used in such noise-suppressing sheets, and it is know n that a noise-suppressing
`effect can be achieved in a wide frequency band if the soft magnetic material is thin and flat.
`(0004) Methods that have been disclosed for fabrication of flat soft magnetic materials include using sendust materials
`produced by water atomization, as a method for producing flaky or flat Fe-Si-A 1 alloy powder, in JP No. S62-238305 A
`(Document 1) and JP No.H1 -294802 A (Document 2), for example. Also, JP No. 2003-332 11 3 A (Document 3) and JP
`No. 2005-123531 A (Document 4) disclose using fl at soft magnetic metal powders, or materials produced by gas atom-
`ization. In addition, JP No. 2001-303 11 1 A (Document 5) discloses a method in w hich a fatty acid and an organic solvent
`such as an alcohol are included during pulverization in the mechanical flat working of a soft magnetic metal powder
`grinding medium by atomization using a pulverizer. Finally, JP No. H5-98301 A (Document 6) discloses, as an example,
`flattening treatment of sendust powder produced by water atomization together w ith ethanol, using an attritor.
`
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`
`SUMMARY OF THE INVENTION
`
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`(0005) Documents 1, 2, 5 and 6 deal with soft magnetic materials for use in magnetic cards, while Documents 3 and
`4 focus on the oxygen contents of the soft magnetic materials. None of the soft magnetic materials produced by the
`processes described in Documents 1-6 have had high enough magnetic permeability to exhibit sufficient sheet properties
`when they are used as noise-suppressing magnetic sheets.
`It is therefore an object of the present invention to provide a flat soft magnetic material that can be used to form
`(0006)
`a noise-suppressing magnetic sheet with sufficiently high magnetic permeability, as well as a process for its production.
`(0007) The invention provides a fl at soft magnetic material to be used for a noise-suppressing magnetic sheet, w herein
`the 50% particle size D50 (µm), coercive force He (Alm) and bulk density BD (Mg/m3) of the flat soft magnetic material
`satisfy the following formula ( 1 ).
`
`D5o/(Hc x BD) > 1.5 (1)
`
`(0008) By using a flat soft magnetic material satisfying these conditions, it is possible to form a noise-suppressing
`magnetic sheet with sufficiently high magnetic permeability. The magnetic permeability at high frequency can be repre(cid:173)
`sented as the complex magnetic permeability (µ = µ ' - j µ") w here µ ' is the real permeability and µ " is the imaginary
`permeability. The magnetic shielding effect is dependent on the size of the real permeabilityµ', while the noise-absorbing
`effect is dependent on the size of the imaginary permeabilityµ".
`(0009) The noise-suppressing magnetic sheet performs noise absorption utilizing the imaginary partµ" of the complex
`magnetic permeability of the magnetic material in the frequency band in which noise is generated, and the maximum
`value of µ" is larger with a larger µ', at low frequency. Such a high magnetic permeability (high µ ) sheet can be obtained
`by high density packing of flat powder with a low coercive force He and a large particle size.
`(001 OJ The present inventors have conducted diligent research on the relationship between the physical properties
`and the magnetic permeabilityµ' (sheet property) of flat powder in a magnetic sheet produced using flat powder obtained
`by flattening of soft magnetic alloy powder, and the research has shown that a larger value of D50/(Hc x BD) for the flat
`powder results in a larger µ ' of the magnetic sheet, given a constant fill factor for the magnetic material. Because the
`
`2
`
`Petitioner Samsung and Google
`Ex-1017, 0002
`
`

`

`EP 2 117 017 A1
`
`He value tends to be smaller with a larger flat powder particle size, the inventors believe that using a sufficiently flattened
`magnetic material with a large particle size is an essential condition for obtaining a magnetic sheet with a high µ .
`[0011] The fl at soft magnetic material of the invention preferably has an aspect ratio of 20 or greater and a D50 of 50
`µm or greater. By using such a flat soft magnetic material, it is possible to form a noise-suppressing magnetic sheet
`with even higher magnetic permeability.
`[0012) The flat soft magnetic material preferably contains an Fe-Si-Al based alloy (hereinafter also referred to as
`"sendust"). Sendust has sufficiently low coercive force and can therefore further increase the magnetic permeability. In
`addition, since sendust does not contain expensive metals, it provides the further advantage of cost reduction.
`[0013) The invention provides a process for production of the aforementioned flat soft magnetic material, which process
`comprises a heat treatment step in which soft magnetic alloy powder produced by an atomization method is heat treated
`in an inert atmosphere at 800-1200°C to obtain heat treated powder, and a flattening step in w hich the heat treated
`powder is flattened in the presence of an organic solvent.
`[0014) The production process described above allows production of a flat soft magnetic material that can be used to
`form a noise-suppressing magnetic sheet with a suffi ciently high magnetic permeability.
`[0015) According to the production process of the invention, the porosity of the heat treated powder is preferably no
`greater than 0.15 m3/Mg and the average crystal grain size is preferably at least 6 µ m. By using such heat treated
`powder it is possible to obtain a fl at soft magnetic material with an even smaller He value.
`[0016)
`In the production process described above, the organic solvent is preferably a C2-4 monohydric alcohol in
`order to obtain a high yield of flat powder w ith a large particle size, without using a flattening aid. The alcohol used for
`flattening will thus be easy to recover and reutilize.
`[0017) According to the invention it is possible to provide a flat soft magnetic material that can be used to form a noise(cid:173)
`suppressing magnetic sheet with sufficiently high magnetic permeability, as well as a process for its production.
`
`BRIEF DESCRIPTION OF THE DRAW INGS
`
`[0018) Fig . 1 is a graph showing the results of measurement of a mercury porosimeter for Fe-Si-Al based alloy powder
`prepared by atomization; and
`Fig. 2 is a graph showing the relationship between D50/(Hc x BD) for the flat soft magnetic material and µ ' for the
`magnetic sheet.
`
`DESCRIPTION OF THE PREFERRED EMBODIMENTS
`
`<Flat soft magnetic material>
`
`[0019) The flat soft magnetic material of this embodiment (hereinafter also referred to as "flat powder") has a 50%
`particle size D50 (µ m), coercive force He (Alm) and bulk density BD (Mg/m3) that satisfy the following formula (1 ).
`
`D5o/{Hc x BD) > 1.5 (I)
`
`[0020) The flat soft magnetic material can be produced by flattening soft magnetic alloy powder.
`[0021) The soft magnetic alloy powder is preferably an alloy with a low coercive force, more preferably an Fe-Si-Al
`based alloy, known as "sendust" or an Fe-Ni based alloy, known as "permalloy", and even more preferably sendust,
`since it can result in an even smaller He value.
`[0022) The soft magnetic alloy powder may be produced by a water atomization method, gas atomization method or
`gas-water atomization method. A water atomization method is a method in which high-pressure water is injected into
`molten metal of a soft magnetic alloy falling as starting material from a nozzle, for w ater-cooling to solidify and powderize
`the soft magnetic alloy. A gas atomization method is a method in w hich high-pressure gas is injected into molten metal
`of a soft magnetic alloy falling as starting material from a nozzle, for air-cooling to solidify and powderize the soft magnetic
`alloy . The gas used may be air or an inert gas, but preferably an inert gas is used for sendust. A gas-water atomization
`method is a combination of gas atomization and water atomization, in which high-pressure gas is injected into molten
`metal of a soft magnetic alloy falling as starting material from a nozzle, prior to water-cooling to solidify and powderize
`the soft magnetic alloy.
`[0023) According to the invention, it is preferred to use soft magnetic alloy powder produced by a gas atomization or
`gas-water atomization method, because these allow the porosity to be reduced.
`[0024) While a larger particle size of the flat powder allows the µ ' of the magnetic sheet to be increased given the
`same fill factor, this also makes high-density packing more difficult and roughens the sheet surface, and therefore the
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`3
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`Petitioner Samsung and Google
`Ex-1017, 0003
`
`

`

`EP 2 117 017 A1
`
`50% particle size D50 of the soft magnetic alloy powder is preferably about 50-100 Pm.
`(cid:3)[0025] The flat soft magnetic material can be produced by a method comprising a heat treatment step in which soft
`magnetic alloy powder is heat treated in an inert atmosphere at 800-1200°C to obtain heat treated powder, and a flattening
`step in which the heat treated powder is flattened in the presence of an organic solvent. This process will now be explained.
`
`(Heat treatment step)
`(cid:3)[0026] As pretreatment prior to flattening of the soft magnetic alloy powder, the soft magnetic alloy powder obtained
`by different atomization methods is heated treated at a prescribed temperature in an inert atmosphere containing an
`introduced inert gas such as argon gas, to obtain a heat treated powder.
`(cid:3)[0027] The heat treatment temperature is 800-1200°C, and more preferably 900-1100°C. Heat treatment in this tem-
`perature range can increase the crystal grain size of the soft magnetic alloy powder. If the treatment temperature exceeds
`1200°C, the soft magnetic alloy powder will undergo extensive aggregation or sintering, thus hampering the flattening
`process.
`(cid:3)[0028] The heat treatment time is preferably about 10 minutes-(cid:3)5 hours and more preferably 1-3 hours. A heat treatment
`time of less than 10 minutes will not result in a sufficiently large crystal grain size, while a time of greater than 5 hours
`will not result in any greater crystal grain size and thus lowers productivity.
`(cid:3)[0029] The porosity of the heat treated powder is preferably no greater than 0.15 m3/Mg, more preferably no greater
`than 0.10 m3/Mg and even more preferably no greater than 0.07 m3/Mg. A lower porosity will result in an increased 50%
`particle size of the soft magnetic material after flattening, thus tending to increase the P’ of the magnetic sheet.(cid:3) The
`porosity of the heat treated powder can be measured with a mercury porosimeter.
`(cid:3)[0030] Fig. 1 is a graph showing the measurement results for Fe-(cid:3)Si-(cid:3)Al based alloy powder prepared by different
`atomization methods, using a mercury porosimeter. As seen in Fig. 1, the porosity of the soft magnetic alloy powder
`depends on the atomization method, with increasing porosity in the following order: gas atomization < gas-(cid:3)water atom-
`ization < water atomization. The change in porosity of the soft magnetic alloy powder due to heat treatment temperature
`is minimal.
`(cid:3)[0031] The average crystal grain size of the heat treated powder is preferably at least 6 Pm, more preferably at least
`8 Pm and even more preferably at least 9 Pm. A average crystal grain size of less than 6 Pm will result in a small 50%
`particle size of the flat soft magnetic material, thus tending to decrease the P’ of the magnetic sheet. The average crystal
`grain size is the value determined by image analysis when the soft magnetic alloy powder or heat treated powder is
`embedded in a resin, mirror-(cid:3)polished and then etched, and photographed with a scanning electron microscope (SEM).
`
`(Flattening step)
`
`The heat treated powder is then flattened.
`(cid:3)[0032] The flattening method is not particularly restricted and may be carried out, for example, using an attritor, ball
`mill, vibrating mill or the like. An attritor is preferably used to allow mixing and pulverization of the starting powder in a
`shorter time than with a ball mill or vibrating mill. The flattening is preferably carried out in a wet system using an organic
`solvent.
`(cid:3)[0033] The organic solvent used may be, for example, toluene, hexane, acetone, methanol or a C2-4 monohydric
`alcohol. C2-4 monohydric alcohols include ethanol, 1-(cid:3)propanol, 2-(cid:3)propanol, 1-(cid:3)butanol, 2-(cid:3)butanol, isobutanol and t-
`butanol.
`(cid:3)[0034] The amount of organic solvent added is preferably 200-2000 parts by weight and more preferably 500-1000
`parts by weight with respect to 100 parts by weight of the heat treated powder. If the organic solvent is added at less
`than 200 parts by weight the particle size of the flat powder will tend to be reduced, and if it is added at greater than
`2000 parts by weight the treatment time will be lengthened, thus lowering the productivity.
`(cid:3)[0035] Even when a friable soft magnetic alloy powder is used, it is possible to obtain a high yield of sufficiently flattened
`flat powder with a large particle size, by adding the organic solvent. Sendust is easily crushed, and it has been difficult
`to obtain high yields of sufficiently flattened flat powder with large particle sizes by conventional methods. According to
`the invention, it is possible to accomplish satisfactory flattening even when using sendust, and to obtain a flat soft
`magnetic material with a average particle size of 50 Pm or greater that is suitable for use in a noise-(cid:3)suppressing magnetic
`sheet.
`(cid:3)[0036] A flattening aid may be used together with the organic solvent in order to increase the particle size of the flat
`powder. Fatty acids such as stearic acid are examples of flattening aids that may be used. The amount of flattening aid
`added is preferably 0.1-5 parts by weight and more preferably 0.5-2 parts by weight with respect to 100 parts by weight
`of the heat treated powder. Adding the flattening aid at greater than 5 parts by weight will not further increase the particle
`size of the flat powder, and will also hamper recovery and reuse of the organic solvent while also increasing contamination
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`4
`
`Petitioner Samsung and Google
`Ex-1017, 0004
`
`

`

`EP 2 117 017 A1
`
`of the heat treatment furnace. When a C2-4 monohydric alcohol is used as the organic solvent, a flat powder with a
`large particle size can be obtained even without adding a flattening aid.
`(cid:3)[0037] The flattening treatment is preferably followed by heat treatment of the obtained flat soft magnetic material in
`an inert atmosphere. This will reduce the coercive force Hc and increase the P’ of the magnetic sheet. The heat treatment
`temperature in this case is 700-900°C and the treatment time is approximately 10 minutes to 3 hours.
`(cid:3)[0038] The aspect ratio (= particle size/(cid:3)thickness) of the flat soft magnetic material produced in the manner described
`above is preferably 20 or greater, more preferably 20-100 and even more preferably 30-50. An aspect ratio of less than
`20 will increase the demagnetizing field, thus lowering the apparent magnetic permeability when the material is used as
`a magnetic sheet, while an aspect ratio of greater than 100 will lower the fill factor (= flat soft magnetic material volume/
`magnetic sheet volume), thus tending to lower the magnetic permeability.
`
`(cid:3)[0039] The 50% particle size D50 of the flat soft magnetic material is preferably at least 50 Pm, more preferably at
`least 55 Pm and even more preferably at least 60 Pm. If the D50 is less than 50 Pm it will be difficult to obtain flat powder
`with a small holding power Hc, and the real permeability P’ will tend to be smaller. If D50 is too large, mixing of the binder
`resin will be more difficult and production of the magnetic sheet will be hampered, and therefore the upper limit for D50
`is about 100 Pm. The value of D50 throughout the present specification was measured by laser diffraction using a dry
`dispersion unit, employing a "HELOS SYSTEM" by Japan Laser Corp.
`(cid:3)[0040] The coercive force Hc of the flat soft magnetic material is preferably no greater than 100A/m and more preferably
`no greater than 80A/m. If Hc exceeds 100A/m, the P’ value of the magnetic sheet will tend to be smaller. Hc may be
`measured using a commercially available Hc meter.
`(cid:3)[0041] The bulk density BD of the flat soft magnetic material is preferably 0.20-0.60 Mg/m3 and more preferably
`0.25-0.50 Mg/m3. If BD is less than 0.20 Mg/m3 the fill factor will tend to be lower upon sheeting, while if it is greater
`than 0.60 Mg/m3 the degree of flattening will be insufficient, thus increasing the demagnetizing field and lowering the
`apparent magnetic permeability. The BD value can be measured using a bulk specific gravity meter, by the method of
`JIS K-(cid:3)5101.
`(cid:3)[0042] The specific surface area SSA of the flat soft magnetic material is preferably no greater than 1.5 m2/g and more
`preferably no greater than 1.0 m2/g. If the SSA is greater than 1.5 m2/g, a greater amount of binder resin will be necessary
`and the fill factor of the magnetic material will tend to be reduced. The SSA value throughout the present specification
`was measured using a "Macsorb Model-(cid:3)1201" fully automatic specific surface area meter by Mountech Co., Ltd.
`(cid:3)[0043] The flat soft magnetic material of the invention has D50, Hc and BD values satisfying the condition represented
`by formula (1) above, and the value calculated by D50/(cid:3)(Hc (cid:22) BD) is 1.5 (Pm/Am-1/Mgm-3) or greater, preferably 2.0 or
`greater and even more preferably 3.0 or greater.
`(cid:3)[0044] Fig. 2 is a graph showing the relationship between D50/(cid:3)(Hc (cid:22) BD) for the flat soft magnetic material and P’ for
`the magnetic sheet. A noise-(cid:3)suppressing magnetic sheet generally performs noise absorption utilizing the imaginary
`part P" of the complex magnetic permeability of the magnetic material in the frequency band in which noise is generated,
`and maximum value of P" is larger with a larger P’ at low frequency. The power of the noise-(cid:3)suppressing sheet can
`therefore be evaluated based on the size of the value of P’. A magnetic sheet with a large value for P’ can be obtained
`by high density packing of flat powder with a low coercive force and a large 50% particle size. When the fill factor of the
`flat powder in the magnetic sheet is constant, a larger value represented by D50/(cid:3)(He (cid:22) BD) corresponds to a larger P’
`value for the flat powder, so that a more excellent noise-(cid:3)suppressing effect is obtained.
`If D50/(cid:3)(Hc (cid:22) BD) is less than 1.5, therefore, the P’ value of the magnetic sheet will be smaller and the noise-
`(cid:3)[0045]
`suppressing effect may be inadequate.
`<Noise-(cid:3)suppressing magnetic sheet>
`(cid:3)[0046] A magnetic sheet may be formed using the flat soft magnetic material described above. There are no particular
`restrictions on the method of forming the magnetic sheet, and the following is an example.
`(cid:3)[0047] The flat soft magnetic material and binder resin may be kneaded together and subjected to press molding or
`extrusion molding to form a sheet. Alternatively, the flat soft magnetic material and binder resin may be dispersed in an
`organic solvent to produce a slurry, and the slurry cast as a film to a prescribed thickness on a support base by doctor
`blading and then dried and rolled with a calender roll to form a sheet.
`(cid:3)[0048] The thickness of the magnetic sheet will be about 0.05-2 mm. Since the noise-(cid:3)suppressing effect is proportional
`to the thickness of the magnetic sheet, it will be difficult to obtain a satisfactory effect if the thickness of the magnetic
`sheet is less than 0.05 mm. On the other hand, a magnetic sheet thickness of greater than 2 mm will result in more
`difficult loading into the narrow spaces inside the packages of electrical equipment.
`(cid:3)[0049] The fill factor of the flat soft magnetic material in the magnetic sheet is preferably 30-60 vol% and more preferably
`40-50 vol%. A fill factor of less than 30 vol% will result in a lower noise-(cid:3)suppressing effect, while a fill factor of greater
`than 60 wt% will prevent the soft magnetic material from being firmly bound by the binder resin, thus lowering the magnetic
`sheet strength.
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`5
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`Petitioner Samsung and Google
`Ex-1017, 0005
`
`

`

`EP 2 117 017 A1
`(cid:3)[0050] The binder resin is an insulating resin for bonding of the flat soft magnetic material. All or a portion of the surface
`of the flat soft magnetic material is coated with the binder resin. As examples of binder resins there may be mentioned
`polyester-(cid:3)based resins, polyethylene resins, polyvinyl chloride-(cid:3)based resins, polyvinyl butyral resins, polyurethane resins,
`cellulose-(cid:3)based resins, ABS resins, nitrile-(cid:3)butadiene-(cid:3)based rubbers, styrene-(cid:3)butadiene-(cid:3)based rubbers, epoxy resins,
`phenol resins and amide-(cid:3)based resins.
`(cid:3)[0051] The amount of binder resin added is preferably 10-40 parts by weight and more preferably 15-25 parts by
`weight with respect to 100 parts by weight of the flat soft magnetic material.
`(cid:3)[0052] The magnetic sheet may further contain a plasticizer, curing agent, dispersing agent, stabilizer, coupling agent,
`diluent or the like if necessary in addition to the flat soft magnetic material and binder resin.
`(cid:3)[0053] When the magnetic sheet has been molded or coated into the prescribed shape, an oriented magnetic field
`may be applied or the material may be mechanically oriented to obtain a magnetic sheet with a high directional property.
`(cid:3)[0054]
`In order to obtain a sufficiently high noise-(cid:3)suppressing effect, the P’ of the noise-(cid:3)suppressing magnetic sheet
`is preferably 130 or greater and more preferably 150 or greater.
`(cid:3)[0055] The magnetic sheet formed in the manner described above has high magnetic permeability and is therefore
`highly useful as a noise-(cid:3)suppressing magnetic sheet.
`(cid:3)[0056] The present invention is not in any way limited to the preferred modes described above.
`
`[Examples]
`(cid:3)[0057] The present invention will now be explained in detail by examples, with the understanding that the invention is
`not limited to the examples.
`
`(Examples 1-6 and Comparative Examples 1-6)
`(cid:3)[0058] Fe-(cid:3)Si-(cid:3)Al (Si = 8-11 wt%, Al = 5-7 wt%) based alloy powders (sendust powders) produced by different atomization
`methods, as shown in Table 1, were prepared and treated at 700-1300°C for 2 hours in an Ar atmosphere to obtain heat
`treated powders. The porosity of the heat treated powders was measured using a mercury porosimeter ("Porosimeter
`Model PASCAL140/440, trade name of CE Instruments). The average crystal grain size of the soft magnetic alloy powder
`was determined by image analysis of an SEM photograph, as described above.
`(cid:3)[0059] Next, a 5.7-(cid:3)fold amount of toluene by weight and 1 wt% stearic acid as a flattening aid were added to the
`untreated or heat treated powder, and an attritor was used for flattening to obtain flat powder. The flattening time was
`adjusted for a bulk density BD of approximately 0.4 Mg/m3. The bulk density of the flat powder was measured using a
`bulk specific gravity meter (measuring sample: 30 ml), according to JIS K-(cid:3)5101. The particle size distribution of the flat
`powder was measured by a laser method ("HELOS SYSTEM", trade name of Japan Laser Corp.). The flat powder was
`then heat treated at 800°C for 2 hours in an Ar atmosphere. The coercive force Hc of the flat powder after heat treatment
`was measured using an Hc meter ("K-(cid:3)HC1000", trade name of Tohoku Steel Co., Ltd.).
`(cid:3)[0060] A slurry was prepared by mixing 100 parts by weight of the obtained flat powder, 17 parts by weight of a binder
`resin (polyvinyl butyral), 2 parts by weight of a plasticizer (diethyl phthalate), and 150 parts by weight of a diluent (mixing
`solvent comprising toluene, xylene, 1-(cid:3)propanol and SOLMIX (trade name of Japan Alcohol Trading Co., Ltd.). The slurry
`was coated onto a PET film and passed through a magnetic field with opposing like poles, for magnetic field orientation
`to form a magnetic sheet layer. After drying, the magnetic sheet layer was peeled from the PET film, and 6 layers were
`hot pressed at 90°C,(cid:3) 77 MPa for 1 hour to produce a magnetic sheet.
`
`(Evaluation of magnetic sheet)
`(cid:3)[0061] The magnetic sheet was punched out into a toroidal shape using a die with an outer diameter of 18 mm and
`an inner diameter of 10 mm, and an impedance analyzer ("E4991A", trade name of Agilent Technologies) was used to
`evaluate the magnetic properties.
`(cid:3)[0062] Table 1 shows the starting materials, flat powders and magnetic sheet properties (where the P’ values of the
`magnetic sheets are calculated for a magnetic material fill factor of 40 vol%).
`(cid:3)[0063]
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`Petitioner Samsung and Google
`Ex-1017, 0006
`
`

`

`5
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`Starting material
`properties
`
`Heat-(cid:3)treated powder properties
`
`[Table 1]
`
`Atomization
`method
`
`Gas-(cid:3)water
`atomization
`
`D50
`
`Pm
`
`83
`
`Heat
`treatment
`temperature
`
`°C
`
`800
`
`900
`
`1000
`
`1100
`
`Porosity
`
`m3/Mg
`
`0.117
`
`0.104
`
`0.11
`
`0.131
`
`Average
`crystal grain
`size
`
`Aspect ratio
`
`Pm
`
`6.6
`
`9.5
`
`10.2
`
`13.6
`
`29
`
`31
`
`34
`
`32
`
`Example 1
`
`Example 2
`
`Example 3
`
`Example 4
`
`Flat powder properties
`
`D50
`
`BD
`
`Hc
`
`Pm Mg/m3
`
`A/m
`
`57
`
`62
`
`66
`
`65
`
`0.39
`
`0.4
`
`0.4
`
`0.41
`
`0.41
`
`91
`
`87
`
`70
`
`84
`
`93
`
`D50/(cid:3)(Hc(cid:22)BD)
`um/Am-(cid:3)
`1/Mgm-3
`
`1.6
`
`1.8
`
`2.4
`
`1.9
`
`1.7
`
`SSA
`
`m2/g
`
`0.89
`
`0.87
`
`0.74
`
`0.75
`
`0.95
`
`Sheet
`property
`
`P’ 1MHz
`(40vol%)
`
`136
`
`152
`
`151
`
`152
`
`144
`
`EP 2 117 017 A1
`
`32
`
`35
`
`14
`
`16
`
`22
`
`23
`
`22
`
`65
`
`69
`
`29
`
`30
`
`46
`
`45
`
`0.39
`
`0.42
`
`0.37
`
`0.42
`
`0.39
`
`72
`
`231
`
`239
`
`115
`
`111
`
`2.5
`
`0.3
`
`0.34
`
`0.95
`
`1
`
`0.65
`
`1.37
`
`1.35
`
`1.01
`
`1.05
`
`**Unusable due to sintering
`
`39
`
`0.35
`
`124
`
`0.9
`
`1.58
`
`187
`
`83
`
`84
`
`124
`
`120
`
`-
`
`126
`
`Example 5
`
`Example 6
`
`Comp. Ex. 1
`
`Comp. Ex. 2
`
`Comp. Ex. 3
`
`Comp. Ex. 4
`
`Comp. Ex. 5
`
`Comp. Ex. 6
`
`Gas
`atomization
`
`Water
`atomization
`
`Gas-(cid:3)water
`atomization
`
`Gas
`atomization
`
`59
`
`55
`
`83
`
`59
`
`1200
`
`1000
`
`None
`
`1000
`
`None
`
`700
`
`1300
`
`None
`
`0.116
`
`0.061
`
`0.199
`
`0.192
`
`0.102
`
`0.1
`-(cid:3)**
`
`0.065
`
`15.3
`
`9.3
`
`3.7
`
`5
`
`3.9
`
`3.4
`-(cid:3)**
`
`5.4
`
`7
`
`Petitioner Samsung and Google
`Ex-1017, 0007
`
`

`

`EP 2 117 017 A1
`In Examples 1-6, the sendust powder prepared by gas atomization or gas-(cid:3)water atomization was heat treated
`(cid:3)[0064]
`at 800-1200°C to obtain flat powder with a D50 of 50 Pm or greater, and the D50/(cid:3)(Hc (cid:22) BD) value was 1.5 or greater.
`The magnetic sheets formed using these flat powders were confirmed to have a P’ of 130 or greater and sufficiently
`high magnetic permeability. In Comparative Examples 1-4 and 6, however, the D50 of the obtained flat powder was less
`than 50 Pm, the D50/(cid:3)(Hc (cid:22) BD) value was less than 1.5, and the P’ of the sheet was less than 130. In Comparative
`Example 5, the heat treatment carried out at 1300°C caused sintering and prevented flattening.
`(cid:3)[0065]
`(cid:3)(Examples 7-11 and Comparative Examples 7-11) Fe-(cid:3)Si-(cid:3)Al (Si = 8-11 wt%, Al = 5-7 wt%) based alloys produced
`by different atomization methods, as shown in Table 2, were prepared and treated at 700-1100°C for 2 hours in an Ar
`atmosphere to obtain heat treated powders. Next, a 5.7-(cid:3)fold amount of 2-(cid:3)propanol by weight was added to the untreated
`or heat treated powder, without using a flattening aid, and an attritor was used for flattening to obtain flat powder. The
`flattening time was adjusted for a BD of approximately 0.2-0.3 Mg/m3. The rest of the treatment and evaluation were
`carried out in the same manner as Exampl