JP6409943B2 - Magnetic sheet for non-contact power transmission - Google Patents

Description

  The present invention relates to a magnetic sheet used for non-contact power transmission to an electronic device or the like.

Non-contact power transmission used in cordless phones, electric shavers, and electric toothbrushes has been developed for use in electronic devices such as smartphones and wearable terminals, taking advantage of the ability to transmit power without using metal contacts or connectors. Yes.
There are two types of power transmission methods in non-contact power transmission: electromagnetic induction method and electromagnetic resonance method, both of which are between the transmission side coil and the reception side coil (both are collectively referred to as “coil”). It uses electromagnetic induction and magnetic resonance. These coils are formed by winding coils, and it is common to use a magnetic sheet in order to reduce interference caused by metal existing in the vicinity and extend the transmission / reception distance.

  Therefore, Patent Document 1 discloses a magnetic sheet composed of a sintered ferrite sheet with a cut and an adhesive layer. Patent Document 2 discloses a coil module including a spiral coil, a magnetic sheet, and a magnetic resin layer.

JP 2011-233740 A JP 2014-027094 A

Smartphones and wearable devices are pursuing multi-functionality while miniaturizing or maintaining the size of the device, so the receiving unit with the receiving coil and magnetic sheet stacked is mounted in a narrow space in the device. Is required. However, since the magnetic sheet of Patent Document 1 uses a plurality of small pieces of hard ferrite sintered sheet, there is a problem that the ferrite sintered sheet pieces fall off from the adhesive layer when the sheet is tightly mounted.
Further, the magnetic sheet of Patent Document 2 has a problem that cracks occur in a magnetic sheet made of hard ferrite when the receiving unit is bent and mounted. There is also a problem that the spiral coil is peeled off from the magnetic sheet by bending. In addition, the abrasion resistance of the surface of the magnetic sheet is weak, and there is a problem that the magnetic sheet is easily damaged when coming into contact with another member.

  An object of this invention is to provide the magnetic sheet for non-contact electric power transmission which can be bent and is excellent in adhesive strength with other members.

  The magnetic sheet for non-contact power transmission of the present invention includes a thermosetting resin, a curing agent, and magnetic particles, and the acid value of the thermosetting resin is 1 to 40 mgKOH / g.

  According to the present invention, by using a thermosetting resin having an acid value in a specific range, the adhesive strength with other members is improved, and further, by the crosslinking reaction between the curing agent and the thermosetting resin, the sheet The resistance to bending (hereinafter referred to as “bending resistance”) was improved.

  According to the present invention, a magnetic sheet for non-contact power transmission that can be bent and has excellent adhesive strength with other members can be provided.

  The magnetic sheet for non-contact power transmission of the present invention can be obtained by molding a magnetic resin composition containing a thermosetting resin, a curing agent, and magnetic particles.

The thermosetting resin is a resin having a plurality of crosslinkable reactive functional groups.
Examples of reactive functional groups include hydroxyl groups, phenolic hydroxyl groups, carboxyl groups, amino groups, epoxy groups, oxetanyl groups, oxazoline groups, oxazine groups, aziridine groups, thiol groups, isocyanate groups, blocked isocyanate groups, silanol groups, and the like. Can be mentioned. Among these, a carboxyl group is essential.

Examples of thermosetting resins having reactive functional groups include acrylic resins, maleic resins, polybutadiene resins, polyester resins, condensation-type polyester resins, addition-type polyester resins, melamine resins, polyurethane resins, polyurethane urea resins, and epoxy resins. Oxetane resin, phenoxy resin, polyimide resin, polyamide resin, phenol resin, alkyd resin, amino resin, polylactic acid resin, oxazoline resin, benzoxazine resin, silicone resin, fluorine resin, and the like. Among these, polyurethane resin, polyurethane urea resin, epoxy resin, addition type polyester resin, polyimide resin, polyamide resin, and polyamideimide resin are preferable from the viewpoint of surface resistance value and abrasion resistance.
The thermosetting resin can be used alone or in combination of two or more.

  The acid value of the thermosetting resin is 1 to 40 mgKOH / g, and more preferably 3 to 25 mgKOH / g. When the acid value is 1 to 40 mgKOH / g, the adhesive strength and bending resistance are improved.

  As for the glass transition temperature (henceforth Tg) of a thermosetting resin, -30-30 degreeC is preferable. Bending resistance is improved when Tg is in the range of -30 to 30 ° C.

  The weight average molecular weight of the thermosetting resin is preferably 20000 to 120,000, and more preferably 25,000 to 100,000. When the weight average molecular weight is 20000 to 120,000, both wear resistance and bending resistance can be achieved at a high level.

In the present invention, a thermoplastic resin can be used in combination with the thermosetting resin.
As thermoplastic resins, polyolefin resins, vinyl resins, styrene / acrylic resins, diene resins, terpene resins, petroleum resins, cellulose resins, polyamide resins, polyurethane resins, polyester resins that do not have the above curable functional groups. , Polycarbonate resin, polyimide resin, fluorine resin and the like.
The polyolefin resin is preferably a homopolymer or copolymer such as ethylene, propylene, and α-olefin compound. Specific examples include polyethylene propylene rubber, olefinic thermoplastic elastomer, α-olefin polymer, and the like.
The vinyl resin is preferably a polymer obtained by polymerization of vinyl ester such as vinyl acetate or a copolymer of vinyl ester and olefin compound such as ethylene. Specific examples include ethylene-vinyl acetate copolymer and partially saponified polyvinyl alcohol.
The styrene / acrylic resin is preferably a homopolymer or copolymer composed of styrene, (meth) acrylonitrile, acrylamides, (meth) acrylic acid esters, maleimides and the like. Specific examples include syndiotactic polystyrene, polyacrylonitrile, acrylic copolymer, ethylene-methyl methacrylate copolymer, and the like.
The diene resin is preferably a homopolymer or copolymer of a conjugated diene compound such as butadiene or isoprene and a hydrogenated product thereof. Specific examples include styrene-butadiene rubber and styrene-isoprene block copolymer. The terpene resin is preferably a polymer composed of terpenes or a hydrogenated product thereof. Specific examples include aromatic modified terpene resins, terpene phenol resins, and hydrogenated terpene resins.
The petroleum resin is preferably a dicyclopentadiene type petroleum resin or a hydrogenated petroleum resin. The cellulose resin is preferably a cellulose acetate butyrate resin. The polycarbonate resin is preferably bisphenol A polycarbonate. The polyimide resin is preferably a thermoplastic polyimide, a polyamideimide resin, or a polyamic acid type polyimide resin.

The curing agent has a plurality of functional groups capable of reacting with the reactive functional group in the thermosetting resin. The curing agent is preferably an epoxy compound, an acid anhydride group-containing compound, an isocyanate compound, an aziridine compound, dicyandiamide; an amine compound such as an aromatic diamine; a phenol compound such as a phenol novolac resin.
A hardening | curing agent can be used individually or in combination of 2 or more types.

  It is preferable that 1-50 weight part is contained with respect to 100 weight part of thermosetting resins, as for a hardening | curing agent, 3-30 weight part is more preferable, and 3-20 weight part is further more preferable.

In the present invention, the magnetic particles impart magnetic permeability and magnetic loss as desired to the magnetic sheet. As the magnetic particles, known materials can be used, and soft magnetic particles made of a soft magnetic material are preferable. Soft magnetic particles include, for example, oxide magnetic materials such as ferrite, Fe-based, Co-based, Ni-based, Fe-Ni-based, Fe-Co-based, Fe-Al-based, Fe-Si-based, Fe-Si-Al-based Fe-Si-Cr-based, Fe-Co-V-based, Fe-Ni-Mo-based, and Fe-Ni-Si-Al-based magnetic materials, and their microcrystalline metallic magnetic materials, Fe-Si -B, Fe-Si-BC, Co-Si-B, Co-Zr, Co-Nb, Co-Ta, Fe-Si-Cr-B, Fe-Si-Al-Ni- Examples thereof include particles of an amorphous metal magnetic material such as a Cr-based material.
Magnetic particles can be used alone or in combination of two or more.

  The shape of the magnetic particles is not limited as long as desired magnetic permeability and magnetic loss can be obtained. The shape is preferably, for example, spherical, flake-like, leaf-like, dendritic, plate-like, needle-like, rod-like, or grape-like.

  1-100 micrometers is preferable and, as for the average particle diameter (D50 average particle diameter) of a magnetic particle, 3-70 micrometers is more preferable. The D50 average particle size is a numerical value obtained by measuring magnetic particles with a tornado dry powder sample module using a laser diffraction / scattering particle size distribution analyzer LS13320 (manufactured by Beckman Coulter, Inc.). The cumulative value in the cumulative particle size distribution is a particle size of 50%. The refractive index was set to 1.6.

  The magnetic particles are preferably blended in an amount of 50 to 1500 parts by weight, more preferably 100 to 1000 parts by weight, with respect to 100 parts by weight of the thermosetting resin.

  Moreover, it is preferable that a magnetic resin composition contains a thickener further. By containing a thickener, the sedimentation of the magnetic particles in the magnetic resin composition can be suppressed, and coating troubles such as coating unevenness and streaks during sheet molding can be suppressed. As the thickener, for example, silica powder, organic bentonite, polycarboxylic acid compound, polyurethane compound, urea compound, polyamide compound and the like are preferable.

  The magnetic resin composition further comprises a silane coupling agent, a rust inhibitor, a reducing agent, an antioxidant, a pigment, a dye, a tackifier resin, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling regulator, a filler, a difficult agent. A flame retardant etc. can be mix | blended.

  The magnetic resin composition can be obtained by mixing and stirring a thermosetting resin, a curing agent, and magnetic particles. For the stirring, a known stirring device can be used, and a disperse mat or a homogenizer is preferable.

  The magnetic sheet for non-contact power transmission can be molded, for example, by coating a magnetic resin composition on a peelable sheet. Or it can shape | mold by extruding a magnetic resin composition in a sheet form with an extruder, such as T-die.

  Coating, for example, gravure coating method, kiss coating method, die coating method, lip coating method, comma coating method, blade method, roll coating method, knife coating method, spray coating method, bar coating method, spin coating method, dip coating method A known coating method such as can be used. When applying, a drying step may be provided as necessary. For the drying, a known drying device such as a hot air dryer or an infrared heater can be used.

  The thickness of the magnetic sheet can be appropriately designed according to the use, but is preferably about 50 μm to 500 μm, more preferably about 100 μm to 300 μm.

In the magnetic sheet of the present invention, functional layers other than magnetism can be laminated.
The other functional layer is, for example, a pressure-sensitive adhesive layer, a hard coat property, a water vapor barrier property, an oxygen barrier property, a heat dissipation layer, an electromagnetic wave shielding layer, or a layer having functions such as heat resistance.

  The magnetic sheet of the present invention is preferably present in a state where the crosslinkable functional group of the thermosetting resin and the functional group of the curing agent are partially reacted (semi-cured state). And when using a magnetic sheet, for example, after adhering to FPC (flexible printed wiring board) in which an antenna coil was formed, it is often hardened by a thermocompression bonding process, and desired adhesive strength is often obtained.

  The peelable sheet preferably uses a paper or plastic substrate, and a sheet having a known release treatment on one side of the substrate or a pressure sensitive adhesive layer instead of the release treatment is used. It is a formed sheet.

  In many cases, the magnetic sheet is stored in a state where a peelable sheet is attached until just before use, in order to facilitate protection and handling of the magnetic sheet.

  The magnetic sheet of the present invention can also be used in the state of a sheet in which all the crosslinkable functional groups of the thermosetting resin and the functional groups of the curing agent have reacted. When this magnetic sheet is used, an adhesive layer can be formed on one side of the magnetic sheet and attached to the antenna coil via the adhesive.

  The magnetic sheet of the present invention can be used for various antennas used for non-contact power transmission. For example, it can be used for a rigid printed wiring board and a flexible printed wiring board on which a winding coil and an antenna coil are formed.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited only to a following example. The following “parts” are values based on “parts by weight”, and “%” is a value based on “% by weight”.

<Synthesis of thermosetting resin>
[Synthesis Example 1]
A number average molecular weight (hereinafter referred to as “Mn”) obtained from adipic acid, terephthalic acid and 3-methyl-1,5-pentanediol in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube. Diol = 414, dimethylol butanoic acid 8 parts, isophorone diisocyanate 145 parts and toluene 40 parts were charged and reacted at 90 ° C. for 3 hours in a nitrogen atmosphere. To this, 300 parts of toluene was added to obtain a urethane prepolymer solution having an isocyanate group at the terminal. Next, 816 parts of the obtained urethane prepolymer solution was added to a mixture of 27 parts of isophoronediamine, 3 parts of di-n-butylamine, 342 parts of 2-propanol, and 576 parts of toluene. By reacting for a time, a polyurethane polyurea resin solution having a weight average molecular weight (hereinafter referred to as “Mw”) = 54,000 and an acid value of 5 mgKOH / g was obtained. To this, 144 parts of toluene and 72 parts of 2-propanol were added to obtain a polyurethane polyurea resin solution (P-1) having a solid content of 50%.

[Synthesis Example 2]
Mn = 981 obtained from adipic acid, 3-methyl-1,5-pentanediol and 1,6-hexane carbonate diol in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen introduction tube Diol 390, dimethylolbutanoic acid 16 parts, isophorone diisocyanate 158 parts, and toluene 40 parts were charged and reacted at 90 ° C. for 3 hours in a nitrogen atmosphere. To this, 300 parts of toluene was added to obtain a urethane prepolymer solution having an isocyanate group at the terminal. Next, 814 parts of the resulting urethane prepolymer solution was added to a mixture of 29 parts of isophorone diamine, 3 parts of di-n-butylamine, 342 parts of 2-pronol, and 576 parts of toluene. By reacting for a period of time, a polyurethane polyurea resin solution having Mw = 43,000 and an acid value of 10 mgKOH / g was obtained. To this, 144 parts of toluene and 72 parts of 2-propanol were added to obtain a polyurethane polyurea resin solution (P-2) having a solid content of 50%.

[Synthesis Example 3]
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 352 parts of diol having Mn = 1002 obtained from adipic acid and 3-methyl-1,5-pentanediol, dimethylol 32 parts of butanoic acid, 176 parts of isophorone diisocyanate and 40 parts of toluene were charged and reacted at 90 ° C. for 3 hours in a nitrogen atmosphere. To this, 300 parts of toluene was added to obtain a urethane prepolymer solution having an isocyanate group at the terminal. Next, 810 parts of the obtained urethane prepolymer solution was added to a mixture of 32 parts of isophoronediamine, 4 parts of di-n-butylamine, 342 parts of 2-propanol, and 576 parts of toluene, By reacting for a period of time, a polyurethane polyurea resin solution having Mw = 35,000 and an acid value of 21 mgKOH / g was obtained. To this, 144 parts of toluene and 72 parts of 2-propanol were added to obtain a polyurethane polyurea resin solution (P-3) having a solid content of 50%.

[Synthesis Example 4]
Into a reaction vessel equipped with a stirrer, thermometer, dripping device, reflux condenser, and gas introduction tube, 50 parts of methyl ethyl ketone was added, heated to 80 ° C. while injecting nitrogen gas into the vessel, and 3 parts of methacrylic acid at the same temperature, A mixture of 32 parts of n-butyl methacrylate, 65 parts of lauryl methacrylate and 4 parts of 2,2′-azobisisobutyronitrile was added dropwise over 1 hour to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 80 ° C. for 3 hours, then 1 part of azobisisobutyronitrile dissolved in 50 parts of methyl ethyl ketone was added, and the reaction was further continued at 80 ° C. for 1 hour. Cooled down. Next, an acrylic resin (P-4) containing a carboxyl group having a nonvolatile content of 50% was obtained by dilution with methyl ethyl ketone. The weight average molecular weight was 27000, Tg was −40 ° C., and the acid value was 20 mgKOH / g.

[Synthesis Example 5]
Into a reaction vessel equipped with a stirrer, thermometer, dripping device, reflux condenser, and gas introduction tube, 50 parts of methyl ethyl ketone was added, heated to 80 ° C. while injecting nitrogen gas into the vessel, and 3 parts of methacrylic acid at the same temperature, A mixture of 72 parts of n-butyl methacrylate, 25 parts of lauryl methacrylate and 4 parts of 2,2′-azobisisobutyronitrile was added dropwise over 1 hour to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 80 ° C. for 3 hours, then 1 part of azobisisobutyronitrile dissolved in 50 parts of methyl ethyl ketone was added, and the reaction was further continued at 80 ° C. for 1 hour. Cooled down. Next, an acrylic resin (P-5) containing a carboxyl group having a nonvolatile content of 50% was obtained by dilution with methyl ethyl ketone. The weight average molecular weight was 24,000, Tg was 41 ° C., and the acid value was 20 mgKOH / g.

[Synthesis Example 6]
In a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, inlet tube, thermometer, 195.1 parts of polycarbonate diol (Kuraray polyol C-2090), acid anhydride group-containing compound for main chain As a solvent, 29.2 parts of tetrahydrophthalic anhydride (Licacid TH: manufactured by Shin Nippon Rika Co., Ltd.) and 350 parts of toluene as a solvent were added, and the mixture was heated to 60 ° C. with stirring in a nitrogen stream and dissolved uniformly. Subsequently, the flask was heated to 110 ° C. and reacted for 3 hours. Then, after cooling to 40 ° C., 26 parts of bisphenol A type epoxy resin (YD-8125: manufactured by Nippon Steel Chemical Co., Ltd .: epoxy equivalent = 175 g / eq) and 4 parts of triphenylphosphine as a catalyst were added to 110 ° C. The temperature was raised and reacted for 8 hours. After cooling to room temperature, 11.56 parts of tetrahydrophthalic anhydride was added as an acid anhydride group-containing compound for the side chain and reacted at 110 ° C. for 3 hours. After cooling to room temperature, the non-volatile content was adjusted to 50% with toluene to obtain a polyester resin solution (P-6). The weight average molecular weight of the addition-type polyester resin obtained by this synthesis example was 15000, and the acid value of the resin non-volatile content measured was 25 mgKOH / g.

[Synthesis Example 7]
In a 4-neck flask equipped with a stirrer, reflux condenser, nitrogen inlet pipe, inlet pipe, thermometer, 193.8 parts of polycarbonate diol (Kuraray polyol C-2020), acid anhydride group-containing compound for main chain As a solvent, 29.2 parts of tetrahydrophthalic anhydride (Licacid TH: manufactured by Shin Nippon Rika Co., Ltd.) and 350 parts of toluene as a solvent were added, and the mixture was heated to 60 ° C. with stirring in a nitrogen stream and dissolved uniformly. Subsequently, the flask was heated to 110 ° C. and reacted for 3 hours. Then, after cooling to 40 ° C., 34.2 parts of bisphenol A type epoxy resin (YD-8125: manufactured by Nippon Steel Chemical Co., Ltd .: epoxy equivalent = 175 g / eq) and 4 parts of triphenylphosphine as a catalyst were added to form 110 parts. The temperature was raised to 0 ° C. and reacted for 8 hours. After cooling to room temperature, 15.21 parts of tetrahydrophthalic anhydride was added as an acid anhydride group-containing compound for the side chain and reacted at 110 ° C. for 3 hours. After cooling to room temperature, the non-volatile content was adjusted to 50% with toluene to obtain a polyester resin solution (P-7). The weight average molecular weight of the addition-type polyester resin obtained by this synthesis example was 50000, and the acid value of the resin non-volatile content measured was 19 mgKOH / g.

[Synthesis Example 8]
In a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, inlet tube, thermometer, 191.3 parts of polycarbonate diol (Kuraray polyol C-2041), acid anhydride group-containing compound for the main chain 34.6 parts of tetrahydrophthalic anhydride (Licacid HNA-100: manufactured by Shin Nippon Chemical Co., Ltd.) and 350 parts of toluene as a solvent were heated to 60 ° C. with stirring in a nitrogen stream and dissolved uniformly. . Subsequently, the flask was heated to 110 ° C. and reacted for 3 hours. Thereafter, after cooling to 40 ° C., 31.9 parts of bisphenol A type epoxy resin (YD-8125: manufactured by Nippon Steel Chemical Co., Ltd .: epoxy equivalent = 175 g / eq) and 4 parts of triphenylphosphine as a catalyst were added to form 110 parts. The temperature was raised to 0 ° C. and reacted for 8 hours. After cooling to room temperature, 16.78 parts of tetrahydrophthalic anhydride was added as an acid anhydride group-containing compound for the side chain and reacted at 110 ° C. for 3 hours. After cooling to room temperature, the non-volatile content was adjusted to 50% with toluene to obtain a polyester resin solution (P-8). The weight average molecular weight of the addition-type polyester resin obtained by this synthesis example was 132000, and the acid value of the resin non-volatile content measured was 20 mgKOH / g.

[Synthesis Example 9]
Mn = 981 obtained from adipic acid, 3-methyl-1,5-pentanediol and 1,6-hexane carbonate diol in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen introduction tube 432 parts of diol, 137 parts of isophorone diisocyanate, and 40 parts of toluene were charged and reacted at 90 ° C. for 3 hours in a nitrogen atmosphere. To this, 300 parts of toluene was added to obtain a urethane prepolymer solution having an isocyanate group at the terminal. Next, to a mixture of 25 parts of isophoronediamine, 3 parts of di-n-butylamine, 342 parts of 2-propanol, and 576 parts of toluene, 818 parts of the resulting urethane prepolymer solution was added, By reacting for a time, a polyurethane polyurea resin solution having Mw = 48,000 and an acid value of 0 mgKOH / g was obtained. To this, 144 parts of toluene and 72 parts of 2-propanol were added to obtain a polyurethane polyurea resin solution (P-9) having a solid content of 50%.

[Synthesis Example 10]
In a reaction vessel equipped with a stirrer, a thermometer, a dropping device, a reflux condenser, and a gas introduction tube, 101.1 parts of polytetramethylene glycol having a hydroxyl value of 110 mgKOH / g, 21.9 parts of dimethylolbutanoic acid, and methyl ethyl ketone 60 as a solvent The portion was charged, heated to 60 ° C. with stirring under a nitrogen stream, and dissolved until uniform. Subsequently, 52.1 parts of isophorone diisocyanate was added to the reaction vessel, and the reaction was performed at 80 ° C. for 8 hours. After cooling to room temperature, it was diluted with methyl ethyl ketone to obtain a urethane resin (P-10) containing a carboxyl group having a nonvolatile content of 50%. The weight average molecular weight was 28000, Tg was −10 ° C., and the acid value was 47 mgKOH / g.

The acid value, Tg, and weight average molecular weight were measured by the following methods.

<Acid value>
1 g of thermosetting resin was dissolved in 40 ml of methyl ethyl ketone, and an automatic titration apparatus “AT-510” manufactured by Kyoto Denshi Kogyo Co., Ltd. connected to “APB-510-20B” manufactured by the same company as a burette was used. Potentiometric titration was performed using a 0.1 mol / L ethanolic KOH solution as a titration reagent, and the number of mg of KOH per 1 g of resin was calculated.

<Glass transition temperature (Tg)>
Tg was measured by differential scanning calorimetry (“DSC-1” manufactured by METTLER TOLEDO).

<Weight average molecular weight (Mw)>
For measurement of Mw, GPC (gel permeation chromatography) (“HPC-8020” manufactured by Tosoh Corporation) was used. GPC is liquid chromatography that separates and quantifies substances dissolved in a solvent (THF; tetrahydrofuran) based on the difference in molecular size. For the measurement in the present invention, “LF-604” (manufactured by Showa Denko KK: GPC column for rapid analysis: 6 mm ID × 150 mm size) is connected in series to the column, the flow rate is 0.6 ml / min, the column temperature. It carried out on the conditions of 40 degreeC, and the determination of the weight average molecular weight (Mw) was performed in polystyrene conversion.

The magnetic particles, epoxy compounds, and aziridine compounds used in the examples are shown below.
Magnetic particles: Fe-Si-Cr soft magnetic particles (average particle size: 9.8 μm) manufactured by Mitsubishi Steel Co., Ltd. Epoxy compounds: bisphenol A type epoxy resin “JER828” (epoxy equivalent = 189 g / eq) manufactured by Mitsubishi Chemical Corporation・ Aziridine compound: “Chemite PZ-33” manufactured by Nippon Shokubai Co., Ltd.

<Example 1>
100 parts of thermosetting resin, 450 parts of magnetic particles, 15 parts of an epoxy compound as a curing agent and 2.0 parts of an aziridine compound are charged into a container, and toluene: isopropyl alcohol (weight ratio) is set so that the nonvolatile content concentration becomes 60% by weight. The mixed solvent of 2: 1) was added and stirred with a disper for 10 minutes to obtain a magnetic resin composition. Next, the magnetic resin composition was coated on a peelable sheet using a doctor blade so that the dry thickness was 200 μm, and further dried in an electric oven at 100 ° C. for 10 minutes to obtain a magnetic sheet.

<Examples 2-9, Comparative Examples 1-2>
A magnetic sheet was obtained in the same manner as in Example 1 except that the type of raw material in Example 1 was changed as shown in Table 2.

<Abrasion resistance>
The obtained magnetic sheet was prepared so as to have a width of 40 mm and a length of 150 mm. Next, a 75 μm thick polyimide film (“Kapton 300H” manufactured by Toray DuPont) was pressure-bonded to the exposed magnetic sheet surface at 150 ° C., 2 MPa, and 30 min. After the pressure bonding, the peelable sheet is removed, and a load of 200 gf and a reciprocating speed of 30 times / The magnetic sheets were rubbed together under the conditions of min and stroke of 120 mm, and the number of reciprocations until the appearance defect occurred was measured. The evaluation criteria are as follows.
(Double-circle): It is a favorable result 20000 times or more.
○: 10000 times or more and less than 20000 times No problem in practical use.
×: Less than 10,000 times

<Repulsive force>
A magnetic sheet having a width of 1 cm and a length of 6 cm was prepared as a sample. Next, the exposed magnetic sheet surface was pressure-bonded with a polyimide of 25 μm thickness (“Kapton 100H” manufactured by Toray DuPont Co., Ltd.) prepared in a size of 1 cm in width and 6 cm in length under the conditions of 150 ° C., 2 MPa, 30 min. The peelable sheet was peeled off, and the stiffness value was measured under the test conditions described in JPCA-TMJ002 8.4.1. The results were evaluated according to the following criteria. If the value of the repulsive force is too high, there is a possibility that the load will be excessive on the connection part (for example, connector) of the other party (coil, FPC, etc.) to which the magnetic sheet is to be attached, causing damage.
A: Repulsive force is 10 mN / mm or less. It is a good result.
○: The repulsive force exceeds 10 mN / mm and is 15 mN / mm or less. There is no problem in practical use.
X: Repulsive force exceeds 15 mN / mm. Impractical

<Bending resistance>
In order to evaluate bending resistance, an MIT test was performed as folding resistance in accordance with JIS C6471. A magnetic sheet was prepared to have a width of 15 mm and a length of 120 mm. In addition, the adherend to which the magnetic sheet is attached is formed in a shape based on JIS C6471, based on a two-layer CCL obtained by laminating a polyimide film (thickness 12.5 μm) and a copper foil (thickness 18 μm). Next, a cover coat layer having a thickness of 36 μm was formed. Further, a sample was obtained by pressure-bonding the exposed surface of the magnetic sheet to the cover coat layer at 150 ° C. for 30 minutes at 2.0 MPa. The folding resistance of the obtained sample was measured using a MIT tester under the conditions of a radius of curvature of 0.38 mm, a load of 500 g, and a speed of 180 times / min in an atmosphere of a temperature of 25 ° C. and a humidity of 50%. In the evaluation, bending was performed 3000 times and the number of bendings until the wiring was disconnected was measured. The evaluation criteria are as follows.
A: The wiring was not broken even after 3000 times. It is a good result.
◯: 2500 times or more and less than 3000 times before disconnection of wiring No problem in practical use.
X: The wiring was disconnected after less than 2500 times. Not practical.

<Adhesive strength>
A magnetic sheet having a width of 25 mm and a length of 70 mm was prepared as a sample. A polyimide film having a thickness of 50 μm (“Kapton 200EN” manufactured by Toray DuPont) was pressure-bonded to the sample under the conditions of 150 ° C., 2.0 MPa, and 30 min and thermally cured. Next, the peelable sheet of the magnetic sheet was peeled off for the purpose of reinforcing the sample for measuring the adhesive strength, and a polyimide film with a thickness of 50 μm was applied to the exposed surface at 150 ° C. using a commercially available adhesive sheet (manufactured by Toyochem). A laminate having a configuration of “polyimide film / adhesive sheet / magnetic sheet / polyimide film” was obtained by pressure bonding under conditions of 1 MPa and 30 min. Using this tensile tester (manufactured by Shimadzu Corporation) in an atmosphere of 23 ° C.-50% RH, at a peeling speed of 50 mm / min and a peeling angle of 90 °, at the interface between the magnetic sheet and the polyimide film. The adhesive strength was measured. The evaluation criteria are as follows.
A: 6 N / 25 mm or more. It is a good result.
A: 4 N / 25 mm or more and less than 6 N / 25 mm. There is no problem in practical use.
X: Less than 4N / 25mm. Not practical.

Claims (5)

Includes thermosetting resin, curing agent, and magnetic particles
The curing agent is at least one of an epoxy compound and an aziridine compound;
The acid value of the thermosetting resin is 1 to 40 mgKOH / g,
Magnetic resin composition for non-contact power transmission. The magnetic resin composition for non-contact power transmission according to claim 1, wherein the thermosetting resin has a glass transition temperature of -30 to 30 ° C. The magnetic resin composition for non-contact power transmission according to claim 1 or 2, wherein the thermosetting resin has a weight average molecular weight of 20,000 to 120,000. The magnetic resin composition for non-contact power transmission according to any one of claims 1 to 3, comprising 1 to 30 parts by weight of the curing agent with respect to 100 parts by weight of the thermosetting resin. The thermosetting resin is any one selected from the group consisting of polyurethane resin, polyurethane urea resin, epoxy resin, addition type polyester resin, polyimide resin, polyamide resin, and polyamideimide resin.
The magnetic resin composition for non-contact power transmission according to any one of claims 1 to 4.