JP2009224749A - Magnetic sheet, and manufacturing method of magnetic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic sheet capable of reducing unwanted electromagnetic waves discharged from an electronic device, suppressing electromagnetic faults generated in the electronic device, making a magnetic layer have a low temperature-fast curing property, and reducing the thickness change of the magnetic layer under a high temperature and high humidity environment, and to provide a manufacturing method of the magnetic sheet. <P>SOLUTION: The magnetic sheet includes the magnetic layer containing at least a binder, magnetic powders and a curing agent, the binder contains a thermosetting resin, and the curing agent is a heat cation curing agent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic sheet capable of reducing unnecessary electromagnetic waves emitted from an electronic device and suppressing electromagnetic interference generated in the electronic device, and a method for manufacturing the magnetic sheet.

  Applications for which the magnetic sheet is used include noise suppression applications and RFID applications. As noise suppression applications, along with the rapid progress of downsizing and higher frequency of electronic devices typified by personal computers and mobile phones, noise interference caused by external electromagnetic waves in these electronic devices and occurring inside the electronic devices In order to suppress interference between noises, various noise countermeasures are performed. For example, a magnetic sheet (noise suppression sheet) is installed in the vicinity of a noise transmission source or a reception source.

  The magnetic sheet has a magnetic coating containing an alloy (magnetic powder) such as Fe-Si-Al, an epoxy resin, an acrylic resin, and a volatile solvent on the surface of an insulating support such as PET or PET that has been subjected to a peeling treatment. The magnetic powder has the flexibility of being applied and cured by a heat press and formed into a sheet shape, and the magnetic powder has a function as a so-called noise suppressor that suppresses noise. As for the noise suppression effect of the magnetic sheet, it is preferable that μ ″ which is an imaginary part of the magnetic permeability is large.

  On the other hand, as an RFID application, wireless communication using a coil antenna based on an electromagnetic induction system has recently become widespread as represented by a portable information terminal having an IC tag function called RFID (Radio Frequency Identification). . For example, in portable information terminals, various conductors (metals) such as metal casings and metal parts are disposed in the vicinity of antenna elements for transmission and reception due to the miniaturization thereof. In this case, the presence of the metal in the vicinity of the antenna element greatly attenuates the magnetic field that can be used for communication, shortens the RFID communication distance in the electromagnetic induction method, and transmits and receives radio frequencies by shifting the resonance frequency. Can be difficult. Therefore, in order to suppress such electromagnetic interference, a magnetic sheet is disposed between the antenna element and the conductor. As a function of RFID, it is preferable that μ ′ which is a real part of magnetic permeability is large and μ ″ which is an imaginary part is small.

In general, a curing agent (crosslinking agent) for curing a thermosetting organic resin is added to the binder constituting the magnetic layer in the magnetic sheet (for example, Patent Document 1). As described above, the magnetic sheet is cured by adding a curing agent to the binder. In particular, when the polymer material in the magnetic sheet is likely to absorb moisture, the thickness of the magnetic sheet is reduced due to environmental changes in temperature and humidity. There is a problem of changing. Here, in order to sufficiently cure the magnetic sheet, if the curing temperature is increased and the curing time is lengthened, there is a problem that water is wasted and productivity is deteriorated because the cooling time is lengthened. In order to cope with this problem, if the curing temperature is increased and the curing time is shortened, there is a problem in the heat resistance of the insulating support (PET).
In addition, many magnetic sheets having a structure in which a magnetic layer and an insulating support (PET) are bonded via an adhesive have been proposed (for example, Patent Documents 2 to 5). Since both use a pressure-sensitive adhesive or an adhesive, the magnetic layer must be made thinner by the thickness of the pressure-sensitive adhesive or the adhesive. When the magnetic layer is thinned, the magnetic permeability is decreased. Therefore, it is preferable that the magnetic layer and the insulating support (PET) are brought into close contact with each other without using an adhesive or an adhesive to make the magnetic layer as thick as possible. Examples of a method for bringing the magnetic layer and the insulating support (PET) into close contact with each other without using an adhesive or an adhesive include a method in which the magnetic layer and the insulating support (PET) are heated and pressed. However, when the press temperature in the heating press is high, there is a problem that the insulating support (PET) contracts and the magnetic sheet warps. This warpage of the magnetic sheet becomes more prominent when the magnetic sheet is thin.

JP 2007-95829 A JP 2007-165701 A JP 2007-123373 A JP 2006-301900 A JP 2001-329234 A

An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention is capable of reducing unnecessary electromagnetic waves emitted from electronic devices and suppressing electromagnetic interference generated in electronic devices, making the magnetic layer a low temperature-fast curing property, and a magnetic layer in a high temperature and high humidity environment. An object of the present invention is to provide a magnetic sheet and a method for producing the magnetic sheet that can reduce a change in thickness of the magnetic sheet.
Another object of the present invention is to provide a magnetic sheet and a method for producing the magnetic sheet that can reduce warpage due to shrinkage of the concavo-convex forming layer (insulating support).

  As a result of intensive studies in view of the above problems, the present inventor has obtained the following knowledge. That is, a magnetic sheet comprising a magnetic powder containing a magnetic powder, a thermosetting resin and a curing agent in a binder, wherein the curing agent is a thermal cation curing agent, the magnetic layer is formed at a low temperature-fast curing property. Thus, the present inventors have found that the change in thickness of the magnetic layer under a high temperature and high humidity environment can be reduced, and that the warpage due to the shrinkage of the concavo-convex forming layer (insulating support) can be reduced. It came to do.

The present invention is based on the above knowledge of the present inventor, and means for solving the above problems are as follows. That is,
<1> A magnetic layer including at least a binder, magnetic powder, and a curing agent, the binder including a thermosetting resin, and the curing agent being a thermal cationic curing agent. This is a magnetic sheet.
In the magnetic sheet composition according to <1>, since the curing agent is a thermal cationic curing agent, the magnetic layer is made to be low temperature-fast curing, and the change in thickness of the magnetic layer under a high temperature and high humidity environment is reduced. can do. In addition, by making the magnetic layer low temperature-fast curable, the magnetic layer can be cured even when the press temperature in the heat press is low, and thus due to the shrinkage of the concavo-convex forming layer (insulating support). Warpage can be reduced.
<2> The magnetic sheet according to <1>, wherein the thermal cationic curing agent is a sulfonium salt and the binder contains an epoxy resin.
<3> The magnetic sheet according to <2>, wherein the binder contains an acrylic resin.
<4> The magnetic sheet according to any one of <1> to <3>, wherein the thermal cationic curing agent is contained in an amount of 2 to 10 parts by mass with respect to 106.1 parts by mass of the binder.
<5> A magnetic composition containing at least a binder, magnetic powder, and a curing agent, wherein the binder includes a thermosetting resin, and the curing agent is a thermocationic curing agent, is molded and magnetically formed. A magnetic layer forming step of forming a layer, and an unevenness forming layer and a transfer material are laminated and arranged in this order from the magnetic layer side on at least one surface in the thickness direction of the magnetic layer, and then heated and pressed. It is manufactured by a magnetic sheet manufacturing method including a shape transfer step of transferring a surface shape of a transfer material to the surfaces of the unevenness forming layer and the magnetic layer, and joining the unevenness forming layer and the magnetic layer. This is a magnetic sheet.
<6> A magnetic layer formed from a magnetic composition containing at least a binder, magnetic powder, and a curing agent, wherein the binder contains a thermosetting resin, and the curing agent is a thermocationic curing agent. A step of forming a magnetic layer, and an unevenness forming layer and a transfer material are laminated and arranged in this order from the magnetic layer side on at least one surface in the thickness direction of the magnetic layer, and then heated and pressed. A method for producing a magnetic sheet, comprising: transferring a surface shape of a material to the surfaces of the concavo-convex forming layer and the magnetic layer and joining the concavo-convex forming layer and the magnetic layer. It is.
In the method for producing a magnetic sheet according to <6>, in the magnetic layer forming step, at least the binder, the magnetic powder, and the curing agent are contained, and the binder contains the thermosetting resin. Then, the magnetic composition in which the curing agent is the thermal cation curing agent is molded to form the magnetic layer. In the shape transfer step, the unevenness forming layer and the transfer material are laminated and arranged in this order from the magnetic layer side on at least one surface in the thickness direction of the magnetic layer, and then heated and pressed. The surface shape of the transfer material is transferred to the surface of the concavo-convex forming layer and the magnetic layer, and the concavo-convex forming layer and the magnetic layer are directly joined without using an adhesive or the like. As a result, a magnetic sheet can be obtained simply and efficiently at low cost.

  According to the present invention, the above-described problems can be solved, and the magnetic layer can be made to have a low temperature-fast curing property to reduce a change in thickness of the magnetic layer under a high temperature and high humidity environment. Moreover, the magnetic sheet which can reduce the curvature by shrinkage | contraction of an uneven | corrugated formation layer (insulating support body), and the manufacturing method of this magnetic sheet can be provided.

(Magnetic sheet)
The magnetic sheet of the present invention has a magnetic layer, and further has other layers appropriately selected as necessary.

-Magnetic layer-
The magnetic layer has functions of reducing unnecessary electromagnetic waves emitted from the electronic device and suppressing electromagnetic interference caused by interference of unnecessary electromagnetic waves in the electronic device.
The magnetic layer contains a binder, magnetic powder, and a curing agent, and further contains other components appropriately selected as necessary.

There is no restriction | limiting in particular as thickness of the said magnetic layer, Although it can select suitably according to the objective, It is preferable that it is high at the point from which a high magnetic permeability is obtained, and 25 micrometers-500 micrometers are preferable.
When the thickness is less than 25 μm, the magnetic permeability is low, and when the thickness exceeds 500 μm, it is not suitable for a narrow part and does not follow the recent trend of downsizing of electronic devices, and the influence of the thickness on the magnetic permeability. May become smaller. When the thickness is 70 μm or less, the magnetic permeability tends to decrease rapidly.

--Curing agent--
The curing agent is not particularly limited as long as it is a thermal cationic curing agent, and can be appropriately selected according to the purpose.
Examples of the thermal cation curing agent include sulfonium salts (counter anions are SbF ₆ and PF ₆ ) and iodonium salts. From the viewpoint of curing characteristics and availability, for example, the thermal cation curing agent is represented by the formula (1). A sulfonium type cationic curing agent is preferred.

  The sulfonium type cationic curing agent of the formula (1) can be used as a general thermal cationic polymerization initiator for epoxy resins. In this case, an epoxy binder (paste form, film form) containing 100 parts by mass of an epoxy resin and 0.5 parts by mass to 30 parts by mass of the sulfonium type cationic curing agent of the formula (1) as a thermal cationic polymerization initiator is 80 By heating to ℃ to 180 ° C, it is possible to give a cured product that has excellent electric corrosion resistance and is rapidly cured at a low temperature.

  Examples of the sulfonium type cationic curing agent of the formula (1) include San-Aid SI series SI-60L, SI-80L, SI-100L, etc. manufactured by Sanshin Chemical Industry Co., Ltd. SI-60L, SI-80L, and SI-100L are highly active in this order.

--Binder--
The binder is not particularly limited as long as it contains a thermosetting organic resin, and can be appropriately selected according to the purpose. Examples thereof include an acrylic rubber containing a thermosetting organic resin described later. It is done.
The acrylic rubber preferably has an epoxy group. In this case, the reliability is improved by the reaction between the epoxy group and the curing agent. The acrylic rubber preferably further has a hydroxyl group. Adhesiveness can be improved by having this hydroxyl group.
The weight average molecular weight of the acrylic rubber is preferably 10,000 to 450,000 in terms of excellent coatability.
When the weight average molecular weight is less than 10,000, the viscosity of the magnetic sheet composition is decreased, and it may be difficult to apply a heavy magnetic powder. When the weight average molecular weight exceeds 450,000, The viscosity of the magnetic sheet composition may increase, making it difficult to apply.
Further, the glass transition temperature of the acrylic rubber is preferably −10 ° C. to + 15 ° C. from the viewpoint of reliability.
When the glass transition temperature is less than −10 ° C., reliability in a high temperature or high temperature and high humidity environment may deteriorate, and when it exceeds + 15 ° C., the magnetic sheet tends to be hard.

--- Thermosetting organic resin ---
An example of the thermosetting organic resin is an epoxy resin. When an epoxy resin having a low molecular weight is added, the melt viscosity of the binder is further lowered when the magnetic sheet is compressed (molded), so that the magnetic properties can be improved. For example, a polyfunctional epoxy resin can be used. If it uses, the reliability of the magnetic sheet after hardening can be improved more.
Suitable examples of the epoxy resin include cationic curing epoxy resins. The said epoxy resin may be used individually by 1 type, and may use 2 or more types together.

--- Magnetic powder--
There is no restriction | limiting in particular as said magnetic powder, According to the objective, it can select suitably, For example, flat shape, lump shape, fibrous shape, spherical shape, indefinite shape etc. are mentioned. Among these, the flat shape is preferable in that the magnetic powder can be easily oriented in a predetermined direction and the magnetic permeability can be increased.
Examples of the magnetic powder include soft magnetic metal, ferrite, and pure iron particles.
Examples of the soft magnetic metal include magnetic stainless steel (Fe—Cr—Al—Si alloy), sendust (Fe—Si—Al alloy), permalloy (Fe—Ni alloy), and silicon copper (Fe—Cu—Si alloy). Fe-Si alloy, Fe-Si-B (-Cu-Nb) alloy, Fe-Ni-Cr-Si alloy, Fe-Si-Cr alloy, Fe-Si-Al-Ni-Cr alloy, and the like.
Examples of the ferrite include Mn—Zn ferrite, Ni—Zn ferrite, Mn—Mg ferrite, Mn ferrite, Cu—Zn ferrite, and soft ferrite such as Cu—Mg—Zn ferrite, and hard ferrite that is a permanent magnet material. Can be mentioned.
The said magnetic powder may be used individually by 1 type, and may use 2 or more types together.

  The contents of the binder, the magnetic powder, and the curing agent are not particularly limited and may be appropriately selected depending on the purpose. However, the magnetic powder is 400 parts per 106.1 parts by mass of the binder. The thermal cationic curing agent as the curing agent is preferably 2 parts by mass to 10 parts by mass with respect to 106.1 parts by mass of the binder. In addition, it is preferable that the magnetic powder contained in a magnetic sheet is 60 wt%-95 wt%.

  When the content of the magnetic powder is less than 400 parts by mass with respect to 106.1 parts by mass of the binder, excellent magnetic properties may not be obtained, and with respect to the binder 106.1 parts by mass, If it exceeds 1,000 parts by mass, it will be difficult to keep the magnetic powder tied together with the binder, and the thickness of the magnetic sheet will increase or become brittle in a high-temperature and high-humidity environment. In some cases, the magnetic powder may fall from the surface as well as the end face.

  When the content of the thermal cationic curing agent is less than 2 parts by mass with respect to 106.1 parts by mass of the binder, the curing reaction does not occur sufficiently, and when the content exceeds 10 parts by mass with respect to 106.1 parts by mass of the binder. The curing reaction starts before the hot pressing step, causing a decrease in magnetic permeability. Moreover, since the impurity ion concentration becomes high and corrosion easily occurs, it is not preferable.

-Other ingredients-
The other components are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected according to the purpose from various known additives. When the magnetic layer is formed, the magnetic composition For the purpose of improving applicability (adjustment of viscosity) of a product (containing the binder, the magnetic powder, and the curing agent), a solvent can be added. For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; alcohols such as methanol, ethanol, propanol, butanol, isopropyl alcohol; methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl lactate, ethyl glycol acetate Esters such as diethylene glycol dimethyl ether, 2-ethoxyethanol, Tetrahydrofuran, dioxane and the like; benzene, toluene, aromatic hydrocarbon compounds such as xylene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, halogenated hydrocarbon compounds such as chlorobenzene; and the like. These may be used individually by 1 type and may use 2 or more types together. In addition, various additives such as a dispersant, a stabilizer, a lubricant, a silane or titanate coupling agent, a filler, a plasticizer, and an anti-aging agent may be added as necessary.
There is no restriction | limiting in particular as content of the said other component, According to content of the said binder, the said magnetic powder, and the said hardening | curing agent, it can determine suitably.

-Other layers-
The other layer is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose. Examples thereof include a concavo-convex forming layer.

--Concavity and convexity formation layer--
The unevenness forming layer has a function of peeling the magnetic sheet from a member in contact with the magnetic sheet, for example, in an electronic device when the magnetic sheet of the present invention is used.

There is no restriction | limiting in particular about the structure, thickness, and material (material) as said uneven | corrugated formation layer, According to the objective, it can select suitably.
The structure may be a single layer structure or a laminated structure.
The thickness is preferably 2 μm to 100 μm.
When the thickness is less than 2 μm, workability may be deteriorated. When the thickness is more than 100 μm, heat is not easily transmitted to the magnetic layer at the time of hot pressing, and reliability may be lowered.
Examples of the material include synthetic resins, and for example, polyethylene terephthalate (PET) is preferable.

  The concavo-convex forming layer may be a commercially available product or an appropriately produced one. Examples of the commercially available product include mat-treated PET (“Lumorer X44- # 25”; Toray Industries, Inc.). Manufactured), mat-treated PET (“Lumirror 44- # 38”; manufactured by Toray Industries, Inc.), unpeeled PET (“Embred”; manufactured by Unitika Ltd.), non-silicone-exfoliated PET (““ Fluorogen ” RL "; manufactured by Mitsubishi Plastics), silicone release treated PET (" 25GS "; manufactured by Lintec Corporation), and the like. A film on which characters are printed may be used for the unevenness forming layer. The printed surface of the character may be a surface in contact with the magnetic layer, or a surface not in contact with the magnetic layer (opposite surface).

−Use−
The method of using the magnetic sheet of the present invention is not particularly limited and can be appropriately selected depending on the purpose. For example, the magnetic sheet is cut into a desired size and is used as a noise source for electronic equipment. In addition, the magnetic layer side can be disposed close to each other.

-Application-
The magnetic sheet of the present invention can be suitably used for electromagnetic noise suppressors, radio wave absorbers, magnetic shield materials, electronic devices having an IC tag function such as RFID (Radio Frequency Identification), non-contact IC cards, and the like. In particular, it can be suitably used for a mobile phone with an RFID function.

When the magnetic sheet of the present invention has the concavo-convex forming layer, when a high degree of insulation is required, or when it is used under a design (narrow site) in contact with other electronic components Is preferred. In addition, since the magnetic powder in the magnetic layer is a metal, the surface resistance value is as low as 0.01 MΩ / □ to 1 MΩ / □ even when mixed with the resin composition, and when a flame retardant is added Further, since the surface resistance value tends to further decrease, it is preferable that the magnetic sheet having flame retardancy has the unevenness forming layer.
Due to the presence of the unevenness forming layer, the magnetic powder can be prevented from falling off from the surface of the magnetic layer. Further, since the unevenness forming layer is bonded to one surface of the magnetic layer, the moisture absorption area in the magnetic layer is narrowed, and the reliability is improved.
Further, the surface of the concavo-convex forming layer has concavo-convex portions and is excellent in slipperiness, and therefore can be suitably used for a battery pack portion of a mobile phone. In this case, even if the battery pack expands due to heat generation of the lithium battery due to repeated charging, adhesion with the battery pack is suppressed by the unevenness forming layer, so the open / close failure of the battery pack lid is improved. Is done.
When the concave / convex transfer layer is not transferred to the concave / convex forming layer, scratches are formed on the surface by opening and closing the lid of the battery pack, resulting in a poor appearance. If unevenness is formed on the unevenness forming layer by the unevenness transfer, there is an advantage that no scratches are formed on the unevenness forming layer.

  Unlike the conventional magnetic sheet, the magnetic sheet of the present invention may not have an adhesive layer. If the adhesive layer is not provided, it is possible to prevent the failure of the electronic device due to the leakage of the adhesive, which occurs when the electronic device is used at a high temperature. Further, as compared with the conventional magnetic sheet, the thickness of the magnetic layer can be increased by the thickness of the adhesive layer, and therefore the specific gravity is large and the magnetic permeability is high.

  There is no restriction | limiting in particular as the manufacturing method of the said magnetic sheet of this invention, Although it can select suitably according to the objective, It can manufacture suitably with the manufacturing method of the magnetic sheet of the following this invention.

(Magnetic sheet manufacturing method)
The method for producing a magnetic sheet of the present invention includes at least a magnetic layer forming step and a shape transfer step, and further includes other steps appropriately selected as necessary.

<Magnetic layer formation process>
The magnetic layer forming step includes at least a binder, magnetic powder, and a curing agent, the binder includes a thermosetting resin, and the magnetic composition is a thermal cationic curing agent, This is a step of forming a magnetic layer by molding.
The details of the binder and the magnetic powder are as described above. However, the binder is preferably in an uncured state before the heat press described below. Here, if the curing proceeds before the hot pressing, the magnetic layer is not sufficiently compressed and the magnetic permeability cannot be increased. In addition, when the hardened magnetic layer is compressed, strain remains, and when it is repeatedly exposed in a room temperature, high temperature or high temperature and high humidity environment, the thickness changes or the magnetic properties decrease. Or On the other hand, when the binder before the heating press is in an uncured state, the occurrence of these problems is suppressed.

The magnetic composition can be prepared by adding the magnetic powder, the curing agent, and the thermosetting resin to the binder and mixing them.
The magnetic composition can be formed by, for example, applying the magnetic composition on a substrate and drying it.
There is no restriction | limiting in particular as said base material, Although it can select suitably according to the objective, The polyester film (peeling PET) by which peeling processing was performed etc. at the point which can peel the formed said magnetic layer easily. Are preferable.
Further, as the base material, matte PET, unpeeled PET, non-silicone peeled PET (the surface on which the magnetic layer is formed is not peeled), silicone peeled PET (magnetic layer is formed) The surface may not be peeled).
Through the above steps, the magnetic composition is molded to form the magnetic layer.

<Shape transfer process>
In the shape transfer step, an unevenness forming layer and a transfer material are laminated and arranged in this order from the magnetic layer side on one surface in the thickness direction of the magnetic layer, and then heated and pressed to thereby form the surface shape of the transfer material. Is transferred to the surface of the concavo-convex formation layer and the magnetic layer, and the concavo-convex formation layer and the magnetic layer are joined together.

-Concavity and convexity formation layer-
There is no restriction | limiting in particular about the structure, thickness, and material (material) as said uneven | corrugated formation layer, According to the objective, it can select suitably, These details are as above-mentioned.

The surface state of the unevenness forming layer is not particularly limited, and one surface in the thickness direction may be subjected to surface treatment or may not be subjected to any surface treatment. It is preferable that a release treatment without using a silicone resin is performed. In these cases, the slipperiness is improved as compared with those not subjected to any surface treatment. In the case of these surface treatments, since the silicone resin is not used, the silicone oligomer does not bleed out in a high temperature or high temperature and high humidity environment, and is suitable for use inside an electronic device.
The mat treatment is not particularly limited as long as the surface of the unevenness forming layer can be roughened, and can be selected according to the purpose. For example, sand mat treatment, chemical mat treatment, surface embossing treatment Etc. By these treatments, unevenness is formed on the surface of the unevenness forming layer, and slipperiness is improved.

-Transfer material-
The transfer material is not particularly limited in its structure, thickness, and material (material), and can be appropriately selected according to the purpose. However, the transfer material has irregularities on the surface and has good air permeability. Is preferred. In this case, when the unevenness on the surface of the transfer material is transferred to the unevenness forming layer, the unevenness is formed on the surface of the unevenness forming layer, and slipperiness is improved.

The structure may be a single layer structure or a laminated structure.
The thickness is preferably 25 μm to 200 μm.
If the thickness is less than 25 μm, it may not be possible to obtain a magnetic sheet with improved slipperiness, and if it exceeds 200 μm, heat is not easily transferred to the magnetic layer during the hot pressing, and the reliability decreases. Sometimes.
Examples of the material include paper, synthetic fiber, and natural fiber.

  The transfer material may be a commercially available product or an appropriately produced material. Examples of the commercially available product include high-quality paper (“OK Prince Quality 70”; manufactured by Oji Paper Co., Ltd.). , Cushion paper (“TF190” manufactured by Toyo Fiber Co., Ltd.), nylon mesh (“N-NO.110S” manufactured by Tokyo Screen Co., Ltd.), cotton cloth (“Kanakin No. 3” manufactured by Japan Standards Association), Adhesive base paper (“SO base paper 18G”; manufactured by Daifuku Paper Co., Ltd.), double-sided release paper (“100 GVW (high smooth surface)”; Oji Paper Co., Ltd.), double-sided release paper (“100 GVW (low smooth surface) ) "; Manufactured by Oji Paper Co., Ltd.).

-Lamination arrangement-
The stacking method is not particularly limited as long as the unevenness forming layer and the transfer material are stacked in this order from the magnetic layer side on one surface in the thickness direction of the magnetic layer. The release layer and the transfer material are preferably further laminated in this order from the magnetic layer side on the other surface in the thickness direction of the magnetic layer. By interposing the release layer, the other surface of the magnetic layer is protected during the heat press described later to prevent adhesion with the transfer material, and after the heat press, the transfer material is removed from the release layer. It can be easily peeled off from the magnetic layer together with the layer. The surface shape of the transfer material is also transferred to the surface of the magnetic layer located on the release layer side. At this time, bubbles present in the resin composition in the magnetic layer are easily removed, and The reliability of the magnetic sheet is improved. When the transfer material on the release layer side is not used, the magnetic permeability of the magnetic sheet can be improved.

  The release layer is not particularly limited as long as it has a function of preventing adhesion between the other surface in the thickness direction of the magnetic layer and the transfer material during the hot pressing, and is appropriately selected according to the purpose. However, a polyester film (peeled PET) having a surface subjected to a peeling treatment is preferable in that it can be easily peeled off from the magnetic layer after the hot pressing.

-Heating press-
The heating press method is not particularly limited and can be appropriately selected depending on the purpose.For example, as shown in FIG. 1, the magnetic layer, the concavo-convex forming layer, and the transfer material as a laminate, These can be performed by sandwiching them with a laminator or a press from both sides and heating and pressurizing them.
The surface shape (uneven shape) of the transfer material is transferred to the surface of the unevenness forming layer and the magnetic layer by the heating press, and the unevenness forming layer and the magnetic material can be transferred without using an adhesive or the like. The layers are joined directly.

  The conditions for the heating press are not particularly limited and can be appropriately selected according to the purpose. The press temperature is preferably, for example, 80 ° C. to 190 ° C. The press pressure is, for example, 5 MPa to 20 MPa. Preferably, the pressing time is preferably 1 minute to 20 minutes, for example.

Through the above steps, the surface shape of the transfer material is transferred to the surfaces of the unevenness forming layer and the magnetic layer, and the unevenness forming layer and the magnetic layer are joined. As a result, a magnetic sheet having the magnetic layer and the unevenness forming layer is obtained.
The magnetic sheet thus obtained is excellent in slipperiness because the surface shape (surface irregularities) of the transfer material is transferred to the surface of the irregularity forming layer and roughened.

According to the method for producing a magnetic sheet of the present invention, the surface shape of the transfer material is transferred to the surface of the concavo-convex forming layer and the magnetic layer by the heating press, so that the surface of the concavo-convex forming layer is roughened. As a result, slipperiness can be improved.
Moreover, since the said uneven | corrugated formation layer and the said magnetic layer are directly joined by the said heat press, an adhesion layer is unnecessary and a magnetic sheet can be manufactured simply and efficiently at low cost.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
-Production of magnetic sheet-
First, 270 parts by mass of toluene and 120 parts by mass of ethyl acetate, an acrylic rubber having an epoxy group as the binder (“SG80H-3”; manufactured by Nagase ChemteX Corp., number average molecular weight 150,000, weight average molecular weight) 350,000) 83 parts by mass, 23.1 parts by mass of an epoxy resin (“Epicoat 1031S” manufactured by Japan Epoxy Resin Co., Ltd.) as the binder, and a sulfonium-based cationic curing agent (Sun Aid SI-60L as a curing agent) A binder was prepared by dissolving 6.9 parts by mass of Sanshin Chemical Industry Co., Ltd.). To this, 550 parts by mass of flat magnetic powder (“JEM-S”; manufactured by Mitsubishi Materials Corporation) as the magnetic powder was added, and these were mixed to prepare a magnetic composition.

Next, the obtained magnetic composition is used as a base material (unevenness-forming layer) on a polyester film (peeled PET) (“38GS”; manufactured by Lintec, thickness 38 μm) having a release treatment applied to the surface. It applied so that thickness might be set to 100 micrometers-200 micrometers with the bar coater (The magnetic composition was apply | coated to the surface by which the peeling process was carried out).
Next, the film is dried at room temperature for 10 minutes, further dried at 60 ° C. for 10 minutes, and the peeled PET having a layer (magnetic layer) made of a magnetic composition formed on the peeled surface is cut into 250 mm × 250 mm and peeled off. Three pieces of peeled PET having a 250 mm × 250 mm magnetic layer formed on the treated surface were obtained.
Next, the obtained magnetic composition is used as a base material (unevenness-forming layer) on a polyester film (peeled PET) (“38GS”; manufactured by Lintec, thickness 38 μm) having a release treatment applied to the surface. It applied so that thickness might be set to 100 micrometers-200 micrometers with the bar coater (The magnetic composition was apply | coated to the surface which is not peeling-processed).
Next, it was dried at room temperature for 10 minutes, further dried at 60 ° C. for 10 minutes, and the release PET having a layer (magnetic layer) made of the magnetic composition formed on the surface that was not subjected to the release treatment was cut into 250 mm × 250 mm and peeled off. One release PET having a 250 mm × 250 mm magnetic layer formed on the untreated surface was obtained.
Next, with respect to two peeled PETs having a 250 mm × 250 mm magnetic layer formed on the peeled surface, the peeled PET was peeled from the magnetic layer to obtain two 250 mm × 250 mm magnetic layers. Next, two magnetic layers cut into 250 mm × 250 mm are stacked on the magnetic layer side of the peeled PET having a 250 mm × 250 mm magnetic layer formed on the peeled surface, and further, the peeling treatment is not performed. One piece of peeled PET with a 250 mm × 250 mm magnetic layer formed on the surface (so that the magnetic layer and the magnetic layer face each other), both sides of the peeled PET sandwiched, and four pieces of magnetic layer are laminated. Obtained.
Subsequently, on both surfaces of the peeled PET arranged so as to sandwich the laminated magnetic layers, the high-quality paper (“OK Prince fine quality 70”; manufactured by Oji Paper Co., Ltd., thickness: 100 μm, Beck, respectively) Smoothness 6.2 seconds / mL). Then, using a vacuum press (made by Kitagawa Seiki Co., Ltd.), press holding temperature 170 ° C., press holding time (time held at the press holding temperature) 5 minutes, after reaching the press holding temperature (90 ° C. to press holding temperature) The time until the temperature decreases to 90 ° C. for 38 minutes under the condition of a press pressure of 9 MPa, the sheet is heated and pressed with a press plate through the cushioning material, and peeled PET (peeling that forms a magnetic layer on the peeled surface) One (PET) sheet was peeled from the laminated magnetic layer to obtain a magnetic sheet.

(Examples 2 to 7)
-Production of magnetic sheet-
In Example 1, as shown in Table 1, at least one of the blending amount of the sulfonium-based cationic curing agent (Sun Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.), the press holding temperature, and the pressing time is used. A magnetic sheet was produced in the same manner as in Example 1 except for the change.

(Example 8)
-Production of magnetic sheet-
In Example 1, the sulfonium-based cationic curing agent (Sun-Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) as the curing agent was replaced with the sulfonium-based cationic curing agent (Sun-Aid SI-100L; Sanshin Chemical Industry Co., Ltd.). A magnetic sheet was prepared in the same manner as in Example 1 except that the product was changed to ().

(Examples 9 and 10)
-Production of magnetic sheet-
In Example 8, at least one of the blending amount of the sulfonium-based cationic curing agent (Sun Aid SI-100L; manufactured by Sanshin Chemical Industry Co., Ltd.), the press holding temperature, and the press time is shown in Table 2. A magnetic sheet was produced in the same manner as in Example 8 except that the change was made.

(Example 11)
-Production of magnetic sheet-
In Example 2, the sulfonium-based cationic curing agent (Sun-Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) as the curing agent was replaced with the sulfonium-based cationic curing agent (Sun-Aid SI-80L; Sanshin Chemical Industry Co., Ltd.). A magnetic sheet was produced in the same manner as in Example 2 except that the product was changed to ().

Example 12
-Production of magnetic sheet-
In Example 2, except that the flat magnetic powder (“JEM-S”; Mitsubishi Materials Corporation) as the magnetic powder was replaced with a flat magnetic powder (“SP-1”; manufactured by Mate Corporation), A magnetic sheet was produced in the same manner as in Example 2.

(Example 13)
-Production of magnetic sheet-
In Example 1, except that the flat magnetic powder (“JEM-S”; manufactured by Mitsubishi Materials Corporation) as the magnetic powder was replaced with a flat magnetic powder (“SP-1”; manufactured by Mate Corporation). In the same manner as in Example 1, a magnetic sheet was produced.

(Example 14)
-Production of magnetic sheet-
In Example 1, except that the blending amount of the sulfonium-based cationic curing agent (Sun Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) as the curing agent was changed as shown in Table 2, it was the same as Example 1. Thus, a magnetic sheet was produced.

(Comparative Example 1)
-Production of magnetic sheet-
In Example 1, as the curing agent, a sulfonium cationic curing agent (Sun-Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) is used as an imidazole curing agent (“HX3748”; manufactured by Asahi Kasei Chemicals Corporation). A magnetic sheet was produced in the same manner as in Example 1 except that the magnetic sheet was replaced.

(Comparative Example 2)
-Production of magnetic sheet-
In Example 2, a sulfonium-based cationic curing agent (Sun-Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) as the curing agent was replaced with an imidazole-based curing agent (“HX3748”; manufactured by Asahi Kasei Chemicals Corporation). A magnetic sheet was produced in the same manner as in Example 2 except that it was replaced.

(Comparative Example 3)
-Production of magnetic sheet-
In Example 3, a sulfonium-based cationic curing agent (Sun-Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) as the curing agent was used as an imidazole-based curing agent (“HX3748”; manufactured by Asahi Kasei Chemicals Corporation). A magnetic sheet was produced in the same manner as in Example 3 except that it was replaced.

(Comparative Example 4)
-Production of magnetic sheet-
In Example 4, a sulfonium-based cationic curing agent (Sun-Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) as the curing agent was replaced with an imidazole-based curing agent (“HX3748”; manufactured by Asahi Kasei Chemicals Corporation). A magnetic sheet was produced in the same manner as in Example 4 except that it was replaced.

(Comparative Example 5)
-Production of magnetic sheet-
In Example 5, the sulfonium-based cationic curing agent (Sun Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) as the curing agent was replaced with the imidazole-based curing agent (“HX3748”; manufactured by Asahi Kasei Chemicals Corporation). A magnetic sheet was produced in the same manner as in Example 5 except that it was replaced.

(Comparative Example 6)
-Production of magnetic sheet-
In Example 6, a sulfonium-based cationic curing agent (Sun-Aid SI-60L; manufactured by Sanshin Chemical Industry Co., Ltd.) as the curing agent was used as an imidazole-based curing agent (“HX3748”; manufactured by Asahi Kasei Chemicals Corporation). A magnetic sheet was produced in the same manner as in Example 6 except that it was replaced.

(Comparative Example 7)
-Production of magnetic sheet-
In Comparative Example 1, a magnetic sheet was produced in the same manner as in Comparative Example 1, except that the press holding time and the pressing time were changed as shown in Table 5.

(Example 15)
-Production of magnetic sheet-
In Example 2, the same procedure as in Example 2 was used, except that the magnetic composition coated with one layer with a bar coater was used as it was instead of using the four layers composed of the magnetic composition. A magnetic sheet was prepared.

(Comparative Example 8)
-Production of magnetic sheet-
In Comparative Example 7, the same procedure as in Comparative Example 7 was used, except that a magnetic composition coated with one layer with a bar coater was used as it was instead of using a laminate of four layers made of a magnetic composition. A magnetic sheet was prepared.

(Example 16)
-Production of magnetic sheet-
A magnetic composition was prepared at the same blending ratio as in Example 1.

  Next, on the polyester film (peeled PET) (“38GS”; manufactured by Lintec, thickness 38 μm) having a release treatment applied to the surface as the substrate, the magnetic composition was applied with a bar coater, dried, A layer (magnetic layer) made of a magnetic composition was formed. Next, after peeling PET from the layer composed of the magnetic composition (magnetic layer), the magnetic layer is cut into 250 mm × 250 mm, and the polyester film (the surface subjected to the peeling treatment) is formed on both sides of the layer composed of the magnetic composition. And the magnetic layer are in contact with each other) and are cured by hot pressing at 170 ° C. and 9 MPa for 10 minutes to obtain a magnetic sheet. The polyester film is peeled off, and an adhesive layer (No. 5601; manufactured by Nitto Denko Co., Ltd.) and the polyester film (the surface not subjected to release treatment is attached to the adhesive layer) are adhered to the magnetic sheet. A sheet was obtained.

[Permeability]
First, a ring-shaped sample (magnetic layer sample) punched to an outer diameter of 7.05 mm and an inner diameter of 2.945 mm was produced, and a conductive wire was wound around this for 5 turns and soldered to a terminal. Here, the length from the base of the terminal to the bottom of the ring-shaped sample (magnetic layer sample) was 20 mm. Then, using an impedance analyzer (“4294A”; manufactured by Agilent Technologies), an inductance and a resistance value at 1 MHz were measured and converted into magnetic permeability (magnetic permeability of the magnetic layer).
Μ ′ represents the real part of the complex permeability.
The characteristic of μ ′ varies depending on the purpose of use of the magnetic sheet. For example, in the case of improving communication of an RFID device, it is high μ ′ and low μ ″ (imaginary part of complex permeability) at a frequency of 20 MHz or less. Is preferred.
The magnetic sheet of the present invention is a magnetic sheet that can be used in the KHz to GHz band.

〔Reliability test〕
-Thickness change-
First, the thickness of the magnetic layer in the magnetic sheet (thickness not including PET) was measured. Next, the magnetic sheet is put in an oven, heated at 85 ° C./60% for 96 hours, the thickness of the magnetic layer (thickness excluding PET) in the magnetic sheet after taking out from the oven is measured, and the magnetism before and after heating is measured. The change rate of the thickness (thickness not including PET) of the magnetic layer in the sheet was measured.

[Curve evaluation]
An edge portion of the obtained magnetic sheet (250 mm × 250 mm) was cut to prepare a 240 mm × 240 mm magnetic sheet. The 240 mm × 240 mm magnetic sheet (magnetic layer + PET) was placed on a horizontal table, and the maximum value of warpage of the four sides of the magnetic sheet (magnetic layer + PET) was measured. The amount of warpage was measured with a “measure”.

From the results of Tables 1 to 5, the magnetic sheets of Examples 1 to 14 using a sulfonium-based cationic curing agent are in a higher temperature and humidity environment than Comparative Examples 1 to 7 using an imidazole-based curing agent as a curing agent. The dimensional stability was good. This is a combination of Examples and Comparative Examples that differ only in the type of curing agent in the production conditions of the magnetic sheet (Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, Example 4 and Comparative Example 4, Example 5 and Comparative Example 5, Example 6 and Comparative Example 6, Example 8 and Comparative Example 1, Example 9 and Comparative Example 2, Example 11 and Comparative Example 2) As a result, it can be seen that the thickness change rate in the reliability test of the example is smaller than the thickness change rate of the comparative example. In Example 14, the thickness change before and after the reliability test shows a relatively high value of 4.81%, but Comparative Example 6 (the heating press conditions are the same as in Example 14 and the addition of a curing agent is performed. Compared to the thickness change (19.41%) before and after the reliability test (the amount is larger than that of Example 14), it is considerably smaller.
Further, from the results of Tables 1 to 5, when a sulfonium-based cationic curing agent is used, even if the heating temperature is lowered (130 ° C. to 150 ° C.) and the heating temperature is shortened, the thickness change rate is lowered (the magnetic layer is reduced). It can be seen that the amount of warpage can be reduced. On the other hand, when an imidazole-based curing agent is used, it is understood that the curing temperature must be 170 ° C., and the warpage of the magnetic sheet becomes large. This was produced under the production conditions of Comparative Example 7 in which the magnitude of warpage (18 mm) of the magnetic sheet (Example 15) produced under the production conditions of Example 2 was equivalent to that of Example 2. It can be seen from the fact that the warp size (24 mm) of the magnetic sheet (Comparative Example 8) is smaller.
When the magnetic sheet of Example 15 and the magnetic sheet of Example 16 are compared, in the magnetic sheet of Example 15, the magnetic layer can be thickened by the thickness of the adhesive layer, thereby increasing the value of μ ′. I can see that Moreover, in Example 16 using an adhesive, it turns out that the magnitude | size of curvature can be made small.
Moreover, since Examples 1-14 compared with Example 15, since a magnetic sheet is thick, it turns out that curvature is small.
Moreover, since the comparative examples 2 and 3 are hot-pressing at 130 to 150 degreeC using the imidazole hardening | curing agent, hardening reaction has not fully advanced. Therefore, although the warpage is small, the evaluation of the reliability test was not good.
Moreover, since the comparative examples 4-6 had little compounding quantity of the used hardening | curing agent, the hardening defect occurred and the reliability test was unsatisfactory.

  The magnetic sheet of the present invention can be suitably used for, for example, electromagnetic noise suppressors, radio wave absorbers, magnetic shield materials, electronic devices having IC tag functions such as RFID, non-contact IC cards, and the like. It can be suitably used for a mobile phone with a function.

FIG. 1 is a process diagram showing an example of a method for producing a magnetic sheet of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic layer 20 Concavity and convexity formation layer 22 Release layer 30 Transfer material 40 Laminate 50 Press plate

Claims (6)

  It has a magnetic layer containing at least a binder, magnetic powder, and a curing agent, the binder contains a thermosetting resin, and the curing agent is a thermocationic curing agent. Magnetic sheet.   The magnetic sheet according to claim 1, wherein the thermal cationic curing agent is a sulfonium salt, and the binder contains an epoxy resin.   The magnetic sheet according to claim 2, wherein the binder contains an acrylic resin.   The magnetic sheet according to any one of claims 1 to 3, comprising 2 to 10 parts by mass of a thermal cation curing agent with respect to 106.1 parts by mass of the binder. A magnetic layer is formed by molding a magnetic composition containing at least a binder, magnetic powder, and a curing agent, wherein the binder contains a thermosetting resin, and the curing agent is a thermocationic curing agent. A magnetic layer forming step,
The uneven shape forming layer and the transfer material are stacked in this order from the magnetic layer side on at least one surface in the thickness direction of the magnetic layer, and then heated and pressed to change the surface shape of the transfer material to the uneven shape formation. And transferring to the surface of the layer and the magnetic layer, and a shape transfer step of joining the concavo-convex forming layer and the magnetic layer;
A magnetic sheet produced by a method for producing a magnetic sheet comprising: A magnetic layer is formed by molding a magnetic composition containing at least a binder, magnetic powder, and a curing agent, wherein the binder contains a thermosetting resin, and the curing agent is a thermocationic curing agent. A magnetic layer forming step,
The uneven shape forming layer and the transfer material are stacked in this order from the magnetic layer side on at least one surface in the thickness direction of the magnetic layer, and then heated and pressed to change the surface shape of the transfer material to the uneven shape formation. And transferring to the surface of the layer and the magnetic layer, and a shape transfer step of joining the concavo-convex forming layer and the magnetic layer;
A method for producing a magnetic sheet, comprising: