JP2006114725A - Magnetic sheet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic sheet and the manufacturing method thereof wherein it has an excellent flexibility by virtue of embracing internally metal oxide particles by a synthetic resin, even when its content of the metal oxide particles and it is thinned, and the metal oxide particles so exist in its inside at a high filling factor uniformly as to obtain a stable high-quality magnetic characteristic. <P>SOLUTION: The magnetic sheet 1 is formed constitutionally out of a plurality of laminated synthetic resin sheets 2 each of which embraces internally a plurality of metal oxide particles 3. The manufacturing method of the magnetic sheet 1 has constitutionally a slurrying process for slurrying a synthetic resin 4, a solvent, and the metal oxide particles 3; a coating process for coating a supporting body with the obtained slurry; a drying process for drying the slurry used in the coating process; a peeling process for peeling the drily obtained synthetic resin sheet 2 from the supporting body; and a laminating process for laminating by a pressingly bonding or a thermocompression bonding the plurality of peeled synthetic resin sheets 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic sheet that shields the influence of a magnetic field in order to prevent deterioration in communication performance of an antenna mounted on a data carrier, a reader / writer, and the like, and a method for manufacturing the same.

  In recent years, a data carrier system such as an RF-ID system that performs data communication using electromagnetic waves in a band of 13.60 MHz or the like is used in a production line of a factory. The data carrier system uses a reader / writer to read and write information on a data carrier such as an IC tag affixed to a product, etc., without touching it, so that production process history management, process switching management, etc. To achieve efficient operation of the production line.

  FIG. 2 is an assembly diagram of the data carrier, and FIG. 3 is a cross-sectional view of the main part of the data carrier.

  In the figure, 10 is a data carrier, 11 is a front casing, 12 is an antenna, 12a is an antenna substrate, 12b is an antenna pattern made of copper foil or the like formed on the antenna substrate 12a, 13 is a circuit such as a matching circuit, 14 Is a magnetic sheet, 15 is an insulating spacer made of synthetic resin, 16 is a metal plate such as aluminum, and 17 is a rear casing.

  The antenna 12 transmits and receives electromagnetic waves in order to read and write information. The received electromagnetic wave is processed as information by a circuit 13 such as a matching circuit, and is written in a memory on the circuit 13 or corresponding information is transmitted from the antenna 12.

  When an object such as a metal shelf, a wall reinforcing bar, or an electrolyte exists behind the data carrier 10 or its reader / writer, the object is electromagnetically induced by electromagnetic waves from the data carrier 10 or the reader / writer. This causes a magnetic field, which affects the electromagnetic wave, greatly attenuates the antenna sensitivity and lowers the communication performance. Therefore, a magnetic sheet 14 is disposed on the back surface of the antenna 12 such as the data carrier 10 to absorb a magnetic field from behind and prevent deterioration in communication performance. This magnetic sheet 14 is a sheet formed by mixing metal oxide particles such as ferrite with a synthetic resin and is disclosed in, for example, (Patent Document 1).

On the other hand, as a material having the same function as the magnetic sheet 14, a material made of a bulk body of metal oxide particles such as ferrite has been used. However, since the bulk body lacks workability and becomes thin when it is thin, it tends to break or chip, making it difficult to use it for thin electronic parts such as IC tags.
JP 2000-244171 A

  However, the conventional magnetic sheet has the following problems.

  (1) In the magnetic sheet of (Patent Document 1), since the content of the resin as a binder to the metal magnetic powder (metal oxide particles) is larger than that of the conventional bulk body, the magnetic permeability is lower than that of the bulk body. It had the subject that the effect which strengthens was small.

(2) Also, if the resin content is reduced and the number of metal oxide particles is increased, it becomes brittle like a bulk when it is made into a sheet shape, so it cannot be made thin while maintaining sufficient flexibility. It had the subject that it was difficult to use for thin electronic components, such as an IC tag.

  (3) In addition, since the magnetic coating is simply applied to the substrate, dried and peeled off, the metal oxide particles adhere to each other inside the obtained magnetic sheet, and only the portion having a large bulk density and the resin This causes the problem that stable magnetic characteristics cannot be obtained.

  The present invention solves the above-described conventional problems, and has excellent flexibility even when the content of the metal oxide particles is large and when the metal oxide particles are thin because the metal oxide particles are included in the synthetic resin. In addition, an object of the present invention is to provide a magnetic sheet that is formed by laminating synthetic resin sheets, so that metal oxide particles are uniformly present in the sheet at a high filling rate, and stable and high magnetic properties can be obtained.

  In addition, the present invention solves the above-described conventional problems, and provides a method for producing a magnetic sheet that can easily obtain a magnetic sheet having excellent flexibility and stable high magnetic properties. With the goal.

  In order to solve the above problems, the magnetic sheet of the present invention is a magnetic sheet for shielding the influence of a magnetic field, and is formed by laminating a plurality of synthetic resin sheets containing a plurality of metal oxide particles. Have

  As a result, since the metal oxide particles are encapsulated with the synthetic resin, it has excellent flexibility even when the content of the metal oxide particles is large and when the metal oxide particles are thin, and the synthetic resin sheets are laminated. Therefore, it is possible to provide a magnetic sheet in which metal oxide particles are uniformly present in the sheet at a high filling rate and can stably provide high magnetic properties.

  In order to solve the above problems, a method for producing a magnetic sheet according to the present invention is a method for producing a magnetic sheet for shielding the influence of a magnetic field, and kneads a synthetic resin, a solvent for the synthetic resin, and metal oxide particles. A slurrying step for slurrying, a coating step for applying the slurry obtained in the slurrying step on a support, a drying step for drying the applied slurry, and a synthetic resin sheet obtained by drying It has the structure provided with the peeling process which peels from a support body, and the lamination process which laminates | stacks several peeled synthetic resin sheets by pressure bonding or thermocompression bonding.

  Thereby, the manufacturing method of the magnetic sheet which can obtain easily the magnetic sheet which has the outstanding flexibility and the stable high magnetic characteristic can be provided can be provided.

  As described above, according to the magnetic sheet and the manufacturing method thereof of the present invention, the following advantageous effects can be obtained.

  According to the first aspect of the present invention, even when the content of the metal oxide particles is high, the flexibility and the thinness are high, and the durability is high. It can be used for small electronic devices. In addition, since a plurality of metal oxide particles form an aggregated state and are present in the synthetic resin sheet at a high bulk density and are formed by laminating the synthetic resin sheet, the magnetic permeability is high, the loss is high, and the Q is high. Value and high magnetic properties can be stably obtained. Therefore, even if there is an object that affects electromagnetic waves such as metal shelves, wall rebars, electrolytes, etc. behind the data carrier, etc. It is possible to prevent the deterioration of communication performance by shielding the influence of electromagnetic waves.

  According to the second aspect of the present invention, in addition to the effect of the first aspect, the magnetic property is high enough to prevent the deterioration of the communication performance of the antenna having high magnetic permeability, low loss and high Q value. can get. Moreover, since it is formed by laminating synthetic resin sheets containing metal oxide particles, it has excellent flexibility even when the content of metal oxide particles is as large as 86 wt% to 97 wt%.

  According to the third aspect of the invention, in addition to the effect of the first or second aspect, the metal oxide particles are closely packed in the synthetic resin sheet to form an aggregated state, and the flexibility of the sheet is maintained. A magnetic sheet capable of realizing a high content can be provided.

  According to the invention of claim 4, in addition to the effect of any one of claims 1 to 3, the metal oxide particles are prevented from becoming non-uniform inside the synthetic resin sheet, and stable magnetic properties are obtained. can get.

  According to the invention described in claim 5, a plurality of metal oxide particles are formed into a synthetic resin by slurrying a synthetic resin, a solvent, and metal oxide particles, and applying and drying the obtained slurry on a support. Therefore, even if it is thin, it has excellent flexibility and high durability. In addition, since a plurality of metal oxide particles form an agglomerated state and are encapsulated in a high bulk density, the magnetic permeability is high, the loss is high, the Q value is excellent, and excellent magnetic properties are obtained, and the influence of electromagnetic waves is sufficiently reduced. It can be shielded to prevent a decrease in communication performance. Moreover, the synthetic resin sheet obtained by drying is peeled off from the support and laminated to form a magnetic sheet, so that the bulk density of the metal oxide particles becomes uniform in the thickness direction of the sheet, and stable magnetic properties are obtained. It is done.

  According to the sixth aspect of the invention, in addition to the effect of the fifth aspect, by adding a coupling material, the bond between the metal oxide particles and the synthetic resin becomes stronger and the durability is excellent.

  Since the present invention encloses metal oxide particles with a synthetic resin, it has excellent flexibility even when the content of metal oxide particles is large and when it is made thin, and a synthetic resin sheet is laminated. Synthetic resin encapsulating a plurality of metal oxide particles for the purpose of providing a magnetic sheet in which the metal oxide particles are uniformly present at a high filling rate within the sheet and thus can be stably obtained. This was realized by stacking a plurality of sheets.

  Another object of the present invention is to provide a method for producing a magnetic sheet that can easily obtain a magnetic sheet having excellent flexibility and stable high magnetic properties. A slurrying step in which a solvent and metal oxide particles are kneaded to form a slurry; a coating step in which the slurry obtained in the slurrying step is applied onto a support; a drying step in which the applied slurry is dried; and a drying step This was realized by including a peeling step of peeling the synthetic resin sheet obtained from the support and a laminating step of laminating the plurality of peeled synthetic resin sheets by pressure bonding or thermocompression bonding.

  A first invention made to solve the above-described problem is a magnetic sheet for shielding the influence of a magnetic field, which is formed by laminating a plurality of synthetic resin sheets enclosing a plurality of metal oxide particles have.

  This configuration has the following effects.

  (1) Since the synthetic resin sheet is formed so as to surround a plurality of metal oxide particles with the synthetic resin, it is not cracked or chipped even when the content of the metal oxide particles is high. Even if it is formed thin, it is excellent in flexibility.

  (2) In the synthetic resin sheet, the plurality of metal oxide particles form an aggregated state and exist at a high bulk density, and thus have excellent magnetic properties.

  (3) Since a synthetic resin sheet including a plurality of metal oxide particles is laminated and formed, the bulk density of the metal oxide particles becomes uniform in the thickness direction of the sheet, and stable magnetic characteristics can be obtained.

  2nd invention made | formed in order to solve the said subject is a magnetic sheet as described in 1st invention, Comprising: Content of the said metal oxide particle in the said synthetic resin sheet is 30 wt%-98 wt%, Preferably The structure is 86 wt% to 97 wt%.

  With this configuration, in addition to the operation of the first invention, the following operation is provided.

  (1) Since the content of metal oxide particles is 30 wt% to 98 wt%, preferably 86 wt% to 97 wt%, excellent magnetic properties are obtained, and a synthetic resin sheet containing metal oxide particles is laminated. Since it is formed, it has excellent flexibility even when the content of the metal oxide particles is high.

  Here, as the content of the metal oxide particles becomes smaller than 86 wt%, the magnetic permeability and the like are lowered, and the magnetic characteristics cannot be obtained. When the content becomes smaller than 30 wt%, this tendency becomes remarkable, which is not preferable, and as it becomes larger than 97 wt%. When the content of the synthetic resin is reduced and the thickness is reduced, the necessary flexibility is not obtained, and if it is less than 98 wt%, this tendency becomes remarkable, which is not preferable.

  3rd invention made | formed in order to solve the said subject is a magnetic sheet as described in 1st or 2nd invention, Comprising: The average particle diameter of the said metal oxide particle is 1 micrometer-200 micrometers, Preferably it is 30 micrometers-70 micrometers. It has the composition which is.

  With this configuration, in addition to the functions of the first or second invention, the following functions are provided.

  (1) Since the average particle diameter of the metal oxide particles is 1 μm to 200 μm, preferably 30 μm to 70 μm, the metal oxide particles are closely packed in the synthetic resin sheet to form an aggregated state and maintain flexibility. High content can be realized as it is.

  Here, as the average particle diameter of the metal oxide particles becomes smaller than 30 μm, the bulk density tends to become non-uniform and the manufacturing cost for fine pulverization becomes higher. As it becomes larger than 70 μm, voids between the metal oxide particles become larger, the filling rate decreases, and it becomes difficult to form an agglomerated state, and when the magnetic properties are lowered and larger than 200 μm, this tendency becomes remarkable.

  A fourth invention made to solve the above problems is the magnetic sheet according to any one of the first to third inventions, wherein the synthetic resin sheet has a thickness of 5 μm to 1000 μm, preferably 80 μm. It has the structure which is -150 micrometers.

  With this configuration, in addition to the operation of the invention described in any one of the first to third inventions, the following operation is provided.

  (1) Since the thickness of the synthetic resin sheet is 5 μm to 1000 μm, preferably 80 μm to 150 μm, the metal oxide particles are prevented from becoming uneven inside the synthetic resin sheet, and stable magnetic properties can be obtained.

  Here, as the thickness of the synthetic resin sheet becomes smaller than 80 μm, the durability of the sheet decreases and it becomes difficult to enclose the metal oxide particles with the synthetic resin, and the necessary flexibility cannot be obtained. Since the tendency becomes remarkable, it is not preferable, and as it becomes larger than 150 μm, the metal oxide particles become non-uniform inside the synthetic resin sheet and the magnetic characteristics become unstable, and when it becomes larger than 1000 μm, this tendency becomes remarkable.

  A fifth invention made in order to solve the above-mentioned problems is a method for producing a magnetic sheet for shielding the influence of a magnetic field, wherein a slurry is obtained by kneading a synthetic resin, a synthetic resin solvent, and metal oxide particles. From the support, the slurrying step to be converted, the application step of applying the slurry obtained in the slurrying step on the support, the drying step of drying the applied slurry, and the synthetic resin sheet obtained by drying It has the structure provided with the peeling process which peels, and the lamination process which laminates | stacks several peeled synthetic resin sheets by pressure bonding or thermocompression bonding.

  This configuration has the following effects.

  (1) Slurry synthetic resin, solvent, and metal oxide particles, and apply the slurry on a support and dry, so that multiple metal oxide particles are surrounded by synthetic resin, so excellent flexibility In addition, since a plurality of metal oxide particles form an aggregated state and exist at a high bulk density, a magnetic sheet having excellent magnetic properties can be obtained.

  (2) The synthetic resin sheet obtained by drying is peeled off from the support and laminated to form a magnetic sheet, whereby the bulk density of the metal oxide particles becomes uniform in the thickness direction of the sheet, and stable magnetic properties are obtained. can get.

  (3) Since a plurality of synthetic resin sheets are laminated, the magnetic sheet can be formed to an arbitrary thickness.

  Here, the number of laminated synthetic resin sheets in the lamination step is preferably 2 to 15 although it depends on the thickness of the magnetic sheet to be obtained. Note that it is preferable to reduce the number of stacked layers as much as possible from the viewpoint of workability, and it is also preferable in order to prevent dust and the like from being sandwiched between sheets.

  The pressure and heating temperature in the laminating step are preferably 9.8 MPa to 19.6 MPa and 35 ° C. to 60 ° C. As the applied pressure becomes smaller than 9.8 MPa, the adhesion between the sheets becomes insufficient, and as the applied pressure becomes larger than 19.6 MPa, a large pressurizer is required. As the heating temperature becomes lower than 35 ° C, the flexibility of the sheet becomes lower, and as the heating temperature becomes higher than 60 ° C, the plasticizer tends to volatilize.

  A sixth invention made to solve the above problems is a method for producing a magnetic sheet according to the fifth invention, wherein the coupling material is added to the slurry in the slurrying step.

  With this configuration, in addition to the operation of the fifth invention, the following operation is provided.

  (1) By adding a coupling material, the bond between the metal oxide particles and the synthetic resin becomes strong, and a magnetic sheet excellent in durability can be obtained.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a main part of the magnetic sheet according to the first embodiment.

  In FIG. 1, 1 is the magnetic sheet in this Embodiment 1, 2 is a synthetic resin sheet, 3 is a metal oxide particle, 4 is a synthetic resin.

Each synthetic resin sheet 2 is formed to a thickness of 80 μm to 150 μm, includes a plurality of metal oxide particles 3, and the plurality of metal oxide particles 3 forms an aggregated state. As the synthetic resin 4, a thermoplastic resin such as a polyvinyl acetal resin, an epoxy resin, a diallyl phthalate resin, or a polyurethane resin is used. As the metal oxide particles 3, ferrite particles formed by firing and pulverization so that the saturation magnetization, remanence, and coercive force have predetermined values are used, and Fe ₂ O ₃ or Mn—Zn, Ni-Zn-based materials are used. The metal oxide particles 3 having an average particle diameter of 30 μm to 70 μm were used, and the content of the metal oxide particles 3 in the synthetic resin sheet 2 was set to be 86 wt% to 97 wt%.

  A method for manufacturing the magnetic sheet according to the first embodiment configured as described above will be described below.

  First, a synthetic resin such as a polyvinyl acetal resin and a plastic material such as phthalate are dissolved in a solvent such as butyl acetate. A slurry is prepared by kneading 45 wt% of the obtained solution and 55 wt% of Ni, Zn, Cu based ferrite particles (slurry process). Here, the durability of the sheet can be enhanced by adding a coupling material such as silane to the slurry.

  Next, the prepared slurry is applied to the upper surface of a support made of a release material such as polyethylene terephthalate while degassing under reduced pressure using a doctor blade method (application process) and continuously dried at about 90 ° C. (drying) Step), a synthetic resin sheet having a thickness of about 100 μm is prepared.

  After the produced synthetic resin sheet is cut into a predetermined size, it is peeled off from the support (peeling step), and a plurality of synthetic resin sheets are overlaid. At this time, the synthetic resin sheets are superposed in a clean room so that dust, impurities, and the like are not sandwiched between the synthetic resin sheets.

  A magnetic sheet in which a plurality of synthetic resin sheets are laminated is obtained by pressing the laminated synthetic resin sheets at a predetermined pressure using a press machine heated to about 40 ° C. and thermocompression bonding (lamination process).

  As described above, the magnetic sheet and the manufacturing method thereof according to Embodiment 1 are configured, and thus have the following effects.

  (1) A synthetic resin, a solvent, and metal oxide particles are kneaded, coated on a support, and dried to surround a plurality of metal oxide particles with a synthetic resin and a plurality of enclosed metals. A synthetic resin sheet in which oxide particles form an aggregated state is obtained. The obtained synthetic resin sheet is peeled off from the support and laminated to form a magnetic sheet, so that the content of metal oxide particles is high and the metal oxide has excellent flexibility even if it is thin. Since the content of the product particles is large, a magnetic sheet having high magnetic permeability, low loss, high Q value and stable magnetic properties can be obtained.

  (2) Since the content of the metal oxide particles is as large as 86 wt% to 97 wt%, excellent magnetic properties can be obtained, and the metal oxide particles are formed by laminating synthetic resin sheets enclosing the metal oxide particles. Even if the content of the particles is as high as 86 wt% to 97 wt%, it has excellent flexibility.

(3) Since the average particle diameter of the metal oxide particles is 30 μm to 70 μm, the metal oxide particles are closely packed in the synthetic resin sheet to form an aggregated state and maintain a high content while maintaining flexibility. realizable.

  (4) Since the thickness of the synthetic resin sheet is 80 μm to 150 μm, the metal oxide particles are prevented from becoming non-uniform inside the synthetic resin sheet, and stable magnetic characteristics can be obtained.

  Examples of the present invention will be described below.

Example 1
Fe ₂ O ₃ , NiO, ZnO, and CuO are used as metal oxides constituting the metal oxide particles, and these fine powders (average particle diameter: 0.1 μm to ₂ μm) are mixed with 46.0 mol% of Fe ₂ O ₃ , NiO18. 0 mol%, ZnO 18.0 to 22.5 mol%, CuO 8.5 to 12.0 mol% were mixed at a ratio. The finely mixed fine powder was put into a predetermined mold and fired, and the fired product obtained was finely pulverized to produce metal oxide particles having an average particle size of 30 μm to 70 μm. A magnetic sheet of Example 1 was produced in the same manner as in Embodiment 1 using the produced metal oxide particles. The number of laminated resin sheets was 10.

  When the magnetic sheet produced as described above was disposed on the back surface of an antenna such as a data carrier and its Q value was measured, a Q value of 120 or more was measured at a frequency of 13.60 MHz. The Q value was measured by first placing a magnetic sheet prepared on the upper surface of a square aluminum plate having a thickness of 3 mm and a side of 150 mm, and one side made of copper wire having a diameter of 1.6 mm on the upper surface of the magnetic sheet. Were measured using an impedance analyzer (model 4194A, manufactured by Hewlett-Packard Company).

  Since the Q value is 120 or more, it has been found that the use of this magnetic sheet provides an effect of strengthening the magnetic field by eliminating the influence of surrounding metals and the like in an antenna that performs communication by an electromagnetic induction method.

  The present invention relates to a magnetic sheet for shielding the influence of a magnetic field in order to prevent deterioration of communication performance of an antenna mounted on a data carrier, a reader / writer, and the like. Even when the content of the metal oxide particles is large and the thickness is thin, it has excellent flexibility, and can be used for small electronic devices such as data carriers and reader / writers. Since the synthetic resin sheets are laminated, the metal oxide particles are uniformly present in the sheet and uniformly present, providing stable and high magnetic properties, and a metal shelf or wall behind the data carrier, etc. Even when there is an object that affects electromagnetic waves, such as reinforcing bars and electrolytes, it is placed on the back of the antenna to shield the influence of electromagnetic waves from the object and prevent deterioration of communication performance It is possible to provide a magnetic sheet that can Rukoto.

  The present invention also relates to a method for manufacturing a magnetic sheet for shielding the influence of a magnetic field in order to prevent deterioration in communication performance of an antenna mounted on a data carrier, a reader / writer, and the like. It is possible to provide a method for producing a magnetic sheet, which can easily obtain a magnetic sheet having flexibility and stable high magnetic properties.

Sectional drawing of the principal part of the magnetic sheet in this Embodiment 1. FIG. Assembly diagram of data carrier Cross section of the data carrier

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic sheet 2 Synthetic resin sheet 3 Metal oxide particle 4 Synthetic resin 10 Data carrier 11 Front side casing 12 Antenna 12a Antenna board 12b Antenna pattern 13 Circuit 14 Magnetic sheet 15 Spacer 16 Metal plate 17 Back side casing

Claims (6)

A magnetic sheet for shielding the influence of a magnetic field, wherein the magnetic sheet is formed by laminating a plurality of synthetic resin sheets including a plurality of metal oxide particles. 2. The magnetic sheet according to claim 1, wherein the content of the metal oxide particles in the synthetic resin sheet is 30 wt% to 98 wt%, preferably 86 wt% to 97 wt%. 3. The magnetic sheet according to claim 1, wherein an average particle diameter of the metal oxide particles is 1 μm to 200 μm, preferably 30 μm to 70 μm. The magnetic sheet according to any one of claims 1 to 3, wherein the synthetic resin sheet has a thickness of 5 µm to 1000 µm, preferably 80 µm to 150 µm. A method of manufacturing a magnetic sheet for shielding the influence of a magnetic field,
A slurrying step of kneading a synthetic resin, a solvent of the synthetic resin and metal oxide particles into a slurry;
An application step of applying the slurry obtained in the slurrying step onto a support;
A drying step of drying the applied slurry;
A peeling step of peeling the synthetic resin sheet obtained by drying from the support;
A laminating step of laminating the plurality of peeled synthetic resin sheets by pressure bonding or thermocompression bonding;
A method for producing a magnetic sheet, comprising: The method for producing a magnetic sheet according to claim 5, wherein a coupling material is added to the slurry in the slurrying step.

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