JP2010260239A - Uniform characteristic ferrite plate and manufacturing method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a uniform characteristic ferrite plate obtained by successively laminating a ferrite, a self-adhering layer and a plastic film, with a uniform inductance across the entire area. <P>SOLUTION: The laminate obtained by laminating a plate-like sintered ferrite, a double-side self-adhering tape and a PET film, is sandwiched between two pieces of rubber sheet, on both sides in the lamination direction, and rolled horizontally (direction along the plane) by allowing the laminate to pass through the clearance formed by a biaxial roll. Before and after the rolling process, the inductance is measured at the positions A and E of both ends of the laminate, the position C of the center of the laminate, etc. Compared with the inductance (A) before the rolling process, the inductance (B) after the rolling process shows that the inductance at the position C of the center etc. is lowered down to the level in the neighborhood of the inductance at the positions A and E, etc. of both ends of the laminate. Thus, the inductance is equalized over the entire area. Also, the density is reduced by 0.9%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ferrite plate formed by sequentially laminating a ferrite sintered in a plate shape, an adhesive layer, and a plastic film, and more specifically, a characteristic uniformizing ferrite plate having uniform inductance over the entire surface thereof and It relates to the manufacturing method.

  Conventionally, it has been proposed to improve the communication performance of an antenna by disposing a plate including a magnetic material such as ferrite between an RFID antenna or the like and a conductive material such as a housing. In addition, if the ferrite breaks and the powder is scattered, it adversely affects the surrounding electrical circuit. Accordingly, it has been proposed to sequentially laminate a low-viscosity resin layer and a high-viscosity resin layer on one side of a plate-like ferrite to suppress the scattering of ferrite powder (see, for example, Patent Document 1). .

  Further, in Patent Document 1, the ferrite is crushed by laminating a double-sided adhesive tape on the other surface of the ferrite, or by passing a roller through a laminate of ferrite and the double-sided adhesive tape. It has also been proposed to improve flexibility.

JP 2007-123575 A

  However, in Patent Document 1 described above, no consideration is given to uniformizing magnetic characteristics such as inductance over the entire surface of the plate. In general, in the plate-like ferrite, the inductance of the peripheral portion is extremely reduced as compared with the central portion. For this reason, the antenna cannot be provided to the very periphery of the ferrite, which has hindered the miniaturization of the antenna.

  Therefore, the present invention has been made for the purpose of providing a ferrite plate formed by sequentially laminating ferrite, an adhesive layer, and a plastic film, and a uniform ferrite plate having uniformed inductance over the entire surface thereof. .

  In order to achieve the above object, the present invention provides a characteristic uniformizing ferrite plate obtained by sequentially laminating a ferrite sintered in a plate shape, an adhesive layer, and a plastic film, the ferrite and the adhesive layer. And the plastic film are sequentially laminated and rolled to adjust the inductance at the center to a value sandwiched between the inductances at both ends.

  The applicant of the present application experimentally performed various treatments on a ferrite plate formed by sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film. As a result, by rolling after sequentially laminating the ferrite, the adhesive layer, and the plastic film, if the rolling conditions are appropriately set, the density of the ferrite is reduced, and the inductance at the center is reduced at both ends. It was discovered that the value can be adjusted between each inductance. The cause of this is still unclear, but there is a gap between the ferrite cracked by rolling, and the inductance of the other part approaches the inductance that the ferrite sintered in the plate shape had at the periphery. It seems to be because.

  In the characteristic uniform ferrite plate of the present invention, the inductance at the center is adjusted to a value sandwiched between the inductances at both ends by performing the rolling. Therefore, the characteristically uniformed ferrite plate of the present invention has a uniform inductance over the entire surface.

  Further, the present invention is a characteristic uniformizing ferrite plate obtained by sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film, the ferrite, the adhesive layer, and the plastic film. The density of the ferrite may be reduced by 0.9 to 20% as compared with that before rolling by performing rolling after sequentially laminating.

  The applicant of the present application experimentally performed various treatments on a ferrite plate formed by sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film. As a result, if the rolling conditions are appropriately set by rolling after sequentially laminating the ferrite, the adhesive layer and the plastic film, the density of the ferrite is reduced by 0.9 to 20% compared to before rolling. Then, it has been found that the inductance can be made uniform well over the entire surface of the ferrite plate. The cause of this is still unclear, but there is a gap between the ferrites cracked by rolling, and the inductance of the other part approaches the inductance of the ferrite sintered in the plate shape at the periphery. It seems to be because.

  In the property uniformized ferrite plate of the present invention, the density of ferrite is reduced by 0.9 to 20% by performing the above rolling as compared to before rolling. Therefore, the characteristically uniformed ferrite plate of the present invention also has a uniform inductance over the entire surface. If the decrease in density is less than 0.9%, the inductance may not be sufficiently uniformed. If the decrease in density exceeds 20%, so-called ferrite powder is mixed into the resin as a filler. There is a possibility that the inductance will be as low as that of the magnetic sheet.

  Still further, the present invention is a property uniformizing ferrite plate obtained by sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film, the ferrite, the adhesive layer, and the plastic film, May be characterized in that the inductance is made uniform over the entire surface by rolling after sequentially laminating.

  The applicant of the present application experimentally performed various treatments on a ferrite plate formed by sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film. As a result, it was discovered that by rolling after laminating the ferrite, the adhesive layer and the plastic film in order, the inductance can be uniformly uniform over the entire surface of the ferrite plate by appropriately setting the rolling conditions. did. The cause of this is still unclear, but there is a gap between the ferrite cracked by rolling, and the inductance of the other part approaches the inductance that the ferrite sintered in the plate shape had at the periphery. It seems to be because.

  In the characteristic uniform ferrite plate of the present invention, the inductance is made uniform over the entire surface by performing the rolling. Therefore, the characteristically uniformed ferrite plate of the present invention has a uniform inductance over the entire surface. Here, the term “uniform” does not mean that the values are completely the same, and for example, variations in values that fall within the range of measurement error are allowed.

  In addition, the method of manufacturing the characteristic uniformed ferrite plate of the present invention is to laminate the ferrite sintered in a plate shape, the adhesive layer, and the plastic film in order, and then perform rolling to reduce the inductance of the central portion. It is characterized by adjusting to a value sandwiched between the inductances at both ends.

  The applicant of the present application experimentally performed various treatments on a ferrite plate formed by sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film. As a result, by rolling after sequentially laminating the ferrite, the adhesive layer, and the plastic film, if the rolling conditions are appropriately set, the density of the ferrite is reduced, and the inductance at the center is reduced at both ends. It was discovered that the value can be adjusted between each inductance. The cause of this is still unclear, but there is a gap between the ferrite cracked by rolling, and the inductance of the other part approaches the inductance that the ferrite sintered in the plate shape had at the periphery. It seems to be because.

  In the method for producing a characteristic uniform ferrite plate according to the present invention, the inductance at the center is adjusted to a value sandwiched between the inductances at both ends by performing the rolling. Therefore, in the method for producing a characteristic uniform ferrite plate of the present invention, a characteristic uniform ferrite plate having uniform inductance over the entire surface can be produced satisfactorily.

  In addition, the method for producing the characteristic uniform ferrite plate according to the present invention includes a method in which the ferrite density is increased by sequentially laminating a plate-sintered ferrite, an adhesive layer, and a plastic film, followed by rolling. It may be characterized by being reduced by 0.9 to 20% compared to before rolling.

  The applicant of the present application experimentally performed various treatments on a ferrite plate formed by sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film. As a result, if the rolling conditions are appropriately set by rolling after sequentially laminating the ferrite, the adhesive layer and the plastic film, the density of the ferrite is reduced by 0.9 to 20% compared to before rolling. Then, it has been found that the inductance can be made uniform well over the entire surface of the ferrite plate. The cause of this is still unclear, but there is a gap between the ferrite cracked by rolling, and the inductance of the other part approaches the inductance that the ferrite sintered in the plate shape had at the periphery. It seems to be because.

  In the method for producing a uniform ferrite sheet according to the present invention, the density of ferrite is reduced by 0.9 to 20% compared to before rolling by performing the above rolling. Therefore, in the method for producing a characteristic uniform ferrite plate of the present invention, a characteristic uniform ferrite plate having uniform inductance over the entire surface can be produced satisfactorily. If the decrease in density is less than 0.9%, the inductance may not be sufficiently uniformed. If the decrease in density exceeds 20%, so-called ferrite powder is mixed into the resin as a filler. There is a possibility that the inductance will be as low as that of the magnetic sheet.

In addition, the method for producing a characteristic uniform ferrite plate of the present invention is a method in which the ferrite is sintered in a plate shape, the adhesive layer, and the plastic film are sequentially laminated, and then rolled to perform the inductance over the entire surface. And uniform.
It may be a thing.

  The applicant of the present application experimentally performed various treatments on a ferrite plate formed by sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film. As a result, it was discovered that by rolling after laminating the ferrite, the adhesive layer and the plastic film in order, the inductance can be uniformly uniform over the entire surface of the ferrite plate by appropriately setting the rolling conditions. did. The cause of this is still unclear, but there is a gap between the ferrites cracked by rolling, and the inductance of the other part approaches the inductance of the ferrite sintered in the plate shape at the periphery. It seems to be because.

  In the method for producing a uniform ferrite plate according to the present invention, the inductance is made uniform over the entire surface by performing the rolling. Therefore, in the method for producing a characteristic uniform ferrite plate of the present invention, a characteristic uniform ferrite plate having uniform inductance over the entire surface can be produced satisfactorily. Here, the term “uniform” does not mean that the values are completely the same, and for example, variations in values that fall within the range of measurement error are allowed.

  Further, in the method for producing a characteristic uniformed ferrite plate according to any one of the above, a laminate in which the ferrite, the adhesive layer, and the plastic film are sequentially laminated is sandwiched between two rubber sheets from both sides in the lamination direction. And you may perform the said rolling with a roll.

  In order for the plate-like ferrite to crack and form a gap as described above by rolling, it is preferable to apply stress to the plate-like ferrite in a direction spreading along the surface. When the ferrite, the adhesive layer, and the plastic film are sequentially laminated, sandwiched between two rubber sheets from both sides in the laminating direction and then rolled by a roll, the rubber sheet will spread in the direction along the surface. Therefore, stress is also applied to the ferrite in a direction spreading along the surface. Therefore, when rolling with a roll sandwiched between rubber sheets as described above, the ferrite can be further reduced in density and the inductance thereof can be evenly uniformed over the entire surface.

  In this case, the two rubber sheets may have different tackiness. In that case, there is a difference between the stress applied to the ferrite side along the surface and the stress applied to the plastic film side along the surface. For this reason, since it becomes easier to break a ferrite and it becomes easy to make a clearance gap, the density of a ferrite can be further reduced and the inductance can be made more uniform over the entire surface.

It is sectional drawing which represents typically the structure and manufacturing method of the characteristic uniformization ferrite plate to which this invention was applied. It is explanatory drawing showing the measuring method of the characteristic of the characteristic uniformization ferrite plate. It is a graph showing the change of the said characteristic before and behind a rolling process. It is explanatory drawing showing the principle of the change of the said characteristic. It is a top view showing the structure of the RFID antenna using the said characteristic uniformization ferrite plate.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a cross-sectional view schematically showing a configuration of a characteristic uniformizing ferrite plate 10 to which the present invention is applied. As shown in FIG. 1A, the characteristic uniforming ferrite plate 10 of this embodiment is a single-sided plate-like ferrite 11 made of a sintered body of soft magnetic ferrite (for example, Ni—Zn ferrite). Further, a double-sided adhesive tape 12 as an example of an adhesive layer and a PET film 13 as an example of a plastic film are sequentially laminated, and a double-sided adhesive tape 15 is laminated on the other surface of the ferrite 11. In addition, in each figure attached to this application, each part is expanded and drawn in the thickness direction for convenience of explanation.

  In addition, the ferrite 11 is cracked by the following processing to form a gap. That is, as shown in FIG. 1 (B), after sandwiching a laminate 14 in which the ferrite 11, the double-sided adhesive tape 12 and the PET film 13 are sequentially laminated with two rubber sheets 17 from both sides in the lamination direction, By performing the rolling process with a roll, the ferrite 11 is cracked and has a gap. For this reason, the density of the ferrite 11 is reduced, and the inductance is made uniform over the entire surface.

  Hereinafter, the effect of this rolling process will be described based on specific examples. In this example, first, a ferrite 11 having a thickness of 0.3 mm sintered in a plate shape (N-Zn soft ferrite was used but other ferrites may be used) and a thickness based on an acrylic resin as a base material. A laminate 14 was obtained by laminating a 0.035 mm double-sided adhesive tape 12 and a 0.05 mm thick PET film 13. The planar shapes of the ferrite 11, the double-sided adhesive tape 12, and the PET film 13 were all 22 × 14 mm rectangles.

  This laminated body 14 is sandwiched between two rubber sheets 17 having a thickness of 3 mm (made of acrylic rubber, but other rubber may be used) from both sides in the laminating direction, and between two biaxial rolls (not shown) having a diameter of 50 mm And rolled in the horizontal direction (direction along the surface). The roll interval was 80% or less (5 mm in this example) with respect to the total thickness of the laminate 14 and the rubber sheet 17. Moreover, this rolling process was performed by passing the roll 5 times in each of the vertical direction and the horizontal direction in the rectangular planar shape. A 0.03 mm thick double-sided pressure-sensitive adhesive tape 15 is attached to the surface of the ferrite 11 after the rolling process where the double-sided pressure-sensitive adhesive tape 12 and the PET film 13 are not laminated, thereby obtaining a uniform characteristic ferrite plate 10. It was.

  Then, the change of the characteristic of the ferrite 11 by the said rolling process was measured as follows. That is, before and after the rolling process, the electric wire 51 was disposed at a position indicated by any of A to E in FIG. 2 of the laminate 14, and the inductance around the electric wire 51 when measured at each position was measured. . FIG. 2 is a view of the laminate 14 as viewed from a direction parallel to the short side (that is, the side of 14 mm). Further, for measuring the inductance, “E4991A” (trade name: manufactured by Agilent Technologies) was used as a measuring instrument.

  Table 1 shows the inductance (nH) of the laminate 14 before the rolling treatment, and Table 2 shows the inductance (nH) of the laminate 14 after the rolling treatment. Table 3 shows the inductance (nH) of a so-called magnetic sheet in which ferrite powder is mixed as a filler in a resin. This resin sheet is obtained by mixing 90 wt% of ferrite powder obtained by pulverizing the same ferrite as in the present example into chlorinated polyethylene resin, kneading with a kneader, pulverizing, and then forming a sheet using a roll. . The size of this sheet was also the same as that of the laminate 14.

  Also, the data of Tables 1, 2, and 3 written in graphs are (A), (B), and (C) in FIG. As shown in each table and FIG. 3, the laminate 14 before the rolling process had the highest inductance at the center position C and the like, and the inductance decreased at the positions A and E at both ends.

  On the other hand, in the laminated body 14 after the rolling process, the inductance at the position C or the like in the central portion decreases to the vicinity of the inductance at the positions A and E or the like at both ends, and the inductance is uniform throughout the positions A to E. It became. For this reason, the inductance at the position C at the center is a value sandwiched between the inductances at the positions A and E at both ends. Further, in the above inductance measuring method, an error due to the measuring instrument accuracy and the reproducibility of the mounting position of the electric wire 51 is about ± 2%. For this reason, it can be considered that the inductance variation in the laminated body 14 after the rolling process is substantially uniform over the entire surface of the laminated body 14 within the range of the measurement error. Moreover, although the inductance was uniform in the said magnetic sheet, in any position AE, it did not greatly reach the inductance of the laminated body 14 before and behind a rolling process.

  Furthermore, the density of the ferrite 11 after the rolling treatment was reduced by 0.9% compared to the density of the ferrite 11 before the rolling treatment. The density of the magnetic sheet was 23.7% smaller than the density of the ferrite 11 before the rolling treatment. The density before and after the rolling process is a value converted from the weight measured for the laminate 14 to the density of the ferrite 11 alone.

  Thus, in this example, by reducing the density of the ferrite 11 by a rolling process by 0.9%, the inductance at the position C in the central portion is set as a value sandwiched between the inductances at the positions A and E at both ends. The inductance could be made uniform over the entire surface. As described below, the decrease in density is considered to contribute greatly to the uniformization of inductance, and even if the density is decreased by 0.9% or more, it is considered that the effect of the above equalization is produced. If the decrease of 20% exceeds 20%, it is considered that the inductance becomes as low as that of the magnetic sheet.

  The reason why the inductance of the ferrite 11 is made uniform by the rolling process is still unclear, but a gap is formed between the ferrites cracked by the rolling, and the ferrite 11 sintered in a plate shape is formed at the peripheral portion. This is probably because the inductance of the other part approaches the inductance.

  That is, as shown in FIG. 4A, when the electric wire 51 is disposed on one side of the plate-like ferrite 11, the magnetic flux φ (Wb) inside the ferrite 11 is expressed by the equation φ = Fm / (Rmc + Rma). It is represented by

  However, Rmc is the magnetic resistance (AT / Wb) of the ferrite 11, and is expressed as Rmc = Lc / μcSc, where Lc, μc, and Sc are the magnetic path length, permeability, and cross-sectional area of the magnetic path in the ferrite 11. . Rma is a magnetic resistance (AT / Wb) in the air, and is expressed as Rma = La / μaSa, where La, μa, and Sa are the magnetic path length, permeability, and magnetic path cross-sectional area in the air. Note that μc is several hundred times μa, and the magnetic path length La increases when the gap S of the ferrite 11 increases from the state indicated by A in FIG. 4A to the state indicated by A ′. As shown in 4 (B), it decreases in inverse proportion. On the other hand, since the magnetic path length La in the air was originally large as shown at B in FIG. 4A at the end of the ferrite 11, the magnetic flux φ does not decrease so much even if the gap S widens as shown at B ′. . Note that FIG. 4B shows the values of the magnetic flux φ corresponding to the states A, A ′, B, and B ′ in FIG.

  For this reason, when the rolling process is performed as described above, the inductance at the center position C and the like approaches the inductances at the positions A and E at both ends, and the inductance is uniformized over the entire surface of the ferrite 11. Conceivable. Note that the adhesive of the double-sided pressure-sensitive adhesive tape 12 may enter the gap S of the ferrite 11, but the permeability of the adhesive is extremely small compared to the permeability of the ferrite 11 as well as the permeability in air. Therefore, the same consideration as described above is possible.

  As described above, in this example, the inductance of the characteristic uniformizing ferrite plate 10 can be uniformly uniform over the entire surface. Further, the surface of the rubber sheet 17 has tackiness (slight adhesion) and tends to spread in the direction along the surface of the laminate 14 during the rolling process. For this reason, a force along the above-described surface is applied to the ferrite 11 and the ferrite 11 is more easily broken and a gap is also easily formed. Therefore, the ferrite 11 is further reduced in density and its inductance is further improved over the entire surface. Can be made uniform.

  For this reason, when the characteristic uniformizing ferrite plate 10 of the present embodiment is applied to improve the communication performance of the RFID antenna 1, for example, as shown in FIG. Up to ten margins can be provided. Therefore, the downsizing of the RFID antenna 1 can be favorably promoted. An IC chip (not shown) is disposed at the center portion 21 of the antenna pattern 20. By arranging the characteristic uniforming ferrite plate 10 of the present embodiment between the antenna pattern 20 and another conductive material (not shown) (not shown), the communication distance of the RFID antenna 1 is ensured satisfactorily. be able to. Such a configuration can be applied to the RFID antenna 1 for the UHF band (950 MHz band) and the 2.4 GHz band, for example.

  In addition, this invention is not limited to the said embodiment at all, It can implement with a various form in the range which does not deviate from the summary of this invention. For example, if the tackiness of the two rubber sheets 17 is made different, a difference is generated between the PET film 13 side and the ferrite 11 side in the force applied in the direction along the surface during the rolling process. For this reason, since the ferrite 11 becomes easier to crack and a gap becomes easier, the density of the ferrite 11 can be further reduced and the inductance thereof can be made more uniform over the entire surface. Further, by using urethane or an elastomer material instead of the PET film 13, the movement may be accelerated by rolling.

  Further, workability is improved by rolling using a roll whose surface is coated with rubber. Furthermore, if the temperature is applied to the roll, the number of rolling operations can be reduced. In this case, it is more efficient if a heat conductive material is mixed as a filler in the rubber coating the roll. Also, if the rolls are provided with fine irregularities, the irregularities intrude into the ferrite 11, which makes the ferrite 11 more easily cracked and more easily formed. Therefore, the density of the ferrite 11 is further reduced and the inductance is further increased. It can be made uniform over the entire surface. Furthermore, rolling methods other than rolls are also applicable. However, when the conditions are set such that the density of the ferrite 11 is increased by rolling, the above-described effects may not be obtained.

DESCRIPTION OF SYMBOLS 1 ... RFID antenna 10 ... Characteristic equalization ferrite plate 11 ... Ferrite 12, 15 ... Double-sided adhesive tape 13 ... PET film 14 ... Laminate 17 ... Rubber sheet 20 ... Antenna pattern

Claims (8)

A ferrite plate sintered in a plate shape, a pressure-sensitive adhesive layer, and a plastic film and a uniform characteristic ferrite plate,
The characteristic uniformed ferrite plate characterized by adjusting the inductance of the central part to a value sandwiched between the inductances of both ends by rolling after sequentially laminating the ferrite, the adhesive layer and the plastic film . A ferrite plate sintered in a plate shape, a pressure-sensitive adhesive layer, and a plastic film and a uniform characteristic ferrite plate,
Uniform characteristics characterized by reducing the density of the ferrite by 0.9-20% compared to before rolling by rolling after sequentially laminating the ferrite, the adhesive layer and the plastic film. Ferrite plate. A ferrite plate sintered in a plate shape, a pressure-sensitive adhesive layer, and a plastic film and a uniform characteristic ferrite plate,
A characteristic uniformed ferrite plate, wherein the inductance is made uniform over the entire surface by rolling after sequentially laminating the ferrite, the adhesive layer and the plastic film.   It is characterized by adjusting the inductance of the central part to a value sandwiched between the inductances of both ends by performing rolling after sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film. A method for producing a characteristically uniformed ferrite plate.   It is possible to reduce the density of the ferrite by 0.9 to 20% compared to before rolling by performing rolling after sequentially laminating ferrite sintered in a plate shape, an adhesive layer, and a plastic film. A method for producing a characteristically uniform ferrite plate.   A ferrite plate sintered in a plate shape, an adhesive layer, and a plastic film are sequentially laminated and then rolled to make the inductance uniform over the entire surface. Production method.   7. The rolling is carried out by a roll after sandwiching a laminate of the ferrite, the adhesive layer and the plastic film sequentially from two sides in the laminating direction with two rubber sheets. A method for producing a characteristically uniformed ferrite plate according to any one of the above.   The method for producing a uniform ferrite sheet according to claim 7, wherein the two rubber sheets have different tackiness.