JP2005216518A - High-dielectric-constant dielectric material and antenna using the dielectric material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric material with a high dielectric constant and with high dimensional accuracy allowing easy manufacture, processing and handling, and to provide an antenna using the dielectric material for an RFID tag or reader/writer which operates in an UHF or SHF band. <P>SOLUTION: Titanium oxide, strontium carbonate, etc. are mixed, granulated and roasted. The resulting material is crushed by using a hammer mill, a roller mill or the like, and then ground by using a ball mill, a vibrating mill, an attritor or the like, or ground by using an organic solvent to obtain a ferromagnetic ceramic powder having a predetermined particle diameter. The ferromagnetic ceramic powder is then mixed with a plastic, e.g., a thermoplastic resin such as nylon, polyethylene, polypropylene, polycarbonate, vinyl chloride resin, methacrylic resin, polystylene, ABS resin, acetal resin and fluororesin, or a thermosetting resin such as phenolic resin, urea resin and alkyd resin, or rubber at a predetermined ratio, and the resulting material is molded by a method such as extrusion, rolling, injection molding, and compression molding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high dielectric constant dielectric, and more particularly to a high dielectric constant dielectric suitable for use in an RFID tag or RFID reader / writer antenna operating in the UHF or SHF band, and an antenna using the dielectric.

  In recent years, RFID systems that perform data communication between a tag including an IC chip and a reader, writer, or reader / writer (hereinafter collectively referred to as a reader / writer) have become widespread. Since this RFID system communicates data using the antennas provided to each of the tag and the reader / writer, it can communicate even when the tag is separated from the reader / writer, and it is resistant to dirt, etc. It has come to be used for various purposes such as factory production management, logistics management, and entrance / exit management.

  In the RFID system, the communicable distance differs depending on the frequency band to be used. For example, in the short wave band of about 13.56 MHz, the communication distance is several centimeters to several tens of centimeters. When this system is used for entrance / exit management or the like, the tag is used close to the reader / writer. However, a longer communication distance is more advantageous for applications such as logistics management. Therefore, in such an application, a higher frequency band such as a UHF band or an SHF band is used.

  As a tag antenna, a loop antenna is usually used in a short wave band, but in a frequency band such as a UHF band or an SHF band, a dipole antenna (for example, JP-A-2003-249820) or one surface of a substrate is used. A microstrip line type antenna or the like in which a microstrip conductor is formed on the surface and a back surface grounding conductor is formed on the surface on the article side is used.

JP 2003-249820 A (page 4-8, FIG. 1)

  The size of the antenna used in the frequency band such as the UHF band or the SHF band needs to be 1 / integer of an even number of wavelengths, for example, 1/2 times the length. In addition, inside the dielectric, the wavelength of the radio wave is inversely proportional to the square root of the dielectric constant. For this reason, when a material having a high dielectric constant is used, the size of the antenna can be reduced.

  Here, as a material having a high dielectric constant, there are sintered ceramics such as titanium oxide, calcium titanate, strontium titanate, and strontium zirconate. These ceramic materials have good dielectric properties, but sintered bodies have poor dimensional accuracy, and grinding to increase dimensional accuracy increases the manufacturing cost of the dielectric, which requires RFID to be reduced in price. This is a major drawback in the system. In addition, the RFID system tag and the reader / writer antenna are preferably thin because they are used by being attached to the surface of an article or the casing of an electronic circuit. Therefore, it is required that the dielectric is also thin. Since it is fragile, if it is made thin, it may come into contact with other articles during the assembly process or use of the antenna and crack.

  On the other hand, plastic can also be used as a dielectric, and plastic can be manufactured with high dimensional accuracy by injection or the like. Also, since it is flexible, it has the advantage of being hard to crack even if thin, but the dielectric constant is low Therefore, loss cannot be suppressed. Organic ferroelectrics such as PVDF (polyvinylidene fluoride), P (VDF / TrEE (ethylene fluoride)), and P (VDCN (vinylidene cyanide) / Vac. (Vinyl acetate)) are cracked even if they are thin. Although it has the advantage that it is difficult, since it contains fluorine, cyan group, etc., there is a problem that toxic gas is generated when it is burned, and the dielectric constant is not so high.

  Such problems are not limited to dielectrics used in RFID tags and reader / writer antennas, but also occur in dielectrics used in other high-frequency antennas, with high dimensional accuracy, manufacturing, processing, and handling. Therefore, there is a demand for a high dielectric constant dielectric material that can be easily processed.

  The present invention has been made in view of the above problems, and its main object is to provide a high dielectric constant, particularly a UHF band or SHF, which has high dimensional accuracy and is easy to manufacture, process and handle. An object of the present invention is to provide a high dielectric constant dielectric suitable for use in an RFID tag or reader / writer antenna operating in a band, and an antenna using the dielectric.

  In order to achieve the above object, the dielectric of the present invention comprises a composite material formed using at least a ferroelectric ceramic powder and plastic or rubber.

  In the present invention, the content of the ferroelectric ceramic powder is preferably about 70% or less by volume ratio.

In the present invention, the ferroelectric ceramic powder is formed by dry pulverization, and the maximum particle size of the powder is approximately 100 μm or less, or formed by wet pulverization using an organic solvent. Preferably, the particle size of the powder is approximately 0.1 μm to 10 μm or chemically generated TiO ₂ , and the particle size of the powder is approximately 0.1 μm to 10 μm.

  The RFID tag or RFID reader / writer antenna operable in the UHF band or SHF band according to the present invention comprises the dielectric and an antenna pattern disposed on the dielectric surface. .

  The RFID tag or RFID reader / writer antenna operable in the UHF band or the SHF band of the present invention includes the dielectric, an antenna pattern disposed on the dielectric surface, and the dielectric surface. It is comprised with the conductor arrange | positioned in the position facing an antenna pattern.

  In this invention, it can be set as the structure by which the magnetic body is inserted between the said dielectric material and the said conductor, or between the said antenna pattern and the said dielectric material.

  In the present invention, a second dielectric may be disposed on the dielectric so as to cover the antenna pattern.

  As described above, in the present invention, the dielectric is formed by using a composite material in which at least a ferromagnetic ceramic powder having a predetermined particle diameter and plastic are mixed at a predetermined ratio, so that the dielectric constant of the dielectric is increased. In addition, the dimensional accuracy can be increased, manufacturing and processing can be facilitated, and even if it is thinned, it is difficult to break. By using the dielectric for an RFID tag or a reader / writer antenna, an antenna having a desired performance can be manufactured with a small size.

  As described above, the dielectric body of the present invention and the antenna including the dielectric body have the following effects.

  The first effect of the present invention is that the dielectric constant of the dielectric can be increased, the dimensional accuracy can be increased, the manufacturing and processing can be facilitated, and even if it is thinned, it is difficult to break. It can be done.

  The reason is that a ceramic sintered body, plastic, or organic ferroelectric material is not used as the dielectric, but at least a ferromagnetic ceramic powder having a predetermined particle diameter formed by dry or wet and plastic or rubber. This is because a composite material formed by mixing at a predetermined ratio is used.

  The second effect of the present invention is that the size of the antenna of the RFID tag or reader / writer operating in the UHF band or the SHF band can be reduced.

  The reason is that loss can be reduced by using the composite material as a substrate for an RFID system tag, reader, or reader / writer antenna.

  As shown in the prior art, there is a ceramic sintered body as a ferroelectric material. However, ceramics have poor dimensional accuracy, and the cost increases when processed by grinding to increase the dimensional accuracy. In addition, when a dielectric is used for an RFID system tag or a reader / writer antenna, it is required to be thin. However, since ceramics are brittle, there is a problem that thinning tends to cause damage during assembly and use. In addition, plastic has high dimensional accuracy and high flexibility, so it is difficult to break, but the dielectric constant cannot be increased. Further, the organic ferroelectric material is difficult to crack even if it is thin, but there is a problem that when it is burned, a toxic gas is generated and the dielectric constant cannot be increased so much.

  Therefore, in the present invention, a composite material of ferromagnetic ceramic powder and plastic or rubber is used in order to eliminate the disadvantages of the conventional dielectric. That is, the ceramic powder and plastic or rubber are kneaded, extruded, rolled, injection molded, compression molded, applied, etc. By using such a material, the dielectric constant can be increased, the dimensional accuracy can be increased, and the manufacturing and processing can be facilitated.

  In the above composite material, the higher the ceramic powder content, the greater the dielectric constant. However, when the content exceeds 70%, plasticity is lost, and kneading, extrusion, rolling, injection molding, etc. become impossible, and the fluidity is lost. Can not. Also in the case of compression molding, if a material exceeding 70 v% is compression molded, voids remain, and ceramic cannot obtain a material exceeding 70 v% of the volume including the voids. Therefore, the content of the ceramic powder is 70 v% or less, preferably 60 v% to 65 v% in consideration of process variation. In addition, since the flexibility deteriorates when the content of ceramics increases, the content of ceramics is appropriately reduced in the case of bending and using. Also,

  This ceramic powder is made by mixing titanium oxide and strontium carbonate, etc., granulating and roasting the material using a hammer mill, roller mill, etc., and then dry pulverizing using a ball mill, vibration mill, attritor, etc. Can be manufactured. When the ceramic particle size is large, jigs such as kneading and extruding are worn, and when the dielectric is thin, the characteristics become non-uniform. Therefore, the maximum particle size is desired to be 100 μm or less.

  In order to obtain a finer powder, wet pulverization in a liquid can be used. In wet pulverization, water that is inexpensive, toxic, and does not pose a risk of ignition is usually used as a liquid. However, when a material containing alkaline earth metal with good dielectric properties is used, some of the alkaline earth metal ions are used. Dissolve in water. Here, in a normal method for manufacturing a ceramic ferroelectric, ceramic powder suspended in water is heated and dried, but the dried powder contains alkaline earth metal dissolved in water. Because it is recombined, there is no support. However, when the powder in this state is used as a raw material for the composite material, the characteristics are not good because a part of the alkaline earth metal is separated. In order to prevent this, it is preferable to grind using an organic solvent that does not dissolve alkaline earth metal ions as a liquid. As this organic solvent, alcohol, acetone, benzene, liquid paraffin, chlorofluorocarbon, etc. can be used, and fine powder can be obtained by evaporating and removing the organic solvent by heating after pulverization.

In addition, since TiO ₂ is a fine powder produced chemically, it may be used as it is as a ceramic powder. As a method of chemically generating TiO ₂ , there are a method of heating and dehydrating a hydroxide obtained by hydrolyzing sulfate, a method of thermally decomposing TiCl ₄ and the like.

  On the other hand, as thermoplastics, thermosetting such as nylon, polyethylene, polypropylene, polycarbonate, vinyl chloride resin, methacrylic resin, polystyrene, ABS resin, acetal resin, fluorine resin, phenol resin, urea resin, alkyd resin, etc. Resin or the like can be used. The higher the dielectric constant resin is used, the higher the dielectric constant of the composite material. However, the plastic to be used may be set in consideration of the working environment such as workability and temperature, and necessary mechanical characteristics.

  The plastic and ceramic powder may be mixed by heating and kneading with a kneader to form pellets, or by dissolving plastic or its monomer in a solvent and immersing the ceramic powder, followed by drying with stirring. When pulverization is performed in an organic solvent, the plastic may be melted in the organic solvent during or after pulverization and then dried. And the material which mixed ceramic powder and the plastic is shape | molded by the normal plastic shaping | molding methods, such as extrusion, injection, rolling, compression, and casting. In the case of coating, a paint is prepared by suspending ceramic powder in an organic solvent in which plastic is dissolved. This paint is applied to a conductive material placed in contact with a metal body and dried. Alternatively, a copper foil in which an antenna element is bonded to a plastic film is formed by etching, and the plastic film is applied and dried.

  The dielectric manufactured in this way can be a flexible and thin member having a high dielectric constant. Therefore, when this dielectric is used, it operates in the UHF band or the SHF band, and is a metal article. A thin RFID tag or reader / writer antenna that can be used in close contact with the antenna can be manufactured. The materials and manufacturing methods described above are examples, and other materials and manufacturing methods can be used as long as a dielectric having a desired dielectric constant can be manufactured.

  In order to describe the above-described embodiment of the present invention in more detail, a high dielectric constant dielectric and an antenna using the dielectric according to an embodiment of the present invention will be described with reference to FIGS. . FIG. 1 is a diagram schematically illustrating a general configuration of an RFID system, and FIGS. 2 to 9 are diagrams schematically illustrating a configuration of an antenna according to the present embodiment. FIG. 10 is a diagram showing the structure of an antenna manufactured for explaining the effect of the present embodiment. In the following description, the dielectric of the present invention is applied to a tag antenna. However, the present invention is not limited to the following embodiments, and the dielectric of the present invention is applied to a reader / writer antenna. May be.

  As shown in FIG. 1, the RFID system 1 according to the present embodiment includes a tag 2 and a reader / writer (or reader) 6 that perform data communication using a frequency band such as a UHF band or an SHF band. Includes an antenna 3 and a capacitor 4 (which are not necessarily required when the IC chip 5 has a built-in capacitor) and an IC chip 5 for storing information, and a reader / writer (or reader). 6 includes a reader / writer antenna 7 that communicates with the antenna 3 of the tag 2, and a control unit 8 such as a communication circuit 8a for converting a transmission / reception signal and an arithmetic processing circuit 8b for decoding the transmission / reception signal. The tag 2 is driven using a built-in power source or a power source supplied from the reader / writer 6. Data communication is performed by matching the resonance frequency of the tag 2 and the reader / writer antenna 7 with the carrier frequency.

  As shown in FIG. 2, the antenna of the RFID system 1 (here, the antenna 3 for the tag 2) has a predetermined antenna pattern formed on a dielectric 10 made of a high dielectric constant composite material, which is a feature of the present invention. The antenna element 9 is arranged, and this antenna is installed on the surface of the article or the case, particularly on the article or case (metal body 11) containing a metal material.

  FIG. 2 shows a configuration in which a conductor (antenna element 9) is formed on one surface of the dielectric 10, and when the metal 11 is made of a nonmagnetic material such as aluminum, magnesium, copper alloy, etc. However, when the metal body 11 is an iron plate, the loss increases. In this case, as shown in FIG. 3, the antenna element 9 is disposed on one surface of the dielectric 10, and the conductor 12 serving as the back ground conductor is disposed on the other surface (the metal body 11 side) (micro A strip path or the like may be used. With such a configuration, the antenna can be stably operated regardless of the type of the metal material constituting the metal body 11.

  The antenna may be configured to be able to communicate data using a frequency band such as the UHF band and the SHF band, and the shape, thickness, material, fixing method, and the like of the antenna element 9 are not particularly limited. In addition, as described above, the dielectric 10 is made by mixing titanium oxide and strontium carbonate, granulating, and then crushing the roasted material using a hammer mill, a roller mill or the like, and further, a ball mill, a vibration mill, Ferromagnetic ceramics powder with a specified particle size that is manufactured by pulverization using an attritor or the like, or pulverization using an organic solvent, or chemically, nylon, polyethylene, polypropylene, polycarbonate, vinyl chloride resin, meta Plastic powder and rubber such as thermoplastic resin such as acrylic resin, polystyrene, ABS resin, acetal resin, fluorine resin, thermosetting resin such as phenol resin, urea resin, alkyd resin, etc. The content of ceramic powder is 70v% or less , Preferably kneaded so as to be 60 to 65 v% for extrusion, rolling, injection molding, compression molding, etc. Ri can be used molded. Further, the shape, film thickness, material, method of fixing the dielectric 12 and the like are not limited.

  2 and 3, the dielectric 10 is disposed only on the lower layer (article side) of the antenna element 9, but the dielectric 10 is disposed on the upper layer of the antenna element 9 as shown in FIG. Thus, the antenna element 9 may be surrounded by the dielectric 10. By setting it as such a structure, the fluctuation | variation of the antenna characteristic resulting from the member which adjoins the antenna element 9 upper part can be suppressed, and the antenna element 9 can be protected. Also in this structure, the conductor 12 may be disposed between the metal body 11 and the dielectric 10 so that the antenna characteristics are not changed by the material of the metal body 11.

  In FIGS. 2 to 5, the antenna is composed of the antenna element 9, the dielectric 10, and the conductor 12 as necessary. However, the influence of the metal 11 is further suppressed and the characteristics of the antenna are improved. Therefore, the magnetic body 13 can be provided. In that case, as shown in FIG. 6, a magnetic body 13 may be disposed between the dielectric 10 and the conductor 12, or between the antenna element 9 and the dielectric 10 as shown in FIG. The magnetic body 13 may be disposed on the surface. Even in such a structure, in order to protect the antenna element 9 and to suppress the influence of the member disposed on the upper surface, the dielectric 10 is also arranged on the upper portion of the antenna element 9 as shown in FIGS. The antenna element 9 may be provided and surrounded by the dielectric 10.

  The material and manufacturing method of the magnetic body 13 are not particularly limited, but are rapidly solidified material of amorphous alloy, permalloy, electromagnetic steel, silicon steel, sendust alloy, Fe-Al alloy or soft magnetic ferrite, cast material, rolled material, forged material. Or sintered material, amorphous foil or laminated material of amorphous foil, metal powder, carbonyl iron powder, reduced iron powder, atomized powder (pure such as iron containing pure iron, Si, Cr, Al, permalloy, Co-Fe, etc. ), Amorphous (a powder obtained by water atomizing or gas atomizing iron, cobalt, nickel alloy containing B, P, Si, etc.) or a composite material of flakes and organic matter such as plastic, rubber, or the above powder Or it can form by the coating film etc. of the coating material containing a flake. In addition, as a use of the present invention, a composite material that is flexible and hardly cracked and has little loss even at a high frequency is preferable.

  Next, in order to confirm the effect of this example, dielectric 10 was manufactured using powders A to F shown below, and experiments of Examples 1 to 29 and Comparative Examples 1 to 6 were performed. The contents and results of the experiment will be described.

Powder A: Ceramic dielectric (strontium titanate sintered body, dielectric constant 255) was roughly crushed with a hammer mill and then pulverized with a ball mill (maximum particle size: about 200 μm).
Powder B: A is further pulverized with a ball mill (maximum particle size: about 100 μm),
Powder C: B was pulverized with an attritor using water and dried by heating (particle size: about 0.1 μm to 10 μm),
Powder D: B was pulverized with acetone using acetone, heated under reduced pressure and dried (particle size: about 0.1 μm to 10 μm),
Powder E: commercially available chemically produced rutile titanium oxide (average particle size: 0.5 μm),
Powder F: Commercially produced chemically produced anatase titanium oxide (average particle size: 0.5 μm).

  First, in a sample (Comparative Example 1) in which powder A: 85 w% (50 v%) and nylon: 15 w% (50 v%) were kneaded and rolled to form a plate having a thickness of 0.5 mm, the ceramic particles were visually discriminated. Since it was possible and the distribution was uneven, it was judged that it could not be used. On the other hand, in a sample (Example 1) in which powder B: 85 w% (50 v%) and nylon: 15 w% (50 v%) were kneaded and rolled to form a plate having a thickness of 0.5 mm, the roll was slightly damaged. However, the visual observation was uniform and good. The dielectric constant measured at 900 MHz was 82, which was found to be significantly higher than the dielectric constant of nylon (3.3). From the above results, it was found that in the case of dry pulverization, a dielectric that can be used as an antenna substrate can be manufactured by reducing the particle size of the ceramic powder (approximately 100 μm or less).

  In addition, a dielectric constant at 900 MHz was measured for a sample (Comparative Example 2) in which powder C: 85 w% (50 v%) and nylon: 15 w% (50 v%) were kneaded and rolled to form a 0.5 mm thick plate. As a result, it was 6.2, which was found to be significantly deteriorated as compared with the sample of Example 1. On the other hand, in the sample (Example 2) which knead | mixed and rolled powder D: 85w% (50v%) and nylon: 15w% (50v%) and was made into the plate of thickness 0.5mm, it is a rolling roll. No flaws were observed, and the visual observation was uniform and good, and the dielectric constant at 900 MHz was measured to be 35, which was found to be significantly improved from the dielectric constant of nylon (3.3). From the above results, it was found that in the case of wet pulverization, the dielectric 10 having a higher dielectric constant can be produced by pulverizing in an organic solvent than by pulverizing in water even with the same particle size.

  Next, powder E: 85 w% (50 v%) and nylon: 15 w% (50 v%) were kneaded and rolled to obtain a 0.5 mm thick plate (Example 3-1). No flaws were observed, the visual observation was uniform and good, and the dielectric constant at 900 MHz was measured to be 22, which was found to be significantly higher than the dielectric constant 3.3 of nylon. From the above results, it was found that a dielectric having a high dielectric constant can be produced even using chemically generated rutile titanium oxide.

  Similarly, powder F: 85 w% (50 v%) and nylon 15 w% (50 v%) were kneaded and rolled to obtain a 0.5 mm thick plate (Example 3-2). No visual observation was observed, the visual observation was uniform and good, and the dielectric constant measured at 900 MHz was 21, which was found to be significantly higher than that of nylon 3.3. As a result, it was found that a dielectric having a high dielectric constant can be produced even using chemically generated anatase titanium oxide.

  Next, samples (Examples 4 to 15 and Comparative Example 3) having a thickness of 0.5 mm were prepared by changing the mixing ratio of powder D and nylon in the range of 5 v% to 75 v%, and the dielectric constant. Was measured. The results are shown in Table 1.

  According to Table 1, a sound material was obtained when the mixing ratio of the powder D was in the range of 5 v% to 70 v%. In addition, the higher the ceramic content, the harder the material and the less flexible.

  Similarly, a sample (Example 16 to Example 27, Comparative Example 4) having a thickness of 0.5 mm was prepared by changing the mixing ratio of powder E and nylon in the range of 5 v% to 75 v%, and the dielectric constant was changed. It was measured. The results are shown in Table 2.

  From Table 2, a sound material was obtained when the mixing ratio of the powder E was 5 v% to 70 v%. However, when the mixing ratio was 75 v%, the kneading apparatus was clogged with the material, and a sample could not be manufactured. Further, as the ceramic content increased, the material became harder and the flexibility decreased. At 70%, the material was harder and almost not flexible. Further, even when the ceramic content was 5 v%, the dielectric constant was higher than that of nylon, and the dielectric constant increased as the content increased.

  Moreover, when the composite material using the powder D (Examples 4 to 15) and the composite material using the powder E (Examples 16 to 27) were compared, the composite material using the powder D used the powder E. Although the dielectric constant is higher than that of the composite material having the same content, the composite material using the powder E is superior in flexibility to the composite material using the powder D having the same content. From the above results, the content of ceramics is 70V% or less, and considering the process variation, etc., 60v% to 65v% is appropriate. Furthermore, considering the flexibility, the mixing ratio and powder type should be set appropriately. I knew it would be good.

  Next, as shown in FIG. 10, a microstrip antenna is formed on the upper copper foil 14 (corresponding to the antenna element 9), and the copper foil 15 (conductor 12 or metal) is also formed on the lower side with the dielectric 10 interposed therebetween. An antenna having a structure corresponding to the body 11 was fabricated, and its resonance frequency was measured.

  Specifically, a glass epoxy (dielectric constant 4.2) having a thickness of 0.5 mm having copper foils 14 and 15 on both sides is cut into a 100 mm square, and the dimensions of the copper foil 14 on the upper surface (A in the figure) are determined. The square was cut into a square and the resonance frequency was measured (Comparative Example 5). In addition, copper foils 14 and 15 having a thickness of 35 μm are bonded to both sides of nylon 6-6 (dielectric constant 3.3) having a thickness of 0.5 mm and 100 mm square, and the dimensions of the copper foil 14 on the upper surface are changed to form a square. After cutting, the resonance frequency was measured (Comparative Example 6).

  On the other hand, copper foils 14 and 15 having a thickness of 35 μm are bonded to both sides of a 50 mm square and 0.5 mm thick rolled material of nylon (dielectric constant 27) containing 65% by weight of powder D, and the dimensions of the upper surface copper foil 14 are measured. Were cut into squares, and the resonance frequency was measured (Example 28). Also, copper foils 14 and 15 having a thickness of 35 μm are bonded to both sides of a 50 mm square and 0.5 mm thick rolled material of nylon (dielectric constant 25.4) containing 65% of powder E, and the upper copper foil 14 The dimensions were changed to squares, and the resonance frequency was measured. The results are shown in Table 3.

  From Table 3, the dimensions that give substantially the same resonance frequency are 81 mm square in Comparative Example 5 and 92 mm square in Comparative Example 6, whereas 32 mm square in Example 28 and 33 mm square in Example 29 are small. It has been found that the size of the antenna itself can be reduced by using the dielectric 10 of the invention.

  Thus, by using the dielectric 10 formed by the above method, the dielectric constant can be increased, and it can be easily manufactured with high dimensional accuracy, and even if it is thinned, it is difficult to be damaged. Can do. By using this dielectric 10 for an antenna operating in the UHF band or the SHF band, a small antenna with little loss can be formed.

  The dielectric of the present invention can be used not only for antenna applications in RFID systems but also for any application that can use a dielectric having a high dielectric constant, such as a high-frequency antenna.

1 is a diagram schematically illustrating a general configuration of an RFID system. It is sectional drawing which shows typically the structure of the antenna for tags concerning one Example of this invention. It is sectional drawing which shows typically the structure of the antenna for tags concerning one Example of this invention. It is sectional drawing which shows typically the structure of the antenna for tags concerning one Example of this invention. It is sectional drawing which shows typically the structure of the antenna for tags concerning one Example of this invention. It is sectional drawing which shows typically the structure of the antenna for tags concerning one Example of this invention. It is sectional drawing which shows typically the structure of the antenna for tags concerning one Example of this invention. It is sectional drawing which shows typically the structure of the antenna for tags concerning one Example of this invention. It is sectional drawing which shows typically the structure of the antenna for tags concerning one Example of this invention. It is a figure which shows the structure of the antenna for tags for demonstrating the effect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RFID system 2 Tag 3 Antenna 4 Capacitor 5 IC chip 6 Reader / writer 7 Reader / writer antenna 8 Control unit 8a Communication circuit 8b Arithmetic processing circuit 9 Antenna element 10 Dielectric 11 Metal body 12 Conductor 13 Magnetic body 14, 15 Copper foil

Claims (10)

  A dielectric comprising at least a composite material formed using a ferroelectric ceramic powder and plastic or rubber.   The dielectric according to claim 1, wherein the content of the ferroelectric ceramic powder is approximately 70% or less by volume ratio.   3. The dielectric according to claim 1, wherein the ferroelectric ceramic powder is formed by dry pulverization, and the maximum particle size of the powder is approximately 100 μm or less.   3. The ferroelectric ceramic powder is formed by wet pulverization using an organic solvent, and the particle size of the powder is approximately 0.1 μm to 10 μm. Dielectric.   5. The dielectric according to claim 4, wherein the ferroelectric ceramic powder includes an alkaline earth metal. 3. The dielectric according to claim 1, wherein the ferroelectric ceramic powder is chemically generated TiO ₂ , and the particle size of the powder is approximately 0.1 μm to 10 μm.   An RFID tag or RFID reader / writer that is operable in the UHF band or SHF band, comprising the dielectric according to any one of claims 1 to 6 and an antenna pattern disposed on the surface of the dielectric. Antenna.   A dielectric according to any one of claims 1 to 6, an antenna pattern disposed on the surface of the dielectric, and a conductor disposed at a position facing the antenna pattern on the surface of the dielectric. An RFID tag or RFID reader / writer antenna operable in the UHF band or SHF band.   9. The RFID tag or RFID according to claim 7, wherein a magnetic material is inserted between the dielectric and the conductor, or between the antenna pattern and the dielectric. Reader / writer antenna.   10. The RFID tag or the RFID reader / writer according to claim 7, wherein a second dielectric is disposed on the dielectric so as to cover the antenna pattern. antenna.

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