JP2015005794A - Antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized antenna of which the communication distance per unit area of a silver conductive film is longer in comparison with a conventional antenna used for an RFID tag or the like.SOLUTION: In an antenna, a linearly extending silver conductive film (a silver conductive film including a sintered body of silver particles) 10 is formed on a substrate. The silver conductive film 10 includes: a loop part 10a extending with the substantially equal line width in a loop shape so as to surround a substantially rectangular plane shape; and a pair of extension parts 10b extending with the substantially equal line width reversely to each other from both ends of one of four linear parts which linearly extend in the loop part 10a. Each of the extension parts 10b is formed from a plurality of parallel parts 10c which extend substantially in parallel with the one linear part, and a plurality of vertical parts 10d extending substantially vertically to these parallel parts 10c. One of these parallel parts 10c is connected to the one linear part, and the parallel parts 10c and the vertical parts 10d are alternately and continuously formed.

Description

  The present invention relates to an antenna, and more particularly to an antenna used for an RFID tag or the like.

  The RFID tag is a tag using RFID (Radio Frequency IDentification (individual identification technology by wireless communication)), and is a thin type equipped with a semiconductor chip for storing data such as an identification number and an antenna for transmitting and receiving radio waves. It is a lightweight small electronic device.

  Such an RFID tag is expected to be widely used in various usage environments in various fields such as physical distribution management, and it is desired to reduce the manufacturing cost by mass production and spread it. In addition, the RFID tag antenna needs to have low electrical resistance in order to increase the data transmission / reception possible distance (communication distance) and reduce data loss during transmission / reception. Furthermore, RFID tags should be used in various logistics management fields (eg, tracking of transport containers, traceability, location information management, and clothing management by clothing washers like laundry tags). Therefore, even if it is repeatedly bent, it can be prevented from being used as an RFID tag due to deterioration of antenna characteristics such as disconnection due to metal fatigue of the antenna or an increase in electrical resistance. Therefore, it is necessary that the flexibility be good.

  The RFID tag antenna circuit (conductive circuit) can be formed by using a coil or wire of copper wire as an antenna, a method of transferring a metal foil such as copper foil or aluminum foil onto a substrate, or a substrate such as a plastic film. For example, there is a method of etching the metal foil after masking the metal foil laminated on the material with an etching resistant ink by printing an antenna circuit pattern.

  However, these methods are limited in productivity and are not suitable for mass production, so that it is difficult to further reduce manufacturing costs. Of these methods, in the method of transferring the metal foil to the substrate and the method of etching the metal foil, the metal foil is manufactured by rolling or the like, but the ratio of the metal in the metal foil is almost 100%. Since the value is high, the RFID tag in which the antenna circuit is formed of the metal foil has a problem that the electrical property is good but the flexibility is poor. In addition, in an RFID tag in which an antenna circuit is formed of a metal foil, a metal foil with a film thickness of about 10 to 50 μm is generally used. However, if the metal foil is too thick, the properties of the metal plate become close to the substrate. There is a possibility that the metal foil peels off from the base material when the RFID tag is bent. Furthermore, since the ratio of the metal in the metal foil is high, stress is concentrated on the bent surface when the RFID tag is bent, and cracks are likely to occur on the bent surface, resulting in deterioration of electrical characteristics and disconnection, It will not function as an RFID tag antenna. On the other hand, in order to improve the flexibility of the RFID tag, instead of metal foil, using a conductive film composed of a metal component and a resin component to reduce the metal ratio generally improves the flexibility by stress relaxation. However, when the amount of the metal component is reduced, the electrical resistance is deteriorated and the characteristics sufficient for the RFID tag antenna are not satisfied.

  As a method of manufacturing an RFID tag antenna that forms a conductive circuit with good adhesion to a substrate without using a metal foil, a water-based conductive ink containing 40% by mass or less of silver particles is formed into a film by flexographic printing. By applying and drying on the surface of the base material, a conductive film having a thickness of 0.1 to 0.5 μm is formed on the surface of the film-like base material to manufacture an antenna for an IC tag which is a kind of RFID tag. A method has been proposed (see, for example, Patent Document 1).

JP 2010-268073 A (paragraph numbers 0030 and 0059)

  However, in the method of Patent Document 1, it is possible to mass-produce IC tag antennas with low electrical resistance and reduce the manufacturing cost. However, since the communication distance is short, it is desired to further extend the communication distance. .

  Accordingly, in view of the above-described conventional problems, the present invention aims to provide a small antenna having a long communication distance per unit area of a silver conductive film as compared with a conventional antenna used for an RFID tag or the like. To do.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have found that in an antenna in which a linearly extending silver conductive film is formed on a substrate, the silver conductive film is looped so as to surround a substantially rectangular planar shape. A pair of loop portions having substantially the same line width and substantially the same line width in opposite directions from both ends of one straight portion of the four straight portions extending substantially linearly of the loop portion. It is found that a small antenna having a longer communication distance per unit area of the silver conductive film can be manufactured than the conventional antenna used for an RFID tag or the like, and the present invention is completed. It came to do.

  That is, the antenna according to the present invention is a loop in which a silver conductive film extending on a substrate is formed on a substrate, and the silver conductive film extends in a loop shape with substantially the same line width so as to surround a substantially rectangular planar shape. And a pair of extensions extending from each of the ends of one of the four straight portions of the loop portion in a substantially straight line shape with substantially the same line width in opposite directions. To do.

  In this antenna, the pair of extension portions are preferably arranged symmetrically with respect to a straight line extending substantially perpendicularly from the substantially central portion of the one straight portion to the one straight portion. It is preferable that each of the end portions of each has substantially the same line width as the other portions of the extension portion.

  Moreover, it is preferable that each of a pair of extension part consists of a parallel part extended substantially parallel with respect to said one linear part, and a perpendicular part extended substantially perpendicular | vertical with respect to this parallel part. In this case, there are a plurality of parallel parts and vertical parts of each extension part of the pair of extension parts, and one of these parallel parts is connected to the one straight part, and the parallel parts and the vertical parts are alternately continuous. It is preferable that it is formed. In this case, it is preferable that the lengths of the plurality of parallel portions of the extension portions of the pair of extension portions are substantially the same length. Further, the length of the vertical portion of each extension portion of the pair of extension portions is substantially the same as the length of the straight portion extending substantially perpendicular to the one straight portion of the four straight portions of the loop portion. Preferably there is. Alternatively, the length of the vertical portion of each extension portion of the pair of extension portions may be longer than the straight portion extending substantially perpendicular to the one straight portion of the four straight portions of the loop portion.

  Moreover, each of a pair of extension part may extend in the shape of a curve, meandering from said one linear part. In this case, it is preferable that each of the pair of extension portions meander between the extension line of the one straight portion of the four straight portions and the extension line of the straight portion parallel to the straight portion. . Further, each of the pair of extension portions is directed from one to the other and one to the other of the extension line of the one straight portion of the four straight portions and the extension line of the straight portion parallel to the straight portion. Each part preferably has a part extending so as to approach the loop part. Further, each of the pair of extension portions is in the vicinity of the extension line of the one straight portion of the four straight portions, and the extension line of the straight portion parallel to the one straight portion of the four straight portions. In the vicinity, it is preferable to have a portion extending in a substantially semicircular shape.

Moreover, it is preferable that the area of a silver electrically conductive film is 135-265 mm < ² >, and the line | wire width of a silver electrically conductive film is 1.0 mm or less, and it is preferable that the thickness of a silver electrically conductive film is 1-10 micrometers. Further, the silver conductive film preferably contains a sintered body of silver particles.

  ADVANTAGE OF THE INVENTION According to this invention, compared with the conventional antenna used for an RFID tag etc., the small antenna with a long communication distance per unit area of a silver electrically conductive film can be provided.

It is a figure explaining the shape of embodiment of the antenna by this invention. It is a figure explaining the shape of the modification of embodiment of the antenna by this invention. It is a figure explaining the shape of the other modification of embodiment of the antenna by this invention. It is a figure explaining the shape of the other modification of embodiment of the antenna by this invention. It is a figure which expands and shows the IC chip mounting part of the antenna of FIGS.

  As shown in FIGS. 1 to 4, an antenna according to an embodiment of the present invention is an antenna in which a linearly extending silver conductive film (a silver conductive film including a sintered body of silver particles) 10 is formed on a substrate. The silver conductive film 10 has a loop portion 10a extending in a loop shape with substantially the same line width so as to surround a substantially rectangular planar shape, and one of four linear portions extending in a substantially linear shape of the loop portion 10a. It consists of a pair of extension part 10b extended from each of the both ends of a linear part to the mutually opposite direction by the substantially the same line | wire width. The pair of extension portions 10b are arranged symmetrically with respect to a straight line extending substantially perpendicularly from the substantially central portion of the one straight portion to the one straight portion. Moreover, each front-end | tip part of a pair of extension part 10b has a line width substantially the same as the other part of the extension part 10b.

  As shown in FIGS. 1-3, each of a pair of extension part 10b is substantially perpendicular | vertical with respect to several parallel part 10c extended substantially parallel with respect to said one linear part, and these parallel parts 10c. A shape in which the plurality of vertical portions 10d extend, one of the parallel portions 10c is connected to the one straight portion, and the parallel portions 10c and the vertical portions 10d are alternately and continuously formed is preferable. The lengths of the plurality of parallel portions 10c of the extension portions 10b of the pair of extension portions 10b are preferably substantially the same length. In addition, the length of the vertical portion 10d of each extension portion 10b of the pair of extension portions 10b is the length of the straight portion extending substantially perpendicular to the one straight portion of the four straight portions of the loop portion 10a. Are preferably substantially the same. Alternatively, the length of the vertical portion 10d of each extension portion 10b of the pair of extension portions 10b is longer than the straight portion extending substantially perpendicular to the one straight portion of the four straight portions of the loop portion 10a. May be.

  As shown in FIG. 4, each of the pair of extending portions 10b may have a shape extending in a curved shape while meandering from the one straight portion. Each of the pair of extension portions 10b preferably meanders between the extension line of the one straight portion of the four straight portions and the extension line of the straight portion parallel to the straight portion. Further, each of the pair of extension portions 10b extends from one of the four straight portions to the other and one from the other of the straight portions parallel to the straight portion. It is preferable to have a portion extending so as to approach the loop portion 10a in each of the facing portions. In addition, each of the pair of extension portions 10b is in the vicinity of the extension line of the above-described one straight portion of the four straight portions, and in the vicinity of the extension line of the straight portion parallel to one of the four straight portions. In this case, it is preferable to have a portion extending in a substantially semicircular shape.

  1 to 5, reference numeral 12 denotes an IC chip mounting portion to which a semiconductor chip such as an RFID tag chip is attached.

The area of the electro-conductive silver film is 135～265Mm ² and the line width of the electro-conductive silver film (the loop portion and the extension of) is preferably at 1.0mm or less. If the area of the silver conductive film is 135 to 265 mm ² and the line width of the silver conductive film is 1.0 mm or less, when the RFID tag chip is attached and the RFID tag chip mounted antenna is manufactured (the amount of silver used is reduced). Therefore, even if the area of the silver conductive film is reduced, the communication distance is increased.

  Furthermore, the thickness of the silver conductive film is preferably 1 to 10 μm. The thinner the silver conductive film, the more advantageous in terms of cost. However, when it is less than 1 μm, when used as an RFID tag antenna, the electrical resistance in the UHF band increases due to the skin effect and the communication distance becomes shorter. .

  Moreover, the embodiment of the antenna according to the present invention is formed by applying the silver particle dispersion liquid containing 50 to 80% by mass of silver particles to the substrate and then baking it to form the above silver conductive film on the substrate. Can be manufactured. When the silver particle content in the silver particle dispersion is less than 50% by mass, it becomes difficult to form the silver conductive film on the substrate, and the amount of the sintered body of silver particles in the silver conductive film is too small. When the electrical conductivity is deteriorated and the electric resistance is increased and the amount exceeds 80% by mass, the viscosity of the silver particle dispersion becomes high, and it becomes difficult to apply by flexographic printing or the like.

  In this antenna manufacturing method, the silver particle dispersion is preferably applied to the substrate by flexographic printing, and the flexographic printing may be repeated a plurality of times. Moreover, it is preferable that the average particle diameter of a silver particle is 20 nm or less, and it is preferable that it is 5-15 nm. When the average particle size of the silver particles is about several nanometers to several tens of nanometers, the specific surface area increases and the melting point decreases dramatically. (That is, the low-temperature sinterability of the silver nanoparticles can be obtained). However, when the average particle size of the silver particles is larger than 20 nm, it is difficult to obtain the low-temperature sinterability of the silver nanoparticles. In order to sinter silver particles by firing at such a low temperature, a hot-air circulating dryer or an IR firing furnace can be used.

  In the present specification, the “average particle diameter of silver particles” refers to an average primary particle diameter that is an average value of primary particle diameters obtained by transmission electron micrographs (TEM images) of silver particles.

  The average particle size (average primary particle size) of the silver particles is, for example, 60% by mass Ag particles (silver particles having an average particle size of 10 nm), 3.0% by mass vinyl chloride copolymer latex, and 2.0% by mass polyurethane. 2 parts by mass of Ag ink containing silver particles, such as Ag ink containing Pt-Chem Associates, Inc. (PFI-Associates, Inc.) containing 2.5% by mass of propylene glycol, 96 parts by mass of cyclohexane and 2 parts by mass of oleic acid After being added to the mixed solution and dispersed by ultrasonic waves, the obtained dispersed solution is dropped onto a Cu microgrid with a supporting film and dried, and silver particles on the microgrid are transferred to a transmission electron microscope (JEOL Ltd.) JEM-100CXMark-II type) made in bright field at an acceleration voltage of 100 kV, taken at a magnification of 300,000 And can be calculated from the obtained TEM image. The primary particle average diameter of the silver particles can be calculated using, for example, image analysis software (A Image-kun (registered trademark) manufactured by Asahi Kasei Engineering Co., Ltd.). This image analysis software discriminates and analyzes individual particles based on color shading. For example, for a 300,000-fold TEM image, the “particle brightness” is “dark” and “noise removal filter”. Is “Yes”, “Circular threshold” is “20”, and “Overlapping degree” is “50”, and circular particle analysis is performed to measure the primary particle diameter of 200 or more particles. An average diameter can be calculated | required and it can be set as an average primary particle diameter. In addition, what is necessary is just to make measurement impossible when there are many condensed particles and irregular-shaped particles in a TEM image.

  Hereinafter, embodiments of the antenna according to the present invention will be described in detail.

[Examples 1-12, Comparative Examples 1-12]
First, 60% by mass of Ag particles (silver particles having a primary particle size of 15 nm and a secondary particle size of 340 nm), 3.0% by mass of vinyl chloride copolymer latex, 2.0% by mass of polyurethane thickener, 2.5 Ag ink (PFI-700 type manufactured by P-Chem Associates, Inc.) containing mass% propylene glycol was prepared.

Next, a roll-to-roll continuous flexographic printing machine (manufactured by KPG) and a flexographic printing plate (manufactured by Watanabe Gosando Co., Ltd.) were used, with an anilox capacity of 8 cc / m ² and a printing speed of 15 m / min. 1 on a base material made of PET (polyethylene terephthalate) film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.) (95 mm wide × 8.2 mm vertical) with a loop portion having a line width of 1 After printing the above Ag ink so as to form an antenna-shaped film (0.0 mm, extension line width 0.8 mm), a hot blast furnace (set temperature 140 ° C.) and an IR heating furnace (set at a printing path) An RFID antenna made of a silver conductive film having a thickness of 1.6 μm was manufactured by firing with an IR lamp of 1.95 kW × 10) at an IR output of 10%. In addition, the film thickness of a silver electrically conductive film uses the laser microscope (model VK-9700 by Keyence Corporation), and the height difference between the surface of the base material in which the silver electrically conductive film was formed, and the surface of a silver electrically conductive film. It measured by measuring 100 places and calculating | requiring the average value.

  In the antennas of the respective examples and comparative examples, the number of vertical portions of each extension extending from the loop portion (for example, in the antenna shape shown in FIG. 1, the number of vertical portions of each extension extending from the loop portion is 7 1), the area ratio of the silver conductive film formed on the base material, and the area ratio of the silver conductive film to the silver conductive film formation region on the base material (rectangular portion of 95 mm wide × 8.2 mm long). (The amount of silver in the silver conductive film is also shown in Table 1). The line width and area of the silver conductive film were measured with an appearance inspection machine (NC-FLX manufactured by Navitas Vision Solution).

  Next, an anisotropic conductive adhesive (ACP) (TAP0604C (Au / Ni coated polymer particles) manufactured by Kyocera Chemical Co., Ltd.) is thinly applied to the IC chip mounting portion of the RFID antenna thus manufactured, and the IC chip is formed on the ACP. (Monza 3 manufactured by Impinj) was placed, and then a pressure of 1.0 N was applied at a temperature of 160 ° C. for 10 seconds with a thermocompression bonding apparatus (TTS300 manufactured by Mühlbauer) to fix the IC chip to the RFID antenna. Then, the IC chip was mounted on the RFID antenna.

  The RFID tag chip-mounted antenna thus produced is used in a frequency range (ISO / IEC) of 800 MHz to 1100 MHz using a communication distance measuring device (Voantic tagformance) in an anechoic box (MY1530 manufactured by Micronics). The communication distance (based on 18000-6C standard) was measured. Prior to this measurement, the environment was set under these conditions (setting using a reference tag attached to tagformance). Table 1 shows the measured communication distance and the communication distance per unit area of the silver conductive film.

[Examples 13 to 21, Comparative Examples 13 to 24]
An RFID antenna made of a silver conductive film having a thickness of 1.6 μm was produced in the same manner as in Example 1 except that the line width of the extension portion was 1.0 mm, and an RFID tag chip mounted antenna was produced. In the antennas of the examples and comparative examples, the number of vertical portions of each extension extending from the loop portion, the area of the silver conductive film formed on the base material, and the silver conductive film formation region on the base material The area ratio of the silver conductive film was the number, area, and area ratio shown in Table 2, respectively (Table 2 also shows the amount of silver in the silver conductive film).

  Table 2 shows the communication distance and the communication distance per unit area of the silver conductive film measured by the same method as in Example 1 for the RFID tag chip mounted antenna thus manufactured.

[Comparative Examples 25-43]
An RFID antenna made of a silver conductive film having a thickness of 1.6 μm was produced in the same manner as in Example 1 except that the line width of the extended portion was 1.2 mm, and an RFID tag chip mounted antenna was produced. In the antennas of the examples and comparative examples, the number of vertical portions of each extension extending from the loop portion, the area of the silver conductive film formed on the base material, and the silver conductive film formation region on the base material The area ratio of the silver conductive film was defined as the number, area, and area ratio shown in Table 3, respectively (Table 3 also shows the amount of silver in the silver conductive film).

  Table 3 shows the communication distance and the communication distance per unit area of the silver conductive film, measured by the same method as in Example 1, for the RFID tag chip mounted antenna thus manufactured.

[Comparative Examples 44-60]
An RFID antenna made of a silver conductive film having a thickness of 1.6 μm was produced in the same manner as in Example 1 except that the line width of the extension portion was 1.4 mm, and an RFID tag chip mounted antenna was produced. In the antennas of the examples and comparative examples, the number of vertical portions of each extension extending from the loop portion, the area of the silver conductive film formed on the base material, and the silver conductive film formation region on the base material The area ratio of the silver conductive film was defined as the number, area, and area ratio shown in Table 4, respectively (Table 4 also shows the amount of silver in the silver conductive film).

  Table 4 shows the communication distance and the communication distance per unit area of the silver conductive film, measured by the same method as in Example 1, for the RFID tag chip mounted antenna thus manufactured.

[Comparative Examples 61-76]
An RFID antenna made of a silver conductive film having a thickness of 1.6 μm was produced in the same manner as in Example 1 except that the line width of the extension portion was 1.6 mm, and an RFID tag chip mounted antenna was produced. In the antennas of the examples and comparative examples, the number of vertical portions of each extension extending from the loop portion, the area of the silver conductive film formed on the base material, and the silver conductive film formation region on the base material The area ratio of the silver conductive film was defined as the number, area, and area ratio shown in Table 5, respectively (Table 5 also shows the amount of silver in the silver conductive film).

  Table 5 shows the communication distance and the communication distance per unit area of the silver conductive film measured by the same method as in Example 1 for the RFID tag chip mounted antenna thus manufactured.

From these results, as in Examples 1 to 21, if the area of the silver conductive film is 135 to 265 mm ² and the line width of the silver conductive film (loop portion and extension thereof) is 1.0 mm or less, It can be seen that the communication distance per unit area of the silver conductive film is as long as 0.026 m / mm ² or more.

[Comparative Example 77]
Conventional antenna shape (95 mm wide × 8.2 mm long) (the area of the silver conductive film formed on the substrate is 399 mm ² ) so that the line width of the silver conductive film is different (not shown) The area ratio of the silver conductive film with respect to the upper silver conductive film formation region (rectangular portion 70 mm wide × 14.5 mm long) was 52%, and the amount of silver in the silver conductive film was 1.47 mg). In the same manner as in Example 1, an RFID antenna made of a 1.6 μm-thick silver conductive film was produced, and an RFID tag chip mounted antenna was produced. With respect to the RFID tag chip mounted antenna thus produced, the communication distance was measured by the same method as in Example 1 and the communication distance per unit area of the silver conductive film was determined. The communication distance was 7.2 m. The communication distance per unit area of the silver conductive film was 0.018 m / mm ² .

[Example 22]
Using a base material made of coated paper (DF color M70 manufactured by Mitsubishi Paper Industries Co., Ltd.) and an anilox capacity of 13 cc / m ² , as shown in FIG. 2 (width 70 mm × length 14.5 mm, line width) 0.8 mm) antenna shape (the number of vertical portions of each extension extending from the loop portion is 6, the area of the silver conductive film formed on the base material is 222 mm ² , the silver conductive film formation region on the base material) The area ratio of the silver conductive film with respect to (rectangular portion of 70 mm wide × 14.5 mm long) was 22%, and the amount of silver in the silver conductive film was 1.33 mg), and an IC chip (Monza4 manufactured by Impinj) was formed. In the same manner as in Example 1, an RFID antenna made of a silver conductive film having a thickness of 2.2 μm was produced to produce an RFID tag chip mounted antenna. With respect to the RFID tag chip mounted antenna thus produced, the communication distance was measured by the same method as in Example 1 and the communication distance per unit area of the silver conductive film was determined. The communication distance was 9.0 m. The communication distance per unit area of the silver conductive film was 0.041 m / mm ² .

[Example 23]
As shown in FIG. 4, the number of curve portions corresponding to each extension portion extending from the loop portion of FIGS. 1 to 3 is 70 mm (width 70 mm × length 14.5 mm and line width 0.8 mm). Six, the area of the silver conductive film formed on the base material is 212 mm ² , and the area ratio of the silver conductive film to the silver conductive film formation region on the base material (rectangular portion 70 mm wide × 14.5 mm long) is 21 %, The amount of silver in the silver conductive film was 1.27 mg), and an RFID antenna made of a silver conductive film having a thickness of 2.2 μm was produced by the same method as in Example 22, and the RFID tag chip An on-board antenna was produced. With respect to the RFID tag chip mounted antenna thus manufactured, the communication distance was measured by the same method as in Example 1 and the communication distance per unit area of the silver conductive film was determined. The communication distance was 8.4 m. The communication distance per unit area of the silver conductive film was 0.040 m / mm ² .

[Comparative Example 78]
Conventional antenna shape (70 mm wide × 14.5 mm long) (the area of the silver conductive film formed on the substrate is 578 mm ² ) so that the line width of the silver conductive film is different (not shown) The area ratio of the silver conductive film to the upper silver conductive film formation region (rectangular portion of 70 mm wide × 14.5 mm long) was 57%, and the amount of silver in the silver conductive film was 3.47 mg). In the same manner as in Example 22, an RFID antenna made of a silver conductive film having a thickness of 2.2 μm was produced, and an RFID tag chip mounted antenna was produced. With respect to the RFID tag chip mounted antenna thus produced, the communication distance was measured by the same method as in Example 1 and the communication distance per unit area of the silver conductive film was determined. The communication distance was 6.9 m. The communication distance per unit area of the silver conductive film was 0.012 m / mm ² .

[Example 24]
A base material made of coated paper (DF color M70 manufactured by Mitsubishi Paper Industries Co., Ltd.) is used, the anilox capacity is 13 cc / m ^2, and the size shown in FIG. 8 mm) antenna shape (the number of vertical portions of each extension extending from the loop portion is 3, the area of the silver conductive film formed on the substrate is 239 mm ² , and the silver conductive film formation region (horizontal) on the substrate The area ratio of the silver conductive film with respect to the 50 mm × 30 mm long rectangular portion) was 16%, and the amount of silver in the silver conductive film was 1.41 mg). An RFID antenna made of a 2.2 μm thick silver conductive film was produced, and an RFID tag chip mounted antenna was produced. With respect to the RFID tag chip mounted antenna thus produced, the communication distance was measured by the same method as in Example 1 and the communication distance per unit area of the silver conductive film was determined. The communication distance was 6.9 m. The communication distance per unit area of the silver conductive film was 0.029 m / mm ² .

[Comparative Example 79]
Conventional antenna shape (50 mm wide x 30 mm long) (the area of the silver conductive film formed on the base material is 710 mm ² ) so that the line width of the silver conductive film is different (not shown) Example 24, except that the area ratio of the silver conductive film to the silver conductive film formation region (rectangular portion of 50 mm wide × 30 mm long) was 47%, and the amount of silver in the silver conductive film was 4.26 mg. By the same method as described above, an RFID antenna made of a silver conductive film having a thickness of 2.2 μm was produced, and an RFID tag chip mounted antenna was produced. With respect to the RFID tag chip mounted antenna thus manufactured, the communication distance was measured by the same method as in Example 1, and the communication distance per unit area of the silver conductive film was determined. The communication distance was 4.5 m. The communication distance per unit area of the silver conductive film was 0.006 m / mm ² .

  From these results, in the antenna shapes of Examples 22 to 24, the communication distance per unit area of the silver conductive film is extremely long as compared with the conventional antenna shapes of Comparative Examples 78 and 79 having the same size. Recognize.

  If the antenna according to the present invention is used as an antenna for an RFID tag, an FEID tag having an antenna with a practical communication distance can be manufactured.

10 Silver conductive film 10a Loop portion 10b Extension portion 10c Parallel portion 10d Vertical portion 12 IC chip mounting portion

Claims (15)

In an antenna in which a linearly extending silver conductive film is formed on a substrate, the silver conductive film has a loop portion extending substantially in the same line width in a loop shape so as to surround a substantially rectangular planar shape, and an approximately of the loop portion. An antenna comprising: a pair of extension portions extending from each of both ends of one straight portion of four straight portions extending in a straight line shape with substantially the same line width in opposite directions. 2. The antenna according to claim 1, wherein the pair of extension portions are arranged symmetrically with respect to a straight line extending substantially perpendicularly from the substantially central portion of the one straight line portion to the one straight line portion. . 3. The antenna according to claim 1, wherein a tip end portion of each of the pair of extension portions has substantially the same line width as other portions of the extension portions. Each of the pair of extension portions includes a parallel portion extending substantially parallel to the one straight portion and a vertical portion extending substantially perpendicular to the parallel portion. 4. The antenna according to any one of 3. Each of the pair of extension portions has a plurality of parallel portions and vertical portions, and one of these parallel portions is connected to the one straight portion, and the parallel portions and the vertical portions are alternately and continuously formed. The antenna according to claim 4, wherein 6. The antenna according to claim 5, wherein the length of the plurality of parallel portions of each of the extension portions of the pair of extension portions is substantially the same length. The length of the vertical portion of each extension portion of the pair of extension portions is substantially the same as the length of the straight portion extending substantially perpendicular to the one straight portion of the four straight portions of the loop portion. The antenna according to any one of claims 4 to 6, characterized by the above. The length of the vertical portion of each extension portion of the pair of extension portions is longer than the straight portion extending substantially perpendicular to the one straight portion of the four straight portions of the loop portion. The antenna according to any one of claims 4 to 6. 4. The antenna according to claim 1, wherein each of the pair of extension portions extends in a curved shape while meandering from the one linear portion. 5. Each of the pair of extension portions meanders between an extension line of the one straight portion of the four straight portions and an extension line of a straight portion parallel to the straight portion. The antenna according to claim 9. Each of the pair of extension portions is directed from one of the four straight portions to the other and from the other to one of an extension line of the straight portion parallel to the straight portion. 11. The antenna according to claim 9, further comprising a portion that extends toward the loop portion. Each of the pair of extension portions is in the vicinity of an extension line of the one straight portion of the four straight portions, and in the vicinity of an extension line of a straight portion parallel to the one straight portion of the four straight portions. The antenna according to claim 9, further comprising a portion extending in a substantially semicircular shape. The antenna according to any one of claims 1 to 12, wherein an area of the silver conductive film is 135 to 265 mm ² and a line width of the silver conductive film is 1.0 mm or less. The antenna according to claim 1, wherein the silver conductive film has a thickness of 1 to 10 μm. The antenna according to any one of claims 1 to 14, wherein the silver conductive film includes a sintered body of silver particles.

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