TWI837608B - RFID tag and method for manufacturing the same - Google Patents

Abstract

The RFID tag comprises: an embedding portion having an IC chip recording identification information and a slot antenna connected to the IC chip; and a magnetic sheet stacked on the side of the embedding portion to be attached. The slot antenna is formed of a metal film, and a slot hole is provided on the slot antenna in which a portion of the metal film is cut out in a long and thin shape. A slit is provided on the magnetic sheet to distinguish the magnetic layer having magnetic properties. This slit is arranged in an area overlapping with the slot hole of the embedding portion when the magnetic sheet and the embedding portion are stacked.

Description

RFID tag and method for manufacturing the same

The present invention relates to RFID tags and methods for manufacturing RFID tags.

RFID (Radio Frequency Identification) tags that are attached to objects for logistics management or product management have become popular. RFID tags have an IC chip and an antenna electrically connected to the IC chip. RFID tags are also called wireless tags, IC tags, RF-ID tags, and RF tags.

If the object to which such an RFID tag is attached is made of metal, communication cannot be performed via the antenna inside the tag, and the reading of identification information may fail. It is speculated that this is because when metal is located around the RFID tag, the electromagnetic waves sent from the reader/writer for transmitting and receiving data to the RFID tag are lost in the form of eddy current in the metal part, so the energy used to transmit data back to the antenna from the IC chip cannot be effectively obtained.

As a means of solving such a problem, the use of magnetic sheets is known to be effective. By inserting a magnetic sheet between the RFID tag and the metal to which it is attached, the electromagnetic waves received by the antenna can be circulated inside the magnetic sheet, and the energy to be supplied to the IC chip can be effectively transmitted (for example, refer to non-patent document 1). [Prior art document] (Non-patent document)

Non-patent document 1: Fukase Mikiko and Takemoto Satoshi, "Development of magnetic sheets for UHF band metal-compatible RFID tags," Electrical Steelmaking, Vol. 82, No. 1, pp. 23-30, 2011.

[Problem to be solved by the invention] However, the frequency band used for communication of RFID tags has a higher demand for the UHF band (radio wave method) that can communicate over long distances and read multiple objects at the same time, compared to the HF band (13.56MHz, electromagnetic induction method). However, in the structure in which a magnetic sheet is sandwiched between the known RFID tag and the metal, it may not be possible to communicate using the UHF band.

The purpose of this disclosure is to provide an RFID tag and a method for manufacturing an RFID tag that can improve communication performance. [Technical means to solve the problem]

An RFID tag in one embodiment of the present invention is to be attached to an attachment object and comprises: an embedding portion having an IC chip recording identification information and a slot antenna connected to the IC chip; and a magnetic sheet stacked on the attachment object side of the embedding portion; wherein the slot antenna is formed of a metal film, a slot hole is provided on the slot antenna in which a portion of the metal film is cut out in an elongated shape, a slit is provided on the magnetic sheet to distinguish a magnetic layer having magnetic properties, and the slit is arranged in a region overlapping with the slot hole of the embedding portion when the magnetic sheet and the embedding portion are stacked.

Similarly, a manufacturing method of an RFID tag in one embodiment of the present invention includes: a step of forming a magnetic sheet, the step of forming a magnetic sheet, the magnetic sheet being provided with a slit for distinguishing a magnetic layer having magnetic properties; and a stacking step of stacking an embedding portion with the magnetic sheet formed in the step of forming the magnetic sheet, the embedding portion having an IC chip recording identification information and a slot antenna connected to the IC chip; wherein the slot antenna is formed of a metal film, a slot hole formed by cutting a portion of the metal film in a long and thin shape is provided on the slot antenna, and the slit is arranged in a region overlapping with the slot hole of the embedding portion when the magnetic sheet and the embedding portion are stacked. [Effect of the invention]

Through the present disclosure, an RFID tag and a method for manufacturing the RFID tag that can improve communication performance can be provided.

In the following, the embodiments are described with reference to the accompanying drawings. To facilitate the understanding of the description, the same components in each drawing are given the same symbols as much as possible, and repeated descriptions are omitted.

In addition, in the following description, the x-direction, y-direction, and z-direction are mutually perpendicular directions. The x-direction is the long side direction of the embedding portion 101 and the magnetic sheet 102, and is the extension direction of the parallel portion 22 and the slit 30 of the slot 21. The y-direction is the short side direction of the embedding portion 101 and the magnetic sheet 102, and is the extension direction of the vertical portion 23 of the slot 21. The z-direction is the stacking direction of each component of the RFID tag 100 such as the embedding portion 101 and the magnetic sheet 102. In addition, for the sake of convenience in the following description, the positive z-direction side may be represented as the upper side and the negative z-direction side may be represented as the lower side.

FIG. 1 is a stacked cross-sectional view of an implementation form of the RFID tag 100. FIG. 2 is an exploded oblique view of the RFID tag 100 shown in FIG. 1. FIG. 3 is a plan view of the RFID tag 100 shown in FIG. 1 as viewed from above. The RFID tag 100 is a roughly planar device to be attached to an attachment object 200. As shown in FIG. 1 to FIG. 3, the RFID tag has an embedding portion 101, a magnetic sheet 102, and a dielectric layer 103. The attachment object 200 is, for example, a metal. As a metal, in addition to metals such as iron, aluminum, and copper, metal alloys such as iron alloys, aluminum alloys, and copper alloys are also included. Furthermore, the attachment object 200 also includes other materials other than metals, for example, plastics, paper, ceramics, etc.

The main use of the RFID tag 100 in the embodiment is to attach it to relatively large metal products such as iron drums and H-shaped steels, and can be used to track the distribution paths of these metal products, including inventory management, etc. In addition to metal products, the tag of this case can also be attached to other items for use.

Furthermore, the RFID tag of this embodiment is flexible and can be attached even if the surface of the adherend is curved. Even when bent, it can still demonstrate good communication performance, and the RFID tag of this embodiment can be used to identify objects with curved surfaces such as drums and spray cans, thereby achieving a variety of uses.

The embedding part 101 is a part that includes components related to the functions of the RFID tag 100. As shown in FIG. 2 and FIG. 3, it has an IC chip 10 that records identification information and a slot antenna 20 connected to the IC chip 10. The slot antenna 20 is formed of a metal film. The slot antenna 20 is provided with a slot 21 formed by cutting a part of the metal film into a long shape. The embedding part 101 is formed by attaching an aluminum sheet to a PET (polyethylene terephthalate) film in a dry lamination manner to form the slot antenna 20, and the IC chip 10 is mounted at a predetermined position.

The IC chip 10 is arranged at the center of the main surface of the embedding portion 101. The slot 21 of the slot antenna 20 has: a pair of parallel portions 22 that sandwich the IC chip 10 and extend in parallel in a predetermined direction (the x direction in the example of FIG. 2 and FIG. 3); and a pair of vertical portions 23 that extend in a direction (y direction) orthogonal to the pair of parallel portions 22. The pair of vertical portions 23 sandwich the IC chip 10 and are arranged at positions approximately equally spaced in the x direction.

Furthermore, the frequency characteristics of the impedance of the IC chip 10 are as follows. ･866MHz: 15-j265(Ω) ･915MHz: 14-j252(Ω) ･953MHz: 13-j242(Ω)

The impedance of the slot antenna 20 is designed to match the impedance of the IC chip 10 at 915 to 920 MHz. By matching the impedance in this way, the current loss is reduced, and the communication distance can be increased due to the reduction of the loss.

The magnetic sheet 102 is a sheet containing a magnetic material and is stacked on the attachment object 200 side of the embedding portion 101. The magnetic sheet 102 is formed by evenly and directionally dispersing magnetic powder such as a stainless alloy in a rubber material and a resin and kneading the mixture. As shown in FIG. 2 and FIG. 3, a slit 30 is provided on the magnetic sheet 102 to distinguish the magnetic layer having magnetic properties. The slit 30 is arranged in a region overlapping with the slot 21 of the embedding portion 101 when the magnetic sheet 102 and the embedding portion 101 are stacked.

The slit 30 is formed, for example, as shown in FIG. 3 , at the center of the magnetic sheet 102 in the y direction so as to extend in the x direction. Furthermore, the slot 21 of the slot antenna 20 and the slit 30 of the magnetic sheet 102 are arranged, for example, as shown in FIG. 3 , so that at least one pair of parallel portions 22 in the slot 21 are entirely included in the area of the slit 30.

The magnetic sheet 102 is preferably a sheet having excellent magnetic shielding properties for UHF band radio waves. The magnetic sheet 102 can be obtained by applying a magnetic coating containing components such as a magnetic filler and an adhesive resin on a support and drying the magnetic coating. In order to make the magnetic sheet 102 have excellent magnetic shielding properties for UHF band radio waves, the magnetic sheet 102 after drying is preferably coated with the magnetic coating in a manner that is less than 500 μm, and more preferably less than 300 μm. Furthermore, the magnetic sheet 102 after drying is preferably coated with the magnetic coating in a manner that is greater than 50 μm, and more preferably greater than 100 μm.

Similarly, in order to make the magnetic sheet 102 have excellent magnetic shielding properties for UHF band radio waves, the loss coefficient tanδ(μ´/μ´´) of the complex relative permeability of the magnetic sheet in the 860-960MHz frequency band is preferably 0.3 or less, and more preferably 0.28 or less. In addition, the loss coefficient tanδ(μ´/μ´´) of the complex relative permeability of the magnetic sheet in the 860-960MHz frequency band is preferably 0.05 or more, and more preferably 0.1 or more.

Furthermore, the thickness of the label in this embodiment (excluding the release paper) is 200μm to 1000μm, preferably 300μm to 400μm. In addition, the thickness of the state after the magnetic sheet and the embedding portion are bonded (excluding the label paper and the release paper) is 150μm to 250μm, preferably 190μm to 210μm, and more preferably about 200μm. The thickness of the label paper, including the adhesive layer, is 50μm to 300μm. The thickness of the release paper is 50μm to 300μm.

Similarly, in order to make the magnetic sheet 102 have excellent magnetic shielding properties for UHF band radio waves, the real part μ' of the complex relative permeability of the magnetic sheet in the 860-960MHz frequency band is preferably 5.0 or more, and more preferably 5.2 or more. In addition, the real part μ' of the complex relative permeability of the magnetic sheet in the 860-960MHz frequency band is preferably 7.0 or less, and more preferably 6.0 or less.

Furthermore, in order to satisfy the above-mentioned multiple relative permeabilities, the material of the magnetic filler contained in the magnetic coating is preferably a Fe-Cr alloy. Furthermore, the mass ratio of the magnetic filler to the solid component of the binder (mass of the magnetic filler/mass of the solid component of the binder) is preferably 70/30 or more, more preferably 75/25 or more, and further preferably 80/20 or more. Furthermore, the mass ratio of the magnetic filler to the solid component of the binder (mass of the magnetic filler/mass of the solid component of the binder) is preferably 95/5 or less, more preferably 90/10 or less, and further preferably 85/15 or less.

Furthermore, the binder resin contained in the magnetic coating is one or more resins selected from the group consisting of epoxy resins, urethane resins and polyester resins, and is preferably epoxy resin.

The dielectric layer 103 is further stacked on the side of the magnetic sheet 102 to which the object 200 is to be attached, and is arranged between the magnetic sheet 102 and the object 200 to which the object is to be attached. In FIG. 2, the dielectric layer 103 is integrally illustrated below the magnetic sheet 102. The dielectric layer 103 is preferably formed as an insulator such as a sheet of thick paper, woven and non-woven fabrics composed of fibers such as synthetic resins, and inorganic materials such as ceramic glass. In the present embodiment, the dielectric layer 103 is formed of, for example, foamed PET. The material of the dielectric layer 103 is preferably a material having a relative dielectric constant of approximately 1.2 to 3.0, thereby increasing the communication distance of the RFID tag 100.

Furthermore, as shown in FIG. 1 , the dielectric layer 103 also functions as a spacer so that the embedding portion 101 and the magnetic sheet 102 are arranged in a state where only the thickness of the dielectric layer 103 is separated from the attachment object 200. The dielectric layer 103 is preferably formed of a material that can be arbitrarily deformed together with the embedding portion 101 and the magnetic sheet 102 in response to an external force, thereby making it possible to easily attach the RFID tag 100 even when the attachment surface of the attachment object 200 is curved, and to improve versatility.

In the RFID tag 100, as shown in FIG. 2, an adhesive layer 104 (not shown in FIG. 1) is disposed between the embedding portion 101 and the magnetic sheet 102. When stacked, the adhesive layer 104 enters the gap formed by the slit 30 of the magnetic sheet 102 and the dielectric layer 103 thereunder and can fill the gap.

In the RFID tag 100 of the present embodiment, a label paper (film-based adhesive paper) 105 is further arranged above the embedding portion 101. The label paper 105 can be printed on the surface on the positive z direction side. The raw material of the label paper can be appropriately selected.

Furthermore, as shown in FIG. 1, an adhesive 106 is applied on the back side of the label paper 105 on the negative z direction side. The label paper 105 is formed larger than the embedding portion 101, the magnetic sheet 102, and the dielectric layer 103. As shown in FIG. 2, the label paper 105 is formed in such a way that its outer edge portion 105A can surround the entire outer shape of the embedding portion 101, the magnetic sheet 102, and the dielectric layer 103. Thereby, as shown in FIG. 1, when the RFID tag 100 is attached to the attachment object 200, the outer sides of the embedding portion 101, the magnetic sheet 102, and the dielectric layer 103 are completely covered by the label paper 105, and the outer edge portion 105A of the label paper 105 is in contact with the attachment object 200. That is, the entire RFID tag 100 is attached to the attachment object 200 by the adhesive 106 on the outer edge portion 105A of the label paper 105.

In addition, the adhesive 106 can be used in an environment where the object is used for a long time. However, if the adhesive hardens, it may be difficult to peel off. In contrast, the adhesive can be used to peel off the RFID tag from the object by manual operation of the operator. Furthermore, depending on the type of adhesive, the RFID tag can be attached again after peeling off, so that the RFID tag can be reused.

Furthermore, in the case of the structure in which the RFID tag 100 is attached by the adhesive 106 of the label paper 105 as shown in FIG. 1 , the adhesive may not be applied between the dielectric layer 103 and the attached object 200 and the dielectric layer 103 may not be bonded (adhered) to the attached object 200.

Furthermore, as shown in FIG. 2, a release paper 107 is arranged below the dielectric layer 103 on the RFID tag 100 before use. The size of the release paper 107 is, for example, the same as or larger than the size of the label paper 105, and the label paper 105 and the release paper 107 are closely attached to each other by the adhesive 106 on the outer edge portion. This prevents the adhesive 106 on the outer edge portion 105A of the label paper 105 from being exposed to the outside before being attached to the attachment object 200, and the adhesive force can be maintained. When the RFID tag 100 is used, the release paper 107 is peeled off from the RFID tag 100, and the RFID tag 100 is attached to the attachment object 200 using the adhesive 106 on the exposed label paper 105.

Furthermore, the release paper 107 may be formed larger than the release paper shown in FIG. 2 so that a plurality of RFID tags 100 may be arranged on one release paper 107. Thus, the manufacturing efficiency and the conveying efficiency can be improved.

Regarding the adhesive 106 on the bottom surface of the label paper 105, it is preferred that more than 50% of the area of the RFID tag 100 is adhered to the release paper 107. In the manufacturing step of the RFID tag 100, a plurality of RFID tags 100 are arranged on the release paper 107 extending in one direction, and the release paper 107 including the RFID tags 100 is rolled into a roll. In the printing step, the roll-shaped release paper 107 is pulled out and the printing process is performed on each RFID tag 100. After the printing process is completed, it is rolled into a roll again for storage. This is to prevent the RFID tag 100 from being separated from the release paper 107 wound into a roll shape during such manufacturing steps and printing steps.

Furthermore, the stacking structure of the RFID tag 100 is not limited to the structure shown in Figures 1 and 2. Figure 21 is a stacking cross-sectional view of a modified RFID tag 100A. As shown in Figure 21, the label paper 105 may also be a structure whose size is formed to be the same as the size of the embedding portion 101, the magnetic sheet 102, and the dielectric layer 103. In this case, the outer edge of the label paper 105 cannot contact the attached object 200, so an adhesive 106 is applied to the bottom surface of the dielectric layer 103 opposite to the attached object 200, and is bonded to the attached object 200 through the dielectric layer 103, and the RFID tag 100A is attached to the attached object 200 as a whole.

The shapes of the slot 21 of the slot antenna 20 shown in Fig. 2 and Fig. 3 are examples and are not limited to the shapes shown in Fig. 2 and Fig. 3. Fig. 4 is a plan view showing an example of a slot 21A of another shape of the slot antenna 20.

The shape of the slot of the slot antenna 20, such as the slot 21A shown in FIG. 4, may also be a shape having only a pair of parallel portions 22A without a vertical portion. In the example of FIG. 4, the parallel portion 22A extends in the direction of the vertical portion 23 of FIG. 3, and its opening area is larger than that of the parallel portion 22 of FIG. 3 and the width in the y direction is larger. In the example of FIG. 4, the width of the slit 30 is formed so that the pair of parallel portions 22A of the slot 21A are included in the region of the slit 30.

Fig. 5 is a flow chart showing an example of a method for manufacturing the RFID tag 100 of the embodiment. In step S1, a magnetic sheet 102 (slit-shaped magnetic sheet) is formed, in which slits 30 for separating the magnetic layer having magnetic properties are provided.

Such a magnetic sheet 102 with slits can be formed, for example, by the following method: a polyester synthetic film (manufactured by Toyobo Co., Ltd., "CRISPER K1211 #38μ") is conveyed at a speed of 3 m/min by a roll-to-roll method, a stripe pattern produced by a magnetic shielding coating is formed on the film using a coating machine, and the film is passed through a 30m curing furnace while the temperature is raised from 40°C to 80°C.

In step S2, the magnetic sheet 102 with slits and the embedding portion 101 formed in step S1 are stacked.

Furthermore, the slit 30 provided on the magnetic sheet 102 in step S1 is formed in such a manner that the slit 30 is arranged in a region overlapping with the slot 21 of the embedding portion 101 when the magnetic sheet 102 and the embedding portion 101 are stacked together in step S2.

In step S3, the dielectric layer 103 is stacked on the surface of the magnetic sheet 102 on the side opposite to the embedding portion 101. Furthermore, step S2 and step S3 may also be performed in reverse order, where the embedding portion 101 is stacked on the magnetic sheet 102 after the magnetic sheet 102 and the dielectric layer 103 are stacked.

In step S4, a film-based adhesive paper (label paper) 105 is stacked on the surface of the embedding portion 101 on the side opposite to the magnetic sheet 102.

Thus, the RFID tag 100 of the present embodiment comprises: an embedding portion 101 having an IC chip 10 recording identification information and a slot antenna 20 connected to the IC chip 10; and a magnetic sheet 102 stacked on the side of the embedding portion 101 to which the object 200 is attached. The slot antenna 20 is formed of a metal film, and a slot hole 21 is provided on the slot antenna 20 in which a portion of the metal film is cut off in an elongated shape. A slit 30 is provided on the magnetic sheet 102 to distinguish a magnetic layer having magnetic properties. This slit 30 is arranged in a region overlapping with the slot hole 21 of the embedding portion 101 when the magnetic sheet 102 and the embedding portion 101 are stacked.

By providing the slits 30 on the magnetic sheet 102 in this manner, the communication distance of the RFID tag 100 in the UHF band can be increased and the communication performance can be improved regardless of the type of the attached object 200 (see FIG. 22 described later). In addition, compared to the HF band, long-distance communication and simultaneous reading of multiple objects are possible, and the communication distance of the UHF band can be increased, thereby realizing a highly versatile RFID tag 100.

Furthermore, if the attached object 200 is made of metal, the previous RFID tag cannot communicate based on the antenna inside the tag, which may cause obstacles to the reading of identification information. Therefore, the effect of improving the communication performance of the RFID tag 100 of this embodiment becomes particularly significant when the attached object 200 is made of metal.

Furthermore, in existing metal RFID tags that do not use magnetic sheets, in order to suppress the reduction in communication performance due to the influence of the metal as the adherend, a relatively large distance is required between the embedded part and the adherend. In order to ensure this distance, the overall thickness of the RFID tag is more than 3.5 mm, making it difficult to reduce the thickness.

In contrast, the thickness of the RFID tag of this embodiment is less than 1 mm, which can be thinner than the previous RFID tag that does not use a magnetic sheet. For example, the thickness of the RFID tag including the label paper and the release paper can be made to be about 350 μm, which is significantly thinner than a metal RFID tag.

Furthermore, since the device can be significantly thinned, a commonly used (general-purpose) label printer can be used to simultaneously print labels and write information on IC chips, thereby further improving manufacturing efficiency.

In addition, the RFID tag 100 of this embodiment further has a dielectric layer 103 stacked on the side of the magnetic sheet 102 on which the object 200 is to be attached, thereby further increasing the communication distance in the UHF band and thus further improving the communication performance.

The RFID tag 100 of this embodiment can be applied to any of electromagnetic induction type wireless tags and radio wave type wireless tags. In particular, when the RFID tag 100 is applied to a radio wave type wireless tag, a predetermined wireless communication distance with a reader can be ensured. The predetermined wireless communication distance is, for example, in the range of 0m to 20m.

The RFID tag 100 of this embodiment can be applied not only to radio waves of the UHF band, but also to radio waves of the VHF band, SHF band, etc. When the operating frequency of the RFID tag 100 is a frequency of the UHF band, such as 860 to 960 MHz, 915 to 925 MHz, etc., the UHF band has a higher frequency and a shorter wavelength than the VHF band, which is beneficial for miniaturization of the antenna. Therefore, by making the RFID tag 100 into a shape suitable for radio waves of the UHF band, it is possible to miniaturize the IC chip 10 and obtain a wireless tag with a small memory capacity but low price. (Example)

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

<Influence of slit width> Examples 1 to 5 and Comparative Examples 1 to 2 were set as follows to verify the influence of the change in the width of the slit 30 corresponding to the magnetic sheet 102 on the communication performance.

[Example 1] The RFID tag 100 shown in FIG. 1 is made by stacking an embedding portion 101, a magnetic sheet 102 with a thickness of 100 μm, and a dielectric layer 103 made of foamed PET with a thickness of 38 μm. The embedding portion 101 is formed by attaching a 10 μm aluminum sheet to a PET film with a thickness of 38 μm by dry lamination to form a slot antenna 20, and an IC chip 10 is mounted at a predetermined position. The label paper 105 is removed. The antenna pattern of the slot 21 of the slot antenna 20 is made into the shape shown in FIG. 2. The dimensions of each part of the slot antenna 20 and the slot 21 are shown in FIG. 6.

The magnetic sheet 102 was prepared as follows. First, the magnetic coating was prepared by mixing 55.2 parts by mass of Fe-Cr alloy ("FKTE231" manufactured by Sanyo Tokugawa Steel Co., Ltd.) as a magnetic filler, 9.9 parts by mass of polyester polyurethane ("Iuliano 2456" manufactured by Arakawa Chemical Industries, Ltd., weight average molecular weight 30,000) as a binder resin, 22.6 parts by mass of toluene as an organic solvent, 0.4 parts by mass of polyphosphate dispersant ("BYK-111" manufactured by BYK Japan Co., Ltd.) as a dispersant, and 0.2 parts by mass of non-silicone defoaming agent ("BYK-1752" manufactured by BYK Japan Co., Ltd.) as a defoaming agent. Next, a polyester synthetic film ("CRISPER K1211 #38μ" manufactured by Toyobo Co., Ltd.) was conveyed at a speed of 3 m/min by a roll-to-roll method, and a stripe pattern was formed on the film using a coating machine using a magnetic shielding coating (using the magnetic coating obtained above), and the film was passed through a curing furnace for 30 m while the temperature was raised from 40°C to 80°C. Thus, a magnetic sheet 102 with slits 30 was obtained.

As shown in FIG. 3 , the slit 30 of the magnetic sheet 102 is formed so that the center of the y direction of the magnetic sheet 102 is the center position in the width direction and the width in the y direction becomes 2 mm.

The RFID tag 100 thus produced was attached to a stainless steel (SUS) plate as an attachment object 200, and the frequency characteristics of the RFID tag 100 were measured using an RFID tag performance tester (Tagformance Pro, manufactured by Voyantic). The measurement frequency band of the wireless communication radio wave was set to 700 to 1200 MHz, and the EIRP (Equivalent Isotropically Radiated Power) was set to 3.2 W.

[Example 2] The RFID tag 100 was prepared in the same manner as in Example 1 except that the width of the slit 30 of the magnetic sheet 102 was set to 5 mm, and the frequency characteristics were measured.

[Example 3] The RFID tag 100 was prepared in the same manner as in Example 1 except that the width of the slit 30 of the magnetic sheet 102 was set to 10 mm, and the frequency characteristics were measured.

[Example 4] The RFID tag 100 was prepared in the same manner as in Example 1 except that the width of the slit 30 of the magnetic sheet 102 was set to 18 mm, and the frequency characteristics were measured.

[Example 5] The RFID tag 100 was prepared in the same manner as in Example 1 except that the width of the slit 30 of the magnetic sheet 102 was set to 25 mm, and the frequency characteristics were measured.

[Comparative Example 1] Except that the slit 30 is not provided in the magnetic sheet 102, the RFID tag 100 is produced in the same manner as in Example 1, and the frequency characteristics are measured.

[Comparative Example 2] Except for removing the magnetic sheet 102, the RFID tag 100 is made in the same manner as in Example 1. That is, the embedding portion 101 and the dielectric layer 103 with a thickness of 38 μm are stacked to make the RFID tag. In addition, the frequency characteristics of the made RFID tag are measured using the same method as in Example 1.

FIG. 7 is a graph showing the frequency characteristics of the RFID tags of Examples 1 to 5 and Comparative Example 2. In FIG. 7, (A) represents the frequency characteristics of Example 1, (B) represents the frequency characteristics of Example 2, (C) represents the frequency characteristics of Example 3, (D) represents the frequency characteristics of Example 4, (E) represents the frequency characteristics of Example 4, and (F) represents the frequency characteristics of Comparative Example 2. The horizontal axis of each figure represents the frequency of the radio wave for wireless communication, and the vertical axis represents the communicable distance from the RFID tag 100 to the reader.

In FIG. 7, the frequency bands not shown in the characteristic graph indicate that wireless communication cannot be performed between the RFID tag 100 and the reader. As shown in FIG. 7 (F), in Comparative Example 2 without the magnetic sheet 102, wireless communication cannot be performed in the frequency band below about 870 MHz. Furthermore, although not shown in FIG. 7, in Comparative Example 1 without the slit 30 in the magnetic sheet 102, wireless communication cannot be performed in all frequency bands.

As shown in FIG. 7 , the communicable distance at the prescribed frequency of 920 MHz included in the UHF band is approximately 2.0 m in Example 1, approximately 3 m in Example 2, approximately 4.5 m in Example 3, approximately 4.5 m in Example 4, approximately 2.5 m in Example 5, and approximately 1.5 m in Comparative Example 2.

As shown in FIG. 7 (A) to (D), in the structure of embodiments 1 to 4 in which a slit 30 is provided in the magnetic sheet 102, as the width of the slit 30 increases, the communicative distance also increases, and when the slit width is 10 to 18 mm, the communicative distance becomes a maximum of about 4.5 m. In addition, the position of the peak of the frequency characteristic is included in the frequency range of 860 to 960 MHz in the UHF band. Furthermore, in embodiment 5 shown in FIG. 7 (E), if the slit width is further increased, the position of the peak of the frequency characteristic moves to the high frequency side, and the communicative distance of the UHF band (for example, near 920 MHz) is reduced.

As shown in FIG. 7(F), in Comparative Example 2 without the magnetic sheet 102, the peak position of the frequency characteristic is further shifted toward the high frequency side compared to the case of Example 5 shown in FIG. 7(E). In Comparative Example 2, the antenna size needs to be increased in order to be used in the UHF band.

According to the test results shown in FIG. 7 , by providing a magnetic sheet 102 in the RFID tag 100 and further providing a slit 30 on the magnetic sheet, it is shown that the communicative distance can be increased, especially the communicative distance in the UHF band can be increased.

Furthermore, for the slot antenna 20 having the dimensions of each part shown in FIG. 6, if the width of the slit 30 is set to 10 to 18 mm, it is shown that the communicable distance can be maximized. In other words, it is shown that there is an optimal range for the width of the slit 30. If this condition is shown in relation to the slot 21 of the slot antenna 20, the following various situations can be shown: the parallel portion 22 of the slot 21 is completely included in the range of the slit 30, the parallel portion 22 and the vertical portion 23 of the slot 21 are completely included in the range of the slit 30, and the width of the slit 30 is roughly the same as the length (size) of the vertical portion 23.

<Influence of magnetic properties of magnetic sheet> Examples 6 to 9 are set as follows to verify the influence of the magnetic properties of the magnetic sheet 102, specifically the influence of the change in the ratio of magnetic powder on the communication performance.

[Example 6] The width of the slit 30 of the magnetic sheet 102 is set to 18 mm, which is within the optimal range of Examples 1 to 5. The magnetic layer 102A of the magnetic sheet 102 has a magnetic powder ratio of 100% and a dielectric powder ratio of 0%. The RFID tag 100 is made in the same manner as in Example 1, and the frequency characteristics are measured.

[Example 7] Except that the ratio of magnetic powder in the magnetic layer 102A of the magnetic sheet 102 is set to 70% and the ratio of dielectric powder is set to 30%, the RFID tag 100 is made in the same manner as in Example 6, and the frequency characteristics are measured.

[Example 8] Except that the ratio of magnetic powder in the magnetic layer 102A of the magnetic sheet 102 is set to 30% and the ratio of dielectric powder is set to 70%, the RFID tag 100 is made in the same manner as in Example 6, and the frequency characteristics are measured.

[Example 9] Except that the ratio of magnetic powder in the magnetic layer 102A of the magnetic sheet 102 is set to 0% and the ratio of dielectric powder is set to 100%, the RFID tag 100 is made in the same manner as in Example 6, and the frequency characteristics are measured.

FIG. 8 is a diagram showing the frequency characteristics of the RFID tags of Examples 6 to 9. In FIG. 8, (A) shows the frequency characteristics of Example 6, (B) shows the frequency characteristics of Example 7, (C) shows the frequency characteristics of Example 8, and (D) shows the frequency characteristics of Example 9. The overview of each figure is the same as that of FIG. 7.

As shown in FIG. 8 , the communication distance at the predetermined frequency of 920 MHz included in the UHF band is about 4.5 m in Example 6, about 3.5 m in Example 7, about 2.5 m in Example 8, and about 1.8 m in Example 9. The peak position of the frequency characteristic is about 900 to 960 MHz in Example 6, about 940 to 1025 MHz in Example 7, about 1010 to 1060 MHz in Example 8, and about 1010 MHz in Example 9.

According to the test results shown in FIG. 8 , with respect to the composition of the magnetic layer 102A of the magnetic sheet 102, it is believed that the higher the ratio of magnetic powder, the more the resonance frequency can be shifted to the low frequency side. The fact that the resonance frequency can be shifted to the low frequency side means that the antenna can be miniaturized. With respect to the composition of the magnetic sheet, by increasing the ratio of magnetic powder, it is believed that a smaller and thinner RFID tag 100 can be realized. Furthermore, according to the test results shown in FIG. 8 , because the range of overlap between the peak of the frequency characteristic and the UHF band increases as the ratio of magnetic powder increases, it is shown that the communication distance in the UHF band can be improved and the communication performance of the RFID tag 100 can be enhanced.

<Influence of dielectric layer> Examples 10 to 13 are set as follows to verify whether the presence of the corresponding dielectric layer 103 has an influence on the communication performance.

[Example 10] Similar to Example 5, the width of the slit 30 of the magnetic sheet 102 is set to 25 mm and the thickness of the magnetic sheet 102 is set to 100 μm to produce an RFID tag 100. The produced RFID tag 100 is attached to a steel cabinet, and the communication distance is measured using an existing handheld reader (trade name: AsReaderGUN, manufactured by Asterisk, output 1W).

[Example 11] Except for removing the dielectric layer 103, the RFID tag 100 was made in the same manner as in Example 10, and the frequency characteristics were measured.

[Example 12] Except that the thickness of the magnetic sheet 102 was set to 200 μm, the RFID tag 100 was prepared in the same manner as in Example 10, and the frequency characteristics were measured.

[Example 13] Except for removing the dielectric layer 103, the RFID tag 100 was made in the same manner as in Example 12, and the frequency characteristics were measured.

The measurement results of the communication distances of the RFID tags of Examples 10 to 13 are shown in Table 1.

[Table 1] Communication distance [cm] Embodiment 10 120～400 Embodiment 11 120～220 Embodiment 12 300 Embodiment 13 220

As shown in Table 1, in Examples 10 and 11, where the thickness of the magnetic sheet 102 is the same as 100 μm, Example 10 having the dielectric layer 103 can increase the communicative distance. In addition, in Examples 12 and 13, where the thickness of the magnetic sheet 102 is the same as 200 μm, Example 12 having the dielectric layer 103 can increase the communicative distance. According to the above results, it is shown that regardless of the change in the thickness of the magnetic sheet 102, the structure in which the dielectric layer 103 is provided on the RFID tag can improve the communication performance.

<Influence of the shape of the slot antenna> Examples 14 to 19 are set as follows to verify the influence of the change in the shape of the slot antenna 20 on the communication performance. Specifically, the shape of the slot antenna 20 is changed in a simulation to confirm the change in impedance.

[Example 14] FIG. 9 is a diagram showing the shape of the slot antenna 20-1 used in Example 14. A model of the slot antenna 20-1 in the shape shown in FIG. 9 is made in a simulation manner. The shape and dimensions of each part of the slot antenna 20-1 shown in FIG. 9 are the same as the shape and dimensions of each part of the slot antenna 20 formed in Example 1 and the like shown in FIG. 6. Using the model of the slot antenna 20-1 made in this way, impedance measurement is performed after simulation.

FIG. 10 is a graph showing the measurement results of the impedance characteristics of the slot antenna 20-1 of Example 14. The vertical axis of FIG. 10 represents the values of real numbers and imaginary numbers of impedance. The horizontal axis of FIG. 10 represents frequency [MHz]. The one-point chain curve (curve with circles) shown in FIG. 10 is a curve in which the real numbers of impedance corresponding to each frequency are plotted. The solid line curve (curve with squares) shown in FIG. 10 is a curve in which the imaginary numbers of impedance corresponding to each frequency are plotted.

[Example 15] FIG. 11 is a diagram showing the shape of the slot antenna 20-2 used in Example 15. The slot antenna 20-2 of Example 15 forms the slot 21 in a manner such that the length of the parallel portion 22 of the slot 21 is shorter than the length of the parallel portion 22 of the slot 21 of the slot antenna 20-1 of Example 14. Using the model of the slot antenna 20-2 thus made, after simulation, impedance measurement is performed. FIG. 12 is a diagram showing the measurement results of the impedance characteristics of the slot antenna 20-2 of Example 15. The outline of FIG. 12 is the same as that of FIG. 10.

[Example 16] FIG. 13 is a diagram showing the shape of the slot antenna 20-3 used in Example 16. The slot antenna 20-3 of Example 16 forms the slot 21 in a manner such that the length of the parallel portion 22 of the slot 21 is shorter than the length of the parallel portion 22 of the slot 21 of the slot antenna 20-2 of Example 15. Using the model of the slot antenna 20-3 made in this manner, after simulation, impedance measurement is performed. FIG. 14 is a diagram showing the measurement results of the impedance characteristics of the slot antenna 20-3 of Example 16. The outline of FIG. 14 is the same as that of FIG. 10.

[Example 17] FIG. 15 is a diagram showing the shape of the slot antenna 20-4 used in Example 17. The slot antenna 20-4 of Example 17 forms the slot 21 in a manner that the slot 21 has no vertical portion 23 but only a parallel portion 22. The length of the parallel portion 22 of the slot 21 is the same as the parallel portion 22 of the slot 21 of the slot antenna 20-1 of Example 14. Using the model of the slot antenna 20-4 made in this way, after simulation, impedance measurement is performed. FIG. 16 is a diagram showing the measurement results of the impedance characteristics of the slot antenna 20-4 of Example 17. The outline of FIG. 16 is the same as that of FIG. 10.

[Example 18] FIG. 17 is a diagram showing the shape of the slot antenna 20-5 used in Example 18. The slot antenna 20-5 of Example 18 forms the slot 21 in a manner such that the width of the parallel portion 22 of the slot 21 is larger than the width of the parallel portion 22 of the slot 21 of the slot antenna 20-4 of Example 17. Using the model of the slot antenna 20-5 thus made, after simulation, impedance measurement is performed. FIG. 18 is a diagram showing the measurement results of the impedance characteristics of the slot antenna 20-5 of Example 18. The outline of FIG. 18 is the same as that of FIG. 10.

[Example 19] FIG. 19 is a diagram showing the shape of the slot antenna 20-6 used in Example 19. The slot antenna 20-6 of Example 19 is formed in such a way that the dimension in the short side direction (y direction) is shorter than the dimension in the short side direction of the slot antenna 20-1 of Example 14. The shape of the slot 21 is the same as that of the slot antenna 20-1 of Example 14. Using the model of the slot antenna 20-6 made in this way, after simulation, impedance measurement is performed. FIG. 20 is a diagram showing the measurement results of the impedance characteristics of the slot antenna 20-6 of Example 19. The outline of FIG. 20 is the same as that of FIG. 10.

The comparative verification of each of the embodiments 14 to 19 was performed based on the impedance characteristics of the slot antenna 20-1 of the embodiment 14 which has the same shape and dimensions of each part as the actual slot antenna 20 used in the above-mentioned embodiment 1, etc. For example, in an embodiment having the same impedance characteristics as that of the embodiment 14, even if an antenna is actually manufactured in the shape of the embodiment, it is assumed that the same performance as that of the actual slot antenna 20 of the embodiment 1, etc. can be obtained.

When comparing Examples 14 to 16, as shown in FIG. 10, FIG. 12, and FIG. 14, if the length of the parallel portion 22 of the slit 30 is changed, that is, the length of the long side direction (x direction) of the slit 30 is changed, it can be seen that the impedance characteristics of the slot antenna change significantly. On the other hand, when comparing Example 14 with Examples 17 and 18, as shown in FIG. 10, FIG. 16, and FIG. 18, even if the length of the short side direction (y direction) of the slit 30 is changed by making the slit have no vertical portion 23 or increasing the width of the parallel portion 22, after simulation, it is found that the impedance characteristics of the slot antenna are almost unchanged. Similarly, when comparing Example 14 and Example 19, as shown in FIG. 10 and FIG. 20 , even if the dimension of the short side direction (y direction) of the slot antenna is changed, the impedance characteristics of the slot antenna are hardly changed.

According to the above, after simulation, it is shown that the length of the long side direction (x direction) of the slit 30 is important for the impedance characteristics of the slot antenna.

Fig. 22 is a diagram showing the evaluation results of the RFID tag of Example 1 in the present embodiment, with respect to the influence of various metals as the attached object 200. In this evaluation, the label paper 105 is not used, and both ends of the label are fixed to the metal plate with adhesive tape for evaluation.

From the evaluation results in FIG. 2 , it can be seen that the RFID tag of this embodiment can exhibit good communication performance with various metals.

The above describes the present embodiment with reference to specific examples. However, the present disclosure is not limited to these specific examples. As long as the features of the present disclosure are present, even if the industry adds appropriate design changes to these specific examples, they are also included in the scope of the present disclosure. The various components and the configuration, conditions, shapes, etc. of the aforementioned specific examples are not limited to those illustrated, and can be appropriately changed. As long as there is no technical contradiction, the combination of the various components of the aforementioned specific examples can be appropriately changed.

This international application claims priority based on Japanese Patent Application No. 2021-040664 filed on March 12, 2021, and the entire contents of Japanese Patent Application No. 2021-040664 are hereby incorporated by reference into this international application.

10: IC chip 20,20-1,20-2,20-3,20-4,20-520-6: slot antenna 21,21A: slot 22,22A: a pair of parallel parts 23: a pair of vertical parts 30: slit 100,100A: RFID tag 101: embedding part 102: magnetic sheet 103: dielectric layer 104: adhesive layer 105: label paper (film adhesive paper) 105A: outer edge part 106: adhesive 107: release paper 200: attached object

FIG. 1 is a stacked cross-sectional view of an RFID tag of an embodiment. FIG. 2 is an exploded oblique view of the RFID tag shown in FIG. 1. FIG. 3 is a plan view of the RFID tag shown in FIG. 1 as viewed from above. FIG. 4 is a plan view showing an example of a slot of another shape of a slot antenna. FIG. 5 is a flow chart showing an example of a method for manufacturing an RFID tag of an embodiment. FIG. 6 is a diagram showing the dimensions of each part of the slot antenna and the slot used in Embodiment 1. FIG. 7 is a diagram showing the frequency characteristics of the RFID tags of Embodiments 1 to 5 and Comparative Example 2. FIG. 8 is a diagram showing the frequency characteristics of the RFID tags of Embodiments 6 to 9. FIG. 9 is a diagram showing the shape of the slot antenna used in Embodiment 14. FIG. 10 is a diagram showing the measurement results of the impedance characteristics of the slot antenna of Embodiment 14. FIG. 11 is a diagram showing the shape of the slot antenna used in Example 15. FIG. 12 is a diagram showing the measurement results of the impedance characteristics of the slot antenna of Example 15. FIG. 13 is a diagram showing the shape of the slot antenna used in Example 16. FIG. 14 is a diagram showing the measurement results of the impedance characteristics of the slot antenna of Example 16. FIG. 15 is a diagram showing the shape of the slot antenna used in Example 17. FIG. 16 is a diagram showing the measurement results of the impedance characteristics of the slot antenna of Example 17. FIG. 17 is a diagram showing the shape of the slot antenna used in Example 18. FIG. 18 is a diagram showing the measurement results of the impedance characteristics of the slot antenna of Example 18. FIG. 19 is a diagram showing the shape of the slot antenna used in Example 19. FIG. 20 is a diagram showing the measurement results of the impedance characteristics of the slot antenna of Example 19. FIG. 21 is a stacked cross-sectional diagram of a variation of the RFID tag. FIG. 22 is a diagram showing examples of the characteristics of the RFID tag of the embodiment for various metals.

Domestic storage information (please note in the order of storage institution, date, and number) None Foreign storage information (please note in the order of storage country, institution, date, and number) None

Claims (8)

An RFID tag is to be attached to an object to be attached, and comprises: an embedding portion having an IC chip recording identification information and a slot antenna connected to the IC chip; a magnetic sheet directly stacked on the embedding portion via an adhesive layer on the embedding portion's side to be attached; and a dielectric layer stacked on the magnetic sheet's side to be attached; wherein the slot antenna is formed of a metal film, a slot hole formed by cutting a portion of the metal film in a long and narrow shape is provided on the slot antenna, a slit is provided on the magnetic sheet to distinguish a magnetic layer having magnetic properties, and the slit is arranged in a region overlapping with the slot hole of the embedding portion when the magnetic sheet and the embedding portion are stacked. The RFID tag as described in claim 1, wherein the object to be attached is made of metal. The RFID tag as described in claim 1, wherein the IC chip is disposed at the center of the main surface of the embedding portion, and the slot of the slot antenna has a pair of parallel portions that sandwich the IC chip and extend parallel to a specified direction. An RFID tag as described in claim 3, wherein the slot has a vertical portion extending in a direction orthogonal to the pair of parallel portions. The RFID tag as described in claim 3, wherein the aforementioned slit is formed in such a way that when the aforementioned magnetic sheet and the aforementioned embedding portion are stacked, the entire pair of parallel portions of the aforementioned slot of the aforementioned embedding portion are contained within the area of the aforementioned slit. The RFID tag as described in any one of claim items 1 to 4 uses a frequency in the UHF band. The RFID tag as described in claim 1 is a radio wave wireless tag. A method for manufacturing an RFID tag, the RFID tag is to be attached to an attached object, the manufacturing method is implemented by an RFID tag manufacturing device, comprising: a step of forming a magnetic sheet, the step of forming a magnetic sheet, the magnetic sheet being provided with a slit for distinguishing a magnetic layer having magnetic properties; a step of laminating an embedding portion and the magnetic sheet, the magnetic sheet formed in the step of forming the magnetic sheet being directly laminated on the aforementioned attachment object side of the embedding portion via an adhesive layer; An embedding part, the embedding part has an IC chip recording identification information and a slot antenna connected to the IC chip; a step of stacking dielectric layers, stacking the dielectric layers on the attachment object side of the magnetic sheet; wherein the slot antenna is formed of a metal film, and a slot hole is provided on the slot antenna, in which a part of the metal film is cut off in a long and thin shape, and the slit is arranged in a region overlapping with the slot hole of the embedding part when the magnetic sheet and the embedding part are stacked.