JP2003188765A - Tag for rfid, control method for resonance frequency and resonance frequency controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for a tag for RFID, a control method for a resonance frequency and a resonance frequency controller in which the resonance frequency of the tag for RFID with a built-in resonance circuit can be controlled after sticking on an article. <P>SOLUTION: A resonance circuit 2a composed of a capacitor 5 and a coil 4 is formed on a substrate 6, the resonance frequency of an RFID tag 2 covering the surface with a cover sheet 9 is measured in the state of attaching on the article and when a measured value is smaller than a target value, the conductive sheet of Al foil 10a or the like is stuck or paste containing a conductive member is applied on the surface of the cover sheet 9 to the inner area of the coil 4. Then, the resonance frequency is increased by reducing the inductance of the coil 4 and when the measured value is larger than the target value, a magnetic sheet is stuck or paste containing a magnetic member is applied from the surface of the cover sheet 9 to an area overlapped with the coil 4 so that the inductance of the coil 4 can be enlarged and the resonance frequency can be decreased. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RFID (Radio Frequency Identification) tag having a built-in resonance circuit, and more particularly, to an RF whose resonance frequency can be adjusted after manufacturing.
The present invention relates to a structure of an ID tag, a resonance frequency adjusting method, and a resonance frequency adjusting device.

[0002]

2. Description of the Related Art In recent years, an R which performs data communication between a tag equipped with an IC chip and a reader / writer (or reader).
FID systems are widespread. Since this RFID system uses a tag and an antenna provided in each of the reader / writer to communicate data, it is possible to communicate even if the tag is several cm to several tens of cm away from the reader / writer, and there is no contamination or dirt. Because of its strength against static electricity, it has come to be used in various fields such as factory production control, logistics control, and room access control.

The basic circuit elements of this tag are a resonance circuit consisting of an antenna coil and a capacitor, and an IC chip, which has a desired frequency band (for example, 13.56 MH).
In order to perform data communication in z), it is necessary to accurately adjust the resonance frequency f set by the inductance L of the antenna coil and the capacitance C of the capacitor forming the resonance circuit to the above frequency.

Here, when a label-type tag is used as the tag, an antenna coil is formed on one surface of a flexible sheet-like substrate and an electrode facing the antenna coil is formed on the other surface of the substrate to form the substrate. A capacitor as a dielectric is formed. Then, the inductance is adjusted by the number of turns and the area of the antenna coil, and the electrostatic capacitance is adjusted by the area of the overlapping portion of the opposing electrodes and the distance between the electrodes.

The number of turns and the area of these antenna coils, the area of the overlapping portion of the opposing electrodes, etc. are basically set at the design stage of the tag, and the antenna coil and the capacitor are formed as designed. For example, a tag with a desired resonance frequency can be manufactured in a single state, but in reality it is due to an error in the manufacturing process of the antenna coil or capacitor and interaction with the item to which the tag is attached after manufacturing. A shift occurs in the resonance frequency.

To solve the problem of the shift of the resonance frequency at the manufacturing stage, in Japanese Patent Laid-Open No. 10-84075, one electrode forming a capacitor has a comb-shaped structure in which a large number of fingers extend from the base to form a comb-shaped electrode. A method of adjusting the resonance frequency by changing the electrode area of the capacitor, that is, the capacitance by sequentially cutting the fingers is described. The adjustment method of the above publication will be described with reference to the drawings.

FIG. 7 is a diagram schematically showing the structure of the capacitor portion of the resonance circuit incorporated in the above-mentioned conventional tag.
(A) is a plan view and (b) is a sectional view taken along the line CC 'of (a). As shown in FIG. 7, a comb-shaped electrode 7 (solid line in (a)) is provided on one surface with a substrate 6 made of an insulator interposed therebetween.
However, the counter electrode 8 (broken line of (a)) is formed on the other surface. The comb-shaped electrode 7 is formed by arranging fingers 7b having the same width side by side on the base portion 7a. On the other hand, the counter electrode 8 has a rectangular electrode 7 when viewed from the normal direction of the substrate 6.
It is formed so as to overlap with b.

In the above structure, the electrostatic capacitance C is proportional to the area of the portion where the opposing electrodes (finger 7b and opposing electrode 8 in the figure) overlap and is inversely proportional to the distance between the electrodes. Therefore, by cutting the cut portion 7c at the base of the finger 7b, the electrode area of the capacitor is reduced and the capacitance C
Can be decreased and the resonance frequency f can be increased.
Therefore, the resonance frequency f can be adjusted to a desired value by increasing the capacitance of the capacitor before cutting the finger 7b and cutting the finger 7b.

[0009]

However, the technique described in the above publication is intended to adjust the resonance frequency in the middle stage of manufacturing the tag, and when the completed tag is attached to an article and used, The interaction between the article and the tag, that is, the capacitance of the resonance circuit capacitor and the inductance of the coil change according to the physical properties such as the relative permeability, relative permittivity, and conductivity of the article, and the resonance frequency changes significantly. Resulting in. In this case, the surface of the tag is the substrate 6
Since it is covered with a cover sheet or the like to protect the electrodes and ICs formed thereon, the resonance frequency cannot be adjusted by the above method during use (after attachment).

Therefore, when manufacturing an RFID tag (particularly, a label-type tag), the resonance frequency change amount α when it is attached to an article is estimated in advance, and the resonance frequency estimated at the manufacturing stage is obtained. (Eg, 13.
56 MHz ± α MHz). However, since the amount of change in the resonance frequency shifts by several tens of kHz to several hundreds of kHz depending on the size, shape, and material of the article to be attached, the resonance frequency cannot be kept within a desired range, and is outside the range. The product will be a defective product because the communication distance is reduced.

The present invention has been made in view of the above problems, and its main purpose is to provide an R which incorporates a resonance circuit.
It is an object of the present invention to provide a structure of an RFID tag capable of adjusting the resonance frequency of the FID tag after being attached to an article, a method of adjusting the resonance frequency, and a resonance frequency adjusting device.

[0012]

In order to achieve the above object, in the RFID tag of the present invention, a resonance circuit composed of a capacitor and an antenna coil is formed on a substrate, and the surface of the resonance circuit is a protective layer. An RFID tag covered with, wherein frequency adjusting means for changing the inductance of the antenna coil is added on the protective layer, and the resonance frequency of the resonance circuit is adjusted by the frequency adjusting means. is there.

In the present invention, the frequency adjusting means is made of a sheet made of a conductive member or a paste containing a powder of the conductive member, and the antenna coil of the antenna coil when viewed from the normal direction of the substrate. The sheet may be attached or the paste may be applied on the protective film on the inner side, and the conductive member may be Al or C.
It is preferable to include any one material of u, Fe, Ag, and carbon.

Further, in the present invention, the frequency adjusting means is made of a sheet made of a magnetic member or a paste containing a powder of the magnetic member, and the antenna coil and the antenna coil when viewed from the normal direction of the substrate. On the protective film in the overlapping region, the sheet may be pasted or the paste is applied, the magnetic member is an amorphous alloy, iron-nickel alloy, nickel-zinc alloy,
It is preferable to include either one of a manganese-zinc alloy and pure iron.

Further, in the present invention, it is also possible to adopt a constitution in which a marker for clearly indicating a mounting position of the adjusting means is formed on the protective layer.

The resonance frequency adjusting method of the present invention is
A method of adjusting a resonance frequency of an RFID tag, wherein a resonance circuit composed of a capacitor and an antenna coil is formed on a substrate, and the surface of the resonance circuit is covered with a protective layer,
By adding frequency adjusting means for changing the inductance of the antenna coil on the protective layer, the resonance frequency of the resonance circuit is adjusted after the RFID tag is attached to an article.

In the present invention, the frequency adjusting means is made of a sheet made of a conductive member or a paste containing a powder of the conductive member, and the frequency of the antenna coil of the antenna coil when viewed from the normal direction of the substrate. A structure in which the sheet is pasted or the paste is applied on the protective film on the inside to increase the resonance frequency of the resonance circuit, or the frequency adjusting means is a sheet made of a magnetic member or the magnetic member. A paste containing a powder, viewed from the normal direction of the substrate, affixing the sheet or applying the paste on the protective film in a region overlapping with the antenna coil, the resonance frequency of the resonance circuit. It can be configured to decrease.

Further, in the present invention, it is preferable to adjust the increase / decrease amount of the resonance frequency of the resonance circuit by adjusting the number or size of the sheets to be stuck or the application area of the paste.

Further, in the resonance frequency adjusting device of the present invention, a resonance circuit composed of a capacitor and an antenna coil is formed on a substrate, and the resonance frequency of the RFID tag in which the surface of the resonance circuit is covered with a protective layer. An adjusting device, which conveys an article to which the RFID tag is attached, a means for measuring a resonance frequency of the resonance circuit, a target value of a predetermined resonance frequency, and a conductive member or a magnetic member. And a value for increasing / decreasing the resonance frequency per unit addition amount of the frequency adjusting means, and referring to the measured value, the target value and the increase / decrease value, means for calculating the amount of the frequency adjusting means to be added. , When viewed from the normal direction of the substrate, the calculated additional amount of the frequency adjusting means is inside the antenna coil of the RFID tag or in front of a region overlapping with the antenna coil. Those having at least a means of disposing on the protective layer.

In the present invention, in the arrangement means, when the measured value is smaller than the target value, the sheet-like or paste-like frequency adjusting means made of the conductive member is provided inside the antenna coil. Affix or apply to
When the measured value is larger than the target value, it is preferable that the sheet-shaped or paste-shaped frequency adjusting unit made of the magnetic member is attached or applied to a region overlapping with the antenna coil.

As described above, according to the present invention, a sheet made of a conductive member or a magnetic member is attached to the inside of a coil constituting a resonance circuit of an RFID tag or a cover sheet overlapping with the coil, or a material thereof is used. By applying the paste containing the powder of 1., it is possible to increase the resonance frequency when the conductive member is arranged inside the coil and decrease the resonance frequency when the magnetic member is arranged on the coil. Therefore, the resonance frequency can be adjusted to a desired value easily and reliably. Further, since the deviation of the resonance frequency can be adjusted in the state where the manufactured RFID tag is attached to the article, it is not necessary to strictly adjust the frequency in the manufacturing stage, and there is an effect that the manufacturing becomes easy. .

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION In a preferred embodiment of the method for adjusting the resonance frequency of an RFID tag according to the present invention, a resonance circuit composed of a capacitor and a coil is formed on a substrate, and the surface thereof is When the resonance frequency of the RFID tag covered with the cover sheet is measured with the RFID tag attached to the article and the measured value is smaller than the target value, the conductive sheet such as Al foil is placed on the inside area of the coil from above the cover sheet. Affix or apply a paste containing a conductive member,
If the measured value is higher than the target value by decreasing the inductance of the coil and increasing the resonance frequency, attach a magnetic sheet from the top of the cover sheet to the area that overlaps with the coil, or apply a paste containing a magnetic member to the coil. The inductance is increased to reduce the resonance frequency.

The principle of the above adjusting method will be described. The resonance frequency f is determined by the inductance L of the coil, which is a component of the label tag, and the electrostatic capacitance C of the sheet capacitor, and is given by the following equation.

[0024]

Therefore, the resonance frequency is adjusted by changing the L value of the coil. That is, when the L value is increased, the resonance frequency f ₀ is decreased, and when the L value is decreased, the resonance frequency f ₀ is increased. For example, as shown in FIG. 2, if a conductive member such as a small piece of Al foil 10a is attached to a position corresponding to the inside of the coil 4 on the surface of the cover sheet 9 of the label-type tag 2, the effective antenna area is reduced and L The value decreases, and if a small piece of the magnetic sheet 10b is attached to a position corresponding to the coil 4 on the surface of the cover sheet 9 as shown in FIG. 5, the magnetic flux near the outer circumference of the coil is linked to the coil via the magnetic sheet. However, since the L value increases, the resonance frequency f ₀ can be increased or decreased by attaching any member. Then, the amount of increase or decrease of the resonance frequency f ₀ can be adjusted by adjusting the size, the number, or the area of the Al foil 10a or the magnetic sheet 10b to be attached. By using such a method, even after the RFID tag 2 is attached to an article, it is possible to easily adjust the RFID tag 2 to have a desired resonance frequency.

[0026]

EXAMPLES Examples of the present invention will be described with reference to the drawings in order to describe the above-described embodiments of the present invention in more detail.

[Embodiment 1] First, an RFID tag structure, a resonance frequency adjusting method, and a resonance frequency adjusting apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a diagram schematically showing the overall configuration of an RFID system, and FIG. 2 is an RFID of this embodiment.
It is a figure which shows an example of the structure of the label tag for use. Also, FIG.
FIG. 4 is a diagram for explaining the effect of the present embodiment, and FIG.
[Fig. 3] is a diagram showing a structure that clearly indicates the position where the Al foil is attached.

As shown in FIG. 1, the RFID system 1
Is a reader / device that communicates data using the antenna 3a.
The reader / writer 3 includes a writer 3 and a tag 2 having various shapes such as a label type, a coin type, and a sheet type. The reader / writer 3 includes a communication circuit unit 3a for converting a transmission / reception signal and a transmission / reception signal for decoding. The arithmetic processing unit 3b is connected. Further, the tag 2 includes a resonance circuit 2a including a coil and a capacitor therein, and when the tag 2 side also generates a signal, an IC 2b for calculating and storing data is connected to the resonance circuit 2a. It is driven by using a built-in power supply or a power supply supplied from the reader / writer 3.

Further, as shown in FIG. 2, the resonance circuit of the label-type tag 2 is generally composed of conductive film patterns formed on both sides of the substrate 6, and is provided on both sides of the substrate 6 made of a flexible insulating sheet. The pattern of the coil 4, the comb-shaped electrode 7, the trunk electrode 12, and the counter electrode 8 is formed by removing the conductive film such as Al or Cu by etching or applying a conductive paste by screen printing. As described above, the comb-teeth electrode structure is used to adjust individual differences in pattern shape caused by manufacturing errors such as etching and screen printing accuracy in the pattern forming step.

By thus cutting the fingers 7b of the comb-teeth electrode 7, it is possible to adjust the deviation of the resonance frequency caused by the error at the manufacturing stage. As described above, the adjusted tag 2 is attached to the article. However, the capacitance of the capacitor and the inductance of the antenna coil change depending on the material, size, shape, etc. of the article, causing a shift in the resonance frequency.

Here, in order to measure the amount of deviation of the resonance frequency when the RFID tag 2 is actually attached to an article (here, a book is described), the resonance frequency f ₀ is determined by using the comb-teeth electrode 7. The label-type RFID tag 2 adjusted to about 13.64 MHz (set 0.08 MHz larger than 13.56 MHz in anticipation of the amount of decrease) is attached to 17 books with different sizes and thicknesses, and resonance before and after attachment When the frequency value and the amount of decrease thereof were examined, the resonance frequency decreased in the range of 0.10 MHz to 0.25 MHz. The results are shown in Table 1.

[0032]

[Table 1] Relationship between type of book and amount of decrease in resonance frequency

As can be seen from Table 1, No. 5, 7,
8, 10 to 12, 15, and 16 have a small decrease in the resonance frequency due to attachment to the book (0.1 to 0.15 MH
z), the resonance frequency after attachment is 13.51 MHz or more, which is close to the target value (13.56 MHz) and within the allowable range, but otherwise, the resonance frequency after attachment is 13.4 MHz.
8 MHz or less, which results in a communication distance d of 10.3
% Or more.

Therefore, in No. 1 where the deviation of the resonance frequency is large.
As for 1 to 4, 6, 9, 13, 14, and 17, as shown in FIG. 2, a small piece (10 mm) of the Al foil 10a is placed at a position corresponding to the inside of the coil 4 on the surface of the cover sheet 9 of the tag 2.
□) was attached, and the resonance frequency was measured again. Table 2 shows the number of pasted Al foils 10a and the resonance frequency before and after pasting.
Table 3 and FIG. 3 show the relationship between the number of attached sheets and the increase amount of the resonance frequency.

[0035]

[Table 2]

[0036]

[Table 3]

As can be seen from Table 2, by sticking 1 to 3 sheets of Al foil 10a, the resonance frequency became 13.51 MHz or more in all cases. This is the target value (f
₀ = 13.56 MHz), and the desired communication distance was obtained by performing such adjustment. Further, from Table 3 and FIG. 3, the resonance frequency also increases substantially in proportion to the increase in the number of the Al foils 10a attached, and the number of the Al foils 10a to be attached can be easily calculated from the deviation from the target value. I understand.

The material to be applied is Al foil 10a.
However, the material is not limited to copper, iron, silver, carbon (graphite), and the like, and the shape is not limited to a sheet shape such as a foil, and may be a wire shape or a block shape. , A conductive coating material containing silver powder, graphite powder, copper powder or the like, or a metallic luster coating material containing Al powder, or PE, PET, PP, P
A mode in which the above paste is applied to an organic base material such as VC may be used. The material and the form can be set in consideration of the shape, surface condition, adjustment range of resonance frequency, adjustment accuracy, workability, etc. of the RFID tag 2 comprehensively.

The position where the conductive sheet or paste is attached or applied is not limited to the structure shown in FIG. 2 and may be any region inside the coil 4 when viewed from the direction normal to the substrate 6. In this case, the attaching position may be clearly indicated on the cover sheet 9 in order to clarify the attaching or applying position.

For example, if the cover sheet 9 is transparent, the position of application is clear. However, when the cover sheet 9 is not transparent or when a paste-like conductive member is applied, the position of application and application are performed. The area may be difficult to understand. In that case, for example, as shown in FIGS. 4 (a) and 4 (b), by forming a marker 11 on the cover sheet 9 where the sheet is pasted or the paste is applied, uneven or colored markers 11 are formed, Even when the coil 4 cannot be visually observed, the conductive member can be arranged at the correct position. Further, the shape of the conductive member is not limited to the quadrangular shape, but may be any shape such as a strip shape or a circular shape.

As a device for realizing the resonance frequency adjusting method using the conductive member such as the Al foil 10a, a device for measuring the resonance frequency of the RFID tag 2 attached to the article and a predetermined device are used. The difference between the target value and the measured value of the resonant frequency is calculated, and the number of conductive members to be attached is calculated from the amount of change in the resonant frequency per unit quantity of the conductive member (for example, per Al foil) obtained by experiments. Any device may be used as long as it has means for calculating size, area, etc., and means for attaching or applying a conductive member to the RFID tag based on the calculation result.

For example, a resonance frequency is measured by installing a measurement antenna on a conveyance path for conveying an article to which the RFID tag 2 is attached, and the result is transmitted to a computer. The number of sheets to be pasted is calculated from the amount of increase in the resonance frequency per foil and the measured value, and a predetermined number of Al foils 10a are pasted at the position detected by the marker detecting means, thereby automatically It is possible to adjust the resonance frequency.

As described above, according to the structure of the RFID tag, the method of adjusting the resonance frequency, and the resonance frequency adjusting apparatus of this embodiment, the conductive material that reduces the inductance of the coil 4 forming the resonance circuit is formed. The resonance frequency can be increased by sticking or applying it on the cover sheet 9 of the tag 2 later. Therefore, by setting the resonance frequency to a small value in advance at the manufacturing stage, and attaching the conductive sheet after attaching the article to the article, the resonance frequency can be accurately adjusted in an actual usage pattern.

[Embodiment 2] Next, an RFID tag structure, a resonance frequency adjusting method, and a resonance frequency adjusting apparatus according to a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. . FIG. 5 is a diagram showing an example of the structure of the RFID label tag of the present embodiment, and FIG. 6 is a diagram for explaining the effect of the present embodiment.

In the above-mentioned first embodiment, a method for adjusting the resonance frequency by substantially reducing the antenna area by attaching a conductive sheet such as Al foil 10a to the inside of the coil 4 of the tag 2 is described. However, the resonance frequency can be changed by attaching a magnetic sheet instead of the conductive sheet so as to overlap the coil 4. Specifically, as shown in FIG. 5, when the magnetic sheet 10b is attached on the cover sheet 9 so as to overlap the coil 4 around the tag 2, the mutual inductance increases and the resonance frequency can be reduced.

The following experiment was conducted to confirm this effect. First, a label type RFID tag having a resonance frequency f ₀ = 13.56 MHz, which was designed to be attached to the flat surface of the resin tray bottom, was attached to a φ100 resin pipe, and the resonance frequency f ₀ was increased to 13.68 MHz. Increased (increased amount 0.12 MHz, increased rate + 0.88%). As a result, the communication distance d was reduced by 9.0% as compared with that before attachment.

Therefore, as shown in FIG. 5, the magnetic sheet 1
When 0b (10 mm □) was pasted on the surface of the cover sheet 9 on the coil 4 at a corresponding position, the resonance frequency f ₀
Was decreased by 0.14 MHz to 13.54 MHz.
This is within the allowable range of the design value (f ₀ = 13.56 MHz), and the desired communication distance was obtained by performing this adjustment. Table 4 and FIG. 6 show the relationship between the number of magnetic sheets 10b attached and the amount of decrease in the resonance frequency at that time.

[0048]

[Table 4]

From Table 4 and FIG. 6, the resonance frequency decreases substantially in proportion to the number of magnetic sheets 10b to be pasted, and the magnetic sheets 10b to be pasted from the amount of deviation from the target value.
It turns out that the number of sheets can be easily calculated. In this way, the resonance frequency can be adjusted simply and reliably by simply sticking the magnetic sheet 10b so as to overlap the coil 4 of the tag 2.

As the magnetic sheet material, amorphous alloy (thin body, flake, fiber, powder, etc.), permalloy (iron-nickel alloy), ferrite (NiZn).
System, MnZn system), pure iron (atomized iron powder, carbonyl iron powder, electrolytic iron powder) and the like can be used, and the form is not limited to a sheet, and may be a foil, a thin plate, or a fiber. . In addition, the above materials are phenol, epoxy,
A form in which a binder dispersed in rubber, vinyl, acrylic, etc. or a paste such as an alcohol, toluene, butyl acetate, a diluent dispersed in water, etc. is applied, or PE, PET,
A form in which the above paste is applied to an organic base material such as PP or PVC may be used.

Further, the position where the conductive sheet 10b or the paste is applied or applied is not limited to the structure shown in FIG. 5, but may be a region overlapping the coil 4 when viewed in the normal direction of the substrate 6,
To clarify the area to be attached or applied, the tag 2 may be provided with a marker 11 as shown in FIG. Further, the shape of the material is not limited to the quadrangular shape, and may be any shape such as a strip shape or a circular shape.

As a device for realizing the resonance frequency adjusting method using a magnetic member such as the magnetic sheet 11b, a device for measuring the resonance frequency of the RFID tag 2 attached to an article and a device for measuring the resonance frequency of a predetermined resonance frequency are used. Calculate the difference between the target value and the measured value, and determine the number, size, area, etc. of the magnetic members to be affixed from the amount of change in the resonance frequency per unit number of magnetic members (for example, per magnetic sheet) obtained by experiment. Any device may be used as long as it is provided with a calculation means and a means for attaching or applying a magnetic member to the RFID tag based on the calculation result.

As described above, according to the structure of the RFID tag, the method of adjusting the resonance frequency, and the resonance frequency adjusting apparatus of this embodiment, the magnetic member for increasing the inductance of the coil 4 forming the resonance circuit is formed after the formation. By sticking or applying it on the cover sheet 9 of the tag 2, the resonance frequency can be reduced. Therefore, by setting a large resonance frequency in advance at the manufacturing stage and attaching the magnetic sheet after attaching the magnetic sheet to the article, the resonance frequency can be accurately adjusted according to the actual usage pattern.

In each of the above embodiments, the capacitor 5 of the resonance circuit is formed by the comb-teeth electrode 7. However, the present invention allows the resonance frequency to be adjusted after the tag 2 is manufactured. The electrode does not necessarily have to have a frequency adjusting function, and may be a capacitor in which ordinary plate electrodes are combined. In addition, although the configuration in which the Al foil 10a is attached in the first embodiment and the configuration in which the magnetic sheet 10b is attached in the second embodiment are described, the attachment of the sheet-shaped member and the application of the paste-shaped member are used together. Alternatively, a conductive member and a magnetic member may be used in combination.

[0055]

As described above, the RFID of the present invention
According to the structure of the tag for use, the method of adjusting the resonance frequency, and the resonance frequency adjusting device, the following effects are achieved.

The first effect of the present invention is during use (after attachment)
It means that the resonance frequency of the tag can be adjusted.

The reason is that after the completion of the tag, a sheet made of a conductive member or a magnetic member is attached to the tag, or a paste containing powder of the above member is applied to increase or decrease the inductance of the antenna coil to reduce the resonance frequency. This is because it can be increased or decreased.

The second effect of the present invention is that the resonance frequency can be adjusted even when the tag is attached to articles having different sizes, shapes and materials and the resonance frequency is largely shifted, and the communication distance is reduced. It can be prevented.

The reason for this is the number and size of sheets to be attached,
This is because the amount of increase / decrease of the resonance frequency can be freely set and the resonance frequency can be adjusted to a desired value by increasing / decreasing the application area of the paste.

As described above, according to the present invention, the resonance frequency can be adjusted regardless of the size, shape and material of the article to which the RFID tag is attached, and the present invention can be applied to a wide range of applications.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an RFID system.

FIG. 2 is a diagram showing a structure of an RFID tag according to a first embodiment of the present invention and a form of attaching a conductive sheet.

FIG. 3 is a diagram showing an effect of the resonance frequency adjusting method according to the first embodiment of the present invention, and is a diagram showing a relationship between the number of conductive sheets attached and an increase amount of the resonance frequency.

FIG. 4 is a diagram showing another structure of the RFID tag according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a structure of an RFID tag and a magnetic sheet attachment mode according to a second embodiment of the present invention.

FIG. 6 is a diagram showing an effect of the resonance frequency adjusting method according to the second embodiment of the present invention, and is a diagram showing a relationship between the number of magnetic sheets attached and a reduction amount of the resonance frequency.

FIG. 7 is a diagram showing a structure of a capacitor section of a resonance circuit of a conventional RFID tag.

[Explanation of symbols]

1 RFID system 2 tags 2a Resonant circuit 2b IC 3 Reader / Writer 3a antenna 3b Communication circuit section 3c arithmetic processing unit 4 coils 4a Top coil 4b Bottom coil 5 capacitors 6 substrate 7 Comb type electrode 7a base 7b finger 7c cut part 8 Counter electrode 9 cover sheet 10a Conductive sheet (Al foil) 10b Magnetic sheet 11 markers 12 Executive electrodes

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koichi Ishiyama             1-12-14 Koishikawa, Bunkyo-ku, Tokyo Mitsubishi Mate             Real Co., Ltd. RFID Business Center F term (reference) 5B035 AA03 AA04 BA05 BB09 BC00                       CA08

Claims (15)

[Claims] 1. An RFID tag in which a resonance circuit composed of a capacitor and an antenna coil is formed on a substrate, and the surface of the resonance circuit is covered with a protective layer, wherein the antenna is provided on the protective layer. A RFID tag characterized in that a frequency adjusting means for changing the inductance of the coil is added, and the resonance frequency of the resonance circuit is adjusted by the frequency adjusting means. 2. The frequency adjusting means is composed of a sheet made of a conductive member or a paste containing powder of the conductive member, and the inside of the antenna coil is viewed from a normal direction of the substrate. The RFID tag according to claim 1, wherein the sheet is attached or the paste is applied on a protective film. 3. The conductive member is made of Al, Cu, Fe, A
The RFID tag according to claim 2, wherein the RFID tag contains one of g and carbon. 4. The frequency adjusting means is made of a sheet made of a magnetic member or a paste containing a powder of the magnetic member, and in a region overlapping with the antenna coil when viewed in the normal direction of the substrate. The RFID tag according to claim 1, wherein the sheet is attached or the paste is applied on a protective film. 5. The RFID tag according to claim 4, wherein the magnetic member contains any one of amorphous alloy, iron-nickel alloy, nickel-zinc alloy, manganese-zinc alloy, and pure iron. . 6. The RFID tag according to any one of claims 1 to 5, wherein a marker that clearly indicates a mounting position of the adjusting means is formed on the protective layer. 7. A method of adjusting a resonance frequency of an RFID tag, wherein a resonance circuit composed of a capacitor and an antenna coil is formed on a substrate, and the surface of the resonance circuit is covered with a protective layer. A resonance frequency adjusting method, wherein the resonance frequency of the resonance circuit is adjusted after the RFID tag is attached to an article by adding a frequency adjusting means for changing the inductance of the antenna coil on the layer. 8. The frequency adjusting means is made of a sheet made of a conductive member or a paste containing a powder of the conductive member, and the frequency adjusting means is provided inside the antenna coil when viewed from a direction normal to the substrate. The resonance frequency adjusting method according to claim 7, wherein the resonance frequency of the resonance circuit is increased by applying the sheet or coating the paste on a protective film. 9. The conductive member is made of Al, Cu, Fe, A
9. The method for adjusting resonance frequency according to claim 8, further comprising a material of g or carbon. 10. The frequency adjusting means is made of a sheet made of a magnetic member or a paste containing a powder of the magnetic member, and in a region overlapping with the antenna coil when viewed in the normal direction of the substrate. 8. The resonance frequency adjusting method according to claim 7, wherein the resonance frequency of the resonance circuit is reduced by applying the sheet or applying the paste on a protective film. 11. The magnetic member is an amorphous alloy, an iron nickel alloy, a nickel zinc alloy, a manganese zinc alloy,
Alternatively, the method for adjusting the resonance frequency according to claim 10, further comprising any one of pure iron materials. 12. The increase / decrease amount of the resonance frequency of the resonance circuit is adjusted by adjusting the number or size of the sheets to be attached or the application area of the paste. A method for adjusting a resonance frequency according to item 1. 13. The resonance frequency adjusting method according to claim 7, wherein a marker is formed on the protective layer to clearly indicate a mounting position of the adjusting means. 14. A resonance frequency adjusting device for an RFID tag, wherein a resonance circuit composed of a capacitor and an antenna coil is formed on a substrate, and the surface of the resonance circuit is covered with a protective layer. Per unit added amount of means for conveying an article to which a tag is attached, means for measuring the resonance frequency of the resonance circuit, target value of a predetermined resonance frequency, and frequency adjusting means composed of a conductive member or a magnetic member The resonance frequency increase / decrease value, and a unit for calculating the amount of the frequency adjusting unit to be added with reference to the measured value, the target value, and the increase / decrease value, and the frequency adjustment of the calculated addition amount. A means for arranging the means on the protective layer in the antenna coil of the RFID tag or in a region overlapping with the antenna coil when viewed from the normal direction of the substrate is reduced. And a resonance frequency adjusting device. 15. In the arranging means, when the measured value is smaller than the target value, the sheet-like or paste-like frequency adjusting means made of the conductive member is attached to the inside of the antenna coil or Applying, when the measured value is larger than the target value, the sheet-shaped or paste-shaped frequency adjusting means made of the magnetic member is attached or applied to a region overlapping with the antenna coil. The resonance frequency adjusting device according to claim 14.