RFID tag, blood collection tube, and antenna

Abstract

To provide an RFID tag to be attached to a container for accommodating a liquid, which offers good communication distance regardless of the present / absence of a liquid.SOLUTION: An RFID tag provided herein is designed to be attached to a container for accommodating a liquid, and comprises an IC chip for recording identification information and an antenna formed of a loop-shaped conductor connected to the IC chip, the antenna having a T-shaped opening having no conductor formed therein.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an RFID (Radio Frequency Identification) tag, a blood collection tube, and an antenna. [Background technology]

[0002] RFID labels that are affixed to adherends are becoming widespread for logistics management and product management. An RFID label is a label that has an RFID tag. An RFID tag has an IC chip and an antenna that is electrically connected to the IC chip. RFID tags are also called wireless tags, IC tags, RF-ID tags, and RF tags.

[0003] Also, as an antenna for an RFID tag, an antenna is known which is configured with a power supply terminal to which an IC chip is connected, a loop antenna connected to the power supply terminal, and a bypass conductive line that bypasses the loop of the loop antenna (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-19905 A [Patent Document 2] International Publication No. 2006 / 077645 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent documents 1 and 2 show that by resonating the capacitance component inside the IC chip with the inductance component of the bypass conductive wire of the antenna, a good communication distance can be obtained in the frequency band in which RFID tags communicate wirelessly.

[0006] However, for example, in the case of RFID tags that are affixed to containers for holding liquids, such as blood collection tubes used in blood tests, there is a problem in that the impedance characteristics of the antenna change when liquid is poured into the container, shortening the communication distance.

[0007] One embodiment of the present invention has been made in consideration of the above problems, and aims to provide an RFID tag to be affixed to a container for holding liquid, which can obtain a good communication distance regardless of whether liquid is present or not. [Means for solving the problem]

[0008] In order to solve the above problems, an RFID tag according to one embodiment of the present invention is an RFID tag to be attached to a container for holding a liquid, and includes an IC chip in which identification information is recorded, and an antenna formed of a loop-shaped conductor connected to the IC chip, and the antenna has a T-shaped opening where the conductor is not formed. The antenna has a rectangular outer shape, the IC chip is electrically connected to a central portion of one side of the rectangle, and the opening includes a first opening extending in a direction parallel to the one side and a second opening connected to the central portion of the first opening, perpendicular to the one side, and extending in a direction opposite to the one side. Effect of the Invention

[0009] According to one embodiment of the present invention, it is possible to provide an RFID tag that is attached to a container for holding liquid and that can obtain a good communication distance regardless of whether or not liquid is present. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of the appearance of a blood collection tube to which an RFID tag according to an embodiment is affixed; [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of an antenna of an RFID tag according to an embodiment. [Diagram 3] FIG. 2 is a diagram showing the shape of an antenna according to an embodiment; [Figure 4] FIG. 4 is a diagram illustrating an example of impedance characteristics of an antenna according to an embodiment. [Diagram 5] 1A and 1B are diagrams illustrating examples of the shape of an antenna according to a comparative example. [Figure 6]FIG. 11 is a diagram showing an example of impedance characteristics of an antenna according to a comparative example. [Figure 7] 11A and 11B are diagrams illustrating examples of the shape of an antenna according to a first modified example. [Figure 8] FIG. 11 is a diagram showing an example of impedance characteristics of an antenna according to a first modified example. [Figure 9] 13A and 13B are diagrams illustrating examples of the shape of an antenna according to a second modified example. [Figure 10] FIG. 11 is a diagram showing an example of impedance characteristics of an antenna according to a second modified example. [Figure 11] 13A and 13B are diagrams illustrating examples of the shape of an antenna according to a third modified example. [Figure 12] FIG. 13 is a diagram showing an example of impedance characteristics of an antenna according to a third modified example. [Figure 13] 13A and 13B are diagrams illustrating examples of the shape of an antenna according to a fourth modified example. [Figure 14] FIG. 13 is a diagram showing an example of impedance characteristics of an antenna according to a fourth modified example. [Figure 15] 13A and 13B are diagrams illustrating examples of the shape of an antenna according to a fifth modified example. [Figure 16] FIG. 13 is a diagram showing an example of impedance characteristics of an antenna according to a fifth modified example. [Figure 17] 13A and 13B are diagrams illustrating examples of the shape of an antenna according to a sixth modified example. [Figure 18] FIG. 13 is a diagram showing an example of impedance characteristics of an antenna according to a sixth modified example. [Figure 19] FIG. 2 is a diagram showing an example of an arrangement pattern of blood collection tubes according to an embodiment. [Figure 20] FIG. 11 is a diagram showing an example of an evaluation result of an RFID tag according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of the present invention will be described in detail with reference to the drawings. In the following description, common parts in each drawing may be denoted by the same reference numerals and description thereof may be omitted. In addition, in order to facilitate understanding, the scale of each member in each drawing may differ from the actual scale. In each embodiment, deviations in directions such as parallel, perpendicular, horizontal, vertical, up / down, left / right, etc., are permitted to a degree that does not impair the effects of the present invention. In addition, the X-axis direction, the Y-axis direction, and the Z-axis direction each include a direction parallel to the X-axis, a direction parallel to the Y-axis, and a direction parallel to the Z-axis, respectively. The X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The XY plane, the YZ plane, and the ZX plane each include a virtual plane parallel to the X-axis direction and the Y-axis direction, a virtual plane parallel to the Y-axis direction and the Z-axis direction, and a virtual plane parallel to the Z-axis direction and the X-axis direction, respectively. In the X-axis direction, the direction indicated by the arrow is the positive X-axis direction, and the opposite direction to the said direction is the negative X-axis direction. In the Y-axis direction, the direction indicated by the arrow is the positive Y-axis direction, and the opposite direction to the said direction is the negative Y-axis direction. In the Z-axis direction, the direction indicated by the arrow is the positive Z-axis direction, and the opposite direction is the negative Z-axis direction.

[0012] <Appearance of blood collection tube> Fig. 1 is a diagram showing an example of the appearance of a blood collection tube to which an RFID tag according to one embodiment is affixed. In the example of Fig. 1, the appearance of a blood collection tube 10 is shown as an example of a container for holding a liquid. An RFID tag 100 is affixed to the blood collection tube 10 within a predetermined affixing area 12 on the outer periphery. Preferably, a cap 11 is provided at the tip of the blood collection tube 10.

[0013] The blood collection tube 10 is made of, for example, plastic such as polyethylene terephthalate. However, the blood collection tube 10 is not limited to this, and may be made of other materials such as glass.

[0014] Note that the blood collection tube 10 is an example of a container for holding liquid. For example, it may be a container other than the blood collection tube 10 such as a test tube, a urine collection tube, an ampule, etc. Also, blood is an example of the liquid to be put into the container. For example, it may be a liquid other than blood such as urine, a drink, a drug, water, etc. Here, as an example, the following description will be made assuming that the container for holding liquid is the blood collection tube 10.

[0015] <Configuration of RFID Tag> FIG. 2 is a diagram showing a configuration example of an RFID tag according to an embodiment. The RFID tag 100 includes, for example, a strip-shaped sheet 200, an IC chip 210 in which identification information is recorded, and an antenna 220 formed of a loop-shaped conductor connected to the IC chip 210. Also, the shape of the inner circumference 221 of the antenna 220 is T-shaped.

[0016] The sheet 200 and the antenna 220 have an outer shape corresponding to the blood collection tube 10 as shown in FIG. 1, for example. For example, it is desirable that the depth D0 of the sheet 200 and the depth D1 of the antenna 220 are shorter than the minimum value of the outer circumference within a predetermined pasting range 12 of the blood collection tube 10. Thereby, for example, as shown in FIG. 1, the RFID tag 100 can be pasted on the blood collection tube 10 so that the RFID tags 100 do not overlap. Also, it is desirable that the width W0 of the sheet 200 and the width W1 of the antenna 220 are within the predetermined pasting range 12 of the blood collection tube 10.

[0017] Note that the width W1 and the depth D1 of the antenna 220 can be arbitrarily determined within the above range. For example, when the operating frequency of the RFID tag 100 is 920 MHz, W1 can be 20.00 mm to 50.00 mm, preferably 30.00 mm to 40.00 mm. Also, D1 can be 13.00 mm to 18.00 mm, preferably 15.00 mm to 17.00 mm.

[0018] The sheet 200 is, for example, a film formed in a band shape by laminating a plurality of synthetic resin films such as polyethylene terephthalate, polypropylene, etc. However, the sheet 200 is not limited to this, and may be paper, etc. The IC chip 210 and the antenna 220 are disposed so as to be sandwiched between, for example, a plurality of laminated synthetic resin films etc. The RFID tag 100 may be provided on a label to be attached to the blood collection tube 10.

[0019] IC chip 210 is an integrated circuit for an RFID system in which identification information is recorded, and is electrically connected to antenna 220. IC chip 210 receives radio waves transmitted at a predetermined radio frequency (for example, 920 MHz band: 860 MHz to 960 MHz) from a tag reader of the RFID system at antenna 220, and generates power from the received radio waves to activate itself. IC chip 210 also transmits radio waves including identification information pre-recorded in IC chip 104 to the tag reader using the generated power.

[0020] The antenna 220 is formed in a loop shape from a highly conductive conductor (for example, a metal such as copper or aluminum). The inner circumference 221 of the antenna 220 is T-shaped, and no conductor is formed inside this inner circumference 221. In this embodiment, the part inside this inner circumference 221 where no conductor is formed is called an opening 222. In this way, the antenna 220 is formed from a loop-shaped conductor connected to the IC chip 210, and has a T-shaped opening 222 where no conductor is formed.

[0021] Preferably, the outer shape of antenna 220 is a rectangle with a width W1 and a depth D1, as shown in Fig. 2. Also, opening 222 includes a first opening 223 extending in a direction (X-axis direction) parallel to one side of the rectangle on which IC chip 210 is mounted, and a second opening 224 connected to the center of first opening 223 and extending in a direction (negative Y-axis direction) perpendicular to one side of the rectangle on which IC chip 210 is mounted. Note that in Fig. 2, the two-dot chain line indicating the boundary between first opening 223 and second opening 224 is an imaginary line and does not actually exist.

[0022] Preferably, the RFID tag 100 is attached to the blood collection tube 10 so that the longitudinal direction of the blood collection tube 10 and the direction in which the first opening 223 extends (X-axis direction) are approximately parallel. This allows for better communication characteristics to be obtained. Note that, when attaching the RFID tag 100 to the blood collection tube 10, no significant difference was observed in communication characteristics between when the RFID tag 100 is oriented in the X-plus direction shown in FIG. 2 toward the cap 11 side of the blood collection tube 10 and when the RFID tag 100 is oriented in the X-minus direction.

[0023] The RFID tag 100 can also be attached to the blood collection tube 10 so that the longitudinal direction of the blood collection tube 10 and the direction in which the first opening 223 extends intersect, for example.

[0024] The width W2 and depth D2 of the first opening 223 and the width W3 and depth D3 of the second opening 224 can be determined arbitrarily. For example, when the frequency used by the RFID tag 100 is 920 MHz, W2 can be set to 18.00 mm to 25.00 mm, preferably 20.00 mm to 23.00 mm, and more preferably 21.10 mm to 22.10 mm. D2 can be set to 1.00 mm to 7.00 mm, preferably 3.00 mm to 5.00 mm, and more preferably 3.50 mm to 4.50 mm. W3 can be set to 1.00 mm to 7.00 mm, preferably 3.00 mm to 5.00 mm, and more preferably 3.7 mm to 4.7 mm. D3 can be set to 3.00 mm to 9.00 mm, preferably 5.00 mm to 7.00 mm, and more preferably 5.50 mm to 6.5 mm.

[0025] Antenna 220 is formed of a conductor, for example, by pressing, etching, or plating a metal foil such as copper or aluminum, or by silk screen printing of a metal paste. When the conductor is aluminum, the thickness of the conductor can be, for example, 5 μm to 40 μm, and preferably 7 μm to 30 μm. In addition, antenna 220 is hatched in FIG. 2 and other drawings, but this hatching indicates that antenna 220 is made of metal and does not indicate a pattern.

[0026] In the above configuration, IC chip 210 has an internal capacitance, and a resonant circuit (matching circuit) is formed by this internal capacitance and the inductance component of antenna 220. In this resonant circuit, at a resonant frequency where the internal capacitance of IC chip 210 and the inductance component of antenna 220 resonate, the imaginary component becomes nearly zero, thereby matching the impedance and ensuring a sufficient communication distance.

[0027] The RFID tag 100 is configured to obtain a good communication distance at a frequency of, for example, 920 MHz band (860 MHz to 960 MHz, preferably 915 MHz to 935 MHz) regardless of the presence or absence of liquid (for example, blood) inside the blood collection tube 10.

[0028] <Antenna shape and impedance characteristics> FIG. 3 is a diagram showing the shape of an antenna according to an embodiment. This diagram shows an example of the shape of the antenna 220 that provides good communication characteristics. In FIG. 3, the width W1 of the antenna 220 is 35.00 mm, the depth D1 is 16.00 mm, and the opening 222 is formed so as to be symmetrical with respect to the center line 225. Note that the symmetry is allowed to have an error or deviation to the extent that does not impair the effect of the present invention. In addition, the T-shaped shape of the opening 222 of the antenna 220 was changed, and prototypes were manufactured and measured, and the T-shaped shape of the opening 222 was determined so that good communication characteristics could be obtained regardless of the presence or absence of liquid.

[0029] As a result, when the width W2 of the first opening 223 was set to 21.60 mm, the depth D2 was set to 4.00 mm, and the width W3 of the second opening 224 was set to 4.20 mm, and the depth D3 was set to 6.00 mm, good communication characteristics were obtained regardless of the presence or absence of liquid inside the blood collection tube 10. The width D4 of the conductor portion connecting the IC chip 210 was set to 1.00 mm. Aluminum (thickness: 10 μm) was used as the conductor forming the antenna 220.

[0030] Fig. 4 is a diagram showing an example of impedance characteristics of an antenna according to an embodiment. Fig. 4(A) shows a simulation result of the impedance characteristics of the antenna 220 when no liquid is contained in the blood collection tube 10. Fig. 4(B) shows a simulation result of the impedance characteristics of the antenna 220 when liquid (water) is contained in the blood collection tube 10.

[0031] 4(A) and (B), the impedance Z of antenna 220 is set to "Z=R+jX," and the vertical axis indicates the real part R and imaginary part X of impedance Z. The horizontal axis indicates frequency. Note that the solid line graph is a plot of the real part R corresponding to each frequency, and the dashed line is a plot of the imaginary part X corresponding to each frequency.

[0032] In the example of Fig. 4(A), it is shown that at 920 MHz, which is the center frequency of the frequency band used by the RFID tag 100 for communication, the value of the real part R of the impedance Z of the antenna 220 is about 4.4 Ω, and the value of the imaginary part X is about 213.0 Ω. In the example of Fig. 4(B), it is shown that at a frequency of 920 MHz, the value of the real part R of the impedance Z of the antenna 220 is about 305.0 Ω, and the value of the imaginary part X is about 236.0 Ω. In this way, the impedance Z of the antenna 220 changes depending on whether or not there is liquid in the blood collection tube 10.

[0033] Furthermore, from the results of prototyping multiple antennas, it was found that good communication characteristics can be obtained when the value of the imaginary part X at a frequency of 920 MHz is around 213 Ω (for example, about 190 Ω to 240 Ω). From this, it is considered that when the value of the imaginary part X of the impedance Z of the antenna is around 213 Ω, the internal capacitance of the IC chip 210 and the inductance component of the antenna 220 resonate in the 920 MHz band, and the impedances are matched.

[0034] 4(A) and (B), the value of the imaginary part X of the impedance Z of the antenna 220 is between 190Ω and 240Ω at 920 MHz, and it is considered that good communication characteristics can be obtained regardless of the presence or absence of liquid inside the blood collection tube 10. The evaluation results of the communication characteristics of the RFID tag 100 equipped with the antenna 220 will be described later.

[0035] (Comparative Example) Fig. 5 is a diagram showing an example of the shape of an antenna according to a comparative example. Antenna 500 shown in Fig. 5 has the same outer shape (W1 = 35.00 mm, D1 = 16.00 mm) as antenna 220 according to an embodiment shown in Fig. 3, and opening 502 on the inside of inner periphery 501 of antenna 500 is formed in a rectangular shape. Moreover, antenna 500 is formed so that the area of ​​opening 502 is the same as the area of ​​opening 222 of antenna 220 according to an embodiment shown in Fig. 3.

[0036] 6 is a diagram showing an example of the impedance characteristic of an antenna according to a comparative example. FIG. 6(A) shows a simulation result of the impedance characteristic of the antenna 500 when there is no liquid in the blood collection tube 10. In the example of FIG. 6(A), it is shown that at a frequency of 920 MHz used for communication by the RFID tag 100, the value of the real part R of the impedance Z of the antenna 500 is about 3.8Ω, and the value of the imaginary part X is about 204.7Ω. Thus, when there is no liquid in the blood collection tube 10, the impedance Z of the antenna 500 according to the comparative example has impedance characteristics close to those of the antenna 220 according to the embodiment shown in FIG. 3.

[0037] On the other hand, Fig. 6(B) shows a simulation result of the impedance characteristic of the antenna 500 when liquid (water) is contained in the blood collection tube 10. In the example of Fig. 6(B), it is shown that at a frequency of 920 MHz, the value of the real part R of the impedance Z of the antenna 500 is about 164.8Ω, and the value of the imaginary part X is about 285.5Ω. As described above, it can be seen that the impedance Z of the antenna 500 according to the comparative example changes to about 285Ω in the case where liquid is contained in the blood collection tube 10.

[0038] As described above, it can be seen that the antenna 220 according to the embodiment shown in FIG. 3 has a smaller change in the value of the imaginary part X of the impedance Z, i.e., the resonant frequency, compared to the antenna 500 according to the comparative example shown in FIG. 5, particularly when the blood collection tube 10 contains liquid.

[0039] <Modification> Next, the change in impedance characteristics when the T-shape of opening 222 of antenna 220 is changed will be described by taking a number of modified examples as examples.

[0040] (First Modification) Fig. 7 is a diagram showing an example of the shape of an antenna according to a first modified example. Antenna 700 according to the first modified example shown in Fig. 7 has the same outer diameter (W1 = 35.00 mm, D1 = 16.00 mm) as antenna 220 according to an embodiment shown in Fig. 3. In addition, antenna 700 is formed such that the area of ​​opening 702 on the inside of inner circumference 701 is larger than the area of ​​opening 222 of antenna 220 according to an embodiment shown in Fig. 3.

[0041] Fig. 8 is a diagram showing an example of impedance characteristics of the antenna according to the first modified example. Fig. 8(A) shows a simulation result of the impedance characteristics of the antenna 700 when no liquid is contained in the blood collection tube 10. Fig. 8(B) shows a simulation result of the impedance characteristics of the antenna 700 when liquid (water) is contained in the blood collection tube 10.

[0042] The example of Fig. 8(A) shows that the real part R of the impedance Z of the antenna 700 is approximately 10.7Ω and the imaginary part X is approximately 332.0Ω at a frequency of 920 MHz used for communication by the RFID tag 100. The example of Fig. 8(B) shows that the real part R of the impedance Z of the antenna 700 is approximately 442.0Ω and the imaginary part X is approximately -139.0Ω at a frequency of 920 MHz.

[0043] In addition, in FIG. 8A, the frequency at which the value of the imaginary part X of the impedance Z of the antenna 700 is around 213 Ω varies down to a low frequency of around 700 MHz.

[0044] In this manner, by increasing the area inside the T-shape of opening 222 of antenna 220 according to the embodiment shown in FIG. 3, the resonance frequency of antenna 220 can be changed (adjusted) in the lower direction.

[0045] (Second Modification) Fig. 9 is a diagram showing an example of the shape of an antenna according to a second modified example. An antenna 900 according to the second modified example shown in Fig. 9 has the same outer shape (W1 = 35.00 mm, D1 = 16.00 mm) as the antenna 220 according to the embodiment shown in Fig. 3. In addition, the area of ​​an opening 902 on the inside of an inner circumference 901 of the antenna 900 is formed smaller than the area of ​​the opening 222 of the antenna 220 according to the embodiment shown in Fig. 3.

[0046] Fig. 10 is a diagram showing an example of impedance characteristics of an antenna according to the second modified example. Fig. 10(A) shows a simulation result of the impedance characteristics of the antenna 900 when no liquid is contained in the blood collection tube 10. Fig. 10(B) shows a simulation result of the impedance characteristics of the antenna 900 when liquid (water) is contained in the blood collection tube 10.

[0047] The example of Fig. 10(A) shows that at a frequency of 920 MHz used for communication by the RFID tag 100, the real part R of the impedance Z of the antenna 900 has a value of approximately 2.6 Ω, and the imaginary part X has a value of approximately 141.7 Ω. The example of Fig. 10(B) shows that at a frequency of 920 MHz, the real part R of the impedance Z of the antenna 900 has a value of approximately 171.9 Ω, and the imaginary part X has a value of approximately 205.0 Ω.

[0048] In addition, in FIG. 10A, the frequency at which the value of the imaginary part X of the impedance Z of the antenna 900 is around 213 Ω varies up to a high frequency around 1150 MHz.

[0049] In this way, by reducing the area of ​​the opening 222 of the antenna 220 according to the embodiment shown in FIG. 3, the resonance frequency of the antenna 220 can be changed (adjusted) in the higher direction.

[0050] (Third Modification) Fig. 11 is a diagram showing an example of the shape of an antenna according to a third modified example. The antenna 1100 according to the third modified example shown in Fig. 11 has the same outer shape (W1 = 35.00 mm, D1 = 16.00 mm) as the antenna 220 according to the embodiment shown in Fig. 3. The antenna 1100 according to the third modified example is formed so that the area of ​​the opening 1104 on the inside of the inner circumference 1101 is larger than the area of ​​the opening 222 of the antenna 220 by changing the size (area) of the two rectangular parts 1102 and 1103 shown in Fig. 11. The two-dot chain line in Fig. 11 is a virtual line for explaining the positions of the rectangular parts 1102 and 1103, and does not actually exist.

[0051] Fig. 12 is a diagram showing an example of impedance characteristics of an antenna according to the third modified example. Fig. 12(A) shows a simulation result of the impedance characteristics of the antenna 1100 when no liquid is contained in the blood collection tube 10. Fig. 12(B) shows a simulation result of the impedance characteristics of the antenna 1100 when liquid (water) is contained in the blood collection tube 10.

[0052] The example of Fig. 12(A) shows that the real part R of the impedance Z of the antenna 1100 is about 5.54Ω and the imaginary part X is about 236.2Ω at a frequency of 920 MHz used for communication by the RFID tag 100. The example of Fig. 12(B) shows that the real part R of the impedance Z of the antenna 1100 is about 392.3Ω and the imaginary part X is about 181.4Ω at a frequency of 920 MHz.

[0053] Also, in FIG. 12(A), it can be seen that the frequency at which the value of the imaginary part X of the impedance Z of the antenna 1100 is around 213 Ω is around 870 MHz.

[0054] In this way, when increasing the area of ​​opening 222 of antenna 220 according to one embodiment shown in FIG. 3, the impedance characteristics of antenna 220 can be fine-tuned by reducing the size (area) of rectangular portions 1102, 1103.

[0055] (Fourth Modification) Fig. 13 is a diagram showing an example of the shape of an antenna according to a fourth modified example. An antenna 1300 according to a fourth modified example shown in Fig. 13 has the same outer shape (W1 = 35.00 mm, D1 = 16.00 mm) as the antenna 220 according to an embodiment shown in Fig. 3. In addition, the antenna 1300 according to the fourth modified example is formed so that the area of ​​an opening 1302 on the inside of an inner circumference 1301 is smaller than the area of ​​an opening 222 of the antenna 220 by changing the size (area) of two rectangular parts 1102 and 1103.

[0056] Fig. 14 is a diagram showing an example of impedance characteristics of an antenna according to the fourth modified example. Fig. 14(A) shows a simulation result of the impedance characteristics of the antenna 1300 when no liquid is contained in the blood collection tube 10. Fig. 14(B) shows a simulation result of the impedance characteristics of the antenna 1300 when liquid is contained in the blood collection tube 10.

[0057] 14A shows that the real part R of the impedance Z of the antenna 1300 is about 3.45Ω and the imaginary part X is about 193.0Ω at a frequency of 920 MHz used for communication by the RFID tag 100. The example of Fig. 14B shows that the real part R of the impedance Z of the antenna 1300 is about 210.6Ω and the imaginary part X is about 254.2Ω at a frequency of 920 MHz.

[0058] Also, in FIG. 14(A), it can be seen that the frequency at which the value of the imaginary part X of the impedance Z of the antenna 1300 is around 213 Ω is around 950 MHz.

[0059] In this way, when reducing the area of ​​opening 222 of antenna 220 according to one embodiment shown in FIG. 3, the impedance characteristics of antenna 220 can be fine-tuned by increasing the size (area) of rectangular portions 1102, 1103.

[0060] (Fifth Modification) Fig. 15 is a diagram showing an example of the shape of an antenna according to a fifth modified example. An antenna 1500 according to a fifth modified example shown in Fig. 15 has the same outer shape (W1 = 35.00 mm, D1 = 16.00 mm) as the antenna 220 according to an embodiment shown in Fig. 3. In addition, when the area of ​​the opening 222 of the antenna 220 according to an embodiment shown in Fig. 3 is increased, the antenna 1500 according to the fifth modified example increases the area of ​​the opening 1502 inside the inner circumference 1501 while maintaining a similar T-shaped shape (similarity).

[0061] Fig. 16 is a diagram showing an example of impedance characteristics of an antenna according to the fifth modified example. Fig. 16(A) shows a simulation result of the impedance characteristics of the antenna 1500 when no liquid is contained in the blood collection tube 10. Fig. 16(B) shows a simulation result of the impedance characteristics of the antenna 1500 when liquid (water) is contained in the blood collection tube 10.

[0062] The example of Fig. 16(A) shows that at a frequency of 920 MHz used for communication by the RFID tag 100, the real part R of the impedance Z of the antenna 1500 has a value of approximately 0.93 Ω, and the imaginary part X has a value of approximately 287.0 Ω. The example of Fig. 16(B) shows that at a frequency of 920 MHz, the real part R of the impedance Z of the antenna 1500 has a value of approximately 492.4 Ω, and the imaginary part X has a value of approximately 37.7 Ω.

[0063] Also, in FIG. 16(A), it can be seen that the frequency at which the value of the imaginary part X of the impedance Z of the antenna 1500 is around 213 Ω is around 750 MHz.

[0064] In this way, when increasing the area of ​​opening 222 of antenna 220 according to one embodiment shown in FIG. 3, the impedance characteristics of antenna 220 can be changed more significantly by increasing the area of ​​opening 222 while maintaining the T-shape similarity (similarity).

[0065] (Sixth Modification) Fig. 17 is a diagram showing an example of the shape of an antenna according to a sixth modified example. The antenna 1700 according to the sixth modified example shown in Fig. 17 has the same outer shape (W1 = 35.00 mm, D1 = 16.00 mm) as the antenna 220 according to the embodiment shown in Fig. 3. In addition, when reducing the area of ​​the opening 222 of the antenna 220 according to the embodiment shown in Fig. 3, the antenna 1700 according to the sixth modified example reduces the area of ​​the opening 1702 inside the inner circumference 1701 while maintaining a similar T-shaped shape (similarity).

[0066] Fig. 18 is a diagram showing an example of impedance characteristics of an antenna according to the sixth modified example. Fig. 18(A) shows a simulation result of the impedance characteristics of the antenna 1700 when no liquid is contained in the blood collection tube 10. Fig. 18(B) shows a simulation result of the impedance characteristics of the antenna 1700 when liquid (water) is contained in the blood collection tube 10.

[0067] In the example of FIG. 18(A), it is shown that at a frequency of 920 MHz used for communication by the RFID tag 100, the value of the real part R of the impedance Z of the antenna 1700 is approximately 1.79 Ω, and the value of the imaginary part X is approximately 137.3 Ω. In the example of FIG. 18(B), it is shown that at a frequency of 920 MHz, the value of the real part R of the impedance Z of the antenna 1700 is approximately 66.0 Ω, and the value of the imaginary part X is approximately 181.7 Ω.

[0068] Also, in FIG. 18(A), it is estimated that the frequency at which the value of the imaginary part X of the impedance Z of the antenna 1800 becomes around 213 Ω is 1200 MHz or higher.

[0069] Thus, when reducing the area of the opening 222 of the antenna 220 according to the embodiment shown in FIG. 3, while maintaining the T-shaped similarity, by reducing the area of the opening 222, the impedance characteristics of the antenna 220 can be changed more significantly.

[0070] From the above, it is considered that the antenna 220 according to the embodiment shown in FIG. 3 can adjust the resonance frequency of the antenna 220 according to the area inside the T-shape of the inner circumference 221.

[0071] Also, it is considered that the antenna 220 can adjust the impedance of the antenna 220, particularly the impedance when the collecting tube 10 contains liquid, due to the T-shaped shape of the inner circumference 221.

[0072] <Evaluation Results of RFID Tag> Subsequently, the evaluation results of attaching the RFID tag 100 having the antenna 220 according to the embodiment shown in FIG. 3 to the collecting tube 10 and evaluating the reading characteristics of the identification information (tag ID) will be described.

[0073] 19A to 19D are diagrams showing examples of arrangement patterns of blood collection tubes according to an embodiment. Here, as shown in Fig. 19A to 19D, a total of 100 blood collection tubes 10 arranged in 10 columns and 10 rows were set in a tag ID reader, and tag IDs were read 100 times to measure the number of times the tag IDs of all 100 tubes were read.

[0074] The blood collection tubes 10 used were made of plastic (polyethylene terephthalate). The RFID tag 100 was attached to each blood collection tube 10 so that the X-plus direction of the RFID tag 100 as shown in FIG. 2 was on the cap 11 side and the longitudinal direction of the blood collection tube 10 and the longitudinal direction of the RFID tag 100 were approximately parallel to each other.

[0075] Here, as shown in FIG. 19(A), an arrangement pattern in which four blood collection tubes 10 are arranged as a set with the RFID tags 100 facing inward of the four blood collection tubes 10 is called "arrangement pattern 1". Also, as shown in FIG. 19(B), an arrangement pattern in which the RFID tags 100 of the blood collection tubes 10 are arranged in one direction (for example, forward) is called "arrangement pattern 2". Furthermore, as shown in FIG. 19(C), an arrangement pattern in which the RFID tags 100 of the blood collection tubes 10 in the outermost row are arranged facing outward, and the other blood collection tubes 10 are arranged as shown in FIG. 19(C) is called "arrangement pattern 3". Furthermore, as shown in FIG. 19(D), an arrangement pattern in which the RFID tags 100 of the blood collection tubes 10 in the outermost row are arranged facing inward, and the other blood collection tubes 10 are arranged as shown in FIG. 19(D) is called "arrangement pattern 4".

[0076] Fig. 20 is a diagram showing the evaluation results of the RFID tag according to one embodiment. As the evaluation content, the RFID tag 100 equipped with the antenna 220 according to one embodiment shown in Fig. 3 was attached to a blood collection tube 10, and the tag ID was read by a reader 100 times for each of the arrangement patterns 1 to 4. The transmission output level of the reader was set to 19 dBm.

[0077] For reference, a similar reading was also performed on blood collection tubes equipped with existing RFID tags.

[0078] Figure 20(A) shows the evaluation results in which the tag IDs were read 100 times for each of array patterns 1 to 4 when the blood collection tube 10 was empty (contains no liquid), and the number of times that all (100) were successfully read was recorded.

[0079] 20(A), the blood collection tubes 10 to which the RFID tag 100 according to this embodiment is attached were successfully read all 100 times in each of the arrangement patterns 1 to 4. On the other hand, for the blood collection tubes to which the conventional RFID tag is attached, reading failed in the arrangement patterns 1, 3, and 4, and in particular, in the arrangement pattern 1, the number of times that all the tags were successfully read was 0.

[0080] Figure 20(B) shows the evaluation results in which the tag IDs were read 100 times for each of array patterns 1 to 4 when water (an example of a liquid) was contained in the blood collection tube 10, and the number of times that all IDs (100 IDs) were successfully read was recorded.

[0081] 20(B), the blood collection tubes 10 to which the RFID tag 100 according to this embodiment is attached were successfully read all 100 times in each of the arrangement patterns 1 to 4. On the other hand, the blood collection tubes to which the conventional RFID tag is attached were successfully read all 100 times in the arrangement patterns 2 to 4, but in the arrangement pattern 1, all (100) were successfully read only four times.

[0082] Thus, according to this embodiment, in the RFID 100 tag attached to a container for holding liquid, such as a blood collection tube 10, a good communication distance can be obtained regardless of whether or not liquid is present.

[0083] Furthermore, the antenna 220 provided in the RFID tag 100 according to this embodiment can change the resonant frequency of the antenna 220 by changing the area of ​​the opening without changing the external shape, making it suitable for small containers with limited external shapes.

[0084] Furthermore, in the antenna 220 of this embodiment, for example, by changing the T-shape of the opening (to a non-similar shape) while maintaining the area of ​​the opening 222 where no conductor is formed, it becomes easy to adjust the impedance characteristics when liquid is poured into it.

[0085] As described above, according to the embodiment of the present invention, it is possible to provide RFID tag 100 that is attached to a container for holding liquid and that can obtain a good communication distance regardless of whether liquid is present or not.

[0086] The configurations shown in the above embodiments are examples of the contents of the present invention, and may be combined with other known technologies. Parts of the configurations may be omitted or modified without departing from the gist of the present invention. [Explanation of symbols]

[0087] 10 Blood collection tube (an example of a container) 100 RFID Tags 210 IC chip 220 Antenna 221 Inner circumference of antenna 222 Opening 223 First Opening 224 Second Opening

Claims

1. An RFID tag to be attached to a container for holding a liquid, An IC chip in which identification information is recorded; an antenna formed of a loop-shaped conductor connected to the IC chip; the antenna has a T-shaped opening where the conductor is not formed, The antenna has a rectangular outer shape, the IC chip is electrically connected to a central portion of the rectangular piece; The opening is a first opening extending in a direction parallel to the strip; a second opening connected to a central portion of the first opening and extending perpendicular to the first strip and in a direction opposite to the first strip; Including, RFID tag.

2. The RFID tag according to claim 1 , wherein the resonant frequency of the antenna is adjusted according to an area of ​​the opening.

3. The RFID tag according to claim 1 , wherein the impedance of the antenna is adjusted by the T-shape of the opening.

4. The RFID tag of claim 3 , wherein the T-shape of the opening adjusts the impedance of the antenna when the container contains liquid.

5. The RFID tag according to claim 1 , wherein the frequencies used by the RFID tag for communication include the 920 MHz band (860 MHz to 960 MHz).

6. The RFID tag according to claim 1 , wherein the container is a blood collection tube for holding blood.

7. A blood collection tube having the RFID tag according to any one of claims 1 to 6 attached thereto.

8. An antenna used in an RFID tag attached to a container for holding a liquid, It is formed of a loop-shaped conductor, the loop-shaped conductor has a T-shaped opening where the conductor is not formed, The antenna has a rectangular outer shape, An IC chip on which identification information is recorded is electrically connected to the central portion of the rectangular piece; The opening is a first opening extending in a direction parallel to the strip; a second opening connected to a central portion of the first opening and extending perpendicular to the first strip and in a direction opposite to the first strip; Including, antenna.

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