JP5156609B2 - Non-contact information medium - Google Patents

Description

  The present invention relates to a non-contact information processing medium that exchanges information with the outside by using radio waves.

  A coil antenna used for exchanging information using electromagnetic induction is constituted by a resonance circuit, and normally, the resonance frequency is adjusted (tuned) in order to efficiently exchange information. Important parameters that determine the resonant frequency of the resonant circuit include the self-inductance and capacitance of the resonant circuit. The resonance frequency is usually adjusted by changing these self-inductance and capacitance values.

  On the other hand, mutual inductance occurs when a plurality of electric circuits having self-inductance are arranged close to each other. This mutual inductance is also an important parameter for efficient transmission and reception of information. Usually, it is as large as possible in the assumed usage environment for the purpose of strengthening the coupling of both antennas on the transmission / reception side of communication. Designed to be

  Incidentally, a non-contact information medium is one of applications using a coil antenna. Since the non-contact information medium is not in contact with the reader / writer, it does not cause a contact failure and can be used at a position away from the reader / writer. In addition, the non-contact method has features such as resistance to dirt, rain, and static electricity, and demand is increasing due to its high security level.

  The non-contact information medium obtains operating power by electromagnetic induction using radio waves received from the reader / writer, and exchanges information with the reader / writer using radio waves of a predetermined frequency. For this reason, the non-contact information medium and the reader / writer have a built-in coil antenna for transmitting and receiving radio waves of a predetermined frequency.

  Here, a conventional non-contact information medium basically includes a coil that forms a loop antenna that receives power from outside and transmits and receives information, a capacitor that forms a resonance circuit with the coil, and a non-contact And an IC chip for controlling the processing operation of the information medium. In order to operate such a non-contact information medium, the non-contact information medium is disposed within a communication range near the reader / writer. As a result, an interaction occurs between the resonance circuit of the non-contact information medium and the resonance circuit of the reader / writer, and an induced current is generated in the coil forming the loop antenna of the non-contact information medium. Using this induced current as an operating power supply, the IC chip operates and transmits information to the reader / writer via a coil forming a loop antenna. In this way, the non-contact information medium and the reader / writer perform wireless communication to transmit / receive information (see, for example, Patent Document 1).

  However, when a plurality of non-contact information media are arranged in the vicinity of the reader / writer, an interaction occurs not only between the non-contact information medium and the reader / writer but also between the non-contact information media. In such a case, the environment at the time of use differs from the environment assumed at the time of design, the resonance frequency of the non-contact information medium changes, and the influence of the interaction with the reader / writer is affected. In many cases, communication becomes impossible.

  In order to solve these problems, a chip coil (lumped constant type inductor) is provided in a part of the coil of the non-contact information medium to reduce the interaction between the non-contact information medium and the frequency of the radio wave used for communication. A technique for improving the reading performance when a plurality of non-contact information media are arranged in the vicinity of the reader / writer by matching the resonance frequency of the non-contact information medium is disclosed (for example, see Patent Document 2). ).

JP 2001-34725 A JP 2006-67479 A

  However, since mutual inductance still exists between the coil antennas built in each of the two overlapping non-contact information media, it is different if it is assumed that more non-contact information media are read in layers. Countermeasures were needed. As an example of this measure, it is conceivable to increase the self-inductance of the chip coil. However, in this case, the shape of the chip coil becomes large, which is an obstacle to downsizing the non-contact information medium.

  The present invention has been made in view of the above, and even when a large number of identical objects are stacked, information can be exchanged with the outside via radio waves individually and reliably. An object is to provide a suitable non-contact information medium.

  In order to solve the above-described problems and achieve the object, a non-contact information medium according to the present invention includes a main loop that circulates an outer edge of a predetermined region on a plane over substantially the entire circumference, and the main loop on the plane. A loop antenna that is wound around a region having a smaller area than a region surrounding the main loop, and has a coil connected in series to the main loop, and transmits and receives radio waves to and from the outside, and a capacitor connected in parallel to the main loop And an IC chip that is connected in parallel to the capacitor and receives a radio wave propagated from outside and transmits a radio wave responding to the received radio wave to the outside, and passes through the plane within the predetermined area. And a pattern having a rotational symmetry of 180 degrees about a straight line orthogonal to the plane as a rotation axis, and overlapping the coil along a direction orthogonal to the plane. An electric conductor disposed, characterized in that it comprises a.

  In the non-contact information medium according to the present invention, in the above invention, the loop antenna includes a plurality of the coils, and the arrangement pattern of the plurality of coils has a rotational symmetry of 180 degrees with respect to the rotation axis. It is characterized by having.

  Further, the non-contact information medium according to the present invention has a plate shape according to the above invention, and the loop antenna, the capacitor, the IC chip, and the electric conductor are provided on any of the surfaces parallel to the plane. It further comprises a substrate.

  In the non-contact information medium according to the present invention as set forth in the invention described above, the base material has a rotational symmetry of 180 degrees with respect to the rotation axis together with the arrangement pattern of the electric conductor.

  In the non-contact information medium according to the present invention, in the above invention, the base material has a shape having rotational symmetry of 180 degrees with at least one straight line passing through the surface as a second rotation axis, and the coil Is moved to a region where the coil is located before the rotation and a region which does not overlap along the direction perpendicular to the surface when rotated 180 degrees around the second rotation axis. .

  According to the present invention, since the surfaces of the coil and the electric conductor overlap each other along a predetermined direction, when two non-contact information media overlap, either one of the non-contact information media The coil included in is placed between the electric conductor of its own and the electric conductor of another non-contact information medium. As a result, the self-inductance of the coil sandwiched between the two electric conductors decreases, and the resonance frequency of the resonance circuit constituted by the coil and the capacitor increases. In this way, in the present invention, since the resonance frequency of the resonance circuit is once raised, even if the resonance frequency is gradually lowered by further overlapping the non-contact information medium thereafter, reading is performed from the outside. The number of sheets can be increased more than before until the minimum possible value is reached. Therefore, even when many identical objects are stacked, information can be exchanged with the outside via radio waves individually and reliably.

  Further, according to the present invention, since the shielding effect by the electric conductor is expected, there are few limitations on the self-inductance and shape of the coil. Therefore, a non-contact information medium suitable for downsizing can be provided.

  The best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described below with reference to the accompanying drawings. Note that the drawings referred to in the following description are schematic, and when the same object is shown in different drawings, dimensions, scales, and the like may be different.

(Embodiment 1)
FIG. 1 is a plan view showing a configuration of a non-contact information medium according to Embodiment 1 of the present invention. 2 is a cross-sectional view taken along line AA in FIG. The non-contact information medium 1 shown in these figures includes a plate-like base material 2 having a rectangular surface, a loop antenna 3 that receives a radio wave propagating from the outside and transmits a radio wave that responds to the radio wave. The capacitor 4 connected in parallel to the loop antenna 3, the IC chip 5 connected in parallel to the capacitor 4, and the two electric conductors 6 provided on the other surface of the substrate 2 are provided.

The substrate 2 has a rotational symmetry of 180 degrees with a straight line that is parallel to the long side of the surface rectangle and passes through the center of the rectangle as the rotation axis O ₁ . Further, the substrate 2, a straight line passing through the are and the center of the rectangle parallel to the rectangular shorter sides of the surface as a rotation axis O ₂ having a rotational symmetry of 180 degrees. That is, the rotation axes O ₁ and O ₂ correspond to the second rotation axis.

The loop antenna 3 is formed on the surface of the base material 2 by, for example, etching a conductor, and includes a main loop 31 composed of a conductive wire that circulates around the outer periphery of the base material 2 over substantially the entire periphery, and a region surrounding the main loop 31. And a coil 32 connected to the main loop 31 in series. The coil 32 is formed of a conductive wire wound in a square spiral shape in a small area. When the coil 32 is rotated 180 degrees around the rotation axes O ₁ and O ₂ , respectively, the region in which the coil 32 is located before the rotation and the direction perpendicular to the surface of the substrate 2 (the paper surface of FIG. 1). Move to a non-overlapping area along the vertical direction. Specifically, the coil 32 located in the upper left region of the substrate 2 in FIG. 1 moves to the lower left region of the substrate 2 by rotating 180 degrees around the rotation axis O ₁ while rotating. The substrate 2 is moved to the upper right region by rotating 180 degrees around the axis O ₂ . By arranging the coil 32 in this way, even if the two non-contact information media 1 are overlapped with each other in an inverted state, the coils 32 do not overlap each other.

  The main loop 31 has one winding of the conductive wire, and has a smaller self-inductance than the case of having a plurality of main loops as in the technique described in Patent Document 1. For this reason, the self-inductance value of the entire loop antenna 3 is adjusted by the self-inductance of the coil 32. The shape of the main loop 31 can be changed as appropriate according to the shape of the substrate 2. The winding shape of the coil 32 may also be a spiral shape other than a square.

  The capacitor 4 is provided on the inner peripheral side of the main loop 31 on the surface of the base material 2 where the loop antenna 3 is provided, and is connected in parallel to the main loop 31. The capacitor 4 forms a resonance circuit with the loop antenna 3.

  The IC chip 5 is provided on the inner peripheral side of the main loop 31 on the surface of the substrate 2 on which the loop antenna 3 is provided. The IC chip 5 receives a signal based on a radio wave propagated from the outside and received by the loop antenna 3 and stores various information including identification information for identifying the non-contact information medium 1, and the received signal Includes a signal processing unit 52 that reads information corresponding to a request included in the storage unit 51, transmits a signal corresponding to the read information to the loop antenna 3, and a control unit 53 that controls the operation of the IC chip. . The IC chip 5 starts its operation when it reaches a voltage that can be operated by an induced current generated according to a radio wave propagated from the outside.

The two electric conductors 6 are realized by a thin film metal or the like, and are provided on a part of the surface (the back side in FIG. 1) different from the surface on which the loop antenna 3 or the like is provided among the surfaces of the base material 2. Yes. The surface of each electric conductor 6 has a rectangular shape, and the longitudinal direction thereof is arranged in parallel with the short direction of the substrate 2. The two electric conductors 6 pass through a rectangular center (intersection of the rotation axes O ₁ and O ₂ ) forming the surface of the substrate 2 and are 180 degrees with a straight line orthogonal to the surface as the rotation axis O ₃ . It has a pattern with rotational symmetry. Further, the electric conductor 6 overlaps with the coil 32 along a direction orthogonal to the surface of the substrate 2. Since the electrical conductor 6 and the coil 32 have the above-described positional relationship, when a magnetic flux is generated in the coil 32, an eddy current is generated in the electrical conductor 6 and the magnetic flux in the coil 32 is weakened. As a result, the self-inductance of the coil 32 is reduced. Therefore, by providing the electric conductor 6 in the vicinity of the coil 32, the resonance frequency of the resonance circuit of the non-contact information medium 1 is increased.

  FIG. 3 is a diagram showing a schematic configuration of a reader / writer that reads information recorded by the non-contact information medium 1 having the above configuration. The reader / writer 7 shown in FIG. 1 includes an input unit 71 to which various information including an operation instruction signal is input, an output unit 72 to output various information including information obtained through communication with the non-contact information medium 1, a predetermined While transmitting a radio wave having a frequency of 1 to the outside, a loop antenna 73 that receives the radio wave from the outside and a signal corresponding to the radio wave transmitted by the loop antenna 73 are generated, while information contained in the radio wave received by the loop antenna 73 is A signal processing unit 74 for extraction and a control unit 75 for controlling the operation of the reader / writer 7 are included. The reader / writer 7 has an anti-collision function that can collectively receive information from a plurality of non-contact information media 1.

  When the non-contact information medium 1 receives a radio wave corresponding to the request information Da requesting a reply from the reader / writer 7, an induced current is generated in the resonance circuit constituted by the loop antenna 3 and the capacitor 4, and the IC chip 5 is powered. Is supplied. The IC chip 5 activated by this power extracts the request information Da, generates response information Db for the extracted request information Da, and outputs a signal corresponding to the response information Db. The loop antenna 3 transmits a radio wave corresponding to this signal. In order to ensure such communication, the resonance frequency of the resonance circuit of the non-contact information medium 1 is adjusted to match the frequency of the radio wave transmitted by the reader / writer 7.

  FIG. 4 is a diagram showing a state in which two non-contact information media 1 are arranged in an overlapping manner, and each non-contact information medium 1 is a cross-sectional view seen from the same cut surface as FIG. In FIG. 4, in order to distinguish the two non-contact information media 1, the reference numeral of the non-contact information medium 1 positioned on the lower side in FIG. 4 is “1a”, while the non-contact information medium 1 positioned on the upper side in FIG. The code of the contact information medium 1 is “1b”. Correspondingly, in FIG. 4, “a” and “b” are also added to the end of the reference numerals of the constituent elements of the non-contact information medium 1.

  In FIG. 4, the coil 32a is sandwiched from above and below in the figure by the electrical conductors 6a and 6b. In this case, since eddy currents are generated in the electric conductors 6a and 6b located in the vicinity of the coil 32, the self-inductance of the coil 32a is reduced. In the first embodiment, the shapes of the coils 32a and 32b are determined so that the decrease of the self-inductance of the coil 32a is greater than the influence of the mutual inductance of the coil 32b.

FIG. 5 is a diagram showing a resonance curve of the resonance circuit of the non-contact information medium 1a. Specifically, a curve L1 indicated by a broken line is a resonance curve when the non-contact information medium 1a is a single piece, and a curve L2 indicated by a solid line is a resonance curve when the non-contact information medium 1b is superimposed on the non-contact information medium 1a. It is. In FIG. 5, the horizontal axis is the frequency f, and the vertical axis is the square of the absolute value of the amplitude I ₀ of the current flowing through the resonance circuit | I ₀ | ² . As described above, in the first embodiment, when the non-contact information medium 1b is stacked on the non-contact information medium 1a, the influence of the reduction in the self-inductance of the coil 32a sandwiched between the electric conductors 6 is affected by the coil 32b. It is larger than the influence of mutual inductance. Therefore, the resonance frequency f ₂ when the non-contact information medium 1 b is overlapped is higher than the resonance frequency f _{1 in} the case of a single body.

FIG. 6 is a diagram illustrating a state in which one non-contact information medium 1 is further stacked from the state illustrated in FIG. Hereinafter, the reference numeral of the third non-contact information medium 1 is “1c”, and “c” is added to the end of the reference numerals of the constituent elements of the non-contact information medium 1 c. In FIG. 6, the coil 32b is shielded from both the upper and lower sides of the figure by the electric conductors 6b and 6c. Therefore, the value of the resonance frequency of the resonance circuit of the non-contact information medium 1b is f ₂ as with the resonance frequency of the resonance circuit of the non-contact information medium 1a when two sheets are stacked (curve L2 in FIG. 5).

On the other hand, since the self-inductance of the coil 32a is almost the same as when two coils are stacked, the resonance circuit of the non-contact information medium 1a is affected by the mutual inductance of the coil 32c. As a result, the resonance curve of the resonance circuit of the non-contact information medium 1a is given by the curve L3 shown in FIG. The resonance frequency f _{3 in} this case is smaller than the resonance frequency f _{2 in} the case of two sheets being stacked. In addition, the resonance frequency f ₃ is greater than the resonance frequency f ₁ . This means that the influence of sandwiching the coil 32a between the electric conductors 6a and 6b in the vertical direction in FIG. 4 is larger than the influence of the mutual inductance of the coil 32c.

  Thereafter, when the non-contact information medium 1 is further stacked with four, five,..., The resonance frequency of the resonance circuit of the non-contact information medium 1a, 1b gradually decreases. The resonance frequency of the resonance circuit of the non-contact information medium 1c increases once when the fourth sheet is stacked, and then gradually decreases every time the fifth and subsequent sheets are stacked.

  As described above, in the first embodiment, since the electric conductor 6 is provided on one surface side of the coil 32, another non-contact information medium 1 is stacked on the other surface side of the coil 32. The coil 32 is sandwiched between the upper and lower surfaces of the electric conductor 6, and the resonance frequency of the resonance circuit of the non-contact information medium 1 increases greatly once. Thereafter, as the number of sheets is further increased, the resonance frequency gradually decreases due to the influence of the mutual inductance of the coil 32 of the newly overlapped non-contact information medium 1, but since the initial increase is large, a large number of sheets Even if the information is stacked, the situation in which the reader / writer 7 can read the information continues for a long time, and the performance of the non-contact information medium 1 can be maximized. In addition, the number in this Embodiment 1 is ten or more sheets, for example.

  According to the first embodiment of the present invention described above, since the surfaces of the coil and the electric conductor overlap each other along a predetermined direction, when two non-contact information media overlap, The coil included in any one of the non-contact information media is sandwiched between its own electrical conductor and the electrical conductor of the other non-contact information medium. As a result, the self-inductance of the coil sandwiched between the two electric conductors decreases, and the resonance frequency of the resonance circuit constituted by the coil and the capacitor increases. In this way, in the first embodiment, since the resonance frequency of the resonance circuit is once raised, even if the resonance frequency is gradually lowered by further overlapping the non-contact information medium after that, The number of sheets can be increased more than before until the minimum value that can be read is reached. Therefore, even when many identical objects are stacked, information can be exchanged with the outside via radio waves individually and reliably.

  Further, according to the first embodiment, since the shielding effect by the electric conductor is expected, there are few limitations on the mutual inductance and shape of the coil. Therefore, a non-contact information medium suitable for downsizing can be provided. Further, since a generally designed coil can be used, cost reduction can be realized.

FIG. 8 is a plan view showing a configuration of a non-contact information medium according to a modification of the first embodiment. The non-contact information medium 8 shown in the figure is different from the non-contact information medium 1 described above in the configuration of the loop antenna. Specifically, the loop antenna 9 provided in the non-contact information medium 8 includes a main loop 33 that is wound around the outer periphery of the base material 2 over substantially the entire circumference, and two coils 32. The two coils 32 overlap with different electrical conductors 6 along a direction orthogonal to the surface of the substrate 2. Further, the two coils 32 have a rotational symmetry of 180 degrees with a straight line passing through the center of the base material 2 together with the two electric conductors 6 and orthogonal to the base material 2 as a rotation axis. Further, when the two coils 32 are rotated 180 degrees around the rotation axes O ₁ and O ₂ , respectively, a region where the two coils 32 are located before the rotation and a direction orthogonal to the surface of the base material 2 It moves to the area | region which does not overlap along (the direction perpendicular | vertical to the paper surface of FIG. 8). As a result, even if the non-contact information medium 8 is turned upside down, the coils 32 included in the adjacent non-contact information medium 8 do not directly overlap without passing through the electric conductor 6.

  The non-contact information medium 8 having the above configuration can perform information exchange with the outside via radio waves individually and reliably even when many identical objects are stacked, and is suitable for downsizing. There is an effect that it is possible to reduce the cost.

(Embodiment 2)
FIG. 9 is a plan view showing the configuration of the non-contact information medium according to Embodiment 2 of the present invention. The non-contact information medium 10 shown in the figure includes a base plate 2 having a rectangular surface, a loop antenna 11 that receives radio waves propagating from the outside and transmits radio waves that respond to the radio waves, A capacitor 4 connected in parallel to the loop antenna 11, an IC chip 5 connected in parallel to the capacitor 4, and an electric conductor 12 provided on the other surface of the substrate 2 are provided.

The loop antenna 11 is provided on the surface of the base material 2, and has a one-turn main loop 111 that circulates around the outer periphery of the base material 2 over substantially the entire circumference, and a rectangular area in a region smaller than the region surrounded by the main loop 111. It has a coil 112 made of a conductive wire wound in a spiral shape and connected in series to the main loop 111. When the coil 112 is rotated 180 degrees around the rotation axes O ₁ and O ₂ , respectively, the region where the coil 112 was located before the rotation and the direction perpendicular to the surface of the substrate 2 (the paper surface of FIG. 9). Move to a non-overlapping area along the vertical direction. By disposing the coil 112 in this way, even if the two non-contact information media 10 are overlapped with each other turned over, the coils 112 do not face each other and overlap each other.

The electric conductor 12 is disposed at the center of the base material 2 and passes through a rectangular center (intersection of the rotation axes O ₁ and O ₂ ) forming the surface of the base material 2 and rotates a straight line orthogonal to the surface. A pattern having a rotational symmetry of 180 degrees is formed as an axis (corresponding to the rotation axis O ₃ in FIG. 2). Further, the electric conductor 12 overlaps with the coil 112 along a direction orthogonal to the surface of the substrate 2.

  As described above, in the second embodiment, since the electric conductor 6 is provided on one surface side of the coil 112, another non-contact information medium 10 is overlapped on the other surface side of the coil 112. The coil 112 is sandwiched between the upper and lower surfaces of the electric conductor 12, and the resonance frequency of the resonance circuit of the non-contact information medium 10 increases greatly once. Thereafter, as the number of sheets is further increased, the resonance frequency gradually decreases due to the influence of the mutual inductance of the coil 112 of the newly overlapped non-contact information medium 10. Even if the information is stacked, the situation in which the reader / writer 7 can read the information continues for a long time, and the performance of the non-contact information medium 10 can be maximized.

  According to the second embodiment of the present invention described above, as in the first embodiment, even when a large number of identical objects are stacked, information exchange with the outside via radio waves is performed individually and reliably. Therefore, it is possible to provide a non-contact information medium that is suitable for downsizing and can reduce costs.

FIG. 10 is a plan view showing a configuration of a non-contact information medium according to a modification of the second embodiment. The non-contact information medium 13 shown in the figure is different from the above-described non-contact information medium 10 in the configuration of the loop antenna. Specifically, the loop antenna 14 included in the non-contact information medium 10 includes a main loop 141 that is wound around the outer periphery of the base material 2 over substantially the entire periphery, and two coils 142. The two coils 142 overlap with each other in a region different from the electric conductor 12 along the direction orthogonal to the surface of the substrate 2. Further, the two coils 142 have a rotational symmetry of 180 degrees with a straight line passing through the center of the base material 2 and perpendicular to the base material 2 together with the two electric conductors 12 as a rotation axis. Further, when the two coils 142 are rotated by 180 degrees around the rotation axes O ₁ and O ₂ , respectively, a region where the two coils 142 are located before the rotation and a direction orthogonal to the surface of the base material 2. It moves to the area | region which does not overlap along (the direction perpendicular | vertical to the paper surface of FIG. 10). Thereby, even if the non-contact information medium 13 is turned upside down, the coils 142 included in the adjacent non-contact information medium 13 do not directly overlap without passing through the electric conductor 12.

  The non-contact information medium 13 having the above-described configuration can transmit and receive information to and from the outside individually via radio waves even when many identical objects are stacked, and is suitable for downsizing. There is an effect that it is possible to reduce the cost.

(Embodiment 3)
FIG. 11 is a plan view showing the configuration of the non-contact information medium according to Embodiment 3 of the present invention.
The non-contact information medium 15 shown in the figure includes a base plate 2 having a rectangular surface, a loop antenna 16 that receives a radio wave propagating from the outside and transmits a radio wave that responds to the radio wave, A capacitor 4 connected in parallel to the loop antenna 16, an IC chip 5 connected in parallel to the capacitor 4, and two electric conductors 17 provided on the other surface of the substrate 2 are provided.

The loop antenna 16 is provided on the surface of the base material 2, and has a single main loop 161 that circulates in the vicinity of the outer periphery of the base material 2 over substantially the entire circumference, and a region that is smaller in area than each region surrounded by the main loop 161. It has four coils 162 made of a conductive wire wound in a square spiral shape and connected in series to the main loop 161. When the four coils 162 are rotated 180 degrees around the rotation axes O ₁ and O ₂ , respectively, the region in which the coils 162 are located before the rotation and the direction orthogonal to the surface of the substrate 2 (in FIG. 11). Move to a non-overlapping area along the direction perpendicular to the page. The four coils 162 pass through a straight line passing through the center of the rectangle forming the surface of the substrate 2 (intersection of the rotation axes O ₁ and O ₂ ) and orthogonal to the substrate 2 (rotation axis O in FIG. 2). (Corresponding to ₃ ), it has a rotational symmetry of 180 degrees. By arranging the four coils 162 in this way, even if the two non-contact information media 15 are overlapped in an inverted state, the coils 162 do not overlap each other.

  The two electric conductors 16 are realized by a thin film metal or the like, and are provided on a part of the surface (the back surface side in FIG. 11) different from the surface on which the loop antenna 16 or the like is provided on the surface of the base material 2. Yes. The surface of each electric conductor 16 has a rectangular shape, and its longitudinal direction is arranged in parallel with the longitudinal direction of the substrate 2. The electric conductor 16 overlaps with the two coils 162 along the direction orthogonal to the surface of the substrate 2. The two electric conductors 16 together with the two coils 162 have a pattern having a rotational symmetry of 180 degrees with a straight line passing through the center of the rectangle forming the surface of the substrate 2 and orthogonal to the surface as a rotation axis. There is no.

  As described above, in the third embodiment, since the electric conductor 16 is provided on one surface side of the coil 162, another non-contact information medium 15 is stacked on the other surface side of the coil 162. The coil 162 is sandwiched by the electric conductor 16 from both the upper and lower surfaces, and the resonance frequency of the resonance circuit of the non-contact information medium 15 increases greatly once. Thereafter, when the number of sheets is further increased, the resonance frequency gradually decreases due to the influence of the mutual inductance of the coil 112 of the newly overlapped non-contact information medium 15, but since the initial increase is large, a large number of sheets Even if the information is stacked, the situation in which the reader / writer 7 can read the information continues for a long time, and the performance of the non-contact information medium 15 can be maximized.

  According to the third embodiment of the present invention described above, as in the first and second embodiments, even when a large number of identical objects are stacked, information exchange with the outside via radio waves is performed individually and reliably. It is possible to provide a non-contact information medium that can be performed, is suitable for downsizing, and can reduce costs.

  In the third embodiment, the coil 162 may be disposed only on one of the two electric conductors 16. Further, the number of coils 162 disposed on one electrical conductor 16 may be three or more.

  So far, the first to third embodiments have been described in detail as the best mode for carrying out the present invention, but the present invention should not be limited by these embodiments. For example, the electric conductor may be provided on the same surface as the coil to cover the coil. Thus, the present invention can include various embodiments and the like not described herein, and various design changes and the like can be made without departing from the technical idea specified by the claims. It is possible to apply.

It is a top view which shows the structure of the non-contact information medium which concerns on Embodiment 1 of this invention. It is the sectional view on the AA line of FIG. It is a figure which shows the structure of the reader / writer which reads the information which the non-contact information medium which concerns on Embodiment 1 of this invention records. It is a figure which shows the state which has arrange | positioned two non-contact information media which concern on Embodiment 1 of this invention. It is a figure which shows typically the change of the resonant frequency of the resonant circuit of the non-contact information medium at the time of overlapping two sheets. It is a figure which shows the state which has arrange | positioned three non-contact information media which concern on Embodiment 1 of this invention. It is a figure which shows typically the change of the resonant frequency of the resonant circuit of a non-contact information medium at the time of overlapping three sheets. It is a top view which shows the structure of the non-contact information medium which concerns on the modification of Embodiment 1 of this invention. It is a top view which shows the structure of the non-contact information medium which concerns on Embodiment 2 of this invention. It is a top view which shows the structure of the non-contact information medium which concerns on the modification of Embodiment 2 of this invention. It is a top view which shows the structure of the non-contact information medium which concerns on Embodiment 3 of this invention.

Explanation of symbols

1, 1a, 1b, 1c, 8, 10, 13, 15 Non-contact information medium 2 Base material 3, 9, 11, 14, 16, 73 Loop antenna 4 Capacitor 5 IC chip 6, 6a, 6b, 6c, 12, 17 Electrical conductor 7 Reader / writer 31, 33, 111, 141, 161 Main loop 32, 32a, 32b, 32c, 112, 142, 162 Coil 51 Storage unit 52, 74 Signal processing unit 53, 75 Control unit 71 Input unit 72 Output part L1, L2, L3 Resonance curve

Claims (5)

A main loop that wraps around the entire outer edge of a predetermined region on a plane, and a region that is smaller in area than the region surrounding the main loop on the plane, and is connected in series to the main loop. A loop antenna that has a coil and transmits and receives radio waves with the outside,
A capacitor connected in parallel to the main loop;
An IC chip that is connected in parallel to the capacitor and receives radio waves propagated from the outside and transmits radio waves that respond to the received radio waves to the outside;
A pattern that has a rotational symmetry of 180 degrees passing through the plane within the predetermined area and that has a straight line orthogonal to the plane as a rotation axis, and overlaps the coil along a direction orthogonal to the plane. An electrical conductor disposed in a position;
A non-contact information medium comprising: The loop antenna has a plurality of the coils,
The non-contact information medium according to claim 1, wherein the arrangement pattern of the plurality of coils has a rotational symmetry of 180 degrees with respect to the rotation axis.   3. The substrate according to claim 1, further comprising a base plate having a plate shape and provided with the loop antenna, the capacitor, the IC chip, and the electric conductor on any surface parallel to the plane. Non-contact information medium. The substrate is
4. The non-contact information medium according to claim 3, wherein the non-contact information medium has a rotational symmetry of 180 degrees with respect to the rotation axis together with the arrangement pattern of the electric conductor. The substrate is
A shape having a rotational symmetry of 180 degrees with at least one straight line passing through the surface as a second rotation axis,
The coil is
2. When rotating 180 degrees around the second rotation axis, the coil moves to a region where the coil is located before the rotation and a region that does not overlap along a direction perpendicular to the surface. 4. The non-contact information medium according to 4.

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