Abstract:
The present invention provides an RFID tag that is very effective in preventing fraudulent uses. The RFID tag includes a base, an antenna pattern provided on the base, a breakdown pattern provided on the base, a circuit chip connected to both the antenna pattern and the breakdown pattern, and a cover that is bonded to the base in a strippable condition so as to cover the antenna pattern, the breakdown pattern and the circuit chip and is caused to come off together with all or a part of the breakdown pattern during stripping from the base. The breakdown pattern is transparent, or the cover conceals a remaining part of the breakdown pattern, or the breakdown pattern has a specific part that produces predetermined electrical properties and the cover conceals the specific part.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an RFID (Radio Frequency Identification) tag that performs information exchange with external equipment in a noncontact manner. Incidentally, among those skilled in the art related to the technical field of the present application, the “RFID tag” used in the specification of the present application may sometimes be called an “inlay for RFID tag” by regarding the “RFID tag” as an internal component member (inlay) for “RFID tag.” Or alternatively, in some cases, this “RFID tag” may be referred to as “a radio IC tag.” Also, a noncontact type IC card is included in this “RFID tag.” 
         [0003]     2. Description of the Related Art  
         [0004]     In recent years, there have been proposed various RFID tags that perform information exchange with external equipment represented by a reader/writer in a noncontact manner by use of radio waves. As one kind of this RFID tag, there has been proposed an RFID tag in which an antenna pattern for radio communication and an IC chip are mounted on a base sheet made of plastics or paper. A conceived mode of using an RFID tag of this type is such that the RFID tag is stuck to an article and the like and performs the identification of the article by exchanging information on the article with external equipment.  
         [0005]     In this mode of using an RFID tag of this type, there is excepted a fraudulent use in which an RFID tag stuck to an article is stripped off from the article and then this RFID tag is stuck to another article in order to mislead external equipment in the identification of the article, whereby, for example, an expensive article is obtained as if it were an inexpensive one. Therefore, a technique for preventing such fraudulent uses is demanded.  
         [0006]     Against this background, there have been proposed techniques for making communication impossible by causing an antenna pattern to be broken down during the stripping of an RFID tag (refer to the U.S. Patent Laid-Open No. 2003/075608, the U.S. Pat. No. 6,421,013 and the National Publication of International Patent Application No. 2003-524811, for example).  
         [0007]     FIGS.  1 (A) and  1 (B) are a front view and a side view, respectively, of an RFID tag of conventional technique in a condition before stripping.  
         [0008]     An RFID tag  1  shown in FIGS.  1 (A) and  1 (B) is constituted by an antenna pattern  12  provided on a base sheet  13 , an IC chip  11  connected to the antenna pattern  12  via a bump  16 , and a cover sheet  14  bonded to the base sheet with an adhesive  15  so as to cover the antenna pattern  12  and the IC chip  11 .  
         [0009]     This RFID tag  1  is used, with the base sheet  13  side thereof stuck to an article, and the adhesive force of the adhesive  15  is weaker than the adhesive force with which the base sheet  13  side of the RFID tag  1  is bonded to the article. For this reason, when the RFID tag  1  is stripped off by a person who attempts fraudulent uses, the cover sheet  14  comes off from the base sheet  13 .  
         [0010]     Also, the antenna pattern  12  has portions that are weak in adhesion to the base sheet  13  from place to place.  
         [0011]     FIGS.  2 (A) and  2 (B) are a front view and a side view, respectively, of an RFID tag of conventional technique in a condition after stripping.  
         [0012]     When the cover sheet  14  shown in FIGS.  1 (A) and  1 (B) is stripped off from the base sheet  13 , the antenna pattern  12  comes off together with the cover sheet  14  in a portion  12   a  with weak adhesion to the base sheet  13 , whereby the antenna pattern  12  loses the function as a communication antenna and communication becomes impossible.  
         [0013]     As a technique for preventing fraudulent uses, there is also proposed a technique in which a dedicated pattern that is broken down during stripping is provided in the RFID tag in addition to the antenna pattern and a breakdown of the dedicated pattern is detected by use of an IC chip.  
         [0014]     FIGS.  3 (A) and  3 (B) are a view of another RFID tag of conventional technique in a condition, respectively, before and after stripping.  
         [0015]     An RFID tag  2  shown in FIGS.  3 (A) and  3 (B) is provided with an antenna pattern  22 , an IC chip  21  connected to the antenna pattern  22 , and a breakdown pattern  23  that is cause to conduct by a conductive ink  24 , and as with the RFID tag  1  shown in FIGS.  1 (A) and  1 (B), the RFID tag  2  is also provided with a base sheet and a cover sheet, which are omitted in the figures.  
         [0016]     Also in the case of this RFID tag  2 , if the RFID tag  2  is stripped off by a person who attempts fraudulent uses, the cover sheet comes off from the base sheet. And in this RFID tag  2 , the conductive ink  24  spatters while the cover sheet is coming off, thereby bringing the breakdown pattern  23  into an insulating condition, and the IC chip  21  detects this insulating condition in the breakdown pattern  23 . Also, the breakdown is visually ascertained from the conductive ink  24  that has spattered.  
         [0017]     In the case of the RFID tag  2  shown in FIGS.  3 (A) and  3 (B), the antenna pattern  22  and its communication function are maintained even when the cover sheet comes off, and the antenna pattern  22  informs external equipment of the stripping of the RFID tag  2  during communication with the external equipment.  
         [0018]     However, in conventional techniques as described above, the fact that due to the stripping of an RFID tag, part of the tag is broken down and the place where the tag is broken down are clear to the person who attempts fraudulent uses. Therefore, this gives the person who attempts fraudulent uses a motivation and an opportunity for repairing the broken place, posing the problem that the prevention of fraudulent uses is insufficient.  
       SUMMARY OF THE INVENTION  
       [0019]     In view of the circumstances described above, the present invention provides an RFID tag that is every effective in preventing fraudulent uses.  
         [0020]     The present invention provides, as the first RFID tag of the invention, an RFID tag that comprises: a base; a first pattern that is provided on the base and forms an antenna for communication; a second pattern that is provided on the base and is formed from a transparent conductor; a circuit chip that is electrically connected to the first pattern and the second pattern and performs radio communication via the antenna and detects a breakdown of the second pattern; and a cover that is bonded to the base in a strippable condition so as to cover the first pattern, the second pattern and the circuit chip and is caused to come off together with all or a part of the second pattern during stripping from the base.  
         [0021]     According to the first RFID tag of the invention, because the second pattern is transparent, the person who has stripped off an RFID tag in order to attempt fraudulent uses does not become aware that part of the second pattern has been broken down or does not become aware of the broken place. For this reason, no motivation for repairing the broken place or the like arises and the breakdown of the second pattern is positively detected by the circuit chip. Thus, the first RFID tag of the invention is very effective in preventing fraudulent uses.  
         [0022]     The second RFID tag of the invention comprises: a base;  
         [0023]     a first pattern that is provided on the base and forms an antenna for communication; a second pattern that is provided on the base and is formed from a conductor; a circuit chip that is electrically connected to the first pattern and the second pattern and performs radio communication via the antenna and detects a breakdown of the second pattern; and a cover that is bonded to the base in a strippable condition so as to cover and conceal the first pattern, the second pattern and the circuit chip and is caused to come off separately as a concealing part and an exposure part during stripping from the base and to come off while bringing a portion of the second pattern corresponding to the exposure part.  
         [0024]     According to the second RFID tag of the invention, the part of the second pattern that remains on the base after the stripping of the cover is concealed by the concealing part and a broken place of the second pattern becomes unclear. For this reason, as with the first RFID tag, this does not give a motivation or the like for repairing the broken place to a person who attempts fraudulent uses. Thus, the second RFID tag of the invention is very effective in preventing fraudulent uses.  
         [0025]     The third RFID tag of the invention comprises: a base; a first pattern that is provided on the base and forms an antenna for communication; a second pattern that is provided on the base and has a specific part in which a conductor is arranged so as to produce prescribed electrical properties; a circuit chip that is electrically connected to the first pattern and the second pattern and performs radio communication via the antenna and detects electrical properties generated by the presence of the specific part in the second pattern; and a cover that is bonded to the base in a strippable condition so as to cover the first pattern, the second pattern and the circuit chip and conceal at least the specific part of the second pattern and is caused to come off together with the specific part during stripping from the base.  
         [0026]     According to the third RFID tag of the invention, the specific part of the second pattern is concealed by the cover and this specific part is caused to come off during stripping. For this reason, the construction of the specific part is prevented from becoming known to human beings. When a complicated construction is adopted in the specific part, it becomes impossible for a person who attempts fraudulent uses to repair the specific part.  
         [0027]     It is preferred that in the second and third RFID tags of the invention, the second pattern be formed from a transparent conductor.  
         [0028]     By adopting the second pattern formed from a transparent conductor in the second and third RFID tags of the invention, it is ensured that the effect of the first RFID tag of the invention is exerted in a synergistic manner and it becomes more impossible to recognize the breakdown of the second pattern. Therefore, the effect on the prevention of fraudulent uses is also improved.  
         [0029]     Also, it is preferred that in the second and third RFID tags of the invention, the cover have, on the side thereof in contact with the second pattern, the same color as the color of the conductor of the second pattern.  
         [0030]     The fact that the conductor and cover of the second pattern have the same color also makes it difficult to recognize the presence of the conductor and it becomes more impossible to recognize the breakdown of the second pattern. Therefore, the effect on the prevention of fraudulent uses is also improved.  
         [0031]     As described above, the RFID tags of the invention are very effective in preventing fraudulent uses. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]     FIGS.  1 (A) and  1 (B) are a front view and a side view, respectively, of an RFID tag of conventional technique in a condition before stripping;  
         [0033]     FIGS.  2 (A) and  2 (B) are a front view and a side view, respectively, of an RFID tag of conventional technique in a condition after tripping;  
         [0034]     FIGS.  3 (A) and  3 (B) are a view of another RFID tag of conventional technique in a condition, respectively, before and after stripping;  
         [0035]     FIGS.  4 (A) and  4 (B) are a front view and a side view, respectively, of an RFID tag of the first embodiment of the invention;  
         [0036]     FIGS.  5 (A) and  5 (B) are a front view and a side view, respectively, of an RFID tag of the first embodiment of the invention in a condition after stripping;  
         [0037]     FIGS.  6 (A) and  6 (B) are a front view and a side view, respectively, of an RFID tag of the second embodiment of the invention;  
         [0038]     FIGS.  7 (A) and  7 (B) are a front view and a side view, respectively, of an RFID tag of the second embodiment of the invention in a condition after stripping;  
         [0039]      FIG. 8  is a drawing of an RFID tag of the third embodiment of the invention; and  
         [0040]     FIGS.  9 (A) and  9 (B) are each a drawing of an RFID tag of the third embodiment of the invention in a condition after stripping. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]     Embodiments of the present invention will be described below by referring to the drawings.  
         [0042]     FIGS.  4 (A) and  4 (B) are a front view and a side view, respectively, of an RFID tag of the first embodiment of the invention.  
         [0043]     An RFID tag  100  of the first embodiment is provided with a base sheet  105  made of PET, a copper antenna pattern  102  provided on the base sheet  105 , a breakdown pattern constituted by a copper wire part  103   a  and a transparent ITO (Indium Tin Oxide) part  103   b , and an IC chip  101  electrically connected to the antenna pattern  102  via a bump  109 . The ITO part  103   b  of the breakdown pattern is formed on a sub sheet  104  made of PET, connected to the copper wire part  103   a  with a conductive adhesive and electrically connected to the IC chip  101  via the copper part  103   a  and the bump  109 . The IC chip  101  performs communication with external equipment represented by a reader/writer via the antenna pattern  102 . The IC chip  101  has also the function of detecting the presence or absence of the ITO part  103   b  in the breakdown pattern. This RFID tag  100  is also provided with a PET cover sheet  106  that is bonded to the base sheet  105  with an adhesive  107  so as to cover the antenna pattern  102 , the IC chip  101 , etc., and this cover sheet  106  and the sub sheet  104  are bonded together with a strong adhesive  108 .  
         [0044]     In this first embodiment, the base sheet  105  corresponds to an example of the base of the invention, the antenna pattern  102  corresponds to an example of the first pattern of the invention, the ITO part  103   b  of the breakdown pattern corresponds to an example of the second pattern of the invention, the IC chip  101  corresponds to an example of the circuit chip of the invention, and the cover sheet  106  corresponds to an example of the cover of the invention.  
         [0045]     Externally to the eyes, in the RFID tag  100  constructed in this manner, the IC chip  101 , the antenna pattern  102  and the copper wire part  103   a  are recognized and the presence of the transparent ITO part  103   b  is not recognized.  
         [0046]     This RFID tag  100  is used, with the base sheet  105  side thereof stuck to an article, and the adhesive force of the adhesive  107  is weaker than the adhesive force with which the base sheet  105  side of the RFID tag  100  is bonded to the article. For this reason, when the RFID tag  100  is stripped off by a person who attempts fraudulent uses, the cover sheet  106  comes off from the base sheet  105 . Furthermore, the sub sheet  104  is bonded to the cover sheet  106  with the strong adhesive  108 . Therefore, while the cover sheet  106  is coming off from the base sheet  105 , the sub sheet  104  comes off from the base sheet  105  together with the ITO part  103   b  following the cover sheet  106 .  
         [0047]     FIGS.  5 (A) and  5 (B) are a front view and a side view, respectively, of an RFID tag of the first embodiment of the invention in a condition after stripping.  
         [0048]     When the cover sheet comes off, the IC chip  101 , the antenna pattern  102  and the copper wire part  103   a  remain on the base sheet  105 , and the IC chip  101  detects the absence of the ITO part  103   b  shown in FIGS.  4 (A) and  4 (B) and gives external equipment an alarm via the antenna pattern  102  to the effect that the cover sheet has come off.  
         [0049]     Externally to the eyes, the condition of the cover sheet that has come off is the same as the condition of the cover sheet before coming off as viewed to the eyes. Therefore, a person who attempts fraudulent uses cannot recognize the absence of the ITO part  103   b  and hence this person does not think of the correction of the missing portion. Therefore, an attempt to perform fraudulent uses is positively found out by the above-described alarm and positive prevention of fraudulent uses is realized. Furthermore, because the ITO part  103   b  can be formed in a fine pattern of 30 μm or so and the visibility of the ITO part  103   b  formed in such a fine pattern is very low, the prevention of fraudulent uses becomes more positive.  
         [0050]     FIGS.  6 (A) and  6 (B) are a front view and a side view, respectively, of an RFID tag of the second embodiment of the invention.  
         [0051]     An RFID tag  200  of the second embodiment is constituted by a base sheet  205  made of PET, an antenna pattern  202  provided on the base sheet  205 , a breakdown pattern  203  made of a silver paste, an IC chip  201  electrically connected to both the antenna pattern  202  and the breakout pattern  203  via a bump  209 , a concealing layer  207  that covers and conceals the IC chip  201 , the antenna pattern  202  and the breakdown pattern  203  and is formed from an opaque ink having the color of silver, and a transparent cover sheet  206  bonded to the base sheet  205  via the concealing layer  207 .  
         [0052]     In this second embodiment, the base sheet  205  corresponds to an example of the base of the invention, the antenna pattern  202  corresponds to an example of the first pattern of the invention, the breakdown pattern  203  corresponds to an example of the second pattern of the invention, the IC chip  201  corresponds to an example of the circuit chip of the invention, and the cover sheet  206  and the concealing layer  207  constitute an example of the cover of the invention.  
         [0053]     The cover sheet  206  and the concealing layer  207  have the same construction as what is called a forgery-preventive label, and the concealing layer  207  is so constructed as to be easily separated into a part on the cover sheet  206  side and a part on the base sheet  205  side, as shown by a dotted line in  FIG. 6 (B). However, a strong adhesive  208  is also embedded in the concealing layer  207  and a portion of the breakdown pattern  203  is strongly bonded to the cover sheet  206 .  
         [0054]     Also in the second embodiment shown in FIGS.  6 (A) and  6 (B), the RFID tag  200  is used, with the base sheet  205  side thereof stuck to an article. And the concealing layer  207  is separated into a part on the cover sheet  206  side and a part on the base sheet  205  side with a force that is weaker than the adhesive force with which the base sheet  205  side is bonded to the article.  
         [0055]     FIGS.  7 (A) and  7 (B) are a front view and a side view, respectively, of an RFID tag of the second embodiment of the invention in a condition after stripping.  
         [0056]     When the cover sheet  206  is caused to come off, an exposure part  207   a  of the concealing layer is caused to come off together with the cover sheet  206  and a concealing part  207   b  of the concealing layer remains on the base sheet  205  side. As a result of this, on the front side of the RFID tag there appears a marking from which the fact that the tag has been stripped off can be ascertained at a glance. A breakdown part  203   a  of the breakdown pattern is caused to come off from the base sheet  205  together with the cover sheet  206  due to the presence of the strong adhesive  208 , and the breakdown pattern comes to an insulating condition. As with the first embodiment, the insulating condition of the breakdown pattern is detected by the IC chip  201  and the detection is communicated to an external equipment.  
         [0057]     Because the remaining part  203   b  of the breakdown pattern that remains on the base sheet  205  side is concealed by the concealing part  207   b  of the concealing layer and the breakdown part  203   a  adhering to the cover sheet  206  side has the color of silver, which is the same cooler as the concealing layer, the fact that the breakdown pattern has been broken down, the broken part and the like are not recognized. For this reason, also in the second embodiment, a motivation for repairing does not arise and positive prevention of fraudulent uses is realized.  
         [0058]     Incidentally, a form in which the breakdown pattern of this second embodiment is made of ITO as with the first embodiment is also useful. In a form in which the breakdown pattern of this second embodiment is made of ITO like this, the color of the ink of the concealing layer can be freely selected and, therefore, it is possible to increase the color variations of the tag and the like. As an inexpensive form of RFID tag it is possible to prepare the breakdown pattern from copper. In such an inexpensive form, there is a possibility that a breakdown part adhering to the cover sheet side might be noticed. However, it is rare that one takes the trouble to check the rear side of a cover sheet that has come off, and hence even this form is sufficiently effective in preventing fraudulent uses.  
         [0059]      FIG. 8  is a drawing of an RFID tag of the third embodiment of the invention.  
         [0060]     An RFID tag  300  of the third embodiment is provided with a base sheet  305 , an antenna pattern  302  provided on the base sheet  305 , a breakdown pattern  303  made of a silver paste, an IC chip  301  connected to both the antenna pattern  302  and the breakout pattern  303 , and a cover sheet  306  that covers the antenna pattern  302 , the breakdown pattern  303  and the IC chip  301 , and this cover sheet  306  has a concealing part  304  having the color of silver that conceals the breakdown pattern  303 .  
         [0061]     In this third embodiment, the base sheet  305  corresponds to an example of the base of the invention, the antenna pattern  302  corresponds to an example of the first pattern of the invention, the breakdown pattern  303  corresponds to an example of the second pattern of the invention, the IC chip  301  corresponds to an example of the circuit chip of the invention, and the cover sheet  306  corresponds to an example of the cover of the invention.  
         [0062]     In this third embodiment, a long pattern of complicated shape is used as the breakdown pattern  303  and a prescribed value of resistance Ri is produced. The IC chip  301  monitors resistance values in the breakdown pattern  303 .  
         [0063]     Also the RFID tag  300  of this third embodiment is used, with the base sheet  305  stuck to an article in the same manner as in the first embodiment and the like, and the cover sheet  306  is bonded to the base sheet  305  with an adhesive force weaker than the adhesive force with which the base sheet  305  is bonded to the article. And when a force that works so as to strip off the RFID tag  300  from the article is applied, the cover sheet comes off from the base sheet  305 . The concealing part  304  of the cover sheet  306  is strongly bonded to the breakdown pattern  303 , and when the cover sheet  306  comes off from the base sheet  305 , the breakdown pattern  303  comes off from the base sheet  305  while being stuck to the concealing part  304 .  
         [0064]     FIGS.  9 (A) and  9 (B) are each a drawing of an RFID tag of the third embodiment of the invention in a condition after stripping.  
         [0065]     As shown in  FIG. 9 (A), the antenna pattern  302  and the IC chip  301  remain on the base sheet  305  after stripping, and the breakdown pattern  303  is caused to come off as shown in  FIG. 9 (B). For this reason, the IC chip  301  detects a substantial increase in the resistance value, confirms an insulating condition and can inform external equipment of the insulating condition. Even when a person who attempts fraudulent uses has formed a repaired path  310  by use of copper tape or solder, the IC chip  301  readily detects the repair and can inform the repair to external equipment, because the resistance value Rr of the repaired path  310  is much smaller than the resistance value Ri of the original breakdown pattern  303 . The breakdown pattern  303  is long and has a complicated shape. In addition, because the breakdown pattern  303  is formed from a silver paste and adheres to the concealing part having the color of silver, the visibility is low. For this reason, a person who attempts fraudulent uses cannot reproduce the essential resistance value Ri and positive prevention of fraudulent uses is realized. A form in which the breakdown pattern  303  is made of ITO and a form in which the breakdown pattern  303  is formed in a fine pattern of ITO are also useful.  
         [0066]     Incidentally, although in the above descriptions, a cover sheet made of PET and a base sheet made of PET are mentioned as an example of the cover and base of the invention, the cover and base of the invention may be formed from materials other than PET and may have a shape other than the shape of a sheet.  
         [0067]     Also, although in the above descriptions, a copper antenna pattern is mentioned as an example of the first pattern of the invention, the first pattern of the invention may be formed from a silver paste.  
         [0068]     Furthermore, although in the above descriptions, examples in which the base sheet is bonded to an article are shown, the cover side of the RFID tag according to the invention may be bonded to the article.