Patent Abstract:
The present invention relates to an RFID tag performing exchange of information with an external device without contact, and is to improve the resistance to bending while avoiding an increase in the thickness of the RFID tag. A circuit chip is bonded to a base portion of a base with a thermosetting adhesive. The base is folded, and an ultraviolet curing adhesive is applied on the circuit chip. The fold-back portions of the base are folded back onto the circuit chip, to which portions ultraviolet light is irradiated, as a result, both of the surfaces of the circuit chip are bonded to the base with the adhesives.

Full Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an RFID (Radio Frequency IDentification) tag performing exchange of information with an external device without contact. Noted that the term “RFID tag”, as used herein, may be referred to as “RFID tag inlay” as an internal component (inlay) for the “RFID tag” among those skilled in the art. Alternatively, the “RFID tag” may be referred to as a “radio IC tag”. Further, the “RFID tag” also includes a non-contact IC card. 
   2. Description of the Related Art 
   In recent years, there have been proposed various types of RFID tags which exchange information with an external device in a non-contact manner by means of radio waves, as represented by a reader-writer. There is proposed a kind of the RFID tag which is constituted by mounting an antenna pattern and a circuit chip (IC chip) for radio communication on a base sheet consisting of aplastic, a paper and the like (see, for example, Japanese Patent Laid-Open No. 2000-311226, Japanese Patent Laid-Open No. 2000-200332, Japanese Patent Laid-Open No. 2001-351082). As for the RFID tag of this type, a using form is considered in which the RFID tag attached to an article and the like performs exchange of information about the article with an external device, thereby effecting identification of the article and the like. 
     FIG. 1  is a top view showing an example of an RFID tag. 
   The RFID tag  1  shown in  FIG. 1  is constituted by an antenna  12  provided on a base  13  which consists of a sheet-like PET film and the like, and by a circuit chip  11  which is electrically connected to the antenna  12  by soldering and the like and which is secured to the base  13  with an adhesive. 
   The Circuit chip  11  constituting the RFID tag  1  is capable of performing radio communication and exchange of information with an external device via the antenna  12 . 
   Here,  FIG. 1  shows, as the antenna  12  of the RFID tag  1 , an antenna having a shape extending from the circuit chip  11  placed in the center of the RFID tag to the both sides of the circuit chip. However, the antenna  12  is not limited to this type, and a loop-shaped antenna and antennas having other various shapes may be employed as the antenna  12 . 
     FIG. 2  is a figure explaining a state on the occurrence of a problem in a conventional RFID tag.  FIG. 3  shows an enlarged view showing a portion within a circle R shown in Part (B) of  FIG. 2  and explaining the problem which occurs in the state shown in Part (B) of  FIG. 2 . 
   Noted that the antenna is not shown in  FIG. 2 ,  FIG. 3  and in each of figures hereafter explained. 
   Depending on the application of the RFID tag  1 , in addition to the using form in which the RFID tag  1  is attached in the flat state as it is as shown in Part (A) of  FIG. 2 , the RFID tag  1  may be stuck to a curved surface so that bending force is applied to the RFID tag, as shown in Part (B) of  FIG. 2 . 
   When bending force is applied to the RFID tag  1  as shown in Part (B) of  FIG. 2 , the problem may arise that an adhesive  14  is peeled from a base  13 , as a result of which the electrical connection between a circuit chip  11  and an antenna (not shown, see  FIG. 1 ) is not maintained and thereby the communication function is obstructed. 
     FIG. 4  is a figure showing an example of a preventive measure against the peeling shown in  FIG. 3 . 
   In  FIG. 4 , a circuit chip  11  on a base  13  is sealed with a mold resin  15 . When such sealing processing by means of the mold resin is applied, the flexural strength is improved, but the entire thickness is increased, which leads to a result going against the demand for the reduction in thickness and size. 
   In view of the above described circumstances, the present invention provides an RFID tag having significantly enhanced resistance to bending force with little increase in the thickness. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of the above circumstances and provides an RFID tag including: a base; a communication antenna provided on the base; and a circuit chip which is connected to the antenna and which performs radio communication via the antenna, wherein the base is folded to sandwich the circuit chip, and wherein the circuit chip is attached to the both surfaces of the folded base, the surfaces facing the circuit chip. 
   The RFID tag according to the present invention has a structure in which the circuit chip is sandwiched by the base. The base may be made of a thin sheet material so that the thickness can be hardly increased and at the same time the resistance against bending force can be significantly improved. 
   Here, in the RFID tag according to the present invention, the base may include: a base portion on which the circuit chip is placed; a first fold-back portion which is extended from the base portion and folded back to cover one half portion of the circuit chip; and a second fold-back portion which is extended from the base portion in the direction opposite to the first fold-back portion and folded back to cover the remaining half portion of the circuit chip except the half portion covered by the first fold-back portion. Alternatively, the base may include: a base portion on which the circuit chip is placed; and a fold-back portion which is extended from the base portion to cover the entire surface of the circuit chip. 
   According to the present invention, as described above, an RFID tag which is thin and strong against folding is realized. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a top view showing an example of an RFID tag; 
       FIG. 2  is a figure explaining a state on the occurrence of a problem in a conventional RFID tag; 
       FIG. 3  is an enlarged view showing a portion in a circle R shown in Part (B) of  FIG. 2 , and explaining the problem which occurs in the state shown in  FIG. 2 ; 
       FIG. 4  is a figure showing an example of a preventive measure against the peeling shown in  FIG. 3 ; 
       FIG. 5  is a side view of an RFID tag as an embodiment according to the present invention; 
       FIG. 6  is a top view of the RFID tag shown in  FIG. 5 ; 
       FIG. 7  is a figure showing a manufacturing process of the RFID tag shown in  FIG. 5  and  FIG. 6 ; 
       FIG. 8  is a side view of an RFID tag as another embodiment according to the present invention; 
       FIG. 9  is a top view of the RFID tag shown in  FIG. 8 ; and 
       FIG. 10  is a figure explaining a manufacturing process of the RFID tag shown in  FIG. 8  and  FIG. 9 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the following, embodiments according to the present invention will be described. 
     FIG. 5  is a side view of an RFID tag as an embodiment according to the present invention, and  FIG. 6  is a top view of the RFID tag shown in  FIG. 5 . 
   The RFID tag  10  shown in  FIG. 5  and  FIG. 6  has a structure in which a base  13  is folded back so as to sandwich a circuit chip  11 . 
   The base  13  has a base portion  131  which is in contact with a lower surface  111  of the circuit chip  11 , a first fold-back portion  132  which is extended from the base portion  131 , and which is folded back to be in contact with and to cover a half portion of an upper surface  112  of the circuit chip  11 , and a second fold-back portion  133  which is extended from the base portion  131  in the direction opposite to the first fold-back portion  132 , and which is fold back to be in contact with and to cover the remaining half portion of the upper surface  112  of the circuit chip  11  except the half portion covered by the first fold-back portion  132 . 
   Further, the side of the lower surface  111  of the circuit chip  11  is bonded with an adhesive  141  to the surface of the base portion  131 , the surface facing the side of the circuit chip, and the side of the upper surface  112  of the circuit chip  11  is bonded with an adhesive  142  to surfaces of the first fold-back portion  132  and the second fold-back portion  133 , the surfaces facing the side of the circuit chip. 
   In the RFID tag  1  according to the embodiment shown in  FIG. 5  and  FIG. 6 , the thickness needs to be increased only by a sheet of thin base, as compared with the prior art form shown in  FIG. 1  to  FIG. 3 , so that it is possible to greatly improve the resistance against bending force by hardly increasing the thickness of the RFID tag. 
     FIG. 7  is a figure showing a manufacturing process of the RFID tag shown in  FIG. 5  and  FIG. 6 . 
   First, an antenna (not shown; see  FIG. 1 ) is formed on a base  13  (Part (a) of  FIG. 7 ), on which a thermosetting adhesive  141  is applied by a nozzle  51  (Part (b) of  FIG. 7 ), and a circuit chip  11  is arranged on the adhesive  141 . The circuit chip  11  and the antenna are heated and compressed by a heating/compressing head  52  so as to be solder-connected with each other (Part (c) of  FIG. 7 ), and the circuit chip  11  is fixed on a base portion  131  of the base  13  by thermally curing the adhesive  141 . 
   Next, the base portion  131  of the base  13  is forced into a recess  521  which is formed in a plate  55  (Part (d) of  FIG. 7 ), and an adhesive  142  which is cured by receiving the irradiation of ultraviolet light is applied on the circuit chip  11  by the nozzle  51  (Part (e) of  FIG. 7 ). Then, the base  13  is folded by a roller  53  (Part (f) of  FIG. 7 ), and the adhesive  142  is cured by receiving irradiation of ultraviolet rays  541  from an ultraviolet lamp  54  (Part (g) of  FIG. 7 ). Thereby, the circuit chip  11  is fixed to the first fold-back portion  132  and the second fold-back portion  133  of the base  13  (Part (h) of  FIG. 7 ). The RFID tag shown in  FIG. 5  and  FIG. 6  is formed through these processes. 
     FIG. 8  is a side view of an RFID tag as another embodiment according to the present invention, and  FIG. 9  is a top view of the RFID tag shown in  FIG. 8 . 
   Similarly to the RFID tag  10  shown in  FIG. 5  and  FIG. 6 , an RFID tag  20  shown in  FIG. 8  and  FIG. 9  has a structure in which a base  13  is folded back so as to sandwich a circuit chip  11 . 
   However, the base  13  has a base portion  131  on which a circuit chip  11  is placed and which is in contact with a lower surface  111  of the circuit chip  11 , and a fold-back portion  134  which is extended from the base portion  131  and folded back so as to be in contact with the entire surface of an upper surface  112  of the circuit chip  11 , thereby covering the entire surface of the circuit chip  11 . 
   The side of the lower surface  111  of the circuit chip  11  is bonded with an adhesive  141  to the surface of the base portion  131  of the base  13  on the side of the circuit chip  11 , and the side of the upper surface  112  of the circuit chip  11  is bonded with an adhesive  142  to the surface of the fold-back portion  134  of the base  13  on the side of the circuit chip  11 . 
   Also in the case of the RFID tag  20  shown in  FIG. 8  and  FIG. 9 , the thickness needs to be increased only by a sheet of thin base, as compared with the prior art form shown in  FIG. 1  to  FIG. 3 , so that it is possible to greatly improve the resistance against bending force by hardly increasing the thickness of the RFID tag. 
     FIG. 10  is a figure explaining a manufacturing process of the RFID tag shown in  FIG. 8  and  FIG. 9 . 
   Here, similarly to the processes shown in Part (a) of  FIG. 7  to Part (c) of  FIG. 7 , an antenna (not shown) is formed on a base  13 . A thermosetting adhesive  141  is applied to one end of the base  13  and a circuit chip  11  is placed on the adhesive  141 . The circuit chip  11  and the antenna are heated and compressed so as to be connected with each other, and the circuit chip  11  is fixed to the base  13  by the adhesive  141 . 
   Next, similarly to the process shown in Part (d) of  FIG. 7 , the base portion  131  of the base  13  is forced into the recess  521  of the plate  55  so that the fold-back portion  134  is folded back. Then, similarly to the processes shown in Part (e) of  FIG. 7  to Part (g) of  FIG. 7 , the ultraviolet curing adhesive is applied on the upper surface  112  of the circuit chip  11 , the fold-back portion  134  is then further folded back, and the adhesive is cured by receiving irradiation of ultraviolet light. As a result, the RFID tag  20  having a shape shown in  FIG. 8  and  FIG. 9  is formed. 
   The RFID tag according to the present invention, as shown in the two embodiments described above, has a structure in which the circuit chip  11  is sandwiched by the base  13 , and both the lower surface  111  and the upper surface  112  of the circuit chip  11  are bonded to the base  13 . As a result, in the RFID tag according to the present invention, it is possible to greatly improve the resistance against bending force by hardly increasing the thickness of the RFID tag, as compared with the prior art form shown in  FIG. 1  to  FIG. 3 .

Technology Classification (CPC): 7