Abstract:
A Radio Frequency Identification (RFID) tag includes an integrated circuit (IC) chip and an antenna. The IC chip is enclosed inside a coating of endothermic material. The endothermic material includes silicon resin or ceramic resin or both.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a Radio Frequency Identification (RFID) tag.  
         [0003]     2. Description of the Related Art  
         [0004]     Various applications of RFID tags are being considered, such as identifying and managing people and objects, and as a basic technology for promoting automation in the society. Communication is performed through electric waves and electromagnetic waves between an RFID tag (also referred to as an IC tag) including an IC chip for storing information and an antenna for performing wireless communication, and a reader/writer that reads information inside the RFID tag in a noncontact manner.  
         [0005]     One application is to attach an RFID tag to a product instead of a conventional barcode. The RFID tag stores identification information on the product. RFID tags are more advantageous than barcodes in that RFID tags can store a large amount of information, a plurality of RFID tags can be simultaneously read by a reader/writer, and information in an RFID tag can be overwritten. Thus, RFID tags are expected to promote efficiency in commercial distribution.  
         [0006]     Japanese Patent Application Laid Open Nos. 2001-317741 and 2005-242629 disclose a technology for attaching an RFID tag to a container for containing cooking ingredients, and storing a preparation method for the ingredients in the container. Specifically, a microwave oven reads the preparation method stored in the RFID tag attached to the container, and controls cooking time based on the information read.  
         [0007]     However, when a container to which an RFID tag has been attached is heated in a microwave oven, the RFID tag is destroyed by strong electromagnetic waves generated by the microwave oven and components of the RFID tag scatter and damage the microwave oven. When a typical RFID tag is heated in a microwave oven, the RFID tag is heated to a high temperature just in a few seconds. Sometimes the IC chip in the hot RFID tag explodes, and metal components of the RFID tag scatter inside the microwave oven.  
         [0008]     RFID tags are becoming increasingly popular. It is expected that RFID tags will be attached to a wide variety of food products in the future. Accordingly, there will be higher chance that an RFID tag attached to a food product is heated by a microwave oven. Thus, there is a need to develop an RFID tag that is not destroyed when heated in a microwave oven.  
       SUMMARY OF THE INVENTION  
       [0009]     It is an object of the present invention to at least solve the problems in the conventional technology.  
         [0010]     According to an aspect of the present invention, a radio frequency identification (RFID) tag includes an integrated circuit (IC) chip configured to store therein information; an antenna configured to perform wireless communication with outside; and a coating of endothermic material configured to enclose the IC chip.  
         [0011]     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic of an RFID tag according to an embodiment of the present invention;  
         [0013]      FIG. 2  is an enlarged view of an IC chip shown in  FIG. 1 ; and  
         [0014]      FIG. 3  is a schematic of a conventional RFID tag  100 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     Exemplary embodiments of the present invention will be described below with reference to accompanying drawings. The present invention is not limited to these embodiments.  
         [0016]      FIG. 3  is a schematic of a conventional RFID tag  100 . The RFID tag  100  includes an IC chip  110  and an antenna  120 . The IC chip  110  is a semiconductor circuit including a memory for storing information and a control circuit for controlling communication between a reader/writer. The antenna  120  is provided for performing wireless communication between the reader/writer.  
         [0017]     When the RFID tag  100  is heated in a microwave oven, the antenna  120  resonates with an electromagnetic wave of 2.45 GHz generated by magnetron incorporated in the microwave oven, and generates heat and causes electrical discharge. The heat and discharge is transferred to the IC chip  110  and destroys the IC chip  110 .  
         [0018]     The IC chip  110  is destroyed only a few seconds after the heating starts, which is shorter than time required for cooking food in the microwave oven. Accordingly, when food attached with a conventional RFID tag is heated in the microwave oven, the RFID tag is destroyed before cooking is completed, and therefore, the microwave oven will be damaged.  
         [0019]      FIG. 1  is a schematic of an RFID tag  200  according to an embodiment of the present invention. The RFID tag  200  includes an IC chip  210 , an antenna  220 , and a low-pass filter  230 .  
         [0020]     The IC chip  210  is a semiconductor circuit including a memory for storing information and a control circuit for controlling communication between a reader/writer. The IC chip  210  has the same function as the IC chip  110 ; however, the IC chip  210  is embedded in endothermic material as shown in  FIG. 2 . This improves heat resistance, so that the IC chip  210  is hard to destroy.  
         [0021]     Silicon resin, ceramic resin, or a mixture of these resins is effective as the endothermic material. Heat resistance can be further improved by adding silica gel to either one of the resins or the mixture.  
         [0022]     The antenna  220  is provided for performing wireless communication between the reader/writer. The antenna  220  has the same function as the antenna  120 ; however, the antenna  220  is shaped so that one part is thinner than another part. When the RFID tag  200  is heated in a microwave oven, the thinner part becomes disconnected due to heat and electric discharge, so that heat is prevented from being transferred to the IC chip  210 . The same effect can be obtained by disconnecting a part of the antenna  220  beforehand.  
         [0023]     The low-pass filter  230  blocks an electromagnetic wave of 2.45 GHz. By inserting the low-pass filter  230  midway in the antenna  220 , the antenna  220  is prevented from resonating with electromagnetic waves generated by the magnetron. The low-pass filter  230  can be realized by a ceramic material of approximately a 1 mm angle.  
         [0024]     The embodiment prevents resonation by inserting a low-pass filter in an antenna, prevents heat from being transferred to an IC chip by shaping the antenna to be easily disconnected, and improves heat resistance by embedding the IC chip in endothermic material. This configuration realizes an RFID tag that is not destroyed even when heated in a microwave oven.  
         [0025]     According to an aspect of the present invention, heat resistance of an IC chip is improved.  
         [0026]     Furthermore, heat is prevented from being transferred to the IC chip.  
         [0027]     Moreover, resonance caused by electromagnetic waves generated by magnetron is prevented.  
         [0028]     Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.