text: 1. Field of the Invention
  The present invention relates to a wireless integrated circuit (IC) device applied to a radio-frequency identification (RFID) system that performs data communication in a non-contact manner using electromagnetic waves.
  2. Description of the Related Art
  In recent years, an RFID system that transmits information using contactless communication between a reader/writer generating induction fields and a wireless IC device being attached on an article and storing predetermined information has been being used as a merchandise management system.
  FIGS. 1A and 1B illustrate an example of a contactless IC tag (wireless IC device) in which an IC tag label is attached to an IC tag antenna disclosed in Japanese Unexamined Patent Application Publication No. 2003-243918. FIG. 1A is a plan view thereof, and FIG. 1B is an enlarged cross-sectional view taken along the line A-A in FIG. 1A. The contactless IC tag antenna is constituted by two pieces of separated antenna patterns 91 and 92. The antenna patterns 91 and 92 are formed from a thin metal layer.
  A label base 82b of a contactless IC tag label 82 is provided with antennas 101 and 102 on which an IC chip 85 is implemented. The antennas 101 and 102 of the contactless IC tag label 82 are attached to the antenna patterns 91 and 92 so as to be in contact therewith an anisotropic conductive adhesive 84 disposed therebetween, thereby forming a contactless IC tag 90.
  A sealant film 83 is disposed on the surface of the label base 82b to prevent the IC tag label from peeling off. In such a manner, a package with an IC tag, 81, is finally formed.
  A contactless IC tag and a package with the tag attached described in Japanese Unexamined Patent Application Publication No. 2003-243918 have the following problems.
  (a) A step of forming an antenna is necessary because the antenna is not formed in the same step of forming a package. This leads to an increase in the duration of a manufacturing process and to an addition of elements, thereby increasing the manufacturing cost of the package.
  (b) It is necessary to have a large antenna pattern to obtain sufficient radiation characteristics, which means that an IC tag cannot be attached on a small article.
  (c) An IC tag is attached on the base of an article and is covered with another film, thereby resulting in the thickness of the IC-tag formed portion being increased.