The present invention provides an RFID tag substrate in which communication characteristics of an RFID tag do not vary by an influence of contents in a container, the communication characteristics of the RFID tag are not deteriorated even if a metal container is used, the communication characteristics of the RFID tag can be excellently maintained irrespective of a material or contents of a container, and the tag can be reduced in thickness/size, and which can use a general-purpose RFID tag as it is and is suitable for a microwave type RFID tag that uses a UHF band or a frequency band of, e.g., 2.45 GHz in particular.
There is provided an RFID tag substrate 10 on which an RFID tag 20 that performs wireless communication with a reader/writer is disposed, comprising: a substrate layer 11; and a functional layer 12 formed of a high-dielectric-constant layer 12a and a high-permeable layer 12b having different characteristics, wherein the functional layer having predetermined relative dielectric constant and relative permeability is provided, and a product of the relative dielectric constant and the relative permeability is not smaller than 250.