Since personal information is recorded on credit cards, employee identification cards, company worker identification cards, membership cards, student identification cards, alien registration cards, and various licenses, security processes are applied to these cards so that forgery as well as falsification is not easily performed.
For example, Japanese Patent Application Laid-Open to Public Inspection No. 53-9600 and Japanese Patent Examined Publication No. 54-22326 disclose bar code printed cards secured against forgery and falsification, comprising an infrared ray emitting layer which absorbs infrared rays, and subsequently emits infrared rays having different wavelengths from the absorbed infrared rays. Further, forgery and falsification are thwarted by providing an optical variation element image.
In recent years, from the viewpoint of further enhancing security, IC cards have been employed which comprise, in their interior, an electronic element comprising memory medium featuring a so-called IC (integrated circuit).
In such IC cards, security is enhanced by utilizing cryptographic techniques as well as key techniques. In an IC card comprising information described on its surface, it is important that it is possible to confirm that contents described on the surface coincide with information stored in the memory of the electronic part provided in the IC card. Namely, there may be a case in which only its surface is forged through replacement and the function of the IC card is put to improper use.
In order to prevent such cases, it is recommended to always confirm that items described on the surface coincide with the contents stored in the memory. However, at present, it is very difficult to realize the foregoing.
Further, in order to enhance security of IC cards, a printed image such as a logo printed pattern is occasionally provided in the interior of the cards. On the other hand, occasionally, it is desired to confirm the structure of an IC chip or an antenna which can be viewed through its surrounding medium. In such a case, providing the printed image occasionally hinders to confirm the structure of the IC chip as well as the antenna.
Still further, electronic parts such as an IC chip and an antenna, which are provided in the interior of the cards, occasionally shield a printed image, included as a watermark, and degrade readability of the printed image.