| 摘要 |
PROBLEM TO BE SOLVED: To improve the safety. SOLUTION: A first and a second bar codes 4, 5 consisting of thermosensitive bodies reversibly to develop a color and to become transparent by temperature, to develop a color in a temperature range lower than a certain temperature and to become transparent in a temperature range higher than the certain temperature are provided on a base material 1 of a recording medium. Bar code parts of the bar codes 4, 5 are heated at different temperature, the first and the second bar codes 4, 5 are successively made to be transparent, read by a color difference sensor, plural pieces of read data are compared with preset true data and the truth/falseness of the bar codes is judged. |
