| 摘要 |
PROBLEM TO BE SOLVED: To provide a printed matter, the forging of which is hard to realize. SOLUTION: A gradation printing layer 2 is formed with an infrared absorbing ink on the basic sheet 1 of the printed matter. A concealing printing layer 3 is formed with a visible-light-reflecting ink on the gradation printing layer. By irradiating infrared rays over the resultant printed matter, its reflected light is detected so as to differentiate the detected detection output in order to judge the existence of the gradation printing layer from the shape of the differentiated value, resulting in judging the authenticity of the printed matter. |
