| 摘要 |
<p>PROBLEM TO BE SOLVED: To give extremely effective forgery preventing, falsification preventing and copy preventing functions to a valuable printed matter such as a paper money, a passport, securities, stamp or the like by a simple means. SOLUTION: A printing surface of a passport book 1 of one example of a valuable printed matter is protected by a laminated film. Grooves 9 are formed on a partial or entire area of the film by a laser beam and thermal influence is given to printing 5 included on the area. When an ultraviolet ray is emitted to the printing 5, it is colored with a light having a wavelength except an ultraviolet band region, thereby deciding its truth or a falsehood.</p> |
