| 摘要 |
PROBLEM TO BE SOLVED: To provide specific ink for writing utensils capable of preventing secret information such as personal identification number from a furtive glance by other person when a person writes the secret information on the surface of upper paper (1P) and a writing utensil using the ink. SOLUTION: Specific ink for writing utensils obtained by formulating a fluorescent substance into a vehicle and capable of emitting light and visualizing characters, by ultraviolet irradiation though the ink can not visualized under ordinary light is used as the specific ink. When the writing utensil is unused, the ink exhibits viscosity not causing liquid drop and when the writing utensil is used, viscosity of the ink is lowered and has thixotropic property capable of writing down. This writing utensil encloses the specific ink for writing utensils in an ink storage part and further preferably is equipped with an ultraviolet irradiation device. |
