| 摘要 |
PURPOSE:To prevent leakage of secret of confidential documents through copying, by making objects in such a way that the color contrast between the ground of paper and characters and graphs written on the paper can be discriminated by naked eyes but hardly discriminated by lights for copying. CONSTITUTION:An object 9 is a sheet of vermilion color 8, on which characters 2, graphs, etc., are printed in black, and the black characters, etc., can be read by naked eyes against the vermilion color of the ground. When the object 9 is put on a PPC copying machine and a copying light 4 for forming electrostatic image is irradiated upon the object 9, the contrast between the ground color and the color of characters, etc., is very inferior and the characters 2 cannot be read. Therefore, the copy 10 of the object 9 has a black ground 11 for the whole surface by the toner. Thus the object 9 cannot be copied. In this way leakage of secrets of confidential documents through copying can be prevented. |
