| 摘要 |
PURPOSE:To ensure that a latent image appears as a warning when an image is dupli cated and interpretating an image is made impossible by printing a latent image using an ink containing a reversible, thermally discoloring material which thermally colors, on the surface of a base. CONSTITUTION:A sheet consists of an electron-donative coloring organic compound, an electron-receptive compound, a discoloration temperature adjusting agent and a low voltatility solvent as essential elements. If the sheet is set on a contact glass of a copy mounting table and then is exposed to light for duplication, the electron- donative coloring organic compound and the electron-receptive compound become colored and a latent image is visualized as a visual image and duplicated. Then a copy is taken out of the glass and cooled. Consequently, the latent image pattern is discharged again and becomes invisible. The required reversible, thermally discoloring material is the one which is colorless as long as it is exposed to a normal temperature, and is so highly responsive that a color of high density is thermally developed and has a high coloring density. The preferable electron-donative coloring organic com pound is a material which absorbs a large amount of light, especially in the photosensi tive wavelength zone during color development among other indolenophthalide compounds. |
