| 摘要 |
PURPOSE:To form an image of sharp color tone with high recording sensitivity and almost free from color contamination or ink run by using at least one kind of specific phenol substance as a coloring agent. CONSTITUTION:A dichromatic thermal recording medium contains at least, one kind of compound shown in formula I (R1 to R4 are hydrogen atoms or alkyl groups with 1 to 4C) as a coloring agent in a leuco coloration layer. The typical example of the compound is 1.1-bis (4-hydroxyphenyl)-1-phenyl ethane which is preferably used. This coloring agent is less susceptible of the adverse effects of a discharging agent during the storage of a recording medium, and also characteristic of its density adequacy during recording. Therefore, a dichromatic recording medium with high preservability can be obtained. However, if the coloring agent is used as one for a low temperature coloration layer, it is subject to the instantaneous action of a discharging agent during heating at high temperature and also produces a uniform and sharp color image at high temperature as properties. Therefore, the coloring agent is best suited to a low-temperature coloration layer. |
