| 摘要 |
PURPOSE:To raise the sensitivity of a tonal type thermal recording material as well as improve its tonal property by a method in which a color-forming layer is laminated in two layers, the first color-forming layer is allowed to color at a lower temperature than the second color-forming layer, and the color tones of both the first and second layers are equalized. CONSTITUTION:The melting point of the developer to be used in the first color-forming layer is lower than that of the developer to be used in the second color-forming layer, and the preferred melting pint is 120 deg.C or lower for the first color-forming layer and 150 deg.C or higher for the second color-forming layer. The preferred proportion of color- forming agents to be used in the first and second color-forming layers is 1:2-1:5 by weight, and the preferred amounts of the color-forming agents to be used are 0.3g/m<2> or less for the first layer and 0.3g/m<2> or more for the second layer. In case where the amount of the color-forming agent to be used in the first layer exceeds 1/2 the amount of the color-forming agent in the second layer or below 1/5 the amount of the color-forming agent, the thermal sensitivity and tonal pictures become insufficient. At lower temperatures (low energy section), the first color-forming layer is preferentially colored, and at the temperature of thermal head, the second color-forming layer is colored, showing a two-stage coloring condition. |
