| 摘要 |
PROBLEM TO BE SOLVED: To improve record sensitivity and record image quality by adding an organic pigment as a pigment having a through hole into an undercoat layer and setting a thermal conductivity of the undercoat layer according to an a.c.-fed heating method to be not larger than a specific value. SOLUTION: An organic pigment as a pigment having a through hole is added into an undercoat layer, and a thermal conductivity of the undercoat layer according to an a.c.-fed heating method is set to be not larger than 1.2 W/m.. When the thermal conductivity is measured according to the a.c.-fed heating method, errors are lessened. An oil absorption of the organic pigment with the through hole is preferably not smaller than 100 ml/100 g because of less adhesion to a thermal head at the time of recording. The smaller the thermal conductivity of the undercoat layer is, the better the heat is insulated. Heat energy fed from the head is stored in a heat-sensitive coloration layer, and consequently coloration sensitivity is improved. From a viewpoint of balance between the thermal conductivity and oil absorption, a volume average particle size of the organic pigment with the through hole is preferably 0.1-2.0 μm. |
