activation temperature for the thermal activation sheet n u2192 a standard activation speed v 0 is set as the activation speed b the temperature of the radiator plate 22 is within the range of 0 3 to 0 4 times the activation temperature u2192 a speed v 1 is set as the activation speed c the temperature of the radiator plate 22 is within the range of 0 4 to 0 5 times the activation temperature u2192 a speed v 2 is set as the activation speed d the temperature of the radiator plate 22 is equal to or higher than 0 5 times the activation temperature u2192 a speed v 3 is as the activation speed herein the standard activation speed v 0 refers to a transport speed suitable for activating the thermal activation sheet n with the radiator plate 22 being at room temperature further the speeds v 1 to v 3 are values within the range of for example 1 05 to 1 8 times the standard activation speed v 0 and satisfy a relationship of speed v 1 gt speed v 2 gt speed v 3 the respective values of the speeds v 1 to v 3 vary according to such factors as the surface area or speed of contact between the radiator plate 22 and the thermal activation sheet n and also the kind of the thermal activation sheet n and are dictated by how much the thermal activation sheet n is elevated in temperature through preheating with the radiator plate 22 then once the setting of the thermal activation energy is completed through the processing of steps j 19 to j 25 then in step j 26 the thermal activation sheet n is advanced by a.