| 摘要 |
PURPOSE:To obtain a uniform printing density even when a dot pattern changes, by disposing a group of subordinate heating resistors nearer onto the thermal head scan direction side than a group of main heating resistors on a base plate. CONSTITUTION:A main heating resistor group 2 and a subordinate heating resistor group 3 are disposed on a base plate 1, and the resistor group 3 is positioned on the thermal head scan direction side. Electrification pulses A and B are applied to the resistor groups 2 and 3. The resistance value of the resistor group 3 is made higher than that of the resistor group 2. When a dot pattern is a non-color-developing dot 0, the electrification pulse B becomes high and thereby thermal color developing paper is preheated. When a subsequent dot pattern is a color developing dot 1, the resistor group 2 is heated by the electrification pulse A, and thereby the highest temperature of the paper becomes higher than a threshold value. When a subsequent dot pattern is the color developing dot 1, the highest temperature of the paper becomes sufficiently higher than the threshold value. In this way, a uniform printing density can be obtained at all times even when the dot pattern changes. |
