Thermal history control technology of TPH

Thermal history control technology

The thermal print head realizes printing through the instantaneous rise and fall of the resistance temperature of the heating element, and the process of rising and falling of the temperature of each heating element unit will be affected by its own initial temperature (heat storage) and the transmission of the surrounding heating element resistance units. heat effect. In general, complex control is not required for heat-generating body printing with a constant temperature state. But in fact, if the influence of the above-mentioned heat storage and heat transfer is considered, it is necessary to control the printing energy applied to the heating element. Especially in the case of high-speed printing, the heat storage of the heating element has a great influence, so the adjustment of the printing energy is very important. It is very important, we call this process of adjusting and controlling the applied energy of the heating body as thermal history control. Usually, the thermal history control is realized by adjusting the heating time (Ton) of the heating element. Specifically, in order to obtain a higher printing speed, it is necessary to shorten the cooling time of the heating element. If the heat generating unit does not release heat fast enough, the next pulse may be applied before the temperature has dropped to the reference level, resulting in too high print energy for the next dot, which can result in poor print quality and even shorten the print life of the head. Thermal history control means that a dot can be printed by adjusting the print width of a shorter pulse when the same heater unit retains heat due to printing the previous line. It can be provided on the print head by a thermal history control driver IC, or it can be implemented by the print controller with multiple pulse widths within a cycle time. Therefore, the purpose of thermal history control is to improve the printing speed of TPH while ensuring the printing quality.

■ Realization of thermal history control

As mentioned above, if it is known that the heating element unit maintains part of the printing heat of the previous line, the thermal history control is a set of techniques aimed at reducing the pulse width of the current printing, that is, using different pulse widths point by point. Generally, the heating time of all heating element units selected by STROBE signal activation is the same. The printer controller can achieve thermal history control by loading different data into the print head several times in a single print line and briefly activating the heating element unit, resulting in a different total pulse width at each point. The burden on the controller is used to calculate which heater units need to receive how many supplemental pulses.