Segmented Multi-Digit Thermal Printhead

Abstract

Current thermal printing applications are dominated by the line-type printheads, although other types have been utilized in the past. A new, segmented printhead type has been developed having multiple digit / character capability that offers simpler mechanical operation than either as no transverse movement between the printhead and thermal media is required. Electronic control is simpler, as well, as the number of segments or dots to drive are fewer to form the figure. For example, one figure can be formed by controlling 8 segments while 35 dots are required if formed using a traditional 5x7 matrix. The drawback of the segment type is that the range of figures is pre-determined; mainly suitable for numeric and special character figures. A demonstrable product has been developed having four numeric, three alpha symbols and punctuation. Challenges were to enhance readability by minimizing gaps between segments and to minimize production cost. Each figure consists of one common electrode and multiple heating element or segment electrodes. A multiplexing driver circuit minimizes the number of connections. Image density is adjusted by controlling supplied energy (applied voltage), “on time” or duty cycle; based on the thermal history.