Patent ID: 7950860

Claim:
A thermal printer comprising: a first thermal head which is so provided as to be brought into contact with one side of a paper and energizes a plurality of heater elements to print dot image data on the one side of the paper; a second thermal head which is so provided as to be brought into contact with the other side of the paper and energizes a plurality of heater elements to print dot image data on the other side of the paper; a controller configured to shift the energization time between the first thermal head and second thermal head; a first image buffer and a second image buffer that are configured to receive the dot image data, the first image buffer receives dot image data corresponding to the one side of the paper, and the second image buffer receives dot image data corresponding to the other side of the paper; a processor configured to convert the dot image data in the first image buffer and the second image buffer into a first pixel count and a second pixel count; a determination section configured to determine whether a summation of the first pixel count to be printed by the first thermal head and the second pixel count to be printed by the second thermal head exceeds a threshold value; and a mode setting section configured to set an asynchronous mode when the determination section has determined that the summation has exceeded the threshold value while setting a synchronous mode when the determination section has determined that the summation has not exceeded the threshold value.