| 摘要 |
<p>PURPOSE:To reduce print irregularities, that is, density or feed irregularities caused when a printing speed is switched to a high or low level by providing means for setting a printing time for each of at least four blocks of a plurality heating elements while shifting sequentially. CONSTITUTION:A thermal head is driven in four divided actions, if the percentage of black dots in blocks a, b, c, d is higher than 50%, and prints a maximum two blocks simultaneously. If the percentage of black dots in either of the blocks is higher than 50%, the number of blocks to be printed simultaneously is a maximum 1. Then if the movement of recording paper in a subscan direction is almost at constant speed, the misalignment value of the block(a) from the block(b) or the block(b) from the block(c) or the block(c) from the block(d), of printing dots in the first and second lines in a subscan direction is 1/5 line width. In the meantime, the disalignment value of the block(a) from the block(b) or the block(b) from the block(c) or the block(c) from the block(d), of printing dots in the third and fourth lines in a subscan direction is 1/4 line width. Even when lateral lines are drawn, they are hardly visually conspicuous. Furthermore, there are almost no changes in the gaps between the blocks(b), (d) at a transition point from the second line to the third line and the fourth line to the fifth line. Thus no visual uncomfortableness is present.</p> |
