| 摘要 |
PURPOSE:To enable a halftone expression with a multicontrast while improving the printing quality in a low density area by connecting multiple sets of resistor elements varied in the energy to be applied per unit surface unit at the energization of a unit current in series to form a heat generating resistor. CONSTITUTION:A heat generating resistor 5 is made up of three kinds of rectangular-prism-shaped resistor elements 5a, 5b and 5c varied in the value of energy to be applied per unit surface area. The energy to be applied per unit surface area increases with the less product of the square value of the width of the resistor element and the thickness thereof and hence, the ease of printing increases in the order of the resistor elements 5c, 5b and 5a. When the energy to be applied to the resistor exceeds the critical value, printing starts to print a dot 31 almost coinciding with the area of the resistor element 5a. Thereafter, dots 32 augments stably with an increase in the energy to be applied. With further increase in the energy to be applied, the process of starting printing almost simultaneously over the entire area of the resistor element 5b is repeated to increase the area of the dot 33.
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