JPS6453872A - Thermal head - Google Patents

Abstract

PURPOSE:To eliminate harshness of images and produce favorable images, by setting the thickness of a resistor element in a thermal head for expressing intermediate tones to be smaller at a central part of the element, gradually increased toward end parts of the element, and substantially uniform in the width direction of the element. CONSTITUTION:The thickness of a resistor element 2 is so set that the thickness at a given point is smaller as the given point is closer to the top of a glaze layer 4, and larger as the given point is farther from the top of the glaze layer 4. The thickness is substantially uniform in the width direction of the element 2, so that the resistance of the element 2 at a given point is lower as the given point is farther from a central part of the element 2. Therefore, in a low energy region, heat is generated in the vicinity of the central part of the element 2, and as the energy is increased, the heat generating part is extended to end parts of the element 2. Because of the uniformity in the width direction, both for the central part and for the end parts, the size of a dot is maintained to be substantially constant, and it is possible to obtain favorable image quality in the range from low density areas to high density areas. Unlike in a conventional system, the dot size is large even in the low density areas, whereas microscopic density is low in the low density areas, so that the bright ground of a recording paper is hidden, and harshness is eliminated.