EFFECTS OF PORES IN THICK-FILM RESISTOR ELEMENTS ON THE PRINTING EFFICIENCY OF A THERMAL HEAD

An effect of the distribution of vacant pores in RuO2 heating resistor elements on the printing characteristics of a thick film thermal prin ting head was examined. The head had an RuO2-glass heating resistor el ement which had some vacant pores attributed to gas evolution during t he manufacturing process. The distribution of the vacant pores in each heating element was observed and quantitatively analyzed by an image processing technique using photomicrographs of the elements in correla tion with the printing efficiency. The vertical distribution of the po res in the heating resistor elements significantly affected the printi ng characteristic. A poor thermal conductivity of vacant pores prevent ed heat conduction to a heat-sensitive paper and to a substrate, resul ting in lower and higher efficiency for thermal printing, respectively .