1. Field of the Invention
The present invention relates to a novel thermal printhead and, more particularly, to a thermal printhead having heat generating resistors made of a Cr-Si-SiO alloy.
2. Description of the Prior Art
Hitherto, the heat generating resistor for use in thermal printhead has been produced either from (1) a Cr-Si alloy as disclosed in the specification of U.S. Pat. No. 4,343,986 or (2) a Cr-SiO alloy as disclosed in IBM Technical Disclosure Bulletin Vol. 23, No. 2, July 1980.
The heat generating resistor made of Cr-Si alloy, however, suffers from the following disadvantages (a) and (b), while the heat generating resistor made of Cr-SiO alloy suffers from the following disadvantages (c) and (d) in addition to the disadvantages (a) and (b) common to the heat generating resistor made of Cr-Si alloy.
(Disadvantages of Heat Generating Resistor Made of Cr-Si Alloy)
(a) The maximum electric power density is as small as several W/mm.sup.2.
(b) Resistance value is undesirably changed when the heat generating resistor is used for a long time at a high temperature. For instance, 3 to 7% change in resistance value is caused as compared with the initial resistance value (resistance value after a heat treatment up to high temperature, for instance 400.degree. C., following the film formation by sputtering) after 600 hours operation at 200.degree. C.
(Disadvantage of Heat Generating Resistor Made of Cr-SiO Alloy)
The following disadvantages (c) and (d) are encountered besides the above-mentioned disadvantages (a) and (b).
(c) Only negative temperature coefficient is available so that the use is impractical for heat treatment resistor application.
(d) Etching speed is too low.
Under this circumstance, there is an increasing demand for resistor material having improved performance as the material of, for example, thin film thermal printhead.