JP2870692B2 - Thin-film thermal head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-film thermal head, and more particularly to a thin-film thermal head having an improved thin-film heating resistor. [0002] Thin-film thermal heads using thin-film heating resistors are widely used as print heads in computer printers, word processors, facsimile machines and the like. The thermal head arranges a large number of resistive heating element dots and selectively energizes them to generate heat in a desired pattern or character shape, thereby thermally transferring or coloring the color material of the print ribbon to the paper surface. It is supposed to. The resistance heating element are known various ones, or have been used, Ni-Cr as a material often _{used, Ta 2 N, Ta-SiO} 2, Cr-S
i. These have excellent characteristics as resistance heating elements for thermal heads, but also have various disadvantages. Metallic heating resistors such as alloys are inferior in heat resistance and oxidation resistance. When the energy required for printing is repeatedly applied, the heating resistor generates an oxidation phenomenon due to heat generation, resulting in an increase in resistance value and printing. This leads to deterioration of characteristics. In addition, these metal-based heating resistors greatly expand and contract when subjected to a rapid thermal cycle due to heat pulses caused by repeated energization, causing large stress between the underlying substrate and the surface wear-resistant protective film. It may cause cracks. On the other hand, in the case of oxides or nitrides such as TaSiO ₂ , the thermal conductivity is low, so that the uniformity in the heating element is lacking, and the printing quality is deteriorated. Further, a metal-based heating resistor has a small resistivity (specific resistance), and the above-mentioned compound-based heating resistor also has a small resistivity (200 N in Ta ₂ N).
~300μΩcm, Ta-SiO ₂ even about 2000μΩ
cm), in order to obtain a sheet resistance of about 1 kΩ / □ required for a thermal head, it is necessary to realize a heating resistor having a thin film of several tens of mm, and it is difficult to stably manufacture the heating resistor. A typical manufacturing method is a well-known semiconductor process technology such as sputtering, ion plating, and CVD, but it is difficult to control the process unless the film thickness is about 1000 mm. Further, the resistance temperature coefficients of these heating element materials are relatively insensitive to the component ratio, and it is difficult to control them to desired values. Further, in the case of a metal-based material, a reaction occurs between the heating element and the power supply electrode, which causes a defect such as a change in the resistance value of the heating resistor and disconnection. Accordingly, an object of the present invention is to provide a thin-film type using a thin-film heating resistor having high heat resistance, a long life, a large resistivity, and an adjustable temperature coefficient. An object of the present invention is to provide a thermal head. SUMMARY OF THE INVENTION According to the present invention, Ti, Mo, W, Hf, Ni, V, Zr, La, F
a heating resistor thin film mainly composed of at least one refractory metal selected from the group consisting of e and Co, silicon, nitrogen and oxygen, and on the surface thereof, the heating resistor comprising silicon, nitrogen and oxygen. A thin-film thermal head in which a wear-resistant protective film having a resistance greater than that of the body thin film is formed, and a power supply electrode is connected to the resistor, wherein the wear-resistant protective film is formed of the heating resistor thin film. The thin-film thermal head according to claim 1, wherein the thin-film thermal head contains at least one kind of the high-melting-point metal in a smaller amount than the high-melting-point metal therein, and the power supply electrode is a single layer of Al. [0006] Due to the presence of the high melting point metal, the resistivity of the heating element does not change for a long time even by repeated heat pulses, and a stable thermal head can be obtained. Also unlike metal cases,
Since it is an oxy-nitride, thermal expansion and contraction are small, and there is no generation of large internal stress due to the difference in thermal expansion coefficient between the upper and lower layers, and thus no crack. When the amount of the metal exceeds the amount ratio of the oxide and the nitride, the thermal conductivity is improved and the heat uniformity is improved. In addition, the characteristics are stabilized without fear of oxidation with time due to the presence of sufficient oxygen and nitrogen. Further, since the resistivity greatly changes with respect to the content of the refractory metal, controlling the content thereof increases the control range of the characteristics of the thermal head, for example, 10 ⁴ μΩcm, the temperature coefficient of resistance ± 100 ppm.
Heating element resistance such as / ° C can be easily designed. With such a high resistivity, the thickness of the thin film of the heating element is preferably around 1000 °, and the film formation becomes easy. According to the present invention, since the wear-resistant protective film is composed of the same kind of high-resistance material as the heat-generating resistor, the heat-generating resistor and the wear-resistant protective film fit well, and the difference in the coefficient of thermal expansion is small. Few. FIG. 1 schematically shows the structure of a thin film thermal head according to the present invention. In the figure, reference numeral 1 denotes a glazed ceramic substrate, on which a glaze layer 2 is formed. The glaze layer 2 is an oxide corresponding to the glaze of porcelain, and includes silicon and aluminum oxides.
The thin-film resistance heating element 3 of the present invention is formed on the glaze layer 2 by, for example, a known sputtering method, and a power supply electrode (Ni, Cr, Al, etc., particularly Al) 4 is formed by vapor deposition or sputtering. is film, the last known wear-resistant protective film (e.g., Si-O-based, Ta ₂ O _5, SiC system, etc.) 6 is formed by sputtering or the like. According to the present invention, the heating resistor 3 is made of silicon and high melting point metal M (Ti, Mo, W, Hf, N
i, V, Zr, La, Fe, and Co). This metal has a different function depending on the kind, but the resistivity and the temperature coefficient of resistance of the heating resistor are 10 ⁷ to 10 ² μΩcm and −1500 to +500 pp, respectively, singly or in any combination.
It fluctuates greatly in the range of m / ° C. Therefore, by selecting a specific refractory metal content, a heating element having a desired temperature coefficient at a desired resistivity can be designed. For example, resistivity 1
0 ⁴ thickness by selecting those μΩcm can without the least 1000 Å. Generally, the high melting point metal can be selected in the range of 10 to 60 wt%. This point will be specifically described with reference to examples. [0008] Si, O, and N can form a heat-resistant and oxidation-resistant substance. By changing the ratio, the resistivity can be changed while maintaining the heat resistance. For example, Si _0.3 O _0.4 N _0.3 has a resistivity >> 10 ⁷ μΩcm and a temperature coefficient <−1500 ppm / ° C.
Is 10 wt% or more and 10 ⁷ μΩcm or less, −1
00 ppm / ° C or more can be obtained. Si, O, N
If the abrasion-resistant protective layer 6 containing at least one of the above three types and optionally M (above) is selected, the heating resistor of the present invention is well adapted to the abrasion-resistant protective layer, and the difference in the coefficient of thermal expansion is small. It is preferable because it is less. Furthermore, if Al is used for the electrodes 4 and 5, the affinity between the electrodes and the heating resistor is similarly improved, which is preferable. The heating resistor of the present invention can be manufactured by a sputtering method. For example, a solid material powder having a desired composition ratio is produced in advance, and it is compression-molded and pelletized. Using this as a target, Ar is used as a sputtering gas, and O ₂ , N ₂ gas, and the like are coexisted as necessary. , Ar ions are bombarded on the target, and the released ions or atoms are deposited on the substrate. The film composition can be adjusted by changing the composition of the pellet and the sputtering conditions. DETAILED DESCRIPTION OF THE INVENTION A pellet having a composition of Mo _x Si _0.25 O _0.42 N _0.33 is used as a target and Ar of 1 to 6 mTorr is used as a sputtering gas.
By adjusting the conditions of power of 1 to 10 w / cm ² and substrate temperature of 200 to 400 ° C., a heating resistor having the above composition was manufactured, and further, an Al electrode and a protective film were sequentially formed to form a thermal head. The protective film contained a small amount of Mo in addition to Si. The following test was performed on the obtained thermal head. FIG. 2 shows the resistance value change rate when a heat pulse having a pulse width of 0.3 ms and a period of 2 ms was applied to the sample of x = 0.12. FIG. 3 shows the resistivity and the temperature coefficient of resistance depending on the Mo content. FIG. 2 also shows the results of a heat-resistant pulse test on a conventional Ta ₂ N heating resistor A and a Zr—Si heating resistor C as target samples. FIG. 2B shows a thermal head using the heating resistor according to the present invention. As can be seen from FIG. 2, the Mo-S of the present invention is used.
The thermal head using the i-O-N-based heating resistor B does not change its resistance value even when a large number of heat pulses are applied, and has good heat resistance. Conventional heating resistors A (Ta ₂ N) and C (Zr-S
In the case of i), the resistance changes greatly after a certain heat pulse. As can be seen from FIG. 3, the resistivity and the temperature coefficient of resistance of the heating resistor of the present invention greatly vary depending on the content of the high melting point metal. Therefore, these values can be designed to be desired values by adjusting the content of the high melting point metal. It is considered that the improvement in heat resistance is due to the uniformity of the temperature distribution in the plane of the heating element and the decrease in the coefficient of thermal expansion. Further, at least 3 of Mo, Si, O, and N is contained in the wear-resistant protective film.
If a material containing seeds is used, the compatibility between them will be improved, and the adhesion will be improved.
The occurrence of peeling or the like is suppressed. Further, the heat generating resistor of the present invention has excellent chemical resistance and is hardly affected by alkali or moisture.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a structure of a thermal head. FIG. 2 is a graph showing a thermal head using a heating resistor of the present invention and a heat resistance test of a conventional example. FIG. 3 is a graph showing the relationship between the refractory metal contained in the heating resistor and the resistivity and the temperature coefficient of resistance in the thermal head of the present invention.

Continuation of the front page (56) References JP-A-53-11037 (JP, A) JP-A-53-25442 (JP, A) JP-A-54-92276 (JP, A) JP-A-61-276201 (JP) , A) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B41J 2/335

Claims (1)

(57) [Claims] Ti, Mo, W, H on a base substrate having a heat insulating layer
a heating resistor thin film mainly composed of at least one refractory metal selected from the group consisting of f, Ni, V, Zr, La, Fe, and Co, silicon, nitrogen and oxygen; A thin-film thermal head, comprising: a wear-resistant protective film comprising nitrogen, oxygen and nitrogen, and having a resistance higher than that of the heat-generating resistor thin film; and connecting a power supply electrode to the resistor. 2. 2. The thin-film thermal head according to claim 1, wherein said wear-resistant protective film contains at least one kind of said high melting point metal in said heating resistor thin film in a smaller amount than said high melting point metal. 3. 2. The thin-film thermal head according to claim 1, wherein the power supply electrode is an Al single layer.