JPS6249193B2 - - Google Patents

Description

[Detailed description of the invention]

A thermal head is a head that selectively generates heat through a heating resistor through a wiring conductor for power supply, and applies the generated heat to the thermal paper to color a predetermined area of the thermal paper and print or print. be. This type of recording method is called a thermal recording method.
It has features such as the ability to make the device smaller and cheaper, requires no maintenance effort, and does not emit noise or odor. The development of low-cost thermal heads is actively underway. There are three types of thermal heads: semiconductor type, thick film type, and thin film type, depending on how they are manufactured, but the thin film type is superior in terms of resolution and printing quality, and is considered the mainstream thermal head. It is considered. However, the manufacturing process for thin film thermal heads is relatively more complicated than that for thick film heads, and there are problems in terms of mass production. One of the complicating factors is the problem of preventing oxidation due to heating of the heating resistor.The present invention uses a new material to make it possible to create a wear-resistant protective film with an oxidation-preventing effect in a simple process, making it possible to mass-produce it. The purpose is to improve the results. By the way, thermal heads are used by repeatedly heating and cooling at high temperatures while sliding against thermal paper, so deterioration of the heating resistor and wear of the abrasion-resistant protective film are the most important factors for the reliability of the head. It is a factor. The thickness of the heating resistor layer of a thin film type thermal head is usually several hundred angstroms, so preventing oxidation due to high temperature heating is important to prevent deterioration. Nichrome (Ni-Cr) or tantalum nitride (Ta ₂ N) heating resistors, which are generally used as heating resistors, also have poor oxidation resistance and deterioration when heated at high temperatures. For this reason, a thermal head using the above-mentioned heat generating resistor conventionally has a structure in which an oxidation-resistant film is formed as shown in FIG. In FIG. 1, 1 is a wear-resistant protective film, such as tantalum oxide (Ta ₂ O ₅ ) or silicon carbide (SiC), and 2 is an anti-oxidation film, such as SiO ₂
The films 3 and 4 are wiring conductors, and the wiring conductor 4 is a layer for improving adhesion to the heating resistor. 5 is a heating resistor layer made of nichrome (NiCr) or tantalum nitride. 6 is a glass glaze layer, and 7 is an alumina substrate. The reason why the wear-resistant protective layer has such a two-layer structure is as follows. That is, the parts that directly slide against the thermal paper are subject to wear, and therefore require a material that is highly hard and resistant to wear. Such materials include oxides, carbides, and nitrides, but generally the oxidation prevention effect of heating resistors is insufficient. For example, when commonly used Ta ₂ O ₅ , Al ₂ O ₃ and SiC films are directly formed and used on a heat generating resistor, the heat generating resistor deteriorates due to oxidation. By the way, it has been discovered that SiO ₂ is a material that has such an antioxidant effect, but experiments have also found that the wear resistance of the SiO ₂ film is poor. For the above reasons, the wear-resistant protective layer portion has a two-layer structure. However, the head having such a structure has the following problems. (1) The wear-resistant film formation process becomes complicated. The thickness of the SiO ₂ film to obtain a sufficient oxidation prevention effect is 2μ, and since this film is necessary even though it has little effect as an anti-wear protective film, it not only complicates the process but also However, there is a problem that the processing time becomes long. (2) Thermal efficiency decreases. In order to efficiently transfer the heat generated by the heating resistor to the thermal paper, the better the thermal conductivity of the wear-resistant protective film is, the better. However,
Thermal efficiency cannot be increased because the thermal conductivity of the SiO ₂ film is poor. (3) The heat generation temperature distribution is uneven. The temperature rise due to electrical heating of the heating resistor portion is high at the center and becomes lower toward the periphery, as shown by characteristic a in FIG. The heat generation temperature distribution is better if the center is flat, as shown in characteristic b in Figure 2.
Due to the poor thermal conductivity of the oxidation-preventing SiO ₂ film, heat from the center does not move to the periphery, and in the past, only characteristic a in FIG. 2 was observed, resulting in insufficient print quality. As a method of solving the above-mentioned conventional problems, it has been attempted to form a heating resistor having particularly good oxidation resistance. As such a heating resistor, there is a Si--Ta alloy film. As is well known, Si is a material with very good oxidation resistance. Therefore, Si−
The Ta alloy resistor has a higher concentration on the resistor layer.
The structure uses a Si-Ta alloy layer containing Si as an oxidation prevention film. Although the problems of the conventional method are solved by using this heating resistor, there are other problems such as the resistor formation technology is complicated and the wiring conductor tends to react with Si, so it is not satisfactory. It's not a kimono. In other words, if a material with excellent oxidation resistance and abrasion resistance can be obtained as a wear-resistant protective layer,
The above-mentioned problems are solved, the resistor forming technique and the wear-resistant protective layer forming process are simplified, and this can greatly contribute to improving the mass productivity of thermal heads. The present inventor focused on the fact that Si is a material with excellent oxidation resistance, good thermal conductivity, and relatively high hardness, and mixed Si with oxides, carbides, nitrides, etc. that have excellent wear resistance. The abrasion resistance and oxidation resistance of the film were investigated. As a result, it was found that a film containing Si can be obtained with excellent oxidation resistance without impairing wear resistance. The amount of Si mixed varies depending on the wear-resistant material, but as shown in Table 1, results satisfying both oxidation resistance and wear resistance were obtained in all cases.

[Table] When using a mixture, it was observed that the amount of silicon mixed was slightly different from the amount shown in Table 1, but it was found that there is a amount of silicon mixed that can satisfy oxidation resistance and wear resistance. Ta. Below, as an example of the present invention, a case where SiC is used as the wear-resistant material will be described. High frequency sputtering is the simplest method for obtaining a mixed film, and a mixed film of any composition can be obtained by placing Si on a SiC target at an appropriate area ratio and performing high frequency sputtering. Note that this film can also be obtained by vapor deposition. The hardness of the film decreases as the amount of Si mixed increases, but even with an addition amount of about 10%, the Knoop hardness is about 2200.
Kg/mm ² , which is harder than Ta ₂ O ₅ film, which has a hardness of 650 Kg/mm ² , and showed sufficient wear resistance. It was also found that oxidation resistance can be protected with a film with an additive amount of about 10%. Note that a similar film can also be obtained by impregnating a SiC target with Si at high temperature as a method for producing a mixed film. FIG. 3 shows a sectional view of a thin film type thermal head according to the present invention, and the steps up to the formation of the heating resistor 5 and the wiring conductors 3 and 4 are the same as the conventional one, but the wear-resistant protective film process is different from that described above. The process is simple as it is only necessary to form a mixed film using the method described above.
In addition, in FIG. 3, 8 is a wear-resistant protective film mixed with Si in the present invention. It goes without saying that the method of this example is not specific to SiC, but can also be performed with other oxides, nitrides, or carbides. Improvements are possible. As described above, by using the wear-resistant protective film mixed with Si according to the present invention, it is possible to form a protective film with excellent oxidation resistance and wear resistance in a simple manner, and the method for manufacturing a thin-film thermal head It is possible to make a simple and reliable head.
In addition, the protective film has good thermal conductivity, which improves temperature distribution, improves printing quality, and enables a head with excellent thermal efficiency.
Since Si improves the adhesion of the wiring conductor, the adhesion is also improved, and the present invention can provide extremely effective effects for thin film type thermal heads.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional thin film type thermal head, Figure 2 is a diagram showing the temperature distribution of the heat generating part in the conventional head (characteristic a) and the head of the present invention (characteristic b), respectively. 1 is a sectional view showing the structure of a thin film type thermal head according to an embodiment of the present invention. 3, 4...Wiring conductor, 5...Heating resistor, 6
...Glass glaze layer, 7...Alumina substrate, 8
...Wear-resistant protective film.

Claims (1)

[Claims] 1. A thin film type thermal head comprising a heating resistor formed on an insulating substrate, a wiring conductor for supplying power to the heating resistor, and an abrasion-resistant protective film for protecting the heating resistor and wiring conductor. A thin film thermal head characterized in that a film made of a mixture of oxide, carbide, or nitride with silicon is used as a wear-resistant protective film.