JPS6017708B2 - thin film thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film thermal head used in various types of heat-sensitive recording.

A thin film thermal head has a plurality of heating resistor films as printing elements provided on an insulating substrate, and usually has a structure in which electricity can be selectively applied.

In this printing method, heat-sensitive recording paper is placed in contact with a thermal head, and a predetermined portion of the heat-sensitive recording paper is heated and colored by selectively energizing the heating resistor film in pulses. In order to perform continuous printing, the heat-sensitive recording paper comes into contact with and slides on the heat-generating resistor film, and for this purpose, a wear-resistant protective film is usually provided on the heat-generating resistor film. It goes without saying that this wear-resistant protective film is required to be sufficiently hard, but it is also possible that the wear-resistant protective film may crack or crack due to thermal stress associated with pulsed current application to the heat-generating resistor film. Full consideration must also be given to oxidation of the heat generating resistor film due to the diffusion of oxygen inside. For this reason, it has also been proposed to interpose an oxidation-preventing film between the wear-resistant protective film and the heating resistor film. FIG. 1 shows the main structure of an example of such a thin film thermal head.

Reference numeral 1 denotes an insulating substrate such as glazed alumina, on which a Ta2N film 2 is provided as a heating resistor film, and a Cr-Au film 3 is provided as an electrode film for conducting current to this Ta2N film. On top of that, Si0 is used as an anti-oxidation film.
A Ta2Q film 5 is provided as a wear-resistant protective film with the two films 4 interposed therebetween.

Although the Ta205 film 5 is hard, it does not have the function of preventing oxygen diffusion, so the Si02 film 4 is interposed therebetween. However, in such a structure, since the heating resistor film, the anti-oxidation film, and the wear-resistant protective film are each made of different materials, it is difficult to ensure sufficient adhesion strength at each interface.

Therefore, when the heat-generating resistor film and its surroundings are heated by application of a current pulse, stress is built up at each interface, resulting in a disadvantage that peeling or cracking is likely to occur along the interface. Furthermore, hard materials are generally strong against compressive stress and weak against tensile stress. Especially Ta20 obtained by sputtering method
5 membrane has a large tensile stress within the pus, approximately 8×1 to 9 d/e/, which makes cracks more likely to occur. Ta
When a crack occurs in the Si02 film, a crack also appears at the same time in the Si02 film, and the heating resistor film is rapidly oxidized due to the intrusion of oxygen, making it impossible to record. The purpose of this invention is to provide an inexpensive and highly reliable thin-film thermal head that eliminates the above-mentioned drawbacks. do.

Here, x, y, and z represent the component ratio, and x 0, y 0,
Z sheep is 0. Further, in this case, the multiple layers of protective film are x/
The one with the smallest value of y is on the heating resistor film side, and
They are stacked so that the value of y becomes large. The top layer TaxSiy○z film with large x/y is hard and exhibits wear resistance.

x/y nozzle, TaxSiy○z on heating resistor film side
The film has a slightly rough texture, which acts as a thermal stress-relieving layer and as an oxidation-preventing film that suppresses oxygen diffusion.
Therefore, according to the present invention, for example, by using the TaxSiy○z film as the heating resistor film in the same way as the wear-resistant protective film, it is possible to effectively prevent the occurrence of cracks due to thermal stress and the oxidation of the heating resistor film. I can do it.

In order to selectively energize the heating resistor film to generate heat, it is desirable that the resistivity of the abrasion-resistant protective film in direct contact thereon is approximately 100 times or more greater than that of the heating resistor film.

Therefore, in this invention, TaxS is used as the heating resistor film.
In order to satisfy this condition using the iy○z film, the value of (x+y)/z at the waist of the heating resistor must be made larger than that at the layer in contact with the heating resistor film of the wear-resistant protective film. is necessary. FIG. 2 shows the main structure of an embodiment of this invention.

In the figure, reference numeral 11 is an insulating substrate such as glazed alumina with a glass layer of about 60 mm thick, and a heating resistor film made of TaSio. 70,. 3 membranes 12
is provided, and as an electrode film for energizing it, a C
An r-Au film 13 is provided. On top of this, a wear-resistant protective film 14 is made of TaSi50,2 with a thickness of IAw.
Membrane 1 4. and 5 mm thick TaSio. Stool 02 $ Membrane 142
are stacked in sequence. Such a protective pus 14 has, for example, a Ta205 target and a Si02 target,
This can be easily obtained by switching the sputtering speed using a sputtering device that can independently control each sputtering speed. According to the inventors' experiments, Ta2Q and SiQ
It has been confirmed that even when Ta205 is mixed in a range of 0 to 10 mol%, its wear resistance is not comparable to that of Ta205. Also, T
When 5 mol% or more of Si02 is mixed into a205, T also becomes 0.
It has also been confirmed that the diffusion of oxygen is more suppressed than in the conventional structure that combines the Si02 film and the Si02 film. On the other hand, as shown in FIG. 3, it has been confirmed that the tensile stress of the Ta205 film is reduced by the inclusion of Si02. According to this embodiment, therefore, TaSio. o502.6 membrane 142
shows sufficient wear resistance, and TaSi50,2 film 14,
As a result, a highly reliable thin film thermal head can be obtained as a result of functioning as a stress relaxation layer and an oxidation prevention layer.

In addition, TaSio. 70,. 3 membrane 1
2 has a specific resistance of approximately 5×10-30 arc, which is less than 1/100 of the specific resistance of the TaSi50,2 film 14 that is in direct contact with it, and selective heat generation is fully possible. . The most characteristic feature of this example is that the heating resistor film and the wear-resistant protective film laminated thereon are both Ta-Si-○-based compound films, so the adhesion strength at their interfaces is high. It's a strong thing. Therefore, peeling and cracking at the interface can be effectively suppressed. In addition, it is cheaper than the conventional method in which an anti-oxidation film is made of a material different from that of the heating resistor and the wear-resistant protective film.
FIG. 4 shows the results of an energization life test using pulses with an interval of 2 seconds and a width of 1.9 hsec while maintaining the temperature at 450°C.

Characteristic B is obtained by the thin film thermal head of the above example, and characteristic A is obtained by interposing a Si02 film with a thickness of lr as an oxidation prevention film, and a Ta2Q film with a thickness of 5 mounds on top of it as a wear-resistant protective film. The thin film thermal head was obtained using the same materials, shape, and manufacturing conditions as in the above embodiments except for the above embodiments. Characteristics A and B have the same resistance value change rate, and this is thought to be due to oxidation of the heating resistor film surface due to oxygen dissipation during wear-resistant protection. but,
It can be seen that in characteristic B, the value of the variable P ratio is suppressed to about one order of magnitude smaller than that in characteristic A. Also, characteristic A is 1 eq.
However, it has been confirmed that this is the result of cracks occurring in the wear-resistant protective film. In the above example, the wear-resistant protective film is x/y
Although a two-layer structure of TaxSiy02 with different values is used, it is of course possible to stack three or more layers.

In this case, the value of x/y is the smallest on the heating resistor film side,
The value of x/y may be made to increase sequentially as it goes upward. As explained above, according to the present invention, an inexpensive and highly reliable thin film thermal head can be realized by laminating multiple layers of Ta-Si-○ compound films with different component ratios as wear-resistant protective films. be able to.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a diamond part of an example of a conventional thin-film thermal head, Fig. 2 is a cross-sectional view of a thin-film thermal head of an embodiment of the present invention, and Fig. 3 is a cross-sectional view of a diamond part mixed with Ta20 or SiQ. FIG. 4 is a diagram showing the results of the energization life test of the above embodiment in comparison with the conventional example. 1 1... Insulating substrate, 12... TaSio. 70
、． 3 film (heating resistor film), 13...Cr-Au film (
electrode film), 14...wear-resistant protective film, 14,...TaSi5
0,2 film, 142...TaSio. 502.6 membrane. 1st
Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A thin film thermal head having a heating resistor film and an electrode film for supplying electricity to the heating resistor film on an insulating substrate, and further having a wear-resistant protective film on the surface thereof, wherein the wear-resistant protective film is , Ta
_xSi_yO_z (where x, y, z represent the component ratio, x≠0, y≠0, z≠0) is the main component, and x
1. A thin film thermal head comprising a plurality of laminated layers in which the value of x/y increases sequentially, with the layer having the minimum value of /y disposed on the heating resistor film side. 2. The heating resistor film has Ta_xSi_yO_z as a main component, and the value of (x+y)/z is larger than that of the wear-resistant protective film in contact with the heating resistor film. thin film thermal head.