JPS6017709B2 - thin film thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film thermal head used for various types of thermal 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, a thermal recording paper is placed in contact with a thermal head, and a predetermined portion of the thermal 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 must slide on the heat-generating resistor film, and for this purpose, a wear-resistant protective film is usually provided on the heat-generating resistor film. Of course, this wear-resistant protective film is required to be sufficiently hard, but it is also important that the wear-resistant protective film cracks due to the thermal stress caused by the pulse passing through the heat-generating resistor film. Oxidation of the heating resistor film due to diffusion of oxygen in the film must also be sufficiently considered. For this reason,
It has also been proposed to interpose an antioxidant 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-A layer 3 is provided as an electrode film that conducts current to this Ta2N film. On top of that, SiQ is used as an oxidation prevention film.
A T and Q film 5 is provided as a wear-resistant protective film via the film 4.

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 heating resistor film and its surroundings are heated by application of a current pulse, stress is concentrated 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
In No. 5, the tensile stress within the film is approximately 8×1 to 9 d/e/suddenly large, which makes cracks more likely to occur. Ta2
When the four films crack, the Si02 film also cracks almost simultaneously, and the heating resistor film is rapidly oxidized due to the intrusion of oxygen, making it impossible to record. An object of the present invention is to provide an inexpensive and highly reliable thin film thermal head that eliminates the above-mentioned drawbacks.

In this invention, the wear-resistant protective film is
Formed by a film containing ○z as the main component.

Here, x, y, z represent the component ratio, x sheep 0, y sheep 0,
z is primarily 0. In this case, it is assumed that the component ratio of the TaxSiy○z film is controlled so that the value of x/y is minimum on the heating resistor film side and changes continuously in the thickness direction.

The top layer portion with a large x/y is hard and exhibits wear resistance. The portion on the heating resistor film side where x/y is small is somewhat soft, and this acts as a thermal stress relaxation layer and also as an oxidation prevention film that suppresses oxygen diffusion. Therefore, according to the present invention, for example, by using the TaxSiy0z film as the heating resistor film as well as the wear-resistant protection, it is possible to effectively prevent the occurrence of cracks due to thermal stress and oxidation of the heating resistor film.

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, the TaxS
In order to satisfy this condition using the iyQ film, it is necessary to make the value of (x+y)/z at the heating resistor film larger than that at the part of the wear-resistant protective film that is in contact with the heating resistor film. It is. 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, on which a heating resistor film of about 60 mm is applied. 〃thickness of TaSiM0, . 3 films 12 are provided, and a 2Aw thick Cr-A film is used as an electrode film to conduct electricity to this film.
A U film 13 is provided. A TaxSiy○z film 14 having a thickness of 6 mm is provided thereon as an abrasion-resistant protective film.

The surface portion of the TaxSiy○z film 14 is TaSjpi. 502
．． TaSi has a composition of 6, and the composition changes continuously.
M○,. The portion in contact with the third waist 12 has a composition of TaSi50.2.

Such a protective film is made of, for example, a Ta target and a Si target.
This can be easily obtained by continuously changing the ratio of sputtering speeds using a sputtering device that has a 0.02 target and can independently control each sputtering speed. According to experiments conducted by the inventors, it has been confirmed that even when Ta2Q is mixed with SjQ in a range of 0 to 10 mol%, its wear resistance is not comparable to that of Ta205.

It has also been confirmed that when 5 mol % or more of Si02 is mixed into Ta205, oxygen diffusion is suppressed more than in the conventional structure combining Ta205 and Si02 films. On the other hand, as shown in Figure 3, the tensile stress at T is 05 is S
It has also been confirmed that the incorporation of i02 results in a decrease in the thickness of 4. Therefore, according to this embodiment, the TaxSiy0z film 1
The surface portion of No. 4 exhibits sufficient abrasion resistance, and the inside acts as a stress-relaxing layer and an oxidation-preventing film, resulting in a highly reliable thin-film thermal head.

In addition, TaSjo. which is a heating resistor film. 70,. 3 membrane 1
2 has a specific resistance of about 5×10-30, which is less than 1/100 of the specific resistance of the lowest layer of the TaxSiyQ film 14 that is in direct contact with it, and selective heat generation is fully possible. It is. 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 the interface is strong. That's true. Therefore, the occurrence of peeling and cracks at the interface can be effectively suppressed.
In addition, it is cheaper than the conventional method in which an oxidation prevention film is made of a material different from the heating resistor film and the wear-resistant protective film. FIG. 4 shows the results of an energization life test using pulses with an interval of 2 hsec 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 the thin film thermal head of the above example.
A thin film thermal head was obtained using the same material shape and manufacturing conditions as in the above example, except that the i02 film was interposed as an oxidation-preventing film and the T05 film with a five-sided skin thickness was provided as an abrasion-resistant protective film. It is something. The resistance value change and the G rate of characteristics A and B are equally difficult, and this is thought to be due to oxidation of the surface of the heating resistor film due to the diffusion of oxygen in the wear-resistant protective film. However, it can be seen that the value of the variable G rate in characteristic B is suppressed to be about one order of magnitude smaller than that in characteristic A.
Further, characteristic A shows a rapid increase in resistance after 1 ec, but it has been confirmed that this is the result of cracks occurring in the wear-resistant protective film. As explained above, according to the present invention, by using a Ta-Si-○ compound film in which the component ratio changes continuously as an abrasion-resistant protective film, a thin film thermal head with excellent mirror reliability can be produced at low cost. It can be realized.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a main part of an example of a thin-film thermal head according to the present invention, Fig. 2 is a cross-sectional view of a main part of a thin-film thermal head according to an embodiment of the present invention, and Fig. 3 is a cross-sectional view of a main part of a thin-film thermal head according to an embodiment of the present invention. 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
M film (heating resistor film), 13...Cr-Au film (electrode film), 14...TaxSiyQ film (wear-resistant protective film)
. Figure 1 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, x≠0) is the main component, and x
1. A thin film thermal head characterized in that the value of /y changes continuously in the thickness direction so that the value of /y becomes minimum on the heating resistor film side. 2. The heat-generating resistor film has Ta_xSi_yO_z as its main component, and the value of (x+y)/z is larger than that of the wear-resistant protective film at the portion in contact with the heat-generating resistor film. thin film thermal head.