JPS592626B2 - Thin film thermal head - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a thin-film thermal head for stably coloring thermal paper using Joule heat from a small thin-film resistor, which has particularly excellent thermal shock resistance, oxidation resistance, and stability. The present invention provides a thin film type thermal head.

In general, Ta2N and NiCr are well-known examples of heating resistors used in thin-film thermal heads, and their structure consists of a glass layer of several tens of microns thick as a protective layer on a ceramic substrate, and T as a heating resistor
A thin film of a2N, NiCr, etc. is formed with a film thickness of about 0.1μ, and an electrode is further formed on this heating resistor to constitute a heating element, and a part of the heating resistor and electrode is covered. It is constructed by forming an anti-oxidation film and a wear-resistant layer on the surface.

By the way, Na2N, NiCr, etc. have a specific resistance ρ of 5×10
-4Ω], the resistance value R required for a thermal head is 100 to 300Ω, and the L/W of the heating dot (
Since L is the length of the dot and W is the width of the dot), it is necessary to set the heat generating resistor to an extremely thin film thickness of about 0.1 μm because of the requirement that the value is 1 to 3.

However, since thermal heads are used by repeatedly applying thermal pulses that reach 300 to 400 degrees Celsius, the thermal expansion coefficient with the substrate is low when using such a thin heat generating resistor due to its low mechanical strength. Due to the difference, cracks occur in the thin heating resistor, resulting in extremely poor thermal shock resistance. In order to eliminate this drawback, we have developed a conventional Ta2
Ta, Mo, Ti,
A method using an alloy of high melting point metals such as W and Zr and Si was previously proposed.

That is, a heat generating resistor made of an alloy of a high melting point metal and Si can have a larger specific resistance ρ than a conventional thin film resistor made of a thin film of Ta2N, NiCr or the like.

Therefore, when an alloy of high melting point metal and Si is used as the heating resistor of the thermal head, the required resistance is 100 to 30.
In order to obtain 0Ω, the film thickness can be increased compared to the conventional one, and the above-mentioned problem of cracks in the heating resistor made of Na2N, NiCr, etc. can be eliminated.

In fact, in the thermal head previously proposed by the present inventors, in order to obtain excellent thermal shock resistance and oxidation resistance, the above-mentioned Ta and M
By appropriately determining the weight ratio M/Si of the alloy of high melting point metal Ta such as O, Ti, W, and Zr and Si, the specific resistance ρ can be set to about 1XI0-3 to 5x10-2Ωo, which is the conventional heating resistor. By increasing the film thickness by one to two orders of magnitude and setting the film thickness to 0.1 μm or more and several μm, it was used as a heating resistor for a thermal head.

However, on the other hand, the specific resistance ρ is 1×10−3 to 5×1
The weight ratio M of high melting point metal and Si is set to 0-2Ωo.
It has become experimentally clear that it is very difficult to adjust /Si and stably form it on the insulating substrate 1 in terms of manufacturing.

That is, FIG. 2 shows the weight ratio M/Si of alloys of high melting point metals M such as Ta, MO, Ti, W, and Zr and Si.
As is clear from the figure, in the range of resistivity ρ from 1 x 10-3 to 5 is changing rapidly.

Therefore, in this range of resistivity ρ, high melting point metal and Si
It is very difficult to stably form a heating resistor on an insulating substrate by adjusting the weight ratio M/Si. On the other hand, when the resistivity .rho. is in the range of 5.times.10@4 to 5.times.10@-3 .OMEGA.G, the change in the resistivity .rho. is small with respect to the change in the weight ratio M/Si, and it can be stably formed as a heating resistor for a thermal head. In summary, Ta, MO, Ti, W, Zr
When using an alloy of Si and a high-melting metal such as
It is desirable that the film thickness be as low as Ωo, so when used as a heating resistor for a thermal head, the film thickness will be lower than that of the conventional Ta2.
As in the case of N, NiCr, etc., the thickness was about 0.1μ, and the thermal shock resistance could not be sufficiently increased. The present invention combines such high melting point metals such as Ta, MO, Ti, W, and Zr with S
In the heating resistor made of an alloy with i, its film thickness is 0
．． The purpose is to obtain sufficient thermal shock resistance and oxidation resistance even when the thickness is as thin as about 1 μm.

That is, the thin film type thermal head of the present invention is characterized in that a heat generating resistor made of an alloy of a high melting point metal and Si is formed on an insulating substrate having a glass layer on at least the surface via an insulating Si thin film. shall be.

The insulating Si thin film effectively acts as a buffer layer between the insulating substrate and the heating resistor, and the thickness of the heating resistor is 0.1.
A thermal head with sufficient thermal shock resistance and oxidation resistance can be obtained even if the thickness is around μ. Hereinafter, the thin film type thermal head of the present invention will be explained with reference to the drawings of FIGS. 1 to 3.

FIG. 1 shows a thin film thermal head according to an embodiment of the present invention, in which 1 is an insulating substrate made of alumina or the like;
2 is a glass layer formed on the surface of this insulating substrate 1, 3 is an insulating Si thin film with high specific resistance formed on this glass layer 2, and on this insulating Si thin film 3 are the aforementioned Ta, MO, T, etc.
A heat generating resistor 4 is formed which is made of an alloy of high melting point metal such as i, W, Zr, etc. and Si and has a low specific resistance ρ of about 5 x 10-4 to 5 x 10-3. is electrode 5
is electrically connected and pulled out.

6 is a wear-resistant layer.

Here, the number of insulating substrates 1? A thick glass plate may be used, and in this case, the glass layer 2 may not be formed. Next, the function and effect of the insulating Si thin film 3 will be explained.

Figure 3 shows the results of a thermal shock test on a heating resistor.
The characteristics shown in Fig. 3 are 20 m with a pulse width of 6 msec.
The change in resistance after repeatedly applying pulses every sec for 30 minutes is expressed as power (G''/Wlt) normalized by area.

In addition, the area of the heat generating part is approximately 0.015Td to 0.03T!
It is about RIL. In addition, in Figure 3, characteristic A is insulating Si.
When the thin film 3 is present, characteristic B is the case when this insulating Si thin film 3 is not present. As is clear from Figure 3, A,
Both B exhibit properties superior to conventional NiCr, Ta2N, etc.

Further, in the case of A and B, that is, in the case of an alloy of high melting point metal M and Si, good characteristics can be obtained without providing a protective layer or the like on the surface of the heat generating part. Here, the reason why A is particularly superior to B, that is, the reason why the case where the insulating Si thin film 3 is provided shows superior thermal shock resistance is that the insulating Si thin film 3
This is thought to be due to the phenomenon of relaxation of thermal stress between the glass layer 2 and the heat generating resistor 4 due to the above. In other words, if the heating resistor 4 with a film thickness of several hundred amps and a small resistivity is formed directly on the glass layer 2 (grayst alumina, etc.), the heating resistor 4 will crack in the direction perpendicular to the current direction due to thermal stress. occurs and the heating element is destroyed. At this time, if an insulating Si thin film 3 is formed between the glass layer 2 and the resistance heating element 4,
The insulating S1 thin film 3 acts as a buffer against thermal stress caused by heat generation during use as a thermal head, making it difficult for cracks to occur and extending the life of the heating resistor.
Further, by providing the insulating Si thin film 3, the adverse effects of gas components such as O2 and H2 on the heat generating resistor 4 during manufacturing can be alleviated, resulting in the advantage that the heat generating resistor 4 can be formed stably. That is, the heat generating resistor 4 made of an alloy of high melting point metal and Si has a temperature of 02,H during film formation.
A heating resistor film containing a large amount of gas has a high specific resistance immediately after formation, and gas is released due to thermal stress, causing resistance deterioration (resistance reduction). In this case, if there is an insulating Si thin film 3, 01. ,H
It is possible to adsorb gas components such as No. 2, etc., and alleviate the adverse effects on the heating resistor 4.

Furthermore, when Si is used as the insulating thin film, the adhesion between the glass layer 2 and the heating resistor 4 becomes better than when the heating resistor 4 is formed directly on the glass layer 2.

This is considered to be because the insulating Si thin film 3 has a large 02 occlusion effect, and a strong adhesive force is generated between the glass layer 2 and the heating resistor 4 via the 02.

Furthermore, in such a thin film type thermal head, a pattern is formed by depositing a thin film of the heating resistor 4 on the insulating substrate 1 and then etching it.
In particular, when Ta is used as M, it is necessary to use a fluoronitric acid-based etching solution, which etches not only the heating resistor 4 but also the glass layer 2 (or the substrate itself if a glass substrate is used). It will be done. The presence of the insulating thin film 3 is effective to prevent this, and even if a material that is etched with a fluoro-nitric acid-based etching solution is used, the thickness of the heating resistor 4 is several times the thickness of about 0.1 μm. If the thickness is increased, selective etching without etching the glass layer 2 can be performed.

As is clear from the above description, the thin film thermal head of the present invention has a heating resistor made of an alloy of Si and a high melting point metal such as Ta, MO, Ti, W, or Zr, which is connected to the heating resistor through an insulating Si thin film. It is formed on an insulating substrate that has a glass layer on at least the surface, such as an alumina substrate or a glass substrate that has a glass layer on its surface.The insulating Si thin film acts extremely effectively as a buffer layer and makes the thermal head heat resistant. Not only can it have excellent impact resistance and oxidation resistance, but also the stability of the heating resistor during manufacturing can be improved.

Furthermore, when a heating resistor such as Ta-Si is used, selective etching with respect to the glass layer is possible, and etching of the glass layer can be prevented. In addition, when an alloy of high melting point metal and Si that forms silicide, such as TaSi2, Ta5Si3, Ta2Si, etc., is formed at high temperature, the film thickness is 500A.
Sufficient strength can be obtained even at a low level, there is little variation in specific resistance, and manufacturing stability is good.

As described above, the thin film type thermal head of the present invention has excellent effects and can greatly contribute to future technological development in this field.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a thin film thermal head according to an embodiment of the present invention, FIG. 2 is a correlation diagram between the weight ratio M/Si of an alloy of high melting point metal M and Si, and specific resistance. FIG. 3 is a characteristic diagram showing the results of a thermal shock test for explaining the effects of the thin film type thermal head of the present invention. 1... Insulating substrate, 2... Glass layer,
3... Insulating Si thin film, 4... Heat generating resistor.

Claims (1)

[Claims] 1. A thin film type thermal head in which a heating resistor made of an alloy of a high melting point metal and Si is formed on an insulating substrate having a glass layer on at least the surface thereof via an insulating Si thin film.