JPS598233B2 - thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head having a thin film heating resistor made of zirconium boride and oxygen, and also to a method for manufacturing the same.

A thermal head used for thermal print recording includes a plurality of heat generating resistors on a substrate having an electrical insulator such as glass and a smooth surface, and an electric conductor for supplying power to the heat generating resistors. Recording is performed by applying a current to the corresponding heat-generating resistor through an electric conductor to generate heat, and contacting the recording medium with a corresponding heat-generating resistor so as to obtain the necessary thermal pattern according to the information to be recorded. be.

Heat generating resistors used therein include conventional thin film heat generating resistors such as tantalum nitride and dichrome tin oxide, thick film heat generating resistors using silver-palladium, etc., and semiconductor heat generating resistors using silicon semiconductor. Among these, thermal heads using thin film heating resistors have better thermal response, superior heat resistance and thermal shock resistance, longer lifespan, and higher reliability than thick film heating resistors, semiconductor heating resistors, etc. It has the following characteristics.
Conventionally, tantalum nitride has been used for this thin film heating resistor, which has excellent heat resistance, high reliability, and has a specific resistance value of 250 to 3.
00 μΩ? Since the value is relatively high and the controllability of manufacturing is good,
Especially often used. However, tantalum nitride has about 300
At high temperatures above .degree. C., it is rapidly oxidized and its resistance value increases rapidly, which has the disadvantage of deteriorating the print density when printing on recording paper.

Generally, silicon oxide (SiO2) is used to compensate for this drawback.
) is provided with an oxidation-resistant protective layer of tantalum oxide (T
Although a wear-resistant layer of a2O3) is provided and used as a thermal head, the change in resistance when the thermal head is operated for a long time is still not fully satisfactory. Particularly in recent years, as the demand for high-speed thermal heads has increased, it is necessary to shorten the energizing pulse width of the head to color the thermal paper.This means that the electric power required is higher than before, and the heating resistor is heated to even higher temperatures. Therefore, the lifespan becomes shorter. Therefore, there is a demand for a heating resistor with even higher heat resistance. Also, the sheet resistance of tantalum nitride is usually 50μ
The resistance value is around 100 Ω/hole even when the thermal head is made particularly large.In order to further increase the resistance value, methods such as trimming or thinning the film are used, but in this case manufacturing There are disadvantages such as the process becomes complicated and the lifespan is adversely affected.

In this way, the tantalum nitride thin film heating resistor cannot have a large sheet resistance, so in order to supply enough power to heat the resistor, the current inevitably becomes large, and the resistance value of the electric conductor becomes a problem. .

In other words, since the resistance value of the electric conductor cannot be ignored compared to the resistance value of the thin film heating resistor, the amount of heat generated by each resistor will differ due to the difference in the distance of each electric conductor connected to the resistor, and the recording pattern will be different. There will be a difference in density between the images and the recording quality will be poor. Furthermore, if the size of the thin film heating resistor is reduced in order to increase the recording density, the sheet resistance value of the thin film heating resistor remains unchanged and only the resistance value of the electrical conductor increases, so power consumption in the electrical conductor becomes a problem. Furthermore, if the thickness of the electrical conductor is made extremely large in order to avoid this, in the case of multi-layer wiring, the surface becomes extremely uneven and becomes susceptible to abrasion, resulting in major structural problems.

In addition, the large current also causes disadvantages such as the need to increase the capacity of the heating power source, switching circuit, etc. The present invention improves the above points and provides a thermal head using a thin film heating resistor that is resistant to oxidation, has a stable resistance value, and allows the specific resistance to be selected up to a high value. The heating resistor consists of oxygen.

In this heating resistor, zirconium boride and oxygen are mixed on an atomic scale. A detailed description will be given below with reference to the drawings.

FIG. 1 is a sectional view of a main part of an example of the shape of a thermal head applied to the present invention. Reference numeral 1 in the figure is a substrate made of an electrical insulator such as ceramics, glass, or crystal ceramics. 2 is a thin film heating resistor according to the present invention made of zirconium boride and oxygen.

Reference numeral 3 denotes an electric conductor for supplying power to the thin film heating resistor, which is made of a good electric conductor such as aluminum or gold.

4 is a protective layer for the thin film heating resistor and electric conductor, for example, a multilayer structure made of silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, or a combination of these, manufactured by electron beam evaporation, sputtering, etc.; This makes it possible to further extend the life of the thermal head.

The thin film heating resistor of the present invention made of zirconium boride and oxygen can be manufactured by either sputtering or electron beam evaporation, but manufacturing by electron beam evaporation is superior in manufacturing large-area thermal heads and in mass production. There is. To manufacture a thermal head made of zirconium boride and oxygen by electron beam evaporation, approximately 100 kg of zirconium boride powder is required.
It is possible to make a tablet by pressing at a pressure of more than g/CTll and deposit it on a substrate that has been kept at a constant temperature in advance at a high vacuum level of 4T0rr or more. At this time, in order to control the oxygen content, it is also possible to introduce a gas containing oxygen during electron beam evaporation using a needle valve or the like. In this way, the heating resistor can contain oxygen and zirconium in an atomic ratio of 0.005 or more. If the oxygen content is too low, it will not be effective, and if it is too high, it will be difficult to control the specific resistance and the heat resistance will deteriorate, so 0.01 to 1.0 (atomic ratio) of zirconium is appropriate 0.05 to 0.6 is more preferable, and 0.1 to 0.3 is most preferable. Also, during electron beam evaporation, 200°C
By heating the substrate to 500 DEG C., the adhesion of the thin film heating resistor of the present invention to the substrate is improved and the stability of the film is also improved. The heat generating resistor manufactured in this way has a specific resistance value of 80 μΩ or more, depending on the amount of oxygen introduced during electron beam evaporation, the substrate heating temperature, etc. ~5000μΩ? It is possible to select up to.

In other words, if the specific resistance value is high, the manufacturing process will be easier because the electrode resistance value can be high to a certain extent, and the electrode can be made thinner, so the surface unevenness will be reduced, which will improve the abrasion resistance and improve the electrode part. Since the voltage drop at
Electrode pattern design (support) such as matrix wiring {Freedom. The heating resistor thus obtained is made of zirconium boride and oxygen, but usually contains some impurities such as nitrogen and carbon.

Next, an explanation will be given based on an example. Example 1 100% of zirconium boride powder (manufactured by Mitsuwa Chemicals)
A tablet is made by pressing at a pressure of more than kg/d, and after heating the substrate to 300℃ and vacuuming it to a vacuum level of 2×10-6T0rr on a creste ceramic substrate that has been thoroughly cleaned in advance, dry air is introduced using a needle valve. At the same time, electron beam evaporation was performed to a thickness of 1000λ at a vacuum degree of 5×10 −6 T0rr.

This area resistance is approximately 80Ω/mouth (specific resistance value is approximately 800P)
0c:m). When the composition of this film was examined using an ion microanalyzer, oxygen was found to be 0.18% of zirconium.
(atomic ratio) included. On top of this, titanium 20λ and aluminum were deposited to a thickness of 1 μm by electron beam evaporation, and a thermal head pattern with a resolution of 4 lines/mm was formed by selective etching, and this was designated as thermal head A1. Furthermore, silicon oxide (SiO2) with a thickness of 1 μm is added as a protective layer on top of this.
Tantalum monoxide (Ta2O5) was continuously laminated to a thickness of 10 μm by sputtering to form a thermal head A2. For comparison, tantalum was targeted by high frequency bipolar reactive sputtering and the total pressure of argon and nitrogen was 8X10.
-2T0rr1 A thermal head B1 of a tantalum nitride thin film heating resistor having a thickness of 1000 was fabricated under the condition that the nitrogen partial pressure was 1 x 10-4T0rr.

This tantalum nitride thin film heating resistor has a specific resistance of 260 μΩ.
? The area resistance was 26Ω/mouth. Thermal head B
1, silicon oxide (SiO2
) was continuously laminated with 10 μm of tantalum oxide (Ta2O5) by sputtering to form a thermal head B2.
These thermal heads were subjected to an acceleration test using a 6 ms rectangular wave at 50 z while increasing the power by 1 w/MI every 30 minutes. The results are shown in FIG. As is clear from the figure, it was found that the thermal head having a thin film heating resistor produced by the manufacturing method according to the present invention can withstand high applied power and has little change in resistance at high temperatures. In other words, while the comparative example is difficult to put into practical use without a protective film, the thermal head according to Moto's invention can be put into practical use without a protective film, and when a protective film is attached, very good heat resistance can be obtained. Ta. Example 2 Zirconium boride (ZrB2) powder at 100 kg/C
A tablet is made by pressing at a temperature of d or higher, and the substrate is heated at 500°C on a claest ceramic substrate that has been thoroughly cleaned in advance.While dry air is introduced, the degree of vacuum is 4 x 10-5.
Electron beam evaporation was performed at T0rr to a thickness of 800λ.

At this time, the area resistance is 70Ω/mouth (specific resistance value is 560μ
ΩCrlL). On top of this, add 30λ of vanadium,
Gold was attached using a 1.5 μm electron beam and selectively etched to 4
A thermal head pattern with a resolution of 1/M7lt was formed, and additionally 23 μM SlO, . A thermal head was made by continuously laminating Al2O with a thickness of 36 μm by sputtering. When this thermal head was subjected to the same acceleration test as in Example 1, the rate of change in resistance up to 20w/ml was within 2%, which was much better than when tantalum nitride was used as the heating resistor. The results were obtained. Example 3 Zirconium boride (ZrB2) powder at 100k9/C
A tablet was made by pressing at a temperature higher than R.I.T., and then an electron beam was applied to a 800-meter thick plate at a vacuum level of 2 x 10-5 T0rr while heating the substrate at 200°C and introducing oxygen using a needle valve onto a claest ceramic substrate that had been thoroughly cleaned in advance. Deposited.

At this time, the area resistance is 150 Ω/mouth (the specific resistance value is 120
It was 0,Ω (sha). On top of this, 30 pieces of titanium and 1.5 μm of gold were added using an electron beam, and 4 pieces/piece were selectively etched.
Forms a thermal head pattern with a resolution of
Further, 6 μm of MgO was continuously laminated by sputtering to form a thermal head.

When this thermal head was subjected to the same acceleration test as in Example 1, the resistance change rate up to 21w/M7l was within 2%, which was much better than when tantalum nitride was used as the heating resistor. The results were obtained.

Example 4 A tablet was made by pressing 100 kg/d or more of zirconium boride (ZrB2) powder, and the tablet was heated 3 times on a creest ceramic substrate that had been thoroughly cleaned in advance.
8×10− while introducing oxygen at 00℃ with a needle valve.
Electron beam evaporation was performed at 5T0rr to a thickness of 800 mm.

At this time, the area resistance is 520 Ω/mouth (the specific resistance value is 410
It was 0μΩ (1-JmoV!). 30 titanium on top of this
λ, aluminum was attached with a 1.5 μm electron beam, a thermal head pattern with a resolution of 4 lines/ml was formed by selective etching, and 23 μM of SlO, .Ta2O
A thermal head was formed by continuously laminating 56 μm thick layers by sputtering.

When this thermal head was subjected to the same acceleration test as in Example 1, the resistance change rate up to 23w/MI was 2.
%, and very good results were obtained compared to the case where tantalum nitride was used as the heating resistor.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an example of the shape of a thermal head according to the present invention. FIG. 2 is a characteristic diagram showing the effects of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Thin film heating resistor, 3... Electric conductor, 4... Protective layer.

Claims (1)

[Scope of Claims] 1. A thermal head having a substrate, a heating resistor formed on the substrate, and an electric conductor for supplying power to the heating resistor, in which the heating resistor is composed of zirconium boride and oxygen. A thermal head comprising: 2. Claim 1 in which the heating resistor has an oxygen content of 0.005 (atomic ratio) or more of zirconium.
Thermal head described in section. 3. The thermal head according to claim 1, wherein the heating resistor has an oxygen content of 0.01 to 1.0 (atomic ratio) of zirconium. 4. The thermal head according to claims 1 to 3, wherein the heating resistor is covered with a silicon oxide thin film. 5 Claim 1 having a tantalum oxide protective film
The thermal head according to items 1 to 4. 6. The thermal head according to claims 1 to 4, which has a protective film of aluminum oxide. 7. The thermal head according to claims 1 to 4, which has a protective film of magnesium oxide. 8. A method for manufacturing a thermal head, characterized in that a heating resistor made of zirconium boride and oxygen is manufactured by electron beam evaporation. 9. The manufacturing method according to claim 8, in which electron beam evaporation is performed while introducing a gas containing oxygen. 10. The manufacturing method according to claim 8 or 9, wherein electron beam evaporation is performed while heating the substrate at 200°C to 500°C.