JPS6016083B2 - thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head having a shelved tantalum thin film and to a method for manufacturing the same.

A thermal head used for thermal print recording includes a plurality of heating resistors on a substrate having electrical insulation and a smooth surface, such as glass, and an electric conductor for supplying power to the heating resistors. The device is equipped with a heat generating resistor, and generates heat by passing a current through the corresponding heat generating resistor through an electric conductor so as to obtain the necessary heat 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 nichrome, thick film heat generating resistors using silver-palladium, 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, as it has relatively excellent heat resistance, high reliability, and has a resistance value of 250~
It is particularly widely used because it has a relatively high value of 300 mm and good controllability in production. However, tantalum nitride is rapidly oxidized at high temperatures of about 300° C. or higher, resulting in a rapid increase in its resistance value, which has the disadvantage of deteriorating print density when printing on recording paper.

Generally, silicon oxide {Si0
2) An oxidation-resistant protective layer is provided on top of which tantalum oxide (
Although a wear-resistant layer of Ta2Q) was provided and used as a thermal head, the change in resistance when the thermal head was driven for a long time was not small, and the result was still not fully satisfactory. In particular, as the demand for high-speed thermal heads has increased in recent years, it is necessary to shorten the energizing pulse of the head to color the thermal paper, which results in an increase in electric power compared to the conventional one, and the heating resistor becomes even hotter. Therefore, the lifespan becomes shorter. Therefore, there is a demand for a heating resistor with even higher heat resistance. The present invention aims to improve the above points and provide a thermal head having a thin film heating resistor that is resistant to oxidation and has a stable resistance value. The present invention provides a thermal head using the above, a combination with a protective film covering the heating element, and a method for manufacturing the thin film heating resistor. 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. 1 in the figure is a substrate made of an electrical insulator such as ceramic glass or glazed ceramics. 2 is a thin film heating resistor made of shelved tantalum.

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

Further, 4 is a protective layer for the thin film heating resistor and electric conductor, for example, silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, etc. produced by electron beam evaporation, sputtering, etc., or a multilayer structure made by combining these with silk is used. This makes it possible to further extend the life of the thermal head. The thin film heating resistor made of tantalum shelving can be manufactured by both electron beam deposition and sputtering.For production by electron beam evaporation, tantalum shelving powder is pressed under a pressure of about 100 kg' or more. It is possible to make a tablet and deposit it on a substrate kept at a constant temperature in advance in a high vacuum of 1 x 4 tons or more.

On the other hand, when producing by sputtering, there are a method using shelved tantalum as a target, a method using shelved tantalum and metal tantalum as targets at the same time, and a method using active sputtering using only metal tantalum as a target. When targeting shelved tantalum, for example, it can be used as a target by placing the shelved tantalum in a powdered, pillow-like or pressed state on a quartz dish, etc., but it can be used as a target in advance by vacuum hot pressing at 1100 pm or more. It is easier to control sputtering by using a target that has been solidified. In addition, when targeting shelving elements and tantalum metal at the same time, the shelving and tantalum metal can be mixed, or one can be embedded in the other or placed on a part of the surface. In either case, it is best to carry out in an argon atmosphere of 1×10-3 Torr to 5×10-ITon, preferably 1×10-ITon.
Cloth otr~1×10-ITon is good. In addition, when active sputtering is performed, a single metal such as a metal tantalum plate is used as a target in an atmosphere of a mixed gas of argon and diborane, and the gas pressure at that time is the total gas pressure of argon and diborane of 1 × 10 - orr. ~5×10-ITo
rr is preferably 1×10-orr~5×10-2
Ton, diborane is 1 to 10% of the total pressure, preferably 2
~6% is good.

Further, by heating the substrate for 20,000 to 500 pm during sputtering or electron beam evaporation, the adhesion of the tantalum shelving to the substrate is improved and the stability of the film is also improved. Furthermore, after sputtering or electron beam evaporation, 200qC~650pm○
By performing heat treatment in a vacuum, air, or atmosphere such as argon gas at a temperature of It is effective against When the heat treatment temperature is below 20,000, the change in resistance value is very small, so a long heat treatment time is required.On the other hand, when the heat treatment temperature is above 650 oo, the change in resistance value occurs suddenly, and substrates such as glass can no longer be used. Due to the above restrictions or difficulty in control, the heat treatment temperature is 20,000 yen.
~650qo is desirable. The thermal head of shelved tantalum obtained in this way is difficult to oxidize and is stable.
While the power usage limit of the conventional thermal head using tantalum nitride was 17 to 18 W' at maximum, it can be used sufficiently for power supply of up to 22 to 23 W/grandson. This is also suitable for a thermal head for high-speed printing, which generates a high temperature by applying a large amount of power to the heating resistor. The specific resistance value of this shelved tantalum thin film resistor is 80μ○
Since you can choose from a wide range of resistance values ranging from 1 to 5 x 1, the current required to generate heat can be reduced by setting a high resistance value, and the electrodes can be made thinner, which simplifies the manufacturing process. , it also becomes more resistant to wear because there are fewer irregularities. Further, the amount of heat generated by the thin film heating resistor due to the influence of the resistance of the electrode portion can be ignored. Next, it will be explained based on an example.

Example 1 Shelved tantalum Ta hot-pressed at 1300 qo on a glazed ceramic substrate that had been thoroughly cleaned in advance
& [manufactured by Pentron, USA, purity 99.7%] as a target, a heating element with a thickness of 700A was produced using high frequency bipolar sputtering under conditions of a total argon pressure of 5 x 10-2 Torr and a substrate heating temperature of 200oo. did.

This specific resistance value was about 21010, and the area resistance at this time was about 300/mouth. After evaporating titanium on this with a 10A and aluminum 1.5mm electron beam, selective etching was performed using thermal heads A, .
was formed. Then the thermal heads A, . Thermal heads A and 2 had tantalum oxide deposited to a thickness of 6 mm by electron beam evaporation as a protective layer, Thermal heads A and 3 had aluminum oxide deposited to a thickness of 8 mm, and magnesium oxide was deposited to a thickness of 5 mm. Thermal heads A and 4 were prepared, and thermal heads A and 5 were prepared in which silicon oxide was deposited in a two-layer structure with a thickness of 1.5 mm and tantalum oxide was deposited in a two-layer structure with a thickness of 6 mm.

For comparison, tantalum was targeted by high-frequency bipolar reactive sputtering, and the total pressure of argon and nitrogen was 8×10-2Ton, and the partial pressure of nitrogen was lxlo-4Tor.
Thermal heads B, . was created.

When this thin film was analyzed by X-ray diffraction, T was also N.
Further, the specific resistance value was about 245 mm arc, and the area resistance value at this time was about 350/mouth. Then the thermal head B
B, 2, in which a tantalum oxide protective layer with a thickness of 6 am is provided by sputtering on the 2nd layer, and a tantalum oxide film with a thickness of 6 am is further provided on top of that with a silicon oxide film of 1.5 am thick. B3 having layers was prepared. A repeated voltage of 50Hz with a pulse width of 6 was applied to these prepared thermal heads, and the supplied power was increased to 3.
FIG. 2 shows the measurement results of the resistance rate xloo (%) when accelerated strikes were performed with IWatt/fence increasing each time the load was increased.

Here, R is the resistance value before the test, and ΔR is the change in resistance value. Shelved tantalum thin film heating resistors A, . are tantalum nitride thin film heating resistors B, . It is possible to supply approximately 1.7 times more power per unit area compared to the conventional method.

In addition, by providing a protective layer, the power that can be supplied per unit area is greatly improved, but the shelved tantalum thin film heating resistor is made of tantalum oxide (A,2) produced by electron beam evaporation, aluminum oxide ( A, 3), even when only one protective layer of magnesium oxide (A, 4) is used, the thermal head B3, which is a tantalum nitride thin film heating resistor, has two protective layers, and the thermal head B3 has two protective layers. Thermal head B2 of tantalum nitride thin film heating resistor having
It was much better than that. Further, the thermal heads A and 5, in which a two-layer protective layer of silicon oxide and tantalum oxide was provided on the shelved tantalum, were further improved. This increase in the maximum power supply means that in the case of constant power driving, deterioration of the heating resistor due to heat generation phenomenon is reduced. usually,
The power supplied when transmitting thermal energy to thermal recording paper varies depending on the contact pressure, but approximately 11 to 14 W/W is sufficient, so in the case of tantalum nitride thin film heating resistors, two layers such as a combination of silicon oxide and tantalum oxide are used. In contrast, in the case of shelved tantalum thin film heating resistors, only one protective layer such as tantalum oxide, aluminum oxide, magnesium oxide, etc. is sufficient for printing, and two protective layers are required. It can be seen that if there is, the lifespan will be further extended. Example 2 The same thermal heads A, . Thermal head 2 has tantalum oxide sputtered to a thickness of 6 Am as a protective layer, Thermal head 3 has sputtered aluminum oxide to a thickness of 84 mm, and Thermal head has sputtered magnesium oxide to a thickness of 5 mm. Thermal head A was prepared by sputtering a two-layer protective layer of 1.5 μm of silicon oxide and 6 μm of tantalum oxide.

These thermal heads were subjected to the same test as in Example 1 to measure the rate of change in resistance. As a result, the power limit per unit area at which the rate of resistance change rapidly increases is 2
20.5W/masu for A momme, 21W/ground for A momme, 2 for Akyo.
1W/Kyo, N5 was a 23W' fence and showed very good results. Example 3 Shelved tantalum TaB [manufactured by Pentron, USA, purity 99.
7%] powder was pressed at 100k9/yen or higher, and the substrate was heated to 300°C and the vacuum level was 5x1 on a glazed ceramic substrate that had been thoroughly cleaned in advance.
It was deposited by electron beam to a thickness of 1000A at 0-6 Tom.

This specific resistance value was about 600 arcs, and the area resistance at this time was about 600'. Next, add 10A of titanium on top of this.
After depositing aluminum with an electron beam of 1.5 french, selective etching is performed to form a pattern with a resolution of 4 lines/leg, and thermal heads C, . And so. This thermal head C, . Thermal head C, 2 has tantalum oxide deposited as a protective film to a thickness of 6 mounds by electron beam evaporation, Thermal head C, 3 has aluminum oxide deposited in a film thickness of 8 mounds, Magnesium oxide is evaporated to a film thickness of 5 mounds. A thermal head C, 4 and a thermal head C, 5 having a two-layer structure of 1.5 μm of silicon oxide and 6 μm of tantalum oxide deposited were prepared, and the same tests as in Example 1 were conducted. As a result, the power limits per unit area at which the rate of resistance change rapidly increases are C, . Then 11W'Hiro, C
, 2 is 18.0W'Iso, C, 3 is 18.5W/Son,
It was 18.5W/ground for C.4 and 20.5W/ground for C.5.

The shelved tantalum heating resistor produced by electron beam evaporation in this example was also much better than the tantalum nitride heating resistor.
Example 4 Thermal heads C, . A protective layer was formed by sputtering, and the thermal head C22 was made of tantalum oxide with 6 μm, the thermal head C23 was made with 8 μm of aluminum oxide, the thermal head C was treated with 5 μm of magnesium oxide, and the thermal head C was treated with 1.5 μm of silicon oxide. Next, a thermal head C25 having a two-layer structure of tantalum oxide 6A was prepared.

These thermal heads were subjected to the same test as in Example 1 to measure the rate of change in resistance.

As a result, the power limit values per unit area at which the rate of resistance change rapidly increases are 19.5 W/fence for C2 and 19.5 W/fence for C2, respectively.
20.0W/fence for 3, 20.0W/fence for C24, C
25, it was 22W/me. Example 5 A 6 inch diameter tantalum metal plate was used as a target.

Thoroughly cleaned glazed ceramic substrate
The substrate was heated to 0.degree. C. and active sputtering was performed in an argon diborane mixed gas atmosphere. The pressure of argon + diporane is 3.5 × 10-orr, and the partial pressure of diborane is 1.5 ×
1000A with high frequency bipolar sputtering at 10-4 Torr
A film thickness of . This inherent low resistance value was 500 mm○ skin, and the area resistance at this time was 500/mouth. After evaporating vanadium and 100A gold using a one-column electron beam, a thermal head pattern having a resolution of 4 lines/rib was formed using zero selective etching. Next, 10 layers of aluminum oxide (AI203) were deposited as a protective film by sputtering. When this thermal head was subjected to the same acceleration test as in Example 1, the resistance change rate was within ±2% up to 21 W/. This example also gave much better results than the thermal head using tantalum nitride in the comparative example. Example 1 dawned on a 66 inch flea metal tantalum slope
A target was used in which a large number of boron plates with a diameter of /4 inch were placed so that the surface area ratio of tantalum metal to shelf element was approximately 1:2.

50 ml of thoroughly cleaned glazed ceramic substrates
Heating the substrate to 0qo and argon pressure: 3 x 10-2 Tor
Sputtering was performed using R, F, and two poles. Sputter rate is 12
By sputtering at 0 A/min, a thin film heating resistor with a film thickness of 800 mm, a specific resistance value of 1200 μm, and a sheet resistance of 1500 μm was obtained. Chita on top of this. A thermal head pattern with a resolution of 4 lines/side was formed by selective etching. Next, tantalum oxide (Ta205) was used as a protective film.
) loAm was laminated by sputtering.

When this thermal head was subjected to the same acceleration test as in Example 1, the resistance change rate was 2.
%, much better results were obtained than thermal heads using tantalum nitride. Example A shelved tantalum powder was placed in a 75-inch diameter quartz dish to serve as a target.

High-frequency bipolar sputtering was performed on the thoroughly cleaned glazed ceramic substrate with substrate heating of 200 q○ and argon partial pressure of 5×10 −2 Ton. Sputter rate 100A/mi
After sputtering with n for 10 minutes, the specific resistance value was 400 μm○
At this time, a shelved tantalum thin film heating resistor with a sheet resistance of 400/□ was obtained. After evaporating titanium at 100A and gold at 100A using an electron beam, selective etching was performed to form a thermal head pattern having 4 wires/willow disassembly.
Next, heat treatment was performed in air at 55,000 liters for 1q hours.
The resistance value of the heating resistor increased from 400/hole to 1000'/hole. Thermal heads D and 2 were obtained by sputtering magnesium oxide (Mg◯) as a protective film onto the heat generating resistor to a thickness of 8 cm. For comparison, thermal heads D, . We also prepared FIG. 3 shows the measurement results of the resistance change rate when a rectangular wave of 50 Hz, 6 seconds, 15 Wa ratio/fence was continuously applied to these thermal heads.

D, . with one application pulse number. The resistance change rate is 12%
On the other hand, D,2 was 6%, and the resistance change was reduced and stabilized by heat treatment.

Example 8 When the heat treatment in Example 7 was changed to 650° C. for 2 hours in Ar, the resistance changed to 350/mouth.

Here, 8 m of magnesium oxide (M) was sputtered as a protective film to obtain thermal heads D and 3. Here, the same durability test as in Example 7 was conducted. The results are shown in FIG. 3, and the results are better than those of Example 7, with 1
Low resistance change by 2% even with one pulse application
was.

[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. FIGS. 2 and 3 are characteristic diagrams showing the effects of the present invention. 1...
...Substrate, 2...Thin film heating resistor, 3...
...Electric conductor, 4...Protective layer. Longevity drawing drawing drawing 2

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, wherein the heating resistor is made of tantalum boride. A thermal head featuring: 2. The thermal head according to claim 1, wherein the heating resistor is covered with a silicon oxide thin film. 3 Claim 1 having a tantalum oxide protective film
The thermal head according to item 1 or 2. 4. The thermal head according to claim 1 or 2, which has a protective film of aluminum oxide. 5. The thermal head according to claim 1 or 2, which has a protective film of magnesium oxide. 6. A method for manufacturing a thermal head, comprising manufacturing a boride thin film on a substrate by electron beam evaporation. 7. The manufacturing method according to claim 6, wherein electron beam evaporation is performed while heating the substrate at 200°C to 500°C. 8. The manufacturing method according to claim 6 or 7, wherein heat treatment is performed at 200°C to 650°C after electron beam evaporation. 9. A method for manufacturing a thermal head, which comprises manufacturing a heating resistor made of a tantalum boride thin film on a substrate by sputtering. 10. The manufacturing method according to claim 9, wherein the sputtering target is hot-pressed tantalum boride. 11. The manufacturing method according to claim 9, wherein active sputtering is performed using tantalum metal as a target in a mixed gas atmosphere of argon and diborane. 12. The manufacturing method according to claim 9, wherein tantalum metal and boron are arranged so as to be targets at the same time. 13 1×10^-^3Torr~5×10^-^1T
13. The manufacturing method according to claim 9, 10, or 12, wherein the sputtering is performed in an argon atmosphere. 14 Claim 9, in which sputtering is performed while heating the substrate at 200°C to 500°C.
The manufacturing method according to Items 1 to 13. 15. The manufacturing method according to claims 9 to 14, wherein heat treatment is performed at 200°C to 650°C after sputtering.