JPS6013282B2 - thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head having a shelved molybdenum 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. Recording is performed by applying a current to the corresponding heat-generating resistor through an electric conductor to generate heat so as to obtain a necessary thermal pattern according to the information to be recorded, and bringing the heat-generating resistor into contact with the recording medium.

Heat generating resistors used therein include conventional thin film heat generating resistors such as tantalum nitride to nichrome, 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.). Conventionally, tantalum nitride has been used as a thin film heating resistor, which has relatively excellent heat resistance, high reliability, and has a specific resistance value of 250 to 3.
It is particularly widely used because it has a relatively high value of 00〃Q, and the controllability of manufacturing is good. However, tantalum nitride is about 30
When exposed to high temperatures of 0.000 or higher, it is rapidly oxidized and its resistance value increases rapidly, which has the disadvantage of deteriorating print density when printing on recording paper.

Generally, silicon oxide (Si02) is used to compensate for this drawback.
) is provided with an oxidation-resistant protective layer of tantalum oxide (T
A2Q) was provided with an abrasion resistant layer and used as a thermal head, but the change in resistance when the thermal head was driven for a long time was not small and 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 generate color in the heat-sensitive material, which means that the power consumption is higher than before, and the heat-generating resistor is even more expensive. The lifespan will be shorter due to higher temperatures. 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 4 head having a thin film heating resistor that is resistant to oxidation and has a stable resistance value. The present invention includes a thermal head using molybdenum, a combination with a protective film covering the heating element, and a method for manufacturing a 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. The tortoise 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 molybdenum.

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, silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, etc. produced by electron beam evaporation, sputtering, etc., or a multilayer structure made by sewing these together. This makes it possible to further extend the life of the thermal head. A thin-film heat generating resistor made of shelved molybdenum can be manufactured by both electron beam evaporation and sputtering.For production by electron beam evaporation, shelved molybdenum powder is pressed at a pressure of about 100 kg' or higher to form a tablet. Using a high vacuum of 1×10-4 tons, it can be deposited onto a substrate that has been kept at a constant temperature in advance.

On the other hand, when manufacturing by sputtering, there are a method using shelved molybdenum as a target, a method using shelved molybdenum and metal molybdenum as targets at the same time, and a method using active sputtering using only metal molybdenum as a target. When using shelved molybdenum as a target, for example, it can be used as a target by placing the shelved molybdenum in a powder state or pressed state on a quartz dish, etc., but it is possible to use it as a target by placing the shelved molybdenum in a powdered or pressed state on a quartz dish, etc. It is easier to control sputtering if a target is used. In addition, when shelving elements and metal molybdenum are targeted at the same time, the shelving elements and metal molybdenum 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 x 10-3 to 5 x 10-ITom, preferably 1 x 10-ITom.
n to 1×10-ITorr is preferable. In addition, when active sputtering is performed, a single metal such as a metal molybdenum plate is used as a target in a mixed gas atmosphere of argon and diborane, and the gas pressure at that time is 1 × 10 - 5 on - 5 x 10-ITorr, preferably 1 x 10-2 Tom to 5 x 10-ITorr, and diborane is 1 to 10% of the total pressure, preferably 2 to 6%. Furthermore, heating the substrate to 200° C. to 500° C. during sputtering or electron beam evaporation improves the adhesion of the shelved molybdenum to the substrate and is effective in improving the stability of the film. Furthermore, after sputtering or electron beam evaporation, the resistance value can be controlled to the required value by performing heat treatment at a temperature of 200°C to 65°C in vacuum, air, or an atmosphere such as argon gas. It also increases stability when used as a thermal head, which has an effect on longevity. When the heat treatment temperature is 200qo or less, the change in resistance value is very small, so a long heat treatment time is required;
Heat treatment temperature is set at 200°C to 650°C due to usage restrictions such as rapid change in resistance value or unavailability of use with substrates such as glass at 0°C or higher, or difficulty in control.
is desirable. The shelved molybdenum thermal head obtained in this way is stable and difficult to oxidize, and the power usage limit of the conventional thermal head using tantalum nitride was 17 to 18 W/m, while the maximum power consumption was 20 W/m. ~21
It can also be used to supply power to W's grandchildren. This is also suitable for a thermal head for high-speed printing, in which a large amount of power is applied to the heating resistor to raise the temperature to a high temperature. Furthermore, the specific resistance value of this shelved molybdenum thin film low antibody is 100〃○ skin~
You can choose from a wide range of 5 x 1 resistance, so if you set it to a high resistance value, you will need less current to generate heat, and the electrodes can be made thinner, which simplifies the manufacturing process and eliminates unevenness. Because it is less, it is also more resistant to wear.
Furthermore, 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, the explanation will be based on examples.

Example 1 Shelf molybdenum (molded molybdenum) was hot-pressed at 1300 pm on a glazed ceramic substrate that had been thoroughly cleaned in advance.
MOB) [manufactured by Pentron, USA, purity 99%] as a target, a heating element with a thickness of 1000 A was produced by high frequency bipolar sputtering under conditions of a total argon pressure of 5 x 10-2 Tmr and a substrate heating temperature of 20,000.

This specific resistance value was about 350 mm, and the area resistance at this time was about 350'. After evaporating titanium at 10A and aluminum at 1.5A using a Fukugawa electron beam, selective etching was performed on the thermal head A with a disassembly of 4 sails.
．． was formed. Then the thermal heads A, . Thermal heads A and 2 had tantalum oxide deposited to a thickness of 6mm by electron beam evaporation as a protective layer, Thermal heads A and 3 had aluminum oxide deposited to a thickness of 8mm, and magnesium oxide was deposited to a thickness of 5mm. Thermal heads A and 4 and thermal heads 5 were prepared in which silicon oxide was deposited in a two-layer structure with a film thickness of 1.5 rm, followed by tantalum oxide with a film thickness of 6 rm.

For comparison, tantalum was targeted by high-frequency bipolar reactive sputtering, and the total pressure of argon and nitrogen was 8 × 10-2 Torr, and the partial pressure of nitrogen was 1 × 10-4 Torr.
Thermal heads B, . was created.

When this thin film was analyzed by X-ray diffraction, it was found to be Ta2N. Also, the area resistance value is 240' (specific resistance value is 240A)
Q arc). Next, a tantalum oxide protective layer with a thickness of 6k was provided on the thermal head B by sputtering. 2 and B3 having a two-layered protective layer in which a silicon oxide film was provided with a 1.5-layer thickness and a tantalum oxide film with a 6-layer thickness was further provided thereon. A voltage with a pulse width of 6 ms and 50 Hz was repeatedly applied to these prepared thermal heads, and the supplied power was increased to 3 N.
FIG. 2 shows the measurement results of the resistance change rate xloo (%) when the acceleration test was carried out by increasing the resistance by t/rail.

Here, R is the resistance value before the test, and ΔR is the change in resistance value. To the shelved molybdenum thin film heating resistor fabricated by sputtering, tantalum nitride thin film heating resistor 3, . It can supply more power per unit area.

In addition, by providing a protective layer, the power that can be supplied per unit area is greatly improved, but the shelved molybdenum thin film heating resistor is made of tantalum oxide (A, 2) produced by electron beam evaporation, aluminum oxide ( A.3), when one protective layer of magnesium oxide (A,4) was used, it was much better than thermal head B,2 of tantalum nitride thin film heating resistor with one protective layer made by sputtering. . Further, thermal heads A and 5, which have two protective layers of silicon oxide and tantalum oxide on shelved molybdenum, have been 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.

Normally, the power supplied when transmitting thermal energy to thermal recording paper varies depending on the contact pressure, but approximately 11 to 14 W/boil is sufficient, so in the case of a tantalum nitride thin film heating resistor, two such as a combination of silicon oxide and tantalum oxide are used. While a layered protective layer is essential, in the case of shelved molybdenum thin film heating resistors, printing can be achieved with just one protective layer such as tantalum oxide, aluminum oxide, magnesium oxide, etc.
It can be seen that having two protective layers further extends the lifespan.
Example 2 The same thermal heads A, . Thermal head 2 was sputtered with tantalum oxide to a thickness of 6 mm as a protective layer, thermal head 3 was sputtered with aluminum oxide to a thickness of 8 mm, and thermal head was sputtered with magnesium oxide to a thickness of 5 mm. A thermal head 5 was prepared by sputtering a two-layer protective layer having a thickness of 1.5 mm, 1.5 mm silicon oxide, and 6 mm 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 value per unit area at which the rate of resistance change rapidly increases is A2.
Then 180w/Kyo, 18.5w' fence at A23, A24
It was boiled at 18.5w' for A25, and at 21w' for A25, and showed very good results. Better results were obtained when the protective layer was prepared by sputtering than by electron beam evaporation. Example 3 Shelved molybdenum MOB [manufactured by Pentron, USA, purity 99%
A tablet is made by pressing the powder at a weight of 100 kg or more, and the tablet is placed on a glazed ceramic substrate that has been thoroughly cleaned in advance at a substrate heating rate of 300 qo and a vacuum level of 5 x 10-
Electron beam evaporation was performed at 6 Tom to a thickness of 1000A.

This specific resistance value was about 800 French Q skin, and the sheet resistance at this time was about 800'. Next, add 10A of titanium on top of this.
After evaporating 1.5 mm of aluminum using a kite electron beam, a pattern with 4 holes per leg was formed by selective etching to form thermal heads C, . And so. These thermal heads C, . Thermal head C has a protective layer of tantalum oxide deposited by electron beam evaporation to a thickness of 6 mm.
, 2. Thermal head C with aluminum oxide vapor deposited to a thickness of 8 Am, 3. Thermal head C with vapor deposited magnesium oxide to a film thickness of 5 Am, 4, and two layers of silicon oxide 1.5 Am and then tantalum oxide 6 Am. Thermal head deposited on the configuration C. 5 was prepared and the same test as in Example 1 was conducted. As a result, the limit values of power per unit area at which the resistance change rate increases rapidly are C, . So 11.5w/
17.5w/Kyo, C, 2, 18. skin/
Grandson, C, 4, 18. Hada'Iso, C, 5 is 19.5w'
It was boiled.

The shelved molybdenum heating resistor fabricated 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, thermal head C22 with 6 tantalum oxide, thermal head C23 with 8 aluminum oxide, thermal head C pine with 5 magnesium oxide, 1.5r silicon oxide, then tantalum oxide. A thermal head C25 having a two-layer structure of 6 layers 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 18w/Kyo for C22, 18.5w/Iso for C, 18.5w for C24, and 20.5w for C. /It was boiled. Example 5 A 6 inch diameter metal molybdenum plate was used as a target.

400 thoroughly cleaned glazed ceramic substrates
The substrate was heated to qo, and active sputtering was performed in an argon and diborane mixed gas atmosphere. The pressure of argon + diborane was 3.5 x 10-orr, and the partial pressure of diborane was 1.5 x 10-4 Torr.
A film thickness of 000A was applied. This specific resistance value is 800 French○
The area resistance at this time was 800/mouth. After evaporating vanadium at 100A and gold at 1M using an electron beam, selective etching was performed to form a thermal head pattern with a resolution of 4 lines/layer. 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 19.0W. This example also gave much better results than the thermal head using tantalum nitride in the comparative example. Example 6 A target was used in which a large number of 1'4-inch diameter boron plates were placed on a 6-inch metal molybdenum slope so that the surface area ratio of metal molybdenum to shelf element was approximately 1:1.

500 thoroughly cleaned glazed ceramic substrates
The substrate was heated to R.q.o. under an argon pressure of 3×10-2 Ton. F. Sputtering was performed using two electrodes. Sputter rate is 200A
Sputtering was performed for 4 minutes at a speed of 1/min to obtain a thin film heating resistor with a film thickness of 800 A, a specific resistance value of 960 mm, and a sheet resistance of 1200'. 10A titanium on top of this
After aluminum was deposited using an LRW electron beam, a thermal head pattern with a resolution of 4 lines/side was formed by selective etching. Next, tantalum oxide (T) was used as a protective layer.
a205) 10 gunwales were laminated 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 one plow, which was much better than the thermal head using tantalum nitride. . Example 7 A 5 inch diameter quartz blood was targeted using shelved molybdenum powder.

A thoroughly cleaned glazed ceramic substrate was subjected to high-frequency bipolar sputtering at a substrate heating temperature of 200° C. and an argon partial pressure of 5×10 −2 Tom. Sputter rate 100A'mi
After sputtering at n for 10 minutes, the specific resistance value was approximately 350r.
Therefore, a shelved molybdenum thin film heating resistor with a sheet resistance of about 350' was obtained. 100% titanium on top of this
After A-gold was deposited using a lAm electron beam, a thermal head pattern with a four-way resolution was formed by selective etching. Next, when heat treated in air at 550qC for 1 hour, the resistance value of the heating resistor changed from 350/□ to 1000'.
Enlarged in mouth. Magnesium oxide (Mg◯) was sputtered as a protective film on this heating resistor to a thickness of 8 mounds to obtain thermal heads ◯ and 2. For comparison, thermal heads D, . We also prepared 6Ms at 50Hz to these thermal heads, 14
Figure 3 shows the results of measuring the rate of change in resistance when a rectangular wave of the W-band fence was continuously applied.

The number of applied pulses is D, . The resistance change rate is 12%
On the other hand, D,2 was 9%, and the resistance change was reduced and stabilized by heat treatment.

Example 8 When the heat treatment in Example 7 was changed to 65,000 in Ar for 2 hours, the resistance changed from 350/0 to 330'.

Here, a thermal head D, 3 was obtained by sputtering magnesium oxide (Mg0) 8A kite as a protective film.

Here, the same durability test as in Example 7 was conducted.

The results are shown in Fig. 3, and the results were better than those of Example 7, and the resistance change G rate was approximately 5% even when the number of pulses was applied 1×1 times. .

[Brief explanation of the drawing]

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... Electrical conductor, 4... Protective layer. Little brother' tu Qin 2 tu riding fig.

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 molybdenum 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, which comprises manufacturing a molybdenum 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, comprising manufacturing a heating resistor of a thin molybdenum boride film on a substrate by sputtering. 10. The manufacturing method according to claim 9, wherein the sputtering target is hot-pressed molybdenum boride. 11. The manufacturing method according to claim 9, in which active sputtering is performed in a mixed gas atmosphere of argon and diborane, using metal molybdenum as a target. 12. The manufacturing method according to claim 9, wherein metal molybdenum 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 sputtering is performed in an argon atmosphere. 14. The manufacturing method according to claims 9 to 13, wherein sputtering is performed while heating the substrate at 200°C to 500°C. 15. The manufacturing method according to claims 9 to 14, wherein a heat treatment is performed at 200°C to 650°C after sputtering.