JPS6013281B2 - thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head having a shelved tungsten 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 electrical conductor for supplying power to the heating resistors. Recording is performed by passing a current through the corresponding heating resistor through an electric conductor to generate heat, and contacting the recording medium with the corresponding heating resistor so as to obtain the necessary thermal pattern according to the information to be recorded. .

The heating resistors used therein include thin film heating resistors made of tantalum nitride, nichrome, etc., thick film heating resistors made of silver-palladium, etc., and semiconductor heating resistors made of silicon semiconductor. Among these, thermal heads that use thin-film heating resistors have better thermal response, superior heat resistance, and thermal shock resistance than thick-film heating resistors, semiconductor heating resistors, etc., and have a long life and "high reliability." 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.
Since the value is relatively high compared to 00mu○ and the controllability of manufacturing is good,
Especially often used. However, tantalum nitride is about 3
When exposed to high temperatures of 0,000 or higher, it is rapidly oxidized and its resistance value increases rapidly, which has the drawback 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 resistance change was not small when the thermal head was driven for a long time, and it 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 means that the power consumption is higher than before, and the heating resistor is heated to an even higher temperature. As a result, 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 is characterized by using magnetized tungsten as the thin film heating resistor. The invention lies in the thermal head used, the combination with the protective film covering the heating element, and the 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 tungsten.

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 electrical heating resistor and the electrical conductor, for example, silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, or a multilayer structure made by combining these with silk, which is produced by electron beam evaporation, sputtering, etc.; This makes it possible to further extend the life of the thermal head. A thin film heat generating resistor made of shelved tungsten can be manufactured by both electron beam evaporation and sputtering.For manufacture using electron beam evaporation, tungsten shelved powder is pressed at a pressure of approximately 100 k9' or more to form a doublet. It can be deposited on a substrate that has been kept at a constant temperature in advance under a high degree of vacuum of 10-4 Torr or higher.

On the other hand, when manufacturing by sputtering, there are a method of using conditioned tungsten as a target, a method of using shelf elements and metallic tungsten as targets at the same time, and a method of performing active sputtering using only metallic tungsten as a target. When targeting shelved tungsten,
For example, it is possible to use shelved tungsten as a target by placing it in a powdered or pressed state on a quartz dish, etc., but it is better to use a target that has been bonded in advance by vacuum hot pressing of 1100 qo or more to prevent sputtering. is easy to control. In addition, when using shelf elements and metallic tungsten as targets at the same time, it is possible to mix the shelf elements and metallic tungsten, or to embed one in the other or to place one on a part of the surface. In either case, 1×10-3Ton~5
It is best to carry out in an argon atmosphere of ×10-ITom, preferably 1×10-orr to 1×10-ITorr. In addition, when performing active sputtering, a single metal such as a metal tungsten plate is used as a target in a mixed gas atmosphere of argon and diborane, and the gas pressure at that time is the total gas pressure of argon and diborane of 1 × 10-2To.
m to 5×10-ITorr, preferably 1×10-2
Ton ~ 5 x 10-2 Ton, diborane is 1 ~ 1 of the total pressure
Preferably 10%. is preferably 2 to 6%. Also, during sputtering or electron beam evaporation,
Heating the substrate for 500 minutes improves the adhesion of the shelved tungsten to the substrate, and also has an effect on the safety of the film. Furthermore, after sputtering or electron beam evaporation, the resistance value can be controlled to the required value by heat treatment at a temperature of 200 to 650 oo in vacuum, air, or atmosphere such as argon gas, and it can be used as a thermal head. It also increases stability during use, which has an effect on longevity. If the heat treatment temperature is 20,000 degrees Celsius or lower, there will be very little change in the low resistance value, so a long heat treatment time is required, while if it is higher than 650 degrees Celsius, the resistance value will change rapidly, or it may become unusable with substrates such as glass. Due to the above restrictions or the difficulty of control, the heat treatment temperature is preferably 200 to 650 oo. The shelved tungsten thermal head obtained in this way is stable and difficult to oxidize, and the power consumption limit of the conventional thermal head using tantalum nitride was 17 to 18 W'; It can be used sufficiently for power supply of ~22W/ground. This is also suitable for use in thermal heads for high-speed printing, which apply a large amount of power to the heat-generating resistor to generate high temperatures.Furthermore, the specific resistance value of this shelved tungsten thin film resistor is 100〆○~5×1. You can choose from a wide range of resistance values, so if you set a high resistance value, the current required to generate heat will be small, and the electrodes can be made thinner, which simplifies the manufacturing process and reduces unevenness. Therefore, it is resistant to abrasion.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, explanation will be given with reference to examples.

Example 1 High-frequency 2
With extreme sputtering, the total pressure of argon is 5 x 10 -
A heating element with a thickness of 500 A was produced under the conditions of 200 qo and a substrate heating temperature of 200 qo.

This area resistance is approximately 500' (specific resistance value is 250〆○
ribs). After evaporating titanium at 10A and aluminum using a 1.5mm electron beam, selective etching was performed on the thermal heads A, . was formed. Then the thermal heads A, . Thermal heads A and 2 have tantalum oxide deposited as a protective layer by electron beam evaporation to a thickness of 6mm, Thermal heads A and 3 have aluminum oxide deposited to a thickness of 8r, and Thermal heads have magnesium oxide deposited to a thickness of 5r. Thermal heads A and 5 were prepared in which a two-layer structure of silicon oxide with a thickness of 1.5 mm and tantalum oxide with a thickness of 6 mm was deposited. For comparison, tantalum nitride with a thickness of 500 mm was prepared by targeting tantalum by high-frequency bipolar reactive sputtering under the conditions of a total pressure of argon and nitrogen of 8 × 10-2 Ton and a partial pressure of nitrogen of 1 × 10-4 Ton. Thermal head B of the heating resistor. was created. When this thin film was analyzed by X-ray diffraction, it was found to be Ta2N. Also, the area resistance value is 40
0/mouth (specific resistance value was 200 yen). Next, on the thermal head B, a tantalum oxide protective layer with a 6-layer thickness was provided by sputtering, and a 1.5-layer silicon oxide film was provided on the thermal head B, and a tantalum oxide layer with a 6-layer thickness was provided on top of that. A sample B3 having a two-layer protective layer was prepared. When a voltage with a pulse width of 6 ws 50 Hz was repeatedly applied to these prepared thermal heads, and the supplied power was increased by 3 Piga IWatt'copies to perform an accelerated test, the rate of change in resistance, etc. xloo (%) The measurement results are shown in Figure 2.

Here, R is the resistance value before the test, and ΔR is the change in resistance value. Shelf tungsten thin film heating resistors A, . can supply about 1.5 times more power per unit area than the tantalum nitride thin film heating resistor B.

In addition, by providing a protective layer, the power that can be supplied per unit area can be greatly improved. , 3) Even when only one protective layer of magnesium oxide (A, 4) is used, it is superior to thermal head B, 3, which is a tantalum nitride thin film heating resistor, which has two protective layers; Thermal head B of tantalum nitride thin film heating resistor with
, much better than 2. Further, thermal heads A and 5, which have two protective layers of silicon oxide and tantalum oxide on shelved tungsten, 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 combined power required to transfer thermal energy to thermal recording paper varies depending on the contact pressure, but is approximately il~14W/
In the case of a tantalum nitride thin film heating resistor, a two-layer protective layer such as a combination of silicon oxide and tantalum oxide is essential, since a square is sufficient, whereas in the case of a shelved tungsten thin film heating resistor, It can be seen that printing is sufficient with just one protective layer such as tantalum oxide, aluminum oxide, magnesium oxide, etc., and that the life span is further extended when two protective layers are provided. Example 2 The same thermal heads A, . Thermal head 2 is sputtered with tantalum oxide to a thickness of 6 mm as a protective layer, Thermal head 3 is sputtered with aluminum oxide to a thickness of 8 mm,
Thermal head 4 has magnesium oxide sputtered to a thickness of 5 mm, and the thermal head A25 has a two-layer protective layer sputtered to a thickness of 1.5 mm silicon oxide and 6 mm thick tantalum oxide. Prepared.

Using these thermal heads, the same test as in Example 1 was conducted to measure the rate of change in resistance. As a result, the power limit per unit area at which the resistance change rate increases rapidly is A
In 22, it was 19W'secret, in 3, it was 19.5W/masu, in A you, it was 19.5W', and in 5, it was 22W'co-op, which showed very good results. Better results were obtained when the protective layer was prepared by sputtering than by electron beam evaporation. Example 3 Powder of shelved tungsten (manufactured by Pentron, Inc., USA) was
Create a tablet pressed with 0k9/crap or more, and place it on a glazed ceramic substrate that has been thoroughly cleaned in advance with substrate heating of 300q○ and vacuum level of 5 x 10-orr.
The prostheses were attached using an electron beam to a thickness of 000△.

This area resistance is approximately 650' (specific resistance value is approximately 650)
Q arc). Next, titanium was deposited on top of this using an electron beam of 10 mm and aluminum was evaporated using an electron beam of 1.5 mm, and then a pattern with a resolution of 4 lines was formed by selective etching to form thermal heads C, . And so. These thermal heads C, . Thermal head C, 2 has tantalum oxide coated with a film thickness of 6mm as a protective film by electron beam evaporation, and Thermal head C has aluminum oxide deposited with a film thickness of 8mm.
, 3 "Thermal head C, 4 in which magnesium oxide was vapor-deposited with a film thickness of 5 mm, and the thermal head C, 5 in which a two-layer structure of silicon oxide 1.5 mm film thickness and tantalum oxide 6R skin were vapor-deposited were prepared. The same test as in 1 was conducted.As a result, the limit value of power per unit area at which the rate of resistance change increases rapidly is 11.0 W/Iso, C, 2.
In 17.5W'Iso, C, 18.0W'Fence in 3,C,
It was 18.0W' for C and 5, and 19.5W' for C and 5.

The shelved tungsten 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 on the thermal head C22 with a tantalum oxide 6mm surface, a thermal head C23 with an aluminum oxide 8mm surface, a thermal head C% with a 5magnesium oxide surface, and a thermal head C% with a silicon oxide 1.5mm surface, followed by oxidation. A thermal head C25 with a two-layer structure of tantalum 6 Buddha skin 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 18.5 W' for C2 and 18.5 W' for C2, respectively.
3 after 19.0W', C24 after 19.0W', C
25 was 20.5W' ground. Example 5 A 6-inch metal tungsten plate was used as a target.

400 thoroughly cleaned glazed ceramic substrates
Active sputtering was performed in an argon and diporane mixed gas atmosphere by heating the substrate to 0.000 m. The pressure of argon + diborane was 3.5 x 10-2 Torr, the partial pressure of didiborane was 1.5 x 10-4 Ton, and a film thickness of 1000 A was formed by high frequency bipolar sputtering. The area resistance is 400/mouth (
The specific resistance value was 400 AQ arc). After evaporating vanadium at 100A and gold using an electron beam at 1Am,
A thermal head pattern with four ribs was formed by selective etching. Next, as a protective layer, a mirror layer of aluminum oxide (AI2Q) 10 mounds was formed by sputtering. When this thermal head was subjected to the same acceleration test as in Example 1, the resistance change rate was 2% up to 20.5W'.
It was within This example also gave much better results than the thermal head using tantalum nitride in the comparative example. Example 6 1'4 dawned on a 6 inch diameter metal tungsten slope
A target was used in which a large number of inch-sized boron plates were used so that the surface area ratio of metallic tungsten to shelf element was approximately 1:2.

500 thoroughly cleaned glazed ceramic substrates
The substrate was heated to R.C. under an argon pressure of 3×10-2 Torr. Sputtering was performed using F42 electrode. Sputter rate is 100A
When sputtered for 8 minutes at a speed of 800 A, a thin film heating resistor with a resistivity of 800 A, a resistivity of 1,280 peaks, and a sheet resistance of 1,600' was obtained. After evaporating titanium and aluminum using a lAm electron beam, selective etching was performed to form a thermal head pattern with a four-line resolution. Next, as a protective film, tantalum oxide (T is also 05) 1
0mm skin was layered horizontally using sputtering. When this thermal head was subjected to the same acceleration test as in Example 1, it was found that 20
The resistance change rate up to the W' fence was within 2%, which was a much better result than the thermal head using tantalum nitride. Example A shelved tungsten powder was placed in a 75-inch diameter quartz dish to serve as a target.

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 Ton. Sputter rate 100A'm
After sputtering at Jn for 10 minutes, a 300' shelved tungsten thin film heating resistor was obtained. After evaporating titanium at 100A and gold at 1M using an electron beam, a thermal head pattern with a resolution of 4 lines/side was formed by selective etching. Next, when heat treated in air at 55,000 for one hour, the resistance value of the heating resistor increased from 30Q'□ to 13Q'□. Magnesium oxide (Mg0) was sputtered as a protective film onto this heating resistor to a thickness of 8 Am to obtain a thermal head ◯, 2. For comparison, thermal heads D, .
We also prepared 6m at 50Hz to these thermal heads
Figure 3 shows the results of measuring resistance changes when a rectangular wave with a ratio of 14W and 14W was continuously applied. D, . with the number of applied pulses of 5×1 times. The rate of change in resistance of D,2 was 10%, whereas the rate of change in resistance was 12% or more, and the heat treatment reduced the change in resistance and stabilized it.

Example 8 When the heat treatment in Example 7 was changed to 65,000 ℃ in Ar for 2 hours, the resistance changed from 300'□ to 280'□.

Here, a thermal head ○, 3 was obtained by sputtering magnesium oxide (Mg○) 8mm skin as a protective film. Here, the same durability test as in Example 7 was conducted.

The results are shown in Figure 3, and the results are better than those of Example 7. Even when 5 x 1 pulses were applied, the resistance change rate was 1 or about 5%. .

[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... Electric conductor, 4... Protective layer. Group' figure 2 back view

Claims (1)

[Scope of Claims] 1. In a thermal head having a substrate, a heating resistor formed on the substrate, and an electric conductor for supplying power to the heating resistor, the heating resistor is made of tungsten 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, having 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 tungsten 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, characterized by manufacturing a heating resistor of a tungsten boride thin film on a substrate by sputtering. 10. The manufacturing method according to claim 9, wherein the sputtering target is hot-pressed tungsten boride. 11. The manufacturing method according to claim 9, wherein active sputtering is performed in a mixed gas atmosphere of argon and diporane, using metallic tungsten as a target. 12. The manufacturing method according to claim 9, wherein metallic tungsten 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 heat treatment is performed at 200°C to 650°C after sputtering.