JPS6016084B2 - thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head having a shelved titanium 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 made of tantalum nitride, nichrome, etc., 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, better 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 as a thin film heating resistor because it has relatively excellent heat resistance, high reliability, and a specific resistance value of 250 to 30.
It is particularly widely used because it has a relatively high value of 0rQ arc and improves manufacturing controllability. However, tantalum nitride is about 30
When exposed to high temperatures of 0° C. 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 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 requires more power than before, and the heating resistor becomes even hotter. Lifespan becomes shorter. Therefore, there is a demand for a heating resistor with even higher heat resistance. In addition, the sheet resistance of tantalum nitride is usually around 500/square, and even when it is made especially large as a thermal head, it is around 1000/□. In order to further increase the resistance value, methods such as trimming or thinning the thick layer are required. However, there are disadvantages such as complicating the manufacturing process and adversely affecting the product life. In this way, tantalum nitride thin film heating resistors cannot have a large sheet resistance, so in order to supply enough power to heat the resistor, a large current is required, and the resistance of the electrical conductor used for electrodes and wiring increases. Value matters. In other words, since the resistance value of the electrical 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 between each electrical conductor connected to the resistor, and the recorded pattern will vary. 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. Moreover, if the thickness of the electric conductor is made extremely large in order to avoid this, a major structural problem will occur. 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 aims to improve the above-mentioned points and provide a thermal head having 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. , a thermal head using shelved titanium as a thin film heating resistor, 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. Reference numeral 1 in the figure is a substrate made of an electrically insulating material such as ceramic glass or glazed ceramic. 2 is a thin film heating resistor made of titanium shelving.

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 heat generating resistor and electric conductor, for example, a multilayer structure made of silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, etc., or a combination of these, manufactured by electron beam evaporation, sputtering, etc., is used. This makes it possible to further extend the life of the thermal head. Both electron beam evaporation and sputtering can be used to manufacture a thin film heating resistor made of titanium shelving, and manufacturing by electron beam evaporation requires approximately 100 kg of titanium shelving powder.
Press with pressure above 9/ to make a tablet, 1x
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 tons or more.

On the other hand, when manufacturing by sputtering, there are a method using shelved titanium as a target, a method using shelved titanium and metallic titanium as targets at the same time, and a method using active sputtering using only metallic titanium as a target. When using shelved titanium as a target, for example, it can be used as a target by placing the conditioned titanium in a powder state or pressed state on a quartz dish, etc., but it can be used as a target by placing the conditioned titanium in a powder state or a pressed state on a quartz dish, etc. It is easier to control sputtering by using a target that has been adjusted. In addition, in the case where a side element and a metal are used as targets at the same time, the side element and metal titanium can be mixed together, or one can be embedded in the other or placed 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-ITon. In addition, when performing active sputtering, a single metal such as a metal titanium plate is used as a target, and it is performed in a mixed gas atmosphere of argon and diborane, and the gas pressure at that time is 1 × 10 - 5 on - 5. ×1
0-ITorr, preferably 1×10-2Ton to 5
×10-2 Ton, diborane should be 1 to 10%, preferably 2 to 6%, of the total pressure. Furthermore, heating the substrate to 200 DEG C. to 500 qo during sputtering or electron beam deposition improves the adhesion of the titanium shelving 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 heat treatment at a temperature of 200°C to 650°C in vacuum, air, or an atmosphere such as argon gas. It also increases stability when used as a head, which has an effect on longevity. If the heat treatment temperature is below 200°C, the change in resistance value will be very small and a long heat treatment time will be required.If the heat treatment temperature is above 650°C, the change in resistance value will occur rapidly or it may become unusable with substrates such as glass. Due to restrictions or difficulty in control, the heat treatment temperature is 200~6.
50qo is desirable. The shelved titanium thermal head obtained in this way is stable and resistant to oxidation, and the power consumption limit of the conventional thermal head using tantalum nitride was 17 to 18 W/K, while the maximum Matsu~2
It can also be used for power supply of 3W/tub. 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 titanium thin film resistor is less than 200 mountains.
Since you can choose from a wide range of 5 x 1 resistance values, if you set 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 reduces unevenness. It also becomes more resistant to abrasion as it reduces the amount of friction. 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, it will be explained based on an example.

Example 1 Shelved titanium [Ti
B. Manufactured by Sanmizo Kagakuyaku, Ti ship. 70%, B30.72
%], a heating element with a thickness of 400 A was produced by high-frequency bipolar sputtering under the conditions of a total argon pressure of 5 x 10-orr and a substrate heating temperature of 200 pm.

This specific resistance value was about 360 mm arc, and the area resistance at this time was about 900/mouth. After evaporating titanium and aluminum using an electron beam of 10A and 15A, selective etching was performed using a thermal head A with a resolution of 4 lines/side.
was formed. Then the thermal heads A, . Thermal heads A and 2 have a protective layer of tantalum oxide deposited on them by electron beam evaporation to a thickness of 6 mm, and thermal head A.2 has a protective layer of aluminum oxide deposited to a thickness of 8 mm. 3. Thermal head A, 4 in which magnesium oxide was vapor-deposited to a film thickness of 5 mm, and thermal head A, 5 in which silicon oxide was vapor-deposited in a two-layer structure with a film thickness of 1.5 mm and tantalum oxide to a film thickness of 6 mm. prepared.

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

Analysis of this thin film by X-ray diffraction revealed Ta.
Further, the specific resistance value was 240 #○, and the area resistance value at this time was 600/mouth. Next, the thermal heads B, . B, 2 has a tantalum oxide protective layer with a thickness of 6 cm by sputtering, and a two-layer structure with a tantalum oxide film with a thickness of 6 cm on top of which a silicon oxide film has a thickness of 1.5 cm. Samples B and 3 having a protective layer were prepared. These thermal heads were prepared with a pulse width of 6 seconds.
Apply a repeated voltage of 50Hz, and the combined power is 3
■Resistance rate, etc. xl when accelerating tests are performed by increasing the needle IWatt/fence. . (%) Show the results of the sailing boat.

Here, R is the resistance value before the test, and ΔR is the change in resistance value. Shelved titanium thin film heating resistors A, . are tantalum nitride thin film heating resistors B, . Approximately 1. Can supply electricity for needle sounds.

In addition, by providing a protective layer, the power that can be supplied per unit area is greatly improved, but the shelved titanium thin film heating resistor is made of tantalum oxide (tantalum oxide) made by electron beam evaporation.
Even when using only one protective layer of A, 2), aluminum oxide (A, 3), and magnesium oxide (N 4),
It was almost equivalent to thermal head B3, which is a tantalum nitride thin film heating resistor having two protective layers, and was far superior to thermal head B2, which is a tantalum nitride thin film heating resistor having one protective layer. In addition, thermal heads A and 5, which have two protective layers of silicon oxide and tantalum oxide on shelved titanium, 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/W is sufficient, so in the case of a tantalum nitride thin film heating resistor, a combination of silicon oxide and tantalum oxide, etc. While a two-layer protective layer is essential, in the case of shelved titanium 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 the presence of layers further extends the lifespan. Example 2 The same thermal head A as prepared in Example 1,
．． 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, and thermal head is sputtered with magnesium oxide to a thickness of 5 mm. Dodon 4,
A thermal head A was prepared in which a two-layer protective layer was formed by sputtering to a thickness of 1.5 m of silicon oxide and 6 m 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 value per unit area at which the rate of resistance change rapidly increases is A2.
2 was 18 W/fence, A23 was 18.5 W/m, N4 was 19.0 W/m, and N5 was 23 W/m, showing very good results. Better results were obtained when the protective layer was prepared by sputtering than by electron beam evaporation. Example 3 Shelf titanium [TiB2, manufactured by Mitatsunowa Chemicals, Ti687
0%, B30.72%] powder was pressed at 100k9/yen or more to make a tablet, and the tablet was placed on a glazed ceramic substrate that had been thoroughly cleaned in advance at 1000 A with a substrate heating of 30 psi and a vacuum of 5 x 10-6 Ton. The thickness was deposited using an electron beam.

This specific resistance value was about 1000 yen, and the area resistance at this time was about 1000/□. Next, add 10 titanium on top of this.
A. After depositing aluminum using a 1.5A electron beam, a pattern with this resolution of 4 lines/side is formed by selective etching, and thermal heads C, . And so. These thermal heads C, . Thermal head C, 2 has tantalum oxide deposited to a thickness of 6 mm as a protective film by electron beam evaporation, Thermal head C, 3 has aluminum oxide deposited to a thickness of 8 mm, Magnesium oxide is evaporated to a thickness of 5 mm. thermal head C,4, and silicon oxide 1.5
The same test as in Example 1 was conducted using a thermal head C, which was deposited on a two-layer structure of tantalum oxide (A) and tantalum oxide (6). As a result, the limit values of power per unit area at which the resistance change rate increases rapidly are C, . So 10.5
W/Kyo, C. 2 is 16.0W' fence, C, 3 is 16.
5W' fence, C. 4: 16.5W/no, C, 5: 19
．． It was 5W/me.

The shelved 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 of tantalum oxide 6 ridge, thermal head C23 of aluminum oxide 8r, thermal head C24 of magnesium oxide 5rm, silicon oxide 1.5 rm, then tantalum oxide 6. A thermal head C25 having a two-layer skin structure was prepared.

These thermal heads were subjected to the same test as in Example 1, and the rate of change in resistance was measured.

As a result, the power limit values per unit area at which the rate of resistance change rapidly increases are 18.5 W/co for C2 and 18.5 W/co for C2, respectively.
3: 19W/masu, C24: 20W/iso, C: 2
It was 2W'. Example 6 A 6 inch diameter metal titanium plate was used as a target.

400 thoroughly cleaned glazed ceramic substrates
The substrate was heated to 0.degree. C. and active sputtering was performed in an argon/diborane mixed gas atmosphere. The pressure of argon diborane is 3.5×10-orr, and the partial pressure of diborane is 1
．． 800 with high frequency bipolar sputtering at 5×10-4Ton
The film thickness was set to A. The specific resistance value was 1100/□ on the surface of a rocky surface. After evaporating vanadium at 100A and gold using an electron beam at 1Am,
A thermal head pattern with a four-line/side resolution was formed by selective etching. Next, a 10 μm layer of aluminum oxide (AI2Q) was deposited as a protective film by sputtering. When this thermal head was subjected to the same acceleration test as in Example 1, the rate of change in resistance was within ±2% up to 20 W/square. This example also gave much better results than the thermal head using tantalum nitride in the comparative example.
Example 1 was deposited on a 66-inch diameter titanium plate.
A target was used in which a large number of boron plates with a diameter of /4 inch were used so that the surface area ratio of titanium metal to shelf element was approximately 1:2.

500 thoroughly cleaned glazed ceramic substrates
Heating the substrate to 0.00 and argon pressure; R
．． F. It crashed at two poles. The sputtering rate was 100A/min for 10 minutes, the film thickness was 1000A, the specific resistance was 1500F, and the specific resistance at this time was 1500/min.
A thin film heating resistor of □ was obtained. 10 titanium on top of this
A: Aluminum was deposited using an electron beam over a single peak, and then selectively etched to form a thermal head pattern with a four-line/side resolution. Next, as a protective film, tantalum oxide (
Ta205) A key layer of 10 pieces was formed 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 18.5W/fence.
Much better results were obtained than thermal heads using tantalum nitride. Example 7
, Shelved titanium powder was placed in a 5-inch diameter quartz dish as a target. A thoroughly cleaned glazed ceramic substrate was subjected to high-frequency bipolar sputtering at a substrate heating temperature of 20,000 ℃ and an argon partial pressure of 5×10 −2 Tom. When sputtering was performed for 6 minutes at a sputtering rate of 150 A/min, the specific resistance was 990, and the area resistance at this time was 1100.
A shelved titanium thin film heating resistor with a diameter of 1/2 mm was obtained. After evaporating titanium with an electron beam of 100 A and gold with an electron beam of 1 F, a thermal head pattern having 4 lines/skin separation area was formed by selective etching. Next, when heat treated in air at 550℃ for 1 hour, the resistance value of the heating resistor was 1100/
It increased from mouth to 1800/mouth. Thermal heads D and 2 were obtained by sputtering magnesium oxide (Mg◯) as a protective film onto the heating resistor to a thickness of 8 mounds. For comparison, thermal heads D, . We also prepared 50Hz to these thermal heads
FIG. 3 shows the measurement results of the resistance change rate when a rectangular wave of 15 Wa ratio/fence was continuously applied for 6 ms.

D, . with the number of applied pulses of 5×1 times. The rate of change in resistance is 1
While it was 2% or more, D8 was 6%, and the resistance change was reduced and stabilized by heat treatment.

Example 8 The heat treatment of Example 7 was performed at 65,000 in Ar for 2
When I changed it to time, the resistance was 1100/1000/from the mouth.
It changed into a mouth.

Here, 8 mounds of magnesium oxide (Mg0) were 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 were better than those of Example 7, and the rate of change in resistance was 4% or less even when 5×1 pulses were applied.

[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. Figure 2 Figure 2

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 titanium 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 titanium 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 titanium boride thin film on a substrate by sputtering. 10. The manufacturing method according to claim 9, wherein the sputtering target is hot-pressed titanium 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 metallic titanium as a target. 12. The manufacturing method according to claim 9, wherein titanium 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 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.