JPS6022801B2 - thermal head - Google Patents

Description

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

The thermal head used for thermal print recording has a plurality of heating resistors on a substrate with electrical insulation and a smooth surface, such as glass, and a fin gas conductor for supplying power to the heating resistors. Recording is performed by causing a current to flow through the corresponding heating resistor electric conductor to generate heat and contacting the recording medium so as to obtain the necessary thermal pattern according to the information to be recorded. .

Heat generating resistors used therein include conventional thin film heat generating resistors made of tantalum nitride, nichrome, etc., 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, excellent heat resistance and thermal shock resistance, long life, and high reliability compared to 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 especially widely used because it has a relatively high value of 0mQ and has good manufacturing controllability. However, tantalum is about 30
When exposed to high temperatures of 0 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 addition, the resistance heating elements for thermal heads described in Tokukan Sho 52-109 Ban No. 7 include Ti, Mo, W, V,
Low-resistance, hard, heat-resistant materials such as Nb, Zr, Ta, etc., such as frogides, carbides, shelvings, nitrides, or nichrome, and cartan, as well as Si02, Zr02, Tho2, MgO, are being used, especially in recent years, as the demand for high-speed thermal heads has been increasing. It is necessary to make the thermal paper colored by shortening the current pulse of the head, and therefore the electric power is increased compared to the conventional method, and the heat generating resistor becomes even hotter, so its life becomes shorter.
Therefore, there is a demand for a heating resistor with even higher heat resistance. oxides such as glass, nitrides of Si3N4 and AIN, or any one of high cost resistance elements such as Si, or a mixture thereof with an electrically insulating material.

Conventionally, it was thought that in order to increase the resistance value, it was necessary to mix the resistor material with a high-resistance material.

The resistance heating element for a thermal head described in Tokukan Sho 52-109947 was also developed based on the above concept. However, when a resistor material and a high-resistance material are mixed, the specific resistance changes greatly due to slight fluctuations in the mixing ratio or mixing state, which poses a major problem in the reproducibility of the resistance value.

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 multi-layer structure including aluminum oxide, tantalum oxide, aluminum oxide, tantalum oxide, etc., or a combination of these, can be used to further extend the life of the thermal head.

The thin film heating resistor of shelved chromium is manufactured by electron beam evaporation,
Both sputtering and electron beam evaporation are possible, and production by electron beam evaporation involves pressing shelved chromium powder at a pressure of about 100 k9/min or more to make tablets, and forming tablets of 1×10-4 Tom.
Vapor deposition can be performed on a substrate that has been kept at a constant temperature in advance at a high degree of vacuum.

On the other hand, when manufacturing by sputtering, a method using shelved chromium as a target, and shelved chromium and metal chromium will be explained in detail 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 chromium. 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.

4 is a protective layer for a thin film heating resistor and electric conductor; for example, a method using silicon oxide and magnesium oxide prepared by electron beam evaporation, sputtering, etc. as targets at the same time, and a method using active sputtering using only metal chromium as a target. There is. When targeting chromium shelving, for example, place chromium shelving in powder form on a quartz plate, etc.
It can also be used as a target by placing it in the
It is easier to control sputtering by using a target that has been solidified by vacuum hot pressing at a temperature higher than qo. In addition, when targeting shelf elements and metallic chromium at the same time, it can be done by mixing them, or by embedding one in the other or arranging one on a part of the surface. In either case 1×10-汀orr〜5×10
-ITom is preferably carried out in an argon atmosphere, preferably 1 x 1 orr to 1 x 10 -ITon. In addition, when performing active sputtering, a single metal such as a metal chromium plate is used as a target, and it is performed in a mixed gas atmosphere of argon and ciporane, and the gas pressure at that time is 1 × 10 - 5 on - 5 ×10-IT
orr preferably from 1×10-2 Tom to 5×10-
2 and diborane is 1 to 10% of the total pressure, preferably 2 to 6
% is good. Furthermore, heating the substrate to 2000° to 500° during sputtering or electron beam evaporation improves the adhesion of the shelved chromium to the substrate, and is also effective in improving safety. 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 65,000 ℃ in vacuum, air, or an atmosphere such as argon gas, and moreover, it can be used as a thermal head. It also increases stability when used, which has an effect on longevity. When the heat treatment temperature is 200 qo or less, the change in resistance value is very small, so a long heat treatment time is required;
If it is more than 0, the resistance value changes rapidly or it becomes impossible to use a substrate such as glass, which may lead to restrictions in use or difficulty in control. Therefore, the heat treatment temperature is preferably 200 to 6500°. The shelved chromium thermal head obtained in this way is stable and resistant to oxidation, and the power usage limit of the conventional thermal head using tantalum nitride is 17~
Although it was 18W/me, it can be used for a maximum power supply of 21 to 22W/a. 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 chromium thin film resistor can be selected from a wide range of 70 mm to 5×1 mm, so if you set it to a high resistance value, you will need less current to generate heat. The electrode can be made thinner, which simplifies the manufacturing process, and it also has fewer irregularities, making it more 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. Furthermore, as is clear from the above description, the thermal head of the present invention does not contain a high-resistance material as a heating resistor. Therefore, there is no need to consider the mixing ratio or mixing state of materials, and a predetermined resistance value can be easily obtained. Next, it will be explained based on an example.

Example 1 Shelved chromium CrB2 hot-pressed at 110 mm on a glazed ceramic substrate that had been thoroughly cleaned in advance
(Made by Pentron, USA, Cr70.2%, B29.3%
) using high frequency bipolar sputtering as a target.
A heating element with a thickness of 1000 A was fabricated under conditions of a total argon pressure of 5 x 10 orr and a substrate heating temperature of 20 pm.

This specific resistance value was about 250 French Q arc, and the area resistance at this time was about 250/mouth. After depositing 10A of titanium and 1.54mm of aluminum using a kite electron beam, selective etching was performed on the thermal head A with a resolution of 4 wires/leg.
．． was formed. Next, the thermal heads A, . Tantalum oxide is applied as a protective layer by electron beam evaporation to a thickness of 6 mm.
Thermal head A, 2 has aluminum oxide deposited on it, Thermal head A, 3 has aluminum oxide deposited on it to a thickness of 8 degrees, Thermal head A, 4 has magnesium oxide deposited on it, 5 degrees thick, and 1.5 thick silicon oxide. Next, thermal head A, 5 in which tantalum oxide was deposited in a two-layer structure with a film thickness of 6 mounds.
prepared.

For comparison, tantalum was targeted by high-frequency bipolar reactive sputtering, and a 1000A thick tantalum nitride heat-generating film was generated under conditions of a total pressure of argon and nitrogen of 8×10-2Ton and a partial pressure of nitrogen of 1×10-Ton. Resistor thermal head B, . was created.

When this thin film was analyzed by X-ray diffraction, it was found to be Ta2N. Further, the specific resistance value was 240 peaks Qm, and the area resistance value at this time was 240/mouth. Next, the thermal heads B, .
B. A tantalum oxide protective layer with a thickness of 6 mm is provided by sputtering. 2 and 2, in which a silicon oxide film of 1.5W was provided, and a tantalum oxide film with a thickness of 6 peaks was further provided on top of it.
A sample B3 having a layered structure including a protective layer was prepared. For these prepared thermal heads, a pulse width of 6 s
, 5 msec of voltage was applied repeatedly, and the supplied power was increased to 30 msec.
Figure 2 shows the measurement results of ``Regular Shugaku x 1 Blood'' (%) when the speed test was performed by increasing the amount of blood by 1 tt/kyo per minute.

Here, R is the resistance value before the test, and ΔR is the change in resistance value. Shelved chromium thin film heating resistors A, . are tantalum nitride thin film heating resistors B, . It can supply approximately 1.2 times more fin force per unit area than the previous one. or,
By providing a protective layer, the power that can be delivered per unit area is greatly improved, but the shelved chromium thin film heating resistor is made of tantalum oxide (A
, 2), Even when only one protective layer of aluminum oxide (A, 3) and magnesium oxide (A, 4) is used, it is almost the same as thermal head B3, which is a tantalum nitride thin film heating resistor with two protective layers. The thermal head B and 2, which were made of a tantalum nitride thin film heating resistor having a single protective layer, were far more shielded. Also, shelving. Thermal heads A and 5, which have a two-layer protective layer of silicon oxide and tantalum oxide on the thermal head, 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 thermal energy is transferred to thermal recording paper varies depending on the contact pressure, but is approximately 11 to 14 W/m, so in the case of a tantalum nitride thin film heating resistor, a two-layer structure such as a combination of silicon oxide and tantalum oxide is used. In contrast, in the case of shelved chromium 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 the lifespan is further extended. (Example
2) The same thermal heads A, . Thermal head A2 has tantalum oxide sputtered to a thickness of 6 mm as a protective layer, thermal head 3 has aluminum oxide sputtered to a thickness of 8 mm, and thermal head 3 has sputtered magnesium oxide to a thickness of 5 mm. A thermal head A was prepared in which a two-layer protective layer was formed by sputtering, having a thickness of 4 mm, 1.5 mm thick silicon oxide, and 6 mm thick tantalum oxide.

These thermal heads were subjected to the same test as in Example 1, and the resistance change G rate was measured. As a result, the rate of resistance change increases rapidly.The power limit values per unit area are 19.5W/K for A2, 20.0W/K for A23, and 20.0W/K for A23, respectively.
24 had a power consumption of 20.0W/job 2, and A25 had a power consumption of 22W/grandchild, showing very good results. Better results were obtained when the protective layer was prepared by sputtering than by electron beam evaporation. (Example 3) Shelf chromium Cr & (Cr 70.2% manufactured by Pentron, USA)
, B29.3%) was pressed at a pressure of 100k9/m2 or higher to form a tablet, which was then placed on a glazed ceramic substrate that had been thoroughly cleaned in advance to a thickness of 1000A with substrate heating at 300°C and vacuum level at 5x10-6Ton. Swallowed with an electron beam.

This specific resistance value was about 750 mm, and the area resistance at this time was about 750/mouth. Next, add 10A of titanium on top of this.
After evaporating aluminum using a 1.5 Yamakawa electron beam, a pattern with a resolution of 4 lines/wind was formed by selective etching, and thermal heads C, . And so. These thermal heads C, . Thermal head C has tantalum oxide deposited as a protective film to a thickness of 6 μm by electron beam evaporation.
, 2. Thermal head C with aluminum oxide vapor deposited to a thickness of 8 degrees, 3. Thermal head C made of magnesium oxide vapor deposited to a thickness of 5 r, 4, and a layer of silicon oxide of 1.5 degrees followed by tantalum oxide of 6 degrees. A thermal head C, 5 having the same structure as that deposited 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, . Then 11W/dislike, C,
2 is 18W/fence, C, 3 is 18.5W/fence, C, 4
In the case of C, it was 18.5W/Kyo, and in C, 5 it was 20W/track.

The shelved chromium 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, and a thermal head C22 containing 6 tantalum oxide, 8 thermal head C23 containing aluminum oxide, 5 thermal head C24 containing 5 magnesium oxide, 1.5 silicon oxide, and then tantalum oxide. A thermal head C25 having a two-layer structure with six mountain surfaces 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 value per unit area at which the resistance change rate increases rapidly is 19 W/matsu for C2 and 1 W/matsu for C2.
It was 9.5W/Kyo, 19.5W/in C24, and 22W/in C fog. (Example 5) A 6-inch diameter metal chrome plate was used as a target.

Thoroughly cleaned glazed ceramic substrate
The substrate was heated to .degree. C., and active sputtering was performed in an argon/diborane mixed gas atmosphere. The pressure of argon diborane is 35×10-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. This specific resistance value was 440 rQ, and the area resistance at this time was 550/mouth. 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, 10 layers of aluminum oxide (AI208) were deposited as a protective film by sputtering. When the same acceleration test as in Example 1 was performed on this thermal head, the resistance change rate was 2% until it reached 19W/no power.
It was within This example also gave much better results than the thermal head using tantalum nitride in the comparative example. (Example 6) A target was prepared by placing a large number of 1'4 inch diameter boron plates bonded together on a 6 inch diameter metal chromium slope so that the surface area ratio of metal chromium:shelf elements was approximately 1:2. Using.

500 thoroughly cleaned glazed ceramic substrates
Heating the substrate to 0.00 and argon pressure: 3×10 orr.
R. F. Sputtering was performed using two electrodes. Sputtering rate is 100A/
After sputtering for 1 minute, the specific resistance value of the film at 1000A was . At this time, a thin film heating resistor with an area resistance of 900/hole was obtained with 900 peaks and arcs. 10A titanium on top of this
, aluminum was vapor-deposited using a 1 rm electron beam, and then a thermal head pattern with a four-line/side resolution was formed by selective etching. Next, tantalum oxide (Ta) was used as a protective film.
205) A layer of 10 m was laminated by sputtering. When this thermal head was subjected to the same acceleration test as in Example 1, the resistance change and G rate were within 2% up to 19.5 W/m, which was a much better result than the thermal head using tantalum nitride. was gotten. (Example 7) Shelved chromium powder was placed on a 5-inch diameter quartz dish to serve as a target.

A thoroughly cleaned glazed ceramic substrate was subjected to high-frequency bipolar sputtering with substrate heating at 20 pm and argon partial pressure at 5 x 10-2 Ton. Sputter rate 100A/mi
After sputtering with n for one night, the specific resistance value was 350〆Q
Therefore, a Yanagawa Hichrome thin film heating resistor with a sheet resistance of 350/unit was obtained. After evaporating titanium at 100A and gold at 1Aw using a fin beam, selective etching was performed to form a thermal head pattern with a capacity of 4 heads per job. Next, when heat-treated in air at 55,000 for one feeding hour, the resistance value of the heating resistor increased from 350 to 1,400/mouth. Magnesium oxide (Mg○) was sputtered on the heating resistor to a thickness of 8 mm as a protective film to form a thermal head D. I got 2. For comparison, thermal heads D, . We also prepared
6ms, 14W at 50Hz to these thermal heads
FIG. 3 shows the measurement results of the resistance change rate when the rectangular wave of tt/fence was continuously applied.

D, . with one pulse application. 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) The heat treatment of Example 7 was carried out in 650q of Ar.
When I changed it to 2 hours at o, the resistance was 350/310 from the mouth.
/ Changed into a mouth.

Here, 8 mounds of magnesium oxide (Mg◯) 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 even better than those of Example 7, and the rate of change in resistance was about 14% even with one pulse application.

[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 l Figure 2 Younger brother figure

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