JPS6046029B2 - thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head that has good adhesion between a heating resistor of the thermal head and an electric conductor that supplies power to the heating resistor.

A thermal head used for thermal print recording, for example, has a plurality of heating resistors on a substrate with 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 and contacting the recording medium so as to obtain the necessary thermal pattern according to the information to be recorded. It is.

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, 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 as a thin film heating resistor because it has relatively excellent heat resistance, high reliability, and has a specific resistance value of 250~250.
It is particularly widely used because it has a relatively high value of 300 μΩα and has good manufacturing controllability. However, tantalum nitride is rapidly oxidized at high temperatures of about 000° 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, in order to compensate for this drawback, an oxidation-resistant protective layer of silicon oxide (SiO2) is provided, and then a wear-resistant layer of tantalum oxide (Ta2O5) is provided on top of this to be used as a thermal head. The resistance change when driven was not small and was still not completely satisfactory. In particular, as the demand for high-speed thermal heads has increased in recent years, it is necessary to shorten the energizing pulse width of the head to color the thermal paper, which means that the electric power is higher than before, and the heating resistor becomes even hotter. lifespan becomes shorter. Therefore,
Furthermore, heat-resistant heating resistors are required. As a result of various studies to improve the above drawbacks, the inventors of the present invention found that
It has been found that a heating resistor based on a metal boride is very satisfactory.

This heating resistor mainly composed of metal boride has a temperature of approximately 500°C.
It has high heat resistance, is resistant to oxidation, has a stable resistance value, and can have a specific resistance of up to a high value. Further, as for the manufacturing method thereof, unlike the conventional tantalum nitride thin film heating resistor which can be manufactured only by reactive sputtering, it can be manufactured by any of electron beam evaporation, sputtering, and reactive sputtering. However, as a result of various further studies by the present inventors, when an electric conductor for supplying power to the boride thin film heating resistor was deposited,
It became clear that there was a problem with the adhesion.

In other words, the electrical conductor of the thermal head is generally a good electrical conductor such as gold, silver, copper, aluminum, etc., which has a low specific resistance value for a certain film thickness and is chemically and thermally stable. alloy was used.

Among these electrically conductive materials, copper, aluminum, and their alloys generally have strong adhesion, but gold and silver have poor adhesion, so a thin film of chromium or dichromium is used as an undercoat layer. By providing this, the adhesion was improved. However, it has been found that the above-mentioned undercoat layer is not sufficiently effective for heating resistors whose main component is metal boride. An object of the present invention is to provide a thermal head that has a stable resistance value, can select a specific resistance up to a high value, has excellent stability and reliability, and provides excellent images that are stable over time. This is because a titanium layer or an alloy layer mainly composed of titanium is provided between the heating resistor mainly composed of metal boride and the electrical conductor for power supply.

Metal borides applicable to the present invention include zirconium boride,
Examples include hafnium boride, lanthanum boride, chromium boride, titanium boride, tantalum boride, niobium boride, tungsten boride, molybdenum boride, and vanadium boride. These metal borides may be used alone or as a mixture of two or more of these metal borides as a thin film heating resistor. Further, oxygen, carbon, and nitrogen may be contained in an atomic ratio of about 0.005 to 1.0 with respect to the total amount of metal in the heating resistor. Alternatively, Si. ．． G
elTi. ．． Zr. ．． Hf. ．． V. ．． Nb. ．． Ta...
Cr. ．． MO,. W. ．． CulAg. ．． Au. ．． La.
．． Ga,. Sm,. Mn,. Fe. ．． C.O. ．． NilP
t. ．． Rh. ．． Pd,,Os,. Ir. ．． A metal such as Ru may be added in an amount of 0.5m01% to 50m1101%.
In addition, metal borides include MOSl2, WSl2, VSi2,
NbSj2, TaSj2, Crsi2, NrSi2, T
iSi2, Cr3Sj, . A conductive silicide such as Fe3Sj may be added in an amount of 1m01% to 40n101%. If the thickness of the titanium layer or the alloy layer containing titanium as a main component is too thin, the adhesion effect will not be sufficient, and if it is too thick, the adhesion effect will be saturated, so it is preferably 5A to 1000.
A is good, more preferably 10A to 500A, and even more preferably 20A to 300A.The metals forming an alloy with titanium include 7A1, Au. ．． CuNAg. ．． Z
r. ．． Hf. ．． Nb,. V. ．． Ta. ．． CrlMO,W
etc. apply. These titanium layers or titanium-based alloy layers can be formed by resistance heating evaporation, electron beam evaporation,
It can be manufactured by a sputtering method or the like.
The thermal head configured as described above can select a specific resistance up to a high value, and can withstand the flow of a large current within a short pulse in order to speed up printing.

Furthermore, since the adhesion between the head portion and the wiring portion is good, it has excellent heat resistance and is stable for a long period of time even when repeated pulses are applied. There is no need to limit the manufacturing method to a special method, and any method such as resistance heating evaporation method, electron beam evaporation method, sputtering method, etc. can be applied. moreover,
When printing using this thermal head, it is possible to provide an image that is stable over time. Next, an example will be described.

Example 1 Titanium boride (Ti type), zirconium boride (ZrB2),
Hafnium boride (HfB2), vanadium boride (VB2)
), niobium boride (NbB2), tantalum boride (TaB,
), chromium boride (CrB2), molybdenum boride (MOB
), tungsten boride (WBI: mixture of .WB2),
2x10 targeting lanthanum boride (LlB6)
A film thickness of 1000 A was formed on each film by sputtering at an argon partial pressure of -2T0rr.

In order to measure the adhesion between these metal boride thin films and electrical conductors (gold, silver, copper, and aluminum), samples were prepared with and without an undercoat layer between them. Created. The undercoat layer consists of three types of chromium layer, nichrome layer, and titanium layer each having a thickness of 100A to 200A at 5×10−
The layer was formed by electron beam evaporation at a vacuum level of 6T0rr. For each of these, electrical conductor layers of gold, silver, copper, and aluminum were laminated to a thickness of 5000 Å by electron beam evaporation. As a test for adhesion, the sample was subjected to a one-part ultrasonic cleaning test in isopropyl alcohol, and peeling of the electrically conductive material was examined.

The results are shown in Table 1. In the samples in which gold and silver were directly deposited on boride, the gold and silver were completely peeled off. In the case of copper and aluminum, peeling was observed in some areas. Samples in which chromium, nichrome, and titanium were vapor-deposited to improve adhesion showed that the chromium, and the gold and silver electrical conductors of nichrome, were partially peeled off. As is clear from the results in Table 1, the adhesion is greatly improved by providing chromium, nichrome, and titanium, and it is clear that the adhesion of titanium in particular is greatly improved.

Example 2 The same sample as prepared in Example 1 was heat treated at 450'CX for 5 hours to test its thermal stability, and the electrical resistance values before and after the heat treatment were examined.

Table 3 shows the amount of change in resistance before and after heat treatment. As is clear from Table 1, it is clear that titanium exhibits very little resistance change due to heat treatment and is stable.
For gold and silver, if there is no subbing layer, the adhesion with the boride will be poor, and the film will peel off, resulting in poor contact.

Observations of chromium and nichrome before and after heat treatment indicate that they react violently with boride, which seems to impair the contact between the boride thin film and the electrically conductive material. Example 3 In place of the titanium layer in Examples 1 and 2, a titanium alloy layer was used: (1) an alloy with a weight ratio of titanium and aluminum of 9:1 (2) an alloy with a weight ratio of titanium and gold of 9:1 (3) An alloy with a weight ratio of titanium and copper of 9:1 (4) An alloy with a weight ratio of titanium and silver of 9:1 (5)
An alloy with a weight ratio of titanium and zirnium of 8:2 (6) an alloy with a weight ratio of titanium and hafnium of 8:2 (7) an alloy with a weight ratio of titanium and niobium of 8:2 (8) an alloy with a weight ratio of titanium and vanadium Alloy J with a weight ratio of titanium to tantalum of 8:2 (10) Alloy with a weight ratio of titanium to chromium of 8:2 (11) Titanium to molybdenum weight ratio of 8
:2 alloy (12) Weight ratio of titanium and tungsten is 8
:2 No Alloy (13) Weight ratio of titanium and lanthanum is 8
:2 alloys were prepared by electron beam evaporation and similar measurements were performed, and almost the same results were obtained.

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 mainly made of metal boride. 1. A thermal head characterized in that a titanium layer or an alloy layer containing titanium as a main component is provided between the heating resistor and the electric conductor. 2. The thermal head according to claim 1, wherein the titanium layer or the titanium-based alloy layer has a thickness of 5 Å to 1000 Å.