JPS6046028B2 - 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 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 passing a current through 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 something.

The heat generating resistor used in this case is conventionally nitride tantalum. Shipiro lkma ιj''-Ray 1 yo top L
There are thick film heating resistors using An-1, . . . , and semiconductor heating resistors using silicon semiconductors. 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 and high reliability, and also has a relatively high specific resistance value of 250 to 300 μΩα and good manufacturing controllability. It is often used. 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 drawback of deteriorating print density when printing on recording paper. Generally, silicon oxide (SIO) is used to compensate for this drawback.
An oxidation-resistant protective layer of 0) is provided on top of which tantalum oxide (
Although a wear-resistant layer of Ta2O5) was provided and used as a thermal head, the resistance change was not small when the thermal head was driven for a long time, and the result 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 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, there is a demand for a heating resistor with even higher heat resistance. The inventors of the present invention have made various studies to improve the above-mentioned drawbacks, and have found that a heating resistor containing metal boride as a main component is very satisfactory.

This heating resistor whose main component is metal boride is approximately 500'
It has the heat resistance of C, is not easily oxidized, has a stable resistance value, and can have a high specific resistance. Further, as for the manufacturing method thereof, while the conventional tantalum nitride thin film heating resistor can only be manufactured by reactive sputtering, it can be manufactured by any of electron beam evaporation, sputtering, and reactive sputtering. However, as a result of various studies conducted by the present inventors, it has become clear that when an electric conductor for supplying power to the boride thin film heating resistor is deposited, there is a problem in its adhesion.

In other words, the electrical conductor of the thermal head is generally
Its specific resistance value is low for a certain film thickness, and chemical,
Thermally stable electrical conductors such as gold, silver, copper, and aluminum, as well as their alloys, were 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 nichrome must be provided as an undercoat layer. This improved adhesion. 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, allows the specific resistance to be selected up to a high value, has excellent stability and reliability, and provides excellent images that are stable over time. The reason for this is that an alloy layer containing vanadium as a main component is provided between a heating resistor containing a metal boride as a main component and an electric 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. Furthermore, oxygen, carbon, and nitrogen are added in an atomic ratio of 0.005 to 0.005 to the total amount of metal in the heating resistor.
The content may be about 1.0. Alternatively, Si. ．． GelTi. ．． Zr. ．． Hf. ．． V,. Nb.
．． Ta... Cr,. M.O. ．． W,. CulAg. sAu
．． sLa, sGa. ．． SmlMn. ．． Fe. ．． C.O. ．．
NilPt. ．． Rh. ．． PdlOs. ．． Ir. ．． A metal such as Ru may be added in an amount of 0.5m01% to 50rr101%. In addition, metal borides include MOSl2, WSl2, VS
l2, NbSi2, TaSi2, Crsi2, Zrsl
2, TiSi2, Cr3Sj. A conductive silicide such as sFe3Si may be added in an amount of 1m01% to 40rT101%. If the thickness of the vanadium layer or the alloy layer whose main component is vanadium is too thin, the adhesion effect will not be sufficient, while if it is too thick, the adhesion effect will be saturated.
Preferably 5A to 1000A, more preferably 1
0 to 500A, more preferably 20 to 300A.
Here, the metals that form an alloy with vanadium are A1 and A.
u. ．． Cu. , Ag. ．． Zr. HflNb. ．． Ti. ．．
Ta... Cr. ．． MOl■, Kg, etc. are applied. These vanadium layers or alloy layers containing vanadium as a main component can be formed by a resistance heating evaporation method, an electron beam evaporation method, 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.

In addition, since the adhesion between the head portion and the wiring portion is good, it has excellent heat resistance and is stable for a long 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 (TiB2), zirconium boride (ZrB2) on a thoroughly cleaned glazed ceramic substrate
, hafnium boride (HfB2), vanadium boride (V8), niobium boride (NbB2), tantalum boride (TaB2)
), chromium boride (CrB2), molybdenum boride (MOB
), tungsten boride (mixture of WB and WB2), and lanthanum boride (LlB6) at 2×10−2
1 each by sputtering with an argon partial pressure of T0rr.
A film thickness of 000A was applied.

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. As the undercoat layer, three types of chromium layer, nichrome layer, and vanadium layer with a thickness of 100A to 200A are each used at 5×1.
The layer was formed by electron beam evaporation at a vacuum degree of 0-6T0rr. 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, and in the case of copper and aluminum, peeling was observed in some areas. Some of the good electrical conductors of chromium, nichrome, and gold and silver were peeled off for samples in which chromium, nichrome, and panadium were vapor-deposited to improve adhesion. As is clear from the results in Table 1, the adhesion is improved by providing chromium, nichrome, and vanadium, and it is clear that the adhesion of vanadium in particular is greatly improved.

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

Table ■ shows the amount of change in resistance before and after heat treatment.ノ table ■,
As is clear from the above, it is clear that the resistance change of vanadium due to heat treatment is very small and 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 A vanadium alloy layer was used instead of the vanadium layer in Examples 1 and 2. (1) An alloy with a weight ratio of vanadium and aluminum of 9:1 (2) An alloy with a weight ratio of vanadium and gold of 9:1 (3) Alloy with vanadium and copper in weight ratio of 9:1 (4) Alloy with vanadium and silver in weight ratio of 9:1 (5) Alloy with vanadium and zirconium in weight ratio of 8:2 (6) Vanadium and Alloy with hafnium weight ratio of 8:2 (7) Alloy with vanadium to niobium weight ratio of 8:2 (8) Vanadium to titanium weight ratio of 8:
Alloy 2 (9) Weight ratio of vanadium and tantalum is 8:2
Alloy (10) The weight ratio of vanadium to chromium is 8:2 Alloy (11) The weight ratio of vanadium to molybdenum is 8:2
Alloy (12) with a weight ratio of vanadium and tungsten of 8
:2 alloy (13) Weight ratio of vanadium to 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 composed of a metal boride. A thermal head characterized in that a vanadium layer or an alloy layer containing vanadium as a main component is provided between the heating resistor and the electric conductor. 2. Claim 1, wherein the vanadium layer or the alloy layer containing vanadium as a main component has a thickness of 5 Å to 1000 Å.
Thermal head described in section.