JPH0640526B2 - Thermal head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head for thermal printing such as a facsimile and a printer, and more particularly to a stable and highly reliable heating resistor.

2. Description of the Related Art Thermal heads for thermal printing can be broadly classified into thick film thermal heads and thin film thermal heads depending on the method of forming the heating resistor. The thick film thermal head is formed by a so-called thick film technique such as screen printing, and is characterized by low manufacturing cost and excellent durability. The thin film thermal head is formed by a so-called thin film technique such as a vapor deposition technique or a sputtering technique, and has features such that fine patterning is possible, high printing quality is obtained, and printing speed is high.

In recent years, the demand for high-speed thermal heads has increased, and the power printed on heating resistors has increased. Conventionally, a heating resistor that is _{developed, Ta 2 N, TaSi x,} TaS
_i O _x, it can be listed TiC, ZrB, NiCr, a metal compound such NbSi.

Problems to be Solved by the Invention Since the conventional heating resistor is composed of one layer of the metal compound, when the driving power is high, the rate of change of the resistance value of the resistor is large and the resistor peels off. It had a drawback.

Means for Solving the Problems The heating resistor has a three-layer structure of “oxide layer of metal compound / metal compound / oxide layer of metal compound”.

Action The present invention uses the above means to enhance the adhesive force between the heat radiating substrate and the heat radiating substrate as the first layer, which is the oxide layer of the metal compound, and to buffer the thermal strain due to the difference in the coefficient of thermal expansion. To act. The oxide layer of the metal compound, which is the third layer, enhances the adhesive force with the upper protective film and acts as a buffer layer against thermal strain. Further, these two layers have the function of suppressing the oxidation of the metal compound layer (second layer), which is the main heating resistance layer, and suppressing the change in resistance value.

Embodiment FIG. 1 is a sectional view of a thermal head. Reference numeral 1 is a substrate, which is a hollow substrate using a low-alkali crystallized glass such as Mg ₂ B ₂ O ₅ or BaMg ₂ Si ₂ O ₇ .
Reference numeral 2 is a heating resistor, which is a TaSi-based metal compound shown in Table 1 and used a TaSi target in a mixed gas atmosphere with an argon partial pressure of 6 Pa and an acid partial pressure of 0.1 Pa as needed. It was formed by the DC sputtering method.

The specific resistance of the formed thin film resistor is TaSiO _x (x =
0.4 to 1.5; analysis value) was 1 to 7 × 10 ⁻² Ω · cm, and TaSi was a value that was almost double digits lower than this.

The heating resistor was patterned by the dry etching method. Chromium and copper were laminated thereon by a vapor deposition method, and a lead electrode 3 for power supply was formed by a selective etching method. 4,
Reference numeral 5 denotes a protective film and a wear resistant layer, respectively, which are for the purpose of preventing oxidation of the heating resistor and wear resistance, and are a laminated film of SiO ₂ (1 μm) and SiC (4 μm) formed by the RF sputtering method. In addition, the patterned thermal head has 8
Books / mm.

Now, with the above thermal head, 0.5W, 4 for each dot
FIG. 2 shows the resistance change rate of the heating resistor when a msec pulse is continuously applied at 16 msec intervals. As is clear from the figure, the NO. 3 according to the present invention is the conventional NO. 1 and NO.
It has a longer life than No.2. Further, during the experiment, the conventional NO.1 was partially peeled from the substrate, but the heating resistor of NO.3 existed stably.

As is clear from the above results, when the metal compound is expressed as M _x X _y rather than using a single layer of the metal compound as the heating resistor of the thermal head, M _x X _y O _z / M _x X _y / M x _X y _O z by a three-layer structure represented by _'was found to be longer than the operation life conventional thermal head. 3
The composition of each interface of the layers may be continuously changed from the metal compound to the oxide layer.

Table 2 shows the other experimental results when the heating resistor is made of a single layer of a metal compound and has the above-mentioned three-layer structure. Table-
2 shows the rate of resistance change (%) at the time of 10 ⁷ times under the experimental conditions shown in the above example.

Or the type of metal compound used for the apparent exothermic resistor from the results in Table 2ゝWarazu, be a three-layer structure of _{M x X y O z / M} x X y / M x X y O z It was found that the driving life of the thermal head can be dramatically improved. The method of forming the three-layer structure can be performed in almost the same process as the process of forming the single layer, and oxygen may be simply introduced as necessary when the heating resistor is sputtered or vapor-deposited.

The present invention is not limited to the above embodiment, and a ceramic substrate such as alumina, beryllia or sapphire having a glaze coating may be used instead of the holo substrate. The protective film is made of A ₂ O ₃ , MgO, Z instead of SiO _2.
An oxide such as rO ₂ , Ta ₂ O ₅ or the like may be omitted. Further, the wear resistant layer may be a hard material such as diamond-like carbon or Ta ₂ O ₅ instead of SiC. Also,
Lead electrode is Au, A, NiC instead of Cr / Cu
It may be r or the like and is not particularly limited.

EFFECTS OF THE INVENTION The present invention uses a metal compound layer for a heating resistor, and provides an oxide layer of a metal compound as an upper layer and a lower layer of the metal compound layer to suppress the resistance change of the resistor when the thermal head is driven, It is intended to provide a highly reliable thermal head having a long life and good adhesion to a substrate and a protective film.

[Brief description of drawings]

FIG. 1 is a sectional view of a thermal head according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing a resistance change rate in pulse driving of a thermal head using the thermal head and a conventional TaSi heating resistor. is there. 1 ... Substrate, 2 ... Heating resistor, 3 ... Lead electrode, 4
…… Protective film, 5 …… Abrasion resistant layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Yoshida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-53-52997 (JP, A) JP-A-58-53459 (JP, A)

Claims (3)

[Claims] 1. A heating element made of a metal compound is provided on a substrate, and a lead electrode for supplying power to the heating element is provided. When the heating element represents the metal compound as M _x X _y , M _x X _y O _z / M
A thermal head having a three-layer structure that can be expressed as _x X _y / M _x X _y O _{z '} . 2. M is hafnium, tantalum, titanium, tungsten, niobium, molybdenum, chromium, lanthanum,
The thermal head according to claim 1, wherein the thermal head is one of transition metals of zirconium, vanadium and nickel, and X is one of silicon, nitrogen, boron and carbon. 3. The thermal head according to claim 1, which is a holo substrate in which the surface of a metal base material is coated with low-alkali crystallized glass.