JPH0770371B2 - Thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermal head used for performing thermal recording.

(Prior Art) A thermal head is used as a recording device of a device such as a facsimile or a printer, and the size and weight of the device are reduced and maintenance-free.
It greatly promotes high reliability and low price, and contributes greatly to its progress.

A conventional thermal head has a structure in which a heating resistance film made of tantalum nitride (Ta ₂ N) and electrodes made of aluminum (Al), copper (Cu), etc. are sequentially laminated on a substrate made of an electrically insulating material such as alumina or glass. It has a function as a thermal head by applying a constant electric power to the heating resistance film through the electrodes and causing Joule heat generation in the heating resistance film.

Incidentally, in this conventional thermal head, normally, in order to protect the heating resistance film and the electrode from contact abrasion by the thermal recording paper or the thermal transfer ribbon and oxidation due to contact of oxygen in the atmosphere, silicon oxide is formed on the outer surface of the heating resistance film and the electrode. A protective film having a two-layer structure of (SiO ₂ ) and tantalum pentoxide (Ta ₂ O ₅ ) or a protective film having a single-layer structure of silicon oxynitride (SiN _X O _Y : X ≠ 0, Y ≠ 0) is deposited. Has been formed.

(Problems to be Solved by the Invention) In this conventional thermal head, the specific resistance of tantalum nitride constituting the heating resistance film is relatively small at about 250 μΩcm, and in order to instantly heat the heating resistance film to a desired temperature, Inevitably, the heating resistance film must be thinned to about 50Å or the film width must be narrowed to increase the resistance value. However, in a thermal head having a large number of heating resistance films such as a line type thermal head, it is extremely difficult to make all the heating resistance films have the same film thickness and the same film width. However, as a result, there is a defect that the Joule heat generation amount of each heat generation resistance film is different and a printing defect occurs.

In addition, since this conventional thermal head is not well compatible with tantalum nitride, which is the material of the heating resistance film, and aluminum, copper, etc., which is the material of the electrode, the bonding strength between the heating resistance film and the electrode is extremely weak, and external force is applied during operation. Is applied, the electrode is easily peeled off from the heating resistance film, and it becomes impossible to apply the specified power to the heating resistance film. For this reason, this thermal head has the drawbacks that the heating resistance film cannot generate Joule heat to a desired temperature and does not function as a thermal head, or printing defects occur.

(Object of the Invention) As a result of various experiments conducted by the present inventors in view of the above-mentioned drawbacks, Ta _x SiN _y O _z (1 <X <9,3 <Y <8,0.3 <
By using Z ≦ 2) and using aluminum, which is an active metal material, as an electrode that conducts electricity to the heating resistance film, a heating resistance film having an extremely high specific resistance can be obtained, and at the same time, aluminum and the electrode material are used. It has been found that the heating resistance film and the electrode can be firmly bonded to each other and the change in resistance value due to crystallization of the heating resistance film and heat loss of the heating resistance film can be effectively prevented. It was

The present invention is based on the above findings, and uses a material having a high specific resistance as the material of the heating resistance film and having good compatibility with the electrodes to eliminate printing unevenness and to obtain stable printing over a long period of time with high reliability. Its purpose is to provide a head.

(Means for Solving the Problems) The thermal head of the present invention is formed by Ta _X SiN _Y O on an insulating substrate.
_A heating resistor film made of _Z (1 <X <9,3 <Y <8,0.3 <Z≤2), and an electrode made of aluminum for energizing the heating resistor film. It is a thing.

The tantalum (Ta) used in the heating resistance film of the thermal head of the present invention is a component for imparting conductivity to the heating resistance film and having a predetermined specific resistance, and the X value which is the atomic ratio of Ta. Is not X ≦ 1, the desired properties described above are not imparted, and X ≧
If it is 9, the specific resistance of the heating resistance film becomes small and the heating resistance film cannot be heated to a desired temperature. Therefore, the X value is specified in the range of 1 <X <9.

Nitrogen (N) is a component for suppressing crystallization of the heat generating resistance film, and if the Y value, which is the atomic ratio of N, is Y ≦ 3, the desired properties described above are not provided, and Y ≧ 8. In that case, the power resistance of the heating resistance film is deteriorated: When power is applied to the heating resistance film, the resistance film is thermally damaged and loses its function as a thermal head. Therefore, the Y value is 3 <Y <8. Specified in the range of.

Further, oxygen (O) is a component for improving the adhesion between the heating resistance film and the electrode made of aluminum, and the above-mentioned desired properties are imparted when the Z value, which is the atomic ratio of O, is Z ≦ 0.3. If Z> 2, and the electric power is applied to the heating resistive film, the resistive film is thermally damaged and loses its function as a thermal head. Therefore, the Z value is specified in the range of 0.3 <Z ≦ 2. .

Silicon (Si) is a component that prevents the heat generation temperature of the heat generating resistance film from becoming unstable due to variations in the specific resistance of the compound of Ta, N and O at high temperatures.

(Example) Next, the present invention will be described in detail based on an example shown in the accompanying drawings.

FIG. 1 shows an embodiment of the thermal head of the present invention.
Is a substrate made of an electrically insulating material such as alumina.

A heating resistance film 2 is attached to the insulating substrate 1,
An electrode 3 is attached on the heating resistance film 2.

The heating resistance film 2 is formed of Ta _x SiN _y O _z (1 <X <9,3 <Y <8,0.
3 <Z ≦ 2), and the heating resistance film 2 is made of silicon (S
tantalum (Ta), nitrogen (N) and oxygen (O) for i)
The specific resistance of the heating resistance film 2 can be set to 1000 to 5000 μΩcm by changing the atomic ratio of.

Since the heat generating resistance film 2 has a predetermined electric resistance, when a constant electric power is applied, Joule heat is generated to generate heat at a temperature required for printing, for example, a temperature of 300 to 500 ° C.

The specific resistance of the heating resistance film 2 is X value of Ta _x SiN _y O _z , Y
Since the value can be adjusted to an arbitrary value by changing the value and the Z value, the heat generation temperature of the heat generating resistance film 2 can be adjusted to a desired value, and the applicable range of the thermal head can be widened.

In addition, the heating resistance film 2 is formed of Ta _x S that constitutes the resistance film 2.
iN _y O _z (1 <X <9,3 <Y <8,0.3 <Z ≦ 2) has a specific resistance of 1
Since it is as large as 000 to 5000 μΩcm, there is no need to increase the resistance value of the resistance film 2 by reducing the film thickness.
The thickness of all the heating resistance films 2 can be made substantially uniform. As a result, the resistance values of all the heating resistance films 2 become substantially the same, and the resistance films 2
The printing quality can be made extremely excellent by making the Joule calorific value of (1) uniform. In particular, if the thickness of the heating resistance film 2 is set to 200 to 1000Å, all the heating resistance films 2 can be made uniform in thickness so that the Joule heating value generated by each heating resistance film 2 can be made substantially the same. The film thickness is
It is preferably in the range of 200 to 1000Å.

The electrode 3 on the heating resistance film 2 is made of aluminum (Al) which is an active metal material, and the electrode 3 applies electric power to cause Joule heat generation to the heating resistance film 2.

Ta _x SiN _y O _z (1 <X <9,3, which is the material of the heating resistance film 2
<Y <8, 0.3 <Z ≦ 2) has a very good affinity with aluminum (Al), which is the material of the electrode 3, and since both are firmly bonded, even if an external force is applied during operation, etc., the heating resistance film No peeling occurs between the electrode 2 and the electrode 3.

The heating resistance film 2 made of Ta _x SiN _y O _z has an X value of 3 to
7. When the Y value is 4 to 6 and the Z value is 0.6 to 1.5, the Joule heat generation temperature of the heat generating resistance film 2 is about 400 ° C., the print quality is extremely good and the bonding strength with the electrode 3 is also extremely high. Therefore, it is preferable that the X value is 3 to 7, the Y value is 4 to 6, and the Z value is 0.6 to 1.5.

Further, tantalum pentoxide (Ta ₂ O ₅ ) or the like having excellent wear resistance is provided on the heat generating resistance film 2 and the electrode 3 in order to prevent the heat generating resistance film 2 and the like from being abraded by contact with thermal paper. A protective film 4 made of is formed.

The heating resistance film 2 is formed by a sputtering method or an electron beam evaporation method described later, and the electrode 3 and the protective film 4 are formed by a conventionally known vacuum evaporation method or a sputtering method.

Next, a method of forming the heat generating resistance film in the thermal head of the present invention will be described in detail.

The heat generating resistance film 2 in the thermal head of the present invention is formed by a high frequency sputtering method, specifically, by using a high frequency sputtering apparatus as shown in FIG. This high-frequency sputtering apparatus has a structure in which two cathodes 12a and 12b and an anode 13 are arranged in a vacuum container 11.

In order to form the heat generating resistance film 2 by the high frequency sputtering device, first, the first electrodes 12a and 12b are formed on the respective electrodes 12a and 12b.
The targets 14 and 15 having the compositions shown in the table are attached, and the insulating substrate 1 is attached to the anode 13. Next, the vacuum container 11
The degree of vacuum inside is 10 ^-2 to 10 ^-3 Torr and is filled with argon gas or argon gas containing O ₂ and N ₂ .
High frequency power (5 MHz, 3 KW) is applied between 12b and the anode 13 to release argon ions, oxygen ions and nitrogen ions. Then, the argon ions or the like are made to collide with the targets 14 and 15 to scatter a part of the targets 14 and 15 and Ta
_x SiN _y O _z (1 <X <9,3 <Y <8,0.3 <Z ≦ 2) is generated and deposited on the surface of the insulating substrate 1. As a result, the heating resistance film 2 is deposited on the insulating substrate 1.

When the heating resistance film is formed on the surface of the insulating substrate by the high frequency sputtering method or the like, the temperature of the substrate is 200 to 500 ° C.
It is possible to improve the adhesion between the substrate and the heat generating resistive film by heating the substrate to 200 ° C.
It is desirable to heat to a temperature of ~ 500 ° C. The heating resistance film is usually formed at a rate of about 100Å / min.

Next, various experimental results of the example product of the present invention and the conventional example product will be described.

First, in the thermal head having the cross section shown in FIG. 1, a resistor having a composition shown in Table 2 below was used to prepare a heating resistance film sample having a width of 100 μm, a length of 200 μm and a resistance value of 1000Ω.

For each of these samples, 1.0 [W / do
The electric power of [t] was applied and the actual printing life test on the thermal paper was performed. The results are shown in FIG.

From this result, the conventional product using tantalum nitride (Ta ₂ N) as a heating resistance film loses its function as a thermal head when it peels from the electrodes when the thermal paper is continuously fed for about 70 km. On the other hand, Ta _x SiN _y O _z within the composition range of the present invention
The heat-resisting film used as a sheet does not cause peeling between the electrode and the electrode even if the thermal paper is continuously fed for 150 km or more, and the rate of change in resistance value is within 4%, enabling extremely stable printing. .

For each of the above samples, pulse width 1.0 ms, pulse period 10
A step stress test was also performed in ms. The result is the fourth
Shown in the figure.

From this result, the conventional product using tantalum nitride (Ta ₂ N) as the heating resistance film has a large variation in the resistance value with the printing power of 1.4 [W / dot], and the print quality is deteriorated. On the other hand, in the case of using Ta _x SiN _y O _z within the composition range of the present invention, there is no large change in the resistance value up to the applied power of 1.7 [W / dot], and it can be seen that the printing quality can be made high.

(Effects of the Invention) Thus, according to the thermal head of the present invention, Ta _x SiN _y O _z (1 <X <9,3 <Y as a material of the heating resistance film has a high specific resistance.
By using <8, 0.3 <Z ≦ 2), the resistance value of the heating resistance film can be increased without reducing the film thickness or the film width, and the film thickness can be made uniform. The resistance values of all the heating resistance films are substantially the same, and a thermal head of extremely high print quality with no variation in print density can be obtained.

Further, according to the thermal head of the present invention, Ta _x SiN _y O _z (1 <X <9,3 <Y <8,0.3 <Z ≦ 2, which is extremely compatible with the electrode made of aluminum as the material of the heating resistance film, is used. The use of () makes it possible to firmly bond the heat generating resistance film and the electrode, and to effectively prevent a change in resistance value due to crystallization of the heat generating resistance film and heat loss of the heat generating resistance film. Therefore, even if an external force is applied during operation, the electrode does not peel off from the heating resistance film at all, and the specified power is always applied to the heating resistance film, and all the heating resistance films can generate Joule heat at a predetermined temperature. . Therefore, stable printing is possible for a long period of time.

[Brief description of drawings]

FIG. 1 is a sectional view of a main portion of a thermal head of the present invention, FIG. 2 is a sectional view of a high frequency sputtering apparatus for forming a heating resistance film in the thermal head of the present invention, and FIG. FIG. 4 is a characteristic diagram showing the result of the actual print life test of the conventional example product, and FIG. 4 is a characteristic diagram showing the result of the step stress test of the example product of the present invention and the conventional example product. 1 ... Insulating substrate, 2 ... Heating resistance film 3 ... Electrode

Claims (1)

[Claims] 1. Ta _X SiN _Y O _Z (1 <X <9,3 <
A thermal head comprising a heating resistance film made of Y <8, 0.3 <Z ≦ 2) and an electrode made of aluminum for energizing the heating resistance film.