JPH067521B2 - Thin-film thermal head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film type thermal head used for thermal recording printing.

2. Description of the Related Art Generally, a thermal head used for thermal printing recording is provided with a plurality of heat generating resistors on an insulating substrate and electrodes for supplying power to the heat generating resistors, and each heat generating resistor is provided with a power source. Is supplied to generate Joule heat, whereby printing and recording are performed.

As a heat generating resistor used for these, a thin film heat generating resistor is excellent in that it has good thermal responsiveness, high resolution, high reliability, and low power consumption.

As a conventional thin film heating resistor, for example, JP-A-52-1438
As disclosed in Japanese Patent No. 41, Ta-Si alloys and the like have excellent heat resistance. However, in order to realize high-speed thermal printing recording of a thermal head in recent years, it is necessary to perform recording with a short printing pulse of several milliseconds, and for that purpose, a large amount of electric power is applied to the thin film heating resistor. It is necessary to charge it and generate a temperature of 400 ° C. or higher. In addition, the increase in power inevitably increases the current unless the resistance value of the thin-film heat generating resistor is increased, which causes the following two problems. 1
One is that the resistance value of the electrode that supplies power to the thin-film heating resistor cannot be ignored with respect to the resistance value of the thin-film heating resistor. However, there is a difference in density between recording patterns, and power consumption at the electrodes becomes a problem especially when the resolution is increased. In order to avoid this, it is conceivable to make the thickness of the electrode extremely large, but this causes a great inconvenience in the structure. Another problem is that the current capacity of the driving system such as the heating power source and the switching circuit must be increased.

From the above points, it is necessary for the thin-film heat generation resistance pair to have at least two characteristics, that is, high temperature stability and high resistance. Considering the Ta-Si alloy from these points,
In this Ta-Si alloy, the region where the heat resistance is relatively stable is as small as about 200 to 250 μΩ-cm, and therefore, if a large resistance value is to be obtained, for example, L / W = 2 (L is heat generation) In order to obtain a resistance value of 500 Ω (resistor length, W is width) (in the flow of recent technology, a higher resistance value is required), the film thickness is very thin, about 100Å,
It is extremely difficult to control during manufacturing, and the film quality becomes unstable. In order to avoid this, it is possible to increase the resistance value by increasing the thickness of the Ta-Si alloy, forming a pattern in a meandering shape, etc., and increasing the L length. This method is extremely difficult to manufacture.

Further, the Ta-Si alloy is still insufficient in heat resistance at the time of driving with a short pulse width. Therefore, the Ta-Si alloy is not sufficient in terms of high speed and high heat resistance required for the thermal head. .

Problems to be Solved by the Invention As described above, the Ta-Si alloy, which is the material for the thin-film heating resistor of the conventional thermal head, still has sufficient characteristics for speeding up and high heat resistance of the thermal head. I haven't.

From this point of view, the present invention provides a thin-film heat-generating resistor that has the necessary conditions for high speed and high heat resistance of the thermal head, that is, a high resistance value and thus a high specific resistance, excellent high temperature stability, and high heat resistance. An object of the present invention is to provide a thin film type thermal head provided with the thin film thermal head.

Means for Solving the Problems The present invention, in order to solve the above problems, as a thin film heating resistor, a transition metal carbide and silicon carbide, in particular, as the transition metal carbide titanium carbide (TiC) This is a thin film type thermal head constructed by using this and a material made of silicon carbide (SiC).

Operation Titanium carbide in the above configuration (hereinafter referred to as TiC)
The thin-film heat-generating resistor made of silicon carbide (hereinafter referred to as SiC) has excellent high-temperature stability in both TiC and SiC, but the specific resistance of TiC alone is as low as 250 μΩ-Cm.
It is a mixture of C to increase and stabilize the resistivity.

Further, the thin-film heating resistor made of TiC and SiC has the following features. That is, if the same material system is used, Ti
And SiC, or TiC and Si,
All of these are simple elements such as Ti and Si.
Reacts with C _X and TiC _X (x <1) to form an intermediate compound, which results in graining, but in the case of TiC and SiC, each is in a stable compound state and is difficult to grow.

In addition, since it is a material system that does not contain nitrogen, oxygen, etc. at the time of creation, the generation of instability factors such as TiO _x (x2) is small,
It can be mentioned that it can be created with extremely good controllability.

As described above, by using a thin-film heating resistor made of TiC and SiC, a thin-film thermal head with good controllability, high specific resistance (high resistance value), excellent high-temperature stability, and high heat resistance can be constructed. .

Practical Example FIG. 1 shows the basic structure of a thin film thermal head according to the present invention. In this embodiment, the thin-film heating resistor made of transition metal carbide and silicon carbide is made of TiC and SiC.

Now, referring to FIG. 1, a thin film heating resistor 2 made of TiC and SiC is formed on the electrically insulating substrate 1 by a thin film forming technique such as sputtering, and a thin film heating resistor 2 for energizing the thin film heating resistor 2 is formed on the thin film heating resistor 2. After the electrode 3 is formed, a pattern is formed by a photolinography technique, and a protective layer 4 made of an insulator, a semiconductor or the like is formed on the electrode 3 (the protective layer 4 is usually used for preventing the thin film heating resistor 2 from being oxidized and for printing on paper Existing in order to prevent contact wear at the time of).

FIG. 2 shows, as an example of the sputtering target, a sputtering target when the thin-film heating resistor 2 made of TiC and SiC used in this example was prepared. The structure is such that the SiC plate 6 is arranged on the 150φ TiC target 5. SiC plate 6
By changing the area ratio of TiC and SiC, the Ar gas pressure is 1.5 × 10 ^-2 Torr, the RF power is 400 W, and the substrate temperature is 300.
RF sputtering was performed at a temperature (constant) to form a thin film heating resistor 2 on the electrically insulating substrate 1. FIG. 3 shows the relationship between the SiC target area ratio (horizontal axis), the specific resistance ρ, and the temperature coefficient of resistance (TCR) (vertical axis) at this time.
In the figure, curves 7 and 8 are the specific resistance and resistance temperature coefficient of the film (= assputter film) immediately after sputtering at a substrate temperature of 300 ° C., and curves 9 and 10 are respectively after sputtering in different vacuum, The specific resistance and the temperature coefficient of resistance of the film (anneal film) after the heat treatment at 650 ° C. (2 hours).

From this, it is understood that the changes in the specific resistance and the temperature coefficient of resistance with respect to the SiC composition are gradual, and the specific resistance hardly changes at 300 to 650 ° C. The temperature coefficient of resistance is slightly improved by the heat treatment. From such a point, it is considered that the thin-film heating resistor made of TiC and SiC can have a wide range of formation temperature control, and control during production is considered to be extremely easy. In these, TiC and SiC are each stable in the compound state, and grain growth is difficult,
Further, it is considered that SiC is particularly preferable because it has a good chemical stability such that it does not easily combine with other elements.

By the way, as shown in FIG. 3, the specific resistance of 2000 μΩ-cm and the temperature coefficient of resistance of −130 130 ppm / deg are 10 times higher than those of the conventional Ta—Si alloy with respect to the same temperature coefficient of resistance. . By the way, comparing with Ti and SiC thin films, TiC and Si thin films, and TiC and SiC ₂ thin films, TiC and Si
It was found that the thin film made of C had the least influence on the forming temperature and had excellent controllability and reproducibility. This is Ti and SiC
The former is Ti, and the latter is TiC and Si.
The latter is grain growth of Si and the former is TiC, Ti
O _x, TiSi _x latter SiC, SiO _x, the production of such TiSi _x conceivable, also made by TiC and SiO ₂ is of SiO ₂ dissociation O and T
In contrast to the possibility that TiO _x is generated by the reaction with iC, TiC and SiC are stable in the compound state of TiC and SiC, and it is difficult to grow grains, and the supply source of oxygen etc. It can be considered that an intermediate product is less likely to be generated due to the small amount.

Next, after the thermal head having the structure shown in FIG. 1 was applied, a continuous pulse was applied to this with a pulse width of 1 msec and a pulse period of 10 msec, and when a pulse was applied 6 × 10 ⁴ times,
The applied power (W / mm ² ) per unit area of the thin-film heating resistor that gives a resistance variation of + 10% (= called breaking power) is Ta
-Si alloys and thin-film heating resistors made of TiC and SiC (650
After heat treatment at ℃) is shown in the table below.

From the table, it is clear that also in terms of heat resistance, the thin-film heating resistor made of TiC and SiC is significantly improved as compared with the Ta-Si alloy thin-film heating resistor.

In addition, as an example of resistance change characteristics, a pulse width of 1 m is shown in FIG.
sec, pulse cycle 20 msec, resistance change rate when continuous pulse is applied with applied power 64 W / mm ² . In the figure, the horizontal axis represents the number of pulse applications and the vertical axis represents the resistance change rate.

A curve 11 shows the resistance change characteristics of the Ta-Si alloy thin film heating resistor, and a curve 12 shows the resistance change characteristics of the thin film heating resistor of TiC and SiC of the present invention (hereinafter abbreviated as TiC-SiC).

For comparison, a thin-film heating resistor made of TiC and Si (hereinafter abbreviated as TiC-Si) and TiC and SiO _{2 made} of (hereinafter TiC-SiO ₂
Abbreviated as “curve 1” for the resistance change characteristics of the thin film heating resistor.
It is additionally noted as 3,14.

From the figure, in the conventional Ta-Si alloy thin film heating resistor, the resistance change abruptly shifts in the negative direction at a relatively fast number of pulses,
Due to the excessive input of electric power (due to the grain growth of Ta-Si), destruction is likely to occur.
All of C-SiC, TiC-Si, and TiC-SiO ₂ have remarkably improved resistance change characteristics. Among them, the TiC-SiC thin-film heating resistor of the present invention is particularly excellent. this is,
This is because TiC and SiC are less likely to grow grains and are stable against oxidation.

Thus, the thin-film heat-generating resistor composed of titanium carbide and silicon carbide has high specific resistance, high temperature stability, and excellent heat resistance,
The resistance change is small and the controllability at the time of fabrication is good, and the thin film thermal head using this can easily cope with high speed and high heat resistance.

In this example, titanium carbide was used as the transition metal carbide, but other high melting point transition metal carbides, for example, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, molybdenum carbide, tungsten. Even if carbides are used, they are hard, have high temperature stability, and are chemically stable. Therefore, by appropriately mixing silicon carbide with these to form a thin film heating resistor, the same effect can be obtained. Can be obtained.

EFFECTS OF THE INVENTION As described above, according to the present invention, the controllability at the time of preparation made of transition metal carbide and silicon carbide is high, the specific resistance is high, the thermal stability is high, the heat resistance is rich, and the resistance change is small. This is a thin-film thermal head equipped with a thin-film heating resistor, which makes it possible to easily cope with higher speeds and higher heat resistance of the thermal head, and its industrial value is extremely high.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a basic structure of a thin film type thermal head according to the present invention, and FIGS. 2 to 4 are each a sputtering target shape of a thin film heating resistor as an embodiment of the present invention. FIG. 3 is a top view showing an example, and a characteristic diagram showing specific resistance, resistance temperature coefficient, and resistance change characteristics. 1 ... Electrically insulating substrate, 2 ... Thin film heating resistor made of transition metal carbide and silicon carbide, 3 ... Electrode, 4 ... Protective layer.

Claims (2)

[Claims] 1. A thin-film type thermal head comprising a thin-film heating resistor made of a transition metal carbide and silicon carbide. 2. The thin film type thermal head according to claim 1, wherein the transition metal carbide is titanium carbide.