JPH09118031A - Thermal print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive print head of high productivity which nearly eliminates a change of a resistance value of a heat-generating resistance body when used at high temperatures, achieves an improvement in power resistance properties, and realizes fine and high-speed printing. SOLUTION: This thermal print head is provided with a heat-generating resistance formed on a supporting substrate and an electrode connected to the heat-generating resistance. A film thickness of the heat-generating resistance is 0.15-0.30μm, and a specific resistance of the heat-generating resistance is 10-80mΩ.cm. In the thermal print head, the heat-generating resistance is formed on the supporting substrate via a glaze glass layer and is connected to the electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head used in a thermal recording apparatus such as a facsimile machine, a video printer, and various kinds of AA equipment represented by a plate making machine.

[0002]

2. Description of the Related Art A thermal print head has many advantages such as low noise, low maintenance cost, low running cost, etc., and is therefore widely used in a thermal recording apparatus of various kinds of AA equipment represented by a facsimile, a video printer and the like. Has become.

Generally, a thermal print head has the following configuration. That is, as shown in FIG. 6, a glaze glass layer 2 is formed on an alumina substrate 1, a heating resistor layer and a conductive layer such as aluminum are formed on the glaze glass layer 2, and then a photoengraving process is performed. A heating resistor 4 having a heating portion 3, an individual electrode pattern 5 and a common electrode pattern 6 are formed. Further, the heating resistor 4, the individual electrode pattern 5 and the common electrode pattern 6 are formed with a protective layer 7 by a thin film forming method such as a sputtering method. There is also a thermal print head having a structure in which a film made of Si—N—O system or the like is formed instead of the glaze glass layer 2.

In recent years, in thermal recording devices for various kinds of AA equipment, finer printing and higher speed are increasingly required, and 400 dpi (dots p) for hole printing.
er inch) and higher resolution thermal print heads have also appeared.

In the thermal print head, in order to achieve finer printing and higher speed of printing, it is indispensable to miniaturize the heating resistor and increase the energy density input to the heating resistor. When the shape is miniaturized, the heat load per unit area of the heating resistor increases, and the heating temperature of the heating resistor rises. Therefore, generally, the resistance value of the heating resistor changes with the lapse of operating time, and eventually exceeds the specified resistance value range, and the thermal print head becomes unusable.

When a high-power pulse is applied to the heat-generating resistor of the thermal print head in order to cope with high-speed printing of the thermal recording device, the heat-generating temperature of the heat-generating resistor rises and the heat-generating resistor is heated. Similar to the case where the body shape is miniaturized, the resistance value of the heating resistor deviates from the specified resistance value range and cannot be used.

One of the major factors that cause such a change in the resistance value of the heating resistor is the diffusion of oxygen or impurities from the glaze glass layer into the heating resistor. Therefore, in order to suppress the diffusion of oxygen or impurities into the heating resistor, as disclosed in JP-A-61-297159, SiNxOy (0.2 <x <is provided between the glaze glass layer and the heating resistor. 1.1, 0.2 <y <1.
A method of interposing a barrier layer composed of 8) has been proposed. In addition, Si is provided between the glaze glass layer and the heating resistor.
A method has also been proposed in which an inorganic insulating barrier layer made of O ₂ or the like is interposed to suppress the reaction between the glaze glass layer and the heating resistor. In any case, the barrier layer is appropriately selected in consideration of the diffusion inhibiting force of oxygen or impurities from the glaze glass layer to the heating resistor, the adhesive force between the layers, and the like.

As a method other than providing the barrier layer under the heating resistor, a supporting substrate having a glass glaze layer in a reducing gas atmosphere, a nitriding gas atmosphere, an inert gas atmosphere or a vacuum is used. There is proposed a method of firing the glass in a temperature range above the glass transition point of the glass glaze layer. According to this method, the oxygen content in the vicinity of the interface in contact with at least the heating resistor of the glass glaze layer is equal to or lower than the oxygen content of the heating resistor, so that the oxygen from the glass glaze layer to the heating resistor is reduced. That is, the diffusion does not occur.

However, as a result of trial production of thermal print heads using various materials for the barrier layer and the heating resistor and confirmation of the characteristics, it was found that the method of providing the barrier layer had the following problems.

That is, the power resistance of the thermal print head greatly varies due to a slight change in the composition of the barrier layer, and the degree thereof varies depending on the combination of the heating resistor and the material of the barrier layer. That is,
The power endurance of the thermal print head is not necessarily improved only by defining the components and the composition range of the barrier layer. Note that the power resistance is, for example, "the rate of change in the resistance value of the heating resistor at the time when a pulse of W / dot is applied 3 × 10 ⁷ times in the same resistor shape, the same pulse width and the same pulse period. It is a concept defined by "whether to indicate 10%". That is, when the thermal head A applies a pulse of 0.15 W / dot 3 × 10 ⁷ times, the rate of change in the resistance value of the heating resistor is + 10%, and the thermal head B is 0.18 W / dot. If the resistance change rate of the heating resistor is + 10% at the time of applying the pulse 3 × 10 ⁷ times, it means that the thermal head B is 20% more excellent in power resistance than the thermal head A. To do.

Further, although the barrier layer is usually formed by a sputtering method or the like, therefore, the surface of the barrier layer cannot be made smooth (the surface roughness increases), and the surface of the barrier layer is more difficult than the glass glaze layer. The smoothness will be poor.
Therefore, the resistance value of the heating resistor layer formed on the upper portion is higher than that of the heating resistor layer formed on the glass glaze layer, and the extent thereof also reflects the surface roughness.

When the barrier layer is formed by a sputtering method or the like, foreign matter (particles) may be trapped inside or on the surface of the barrier layer. In the thermal print head in which foreign matter is taken into the barrier layer, the variation in the resistance value of the heating resistor layer formed on the top of the thermal print head when driving the thermal print head becomes large. Becomes

In addition, the formation of the barrier layer causes an increase in manufacturing cost, which is a serious problem in manufacturing cost when the thermal print head is commercialized.

On the other hand, it has been found that the method of firing a supporting substrate having a glass glaze layer in a temperature range above the glass transition point of the glass glaze layer has the following problems. That is, in the method of firing a supporting substrate having a glass glaze layer in a temperature range equal to or higher than the glass transition point of the glass glaze layer, the reproducibility of the firing effect is poor particularly at the mass production level, and the variation in individual glass glaze layers is large. I understand. This is a heat treatment (baking) of all batches / lots of the supporting substrate having the glass glaze layer in the exactly same atmosphere, especially in a gas atmosphere.
It is difficult to do so, that is, it is difficult to exactly match the gas flow rate, temperature, etc. on the surface of each glass glaze layer. Further, even if the same type of supporting substrate is used, there are subtle variations in the composition and thermophysical properties of the glass glaze layer, and these subtle variations produce large differences in device characteristics due to heat treatment.

It was also found that, depending on the type of the glass glaze layer, not only the effect of firing the supporting substrate cannot be obtained, but conversely, the thermal print head has poor power resistance. This tendency was higher in the glass glaze layer having a higher glass transition point.

Generally, the development trend of the glass glaze layer is as follows.
It is to raise the glass transition temperature and reduce impurities such as Ba and Ca. According to the trial production by the present inventors, when the supporting substrate having the glass glaze layer is not heat-treated, a thermal print head having a glass glaze layer having a high glass transition point and a low impurity concentration has a higher power resistance. It became an excellent one. For example, the glass transition point is 670 ℃
The thermal resistance of the thermal print head having the glass glaze layer having a glass transition point of 770 ° C. is 10% higher than that of the thermal print head having the glass glaze layer of No. In addition, a supporting substrate having a glass glaze layer having a glass transition point of 670 ° C. was added with 90% in a 5% H ₂ —N ₂ atmosphere.
When the firing (heat treatment) is performed at 0 ° C., the power resistance of the thermal head is improved by 8% as compared with the case where the heat treatment is not performed.

However, a supporting substrate having a glass glaze layer having a glass transition point of 770 ° C. was added with 5% H ₂ —N ₂
When firing (heat treatment) is performed at 1000 ° C. in the atmosphere, the power resistance of the thermal print head is reduced by 3% as compared with the case where the heat treatment is not performed on the supporting substrate having the same glass glaze layer.

Since no synergistic effect is observed between the glass glaze layer having a high glass transition point and the firing (heat treatment) as described above, in a reducing gas atmosphere, a nitriding gas atmosphere, or an inert gas atmosphere. In the method of firing the supporting substrate having the glass glaze layer in the temperature range above the glass transition point of the glass glaze layer in the middle or in vacuum, it was limited to improve the power resistance of the thermal print head by 10%.

However, as described above, in recent years, there has been an increasing demand for finer printing and faster printing. In order to achieve finer printing and faster printing, the thermal print head must be 30% power resistance
Need to improve. Specifically, the thermal print head has a pulse width of 0.5 ms and a repetition period of 3.0 m.
As s, the pulse rate of the electric power of 0.30 W / dot is continuously applied, and the rate of change of the resistance value is within ± 10% when the pulse is applied 1 × 10 ⁸ times. However, in the conventional method of interposing a barrier layer between the glaze glass layer and the heating resistor and the method of firing the supporting substrate having the glass glaze layer in a temperature range higher than the glass transition point of the glass glaze layer, it is necessary. It is difficult to improve the power resistance of the thermal print head, and the thermal print head that has improved power resistance has a low yield and cannot be commercialized. Further, these problems also occurred when a film made of Si—N—O system or the like was formed instead of the glaze glass layer.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. In the use at high temperature, the change in the resistance value of the heating resistor is almost eliminated, and the power resistance is improved. It is an object of the present invention to provide a thermal print head that realizes finer printing and higher speed, has excellent productivity, and is inexpensive.

[0021]

A thermal print head according to the present invention is a thermal print head comprising a heating resistor formed on a supporting substrate and electrodes connected to the heating resistor, wherein the heating resistor is provided. Has a film thickness of 0.15
˜0.30 μm, and the specific resistance value of the heating resistor is 10 to 80 mΩ · cm.

Further, the thermal print head of the present invention comprises a heating resistor formed on a supporting substrate via a glaze glass layer, and an electrode connected to the heating resistor. The film thickness of the heating resistor is 0.15 to 0.30 μm, and the specific resistance value of the heating resistor is 10 to 80 mΩ · cm.

The present invention is effective in a thermal print head in which a glaze glass layer is formed on a supporting substrate, and in a thermal print head in which the temperature of the heating resistor during driving is equal to or higher than the glass transition point of the glaze glass layer. Especially effective. Further, it is naturally effective when a film made of Si—N—O system or the like is formed instead of the glaze glass layer. Furthermore, the present invention is also effective in a thermal print head in which an inorganic barrier layer is provided on the glaze glass layer.

That is, the present invention is effective in general thermal print heads having a structure in which oxygen and impurities diffuse into the heating resistor.

The basic idea of the present invention is to form a heating resistor having a sufficient thickness (distance) with respect to the mutual diffusion distance of impurities between the heating resistor and the layers located above and below it. The purpose is to sufficiently reduce the influence of mutual diffusion of impurities on the heating resistor.

That is, when the lower layer of the heating resistor is a glaze glass layer, the impurity concentration gradient between the heating resistor and the glaze glass layer, the diffusion coefficient of the heating resistor and the glaze glass layer, and the temperature conditions are determined. Therefore, impurities such as oxygen, Ba, and Ca diffuse into the heating resistor and invade the heating resistor, causing an increase in the resistance value of the thermal print head. The increase in the resistance value of the thermal print head becomes more remarkable when the temperature of the heating resistor becomes higher than the glass transition point of the glaze glass layer.

When an inorganic barrier layer made of Si—N—O system or the like is provided as the lower layer of the heating resistor, focusing attention on oxygen, for example, the oxygen concentration of the barrier layer is determined by the oxygen concentration of the heating resistor layer. When the concentration is higher than the concentration, oxygen is likely to move from the barrier layer toward the heating resistor, which causes an increase in the resistance value of the thermal print head. On the other hand, when the oxygen concentration of the barrier layer is lower than the oxygen concentration of the heating resistor, oxygen is likely to move from the heating resistor to the barrier layer, and the resistance value of the thermal print head decreases from the initial value. As a result, excessive power is inevitably applied to the thermal print head, so that the heating resistor is destroyed and the life characteristic is deteriorated. This phenomenon is due to the fact that the Si
The same applies to the case where an inorganic protective layer made of —NO system or the like is provided.

Further, when the heat generating resistor is previously subjected to sufficient heat treatment by annealing or aging, the change in the resistance value during the driving of the thermal print head appears in the rising mode. According to these experiments, it is clear that this phenomenon is dominated by the solid-state reaction between the glaze glass layer and the heating resistor.

The change in the resistance value of the thermal print head due to the mutual diffusion between the heat generating resistor and the layers located above and below the heat generating resistor is due to the concentration gradient of the component composition and the accompanying diffusion between the two or the three. As described above, it is difficult to avoid, and the change in the resistance value of the thermal print head becomes more remarkable as the high power pulse is applied to the heating resistor, or simply as the heating temperature increases.

According to a general model calculation, the rate of change in resistance value of the thermal print head is inversely proportional to the square of the film thickness of the heating resistor, but when the thermal print head is actually driven, In the high temperature region, the measured value of the resistance change rate is considerably smaller than the calculated value and is stable.
This is a model in which the calculation of the rate of change of resistance value is a model in which the whole is simply heated in the two solid phases of the glaze glass layer and the heating resistor, whereas in the actual driving of the thermal print head, the heat is in the form of pulses. It is presumed that there are differences such as a protective layer and electrodes in the actual thermal print head. In particular, in the high temperature region, the change in resistance value of the thermal print head becomes smaller than expected.

Therefore, it was expected that the change in the resistance value of the thermal print head could be sufficiently reduced by increasing the film thickness of the heating resistor to reduce the relative proportion of the reaction region. Of.

Based on this prediction, the inventors of the present invention conducted an experiment and concluded that the film thickness of the heating resistor capable of sufficiently reducing the effect of mutual diffusion of impurities is 0.15 μm or more. By setting the thickness of the heating resistor to 0.15 μm or more, not only the stability of the resistance value but also the action of suppressing the variation in the resistance value is significantly improved. The value of “0.15 μm” is the resistance of the thermal print head due to the diffusion and penetration of impurities into the heating resistor or the movement from the heating resistor even in the thermal print head driven under the most thermally severe conditions. It is a threshold value that can prevent a change in value.

The film thickness of the heating resistor becomes considerably thicker than 0.15 μm, which is acceptable in terms of stability of resistance value. However, in consideration of the productivity as well, the film thickness of the heating resistor may be in the range of 0.15 to 0.30 μm, preferably 0.18 to 0.30 μm.

Further, generally, when the film thickness of the heating resistor is increased, the sheet resistance value of the heating resistor is lowered and it becomes difficult to maintain the original product resistance value. Therefore, the range of the specific resistance value of the heating resistor is set to 10 to 80 mΩ · cm to cope with the reduction of the sheet resistance value of the heating resistor by increasing the film thickness of the heating resistor.

The specific resistance value of the heating resistor is 10 to 80 mΩ.
In the case of a cermet material, adjustment to the cm range can be easily achieved by increasing the insulating component in the target used during sputtering.

In the present invention, as a preferable component of the heating resistor, a Τa-Si-0 type cermet material or the like can be mentioned, but a cermet material such as Τi-Si-O type or Cr-Si-O type may be used. Furthermore, the material is not limited to the cermet material. The heating resistor is finally formed by a photoengraving process after forming a heating resistor layer by sputtering such as RF sputtering.

Various ceramic materials such as alumina ceramics can be used as the supporting substrate.
It is also possible to add additives such as a sintering aid at the time of molding the supporting substrate. In addition to the ceramic material, various insulating materials can be used for the supporting base, if necessary.

When the glaze glass layer is formed on the supporting substrate, the glaze glass layer has a film thickness of 3 by a printing method or the like.
The thickness is about 0 to 70 μm. SiO ₂ is generally used as the main component of the glaze glass layer, but it is not particularly limited, and impurities such as Ba and Ca may be mixed. Further, instead of the glaze glass layer, a film made of Si-NO system may be formed.

When an inorganic barrier layer or protective layer is formed above or below the heating resistor, the components of the barrier layer or protective layer are
Usually, it is made of Si-NO system, but these components are appropriately selected according to need.

[0040]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Example 1) A glass transition point of 6 was obtained by a printing method on the surface of a ceramic substrate containing alumina as a main component.
A 70 ° C. glaze glass layer was formed with a thickness of 40 μm. Various methods such as a spray method can be applied to the formation of the glaze glass layer. Glass transition point is 670
The glaze glass layer, which is in degrees Celsius, is a typical glaze glass layer commonly used in current thermal printheads.

Next, four kinds of heating resistor layers having different thicknesses were formed on the glaze glass layer by RF sputtering. RF sputtering was performed using T a as a target: 47 mol%, SiO ₂ : 53 mol%
Using a sintered body obtained by sintering a powder consisting of, in an Ar atmosphere, pressure 1.1 Pa, RF power density 3.3 W / cm ²
It went on condition of. The specific resistance value of the obtained Τa-Si-O-based heating resistor layer was 12 mΩ · cm, and the film thickness was (a) 0.05 μm, (b) 0.1 μm, (c), respectively.
0.15 μm and (d) 0.2 μm. The sheet resistance values are (a) 2400Ω and (b) 1 respectively.
It was 200Ω, (c) 800Ω, and (d) 600Ω.

After forming the heating resistor layer in this way, thermal annealing treatment is performed at 800 ° C. for 10 minutes in a vacuum, and the resistance value is reduced due to structural relaxation of the heating resistor due to heat generation when the thermal print head is driven. I tried not to get up.

Then, an Al electrode layer is formed on the heating resistor layer of each sample, and patterning is performed by a photoengraving process. Finally, a Si—N—O type protective film having a thickness of 3 μm is formed. Formed. Further, through a normal mounting process, a thermal print head for a plate making machine having a heating resistor shape of 40 μm in the sub-scanning direction and 30 μm in the main scanning direction and a resolution of 400 dpi was manufactured.

A pulse width of 0.5 ms and a repetition period of 3.0 ms were continuously applied to the thermal print head thus manufactured to apply a pulse of electric power of 0.30 W / dot to track the change of the resistance value change rate to obtain the life. It was a characteristic test. The temperature of each heating resistor reached a maximum of 730 ° C. during the life characteristic test. The result is shown in FIG.

As is apparent from FIG. 1, the thickness of the heating resistor is (a) 0.05 μm, (b) 0.1 μm, (c).
0.15 μm, (d) 0.2 μm,
The resistance value increases as the pulse is applied, but the rate of increase decreases as the film thickness of the heating resistor increases.

The film thickness of the heating resistor is (a) 0.0.
In the case of 5 μm, the rate of change in resistance value exceeds + 10% after applying 4 × 10 ⁶ pulses, and in the case of (b) 0.1 μm film thickness of the heating resistor, 7 × 10 ^The resistance change rate exceeds + 10% after applying ⁷ pulses. In any case, the thickness of the heating resistor is (a)
In the case of 0.05 μm and (b) 0.1 μm, the improvement in the power resistance of the thermal print head necessary for achieving finer printing and higher speed has not been achieved.

On the other hand, the thickness of the heating resistor is (c) 0.15
In the case of μm and (d) 0.2 μm, the resistance change rates are +3 and +4, respectively, even when the pulse is applied 1 × 10 ⁸ times.
%, The improvement in the power resistance of the thermal print head required to achieve finer printing and higher speed has been achieved.

As is clear from the above, there is a large difference in the rate of change in resistance between the case where the film thickness of the heating resistor is (b) 0.1 μm and the case (c) is 0.15 μm. Yes,
It is very significant to set the thickness of the heating resistor to 0.15 μm or more in order to improve the power resistance of the thermal print head.

The thickness of the heating resistor is set to (c) 0.15.
Comparing the case of μm and the case of (d) 0.2 μm, the resistance value change rate does not change so much. Therefore, when the film thickness of the heating resistor is 0.15 μm or more, It can be seen that it may be appropriately determined in consideration of the sex.

(Example 2) From Example 1, it was shown that a thermal print head having extremely excellent power resistance can be realized by setting the film thickness of the heating resistor to 0.15 μm or more. However, if the film thickness of the heating resistor is increased, the problem that the sheet resistance value is inevitably reduced occurs. For example, when a thermal print head having a sheet resistance value of 6 kΩ is desired, the film thickness of the heating resistor is 0.0
It must be formed to a thickness of about 2 μm.

Therefore, so that the sheet resistance value can be kept high even if the film thickness of the heating resistor is increased, the target used during RF sputtering is Τa: 45 mol%, SiO ₂ :
55 mol% mixed sintered body was used, and other conditions were the same as in Example 1.
Similarly to the above, the specific resistance value on the glaze glass layer: 36 mΩ
A cm heating resistor layer was formed. The thickness of this heating resistor layer is 0.15 μm, and the sheet resistance value is 2400Ω.
showed that. Then, through the same process as in Example 1,
A thermal print head for a plate making machine having the same specifications as in Example 1 was obtained.

As in Example 1, a pulse width of 0.5 ms and a repetition period of 3.0 ms were continuously applied to the thermal print head manufactured in this manner, and a pulse of 0.30 W / dot was applied to the resistance value change rate. The transition was traced and a life characteristic test was conducted. The temperature of each heating resistor reached a maximum of 730 ° C. during the life characteristic test. FIG. 2 shows the result.

As is apparent from FIG. 2, in Example 2, the resistance value increased with the pulse application, but the rate of increase was as small as (c) of Example 1 and 1 × 10 ⁸ times. Even when the pulse is applied, the resistance value change rate is + 4.5%, and the improvement in the power resistance of the thermal print head necessary for achieving finer printing and higher speed has been achieved.

From the above, the thickness of the heating resistor is set to 0.15 μm.
It can be understood that the improvement of the power resistance of the thermal print head was achieved while avoiding the problem of the reduction of the sheet resistance value due to the setting of m or more.

(Example 3) From Example 1, it was shown that a thermal print head having extremely excellent power resistance can be realized by setting the thickness of the heating resistor to 0.15 μm or more. In order to further study the effect of increasing the film thickness of the body, samples (e) to (h) of the thermal print head were prepared by combining glaze glass having different glass transition points and heating resistors having different film thicknesses. Then, the life characteristic test was performed. This combination is shown in Table 1.

[0057]

[Table 1] In this example, except that the glaze glass having a glass transition point of 770 ° C. was used in the samples (f) and (h), the preparation conditions of the thermal print head, the specifications, and the conditions of the life characteristic test were the same as those in Example 1. Is exactly the same as. Therefore, the sheet resistance values of these heating resistors are 2400Ω for samples (e) and (f), and 800Ω for samples (g) and (h), and the temperature of each heating resistor during the life characteristic test is The maximum temperature reached 730 ° C. FIG. 3 shows the result of the life characteristic test.

As shown in FIG. 3, in sample (e), 2
The rate of change in resistance value is +1 after applying 10 ⁶ pulses.
In contrast to 0%, the resistance change rate of sample (f) exceeded + 10% after applying 9 × 10 ⁷ pulses.
This is the effect of using glaze glass having a high glass transition point. That is, the high glass transition point of the glaze glass means that it is excellent in chemical stability against heat, which means that the reaction between the glaze glass and the heating resistor due to heat is suppressed. That is, since oxygen in the glaze glass having a glass transition point of 770 ° C. has a higher binding energy than oxygen in the glaze glass having a glass transition point of 670 ° C., even if heat energy is applied, the oxygen can be easily converted into a heating resistor. The increase in resistance value due to oxidation of the heating resistor was suppressed without diffusion and penetration.

As is clear from this, when the thickness of the heating resistor is set to 0.05 μm, a glaze glass having a high glass transition point must be used in order to suppress the rate of change in resistance value, and the resistance to resistance is increased. It can be seen that even if the glaze glass having the glass transition point of 770 ° C. is used, it is insufficient to obtain the thermal print head in which the improvement of the power property is achieved.

On the other hand, for samples (g) and (h), 1 × 10 ⁸
The rate of change of the resistance value when the pulse is applied once is almost the same,
Improvement in the power resistance of the thermal print head, which is necessary for achieving finer printing and higher speed, has been achieved. Here, the effect obtained by using the glaze glass having a high glass transition point is not particularly recognized. That is, it is shown that by setting the film thickness of the heating resistor to 0.15 μm, the resistance value change rate of the heating resistor can be suppressed even if the heating resistor is driven at a temperature exceeding the glass transition point of the glaze glass. ing.

As is clear from the above, as long as the thickness of the heating resistor is 0.15 μm, the rate of change in the resistance value of the heating resistor can be suppressed regardless of the glass transition point of the glaze glass, and the resistance of the thermal print head can be reduced. It can be seen that improved power performance is achieved.

The thickness of the heating resistor is 0.15 μm.
If the glass transition point of glaze glass is (g)
Since the rate of change in resistance value of the heating resistor hardly changed between 670 ° C. and (h) 770 ° C., it can be understood that the glaze glass may be appropriately determined in consideration of productivity. For example, the price of an alumina substrate on which a glaze glass layer is formed is ¥ 1400 / sheet for an alumina substrate on which a glass transition point is 770 ° C., while the glass transition point is 670 ° C. The layered alumina substrate is 700 yen / sheet. Therefore, according to the present invention, an alumina substrate having a glaze glass layer of 670 ° C. formed by forming a heating resistor having a film thickness of 0.15 μm can be used, so that finer printing and higher speed can be achieved. Therefore, it is possible to inexpensively provide the thermal print head in which the improvement in the power resistance necessary for achieving the above is achieved.

(Example 4) For the purpose of reducing the influence of the glaze glass layer on the heating resistor, an Si-O-N layer may be formed as an underlayer between the glaze glass layer and the heating resistor. . However, when the Si—O—N layer is formed, the obtained Si—O—N layer has many variations in physical properties. Therefore, in order to study the effect of the present invention when the Si—O—N layer is formed, a Si—O—N layer having a different oxygen content and a heating resistor (having the same oxygen content) having a different film thickness are used. Samples (i) to (l) of the thermal print head were produced by the combination of the above, and the life characteristic test was performed. This combination is shown in Table 2.

[0064]

[Table 2] In this example, a Si—O—N film having a thickness of 1 μm was formed as an underlayer between the glaze glass layer and the heating resistor.
The conditions for making the thermal print head, the specifications, and the conditions for the life characteristic test were completely the same as in Example 1 except that the layers were formed by the sputtering method. Therefore, the sheet resistance values of these heating resistors are 2 in Samples (i) and (j).
400Ω, 800Ω for samples (k) and (l).
FIG. 4 shows the result of the life characteristic test.

As shown in FIG. 4, in the sample (i), the resistance value rapidly increased from the initial value, and in the sample (j), the resistance value decreased from the initial value and then started to increase, and the resistance value change rate exceeded + 10%. In both cases, the pulse is applied 2 × 10 ⁵ times. The reason why the behavior of the resistance value change rate is exhibited is qualitatively explained as follows. That is, in the sample (i), since the oxygen content of the Si-O-N layer is higher than that of the heating resistor, the heat input due to the pulse application serves as a driving force and the heating resistance from the Si-O-N layer increases. Oxygen moves to the body, and this oxygen oxidizes the heating resistor, causing a rapid increase in resistance value. On the contrary to the sample (i), in the sample (j), since the oxygen content of the heating resistor is higher than that of the Si—O—N layer, oxygen moves from the heating resistor to the Si—O—N layer, As a result, the heating resistor is reduced and the resistance value is lowered. Then, when the resistance value decreases, excessive power is applied to the heating resistor, so that the temperature of the heating resistor further rises and the resistance value further decreases, and finally the heating resistor is destroyed and the resistance value rapidly increases. It was observed.

On the other hand, in the samples (k) and (l), the tendency of the variation of the resistance value corresponding to the samples (i) and (j) is recognized, but the stability of the samples (k) and (l) is stable. It is excellent and the rate of change in resistance value of the heating resistor remains at 3% even when 1 × 10 ⁸ pulses are applied. This can be considered similarly to the third embodiment. That is, if the film thickness of the heating resistor is set to 0.15 μm, the rate of change in the resistance value of the heating resistor can be suppressed regardless of the difference in the physical properties of the Si—O—N layer, thus improving the power resistance of the thermal print head. It can be understood that is achieved. As described above, since the formed Si-O-N layer generally tends to cause variations in physical properties, the present invention provides Si-O-.
It is particularly useful for a thermal print head having an N layer.

(Example 5) SUS304 as a supporting substrate
A 0.8 mm-thick plate made of Si-O- having a thickness of 20 μm is formed by omitting the glaze glass layer on the plate.
Except that the N layer was formed by the sputtering method, the preparation conditions, specifications and life characteristic test conditions of the thermal print head were made completely the same as in Example 4, and S with different oxygen contents was used.
Samples (i) to (l) of the thermal print head were prepared by combining the i-O-N layer with a heating resistor having a different film thickness (oxygen content is the same), and a life characteristic test was performed.
This combination is shown in Table 3.

[0068]

[Table 3] The sheet resistance value of these heating resistors is the sample (m).
And (n) are 2400Ω, and samples (o) and (p) are 800Ω. FIG. 5 shows the result of the life characteristic test.

As shown in FIG. 5, in the sample (m), the resistance value rapidly increased from the initial value, and in the sample (n), the resistance value decreased from the initial value and then started to increase, and the resistance value change rate exceeded + 10%. Indicates that the pulse was applied 2 × 10 ⁶ times and 8 × 10 ⁵ times, respectively. The reason why the behavior of the resistance value change rate is exhibited is explained in the same manner as the samples (i) and (j) of Example 4. That is, in the sample (m), the oxygen content of the Si—O—N layer is higher than that of the heating resistor, so the heat input due to the pulse application serves as a driving force, and the heating resistance from the Si—O—N layer increases. Oxygen moves to the body, and this oxygen oxidizes the heating resistor, causing a rapid increase in resistance value. In contrast to the sample (m), the sample (n) has a higher oxygen content in the heating resistor than the Si-O-N layer.
Oxygen moves to the -N layer, and as a result, the heating resistor is reduced and the resistance value decreases. Then, when the resistance value decreases, excessive power is applied to the heating resistor, so that the temperature of the heating resistor further rises and the resistance value further decreases, and finally the heating resistor is destroyed and the resistance value rapidly increases. It was observed.

On the other hand, both the samples (o) and (p) are excellent in stability, and the rate of change in resistance value of the heating resistor remains at 3% even when the pulse is applied 1 × 10 ⁸ times. this is,
It can be considered in the same manner as the samples (k) and (l) of Example 4.

That is, the film thickness of the heating resistor is set to 0.15 μm.
Since it is possible to suppress the resistance value change rate of the heating resistor regardless of the difference in physical properties of the Si-O-N layer if m is set, it can be understood that the power resistance of the thermal print head is improved. As described above, since the formed Si-O-N layer generally tends to cause variations in physical properties, the present invention is particularly useful for a thermal print head formed with the Si-O-N layer.

[0072]

As described above, according to the present invention, the thickness of the heating resistor is set to 0.15 to 0.30 μm,
Further, since the specific resistance value of the heating resistor is adjusted to 10 to 80 mΩ · cm, the influence of the upper and lower layers on the heating resistor can be almost completely eliminated, and the resistance value of the heating resistor in use at high temperature. It is possible to provide a thermal print head which has almost eliminated the change of the above, improved the power resistance, realized the finer printing and the higher speed, and which has excellent productivity and is inexpensive.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the number of pulses applied and the rate of change in resistance of a heating resistor.

FIG. 2 is a diagram showing the relationship between the number of pulses applied and the rate of change in resistance of the heating resistor.

FIG. 3 is a diagram showing the relationship between the number of pulses applied and the rate of change in resistance of the heating resistor.

FIG. 4 is a diagram showing the relationship between the number of pulses applied and the rate of change in resistance value of a heating resistor.

FIG. 5 is a diagram showing the relationship between the number of pulses applied and the rate of change in resistance of the heating resistor.

FIG. 6 is a diagram showing a configuration of a general thermal print head.

[Explanation of symbols]

 1 ... Alumina substrate 2 ... Glaze glass layer 3 ... Heating part 4 ... Heating resistor 5 ... Individual electrode pattern 6 ... Common electrode pattern 7 ... Protective layer

Claims (7)

[Claims] 1. A thermal print head comprising a heating resistor formed on a supporting substrate and an electrode connected to the heating resistor, wherein the thickness of the heating resistor is 0.1.
The thermal print head is characterized in that it is 5 to 0.30 μm, and the specific resistance value of the heating resistor is 10 to 80 mΩ · cm. 2. A thermal print head comprising a heating resistor formed on a supporting substrate via a glaze glass layer and an electrode connected to the heating resistor, wherein the heating resistor has a thickness of 0. .15 to 0.30 μm, and the specific resistance value of the heating resistor is 10 to 80 mΩ · cm.
The thermal print head characterized in that 3. The glass transition point of the glaze glass layer is
The thermal print head according to claim 2, wherein the temperature is lower than the temperature when the heating resistor is driven. 4. The thermal print head according to claim 1, further comprising an inorganic barrier layer formed under the heating resistor. 5. The inorganic barrier layer is SiNxOy.
The thermal print head according to claim 4, wherein (0.2 <x <1.1, 0.2 <y <1.8). 6. The thermal print head according to claim 1, wherein the heating resistor is made of cermet. 7. The thermal print head according to claim 6, wherein the cermet is a Ta—Si—O cermet.