JPH06143637A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head comprising a heating resistor layer, an electrode layer, and a protective layer formed on a substrate in which the power saving and high image quality are embodied by improving characteristics of the heating resistor layer. CONSTITUTION:A heating resistor layer 10 is formed of an oxide containing barium, ruthenium, and titanium, wherein resistance of heating element 15 is increased by increasing resistivity of the heating resistor layer 10 and variation of resistance is prevented at the time of heating by setting temperature coefficient of resistance of the heating resistor layer 10 close to + or -0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in a thermal printer or the like.

[0002]

2. Description of the Related Art Currently, R / J (Receipt) of thermal printers, color printers, bar code printers, facsimiles and electronic cash registers using a thermal head are used.
/ Journal) Used for printers. In addition, such a thermal printer requires power saving, high speed, high image quality, long life, and the like. To achieve these, a heating resistor layer forming a heating element of a thermal head. It is necessary to improve the characteristics of.

That is, in order to reduce the power consumption of the thermal head, it is necessary to increase the resistance of the heating element in order to reduce the drive current. Further, in order to increase the speed of the thermal head, it is necessary to improve the heat resistance of the heating resistor layer in order to raise the surface temperature of the heating element in a short time.
Furthermore, in order to achieve high image quality of the thermal head, the TCR (Temperature) of the heating resistor layer is used so that the printed image is clear for each pixel and tailing does not occur even in continuous printing.
ture Coefficient of Resistance) is required to be an appropriate value. Further, in order to achieve a long life of the thermal head, it is necessary to have abrasion resistance of the protective layer that shields the heating resistor layer, but in this case, in order to prevent deterioration over time, the heating resistor layer Corrosion resistance is required.

As described above, in order to increase the resistance of the heating element in order to save the power of the thermal head, it is necessary to increase the specific resistance of the material of the heating resistor layer forming the heating element. For example, in order to form a high resistance heating element with a heating resistor layer having a low specific resistance of the material, it is necessary to reduce the thickness of the heating resistor layer. Will increase, and productivity and durability will be impaired. Therefore, in order to increase the resistance of the heating element without having such a problem, it is necessary to form the heating resistor layer with a material having a high specific resistance as described above.

As such a thermal head, a thermal head having a heating resistor layer formed of a material containing ruthenium oxide as a main component is proposed in Japanese Patent Laid-Open No. 60-157884. Therefore, here, the thermal head disclosed in the above publication will be described as a conventional example with reference to FIG. First, in the thermal head 1, the glass glaze layer 3 is uniformly laminated and formed on substantially the entire surface of the ceramic substrate 2, and the heating resistor layer 4 having a predetermined shape is partially formed on the glass glaze layer 3. ing. Then, by forming electrode layers 5 and 6 having a predetermined shape made of Ti-Au or the like at positions from both sides of the heating resistor layer 4 to the glass glaze layer 3, these electrode layers 5 and 6 are formed. A heating element 7 is formed by the heating resistor layer 4 located between them. In addition, in such a thermal head 1, a protective layer (not shown) for improving corrosion resistance and wear resistance is actually formed on the surfaces of the heating element 7 and the electrode layers 5 and 6 as described above. Will be done.

In this thermal head 1, ruthenium oxide (RuO ₂ ) is the main component, and M (where M is Ca,
The heating resistor layer 4 is formed of a metal oxide containing at least one oxide selected from Sr, Ba, Pb, Bi, and Tl) in an amount of M / Ru = 0.6 to 2.0 (at%). . Therefore, here, Ba is selected as M of the heating resistor layer 4 of the thermal head 1 and the heating resistor layer 4 is formed of BaRuO ₃ having a Ba / Ru of 1.0 (at%). Detailed description.

First, when the heating resistor layer 4 is formed of such BaRuO ₃ , the raw material thereof is deposited on the glass glaze layer 3 by the sputtering method, and then 600-70.
Crystallize by annealing in an atmosphere of 0 (° C).
By doing so, the resistance value of the heating resistor layer 4 becomes a predetermined value, so that the heating resistor layer 4 is slightly deteriorated as long as it is used at a temperature not higher than the annealing temperature. Further, since the heat generating resistor layer 4 is originally an oxide, it has good corrosion resistance and little deterioration over time.

[0008]

As described above, BaRu is used.
The thermal head 1 having the heating resistor layer 4 formed of O ₃ is
It is effective for speeding up and extending the life.

However, such a thermal head 1 is
Actually, it is inferior to high image quality and power saving. That is,
The heating resistor layer 4 made of BaRuO ₃ or the like is
Since the CR is extremely high at about 800 (ppm / K), the resistance value increases and the driving power decreases when the heat generation temperature rises, and the responsiveness at the rise of the print density decreases and the image quality is impaired. ing. In particular, in such a thermal head 1, when only one pixel is printed by the driving power such that the printing density becomes a predetermined value in continuous image printing, the heating temperature of the heating element 7 driven for an extremely short time is Since it is difficult to reach the temperature required for printing, printing defects easily occur.

Further, since the specific resistance of the heating resistor layer 4 made of BaRuO ₃ or the like is as low as 2500 (μΩcm), it is difficult to increase the resistance value of the heating element 7 and the thermal head 1 consumes less. The power will increase.
That is, when the heating element 7 having a square planar shape is formed by such a heating resistor layer 4, its resistance value is 1.0 (KΩ).
In order to achieve this, it is necessary to reduce the film thickness to about 250 (Å), but it is difficult to implement a thin film layer having such a film thickness with existing thin film technology such as sputtering.

The present invention provides a thermal head capable of saving power and improving image quality.

[0012]

In a thermal head having a heating resistor layer, an electrode layer and a protective layer formed on a substrate,
The heating resistor layer was formed of an oxide containing barium, ruthenium and titanium.

[0013]

The function of the heating resistor layer can be increased by increasing the specific resistance of the heating resistor layer, and the TCR of the heating resistor layer can be made closer to ± 0 to prevent the resistance value from changing during heating. Therefore, it is possible to obtain a thermal head capable of saving power and improving image quality.

[0014]

Embodiments of the present invention will be described with reference to FIGS. First, in this thermal head 8, as illustrated in FIG. 1, a heating resistor layer 10 is formed by laminating an oxide containing barium, ruthenium, and titanium on almost the entire surface of a glaze alumina substrate 9. There is. And
On the heating resistor layer 10, a first electrode layer 11 made of titanium or the like and a second electrode layer 12 made of aluminum or the like are sequentially laminated and patterned, whereby the heating resistor layer 1 is formed.
An individual electrode layer 13 and a common electrode layer 14 each having a predetermined shape are formed on the substrate 0. Therefore, the heating resistor layer 10 located between the electrode layers 13 and 14 forms the heating element 15. Further, in this thermal head 8, a first protective layer 16 made of mullite and the like and a second protective layer 17 made of silicon carbide and the like are sequentially laminated on substantially the entire surfaces of the heating elements 15 and the electrode layers 13 and 14. is doing.

In this thermal head 8, a large number of heating elements 15 are actually arranged in a line in the sub-scanning direction or the main scanning direction to form a serial type or line type thermal head 8. .

In such a structure, in the thermal head 8, a predetermined driving voltage is applied between the electrode layers 13 and 14 to selectively heat the desired heating element 15 so as to drive the heating paper (not shown). Image) in a dot matrix format.

Here, a method of manufacturing the thermal head 8 actually manufactured by the applicant will be described below. First, the heating resistor layer 10 is formed on the surface of the glaze alumina substrate 9 by RF.
(Radio-Frequency) Sputtering is used to form a film. At this time, the target 18 used in this RF sputtering
As illustrated in FIG. 2, a plurality of 10 × 10 × 2.0 (mm) chips 20 made of Ti are provided on a disc-shaped sintered body 19 made of BaRuO ₃ on the circumference where a magnetic field is concentrated. It is in the form of arrangement. Therefore, the target 1 as described above
8 is used to RF the heating resistor layer 10 on the glazed alumina substrate 9 in 1.0 (Pa) Ar gas-50 (%) O ₂ gas.
The heating resistor layer 10 is formed by sputtering to 700
Stabilized by a heat treatment of 1.0 (H) at (° C).

Next, a Ti film having a thickness of 1000 (Å) is sputtered on the heating resistor layer 10 formed as described above.
A (titanium) layer and an Al (aluminum) layer having a film thickness of 9000 (Å) were sequentially formed and patterned by photolithography to form the electrode layers 13 and 14 and the heating element 15. At this time, in the thermal head 8 prototyped by the applicant, a rectangular heating element 15 having a shape of 132 × 120 (μm) is used.
It was arranged at a density of 7.6 (Dot / mm). Furthermore, 3A on this
The first protective layer 16 made of l ₂ O ₃ .2SiO ₂ (mullite) and having a thickness of 3.0 (μm), and the film thickness made of SiC (silicon carbide) and having a thickness of 2.0.
The thermal head 8 was manufactured by sequentially depositing the second protective layer 17 (of μm) by RF sputtering.

As described above, in the thermal head 8, the heating resistor layer 10 is formed of the oxide containing barium, ruthenium and titanium. Therefore, the heating resistor layer 10 contains barium and ruthenium. It has characteristics different from the heating resistor layer 4 of the conventional thermal head 1 made of the above oxide. Therefore, the present applicant has adopted the above-mentioned R
Characteristics were evaluated by changing the composition of the heating resistor layer 4 by increasing or decreasing the number of chips 20 of the F sputtering target 18. In addition, in such evaluation,
Actually, the heating resistor layer 1 is formed on the glaze alumina substrate 9.
Samples were prepared by forming only 0, or not forming the protective layers 16 and 17.

First, the applicant of the present invention has made BaRuO ₃ sintered body 1
The number of Ti chips 20 loaded on 9 is 6, 12
The heat generating resistor layer 10 of the present invention was formed on the glaze alumina substrate 9 as 18 and the heat generating resistor layer 4 corresponding to the conventional example was formed with the number of chips 20 being 0. Then, the heating resistor layers 4 thus formed
When the specific resistance and TCR of 10 were measured, it was found that the specific resistance increased and the TCR decreased as the number of chips 20 was increased, as illustrated in FIG.

More specifically, Ti in the target 18 is
In the conventional heating resistor layer 4 containing 0 chips and having no titanium, the specific resistance was extremely low at about 2300 (μΩcm) and the TCR was extremely high at around +800 (ppm / K). However, as the number of chips 20 increases, the specific resistance increases and the TCR decreases. For example, in the case of the heating resistor layer 10 of the present invention containing titanium with the number of Ti chips 20 being 18, the specific resistance is It is extremely high at about 10,000 (μΩcm), and the TCR is very close to ± 0 at about -100 (ppm / K).

Particularly, regarding this TCR, as described above, the heating resistor layer 10 having 18 Ti chips 20 is used.
Is about -100 (ppm / K), and the number of Ti chips 20 is about +350 (ppm / K) in the 12 heating resistor layers 10, therefore, for example, the number of Ti chips 20 is 16
It can be inferred that the TCR can be set to approximately ± 0 by setting the number to be 17, or the like.

That is, as described above, by arranging a predetermined number of Ti chips 20 in the target 18 to form the heating resistor layer 10 containing titanium, the heating resistor layer 10 is formed.
Since it is possible to increase the specific resistance of the heating element 15 to increase the resistance value of the heating element 15, it is possible to contribute to the power saving of the thermal head 8. Furthermore, by bringing the TCR of the heating resistor layer 10 close to ± 0 as described above, it is possible to prevent the drive power from varying due to the change in the resistance value when the heating temperature rises. It is possible to prevent a change in print density of No. 8 and contribute to high image quality.

Further, the present applicant has made the composition of the four kinds of heating resistor layers 4 and 10 produced as trials as described above into RBS (Ruthe
When the number of chips 20 of the target 18 is increased, Ti (titanium) in the heating resistor layer 10 is investigated as shown in Table 1 below.
It was found that the content of Ru (ruthenium) decreased as the content of Ru increased.

[0025]

[Table 1]

Here, the chip 2 of the target 18 is used.
The four types of samples in which the heating resistor layer 10 is formed with the number of 0s set to 0 to 18 are denoted by.

Next, the present applicant applied a driver IC (Integrate) to the electrode layers 13 and 14 of the sample prototyped as described above.
d circuit) and other circuit components (not shown) are connected, and drive power is applied to the heating resistor layer 10 to change the print density.
(Optical Density) method. In this experiment, a driving power with a pulse width of 0.7 (ms) and a period of 2.0 (ms) was applied to continuous 32 dots by 5000 pulses, and the driving power applied in this way was 0.3 (W) to 0.1 (ms). W) increased by one. Then, the density printed in this way was measured with a Macbeth densitometer at a position 10 (mm) from the printing start position.

Then, as illustrated in FIG. 4, it has been found that the thermal head 8 having a large number of chips 20 when the heating resistor layer 10 is formed, can obtain a predetermined print density even with a small driving power. For example, in the conventional heating resistor layer 4 that does not contain titanium when the number of chips 20 is 0,
The drive power at which the print density is saturated is as high as about 0.6 (W), but the drive resistance at which the print density is saturated is 0.4 in the heating resistor layer 10 of the present invention in which the number of chips 20 is 18 and a large amount of titanium is contained. (W), which is extremely low.
That is, the thermal head 8 having a lower TCR of the heating resistor layer 10 has a better rise of the heating temperature and can reduce the driving power, which can contribute to the power saving of the thermal head 8.

Further, the present applicant actually made a prototype.
The same driving power was applied to one of the heating elements 7 and 15 of the thermal heads 1 and 8 to print a ruled line having a width of 1 dot, and this was visually observed to evaluate the print quality. Then, it was confirmed that the conventional thermal head 1 having a high TCR of the heating resistor layer 4 caused printing failure, and the thermal head 8 of the present invention having a low TCR of the heating resistor layer 10 had good printing quality.

The applicant of the present invention has also proposed the thermal head 8 of the present invention.
In order to evaluate the heat resistance and corrosion resistance of the protective layers 16 and 17
The thermal heads 1 and 8 in which the heating elements 7 and 15 were exposed without forming a film were prepared and a running test was performed. In this experiment, the drive power of each thermal head 1 and 8 was set to 0.60 (W) and 0.42 at which the print density saturates.
(W) with a pulse width of 0.7 (ms) and a cycle of 2.0 (ms)
And Then, the number of pulses of the driving power applied in this way was counted, and the rate of change in the resistance value of the heating elements 7 and 15 was measured over time.

Then, as illustrated in FIG. 5, the thermal heads 1 and 8 of the related art and the present invention are both heating elements 7 and 1.
Although the heat generation temperature in the central portion of No. 5 was about 400 (° C.), the rate of resistance change remained stable at a negative value even when the number of driving power pulses reached 10 ⁸ . In particular, it was confirmed that the thermal head 8 of the present invention has a minute rate of change in resistance as compared with the conventional thermal head 1 and maintains excellent heat resistance and corrosion resistance.

[0032]

As described above, according to the present invention, since the heating resistor layer is formed of the oxide containing barium, ruthenium and titanium, the resistivity of the heating resistor layer is increased and the resistance of the heating element is increased. Since the value can be increased and the TCR of the heating resistor layer can be brought close to ± 0 to prevent the resistance value from changing during heat generation, thermal power saving and high image quality can be achieved. This has the effect of obtaining a head.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing an embodiment of the present invention.

FIG. 2 is a plan view showing a manufacturing process.

FIG. 3 is a characteristic diagram showing the relationship between the number of titanium chips during sputtering and the specific resistance of the heating resistor layer.

FIG. 4 is a characteristic diagram showing a relationship between drive power and print density during image printing.

FIG. 5 is a characteristic diagram showing the relationship between the number of pulses of drive power and the resistance change rate of the heating resistor layer.

FIG. 6 is a vertical sectional front view showing a conventional example.

[Explanation of symbols]

 8 Thermal Head 9 Substrate 10 Heating Resistor Layer 13, 14 Electrode Layer 16, 17 Protective Layer

Claims (1)

[Claims] 1. A thermal head having a heating resistor layer, an electrode layer and a protective layer formed on a substrate, wherein the heating resistor layer is formed of an oxide containing barium, ruthenium and titanium. Thermal head.