JP2910895B2 - Thermal head - Google Patents

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 for a thermal printer or the like.

[0002]

2. Description of the Related Art In general, thermal printing recording apparatuses are of the type using thermal paper, those using thermal transfer of ink to plain paper using an ink ribbon, those using sublimable dyes for recording with ink vapor, and the like. There are various types. In such a thermal print recording device, high speed,
Colorization, multiplex recording, gradation recording, and the like are in progress.

In order to achieve such high functionality,
It is necessary to improve the performance of the thermal head. First, in order to increase the speed of the thermal head, it is necessary to shorten the energizing time to the heating resistor of the thermal head and further increase the applied power to improve the heating temperature of the heating resistor layer. Therefore, as a thermal head that meets such demands,
The heating resistor layer is made of Ta-SiO ₂ and the electrode layer is made of Cr / P
Japanese Patent Publication No. 56-37071 discloses that the heating resistor layer is made of Zr—Al ₂ O ₃ and the electrode layer is made of C / b.
Japanese Patent Publication No. Sho 63-7442 discloses that the heating resistor layer is made of Cr-CrO-Si-SiO and the electrode layer is made of C / Al.
Japanese Patent Application Laid-Open No. 60-157888 discloses a heating resistor layer made of ruthenium oxide and an electrode layer made of Ti / Au.
JP-A-2-177502 discloses that the heating resistor layer is made of ruthenium oxide and the electrode layer is made of Au.

[0004] In order to extend the life of the thermal head, it is necessary to prevent corrosion of the thermal head. Therefore, as a thermal head that meets such a demand, the heating resistor is made of Ta ₂ N and the electrode layer is made of Al / Al.
Japanese Unexamined Patent Publication No. Sho 62-97391 proposes to use Mo, and Japanese Unexamined Patent Publication No. 62-158063 proposes that the heating resistor is made of Ta ₂ N and the electrode layer is made of Al / Ni.

FIG. 3 shows another conventional example of a mulled head disclosed in Japanese Patent Application Laid-Open No. 01-72862 filed by the present applicant. In A, a glass glaze layer 2 and a heating resistor layer 3 such as ruthenium oxide (RuO ₂ ) are uniformly laminated on the surface of an alumina substrate 1, and Al · Si is formed on the heating resistor layer 3. An electrode layer 6 is formed as a pair having a double structure of the layer 4 and the Al layer 5. The electrode layer 6 and the heating resistor layer 3 are patterned into a predetermined cross-sectional shape as shown in FIG. 3, so that the heating resistor layer 3 at a portion located between both poles of the pair of electrode layers 6 generates heat. An Al ₂ O ₃ protective layer 7 and a Si layer were formed on the heating resistor layer 3 and the electrode layer 6 thus patterned.
A composite protective layer 9 including a C protective layer 8 is uniformly laminated.

[0006]

In the thermal head having the structure shown in FIG. 3, the heating resistor layer 3 located between the poles of the pair of electrode layers 6 can locally generate heat. Therefore, by controlling this heat generation operation, an image can be printed on thermal paper or the like. Here, for the electrode layer 6 of the thermal head as described above, conditions such as sufficiently low electric resistivity, adhesion to the heating resistor layer 6, etc., heat resistance, corrosion resistance, and the like are required. Further, in order to realize high-speed image printing and high resolution of the thermal printer, it is necessary to increase the heat generation temperature of the thermal head.
It is required to be 0 to 450 (° C.). Here, for example, as a material having a low electric resistivity, copper or gold is used in addition to the above-mentioned aluminum, but these copper and gold have poor adhesion to the heating resistor layer 3 and the like. Copper is not preferred because of insufficient corrosion resistance.

On the other hand, in the structure shown in FIG. 3, aluminum and aluminum alloy have good adhesion to the heating resistor layer 3 and the like and enable bonding, so that productivity is good. However, an unstable contact resistance occurs at the joint, and aluminum has a low melting point and a recrystallization temperature of 200.
(° C), the heat resistance is not enough due to the low temperature.

Furthermore, if the heat resistance of the electrode layer 6 is not sufficient as described above, the base material on which the protective layer 7 is formed, that is, the alumina substrate on which the heating resistor layer 3, the electrode layer 6, etc. are formed, is formed. Since it is necessary to keep the temperature of 1 low, this is not preferable because conditions such as a method of forming the protective layer 7 are limited. In the thermal head disclosed in each of the above publications, the heating resistor layer is made of a material that raises the heating temperature, but the electrode layer is made of Au, Cr, Al or the like, so that heat resistance, adhesion, etc. There is a problem.

The present invention solves the above-mentioned problems by selecting the material used for the above-mentioned electrode layer, and improves the heat resistance, adhesion and corrosion resistance to improve the thermal performance and the reliability and the productivity. A head is provided.

[0010]

In a thermal head in which at least a heating resistor layer, an electrode layer and a protective layer are sequentially formed on a substrate, the heating resistor layer is formed of a material containing an oxide. At least a portion of the electrode layer that is joined to the heating resistor layer is represented by element symbols Ti, Zr, Hf, V,
At least one of the metals represented by Nb, Ta, Cr, Mo, and W is formed of a material containing nitrogen as a main component. , Formed of a material containing at least one metal represented by Hf as a main component and containing nitrogen.

[0011]

[Function] Since both the heat resistance of the electrode layer and the adhesion to the heating resistor layer can be improved, it is possible to improve the heat generation temperature of the thermal head, thereby contributing to faster image printing and higher resolution. Further, it is possible to raise the substrate temperature when forming the protective layer and to contribute to the improvement of the productivity of the thermal head.Also, it is possible to improve the productivity of the electrode by ions or the like entering from pinholes and cracks of the protective layer. Since corrosion can be prevented, a thermal head with high performance and good reliability and productivity can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. First, as shown in FIG. 1, in this thermal head 10, a glaze layer 12 is uniformly formed on a ceramic substrate 11 made of alumina or the like, and a heating resistor containing an oxide such as ruthenium oxide is formed thereon. The body layer 13 is formed by lamination. The electrode layer 14 formed on the heating resistor layer 13 has a first electrode layer 15 made of a material containing nitrogen as a main component, which is a so-called refractory metal such as niobium, and a second electrode layer made of aluminum or the like. It has a two-layer structure in which an electrode layer 16 and a protective layer 17 are formed on the first protective layer 18 made of Si-ON or the like.
And a second protective layer 19 made of SiC or the like.

In the thermal head 10, since the heating element 20 can be formed by the heating resistor layer 13 located between both poles of the electrode layers 14 and 14 patterned in a predetermined shape, such a heating element 20 is sub-scanned. The serial or line type thermal head 10 can be realized by connecting the thermal head 10 in the direction or the main scanning direction.

In such a configuration, the thermal head 10 controls a voltage applied between both electrodes of the electrode layers 14 and 14 to generate a desired heating element 20 to generate a dot matrix image on thermal paper or the like. Printing is performed.

Here, a specific example of a method of manufacturing such a thermal head 10 will be described below. First, the heating resistor layer 13 of the thermal head 10 includes, for example, a barium / ruthenium oxide (BaRuO ₃ ) target, a mixed target of barium / ruthenium oxide (BaRuO ₃ ) and barium titanate (BaTiO ₃ ), titanium oxide and oxide A material containing an oxide, such as a mixed target of ruthenium, a mixed target of tantalum and silicon oxide, or a mixed target of niobium and silicon oxide, is subjected to RF (Radio-Frequency) sputtering to a thickness of 5 nm.
It is formed by forming a film in the range of 00 to 3000 (Å).

The first electrode layer 15 located on the heating resistor layer 13 formed as described above is made of, for example, a niobium target or a mixed target of niobium and titanium (Nb: Ti = 9: 1 (wt. %)), And so on, at a total pressure (argon + nitrogen)
In a mixed gas of 4.0 to 20.0 (mTorr) and a flow rate of nitrogen / total gas (argon + nitrogen) of 0 to 50 (%), power 2
It is formed by, for example, forming a film with a thickness of 200 to 2000 (Å) by reactive RF sputtering of 00 to 1500 (W).

Next, the second electrode layer 16 located on the first electrode layer 15 formed as described above is formed by sputtering aluminum to a thickness of 1.0 to 2.0 (μm). And the first and second electrode layers 15,
The electrode layer 14 is formed by patterning 16 into a predetermined shape by photolithography.

The first and second protective layers 18 and 19 located on the heating resistor 13 and the electrode layer 14 formed as described above are used to form Si-ON and SiC by RF sputtering, respectively. The film is formed by forming a film to a thickness of 2 (μm), and the substrate temperature at that time is set to about 150 (° C.). Further, the Si—O—N of such a protective layer 17 can also be formed by a plasma CVD method (Chemical Vapor Deposition). For forming the protective layer 17 by the plasma CVD method, SiH ₄ , N ₂ O, NH ₃ , N ₂ gas is used, and the substrate temperature at that time is 300 to 400
(° C.) is required.

The protective layer 17 as described above includes
A mixed film of alumina and silicon oxide (Al
It is also possible to use silicon carbide (SiC) for the second protective layer 19 using ₂ O ₃ .SiO ₂ ). Further, a mixed film of alumina and silicon oxide (Al ₂ O ₃ .SiO ₂ ) is used for the second protective layer 19 using Si—O—N for the first protective layer.
And a three-layer protective layer (not shown) using silicon carbide (SiC) for the third protective layer is also feasible. The thickness of each layer of the protective layer of such a three-layer structure, (Si-ON) / ( Al 2 O 3 · SiO 2) / (SiC) = 2.0 (μm) / 5000 (Å) / 2.
It is desirable to set it to about 0 (μm). Similarly, a protective layer (not shown) having a four-layer structure is formed by (Si-ON) / (SiC) / (Si-ON) / (SiC) = 2.0 (μm) / 5000 (Å) / 50
00 (Å) /2.0 (μm) (Si-ON) / (SiC) / (Al ₂ O ₃・ SiO ₂ ) / (SiC) = 2.0 (μm) / 5000
(Å) / 5000 (Å) /2.0 (μm), and a five-layer protective layer (not shown) may be formed by (Si-ON) / (Al ₂ O ₃ .SiO ₂ ) / (SiC) / (Al ₂ O ₃・ SiO ₂ ) / (SiC) =
It is also feasible to form as 2.0 (μm) / 5000 (Å) / 5000 (Å) / 5000 (Å) /2.0 (μm).

In view of the above, the present applicant prototyped various thermal heads using aluminum as the material for the second electrode layer and using different materials for the first electrode layer and the heating resistor layer by the above-described manufacturing method. These prototype thermal heads were left at the set temperature for one hour, and then the set temperature was increased with time to measure the resistance change rate. Therefore, the results of this experiment will be described below together with various conditions and evaluation criteria.

1. Composition of heating resistor layer Material (α): Ba-Ru-O (film composition ratio, Ba: Ru = 1: 1
) Material (β) ... Ti-Ru-O (film composition ratio, Ti: Ru = 2: 3
) Material (γ) ... Ta-Si-O (Target composition ratio, T
a: SiO ₂ = 53: 47 (mol%)) Material (δ) ... Nb-Si-O (Target composition ratio, N
b: SiO ₂ = 50: 50 (mol%)) Composition of First Electrode Layer Material (1) None Material (2) Al-Si material (3) Nb material (4) Nb-Ti material (5) Nb-N material (6) Nb-Ti -N3. Definition of resistance change rate (difference in resistance before and after heat treatment / resistance before heat treatment) x 10
0 (%) 4. Definition of heat resistant temperature Temperature at which the rate of change of resistance ≥ 5 (%) Evaluation criteria for heat resistance temperature A: 500 (° C) or more B: 400 to 500 (° C) C: 300 to 400 (° C) D: 300 (° C) or less

[0022]

[Table 1]

As is evident from Table 1 above, the first electrode layers (5) and (6) formed of a material containing niobium as a main component and containing nitrogen have a low electric resistance even when subjected to a high-temperature heat treatment. It was found that the change was kept small.

Next, in order to investigate the adhesiveness between the heating resistor layer and the first electrode layer, the applicant of the present invention used the above-mentioned material (α) made of Ba-Ru-O as the heating resistor layer. Of the first electrode layer to be laminated on the IP
It was immersed in A (isopropyl alchol) and subjected to an ultrasonic cleaning test for 20 minutes to confirm the presence or absence of peeling of the first electrode layer. Here, the experimental results are shown in Table 2.

[0025]

[Table 2]

As is clear from Table 2 above, A
The first electrode layers (2), (5), and (6) made of l-Si, Nb-N, and Nb-Ti-N have close contact with the heating resistor layer (α) made of Ba-Ru-O. Was found to be good. In addition, such a first electrode layer (2), (5),
When the adhesion between (6) and the other heating resistor layers (β), (γ), and (δ) was similarly tested, it was confirmed that in these cases, the adhesion did not occur and the adhesion was good. Was done. In other words, by forming a first electrode layer containing niobium as a main component and containing nitrogen on the heating resistor layer containing oxide, the first electrode layer has heat resistance and adhesion to the heating resistor layer. And both were found to be good.

Next, the present applicant prototyped a thermal head on which circuit components such as a driver IC were actually mounted, and changed the driving pulse applied thereto to investigate the life of the device. Here, a thermal head (not shown) in which a first electrode layer (2) made of Al-Si is formed on a heating resistor layer made of Ba-Ru-O is similarly used as a conventional example as a comparative object. An experiment was performed. In this experiment, the thermal head was driven in a blank printing state without using thermal paper, and the driving pulse was set to have a pulse width of 0.65 (msec) and a pulse period of 2 (msec). Accordingly, the contents of the samples of such an experiment are illustrated below as Table 3 and the results are illustrated in FIG.

[0028]

[Table 3]

Therefore, as is apparent from the graph of FIG. 2, the thermal head of the sample e manufactured as the conventional example has a resistance change rate of about + 6% when the number of applied pulses is “1 × 10 ⁸ ”. In the thermal heads of the samples a to d manufactured as the present embodiment, the resistance change rate is negative even when the number of applied pulses is “4 × 10 ⁸ ”. It was confirmed that the characteristics were stable.

In order to confirm the superiority of the heating resistor layer made of a material containing an oxide, the present applicant manufactured the heating resistor layer by RF sputtering using a mixed target as exemplified below and prepared the heating resistor layer as described above. When driving experiments as described above were performed, all of the samples a to d in Table 3 above were performed.
It was confirmed that the resistance change rate was maintained negative as in the case of (1). 1. 1. Calcium ruthenium oxide (CaRuO ₃ ) 2. Strontium ruthenium oxide (SrRuO ₃ ) 3. silicon oxide-ruthenium oxide 4. titanium oxide-ruthenium oxide 5. Tungsten oxide-ruthenium oxide 6. Zirconium oxide-ruthenium oxide 7. Chromium-silicon oxide 8. Titanium-silicon oxide Zirconium-aluminum oxide

Further, the applicant of the present invention confirmed the superiority of the electrode layer containing niobium as the main component and nitrogen and performed the electrode formation by reactive RF sputtering using a mixed target as exemplified below in a gaseous mixture with argon. When the layer was manufactured and the above-described driving experiment was performed, it was confirmed that a similar result was obtained. 1. Niobium-Chromium (Nb: Cr = 9: 1)
(Wt%)) 2. Niobium-Molybdenum (Nb: Mo = 9: 1)
(Wt%)) 3. Niobium-tantalum (Nb: Ta = 9: 1)
(Wt%)) 4. Niobium-zirconium (Nb: Zr = 9: 1
(Wt%)) 5. Niobium-Vanadium (Nb: V = 9: 1
(Wt%)) 6. Niobium-tungsten (Nb: W = 9: 1)
(Wt%)) 7. Niobium-Hafnium (Nb: Hf = 9: 1
(Wt%))

In the above description, niobium (N) is used as the metal which is the main component of the first electrode layer to be joined to the heating resistor.
Although b) has been exemplified, the present invention is not limited to metals of the above-mentioned elements, but may be titanium (Ti), zirconium (Zr), hafnium (Hf), or vanadium as metals that are main components of this electrode layer. (V), tantalum (Ta),
One of chromium (Cr), molybdenum (Mo), and tungsten (W), or a combination thereof may be used, and similar results can be obtained by containing nitrogen by the same process as described above. Applicants have confirmed that it can be obtained. The table of the experimental results is shown below.

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

[Table 7]

[0037]

[Table 8]

[0038]

[Table 9]

Further, the present applicant has made the electrode layer a reactive RF sputtering using a mixed target as exemplified below in a mixture with argon as a material containing nitrogen as a main component of the metals shown in the above table. When an electrode layer was manufactured and a driving experiment as described above was performed, it was confirmed that a similar result was obtained. 1. Titanium-chromium (Ti: Cr = 9: 1)
(Wt%)) 2. Titanium-molybdenum (Ti: Mo = 9: 1)
(Wt%)) 3. Titanium-tantalum (Ti: Ta = 9: 1)
(Wt%)) 4. Titanium-niobium (Ti: Nb = 9: 1
(Wt%)) 5. Titanium-Vanadium (Ti: V = 9: 1
(Wt%)) 6. Titanium-zirconium (Ti: Zr = 9: 1
(Wt%)) 7. Titanium-hafnium (Ti: Hf = 9: 1
(Wt%)) 8. Molybdenum-chromium (Mo: Cr = 9: 1)
(Wt%)) 9. Molybdenum-niobium (Mo: Nb = 9: 1)
(Wt%)) 10. Molybdenum-tantalum (Mo: Ta = 9:
1 (wt%)) Molybdenum-zirconium (Mo: Zr = 9:
1 (wt%) 12. Molybdenum-vanadium (Mo: V = 9:
1 (wt%) 13. Molybdenum-tungsten (Mo: W = 9:
1 (wt%)) Molybdenum-hafnium (Mo: Hf = 9:
1 (wt%)) The same applies hereinafter.

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

As described above, according to the present invention, in a thermal head in which at least a heating resistor layer, an electrode layer and a protective layer are sequentially formed on a substrate, the heating resistor layer is made of a material containing an oxide. The first electrode layer formed and bonded to at least the heating resistor layer of the electrode layer is represented by element symbols Ti, Z
The second electrode layer is formed of a material containing at least one of the metals represented by r, Hf, V, Nb, Ta, Cr, Mo, and W as a main component and containing nitrogen, and a second electrode layer to be stacked thereover has an element symbol A
By using the metal represented by l, corrosion of the electrode can be prevented, and the heat resistance of the electrode layer and the adhesion to the heating resistor layer can both be improved. It can contribute to high-speed and high-resolution image printing by improving the quality. In addition, since aluminum is used for the second electrode layer, bonding to a driving IC can be performed, and further, a protective layer is formed. By increasing the temperature of the base material during the heat treatment, it is possible to contribute to improving the productivity of the thermal head, and it is possible to obtain a thermal head having high performance and good reliability and productivity.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing a change with time of a resistance change rate.

FIG. 3 is a vertical sectional front view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermal head 11 Substrate 13 Heating resistor layer 14 Electrode layer 17 Protective layer

Claims (2)

(57) [Claims] In a thermal head in which at least a heating resistor layer, an electrode layer and a protective layer are sequentially formed on a substrate, the heating resistor layer is formed of a material containing an oxide, and at least one of the electrode layers is formed. The first electrode layer to be joined to the heating resistor layer is represented by element symbols Ti, Zr, Hf, V, Nb,
At least one of the metals represented by Ta, Cr, Mo, and W is used as a main component and formed of a material containing nitrogen .
The second electrode layer laminated on the protective layer side is represented by an element symbol Al.
A thermal head characterized by being formed of a metal to be formed . 2. A thermal head in which at least a heating resistor layer, an electrode layer, and a protective layer are sequentially formed on a substrate, wherein the heating resistor layer is formed of a material containing an oxide, and at least one of the electrode layers is formed. 2. The thermal head according to claim 1, wherein a portion to be joined to the protective layer is formed of a material containing at least one of metals represented by element symbols Ti, Zr, and Hf and containing nitrogen.