JP4360876B2 - Thermal head - Google Patents

Description

  The present invention relates to a thermal head mounted as a heat source in, for example, a thermal printing apparatus, and more particularly to a thermal head including a heating resistor layer made of a semiconductor.

  In recent years, thermal heads have been widely used as heat generation sources in the image forming field in which images are formed using thermal energy. A thermal head is a device having a heating resistor layer for heat generation. If an image forming apparatus (for example, a thermal printing apparatus) equipped with this thermal head is used, the thermal energy generated in the heating resistor layer is reduced. It is possible to form (print) an image on an image forming medium (for example, a printing medium such as thermal paper).

  FIG. 7 shows a cross-sectional configuration of a main part (heat generating part 100A) of a conventional thermal head. As shown in FIG. 7, the heat generating portion 100A includes a heat storage glaze layer 102, a heat generating resistor layer 103, and a pair of energizing electrode layers 104 (104A, 104B) on a substrate 101. And a protective protective layer 105 are stacked in this order. In FIG. 7, only a pair of electrode layers 104 is shown, but the pair of electrode layers 104 are arranged in parallel over a plurality of sets along the Y-axis direction in the drawing.

  The heating resistor layer 103 constituting the heating portion 100A is made of a refractory metal such as tantalum (Ta), titanium (Ti), chromium (Cr), molybdenum (Mo), niobium (Nb), or tungsten (W). It is comprised including the carbide | carbonized_material, oxide, or nitride of this. In addition, the electrode layer 104 includes a highly conductive material such as aluminum (Al), for example. However, when the heating resistor layer 103 is formed using a carbide, oxide or nitride of a refractory metal, there are the following problems. First, for example, when the heating resistor layer 103 is formed over a large area using sputtering, a large atomic weight is formed between the refractory metal constituting the heating resistor layer 103 and other constituent elements. Due to the difference, the composition distribution in the film formation surface becomes non-uniform, and it becomes difficult to make the resistance of the heating resistor layer 103 uniform. Second, refractory metals generally do not have sufficient resistance to oxidation at high temperatures, so that the heat generating resistor layer 103 is oxidized under the influence of thermal energy generated during the operation of the thermal head. The resistance characteristic of the resistor layer 103 becomes unstable. In this case, since the heating resistor layer 103 cannot be used under a high temperature condition, high-speed printing with a thermal head becomes difficult.

In order to improve the problem of this type of thermal head, recently, for example, a technique for forming the heating resistor layer 103 using a semiconductor such as polycrystalline silicon doped with boron (B) or phosphorus (P). Has been proposed (see, for example, Patent Documents 1 to 3). In this technique, the heating resistor layer 103 is formed over a large area by forming the heating resistor layer 103 made of polycrystalline silicon by using low pressure CVD (Chemical Vapor Deposition). In this case, the composition distribution in the film forming surface can be made uniform. In addition, since polycrystalline silicon is superior in oxidation resistance at high temperatures compared to refractory metal carbides, oxides or nitrides, it is possible to stabilize the resistance characteristics of the heating resistor layer 103. It becomes. In particular, as technology for doping polycrystalline silicon with boron or phosphorus, it is possible to use an existing semiconductor process that is generally used in the semiconductor field, so heat is generated using the existing semiconductor process. The resistor layer 103 can be easily formed.
JP 62-168375 A Japanese Patent Laid-Open No. 01-215560 JP-A-01-283161

  Incidentally, in order to ensure the operating characteristics of the thermal head, for example, it is necessary to stabilize the resistance characteristics of the heating resistor layer 103 as much as possible. However, in the conventional thermal head, the use of polycrystalline silicon to form the heating resistor layer 103 eliminates instability of resistance characteristics caused by heat, while the semiconductor is made of polycrystalline silicon or the like. The resistance characteristics are unstable due to other factors other than heat, based on the structural factor that the heating resistor layer 103 is in contact with the electrode layer 104 made of a highly conductive material such as aluminum. There was a problem that could be converted. This problem becomes prominent when, for example, the heating resistor layer 103 is formed using P-type polycrystalline silicon. Therefore, in order to ensure the operating characteristics of the thermal head, the establishment of a technique capable of stabilizing the resistance characteristics even when the heating resistor layer 103 is configured using a semiconductor typified by polycrystalline silicon. There is an urgent need.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a thermal head capable of stabilizing the resistance characteristics and ensuring the operating characteristics even when the heating resistor layer is formed using a semiconductor. Is to provide.

The first sub Maruheddo of the present invention, a heating resistor layer comprises polycrystalline silicon, and an electrode layer electrically connected to the heating resistor layer, between these heat generating resistor layer and the electrode layer An intermediate layer for providing ohmic contact between the heating resistor layer and the electrode layer, and the intermediate layer includes germanium .

In the first sub Maruheddo of the present invention, between the heating resistor layer and the electrode layer including polycrystalline silicon, an intermediate layer containing germanium is provided. Accordingly, since the heating resistor layer and the electrode layer through the intermediate layer is in ohmic contact, contact resistance between the heating resistor layer and the electrode layer is sufficiently reduced.

The second thermal head of the present invention is doped with a heating resistor layer containing polycrystalline silicon and an ohmic contact promoting substance electrically connected to the heating resistor layer and in ohmic contact with the heating resistor layer. provided and the electrode layer, an ohmic contact promoting substance is intended to include germanium beam.

In the second thermal head of the present invention, the electrode layer, an ohmic contact promoting substance containing germanium arm is doped. As a result, the electrode layer makes ohmic contact with the heating resistor layer containing polycrystalline silicon using the ohmic contact promoting substance, so that the contact resistance between the heating resistor layer and the electrode layer is sufficiently reduced.

According to a first sub Maruheddo of the present invention, contact with for polycrystalline containing silicon heating resistor layer and the electrode layer and Gao Mikku contact via an intermediate layer containing germanium, heating resistor layer and the electrode layer Resistance decreases sufficiently . Thus, not provided with an intermediate layer, different from the conventional thermal head contact resistance between the heating resistor layer and the electrode layer is too large, the resistance characteristics of the heat generation resistor layer is stabilized. Therefore, even when the heating resistor layer is configured using a semiconductor, the resistance characteristics can be stabilized and the operation characteristics can be ensured.

According to the second thermal head of the present invention, ohmic contact promoting substance containing germanium arm to the electrode layer are doped, since the electrode layer is in ohmic contact with the heating resistor layer, the heating resistor layer and the electrode layer The contact resistance is sufficiently reduced. Therefore, even when the heating resistor layer is configured using a semiconductor, the resistance characteristics can be stabilized and the operation characteristics can be ensured.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
First, the configuration of the thermal head according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an external configuration of the thermal head 10.

  The thermal head 10 according to the present embodiment is a device mounted as a heat source in, for example, a thermal printing apparatus (that is, a printer). For example, as shown in FIG. 1, the thermal head 10 includes a heat generating unit 10A and a drive unit 10B for driving the heat generating unit 10A, and the heat generating unit 10A is mounted on the drive unit 10B. Have.

  The drive unit 10B controls the driving state of the heat generating unit 10A by energizing and driving the heat generating unit 10A. The drive unit 10B is connected to a heat sink 11 made of, for example, aluminum (Al) so that a printed circuit board (PCB) 12 partially overlaps, and one surface of the printed circuit board 12 is connected. A driver IC (Integrated Curcuit) 13 is attached to the (upper surface), and a connector 14 for external connection is attached to the other surface (lower surface). The driver IC 13 is a device for driving the heat generating portion 10A. For example, the driver IC 13 is embedded in the IC resin film 15, and further, the IC resin is formed by an IC cover 16 attached to one surface of the printed circuit board 12. It is covered with the film 15.

  The heat generating portion 10A is driven to generate heat when energized from the drive portion 10B, and is fixed to the heat radiating plate 11 of the drive portion 10B via a silicon-based adhesive 17, for example. The detailed configuration of the heat generating unit 10A will be described later.

  Next, a detailed configuration of the heat generating portion 10A will be described with reference to FIGS. 2 and 3 show an enlarged detailed configuration of the heat generating portion 10A, FIG. 2 shows a cross-sectional configuration, and FIG. 3 shows a planar configuration. 2 shows a cross-sectional configuration along the line II-II shown in FIG.

For example, as shown in FIG. 2, the heat generating portion 10 </ b> A includes a glaze layer 2, a heat generating resistor layer 3, and a pair of electrode layers 4 on a substrate 1 made of, for example, aluminum oxide (Al ₂ O ₃ ; alumina). And the protective layer 5 are laminated in this order, and the heating resistor layer 3 and the electrode layer 4 are in ohmic contact with each other between the heating resistor layer 3 and the electrode layer 4. Therefore, the intermediate layer 6 is provided.

  The glaze layer 2 stores heat generated in the heating resistor layer 3 so that the heat does not escape to the substrate 1, and is made of, for example, a low heat conductive material such as glass. Yes.

  The heating resistor layer 3 generates heat by being energized through the electrode layer 4, and includes, for example, polycrystalline silicon (Poly-Si). Examples of the polycrystalline silicon include P-type polycrystalline silicon doped with boron (B) and n-type polycrystalline silicon doped with phosphorus (P).

  The pair of electrode layers 4 are for energizing the heating resistor layer 3, and are electrode layers 4A (first electrode layers) and 4B (second electrodes) arranged to face each other with a predetermined gap G interposed therebetween. Layer). These electrode layers 4A and 4B are both made of a highly conductive material such as aluminum (Al).

The protective layer 5 prevents the heating resistor layer 3 and the electrode layer 4 from being worn or damaged due to contact with the printing medium when the thermal head 10 is used to print an image on the printing medium. Is to do. The protective layer 5 includes, for example, a material having silicon (Si), boron (B), and phosphorus (P), and specifically, silane (SiH ₄ ), diborane (B ₂ H ₆ ). And a silicon-boron-phosphorus compound (SiBP) formed by plasma CVD (Chemical Vapor Deposition) using phosphine (PH ₃ ) or the like.

  As described above, the intermediate layer 6 is for making ohmic contact between the heating resistor layer 3 and the electrode layer 4, and one of the intermediate layers 6 provided between the heating resistor layer 3 and the one electrode layer 4A. The intermediate layer 6A (first intermediate layer) and the other intermediate layer 6B (second intermediate layer) provided between the heating resistor layer 3 and the other electrode layer 4B are configured. . Briefly describing the role of the intermediate layer 6, the intermediate layer 6 is interposed between the heating resistor layer 3 made of a semiconductor such as polycrystalline silicon and the electrode layer 4 made of a highly conductive material such as aluminum. The heating resistor layer 3 and the electrode layer 4 are in ohmic contact with each other through the intermediate layer 6, that is, the contact resistance between the heating resistor layer 3 and the electrode layer 4 is the heating resistor layer. 3 to a level that does not affect the resistance characteristics. The intermediate layer 6 includes, for example, at least one of germanium (Ge) and platinum (Pt) within a range of 0.1 atomic% to 100 atomic%. Examples of the constituent material of the intermediate layer 6 include germanium, silicon-germanium compound (Si-Ge), aluminum-germanium compound (Al-Ge), aluminum-silicon-germanium compound (Al-Si-Ge), platinum, Silicon-platinum compound (Si-Pt), aluminum-platinum compound (Al-Pt), aluminum-silicon-platinum compound (Al-Si-Pt), germanium-platinum compound (Ge-Pt), silicon-germanium-platinum compound (Si-Ge-Pt), aluminum-germanium-platinum compound (Al-Ge-Pt), and at least one of the group comprising aluminum-silicon-germanium-platinum compound (Al-Si-Ge-Pt) The material to include is mentioned.

  In the heat generating portion 10A, for example, as shown in FIG. 3, the electrode layers 4 (4A, 4B) are arranged in parallel along the Y-axis direction over a plurality of sets. In addition, a plurality of heating resistor layers 3 are arranged in parallel in the same direction. Of the electrode layers 4, one electrode layer 4A functions as a common electrode and is connected to each other between each pair of electrode layers 4, whereas the other electrode layer 4B functions as a lead electrode. The electrode layers 4 are separated from each other. Each electrode layer 4B functioning as the lead electrode is connected to a driver IC 13 (see FIG. 1) of the drive unit 10B, and can be energized independently of each other through the driver IC 13. The intermediate layer 6 is disposed corresponding to the electrode layer 4, for example, and has the same configuration as that of the electrode layer 4, that is, one intermediate layer 6A is connected to each other corresponding to the electrode layer 4A. The other intermediate layer 6B is separated from each other corresponding to the electrode layer 4B. In FIG. 3, the protective layer 5 is not shown and the electrode layer 4 is shaded in order to make it easy to see the positional relationship between the heating resistor layer 3 and the electrode layer 4 (4A, 4B). Yes.

  Next, the operation of the thermal head 10 will be described with reference to FIGS.

  In the thermal head 10, for example, the electrode layer 4 (4A, 4B) is energized through the driver IC 13 based on the image pattern information in a state where the thermal head 10 is connected to the thermal printing apparatus or the like via the connector 14 of the driving unit 10B. Then, the heating resistor layer 3 generates heat based on the current supplied from the electrode layer 4 to generate heat for printing. The heat generated at this time passes through the protective layer 5 and is finally conducted to a printing area of a printing medium (not shown).

  At this time, an intermediate layer 6 is provided between the heating resistor layer 3 and the electrode layer 4, and the heating resistor layer 3 and the electrode layer 4 are in ohmic contact with each other through the intermediate layer 6. The contact resistance between the heating resistor layer 3 and the electrode layer 4 is sufficiently reduced. Thereby, linearity is obtained regarding the current-voltage characteristic between the heating resistor layer 3 and the electrode layer 4.

  In the thermal head 10 according to the present embodiment, as shown in FIGS. 1 to 3, an intermediate layer 6 is provided between the heating resistor layer 3 and the electrode layer 4, and the intermediate layer 6 is used to generate heat. Since the resistor layer 3 and the electrode layer 4 are brought into ohmic contact, the contact resistance between the heating resistor layer 3 and the electrode layer 4 is sufficiently lowered as described above as “operation of the thermal head 10”. To do. In this case, unlike the conventional thermal head (see FIG. 7), which does not include the intermediate layer 6 and the contact resistance between the heating resistor layer 103 and the electrode layer 104 is too large, it is represented by polycrystalline silicon. Even in the case where the heating resistor layer 3 is configured using the semiconductor to be formed, the resistance characteristic of the heating resistor layer 3 is stabilized. Of course, the stabilization tendency related to the resistance characteristics of the heating resistor layer 3 can be obtained even when the heating resistor layer 3 is formed using P-type polycrystalline silicon. Therefore, in the present embodiment, even when the heating resistor layer 3 is configured using a semiconductor, the resistance characteristics can be stabilized and the operating characteristics of the thermal head 10 can be ensured.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  4 and 5 show an enlarged detailed configuration of the main part (heat generating part 10A) of the thermal head according to the present embodiment, and FIG. 4 shows a cross-sectional configuration corresponding to FIG. Shows a planar configuration corresponding to FIG. FIG. 4 shows a cross-sectional configuration along the line IV-IV shown in FIG. 4 and 5, the same components as those described in the first embodiment are denoted by the same reference numerals.

  In the thermal head according to the present embodiment, for example, as shown in FIGS. 4 and 5, the intermediate layer 6 is provided between the heating resistor layer 3 and the electrode layer 4. The configuration of the heat generating part 10A is different from the thermal head 10 (see FIGS. 1 to 3) of the embodiment, and specifically includes an electrode layer 24 (24A, 24B) instead of the electrode layer 4 (4A, 4B), The thermal head 10 has the same configuration as that of the thermal head 10 except that the intermediate layer 6 is not provided between the electrode layer 24 and the heating resistor layer 3. The electrode layer 24 has a function of energizing the heating resistor layer 3 and is in ohmic contact with the heating resistor layer 3 itself, and is made of a highly conductive material such as aluminum. Contains an ohmic contact promoting material for ohmic contact. The electrode layer 24 includes, for example, the constituent material of the intermediate layer 6 enumerated in the first embodiment as an ohmic contact promoting substance, and specifically, of germanium (Ge) and platinum (Pt). At least one is included in the range of 0.1 atomic% to 100 atomic%. Examples of the ohmic contact promoting substance include germanium, silicon-germanium compound (Si-Ge), aluminum-germanium compound (Al-Ge), aluminum-silicon-germanium compound (Al-Si-Ge), platinum, silicon- Platinum compound (Si-Pt), aluminum-platinum compound (Al-Pt), aluminum-silicon-platinum compound (Al-Si-Pt), germanium-platinum compound (Ge-Pt), silicon-germanium-platinum compound (Si -Ge-Pt), aluminum-germanium-platinum compound (Al-Ge-Pt), and at least one of the group comprising aluminum-silicon-germanium-platinum compound (Al-Si-Ge-Pt). . The electrode layer 24 can be formed, for example, by doping a highly conductive material such as aluminum with an ohmic contact promoting substance. The distribution state of the ohmic contact promoting substance in the electrode layer 24 may be, for example, substantially uniform throughout, or the concentration of the ohmic contact promoting substance is high on the side close to the heating resistor layer 3. A concentration gradient may be provided in the electrode layer 24 in the thickness direction. The heating resistor layer 3 is composed of polycrystalline silicon, as in the first embodiment.

  In the thermal head according to the present embodiment, since the electrode layer 24 contains an ohmic contact promoting substance, the electrode layer 24 itself makes ohmic contact with the heating resistor layer 3 using the ohmic contact promoting substance. Accordingly, since the contact resistance between the heating resistor layer 3 and the electrode layer 24 is sufficiently lowered, the heating resistor layer 3 is configured using a semiconductor by the same action as in the first embodiment. Even in this case, the resistance characteristics can be stabilized and the operating characteristics of the thermal head can be ensured.

  The configuration and operation of the thermal head of the present embodiment other than those described above are the same as those in the first embodiment.

  Next, specific examples of the present invention will be described.

  As a representative of the thermal head of the present invention described in each of the above embodiments, a resistance characteristic test was performed using the thermal head shown in FIGS. 1 to 3 in the first embodiment. The results shown in are obtained. FIG. 6 shows changes in the resistance characteristics of the thermal head, where the “horizontal axis” shows the normalized applied power ratio (normalized applied power ratio), and the “vertical axis” shows the resistance change rate (%). Yes. As the main configuration of the thermal head, the heating resistor layer, the electrode layer, and the intermediate layer were each composed of polycrystalline silicon, aluminum, and an aluminum-silicon-germanium compound (Al-Si-Ge). When the change in the resistance characteristic of the thermal head of the present invention was examined, the change in the resistance characteristic of the conventional thermal head shown in FIG. 7 was also examined in order to compare and evaluate the performance. “◯” shown in FIG. 6 indicates the result regarding the thermal head of the present invention, and “Δ” indicates the result regarding the conventional thermal head. The above-mentioned “standardized applied power ratio” means that the initial resistance value (before applying the pulse voltage) is applied by changing (increasing) the pulse voltage over 60000 times between the electrode layers of the conventional thermal head. The applied power W1 when the resistance change rate reaches ± 3% with respect to the resistance value) is examined, and the applied power W1 is also applied to the thermal head of the present invention while changing (increasing) the pulse voltage in the same manner. The applied power ratio W2 / W1 is shown when the applied power W2 corresponding to is examined and the applied power W1 is 1.

  As can be seen from the results shown in FIG. 6, the rate of change in resistance of the thermal head decreases in the negative direction as the normalized applied power ratio increases in both the present invention (◯) and the conventional (Δ). It became bigger. However, when the change state of the resistance change rate is compared between the present invention and the prior art, the negative resistance change rate has suddenly increased near the normalized applied power ratio = 1.0 in the past. In the invention, the negative resistance change rate suddenly increased near the normalized applied power ratio = 3.0. More specifically, the practical reference value for the resistance change rate of the thermal head is set as the resistance change rate = −3.0%, that is, the practical resistance change rate of the thermal head is within −3.0%. When it is desired to keep, the standardized applied power ratio at which the resistance change rate = −3.0% is the standardized applied power ratio = about 1.0 in the past, whereas in the present invention, the standardized applied power ratio is about 1.0. The ratio was about 3.5, and in the present invention, it was three times larger than the prior art. Therefore, unlike the conventional thermal head, the thermal head of the present invention stabilizes the resistance characteristics even when the heating resistor layer is configured using a semiconductor typified by polycrystalline silicon, and the operating characteristics are improved. It was confirmed that it could be secured.

  Although not specifically shown and described, a series of germanium-based and platinum-based materials listed in the first embodiment is used instead of the aluminum-silicon-germanium compound (Al-Si-Ge). When changes in the resistance characteristics of the thermal heads used to form the intermediate layer were examined, results similar to those shown in FIG. 6 were obtained for these thermal heads. From this, it is not limited to a thermal head in which a heating resistor layer is formed using an aluminum-silicon-germanium compound (Al-Si-Ge), but an intermediate using a series of other germanium-based and platinum-based materials. It was confirmed that even in the thermal head composed of layers, the resistance characteristics can be stabilized and the operating characteristics can be secured.

Although the present invention has been described with reference to some embodiments and examples, the present invention is not limited to the above-described embodiments, and various modifications can be made .

  The thermal head according to the present invention can be applied to a thermal head provided with a heating resistor layer made of a semiconductor.

It is a figure showing the external appearance structure of the thermal head which concerns on the 1st Embodiment of this invention. It is sectional drawing which expands and represents the cross-sectional structure of the heat generating part shown in FIG. It is a top view which expands and represents the plane structure of the heat generating part shown in FIG. It is sectional drawing showing the cross-sectional structure of the heat-emitting part among the thermal heads concerning the 2nd Embodiment of this invention. It is a top view showing the plane structure of the heat generating part shown in FIG. It is a figure showing the change of the resistance characteristic of a thermal head. It is sectional drawing showing the cross-sectional structure of the principal part of the conventional thermal head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Glaze layer, 3 ... Heat-generating resistor layer, 4 (4A, 4B), 24 (24A, 24B) ... Electrode layer, 5 ... Protective layer, 6 (6A, 6B) ... Intermediate layer, 10 ... Thermal head, 10A ... heating unit, 10B ... driving unit, 11 ... heat sink, 12 ... printed circuit board, 13 ... driver IC, 14 ... connector, 15 ... IC resin film, 16 ... IC cover, 17 ... adhesive, G ... gap.

Claims (9)

  A heating resistor layer containing polycrystalline silicon, an electrode layer electrically connected to the heating resistor layer, and provided between the heating resistor layer and the electrode layer, the heating resistor layer and the electrode layer An intermediate layer for making ohmic contact with the electrode layer, wherein the intermediate layer contains germanium (Ge).   The intermediate layer includes germanium, silicon-germanium compound (Si-Ge), aluminum-germanium compound (Al-Ge), aluminum-silicon-germanium compound (Al-Si-Ge), germanium-platinum compound (Ge-Pt). , Silicon-germanium-platinum compound (Si-Ge-Pt), aluminum-germanium-platinum compound (Al-Ge-Pt), and aluminum-silicon-germanium-platinum compound (Al-Si-Ge-Pt) The thermal head according to claim 1, comprising at least one kind.   The electrode layer includes first and second electrode layers disposed opposite to each other with a predetermined gap therebetween, and the intermediate layer is provided between the heating resistor layer and the first electrode layer. 3. The method according to claim 1, further comprising: a first intermediate layer; and a second electrode layer provided between the heating resistor layer and the second electrode layer. Thermal head.   Furthermore, it is provided so as to cover the heating resistor layer and the electrode layer, and includes a protective layer for protecting the heating resistor layer and the electrode layer. The protective layer includes silicon (Si), boron (B The thermal head according to any one of claims 1 to 3, further comprising a material having phosphorus and phosphorus (P).   5. The electrode layer according to claim 1, wherein a plurality of the electrode layers are arranged in parallel, and the intermediate layer is arranged corresponding to the electrode layer. 6. Thermal head.   The thermal head according to any one of claims 1 to 5, wherein the electrode layer is made of aluminum (Al). A heating resistor layer comprising polycrystalline silicon; and an electrode layer electrically connected to the heating resistor layer and doped with an ohmic contact promoting substance for making ohmic contact with the heating resistor layer; A thermal head characterized in that the contact promoting substance contains germanium (Ge 2 ) . The ohmic contact-promoting substances are, germanium, silicon - germanium compound (Si-Ge), aluminum - germanium compound (Al-Ge), aluminum - silicon - germanium compound (Al-Si-Ge), gate Rumaniumu - platinum compounds (Ge -Pt), silicon-germanium-platinum compound (Si-Ge-Pt), aluminum-germanium-platinum compound (Al-Ge-Pt), and aluminum-silicon-germanium-platinum compound (Al-Si-Ge-Pt) The thermal head according to claim 7, comprising at least one of the above.   The thermal head according to claim 7, wherein the electrode layer is made of aluminum (Al).

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