Thermal print head and thermal printer

Abstract

To provide a thermal print head which further reduces a cost and suppresses the unexpected high voltage generated between wires, and provide a thermal printer including the thermal print head.SOLUTION: A thermal print head having a heating resistor part comprises: a common electrode which is in contact with the heating resistor part; an individual electrode which is electrically connected to the common electrode via the heating resistor part; a ground electrode being the target to which the ground potential to the thermal print head is supplied; a drive IC which is electrically connected to the individual electrode and the ground electrode; a power source electrode being the target to which the power source potential to the thermal print head is supplied; and a surge protection element which is electrically connected to the power source electrode and the ground electrode. The common electrode and the individual electrode include metal particles.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present embodiment relates to a thermal printhead and a thermal printer. [Background technology]

[0002] A thermal printhead, for example, has a number of heat generating parts arranged in the main scanning direction on a head substrate. Each heat generating part is formed by laminating a common electrode and an individual electrode with their ends facing each other on a resistor layer formed on the head substrate via a glaze layer, with a portion of the resistor layer exposed. When electricity is applied between the common electrode and the individual electrodes, the exposed portion (heat generating part) of the resistor layer generates heat by Joule heat.

[0003] In addition, in forming a wiring layer that energizes the resistor through the common electrode and the individual electrodes, a wiring pattern is formed using a paste that uses gold. Since the paste that uses gold is expensive, in order to reduce the cost of the product, techniques that reduce the amount of gold used or pastes that use metals other than gold have been proposed. Many techniques that use silver, a relatively inexpensive metal with good electrical conductivity, have been proposed.

[0004] For example, in order to reduce the interfacial resistance between conductor layers while at the same time avoiding the occurrence of "voids" in which the film thickness becomes thin due to repeated firing processes, or the resulting problems of increased conductor resistance or disconnection, an alloy has been disclosed that contains an organic silver compound and an organic nickel compound, which are mixed with a resin to form a paste, and the metal element components are 95 to 99% by weight of silver and 1 to 5% by weight of nickel.

[0005] Also, in order to further reduce costs, there is an increasing demand for flip-chip mounting, which does not use wiring and brings the driver IC into direct contact with solder bumps.

[0006] However, simply changing the wiring material from gold to silver and mounting the flip chip using solder bumps can lead to problems with short circuits between the wiring due to ion migration, and the sudden application of high voltage between the wiring can cause defects in the product, making it possible that the performance may not be sufficient for practical use. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 5-89716 [Patent Document 2] Japanese Patent Application Publication No. 6-132338 Summary of the Invention [Problem to be solved by the invention]

[0008] One aspect of the present embodiment provides a thermal printhead that can reduce costs and suppress sudden high voltages occurring between wirings. Another aspect of the present embodiment provides a thermal printer including the thermal printhead. [Means for solving the problem]

[0009] In this embodiment, a surge protection element is provided between the wirings, thereby further reducing costs and suppressing sudden high voltages occurring between the wirings. One aspect of this embodiment is as follows.

[0010] One aspect of this embodiment is a thermal print head having a heat generating resistor portion, the thermal print head including a common electrode in contact with the heat generating resistor portion, individual electrodes electrically connected to the common electrode via the heat generating resistor portion, a ground electrode to which a ground potential for the thermal print head is supplied, a driving IC electrically connected to the individual electrodes and the ground electrode, a power supply electrode to which a power supply potential for the thermal print head is supplied, and a surge protection element, the common electrode and the individual electrodes containing metal particles. fruit , The power supply potential includes a first potential supplied to the driving IC and a second potential supplied to the common electrode, and the surge protection element is connected between the first potential and the ground electrode. It is a thermal print head.

[0011] Another aspect of the present embodiment is a thermal printer including the thermal printhead described above. Effect of the Invention

[0012] According to the present embodiment, it is possible to provide a thermal printhead that can reduce costs and suppresses sudden high voltages occurring between wirings. Another aspect of the present embodiment is to provide a thermal printer that includes the thermal printhead. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a wiring diagram illustrating a thermal printhead according to this embodiment. [Diagram 2] FIG. 2 is an enlarged view of the IC1 area in FIG. [Diagram 3] FIG. 3 is a wiring diagram illustrating a configuration in which a surge protection element is provided between a ground electrode (GND) and a common electrode (VH). [Figure 4] FIG. 4 is a plan view showing the thermal printhead according to the present embodiment. [Diagram 5] FIG. 5 is a plan view showing the essential parts of the thermal printhead according to this embodiment. [Figure 6] FIG. 6 is an enlarged plan view of the essential parts of the thermal printhead according to this embodiment. [Figure 7] FIG. 7 is a cross-sectional view taken along line IV-IV in FIG. [Figure 8] FIG. 8 is a plan view showing the essential parts of the thermal printhead according to this embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing a main part of a thermal printhead according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Next, the present embodiment will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and planar dimensions of each component is different from the actual relationship. Therefore, the specific thickness and dimensions should be determined with reference to the following description. In addition, it goes without saying that the drawings include parts with different dimensional relationships and ratios.

[0015] The following embodiments are merely examples of devices and methods for embodying the technical ideas, and do not specify the materials, shapes, structures, arrangements, etc. of each component. Various modifications can be made to the present embodiments within the scope of the claims.

[0016] A specific aspect of this embodiment is as follows.

[0017] <1> A thermal printhead having a heating resistor portion, comprising: a common electrode in contact with the heating resistor portion; individual electrodes electrically connected to the common electrode via the heating resistor portion; a ground electrode to which a ground potential for the thermal printhead is supplied; a driving IC electrically connected to the individual electrodes and the ground electrode; a power supply electrode to which a power supply potential for the thermal printhead is supplied; and a surge protection element electrically connected to the power supply electrode and the ground electrode, wherein the common electrode and the individual electrodes contain metal particles.

[0018] <2> The metal particles include at least one selected from the group consisting of copper and silver, <1> 2. The thermal print head according to claim 1 .

[0019] <3> The surge protection element is a Zener diode. <1> or <2> 2. The thermal print head according to claim 1 .

[0020] <4> The power supply potential is a first potential supplied to the driving IC. <1> ~ <3> 13. The thermal printhead according to claim 12 .

[0021] <5> the other power supply potential for the thermal printhead is a second potential supplied to the common electrode; <4> 2. The thermal print head according to claim 1 .

[0022] <6> The second potential is equal to or higher than the first potential. <5> 2. The thermal print head according to claim 1 .

[0023] <7> <1> ~ <6> 13. A thermal printer comprising the thermal printhead according to any one of claims 1 to 12.

[0024] <Thermal print head> The thermal printhead according to this embodiment will be described with reference to the drawings.

[0025] Fig. 1 is a wiring diagram for explaining a thermal printhead according to this embodiment. The thermal printhead A1 of this embodiment includes a common electrode having a heat generating resistor portion and contacting the heat generating resistor portion, individual electrodes electrically connected to the common electrode via the heat generating resistor portion, a ground electrode (GND) to which a ground potential for the thermal printhead A1 is supplied, driving ICs (driving IC1 to IC3 in Fig. 1) electrically connected to the individual electrodes and the ground electrode, power supply electrodes (VDD and VH) to which a power supply potential for the thermal printhead A1 is supplied, and a surge protection element 10 electrically connected to the power supply electrode and the ground electrode. In other words, when the thermal printhead A1 is used, a ground potential is supplied to the ground electrode (GND), and a power supply potential is supplied to the power supply electrodes (VDD and VH).

[0026] A more detailed explanation will be given with reference to FIG. 2, which is an enlarged view of the vicinity of the driving IC 1 shown in FIG. 1. Around the driving IC 1, power supply wiring and signal wiring, such as a ground electrode to which a ground potential (Vgnd) is supplied when the thermal printhead A1 is used, a driving IC power supply electrode to which a driving IC potential (Vdd) is supplied, and a common electrode to which a common potential (Vh) is supplied, are densely packed. The heating resistor part of the thermal printhead A1 described later and its surroundings are covered with an overcoat glass layer, so that moisture from the outside does not reach the wiring. Therefore, ion migration of the metal, which is the material of the wiring, does not occur. However, no glass layer is provided around the driving IC 1 or immediately below the driving IC. Ion migration is more likely to occur as the electric field strength between each power supply wiring and signal wiring is greater, so that the vicinity of the driving IC 1 and immediately below the driving IC, where the power supply wiring and signal wiring are densely packed, are locations where ion migration is likely to occur. In general, the common potential (Vh) supplied to the common electrode is higher than the driving IC potential (Vdd) supplied to the driving IC 1. In some cases, the common potential (Vh) and the driving IC potential (Vdd) are equal.

[0027] Here, we will briefly explain ion migration when silver is used as the wiring material. Silver (Ag), the wiring material, is ionized as follows due to the potential difference between electrodes (for example, between a common electrode and an individual electrode) and the presence of water adsorbed on the surface from the surrounding atmosphere.

[0028] [ka]

[0029] Next, silver ions (Ag + ) and hydroxide ion (OH - ) reacts on the common electrode side to produce silver hydroxide (AgOH), which deposits on the surface of the common electrode.

[0030] [ka]

[0031] The silver hydroxide (AgOH) on the common electrode side is decomposed into silver oxide (Ag2O) and dispersed in a colloidal form.

[0032] [ka]

[0033] The hydration reaction produces silver ions (Ag + ) migrates toward the individual electrodes, causing dendritic deposition of silver (Ag).

[0034] [ka]

[0035] As described above, ion migration occurs when water from the outside reaches the wiring. Here, wiring using silver is exemplified, but ion migration can occur with other metals as well, and the likelihood of ion migration varies depending on the metal's properties, the magnitude of ionization tendency, and the like. For example, when comparing silver and copper, due to the properties of silver, silver is more likely to cause ion migration at a lower voltage than copper. When comparing silver and gold, silver is more likely to become a positive ion than gold due to its ionization tendency, and silver is more likely to cause ion migration than gold.

[0036] The driving IC 1 is mounted on the substrate by electrically connecting it to the wiring via solder bumps provided on the substrate. The solder bumps also function as a support for supporting the substrate. In this embodiment, after mounting the driving IC 1, the surge protection element 10 is provided between the ground electrode (GND) and the high power supply electrode (VDD) so as to be electrically connected thereto. The anode of the surge protection element 10 is electrically connected to the ground electrode (GND), and the cathode is electrically connected to the high power supply electrode (VDD). When the thermal printhead A1 is used, the driving IC controls the conductive state of the heat generating resistor 41 based on a signal from the control unit. Specifically, the driving IC is electrically connected to each of the ground electrode, the high power supply electrode, and the common electrode. When the thermal printhead A1 is used, the conductive state of the heat generating resistor 41 is controlled by allowing a current to flow from the common electrode in contact with the heat generating resistor 41 to the ground power supply via the heat generating resistor 41 and the individual electrodes based on a signal from the control unit.

[0037] In this specification, "electrically connected" includes a case where the connection is made via "something having some electrical action". Here, the "something having some electrical action" is not particularly limited as long as it enables the transmission and reception of an electrical signal between the connection objects. For example, the "something having some electrical action" includes an electrode, a wiring, a switching element, a resistive element, an inductor, a capacitive element, and other elements having various functions.

[0038] The surge protection element 10 has a function of suppressing the sudden application of high voltage between wirings, and can be used to prevent a product from being damaged when, for example, an unspecified large current flows temporarily through the product's circuit, and to keep the supplied voltage constant. Examples of the surge protection element 10 include a Zener diode, a varistor, and an ESD suppressor, with a Zener diode being preferable.

[0039] 3, the surge protection element 10 may be provided between the ground electrode (GND) and the common electrode (VH) so as to be electrically interposed therebetween. The anode of the surge protection element 10 is electrically connected to the ground electrode (GND), and the cathode is electrically connected to the common electrode (VH). The surge protection element 10 may be provided at least between the ground electrode (GND) and the high power supply electrode (VDD) or between the ground electrode (GND) and the common electrode (VH). The common potential (Vh) supplied to the common electrode (VH) may be higher than or equal to the potential (Vdd) supplied to the high power supply electrode (VDD). For example, a single power supply may be used both as the power supply that supplies the potential (Vdd) and the power supply that supplies the common potential (Vh).

[0040] In addition, although a plurality of surge protection elements 10 are provided in FIG. 1, the present invention is not limited to this, and it is sufficient that one type of power source is electrically connected to the ground electrode (GND) via at least one surge protection element 10.

[0041] In this embodiment, the common electrode and individual electrodes, as well as the wiring, contain metal particles, which are copper, silver, palladium, iridium, platinum, and gold. From the viewpoint of the ionization tendency of the metal, copper, silver, platinum, and gold are preferred, and from the viewpoint of the ionization tendency of the metal and cost reduction, copper and silver are more preferred.

[0042] The gap between the substrate and the driver IC 1 is filled with resin that acts as an underfill material, and the hardened underfill material is provided. When the resin acts as an underfill material and hardens, the resin is poured to seal, but air bubbles may get mixed into the resin at this time, and the resin may not easily reach the back side of the solder bumps (the side toward which the resin flows), resulting in voids. If there are many solder bumps, the probability of voids occurring increases, which may affect the reliability of the driver IC 1. On the other hand, if there are too few solder bumps, the function as a support is reduced, so it is preferable to appropriately adjust the arrangement and number of solder bumps, taking these factors into consideration.

[0043] Here, the description has been given using the driving IC1, but the driving IC2 and driving IC3 are similar to the driving IC1.

[0044] 4 is a plan view of the thermal printhead A1 of this embodiment, FIG. 5 is a plan view of the essential parts, FIG. 6 is an enlarged plan view of the essential parts, and FIG. 7 is a cross-sectional view taken along line IV-IV in FIG.

[0045] The thermal printhead A1 of this embodiment includes a substrate 1, a connection substrate 5, and a heat dissipation member 8. The substrate 1 and the connection substrate 5 are mounted adjacent to each other in the sub-scanning direction y on the heat dissipation member 8. The substrate 1 is formed with a plurality of heat generating resistor portions (heat generating portions) 41 arranged in the main scanning direction x. The heat generating resistor portions 41 are driven to selectively generate heat by a drive IC mounted on the connection substrate 5. The heat generating resistor portions 41 print on a print medium 92, such as thermal paper, pressed against the heat generating resistor portions 41 by a platen roller 91 (see FIG. 7), in accordance with a print signal transmitted from the outside via a connector 59.

[0046] The substrate 1 has a planar shape of an elongated rectangle with the main scanning direction x as the longitudinal direction and the sub-scanning direction y as the transverse direction. The size of the substrate 1 is not limited, but as an example, the dimension in the main scanning direction x is, for example, 50 to 150 mm, the dimension in the sub-scanning direction y is, for example, 2.0 to 5.0 mm, and the dimension in the thickness direction z is, for example, 725 μm. In the following description, the side of the substrate 1 closer to the driving IC in the sub-scanning direction y is referred to as the top. flow The side farther from the driver IC is called the bottom side. flow It's called side.

[0047] The substrate 1 is made of ceramic or a single crystal semiconductor. As the ceramic, for example, alumina can be used. As the single crystal semiconductor, for example, silicon can be used.

[0048] The connection board 5 may be, for example, a printed wiring board. The connection board 5 has a structure in which a base layer and a wiring layer (not shown) are laminated. The base layer may be, for example, a glass epoxy resin. The wiring layer may be, for example, the above-mentioned metal particles.

[0049] The heat dissipation member 8 has a function of dissipating heat from the substrate 1. The substrate 1 and the connection substrate 5 are attached to the heat dissipation member 8. The heat dissipation member 8 may be made of a metal such as aluminum.

[0050] The insulating layer 19 covers the substrate 1. The insulating layer 19 can be made of an insulating material, such as silicon oxide or silicon nitride. do. The thickness of the insulating layer 19 is not particularly limited and is, for example, 5 to 15 μm, and preferably 5 to 10 μm. Note that the insulating layer 19 may not be provided.

[0051] The resistor layer 4 generates heat at the portion where the current from the electrode 3 flows. This heat generation forms print dots. The resistor layer 4 is made of a material having a higher resistivity than the material constituting the electrode 3, and may be made of, for example, tantalum nitride or silicon oxide containing tantalum. The resistor layer 4 may be made of ruthenium oxide. As shown in FIG. 5, the resistor layer 4 includes a heating resistor portion 41. In this embodiment, the resistor layer 4 has a thickness of, for example, about 0.05 to 0.2 μm.

[0052] The electrode 3 constitutes a path for passing electricity through the resistor layer 4. The electrode 3 includes a plurality of individual electrodes 31 formed on the substrate 1 and a common electrode 32. The electrode 3 is made of a conductor. As the conductor, for example, the above-mentioned metal particles such as silver or the like can be used. In this embodiment, the thickness of the electrode 3 is, for example, about 0.2 to 0.8 μm.

[0053] Each individual electrode 31 has a band shape extending generally in the sub-scanning direction y, with its lower end extending to the position of the region 13. The individual electrodes 31 are not electrically connected to each other. Therefore, when a printer incorporating the thermal printhead is used, different potentials can be applied to each individual electrode 31. An individual pad portion 311 is formed on the upper end of each individual electrode 31.

[0054] The common electrode 32 is a portion that has an electrically opposite polarity to the individual electrodes 31 when a printer incorporating the thermal printhead is used. The common electrode 32 has a plurality of comb-tooth portions 324 and a common portion 323 that commonly connects the plurality of comb-tooth portions 324. The common portion 323 is formed in the main scanning direction x along the upper edge of the substrate 1, and each comb-tooth portion 324 has a strip shape that branches off from the common portion 323 and extends in the sub-scanning direction y, with its upper tip facing the tip of each individual electrode 31 at a predetermined interval.

[0055] The electrodes 3 and the resistor layer 4 are covered with a protective film. The protective film can be made of an insulating material, such as silicon nitride, silicon oxide, etc. The thickness of the protective film is, for example, about 3 to 8 μm.

[0056] The driving IC is mounted on the connection board 5 via solder bumps, and is provided to individually energize the heating resistors 41. The driving IC and each individual pad 311 of each individual electrode 31 are connected by a wire (not shown) connected to wiring on the connection board 5. A print signal transmitted from the outside via a connector 59 is input to the driving IC. Development The thermal resistors 41 are individually energized in accordance with a print signal, and are selectively made to generate heat.

[0057] Illustrated here is a cross-sectional view of an example of a thermal printhead including the components described above.

[0058] The above-mentioned components will be described in detail with reference to Figures 8 and 9. The thermal printhead shown in Figures 8 and 9 includes a substrate 35, a heat storage layer 33 on the substrate 35, individual electrodes 31 and a common electrode 32 on the heat storage layer 33, heat generating resistor portions 41 on the individual electrodes 31 and the common electrode 32, and a protective film 34 on the heat generating resistor portion 41.

[0059] Substrate 35 corresponds to substrate 1 described above.

[0060] An insulating material can be used for the heat storage layer 33, and it is preferable to use, for example, silicon oxide or silicon nitride, which are the main components of glass. The thickness of the heat storage layer 33 is not particularly limited, and is, for example, 5 to 15 μm, and preferably 5 to 10 μm.

[0061] As described above, the individual electrodes 31, the common electrode 32, and the heat generating resistor portion 41 are detailed. The individual electrodes 31 and the common electrode 32 may be patterned using a printing machine, or may be patterned in a photolithography process.

[0062] The protective film 34 corresponds to the protective film that covers the electrodes 3, the resistor layer 4, and the like.

[0063] Here, a method for manufacturing the thermal printhead of this embodiment will be described.

[0064] First, the heat storage layer 33 is formed on the substrate 35, and then the individual electrodes 31 and the common electrode 32 are formed. Furthermore, wiring, pads, etc. are also formed at the same time as the individual electrodes 31 and the common electrode 32 are formed. For example, glass is formed on an alumina substrate, and a conductor that will become the individual electrodes 31 and the common electrode 32 is formed on the glass. Thereafter, a pattern of electrodes, wiring, pads, etc. is formed on the conductor by screen printing using a printer or a photolithography process, thereby forming the individual electrodes 31, the common electrode 32, wiring, pads, etc. The conductor can be formed using, for example, silver or the like.

[0065] Next, an auxiliary electrode is formed which is electrically connected to the common electrode 32. The auxiliary electrode is electrically connected to the common electrode 32 and is therefore maintained at the same potential. In other words, the auxiliary electrode functions as a common connection portion for all portions of the common electrode 32. Since the auxiliary electrode has a large area, it expands the current path and substantially eliminates voltage drop in the longitudinal direction of the thermal print head. Therefore, even when the heating resistor portion 41 generates heat over a wide area (for example, when performing "solid printing"), a sufficient current can be passed and deterioration of print quality can be suppressed. The auxiliary electrode can be formed using, for example, silver, aluminum, etc.

[0066] Next, the heat generating resistors 41 are formed on the individual electrodes 31 and the common electrode 32. After that, an overcoat glass layer is formed as the protective film .

[0067] Next, the substrate 35 on which the heat storage layer 33, the individual electrodes 31, the common electrode 32, the heat generating resistors 41, etc. are mounted is divided into individual pieces. For example, a dicer can be used to divide the substrate 35. Furthermore, the substrate 35 can be divided into individual pieces using a laser or the like. For example, a solid-state laser such as a fiber laser can be used as the laser.

[0068] Next, the drive IC and Zener diode, which is a surge protection element, are mounted on the individualized substrate (also called individual substrate). For mounting, solder bumps are provided between the individual substrate and the drive IC, and heat treatment is performed in a reflow furnace under an inert gas atmosphere such as nitrogen to melt the solder bumps and join the solder to the conductor, electrically connecting the individual substrate and the drive IC.

[0069] Next, the resin that will become the underfill material filled between the individual substrates and the drive ICs is thermally cured to form the underfill material.

[0070] Through the above steps, the thermal printhead of this embodiment can be manufactured.

[0071] According to this embodiment, it is possible to obtain a thermal print head that can form wiring etc. using a relatively inexpensive metal material with good electrical conductivity in order to reduce costs, while suppressing sudden high voltages that occur between the wiring etc.

[0072] <Thermal printer> The thermal printer of this embodiment can include the thermal printhead described above. The thermal printer prints on a print medium. Examples of print media include thermal paper for creating barcode sheets and receipts.

[0073] The thermal printer includes, for example, a thermal printhead A1, a platen roller 91 (see FIG. 7), a main power supply circuit, a measurement circuit, and a control unit. The platen roller 91 faces the thermal printhead A1.

[0074] The main power supply circuit supplies power to the multiple heating resistor sections 41 in the thermal print head A1. The measurement circuit measures the resistance value of each of the multiple heating resistor sections 41. The measurement circuit measures the resistance value of each of the multiple heating resistor sections 41, for example, when no printing is being performed on the print medium. This makes it possible to confirm the life of the heating resistor sections 41 and whether or not there is a faulty heating resistor section 41. The control section controls the drive state of the main power supply circuit and the measurement circuit. The control section controls the power supply state of each of the multiple heating resistor sections 41. The measurement circuit may be omitted.

[0075] A connector 59 (see FIG. 7) is used for communication with devices outside the thermal printhead A1. Through the connector 59, the thermal printhead A1 is electrically connected to a main power supply circuit and a measurement circuit. Through the connector 59, the thermal printhead A1 is electrically connected to a control unit.

[0076] The driving IC receives a signal from the control unit via the connector 59. Based on the signal received from the control unit, the driving IC controls the energization state of each of the plurality of heating resistor parts 41. Specifically, the driving IC selectively energizes the plurality of individual electrodes 31 to arbitrarily cause any of the plurality of heating resistor parts 41 to generate heat.

[0077] Next, how to use the thermal printer will be described.

[0078] When printing on the print medium, a potential v11 is applied to the connector 59 from the main power supply circuit as the potential V1. In this case, the plurality of heating resistors 41 are selectively energized and generate heat. The heat is transferred to the print medium, thereby printing on the print medium. As described above, when a potential v11 is applied to the connector 59 from the main power supply circuit as the potential V1, a current path to each of the plurality of heating resistors 41 is ensured.

[0079] When printing is not performed on the print medium, the resistance value of each heating resistor 41 is measured. During this measurement, no potential is applied from the main power supply circuit to the connector 59. During measurement of the resistance value of each heating resistor 41, a potential v12 is applied from the measurement circuit to the connector 59 as the potential V1. In this case, the heating resistors 41 are energized in order (for example, in order from the heating resistor 41 located at the end of the main scanning direction x). Based on the value of the current flowing through the heating resistor 41 and the potential v12, the measurement circuit measures the resistance value of each heating resistor 41. As described above, when a potential v11 is applied from the main power supply circuit to the connector 59 as the potential V1, the current path to each of the heating resistors 41 is substantially cut off. This allows the measurement circuit to more accurately measure the resistance value of each heating resistor 41, and the life of the heating resistor 41 and the presence or absence of a broken heating resistor 41 can be confirmed.

[0080] According to this embodiment, since the thermal printer is equipped with the above-mentioned thermal print head, it is possible to obtain a thermal printer that can form wiring etc. using a relatively inexpensive metal material with good electrical conductivity in order to reduce costs, while suppressing sudden high voltages that occur between the wiring etc.

[0081] [Other embodiments] As described above, several embodiments have been described, but the descriptions and drawings forming part of the disclosure are illustrative and should not be understood as limiting. From this disclosure, various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art. Thus, the present embodiment includes various embodiments not described herein. [Explanation of symbols]

[0082] 1 Board 3 electrodes 4 Resistor layer 5 Connection board 8 Heat dissipation material 10 Surge protection devices 13 areas 19 Insulating layer 31 Individual electrodes 32 Common electrode 33 Heat storage layer 34 Protective film 35 Substrate 41 Heating resistor 59 Connector 91 Platen roller 92 Print media 311 Individual pad section 323 Common section 324 Comb teeth A1 thermal printhead IC Driver IC IC1 Driver IC IC2 Driver IC IC3 Driver IC GND ground electrode Vdd high potential VDD high power electrode Vgnd Ground potential Vh common potential VH common electrode

Claims

1. A thermal print head having a heat generating resistor, a common electrode in contact with the heat generating resistor; an individual electrode electrically connected to the common electrode via the heat generating resistor; a ground electrode to which a ground potential for the thermal printhead is applied; a driving IC electrically connected to the individual electrodes and the ground electrode; a power supply electrode to which a power supply potential for the thermal print head is supplied; A surge protection element, the common electrode and the individual electrodes contain metal particles; the power supply potential includes a first potential supplied to the driving IC and a second potential supplied to the common electrode; The surge protection element is connected between the first potential and the ground electrode. Thermal print head.

2. The thermal printhead of claim 1 , wherein the metal particles comprise at least one selected from the group consisting of copper and silver.

3. 3. The thermal printhead according to claim 1, wherein the surge protection element is a Zener diode.

4. The thermal printhead of claim 1 , wherein the second potential is the same as or higher than the first potential.

5. A thermal printer comprising the thermal printhead according to any one of claims 1 to 4.

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