Thermal printhead and method of manufacturing the same, and thermal printer

Abstract

A thermal head capable of inhibiting disconnection of a comb-tooth portion of a common electrode is provided. In addition, a manufacturing method of the thermal head and a thermal printer having the thermal head are provided. The thermal head of the present invention includes: an individual electrode on a heat accumulating layer; a common electrode having a comb-tooth portion spaced apart from the individual electrode and opposed to the individual electrode; a heat generating resistor on the individual electrode and the comb-tooth portion; a connection electrode composed of a different material from the common electrode and in contact with the common electrode; a first protective film covering a part of the common electrode and the wiring; and a second protective film covering the connection electrode, an end portion of the common electrode in a sub-scanning direction is covered by the connection electrode, one side surface of the connection electrode in the sub-scanning direction is in contact with the second protective film, and the other side surface is in contact with the first protective film.

Description

Technical Field

[0001] This embodiment relates to a thermal printhead and its manufacturing method, as well as a thermal printer. Background Technology

[0002] A thermal printhead, for example, has a large number of heating elements arranged in the main scanning direction on a printhead substrate. Each heating element is formed by stacking a common electrode and an individual electrode on a resistive layer formed on the printhead substrate with a glaze layer in between, such that a portion of the resistive layer is exposed, wherein the ends of the common electrode and the individual electrode face each other. When an electric current is applied between the common electrode and the individual electrode, the exposed portion of the resistive layer (the heating element) heats up due to Joule heating. This heat is transferred to a printing medium (such as thermal paper used to make barcode labels or receipts), thereby enabling printing on the printing medium.

[0003] Common electrodes and individual electrodes are formed by screen printing a paste containing metals such as gold to create electrode patterns.

[0004] In addition, the common electrode and the independent electrode are in contact with the connecting electrode and wiring, respectively, for supplying voltage to the common electrode and the independent electrode from the outside. The connecting electrode pattern is formed by screen printing using a paste of metals such as silver, while the wiring is formed by photolithography using metals such as gold and silver. Due to the high price of gold, from the perspective of reducing product costs, a technology using silver as a relatively inexpensive and highly conductive metal has been proposed.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent document 1: Japanese Patent Application Publication No. 2000-141729.

[0008] Patent document 2: Japanese Patent Application Publication No. 5-89716. Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] However, when the materials of the common electrode and the connecting electrode are dissimilar metals, the Kirkendall effect occurs, where the interface between the common electrode and the connecting electrode shifts due to heating. For example, when the common electrode is made of gold and the connecting electrode is made of silver, the silver, as the material of the connecting electrode, diffuses into the common electrode due to heating. This diffusion causes Kirkendall voids to form in the common electrode. If these Kirkendall voids form at the comb teeth of the common electrode, they may cause wire breakage because the comb teeth are relatively fine electrodes. In addition, the diffusion of silver reduces the ductility of the gold, which is the material of the common electrode, and the comb teeth may be subjected to tension due to heating, potentially leading to wire breakage.

[0011] One aspect of this embodiment provides a thermal printhead capable of suppressing wire breakage at the comb teeth of the common electrode. Another aspect of this embodiment provides a method for manufacturing the thermal printhead. Furthermore, yet another aspect of this embodiment provides a thermal printer having the thermal printhead.

[0012] Technical means for solving problems

[0013] In this embodiment, after forming a first protective film covering the heating resistor, individual electrodes, a portion of the common electrode, and the wiring in contact with the individual electrodes, a connecting electrode is formed that contacts the common electrode. Thus, the end of the common electrode in the sub-scanning direction is covered by the connecting electrode, one side of the connecting electrode in the sub-scanning direction contacts the second protective film, and the other side of the connecting electrode in the sub-scanning direction contacts the first protective film. This structure narrows the path of material diffusion from the connecting electrode to the comb-tooth portion of the common electrode, suppressing the diffusion area from reaching the comb-tooth portion. Therefore, wire breakage in the comb-tooth portion of the common electrode can be suppressed. One aspect of this embodiment is described below.

[0014] One aspect of this embodiment provides a thermal printhead, comprising: a heat storage layer; independent electrodes on the heat storage layer; a common electrode having comb-like portions spaced apart from and opposite to the independent electrodes; heating resistors on the independent electrodes and the comb-like portions; a connecting electrode made of a different material from the common electrode and in contact with the common electrode; a first protective film covering a portion of the heating resistors, the independent electrodes, and the common electrode; and a second protective film covering the connecting electrode, wherein an end of the common electrode in a sub-scanning direction is covered by the connecting electrode, one side of the connecting electrode in the sub-scanning direction is in contact with the second protective film, and another side of the connecting electrode in the sub-scanning direction is in contact with the first protective film.

[0015] Furthermore, another aspect of this embodiment provides a thermal printer having the aforementioned thermal printhead.

[0016] Furthermore, another aspect of this embodiment provides a method for manufacturing a thermal printhead, wherein a heat storage layer is formed, an independent electrode and a common electrode having comb teeth are formed on the heat storage layer, a wiring in contact with the independent electrode is formed, a heating resistor is formed on the independent electrode and the common electrode, a first protective film is formed covering the heating resistor, the independent electrode, a portion of the common electrode and the wiring, after the first protective film is formed, a connecting electrode in contact with another portion of the common electrode is formed, and a second protective film is formed covering the connecting electrode, wherein the independent electrode is spaced apart from and opposite to the comb teeth of the common electrode, and the common electrode is made of a different material than the connecting electrode.

[0017] Invention Effects

[0018] This embodiment provides a thermal printhead capable of suppressing wire breakage at the comb teeth of the common electrode. Furthermore, a method for manufacturing this thermal printhead can be provided. Ultimately, a thermal printer having this thermal printhead can be provided. Attached Figure Description

[0019] Figure 1 This is a top view illustrating the thermal printhead 100A of this embodiment.

[0020] Figure 2 It is along Figure 1 A cross-sectional view along line AA.

[0021] Figure 3 This is a top view (1) illustrating the manufacturing method of the thermal printhead 100A according to this embodiment.

[0022] Figure 4 It is along Figure 3 A cross-sectional view along line AA.

[0023] Figure 5 This is a top view (2) illustrating the manufacturing method of the thermal printhead 100A according to this embodiment.

[0024] Figure 6 It is along Figure 5 A cross-sectional view along line AA.

[0025] Figure 7 This is a top view (3) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0026] Figure 8 It is along Figure 7 A cross-sectional view along line AA.

[0027] Figure 9This is a top view (4) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0028] Figure 10 It is along Figure 9 A cross-sectional view along line AA.

[0029] Figure 11 This is a top view (5) illustrating the manufacturing method of the thermal printhead 100A according to this embodiment.

[0030] Figure 12 It is along Figure 11 A cross-sectional view along line AA.

[0031] Figure 13 This is a top view (6) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0032] Figure 14 It is along Figure 13 A cross-sectional view along line AA.

[0033] Figure 15 This is a top view (7) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0034] Figure 16 It is along Figure 15 A cross-sectional view along line AA.

[0035] Figure 17 This is a cross-sectional view illustrating the thermal printhead 100B of this embodiment.

[0036] Figure 18 This is a cross-sectional view illustrating the implementation of the thermal printhead 100C.

[0037] Figure 19 This is a cross-sectional view illustrating the implementation of the thermal printhead 100D.

[0038] Figure 20 This is a cross-sectional view illustrating the thermal printhead of this embodiment.

[0039] Explanation of reference numerals in the attached figures

[0040] 5 Connecting substrate

[0041] 7 Driver IC

[0042] 8 Heat dissipation components

[0043] 15 substrate

[0044] 31 Independent Electrodes

[0045] 32 Common Electrode

[0046] 32A Comb teeth section

[0047] 32B Public Department

[0048] 33 Heat Storage Layer

[0049] 41 Wiring

[0050] 42, 42a Connecting electrodes

[0051] 50 Heating Resistor

[0052] 51 Heating resistor section

[0053] 52, 54 Protective film

[0054] 59 Connector

[0055] 81 lead wire

[0056] 82 Resin Section

[0057] 91 Paper Press Roller

[0058] 92 Printing Media

[0059] 100A, 100B, 100C, 100D thermal printheads Detailed Implementation

[0060] Next, this embodiment will be described with reference to the accompanying drawings. In the drawings described below, the same or similar parts are labeled with the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the thickness and planar dimensions of each component differ from those of a real product. Therefore, specific thicknesses and dimensions should be determined by referring to the following description. Furthermore, the drawings naturally include parts with different dimensional relationships and scales.

[0061] Furthermore, the embodiments shown below illustrate apparatus and methods for embodying the technical concept, but they do not limit the material, shape, structure, or arrangement of the constituent components. Various modifications can be made within the scope of the inventive concept.

[0062] One aspect of this specific embodiment is described below.

[0063] <1> A thermal printhead includes: a heat storage layer; an independent electrode on the heat storage layer; a common electrode having a comb portion spaced apart from and opposite to the independent electrode; a heating resistor on the independent electrode and the comb portion; a connecting electrode made of a different material from the common electrode and in contact with the common electrode; a first protective film covering a portion of the heating resistor, the independent electrode, and the common electrode; and a second protective film covering the connecting electrode, wherein the end of the common electrode in the sub-scanning direction is covered by the connecting electrode, one side of the connecting electrode in the sub-scanning direction is in contact with the second protective film, and the other side of the connecting electrode in the sub-scanning direction is in contact with the first protective film.

[0064] <2> The thermal printhead as described in <1>, wherein the common electrode comprises gold and the connecting electrode comprises silver.

[0065] <3> The thermal printhead as described in <1> or <2> further includes wiring in contact with the independent electrode, wherein the connecting electrode is thicker than the wiring.

[0066] <4> The thermal printhead as described in any one of <1> to <3>, wherein the connecting electrode has a protrusion that contacts at least a portion of the upper surface of the first protective film.

[0067] <5> The thermal printhead as described in any one of <1> to <4>, wherein the second protective film covers the first protective film.

[0068] <6> The thermal printhead as described in any one of <1> to <5>, wherein the second protective film is in contact with the upper surface of the first protective film and the upper surface of the connecting electrode.

[0069] <7> A thermal printhead as described in any one of <1> to <6>, wherein the independent electrode is spaced apart from the comb portion in the main scanning direction.

[0070] <8> A thermal printer having a thermal printhead as described in any one of <1> to <7>.

[0071] <9> A method for manufacturing a thermal printhead, wherein a heat storage layer is formed, an independent electrode and a common electrode having comb teeth are formed on the heat storage layer, a wiring in contact with the independent electrode is formed, a heating resistor is formed on the independent electrode and the common electrode, a first protective film is formed covering the heating resistor, the independent electrode, a portion of the common electrode and the wiring, a connecting electrode in contact with another portion of the common electrode is formed after the first protective film is formed, a second protective film is formed covering the connecting electrode, the independent electrode is spaced apart from and opposite to the comb teeth of the common electrode, and the common electrode is made of a different material than the connecting electrode.

[0072] <10> The method for manufacturing a thermal printhead as described in <9>, wherein the end of the common electrode in the sub-scanning direction is covered by the connecting electrode, one side of the connecting electrode in the sub-scanning direction is in contact with the second protective film, and the other side of the connecting electrode in the sub-scanning direction is in contact with the first protective film.

[0073] <11> A method for manufacturing a thermal printhead as described in <9> or <10>, wherein the common electrode comprises gold and the connecting electrode comprises silver.

[0074] <12> A method for manufacturing a thermal printhead as described in any one of <9> to <11>, wherein the connecting electrode is thicker than the wiring.

[0075] <13> A method for manufacturing a thermal printhead as described in any one of <9> to <12>, wherein the connecting electrode has a protrusion that contacts at least a portion of the upper surface of the first protective film.

[0076] <14> A method for manufacturing a thermal printhead as described in any one of <9> to <13>, wherein the second protective film covers the first protective film.

[0077] <15> A method for manufacturing a thermal printhead as described in any one of <9> to <14>, wherein the second protective film is in contact with the upper surface of the first protective film and the upper surface of the connecting electrode.

[0078] <16> A method for manufacturing a thermal printhead as described in any one of <9> to <15>, wherein the connecting electrode is formed by screen printing a metal paste, and the wiring is formed by a photolithography process.

[0079] <Thermal Printhead>

[0080] The thermal printhead of this embodiment will be described using the accompanying drawings.

[0081] Figure 1This is a top view of the thermal printhead. Figure 2 It is along Figure 1 A cross-sectional view along line AA. Figure 1 and Figure 2 This represents a portion of a thermal printhead (equivalent to one thermal printhead), which in this embodiment is referred to as a single-piece thermal printhead 100A. The thermal printhead 100A includes: a substrate 15; a heat storage layer 33 on the substrate 15; a plurality of independent electrodes 31 on the heat storage layer 33 and a common electrode 32 having comb-like portions 32A; heating resistors 50 on the independent electrodes 31 and on the comb-like portions 32A of the common electrode 32; wiring 41 in contact with the independent electrodes 31; a connecting electrode 42 in contact with the common electrode 32; a protective film 52 covering the heat storage layer 33, the independent electrodes 31, a portion of the common electrode 32, the heating resistors 50, and the wiring 41; and a protective film 54 covering the connecting electrode 42. Furthermore, the independent electrodes 31 are spaced apart from the comb-like portions 32A of the common electrode 32 in the main scanning direction X, and are opposite to the comb-like portions 32A. The common electrode 32 is made of a different material than the connecting electrode 42. The end of the common electrode 32 in the sub-scanning direction is covered by the connecting electrode 42. One side of the connecting electrode 42 in the sub-scanning direction is in contact with the protective film 54, and the other side of the connecting electrode 42 is in contact with the protective film 52.

[0082] The heating resistor 50 includes a plurality of heating resistor sections 51 that are heated by an electric current flowing in the individual electrode 31 and the common electrode 32. Each heating resistor section 51 is independently formed between the individual electrode 31 and the common electrode 32. Figure 1 Multiple heating resistor sections 51 are omitted. The multiple heating resistor sections 51 are arranged in a straight line on the heat storage layer 33. Furthermore, for ease of understanding, Figure 1 The protective film 54 was omitted.

[0083] In this embodiment, the main scanning direction X is the direction in which the plurality of heating resistors 51 extend in a straight line; the secondary scanning direction Y is the direction perpendicular to the main scanning direction X and parallel to the upper surface of the substrate 15; and the thickness direction Z is the direction corresponding to the thickness of the substrate 15. In other words, the thickness direction Z is a direction perpendicular to both the main scanning direction X and the secondary scanning direction Y.

[0084] The substrate 15 is made of ceramic or single-crystal semiconductor. For example, alumina can be used as a ceramic. For example, silicon can be used as a single-crystal semiconductor. From a heat dissipation perspective, alumina, which has a high thermal conductivity, is preferred for the substrate 15.

[0085] A heat storage layer 33 (also called a glaze layer) with heat storage function is laminated on a substrate 15 made of alumina or the like. The heat storage layer 33 stores the heat generated from the heating resistor 51, which will be described later. The heat storage layer 33 can be made of an insulating material, such as silicon oxide or silicon nitride, which are the main components of glass. The dimension of the heat storage layer 33 in the thickness direction Z is not particularly limited, for example, it is 30 to 80 μm, preferably 40 to 60 μm.

[0086] Individual electrodes 31 and common electrodes 32 formed of metal paste are disposed on the heat storage layer 33. The individual electrodes 31 and common electrodes 32 are obtained by forming electrode patterns by coating metal paste using methods such as screen printing.

[0087] As a metal paste, a paste containing metal particles such as copper, silver, palladium, iridium, platinum, and gold can be used. From the viewpoint of the properties and ionization tendency of metals, copper, silver, platinum, and gold are preferred, and gold is more preferred. In addition, the solvent contained in the metal paste has the function of uniformly dispersing the metal particles. Examples of solvents include one or a mixture of two or more of the following: ester solvents, ketone solvents, ethylene glycol ether solvents, aliphatic solvents, alicyclic solvents, aromatic solvents, alcohol solvents, and water, but are not limited to these.

[0088] Examples of ester-based solvents include ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and dimethyl carbonate. Examples of ketone-based solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone benzene, diisobutyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Examples of glycol ether-based solvents include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, and other monoether acetates, as well as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether.

[0089] Examples of aliphatic solvents include n-heptane, n-hexane, cyclohexane, methylcyclohexane, and ethylcyclohexane. Examples of alicyclic solvents include methylcyclohexane, ethylcyclohexane, and cyclohexane. Examples of aromatic solvents include toluene, xylene, and tetrahydronaphthalene. Examples of alcohol solvents (excluding the ethylene glycol ether solvents mentioned above) include ethanol, propanol, and butanol.

[0090] Metal pastes can contain dispersants, surface treatment agents, abrasion modifiers, infrared absorbers, ultraviolet absorbers, fragrances, antioxidants, organic pigments, inorganic pigments, defoamers, silane coupling agents, titanate coupling agents, plasticizers, flame retardants, humectants, ion scavengers, etc., as needed.

[0091] Each individual electrode 31 is a strip extending approximately along the sub-scanning direction Y, and they are not electrically connected to each other. Therefore, when a printer equipped with a thermal printhead is used, each individual electrode 31 can be applied with a different potential. Each individual electrode 31 has an individual pad connected to its end. The individual pad is configured to be located away from the heating resistor 50 and in contact with the wiring 41.

[0092] The common electrode 32 is the portion whose polarity is opposite to that of the multiple individual electrodes 31 when the printer with the thermal printhead is used. The common electrode 32 includes comb teeth 32A and a common portion 32B that connects the comb teeth 32A together. The common portion 32B is formed along the upper edge of the substrate 15 in the main scanning direction X. In the sub-scanning direction Y, the direction in which the common electrode 32 is located when viewed from the individual electrodes 31 is defined as the upper side of the sub-scanning direction Y. Each comb tooth 32A is a strip extending in the sub-scanning direction Y. The front end of each comb tooth 32A is located in the region between the front ends of two adjacent individual electrodes 31 and is spaced apart from these two individual electrodes 31 along the main scanning direction X by a predetermined interval.

[0093] The front end of each comb tooth portion 32A may also be spaced apart from the front end of each individual electrode 31 along the sub-scanning direction Y. In this case, it is preferable to form the heating resistor portion 51 only in the region where the front end of the comb tooth portion 32A is opposite to the front end of the individual electrode 31. In other words, it is preferable that, in the main scanning direction X, the heating resistor portion 51 is not arranged in the region other than the region where the front end of the comb tooth portion 32A is opposite to the front end of the individual electrode 31.

[0094] In the heating resistor 50, the portion through which current flows from the individual electrode 31 and the common electrode 32 heats up. Specifically, according to a print signal sent from an external source to a driver IC, the heating resistor 50 is independently energized with a heating voltage, enabling selective heating. The heating resistor section 51 is independently energized according to the print signal, thereby selectively heating. Printed dots are formed by heating in this way. The heating resistor 50 uses a material with a higher resistivity than the materials constituting the individual electrode 31 and the common electrode 32, such as ruthenium oxide. The heating resistor 50 can be formed by supplying resistor paste using screen printing or a dispenser and then sintering it. In this embodiment, the dimension in the thickness direction Z of the heating resistor 50 is, for example, about 1 to 10 μm.

[0095] Wiring 41 is in contact with independent electrode 31. Wiring 41 has the function of supplying voltage to independent electrode 31 from the outside, for example, by using a photolithography process using metals such as gold or silver.

[0096] The connecting electrode 42 is in contact with the common electrode 32. The connecting electrode 42 has the function of supplying voltage to the common electrode 32 from the outside, for example, by forming an electrode pattern by coating a metal paste such as silver using a screen printing method. This electrode pattern is formed by sintering the coated metal paste, but the metal paste before sintering has higher fluidity than the metal paste after sintering. This high fluidity may cause the electrode pattern to be formed off-center from the set position. For example, the surface area of ​​the connecting electrode 42 in contact with the surface of the common electrode 32 (the surface of the connecting electrode 42) may increase. However, in this embodiment, since the connecting electrode 42 is formed after the protective film 52 described later is formed, the flow of the metal paste can be suppressed by the protective film 52 even before the metal paste is sintered. The protective film 52 can suppress the expansion of the surface area of ​​the connecting electrode 42 in contact with the surface of the common electrode 32, and can narrow the path of material of the connecting electrode 42 diffusing towards the comb portion 32A side of the common electrode 32.

[0097] Furthermore, the connecting electrode 42 formed using screen printing is thicker than the wiring 41 formed by photolithography. Since the amount of material diffusion varies depending on the thickness, when the materials of the connecting electrode 42 and wiring 41 are the same, and the materials of the common electrode 32 and independent electrode 31 are the same but different from the materials of the connecting electrode 42 and wiring 41, the amount of material from the connecting electrode 42 diffusing into the common electrode 32 is greater than the amount of material from the wiring 41 diffusing into the independent electrode 31. Therefore, by setting the protective film 52 (described later) to contact one side of the connecting electrode 42 in the sub-scanning direction, and setting the protective film 54 to contact the other side of the connecting electrode 42 in the sub-scanning direction, it is possible to suppress contact between the connecting electrode 42 and the comb tooth portion 32A near the bottom surface of the common electrode 32, which is in contact with the protective film 52.

[0098] The protective film 52 covers the individual electrode 31, a portion of the common electrode 32, the wiring 41, and the heating resistor 50, protecting them from wear, corrosion, oxidation, etc. The protective film 52 can be made of an insulating material, such as amorphous glass. The protective film 52 is formed by thick-film printing using glass paste, followed by sintering. The thickness dimension of the protective film 52 in the Z-direction is, for example, about 3 to 8 μm.

[0099] The protective film 54 at least covers the connecting electrode 42. In this embodiment, the protective film 54 covers both the protective film 52 and the connecting electrode 42, and is in contact with the upper surface of both the protective film 52 and the upper surface of the connecting electrode 42. The protective film 54 is the outermost protective film that directly rubs against the printing medium, and can be, for example, a protective film with a hardness of approximately 1000 to 2000 HK as its main component, consisting of amorphous glass, sialon, silicon carbide, or silicon nitride. The thickness dimension of the protective film 54 in the Z-direction is, for example, 5 to 8 μm.

[0100] Here, the manufacturing method of the thermal printhead 100A of this embodiment will be described.

[0101] like Figure 3 and Figure 4 As shown, a substrate 15 is first prepared, and a glass paste is applied to the substrate 15 by screen printing or the like. The applied glass paste is then dried, and a heat treatment is performed to form a heat storage layer 33 on the substrate 15. The sintering process is performed, for example, at 850 to 1200°C for 1 to 5 hours.

[0102] Next, as Figure 5 and Figure 6 As shown, multiple individual electrodes 31 and a common electrode 32 are formed on the heat storage layer 33. The common electrode 32 includes a comb-tooth portion 32A and a common portion 32B that connects the comb-tooth portions 32A together. The individual electrodes 31 and the common electrode 32 can be obtained by forming an electrode pattern by coating the aforementioned metal paste using methods such as screen printing.

[0103] Next, as Figure 7 and Figure 8 As shown, multiple wirings 41 are formed that contact multiple independent electrodes 31. The wirings 41 can be formed, for example, by using a photolithography process with metals such as gold or silver.

[0104] Next, as Figure 9 and Figure 10 As shown, a heating resistor 50 (heating resistor portion 51) is formed on the individual electrode 31 and the comb portion 32A of the common electrode 32 using a thick film forming technique. The heating resistor 50 is formed by supplying a resistor paste using screen printing or a dispenser and then sintering it. The resistor paste may contain, for example, ruthenium oxide.

[0105] Next, as Figure 11 and Figure 12 As shown, a protective film 52 is formed covering the individual electrode 31, a portion of the common electrode 32, the wiring 41, and the heating resistor 50. The protective film 52 is made of, for example, amorphous glass. The protective film 52 is formed by thick-film printing using glass paste, followed by sintering.

[0106] Next, as Figure 13 and Figure 14 As shown, a connecting electrode 42 is formed that contacts the common electrode 32. The connecting electrode 42 is obtained, for example, by coating a metal paste such as silver using a screen printing method to form an electrode pattern. Before the metal paste is sintered, the protective film 52 inhibits the flow of the metal paste, thus the expansion of the surface area of ​​the connecting electrode 42 in contact with the surface of the common electrode 32 can be inhibited by the protective film 52.

[0107] Next, as Figure 15 and Figure 16 As shown, a protective film 54 is formed that at least covers the connecting electrode 42. The protective film 54 is the outermost protective film that directly rubs against the printing medium, and can be, for example, a protective film with a hardness of approximately 1000–2000 HK, primarily composed of amorphous glass, sialon, silicon carbide, or silicon nitride. The thickness dimension of the protective film 54 in the Z-direction is, for example, 5–8 μm.

[0108] The thermal printhead of this embodiment can be manufactured through the above steps.

[0109] In this embodiment, since the connecting electrode 42 is formed after the protective film 52 is formed, the flow of the metal paste can be suppressed even before the metal paste is sintered. The protective film 52 can suppress the expansion of the surface area of ​​the connecting electrode 42 in contact with the surface of the common electrode 32, and can narrow the path of material diffusion from the connecting electrode 42 to the comb tooth portion 32A of the common electrode 32. Furthermore, by setting the protective film 52 to contact one side of the connecting electrode 42 in the sub-scanning direction, and setting the protective film 54 to contact the other side of the connecting electrode 42 in the sub-scanning direction, it is possible to suppress contact between the connecting electrode 42 and the comb tooth portion 32A of the common electrode 32 near the bottom surface of the protective film 52. Therefore, wire breakage at the comb tooth portion 32A of the common electrode 32 can be suppressed.

[0110] (Other implementation methods)

[0111] The foregoing description of one embodiment is exemplary, but the description and drawings that form part of this disclosure are exemplary and should not be construed as limiting. Those skilled in the art will be able to identify various alternative embodiments, examples, and applications based on this disclosure. Therefore, this embodiment includes various embodiments not described herein.

[0112] For example, in thermal printhead 100B, a modified example of thermal printhead 100A, such as Figure 17 As shown, a connecting electrode 42a with a protrusion can be provided instead of a connecting electrode 42. The metal slurry forming the connecting electrode 42 before sintering has high fluidity, so it may sometimes pass over the protective film 52, and the aforementioned protrusion comes into contact with at least a portion of the upper surface of the protective film 52.

[0113] In addition, such as Figure 18 The thermal printhead 100C shown, and Figure 19 As shown in the thermal printhead 100D, the protective film 54 can also be configured not to cover the entire surface, but to at least cover the connecting electrode 42.

[0114] <Thermal Printer>

[0115] The thermal printhead of this embodiment (e.g., thermal printhead 100A) also... Figure 20 As shown, the system includes a substrate 15 (the heat storage layer 33, independent electrodes 31, and common electrodes 32 on the substrate 15 are not shown), a connecting substrate 5, a heat dissipation component 8, a driver IC 7, multiple leads 81, a resin section 82, and a connector 59. The substrate 15 and the connecting substrate 5 are mounted adjacent to each other on the heat dissipation component 8 in the sub-scanning direction Y. Multiple heating resistor sections 51 arranged along the main scanning direction X are formed on the substrate 15. These heating resistor sections 51 are selectively heated by the driver IC 7 mounted on the connecting substrate 5. The heating resistor sections 51 are printed on a printing medium 92, such as thermal paper, pressed onto the heating resistor sections 51 by a paper pressure roller 91, according to a printing signal sent from the outside via the connector 59.

[0116] The connection substrate 5 can be, for example, a printed wiring board. The connection substrate 5 has a structure formed by laminating a substrate layer and a wiring layer (not shown). The substrate layer can be, for example, glass epoxy resin. The wiring layer can be, for example, metals such as copper, silver, palladium, iridium, platinum, and gold.

[0117] The heat dissipation component 8 has the function of releasing heat from the substrate 15. The substrate 15 and the connecting substrate 5 are mounted on the heat dissipation component 8. The heat dissipation component 8 can be made of metal such as aluminum.

[0118] The leads 81 can be made of conductors such as gold. Multiple leads 81 are present, some of which are soldered to connect the driver IC7 to individual electrodes. Additionally, a portion of the other leads 81 are soldered to connect the driver IC7 to the connector 59 via a wiring layer in the connecting substrate 5.

[0119] The resin section 82 can be made of, for example, black resin. Epoxy resin, silicone resin, etc., can be used as the resin section 82. The resin section 82 covers the driver IC7 and the multiple leads 81, protecting the driver IC7 and the multiple leads 81. The connector 59 is fixed to the connection substrate 5. Wiring for supplying power to the thermal printhead from the outside and for controlling the driver IC7 are connected to the connector 59.

[0120] The thermal printer of this embodiment can have the aforementioned thermal printhead. The thermal printer prints on a printing medium that is conveyed along the sub-scanning direction Y. Typically, the printing medium is conveyed from the connector 59 side to the heating resistor 51 side. Examples of printing media include thermal paper used for making barcode labels or receipts.

[0121] A thermal printer includes, for example, a thermal printhead 100A, a paper pressure roller 91, a main power supply circuit, a measurement circuit, and a control unit. The paper pressure roller 91 is directly opposite the thermal printhead 100A.

[0122] The main power supply circuit supplies power to the multiple heating resistors 51 in the thermal printhead 100A. A measuring circuit measures the resistance value of each of the multiple heating resistors 51. The measuring circuit measures the resistance value of each of the multiple heating resistors 51, for example, when no printing is being performed on the printing media. This allows the lifespan of the heating resistors 51 to be determined and whether any heating resistors 51 have failed. A control unit controls the drive state of the main power supply circuit and the measuring circuit. The control unit controls the energizing state of each of the multiple heating resistors 51. The measuring circuit may sometimes be omitted.

[0123] Connector 59 is used for communication with devices other than the thermal printhead 100A. The thermal printhead 100A is electrically connected to the main power supply circuit and the measurement circuit via connector 59. The thermal printhead 100A is also electrically connected to the control unit via connector 59.

[0124] The driver IC7 receives a signal from the control unit via connector 59. Based on the signal received from the control unit, the driver IC7 controls the energizing state of each of the plurality of heating resistors 51. Specifically, the driver IC7 heats up any one of the plurality of heating resistors 51 by selectively energizing multiple independent electrodes.

[0125] Next, the usage of the thermal printer will be explained.

[0126] When printing on the printing medium, a potential v11 is applied from the main power circuit to the connector 59 as potential V1. In this case, the plurality of heating resistors 51 are selectively energized and heated. By transferring this heat to the printing medium, printing can be performed on the printing medium. As described above, when a potential v11 is applied from the main power circuit to the connector 59 as potential V1, a power supply path for each of the plurality of heating resistors 51 can be ensured.

[0127] When no printing is being performed on the printing medium, the resistance value of each heating resistor 51 is measured. During this measurement, no potential is applied from the main power supply circuit to the connector 59. When measuring the resistance value of each heating resistor 51, a potential v12 is applied from the measuring circuit to the connector 59 as potential V1. In this case, the multiple heating resistors 51 are energized sequentially (for example, starting from the heating resistor 51 located at the end in the main scanning direction X). The measuring circuit measures the resistance value of each heating resistor 51 based on the value of the current flowing in the heating resistor 51 and the potential v12. As described above, when a potential v11 is applied from the main power supply circuit to the connector 59 as potential V1, the power supply path to each of the multiple heating resistors 51 is essentially cut off. Therefore, the resistance value of each heating resistor 51 can be measured more accurately using the measuring circuit, and the lifespan of the heating resistor 51 and whether any heating resistor 51 has failed can be confirmed.

[0128] By employing this embodiment, a thermal printer capable of suppressing line breakage in the comb section of the common electrode can be obtained.

[0129] This invention relates to the subject matter of Japanese Patent Application 2020-167708, filed on October 2, 2020, the entire disclosure of which is incorporated herein by reference.

Claims

1. A thermal printhead, characterized in that, include: Heat storage layer; The independent electrodes on the heat storage layer; A common electrode having comb-like teeth spaced apart from and opposite to the individual electrodes; The independent electrode and the heating resistor on the comb teeth; A connecting electrode, which is made of a different material than the common electrode and is in contact with the common electrode; A first protective film covers a portion of the heating resistor, the individual electrodes, and the common electrode; and A second protective film covers the connecting electrodes. The end of the common electrode in the sub-scanning direction is covered by the connecting electrode. One side of the connecting electrode in the sub-scanning direction contacts the second protective film, and the other side of the connecting electrode in the sub-scanning direction contacts the first protective film. The connecting electrode has a protrusion. The protrusion is in contact with at least a portion of the upper surface of the first protective film.

2. The thermal printhead as described in claim 1, characterized in that: The common electrode contains gold. The connecting electrode contains silver.

3. The thermal printhead as described in claim 1 or 2, characterized in that: It also includes wiring that contacts the individual electrodes. The connecting electrode is thicker than the wiring.

4. The thermal printhead as described in claim 1 or 2, characterized in that: The second protective film covers the first protective film.

5. The thermal printhead as described in claim 1 or 2, characterized in that: The second protective film is in contact with the upper surface of the first protective film and the upper surface of the connecting electrode.

6. The thermal printhead as described in claim 1 or 2, characterized in that: The independent electrode is spaced apart from the comb section in the main scanning direction.

7. A thermal printer, characterized in that, It has the thermal printhead as described in claim 1 or 2.

8. A method for manufacturing a thermal printhead, characterized in that: Forming a heat storage layer, Independent electrodes and a common electrode with comb-like teeth are formed on the heat storage layer. Forming wiring that contacts the individual electrodes. A heating resistor is formed on the individual electrode and the common electrode. A first protective film is formed to cover the heating resistor, the individual electrodes, a portion of the common electrode, and the wiring. After the first protective film is formed, a connection electrode is formed that contacts another part of the common electrode. A second protective film is formed covering the connecting electrodes. The independent electrode is spaced apart from the comb teeth of the common electrode and is opposite to the comb teeth. The common electrode is made of a different material than the connecting electrode. The connecting electrode has a protrusion. The protrusion is in contact with at least a portion of the upper surface of the first protective film.

9. The method for manufacturing a thermal printhead as described in claim 8, characterized in that: The end of the common electrode in the sub-scanning direction is covered by the connecting electrode. One side of the connecting electrode in the sub-scanning direction contacts the second protective film, and the other side of the connecting electrode in the sub-scanning direction contacts the first protective film.

10. The method for manufacturing a thermal printhead as described in claim 8 or 9, characterized in that: The common electrode contains gold. The connecting electrode contains silver.

11. The method for manufacturing a thermal printhead as described in claim 8 or 9, characterized in that: The connecting electrode is thicker than the wiring.

12. The method for manufacturing a thermal printhead as described in claim 8 or 9, characterized in that: The second protective film covers the first protective film.

13. The method for manufacturing a thermal printhead as described in claim 8 or 9, characterized in that: The second protective film is in contact with the upper surface of the first protective film and the upper surface of the connecting electrode.

14. The method for manufacturing a thermal printhead as described in claim 8 or 9, characterized in that: The connecting electrodes are formed by screen printing metal paste. The wiring is formed by a photolithography process.

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